Pressure sensitive sensor

Details Pressure sensitive sensor Pressure sensitive sensor

2001-12-26

2004-05-25

Lefkowitz, Edward (Department: 2855)

Measuring and testing

Fluid pressure gauge

Electrical

C073S726000, C073S862629, C029S407080

Reexamination Certificate

active

06739198

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure sensitive sensor.
2. Description of Background Information
A conventional pressure sensitive sensor, such as the sensor described in Japanese Patent Publication (Kokai) Hei No. 10-281906, is shown in FIG. 8. The conventional pressure sensitive sensor includes a cavity
1
a
that extends along the inside of a long narrow elastic insulator
1
in a longitudinal direction, and a plurality of electrode wires
3
A to
3
D are buried in the thickness of the elastic insulator
1
at intervals along the periphery in a circumferential direction. The plurality of electrode wires
3
A to
3
D are spirally twisted around the cavity
1
a
, and one section of a peripheral surface of each electrode wire
3
A to
3
D is exposed in the cavity
1
a
. Further, when the elastic insulator
1
is elastically deformed, as when the cavity
1
a
is crushed by pressing, the electrode wires
3
A to
3
D are brought into conducting contact with each other, therefore external pressure can be detected.
A method of producing the pressure sensitive sensor includes preparing a twisted wire by twisting a spacer, which is of the same shape as the cavity
1
a
, with a plurality of electrode wires
3
A to
3
D, and pulling the spacer out after coating the twisted wire with the elastic insulator
1
.
However, in the case of the conventional pressure sensitive sensor, complicated production steps of twisting the spacer with the electrode wires
3
A to
3
D and pulling out the spacer afterward are required to form the structure, and there is a problem of high cost.
Further, the cross-section of the sensor is large in size because of the necessity of forming the cavity
1
a
in a central location, and the necessity of burying the electrode wires
3
A to
3
D in the thickness of the elastic insulator
1
. For these and other reasons, it is not suitable to make the sensor in a small size.
Further, since there is no procedure for positively separating each of the electrode wires
3
A to
3
D to insulate them, there is also a danger that when the pressure sensitive sensor is arranged in a warped or kinked section of the insulator, the electrode wires
3
A to
3
D will be brought in contact with each other by mistake to cause an error in detection.
SUMMARY OF THE INVENTION
Accordingly, considering the above-mentioned problems, it is an object of the present invention to provide a pressure sensitive sensor with a simple structure that can be produced easily and at low cost.
Further, another object of the present invention is to provide a pressure sensitive sensor that is appropriate for production with a small cross-sectional area and that can appropriately function even if it is arranged in a warped section with a sharp curvature.
According to an aspect of the present invention, the technical procedure for attaining the above-mentioned objects is to provide a pressure sensitive sensor for detecting pressure by electrical conduction caused by mutual contact by pressing the first and the second electrode members, which are positioned separated from each other, wherein a net braid member that includes an insulating material allows the electrical contact between the first electrode member and the second electrode member through the gap portion of its mesh at the pressure location, and then separates to insulate the first electrode member and the second electrode member when no pressure is provided between the first electrode member and the second electrode member. Preferably, the net braid member is formed by knitting a plurality of yarn materials which are formed of an insulating fiber, and the yarn materials are bundled by coating an insulating resin or rubber on its surface or being impregnated with the insulating resin.
According to a further aspect of the present invention, the first electrode member is an elastic electroconductive tube that includes an elastic electroconductive material, the second electrode member has a long narrow shape that can be bent and extends longitudinally in one direction and a central electrode member which is provided in the elastic electroconductive tube, and the net braid member is provided between the central electrode member and the elastic electroconductive tube so that it covers the outer peripheral surface of the central electrode member.
Further, preferably, the central electrode member has the property that it can recover its shape against a fixed tensile strength and bending deformation, and is provided with a long, narrow central member at least whose outer peripheral portion has elasticity, and an electroconductive metal wire horizontally wound around the outer peripheral portion of the central member in a coil form.
In another aspect of the present invention, the central electrode member is further provided with an electroconductive coating layer including an electroconductive resin or an electroconductive rubber that is provided on the inside of the net braid member so that the outer peripheral surface of the central member is covered outside of the metal wire.
In a further aspect of the present invention, the elastic electroconductive tube is formed by extrusion molding the elastic electroconductive material on the outer peripheral surface of the central electrode member on the outside of the net braid member.
Moreover, preferably, the central electrode member is formed by twisting or bundling a plurality of single metal wires.
Further, the central electrode member may include a single metal wire.
According to an aspect of the present invention, a pressure sensitive sensor for detecting pressure by electrical conduction caused by pressing into contact with each other a first electrode member and a second electrode member provided in a spaced arrangement in an unpressed state is provided including an insulative member provided between the first electrode member and the second electrode member, the insulative member including an insulating material that allows electrical contact between the first electrode member and the second electrode member when pressed and insulates the first electrode member and the second electrode when not pressed. The insulative member may include a net braid member provided between the first electrode member and the second electrode member, the net braid member allowing electrical contact between the first electrode member and the second electrode member through a gap portion in its mesh when pressed, and insulating the first electrode member and the second electrode when not pressed. The net braid member may further be formed by knitting a plurality of yarn strands. The yarn strands may further include an insulating fiber coated on its surface with an insulating resin or rubber, or an insulating fiber impregnated with an insulating resin or rubber.
According to a further aspect of the present invention, the first electrode member may include an elastic electroconductive tube including an elastic electroconductive material, the second electrode member may include a central electrode member having a long narrow bendable shape provided inside the elastic electroconductive tube, and the insulative member may be provided between the central electrode member and the elastic electroconductive tube so that the insulative member covers an outer peripheral surface of the central electrode member. The central electrode member may be restorable to its shape from tensile and bending deformation, and the central electrode member may be provided with a central member having a long narrow shape and having at least an outer elastic peripheral portion and an electroconductive metal wire wound on the outer periphery of the central member in a coil.
In a further aspect of the present invention, the central electrode member may be provided with an electroconductive coating layer including an electroconductive resin or an electroconductive rubber provided on the inside of the insulative member so that an outer peripheral surface of the central member is covered underneath the

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