Load cells in an instrument drive

Patent metadata

Field	Value
Publication number	US-11045266-B2
Application number	US-202016848734-A
Country	US
Kind code	B2
Filing date	Apr 14, 2020
Priority date	Apr 21, 2015
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

A drive unit for providing drive from a robot arm to an instrument comprises a plurality of drive elements for engaging corresponding elements of the instrument, and a load cell structure. Each drive element is movable along a drive axis and the drive axes of each of the drive elements are substantially parallel to each other. The load cell structure includes a plurality of deflectable bodies coupled to the drive elements for sensing load on the drive elements parallel to their drive axes, and a frame. The frame includes an integral member supporting the deflectable bodies in such a way as to isolate each deflectable body from the load applied to the or each other deflectable body.

First claim

The invention claimed is:

1. A drive unit for providing drive from a robot arm to an instrument, the drive unit comprising:
a plurality of drive tabs configured to engage corresponding elements of the instrument, each drive tab of the plurality of drive tabs being movable along a respective drive axis, and the respective drive axes of the plurality of drive tabs being substantially parallel to each other; wherein at least two of the respective drive axes are aligned along a first line and a third respective drive axis is positioned on a second line, the second line being parallel to and offset from the first line and
a load cell structure configured to sense a load on the plurality of drive tabs parallel to the respective drive axes, the load cell structure including comprising:
a plurality of membranes coupled to the plurality of drive tabs; and
a frame supporting the plurality of membranes in such a way as to isolate each membrane of the plurality of membranes from the load applied to the or each other membrane of the plurality of membranes.

2. A drive unit as claimed in claim 1 , wherein:
the drive unit includes a plurality of lead screws, each of the plurality of drive tabs being in threaded interengagement with a respective one of the plurality of lead screws; and
the frame defines a set of apertures, the plurality of lead screws extending through the set of apertures and the plurality of membranes extending across the set of apertures from the frame to the lead screws.

3. A drive unit as claimed in claim 2 , wherein each of the plurality of membranes is coupled to a respective one of the plurality of lead screws via at least one respective bearing configured to permit the respective one of the plurality of lead screws to rotate freely about a respective one of the respective drive axes with respect to the membrane.

4. A drive unit as claimed in claim 1 , wherein the plurality of membranes are disposed side-by-side in a plane perpendicular to the respective drive axes of the plurality of drive tabs.

5. A drive unit as claimed in claim 1 , wherein the plurality of membranes are substantially planar and extend perpendicular to the respective drive axes of the plurality of drive tabs.

6. A drive unit as claimed in claim 1 , wherein the frame is substantially rigid.

7. A drive unit as claimed in claim 1 , wherein the frame is integral with the plurality of membranes.

8. A drive unit as claimed in claim 1 , wherein each of the plurality of membranes is coupled to a respective strain gauge configured to sense deflection of the membrane of the plurality of membranes.

9. A drive unit as claimed in claim 1 , further comprising:
a plurality of motors configured to drive the plurality of drive tabs to move; and
a rigid housing supporting the plurality of drive tabs and the plurality of motors, the housing including two components, a first component to which the plurality of motors are attached and a second component comprising apertures within which the plurality of drive tabs are movable, the load cell structure being sandwiched between the first component and the second component.

10. A drive unit as claimed in claim 9 , wherein at least one of a wall or rib of the second component of the housing is configured to prevent rotation of the plurality of drive tabs about the respective drive axes.

11. A drive unit as claimed in claim 9 , wherein:
the drive unit includes a plurality of lead screws, each of the plurality of drive tabs being in threaded interengagement with a respective one of the plurality of lead screws;
the frame defines a set of apertures, the plurality of lead screws extending through the set of apertures and the plurality of membranes extending across the set of apertures from the frame to the lead screws; and
the drive unit includes a respective splined coupling between each motor of the plurality of motors and a respective one of the plurality of lead screws, each splined coupling being configured to permit axial play between the motor of the plurality of motors and the respective lead screw of the plurality of lead screws.

12. A drive unit as claimed in claim 1 , wherein the load cell structure comprises a plurality of flanges, each flange surrounding a respective one of the respective drive axes and being associated with a respective one of the plurality of membranes, wherein each membrane extends wholly across the area between the frame and a respective one of the plurality of flanges.

13. A surgical robot comprising the drive unit as claimed in claim 1 .

14. A surgical robot as claimed in claim 13 , wherein the drive unit is disposed at a distal end of the arm of the robot.

15. A surgical robot as claimed in claim 14 , having a mobile arm that includes the drive unit and an instrument engaged with the arm, the instrument including corresponding elements engaged with the plurality of drive tabs so as to be driven thereby.

Assignees

• Cmr Surgical Ltd

Inventors

• Marshall Keith
• Phoolchund Nikki Priyam Su-Ling
• Jackson Thomas Bates

Classifications

• F16C19/522

  related to load on the bearing, e.g. bearings with load sensors or means to protect the bearing against overload · CPC title

• F16C2361/61

  Toothed gear systems, e.g. support of pinion shafts · CPC title

• A61B2090/064

  for measuring force, pressure or mechanical tension · CPC title

• G01L5/009

  Force sensors associated with material gripping devices · CPC title

• A61B2017/00477

  Coupling (A61B2017/0046 takes precedence) · CPC title