An Internal Gear may be described as the opposite of an external gear
in that the teeth point towards rather than away from the center, and
addendum and dedendum take reverse positions. Internal Gears provide
a compact parallel shaft transmission drive with large speed
reduction. Used with a stock spur pinion the ratio is the same as that of
two external gears, but the center distance is much smaller. In cases
where it is necessary to have two parallel shafts rotate in the same
direction, the internal gear eliminates the use of an idler gear.
Internal Gears possess several advantages when properly applied.
One such advantage is reduced sliding action. The corresponding
working surfaces of the teeth of an internal gear and pinion are more
nearly of the same length than is the case with an external gear and
pinion having the same tooth ratio and tooth length. Therefore the
relative slippage of the teeth is less in the case of the internal. This point
presents one of the advantages of using Internal Gears. The sliding
action of one tooth over another causes friction; and as friction results
in tooth wear, a reduction in the amount of sliding action is desirable.
Internal Gear drives may be operated with the gear in a fixed position
and the pinion rotating along the pitch line, or the gear may be free to
rotate with the pinion rotating in a fixed position.
When mating pinions are too close in size to the gear, interference may
result. Therefore, the difference in teeth of the pinion to the gear should
not be less than 15.
RUSH GEARS inc. offers standard Internal Gears in STEEL,
STAINLESS STEEL, CAST IRON, BRONZE, ALUMINUM, DELRIN
and NON-METALLIC (PHENOLIC). We will gladly manufacture
made to order Internal Gears to your requirements.