POWER CONTROL UNIT WARNING
CONVEYOR SHAFT ENCODER
'-c
TAKEAWAY UNIT
SORT GATE
CONVEYOR SHAFT ENCODER
I
FEEDER
SORT POCKETS DC MOTOR
( VELOCITY SERVO DRIVE)
RIQOOIB
TACHOMETER
Figure 4- 2. Document Transport System
The document is squared and centered with the conveyor vacuum belt by the edger. The edger vacuum belt, which is angled slightly to the left. takes hold of the document as it leaves the feeder and pulls the document towards an edging wall. Vacuum pressure on the belt allows for some document movement so that the document aligns itself as it is moved along the edging wall. A linear speed variation of approximately 7 percent between the edger and feeder
causes a gap, proportional to document length. between documents.
In the document load mode the conveyor vacuum belt, moving at the same linear speed as the edger vacuum belt, transports the document to the read area at a speed of 40 inches per second. When the leading edge of the document passes the read zone photosensor (located approximately 1 inch upstream from the read station), the transport servo is commanded by the BC to stop the document at the document-ready position or first line position as deter-mined by the controlware program.
The operator then presses the READY switch on the operator control panel, sending a Ready signal to the BC. If the reader and BC are in a ready condition (no fault conditions exist) signals from the BC light the system READY indicator. When the system READY indicator lights, the BC initiates program commands for the transport drive, takeaway drive (Models F, G, H, and J) and mirror drive servo motors. The document is scanned line-by-line while being stepped through the read zone.
When the document has passed through the read zone it is picked up by a pair of takeaway belts which accelerate the document to 70 inches per second. A solenoid-operated sort gate either allows the document to pass through on the takeaway belts to sort pocket 2 or peels the document off the takeaway belts, causing it to drop into sort pocket 1. The sort gate solenoid operates via BC commands. Photosensors provide the BC with signals which cor-respond to document position in the takeaway area. The LOAD indicator goes out after the last document has been processed.
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FEEDUP TABLE'
Documents are, loaded manually onto the feedup table. face up. with the leading edge towards ([
the feeder. The top document is fed first. A,.. wedge. mounted on the feedup table drive belt.
positions the stack of docl,lments for proper feeding. The belt carries the stack of. documents
to the feeder and isdrive:i1 via a friction roller which is. connected through a clutch toa
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constantly running motor. The clutch solenoid is energized by a sensor on the feeder which "'-sens.es the prpximity.of documents to the feeder rollers. Press~ng the ENABLE FEED UP
switch on the operator control panel deenergizes the clutch solenoid during loading. The ( ..
feed).lp belt stops
and
the wedge is pulled back to make room for documents. Tl:Ie feedup guide plates are adjusted for different widths by the PAPER GUIDE WIDTH ADJUST switch on thedocument adjustment panel. (
FEEDER
The feeder consists of three roller assemblies: the pre-feed. the feed, and the dedoubler rollers. The pre-feed roller assembly pulls the top document off the stack and feeds the docu-ment towards the feed roller, which feeds the docudocu-ment onto the edger. The feed roller is positioned over the dedoubler roller. Having a higher coefficient of friction on paper than the dedoubler roller, the feed roller will drive a single document towards the edger when the document passes between the two rollers. The feed and dedoubler rollers both turn in a clockwise direction. When more than one document is fed between the two rollers. the lower document comes in contact with the dedoubler roller and is driven back towards the feedup table because the friction of paper to paper is less than the friction of the dedoubler roller to paper.
Adjustment of the vertical position of the dedoubler roller is made by turning the DOCUMENT THICKNESS ADJUST knob on the document adjustment panel. Adjustment is required to compensate for variations in paper thickness and for roller wear.
The feed, pre-feed, and dedoubler roller assemblies are all driven by the same motor that drives the conveyor andedge~. Linear speed of the feeder assembly rollers is approximately 7 percent less than the speed of the edger and conveyor belts. causing a gap to develop between documents.
EDGER
The edger centers and squares documents coming from the feeder before they are moved through the read station by the conveyor. The edger contains a vacuum belt inclined at a small angle and driven at the same speed as the conveyor. The angle of the vacuum belt tends to push the document to the left. The document comes in contact with an edging wall which is aligned parallel with the conveyor centerline. The vacuum on the edgirtg belt is controlled so that. as the document slides along the edging wall, document movement on the belt is possible and the document aligns itself to the conveyor. A cover at the edging wall reduces buckling of the document.
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The PAPER GUIDE WIDTH ADJUST switch on the document adjustment panel mov~s the edging wall simultaneously with the feedup table guide walls so that a document, when ed~d, is
accurately centered on the. conveyor. '\
4-4
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CONVEYOR
The conveyor moves the squared and centered documents from the edger through the read area.
At the read area documents are formed into a concave surface, accurately located to be in focus for scanning. The conveyor stops the document while a line is scanned, and then rapidly steps the document to the next line to be scanned.
The conveyor consists of a 2-inch wide vacuum belt, a two-sectioned trough, a bar which supports mylar fingers, and conveyor drive elements. The vacuum belt moves the documents over a vacuum chamber and between the two trough sections. The mylar fingers hold the documents in contact with the concave surface at the read area. The conveyor drive elements are as follows: driven and idler rollers, a belt tensioner, a transport velocity servo drive
system, a shaft position encoder, and timing belts, pulleys, and bearings.
TRANSPORT SERVO DRIVE SYSTEM
The transport velocity servo drive system synchronously drives the feeder, edger, and conveyor through a system of notched timing belts, pulleys, and tensioners. The system operates under controlware resident in the BC which is subject to status signals from the operator control panel and document sensor system as shown in figure 4- 3. For a discus-sion of the generation of servo command signals, refer to the Controller Customer
Engineering Maintenance Manual, Pub. No. 60324700. Driving power for the system is provided by a dc motor with a tachometer generator fastened to the shaft. The tachometer generator provides velocity feedback signals to the BC servo system. A position encoder is attached to the shaft of the conveyor drive assembly which provides position feedback signals to the BC.
The transport velocity servo drive system advances the conveyor vacuum belt to provide line-by-line document motion. Transport commands, as shown in figure 4-3, are generated by the BC after receiving line position correction data from the character recognition system.
The BC determines from the line position correction data if the line being scanned is either above or below the optical centerline. The document can be advanced a minimum step dis-tance of O. 024 inch (24 mils). Other step distances possible are 24 mils plus integral mul-tiples of O. 008 inch (8 mils). If the character line is above the optical center, the document would be advanced the normal step distance less the distance above optical center. If the character line is below the optical center, the document would be advanced the normal step distance plus the distance below the optical center.
Each of the five velocity commands from the BC is routed to a digital-to-analog converter circuit in the reader as shown in figure 4-4. A logical 1 on an input line produces an analog signal corresponding to the associated conveyor belt velocity. Five velocities may be enabled: 5, 12.5, 20, or 40 inches per second, or 5 inches per second reverse. The velocity profiles used are related to the distance the document must travel to position the character line in the center of the read zone. The distances versus velocity profiles are shown in figure 4-5.
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