Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Knee
Patent
1995-01-23
1998-09-01
Weiss, John G.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Knee
623 44, 623 45, A61F 264
Patent
active
058005668
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an artificial joint equipped with a hydraulic damping cylinder and a hydraulic damping cylinder designed to be a part of an artificial joint, especially of such an artificial knee joint, in which it is not possible to install conventional damping cylinders with a cylinder block into and out of which a piston rod reciprocates. The present invention is especially adapted to be used with artificial knee joints of the type with seven pivot points which is further described in the Swedish patent application no. 91001183-4 and PCT/SE91/00240, but damping cylinders according to the present invention can also be utilized with artificial joints of other types such as with polycentric knee joints with four pivot points and even with joints having one single pivot point.
The artificial joint type with seven pivot points which is described in the above mentioned patent publication makes great progress in relation to the previous state of the art. Equipped with a hydraulic damping cylinder as described below and according to the claims the joint is also given a control of the swing phase which, together with the quality of stability of the joint, produces an artificial knee joint which function very close to a natural leg despite the lack of active components to replace muscle force.
DESCRIPTION OF THE BACKGROUND ART
It is known in the art to arrange hydraulic damping cylinders with other artificial joints, see for instance EP 0097226. In its simplest design, the damping cylinder comprises a piston and channels with chokes in the cylinder between the opposite sides of the piston. The present invention also relies on this principle. But in the present invention, a piston rod moving into or out of the damping cylinder is not used, because it will involve disadvantages and difficulties in building such conventional damping cylinders into, for instance, knee joints with multiple pivot points as mentioned above.
It has also been known for a long time, from the Swiss patent publication no. 248 586, to arrange hydraulic damping cylinders in such a way that the longitudinal movement of the piston is directly transferred to a turning movement by means of gear teeth on the piston in mesh with a gearwheel. This construction, mainly intended for door closers, has a built in spring with a spring force acting on the piston in one direction while the piston includes a spring loaded valve opening on movement against the spring force and a channel damping the return movement. While this construction has been known since 1947, until the present invention no similar construction has been used with am artificial joint, or been adapted for it according to the present invention.
SUMMARY OF THE INVENTION
An object of the present invention is to achieve an artificial joint with multiple pivot points integrated with a hydraulic damping cylinder in such a way that it insignificantly adds length to the joint or otherwise deteriorates the function of the joint.
A second object is to achieve a damping cylinder, the damped movement of which consists of a turning of an axis instead of an axial movement, whereby tightening against leakage of hydraulic oil can better can be achieved.
A third object of the present invention is to bring about a damping cylinder in which the damping can take place in several stages with different magnitude.
A further object of the invention is to place the damping cylinder in such a way in the joint that heat produced in it will be dissipated to avoid too high a temperature.
These and other objects are achieved with an artificial joint and a damping cylinder having a piston having a rack-gearing along one side thereof. A hydraulic cylinder has a longitudinal opening in which the piston is mounted. The piston is completely contained within the cylinder and the piston being reciprocable in the hydraulic cylinder. The cylinder further has channels interconnecting opposed ends of the cylinder on opposite sides of the piston whereby hydraulic fluid can flow theret
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Snow Bruce E.
Weiss John G.
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