Serial data communication system for a reproduction machine

Description Submit all comments and votes

RELATED APPLICATIONS

Ser. No. 829,011 filed Aug. 30, 1977

Ser. No. 829,013 filed Aug. 30, 1977

Ser. No. 829,014 filed Aug. 30, 1977

Ser. No. 829,015 filed Aug. 30, 1977

TABLE OF CONTENTS

Subject

Background of the invention

Field of the Invention

Description of the Prior Art

Summary of the invention

Brief description of the drawings

Detailed description of the preferred embodiment

System Overview

Machine Description

Master/Area Communication System

Macs optical Link

Macs i/o instructions and Operational Overview

Table 1

Simultaneous Area Operation

Status Read and Write Commands

Table 2

Table 3

Table 4

Master Controller

Master I/O Interface

Parity Generator

Clock Generator

Shift Controls

Address Decoder

Status Input and Output Control

Interrupt Flip-Flop

Area I/O Interface

Area Controller Operation

Port Structure

Area Microprocessor and Interface

Pseudo-Interrupt Operation

Table 5

Table 5a

Machine Clock Interrupt

Real Time Interrupt

Software Description and Organization

State Checker

Table 6

Interrupt Handler

Paper Path Area Controller

Table 7

Rdh/adf control Console--Controller 8

Table 8

Rdh/platen Servos--Controller 10

Table 9

Master/Servo Software Communications

Table 10

Phase Lock Loop Control

Servo Controller Software

Process Controller 12

Master/PCR Software Communication

Table 11

Table 12

Pcr software

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is in the field of electrophotographic reproduction machines, and particularly those machines controlled by digital computers.

2. Description of the Prior Art

Electrophotographic copying machines are well known within the prior art and typically employ mechanical or combinations of mechanical and electrical control logic for system control. Such control means is responsible for maintaining synchronism between the various operational stations of the reproduction machine and to ensure proper operation of the machine during the various operating modes. These control devices have become increasingly complex as the level of sophistication has increased within the reproduction machine itself. With the advent of variable magnification machines and color copiers the logical control means necessary to achieve proper synchronization and operation has become increasingly complex and expensive. Consequently, attempts to obtain efficient operation of these machines has developed utilizing digital computing device controllers which are programmed to carry out a sequence of operational tasks. Some of these digital device controls are quite specialized and govern only particular localized tasks or operations of the machine such as disclosed in U.S. Pat. No. 3,876,106. System operation as a whole has also been achieved in the prior art utilizing computers with relatively large CPU and memory storage units. Examples of these prior art devices are disclosed in U.S. Pat. Nos. 3,936,182, 3,914,047 and 3,940,210.

With the advent of larger and more complex photo-reproduction machines the various tasks needed to be performed by the machine have become increasingly large. Particularly, an operator may select from a variety of modes of operation, each one designating a particular sequence of operations which must be stored in the computer control means. In some cases the advantages of speed and efficiency of the computer control system has been outweighed by its prohibited cost and large physical dimensions required to store and execute programs defining the desired number and permutations of operational tasks. Still further cost and size restraints come into play when system flexibility is desired by way of expanding the computer control to various other controlled devices or operating stations as would be typical in the offering of a single model copier with various optional attachments. Thus, special purpose hardware may typically be employed as an alternative or addition to the utilization of the central digital computing controller.

Yet another disadvantage of the prior art in computer control devices lies in malfunctioning of the computers due to noise and radio frequency interference resulting primarily from the computer being exposed to the various electrical transients produced by operation of solenoids, motors, relays and the like. Consequently, there exists a need for an ever expanding digital computer capability and at the same time a need to isolate and remove the central controller from the environment of the reproduction machine to achieve error free operation.

SUMMARY OF THE INVENTION

Consequently, it is an object of the invention to eliminate the disadvantages of the prior art by providing an electrophotographic reproduction machine utilizing a distributed microprocessor controller.

Another object of the invention is to provide a reproduction machine having a central or master micro-controlled processor operable in conjunction with an area micro-controlled processor wherein certain system tasks are allocated to the master microprocessor and certain other particular device oriented tasks are allocated to the area microprocessor.

Yet another object of the invention is to provide a micro-controlled photographic reproduction machine utilizing an optical communication link between a central master controller and the various controlled devices so as to achieve an effective error free operation of the master microprogram controller from radio frequency interference generated within the reproduction machine.

Yet another object of the invention is to provide a computer controlled electrophotographic reproduction machine utilizing a single interrupt scheme for enabling simultaneous monitoring of a plurality of control devices in a bit serial communication fashion.

Yet a further object of the invention is to provide a computer controlled photographic reproduction machine wherein a central master controller is interconnected via optical links to at least one passive area controller and at least one active area controller wherein each active controller incorporates a separate microprocessor for controlling specific device tasks, and the passive and active controllers operate together in operative relationship with the master controller to maintain a synchronous control of the entire machine.

The foregoing and other objects of the present invention are attained utilizing a master microprogram controller which is operatively connected to various devices within the operating stations of the photographic reproduction machine and an active microprogrammed controller for controlling a particular device or devices (or portions thereof) such as those devices associated with a particular operating station. The master and active controller are interconnected via an optical link which serves to isolate the master controller from the direct I/O environment. Additional optical links may be provided to interface the master controller with a plurality of passive controllers which serve to latch the output of the master controller to the various controlled devices and serve to forward sensed output data from the operating station to the master controller for processing. The master, passive, and active controllers are all operably connected to one another to control the various devices of the machine.

More generally, the invention provides a reproduction machine having a plurality of operating stations and a plurality of devices for controlling operational tasks within the operating stations. The machine comprises a master programmable controller for controlling some of the devices and an area programmable controller for controlling other of the devices. The master and area controllers are cooperatively operative to control the operating task of the operating stations.

A further object of the invention is to provide a data communications system comprising a programmable master controller having memory storage means and command byte generating means and a plurality of area controllers each having means for receiving command bytes from the master controller and means for providing input data bytes to the master controller. The additional controllers are interconnected to the master controller and have corresponding input data bits of their input data bytes ORed together. The additional controllers simultaneously transmit bytes in response to a pre-determined command byte from the master controller and corresponding bits of the simultaneously transmitted bytes have mutually exclusive data therein. The communications system may be utilized in a reproduction machine or more generally for data communications or for control of other types of machines. The simultaneous transmission technique may be utilized to quickly poll a plurality of additional controllers, and the programmable controller may be configured such that the simultaneously received bytes serve to interrupt the master programmable controller in response to the bits received to cause program interrupt jumps to sub-routines servicing the additional controllers.

The invention is additionally directed to a reproduction machine having a plurality of operating stations and a plurality of devices for controlling operational tasks of the operating stations wherein are provided means for sensing various operational parameters associated with said devices, a master controller having an arithmetic and logic control means for controlling the devices in accordance with the sensed operational parameters and a stored operation program and interface means connected in a communication path between the master controller and the devices, the interface means comprising a fiber-optic communication path which isolates the master controller from electrical noise and transients associated with said devices.

The invention is also directed to a copier/duplicator machine having a plurality of devices for controlling different operations within the machine and comprising a programmable controller including program memory storage means, addressing means, arithmetic and logic means, and means for generating data words for controlling some of the machine devices. The machine utilizes a first document exposure station, means for imaging the document along a first optical path, a second document exposure station which is distinct from the first exposure station, means for imaging the document at the second exposure station along a second optical path, and means for imaging the document along both the first and second optical paths onto a receiving means. The first and second optical paths have at least some portions thereof distinct from one another and the optical imaging means is controlled by the programmable controller.

Yet another feature of the invention is directed to a control system for a reproduction machine which comprises a programmable controller having program storage means for storing an operational program controlling at least some portion of the machine, means for sensing analog data from the machine, analog-to-digital conversion means for generating digital data for processing in said controller in accordance with said operational program, digital-to-analog conversion means for converting the process data into analog signals, and means for controlling at least some portion of said machine in response to the analog signals.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the instant invention will become clear in reference to the foregoing specification taken in conjunction with the drawings wherein:

FIG. 1 is a block diagram of the overall master/area communication system;

FIG. 2 is a schematic illustration of various mechanical components of the copier/duplicator;

FIG. 3 is a block diagram showing the major components of the master unit and an active and passive area controller;

FIGS. 4A and 4B illustrate the master I/O interface and its input and output lines for interconnection to an area controller;

FIG. 4C shows a fiber optic interconnection link utilized for the communication channels;

FIGS. 5 and 6 illustrate the transmission format for data communicated between the master and area controllers;

FIGS. 7A and 7B illustrate the interconnection of various data and address lines from the master tri-state bus to the master I/O interface;

FIG. 8 shows a schematic drawing of key registers utilized in the master I/O interface for transmitting a command and data word;

FIGS. 9A and 9B are schematic drawings illustrating the key input registers in the master I/O interface;

FIG. 10 is a schematic drawing of the parity generator circuit utilized in the master I/O interface;

FIG. 11 shows the clock generating circuit utilized in the master I/O interface;

FIG. 12 shows the logic and timing control circuitry utilized in shifting input data into the master I/O interface;

FIG. 13 shows a timing chart illustrating the overall timing sequence for transmitting and receiving data between the master and area controllers;

FIGS. 14A and 14B are schematic diagrams of further timing and control circuits utilized in the master I/O interface;

FIGS. 15 and 16 show decode logic for the master I/O interface;

FIG. 17 is a schematic diagram of the status write register utilized in the master I/O interface;

FIGS. 18A and 18B are schematic diagrams of the status read register utilized in the master I/O interface;

FIG. 19 is a schematic diagram of the interrupt flip-flop;

FIGS. 20A-20C show schematic diagrams of the key input and output registers and control logic for the area controllers;

FIG. 21 shows the clock generating circuitry utilized in the area controllers;

FIG. 22 is a timing diagram showing the timing sequence of data within the area controller;

FIGS. 23A and 23B show input and output port connections between the host machine and the area controller;

FIG. 24 shows a block diagram of the area microprocessor and its interface circuitry within the area controller;

FIG. 25A is a block diagram showing details of the area microprocessor external memory;

FIG. 25B is a block diagram showing details of the I/O buffers and selection circuit for the area microprocessor;

FIG. 25C is a block diagram showing details of the area microprocessor interrupt and clock detection circuits;

FIG. 26 illustrates details of the area microprocessor interface circuitry for the area controller;

FIG. 27 is a block diagram illustrating input and output port connections for a psuedo interrupt operation;

FIG. 28 is a block diagram showing the different computer states in accordance with the present invention;

FIG. 29 is a flow chart illustrating the overall structure of a machine state;

FIG. 30 is a flow chart of the state checker module for controlling changes of state within the machine;

FIG. 31 is a block flow diagram indicating construction of the Q TABLE utilized to control events in the machine;

FIGS. 32A and 32B are partial flow charts showing the interrupt handler module;

FIG. 33 is a block schematic diagram showing the major portions of the paper path controller utilized in accordance with the invention;

FIG. 34 is a schematic illustration of the major mechanical and electrical sensors and actuators utilized in the paper path area controller;

FIG. 35 is a block diagram showing the major components of the RDH/ADF control console controller;

FIG. 36 is a schematic drawing illustrating the major mechanical and electrical sensors and actuators utilized in the RDH/ADF control console controller as well as the servo controller;

FIG. 37 illustrates a block diagram of the servo controller showing the key components thereof;

FIG. 38 is a schematic drawing of the key platen scanning components;

FIG. 39 is a block diagram showing the port structure utilized for the master-servo controller communication path;

FIG. 40 is a flow chart showing the major steps utilized for the communication routine between the master and area servo controller;

FIGS. 41-43 show logic circuitry utilized in the phase lock loop control of the servo controller;

FIG. 44 illustrates an overall flow chart of the operation of the servo controller software;

FIG. 45 is a flow chart showing the executive routine utilized in the servo area controller;

FIG. 46 is a flow chart showing the phase lock state utilized in the servo area controller;

FIG. 47 is a flow chart showing the various scroll states applicable in the servo area controller;

FIGS. 48-54 show various state flow charts for controlling the platen scanning lamp and carriage applicable in the servo area controller;

FIG. 55 is a block diagram showing the input and output port connections utilized in the process area controller;

FIG. 56 is a flow chart showing the overall sequence governing the communications between the process controller and the master unit;

FIG. 57 illustrates the different filtering techniques utilized in performing the analog-to-digital readings utilizing the process controller; and

FIGS. 58 and 59 are flow charts showing the key operational steps utilized in operating the process controller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

System Overview

FIG. 1 is a block diagram of the overall Master/Area Communication System (MACS) utilized in controlling the copier/duplicator in accordance with the instant invention. MACS comprises a master 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 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, 8, 10, 12, 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. FIG. 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 FIG. 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, 8, 10, 12, 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.

Machine Description

For a general understanding of an electrophotographic printing machine in which the features of the present invention may be incorporated, reference is had to FIG. 2 which depicts schematically the various components thereof. Although the control logic employed in the electrophotographic printing machine of FIG. 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 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, through the various processing stations. One type of suitable photoconductive material is a selenium alloy such as described in U.S. Pat. No. 2,970,906 issued to Bixby in 1961. Preferably, the conductive substrate is aluminum.

Initially drum 110 rotates a portion of photoconductive surface 112 through charging station A. Charging station A employs a corona generating device, indicated generally by the reference numeral 116, to sensitize a portion of photoconductive surface 112. Corona generating device 116 is positioned closely adjacent to photoconductive surface 112. When energized, corona generating device 116 charges the portion of photoconductive surface 112 therebeneath to a relatively high substantially uniform potential. A suitable corona generating device may be of the type described in co-pending application Ser. No. 748,805 filed in Dec. 8, 1976, now U.S. Pat. No. 4,086,650, issued Apr. 25, 1978, the relevant portions thereof being hereby incorporated into the present application. As described therein, the corona generating device includes a corona discharge electrode having a conductive shield located adjacent thereto. The electrode is coated with a relatively thick dielectric material so as to substantially prevent the flow of conductive current therethrough. Photoconductive surface 112 is charged by means of a displacement current or capacitive coupling through the dielectric material. The flow of the charge to photoconductive surface 112 is regulated by means of a D.C. bias applied to the shield.

Thereafter, drum 110 rotates the charged portion of photoconductive surface 112 to exposure station B. Exposure station B is arranged to produce a light image of an original document or series of documents being reproduced. In the electrophotographic printing machine depicted in FIG. 2, exposure station B operates in one of two modes. In one mode, a plurality of original documents are recirculated in an automatic document handling system (ADH) so that sets of collated copies may be formed by the printing machine. In the other mode of operation, a single original document is placed on the platen and reproduced by the printing machine. If the platen scan optics are used, mirrors 118 and 120 are moved into the operative position depicted in FIG. 2. An original document is placed face down upon a transparent platen 122, such as a glass plate or the like. Lamp 124 illuminates the original document disposed on platen 122. 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 126 to half rate mirror 128. Half rate mmirror 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 photoconductive 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 image thereon corresponding to the information areas of the original document disposed to the informational areas of the original document disposed on platen 122.

In the automatic document handling system for making pre-collated copy sets, the 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. This web is wound between two spaced web scrolls positioned and wound so as to obtain the document between the turns of the web scrolls. The web is repeatedly wound and unwound 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. The documents are optically exposed on the web between scrolls for copying. The details of the automatic document handling system are more fully disclosed in U.S. Pat. No. 4,008,956 issued to Stemmle et al in 1977, the relevant portions thereof being hereby incorporated into the present application. 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 rotatable 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 90.degree. about its axis and reflects the light rays transmitted from the original document onto mirror 144. Mirror 138 also rotates 90.degree. about its axis to receive the light rays transmitted from light rays 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. At this time, mirrors 118 and 120 are positioned remotely from the optical light. The foregoing optical system for the ADH system is disclosed in U.S. Pat. No. 4,008,958 issued to Kingsland in 1977, the relevant portions thereof incorporated hereby into the present application. 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 particles 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 FIG. 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 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 photoconductive 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 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 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 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. 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. Preferably, corona generating device 158 is also of the type described in copending patent application Ser. No. 748,805 filed in 1976, the relevant portions thereof being hereby incorporated into the present application.

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. A scavenging roller 160 is provided for removing these carrier granules. Scavenging roller 160 comprises a magnetic member and a rotatable, non-magnetic tubular member interfit telescopically thereover. The tubular member rotates relative to the magnetic member. In this manner, the magnetic carrier granules are attracted from photoconductive surface 112, while the toner powder images remain undisturbed thereon.

With continued reference to FIG. 2, a sheet of support material is advanced by sheet feeding apparatus 162 or 164 from either tray 166 or tray 168. Conveyer system 170 advances the sheet of support material to transfer station D. Rollers 172 speed up or slow down the advancing sheet of support material so as to ensure that it moves into contact with drum 110 in a timed 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 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. Preferably, corona generating device 174 is also of a type described in copending U.S. patent application Ser. No. 748,805 filed in 1976, the relevant portions thereof being hereby incorporated into the present application.

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 photoconductive 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 roll 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. Preferably, fusing assembly 178 is of a type described in U.S. Pat. No. 3,912,901 issued to Strella et al in 1975.

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, the sheet of support material with the toner powder image permanently affixed on one side thereof is advanced to duplex tray 183. In the ADH mode of operation, a plurality of sheets are stored in duplex tray 183 having the corresponding toner powder images permanently affixed to one surface thereof. 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 conveyer 185. Duplex conveyer 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. This duplexing arrangement is described more fully in copending application Ser. No. 767,012 filed Feb. 9, 1977, the relevant portions thereof being hereby incorporated into the present application.

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 tr