[GreenKeys] Paper feeds, platens, sprockets, pins, and tractors, etc.

[DR HOUSE]

Every once in a while I feel the need to explain.
Friction feed is easy to understand. The roll paper is suspended on a  
spindle and comes off the bottom of the roll.  The paper feeds under  
the platen and feeds with the assistance of spring loaded rollers.
Paper tape on most machines is also suspended on a spindle and comes  
off the bottom of the roll, feeds through guide rollers and through  
the punch.  On some machines the tape comes off the top of the roll.   
Sprocket feed is a bit different, the paper is stored behind the  
machine in a metal paper box that feeds the paper under a form  
accumulating shelf and into a slot on the back of the machine.  On  
M33s there is no slot, it just feeds under the platen.  The 28,35,37  
machines have a paper guide that is spring clipped to the back of the  
cabinet on a 28 or the back of the cover on a 35.  Model 37s have a  
unique way of handling sprocket feed paper that goes back to the idea  
of the paper being kept under the printer in the cabinet and coming up  
through a slot. I know that some Model 15s have sprocket platens but I  
have never seen one in operation and am not familiar with the paper  
handling.  I assume it is similar to the model 35 in that the paper  
probably goes through the cover from a rear mounted paper box.

Getting to the platen on a sprocket feed machine, the paper is started  
under the platen similarly to a friction feed machine except a  
sprocket feed machine has cam driven pins on each side of the platen  
to positively feed the paper.  These typing units usually have form  
feed out, as well as vertical tabs.  Some have horizontal tabs on the  
front plate.  The 33 only has form feed without vertical or horizontal  
tabs.  Some can be set for either 5 1/2 inch form feed or 11 inch form  
feed, others are only 11 inch.  The M37 has several options for form  
feed, vertical and horizontal tabs, plus on-line tab set and clear  
under control of cables connected to levers in the stunt box.

Lastly some of the later Teletype machines such as the 43, 40 and 45  
as well as the AT&T 5300 series used a tractor feed mechanism.   
Tractor feed differs significantly from sprocket feed in that the  
paper is advanced by pins that are on belts at either side of the  
paper and not handled by sprockets at the ends of the platen.  Some of  
the machines have the tractors permanently incorporated into the  
printer design, others like the 43 and 5300 are separate mechanisms  
that are attached to the printer.

Lastly we have three oddities that you don't see very often.  The  
Model 12 and 26 as well as the WUTCo 100 series have moving platens  
with stationary print mechanisms... you can't really call them  
carriages as they do not move horizontally. These machines use unique  
paper handling system where the roll of paper is suspended on a  
spindle that moves back and forth with the platen.  Lastly I mention  
fan-fold friction feed paper and roll sprocket feed paper.  Fan fold  
paper is folded in a box similar to sprocket paper except there are no  
holes in the paper.  The paper sits behind the machine in its box and  
the friction feed platen handles it as if it were roll paper... The  
roll sprocket paper is an oddity that may have been used with sprocket  
feed or tractor feed printers where there was no room for a paper box  
behind or under the machine.

Any now I return you to your regular programing.  Should you wish to  
see examples reply off list and I can send you some examples.

73,
Don K9TTY