Artificial multi-axis knee joint

1. An artificial multi-axis knee joint comprising an upper leg portion ( 1 ) and a lower leg portion ( 2 ), said upper leg portion and said lower leg portion being pivotally connected to each other by means of a front link ( 3 ), which front link ( 3 ) at one end thereof is pivotally connected to the upper leg portion ( 1 ) for pivoting the front link and the upper leg portion relative to each other around a first geometrical pivot axis ( 5 ) and at the other end thereof is pivotally connected to the lower leg portion ( 2 ) for pivoting the front link and the lower leg portion relative to each other around a second geometrical pivot axis ( 6 ), and by means of at least one rear link ( 4 ), which rear link ( 4 ) at one end thereof is pivotally connected to the upper leg portion ( 1 ) for pivoting said at least one rear link and the upper leg portion relative to each other around a third geometrical pivot axis ( 7 ) and at the other end thereof is pivotally connected to the lower leg portion ( 2 ) for pivoting said at least one rear link and the lower leg portion relative to each other around a fourth geometrical pivot axis ( 8 ), in addition to the front link ( 3 ) and said at least one rear link ( 4 ) the knee joint further comprising a further means ( 9 ) for controlling the bending characteristics of the knee joint, wherein the controlling means ( 9 ) is integrated in one of the front link ( 3 ) and said at least one rear link ( 4 );

wherein the controlling means ( 9 ) is arranged internally of the front link ( 3 ) or said at least one rear link ( 4 );

wherein the controlling means ( 9 ) includes pivot axes consisting of the first and second geometrical pivot axes.

2. Knee joint according to claim 1 , wherein the controlling means ( 9 ) is integrated in the front link ( 3 ).

3. Knee joint according to claim 1 , wherein the controlling means ( 9 ) is arranged to control the requisite torque for bending the knee joint.

4. Knee joint according to claim 3 , wherein the controlling means ( 9 ) comprises a cylinder ( 10 ) having two chambers ( 12 , 13 ), a working fluid and a piston ( 11 ) movably arranged in the cylinder for controlling the requisite torque for bending the knee joint.

5. Knee joint according to claim 4 , wherein the upper leg portion ( 1 ) is arranged to transmit a relative pivot motion of the upper leg portion ( 1 ) and the lower leg portion ( 2 ) is arranged to transmit a rectilinear motion of the piston ( 11 ) in the cylinder ( 10 ) during bending of the knee joint, by means of a crank shaft ( 14 ).

6. Knee joint according to claim 5 , wherein the rotation axis ( 15 ) of the crank shaft ( 14 ) extends along said first geometrical pivot axis ( 5 ) of the front link ( 3 ) at said upper leg portion ( 1 ).

7. Knee joint according to claim 6 , wherein the cylinder ( 10 ) is pivotally connected to said lower leg portion ( 2 ) for pivoting the cylinder ( 10 ) and said lower leg portion ( 2 ) relative to each other around said second geometrical pivot axis ( 6 ) of said front link ( 3 ).

8. Knee joint according to claim 4 , wherein the cylinder ( 10 ) is provided with a coil pipe ( 41 ) for the working fluid which coil pipe connects both chambers ( 12 , 13 ) of the cylinder on each side of the piston ( 11 ).

9. Knee joint according to claim 8 , wherein said coil pipe ( 41 ) is provided with a valve ( 19 ) for regulating the flow of the working fluid in the coil pipe and controlling the requisite torque for bending the knee joint.

10. Knee joint according to claim 9 , wherein the controlling means ( 9 ) comprises a motor ( 20 ) for operating the valve ( 19 ).

11. Knee joint according to claim 10 , wherein the motor ( 20 ) is arranged to drive the valve disk ( 24 ) and to pivot this disk for operating the percentage opening of the valve ( 19 ).

12. Knee joint according to claim 9 , wherein the valve ( 19 ) comprises a valve housing ( 23 ) and a disk ( 24 ) pivotably arranged in the valve housing, the pivot position of which relative to the valve housing ( 23 ) determines the percentage opening of the valve ( 19 ) and thus regulates the flow in the coil pipe.

13. Knee joint according to claim 12 , wherein the disk ( 24 ) has a radially directed periphery surface ( 25 ) the distance of which relative to the geometrical pivot axis of the disk ( 24 ) varies along the circumference of the disk.

14. Knee joint according to claim 13 , wherein the contour of the disk along the circumference thereof as regards said periphery surface ( 25 ) has the shape of an involute.

15. Knee joint according to claim 9 , wherein the knee joint is provided with only one valve ( 19 ) for controlling the requisite torque for bending the knee joint by means of the controlling means ( 9 ).

16. Knee joint according to claim 1 , wherein the knee joint has a total of four said external pivot axes ( 5 , 6 , 7 , 8 ) for forming the geometrical pivot centre of the knee joint and arranging said controlling means ( 9 ).

17. Knee joint according to claim 1 , wherein the knee joint has two rear links ( 4 ) arranged spaced apart from each other which both are pivotally connected to the upper leg portion ( 1 ) and the lower leg portion ( 2 ) for pivoting around the third ( 7 ) and fourth ( 8 ) geometrical pivot axis, respectively.