Abstract: A double-chain conveyor is assembled of trough sections defining a bottom plate provided with lateral guiding walls for scraper elements and intermediate guides extending along the entire length of the conveyor and guidingly engaging lateral edges of flat chain elements arranged parallel to the bottom plate of the trough. The flat chain elements are provided with oblong holes extending in the direction of the chain and linking vertically directed ring-shaped chain elements with a play which permits shifting movements of all chain elements in the longitudinal direction. Intermediate drives are provided between superposed bottom plates of the trough and drive a chain wheel engaging the flat chain elements both in the upper and in the lower flight of the conveying chain.

Abstract: A mine roof support structure includes a floor skid, a supporting shield pivotally connected thereto by a pair of rocker arms forming a lemniscate guide, a roof cap pivotally connected at a roof cap joint to the shield, and hydraulic props supporting the roof cap. A hydraulic actuator is pivotally connected at opposite ends to the skid and to one of the arms, and the other of the rocker arms is disposed nearer the coal-face end of the support than the one arm. Such other arm is longitudinally adjustable and is pivotally connected at opposite ends to the skid and to the shield. This other arm is so constructed that its opposite ends may be adjusted relative to one another to enable the cap and the roof cap joint to follow a lemniscate path during settling of the roof and to follow a circular arc during a lowering of the cap toward the skid upon actuation of the hydraulic actuator.

Abstract: Disclosed is a device comprising a connecting bolt having a gripping profile near one end and a coupling element having a profile adapted to engage the profile of the connecting bolt. The profile of the connecting bolt is a plurality of projecting teeth separated by grooves where the spacing between at least some of the teeth and the depth of at least some of the grooves increases toward the end of the connecting bolt. The profile of the coupling element is a plurality of teeth separated by grooves which generally correspond to the profile of the teeth of the connecting bolt. However, the spacing between at least some of the grooves relative to the teeth on the connecting bolt is slightly greater and becomes increasingly greater from the groove adapted to engage the tooth of the connecting bolt nearest the end of the bolt to the groove adapted to engage the tooth of the connecting bolt furthest from the end of the bolt.

Abstract: An axial piston machine of the swash plate type includes a valve plate provided in a front face thereof with control openings which communicate at opposite ends through bores with the rear face of the valve plate. A plurality of shallow pockets, respectively forming hydrostatic bearings, are also provided in said front face, which communicate through connecting bores respectively with throttle bores, which in turn communicate at inner ends with respective control openings, and in which spring loaded throttle pins are arranged with small clearance for oscillating movement.