| 摘要 |
1,164,401. Mechanical interrupters. E. W. BLISS CO. 12 Sept., 1967 [19 Sept., 1966], No. 41556/67. Heading H1N. A repeating cycle time switch having independently adjustable "on" and "off" periods comprises a pointer C continuously oscillated between pointers A and B and arranged to actuate switch contacts as the pointer C passes through the datum position shown. Pointers A and B are manually settable against "on" and "off" scales 14 and 16, respectively, by means of knobs 20 and 24, and thus each determines the duration of the respective "on" or "off" period without interfering with the other. The pointer C is secured to one end of a shaft 26 (Fig. 5) about which a timing plate E is free to revolve. A synchronous motor (64, Fig. 2, not shown) and suitable gearing drives two gearwheels (46 and 54), close to, and coaxial with, timing plate E, in opposite directions and these mesh respectively with two pinions (78 and 80) on shafts 86 journalled in the plate E and also carrying ratchet wheels 82 and 84 (Fig. 5) which thus revolve continuously in opposite directions, as indicated. A pawl 110 is pivoted at X on a bracket 118 attached to plate E and an overcentre spring 116 urges the end 111 into locking engagement with one of the ratchet wheels 82 and 84. A timing control plate G is secured to shaft 26 (and hence to pointer C) and has lugs 112, 114 straddling spring 116 and lugs 106, 108 straddling pawl 110. While pawl 110 is locking wheel 82 (as shown) the plate E, together with control plate G and pointer C, is driven clockwise until pointer C engages a flange on pointer B whereupon control plate G is arrested and lug 114 moves spring 116 overcentre. Lug 106 ensures that pawl 110 frees wheel 82 and snaps over to lock wheel 84, whereupon plate E commences reverse rotation until pointer C is impeded by pointer A and the cycle repeated. Two teeth 164 on plate E co-operate with a Geneva gear on shaft 172 as pointer C passes through its datum position and cause cams on the other end of shaft 172 to actuate two switch units (160, 162, Figs. 2, 3 and 4, not shown) on and off alternately. Coil springs (100, Fig. 6) on the bosses of ratchet wheels 82 and 84 provide sufficient frictional resistance to their reverse rotation to prevent inertial overshoot of plate E when the pawl 110 is released but permit pointers A and B to be reset during operation even to shorter times than that being instantaneously indicated by pointer C. |
