CA1286912C - Acoustically soft ink jet nozzle assembly - Google Patents
Acoustically soft ink jet nozzle assemblyInfo
- Publication number
- CA1286912C CA1286912C CA000539291A CA539291A CA1286912C CA 1286912 C CA1286912 C CA 1286912C CA 000539291 A CA000539291 A CA 000539291A CA 539291 A CA539291 A CA 539291A CA 1286912 C CA1286912 C CA 1286912C
- Authority
- CA
- Canada
- Prior art keywords
- nozzle
- ink
- transducer
- energy
- disturbing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
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- 229920013632 Ryton Polymers 0.000 claims description 9
- 239000004736 Ryton® Substances 0.000 claims description 9
- 239000007779 soft material Substances 0.000 claims description 9
- 229920004943 Delrin® Polymers 0.000 claims description 6
- 239000007767 bonding agent Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 229920005123 Celcon® Polymers 0.000 claims description 5
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- QHGVXILFMXYDRS-UHFFFAOYSA-N pyraclofos Chemical compound C1=C(OP(=O)(OCC)SCCC)C=NN1C1=CC=C(Cl)C=C1 QHGVXILFMXYDRS-UHFFFAOYSA-N 0.000 claims 1
- 239000012530 fluid Substances 0.000 abstract description 35
- 239000004734 Polyphenylene sulfide Substances 0.000 abstract description 3
- 229920000069 polyphenylene sulfide Polymers 0.000 abstract description 3
- 230000002238 attenuated effect Effects 0.000 abstract 1
- 239000000976 ink Substances 0.000 description 105
- 238000012360 testing method Methods 0.000 description 15
- 230000000712 assembly Effects 0.000 description 10
- 238000000429 assembly Methods 0.000 description 10
- 239000010437 gem Substances 0.000 description 8
- 229910001751 gemstone Inorganic materials 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 7
- 239000002184 metal Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 4
- 125000002777 acetyl group Chemical class [H]C([H])([H])C(*)=O 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- -1 polypropylene Polymers 0.000 description 3
- 238000007639 printing Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 239000004743 Polypropylene Substances 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
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- 239000004593 Epoxy Substances 0.000 description 1
- 239000004727 Noryl Substances 0.000 description 1
- 229920001207 Noryl Polymers 0.000 description 1
- 229920000265 Polyparaphenylene Polymers 0.000 description 1
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- XECAHXYUAAWDEL-UHFFFAOYSA-N acrylonitrile butadiene styrene Chemical compound C=CC=C.C=CC#N.C=CC1=CC=CC=C1 XECAHXYUAAWDEL-UHFFFAOYSA-N 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 238000010276 construction Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
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- 230000001419 dependent effect Effects 0.000 description 1
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- 125000003700 epoxy group Chemical group 0.000 description 1
- ONKUMRGIYFNPJW-KIEAKMPYSA-N ethynodiol diacetate Chemical compound C1C[C@]2(C)[C@@](C#C)(OC(C)=O)CC[C@H]2[C@@H]2CCC3=C[C@@H](OC(=O)C)CC[C@@H]3[C@H]21 ONKUMRGIYFNPJW-KIEAKMPYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
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- 238000002955 isolation Methods 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920006380 polyphenylene oxide Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
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- 229910001220 stainless steel Inorganic materials 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
- B41J29/10—Sound-deadening devices embodied in machines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/02—Ink jet characterised by the jet generation process generating a continuous ink jet
- B41J2/025—Ink jet characterised by the jet generation process generating a continuous ink jet by vibration
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Abstract
ACOUSTICALLY SOFT INK JET
NOZZLE ASSEMBLY
Abstract of the Disclosure An ink jet nozzle assembly is produced from materials, such as polyphenylene sulfide. The resulting assembly is acoustically soft so that undesirable fluid and mechanical resonances are substantially attenuated.
NOZZLE ASSEMBLY
Abstract of the Disclosure An ink jet nozzle assembly is produced from materials, such as polyphenylene sulfide. The resulting assembly is acoustically soft so that undesirable fluid and mechanical resonances are substantially attenuated.
Description
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-L-Background of the Invention This invention relates to drop marking equipment and, in particular, to nozzles used in such drop marking equipment or ink jet devices. Such devices employ inks which are supplied from a reservoir to a nozzleO The nozzle directs ink at a substrate to be marked. By use of a transducer, electrical energy is converted into mechan-ical energy, which is coupled to the ink in the nozzle.
In one example of ink jet operation~ the stream of ink ejected from an orifice at on~ end of the noæzle is broken up in~o a series of regularly spaced, discrete droplets which may be selectively given an electrical ch~rge. In that type of drop marking device, those drops which receive a charge are deflected onto a substrate while those which are not charged are recovered and returned to the ink supply. In another type of droplet marking device, the transducer applies an impulse of energy to the fluid in the nozzle each instance that a droplet is needed.
As is well known by those in the artr the com-plexity of such ink jet nozzles contribute to cost and speed limit~tions~ For example, it is often desirable ~o group together several such nozzles to permit high speed printing on a substrate which may be, for example, magazines, envelopes, labelsr beverage cans on other : . . . - ,. .: : . -: : ........ .. -, - . . :
~ Z ~ 6~2 products ~oving on a conveyor. It is not uncommon for ink jet nozzles in some applications to be spaced as closely as six per inch and thus the need for a low cost, high quality, miniaturized device is apparent.
A significant contributing factor to the com-plexity and cost of producing ink iet nozzles is the presence of both fluid and mechanical resonances in such assemblies which interfere with the nozzle's usefulnesss over the range of frequencies usually employed to form the ink droplets, Such resonances vary with the type of ink employed, temperature, and the geometric dimensions oE the nozzle assembly~ They are also significantly affected by the type of material used to manufacture the nozzle. As a result ink jet printers have required a variety of differ-ent nozzles to permit operation at different frequencies and for different kinds of inks.
Typically, ink jet noz~le assemblies have been manufactured from metal or glass materials and are acoust-ically ~hard" meaning that they support acoustic reson-ances at all three imparting added mechanical energy to the ink stream at specific frequencies. Also a considera-tion in nozzle design is the fluid resonance~ io e., reson-ance in the ink contained within the nozzle body. If a fluid is confined in a chamber having a rigid wall, a standing wave is formed, in thifi case inside the fluid containing chamber. One standard nozzle design techni~ue calls for configuring the nozzle assembly to have a mechan-ical resonance that is outside the operating frequency range of the nozzle, while the fluid chamber and ink are matched to have a fluid xesonance in the operating frequency range. In that type of nozæle assembly, opera-tion is restricted to frequencies substantially coincid~
ental with the fluid ~resonance region because only in that : -..
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region can energy be transmitted to the fluid efficientlyand the droplets be formed reliably. As is well known according to acoustic principles involved in vibrating bodies, these nozzles that have fluid resonance regions also have antiresonance regions. The disturbing energy applied to the nozzle cannot be efficiently transmitted to the fluid to form droplets if the frequency selected for operation is coincidental with an antiresonance frequency region.
The present invention contemplates, at least in one aspect, proceeding contrary to accepted wisdom by designing nozzles without resonance so as to eliminate the antiresonance regions in the operating freguency range and thereby extend the operating frequency range of the nozzle.
To do that, acoustically soft materials were sought so that resonances would be substantially unsupported. This permits only the disturbing energy created by an electro-mechanical transducer, for example, a piezoelectric crystal, operating at a selected frequency to ba transmitted to the fluid.
In the prior art efforts have been made to overcome the difficulties which arise ~rom fluid and mechanical resonances. These are discussed in U.S. Patent Nos. 4,379,303, 4,349r830r and 3,972~474, for example.
Typically, reduction of fluid resonance has been attempted by using either a labyrinth of small passages or ~y making the no~zle body as short as possible. In general, these procedures move portions of the resonances to higher frequencies (usually outside the operating frequency range~. However, harmonics of the undesirable resonances remain and show up in the operating frequency range of the nozzle.
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According to the present invention, a nozzle assembly is disclosed which employs an acoustically soft material which can overcome most or all of the disadvantages of present assemblies and which is more versatile than the latter because it provides additional advantages not heretofore obtainable. Specifically, according to the present invention, (1) the ink is electrically isolated from the transducer permitting the reference potential of the ink to be independently adjusted relative to the driving signal to the transducer, if desired; (2) the nozzle assembly can be formed by molding techniques and mass produced at low cost; (3) the operating frequency range of the nozzle is broadened by eliminating anti-resonance regions; (4) electrolytic action can be controlled by use of an electrode and filter arrangement in the ink system including the nozzle.
Summary of the Invention Various aspects of the invention are as follows:
A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attenuation or the creation of harmonic resonances of a frequency characterizing the disturbing energy.
A nozzle assembly to form ink droplets for an ink jet printer comprising:
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
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(b) a transducer coupled to said nozzle for transmission of a disturbing energy through said tubular member to cause the ink to form droplets, as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of harmonic resonances of a freguency characterizing the disturbing energy.
A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an ori~ice at one end, the 15 other end adapted for connection to a supply o~ ink ~:
containing solvents, said nozzle being formed from a ~:
material which is substantially impervious to said ink and which has a substantially flat response to a driving voltage frequency characterizing the disturbing energy at least over the frequency range of 20KHz to 70KHz, wheraby when the transducer is coupled to said nozzle the disturbing energy thereof is transmitted to : the ink within the nozzle without substantial amplification, attenuation or creation of haxmonic resonances of a freguency characterizing the disturbing energy.
A nozzle assembly to form ink droplets for an ink jet comprising:
: (a~ a tubular member having an orifice at one end, 3C the other end adapted for connection to a supply of ink containing solvents;
~ ~b) a transducer responsive to a driving signal :~ for generating distur~ing energy coupled to said tubular member to cause the ink to form droplets as it leaves the orifice:
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5a (c) said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to the driving signal frequency at least over the frequency range of 20KHz to 70KHz, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of ha:rmonic resonances of one or more frequencies characterizing the disturbing energy.
A nozzle suitable for us,e with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted ~or connection to a supply of ink containing solvents, said nozzle being formed from a material which is~
(a) resistant to said ink, ~b) acoustically soft, and (c) has a substantially flat response to the driving signal frei~uency generating the disturbing energy at least over the ranye of 20KHz to 70KHz, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of harmonic resonances of the driving signal ~requency.
A nozzle suitable for use with a transducer to form ink droplets comprising:
a hollow chamber connected to a supply of ink containing solvents, adapted to confine a volume of said ink to be ejected through an orifice in a wall thereof, said chamber being formed from an acoustically soft material which is substantially resistant to said ink, whereby when a transducer i5 coupled to said chamber the disturbing energy thereof is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic A
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;3~9~2 5b resonances of one or more frequencies characterizing the disturbing energy.
A method of forming ink droplets from a supply of ink comprising the steps of:
supplying the ink to a chamber, ~he walls of which are formed of acoustically soft material and which have at least one outlet therefrom through which ink may pass;
creating a disturbing enlergy characterized by one or more predetermined frequencies;
transmitting said energy to said ink through said acoustically soft chamber walls to form droplets as the ink passes out of the chamber;
whereby the disturbing energy is transmitted to the ink without substantial amplification, attenuation or the creation of harmonic resonances of said one or more frequencies characterizing said disturbing energy.
By way of added explanation, the invention in one aspect involves fabricating nozzle bodies of a material which has a desired acoustic impedance. Specifically, the material from which the nozzles are fabricated is acoustically soft so that resonances are not supported by the nozzle structure. Instead, the driving energy is transmitted directly to the ink stream without amplification or attenuation due to variation in fr~quency response. The materials suitable for use in the present invention are generally described as acoustically soft plastics which can withstand certain solvents typically contained in the inks used for ink jet applications. The nozzles formed from such materials usually have an orifice in a wall of a fluid chamber through which ink is ejected to form droplets.
In one instance, the orifice is formed in a jewel which is embedded in the nozzle body and the transducer is adhesively bonded thereto. The nozzle and transducer are then insorporated into a nozzle assembly.
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It is accordingly an object of an aspect of the present invention to provide an improved ink jet nozzle assembly which minimizes both fluid and mechanical resonances.
It is an object of an aspect of the invention to provide such an assembly which is low in cost and easily produced without the usual machining steps required of present assemblies.
It is an object of an aspect of the present invention to provide a nozzle assembly in which the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or the creation of harmonic resonances of any frequency characterizing the disturbing energy.
It is an object of an aspect of the invention to provide nozzle assemblies having an essentially flat response to frequencies characterizing the driving voltage over an entire range of frequencies at which ink droplets are formed by a transducer.
An object of an aspect of the invent.ion is to provide a nozzle assembly which permits the ink to be electrically isolated from the transducer whereby the ink can be subjected to an electrical potential independent of the signal applied to drive the transducer for the purpose disclosed, for example, in U.S. Patent No. 4,319,251, and for the further purpose of permitting the control of electrolytic action within the ink system of the ink jet device.
: Other:objects and advantages of the invention will be apparent from the remaining portion of the specification.
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Brief Descriptlon of the Drawin~s Figure 1 is an illustration from U,S. Patent 3,702,118 and represents the construction of a typical prior art nozzle assembly.
Figure 2 is a cross sectional view o~ a nozzle assembly according to a preferred embodiment o~ the pre-sent invention.
Figure 3 i~ an enlarged sectional view of the nozzle and tail piece according to the preferred embodi-ment.
Figure 4 is a curve illustrating typical response characteristics of prior art nozæle assemblies.
Figures 5 through 11 are similar curves illus- -trating the response characteristics for a number o~
different materials having various suitability for use in the present invention.
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Detailed Description .
As indicated in the background portion of this specification, the present invention relates to a nozzle assembly for i~k jet printing which has significant advantages over present assemblies which are typically machined ~rom metal, glass or other acoustically ~Ihard~
materials. Such~prior nozzIes, a typical example being illustrated in Figure 1, are somewhat complex to design and manufacture particularly in view of their relatively small size. As a result they are expensive to produce and quality control is a continuin~ problem. By way of example;
one such nozzle assembly made from metal requires a fabrica-tion proce~s that may take as much as 45 minutes or more . . . . - .
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of machining operations by skilled technicians. The nozzle 10 must be carefully machined so as to permit the concentric attachment of one or more transducers 12 in A manner to provide good acoustical coup]ing so that the ink chamber 14 will properly receive acoustic energy.
As known by those skilled in the art, one type of nozzle assembly used in an ink jet device which controls drop flight by electrical forces employs electrically con-ductive ink supplied from a reservoir via a conduit 16 to the nozzle assembly. The nozzle assembly consists of the nozzle 10, a tail piece 18, which interconnects the nozzle with the conduit 16, and the transducer 12. The assembly is usually provided in a block or head 20. Disposed at the front of the nozzle is an orifice 22, for example, a jewel having an opening through which the ink is forced.
Vibrational energy is provided by the transducer and that causes the ink stream to break up into regularly-spaced, discrete droplets which can then be electrically charged and deflected by electrostatic deflection plates in a manner well known in this art.
Because the nozzle assembly shown in Figure 1 is fabricated from metal or glass it is, as indicated, both expensive to make and acoustically hard. As a result it is necessary to test each type of nozzle to determine in what frequency range it can be utilized. Specifically, it must be tested to determine what mechanical and fluid resonances are set up in the nozzle which might interfere -with the intended operationO
This is usually accomplished by testing the nozzle under actual operating conditions. A curve is shown in Figure 4 for a typical metal nozzle assembly.
The curve is a plot of drive voltage as a function of operating frequencyO The plot indicates the voltage : , ' , : : : , .
3~,9~2 needed to produce a constant stream of ink droplets at a specified frequency. As can be seen from Figure 4, there is a range between approximately 20KHz and 40KHz where the drive voltage for the nozzle is relatively low. This indicates that in this frequency range the nozzle is e~fi-cient and the driving voltage remains substantially constant over a limited operating frequency range. On the other hand, in the frequency range of approximately 40KHz to 60KHz and also at frequencie~; below ~OKHz the required drive voltage increases significantly due to an increase in the acoustic impedance of the ink. Those are the anti-resonance regions for the particular nozzle and ink match.
Such variation in drive voltage is undesirable and requires the design of many nozzles in order to have a nozæle which is suitable for all frequency ranges of interest. Specifically~ to operate at any given frequency using inks that have different physical properties requires nozzles having diferent chamber configurations, for example, different lengths. The velocity of sound for each different ink is the physical property having the most significant effect on determining the nozzle configu-ration. Temperature at which the nozzle operates, of course, affects the velocity of sound for the ink used. ~-The resonances in nozzle assemblies are of two types: mechanical resonance and fluid resonance. Exist-ing assemblies, usually formed from stainless steel tubing, have a mechanical resonance which, if in the operating range, ca~ affect operation significantly. One common approach is to design the nozzle so that the mechanical resonance is well above the operating frequency range.
That leaves fluid resonance only as a consideration in nozzle design. The ink chamber structure and the ink composition are matched to provide a fluid resonance region coincidental with the selected operating frequency.
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~36 _9_ These fluid and mechanical resonances are responsible for the limited operating frequencies of existing, acousti-cally hard, nozzle assemblies For a nozzle to be useful over a range of fre-quencies it should operate at a substantially constant drive voltage level at all frequencies in the range required regardless of ink characteristiGs. Typical useful frequencies range from lOKHz to lOOKHz ~and some-times higher). Typical inks suitable for use in ink jet printers have the following range of characteristics:
Surface tension 22 to 72 dyne/cm Viscosity 1.5 to 10 centipoise Density .85 to 1.1 gm/cm3 Velocity of sound 1,000 to 1,650 m/s The last characteristic, the velocity of sound in the ink, is of significant concern in the design of nozzles. The velocity of ssund in such a fluid varies with the temperature of the fluid andr ~herefore, the fluid resonances (related to the velocity of sound) change frequency as a function of temperature changes in the nozzle. Thus, the resonances may be different during initial operation, when the nozzle is cool, than after the nozzle has been in use for a period of time. Also, the ~ -velocity of sound is affected by changes in the composi-tion of the ink due mainly to evaporation of solvents.
According to the present invention these pro-blems are overcome by the use of a nozzle assembly which is acoustically softO Although there are many materials which might meet this criteria, it is necessary to consider the severe operating environment~ The nozzle may need to be extremely small to work in some applications, subjected to continual temperature changes and vibration and, most importantly, is in contact with different inks containing ,~
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69~2 water or various alcohols, ketones and other solvents.
It is necessary, therefore, to select materials which can stand up to this environment in addition ~to being acoustically soft.
Through materials testing a number of materials were identified as being potentially suited for the application. These include acetal homopolymers (such as Delrin),TM acetal copolymers (such as CelconT GC 25), polypropylene, Teflon,TM polyphenylene sulfide (Ryton), polyphenylene oxicle (Noryl).
These materials were selected for testing because they are moldable, have long term stability in contact with the solvents contained in typical inks and they were expected to be acoustically soft. It was believed that at least some of these materials would eliminate or attenuate resonances in the body of the nozzle (mechanical resonance) and in the ink (fluid resonance).
In order to determine which, if any, of these materials were suitable, nozzle bodies were designed, molded and tested.
Figure 3 illustratas the nozzle assembly molded from the various materials for purposes of testing. A
nozzle 30 is an elongated, hollow cylindrical member.
AT one end thereof is a female coupling 32 adapted to receive a tail piece 34 having a male coupling member 36. The tail piece 34, in turn, can be coupled to a conduit member for providing an ink supply to the nozzle 30.
The distal end of the nozzle 30 has a recessed - 30 portion 37 adapted to receive and retain an orifice - jewel 38 therein. Retention is accomplished by dimensioning the recess to provide an interference fit which firmly seats the jewel and prevents leakage. It was found that an interference fit of approximately .0015 inch was adequate to ' .
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retain the jewel in place with a recess depth of approxi-mately two times the thickness of the jewel. With such dimensions the no2zle material closes around the jewel to retain it securely in place~
Prior to testing thle nozzle 30 of Figure 3, a piezoelectric transducer was coupled by adhesive bonding.
The bonding agent was selected to insure a good coupling between the piezoelectric device and the nozzle for trans-mission of energy to the fluid~ Epoxies are preferred and, in particular, a one part binder which is not too viscous is best. This permit~ the binder to ~low well in the space between the nozzle and the piezo electric device to avoid gaps which can cause undesirable variations in the applied energyt require higher drive voltages, contri-bute to mechanical resonance and lead to premature failure of the device. Preferably the bonding material is relati-vely stiff to maintain drive efficiency. One suitable adhesive bonding agent is an anaerobic adhesive sold under the trad~ name Permalok by Permabond International Corporationr Englewood, New Jersey.
Completed test nozzles molded from the materials believed to be suitable were then subjected to testing.
The results of these tests are illustrated in Figures 5 through 8. In each case the drive voltage, RMS or peak-to-peak as noted on the plots, necessary to maintain const~
ant drop formation was plotted over a frequency range of lOKHz to lOOKHz.
Referring to Figure 5, the test results for the acetal homopolymer (Delrin) are shown. As can be seen, the drive voltage in the frequency range 20KHz to 70KHz is reasonably flat and less than approximately 15 volts.
However, in the ranges of lO to ~OKHz and 70 to 90KHz sig- -nificant antiresonances are encountered causing undesirable ~. : .. . ................. , ~ - .
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increases in 'he drive voltages. Nevertheless~ this data compares quite favorably with the data for a typical metallic nozzle shown in Figure 4~
E~igure 6 shows the test data for polypropylene.
It has a variety of antiresonances throughout the fre-quency range of interest and is therefore not suitable for present purposes.
Figure 7 illustrates the test data for the acetal coplymer (Celcon) whic:h has undesirable antireson-ances at 10 to 20 KHz and above 9OKHz.
Figure 8 illustrates the data for polyphenylene sulfide ~Ryton) ~two tests are shown, one in which the nozzle is potted in a block, the other unpotted). As can be seen, the material is much better than the prior art metal nozzles and significantly better than any of the other materials tested. Its response characteristic is essentially flat from lOKHz to lOOKHz. This indicates, particularly in view of the low drive voltage required to maintain constant droplet production, that the material very efficiently couples the piezoelectric device and the fluid while at the same time being acoustically soft to not support fluid resonance. Because it is a molded part and is directly coupled to the driving device by an adhesive, there is little mechanical resonance created.
This material was designated as the preferred material for the production of a new, highly efficient nozzle assembly for ink jat printing. Such a nozzle can be driven at a substantially uniform voltage over the desired operating range of frequencies.
To verify the remarkable properties of this compound, additional tests were run using inks having di~ferent properties and, in particular, different velocity of souAd values. The curves for this testing are :: :
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~r~6~31~ i illustrated in Figures 9 through 11. In each case the response curve for the Ryton was essentially flat over the frequency range of interest.
Although not as good as Ryton, Celcon and Delrin were also deemed to be accept:able materials for use under conditions where the antiresonances are outside the intended operating ~re~uency. Materials found not to be suitable include polyurethane, polyvinyl chloride, styrene, poly-carbonate, acrylic, ABS, and polyphenylene oxide. All of the suitable materials are moldable and chemical resistant thereby providing the desired properties. While these materials are not nonconductive electrically, that charac~
teristic is not a requirement for many applications fo the present invention.
Re~erring to Figure 2 r there is shown a preferred embodiment of the nozzle assembly employing the preferred materials of the present invention. A nozzle 50 formed of Ryton, Celcon or Delrin is coupled to a tail piece 52 pre-ferably ~ormed of the same materials. In turn, the tail piece is coupled to a fitting 54 for connection to an ink supply conduit. A jewel 56 is provided in the forward portion of the nozzle and captured therein by virtue of the dimensions of~the nozzle recess as previously des-cribed. Concentrically mounted over the nozzle 50 is a piezoelectric transducer 58 adhesively bonded in place.
The devices are electrically driven by means o~ a cable 61, the conductors contained therein being soldered to the outside o~ the transducers as indicated. The nozzle assembly is preferably potted and disposed within a nozzle head assembly or block 60. The completed assembly is small enough to permit spacing on the order of six ~ieparate print heads per inch. The nozzles made according to the teach-ings of the present invention have good, long term resist-,, : -.
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~2~69~
ance to ink solvents, are relatively temperature insensi-tive, and can be driven at substantially uniform drive voltages over a wide range of operating frequencies~ At the same time, because they zlre acoustically soft, the fluid does not "experience" a rigid confining wall and does not form standing waves which generate fluid reson-ances within the noz~le body. By eliminating ~luid reson-ances, the antiresonances representing sharp increases in the acoustic impedance of the ink are also eliminated.
Thus, droplet formation is accomplished across a broad frequency ranga by a substantially uniform driving voltage.
If desired, because of the electrical isolation of the ink within the nozzle body, an independently con-trolled potential may be applied to the ink permitting, for example, increased deflection by the techniques taught in U.S. Patent 4,319,251. In addition, phasing of drop formation and drop charging is facilitated by permitting chargin~ currents in the ink to be reliably detected.
While the invention has been described with refer-ence to a preferred embodiment of a nozzle assembly having a single ori~ice through which ink is ejected, it is within the teachings of the present invention to provide a plura-lity of orifi~es in the nozzle assembly configured in an array. Ei~her a separate chamber for each orifice or a common chamber for a plurality of orifices may be used dependent upon which droplet formation technique is desir-able in the particular ink jet device in which the nozzle is employed. There is ink confined to the chamber in either instance~ and forming the wall or walls of the nozzle ink chamber of acoustically soft material in accordance with ~he teachings of the presen~ invention assures that the disturbing energy coupled to the chamber is transmitted to ' ::
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the ink within the chamber without substantial amplifica-tion, attenuation or the creation of harmonic resonances of any frequency characteri2ing the disturbing energy.
The present invention is useful also in ink jet printers that employ a pulsed nozzle to form ~roplets.
Zolton V.S. Patent 3,683,212 discloses one example of that type of nozzleu The impulses of electrical energy used to drive such a no~zle commonly have a duration of 10 micro-seconds to 100 microseconds. A Fourier analysis of those energy pulses manifests that reliable droplet formation necessitates that the nozzle respond consistently to fre-quencies in the range of lOKHz to lOOKHz. It is desirable that the nozzle chamber not support fluid resonances in that frequency range. A nozzle which has a fluid chamber with walls made of acoustically soft material as taught by the present invention will not support resonances in that region, and thus will have a substantially flat response to energy impulses ch~racterized by frequencies that are within the operating frequency range. As a result, droplet formation is more nearly prvportional to the characteristics of the energy pulse applied to the 1uid to improve control and enhance the marking results. In addition, spurious oscillations in the impulse nozzle ink chamber that occur after a pulse has directed formation o~ a droplet are ab-sorbed if the walls are made of acoustically soft material.
Those spurious oscillations can distort the energy applied to the fluid when a succeeding command pulse is transmitted to the fluid. Clearly, an impulse or pulse driven nozzle can be operated more advantageously by following the teach-ings of the present invention.
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While we have shown and described embodiments of the invention~ it will be understood that this description and illustrations are offered merely by way o~ example, and that the invention is to be limited in scope only as to the appended claims.
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-L-Background of the Invention This invention relates to drop marking equipment and, in particular, to nozzles used in such drop marking equipment or ink jet devices. Such devices employ inks which are supplied from a reservoir to a nozzleO The nozzle directs ink at a substrate to be marked. By use of a transducer, electrical energy is converted into mechan-ical energy, which is coupled to the ink in the nozzle.
In one example of ink jet operation~ the stream of ink ejected from an orifice at on~ end of the noæzle is broken up in~o a series of regularly spaced, discrete droplets which may be selectively given an electrical ch~rge. In that type of drop marking device, those drops which receive a charge are deflected onto a substrate while those which are not charged are recovered and returned to the ink supply. In another type of droplet marking device, the transducer applies an impulse of energy to the fluid in the nozzle each instance that a droplet is needed.
As is well known by those in the artr the com-plexity of such ink jet nozzles contribute to cost and speed limit~tions~ For example, it is often desirable ~o group together several such nozzles to permit high speed printing on a substrate which may be, for example, magazines, envelopes, labelsr beverage cans on other : . . . - ,. .: : . -: : ........ .. -, - . . :
~ Z ~ 6~2 products ~oving on a conveyor. It is not uncommon for ink jet nozzles in some applications to be spaced as closely as six per inch and thus the need for a low cost, high quality, miniaturized device is apparent.
A significant contributing factor to the com-plexity and cost of producing ink iet nozzles is the presence of both fluid and mechanical resonances in such assemblies which interfere with the nozzle's usefulnesss over the range of frequencies usually employed to form the ink droplets, Such resonances vary with the type of ink employed, temperature, and the geometric dimensions oE the nozzle assembly~ They are also significantly affected by the type of material used to manufacture the nozzle. As a result ink jet printers have required a variety of differ-ent nozzles to permit operation at different frequencies and for different kinds of inks.
Typically, ink jet noz~le assemblies have been manufactured from metal or glass materials and are acoust-ically ~hard" meaning that they support acoustic reson-ances at all three imparting added mechanical energy to the ink stream at specific frequencies. Also a considera-tion in nozzle design is the fluid resonance~ io e., reson-ance in the ink contained within the nozzle body. If a fluid is confined in a chamber having a rigid wall, a standing wave is formed, in thifi case inside the fluid containing chamber. One standard nozzle design techni~ue calls for configuring the nozzle assembly to have a mechan-ical resonance that is outside the operating frequency range of the nozzle, while the fluid chamber and ink are matched to have a fluid xesonance in the operating frequency range. In that type of nozæle assembly, opera-tion is restricted to frequencies substantially coincid~
ental with the fluid ~resonance region because only in that : -..
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region can energy be transmitted to the fluid efficientlyand the droplets be formed reliably. As is well known according to acoustic principles involved in vibrating bodies, these nozzles that have fluid resonance regions also have antiresonance regions. The disturbing energy applied to the nozzle cannot be efficiently transmitted to the fluid to form droplets if the frequency selected for operation is coincidental with an antiresonance frequency region.
The present invention contemplates, at least in one aspect, proceeding contrary to accepted wisdom by designing nozzles without resonance so as to eliminate the antiresonance regions in the operating freguency range and thereby extend the operating frequency range of the nozzle.
To do that, acoustically soft materials were sought so that resonances would be substantially unsupported. This permits only the disturbing energy created by an electro-mechanical transducer, for example, a piezoelectric crystal, operating at a selected frequency to ba transmitted to the fluid.
In the prior art efforts have been made to overcome the difficulties which arise ~rom fluid and mechanical resonances. These are discussed in U.S. Patent Nos. 4,379,303, 4,349r830r and 3,972~474, for example.
Typically, reduction of fluid resonance has been attempted by using either a labyrinth of small passages or ~y making the no~zle body as short as possible. In general, these procedures move portions of the resonances to higher frequencies (usually outside the operating frequency range~. However, harmonics of the undesirable resonances remain and show up in the operating frequency range of the nozzle.
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According to the present invention, a nozzle assembly is disclosed which employs an acoustically soft material which can overcome most or all of the disadvantages of present assemblies and which is more versatile than the latter because it provides additional advantages not heretofore obtainable. Specifically, according to the present invention, (1) the ink is electrically isolated from the transducer permitting the reference potential of the ink to be independently adjusted relative to the driving signal to the transducer, if desired; (2) the nozzle assembly can be formed by molding techniques and mass produced at low cost; (3) the operating frequency range of the nozzle is broadened by eliminating anti-resonance regions; (4) electrolytic action can be controlled by use of an electrode and filter arrangement in the ink system including the nozzle.
Summary of the Invention Various aspects of the invention are as follows:
A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attenuation or the creation of harmonic resonances of a frequency characterizing the disturbing energy.
A nozzle assembly to form ink droplets for an ink jet printer comprising:
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
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(b) a transducer coupled to said nozzle for transmission of a disturbing energy through said tubular member to cause the ink to form droplets, as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of harmonic resonances of a freguency characterizing the disturbing energy.
A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an ori~ice at one end, the 15 other end adapted for connection to a supply o~ ink ~:
containing solvents, said nozzle being formed from a ~:
material which is substantially impervious to said ink and which has a substantially flat response to a driving voltage frequency characterizing the disturbing energy at least over the frequency range of 20KHz to 70KHz, wheraby when the transducer is coupled to said nozzle the disturbing energy thereof is transmitted to : the ink within the nozzle without substantial amplification, attenuation or creation of haxmonic resonances of a freguency characterizing the disturbing energy.
A nozzle assembly to form ink droplets for an ink jet comprising:
: (a~ a tubular member having an orifice at one end, 3C the other end adapted for connection to a supply of ink containing solvents;
~ ~b) a transducer responsive to a driving signal :~ for generating distur~ing energy coupled to said tubular member to cause the ink to form droplets as it leaves the orifice:
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5a (c) said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to the driving signal frequency at least over the frequency range of 20KHz to 70KHz, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of ha:rmonic resonances of one or more frequencies characterizing the disturbing energy.
A nozzle suitable for us,e with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted ~or connection to a supply of ink containing solvents, said nozzle being formed from a material which is~
(a) resistant to said ink, ~b) acoustically soft, and (c) has a substantially flat response to the driving signal frei~uency generating the disturbing energy at least over the ranye of 20KHz to 70KHz, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attenuation or creation of harmonic resonances of the driving signal ~requency.
A nozzle suitable for use with a transducer to form ink droplets comprising:
a hollow chamber connected to a supply of ink containing solvents, adapted to confine a volume of said ink to be ejected through an orifice in a wall thereof, said chamber being formed from an acoustically soft material which is substantially resistant to said ink, whereby when a transducer i5 coupled to said chamber the disturbing energy thereof is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic A
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;3~9~2 5b resonances of one or more frequencies characterizing the disturbing energy.
A method of forming ink droplets from a supply of ink comprising the steps of:
supplying the ink to a chamber, ~he walls of which are formed of acoustically soft material and which have at least one outlet therefrom through which ink may pass;
creating a disturbing enlergy characterized by one or more predetermined frequencies;
transmitting said energy to said ink through said acoustically soft chamber walls to form droplets as the ink passes out of the chamber;
whereby the disturbing energy is transmitted to the ink without substantial amplification, attenuation or the creation of harmonic resonances of said one or more frequencies characterizing said disturbing energy.
By way of added explanation, the invention in one aspect involves fabricating nozzle bodies of a material which has a desired acoustic impedance. Specifically, the material from which the nozzles are fabricated is acoustically soft so that resonances are not supported by the nozzle structure. Instead, the driving energy is transmitted directly to the ink stream without amplification or attenuation due to variation in fr~quency response. The materials suitable for use in the present invention are generally described as acoustically soft plastics which can withstand certain solvents typically contained in the inks used for ink jet applications. The nozzles formed from such materials usually have an orifice in a wall of a fluid chamber through which ink is ejected to form droplets.
In one instance, the orifice is formed in a jewel which is embedded in the nozzle body and the transducer is adhesively bonded thereto. The nozzle and transducer are then insorporated into a nozzle assembly.
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It is accordingly an object of an aspect of the present invention to provide an improved ink jet nozzle assembly which minimizes both fluid and mechanical resonances.
It is an object of an aspect of the invention to provide such an assembly which is low in cost and easily produced without the usual machining steps required of present assemblies.
It is an object of an aspect of the present invention to provide a nozzle assembly in which the disturbing energy is transmitted to the ink within the nozzle without substantial amplification, attenuation or the creation of harmonic resonances of any frequency characterizing the disturbing energy.
It is an object of an aspect of the invention to provide nozzle assemblies having an essentially flat response to frequencies characterizing the driving voltage over an entire range of frequencies at which ink droplets are formed by a transducer.
An object of an aspect of the invent.ion is to provide a nozzle assembly which permits the ink to be electrically isolated from the transducer whereby the ink can be subjected to an electrical potential independent of the signal applied to drive the transducer for the purpose disclosed, for example, in U.S. Patent No. 4,319,251, and for the further purpose of permitting the control of electrolytic action within the ink system of the ink jet device.
: Other:objects and advantages of the invention will be apparent from the remaining portion of the specification.
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Brief Descriptlon of the Drawin~s Figure 1 is an illustration from U,S. Patent 3,702,118 and represents the construction of a typical prior art nozzle assembly.
Figure 2 is a cross sectional view o~ a nozzle assembly according to a preferred embodiment o~ the pre-sent invention.
Figure 3 i~ an enlarged sectional view of the nozzle and tail piece according to the preferred embodi-ment.
Figure 4 is a curve illustrating typical response characteristics of prior art nozæle assemblies.
Figures 5 through 11 are similar curves illus- -trating the response characteristics for a number o~
different materials having various suitability for use in the present invention.
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Detailed Description .
As indicated in the background portion of this specification, the present invention relates to a nozzle assembly for i~k jet printing which has significant advantages over present assemblies which are typically machined ~rom metal, glass or other acoustically ~Ihard~
materials. Such~prior nozzIes, a typical example being illustrated in Figure 1, are somewhat complex to design and manufacture particularly in view of their relatively small size. As a result they are expensive to produce and quality control is a continuin~ problem. By way of example;
one such nozzle assembly made from metal requires a fabrica-tion proce~s that may take as much as 45 minutes or more . . . . - .
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of machining operations by skilled technicians. The nozzle 10 must be carefully machined so as to permit the concentric attachment of one or more transducers 12 in A manner to provide good acoustical coup]ing so that the ink chamber 14 will properly receive acoustic energy.
As known by those skilled in the art, one type of nozzle assembly used in an ink jet device which controls drop flight by electrical forces employs electrically con-ductive ink supplied from a reservoir via a conduit 16 to the nozzle assembly. The nozzle assembly consists of the nozzle 10, a tail piece 18, which interconnects the nozzle with the conduit 16, and the transducer 12. The assembly is usually provided in a block or head 20. Disposed at the front of the nozzle is an orifice 22, for example, a jewel having an opening through which the ink is forced.
Vibrational energy is provided by the transducer and that causes the ink stream to break up into regularly-spaced, discrete droplets which can then be electrically charged and deflected by electrostatic deflection plates in a manner well known in this art.
Because the nozzle assembly shown in Figure 1 is fabricated from metal or glass it is, as indicated, both expensive to make and acoustically hard. As a result it is necessary to test each type of nozzle to determine in what frequency range it can be utilized. Specifically, it must be tested to determine what mechanical and fluid resonances are set up in the nozzle which might interfere -with the intended operationO
This is usually accomplished by testing the nozzle under actual operating conditions. A curve is shown in Figure 4 for a typical metal nozzle assembly.
The curve is a plot of drive voltage as a function of operating frequencyO The plot indicates the voltage : , ' , : : : , .
3~,9~2 needed to produce a constant stream of ink droplets at a specified frequency. As can be seen from Figure 4, there is a range between approximately 20KHz and 40KHz where the drive voltage for the nozzle is relatively low. This indicates that in this frequency range the nozzle is e~fi-cient and the driving voltage remains substantially constant over a limited operating frequency range. On the other hand, in the frequency range of approximately 40KHz to 60KHz and also at frequencie~; below ~OKHz the required drive voltage increases significantly due to an increase in the acoustic impedance of the ink. Those are the anti-resonance regions for the particular nozzle and ink match.
Such variation in drive voltage is undesirable and requires the design of many nozzles in order to have a nozæle which is suitable for all frequency ranges of interest. Specifically~ to operate at any given frequency using inks that have different physical properties requires nozzles having diferent chamber configurations, for example, different lengths. The velocity of sound for each different ink is the physical property having the most significant effect on determining the nozzle configu-ration. Temperature at which the nozzle operates, of course, affects the velocity of sound for the ink used. ~-The resonances in nozzle assemblies are of two types: mechanical resonance and fluid resonance. Exist-ing assemblies, usually formed from stainless steel tubing, have a mechanical resonance which, if in the operating range, ca~ affect operation significantly. One common approach is to design the nozzle so that the mechanical resonance is well above the operating frequency range.
That leaves fluid resonance only as a consideration in nozzle design. The ink chamber structure and the ink composition are matched to provide a fluid resonance region coincidental with the selected operating frequency.
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~36 _9_ These fluid and mechanical resonances are responsible for the limited operating frequencies of existing, acousti-cally hard, nozzle assemblies For a nozzle to be useful over a range of fre-quencies it should operate at a substantially constant drive voltage level at all frequencies in the range required regardless of ink characteristiGs. Typical useful frequencies range from lOKHz to lOOKHz ~and some-times higher). Typical inks suitable for use in ink jet printers have the following range of characteristics:
Surface tension 22 to 72 dyne/cm Viscosity 1.5 to 10 centipoise Density .85 to 1.1 gm/cm3 Velocity of sound 1,000 to 1,650 m/s The last characteristic, the velocity of sound in the ink, is of significant concern in the design of nozzles. The velocity of ssund in such a fluid varies with the temperature of the fluid andr ~herefore, the fluid resonances (related to the velocity of sound) change frequency as a function of temperature changes in the nozzle. Thus, the resonances may be different during initial operation, when the nozzle is cool, than after the nozzle has been in use for a period of time. Also, the ~ -velocity of sound is affected by changes in the composi-tion of the ink due mainly to evaporation of solvents.
According to the present invention these pro-blems are overcome by the use of a nozzle assembly which is acoustically softO Although there are many materials which might meet this criteria, it is necessary to consider the severe operating environment~ The nozzle may need to be extremely small to work in some applications, subjected to continual temperature changes and vibration and, most importantly, is in contact with different inks containing ,~
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69~2 water or various alcohols, ketones and other solvents.
It is necessary, therefore, to select materials which can stand up to this environment in addition ~to being acoustically soft.
Through materials testing a number of materials were identified as being potentially suited for the application. These include acetal homopolymers (such as Delrin),TM acetal copolymers (such as CelconT GC 25), polypropylene, Teflon,TM polyphenylene sulfide (Ryton), polyphenylene oxicle (Noryl).
These materials were selected for testing because they are moldable, have long term stability in contact with the solvents contained in typical inks and they were expected to be acoustically soft. It was believed that at least some of these materials would eliminate or attenuate resonances in the body of the nozzle (mechanical resonance) and in the ink (fluid resonance).
In order to determine which, if any, of these materials were suitable, nozzle bodies were designed, molded and tested.
Figure 3 illustratas the nozzle assembly molded from the various materials for purposes of testing. A
nozzle 30 is an elongated, hollow cylindrical member.
AT one end thereof is a female coupling 32 adapted to receive a tail piece 34 having a male coupling member 36. The tail piece 34, in turn, can be coupled to a conduit member for providing an ink supply to the nozzle 30.
The distal end of the nozzle 30 has a recessed - 30 portion 37 adapted to receive and retain an orifice - jewel 38 therein. Retention is accomplished by dimensioning the recess to provide an interference fit which firmly seats the jewel and prevents leakage. It was found that an interference fit of approximately .0015 inch was adequate to ' .
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retain the jewel in place with a recess depth of approxi-mately two times the thickness of the jewel. With such dimensions the no2zle material closes around the jewel to retain it securely in place~
Prior to testing thle nozzle 30 of Figure 3, a piezoelectric transducer was coupled by adhesive bonding.
The bonding agent was selected to insure a good coupling between the piezoelectric device and the nozzle for trans-mission of energy to the fluid~ Epoxies are preferred and, in particular, a one part binder which is not too viscous is best. This permit~ the binder to ~low well in the space between the nozzle and the piezo electric device to avoid gaps which can cause undesirable variations in the applied energyt require higher drive voltages, contri-bute to mechanical resonance and lead to premature failure of the device. Preferably the bonding material is relati-vely stiff to maintain drive efficiency. One suitable adhesive bonding agent is an anaerobic adhesive sold under the trad~ name Permalok by Permabond International Corporationr Englewood, New Jersey.
Completed test nozzles molded from the materials believed to be suitable were then subjected to testing.
The results of these tests are illustrated in Figures 5 through 8. In each case the drive voltage, RMS or peak-to-peak as noted on the plots, necessary to maintain const~
ant drop formation was plotted over a frequency range of lOKHz to lOOKHz.
Referring to Figure 5, the test results for the acetal homopolymer (Delrin) are shown. As can be seen, the drive voltage in the frequency range 20KHz to 70KHz is reasonably flat and less than approximately 15 volts.
However, in the ranges of lO to ~OKHz and 70 to 90KHz sig- -nificant antiresonances are encountered causing undesirable ~. : .. . ................. , ~ - .
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increases in 'he drive voltages. Nevertheless~ this data compares quite favorably with the data for a typical metallic nozzle shown in Figure 4~
E~igure 6 shows the test data for polypropylene.
It has a variety of antiresonances throughout the fre-quency range of interest and is therefore not suitable for present purposes.
Figure 7 illustrates the test data for the acetal coplymer (Celcon) whic:h has undesirable antireson-ances at 10 to 20 KHz and above 9OKHz.
Figure 8 illustrates the data for polyphenylene sulfide ~Ryton) ~two tests are shown, one in which the nozzle is potted in a block, the other unpotted). As can be seen, the material is much better than the prior art metal nozzles and significantly better than any of the other materials tested. Its response characteristic is essentially flat from lOKHz to lOOKHz. This indicates, particularly in view of the low drive voltage required to maintain constant droplet production, that the material very efficiently couples the piezoelectric device and the fluid while at the same time being acoustically soft to not support fluid resonance. Because it is a molded part and is directly coupled to the driving device by an adhesive, there is little mechanical resonance created.
This material was designated as the preferred material for the production of a new, highly efficient nozzle assembly for ink jat printing. Such a nozzle can be driven at a substantially uniform voltage over the desired operating range of frequencies.
To verify the remarkable properties of this compound, additional tests were run using inks having di~ferent properties and, in particular, different velocity of souAd values. The curves for this testing are :: :
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~r~6~31~ i illustrated in Figures 9 through 11. In each case the response curve for the Ryton was essentially flat over the frequency range of interest.
Although not as good as Ryton, Celcon and Delrin were also deemed to be accept:able materials for use under conditions where the antiresonances are outside the intended operating ~re~uency. Materials found not to be suitable include polyurethane, polyvinyl chloride, styrene, poly-carbonate, acrylic, ABS, and polyphenylene oxide. All of the suitable materials are moldable and chemical resistant thereby providing the desired properties. While these materials are not nonconductive electrically, that charac~
teristic is not a requirement for many applications fo the present invention.
Re~erring to Figure 2 r there is shown a preferred embodiment of the nozzle assembly employing the preferred materials of the present invention. A nozzle 50 formed of Ryton, Celcon or Delrin is coupled to a tail piece 52 pre-ferably ~ormed of the same materials. In turn, the tail piece is coupled to a fitting 54 for connection to an ink supply conduit. A jewel 56 is provided in the forward portion of the nozzle and captured therein by virtue of the dimensions of~the nozzle recess as previously des-cribed. Concentrically mounted over the nozzle 50 is a piezoelectric transducer 58 adhesively bonded in place.
The devices are electrically driven by means o~ a cable 61, the conductors contained therein being soldered to the outside o~ the transducers as indicated. The nozzle assembly is preferably potted and disposed within a nozzle head assembly or block 60. The completed assembly is small enough to permit spacing on the order of six ~ieparate print heads per inch. The nozzles made according to the teach-ings of the present invention have good, long term resist-,, : -.
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ance to ink solvents, are relatively temperature insensi-tive, and can be driven at substantially uniform drive voltages over a wide range of operating frequencies~ At the same time, because they zlre acoustically soft, the fluid does not "experience" a rigid confining wall and does not form standing waves which generate fluid reson-ances within the noz~le body. By eliminating ~luid reson-ances, the antiresonances representing sharp increases in the acoustic impedance of the ink are also eliminated.
Thus, droplet formation is accomplished across a broad frequency ranga by a substantially uniform driving voltage.
If desired, because of the electrical isolation of the ink within the nozzle body, an independently con-trolled potential may be applied to the ink permitting, for example, increased deflection by the techniques taught in U.S. Patent 4,319,251. In addition, phasing of drop formation and drop charging is facilitated by permitting chargin~ currents in the ink to be reliably detected.
While the invention has been described with refer-ence to a preferred embodiment of a nozzle assembly having a single ori~ice through which ink is ejected, it is within the teachings of the present invention to provide a plura-lity of orifi~es in the nozzle assembly configured in an array. Ei~her a separate chamber for each orifice or a common chamber for a plurality of orifices may be used dependent upon which droplet formation technique is desir-able in the particular ink jet device in which the nozzle is employed. There is ink confined to the chamber in either instance~ and forming the wall or walls of the nozzle ink chamber of acoustically soft material in accordance with ~he teachings of the presen~ invention assures that the disturbing energy coupled to the chamber is transmitted to ' ::
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the ink within the chamber without substantial amplifica-tion, attenuation or the creation of harmonic resonances of any frequency characteri2ing the disturbing energy.
The present invention is useful also in ink jet printers that employ a pulsed nozzle to form ~roplets.
Zolton V.S. Patent 3,683,212 discloses one example of that type of nozzleu The impulses of electrical energy used to drive such a no~zle commonly have a duration of 10 micro-seconds to 100 microseconds. A Fourier analysis of those energy pulses manifests that reliable droplet formation necessitates that the nozzle respond consistently to fre-quencies in the range of lOKHz to lOOKHz. It is desirable that the nozzle chamber not support fluid resonances in that frequency range. A nozzle which has a fluid chamber with walls made of acoustically soft material as taught by the present invention will not support resonances in that region, and thus will have a substantially flat response to energy impulses ch~racterized by frequencies that are within the operating frequency range. As a result, droplet formation is more nearly prvportional to the characteristics of the energy pulse applied to the 1uid to improve control and enhance the marking results. In addition, spurious oscillations in the impulse nozzle ink chamber that occur after a pulse has directed formation o~ a droplet are ab-sorbed if the walls are made of acoustically soft material.
Those spurious oscillations can distort the energy applied to the fluid when a succeeding command pulse is transmitted to the fluid. Clearly, an impulse or pulse driven nozzle can be operated more advantageously by following the teach-ings of the present invention.
.
.. : ,. . : : , . . , - . . - ~. . -: ' :
.. ,, ~ ,- . : , :
~ ~f~69'1~
-16~
While we have shown and described embodiments of the invention~ it will be understood that this description and illustrations are offered merely by way o~ example, and that the invention is to be limited in scope only as to the appended claims.
. . . ~ , - ~ . - . ~ - .
.
Claims (16)
1. A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or the creation of harmonic resonances of a frequency characterizing the disturbing energy.
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or the creation of harmonic resonances of a frequency characterizing the disturbing energy.
2. The nozzle according to Claim 1 wherein said nozzle is molded as a single piece from a material selected from the group comprising: Celcon, Delrin, Ryton.
3. The nozzle according to Claim 1 wherein the nozzle has a substantially flat response to the driving voltage frequency generating the disturbing energy over the range of approximately 10KHz to 100KHz.
4. A nozzle assembly to form ink droplets for an ink jet printer comprising:
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
(b) a transducer coupled to said nozzle for transmission of a disturbing energy through said tubular member to cause the ink to form droplets, as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplifica-tion, attentuation or creation of harmonic resonances of a frequency characterizing the disturbing energy.
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
(b) a transducer coupled to said nozzle for transmission of a disturbing energy through said tubular member to cause the ink to form droplets, as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which is acoustically soft, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplifica-tion, attentuation or creation of harmonic resonances of a frequency characterizing the disturbing energy.
5. The nozzle according to Claim 4 wherein said transducer is mounted on said tubular member and coupled thereto by adhesive bonding with a bonding agent which is relatively stiff to insure efficient coupling of the dis-turbing energy to the tubular member.
6. The nozzle according to Claim 5 wherein said bonding agent is an anaerobic adhesive.
7. A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to a driving volt-age frequency characterizing the disturbing energy at least over the frequency range of 20KHz to 70KHz, whereby when the transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or creation of harmonic resonances of a fre-quency characterizing the disturbing energy.
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to a driving volt-age frequency characterizing the disturbing energy at least over the frequency range of 20KHz to 70KHz, whereby when the transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or creation of harmonic resonances of a fre-quency characterizing the disturbing energy.
8. The nozzle according to Claim 7 wherein said nozzle is molded as a single piece from a material selected from the group comprising: Celcon, Delrin, Ryton polymers.
9. The nozzle according to Claim 7 wherein said nozzle is molded as a single piece from Ryton and the res-ponse to the transducer disturbing frequency is substan-tially flat over the frequency range of 10KHz to 100KHz.
10. A nozzle assembly to form ink droplets for an ink jet comprising:
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
(b) a transducer responsive to a driving signal for generating disturbing energy coupled to said tubular member to cause the ink to form droplets as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to the driving signal frequency at least over the frequency range of 20KHz to 70KHz, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplifica-tion, attentuation or creation of harmonic resonances of one or more frecluencies characterizing the disturbing energy.
(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;
(b) a transducer responsive to a driving signal for generating disturbing energy coupled to said tubular member to cause the ink to form droplets as it leaves the orifice;
(c) said nozzle being formed from a material which is substantially impervious to said ink and which has a substantially flat response to the driving signal frequency at least over the frequency range of 20KHz to 70KHz, whereby the disturbing energy is transmitted to the ink within the nozzle without substantial amplifica-tion, attentuation or creation of harmonic resonances of one or more frecluencies characterizing the disturbing energy.
11. The nozzle according to Claim 10 wherein said transclucer is coupled to said tubular member by adhesive bonding with a bonding agent which is relatively stiff to insure efficient coupling of the disturbing energy to the tubular member.
12. The nozzle according to Claim 10 wherein said bonding agent is an anaerobic adhesive.
13. A nozzle suitable for use with a transducer to form ink droplets comprising:
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is:
(a) resistant to said ink, (b) acoustically soft, and (c) has a substantially flat response to the driving signal frequency generating the disturbing energy at least over the range of 20KHz to 70KHz, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or creation of harmonic resonances of the driving signal frequency.
a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is:
(a) resistant to said ink, (b) acoustically soft, and (c) has a substantially flat response to the driving signal frequency generating the disturbing energy at least over the range of 20KHz to 70KHz, whereby when a transducer is coupled to said nozzle the disturbing energy thereof is transmitted to the ink within the nozzle without substantial amplification, attentuation or creation of harmonic resonances of the driving signal frequency.
14. The nozzle according to Claim 13 wherein said nozzle is molded as a single piece from Ryton and the response to the transducer driving signal is substantially flat over the frequency range of 10KHz to 100KHz.
15. A nozzle suitable for use with a transducer to form ink droplets comprising:
a hollow chamber connected to a supply of ink containing solvents, adapted to confine a volume of said ink to be ejected through an orifice in a wall thereof, said chamber being formed from an acoustically soft material which is substantially resistant to said ink, whereby when a transducer is coupled to said chamber the disturbing energy thereof is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic resonances of one or more frequencies characterizing the disturbing energy.
a hollow chamber connected to a supply of ink containing solvents, adapted to confine a volume of said ink to be ejected through an orifice in a wall thereof, said chamber being formed from an acoustically soft material which is substantially resistant to said ink, whereby when a transducer is coupled to said chamber the disturbing energy thereof is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic resonances of one or more frequencies characterizing the disturbing energy.
16. A method of forming ink droplets from a supply of ink comprising the steps of:
supplying the ink to a chamber, the walls of which are formed of acoustically soft material and which have at least one outlet therefrom through which ink may pass;
creating a disturbing energy characterized by one or more predetermined frequencies;
transmitting said energy to said ink through said acoustically soft chamber walls to form droplets as the ink passes out of the chamber;
whereby the disturbing energy is transmitted to the ink without substantial amplification, attenuation or the creation of harmonic resonances of said one or more frequencies characterizing said disturbing energy.
supplying the ink to a chamber, the walls of which are formed of acoustically soft material and which have at least one outlet therefrom through which ink may pass;
creating a disturbing energy characterized by one or more predetermined frequencies;
transmitting said energy to said ink through said acoustically soft chamber walls to form droplets as the ink passes out of the chamber;
whereby the disturbing energy is transmitted to the ink without substantial amplification, attenuation or the creation of harmonic resonances of said one or more frequencies characterizing said disturbing energy.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/883,707 US4727379A (en) | 1986-07-09 | 1986-07-09 | Accoustically soft ink jet nozzle assembly |
| US883,707 | 1986-07-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1286912C true CA1286912C (en) | 1991-07-30 |
Family
ID=25383169
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000539291A Expired - Fee Related CA1286912C (en) | 1986-07-09 | 1987-06-10 | Acoustically soft ink jet nozzle assembly |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4727379A (en) |
| EP (1) | EP0252593B1 (en) |
| JP (1) | JPH0655504B2 (en) |
| AT (1) | ATE73051T1 (en) |
| AU (1) | AU587336B2 (en) |
| CA (1) | CA1286912C (en) |
| DE (1) | DE3776992D1 (en) |
| MX (1) | MX171176B (en) |
| ZA (1) | ZA873541B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR0165677B1 (en) * | 1989-01-20 | 1999-05-01 | 요하네스 야코부스 스모렌버그 | Nozzle for an ink jet printing apparatus |
| US5196860A (en) * | 1989-03-31 | 1993-03-23 | Videojet Systems International, Inc. | Ink jet droplet frequency drive control system |
| WO1990014956A1 (en) * | 1989-05-29 | 1990-12-13 | Leningradsky Institut Tochnoi Mekhaniki I Optiki | Electric drop-jet generator and method for adjusting it |
| US5063393A (en) * | 1991-02-26 | 1991-11-05 | Videojet Systems International, Inc. | Ink jet nozzle with dual fluid resonances |
| US5901425A (en) | 1996-08-27 | 1999-05-11 | Topaz Technologies Inc. | Inkjet print head apparatus |
| US6070973A (en) | 1997-05-15 | 2000-06-06 | Massachusetts Institute Of Technology | Non-resonant and decoupled droplet generator |
| IL127484A (en) * | 1998-12-09 | 2001-06-14 | Aprion Digital Ltd | Printing device comprising a laser and method for same |
| EP1080915B1 (en) | 1999-09-03 | 2011-07-20 | Canon Kabushiki Kaisha | Liquid ejecting head unit |
| US6675914B2 (en) * | 2002-02-19 | 2004-01-13 | Halliburton Energy Services, Inc. | Pressure reading tool |
| US7077334B2 (en) * | 2003-04-10 | 2006-07-18 | Massachusetts Institute Of Technology | Positive pressure drop-on-demand printing |
| EP1637329A1 (en) | 2004-09-15 | 2006-03-22 | Domino Printing Sciences Plc | Droplet generator |
| US20080191066A1 (en) * | 2007-02-13 | 2008-08-14 | Ted Jernigan | Water cutting assembly and nozzle nut |
| GB0719374D0 (en) * | 2007-10-04 | 2007-11-14 | Eastman Kodak Co | Continuous inkjet printing |
| FR3088242A1 (en) * | 2018-11-14 | 2020-05-15 | Dover Europe Sarl | METHOD AND DEVICE FOR FORMING DROPS USING A CAVITY WITH DEGRADED QUALITY FACTOR |
Family Cites Families (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3334350A (en) * | 1964-08-19 | 1967-08-01 | Dick Co Ab | Magnetostrictive ink jet |
| US3281859A (en) * | 1964-08-20 | 1966-10-25 | Dick Co Ab | Apparatus for forming drops |
| US3281860A (en) * | 1964-11-09 | 1966-10-25 | Dick Co Ab | Ink jet nozzle |
| US3512172A (en) * | 1968-08-22 | 1970-05-12 | Dick Co Ab | Ink drop writer nozzle |
| US3946398A (en) * | 1970-06-29 | 1976-03-23 | Silonics, Inc. | Method and apparatus for recording with writing fluids and drop projection means therefor |
| US3683396A (en) * | 1970-08-05 | 1972-08-08 | Dick Co Ab | Method and apparatus for control of ink drop formation |
| US3683212A (en) * | 1970-09-09 | 1972-08-08 | Clevite Corp | Pulsed droplet ejecting system |
| US3708118A (en) * | 1971-04-19 | 1973-01-02 | Dick Co Ab | Filtering apparatus for a drop writing system |
| US3736593A (en) * | 1971-10-12 | 1973-05-29 | Dick Co Ab | Ink drop writing system with nozzle drive frequency control |
| US3832579A (en) * | 1973-02-07 | 1974-08-27 | Gould Inc | Pulsed droplet ejecting system |
| US3850717A (en) * | 1973-12-03 | 1974-11-26 | Dick Co Ab | Prestressing and damping of piezo ceramic type nozzles |
| US3972474A (en) * | 1974-11-01 | 1976-08-03 | A. B. Dick Company | Miniature ink jet nozzle |
| JPS5928471B2 (en) * | 1976-12-17 | 1984-07-13 | シャープ株式会社 | Liquid jet supply mechanism |
| US4153901A (en) * | 1976-12-20 | 1979-05-08 | Recognition Equipment Incorporated | Variable frequency multi-orifice IJP |
| JPS53123458A (en) * | 1977-04-04 | 1978-10-27 | Fujitsu Ltd | Plastic article |
| US4201995A (en) * | 1978-12-04 | 1980-05-06 | Xerox Corporation | Coincidence gate ink jet with increased operating pressure window |
| US4248823A (en) * | 1978-12-15 | 1981-02-03 | Ncr Corporation | Method of making ink jet print head |
| JPS594310B2 (en) * | 1979-06-30 | 1984-01-28 | 株式会社リコー | inkjet recording device |
| US4257052A (en) * | 1979-10-29 | 1981-03-17 | The Mead Corporation | Molded orifice plate assembly for an ink jet recorder and method of manufacture |
| JPS5727761A (en) * | 1980-07-29 | 1982-02-15 | Hitachi Ltd | Nozzle for ink jet recording device |
| US4319251A (en) * | 1980-08-15 | 1982-03-09 | A. B. Dick Company | Ink jet printing employing reverse charge coupling |
| US4349830A (en) * | 1980-11-12 | 1982-09-14 | Burroughs Corporation | Conical nozzle for an electrostatic ink jet printer |
| US4395719A (en) * | 1981-01-05 | 1983-07-26 | Exxon Research And Engineering Co. | Ink jet apparatus with a flexible piezoelectric member and method of operating same |
| US4376944A (en) * | 1981-04-13 | 1983-03-15 | Ncr Corporation | Ink jet print head with tilting nozzle |
| JPS5954568A (en) * | 1982-09-21 | 1984-03-29 | Seiko Epson Corp | Ink jet head |
-
1986
- 1986-07-09 US US06/883,707 patent/US4727379A/en not_active Ceased
-
1987
- 1987-05-18 ZA ZA873541A patent/ZA873541B/en unknown
- 1987-05-20 EP EP87304465A patent/EP0252593B1/en not_active Expired - Lifetime
- 1987-05-20 AT AT87304465T patent/ATE73051T1/en not_active IP Right Cessation
- 1987-05-20 DE DE8787304465T patent/DE3776992D1/en not_active Expired - Fee Related
- 1987-05-29 MX MX006716A patent/MX171176B/en unknown
- 1987-06-10 CA CA000539291A patent/CA1286912C/en not_active Expired - Fee Related
- 1987-07-06 AU AU75254/87A patent/AU587336B2/en not_active Expired
- 1987-07-08 JP JP62168907A patent/JPH0655504B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE3776992D1 (en) | 1992-04-09 |
| ATE73051T1 (en) | 1992-03-15 |
| EP0252593A2 (en) | 1988-01-13 |
| JPS6325050A (en) | 1988-02-02 |
| JPH0655504B2 (en) | 1994-07-27 |
| AU587336B2 (en) | 1989-08-10 |
| ZA873541B (en) | 1987-11-11 |
| AU7525487A (en) | 1988-01-14 |
| MX171176B (en) | 1993-10-06 |
| EP0252593A3 (en) | 1989-06-07 |
| EP0252593B1 (en) | 1992-03-04 |
| US4727379A (en) | 1988-02-23 |
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