Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Knee
Patent
1995-10-03
1998-03-17
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Knee
267124, A61F 264
Patent
active
057281742
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a swing phase control for an artificial knee joint comprising a cylinder having one end closed by a head member and the other end closed by a base member, a piston reciprocally movable within the cylinder in axial direction thereof and having a piston rod passing outwards through a bore provided in the head member for connection with the thigh part of a prosthesis, a head side first chamber defined by the piston and a base side second chamber.
Such an apparatus is known from the U.S. Pat. No. 5,062,857.
It is the object of the invention to provide a swing phase control of the above defined kind which has good damping properties for movements of varying speed and nevertheless is of a simple construction.
This object is achieved by a swing phase control of the above defined kind which is characterized in that the head member comprises a channel connecting the first chamber with the ambient and including a check valve blocking the communication between the first chamber and the ambient, that the first and second chamber are connected through a throttle passage and that the base member comprises a vent bore connecting the second chamber with the ambient and a first spring biasing the piston towards the head member.
This solution provides for an extreme simple and light weight swing phase control.
According to a preferred embodiment a second spring having a shorter length of pass is provided for a second biasing stage. This accelerates the extension.
Further developments of the invention are defined in the sub-claims.
Further features and functionalities of the invention will be apparent from the description of embodiments with reference to the figures.
In the figures:
FIG. 1 shows a section through a first embodiment;
FIG. 2 shows a section through a second embodiment in a first operating position; and
FIG. 3 shows the second embodiment in a second operating position.
As best seen in FIG. 1 a second chamber 10 has a compression spring 22 provided coaxially therein and having a first end resting against an abutment face of the base member 3 and the opposite end resting on an abutment surface of the piston 7 for biasing the piston in a direction towards the head member 2. The second chamber 2 communicates with the ambient through a bore 23. Moreover, bores 24 are provided at the base member for connection with the lower leg. The piston 7 has an annular rubber cushion 24' provided on the top side thereof.
In operation the spring 22 dampens the flexional movement but accelerates the extensional movement. On the other hand, a dampening action is obtained by the air cushion developing within the first chamber 9. The dampening grade is determined by the axial position of the valve rod 16 or the cross section of the throttling passage defined thereby.
As best shown in FIG. 1 a channel formed as a bore 12 connecting the interior of the first chamber 9 with the ambient is provided in the head member 2. A check valve 13 formed as a flutter valve is arranged in the bore and formed to clear the communication from the ambient to the first chamber but to block the channel in opposite direction. The outside of the bore is covered by a dust filter 14. As shown in FIG. 1 the piston 7 has a coaxial bore 15 having a conical cross-section tapering towards and opening into the second chamber 10. The piston rod 6 is hollow and has a coaxially extending valve rod 16 disposed therein. The valve rod 16 has a shaft extending in axial direction and having an end at the bore 15 which has a conical portion 17 with a cone angle which is substantially equal to the angle of the conical bore 15. The valve rod is guided in a thread. The end of the valve rod opposite to the bore 15 has a knurled portion 18 which is accessible for adjusting the axial position of the valve rod. A seal 19 providing an outward seal is arranged between the access portion and the conical portion 17. The diameter of the valve rod in the portion thereof adjacent to the conical portion 17 is smaller than the inner diameter of the piston rod 6. Th
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Biedermann Motech GmbH
Neuner George W.
Willse David H.
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