Mechanism and method to engage/disengage a sprag clutch based on coefficients of thermal expansion

Patent metadata

Field	Value
Publication number	US-11339836-B2
Application number	US-202016926451-A
Country	US
Kind code	B2
Filing date	Jul 10, 2020
Priority date	Jul 10, 2020
Publication date	May 24, 2022
Grant date	May 24, 2022

Abstract

A clutch has an inner race, an outer race spaced from the inner race and forming a radial cavity between the races, and a plurality of sprags disposed in the radial cavity. The sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races, and a sprag cage retains the sprags at a uniform spacing within the radial cavity. When the clutch is at a first temperature, a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged. When the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

First claim

What is claimed is:

1. A clutch comprising:
an inner race;
an outer race spaced from the inner race and forming a radial cavity between the races;
a plurality of sprags disposed in the radial cavity, wherein the sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races; and
a sprag cage positioned to retain the sprags at a uniform spacing within the radial cavity;
wherein when the clutch is at a first temperature a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged; and
wherein when the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

2. The clutch of claim 1 , wherein the first temperature is greater than the second temperature.

3. The clutch of claim 1 , wherein the second temperature is greater than the first temperature.

4. The clutch of claim 1 , wherein the sprags are each of a same material selected from the group consisting of a metal, a composite, a ceramic, and combinations thereof.

5. The clutch of claim 1 , wherein the sprags are of a material having a similar CTE as a material of either the inner race or the outer race.

6. The clutch of claim 1 , wherein the sprags and the sprag cage are of a material having a similar CTE.

7. The clutch of claim 1 , further comprising a heat exchange system associated with the clutch, the heat exchange system configured to cool or heat the inner race, the plurality of sprags, and/or the outer race, wherein the heat exchange system is capable of subjecting the clutch to a temperature change.

8. A method of engaging and disengaging a clutch, the method comprising:
inputting a rotation force to the clutch, the clutch comprising:
an inner race;
an outer race;
a radial cavity between the inner and outer races;
a plurality of sprags disposed in the radial cavity between the inner and outer races, wherein the sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both the inner and outer races;
a sprag cage positioned to retain each of the sprags at a uniform spacing within the radial cavity;

operating the clutch at a first temperature, wherein the clutch is disengaged when the clutch operates at the first temperature; and
operating the clutch at a second temperature, wherein the clutch is engaged at the second temperature.

9. The method of claim 8 , wherein the method includes subjecting the clutch to a change in temperature, wherein the change in temperature causes the clutch to change between the first temperature and the second temperature.

10. The method of claim 9 , further comprising eliminating a gap between the sprags and the outer race when the sprags and the outer race have different CTEs.

11. The method of claim 10 , wherein eliminating the gap occurs when the clutch changes from the first temperature to the second temperature and the sprags expand with the temperature change toward the outer race until the sprags are in contact with the inner and outer races.

12. The method of claim 10 , wherein eliminating the gap occurs when the clutch changes from the first temperature to the second temperature and the sprags expand with the temperature change toward the inner race until the sprags are in contact with the inner and outer races.

13. The method of claim 10 , further comprising engaging the clutch by eliminating the gap, wherein the clutch is engaged when the sprags contact the inner and outer races.

14. An aircraft having a clutch comprising:
at least one engine affixed to the aircraft and operably coupled to a drivetrain;
the clutch coupling the at least one engine to the drivetrain, the clutch further comprising:
an inner race;
an outer race;
a radial cavity between the inner and outer races;
a plurality of sprags disposed in the radial cavity between the inner and outer races, wherein the sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, and/or both the inner and outer races; and
a sprag cage positioned to retain the sprags at a uniform spacing within the radial cavity;

wherein when the clutch is at a first temperature a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged; and
wherein when the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

15. The aircraft of claim 14 , wherein the first temperature is greater than the second temperature.

16. The aircraft of claim 14 , wherein the second temperature is greater than the first temperature.

17. The aircraft of claim 14 , wherein the sprags are each of a same material selected from the group consisting of a metal, a composite, a ceramic, and combinations thereof.

18. The aircraft of claim 14 , wherein the sprags are of a material having a similar CTE as a material of either the inner race or the outer race.

19. The aircraft of claim 14 , wherein the sprags and the sprag cage are of a material having a similar CTE.

20. The aircraft of claim 14 , further comprising a heat exchange system associated with the clutch, the heat exchange system positioned to provide cooling or heating to the inner race, the plurality of sprags, and/or the outer race, wherein the heat exchange system is capable of subjecting the clutch to a temperature change.

Assignees

• Bell Textron Inc
• Textron Innovations Inc

Inventors

• Morales Gilberto
• Fenny Carlos Alexander
• Anderson Cody

Classifications

• F16D41/084

  the intermediate coupling members wedging by pivoting or rocking · CPC title

• F16D43/25

  controlled by thermo-responsive elements · CPC title

• F16D41/076

  the wedging coupling members being non-releasably joined to form a single annular piece, e.g. either the members being integral projections from the piece, or the piece being an elastic ring cast round the radial centres of the members · CPC title

• F16D2300/021

  Cooling features not provided for in group F16D13/72 or F16D25/123, e.g. heat transfer details · CPC title

• F16D41/07 Primary

  between two cylindrical surfaces · CPC title