ACTUATOR AND HEAT STORE FOR ACTUATOR

Abstract

The invention relates to an actuator for an orthopedic device with an actuator housing and a heat store for storing the heat produced during operation of the actuator, the heat store having a heat store housing that has a cavity and a heat storage medium present therein, or consisting of a heat storage medium. The heat store is designed to be attachable to or in the actuator housing and has a receiving region that matches an actuator housing region and, when the heat store is mounted, is in heat-transferring contact with the actuator housing.

Claims

1. An actuator for an orthopedic device, the actuator having an actuator housing and a heat store for storing the heat produced during operation of the actuator; wherein the heat store has a heat store housing, which has a cavity and a heat storage medium present therein, or wherein the heat store consists of the heat storage medium; wherein the heat store is designed in such a way that it can be fixed on or in the actuator housing and has a receiving region, which is designed to correspond to an actuator housing section and which, in an installed state of the heat store, is in heat-transferring contact with the actuator housing.

2. The actuator as claimed in claim 1, wherein the heat store is fastened detachably on the actuator housing, in particular nonpositively and/or positively.

3. The actuator as claimed in claim 1, wherein fastening devices, in particular screw sockets, undercuts, clips, clamping elements, plugs, plug receptacles, magnets, ferromagnetic elements and/or hook-and-loop fastening elements, are arranged or formed on the heat store and the actuator housing.

4. The actuator as claimed in claim 1, wherein positive engagement elements are arranged or formed on a side of the receiving region which faces the actuator, said positive engagement elements being designed to correspond to positive engagement elements on an outer side of the actuator housing.

5. The actuator as claimed in claim 1, wherein the heat store is designed to be at least partially flexible on a side of the receiving region which faces the actuator.

6. The actuator as claimed in claim 1, wherein the heat store is designed to be at least partially rigid on a side which faces away from the actuator.

7. The actuator as claimed in claim 1, wherein the heat store is formed from different materials, and the material in the receiving region has a thermal conductivity λ.sub.M1 which is higher than the thermal conductivity λ.sub.M2 of a second material outside the receiving region.

8. The actuator as claimed in claim 1, wherein an outer contour of a side of the heat store which faces away from the actuator and/or a contour of the receiving region have/has a contour which is designed to correspond to a contour of the outer side of the actuator housing.

9. The actuator as claimed in claim 1, wherein at least one heat conductor, in particular a thermal paste, a heat-conducting mat and/or a heat-conducting plate, is arranged between the actuator housing and the heat store.

10. The actuator as claimed in claim 1, wherein it is designed as a hydraulic actuator, in particular as a hydraulic damper.

11. The actuator as claimed in claim 1, wherein the heat store surrounds the actuator housing circumferentially.

12. The actuator as claimed in claim 1, wherein the heat store is of multi-part design.

13. The actuator as claimed in claim 1, wherein the heat storage medium has a specific heat capacity of at least c.sub.p=1 J/(g*K) at a temperature of T=25° C.

14. The actuator as claimed in claim 1, wherein the heat storage medium has a specific enthalpy of fusion of at least h.sub.WM=100 kJ/kg.

15. The actuator as claimed in claim 1, wherein the specific heat capacity of the heat storage medium is higher than the specific heat capacity of the actuator housing.

16. The actuator as claimed in claim 1, wherein the heat storage medium is in the form of a wax, paraffin, a salt, salt hydrate, metastable salt hydrate, in particular sodium acetate trihydrate, or a dimensionally stable silica gel.

17. The actuator as claimed in claim 1, wherein the heat storage medium is designed to be actively triggerable.

18. An orthopedic device having an actuator as claimed in claim 1.

19. A heat store having a heat store housing as claimed in claim 1 for fastening on an actuator of an orthopedic device.

20. An actuator for an orthopedic device comprising: an actuator housing and a heat store for storing the heat produced during operation of the actuator, wherein the heat store has a heat store housing which has a cavity and a heat storage medium present therein, or wherein the heat store consists of the heat storage medium; and wherein the heat store is configured to be detachably fixed on or in the actuator housing by a fastening device, and wherein the heat store has a receiving region which is designed to correspond to an actuator housing section and which, in an installed state of the heat store, is in heat-transferring contact with the actuator housing.

Description

[0022] FIG. 1—shows an isometric view of a hydraulic actuator with a heat store housing arranged thereon;

[0023] FIG. 2—shows a front view of the hydraulic actuator according to FIG. 1 with an open heat store housing;

[0024] FIG. 3—shows a variant of FIG. 2;

[0025] FIG. 4—shows a sectional illustration with two different heat storage media;

[0026] FIG. 5—shows a schematic illustration of the use of the invention;

[0027] FIG. 6—shows a perspective view of a heat store;

[0028] FIG. 7—shows a heat store according to FIG. 6 without a receiving region;

[0029] FIG. 8—shows an illustration of FIG. 6 with a partially sectioned outer wall;

[0030] FIG. 9—shows a view of FIG. 8 without the outer wall;

[0031] FIG. 10—shows a side view of FIG. 9;

[0032] FIG. 11—shows a frontal view of FIG. 10; and

[0033] FIG. 12—shows a plan view of FIG. 11.

[0034] In FIG. 1, in a perspective view, there is an actuator 1 in the form of a hydraulic damper having an actuator housing 10, in which a cylinder is formed, in which a piston (not visible) can be coupled to an orthopedic device via a piston rod 12. The hydraulic actuator 1 can be designed either as a hydraulic damper or as an active drive. Arranged on the actuator housing 10 is an attachment 15, in which an energy store, e.g. an accumulator, a motor drive for driving a pump or for adjusting one or more valves or the like, can be arranged. In addition, sensors, microprocessors as part of a control device and the like can be accommodated in the attachment 15; alternatively, the drive with all other components can be arranged in the actuator housing 10.

[0035] A heat store 2 with a heat store housing 20, in which a heat storage medium is located, is arranged outside the actuator housing 10. The heat store housing 20 has an outer wall 22, which consists of a rigid, dimensionally stable material, e.g. a light metal. On the inner side of the heat store housing 20, which faces the actuator housing 10, a receiving region 21 is formed which is designed to correspond to an actuator housing section 11 on the outer side of the actuator housing 10. The part of the heat store 2 which is intended to absorb heat and, if appropriate, to pass it on to the heat storage medium 26 is arranged on the receiving region 21 of the actuator housing 10. In the exemplary embodiment illustrated, the actuator housing section 11 extends from the ends of the actuator housing 10 over the entire length of the outer side of the actuator housing 10 up to the attachment 15. The piston rod 12 projects from one, visible, end of the actuator housing 10. The opposite end is provided, for example, with a fastening device for fixing on an orthopedic device, e.g. a prosthesis, orthosis or an exoskeleton.

[0036] In FIG. 2, in a frontal view with a partially sectioned heat store housing 20, the receiving region 21 can be seen, which is represented by a dashed line. The receiving region 21 rests against the actuator housing section 11 on the outer side of the actuator housing 10. As a result, the heat emitted by the actuator housing 10 can be dissipated through the receiving region 21 into the cavity 25 containing the heat storage medium 26. The heat storage medium 26, e.g. wax, stores the heat and smoothes dissipation peaks, and makes possible extended operation of the actuator 1 at high loads, with a comparatively low weight by virtue of the hollow configuration of the heat store 20 and the choice of material for the heat storage medium 26, which is adapted to the function.

[0037] A heat conductor 40, for example a thermal paste, a heat-conducting mat and/or a heat-conducting plate made of a material which is a particularly good conductor of heat, can be arranged between the actuator housing section 11 and the receiving region 21. Free spaces between the outer side of the actuator housing 10 and the receiving region 21 can be compensated for by means of the heat conductor 40.

[0038] At the transition to the attachment 15, the heat store housing 20 can have inwardly directed projections which extend into a gap or into a slot between the attachment 15 and the actuator housing 10 in order in this way to be able to perform positive locking on the actuator housing 10. For this purpose, either only the projections or the entire heat store housing 20 can be designed to be elastically expandable, thus enabling the actuator housing 10 to be placed in the receiving region, pushed in and fixed thereon by resilient positive locking. Alternatively, positive engagement elements, such as springs, plugs or, alternatively, screw connections, can be provided and arranged or formed on the actuator housing 10 and the heat store housing 20 in order to be able to perform detachable and, advantageously, reusable fastening of the heat store 2 on the actuator housing 10. Permanent connection is possible, e.g. by means of an adhesive bond, for example by means of an adhesive heat conductor. As an alternative or in addition, a nonpositive connection can be produced by means of magnetic coupling.

[0039] FIG. 3 shows a variant of the invention according to FIG. 2, in which, instead of a hollow body with a filling comprising a heat storage medium 26, the heat store 2 is formed from the heat storage medium 26. The heat storage medium 26 of the heat store 2 is preferably a material with a very high heat absorption capacity, e.g. a silica gel, which is applied directly to the actuator housing 10 and fixed thereon. The heat store 2 would then not have a separate heat store housing 20, and, in this case, fixing can take place in a detachable and repeatably attachable manner on the actuator housing 10.

[0040] A further variant of this embodiment is shown in FIG. 4, in which only the actuator housing 10 with the actuator housing section 11, against which the respective variant of the heat store 2′, 2″ rests, is shown. In the exemplary embodiment illustrated, the respective heat store 2′, 2″ is arranged on the outer side of the actuator housing 10. FIG. 4 illustrates two variants of the heat store 2, the first variant with the heat store 2′ consisting of a material containing salt or predominantly salt, in particular metastable salt. The second variant of the heat store 2″ is formed from paraffin and has a greater thickness D2 than the first variant of the heat store 2′ with a first thickness D1. This is due to the fact that the enthalpy of the salt and its density is greater than that of paraffin and thus, by comparison, less volume of heat storage medium 26 is required. Both heat stores 2′, 2″ rest against the actuator housing section 11, which is provided for heat exchange or heat transfer from the actuator housing 10 to the heat store 2′, 2″.

[0041] If the respective heat storage medium 26 of the heat store 2′, 2″ is not dimensionally stable, it is possible, instead of forming the heat store 2′, 2″ from the respective heat storage medium 26, to arrange around it a corresponding shell, which serves as a heat store housing and forms a cavity in which the respective heat storage medium is arranged. Particularly in the case of an arrangement having a flexible heat store housing, or at least a partially flexible heat store housing, it is possible to use a deformable heat storage medium which is applied to the actuator housing 10 in a deformable state and is then solidified or crystallized. This facilitates close and full-surface contact in the region of the outer side of the actuator housing 10 which is provided for heat transfer.

[0042] FIG. 5 shows a variant of the invention in which the actuator 1 is designed as part of an orthopedic device. A pyramid adapter 13 is arranged on the upper end of the actuator housing 10 in order to connect the actuator 1 to, for example, an upper part of a leg orthosis or prosthesis. The piston rod 12 projects from the actuator housing 10 and leads to a lower part 15 of the orthopedic device. The heat store 2 with a heat store housing 20 is arranged on the outer side of the actuator housing 10. In the illustration on the left, the heat storage medium 26 is arranged in a solid state inside the heat store housing 2, on the receiving region 21 of the actuator housing 10. If, for example, frictional energy is then converted into heat or electrical energy is dissipated into heat by actuation of the actuator 1, this thermal energy is stored both in the actuator 1 and in the heat store 2. As a result, the maximum operating time of the actuator 1 and thus also of the orthopedic device is extended since the actuators have a maximum operating temperature which must not be exceeded. If, for example, an actuator temperature of 80° C. is reached, the user must wait until the thermal energy has been released to the environment and the joint or the orthopedic device has cooled sufficiently. With the heat store 2 arranged on the receiving region 21, it is possible to absorb the thermal energy and store it in the heat storage medium in order then to release the absorbed energy at another, definable time, for example during a rest phase. The user therefore no longer has to wait until the joint can be used again, or else the joint or the orthopedic device can be used for a longer period of time with the same cooling time. The heat store is preferably fixed on the actuator in such a way that it can be removed in a simple manner and can be fitted again in a simple manner. In particular, the heat store can be fixed to and removed from the actuator without tools, thus enabling a user to change, in particular extend, the heat storage capacity and thus the operating time of the actuator. The removed heat store can cool down, while the newly arranged substitute heat store can absorb heat from the actuator housing.

[0043] The right-hand illustration shows the state of the heat store 2 which is assumed when heat is stored in the heat store 2. The heat storage medium 26 has melted and accordingly is liquid or of low viscosity. Thermal energy from the actuator 1 is absorbed in the heat storage medium 26 of the heat store 2. At a later time, the heat store 2 and, where applicable, also the actuator 1 are then cooled, this being shown in the central, lower figure. The heat storage medium 26 within the heat store 2 is initiated with a freely selectable event, which is, if appropriate, manually triggered by a trigger signal. If, for example, a metastable salt is used, there is the possibility of defining the time when the thermal energy is to be released again. If the orthopedic device or the joint or actuator 1 overheats, it is no longer absolutely necessary to wait until all the thermal energy has been released to the environment before the actuator can be used again. On the contrary, the energy is stored in a chemical reaction and can be released at any time. The waiting time until a joint or an orthopedic device is ready for use again after overheating is thereby shortened. Particularly in the case of a rapidly exchangeable heat store 2, the service life can thus be greatly extended. The energy of entropy is not automatically released by the salt or metastable salt as the heat storage medium; on the contrary, only the energy of the specific heat capacity of the actuator 1 has to be released. The cooling time is thereby considerably shortened. The remaining energy of entropy can be released at any desired, specifiable time. Until recrystallization is initiated, the joint can continue to release the energy at the level of the specific heat capacity of the orthopedic device or of the actuator 1. Once the thermal energy has been released from the heat store 2, the state on the left in FIG. 5 is established.

[0044] The recrystallization of a salt can be initiated, for example, by a pressure wave, for example by actuation of a metal plate or else by a vibration motor or by switching on another trigger or trigger mechanism 30. The trigger mechanism 30 is illustrated schematically in FIG. 5 and can be arranged directly on the heat store 2 so as to be accessible from the outside. For example, a button, a switch or a flexible location can be formed on the heat store housing, by means of which the metal plate or some other actuator can be activated in order to trigger a pressure wave by means of which the crystallization of the heat storage medium 26 can take place at the respectively desired time. By using a latent heat store in the form of a salt, it is possible to provide a comparatively lightweight heat store with a small volume. Compared with paraffin, the enthalpy of salt is greater, but the heat capacity is lower.

[0045] A further variant of the invention is illustrated in FIG. 6, in which the heat store 2 is illustrated with an outer wall 22 and a receiving region 21. The actual actuator is not illustrated and can be designed as a damper or as a motor drive. Together with the outer wall 22, the receiving region 21 forms a cavity and thus, overall, a heat store housing 20 which advantageously has a heat storage medium and is, in particular, filled therewith. The heat storage medium is, for example, wax or some other heat storage material with which it is possible to dissipate and absorb thermal energy from the actuator via the receiving region 21. A projection or a positive engagement element is arranged or formed on the receiving region 21 as a fastening device 3 for fixing to the actuator (not illustrated). A correspondingly shaped positive engagement element is arranged or formed in the actuator. Other forms of positive engagement elements such as hook-and-loop fasteners, clips, undercuts, screws or the like can be used as fastening devices 3. Instead of a positive engagement element, the fastening device 3 can also be designed as a magnet or clamping element in order to allow nonpositive fastening.

[0046] In FIG. 7, the heat store 2 is illustrated without the receiving region 21, which can be designed, for example, as a conductive metal. A heat conductor or a heat-conducting coating can be formed or arranged on the underside of the receiving region 21 or on the side of the receiving region which faces the actuator in order to facilitate or allow heat transfer from the actuator to the heat store 2. Within the heat store housing 20, which can be adhesively bonded to the receiving region 21 or fixed thereon in some other way, a cavity is formed, which will be explained in greater detail with reference to FIG. 8. The heat store housing 20 with the outer wall 22 is closed toward the receiving region 21, and therefore the heat store housing 20 can be designed as an independent module which is subsequently fixed on the receiving region 21.

[0047] A partially sectioned illustration of the heat store housing 20 mounted on the receiving region 21 is illustrated in FIG. 8. Together with the inner wall 22′, the outer wall 22 forms the cavity 25 in which the heat storage medium 24 can be arranged. In the illustrated exemplary embodiment, three dividing elements 24 extend from the inner wall 22′ in the direction of the outer wall 22, and, in the illustrated exemplary embodiment, extend parallel upward away from the receiving section 21, with the result that a total of four compartments is formed within the cavity 25. The compartments are connected to one another, and therefore heat exchange and possibly material exchange can take place in the case of a liquefied heat storage medium.

[0048] FIG. 9 shows the arrangement with the receiving region 21 and the heat store housing 20 without the outer wall but with the inner wall 22′ and the dividing walls 24 projecting upwards therefrom. The dividing walls 24 can be formed in one piece with the inner wall 22′; alternatively, the dividing walls 24 can be arranged subsequently on the inner wall 22′ and fastened thereon.

[0049] FIG. 10 shows the view according to FIG. 9 in a side view. It can be seen from FIG. 10 that the inner wall 22′ does not extend over the entire receiving region 21, but that a cutout is left free which is not covered over by the heat store 2. In principle, it is possible to cover over the entire area of this region as well and to cover it with the heat store 2.

[0050] The view according to FIG. 11 shows the parallel alignment of the three dividing walls 24 and the substantially vertically upward orientation.

[0051] The plan view in FIG. 12 shows the cutout in the front region of the heat store housing 20, in which the receiving region 21 is not covered over by the heat store housing 20 and the inner wall 22′.

[0052] In addition to a subdivision function and separation of individual chambers, the dividing elements 24 also have other functions, namely the stabilization of the heat store 2 and heat conduction from the receiving region 21 and the inner wall 22′ into the interior of the heat store 2. The heat storage medium arranged in the cavity 25 is heated more uniformly by the dividing elements 24 which project into the cavity 25 than if heat conduction were to take place only via the walls. For this purpose, the dividing elements 24 can consist of a material which has a good thermal conductivity, for example of a material which has a thermal conductivity of the receiving region 21. By virtue of the transfer of heat via the dividing elements 24, the heat storage medium in the cavity 25 is heated more uniformly. In addition to the edge zones, heat is also applied to the core of the cavity 25, thereby enabling improved heat dissipation from the actuator to take place.