US3240221A - Fluid amplifiers - Google Patents

Description

2 Sheets-Sheet 1 Filed May 8, 1963 FIG.2

5'0 6'0 POWER JET SUPPLY PRESSURE (PS) INVENTOR.

(POUNDS /|N CODA H.T. PAN

ATTO R N EY March 15, 1966 c. H. T. PAN 3,240,221

FLUID AMPLIFIERS Filed May 8, 1963 2 Sheets-Sheet 2 .3-- TAN e INVENTOR. CODA H.T. PAN

ATTORNEY United States Patent 01 3,240,221 FLUID AMPLIFIERS Coda H. T. Pan, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Filed May 8, 1963, Ser. No. 278,887 Claims. (Cl. 13781.5)

This invention relates to fluid control devices and has particular relation to digital and analog type fluid amplitiers.

Fluid amplifiers have the potential for wide application in various fields due primarily to their reliability, temperature insensitivity, shock resistance, and ease of fabrication. These devices may be employed as digital and analog computing elements and also as power devices to operate valves and the like. Fluid amplifiers may be operated as pneumatic devices employing a compressible fluid, such as gas or air, or as hydraulic devices utilizing an incompressible fluid, such as water or oil.

One of the two basic types of fluid amplifiers is of the momentum exchange type wherein a main or power fluid jet is deflected by one or more control jets directed laterally at the power jet from opposite sides thereof. The power jet is normally directed midway between two fluid receivers, channels or apertures, and is deflected relative to the receivers by an amount proportional to the net sideways momentum of the control jets. This device is therefore often referred to as a proportional or analog device.

In the case of the analog fluid amplifier, the amount of amplification is determined by the magnitude of angular deflection of the power jet from its central position, and the gain of the amplifier is a function of the ratio of this angular deflection to the differential momentum provided by the difference in pressure between the two control jets. It follows, therefore, that the greater the angular deflection of the power jet for a fixed amount of differential momentum, the greater the gain.

It is, therefore, an object of the present invention to provide a fluid amplifier embodying improved means for the control thereof. i

It is an important object of the present invention to provide an analog type fluid amplifier providing greater gain than has heretofore been possible in such analog devices.

It is another object of this invention to provide an analog fluid amplifier with enhanced gain obtained in a fluid amplifier having a simple structural geometry.

The above objects are accomplished in accordance with the principles of the invention by providing a cavity, chamber or recess in the side wall located between the source of the power jet and the control jet port. The cavity or recess, at one end thereof, provides a partition or cusp formed by the juncture of the wall of the control port and the wall of the cavity or recess, the cavity itself being concave toward the region of power jet flow.

With a cavity of this type on each side of the power jet flow and between the control jet ports and the power jet source, there is provided effective means for enhancing the angular deflection of the power jet with the application of a puressure differential between control jets. In the neutral or null position wherein the pressure of the two control jets is the same, the power jet continues along its centrally directed path. With increased pressure from one of either side, the power jet is deflected toward the other side and commences forming a vacuum in the cavity on that side. The decrease in pressure in this cavity tends to pull the power jet even closer, thereby increasing the angular deflection of the power jet over what would have been the case had the cavity not been present.

In the prior art analog fluid amplifiers, the angular deflection bears a desirably linear relationship to the differof the boundary layer effect type.

3,249,221 Patented Mar. 15, 1966 ice ential in momentum between the control jets. It is an important feature of this invention, that this linear relationship is maintained over a wide operating ran e, even though the gain provided in accordance :with the principles of the invention is greatly increased over that of the prior art. Thus, in accordance with the invention, desirable operating characteristics of the analog fluid amplifler of the prior art are not disturbed, while gain is enhanced.

In the analog fluid amplifier, when the cavity is positioned sufliciently close to the path of the power jet, the application of a control jet differential pressure sufliciently great to deflect the power jet by a large angle may result in providing a vacuum sufficiently great in the cavity to cause the jet to latch to that side. Thus, when the pressure differential is removed, the power jet may stay deflected to that side, due solely to the cavity vacuum. Therefore, by a proper relationship between cavity and power jet parameters in the analog fluid amplifier, a latch- 'ing action at a particular threshold of control jet differential may be obtained.

The analog fluid amplifier previously mentioned is a dual polarity type device in that deflection from the center to one side may be considered a positive signal, while deflection to the other side may 'be considered a negative signal. In another embodiment of the invention, a single polarity analog fluid amplifier is provided with a control jet and a cavity solely on one side. In such an ar' rangement, the cavity provides the salutary effect of more quickly restoring the deflected signal to its central or null position upon the removal of the control jet signal.

The second of the two basic types of fluid amplifiers is In this device power jet deflection is effected by the side walls of an interaction chamber which are shaped in such a way that the power jet will attach to one or the other of the side walls but not to both side walls. This is brought about by the entrainment action of the power jet wherein the power jet tends to entrain air trapped between it and an adjacent side wall, the entrainment becoming more effective as the power jet approaches the adjacent side wall. This type of amplifier is basically a two position device and for this reason is generally referred to as a digital device.

The binary fluid amplifier of the prior art therefore requires the use of one or more control jets to obtain the binary digital switching action.

In another embodiment digital switching is provided Without control jets by employing a digital fluid amplifier having a power jet source and two side recesses or cavities similar to the ones previously mentioned with respect to the analog fluid amplifier. Thus, there is a cavity in each of the two walls on opposite sides of the power jet and concave towards the power jet, but the device has no control jet ports at all. Each of the cavities has a vent which may be either open or closed. With both cavity vents open, the power jet proceeds along its centrally directed path in its null or undefiected condition. This is because the vacuum type of action of the power jet relative to the cavities is nullified by flow out the vents from the two cavities. With one of the vents closed, however, a vacuum pump action takes place in that cavity, while the vented cavity does not have such an action. Accordingly, the vacuum built up in the cavity with the closed vent tends to draw the power jet toward it and provides a new type of latching action. Digital operation is thus provided by selectively opening and closing the vents to the cavities.

In the discussion hereinafter, the term boost cavity" will be used for the cavities, recesses, or chambers which enhance the gain of the analog fluid amplifier or provide the latching action described for the digital device, in accordance with the principles of the invention.

ance with the principles of the invention;

FIGS. 2 and 3 are graphical representations of certain characteristics of the fluid amplifier of FIG. 1;

FIG. 4 is a plan view of a variant form of the fluid amplifier of FIG. 1; and

FIG. 5 is a diagrammatic view in perspective illustrating a digital fluid amplifier embodiment constructed according to the invention.

Referring now to the drawings in greater detail, there is illustrated in FIG. 1 an embodiment of the invention,

given by way of example, in the form of an analog type fluid amplifier represented generally by the numeral 10. The device is diagrammatically shown in FIG. 1 as including a plate 11 formed of suitable material, such as metal, plastic or the like, which is slotted in a special configuration to provide passages for fluid. The various slots in the plate 11 may be formed in any suitable manner and may extend entirely through the plate or may be of lesser depth as desired. In the illustrated embodiment,

the slots in the plate 11 are shown extending only partially therethrough.

The plate includes a main opening 12 into which extends a conduit or passage 13 which carries pressurized fluid into the opening 12, it being understood that suitable enclosure such as a covering plate 9 is positioned on top side of plate 11 to confine fluid to the various slots of the plate 11.

The fluid utilized in the control device may assume a variety of forms. For example, the fluid may constitute a compressible fluid, such as air, to provide a pneumatic device. As a further example, the fluid may be incompressible, such as oil or water, to provide a hydraulic device.

Communicating with the opening 12 is a restricted slot 14 constituting a power nozzle from which issues a jet ,of fluid emanating from the conduit 13. At a distance from the juncture of nozzle 14 and opening 12, and on opposite sides of the centerline extension of nozzle 14, are located a pair of slots 15 and 16 which may be designated control slots and into which extend conduits or passages 17 and 18 for introducing pressurized fluid into the control slots. The conduits 17 and 18 may be supplied with pressurized fluid in any suitable manner, such as from the same source which supplies the conduit 13 or from independent sources as desired. As is understood in the art, pressurized fluid in the control slots 15 and 16 cooperate upon a pressure difierential basis to deflect the jet issuing from nozzle 14.

In the illustrated embodiment, plate 11 is formed with two elongated diverging fluid receiving passages 22 and 24, which selectively receive fluid of the power jet depending upon the direction and magnitude of angular deflection of the power jet. The passages or channels 22 and 24 are separated by a third channel 23, whose centerline is a co-linear extension of that of nozzle 14. The downstream end of receiver 23 may be vented to the atmosphere or may be employed to drive some useful load. A major portion of the power jet flow from nozzle 14 passes into and through receiver 23 when there is a null pressure diiferential between the control jets from slots 15 and 16. When the pressure of the control jet from either of the two slots 15 or 16 is greater than that of the other, the power jet from nozzle 14 is deflected in the direction of the side wherein the control jet pressure is lower. The angular deflection 6 of the power jet, with 0 being measured from the centerline of slot 14 to the centerline of the deflected power jet, determines what portion of the power jet enters receiver 22 or 24 and what portion enters the null receiver 23. When 0 is at its magnitude 0 there is alignment of the centerline of the jet with the centerline of receiver 22 or 24, with little of the power jet exiting through the null receiver 23. Thus, the portion of the power jet entering receiver 22 or 24 is a continuously variable analog signal proportional to the angle 0, and therefore directly proportional to the control jet pressure diiferential.

The geometry and operating characteristics of the fluid amplifier of FIG. 1, as thus far described, is that of a conventional analog fluid amplifier. However, the amplifier of FIG. 1 is not conventional in the geometry of the walls between nozzle 14 and control slots 15 and 16. Thus, directly between the constricted throat 14 and control port 15, and forming the wall boundary therebetween, is a boost cavity 31, or recess, having an arc-uate configuration, which may be substantially semicircular, and oriented concave toward the path of the power jet. Cavity 31 formed in this manner is defined in part by a wall section 33 which constitutes a partition, septum or cusp formed between the walls of cavity 31 and control port 15. Thus, the control jet issuing tion, septum or cusp formed between the walls of cavity 31, or putting it another way, the cavity 31 is shielded from the effect of the control jet by septum 33. On the other side of the power jet path the wall between control port 16 and throat 14 is similarly formed as a cavity or recess 35 with a similar septum 37. The ends 43 and 47 of the septa 33 and 37 are spaced from each other and from the power jet boundary sufliciently so that the pressure in boost cavities 31 and 35 is approximately the same as the fluid pressure at the exit of control jet ports 15 and 16 when the power jet is in its null position and received mainly by null receiver 23.

In operation, when the control jet pressure on one side is greater than that on the other, for example when the pressure from control port 15 is the greater, then the clearance between the boundary of the power jet on the right and cavity 35 is reduced. This results in a partial vacuum being created in boost cavity 35, which in turn results in a larger effective control pressure differential, and therefore results in a larger deflection angle 0 than would be the case had the boost cavity 35 not been there. Conversely, if the pressure from port 16 had been the greater, deflection would have been to the left toward boost cavity 31, with a similar type of enhanced action in the opposite angular direction.

To more fully appreciate the gain enhancement provided by the boost cavities 31 and 35 in accordance with the principles of the invention, there are presented in FIG. 2 curves 48 and 49 which represent functions of the angular deflection for prior art fluid amplifiers and a fluid amplifier of the invention, respectively, at various power jet supply pressures. The ordinate of FIG. 2 is position gain, which is a function of the power jet angular deflection normalized with respect to the variables of control pressure differential, and control port and power nozzle dimensions. More specifically, the ordinate is equal to:

AtanB the prior art analog fluid amplifiers. All pressures mentioned are gauge pressures, with the gauge reference being the pressure in the interaction chamber.

In FIG. 3, are shown curves 51 and 52 which represent the angular deflection obtained in a fluid amplifier in accordance with the invention, as a function of control jet pressure differential, and more specifically, as a func- Curves 5-1 and 52 are for power jets having supply pressure of 15 and 44 pounds per square inch, respectively. It may be noted that the relationship between angular deflection and control jet differential pressure is maintained substantially linear over a wide operating range.

In the construction of the fluid amplifier of FIG. 1, it is believed that certain relationships in the geometry of the amplifier should preferably be provided. Thus, for example, the distance of receivers 22, 23 and 24 from the power jet nozzle 14 is preferably five to eight times the width d of the power jet nozzle. The spacing of receivers 22 and 24 from the center line may be selected dependent upon whether pressure recovery or power recovery is of more importance. It pressure recovery is of main interest, then the idealized point location of the receiver from the power jet nozzle center line should be 0.6 where y is the lateral distance from the jet axis to the point where the velocity of the power jet is half that of the velocity of the power jet at its center line. Where power recovery is of more interest, optimum power recovery is obtained with a receiver having a width equal to 2y Furthermore, with two receivers of this width spaced with each a distance y from the center line, the resulting configuration provides the greatest power gain (but such an arrangement precludes a center receiver).

It may be noted from the curves of FIG. 2 that position gain is a function of power jet supply pressure, and that gain decreases with an increase in supply pressure. This is due in part to the fact that increased power jet supply pressure results in the pivot point 26 (FIG. 1), which effectively defines the point at which angular deflection 6 commences, moving downstream. The greater the supply pressure, the greater the distance downstream that pivot point 26 is moved, and angular deflection decreases as a consequence.

In the analog fluid amplifier of FIG. 1, deflection of the power jet to the angle 9 which provides a complete correspondence between the power jet and one of the receivers 22 or 24, results in bringing the boundary of the power jet in intimate association with the boost cavity cusp. Accordingly, the vacuum within the boost cavity at that angular deflection is ordinarily sufliciently great such that when the pressure diflerential between the control jets is removed, the power jet remains fixed in its 9 deflected position. Accordingly, the amplifier of FIG. 1 not only provides analog amplification but also provides a latching function in that when the control jet pressure differential reaches a particular threshold level, the jet remains latched to that side.

Referring to FIG. 4, there is shown a plan view of an analog type fluid amplifier of the same type as that of FIG. 1, except that solely one boost cavity 61 and control jet port 62 appear, and only one receiver 64 other than the null receiver 65 is provided. In the embodiment of FIG. 4, deflection is by a control jet from port 62 on the same side as the boost cavity 61 and accordingly, deflection of the power jet is away from boost cavity 61. Removal of the control jet pressure results in the power jet resuming its null condition and exiting through receiver 65. Due to the boost cavity 61 on the side toward which the deflected power jet returns, some vacuum is created in boost cavity 61 as the power jet is in the process of returning from its deflected position.

'6 This tends to increase the speed of return and tends to snap the jet back to the null position.

In the embodiment of FIG. 5, a digital fluid amplifier is represented in accordance with the principles of the invention. It may be noted that this digital device has a structure which varies from that of the analog device of FIGS. 1 and 4 in several respects. Thus, there are no control jet ports at all. The boost cavities 71 and 72 which are located adjacent the end of power jet nozzle 74 are substantially similar to those of FIG. 1. However, each of the boost cavities is veritable by a vent pipe as shown. Fluid flow through vent pipe 75 for cavity 71 is controlled by valve 76 which is preferably of the type that is normally fully open or closed and may be rapidly switched from one state to the other. A similar valve 77 is provided in the vent pipe 78 for the other boost cavity 72.

In operation, closing of valve 76 while leaving valve 77 open results in vacuum pump action building up in cavity '71, to thereby cause the power jet .to deflect toward boost cavity 71. This is a positive feedback type of action such that the deflection continues until the boundary layer of the power jet is in contact with the cusp 79 of boost cavity 71. Accordingly, the power jet remains latched to that side. This provides one of the two binary switching positions for this binary type fluid amplifier. If it is desired to switch the power jet to the opposite side and therefore to the second of the binary positions, valve 76 for cavity 71 is opened while simultaneously, valve 77 for boost cavity 72 is closed. The conditions are thereby reversed. The vacuum that had been created in boost cavity 71 is broken, and pressure builds up, while vacuum pump action commences in boost cavity 72 because of the closed vent 77. In this way, binary switching action is obtainable and flip-flop action is provided without the need for control jet ports and control jet supplies. Simple electromechanical switching means may be employed if desired for automatically actuating the vent valves for providing the desired switching action.

While the principles of the invention have now been made clear in illustrative embodiments, there will be immediately obvious .to those skilled in the art many modifications in structure, arrangement, proportions, the elements, materials, and components, used in the practice of the invention, and otherwise, which are particularly adapted for specific environments and operating requirements, without departing from those principles. The appended claims are therefore intended to cover and embrace any such modifications, within the limits only of the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A fluid amplifier comprising: a power jet nozzle for projecting a fluid power jet having a boundary layer; a plurality of fluid receiving means positioned downstream from said power jet nozzle; a control jet port adjacent said nozzle for directing a first fluid control jet at said power jet; and a concave recess in the wall formed between the wall forming said nozzle and the Wall forming said port, the terminating points of said concave recess being positioned adjacent the boundary layer of said fluid power jet whereby a low pressure is formed in said concave recess to exert a force on said jet.

2. A fluid amplifier as recited in claim 1 wherein said recess is concave toward the path of said power jet.

3. A fluid amplifier as recited in claim 2 wherein the boundary forming said recess is arcuate in shape.

4. A fluid amplifier as recited in claim 2 wherein said concave recess has an end wall portion forming a cusp with an end wall portion of said control port.

5. A fluid amplifier as recited in claim 4 wherein said cusp is spaced a distance from the boundary layer of said power jet for all power jet supply pressures in the operating range of said fluid amplifier.

6. A fluid amplifier as recited in claim 1 including a 7 second control jet port on the opposite side of said power jet nozzle from said first control jet port; and a second concave recess in a wall formed between said nozzle and said second control jet port.

7. A fluid amplifier as recited in claim 6 wherein said second concave recess is concave toward the path of said power jet.

8. A fluid amplifier comprising: a power jet nozzle for projecting a fluid power jet having a boundary layer; a plurality of fluid receivers positioned downstream from said power jet nozzle; a control jet port adjacent said nozzle for directing a first fluid control jet at said power jet; and means comprising a cavity disposed between said nozzle and said port, said cavity having an opening adjacent to a portion of the boundary layer of said power jet for decreasing fluid pressure in a region contiguous to said portion of said boundary layer when said power jet is deflected from a given angular orientation.

9. A fluid amplifier comprising: a jet nozzle for projecting a jet of fluid along a path, said jet of fluid having a boundary layer; a plurality of fluid receiving means positioned downstream from said jet nozzle; and control means positioned adjacent said path and said boundary layer for varying the direction of said path, said control means comprising a control jet port adjacent said nozzle for directing a fluid control jet at said power jet and means defining a cavity having an opening adjacent said boundary layer, said cavity being positioned between said jet nozzle and said control jet port, said cavity producing, in response to the passage of said jet of fluid adjacent to said opening, a region of reduced fluid pressure contiguous to said boundary layer and including said cavity.

10. A fluid amplifier comprising: a jet nozzle for the projection of a jet of fluid along a path, said jet of fluid having a boundary layer; a plurality of fluid receiving means positioned downstream from said jet nozzle; and control means for changing the direction of said path, said control means comprising a control jet port adjacent said nozzle for directing a fluid control jet at said power jet and means defining at least one concave recess disposed adjacent the boundary layer of said jet of fluid for producing a reduction in fluid pressure in a region contiguous to said boundary layer and including said recess in response to the projection of said jet of fluid, said recess being positioned between said jet nozzle and said control jet p-ort.

References Cited by the Examiner UNITED STATES PATENTS 3,080,886 3/1963 Severson 13781.5 3,122,062 2/1964 Spivak et a1. 13781.5 3,144,037 8/1964 Cargill et al. 137-815 3,148,691 9/1964 Greenblott l378l.5

M. CARY NELSON, Primary Examiner.

LAVERNE D. GEIGER, Examiner.

Claims (1)

1. A FLUID AMPLIFIER COMPRISING: A POWER JET NOZZLE FOR PROJECTING A FLUID POWER JET HAVING A BOUNDARY LAYER; A PLURALITY OF FLUID RECEIVING MEANS POSITIONED DOWNSTREAM FROM SAID POWER JET NOZZLE; A CONTROL JET PORT ADJACENT SAID NOZZLE FOR DIRECTING A FIRST FLUID CONTROL JET AT SAID POWER JET; AND A CONCAVE RECESS IN THE WALL FORMED BETWEEN THE WALL FORMING SAID NOZZLE AND THE WALL FORMING SAID PORT, THE TERMINATING POINTS OF SAID CONCAVE RECESS BEING POSITIONED ADJACENT THE BOUNDARY LAYER OF SAID FLUID POWER JET WHEREBY A LOW PRESSURE IS FORMED IN SAID CONCAVE RECESS TO EXERT A FORCE ON SAID JET.

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