US3587393A

US3587393A - Hydraulic circuit breaker

Info

Publication number: US3587393A
Authority: US
Inventors: Ralph L Vick
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1969-12-29
Filing date: 1969-12-29
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28
Also published as: JPS544031B1; CA923404A; DE2063318C3; DE2063318B2; GB1299658A; FR2073503A1; FR2073503B1; DE2063318A1

Abstract

A CIRCUIT BREAKER DEVICE IS DISCLOSED WHICH IS INTERPOSED BETWEEN A SOURCE OF FLUID UNDER PRESSURE AND A UTILIZATION DEVICE SUCH AS AN ACTUATOR. A PISTON-TYPE SHUTOFF VALVE IS INCLUDED WHICH IS SPRING BIASED TOWARD ITS OPEN POSITION. A PAIR OF FIXED ORIFICES MEASURE THE FLOW TOWARD THE UTILIZATION DEVICE AND FROM THE UTILIZATION DEVICE TO THE RETURN SIDE OF THE FLUID PRESSURE SOURCE. THE PRESSURE DROP ACROSS THESE ORIFICES IS CONTROLLED BY MEANS OF A SLIDE VALVE BIASED IN ONE DIRECTION WITH A LIGHT SPRING. SHOULD A GREATER THAN NORMAL FLOW APPEAR DOWNSTREAM OF THE CIRCUIT BREAKER IN THE CONDUIT TO THE UTILIZATION DEVICE OR A SIGNIFICANTLY REDUCED FLOW IN THE RETURN LINE, THIS WILL BE REFLECTED IN A LOWERED PRESSURE ON ONE SIDE OF THE SHUTOFF VALVE, AND IT WILL BEGIN TO MOVE IN A CLOSING DIRECTION. DAMPING ORIFICES ARE CONNECTED TO LIMIT THE VELOCITY OF MOVEMENT OF THE SHUTOFF VALVE TO AVOID PREMATURE CLOSING DUE TO TRANSIENT CONDITIONS. WHEN THE UTILIZATION DEVICE DEMANDS A GREATER FLOW THAN REQUIRED FOR STEADY STATE OPERATION, A MOMENTARY INCREASED PRESSURE DROP APPEARS ACROSS THE SLIDE VALVE, OPENING SUBSTANTIAL ORIFICES IN PARALLEL WITH THE FIXED ORIFICES AND PERMITTING GREATER FLOW THROUGH THE CIRCUIT BREAKER SO THAT THE PRESSURE DROP REMAINS SUBSTANTIALLY CONSTANT WHILE THE REQUIRED INCREASED FLOW IS PROVIDED. THIS ALSO PERMITS FASTER MOVEMENT OF THE SHUTOFF VALVE IN CASE OF A LEAK TO AVOID EXCESSIVE LOSS OF FLUID.

Description

United States Patent [72] Inventor Ralph L. Vick Granada Hills, Calif. [2]] Appl. No. 888,692 [22] Filed Dec. 29.1969 [45] Patented June 28, 1971 173] Assignee The Bendix Corporation [54] HYDRAULIC CIRCUIT BREAKER l0 Claims,2 Drawing Figs.

[52] US. Cl 91/29, 91/420, 91/446,137/102 [51] Int. Cl ..Fl5b l1/08, F 15b 13/042 (50] Field ol'Search 91/28-30, 420,445 (PR), 445,444, 468, 446, 447; 137/100, 102 (lnquired) [56] References Cited UNITED STATES PATENTS 2,186,266 1/1940 Onions 91/420(X) 2,328,980 9/1943 Herman et a1. 91/420 2,522,481 9/1950 Martin 91/30 2,860,607 11/1958 Orlofi..... 91/445(PR) 2,872,903 2/1959 Richey 91/420 Primary ExaminerMartin P. Schwadron Assistant Examiner-Irwin C. Cohen Attorneys-Robert C. Smith and Plante, Arens, Hartz, Smith and Thompson ABSTRACT: A circuit breaker device is disclosed which is interposed between a source of fluid under pressure and a utilization device such as an actuator. A piston-type shutoff valve is included which is spring biased toward its open position. A pair of fixed orifices measure the flow toward the utilization device and from the utilization device to the return side of the fluid pressure source. The pressure drop across these orifices is controlled by means of a slide valve biased in one direction with a light spring. Should a greater than normal flow appear downstream of the circuit breaker in the conduit to the utilization device or a significantly reduced flow in the return line, this will be reflected in a lowered pressure on one side of the shutoff valve, and it will begin to move in a closing direction. Damping orifices are connected to limit the velocity of movement of the shutoff valve to avoid premature closing due to transient conditions. When the utilization device demands a greater flow than required for steady state operation, a momentary increased pressure drop appears across the slide valve, opening substantial orifices in parallel with the fixed orifices and permitting greater flow through the circuit breaker so that the pressure drop remains substantially constant while the required increased flow is provided. This also permits faster movement of the shutoff valve in case of a leak to avoid excessive loss of fluid.

IlllflDllllAULIC QIMCUIT BREAKER BACKGROUND OF THE INVENTION In large aircraft currently available and under development, many separate hydraulic actuators may be used to operate control surfaces, landing gear, and other hydraulically operated devices. In the case of actuators for control surfaces, it has become a rather common feature of design to include paralleled actuators arranged for redundant control such that if one actuator fails or sticks, another will make possible either partial or complete operation of the control surface. This large number of hydraulic actuators, of course, requires that a source of a good quantity of hydraulic fluid under pressure be available. It is apparent that the loss of a substantial proportion ofthe available hydraulic fluid may cause impairment ofa number of the actuator functions, even though redundancy is provided. There is, therefore, a need for means which will sense a loss or leakage of fluid and will act to block certain passages to eliminate this fluid loss so that a sufficient-supply will remain to operate control surfaces even though one or more actuators may be inoperative. Such a sensing and control device should not introduce substantial problems of its own, either as to operation or as to safety.

SUMMARY OF THE INVENTION Applicant has provided a hydraulic safety mechanism in the form of a circuit breaker device which sensesand responds to a flow of fluid greater than required for normal control and which is thus indicative of leaks in hydraulic conduits to block the flow offluid from the source. The circuit breaker is basi' cally a pressure conduit and return conduit flow measuring, comparing and error integrating device. The pressure conduit and return conduit flows are continually measured using the combination of fixed and variable area orifices. The resulting differential pressures are compared (summed) across a pistontype shutoff valve. Any difference between the flows above a given threshold results in movement of the shutoff valve. A predetermined value of flow error for a given period .of time will cause sufficient displacement of the piston so that the pressure conduit flow is shutoff.

During transient operation requiring .flows above steady values, a sufficient pressure is created to actuate a variable orifice assembly to provide additional variable flow-measuring areas in parallel with the fixed orifices operable in steady state conditions. These variable areas are effective during transient operation to provide damping in parallel with the fixed damping orifices. These larger variable damping areas are effective to increase the velocity of the shutoff valve to prevent excessive fluid loss while accomplishing shutoff DESCRIPTION OF THE DRAWINGS FIG. l is a schematic diagram of a simple hydraulic. circuit showing the manner in which my circuit breaker may be incorporated therein.

FIG. 2 is a sectional view of a hydraulic circuit breaker incorporating my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I, a pump I is shown for supplying fluid through a conduit 12 to an inlet port 1T3 of a hydraulic circuit breaker device shown generally at numeral M. The continuation of conduit 12 is shown as a line I6 connecting an outlet port 17 (FIG. 2) to a control valve 115 receiving a mechanical input signal from a control rod 119. Control valve supplies high pressure fluid to one side or the other of a utilization device 118 shown as an actuator or hydraulic motor including a cylinder 20, a piston 22 movable in said cylinder, and an output shaft 24 attached to the piston which may operate a control surface or perform other work. Return fluid from the actuator 18 flows through control valve 15 into a conduit 26 which is connected to a return flow inlet port 28 (FIG. 2) of the hydraulic circuit breaker flows by way of an outlet port 30 (FIG. 2), a conduit 32 containing a check valve 36, to a reservoir 35, and to the low pressure side of the pump T0.

In FIG. 2, a stepped piston shutoff valve 36 is movable in a chamber 38 which is bored to two different diameters such that four pressure-sensing chambers A0, 412, M and 46 are defined. A spring 46 in chamber 46 urges the piston valve 36 toward its open position, as shown.

Another bore 50 in the housing of circuit breaker I41 has positioned therein a manifold 52 within which is positioned a spool valve member 54 having a plurality oflands and annular passages cooperating with the manifold 52 to direct flow through several passageways to be described. A light spring 56 in a chamber 58 biases valve member 56 toward the left, as shown. Fluid at high pressure is supplied from pump It) to inlet port 13 and into a chamber 60 where it exerts a force against an area on the left end of spool valve 54 tending to urge valve 56 to the right. Fluid at this pressure is also supplied through. a passageway 62 to an annular chamber 64, which is blocked when valve 54 is positioned as shown.

A fixed orifice 66 in a passageway 66 provides restricted communication between inlet port 13 and an annular chamber 70 in manifold 52 which communicates through a passageway 72 with pressure-sensing chamber 40. An additional fixed orifice 74 in a passageway 76 connects inlet port 13 with a passage 78 which communicates with pressure chamber 38. Chamber 58 is also n communication with passage 78 through passageways 80 and 82 and annular chamber 84.

Return fluid from actuator 20 flowing through conduit 26 appears at return inlet port 28 and flows through a passage 86 and manifold 52 to an annular chamber 88 which is arranged so that the pressures acting against valve member 54 are balanced. A short passage 90communicates with an additional annular chamber 92 shown dead ended with the valve member 54 positioned as illustrated. A passage as containing an orifice 96 provides communication between chamber 92 and the return outlet port 30 which also communicates through a passage 97 with chamber 412. An additional annular chamber 96 is formed in manifold 62 which communicates with a passage I90 connected to chamber 66. Return fluid pressure in passage 86 communicates with passage 100 through a passage 102 containing a restriction IM.

In normal operation involving small corrections in the posi tion of piston 22, which may be considered steady-state operation, substantially equal flows are measured by the orifice 74 in the pressure conduit and orifice 96 in the return conduit. The differential pressure generated] across orifice 74 at required flow for steady state operation is insufficient to overcome the load of spring 56. The differential pressures across orifices 74 and 96 are summed or compared on piston valve 36 and will cause valve 36 to being moving in a closing direction if the return flow is less than the pressure line flow by more than a predetermined amount. Thus leakage downstream of the port 17 will actuate the circuit breaker into the shutoff condition. This threshold characteristic can also be used to compensate for a certain degree of unbalance in the actuator llfl. As illustrated, actuator 16 has an output shaft on one side of piston 22 which is not balanced on the opposite side. Thus, as piston 22 moves toward the left, more fluid must enter on the right side from conduit 116 than flows out of the left side into return conduit 26. This condition produces the same effect as that indicating a leak in line 26, and piston valve 36 will begin moving in a closing direction. By controlling the velocity of piston 36, as through the proper sizing of the

damping orifices

66 and 104, the piston shutoff valve will not reach a closed position until some time after the actuator has traveled full stroke. If unbalanced flows persist after the actuator reaches the end of its travel, an actual leak is indicated, and the valve 36 will close, shutting off all additional flow to the actuator. In normal operation the unbalanced flow condition will no longer prevail, the fluid pressures acting on the right end of valve 36 will increase to normal values, and piston 36 will return to the position illustrated.

During transient operation, additional flow is required above that required for steady-state operation. The additional flow demand at the actuator l8 creates sufficient differential pressure across orifice 74, and hence across the left land of spool valve So, to move the spool to the right, thus opening additional variable flow-measuring areas in parallel with orifices 74 and 96. Thus, the pressure drop across the circuit breaker remains essentially constant for transient operation even though flow through the unit may be considerably greater than for steady state.

The additional damping areas in parallel with orifices as and 104 are also needed to increase the velocity of shutoff valve 36 to prevent excessive fluid loss while accomplishing shutoff during transient operation and also to minimize pressure losses. The size of the variable area damping orifices must be sufficiently small to prevent piston valve 36 from closing too rapidly during an unbalanced actuator's maximum velocity condition or any other short duration, transient, out of balance flow conditions. However, the damping orifice areas must be large enough to allow sufficient velocity of piston shutoff valve 36 to prevent excessive fluid loss.

While the present invention has been illustrated in connection with flow to a specific unbalanced actuator, it is obviously applicable to balanced actuators, servo-controlled actuators, and other utilization devices. The housing of circuit breaker 14 is shown as a single unit, but may include separate housing structures for each of the spool valve and

manifold assembly

52, 54 and the shutoff valve 1% with passageways 72, 73, 86, 97 and extended as needed. Those skilled in the art will recognize that a number of modifications as to valving and porting are possible within the scope of the present invention. As an example, applicant has used a double poppet valve arrangement in place of the stepped motor 36, and other similar arrangements for comparing the flows across the control orifices may be used.

lclaim:

1. For use with a fluid pressure control system including a source of fluid under pressure, a fluid pressure operated utilization device, a first conduit connecting the high pressure side of said source with said utilization device and a second conduit connecting said utilization device with the return side of said source, a hydraulic circuit breaker device comprising:

a shutoff valve member disposed in said first and second conduits and movable to block said first conduit and resilient means urging said cutoff valve in an opening direction,

means measuring the flow in said first conduit and said second conduit and flow summing means associated with said valve member causing said valve member to move in a closing direction responsive to said measuring means when the flow in said first conduit exceeds the flow in said second conduit by a predetermined amount, and

control valve means disposed in said first and second conduits and effective in response to small pressure differentials reflecting increases in flow demand by said utilization device to increase the flow through said circuit breaker device to maintain a substantially constant pressure differential thereacross.

2. A hydraulic circuit breaker device as set forth in claim l wherein said flow measuring means includes restricted passage means and pressure regulating means across said restricted passage means.

3. A hydraulic circuit breaker device as set forth in claim I wherein damping means are operatively connected to said valve member for controlling its velocity of movement.

4. A hydraulic circuit breaker device as set forth in claim I wherein said control valve means comprises a valve member movable in response to changes in the differential between the fluid pressures acting in said first conduit at the inlet to said circuit breaker device and downstream of said circuit breaker.

5. A hydraulic circuit breaker device as set forth in claim 2 wherein said control valve means constitutes the pressure regulating means across said restricted passage means.

6. A hydraulic circuit breaker device as set forth in claim I wherein said flow summing means comprises, in addition to said resilient means, a first control surface on said valve member which is exposed to the fluid pressure at the inlet to said circuit breaker device, said inlet pressure acting to oppose the force of said resilient means,

a second control surface exposed to the pressure in said first conduit downstream of said circuit breaker device, said downstream pressure acting in aiding relation to the force of said resilient means,

a third control surface exposed to the pressure in said second conduit at the return side of said utilization device, said return pressure acting in aiding relationship to the force of said resilient means, and

a fourth control surface exposed to the pressure at the return side of said source.

7. A hydraulic circuit breaker device as set forth in claim 6 wherein said control valve means comprises a valve member movable in response to changes in the differential between the fluid pressures acting in said first conduit at the inlet to said circuit breaker device and downstream of said circuit breaker.

8. A hydraulic circuit breaker device as set forth in claim 6 wherein said control valve means constitutes the pressure regulating means across said restricted passage means.

9. For use with a fluid pressure control system including a source of fluid under pressure, a fluid pressure operated utilization device, a first conduit connecting the high pressure side of said source with said utilization device and a second conduit connecting said utilization device with the return side of said source, a hydraulic circuit breaker device comprising:

housing means interconnecting said first and second conduits including a first port communicating with the high pressure side of said source, a second port communicating through said first conduit with said utilization device, a third port communicating through said second conduit with said utilization device, and a fourth port communicating with the return side of said source;

a piston shutoff valve member in said housing movable to close said first conduit having a plurality of control surfaces, and resilient means acting against one of said surfaces to urge said valve member in an opening direction;

restricted passage means connecting said first port with said second port for measuring flow in said first conduit and said third port with said fourth port for measuring fiow in said second conduit, and summing means on said shutoff valve member connected with said passage means which causes said valve member to move in a closing direction when flow in said second conduit is exceeded by flow in said first conduit by a predetermined amount,

damping means operatively connected to said piston shutoff valve member for controlling its velocity of movement, and control valve means disposed in said first and second conduits and effective to open orifices in parallel with said restricted passage means in response to slight pressure differentials reflecting increases in flow demand by said utilization device to thereby maintain a substantially constant pressure differential across said housing means.

10. For use with a fluid pressure control system including a source of fluid under pressure, a fluid pressure operated utilization device, a first conduit connecting the high pressure side of said source with said utilization device and a second conduit connecting said utilization device with the return side of said source, a hydraulic circuit breaker device comprising:

housing means interconnecting said first and second circuits including a first port communicating with the high pressure side of said source, a second port communicating through said first conduit with said utilization device, a third port communicating through said second conduit with said utilization device, and a fourth port communicating with the return side of said source;

a shutoff valve member in said housing movable to block said first conduit having a plurality of control surfaces and resilient means acting against a first of said surfaces to urge said valve member in an opening direction,

with a fourth of said control surllaces against which fluid pressure acts in opposition to said resilient means, and

control valve means disposed in said first and second conduits and effective to open orifices in parallel with said second and third restricted passageways in response to slight increases in the fluid pressure differential between said first and second ports suclh that the pressure diffcrential across said housing means remains substantially constant irrespective of the flow requirements of said utilization device.