High power/weight ratio braking device based on shape memory material technology

• US 8,087,498 B2
• Filed: 04/19/2004
• Issued: 01/03/2012
• Est. Priority Date: 04/17/2003
• Status: Active Grant

• Current Assignee: Victhom Laboratory Inc (Ergoresearch Ltd.)
• Original Assignee: Victhom Human Bionics Inc. (Ergoresearch Ltd.)
• Inventors: Bedard, Stephane, Roy, Pierre-Olivier, Dupuis, Daniel
• Primary Examiner(s): NGUYEN, XUAN LAN T
• Application Number:
  US10/553,579
• Publication Number:
  US 20060201757A1
• Time in Patent Office: 2,815 Days
• Field of Search: 188 67- 69, 188/64, 188 651- 655, 188156-158, 188/162, 623/43
• US Class Current: 188/68
• CPC Class Codes: A61F 2/60 Artificial legs or feet or parts thereof
• CPC Class Codes: A61F 2/64 Knee joints
• CPC Class Codes: A61F 2/6607 Ankle joints
• CPC Class Codes: A61F 2/70 electrical
• CPC Class Codes: A61F 2002/6614 Feet
• CPC Class Codes: A61F 2002/6818 for braking
• CPC Class Codes: A61F 2002/6863 magnetic magnetic prosthetic parts A61F2002/30079
• CPC Class Codes: A61F 2002/701 operated by electrically controlled means, e.g. solenoids or torque motors
• CPC Class Codes: A61F 2210/0014 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2210/0033 electrically, e.g. heated by resistor
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: F16D 2121/32 using shape memory or other thermo-mechanical elements
• CPC Class Codes: F16D 2127/02 Release mechanisms
• CPC Class Codes: F16D 49/00 Brakes with a braking member co-operating with the periphery of a drum, wheel-rim, or the like similar clutches F16D13/10

Abstract

The braking device is provided a set of shape memory alloy activators positioned, in an agonistic-antagonistic configuration on each side of a brake lever. Braking and releasing phases are dictated by the austenitic transformation of the shape memory alloy activators. During brake activation, shrinking of the braking activator brings the friction pad in contact with a rotating drum creating a braking friction torque. Once the brake has been activated, deformation of a flexible fiberglass component prevents brake releasing by applying sufficient normal force between the drum and the friction pad. Conversely, upon heating of the releasing activator, the pad looses its grip and the drum is free to rotate.

Claims

1. A friction brake assembly to act between a main actuator and a linear shaft relatively moveable with respect to said main actuator, comprising:

a linear shaft;

a brake member connected to said linear shaft,

a carrier connected to said main actuator;

a friction pad attached to said carrier for removable engagement with said brake member;

a first actuator comprising a plurality of shape memory alloy rods arranged in parallel, said first actuator being operatively coupled to said carrier and actuatable to move said friction pad into engagement with said brake member to apply a braking force on the brake member, wherein the engagement of said friction pad with said brake member inhibits movement of said linear shaft;

a second actuator comprising a plurality of shape memory alloy rods arranged in parallel, said second actuator operatively coupled to said carrier and actuatable to move said friction pad away from said brake member to remove said braking force, wherein the moving away of said friction pad from said brake member allows movement of said linear shaft; and

a control circuit to operate selectively said first and second actuator,

wherein the first and second actuators are configured to change in length only when an electric current is applied thereto such that the length of the first and second actuators remains unchanged upon removal of the current, thereby allowing the friction pad and brake member to remain in a stable position without the continued application of electrical power to the first and second actuators.

2. The friction brake assembly of claim 1, wherein the linear shaft is configured to displace longitudinally with respect to the main actuator.

3. A friction brake assembly according to claim 1 wherein a resilient element is interposed between said first actuator and said carrier to maintain a bias against said brake member.

4. A friction brake assembly according to claim 3 wherein said resilient element is a beam projection from said carrier.

5. A friction brake assembly according to claim 1 wherein said shape memory alloy rods are tensile elements and said control circuit changes the length of said elements to actuate said brake.

6. A friction brake assembly according to claim 5 wherein said control circuit supplies an electrical current to respective ones of said elements to change the length thereof.

7. A friction brake assembly according to claim 1 wherein said brake member is a drum rotatably mounted on said main actuator and said carrier is pivotally secured to said first and second actuators for movement into or out of engagement with said drum.

8. A friction brake assembly according to claim 7 wherein said carrier includes a third member extending radially relative to said drum and said first and second actuators act between said linear shaft and said third member.

9. A friction brake assembly according to claim 8 wherein said third member is a flexible beam to couple resiliently said first and second actuators to said carrier.

10. A friction brake assembly according to claim 8 wherein said first and second actuators are tensile members formed from a shape memory alloy.

11. A friction brake assembly according to claim 10 wherein said tensile members are electrically connected in series and a current passing through said tensile members effects foreshortening of said tensile members.

12. A friction brake assembly according to claim 7 wherein said carrier is pivotally mounted for movement about an axis parallel to but spaced from the axis of rotation of said drum.

13. A prosthesis having a pair of limbs pivotally connected on one another by a mechanical joint, an actuator connected between said limbs to effect relative rotation there between and a friction brake assembly as claimed in claim 1 acting to inhibit such relative motion, said friction brake assembly being operative upon said actuator to inhibit further movement in said joint.

14. A prosthesis according to claim 13 wherein said actuator includes a pair of relatively displaceable components to change the length of said actuator and said friction brake assembly acts between said displaceable components.

15. A prosthesis according to claim 14 wherein said components are interconnected by a screw thread such that relative rotation there between causes a change in the length of said actuator and said friction brake assembly acts to inhibit relative rotation.

16. A prosthesis according to claim 13 wherein a resilient element is interposed between said first friction brake assembly actuator and said carrier to maintain a bias against said brake member.

17. A prosthesis according to claim 16 wherein said resilient element is a beam projection from said carrier.

18. A prosthesis according to claim 13 wherein said shape memory alloy rods are tensile elements and said controller changes the length of said elements to actuate said brake.

19. A prosthesis according to claim 18 wherein said controller supplies an electrical current to respective ones of said elements to change the length thereof.

20. A prosthesis according to claim 13 wherein said brake member is a drum rotatably mounted on said other member first component and said carrier is pivotally secured to said friction brake assembly actuators for movement into or out of engagement with said drum.

21. A prosthesis according to claim 20 wherein said carrier includes a member extending radially relative to said drum and said friction brake assembly actuators and act between spaced locations on said other member second component and said member, respectively.

22. A prosthesis according to claim 21 wherein said member is a flexible beam to couple resiliently said friction brake assembly actuators to said carrier.

23. A prosthesis according to claim 21 wherein said friction brake assembly actuators are tensile members formed from a shape memory alloy.

24. A prosthesis according to claim 23 wherein said tensile members are electrically connected in series and a current passing through said tensile members effects foreshortening of said tensile members.

25. A prosthesis according to claim 20 wherein said carrier is pivotally mounted for movement about an axis parallel to but spaced from the axis of rotation of said drum.