Zero load adjustment apparatus for spring weighing scale

Details Zero load adjustment apparatus for spring weighing scale Zero load adjustment apparatus for spring weighing scale

1976-03-23

1977-09-13

Hartary, Joseph W.

Weighing scales

Self-positioning

Electrical current generating or modifying

177DIG6, 250237G, 356169, G01G 2326

Patent

active

040475867

ABSTRACT:
A spring weighing scale includes an optical detector which generates a moire fringe pattern and moves the pattern as an optically amplified function of scale tare deflection. A first of a pair of parallel optical gratings moves with a scale tare structure, while a second reticle grating remains fixed. Passing through both gratings is a light beam which projects a fringe pattern upon a photodetector array. Placement of a load upon the scale results in movement of successive fringes across the photodetectors and the sequential generation of weight indicative signals which are counted to determine load weight. Automatic zero load adjustment is effected by a displacement linkage driven by a stepping motor to provide displacement of the photodetector array along the axis of pattern movement. The motor is controlled by a counter monitor to register the photodetector array with the pattern image no load position such that a null count is produced. The linkage employs a twin parallel threaded worm and socket to provide any requisite compensatory shift of a chassis which carries the photodetector array. In a further embodiment, the photodetector chassis is supported by a pair of parallel leaf springs which bias the chassis against an adjustment worm driven by the motor. Alternately, a sine bar sliding wedge is worm driven against the bias of the leaf springs to displace the chassis.

REFERENCES:
patent: 3757126 (1973-09-01), Tumbush
patent: 3867037 (1975-02-01), Litke
patent: 3923110 (1975-12-01), Dan

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