Electropneumatic positioner

• US 5,159,949 A
• Filed: 06/10/1991
• Issued: 11/03/1992
• Est. Priority Date: 12/23/1988
• Status: Expired due to Fees

• Current Assignee: Dresser Industries Incorporated (Halliburton Company)
• Original Assignee: Dresser Industries Incorporated (Halliburton Company)
• Inventors: Prescott, Robert C., Sanford, Philip H., Simpson, Donald C., Nudd, Howard W.
• Primary Examiner(s): Cohan, Alan
• Application Number:
  US07/712,507
• Time in Patent Office: 512 Days
• Field of Search: 137/84, 137/82, 137/487.5, 251/129.04
• US Class Current: 137/84
• CPC Class Codes: F15B 5/003 characterised by variation of the pressure in a nozzle or the like, e.g. nozzle-flapper system
• CPC Class Codes: H01F 7/145 Rotary electromagnets with variable gap with fixed gap or torque motors H02K26/00
• CPC Class Codes: Y10T 137/2278 Pressure modulating relays or followers
• CPC Class Codes: Y10T 137/2365 Plural series units

Abstract

A transducer having an explosion-proof housing with a divider forming two compartments, and the divider having formed therein a well. A magnet and flapper arm arrangement is suspended within the well. A coil winding is fixed in the other compartment around the well so that a magnetic field generated thereby influences the pivotal position of the magnet. Set screws adjustable in the bottom of the well are effective to preset a rest position of the magnet.

Claims

1. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said transducer further comprises;

at least one bearing attached to said magnet for allowing pivotal movement of the magnet about an axis extending through said magnet in response to said magnetic field; and

a bearing support structure to which said bearing is attached for suspending said magnet and said bearing within the space encompassed by said coil winding.

2. A process control system in accordance with claim 1, further comprising a relay for amplifying the gas pressure in said supply line and for applying the thus amplified gas pressure to said valve actuator such that said valve actuator is responsive to gas pressures amplified by said relay for setting said valve stem to a desired position responsive to the gas pressure in said supply line.

3. A process control system in accordance with claim 1, further including an adjustment mechanism for adjusting a rest position of the flapper arm to achieve a desired spacing of said flapper arm with respect to the nozzle.

4. A process control system in accordance with claim 1, further including a supply of laminar flow air coupled to said supply line.

5. A process control system in accordance with claim 4, wherein said supply of laminar flow air comprises a restrictor and a regulator for controlling a pressure drop across the restrictor to a predetermined range of air pressures.

6. A process control system in accordance with claim 5, wherein said supply of laminar flow air maintains a laminar flow of air through said nozzle.

7. A process control system in accordance with claim 1, wherein each said bearing comprises a pair of flexure strips, and wherein said bearing support structure comprises a pair of support elements with each support element being connected to said magnet by a respective pair of flexure strips.

8. A process control system in accordance with claim 7, wherein said magnet has a shape defined by opposing rounded ends and opposing linear sides, wherein each bearing is connected to a respective linear side of said magnet, and wherein said coil winding is generally diamond-shaped for surrounding said magnet and said bearing support structure.

13. A process control system in accordance with claim 1, wherein said nozzle has an orifice for outputting a gas stream in response to gas pressure at the input to said nozzle, said nozzle having an annular frontal face tapered rearwardly from said orifice, and wherein said flapper arm has a flat surface adjacent said nozzle such that said nozzle directs said gas stream towards said flat surface for providing an at least substantially linear conversion of pressure of the gas stream to force on said flapper arm.

16. A process control system in accordance with claim 13, wherein said frontal face of said nozzle is tapered with an angle of about 45°

.

17. A process control system in accordance with claim 16, wherein said flat surface of the flapper arm is a raised circular surface.

18. A process control system in accordance with claim 13, wherein said flat surface comprise a hardened material formed in a plastic flapper arm.

19. A process control system in accordance with claim 13, further comprising air supply means for maintaining a laminar flow of air through said nozzle.

20. A process control system in accordance with claim 19, wherein said air supply means provides an air pressure in the range of about 5 to about 15 psi to said nozzle.

21. A process control system in accordance with claim 1, further including an arm attached to said magnet for providing a mechanical output from said transducer in response to an electrical input.

22. A process control system in accordance with claim 21, further including a counterweight attached to one of said arm and said magnet to provide balance about an axis extending through said bearing.

23. A process control system in accordance with claim 1, wherein said magnet has a shape defined by rounded opposing ends and linear opposing ends.

24. A process control system in accordance with claim 23, wherein each bearing is connected to a respective linear side of said magnet.

25. A process control system in accordance with claim 24, wherein said winding is generally diamond-shaped for surrounding said magnet and said bearing support structure.

26. A process control system in accordance with claim 1, further including a housing for enclosing said winding and said magnet, said housing having a divider for defining two compartments each isolated from each other, and further including a well formed in said divider, and wherein said magnet is suspended in said well in one compartment by said bearing support structure, and said winding is disposed around said well in a different compartment.

27. A process control system in accordance with claim 26, wherein said housing divider is effective to isolate electrical current carrying components in one compartment to provide an explosion-proof enclosure.

28. A process control system in accordance with claim 27, wherein sidewalls of said well are formed of anon-magnetic material.

29. A process control system in accordance with claim 28, wherein said well is formed of a electrically conductive material to provide eddy current dampening of movements of said magnet.

30. A process control system in accordance with claim 1, further including biasing means for biasing the magnet to arrest position.

31. A process control system in accordance with claim 30, wherein said biasing means comprises means for producing a magnet bias.

32. A process control system in accordance with claim 30, wherein said biasing means comprises a permanent magnet.

33. A process control system in accordance with claim 1, further including an adjustment screw formed of a magnetic material adjustably disposed in a position influenced by a magnetic field of the magnet.

9. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said magnet is mounted for pivotal movement about an axis, and

wherein said transducer further comprises means for balancing said magnet and said flapper arm about said axis so that said transducer is substantially insensitive to the orientation thereof.

10. A process control system in accordance with claim 9, wherein said means for balancing comprises a counterweight attached to one of said flapper arm and said magnet to provide balance about said axis.

34. A process control system in accordance with claim 10, wherein said counterweight comprises a non-magnetic material.

35. A process control system in accordance with claim 9, wherein said flapper arm is elongate and extends outwardly in one direction from said axis, and said magnet has attached thereto a counterbalance weight that extends outwardly in a different direction form said axis.

36. A process control system in accordance with claim 35, wherein said counterbalance weight is the same shape as said magnet.

11. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said transducer further comprises a housing for containing components of the transducer, said housing having a divider therein for defining two compartments isolated from each other, said divider having a well formed therein, said well having sidewalls and a bottom, said coil winding being disposed about said well in one of said compartments, said magnet and a bearing for said magnet being disposed in the other of said compartments, said bearing being mounted with respect to said magnet for pivotally supporting said magnet about an axis, a support fixed at one end with another end extending into said well, said another end being connected to said bearing for suspending said bearing and said magnet in said well.

37. A process control system in accordance with claim 11, further including a biasing structure attached to said housing for biasing said magnet to a rest position.

38. A process control system in accordance with claim 37, wherein said biasing structure comprises a permanent magnet fixed to said housing in proximity to said magnet for producing a pivotal movement.

39. A process control system in accordance with claim 37, wherein said biasing structure comprises an adjustable screw in a sidewall of said well, said screw being responsive to a magnetic field of the magnet.

40. A process control system in accordance with claim 39, wherein said screw is threaded in the bottom of said well.

41. A process control system in accordance with claim 11, further including an arm fixed to said magnet for providing a mechanical output of said transducer.

42. A process control system in accordance with claim 41, wherein said arm and said magnet are counterbalanced about said axis.

43. A process control system in accordance with claim 11, wherein said well is formed of a conductive, non-magnetic material to provide eddy current dampening of movements of said magnet.

44. A process control system in accordance with claim 11, further including a metallic magnetic return path for said magnet exterior of said coil winding.

45. A process control system in accordance with claim 44, wherein said magnet return path comprises a cylindrical shield circumferentially surrounding both said magnet and said coil winding.

46. A process control system in accordance with claim 44, wherein said magnet return path comprises a bracket to which said coil winding is mounted.

12. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said transducer further comprises a magnetic responsive material adjustably positioned with respect to said magnet for magnetically biasing said magnet and said flapper arm to a rest position in the absence of the magnetic field of the winding.

47. A process control system in accordance with claim 12, wherein said magnetic responsive material comprises at least one screw adjustably positioned with respect to the magnet to adjust a magnetic field influence therebetween.

48. A process control system in accordance with claim 12, wherein said magnetic responsive material comprises a permanent magnet.

14. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said transducer further comprises a housing having a divider defining two housing compartments, a well formed in said divider, said well having sidewalls and a bottom;

wherein said nozzle is mounted in a nozzle structure which is fixed to said housing, said nozzle structure having a pair of depending arms, with each of said arms having a flexure strip bearing;

wherein said flapper arm is mounted in a flapper arm structure having a saddle for holding said magnet, said flapper arm structure being connected to said nozzle structure through said flexure strip bearings so that said magnet is suspended for pivotal movement in said well; and

wherein said coil winding is positioned around the outer surface of the sidewalls of said well.

49. A process control system in accordance with claim 14, wherein said nozzle structure and said flapper arm are formed of a plastic material.

50. A process control system in accordance with claim 14, wherein said magnet is suspended in said well for pivotal movement about an axis which extends through said flexure strip bearings.

51. A process control system in accordance with claim 14, further including at least one adjustable set screw positioned in the bottom of said well for adjusting a rest position of the magnet.

52. A process control system in accordance with claim 14, wherein said well is constructed of a non-magnet and electrically conductive material.

53. A process control system in accordance with claim 14, wherein said well is generally diamond shaped to accommodate said magnet and said depending arms suspended therein.

15. A process control system, comprising:

a transducer having a coil winding for generating a magnetic field responsive to an electrical input to said coil winding, a magnet for producing a pivotal movement in response to the thus generated magnetic field, and a flapper arm mounted with respect to said magnet to produce a movement of said flapper arm corresponding to the thus produced pivotal movement of said magnet;

a supply line adapted to have a pressurized gas therein, a nozzle connected to said supply line, said nozzle being fixed adjacent said flapper arm so that said movement of said flapper arm affects the passage of said pressurized gas through said nozzle and thereby changes the gas pressure of the pressurized gas in said supply line;

a valve actuator for setting a valve stem to a desired position responsive to the gas pressure in said supply line; and

a feedback system comprising a linkage connected to said valve stem such that said linkage moves in correspondence with movement of said valve stem, and a spring connected between said linkage and said flapper arm to modify the position of said flapper arm responsive to the position of said valve stem;

wherein said transducer further comprises a housing for containing components of the transducer, said housing having a divider therein for defining two compartments isolated from each other, said divider having a well formed therein, said well having sidewalls and a bottom, said sidewalls being formed of a non-magnetic, electrically conductive material to provide eddy current dampening of movements of said magnet;

said coil winding being disposed about the outer surface of the sidewalks of said well in one of said compartments, said magnet and at least one bearing for said magnet being disposed in the other of said compartments, a magnetic return path for said magnet being positioned exterior of said coil winding;

said nozzle being mounted in a nozzle structure which is fixed to said housing;

each said bearing being mounted with respect to said magnet for pivotally supporting said magnet about an axis extending through said magnet;

a bearing support structure fixed at one end to said nozzle structure with another end extending into said well, said another end being connected to said at least one bearing for suspending said at least one bearing and said magnet in said well;

said flapper arm being elongate and extending outwardly in one direction from said axis, means for balancing said magnet and said flapper arm about said axis so that said transducer is substantially insensitive to the orientation thereof;

magnetic responsive material adjustably positioned with respect to said magnet for biasing said magnet and said flapper arm to a rest position; and

said nozzle having an orifice for outputting a gas stream in response to gas pressure at the input to said nozzle, said nozzle having an annular frontal face tapered rearwardly from said orifice, said flapper arm having a raised flat surface adjacent said nozzle such that said nozzle directs said gas stream towards said raised flat surface for providing an at least substantially linear conversion of pressure of the gas stream to force on said flapper arm.