Rotary-linear actuator

• US 6,215,206 B1
• Filed: 10/08/1999
• Issued: 04/10/2001
• Est. Priority Date: 03/28/1996
• Status: Expired due to Term

• Current Assignee: Anorad Corporation (Rockwell Automation, Inc.)
• Original Assignee: Anorad Corporation (Rockwell Automation, Inc.)
• Inventors: Chitayat, Anwar
• Primary Examiner(s): MULLINS, BURTON S
• Application Number:
  US09/415,562
• Time in Patent Office: 550 Days
• Field of Search: 417/415, 417/416, 417/417, 310/156, 310/12, 310/13, 310/14, 310/15, 310/266, 310/112, 310/254, 310/90
• US Class Current: 310/12.14
• CPC Class Codes: A61M 1/34 Filtering material out of the blood by passing it through a membrane, i.e. hemofiltration or diafiltration
• CPC Class Codes: A61M 1/3403 Regulation parameters
• CPC Class Codes: A61M 1/3496 Plasmapheresis; Leucopheresis; Lymphopheresis A61M1/3472 takes precedence
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: B01D 61/14 Ultrafiltration; Microfiltration
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: H02K 2201/18 Machines moving with multiple degrees of freedom
• CPC Class Codes: H02K 41/03 Synchronous motors; Motors moving step by step; Reluctance motors H02K41/035 takes precedence

Abstract

An actuator, with two independent degrees of freedom, rotates a stage about an axis and moves the stage along the axis, the range of motion defining a cylinder or cylindrical section. The stage is mounted on a hollow cylindrical plunger fitting in an annular well. A bearing allows the plunger to move axially and rotationally, in the preferred embodiment the bearing is an air bearing. The plunger has an array of permanent magnets on its external cylindrical face opposite coils in the well. Equal numbers of oppositely-polarized permanent magnets are arranged in a regular cylindrical pattern at 50% packing density forming rings and columns of like-polarity magnets, the rings of one polarity alternating with rings of opposite polarity and the columns of one polarity alternating with columns of opposite polarity. A set of Z-axis coils (for axial movement) curve around the plunger and are shaped to allow a current in them to produce an axial force with respect to the rings of magnets. A set of φ-axis coils (for rotational movement) have longitudinal axes that are parallel to the axis of the plunger and are sized to allow current in them to impel the columns of magnets. Part of the external surface of the plunger has a grid scale, which is encoded by Z-axis and φ-axis optical pickups to provide position information to a controller.

Claims

1. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on one of an outside surface of the plunger element and an inside surface of the motor support;

a first set of coils being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode; and

a second set of coils being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode.

2. The system of claim 1, wherein the array of magnets are arranged so that about one half of the magnets are oriented with the north poles pointing radially outward and about the other half of the magnets are oriented with the north poles pointing radially inward.

3. The system of claim 1, wherein the first set of coils are driven by a first motor and the second set of coils are driven by a second motor.

4. The system of claim 1, wherein the plunger element is limited in its fully retracted position by at least one vertical stop and limit switch assembly.

5. The system of claim 1, wherein the plunger element is limited in its fully extended position by at least one vertical stop and limit switch assembly.

6. The system of claim 1, wherein the bearing element is an air bearing.

7. The system of claim 6, wherein a surface defining the well includes at least one groove through which air can be distributed to form the air bearing.

8. The system of claim 1, wherein the bearing element is a cylindrical bushing with ball bearings held in by a cylindrical cage.

9. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on one of an outside surface of the plunger element and an inside surface of the motor support;

a first set of coils being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode;

a second set of coils being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode; and

an integral air cylinder formed by sealing a space between the motor housing and the plunger element.

10. The system of claim 9, wherein the integral air cylinder is connected to a source of air.

11. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on one of an outside surface of the plunger element and an inside surface of the motor support;

a first set of coils being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode; and

a second set of coils being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode;

wherein the array of magnets are arranged so that about one half of the magnets are oriented with the north poles pointing radially outward and about the other half of the magnets are oriented with the north poles pointing radially inward; and

wherein the array of magnets are arranged such that the about one half of the magnets oriented with the north poles pointing radially outward form a plurality of rings around the plunger element and the about the other one half of the magnets oriented with the north poles pointing radially inward form a plurality of rings around the plunger element, such that adjacent rings alternate between radially outward rings and radially inward rings.

12. The system of claim 11, wherein the rings of the plurality of magnets pointing radially outward form a plurality of rows of magnets with one another and the rings of the plurality of magnets pointing radially inward form a plurality of rows of magnets with one another.

13. The system of claim 12, wherein the array of magnets has a 50% packing density.

14. The system of claim 11, wherein each of the rings formed by the plurality of magnets consist of ten to sixteen magnets per ring.

15. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on one of an outside surface of the plunger element and an inside surface of the motor support;

a first set of coils being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode;

a second set of coils being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode; and

a thin sheet carrying an encoder scale affixed to a surface of the array of magnets.

16. The system of claim 15, wherein the encoder scale is etched with a pattern of reflective and non-reflective regions.

17. The system of claim 16, further including at least one optical pickup for registering movement of the plunger element in a linear direction and at least one optical pickup for registering the movement of the plunger element in a rotational direction.

18. A method for providing a linear actuator system, comprising the steps of:

providing a motor support with a bearing support, the motor support and bearing support defining a well;

providing a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a filly retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

affixing an array of magnets to an outside surface of the plunger element; and

affixing a first motor having a first set of coils to an inside surface of the motor support to apply an axial force on the array of magnets for driving the plunger element in a linear mode; and

affixing a second motor having a second set of coils to the inside surface of the motor support to apply an axial force on the array of magnets for driving the plunger element in a rotational mode.

19. The method of claim 18, wherein the first and second set of coils are embedded in a lamination on the inside surface of the motor support.

20. The method of claim 18, wherein the first and second set of coils are embedded in resin.

21. The method of claim 18, wherein the first set of coils are formed by the steps of:

winding the coils in a standard manner, using copper wire surrounded by a heat-actuated glue;

forming the coils in a straight longitudinal configuration;

applying a current to the coils and bending the coils in a jig to provide a curved shape; and

inserting the coils into slots in laminations on the inside surface of the motor support and applying varnish or epoxy into the laminations.

22. The method of claim 18, wherein the first set of coils are formed by the steps of:

winding the coils in a standard manner, using copper wire surrounded by a heat-actuated glue;

forming the coils in a straight longitudinal configuration;

applying a current to the coils and bending the coils in a jig to provide a curved shape; and

inserting the coils into slots in laminations on the other of the outside surface of the plunger element and the inside surface of the motor support and applying a powder iron held together with epoxy.

23. The method of claim 18, wherein the step of affixing an array of magnets to one of an outside surface of the plunger element and an inside surface of the motor support includes the step of affixing the array of magnets to the plunger element with an adhesive, allowing the adhesive to harden, and machining the exposed surface of the array of magnets to form a precision round surface.

24. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element including an inner cylindrical portion and an outer cylindrical portion, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

a first array of magnets arranged on an outside surface of the inner cylindrical portion of the plunger element;

a second array of magnets arranged on an inside surface of the outer cylindrical portion of the plunger element;

a first set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply an axial force on the first and second array of magnets for driving the plunger element in a linear mode; and

a second set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply a tangential force on the first and second array of magnets for driving the plunger element in a rotational mode.

25. The system of claim 24, wherein the bearing element is an air bearing.

26. The system of claim 25, wherein the surface defining the well includes a groove through which air can be distributed to form the air bearing.

27. The system of claim 24, wherein the bearing element is a cylindrical bushing with ball bearings held in by a cylindrical cage.

28. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing with a motor cylinder, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element including an inner cylindrical portion and an outer cylindrical portion, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

a first array of magnets arranged on an outside surface of the inner cylindrical portion of the plunger element;

a second array of magnets arranged on an inside surface of the outer cylindrical portion of the plunger element;

a first set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply an axial force on the first and second array of magnets for driving the plunger element in a linear mode; and

a second set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply a tangential force on the first and second array of magnets for driving the plunger element in a rotational mode;

wherein the first set of coils are embedded in a lamination-free resin in the motor cylinder.

29. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing with a motor cylinder, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element including an inner cylindrical portion and an outer cylindrical portion, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

a first array of magnets arranged on an outside surface of the inner cylindrical portion of the plunger element;

a second array of magnets arranged on an inside surface of the outer cylindrical portion of the plunger element;

a first set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply an axial force on the first and second array of magnets for driving the plunger element in a linear mode; and

a second set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply a tangential force on the first and second array of magnets for driving the plunger element in a rotational mode;

wherein the second set of coils are embedded in a lamination-free resin in the motor cylinder.

30. A rotary linear actuator system, comprising:

a motor support including a bearing support and a housing, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element including an inner cylindrical portion and an outer cylindrical portion, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

a first array of magnets arranged on an outside surface of the inner cylindrical portion of the plunger element;

a second array of magnets arranged on an inside surface of the outer cylindrical portion of the plunger element;

a first set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply an axial force on the first and second array of magnets for driving the plunger element in a linear mode;

a second set of coils disposed between the first array of magnets and the second array of magnets and being arranged to apply a tangential force on the first and second array of magnets for driving the plunger element in a rotational mode; and

a thin sheet carrying an encoder scale affixed to an outer cylindrical surface of the outer cylindrical portion of the plunger element.

31. The system of claim 30, wherein the encoder scale is etched with a pattern of reflective and non-reflective regions.

32. The system of claim 31, further including at least one optical pickup for registering movement of the plunger element in a linear direction and at least one optical pickup for registering the movement of the plunger element in a rotational direction.

33. A rotary linear actuator system, comprising:

means for supporting a plurality of motors including means for supporting a bearing, the means for supporting the plurality of motors and the means for supporting the bearing forming a well;

means for moving a stage being adapted to be received by the well, the means for moving the stage being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the means for moving the stage being supported by a bearing located between the means for moving the stage and the means for supporting the bearing;

means for providing a magnetic field arranged on the means for moving the stage;

means for applying an axial force on the means for providing the magnetic field for driving the means for moving the stage in a linear mode; and

a means for applying a tangential force on the means for providing the magnetic field for the means for moving the stage in a rotational mode.

34. The system of claim 33, further including means for registering movement of the means for moving the stage in a linear direction and in a rotational direction.

35. The system of claim 33, further including means for limiting movement of the means for moving the stage when the means for moving the stage is in its fully retracted position.

36. The system of claim 33, further including means for limiting movement of the means for moving the stage in its fully extended position.

37. A rotary linear actuator system, comprising:

a motor support including a bearing support, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on an outside surface of the plunger element wherein the array of magnets are arranged as a plurality of rings around the plunger element of alternating polarities forming columns of alternating polarities such that each magnet is separated from each other magnet by a gap of one magnet wide;

a first set of coils disposed in a first motor being coaxial with the plunger element and being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode; and

a second set of coils disposed in a second motor being parallel to the longitudinal axis of the plunger element and being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode.

38. A rotary linear actuator system, comprising:

a motor support including a bearing support, the housing and the bearing support forming a well;

a plunger element adapted to be received by the well, the plunger element being axially movable along its longitudinal axis between a fully retracted position and a fully extended position and rotatable about its longitudinal axis, the plunger element being supported by a bearing located between the plunger element and the bearing support;

an array of magnets arranged on an outside surface of the plunger element wherein the array of magnets are arranged as a plurality of rings around the plunger element of different alternating polarities forming columns of different alternating polarities such that each magnet is separated from each other magnet by a gap of one magnet wide;

a first set of coils disposed in a first motor being coaxial with the plunger element and being arranged to apply an axial force on the array of magnets for driving the plunger element in a linear mode;

a second set of coils disposed in a second motor being parallel to the longitudinal axis of the plunger element and being arranged to apply a tangential force on the array of magnets for driving the plunger element in a rotational mode; and

a thin sheet carrying an encoder scale affixed to an outside surface of the array of magnets, the encoder scale etched with a pattern of reflective and non-reflective regions and at least one optical pickup for registering movement of the plunger element in a linear direction and at least one optical pickup for registering the movement of the plunger element in a rotational direction.

39. The system of claim 38, wherein the encoder scale is formed of separate linear pairs.

40. The system of claim 38, wherein the encoder scale is formed of a single grid scale.