![]() ![]() The key pinion is turned to rotate the collar of the chuck, which turns the screw inside the chuck to move the jaws in or out. A compact arrangement of bevel gears and levers does the trick. The chuck of a power drill has to grip very strongly as it rotates the drill, yet it must be possible to loosen or tighten the chuck by hand. ![]() The feed-dog rises and moves forward between stitches to shift the fabric and then dips and moves back. Both are powered by a wheel driven by the electric motor, synchronizing their movements. One train of cams and cranks moves the feed-dog forward and backward, while the other makes it rise and fall. The Feed-Dog: This moves the fabric forward. The signals from the wheels give the changes in the mouse's position. As the wheel turns, light shines through the slots and produces an electric signal in the photodiodes. Each wheel has one or two pairs of light-emitting diodes and photodiodes. The mouse rolls on a ball that turns two slotted wheels mounted at right angles. ![]()
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