Mechanically decoupled capstan drive

• US 7,391,173 B2
• Filed: 06/30/2006
• Issued: 06/24/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Intuitive Surgical Operations, Inc. (Intuitive Surgical Holdings, LLC)
• Original Assignee: Intuitive Surgical Incorporated (Intuitive Surgical Holdings, LLC)
• Inventors: Schena, Bruce M.
• Primary Examiner(s): Duda; Rina I
• Application Number:
  US11/428,326
• Publication Number:
  US 20080001559A1
• Time in Patent Office: 725 Days
• Field of Search: 318/68, 318/34, 318/41, 318/51, 318/625, 318/135
• US Class Current: 318/34
• CPC Class Codes: G11B 15/60 Guiding record carrier guiding devices structurally associated with magazines or cassettes G11B23/04
• CPC Class Codes: G11B 15/605 without displacing the guiding means

Abstract

A capstan drive includes a first capstan that moves a device on a carriage and a second capstan that receives a second rotary motion to move the carriage. A first power transmission has a driven shaft coupled to the first capstan, a first drive shaft coaxial with the driven shaft to receive a first rotary motion for driving the device, and a second drive shaft coaxial with the driven shaft. A second power transmission couples the second rotary motion to the second drive shaft. The second power transmission has a drive ratio such that if there is no first rotary motion, a first cable is drawn in by the first capstan at the same rate as a second cable is drawn in by the second capstan in response to the second rotary motion.

Claims

1. A capstan drive comprising:

a first capstan to move a device on a carriage;

a first power transmission having a driven shaft coupled to the first capstan, a first drive shaft coaxial with the driven shaft to receive a first rotary motion for driving the device, and a second drive shaft coaxial with the driven shaft;

a second capstan to receive a second rotary motion to move the carriage; and

a second power transmission to couple the second rotary motion to the second drive shaft, the second power transmission having a drive ratio such that if there is no first rotary motion, a first cable is driven by the first capstan at a same rate as a second cable is driven by the second capstan in response to the second rotary motion.

2. The capstan drive of claim 1, wherein:

the first power transmission has a first drive ratio of R1 between the driven shaft and the second drive shaft;

the second power transmission has a second drive ratio of R2 between the second drive shaft and the second rotary motion;

the second capstan has a second pitch diameter, D2; and

the first capstan has a first pitch diameter, D1, that is substantially the same as the second pitch diameter divided by a product of the first drive ratio and the second drive ratio, D2/(R1×

R2).

3. The capstan drive of claim 1, wherein:

the first power transmission is an epicyclic gear train;

the epicyclic gear train has a first drive ratio of 15/16 between the driven shaft and the second drive shaft;

the second power transmission has a second drive ratio of 5/4 between the second drive shaft and the second rotary motion;

the second capstan has a second pitch diameter, D2; and

the first capstan has a first pitch diameter, D1, that is substantially sixty-four/seventy-fifths of the second pitch diameter, D2/(75/64).

4. The capstan drive of claim 1, wherein the first power transmission is a planetary gear arrangement with the driven shaft coupled to a planetary gear carrier, the first drive shaft coupled to a sun gear, and the second drive shaft coupled to a ring gear.

5. The capstan drive of claim 1, wherein the first power transmission is a compound planetary gear train having a first planetary gear arrangement and a second planetary gear arrangement with a planetary gear carrier of the first planetary gear arrangement coupled to a sun gear of the second planetary gear arrangement, the driven shaft coupled to a planetary gear carrier of the second planetary gear arrangement, the first drive shaft coupled to a sun gear of the first planetary gear arrangement, and the second drive shaft coupled to ring gears of the first and second planetary gear arrangements.

6. The capstan drive of claim 1, wherein the second power transmission is a pair of gears.

7. The capstan drive of claim 1, further comprising:

a third capstan that drives a second device on the carriage; and

a third power transmission having a driven shaft coupled to the third capstan, a first drive shaft coaxial with the driven shaft to receive a third rotary motion for driving the second device, and a second drive shaft coaxial with the driven shaft;

wherein the second power transmission is further to couple the second rotary motion to the second drive shaft of the second epicyclic gear train, the second power transmission having a second drive ratio such that a third cable is driven by the third capstan at a same rate as the cable is driven by the second capstan in response to the second rotary motion if there is no third rotary motion.

8. The capstan drive of claim 1, wherein the device is a rotatable instrument driver.

9. A method of moving a device on a carriage, the method comprising:

rotating a first capstan to drive a first cable that moves the device on the carriage;

rotating a second capstan to drive a second cable that moves the carriage; and

coupling rotation of the second capstan to the first capstan to substantially cancel motion of the first cable relative to motion of the second cable that moves the carriage.

10. The method of claim 9, wherein coupling the rotation of the second capstan to the first capstan includes:

coupling the rotation of the first capstan to a first drive shaft of an epicyclic gear train;

coupling the rotation of the second capstan to a second drive shaft of the epicyclic gear train; and

coupling the first capstan to a driven shaft of the epicyclic gear train.

11. The method of claim 10, wherein:

the epicyclic gear train has a first drive ratio of R1 between the driven shaft and the second drive shaft;

the rotation of the second capstan is coupled to the second drive shaft with a second drive ratio of R2 between the second drive shaft and the rotation of the second capstan;

the second capstan has a second pitch diameter, D2; and

the first capstan has a first pitch diameter, D1, that is substantially the same as the second pitch diameter divided by the product of first drive ratio and the second drive ratio, D2/(R1×

R2).

12. The method of claim 10, wherein the epicyclic gear train is a planetary gear arrangement with the first drive shaft coupled to a sun gear, the second drive shaft coupled to a ring gear, and the driven shaft coupled to a planetary gear carrier.

13. The method of claim 10, wherein the epicyclic gear train is a compound planetary gear train having a first planetary gear arrangement and a second planetary gear arrangement with a planetary gear carrier of the first planetary gear arrangement coupled to a sun gear of the second planetary gear arrangement, the first drive shaft coupled to a sun gear of the first planetary gear arrangement, the second drive shaft coupled to ring gears of the first and second planetary gear arrangements, and the driven shaft coupled to a planetary gear carrier of the second planetary gear arrangement.

14. The method of claim 10, wherein coupling rotation of the second capstan to the second drive shaft is with a pair of gears.

15. The method of claim 9, wherein the device is a rotatable instrument driver.

16. The method of claim 9, further comprising:

rotating a third capstan to drive a third cable that moves a second device on the carriage; and

coupling the rotation of the second capstan to the third capstan to substantially cancel motion of the third cable relative to motion of the second cable that moves the carriage.

17. A capstan drive comprising:

a first rotating means to rotate a first capstan to drive a first cable at a first rate that moves a device on a carriage;

a second rotating means to rotate a second capstan to drive a second cable at a second rate that moves the carriage; and

a first rotational coupling means to couple the rotation of the second capstan to the first capstan to cause the first capstan to drive the first cable at the sum of the first rate and the second rate such that the motion of the device on the carriage is substantially decoupled from the motion of the carriage.

18. The capstan drive of claim 17, wherein the first rotational coupling means includes:

a power transmission coupled to the rotation of the second capstan; and

an epicyclic gear train coupled to the power transmission, the first rotating means, and the first capstan.

19. The capstan drive of claim 18, wherein:

the epicyclic gear train has a first drive ratio of R1 between the first capstan and the power transmission;

the power transmission has a second drive ratio of R2 between the epicyclic gear train and the second capstan;

the second capstan has a second pitch diameter, D2; and

the first capstan has a first pitch diameter, D1, that is substantially the same as the second pitch diameter divided by the product of first drive ratio and the second drive ratio, D2/(R1×

R2).

20. The capstan drive of claim 18, wherein the epicyclic gear train is a planetary gear arrangement with the first capstan coupled to a planetary gear carrier, the first rotating means coupled to a sun gear, and the power transmission coupled to a ring gear.

21. The capstan drive of claim 18, wherein the epicyclic gear train is a compound planetary gear train having a first planetary gear arrangement and a second planetary gear arrangement with

a first planetary gear carrier of the first planetary gear arrangement coupled to a second sun gear of the second planetary gear arrangement,

the first capstan coupled to a second planetary gear carrier of the second planetary gear arrangement,

the first rotating means coupled to a first sun gear of the first planetary gear arrangement, and

the power transmission coupled to ring gears of the first and second planetary gear arrangements.

22. The capstan drive of claim 18, wherein the power transmission is a pair of gears.

23. The capstan drive of claim 17, wherein the device is a rotatable instrument driver.

24. The capstan drive of claim 17, further comprising:

a third rotating means to rotate a third capstan to drive a third cable at a third rate that moves a second device on the carriage; and

a second rotational coupling means to couple the rotation of the second capstan to the third capstan to cause the third capstan to drive the third cable at the sum of the third rate and the second rate such that the motion of the second device on the carriage is substantially decoupled from the motion of the carriage.