Prosthetic knee joint

Abstract

The present invention relates to a prosthetic knee joint comprising a lower joint, an upper joint and a hydraulic system with at least one switching valve, wherein: the hydraulic system comprises an extension chamber, a flexion chamber and at least one piston, the volume of the extension chamber and / or the flexion chamber being variable by movement of the piston; the switching valve comprises a valve housing and a switching element movably mounted therein, the switching element being movable between a first position and a second position within the valve housing and dividing the interior space of the valve housing into a first chamber and a second chamber; the switching element is biased by at least one biasing element arranged in the switching valve; the prosthetic knee joint comprises at least one spring element which applies a counter force to the biasing force on the switching element, and at least one fluid connection is arranged in the valve housing and / or the switching element between the first chamber and the second chamber.

Description

[Technical Field]

[0001] The present invention relates to a prosthetic knee joint comprising a lower joint, an upper joint, and a hydraulic system having at least one switching valve, the hydraulic system comprises an extension chamber, a flexion chamber and at least one piston, the movement of which can change the volume of the extension chamber and / or the flexion chamber; the changeover valve has a valve housing and a changeover element movably mounted therein, the changeover element being movable between a first position and a second position within the valve housing and dividing the interior space of the valve housing into a first chamber and a second chamber; the switching element is biased by at least one biasing element arranged on the switching valve, the prosthetic knee joint has at least one spring element that applies a reaction force to the switching element in a direction opposite to the bias. [Background technology]

[0002] Such a prosthetic knee joint is known from DE 10 20 18 111 441 A1.

[0003] Prosthetic knee joints have long been known in the prior art. They are an essential component of prosthetic limbs and should mimic the function of the human knee as closely as possible. The human knee, in this case, allows movement in some situations and blocks movement in others. This is important to provide the necessary stability whenever possible. The versatility of the human knee presents a challenge for prosthetic knees. To enable movements with different speeds and damping, prosthetic knees are often equipped with hydraulic systems. Prosthetic knees equipped with hydraulic systems typically have at least two hydraulic chambers, the so-called extension chamber and the flexion chamber, fluidically connected to each other. At least one connecting line is present for this purpose. Pistons are arranged in both chambers and can move within the chambers, thereby changing the volume of each chamber. The pistons can be formed as a single piston. In this case, the two chambers are located on two opposite sides of a piston, which is preferably formed as a rotating piston. This achieves the following: an increase in the volume of one chamber results in a decrease in the volume of the other chamber. Of course, two pistons may be arranged in each cylinder, each cylinder defining a chamber.

[0004] The upper joint is attached to the lower joint so as to be pivotable about a pivot axis.

[0005] Flexion refers to bending the knee, i.e., the movement of the upper joint relative to the lower joint in a first direction, called the flexion direction. During this movement, hydraulic fluid, e.g., hydraulic oil, flows from the flexion chamber to the extension chamber. The opposite movement, called extension, is the straightening of the prosthetic knee joint. In this case, hydraulic fluid flows from the extension chamber to the flexion chamber. In this case, the extension chamber is the chamber where pressure increases during extension, and the flexion chamber is the chamber where pressure increases during flexion.

[0006] The speed at which the hydraulic fluid reaches from one chamber to the other determines the speed of the joint movement, i.e. the speed of the upper joint movement relative to the lower joint. This speed depends, inter alia, on the flow cross-section of the connecting line. From DE 69312771 T1, a device is known which can be used to control the hydraulic system of a femoral prosthesis.

[0007] Different speeds during different phases of the gait cycle are advantageous, and thus a switching valve is integrated into the prosthetic knee joint. This allows, for example, switching between two different connection lines with different flow cross sections and different flow resistances. The switching valve has a valve housing containing a switching element. The switching element is, for example, formed as a movable piston or slide. The switching element is a component that, by moving to a first or second position, can change the flow cross section or flow rate in the hydraulic system and / or open or close a hydraulic line or fluid connection. The valve housing is a component of the prosthetic knee joint, within which the switching element can move to the first and second positions. It can be formed as a separate component. Alternatively, another component of the prosthetic knee joint, such as the lower or upper joint, can serve as the valve housing. For this purpose, for example, a cavity or hole is present in the respective component, within which the switching element moves.

[0008] The switching element can be moved between a first position and a second position relative to the valve housing. When the valve is in the first position, it is in a first state, for example, opening the first connecting line. In a preferred embodiment, the connecting line has a high flow resistance, which greatly damps the movements of the prosthetic knee joint. This allows only slow, weight-bearing movements of the upper joint relative to the lower joint, which is advantageous, for example, during the stance phase of walking, when sitting, and when descending stairs or slopes.

[0009] On the other hand, when the switching element is moved to a second position relative to the valve housing, the switching valve is in a second state in which another passage for the hydraulic fluid is open, which may be, for example, a second connecting line. When the valve is in this state, it is preferable that the damping of the knee joint movement is small, which may be, for example, This can be achieved by having the second connection line have a lower flow resistance than the first connection line, for example, the second state is advantageous during the swing phase of gait, when the knee is not bearing weight and high damping would be unphysiological in this case.

[0010] The switching element of the corresponding prosthetic knee joint divides the interior space of the valve housing into a first chamber and a second chamber, and is preferably completely contained within the valve housing, and more preferably completely surrounded by the respective hydraulic fluid.

[0011] In order to move the switching element from the first position to the second position and thus switch the switching valve, an actuation mechanism is present, which is capable of exerting a force on the switching element. The switching element is biased by at least one biasing element, for example in the form of a spring, in particular a helical spring. The bias is directed in particular towards the first position of the switching element, which causes higher damping.

[0012] The first position of the switching element relative to the valve housing can depend on many parameters. In some cases, this first position depends on, among other things, the magnitude of the bias, the hydraulic pressure in the hydraulic system, the possible flow paths through the system, particularly from one chamber to another, the general sizing of the prosthesis, particularly the knee prosthesis, and the type of knee prosthesis, to name just a few. However, accurately determining the first position of the switching element relative to the valve housing is crucial because it determines the required travel distance the switching element must travel to reach the first position and the second position. This, in turn, determines how quickly the switching valve responds and when, for example, during a gait cycle, the switching valve switches from a first state in which the switching element is in the first position to a second state. Unfortunately, the biasing element is located within the valve, and therefore often within the hydraulic system and often within the hydraulic fluid, making it difficult or impossible to access at all. Other parameters are often only available once the knee joint is assembled and cannot be determined in advance, or are very difficult to determine. Adjustment of the first position of the switching element relative to the valve housing is therefore either almost impossible or possible only with great effort.

[0013] The prosthetic knee joint further includes a spring element, which is configured to apply a force, i.e., a counterforce, to the switching element. This can be done directly, for example, by mechanically contacting the spring element with the switching element, or indirectly, by transmitting a force to an intermediate part, which then transmits the force directly or indirectly to the switching element. When no additional external force is applied to the spring element to amplify the counterforce, the bias exceeds the counterforce, and the switching element is in the first position. In this position, the flow resistance against the flow of hydraulic fluid through the hydraulic system, particularly the switching valve, is greater than when the switching element is in the second position. In this way, the standard setting of the valve provides a high resistance against pivoting of the upper fitting relative to the lower fitting.

[0014] If an external force is applied to the spring element that increases the reaction force, the external force can overcome the bias and move the switching element from the first position to the second position. If the external force later weakens or disappears completely, the reaction force also decreases, so that the reaction force is again less than the bias. The bias then moves the switching element back to the first position. This happens more quickly the greater the resultant force of the bias and reaction force.

[0015] The invention is therefore based on the problem of improving a prosthetic knee joint in such a way that a first position suitable for controlling the knee joint can be easily reached. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] German Patent Application Publication No. 102018111441 [Patent Document 2] German Patent Application Publication No. 69312771T1 Summary of the Invention

[0017] The present invention solves the problem of a prosthetic knee joint by being characterized in that at least one fluid connection is arranged between the first and second chambers in the valve housing and / or the switching element. In this case, for example, when an external force is applied to the spring element against the bias of the biasing element, the spring element is tightened, particularly preferably compressed, thereby storing potential energy. The spring element thereby exerts a force on the switching element. This can be done directly, for example, by abutting one end of the spring element against the switching element, or indirectly, by the spring element first transmitting its force to one or more other components of the prosthetic knee joint, which then transmit the force directly or indirectly to the switching element.

[0018] If the switching element is to avoid this force, it must be moved against the bias of the biasing element. This causes one of the two chambers in the valve housing to shrink and the other to expand. That is, at least a portion of the hydraulic fluid must leave the shrinking chamber. At the same time, hydraulic fluid must flow into the expanding chamber. For this purpose, at least one fluid connection exists between the first and second chambers, which is located in the valve housing according to the invention. In this case, the cross-section of the at least one fluid connection determines the amount of hydraulic fluid that flows from the shrinking chamber through the at least one fluid connection to the expanding chamber. The placement of the fluid connection, which may also be called a bypass, in the valve housing usually avoids the need to add critical installation space to the prosthetic knee joint. Preferably, there are several fluid connections, for example at least three. These fluid connections can be identical. They can have, for example, the same length and / or the same cross-section, e.g., circular or polygonal, and / or the same cross-sectional area, preferably 1 mm. 2 less than 0.5 mm, particularly preferably 2 Less than 0.385 mm, particularly preferably 2 Preferably, they generate the same flow resistance. For this, identical lengths, identical cross sections, or identical cross-sectional areas are not necessary, but are advantageous. The fluid connections can also be formed differently, for example, and may not generate the same flow resistance.

[0019] When a valve is to be switched, a force must be applied to the switching element, causing it to move from a first position to a second position or vice versa. According to the invention, the switching element divides the interior space of the valve housing into two chambers filled with hydraulic fluid, thereby damping the movement of the switching element within the valve housing. Therefore, to move the switching element, fluid must be guided from one chamber to the other. This is possible only through the fluid connection, regardless of the switching state of the valve, i.e., the position of the switching element. The cross-section of this connection determines how quickly the switching element can react to the impact of external forces.

[0020] By damping this response, it is possible that brief force impulses that normally should not result in a change in the switching state of the valve do not last long enough to transfer a sufficient amount of fluid between the two chambers in the valve housing to switch the valve.

[0021] In a preferred embodiment, the fluid connections are configured to be active in different positions of the switching element. For this purpose, the inner wall of the valve housing that contacts the switching element is provided with a plurality of recesses, such as grooves, grooves, or indentations. These recesses are preferably of different lengths. This can result, on the one hand, in such recesses being closed by the switching element moving from the first position to the second position. On the other hand, such fluid connections can also be opened by the moving switching element.

[0022] To allow the recess in the valve housing's inner wall to form a fluid connection between the first and second chambers, one end of the recess must be located in the area of ​​the inner wall defining the first chamber, and the other end must be located in the area of ​​the inner wall defining the second chamber. When the switching element moves from the first position to the second position, or vice versa, one chamber expands and the other chamber contracts, thereby changing the proportions of the inner walls defining the first and second chambers.

[0023] In particular, at least one fluid connection extends through the switching element. It is particularly preferred that the at least one fluid connection is a hole in a surface of the switching element perpendicular to the direction of movement of the switching element. In particular, there are a plurality of identical or variously formed fluid connections. Alternatively or additionally, it is preferred that a recess is provided in the outer surface of the switching valve.

[0024] Alternatively or additionally, at least one fluid connection extends through the valve housing. It is particularly preferred that such a fluid connection is provided as a recess, groove, or channel in a wall of the valve housing that defines the interior space of the valve housing. Again, in this embodiment, the cross-section of the fluid connection determines the amount of fluid that is forced from the contracting chamber to the expanding chamber by the force applied by the spring element.

[0025] Alternatively or additionally, at least one fluid connection extends between the valve housing and the switching element.

[0026] Regardless of the form and / or number of fluid connections present, the smaller the overall cross section of all available fluid connections, the greater the resistance to movement of the switching element due to the flow resistance of at least one fluid connection.

[0027] When the switching element is in a first position, the hydraulic system provides a high resistance to movement of the lower joint relative to the upper joint. In this state, movement is highly damped. When the switching valve is in a second state, the switching element is in a second position and movement of the lower joint relative to the upper joint is slightly damped. To this end, the prosthetic knee joint has at least one spring element that applies a reaction force to the switching element in a direction opposite to the bias.

[0028] It is preferred that the cross section of at least one fluid connection, preferably all fluid connections, is not variable and / or that each fluid connection, preferably all fluid connections, is not closable.

[0029] Preferably, the at least one spring element is arranged so that application of a force to the at least one spring element for at least a predetermined period of time causes the switching element to transition from the first position to the second position. It is particularly preferred that application of a force to the spring element for a period shorter than the predetermined period of time prevents the switching element from transitioning from the first position to the second position. This configuration ensures that a force impulse of a shorter duration than the predetermined period of time does not cause the switching element to transition from the first position to the second position. Such a force impulse may occur, for example, when the wearer of the prosthetic knee joint stumbles or hits an object. This typically occurs during the swing phase, i.e., when the foot connected to the wearer's body by the prosthetic knee joint is not in contact with the ground. The force impulse compresses the at least one spring element, thus storing energy. The force impulse may be applied, for example, to a spring pin of a cartridge in which the at least one spring element is arranged. The stored energy is released as soon as the force is no longer applied, causing the spring pin to return to its original position. In this case, the time during which mechanical energy is stored in the at least one spring element is too short to move the switching element sufficiently to reach the second position. It is important to note that this does not mean that the switching element will not be moved: movement can certainly occur, but it will not lead to reaching the second position.

[0030] In particular, a force must be applied to at least one spring element in order to move the switching element from the first position to the second position, and it is preferred that no other possibilities for moving the switching element exist.

[0031] In particular, to reduce noise that may occur if a component, such as a spring sleeve, collides with another component, such as a spring housing cover or spring housing, at least one bushing made of plastic, especially thermoplastic, is arranged between each two components that may come into contact with each other in this way. For example, the group of polyoxymethylenes, often abbreviated as POM, is suitable.

[0032] Particularly preferably, the prosthetic knee joint is producible or is produced according to one of the methods described herein, in particular, where the reaction force exerted by the at least one spring element is preferably adjusted.

[0033] The present invention will be described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic cross-sectional view of a prosthetic knee joint according to one embodiment of the present invention. [Figure 2] FIG. 2 is a partial enlarged view from FIG. [Figure 3] FIG. 2 is a diagram of a switching element of a switching valve. [Figure 4] FIG. 1 is a diagram of a spring cartridge for a prosthetic knee joint. [Figure 5] 2 is an enlarged fragmentary view of the cross section according to FIG. 1, with the switching element in one position; [Figure 6] 2 is an enlarged fragmentary view of the cross section according to FIG. 1, with the switching element in another position; [Figure 7] 2 is an enlarged fragmentary view of the cross section according to FIG. 1, with the switching element in another position; [Figure 8] FIG. 1 is a schematic diagram showing the arrangement of fluid connections. [Figure 9] FIG. 10 is a schematic diagram showing another arrangement of fluid connections. [Figure 10] 1A and 1B are schematic diagrams showing alternative arrangements of fluid connections. [Figure 11] FIG. 10 is a schematic diagram of another spring cartridge. DETAILED DESCRIPTION OF THE INVENTION

[0035] Figure 1 shows a schematic cross-section of a prosthetic knee joint with a lower joint 2, an upper joint 4 and a hydraulic system with a switching valve 6. The hydraulic system comprises a flexion chamber 8 and an extension chamber 10 which are fluidically connected to one another. When the knee is extended, i.e. extended, hydraulic fluid flows from the extension chamber 10 to the flexion chamber 8. Conversely, when the knee is flexed, i.e. bent, hydraulic fluid flows from the flexion chamber 8 to the extension chamber 10. Both chambers 8, 10 are separated from one another by a piston 12 which is formed as a pivoting piston in the illustrated embodiment. When the piston 12 moves, one of the two chambers 8, 10 expands and the other of the two chambers 10, 8 contracts.

[0036] On the way from the extension chamber 10 to the flexion chamber 8 and / or vice versa, hydraulic fluid also passes through a switching valve 6. The switching valve 6 has a switching element 14 that can be moved between a first position and a second position.

[0037] FIG. 2 is an enlarged fragmentary view of FIG. 1 , showing the switching valve 6 in more detail. In the illustrated embodiment, the switching element 14 is fully immersed in hydraulic fluid and is movably mounted within the valve housing 16. To this end, a force and / or torque is applied to an outer part 18, which compresses a spring element 20. The spring element is housed in a spring cartridge, which will be described in more detail below. This spring cartridge has a spring pin 22 that is moved by the force exerted by the pre-compressed spring element 20. The spring pin 22 transmits this force to a deflection lever 24 that is pivotably arranged about a deflection axis 26. An arm 28 of the deflection lever 24 abuts against a valve pin 30, which is pushed up by the arm 28, thereby moving the switching element 14 from the first position to the second position.

[0038] The switching element 14 is biased by a biasing element 32. In the illustrated embodiment, the biasing element 32 is formed as a compression spring and presses the switching element 14 downwards, i.e. the bias of the biasing element 32 resists, inter alia, the force exerted by the spring pin 22. Depending on which of the two forces is greater, the switching element 14 moves to the first or second position.

[0039] 3 shows a cross-sectional view of the switching element 14. In the assembled state, the valve pin 30 rests against its underside 34. In the illustrated embodiment, the switching element 14 has a recess 36 at the opposite end, in which the biasing element 32 rests in the assembled state. A fluid connection 38 extends through the switching element 14, fluidically connecting the volume above the switching element 14 with the volume below it. When the switching element 14 is to be moved within the valve housing 16, hydraulic fluid passes through this fluid connection 38.

[0040] 4 shows a spring cartridge containing a spring element 20. In the illustrated embodiment, this spring element 20 is also formed as a compression spring. It is housed in a spring housing 40 which contains a spring sleeve 42 which is movable relative to the spring housing 40. The spring sleeve 42 is provided with a spring pin 22. The spring sleeve 42 is arranged movably relative to the spring housing 40, which has a spring house cover 46 through an opening in the spring house cover through which the spring pin 22 protrudes.

[0041] 5 shows a view of the spring cartridge with the spring pin 22 moved to the left. The spring pin 22 is in its base state and the spring 20 is not compressed. This causes the deflection lever 24 to pivot about the deflection axis 26, which causes the arm 28 to move the valve pin 30 and thus the switching element 14 upwards. This causes the switching element 14 to open the opening 44, which reduces the flow resistance against the hydraulic fluid between the two chambers 8, 10.

[0042] 6, the spring element 20 is relaxed and exerts little or no force. The force exerted by the biasing element 32 is greater and pushes the switching element 14 downwards. This closes the opening 44 and prevents hydraulic fluid from passing through it.

[0043] FIG. 7 shows the arrangement of FIGS. 5 and 6, in which the spring element 20 is compressed. This is achieved, for example, by a force acting on the spring element 20 and / or the spring housing 40 from the outside. The spring housing 40 has been moved to the left compared to the view of FIG. 6, so that the spring pin 22 no longer protrudes from the spring housing. Note that in this case, the spring pin 22 in the view of FIG. 7 has not been moved relative to the other parts of the prosthetic knee joint compared to the view of FIG. 6. In particular, the deflection lever 24 has not been pivoted, and therefore the switching element 14 has not been moved. Therefore, the force acting on the spring element 20 only acts for a very short period of time. If the force acts only for a short time and then suddenly decreases again or disappears, the spring element 20 will relax again without moving the switching element 14. Therefore, the short force impulse is absorbed and the valve will not open.

[0044] Figures 8 to 10 show various possibilities for arranging the fluid connection 38. Each shows a valve housing 16 in which a switching element 14 is movably mounted. In Figure 8, there is an annular fluid connection 38 between the valve housing 16 and the switching element 14. Figure 9 shows the fluid connection 38 extending through the valve housing 16, and Figure 10 shows the fluid connection extending through the switching element 14.

[0045] 11 shows another embodiment of the spring cartridge with a spring house cover 46 and a spring sleeve 42 in which the spring pin 22 is arranged. The spring 20 is shown only diagrammatically. A bushing 48, made of or manufactured from plastic, for example a thermoplastic, is arranged between the spring house 46 and the spring sleeve 42. There is also such a bushing 48 between the lower end of the spring sleeve 42 and the spring housing 40. Two bushings 48 are used in particular to reduce noise. [Explanation of symbols]

[0046] 2 Lower joint 4 Upper joint 6. Switching valve 8 Flexion Chamber 10. Extension Chamber 12 pistons 14 Switching Elements 16 Valve housing 18 External parts 20 Spring Elements 22 spring pin 24 Deflection Lever 26 Deflection axis 28 Arm 30 valve pin 32 Energizing element 34 Bottom side 36 Recess 38 Fluid Connections 40 Spring housing 42 Spring sleeve 44 Aperture 46 Spring house cover 48 Bush The following is a summary of the claims as originally filed: [1] A prosthetic knee joint comprising a lower joint, an upper joint, and a hydraulic system having at least one switching valve, - the hydraulic system comprises an extension chamber, a flexion chamber and at least one piston, the movement of which can change the volume of the extension chamber and / or the flexion chamber; the changeover valve comprises a valve housing and a changeover element movably mounted therein, the changeover element being movable between a first position and a second position within the valve housing and dividing the interior space of the valve housing into a first chamber and a second chamber; - the switching element is biased by at least one biasing element arranged on the switching valve, The prosthetic knee joint has at least one spring element that applies a reaction force to the switching element in a direction opposite to the bias, 1. A prosthetic knee joint, characterized in that at least one fluid connection is arranged between the first chamber and the second chamber in the valve housing and / or the switching element. [2] The prosthetic knee joint of [1], characterized in that at least one fluid connection extends through the switching element. [3] A prosthetic knee joint as described in [1] or [2], characterized in that at least one fluid connection extends through the valve housing. [4] A prosthetic knee joint as described in any one of [1]-3, characterized in that the at least one fluid connection extends between the valve housing and the switching element. [5] A prosthetic knee joint as described in any one of [1]-4, characterized in that the cross section of at least one fluid connection is not variable and / or the fluid connection is not closable. [6] A prosthetic knee joint as described in any one of [1]-5, characterized in that the at least one spring element is arranged so that the switching element can move from the first position to the second position by applying a force to the spring element for at least a predetermined period of time. [7] A prosthetic knee joint as described in any one of [1]-6, characterized in that the switching element cannot move from the first position to the second position when a force is applied to the spring element for a period shorter than the predetermined period.

Claims

1. A prosthetic knee joint comprising a lower joint, an upper joint, and a hydraulic system having at least one switching valve, - the hydraulic system comprises an extension chamber, a flexion chamber and at least one piston, the volume of which can be varied by the movement of the piston, the extension chamber and the flexion chamber being fluidly connected to each other by at least one connecting line; the changeover valve comprises a valve housing and a changeover element movably mounted therein, the changeover element being movable between a first position and a second position within the valve housing and dividing the interior space of the valve housing into a first chamber and a second chamber; - said switching element is biased by at least one biasing element arranged on said switching valve, the prosthetic knee joint has at least one spring element that applies a reaction force to the switching element in a direction opposite to the bias, In a prosthetic knee joint in which hydraulic fluid flows through the switching valve on its way from the extension chamber to the flexion chamber or from the flexion chamber to the extension chamber, 1. A prosthetic knee joint, characterized in that at least one fluid connection is arranged in the valve housing and / or in the switching element, connecting the first chamber and the second chamber.

2. 2. The prosthetic knee joint of claim 1, wherein at least one fluid connection extends through the switching element.

3. 3. A prosthetic knee joint according to claim 1 or claim 2, wherein at least one fluid connection extends through the valve housing.

4. A prosthetic knee joint according to any one of claims 1 to 3, characterized in that the at least one fluid connection extends between the valve housing and the switching element.

5. A prosthetic knee joint according to any one of claims 1 to 4, characterized in that the cross section of said at least one fluid connection is not variable and / or said fluid connection is not closable.

6. The prosthetic knee joint according to any one of claims 1 to 5, characterized in that the at least one spring element is arranged such that application of a force to the at least one spring element for at least a predetermined period of time causes the switching element to move from the first position to the second position.

7. The prosthetic knee joint according to any one of claims 1 to 6, characterized in that the switching element cannot be moved from the first position to the second position by applying a force to the at least one spring element for less than a predetermined period of time.

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