US3613708A

US3613708A - Fluidic displacement transducer

Info

Publication number: US3613708A
Authority: US
Inventors: Robert F Kampe; Albert H White
Original assignee: Chandler Evans Inc
Current assignee: Colt Industries Operating Corp; Colt Industries Inc
Priority date: 1969-11-07
Filing date: 1969-11-07
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19

Abstract

A fluid amplifier is provided with pressure surfaces which are movable in response to the pressure differential between two opposed chambers. A power stream impinges on a splitter element which separates two channels which respectively communicate with the chambers, so that a control stream may direct the power stream into either channel and create a pressure differential between the chambers. When the pressure surfaces move, the splitter element again impinges on the power stream annulling the initial pressure differential. Either the splitting element or the orifice of the power stream is connected to the pressure surfaces so as to be movable therewith to change the relative location of the splitter element and orifice. The amplifier may be employed as either a position or force to pressure transducer or a pressure to position or force transducer. A fluidic closedloop pneumatic actuation system incorporates the amplifier to position a servovalve controlled actuator.

Description

United States Patent [72] Inventors Robert F. Kampe West Hartlord; Albert H. White, Wethersfield, both of Conn. [21] Appl. No. 874,856 [22] Filed Nov. 7, 1969 [45] Patented Oct. 19, 1971 [73] Assignee Chandler Evans Inc.

West Hartford, Conn.

[54] FLUIDIC DISPLACEMENT TRANSDUCER 2 Claims, 8 Drawing Figs.

[52] US. Cl l37/8l.5, 137/83 [51] Int. Cl. F15c 1/14, F15c 3/ 10 [50] Field oiSeareh 137/81.5, 83

[5 6] References Cited UNITED STATES PATENTS 2,447,779 8/1948 Taplin 137/83 X Qia Primary Examiner William R. Cline Attorney-Radford W. Luther ABSTRACT: A fluid amplifier is provided with pressure surfaces which are movable in response to the pressure differential between two opposed chambers. A power stream impinges on a splitter element which separates two channels which respectively communicate with the chambers, so that a control stream may direct the power stream into either channel and create a pressure difierential between the chambers. When the pressure surfaces move, the splitter element again impinges on the power stream annulling the initial pressure differential. Either the splitting element or the orifice of the power stream is connected to the pressure surfaces so as to be movable therewith to change the relative location of the splitter element and orifice. The amplifier may be employed as either a position or force to pressure transducer or a pressure to position or force transducer. A fluidic closed-loop pneumatic actuation system incorporates the amplifier to position a servovalve controlled actuator.

1 FLUIDIC DISPLACEMENT TRANSDUCER BACKGROUND OF THE INVENTION The present invention relates generally to control actuators employed in control systems.

,block of material in which channels, which define a splitting element, have been cut to allow passage of fluid from a power stream orifice. The direction of the power stream relative to the channels is controlled by a control jet, of lesser momentum than the power stream, which impinges on the power stream. A vectorial summation of the momentum of the power stream and control jet will yield the momentum of the output stream. Once the stream has been established in a certain channel, the control let may be shut off and the power stream will return to its original position. In the absence of a pulse from the control jet, the power stream will initially impinge upon the splitting element, dividing the stream into two streams, assuming proper venting.

A great variety of prior art arrangements have been devised to implement the fluid-control concept. For example, a device can be designed to permit the power stream to reset itself to a given channel after the control jet is shut off. Other arrangements include positioning the splitter elements a sufficient distance from the power stream nozzle so as to cause unequal flow in the channels. Other arrangements of the control jets and output channels further include logic devices such as AND" gates and OR gates.

A recent development in servoactuator design is shown in U.S. Pat. No. 3,410,291. This patent discloses a bridge-type fluidic circuit which makes use of the back pressures within vortex amplifiers to control the position of a fluid actuator, the back pressures being controlled by a fluid logic device. The fluid circuit is advantageous in that it has no moving mechanical parts, but requires a relatively complex structural arrangement.

Prior art fluidic actuation systems have generally embodied immovable fluidic components and hence have necessitated the inclusion of sophisticated control circuitry, resulting in attendant weight and volume penalties. Further, prior art systems have not included the use of simplified position feedback techniques.

SUMMARY OF THE INVENTION The instant invention is essentially a basic proportional fluid amplifier which includes a power stream orifice, output channels, and a control jet. A distinguishing feature of the invention makes use of the pressure generated by a deflected power stream to position a pistonlike actuator and eventually cause the power stream to again impinge upon the splitter element to prevent further movement, thus creating an inherent negative feedback arrangement.

Briefly, stated, two amplifier output channels communicate with chambers, oppositely disposed on respective sides of a movable element, the location of which is determinative of the position of the splitter element with respect to the orifice of the power stream. A control jet applied to the power stream will deflect the power stream into one of the channels producing a pressure differential across the movable element, which causes movement thereof. As the movable element moves, the relative position of the orifice and splitter element change,

permitting the power stream to impinge upon the splitter element negating the pressure differential.

The invention not only obviates the inclusion of elaborate control circuitry in a fluidic-controlled actuation system, but also provides an inherent negative feedback arrangement. Also, since the actuator is an integral part of the fluid amplifier, a separate output cylinder is not required, except where large output forces are mandated by the selected application. The attendant weight and volume advantages, associated with a system designed in accordance with the invention, make such a system particularly suitable in environments with stringent weight and volume limitations, such as a missile. The nearly frictionless movement occasioned by an actuator of the invention will inure to the benefit of system efficiency and thereby contribute to overall system weight reduction.

Accordingly, it is a primary object of the present invention to provide a fluidic actuator which requires a minimum of control circuitry.

It is another object of the invention to effect economies in the number of necessary system parts, by utilizing an integral structure of the amplifier as an output member.

It is still another object of the invention to provide a fluidic device which incorporates a position feedback feature.

It is a further object of the invention to provide a fluidic valve operator adaptable for use in a pneumatic or hydraulic actuation system. 7

These and other objects of the invention will be readily apparent from the following detailed description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an embodiment of the invention in which the receiver section is movable relative to the supply section.

FIG. 2 is a plan view of another embodiment of the invention incorporating a pivotable splitter element.

FIG. 3 is a sectional view of still another embodiment of the invention employing a mobile power stream orifice.

FIG. 3a is an enlarged view of the output member of FIG. 3.

FIG. 4 is a further embodiment of the invention, shown partly in section, in which the receiver section is movable relative to the supply section.

FIG. 5 is a sectional view of a still further embodiment of the invention incorporating a power stage valve.

FIG. 5a is a sectional view of a modification of the embodiment of FIG. 5.

FIG. 6 is a block diagram of a closed-loop Fluidic Position Control System.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluidic operator with mobile receiver parts is illustrated in FIG. 1 where, for the sake of clarity, all vents are not shown. A supply pressure 11 generates a power stream, which emerges from the supply orifice 3 in supply section 1, and is divided equally into flows through

output channels

4 and 5 in receiver section 2 by splitting element 6. The flows are discharged through output vents 7 and 8. Vents V, formed between the receiver and supply sections, prevent attachment of the power stream to a wall. The portions of the output channels below pivot P form chambers, the pressure in which is communicated to the surface of splitting element 6 and other surfaces of receiver section 2.

The receiver section 2 includes a pivot P, enabling rotation of the entire receiver section. When the power stream is dis placed by control jet 9 in the direction of channel 5, the receiver section will tend to rotate in a clockwise manner until the apex of the splitting element again impinges on the power stream and the pressure in channel 5 equals that in channel 4. Contrariwise, if the power stream is displaced by control jet 10, the receiver will tend to rotate in a counterclockwise manner.

Turning now to FIG. 2, there is shown a second embodiment of the invention similar to that of FIG. 1, except that the position of the receiver section 2 is fixed relative to the supply section 1, and the splitting element 12 is rotatable on pivot P with respect to the receiver section. A pressure differential, engendered by the deflection of the power stream, will cause movement of the splitting element 12 in the direction of the power stream, until the flow is divided by the splitting element in such a manner that the pressure differential is zero. In order to effectively utilize the rotative motion of the splitting element 12, an output arm 13 is connected to the base of element 12 and slideably passed through vent 7. Output arm 7 could be operatively connected to a valve or other control element.

It should be noted that if either receiver section 2 in FIG. 1 or splitting element 12 in FIG. 2 comprises a relatively large mass, stability problems might be encountered. As explained hereinabove, when the apex of the splitting element begins to impinge upon the power stream, after the streamss deflection, the pressure differential will be reduced in accordance with the degree of apex impingement upon the stream, so that there is less force urging rotative movement as the'apex approaches the center of the power stream. Basically, this is an inherent negative feedback arrangement. If either section 2 or splitting element 12 and their associated output loads are too massive, the angular momentum imparted to section 2 or element 12 may not be sufi'iciently dissipated when the apex of the splitting element nears the center of the power stream so that the apex may be caused to pass the center of the stream to such an extent that undesirable oscillations will result. The provision of voids within the movable members will tend to alleviate stability problems. These stability considerations are also applicable to the embodiments of FIGS. 3-5.

FIG. 3 shows a fluidic-powered circular floating piston, generally indicated at 14, enclosed by a cylinder housing, generally indicated by 15. An integral part of the cylinder housing is a splitter ring 16 circumferentially disposed around the cylinder housing, and forming vents V in the housing walls with cylinder end portions 17 and 18. End portions 17 and 18 are generally cup-shaped structures provided with centrally located apertures for slidingly receiving an output member, generally indicated at 19, which passes through piston

structural members

20 and 21 and is movable therewith. Altematively, the cylinder housing could be used as the output member if design considerations indicate this is desirable.

FIG. 3a shows a detailed construction of the output member 19, which essentially comprises three spaced interconnected concentric hollow shafts. The inner shaft 25 serves as a nozzle supply and control conduit to direct a supply flow to radial nozzle 26. Nozzle 26 is shown as centrally disposed radial cutaway portions, from which the power streams issues in the direction of the splitter ring 16. The annular passage formed by inner shaft 25 and intermediate shaft 24 carries the control flow which emerges as a control jet to control the deflection of the power stream emanating from nozzle 26. The annular passage defined by outer shaft 23 and intermediate shaft 24 provides the necessary venting to prevent attachment of the power stream to a wall portion. It is important to note that the aforementioned three-shaft arrangement could readily be replaced by a two-shaft arrangement (supply flow and venting), wherein the deflection of the power stream would be controlled by a fluidic impact modulator, which is well known to those skilled in the art.

Referring again to FIG. 3, it can be observed that the contoured inner surfaces of the splitter ring 16 and the contoured piston inner surfaces of

structural members

20 and 21 form two radial output channels respectively communicating with

chambers

27 and 28 for the generation of pressures therein. An internal fluidic amplifier with pressure recovery effected near the periphery of a piston, as shown in FIG. 3, eliminates friction between the piston and cylinder walls. Further, an internal fluidic amplifier fabricated as a part of the piston shaft will move with the piston and close a position feedback loop.

In operation, the power stream, issuing radially like a 360 fan from the center of the hollow shaft 25, is deflected relative to the splitter ring 16 by the control jet flow from the annular passage, defined by

shafts

24 and 25, into a radial output channel, thereby causing an increase in pressure in the chamber which communicates with that output channel. Increased chamber pressure contacts the outer piston surfaces and moves the piston and internal amplifier in a negative feedback sense to annul the original deflection of the power stream relative to the splitter ring.

Turning now to the embodiment of FIG. 4, there is illustrated a fluidic bellows-type operator. A novel feature of the instant arrangement is a segmented feedback amplifier generally indicated at 30, which includes

enclosures

31 and 32 joined by a flexible connection 33, which provides an articulation point about which the entire enclosure 31 may pivot. Enclosure 32 comprises an orifice (not shown) from which a power stream is emitted and control flow channels (not shown) for supplying control jets for deflecting the power stream in the conventional manner. Enclosure 31 contains a splitting element (not shown) which divides the power stream into two output channels (not shown). The apex of the splitting element is preferably approximately tangent to the plane of the join to the flexible connection 33 and enclosure 31, although the precise location thereof is not critical. Control input conduits 34 and 35 fluidly communicate with the control flow channels within enclosure 31. Enclosure 32 is fixedly secured to channel member 40, upon which other components of the operator are also mounted.

A bellows and lever arm assembly generally indicated 42 includes two chambers, namely, bellows 44 and 45, each of which is secured to

identical bolts

46 and 47 that pass through apertures in the channel member 40.

Bolts

46 and 47 terminate in respective disclike surfaces, to which bellows 44 and 45 are respectively affixed. Bellows 44 and 45 are interconnected by tubular segment 52, to which an extremity of lever arm 54 is pivotably connected. Lever arm 54 is pivotably mounted on a vertical support projection 56, integral with the channel member 40, so as to permit movement of segment 52 to displace the other extremity 58, of lever arm 54, in an opposite sense. Extremity 58 is received in a small rounded recess 60 in enclosure 31 so as to be in finn contact therewith. An intermediate portion of lever arm 54 is connected to an output member 62 which in turn is operatively associated with valve spool 64, which may be utilized to control fluid flow to an actuator. Bellows 44 and 45 are fluidly connected to

outlet conduits

37 and 38 by

suitable ducts

37a and 38a, which respectively connect with hollow passages in

bolts

46 and 47.

Operation of the FIG. 4 embodiment is as follows: When the power stream is deflected by the control jet a pressure rise is occasioned in that bellows which fluidly communicates with the output channel receiving the deflected stream. As an increase in pressure will cause expansion of the bellows (of course the other bellows will tend to contract because of a resultant decrease in pressure), tubular segment 52 moves, in accordance with this expansion, causing arm 54 to pivot enclosure 31 about 33, thus effecting a recentering of the splitting element relative to the power stream in a manner similar to that discussed with reference to the other embodimerits.

The operator of FIG. 5 is a diaphragm-type actuator which is relatively simple to fabricate. Among the prominent advantages offered by the actuator are low friction and minimum volume. At the top of casing 70, a power stream channel 72 is interposed between control flow channels 74 and 76 which furnish the control jets to deflect a power stream flowing from orifice 78. Mounted within casing is a piston element formed by

outer wall portions

80 and 82, and a central portion containing the splitting element 84, and output channels 86 and 88 formed thereby. Output channels 86 and 88 are initially divergent with respect to the splitting element and then cross one another adjacent the base of the splitting element to respectively emerge at outlets in the

outer wall portions

82 and 80, into

chambers

92 and 90.

Chambers

90 and 92 are formed by casing 70 and the outer walls of the piston element along with two circumferential flexible diaphragms 94 and 97, which interconnect the peripheral outer walls portions and the casing 70.

Output members

100 and 102 are secured to the respective

outer walls

80 and 82 to transmit the motion of the piston element to a using device, such as a valve controlled actuator or electrical pickofl'. The right-hand portion of FIG. 5 shows a valve spool 104, connected to said output member, controlling a flow from a high-pressure actuator duct 106 to

actuator input ducts

108 and 109, which communicate with respective chambers in an actuator. (See FIG. 6)

The embodiment of FIG. 5 may be modified, as shown in FIG. 5a, to obviate the crossed output channels thereof. This is accomplished by placing two immovable vertical walls in respective intermediate locations between the outer wall portions 80a and 82a of the piston element and the central portion thereof, the outer wall portions being connected to the interior periphery of the casing by diaphragms 94a and 97a. Output member 102a interconnects the piston element and a controlled device, shown as a valve.

Chambers

90a and 92a respectively communicate with the output channels 86a and 884 by means of flexible conduits 86b and 88b.

The operation of the embodiment of FIG. 5 is as follows: Deflection of the power stream causes the pressure to increase in one chamber and decrease in the other chamber, as in the other embodiments, producing a pressure differential across the piston element which tends to move the piston element in the direction of the deflection and thereby cause the power stream to again impinge upon the splitting element 84 and annul the pressure differential. Since the valve spool 104 is interconnected with the piston element the valve spool will move in concert with the piston element and control the flow to the actuator chambers.

In all of the illustrated embodiments of the invention a generally linear relationship exists between the differential control flow pressure and the displacement of a movable element at a given supply pressure. Calibration of a device according to the invention is therefore greatly facilitated and the extent of the output members displacement, for a given control flow pressure differential, can be readily and accurately ascertained.

The embodiments of FIGS. 1-5 could also find application as position to pressure transducers. Referring again to FIGS. 1 and 2, a pressure-sensitive device 13a is interconnected between

output channels

4 and 5 for measurement of the pressure differential therebetween. Therefore, if receiver section 2 in FIG. 1 is subjected to either an angular or lateral displacement, in the absence of a control flow, a pressure differential will be engendered between

output channels

4 and 5, which is measurable by pressure sensitive device 13a. Similarly, in the absence of a control flow, displacing

output members

19, 62, and 100, 102 of FIGS. 3-5 respectively will produce a pressure differential between the respective chambers thereof.

It would also be possible to employ the embodiments of FIGS. 1-5 as force to pressure transducers. Assuming the absence of a control flow, a force applied to the output members of FIGS. 1-5 respectively would produce a pressure differential between their respective chambers, which would be of a magnitude determined by the value of the applied force.

FIG. 6 shows a closed-loop fluidic control system as applied to an actuator, generally indicated at 120, in a high-power pneumatic actuation system. The actuator per se has a balanced area piston 122 slidably disposed within housing 124 for axial movement therein. An actuator output shaft 126 is integrally connected to piston 122 and slidable through

apertures

128 and 130 of housing 124. End 132 of shaft 126 is pivotally connected to link 134 which is fixedly secured to a load 136, the load 136 and link 134 being rotatably mounted on fixed shaft 138 such that translation of output shaft 126 causes rotation of both link 134 and load 136 about fixed shaft 138. The load 126 is shown as a control airfoil.

The upper portion of housing 124 has two bores 140 and 142 extending therethrough which respectively place conduits 144 and 146 in fluid communication with the respective sides of actuator piston 122 via

actuator chambers

148 and 150. The conduits 144 and 146 respectively communicate with ducts in closed center valve 142, the construction of which is shown in FIG. 5.

The motion of output shaft 126 controls the output signal AP (X) (a differential pressure AP which is a function of the stroke of shaft 126) from fluidic position transducer 154; this output signal being transmitted to a fluidic compensation network 156, the structure of which is well known to those skilled in the art, to effect the phase lead. The output AP (X, X) of network 156, which is a function of the shaft's stroke and velocity, serves as one of the two inputs to fluidic summing amplifier 158, the other input being the actuator input command signal AP (X*). Fluidic summing amplifier 158 produces an output AP (X, X, X), which is a function of stroke, velocity, and commanded position X". The output of the fluidic summing amplifier is transmitted to a fluidic valve operator 160, a preferred construction of which is illustrated in FIG. 5, for positioning of the power stream thereof. The output of operator (X VALVE) acts to position closed center valve 152. It should be evident that the fluidic valve operator 160 could comprise any one of the fluidic displacement transducers illustrated in FIGS. 1-5. The fluidic control components (154, 156, 158, 160) are supplied with a lowpressure fluid at a pressure Ps-low, since their efficient operation does not mandate a high-pressure input, while the closed center valve is supplied with a high-pressure fluid Ps-high, since operation of the actuator requires a greater expenditure of energy.

The fluidic compensation network 156 may alternately be positioned between amplifier 158 and operator 160, if circumstances indicate that such is desirable, without impairing system operation. If the fluid employed in the fluidic components is a liquid (hydraulic control system), the network may be eliminated in its entirety. Also the actuator may be of the rotary variety instead of the linear type illustrated in FIG. 6.

In operation, fluidic summing amplifier 158 compares the input command signal AP (X*) and feedback signal AP (X, X), the latter signal being derived from fluidic position transducer 154 via fluidic compensation network 156. The summing amplifier generates an error signal AP (X, X, X) which is directed to a fluidic valve operator 160 (FIG. 5). When this error signal is zero, the valve operator 160 will be in a neutral position and hence the closed center valve 152 will similarly occupy a neutral position, as illustrated in FIG. 5. Therefore, as the commanded position is approached, the error signal from the amplifier 158 will continuously decrease. Therefore, a proportional relationship exists between the input command signal and the position of piston 122.

While we have shown and described specific forms of our invention, it is to be understood that various changes and modifications may be made without departing from the scope or spirit of the invention.

We claim:

1. A fluidic operator comprising a casing having a chamber with an orifice therein, means to generate a fluid power stream from the orifice, means to generate a control flow for deflecting and positioning the power stream emanating from the orifice, a piston element having two outer wall portions mounted within the casing chamber in spaced relationship to the casing for axial movement therein, the central portion of the piston element having two output channels for receiving the power stream and a splitting element defined therebetween. the casing comprising two walls respectively located in the casing chamber intermediate the central portion of the piston element and the outer wall portions of the piston element. the piston element extending through the casing walls in spaced relationship thereto, two flexible diaphragms respectively secured to the outer wall portions and the casing such that two difi'erential between the pressure chambers caused by initial deflection of the power stream, a device adapted to be controlled by the motion of the piston element, and an output member spaced from the casing operatively interconnecting the piston element and the device to transmit the motion of the piston element to the device.

2. A fluidic operator, as defined in claim I, wherein the interconnecting means comprises two flexible conduits respectively interconnecting the output channels and the chambers.

Claims

1. A fluidic operator comprising a casing having a chamber with an orifice therein, means to generate a fluid power stream from the orifice, means to generate a control flow for deflecting and positioning the power stream emanating from the orifice, a piston element having two outer wall portions mounted within the casing chamber in spaced relationship to the casing for axial movement therein, the central portion of the piston element having two output channels for receiving the power stream and a splitting element defined therebetween, the casing comprising two walls respectively located in the casing chamber intermediate the central portion of the piston element and the outer wall portions of the piston element, the piston element extending through the casing walls in spaced relationship thereto, two flexible diaphragms respectively secured to the outer wall portions and the casing such that two pressure chambers are respectively defined in the casing chamber between the casing walls and the outer wall portions, the diaphragms serving to maintain the piston element in spaced relationship to the casing, provide for untrammeled movement of the piston element, maintain proper orientation between the output channels and the orifice, and provide high amplification of the pressure differential between the pressure chambers, means to interconnect the output channels to the respective pressure chambers such that the piston element follows the deflection of the power stream to annul the pressure differential between the pressure chambers caused by initial deflection of the power stream, a device adapted to be controlled by the motion of the piston element, and an output member spaced from the casing operatively interconnecting the piston element and the device to transmit the motion of the piston element to the device.

2. A fluidic operator, as defined in claim 1, wherein the interconnecting means comprises two flexible conduits respectively interconnecting the output channels and the chambers.