The invention relates to 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. In particular, the orthopedic joint device is in the form of a prosthesis or orthosis.
Prostheses serve to replace missing or lost extremities, and often comprise a joint device for an articulated interconnection between two prosthesis components. The movement of the two prosthesis components in relation to one another can be influenced by damper devices, this case relating to passive prosthetic joint devices. A corresponding statement applies to orthoses which are applied to extremities present. In this case, too, joint devices interconnect two components in articulated fashion. A relative movement between the two components is actively caused or assisted when an orthopedic joint device is provided with an actuator. To this end, at least one drive is provided, the latter being coupled to a source of power such that the movement behavior can be actively influenced. The actuator may comprise an electric motor which is used to move further components of the actuator, for example parts of a hydraulic pump or a transmission device.
Hydraulic pumps, especially hydraulic pumps in orthopedic devices, are driven by a motor, especially by an electric motor. The motors need to be comparatively small and light, and the motor or motors is or are optionally coupled to the remaining components of the hydraulic pump by way of a transmission. When designing the hydraulic pump and the entire so-called drivetrain, it is necessary to define a work point for the motor when the construction starts. The work point defines the rotational speed and an optimal torque which allows the motor to operate optimally, for example have the best efficiency. In relation to the hydraulic pump, this means that the pump has an appropriate flow rate at this work point or conveys a certain volumetric flow rate and builds up appropriate pressure. Should the desired pressure and volumetric flow rate not be able to be obtained by direct connection between motor and driveshaft, it is necessary to provide a required gear reduction by way of an interposed transmission, depending on work point and drive. The work range of a drivetrain then emerges from the characteristic of the motor and the chosen gear reduction of the transmission.
Very high forces and torques act on orthopedic joint devices. At the same time, there is little installation space available and there are restrictions in relation to the weight. Therefore, small, fast-running electric motors are used as drives for orthopedic devices, and these are coupled to transmissions in order to apply the desired forces and torques.
Electric motors with permanent magnets, what are known as permanent magnet-excited or external magnet-excited electric motors, have a comparatively stiff characteristic, that is to say in comparison with other motor technologies the rotational speed only drops slightly in the case of an increased load. Such a behavior is desirable for many applications. Specifically for applications in the field of prostheses and orthoses, it would sometimes be advantageous to be able to adapt the characteristic of the drivetrain to the respective application without efficiency losses or without substantial efficiency losses.
A correspondingly high rotational speed of the motor with a correspondingly low torque is desired when a hydraulic actuator assists a patient with walking in the plane, for example within the scope of prosthetic or orthotic care, and this corresponds to a high flow rate at a comparatively low pressure. However, should there be increased assistance, for example when walking uphill, climbing stairs or getting up, it is high forces, and hence high pressures, at a comparatively low flow rate that are required, rendering a low rotational speed necessary. It is not possible to cover both work points, or only difficult to cover both work points, in the case of a drivetrain defined once from a structural point of view with a fixed transmission ratio or gear reduction. A further limitation here is also given by the maximum current of the power storage device, for example a rechargeable battery, which is directly proportional to the motor torque. The size of the power storage device is limited, especially also for reasons of space and weight. Hence, an increase in the gear reduction would be required to obtain higher torques.
Upper extremity prostheses use change gears that facilitate two work points. Load-dependent clutches that require a complex structure are provided to this end. Moreover, the switching steps are defined, and so an adjustment, advantageously a continuous adjustment, to different load situations is not possible.
It is an object of the present invention to provide an orthopedic device that renders an increase in the work range of drivetrains possible.
According to the invention, this object is achieved by an orthopedic joint device having the features of the main claim. Advantageous embodiments and developments of the invention are disclosed in the dependent claims, the description and the drawings.
The 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 provides for the force transmission device to comprise a load-dependently adjustable force transmission element. In order to cause an automatic load-dependent adjustment of the force transmission element, the latter is preferably mounted in elastically prestressed fashion. If there is a change in the load, and hence resistance, on the force transmission element, the force transmission element adjusts automatically and causes a change in the transmission ratio or in the force transmission, for example a change in a piston stroke. By changing the position of the force transmission element, it is possible to alter the characteristic of the drive or type of drive and automatically load-dependently adapt these to the respective conditions. In the case of an increasing resistance, for example pressure or torque, there is a change in the position of the force transmission element; by way of example, there is a change in the piston stroke or in the position and transmission ratio of a transmission such that lower pressures or lower forces or torques are provided.
In an embodiment of the invention, the orthopedic joint device comprises a hydraulic pump which has a housing and which is assigned a drive, in particular an electric motor. The electric motor is coupled to the driveshaft and may be disposed within the housing of the hydraulic pump or fastened to the housing of the hydraulic pump. Should the motor be activated and rotate the driveshaft, the driven element in the form of a displacement element is displaced, for example rotated or axially displaced in the case of an axial piston pump. The adjustable force transmission element is disposed between the driveshaft and the displacement element, which sucks the hydraulic fluid into the pump chamber and then ejects it from the latter again. To cause a load-dependent automatic adjustment of the force transmission element, the latter is preferably mounted in elastically prestressed fashion. If there is a change in the load, that is to say in the resistance on the force transmission element as a result of the displacement element, there is an automatic adjustment of the force transmission element, and this causes a change in the stroke of the at least one displacement element. The volumetric flow rate of the pump can be influenced by changing the stroke. The position of the force transmission element changes when the pressure increases; by way of example, the piston stroke changes as a result of a change in the inclination of a swash plate or changes as a result of a change in the eccentricity of a cam such that the effective stroke of the displacement element is decreased in the case of increasing pressure and the volumetric flow rate drops.
A development of the invention provides for the displacement element to be in the form of a piston of an axial piston pump and for the force transmission element to be in the form of a swash plate. The swash plate may be mounted on a carrier in elastically prestressed or resilient fashion such that there is a load-dependent change in the inclination of the swash plate depending on the pressure exerted by the piston or pistons on the force transmission element or on the swash plate. A further variant of the invention provides for the displacement element to be in the form of a piston of a radial piston pump, with the force transmission element then being in the form of a cam. The load-dependently changeable cam eccentricity can be obtained by way of a shaft cam, for example, which can rotate in relation to a second cam. An effective summated eccentricity arises depending on the relative angle position between the two cams and said summated eccentricity load-dependently changes on account of the elastic mount of the cams with respect to one another. Furthermore, it is possible for the displacement element to be in the form of a rotor of a sliding vane rotary pump and for the force transmission element to be in the form of a cam. The eccentricity in this case may also be altered by rotating two cams relative to one another, with the rotation being implemented load-dependently, preferably against a prestressing force.
To be able to bring about the load-dependent change in the stroke of the at least one displacement element, at least one spring element which is compressed when the load increases is advantageously disposed between the driveshaft and the displacement element. The displacement element need not be disposed directly on the driveshaft; instead, it is possible for a carrier or a support to be disposed on the driveshaft, with the carrier element being elastically mounted on said carrier or on said support. One or more spring elements which is or are compressed when the load increases may be disposed on the displacement element. The spring element or the spring elements may be interchangeably disposed on the displacement element in order to facilitate an adjustment of the change behavior of the displacement element. A harder spring element is used if the change in the stroke should be implemented over a relatively large force range or resistance range, while a softer spring element is chosen if there should be a stroke change with a faster response. A different maximum stroke can be defined by way of interchangeable spring elements in order to be able to specify structurally different limits.
The spring element may be in the form of an elastomeric spring, coil spring, spiral coil spring, Belleville spring, Belleville spring assembly and/or leaf spring. It is possible to use different types of spring elements together; it is likewise possible to use differently hard or soft spring elements of the same type or of different types in order to achieve the desired change behavior.
A development of the invention provides for the force transmission device to be in the form of a continuously variable, adjustable transmission, for example as a friction gear with conical rollers rolling against one another or a belt transmission or friction drive, in which axially displaceable pulley pairs are disposed on two substantially parallel shafts. If the pulleys of a pair are moved toward one another, a belt or a rolling element migrates outward since there is a change in the diameter of the area of contact. The other pulley pair is correspondingly moved apart such that the effective diameter of the area of contact reduces there. This allows the attainment of a continuously variable, load-dependent change in the transmission ratio between driveshaft and driven shaft.
The force transmission element can be in the form of a conical pulley which is part of the force transmission device. The force transmission element is formed on the driveshaft or a driven shaft so as to be displaceable along the latter's longitudinal extent, for example displaceably mounted on a splined shaft or mounted on a thread so as to be rotatable relative to the respective shaft, and prestressed against a rotation. The prestress can be produced by way of a spring element which is coupled to the conical pulley. The spring, for example a torsional spring, is stressed if a greater drive torque is transmitted, as a result of which a relative rotation sets in between the shaft and the conical pulley. If two conical pulleys are present, both can in the case of an adjustment be moved away from one another or toward one another simultaneously as a result of opposing threads. The movement is reversed if the transmitted drive torque is reduced. By way of example, the force is transmitted between the driveshaft and the driven shaft by way of rolling elements, one or more belts or chains, especially in correspondingly constructed conical pulley pairs. The two conical pulley pairs may be directly coupled to one another by way of levers or guide rods such that a separating movement of the one conical pulley pair brings about a converging movement of the other conical pulley pair, and vice versa.
The respective spring element may have a linear, degressive or progressive spring characteristic in order to be able to optimally adjust the conveying characteristic of the hydraulic pump to the respective demands.
The orthopedic joint device is provided in particular for the use in prostheses, orthoses and, as a special case thereof, exoskeletons. In principle, it is also possible to assemble the actuator of the hydraulic pump, optionally with an integrated motor or a motor securely coupled therewith and with an energy storage device, to other orthopedic devices, for example wheelchairs, joint movers or the like.
Exemplary embodiments of the invention are explained in more detail below on the basis of the attached drawings, in which:
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
An alternative solution for a hydraulic pump is schematically depicted in
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.
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.
An example to this end is depicted in
Number | Date | Country | Kind |
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10 2019 130 326.5 | Nov 2019 | DE | national |
This is a national phase application of International Application No. PCT/EP2020/081294, filed 6 Nov. 2020, which claims the benefit of German Patent Application No. 10 2019 130 326.5, filed 11 Nov. 2019, the disclosures of which are incorporated herein, in their entireties, by this reference.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2020/081294 | 11/6/2020 | WO |