PROXIMITY SENSOR

• US 20110209287A1
• Filed: 05/11/2011
• Published: 09/01/2011
• Est. Priority Date: 04/27/2005
• Status: Abandoned Application

• Current Assignee: Roho Incorporated (Permobil Holding AB)
• Original Assignee: Roho Incorporated (Permobil Holding AB)
• Inventors: Call, Evan William, Mabey, Kent Walker
• Application Number:
  US13/105,344
• Publication Number:
  US 20110209287A1
• Time in Patent Office: Days
• US Class Current: 5/658
• CPC Class Codes: A47C 27/082 with non-manual inflation, e.g. with electric pumps
• CPC Class Codes: A47C 27/083 with pressure control, e.g. with pressure sensors
• CPC Class Codes: A61B 2562/0257 Proximity sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1117 Fall detection
• CPC Class Codes: A61B 5/447 specially adapted for aiding the prevention of ulcer or pressure sore development, i.e. before the ulcer or sore has developed
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: A61B 5/6894 Wheel chairs
• CPC Class Codes: A61G 2203/40 for distance
• CPC Class Codes: A61G 5/1043 Cushions specially adapted for wheelchairs
• CPC Class Codes: A61G 5/1045 for the seat portion
• CPC Class Codes: A61G 7/05769 with inflatable chambers
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/975 using a capacitive movable element
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe
• CPC Class Codes: H03K 2217/960715 Rc-timing; e.g. measurement of variation of charge time or discharge time of the sensor

Abstract

An immersion sensor for use with a cushion or mattress for determining the relative immersion of a person within the cushion or mattress comprising a sensor, a ground and a circuit for measuring capacitance. The sensor comprises a sheet of conductive material, and the ground comprises a second sheet of conductive material. The circuit is adapted to send short bursts of electrical current to the sensor and a capacitor. The circuit is further adapted to measure the length of time the burst of current takes to charge the capacitor. Based upon the measured time, the circuit calculates the proximity of the object based upon the time taken to charge the capacitor. A method that may be implemented with the immersion sensor is also disclosed.

Claims

1. An immersion sensor assembly for use with a cushion or mattress for measuring the depth of immersion of a person within the cushion or mattress comprising:

a sensor comprising a conductive material;

a ground comprising a second conductive material electrically isolated from the sensor and at least partially surrounding the sensor, the ground electrically connected to and maintained at a ground electrical potential;

a circuit comprising a microprocessor and a reference capacitor, the circuit adapted to send short bursts of electrical current to the sensor and the reference capacitor, the circuit adapted to measure the length of time the burst of current takes to charge the reference capacitor and the circuit adapted to calculate the immersion of the person into the cushion or mattress based upon the time taken to charge the reference capacitor; and

wherein the sensor and the ground when the immersion sensor is laid flat, are nominally coplanar.

2. The immersion sensor assembly of claim 1 further comprising at least one layer of nonconductive material disposed over the sensor and the ground.

3. The immersion sensor assembly of claim 2 wherein the nonconductive material is foam.

4. The immersion sensor assembly of claim 1 wherein the sensor is disposed within a protective encasement of neoprene rubber.

5. The immersion sensor assembly of claim 1 wherein the circuit comprises a capacitive sensor.

6. The immersion sensor assembly of claim 1 further comprising a driven shield to isolate the sensor from the effect of electromagnetic interference or metallic objects in the direction of the driven shield from the sensor.

7. The immersion sensor assembly of claim 1 comprising a plurality of sensors and a plurality of grounds.

8. The immersion sensor assembly of claim 7 wherein the circuit is attached to two or more of the plurality of sensors to simultaneously determine the proximity of people to each of the sensors.

9. The immersion sensor assembly of claim 8 wherein the circuit is adapted to obtain a proximity measurement from a second sensor to determine a scale of proximity for proximity measurements from a first sensor.

10. The immersion sensor assembly of claim 7 wherein the circuit comprises a multiplexer, the multiplexer being attached to two or more of the sensors and also to the circuit and adapted to selectively connect the sensors to the circuit.

11. An immersion sensor assembly comprising:

a cushion or mattress having an adjustable depth of immersion of a person on the cushion or mattress;

a sensor comprising a sheet of conductive material;

a grounding plane being in the area around the sensor and allowing a capacitance measurement to be made relative to the distance between a person and the sensor;

a shield comprising a second sheet of conductive material located adjacent to and having generally the same shape and area as the sensor;

a circuit comprising a reference capacitor, the circuit adapted to

send short bursts of electrical current to the sensor and the reference capacitor,

measure the length of time the burst of current takes to charge the reference capacitor and the circuit adapted to calculate the relative proximity of the person based upon the time taken to charge the reference capacitor,

drive the shield to electrically isolate the shield from external capacitance or electromagnetic interference, and

provide an indication when the person is too deeply immersed within the cushion or mattress.

12. A bed assembly for the support of an individual positioned on the bed, the bed assembly comprising:

a bed frame, said bed frame comprising metal components;

a mattress on the bed; and

a sensor operatively associated with the mattress, the sensor comprising,

a microcontroller,

a ground layer surrounding the sensor;

a shield layer comprising a sheet of conductive material and driving the shield to isolate the sensor from the effect of stray capacitance and electromagnetic interference from the metal bed frame components;

a circuit for detecting the capacitive effect of the individual on the mattress and providing a relative output for the microcontroller;

wherein the planes formed by the sensor and the shield, when the immersion sensor is laid flat, are nominally parallel; and

wherein the circuit is adapted to provide an indication when the individual is too deeply immersed within the mattress or when the individual is off the mattress.

13. The bed assembly of claim 12 wherein the sensor further comprises at least one layer of nonconductive material disposed over the sensor.

14. The bed assembly of claim 12 wherein the sensor is integrally formed with a mattress.

15. The bed assembly of claim 12 wherein the sensor comprises a plurality of sensors and the shield is sized to isolate the plurality of sensors.

16. The bed assembly of claim 15 wherein the circuit comprises a multiplexer, the multiplexer being attached to two or more of the sensors and also to the circuit and adapted to selectively connect the sensors to the circuit.

17. In a bed assembly comprising a bed frame and a mattress, a method of determining the proper immersion of a person within the mattress comprising the steps of:

providing a first sensor below mattress comprising a sheet of conductive material;

providing a ground layer comprising a sheet of conductive material that is nominally coplanar and maintained at a ground potential below the cushion or mattress;

providing a shield layer comprising a sheet of conductive material and driving the shield to isolate the sensor from the effect of stray capacitance and electromagnetic interference from the bed frame.

sending short bursts of electrical current to the sensor and a capacitor;

measuring the length of time the burst of current takes to charge the capacitor;

calculating the proximity of the person based upon the time taken to charge the capacitor; and

providing an indication when the person is either over-immersed or under-immersed within mattress.

18. The method of claim 17 further comprising the steps of:

providing a second sensor of smaller area than the first sensor comprising a second sheet of conductive material;

sending short bursts of electrical current to the second sensor and the capacitor;

measuring the length of time the burst of current takes to charge the capacitor; and

calculating the proximity of the person based upon the time taken to charge the capacitor; and

determining a scale for the calculation from the first sensor from the calculation obtained from the second sensor.