US3659171A

US3659171A - Valve control system

Info

Publication number: US3659171A
Application number: US57990A
Authority: US
Inventors: John A Morgan
Original assignee: Phillips Petroleum Co
Current assignee: Applied Automation Inc
Priority date: 1970-07-24
Filing date: 1970-07-24
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25

Abstract

Apparatus is provided for actuating an intermittent motion control element, such as a rotary valve. A pulse generator establishes periodic actuating pulses at a frequency corresponding to the amplitude of a control signal. Rotation of a motor is regulated by these pulses through control circuits which can include a time delay relay to hold the motor stationary for a given time at a selected point in the cycle.

Description

United States Patent Morgan [4 Apr. 25, 1972 54] VALVE CONTROL SYSTEM 3,467,905 9/1969 Thornhill et a]. ..3l8/443 [72] Inventor: John A. Morgan, Bartlesvllle, Okla. Primary Examiner aemard A. Gilheany [73] Assignee: Phillips Petroleum Company Assistant Examiner-W. E. Duncanson, Jr. [22} Filed: July 24, 1970 Attorney-Young and Quigg [21] Appl. No.: 57,990 57 B TR CT Apparatus is provided for actuating an intermittent motion [52] "318/443 control element, such as a rotary valve A pulse generator [51] "H02? 5/10 establishes periodic actuating pulses at a frequency cor- [58] Field of Search ..3 1 8/443, 444, 466 responding to the amplitude of a comm] signaL Rotation of a motor is regulated by these pulses through control circuits [56] References Cited which can include a time delay relay to hold the motor sta- UNn-ED STATES PATENTS tionary for a given time at a selected point in the cycle. 3,257,598 6/1966 Settles 1 8/443 6 Claims, 2 Drawing Figures 24 3= PULSE/ 25 2a 29 (o GENERATOR :U i r 2 3| as 2 I [33 l i 37 I Patented April 25, 1972 CATALYST COMPUTER SOLVENT PRODUCT MONOMER COOLANT 5 a WT 4 II 4 3 L M M 5 4 3 a 0 llrw \f \l, K a a 5 R 4 m fl M fiE m We T 3 INVENTOR. J. A. MORGAN FIG. 2

ATTORNEYS VALVE CONTROL SYSTEM In various types of chemical operations it is desirable to introduce materials in discrete masses rather than continuously. One such example occurs in polymerization reactions. utilizing solid catalysts which are introduced into a reactor in the form of a slurry. It is difficult to introduce such a material continuously at relatively low flow rates because the solid particles may bridge and plug the control valve. In order to overcome this problem, rotary valves have been developed, such as described in U.S. Pat. No. 3,l67,398. These valves employ a rotary plug which has a chamber therein to receive a predetermined quantity of material to be metered. In one position the chamber is filled with the material, and in another position the material is forced through the valve. When such a valve is employed in an automatic control system, a need exists for apparatus to move the valve intermittently between such positions at a rate which is proportional to'the amplitude of a control signal. One example of apparatus which can be employed for this purpose is described in U.S. Pat. No. 3,467,905.

In accordance with the present invention, improved apparatus is provided which is capable of intermittently operating equipment such as a rotary valve. This apparatus utilizes relays, including a time delay relay, to control the application of current to a motor which is employed to rotate the valve. A selector switch is actuated in response to rotation of the motor to control the desired intermittent operation. The apparatus of this invention can be constructed of relatively simple components which are readily available commercially.

In the accompanying drawing,

FIG. 1 is a schematic representation of a polymerization reactor having the valve control apparatus of this invention incorporated therein.

FIG. 2 is a schematic circuit drawing of an embodiment of the control apparatus of this invention.

Referring now to the drawing in detail and to FIG. 1 in particular, there is shown a polymerization reactor which is provided with a jacket 11 through which a coolant can be circulated. Such a coolant is introduced through a conduit 12 and withdrawn through a conduit 13. Monomer, solvent and catalyst are introduced into reactor 10 through

respective conduits

14, 15 and 16. The product is withdrawn through a conduit 17. Catalyst, which preferably is supplied in the form of a slurry, is introduced through conduit 16 at a rate which is controlled by the frequency at which a rotary valve l8'is actuated.

The polymerization system of FIG. 1 can be controlled by means of a heat balance computer 19 of the type described in U.S. Pat. No. 3,078,265. This computer receives signals representing variables in the reaction system and provides an output signal which is representative of the polymerization rate. This output signal is applied to the input of a controller 20. Controller 20 also receives a set point signal 21 which is representative of the desired rate of polymer production. In response to a comparison of two input signals, controller 20 establishes an output signal which is applied to valve control means 22 to operate valve 18 to control the rate of catalyst addition.

Control means 22 is illustrated in FIG. 2. Controller 20 provides an output electrical signal, the amplitude of which is representative of the desired rate of catalyst flow through conduit 16. This signal is applied to input terminals 23aand 23b'of FIG. 2.

Terminals

23a and 23b are connected to the input of a pulse generator. 24 which establishes output pulses at a frequency which is proportional to the amplitude of the input signal. The output signal from pulse generator 24 actuates a relay 25 which serves to move a switch 26 into engagement with a terminal 27 when the relay is energized. Switch 26 is thus closed at a frequency which is proportional to the amplitude of the output signal from controller 20. A linear integrating totalizer of the type described in Data Sheet 197-101 of Moore Industries, Inc. of Van Nuys, California can be employed as the pulse generator, for example. Such a totalizer actually includes switch 26 as an integral part thereof. The pulse generator can be selected to provide approximately 330 pulses per hour, for example, when a maximum amplitude output signal is received from controller 20.

The apparatus of FIG. 2 includes two

additional relays

28 and 29, the latter being a time delay relay on closing which can be of the order of 2 seconds, for example. When relay 28 is energized, switches 30 and 32 engage

respective terminals

31 and 33. When relay 29 is energized, a switch 34 engages terminal 35 after the delay. At the same time, a switch 36 is moved out of engagement with a terminal 37.

Relays

28 and 29 are energized from a voltage source 40, which can be either a direct or alternating source, depending on the type of relays employed. The first terminal of source 40 is connected to a switch 41 which selectively engages either a terminal 42 or a terminal 43. Switch 41 is controlled by a cam 44 which is mounted on the drive shaft of a motor 45. A voltage source 46 is connected to motor 45 by

parallel switches

34 and 30. The drive shaft of motor 45 is connected to valve 18 to actuate the valve in the manner to be described. Terminal 42 is connected to switch 26 and to terminal 33. Terminal 43 is connected to switch 36 and to one terminal of relay 29. The second terminal of relay 29 is connected to the second terminal of voltage source 40. Terminal 27 is connected to one terminal of relay 28, the second terminal of which is connected to the second terminal of voltage source 40. Switch 32 is connected in parallel with switch 26.

Valve 18 is illustrated schematically in FIG. 2. This valve includes a rotatable plug 18a which is provided with a central chamber 18b. A ball 18c is disposed in chamber 18b so as to be free to move longitudinally through chamber 18b, thereby forming a rotary check valve. When the plug is in the position illustrated, catalyst slurry fills valve chamber 18b above ball 18c. When the plug is rotated this slurry is trapped in the plug. When the plug is rotated an additional 90, the trapped slurry is displaced from the valve and flows into reactor 10.

In order to describe the operation of the apparatus of FIG. 2, it will be assumed that plug initially is in a position 90 from that illustrated and switch 41 is in engagement with terminal 42. When an output pulse is received by relay 25, switch 26 is closed to energize relay 28. This closes switches 30 and 32, the latter serving to latch relay 28 in the energized position. Closure of switch 30 results in motor 45 being energized to rotate plug 18a approximately 90 to the position illustrated. After this 90 rotation, cam 44 moves switch 41 out of engagement with terminal 42 and into engagement with terminal 43, thereby deenergizing relay 28 to terminate rotation of motor 45. Switch 41 then applies current to time delay relay 29, which results in the relay being actuated after the short delay. This delay permits the catalyst slurry previously trapped in chamber 18b to be emptied and a new mass of slurry to fill the chamber. When relay 29 is actuated, switch 34 is closed to once again energize motor 45. Rotation of plug 18a continues for another 90, at which time cam 44 moves switch 41 out of engagement with terminal 43 and into engagement with terminal 42. Motor 45 then remains stationary until another pulse is received by relay 25 to initiate another cycle of operation. Cam 44.is designed so that the foregoing operation is repeated when the cam is rotated the following 180. An indicating lamp 50 is connected between terminal 37 and the second terminal of'voltage source 40. Each time relay 29 is energized, lamp 50 is extinguished to provide a visual indication that the circuit is operating. As an alternative, lamp 50 can be actuated by the closing of a switch corresponding to 36 in response to relay 29 being energized. A terminal 51 is connected to relay 28 so that the application of a potential to terminal 51 results in relay 28 being energized. This permits the apparatus to be operated manually by applying a potential to terminal 51.

7 While this invention has been described in conjunction with .a presently preferred embodiment, it obviously is not limited first switching means actuated by rotation of said motor to move periodically between first and second positions;

second switching means;

means responsive to the input signal to close said second switching means periodically at a rate representative of said input signal;

first control means including said first and second switching means to connect said source of current to said motor when said first switching means is in said first position and said second switching means is closed, said first control means including latching means actuated by said second switching means to retain said source of current connected to said motor until said first switching means is moved to said second position; and

second control means including said first switching means to connect said source of current to said motor when said first switching means is in said second position.

2. The apparatus of claim 1 wherein said second control means includes time delay means to delay the connection of said source of current to said motor after said first switching means is moved to said second position.

3. The apparatus of claim 1 wherein said input signal is an to close said second switching means comprises a pulse generator-adapted to provide a series of output pulses at a frequency proportional to the amplitude of said input signal.

4. The apparatus of claim 1 wherein said first switching means is actuated by a cam which is rotated by said motor, said cam being of such configuration that said first switch is moved each time said cam is rotated approximately 90.

. electrical signal of variable amplitude, and wherein said means 5. The apparatus of claim 1, wherein said control element comprises a plug valve, said plug valve having a rotatable plug with a chamber therein, and a ball movable through said chamber to form a double check valve.

6. Apparatus for actuating an intermittent motion control element in response to an input signal comprising:

a motor connected to said control element;

a first source of current to energize said motor;

first, second, third and fourth switches;

means responsive to said input signal to close said first switch periodically at a rate representative of said input signal;

a fifth switch actuated by rotation of said motor to engage first and second contacts periodically;

a first relay to close said secondand third switches when energized; k

a time delay relay to close said fourth switch a predetermined time after being energized;

a second source of current;

first circuit means to connect said first source of current to said motor when either of said second and fourth switches is closed;

second circuit means to connect said first relay to said second source of current when said fifth switch engages said first contact and either of said first and third switches is closed; and

third circuit means to connect said time delay relay to said second source of current when said fifth switch engages said second contact.

Claims

1. Apparatus for actuating an intermittent motion control element in response to an input signal comprising: a motor connected to said control element; a source of current to energize said motor; first switching means actuated by rotation of said motor to move periodically between first and second positions; second switching means; means responsive to the input signal to close said second switching means periodically at a rate representative of said input signal; first control means including said first and second switching means to connect said source of current to said motor when said first switching means is in said first position and said second switching means is closed, said first control means including latching means actuated by said second switching means to retain said source of current connected to said motor until said first switching means is moved to said second position; and second control means including said first switching means to connect said source of current to said motor when said first switching means is in said second position.

3. The apparatus of claim 1 wherein said input signal is an electrical signal of variable amplitude, and wherein said means to close said second switching means comprises a pulse generator adapted to provide a series of output pulses at a frequency proportional to the amplitude of said input signal.

4. The apparatus of claim 1 wherein said first switching means is actuated by a cam which is rotated by said motor, said cam being of such configuration that said first switch is moved each time said cam is rotated approximately 90* .

5. The apparatus of claim 1, wherein said control element comprises a plug valve, said plug valve having a rotatable plug with a chamber therein, and a ball movable through said chamber to form a double check valve.

6. Apparatus for actuating an intermittent motion control element in response to an input signal comprising: a motor connected to said control element; a first source of current to energize said motor; first, second, third and fourth switches; means responsive to said input signal to close said first switch periodically at a rate representative of said input signal; a fifth switcH actuated by rotation of said motor to engage first and second contacts periodically; a first relay to close said second and third switches when energized; a time delay relay to close said fourth switch a predetermined time after being energized; a second source of current; first circuit means to connect said first source of current to said motor when either of said second and fourth switches is closed; second circuit means to connect said first relay to said second source of current when said fifth switch engages said first contact and either of said first and third switches is closed; and third circuit means to connect said time delay relay to said second source of current when said fifth switch engages said second contact.