MACHINE FOR DRIVING MINE ROOF PINS

A machine for driving mine roof pins having a pin-centering support extending along a cylinder and supported by a piston so as to move with the piston when the piston drives the pin along the cylinder and into a mine roof, the pin-centering support engaging the pin to guide and support the pin after the pin is driven, and moving laterally out of the cylinder as it disengages from that portion of the pin about to enter the mine roof. The pin-centering support includes a plurality of support lengths engaging the side of the pin about the pin periphery, each support length having a plurality of interengaging, relatively movable support members. A secondary power mechanism is operatively connected to the support lengths for urging the support lengths back into the cylinder incident to retraction of the piston. Each support length engages the pin with substantially no relative movement therebetween and moves relative to the cylinder as the pin is driven by the piston means. In one embodiment, the support lengths are spaced substantially equidistantly about the pin periphery, and adjacent support members of each support length have substantially continuous and aligned pin-engaging surfaces to provide a substantially continuous, longitudinal support for the pin. Further, adjacent support members of the support lengths are pivotally interconnected to provide chains. A receiving assembly is provided to guide the support as it moves laterally from the cylinder. An auxiliary support selectively engages the side of the pin about the pin periphery in the region unsupported by the primary pin-centering support near the top of the cylinder and selectively disengages from the side of the pin and out of the path of the piston means to enable complete insertion of the pin by the piston.