US 4,359,179 AGranted

Apparatus for detecting a malfunction in the paper feed system of a printer

AssigneeTeletype Corporation

InventorJohn R. Waiss

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Abstract

The drive shaft 30 of a printer 10 engages a tractor 16 which, in turn, moves a paper web 12 across a print mechanism 14. Located on the drive shaft 30 is a drive shaft advance cam 78 which is fixed to drive the shaft 30 and rotate therewith. Additionally, located upon the drive shaft 30 for limited rotational movement with respect to the drive shaft advance cam 78 is a paper advance cam 90. The shape of the drive shaft cam 78 is similar to the shape of the paper advance cam 90. The paper advance cam 90 carries an O-ring 102 defining a high frictional surface for engaging the paper web 12. The door 50 of the tractor 16 carries a paper pressure roller 104 having a circumferential groove 106 positioned for cooperation with the O-ring 102. During normal paper web 12 drive, the cams 78, 90 are out of registration and rotate in unison. In response to a paper web jam condition, the paper drive cam 90 driven by the paper web 12 momentarily stops and the cam falls 78, 90 are forced into registration resulting in the actuation of a switch 60.

An apparatus for detecting a malfunction in the paper web (12) feed system of a printer wherein the paper web (12) is transported along a predetermined path by a drive mechanism (16, 30) engaging the paper web (12) and thereby imparting a desired movement to the paper web (12) comprising:

a first cam (78) coupled to said drive mechanism (16, 30) and providing an indication of the desired movement of the paper web (12);
a second cam (90) coupled to the paper web (12) and providing an indication of the actual movement of the paper web (12);
first means (114) responsive to said first and second cams (78, 90) for providing an indication in response to the relative positions of said first and second cams which indication is related to the actual movement as compared to the desired movement of the paper web (12);
said second cam (90) including a resilient O-ring (102) located about an outer surface thereof, said second cam (90) positioned so that said O-ring (102) is in frictional driven engagement with the paper web (12);
a pressure roller (104) having a circumferential groove (106);
means (54, 56) for biasing said pressure roller (104) against said second cam (90), said pressure roller (104) being positioned so that the groove (106) of said pressure roller (106) is adjacent said O-ring (102) thereby assuring that the paper web (12) and said O-ring (102) are in frictional driving engagement;
a follower (114) responsive to said first (78) and second (90) cams;
a switch (60);
a second means (66) responsive to the position of said follower for actuating said switch (60) in response to a predetermined relative position of said first and second cams (78, 90);
a pivotably supported switch actuating arm (66) positioned for selective actuation of said switch (60), said switch actuating arm being movable between a switch engaging position and a switch release position;
a switch actuating arm release lever (124):
third means (130) for urging said lever (124) into predetermined position relative to said follower (114) and said lever (124) having means (126) for selectively engaging said switch actuating arm;
and
said release lever (124) having a first position engaging said actuating arm (66) determined by a first relative position of said cams (78, 90) for holding said actuating arm (66) in said switch engaging position and a second position determined by a second relative position of said cams (78, 90) for releasing said actuating arm (66) for movement to said switch release position.

11 more elements

Abstract

Claims4