VALVE AND PROSTHETIC KNEE JOINT HAVING SUCH A VALVE

Abstract

A valve with an inlet, an outlet that is connected to the inlet via a fluid connection, and a valve body, which can be brought by displacing it along a displacement direction into a first position, in which the fluid connection is blocked, and a second position, in which the fluid connection is open, wherein the inlet is designed and arranged in such a way that a fluid entering through the inlet exerts a total force on the valve body that at least also acts in a force direction which is perpendicular to the displacement direction when the valve body is in the first position.

Claims

1. A prosthetic knee joint, comprising a valve that comprises an inlet, an outlet that is connected to the inlet via a fluid connection, and a valve body which is movable into a first position in which the fluid connection is blocked, and wherein the valve body is moveable into a second position in which the fluid connection is open; a lower leg part; and an upper leg part arranged on the lower leg part such that the upper leg part is moveable relative to the lower leg part when the fluid connection is open, wherein the valve body is configured such that a switch force is required to be applied to the valve body to move the valve body from the first position to the second position, wherein the valve body is configured such that the valve body is maintained in the second position when a fluid is flowing in the fluid connection and a pressure of the fluid is greater than a predetermined threshold even if the switch force is no longer present.

2. The prosthetic knee joint of claim 1, wherein the switch force required to be applied to the valve body to move the valve body from the first position to the second position occurs when the prosthetic knee joint is subjected to an external load.

3. The prosthetic knee joint of claim 1, wherein the valve body is only moveable from the first position to the second position when the prosthetic knee joint is extended.

4. The prosthetic knee joint of claim 1, wherein the valve body is immovable from the first position to the second position when the pressure of the fluid is greater than a predetermined limit.

5. The prosthetic knee joint of claim 1, wherein the valve is configured such that an increase in pressure of the fluid at the inlet counteracts a displacement of the valve body from the first position into the second position.

Description

[0020] In the following, an example of an embodiment of the present invention will be explained in more detail by way of the attached figures: They show

[0021] FIGS. 1, 3, 5 and 7schematic sectional views through a prosthetic knee joint in various situations,

[0022] FIGS. 2, 4, 6 and 8enlarged sections from the respective preceding figures,

[0023] FIG. 9the schematic representation of the further embodiment of the present invention and

[0024] FIGS. 10-11schematic views of a valve according to an example of an embodiment of the present invention.

[0025] FIG. 1 depicts a sectional view through a prosthetic knee joint according to a first example of an embodiment of the present invention. It comprises an upper part 2 with an upper fixing element 4, on which, for example, a prosthesis shaft or another prosthetic component can be arranged. The upper part 2 is arranged on a lower part 6 such that it can be swivelled, said lower part comprising a first component 8 and a second component 10, which features a lower fixing element 12 that is designed as a tube clamp for a lower leg tube in the example of an embodiment shown. The first component 8 is arranged on the second component such that it can be swivelled about a control axis 14.

[0026] In the prosthetic knee joint there is a hydraulic arrangement with an extension chamber 16, a flexion chamber 18 and a valve 20, which is arranged in a fluid connection 22, by means of which the extension chamber 16 is connected to the flexion chamber 18. The extension chamber 16 is separated from the flexion chamber 18 by a piston 24, which moves in the volume, formed by the extension chamber 16 and the flexion chamber 18, when the knee is moved, i.e. the upper part 2 is swivelled relative to the lower part 6. As a result, fluid in the hollow space is guided from the extension chamber 16 into the flexion chamber 18 or vice-versa. In the example of an embodiment shown, a bore 54 is shown in the piston 24, wherein a non-return valve 56 is situated inside the bore. This bore 54 represents an additional fluid connection between the extension chamber 16 and the flexion chamber 18, which allows for a flow of fluid from the extension chamber 16 into the flexion chamber 18 but prevents such a flow in the opposite direction. In the figures shown, the position of the schematically depicted non-return valve 56 does not correspond to the actual position, but rather should serve only to illustrate the arrangement of the non-return valve 56.

[0027] FIG. 2 depicts an enlarged section. The valve 20 features a valve body 26, which is in the first position in the situation shown in FIG. 2. The valve comprises an inlet 28, an outlet 30 and a throttle outlet 32. A hydraulic fluid that enters the valve through the inlet 28 along the arrow 34 cannot leave the valve through the outlet 30, as the valve body 26 is in the first position. In this position it is spring-loaded by a spring 36. However, in the example of an embodiment shown the fluid can pass through the valve body 26 and leave the valve through the throttle outlet 32. A clockwise swivelling of the piston 24 is consequently opposed by a large flow resistance.

[0028] The fluid that enters the valve through the inlet 28 strikes the valve body 26 and exerts a total force on this valve body 26, said force at least also comprising one component which is perpendicular to a displacement direction, along which the valve body 26 can be displaced. In the representations shown, the displacement direction extends from top to bottom. The total force applied results in a counter force F.sub.n, which acts on an opposite side, on which the valve body 26 rests on a housing wall 38. The valve 20 also features a switch pin 40, which can exert a switch force F.sub.s on the valve body 26 from below in the example of an embodiment shown in order to displace said valve body from the first position depicted into the second position. Due to the static friction, the counter force F.sub.n generates a frictional force F.sub.r, which is a result of the product of the counter force F.sub.n and the static force coefficients .

[0029] A feedback spring 42 is arranged about the switch pin, said feedback spring being used to bring the switch pin 40 back into the starting position following the completion of a switch cycle.

[0030] FIG. 3 shows the prosthetic knee joint from FIG. 1 in a second situation. Due to, for example, a load on the forefoot, i.e. a force acting on the lower part 6, whose pitch line lies in front of the control axis 14, i.e. left of the control axis 14 in the example of an embodiment shown, the first component 8 is swivelled about the control axis 14 relative to the second component 10. In this case, a switch lever 46 is moved by way of a switch screw 44, the switch lever striking the switch pin 40 from below and thereby transferring a switch force to the switch pin 40.

[0031] FIG. 4 depicts an enlarged section. The switch lever 46, which has displaced the switch pin 40 upwards, is clearly recognizable, which has caused the valve body 26 to be displaced from the first position, which was depicted in FIGS. 1 and 2, into the second position. The fluid can now flow out of the flexion chamber 18, along the arrow 34, and through the valve, and leave the valve not only through the throttle outlet 32, but also through the outlet 30. The damping resistance that opposes the fluid is thus considerably lower than in the situation in FIGS. 1 and 2.

[0032] FIG. 5 shows the prosthetic knee joint in another situation. It is clear that the upper part 2 has been swivelled relative to the lower part 6. The extension chamber 16 is considerably larger. However, the first component 8 is no longer swivelled relative to the second component 10 of the lower part 6 and the switch pin 40 has returned to its original position. Nevertheless, the valve body 26 remains in the second position.

[0033] FIG. 6 depicts an enlarged section. The switch lever 46 has returned to the position from FIG. 1 and the switch pin 40 is no longer in contact with a lower side of the valve body 26. However, the swivelling of the upper part 2 relative to the lower part 6 of the prosthetic knee joint results in a swivelling of the piston 24, which causes fluid to be pushed through the valve along the arrow 34. An overpressure occurs inside the valve 20, as a flow resistance is produced by the outlet 30 and the throttle outlet 32.

[0034] A connection channel 48 is situated above the spring 36, said channel connecting the volume in which the spring 36 is located to the extension chamber 16. This area exhibits a negative pressure of the hydraulic fluid. Given that there is an overpressure below the valve body 26 and a negative pressure above the valve body 26, the valve body 26 is also held in the second position, shown in FIGS. 5 and 6, against the spring pressure of the spring 26, even if the switch force F.sub.s applied by the switch pin 40 is no longer there. The flexion of the knee is consequently only possible with a relatively low flow resistance and thus low damping.

[0035] FIG. 7 shows the situation during the reversal of movement. In this case, the upper part 2 should be swivelled relative to the lower part 6 in such a way that the knee is extended. This results in an anti-clockwise movement of the piston 24.

[0036] FIG. 8 shows an enlarged section, from which it is clear that, due to the overpressure in the extension chamber 16 caused by the reversal of movement, this pressure is also transferred via the connection channel 48 into the volume in which the spring 36 is located. As a result, the pressure situation shown in FIG. 6, which ensures that the valve body 26 remains in the depicted second position, is no longer applicable. Rather, the spring 36 and the overpressure applied via the connection channel 48 push the valve body 26 back into the first position, in which fluid can no longer enter the valve through the outlet 30, but rather only through the throttle outlet 32, wherein the fluid leaves said valve through the inlet 28 and enters the flexion chamber 18.

[0037] FIG. 9 depicts an enlarged section of the valve arrangement. In particular, a switch spring 50 is depicted, which is arranged between the switch pin 40 and a transmission pin 52. The switch lever 46 strikes the switch pin 40, which moves as a result. However, this movement is not immediately transferred to the valve body 26, but rather is initially transferred from the switch pin 40 to the switch spring 50. This initially transfers the switch force to the transmission pin 52 and hence to the valve body 26.

[0038] By selecting the spring constant of the switch spring 50, the force has an upper limit, at least in the short term. The force that can be applied to the valve body 26 via the switch spring 50 to switch the valve is selected in such a way that it is enough to overcome the spring pressure Pa and to displace the valve body 26 out of the first position depicted into the second position when there is no or only a very small counter force F.sub.n. However, if a total force is exerted on the valve body 26 by the incoming fluid and the counter force F.sub.n thus produced, the switch force F.sub.s, which is transferred to the valve body 26 by the switch spring 50 and the switch pin 40, is not sufficient to switch the valve.

[0039] FIGS. 10 and 11 show an isolated image of the valve 20. Whereas the valve body 26 in the image in FIG. 10 is in the second position and the inlet 28 is therefore free, this is not the case in FIG. 11. The valve body 26 is in the first position, meaning that a fluid entering the valve 20 through the inlet 28 strikes the valve body 26 and exerts a force. It is clear that the inlet 28 covers a section of the circumference of the valve and thus also the valve body 26, said section being smaller than 180 in the example of an embodiment shown.

REFERENCE LIST

[0040] F.sub.n counter force [0041] F.sub.s switch force [0042] F.sub.r frictional force [0043] 2 upper part [0044] 4 upper fixing element [0045] 6 lower part [0046] 8 first component [0047] 10 second component [0048] 12 lower fixing element [0049] 14 control axis [0050] 16 extension chamber [0051] 18 flexion chamber [0052] 20 valve [0053] 22 fluid connection [0054] 24 piston [0055] 26 valve body [0056] 28 inlet [0057] 30 outlet [0058] 32 throttle outlet [0059] 34 arrow [0060] 36 spring [0061] 38 housing wall [0062] 40 switch pin [0063] 42 feedback spring [0064] 44 switch screw [0065] 46 switch lever [0066] 48 connection channel [0067] 50 switch spring [0068] 52 transmission pin [0069] 54 bore [0070] 56 non-return valve