"ACTUATOR COMPRISING A PAIR OF HELICAL ELEMENTS IN SHAPE

MEMORY ALLOY MATERIAL"

[0001 ] This invention relates to an actuator.

[0002] An actuator is a component suitable to execute, on command, a mechanical action on an external component, for example an action on a button or a switch.

[0003] The main requirement of actuators in general is that of having an effective behaviour, i.e., an operation that is precise, correct and reliable over time, which is to say, reproducible over time for example for thousands of cycles .

[0004] The design and evolution of the actuators is therefore in constant state of development; in fact, in order to meet the above requirements, innovations in this area are very frequent.

[0005] Only recently has the use of components selected from the group of Shape Memory Alloys, or SMAs, found applications in actuators. Said actuators exploit the characteristic change of shape of such components to perform the desired actuation.

[0006] The actuator object of the present invention is comprised in this latter type of actuator, comprising one or more elements made of a material selected among the shape memory alloys; the invention constitutes a new, more advanced solution specifically suited to improve the performance of the actuator in terms of efficiency and reliability, with respect to the currently known actuators .

[0007] In fact, the purpose of this invention is to provide a new actuator suitable to achieve marked results in terms of efficiency and reliability by exploiting the properties of shape memory alloys. This purpose is achieved by means of. an actuator according to claim 1. The dependent claims show variants of preferred embodiments and further characteristics providing a series of new advantages.

[0008] The object of this invention will now be described in detail, with the help of the accompanying drawings, wherein :

[0009] - Figure 1 represents an exploded perspective view of the actuator covered by this invention according to a preferred embodiment;

[0010] - Figure 2 shows a section view of the actuator of Figure 1;

[001 1] - Figure 3 illustrates a part of the frame comprised in the actuator according to the embodiment shown in Figures 1 and 2;

[0012] - Figures 4 and 4a represent, respectively, a perspective view and a plan view of the slide comprised in the actuator in the embodiment shown in Figures 1 to 3, and in particular a box structure of the slide;

[0013] - Figure 5 shows, in perspective, two pairs of helical elements accommodated in the slide in the embodiment shown in Figures 4 and 4a;

[0014] - Figure 6 illustrates the electrical diagram applied to the embodiment with two pairs of helical elements ;

[0015] - Figure 7 represents a schematic of a test bench on which the actuator is suitable to be tested;

[0016] - Figure 8 shows a graph that, in relation to time, shows, respectively, the power supply of the first helical element, the power supply of the second helical element, the power supply of the cooling fan and the axial position of the slide.

[0017] In Figures 1 to 6, the actuator is always represented in a configuration wherein the respective first helical element of each pair of helical elements is excited and thus modified in its shape. This graphic representation is not limiting to a specific form of the actuator, according to what is described below in detail.

[0018] With reference to the above-mentioned figures, reference number 1 identifies, in its entirety, an actuator covered by this invention.

[0019] The actuator 1 comprises a slide 10 adapted to move along a main axis X-X in a reciprocating motion. Preferably, the main axis X-X has a rectilinear trajectory; in further embodiments, the main axis X-X has a curvilinear trajectory.

[0020] Preferably, the actuation action corresponds to the movement of the slide 10; in other words, at least one end of slide 10 is suitable to interact with the external environment, when the slide 10 is moved into an actuation position, translated along the main axis X-X.

[0021] According to a preferred embodiment, the slide 10 has a box-like shape, identifying a box structure 10' , having inside a cavity 150 that extends along the main axis X-X.

[0022] In addition, the slide 10 comprises at least one pair of helical elements 100 in a material selected from among the shape memory alloys.

[0023] Preferably, the two helical elements that comprise the pair of helical elements 100 are arranged consecutively along the axis X-X.

[0024] Preferably, the pair of helical elements 100 is accommodated in the cavity 150.

[0025] According to a preferred embodiment, the actuator 1 comprises a fixed frame 20. Preferably, the frame 20 is suitable to provide a guide to the slide 10, so that it is supported in its movement along the main axis X-X. [0026] In a preferred embodiment, the frame 20 comprises inside it a guide 250, having a shape such as to accommodate the slide 10 in such a way that it is supported, for example on its sides or ^■ bottom, and is free to slide in the direction the main axis X-X. In other words, the guide 250 has a prismatic coupling with the slide 10.

[0027] According to a preferred embodiment, the frame 20 is composed of two shells 21, 22 in such a way that the mutual engagement of the two shells 21, 22 delimits the guide 250.

[0028] Preferably, the size and shape of the guide 250 that, as said, are related to the shape of the slide 100 and are also a function of the material of the frame and the slide, so that the guide 250 requires tolerances such as to allow the sliding of the slide 100 also following variations of shape, for example, due to thermal expansion or contraction of the different components.

[0029] In a preferred embodiment, the frame 20, and in particular, the two shells 21, 22 and the box structure of the slide 10 are in a material chosen from the group of polymers, preferably, a material with a low thermal coefficient and low electrical conductivity.

[0030] Furthermore, in a preferred embodiment, the frame 20 comprises locking elements 200 that extend transversely to the slide 10 to lock it in a predefined axial position. Preferably, the locking elements 200 extend perpendicularly to the main axis X-X. Preferably, the locking elements 200 extend in such a way as to protrude on both sides of the slide 10 to be thus engaged with the two shells 21, 22.

[0031] In other words, the locking elements 200 are suitable to provide a point of attachment of the slide 10 to the frame 20. In yet further other words, the slide 10 is pivoted to the frame 20 by means of said locking elements 200.

[0032] In a preferred embodiment, the pair of helical elements 100 includes at least a first helical element 101 and at least a second helical element 102 arranged respectively on the sides of the locking elements 200. Preferably, the first helical element 101 and the second helical element 102 have, respectively, a first end 111, 112 operatively connected to said locking elements 200 and a second end 121, 122 operatively connected to the slide 10. The change of shape, by means of changing the temperature of the first helical element 101 and/or the second helical element 102 thus causes a movement of the slide 10 with respect to the locking elements 200.

[0033] According to the desired characteristics of the actuator, for example with the desired travel that this must have, embodiments are foreseeable wherein the first helical element 101 has the same characteristics as the second helical element 102, for example the same material and/or the same helical shape; embodiments are also foreseeable where, instead, the first helical element 101 differs from the second helical element 102 for example in the material and/or in the shape of its helix.

[0034] According to a preferred embodiment, the actuator 1 comprises control means 30 suitable to control the heating and/or cooling of the first element 101 and/or of the second element 102 so as to vary the temperature and thus the shape resulting in the movement of the slide 10.

[0035] According to a preferred embodiment, the slide 10 comprises a number of pairs of helical elements 100 that extend parallel to the main axis X-X, presenting the respective first helical elements 101 and the respective second helical elements 102 positioned parallel to each other. Preferably, the number of pairs of helical elements 100 comprised in the slide 10 is equal. For example, a preferred embodiment, such as that shown in the accompanying figures, comprises two pairs of helical elements 100.

[0036] According to a preferred embodiment, the slide 10 comprises a number of cavities 150 equal to the number of pairs of helical elements 100. In other words, each pair of helical elements 100 is housed in a respective cavity 150, wherein each cavity 150 is separated from the adjacent cavity 150 by an insulating wall 159 that extends along the main axis X-X.

[0037] According to further embodiments, the actuator 1 modularly comprises more than one slide 10, for example two slides 10 placed one above the other, having mutually fixed to each other their respective box structures 10' .

[0038] According to a preferred embodiment, the locking elements 200 comprise a first locking element 201 and a second locking element 202 respectively operating with a first helical element 101 and a second helical element 102.

[0039] Preferably, the locking means 200 further comprise, a separator plate 205 disposed between the first locking element 201 and the second locking element 202 to mutually separate them from each other, isolating the first helical element 101 from the second helical element 102. In other words, the separator plate 205 is suitable to isolate, dividing the cavity 150 into two distinct chambers 151, 152, in which, the pair of helical elements 100 is housed; preferably, wherein in each chamber 151, 152 is housed the respective helical element 101, 102.

[0040] Preferably each locking element 201, 202 comprises a pin 211, 212 that extends in length through the slide 10 and a locking clamp 221, 222 fitted on the pin 210 and suitable to engage with the respective helical element 101, 102 to block the respective first end thereof 111, 112.

[0041 ] According to a preferred embodiment that comprises more than one pair of helical elements 100, each locking element 201, 202 has a pin 211, 212 and a number of terminals 221, 222 fitted thereon equal to the number of pairs of helical elements 100.

[0042] Each terminal 221, 222, as shown in the figures, without these being limiting to its particular embodiment shown, has a fixing portion suitable to press on the respective first ends 111 and 112 to perform the block; the fixing portion acts in the execution of said block, for example by means of specific fixing grub screws, insertable and operable through a specific side hole.

[0043] Preferably, a solution similar to that of the terminals, specific to the first ends 111 and 112 of the helical elements 101 and 102, is actuated to perform blocking of the second ends 121 and 122 of the helical elements 101, 102 to the slide 10, for example, operating with specific blocking protrusions 12 close to the ends of the slide 10.

[0044] The movement of the slide 10, by means of an action aimed at changing the shape, by means of the change of the temperature, of the helical elements, is controlled by control means 30 comprised in the actuator 1.

[0045] Preferably, the control means comprise heating means 310 suitable to heat one or more helical elements 101, 102 electrically acting on them through the locking elements 200.

[0046] According to a preferred embodiment, the heating means 310 act through the pins 210 and through the terminals 220. Preferably, the pins 210 are united to specific and suitable lugs 311 that, through a power supply, transmit electricity to them such as to change the temperature of the respective helical element.

[0047] Preferably, the possible plurality of first helical elements 101 are joined electrically in series with each other and/or the plurality of second helical elements 102 are joined electrically to each other in series (an example of an electrical diagram comprising two pairs of helical elements 100 is shown in Figure 6) .

[0048] Moreover, in a preferred form of embodiment, the control means 30 comprise cooling means 320 suitable to cool one or more helical elements 101, 102 by moving air inside the slide 10.

[0049] In fact, preferably, the slide 10 and, in particular, box structure 10' , has specific openings or channels 180, on at least one of its faces and facing the helical elements 101, 102, preferably along a section parallel to the main axis X-X.

[0050] Preferably, there is a specific channel 180 in correspondence of each elastic element; in some embodiments a channel 180 is shaped to be suitable to result in ^" the cooling of two parallel elastic elements.

[0051 ] Preferably, the slide 10 has first channels 181 facing the first helical elements 101 and second channels 182 facing the second helical elements 102.

[0052] Preferably, the slide 10, and in particular its box structure 10' , on a face different from that where the channels 180 are formed, also has vent holes 190 suitable to allow the exit of air from its inside to the outside.

[0053] According to a preferred embodiment, the cooling means 320 comprise a cooling fan 321 housed in the frame 20.

[0054] Preferably, the cooling fan 321 is housed in a cooling aperture 25 present in the frame 20, in which the cooling aperture 25 extends perpendicularly from the main axis X-X.

[0055] Preferably, the cooling aperture 25 from the slide 10 to the cooling fan 321 has a tapered shape, so as to facilitate the flow of air moved by the fan 321 to the slide 10.

[0056] Furthermore, according to a preferred embodiment, the cooling means 320 comprise adjustment means 325 suitable to vary the intensity of action of the cooling 32 and, in particular, of the cooling fan 320, depending on the axial position of the slide 10.

[0057] In other words, by means of the adjustment means 325, the position of the slide 10 is assessed, directly as a function of temperature, and therefore the heating, of one or more of the helical elements and, as a function of this position, the action of the fan is thus varied to speed the cooling the helical elements and therefore their return in axial position.

[0058] For example, as shown in the diagram of a test bench in Figure 7, the actuator 1 covered by this invention comprises adjustment means 325 consisting of limit switches 326 and intermediate switches 327; depending on the type of switches actuated by the slide 10 in its axial movement due to the heating of the helical elements, the heating means 310 vary the action of the cooling fan 320.

[0059] According to the above, the trend, as a function of time, of the respective components of the actuator 1, and the position of the slide 10, is, for example, diagrammed in Figure 8.

[0060] Innovatively, the actuator covered by this invention fully satisfies its purpose, which is to provide an effective and reliable actuator.

[0061] Advantageously, the components comprised in the actuator and, in particular the pair of helical elements in a shape-memory alloy, are easily controllable by respectively heating or cooling said helical elements as a function of the position of the slide.

[0062] Moreover, advantageously, the actuation effect is easily manageable thanks to the pair of elements in a shape memory material, one opposed to the other, that only work when commanded, i.e., when heated by the electrical heating means or cooled by the cooling means. In other words, in a pair of helical elements, when a helical element is heated and thus changes shape, according to its metallurgical composition and thus its phase transformation, the other is not energised and remains passive so as to exert a limited mechanical resistance on the first; the first helical element will be cooled, in order to return to its original shape, and thus to return the sled in its starting position.

[0063] A further advantage resides in the easy to produce and manage circuit construction and, in particular in the embodiment with an even number of pairs of helical elements, in which are electrically arranged in series the respective first helical elements and the respective second helical elements. [0064] A still further advantage lies in the manner with which is actuated the locking and electrical powering of the helical elements, which are locked and powered in a simple, direct and safe way. Moreover, advantageously, thanks to the locking elements, and the circuit arrangement, wires and flying circuitries are avoided since all the electrical components are housed in the actuator itself.

[0065] Advantageously, the cooling of two helical elements is also easy to obtain and manage, in particular by using a single cooling fan, the cooling of both helical elements making up a pair is manageable and attainable.

[0066] Moreover, advantageously, the first helical element and the second helical element are mutually isolated from one another. Advantageously, the phase transformation of the first helical element, compared to the second helical element, is controllable, thereby making the actuator itself extremely reliable; for example, electrical excitation of a helical element can only be initiated following the total cooling of the other helical element. In other words, an actuator that is more reliable over time is attainable.

[0067] Advantageously, the actuator offers remarkable flexibility of use and, in fact, if faster cycle times are required, a simultaneous cooling of the second helical element is foreseeable during the heating of the first helical element.

[0068] A further advantage resides in the fact that each pair of helical elements is isolated from the other, housed in a separate cavity within the slide so as to avoid any electrostatic currents between them, which allows the actuator to be significantly reliable and safe .

[0069] Furthermore, advantageously, the actuator of ers a marked flexibility of use having an excellent size/power ratio and thus being suitable to find applications in fields that require extremely small size, but high actuation powers, such as, for example, home automation.

[0070] Moreover, advantageously, the actuator is easy to produce and implement, being modular in its parts. For example, embodiments are foreseeable comprising a plurality of slides positioned in parallel along the main axis .

[0071] Advantageously, the actuator offers significant design flexibility, its actuation power being a function of the number of pairs of helical elements present; therefore, as a function of the needs, a designer can design the actuator with a plurality of pairs of helical elements.

[0072] Advantageously, the heating elements act directly through the locking elements, thus avoiding the presence of electrical wires outside the actuator.

[0073] To the embodiments of said actuator, one skilled in the art, in order to meet specific needs, may make variants or substitutions of elements with others functionally equivalent.

[0074] In a further embodiment, the slide 10 is guided in its translational movement with respect to the frame 20 by means of the locking elements 200. In fact, preferably, an embodiment is foreseen, wherein the locking elements 200 are suitable to guide and support the slide 10 in its translation, for example by sliding in specific sliding guides, specially formed and shaped on the box structure 10' of the slide 10. For example in the accompanying figures, this function could be performed, even though here it is performed by the guide 250, by the vent holes 190. In this embodiment, the frame 20 has a structure radically different since the presence of the guide 250 is not necessary in prismatic shape coupling with the sled 10.

[0075] Even these variants are contained within the scope of protection, as defined by the following claims.