US-12616589-B2 - Systems and methods for an ankle prosthesis

Abstract

The ankle prosthesis of the present disclosure includes a load directing mechanism that alters the internal load path during weight bearing, guiding the load directly into the structural frame. By changing the load path with the load directing mechanism, both vertical and horizontal loads can be supported directly by the ankle's structure through a cam roller.

Inventors

• James Lipsey
• Tom Pickerill

Assignees

• REHABILITATION INSTITUTE OF CHICAGO

Dates

Publication Date

20260505

Application Date

20210831

Claims (19)

1. 1 . A semi-active ankle prosthesis, comprising: an ankle prosthesis including: a structural frame; an ankle joint operatively mounted on the structural frame that pivots with respect to the structural frame about an ankle axis; a cam transmission including a cam follower, wherein the cam transmission pivots the ankle joint about the ankle axis; an actuator operatively coupled to the cam transmission to cause lateral translation of the cam transmission; and a load directing mechanism defined along a cam roller of the cam transmission that directs a load imposed upon the ankle prosthesis into the structural frame during a loaded state, the load directing mechanism accommodating an unloaded state and a loaded state; wherein in the unloaded state the cam roller is biased with an upward bias force applied in a first direction such that the cam roller contacts the cam follower and an air gap is defined between the cam roller and the structural frame, and wherein in the loaded state the cam roller is compressed between the cam follower and the structural frame such that the load imposed upon the ankle prosthesis exceeding the upward bias force is directed into the structural frame.
2. 2 . The semi-active ankle prosthesis of claim 1 , wherein the load directing mechanism includes a biasing component that biases the cam roller of the cam transmission against the cam follower of the cam transmission.
3. 3 . The semi-active ankle prosthesis of claim 2 , wherein the load directing mechanism further includes a slider collar and a shaft in association with the cam roller and the biasing component, the slider collar positioned within a coaxial channel defined within the cam roller and including a slot defined coaxially therethrough, the shaft housed within the slot, and the biasing component positioned between the shaft and a first surface of the slot.
4. 4 . The semi-active ankle prosthesis of claim 3 , wherein the shaft of the load directing mechanism defines a square profile and wherein the slot of the slider collar defines a rectangular profile such that the slider collar is moveable in a second direction when the biasing component is compressed between the shaft and the first surface of the slot.
5. 5 . The semi-active ankle prosthesis of claim 2 , wherein the biasing component applies the upward bias force to the cam roller such that the cam roller contacts a curved surface of the cam follower and the cam roller is lifted above a track of the structural frame when in the unloaded state.
6. 6 . The semi-active ankle prosthesis of claim 5 , wherein the cam roller is operable for unimpeded rotation about a rotational roller axis by the curved surface of the cam follower when in the unloaded state.
7. 7 . The semi-active ankle prosthesis of claim 2 , wherein the cam follower applies a load force to the cam roller in a second direction when in the loaded state, wherein the load force is associated with the load placed on the ankle and wherein the load force includes a downward load component and a lateral load component.
8. 8 . The semi-active ankle prosthesis of claim 7 , wherein the biasing component is compressed in the second direction by the downward load component applied to the cam roller when the downward load component exceeds the upward bias force applied to the cam roller by the biasing component.
9. 9 . The semi-active ankle prosthesis of claim 8 , wherein the cam roller is actuated in the second direction by the cam follower such that the cam roller contacts a track of the structural frame when the biasing component is compressed.
10. 10 . The semi-active ankle prosthesis of claim 5 , wherein the track of the structural frame includes a high coefficient of friction such that rotation of the cam roller is impeded by the track of the structural frame when in the loaded state.
11. 11 . The semi-active ankle prosthesis of claim 1 , wherein the cam transmission comprises a roller carrier, a first cam roller and a second cam roller carried by the roller carrier; and the cam follower operatively associated with the first cam roller and the second cam roller and pivotable about the ankle axis.
12. 12 . The semi-active ankle prosthesis of claim 11 , wherein a ground force applied at a toe-end of the ankle prosthesis generates a reaction torque force directed in a first clockwise or counterclockwise direction about the ankle axis.
13. 13 . The semi-active ankle prosthesis of claim 12 , wherein the reaction torque force induces a load force including a downward component in a second direction and a lateral component in a first lateral direction or an opposite second lateral direction that is applied to the first cam roller or the second cam roller by the cam follower, wherein the ankle prosthesis assumes the loaded state when the downward component exceeds the upward bias force associated with the first or second cam roller.
14. 14 . The semi-active ankle prosthesis of claim 12 , wherein the first cam roller or the second cam roller is actuated in the second direction such that the first cam roller or the second cam roller contacts a track of the structural frame.
15. 15 . The semi-active ankle prosthesis of claim 1 , wherein the actuator includes a motor and a leadscrew rotatable by the motor.
16. 16 . The semi-active ankle prosthesis of claim 15 , wherein the leadscrew of the actuator is in operative association with a roller carrier of the cam transmission such that the actuator causes lateral movement of the roller carrier in a first or opposite second lateral direction when the ankle prosthesis is in the unloaded state.
17. 17 . The semi-active ankle prosthesis of claim 16 , wherein lateral movement of the roller carrier in a first lateral direction causes rotation of the cam follower in a first clockwise or counterclockwise direction about the ankle axis and wherein lateral movement of the roller carrier in a second lateral direction causes rotation of the cam follower in an opposite second clockwise or counterclockwise direction about the ankle axis.
18. 18 . The semi-active ankle prosthesis of claim 17 , wherein the cam transmission includes a first cam roller and a second cam roller, wherein the first cam roller and the second cam roller are each biased by a biasing component of the load directing mechanism in a first direction when in the unloaded state such that the first cam roller and the second cam roller contact the cam follower.
19. 19 . The semi-active ankle prosthesis of claim 18 , wherein the lateral movement of the roller carrier in the first lateral direction causes the first cam roller to direct a first roller force to the cam follower in the opposite second lateral direction such that the cam follower is consequently rotated about the ankle axis in the first clockwise or counterclockwise direction, and wherein the lateral movement of the roller carrier in the opposite second lateral direction causes the second cam roller to direct a second roller force to the cam follower in the first lateral direction such that the cam follower is consequently rotated about the ankle axis in the opposite second clockwise or counterclockwise direction.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present PCT patent application claims the benefit of U.S. provisional patent application No. 63/072,717 filed on Aug. 31, 2020, which is hereby incorporated by reference to its entirety. FIELD The present disclosure generally relates to adaptive prosthetic devices; and in particular, to a system and associated method for an adaptive prosthetic ankle that re-directs a force onto a structural frame of the ankle to reduce a load on an actuator of the ankle. BACKGROUND Most commercially available lower limb prostheses are passive devices designed with constant or variable resistances at the joint level. They are lightweight, quiet and robust. They can be effective at activities such as level ground walking and standing, but provide limited function for other activities, such as stairs and ramps, getting into and out of a seated position and ensuring proper foot clearance to prevent falls. In these cases, the user must compensate for the lack of functionality. Powered prostheses attempt to overcome these limitations by motorizing prosthetic joints to provide power generation and joint positioning. This enables the user to perform more activities. However, it comes at the cost of additional weight (2-4 times in many cases) plus the need to continuously charge batteries and noisy actuators. Existing powered devices use actuators that accommodate a wide range of speeds and torques to assist with a wide range of activities and require power over the course of an entire day. The devices consume power even during zero net energy tasks such as walking and standing. There is a need for lower limb prostheses that provide some of the most useful functions of existing powered devices, while keeping weight and size low enough to be useful for a wider range of amputees. It is with these observations in mind, among others, that various aspects of the present disclosure were conceived and developed. SUMMARY In some examples, the present disclosure takes the form of a semi-active ankle prosthesis device comprising an ankle prosthesis including a structural frame, an ankle joint operatively mounted on the structural frame that pivots with respect to the structural frame about an ankle axis and a cam transmission including a cam follower, wherein the cam transmission pivots the ankle joint about the ankle axis. The ankle prosthesis further includes an actuator operatively coupled to the cam transmission to cause lateral translation of the cam transmission and a load directing mechanism defined along a cam roller of the cam transmission that directs a load imposed upon the ankle prosthesis into the structural frame during a loaded state, the load directing mechanism accommodating an unloaded state and a loaded state. In the unloaded state the cam roller is biased with an upward bias force applied in a first direction such that the cam roller contacts the cam follower and an air gap is defined between the cam roller and the structural frame, and in the loaded state the cam roller is compressed between the cam follower and the structural frame such that the load imposed upon the ankle prosthesis exceeding the upward bias force is directed into the structural frame. In some examples, the load directing mechanism includes a biasing component that biases the cam roller of the cam transmission against the cam follower of the cam transmission. In general, the proximal portion of the ankle prosthesis is configured for engagement (mounting or temporary connection) with a residual limb socket or other prosthetic component, and distal portion of the ankle prosthesis is configured for coupling to a prosthetic foot. In some examples, the ankle prosthesis is an adaptive ankle prosthesis such that the ankle prosthesis regulates the ankle position only during non-weight bearing activities. Such an ankle prosthesis is actively positioned during walking to increase toe clearance, reducing the risk of trips and falls. It also adapts the ankle angle to different terrains, such as ramps and stairs, to provide more stability and comfort. It does not attempt to provide net-energy during weight bearing phases of gait, meaning the actuator's power requirements can be relaxed leading to a significantly lighter and smaller design. In some examples, the present novel disclosure takes the form of a method of making an ankle prosthesis, comprising the steps of forming an ankle prosthesis, including providing a structural frame, mounting an ankle joint operatively along the structural frame that pivots with respect to the structural frame about an ankle axis, providing a cam transmission including a cam follower, wherein the cam transmission pivots the ankle joint about the ankle axis, operatively coupling an actuator to the cam transmission to cause lateral translation of the cam transmission, and forming a load directing mechanism defined along a cam roller of the cam transmission that directs a load imposed upon th