| 摘要 |
1,261,244. Variable resistors. LUCERNE PRODUCTS Inc. 31 Jan., 1969 [1 Feb., 1968], No. 5485/69. Heading HIS. A resistance control arrangement, e.g. for a motor M, Fig. 15, includes switches 48, 48a and 52, 52a, 52b provided with bridging contacts 60, 62 operable by a control (trigger member 13, Fig. 7) which also operates the moving contacts of a variable resistor arrangement 78a, 78b, 78c. Variation of the resistance when switch contacts 48, 48a and 52, 52a are interconnected may vary the ignition point of a neon tube 98, thus varying the firing point of a controlled rectifier 124 through which capacitor 96 discharges to energize the motor in alternate half-cycles. Instead of 124 a device ("triac", Fig. 15A, not shown), conducting in both directions on firing, may be used. The resistor may be a carbon layer 74a, Figs. 14 and 14B, divided by grooves 78, 81, 79, the layer portions 78a, 78b being contacted by projections 100a on a movable carrier member 72 guided by its flexible arms 99a (which press against the inside of the casing) and operated through a projecting part 100b by the trigger 13, Fig. 7. A trimmer resistance device is provided by a contact 104 which is movable (by an arm 82) over part of the resistance layer and thus provides a variable resistance 78c in parallel with the resistance part 78b. When the trigger is in the "off" position, the bridging contacts 60, 62 rest on projections 69 of the insulating casing (44, Figs. 11 and 12, not shown). When the trigger is moved these contacts move on to the stationary contacts 48a, 52a. When the trigger is in the "full-on" position, the contact 62 moves on to stationary contact 52b causing the speed control circuit to be by-passed. The trigger may be locked in this position by a spring-biased pin arrangement (Fig. 13A, not shown).
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