The mechanism for actuating the feed at the end of the return stroke only, is shown in [Fig. 1547]. The shaft v (which is also seen in a dotted circle in [Fig. 1545]) carries a flange c, on each side of which is a leather disk, so that the pressure of the bolts which secure b to the sleeve a causes c to revolve under friction, unless sleeve a, slotted bar b, and flange c all revolve together, or, in other words, c revolves under friction when it revolves within a b.
Fig. 1548.
[Fig. 1548] is an end view of [Fig. 1547].
Fig. 1549.
[Fig. 1549] gives a cross-sectional view of the shaft sleeve, &c. The sleeve a is provided with two pins i, i, and a pin k is fast in the frame of the machine, and it is seen that a and v may revolve together in either direction until such time as one of the pins i meets the stationary pin k, whereupon the further revolving of a will be arrested and v will revolve within a, and as flange c, [Fig. 1547], revolves with v, it will do so under the friction of the leather washers. The pins i and the pin k are so located that a can have motion only when the ram or sliding-bar is at the end of the return stroke, and the feed-rod f, being connected to b, is therefore actuated at the same time.
Among the various mechanisms employed to give a quick return to the tool-carrying slide of shaping machines, those most frequently employed are a simple crank, a vibrating link, and the Whitworth quick-return motion, the latter being the most general one.