GB2273356A

GB2273356A - Roll-independent inclinometer

Info

Publication number: GB2273356A
Application number: GB9323849A
Authority: GB
Inventors: Noel John Granger
Original assignee: TILT MEASUREMENT Ltd
Current assignee: TILT MEASUREMENT Ltd
Priority date: 1992-11-21
Filing date: 1993-11-19
Publication date: 1994-06-15
Anticipated expiration: 2013-11-19
Also published as: GB2273356B; GB9224475D0; GB9323849D0

Abstract

A roll-independent inclinometer including a main body 2, 3 having an internal cavity 4, 5 whose surface is in the form of a solid of revolution and contains a part filling of a liquid providing space for a bubble forming gas, and further including electrodes 9, 10 co-axial with the major axis of the solid of revolution, the arrangement being such that rotation of the inclinometer around said major axis does not cause relative movement of the liquid and bubble. It may be of bipartite construction with a ring electrode 8 at least partly circumscribing the chamber at the join. The liquid may be electrically conductive and the gas non-conductive. The inclinometer may be connected to an a.c. bridge (not shown) across electrodes 9, 10. <IMAGE>

Description

ROLL INDEPENDENT INCLINOMETERS This invention relates to roll independent inclinometers.

Inclinometers are known which incorporate coaxial cylinders defining a fluid tight envelope symmetrical about the axis of the cylinder pair. The envelope is partially filled with a liquid and in contact with electrical conductors. An electrical circuit is connected to the conductors, the circuit being responsive to the inclination of the fluid within the envelope.

Single cylinder constructions are known which include a barrier midway along the length thereby to separate the unit into two sections. A quantity of mercury is contained in each section to provide variable inner electrodes.

It is an object of the present invention to provide an inclinometer construction which, when- in use, at least reduces problems inherent in use of the known inclinometer arrangements.

Broadly, according to a first aspect of the present invention there is * provided a roll independent inclinometer including a main body having an internal cavity the surface of which is in the form of a non-cylindrical body of revolution.

Preferably, the hollow main body is of abipartite formation.

A further aspect of the invention provides a roll independent inclinometer including a main body having an internal cavity the surface of which is in the form of a non-cylindrical body of revolution and containing a part filling of a liquid providing space for a bubble forming gas, and further including electrodes that are arranged to be co-axial with the major axis of the solid of revolution, the arrangement being such that rotation of the inclinometer around said major axis causes no movement of the liquid and bubble.

In a particular construction the roll independent inclinometer includes further electrodes that are arranged to be co-axial with the major axis of the solid of revolution, the arrangement being such that when the inclinometer is connected to an A.C. bridge rotation of the inclinometer around said major axis neither causes movement of the liquid and bubble nor change in the resistance values of the A.C. bridge when connected across said electrodes.

Preferably, the connection between the two parts of a bipartitie construction includes an electrode arrangement which circumscribes the region of join at least around a predetermined length of the circumference, with the interior of the main body intended to receive a partial filling of an electically conductive fluid and a predetermined quantity of a non-conductive bubble forming gas, and at least one further electrode within the interior of the main body.

Conveniently,- when . there are two such further electrodes they are located at opposite ends of the interior of the main body and are equidistantly spaced from the first mentioned electrode.

For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawing in which: Figure 1 is a cross-sectional view of a first embodiment of a roll independent inclinometer incorporating the concepts of the invention; Figure 2, schematically illustrates the internal profile of the inclinometer of Figure l; and Figure 3 is an end view of the inclinometer of Figure 1.

Referring now to the drawings and more particularly to Figure 1 the inclinometer shown therein includes a main body 1 comprising two similar elements 2,3 each with an internal cavity 4,5 and first and second end faces 6,7 respectively.

The elements 2,3 are secured together in face-to-face relationship in such manner that the internal cavities 4,5 combine to provide a single internal volume. Thus the faces of the two elements 2,3 are securely connected one to the other by way of suitable adhesives or any other convenient means, therebing a circumscribing ring electrode 8 interposed between the two faces 6,7.

The main body 1 is formed from electrically insulating material Two further electrodes 9,lU are provided within the interior of the main body, these electrodes being located at opposite ends ll,1i of the main body so as to be located one opposite the other.

To provide for electrical connection with these electrodes 9,10 Lhese electrodes connect with connector arrangements 1 which pass exLernally of the main body by means of suitable seals 15,16.

The electrodes 9,10, are formed from any convenient material. For example, one such material being Platinum another being a secondary material which is Platinum faced.

As may be particularly seen from the Figure 2, the internal wall 17 of the cavity is in the form of a solid of revolution, and in particular of an ellipsoid form.

The aspect ratio between the minor and major axes 18,19 is of a value found appropriate. In a particular construction one such ratio is selected to be two to one, that is the length of the major axis is twice that of the minor axis.

A through bore 20 is provided at one end of the main body.

This bore 20 can be utilised as a filling bore for the introduction of the conductive liquid material 21 and a non-conductive gas into the interior of the main body and is subsequently closed afte-r such filling.

The quantity of gas introduced into the interior of the body, in relation to the liquid content produces a gas bubble of the requisite size in relation to the overall volume and dimensions of'the cavity.

In operation, it is intended that the main body should be required to tilt about a minor axis 18, it will be appreciated that relative motion will then take place between the wall l7 of the cavity and the liquid.

This movement will change the volume of liquid between the electrode 9 or lu and the ring electrode 8.

In order to ensure that the liquid rapidly settles down positionwise after a displacement of the main body the liquid needs to have a requisite viscosity.

For the purposes of reducing the possibilities of bubble breakdown into more than one bubble the surface tension of the liquid has to be able to ensure that such breakdown does not easily arise.

In addition, the liquid/gas temperature characteristics need to be such that no change of physical state occurs throughout the desired/expected operating temperature range.

In other words the material serving as the fluid filling is selected to be of such characteristics that it provides the requisite conductivity, viscosity, surface tension and operating temperature range.

In practical use the above discussed tilt sensing device is arranged to provide two arms of an A.C. bridge which can be of any convenient type.

Since the particular electrical/electronic configuration of the bridge forms no part of the present invention it is not thought that a detailed description of an A.C. bridge is required in the present specification.

Thus it is considered sufficient to indicate that in use the bubble poSition within the cavity is determined by comparing the resistance through the liquid between the central electrode and the two end electrodes.

The position of the bubble within the main body is indicative of the absolute tilt of the main body about a horizontal axis.

The Figure 1 illustrates the inclinometer setting in which a major axis is horizontal and thus can be regarded as establishing a base or reference resistance value through the conductive liquid.

It will be seen from the Figures that the range of tilt in a particular direction for the inclinometer of the invention is set by the relative dimensions of the bubble and the separation between the ring electrode 8 and the end electrodes 9/10.

Claims

1. A roll independent inclinometer including a main body having an internal cavity the surface of which is in the form of a non-cylindrical body of revolution.

2. A roll independent inclinometer as claimed in claim 1, and wherein the hollow main body is of a bipartite formation.

3. A roll independent inclinometer including a main body having an internal cavity the surface of which is in the form of a non-cylindrical body of revolution and containing a part filling of a liquid providing space for a bubble forming gas, and further including electrodes that are arranged to be co-axial with the major axis of the solid of revolution, the arrangement being such that rotation of the inclinometer around said major axis causes no movement of the liquid and bubble.

4. A roll independent inclinometer as claimed in claim 3, and including further electrodes that are arranged to be co-axial with the major axis of the solid of revolution, the arrangement being such that when the inclinometer is connected to an A.C. bridge rotation of the inclinometer ' around said major axis neither causes movement of the liquid and bubble nor change in the resistance values of the A.C. bridge when connected across said electrodes.

5. A roll independent inclinometer as claimed in claim 3 or 4, and wherein the connection between the two parts of a biparite construction includes an electrode arrangement which circumscribes the region of join at least around a predetermined length of the circumference, with the interior of the main body intended to receive a partial filling of an electically conductive fluid and a predetermined quantity of a non-conductive bubble forming gas, 'and at least one further electrode within the interior of the main body.

6. A roll independent inclinometer as claimed in claim 5, and including two said further electrodes, said further electrodes being located at opposite ends of the interior of the main body and are equidistantly spaced from the first mentioned electrode.

7. A roll independant inclinometer constructed and arranged to operate substantially as hereinbefore described with reference to the accompanying drains.