Monday, February 5, 2024

Adjusting the paper feed mechanism - part 1

ASSEMBLED PAPER FEED MECHANISM NOT WORKING CORRECTLY

The rollers should be pressed up against the platen across its width thus gripping the paper and holding it stationary. When the paper release lever is operated, it should lower the rear rollers more than the front rollers so that new paper can be easily fed into the typewriter. 

Instead, the rear rollers are against the platen but the front rollers barely touch near the center and have a large gap at the two ends, even with the mechanism moved as far as it possibly can go. The FE procedures don't provide any adjustments that will correct this. 

I therefore had to study the mechanism and figure out what is wrong. The first diagram shows how the platen should sit on the rollers and the primary lever pulled by a spring that pushes the front roller up against the platen.

The primary lever should push front roller up to platen

The rest of the mechanism is best understood by the second diagram below, with my annotations. 


As the primary lever arm is moved back by the spring, it pivots to push the front feed roller arm upwards. The rear feed roller arm pivots around a front stud attached to the paper feed mounting arm. Since it is also connected at its midpoint to the front feed roller arm, when the front arm moves up, it rotates the rear feed roll arm to push the rear feed upward. 

Because of the midpoint connection of the two feed arms, they scissor together so that the front and rear feed rollers move towards each other as the primary lever arm is moved upwards. They should be pinching the platen so that both rollers are against the platen surface. 

The Paper Release Lever moves the Feed Roll Release Arm which pivots the primary lever (Front Feed Roll Arm) forwards, moving the rollers down and scissored out away from the platen. 

However, the relative position of the rollers and the platen are not correct. The primary lever arm, moved all the way back so the front roller is all the way up, does not touch the platen surface at the two ends of the page width. The center did have the rollers touching. I have exaggerated this by changing the first diagram and placing it below.

Rollers not meeting Platen

FEED RELEASE ROD BOWED UPWARDS BY MISADJUSTED CENTER SUPPORT

The center fixed support holds the Feed Roll Release lever around which the primary lever arm moves, at its midpoint on the page width. This should be adjusted so that it just touches the Feed Roll Release Arm but it was pushing the rod upwards, putting a bow in the rod. That explains why the center of the page width was able to touch the platen; unfortunately that is not the proper way to fix whatever problem exists with the assembly.  

I fixed the center support position which put the rollers uniformly away from the Platen, which is progress. Now to get them in the right position. 

Center support with red arrow

SUSPICION IS THAT THE PLATEN POSITION IS OFF RELATIVE TO THE FEED ROLL ARMS

The Front Feed Roller Arm should be able to pivot up to have the rollers touching the Platen, actually pressing with about two and a half pounds of force with the spring pivoting the arm. It won't reach the platen, so something is seriously off. 

The Platen and the feed roller arm assembly are not in the proper relationship, so in a sense the platen is rotated up and away from the rollers. 

I THINK I CAN ADJUST THE PLATEN POSITION

The platen position is adjustable in two axes as shown in the picture below. I believe I might be able to move the platen down and in contact with the front feed rollers. I will try this tomorrow. 

Pivots at green, adjustment at yellow moves platen at red

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