US3538931A

US3538931A - Fluidic control systems

Info

Publication number: US3538931A
Application number: US672062A
Authority: US
Inventors: Robert L Blosser Jr; Donald F Folland; Wayne P Russon
Original assignee: Sperry Rand Corp
Current assignee: Sperry Corp
Priority date: 1967-10-02
Filing date: 1967-10-02
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

C Unlted States Patent 11113,538,9 31

[72] Inventors goberitfLl. Blosser, Jr. 56] References cited oun u Donald F. Folland, Salt Lake City; Wayne UNITED STATES PATENTS Russo, American Fork, Utah 3,238,960 3/1966 Hatch 137/815 [2'] AppL No. 72 2 3,250,285 5/1966 Vockroth 137/815 [22] Filed Oct. 2, 1967 3,277,914 1966 Manion 137/815 Patented No 10, 1970 3,323,532 6/1967 Campagnolo... 137/815 [73] Assign Sperry Rand Corporation 3,335,737 8/1967 Gesell 137/815 a worm Delaware 3,340,885 9/1967 Bauer 137/815 3,382,883 5/1968 Laakaniemi. 137/815 3,388,713 6/1968 Bjonsen 137/815 3,378,022 4/1968 Sorenson..... 137/8 1 .5 3,404,701 10/1968 Shiiki 137/815 3,407,828 l0/1968 Jones 137/315 Primary Examiner-Samuel Scott 541 FLUIDIC CONTROL SYSTEMS Yeam 8 Claims, 4 Drawing Figs.

[52] US. Cl. 137/815 CT: Flui i n rol systems having a minimum of [51] Int. C1,... Fls 1/12 moving parts for controlling variables such as liquid level, flow Field of Search 137/815 and density in response to low initial pressure signals.

AI R .r 72 SUPPLY 73 I DISTRIBUTION MANIFOLD 685 a2 7? 575 l i J 61 79 76\.. &

/ OUTPUT AMPLIFIER as f 90 U as i 1 PUMP AIR

SUPPLY Patented Nov. 10, 1970 Sheet FIG.1.

INVENTORS ROBERT L. BLOSSE/P JR. 00mm F. FOLLA/VD WAYNE R ussa/v ATTORNEY 1 EL DIQ coarser sYsrEMs ancigonouuoon rrismveurlou- 7 inaccurate with use but they, are also subject. to jamming; or

sticking. in addition, it is particularly, difficult to de signproportionalgsystetns. They. are sensitive. to in-line pressure, changes and; therefore must be carefully compensated. Another problem-isrthat they. require. complex; interface apparatus, Generally. the prior-art systems are; substantially more expensive than the fluidic control systems of thepresent invention .suMmmcnrusiuvaunou.

. The present,invention;utilizesaplurality of interconnected,

fluidic componentshaving no moving parts exceptthe fluid it- .self movingthiethrough; Generally, the-fluidic control systems of the present; invention compare theactual conditions by means of fluidsignals with -.a reference :condition also defined by means of'fluid; signals, and any. difference therebetween provides a control signal which may. be; am. plified to drive a load member-in a mannertotendto eliminate.

the aforementioned difference.

BRIEF DESQRiPTiO-NIQF THEDRAWINGS' FlG 1 is. a sche matie diagramaof'; a-fluidiqgflow control system; i

FIG. Zisa schematic diagram of a fluidicliquid level control system;

HQ. 3 is a schematic diagram of an alternative fluidicliquid level control system; and V FIG. 4 is .a schematic diagram of a fluidic. density control system, i v

=-DEscRiPr|ou.oETHE PREEE -R EMB IMEms.

Referring to FIG; 1Qthefluidic control1system-l0 shwn controls the flow. of fluid inn conduit. 11- which may, for example, in a gold extractionprocess heinthe neighborhood of 600 gallons per minute of gold bearing solution Thelfluidic flow control system establishes a reference.signal representative of the desired flow thr oug h the conduit .11 between zero and 100 percent of. flow. and byfl m'eansof the fluidic .servoloop, to

be. described; controls -.the,fflo u /.;..through theconduit .11 with respect to the de siredflow An air source ll is'connected througha precision regulator 1 d s r but o rmani o dil iW hi uppli s ai underip es, sure to an amplifier 15: a transverserimpact modulator '16, a 1

proportionalamplifierl7t3l'ld a, control amplifier- 18- viaconduits incl uding; respective fiiged fluidic; restrictors-19, 20, 21;

and 22. The'restrictorilll determines theproperflow rate for one powerinput jet-2339f the transverseiimpact modulator 16 while unothcnrestrictor' 24 defines. the.. flow =rate for the hulzmcingpowcr input -jels 23g-;'l'he,output conduit 270i the point establishedby adjustment of thevariable restrictor 31 is maintained constant. Theother control stream port 43 of the proportional amplifier 17 is connected via a fluidic differential pressure cell 32 to an orifice plate 33 in the conduit 11 through which thefiow is being controlled. The cell 32 may be of the type shown in U.S. Pat. application Ser. No. 631,957 entitled Fluidic Diodev or Sensor Device of R.L. Blosser, Jr. filed Apr. l9, 1967. The actual flow signal through the diode 32'. is attenuated by means of a variable restrictor 34 which permits a portion .of the pressure to be bled off to properly matchthe signal from'the'diode 32'with the characteristics of the amplifier 17 inorder that the actual flow signal via control port43 can-be accurately compared with the reference signal via the controlport 29. The output port 35 of the amplifier 17 isconnected to the control port 360i the power amplifier 18.

The output; port 37 of the power amplifier 18 is connected to control a-valve 38 such as a Mason Neilan valve disposed in the conduit 11 to controithe flow therethrough.

in operation, the reference signal. applied to the control stream port 29 is determined by adjustment of the variable restrictor 31. Any variations in the. air pressure from the manifold 14 are applied-through the restrictor l9 and if there is anincrease'inpressure, for. example, anincreased flow via the output port 28 ofitheamplifier l5 willbe introduced atthe control port 26=to cause increased: flow from'the control stream: which. deflects; the power stream emanating via the power stream port23 causing less flow to occur via the output port 27; This-reduces the control stream flow emanating from the inputport 81in the proportional amplifier l5 and reduces theoutput flow from the-output port 28 proportionately to maintainthereference pressure signal constant at the control stream port 29 'of the amplifier 17. Theopposite will occur on reduced-pressure in-the manifold 14 thereby tending to maintain the referencepressure signal constant.

Theactual flow signal .from the orifice plate 33 in the conduit ll is attenuated by the cell 32. and variable restrictor'34 andthenx-applied to the control stream port 43 of the proportional amplifier l7. if the actual flow signal at the control port 43 is equal to the reference signal at the control port 29, the power stream-provided atthe. power input'port 40 of the am.- plifier l7 will divideequallyand the output pressure atoutput ports35 and 41'will be equalwith the-output port 41 vented to atmosphere and there will be no change in the actuation'of the valve 38. if the flow through the conduit 11 is too high, the signuiappeuring'at the control port 43 will be greater than that at thccontrol port '29.. The power jet will then be deflected so that more oi the flowgoes through the output port 35 providing a controlsignal at control port 36 which is amplified in the power amplifier 18 to cause the valve 38 torestrict the flow in theconduitll until there is no difference between the desired flowandthe actual flow.

Assumingthat theflowis less than thedesired flow through thev conduit 11,- thesignal: at the control port 29 will exceed that atthecontrolport. 43. thereby causing less fluid to flow through. the output port 35 and reducing the'signal to be amplified in .thepoweramplifier 18 to'cause the valve- 38 to permit more-flow throughthe conduit 11.

' atank 5 1 'to sense the level of a liquid within the tank in order trunsvcrse impact modulator/16pm connected-to. a control stream port .fl'oi the'. proportionalamplifier; Normally, an

connected'toa controlstream port:29*of the-.proportional'amplifier 1 7; Theoutput port 28 alsoconnects through a variable fluidic restrictor 30 to th'econtrol streamport 26-of the modulator 16. t The joutputport- 28' :isffurther {connected to atmosphere through a set point variable restrictor 31, thesetting of whichestablishestthe ldesiredyreferenceflow;signal, The function of the pro portionaiamplifier :-l5-and:modulator l6-is to automatically compensate. for pressure variations in theair supply through the ma nifold 14 in order thatthe reference set output is provided. through. the;-output.conduit.28- which is} to;-muiritain the liquid at a. predetermined height. A fluidic diode or differential pressure cell 521s provided with air from a regulated pressure source53 via a fluidic variable restrictor [54. One-outputof the diode 52 is connected to the probe 50 while its alternative output is connected to a capacitance or delay tank 55; The output of the delay tank 55 is connected through'a variablerestrictor 56'to an input port of a fluidic Schmitt trigger device .57; The other input ports of the Schmitt trigger. device 57are connected to the pressure source 53 'via

variable restrictors

58 and 59. The output ports of the Schmitt trigger device 57 are connected to the input control ports of a fluidic bistable flip-fiop62 which has its outputs connected to a hydraulicallyoperated: pump 63 for controlling the liquid levelin the tank 51.

In operation, with the liquid level below the lower extremity of the probe 50, the air will flow through the diode 52 and out the probe 50 thereby providing no output signal to the delay tank 55 which causes no change in the actuation of the pump 63. When the level of the liquid in the tank 51 reaches the lower extremity of the probe 50 which is located at the desired height of the liquid, the air is prevented from going through the probe 50 and is diverted within the diode 52 to enter the delay tank 55. The function of the delay tank 55 is to prevent a single spurious signal from accidentally activating the Schmitt trigger 57 in the event the probe 50 is disposed in a tank where the liquid is agitated or turbulent. The delay tank 55 provides an integrating or capacitive effect. When the capacitive effect has taken place, a fluidic signal from the delay tank 55 is provided to the Schmitt trigger device 57 which is then energized to provide a signal to the bistable flip-flop 62. The bistable flip-flop 62 energizes the pump 63 to cause it to extract liquid from the tank 51 until the bottom of the probe 50 is again exposed. This permits air to exhaust through the probe 50 thereby maintaining the liquid in the tank at a predetermined level defined by the lower extremity of the probe 50.

An alternative liquid level control system is shown in FIG. 3 in which a bubbler tube or sensing probe 70 is inserted a predetermined distance below the level of the fluid in a tank 71. Air is supplied from a regulated pressure source 72 to a manifold 73 and thence through a fixed restrictor 74 to the power stream port 75 of a proportional amplifier 76. The manifold 73 also provides the reference level control signal to the control stream port 77 of the amplifier 76 via a fixed restrictor 78 and a set point variable restrictor 79, the setting of which establishes the desired liquid level signal. The manifold 73 further provides air to the bubbler probe 70 via a variable restrictor 80. The probe 70 is also connected via a variable restrictor 81 to provide a signal representative of the actual level of the fluid in the tank 71 to the control stream port 82 of the proportional amplifier 76. A power amplifier 83 has its power stream port 84 connected to be provided with air from the distribution manifold 73 via a fixed restrictor 85 and has its control stream port 86 connected to the operative output port 87 of the proportional amplifier 76. The output port 88 of the power amplifier 83 is connected to a variable speed pump or valve 89 to control the level of the liquid in the tank 71. The output port 88 is also connected in feedback fashion via a variable restrictor 90 effectively to the control port 82 of the amplifier 76.

in operation the material to be controlled is flowing into the tank 71 and the control ofthe level ofthe liquid in the tank 71 is accomplished by means of the variable speed pump 89 whose speed is controlled by the fluidic level control system. As the level in the tank 71 increases, the back pressure signal in the bubbler probe 70 is compared at port 82 with the reference pressure signal at port 77. The difference in pressure, if any, appearing at the ports 77 and 82 of the proportional amplifier 76 causes a proportionately greater or lesser output flow from the output port 87 as a function of the relative difference as explained above. The fluidic output signal from the proportional amplifier 76 is amplified in the power amplifier 83 to control the speed of the pump 89 to maintain the liquid in the tank 71 at the desired level. The feedback connection from the output of the power amplifier 83 to the input of the proportional amplifier 76 can be adjusted by means of the variable restrictor 90 to provide the desired stability and sensitivity for any specific application.

Referring now to FIG. 4, a fluidic density control system will be described which measures and controls the density of a material in a tank 91. The density sensor may comprise two probes 92 and 93 mounted one above the other such that the probes 92 and 93 measure the head of material at different depths in the material. The basic purpose of the density control system is to detect small changes in the differential head pressure when comparing the pressure seen by the two probes since changes in this differential are proportional to the change in density of the material. The output from each of the probes 92 and 93 is connected to respective

control stream ports

94 and 95 of a proportional amplifier 96. The probes are provided with air from a regulated air supply 97 connected to a manifold 98. The probes 92 and 93 are connected via respective variable restrictors 100 and 101 to the manifold 98. The power stream port 102 of the amplifier 96 is connected to the manifold 98 via a fixed restrictor 103. The output signal from the proportional amplifier 96 is further amplified in cascaded

amplifiers

105 and 106. Each of the amplifiers 10S and 106 has its respective power stream port connected via respective fixed restrictors to the manifold 98 for providing increasingly higher pressure at each stage. For example, a supply pressure of 3 psi. may be provided to the power port 102 of the amplifier 96; 16 psi. to that of the

amplifier

105, and 30 p.s.i. to that of the amplifier 106.

The output port 107 of the amplifier 106 is connected to the control stream port 108 of the amplifier 109. The other control stream port 110 of the amplifier 109 is is connected via a variable restrictor 111 and a fixed restrictor 112 to the manifold 98 to provide a reference or desired density signal to the control stream port 110. The signal representative of the actual density the material is applied to the control stream port 108. Any difference between the reference and actual density signals provides an output signal via the output port 113 which is coupled to the control stream port 114 of a power amplifier 115 via a variable restrictor 116. The amplified output signal from the output port 117 of the amplifier 115 is utilized to vary the density of the material in the tank 91 until the actual density signal appearing at control port 108 is equal to the desired density signal appearing at control port 110. A feedback connection for stability and sensitivity purposes may be provided from the output port 117 via a variable restrictor 118 to the control port 108. The output signal from the amplifier 115 may be used to control a pump, for example, to add dilutant to the tank 91,

It will be appreciated that suitable meters and indicators may be provided in the systems to accurately adjust and measure the various pressures but have not been shown for purposes of simplicity.

We claim:

1. A fluidic control system comprising condition sensing means responsive to actual conditions for providing fluidic signals in accordance with said actual conditions, fluidic threshold defining means responsive to said fluidic actual condition signals for providing fluidic control signals when said actual condition signals deviate from a desired condition, fluidic amplifying means responsive to said control signals for providing amplified control signals, and controllable load means responsive to said amplified control signals for controlling said actual conditions to tend to return said actual conditions to said desired condition; said fluidic threshold defining means includes fluidic flow path defining means having a preferred flow path coupled to said condition sensing means and a nonpreferred flow path that becomes operative to provide said fluidic actual condition signals when said preferred flow path becomes inoperative, and fluidic switch means coupled to said nonpreferred flow path and responsive to said fluidic actual condition signals when said preferred flow path becomes inoperative for providing said fluidic control signals; and fluidic delay means coupled between said fluidic flow path defining means and said fluidic switch means for delaying the effectiveness of said fluidic actual condition signals to prevent spurious signals from becoming effective.

2. A fluidic control system of the character recited in claim 1 in which said fluidic delay means is a delay tank.

3. A fluidic control system of the character recited in claim 1 in which said fluidic switch means is a fluidic Schmitt trigger means.

4. A fluidic control system comprising condition sensing means responsive to actual conditions for providing fluidic signals in accordance with said actual conditions, l'luidic threshold defining means responsive to said fluidic actual condition signals for providing fluidic control signals when said actual condition signals deviate from a desired condition,

fluidic amplifyingmeans responsive to said control signals for providing amplified control signals, and controllable load means responsive to said amplified control signals for controlling saidiactual conditions to tend to return said actual conditions to said desired condition; said fluidic threshold defining means having a l'l'uidic reference signal generating means for providing fluidic reference signals in accordance with said desiredcondition and comparison means responsive to said actual signals and said reference signals for providing a comparison "therebetween; said fluidic reference signal generating means having a means for compensating for undesired pressure fluctuations to provide substantially constant fluidic reference signals, and said compensating means includes a proportional amplifier means and transverse impact modulator means interconnected to each other and coupled between a fluid pressure source and said comparison means for compensating for undesired pressure fluctuations of said fluid pressure source thereby to provide substantially constant fluidic reference signals. g

5. A fluidic control system comprising condition sensing means responsive to actual conditions for providing fluidic signals in accordance with said actual conditions, fluidic threshold defining means responsive to said fluidic actual condition signals for providing fluidic control signals when said actual condition signals deviatefrom a desired condition, fluidic amplifying means responsive to said control signals for providing amplified control signals, and controllable load means responsive to said amplified control signals for controlling said actual conditions to tend to return said actual conditions to said desired condition; said fluidic threshold defining means having a reference signal source and a proportional fluid amplifying means having -a pair of input control nozzles associated therewith, one of said input control nozzles being coupled to said reference signal source, the other of said control nozzles being coupled to said sensing means and a variable restrictor means coupling the output of said fluidic amplifying means to the said other control nozzle whereby the stability and sensitivity of the system can be controlled.

6. A fluidic control system of the character recited in claim 5 in which said proportional amplifying means includes a plurality of cascaded proportional amplifiers having successively higher pressure power streams.

7. A fluidic control system of the character recited in claim 5 in which said condition sensing means includes probe means disposed with respect to the substance being measured such that the location of said probe means defines a desired condition at least in part.

8. A fluidic control system of the character recited in claim 7 in which said probe means is responsive to pressure heads of a substance at two different levels for providing a measure proportional to the density of said substance.