Fluid handling – Systems – With selective motion for plural valve actuator
Patent
1997-06-05
1998-10-13
Michalsky, Gerald A.
Fluid handling
Systems
With selective motion for plural valve actuator
91523, 1375961, F15B 1302
Patent
active
058198008
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic pilot valve employed in an operating device of a crawler type vehicle having a hydraulic steering clutch and a hydraulic steering brake.
BACKGROUND ART
As a hydraulic pilot valve, various valves have been known, for example, as shown in Japanese Unexamined Utility Model Publication (Kokai) No. Heisei 2-143581, a pressure reduction valve, a piston adapted to be returned to a neutral position by means of a spring for actuating the pressure reduction valve, a pushing member for pushing down the piston, and an operation lever rockable between the neutral position and an operating position. When the operation lever is placed at the neutral position, the piston is held in an upper position by the spring to block an inlet port and an outlet port of the pressure reduction valve. By operating the operation lever so that it moves from the neutral position to the operating position, the pushing member is depressed against the spring to push down the piston to situate the pressure reduction valve in a pressurized fluid supply condition, namely the inlet port is communicated with the outlet port of the pressure reduction valve via an opening area proportional to the operation magnitude of the operation lever.
On the other hand, as a driving device for a crawler type vehicle, there has been known an engine output which is transmitted to left and right drive tumblers via a left and right pair of hydraulic steering clutches and a left and right pair of hydraulic steering brakes for driving left and right crawlers by the left and right drive tumblers. Furthermore, there has been known an operation device for performing steering operation by controlling a pair of left and right hydraulic steering clutches and a pair of left and right hydraulic steering brakes.
The foregoing conventional steering device is constructed as shown in FIG. 1, for example.
There are provided a left hydraulic steering clutch 2 and a right steering clutch 3 at left and right ends of a transverse axle 1, left and right clutch cylinders 6 and 7 for driving the left and right hydraulic steering clutches 2 and 3, respectively in the vicinity of the latter, a left hydraulic steering brake 4 and a right hydraulic steering brake 5 at output sides of the left and right hydraulic steering clutches 2 and 3, and left and right brake cylinders 10 and 11 respectively driving the left and right hydraulic steering brakes 4 and 5 in the vicinity of the latter. When pressurized fluid is supplied to pressure receiving chambers 8 and 9 of the left and right clutch cylinders 6 and 7, the left and right hydraulic steering clutches 2 and 3 are disconnected, and when the pressurized fluid is not supplied, the clutches are connected. When pressurized fluid is charged into pressure receiving chamber 12 and 13 of the left and right brake cylinders 10 and 11, the left and right hydraulic steering brakes 4 and 5 are in braking conditions, and if the pressurized fluid is not supplied, the brakes are in non-braking condition.
A hydraulic pilot valve 20 includes first, second, third and fourth pressure reduction valves 22, 23, 24 and 25, and an operation lever 26 for respectively operating the first, second, third and fourth pressure reduction valves 22, 23, 24 and 25 via pistons 22a, 23a, 24a and 25a. When the operation lever 26 is moved from the neutral position in one direction (direction of arrow a), the inlet ports 27 and the output ports 28 of the first and third pressure reduction valves 22 and 24 are communicated with each other. When the operation lever 26 is moved from the neutral position in the other direction (direction of arrow b), the inlet ports 27 and the output ports 28 of the second and fourth pressure reduction valves 23 and 25 are communicated with each other.
Then, the outlet port 28 of the first pressure reduction valve 22 is connected to the pressure receiving chamber 12 of the left brake cylinder 10 via a first circuit 29. The outlet port 28 of the second pressure reduction valve 23 is conne
REFERENCES:
patent: 5184646 (1993-02-01), Hori et al.
patent: 5558127 (1996-09-01), Maruyama et al.
Hori Shuji
Kawabata Kei
Maruyama Jun
Komatsu Ltd.
Michalsky Gerald A.
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