Portable hydraulically operated device incorporating automatic drain valve
First Claim
1. A hydraulically operated device comprising:
- a working tool;
a single-acting cylinder having a piston for operating said working tool, a pressure chamber for applying a hydraulic pressure to move the piston from an original position to an operated position, and a return spring for biasing the piston toward the original position;
a housing which carries said single-acting cylinder;
a handle fixed to said housing for holding said hydraulically operated device;
a hydraulic pump incorporated in said housing, for delivering a pressurized fluid to be fed into said pressure chamber of said single-acting cylinder;
an electric motor incorporated in said housing, for operating said hydraulic pump;
a switch carried by said handle, for turning on and off said electric motor; and
an automatic drain valve, incorporated in said housing, for inhibiting the pressurized fluid from being discharged from said pressure chamber of said cylinder while a difference by which a delivery pressure of said hydraulic pump is higher than a pressure in said pressure chamber exceeds a predetermined value, said automatic drain valve allowing the pressurized fluid to be discharged from said pressure chamber when said difference is reduced to a value smaller than said predetermined value, whereby said pressure chamber is automatically drained when said hydraulic pump is turned off with said motor turned off by said switch.
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Accused Products
Abstract
A hydraulically operated device including a single-acting cylinder having a piston for operating a working tool, a pressure chamber for applying a hydraulic pressure to the piston from an original position to an operated position, and a return spring for biasing the piston toward the original position. The device includes a hydraulic pump for delivering a pressurized fluid to be fed into the pressure chamber of the cylinder, and an automatic drain valve for inhibiting the pressurized fluid from being discharged from the pressure chamber while a difference by which a delivery pressure of the pump is higher than a pressure in the pressure chamber exceeds a predetermined value. When the difference becomes smaller than the predetermined value, the automatic drain valve is operated to allow the pressurized fluid to be discharged from the pressure chamber. Thus, the automatic drain valve automatically drains the pressure chamber when the pump is turned off.
41 Citations
10 Claims
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1. A hydraulically operated device comprising:
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a working tool; a single-acting cylinder having a piston for operating said working tool, a pressure chamber for applying a hydraulic pressure to move the piston from an original position to an operated position, and a return spring for biasing the piston toward the original position; a housing which carries said single-acting cylinder; a handle fixed to said housing for holding said hydraulically operated device; a hydraulic pump incorporated in said housing, for delivering a pressurized fluid to be fed into said pressure chamber of said single-acting cylinder; an electric motor incorporated in said housing, for operating said hydraulic pump; a switch carried by said handle, for turning on and off said electric motor; and an automatic drain valve, incorporated in said housing, for inhibiting the pressurized fluid from being discharged from said pressure chamber of said cylinder while a difference by which a delivery pressure of said hydraulic pump is higher than a pressure in said pressure chamber exceeds a predetermined value, said automatic drain valve allowing the pressurized fluid to be discharged from said pressure chamber when said difference is reduced to a value smaller than said predetermined value, whereby said pressure chamber is automatically drained when said hydraulic pump is turned off with said motor turned off by said switch. - View Dependent Claims (2, 3)
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4. A hydraulically operated device including a single-acting cylinder having a piston for operating a working tool, a pressure chamber for applying a hydraulic pressure to move the piston from an original position to an operated position, and a return spring for biasing the piston toward the original position, said device comprising:
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a hydraulic pump for delivering a pressurized fluid to be fed into said pressure chamber of said single-acting cylinder; and an automatic drain valve for inhibiting the pressurized fluid from being discharged from said pressure chamber of said cylinder while a difference by which a delivery pressure of said hydraulic pump is higher than a pressure in said pressure chamber exceeds a predetermined value, said automatic drain valve allowing the pressurized fluid to be discharged from said pressure chamber when said difference is reduced to a value smaller than said predetermined value, whereby said pressure chamber is automatically drained when said hydraulic pump is turned off, said automatic drain valve comprising;
(a) means for defining a valve chamber;
(b) a primary valve member slidably received in said valve chamber and having a bore formed in an axial direction, said primary valve member cooperating with said means for defining a valve chamber, to define a first fluid chamber to which a delivery passage connected to said hydraulic pump is open, and a second fluid chamber to which a drain passage communicating with said oil reservoir and a feed-discharge passage communicating with said pressure chamber of said cylinder are open said delivery pressure being applied to said first fluid chamber and acting on said primary valve member in a first direction, while said pressure in said pressure chamber being applied to said second fluid chamber and acting on said primary valve member in a second direction opposite to said first direction;
(c) primary biasing means for biasing said primary valve member in said second direction, said primary valve member being moved to allow fluid communication between said delivery passage and said feed-discharge passage and prevent fluid communication between said feed-discharge passage and said drain passage, when a thrust force based on said difference exceeds a biasing force of said primary biasing means; and
(d) a secondary valve member including a first portion slidably engaging said bore of the primary valve member, and a second portion which projects from said bore so as to allow and prevent fluid communication between said drain passage and said second fluid chamber, and secondary biasing means for biasing said secondary valve member toward an end of said drain passage which opens to said second fluid chamber. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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Specification