US3823726A - Pneumatic control unit - Google Patents

Pneumatic control unit Download PDF

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Publication number
US3823726A
US3823726A US26800572A US3823726A US 3823726 A US3823726 A US 3823726A US 26800572 A US26800572 A US 26800572A US 3823726 A US3823726 A US 3823726A
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United States
Prior art keywords
piston
pistons
bellows
pressure
feedback
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Expired - Lifetime
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English (en)
Inventor
T Umeda
T Shiga
M Ando
N Wada
T Akiyama
R Fikuda
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Honeywell Inc
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Honeywell Inc
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Priority to JP5236071A priority Critical patent/JPS5437278B1/ja
Application filed by Honeywell Inc filed Critical Honeywell Inc
Priority to US26800572 priority patent/US3823726A/en
Priority to IT5140672A priority patent/IT960992B/it
Priority to DE2233685A priority patent/DE2233685A1/de
Priority to FR7225422A priority patent/FR2145663B1/fr
Priority to GB3276372A priority patent/GB1393259A/en
Application granted granted Critical
Publication of US3823726A publication Critical patent/US3823726A/en
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Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15C—FLUID-CIRCUIT ELEMENTS PREDOMINANTLY USED FOR COMPUTING OR CONTROL PURPOSES
    • F15C4/00—Circuit elements characterised by their special functions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/2278—Pressure modulating relays or followers
    • Y10T137/2365—Plural series units
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/2278—Pressure modulating relays or followers
    • Y10T137/2409—With counter-balancing pressure feedback to the modulating device
    • Y10T137/2452—With counter-counter balancing pressure feedback

Definitions

  • ABSTRACT A precision pneumatic proportional derivative or proportional integral derivative controller having a plurality of pistons each one of which forms a different portion of a balancing beam. Each piston is arranged to pass'through a different one of several spaced apart cylindrical passageways formed by inner wall portions of the casing of said controller. A separate rolling diaphragm is connected in fluid tight sealing engagement with each piston and with its associated wall portion to form a rolling seal therebetween. The diameters of these pistons are of predetermined sizes in relation to theirassociated passageway diameters. As a result, a
  • PAIENTEDJUU 812m 3323-326 saw so: a
  • the present invention relates to a pneumatic proportional and integrating (Pl) control unit or a pneumatic proportional integrating and differentiating (PlD) control unit and more particularly to an improved pneumatic type automatic integrating control unit with reset means wherein the output off-set thereof is substantially eliminated by providing a suitable difference between positive and negative feedback quantities.
  • Pl pneumatic proportional and integrating
  • PlD pneumatic proportional integrating and differentiating
  • Another object of this invention is to provide an improved pneumatic proportional integrating and differentiating control unit in which the output off-set of the pneumatic type automatic control unit with reset means is substantially eliminated.
  • a pneumatic proportional integrating control unit comprising l a pneumatic operational amplifier including a balancing beam; a casing having a cylin drical opening communicating at its opposite ends with the atmosphere and adapted to receive the balancing beam, and a pair of cylindrical air chambers formed in the casing, the cylindrical air chambers being coaxial with the cylindrical openings; a pair of pressure receiving members, each dividing its respectively associated air chamber into an input pressure receiving chamber and a feedback pressure receiving chamber, the stationary end of each pressure receiving member being sealed to the inner wall of each air chamber and the movable end of the pressure receiving member being sealed to the balancing beam at a predetermined portion thereof; a pair of rolling diaphragms respectively for the input and the feedback chambers, the rolling diaphragms sealing the cylindrical openings of the respective pressure receiving chambers; conduits for transmitting corresponding pressure signals to respective pressure receiving chambers; a nozzle-flapper device for converting the displacement of the
  • a pneumatic proportional integrating control unit comprising l a pneumatic operational amplifier including a pair of input pressure receiving chambers, a pair of feedback pressure receiving chambers, a plurality of pressure receiving members, each partitioning each pair of the pressure receiving chamber, a balancing beam connected to the pressure receiving members to be displaced thereby, and a nozzle-flapper device for generating a pneumatic pressure signal corresponding to the displacement of the balancing beam, the pneumatic operational amplifier providing a predetermined difference between a negative feedback quantity created by an output pressure and a positive feedback quantity created by a reset pressure, (2) a first feedback circuit for.
  • a pneumatic proportional integrating control unit comprising, (1) a pneumatic operational amplifier including a pair of input pressure receiving chambers, a pair of feedback pressure receiving chambers, a plurality of input pressure receiving members, each partitioning each pair of the pressure receiving chambers, a balancing beam connected to the pressure receiving members to be displaced thereby, and a nozzle-flapper device for producing an air pressure signal corresponding to the displacement of the balancing beam, the pneumatic operational amplifier providing a difference of a definite quantity between a negative feedback quantity created by an output pressure and a positive feedback quantity created by a reset pressure, (2) a first feedback circuit, for transmitting a negative feedback pressure to the first feedback pressure receiving chamber of the pneumatic operational amplifier, and a second feedback circuit for transmitting a positive feedback pressure to the second feedback pressure receiving chamber of the pneumatic operational amplifier, (3) a pair of input circuits respectively transmitting a control quantity signal pressure and a set value signal pressure to said pair of input pressure receiving chambers of the pneumatic
  • FIG. 1 shows a diagrammatic connection diagram of a pneumatic control apparatus embodying the invention
  • FIG. 2a shows a longitudinal section of an opera tional amplifier unit utilized in this invention
  • FIG. 2b shows a longitudinal section of an assembly incorporating the operational amplifier unit
  • FIG. 20 is a partial bottom view of the assembly shown in FIG. 2b;
  • FIG. 3 shows a longitudinal section of a switch
  • FIG. 4 is a diagram showing a pneumatic I:l relay
  • FIG. 5 shows a graph adapted to explain the operation of the pneumatic l:l relay
  • FIG. 6 is a diagram showing a rate unit
  • FIG. 7 shows a longitudinal section of the rate unit
  • FIG. 8 is a perspective view showing an orifice throttle and an orifice plate utilized in the rate unit shown in FIG. 7;
  • F IG. 9 is a graph showing the input-output characteristic of the rate unit shown in FIG. 7;
  • FIG. 10 is a longitudinal sectionalview of one example of a pneumatic pilot valve
  • FIG. 11 shows an electrical equivalent circuit and a characteristic of a pressure dividing circuit utilizing screw throttles or restrictions
  • FIGS. 12, 13, 14, 15 and 16 show block diagrams for explaining the operation of this invention.
  • FIG. 17 is a Bode diagram.
  • the PID pneumatic control apparatus shown therein comprises a pneumatic operational amplifier unit 45 including a pair of air inlet ports 86 and 87, a pair of feedback air inlet ports 88 and 89, and a nozzle flapper mechanism constituted by a flapper 68 and a nozzle 69 and functions to convert the displacement of a balancing beam into a corresponding output air pres sure; a screw throttle R a cylindrical fixed restriction R and a transfer switch SW which constitutes proportional band adjusting means on the input side; restrictions R and R, which constitute proportional band adjusting means on the input side; a reset restriction R and a reset capacitor C, which constitute a reset unit; a rate unit 46; a first 111 pneumatic relay 41 which functions to transmit the reset pressure to the pneumatic amplifier unit 45 at a ratio of one to one and to prevent the leakage of the air pressure from the reset unit to the proportional band adjusting means on the feedback side; a second
  • the rate unit 46 comprises a bellows unit 38, a rate throttle R and a rate capacitor C Like the reset throttle R rate throttle R takes the form of a nozzle-flapper type variable throttle. As shown in FIG.
  • the rate throttle R comprises a casing 144 containing a nozzle 143, a flapper 145 fulcrumed by a shoulder of the nozzle, a leaf spring 146.for biasing the flapper and means for adjusting the inclination of the flapper to adjust the degree of throttling.
  • the casing 144 is provided with air inlet ports 141 and 142.
  • Means for adjusting the inclination of the flapper, that is the degree of throttling comprises an eccentric cam 147, an operating knob for the eccentric cam, not shown, a cam follower 149 and an adjustable screw for urging one end of flapper 145 against cam follower 149.
  • the l:l pneumatic relays 41 and 42 have the same construction.
  • the relay comprises a casing 120, a diaphragm 125 dividing the interior of the casing into two air chambers 128 and 129, and a nozzle shaped discharge port 126 opening into chamber 128.
  • An air pressure supply conduit 122 is communicated with chamber 128 through a restriction 123, whereas output pressure conduit 124 is communicated directly with the chamber 128.
  • Another input pressure conduit 121 is connected directly to the other air chamber 129.
  • the pneumatic operational amplifier unit 45 comprises a casing 57, containing a pair of input pressure receiving chambers 51 and 52, a pair of feedback pressure receiving chambers 53 and 54, an input pressure receiving member and a feedback pressure receiving member 76, both in the form of bellows, and a balancing beam 67 connected between the movable ends of the pressure receiving members to be displaceable in response to the received air pressure signals.
  • casing 57 Within casing 57 are contained two pairs of cylinders 81, 82 and 83, 84 which are aligned on a straight line and arranged coaxialy with the balancing beam 67. These cylinders are communicated with the atmosphere at their one ends.
  • Cyplinders 82 and 83 are formed integral and are vented to the atmo sphere through a vent passage 55. These cylinders have the same inner diameter. Provision of the cylinders communicates all pressure receiving chambers with the atmosphere so that it is necessary to seal these chambers against the atmosphere.
  • rolling diaphragms 71, 72, 73 and 74 are provided. Each rolling diaphragm is mounted by securing its movable end to the balancing beam 67 and its stationary end to one end of the cylinder.
  • Respective cylinders contain pistons 61, 62, 63 and 64, respectively.
  • Respective pistons are secured to balancing beam 67 such that, at the zero position of the balancing beam, the heads of the pistons coincides with the ends of the corresponding cylinders phragms.
  • the outer diameter of the piston is essential to the improvement of the off-set. More particularly, as shown exaggerated in FIG. 2a, the outer diameter d, of piston 64 is smaller than that a, ofopposed piston 63. Another pair of opposed pistons 61 and 63 have the same outer diameter d, which is the same as that of piston 63. For this reason, it is advantageous to form pistons 62 and 63 as an integral unit to be received in integral cylinders 82 and 83.
  • the purpose ofthe balancing beam 67 is to derive the resultant displacement of a pair of pressure receiving elements 75 and 76.
  • a balancing beam assembly shown in FIG. 2b for the purpose of utilizing rolling diaphragms driven by pistons to provide the seals and to differentiate the piston diameters in order to improve the characteristic of the apparatus.
  • the balancing beam assembly shown in FIG. 2b comprises a balancing beam 67, pistons 61, 62, 63 and 64, and piston type bellows mountings 65 and 66.
  • Piston 74 is welded to the rear surface of the balancing beam 67.
  • diaphragm 74, bellow mounting 66, diaphragm 73, pistons 63 and 62, diaphragm 72, bellow mounting 65 and diaphragm 71 are mounted on the balancing beam in the order mentioned and finally piston 61 is bolted to the balancing beam 67 for fastening the movable ends of respective rolling diaphragms and the movable ends of the bellows thus completing the balancing beam assembly.
  • the balancing beam assembly is biased in the upward and downward directions within the casing of the operational amplifier unit 45 by means ofcoil springs 96 and 92.
  • the lower coil spring 92 is engaged by a zero adjusting member 93 having an operating knob 94.
  • the screw throttle R acting as the proportional band adjusting means on the input side utilizes a small gap between the male and female screw threads (usually such a gap is not desirable) as the throttle for the passage. of air.
  • the screw throttle R comprises a casing 101 formed with a female screw 102 between an inlet chamber106 and an outlet chamber 107 and a male screw 103 having screw threads of the same diameter and pitch as the female screw, an O-ring being provided around the head of the male screw. Accordingly, the screw throttle R, can be manufactured very easily and can be adjusted readily. It is important to note that the screw throttle greatly contributes to the improvement of the characteristic of the apparatus.
  • a pressure dividing circuit including a series screw thread R, and a parallel cylindrical throttle R as shown in FIG. 11 has an excellent operating characteristic. It was also confirmed by experiment that the operating characteristic of such a pressure dividing circuit is nearly straight when it is set to provide a ratio of pressure division of :1.
  • the proportional band adjusting circuit on the input side is constituted by a pressure diving circuit including throttles R, and R actually the circuit operates either to not divide the input pressure IPV-SPI or divide it at a ratio of 10:1, so that it is possible to adjust in the factory the throttle R, so as to provide the desired pressure division when it is combined with fixed throttle R and then fix the adjusting member by means of a synthetic resin, for example, thus making it impossible to adjust the throttle R, in the field.
  • the proportional band on the input side is set to only one ratio 1201 and the transfer switch SW utilized to provide this ratio is constructed to be free from any leakage as diagrammatically shown in FIG. 3. Since this switch SW is constructed substantially identically to automatic-manual transfer switches SW,, SW, and SW, except that it can be operated manually, its description is believed unnecessary.
  • the proportional band adjusting circuit on the feedback side is constituted by a pressure division circuit including a series throttle R and a parallel throttle R,, as shown in FIG. 1. These throttles are required to have the same characteristic.
  • both throttles take the form of needle throttle valves in which throttle R, is fixed and throttle R is variable.
  • throttle R is provided with an adjusting knob cooperating with a suitable scale, not shown. Utilization of throttles of the same characteristic to form the pressure dividing circuit is advantageous to improve the linearity.
  • throttles of the same characteristic provide a pressure division circuit of excellent linearity.
  • the proportion band adjusting circuit on the feedback circuit having such an excellent linearity that causes the operational amplifier unit to attain the desired object of improving the off-set.
  • l pneumatic relays 41 and 42 also contribute to this object.
  • each of the 1:1 pneumatic relay 41 and 42 hasthe construction shown in FIG. 4.
  • a 1:1 pneumatic relay inherently accompanies an output off-set so that its input-output characteristic deviates from an ideal 1:1 characteristic line A to line B shown in FIG. 5.
  • Such deviation is caused by the construction of the pneumatic relay.
  • the pneumatic relay has an air supply port 122 and'an air outlet port 126 which is faced to one side of diaphragm 125.
  • 1:1 pneumatic relay 41 it is important to connect the 1:1 pneumatic relay 41 in the reset circuit such that its air chamber 129 (FIG. 4) is connected to reset capacitor C, in order to prevent air leakage from the reset circuit to the proportional band adjusting circuit on the feedback side. If there is some cause that results in an error in the feedback circuit, the off-set eliminating function of the improved pneumatic operational amplifier unit 45 utilized in this circuit would be nullified.
  • 1:1 pneumatic relay 41 to oppose 1:1 relay 41 included in the positive reset circuit, is included in the negative feedback circuit 1:1 pneumatic relay 42 having the same characteristic thus completely eliminating the output offset from the differential signal between positive and negative feedback circuits. It is also possible to use 1:1 pneumatic relay 41 in a control apparatus including a rate unit for the purpose of preventing air leakage from the rate circuit to the proportional band adjusting circuit on the feedback circuit.
  • FIG. 7 shows a longitudinal sectional view of the balancing unit 47' which comprises a pressure receiving section and a unique nozzle-flapper section.
  • FIG. 7 comprises an orifice plate 177 including an orifice opening 178, means for deriving out the nozzle back pressure P from a point on the downstream side of nozzle opening 178, a clamping member 176, a nozzle 161 on one end of the clamping member, and means for admitting inlet air pressure.
  • the orifice plate 177 is shown on the lower side of FIG. 8, whereas clamping member 176 is shown on the upper side.
  • Clamping member 176 has a central bore 181 and radial slots 183 are formed through the inner end 182 of the clamping member 176 for deriving the back pressure.
  • a plug 175 for supporting the orifice is provided with inlet air passages 191 and 196 and a passage 192 for deriving out the nozzle back pressure, the communication between passages 191 and 192 being interrupted by an O-ring 196.
  • the plug 175 is coupled to a base block 151 through screw threads 193 and 194.
  • the base block 151 is formed with a passage 171 leading to a nozzle 161 and an axial chamber 185 which is sealed against the atmosphere by means of a metal ball 186.
  • the seal between the chamber 185 and the passage 192 for deriving out the nozzle back pressure is provided by the engagement at 197 between base block 151 and plug 175.
  • the pressure receiving section comprises a pair of pressure receiving chambers 154 and 155, a pair of pressure receiving members 156 and 157 such as diaphragms for defining the pressure receiving chambers, and a member 158 contacting the pressure receiving members for transmitting the displacement thereof to a flapper 160.
  • the left hand end of flapper 160 is connected to block 151 through a leaf spring 162 and a screw 163.
  • Flapper 162 is suitably biased by means of a pair of coil springs 164 and an adjusting member 165.
  • Clamps 159 are used to clamp diaphragms 156 and 157 in position and the operating air is supplied to chambers I54 and 157 through passages 152 and 153 in block 151.
  • the pair of pressure receiving chambers have substantially the same configuration so as to equalize the effective areas of respective pressure receiving elements. Accordingly, the vertical displacement of flapper 160 is proportional to the difference between two received air pressure signals P, and P and the direction of the displacement is determined by the sign of the difference (P, P In the embodiment.
  • the pneumatic output signal P (kg/cm) of the balancing unit 47 will vary as shown by FIG. 9 wherein the abscissa represents the distance X (mm) between the nozzle and the flapper while the ordinate the magnitude of the output air pressure signal P (kg/cm P, represents the input air pressure which is supplied from a source ofclean air of 1.4 kg/cm", for example, not shown, and the origin 0 represents the atmospheric pressure.
  • the abscissa represents the distance X (mm) between the nozzle and the flapper
  • the ordinate the magnitude of the output air pressure signal P (kg/cm P represents the input air pressure which is supplied from a source ofclean air of 1.4 kg/cm", for example, not shown, and the origin 0 represents the atmospheric pressure.
  • the nozzle-flapper used in this invention can produce an output air pressure signal P lower than the atmospheric pressure so that it is characterized by a high gain and excellent linearity in the operating range.
  • FIG. 10 shows one example of a pilot valve including a casing 200, a first diaphragm 209, a second dia phragm 210, coupling means 213 for assuring said two diaphragms as an integral body to vibrate, a first valve seat 211 formed in said coupling means 213, a second valve seat 214 fixed to the casing 200, a poppet valve assembly 220 having a valve 212 responsive to the first valve seat 211 and the other valve 215 responsive to the second valve seat 214, a coiled spring 217 applying said poppet valve 220 with an upward biasing force, the other coiled spring 216 applying the first and second diaphragms with an upward biasing force and a clamper or bolt 219.
  • Numerial orders 201, 202, 203 and 204 represent a pressure receiving port, an output pressure port, an air inlet port and an air discharge port, respectively.
  • air conduits 13 and 14 are connected to the pressure receiving port 201 and the output pressure port 202 set forth, respectively.
  • the quantity a is generally defined as the output off-set of the pneumatic control system and IOO/(i as the integration gain.
  • the output off-set is represented by l/AG while the integration gain by AG as is illustrated in FIG. 12.
  • the invention contemplates the provision of an improved pneumatic control apparatus capable of reducing the output off-set substantially to zero while maintaining the loop gain BG at a proper value.
  • the output off-set can be decreased substantially to zero by differentiating the feed back quantities while maintaining the loop gain BG at a proper value.
  • the actual output of the control apparatus is the output from the pilot valve PILOT
  • the pilot valve PILOT as shown in FIG. operates as an amplifier
  • two pressure receiving members are provided in this invention, one on the input side and other on the feedback side.
  • two pressure receiving members are required respectively on the input and feedback sides.
  • since only one pressure receiving element is used on the input side as well as on the feedback side it is not necessary to consider the difference in the effective areas of the pressure receiving members.
  • this problem can also be solved readily by. the adoption of a rolling diaphram.
  • the effective area of the rolling diaphram can be maintained at a constant value regardless of the variation in the displacement and pressure, provided that the diameters of the piston and cylinder are maintained constant.
  • the effective area of the rolling diaphram is much smaller than that of the bellows acting as the pressure receiving elements.
  • a pair of rolling diaphrams are provided on both input and feedback sides for providing seals so that the difference in the effective areas between opposing diaphrams should be considered. Fortunately, it is possible to manufacture the pistons and cylinders and to fabricate the rolling diaphragms so as to provide a difference between effective areas ofa value of about 0.5 to 1.0 percent.
  • the effective area of the rolling diaphrams is considerably smaller than that of the bellows.
  • the problem caused by the difference in the effective areas can be efficiently solved by using a pair of rolling diaphrams in each pressure receiving chamber for providing seals.
  • the provision of the seals does not increase the output off-set.
  • the construction required for the substantial improvement in the off-set is related to the seals.
  • the difference in the feedback quantity shown by equations (I) AND (2) is provided by the unique construction of the seals.
  • a single feedback pressure receiving element 76 is used to define two feedback pressure receiving chambers.
  • a pair of rolling diaphrams having the same characteristic but having a proper difference between their effective areas are used to form seals for the pair of feedback chambers.
  • the effective area of the rolling diaphragm is expressed by the area of an circle having a diameter equal to that of the movable end of the rolling diaphragm, the effective areas of rolling diaphragms 73 and 74 are shown by following equations.
  • the effective area S of a bellows is shown by the area of a circle having a diameter equal to one half of the sum of its inner diameter and outer diameter.
  • the bellows 76 having an effective area 8, (cm is applied with RESET (kg/cm prevailing inside the bellows 76 and in turn applies a downward force of RESET X S (kg) upon the balancing beam 67
  • the diaphragm 74 having an effective area s (cm applies the balancing beam 67 with an upward force of RESET X s (kg).
  • the other air pressure that is the feedback air pressure OUT (kg/cm causes simultaneously an upward force of OUT X S (kg) and a downward force of OUT X s, (kg) on the balancing beam 67.
  • Equation (7) can be rewritten as follows S is equal to the force S, which is applied upon bellows 76 by the negative feedback air pressure signal OUT whereas S As is equal to the force caused by the positive feedback air pressure signal RESET so that equation (8) represents the ratio between two forces, that is the ratio between two feedback quantities B, and 8,, thus showing that equations (1) and (2) are satisfied.
  • equations (3) (4) (5) and (6) as it is possible to determine the values of S and As by the suitable design of the dimensions and configurations of the bellows, rolling diaphragms, cylinders and pistons, it is easy to design to satisfy equation (7).
  • FIG. 1 shows a block diagram of a conventional pneumatic type automatic control apparatus with reset means under the steady state.
  • An ideal primary system can be obtained by adding throttle R and reset capacitor C, to the feedback side.
  • the ideal system is expressed by the following equation RESET/OUT l/l T, where T represents the time constant of the integrating throttle and s the operator of the Laplace transformation.
  • the feedback circuit of this invention re-' quires the use the 1:1 pneumatic relay which is not necessary for the circuit arrangement shown in FIG. 2a.
  • the 1:1 pneumatic relay is designed to have the characteristic B which is displaced a little from the ideal characteristic A.
  • a compensating relay 42 is included in the negative feedback circuit to apply both OUT and RESET to corresponding feedback pressure receiving chambers after transforming them according to the characteristic which is slightly shifted from the ideal characteristic.
  • output off-set of a pneumatic PI control or a pneumatic PlD control apparatus is substantially eliminated by providing a suitable difference between the positive and negative feedback quantities, that is by using a novel pneumatic operational amplifier unit. More particularly, the off-set caused by the difference in the effective areas of the pressure receiving members is eliminated by using a single bellows. Further, the problem of the seal caused by the use ofa single bellows and the problem caused by the difference in the effective areas of a pair of rolling diaphragms used to form the seals are solved by the proper selection of the preferred characteristic of the rolling diaphragms and by the prope'r selection of the dimensions of the cylinders and pistons which cooperate with the rolling diaphragms.
  • the required difference in the feedback quantities is provided by equalizing the diameter of a pair of opposed cylinders and by providing a suitable difference between the outer diameters of pistons 63 and 64 disposed in the cylinders for driving the rolling diaphragms.
  • the off-set is efficiently eliminated by compensating the output off-set of 1:1 pneumatic relay 41 by the 1:1 pneumatic relay 42 having substantially the same characteristic.
  • a balancing beam extending through said passageways in alignment with the axis of said housing and arranged for axial movement with said pistons in their associated passageways, the diameter of the piston in one end of said housing being smaller than the diameter of the other pistons.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Feedback Control In General (AREA)
  • Fluid-Pressure Circuits (AREA)
US26800572 1971-07-13 1972-06-30 Pneumatic control unit Expired - Lifetime US3823726A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
JP5236071A JPS5437278B1 (enExample) 1971-07-13 1971-07-13
US26800572 US3823726A (en) 1971-07-13 1972-06-30 Pneumatic control unit
IT5140672A IT960992B (it) 1971-07-13 1972-07-07 Perfezionamento nei servosistemi pneumatici
DE2233685A DE2233685A1 (de) 1971-07-13 1972-07-08 Pneumatischer pi-regler
FR7225422A FR2145663B1 (enExample) 1971-07-13 1972-07-13
GB3276372A GB1393259A (en) 1971-07-13 1972-07-13 Pneumatic control unit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP5236071A JPS5437278B1 (enExample) 1971-07-13 1971-07-13
US26800572 US3823726A (en) 1971-07-13 1972-06-30 Pneumatic control unit

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US3823726A true US3823726A (en) 1974-07-16

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US26800572 Expired - Lifetime US3823726A (en) 1971-07-13 1972-06-30 Pneumatic control unit

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US (1) US3823726A (enExample)
JP (1) JPS5437278B1 (enExample)
DE (1) DE2233685A1 (enExample)
FR (1) FR2145663B1 (enExample)
GB (1) GB1393259A (enExample)
IT (1) IT960992B (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083375A (en) * 1976-02-18 1978-04-11 Johnson Dwight N Pilot regulator
US11174962B2 (en) * 2017-05-31 2021-11-16 Hamilton Sundstrand Corporation Pneumatic servo valve with adjustable drive unit
US11214375B2 (en) * 2017-05-31 2022-01-04 Hamilton Sundstrand Corporation Spring sealed pneumatic servo valve

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3035990A1 (de) * 1980-09-24 1982-04-29 Eckardt Ag, 7000 Stuttgart Pneumatische nachfuehreinheit

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US2712321A (en) * 1951-04-17 1955-07-05 Honeywell Regulator Co Control apparatus
US3020490A (en) * 1957-11-21 1962-02-06 Phillips Petroleum Co Process controller
US3326228A (en) * 1963-03-06 1967-06-20 Robertshaw Controls Co Pneumatic relay
US3394722A (en) * 1966-06-30 1968-07-30 Texaco Inc Automatic control system
US3411529A (en) * 1964-06-24 1968-11-19 Honeywell Inc Fluid regulating apparatus
US3465768A (en) * 1966-08-16 1969-09-09 Ici Ltd Gain-adaptive control system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2712321A (en) * 1951-04-17 1955-07-05 Honeywell Regulator Co Control apparatus
US3020490A (en) * 1957-11-21 1962-02-06 Phillips Petroleum Co Process controller
US3326228A (en) * 1963-03-06 1967-06-20 Robertshaw Controls Co Pneumatic relay
US3411529A (en) * 1964-06-24 1968-11-19 Honeywell Inc Fluid regulating apparatus
US3394722A (en) * 1966-06-30 1968-07-30 Texaco Inc Automatic control system
US3465768A (en) * 1966-08-16 1969-09-09 Ici Ltd Gain-adaptive control system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083375A (en) * 1976-02-18 1978-04-11 Johnson Dwight N Pilot regulator
US11174962B2 (en) * 2017-05-31 2021-11-16 Hamilton Sundstrand Corporation Pneumatic servo valve with adjustable drive unit
US11214375B2 (en) * 2017-05-31 2022-01-04 Hamilton Sundstrand Corporation Spring sealed pneumatic servo valve

Also Published As

Publication number Publication date
FR2145663A1 (enExample) 1973-02-23
FR2145663B1 (enExample) 1978-02-10
JPS5437278B1 (enExample) 1979-11-14
DE2233685A1 (de) 1973-02-01
GB1393259A (en) 1975-05-07
IT960992B (it) 1973-11-30

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