Two-axis magnetically coupled robot

• US 5,227,708 A
• Filed: 01/22/1991
• Issued: 07/13/1993
• Est. Priority Date: 10/20/1989
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Lowrance, Robert B.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US07/644,852
• Time in Patent Office: 903 Days
• Field of Search: 318/560-638, 318/647, 318/640, 318/654, 318/130, 318/254, 318/439, 310/90.5, 310/166, 901/3, 901/6, 901/7, 901/8, 901/9, 901/12, 901/13, 901/15-23, 901/29, 901/31, 901/32, 901/40, 901/45, 414/217, 414/222, 414/223, 414/730, 414/731, 414/732, 414/744, 414/331, 118/50, 118/719, 118/730, 118/779, 156/345, 156/643, 204/298.23, 204/298.25, 204/298.26, 204/298.35
• US Class Current: 318/640
• CPC Class Codes: B25J 21/005 Clean rooms
• CPC Class Codes: B25J 9/107 of the froglegs type
• CPC Class Codes: B25J 9/126 Rotary actuators
• CPC Class Codes: H01L 21/67742 Mechanical parts of transfer devices robots in general in B25J
• CPC Class Codes: Y10S 414/135 Associated with semiconductor wafer handling
• CPC Class Codes: Y10S 414/137 including means for charging or discharging wafer cassette
• CPC Class Codes: Y10S 414/139 including wafer charging or discharging means for vacuum chamber

Abstract

A robot having a pair of magnetic couplings that each couple a motor in a cylindrical first chamber to an associated cylindrical ring closely spaced from the cylindrical wall of said first chamber. The robot includes a mechanism to convert rotation of each of these rings into separate motions of the robot. In the preferred embodiment, these separate motions are radial and rotational.

Claims

1. A robot comprising:

a first magnetic coupling that magnetically couples a first motor across a first cylindrical section of wall to a first member that is rotatable about an axis of rotational symmetry of said first cylindrical section of wall;

a second magnetic coupling that magnetically couples a second motor across a second cylindrical section of wall to a second member that is rotatable about an axis of rotational symmetry of said second cylindrical section of wall;

means for converting rotations of the first and second rotatable members into a pair of independent motions of said robot.

2. A robot as in claim 1 wherein said independent motions comprise a rotation of said robot about a robot axis and a linear radial extension of an element of said robot.

3. A robot as in claim 2 wherein the robot element that is extended radially comprises a wafer blade.

4. A robot as in claim 1 wherein said first and second cylindrical sections of wall are sections of a unitary wall that extends from a bottom wall of a robot chamber containing said robot to a top wall of said robot chamber, whereby said unitary wall prevents vertical displacement of said robot as pressure within said robot chamber is varied.

5. A robot as in claim 4 wherein said unitary wall encircles a common motor chamber that is accessible from above through an opening sufficiently large that said first and second motors can be transferred through said opening into said common motor chamber, thereby simplifying motor repair and replacement.

6. A robot as in claim 5 wherein said motors are held in place by alignment pins and gravity, whereby each of said motors can be removed from said common motor chamber simply by lifting said motor vertically through the opening in the top of the common motor chamber.

7. A robot as in claim 1 wherein said first magnetic coupling comprises:

a first cluster of magnets adjacent to an inside surface of said first cylindrical section of wall; and

a second cluster of magnets adjacent to an outside surface of said first cylindrical section of wall;

each of said two clusters of magnets being rotatably mounted for circular rotation about the axis of rotational symmetry of said first cylindrical section of wall.

8. A robot as in claim 1 wherein said first magnetic coupling comprises:

a first ring of magnets adjacent to an inside surface of said first cylindrical section of wall; and

a second ring of magnets adjacent to an outside surface of said first cylindrical section of wall;

each of said two rings of magnets being rotatably mounted for circular rotation about the axis of rotational symmetry of said first cylindrical section of wall.

9. A robot as in claim 8 wherein all of the magnets in said first ring having North poles oriented along the same circumferential direction and all of the magnets in said second ring having North poles oriented along the circumferential direction opposite to that of the magnets in the first ring.

10. A robot as in claim 8 wherein said second magnetic coupling comprises:

a third ring of magnets adjacent to an inside surface of said second cylindrical section of wall; and

a fourth ring of magnets adjacent to an outside surface of said second cylindrical section of wall;

each of said two clusters of magnets being rotatably mounted for circular rotation about the axis of rotational symmetry of said cylindrical section of wall.

11. A robot as in claim 8 wherein all of the magnets in said first and second rings having North poles oriented along a circumferential direction and wherein, in each ring, successive magnets around said ring alternately point in opposite circumferential directions.

12. A robot as in claim 1 wherein said first cylindrical section of wall across which said first magnetic coupling couples is coated with a conductive coating, whereby Eddy currents in said coating dampen oscillations arising during operation.

13. A robot as in claim 1 wherein said first cylindrical section of wall across which said first magnetic coupling couples is made of a conductive material, whereby Eddy currents in said section of wall dampen oscillations arising during operation.

14. A robot as in claim 1 wherein said means for converting rotations of the first and second rotatable members into a pair of independent motions of said robot comprises a frog leg type connection having first and second frog legs.

15. A robot as in claim 14 wherein said first frog leg connects said first magnetic coupling to a wafer blade and said second frog leg connects said second magnetic coupling to said wafer blade.

16. A robot as in claim 15 wherein each of the first and second frog legs is pivotally attached to said wafer blade at an outer end of that frog leg, said frog leg type connection further comprising:

a first gear rigidly attached to the outer end of the first frog leg;

a second gear rigidly attached to the outer end of the second frog leg and intermeshed with the first gear, whereby said intermeshing pair of gears preserves an alignment of said wafer blade such that any line on said wafer blade makes a constant angle with a line from the axis of rotational symmetry of said first cylindrical section of wall to any point on said line on the wafer blade.

17. A robot as in claim 14 wherein said gears are loosely meshed to reduce particulate production, said robot further comprising means for producing rotation of said two gears in opposite directions to produced controlled pressure between said two gears.

18. A robot as in claim 14 wherein each of said frog legs comprises a pair of struts connected at a pivot point and wherein each strut is a four-sided box sheet metal structure, thereby providing torsional stiffness to each of said struts.

19. A robot as in claim 1 wherein said first motor is located on a concave side of said first cylindrical section of wall, whereby the power from the motor is transferred in a radially outward direction across said cylindrical section of the motor chamber wall.

29. A magnetic coupling mechanism as defined in claim 7, wherein:

the desired sequences of poles around the first and third circles are

NSNSNSNS . . . and

SNSNSNSN . . . ,

to provide for attractive coupling between the first and third sets of magnets; and

the desired sequences of poles around the second and fourth circles are

NSSNNSSN . . . and

SNNSSNNS . . . ,

to provide for attractive coupling between the second and fourth sets of magnets;

whereby the pole alignment between magnets in the first and fourth, or the second and third sets is of the form

NSNSNSNS . . . and

SNNSSNNS . . . ,

which provides for alternate attraction and repulsion, and minimizes coupling between the first and fourth, and the second and third sets of magnets.

20. Robot apparatus for controlling the position of a robot arm, comprising:

first and second struts, each having an inner end and an outer end, the inner end of the first strut being attached to a first rotation means for controllably revolving the inner end of the first strut about an axis of revolution, and the second strut being attached to second rotation means for controllably revolving the inner end of the second strut about said axis of revolution;

third and fourth struts, each having an inner end and an outer end, the inner end of the third strut being pivotally attached to the outer end of the first strut by a first pivot, and the inner end of the fourth strut being pivotally attached to the outer end of the second strut by a second pivot;

a robot arm;

a third pivot for pivotally attaching the outer end of the third strut to the robot arm; and

a fourth pivot for pivotally attaching the outer end of the fourth strut to the robot arm; and

wherein

the first rotation means includes a first ring attached to the inner end of the first strut, the first ring being mounted so as to be rotatable about said axis of revolution, whereby rotation of the first ring causes the inner end of the first strut to revolve about said axis of revolution; and

the second rotation means includes a second ring attached to the inner end of the second strut, the second ring being mounted so as to be rotatable about said axis of revolution, whereby rotation of the second ring causes the inner end of the second strut to revolve about said axis of revolution.

21. Robot apparatus according to claim 20,

wherein the first rotation means further includes a third ring mounted inside of, and concentric with, the first ring, and a first rotational drive unit for rotating the third ring about said axis of revolution, and wherein the first and third rings each include corresponding magnets arranged to magnetically couple the first and third rings so that rotation of the third ring by the first rotational drive unit causes rotation of the first ring;

wherein the second rotation means further includes a fourth ring mounted inside of, and concentric with, the second ring, and a second rotational drive unit for rotating the fourth ring about said axis of revolution, and wherein the second and fourth rings each include corresponding magnets arranged to magnetically couple the second and fourth rings so that rotation of the fourth ring by the second rotational drive unit causes rotation of the second ring;

22. A robot mechanism, comprising:

a motor chamber containing first and second motors;

a robot chamber containing first and second rotatable members and a movable robot arm, the motor chamber and the robot chamber having an airtight seal between them;

means for coupling rotational movement of the first and second motors to the first and second rotatable members, respectively, in the robot chamber; and

means for converting rotational movements of the first and second rotatable members into a desired combination of rotational movement and linear radial movement of the robot arm;

wherein the means for coupling rotational movement includes

first and second sets of magnets mounted in the motor chamber, for rotation by the first and second motors, respectively; and

third and fourth sets of magnets carried by the first and second rotatable members, respectively, in the robot chamber;

and wherein there is close magnetic coupling between the first and third sets of magnets and between the second and fourth sets of magnets, such that rotation of the first and second motors causes corresponding rotation of the first and second rotatable members.

23. A robot mechanism as defined in claim 22, wherein:

the first and second sets of magnets present desired sequences of north and south magnetic poles around the circumferences of first and second circles; and

the third and fourth sets of magnets present corresponding desired sequences of north and south magnetic poles around the circumferences of third and fourth circles located closely adjacent to the first and second circles, respectively, such that the magnetic poles on the first and second circles are attractively coupled to opposite magnetic poles on the third and fourth circles.

24. A robot mechanism as defined in claim 23, wherein:

the desired sequences of poles around the first and third circles are

NSNSNSNS . . . and

SNSNSNSN . . . ,

to provide for attractive coupling between the first and third sets of magnets; and

the desired sequences of poles around the second and fourth circles are

NSSNNSSN . . . and

SNNSSNNS . . . ,

to provide for attractive coupling between the second and fourth sets of magnets;

whereby the pole alignment between magnets in the first and fourth, or the second and third sets is of the form

NSNSNSNS . . . and

SNNSSNNS . . . ,

which provides for alternate attraction and repulsion, and minimizes coupling between the first and fourth, and the second and third sets of magnets.

25. A robot mechanism, comprising:

a motor chamber containing first and second motors;

a robot chamber containing first and second rotatable members and a movable robot arm, the motor chamber and the robot chamber having an airtight seal between them;

means for coupling rotational movement of the first and second motors to the first and second rotatable members, respectively, in the robot chamber; and

means for converting rotational movements of the first and second rotatable members into a desired combination of rotational movement and linear radial movement of the robot arm;

wherein the means for converting rotational movements of the first and second rotatable members into a desired combination of rotational movement and linear radial movement of the robot arm, includes

a first pivot arm, pivotally attached by one end to the first rotatable member and by the other end to the robot arm; and

a second pivot arm, pivotally attached by one end to the second rotatable member and by the other end to the robot arm;

whereby rotation of the first and the second rotatable members at the same speed and in the same direction causes similar rotation of the robot arm, but rotation of the first and second rotatable members in opposite directions results in linear movement of the robot arm in a radial direction with respect to the axis of rotation of the first and second rotatable members.

26. A magnetic coupling mechanism for connecting respective rotational movements of first and second motors with first and second coaxial rotatable members located in a chamber that is separated from the motors by an airtight seal, the coupling mechanism comprising:

first and second sets of magnets mounted for rotation by the first and second motors, respectively, and located on one side of the airtight seal; and

third and fourth sets of magnets carried by the first and second rotatable members, respectively, and located on the other side of the airtight seal;

and wherein there is close magnetic coupling between the first and third sets of magnets and between the second and fourth sets of magnets, but not between the first and fourth sets of magnets or between the second and third sets of magnets, such that rotation of the first and second motors on one side of the airtight seal causes corresponding rotation of the first and second rotatable members on the other side of the airtight seal.

27. A magnetic coupling mechanism as defined in claim 26, wherein:

the first and second sets of magnets present desired sequences of north and south magnetic poles around the circumferences of first and second circles; and

the third and fourth sets of magnets present corresponding desired sequences of north and south magnetic poles around the circumferences of third and fourth circles located closely adjacent to the first and second circles, respectively, such that the magnetic poles on the first and second circles are attractively coupled to opposite magnetic poles on the third and fourth circles.

28. A magnetic coupling mechanism as defined in claim 27, wherein:

there is a first sequence of poles around the first and third circles, and a second sequence of poles around the second and fourth circles;

wherein the first and second sequence of poles are selected to provide magnetic attraction between the first and third sets of magnets, and between the second and fourth set of magnets, but a net zero magnetic attraction between the first and fourth sets of magnets, and between the second and third sets of magnets, whereby unwanted cross-coupling is minimized.