CA1111490A - Recording element for electrophotographic copier - Google Patents
Recording element for electrophotographic copierInfo
- Publication number
- CA1111490A CA1111490A CA313,194A CA313194A CA1111490A CA 1111490 A CA1111490 A CA 1111490A CA 313194 A CA313194 A CA 313194A CA 1111490 A CA1111490 A CA 1111490A
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- Prior art keywords
- recording element
- indicia
- web
- lcu
- signals
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Abstract
RECORDING ELEMENT FOR
ELECTROPHOTOGRAPHIC COPIER
ABSTRACT OF THE DISCLOSURE
The recording element of an electrophotographic copier is provided with a plurality of equally spaced timing marks or other indicia along one edge thereof.
Sensing means, positioned adjacent to the path along which the recording element is advanced during the electro-photographic copying process, act to sense the passage of the marks and to generate signals from which the position of each image area of the recording element can be accurately determined. The output signals from the sensing means are fed to a logic and control apparatus (e.g. a programmed digital computer) which controls the activation of the various processing stations in timed relation with the receipt of signals.
ELECTROPHOTOGRAPHIC COPIER
ABSTRACT OF THE DISCLOSURE
The recording element of an electrophotographic copier is provided with a plurality of equally spaced timing marks or other indicia along one edge thereof.
Sensing means, positioned adjacent to the path along which the recording element is advanced during the electro-photographic copying process, act to sense the passage of the marks and to generate signals from which the position of each image area of the recording element can be accurately determined. The output signals from the sensing means are fed to a logic and control apparatus (e.g. a programmed digital computer) which controls the activation of the various processing stations in timed relation with the receipt of signals.
Description
`~ 114~0 BACKGROUND OF T~E INVENTION
'' This invention relates to apparatus for controlling the operation of the various processing stations of electro-pho~ographic copying apparatus.
In a common form of electrophotographic copying apparatus, a toner image of an information medium, such as a document, is formed on a photoconductive recording element, ~rd then transferred to a paper CQpy sheet. To initially form the toner image on the recording element, the latter is transported along a path past a plurality of processing stations, each of which is selectively operable to perform one of the steps of Ihe electrophotographic copying process. Such stations include:
,:.
a charging station at which a uniform charge is deposited on the photoconductive surface of the recording element; an ex-posure station at which the charged photoconductive surface is magewise exposed to actinic radiation from the medium to create hn electrostatic image of the medium in the recording element;
.
a developing station at which the electrostatic image is con-tacted with finely divided charged markina particles (i.e.
toner) to render the electrostatic image visible; a transfer station at which a copy sheet is advanced into contact with the toner-bearing surface of the recording element to transfer the toner particles, in image configuration, to the copy sheet; and a cleaning station at which residual toner is removed from the surface of the recording element so that the recording element may be recycled through the electrophotographic process.
In electrophotographic apparatus which process the recording element automatically, it is necessary to precisely control the activation and the deactivation of the various proces-sing stations in timed relation with the movement of the recording element. Otherwise, the copy sheet, for instance, could be advanced to the transfer station before or after the toner image . ~
:`
arrives thereat, the result being imperfect registration of the transferred toner image with the edges of the copy sheet.
To provide such contrd, it is, of course, necessary that the control dcvice bc continuously updated on the precise position of the recording eLement during its travel along the path past the processing stations In applications in which the recording element is continually recycled, it is typically constructed in the form of a drum or an endless web. When in a drum configuration, the recording element is mounted for rotation on a driven shaft, and synchronization of the operation of the various processing s~ations with movement of the drum is commonly controlled by a bank of cams which also rotate with the drive shaft. Because both the recording element and the cam bank are fixedly mounted on the drive shaft, the position of each cam always reflects the precise position of the recording element Thus, synchronizing ;`~ the actuation of the processing stations is straight forward.
However, when the recording element is an endless web con-f;guration, such synchronization is not as simple.
When in a web configuration, the recording element is trained about a plurality of spaced rollers and is driven by either a sprocket or a friction drive mechanism. By using a sprocket drive, it is relatively simple to correlate the position of the recording element with the angular posLtion of the sprocket drive shaft as long as there is substantially no slippage between the sprocket and the web. However, in any sprocket drive, there is a`tendency for the driving sprocket to eventually tear or enlarge the web perforations which it drivingly engages. As the web perforations enlarge, control of the position of the recording element diminishes because there is a slippage between the driving sprocket and the web.
While the friction drive approach has little tendency to tear ' : - ? -the web, there is even more of a tendency for the web to slip reLative to the roll by which it is frictionally engaged and driven. Thus, the position of the shaft of the drive roll cannot be correlated with web position and, hence, cannot be used to synchronize the operation of the various processing .
- stations.
One approach to the above problem has been to place a timing mark on one edge of the recording element and to use : .
the mark to generate a signal to activate a cam banlc, which operates independently of the web movement to control the operation of the processing stations. See, for instan-e, U.S.
Patent No. 3,606,532. In essence, this approach provides the processing station control apparatus with an update of the web position at the start of each copy cycle. A disadvantage of this approach, however, is that registration problems will still exist if there is any slippage between the web and the friction drive after initiation of the timing cycle by the t ming mark. Also, when the web defines several frame areas, a separate cam bank and multiple switch arrangement is needed for each frame area of the web. Such a complex electro-mechanical control system is subject to reliability problems.
; , .
SU~RY OF THE INVENTION
;:
- An object of the invention, therefore, is to provide an improved method and apparatus for synchronizing the actuation of the various processing stations which comprise an electro-photographic copying apparatus with the movement of the recording element.
- According to a preferred embodiment of the invention, one edge of the recording element of an electrophotographic copier is provided with indicia, such as a plurality of per-- forations, which serve as timin~ marks. Sensing means, fixedly ~sit;~ne~ adiacent the patl- along which the recording element is advanced, sense the passage ~f the indicia and produce clock ., pulses in respe e thereto. Such cloc~ pu~ es provide a logic and control unit, preferably including a digital computer ~ 9 O
,:
which is programmed to actuate the various processing stations according to a predetermined sequence, with information from w~ich it accurately determines the position and rate of movement of the image frame of the recording element. Using this position information, the logic and control unit synchronizes the operation of the various processing stations with the move-ment of the recording element along its path.
BRIEF DESCRIPTION OF THE DRA~INGS
Figure 1 is an illustration of an electrophotographic copying apparatus embodying the invention;
Figure 2 is a partial perspective view showing in detail ~ portion of the photoconductive recording element of the Fig. 1 apparatus;
Figure 3 is a block diagram of the various components o. the logic and control unit shown in Figure l;
, Figure 4 is a diagram which shows the timing cycle ` of the apparatus shown in Figure 1.
- DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
- To better ùnderstand the present invention, the operation of an electrophotographic copier embodying the in-vention will be briefly described. It is to be understood, , .
however, that the apparatus of the present invention could be ` used with equal facility and advantage in other copying machines and, therefore, the following description of apparatus related to, but not Eor,;lLng a part of, the invention is provided for illustrative purposes only.
Electrophoto~raphic Apparatus .
Reference is now made to Figure 1 wherein an electro-photographic copier embodying the invention is schematically illustrated. As shown, the copier includes a reusable photo-conductive recor(ling elelnent 1() which is in the form of an 1~ .
` lil~4~Q
endless web 16. The recording element is a multi-layer structure, including a conductive laycr disposed between a photoconductive layer and a transparent support. Preferably, the conductive layer is transparent to permit exposure of the photoconductive layer from both sides thereof. Means (no~
shown) are provided for electrically grounding the conductive layer. The photoconductive layer may be formed from, for instance, a heterogeneous photoconductive composition of the ~ype disclosed in U.S. Patent 3,615,414, issued October 24, 1971.
Web 16 is trained about transport rollers 4-9, at least one of which is continuously rotatably driven to frictionally engage the transparent support of web 16 to continuously ad-vance the web in a clockwise direction, as viewed in Figure 1.
l'he dimensions of web 16 define several image areas or frames which are spacedly arranged side-by-side. The splice by which web 16 is rendered endless is, by means of the control ap-paratus of the invention, always maintained at an interframe position so as not to interfere with and degrade image formation and quality.
Arranged at fixed locations adjacent to the path along which recording element lO is advanced are the various proces-sing stations which collectively serve to form a transferable toner image on the various image areas of the recording element.
Such~ stations includ~e: a charging station 18, at which a uniform charge is deposited on the photoconductive layer of recording element lO to initiate the copying process; an exposure station 20 at which the uniformly charged surface of the recording element is imagewise exposed to an information medium 13, such as a document, to selectively dissipate the charge on the recording element and thereby form a latent electrostatic image of the information medium;and a developing station 22 at which electroscopic toner particles are applied to the recording element to render visible the elcctrostatic image borne thereby. Also positioned adjacent the path of the re-..
~_rding element are: a transfer station 24 at which the developedimage is transferred in imagewise configuration to a paper copy sheet, and a cleaning station 17 which serves to remove residual toner particles from the recorcling element following transfer. In addition to the above stations, more details of which are provided hereinbelow, the copying apparatus in-cludes an auxiliary erase lamp 33 which, when actuated, flood exposes the photoconductive layer of the web to dissipa~e and thereby prevent development of, any undesired charge pro-~uced on the recording element during the initial start-up or shlt-down of the copier, and a post development erase lamp 23 wllich, when actuated, serves to flood expose the photoconductive la-~er of the recording element imm~diately after development .: .
to reduce photoconductor "fatigue" and to facilitate transfer of the toner image.
In addition to those processing stations physically po,itioned adjacent to the path of the recording element, the c~pying apparatus also includes a pair of copy sheet feeding stations 21 and 27, a registration station 19 at which a copy sheet advanced from stations 21 or 27 is placed in registration ,, .
with a toner image advancing toward the transfer station 24, `" and a fusing station 30 at which the transferred toner image is permanently fixed to the copy sheet.
Although not shown, charging station 18 typically comprises a corona generator t such as disclosed in the commonly assigned U.S. Patent 3,527,941. Charging station 18 operates under the control of a logic and control unit 9, hereinafter referred to as the "LCU", as do all other stations and accessories of the copying apparatus. Control of station 18 by the LCU is effected via lead 18a.
Exposure station 20 preferably comprises a pair of selectively energizable xenon flash lamps 14 which are arranged paralLel to one another outside opposing edges of the information ; 6 ... . .
medillm 13. ~hen energized by the LCU via leads 14a, lamPs 14 momentarily illuminate the information medium and image there~
of is proJected by lens 15 upon the uniformly charged photo-c~n~uc~ive surface of web 16. Because of the intense output of lamps L4 imagewise exposure of web 16 is accomplished "on the fly", i.e. without stopping the web As will become more apparent from the description of the LCU, the LCU is capable of storing information concerning the total number of copies produced by the copying apparatus. Due to this capability and other features of the LCU discussed below, the LCU can be used to periodically increase the output power ot the flash lamp to compensate for any loss of photoconductor speed with usage of the web.
Developing station 22 may comprise a double magnetic brush apparatus, such as disclosed in the commonly assigned U.S. Patent 3,543,720, issued to Drexler et al. LCU 9 can used to automatically control the electrical bias of the magnetic brushes, which act as development electrodes, in accordance with the charge density in the background areas of the ~lectrostatic image. Sensing of such charge density may be ~ffected by positioning a metal plate (not shown) adjacent to the web path, upstream from the developing station, monitoring the charge induced thereon, and feeding a signal proportional .
thereto to the LCU. The LCU can properly bias the magnetic brushes via lead 22a. Alternatively, the bias level can be manually set through the LCU.
Transfer station 24 may comprise,as shown, a pair of corona generators 25 and 26.- Corona generator 25 acts to charge the paper copy sheet so as to render it attractive to the toner image. Assuming the toner particles are initially char~ed to a positive polarity so as to be attracted to the negative charge deposited by the primary charger 18,then the corona gcnerator 25 shoul~i be powered by a negative D.C.
~ ~' 1111490 power supply. Corona generator 26 is known as a "detacking corona" and serves to neutralize the electrostatic forces bonding the copy sheet to the web 16 following image transfer.
As shown the detacking corona is powered by a positively biased A.C. power supply. LCU control of both power supplies of the transfer station is effected via lead 25a.
Following transfer of the toner image to a copy sheet, the latter is stripped from web 16 as the web bends shlrply over small transport roll 8. Vacuum transport 29 ~elivers the copy ~eet to the nip of a roller fusing device 30 which comprises an internally heated fusing roll 30c which :
se ectively cooperates with a pressure roll 30b. The latter is movable into engagement with fusing roll 30c in response to a signal provided by the LCU on lead 30a.
~;, I
. I After fusing, the copy sheet follows either of the r aths labeled 31 or 32 in exiting from the machine to either a nopper 34 or a copy handling accessory 36, such as a sorter.
~ LCU 9 can be used to control the path followed by the copy sheet s via a signal applied to lead 36a which controls a movable de-flector plate in the paper path.
Cleaning station 17 may include an erase lamp, D.C.-biased A.C. corona and a vacuum cleaner (see Fig. 4), all of which operate under the control of the control apparatus of the - invention.
As mentioned above, the various processing stations of the Fig. 1 apparatus, in addition to the other components of the copying apparatus discussed hereinbelow, are selectively activated by and operate under the control of logic and control unit 9. This unit, the LCU, preferably includes a digital computer 74 (see Fig. 2) .;. ; .~
which is programmed to control the operation of the various work stations according to a predetermined sequence and in timed re-lation with the receipt of signals indicative of the rate of movement and the instantaneous position of the recording element.
Such signals are generated by transducers 76a and 76b which are fixedly arranged relative to the web path and which sense indicia carried by the recording element, preferably in the form of perforations. These signals provide the computer with up-to-date information (which may also appropriately be called "real time"
information) regarding the precise location of each image area of the recording element, and are used by the computer to determine when certain work activities should commence and terminate.
The output of the LCU selectively controls such activities accordingly. The manner in which the LCU derives position information from the recording element and uses such information to control the operation of the various work stations is des-cribed in detail below, Recordin~ Element As mentioned above, the length of web 16 is such as to enable a plurality of copies, such as six, to be made each time the web is cycled through the electrophotographic process.
Assuming web 16 defines six image or frame areas, this means that each frame area occupies approximately a 60 degree segment of the web. Actually, each frame area is slightly less than 60 degrees to allow for a small interframe area.
As shown in Fig. 2, one edge of web 16 is provided with two parallel rows of equally spaced indicia, shown as perforations 16a and 16b. Perforations 16a and 16b are herein-after occasionally referred to as "F" and "C" perfs, respectively.
, ` - 1111490 The number of F perfs on the web exactly equals the number of frame areas, and each F perf is located at a predetermined p~sition with regard to each frame area. As will be seen ~elow, each F perf cooperates with transducer 76a to provide the LCU with information regarding the position of the leading edge of all the image areas on the recording element. Also, it is the F perf which signals the LCU to initiate flash exposure and to feed a copy sheet to the transfer station 24.
~e C perfs, in effect, finely divide each frame area of the web into a plurality of increments, for instance, fifty-one.
As will be seen belo~, the C perfs cooperate with transducer 76b to provide the LCU with clock pulses from which it determineS web speed, and hence, frame position after it departs . . .
from the exposure station. As will be seen below, the LCU
eomprises counting means (e.g. a shift register) for counting ircoming F and C perf signals and means ~r actuating the various stations in response to a predetermined F and C perf count. Each time an F perf is received by the LCU, the C perf is reset to zero.
Electromechanical Transducers As shown in Figs. 1 and 2, the copying apparatus includes a pair of electromechanical transducers 76a and 76b which are fixedly arranged relative to web 16 to sense the passage of the F and C perfs, respectively. Transducers 76a and 76b are commonly referred to as "bimorph sensors".
Bimorph sensors which are suitable for use in the . . .
present invention are described in commonly assigned U.S. Patent 3,723,650 in the name of Bradley et al, issued March 27, 1973.
Briefly, each ~morph sensor includes a piezoelectrical crystal ~ .
82 which has attached thereto a single step sensor 83 element, the distal end 84 of which bears on and slides against the moving web member 16. When a perforation in the web member 16 moves b2neath the distal end of the sensor element, the end abruptIy drops over the leading edge of the perforation and distorts or otherwise induces mechanical movement of its associated transducer. As the web member 16 continues to move, the sensor element 83 is forced out of the perforation by engage-mcnt with the trailing edge of the perforation, and once again t~.e sensor element distorcs its associated piezoelectric trans-ducer. By means of electrodes or other suitable current collecting ans attached to the sensors, voltage signals generated by the distortion of the transducer are transmitted to the computer 74.
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~l Other types of perforation sensors which produce output signals ..
~uch as optical perforation sensors or other types of ceramic ~ ~ ansducers responsive to compression, bending or cther forms ; , of phy6ical distortion, may be substituted for the depicted bimorph sensors.
- Lo~ic and Control Unit Turning now to Fig. 3, there is shown in block ; diagram form the Logic and Control Unit which interfaces with the various processing stations and the bimorph sensors. As indicated above, the LCU preerably comprises a progranmable ; ~ digital computer 74. The LCU could, however, be hardwired logic circuitry which would include shift registers, counters and decoding matrixes. An example o such hardwired logic which could be adapted for use with the present structure is shown in commonly assigned U.S. Patent 3,732,005 to Lloyd. In such patent, there is disclosed a control apparatus for an electrophoto-graphic machine whicn in response to cloclc pulses timed from the motor drive shaft of such machine produces control signals fQr actuating and deactuating work stations in timed relation to movement of the web. The disclosed apparatus includes counters and decoding matrixes. However, it has been determined, in accordance with the invention, that a miniature digital computer is especially adaptable to provide the functions of the LCU
mentioned above, in addition to other copier functions. For instance, a computer can periodically interrogate a toner con-centration monitoring device and actuate a toner replenishing mechanism at an appropriate time. Further, it can be used to i periodically interrogate paper jam and misfeed detectors in the copy machine and shut down the machine if necessary. Further, it can monitor the number of copies made, compare this number ~.th the number of copies requested and inactivate the machine at the appropriate time. Various other functions which the computer may serve are discussed later herein.
Computer 74 may take various forms known in the art, some of which are commercially available as programmable mini-computers and programmable micro-processors. The Model , *
8080 Micro Computer manufactured by Intel Corporation of Santa Cl~ra, California is an example of a suitable micro-processor.
T~1e GEPAC 30, manufactured by the General Electric Corporation;
~he Interdate Model I and the Varian Data Machines Model 520/i are specific examples of suitable mini-computers. The instructions and methods of programming such devices is set forth in the text-book, "Mini-Computers for Engineers and Scientists", by * Trade Mark ' ' .
, ~ 11114gO, `~
Gravino ~. Korn, published by Mc~r~w Hill Book Comp~ly, ` (1973).
Microprocessors are similar to mini-computers, but there are some basic differences. For instance, a micro-processor, unlike a mini-computer, is generally fabricated with only one or a small number of integrated circuits. Moreover, it : does not have a very high computing storage memory and, hence, is relatively inexpensive. However, its speed is fast enough to make it entirely suitable for controlling all work operations of a very high speed electrophotographic apparatus. As is well ; known, the curren~ rnicroprocessors require a read and write :, memory (RAM), for data storage; a read only memory (ROM), for program storage; and circuits for obtaining access to the ~pparatus under the control of the microprocessor. It is ~ecoming quite common to convert all the hard-wired logic functions into programs which are stored in the ROM. The functions disclosed by the hard-wired logic in the above-referenced Lloyd disclosure all can be performed by a micro-processor.
With respect to the Intel microprocessor, Model 8080, such a device operates on a word size of one byte or eight bits and has an instruction time of between two and six microseconds, and used a memory size of 65,536 bytes. The number of instructions which implement such microprocessor is 48; and it has interrupt capability, address models of operation, and five 8-bit registers in addition to a progran control register and an unlimited stack.
The above-discussed RAM and ROM are standard with th~ unit. More ; particularly~ the Intel 8080.contains instructions registers, local memory, arithmetic output and input-output buffers. Of course, there are a num~er of oth~r su.tab~e microprocesso-Ls.
'~ * Trade Mark '~ 49~
~, ~ On~ of the most popular is Intel 4004 microprocessor. This . ~ .
microprocessor contains five functional st~tions, address register and stack with an address-incrementing circuit, a set of 1~, four-bit arithmetic and logic unit, and eight-bit instruction register and decoder and peripheral circuitry.
The following material discloses how to translate hard-wired logic into microprocessor sequences: John B.
Peatman, "Design of Digital Systems," pp. 211-216 and secs.
6-6, 6-7, McGraw-Hill Book Co., 1972; "MCS-4 Microcomputer Set User's Manual," Intel Corp., July 1972; and "8080, 8-bit Parallel Central Processor Unit," Intel Corp., November 1972.
As shown in Fig. 3, computer 74 comprises a tem-porary data storage memory 90, a central processing unit 92, a timing and cycle control unit 94, and a stored control program 96. The temporary data storage memory stores such infor-mation as the number of copies requested for each machine opera-tion, the total number of copies made by a particular recording element, etc. Some of the information stored by memory 90 need ..,,.:
only to be stored for one machine operation. The number of copies requested is exemplary of such information. Other information stored by memory 90 must be stored for several machine operations. The total number of copies produces by a particular recording element is exemplary of this type of information. Thus, the temporary data storage memory includes ~oth a volatile and a non-volatile Read/Write Memory (RAM).
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The control program 96 may be embodied by a commercially available ; Read Only Memory (ROM). The ROM would contain the operation~l * Trade Mark program in the form of instructions and fixed binary numbers corresponding to numeric constants. Such programs are p~nmanently stored in the ROM and, of course, cannot be altered by computer operation. Preferably, the ROM is programmed at the point of manufacture and the instructions programmed provide the required control functions such as sequential actuation of the processing stations, jam recovery, operator observable logic and machine timing. For a specific example, the total ROM
capacity could be approximately 5,000 words, with each word being : ' 8 bits in length. Data input to the computer and the computer output is performed sequentially according to the control programO
Input d ta from the bimorph sensors is fed to the central processing unit through an interrupt signal processor 104 (dis-closed below). Other input signals such as the output signals ' of a toner monitoring device, paper misfeed sensors, copy count i sensors, are applied to the central processing unit through an ~.: ., .
input signal buffer 100 and a multiplexer. The output data and control signals are applied to storage latches 106 (e.g. con-3 ventional flip-flops) which provide inputs to suitable output - drivers 108 dlrectly coupled to the leads for the processing station. More specifically, the output signals from the LCU are logic level, digital signals which are buffered and amplified to provide drive signals`to various clutches, bralces, solenoids, power switches and numeric displays of the copying apparatus.
The LCU processing functions can be programmed by merely changing the instructions stored in the computer memory. This provides a flexible machine logic and timing arrangement and extends the 1111~0 LCU capability to include the capac ty for performing service ~ia~nostics.
q, Computer Interrupt As noted above, the LCU controls, by a counting :,... .
~-~ technique, the copying cycle and activates the processing , .. ~
stations which perform the required operation in the processing of each active and inactive image area on the web. Also noted, is the fact that the mechanism for selecting the appropriate input signal processing technique is a program stored in the LCU computer. Since the computer 74 cannot operate on all inputs and outputs simultaneously, a technique for selecting . ~ , those signals to be processed, during each phase of the copy - cycle, has been developed. `Again, the F perf and C perf are ~' the key factors to selecting the appropriate control programs.
As mentioned above, the F perf and C perf signals are counted ,i - ~nd stored in the memory 90 of the LCU computer. ~he location ~f active and inactive image areas along the web path can be determined from the F perf and C perf count. Thus, those signals critical to the process, that should be occurring at any particular count in the cycle, can be selected for processing by the LCU. Other none critical signals are processed periodically, l when the LCV is not required to recognize a C perf or F perf signal. The C perf and F perf signals override other inputs to the LCU computer, by interrupting the computer; thus, the occurrence of these signals is always detected by the LCU.
The use of a computer interrupt is well known in the computer art. For a complete explanation of this technique, see the - I above-referenced text, "Mini-Computers for Engineers and Scientists."
~eration . .
As indicated above, proper sequencing of machine control signals is critical to the production of high quality ' ; ~o~ies and to prevent paper misfeeds, misregistration and erratic operation. The primary approach for controlling the - timed sequence of events and their relationship to each other '.:-is, as noted above, to sense the location of the image areas ' of the web as they continually cycle, and to synchronize the ~J
various control mechanisms with the movement ofthe image areas.
The technique for accomplishing this, as previously noted, is l to sense equally spaced perforations formed in the edge of , web 16, such perforations occupying a known position relative . .
: to each image area. The web member, as noted above, is prefer-..
ably divided into 6 image frames, each designated by an F perf, and the space between each F perf is subdivided into 51 increments by 51 C perfs. Machine sequencing control is implemented in the LCU by converting signal timing and combinational logic require-ents to programs that control the LCU computer. These control programs establish the basic operating mode and sequence of events for the machine subsystems.
The electrophotographic cycle is initiated by actuation of switches on a conventional operator's control panel (not shown). The appropriate switch on the panel may be selected for one or two'sided copying. The LCU 9 accepts input signals from the operator's panel, stores the signals in the computer memory 90, and decodes the signals to select the program which will initiate and control the electrophoto-graphic cycle. In addition to selecting a machine operating ~.~
~ ~ ,. 1111~90 - mode, the operator input panel is also used to select a quantity of copies. This information, also stored in the LCU computer memory 90, is compared to the quantity of copies ; ~o~pl~ted during the cycling of the machine. Upon delivery o~ the requested number of copies, the LC~l develops output signals to deactivate the copying mode.
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During the copying cycle, the F and C perf signals provided by the bimorph sensors are the primary control signal inputs to the LCU, and provide the synchronizing signals for the control of events. The LCU computer counts F perfs and C perfs and stores this information, together with fixed data, (e.g. the maximum number of active image elements and the distance between adjacent C perfs on the web). The LCU
computer determines where each active and inactive image element is with respect to the F perf sensor. This information is combined with knowledge of the spacing between various pro-cessing stations along the web path to develop control signals ~hich activate these processing stations at the required point in the cycle. Thus, the speed of web 16 need not be precisely known. The length of web 16, the spacing between perforations, qnd the location of the processing stations relative to the r perf sensor must be known and fixed.
Reference is now made to Fig. 4 wherein a typical ^opy cycle consisting of a single copy is used to illustrate ~hen, during the movement of the recording element, certain events occur, and the duration of such occurrences. The angular spacing of the various processing stations shown in Fig. 4 is equivalent to the linear spacing between such stations in the Fig. 1 npparatus. The film path is represented by the inner circular path of the annulus or Fig. 4. It is assumed that web 16 defines six image areas, each subtending an arc of approximately 60 degrees. Actually, each image area subtends an arc of slightly less than 60 degrees to allow for an interframe spacing, one of which includes the splice in the recording element. Because of its six image areas, web 16 is provided with six equally spaced F perfs, each occupying the same location with regard to its associa-ted image area. The area between each F perf is subdivided, as noted above, by 51 C perfs, thus dividing the entire recording element into a total of 606 incremen~ The letters A - J are used to indicate the location at which various events occur as the leading edge of an image area passes such : ~ .
~-~ locations during its clockwise movement around the endless ~1 path. The signals developed by the LCU computer during the ~ copy cycle are indicated in timed sequence in Table I. As ; shown in Table I, as the leading edge of the image frame passes position A, certain processing stations are turned ON.
- l`hese include those stations which remain ON throughout the . . .
copying cycle, as well as those whch are only required for the initial portion of the copying cycle. The system components which remain ON continuously include the post-development erase lamp 23 and the various components of the cleaning sitation 17 which, as shown, may include an erase lamp, a corona and a cleaning vacuum. As the recording element passes point B, the C perf count stored by memory 90 is reset to zero by the F
perf pulse. From this point on, all events are controlled simply by counting a specific number of F and C perfs and controlling the events according to the number of F and C perfs counted, and whether or not the requested [lumber of copies has been made.
' - -19_ ~` ~
~ -` 11114~90 ..
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, ' TABLE
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..... .
'.' SEO~UENCE OF EVENTS FOR SINGLE COPY RUN
.,, FIGURE 4 CONTROLI.ED EVENTS
, FILM POSITION
.
A START Switch Actuated : System Operate ON
Primary Charger 0~
Auxiliary Erase Lamp ON
B Reset C Perforation Count to Zero ~I C Illumination Power Supply "Initiated"
O
D Flash Exposure . ~ ' .
E Auxiliary Erase Lamp OFF
Monitor Enable ON
~ .
.
: F Auxiliary Erase Lamp ON
! primary Charger OFF
-;
G Paper Peed.
H - Transfer Charger ON
. Detact Charger ON
'' - I Transfer Charger OFF
Detact Charger OFF
STOP
System Operate OFF
Auxilidry Erase Lamp OFF
.
~ . . . .
Table II illustrates the information stored in the LCU during a multiple-copy cycle. A Run flip-flop and a PRINT flip-flop, although not shown, will be understood to be located in the central processing unit 92 of the computer 74. These flip-flops are actuated and, as shown in Table II, are switched to a logical "1" by depressing the START button.
When the stored C count first reaches 51 and an F perforation is detected, the LCU stores a logical 1 in a five-bit shift register disposed in the processor 92 which counts and stores the number of F perforations sensed. At the same time as when the third F perforation signal is fed to the five-bit shift register, a first binary signal is sent to an 8-bit paper shift register. At this time, the computer not only causes an image of a document to be~exposed on the web, but also causes a first copy sheet to be fed to the transfer station. Thus, three "F"
~erf signals must be sensed before a developed toner image area is disposed adjacent the transfer station. The 8-bit shift register, of course, counts and stores the number of copy sheets fed. As shown in Table II, if ten or more copies are to be made, both shift registers will become full. The machine will continue to imagewise expose the recording element until ~e number of copies requested equals the number stored in the "copies requested"counter (in Table II, it is ten). At this time, a time-out cycle will commence, causing the PRINT flip-~ . ...
flop to be reset to a zero state. In this state, further exposure of the recording element is inhibited. During the , time-out cycle, successive F perorations signals clear the .'~ .
. .
, 4~0 shift reglsters as indicated in the table. As successive F
perforations are detected, copy sheets are fed into the tr~nsfer station. At the end of the cycle, the machine is ' , set in a stand-by mode.
. . , "'~' : ' .
`,;~ 90 T~T~7 .~ T I
- SE(~UENCE 07' EVEilTS FOR ~IULTIPLE CO?Y, ONE-SIDE COPY ~10DE
. .
. 'RUN PRINT SHIFT SHIFT C F
FLIP-FLOP FLIP-FLOP REGISTER REGISTER COUNT COUNT
; S t art 1 l O O any O
: ~ 1 l 0000100000000 51 :., :~ 1 1 0001100000000 51 2 . ~
, 1 1 0011100000001 51 3 ' ~ 1 1 OllllOOOOOOll .5l 4 lllll00000111 51 5 . .
., .
; 3 1 1 11111 11111111 51 lo ~ - 1 o llllo 11111111 5 ,., ~ . .
.~.; j . .
:, 1 0 11100 11111111 51 12 ~ 1 0 11000 11111110 51 13 ., , ' 1 0 1000011111100 51 14 , 1 ~ .
,,"~ s .-; .
~i ' , Misc~;lan~cus LCU Functi~ns In addition to controlling the operation of the various processing stations, the LCU computer 74 can be used, with suitable sensing elements, to detect copy sheet jams and copy sheet misfeeds.
Paper Jam and Misfeed Lo~ic The paper path is shown in Figure 1. As discussed with ~spect to the timing diagram (Figure 4), the paper feeding is initiated by the LCU 9. Paper registration is accomplished by mechanical means and is controlled by the registration mechanism 19. A number of sensors may be located along the paper path to detect paper feeding or mis-feeds and produce signals to the LCU at properly selected positions. These signals may include (1) leading edge detector in the paper feed mechanism, (2) transfer jam , detector, (3) side exit/top exit jam detectors, (4) sorter jam detection. The jam signals are monitored by the LCU
computer and in the event of a paper jam, the computer 74 is programmed to develop control signals for a machine shut-down with indication to the operator to check the paper path.
The machine jam c~etection logic incorporates signal sensing and control which reduces the potential of mechanism damage caused by a paper jam.
In the copying mode, the flow of paper from the supply to the exits under nominal conditions is completely predictable. The time between initiation of paper feed and the arrival of paper at any of these paper sensing switches
'' This invention relates to apparatus for controlling the operation of the various processing stations of electro-pho~ographic copying apparatus.
In a common form of electrophotographic copying apparatus, a toner image of an information medium, such as a document, is formed on a photoconductive recording element, ~rd then transferred to a paper CQpy sheet. To initially form the toner image on the recording element, the latter is transported along a path past a plurality of processing stations, each of which is selectively operable to perform one of the steps of Ihe electrophotographic copying process. Such stations include:
,:.
a charging station at which a uniform charge is deposited on the photoconductive surface of the recording element; an ex-posure station at which the charged photoconductive surface is magewise exposed to actinic radiation from the medium to create hn electrostatic image of the medium in the recording element;
.
a developing station at which the electrostatic image is con-tacted with finely divided charged markina particles (i.e.
toner) to render the electrostatic image visible; a transfer station at which a copy sheet is advanced into contact with the toner-bearing surface of the recording element to transfer the toner particles, in image configuration, to the copy sheet; and a cleaning station at which residual toner is removed from the surface of the recording element so that the recording element may be recycled through the electrophotographic process.
In electrophotographic apparatus which process the recording element automatically, it is necessary to precisely control the activation and the deactivation of the various proces-sing stations in timed relation with the movement of the recording element. Otherwise, the copy sheet, for instance, could be advanced to the transfer station before or after the toner image . ~
:`
arrives thereat, the result being imperfect registration of the transferred toner image with the edges of the copy sheet.
To provide such contrd, it is, of course, necessary that the control dcvice bc continuously updated on the precise position of the recording eLement during its travel along the path past the processing stations In applications in which the recording element is continually recycled, it is typically constructed in the form of a drum or an endless web. When in a drum configuration, the recording element is mounted for rotation on a driven shaft, and synchronization of the operation of the various processing s~ations with movement of the drum is commonly controlled by a bank of cams which also rotate with the drive shaft. Because both the recording element and the cam bank are fixedly mounted on the drive shaft, the position of each cam always reflects the precise position of the recording element Thus, synchronizing ;`~ the actuation of the processing stations is straight forward.
However, when the recording element is an endless web con-f;guration, such synchronization is not as simple.
When in a web configuration, the recording element is trained about a plurality of spaced rollers and is driven by either a sprocket or a friction drive mechanism. By using a sprocket drive, it is relatively simple to correlate the position of the recording element with the angular posLtion of the sprocket drive shaft as long as there is substantially no slippage between the sprocket and the web. However, in any sprocket drive, there is a`tendency for the driving sprocket to eventually tear or enlarge the web perforations which it drivingly engages. As the web perforations enlarge, control of the position of the recording element diminishes because there is a slippage between the driving sprocket and the web.
While the friction drive approach has little tendency to tear ' : - ? -the web, there is even more of a tendency for the web to slip reLative to the roll by which it is frictionally engaged and driven. Thus, the position of the shaft of the drive roll cannot be correlated with web position and, hence, cannot be used to synchronize the operation of the various processing .
- stations.
One approach to the above problem has been to place a timing mark on one edge of the recording element and to use : .
the mark to generate a signal to activate a cam banlc, which operates independently of the web movement to control the operation of the processing stations. See, for instan-e, U.S.
Patent No. 3,606,532. In essence, this approach provides the processing station control apparatus with an update of the web position at the start of each copy cycle. A disadvantage of this approach, however, is that registration problems will still exist if there is any slippage between the web and the friction drive after initiation of the timing cycle by the t ming mark. Also, when the web defines several frame areas, a separate cam bank and multiple switch arrangement is needed for each frame area of the web. Such a complex electro-mechanical control system is subject to reliability problems.
; , .
SU~RY OF THE INVENTION
;:
- An object of the invention, therefore, is to provide an improved method and apparatus for synchronizing the actuation of the various processing stations which comprise an electro-photographic copying apparatus with the movement of the recording element.
- According to a preferred embodiment of the invention, one edge of the recording element of an electrophotographic copier is provided with indicia, such as a plurality of per-- forations, which serve as timin~ marks. Sensing means, fixedly ~sit;~ne~ adiacent the patl- along which the recording element is advanced, sense the passage ~f the indicia and produce clock ., pulses in respe e thereto. Such cloc~ pu~ es provide a logic and control unit, preferably including a digital computer ~ 9 O
,:
which is programmed to actuate the various processing stations according to a predetermined sequence, with information from w~ich it accurately determines the position and rate of movement of the image frame of the recording element. Using this position information, the logic and control unit synchronizes the operation of the various processing stations with the move-ment of the recording element along its path.
BRIEF DESCRIPTION OF THE DRA~INGS
Figure 1 is an illustration of an electrophotographic copying apparatus embodying the invention;
Figure 2 is a partial perspective view showing in detail ~ portion of the photoconductive recording element of the Fig. 1 apparatus;
Figure 3 is a block diagram of the various components o. the logic and control unit shown in Figure l;
, Figure 4 is a diagram which shows the timing cycle ` of the apparatus shown in Figure 1.
- DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
- To better ùnderstand the present invention, the operation of an electrophotographic copier embodying the in-vention will be briefly described. It is to be understood, , .
however, that the apparatus of the present invention could be ` used with equal facility and advantage in other copying machines and, therefore, the following description of apparatus related to, but not Eor,;lLng a part of, the invention is provided for illustrative purposes only.
Electrophoto~raphic Apparatus .
Reference is now made to Figure 1 wherein an electro-photographic copier embodying the invention is schematically illustrated. As shown, the copier includes a reusable photo-conductive recor(ling elelnent 1() which is in the form of an 1~ .
` lil~4~Q
endless web 16. The recording element is a multi-layer structure, including a conductive laycr disposed between a photoconductive layer and a transparent support. Preferably, the conductive layer is transparent to permit exposure of the photoconductive layer from both sides thereof. Means (no~
shown) are provided for electrically grounding the conductive layer. The photoconductive layer may be formed from, for instance, a heterogeneous photoconductive composition of the ~ype disclosed in U.S. Patent 3,615,414, issued October 24, 1971.
Web 16 is trained about transport rollers 4-9, at least one of which is continuously rotatably driven to frictionally engage the transparent support of web 16 to continuously ad-vance the web in a clockwise direction, as viewed in Figure 1.
l'he dimensions of web 16 define several image areas or frames which are spacedly arranged side-by-side. The splice by which web 16 is rendered endless is, by means of the control ap-paratus of the invention, always maintained at an interframe position so as not to interfere with and degrade image formation and quality.
Arranged at fixed locations adjacent to the path along which recording element lO is advanced are the various proces-sing stations which collectively serve to form a transferable toner image on the various image areas of the recording element.
Such~ stations includ~e: a charging station 18, at which a uniform charge is deposited on the photoconductive layer of recording element lO to initiate the copying process; an exposure station 20 at which the uniformly charged surface of the recording element is imagewise exposed to an information medium 13, such as a document, to selectively dissipate the charge on the recording element and thereby form a latent electrostatic image of the information medium;and a developing station 22 at which electroscopic toner particles are applied to the recording element to render visible the elcctrostatic image borne thereby. Also positioned adjacent the path of the re-..
~_rding element are: a transfer station 24 at which the developedimage is transferred in imagewise configuration to a paper copy sheet, and a cleaning station 17 which serves to remove residual toner particles from the recorcling element following transfer. In addition to the above stations, more details of which are provided hereinbelow, the copying apparatus in-cludes an auxiliary erase lamp 33 which, when actuated, flood exposes the photoconductive layer of the web to dissipa~e and thereby prevent development of, any undesired charge pro-~uced on the recording element during the initial start-up or shlt-down of the copier, and a post development erase lamp 23 wllich, when actuated, serves to flood expose the photoconductive la-~er of the recording element imm~diately after development .: .
to reduce photoconductor "fatigue" and to facilitate transfer of the toner image.
In addition to those processing stations physically po,itioned adjacent to the path of the recording element, the c~pying apparatus also includes a pair of copy sheet feeding stations 21 and 27, a registration station 19 at which a copy sheet advanced from stations 21 or 27 is placed in registration ,, .
with a toner image advancing toward the transfer station 24, `" and a fusing station 30 at which the transferred toner image is permanently fixed to the copy sheet.
Although not shown, charging station 18 typically comprises a corona generator t such as disclosed in the commonly assigned U.S. Patent 3,527,941. Charging station 18 operates under the control of a logic and control unit 9, hereinafter referred to as the "LCU", as do all other stations and accessories of the copying apparatus. Control of station 18 by the LCU is effected via lead 18a.
Exposure station 20 preferably comprises a pair of selectively energizable xenon flash lamps 14 which are arranged paralLel to one another outside opposing edges of the information ; 6 ... . .
medillm 13. ~hen energized by the LCU via leads 14a, lamPs 14 momentarily illuminate the information medium and image there~
of is proJected by lens 15 upon the uniformly charged photo-c~n~uc~ive surface of web 16. Because of the intense output of lamps L4 imagewise exposure of web 16 is accomplished "on the fly", i.e. without stopping the web As will become more apparent from the description of the LCU, the LCU is capable of storing information concerning the total number of copies produced by the copying apparatus. Due to this capability and other features of the LCU discussed below, the LCU can be used to periodically increase the output power ot the flash lamp to compensate for any loss of photoconductor speed with usage of the web.
Developing station 22 may comprise a double magnetic brush apparatus, such as disclosed in the commonly assigned U.S. Patent 3,543,720, issued to Drexler et al. LCU 9 can used to automatically control the electrical bias of the magnetic brushes, which act as development electrodes, in accordance with the charge density in the background areas of the ~lectrostatic image. Sensing of such charge density may be ~ffected by positioning a metal plate (not shown) adjacent to the web path, upstream from the developing station, monitoring the charge induced thereon, and feeding a signal proportional .
thereto to the LCU. The LCU can properly bias the magnetic brushes via lead 22a. Alternatively, the bias level can be manually set through the LCU.
Transfer station 24 may comprise,as shown, a pair of corona generators 25 and 26.- Corona generator 25 acts to charge the paper copy sheet so as to render it attractive to the toner image. Assuming the toner particles are initially char~ed to a positive polarity so as to be attracted to the negative charge deposited by the primary charger 18,then the corona gcnerator 25 shoul~i be powered by a negative D.C.
~ ~' 1111490 power supply. Corona generator 26 is known as a "detacking corona" and serves to neutralize the electrostatic forces bonding the copy sheet to the web 16 following image transfer.
As shown the detacking corona is powered by a positively biased A.C. power supply. LCU control of both power supplies of the transfer station is effected via lead 25a.
Following transfer of the toner image to a copy sheet, the latter is stripped from web 16 as the web bends shlrply over small transport roll 8. Vacuum transport 29 ~elivers the copy ~eet to the nip of a roller fusing device 30 which comprises an internally heated fusing roll 30c which :
se ectively cooperates with a pressure roll 30b. The latter is movable into engagement with fusing roll 30c in response to a signal provided by the LCU on lead 30a.
~;, I
. I After fusing, the copy sheet follows either of the r aths labeled 31 or 32 in exiting from the machine to either a nopper 34 or a copy handling accessory 36, such as a sorter.
~ LCU 9 can be used to control the path followed by the copy sheet s via a signal applied to lead 36a which controls a movable de-flector plate in the paper path.
Cleaning station 17 may include an erase lamp, D.C.-biased A.C. corona and a vacuum cleaner (see Fig. 4), all of which operate under the control of the control apparatus of the - invention.
As mentioned above, the various processing stations of the Fig. 1 apparatus, in addition to the other components of the copying apparatus discussed hereinbelow, are selectively activated by and operate under the control of logic and control unit 9. This unit, the LCU, preferably includes a digital computer 74 (see Fig. 2) .;. ; .~
which is programmed to control the operation of the various work stations according to a predetermined sequence and in timed re-lation with the receipt of signals indicative of the rate of movement and the instantaneous position of the recording element.
Such signals are generated by transducers 76a and 76b which are fixedly arranged relative to the web path and which sense indicia carried by the recording element, preferably in the form of perforations. These signals provide the computer with up-to-date information (which may also appropriately be called "real time"
information) regarding the precise location of each image area of the recording element, and are used by the computer to determine when certain work activities should commence and terminate.
The output of the LCU selectively controls such activities accordingly. The manner in which the LCU derives position information from the recording element and uses such information to control the operation of the various work stations is des-cribed in detail below, Recordin~ Element As mentioned above, the length of web 16 is such as to enable a plurality of copies, such as six, to be made each time the web is cycled through the electrophotographic process.
Assuming web 16 defines six image or frame areas, this means that each frame area occupies approximately a 60 degree segment of the web. Actually, each frame area is slightly less than 60 degrees to allow for a small interframe area.
As shown in Fig. 2, one edge of web 16 is provided with two parallel rows of equally spaced indicia, shown as perforations 16a and 16b. Perforations 16a and 16b are herein-after occasionally referred to as "F" and "C" perfs, respectively.
, ` - 1111490 The number of F perfs on the web exactly equals the number of frame areas, and each F perf is located at a predetermined p~sition with regard to each frame area. As will be seen ~elow, each F perf cooperates with transducer 76a to provide the LCU with information regarding the position of the leading edge of all the image areas on the recording element. Also, it is the F perf which signals the LCU to initiate flash exposure and to feed a copy sheet to the transfer station 24.
~e C perfs, in effect, finely divide each frame area of the web into a plurality of increments, for instance, fifty-one.
As will be seen belo~, the C perfs cooperate with transducer 76b to provide the LCU with clock pulses from which it determineS web speed, and hence, frame position after it departs . . .
from the exposure station. As will be seen below, the LCU
eomprises counting means (e.g. a shift register) for counting ircoming F and C perf signals and means ~r actuating the various stations in response to a predetermined F and C perf count. Each time an F perf is received by the LCU, the C perf is reset to zero.
Electromechanical Transducers As shown in Figs. 1 and 2, the copying apparatus includes a pair of electromechanical transducers 76a and 76b which are fixedly arranged relative to web 16 to sense the passage of the F and C perfs, respectively. Transducers 76a and 76b are commonly referred to as "bimorph sensors".
Bimorph sensors which are suitable for use in the . . .
present invention are described in commonly assigned U.S. Patent 3,723,650 in the name of Bradley et al, issued March 27, 1973.
Briefly, each ~morph sensor includes a piezoelectrical crystal ~ .
82 which has attached thereto a single step sensor 83 element, the distal end 84 of which bears on and slides against the moving web member 16. When a perforation in the web member 16 moves b2neath the distal end of the sensor element, the end abruptIy drops over the leading edge of the perforation and distorts or otherwise induces mechanical movement of its associated transducer. As the web member 16 continues to move, the sensor element 83 is forced out of the perforation by engage-mcnt with the trailing edge of the perforation, and once again t~.e sensor element distorcs its associated piezoelectric trans-ducer. By means of electrodes or other suitable current collecting ans attached to the sensors, voltage signals generated by the distortion of the transducer are transmitted to the computer 74.
~: ~
~l Other types of perforation sensors which produce output signals ..
~uch as optical perforation sensors or other types of ceramic ~ ~ ansducers responsive to compression, bending or cther forms ; , of phy6ical distortion, may be substituted for the depicted bimorph sensors.
- Lo~ic and Control Unit Turning now to Fig. 3, there is shown in block ; diagram form the Logic and Control Unit which interfaces with the various processing stations and the bimorph sensors. As indicated above, the LCU preerably comprises a progranmable ; ~ digital computer 74. The LCU could, however, be hardwired logic circuitry which would include shift registers, counters and decoding matrixes. An example o such hardwired logic which could be adapted for use with the present structure is shown in commonly assigned U.S. Patent 3,732,005 to Lloyd. In such patent, there is disclosed a control apparatus for an electrophoto-graphic machine whicn in response to cloclc pulses timed from the motor drive shaft of such machine produces control signals fQr actuating and deactuating work stations in timed relation to movement of the web. The disclosed apparatus includes counters and decoding matrixes. However, it has been determined, in accordance with the invention, that a miniature digital computer is especially adaptable to provide the functions of the LCU
mentioned above, in addition to other copier functions. For instance, a computer can periodically interrogate a toner con-centration monitoring device and actuate a toner replenishing mechanism at an appropriate time. Further, it can be used to i periodically interrogate paper jam and misfeed detectors in the copy machine and shut down the machine if necessary. Further, it can monitor the number of copies made, compare this number ~.th the number of copies requested and inactivate the machine at the appropriate time. Various other functions which the computer may serve are discussed later herein.
Computer 74 may take various forms known in the art, some of which are commercially available as programmable mini-computers and programmable micro-processors. The Model , *
8080 Micro Computer manufactured by Intel Corporation of Santa Cl~ra, California is an example of a suitable micro-processor.
T~1e GEPAC 30, manufactured by the General Electric Corporation;
~he Interdate Model I and the Varian Data Machines Model 520/i are specific examples of suitable mini-computers. The instructions and methods of programming such devices is set forth in the text-book, "Mini-Computers for Engineers and Scientists", by * Trade Mark ' ' .
, ~ 11114gO, `~
Gravino ~. Korn, published by Mc~r~w Hill Book Comp~ly, ` (1973).
Microprocessors are similar to mini-computers, but there are some basic differences. For instance, a micro-processor, unlike a mini-computer, is generally fabricated with only one or a small number of integrated circuits. Moreover, it : does not have a very high computing storage memory and, hence, is relatively inexpensive. However, its speed is fast enough to make it entirely suitable for controlling all work operations of a very high speed electrophotographic apparatus. As is well ; known, the curren~ rnicroprocessors require a read and write :, memory (RAM), for data storage; a read only memory (ROM), for program storage; and circuits for obtaining access to the ~pparatus under the control of the microprocessor. It is ~ecoming quite common to convert all the hard-wired logic functions into programs which are stored in the ROM. The functions disclosed by the hard-wired logic in the above-referenced Lloyd disclosure all can be performed by a micro-processor.
With respect to the Intel microprocessor, Model 8080, such a device operates on a word size of one byte or eight bits and has an instruction time of between two and six microseconds, and used a memory size of 65,536 bytes. The number of instructions which implement such microprocessor is 48; and it has interrupt capability, address models of operation, and five 8-bit registers in addition to a progran control register and an unlimited stack.
The above-discussed RAM and ROM are standard with th~ unit. More ; particularly~ the Intel 8080.contains instructions registers, local memory, arithmetic output and input-output buffers. Of course, there are a num~er of oth~r su.tab~e microprocesso-Ls.
'~ * Trade Mark '~ 49~
~, ~ On~ of the most popular is Intel 4004 microprocessor. This . ~ .
microprocessor contains five functional st~tions, address register and stack with an address-incrementing circuit, a set of 1~, four-bit arithmetic and logic unit, and eight-bit instruction register and decoder and peripheral circuitry.
The following material discloses how to translate hard-wired logic into microprocessor sequences: John B.
Peatman, "Design of Digital Systems," pp. 211-216 and secs.
6-6, 6-7, McGraw-Hill Book Co., 1972; "MCS-4 Microcomputer Set User's Manual," Intel Corp., July 1972; and "8080, 8-bit Parallel Central Processor Unit," Intel Corp., November 1972.
As shown in Fig. 3, computer 74 comprises a tem-porary data storage memory 90, a central processing unit 92, a timing and cycle control unit 94, and a stored control program 96. The temporary data storage memory stores such infor-mation as the number of copies requested for each machine opera-tion, the total number of copies made by a particular recording element, etc. Some of the information stored by memory 90 need ..,,.:
only to be stored for one machine operation. The number of copies requested is exemplary of such information. Other information stored by memory 90 must be stored for several machine operations. The total number of copies produces by a particular recording element is exemplary of this type of information. Thus, the temporary data storage memory includes ~oth a volatile and a non-volatile Read/Write Memory (RAM).
, . ..
The control program 96 may be embodied by a commercially available ; Read Only Memory (ROM). The ROM would contain the operation~l * Trade Mark program in the form of instructions and fixed binary numbers corresponding to numeric constants. Such programs are p~nmanently stored in the ROM and, of course, cannot be altered by computer operation. Preferably, the ROM is programmed at the point of manufacture and the instructions programmed provide the required control functions such as sequential actuation of the processing stations, jam recovery, operator observable logic and machine timing. For a specific example, the total ROM
capacity could be approximately 5,000 words, with each word being : ' 8 bits in length. Data input to the computer and the computer output is performed sequentially according to the control programO
Input d ta from the bimorph sensors is fed to the central processing unit through an interrupt signal processor 104 (dis-closed below). Other input signals such as the output signals ' of a toner monitoring device, paper misfeed sensors, copy count i sensors, are applied to the central processing unit through an ~.: ., .
input signal buffer 100 and a multiplexer. The output data and control signals are applied to storage latches 106 (e.g. con-3 ventional flip-flops) which provide inputs to suitable output - drivers 108 dlrectly coupled to the leads for the processing station. More specifically, the output signals from the LCU are logic level, digital signals which are buffered and amplified to provide drive signals`to various clutches, bralces, solenoids, power switches and numeric displays of the copying apparatus.
The LCU processing functions can be programmed by merely changing the instructions stored in the computer memory. This provides a flexible machine logic and timing arrangement and extends the 1111~0 LCU capability to include the capac ty for performing service ~ia~nostics.
q, Computer Interrupt As noted above, the LCU controls, by a counting :,... .
~-~ technique, the copying cycle and activates the processing , .. ~
stations which perform the required operation in the processing of each active and inactive image area on the web. Also noted, is the fact that the mechanism for selecting the appropriate input signal processing technique is a program stored in the LCU computer. Since the computer 74 cannot operate on all inputs and outputs simultaneously, a technique for selecting . ~ , those signals to be processed, during each phase of the copy - cycle, has been developed. `Again, the F perf and C perf are ~' the key factors to selecting the appropriate control programs.
As mentioned above, the F perf and C perf signals are counted ,i - ~nd stored in the memory 90 of the LCU computer. ~he location ~f active and inactive image areas along the web path can be determined from the F perf and C perf count. Thus, those signals critical to the process, that should be occurring at any particular count in the cycle, can be selected for processing by the LCU. Other none critical signals are processed periodically, l when the LCV is not required to recognize a C perf or F perf signal. The C perf and F perf signals override other inputs to the LCU computer, by interrupting the computer; thus, the occurrence of these signals is always detected by the LCU.
The use of a computer interrupt is well known in the computer art. For a complete explanation of this technique, see the - I above-referenced text, "Mini-Computers for Engineers and Scientists."
~eration . .
As indicated above, proper sequencing of machine control signals is critical to the production of high quality ' ; ~o~ies and to prevent paper misfeeds, misregistration and erratic operation. The primary approach for controlling the - timed sequence of events and their relationship to each other '.:-is, as noted above, to sense the location of the image areas ' of the web as they continually cycle, and to synchronize the ~J
various control mechanisms with the movement ofthe image areas.
The technique for accomplishing this, as previously noted, is l to sense equally spaced perforations formed in the edge of , web 16, such perforations occupying a known position relative . .
: to each image area. The web member, as noted above, is prefer-..
ably divided into 6 image frames, each designated by an F perf, and the space between each F perf is subdivided into 51 increments by 51 C perfs. Machine sequencing control is implemented in the LCU by converting signal timing and combinational logic require-ents to programs that control the LCU computer. These control programs establish the basic operating mode and sequence of events for the machine subsystems.
The electrophotographic cycle is initiated by actuation of switches on a conventional operator's control panel (not shown). The appropriate switch on the panel may be selected for one or two'sided copying. The LCU 9 accepts input signals from the operator's panel, stores the signals in the computer memory 90, and decodes the signals to select the program which will initiate and control the electrophoto-graphic cycle. In addition to selecting a machine operating ~.~
~ ~ ,. 1111~90 - mode, the operator input panel is also used to select a quantity of copies. This information, also stored in the LCU computer memory 90, is compared to the quantity of copies ; ~o~pl~ted during the cycling of the machine. Upon delivery o~ the requested number of copies, the LC~l develops output signals to deactivate the copying mode.
:.
During the copying cycle, the F and C perf signals provided by the bimorph sensors are the primary control signal inputs to the LCU, and provide the synchronizing signals for the control of events. The LCU computer counts F perfs and C perfs and stores this information, together with fixed data, (e.g. the maximum number of active image elements and the distance between adjacent C perfs on the web). The LCU
computer determines where each active and inactive image element is with respect to the F perf sensor. This information is combined with knowledge of the spacing between various pro-cessing stations along the web path to develop control signals ~hich activate these processing stations at the required point in the cycle. Thus, the speed of web 16 need not be precisely known. The length of web 16, the spacing between perforations, qnd the location of the processing stations relative to the r perf sensor must be known and fixed.
Reference is now made to Fig. 4 wherein a typical ^opy cycle consisting of a single copy is used to illustrate ~hen, during the movement of the recording element, certain events occur, and the duration of such occurrences. The angular spacing of the various processing stations shown in Fig. 4 is equivalent to the linear spacing between such stations in the Fig. 1 npparatus. The film path is represented by the inner circular path of the annulus or Fig. 4. It is assumed that web 16 defines six image areas, each subtending an arc of approximately 60 degrees. Actually, each image area subtends an arc of slightly less than 60 degrees to allow for an interframe spacing, one of which includes the splice in the recording element. Because of its six image areas, web 16 is provided with six equally spaced F perfs, each occupying the same location with regard to its associa-ted image area. The area between each F perf is subdivided, as noted above, by 51 C perfs, thus dividing the entire recording element into a total of 606 incremen~ The letters A - J are used to indicate the location at which various events occur as the leading edge of an image area passes such : ~ .
~-~ locations during its clockwise movement around the endless ~1 path. The signals developed by the LCU computer during the ~ copy cycle are indicated in timed sequence in Table I. As ; shown in Table I, as the leading edge of the image frame passes position A, certain processing stations are turned ON.
- l`hese include those stations which remain ON throughout the . . .
copying cycle, as well as those whch are only required for the initial portion of the copying cycle. The system components which remain ON continuously include the post-development erase lamp 23 and the various components of the cleaning sitation 17 which, as shown, may include an erase lamp, a corona and a cleaning vacuum. As the recording element passes point B, the C perf count stored by memory 90 is reset to zero by the F
perf pulse. From this point on, all events are controlled simply by counting a specific number of F and C perfs and controlling the events according to the number of F and C perfs counted, and whether or not the requested [lumber of copies has been made.
' - -19_ ~` ~
~ -` 11114~90 ..
:
, ' TABLE
. , .
..... .
'.' SEO~UENCE OF EVENTS FOR SINGLE COPY RUN
.,, FIGURE 4 CONTROLI.ED EVENTS
, FILM POSITION
.
A START Switch Actuated : System Operate ON
Primary Charger 0~
Auxiliary Erase Lamp ON
B Reset C Perforation Count to Zero ~I C Illumination Power Supply "Initiated"
O
D Flash Exposure . ~ ' .
E Auxiliary Erase Lamp OFF
Monitor Enable ON
~ .
.
: F Auxiliary Erase Lamp ON
! primary Charger OFF
-;
G Paper Peed.
H - Transfer Charger ON
. Detact Charger ON
'' - I Transfer Charger OFF
Detact Charger OFF
STOP
System Operate OFF
Auxilidry Erase Lamp OFF
.
~ . . . .
Table II illustrates the information stored in the LCU during a multiple-copy cycle. A Run flip-flop and a PRINT flip-flop, although not shown, will be understood to be located in the central processing unit 92 of the computer 74. These flip-flops are actuated and, as shown in Table II, are switched to a logical "1" by depressing the START button.
When the stored C count first reaches 51 and an F perforation is detected, the LCU stores a logical 1 in a five-bit shift register disposed in the processor 92 which counts and stores the number of F perforations sensed. At the same time as when the third F perforation signal is fed to the five-bit shift register, a first binary signal is sent to an 8-bit paper shift register. At this time, the computer not only causes an image of a document to be~exposed on the web, but also causes a first copy sheet to be fed to the transfer station. Thus, three "F"
~erf signals must be sensed before a developed toner image area is disposed adjacent the transfer station. The 8-bit shift register, of course, counts and stores the number of copy sheets fed. As shown in Table II, if ten or more copies are to be made, both shift registers will become full. The machine will continue to imagewise expose the recording element until ~e number of copies requested equals the number stored in the "copies requested"counter (in Table II, it is ten). At this time, a time-out cycle will commence, causing the PRINT flip-~ . ...
flop to be reset to a zero state. In this state, further exposure of the recording element is inhibited. During the , time-out cycle, successive F perorations signals clear the .'~ .
. .
, 4~0 shift reglsters as indicated in the table. As successive F
perforations are detected, copy sheets are fed into the tr~nsfer station. At the end of the cycle, the machine is ' , set in a stand-by mode.
. . , "'~' : ' .
`,;~ 90 T~T~7 .~ T I
- SE(~UENCE 07' EVEilTS FOR ~IULTIPLE CO?Y, ONE-SIDE COPY ~10DE
. .
. 'RUN PRINT SHIFT SHIFT C F
FLIP-FLOP FLIP-FLOP REGISTER REGISTER COUNT COUNT
; S t art 1 l O O any O
: ~ 1 l 0000100000000 51 :., :~ 1 1 0001100000000 51 2 . ~
, 1 1 0011100000001 51 3 ' ~ 1 1 OllllOOOOOOll .5l 4 lllll00000111 51 5 . .
., .
; 3 1 1 11111 11111111 51 lo ~ - 1 o llllo 11111111 5 ,., ~ . .
.~.; j . .
:, 1 0 11100 11111111 51 12 ~ 1 0 11000 11111110 51 13 ., , ' 1 0 1000011111100 51 14 , 1 ~ .
,,"~ s .-; .
~i ' , Misc~;lan~cus LCU Functi~ns In addition to controlling the operation of the various processing stations, the LCU computer 74 can be used, with suitable sensing elements, to detect copy sheet jams and copy sheet misfeeds.
Paper Jam and Misfeed Lo~ic The paper path is shown in Figure 1. As discussed with ~spect to the timing diagram (Figure 4), the paper feeding is initiated by the LCU 9. Paper registration is accomplished by mechanical means and is controlled by the registration mechanism 19. A number of sensors may be located along the paper path to detect paper feeding or mis-feeds and produce signals to the LCU at properly selected positions. These signals may include (1) leading edge detector in the paper feed mechanism, (2) transfer jam , detector, (3) side exit/top exit jam detectors, (4) sorter jam detection. The jam signals are monitored by the LCU
computer and in the event of a paper jam, the computer 74 is programmed to develop control signals for a machine shut-down with indication to the operator to check the paper path.
The machine jam c~etection logic incorporates signal sensing and control which reduces the potential of mechanism damage caused by a paper jam.
In the copying mode, the flow of paper from the supply to the exits under nominal conditions is completely predictable. The time between initiation of paper feed and the arrival of paper at any of these paper sensing switches
- 2~
can be expressed in terms of film perforation signals (F and C perfs.~. The film perforation signal count is stored in the computer and at designated perforation count intervals, the paper sensing switches are interro-gated. If paper has not arrived at the sensing switch within the nominal perforation count interval, a jam is detected. Likewise, if paper has not cleared a switch within a specified perforation count interval, a jam is indicated. It should be noted that the paper jam detection is not based on time measurement. It is based on perforation counting by the computer; i.e., the flow of paper through , , . the machine is expressed in terms of perforation counts.
;, If a copy sheet is not fed from the paper supplies 21 and 27, the failure is classed as a "misfeed". This failure need not result in a machine shutdown. If a single misfeed occurs, the computer 74 adjusts the paper shift register contents to account for the loss of one copy in the control logic. If two consecutive misfeeds occur, the paper in the paper path completes the transition through the printed to an exit and the machine is shut down. The number of copies processed and delivered is stored in the LCU computer 74 and a check paper path indicator is turned ON. The operator would normally clear the misfeed sheets and restart the copy cycle. Since the delivered count is stored during the misfeed recovery, the cycle restarts where it left off and the number of copies required to complete the run are delivered to the exit.
:
111~4~0 While the invention has been disclosed with particular reference to preferred embodiments, it should be apparent that many modifications can be made to the apparatus and method disclosed without substantially departing from the spirit of the invention. For instance, while particular - reference has been made to a recording element in the form of an endless flexible web, it should be apparent that the invention would have`utility with any recording eIement format, including drum and open-ended webs. The inventive concept is to use indicia on the recording element, regardless of its format, to continuously update the control mechanism which selectively actuates the processing stations with the - position of each active area of the recording element as it moves along its predetermined path. Also, while reference has been made to a recording element comprising six image areas, each identified by an F perf and subdivided by 51 C perfs, it should be apparent that these numbers merely ~` are illustrative of a preferred recording element. Obviously, the more C perfs, the more precise the recording element position can be determined. Preferably, however, the number of C perfs should exceed 20 per image area on the recording element.
~ -26-
can be expressed in terms of film perforation signals (F and C perfs.~. The film perforation signal count is stored in the computer and at designated perforation count intervals, the paper sensing switches are interro-gated. If paper has not arrived at the sensing switch within the nominal perforation count interval, a jam is detected. Likewise, if paper has not cleared a switch within a specified perforation count interval, a jam is indicated. It should be noted that the paper jam detection is not based on time measurement. It is based on perforation counting by the computer; i.e., the flow of paper through , , . the machine is expressed in terms of perforation counts.
;, If a copy sheet is not fed from the paper supplies 21 and 27, the failure is classed as a "misfeed". This failure need not result in a machine shutdown. If a single misfeed occurs, the computer 74 adjusts the paper shift register contents to account for the loss of one copy in the control logic. If two consecutive misfeeds occur, the paper in the paper path completes the transition through the printed to an exit and the machine is shut down. The number of copies processed and delivered is stored in the LCU computer 74 and a check paper path indicator is turned ON. The operator would normally clear the misfeed sheets and restart the copy cycle. Since the delivered count is stored during the misfeed recovery, the cycle restarts where it left off and the number of copies required to complete the run are delivered to the exit.
:
111~4~0 While the invention has been disclosed with particular reference to preferred embodiments, it should be apparent that many modifications can be made to the apparatus and method disclosed without substantially departing from the spirit of the invention. For instance, while particular - reference has been made to a recording element in the form of an endless flexible web, it should be apparent that the invention would have`utility with any recording eIement format, including drum and open-ended webs. The inventive concept is to use indicia on the recording element, regardless of its format, to continuously update the control mechanism which selectively actuates the processing stations with the - position of each active area of the recording element as it moves along its predetermined path. Also, while reference has been made to a recording element comprising six image areas, each identified by an F perf and subdivided by 51 C perfs, it should be apparent that these numbers merely ~` are illustrative of a preferred recording element. Obviously, the more C perfs, the more precise the recording element position can be determined. Preferably, however, the number of C perfs should exceed 20 per image area on the recording element.
~ -26-
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A photoconductive recording element adapted for use in an electrophotographic copying apparatus which includes a plurality of selectively actuatable processing stations, said recording element being adapted to have a plurality of images formed thereon at predetermined locations along the length thereof, said recording element being characterized by:
means defining first and second sets of indicia on said recording element for controlling the selective actuation of the processing stations, the number of indicia of said first set being equal to the number of images which can be formed on said recording element, each indicium of said first set occupying a predetermined posi-tion with respect to the image locations to identify said locations, said second set of indicia being equal in number of some multiple of the number of images which can be formed on said recording element.
means defining first and second sets of indicia on said recording element for controlling the selective actuation of the processing stations, the number of indicia of said first set being equal to the number of images which can be formed on said recording element, each indicium of said first set occupying a predetermined posi-tion with respect to the image locations to identify said locations, said second set of indicia being equal in number of some multiple of the number of images which can be formed on said recording element.
2. The invention as set forth in Claim 1 wherein the indicia of said first and second sets of indicia comprise perforations.
3. The invention as set forth in Claims 1 and 2 wherein the indicia of said first set are equally spaced and arranged in a linear array which is parallel to one edge of the recording element.
4. The invention as set forth in Claim 1 wherein said recording element is endless.
5. The invention as set forth in Claim 1 wherein said recording element comprises a flexible web.
6. The invention as set forth in Claim 5 wherein the linear arrays in which the indicia of said first and second sets of indicia are arranged are positioned adjacent to each other along one edge of the flexible web.
7. The invention as set forth in Claim 6 wherein the indicia of said second set is positioned closer to said edge then the indicia of said first set.
8. The invention set forth in Claim 7 wherein the number of indicia of said second set is at least twenty times greater than the number of indicia of said first set.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,194A CA1111490A (en) | 1973-10-01 | 1978-10-12 | Recording element for electrophotographic copier |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40222373A | 1973-10-01 | 1973-10-01 | |
| US402,223 | 1973-10-01 | ||
| CA210,239A CA1056443A (en) | 1973-10-01 | 1974-09-27 | Synchronizing control apparatus for electrophotographic apparatus utilizing digital computer |
| CA313,194A CA1111490A (en) | 1973-10-01 | 1978-10-12 | Recording element for electrophotographic copier |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111490A true CA1111490A (en) | 1981-10-27 |
Family
ID=27163640
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA313,194A Expired CA1111490A (en) | 1973-10-01 | 1978-10-12 | Recording element for electrophotographic copier |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1111490A (en) |
-
1978
- 1978-10-12 CA CA313,194A patent/CA1111490A/en not_active Expired
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