Machinery's Handbook, 31st Edition
2294
Ratchet Gearing Ratchet Gearing
Ratchet gearing may be used to transmit intermittent motion, or its only function may be to prevent the ratchet wheel from rotating backward. Ratchet gearing of this latter form is commonly used in connection with hoisting mechanisms of various kinds, to prevent the hoisting drum or shaft from rotating in a reverse direction under the action of the load. Types of Ratchet Gearing
a b
c
Fig. a.
Fig. b.
Fig. c.
d
e
Fig. d.
Fig. e.
Fig. f.
f
g
h
Fig. g. Fig. i. Ratchet gearing in its simplest form consists of a toothed ratchet wheel a (see Fig. a), and a pawl or detent b , and it may be used to transmit intermittent motion or to prevent relative motion between two parts except in one direction. The pawl b is pivoted to lever c which, when given an oscillating movement, imparts an intermittent rotary movement to ratchet wheel a . Fig. b illustrates another application of the ordinary ratchet and pawl mechanism. In this instance, the pawl is pivoted to a stationary member and its only function is to pre vent the ratchet wheel from rotating backward. With the stationary design, illustrated at Fig. h.
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