Prosthetic joint

Abstract

The invention relates to a prosthetic joint comprising an upper part (10) and a lower part (20), which are pivotably fastened to one another about a pivot axis (30), and a drive (40), which is coupled to the upper part and the lower part and at least influences a pivoting movement of the upper part relative to the lower part, wherein the drive comprises a motor (42) and a transmission (44) coupled to the motor, wherein the transmission is designed as a continuously variable transmission having two pulley sets (5, 6) with pulleys (52, 54, 56, 62, 64, 66), which are coupled to one another via at least one drive belt (70, 72).

Description

[0001] ' U > - 1 ' ^ M i

[0002]

[0003] inte ! I ectua I profitty Otto Bock Healthcare Products GmbH Lawyer's file:

[0004] Brehmstraße 16 0108-2093 PCT-1 1110 Vienna

[0005] Austria Date:

[0006] April 8, 2026

[0007] prosthetic joint

[0008] The invention relates to a prosthetic knee joint with an upper part and a lower part which are pivotably attached to each other about a pivot axis, with a drive which is coupled to the upper part and the lower part and at least influences a pivoting between the upper part relative to the lower part, wherein the drive has a motor and a gearbox coupled to the motor.

[0009] Prostheses replace a missing or missing limb and serve to provide functionality that approximates that of the natural limb as closely as possible. Furthermore, prostheses aim to provide the prosthesis user with the most natural appearance possible. If the limb to be replaced includes a joint, the corresponding prosthetic joint has an upper and a lower part that are articulated together. The prosthetic joint connects the upper part to the lower part, which may include further prosthetic components, such as a socket to accommodate a stump or a replica of a distal limb. The prosthetic joint can be designed, for example, as a prosthetic knee joint or a prosthetic ankle joint. In a prosthetic knee joint configuration, a lower leg tube or a prosthetic foot may be detachably attached to the lower part.For example, a prosthetic socket for receiving a thigh stump or lower leg stump can be attached to the upper part.

[0010] To influence the pivotability of the upper and lower parts, actuators are arranged between them. These actuators can be purely passive, damping any pivoting movement. This is achieved using adjustable resistance devices, allowing for a customized resistance profile. Examples of such devices include brakes, hydraulic dampers, pneumatic dampers, and magnetorheological dampers. Passive actuators operate purely dissipatively. In this case, energy is extracted from the movement of the upper part relative to the lower part, potentially generating very high torques or forces. In an open state, for example, when no valves are closed or throttles are activated in a hydraulic damper, only very little resistance is encountered during pivoting.With passive actuators, it is not possible to introduce energy into the movement to support the movement, to actively counteract the movement, or to initiate a change from a state of rest.

[0011] To provide assistance, so-called semi-active actuators are used, which incorporate an energy storage device. Mechanical energy storage devices can be located in the upper or lower part, allowing movement assistance to be achieved by releasing energy stored in the mechanical energy storage device. Examples of mechanical energy storage devices include springs, elastomer elements, and pneumatic and hydraulic energy storage devices.

[0012] Prostheses with motorized drives are known from the prior art. In these drives, movement is initiated, assisted, or decelerated by activating, deactivating, or modulating the drive. Stored energy, such as electrical energy from a battery or accumulator, is converted within the drive for this purpose. The motorized drives serve to pivot the components relative to each other from a rest position or to influence the movement between the components, for example, to assist or decelerate a pivoting movement. Motorized drives can also be operated in generator mode to decelerate a movement; the resulting electrical energy can be stored. Active drives can also be coupled with mechanical energy storage devices.

[0013] The WO 2011 / 080556 A2 concerns a lower extremity prosthesis comprising a foot component, a lower leg component, and an ankle joint, as well as, optionally, a prosthetic knee joint. The ankle joint is driven by a motor, and a microprocessor controls the joint's behavior to achieve the most natural gait possible.

[0014] US patent 2006 / 0249315 A1 describes, among other things, a prosthetic device comprising a prosthetic knee joint and a prosthetic ankle joint, as well as an actuation system that operates across the joints. A knee joint component is coupled to a motor and a parallel adjustable damper.

[0015] The motors in active prostheses are subject to diverse, sometimes conflicting, requirements. On the one hand, they should be as light and small as possible; on the other hand, they should be capable of both rapid adjustment and, with slow adjustment, the generation of high forces and torques, for example, to enable or assist stair climbing or standing up. Furthermore, there are numerous different usage scenarios with varying movement patterns that require different support or influence. For instance, when walking on level ground, high knee angular velocities in the flexion direction are needed during the initiation of the swing phase in the knee joint, without requiring the application of large forces. In contrast, comparatively high torques with low knee angular velocities in the extension direction are required during the stance phase extension of walking on level ground.To generate high torque while using the smallest possible motors, a gearbox is paired with the motor so that the drive train, consisting of energy storage, motor, and gearbox, meets the requirements as effectively as possible. The design of the drive train is not optimized for one requirement over another, but rather to achieve the best possible compromise for all applications.

[0016] From WO 2021 / 113847 A1, a prosthetic knee joint with at least one actuating component for moving the knee joint is known. A multitude of sensors are arranged along the at least one actuating component and send signals to a control system, which includes an active control system and a passive control system. The active control system controls a drive, and the passive control system controls a passive resistance device. A variable transmission mechanism allows for a change in the mechanical force transmission ratio to optimize the mechanical force transmission profile for active and passive tasks. This is achieved by changing the position of a push-pull rod on a lever. Furthermore, a CVT (Continuously Variable Transmission) is described for adjusting the mechanical transmission ratio.By using the CVT, the transmission ratio can be adjusted with regard to the required speed and torque for each task of the prosthetic knee joint.

[0017] The object of the present invention is to provide a prosthetic joint that enables simple, reliable and easy adaptation of the drive train to the respective requirements.

[0018] This problem is solved by a prosthetic joint with the features of the main claim. Advantageous embodiments and further developments of the invention are disclosed in the description, the figures, and the dependent claims.

[0019] The prosthetic joint, comprising an upper part and a lower part which are pivotably mounted to each other about a pivot axis, with a drive coupled to the upper part and the lower part and which at least influences a pivoting between the upper part relative to the lower part, wherein the drive comprises a motor and a gearbox coupled to the motor, is characterized in that the gearbox is designed as a continuously variable gearbox with two sets of pulleys which are coupled to each other via at least one drive belt.The prosthetic joint, comprising the upper and lower parts and the drive mechanism for pivoting the upper part relative to the lower part, includes a continuously variable transmission in addition to the motor. This transmission has at least two pulleys per pulley set, with one drive-side pulley set coupled to the motor and the other, driven-side pulley set to the joint component being driven. When the motor is driven in one direction or the other, forces are transmitted from the drive-side pulley set to the driven-side pulley set via at least one drive belt. The pulley sets include pulleys through which forces and torques are transmitted from the drive belt to the respective component of the prosthetic knee joint. Drive belts offer the advantages of being lightweight, quiet, and allowing for a high degree of flexibility in terms of mounting position.The pulley sets can be positioned almost anywhere, allowing for a great deal of design flexibility regarding the arrangement of both the drive and the gearbox. Furthermore, no tensioning rollers are required to maintain the necessary belt tension.

[0020] In one embodiment, the transmission changes the gear ratio depending on the load. With a higher load, the gear ratio increases, while the effective diameter, and thus the rotational speed of the belt-driven pulley set, decreases at the same engine speed. This makes it possible to generate higher torques through the forces applied to the driven pulley set. As a result, greater pivoting resistance can be overcome, and the upper part can pivot relative to the lower part at a lower rotational speed and angular velocity compared to a low load.If the rotary motion encounters high resistance, such as high extension resistance when standing up or climbing stairs, a high drive torque is applied at a low adjustment speed. Conversely, with low resistance, such as during momentum phase extension, a high angular velocity is achieved during adjustment at a low gear ratio, without requiring a change in motor speed. The motor can thus always operate within its optimal operating range or point, while the gearbox generates the appropriate rotational speed for the belt-driven pulley set.

[0021] In one embodiment, the pulley sets are mounted rigidly to the shafts, with at least one pulley of a pulley set being axially displaceable. This makes it possible to change the distance between the pulleys of a pulley set, which, depending on the design of the pulleys and / or belt(s), results in a changing transmission ratio. For example, if the two pulleys of the drive-side pulley set driven by the motor are moved axially towards each other, the belt between the two pulleys is moved outwards to a larger radius, which, conversely, pushes the pulleys of the driven-side pulley pair apart due to the constant length of the belt.As a result, the belt runs on a smaller radius on the output side compared to pulleys that are closer together, thus changing the transmission ratio.

[0022] Advantageously, the pulleys are elastically preloaded in the axial direction so that they each assume a preferred position relative to one another. The pulleys are elastically preloaded on a first axis in the direction towards each other and on a second axis in the direction away from each other. In particular, on the drive side, they are elastically preloaded on the first axis in the direction towards each other, and on the driven side, they are elastically preloaded on the second axis in the direction away from each other. In an alternative embodiment, the driven-side pulleys are preloaded in the direction towards each other, while the drive-side pulleys are elastically preloaded in the direction away from each other.Output pulleys are those pulleys in a pulley set that are driven by the drive belt(s), while input pulleys are those driven by the motor, in particular directly by the motor. Preloading the output pulleys away from each other ensures a low transmission ratio in the initial state; that is, the ratio of the effective diameter of the output pulleys to the effective diameter of the input pulleys is small. This is because the belt(s) on the input pulley set rotate over a small effective diameter due to the initially separated pulleys, while on the input side, the compressed pulleys result in a large effective diameter.When an increased resistance torque is applied to an adjustment, the driven pulleys are moved towards each other, thereby increasing the effective diameter, while the driven pulleys are moved away from each other, thereby decreasing the effective diameter on the driven side. This increases the transmission ratio between the pulley sets.

[0023] A further development provides that a pulley set comprises two outer pulleys and at least one intermediate pulley, allowing two belts to rotate simultaneously on the intermediate pulley within the pulley set, thereby significantly increasing the transmittable force. The distance between the intermediate pulley and the two outer pulleys is reduced by only half the distance in each case. With additional intermediate pulleys and belts, the axial displacement is further reduced if the intermediate pulley(s) are axially displaceable and, in particular, rotationally fixed to the shaft. Advantageously, in an embodiment with two outer pulleys and one intermediate pulley, one outer pulley is axially fixed to a shaft, while both the intermediate pulley and the other outer pulley are axially displaceable.By axially displacing the axially movable outer disk, the axially movable intermediate disk is simultaneously displaced in order to change the transmission ratio.

[0024] In one embodiment, a pulley is connected on the output side to a helical-toothed output gear, which in turn meshes with a drive gear. This makes it possible to easily adjust the pulleys relative to each other in a load-dependent manner, without requiring increased control engineering complexity or a separate drive for adjusting the distance between the pulleys. Advantageously, the pitch has an orientation that, in a direction of rotation that results in increased torque requirements, exerts a force component on the pulley, loading it towards the other pulley and thus reducing the distance between the two pulleys.This increases the effective diameter, so that with increased resistance to the corresponding pivoting movement, the transmission ratio is simultaneously changed to provide a lower pivoting speed with a higher transmitted torque. An example of this is an extension movement during the standing phase, for example, when standing up or climbing stairs. In another embodiment, this concept is applied to a flexion movement, so that the gradient is reversed and, in a direction of rotation that leads to a flexion movement, increased resistance is provided and the pulleys are adjusted accordingly relative to each other. An example of this is bending an elbow joint to lift objects.

[0025] In a further development, a stop is assigned to the axially displaceable pulley. In one embodiment, this stop is adjustable to set the adjustment movement and thus the maximum or minimum achievable effective diameter of the pulleys. Furthermore, the adjustable stop allows for adjustment of the spring preload acting on the pulleys, and consequently, the belt tension.

[0026] The prosthetic joint is designed as a prosthetic knee joint. A further gearbox, for example a planetary gearbox, can be connected upstream and / or downstream of the gearbox to allow adjustment of the input and / or output speeds and / or directions of rotation to suit the desired application.

[0027] In one embodiment, the pulleys are designed to widen radially inwards, so that the space between two pulleys tapers radially inwards, for example by means of belt contact surfaces oriented conically to each other, on which the belts run or between which the belts are clamped. The belt contact surfaces converge radially inwards, either in a straight line or with curved surface contours.

[0028] The drive belts are designed to be flexible and inelastic in order to transmit tensile forces, thus enabling the transfer of forces from the drive-side pulley set to the driven-side pulley set. The belts are designed, in particular, to prevent or minimize elongation, for example, through embedded reinforcements made of steel wires or high-strength fibers such as aramid fibers. In one embodiment, the prosthetic joint is coupled to a passive resistance device, such as a hydraulic damper, in addition to the motor. This resistance device is positioned between the upper and lower parts of the joint. The passive resistance device can be coupled to a mechanical energy storage device and, via a control unit, provide situationally adapted resistance to pivoting and / or support for a pivoting movement based on sensor data.

[0029] In a further development, the drive belt is positioned laterally next to the upper and lower parts under a cover, thus eliminating or at least reducing the risk of it becoming trapped between the drive belt and the pulleys. This lateral arrangement makes it possible to retrofit a prosthetic joint with a motorized drive and a gear arrangement as described above, provided it already has a passive or semi-passive resistance device with an energy storage unit.

[0030] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. The same reference numerals denote identical components. The figures show:

[0031] Figure 1 - a cross-sectional view through a prosthetic knee joint;

[0032] Figure 2 - a detailed view of the gear arrangement in cross-sectional view;

[0033] Figure 3 - a perspective oblique view of a prosthetic knee joint;

[0034] Figure 4 - a detailed sectional view of the output-side pulley set;

[0035] Figure 5 - a schematic representation of the pulley arrangement; as well as

[0036] Figure 6 - Sectional views of various pulleys.

[0037] Figure 1 shows a sectional view of a prosthetic joint in the form of a prosthetic knee joint with an upper part 10 and a lower part 20, which are pivotably mounted relative to each other and against each other about a pivot axis 30. A device for attaching a prosthetic stem or a femoral tube in the form of a pyramid adapter is arranged on the upper part 10. Receptacles for further prosthetic components are arranged or formed on the lower part 20, for example, for a passive resistance device, e.g., a hydraulic damper, a control unit, and mechanical components such as a lower leg tube for attaching a prosthetic foot to the lower part 20.

[0038] The prosthetic joint also has a drive 40, which includes an electric motor 42. In the illustrated embodiment, the electric motor 42 is mounted on the lower part 20 and has a shaft 61 that rotates in one direction or the other depending on the direction of rotation of the motor 42. A pulley assembly 6 is mounted on the shaft 61, which in the illustrated embodiment has two pulleys 62, 66 that are rigidly connected to the shaft 61. The pulley assembly 6 is located laterally next to the lower part 20 and has an axially displaceable pulley 62, which is mounted on the shaft 61. The second pulley 66 is either formed integrally with the shaft 61 or rigidly attached to it. The axially displaceable, inner pulley 62 is axially pre-tensioned in the direction of the axially rigid pulley 66.For this purpose, at least one spring element is arranged between a shaft shoulder and the axially displaceable pulley 62, which will be explained in more detail later.

[0039] The pulleys 62, 66 have belt contact surfaces on their facing surfaces, which will be explained in more detail later. The pulleys 62, 66 become radially narrower from the inside out, resulting in an outwardly increasing gap between the two pulleys 62, 66, which widens conically in cross-section. A drive belt 70 is guided between the two pulleys 62, 66, via which the rotary motions generated by the motor 42 are transmitted to a second pulley set 5, which is coupled to the upper part 10. The second pulley set 5 also consists of two pulleys 52, 56, wherein, in the illustrated embodiment, the axially inner pulley 56 is fixed in the axial direction and the axially outer pulley 52 is axially displaceable along the axis of rotation of the pulleys 52, 56. Both pulleys 52, 56 are mounted on the shaft 51.The drive belt 70 is guided between the two pulleys 52, 56. The drive belt 70 has a substantially triangular cross-section and its side surfaces rest against the belt contact surfaces, which are inclined obliquely outwards in opposite axial directions. In the illustrated embodiment, the two pulleys 52, 56 are moved as close together as possible, so that the drive belt 70 runs on the output-side pulley set 5 at its largest effective diameter. The two pulleys 52, 56 are biased away from each other by a spring element, which will be described in more detail later, and are moved towards each other by an adjustment mechanism that operates depending on the load.

[0040] Because the circulating drive belt 70 is essentially constant in length when the pulley sets 5, 6 are moved without external resistance forces, the output-side pulleys 52, 56 are moved to their maximum extent apart, and conversely, the input-side pulleys 62, 66 of the input-side pulley set 6 are moved to their maximum extent towards each other. This results in a small transmission ratio between the effective pulley diameter on which the drive belt 70 runs in the output-side pulley set 5 and the effective pulley diameter on which the drive belt 70 runs on the input-side pulley set 6.As soon as an increased load against pivoting occurs, an axial displacement of the axially movable pulley 52 towards the pulley 56 is caused, which, due to the conical or outwardly widening design of the inner surfaces of the pulleys 52, 56, causes the drive belt 70 to move outwards and increases the effective pulley diameter. Correspondingly, the effective pulley diameter of the driven-side pulleys 62, 66 decreases until it reaches the state shown in Figure 1, thus increasing the transmission ratio between the driven-side pulley set 5 and the drive-side pulley set 6.

[0041] To enable load-dependent displacement of the pulleys 52, 56, and thus of the pulleys 62, 66, against the axial preload force, the shaft 51 is coupled to a helical gear on the output side. This gear is formed on a shaft and coupled to a drive gear, which in turn drives a downstream gearbox 100, e.g., in the form of a planetary gearbox. The upper part 10 is pivoted via the gearbox in accordance with the direction of rotation of the gearbox 100. The helical gear 80 exerts an axial force component on the shaft of the helical gear 80 and thus on the shaft 51, on which the axially displaceable pulley 52 is mounted.The orientation of the helical gear 80 is chosen such that, in the event of increased resistance to pivoting in the selected direction of movement, for example, increased resistance in the extension direction, the pulleys 52, 56 of the output-side pulley set 5 are shifted towards each other, thus increasing the effective pulley diameter. This slows the pivoting speed of the upper part 10 relative to the lower part. Simultaneously, due to the increased effective pulley diameter, higher torques are transmitted to the shaft 51. Consequently, greater forces and torques are applied via the output-side gear 80 and the drive gear 81 to adjust the upper part 10 relative to the lower part 20. This allows for load-dependent adjustment of the gear ratio without requiring a control system to change the distance between the pulley pairs.The selected method of preloading the pulleys 52, 56, 62, 66 towards or away from each other initially establishes a low gear ratio, allowing for a high adjustment speed. As the resistance increases, the adjustment speed decreases due to the changing gear ratios, thereby providing a greater force for adjustment. A stop 90, advantageously adjustable, is provided to limit the maximum adjustment travel. The stop 90 determines how far the pulleys 52, 56 can be moved towards each other, thus setting the maximum effective pulley diameter of the output-side pulley set 5. A stop is also provided in the opposite direction, so that the maximum distance between the pulleys 52, 56 is fixed and adjustable.

[0042] Figure 2 shows a detailed, enlarged view of the continuously variable transmission 44 without the motor. Here, too, the output-side pulleys 52 and 56 are in a state of maximum convergence, while the input-side pulleys 62 and 66 are maximally separated. Figure 2 shows the spring elements 110, which are arranged between a bearing surface and the axially displaceable pulley 62. These spring elements bias the pulley 62, which is mounted on the hollow shaft 61 so as to be rotationally and axially movable, towards the outer, rigid pulley 66. The spring element 110 is designed, for example, as a disc spring, a pair of disc springs, or another type of spring element. On the output-side pulley assembly 5, the spring element 110 is positioned between the pulleys 52 and 56 and pushes them apart. In the illustrated state, the spring elements 110 are maximally compressed.The gearbox 44 with the pulleys 62, 66, 52, 56 has belt contact surfaces 520, 560, 620, 660, as described above, which face each other and on which the drive belt 70 with its substantially triangular cross-section rests. The belt contact surfaces 520, 560, 620, 660 diverge radially outwards from each other, so that in the illustrated embodiment with substantially straight belt contact surfaces 520, 560, 620, 660, a conical gap is formed in which the drive belt 70 is guided. At the outer end of the shaft 51, which is coupled to the axially displaceable pulley 52, the helical gearing 80 can be seen, which causes the axial movement indicated by the double arrow.As soon as the axial force component, which is eliminated due to a load opposing a pivoting movement through the helical gearing 80, ceases, the spring element 110 increases the distance between the output-side pulleys 52, 56 and reduces the transmission ratio accordingly. Correspondingly to the extent that the output-side pulleys 52, 56 move away from each other when the load is removed, the input-side pulleys 62, 66 move towards each other due to the externally acting compressive force of the spring element 110.

[0043] Figure 3 shows a perspective view of the prosthetic joint as a prosthetic knee joint with the upper part 10 and the lower part 20. The drive-side pulley set 6 protrudes laterally from a housing-like lower part 20 and drives the drive belt 70, which in turn runs on the output-side pulley set 5. The output-side pulley set 5 then moves the upper part 10 either directly or via a further gear reduction. The entire continuously variable transmission 44 is located laterally next to the prosthetic joint and is protected by a cover cap during operation.

[0044] Figure 4 shows a variant of the output-side pulley arrangement. The basic structure is as explained above; however, in the illustrated embodiment, two drive belts 70, 72 are provided, which are guided parallel to each other between the pulleys 52, 54, 56.

[0045] In addition to the outer pulleys 52, 56, which are constructed and arranged as described above, an intermediate pulley 54 is arranged between the two outer pulleys 52, 56. This intermediate pulley has two opposing belt contact surfaces 540, which are opposite the respective belt contact surfaces 560, 520 of the outer pulleys 56, 52. Corresponding spring elements 110 are arranged between the outer pulleys 52, 56 and the intermediate pulley 54. These spring elements push the pulleys 52, 54, 56 apart when unloaded. If an axial force is applied under increased load against an adjustment via the helical gear 80, displacing the outer pulley 52 towards the inner pulley 56, the spring elements 110 are compressed, and the outer pulley 52 is displaced under the compression of the spring elements 110.The intermediate pulley 54 is mounted rigidly to the torsion and axially movable on the axially movable shaft 51 and, with the same spring force of the spring element 110, moves by half the displacement of the outer pulley 52 towards the inner pulley 56. The drive belts 72, 70 move outwards according to the displacement and the inclination of the belt contact surfaces. If the external force generated by the axial force component of the helical gearing 80 is eliminated or reduced by decreasing the resistance to pivoting, the axially movable pulleys 52, 54 move outwards or to the right accordingly. The stop 90 limits the axial displacement in the direction of the axially fixed pulley 56. The stop 90 can be designed as a stop nut that is adjustable on the shaft with the helical gearing 80.

[0046] Figure 5 shows a schematic representation of the embodiment shown in Figure 4. The spring elements 110 act between the pulleys 52, 54, and 56, pushing them outwards. If an axial force 11 is applied externally to the axially displaceable pulley 52, it is displaced towards the axially rigid pulley 56. Correspondingly, the axially displaceable intermediate pulley 54 is also moved towards the pulley 56, albeit by a shorter displacement, which is indicated by the slightly shorter double arrow compared to the outer pulley 52. ​​When the force F is removed, a corresponding return movement is initiated by the spring elements 110.

[0047] Figure 6 shows different shapes of belt contact surfaces 560 of a pulley 56. Instead of a straight contact surface 560 inclined to a plane perpendicular to the axis of rotation, this surface is shown rounded in Figure 6, so that different transmission ratios can be set towards or away from each other via the adjustment range of the pulleys.

Claims

* nin te il ect ua ä p rope r ty Otto Bock Healthcare Products GmbH Lawyer's file: Brehmstraße 16 0108-2093 PCT-1 1110 Vienna Austria Date: April 8, 2026 Patent claims 1. Prosthetic joint with an upper part (10) and a lower part (20) which are pivotably attached to each other about a pivot axis (30), and with a drive (40) which is coupled to the upper part (10) and the lower part (20) and at least influences a pivoting between the upper part (10) relative to the lower part (20), wherein the drive (40) comprises a motor (42) and a transmission (44) coupled to the motor (42), characterized in that the transmission (44) is designed as a continuously variable transmission with two sets of pulleys (5, 6) with pulleys (52, 54, 56, 62, 64, 66) which are coupled to each other via at least one drive belt (70, 72).

2. Prosthetic joint according to claim 1, characterized in that the transmission (44) is designed to change the transmission ratio depending on the load and to increase the transmission ratio in the case of a higher load.

3. Prosthetic joint according to claim 1 or 2, characterized in that the pulley sets (5, 6) are arranged torsionally rigidly on shafts (51 , 61 ) and at least one pulley (52, 54; 62, 64) of a pulley set (5, 6) is mounted axially displaceably.

4. Prosthetic joint according to one of the preceding claims, characterized in that the pulleys (52, 54, 56, 62, 64, 66) are elastically prestressed in the axial direction.

5. Prosthetic joint according to one of the preceding claims, characterized in that the pulleys (62, 64, 66) are elastically prestressed towards each other on a first axis and the pulleys (52, 54, 56) are elastically prestressed away from each other on a second axis.

6. Prosthetic joint according to one of the preceding claims, characterized in that a pulley set (5, 6) comprises two outer pulleys (52, 56, 62, 66) and at least one intermediate pulley (54, 64).

7. Prosthetic joint according to one of the preceding claims, characterized in that a pulley (56) is connected on the output side to a helical output gear (80) which meshes with a drive gear (81).

8. Prosthetic joint according to one of the preceding claims, characterized in that a stop (90) is assigned to the axially displaceable pulley (56, 66).

9. Prosthetic joint according to one of the preceding claims, characterized in that the stop (90) is adjustable.

10. Prosthetic joint according to one of the preceding claims, characterized in that the prosthetic joint is designed as a prosthetic knee joint.

11. Prosthetic joint according to one of the preceding claims, characterized in that a transmission (100) is connected upstream and / or downstream of the transmission (44).

12. Prosthetic joint according to one of the preceding claims, characterized in that the pulleys (52, 54, 56, 62, 64, 66) have belt contact surfaces (520, 540, 560, 620, 640, 660) that converge axially inwards and are oriented towards each other.

13. Prosthetic joint according to one of the preceding claims, characterized in that the drive belt (70, 72) is flexible and inelastic.

14. Prosthetic joint according to one of the preceding claims, characterized in that the drive (40) is coupled to a passive resistance device arranged between the upper part (10) and the lower part (20).

15. Prosthetic joint according to one of the preceding claims, characterized in that the drive belt (70, 72) is arranged laterally next to the upper part (10) and lower part (20) under a cover.

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