GB2259145A - Device for measuring or monitoring pressure - Google Patents

Description

-) 2 _) 914 5 C- 1 DEVICE FOR MEASURING OR MONITORING PRESSURE The present

invention relates to a device for use in measuring or monitoring hydraulic pressure and, particularly, to a device designed to be usable with mining equipment.

A device is known from DE-OS-3937573 which employs a compact cylindrical cartridge - like housing assembled from a number of parts. More particularly, the housing has a central sleeve closed at one end by a closure forming a coupling piece and at the opposite end by a bushing provided with an electrical connector. The coupling piece is an integral metal turning with a plug pin for sealably engaging with a socket of some hydraulic equipment and a screw-threading with which it is connected to the central sleeve. The coupling piece has an internal bore which terminates at a thin wall providing a flexible diaphragm which flexes, deforms and deflects according to the pressure of the hydraulic fluid. A sensor with one or more strain gauges is provided on the side of the diaphragm remote from the" bore and hydraulic fluid. The sensor provides electrical signals dependent on the mechanical deformation of the diaphragm and hence the hydraulic pressure acting on the diaphragm. The signals are amplified and are taken off 2 from the device via the electrical connector provided on the bushing opposite the coupling piece. In practice, it has been found that the signals provided by strain gauge arrangement were subject to drifting and precise measurements are difficult to achieve.

An object of the present invention is to provide an improved form of device of the aforementioned kind.

According to the invention there is provided a unitary device for measuring or monitoring hydraulicpressure; said device comprising a multipart housing, a deformable diaphragm in part of the housing, means for establishing connection between hydraulic pressure fluid and the diaphragm, a strain gauge sensor mounted on the diaphragm to produce signals dependent on the pressure of the fluid acting on the diaphragm and an amplifier connected to the sensor to amplify the signals; wherein part of the housing is relieved with a groove or aperture to surround the diaphragm and the sensor.

The.provision of the groove or aperture improve:T the response of the pressure sensing operation and reduces errors due to drifting of the gauges. This is because the stresses which occur in the material surrounding the diaphragm and the gauges no longer affect the measurement results.

Conveniently, the groove is of annular form spaced j 3 f rom the diaphragm and the strain gauges and extending deep into the solid material axially of the device. Preferably the groove has a rectangular cross-section. The groove can extend from an end face of the housing part which can take the form of a coupling component as known in the aforementioned prior publication.

The invention may be understood more readily, and various other aspects and features of the invention may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing; wherein Figure 1 is a part longitudinal -sectional view of a device constructed in accordance with the invention; Figure 2 is an enlarged sectional view of part of the device shown in Figure 1; and Figure 3 is a schematic end view of part of the device.

The Figures of the drawing depict a device 1 constructed in accordance with the invention which serves to sense hydraulic pressure and provides electrical signals representing the sensed pressure. Typically the device would be used with mining equipment in which various appliance are operated by hydraulic fluid and are 4 connected to a hydraulic pressure line by way of control valves.

The device 1 is suitable for connection to the pressure line to monitor the prevailing pressure. The device 1 taken the form of a compact cylindrical cartridge composed of three main components; namely a central casing or sleeve 2, a coupling component 3 and a bushing 4. The bushing 4 and the coupling component 3 are connected to the sleeve 2 with screwthreads and more particularly the sleeve 2 has inner threaded portions 10, 29 at its ends which mate with complementary external threaded portions of the coupling component 3 and the bushing 4. The"bushing 4 contains an electrical connector block 5 which receives electrical leads 6 representing the output from the amplifier 7 mounted in the sleeve 2. The block 5 mates with another connector 27 with an external lead 28 with a plug-in connection. A recess 26 in the bushing 4 accommodates this pluginconnection. The lead 28 can be coupled, for example,- to an electrical display or recording apparatus.

The coupling component 3 is an integral one-piece metal turning with a plug pin 8 at one end projecting axially outwardly from the sleeve 2 and a portion 9 with screw-threads engaging with the threaded portion 10 of the sleeve 2.

The plug pin 8 is conventional in the mining field and serves to engage with a socket to form a sealed connection with some hydraulic equipment, such as a valve block, connected to a conduit or the like conveying pressure fluid. The coupling component 3 has an internal bore 11 extending from the plug pin 8 to terminate with the screw-threaded portion 9 at a thin transverse wall which forms a flexible diaphragm 12 (Figure 2) which deforms and deflects according to the pressure of the hydraulic fluid in the bore 11. On the rear side surface 13 of the diaphragm 12 remote from the bore 11 there is a sensor 14 with one or more strain gauges which provides electrical signals dependent on the mechanical deformation of the diaphragm 12 and hence the pressure of the fluid causing the deformation.

An annular groove 30 extends axially of the screwthreaded portion 9 of the coupling component 3 and surrounds the diaphragm 12 and the sensor 14.

The groove 30 may have any cross-sectional shape but rectangular may be preferred. The groove 30 effectively isolates the diaphragm 12 from the solid material making up the bulk of the coupling component 3 so that, as shown, the bore 11 extends into an axial column radially separated from the rest of the coupling 1 6 component 3. This ensures the diaphragm 12 is not subjected to extraneous deformation forces due to stresses in the solid material of the coupling component 3 and this gives more accurate measurement results.

The sensor 14 is secured to the surface 13 of the diaphragm 12 with the aid of adhesive and preferably a coating of synthetic resin 15 binds and seals the sensor 14 to the surface 13. The sensor 14 can be composed of four strain gauges connected together as a Wheatstone bridge. The four signals from the sensor 14 are taken off with the aid of electrical leads 16 which can be bare wires.

As shown in Figure 2, the coupling component 3 has an annular end surface 17 disposed nearer the bushing 4 then the diaphragm 12 and the sensor 14. The groove 30 extends inwardly from this surface 17. The amplifier 7 connected to the leads 16 is supported by the end surface 17. The amplifier 7 is composed of electrical components mounted on the substrate 18, such as a p.c. board., convenientl y of circular shape. The substrate 18 is supported by four thin rod-like support elements 19 evenly spaced around the substrate 18. The elements 19 are electrically conductive and also serve to connect the leads 16 to the amplifier 7. The elements 19 are mechanically and electrically connected with solder 1 V It 7 joints to the leads 16 on metal plates or blocks 20. The plates 20 are isolated from one another and from the metal structure of the device with the aid of an insulating ring 22 abutting on the end surface 17 of the coupling component 3.

The ring 22 can be bonded to the end surface 17 with the aid of adhesive. Alternatively an insulating plastics coating or layer can be applied directly to the end surface 17. The four leads 16 from the strain gauges of the sensor 14 are attached to the contact plates 20 as solder joints or terminals 23. Electrical connection is thus established between the sensor 14 and the amplifier 7 via the leads 16, the plates 20 and the elements 19 while the amplifier 7 is suspended and mechanically supported by the elements 19.

The use of soldered joints to connect the elements 19 to the leads 16 is not essential and other forms of electrical connection can be used. For example, the leads or wires 16 can be trapped beneath the plates 20 in contact therewith and then bonded - in with an adhesive with insulating properties to the end surface 17. In another version the p.c. board 18 is plugged with the elements 19 into complementary sockets forming the terminals 23 electrically connected to the leads 16 or forming terminals on the p.c. board 18. Conversely, the 11 1 8 elements 19 can be fixed to the terminals 23 on the end surface 17 and the elements 19 can plug into sockets on the p.c.board 18.

The coupling component 3 with its diaphragm 12, the sensor 14 and the amplifier 7 supported with the elements 19 collectively form a unit which is screwed into the central sleeve or casing 2 with the amplifier 7 and the sensor 14 occupying a protected position in a chamber 24.

The bushing 4 which is screwed into the sleeve 2 from below closes off the interior chamber 24. The connector block 5 mounted in the bushing 4 can itself be screwed into a threaded bore 25 in the bushing 4 or simply pushed in and clamped. The connector block 5 has plugs or sockets which mate with complementary sockets or plugs on the end of the cables 6 carrying output signals from the amplifier 7.

1.

s_t 11 9

Claims (15)

1. A unitary device for measuring or monitoring hydraulic pressure; said device comprising a multi-part housing, a deformable diaphragm in part of the housing means for establishing connection between hydraulic pressure fluid and the diaphragm, a strain gauge sensor mounted on the diaphragm to produce signals dependent on the pressure of the fluid acting on the diaphragm and an amplifier connected to the sensor to amplify the signals; wherein part of the housing is relieved with the groove or aperture which surrounds the diaphragm and the sensor.

2. A device according to Claim, wherein the groove or aperture extends from an end face of the part.

3. A device according to Claim 1 or 2 wherein the housing part is an integral coupling component with a connector at one end leading to a bore for receiving the hydraulic pressure fluid.

4. A device according to Claim 3 wherein there is a casing or-sleeve detachably secured to the coupling component with inter-engageable screw-threads.

5. A device according to Claim 4 wherein the sleeve surrounds and protects the amplifier the diaphragm and the sensor.

6. A device according to any one of Claims 1 to 5 and further comprising a plurality of electrically conductive 1 support elements which mount the amplifier at a distance from the diaphragm with output leads from the sensor being electrically connected to the amplifier via the support elements.

7. A device according to Claim 6 wherein the support elements take the form of a thin metal pins.

8. A device according to Claim 6 or 7, wherein the support elements terminate with plates or terminals adjacent the diaphragm and the leads from the sensor are electrically connected to the plates or terminals.

9. A device according to Claim 8, wherein the plates are thin metal discs or rings.

10. A device according to Claim 8 or 9 when appended to Claim 3, wherein the terminals are insulated and bonded to an end face of the coupling component with adhesive.

11. A device according to any one of Claims 6 to 9 when appended to Claim 3 wherein the support elements engage with an end face of the coupling component and means providing electrical insulation is disposed to insulate the support elements from the coupling component.

12. A device according to any one of Claims 5 to 11 wherein the amplifier is composed of electrical components mounted on a p.c. board and the support S 1 1 0 7 11 elements are also mounted to the p.c. board.

13. A device according to Claim 4 or any one of Claims 5 to 12 when appended to Claim 4 wherein the housing further comprises a bushing detachably secured to the casing at an end region remote from the coupling component and an electrical connector block is provided in the bushing for receiving output leads from the amplifier and a cable leading from the device.

14. A device according to any one of the preceding claims wherein the groove or aperture has a rectangular cross-section.

15. A device substantially as described with reference to, and as illustrated in the accompanying drawings.