United States Patent 3621880

Disclosed is a jet pipe-type servo valve wherein the feed tube is disposed angularly with respect to a flapper to which it is affixed and which is movable by a torque motor the armature of which is connected to the flapper. The feed tube has one end thereof affixed rigidly to the housing and the other end thereof terminating in a nozzle which is positioned adjacent a receiver. The output ports of the receiver are connected to the end chambers of a cylinder within which a power control valve is slidably positioned so as to control the flow of fluid under pressure from a source thereof to an apparatus to be positioned such as an actuator. The jet pipe stage and the power control valve stage are isolated from each other.

Jessee, James M. (Granada Hills, CA)
Niederer, Ernest (Hollywood, CA)
Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
137/83, 137/625.63
International Classes:
F15B13/043; (IPC1-7): F15B13/044
Field of Search:
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US Patent References:

Primary Examiner:
Cohan, Alan
What is claimed is

1. A jet pipe servovalve comprising:


Jet pipe servovalves have long been known and typical examples of such apparatus are shown in U.S. Pat. Nos. 2,884,906; 2,884,907; 2,996,072 and 3,017,864. As can be seen from these prior art patents, typical jet pipe servovalves are constructed in such a manner that the feed tube and the armature of the torque motor are an integral unit or at the most the feed tube is axially an extension of the torque motor armature. As a result the degree of movement of the nozzle tip, which terminates the feed tube, is limited by the amount of movement of the armature in the torque motor. Furthermore, alignment between the jet pipe nozzle orifice and the receiver ports is somewhat difficult to obtain and there is little or no adjustment available.


FIG. 1 is a schematic diagram shown in perspective of a jet pipe servovalve constructed in accordance with the present invention;

FIG. 2 is a cross-sectional view of the servovalve illustrated in FIG. 1, taken about the line 2--2;

FIG. 3 is a fragmentary cross-sectional view taken about the line 3--3 of FIG. 2; and

FIG. 4 is a cross-sectional view taken about the line 4--4 of FIG. 2.


Referring now to FIG. 1 there is illustrated a jet pipe servovalve which includes a torque motor 11 having pole pieces 12 and 13 with an armature 14 disposed therebetween. A pair of coils 15 and 16 are disposed to received an input signal upon leads 17 thereby to provide movement of the armature and, as indicated by the arrow 18, which is proportional to the magnitude of the input signal.

A flapper 21 is rigidly connected to the armature 14 so as to move as indicated by the arrow 20 in response to movement of the armature 14. The flapper 21 is suspended within a torque tube 22 so as to provide a seal between the fluid sections of the servovalve and the torque motor. Such a suspension is well known and, for example, is illustrated in U.S. Pat. No. 3,221,760. A feed tube 23 has one end thereof rigidly affixed to a retainer member 24 which in turn is rigidly affixed to the body portion 25 of the housing. The feed tube 23 is constructed of a hollow flexure tube which is movable with respect to the housing. Movement is imparted to the tube 23 by way of a flexible connection such as the link or spring clip 26 which is rigidly affixed to the flapper 21, but is releasably attached to the tube 23 by being inserted through an opening 27 defined by the clip 26. Thus, as the flapper 21 moves the feed tube 23 also is caused to move as indicated by the arrow 28. As is illustrated by the difference in arrows 20 and 28, the mechanical interconnection provides amplification of movement of the nozzle tip as compared to the flapper 21. Thus, small armature movement results in larger nozzle tip movement. The feed tube terminates in an ejector end having a nozzle 29 which is positioned adjacent openings 31 in a receiver port means 32.

Fluid under pressure is provided from a source thereof (not shown) through conduits 33 and 34 to the fixed or receiving end portion of the feed tube 23. As the nozzle 29 moves with respect to the receiver ports 31, differential pressure is applied through conduits 35 and 36 to the end chambers 37 and 38, respectively, of the power control valve spool shown generally at 40. The structure of a flow control valve spool is well known in the prior art and, for example, detailed description thereof may be found in the above referenced patents. Generally movement of the valve spool 41 in response to differential pressure thereacross in the end chambers 37 and 38 as indicated by the arrow 42, causes fluid under pressure to flow through the conduits 33, and 43 or 44 to an actuator connected to cylinder ports 45 and 46 depending upon the direction of movement of the valve 41. As the valve 41 thusly moves, such movement is transmitted by way of a feedback spring 47 which is affixed to the armature 14.

Referring now more particularly to FIG. 2, the manner in which the feed tube is rigidly affixed to the body 25 is illustrated. As is therein illustrated, the end 51 of the feed tube is rigidly affixed as by brazing or the like to an opening 52 provided in the retainer 24. The retainer 24 defines a bevelled surface 53 which mates with a bevelled shoulder 54 defined by the bore 55 into which the retainer 24 is inserted. The retainer 24 defines a reentrant bore 56 which receives a cup-shaped member 57 defining a restriction orifice 58, the function of which is well known in the art. It should be understood that the restriction orifice is used only in instances of high fluid pressure where it is deemed desirable to drop some pressure prior to the fluid reaching the nozzle orifice. A plug 59 is also received within the bore 55 and is utilized to force the surface 53 into engagement with the shoulder 54 thereby effecting a metal-to-metal seal against the leakage of fluid under pressure. This function is accomplished through the shoulder 62 which abuts the end edge 63 of the retainer 24. A lock screw 64 is then threaded into the bore 55 and urges the plug 59 against the retainer 24 thereby causing the entire assembly to firmly seat in place. A wire screen filter 65 is seated within a reduced diameter area of the retainer 24 and is also held in place by the plug 59. Fluid under pressure enters the body 25 through an opening 66 provided therein. An auxiliary opening 67 is also provided in the body and communicates between the opening 66 and the reentrant bore 56 provided in the retainer 24 through the openings 68 formed in the rear edge 63 of the retainer 24.

As is also illustrated in FIG. 2, the valve spool 41 is slidably disposed within a sleeve 71 which is seated within a bore 72 provided in the body 25. The sleeve 71 is provided with a land 73 which provides a seal about an opening 74 defined by the body 25 and through which the feedback spring 47 passes. The land 73 is relieved to provide an opening 75 through which the feedback spring 47 also passes. As is illustrated, the feedback spring 47 terminates in a ball 76 which is disposed within an opening 77 provided in the spool valve 41. As is clear from FIGS. 1 and 2, the feed tube is positioned solely within the body of the housing thus eliminating the usual external plumbing to provide fluid under pressure to the feed tube.

By reference to FIG. 3, a more detailed understanding in the manner which the feed tube 23 is connected to the flapper 21 can be had. As is therein shown, the spring clip 26 comprises a body section 81 terminating in one end portion 82 which is wrapped around the flapper 21 and is rigidly affixed thereto as by brazing or the like. The body 81 terminates in a second end portion 83 which is bent so as to provide a V-shaped section with the body portion 81. The body 81 and the end portion 83 each define axially aligned openings therethrough and through which the feed tube 23 is disposed. The end portion 83 may be compressed toward the body section 81 to align the various portions of the apparatus. Once such alignment has occurred, the end portion 83 may be released and the spring tension of the body portion 81 and the end portion 83 moving outwardly causes the spring clip 26 to grip the feed tube 23 and holds it firmly in place with respect to the flapper 21. As can clearly be seen the axes of the feed tube 23 and the flapper 21 are offset and nonintersecting.

Referring now more particularly to FIG. 4, various details, as above described, are further illustrated and particularly the valve spool 41 is shown to have a central land 91 having sealing edges 92 and 93 which engage the sleeve 71 to provide the isolation between the jet pipe stage and the power valve stage as above described. It should also be particularly noted that the axes of the flapper 21 and feedback spring 47 are aligned.

As is illustrated, particularly in FIGS. 1 and 2, the receiver port means 32 is received within a bore 94 defined in the body portion 25 of the housing. To accomplish alignment between the receiver ports 31 and the nozzle 29 orifice the receiver port means 32 may be rotated about its axis 95 as shown by arrow 96. Also the receiver port means may be moved axially within the bore 94. Thus, once the feed tube is positioned within the body portion 25 of the housing and affixed to the flapper 21, the receiver ports may be adjusted to effect the desired null balance relationship (assuming no input signal to the torque motor).