GB785245A - Improvements in or relating to mechanism for presenting rotation of a first member relative to a second member, e.g., in a displacement indicator - Google Patents

Abstract

785,245. Machine-tool details. GIDDINGS & LEWIS MACHINE TOOL CO. July 20, 1955 [July 28, 1954], No. 21003/55. Class 83 (3). [Also in Group XXIV] An indicator for measuring the linear displacement of a translatable member, e.g. the tool or work-holder of a machine-tool, or the angular displacement of a rotatable member, comprises a shaft 10 j ournalled by a bearing 11 in the housing 12 of equipment in which the indicator is used, and having secured thereto a gear 14 driven by the member whose displacement is to be measured. Fixed to the shaft by a key 25 are a pinion 40 and a flange 24 supporting an annular dial 15. Pinion 40 drives a number of floating pinions 41 which mesh with a member 42 fixed to housing 12, an annular dial 19, and a ring 18. Member 42 and ring 18 each have the same number of teeth so that ring 18 is held stationary during rotation-of the pinions, whereas dial 19 has at least one extra tooth so that it is turned in timed relation to shaft 10. Flanged members 48 within pinions 41 contain spring-pressed balls 49 to urge flange 24 and a member 22 secured thereto against a shoulder 21 on the shaft, and also to urge the members 42, 19, 18 towards the housing. Dial 19 may be graduated, e.g. to record a displacement of 39 inches in divisions of 1/ 5 inch, whereas dial 15 may have 200 divisions each of <SP>1</SP>/ 1000 inch, and the dials are read against a mark 16 on ring 18. A counterweight 20 is journalled in shaft 10 and connected by gears 36, 38 to the dial 15, so that rotation of the weight in one direction causes rotation of the dial in the opposite direction relatively to members 24, 22, and the dial may be set or indexed relatively to shaft 10. In order to prevent rotation of the dial 15 relatively to the shaft when the latter is driven, the moment of inertia of counterweight 20 is so arranged that when multiplied by the mechanical advantage of the gear drive, it equals the moment of inertia of dial 15. Thus during acceleration or deceleration of the shaft both members 15, 20 will tend to rotate in the same direction due to inertia forces which oppose and counterbalance one another.