GB2077212A

GB2077212A - Conveyors for Mine Workings

Info

Publication number: GB2077212A
Application number: GB8115995A
Authority: GB
Original assignee: RICH ROY SERVICES Inc
Current assignee: RICH ROY SERVICES Inc
Priority date: 1980-06-07
Filing date: 1981-05-26
Publication date: 1981-12-16
Also published as: GB2077212B

Abstract

In a conveyor for a mine working, having a chain, or chains, 20, 22, passing round a driven sprocket 6, sensing means is provided responsive to the force between the sprocket and the chain(s). Preferably a load cell is provided between the sprocket bearings, 16, 18 and the sprocket bearing housing 16a, 18a. The load cell is located on a radial line of the sprocket which extends parallel to the length of the conveyor, and produces an output which is proportional to the loading on the conveyor chain. When the output signal exceeds a desired level, signalling means may be operated to actuate an alarm, or to reduce the load on the conveyor chain. Alternatively, a strain gauge may be provided on the drive shaft by the sprocket. <IMAGE>

Description

SPECIFICATION Improvements Relating to Conveyors for Mine Workings A conveyor for a mine working conventionally comprises two, spaced apart sprockets, and at least one endless chain extending between and around sprockets. Scraper bars are provided, secured to the chain at spaced intervals, and in the operation of the conveyor, the sprockets rotate and the scraper bars carry mineral material away from one of the sprockets towards the other.

During operation of the conveyor, the chain is subject to a considerable loading which elastically stretches the chain. Additionally, there is some non-elastic stretching of the chain, due to wear.

Where the run of the conveyor is large, stretching of the chain causes problems, due to the creation of slack chain. Particularly when it is necessary to restart the conveyor after a temporary halt, this slack can be dangerous, in that the chain is subjected to shock loading when the slack is taken in.

To reduce this problem it is conventional practice to pre-tension the chain prior to operation of the conveyor. This is commonly effected by applying a load to the chain to draw two parts of the chain together, and removing one or more links of the chain.

On a long run of conveyor, to reduce significantly the problems of creation of slack chain, it would be desirable to subject the chain (over one or both runs) to a pre-load which is a significant proportion of the safe working load of the chain. For example, where the safe working load of the chain is 50 tons, it may be desirable to subject the chain to a pre-loading of 20 tons.

However, this would result in the chain being subjected to loadings relatively close to its safe working load, particularly during initial operation of the conveyor, such as start-up, during periods shortly after a pre-tensioning operation.

According to this invention there is provided a conveyor for a mine working, comprising a sprocket around which the chain extends, mounting means in which the sprocket is mounted for rotation, and drive means which in the operation of the conveyor causes the sprocket to rotate, wherein the conveyor comprises sensing means comprising at least one load cell responsive to the force exerted between the sprocket and the chain, and means operative in the event that said force exceeds a desired level.

Most conveniently the load cell is operative between the sprocket and the mounting means.

Thus, the mounting means may conveniently comprise a housing for bearings for a shaft of the sprocket, and the load cell may conveniently be located between the housing and the bearing. By locating the load cell on a radial line of the sprocket, which extends parallel to the length of the conveyor, the load applied to the load cell may be directly proportional to the loading on the conveyor chain.

However, alternative locations for the load cell will readily be appreciated: thus the load cell may be afforded by a strain gauge located on the drive shaft extending between the drive motor and the sprocket, or on the sprocket itself, located at such a position and constructed and arranged to provide an output signal proportional to the loading on the conveyor chain.

Thus by the use of this invention, in the event that the loading on the chain, as determined by the load cell, exceeds what is considered to be the practical safe working load, means may operate to actuate an alarm or may operate to shut down the conveyor. Alternatively, said means may operate to take other action to reduce the load on the conveyor chain, such as reducing the power applied to the sprocket by the drive motor.

Where the chain extends between and around two sprockets, and only the sprocket at one end of the conveyor is driven, the other being an idle sprocket, preferably the load cell is associated with the driven sprocket. However, particularly where both sprockets are driven, desirably load cells are utilised in association with both sprockets.

The invention may be utilised whether one or both runs of the conveyor are subject to a pretensioning operation: indeed, the invention may be used where no significant pre-tensioning operation is carried out, and may be utilised simply as a means of measurement of the loading on the conveyor chain.

Particularly where the conveyor comprises two chains running in parallel, with scraper blades extending between the chains, desirably the sensing means comprises two load cells responsive to the force exerted between the sprocket and the mounting means at positions which are spaced widthwise of the sprocket. In this manner, one load cell may be responsive to a greater extent to the load exerted on one chain, and one load cell may be responsive to a greater extent to the load exerted on the other chain.

Thus, where the housing comprises two bearings for the shaft of the sprocket, one load cell may be located between the housing and each bearing.

This invention also provides a method sensing the loading on the chain of a mining conveyor, in which a load cell is located between the sprocket, or part thereof or parts secured thereto, and mounting means for the sprocket or such part.

There will now be given a detailed description, to be read with reference to the accompanying drawings of a mining conveyor which is a preferred embodiment of this invention, and which has been selected for the purposes of illustrating this invention by way of example.

In the accompanying drawings: Figure 1 is a plan view of part of the conveyor; Figure 2 is a schematic side view of the conveyor, in a condition of rest; Figure 3 is a view similar to Figure 2, subsequent to the application of a preloading to the conveyor chain; and Figure 4 is a view similar to Figure 3, subsequent to initiation of use of the conveyor.

The conveyor which is the preferred embodiment of this invention is for an underground mine working and is specifically of the type commonly referred to as an armoured face conveyor. Thus, the conveyor extends along the face of a long wall W being worked, from which face mineral material is cut and deposited on a stationary floor F of the conveyor.

At one end, the conveyor comprises a sprocket 6, comprising a shaft 8 which in the operation of the conveyor is driven by a motor 10 through gearing 12. The conveyor comprises a housing 14, comprising arms 1 4a, 1 4b which extend on opposite sides of the sprocket 6, providing a mounting for bearings 16, 18 in which the shaft 8 is rotatably mounted.

Extending between the two sprockets are two chains 20, 22, and extending between the two chains, at spaced intervals along the length thereof, are scraper bars (not shown). When the sprocket 6 is driven, the chains 20, 22 move the scraper bars along the floor F of the conveyor conveying mineral material in the general direction indicated by the arrow A in figure 1.

Figure 2 shows schematically the conveyor in a condition of rest, both the upper and lower runs U, L being slack. This is the condition adopted by the conveyor after a period of use and after some stretching of the chain has taken place, albeit with some exaggeration.

With the sprocket 6 held captive against rotation, spaced portions of the upper runs of the chains 20, 22 are drawn together under load, and links of the chains are removed. Thus, a tension T, is applied to the upper run U of each of the chains 20, 22, and a tension t2 to the lower runs. A force L1,which is proportional to the sum of the pre loading applied to the two chains is thus exerted on sprocket 6. In the conveyor which is the preferred embodiment of this invention, this pre loading appears as a compressive force between the bearings 1 6, 18 and faces 1 6a, 1 8a of the housing 14. Specifically, the force L, is transmitted to the housing along two lines which extend radially of the shaft 8, in a direction parallel to the length of the conveyor.

Since the two bearings 16 and 18 are each outboard of one of the chains 20, 22 respectively, the load applied between the bearing 1 6 and the face 1 6a will be generally functional of the tension in the chain 20, and the load applied between the bearing 18 and the face 1 8a will be functional of the tension in the chain 22.

The conveyor comprises sensing means, comprising a first load cell positioned between the bearing 1 6 and the face 1 6a and a second load cell positioned between the bearing 1 8 and the face 1 8a. The positions of these load cells circumferentially of the bearings is such that a line drawn radially of the shaft and passing through the load cells extend towards the axis of the sprocket 7.

The combined force sensed by the two load cells is proportional to the sum of the tension in the upper and lower runs of the two chains 20 and 22.

Whereas the pre-loading applied to the upper runs of the chains 20 and 22 is a force T1, in the use of the conveyor, on rotation of the sprocket 6 in the direction shown in Figure 4, the tension in the upper runs of the two chains will increase, for example to a level T3, and the tension in the lower runs will decrease. In the event that the loading on either of the chains 20 and 22 increases above what is considered to be a practical safe working load, the output from the first or second load cells may be utilised to activate an alarm, and/or to cut off power to the motor 10 and/or to take any other action to reduce the tension in the chains, such as to reduce the power applied to the drive shaft 8.Where only the sprocket 6 is driven, and the tension in the lower run decreases as the tension in the upper run increases, it will in general not be possible to arrange for the signalling means to become operative, until the load L2 between the bearing and the housing exceeds the loading L1, that is until the tension T3 in the upper run exceeds the combined tensions T, and T2 applied to the chain as a preloading.

However, since it is highly unlikely that it would be desired to exert a preloading on the chain which is greater than 50% of its safe working load, this presents no practical problem.

Conversely, where both sprockets are driven, and tension is maintained on both the upper and lower runs, the load determined by the load cell will be functional of the tension maintained in both the upper and lower runs, and it will therefore be necessary to arrange that the load cell does not activate the signalling means until a higher load is measured, than is the case when only one of the sprockets is driven.

However, the difficulties set out in the last two preceding paragraphs, and other difficulties, may be solved by an appropriate calibration of the load cell, and in particular a determination of the level at which the output from the load cell activates the signalling means.

In this manner the pre-tension applied to the chains 20 and 22 may be a higher proportion of the safe working load of the chains, allowing the conveyor to be utilised on long runs whilst reducing the problems associated with the creation of slack chain. By the provision of the sensing means, and the sensing means associated therewith, the dangers associated with pre-tensioning the chains to a level which is a significant proportion of the safe working load may be reduced relatively conveniently.

It will be appreciated that, whilst in the preferred embodiment, the load cells are placed between the bearings 16 and 18, and the faces of the housing upon which the loading of the ~ sprocket is, in the use of the conveyor, taken, the load cells may be applied to any other part of the conveyor at which this loading appears. Thus, the load cells may be in the form of strain gauges secured to a part of the housing which, in the use of the conveyor, is under a compressive stress proportional to the tension in the chains of the conveyor.

Claims

1. A conveyor for a mine working, comprising a sprocket around which a chain extends, mounting means in which the sprocket is mounted for rotation, and drive means which in the operation of the conveyor causes the sprocket to rotate, wherein the conveyor comprises sensing means comprising at least one load cell responsive to the force exerted between the sprocket and the chain, and means operative in the event that said force exceeds a desired level.

2. A conveyor according to Claim 1 wherein the load cell is operative between the sprocket and the mounting means.

3. A conveyor according to Claim 2 wherein the mounting means comprises a housing for bearings for a shaft of the sprocket, and the load cell is located between the housing and the bearing.

4. A conveyor according to Claim 3 wherein the load cell is located on a radial line of the sprocket which extends parallel to the length of the conveyor.

5. A conveyor according to any one of the preceding claims wherein the chain extends between and around two sprockets, the conveyor comprising mounting means for each sprocket at opposite ends of the mine working.

6. A conveyor according to Claim 5 wherein only the sprocket at one end of the conveyor is driven, the other being an idle sprocket, the load cell being associated with the driven sprocket.

7. A conveyor according to Claim 5 wherein both sprockets are driven, the sensing means comprising load cells in association with each of said sprockets.

8. A conveyor according to any one of the preceding claims comprising two chains in parallel, the sensing means comprising two load cells responsive to the force exerted between the sprocket and the chain at positions which are spaced widthwise of the sprocket

9. A conveyor according to Claim 8 wherein the housing comprises two bearings for the shaft of the sprocket, one cell being located between the housing and each bearing.

10. A conveyor according to any one of the preceding claims wherein said means is operative to actuate an alarm.

11. A conveyor according to any one of the preceding claims wherein said means is operative to shut down the conveyor.

12. A conveyor according to any one of Claims 1 to 10 wherein said means is operative to reduce the load on the conveyor chain.

13. A method of sensing the loading on the chain of a mining conveyor, in which a load cell is located between the sprocket, or part thereof or parts secured thereto, and mounting means for the sprocket or such part.

14. A conveyor for a mine working constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

1 5. A method of sensing the loading on the chain of a mining conveyor, when carried out substantially as hereinbefore described with reference to the accompanying drawings.

1 6. Any novel feature or novel combination of features herein before described and/or shown in the accompanying drawings.