Generally divided into single-piston pump piston pump, horizontal piston pump, axial piston pumps and radial piston pumps. Single-piston pump There are eccentric structures, plunger, spring, cylinder, two-way valve. Closed volume is formed between the plunger and the cylinder bore. Eccentric rotation of a turn, reciprocates a plunger up and down, the downward movement of the suction, the upward movement of oil discharge. Pump oil volume per revolution is called a turn discharge displacement, displacement is only concerned with the structural parameters of the pump. Horizontal Piston Pump Horizontal piston pumps are installed in parallel by several plunger (typically 3 or 6), with a crankshaft via connecting rod slider or by the eccentric shaft is directly driven reciprocating plunger to achieve suction, exhaust fluid hydraulic pump. They are also using valve type flow device, and mostly quantitative pump. Mine hydraulic support systems are generally horizontal piston pump emulsion. Emulsion pump for the coal face, to provide hydraulic support for the emulsion, works by the rotation of the crankshaft driven piston reciprocating motion, to realize aspiration and drainage. Axial formula Axial piston pump is a reciprocating movement direction of the piston and the cylinder center axis parallel to the piston or plunger. Use and transmission shaft parallel axial piston pump plunger reciprocates volume change produced by the plunger bore in to work. Since the plunger and the plunger hole are circular parts, the processing can be achieved with high accuracy, and therefore high volumetric efficiency. Straight axis swashplate Straight axis swashplate piston pump into pressure from the sucking oil type and type two. Pressure type oil pump are mostly used have pressure tank, after pressure by hydraulic oil tank after each start the machine, such as hydraulic stains box must use air pressure, to operate machinery. Such as insufficient hydraulic pressure to start the machine tank, pump will cause the inner shoe and pull off phenomenon, can cause abnormal wear of the pump body board and return the platen.