GEARED ROLL DRIVE FOR MEDICAL INSTRUMENT
A medical instrument includes a roll mechanism that rotates an instrument shaft. The roll mechanism may include a first gear coupled to the instrument shaft and meshed with a second gear. One of gears may be a spur gear while the other gear may be a beveloid gear. Further, the spur gear and the beveloid gear may be in a gear train containing a compressible gear, e.g., a gear with an inner center piece, an outer ring, and a flexible interconnecting structure between the inner center piece and the outer ring. With a compressible gear, an interference fit of in the gear train may be within manufacturing variations of the gear train, and the compressible gear may deflect radially away from the interference fit.
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This patent application claims priority to and the filing date benefit of U.S. Provisional Patent Application No. 62/362,340, entitled “GEARED ROLL DRIVE FOR MEDICAL INSTRUMENT” filed Jul. 14, 2016, which is incorporated by reference herein in its entirety.
BACKGROUNDMinimally-invasive medical procedures often employ medical instruments having a tool or manipulator apparatus (often called an “end effector”) at the distal end of an elongated instrument shaft. During a minimally-invasive medical procedure, the distal ends of one or more medical instruments may be inserted through one or more small incisions and/or natural lumens in order to position the tools at a work site in a patient. A surgeon or other user may then control the tools to perform desired clinical functions at the work site, e.g., endoscopy, laparoscopy, arthroscopy, hypodermic injection, air-pressure injection, subdermal implants, refractive surgery, percutaneous surgery, cryosurgery, microsurgery, keyhole surgery, endovascular surgery such as angioplasty, coronary catheterization, placement of internal electrodes, and stereotactic surgery.
The manipulations required or desired to effectively complete medical procedures can be complex and intricate. Accordingly, medical instruments for minimally-invasive medical procedures may need to provide precise control of many mechanical degrees of freedom of movement. For example, a user performing a procedure may need to position and orient a distal tool to target the distal tool on specific tissue and the tool must be able to maneuver at the work site to achieve the desired position and orientation. The user may then need to move the distal tip of the tool to interact with the target tissue and perform a clinical function of the tool, e.g., clamping, cutting, or cauterizing of the target tissue. Some of the of the degrees of freedom required for such manipulations may include: translation of distal tip of the instrument shaft in an insertion direction; actuation of one or more joints located along the instrument shaft or in the tool; rotation of the instrument shaft about a length axis of the instrument shaft; and opening and closing of a grip or scissors feature of the distal tool. Since directly controlling multiple degrees of freedom may be difficult for a human operator, some advanced medical systems employ a robot to aid in the control of the degrees of freedom of medical instruments and thereby provide the user with a more intuitive operation. (As used herein, the terms “robot” or “robotically” and the like include teleoperation or non-teleoperation aspects, as well as telerobotic and non-telerobotic aspects.) Medical instruments that provide all of the degrees of freedom required or desired for medical procedures and that are suitable for use with robotic systems are often complex and difficult to assemble.
SUMMARYIn accordance with an aspect of the invention, a medical instrument may include a roll mechanism that rotates an instrument shaft, and the roll mechanism may include a spur gear and a beveloid gear to accommodate an angle between the instrument shaft and a rotation axis of an input spindle. The spur gear and the beveloid gear may further be in a gear train containing a compressible gear. With a compressible gear, an interference fit of in the gear train may be within manufacturing variations of the gear train because the compressible gear is able to deflect radially away from the interference.
One specific implementation is a medical instrument that includes an instrument shaft and a roll mechanism coupled to rotate of the instrument shaft. The roll mechanism may particularly include a first gear coupled to the instrument shaft and a second gear meshed with the first gear. One of the first gear and the second gear is a beveloid gear, and the other of the first and second gears may be a spur gear, a helical cylindrical gear, or another beveloid gear.
Another specific implementation is a mechanism including a compressible gear. The compressible gear may particularly include a center inner piece, an outer ring, and an interconnecting member that connects the inner piece to the outer ring and allows the outer ring to radially compress inward toward the center in response forces that result from interactions with adjacent gears.
The drawings illustrate examples for the purpose of explanation and are not of the invention itself. Use of the same reference symbols in different figures indicates similar or identical items.
DETAILED DESCRIPTIONA single-port medical system instruments may deploy the shafts of multiple medical instruments through a single port, e.g., an incision, so that tools at the distal ends of the instrument shafts can work close to each other.
Backend mechanism 116 as shown in
Tapering of the housing of backend mechanism 116 at nose 118 allows a compact arrangement of instruments as described above but also limits the available space in nose 118 for input spindles. Input spindle 226, which controls roll rotations of shaft 114, is accordingly offset from the location from which instrument shaft 114 exits backend mechanism 116. For this configuration, backend mechanism 116 needs a roll mechanism to transmit rotation of input spindle 226 across a distance to cause rotation of instrument shaft 114. The roll mechanism needs to fit into the tapered space available at nose 118 of backend mechanism 116, needs to exhibit low backlash for precise control of the angular position of instrument shaft 114, and needs to accommodate the difference in the orientations or input spindle 226 and instrument shaft 114, e.g., the angle between the rotation axis of input spindle 226 and the rotation axis of instrument shaft 114. The roll mechanism also would ideally be easy to manufacture and assemble.
One method for transferring rotation and accommodating an angle between rotation axes employs bevel gears.
Each bevel gear 310 or 320 is generated from a conical surface.
Beveloid or taper gear 330, in contrast to bevel gears 310 and 320, has a tooth pattern generated from a cylindrical surface.
Gear 340 of
Gears 410, 420, 430, and 440 may be aligned so that shafts 415, 425, and 435 of gears 410, 420, and 430 are parallel and lie in the same plane, which may allow smooth operation mechanism 400 by avoiding interference or backlash. In an exemplary embodiment, shaft 455 of gear 450 is at an angle of about 5° with input shaft 415 of gear 410 and input spindle 226, and gear 450 and beveloid gear 440 may have a helical tooth pattern, so that shaft 455 is not in the same plane as shafts 415, 425, and 435. The center of gear 450 may, however, be in the plane of shafts 415, 425, and 435 to closely approximate a gear train having all rotation shafts parallel and coplanar. In general, backlash can be reduced when a gear train has gears with co-planar shafts when compared to a gear train in which the shaft of one or more gears is offset from a plane containing the shafts of other gears.
The shafts of interacting gears, such as in mechanism 400 of
In one implementation, roll mechanism 400 employs single piece plastic gears that can be produced inexpensively by injection molding. To minimize backlash, one or more of gears 410, 420, 430, 440, and 450 may be fit tightly in mechanism 400 for low backlash and may be compressible to compress to avoid interference even when the precision or tolerance in the manufacture of the gear train suggests that rigid gears would interfere with each other for some range of the manufacturing tolerance.
The illustrated specific implementation of flexible interconnecting member 616 illustrated in
For example,
As another example,
The amount of backlash that is acceptable in a medical instrument may be related to the allowable position error of the tip of the instrument. For example, if the length between joints 211 and 212 in instrument 110 of
A process for designing a gear train such as used in roll mechanism 400 of
Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Aspects have been described in the context of a shaft roll mechanism, but these aspects apply to other implementations in medical instrument or medical robotic systems. And, although aspects have been described within a medical context or for a medical procedure, the techniques described herein can also be used within non-medical contexts and non-medical procedures.
Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims.
Claims
1. A medical instrument comprising:
- an instrument shaft; and
- a roll mechanism coupled to rotate the instrument shaft, the roll mechanism comprising a first gear coupled to the instrument shaft and a second gear meshed with the first gear;
- wherein one of the first gear and the second gear is a beveloid gear.
2. The medical instrument of claim 1, wherein the second gear is the beveloid gear.
3. The medical instrument of claim 2, further comprising:
- a third gear mounted on a common shaft with the second gear; and
- a fourth gear meshed with the third gear;
- wherein the third gear is a spur gear.
4. The medical instrument of claim 3, wherein the second gear and the third gear are formed as a single monolithic piece.
5. The medical instrument of claim 1, wherein one or both of the first gear and the second gear is a compressible gear.
6. The medical instrument of claim 1, wherein the roll mechanism further comprises:
- an input spindle shaped to engage an actuator, the input spindle having a rotation axis at a non-zero angle relative to a central axis of the instrument shaft; and
- a third gear on the input spindle and coupled to rotate the second gear.
7. The medical instrument of claim 6, wherein one or more of the first gear, the second gear, and the third gear is a compressible gear.
8. The medical instrument of claim 6, further comprising:
- a fourth gear that acts as an idler gear between the third gear and the second gear.
9. The medical instrument of claim 8, wherein one or more of the first gear, the second gear, the third gear, and the fourth gear is a compressible gear.
10. The medical instrument of claim 8, further comprising:
- a fifth gear mounted on a common axis with the second gear;
- wherein the third gear meshes with the fourth gear; and
- wherein the fourth gear meshes with the fifth gear.
11. The medical instrument of claim 5, wherein the compressible gear comprises:
- an inner hub piece;
- an outer ring surrounding the inner hub piece; and
- a flexible interconnecting member that connects the inner hub piece to the outer ring and allows the outer ring to radially compress inward.
12. The medical instrument of claim 1, wherein teeth of the beveloid gear differ between a toe of the beveloid gear and a heel of the beveloid gear such that variation in an axial position of the second gear does not change a backlash between the first gear and the second gear.
13. The medical instrument of claim 1, wherein teeth of the beveloid gear have a helix angle that accommodates a skew of a shaft of the beveloid gear relative to a shaft of a spur gear meshed with the beveloid gear.
14. The medical instrument of claim 1, wherein the second gear is the beveloid gear, and the first gear is selected from a group consisting of a spur gear, a cylindrical gear, a helical cylindrical gear, and a second beveloid gear.
15. A mechanism comprising a compressible gear, wherein the compressible gear comprises:
- an inner piece;
- an outer ring surrounding the inner piece; and
- an interconnecting member that connects the inner piece to the outer ring and allows the outer ring to radially compress inward in response to a force that results from meshing with an adjacent gear.
16. The mechanism of claim 15, wherein the interconnecting member comprises:
- a middle ring;
- a plurality of first spokes connecting the inner piece to the middle ring; and
- a plurality of second spokes connecting the middle ring to the outer ring, wherein the second spokes are not radially aligned with the first spokes.
17. The mechanism of claim 15, wherein:
- the interconnecting member comprises a plurality of spokes that extend between the inner piece and the outer ring; and
- each spoke of the plurality of spokes comprises: a first portion attached to the inner piece; a second portion attached to the outer ring; and a cantilever extending circumferentially between the first portion of the spoke and the second portion of the spoke.
18. The mechanism of claim 15, wherein the compressible gear is a molded part.
19. The mechanism of claim 15, wherein:
- the mechanism comprises a gear train including the compressible gear;
- an interference fit of the compressible gear in the gear train is within manufacturing variations of the gear train; and
- flexibility of the outer ring allows teeth of the compressible gear to deflect radially away from the interference fit.
20. The mechanism of claim 15, wherein:
- the outer ring comprises a supported edge and an unsupported edge;
- the interconnecting member connects the inner piece to the outer ring only along the supported edge of the outer ring; and
- the unsupported edge of the outer ring is radially compressible inward in response to the force that results from meshing with the adjacent gear.
21. (canceled)
22. The medical instrument of claim 1, further comprising a gear train, the gear train comprising the first and second gears, and one or more gears of the gear train being compressible.
23. The medical instrument of claim 22, the gear train comprising a third gear, the first and second gears being incompressible, and the third gear being compressible.
Type: Application
Filed: Jun 22, 2017
Publication Date: Aug 1, 2019
Applicant: Intuitive Surgical Operations, Inc. (Sunnyvale, CA)
Inventors: Bram Gilbert Antoon LAMBRECHT (Sunnyvale, CA), Thomas G. COOPER (Sunnyvale, CA)
Application Number: 16/317,211