US2939283A - Self-contained power actuator - Google Patents

Description

June 7, 1960 B. N. ASHTON SELF-CONTAINED POWER AcTUAToR Filed Feb. 14, 1957 United States Patent O Benjamin N. Ashton, Kingston, N.Y., assgnor to Electrol Incorporated, Kingston, N.Y., a corporation of Delaware Filed Feb. 14, 1957, ser'. No. 640,124

s claims. (cl. so-52) This invention relates to improvements in hydraulic actuators and more particularly to improvements in electromagnetically operated hydraulic actuators in which both electromagnetic and hydraulic components are incorporated in self-contained units.

Self-contained hydraulic actuators are used, for example, to operate control surfaces and other movable parts of airplanes, a number of actuators being provided for each plane. In this fashion, the planes are freed of extensive, complex networks of relatively delicate hydraulic tubing, the damaging of any part of which could possibly render an entire control system inoperative. Also, being controlled electrically, a large number of self-contained hydraulic actuators can be operated from one or more remote control centers without introducing prohibitive equipment bulk or weight at the centers. A representative self-contained hydraulic actuator is illustrated and described in U.S. Patent No. 2,672,731. The present invention represents an improvement in the form of simpliiication in both operation and construction of the actuator of said patent.

In accordance with the present invention an array of electromagnetically controlled selector valves are incorporated in a common housing with a hydraulic jack, a fluid reservoir, and a motor driven pump, all interconnected by ducts. .The electrical control circuit is so arranged that Ithe motor driven pump and the selector valves can be energized -in leither of two combinations of ways, depending upon the position the hydraulic jack is to assume. The cross-connected selector valves are so arranged that they are closed at all times, with electromagnetic means acting to relieve in part the spring forces normally imposed thereon. The pressure of the hydraulic iluid is utilized to overcome the spring forces remaining on the particular valves chosen for actuation by the control circuit. The jack and the electrical control system are coupled by a mechanical linkage which establishes the limit position for the jack, while the remote control switch means for initiating movement of the jack to either extreme is highly simplifiedV to minimize remote Wiring connections. L

l-A representativeembodiment of the invention in the form of a self-contained, electromagnetically controlled hydraulic `actuator is described below having reference to the accompanying drawing in which:

Figurel is a view in side elevation partly broken away in vertical section, and also partly diagrammatic in form to show continuous duct paths in a common plane, of a hydraulic actuator; and

Figure 2 is a wiring diagram of the electromagnetic control circuit of the hydraulic actuator of Figure 1.

Referring to Figure 1, the hydraulic actuator formed in accordance with the present invention comprises a unitary housing assembly including a hydraulically driven motor such as a hydraulic jack 10, including a piston 11 and an output connecting rod 11a, a fluid reservoir or tank 12, including pressurizing means 13 and limit control Patented une 7,- 1960 ice switch means ,14, a selector valve array 15, a hydraulic pump 16 and a motor 17.

The selector valve array 15 includes four valves 18a, 18b, 18C, and 18d, of which the former two are paired for complementary action as are the latter two. The actuating means for each of the four valves canV be substantially identical, as shown, and only one actuating assembly is, therefore, described in detail. Like parts of the other valves are identified in part by like reference numbers modified, however, by appropriate sub-case letters. The valve 18a, which can take the form of a ball, is urged against its seat 19a, by a cup-shaped head 20a engaged by the outer end of a plunger 21a movable in and out of a core 22a of a solenoidwinding 23a. vThe plunger 21a is urged outwardly of the core of the winding 23a by means of a compression spring 24a and also by means of a compression spring 25a compressed between the cup-shaped head 20a and the outermost surface 26a of the casing 27a for the solenoid.

The valves 18a and 18d are cross-connected by a duct 28 in opposed fashion so that positive hydraulic pressure in the duct will tend to unseat the valve 18a and seat the valve 18d. The valves 18b and 18c are similarly crossconnected by a duct 29, positive 'fluid pressure therein tending to seat the former and unseat the latter.

The pump 16 includes an inlet or suction connector 30 jointed by a duct 31 to the iluid reservoir 12, by a duct 32 to the inner side of the valve 18e, and by a duct 33 to the inner side of the valve 18a (the duct 33 passing -around the chamber of the valve 18d without connection thereto). The pump ,16 has an outlet or pressure connector 34 connected by a duct 35 to the outer side of the valve 18d and by a duct 36 to the outer side of the valve 18b.

A pressure relief valve assembly 37 is provided between the ducts 31 and 35 to guard the pressure line against excessive pressure surges and a pair of thermal relief valve assemblies 38 and 39 are provided respectively between the ducts 29 and 32 and 28 and 311 to prevent excessive pressure rise due to thermal expansion of iluid on either side of the piston 11 in the cylinder of the jack 10. It will be observed that the duct 29 connects t0 the right hand side or out stroke space of the cylinder of the jack 10 whereas the duct 28 connects to the left hand or in stroke side. When the thermal relief valves -38 and 39 open, pressure lis relieved via ducts 32 and 31, respectively, to the iluid reservoir 12.

The reservoir 12 is closed at its right hand end by a fixed barrier 40 and atits left hand end by means of a piston 41 urged to the right by a compression spring 41a. The piston 41 is slidably mounted on a iixed sleeve 42 joined to the barrier 40 at its right hand end and to a mounting -tting `43a for the limit switch means V14 at its left. Suitable seals are Provided throughout to prevent the passage of huid. The tank 12 thus acts as a pressurized reservoir in which fluid pressure is continuously maintained through the action of the spring 41a.

The piston 11 has connected to its right hand side the connecting rod 11a and to its left hand side a hollow tube or sleeve 43 which passes slidably through the ixed barrier 40 in iluid tight relationship of terminate wit-hin the sleeve 42 in an apertured, shouldered head `44. The sleeve 43, which is concentrically and slidably received within the iixed sleeve 42, receives in turn a switchactuating rod 45 having a head 46 for operating the limit switch means 14. The limit switch means 14 can take the form of a double-throw push button switch having one pair of contacts, as described below, normally closed by spring action and another pair normally open. The switch 14, which is carried by the fitting 43a, is received in a chamber 47 in an end cap48 for the pressurizing means 13 and includes a push button 49 adapted to be y engaged by the headr46 of the rod 45 to close its normally opencontacts when the jack 10 is disposed in its in-stroke A assasss insideright hand end of the slidable sleevef43.y whenv the jack is initsin-st-roke position. (as .shown-)t The shoulder 50ais adapted to be engaged bythe shoulderedf head 44 on theinsideleft hand end ofY the. sleeve 43. when the jack is moved to its out-stroke position,ktherehyv to Vshift the Vrod 4S'to the right to release the push button 49 of the Y groove 52a. Y Y Y In order to remove airfrom the system a pair of bleed plugs 65 and 66 are respectively connected to'the'ducts 28 and 29, thereby protecting'bothy the out-and-in-stroke spaces of the cylinder of the hydraulic jack 10.

Referring, in particular, to the wiring diagram of Figure 2, there is 'shown' a suitable source of electrical power such as a battery 52, one terminal of which is connected by a conductor 53 to one terminal of the motorY 17 andto one terminal of each of the four solenoid windings 23a, 23b, 23e, and 23d, and other Vternu'nal of which is connected by a conductor 54 to the movable contact 55 of the double-throwV push button-type limit switch means 14. The limit switch means 14 includes a stationary contact 56, to which the movable contact 55 is normally biased by the inherent spring pressure, andV a second lixed contact 57 to which the movable contact 55 is forced by the action of the switch actuating rod 45 on the push button 49 (Figure 1).V The iixed contacts 56 and 57 of the switch means 14 areeconnected by conductors 58 and 59 respectively to'xed contacts 60 and 61. of a remote control switch 62 which can take the form of a simple double-throw toggle switch.' The conductor 58 is also Y connected tothe second terminals of the solenoid'wind- .ings' 23a and 23h and the conductor 59 isV also connected to the second terminals of the solenoid windings 23'c and 23d. The double-throw toggle switch 62 includes a movable contact 63 connected by a conductor 64 to the second terminal of the motor .17 which, it Will be recalled, drives the hydraulic pump 16. Y

In operation, assuming the hydraulic jack 10 to heV disposed at its Yin-stroke extreme, as indicated in'` the drawing, in which the contacts 60 and 63 of the toggle switch 62 are closed and contacts V55 and 57' ofthe push button switch 14 are also closed, action is initiated to drive the piston 11 to the right by throwing the movable contact 63 `of the toggle switch 62 to the contact 61 to completea circuit across the terminals of the motor 17 and across the terminals of the solenoid windings Y23C Y and 23d. The plungcrs 21e and 21d are thus drawn into their corresponding solenoid windings against the action ofV the compression springs 24s` and 24d, respectively.

' because the latteru valveis' huelda closed" by the' mbined forces of the springs24b and 25b. The opening of the valve 18d admits iluid under pressurer to the inner or left hand side of the piston 11 through the duct28, driving the piston to the right.V The Ifluid disposed on the outer or right hand side of the piston 11 is forced through the duct 2,9 against theY unseating side of the valve 18e, which it will be recalled, has been: relieved of part of its spring closingforcev due to.- the.- energizationr of the solenoid winding 23e. The opening of the valve 18C establishes a iiowofjliuid through the duct`32to` the duct 31 and back to the suction connector 30V of`thel.op'eratingpumpY 16. Extra quantities of uid can ow to the reservoir via the duct 31:' or a deliciency' canybe made up from the reservoir. p Y p At the end of the out-strokel of the piston 11, the shouldered head 44 on the sliding sleeve 43, which moves with the piston 11, engages the shoulder 50a on the switch actuating rod 45 and moves itto the right4 to release the push button 49 of the limit switch means 14. This re sults in movement ofthe contact of that switch from the cont-act 57 to the contact 56 to deenergize the. motor 17 as well as the solenoid windings `23e and23d.

The hydraulic jack 10,A will, therefore, remain in its extended position until such time' as the toggle switch 63 is thrown back to the contact k60 to energize the motor 17 and the solenoid. windings 23a and 23b through the then closed contacts 55 and 56 of theV double-throw push button switch 14.V The pressure in Vthe duct 36 is then able to lift the valve 18b, because the force of the spring 24b has been relieved therefrom, to direct a flow of uid under pressure through therduct 29l to' the-out-stroke side of the piston 11 driving it tothe left. Movement of the piston 1'1 to the leftdrivestheliuid on that side ofthe pistonthrough theV duct 28 to the'unseating side of the valve 18a which, Yrelieved ofpart of its spring closing pressure, unseats topass.- theV fluid flow through the duct 33 to the duct 31 from-whichY point it` tlows, as needed, to the suction connector v350 of the pump.16. Surplus fluid can returnto the reservoir.. through the duct. 31V or a deficiency obtained fromthe reservoir through the same duct. Movement of the jack continues until such time as theshoul'der 44a ofv the right hand end of the sleeve 43 engages shoulder'` 50h on the push rod 45 to force its head 46 against the push button 49 to close the contacts 55 and 57- of the switch 14 to deenergize the moto-r 17 and the solenoidY windings 23a and 23h, thereby conditioning the system for the next action of ,the toggle switch 62. Y Y

It will be understood, therefore, that a highly simplified self-contained hydraulic .actuator is providedr in accordwhich the valve actionV is controlled partly hydraulically The valves 18e and 18d remain urged/against their'seats only by the action of the second compression springs 25C and 25b acting onV the cup-shaped, ball-engaging members 20c and 20a?,V respectively, the plungers 21o and"21d having been withdrawn from the cup-'shaped members. j The gear pump 16, driven by the energized electric motor 17 sucks uid from the reservoir 12 through the duct 31 and the inlet connector' 3G and delivers it through the pressure connector 34. to the Yducts 35 and 36. The uid pressure opens the valve 18d, which has been relieved of part of its spring lbiasing pressure, Vbut does not open thevalve 18 b (to which the duct 35 also; comnninicates)l and'partly electromagnetically. It. willbeeunderstood also that the installation of thez hydraulic-actuator requires, in additionof courseto the physical attachment of the actuator frame adjacentthe movable part to be driven thereby, only the connection of an electrical cable through suitable fittings 67` and68. This cable need include only tive wires, two from the Vpower source 52 and three from the remote control toggleY switch 62.A

The general arrangement of the elements of the hydraulic actuator can be modified to conform to the conditions under which it Yis used and it can be made in various sizes and forms without departing from the invention, which should not, therefore, be regarded .as limited except as defined by thefollowing claims.

Iclaim: l Y

1. In a hydraulic actuator, a hydraulically driven motor, and means to establish a Huid pressure diierential across the motor comprising, a source of uid pressure dilerential, rst and second ducts respectively connecting the same side of said Lsource to opposite sides of Vsaid motor, first, and second selectorvalve means disposed respectively in the first and second ducts, each selector valve means including at least two mutually independent spring means to close the valve against the uid pressure differential, and control means to selec tively release one of the spring means from either one of the valves to enable that Valve to be opened by the pressure differential.

2. A hydraulic actuator as set forth in claim 1, each of said valves comprising a movable valve member, said first spring means urging the valve member to its closed position, a plunger to detachably engage the valve member, said second spring urging the plunger toward the valve to close the latter, and a solenoid winding to urge the plunger away from the member.

3. A hydraulic actuator as-set forth in claim 1, including third and fourth duct means respectively connecting the other side of the pressure differential source to opposite sides of the motor, third and fourth selector valve means disposed respectively in the third and fourth duct means, each selector valve means including at least two mutually independent spring means to close the valve against the uid pressure differential, said control means being operative to selectively release one of the spring means from either the rst and third valve means or the second and fourth valve means to enable liuid under pressure to pass in either of two directions through the motor,

4. A hydraulic actuator as set forth in claim 3, said means .to establish the source of pressure differential including a pump and said hydraulically driven motor comprising a cylinder and piston, means to energize the pump, and means responsive to completion of a stroke of the piston to deenergize the pump and to reapply the released spring means.

5. A hydraulic actuator as set forth in claim 4, each of said four valve means comprising a movable valve member, said rst spring means urging the valve member to its closed position, a plunger to detachably engage the valve member, said second spring urging the plunger toward the valve to close the latter, and a solenoid winding to urge the plunger away from the member.

6. In a hydraulic actuator, a hydraulically driven motor, and means to establish a uid pressure differential across the motor comprising a source of iluid pressure differential, lirst and second ducts respectively connecting the same side of said source to opposite sides of said motor, first and second selector valve means disposed respectively in the rst and second ducts, third and fourth duct means respectively connecting the other side of the pressure differential source to opposite sides of the motor, third and fourth selector valve means disposed respectively -in the third and fourth duct means, each of said selector valve means including double spring means to close the valve against the liuid pressure, and control means to selectively relieve the pressure of one of the spring means from either said rst and third valve means and either the second and fourth valve means to enable those valve means having spring pressure relieved thereon to be opened bythe uid pressure differential.

References Cited in the le of this patent UNITED STATES PATENTS 1,845,176 Palm ...t Peb. 16, 1932 1,849,044 Summey Mar. 8, 1932 1,970,286 Dunn Aug, 14, 1934 2,096,574 Denny Oct. 19, 1937 2,443,568 Palm I-- June 15', 1948 2,455,948 Ray Dec. 14, 1948 2,486,707 Elkington Nov. 1, 1949 2,529,777 Mclnnis VNov. 14, 1950 2,597,050 Audemar May 20, 1952- 2,633,871 Parsons ..Y.-----.....- Apr. 7, 1953

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