US 4,785,712 AGranted

Hydraulic operating apparatus for electric circuit breaker

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorsToshiaki Yoshizumi, Tsutomu Sugiyama

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Abstract

A hydraulic operating apparatus in which a differential piston is used as a drive unit, and in which the differential piston is driven by applying a high pressure fluid on a large piston face side through a hydraulic pressure control device for controlling the hydraulic pressure, and a high pressure fluid always being applied on the small piston face side. The hydraulic operating apparatus is constructed such that a high pressure fluid is applied concurrently on both piston faces when the differential piston stops at its receded position, and a thrust generated due to the difference between the forces applied on the both piston faces is held in check by a holding device acting on the differential piston or its extension. The differential piston is moved forward upon the removal of the holding force of the holding device, and the piston is moved backward upon the removal of the high pressure fluid on the large piston face side.

Claims16

Dependent claims

A hydraulic operating apparatus comprising:

a source of high pressure fluid;
a source of low pressure fluid;
a hydraulic pressure control circuit connected to said sources of pressure fluid;
a cylinder;
a differential piston drive unit movable in said cylinder between retracted and advanced positions and having a small end face continuously supplied with high pressure fluid and a large end face selectively supplied with high pressure fluid and low pressure fluid from said sources by said hydraulic pressure control circuit;
a valve included in said hydraulic pressure control circuit having an actuating piston and a pilot chamber continuously connected to said high pressure fluid source and receiving said valve actuating piston;
a first input unit connected to said hydraulic pressure control circuit and operable to shift said valve to supply low pressure fluid to said large piston face and cause said drive unit to move from the advanced to the retracted position;
a holding device engageable with said drive unit upon movement of the latter to the retracted position;
said holding device being releasable to allow the drive unit to move to the advanced position in response to concurrent application of high pressure fluid to both end faces of said drive unit;
said first input unit also being operable to disconnect said pilot chamber from said low pressure fluid source while the connection of said pilot chamber to said high pressure fluid source is maintained;
and
a restricted orifice in the connection between said pilot chamber and said high pressure fluid source, said restricted orifice causing a delay in the supply of high pressure fluid to said pilot chamber, upon operation of said first input unit to disconnect said pilot chamber from said low pressure fluid source, until after said holding device is completely engaged to hold said drive unit against forward thrust generated due to the difference in area between the large and small piston faces when high pressure fluid is concurrently applied thereto, the high pressure fluid being at a pressure high enough to substantially prevent gas dissolved in the fluid from forming gas bubbles.

9 more elements

A hydraulic operating apparatus comprising:

a cylinder;
a differential piston movable in said cylinder between retracted and forward positions;
a hydraulic pressure control device;
said differential piston having a large piston face selectively connected by said hydraulic pressure control device to a source of high pressure fluid and a source of low pressure fluid and a small piston face continuously connected to the source of high pressure fluid;
a first valve included in said hydraulic pressure control device and operated to control said differential piston, said first hydraulic valve being operable to supply low pressure fluid to said large piston face to return said differential piston from the forward position to the retracted position and operable responsive to said differential piston being fully retracted to the retracted position to supply high pressure fluid to said large piston face such that high pressure fluid is applied concurrently to both said large piston face and said small piston face when said differential piston is in the retracted position;
a holding device engageable with said differential piston to hold said differential piston in the retracted position against forward thrust generated due to the difference in area between said large piston face and small piston face when high pressure fluid is concurrently applied thereto;
one input unit connected to receive an electrical operating signal, amplifying the electrical operating signal, and connected to supply the amplified operating signal to said holding device;
another input unit connected to receive an electrical input signal, amplifying the electrical input signal hydraulically to produce a hydraulic input signal, and connected to supply the hydraulic input signal to said hydraulic pressure control device, and
a pressure releasing function member opening and closing a fluid passage in response to the movement of said differential piston to the retracted position and operable to actuate said first valve responsive thereto, the fluid passage connecting a pressure accumulator for maintaining a high pressure to said first valve.

6 more elements

A hydraulic operating apparatus comprising:

a cylinder;
a differential piston movable in said cylinder between retracted and forward positions;
a hydraulic pressure control device;
said differential piston having a large piston face selectively connected by said hydraulic pressure control device to a source of high pressure fluid and a source of low pressure fluid and a small piston face continuously connected to the source of high pressure fluid;
a first input unit connected to said hydraulic pressure control device and having first and second states;
a first hydraulic valve included in said hydraulic pressure control device and operated by said first input unit to control said differential piston, said first hydraulic valve being operable responsive to actuation of said first input unit to the first state to supply low pressure fluid to said large piston face to return said differential piston from the forward position to the retracted position, said first hydraulic valve being operable responsive to operation of said first input unit to the second state to supply high pressure fluid to said large piston face;
said hydraulic pressure control device including a pressure releasing member opening and closing in response to the movement of said differential piston and closing when said differential piston is retracted to operate said first hydraulic valve;
and
a hydraulically-engaged holding device engageable with said differential piston after said differential piston is retracted to hold said differential piston in the retracted position against forward thrust generated due to the difference in area between said large and small piston faces when high pressure fluid is concurrently applied thereto such that the high pressure fluid is maintained at a pressure high enough to substantially prevent gas dissolved in the high pressure fluid from forming gas bubbles, said holding device being releasable from said differential piston in response to an operating command to permit said differential piston to move from the retracted position to the forward position responsive to the forward thrust.

6 more elements

Dependencies are inferred from the claim text.