Robot having arm with unequal link lengths

1. A transport apparatus comprising:

a drive comprising coaxial drive shafts, where the coaxial drive shafts comprise only three coaxial drive shafts;

a first arm connected to the drive, where the first arm comprises a first link, a second link and a first end effector connected in series with the drive, where the first and second links have different effective lengths; and

a second arm connected to the drive, where the second arm comprises a third link, a fourth link and a second end effector connected in series with the drive,

where a first mechanical connection of the first arm with the drive and a second mechanical connection of the second arm with the drive each comprise a band drive having at least one non-circular pulley, and each of the first and second mechanical connections including their at least one non-circular pulley are configured to limit movement of the links of each respective arms relative to each other such that the mechanical connections allow only straight movement of the end effectors relative to the drive when the first and second arms are extended or retracted.

2. A transport apparatus as in claim 1 where the effective length of the first link is longer than the effective length of the second link.

3. A transport apparatus as in claim 1 where the first end effector comprises a lateral offset between a wrist joint with the second link and a centerline of a substrate support section which is about equal to a difference in the effective lengths of the first and second links.

4. A transport apparatus as in claim 3 where the first mechanical connection is configured to translate the first end effector when the first arm is extended or retracted with the wrist joint being maintained at the lateral offset relative to a center axis of rotation of the drive.

5. A transport apparatus as in claim 1 where the first mechanical connection comprises a first band on a first one of the non-circular pulleys, where the first non-circular pulley is located at a joint of the first and second links.

6. A transport apparatus as in claim 5 where the first mechanical connection comprises a second one of the non-circular pulleys located at a joint of the second link with the first end effector, where a second band extends between the first and second non-circular pulleys.

7. A transport apparatus as in claim 5 where the first mechanical connection comprises a circular pulley located at a joint of the second link with the first end effector, where a second band extends between the first non-circular pulley and the circular pulley.

8. A transport apparatus as in claim 1 where the first mechanical connection comprises a first band on a first one of the non-circular pulleys, where the first non-circular pulley is located at a joint of the second link with the first end effector.

9. A transport apparatus as in claim 1 where the first mechanical connection is configured to provide substantially only non-radial movement of the first end effector relative to the drive when the first arm is extended or retracted.

10. A method comprising:

moving a first arm by a drive, where the drive comprises coaxial drive shafts, and where the coaxial drive shafts comprise only three coaxial drive shafts, where:

a first link of the first arm is rotated by rotating

a first one of the coaxial drive shafts;

a second link of the first arm is rotated on the first link when the first link is rotated by the first coaxial drive shaft, where the first and second links have different effective lengths; and

a first end effector on the second link is rotated on the second link when the first link is rotated by the first coaxial drive shaft, and where a first mechanical connection of the first arm with the drive comprises a belt drive including a first non-circular pulley, and the first mechanical connection including the first non-circular pulley limits movement of the first and second links relative to each other such that the first mechanical connection allows only straight movement of the first end effector relative to the drive when the first arm is extended or retracted; and

moving a second arm by the drive, where:

a third link of the second arm is rotated by rotating a second one of the coaxial drive shafts;

a fourth link of the second arm is rotated on the third link when the third link is rotated by the second coaxial drive shaft; and

a second end effector on the fourth link is rotated on the third link when the third link is rotated by the second coaxial drive shaft, where the third and fourth links have different effective lengths, and where a second mechanical connection of the second arm with the drive comprises a second non-circular pulley, and the second mechanical connection limits movement of the third and fourth links relative to each other such that the second mechanical connection allows only straight movement of the second end effector relative to the drive when the second arm is extended or retracted.

11. A method as in claim 10 where the first arm is extended and retracted by rotating the first coaxial drive shaft and keeping the other coaxial drive shafts stationary.

12. A method as in claim 10 where the first non-circular pulley is connected to a joint of the first and second links, and at least one band connects the first non-circular pulley to at least one other pulley at a center axis of the drive and/or at a joint of the second link to the first end effector.

13. A method as in claim 12 where the at least one other pulley comprises at least one other non-circular pulley.

14. A method as in claim 12 where the at least one other pulley comprises at least one circular pulley.

15. A method as in claim 10 where the first end effector comprises a lateral offset between a wrist joint with the second link and a centerline of a substrate support section which is about equal to a difference in the effective lengths of the first and second links.

16. A method as in claim 10 where rotating the first end effector on the second link results in translation motion only of the first end effector when the first arm is extended or retracted, where a wrist joint at the second link being maintained at a lateral offset relative to a center axis of rotation of the drive.

17. A method as in claim 10 where rotating the first end effector provides substantially only non-radial movement of the first end effector relative to the drive when the first arm is extended or retracted.

18. A transport apparatus comprising:

a drive comprising coaxial drive shafts, where the coaxial drive shafts comprise only three coaxial drive shafts;

a first arm connected to the drive, where the first arm comprises a first link, a second link and a first end effector connected in series with the drive, where the first and second links have different effective lengths relative to each other; and

a second arm connected to the drive, where the second arm comprises a third link, a fourth link and a second end effector connected in series with the drive, where the third and fourth links have different effective lengths relative to each other, where a first mechanical connection of the first arm with the drive comprises a band drive including a first non-circular pulley and a first band, and where a second mechanical connection of the second arm with the drive comprises a second non-circular pulley and a second band, where the first mechanical connection including the first non-circular pulley limits movement of the first end effector to only straight extension or retraction relative to the drive.

19. A transport apparatus as in claim 18 where the effective length of the first link is longer than the effective length of the second link, where the first end effector comprises a lateral offset between a wrist joint with the second link and a centerline of a substrate support section which is about equal to a difference in the effective lengths of the first and second links, where the first mechanical connection is configured to translate the first end effector when the first arm is extended or retracted with the wrist joint being maintained at the lateral offset relative to a center axis of rotation of the drive, where the first mechanical connection is configured to provide substantially only non-radial movement of the first end effector relative to the drive when the first arm is extended or retracted.