CA2175086A1 - Drop marking control system responsive to acoustical properties of ink - Google Patents
Drop marking control system responsive to acoustical properties of inkInfo
- Publication number
- CA2175086A1 CA2175086A1 CA002175086A CA2175086A CA2175086A1 CA 2175086 A1 CA2175086 A1 CA 2175086A1 CA 002175086 A CA002175086 A CA 002175086A CA 2175086 A CA2175086 A CA 2175086A CA 2175086 A1 CA2175086 A1 CA 2175086A1
- Authority
- CA
- Canada
- Prior art keywords
- ink
- reservoir
- acoustic
- return
- fresh
- 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.)
- Abandoned
Links
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
- 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
- B41J2/17—Ink jet characterised by ink handling
- B41J2/195—Ink jet characterised by ink handling for monitoring ink quality
Abstract
A control system (40) is disclosed for an ink jet printer. The control system employs acoustic transducers (12, 13, 15) to determine the velocity of sound in the ink and in a reference chamber (10) containing only fresh ink. By comparing the two measurements it can be determined when to add additional solvent to the system to maintain solids concentration substantially constant.
Description
W0 95113192 2 ~ 7 ~ ~ 8 ~ r~ IS
DROP MARKING CONTROL SYSTEM
RESPONSIVE TO ACOUSTICAL PROPERTES OF INK
This invention relates to the field of drop marking systems of the type in which a liquid ink is forced under pressure through a nozzle which converts the liquid into droplets which can then be controlled by various means while projected toward a substrate for marking purposes.
Examples of such systems include the familiar ink jet marking systems used for high speed label printing, product i~lrn~ifirl~rir,n and the like, although there are other drop marking systems known in the art. One particular type of system which ~Jv ~ 'y employs the present invention is the continuous stream, ink jet printer. Such a system typically includes an ink reservoir and a remotely located nozzle connected to the reservoir by a conduit. Ink is forced under pressure from the reservoir to the nozzle which emits a continuous stream of ink drops.
The ink, which is electrically conductive, is provided with a charge as the drops leave the no~zle.
The drops then pass through a deflection field which causes selected drops to be deflected so that some of the dro~s are deposited onto a substrate while the remaining drops are retumed to the reservoir by a suitable ink return means.
In order to produce high quality marking, it is important that the ink is maintained at its formulated . of V.~ , solids. Ink drop formation, drop electrical charge, drop velocity, spot placement accuracty, spot placement precision, spot adhesion, spot drying time, and spot optical properties are printing parameters that have some ~' L I on ink properties. These ink properties include rnmrSi~ n electrical ~ ' vily, density, acoustic velocity, surface tension, and viscosity. These ink properties have a ~1 ~. 1. --- c on solids So, if ink solids crn~rn~ n deviates from ~I ~ ; ri ~l i. - the print quality may wo 95/13192 2175~8~
also deviate from acceptable standards.
Print quality is highly dependent on drop velocity. In turn, drop velocity is dependent on ink viscosity. Ink viscosity is highly dependent on ink solids ~~ Thus, drop 5 velocity and print quality are strongly dependent on rnk solids ... ~ .. " . ,.l ;....
The condition of constant ink drop velocity through the deflection field is necessary to provide consistent print quality and requires that the flow rate of liquid through the nozzle be sl~hct~ti~lly constant. Prior ink marking systems have attempted to a~.. ,~n.l lr this 10 ~ lli by various means.
One such system employs a specific gravity detector which signals when it is necessary to add solvent to the ink supply. This system is unsuitable for use in systems where the printer must: ' many different types of inks, each with its own specific gravity parameters.
Another ~.UIIIIII~ ;al system which tries to deal with the problem of changing drop velocity was ' I by the IBM ('nTn~tinn In this device the ink pressure is responsive to signals from a deflection detector. The deflection detector is located in the electric field through which the drops pass. The detector signals the pump to increase or decrease pressure, 20 as necessary, to maintain drop velocity at an appropriate value. The system provides feedback control of drop velocity. The technique, however, is not entirely ~ r~ y because of the CCIIII~ .A;IY and cost of the cu".~,, and the need for a fragile deflection detector at the remote print head location.
W0 9!~113192 2 ~ 7 5 ~ 8 6 r~ 13 Another inYention, disclosed in U.S. Patent No. 4,555,712, monitors the inlc flow rate, monitors the velocity of the drops of ink in the charge field and, by use of an electronic controller, adjusts the ink parameters to maintain a desired flow rate which insures a ~Iy constant drop velocity.
It is an object of the present invention to incorporate direct feedback control into an ink solids . control system wbich is simpler, reliable and low in cost.
Another object of the invention is to provide a velocity control system for an ink jet 10 printer which maintains substantially constant velocity of ink entering a deflection field thereby insuring accurate location of spots on the substrate to be marked.
In a frist aspect the present invention provides ink control apparatus for a drop marking system which includes a reservoir, a printhead receiving ink from the reservoir, means for 15 returning unused ink to the reservoir, the apparatus ~. ,., .1,, ;~;, .~"
a) a solvent supply including a valuve for controlling the addition of solvent to the ink in the reservoir;
b~ a reference chamber containing fresh ink; and ~ d by further CC" ' 'I " ;~
c) an acoustic transrnitter associated with said reference chamber oriented to transmit acoustic pulses through the ink and to detect said acoustic pulses after travelling WO 9~/13192 r~
217~08~
through the ink, the time delay between i of a pulse and its reception being a function of the solids: r~n of the ink in the chamber;
d) a second acoustic transmitter associated with said resèrvoir oriented to send S acoustic pulses through the ink and a second acoustic receiver associated with said reservoir arranged to detect said acoustic pulses after travelling through the ink the time delay between of a pulse and its reception being a function of the solids . ~ of the ink in the reservoir;
e) means for comparing the time delays of echo retums from the reference chamber and the reservoir and for controlling operation of the solvent supply valve as a function of the said difference;
whereby solvent is added to the ink received in the reservoir as necessary to keep 15 the solids r~ .. therein substantially the same as the ink in the reference chamber.
Thus the invention provides an electronic control system employing acoustic transducers to measure the velocity of sound in ink to pemlit accurate control of the addition of solvent to the ink.
The invention also provides a flow control means for an ink system which is located entirely separate from the print head nozzle and yet maintains a substantially constant flow rate through the nozzle.
~ WO 95113192 2 ~ 7 5 ~ 8 ~ r ~
In a second aspect the present invention provides ink control apparatus for a drop marking system including a reservoir to supply ink to a print head that has at least one orifice for projecting a stream of droplets towards the surface to be marked, the individual droplets being cl.,~ ic~lly controlled and directed towards the surface to mark it or to a catcher to be 5 captured and returned to the ink reservoir, and having a source of fresh ink and a source of solvent which is selectively connected to the ink reservoir to replenish it and ~ by ink c~ ~ ~
a) frrst means measuring acoustic properties of the fresh ink to obtain a reference signal value relating to ink solids concentration.
b) second measuring mcans measuring the acoustic properties of the captured ink to obtain a signal value II,~ of the ink solids ~ in the captured ink.
c) means for comparing said reference signal value and said l.,~lC:~Clll~lliVC signal value to generate an error signal proportion to the solids . variation between the captured ink and the fresh ink, and d) means for controlling the addition of the solvent in response to said error signal whereby the solids ~ of the ink and the ink reservoirs maintained y constant.
Other objects and advantage of the inYention Will be apparent from the remaming portion
DROP MARKING CONTROL SYSTEM
RESPONSIVE TO ACOUSTICAL PROPERTES OF INK
This invention relates to the field of drop marking systems of the type in which a liquid ink is forced under pressure through a nozzle which converts the liquid into droplets which can then be controlled by various means while projected toward a substrate for marking purposes.
Examples of such systems include the familiar ink jet marking systems used for high speed label printing, product i~lrn~ifirl~rir,n and the like, although there are other drop marking systems known in the art. One particular type of system which ~Jv ~ 'y employs the present invention is the continuous stream, ink jet printer. Such a system typically includes an ink reservoir and a remotely located nozzle connected to the reservoir by a conduit. Ink is forced under pressure from the reservoir to the nozzle which emits a continuous stream of ink drops.
The ink, which is electrically conductive, is provided with a charge as the drops leave the no~zle.
The drops then pass through a deflection field which causes selected drops to be deflected so that some of the dro~s are deposited onto a substrate while the remaining drops are retumed to the reservoir by a suitable ink return means.
In order to produce high quality marking, it is important that the ink is maintained at its formulated . of V.~ , solids. Ink drop formation, drop electrical charge, drop velocity, spot placement accuracty, spot placement precision, spot adhesion, spot drying time, and spot optical properties are printing parameters that have some ~' L I on ink properties. These ink properties include rnmrSi~ n electrical ~ ' vily, density, acoustic velocity, surface tension, and viscosity. These ink properties have a ~1 ~. 1. --- c on solids So, if ink solids crn~rn~ n deviates from ~I ~ ; ri ~l i. - the print quality may wo 95/13192 2175~8~
also deviate from acceptable standards.
Print quality is highly dependent on drop velocity. In turn, drop velocity is dependent on ink viscosity. Ink viscosity is highly dependent on ink solids ~~ Thus, drop 5 velocity and print quality are strongly dependent on rnk solids ... ~ .. " . ,.l ;....
The condition of constant ink drop velocity through the deflection field is necessary to provide consistent print quality and requires that the flow rate of liquid through the nozzle be sl~hct~ti~lly constant. Prior ink marking systems have attempted to a~.. ,~n.l lr this 10 ~ lli by various means.
One such system employs a specific gravity detector which signals when it is necessary to add solvent to the ink supply. This system is unsuitable for use in systems where the printer must: ' many different types of inks, each with its own specific gravity parameters.
Another ~.UIIIIII~ ;al system which tries to deal with the problem of changing drop velocity was ' I by the IBM ('nTn~tinn In this device the ink pressure is responsive to signals from a deflection detector. The deflection detector is located in the electric field through which the drops pass. The detector signals the pump to increase or decrease pressure, 20 as necessary, to maintain drop velocity at an appropriate value. The system provides feedback control of drop velocity. The technique, however, is not entirely ~ r~ y because of the CCIIII~ .A;IY and cost of the cu".~,, and the need for a fragile deflection detector at the remote print head location.
W0 9!~113192 2 ~ 7 5 ~ 8 6 r~ 13 Another inYention, disclosed in U.S. Patent No. 4,555,712, monitors the inlc flow rate, monitors the velocity of the drops of ink in the charge field and, by use of an electronic controller, adjusts the ink parameters to maintain a desired flow rate which insures a ~Iy constant drop velocity.
It is an object of the present invention to incorporate direct feedback control into an ink solids . control system wbich is simpler, reliable and low in cost.
Another object of the invention is to provide a velocity control system for an ink jet 10 printer which maintains substantially constant velocity of ink entering a deflection field thereby insuring accurate location of spots on the substrate to be marked.
In a frist aspect the present invention provides ink control apparatus for a drop marking system which includes a reservoir, a printhead receiving ink from the reservoir, means for 15 returning unused ink to the reservoir, the apparatus ~. ,., .1,, ;~;, .~"
a) a solvent supply including a valuve for controlling the addition of solvent to the ink in the reservoir;
b~ a reference chamber containing fresh ink; and ~ d by further CC" ' 'I " ;~
c) an acoustic transrnitter associated with said reference chamber oriented to transmit acoustic pulses through the ink and to detect said acoustic pulses after travelling WO 9~/13192 r~
217~08~
through the ink, the time delay between i of a pulse and its reception being a function of the solids: r~n of the ink in the chamber;
d) a second acoustic transmitter associated with said resèrvoir oriented to send S acoustic pulses through the ink and a second acoustic receiver associated with said reservoir arranged to detect said acoustic pulses after travelling through the ink the time delay between of a pulse and its reception being a function of the solids . ~ of the ink in the reservoir;
e) means for comparing the time delays of echo retums from the reference chamber and the reservoir and for controlling operation of the solvent supply valve as a function of the said difference;
whereby solvent is added to the ink received in the reservoir as necessary to keep 15 the solids r~ .. therein substantially the same as the ink in the reference chamber.
Thus the invention provides an electronic control system employing acoustic transducers to measure the velocity of sound in ink to pemlit accurate control of the addition of solvent to the ink.
The invention also provides a flow control means for an ink system which is located entirely separate from the print head nozzle and yet maintains a substantially constant flow rate through the nozzle.
~ WO 95113192 2 ~ 7 5 ~ 8 ~ r ~
In a second aspect the present invention provides ink control apparatus for a drop marking system including a reservoir to supply ink to a print head that has at least one orifice for projecting a stream of droplets towards the surface to be marked, the individual droplets being cl.,~ ic~lly controlled and directed towards the surface to mark it or to a catcher to be 5 captured and returned to the ink reservoir, and having a source of fresh ink and a source of solvent which is selectively connected to the ink reservoir to replenish it and ~ by ink c~ ~ ~
a) frrst means measuring acoustic properties of the fresh ink to obtain a reference signal value relating to ink solids concentration.
b) second measuring mcans measuring the acoustic properties of the captured ink to obtain a signal value II,~ of the ink solids ~ in the captured ink.
c) means for comparing said reference signal value and said l.,~lC:~Clll~lliVC signal value to generate an error signal proportion to the solids . variation between the captured ink and the fresh ink, and d) means for controlling the addition of the solvent in response to said error signal whereby the solids ~ of the ink and the ink reservoirs maintained y constant.
Other objects and advantage of the inYention Will be apparent from the remaming portion
2 2~75t~S
of the (l~c,-rir~ jOn The present invention employs sound velocity ~ . to determine ink A transducer is used to emit an acoustic pulse in a reference chamber fed directly S by a fresh ink supply. This reference Illl,..o~.._.Ll~,lll is used as the control input to a feedback control system. A similar acoustical . . is taken in either the retum reservoir or the high pressure supply reservoir, or both, by additional ' These . ., ~ are also fed to the control system, for example, a l~uc~u~ c~ , which determines the difference and directs appropriate: l, in ink . by adding solvent or if fluid level is low, 10 adds fresh in~.
In addition to the previously mentioned advantages, this system e liminates the need for float based level sensors and evaporated loss . c as are frequently used in the prior art to maintain fluid levels and viscosity. In the supply and retum reservoirs the acoustic 15 transducer will receive a second acoustic pulse reflected from the liquid surface indicative of fluid level and flow rate. While the resulting fluid level data is not required for .
control, this data can be used to maintain optimal fluid levels and to provide flow rate lliO m the system.
In a typical ~rr~ ti~-n the ink flow rate and drop velocity are irlitially set using fresh ink by adjustment of the pressure in the ink flow line, to a condition which yields proper drop spacing. Thereafter the acoustic Clll~lllo from either the supply or return reservoirs coupled with signals from the reference cbamber permit precise ink control.
_ , , . , ... .. . . . .. . .. . . _ _ _ . . .. . .. . . ... . . . . . . .. .. .. .. .. .
W095113192 217~8 G P~
Apparatus embodying the invention will now be described by way of example only with reference to the ac~u~ ly;llg ~ ,- " ~ figures in which;
Figure I is a schematic drawing of an ink jet printing system illuUllJUla~ , the elements 5 of the present inYention;
Figure 2 is a block diagram of a closed-loop electronic control system suitable for practicing the invention; and hgure 3 is a waveform diagram showing the acoustic pulses and the luL~Liull~lu~ of the return pulses used to generate error signals.
~ eferring to Figure 1, a ~ schematic of the invention, applied to a typical ink drop marl~ing system, is shown. In a typical ink drop marking system a plurality of ink drops 15 separated by a pre-determined spacing emanate from an ink jet nozzle 32. The nozzle 32 is acted upon a piezo electric device in a manner well known in the alt (see, for example, U.S. Patent No.
of the (l~c,-rir~ jOn The present invention employs sound velocity ~ . to determine ink A transducer is used to emit an acoustic pulse in a reference chamber fed directly S by a fresh ink supply. This reference Illl,..o~.._.Ll~,lll is used as the control input to a feedback control system. A similar acoustical . . is taken in either the retum reservoir or the high pressure supply reservoir, or both, by additional ' These . ., ~ are also fed to the control system, for example, a l~uc~u~ c~ , which determines the difference and directs appropriate: l, in ink . by adding solvent or if fluid level is low, 10 adds fresh in~.
In addition to the previously mentioned advantages, this system e liminates the need for float based level sensors and evaporated loss . c as are frequently used in the prior art to maintain fluid levels and viscosity. In the supply and retum reservoirs the acoustic 15 transducer will receive a second acoustic pulse reflected from the liquid surface indicative of fluid level and flow rate. While the resulting fluid level data is not required for .
control, this data can be used to maintain optimal fluid levels and to provide flow rate lliO m the system.
In a typical ~rr~ ti~-n the ink flow rate and drop velocity are irlitially set using fresh ink by adjustment of the pressure in the ink flow line, to a condition which yields proper drop spacing. Thereafter the acoustic Clll~lllo from either the supply or return reservoirs coupled with signals from the reference cbamber permit precise ink control.
_ , , . , ... .. . . . .. . .. . . _ _ _ . . .. . .. . . ... . . . . . . .. .. .. .. .. .
W095113192 217~8 G P~
Apparatus embodying the invention will now be described by way of example only with reference to the ac~u~ ly;llg ~ ,- " ~ figures in which;
Figure I is a schematic drawing of an ink jet printing system illuUllJUla~ , the elements 5 of the present inYention;
Figure 2 is a block diagram of a closed-loop electronic control system suitable for practicing the invention; and hgure 3 is a waveform diagram showing the acoustic pulses and the luL~Liull~lu~ of the return pulses used to generate error signals.
~ eferring to Figure 1, a ~ schematic of the invention, applied to a typical ink drop marl~ing system, is shown. In a typical ink drop marking system a plurality of ink drops 15 separated by a pre-determined spacing emanate from an ink jet nozzle 32. The nozzle 32 is acted upon a piezo electric device in a manner well known in the alt (see, for example, U.S. Patent No.
3,512,172). The drops pass adjacent a charging electrode and then through an electrical deflection field (not shown). Ink flows to the nozzle 32 by way of a flexible conduit 11 from a I ' reservoir 20 which is usually located remotely from the print head 26. If desired, 20 the high pressure reservoir 20 may supply ink to several such print heads 32.
The high pressure reservoir 20 is supplied with ink by various suitable means, many forms of which are known in the art. Typically, a l1.u~uhl~iul. system will include an ink drop retum cûnduit 34 to retum unused ink drops to a return ink reservoir ~ 8 using vacuum pressure.
WO 9~/13192 1 ~I,. 1. 13 2175~
Typical ink I~UilUULl~iOII systems also include means for 1" ' ' ~ ink and solvent in order to make up for depletion during operation.
According to the present invention, an ink reference chamber 10 is 5 positioned between the fresh ink supply and an ink flow control value 28. Mounted on the bottom exterior of the base of the reference chamber 10 is an acoustic transduoer 12, which emits an initial acoustic pulse through the fresh ink to a reflector 14, wmch in this case may be the top of the chamber. A reflection occurs at the reflector 14 and the return pulse is detected by the transducer 12. The time delay required for the reflection and return of the return pulse is a 10 function of the velocity of sound through the fresh in~. The resultant informatior. is used as one input to the control system in Figure 2.
It is also within the teacmngs of the present invention to rlleasure other acoustic properties of ink utili~ing acoustic sensors that relate ink solids to ink density and 15 irlk viscosity for example.
A transducer 15 or 13 is also mounted on the bottom of the high pressure ink reservoir 20 or the return ink reservoir 18 (or both) I~ ,ly. For these reservoirs acoustic reflection to generate a return pulse can be provided by a solid surface or a change in the acoustical 20 impedance of the fluid column produced, for example, by a change in diameter at a point 16 in reservoir 18 and at a point 21 in reservoir 20. Preferably, the ink Ul ' reference chamber 10 and the reservoirs 18 and 20 are constructed so that the acoustical paths through the ink are identical in length, thereby obviating the need to: , for chamber geometry, etc.
~ W09S113192 2 1 7~0 8 fi ~ 3 The ~ ~ilU~Lio~l refereQce signal from transducer 12 and the retum reservoir - signal, refiected from the ~ i- .., point l 6 from the retum reservoir transducer 13, are fed to the closed loop control system depicted in Figure 2. Ariy difference in the two signalis will be due to eYaporation of solvent from the ink in use and generates an error signai S for the controiller 40, which in tum generates a solvent-add signai for operating the solvent flow control valve 30. Solvent is thereby added as needed to the ink retum system to maintain the reservoir 20 ink supply sllhc~ ly identicail in concentration to that present in reference chamber 10. The controller 40 may be a soilid state logic system or a ~ L. - ' computer as, for example, a ~ ulu~ computer system of the type typicaily used for process control.
10 As the ini~ in the retum reservoir is diluted with solvent, its sound velocity begins to match the sound velocity in the control charnber. This reduces the magnitnde of the error signai. ~n tum, this reduces the rate of addition and ultimately terminates the flow of solvent.
There is an additional benefit from using the sound l ' according to the 15 invention Fiioat-based sensors such as used in the prior art are vulnerable to errors caused by binding, triggering errors, hysteresis and ini~ foam 24 as shown in Figure 1. Solid state of fluid level extemai of the reservoir avoids these errors. Without any additionai hardware, fluid levels can be measured and regulated. In either reservoir 18 or 20 the transducer 13 or 15 lc~iv~ wiill receive a second retui-n pulse reflected from the liquid 20 surface, for example æ in the retum reservoir 18.
A fluid level controller using the second retum pulse data from the tr~insucer 13 can maintain optimum levels in the reservoirs by controiling the supply of fresh ink through flow control value 28. Figui-e 3 shows the ~aris~itted and ~ceived pulses ~s described herein. iTt will W0 95/13192 I ~ 3 1~
217~G
be apparent to those skilled in the art that one controller 40 can perform both functions, that is, regulate the addition of solvent and fresh ink to the system. The timing of the second return pulse relative to the initial pulse defunes a time interval which correlates with the irlk level in the retum reservoir 18 for transducer 13 or the high pressure reservoir 20 for the tr~nsducer 15. The 5 time interval may be compared with a reference value stored in a controller memory and the result of that ...,..~ .. used to control operation of the fresh ink valve 28 in the same manner as the solvent value 30 is operated.
While preferred .. 1,~.1;",.. '~ of the present invention have been illustrated and 10 described, it will be understood by those of ordinary skill in the art that changes and rnn~lifi~ nc can be rnade without departing from the invention in its broader aspects, and in particular although the I~ Jd;~ described senses speed of sound changes using a single transducer by a time of transit reflection technique, it would be possible to serlse speed of sound changes using two i ' by a direct path time of transit technique.
The high pressure reservoir 20 is supplied with ink by various suitable means, many forms of which are known in the art. Typically, a l1.u~uhl~iul. system will include an ink drop retum cûnduit 34 to retum unused ink drops to a return ink reservoir ~ 8 using vacuum pressure.
WO 9~/13192 1 ~I,. 1. 13 2175~
Typical ink I~UilUULl~iOII systems also include means for 1" ' ' ~ ink and solvent in order to make up for depletion during operation.
According to the present invention, an ink reference chamber 10 is 5 positioned between the fresh ink supply and an ink flow control value 28. Mounted on the bottom exterior of the base of the reference chamber 10 is an acoustic transduoer 12, which emits an initial acoustic pulse through the fresh ink to a reflector 14, wmch in this case may be the top of the chamber. A reflection occurs at the reflector 14 and the return pulse is detected by the transducer 12. The time delay required for the reflection and return of the return pulse is a 10 function of the velocity of sound through the fresh in~. The resultant informatior. is used as one input to the control system in Figure 2.
It is also within the teacmngs of the present invention to rlleasure other acoustic properties of ink utili~ing acoustic sensors that relate ink solids to ink density and 15 irlk viscosity for example.
A transducer 15 or 13 is also mounted on the bottom of the high pressure ink reservoir 20 or the return ink reservoir 18 (or both) I~ ,ly. For these reservoirs acoustic reflection to generate a return pulse can be provided by a solid surface or a change in the acoustical 20 impedance of the fluid column produced, for example, by a change in diameter at a point 16 in reservoir 18 and at a point 21 in reservoir 20. Preferably, the ink Ul ' reference chamber 10 and the reservoirs 18 and 20 are constructed so that the acoustical paths through the ink are identical in length, thereby obviating the need to: , for chamber geometry, etc.
~ W09S113192 2 1 7~0 8 fi ~ 3 The ~ ~ilU~Lio~l refereQce signal from transducer 12 and the retum reservoir - signal, refiected from the ~ i- .., point l 6 from the retum reservoir transducer 13, are fed to the closed loop control system depicted in Figure 2. Ariy difference in the two signalis will be due to eYaporation of solvent from the ink in use and generates an error signai S for the controiller 40, which in tum generates a solvent-add signai for operating the solvent flow control valve 30. Solvent is thereby added as needed to the ink retum system to maintain the reservoir 20 ink supply sllhc~ ly identicail in concentration to that present in reference chamber 10. The controller 40 may be a soilid state logic system or a ~ L. - ' computer as, for example, a ~ ulu~ computer system of the type typicaily used for process control.
10 As the ini~ in the retum reservoir is diluted with solvent, its sound velocity begins to match the sound velocity in the control charnber. This reduces the magnitnde of the error signai. ~n tum, this reduces the rate of addition and ultimately terminates the flow of solvent.
There is an additional benefit from using the sound l ' according to the 15 invention Fiioat-based sensors such as used in the prior art are vulnerable to errors caused by binding, triggering errors, hysteresis and ini~ foam 24 as shown in Figure 1. Solid state of fluid level extemai of the reservoir avoids these errors. Without any additionai hardware, fluid levels can be measured and regulated. In either reservoir 18 or 20 the transducer 13 or 15 lc~iv~ wiill receive a second retui-n pulse reflected from the liquid 20 surface, for example æ in the retum reservoir 18.
A fluid level controller using the second retum pulse data from the tr~insucer 13 can maintain optimum levels in the reservoirs by controiling the supply of fresh ink through flow control value 28. Figui-e 3 shows the ~aris~itted and ~ceived pulses ~s described herein. iTt will W0 95/13192 I ~ 3 1~
217~G
be apparent to those skilled in the art that one controller 40 can perform both functions, that is, regulate the addition of solvent and fresh ink to the system. The timing of the second return pulse relative to the initial pulse defunes a time interval which correlates with the irlk level in the retum reservoir 18 for transducer 13 or the high pressure reservoir 20 for the tr~nsducer 15. The 5 time interval may be compared with a reference value stored in a controller memory and the result of that ...,..~ .. used to control operation of the fresh ink valve 28 in the same manner as the solvent value 30 is operated.
While preferred .. 1,~.1;",.. '~ of the present invention have been illustrated and 10 described, it will be understood by those of ordinary skill in the art that changes and rnn~lifi~ nc can be rnade without departing from the invention in its broader aspects, and in particular although the I~ Jd;~ described senses speed of sound changes using a single transducer by a time of transit reflection technique, it would be possible to serlse speed of sound changes using two i ' by a direct path time of transit technique.
Claims (14)
1. Ink control apparatus for a drop marking system which includes a reservoir, a printhead receiving ink from the reservoir, means for returning unused ink to the reservoir, the apparatus comprising:
a) a solvent supply including a valve for controlling the addition of solvent to the ink in the reservoir;
b) a reference chamber contain fresh ink and characterised by further comprising;
c) an acoustic transmitter associated with said reference chamber oriented to transmit acoustic pulses through the ink and an acoustic receiver associated with said reference chamber arranged to detect said acoustic pulses after travelling through the ink, the time delay between transmission of a pulse and its reception being a function of the solids of the ink in the chamber;
d) a second acoustic transmitter associated with said reservoir oriented to send acoustic pulses through the ink and a second acoustic receiver associated with said reservoir arranged to detect said acoustic pulses after travelling through the ink, the time delay between transmission of a pulse and its reception being a function of the solids concentration of the ink in the reservoir;
e) means for comparing the time delays of echo returns from the reference chamber and the reservoir and for controlling operation of the solvent supply valve as a function of the said difference;
whereby solvent is added to the ink received in the reservoir as necessary to keep the solids concentration therein substantially the same as the ink in the reference chamber.
a) a solvent supply including a valve for controlling the addition of solvent to the ink in the reservoir;
b) a reference chamber contain fresh ink and characterised by further comprising;
c) an acoustic transmitter associated with said reference chamber oriented to transmit acoustic pulses through the ink and an acoustic receiver associated with said reference chamber arranged to detect said acoustic pulses after travelling through the ink, the time delay between transmission of a pulse and its reception being a function of the solids of the ink in the chamber;
d) a second acoustic transmitter associated with said reservoir oriented to send acoustic pulses through the ink and a second acoustic receiver associated with said reservoir arranged to detect said acoustic pulses after travelling through the ink, the time delay between transmission of a pulse and its reception being a function of the solids concentration of the ink in the reservoir;
e) means for comparing the time delays of echo returns from the reference chamber and the reservoir and for controlling operation of the solvent supply valve as a function of the said difference;
whereby solvent is added to the ink received in the reservoir as necessary to keep the solids concentration therein substantially the same as the ink in the reference chamber.
2. Apparatus as claimed in claim 1 in which the drop marking system includes a pressure reservoir and a return reservoir, the printhead receiving ink from the pressure reservoir and the unused ink being returned to the return reservoir and means for communicating ink from the return reservoir to the pressure reservoir and in which solvent is added to the ink received in the return reservoir to keep the solids concentration therein substantially the same as the ink in the reference chamber.
3. Apparatus as claimed in claim 2 in which the second acoustic transmitter and receiver are associated with the return reservoir.
4. Apparatus as claimed in claim 2 in which the second acoustic transmitter and receiver are associated with the pressure reservoir.
5. Apparatus as claimed in any preceding claim in which the first acoustic transmitter and first acoustic receiver are combined in a single first acoustic transducer.
6. Apparatus as claimed in any preceding claim in which the second acoustic transmitter and second acoustic receiver are combined in a single second acoustic transducer.
7. Apparatus as claimed in Claim 5 in which said reference chamber incorporates a reflector surface positioned opposite the transducer to produce said echo return after the pulse passes through the ink.
8. Apparatus as claimed in Claim 6 wherein said return reservoir includes a first portion connected to a second portion of dissimilar physical configuration, said echo return being produced by the discontinuity at the point of connection of the two portions.
9. Apparatus as claimed in Claim 6 wherein said pressure reservoir includes a first portion connected to a second portion of dissimilar physical configuration, said echo return being produced by the discontinuity at the point of connection of the two portions.
10. Apparatus as claimed in claim 8 or claim 9 in which the or each first portion is of substantially equal height to said reference chamber, whereby the echo returns from each can be directly compared, without need for calibration for any difference in volume or path length through the ink.
11. Apparatus as claimed in Claim 6 and further including means for controlling the addition of fresh ink to the return reservoir, said means comprising:
a) a fresh ink supply and an ink valve associated therewith for communicating ink to the return reservoir, b) means for comparing the time interval between transmission of an acoustic pulse and receiving an echo return in the return reservoir related to the ink level in said return reservoir with a value representative of a desired ink level and for operating said ink valve to add fresh ink as necessary.
a) a fresh ink supply and an ink valve associated therewith for communicating ink to the return reservoir, b) means for comparing the time interval between transmission of an acoustic pulse and receiving an echo return in the return reservoir related to the ink level in said return reservoir with a value representative of a desired ink level and for operating said ink valve to add fresh ink as necessary.
12. Apparatus as claimed m Claim 6 and further including means for controlling the addition of fresh ink to the return reservoir, said means comprising:
a) a fresh ink supply and an ink valve associated therewith for communicating ink to the return reservoir;
b) means for comparing the time interval between transmission of an acoustic pulse and receiving an echo return in the pressure reservoir related to the ink level in said pressure reservoir with a value representative of a desired ink level and for operating said ink valve to add fresh ink as necessary.
a) a fresh ink supply and an ink valve associated therewith for communicating ink to the return reservoir;
b) means for comparing the time interval between transmission of an acoustic pulse and receiving an echo return in the pressure reservoir related to the ink level in said pressure reservoir with a value representative of a desired ink level and for operating said ink valve to add fresh ink as necessary.
13. Ink control apparatus for a drop marking system including a reservoir to supply ink to a print head that has at least one orifice for projecting a stream of droplets towards the surface to be marked, the individual droplets being electrically controlled and directed towards the surface to mark it or to a catcher to be captured and returned to the ink reservoir, and having a source of fresh ink and a source of solvent which is selectively connected to the ink reservoir to replenish it and characterised by ink comprising;
a) first means measuring acoustic properties of the fresh ink to obtain a reference signal value relating to ink solids concentration.
b) second measuring means measuring the acoustic properties of the captured ink to obtain a signal value representative of the ink solids concentration in the captured ink.
c) means for comparing said reference signal value and said representative signal value to generate an error signal proportion to the solids concentration variation between the captured ink and the fresh ink, and d) means for controlling the addition of the solvent in response to said error signal whereby the solids concentration of the ink and the ink reservoirs are maintained substantially constant.
a) first means measuring acoustic properties of the fresh ink to obtain a reference signal value relating to ink solids concentration.
b) second measuring means measuring the acoustic properties of the captured ink to obtain a signal value representative of the ink solids concentration in the captured ink.
c) means for comparing said reference signal value and said representative signal value to generate an error signal proportion to the solids concentration variation between the captured ink and the fresh ink, and d) means for controlling the addition of the solvent in response to said error signal whereby the solids concentration of the ink and the ink reservoirs are maintained substantially constant.
14. A method for maintaining print quality utilizing an ink jet printer which has a reservoir to supply ink to a print heat that has at least one orifice for projecting a stream of droplets toward a surface to be marked, the individual droplets being electrically controlled to be directed toward the surface to mark it or to a catcher to be captured and returned to the ink reservoir, and having a source of fresh ink and a source of solvent which are selectively connected to the ink reservoir to replenish it, characterised by comprising the steps of;
a) measuring acoustic properties of the fresh ink to obtain a reference signal value related to ink solids concentration, b) measuring the acoustic properties of the captured ink to obtain a signal value representative of the ink solids concentration in the captured ink, c) comparing said reference signal value and said representative signal value togenerate an error signal proportional to the solids concentration variation between the captured ink and the fresh ink, and d) controlling the addition of the solvent in response to said error signal, whereby the solids concentration of the ink in the ink reservoir is maintained substantially constant.
a) measuring acoustic properties of the fresh ink to obtain a reference signal value related to ink solids concentration, b) measuring the acoustic properties of the captured ink to obtain a signal value representative of the ink solids concentration in the captured ink, c) comparing said reference signal value and said representative signal value togenerate an error signal proportional to the solids concentration variation between the captured ink and the fresh ink, and d) controlling the addition of the solvent in response to said error signal, whereby the solids concentration of the ink in the ink reservoir is maintained substantially constant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/148,392 US5424766A (en) | 1993-11-08 | 1993-11-08 | Ink jet printer control system responsive to acoustical properties of ink |
| US08/148,392 | 1993-11-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2175086A1 true CA2175086A1 (en) | 1995-05-18 |
Family
ID=22525580
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002175086A Abandoned CA2175086A1 (en) | 1993-11-08 | 1994-10-27 | Drop marking control system responsive to acoustical properties of ink |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US5424766A (en) |
| EP (1) | EP0730529B1 (en) |
| JP (1) | JPH09504756A (en) |
| AT (1) | ATE156424T1 (en) |
| AU (1) | AU7945394A (en) |
| CA (1) | CA2175086A1 (en) |
| DE (1) | DE69404858T2 (en) |
| WO (1) | WO1995013192A1 (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6003965A (en) * | 1995-09-01 | 1999-12-21 | Videojet Systems International, Inc. | Ink and solvent container for ink jet printers |
| US6044694A (en) * | 1996-08-28 | 2000-04-04 | Videojet Systems International, Inc. | Resonator sensors employing piezoelectric benders for fluid property sensing |
| US6561635B1 (en) * | 1997-04-30 | 2003-05-13 | Eastman Kodak Company | Ink delivery system and process for ink jet printing apparatus |
| US6099113A (en) * | 1998-03-13 | 2000-08-08 | Iris Graphics | Continuous jet printer mixing system |
| US7375857B1 (en) | 2000-09-22 | 2008-05-20 | Eastman Kodak Company | Print proofing with color and screen matching |
| RU2197717C2 (en) * | 2000-12-29 | 2003-01-27 | Безруков Виктор Иванович | Hydraulic system of electric ink-drop and-jet printer, trap for unused drops for hydraulic system of electric ink-drop and-jet printer |
| US6786565B2 (en) | 2001-09-24 | 2004-09-07 | Creo Americas, Inc. | Inkjet proofing with matched color and screen resolution |
| US6932097B2 (en) | 2002-06-18 | 2005-08-23 | Picoliter Inc. | Acoustic control of the composition and/or volume of fluid in a reservoir |
| AU2003256276A1 (en) * | 2002-06-18 | 2003-12-31 | Picoliter Inc. | Acoustic assessment and/or control of fluid content in a reservoir |
| JP4045917B2 (en) * | 2002-10-17 | 2008-02-13 | 凸版印刷株式会社 | Liquid component concentration measuring device |
| WO2008102657A1 (en) * | 2007-02-20 | 2008-08-28 | Seiko I Infotech Inc. | Liquid feed system, inkjet printer, and method of feeding ink |
| US20100079559A1 (en) * | 2008-09-29 | 2010-04-01 | Greg Justice | Fluid Circulation System |
| CN102126351A (en) * | 2011-01-05 | 2011-07-20 | 武汉镭德杰科技发展有限公司 | Ink box structure of inkjet printing machine |
| US9764561B2 (en) | 2012-04-04 | 2017-09-19 | Xerox Corporation | System and method for clearing weak and missing inkjets in an inkjet printer |
| PT3071413T (en) * | 2013-11-19 | 2020-02-28 | Archroma Ip Gmbh | Inkjet printing system |
| JP7109926B2 (en) * | 2018-01-25 | 2022-08-01 | キヤノン株式会社 | recording device |
| US11397146B2 (en) | 2019-06-19 | 2022-07-26 | Pad Peripheral Advanced Design Inc. | Vibrational viscosimeter |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3771456A (en) * | 1972-07-10 | 1973-11-13 | Catalyst Research Corp | Explosive primer with actuating means |
| US3930258A (en) * | 1975-01-13 | 1975-12-30 | Dick Co Ab | Ink monitoring and automatic fluid replenishing apparatus for ink jet printer |
| US4121222A (en) * | 1977-09-06 | 1978-10-17 | A. B. Dick Company | Drop counter ink replenishing system |
| US4317124A (en) * | 1979-02-14 | 1982-02-23 | Canon Kabushiki Kaisha | Ink jet recording apparatus |
| JPS5746897A (en) * | 1981-07-22 | 1982-03-17 | Sharp Corp | Diluting liquid for ink to be jetted |
| US4555712A (en) * | 1984-08-03 | 1985-11-26 | Videojet Systems International, Inc. | Ink drop velocity control system |
| JPS6328651A (en) * | 1986-07-22 | 1988-02-06 | Ricoh Co Ltd | Ink viscosity control device of ink jet recorder |
| US4827280A (en) * | 1988-08-09 | 1989-05-02 | A. B. Dick Company | Flow rate control system |
| FR2636884B1 (en) * | 1988-09-29 | 1990-11-02 | Imaje Sa | DEVICE FOR MONITORING AND REGULATING AN INK AND ITS TREATMENT IN A CONTINUOUS INK JET PRINTER |
-
1993
- 1993-11-08 US US08/148,392 patent/US5424766A/en not_active Expired - Fee Related
-
1994
- 1994-10-27 WO PCT/GB1994/002313 patent/WO1995013192A1/en active IP Right Grant
- 1994-10-27 EP EP94930293A patent/EP0730529B1/en not_active Expired - Lifetime
- 1994-10-27 AU AU79453/94A patent/AU7945394A/en not_active Abandoned
- 1994-10-27 DE DE69404858T patent/DE69404858T2/en not_active Expired - Fee Related
- 1994-10-27 AT AT94930293T patent/ATE156424T1/en not_active IP Right Cessation
- 1994-10-27 CA CA002175086A patent/CA2175086A1/en not_active Abandoned
- 1994-10-27 JP JP7513648A patent/JPH09504756A/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| EP0730529A1 (en) | 1996-09-11 |
| AU7945394A (en) | 1995-05-29 |
| DE69404858D1 (en) | 1997-09-11 |
| DE69404858T2 (en) | 1997-11-27 |
| WO1995013192A1 (en) | 1995-05-18 |
| JPH09504756A (en) | 1997-05-13 |
| US5424766A (en) | 1995-06-13 |
| ATE156424T1 (en) | 1997-08-15 |
| EP0730529B1 (en) | 1997-08-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |