I'm getting into some very interesting mechanisms inside my retired Canon Pixma MX340 multi-function inkjet. After taking a look at its ink disposal peristaltic pump, my next focus is on a gear shift mechanism I identified earlier as the starting point to feed a single sheet of paper. With the cover removed, I can see it is a lever riding on one gear axle and with two other gears on either arm of the lever. This center gear always turns when the paper feed motor turns, driving the ink disposal pump.

When "Forward" gear is engaged (circled in red) it conveys motion to the large black gear.

When "Reverse" is engaged, power from the same driveshaft (but a different gear riding on the same shaft) is transmitted to a gear driving the paper tray large roller.

Under and to the left of that mechanism is the print carriage parking pawl, sitting on the same axis as the gear conveying power from the paper feed motor. Earlier I was curious if this pawl also played some gear-shifting role. Now I have my answer: It does not.

It wasn't just sitting loosely on that gear, though. A length of spring steel maintained a level of tension/friction so the pawl will always move in response to a change in direction. I found a similar mechanism in its lid closing damper.

Anyway, back to the shifter. Removing it from the assembly showed that forward and reverse gears are offset from each other in order to engage adjacent gears riding on the same shaft.

I thought understanding this lever would tell me how this gearbox worked, but I underestimated the amount of mechanical wizardry I would find within. This was just the tip of the iceberg. The more I look, the more I find.

This teardown ran far longer than I originally thought it would. Click here to rewind back to where this adventure started.