Abstract
An orthopedic joint device is provided, the device having an upper part, a lower part pivotably mounted thereon and an actuator fastened to the upper part and the lower part and having a drive shaft coupled to an output element via a force transmission device, the force transmission device having a load transmission element that can by adjusted depending on the load.
Claims
1. An orthopedic joint device having an upper part, a lower part pivotably disposed thereon, and an actuator which is fastened to the upper part and lower part and which comprises a driveshaft coupled to a driven element by way of a force transmission device, wherein the force transmission device comprises a load-dependently adjustable force transmission element.
2. The orthopedic joint device as claimed in claim 1, wherein the force transmission element is mounted elastically.
3. The orthopedic joint device as claimed in claim 1, wherein the actuator comprises a hydraulic pump having a housing and at least one displacement element as driven element, the latter being coupled to the driveshaft and being mounted in the housing in a pump chamber, with the force transmission element being disposed between the at least one displacement element and the driveshaft and bringing about a load-dependent change in the stroke of the at least one displacement element.
4. The orthopedic joint device as claimed in claim 3, wherein the displacement element is in the form of a piston of an axial piston pump and the force transmission element is in the form of a swash plate, or in that the displacement element is in the form of a piston of a radial piston pump and the force transmission element is in the form of a cam, or in that the displacement element is in the form of a rotor of a sliding vane rotary pump and the force transmission element is in the form of a cam.
5. The orthopedic joint device as claimed in claim 3, wherein at least one spring element, which is compressed in the case of an increasing load, is disposed between the driveshaft and the displacement element.
6. The orthopedic joint device as claimed in claim 5, wherein the spring element is in the form of an elastomeric spring, coil spring, spiral coil spring, Belleville spring, Belleville spring assembly or leaf spring.
7. The orthopedic joint device as claimed in claim 1, wherein the force transmission device is in the form of a continuously variable, adjustable transmission.
8. The orthopedic joint device as claimed in claim 7, wherein the force transmission element is in the form of a conical pulley which is formed as a driven element on the driveshaft or a driven shaft so as to be displaceable along the latter's longitudinal extent.
9. The orthopedic joint device as claimed in claim 8, wherein the conical pulley is coupled to a spring element which is prestressed against a displacement of the force transmission element.
10. The orthopedic joint device as claimed in claim 5, wherein the spring element has a linear, degressive or progressive spring characteristic.
11. An orthopedic joint device comprising: an upper part; a lower part pivotably disposed on the upper part; and an actuator fastened to the upper part and lower part, the actuator further comprising a hydraulic pump and a driveshaft, the driveshaft being coupled to a driven element by a force transmission device; wherein the force transmission device comprises a load-dependently adjustable and elastically-mounted force transmission element.
12. The orthopedic joint device of claim 11, wherein the hydraulic pump has a housing and at least one driven element coupled to the driveshaft and mounted in the housing in a pump chamber.
13. The orthopedic joint device of claim 12, wherein the force transmission element is disposed between the driven element in the form of a displacement element and the driveshaft to cause a load-dependent change in the stroke of the displacement element.
14. The orthopedic joint device of claim 13, wherein the displacement element is a piston of an axial piston pump and the force transmission element is a swash plate.
15. The orthopedic joint device of claim 13, wherein the displacement element is a piston of a radial piston pump and the force transmission element is a cam.
16. The orthopedic joint device of claim 13, wherein the displacement element is a rotor of a sliding vane rotary pump and the force transmission element is a cam.
17. The orthopedic joint device of claim 13, wherein at least one spring element is disposed between the driveshaft and the displacement element.
18. The orthopedic joint device as claimed in claim 17, wherein the spring element is an elastomeric spring, coil spring, spiral coil spring, Belleville spring, Belleville spring assembly or leaf spring.
19. An orthopedic joint device comprising: an upper part; a lower part pivotably disposed on the upper part; and an actuator fastened to the upper part and lower part, the actuator further comprising a hydraulic pump and a driveshaft, the driveshaft being coupled to a driven element by a continuously variable, adjustable transmission; wherein the force transmission device comprises a load-dependently adjustable and elastically-mounted conical pulley.
20. The orthopedic joint device of claim 19, wherein the conical pulley is coupled to a spring element which is prestressed against a displacement of the force transmission element.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Exemplary embodiments of the invention are explained in more detail below on the basis of the attached drawings, in which:
[0021] FIG. 1 shows a schematic representation of a joint device;
[0022] FIG. 2 shows a schematic cross-sectional view of a radial piston pump according to the prior art;
[0023] FIG. 3 shows a schematic longitudinal section representation of an axial piston pump according to the prior art;
[0024] FIG. 4 shows a schematic, perspective representation of a load-dependently adjustable cam;
[0025] FIG. 5 shows a schematic longitudinal sectional representation of a load-dependently adjustable swash plate;
[0026] FIG. 6 shows a comparison of characteristics of a radial piston pump with a fixed cam and a load-dependently variable cam;
[0027] FIG. 7 shows a schematic representation of a continuously variable transmission; and
[0028] FIG. 8 shows a detailed representation of a load-dependent adjustment mechanism.
DETAILED DESCRIPTION
[0029] FIG. 1 shows a schematic representation of an orthopedic joint device in the form of a prosthesis of a lower extremity, having an upper part 10 and a lower part 20 which are mounted on one another in articulated fashion about a pivot axis 12. In the exemplary embodiment illustrated, the upper part 10 has a prosthetic shaft which serves to receive an above-knee stump. Other orthopedic devices, such as upper extremity prostheses and upper or lower extremity orthoses should likewise be considered to be orthopedic joint devices if the components thereof are mounted on one another in articulated fashion. An actuator 15 is disposed between the upper part 10 and the lower part 20. In the illustrated exemplary embodiment, the actuator 15 is in the form of a linear-action actuator 15 and comprises a drive 14 in the form of an electric motor for the purposes of bringing about an adjustment in the position of the upper part 10 relative to the lower part 20. By way of example, the actuator 15 can be in the form of a hydraulic-action actuator and may comprise a pump that is driven by the drive 14. A hydraulic fluid is pumped via the pump into a pump chamber or into a chamber closed off by a piston. The piston is coupled to a piston rod, which is mounted on the upper part 10 or the lower part 20. By appropriately pumping the hydraulic fluid into the pump chamber, the piston rod is moved in one direction or the other, and the upper part 10 is pivoted relative to the lower part 20. As a result, an extension movement or a flexion movement of the joint device can be implemented, braked or assisted. As an alternative to a hydraulic embodiment of the actuator 15, the latter may also have a mechanical form such that a spindle, for example, is driven by way of the drive 14. The spindle may then enter or leave an actuator housing in order to bring about an extension or flexion of the orthopedic joint device.
[0030] One option for providing a force that is to be applied to the upper part 10 or lower part 20 so that a torque about the pivot axis 12 arises consists in the provision of hydraulic fluid via a hydraulic pump. An example of a radial piston pump is depicted in FIG. 2. Four pistons 3 as displacement elements are disposed in a housing 2. The pistons 3 are longitudinally displaceably mounted in cylinder bores within the housing 2 and each form a pump chamber 5, the volume of which is changed when the displacement elements 3 are displaced accordingly. The displacement is caused by a force transmission element 6, which is a cam in the exemplary embodiment of a radial piston pump. The cam 6 revolves in a bore within the housing and causes a radially outward displacement of the pistons when the cam 6 approaches the extent of the bore within the housing. When the cam moves away, the pistons 3 are moved back and the pump chambers 5 become larger. When there is an increase in the pump volume, hydraulic fluid is sucked in, and this is accordingly ejected in the case of a reduction.
[0031] An alternative solution for a hydraulic pump is schematically depicted in FIG. 3. FIG. 3 shows the schematic representation of an axial piston pump with a force transmission element 6 mounted on a driveshaft 4. The displacement element 6 is in the form of a swash plate and is supported on two displacement elements 3, or more displacement elements 3, within the pump housing 2. Depending on the position of the swash plate 6, the piston 3 is pushed into the housing 2 in order to reduce the size of the pump chamber 5, or facilitates a reverse movement out of the housing 2 in order to increase the size of the pump chamber 5.
[0032] In both pump types, the hydraulic fluid is conveyed as a result of the oscillations of the pistons 3 as displacement elements. The diameter and the stroke of the piston 3 or of the pistons 3 together with the rotational speed determine the volumetric flow rate. The stroke is dependent on the eccentricity of the cam as force transmission element 6 in the case of radial piston pumps and dependent on the inclination of the swash plate as force transmission element 6 in the case of axial piston pumps.
[0033] FIG. 4 shows a partial illustration of a radial piston pump. The basic design corresponds to that of FIG. 2, with the embodiment of the force transmission element 6 in the form of the cam 6 having been modified in relation to the structure in FIG. 2. According to FIG. 4, the force transmission element is in the form of a double cam which has a shaft cam 61, with the cam 6 being able to rotate in relation thereto. The cam 6 is mounted on the driveshaft 4 so as to be rotatable around the shaft cam 61, with the cam 6 as force transmission element being held in an initial position by way of a spring 7. By way of example, if the driveshaft 4 is driven by an electric motor 14, the cam 6 would completely abut against the wall of the bore within the housing 2 and maximally displace the pistons 3 radially to the outside in the case of a lack of counter pressure. However, if the counter pressure in the respective pump chambers 5 increases, there simultaneously is an increase in the resistance to a displacement as a result of the cam 6. This leads to the cam 6 being rotated around the shaft cam 61 counter to the spring force by the spring element 7. As a result, the cam 6 is rotated such that it has reduced eccentricity, as a result of which the volumetric flow rate provided by the displacement element 3 is reduced for an unchanged rotational speed. The higher the resistance or the counter pressure in the hydraulic system, the higher the resistance to a displacement of the pistons 3, and so there is a greater reduction in the eccentricity. Consequently, a load-dependent change in the conveying behavior sets in automatically. In the case of the radial piston pump and the cam arrangement according to FIG. 4, the load-dependent adjustment is implemented by the rotation of the cam 6 in relation to the shaft cam 61 and the changing, effective summated eccentricity which arises on the basis of the angular position of the two cams in relation to one another. The relative angle increases with increasing pressure, resulting in a reduction in the summated eccentricity and a drop in volumetric flow rate.
[0034] FIG. 5 shows the load-dependent adjustment, and hence load-dependent adaptation, of the conveyance when maintaining the work point of the electric motor as a result of a resilient mount of the swash plate 6 as force transmission element. The swash plate 6 is mounted by way of a plurality of spring elements 7 on a carrier 8 which is mounted at an angle to the axis of rotation of the driveshaft 4. In the illustrated initial position, the carrier 8 and the swash plate 6 are aligned substantially parallel to one another. If the pressure on the piston 3 increases, for example as a result of an increased hydraulic resistance in the pump chamber (not depicted here), the corresponding spring element 7 is compressed and so the swash plate 6 is displaced in the direction of the carrier 8 that is rigidly fastened to the driveshaft 4. Expressed differently, the piston 3 is displaced with a reduced stroke on account of the resilience of the swash plate 6, leading to a drop in the volumetric flow rate. The higher the resistance, the greater the displacement of the swash plate 6 and the greater the compression of the spring elements 7. In this case, the characteristic of the load-dependent change in the flow rate can be adjusted by changing the elasticities in the spring elements 7. The spring elements 7 can be designed with different levels of stiffness or resilience, they may have a linear, degressive or progressive spring characteristic, or they may also be adjustable in order to retrospectively facilitate an adjustment to the respectively desired behavior of the hydraulic pump.
[0035] FIG. 6 plots the behavior of a radial piston pump, once with a fixed eccentricity, denoted by the index 1, and once with a load-dependent, variable eccentricity, represented with the index 2. In this case, the torsional spring 7 was designed such that an increase of the pressure work range to 145% is obtained. What can be gathered from the diagrams is that the admissible maximum current I.sub.2/I.sub.1max is only reached at a higher pressure ratio P/P.sub.1Max as a result of the work range extension. This results in a steeper drop in the volumetric flow rate Q.sub.2/Q.sub.1Max as a function of pressure, as desired for the application. The efficiency η.sub.2 remains stable over the entire work range.
[0036] FIG. 7 shows a further variant of the invention, in which the actuator 15 is equipped with a drive 14 and a force transmission device 16 in the form of a continuously variable transmission. An electric motor 14 drives a driveshaft 4, on which two conical pulleys 46 are arranged. The two conical pulleys 46 are mounted in torsionally rigid fashion and mounted so as to be displaceable along the longitudinal extent of the driveshaft 4, for example on a longitudinal gearing. A driven shaft 3 is arranged parallel to the driveshaft 4 and likewise has two conical pulleys 26 displaceably disposed thereon. A belt 36 is disposed between the two conical pulley pairs 26, 46 for the purposes of transmitting the torque from the driveshaft 4 to the driveshaft 3. Alternatively, the conical pulley pairs can be coupled by way of one or more rolling elements. As a result of displacing the respective conical pulleys of a conical pulley pair toward one another or away from one another, there is a change in the respectively active radius r.sub.1, r.sub.2, resulting in a change in the respective transmission ratio.
[0037] Pivotable guide rods 56 are disposed between the two conical pulley pairs 26, 46 and convert a displacement of one conical pulley pair into an opposite movement of the opposite conical pulley pair. The movement of the two conical pulleys toward one another or away from one another can be implemented in load-dependent fashion.
[0038] An example to this end is depicted in FIG. 8, where the two conical pulleys 26 on the driveshaft 3 are mounted on two oppositely oriented threaded sections 261, 262. Both conical pulleys 26 are coupled in torsionally rigid fashion and are coupled so as to be displaceable relative to one another by way of a guide pin 263 or by way of a plurality of guide pins 263 that are distributed over the circumference. The left conical pulley 26 is prestressed and elastically mounted by way of a torsional spring 7 which is secured firstly to the driven shaft 3 and secondly to one of the conical pulleys 26. By way of example, if there is an increase in the resistance of the driveshaft 3, this leads to a relative rotation of the conical pulleys 26 in relation to the threaded sections 261, 262. The pitch of the threaded sections 261, 262 is chosen in such a way here that the conical pulleys 26 are moved toward one another in the case of an increased resistance. The belt 36 (not depicted here) migrates away from the axis of rotation of the driven shaft 3 on account of the inclination of the conical pulleys 26. On account of the rigid coupling by way of the guide rods 56, the drive-side conical pulleys 46 are moved apart, the belt 36 accordingly migrates closer to the axis of rotation of the driveshaft 4 on account of the same inclination of the conical pulleys 46. There is a change in transmission on account of the changing radii at the conical pulleys, with the driveshaft 3 having a slower rotation in the case of the same rotational speed of the driveshaft 4. As a result, a reduction in the volumetric flow rate can be achieved depending on the resistance present at the driven shaft 3 without leaving the work point of the drive motor 14.
