Gathering arms for a mining machine

#This invention relates to gathering arms for mining machinery, and to mining machinery having such gathering arms. The invention also relates to a fluid control system for the arms.

#Certain types of mining machines, especially those provided with a turret-operated telescopic cutting head, allow the mined material to fall to the floor of the working and then, by advancing, gather it with a downwardly and forwardly inclined gathering apron, from which it is removed by means of an endless conveyor. Many different types of apron/conveyor construction are possible but the most common is probably to have an apron with a centrally located discharge conveyor, the apron being provided with a pair of gathering arms arranged to sweep material inwardly from the side of the apron to the centre so that as the machine is advanced, so the material will be loaded onto the inclined apron. Alternatively, one could have a side mounted conveyor, in which case a single gathering arm sweeping right across the apron might be sufficient.

#Obviously, the gathering arm(s) should be capable of sweeping through a substantial angle from an outboard position to an inboard position and after sweeping has occurred the or each arm must be effectively shortened in length so that the arm(s) can be returned to an outboard position again, without sweeping the previously swept-in material off the apron. In the past, sweeping of the arm(s) and extension of the arm(s) has been achieved by mechanically operated linkages, most of which have incorporated one or more control cams. Obviously, the gathering arm(s) operate(s) almost continuously and therefore is or are subjected to considerable wear and tear with the result that the mechanisms wear out easily and are difficult and expensive to replace.

#The invention is now described by way of example with reference to the accompanying drawings, in which:

#FIG. 1 is a plan view of a mining machine fitted with gathering arms, one gathering arm being shown schematically in its extended position and at one extreme sweep, i.e. outboard position, and the other gathering arm being shown in its retracted position and its other extreme sweep, i.e. inboard position;

#FIG. 2 is a side elevation;

#Referring to FIGS. 1 and 2, a mining machine 1 is shown with a telescopic boom 3 having a cutting head 5 and beneath the boom is a generally fan-shaped apron 7 which, as can be seen from FIG. 2, is downwardly and forwardly inclined. Extending upwardly and rearwardly from the upper rear end of the apron 7 is an endless central discharge conveyor 9, and the mining machine is generally operated in known manner and provided with caterpillar tracks 11. A pair of gathering or sweeper arms 13 is associated with the apron 7 and the arms are mounted for sweeping or rocking movement about axes 15. The arms are identical and the operation of only one will be described, it being appreciated that normally the two would be operated in synchronism. Each arm is arranged to sweep over the surface of the apron 7 from an outboard position shown generally at 17 to an inboard position shown generally at 19, this sweeping movement being under the control of a hydraulic piston and cylinder device 21 having its piston 23 pivotally connected to a crank lever 25 of the arm 13 at 27 and its cylinder pivotally connected to the machine frame at 29. To operate satisfactorily, the arm must effectively be capable of extension and retraction and for this purpose it is generally hollow so as to receive an extendible portion 31 which can be moved between its extended position shown generally at 33 and a retracted position shown generally at 35 under the control of a piston and cylinder device 37 (see FIG. 4) located within the arm.

#It will thus be appreciated that in a sweeping cycle, the extendible portion 31 will first of all be extended by the device 37 to its extended position 33, whereupon the extended arm will be swept from its outboard position 17 to its inboard position 19 by extension of the device 21 to sweep mined material across the surface of the apron 7 to a central portion of the apron. On completion of this sweeping movement, the device 37 will be retracted to move the portion 31 to its retracted position 35 whereupon the retracted arm will then be swept from its inboard position to its outboard position again by retraction of the device 21. It will of course be appreciated that by retracting the portion 31, this ensures that swept in material is not swept out again.

#The gathering arms shown in FIGS. 1 and 2 are of very simplete construction and in FIG. 3 an alternative construction is shown which is capable of handling a considerably greater volume of material than the arms of FIGS. 1 and 2. In this construction parts similar to the parts of FIGS. 1 and 2 are identified by the same reference numerals used in those FIGS. but followed by the lower case letter a.