GB2113844A - Sensor of rotational movement - Google Patents

Abstract

A fluid seal diaphragm constituted by a non-ferrous plate (27) is mounted between magnets (16) mounted on rotating shaft (1) and stationary magnetic flux sensors (18) to prevent leakage of lubricant from a bearing (2) into electronic circuitry (19, 20) while permitting a substantially interference-free path for magnetic flux enabling the sensors to detect rotational movement of the magnets. As an alternative, an optical detection system using a translucent seal member may be used. The detector is used to determine the position of a mining machine hauled along a working face by machinery of which the shaft (1) is a part. <IMAGE>

Description

SPECIFICATION Sensor means for rotational movement This invention relates to sensor means for rotational movement.

In particular, although not exclusively, the present invention relates to sensor means for sensing shaft rotation, the shaft being mounted in a lubricated bearing.

It is known on a mining machine in an underground mine for the position of the machine along a longwall working face to be determined by magnetic sensor means arranged to sense rotation of a shaft associated with the machine haulage such that sensed shaft rotation is a direct indication of machine travel along the working face. It is necessary to provide electronic circuitry adjacent to the magnetic sensor means in order to derive a signal indicative of the sensed shaft rotation. One problem associated with such an arrangement is that lubricating oil or grease for the shaft bearing tends to find its way into the electronic circuitry tending to give rise to unreliable signals.

In attempts to try and overcome the problem it has been proposed to provide rotary ring seals around the shaft. Unfortunately, such a proposal did not prove successful as it was difficult or costly to maintain sufficient accurate manufacturing tolerances for the seal housing which thereby tended to be misaligned with the rotational axis of the shaft. Another arrangement frequently reverted to was to mount the shaft vertical with the magnetic sensor means provided over the shaft. Unfortunately, such an arrangement does not easily lend itself to adaption on some mining machines where it would be desirable to sense rotation of a horizontally mounted shaft.

An object of the present invention is to provide improved sensor means which are able to sense shaft rotation and avoid or reduce the abovementioned problems.

According to the present invention, sensor means for sensing rotational movement comprise a first component mounted for rotation, a second component mounted to detect rotational movement of the first component, and a fluid seal element mounted between the first and second components, the fluid seal element providing a substantially interference-free path enabling the second component to detect rotational movement of the first component.

The present invention also provides sensor means for sensing rotational movement of a shaft mounted in lubricated bearing means, comprising a first component mounted for rotation with the shaft, a second component mounted to detect rotation of the shaft and to derive a signal indicative of rotation of the shaft, and a fluid seal element mounted between the first and second components, the fluid seal element providing an effective seal against flow of lubricant and providing a substantially interference-free path enabling the second component to detect rotational movement of the first component.

Preferably, the sensor means comprises magnetic sensing means, the fluid seal element comprising a non-ferrous plate providing a substantially interference-free path from the passage of magnetic flux between the first and second components.

Advantageously, the first component comprises at least one magnet and the second component comprises at least one detector of magnetic flux.

Preferably, a plurality of magnets are angularly equi-spaced around the axis of rotation of the shaft.

Preferably, a plurality of magnetic flux detectors are angularly equi-spaced around the axis of rotation of the shaft.

Preferably, the plurality of magnets and the plurality of detectors substantially are radially equi-spaced from the axis of rotation of the shaft.

Advantageously, the or each magnet is mounted on a disc mounted co-axial with the shaft and rotatable with thp shaft.

Preferably, the or each magnet is cqvered by protective window means.

Conveniently, the non-ferrous plate is nonrotatable and mounted substantially co-axially with the rotational axis of the shaft.

Preferably, the non-ferrous plate is fixedly mounted to a generally cylindrical member Jefining at least a part of a wall chamber wall.

By way of example, one embodiment of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 is an incomplete cross-sectional view taken through the rotational axis of a shaft, magnetic sensor means provided in accordance with the present invention are shown in one operational position; and Figure 2 is an incomplete end view looking in a direction shown in a different operational position to that of Figure 1.

Figure 1 shows a rotary shaft 1 of a longwall mining machine which in use traverses to and fro along a longwall working face of an underground mine, the machine having cutter means (not shown) for winning strips of mineral from the longwali working face. Rotation of the shaft 1 is directly proportional to movement of the machine along the face, the direction of the shaft rotation being dependent upon the direction of machine movement along the face.

The shaft is rotatably mounted in a lubricated bearing 2 supported in bearing housing walls 3 and retained in position by a plate 4 which abuts the end face of the bearing and which is retained to the end of the shaft by a bolt having a head 5 abutting the plate 4 and a threaded shank portion 6 screwed into a threaded bore 7 provided in the end of the shaft and co-axial with the shaft axis of rotation 8.

The head 5 of the bolt projects through a hole 9 provided in the casing 10 of the machine's gearbox, the head being recessed by receive a central bore 11 of a disc 12 fixedly secured to the bolt head by screws 1 3 engaging in thread bores 14 provided in the bolt head. The surface 15 of the disc 12 remote from the shaft is recessed to receive a plurality of magnets 1 6 angularly equi spaced around the axis of rotation of the shaft, the magnets being radially equi-spaced from the axis of rotation of the shaft (see particularly Figure 2).

A protective window 1 7 is located over the magnets 1 6, the outer surfaces of the window substantially being flush with the associated outer surface of the disc.

Rotational movement of the plurality of magnets 1 6 is detected by a plurality of magnetic flux sensors 1 8 fixedly mounted on one electrical circuit board 1 9 of a pair of circuit boards 1 9, 20, the plurality of magnetic flux sensors being angularly equi-spaced around the axis of rotation of the shaft and being radially equi-spaced from the axis of rotation of the shaft.

Figure 2 shows the plurality of magnetic flux sensors 18 to be mounted substantially on the centre line 21 of the rotating magnets 1 6. In Figure 2, three magnets and three sensors are shown. In different embodiments different numbers of magnets anchor sensors can be used. Also, the magnets may be arranged at different distances from the axis of rotation so that they are associated with different concentric paths. In such arrangements the magnets might be angularly spaced around the axis of rotation or, alternatively, they might be arranged on the same radially extending plane.

Figure 1 of the drawings shows the rotary disc 12, magnets 16, sensors 18 and circuit boards 19, 20 to be housed within a chamber defined by a generally cylindrical wall 22 and an end cap 23, the end cap being secured to the wall 22 by bolts (not shown). The wall is secured to the gearbox by bolts 24 only one of which is shown which also serve to retain the wall to the gearbox casing. A . seal 25 is provided between the cylindrical wall and the end cap. An electrical socket connection 26 is provided in the cylindrical wall for connecting the circuit boards 1 9, 20 tp machine steering control means (not shown).

Figure 1 shows a fluid seal element constituted by a non-ferrous diaphragm plate 27 made of, for example, stainless steel or brass or plastic fixedly mounted between the magnets 1 6 and the magnetic flux sensors 18. The diaphram plate is sealably clamped in position by an annular retaining block 28 secured to an inwardly directed flange 29 provided on the generally cylindrical wall by screws 30 (only one of which is shown).

The diaphragm plate provides an effective seal for the lubricant and/or grease associated with the shaft bearing and provides a substantially interference-free path for magnetic flux emitted bs the magnets 1 6 thereby enabling the sensor 18 to detect movement of the magnets 16.

It will be appreciated that the present invention greatly assists in the construction and design of the mining machine, it being possible to sense rotation of a horizontally or vertically mounted shaft without the problem of lubricant interfering with electronic circuitry. Also, as it is; not necessary to seal the shaft within the gearbox casing alignment, problems are substantially reduced.

In alternate embodiments of the invention, the magnetic sensor means is replaced by other forms of sensor means, as for example, visual sensor means. The fluid seal element preventing leakage of lubricant and being translucent.

Claims (12)

1. Sensor means for sensing rotational movement, comprising a first component mounted for rotation, a second component mounted to detect rotational movement of the first component, and a fluid seal element mounted between the first and second components, the fluid seal element providing a substantially interferencefree path enabling the second component to detect rotational movement of the first component.

2. Sensor means for sensing rotational movement of a shaft mounted in lubricated bearing means, comprising a first component mounted for rotation with the shaft, a second component mounted to detect rotation of the shaft and to derive a signal indicative of rotation of the shaft, and a fluid seal element mounted between the first and second components, the fluid seal element providing an effective seal against flow of lubricant and providing a substantially interference-free path enabling the second component to detect rotational movement of the first component.

3. Sensor means as claimed in claim 2, in which the sensor means comprises magnetic sensing means, the fluid seal element comprising a non-ferrous plate providing a substantially interference-free path from the passage of magnetic flux between the first and second components.

4. Sensor means as claimed in claim 3, in which the first component comprises at least one magnet and the second component comprises at least one detector of magnetic flux.

5. Sensor means as claimed in claim 4, in which a plurality of magnets are angularly equispaced around the axis of rotation of the shaft.

6. Sensor means as claimed in claim 5, in which a plurality of magnetic flux detectors are angularly equi-spaced around the axis of rotation of the shaft.

7. Sensor means as claimed in claim 6, in which the plurality of magnets and the plurality of detectors substantially are radially equi-spaced from the axis of rotation of the shaft.

8, Sensor means as claimed in claim 7, in which the or each magnet is mounted on a disc mounted co-axial with the shaft and rotatable with the shaft.

9. Sensor means as claimed in any one of the preceding claims 3 to 8, in which the or each magnet is covered by protective window means.

10. Sensor means as claimed in any one of the preceding claims 3 to 9, in which the non-ferrous plate is non-rotatable and mounted substantially co-axially with the rotational axis of the shaft.

11. Sensor means as claimed in claim 10, in which the non-ferrous plate is fixedly mounted to a generally cylindrical member defining at least a part of a chamber wall.

12. Sensor means for sensing rotational movement, substantially as described herein and substantially as shown in the accompanying drawings.