Motors: expansible chamber type – With motive fluid valve – Inlet fluid supplemented by controlled fluid pressurized in...
Patent
1991-02-22
1993-06-15
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Inlet fluid supplemented by controlled fluid pressurized in...
91447, 91451, 13759613, F15B 1304
Patent
active
052188973
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a hydraulic circuit apparatus for supplying fluid under pressure into work implement actuating cylinders to drive work implements such as a boom, an arm and a bucket, etc. mounted on an earth moving vehicle such as a power shovel, etc.
BACKGROUND ART OF THE INVENTION
A boom and arm type work implement provided with a bucket has a boom mounted thereon so that it may be swung up and down by a boom actuating cylinder, an arm connected to the boom so that it may be swung up and down by an arm actuating cylinder, and a bucket connected to the arm so that it may be swung up and down by a bucket actuating cylinder, and is arranged such that the boom, the arm and the bucket are swung up and down to conduct earth excavation work.
The hydraulic circuit for operating this boom and arm type work implement is arranged such that the fluid under pressure discharged by a hydraulic pump is supplied by a boom operating valve into the boom actuating cylinder, the fluid under pressure is supplied by an arm operating valve into the arm actuating cylinder, and the fluid under pressure is also supplied by a bucket operating valve into the bucket actuating cylinder.
The hydraulic circuit for supplying the fluid under pressure discharged by a hydraulic pump by an operating valve into a work implement lifting side chamber and a work implement lowering side chamber of each of the work implement actuating cylinders so as to extend and retract the piston rod in each of the cylinders is well known.
As the operating valves for use with such a hydraulic circuit, a closed-center type operating valve is heretofore known. This closed-center type operating valve is suitable for use in case a plurality of operating valves are operated simultaneously to supply the fluid under pressure discharged by a single hydraulic pump into a plurality of hydraulic cylinders, since when the operating valve is located at its neutral position the pump port thereof is shut off.
The closed-center operating valve has a neutral position where a pump port, a tank port, a first port, and a second port are shut off, a first actuating position where the pump port is communicated with the first port, and the tank port is communicated with the second port, and a second actuating position where the pump port is communicated with the second port, and the tank port is communicated with the first port. This operating valve is arranged such that it is changed over to each of the above-mentioned positions when a spool slidably inserted in the valve body is moved; that is, when the spool is moved from its neutral position towards its first actuating position the tank port is communicated with the second port to thereby open the metering-out side, and when the spool is further moved in the same direction the pump port is communicated with the first port to thereby open the metering-in side, and the area of opening of each port is increased in proportion to the stroke of the spool. This effect can be seen with reference to FIG. 1.
This is applicable to the case where the spool is changed over to the second actuating position.
Further, there are cases where the boom of a boom-and-arm type work implement is lowered by its own weight so as to bring the bucket into contact with the ground to conduct earth compacting operation. In such cases, the boom operating valve is operated from its neutral position to a position where the metering-out side is opened and the metering-in side is opened slightly so as to lower the boom by its own weight.
However, the stroke of the spool which occurs until the metering-in side is opened after the metering-out side is opened is very short, as shown in FIG. 1, and therefore the spool is sometimes moved to a position where the metering-in side is widely opened and the pressure within the boom lowering side chamber is raised with the result that the boom is lowered forcibly by the action of the boom actuating cylinder. As a result, the bucket is vigorously pushed against the ground thus ra
REFERENCES:
patent: 3477347 (1969-11-01), Rice
patent: 4411189 (1983-10-01), Miller
Akiyama Terruo
Ishizaki Naoki
Shinohara Shigeru
Shirai Kiyoshi
Takiguchi Takahide
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Look Edward K.
Lopez F. Daniel
LandOfFree
Hydraulic circuit apparatus for operating work-implement actuati does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic circuit apparatus for operating work-implement actuati, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic circuit apparatus for operating work-implement actuati will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1036278