prosthetic foot component

Abstract

The present invention relates to a prosthetic foot assembly comprising a prosthetic foot and a series elastic pneumatic actuator connected to the prosthetic foot, the series elastic pneumatic actuator being configurable between a first configuration state in which the prosthetic foot is displaced to a first rest position and a second configuration state in which the prosthetic foot is displaced to a second position.

Description

Technical Field

[0001] The present invention relates to the technical field of prosthetic feet, and particularly to a prosthetic foot driven by pneumatic power. Background Art

[0002] The development of actuators is evolving rapidly and new progress is continuously being made in terms of efficiency, power, and force output. Among other applications, pneumatic and hydraulic actuators are rare compared to electrostatic, thermal, and piezoelectric actuators. Research has shown that pneumatic and hydraulic actuators provide the highest force and power density at the microscale.

[0003] One object of the present invention is to provide an alternative actuator that can assist during the extension phase and generates sufficient force to lift and move the user's center of gravity forward without using electricity.

[0004] It is crucial to first understand the biological structure of the leg, the kinematics and dynamics of these structures, and their interactions during movement. When walking on flat ground, the biological plantar flexors generate nearly 80% of the mechanical work required to complete each gait cycle, and typically they generate more positive work than negative work. Normal human-powered prosthetic feet with spring loading using carbon fiber springs can only store and release mechanical energy when in contact with the ground and generate half of the mechanical energy. These prosthetic designs cannot generate net positive work and can only release less than one-eighth of the mechanical power required for propulsion from the biological plantar flexors.

[0005] The design concept used in dynamic prosthetic feet is derived from the function of the Achilles tendon, which stores energy during flat-foot and releases energy during extension. In the past, the functions of the Achilles tendon were divided into two categories: tension transfer; and the storage and release of elastic energy strain during gait. The elasticity of the Achilles tendon enables it to store and release mechanical energy, thus reducing the energy required to lift and move the center of gravity during the extension phase.

[0006] The present invention aims to combine the concept of energy storage and release with power generation, which is the working principle of series elastic elements. Series elastic elements refer to each connective tissue in series with the contractile component (including the Achilles tendon). In below-knee amputations, a part of the series elastic elements is removed along with the ankle joint. This interferes with the function of the series elastic elements because it no longer drives the displacement of the ankle joint. Over the years, some prosthetic designs have proposed a method to replace the series elastic elements by using series elastic actuators to achieve mechanical joint displacement. So far, these series elastic actuators seem to work well and they generate more positive mechanical work than negative mechanical work.

[0007] The object of the present invention is to provide a series elastic actuator that, when used in a prosthetic foot, will generate more mechanical work than the series elastic actuators known in the art. Summary of the Invention

[0008] According to the present invention, a prosthetic foot assembly is provided, comprising:

[0009] a prosthetic foot; and

[0010] a series elastic pneumatic actuator connected to the prosthetic foot, the series elastic pneumatic actuator being configurable between a first configuration state and a second configuration state to displace the prosthetic foot between a first rest position and a second position, respectively.

[0011] It should be understood that the first rest position of the prosthetic foot may correspond to a configuration state in which the plantar surface of the prosthetic foot is substantially horizontal / parallel to the ground during use, and the second position of the prosthetic foot may correspond to the plantar flexion position or the dorsiflexion position of the prosthetic foot during a gait cycle in use.

[0012] During a gait cycle in use, the angle at which the prosthetic foot is configured between the dorsiflexion position and the plantar flexion position may be between 0° and 36°.

[0013] The series elastic pneumatic actuator may include a cylinder (preferably a single-acting cylinder) and a pushing element (such as a spring), the pushing element being linearly or serially connected to a piston extending from the cylinder.

[0014] The prosthetic foot assembly may further include an air circuit including an air compressor in fluid communication with the series elastic pneumatic actuator for supplying compressed air to the series elastic pneumatic actuator to enable the series elastic pneumatic actuator to be configured between the first configuration state and the second configuration state.

[0015] The air circuit may further include an air dryer, a pressure gauge, a compressed air storage tank, a silencer, and a safety valve.

[0016] The air circuit may be connected to the series elastic pneumatic actuator through a suitable conduit.

[0017] The prosthetic foot assembly may further include an exhaust valve that allows air to be released to the atmosphere or to the storage tank or both when the series elastic pneumatic actuator is configured between the first configuration state and the second configuration state. The exhaust valve may be mounted on the pneumatic actuator.

[0018] In one embodiment, the air released back to the storage tank may be pressurized and compressed by the force acting on the prosthetic foot during the heel strike of the prosthetic foot during a gait cycle in use, in addition to (or alternatively) being pressurized by the air compressor.

[0019] The prosthetic foot assembly may further include a control valve, preferably a roller lever valve, which can be mounted on the prosthetic foot. The control valve is arranged to open when applying pressure / force to the prosthetic foot, preferably to the spherical area of the prosthetic foot, during a gait cycle, to allow the compressed fluid (i.e., air) to flow from the air circuit into the series elastic pneumatic actuator, so that the series elastic pneumatic actuator is configured between a first configuration state and a second configuration state.

[0020] The prosthetic foot assembly may include a support device, and the support device includes:

[0021] An upright member located above, which is connected to the cylinder;

[0022] A movable member located below, which is movably connected to the upright member located above;

[0023] A movable connecting member, preferably a pivot connecting member, connects the movable member to the upright member located above;

[0024] A first base, which is fixedly connected to the movable member, is received in the prosthetic foot, and is mounted on or near the plantar surface inside the prosthetic foot. The first base has a distal end disposed near the front end of the prosthetic foot and a proximal end disposed near the rear end of the prosthetic foot; and

[0025] A second base, which is spaced above the first base and is located below the movable connecting member. The second base extends away from the movable member in the direction towards the rear end of the prosthetic foot. The pushing element of the series elastic pneumatic actuator extends between the second base and the free end of the piston. The free end of the piston extends movably towards the direction of the plantar surface of the prosthetic foot. Thus, during a gait cycle in use, when the piston moves between a first configuration state (i.e., the rest position) and a second configuration state (the extended position or the retracted position), the second base drives the movable member to move between the rest position and a second position. When the movable member is in the rest position, the first base is in a first configuration state corresponding to the rest position of the prosthetic foot. When the movable member is in the second position, the first base is displaced to a second configuration state corresponding to the second position of the prosthetic foot. Description of the Drawings

[0026] By referring to the following description of the embodiments of the present invention in conjunction with the drawings, the objectives of the present invention and the ways to achieve them will become more obvious, and the present invention itself will be better understood, wherein:

[0027] Figure 1 A cross-sectional view showing the prosthetic foot assembly according to the present invention;

[0028] Figure 2 Showing Figure 1 the prosthetic foot assembly in the plantar flexion configuration state; and

[0029] Figure 3 display Figure 1 and Figure 2 the foot component in a dorsiflexed configuration state. DETAILED DESCRIPTION

[0030] The following description of the present invention is provided as a teachable implementation of the present invention. Those skilled in the relevant art will recognize that many changes can be made to the described embodiments while still obtaining the beneficial results of the present invention. It is also obvious that some of the desired benefits of the present invention can be achieved by selecting some features of the present invention without using other features. Therefore, those skilled in the art will recognize that modifications and adaptations to the present invention are possible, and even desirable in some cases, and are part of the present invention. Therefore, the following description is provided to illustrate the principles of the present invention, not to limit it.

[0031] As shown in the figure, a foot component generally indicated by reference numeral 10 is provided. The foot component 10 includes a hollow foot 12. The foot 12 is arranged in a first rest position, as Figure 1 shown, in which the plantar surface (i.e., the sole) 14 of the foot 12 is arranged to be substantially flat / parallel to the horizontal plane, and the foot 12 can also be configured in a second position corresponding to as Figure 2 shown in the plantarflexed position, or as Figure 3 shown in the dorsiflexed position, where in one gait cycle, the angular size between the plantarflexed position and the dorsiflexed position is approximately in the range of 0 - 36 degrees.

[0032] Turning attention to Figure 1 , the foot component 10 further includes a pneumatic actuator, here exemplified by a single-acting cylinder 16. A gas chamber 18 is defined within the cylinder 16, and a piston head / piston 20 is slidably displaced within the gas chamber 18, and a piston rod 22 connected to the piston head 20 extends outward from the cylinder 16. A first biasing element, here exemplified by a spring 24, is mounted between the piston head 20 of the cylinder 16 and the closed end 23 for biasing / pushing the piston head 20, such that the piston rod 22 is pushed or biased to an extended configuration state. As can be seen from Figure 1 , the piston rod 22 extends movably in the direction of the foot 12.

[0033] The foot component 10 further includes an exhaust valve (not shown in the figure), typically a poppet valve (not shown in the figure) mounted on the pneumatic actuator 16. The exhaust valve (not shown in the figure) is arranged to release air from the cylinder 16 when the piston head 20 and the piston rod 22 are moved to the extended configuration state, which will be described in further detail below.

[0034] The prosthetic foot assembly 10 further includes an air circuit (partially shown in the figure), which includes a compressor 28, an air storage tank (not shown in the figure), a pressure regulator (not shown in the figure), a safety valve (not shown in the figure), a muffler (not shown in the figure), and ducts (not shown in the figure). The ducts connect the various units of the air circuit (not shown in the figure) to each other and are arranged to deliver compressed air to the cylinder 16 during a gait cycle in use, and to deliver the exhaust air (i.e., the air released from the exhaust valve (not shown in the figure)) back to the compressor 28 and / or the air storage tank (not shown in the figure) and / or the atmosphere. The air circuit (not shown in the figure) is accommodated within the hollow prosthetic foot 12.

[0035] The prosthetic foot assembly 10 further includes a control valve 26, which is exemplified here in the form of a roller lever valve. The control valve 26 is installed within the prosthetic foot 12. The control valve 26 is arranged such that when pressurized, as will be described later, it allows the compressed air in the air circuit (not shown in the figure) to be discharged into the cylinder 16 to move the piston head 22 to the retracted configuration state, enabling the prosthetic foot 12 to move from Figure 1 the first stationary position shown to Figure 2 the plantar flexion position shown.

[0036] The prosthetic foot assembly 10 further includes a support device 30. The support device 30 includes an upper upright member 32. The cylinder 16 is fixed to the upright member 32 by a fixing element 35. The support device 30 further includes a lower movable member 34, which is movably connected to the upper upright member 32 by a pivot joint 36.

[0037] The support device 30 further includes a first base 38, which is fixedly connected to the lower end of the movable member 34. The first base 38 is accommodated within the prosthetic foot 12 and is connected to the inner surface of the plantar surface 14 of the prosthetic foot 12. The first base 38 includes a proximal end 40 near the rear end or heel 17 of the prosthetic foot 12, and also includes a distal end 42 near the front end 15 of the prosthetic foot 12.

[0038] The support device 30 further includes a second base / pedal 44, which is spaced above the first base 38. The second base 44 is located below the movable connecting member 36 and extends away from the movable member 34 in the direction towards the rear end 17 of the prosthetic foot 12. A second pushing element 46 is connected in series with the piston rod 22 and extends between the free end of the piston rod 22 and the second base 44. In the context of the specification, as is known in the art, the combination of the pneumatic actuator 16 and the second pushing element 46 extending from the piston rod 22 of the pneumatic actuator 16 is referred to as a series elastic pneumatic actuator and is indicated here by the reference numeral 50.

[0039] In use, during a gait cycle, the prosthetic foot 12 is first arranged as shown in Figure 1The first stationary position shown, where the series elastic pneumatic actuator is in a stationary configuration. During the initial stage when the prosthetic foot 12 is lifted off the ground or bottom surface (not shown in the figure) or extended, when pressure is applied to the spherical region 21 of the prosthetic foot 12, the control valve 26 is opened / triggered to allow compressed air in an air circuit (not shown in the figure) to flow into the pneumatic actuator 16. Once compressed air is received in the chamber 18, the compressed air pushes the piston head 20 in the direction towards the closed end 23 of the pneumatic actuator 16, while the piston rod 22 moves towards the inside of the chamber 18 to configure the pneumatic actuator 16 in the retracted position and pull the second pushing element 46 in the direction towards the pneumatic actuator 16. When the second pushing element 46 is pulled, the tensile force applied to the second pushing element 46 causes the second base 44 to move in the direction towards the pneumatic actuator 16, causing the movable member 34 to rotate about the pivot joint 36 in the direction of the rear end 17 of the prosthetic foot 12. The displacement of the movable member 34 further causes the first base 38, especially the proximal end 40 of the first base 38, to also move in the direction towards the pneumatic actuator 16 to arrange the prosthetic foot 12 in the Figure 2 plantarflexion position shown.

[0040] When the front end 15 of the prosthetic foot 12 is lifted off the ground (not shown in the figure), the pressure on the spherical region 21 of the prosthetic foot 12 will decrease, which will trigger the closing of the control valve 26. At the same time, when the prosthetic foot 12 is in mid-air, as the piston rod 22 is moved by the first pushing element 24 to the Figure 1 stationary configuration state shown, the exhaust will be released from the pneumatic actuator 16 through an exhaust valve (not shown in the figure), and the prosthetic foot 12 will accordingly return and be reconfigured to the Figure 1 first stationary position shown.

[0041] During the heel strike of the same gait cycle, that is, when the rear end / heel 17 of the prosthetic foot 12 engages with the ground or bottom surface (not shown in the figure), the second pushing element 46 will be compressed on the second base 44, and the piston rod 22 will be gently pushed into the chamber 18. At the same time, the second base 44 will be pushed downward to offset the movable member 34 in the direction towards the front end 15 of the prosthetic foot 12 and accordingly offset the first base 38, especially upward offset its distal end 42, to arrange the prosthetic foot 12 in the Figure 3 dorsiflexion position shown.

[0042] It should be understood that the energy absorbed by the second pushing element 46 during heel strike will be used to minimize the energy required during the extension of the prosthetic foot 12 in the next gait cycle.

[0043] In addition, during the heel strike process, when the heel contacts the ground / surface of the sole, the air discharged by the pneumatic actuator 16 will be compressed by the force acting on the heel 17, and this compressed air can be transferred to the compressor 28 for further compression before being stored in an air storage tank (not shown in the figure), or this compressed air can be directly fed into the air storage tank (not shown in the figure).

[0044] The air pressure returned to the air storage tank (not shown in the figure) is usually regulated by a gas pressure regulator (not shown in the figure) to ensure that the pressure inside the air storage tank (not shown in the figure) is less than the pressure of the compressed air returned to the air storage tank (not shown in the figure) during the gait cycle.

[0045] The prosthetic foot assembly 10 can achieve a wider range of motion than human joints and other active prostheses. It is found that the prosthetic foot assembly 10 composed of a pneumatic actuator 16 with an aperture of 30 mm and a piston rod size of 25 mm can generate a torque of about 5.84 to 8.92 N*m when the pressure of the compressed air is about 30 psi, and can generate a torque of about 11.67 to 17.84 N*m when the pressure of the compressed air is about 60 psi. The torque generated by the prosthetic foot assembly 10 of the present invention is greater than the torque generated by human joints, and the generated torque far exceeds the torque generated by human joints and active prostheses using carbon fiber springs and motors. The prosthetic foot assembly of the present invention is superior to existing passive prosthetic feet because it can generate a net positive torque during walking.

[0046] As mentioned above, within one gait cycle, the angle formed between the dorsiflexion position and the plantarflexion position of the prosthetic foot is between 0° and 36°. By using appropriate software, it is found that the 0° - 36° range of motion of the prosthetic foot 12 of the present invention can be completed within 14 milliseconds, corresponding to a joint speed of 4.5 radians per second. This joint speed exceeds the maximum joint speed of 2.97 radians per second required for normal walking of the human joints. In addition, as is known in the art, the range of motion required for a biological foot during normal walking is 30°; however, the prosthetic foot assembly 10 of the present invention can enable the prosthetic foot 12 to reach a range of motion of 36°, which is superior to the range of motion achievable by biological feet.

Claims

1. A prosthetic foot component, characterized in that, Comprising: An upright member located above and a movable member located below, the movable member being movably connected to the upright member such that the movable member is capable of moving relative to the upright member; A second base extending outwardly from the movable member; A prosthetic foot connected to the movable member and displaced under the drive of the movement of the movable member; A series elastic pneumatic actuator extending between the upright member and the second base, the series elastic pneumatic actuator being configured between a first configuration state where the prosthetic foot is displaced to a first rest position and a second configuration state where the prosthetic foot is displaced to a second position; And A first base connected to the movable member, the first base being received in the prosthetic foot, wherein the first base is displaced between a rest position corresponding to the rest position of the prosthetic foot and a second position corresponding to the second position of the prosthetic foot by the series elastic pneumatic actuator.

2. The prosthetic foot component according to claim 1, characterized in that, The series elastic pneumatic actuator includes a cylinder defining a gas chamber therein, a piston head slidably displaced within the gas chamber, and a piston rod connected to the piston head extending outwardly from the cylinder, wherein a first spring is mounted between the piston head and the closed end of the cylinder, and wherein the series elastic pneumatic actuator further includes a pushing element extending between the piston rod and the second base.

3. The prosthetic foot component according to claim 2, characterized in that, The pushing element extends between the free end of the piston rod and the second base.

4. The prosthetic foot component according to claim 2, characterized in that, The pushing element is a spring.

5. The prosthetic foot component according to any one of claims 1-4, characterized in that, The prosthetic foot assembly includes an air circuit including an air compressor in fluid communication with the series elastic pneumatic actuator for supplying compressed air to the series elastic pneumatic actuator to enable the series elastic pneumatic actuator to be configured between the first configuration state and the second configuration state.

6. The prosthetic foot component according to claim 5, characterized in that, The air circuit is connected to the series elastic pneumatic actuator through a suitable conduit.

7. The prosthetic foot component according to claim 5, characterized in that, An exhaust valve is further included, which allows air to be released to the atmosphere or a storage tank of the air circuit or both when the series elastic pneumatic actuator is configured between the first configuration state and the second configuration state.

8. The prosthetic foot component according to claim 5, characterized in that, A control valve is further included, which is arranged to open when applying pressure to the prosthetic foot in a gait cycle to allow compressed air to flow from the air circuit into the series elastic pneumatic actuator to enable the series elastic pneumatic actuator to be configured between the first configuration state and the second configuration state.

9. The prosthetic foot component according to any one of claims 1-4, characterized in that, The second base is spaced above the first base, and wherein under the driving action of the series elastic pneumatic actuator on the second base, the first base is displaced between a rest position corresponding to the rest position of the prosthetic foot and a second position corresponding to the second position of the prosthetic foot.

10. The prosthetic foot component according to any one of claims 1-4, characterized in that, The second base extends away from the movable member in a direction towards the rear end of the prosthetic foot.

11. The prosthetic foot component according to any one of claims 1-4, characterized in that, The movable member is connected to the upright member through a pivot joint, and the second base is located below the pivot joint.

12. The prosthetic foot component according to any one of claims 2-4, characterized in that, The closed end of the cylinder is fixed to the upright member by a fixing element.

13. The prosthetic foot component according to any one of claims 1-4, characterized in that, The series elastic pneumatic actuator is arranged obliquely with respect to the upright member.

14. The prosthetic foot component according to any one of claims 1-4, characterized in that, The first rest position of the prosthetic foot corresponds to a configuration state in which the plantar surface of the prosthetic foot is arranged substantially parallel to the ground, and the second position of the prosthetic foot corresponds to the plantar flexion position or the dorsiflexion position of the prosthetic foot during a gait cycle in use.

15. The prosthetic foot component according to claim 14, characterized in that, During a gait cycle in use, the angle when the prosthetic foot is configured between the dorsiflexion position and the plantar flexion position is in the range of 0° to 36°.

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