US3405736A

US3405736A - Pure fluid logic element

Info

Publication number: US3405736A
Application number: US403586A
Authority: US
Inventors: Trevor D Reader; Edwin R Phillips
Original assignee: Sperry Rand Corp
Current assignee: Sperry Corp
Priority date: 1964-10-13
Filing date: 1964-10-13
Publication date: 1968-10-15
Anticipated expiration: 1985-10-15
Also published as: NL6513210A; BE670825A; GB1068486A; CH436788A

Description

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T.D.READER ETAL Filed Oct. 15, 1964 zs UTILIZATION MEANS 24 I CONTROL FLUID UTILIZATION MEANS v Fil5. E5 //y60;;,

75 CONTROL l FLUID 14 POWER STREAM FLUID FIG. I

FIG. 2

[WEI/7W5 EDWIN R. PHILLIPS TREVOR D. READER AT T ORNE Y5 United States Patent 3,405,736 PURE FLUID LOGIC ELEMENT Trevor D. Reader, King of Prussia, and Edwin R. Phillips, Rosemont, Pa., assignors to Sperry Rand Corporation, New York, N .Y., a corporation of Delaware Filed Oct. 13, 1964, Ser. No. 403,586 3 Claims. (Cl. 13781.5)

The present invention generally relates to a pure fluid logic element, and more particularly, to a pure fluid inverter having a relatively high power gain.

In pure fluid technology, it is well known that a fluid power stream jet of realtively high energy may be deflected through a small acute angle without losing its integrity by the application thereto of a control fluid jet of lesser energy, generally at a right angle in order to provide maximum deflection per unit of control stream energy. This is the well known stream interaction or momentum exchange type amplifier. Prior art fluid logic elements as, for example, inverters have been built using this approach, i.e., the power fluid jet, when present by itself, is recovered in an output channel leading to some utilization device whereas, with the application of control signal fluid, said power jet is deflected away from the output recovery channel so that no fluid signal is directed to said utilization means. The power gain here is inversely proportional to the energy of the control stream necessary to deflect the power stream jet to a degree where the latter is completely removed from the output recovery channel. Since greater control stream energy is necessary for larger values of power stream deflection, the requirement in such a momentum exchange inverter to completely switch power stream flow away from the output recovery channel thereby lowers the gain of the unit to a value where it is not too attractive.

' The present invention in one aspect thereof reduces, if not completely obviates, the difiiculties leading to rela tively low gain of prior art momentum exchange inverters by placing an attraction wall near the power stream jet on the side opposite the control signal jet, This wall, by virtue of its positioning and dimension, permits the creation of a low pressure boundary layer almost as soon as power stream deflection commences which then acts as an aid to further power stream deflection without, however, subsequently causing any permanent or stable power stream lockon to the attraction wall in the absence of a control stream. Thus, only as the power stream begins its deflection away from the output recovery channel (in response to an impinging control stream) is said boundary layer formed to thereby assist the control stream in completing power stream deflection to the maximum degree whereby no fluid is directed to the utilization means. Upon termination of the impinging control stream, this wall attraction is insuflicient to maintain this large power stream deflection, such that the power stream now swings back towards its normal, undeflected path. In so doing, this reduces and then finally destroys whatever boundary layer had been present during the presence of the control stream. Thus, the same degree or amount of power stream deflection as obtained in prior art momentum exchange inverters can be provided in the present device by a control stream of lesser energy so as to result in higher gain.

Therefore one object of the invention is to provide a novel pure fluid logic element which employs an attraction wall adjacent the deflected path of a fluid power stream in order to increase the gain of the unit.

Another object of the present invention is to provide a pure fluid inverter with an attraction wall therein in such a position as to avoid any permanent lockon of the power stream thereto.

In order to further insure non-stable boundary layer adhesion of the power stream along the attraction wall and to provide for a quick return of the power stream at the termination of the control signal, an additional novel feature of the invention is the use of means providing constant communication of the boundary layer region with a source of fluid whose static pressure is such as to rapidly dissipate the low pressure boundary layer during the swing back of the power stream away from the attraction wall. This source of fluid further acts, at least in one of the embodiments of the invention, as a base reference point on one side of the power stream against which a control static pressure signal operates on the opposite side of the power stream in order to selectively cause deflection thereof. Furthermore, second means can also be provided for communication of the opposite side of the power stream with said source of fluid in order to prevent the formation of any transverse pressure gradient across the power stream due to causes other than control signal ac tivity or the boundary layer region adjacent the attraction wall.

Therefore a further object of the present invention is to provide a fluid logic unit with an attraction wall, wherein there is constant communication of one or both sides of the power stream with a source of fluid at a fixed pressure.

One embodiment of the present invention uses a control fluid jet to provide power stream deflection by virtue of momentum exchange, whereas another embodiment employs a fluid static pressure cushion applied against a relatively long length of the moving power stream. The particular advantage of using said static pressure, rather than the dynamic or kinetic pressure of a moving controljet, is that it permits the power stream to deflect through a greater angle with less control power being required. This novel static pressure control also is of use in other types of pure fluid amplifiers apart from particular embodiments herein with the attraction Wall.

Therefore, another object of the invention is to provide a fluid amplifier unit which includes control means for providing a body or cushion of static pressure fluid as the power stream deflecting agent.

These and other objects of the present invention will become apparent during the course of the following description to be read in view of the drawings, in which:

FIGURE 1 is a plan view in section of a first embodiment of the present invention which employs a control jet for power stream deflection;

FIGURE 2 is a diagrammatic enlarged view of the critical dimensions of the attraction wall used in obtaining high gain; and

FIGURE 3 is a second embodiment of the present invention which employs means for applying control fluid static pressure against the power jet.

FIGURE 1 shows a first embodiment of the novel inverting element which uses the basic principle of an attraction wall in order to enhance its gain. A block or body 10 of fluid impervious material, which can be metal, plastic, or the like, has cut or otherwise formed therein a plurality of interconnected fluid channels and chambers, preferably of rectangular cross-section as is customary in the art. In particular, a power stream input channel 12 receives relatively high energy power stream fluid from some source 14 via a connecting pipe 16, with said power stream input channel IZ'terminating in a nozzle orifice 18 located in one end of a fluid interaction chamber 20. At the opposite chamber end wall, a first power stream output channel 22 is located directly in line with power stream input channel 12, so that the normal undeflected trajectory of power stream fluid across chamber 20 will take it into output channel 22 from whence it is transferred via a pipe 24 to some fluid utilization means 26 (which in turn could be another pure fluid logical element). The side walls of channel 22 need not and do not provide any boundary layer lock on effect, since the flow energy of the power stream is sufficient to establish this path through chamber 20. Also leaving the opposite end of chamber is a second power stream output channel 28 which makes an acute angle with output channel 22 and lies to one side of it at about the juncture of the chamber opposite end wall and one chamber side wall. Channel 28, in the case of a pneumatic amplifier, usually exhausts into the surrounding lower pressure atmosphere which thus acts as a low pressure dump. However, where a gas or fluid other than air is employed, then the output of channel 28 can be connected back to source 14 via a low pressure return manifold or dump. If the power stream fluid from nozzle 18 is deflected (by means subsequently to be described) from its normal undeviated path to a path through channel 28, the fluid normally applied to utilization means 26 is discontinued for the length of time that the power stream deflecting means is in operation. In this way the inverting logical function is performed. It would, of course, also be possible to further connect channel 28 to some form of utilization means which responds to the power stream in its deflected position.

The particular control means in FIGURE 1 for so deflecting the power stream comprises at least one control stream input channel 30 which receives, via a pipe 32, control fluid from a selectively actuated source 34. The control channel 30 terminates in a nozzle orifice 36 located in that side wall of chamber 20 which is opposite to the chamber side wall from which channel 28 branches. By selectively applying fluid to channel 30 from source 34, the channel static fluid pressure is converted by nozzle 36 into a control fluid jet having primarily kinetic energy which issues forth into chamber 30 so as to strike the power stream at about a right angle thereto. By virtue of momentum exchange between the control stream and power stream particles, the direction of the power stream is shifted right to cause flow through channel 28 and eventual exhaust to the low pressure dump. Normally, the angle of power stream deflection is proportional to the energy of the control stream fluid. Since a fairly large angle of deflection is required in FIGURE 1 in order to shift the power stream completely away from output channel 22, it is seen that relatively large control stream energy (although not as large as the power stream energy) might thus be required, which in turn lowers the gain of the device since gain may be defined as the ratio of the output utilization signal (power stream energy) to the control signal energy required for negation of same. If channel 28 does not have any side wall in the direction of power stream deflection, or includes such a side wall which is not strategically placed in the manner taught by the present invention, deflection of the power stream is due entirely to said stream interaction (momentum exchange) in chamber 20. However, in the present invention an attraction wall 38 is placed near the deflected path of the power stream on the side opposite to the control signal jet from orifice 36. Attraction wall 38 may actually be an extension of the side wall of chamber 20 as it turns to follow power stream output channel 28 to the point of exhaustion into the low pressure dump. Also provided in FIGURE 1 is a cavity volume 40 which separates the upstream end of wall 38 from the end wall of chamber 20 in which orifice 18 is located. This cavity 40 is preferably permanently connected to a source of static pressure fluid such as the low pressure dump to which channel 28 is connected by means of a fluid communication channel 42, but this feature is not absolutely necessary in the FIGURE 1 embodiment if the width of cavity 40 mouth along the power stream axis is made sufficiently large. The communication of cavity 40 with the low pressure dump permits a more rapid return of the power stream from channel 28 to channel 22 at termination of control stream activity, since the low pressure of the boundary layer along wall 38 is quickly raised by addition of fluid via cavity 40 and channel 42 once the entrainment ability of the power stream decreases as the switch back is in progress. Where channel 42 is employed, a second cavity 44 is also preferably provided on the opposite side of chamber 20 at a location downstream from control channel 30, with this cavity 44 being in constant communication with the same source of fluid as is channel 42 (illustrated to be the low pressure dump) by means of the large opening 45 in body 10. Cavity 44 cooperates with cavity 40 and channel 42 in equalizing the static pressure across the power stream in chamber 20 so as to insure the absence of power stream lockon to the attraction wall 38 due to causes other than presence of the control signal jet and/ or the creation of the low pressure boundary layer region against wall 38.

FIGURE 2 is an expanded view of the chamber 20 vicinity in the FIGURE 1 fluid amplifier. It is provided for the purpose of explaining the critical dimensions of attraction wall 38, relative to other dimensions of the amplifier, in order to provide a small boundary layer effect to enhance gain but without causing stable power stream flow in output channel 28. The three critical dimensions are shown in FIGURE 2 to be the length A of attraction wall 38, the distance B of the upstream edge of attraction wall 38 from the centerline of power stream nozzle 18, and width C of the cavity 40 mouth. These dimensions are adjusted relative to one another and also to the power stream energy, such that any predetermined degree of power stream deflection into channel 28 thereafter causes a boundary layer effect between it and wall 38 so as to provide some attraction by said wall to the now deflected power stream. Boundary layer effect may be defined as the entrainment of fluid by a flowing stream in a region between said stream and a side wall such that the pressure in said boundary layer region is reduced, thus permitting the stream to be attracted toward the wall. Any such boundary layer effect will obviously reduce the power or energy required of the control stream flu-id in forcing the power stream completely into channel 28. As more of the power stream flows through channel 28 and moves closer to wall 38, its entrainment efi'iciency rises to thereby reduce the boundary layer pressure to an even greater extent which in turn increases the wall attraction effect aiding in the power stream deflection. Consequently, by use of the attractive effect of wall 38, the required degree of power stream deflection can be procured in the present invention with less control stream energy than formerly required in prior art inverters, so as to result in an increase in gain. Restated in a different way, the power stream is deflected by the control signal such that the closer the power stream gets to wall 38, the less power is necessary from the control fluid because the now created boundary layer adjacent the wall itself aids in the power stream deflection. In other words, the wall shares in providing the total force necessary to keep the power stream totally deflected into channel 28. However, wall 38 must be positioned such that maximum boundary layer attraction offered by it to the deflected power stream cannot maintain said power stream in a path through channel 28 during the absence of control signal input. That is to say, when control fluid source 34 subsequently becomes de-energized or de-activated so as to terminate the control fluid jet from nozzle 36 (or alternatively, at least reduced to have lesser energy), the deflected power stream in channel 28 must now be able to tear itself away from wall 38, thus weakening the boundary layer becauseof less efficient power stream entrainment, and then return to its undeflected path through channel 22 at which time the boundary layer is completely destloyed. The attraction wall 38 is thus placed far enough away from the undeflected power jet to have no effect or influence thereon, and comes into play only when the power stream is moved closer thereto by action of the control jet. For any given control fluid energy, a position of wall 38 can be chosen to accomplish the above described functions.

It has been found that the smaller the value B in FIG- URE 2, the greater will be the effect of wall attraction on a deflected power jet. The larger dimension A is, the greater is the effect of said wall attraction, but a change in dimension A has a lesser effect than does a change in dimension B. A change in dimension C apparently produces the greatest effect of changes in any of said three dimension. The smaller C is, the greater the said wall attraction. 1

FIGURE 3 shows a second embodiment of the present invention which also employs the basic feature of an attraction wall to obtain a gain increase, but wherein the control signal applied against the power stream jet is in the form of a fluid body having primarily static pressure energy rather than a mass flow dynamic jet having primarily kinetic energy. .This additional feature will be described in subsequent paragraphs, but generally it may be said here that a control static pressure signal applied over a relatively large power stream area also permits of greater power stream deflection with less control power being required such that the attraction wall inverter of FIGURE 3 has even higher gain than does FIGURE 1. For this reason, too, the use of a control fluid pressure cushion in other types of fluid amplifier units is novel and useful because of the gain increase afforded thereby. The FIGURE 3 embodiment is further capable of operating at very low Reynolds numbers and is responsive to short input pulse rise times. It also permits greater tolerances in element geometry. As inthe FIGURE 1 embodiment, the pure fluid inverter of FIGURE 3 is comprised of a group of interconnected fluid channels formed in a body 50 of fluid impervious material. A power stream input channel 52 and power stream source 54' are provided to produce a power stream jet of relatively large energy which issues forth into a chamber 56 from a nozzle 58 formed in one end wall thereof. Leaving the opposite end wall of chamber 56, and directly in line with channel 52, is a first power stream output channel 60 which receives the normally undeflected power stream jet and conveys same via pipe 62 to some utilization means 64. No boundary layer lockon effect need be provided in channel 60. A second power stream output channel 66 also leaves said opposite chamber end wall at an acute angle with channel 60, with said channel 66 being separated from channel 60 by a divider edge 80 and further including an attraction wall 68 so located in the manner of FIGURE 1 to provide a boundary layer effect which enhances gain for deflection of power stream fluid into said channel 66. A cavity 70 lies between the upstream edge of wall 68 and the nozzle end wall of chamber 56. Although distance B (between the upstream edge or corner of said wall 68 and the power stream flow centerline) is shown to be smaller than in the case of FIGURE 1, it should be noted that the width C of the cavity 70 mouth (measured along the power stream flow axis) is larger so as to compensate for the smaller B dimension. Output channel 66 exhausts to a low pressure dump or return manifold here illustrated to be the atmosphere in the case of a pneumatic inverter.

As has already been mentioned, a different form of fluid control signal is provided in FIGURE 3 from that shown in FIGURE 1. A large chamber 72 is formed in the upstream portion of that side wall of chamber 56 which is opposite to the side wall from which channel 66 branches. The mouth 73 of said chamber 72 is considerably wider (as seen in the illustrated plan view) than the width of control nozzle 36 in FIGURE 1 so that it fronts along the power stream flow path through chamber 56 for a fairly long distance, preferably greater than one-third of the chamber length. This makes the area of the power stream, which is exposed to control fluid force, substantially greater in FIGURE 3 than the power stream area against which the considerably smaller diameter control jet in FIGURE 1 impinges. A control fluid input channel 74 is supplied with fluid from a selectively aetuable control fluid source 76 via pipe 78 so as to fill chamber 72 with fluid to thereby increase the static pressure therein without, however, causing any significant conversion of static fluid pressure to dynamic or kinetic fluid pressure as is the case in channel 30 and nozzle 36 of FIGURE 1. Consequently, a fluid control jet, as such, does not strike the power stream jet in FIGURE 3, but there is rather a cushion of control fluid from chamber 72 bearing against the power jet curtain created by nozzle 58. Although no specific means has been hereinbefore described for use as the sources 34 (FIGURE 1) or 76 of control fluid, one such input, among others, can come from the output of fluid logical 'OR circuit such as the one disclosed in a pending application S.N. 332,554, Fluid OR Gate, by Trevor D. Reader, now US. Patent 3,282,281. Since the control fluid in chamber 72 has little, if any, velocity in the direction of chamber 58, there is no appreciable exchange of momentum between the control and power fluids. Cavity 70 furthermore constantly communicates via an opening 71 in body 50, with a source of static pressure lower than the active signal presure in chamber 72. This last named source may in certain cases conveniently be the same low pressure dump or return manifold to which channel 68 is connected, as shown in FIGURE 3. Any increase in control fluid static pressure at the mouth 73 of chamber 72 above the static fluid pressure existing at the mouth of cavity 70 produces a transverse static pressure differential or gradient across the power stream as it issues from nozzle 58, which in turn deflects said power stream away from channel 60 and towards channel 66. As soon as some power stream fluid commences to flow in channel 66, a boundary layer region is created between it and wall 68. When there is suflicient power stream flow through channel 66, entertainment thereby of fluid in the boundary layer region adjacent wall 68 is at a faster rate than the rate at which fluid may be supplied to said boundary layer region via cavity 70 from the source connected to opening 71. This causes said boundary layer static presure to be reduced below the cavity 70 pressure which thereupon aids the control fluid static pressure differential to further deflect the power stream completely into channel 66. Upon a subsequent and suflicient decrease in the chamber 72 static pressure, as by termination of source 76 activity and withdrawal of fluid from chamber 72, the transverse fluid static pressure differential across the power stream at the region of nozzle 58 thereupon disappears. In order to almost immediately reduce to zero this transverse control signal pressure gradient across the power stream at practically the instant of termination of control source 76 activity, FIGURE 3 can, if desired, also be provided with an additional cavity leading from chamber 58 downstream from mouth 73 in the manner of cavity 44 in FIGURE 1, with said additional cavity being connected to the same source of fluid as is cavity 70, e.g., the low pressure dump to which channel 68 is also connected. The attractive effect exerted by the boundary layer region at wall 68 is by itself insufficient to maintain power stream flow completely in channel 66 and the power stream now begins to switch back 'into channel 60 thus weakening the wall attraction force so that it has a decreasing effect upon the power stream. As an additional aid to fast power stream return into channel 68, the diminishing power stream entrainment in channel 68 finally fails to exhaust fluid from the boundary layer region faster than the rate at which fluid is being supplied to said region from cavity 70. Consequently, the low pressure boundary region very quickly disappears so as to effect a rapid return of power stream flow into channel 60. The particular location of wall 68 relative to other parts of the unit, and the communication of cavity 70 with a body of fluid for replenishing entrained fluid in the boundary layer region, therefore causes power jet fluid in channel 66 to quickly switch back into output channel 60 at the conclusion of control signal activity.

A further feature of FIGURE 3 is the provision of slightly diverging side walls in channel 66 such that said channel acts as a diffuser for power stream flow therethrough. This in turn permits the static pressure at the channel 66 entrance (in the vicinity of divider edge 80) to be lower than the normal quiescent or ambient static pressure existing at the output of channel 60 in the absence of any power stream flow through the latter. This low channel 66 entrance pressure causes some entrainment, by the moving power stream fluid in channel 66, of the quiescent fluid standing in channel 60 so as to cause a small reverse fluid flow in channel 60 in the direction of the dotted arrow. This reverse flow travels a path around edge 80 and into channel 66 for eventual exhaust into the low pressure dump, thereby causing the static pressure at the channel 60 output to utilization means 64 to be slightly lower than the dump pressure. This reverse flow eifect makes even more pronounced the ditfe'rence between the two pressure levels which exist at the output of channel 60 according to the presence or absence of power stream flow therethrough.

While several different embodiments of this invention have been shown and/or described, modifications may obviously be made thereto by those skilled in the art without departing from the novel principles defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fluid inverter comprising; a body member having a fluid interaction chamber disposed therein, said interaction chamber having an end wall in which a fluid power nozzle is disposed, said fluid power nozzle being adapted when subjected to fluid input pressure to project a power jet through the interaction chamber, an output duct positioned to receive the undeflected power jet, said output duct comprising first and second spaced apart wall members located down stream from the power nozzle and on opposite sides of the axis of the power nozzle, a control signal chamber having an input duct at one end thereof for receiving control fluid input signals and a mouth portion at the other end thereof which opens into the interaction chamber on the same side of the power nozzle as the first wall member of the output duct, the said mouth portion extending from the power nozzle to a point at least one third the length of the interaction chamber downstream from the power nozzle, said control signal chamber being operative so that when a control fluid is applied thereto a static pressure signal will exist at said 8 mouth portion thereby to deflect the power jet away from said output duct, a vent for said interaction chamber comprising the area between the said end wall and the second of said wall members comprising said output duct, and a divider block located in the 'said vent dividing said vent into two unloaded vent channels the first vent channel of which is defined by a first surface of said divider block and the said end wall and the second vent channel of which'is' defined by a second surface of said divider block and the second of said wall members of said output duct; the second vent channel providing an exhaust path for the power jet when it is deflected by a suitable pressure applied to the control chamber, said second surface of said divider block forming an acute angle with the axis of the power jet and being positioned and dimensioned to provide'a boundary layer attraction force for the power jetonly when said power jet is in its deflected position, and said first vent acting to reduce the boundary layer attraction force of the second surface of said divider block so that it is insufficient to maintain said power jet in its deflected position in the absence of a suit able control pressure applied to said control orifice.

2. The fluid inverter of claim 1 wherein the said twovent channels exhaust into the same static low pressure dump.

3. The fluid inverter of claim 1 wherein said divider block is shaped to provide the said one-vent channel with a cross sectional area of expanding size.

References Cited UNITED STATES PATENTS 3,001,539 9/1961 Hurvitz 137-815 3,159,168 12/1964 Reader 137-815 3,187,762 6/1965 Norwood 137-81.5 3,204,652 9/1965 Bauer 137-815 3,208,463 9/1965 Hurvitz 137-815 3,258,023 6/1966 Bowles 137-815 3,262,466 7/1966 Adams et al 137-815 3,107,850 10/1963 Watten et a1 137-81.5 X 3,233,622 2/1966 Boothe 137-815 3,275,013 9/1966 Colston 137-815 3,282,281 11/1966 Reader 137-815 FOREIGN PATENTS 1,083,607 6/ 1960 Germany.

SAMUEL SCOTT, Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,405 ,736 October 15 1968 Trevor D. Reader et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 22, "orifice" should read chamber Signed and sealed this 3rd day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

Claims

1. A FLUID INVERTER COMPRISING; A BODY MEMBER HAVING A FLUID INTERACTION CHAMBER DISPOSED THEREIN, SAID INTERACTION CHAMBER HAVING AN END WALL IN WHICH A FLUID POWER NOZZLE IS DISPOSED, SAID FLUID POWER NOZZLE BEING ADAPTED WHEN SUBJECTED TO FLUID INPUT PRESSURE TO PROJECT A POWER JET THROUGH THE INTERACTION CHAMBER, AN OUTPUT DUCT POSITIONED TO RECEIVE THE UNDEFLECTED POWER JET, SAID OUTPUT DUCT COMPRISING FIRST AND SECOND SPACED APART WALL MEMBERS LOCATED DOWN STREAM FROM THE POWER NOZZLE AND ON OPPOSITE SIDES OF THE AXIS OF THE POWER NOZZLE, A CONTROL SIGNAL CHAMBER HAVING AN INPUT DUCT AT ONE END THEREOF FOR RECEIVING CONTROL FLUID INPUT SIGNALS AND A MOUTH PORTION AT THE OTHER END THEREOF WHICH OPENS INTO THE INTERACTION CHAMBER ON THE SAME SIDE OF THE POWER NOZZLE AS THE FIRST WALL MEMBER OF THE OUTPUT DUCT, THE SAID MOUTH PORTION EXTENDING FROM THE POWER NOZZLE TO A POINT AT LEAST ONE THIRD THE LENGTH OF THE INTERACTION CHAMBER DOWNSTREAM FROM THE POWER NOZZLE, SAID CONTROL SIGNALIS CHAMBER BEING OPERATIVE SO THAT WHEN A CONTROL FLUID IS APPLIED THERETO A STATIC PRESSURE SIGNAL WILL EXIST AT SAID MOUTH PORTION THEREBY TO DEFLECT THE POWER JET AWAY FROM SAID OUTPUT DUCT, A VENT FOR SAID INTERACTION CHAMBER COMPRISING THE AREA BETWEEN THE SAID END WALL AND THE SECOND OF SAID WALL MEMBERS COMPRISING SAID OUTPUT DUCT, AND A DIVIDER BLOCK LOCATED IN THE SAME VENT DIVIDING SAID VENT INTO TWO UNLOADED VENT CHANNELS THE FIRST VENT CHANNEL OF WHICH IS DEFINED BY A FIRST SURFACE OF SAID DIVIDER BLOCK AND THE SAID END WALL AND THE SECOND VENT CHANNEL OF WHICH IS DEFINED BY A SECOND SURFACE OF SAID DIVIDER BLOCK AND THE SECOND OF SAID WALL MEMBERS OF SAID OUTPUT DUCT; THE SECOND VENT CHANNEL PROVIDING AN EXHAUST PATH FOR THE POWER JET WHEN IT IS DEFLECTED BY A SUITABLE PRESSURE APPLIED TO THE CONTROL CHAMBER, SAID SECOND SURFACE OF SAID DIVIDER BLOCK FORMING AN ACUTE ANGLE WITH THE AXIS OF THE POWER JET AND BEING POSITIONED AND DIMENSIONED TO PROVIDE A BOUNDARY LAYER ATTRACTION FORCE FOR THE POWER JET ONLY WHEN SAID POWER JET IS IN ITS DEFLECTED POSITION, AND SAID FIRST VENT ACTING TO REDUCE THE BOUNDARY LAYER ATTRACTION FORCE OF THE SECOND SURFACE OF SAID DIVIDER BLOCK SO THAT IT IT INSUFFICIENT TO MAINTAIN SAID POWER JET IN ITS DEFLECTED POSITION IN THE ABSENCE OF A SUITABLE CONTROL PRESSURE APPLIED TO SAID CONTROL ORIFICE.