Variable force brake for a window covering operating system

1. An operating system for a window covering comprising:

a spring motor;

a variable force brake including an outer race and a brake member, said brake member being operatively coupled to said outer race such that said brake member is configured to apply a braking force to said outer race;

a lift spool assembly operatively coupled to a panel for raising and lowering the panel between a raised position and a lowered position;

a shaft operatively coupled to each of said spring motor, said variable force brake, and said lift spool assembly and synchronizing said spring motor, said variable force brake, and said lift spool assembly; and

a cam rotationally coupled to said shaft, said cam defining a cam surface and being configured to actuate a cam follower as said cam is rotated relative to said cam follower, said cam follower being operatively coupled to said brake member and being actuated by said cam in a direction non-parallel to a rotational axis of said cam;

wherein:

said outer race is selectively coupled for rotation with said shaft by a one-way clutch; and

the braking force applied by said brake member to said outer race varies as a function of a position of the panel between the raised and lowered positions.

2. The operating system of claim 1 , wherein:

said cam follower rides along said cam surface as said cam is rotated relative to said cam follower;

said cam follower being operatively coupled to said brake member to vary the braking force as the panel is moved between the raised and lowered positions.

3. The operating system of claim 1 , wherein:

a magnitude of the braking force is varied over a force range as the panel is moved between the raised and lowered positions; and

the force range is adjustable.

4. The operating system of claim 1 , wherein:

said one-way clutch comprises a one-way needle bearing that receives said shaft; and

said one-way needle bearing is mounted for rotation with the said outer race.

5. The operating system of claim 1 , wherein said cam follower is operatively coupled to said brake member via an adjustment mechanism.

6. The operating system of claim 5 , further comprising a spring compressed between said adjustment mechanism and said brake member;

wherein said adjustment mechanism is configured to be actuated to vary the compression of said spring between said adjustment mechanism and said brake member so as to adjust the braking force.

7. The operating system of claim 5 , wherein:

said outer race has a generally cylindrical shape that defines a cylindrical brake surface; and

said brake member comprises a band brake that is in contact with said cylindrical brake surface around at least a portion of an outer circumference of said outer race.

8. The operating system of claim 7 , wherein:

said band brake has a first fixed end and a second movable end; and

said adjustment mechanism is configured to move said second movable end relative to said first fixed end to adjust the braking force applied by said band brake to said outer race.

9. The operating system of claim 1 , wherein:

said cam surface is shaped such that the cam follower is linearly actuated between a first position and a second position as said cam follower rides along said cam surface with rotation of said cam, and

the braking force varies as said cam follower is linearly actuated between said first and second positions.

10. The operating system of claim 9 , wherein a distance of said cam surface from a rotational axis of said cam varies across at least a portion of said cam surface to adjust a position of said cam follower between the first and second positions as said cam follower rides along said cam surface.

11. The operating system of claim 1 , wherein:

the braking force is at a maximum braking force when the panel is at the raised position; and

the braking force is at a minimum braking force when the panel is at the lowered position.

12. The operating system of claim 11 , wherein the braking force is continuously varied as the panel moves along the range of motion between the raised and lowered positions.

13. An operating system for a window covering comprising:

a spring motor;

a variable force brake including an outer race, a brake member, and an adjustment mechanism, said brake member being configured to apply a braking force to said outer race, said adjustment mechanism being operatively coupled to said brake member to adjust the braking force applied to said outer race by said brake member;

a lever coupled to said adjustment mechanism;

a lift spool assembly operatively coupled to a panel for raising and lowering the panel between a raised position and a lowered position; and

a shaft operatively coupled to each of said spring motor, said variable force brake, and said lift spool assembly;

wherein:

said lever is configured to pivot as the panel is being moved between the raised and lowered positions to actuate said adjustment mechanism such that the braking force applied by said brake member to said outer race varies as a function of a position of the panel between the raised and lowered positions.

14. The operating system of claim 13 , wherein said outer race is selectively coupled for rotation with said shaft by a one-way clutch.

15. The operating system of claim 13 , wherein:

said brake member comprises a band brake extending around at least a portion of an outer circumference of said outer race between a first end and a second end; and

said second end of said band brake is configured to be moved relative to said first end of said band brake to adjust the braking force applied by said band brake to said outer race.

16. The operating system of claim 15 , wherein a portion of said adjustment mechanism is configured to engage said second end of said band brake to allow said second end to be moved relative to said first end of said band brake.

17. The operating system of claim 16 , wherein:

said portion of said adjustment mechanism corresponds to a spring compressed between said second end of said band brake and a separate portion of said adjustment mechanism; and

a compressive force of said spring is varied to adjust the position of said second end relative to said first end of said band brake.

18. The operating system of claim 13 , further comprising a cam rotationally coupled to said shaft, said cam being configured to actuate said lever as said shaft is being rotated.

19. The operating system of claim 18 , wherein:

said cam is rotationally coupled to said shaft via a transmission;

said transmission including a gear train that limits rotation of said cam to less than 360 degrees as said shaft is being rotated more than 360 degrees to move the panel between the raised and lowered positions.

20. The operating system of claim 18 , wherein:

said cam is operatively coupled to said lever via a cam follower; and

said cam follower is configured to engage a cam surface of said cam as said cam is rotated with rotation of said shaft.

21. The operating system of claim 20 , wherein:

said cam surface is shaped such that the cam follower is linearly actuated between a first position and a second position as said cam follower rides along said cam surface with rotation of said cam; and

the braking force varies as said cam follower is linearly actuated between said first and second positions.

22. The operating system of claim 13 , wherein:

the braking force is at a maximum braking force when the panel is at the raised position; and

the braking force is at a minimum braking force when the panel is at the lowered position.

23. The operating system of claim 22 , wherein the braking force is continuously varied as the panel moves along the range of motion between the raised and lowered positions.

24. An operating system for a window covering comprising:

a spring motor;

a variable force brake including an outer race and a brake member, said brake member being operatively coupled to said outer race such that said brake member is configured to apply a braking force to said outer race;

a lift spool assembly operatively coupled to a panel for raising and lowering the panel between a raised position and a lowered position;

a shaft operatively coupled to each of said spring motor, said variable force brake, and said lift spool assembly and synchronizing said spring motor, said variable force brake, and said lift spool assembly; and

a cam rotationally coupled to said shaft, said cam defining a cam surface and being configured to actuate a cam follower as said cam is rotated relative to said cam follower, said cam follower being operatively coupled to said brake member via an adjustment mechanism;

wherein:

said outer race is selectively coupled for rotation with said shaft by a one-way clutch;

the braking force applied by said brake member to said outer race varies as a function of a position of the panel between the raised and lowered positions;

said outer race has a generally cylindrical shape that defines a cylindrical brake surface; and

said brake member comprises a band brake that is in contact with said cylindrical brake surface around at least a portion of an outer circumference of said outer race.

25. The operating system of claim 24 , wherein:

said band brake has a first fixed end and a second movable end; and

said adjustment mechanism is configured to move said second movable end relative to said first fixed end to adjust the braking force applied by said band brake to said outer race.