Abstract: Apparatus to advance a multi-unit mining machine along a face conveyor in an underground mine includes a hydraulic unit with an advancing mechanism that extends around a toothed rack. The rack extends over the length of machine movement. The hydraulic unit is an independent unit on a machine body of the mining machine and is used for increasing the advancing force provided by other existing advancing units for the mining machine. The hydraulic unit is narrower than the other units on the machine body and is attached by vertical flanges to adjacent units on the machine body. The hydraulic unit receives a winch casing between oppositely-disposed flanges for guided vertical movement of the casing. The casing has pins extending in the direction of machine movement from opposite top portions thereof to engage with members that slide vertically between guide bars on the flanges for vertical mobility. Clearances between the parts provide limited horizontal mobility.

Abstract: The invention is particularly adapted for use with a longwall mining machine of the type having a rack extending along a track for the mining machine, a gear wheel on the machine engageable with the rack for moving the machine along a track, at least two shearer drums carried by the machine, at least one driving motor on the machine, and gear train means connecting the driving motor to the shearer drums to rotate the same. Two inductive clutches having a common armature are connected through reduction gearing to the aforesaid driving gear wheel; while separate rotors connect the respective clutches to the gear train such that one rotor will rotate in a direction opposite to the other. A magnetically-actuated, spring-biased friction brake is disposed between the two inductive clutches for braking the clutches when the machine is at rest.