Title:
DIRECTION CHANGE-OVER VALVE
Document Type and Number:
Japanese Patent JPS5830501
Kind Code:
A
Abstract:
PURPOSE:To prevent impact pressures from being generated at a tank port and in a passage for return oil leading to the tank port, by providing a damping valve at a junction part of a bypass passage and the passage for the return oil. CONSTITUTION:When a spool 8 is returned to a neutral position, a pressure oil in the bypass passage 14 acts on a valve body 22 of the damping valve 20, so that a difference is generated between the pressure in the bypass passage 14 and the pressure in a spring chamber 24, and the valve body 22 is displaced in the direction for parting from a valve seat 25. On the other hand, the oil in the chamber 24 is discharged through a restricted passage 28, so that the displacement of the valve body 22 takes place slowly. Therefore, communicating passages 31A, 31B, 31C provided in staggered manner in position in the axial direction of the valve body 22 are sequentially opened gradually, whereby the cross- sectional area of the passage for the pressure oil between the bypass passage 14 and the passages 13A, 13B for the return oil is gradually enlarged. Accordingly, the impact pressures generated in the passages 13A, 13B and at the port 5 are damped.
Inventors:
YOSHIDA KUNIHIKO
Application Number:
JP12917881A
Publication Date:
February 23, 1983
Filing Date:
August 18, 1981
Export Citation:
Assignee:
HITACHI CONSTRUCTION MACHINERY
International Classes:
F15B11/00; F15B13/06; (IPC1-7): F15B11/00
Attorney, Agent or Firm:
Kazuhiko Hirose