US3398259A - Photoelectrostatic copying machine - Google Patents

Description

Aug. 20, 1968 .1. L. TREGAY ET PHOTOELECTROSTATIC COPYING MACHINE 8 Sheets-Sheet 1 Filed Aug. 12, 1964 Aug. 20, 1968 T EG Y ETAL 3,398,259

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PHOTOELECTROSTATIC COPYING MACHINE Filed Aug. 12, 1964 8 Sheets-Sheet 8 United States Patent 3,398,259 PHOTOELECTROSTATIC COPYING MACHINE John L. Tregay, Wilmette, and Kristian L. Helland,

Schaumberg, Ill., assignors to Addressograph- Multigraph Corporation, Mount Prospect, IlL, a corporation of Delaware Filed Aug. 12, 1964, Ser. No. 389,037 6 Claims. (Cl. 219-216) ABSTRACT OF THE DISCLOSURE An automatic copying machine has a drive system propelling an Original and copy sheet in synchronism through the machine; the original moving past a light, and the copy sheet moving past charging, exposing, developing and fusing apparatus. A control circuit rapidly brings the machine to a ready condition, and places the machine in an operating condition 'when 'a copy is made. The fuser operates in a high energy condition during warm-up, and in a low energy condition until a copy is made, when it operates in an intermediate energy condition.

The present invention relates to automatic copying machines and, more particularly, to a new and improved automatic copying machine of the photoelectrostatic type.

In automatic copying machines of this type, a copy of a graphic original sheet manually fed into the machine at a feed station is made on a photoconductive copy sheet fed automatically from a supply into the machine in response to feeding an original into the machine. Drive wheels propel the original and the copy sheet in synchronization while the photoconductive copy sheet is electrostatically charged in the dark and is then selectively exposed at an imaging station in accordance with the light image or pattern produced by illuminating the moving original, and the reflected light image from said original is focused by means of an optics assembly onto the charged copy sheet. The exposure of the charged copy sheet produces a latent electrostatic image in accordance with the light pattern focused thereon by dissipating the charge in those areas which are light struck and leaving an electrostatic charge in the unexposed area-s.

The latent electrostatic image is rendered visible by the application of a granular developer mixture comprising magnetically attractable carrier particles in admixture with a colored thermoplastic resin powder or electroscopic powder in a balanced proportion. In the presence of a magnetic field the developer mixture forms up into a brush-like mass to facilitate the application of the electroscopic powder. The electroscopic powder due to the presence of triboelectr-ic forces in the developer mix adheres to the image portions leaving the magnetically attractable carrier particles on the brush.

The resulting powder image is bonded to the copy by passing it through a suitable heating oven maintained at the fusing temperature of the thermoplastic resins but below the char point of the copy paper.

Photoelectrostatic copy machines of this type require a warm-up period, after a time of non-use, such as overnight, in order to produce copies with fixed images thereon. Accordingly, it would be desirable to bring the fusing heat up to the proper temperature as rapidly as possible and thereafter automatically maintain this operating temperature with a minimal energy input when the machines are being used at peak capacity without overheating so as not to char or ignite paper.

At the end of the peak copying demand-s, the fusing system should desirably be capable of automatically going from an operating condition to a ready condition after a predetermined period of non-use. Thereafter, when an occasional copy is required, the fusing system should automatically, and without undue delay, return to an operating condition. Accordingly, this will provide for the most economical use of the electrical energy drawing the necessary power as required and at the same time preventing the working area from becoming uncomfortably warm.

Each time an original is fed into the machine at the feed station a copy sheet is fed into the machine automatically, in synchronization with and in response to the feeding of the original. To simplify and speed up the automatic production of copies it would be desirable to alert the operator when the supply of copy sheets is exhausted, requiring replenishment and hence not hold up the operation of the machine.

Since a wide variety of originals, from any sources, must be processed through automatic copying equipment of this type, it often occurs that creased, folded or otherwise mutilated originals, as well as sheets having staples or paper clips attached thereto when introduced into the machine will tend to interfere with their smooth passage through the feeding and exposing stations. Similarly, the copy sheets having certain other defects tend to jam at the feeding station. To advantage, a removable housing cover containing the various sensing and switching elements at the respective paper feed stations would provide access thereto in permitting the safe removal of the fouled or jammed papers by disconnecting any dangerous high voltage elements exposed by the removal of the housing.

Heretofore, the available incandescent filament illuminating sources responsible for illuminating elemental portions of a moving original and then focusing the reflected light image through an optical system onto a moving copy sheet, gave uneven exposure across the width of the copy. This is due in part to the inefficiencies of the optical system which transmits more light along the lens axis than at the edges thereof. In addition, the emission spectrum from these high intensity sources is rich in infra-red radiation which when absorbed by the original can cause the original to overheat and scorch a valuable original document. Control of the uniformity and kind of radiation that impinges across the width of the original is important in turning out high quality copies on automatic reproduction machines.

The fuser assemblies customarily used include means for transporting or conveying the copy sheet having the unfixed powder image electrostatically held thereon to the fusing station. Various transport means have been used to convey the copy sheet through the fuser oven, but have been lacking because of the tendency of the copy to cling or adhere to the conveyor increasing the time of heat exposure and be scorched or burned in the fusing process. Accordingly, the fused copy sheets should reliably and promptly be removed from the fuser at the conclusion of the fusing step and ejected from the apparatus.

With the production of each copy there occurs a depletion of the electroscopic powder leaving an increased concentration of carrier particles in the developer mix. This imbalance results in the production of inferior images having low density. As the concentration of magnetically attractable carrier particles increases in the developer mix there is a tendency for the iron particles to print out on the copy sheets. One of the important aspects of making quality prints therefore, depends on maintaining a proper ratio of'carrier particles to electroscopic resin particles in the developer mix. It is therefore desirable to provide means which will automatically replenish electroscopic powder in amounts approximate to the quantities removed.

Accordingly, it is an object of the invention to provide an improved photoelectrostatic copier having a warning system actuated by the depletion of copy sheets. Accordingly, it is an object of this invention to provide an improved circuit for controlling certain operating instrumentalities responsible for making copies in an automatic photoelectrostatic copying machine whereby said instrumentalities are maintained at a predetermined operative level when the machine is making copies and said instru mentalities being returned to a ready condition or a safe condition when in a state of non-use.

It is a further object of this invention to provide improved circuits for controlling an automatic photoelectrostatic copying machine, whereby the machine automatically makes the most eflicient use of available energy by drawing the greatest amount of energy when starting up whereby the heat fusing system is rapidly brought to operating temperature, and thereafter automatically adjusts to meet peak copying demands and for periods of infrequent or occasional use.

It is another object of the invention to provide an improved circuit for controlling an automatic photoelectrostatic copying machine whereby the machine when first turned on is in warm-up condition wherein the fuser system is rapidly brought to operating temperature and automatically placed in a ready condition to which it returns after a period of non-use.

Still another object is to provide an improved electroscopic powder dispensing means with a control for automatically replenishing powder in amounts to approximate the quantities depleted as a result of processing copy sheets through the machine, which control includes manual means for adjusting the amount of powder dispensed when said dispenser is actuated.

It is still another object to provide an improved copy machine lamp capable of uniformly illuminating an original to be copied.

Another object of the invention is to provide a photoelectrostatic copier with a novel system of light filters for protecting the original to be copied.

Still another object is to provide an improved fuser for photoelectrostatic copying machines including a conveyor from which a copy sheet may be easily removed after heating.

Still another object is to provide an improved electroscopic powder dispenser with a control for automatically dispensing powder in response to the running length of copy sheet material fed through the machine, which control includes manual means for adjusting the amount of powder so dispensed.

In accordance with these and other objects, an embodiment of the present invention comprises a photoelectrostatic automatic copying machine having a control circuit which is in an initial warm-up condition when first energized. This warm-up condition is characterized by a rapid heating arrangement for the fuser heating elements by connecting these elements in parallel across a voltage source. Means are provided for automatically changing the circuit to a ready condition when the fuser reaches operating temperature. In the ready condition, most of the components of the copy machine are in a nonactuated state, and the fuser heating elements are arranged in a low power series circuit arrangement. When it is desired to make a copy, the circuit is automatically switched to an actuated condition, and the fuser power is increased to provide effective heating of the copy. After a predetermined period of non-use, the circuit automatically returns to its ready condition.

An automatic sheet feeding mechanism feeds copy sheets from a storage chamber in response to the manual feeding of an original. The automatic feeding means includes a shaft and axially mounted rollers which rest on a stack of the copy sheets. When the height of the stack decreases'to a predetermined level as the copy sheets are used, a switch is actuated for automatically disconnecting the sheet feeding means and for turning off a visible indicator lamp.

The copying machine of the present invention also includes a removable housing portion carrying an original sensing switch adapted to be actuated by the entry of an original into the machine and also a copy sensing switch similarly actuated by a copy sheet. The removable housing may also include a number of other circuit elements. In accordance with a feature of the invention, a novel safety switching arrangement is employed for disconnecting the power supply to a set of high voltage corona discharge wires located beneath the removable housing portion when the housing is removed.

The machine also includes an illuminating assembly having a novel lamp with a filament coiled relatively loosely at the center to avoid over-illumination of the central portion of the original. A system of filters adapted to absorb infra-red radiation in the range of 7.5 to 15 microns wave length is placed between the lamp and the original to protect the original from excessive heating without eliminating useful visible light.

A novel conveyor belt in the fuser includes a series of raised ridges for supporting the copy sheet slightly above the main surface of the conveyor. Guide fingers terminating below the level of the ridges serve to remove the sheet from the conveyor.

A developer unit supplies electroscopic powder from a suitable container to form a material image of the electrostatically charged areas of the copy sheet corresponding to the orgiinal. A dispenser cooperates with an electric vibrator to dispense electroscopic powder to maintain the supply of powder in the container at a substantially constant level. A novel control means including a switch actuated by a copy sheet passing through the machine energizes the control means and powder is supplied to the developer unit as a function of the running length of copy sheets fed to the machine. The control means includes a mechanism manually adjustable to vary the amount of powder supplied as required for originals having differing image density.

The invention, together with other objects and advantages, will best be understood from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a perspective view of a photoelectrostatic automatic copying machine embodying the present invention;

FIG. 2 is an enlarged sectional view of the machine of FIG. 1 taken along a line substantially corresponding to the line 2--2 of FIG. 1;

FIG. 3 is a greatly enlarged, fragmentary, sectional view of a portion of the machine of FIG. 1 taken along a line substantially corresponding to the line 33 of FIG. 1 and illustrates particularly the path of travel of an original;

FIG. 4 is an enlarged, fragmentary perspective view, partly broken away, and shows particularly the feeding table of the machine of FIG. 1 with the copy sheet enclosure cover removed; i

FIG. 5 is an isometric view of part of the drive system for the machine of FIG. 1;

FIG. 6 is a sectional view of a light source for the machine;

FIG. 7 is a plan 'view, partly broken, of a removable switching sub-assembly for the copying machine;

FIG. 8 is a schematic circuit diagram of a group of electrical components including several carried by the removable sub-assembly shown in FIG. 7;

FIG. 9 is an enlarged sectional view of a developer and powder dispenser assembly;

FIG. 10 is a sectional view of the developer taken along line 1010 of FIG. 9;

FIG. 11 is a plan view of a powder dispenser control assembly;

FIG. 12 is an elevational view of the assembly shown in FIG. 11;

FIGS. 13 and 14 are fragmentary sectional views of the control assembly of FIG. 11 taken, respectively, along lines 13-13 and 14-14 in FIG. 11 and showing control cams included in the assembly shown in FIG. 11;

FIG. 15 is a schematic diagram of a circuit for controlling the operation of the machine shown in FIG. 1; and

FIG. 16 is an enlarged sectional view of a fuser conveyor.

Referring now to FIG. 1 of the drawings, an automatic photoelectrostatic copying machine characterized by the features of the invention is designated generally as 20. The machine 20 includes a housing or supporting structure 22 supported by a plurality of downwardly extending legs 24 each having an adjustable foot 26 for leveling the machine 20; The front panel of the machine 20 carries a main switch 34 for controlling the connection of the machine to a suitable source of power. As is shown in FIGS. 1 and 2, the machine 20 is provided with a raised hood 36 including a fan vent 38 cooperating with a fan 40 and a fan motor 42 to circulate cooling air in the interior of the machine.

The machine 20 operates in a fully automatic fashion to make one or more copies of an original 30 (FIG. 4). Accordingly, the machine is provided with a feeding table 28 which supports both the original and a stack of copy sheets 32 (FIG. 4) housed within a supply chamber 29 formed by a recess 28a (FIG. 2) in the table covered by an enclosure 50. The table 28 includes a holder and guiding means 44 for storing original sheets 30 to be copied and for guiding each sheet as it is manually fed into the machine where it follows the path of travel illustrated in FIG. 3. The original, which is illuminated by a light unit 46 (FIG. 3) as it travels through the machine 20 is returned to a receiving platform 48 conveniently located at the front of the machine.

A copy sheet is automatically passed through the machine from the chamber 29 in synchronism with the original. As is shown in FIG. 2, the copy sheet 32 first passes through a charging assembly 52 where opposite charges are deposited on its opposed surfaces, and through an exposure area 54 where light reflected from the original is focused onto the copy sheet by means of an optics assembly 56.

The exposed copy sheet leaves the exposure area 54, passes through a guide 58 and enters a developing unit 60 where an electroscopic powder, or toner, is deposited on the copy sheet and adheres to those areas corresponding to the dark areas of the original. The direction of travel of the copy sheet is then reversed in a turnaround assembly 6-2 and is fed through a fuser assembly 64 in which it is heated to render permanent the powder image of the original. The completed copy is then deposited in a copy receiving tray 66 positioned at the front of the machine 20.

The copy sheets 32 may be of any type conventionally used in this art, such as, for example, a paper substrate having one surface treated with a photoconductive material such as zinc oxide dispersed in a resin binder. It is a known characteristic of such copy sheets that they are electrostatically insulating in the dark and capable of 6 accepting a charge which is dissipated by exposing the photoconductive layer to light.

As was indicated above, the storage and supply chamber 29 is formed by a recess 28a disposed between two slabs 28b and 28c at opposed ends of the feeding table 28. A base plate 68 (FIG. 2) secured to the frame of the machine forms the bottomof the chamber and carries a pair of spaced guides 70 which are laterally adjustable within guide slots 68a in the base plate to accommodate copy sheets of various widths. The cover or enclosure 50 (FIG. 1) is hinged on the copy machine 20 and in its closed position extends over the recess 28a to cover the stack of copy sheets 32.

In order to transport a copy sheet 32 from the storage and supply enclosure 50 and to feed it into the machine, there is provided, as shown in FIG. 4, a sheet feeding assembly 74, including a pair of feed rollers 76 resting on top of the stack of copy sheets and mounted upon a rotatable feeder shaft 78. The shaft 78 is mounted between a pair of fixed spaced apart, support plates 79. The opposed ends of the shaft 78 extend through elongated guide slots 79a formed in the plates 79. A lever 80 is provided so that the shaft 78 and the rollers 76 may be manually lifted off of the stack of copy sheets 32 when it is desired to add more sheets or when access to the stack is desired for any other reason. During this operation, the shaft movement is guided and restricted by the slot formations 79a. One end of the feeder shaft 78 carries a sprocket or toothed pulley 82 driven by a toothed belt 84 (FIGS. 4 and 5) to turn the feed rollers 76 and, hence, to advance a copy sheet 32.

As can best be seen in FIG. 5, the toothed belt 84 is driven by means of a sprocket 86 mounted on the end of a clutch shaft 88. Interposed between the sprocket 86 and the clutch shaft 88 is a clutching mechanism 90 of the electrically operated type. When a voltage is applied across suitable terminals (not shown) of the clutch mechanism 90, the clutch shaft 88 is connected to drive the sprocket 86, and the sheet feeding assembly 74 is effective to feed a copy sheet 32. The automatic actuation of the sheet feeding assembly will be described in detail hereinafter in connection with the description of the electrical control circuit of the machine 20. A more detailed description of the structure of a sheet feeding device similar to the sheet feeding assembly 74 may be found in the copending application of Sherell E. Campbell, Ser. No. 291,447, filed June 28, 1963.

A drive motor 92 shown schematically in FIG. 15 drives the various shafts for propelling the copy sheet 32 and the original 30 through the machine. As is shown in FIG. 5, the clutch shaft '88 carries a gear 94 meshed with a second gear 96 mounted upon short shaft 98. The shaft 98 is driven from the drive motor 92 via a drive mechanism including a sprocket 100 and an arrangement of shafts and belts not illustrated.

After being advanced by the sheet feeding assembly 74, the copy sheet 32, as shown in FIG. 2, passes through a paper guiding construction 102 and between a pair of parallel drive rollers 104 and 106. The copy sheet 32 is advanced by the rollers 104 and 106 through the charging assembly 52 and the exposure area 54 and is then passed to another pair of parallel rollers 108- and 110. In the charging assembly 52 a set of spaced corona discharge wires 112 and 114 are arranged to deposit opposite charges on the surfaces of the copy sheet 32. In the exposure area 54, those areas of the charged photoconductive surface of the copy sheet 32 corresponding to the light areas of the original 30 are illuminated to dissipate or discharge the electrical charge thereon.

Referring to FIG. 3, it can be seen that an original 30, when manually fed into the machine, passes through a series of paper guides or baflles 116, and between two spaced pairs of driving rollers one pair of which is identified by reference numerals 118 and 120 while the other pair is identified by reference numerals 122 and 124.

As can best be seen in FIG. 5, the four copy sheet advancing rollers 104, 106, -8 and 110 and the four original sheet advancing rollers 118, 120, 122 and 124 are mounted in a symmetrical relation in the machine 20. Thus the rollers 104 and 106 are alined with the rollers 11-8 and 120; while the rollers 108 and 110 are alined with the rollers 122 and 124. Furthermore, the system of gears, sprockets and belts illustrated in FIG. 5 is effective'to rotate all of the above mentioned rollers in synchronism. For purposes of the description the eight rollers and their associated drive elements are designated as a drive subassembly 126. As was indicated above, the sub-assembly 126 is driven by the main drive motor 92. As illustrated in FIG. 5 the drive sub-assembly 126 is driven by means of a toothed pulley or sprocket 128 connected via a suitable drive arrangement to the sprocket 100. The drive for the rollers 104, 106, 108 and 110 may be transmitted to the other fourrollers in any suitable manner as, for example, by providing a common shaft 123 supporting the rollers 110 and 124 and utilizing a belt and sprocket drive 125 connecting the rollers 124 and 120. An electrically actuated clutching mechanism 130 shown schematically in FIG. and illustrated in FIG. 5, when energized in a manner described hereinafter, completes the drive from the shaft 123 to the drive assembly 125. An electrically operated brake 132, when energized as described below, holds the original feeding rollers 118 and 120 immobile without affecting the operation of the copy sheet feeding shafts 104, 106, 108 and 110. As will be evident from the ensuing description, the brake 132 prevents the original from being advanced until a copy sheet reaches the first pair of rollers 104 and 106 whereupon the brake is automatically released and the clutch 130 energized to permit the original and the copy sheet to advance simultaneously with their leading edges aligned.

An original 30 passes through the pairs of rollers 118, 120 and 122, 124 at exactly the same speed as a copy sheet 32 passes through the pairs of rollers 104, 106 and 108, 110. As the original 30 passes from the rollers 118, 120 to the rollers 122, 124 it is illuminated by the light unit 46, and, at the same time the copy sheet, which is passing from the rollers 104, 106 to the rollers 108, 110 is illuminated by the light reflected from the original and directed to the exposure area 54 by the optics assembly 56. This arrangement of uniformly driven, side by side pairs of rollers for the original and the copy'assures that clear, sharp reproductions of the material on the original will appear on the copy sheet at a position exactly corresponding to that occupied by this material on the original sheet.

As the original 30 advances from the first pair of rollers 118, 120 to the second pair 122, 124, it passes over a transparent plate 134 (FIG. 3) through which it is illuminated by means of the lighting assembly 46. In accordance with one feature of the present invention the lighting assembly 46 includes a new improved light source 142 together with means for preventing damage to the original as it is illuminated. The latter means comprises a filter system 138 for preventing passage to the original 30 of infra-red radiation from the source 142 having a wave length in the range between 7.5 to 15 microns, thereby to prevent radiation in this range from overheating and possibly scorching or burning the original as it passes over the transparent plate 134.

More specifically, the light assembly 46 includes a lamp support 140 for supporting a line type light source 142 in generally parallel relationship with the plane of the copy sheet 30 as it passes over the plate 134. A filter support bracket 144 attached to the lamp support 140 is provided with an aperture 146 to allow light to pass from the light source 142 through the filter system 138 to the transparent plate 134. Flexible clips 148 and 150 are provided on the bracket 144 to clamp or hold in position a set of filter elements 152 and 154 making up the filter system 138. The filters 152 and 154 are of the type which absorb invisible infra-red radiation without reducing the amount of useful visible illumination impinging upon the original 30.

The line light source 142, as can best be seen in FIG. 6, comprises an elongated transparent glass envelope 156 mounted in the lamp support in such manner that light reflected from the support is directed toward the aperture .146. A filament 158 disposed centrally within the envelope 156 has its opposed ends connected to terminal portions 156a to permit electrical connections to be made. In accordance with a feature of the present invention, and in order to illuminate the original 30 uniformly as it passesover the transparent plate 134, the filament 158 is tightly coiled adjacent each of its opposed ends as indicated at 158a, but is loosely coiled at the central portion as indicated at 1581). Since the light intensity imparted by the filament 158 is a function of the filament length, it will be understood that the lightintensity of the filament 158 increases near the tightly coiled ends 158a and decreases near the loosely coiled portion 158b, thereby eliminating difficulties encountered with prior machines in which the central portion of the original has been subjected to more intense light than regions near the side edges. 2

After the original 30 passes over the transparent plate 134 where it is illuminated by the light assembly 46, it is passed between the rollers 122 and 124 to a turnaround passageway 160 where its direction of travel is reversed by means of paper guides or bafiies 162 and 164. The original is then passed between a pair of rollers 166 and 168 for expelling the original30 onto the platform 48. The effective length of the receiving area for the original may be extended, if desired, by a sliding tray 49 best shown in FIGS. 1 and 3. The rollers 166 and 168 may be driven in any suitable fashion, as by an idler gear 170 driven by the assembly 126. 1

The light reflected from the original. 30 while it is passing over the plate 134 is directed onto the copy sheet 32 by a series of mirrors and lenses 136 forming part of the optics assembly 56 shown in FIG. 2. Obviously, light is reflected from the white or light areas of the original 30 but is not reflected from the dark or black areas. The areas of the copy sheet 32 corresponding to the light areas of the original are thus exposed and the charge on these areas is dissipated. The charge on the remaining areas of the copy sheet corresponding to the dark areas of the original remains. After the copy sheet 32 has been exposed in the manner described at the exposure area 54, it is passed through the rollers 108 and 110 and through the paper guiding means 58 to a pair of feed rollers 172 and 174 (FIG. 2) which are driven in a suitable manner by the main drive motor 92 and which serve .to deliver the exposed copy sheet 32 to the developer assembly 60.

The developer 60 is best shown in FIGS. 9 and 10 and includes a developer support frame 176 carrying a guide member 178 and a rotatable magnetic brush assembly 180. The guide member 178 is formed of dielectric material and helps direct the copy sheet from the rollers 172 and 174 to the brush assembly 180. A corona discharge wire 182 and a magnetic cleaning assembly 184 are secured to the frame to improve the clarity of the powder image deposited on the copy sheet during its passage through the developer 60. Nap covered rollers 186 and 188 supported by the frame 176 eject the copy sheet from the developer 60 without disturbing the powder image. The developer includes feeding and distributing elements 190 and 192 for distributing electroscopic powdered developer mix or toner 194 along the length of the :magnetic brush assembly where it mixes with a supply of magnetically attractable particles, such as iron particles or the like. The mixture forms into a brush-like configuration on the assembly 180, and the electroscopic particles are deposited on passing copy sheets. The developer assenrbly 60 is described in greater detail in the copending application of Daniel D. Granzow and John L. Tregay,

9 Ser. No. 307,887, filed Sept 10, 1963, and assigned to the same assignee as the present invention.

As is best shown in FIG. 9, there is provided a dispenser assembly 196 for selectively dispensing the toner powder 194. The structure and operation of the dispenser assembly 196 is described in detail in the copending commonlyl assigned, application of Robert L. Gunto, Ser. No. 353,498, filed Mar. 28, 1964, and will not be further described here, except to note that this assembly includes an electrically operated vibrator 198 for dispensing toner powder only when actuated in a manner to be described in greater detail hereinafter.

It is important that the proper ratio of iron particles and toner be maintained in the developer unit 60. Accordingly, provision must be made to replenish toner that is deposited upon copy sheets as copies are made. If the amount of toner is too small, not only will unsatisfactory copying of the image result, but particles of iron will adhere to the copy sheet. If there is too much toner, the copies will be produced with a dirty or spotted background caused by toner adhering to uncharged areas of the photoconductive layer.

In accordance with a feature of the invention, there is provided a novel control means 200 best shown in FIGS. 11 and 12 for controlling the feeding of toner 194 from the dispenser assembly 196. The control unit 200 automatically maintains the supply of toner mixture at the desired level by replenishing it as it is removed. A novel arrangement is provided to replace toner in an amount proportional to the running length of copy sheets run through the machine without regard to the number of sheets fed. To this end, the control unit 200 includes a switch 202 and a rheostat 204 connected in series with the electrically actuated vibrator 198. Whenever the switch 202 is closed the vibrator 198 is energized to dispense toner to the developer elements 190 and 192. The rheostat 204 is manually adjustable to control the amplitude of vibration of the electrical vibrator 198, thus assuring eflicient operation of the vibrator 198.

In order to support the control unit 200 on the machine 20 there is provided an L-shaped bracket 206 having one leg 206a carrying the rheostat 204. A nut 210 surrounding a shaft 208 clamps the rheostat against the bracket .leg 206a. The rheostat 204 is manually adjustable by means of a handle or dial 211 which is exposed to the operator for manual adjustment. In the illustrated embodiment of the invention, for example, the control unit 200 is mounted at the rear of the automatic copying machine 20.

The other leg 206k of the L-shaped bracket 206 supports a U-shaped bracket 212 carrying a rotary electric motor and gear reduction unit 214 in a position spaced from the leg 206b. The motor unit 214 is held in place by means of suitable fasteners 216 and has an output shaft 218 carrying a cam 220 with a peripheral cam surface 222 shaped as shown in FIG. 14.

The switch 202 includes an actuating arm 224 in the form of a cam follower riding along the cam surface 222. The cam surface 222 gradually increases in radius from a minimum point 222a to a maximum point 22%. When the motor 214 turns the cam 220, a point will be reached where the actuating arm 224 has moved sufficiently to close the switch 202. The point Where this switch closure occurs can be adjusted by altering the position of the switch 202 and its actuating arm 224 relative to the cam surface 222. This is achieved by securing the switch 202 with fasteners 226 to a pivoted switch mounting arm 228. The latter arm includes a first mounting leg 228a which is secured to a spring member 230 by means of a pair of fasteners 232 and the spring member 230 is, in turn, attached to the L-shaped bracket 206 by means of fasteners 234 so that the switch mountin arm 228 may flex or pivot with respect to the fixed, L-shaped bracket 206.

In order to control the position of the switch mounting arm 228, there is provided a manually operable cam element 236 having a peripheral cam surface 238 shaped as shown in FIG. 13. The position of the cam element 236 is adjusted by manually turning a shaft 240 journaled for rotation in the L-shaped mounting bracket 206. The switch mounting arm 228 includes a bent end or cam engaging leg 228b riding on the cam surface 238. A pair of stop surfaces 242 and 244 on the cam limit the rotation of the shaft 240, and between these stop surfaces the cam, periphery increases gradually from a minimum radius point 238a to a maximum radius point 238b.

Rotation of the cam 236 thus pivots the switch mounting arm 228 and changes the position of the switch 202 with respect to the cam surface 222. When the leg 228b is in engagement with a small radius portion of the cam surface 238, the arm 224 is moved towards the cam surface 222 and, hence, the switch 202 will be actuated when the arm 224 is engaged by a relatively small radius portion of the cam 220. Conversely, When the leg 228b engages a large radius portion of the cam surface 238, the arm 224 is moved away from the cam surface 222 and, hence, it will not be actuated until it is engaged by a' relatively large diameter portion of the cam 220.

Means to be described hereinafter are provided for actuating the motor unit 214 for a period of time depending upon time required for the copy sheet, which moves at a substantially constant speed through the machine, to pass a given point. Thus the length of time that the motor 214 is actuated depends upon the length of copy sheets fed through the machine, rather than only upon the number of copy sheets. Thus, if a long sheet or a continuous web of copy sheet material is fed through the machine, the supply of toner will not become depleted, as would be the case in prior machines.

The position of the switch actuating arm 224 with respect to the cam surface 222 will determine the proportion of time during each rotation of the cam element 220 that the switch 202 is closed. Since the toner replenisher or vibrator 198 is actuated whenever the switch 292 is closed, the amount of toner supplied to the developer elements and 192 may be adjusted for different types of copies by manual rotation of the shaft 240. If originals having a high density of image and requiring a large amount of toner are being copied, the shaft 240 may be rotated until the leg 228b lies near the point 23812 on the cam surface 238 so that a relatively large amount of toner is fed. Conversely, if the original has only sparse dark image areas, the operator may turn shaft 240 in the other direction, to decrease the portion for which switch 202 is closed for each rotation of the cam 220.

In a device constructed in accordance with the present invention, paper travels through the machine 20 at the rate of 15 feet per minute, while the motor unit 214 drives the cam 220 through a single revolution each 15 seconds. Thus it will be apparent that when sheets of ordinary 11 inch or 14 inch length are fed through the machine, several sheets will be fed before the cam 220 makes a complete revolution so that toner will not necessarily be dispensed with each passage of a copy sheet. If the machine is used to copy lengthy rolls or a continuous web of material, then cam 220 will make several consecutive revolutions. In either case, the novel control 200 will serve to maintain the supply of toner in the developer 60 at the desired level.

When the copy sheet carrying a loose powder image leaves the developer 60, its direction is reversed by means of the turnaround assembly 62. The assembly 62 includes a motor driven fan unit 248 for blowing air through a duct 250 and a nozzle 252. The stream of air emanating from the nozzle cooperates with a set of guides 254 to feed the copy sheet into the fuse'r assembly 64. A more detailed description of the apparatus for turning around the copy sheet and feeding it into the fus'er 64 may be found in the copending application of Lester R. Rabb,

Ser. No. 306,871, filed Sept. 5, 1963 and assigned to the same assignee as the'present' invention.

The fuser assembly 64 includes a housing 256 enclosing a pair of conveyor belts 258 and 260 (FIG. 2). Disposed within the fuser housing is a' heater assembly 262 including resistance heating elements 264 and 266 supported at their opposed ends by insulated mountings 268. As illustrated schematically in FIG. the resistance heating elements 264 are connected in series, as are-the elements 266 and these two groups are provided with end terminals 270 and 272 and a central terminal 274 so that the two groups can be connected either in series with one another or in parallel or, in the alternative, the group of elements 264 can be used alone. If the groups of'heating elements 264 and 266 are connected in series they act as a 600 watt heater, while if they are connected in parallel they function as a 2300watt heater for the fuser assembly 64. If the group of resistance elements 264 is used alone, they act as a 900 watt heater.

The conveyors 258 and 260 carry the exposed and developed copy sheet past the heater assembly 262 so that the loosely held powder image on the copy sheet 32 is fused into a permanent image before the sheet is-delivered to the platform and extension tray 66. Referring now to FIG. 16, the conveyor 260 comprises an endless belt having a series of continuous, longitudinally extending ridges 276 on top of which the copy sheet may rest as it is carried through the fuser assembly 64. The ridges 276 permit adequate ventilation around both surfaces of the copy sheet 32 as it is heated in the fuser, and facilitate removal of the copy sheet from the conveyor 260. As is shown in FIG. 2, a plurality of side by side fingers 278 extend into the troughs formed by the ridges 276 to pick up the copy sheet 32 as it leaves the fuser and guide it onto the receiving platform 66 and the extension tray 67.

A switching sub-assembly 280 best shown in FIGS. 4, 7 and 8 is mounted above the feeding table 28 and comprises an elongated housing 282 of generally rectangular cross-section enclosing a plurality of switching and signalling devices including a copy switch 284 and an original switch 286.

A removable cover member 287 (FIGS. 1 and 2) having a pin 287a extending from its underside is adapted to protectively fit over the copy side of the housing 280 with the pin 287a being received into the opening 289.

The original switch 286, as best shown in FIG. 3, comprises a housing 288 containing a double throw switch mechanism adapted to be closed by a switch button 290. A pivotally mounted lever arm 292 extends outwardly from the housing 282, and is adapted to be pivoted about a rocker shaft 283 by an original sheet 30 as the latter sheet passes between the rollers 118 and 120. The copy switch 284 is similar and includes a switch arm 294 (FIG. 2) which is actuated by a copy sheet 32 when the latter sheet passes between the rollers 104 and 106.

The housing 282 also contains a manually operable feeder switch 296 (FIGS. 4, 7 and 8), a safety switch 298, a switch light 300 and a relay coil 302 which actuates two sets of relay contacts 302a and 302b. The feeder switch 296 is normally left in its closed position during operation of the machine 20. However, should the operator desire to replenish the supply of copy sheets 32, opening of switch 296 will prevent the actuation of the feeder clutch 90 and the feed system 74.

In accordance with the present invention the cover member 287 is removable to facilitate construction and repair of the automatic copying machine 20. When the cover member 287 is removed, the corona discharge wires 112 and 114 of the charging assembly 52 are exposed. Since these discharge wires operate at a high voltage, danger of injury exists when they are exposed. In order to prevent this dangerous condition, the safety switch 298 is arranged so that when the cover member 287 is removed from the machine 20, the switch 298 opens, thus disconnecting the corona discharge wires 112 and 114.

Referring now to FIG. 15, a control circuit 310 is there shown for controlling the operation of the machine 20. The circuit 310 is illustrated as being segregated into three sub-circuits 312, 314 and 316. The sub-circuit 312 is connected by means of conductors 318 and a plug connector 320 (1316, 2) to a suitable source of electrical power, for example, a 230. volt, 60 cycle AC source. Sub-circuit 314 is energized via conductors 322 and 324 from a center tap 326 of a step down auto transformer 328 which supplies volts AC. The sub-circuit 316 operates from a 90 volt DC potential supplied through conductors 330 and 332 and developed by full wave bridge type rectifier 334.

The operation of the circuit 310 will now be described, assuming the machine 20 to be initially in its illustrated cool condition, such as would arise from having the machine disconnected overnight. With the plug 320 connected to a suitable outlet, the operator starts the machine 20 by turning on the main switch 34 to energize a coil 336 which closes a set of normally open main contactors 336a and 336b. It will be noted that each of the conductors 318 is connected to a fuse 338.

Closing of the contactors 336a and 336b energizes the fan motor 42, which is connected in series with a control rheostat 340 to permit the operator to control the speed of the fan. In addition, the drive motor 92 is energized, as is an exhaust motor 342, which is in series with a suitable heat responsive controlling apparatus 344. Initially, all of the relays are in the condition illustrated in FIG. 15 and, hence, when the main contactors 336a and 3361: are closed the group of series connected fuser heating elements 264 and the group of elements 266 are connected in parallel with each other to generate 2300 watts so that the fuser heater 262 will reach its operating temperature as rapidly as possible. Accordingly, the initial period of time after the machine 20 is energized in its cool condition may be termed a warm-up period, which lasts about 5 or 6 minutes and terminates when the fuser heater reaches operating temperature.

During the warm-up period, the transformer 328 energizes the sub-circuit 314 including a corona power supply 346 which supplies DC power to the upper and lower corona discharge wires 112 and 114. Power supply 346 generates a 12,000 volt DC output, so that the wires 112 and 114 may each be at a potential of either plus or minus 6,000 volts with respect to ground. Additionally, the corona power supply 346 supplies operation voltage for the developer bias corona discharge wire 182. The bias voltage supplied to the wire 182 may be adjusted by means of a manually operated multi-tap control 348, so that the amount of bias may be set to produce clear, sharp copies.

Energization of the sub-circuit 314 also supplies power to the turnaround blower motor and fan 248, as well as to the bridge rectifier 334. It will be observed that, with thecopy switch 284 open, the relay coil 302 is not energized, so that its contacts 302a and 302b are in their normal positions illustrated in FIG. 15. With the switches 284 and 286 both open, neither the copy sheet driving clutch 90 nor the original sheet brake 132 are energized. However the original sheet driving clutch is energized so that the original sheet feeding rollers 118, 120, 122 and 124 are driven.

After a period of five or six minutes has elapsed, the heat generated by the fuser heating elements 264 and 266 raises the fuser temperature to the desired operating level. When this occurs a thermally responsive switch 350 moves its contacts 351 from'the normally open position shown in FIG. 15 to the closed position, thus energizing a main power relay coil 352, which actuates the relay contacts 352a, 352b, 3520, 352d, 3522 and 352i to move each set to the position opposite from that shown in FIG. 15. It will be seen that a copy light transformer 354 connected to energize a lamp 356 has its primary winding parallel with the coil 352 so that the lamp 356 is energized to 13 signal the operator as soon as the fuser has warmed to operating temperature.

The normally closed contacts 352a of the main power relay break the circuit to the stepdown transformer 328, so that the sub-circuits 314 and 316 are deenergized. When the main power relay coil 352 is energized, contacts 352b and 352] interrupt the drive to the main drive motor 92 and the exhaust motor 342. The contacts 352:: and 352d coact with the contacts 35212 to realign the heating elements 264 and 266 so that both groups are connected in series rather than in parallel, whereby the wattage output drops to 600 watts, which is suflicient to maintain the desired operating temperature. Furthermore, the normally closed contacts 352e, when opened, interrupt the circuits to the turnaround blower motor and fan 248 and to the corona power supply 346. Thus, in accordance with an important feature of the invention, as soon as the fuser reaches operating temperature the machine 20 is automatically placed in a ready condition in which most of the circuit components are deactivated while the machine remains ready to make copies at any time. Furthermore, the lamp 356 is illuminated to indicate this ready condition to the operator.

If it is now desired to make a copy, it is only necessary to depress momentarily a start switch 357 and then to feed an original 30 manually into the machine. Depression of the start switch 357 energizes a slow to release relay 358 which opens its normally closed contacts 3580, thus deenergizing the main power relay 352. The characteristics of the relay 358 are such that it remains actuated for a period of approximately 90 seconds following release of the start switch 357. When the relay 352 is deenergized by operation of the relay 358, the contacts 352a revert to their normally closed position to energize the subcircuits 314 and 316 and to turn on the switch light 300, thereby indicating to the operator that an original may be fed into the machine. The contacts 352a revert to their normally closed position to energize the motor 248 and the power supply 346, while the contacts 35% and 352] revert to the positions shown in FIG. 15 to actuate the drive motor 92 and the exhaust motor 342. The contacts 352d return to the position shown in FIG. 15 to interrupt the circuit to the heater elements 266 while the contacts 35'2c complete a circuit to the series connected heating elements 264 to generate900 watts of heat.

When an original 30 is fed into the machine 20, it engages the actuating arm 292 to close the original switch 286 in the manner previously described, thereby breaking the circuit to the original driving clutch 130 and, at the same time, completing a circuit to energize the brake 132. The leading edge of the original sheet is thus held stationary between the inactive rollers 118 and 120 awaiting the feeding of a copy sheet from the stack within the chamber 29. The breaking of the circuit to the clutch 130 prevents driving in opposition to the holding action of the brake 132. When the switch 286 closes, the copy sheet feed clutch 90 is energized and the assembly 74 feeds a single copy sheet 32 from the top of the stack contained in the chamber 29. The copy sheet 32 advances to engage the arm 294, thereby actuating the copy switch 284 in the manner previously described. At this point the leading edges of the sheets 30 and 32 are exactly aligned and the sheets are oriented side by side within the machine in readiness for advancement at equal speed through the drive assembly 126.

Actuation of the copy switch 284 completes an energizing circuit for a relay 302 having two sets of contacts 302a and 302b, one set 3021) of which interrupts the circuit to the brake 132 while the other set 302a completes a circuit to energize the original driving clutch 130. The original sheet 30 is thus advanced along the plate 134 in synchronization with the movement of the copy sheet through the charging assembly 52 and the exposure area 54. Contacts 30% also break the energizing circuit for the copy sheet feed clutch 90 so that the copy sheet feeding apparatus 74 is dormant until another original is subsequently fed to the rollers 118 and 120. In addition, a counter circuit 360 for registering the number of copies made is actuated when the copy sheet closes the switch 284.

Furthermore, closure of the switch 284 by the copy sheet completes a circuit for energizing a relay coil 362 having two sets of contacts 362a and 362b. The contacts 362b supply power to the toner dispensing control unit 200, so that the output shaft 218 (FIG. 11) of the motor unit 214 begins to rotate. As described above, since motor 214 is actuated while the copy sheet is in contact with the arm 294, toner will be dispensed by the control 200 as a function of copy sheet length fed through the machine 20.

A rectifier 199 connected in series with the vibrator 198 provides half wave rectification to supply a unidirectional voltage of proper polarity to operate the vibrator. In addition, a manually operable push button switch 246 is provided to permit the operator to energize the vibrator independently of the control unit 200 for the purpose of adding additional toner to the developer elements 190 and 192 whenever desired. As was indicated above, the rheostat 204 connected in series with the vibrator may be manipulated to adjust the amplitude of the vibrations. In a machine constructed in accordance with the invention, the output shaft 218 of the motor and gear unit 214 turned at the rate of one revolution each 15 seconds, while paper travelled through the machine at a speed of 15 feet per minute.

The contacts 362a of the relay 362, which is actuated by entry of a copy sheet into the machine, complete a circuit for energizing a relay 364 having two sets of contacts 364a and 364b located in a circuit for controlling operation of the lamp 142. With the normally open contacts 364a and 364b both closed the lamp 142 is obviously energized. In the illustrated embodiment, the lamp 142 is rated at 1500 watts, and is in series with an eight ampere fuse 366.

After the copy sheet passes through the second pair of copy sheet feed rollers 108 and 110, it engages and closes a switch 368 (FIGS. 2 and 15) disposed in advance of the guides 58. This switch maintains the relay 364 energized after the copy sheet releases the switch 284, so that the lamp 142 remains on until the trailing edge of the copy sheet has passed through the exposure area 54. When the trailing edge of the copy sheet moves past the switch 284 the relay 362 is obviously deenergized to break the circuit to the relay 364 and also to break the circuit to the control unit 200; With the relay contacts 362a and 362b open, it is apparent that the circuit for energizing the lamp 142 is broken as soon as the trailing edge of the copy sheet moves beyond the switch 368 and, as a consequence, the lamp 142 is deenergized until another copy sheet is subsequently advanced.

It will be recalled that the relay 358 is of the slow to release type and remains energized for a second delay period. The switch light 300, which is off while the copy switch 284 is closed, is illuminated when the copy sheet passes the switch 284, and it remains illuminated for several seconds thereafter or, more specifically, until the relay 358 returns the machine 20 to the ready condition described above. However, another copy may be made as soon as the switch light 300 is illuminated and without waiting for the end of the delay period of the relay 358.

If another original is fed into the machine before the relay 358 is released, it will close the original switch 286, and the above described steps will be repeated. Each time an original is fed the relay 3 58 is reset for a new 90 second release period by current flow through the normally closed contacts 352e, through the contacts 364b when the relay 364 is energized and through the start switch 357 with the latter in its original or nonoperated position.

If the supply of copy sheets 32 in the chamber 29 becomes exhausted, -a load switch 370 mounted with the chamber 29 as shown in FIG. 4 is automatically closed. The switch 370 is positioned adjacent one of the plates 79 and includes a switch actuating lever 371 which is depressed when the shaft 78 drops within the guide slots 79a to a predetermined or lower-most position. Closing of the switch 370, as shown in FIG. 15, completes a circuit for actuating a relay 372 having two sets of normally closed contacts 372a and 372b, one set 372a of which, when opened, interrupts the circuit to the copy sheet feed clutch 90 while the other set 372b, when opened, breaks the circuit to the switch light 300 so that the operator is informed of the shortage of sheets.

Thus, in accordance with the invention, there is provided a novel circuit arrangement whereby the temperature of the fuser or heater is quickly raised and is then held in a ready condition until use. A push button switch conditions the machine to make a single copy automatically of an original fed to the machine, during a 90 second operating cycle at the close of which the machine re turns automatically to the ready condition.

Although the present invention has been described with reference to an illustrative embodiment thereof, it should be understood that numerous other modifications and changes will readily occur to those skilled in the art and it is therefore intended by the appended claims to cover all such modifications and changes that will fall wihin the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A fusing apparatus for heating a powder image on a copy sheet as it moves through an automatic copying machine of the type including means for moving a copy sheet through the machine, said apparatus comprising first and second heating means disposed adjacent the path of the copy sheet, a first circuit operative upon start-up of the machine after a period of non-use to connect said first and second heating means in parallel to heat said fuser rapidly to a predetermined temperature sufiicient to bond a powder image to a copy sheet and insuflicient to char a copy sheet, thermally responsive means operative when said predetermined temperature is reached for connecting said first and second heating means in series to generate heat for maintaining said machine in a ready condition, switch means for conditioning the machine for copy making operation, first means operative in response to operation of said switch means for energizing only said first heating means to generate heat for fusing the powder, and second means operative in response to operation of said switch means to return said machine to the ready condition a predetermined time after the powder is fused.

2. A fusing apparatus for heating a powder image on a copy sheet as it moves through an automatic copying machine of the type including means for moving a copy sheet through the machine, said apparatus comprising first and second heating means disposed adjacent the path of the copy sheet, a first circuit operative upon start-up of the machine after a period of non-use to connect said first and second heating means in parallel to heat said fuser rapidly to a predetermined temperature suflicient to bond a powder image to a copy sheet and insulficient to char a copy sheet, thermally responsive means operative when said predetermined temperature is reached for connecting said first and second heating means in series to generate heat for maintaining said machine in a ready condition, switch means for conditioning the machine for copy making operation, and means operative in response to operation of said switch means for energizing only said MI, a 3 firstheating means to generate heat for fusing the powder.

3. A fusing apparatus for heating a powder image on a copy sheet as it moves through an automatic copying machine of the type including means for moving a copy sheet through the. machine, said..apparatus comprising first and second heating means .disposed adjacent the path of the copy sheet,. a first circuit operative upon start-up of the machine after a period of non-use to connect said first and second heating means in parallel to heatsaid fuserrapidly to a predetermined temperature sufficient to bond a powder image to a copy sheet and insufficient to char a copy sheet, thermally responsive means operative when said predetermined temperature is reached for connecting said first and second heating means inse'ries to generate heat for maintaining said machine in a ready condition, switch means for conditioning the machine for copy making operation, means operative inresponse to operation of said switch means for energizing only said first heating means to generate heat for heating 'the powder, and means including .a' timedelay relay energized 'by operation of said switch means for returning said machine to the ready condition a predetermined time after the powder is fused.

4. A fuser for heating a developed image on a copy sheet movingthrough an automatic copying machine comprising: i

a pair of power supply terminals;

first and second electric resistance heating means;

a first circuit normally connecting said first and second heating means in parallel circuit relation between said supply terminals for generating heat at a high rate for heating the fuser to. an operating temperature;

thermaly responsive means disposed in heat sensing relation to the fuser for sensing the temperatureof the fuser;

and a second circuit controlled by said thermally responsive means for connecting said first and second heating means-in series circuit relation between said power supply terminals for generating heat at a low rate after the operating temperature is attained.

5. The fuser of claim 4 further comprising:

control means operable upon travel of a copy shee through the machine,

and a third circuit operable during operation of said control means for connecting said first heating means between said supply terminals and for deenergizing said second heating means to generate heat at an intermediate rate during passage of a copy sheet through the machine.

6. The fuser of claim 5- further comprising timing means for discontinuing the operation of said control means a predetermined time after travel of a copy sheet through the machine.

References Cited UNITED STATES PATENTS 2,357,889 9/ 1944 Carlson l.7 2,688,281 9/1954 Bornemann 95-89 3,053,962 9/ 1962 Cerasani 219388 3,181,420 5/ 1965 Rautbord' 88*24 3,187,162 6/1965 Hojo '219- 388 3,219,799 11/1965 Trumbull 219-388 3,079,483 2/1963 'Codichini et a1. 219-388 3,298,495 l/ 1967 Acton 19816 3,315,777 4/1967 Margles 198 -16 RICHARD M. WOOD, Primary Examiner. C. L. ALBRITTON, Assistant Examiner.

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