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US 4,047,586 AGranted
Zero load adjustment apparatus for spring weighing scale
AssigneePitney Bowes Inc.
InventorDaniel F. Dlugos
Life of this patent
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AssigneePitney Bowes Inc.
InventorDaniel F. Dlugos
Estimating the term…
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.
A zero load adjustment apparatus for a spring weighing scale having an optical detector and adapted to determine load weight as a function of the detected position of a scale tare, the detector including photodetector means for sensing the image of a modulated light beam, the adjustment apparatus comprising means mounting the photodetector means for movement in a plane transverse to the axis of the light beam and means adapted to provide controlled displacement of the photodetector means with respect to the image of the modulated light beam whereby the photodetector means may be registered with an image configuration at a tare no load position such that the photodetector means will provide a zero load signal to provide compensation for changes in the tare no load position.
A weighing scale comprising a tare structure including load supporting means, means providing linear displacement of the tare structure as a direct function of the mass of a load being weighed, an optical detector for determining the extent of tare movement, the detector including a pair of optical gratings, means interconnecting one of the gratings with the tare for movement therewith, means fixing the other grating with respect to tare movement, means providing a light beam, the gratings being so positioned as to modulate the light beam to have a cyclic optical interference pattern, the pattern including a plurality of spaced moire fringes, movement of the one grating providing movement of the fringes, photodetector means, the photodetector means being positioned in alignment with the pattern and adapted to detect fringe movement, and zero load adjustment means, the adjustment means including means mounting the photodetector means for movement in a plane transverse to the axis of the light beam and means adapted to provide controlled displacement of the photodetector means with respect to an interference pattern image, whereby the photodetector means may be registered with the pattern image configuration at a tare no load position such that the photodetector means will provide a zero load signal to adjustably compensate for changes in the tare no load position.
An optical detector for a spring weighing scale having a tare structure including load supporting means and means providing linear displacement of the tare structure as a direct function of the mass of a load being weighed, the optical detector comprising a pair of optical gratings, means fixing one of the optical ratings with respect to the tare structure, means operatively interconnecting the other grating to the tare structure for movement therewith, means providing a light beam, the gratings being so positioned as to modulate the light beam to have a cyclic optical interference pattern, the interference pattern including a plurality of spaced moire fringes, the movement of the other grating providing movement of the fringes, photodetector means positioned in alignment with the interference pattern and adapted to detect fringe movement, and zero load adjustment means, the adjustment means comprising means mounting the photodetector means for movement in a plane transverse to the axis of the light beam and means adapted to provide controlled displacement of the photodetector means with respect to an image of the interference pattern whereby the photodetector means may be registered with the pattern image configuration at a tare no load position such that the photodetector means wll provide a zero load signal to compensate for changes in the tare no load position.
A method of providing zero load adjustment of a spring weighing scale having a tare structure with load supporting means movable from a no load position to a loaded position and an optical detector adapted to determine load weight as a function of the detected position of the scale tare structure, the detector including photodetector means adapted to sense the image of a light beam which is modulated as a function of tare deflection and provide a corresponding signal, said method comprising the steps of:
Dependencies are inferred from the claim text.