GB2168149A

GB2168149A - Level sensing device

Info

Publication number: GB2168149A
Application number: GB08528665A
Authority: GB
Inventors: Ronald Wilson
Original assignee: MAXOFAR Ltd
Current assignee: MAXOFAR Ltd
Priority date: 1984-12-01
Filing date: 1985-11-21
Publication date: 1986-06-11
Also published as: GB2168149B; GB8528665D0

Abstract

A level sensing device consisting of a metal ball (16) which is free to gravitate within a circular aperture (12) formed in a metal plate (11), the plate (11) being divided to form two halves on a diameter of the aperture thereby to constitute switch contacts closeable by the ball (16). The plate (11) and ball (16) are located within a plastics housing (10) for retaining the m ball (16) within the aperture (12) there being clearance between the ball (16) and the housing (10) sufficient to allow free movement of the ball (16), An audible indicator (18) and or visual indicator (19) may be connected to the two halves of the plate (11) by conductors (14, 15). <IMAGE>

Description

SPECIFICATION Level sensing device This invention relates to a level sensing device.

According to the present invention, there is provided a level sensing device comprising means defining a concave track, a rolling member free to gravitate on the track, retaining means for retaining the rolling member in the vicinity of the track, and sensing means adapted to respond according to position of the rolling member on the track.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective diagrammatic view of a level sensing device in accordance with the present invention; Figure 2 is a diagrammatic front elevation of the device of Fig. 1 in the direction of arrow A in Fig. 1; Fig. 3 is a diagrammatic sectional elevation on the line Ill-Ill in Fig. 1; Figure 4 is a sectional plan on the line IV-IV in Fig. 1; and Figures 5, 6 and 7 are views corresponding with Figs. 2, 3 and 4, but in respect of a modification of the device shown in Fig. 1.

In Figs. 1 to 4 of the drawings, the level sensing device consists of a hollow plastics box or housing 10 within which is centrally located a metal plate 11 having a circular aperture 12 therein. The plate 11 is divided on a diameter of the aperture 12 parallel with one of the sides of the box 10 which is of rectangular configuration, being square on front elevation (arrow A). Thus, the halves of the plate 11 are electrcially insulated one from another by a gap 13. The detailed construction of the box 10 is not shown, but it will be well known in the art of plastics mouldings to provide means suitable for locating the halves of the plate 11 with considerable accuracy.

Means are provided for establishing electrical contract with the halves of the plate 11, and in the drawings, appropriate electrical conductors are designated 14 and 15. A practical size for the aperture 12 is 12.5mm; the plate 11 may therefore be 20mm square and be about 0.5mm thick. The material of the plate is preferably bronze. The edge defined by the circular aperture 12 constitutes means defining a concave track.

A rolling member in the form of a metal sphere 16 is disposed wthin the aperture 12 and is free to gravitate on the track defined by the edge of the aperture. Thus, the sphere or bail 16 will always tend to gravitate to whatever is the lowest position of the track at any time. The transverse dimension of the box 10 is such as to provide just sufficient clearance for free movement of the ball 16, but to constitute a means for retaining the ball in the vicinity of the aperture 12.

Assuming the material of the box 10 to be transparent, and assuming that the plate 11 is divided on a line normal to one side of the box, then the device as described above serves as a level sensor indicating a level position when the ball 16 can be seen to touch both halves of the plate 11.

If required, sensing means may be added to the device described above for the purpose of providing a response according to the position of the ball 16 on the track defined by the aperture 12. For example, the conductors 14 and 15 may be connected to a circuit including a battery or energy source 17, a sounder 18 and/or a visual indicator 19; and the circuit may include a switch 20. It will be apparent that operation of the sensing means constituted by the electrical components is based on the two halves of the plate 11 constituting switch contacts closeable by the ball 16 thereby to operate the electrical circuit.

In Figs. 5 to 7 of the drawings, parts corresponding with those in Figs. 1 to 4 are given the same reference numerals as are used in Figs. 1 to 4.

In Figs. 5 to 7, a second plate 1 1A is provided, having an aperture 1 2A similar to the plate 11 and the aperture 12. The plates 11 and 11 A are arranged symetrically within the box 10 and the ball 16 is supported by the plates 11 and 11 A being disposed on either side of the centre line of the ball 16. The plate 11 A is not divided as is the plate 11, but serves as an additional retaining means. In the embodiments of Figs. 5 to 7, the ball 16 need not be in contact with the inside surfaces of the box 10 during a level-sensing operation, and therefore this embodiment may provide greater sensitivity by virtue of reduced friction influencing free gravitation of the ball 16.

In each of the constructions described above, the ball 16 is preferably of bronze, and about 6.25mm diameter that is, approximately half the diameter of the aperture 12. The size of the gap 13 is conveniently about 0.5mm.

Each of the constructions of sensing device described above is capable of manufacture economically and simply, and yet provides a surprisingly reliable yet compact and responsive level-sensing device. It will be appreciated that, within the scope of the present invention, the means for sensing position of the ball 16 on the track defined by the aperture 12 may be developed to a point of considerable sophistication. For example, the contact plate 11 may be divided into more electrially insulated parts, and logic circuits may be used to identify those parts which are being switchclosed by the ball 16 at any time. Thus, the sensing means may indicate many different positions of the ball with respect to the track which is in fact equivalent to a potential for indicating many positions of the box 10 which may be incorporated in a level or level indicating appliance. In a further modification, the plate 11 may, instead of being divided physically, be divided by the printing thereon of contact strips, using known circuit printing techniques.

Claims

1. A level sensing device comprising means defining a concave track, a rolling member free to gravitate on the track, retaining means for retaining the rolling member in the vicinity of the track, and sensing means adapted to respond according to position of the rolling member on the track.

2. A level sensing device according to claim 1, wherein the means defining the concave track comprises a plate member having an aperture therein.

3. A level sensing device according to claim 2, wherein the aperture is circular.

4. A level sensing device according to any one of the preceding claims, wherein the rolling member is a sphere.

5. A level sensing device according to any one of the preceding claims, wherein the means for retaining the rolling member in the vicinity of the track comprises retaining walls disposed on respectively opposite sides of the plate member parallel therewith and spaced therefrom sufficient to clear the rolling member for free movement.

6. A level sensing device according to any one of the preceding claims, wherein the rolling member is of electrically conductive material, and the sensing means comprises an electrical circuit including mutually insulated electrical contact points or portions of the means defining the concave track for engagement by the rolling member to effect electrical switching of the sensing means according to position of the rolling member on the track.

7. A level sensing device according to claim 6 when dependent from claim 3, wherein the plate member is of electrically conductive material and is divided on a diameter of the circular aperture to define two mutually insulated track portions.

8. A level sensing device comprising a metal ball free to gravitate within a circular aperture formed in a plate divided to constitute switch contacts closeable by the ball, and means to retain the ball within the aperture.

9. A level sensing device according to claim 8, wherein the diameter of the aperture is twice the diameter of the ball or approximately so.

10. A level sensing device according to claim 9, wherein the diameter of the aperture is about 12.5mm.

11. A level sensing device substantially as herein-before described with reference to and as shown in Figs. 1 to 4 or Figs. 1 to 4 as modified by Figs. 5 to 7 of the accompanying drawings.