US3206934A - Electro-pneumatic actuator including a self-contained closed source of restorative - Google Patents

Description

TERA/AL PHYSICAL G. C. CHILDS CLOSED SOURCE OF RESTORATIVE Filed Oct. 25, 1963 ELECTED-PNEUMATIC ACTUATOR INCLUDING A SELF-CONTAINED Sept. 21, 1965 INVENTOR. GfORGf C. C/V/LDS United States Patent ELECTRO-PNEUMATIC ACTUATOR INCLUDING A SELF-CONTAINED CLOSED SOURCE OF RESTORATIVE George C. 'Childs, 114'16 Manorwood Drive, Baton Rouge, La. Filed Oct. 23, 1963, Ser. No. 318,401 6 Claims. (Cl. 60--57) This invention relates to an actuator which includes its own source of pneumatic pressure and which is adapted to respond with accuracy to a signal from a controller of an external physical condition in direct degree of correspondence with the impulse of the signal.

Heretofore actuator devices of this type have relied upon an external source of pneumatic pressure for the actuating gaseous medium, such as compressed air delivery from a compressor drawing from the atmosphere, with the consequence that accurate and effective operation has been retarded, as by the air not being clean, or being subject to atmospheric condition as excess moisture, flow stoppage due to freezing, or stoppage or interference with operation due to the presence of foreign matter carried by the gas or compressed air.

However by providing an inert, compressible medium, as nitrogen or gases of similar characteristics in a closed system, the objections to the use of a gas, as compressed air, from an open system, may well be obviated and overcome. This is especially advantageous where the reaction of the pressure controlled actuator has to be in detailed accuracy and in direct or linear proportion to the impulse or intensity of the signal transmitted. Also, an actuator including a self-contained, closed control gas system may be employed in remote locations, and in places difiicult of access where a source for compressed air or other gas is not available. Also in plants where all apparatus but valves may be electrically controlled with accuracy, the electrical parts of valve control systems may be complemented by self-contained, closed pneumatic actuators to obtain the required degree of accurate valve control.

It is therefore a primary object of this invention to provide an electro-pneumatic actuator with a self-contained, closed source of pressurized gas included thereby whereby to insure detailed accuracy of response to electrical signals transmitted thereto commanding the actuator to react accordingly to an external physical condition controlled by the signal transmitter.

It is also another and further object of this invention to provide an actuator of this class equipped with a selfcontained, closed source of pneumatic pressure designed to react with complete accuracy to signals transmitted thereto.

It is yet another object of this invention to provide an actuator of this class which is employable in remote locations difi'icult of access where ordinary separate sources of compressed gas, as compressed air supplied by a compressor, may not be available.

It is also a further object of this invention to provide an actuator of this class which may be employed in plants otherwise exclusively equipped with electrical controls, to complement an electrical signal transmitter by making response to signals with detailed accuracy not obtainable by electrical means.

Other and further objects may be apparent when the specification herein is considered in connection with the drawings in which:

FIG. 1 is a small scale elevational view, partially diagrammatic, showing generally the apparatus cooperative in a preferred embodiment of the invention, the figure disclosing direction of flow in one phase of operation;

3,206,934 Patented Sept. 21, 1965 FIG. 2 is a small scale view, comparable to the view of FIG. 1, showing direction of fiow in the other phase of operation;

FIG. 3 is an enlarged elevational view showing further details of the apparatus shown in FIGS. 1 and 2;

FIG. 4 is an elevational view, partially diagrammatic, showing apparatus adding refinement of control or amplification to output response to transmitted signal; and

FIG. 5 is a fragmentary elevational view showing another embodiment of the invention in which a hydraulic cylinder is employed in place of the diaphragm housing and diaphragm.

Referring in detail to the drawings in which like reference numerals are applied to like elements in the various views, an actuator system is shown in FIGS. 1 and 2 which is adapted to respond in accurate correspondence with the impulse of a signal transmitted from a control box CB, the response of the actuator being in turn effective upon an EXTERNAL PHYSICAL CON- DITION controlled by the control box CB.

In general the apparatus included by the system comprises a transducer 11 which is electrically connected to the control box CB by insulated electrical conductors 12, 13. The transducer 11 actuates control valve means therein which receives gas of the closed system, as nitrogen, from a high pressure receiver 14 by way of a supply conduit 15 and delivers gas therefrom through an output conduit 16, the valve means also venting the gas through a vent conduit 17 which branches externally of the transducer into a suction conduit 18 and a low pressure delivery conduit 19.

The output conduit 16 connects into an upper diaphragm housing section 20 to communicate with an upper expansible and contractible chamber 21 above :1 diaphragm 22, the periphery of the diaphragm being constrained between the flange of the aforesaid upper diaphragm housing section 20 and the flange of a lower, or low pressure housing section 23. The diaphragm 22 has a shaft 24 connected to its underside centrally thereof and this shaft extends sealably through the low pressure housing section 23 and through a guide housing 25 for connection to correctionally or responsively actuate the aforesaid EXTERNAL PHYSICAL CONDITION responsive to the signals transmitted from the control box CB to the transducer 11. A spring surrounds the shaft 24 and seats upwardly against the diaphragm 22 and downwardly against the low pressure housing section 23.

An electrically driven motor-compressor 26 comprising an electric motor 27 and a compressor 28 is connected to take suction through the suction conduit 18 which branches from the vent conduit 17 and which has a conventional check valve 29 therein yieldably urged seated so as to prevent flow in an upstream direction and disposed adjacent to the compressor 28. On the other hand the low pressure delivery conduit 19 comprising the other branch from the vent conduit 17 connects into the low pressure housing section 23 to communicate with the low pressure chambers 31 enclosed thereby.

The compressor 28 discharges into a discharge conduit 32 having a conventional check valve 33 therein yieldably urged seated so as to prevent flow in an upstream direction and disposed adjacent to the compressor 28. The compressor 28 is shown in FIG. 3 as being of the diaphragm type having a compression spring 34 seated on the bottom of the compressor housing to urge upwardly against the compressor diaphragm 35 in opposition to the downwardly acting pressure exerted by a shaft 36 connected to the upper surface of the diaphragm 35 centrally thereof and which extends through a guide sleeve 37. An eccentric cam 38 on the shaft 39 of the motor 27 bears on the top of the shaft 36 and once each shaft revolution the cam 38 urges the diaphragm 35 downwardly on delivery stroke. Thus, once every revolution of the motor shaft 39 compressed air is delivered by way of the discharge conduit 32 into the receiver 14.

The low pressure chamber 31 communicates with the interior of the adjacent inner end of a bellows type switch 40 having its outer end connected to communicate with the interior of the receiver 14. The switch 40 carries an electrical contact bar 41 which extends parallel to the path of travel of the switch 40 and is disposed to establish contact with a contactor point 42 in one power conductor 43 from a source of electrical power.

The movable contact bar 41 has a power conductor 43 connected thereto of length having play therein to compensate for contact bar travel, and this conductor 43' extends to one terminal T of the motor 27, whereby the bar 41 comprises the switch closing and opening means in series circuit of one power conductor 43. The other power conductor 44 extends from the opposite motor terminal T to the source of electrical power.

The transducer 11 includes a magnet 45 therewithin having a core 46 disposed concentrically within the magnet, and a wound coil 47 is disposed between the magnet 45 and the core 46, the conductors 1'2, 113 from the control box CB being connected at opposite ends to the coil windings. Thus when the control box OB emits a signal, the coil 47 is energized and moves the upper end of a beam 48 to the left fnom the position shown in FIG. 3, so that the beam 48 pivots about its fulcrum 49 to move a vent valve element 50 on the lower end of the beam to the right to reduce the opening or close on a vent valve seat 51 provided by a wall 52 across the transducer 11 which divides the transducer housing into a transducer clramber 53 and a pneumatic control chamber 54.

The outer wall 55 of the chamber 54 has an orifice or choke 56 therein which reduces-the gas or air supply inlet from the conduit 15 to a restricted cross-sectional area whereby the supply gas or air cannot enter the control chamber 54 faster than such air or gas may pass through the vent valve seat into the transducer chamber 53 and therefrom out the vent port 57 in the transducer housing 11 into the vent conduit 17. It can thus be seen that the degree of opening of the vent valve 51 directly determines whether the output pressure of air or gas leaving the chamber 53 through the output port 58 from the control chamber 54 increases or decreases in the out- '.put conduit 16 and in the upper diaphragm housing chamber 21.

In FIG. 3 the diaphragm shaft 24 extends sealably through a bonnet seal 59 provided in the upper part of a 'globe valve 60 and has the globe Valve element 61 on the lower end thereof to seat and unseat from the globe valve seat 62 through the globe valve wall 13 .across the globe valve 60. The valve 60 as shown is disposed in a conduit 64, as a pipe line 65, and downstream from the valve 60 the control box CB is connected into the conduit '64 to respond to a variable condition, which, for example In case the pressure downstream in the conduit 64 is lower than a predetermined desired reading, the globe valve 60 should be urged in further opening direction to permit the transported gas to pass downstream at a greater rate to build up downstream pressure. The control box CB thus responds to the pressure acting thereagainst to transmit a signal to the transducer 11 in the form of electrical current flowing to the coil 47. The coil 47, as energized, moves the upper end of the beam 48 to the right as viewed in FIG. 3, thereby opening the vent valve seat 51 by moving the vent valve element 50 away from its seat. This permits a greater proportion of the closed system'gas or .air to pass through the valve seat 51 and out through the vent port 57 into the vent conduit 17 to pass into the low pressure chamber 31. This reduces the pressure in the upper diaphragm chamber 21 and increases the .pressure in the lower chamber 31 and thereby the spring 30 may urge the diaphragm 22 upwardly as the gas or air is vented from the transducer chamber 53.

The reaction of the spring 30 against the diaphragm 22 is a comparatively slow reaction as the spring 30 can move the diaphragm 22 upwardly no faster than the gas in the upper chamber 21 can be forced out of such upper chamber 21 as the air or gas therebelow in the output conduit 16 is forced back into the pneumatic control chamber 54 and out through the valve seat 51 past the valve element 50 on the lower end of the beam 48.

As the vent conduit 19 exhausts into the low pressure chamber 31 the pressure in this chamber rises causing the bellows switch 40 to expand and move the contact bar 41 into circuit closing contact with the contact point 42 .to close circuit to the motor 27 thereby to drive the compressor 28 to take suction from the suction line or conduit 18 and to discharge into receiver 14. Consequently pressure builds up in the receiver 14 and now falls or decreases in the low pressure chamber 31 with the consequence that the bellows contracts and carries the contact bar 41 out of contact to open the circuit 43, 43.

In case the pressure downstream in the conduit 64 is higher than a predetermined desired reading, the globe valve 60 should be urged further in closing direction to restrict the pipe line gas from passing downstream at a slower rate so as to reduce downstream pressure. The control box CB thus responds to the pressure acting thereagainst to transmit a signal to the transducer 11 in the form of electrical current flowing to the coil .47. The coil 47,as energized, moves the upper end of the beam 48 to the left as viewed in FIG. 3 thereby moving the vent valve element 50 in direction to reduce the opening of or close the valve seat 51. A lesser proportion of the closed system gas or air now bleeds oil? through the valve seat 51 to pass out into the vent line or conduit 17 and into the low pressure chamber 31. Consequently a greater amount of gas or air now passes through the output conduit 16 to build up pressure in the upper chamber 21 whereby the diaphragm 22 is urged downwardly against the upward urging of the spring 30 with the consequence that the shaft 24 urges the valve element 61 downwardly in valve seat closing direction to reduce the opening of said element or to close the valve seat 62.

As this reaction takes place in due time the pressure in the upper chamber 21 builds up to .an operative figure, since it is fed by air or gas from the output conduit 16. The pressure drops in the receiver 14 due to the gas or air passing therefrom out the input or supply conduit 15 and into the pneumatic control chamber 54, all or the greatest proportion thereof passing through the output conduit 16 to the upper chamber 21. Thus the depletion of the gas or air in the receiver 14 causes the bellows 40 to move left in direction of the receiver 14 and the bellows 40 carries with it contact bar 41 as itacts responsive to the pressure overbalance in favor of the chamber 31, and thus circuit making contact is established with the contact point 42 to close the circuit 43, 43 and start the motor-compressor 26 to draw air or gas from the suction conduit 18 to replenish the receiver 14.

In order to amplify the responsiveness or sensitivity of the pneumatic system, the response of gas or air in the output conduit 16 responsive to transmitted signals, an amplifier 66 may be provided and attached to the end of the pneumatic control chamber 54 as indicated in dotted lines in FIG. 3, and as shown in detail in FIIG. 4.

The amplifier 66 includes a housing or block 67 having a by-pass 68 from the input conduit 15 connected thereinto to communicate with a passage 69 provided to extend coaxially with said conduit 15 and by-pass 68. Such passage 69 provides a valve seat 70 against which the outer end or valve element 71 of a valve stem 72 may seat inwardly.

The passage 69 also includes a counterbored chamber 73 providing outwardly a seat for a spring 74 which surrounds the valve stem 72 and bears inwardly against a flange 75 rigidly connected to the valve stem 72. The passage 69 also provides a guide bore 76 for the valve stem 72, and an inner chamber 77 with which the chamber 73 communicates as indicated by the port 78. The inner end of the valve stem 72 comprises a valve element 79 which can seat in a valve seat 80 carried by a diaphragm 81 across the inner chamber 77.

An additional diaphragm 82 is provide in the chamber 77 spaced outwardly of the diaphragm 81 which is in turn spaced from the adjacent end of the block 67 by a control chamber 83 comprising the outer end of the chamber 77. A by-pass vent. 84 extends from the space between the diaphragms 81 and 82 to the vent conduit 17 outwardly of the transducer housing 11; the control chamber 83 communicates, through .a port 85 through the outer wall of the transducer housing 1 1, with the pneumatic control chamber 54; also the output conduit 16 connects into the block 67 to communicate with the chamber 73.

In operation, when the transducer 11 is signalled, the pneumatic pressure in the pneumatic control chamber is changed in direction indicated by the vent valve movement in accordance with the signal. This changes the pressure in the control chamber 83 as operative against the outer diaphragm 82. The inner diaphragm 81 moves responsively with the outer diaphragm 82 and accordingly moves the valve seat 80 carried thereby with relation to the valve element 79 carried on the end of the valve stem 72. As the travel of the valve stem 72 is limited by contact of the flange 75 carried thereby coming into contact with the guide wall 76, this means that the diaphragm 81 can move the valve seat 80 away from the stem end element 79. Conversely the diaphragm 81 can move in direction of the stem 72 and seat upon its end element 79, and urge the valve stem 72 outwardly to unseat the valve element 71, allowing supply gas from input by-pass 68 to pass into the chamber 73 and out therefrom into the output conduit 16.

On the other hand when the valve stem end element 79 is unseated while the valve stem end element 71 is seated, then gas or air can pass from the output conduit 16 through the chamber 73 and port 78 into the inner end of the chamber 77 and through diaphragm valve seat 80 to the vent by-pass conduit 84. It is noticeable that a more positive reaction occurs under each condition under which the output pressure is required to change, whether the change involves building up, or bleeding down the output pressure. it can thus be seen that an amplifier of this class can enhance the rapidity of reaction in either direction.

Although a diaphragm actuated system is shown in FIGS. 1, 2 and 3, the invention may as well be operated by a cylinder in place of the diaphragm housing sections, and such a cylinder 85 is shown in FIG. 5. In this arrangement a piston 86 serves the closure function of the diaphragm 22, and a piston rod or shaft 87 serves the function of the diaphragm shaft 24. Also a spring 30 comparable to the spring 30 serves to yieldably oppose the pressure of gas or air which enters the upper end of the cylinder to pass into a chamber 21' and acts downwardly on the head of the piston 85. In such arrangement the lower end chamber 31' of the cylinder, below the piston 85, is comparable to the low pressure chamber 31 below the diaphragm. correspondingly, therefore, the conduit 19 will connect into the chamber 31' and connection for a switch 40' is provided therefrom.

Various features of construction are shown employed. As the receiver 14 is subject to the build up of high pres sure therein cooling fins 88 may be provided along the receiver housing. As to arrangement of apparatus, it is of importance that all of the components may be assembled and integrally mounted. As a sample of arrangement the motor-compressor 26 is shown mounted structurally on top of the upper diaphragm housing section 20, while the transducer housing 11 is indicated by dotted lines as being connected to the lower diaphragm housing sections.

The invention is not limited to the combination shown in FIG. 3, but, as indicated in FIG. 2, the combinations may include any type of control box and any external physical condition to be controlled thereby. For example the physical condition may be the position of damper in a boiler stack or furnace, the position of a ships rudder, the position of a metering pump feed, the engagement and disengagement of clutches, control of engine throttles, or the position of steam turbine governors.

The invention is therefore not limited to the structures and combinations hereinabove described, but other and further combinations, structures, and usages are included, as long as such fall Within broad spirit of the invention, and within the broad scope of interpretation claimed for and merited by the appended claims.

What is claimed is:

1. An electro magnetic actuator including a housing, a diaphragm thereacross, an actuator shaft extending from said diaphragm sealably through said housing to exert yieldably urged mechanical control upon an external physical condition, an electrical transducer, a controller to transmit a signal to said transducer responsive to the needs of said external physical condition, a control valve in said transducer urged toward opening and closing positions responsive to signal impulses, an input conduit, a fixed orifice therein connected to the upstream end of said control valve, an output conduit leading from said input conduit between said fixed orifice and said control valve to said housing above said diaphragm, and an exhaust conduit from the downstream side of said valve to said housing below said dia phragm, a pressure increaser and drive means therefor, a suction line from said exhaust conduit to said pressure increaser, means to receive high .pressure air delivered thereinto from said pressure increaser, a discharge conduit from said pressure increaser to said receiving means, said input conduit being connected to take discharge from said receiving means, a pressure sensitive device operable at a predetermined pressure differential between said receiving means and said housing below said diaphragm to start said drive means to drive said pressure increaser to withdraw from said suction line and deliver to said receiving means until a predetermined pressure differential is restored between said re ceiving means and said housing below said diaphragm whereby said pressure sensitive device is operated to stop said drive means.

2. An electro-pneumatic actuator including a housing, a diaphragm thereacross, an actuator extending from said diaphragm sealably through said housing therebelow to exert yieldably urged mechanical control upon an external physical condition, an electrical transducer, a controller to transmit a signal to said transducer responsive to the needs of said external physical condition, a control valve in said transducer urged toward opening and closing positions responsive to signal impulses, an input conduit, a fixed orifice therein connected to the upstream end of said valve, an exhaust conduit from the downstream side of said valve to said housing below said diaphragm, an amplifier including a three-way valve operable responsive to pressure downstream of said fixed orifice and also including an input by-pass conduit from said input conduit upstream of said fixed orifice to said three-way valve, a vent conduit from the downstream side of said control valve to said housing below said diaphragm, a vent by-pass conduit from said three-way valve to said vent conduit, an output conduit from said three-way valve to said housing above said diaphragm,

7, a self-contained system comprising an electric driven motor-compressor, a suction line from said exhaust conduit to said compressor, a high pressure receiver, a discharge conduit from said compressor to said receiver, said input conduit being connected to take discharge from said receiver, a differential switch counterpoised between said receiver and said housing below said diaphragm and operable upon the occurrence of a predetermined difierential pressure to start said motor-compres sor to, withdraw from said suction line and deliver to said receiver until predetermined pressures in said receiver and said housing below said diaphragm are restored when said motor-compressor is stopped by said switch.

3. An electro-pneumatic actuator as claimed in claim 2 in which said amplifier also includes an automatically adjustable orifice provided in said output conduit, and a by-pass conduit from said automatically adjustable orifice to said vent conduit.

4. An electro-pneumatic actuator including a housing, closure means across said housing and movable responsive to the diiferential of gas pressure thereabove and therebelow, a shaft means extending from said closure means sealably through said housing therebelow to exert yiedably urged mechanical control upon an external physical condition, a conversion means adapted to convert electrical impulses to pneumatic impulses in corresponding linear realtionship to the intensity thereof, a controller to transmit a signal to conversion means responsive to the needs of said external physical condition, an input conduit, a fixed orifice therein connected to the upstream end of said conversion means, an output conduit leading from said input conduit upstream of said conversion means to said housing above said closure means and an exhaust conduit from the downstream side of said conversion means to said housing below said closure means, a self-contained system comprising an electric driven motor-compressor, a suction line from said exhaust conduit to said compressor, a high pressure receiver, a discharge conduit from said compressor to said receiver, said input conduit being connected to take discharge from said receiver, a differential switch counterpoised between said receiver and said housing below said closure means and operable upon the occurrence of a predetermined diiferential pressure to start said motorcompressor to withdraw from said suction line and deliver to said receiver until predetermined pressures in said receiver and said housing below said closure means are restored when'saidmotor-compressor is stopped by said switch.

5. An electro-pneumatic actuator as claimed in claim 4 in which said motor-compressor is mounted on said housing.

6. An electro-pneumatic actuator as claimed in claim 4 in which said housing, said conversion means, and said, motor-compressor are integrally mounted.

References Cited by the Examiner UNITED STATES PATENTS 1,400,550 12/21 I-I-opwood 137-1 2,758,704 8/56 Spurlin.

2,942,581 6/ Gafi'ney 60-52 3,120,103 2/64 Beard et a1. 60-52 SAMUEL LEVINE, Primary Examiner.

EDGAR W. GEOGHEGAN, JULIUS E. WEST,

Examiners.

Claims (1)

1. AN ELECTRO MAGNETIC ACTUATOR INCLUDING A HOUSING A DIAPHRAGM THEREACROSS, AN ACTUATOR SHAFT EXTENDING FROM SAID DIAPHRAGM SEALABLY THROUGH SAID HOUSING TO EXERT YIELDABLY URGED MECHANICAL CONTROL UPON AN EXTERNAL PHYSICAL CONDITION, AN ELECTRICAL TRANSDUCER, A CONTROLLER TO TRANSMIT A SIGNAL TO SAID TRANSDUCER RESPONSIVE TO THE NEEDS OF SAID EXTERNAL PHYSICAL CONDITION, A CONTROL VALVE IN SAID TRANSDUCER URGED TOWARD OPENING AND CLOSING POSITIONS RESPONSIVE TO SIGNAL IMPULSES, AN INPUT CONDUIT, A FIXED ORIFICE THEREIN CONNECTED TO THE UPSTREAM END OF SAID CONTROL VALVE, AN OUTPUT CONDUIT LEADING FROM SAID INPUT CONDUIT BETWEEN SAID FIXED ORIFICE AND SAID CONTROL VALVE TO SAID HOUSING ABOVE SAID DIAPHRAGM, AND AN EXHAUST CONDUIT FROM THE DOWNSTREAM SIDE OF SAID VALVE TO SAID HOUSING BELOW SAID DIAPHRAGM, A PRESSURE INCREASER AND DRIVE MEANS THEREFOR, A SUCTION LINE FROM SAID EXHAUST CONDUIT TO SAID PRESSURE INCREASER, MEANS TO RECEIVE HIGH PRESSURE AIR DELIVERED THEREINTO FROM SAID PRESSURE INCREASER, A DIS-

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