GB2140512A - Conveyors and drive means including a clutch - Google Patents

Abstract

A conveyor includes drive means which comprises a motor 15 and transmission means 16 capable of connecting the motor to a rotor of the conveyor. The transmission means includes a clutch 34, 35 which, for effecting drive to the rotor, is operative in a first mode under fluid pressure and in a second mode under centrifugal force the magnitude of which is dependent upon the speed of rotation of the rotor. When, with the clutch operating in its said second mode, the rotational speed of the rotor falls below a predetermined value the clutch is caused automatically to disengage and drive from the motor to the conveyor is discontinued. A brake plate 32 acted on by caliper 37 may also be included to aid reduction of rotational speed to facilitate clutch disengagement and add further braking to the conveyor such that its motion due to momentum is rapidly reduced. <IMAGE>

Description

SPECIFICATION Conveyors and drive means therefor This invention relates to conveyors and to drive means therefor.

Hitherto certain conveyors, for example armoured-face conveyors of scraper-chain type, have been driven by an electric motor through the intermediary of a fluid coupling. In practice when the motor was switched off the conveyor tended to run on to an undesirable extent due to the momentum in the moving parts of the conveyor and its driving means. Thus it has not been possible quickly to bring the conveyor to rest, and this has been somewhat hazardous in the event that personnel, equipment or foreign objects have inadvertently fallen on, or otherwise come into engagement with, moving components of the conveyor, often resulting in serious injury to personnel and damage both to the equipment and conveyor.The danger to personnel is particularly great in such chain conveyors known as stage loaders where the stored energy in the rotary components can only be relatively slowly dissipated due to the fact that since a stage loader is only a relatively short conveyor chain friction is limited and hence the conveyor takes a relatively long time to come to a standstill following switching off of the driving motor.

The invention as claimed is intended to provide a remedy. It solves the problem of how to design a conveyor and drive means therefor in which, in the event that personnel, equipment or foreign objects inadvertently come into engagement with moving components of the conveyor, drive to the conveyor can quickly be disconnected and the conveyor then rapidly brought to a standstill.

According to this invention a conveyor includes drive means which comprises a motor and transmission means capable of connecting said motorto a rotor of the conveyor, said transmission means including a clutch which, for effecting drive to said rotor, is operative in a first mode under fluid pressure and in a second mode under centrifugal force the magnitude of which is dependent upon the speed of rotation of said rotor, whereby when with the clutch operating in its said second mode the rotational speed of the rotor falls below a predetermined value the clutch is caused automatically to disengage and drive from the motor to the conveyor is discontinued.

Preferably, brake means is provided in association with the transmission means on that side of said clutch remote from said motor. Preferably also, said motor is an electric motor.

A gear box, for example of the reduction type, may be provided in the drive between said transmission means and said rotor.

The transmission means may be housed in a casing which itself forms a reservoir for liquid, that liquid forming a coolant for dissipation of heat generated in the transmission means.

Fluid pressure for operation of said clutch in its said first mode may be derived from a pump carried upon orwithin said casing and driven by cam means or the like formed on an input member of said transmission means.

Preferably, the fluid for operation of said clutch is the liquid contained in said casing, said pump then in operation drawing that liquid directly from said reservoir so formed by said casing.

The advantages offered by the invention are mainly that if during operation of the conveyor a person falls on to the conveyor, or equipment or foreign objects inadvertently come into engagement therewith, then upon switching off of the motor and/or braking of said conveyor rotor the consequential fall in rotational speed of the rotor results in the clutch automatically becoming disengaged. Thus drive to the rotor is disconnected and the conveyor comes to a standstill more rapidly than hitherto.

One way of carrying out the invention is described in detail below with reference to the accompanying drawings which illustrate only one specific embodiment, in which: Figure 1 is a plan view of a scraper-chain conveyor for use as a stage loader in association with other conveyor equipment in a mine, and Figure 2 is a plan view, partly in cross-section, of part of drive means forming part of the conveyor shown in Figure 1.

As shown, the conveyor 1 comprises a main structure 2, which includes a pair of side members 3, 4 and a deck 5, a drive rotor 6 which includes two axially-spaced sprocket wheels 7, 8 and a driven rotor 9 which includes two axially-spaced sprocket wheels 10, 11. Endless chains, the upper runs of which are shown at 12 and 13, are in engagement with the respective sprocket wheels of the rotors 6 and 9, and a plurality of flight bars 14 are fitted to the chains, spaced one from the other in the manner shown. These flight bars of the upper run are, on operation of the conveyor, caused to slide along deck 5 for impelling mineral material from one end of the conveyor to the other.

The rotor 6 is powered by drive means which comprises an electric motor 15, transmission means 16 and a reduction gear box 17 of right-angled drive type, the output shaft 18 of the gear box being suitably coupled to the rotor. As shown in Figure 2 the transmission means 16 includes a casing 19 having two end walls 20, 21. The output shaft 22 of motor 15 extends into the casing through a sealed aperture at 23 in wall 20. A disc-like member 24 is keyed at 25 to shaft 22 and is provided with a cam formation 26 around its periphery. A cup-shaped member 27 is secured to the member 24 by a plurality of bolts one of which is shown at 28.

The input shaft 29 of the gear box 17 extends into the casing 19 through a sealed aperture 30 in wall 21.

This shaft carries an assembly 31 of components which includes a brake disk 32, liquid-pressureoperable actuator means diagrammatically shown at 33 and six elements or shoes, one of which is shown at 34. These elements are peripherally equi-spaced about the rotational axis of shaft 29 and are operable by the actuator means 33. They are cooperable with the cylindrical interior surface 35 of the member 27 to form a clutch. The elements 34 include linings 36 of suitable friction material for driving engagement with surface 35.

A liquid-pressure-operable caliper type brake unit 37 is provided in association with the disc 32, being mounted within the casing 19 by a bracket 38. Means (not shown) for conducting liquid under pressure to unit 37 suitably passes from the exterior of the transmission means 16 through wall 21 to that unit.

A positive displacement pump diagrammatically shown at 39 is mounted on the casing 19, being driven in suitable manner, through the intermediary of means indicated diagrammatically at 40, by the cam formation 26. The interior 41 of the casing 19 is substantially filled with hydraulic liquid and thus forms a reservoir from which the pump in operation draws its liquid. Liquid under pressure delivered by the pump passes through passages and transfer porting (both not shown) from stationary structure to rotative structure thus to reach actuator means 33 of assembly 31. Actuator means 33 is operable upon push rods 42, one secured to each of the six elements 34, so that when the actuator means is pressurised these rods are operated by output members, as at 43, of the actuator means to urge elements 34 into positive engagement with surface 35.A coil spring 44 is provided in association with each rod 42 in the manner shown in Figure 2.

When it is required to start the conveyor 1 the brake unit 37 is released and the electric motor 15 is switched on so that member 24 commences to rotate and the pump 39 charges actuator means 33 with liquid under pressure. Thus the elements 34 are brought into engagement with surface 35 and the assembly 31 commences to rotate together with its brake disc 32. In consequence drive is transmitted through the gear box 17 to the rotor 6 of the conveyor and the conveyor commences to operate so that flight bars 14 accordingly move with a scraping action along deck 5.

The elements 34 of the clutch are so mounted that when the rotor 6 reaches a predetermined speed the centrifugal force alone on elements 34 is sufficient to hold these elements in positive driven engagement with surface 35 and there is no longer any need to maintain the actuator means 33 charged with liquid under pressure. By means (not shown) the supply to means 33 can therefore be cut off and thus the drive from motor 15 to the conveyor is now maintained solely by the effects of centrifugal force on the elements 34.

If during operation a person falls on to any of the moving components of the conveyor, or, some equipment, or foreign object, inadvertently comes into engagement with any of those components it will be necessary for the electric motor 15 to be switched off as quickly as possible. Switching off of the motor is arranged to cause simultaneous operation of brake unit 37. Thus the speed of the conveyor will commence to fall as will the rotational speed of the rotor 6 and assembly 31. Consequently the centrifugal force on elements 34 carried by rotating assembly 31 will decrease so that friction linings 36 of those elements lose contact with surface 35 of member 27 thereby effecting clutch release. As a result powerfrom motor 15 will no longer be transmitted to assembly 31, shaft 29, gear box 17 and rotor 6, so that the conveyor will commence to run down.Since the conveyor is now disconnected from motor 15, the momentum in the rotor of the motor will not be applied to the conveyor. Continued application of brake unit 37 brings the conveyor to a standstill relatively quickly. Thus less injury to the person, or less damage to the conveyor, equipment or foreign object, is likely to be sustained than with other transmission arrangements hitherto where the drive to the conveyor has been maintained following switching off of the motor with the result that run down to a standstill has taken a relatively long time due to the momentum in the still-connected rotating components. As well as being so applied for emergency operation our above method is used for normal stopping of the conveyor.

In alternative embodiments of this invention the motor 15 and brake unit 37 may be controlled separately. Here for normal stopping of the conveyor, or if an emergency situation arises, the application of unit 37 only can result in such fall in speed of the conveyor that the elements 34 of the clutch are responsive to decrease in centrifugal force to effect clutch release and thus disconnection of drive from the motor to the conveyor. In this case the motor can be switched off separately thereafter as convenient, but meanwhile continued application of the brake unit again brings the conveyor to a standstill relatively quickly.

Although in the embodiment above described with reference to the drawings the liquid-pressureoperable actuator means 33 is disposed in the assembly 31 so as to be rotative therewith, in alternative embodiments of the invention the actuator means is instead carried by non-rotative structure. In this case there is no need to provide transfer porting in the supply line from the pump to the actuator means, but instead mechanical means are suitably provided between the output of the actuator means and the push rods 42 of the elements 34. Such mechanical means would includetransla- tion bearing means between non-rotative components and rotative components.

The invention is of importance on conveyors which are provided with in-built mineral breakers which add to the potential danger particularly to personnel.

Also, the invention has advantages over transmission arrangements hitherto employing fluid couplings in that the motor can be run-up to full speed before the clutch is engaged and thus before the motor is subjected to any load. In consequence a smooth start-up of the conveyor can be achieved upon clutch engagement as a result of the gradual engagement of the friction linings of the clutch. Also motors having more advantageous characteristics can be selected for driving the conveyor over those selected for use with transmission arrangements incorporating fluid couplings.

Further, although in the embodiment above described with reference to the drawings a positive displacement pump for supplying the actuator means is mounted on the casing and this draws liquid from the reservoir formed by the casing, in alternative embodiments of the invention the actuator means is instead supplied with pressurised fluid for its operation from a fluid-pressure-operable system associated with a mine roof support or supports adjacent the conveyor. In this case no pump is required to be mounted on the casing of the drive means for the conveyor and neither is cam means required to be provided within the casing.

Finally, suitable sensing means may be mounted on the conveyor for providing instant detection should personnel, equipment or foreign objects inadvertently fall on to the conveyor, these sensing means being arranged in circuit with the motor and/or the brake unit to cause instant switching off of the motor and/or application of the brake unit should such an emergency situation be detected.

Claims (9)

1. A conveyor including drive means which comprises a motor and transmission means capable of connecting said motor to a rotor of the conveyor, said transmission means including a clutch which, for effecting drive to said rotor, is operative in a first mode under fluid pressure and in a second mode under centrifugal force the magnitude of which is dependent upon the speed of rotation of said rotor, whereby when with the clutch operating in its said second mode the rotational speed of the rotor falls below a predetermined value the clutch is caused automatically to disengage and drive from the motor to the conveyor is discontinued.

2. A conveyor as claimed in claim 1, wherein brake means is provided in association with said transmission means on that side of said clutch remote from said motor.

3. A conveyor as claimed in either claim 1 or claim 2, wherein said motor is an electric motor.

4. A conveyor as claimed in any one of the preceding claims, wherein a gear box is provided in the drive between said transmission means and said rotor.

5. A conveyor as claimed in any one of the preceding claims, wherein said transmission means is housed in a casing which itself forms a reservoir for liquid, that liquid forming a coolant for dissipation of heat generated in the transmission means.

6. A conveyor as claimed in claim 5, wherein fluid pressure for operation of said clutch in its said first mode is derived from a pump carried upon or within said casing.

7. A conveyor as claimed in claim 6, wherein said pump is driven by cam means or the like formed on an input member of said transmission means.

8. A conveyor as claimed in either claim 6 or claim 7, wherein the fluid for operation of said clutch is the liquid contained in said casing, said pump then in operation drawing that liquid directly from said reservoir so formed by said casing.

9. A conveyor substantially as hereinbefore described with reference to the accompanying drawings.