GB2188618A - Tractor-less feed of fan-fold computer stationery - Google Patents

Abstract

This invention relates to a tractor-less drive for computer fan-fold (CFF) web being fed to a reprographic or like machine. When in the CFF-feed mode, travel of the web is monitored by two sensors 26, 36 aligned with the holes along one web border. Both sensors generate hole-transition pulses and, in conjunction with timers, the pulses are compared end timed to detect torn and blocked holes, and slippage or stalling of the web feed. The comparison leads to the feed being continued or stopped. <IMAGE>

Description

SPECIFICATION Feeding of computer fan-fold web In reprography, it is often desirable to be able to reproduce the images on successive faces of computerfan-fold web, o 'CFF web' as it will be called below. This is thewell-known web of indefinite length and having any of a small number of different widths, provided to record the output of conventional computer printers. Each 'sheet' ofthe web is joined to its preceding and succeeding sheet buy a line of perforations, which lines are normally spaced-apart by a standard length of mm. The sheets are folded about each line of perforations in opposite senses, so that a stack ofjoined-together sheets forms a zig-zag, orfan-folded, stack.

Extending along each of the longitudinal edges of the web is a line of sprocket holes, which are4mm ire diameter and which have their centres spaced apart by 12.7 mm (0.5 inch). The holes of such a diameter as to be engaged by domed pins of a procket (which may be in the form of either a wheel or an endless flexible loop) so that the web can be driven axially by rotation ofthe sprocket(s) normally engaging both lines of holes. The sprockets drive forms part of a paper-feed tractor, which is relatively expensive to manufacture.

One ofthe difficulties of feeding CFFweb is that occasionally these sprocket holes are blocked (as by imperfectly-punched holes); they are torn, or corners of the pages are either torn off orturned down, any of which can lead to the web being misfed.

The present invention aims at providing apparatus forfeeding CFF web to and through a copier, without the use of a tractor or a feed nip, and including meansfordetecting a misfeed.

Accordingly the present invention provides apparatus which is as claimed in the appended claims.

US 4485949 discloses a tractorless feed for OFF web, which uses a roller nip to feed the web frictionally. The apparatus uses two sensors, one for measuring the movement of the drive system, and the other for counting the number of sprocket holes in the fed web. The two set of signals are compared with each other to maintain registered stopping positions for the web, so asto compensate for slip in the frictional feeding of the web.

By contrast, in the present invention the web is fed by a driven belt underthe control of signals derived solely from sensing the passage of the sprocket holes, whereby any actual or incipient misregistration is detected and the web feed stopped before the copying cycle is started.

The present invention will now be described by way of example with reference to the accompanying drawings in which: Figure lisa diagrammatic sectional view of a reprographic machine fitted with an automatic documentfeederand having one sensor positioned before, and the other sensor positioned after, the feeder so asto detect the sprocket holes in the CFF web being fed, in accordance with this invention; Figure2 is a view, similarto Figure 1, of a reprographic machine fitted with a recirculating document handler, and accordingly having both sensors positioned in advance ofthefeeder; Figure 3 is a diagrammatic plan view of part of the apparatus of Figure 2, showing the location of the respective sensors relative to a nudger;; Figure 4 is a plan view of part of a length of OFF web, showing the relative positions ofthe sensors of the apparatus of Figure 1 with respect to both the web in its registered position and to a registration edge; FigureS is an illustration of two trains of pulses derived from the sensors shown in either Figure 1 or Figure 2; Figure 6is a viewsimilarto Figure 5, but with the second train of pulses being displaced by half a pitch relative to the first train; Figure 7is a viewoffourtrains of pulses usedto show the signals obtained indicative of various faults intheCFFweborin itsfeeding;; Figure 8 is a timing diagram, showing howtiming intervals is used as an alternative to counting hole transitions, Figure 9 is a flow diagram ofthe algorithm used for feeding OFF web when using a recirculating document handler (RDH), as shown in Figure 2; Figure 10 is the second step of Figure 9, and shows the algorithm bywhich thefeeding of CFFweb tothe registration position is monitored; Figure 11 is an algorithm of a manner in which OFF web is transferred so that the next line of perforations is brought up to the registration position by using either a reprographic machine with an RDH or one with an automatic document feed (ADF), as shown in Figure 1, and Figure 12 is an algorithm of the steps followed when the iast page ofthe OFF web has entered the machine.

The reprographic machine with the automatic document feeder (ADF) shown in Figure 1 includes an endless belt 2 entrained over two rollers 4 and 6, of which at least one is driven. The lower run of belt 2 extends closely adjacentto a platen glass 8 terminating at one end in a movable registration edge 10 provided by member 12 which is driven buy a solenoid (not shown). A stack of out sheets is normally intended to be supported on an inputtray 14. When OFF web is to be fed, the stack of it is placed on a separate shelf or tray and its lead edge is fed manually overthetop of tray 14 and intothe nip of the inlet feed rolls or paddle feeder. One side face of the stack of cut sheets abuts a movable inlet gate 16.

Engaging the top sheet of the stack is a paddle feeder 18 illustrated diagrammatically. When this is rotated, the flexible paddles come into contact with the currenttop sheet of the stack and drive it into the gap between a support surface 20 and a guide surface 22.

Associated with the stack is a sensor 24 designed to indicate when the tray 14 is empty. Aligned with one side of the entry slot to the drive belt 2 is the upstream hole sensor 26, of which the operation will be described infurtherdetail below.

Close to the output slot between belt 2 and platen 8 is a solenoid-operated diverter 28. When in its lower position the diverter acts to deflect the lead edge of a sheet leaving the above-mentioned slot between a pair of guides 30 and into the nip of a pair of feed rolls 32, to result in the sheet being fed to a separate output or other tray.

When the diverter is in the position shown in broken lines in Figure 1,theleadedgeofanysheet leaving the respective slot moves over a guide surface 34to a separate output tray (not shown). In so doing, one edge ofthe sheet passes across the sensing area of a downstream hole sensor36.

In Figure 2, those parts having equivalent functions to the components shown in Figure 1, will be given the same references. In this form of reprographic machine, incorporating a recirculating document handler (RDH), the documents to be copied usually reach the platen 8 by passing along 3 pair of guides 40, being fed on to the platen by means of a feed nip 42.

Documents to be multiply copied are deflected by the diverter 28 and pass along the path defined by guides 30, being extracted from below drive belt 2 by the feed rolls 32, eventuallyto reënterthecopying station along the input path just described. When only one copy is to be taken of a document, orwhen copying CFF web, the deflector 28 is in its upper position, with the resultthat the lead edge of the respective sheet or web passes into a nip provided buy a pair of rolls 44.

When single sheets of CFFweb are to be fed to the copier, they pass undera'nudger' 46, shown as being in the form of an obliquely-mounted wheel which drives one corner of a sheet towards both a remote registration surface 48 and an inlet nip provided by a pair of intermittently-driven feed rolls 50. A sensor 24, similarto the stack sensor 24 of Figure 1, when actuated by a sheet, switches on the nudger and the feed rolls, and hence causes a sheet to be driven after it is correctly registered both in the nip of rolls 50 and againstsurface48. Similarlyto Figure 1, a sensor 26 is positioned close to the inlet of the machine but, in contrast to Figure 1, the second sensor 36 is positioned upstream of both the sensor 26 and the drive belt 2, rather than downstream of the outlet slot.

In view of the significantly-different positioning of the sensors 26 and 36 in the ADF and RDH configurations, for ease of reference in the following description, that sensorwhich first reads the sprocket holes in a CFF web will be called the "first sensor", and thatwhich reads the sprocket holes laterwill be referred to as the "second sensor".

As shown in Figure 4, the sprocket holes along each edge portion of OFF web have their centres spaced 12.7 mm apart, and the holes themselves are 44 mm in diameter. With CFF web, the line of perforations 52 between each respective 'sheet' bisects the space between two adjacent sprocket holes. When in its registered position, the respective line of perforations is aligned with the registration edge 10 provided by registration member 12. When feeding OFF web, the solenoid controlling the position of member 12 is acutated so as to keep the registration surface 10 at or below the level ofthe uppersurfaceofplaten 8, so thatthere is no obstruction to the smooth passage of web acrossthe face of the platen and to the respective output tray.In accordance with one feature of thins invention, both sensors 26 and 36 are positioned an integral multiple of inter-hole spacings (12.7 mm) from the registration edge 10. This ensures thatwhen correctly-punched and perfectCFFweb is being fed, both the sensors detect only paper when the web is correctly registered. The significance ofthis will be pointed out below.

Each sensor 26 and 36 may take the form of a light source positioned on one side of the path of paper, and a photodetector positioned on the other side of the path in line with the source. Alternatively, the sensor may include an appropriately-oriented light source and detector aimed at a mirror or like reflective surface positioned belowthe paper path. In yet another alternative, the photodetector might operate by back-scattered light, using the greater amount of light reflected from the sheets than from a support surface positioned below the paper and on which the light falls on passing through a sprocket hole. Irrespective of the configuration of the sensor, each is connected electrically to associated equipment designed to produce a pulse train, of which one example is shown in Figure 5(a).The reference or 'space' level of the pulse train, corresponds to when the sensor is detecting only paper, whereas the peak or 'mark' value corresponds to the signal produced when the amount of light received by the photodetector is significantly increased, as a consequence ofthe light passing through a sprocket hole and entering the photodetector either directly or after reflection.

When both sensors are positioned an integral multiple ofthe inter-hole spacing from the registration edge 10, then both sensors derive pulses at the sametime as each other, resulting in the synchronicity shown in the Figure 5(a) and Figure 5(b) waveforms. This spacing of the sensors is not essential, but it does make the software much simple. In particular, it enables either sensor to be used to countthe passage of the sprocket holes without needing to work outwhetherthe particular sensor is the first orthesecond one.

If the sensors were positioned so that one was an integral number of inter-hole pitches from the registration mark,buttheotherwasarrangedto coincide with a hole when the other sensorwas reading a space between two holes, then the wave form of Figure 6 would be derived, in which it is assumed that waveform (a) is derived from the leading sensor, and waveform (b) from the trailing one. With this arrangement, it will be appreciated that the pulse from the trailing sensor is 6.3 mm behind a pulse from the leading sensor. Underthese circumstances, if the leading sensor is used to derive the web-stop signal, and fails to generate the desired pulse, because of reading a blocked hole, the web-stop signal must be generated bythetrailing sensor, which signal is inevitably derived only after the web has travelled 6.3 mm pastthedesired registration position.

- In Figure 7, the different pairs ofwaveforms are interpreted as follows.

The gap in waveform A(b) means that a hole downstream of the leading sensor is blocked, resulting in the absence of the corresponding hole-detection pulse.

The elongated pulse shown in waveform B(b) arises from the passage of a damaged hole pastthe trailing sensor,the damage being suchthatthe hole is effectively elongated along the direction of travel, the resulting in lightfalling on the photodetector of the trailing sensor for longerthan usual.

The pulse-less period shown in both waveforms C(a) and C(b) arises when the web comes to an inadvertent stop for a short period, the web stopping in a position in which both sensors are interrogating un-punched paper.

The waveform shown in D(b) could arise from a torn corner of the web, the length of the tear embracing more than the length ofthree holes, thus resulting in the production of the excessively-long hole-detection pulse.

Although the waveforms in Figure 7 have been shown as if detection of the paper produces a lower signal, and the detection of the pulse produces the pulse, as already mentioned above, the apparatus could work with the mark:space pulses having the opposite interpretations, in which case the above explanations of the waveforms shown in Figure 7 would have to be modified.

In the diagram shown in Figure8, itwill beseen thatthe sensors are positioned so that the signal from the second sensor arrives shortly afterthat from the first.

As shown bythethird level of legend, atimerset fora period equivalentto the web's travelling 8mm is started by the leading edge of each pulse from the first sensor. When the timer is running, the holes are not counted. When the timer times out, a second timersetto80mm is started, to function as a 'stall detector'. The occurrence of a stall is signalled if no hole transition is detected during this interval, as shown by the fourth level of legend. The detection of a hole disables the stall timer and triggers the first timer.

Another, or the stall, 80mm timer is triggered by one sensor seeing a transition while the other sees no paper. This 'torn hole detector' works on the assumption thatthe sensors never interrogate two torn holes simultaneously. A 'torn sheet' signal is generated by the respective timertiming outwithout any intervening hole transition.

In the algorithms shown in Figures 9-12, some of the time intervals are represented by spacings in mm. Atthe speed with which the web is intended to be fed, in one form of apparatus of the present invention, the web covers one mm in 3.64 ms,which gives the desired relationship between length and time. Although not shown in the drawings, in practice the state of all the sensors would be monitored at 2 ms intervals.

As already mentioned, the algorithm of Figure 9 is used for a copier incorporating an RDH. This copier is automatically switched into its CFF web-feeding mode when it counts more holes than representthe length of a cut sheet in the feed direction. This causes the RDH to be bypassed. If cut sheets age to be copied, and this is keyed into the machine, then the machine leaves its CFF web-feeding mode, but otherwise it goes through the cycle shown in Figure lOOn restart, the copier revertsto its cut-sheet feeding, hole-counting, mode.

When switched into its OFF mode the desired preset degree of magnification or reduction is made effective, and any test copies are made if desired, using the first sheet of the OFF web. After satisfactory reproduction ofthe test copy, then the necessary number of copies of the first sheet is made. Afterthis, both sensors are used to control the feeding ofthe web, with intermittent stopping of the component sheets when registered, and copying thereof. This cycle is reiterated until the stack sensor 24 detects that there are no more sheets to be copied, after which the sheet currently on the platen is assumed to be the last sheet, is copied, and then the machine leaves its CFFweb-feeding mode.

The steps and decision gates shown in Figure 10 should be self-explanatory in view ofthe above explanation of the operation of a reprographic machine with an RDH, and the dimensions of a OFF web to be fed. This shows that the successive passage of the holes past the two respective sensors leads to the production of a hole-counting sequence.

Knowing the number of holes (22) which have to be counted when a web is fed axially until the next line of perforations is aligned with the registration edge, the desired axial travel oftheweb is detected by counting the holes. Occurrence of an imperfect mark ar space in one of the waveforms is ignored, so that the comparator comparing the two trains of pulses effectively generates a continue-web-feeding signal, so that the occu rrence of an excessively-iong mark or space in one of the waveforms is attributed to a hole defect, and not to the rate at which the web is being fed.However, when the web stalls, as is shown in the Figure 70 waveforms, the concurrent occurrence of two execessively-long marks or spaces is interpreted as meaningthattheweb has become jammed, and the copier is forced to leave its CFFweb-feeding mode, until manually reset by the operator, who would be expected to lookfor, and rectify, the reason why the web feed was interrupted.

The algorithm shown in Figure 11 applies to both the RDH and ADF versions ofthe reprographic machine, and is again regarded as being self-explanatory. Perhaps all that needs to be said at this stage is that the reference "NVM" in one ofthe decision gates is to the value of the count or time currently stored in a non-volatile memory. The lead edge adjustment is made by interrogating the stored NVM value, and adjusting the 'stop' timer accordingly. This stored count corresponds to movementofthe belt through a chosen distance, or for a specified time, so that if the respective interval is detected as being longerthan that pre-set, then that is regarded as indicating a fault condition, and appropriate action taken, as indicated by the algorithm.

Figure 12 shows the algorithm used after the stack sensor 24 has detected that there is no sheet left on the respective inputtray. With the RDH copier,this means that a continuous signal, corresponding to the absence of paper, is generated firstfrom the leading sensor and then from the trailing sensor.

However, undérthese conditions, the absence of any paper-detection signal does not result in the feed belt being stopped, but ensures that a timer is started in orderto timethe movement ofweb off the platen, in orderto bring the final sheet(s) to the registration position, and there be copied, before the copier cycles out by feeding the iast sheet of the web from the registered position on the platen and into the respective output tray. Again, it is thoughtthatthis algorithm is self-explanatory in view of the foregoing description.

Accordingly it will be seen that the present invention provides an inexpensive apparatus for feeding CFF web which uses the normal beltfeed, and at least two sensors aligned with one line of sprocket holes to effect the feeding of damaged or tornOFFweb, butwhich stopsthefeedthereof should the web skew of become stalled.

Claims (6)

1. Apparatusforfeeding computerfan-fold (CFF) web through a reprographic machine employing a drive beltforfeeding original documents and OFF web to and from a platen, including at least two sensors which, when a CFF web is being fed to the machine, are adapted to respond to the passage of sprocket holes pastthem to produce two trains of pulses, with the duration of each pulse or mark being afunction ofthe length of the respective hole in the direction offeed;; meansforcomparing the trains of pulses with each other to detect the passage of a blocked or torn hole past at leastthe leading sensor, and means for stopping the feeding of the web when the signals indicate that the web has become stalled or excessively retarded, and for continuing with the feeding ofthewebwhen a pulse or mark of unacceptable format, corresponding to the passage of a torn or blocked hole, is compared with a pulse or mark derived from an undamaged open hole.

2. Apparatus as claimed in claim 1, in which one sensor is positioned on the upstream side of the platen, and in which the other sensor is positioned on the downstream side thereof.

3. Apparatus as claimed in claim 1, in which both hole-detection sensors are positioned on the upstream side of the platen.

4. Apparatusasclaimed in any preceding claim, including a sheet-detection sensor positioned to detect the absence or presence of a sheet or web on an input tray.

5. Apparatus as claimed in any preceding claim, including a registration edge orfiducial position fixed with respectto the platen, and in which the spacings of the hole-detection sensors are determined with respect to the nearest point of the registration edge.

6. Apparatus as claimed in claim 5, in which each sensor is spaced from the registration edge by an integral number of inter-hole spacings, whereby both sensors are aligned with the web between two holes when the web has one of its perforation lines aligned with the registration edge.