The Art and Science of Programming

A mine roof support unit has a mechanism for adjusting the angular position of an auxiliary cap relative to a main cap, the auxiliary cap and the main cap forming the roof cap of the mine roof support unit. The auxiliary cap is connected to the main cap by a first pivot joint. The cap-positioning mechanism comprises a hydraulic ram and a lever acting between the main cap and the auxiliary cap. The auxiliary cap is provided with an extension arm projecting from the first pivot joint towards the main cap. One end portion of the lever is connected to the arm by a second pivot joint, and the other end of the lever is connected to a block attached to the piston rod of the ram by a third pivot joint. The cylinder of the ram is attached to the main cap.