JPS5740173A - Spool moving method for counter balance valve and device for the same - Google Patents

Abstract

PURPOSE: To shorten the time for change-over of a counter balance valve used in the oil-hydraulic running device etc. of a crawler vehicle and thereby to smooth the change-over operation by providing a pilot check valve at both ends of the spool, opened and closed by the move of spool, and by putting the valve in communication with the supply and discharge lines.

CONSTITUTION: When a change-over valve 27 is set into the operating position, the pressure oil from an oil-hydraulic pump 23 is sent through an oil conduit 31a in the counter balance valve 33 to open the main check valve 39, and delivered to the suction side of an actuator 291 through the supply and discharge line 31. The adovementioned pressure oil is, on the other hand, is sent through a small hole 51 from the oil conduit 31a to press the front face of a poppet 45, that will open a pilot check valve 59 to permit said oil to flow into a damping chamber at the left end of the spool. Thus the spool 37 is moved to the right to exhaust the oil from the damping chamber at the right end of the spool 37, and the spool 37 now moves to the right abruptly. The supply and discharge line 32 at the discharge side of the actuator 29 is thus put into communication abruptly. Thereby, the time for change-over of the counter balance valve can be shortened and the operation smoothed.

COPYRIGHT: (C)1982,JPO&Japio