Strain wave gearbox with over-torque protection

Patent metadata

Field	Value
Publication number	US-11499592-B2
Application number	US-202017118145-A
Country	US
Kind code	B2
Filing date	Dec 10, 2020
Priority date	Dec 10, 2020
Publication date	Nov 15, 2022
Grant date	Nov 15, 2022

Abstract

A strain wave gearbox configured to provide over-torque protection. The strain wave gearbox is designed to include a clutch that is at least partially housed within or positioned inside the internal space (herein labeled a chamber or void space interchangeably with internal space) of a flex spline. In some cases, the internal space is utilized to generate the preload for the clutch, and it may be used to provide room for a clutch preload subassembly. The clutch is located outside the flex spline's internal space and is formed to use geometric friction surfaces in the form of mating rings of teeth on mating surfaces or sides of the first and second clutch plates that once preloaded by the clutch preload subassembly require a greater torque than the design torque to rotate to the next tooth.

First claim

We claim:

1. A strain wave gearbox with over-torque protection, comprising:
a circular spline;
a wave generator disposed within the circular spline;
a flex spline with a sidewall disposed between the circular spline and the wave generator, wherein the sidewall encloses a chamber;
a housing mechanical ground; and
a clutch assembly mechanically coupling the flex spline to the housing mechanical ground, wherein the clutch assembly includes a clutch and a preload subassembly for preloading the clutch and wherein the preload subassembly is disposed within the chamber.

2. The strain wave gearbox of claim 1 , wherein the preload subassembly includes a spring element applying an adjustable preload force upon the clutch.

3. The strain wave gearbox of claim 2 , wherein the preload subassembly further includes a thrust bearing disposed between the spring element and the clutch and a clutch nut abutting the spring element and being rotatable to set the adjustable preload force.

4. The strain wave gearbox of claim 2 , wherein the spring element comprises a disk spring stack.

5. The strain wave gearbox of claim 1 , wherein the clutch comprises a first clutch plate mechanically coupled to the flex spline and a second clutch plate mechanically coupled to the housing mechanical ground, wherein a contact surface of the first clutch plate mates with a contact surface of the second clutch plate, and wherein the contact surfaces each includes a circular ring of teeth adapted to be meshed together when the clutch is engaged or fully seated.

6. The strain wave gearbox of claim 5 , wherein the teeth each have a variable pitch.

7. The strain wave gearbox of claim 5 , wherein each of the teeth has a pair of spaced apart sides angled downward from an intermediate ridge at an angle in the range of 20 to 60 degrees.

8. The strain wave gearbox of claim 5 , wherein, during use of the strain wave gearbox, a contact patch is provided between each mating pair of the teeth on the contact surfaces of the first and second clutch plates, whereby axial and torsional loads are distributed across the contact patches while the clutch is fully seated and during slip.

9. A strain wave gearbox with over-torque protection, comprising:
a flex spline;
mechanical ground; and
a clutch coupling the flex spline to the mechanical ground,
wherein the clutch comprises a first clutch plate mechanically coupled to an output of the flex spline and a second clutch plate coupled to the mechanical ground,
wherein a contact surface of the first clutch plate mates with a contact surface of the second clutch plate,
wherein each of the contact surfaces is circular in shape and includes a plurality of teeth, and
wherein the teeth in the contact surfaces have matching geometries, whereby the teeth in the contact surfaces are meshed together when the clutch is engaged or seated.

10. The strain wave gearbox of claim 9 , wherein each of the teeth has a variable pitch.

11. The strain wave gearbox of claim 9 , wherein each of the teeth has a pair of spaced apart sides angled downward from an intermediate ridge at an angle in the range of 20 to 60 degrees.

12. The strain wave gearbox of claim 9 , wherein, during use of the strain wave gearbox, a pressure area is provided between each mating pair of the teeth on the contact surfaces of the first and second clutch plates, whereby axial and torsional loads are distributed to the contact patches while the clutch is fully seated and during slip.

13. The strain wave gearbox of claim 9 , further comprising a preload assembly positioned within a void space of the flex spline, wherein the preload assembly applies an adjustable preload force upon the first clutch plate of the clutch.

14. The strain wave gearbox of claim 13 , wherein the preload assembly includes a disk spring stack.

15. The strain wave gearbox of claim 14 , wherein the preload assembly further includes a thrust bearing disposed between the disk spring stack and the first clutch plate and a clutch nut abutting the disk spring stack and being rotatable to modify the adjustable preload force applied by the disk spring stack on the clutch.

16. A strain wave gearbox with over-torque protection, comprising:
a circular spline;
a wave generator disposed within the circular spline;
a flex spline at least partially disposed between the circular spline and the wave generator;
an output shaft; and
a clutch assembly coupling an output of the flex spline to the output shaft, wherein the clutch assembly includes a clutch with mating first and second contact surfaces each comprising a plurality of geometric friction elements, wherein the clutch assembly further includes a preload subassembly applying a preload force the clutch, and wherein the preload subassembly is disposed within a void space within the flex spline.

17. The strain wave gearbox of claim 16 , wherein the preload subassembly includes: a spring element applying a preload force upon the clutch; a thrust bearing disposed between the spring element and the clutch; and a clutch nut abutting the spring element and being rotatable to adjust the preload force.

18. The strain wave gearbox of claim 17 , wherein the spring element comprises a disk spring stack.

19. The strain wave gearbox of claim 16 , wherein the geometric friction elements are teeth each having a variable pitch and a matching geometric shape allowing the teeth of the first and second contact surfaces to mesh together.

20. The strain wave gearbox of claim 19 , wherein each of the teeth has a pair of spaced apart sides angled downward from an intermediate ridge at an angle in the range of 20 to 60 degrees.

21. The strain wave gearbox of claim 19 , wherein, during use of the strain wave gearbox, a contact patch is created each mating pair of the teeth on the contact surfaces, whereby axial load is distributed to the contact patches while the clutch is fully seated and during slip.

Assignees

• Disney Entpr Inc

Inventors

• Thompson Kyle Robert
• Lavalley Scott Christopher

Classifications

• F16D11/14

  with clutching members movable only axially (F16D11/02, F16D11/08 take precedence) · CPC title

• F16H35/10

  Arrangements or devices for absorbing overload or preventing damage by overload · CPC title

• F16D7/024 Primary

  with axially applied torque limiting friction surfaces · CPC title

• F16D2011/008

  characterised by the form of the teeth forming the inter-engaging parts; Details of shape or structure of these teeth · CPC title

• F16H49/001

  Wave gearings, e.g. harmonic drive transmissions · CPC title