Weight sensors having centralized loose tolerance universal force and Mx/My moments overload stops
First Claim
1. Automotive seat weight sensor system comprising in operative combination:
- a) a thin, generally planar steel substrate member having spaced, opposed ends, a longitudinal X axis, a lateral Y axis, and a vertical Z axis;
b) said substrate having an array of strain gauges arrayed thereon to determine the amount of load in the Z axis of said substrate;
c) a load stud mounted through a hole in said substrate medial of its ends with springs that are concave, shallow cones oriented in opposed relationship having their centers spaced farther apart than the rims and disposed with the concave side directly in contact with said substrate;
d) said medial substrate hole is configured with loose tolerance with respect to said stud to provide an Mx/My gap there between;
e) a limit stop bracket having an upper and a lower surface mounted spaced from and in association with said substrate, and having a hole through which said load stud passes;
f) stop elements carried by said stud to engage at least one of said upper surface, said lower surface and a wall of said limit stop bracket hole to provide Fz, Fx, FY stops and an Mx/My moment stop; and
g) said limit stop bracket hole having a tolerance configured with respect to said stud to provide a gap smaller than said Mx/My gap so that said Mx/My stop is engaged before moment-induced yield of said substrate occurs.
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Accused Products
Abstract
Automotive load cells having centralized, multi-axis, loose tolerance overload/limit stops provide improved strain gauge response. The modular, integrated stop assemblies magnify sensor substrate deflection by use of opposed concave (Belleville) springs are used in direct contact with the substrate to accommodate ±Z axis deflection and Mx/My moment angular rotation. A flanged guide member on the load stud permits a wide range of geometries. The substrate is thickened around the load stud hole and the outboard support bolt holes. Hollow rivets assist in design modularity. Strain gauges are placed at the yield zones symmetrically with respect to the X axis. The substrate hole Mx/My gap is larger than the stop bracket hole to insure a positive stop for Mx/My moments prior to yield. The inventive multi-axis stop assembly is used in any type load cell, including rectangular, thinned, notched, necked/dogbone, or cantilever substrates with any strain gauge layout configuration.
76 Citations
16 Claims
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1. Automotive seat weight sensor system comprising in operative combination:
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a) a thin, generally planar steel substrate member having spaced, opposed ends, a longitudinal X axis, a lateral Y axis, and a vertical Z axis;
b) said substrate having an array of strain gauges arrayed thereon to determine the amount of load in the Z axis of said substrate;
c) a load stud mounted through a hole in said substrate medial of its ends with springs that are concave, shallow cones oriented in opposed relationship having their centers spaced farther apart than the rims and disposed with the concave side directly in contact with said substrate;
d) said medial substrate hole is configured with loose tolerance with respect to said stud to provide an Mx/My gap there between;
e) a limit stop bracket having an upper and a lower surface mounted spaced from and in association with said substrate, and having a hole through which said load stud passes;
f) stop elements carried by said stud to engage at least one of said upper surface, said lower surface and a wall of said limit stop bracket hole to provide Fz, Fx, FY stops and an Mx/My moment stop; and
g) said limit stop bracket hole having a tolerance configured with respect to said stud to provide a gap smaller than said Mx/My gap so that said Mx/My stop is engaged before moment-induced yield of said substrate occurs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An improved load cell for automotive seat weight determination including presence of a passenger load, wherein said load cell is a load-stop or a non-load-stop design and includes at least one load bearing stud and a substrate plate carrying sensors thereon, the improvement comprising in operative combination:
- securing said load stud to said substrate with springs that are concave, shallow cones oriented in opposed relationship, having their centers spaced further apart than rims and disposed with a concave side facing and directly in contact with said substrate, said concave springs having a stiffness less than said substrate, and said load stud being configured with loose tolerance with respect to said substrate.
- View Dependent Claims (14, 15)
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16. Method of reducing load cell substrate misreading or failure due to Mx and/or My moment-induced yield, comprising the steps of:
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a) mounting a load stud to a sensor substrate with springs that are shallow cones having stiffness less than said substrate said springs having a concave side and an opposed convex side, each of said concave sides facing and in direct contact with said substrate;
b) disposing said springs to compress differentially upon moments Mx and/or My being applied to said stud; and
c) configuring a moment gap between said substrate and said load stud that is larger than a gap to a moment stop associated with said stud so that there is stop engagement under a moment before yield strength of said substrate is exceeded.
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Specification