| 摘要 |
936,441. Ratchet gearing. INTERNATIONAL BUSINESS MACHINES CORPORATION. Jan. 2, 1962 [Jan. 9, 1961], No. 94/62. Addition to 932,113. Classes 80 (2) and 80 (3). In a two-speed ratchet gear, two pawls 26a, 26b on pawl actuating arms 14a, 14b are driven in opposite phase in cyclic manner to move the pawls into and out of engagement with parallel sided notches 30 in a ratchet 28a, 28b, means being provided to latch one pawl arm to prevent that pawl moving the ratchet, whereby the ratchet is driven at a lower speed when the pawl arm is latched. In a punched card feed mechanism, a driving-shaft 12 carries two cams 13a, 13b, 180 degrees out of phase, which oscillate a forked pawl lifting member 34 and pawl arms 14a, 14b, respectively. The lifting member arms 36a, 36b are arranged to lift the pawls out of the notches on the return stroke. A pawl may be held from engagement, to provide a half-speed drive, by electromagnet 41 having a " hold " coil 41a and a " bucking " coil 41b, under which condition the pawl enters a notch to prevent back-running but does not drive the ratchet. In a second embodiment, Fig. 2, (not shown), the pawls are arranged to impart step-by-step motion to linearly moving notched rods.
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