TORQUE IMPULSE DRIVE UNIT FOR POWER TOOL

摘要

A driven input body (24) is coupled to an output body (28) by dogs (30, 30a) capable of riding over one another when rotation of the output body (28) is checked. A further pair of dogs (31, 31a) is provided at a different distance from the rotation axis. The input body (24) has a cylinder (42) and piston (44) defining an internal hydraulic space which communicates with an external hydraulic space (45, 46) via a bleed valve (43) controlling the rate of axial movement of the piston (44) as the dogs ride up one another. A one-way valve (39) allows hydraulic fluid to flow back into the internal hydraulic space as the piston (44) moves downwards after the dogs have ridden over one another. The pressure in the internal space may be relieved just before the dogs ride over one another, to reduce frictional wear of the dogs.