Motors: expansible chamber type – With motive fluid valve – Relatively movable inlet and exhaust valves for single...
Patent
1990-06-20
1992-08-11
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Relatively movable inlet and exhaust valves for single...
91459, 91461, 13759615, 13759616, 251 3002, F15B 1108
Patent
active
051369303
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an apparatus for supplying a pressure oil to hydraulic cylinders employed in working machines or construction machines such as arm-type power shovels and the like provided with a working equipment which is moved up and down by the cylinders.
DESCRIPTION OF THE PRIOR ART
In conventional apparatus for supplying a pressure oil to a lifting-movement pressure chamber or a lowering-movement pressure chamber of a hydraulic cylinder employed in a working machine such as power shovels and the like, the pressure oil is discharged from a hydraulic pump and supplied to a control valve in which the pressure oil is selectively supplied to a first and a second outlet port of the control valve, the first and the second outlet port being connected to the lifting-movement and the lowering movement pressure chamber of the hydraulic cylinder through pressure oil passages, respectively.
Since the conventional apparatus for supplying the pressure oil to the hydraulic cylinder has the above construction, there is a fear that the working equipment such as shovels and the like having been lifted by the cylinder suddenly drops off when the pressure oil passages connected to the lifting-movement pressure chamber of the cylinder is damaged in operation, because the pressure oil confined within the lifting-movement pressure chamber of the cylinder suddenly flows out of the chamber through the damaged passages to permit a piston rod of the hydraulic cylinder to be suddenly retracted.
Hitherto, in this connection, it is known to prevent, in a manner realized with a conventional construction shown in FIG. 8, the working equipment such as shovels and the like employed in the working machine such as power shovels and the like from suddenly dropping off.
In the conventional construction shown in FIG. 8, a directional control valve 1 is connected with a lifting-movement pressure chamber 2a of a hydraulic cylinder 2 employed in the working machine such as power shovel and the like through pressure all passgage 3 connected to a sudden-drop prevention valve assembly 4. In the valve assembly 4, a flow control valve 5 thereof is kept in its first position 5.sub.1 in which: a pressure oil flow is prevented from being issued from the lifting-movement pressure chamber 2a of the cylinder 2 to the directional control valve 1, and another pressure oil flow issued to the lifting-movement pressure chamber 2a of the cylinder 2 is permitted, so that the pressure oil having been confined within the lifting-movement pressure chamber 2a of the cylinder 2 is prevented from flowing out of the chamber 2a even if the pressure oil passages 3 through which the sudden-drop prevention valve assembly 4 is connected with the directional control valve 1 are damaged in operation.
On the other hand, it is required to move down or lower the working equipment in operation, a signal through which the directional control valve 1 is so operated as to be positioned in a move-down or lowering position 1 is also issued to the flow control valve 5 of the sudden-drop prevention valve assembly 4 so that an amount of the pressure oil flowing out of the lifting-movement pressure chamber 2a of the cylinder 2 is controlled so as to correspond to an opening amount of the directional control valve 1, the pressure oil flowing out of the lifting-movement pressure chamber 2a of the cylinder 2 being received in a drain tank, whereby the working equipment such as shovels and the like is moved down or lowered in safety manner in operation without any fear that the equipment suddenly drops off even if the pressure oil passages 3 connected with the lifting-movement pressure chamber 2a of the cylinder 2 are damaged in operation.
In the above conventional construction, since the directional control valve 1 is synchronized in opening amount with the flow control valve 5 of the sudden-drop prevention valve assembly 4, it is required that the directional control valve 1 is larger in opening amount then the flow control valve 5 of the valve as
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Endo Hiroshi
Ishizaki Naoki
Karakama Tadao
Nunotani Sadao
Takano Toshiro
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Look Edward K.
Mattingly Todd
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