GB1604763A - Copier with reduction/magnification capability @ @@@@@@@@ @@@ @ @ - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 604 763 ( 21) Application No 4325/81 ( 22) Filed 31 May 1 l ( 62) Divided out of No 1 604 761 ( 31) Convention Application Nos.

829015 ( 32) Filed 30 Aug.

829 014 829 013 829 012 829 011 ( 33) United States of America (US) ( 44) Complete Specification published 16 Dec 1981 ( 51) INT CL 3 G 03 G 15/00 GO 5 B 15/02 ( 52) Index at acceptance G 2 A 301303304310314320322335 C 5 CH ( 72) Inventors JAMES M DONOHUE RICHARD M MALINICH ANDREW T LING FRANK M NELSON CHARLES P HOLT KENNETH GILLETT JOHN W DAUGHTON STEPHEN P WILCZEK )78 ( 54) COPIER WITH REDUCTION/MAGNIFICATION CAPABILITY ( 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 present invention relates to a copier such as a xerographic copier and more particularly to apparatus for controlling the magnification or reduction capabilities of such a copier by providing relative movement between a document to be copied and imaging optics for transmitting an image of the document to the imaging member of the copier.

According to the invention, the copier includes support means for supporting a document for copying, optical means for transmitting images of the document to the imaging member, and means for providing relative movement between the support means and the optical means comprising a servo motor for providing the relative movement, an amplifier for powering the servo motor, and control means coupled to the amplifier to control the power output from the amplifier to control changes in the relative position between the support means and the optical means and thereby control the reduction/magnification of said copies.

The preferred embodiment of the invention utilizes a feedback control to ensure the output from the control means generates an appropriate response in the servo motor.

Thus, in an application where the servo motor is coupled to a scanning lamp which 40 scans past a copier platen, a tachometer and tachometer encoder are used to detect and compensate for undesirable speed variation in the lamp speed The encoder generates digital inputs to the control means which are 45 used to generate control outputs to the amplifier means.

A copier in accordance with the invention will now be described, by way of example, with reference to the accompanying draw-50 ings, in which:

Figure 1 is a block diagram of the overall master/area communication system of a control system for a copier according to the invention; 55 Figure 2 is a schematic illustration of various mechanical components of a copier/duplicator; Figure 3 is a block diagram showing the major components of the master unit and an 60 active and passive area controller; Figure 4 illustrates a block diagram of a servo controller showing the key components thereof; and Figure 5 is a schematic drawing of the key 65 platen scanning components.

FIGURE 1 is a block diagram of the overall Master/Area Communication System (MACS) utilized in controlling a copier/duplicator MACS comprises a mas 70 ter unit 1 including a master controller 2 in combination with a master I/O interface 4.

The master controller 2 contains a microprocessor and memory units which govern 0 r 1977 in 1 604 763 the various tasks and operational procedures utilized in operating the copier/duplicator The master I/O interface 4 is responsible for interconnecting the various address and data bytes from the master controller 2 to a plurality of area controllers 6, 8, 10, 12 and 14 which are responsible for specific tasks in the operation of the copier/duplicator Each area controller 6-14 is dedicated to performing a group of functions which are physically and/or logically related The area controllers take on two general forms, an active controller which has its own processor control capabilities and a passive controller which has no processing capabilities per se and is simply utilized to latch outputs from the master controller and feed inputs thereto on the command of the master controller FIGURE 1 illustrates five area controllers but it is within the scope of the invention to utilize any number of area controllers consistent with the address capabilities of the master controller Illustrated in FIGURE 1 are three passive area controllers, namely, the paper path controller 6, RDH/ADF control console controller 8 and finishing station controller 14 Two active controllers are illustrated, namely, the RDH/platen servo controller 10 and processor controller 12.

The master controller 2 is responsible for the majority of system control processing tasks whereas the area controllers are responsible for the machine control functions Input and output data are transmitted between the master controller 2 and the area controllers 6-14 in a serial communications path via Master/Area Communication Channels 16 which may take the form of a plurality of fiber optic connections The utilization of fiber optics interconnection for the MACS transmission channels greatly reduces control susceptibility to electromagnetic interference generated in the machine Typically, it is desirable to physically position the area controllers in close proximity to the particular device or devices controlled thereby.

For a general understanding of an electrophotographic printing machine in which the features of the present invention may be incorporated, reference is had to FIGURE 2 which depicts schematically the various components thereof Although the control logic employed in the electrophotographic printing machine of FIGURE 2 is particularly well adapted for use therein, it should become evident from the following discussion that it is equally well suited for use in a wide variety of printing machines and is not necessarily limited in its application to the particular embodiment shown herein.

Inasmuch as the practice of electrophotographic printing is well known in the art, the various processing stations for producing a copy of an original document are herein represented schematically Each processing station will be briefly discussed hereinafter.

As in all electrophotographic systems of 70 the type illustrated, a drum 110 having a photoconductive surface 112 entrained about and secured to the exterior circumferential surface of a conductive substrate is rotated, in the direction of arrow 114, 75 through the various processing stations One type of suitable photoconductive material is a selenium alloy such as described in U S.

Patent No 2,970,906 issued to Bixby in 1961 Preferably, the conductive substrate is 80 aluminum.

Initially drum 110 rotates a portion of photoconductive surface 112 through charging station A Charging station A employs a corona generating device, indicated gener 85 ally by the reference numeral 116, to sensitize a portion of photoconductive surface 112 When energized, corona generating device 116 charges the portion of photoconductive surface 112 therebeneath to a 90 relatively high substantially uniform potential.

Thereafter, drum 110 rotates the charged portion of photoconductive surface 112 to exposure station b Exposure station B is 95 arranged to produce a light image of an original document or series of documents being reproduced In the electrophotographic printing machine depicted in FIGURE 2, exposure station B operates in one of two 100 modes In one mode, a plurality of original documents are recirculated in an automatic document handling system (ADH 132) so that sets of collated copies may be formed by the printing machine In the other mode 105 of operation, a single original document if placed on the platen 122 and reproduced by the printing machine If the platen scan optics are used, mirrors 118 and 120 are moved into the operative position depicted 110 in FIGURE 2 Lamp 124 moves across the original document disposed on platen 122 to illuminate incremental portions thereof.

The light rays transmitted from the original document are reflected by full rate mirror 115 126 to half rate mirror 128 Half rate mirror 128 reflects the light rays through lens 130 onto mirrors 118 and 120 These mirrors reflect the light image of the original document onto the charged portion of photocon 120 ductive surface 112 Drum 110 rotates in synchronism with the movement of the platen scanning optics Thus, the charged portion of photoconductive surface 112 is irradiated to record an electrostatic latent 125 image thereon corresponding to the information areas of the original document disposed on platen 122.

In the automatic document handling system for making pre-collated copy sets the 130 1 604 763 repeated collated imaging of a set of original documents is obtained by placing and retaining the original documents on an elongated windable document holding web 132 The web 132 is wound between two spaced web scrolls 133 a, 133 h positioned and wound so as to obtain the document between the turns of the web scrolls The web is repeatedly wound and unwould from one scroll to the other scroll (recirculated) to repeatedly expose individual documents thereon in an exposed portion of the web extending between the scrolls.

During the forward movement of web 132, a lamp (not shown) illuminates the original documents disposed thereon Mirror 134 reflects the light rays toward stationary mirror 136 which, in turn, reflects the light rays toward rotating mirror 138.

Rotatable mirror 138 transmits the light rays through lens 140 The light image transmitted through lens 140 is reflected by mirror 142 onto the charged portion of photoconductive surface 112 In the ADH mode of operation, mirrors 118 and 120 are positioned remotely from the optical light path.

In the reverse scan mode, i e web 132 advances in the opposite direction to the forward movement, mirror 134 rotates 900 about its axis and reflects the light rays transmitted from the original document onto mirror 144 Thus, mirror 138 directs the light rays received from mirror 144 through lens 140 Once again, the light image transmitted through lens 140 is reflected by mirror 142 onto the charged portion of photoconductive surface 112.

Thus, in either mode or operation, an electrostatic latent image is recorded on photoconductive surface 112.

As drum 110 continues to rotate in the direction of arrow 114, the electrostatic latent image recorded thereon is advanced to development station C Development station C includes a developer unit 146 having a housing 148 with a supply of developer mix contained therein The developer mix comprises carrier granules having toner partides adhering triboelectrically thereto Preferably, the carrier granules are formed from a magnetic material with the toner particles being made from a heat settable plastic Developer unit 146 preferably is a magnetic brush development system In a system of this type, the developer mix is brought through a directional flux field to form a brush thereof As depicted in FIGURE 2, developer unit 146 includes a pair of developer rollers 150 and 152 Each developer roller includes a stationary magnetic member having a non-magnetic, rotatable tubular member interfit telescopically thereover The tubular member is rotated to advance the developer material into contact with the electrostatic latent image recorded on photoconductive surface 112 The developer material is advanced to developer roller 150 and 152 by paddle wheel 154 disposed in the sump of housing 70 148 Developer rollers 150 and 152 advance the developer mix into contact with the electrostatic latent image and the toner particles are attracted electrostatically thereto forming a toner powder image on photoconduc 75 tive surface 112 As successive electrostatic latent images are developed, the toner particles within the developer mix are depleted.

Additional toner particles are stored in toner cartridge 156 A sample electrostatic 80 latent image is recorded on photoconductive surface 112 and developed The density of the toner particles adhering thereto is detected via an ADC sensor 157 (not shown) and compared to a reference 85 density The error signal developed thereby controls the dispensing of toner particles from cartridge 156 In this manner, the concentration of toner particles within the developer mix is maintained substantially 90 constant Developer rollers 150 and 152 are electrically biased to a suitable voltage This voltage is adjustable and depends upon the original document as well as the duration of time that the printing machine is activated 95 After the toner powder image has been developed on photoconductive surface 112, corona generating device 158 applies a charge thereto so as to pre-condition toner powder image for transfer 100 Ideally, carrier granules remain in housing 148 of developer unit 146 However, inasmuch as the sealing arrangement is imperfect, carrier granules may adhere to photoconductive surface 112 of drum 110 105 A scavenging roller 160 is provided for removing these carrier granules Scavenging roller 160 comprises a magnetic member and a rotatable, non-magnetic tublar member interfit telescopically thereover 110 The tubular member rotates relative to the magnetic member In this manner, the magnetic carrier granules are attracted form photoconductive surface 112, while the toner powder images remain undisturbed 115 thereon.

With continued reference to FIGURE 2, a sheet of support material is advanced by sheet feeding apparatus 162 or 164 from either tray 166 or tray 168 Conveyor sys 120 tem 170 advances the sheet of support material to transfer station D Rollers 172 speed up or show down the advancing sheet of support material so as to ensure that it moves into contact with drum 110 in a timed 125 sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D.

Transfer station D includes a corona 130 1 604 763 generating device 174 which charges the backside of the sheet of support material to a level sufficient to attract the toner powder image from photoconductive surface 112.

After transfer of the toner powder image to the sheet of support material, a vacuum stripping system 176 separates the sheet from photoconductive surface 112 and advances it to fusing station E If vacuum stripper 176 fails to separate the sheet from photosensitive surface 112, a redundant mechanical finger, i e stripper finger 198 activated by solenoid 199 (not shown), is provided to ensure separation of the sheet therefrom.

Fusing station E includes a fuser assembly, indicated generally by the reference numeral 178 Fuser assembly 178 fuses the transferred toner powder image to the sheet of support material A suitable fuser comprises a heated fuser roller 180 and a resilient backup roll 182 in contact therewith.

In this manner, the sheet of support material advances between fuser roller 180 and backup roller 182 with the toner powder image contacting fuser roller 180.

After the toner powder image is permanently affixed to the sheet of support material at fusing station E, a series of rollers advance the copy sheet either to finishing station F or to duplex tray 183 when duplex copies are being reproduced in the ADH mode of operation After web 132 with the original documents thereon has advanced through one pass, the odd numbered sheets are copied During the next forward scan, the even numbered sheets are copied and the information contained therein placed on the reverse side of the copy sheet This sequence may be reversed Tray 183 is arranged to hold a plurality of sets of copies therein Each sheet of support material having the toner powder image permanently affixed to one surface thereof is advanced from tray 183 by sheet feeding apparatus 184 onto duplex conveyor 185 Duplex conveyor 185 advances the copy sheet to conveyer system 170 where the sheet once again is advanced to transfer station D so as to receive the toner powder image corresponding to the second side thereof Once again, the reverse side of the copy sheet passes through transfer station D and fusing station E However, at this time the copy sheet is advanced to finishing station F.

After the toner powder image has been permanently fused to the copy sheet, either the duplex or simplex copy sheets are advanced by a series of rollers 186 to finishing conveyers 188 Finishing conveyors 188 advance the copy sheets to trays 190 or 192.

The sheets are stacked in one tray, e g tray with the odd sides up and the even sides face down, while in the other tray, e g tray 192 with the even sides up and the odd sides down This orientation is required because of the forward and reverse movements of web 132 After the requisite number of copies have been stacked in the appropriate tray, i e sufficient copies to define a collated 70 set thereof, staplers 194 and/or 196 are actuated to permanently secure the sheets to one another In this manner, sets of collated copies are stored in trays 190 and 192 with each set having the copies thereof stapled to 75 one another.

Residual toner particles are removed from photoconductive surface 112 at cleaning station G Initially, discharge lamp 204 floods photoconductive surface 112 to assist 80 in the dissipation of any electrostatic charge remaining thereon prior to the cleaning thereof Residual toner particues are then brought under the influence of a corona generating device 200 adapted to neutralize 85 the remaining electrostatic charge on photoconductive surface 112 and that of the residual toner particles.

The neutralized toner particles are cleaned from photoconductive surface 112 90 by a rotatably mounted fibrous brush 202 in contact therewith In addition, subsequent to cleaning, a discharge lamp 206 illuminates photoconductive surface 112 to dissipate any residual electrostatic charge 95 remaining thereon prior to the charging thereof for the next successive imaging cycle.

FIGURE 3 illustrates a more detailed block diagram of the master controller and 100 the active and passive area controllers of FIGURE 1 For simplicity of illustration only one passive area controller such as the paper path controller 6 and a single active controller such as the process control con 105 troller 12 is illustrated The master controller 2 comprises a central processing unit and system controller identified as a master microprocessor 300 A number of existing microprocessor systems may be utilized to prac 110 tice the present invention For example, the INTEL 8080 A-2 CPU and INTEL 8238 System Controller by Intel Corp, Santa Clara, Calif U S A The master microprocessor 300 is shown connected to memory units 115 utilized to store program memory and for temporary storage of various control and sense parameters The memory units comprise a read only memory (ROM) 302, a random access memory (RAM) 304 and a 120 non-volatile memory (NVM) 306 The TOM memory mey be for example a 48 KB (bytes) mask programmable ROM, while the RAM may comprise a 2 KB (byte) static MOS scratch pad memory and a 1 KB (bit) 125 flag storage MOS RAM (bit D 7 of RAM).

The ROM may be fabricated, for example.

using 2 K x 8 ROM chips model No.

831 6 A, and the RAM memory may be implemented using 1 K x 1 chips, model No 130 1 604 763 2102 The NVM may be fabricated using 512 x 1 RAM chips model No 52222 (American Microsystems Inc) Equivalent chips may of course be utilized as for example the NVM may be fabricated from 256 x 4 chips (model No 5101 L) if desired The memory units are interconnected to the master microprocessor 300 by means of a tri-state master bus 308 which is also interconnected to the master I/O interface 4 The tri-state master system bus comprises eight data lines D 0-TS through D 7-TS, sixteen address lines AO-TS through A 15-TS and a number of control and clock lines The master microprocessor 300 is supplied with clock signals from the clock source 310 (INTEL clock generator 8224 for example) and is powered by an external power supply 312 Power for the various circuits in the master controller 2 as well as the master I/O interface 4 are first filtered by means of a filter circuit 314 A power normal signal is also fed to the master controller along line 316 from the power supply to indicate that power is up to normal operating levels A reset signal from reset circuitry 318 is utilized to reset the various registers throughout the master controller and master I/O interface during a power up or initialization sequence The power supply 312 also supplies power to the various remote controllers by means of lines 320.

The passive area controller exemplified by the paper path controller 6 comprises an area I/O interface circuit 340, latches 342 and drivers 344 which provide outputs to one or a plurality of machine controlled devices Sense data is supplied from various sensing means to represent the current device operational state whose function is governed by the particular passive controller of interest The sensed data is fed to buffers 346 and subsequently to the area I/O interface 340 for transmission along the master area communication channel 16 to the master unit 2 The active area controllers are similar in function to the passive area controllers and likewise contain an area I/O interface 340, latches 342 and drivers 344 Sensed data may be provided to the master unit 2 through buffers 346, the I/O interface 340 and the communication channel 16 Additionally, however, the active area controller contains an area microprocessor/interface 348 which is separate and distinct from the master microprocessor 300 Shown in FIGURE 3 the area microprocessor/interface 348 is connected by means of an area system bus 350 to a plurality of latches 354 which feed drivers 344 to control various machine parameters The area microprocessor/interface 348 may additionally provide input information to latches 352 for subsequent feeding to the master unit 2 via the area I/O interface 340.

The area microprocessor/interface 348 may also be utilized to control analog data to various machine devices and to sense analog data from various machine sensing means utilizing D/A converters 364 and A/D con 70 verter 366 respectively Data which is not controlled by the area microprocessor/interface 348 may be fed to and from the master unit 2 by means of the direct paths 360 and 362 as illustrated in FIGURE 3 75 The servo control area controller 10 is similar to the process controller 12 and supplies a machine clock signal to the master unit 2 along channel 370 (see dotted line in FIGURE 3) This signal is derived from the 80 photoreceptor drum of the copier/duplicator and is passed along a fiber optic link of channel 370 to provide an interrupt signal to the master microprocessor 300 The machine clock signal thus enables a sync 85 hronization of the master microprocessor 300 to the actual copier/duplicator machines operation.

The Master Area Communication System utilizes a set of bi-directional communica 90 tion channels 16 which independently couple each area controller 6-14 to the master unit 1 Each channel 16 comprises three groups of signal lines, namely, data-in, data-out and clock The data-in and data 95 out lines are defined relative to the master controller and in the description set forth herein this terminology has been maintained throughout even in relation to data in area controllers 6-14 Data transfers between the 100 master and area controllers is in bit serial form in eight bit increments (bytes) An I/O transaction may be an input only transaction or a combined input/output transaction as specified by an initiating command byte 105 from the master unit 1 Al transmissions are in synchronism with and at the same rate as the 1 25 M Hz clock signal from the master unit 1 All MACS communication is initiated by and under control of the master unit 110 2 Communication is always between the master unit 1 and the area controllers and communication never takes place directly between the area controllers.

FIGURE 4 is an expanded block diagram 115 of the master I/O interface 4, the communication channels 16 and their interconnection with the various area I/O interfaces 340.

The data bus 414 forms part of the master system bus 308 For ease of illustration, only 120 one such area I/O interface 340 is drawn although similar components are utilized for all area controllers.

FIGURE 4 illustrates input data fines and output data lines for as many as six different 125 area controllers One fiber optic interconnecting link 398 is provided for input data between each of the area controllers and the master I/O interface 4 Data from the area controllers (input data) is fed to receiver 130 1 604 763 amplifiers 400 interconnected to each of the fiber optic links 398 The received data is "O Red" by means of OR gate 404 and fed as an input to multiplexer 406 In normal operation the data is only received from a particular area controller in response to a command from the master unit and consequently only one area controller will be active in transmitting data at any one time.

(An exception to this rule exists in the simultaneous transmit and receive mode which will be explained more fully below).

Individual data lines 408 from each of the data-in lines of the area controllers are also fed to multiplexer 406 where they may be selected for particular test modes to isolate faults in a particular area controller Data received from the OR gate 404 is passed through the receiving mux 406 and fed to a Serial Data Input (SDI) register 410 which in turn feeds the data to a Command Check Byte (CCB) register 412 The SDI and CCB registers provide the input data in parallel form to a master data bus 414 which forms the eight data lines DO-TS through D 7-TS of the master system bus 308.

Output address words from the master controller 2 are provided along the master data bus 414 to a Master Command Byte (MCB) register 416 Output data is provided from the data bus 414 directly to a Serial Data Out (SDO) register 418 The MCB register 416 is utilized together with a parity generator 420 to load an Area Command Byte (ACB) register 422 ACB register 422 is ten ( 10) bits long and holds an area command address word whereas the SDO register 418 is an eight ( 8) bit register storing the Data Out Byte Together, these registers provide a serial output data stream of eighteen ( 18) bits to each of the area controllers via the fiber optic interconnecting links 16 The ACB register 422 effectively provides an addressing means to select a particular area controller and to select a particular group of input or output data lines within the selected area controller The SDO register 418 provides the actual data to be transmitted to the designated area and output lines (ports) The gating of the various input registers (SDI register 410, and CCB register 412) and output registers (ACB register 422 and SDO register 418) as well as the MCB register 416 are controlled by a control logic circuit 424 The control logic circuit 424 received address lines AO-TS through A 18-TS as well as a plurality of control lines from the master system bus 308 to effectively decode and control the data on the master data bus 414 Shifting of the registers is synchronized with a 1 25 M Hz clock signal from clock generator 426 which provides a 1 25 M Iz clock signal to each of the area controllers These clock signals are fed along line 428 to drivers 402 for transmission via fiber optic links 398 to the area controllers.

Output data from ACB register 422 and SDO register 418 is likewise shifted at the 1.25 M Hz rate to a master data out line 425 70 and subsequently to drivers 402 and fiber optic links 398 Output data is also fed via a turnaround test line 430 to multiplexer 406 to optionally provide input data to the CCB register 412 and SDI register 410 in a mas 75 ter test mode of operation.

The control logic 424 decodes the address bits on the master system bus 308 address lines to determine if the address decode corresponds to the master I/O interface 4 so 80 that the input and output registers may beappropriately gated.

The area I/O interface 340 comprises area input register 450, area output register 452 and control logic 454 The control logic 454 85 decodes the address received from the ACB register 422 of the master I/O interface 4 and selects particular groups of the input and output lines for providing or receiving data respectively Each area controller is 90 provided with a plurality of output ports 456 and input ports 458.

The area controller 10 governs the RDH and platen servos as diagramatically illustrated in FIGURE 4 The prime purpose of 95 the servo remote controller 10 is to control four motors, namely, the RDH motor 3000, the platen motor 3002, the reduction optics motor 3004 and the scroll motor 3006 The RDH motor 3000 controls the movement of 100 web 132 when utilizing the pre-collating feature available for the recirculating document handler A tachometer 3010 and an encoder 3012 provide various input signals to the area controller 10 as shown A similar 105 tachometer 3014 and encoder 3016 are associated with the platen motor 3002 and additionally provide input signals to the area controller 10 The platen motor 3002 is utilized to drive the scanning lamp 124 (FIG 110 URE 2) for platen scan mode operation of the machine.

Reduction optics motor 3004 provides the drive means for positioning lens 130 (FIGURE 2) enabling use of the variable 115 magnification feature of the machine.

Encoder 3020 is utilized to provide position signals to the area controller 10 which signals are indicative of the position of lens 140.

Scroll motor 3006 is utilized to position 120 the scroll carrying web 132 to provide paper feed input, run position, ADF feed positioning and the like.

FIGURE 5 shows the major optical scanning elements of the machine which are 125 used during platen scan operations The stand-by position for the scanning lamp 124 (which is physically connected to a carriage together with mirror 126 as indicated by dotted lines) is shown as position A, and is 130 1 604 763 used during RDH operations as well as machine stand-by Position A is termed the home or garage position In utilizing the platen scanning mode of operation, the operator selects the desired copy paper size, the desired magnification and initiates platen scan by pushing the start scan button.

From the copy paper size and magnification information, the master unit calculates the required velocity and end of scan (EOS) position of the lamp 124 This information is fed to the servo controller 10 to control the lamp motion Prior to a document scan an initialization or dummy scan is made while other machine devices are preparing for the platen scan mode (copy paper feed, etc).

During this initialization scan, the carriage moves to the leading edge (LE) sensor, position B A document pre-scan takes place from position B to position C after which follows the document scan proper from left to right in FIGURE 5 The distance between position B and C is quite small and the LE sensor will remain active, generating the LE signal until the lamp moves off the sensor going from left to right (document scan) in FIGURE 5 The end of scan (EOS) occurs at position D which, of course, is variable depending on the copy paper size and magnification selected The lamp 124 remains at the EOS position until the end of the initialization step after which a true document scan takes place, e g position D to position C for retrace and pre-scan and position C to position D for document scan.

After scanning, the lamp 124 remains at position D until another document scan is requested, and, if none occurs within a particular time-out alloted, the lamp 124 moves back to the home or garage position A.

The lens 130 is controlled by the reduction optics motor 3004 A lens home signal is generated by a fixed sensor which, together with encoder signals, enables control of the position of lens 130 to enable selection of the desired magnification.

A more detailed description of a control system for a copier which incorporates the present invention is contained in our copending Patent Application No 25027/7850 (Serial No 1 604 761) from which the present application was divided.

A related invention is also the subject matter of application 8 104 324 (Patent No.

1 604 762) 55

Claims (4)

WHAT WE CLAIM IS:-

1 A copier having an imaging member to form copies of an original, and having a reduction/magnification capability; including: 60 support means for supporting a document for copying; optical means for transmitting images of the document to the imaging member; and means for providing relative movement 65 between the support means and the optical means, comprising a servo motor for providing the relative movement, an amplifier for powering the servo motor, and control means coupled to the amplifier to control 70 the power output from the amplifier to control changes in the relative position between the support means and the optical means and thereby control the reduction/magnification of said copies 75

2 The copier of claim 1, wherein the support means comprises a stationary platen and the servo motor is coupled to the optical means.

3 The copier of claim 1 or claim 2, 80 wherein the control means comprises a digital controller having means for receiving status inputs related to said relative movement and further having means for generating control outputs in response to said status 85 inputs for controlling the reduction/magnification.

4 The copier of claim 3 wherein said digital controller comprises means for adjusting said control outputs to maintain 90 the relative speed of movement between the optical means and support means substantially constant as said images are transmitted.

I R GOODE Chartered Patent Agent Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.