Force sensing sheet

• US 9,642,470 B2
• Filed: 07/25/2014
• Issued: 05/09/2017
• Est. Priority Date: 03/15/2008
• Status: Active Grant

• Current Assignee: PatienTech, LLC
• Original Assignee: Stryker Corporation
• Inventors: Taylor, Geoffrey L.
• Primary Examiner(s): DUNLAP, JONATHAN M
• Application Number:
  US14/341,328
• Publication Number:
  US 20140331412A1
• Time in Patent Office: 1,019 Days
• Field of Search: 73862041-862046, 73172, 73818, 73849, 73862474, 73862621, 73862637
• CPC Class Codes: A47C 27/082 with non-manual inflation, e.g. with electric pumps
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G01L 5/228 using tactile array force sensors
• CPC Class Codes: G01N 2203/0623 using piezoelectric gauges
• CPC Class Codes: G01N 3/08 by applying steady tensile or compressive forces G01N3/28 takes precedence
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure

Abstract

A support apparatus includes a force sensing array positioned thereon that includes multiple layers of material that are arranged to define an elastically stretchable sensing sheet. The sensing sheet may be placed underneath a patient to detect interface forces or pressures between the patient and the support structure that the patient is positioned on. The force sensing array includes a plurality of force sensors. The force sensors are defined where a row conductor and a column conductor approach each other on opposite sides of a force sensing material, such as a piezoresistive material. In order to reduce electrical cross talk between the plurality of sensors, a semiconductive material is included adjacent the force sensing material to create a PN junction with the force sensing material. This PN junction acts as a diode, limiting current flow to essentially one direction, which, in turn, reduces cross talk between the multiple sensors.

Claims

1. A support apparatus comprising:

a cushion having a plurality of air bladder cells;

an elastically stretchable sheet positioned on top of the air bladder cells;

a plurality of first conductive paths supported on the elastically stretchable sheet;

a layer of sensing material positioned in contact with the first conductive paths, the layer of sensing material having an electrical characteristic that varies in response to physical forces exerted thereon;

a layer of semiconductive material positioned in contact with the layer of sensing material on a side of the layer of sensing material opposite the plurality of first conductive paths; and

a plurality of second conductive paths positioned in contact with the layer of semiconductive material on a side of the layer of semiconductive material opposite the layer of sensing material.

2. The support apparatus of claim 1 further including a control apparatus in communication with the first and second conductive paths and adapted to detect a pressure exerted by a person onto the elastically stretchable sheet.

3. The support apparatus of claim 2 wherein the control apparatus is adapted to change air pressure inside of the plurality of air bladder cells in response to the detected pressure.

4. The support apparatus of claim 3 wherein the layer of sensing material includes a layer of piezoresistive material.

5. The support apparatus of claim 4 wherein the layer of piezoresistive material is supported by an elastically stretchable substrate.

6. The support apparatus of claim 5 wherein the elastically stretchable substrate is made at least partially of nylon.

7. The support apparatus of claim 6 wherein the plurality of second conductive paths are supported on a second elastically stretchable sheet, and the elastically stretchable sheet and the second elastically stretchable sheet are both made from woven fabric.

8. The support apparatus of claim 3 wherein the plurality of second conductive paths are supported on a second elastically stretchable sheet.

9. The support apparatus of claim 8 wherein the elastically stretchable sheet and the second elastically stretchable sheet are both made from woven fabric.

10. The support apparatus of claim 9 wherein the woven fabric includes nylon.

11. The support apparatus of claim 3 wherein the semiconductive layer is coated onto the layer of sensing material and includes a metallic oxide.

12. The support apparatus of claim 4 wherein the semiconductive layer is coated onto the layer of sensing material and includes a metallic oxide.

13. The support apparatus of claim 5 further including a cover sheet positioned over the cushion and the elastically stretchable sheet, the cover sheet being made of thin, flexible, and elastically stretchable material.