GB734235A - Improvements in or relating to indicating devices - Google Patents

Abstract

734,235. Counting-apparatus; indicating- apparatus. BECKMAN INSTRUMENTS, Inc. May 27, 1953 [March 9, 1953], No. 14751/53. Classes 106 (1) and 106 (4). [Also in Groups XXXVI and XL (c)] A device for indicating the angular position of a rotor comprises a first rotatable indicator connected to the rotor, intermittently operating gear means connecting a second rotatable indicator to the first indicator once per revolution of the latter, and locking means for securing the first indicator and rotor in any desired angular position. As shown, the extent to which a shaft 22, Fig. 1, is rotated, is indicated by a fractional turn or first indicator 67, Fig. 2, mounted rigidly on the shaft 22, and by a coaxial second indicator 38 brought into geared relationship with the first indicator 67 once during each revolution of the latter. The second indicator 38, Fig. 3, has inwardlydirected gear-teeth 43 bearing against two axially-extending annular projections 61 forming a hub about which the second indicator 38 rotates. The annular projections 61 are formed on abase 37. The gear teeth 43 are continually in mesh with a gear-wheel 44 rotatable on a pivot 66 extending from the base-plate 37. The first indicator 67 has a small inwardly directed gear segment 42, Fig. 4, adapted to mesh with the gear-wheel 44, to drive the second indicator 38, once during each revolution of the first indicator 67. To prevent rotation of the second indicator 38 when the gear-wheel 44 is not in mesh with the gear segment 42, alternate teeth on the gear-wheel 44 are made axiaily longer than the teeth there-between, as best shown in Fig. 1. When the gear segment 42 is out of mesh with the gear-wheel 44, two of the elongated teeth 76 on the gear-wheel 44 engage an annular shoulder 77 directed radially inwards on the first indicator 67, thus preventing rotation of the gear-wheel 44 and the second indicator 38. Locking of whole apparatus. A brake shoe 45 is pivoted on a pin 83 on the base-plate 37 and rests against a hub portion 81 of the first indicator 67. The rear face of the brake shoe 45 is so shaped that by appropriately deflecting a finger-piece 89, a cam tab 86 can be wedged between the brake shoe 45 and one of the annular projections 61 to cause the brake shoe 45 to hold the shaft 22 in the position to which it has been set. Variable resistor. The device in Fig. 1 is associated with a variable resistor comprising major turns 14 each wound with a large number of minor turns 14a. The shaft 22 carries a collar 24 keyed to but slidable along the shaft, the collar carrying a contact arm 28 grooved at its end to partly encircle the resistance element 14. As the shaft 22 is rotated, the contact 28 will follow the turns of the resistance element 14. The device is used to indicate the amount of resistance permitted to become effective on rotating the shaft 22.