Drain mechanism for hydraulic power transmission joint

摘要

A drain plug (55) is disposed in a drain hole (56) through which oil is discharged from a high-pressure chamber (59) formed in a valve block (27). Within the drain plug there is arranged a drain pin (60) that slidably opens and closes the drain hole. A fixed pin (54) serves to restrict a displacement of the drain pin. A thermo-switch (67) is located within a low-pressure chamber (66) behind the drain pin in such a manner as to be urged by a return spring (70) so that the drain pin is pressed to keep the drain hole closed. When a predetermined temperature is reached, the thermo-switch allows its head pin (71) to extend, with the reaction force as a result of abutment of the head pin against the fixed pin causing the thermo-switch to retreat to release the pressing force exerted on the drain pin. In consequence, the drain pin is displaced by a high pressure toward the direction in which the drain hole is opened, allowing high-pressure oil to be drained into the low pressure side. <IMAGE>