US3331383A

US3331383A - Electro-hydraulic servo valves

Info

Publication number: US3331383A
Application number: US546355A
Authority: US
Inventors: J D Buchanan
Original assignee: J D Buchanan
Current assignee: HR TEXTRON Inc A CORP OF DE
Priority date: 1966-04-29
Filing date: 1966-04-29
Publication date: 1967-07-18
Anticipated expiration: 1984-07-18

Description

July 18, 1967 J; 0. BUCHANAN 3,331,383

ELECTRO-HYDRAULI C SERVO VALVES Filed April 29, 1966 Sheets-Slugs; l

INVENTOR I W W July 18, 1967 J D. BUCHANAN ELECTRO-HYDRAULIC SERVO VALVES 5 Sheets-Shea 2 Filed April 29, 1966 VATW/KE/ July 18, 1967 J. D. BUCHANAN ELECTED-HYDRAULIC SERVO VALVES 3 Sheets-Sheet 5 Filed April 29, 1966 INVENTOR.

United States Patent 3,331,383 ELECTRQ-HYDRAULIC SERVO VALVES J. D. Buchanan, 1100 Estelle Laue, Newport Beach, Calif. 92660 Filed Apr. 29, 1966, Ser. No. 546,355 6 Claims. (Cl. 137-83) ABSTRACT OF THE DISCLOSURE Electro-hydraulic servo valve combining a polarized torque motor, controlling a jet pipe pilot valve, a rotary mounted jet receiver, a feedback lever between a power valve and the jet receiver to cause said power valve and said jet receiver to follow the pilot valve in response to an electrical signal to the torque motor.

This invention relates to electro-hydraulic servo valves, and more particularly to dry coil servo valves, as shown in my US. Patent No. 3,221,760.

In my US. Patent No. 3,221,760 and US. Patent No. 3,228,423, which use a tube in bending as the pivot between the armature and flapper, it is found that it is almost impossible to balance this design against vibrational forces which unbalance the valve.

An object of the present invention is to avoid this problem. This is accomplished by using a tube in torsion as the center of the masses.

A further object of the present invention is to eliminate a mechanical connection, more particularly a spring feedback, as shown in US Patents Nos. 2,947,268 and 2,884,- 9067, and the centering springs of the second stage valve spool of US. Patent No. 2,767,689. This improvement of the present invention makes for a more reliable valve having more sensitivity, and hence, a higher response for a given electrical input signal.

As the operating environment of servo systems increases in temperature, the elimination of as many springs as possible in the system becomes particularly important, if not an absolute necessity.

My former patent employs a flapper to control opposed pressure jets; whereas, the present invention employs an ejector jet positioned in operative association with two receptor jets. A fluid under pressure is fed to the ejector jet and means are provided to move the ejector jet in response to an electrical signal to cause more or less of the fluid emitting from the ejector jet to enter one or the other of the receptor jets. The diiferential pressure generated across the valve spool and the direction of this differential pressure will depend on the relative proportion of the flow of fluid from the ejector jet which enters the receptor jets.

A feature of the invention is the provision of a torque tube at opposite sides of the armature-ejector jet control element, these tubes being arranged on a pivot axis extending transversely of the longitudinal axis of the control element. One of the tubes acts as a dry coil element, the other tube acting as a conduit to supply high pressure liquid to the ejector jet.

A further feature of the invention is an improved feedback device wherein the receptor jets are arranged at one end of a pivoted lever, the other end thereof being actuated by the valve spool. This provides a follow-up linkage to cause the receptor jets to follow the ejector jet, whereby the spool will assume at all times a position such that the pressures in its opposed control chambers are equal. When the electrical input signal is removed, the torque action of the torque tubes serves to return the ejector jet, as well as the receptor jets, and the valve spool to null position.

A further object of the invention is to obtain a large gain in the ratio of hydraulic output flow from the power spool to the hydraulic input to the jet and thus obtain a high efficiency. This is accomplished by arranging the receptor jets on a pivotal member at a certain radius and operating the member :by a mechanical feedback arm of greater radius.

For further details of the invention, reference may be made to the drawings wherein:

FIG. 1 is a perspective view of an electro-hydraulic servo valve according to the present invention.

FIG. 2 is an enlarged sectional view on the vertical plane indicated by the lines 22 in FIG. 1.

FIG. 3 is a bottom view indicated by line 3-3 in FIG. 2.

FIG. 4 is a sectional view on line 44 of FIG. 2.

FIG. 5 is a top view as indicated by the line 55 in FIG. 4.

FIGS. 6 and 7 are schematic diagrams showing the parts in different positions for different electrical inputs.

FIG. 8 is a partial view showing the fluid path 29 in the jet spool 34 from receptor jet 5 to the annular passage or channel 46, the similar path 28 and channel 37 for the other receptor jet 4 being shown in FIG. 4.

Referring in detail to the drawings, the electro-hydraulic valve 1 comprises, in general, a torque motor, or polarized relay 2 which operates an ejector jet 3 ifi association with receptor jets 4 and 5 which admit pressure to the opposite ends 6 and 7 of the power spool, or valve spool 8, see FIG. 2. The power spool 8 has a mechanical feedback device 9 for the receptor jets 4 and 5.

The torque motor 2 has permanent magnets 10 and 11, as well known, for the armature 12 which has a pivotal support generally indicated at 13 and described in detail later. The pivotal support 13 includes a torque tube 14 and a torque tube 15 on the pivot axis at opposite sides of the ejector jet 3. The lower end of armature 12 has a lateral extension 16 which is fixed to one side of the body of jet 3, as indicated at 17. Surrounding the extension 16, and coaxial with it, is the torque tube 14 which is secured on a base 18 of the extension 16, at one end, the other end of torque tube 14, as indicated at 19, being secured in a bore 20 of the cap, or first stage body 21. Cap 21 is secured on the top of the base, or second stage body, 22 of the casing by means of bolts like 23 and 24, see FIG. 2. The torque motor has a cover 61.

The interior of torque tube 14 opens into a chamber 25 in the cap 21, this chamber mating with a similar chamber 26 in the base 22. The ejector jet 3 and the receptor jets 4 and 5 open into the

chambers

25 and 26 which act as a return chamber to contain the fluid from these jets.

The lateral extension 16 offsets armature 12 from ejector jet 3 armature 12 and jet 3 extending in opposite directions from extension 16. Rotary member 34 is parallel to extension 16 with feedback arm 53 offset from receptor jet 4, whereby feedback arm 53 swings in a plane passing through the center of coil 27, and the center of the cylinder for the power spool is centered with the axis of the coil 27.

The torque tube 14 thus serves the double purpose of sealing off the fluid pressure in

chamber

25 and 26 from the winding 27 of the torque motor 2 as well as providing spring tension which cooperates with the torque tube 15 to urge the ejector jet 3 to null position. The torque tube 15 assists the torque tube 14, as described, in providing a pivotal support for the ejector jet 3 and for urging it to null position, torque tube 15 also serving the additional function of acting as a conduit for high pressure fluid for the ejector jet 3. The jet 3 has a longitudinal axial passage 30 which connects with one end of the tube 15, the other end of tube 15 being fixed, as indicated at 31, in the cap 21 connecting with a passageway 32 which terminates at the inlet marked P P 3 which connects with the inlet pressure P, as shown in the schematic FIGURES 6 and 7. The passage 32 is formed partly in the base 22 and partly in the cap 21, as shown in FIG. 4. Passage 32 is provided with a suitable orifice 33 which reduces the pressure to a suitable value for the jet 3.

As described in my former patent, and as well known, the windings 27 of the torque motor 2 are connected in asuitable manner to an electrical signal producing system which supplies an electrical control signal for swinging the armature 12 about the axis of the

torque tubes

14 and 15. The direction of rotation of armature 12 and consequently of the jet 3 is in accord with the direction of the electrical signal input to the windings 27. The length of the are through which the armature 12 is rotated will be directly proportional to the magnitude of the electrical control signal supplied to the windings 27. The torque tubes 14 and provide a mechanical spring force which resists rotation of the armature 12. When the electrical control signal is cut ofi, the

torque tubes

14 and 15 act to return the armature 12 and the ejector jet 3 to null position.

As shown in FIG. 2, the receptor jets 4 and 5 are longitudinally spaced in the direction of the longitudinal axis of the power spool 8. The jets 4 and 5 are arranged at one end of a cylindrical rotary member 34 which rotates on an axis parallel to the axis of the

torque tubes

14 and 15, being, rotatably carried in a bearing bore 35 in an extension 36 of the cap 21. Extension 36 acts as a support and wall between the return chambers 26 and 52.

As shown in FIGS. 2, 4, 6 and 7, receptor jet 4 connects with a longitudinal and radial passage 28 in the rotary member 34, this passage opening to an annular passage 37 in the periphery of rotary member 34, passage 37 connecting with passage 38 in the extension 36, that passage connecting with passage 39 in the base 22, passage 39 leading to the passage 40 at the end of sleeve 41 in which the power spool 8 reciprocates. The passage 40 connects with a passage 42 at the end of a hollow spacer 43 having a port 44 in its end cap, this port opening into the space 45 at the left end of the power spool 8. Ports 44 and 50 have a stabilizing action, as well known.

The other jet 5 similarly leads to the opposite end of the power spool, or valve spool 8, via the following: passage 29 in the jet spool 34, annular passage 46 in the periphery of rotary member 34, passage 47 in second stage body 22, and passages 48, 49 and 50 leading to the right end of the power spool 8, similar to the

passages

40, 42 and port 44, previously described. The lower end of the extension 36 fits on the upper surface of the bottom wall 51 of a cavity in the base 22, a portion of this cavity consisting of the pressure chamber 26, as previously described, another portion of this cavity consisting of a chamber 52 into which one end of the rotary member 34 projects, as shown in FIG. 4. This projecting end of 34 has a depending mechanical feedback arm 53 which terminates in a ball 54 which frictionally has a bearing fit between the

annular shoulders

55 and 56, as shown in FIG. 2. These shoulders are provided by spaced collars arranged at the middle portion of the power spool 8. The feedback control of the receptor jets 4 and 5 is thus obtained through the coupling by the shoulders 55,

56 and the ball 54 on the arm 53 of the rotary member 34. Movement of the power spool in one direction, or the other, due to an electrical input which changes the position of the ejector jet 3 results in favoring the pressure at one end or the other of the power spool, the resultant movement of the power spool being accompanied by a corresponding movement of the receptor jets 4 and 5. The power spool 8 thus receives maximum pressure at its opposite ends for the null position and for all displaced positions of the receptor jets 4 and 5.

The annular grooves or channels 37 and 46 are housed in the bearing bore 35 in the wall 36. The fluid pressure is hydraulically balanced in each of the annular peripheral grooves or channels 37 and 46 in jet spool 34 for the reason that fluid pressure existing at any point in the periphery of such groove or channel is balanced by an equal and opposite pressure at a diametrically opposite position on the spool. Thus, the position of the jet spool 34 is not influenced in any way by the fluid pressure from the receptor jets to the power spool.

The opposite ends of the base 22 are closed by caps 57 and 58 held in position by suitable bolts, as indicated at 59 and 6t 7 As shown in FIGS. 6 and 7, the jets 4 and 5 remain centered with the jet 3 in all actuated positions of the ejector jet 3.

FIGS. 6 and 7 illustrate a well known arrangement wherein the power spool 8 receives pressure from the inlet P, acting to control pressure to or from cylinders having passages indicated at C and C and exhaust or return, indicated at R.

As previously noted, the mass at opposite sides of the pivot provided by the axis of the

torque tubes

14 and 15, namely the mass of the armature, as compared to the jet 3, may be substantially equal, thus providing mass balance.

Also, as previously noted, the radial length of the ball 54 from the axis of rotary member 34 is large compared to the radial length of the receptor jets 4 and 5 from that axis which is conducive to high efficiency, as previously explained.

From FIGS. 6 and 7 it is apparent that movement of jet 3 in one direction causes power spool 8 to move in the opposite direction, the latter acting on the pivoted feedback arm 53 to move the jets 4 and 5 in the opposite direction to that of the power spool 8, namely in the same direction as jet 3.

I claim:

1. An electro-hydraulic servo valve including the combination of a pilot valve and a power spool, the pilot valve having a polarized relay having a winding and a swinger with an extension having an ejector jet, the power spool controlling cylinder and exhaust ports, the power spool having opposed pressure chambers supplied with fluid under pressure from receptor jets associated with the ejector jet, the improvement wherein said receptor jets are supported by a cylindrical member rotary about a longitudinal axis, wall means providing a bearing support for said cylindrical member, a casing having a cavity, said wall means dividing said cavity into two chambers, one end of said cylindrical member with said receptor jets extending into one of said chambers, the

other end of said cylindrical member extending into the other chamber, where a feedback arm on said cylindrical member is provided for said power spool, and said feedback arm being controlled by said power spool for causing said receptor jets to follow said ejector jet.

2..An electro-hydraulic servo valve comprising an electrically controlled ejector jet, a receptor jet device having receptor jets for said ejector jet, a power spool having opposed pressure chambers supplied with high pressure fluid from said receptor jets, said receptor jet device being in the form of a rotary cylindrical member, a wall having a bearing support for said rotary member, a casing member having a cavity, said wall dividing said cavity into two chambers, said rotary member having one end in one chamber with a feedback connection to said power spool, said one chamber being connected to a return chamber of said power spool, said receptor jets being on the other end of said rotary member in the other chamber, said rotary member having a pair of annular peripheral channels housed in said wall, each of said channels being in a fluid pressure path from one of said receptor jets to the corresponding pressure chamber of said power spool, whereby said spool is hydraulically balanced for fluid pressure in said path.

3. An electro-hydraulic servo valve according to claim 2, said casing member which has said cavity being a second stage body housing said power spool, said wall being an extension on a first stage body for said second stage body, said wall having an inner end abutting a bottom Wall of said cavity, said first stage body having a pivotal support for said ejector jet.

4. An electro-hydraulic servo Valve comprising an electrically controlled ejector jet, a receptor jet device having receptor jets for said ejected jet, a power spool having opposed pressure chambers supplied with high pressure fluid from said receptor jets, said receptor jet device being in the form of a rotary cylindrical member, a wall having a bearing support for said rotary member, a casing member having a cavity, said wall dividing said cavity into two chambers, said cylindrical member having one end in one chamber with a feedback connection to said power spool, said one chamber being connected to a return chamber of said power spool, said receptor jets being on the other end of said cylindrical member in the other chamber, said cylindrical member having a pair of annular peripheral channels housed in said wall, a fluid passage in said cylindrical member from each of said receptor jets to one of said channels, a fluid passage in said wall connecting one of said channels with a fluid passage in said casing member and the pressure chamber at one end of said power spool, and another fluid passage in said Wall connecting the other channel with a fluid passage in said casing member and the pressure chamber at the other end of said power spool, whereby said jet spool is hydraulically balanced for fluid pressure from said receptor jets to said power spool.

5. An electro-hydraulic servo valve comprising an ejector jet, a torque motor controlling said ejector jet, a receptor jet device having receptor jets for said ejector jet, a power spool having opposed pressure chambers supplied with high pressure fluid from said receptor jets, said receptor jet device being in the form of a rotary cylindrical member, a wall having a bearing support for said cylindrical member, a casing member having a chamher at each side of said wall, said cylindrical member having one end in one chamber with a feedback link con nected to said power spool, said jets being on one side of said cylindrical member and said feedback link being on the other side of said cylindrical member, said one chamber being connected to a return chamber for said power spool, said receptor jets being on the other end of said cylindrical member in the other chamber.

6. An electro-hydraulic servo valve including the combination of a pilot valve and a power spool, the pilot valve having a polarized relay having a winding and a swinger with an armature having an ejector jet, the power spool controlling cylinder and exhaust ports, the power spool having opposed pressure chambers supplied with fluid under pressure from receptor jets associated with the ejector jets, the improvement wherein said armature has a lateral extension for said ejector jet, said armature and said ejector jet being laterally oflset from each other and extending in opposite directions from said lateral extension, and torque tube means are provided for pivotally supporting said swinger on an axis extending transversely of the longitudinal axis of said swinger, said transverse axis being located at a position providing balance of the masses of said swinger at opposite sides of said transverse axis, a rotary cylindrical member having a longitudinal axis substantially parallel to the axis of said lateral extension, said rotary member having receptor jets for said ejector jet on one end thereof and having a feedback arm on the other end thereof for said power spool, said power spool having a cylinder centrally located with respect to the axis of said winding, said feedback arm swinging in a plane passing through the axis of said winding.

References Cited UNITED STATES PATENTS 2,724,397 11/ 1955 Ziebolz 13783 2,742,022 4/1956 Jacques 13783 3,017,864 1/1962 Atchley 91-3 3,137,309 6/1964 Blase 13783 3,205,782 9/1965 Tourtellotte 91-3 3,211,182 10/1965 Gyurik 137-625.61 3,233,623 2/1966 Gray 137625.62 X

ALAN COHAN, Primary Examiner.

Claims

1. AN ELECTRO-HYDRAULIC SERVO VALVE INCLUDING THE COMBINATION OF A PILOT VALVE AND A POWER SPOOL, THE PILOT VALVE HAVING A POLARIZED RELAY HAVING A WINDING AND A SWINGER WITH AN EXTENSION HAVING AN EJECTOR JET, THE POWER SPOOL CONTROLLING CYLINDER AND EXHAUST PORTS, THE POWER SPOOL HAVING OPPOSED PRESSURE CHAMBERS SUPPLIED WITH FLUID UNDER PRESSURE FROM RECEPTOR JETS ASSOCIATED WITH THE EJECTOR JET, THE IMPROVEMENT WHEREIN SAID RECEPTOR JETS ARE SUPPORTED BY A CYLINDRICAL MEMBER ROTARY ABOUT A LONGITUDINAL AXIS, WALL MEANS PROVIDING A BEARING SUPPORT FOR SAID CYLINDRICAL MEMBER, A CASING HAVING A CAVITY, SAID WALL MEANS DIVIDING SAID CAVITY INTO TWO CHAMBERS, ONE END OF SAID CYLINDRICAL MEMBER WITH SAID RECEPTOR JETS EXTENDING INTO ONE OF SAID CHAMBERS, THE OTHER END OF SAID CYLINDRICAL MEMBER EXTENDING INTO THE OTHER CHAMBER, WHERE A FEEDBACK ARM ON SAID CYLINDRICAL MEMBER IS PROVIDED FOR SAID POWER SPOOL, AND SAID FEEDBACK ARM BEING CONTROLLED BY SAID POWER SPOOL FOR CAUSING SAID RECEPTOR JETS TO FOLLOW SAID EJECTOR JET.