GB2094859A - Improvements relating to rack drive mechanisms of underground mining machines - Google Patents

Abstract

A mining machine 1 is equipped with two drive wheels 4 which produce the machine advance and which engage in racks 3 situated on opposite sides of a face conveyor 2 extending over the length of the machine track. The drive wheels 4 are situated one opposite the other and are driven only by a single drive motor 11, through a reduction gear 12 in each case, and they are connected to the drive motor 11 via a differential bevel gear 15 which provides uniform load distribution to the two drive wheels 4. <IMAGE>

Description

SPECIFICATION Improvements relating to rack drive mechansims of underground mining machines This invention relates to an underground mining machine having two drive wheels by means of which the machine is advanced by engagement of the drive wheels in racks situated on opposite sides of the face conveyor and extending over the length of the machine track.

In one known form of mining machine traversable over a face conveyor having a rack on each side, engagement in each of the two racks is achieved by a pair of drive gearwheels in each case. Each of the drive gearwheels has its own pressure cylinder which engages, by its toothed piston rod, in a gearwheel adapted to be coupled to the drive gearwheel, and drives the drive wheels by successively actuating the pressure cylinders. During this advance movement, the drive gearwheels are subjected to load only during the period of actuation of their pressure cylinders and only then do they produce an advance force acting in the direction of movement of the machine. During the piston return stroke, all the drive wheels cease to operate as drive means so that irregularities must be expected in the advance force and accordingly fluctuations in the rate of advance.

A uniform rate of advance and a constant advancing force can be obtained only in mining machines driven by rotary drive motors. To ensure that each of the two drive wheels participates in taking the load and transmitting equal advancing forces to the two racks, the two drive wheels must each be provided with their own drive motor. Of course such a step increases the expenditure required for the construction of a mining machine and the control operations required to regulate the machine feed also increase, at least when these drive motors are electric motors.

It is an object of this invention to drive two drive wheels situated on opposite sides of a mining machine by means of a single drive motor, so that the drive wheels always take equal proportions of the load.

Accordingly, this invention provides an underground mining machine having two drive wheels for engagement in racks situated on opposite sides of the face conveyor and which will extend over the length of the machine track, and having a drive motor for producing machine advance connected via a differential gear to two reduction gears each associated with a respective one of the two drive wheels.

By means of the differential gear an exact load distribution over the drive wheels situated on opposite sides of the machine, where they each engage in a rack, is obtained fully automatically and any pitch inaccuracies due to tooth manufacture, and pitch differences at the junctions of the individual rack segments, can be automatically compensated for by the drive wheels. Moreover, the differential gear compensates for any differences in the travel of the outer drive wheel as compared with the inner drive wheel on curves, and particularly also when a machine is dragged along at the face ends, where the cutter drum, used as the mining tool, is driven into the new face, and here again uniform loading is obtained for both drive wheels.

According to a preferred feature of the invention, the differential gear may be a differential bevel gear, in which the two output shafts disposed co-axially of one another are connected to the sun wheel of each of the two planetary gears used as reduction gears. A differential gear of this kind is suitable particularly if the motor driving the two drive wheels is disposed inside the machine body in the longitudinal direction of the machine for the purpose intended. The drive motor may in these conditions be a separate motor used only to produce the advance movement. Alternatively, the motor producing the movement of the mining tool can-be used to produce the advancing movement and be connected by a transmission to the differential gear.

Advantageously, there is provided a transmission stage following the differential gear for an arrangement of two planetary gears in which they are offset from the axis. This step is particularly advantageous if the differential gear and the two reduction gears are disposed in a common housing with the reduction gear for the mining tool carried by a support arm since in that case it is possible for the drive wheel meshing with the teeth of the rack on the face side to be disposed more towards the machine centre, i.e. at a greater distance from the outer end face of the machine body and the support arm pivot axis, because the debris is removed in this area, particularly in the case of drum cutter loaders.

The invention may be performed in various ways and a preferred embodiment thereof will now be described with reference to the accompanying diagrammatic plan view drawing.

A drum cutter loader 1 is situated above a face conveyor 2 which on both the face side and the goaf side is equipped with a rack 3, the racks being formed from individual segments. The racks enable advance movement of the machine 1 by engagement therein of two drive wheels 4 of a feed winch 5. Support arms 6 (one only shown at one end) are mounted for pivoting about horizontal axes of the machine body extending transversely of the direction of the machine traverse. Each arm 6 supports a cutter drum 7 and a clearing plate 8 disposed for pivoting about the drum axis. Also the arms 6 are actuated by servocylinders (not shown), disposed in the region of the face side of the machine 1 and each mounted for pivoting about an axis (not shown) inside the machine frame. The machine 1 consists of individual units 5, 9, 10 which are rigidly interconnected and bolted to the machine frame.

One of these units 5, 9, 10 is the feed winch 5 which encloses the drive motor 11 for the two drive wheels 4 and associated reduction gears 1 2 and a differential gear 13.

In the machine 1 shown in the exemplified embodiment, the drive motor 11 driving the two wheels 4 is disposed with its axis of rotation lying parallel to the machine longitudinal axis. The drive motor 11 engages by its output pinion 14, which is constructed as a bevel gear, in a bevel gear 15 fixed to a housing 1 6 of the differential gear 13, so that during the rotation of the motor two bevel gears 1 7 situated inside the housing 1 6 rotate with bevel gear 15 and the housing 1 6 of the differential gear 13. The bevel gears 17 are each mounted for rotation about an axis parallel to the longitudinal direction of the cutter drum.Bevel gears 1 8 meshing with the two bevel gears 17 also take part in this rotation and are mounted for rotation about axes extending transversely of the longitudinal direction of the machine. The rotary movement is transmitted via pairs of spur gears 19 and the shafts of the two reduction gears 12 and, by way of shafts 20, to the two drive wheels 4 which mesh with the racks 3 disposed along the machine track.

The two bevel gears 1 8 rotate in the same directions and at the same circumferential speeds only if there are equal tooth pressures in the range of engagement of the two bevel gears 17 meshing with them. As long as this condition obtains, the two drive wheels 4 engaging in the racks 3 run in synchronism and act with the same tooth pressure on the rack 3 meshing with them. If this condition changes, e.g. if one of these two drive wheels 4 has a tooth in the rack 3 which is not in bearing contact, i.e. not contributing to transmitting the load it receives, the tooth pressure inside the differential gear 13 also varies.The resulting compensatory movement instantaneously results in an increase in the circumferential speed of the bevel gear 18, which is in driving connection with the non-loaded drive wheel 4 via one of the two reduction gears 1 2. The resulting differential speeds of the two drive wheels 4, i.e. their compensatory movement, therefore instantaneously results in the non-loaded and hence more rapidly rotating drive wheel 4 again coming into contact with the rack teeth and participating in taking the load to an extent such that the tooth pressures of the pairs of bevel gears 17, 1 8 inside the differential housing 1 6 have the same values. It is only as a result of this compensatory movement that the drive from the single motor 11 can be transmitted uniformly to both drive wheels 4 in every situation.

In order further to increase the advance force at the opposite end of the machine 1 it is of course possible to instal another feed winch 5 and to have each drive wheel 4 of this winch 5 engage in each of the two racks 3.

Similarly, using different reduction gears 1 2 it is possible to select a drive wheel arrangement other than the co-axial arrangement if this should be necessary for structural reasons.

Claims (4)

1. An underground mining machine having two drive wheels for engagement in racks situated on opposite sides of the face conveyor and which will extend over the length of the machine track, and having a drive motor for producing machine advance connected via a differential gear to two reduction gears each associated with a respective one of the two drive wheels.

2. A mining machine according to claim 1, wherein the differential gear is a differential bevel gear, in which the two output shafts disposed coaxially of one another are connected to the sun wheel of each of the two planetary gears used as reduction gears.

3. A mining machine according to claim 1 or claim 2, wherein a transmission stage follows the differential gear for an arrangement of two planetary gears in which they are offset from the axis.

4. A mining machine substantially as herein described with reference to the accompanying drawing.