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Publication numberUS3698706 A
Publication typeGrant
Publication dateOct 17, 1972
Filing dateFeb 24, 1971
Priority dateFeb 24, 1971
Publication numberUS 3698706 A, US 3698706A, US-A-3698706, US3698706 A, US3698706A
InventorsAlbin F Berggren Jr, Ronald A Glaser, Steven Mihojevich, Ralph G Ostensen, Arthur S Zerfans
Original AssigneeScm Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrostatic printer
US 3698706 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent Mihojevich et a1. 1 1 Oct. 17, 1972 [54] ELECTROSTATIC PRINTER [56] References Cited [72] Inventors: Steven Mihojevich, Northbrook; UNITED STATES PATENTS rf Elk h Arthur 8 2,295,055 9/1942 Rupp et a1. ..271/9 x G. Ostensen, Morton Grove, Albin F B D Pl 2,536,356 1/1951 Dager ..271/9 X es 3,273,883 9/1966 Baronnie ..271/9 Glaser Arlmgmn 2,235,844 3/1941 Nelson ..271/41 of Ill.

Primary Examiner-Joseph Wegbreit [73] Assignee: SCM Corpor ion Attorney-Pennie, Edmonds, Morton, Taylor and 221 1 11611; Feb. 24, 1971 Adams [211 App]. No.: 118,486 [57] ABSTRACT An electrostatic printing machine having an exposure Related US A li afl n Data station and an imaging station, and having copy sheet supply means for the storage of photoductive copy Contlnuatlon of 821517, sheets, means for moving a copy sheet from said 1968, abandoned, which is a division of Ser. ppl means and past the imaging station, and No. 463,071, June 1 l, 1965, Pat. No. vacuum means for holding the copy sheet at the image 3,416,860. station. The machine includes stop means for uncoupling drive means, and brake means for stopping the movement of the means for moving the copy sheet [52] U.S. Cl. ..27l/9, 271/46, 271/74 past the imaging station. The machine also has a [51 Int. Cl. ..B65h 5/02 rality of copy paper sheet magazines frgm whieh copy [58] Field of Search ..27l/9, 46, 74 sheets may be selectively supplied.

10 Claims, 13 Drawing Figures PATENTEDBEI 17 I972 SHEET 1 BF 4 ZERFAHQ RALPH a. OSTE N5EN H Mm Wu 3 m ARTHUR 5.




GrL ASER INVENTORS ELECTROSTATIC PRINTER This application is a continuation of copending US application Ser. No. 821,517, Oct. 7, 1968, now abandoned which in turn is a division of copending U.S. application Ser. No. 463,07l,filed June 11, 1965 Pat. No. 3 ,4 I 6,860 for Electrostatic Printer.

This invention relates to photocopy apparatus of the electrostatic type. More particularly it refers to a type of photocopy apparatus wherein an object desired to be copied may be positioned at a fixed station and the reflected image of the object is projected onto a charged photoconductive surface.

In the electrostatic photocopy system used by this invention a uniform electrostatic charge is first applied to a paper copy sheet having a photoconductive surface. The image of the subject matter desired to be copied is then projected on to the charged photoconductive surface, selectively discharging the electrostatic charge and reproducing the image in latent form on the photoconductive surface. Areas of the sheet corresponding to areas of the original subject matter having intermediate shade will retain varying proportions of the original charge. The latent electrostatic image is then developed by applying to the photoconductive surface of the copy paper colored particles having a charge opposite in polarity to the charge on the copy paper surface, so that the particles are attracted to the charged portions of the latent image to produce a visible image the substantial duplicate of the original. Finally, this visible image is fixed to the paper surface by heat or other suitable means.

Previously, electrostatic photocopies using a photoconductive copy sheet have transported both the original document to be copied and the copy sheet simultaneously past object and image windows, respectively, in a projection station whereby the document is illuminated and projected line by line on to the copy sheet. Such an apparatus is described in US. patent application Ser. No. 249,248 Photocopy Apparatus, filed Jan. 3, 1963 now abandoned, by Ralph G. Ostensen, and assigned to the assignee of this invention. In such an apparatus the movement of the original document and the copy sheet must be carefully synchronized. Moreover, the original matter to be copied must be a thin, flexible document capable of passing through a conveyor belt or roller assembly transport mechanism. This narrows the potential application of such an apparatus, notably eliminating the copying of bound books or bulky periodicals.

The present invention provides an electrostatic photocopier which projects the complete image of the original subject matter on to the surface of a copy sheet at one time, rather than line by line as in the previous apparatus. By projecting an entire image at one time the subject document and the copy sheet may be held stationary, and complex synchronization problems are eliminated. Since the subject document is not moved during the copying it need not be of any particular form or thickness necessary to pass through rollers or the like; books or other bulky material may be readily copied.

The invention further provides means for holding a coated copy sheet in a stationary imaging position to receive the entire projected image at one time with no image shielding projection on or in contact with the coated surface of the copy sheet. A vacuum belt transport system is arranged to transport the coated copy sheet through a portion of the copy machine on perforated belts without contacting the coated surface of the sheet. Means for stopping and starting the perforated belts at predetermined positions while the copy sheet remains attached to the belts are also included.

To prevent lateral misregistration of the copy sheet on the perforated belts tracking and centering means are provided to retain the belts at a spaced distance apart from one another. A backing member for the perforated belts, including a vacuum platen having an air exhausting mechanism and having openings in one wall of the platen which may register with the openings in the perforated belts to provide a pressure differential, serves to secure the copy sheet to the front surface of the belts.

Means for aligning the edges of the copy sheet with the image of the edges of the object to be copied are'included in the copying machine. A plurality of feed magazines to store and selectively distribute various sizes of copy sheets for use in the copying cycle are provided. Adjustable guides are arranged in the magazines for properly positioning the various widths of copy sheets, and, in particular, one guide in each magazine has two alternate fixed positions while the other guide is adjustable with respect to either of the two fixed positions so as to fix the position of one side edge of the copy sheet relative to the machine.

The magazines are equipped with support means under the copy sheet stacks to centrally engage the underside of each stack near its leading edge to prevent or inhibit sagging due to the side edges of the stack being raised slightly by the guides.

Means are provided for sensing the level or number of copy sheets in each magazine and for giving a sensible signal when the supply in a magazine is exhausted. Also provided are means for selecting and activating a feed mechanism in one or another of the magazines, and means to prevent activation of the feed mechanism in a particular magazine if the supply of copy sheets in that magazine is exhausted.

Other and more specific objects of this invention will become more fully apparent from the following description and appended claims as illustrated by the drawings in which FIG. 1 is a perspective view of the electrostatic printer showing exposure window and copy sheet magazine covers raised;

FIG. 2 is an enlarged fragmentary view of the exposure window cover mounting mechanism;

FIG. 3 is an enlarged and partially cut away perspective view of the vacuum conveyor belt assembly including the braking mechanism utilized in stopping the conveyor;

FIG. 4 is a top view of the belt tensioning roller and counterweight;

FIG. 5 is a side view of the belt tensioning roller and counterweight;

FIG. 6 is a sectional view of the printer shown in FIG. 1 substantially along lines 6-6;

FIG. 7 is a perspective view of the paper magazine tray;

FIG. 8 is an enlarged fragmentary cutaway view showing the mounting of the support buttons in the magazine tray;

FIG. 9 is an enlarged fragmentary side view of the handle showing its mounting to the siderail;

FIG. 10 is an enlarged, partially cutaway sectional view of the retention mechanism beneath the right hand side rail of FIG. 7;

FIG. 11 is a partially sectioned side view of the right hand side rail and bail in FIG. 7 showing the handle in its arm lowering position;

FIG. 12 is a partially sectioned side view of the left hand side rail of FIG. 10 showing the handle in its arm raising position;

FIG. 13 is an enlarged view of the friction brake mechanism which is located beneath the left hand side rail in FIG. 7.

SUMMARY DESCRIPTION Referring now to FIG. 6, the electrostatic printing machine of the present invention functions as follows:

A document 4 is placed on a window 6 covered with a transparent material such as glass which forms the top wall of a raised box-like portion 8 located on the topside of machine housing 2.

The window 6 and document 4 thereon are illuminated by reflector lamp assemblies 10 which are mounted in pairs on the side walls of the housing adjacent portion 8.

The illuminated image of document 4 is reflected by an adjustable mirror 12 into a lens 14. Mirror 12 and lens 14 are mounted on a frame 16 which is in turn adjustably carried by the housing 2. The image is projected by lens 14 onto an electrostatically charged sheet of photoconductive copy paper 18, held to vacuum platen 140. As the image strikes the copy paper, the charge on the latter is reduced by an amount corresponding to the intensity of the image. Dark portions of the image affect the copy paper while light areas of the reflected image may have sufficient light intensity as to almost completely release the latent electrostatic charge on the paper.

The copy paper is stored in a paper supply compartment 22 containing two paper feed trays 24a and 24b. The paper feed trays are constructed to receive varying widths and lengths of copy paper, allowing the operator the flexibility of choosing from one of two sizes stored in the magazine as for example 8 as by 11 inch sheets in one tray and 8 by 14 inch in the other.

The copy paper is fed to a corona charging unit 26 by either feed roller 280 or 28b depending upon which feed tray has been selected for use by the operator. The actual selection of the feed tray is accomplished by the actuation of a selector switch which feeds power to one or the other of the drive mechanism powering feed rollers 28a and 28b. Corona unit 26 imparts an electrostatic charge to the photosensitive surface of the copy paper of approximately 400 volts.

After passing through corona unit 26, the copy paper is transported by perforated conveyor belts 30 over vacuum platen 140 to a predetermined point. At this predetermined point the conveyor belts are stopped and the image, previously alluded to, is projected onto the copy paper.

The reflector lamp assemblies illuminate the glass window 6 on a timed basis. At the end of the timing period the conveyor belts are reactivated, causing the copy paper to pass between pivoting guides 226 and 228 into a developer station 32 via rollers 202 and 204.

The developer station 32 may be of any well known type, but in this instance the paper passes through a pool of liquid developer containing positively charged particles which are attracted to the charged portions of the paper to develop the latent electrostatic image which has been placed thereon.

After passing through the developer station the copy paper is carried by a conveyor belt 34 beneath heat lamps 38a and 38b which remove any excess moisture from the copy paper, and to an exit tray 36 (FIG. I

DETAILED DESCRIPTION As is best seen in FIGS. .1 and 6, housing 2 has a base 38, a pair of supporting side walls 40 extending upwardly from the base, a front wall 42, and a rear wall 44. Housing 2, as shown in FIG. 1 may be provided with removable side panels 46, which shield the functional side walls 40 for ornamental purposes.

The top side of housing 2 has raised box-like portion 8 having a window 6 covered by a transparent material such as glass. Flexible cover member 60 formed of an opaque material is hinged to box 8 and acts as a protective cover for window 6 when the machine is not in use, and also may be used to retain a document on the window 6. When a large document surface is placed against window 6, however, it is advantageous to fold back cover 60 to a fully open position. To insure a completely flat contact between a large document surface and window 6, the hinging arrangement shown in FIG. 2 is utilized. A side portion of box 8 is notched along most of its length, and a rod 66 fastened at both ends to box 8 is carried in this notch. Cover member 60 has a reinforced portion 64 having a molded groove 68 running its entire length. Cover 60 is mounted onto box 8 by forcing rod 66 into groove 68. By positioning rod 66 a spaced distance below the plane of the top window surface 6, cover 60 when folded open will be entirely below said window surface plane, thus removing one cause of possible aberration in the optical system of the machine.

PAPER FEED MECHANISM A hinged door 70 in the topside of housing 2 as shown in FIG. 1 covers a copy sheet supply compartment 22, wherein copy sheets having a photoconductive zinc oxide layer thereon may be stored for use in the machine. Compartment 22 houses a pair of removable paper supply trays 24a and 24b which may be of identical construction as shown in FIGS. 7 to 13. Trays 24a and 24b comprise flat sheet metal plate members 74 having turned down lips 76. The trays are mounted one above the other in the supply compartment by suitable brackets (not shown) to allow easy removal for loading purposes. In this connection, it should be observed that the lower tray may be mounted to the brackets in a more permanent manner, as only the top tray is removed in the paper loading operation so as to permit access to the lower tray.

As shown in FIG. 7 plate member 74 has a pair of upright paper guides 78 slidably mounted thereon to accommodate different widths of paper.

Each guide 78 basically comprises a piece of angle stock having a depending U-shaped foot 80 fastened to the underside edge. Foot 80 protrudes through a cutaway portion or slot 82 which extends substantially across the entire width of plate 74. A rod 84, carried by two tabs (not shown) is inserted through a hole 86 and is positioned centrally in slot 82 below the level of plate 74. Foot ends 800 and 80b each have a hole therein through which rod 84 is positioned so as to slidingly hold foot 80 to the rod.

As best seen in FIGS. 12 and 13 a friction brake 88 is also provided to inhibit but not prevent sliding movement of guide 78.

Brake 88 comprises a shoe 94 having a rounded slot for engagement with rod 84 and a spring 96 which is carried between shoe 94 and a lip 98 on foot 80. Spring 96 then urges shoe 94 against the rod providing the desired braking.

Although both guides can be constructed as described, the preferred embodiment adds a retention mechanism 90 to one guide so as to releasably fix it in one of two given positions with respect to the optical system in the machine so as to provide proper registration between the side edge of a document and its projected image on the copy paper respectively as will presently be described. As best seen in FIGS. and 11, an angle bracket 91 has two notches 93a and 93b which alternately engage one or the other foot ends 80a or 80b. Spring notches 93a and 93b hold the guide 78 fairly immobile in either position yet do allow the guide to be moved to the other position by exerting sufficient force. The bracket 91, however acts as a stop to prevent the guide from moving any further in either direction.

Thus the guide 78 in FIG. 10 is set in a first position for ordinary copy sheets, and then adjusted to a second position when running paper master copy sheets (utilized in offset printing) where a wider margin is desirable. In either of the two positions a stack of copy sheets may be placed against the guide and the opposite guide not so retained may be slidably adjusted to engage the opposite edge of the stack, regardless of the copy sheet width. In the preferred embodiment this adjustment is limited to a minimum proper width of 3 inches and a maximum of 10 inches for practical purposes.

Each guide 78 carries an arm 100 pivotally mounted to the guide 78 on a shaft 102. A snap ring 101 on shaft 102 retains the arm to the shaft 102 without impairing pivotal movement thereon. Arm 100 is formed with a turned-down front portion 104 which extends downwardly from the arm to slightly overhang the front of plate member 74 and guide 78 so as to act as a front stop for the paper stack as it is loaded into the tray.

Adjacent portion 104 on arm 100 is a finger member 106 positioned to overlie the corner edge of the paper stack. Finger members 106 assist the feed rollers 28 in guiding a sheet of paper into the feed system without accidentally carrying the underlying sheets with it.

Obviously, with finger member 106 resting on the paper stack in normal operation, the arm must be raised slightly when a fresh stack of paper is placed in the tray. This can be manually accomplished by grasping the arm and raising it. Each shaft 102 also carries a handle 1 10 which acts to releasably hold arm 100 in an upright position during loading in a manner which will now be described.

Handle 110 is rotatably carried on shaft 102 but as shown in FIG. 9 its rotation is inhibited by a spring 103 which bears on a retaining nut attached to the end of shaft 102. Spring 103 then urges the leg portion of handle against retaining ring 101. Any rotation of handle 110 must be against the frictional drag developed between the handle 110 and the retaining ring.

I-Iandle 110 is formed with projecting lugs 107 and 108 which act as stops to limit the rotation of the handle 110. As best seen in FIG. 11 lug 108 engages an ear 109 or guide 78 when handle 110 is rotated clockwise toward the front of tray 74.

When the handle 110 is rotated counter-clockwise as shown in FIG. 12 lug 107 engages a rearward projection 100a of arm 100 and further rotation pivots the front of the arm, including front portion 107, upwardly. Spring 103, as previously described, acts to inhibit rotation of the handle 110, therefore the arm 100 remains in an upward position. When both arms have been so raised a new supply of copy sheets may be placed in the tray and the arms lowered again by rotating the handles 1 10 forward again as shown in FIG. 1 1.

Due to the thickness of the bottom portion of the guide members, the center of the paper stack may tend to bow somewhat, causing feeding problems. As can be seen in FIGS. 7 and 8 buttons 111 protruding through openings in plate 74 are spring biased to lightly engage the underside of the paper stack to inhibit such bowing.

A collar of shoulder 113 formed on button 111 below a hemispherical surface 112 is of a larger diameter than the opening in plate 74 so as to engage the underside of the plate and act as a stop for the upward movement of the button. A spring 114 resting on a flange 115 formed on the side of lip 76 biases the button upwardly toward the stop position.

The hemispherical surface 112 acts as a cam to urge the button 111 below the surface of the plate against the spring bias when the guide 78 passes over the button 111. Thus, freedom of adjustment of the guides is not sacrificed by the presence of the buttons.

Returning now to feed rollers 28a and 28b, square drive shafts 29a and 29b are employed to respectively mount the rollers 28a and 28b for rotational motion yet allowing lateral adjustment of the rollers 28a and 28b on the shafts. Rollers 28a and 28b may be spring loaded to the shaft to prevent unwanted sliding. A suitable drive mechanism can be employed to impart rotation to the shaft such as that described in US. application, Ser. No. 249,248, now abandoned. In the present invention, two such drive mechanisms are used (one for each tray). Additionally, in each tray a feeler arm 118 (FIG. 6) operationally attached to switches 116A or 1163 is provided to sense depletion of the paper stack. Actuation of switch 116A or 1168 upon depletion of the paper causes a visible signal to appear in indicator lamp 516 of Add Paper or the like. Additionally, through circuitry, described in U.S. Pat. No. 3,416,860, issued Dec. 17, 1968, which is incorporated herein, the particular drive mechanism becomes disabled until the paper supply is replenished.

As in application Ser. No. 249,248, now abandoned referred to, an electro-magnetic clutch is driven through a gear and chain drive which likewise powers the other elements in the feed train to be described. It should be understood that the aforesaid drive mechanism, which performs a critical synchronization function when image projection is done with both document and copy paper moving, is not as critical in this invention because the image projection is done when both subject matter and copy paper are in nonmoving positions.

The copy paper, fed by either feed rollers 28a or 28b, is urged toward a throat formed by rollers 120 and 122. Roller 120 has a fairly large diameter and therefore can function also as a guide for changing the direction of the paper travel. This is accomplished in cooperation with a curved guide 126 which is located immediately beyond roller 122. Guide 126 is shaped to approximately the same radius of curvature as roller 120 to allow smooth transit of the paper therebetween.

The throat or bite of rollers 120 and 122 is vertically positioned so as to operate equally well with copy paper fed to it from either tray. In this connection also, the large diameter of roller 120 is of assistance.

Immediately adjacent guide 126, roller 124 is positioned to receive the copy paper and in cooperation with roller 120, urge the paper toward the corona charging station 26.

As the paper passes between guide 126 and roller 120, a trip lever 128 is engaged by the paper edge, which in turn, operates a switch 130. Switch 130, among other things, actuates circuitry to turn on the corona charging unit 26.

Corona charging unit 26 as best seen in FIG. 6 comprises a pair of rectangular shields 27 each housing a set of very small diameter corona wires 25, so named because of the corona discharge created when a voltage in the order of 4 to 8 kilovolts is applied to them. For a more complete description of the construction and operation of such a unit attention is again invited to application Ser. No. 249,248, now abandoned. The copy sheet passes between the sets of wires and its photosensitive surface becomes negatively charged by the corona ion cloud therein.

VACUUM CONVEYOR SYSTEM After passing through the corona charging unit 26, the copy sheet is picked up and transported by perforated conveyor belts 30. Referring to FIGS. 3 5, it will be seen that three such belts are carried side by side between top roller 132 and bottom roller 134. The belts may be constructed of Mylar or similar material, the main requirements being flexibility and strength. As can be seen in FIG. 3, the belts are perforated by many small, closely spaced holes 136 to allow air to pass therethrough.

Between the two portions of the belt loops, a rectangular vacuum platen or chamber 140 having a series of oval openings 142 on its front surface, cooperates with the perforations 136 in the belts 30. Platen 140 is formed as a shallow box having an exhaust or vacuum fan 144 connected thereto.

Air is drawn in through the belt holes 136, the platen openings 142, and travels through the platen 140 to fan 144. Appropriate baffling (not shown) within the platen 140 insures an even flow of air through all the openings.

The copy sheet, upon reaching the belts 30, is drawn and held to the belts 30 by the pressure differential developed across the belt 30 as the air is pulled into the platen 140 through the perforated openings.

Returning now to the mounting of the belts 30, a tensioning roller system is located behind the platen 140, acting to provide tension on the belts 30 and to aid in proper tracking of the belts 30 and to prevent lateral wander. This is of particular importance in the machine of this invention because any lateral travel of the belts could also shift the copy sheet, causing misregistration as the image of the document is projected thereupon.

An idler roller 146 is therefore provided which extends through the beltss loops bowing them outwardly. Roller 146 is carried by sidewalls 40 of housing 2 in similar fashion to rollers 132 and 134. Counterweighted rollers 152 are provided for each belt 30, and as best seen in FIG. 4 engages the center of each belt 30. The axial roundedness of roller 152, together with its central engagement of the beit 30 causes a lateral bowing of the belt 30 which, it has been found, acts to prevent lateral wander of the belt 30. In this connection it should be noted that upper roller 132 can also be provided with rounded or crowned portions to centrally engage each belt if necessary.

Weighted roller 152 is carried by a bracket 154, which has attached thereto at its opposite extremity a weight 156 which comprises a group of weights having various masses. Bracket 154 is in turn pivotally attached at 158 to rod 160, which is horizontally carried between sidewalls 40. Each belt 30 is provided with such a weighted roller assembly and the weight on each can be adjusted by varying the number of weights used for maximum results.

In addition to the tracking or anti-wander effect of the weighted roller 1S2, circular separators or spacers 167 are provided between the belts 30 and secured in any suitable manner on bottom roller 134 of the conveyor belt assembly. Spacers 167 are of a diameter to protrude beyond the belts 30 and thereby provide rounded protrusions at the bottom of the conveyor belt assembly which perform a primary function as copy sheet removal members. Thus the moving copy sheet upon reaching the separators is carried away from the belts and the pressure differential effects of the perforations therein.

Still referring to FIG. 3, a trip lever 162 is shown projecting between the belts 30 at a point below the bottom of the platen 140 and is attached to an electrical switch mechanism 164. When a copy sheet traveling with the belts 30 reaches this point, lever 162 is carried by the sheet to a switch tripping position (not shown). At this point, switch 164 is actuated, causing, through an electrical circuit described in [1.8. Pat. 3,416,860, issued Dec. 17, 1968 the conveyor belts to stop. The alluded to circuitry controls an electromagnetic clutch (not shown) which provides driving power to upper roller 132 from the gear and chain drive mechanism of application Ser. No. 249,248, now abandoned, previously referred to. Thus, engagement of the trip lever deactivates the drive train to the conveyor. In this connection, still referring to FIG. 3, it should be noted that switch mechanism 164 is mounted to an adjustable bracket 166 which is in turn mounted to sidewall 40 by bolts 168 carried in slots 170 in the sidewall. The The bracket 166, switch 164 and lever 162 can thus be vertically adjusted so as to engage the copy sheet at different points. The adjustment, which need only be made upon initial construction, serves to locate the bottom edge of the copy sheet with respect to the projected image. This relationship can be readily appreciated by referring to the projected images shown in FIG. 20 of U.S. Pat. No. 3,416,860. As shown in that figure, the front edge 200a of the exposure window 6 and document 4 thereon becomes, due to the optical system, edge 200 b on the copy sheet. If the sheet has progressed beyond this point, the projected image will be spaced from the edge of the copy sheet. If the document and copy sheet are of identical size, the opposite edge of the document will be projected beyond the corresponding opposite edge of the copy sheet. The registration between document and copy sheet thus plays an important role in proper performance.

In this same connection it should be noted that the side edge 201a of exposure window 6 and document 4 are projected onto the copy sheet at 201b due to the optical reversal. Positioning of the copy sheet at 201b is accomplished by proper setting of the side rail 100 or guide retention mechanism previously described.

While the initial adjustment of the position of trip lever 162 to a large extent controls the vertical registration, there still exists the possibility of slight overrun due to the momentum of the rollers and belts. For this reason, an additional registration safeguard is built into the system in the form of a brake mechanism.

Referring again to FIG. 3, it will be seen that upper roller 132 carries a large disc 172 on one end. A brake band 174, wrapped around the disc has a first end 180 attached to a lever 182 by pin 184. Lever 182 in turn is pivotally attached to sidewall 40 by a pin 186 at 190. The other end of the brake band 188 is likewise attached to sidewall 40 by pin 186. A spring 176, attached to lever 182 and to a bracket 192 mounted to sidewall 40, urges lever 182 downward, carrying brake band end 180 with lever, to effect a braking action against the periphery of disc 172. The normal position of the mechanism is therefore in a braking position.

To release the brake mechanism described, a solenoid 194, mounted to sidewall 40 adjacent bracket 192, has a plunger 196 attached to the end of lever 182 at pivot point 198.

Under normal conditions, the spring 176 pulling lever 182 downwardly also carries plunger 196 with it. When solenoid 194 is activated, the plunger and lever are raised, overcoming the spring 176 and causing the brake band 174 to release.

The activation of solenoid 194 is accomplished simultaneously with energization of the electromagnetic clutch on the conveyor belt by electrically wiring the solenoid and clutch in parallel. Thus, the copy sheet in tripping lever 162 not only shuts off the driving means for the conveyor belt, but causes the belt to instantly stop by application of the brake mechanism 174 to roller 132.

The copy sheet, after contacting lever 162, is held to the belts 30 in a stationary position. The image of the document to be copied is then projected onto the copy sheet for a fixed increment of time sufficient to selectively discharge the areas of the copy sheet corresponding to the lighter areas of the document, leaving a charge pattern on the photoconductive surface of the copy sheet as is well known in the field of electrophotography.

After the image exposure period, the conveyor belts 30 are reactivated and the brake 174 released, allowing the copy sheet to pass beyond the trip lever 162 and be engaged by the spacers 162. As previously described, the spacers 167 now assist in removing the sheet from the influence of the pressure differential of the perforated belts 30 and vacuum platen 140.

The copy sheet next passes to the developer station 32 (FIGS. 6 and) which comprises a pair of entrance rollers 202 and 204. Upper roller 202 may be a steel roller carried by the sidewalls 40 through insulated bearings. Lower roller 204 may have a rubber surface to provide good frictional contact with the copy sheet for driving purposes.

Beyond the entrance rollers in the developer station, the copy sheet passes through a pool of liquid developer containing positively charged colored particles which are attracted to the remaining negatively charged portions of the copy sheet corresponding to the dark portions of the image which has been projected thereon.

After passing through the pool of liquid developer, the copy sheet is engaged by a second set of rollers 206 and 208 which not only serve to propel the developed copy sheet onward in the feed train, but also perform a wringer or squeegee function. The copy sheet, as it emerges from the pool of liquid developer, has a film of liquid adhering to its surface. Since it is desirous to have a dry copy sheet as the final product of the machine, this wet film must be removed. Rollers 206 and 208 serve to remove most of this liquid film.

As with entrance rollers 202 and 204, the exit rollers may comprise an upper steel roller 206 and a lower rubber roller 208. In the preferred embodiment, the upper steel roller 206 is electrically grounded to the housing while the lower roller 208 is insulated therefrom by insulated bearings. Both rollers 206 and 208 are carried by the sidewalls 40 in similar fashion to rollers 202 and 204.

After passing through exit rollers 206 and 208, the carrier sheet is picked up by a conveyor belt 34 and delivered to exit tray 36. Conveyor belt 34 comprises a pair of rollers 210 and 212 journaled in appropriate bearings in sidewalls 40 and having a series of spaced apart cords or bands 214 which can be of an elastic type material. The conveyor belt 34 is powered through an appropriate spur gear (not shown) to the drive chain previously referred to.

Positioned above the conveyor 34 are a pair of heat lamps 38a and 38b. Any moisture remaining on the copy sheet is removed by the heat lamps, in conjunction with a fan 220 which circulates the warm air above and beneath the copy sheet between the spaced apart cords.

The foregoing description and drawings should be considered as illustrative of preferred embodiments and that changes and modifications may be made without departing from the scope of the invention as measured by the appended claims.

What is claimed is:

1. In a photocopying machine having an imaging station for exposing a light-sensitive copy sheet to a projected image while the copy sheet is maintained stationary, the combination comprising endless belt means for carrying a light-sensitive copy sheet past the f imaging station, mounting means for mounting said endless belt means for movement in a substantially straight line past the imaging station, said mounting means including two spaced shaft means rotatably supported in spaced apart relation and parallel to each other, drive means releasably coupled to one of said shaft means for driving said shaft means to move said endless belt means past the imaging station, means to impart a pressure differential onto the light-sensitive copy sheet being transported past the imaging station to hold the copy sheet on said endless belt means, stop means adjacent said endless belt means and operable in response to engagement by the copy sheet at the imaging station for releasing the coupling of said drive means to said shaft means, and brake means operable on one of said shaft means in response to the operation of said stop means for stopping the movement of said endless belt means past the imaging station to accurately position a copy sheet at the imaging station.

2. A photocopying machine according to claim 1, wherein said means to impart a pressure differential onto the light-sensitive copy sheet comprises means defining a vacuum chamber located between said spaced shaft means and inside the endless belt means carried by said shaft means, said means defining said vacuum chamber including a surface extending substantially parallel with the endless belts at the imaging station with perforations formed therein and opening toward said imaging station to enable air to be drawn therethrough to hold a light-sensitive copy sheet against said endless belt means, and said endless belt means having perforations formed therein to enable air to flow therethrough into said vacuum chamber.

3. A photocopying machine according to claim 2, wherein said mounting means are arranged for mounting said endless belt means formovement past a generally vertical imaging station with one of said shaft means being located beneath said means defining a vacuum chamber, said drive means being releasably coupled to said shaft means located beneath said vacuum chamber means, said other shaft means being located above said vacuum chamber means, and said brake means being operable on said other shaft means.

4. A photocopying machine according to claim 3, the combination further comprising removal means carried by said shaft means located beneath said vacuum chamber means for urging the copy sheet being carried by said endless belts away from the perforated surface of said endless belt means.

5. An electrostatic photocopy machine having an exposure station and a copy sheet imaging station spaced from said exposure station, and a vacuum sheet transport assembly of the type wherein a pressure differential is utilized to retain a sheet member against a backing member comprising:

a. a housing member in said machine;

b. a vacuum chamber carried by said housing and having a perforated front plate thereon;

0. means for feeding a copy sheet toward said chamber;

d. drive means on said housing, including a drive roller positioned above the chamber and a driven 6 the perforated front plate of said vacuum chamber;

f. adjustable stop means positioned between said belts and engaged by the leading edge of said copy sheet to disengage the drive means;

. brake means activated by said stop means and engaging said drive roller to prevent overtravel of said copy sheet after contact with said stop means, said brake means cooperating with said adjustable stop means to provide an accurate positioning of said copy sheet in front of said vacuum chamber; and

h. removal means carried by said driven roller between the belts to urge said sheet member away from said belts.

6. [n a photocopying machine capable of handling different iengths of light-sensitive copy sheets, the combination comprising a magazine for containing a supply of copy paper sheets, another magazine for containing another supply of copy paper sheets, each of said magazines having a floor therein and a pair of adjustable side rails slidably associated therewith and having detent means associated with said floor to locate one of said side rails in one of two given positions, at least one of said magazines being removable from said photocopying machine for replenishing the supply of copy paper sheets in said magazines, sheet feeding means associated with each of said magazines including a pair of feed rollers adjustably mounted on a shaft having a polygonal cross-section for feeding the topmost sheet in each of said magazines into the photocopying machine, and means for selectively activating one of said sheet feeding means for supplying sheets from one of said magazines into said photocopying machine.

7. A photocopying machine according to claim 6, the combination further comprising copy sheet level sensing means associated with each of said magazines for sensing the height of the supply of copy sheets in each of said magazines, and said copy sheet level sensing means being operable in response to the supply of copy sheets in one of said magazines diminishing beneath a given height for selectively deactivating the particular copy sheet feeding means associated with that magazine and for providing a visual signal.

8. In a photocopying machine capable of handling different lengths of light-sensitive copy sheets, the combination comprising a magazine for containing a supply of copy paper sheets, sheet feeding means associated with said magazine for feeding the topmost sheet in said magazine into the photocopying machine, another magazine for containing another supply of copy paper sheets, another sheet feeding means associated with said other magazine for feeding the topmost sheet in said magazine into the photocopying machine, and means for selectively activating one of said sheet feeding means for supplying sheets from one of said magazines into said photocopying machine, and further comprising support means carried by each of said magazines for centrally engaging the underside of the leading sheet of a stack of copy paper sheets placed therein.

9. ln an electrostatic printing machine capable of handling various sizes of copy sheet material:

a. a plurality of copy sheet feed magazines, each of magazines having a floor therein and a pair of adjustable side rails slidably associated therewith;

b. detent means associated with said floor to locate deactivate the respective copy sheet feed means one of said side rails in one of two given positions when said copy sheet supply in that magazine with respect to said magazine floor', diminishes below a give height; and

c. sheet feed means associated with each magazine f- Sheet engaging means carried by said side rails including a pair of feed rollers which contact the above the floor for engaging the front edges of said top sheet of a copy sheet stack to f d th to copy sheets to inhibit double feeding of copy sheet of said stack into the printing machine; Sheetsd. means for selectively activating one of said sheet An electrostatic P t machine according to feed means; claim 9 having support means carried by each said e. copy sheet level sensing means associated with 10 magftzine floor to centrally engage theundetside f the Said magazines to sense the height f the copy leading edge ofastack of copy sheets placed therein. sheet supply in each magazine and to selectively

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U.S. Classification271/9.11, 271/9.1, 271/197, 271/276
International ClassificationB65H5/02, G03G15/00
Cooperative ClassificationG03G15/6597
European ClassificationG03G15/65R