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US 4,585,082 AGranted
Weight scale utilizing a capacitative load cell
OwnerRichard H. Harrington, Charles W. Krapfinventors
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OwnerRichard H. Harrington, Charles W. Krapfinventors
Estimating the term…
A platform weight scale comprising a capacitative load cell sensing means configured to be insensitive to off center loading of the horizontal platform regardless of load amount or location on the platform. The platform is supported by a plurality of springs selected for equal spring rates. The load cell is electrically connected into a FET (Field Effect Transistor), CMOS (Complementary Metal Oxide Semiconductor) or Bi-Polar semiconductor multivibrator circuit selected and designed to sense electric currents on the order of 10.sup.-13 amperes. In one preferred embodiment the load cell comprises a grounded hemispherical surface opposing a flat charged plate. In alternate embodiments the load cell comprises a differential capacitor or a parallel plate capacitor suspended in a manner that is insensitive to off center loading. The differential capacitor load cell embodiment utilizes an alternating switch circuit as a part of the multivibrator circuit. As a third alternative, a frequency modulated system clock circuit that is modulated by the load cell capacitance or differential capacitance may be utilized as the weight sensing circuit and driver for peripheral attachments to the scale circuit.
A platform scale comprising a supporting structure, a platform on the supporting structure for movement relative to the supporting structure in response to a weight placed on the platform,
A variable capacitor comprising a portion of a substantially sphericl electrically conductive surface, a substantially flat electrically conductive surface mounted adjacent the spherical electrically conductive surface, and means to move linearly with freedom of rotation only about the spherical center at least one of the electrically conductive surfaces relative to the other electrically conductive surface.
A platform scale comprising an enclosing case and a weighing surface supported above a portion of the case, the case including electrically conductive means substantially surrounding the interior of the case,
A variable capacitor having one portion thereof affixed to means with a center, said means capable of linear movement of the center relative to the other portion of the capacitor and rotational movement about the center relative to the other portion of the capacitor, and said capacitor configured to provide a change of capacitance upon relative linear movement of the center toward the other portion of the capacitor but no substantial change of capacitance with relative rotational movement of the means about the center.
Dependencies are inferred from the claim text.