GB2161574A - Equipment for use in winning and/or conveying coal - Google Patents

Abstract

Equipment for use in the winning and/or conveying of coal in underground mine workings has means for tensioning and fixing an endless-loop traction chain. An overload clutch (4, 5) between a motor (2) and gearbox (3) is adapted as a slipping clutch having an electronic controller with a rotary speed monitor (8) and comparator (9) which measure the rotary speed of the slipping clutch input and output (4, 5). The electronic controller is connected to an electrohydraulic switch having a valve system for the normal operation of the overload clutch, and to a load measuring instrument (7) as a data pickup. An operating mode selector (11) provides modes "tensioning the chain" and "normal operations". An adjustable reduced pressure compared with the normal operating pressure can be introduced through the operating mode selector (11) to provide slipping of the clutch (4, 5) for the purpose of tensioning the traction chain. The driving motor (2) can be switched off through the rotary speed comparator (9) when the clutch is slipping at the reduced pressure setting, while an hydraulically-actuated holding brake (10) can be applied simultaneously by the electronic controller. <IMAGE>

Description

SPECIFICATION Equipment for use in winning and/or conveying coal This invention reiates to equipment for use in the winning and/or conveying of coal in underground mine workings and having: a driving unit, a working unit drawn by an endlessloop traction chain, and means for tensioning and fixing the traction chain, in which the driving unit has a motor and a single- or multi-stage gearbox, and an overload clutch having two half-clutches is disposed in the torque transmission system, while furthermore there are provided an actuator for the overload clutch and an instrument to measure the working load on the working unit, the means for tensioning and fixing the traction chain incorporating a holding brake.

In known equipment of this type, use is made of an overload clutch constructed as a torque limiter. The torque limiter (DE-PS 25 36 310) consists of at least one radial cylinder and piston as part of the first half-clutch, inlet and outlet ducts for a hydraulic fluid, connected to the cylinder, a cam land associated with the second half-clutch, control members for the inlet and outlet ducts, and a system functioning as the actuator, which is disposed in the outlet duct and reacts to excess pressure on the piston. At a predetermined pressure on the piston, it parts the two half-clutches, and when the pressure threshold is once more crossed it brings them together again.The first half-clutch can be fitted with alink member in the form of a roller at the fulcrum of a two-armed lever, which enters grooves running parallel to the cylinder under the action of tangential force components, while the roller on the lever rests against the free end of the piston, so that when the predetermined torque is exceeded it is actuated by the cam land in such a manner that the pressure exerted on the piston is substantially radial. This has proved sound, but is a relatively complicated arrangement; in particular, it calls for costly technical control gear if it is to be completely functionally reliable. Moreover, the overload clutch in the known equipment functions solely as the torque limiter and cannot be directly adapted as a data pickup for the measuring instrument.

The measuring instrument in the known system is an idependent unit which is integrated with the working unit at some convenient point. This involves additional expense.

Of course the known equipment also incorporates means for tensioning and fixing the traction chain, but in this respect it is simply an additional unit. On the other hand, it is often necessary to tension and fix the traction chain in equipment of the type in question, in the course of carrying out work on the traction chain. The traction chain in fact elongates as a result of wear and/or permanent strain. In conjunction with the tensioning and fixing of the traction chain, manual iabour must be used to trim its length in the slack run. In order to carry out this work, the driving motor is equipped with an additional holding brake.

This forms the key element of the means for tensioning and fixing the traction chain. For the purpose of tensioning and fixing the traction chain, the driving motor is switched on in steps, in the so-called inching mode, and the brake is applied with a corresponding rhythm.

It is impossible to tension the traction chain positively by this technique. Moreover, it is likewise impossible to adjust the traction chain to a specified length, and its performance is consequently impaired.

The object of the invention is to provide equipment of the type initially described which uses a substantially simpler overload clutch, and in which the overload clutch simultaneously acts as data pickup for the measuring instrument and moreover the overload clutch can also be adapted so as to integrate the means for tensioning and fixing the traction chain into the equipment in such a manner that in the course of the operations referred to the traction chain can be preset to a specified tension at a specified length.

According to the present invention, the overload clutch is adapted as a slipping clutch and the holding brake, which has a hydroelectric actuator, is disposed in the torque transmission system,the slipping clutch has an electronic controller with a rotary speed monitor and a rotary speed comparator, which measure the rotary speed of the slipping clutch and the rotary speed difference between the two half-clutches, the electronic controller being connected on one side to a hydroelectric switch having a valve system for the normal operation of the overload clutch and on the other side to the measuring instrument as a data pickup, the electrohydraulic switch also has a pressure-reducing valve system for an adjustable reduced pressure compared with the normal operating pressure, which reduced pressure can be introduced through the operating mode selector in the electronic controller, to provide clutch slip for the purpose of tensioning the traction chain, the driving motor can be switched off through the rotary speed comparator in the electronic controller when the clutch is slipping at the reduced pressure setting, and the holding brake can be applied simultaneously by the electronic controller acting through its hydraulic actuator.

The holding brake is preferably disposed between the slipping clutch and the gearbox.

In this case, the holding brake can be constructed as a disc brake. It can be integrated with the half of the slipping clutch nearer the gearbox.

In the case of one special version of the equipment, viz., one having a multi-stage gearbox with a fore-stage and a main stage, in which the slipping clutch is disposed between the fore-stage and the main stage, the holding brake can be placed between the electric motor and the fore-stage. In this particular case, but not excluding other possible embodiments of the invention, it is preferred to adopt an arrangement whereby, on or after applying the holding brake, the electronic controller can also switch the valve system for normal operation to the hydraulic actuator of the slipping clutch, so that the slipping cutch can be held at the unreduced normal operating pressure. This avoids any unwanted slipping in the clutch.

An embodiment of the invention and of the advantages accruing therefrom will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of equipment for use in the winning and conveying of coal in an underground mine working; and Figure 2 is an axial section, on a much larger scale than Figure 1, through a slipping clutch as in Figure 1 but integrated with a holding brake.

The equipment comprises: a driving unit 1, a working unit 2, 3 drawn by at least one endless-loop traction chain (not shown) and means to be described more precisely below, for tensioning and fixing the traction chain.

The working unit has a motor 2 and a singleor multi-stage gearbox 3. An overload clutch having two half-clutches 4, 5 is disposed in the torque transmission system. There are also provided an actuator 6 for the overload clutch and an instrument 7 to measure the working load on the working unit.

The overload clutch is adapted as a slipping clutch. It has an electronic controller with a rotary speed monitor 8 and a rotary speed comparator 9. The rotary speed monitor 8 can measure the rotary speed of the slipping clutch and any rotary speed difference between the two half-clutches 4, 5. The electronic controller is connected on the one hand to an electro-hydraulic switch having a valve system for normal operations and on the other hand to the measuring instrument as a data pickup.

Between the slipping clutch 4, 5 and the gearbox 3 in the torque transmission system there is a holding brake 10, which has a hudraulic actuator. The electrohydraulic switch has an operating mode selector 11 for the modes "tensioning the traction chain" and "normal operations". It further has a pressure-reducing valve system for an adjustable reduced pressure compared with the normal operating pressure. The reduced pressure can be introduced through the operating mode selector 11 in the electronic controller, to provide slipping in the clutch 4, 5 for the purpose of tensioning the traction chain. The driving motor 2 can be switched off through the rotary speed compartor 9 in the electronic controller when the clutch 4, 5 is slipping at the reduced pressure setting.The hydraulic holding brake 10 can be applied simultaneously by the electronic controller acting through its hydraulic actuator. On or after brake application, moreover, the electronic controller can also switch the valve system for normal operation to the hydraulic actuator of the slipping clutch 4, 5, so that it can be held at the unreduced hydraulic fluid pressure.

The holding brake 10 is shown as a disc brake. In the block diagram in Figure 1, it appears as a separate unit in the torque transmission system, disposed between the slipping clutch 4, 5 and the gearbox 3. In the detailed section shown in Figure 2, this disc brake 10 is shown integrated with the corresponding half 5 of the slipping clutch. Figure 2 further shows that the slipping clutch 4, 5 is constructed as a multiple disc clutch, having a cup-like half-clutch 5 and a second halfclutch 4 inserted therein, and that the second half-clutch 4 is provided with an actuating cylinder-and-piston unit 1 2.

The rotary speed comparator 9 is constructed as an electronic rotary speed comparator having two inductive proximity switches 13, 14, which are associated with the two half-clutches 4, 5 and pulse emitters 15, 1 6 disposed thereon, for example in a ring gear arrangement. At a predetermined rotary speed difference or angular setting difference between the two half-clutches 4, 5, the rotary speed monitor 8 actuates the switch 6 so as to release the overload clutch 4, 5. The rotary speed monitor 8 further controls the measuring instrument 7 when the two half-clutches 4, 5 are both rotating at the same speed. If the equipment alternatively has multi-stage gear box with a main stage and a fore-stage, the slipping clutch is disposed between the main stage and the fore-stage of the gearbox, i.e., when the rotary speed is high and the torque low.

The electrohydraulic switch consists of an arrangement having at least two valve systems for pressure reduction and associated switching valves. Pressure servo-valves can be used as an alternative. The valve systems are supplied with hydraulic fluid from a pressure source. Control is exercised by signals from the electronic controller. On the output side, the electrohydraulic switch 6 is connected by pressure ducts 18, 1 9 to the holding brake 10 on the one hand and the slipping clutch 4, 5 on the other hand.

If the operating mode selector 11 is set for the function "Chain tensioning", the pressure duct 1 9 is supplied at a reduced pressure compared with the normal operating pressure.

This produces a slipping torque on the slipping clutch 4, 5, equivalent to the desired chain pre-tension, which can therefore be adjusted precisely. Consequently, when the diving motor 2 is siwtched on after completing the chain tensioning operation, the slipping clutch 4, 5 starts to slip. This slip is immediately detected by the rotary speed comparator 9 in the electronic controller. The electronic controller responds with the following commands: "switch off the driving motor 2", "apply the holding brake 10", and "increase the pressure in the pressure duct 1 9 to the normal level". The chain, already precisely pre-tensioned at the equivalent to the slipping torque, is now safely arrested and can be lengthened or shortened without risk.

Maximum safety is attained when the holding brake 10 is closed by springs and opened by pressure and is disposed "beyond" the slipping clutch 4, 5 in the torque transmission system. In this case, the chain in need of tensioning cannot be inadvertently slackened, even if the pressure fails because of a fault.

Claims (7)

1. Equipment for use in the winning and/or conveying of coal in underground mine workings and having: a driving unit, a working unit drawn by an endless-loop traction chain, and means for tensioning and fixing the traction chain, in which the driving unit has a motor and a single- or multi-stage gearbox, and an overload clutch having two half-clutches is disposed in the torque transmission system, while furthermore there are provided an actuator for the overload clutch and an instrument to measure the working load on the working unit, the means for tensioning and fixing the traction chain incorporating a holding brake, the over-load clutch is adapted as a slipping clutch and the holding brake, which has a hydroelectric actuator, is disposed in the torque transmission system, the slipping clutch has an electronic controller with a rotary speed monitor and a rotary speed comparator, which measure the rotary speed of the slipping clutch and the rotary speed difference between the two half-clutches, the electronic controller being connected on the one hand to a hydroelectric switch having a valve system for the normal operation of the overload clutch and on the other hand to the measuring instrument as a data pickup, the electrohydraulic switch also having a pressure-reducing valve system for an adjustable reduced pressure compared with the normal operating pressure, which reduced pressure can be introduced through the operating mode selector in the electronic controller,to provide slip in the clutch for the purpose of tensioning the traction chain, the driving motor can be switched off through the rotary speed comparator in the electronic controller when the clutch is slipping at the reduced pressure setting, and the holding brake can be applied simultaneously by the electronic controller acting through its hydraulic actuator.

2. Equipment as in Claim 1, wherein the holding brake is disposed between the slipping clutch and the gearbox.

3. Equipment as in either of Claims 1 and 2, wherein the holding brake is constructed as a disc brake.

4. Equipment as in any one of Claims 1 to 3, wherein the holding brake is integrated with the half of the slipping clutch nearer the gearbox.

5. Equipment as in either of Claims 1 and 3 having a multi-stage gearbox with a fore-stage and a main stage, in which the slipping clutch is disposed between the forestage and the main stage, the holding brake being placed between the electric motor and the fore-stage of the gearbox.

6. Equipment as in any one of Claims 1 to 5, wherein on or after applying the holding brake the electronic controller can also switch the valve system for normal operation to the hydraulic actuator of the slipping clutch, so that the slipping clutch can be held at the unreduced normal operating pressure.

7. Equipment for use in the winning and/or conveying of coal in underground mine workings, substantially as hereinbefore described with reference to the accompanying drawings.