The invention relates to a thermal actuator for a temperature-dependent movement of a valve element, wherein a length of the thermal actuator changes depending on a temperature. Fur thermore, the invention relates to a valve with such a thermal actuator and the use of a thermal actuator for a temperature-dependent adjustment of a valve element.

For a temperature-dependent control of valves, such as radiator valves or valves arranged in the return pipe of a heating system for example, it is common to use a thermal actuator for posi tioning a valve element. Thus, depending on atemperature, such as a water temperature or a room air temperature, a fluid flow through the valve is regulated. In these known solutions, the thermal actuator is designed, for example, in the form of a bellow element having a filling that expands when the temperature increases, so that the size of the bellow element increases in the longitudinal direction. This results in a movement of a valve element, which results in a re duction or increase of the flow through the valve.

It is an object of the invention to provide a thermal actuator that has a variable geometry and is easy to manufacture. Further, the required installation space should be small and the production costs should be low. According to the invention this object is achieved by a thermal actuator having the features of claim 1 , a valve according to claim 16 and the use of such a thermal actuator according to claim 21. Advantageous embodiments are described in the dependent claims.

In a thermal actuator for a temperature-dependent movement of a valve element, wherein a length of the actuator changes depending on the ambient temperature, the actuator is made by an additive method using a temperature dependent material having an essential change in length due to a temperature change.

By means of an additive method, a high variety of shapes of the actuator can be realized. Due to the temperature dependent material, no additional elements are needed to cause a length change depending on a temperature change. Therefore the actuator is easy to manufacture and can be in a small size.

Advantageously the actuator is made by at least two different materials, wherein a first material has an essential change in length over a first temperature range and a second material has an essential change in length over a second temperature range. By the use of two different materi als, which have an essential change in length at different temperature ranges, a relatively large temperature range can be covered in total. This length change can be used directly or indirectly for a corresponding movement of a valve element.

In particular different temperature ranges can be chosen, for example a low temperature range between 15°C and 35 °C or a high temperature range between 60°C to 80° C.

It is particularly preferred that the first temperature range extends between 15 and 25°C, in par ticular between 18°C and 22°C, wherein the second temperature range extends between 15°C and 25°C, in particular between 28°C and 32°C. Thus, the entire temperature range corre sponding to a room air temperature usually desired in houses is covered. Overall, a relatively large coverage and a fine resolution is obtained.

Preferably, the actuator includes a third material in which zones of the first and second materi als are embedded. This third material may then have other desired properties, for example providing enough stability to form the actual shape of the actuator in which the other materials are embedded. The third material may in particular be less expensive than the first and second materials. More than three different materials are possible as well.

In a preferred embodiment, the actuator has at least one mesh, which has an upper longitudinal bar and a lower longitudinal bar in particular parallel thereto, wherein the longitudinal bars are connected at their ends by cross ridges, wherein a free space is formed between the upper lon gitudinal bar and the lower longitudinal bar. The longitudinal bars allow a simple deformability of the actuator, wherein the first and second material form part in the longitudinal bars. The free space allows material and weight savings. Further it provides also a high degree of flexibility and therewith a big change in length of the actuator. The cross ridges can then be made with a higher stiffness. The enlargement of the longitudinal bars due to a rising temperature causes that they bend away from each other, so that the actuator enlarges in the cross direction. Hav ing several meshes in the cross direction one above the other results in a relatively large expan sion and, by means of a plurality of meshes in the longitudinal direction, a relatively high actuat ing force.

It is particularly preferred that in each case at least two longitudinally extending layers are formed in the longitudinal bars, wherein the layers are spaced apart from each other in the cross direction. Zones of the first material and the second material are formed alternately in each layer. Such an arrangement makes it possible to define the deformation of the longitudinal bars due to temperature changes. In particular, it can be secured that the longitudinal bars bend in the cross direction to the outside and not inwardly which results in an enlargement of the ac tuator in the cross direction.

It is particularly preferred that a middle zone of the layer in longitudinal bar, which is positioned close by the free space, is formed by the second material and that in this layer the outer zones are formed by the first material respectively. In the layers that are more distant from the free space a middle zone is formed by the first material and the outer zones are formed by the sec ond material. Such a configuration results in a big change in length. The outer layer undergoes a greater change in length at higher temperatures and thus amplifies the change made by the first layer before. Thus, a high movement can be generated with sufficiently high forces. Further, a symmetrical change in the shape of the actuator is achieved. In a preferred embodiment, the actuator has a plurality of meshes arranged in a grid, wherein meshes adjacent in the cross direction are offset relative to each other in the longitudinal direc tion by a half of a mesh width. Thus, the actuator has a large number of meshes, the change in length of which sum up, so that overall a relatively large movement and force can be generated. In this case, a relatively high density is achieved by the staggered arrangement of the meshes, wherein the upper longitudinal bars of each lower mesh simultaneously form the lower longitudi nal bars of the respective upper mesh. This results in a good material and space utilization.

Preferably, the grid of meshes forms a material web, which is arranged in particular cylindrically or in the shape of a spiral. Therewith the actuator may be formed in a compact size and may generate a relatively big change in length. In particular, by a spiral shape, a relatively long mate rial web, which means a large actuator, can be accommodated in a small room.

In a preferred alternative embodiment, the actuator has a helical spring geometry. In this case, the actuator may have a certain inherent elasticity, which means a spring rate, wherein the spring rate is influenced by the temperature-dependent change of the materials. Further, the length of the spring may be changed because of temperature changes and/or the free spaces between the spring coils may be influenced. Overall, a helical spring geometry provides many possibilities.

In a preferred development, the actuator comprises a heating device. Therewith the change in length of the actuator can be controlled, independent of the ambient temperature. Normally this will be controlled by a voltage supplied to the heating device, which then heats causing the ac tuator to expand.

Preferably, the heating device may be embedded in the thermal actuator, wherein the heater is formed in particular as a heating wire. The heating device can be integrated while manufactur ing the actuator by means of the additive method. The subsequent assembly of the actuator is very simple. This also ensures that the heat can act directly on the materials and is thus used very effectively. In addition, the heating device is protected against mechanical influences.

Advantageously the heating device, in particular the heating wire, is manufactured by means of the additive manufacturing method. Therewith the heating device can be integrated directly when making the actuator itself. In a preferred embodiment, the actuator has an integrated electronic circuit. This can be imple mented into the actuator during the additive manufacturing process. In this case, different and/or a plurality of electronic circuits are can be integrated, for example an electronic circuit providing wireless communication or a sensor that registers a change in length of the actuator. This change in length can then be transmitted wirelessly to a temperature control system or the like. The actuator is therewith equipped with additional features.

In a preferred embodiment, the actuator has multiple layers of different materials that react dif ferently to environmental influences. In addition to the temperature-dependent changes in length, reactions to other environmental influences, such as, for example, the humidity can also be used. In addition, materials with different reaction characteristics can be combined.

In a further embodiment, at least one of the materials is bistable. A bistable material assumes a particular shape in a first state and a different shape in a second state, wherein the respective state is, for example, depending on a temperature. In particular, in combination with a heating device a switchable actuator can be provided.

Furthermore, an energy converter may be integrated in the actuator, which converts a move ment of the actuator into electrical energy. The electrical energy thus obtained can be used for example for the supply of the electronic circuit, so that no additional energy source must be pro vided. Piezoelectric elements can be used as an energy converter, for example. Such an actua tor might work self-sufficient.

The object mentioned above is also achieved by a valve with a thermal actuator as described above, wherein the actuator is connected to anelement of the valve and acts in the closing di rection and/or opening direction of the valve. The element can be a valve element interacting with a valve seat. Alternatively the element can be any other element which is directly or indi rectly connectet to the valve element. In any case the change in length of the actuator is thus converted directly or indirectly into a movement of the element. This allows, for example, an au tomatic temperature control in a heating circuit by regulating the free flow cross-section in the valve. For example, a spring element can act on the valve element in a direction opposite to the actuator.

In a preferred embodiment, the valve comprises a thermostatic device in which the actuator is arranged. The actuator is thus hardly affected by the temperature of a medium conducted through the valve, such as heating water. Rather, the actuator is activated more or less by the surrounding air temperature only.

Preferably, the actuator is connected via a spring element with the element. The spring absorbs overloads, which may result in damages to the valve, because the spring element can absorb peaks of the actuating forces. In other word such a spring is an overpressure spring that if the temperature gets to high and there is a risk that something within the valve will break, the over pressure spring will be actuated and prevent damages,

In a further embodiment, the actuator is arranged within a valve housing like a pipe coupling. The actuator is then controlled by the temperature of the medium flowing through the valve housing and regulates this temperature. It is also conceivable to arrange an actuator within a valve housing and an additional actuator in the valve cap, wherein the actuator within the valve housing counteracts an influence of the temperature of the medium. The actuator arranged in the valve cap is activated by the ambient temperature. This results in a more accurate control based on the ambient temperature.

In an alternative embodiment, the actuator forms a valve element. This allows a very compact design of the valve having only a few elements.

Part of the invention is also the use of a thermal actuator, as described above, for the tempera ture-dependent adjustment of a element. Thus, the inventive thermal element replaces the com monly used bellow elements or waxes that require a relatively large amount of space. Moreover, such a thermal actuator may be lighter in weight and manufactured in a variety of geometries. Furthermore, the actuator can provide additional functions.

Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings showing:

Fig. 1 a a thermal actuator with multiple meshes in an expanded state,

Fig. 1 b the actuator of Fig. 1 a in a contracted state,

Fig. 2 a schematic section through a mesh,

Fig. 3 a possible arrangement of the actuator,

Fig. 4 a valve with thermal actuator, Fig. 5 an alternative valve with thermal actuator and

Fig. 6 a screw spring-shaped actuator.

Figure 1 shows a thermal actuator 1 produced with an additive manufacturing process like 3D printing, which comprises several meshes 2a, 2b, 2c, 2d. The meshes are arranged in a shape of a grid or net. Thus, the actuator 1 takes more or less the form of a material web.

The mesh 2 comprises an upper longitudinal bar 3 and a lower longitudinal bar 4, which are connected to each other via cross ridges 5, 6. In cross direction adjacent meshes are positioned offset by half a mesh width wherein the upper longitudinal bar at the same time represent the lower longitudinal bar of the meshes positioned below.

In this example, the actuator 1 has nine rows of meshes. However, the number of rows is more or less variable and depends on the respective needs.

In Figure 1 a, the actuator 1 is shown in a state in which the longitudinal bars 3, 4 are extended: This means that the thermal actuator 1 is relatively warm. The longitudinal bars 3, 4 are out wardly arched due to the expansion and thus provide for a relatively large free space of the mesh 7. The actuator 1 has thereby increased its length in the cross direction 8.

In Figure 1 b, the thermal actuator 1 is shown at a lower ambient temperature. The longitudinal bars 3, 4 have contracted and the actuator 1 comprises a small extension in the cross direction 8. The difference in the extension in the cross direction 8 illustrates a possible travel of the actu ator 1 which can be used for actuating movement of a valve element.

Figure 2 shows the basic structure of a mesh of the thermal actuator 1. In this example, the ac tuator 1 is made of three materials by means of an additive manufacturing process like 3D print ing. The first material 9 has a significant change in length over a first temperature range be tween 18-22 ° C for example. The second material 10 has a significant change in length over a second temperature range that might be, for example, 28-32 ° C. The third material 1 1 , which gives the actuator 1 its essential shape, has no significant temperature-induced change in length. Thus, the longitudinal bars 3, 4 and the cross rids 5, 6 are formed mainly of the third ma terial, in which the first material 9 and the second material 10 are embedded. In each longitudinal bar 3, 4 are two layers 12a, 12b, 15a, 15b comprising the first material 9 and the second material 10. The first material 9 and the second material 10 are arranged alter nately. In the layer 12a, 12b positioned nearer to the free space, a middle zone 13a, 13b is formed by the first material 9, while the outer zones 14a, 14b, 14c and 14d are formed by the second material 10. In the respective outer layer 15a, 15 b, the arrangement is inverse. The re spective middle zone 16a, 16 b comprises the first material 9, while the outer zones 17a, 17b, 17c, 17d are formed by the second material 10. By this arrangement, a widening of the mesh 2 in the cross direction 8 of the actuator is ensured with rising temperatures, which increases also the free space. 7

FIG. 3 shows an embodiment of the actuator 1 made of band-shaped material that is arranged in the form of a spiral. This allows the installation of an actuator having a relatively large length in a small space. Thus, the actuator can provide a large displacement and high actuating forces.

Figure 4 shows a thermostatic device 18 of a valve having the actuator 1 arranged inside of a . The thermostatic device 18comprises a rotary handle 19. With such a handle, a desired temper ature can be adjusted. In this embodiment, the valve is preferably used for a temperature con trol of a radiator.

The actuator 1 acts via a rod 20 and a spring element 21 on an element 22 which might be con nected to a valve element (not shown) interacting with a valve seat. Thereweith the position of the element 22 controls a free flow cross-section of the valve. If the ambient temperature in creases, the thermal actuator 1 expands, thereby pushing the element 22 inwardly, This move ment is transferred to a valve element (not shown) which results in a reduction of a free flow cross-section. If the ambient temperature decreases, the actuator 1 contracts again and pulls the element 22 in a direction away from the valve. Thus, the free flow cross section increases. This results in an automatic regulation of the flow through the valve as a function of the ambient temperature.

An additional thermal actuator T is disposed the at a side 23 of the thermostatic device facing the valve.. This actuator T is influenced mainly by the temperature of the medium flowing through the valve. The actuator T compensates possible influences of the temperature of the medium on the actuator 1 , so that a very accurate control based on the ambient temperature is achieved and the effect of the temperature of the medium is compensated. FIG. 5 shows an embodiment of the valve 24 in which the thermal actuator 1 is part of the ele ment 22. The element 22 forms a valve element interacting with a valve seat of the valve 24. The structure of the valve 18 is further simplified. This makes it possible to realize a very com pact valve.

FIG. 6 shows an embodiment of the actuator 1 , which has the form of a helical spring. The length of this spring changes depending on the ambient temperature because of a correspond ing length change of the first and second material. This can be used for a controlled movement of a valve element.

The invention is not limited to one of the above-described embodiments, but can be modified in many ways. For example, other materials can be used in order to consider a bigger temperature range or other environmental influences. In addition to the mesh- shaped design of the actuator other geometry are conceivable, for example, a stacked actuator, in which each element of the stack has its own function, or other arrangements. The use of a thermal actuator manufactured by means of the additive method like 3D printing with at least two materials having a substantial length change over different temperature ranges, simplifies the manufacture of valves, in partic ular of valves used in heating systems of building. Here, a variety of new design possibilities be ing opened because the shape of the actuator is not fixed. Further, it is quite simple to integrate additional elements in the actuator providing additional functionalities.

All of the claims, the description and the drawings resulting features and advantages, including design details, spatial arrangements and method steps may be essential to the invention both in itself and in various combinations.

List of references

1 actuator

2 mesh

3 upper longitudinal bar

4 lower longitudinal bar

5 cross ridge

6 cross ridge

7 free space

8 cross direction

9 first material

10 second material

1 1 third material

12 inner level

13 middle zone

14 outer zone

15 outer level

16 middle zone

17 outer zone

18 thermostatic device

19 handle

20 rod

21 spring element

22 element

23 side

24 valve