GB1594488A

GB1594488A - Sheet stacking

Info

Publication number: GB1594488A
Application number: GB4981677A
Authority: GB
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1977-11-30
Filing date: 1977-11-30
Publication date: 1981-07-30

Description

(54) IMPROVEMENTS IN SHEET STACKING (71) We, XEROX CORPORATION of Xerox Square, Rochester, New York, United States of America, a corporation organised under the laws of the State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to apparatus for stacking sheets in offset relation.

Sheet stacking apparatus in which sheets serially delivered thereto are compiled into sets which are offset from. one another to facilitate separation of the sets, take various forms. Thus offsetting may be achieved by moving a sheet registration member or the stacking tray itself between two different positions (see for example U.S. Patent 3,860,127), or it may be achieved by controlling the sheets being fed to the stacking location, as for example in U.S. Patent 3,946,879 where alternate series of sheets are rotated through 90 degrees as they enter the stacking tray and our copending application No. 45281/77 (Serial No. Void) in which alternate series of sheets are shifted sideways on their way to the stacking tray.

The present invention consists in apparatus for stacking sheets in offset relation comprising two registration members and a sheet directing roller movable between a first position in which it directs sheets delivered thereto towards one of the said registration members and a second position in which it directs sheets towards the other registration member.

Preferably the registration members each define a corner and the corners are adjacent each other. The corners may be arranged to offset the sets parallel to each other or they may be relatively inclined.

In a preferred form, the stacker includes control means for automatically adjusting the position of the roller. Suitably the control means is responsive to the passage of sheets to the roller and includes a counter for counting the number of sheets delivered to the roller, the roller being adjusted following the passage of a predetermined number of sheets. The counter may be adjustable for varying the number of sheets in a set.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 is a perspective view of a copying machine incorporating one embodiment of sheet stacking apparatus according to the invention, Figure 2 is a schematic side elevation of the machine shown in Figure 1, Figure 3 is a scrap view showing the sheet stacker in greater detail, and Figure 4 illustrates an alternative form of the invention.

Referring to Figures 1 and 2 there is shown an automatic xerographic reproducing machine 10 incorporating a sheet stacker 100 according to this invention. The copying machine 10 is capable of producing either simplex or duplex copies in sets from a wide variety of originals which may be advanced in recirculating fashion by recirculating document apparatus 12 described in U.S. Patent No. 3,556,512. Although the present invention is particularly well suited for use in automatic xerography, the apparatus generally designated 100 is equally well adapted for use in any number of devices in which cut sheets of material are delivered in a set or stack and the set then separated from a previous set- and forwarded to an output tray.

The processor 10 includes a photosensitive plate comprising a photoconductive layer over a conductive backing. The plate is formed in the shape of a drum 15 mounted on a shaft 17 journalled for rotation in the machine frame.

The xerographic processing apparatus are driven at predetermined speeds relative to each other from a single drive system (not shown) and the operations thereof coordinated in order to produce proper cooperation of the various processing mechanisms.

A document to be reproduced is transported by document handling apparatus 12 from the bottom of a stack to a platen 18 and scanned by means of a moving optical scanning system to produce a flowing light image. After scanning the document is returned and the next advanced and scanned and so on until the entire document stack has been copied at which time the cycle may be repeated as described in the above patent. The scanning system includes an elongated horizontal extended aperture lamp 25 and a movable lens element 28. The lamp and lens element move in coordination across the document supported upon the platen to focus successive incremental bands of illumination reflected from the document onto the moving drum surface. The optical path is folded by means of a pair of image mirrors 19 and 20 interposed between the lens and the drum surface and arranged to place the image on the drum at exposure station B. Prior to the imaging of the drum surface, the drum is first uniformly charged by means of a corona generator 29 at charging station A. Under the influence of the flowing light image, the uniformly charged photoconductive surface is selectively dissipated in the non-imaged areas to form a latent electrostatic image.

The latent electrostatic image is carried on the drum surface from the exposure station into the developing station C where it is developed into visible form by applying developer material to the surface using one of the various well-known xerographic systems of development.

The moving drum surface next transports the developed xerographic image to a transfer station D. Cut sheets of paper are also moved into the transfer station from sheet registering apparatus 34 in synchronous relation with the image on the drum surface. At the transfer station, transfer corotron 35 induces on the sheet a charge having a polarity and magnitude sufficient to attract the toner material from the drum surface to the sheet. This induced charge also electrostatically tacks the final support material to the drum surface and in order to remove the copy sheet from the drum surface, a stripper finger 38 is positioned downstream from the transfer corotron to lift the sheet from the drum surface. The stripped sheet is directed along a predetermined path of travel into contact with a stationary vacuum transport 39.

Residual toner remaining on the drum surface after transfer is removed into a cleaning station E which includes a cleaning corotron 40 and a mechanical cleaning device such as a brush 41 (as shown) or a blade.

The copy sheet, which has been removed from the drum surface after the transfer operation, is moved along stationary transport 39 into fusing station F.

Upon leaving the fuser, the fixed copy sheet is passed through a curvilinear sheet guide system, generally referred to as 49, into co operating advancing rolls 50 and 51. The advancing rolls forward the sheets through a linear sheet guide system 52 into a second pair of advancing rolls 53 and 54. At this point, depending on whether simplex or duplex copies are desired, the simplex copy sheet is either forwarded directly into the stacker 100 via pinch rolls 61, 62 or into upper supply tray 55 by means of a movable sheet guide 56 before the finishing apparatus for the duplexed copy. Movable sheet guide 56, and associated advancing rolls are prepositioned by appropriate machine logic system to direct the individual sheets into the desired path.

As shown in Figures 2 and 3, the sheet stacker 100, includes a tray 101 having a base or sheet support surface 102, an end wall 103 and a side wall 104. The walls 103, 104 together define two adjacent registration corners 10S, 106. A driven sheet directing roller or wheel 107 is mounted to swing between a first position, as shown in Figure 3, in which it directs sheets received in the tray from the pinch rolls 61, 62 into registration corner 105, and a second position indicated by the dotted outline in which it directs sheets into registration corner 106.

The roller 107 is rotatably mounted on an axle 108 journalled between the ends of side pieces 109a, 109b of a bifurcated arm 109. The other end of the arm is pivotally connected to a mounting block 110 so that the roller is freely movable in a vertical plane and rests on the sheets in the tray 101. The roller 107 is driven by a motor M. As shown the motor is mounted off the block 110 and drives the roller via a belt or wire drive 111.

The mounting block 110 is carried from an arm 112 secured to the machine frame and is rotatable about a vertical axis 113 for displacing the roller between its two registration positions. Displacement of the roller is effected by a solenoid 114 and spring 115. The solenoid is arranged to act on a lever 116 which is rigid with the block 110 to rotate the assembly 109, 110 into the position shown. When the solenoid is inactivated the tension spring 115 connected between the solenoid housing and the lever 116 rotates the assembly to position the roller 107 as shown in dotted lines.

Displacement of the roller 107 is controlled in response to the passage of sheets to the tray 101. Sheets passing into the tray are sensed by sensor 117 and counted by a counter 118 which may be adjusted to signal the solenoid 114 after a desired number of copies have been assembled in the tray. A timer 119 is arranged to delay the signal from the counter 118 to the solenoid 114 to ensure that displacement of the roller 107 does not occur until the first sheet to be directed by the roller in its new position is beneath the roller, thus avoiding possible damage to or skewing of the previously registered sheets.

In the embodiment of Figures 1 to 3, the sets S are offset parallel to each other but the registration corners 105, 106 may be inclined to one another as shown in Figure 4.

This permits the use of a fixed sheet stop 121 common to all sheets which acts with the registration corners to stabilise the sheets. Preferably the stacker mechanism is arranged behind the covers of the machine to reduce the risk of accidental damage and also to protect users. This objective is achieved as shown in Figure 1 where the mechanism is housed under the machine top cover and the sets S are retrieved through an opening 120 in the front of the machine and remote from the roller 107.

It will be understood that while particular embodiments have been described, various modifications may be made to the specific details referred to herein without departing from the scope of the invention as defined in the appended claims. For example means, such as a plastics damping strip, may be provided for decelerating the sheets entering the tray 101.

WHAT WE CLAIM IS:- 1. Apparatus for stacking sheets in offset relation comprising two registration members and a sheet directing roller movable between a first position in which it directs sheets delivered thereto towards one of said registration members and a second position in which it directs sheets towards the other registration member.

2. Apparatus according to claim 1 wherein said registration members each define a corner.

3. Apparatus according to claim 2 in which said registration corners are adjacent each other.

4. Apparatus according to claim 2 or 3 wherein said corners are relatively inclined.

5. Apparatus according to any preceding claim further including control means for an automatically adjusting the position of the roller.

6. Apparatus according to claim 5 wherein said control means is responsive to the passage of sheets to the roller.

7. Apparatus according to claim 6, wherein said control means includes a counter for counting the number of sheets delivered to the roller and serves to adjust the roller following the passage of a predetermined number of sheets.

8. Apparatus according to claim 7, wherein said predetermined number is variable.

9. Apparatus according to claim 5, 6, 7 or 8, wherein said roller is moved between its sheet registration positions by a solenoid mechanism actuated by the control means.

10. Apparatus according to any preceding claim, wherein a change in position of the roller is timed to occur only when the (first) sheet to be directed by the roller in its new position is beneath the roller 11. Apparatus according to any of claims 1 to 9 including means for lifting the roller out-of-contact with any sheets therebeneath during movement of the roller between its registration positions.

12. Apparatus for stacking sheets in offset relation, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. risk of accidental damage and also to protect users. This objective is achieved as shown in Figure 1 where the mechanism is housed under the machine top cover and the sets S are retrieved through an opening 120 in the front of the machine and remote from the roller 107. It will be understood that while particular embodiments have been described, various modifications may be made to the specific details referred to herein without departing from the scope of the invention as defined in the appended claims. For example means, such as a plastics damping strip, may be provided for decelerating the sheets entering the tray 101. WHAT WE CLAIM IS:-

1. Apparatus for stacking sheets in offset relation comprising two registration members and a sheet directing roller movable between a first position in which it directs sheets delivered thereto towards one of said registration members and a second position in which it directs sheets towards the other registration member.

10. Apparatus according to any preceding claim, wherein a change in position of the roller is timed to occur only when the (first) sheet to be directed by the roller in its new position is beneath the roller

11. Apparatus according to any of claims 1 to 9 including means for lifting the roller out-of-contact with any sheets therebeneath during movement of the roller between its registration positions.