Fluid handling – Systems – Supply and exhaust
Patent
1993-12-14
1995-03-07
Michalsky, Gerald A.
Fluid handling
Systems
Supply and exhaust
91436, 91451, 1375962, F15B 1304
Patent
active
053949030
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic control valve adapted for use in a construction machine such as a power shovel.
2. Description of Prior Art
A conventional power shovel comprises, as illustrated in FIG. 9, a lower self-propelled movable body 1 driven by a propelling motor, not shown, an upper turntable 2 capable of being turned by a turning motor, not shown, and a working machine 3 mounted at the front portion of the turntable 2.
The working machine 3 has a boom 6 which can be swung rightward and leftward by a swinging cylinder 4 and movable vertically at the tip end thereof by a boom cylinder 5 and an arm 8 pivotally mounted at the tip end of the boom 6 which is turned by an arm cylinder 7.
The arm 8 has a tip end to which a bucket 10 is attached so as to be turned by a bucket cylinder 9. A blade 12 which is vertically movable by a blade cylinder 11 is mounted at the front portion of the movable body 1.
A hydraulic control valve 13 provided at each actuator controls the propelling motor, the turning motor and hydraulic actuators composed of various cylinders. Each hydraulic control valve 13 is, as illustrated in FIG. 10, normally connected with one another.
Each hydraulic control valve 13 comprises, as illustrated in FIG. 11 , a valve body 13a, a spool 14 housed in the valve body 13a for switching oil passages in the valve body 13a, the spool 14 normally being retained at a neutral position by a return spring 13b wherein an oil under pressure supplied to a pump port 13c is drained through a drain port 13d into a tank 16 by way of a port block 15.
The valve body 13a of the hydraulic control valve 13 is, as illustrated in FIG. 12, conventionally formed integrally by casting. However, in the conventional hydraulic control valve 13, a main core for forming a spool port 13h is complex so that narrow passages can not be formed in the hydraulic control valve 13 since a cylinder drain port 13e, a bridge port 13g and the spool port 13h are separately formed in three stages. As a result, this was an obstacle to making the hydraulic control valve compact in size since the diameter of the spool port 13h could not be less than that ranging from 11 mm to 12 mm.
The present invention has been made in view of the problem set forth above and is to provide a hydraulic control valve so that a valve body can be manufactured without using cores having complex structures.
Particularly, the conventional control valve body is, as described above, integrally formed by casting and a passage of a neutral port in a valve chamber is also formed by casting wherein cores are employed for forming the passage of the neutral port at the time of casting. The core is formed, as illustrated in FIG. 13, by casting a main core 19 for forming the spool port 13h and thereafter by jointing joint cores 20 and 21 to the main core 19. There was a problem in that a mold can not be split along the line X--X when forming the core if the jointing cores 20 and 21 are integrated with each other, which involves the following drawbacks.
(1) A jointing operation of the cores is manually made which results in preventing an automatic assembly of the cores, hence this is inefficient.
(2) Jointing deviation between the cores is liable to occur which involves a deteriorated casting accuracy.
(3) Casting flash is liable to occur at the jointing portions of the cores.
(4) Jointing agent causes generating gas at the time of casting which is likely to generate a casting porosity.
Accordingly, it is a second object of the present invention to provide a hydraulic control valve capable of manufacturing a valve body by machining the passage without using the conventional jointing cores, whereas the passage was conventionally formed by the jointing cores.
The valve body 13a of the conventional control valve 13 forms therein, as illustrated in FIG. 14, a parallel port 13f, the bridge ports 13g, cylinder ports 13i and the cylinder drain port 13e wherein a load check valve 17 for allowing the oil under pressu
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Komatsu Zenoah Kabushiki Kaisha
Michalsky Gerald A.
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