Force or pressure sensor and method for applying the same

• US 20060129047A1
• Filed: 08/15/2003
• Published: 06/15/2006
• Est. Priority Date: 08/21/2002
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Finsor Oy (Apple Inc.)
• Inventors: Ruotoistenmaki, Heikki
• Granted Patent: US 7,726,209 B2
• Time in Patent Office: Days
• US Class Current: 600/483
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1102 Ballistocardiography
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025

Abstract

The invention relates to a force or pressure sensor and a method for applying the same. The pressure sensor comprises a substantially rigid, mechanical-load resistant frame (1), a flexible diaphragm (2) secured over its peripheral rim to the frame (1), and a piezoelectric sensor diaphragm (3) applied to the surface of the flexible diaphragm (2). The sensor diaphragm (3) loading element comprises a substantially rigid, mechanical-load resistant cover (4), having its protrusion or shoulder (4a) bearing against a middle section of the flexible diaphragm (2) and thereby prestressing the flexible diaphragm (2) and the piezoelectric sensor diaphragm (3) attached thereto. The frame (1) and the cover (4) define therebetween a closed, hermetically sealed housing chamber, the flexible diaphragm (2) and the piezoelectric sensor diaphragm (3) being located thereinside. The placement of one or more responsive, yet load-resistant sensors in contact with a bed enables measuring a sleeping or lying person for his or her heart rate and respiratory amplitude, as well as frequency.

Claims

1. A force or pressure sensor, comprising a substantially rigid, mechanical-load resistant frame, a flexible diaphragm secured over its peripheral rim to the frame and a piezoelectric sensor diaphragm applied to the surface of the flexible diaphragm wherein the sensor diaphragm loading element comprises a substantially rigid cover capable of carrying mechanical loading of more than 50 kg, wherein the cover includes a protrusion or shoulder, bearing against a middle section of the flexible diaphragm and thus, by deflection, prestressing the flexible diaphragm and the piezoelectric sensor diaphragm attached thereto, and wherein the frame and the cover define therebetween a closed housing chamber, the flexible diaphragm and the piezoelectric sensor diaphragm being located thereinside.

2. The sensor of claim 1, wherein the frame the cover and the diaphragms are rotationally symmetrical relative to the cover protrusion or shoulder.

3. The sensor of claim 1, wherein the flexible diaphragm comprises a thin metal diaphragm, having its peripheral rim secured between the edges of the frame and the cover.

4. The sensor of claim 1, wherein the sensor diaphragm comprises a piezoceramic diaphragm, having a diameter smaller than that of the metal diaphragm, further wherein the sensor diaphragm has its peripheral rim at a distance from the inner periphery of the housing chamber.

5. The sensor of claim 1, wherein a sensor-signal transmitting contact spring is in contact with the sensor diaphragm opposite to the cover protrusion or shoulder (4a).

6. The sensor of claim 1, wherein an amplifier and a circuit board are located in said housing chamber.

7. The sensor of claim 1, wherein the frame and the cover comprise elements in the shape of bodies of revolution.

8. The sensor of claim 1, wherein the sensor has a responsivity, such that the sensor provides an output signal when the change of a load applied to the cover is less than 10⁻

6, times the load rating of the cover.

9. The sensor of claim 6, wherein the amplifier has its input impedance matched to provide a desired settling time, during which the amplifier has its output set substantially to zero, while the loading applied to the cover respectively remains essentially unchanged.

10. The sensor of claim 1, wherein the closed housing chamber is hermetically sealed.

11. The sensor of claim 1, wherein the cover is provided with an adapter element which enables loading of the cover with changes in a fluid or gas pressure.

12. A method for using a force or pressure sensor, comprising a substantially rigid, mechanical-load resistant frame, a flexible diaphragm secured over its peripheral rim to the frame, and a piezoelectric sensor diaphragm applied to the surface of the flexible diaphragm, wherein the sensor diaphragm loading element comprises a substantially rigid cover capable of carrying mechanical loading of more than 50 kg, wherein the cover includes a protrusion or shoulder, bearing against a middle section of the flexible diaphragm and thus, by deflection, prestressing the flexible diaphragm and the piezoelectric sensor diaphragm attached thereto, and wherein the frame and the cover define therebetween a closed housing chamber, the flexible diaphragm and the piezoelectric sensor diaphragm being located thereinside comprising the steps of disposing one or more sensors in contact with a bed and measuring a sleeping or lying person for his or her heart rate and respiratory amplitude, as well as frequency.

13. The method of claim 12, wherein the measurement is implemented with one or more sensors placed under a bed post or posts.

14. The method of claim 12, wherein the measurement is implemented with one or more sensors placed in contact with a bed mattress and the sensor is prevented from sinking in the top mattress and/or the mattress with panels which are more rigid than the mattresses and between which the sensor is positioned.