Abstract: A blade planer utilizes a centering mechanism to locate the centerline of lumber on the datum plane intermediate a pair of offset blade planer heads. The centering mechanism includes a plurality of opposed shoes which are hydraulically or mechanically linked such that displacement of one shoe from a predetermined reference yields a simultaneous equal displacement in the opposing shoe. Biased return to the reference ensures that the shoes are always centered on the datum plane regardless of the separation of the blade planer heads.

Abstract: Apparatus for feeding pieces of lumber along a path with the center lines of the pieces extending along a preselected datum plane in the direction of the path. A plurality of spaced apart, upper and lower transverse members are mounted for rotation about horizontal axes at opposite sides of the datum plane with the lower side of each upper transverse member and the upper side of each lower transverse member traveling in the direction of the path of movement of the lumber to provide oppositely disposed transverse members at opposite sides of the datum plane. Outwardly projecting lumber engaging members carried by the oppositely disposed transverse members are yieldably urged toward the adjacent sides of the pieces of lumber therebetween with substantially equal force to maintain the center line of the pieces of lumber along the preselected datum plane.

Abstract: A mine roof support system having sets of laterally spaced pairs of elongated support members adapted to be moved into and out of abutting relation with a mine roof. Wheel supported frames extend between and connect adjacent end portions of each pair of support members with adjacent wheel supported frames at the ends of the support members being in spaced tandem relation and connected to each other by connector members. Extensible prop members are connected to and move the wheel supported frames and the elongated support members connected thereto selectively toward and away from the mine roof.