Multi-directional piezoresistive shear and normal force sensors for hospital mattresses and seat cushions
First Claim
1. A force sensor for producing an electrical signal proportional to forces exerted on said sensor comprising;
- a. a first type conductive member,b. at least one second type conductive member movable into resiliently deformable, electrically conductive contact with said first type conductive member, the area and electrical conductance of said contact being proportional to forces urging said first and second type conductive member together, said contact being characterised by a surface piezoresistivity inversely related to said forces and greater than the resistivity of said first conductive member,c. means for supporting said first and second type conductive members, andd. means for making external electrical contact to said first and second type conductive members.
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Accused Products
Abstract
Thin, planar sensors for measuring forces exerted by mattresses or chair pads on a patient'"'"'s body include a central conductive elastomeric pad movable in a horizontal plane into more or less intimate contact with flexible peripheral conductors adjacent the central pad, thus varying electrical conductivity between the central pad and peripheral conductors by a surface piezoresistive effect proportional to the magnitude and direction of horizontal shear forces exerted on the pad. The preferred embodiment comprises a matrix area array of thin, square central conductive elastomeric pads, each surrounded by four square peripheral conductive elastomeric pads forming a close pack tiling arrangement that utilizes inner peripheral conductors in the array to function as one of the peripheral conductors for two or three nearest-neighbor sensors. In one embodiment of the invention, a sensor having a thin, flat layer formed of a non-conductive elastomeric polymer matrix filled with electrically conductive particles is sensitive to pressure or normal forces exerted on the sensor, such forces reducing the volume of the layer and therefore its electrical resistance, by a bulk on volume piezoresistive effect.
136 Citations
36 Claims
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1. A force sensor for producing an electrical signal proportional to forces exerted on said sensor comprising;
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a. a first type conductive member, b. at least one second type conductive member movable into resiliently deformable, electrically conductive contact with said first type conductive member, the area and electrical conductance of said contact being proportional to forces urging said first and second type conductive member together, said contact being characterised by a surface piezoresistivity inversely related to said forces and greater than the resistivity of said first conductive member, c. means for supporting said first and second type conductive members, and d. means for making external electrical contact to said first and second type conductive members. - View Dependent Claims (2, 3, 4, 5)
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6. A shear sensor for producing an electrical signal proportional to shear forces exerted thereon comprising;
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a. a base having a generally flat upper surface, b. a conductive resilient pad on said flat upper surface, c. at least one peripheral conductive member adjacent a side wall of said conductive pad, said resilient pad and peripheral conductive member being resiliently contactable in response to relative motion therebetween caused by shear forces exerted on said sensor in a direction parallel to said base, the area and electrical conductance of said contact being proportional to said shear forces. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A piezoresistive pressure sensor comprising;
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a. a first conductive electrode, b. a piezoresistive layer overlying said first electrode, and c. a second conductive electrode overlying said piezoresistive layer, at least one of said first and second electrodes being a uniformly metallized fabric sheet, said uniform metallization enabling said fabric sheet to drape. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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31. A shear sensor array for producing electrical signals proportional to shear forces exerted at various locations over an area in contact with said array, said array comprising;
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a. a thin substrate having first and second substantially parallel surfaces, b. a plurality of shear force sensors mounted to said substrate, each of said shear force sensors comprising, i. a central, square plan-view, thin conductive elastomeric pad mounted parallel to a surface of said substrate, ii. a plurality of square plan-view peripheral conductive elastomeric pads mounted parallel to a surface of said substrate, each of said peripheral pads having a straight side wall adjacent a side wall of said central conductive pad, said side walls being resiliently deformable in response to shear forces to make more or less electrically conductive contact therebetween, said central and peripheral conductive pads arranged in a close-packed tiling pattern whereby some of said peripheral conductive pads contact more than one central conductive pad, and c. means for making electrically conductive connections to each of said central conductive pads and each of said peripheral conductive pads. - View Dependent Claims (32, 33, 34, 35, 36)
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Specification