GB819422A - An improved apparatus for determining the accuracy of a toothed transmission elementor the like - Google Patents

Abstract

819,422. Electric measuring systems. HOFLER, W. Nov. 15, 1955 [Nov. 17, 1954], No. 32594/55. Class 40 (1). Apparatus for determining the degree of irregularity of movement between two members which are coupled together by toothed transmission elements, e.g. gear wheels, comprises two variable capacitors fixed to shafts which are actuated by the two members and arranged to produce equal and opposite variations in capacity with regular movement of the coupled members, whereby the sum of the two capacitances is a constant, and any deviation therefrom is a measure of the degree of irregularity. As shown, for testing two gears 4, 10 (Fig. 1) of the same pitch and diameter, one gear 4 is mounted on a shaft 3 driven by a motor 5, and the other gear 10, mounted on a shaft 11, is adjusted to engage the gear 4. Assembled on shaft 3 is the movable electrode 16 of a variable capacitor 17, the fixed electrode 18 being mounted on the frame 2, and a similar capacitor 20 is mounted on shaft 11, comprising movable electrode 19 and fixed electrode 21, the arrangement being such that as the shafts 3, 11 rotate uniformly the capacitors 17, 20 vary in an equal and opposite manner so that their total capacitance is constant. The capacitors 17, 20 are connected in parallel in the tank circuit of an oscillator whose output frequency variation is therefore indicative of the irregularity of the gears 4, 10. Where the gears are not in a 1: 1 ratio, one shaft 11 is coupled to its variable capacitor 20 through a variable gear ratio comprising a cone 32 (Fig. 4) mounted on shaft 11, and a friction disc 38 mounted on an auxiliary shaft 30 carrying capacitor 20, the gear ratio being varied by moving the disc 38 along the surface of the cone 32 until shafts 3, 30 rotate at the same speed. The test apparatus may also be used in conjunction with bevel gear, worm gear, rack and pinion, &c. In a further embodiment (Fig. 9) the two rotating members are the tool shaft 70 and the mandrel 71 of a gear cutter, whereby the uniformity of the relative angular velocities is checked.