Actuator having elements made of shape memory alloy

Abstract

An actuator (1) has two connection pieces (3, 4) spaced apart from one another in the direction of an actuator main axis (2), a preloading arrangement (26) which applies a preloading force which pushes the connection pieces (3, 4) away from one another in the direction of the actuator main axis (2), and two contraction elements (8) which extend along the actuator main axis (2) between the connection pieces (3, 4) and are formed on the basis of a shape memory alloy (18) and can be controlled so as to shorten their free lengths (15) between the connection pieces (3, 4). The contraction elements (8) extending between the connection pieces (3, 4) are arranged axially and / or rotationally symmetrically to one another in relation to the actuator main axis (2) and extend at the same angles to a reference plane to which the actuator main axis (2) is a surface normal. Parallel to the reference plane, the connection pieces (3, 4) have rectangular outlines (34). The contraction elements (8) are strip-like, extend parallel to a main extension plane and have widths (14) extending parallel to the reference plane. Across their widths (14), the two contraction elements (8) are fixed to the connection pieces (3, 4) on two parallel sides (35) of the outlines (34) of the connection pieces (3, 4). The widths (14) of the contraction elements (8) are at least 50% of the side lengths (37) of the two parallel sides (35) of the outlines (34) of the connection pieces (3, 4).

Description

[0001] ACTUATOR WITH SHAPE MEMORY ALLOY ELEMENTS

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The invention relates to actuators with two connecting pieces spaced apart in the direction of an actuator main axis, a preload arrangement that applies a preload force that pushes the connecting pieces apart in the direction of the actuator main axis, and contraction elements extending along the actuator main axis between the connecting pieces, which are formed from a shape memory alloy and can be controlled to shorten their lengths between the connecting pieces. More specifically, the present invention relates to an actuator with the features of the preambles of independent patent claims 1, 20, and 24.

[0004] Furthermore, the invention relates to a device for clamping and releasing a bolt with a clamping sleeve for receiving a portion of the bolt and with such an actuator which is arranged so that the clamping sleeve is relieved when its contraction elements are controlled to shorten their lengths between the connecting pieces.

[0005] STATE OF THE ART

[0006] An actuator having the features of the preambles of independent patent claims 1, 20, and 24 is known from DE 10 2021 103 203 B3. The actuator has two end pieces elastically supported against one another by a compression spring in the direction of an actuator main axis, and a wire made of a shape memory alloy that is stretched between the end pieces along the actuator main axis and can be controlled to change its length. The wire has at least six contiguous longitudinal sections that are stretched next to one another along the actuator main axis between the end pieces, whereby the arrangement of the end pieces is stabilized against relative tilting. Preferably, the wire has at least 12, more preferably at least 24, and even more preferably at least 36 contiguous longitudinal sections, each of which is stretched between the end pieces along the actuator main axis.The arrangement of the lengths stretched between the end pieces is preferably rotationally symmetrical with respect to the main actuator axis as many times as there are lengths stretched between the end pieces. Specifically, the lengths are stretched between points on the end pieces that are arranged along a circular arc-shaped circumference of the respective end piece, running at a distance around the main actuator axis. The wire can be guided between its lengths via hooks arranged on the circumferences of both end pieces. Equal angles of the lengths to a reference plane, to which the main actuator axis is a surface normal, are preferably 90°, and the lengths stretched between the end pieces are preferably arranged at distances from the main actuator axis that range from one to three times their length between the end pieces.The wire is thermally shortened by applying an electrical voltage between its ends. The compression spring is dimensioned to lengthen the wire again as soon as the wire cools below the transition temperature of its shape memory alloy. The known actuator is specifically designed to force a clamping sleeve into a receptacle in a base body. The force exerted on the clamping sleeve is reduced by shortening the wire. This releases a bolt clamped in the clamping sleeve.

[0007] DE 10 2019 100 694 A1 discloses a shape memory actuator assembly comprising a wire-shaped shape memory element, a first deflecting body, and a second deflecting body. The deflecting bodies are arranged at a distance from one another. The wire-shaped shape memory element is wound several times around the first deflecting body and the second deflecting body, forming an actuator arrangement between them. At least one wire holder region on the respective deflecting body and the sections of the wire-shaped shape memory element contacting the wire holder region are embedded in a potting compound. The potting compound is electrically insulating and thus insulates the individual windings of the wire-shaped shape memory element from one another. Preferably, potting pots are assigned to both deflecting bodies, wherein the potting compound mechanically couples the respective deflecting body to the respective potting pot for transmitting actuator forces.The potting compound completely encloses the respective deflection body. The potting pot comprises a fastening element for dissipating the actuator forces. Grooved wire receptacles are formed in the wire holder area of ​​the respective deflection body. A section of the actuator arrangement between the first deflection body and the second deflection body can be embedded in an actuator potting element that is integrally bonded to the potting compound. The material selected for the actuator potting element is electrically insulating and has sufficient elasticity so that the actuator function is not significantly affected. In all embodiments of the known shape memory actuator arrangement, the width of the actuator arrangement embedded in the actuator potting element between the deflection bodies is significantly less than 20% of the distance between the deflection bodies. In other words, the known shape memory actuator arrangement is narrow and elongated.

[0008] DE 195 297 12 A1 discloses a shape memory actuator for an actuating mechanism, for example, on spacecraft. The actuator comprises a heatable actuator made of a shape memory alloy. The actuator consists of at least one thin wire arranged in several windings. The windings of the wire are electrically insulated from one another and can be heated by a current flowing through them. Specifically, the windings of the wire are electrically insulated from one another by being kept apart by spacers. The windings of the wire are guided around elements that can move relative to one another and are positively attached to these elements.

[0009] DE 197 30383 A1 discloses a method for training elements made of shape memory alloy. To carry out the method, an actuator is provided with the elements made of the shape memory alloy, and the actuator is trained in accordance with the application as an essentially self-contained unit equipped with the untrained elements. A device for carrying out this known method is an actuator with elements made of shape memory alloy. The elements made of shape memory alloy are wires. Windings of the wires form-fittingly wrap around structural elements. In addition to the structural elements to be actuated, removable auxiliary elements are provided. The auxiliary elements comprise a preload spring in conjunction with a guide tube, which is arranged between deflection bodies and has a low rigidity and serves to maintain the shape of the windings of the shape memory alloy wire.Helical grooves are provided on the deflecting elements in such a way that a parallel pull is ensured within the shape memory alloy windings. In a schematic diagram of the deflecting elements with the helical grooves of a predetermined pitch, whose length ratios do not correspond to the other figures and information in DE 197 303 83 A1, the shape memory alloy windings are distributed over a width running transversely to their longitudinal extents, which is approximately 60% of the distance between the windings' support on the deflecting elements.

[0010] EP 0 137 502 A2 discloses an actuator comprising several elements made of shape memory material. The elements are arranged parallel to one another between a stationary connecting piece and a movable connecting piece. The elements can be wires, coil springs, or strips of rectangular cross-section. The stationary connecting piece and the movable connecting piece are elastically supported against one another via a piston and cylinder arrangement with a coil spring located in the cylinder.

[0011] US 2018 / 0 266 400 A1 discloses an actuator with a tubular braid made of electrically insulated shape memory alloy wires. The tubular braid extends between two connectors.

[0012] DE 10 2017 007 596 A1 discloses a shape memory actuator assembly comprising a first deflecting body connected to a first fastening element, a second deflecting body spaced apart from the first deflecting body and connected to a second fastening element, and a one-piece shape memory element connected at its ends to the first deflecting body and / or the second deflecting body. A multiple winding of the one-piece shape memory element extends around the first deflecting body and the second deflecting body.

[0013] EP 2 028 309 B1 discloses a band with a fabric made of threads made of a shape memory alloy.

[0014] OBJECT OF THE INVENTION

[0015] The invention is based on the object of providing actuators and a device for clamping and releasing a bolt with such an actuator that are easier to manufacture and adaptable to the respective application. SOLUTION

[0016] The object of the invention is achieved by actuators having the features of independent patent claims 1, 20 and 24 and a device for tensioning and releasing a bolt with this actuator according to the invention according to patent claim 27. The dependent patent claims relate to preferred embodiments of the actuators according to the invention.

[0017] DESCRIPTION OF THE INVENTION

[0018] In an actuator according to the invention with two connecting pieces spaced apart in the direction of a main axis, a preload arrangement that applies a preload force that pushes the connecting pieces apart in the direction of the actuator's main axis, and with two contraction elements running along the actuator's main axis between the connecting pieces, which contraction elements are formed from a shape memory alloy and can be controlled to shorten their free lengths between the connecting pieces, the contraction elements running between the connecting pieces are arranged axially and / or rotationally symmetrically to one another with respect to the actuator's main axis. The contraction elements run at equal angles to a reference plane, to which the actuator's main axis is a surface normal. Parallel to the reference plane, the connecting pieces have rectangular outlines.The contraction elements are band-shaped, each extending parallel to a main extension plane and having widths parallel to the reference plane. The two contraction elements are fixed to the connecting pieces across their widths on two mutually parallel sides of the connecting pieces' floor plans. The widths of the contraction elements are at least 50% of the side lengths of the two mutually parallel sides of the connecting pieces' floor plans.

[0019] The relatively wide contraction elements each extend along a straight side edge or flat side surface of each of the two connecting pieces and are then secured to these side edges or side surfaces of the two connecting pieces. This allows the contraction elements to be not only easily mounted on the connecting pieces, but also disassembled, for example, to replace the preload assembly or at least parts of the preload assembly or the contraction elements themselves. Such a replacement can be useful for adapting the actuator to its specific application. The distance between the connecting pieces and thus the height of the actuator can be varied by varying the length of the contraction elements between the connecting pieces.

[0020] Preferably, the widths of the contraction elements are at least 60%, more preferably at least 75%, and often at least 90% of the side lengths of the two parallel sides of the footprints of the connecting pieces. In one embodiment, the widths of the contraction elements are approximately the same as their free lengths between the connecting pieces. However, the free lengths of the contraction elements can also be significantly larger than their widths.

[0021] Radial distances of the contraction elements from the main actuator axis are generally no less than 20%, preferably no less than 30%, and often, particularly preferably, no less than 70% of their widths. On the other hand, the radial distances of the contraction elements from the main axis are generally no greater than 100%, preferably no greater than 80%, and often, particularly preferably, no greater than 60% of their widths. In a preferred embodiment, the radial distances of the contraction elements from the main actuator axis are approximately half their widths.

[0022] The two contraction elements can be arranged on the side edges or side surfaces of connecting pieces with square bases. If the sides of the bases of the connecting pieces have different lengths, then the contraction elements are preferably fixed on the sides with the longer side length, i.e., where there is more space. With the two contraction elements located opposite each other across the main actuator axis, a preload arrangement arranged between the connecting pieces remains accessible across their spacing. For example, with a width of the contraction elements equal to their free length between the connecting pieces, this is possible without any risk of actuator instability due to mutual tilting of the connecting pieces.

[0023] The equal angles at which the contraction elements extend to the reference plane to which the actuator main axis is a surface normal are preferably right angles, i.e. they are preferably 90°.

[0024] Each contraction element can be divided in its width direction into, in particular, two partial contraction elements, whose partial widths add up to the width of the respective contraction element. Such a division of the contraction elements can be advantageous for securing the contraction elements to the connecting pieces across their entire widths. For example, cross members for the contraction elements between the partial contraction elements can be supported on a base structure of the respective connecting piece.

[0025] Each contraction element can comprise a band running between the connecting pieces and clamped to the connecting pieces, or a plate made of the shape memory alloy running between the connecting pieces and clamped to the connecting pieces, the band width of which is at least 90% and preferably at least 95% of the width of the respective contraction element. Such a band, and in particular such a plate made of the shape memory alloy, exhibits high dimensional rigidity in the critical directions. Thus, the two connecting pieces are guided mutually with high rigidity by the contraction elements attached to them.

[0026] Alternatively, or in addition to the shape memory alloy strip, each contraction element may comprise at least eight lengths of shape memory alloy wire extending between the terminals and distributed over at least 90%, and preferably at least 95%, of the width of the contraction element. An advantage of using shape memory alloy wire is that, unlike a shape memory alloy strip or sheet, such wire is commercially available in a variety of thicknesses in a trained form. The lengths of wire of each contraction element preferably extend in its main plane of extension or parallel to its main plane of extension. Preferably, each of the contraction elements comprises at least 16, and more preferably at least 32, lengths of shape memory alloy wire.The number of length sections of each contraction element can also be much larger and can reach or even exceed one hundred, for example.

[0027] One-quarter, one-third, or half of the lengths of each contraction element can then be connected, so that each contraction element has four, three, or two non-connected wires made of the shape memory alloy, which can then be connected in parallel when energized for resistive heating above the transition temperature of the shape memory alloy. The connected wires made of the shape memory alloy can be guided around the ends of the respective band-shaped contraction element via end-side deflection elements.These deflection bodies then extend across the width of the respective band-shaped contraction element; and in a preferred embodiment of the actuator according to the invention, they are each formed, at least on their outer circumference, from a thermally and electrically insulating material in order to insulate the individual turns of the shape memory alloy wire both thermally and electrically from the connecting pieces and, in particular, electrically from each other.

[0028] Each contraction element, in particular each contraction element comprising lengths of a shape memory alloy wire, can have a plastic matrix in which the lengths of the wire and optionally reinforcing fibers are embedded. The reinforcing fibers are preferably not electrically conductive. With the aid of the plastic matrix, in particular if reinforcing fibers are embedded therein, a shape stiffening of the contraction elements is achieved similar to that achieved with a shape memory alloy strip, although the contraction elements contain inexpensive, commercially available shape memory alloy wire. The reinforcing fibers can, in particular, be oriented in intersecting directions with a diagonal course to the lengths of the contraction elements between the connecting pieces.

[0029] Alternatively, or in addition to direct electrical, i.e., resistive, heating of strips or wires made of the shape memory alloy, indirect heating can also be implemented in the actuator according to the invention by each contraction element having at least one heating element arranged adjacent to the shape memory alloy. This heating element can also be an electrical heating element that can be controlled to increase the temperature by applying an electrical voltage between its ends.

[0030] The heating elements separated from the shape memory alloy and the strips, plates, or wires formed therefrom have the advantage that the cross-section of the strips, plates, or wires can be increased depending on the required forces to be applied by the contraction elements, without this having an impact on the direct resistive heating of the strips, plates, or wires. The relative arrangement of the heating elements to the strips, plates, or wires made of the shape memory alloy can be fixed in the actuator according to the invention simply by embedding the heating elements and the strips or wires together in the plastic matrix. Thermal insulation provided by the plastic matrix can be utilized in this process. The thermal insulation delays the dissipation of the thermal energy introduced by the heating elements and thus accelerates the heating of the shape memory alloy above its transition temperature.

[0031] In the actuator according to the invention, the shape memory alloy is preferably one that reduces the length of the contraction elements between the connecting pieces when the temperature rises above its transition temperature. The preload force of the preload arrangement can be dimensioned or preloaded such that it lengthens the contraction elements again as soon as the shape memory alloy cools below its transition temperature. However, the shape memory alloy can also be a two-way shape memory alloy that automatically lengthens when its temperature drops below its transition temperature.

[0032] In a preferred embodiment of the actuator according to the invention, a compression spring of the preloading arrangement is supported on one of the connecting pieces via an abutment, the relative position of which is adjustable relative to one of the connecting pieces in the direction of the actuator's main axis. By linearly displacing the abutment relative to one of the connecting pieces in the direction of the actuator's main axis, the preload of the compression spring can be varied and, for example, increased to such an extent that the compression spring elongates the contraction elements again as soon as the shape memory alloy cools below its transition temperature.

[0033] The adjustability of the relative position of the abutment relative to one of the connecting pieces can be achieved by means of adjusting screws aligned along the main actuator axis. Preferably, three adjusting screws are provided in a rotationally symmetrical arrangement around the main actuator axis. With these three adjusting screws, the abutment can be displaced linearly relative to the connecting piece without the need for additional linear guidance for the abutment relative to the connecting piece. If all three adjusting screws are of the same design, it is sufficient to turn all three adjusting screws by the same angle in the same direction of rotation. However, by turning the adjusting screws differently, the angular adjustment of the abutment relative to the connecting piece can also be carried out, for example to compensate for an end face of the compression spring that is not exactly perpendicular to the main actuator axis.Furthermore, the adjusting screws can also be loosened to such an extent that the compression spring can be replaced without the need for further disassembly of the actuator according to the invention if free access to the compression spring is possible between the contraction elements.

[0034] In a further preferred embodiment of the actuator according to the invention, the prestressing arrangement comprises tension wires extending along the actuator's main axis between two further connecting pieces. The two further connecting pieces are arranged on two arms, each extending away from one of the connecting pieces along the actuator's main axis and intersecting along the actuator's main axis, so that the sequence of the further connecting pieces along the actuator's main axis is reversed relative to the connecting pieces rigidly connected to them via the arms. The tension wires can be formed from a superelastic shape memory alloy. The fact that the shape memory alloy of the tension wires is superelastic means that the tension wires are in a superelastic state during the intended use of the actuator and the control of its contraction elements to a length shortening that lengthens the tension wires.The shape memory alloy of the tension wires is located slightly above its transition temperature, and as the tension wires are lengthened, the shape memory alloy is increasingly transferred from its high-temperature phase to its low-temperature phase, in which the tension wires are longer.

[0035] In the last-described embodiment of the actuator, the increase in distance between the additional connecting pieces in the direction of the actuator's main axis resulting from the shortening of the contraction elements can also be tapped and utilized. Furthermore, means can be provided for controlling the tension wires to shorten their length by increasing the temperature of their shape memory alloy above its transition temperature. In particular, the tension wires can be controlled to shorten their length in order to lengthen the contraction elements, which were previously controlled to shorten their length by increasing the temperature and then have already cooled down, back to their original length.

[0036] Typically, the preload arrangement comprises a compression spring that is subjected to a compressive preload between the connecting pieces. The compression spring can, for example, comprise a helical compression spring, a disc spring and / or a friction spring. In this case, a preload arrangement comprising a friction spring with intermeshing ring elements that support one another via conical surfaces (see www.reibungsfeder.de) is generally advantageous in an actuator having the features of the preambles of independent patent claims 1, 20 and 24 and a device for tensioning and releasing a bolt with such an actuator. A high preload force can be applied using a friction spring, with the friction between its ring elements ensuring strong damping of relative movements of the connecting pieces and thus preventing unwanted acceleration of coupled objects in both directions, i.e.both during contraction and during renewed elongation of the contraction elements.

[0037] A friction spring in the shape of a cylinder jacket section, but also any other compression spring in the shape of a cylinder jacket section, can advantageously be combined with bolt-shaped contraction elements made of a shape memory alloy, which are wrapped with heating wires, heating bands, or heating foils in order to control them to shorten their free lengths between the connecting pieces, and which are arranged inside the respective cylinder jacket-shaped compression spring. Such bolt-shaped contraction elements are known, for example, from DE 20 2024 105 238 U1, where they are used together with a pretensioning arrangement comprising bolt-shaped spring elements. For contraction elements arranged inside the cylinder jacket-shaped compression spring, the connecting pieces can be circular disk-shaped, whereby their diameter only needs to be slightly larger, i.e., for example, a maximum of 10% larger, than an outer diameter of the compression spring in order to securely support it.This results in a very compact design in which the contraction elements with the heating wires, heating bands or heating foils run protected between the connecting pieces inside the cylinder jacket section-shaped compression spring.

[0038] In a device according to the invention for clamping and releasing a bolt, comprising a clamping sleeve for receiving a portion of the bolt and an actuator according to the invention, the actuator is arranged such that the clamping sleeve is relieved when the contraction elements of the actuator are controlled to shorten their lengths between the connecting pieces, thus relieving the clamping sleeve of a force applied by the compression spring. Such a device for clamping and releasing a bolt is known in principle, that is, except for the inventive design of the actuator, from DE 102021 103203 B3.

[0039] An actuator according to the invention can also be used for the direct tensioning and releasing of structural elements, for example by having one of its connecting pieces rest against one side of a structural element or several structural elements stacked on top of one another, while an anchor element rests against the other side of this structural element or of the stack of structural elements, which anchor element is supported on the other connecting piece by a tension bolt extending through the structural element or the stack of structural elements, one connecting piece and the compression spring to the other connecting piece. In the case of shortened contraction elements, the anchor element has a maximum distance from one of the connecting pieces at which the structural element or the stack of structural elements can be arranged between one of the connecting pieces and the anchor element.When the shape memory alloy cools and the contraction elements elongate again, the structural element or stack of structural elements is tensioned between one of the connecting pieces and the anchor element. This tension can be specifically relieved by controlling the contraction elements to shorten their length between the connecting pieces.

[0040] Advantageous further developments of the invention emerge from the patent claims, the description and the drawings.

[0041] The advantages of features and combinations of several features mentioned in the description are merely exemplary and can be effective alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0042] With regard to the disclosure content – ​​not the scope of protection – of the original application documents and the patent, the following applies: Further features can be found in the drawings – in particular the illustrated geometries and the relative dimensions of several components to one another, as well as their relative arrangement and operative connection. The combination of features of different embodiments of the invention or features of different patent claims is also possible, deviating from the chosen references of the patent claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features of different patent claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent claims of the granted patent. The number of features listed in the patent claims and the description are to be understood as meaning that exactly this number or a greater number than the stated number is present, without the need for the explicit use of the adverb "at least." Thus, for example, if reference is made to a compression spring, this is to be understood as meaning that exactly one compression spring, two compression springs, or more compression springs are present. The features listed in the patent claims may be supplemented by further features or may be the only features present in the subject matter of the respective patent claim.

[0043] The reference signs contained in the patent claims do not represent a limitation of the scope of the subject-matter protected by the patent claims. They serve solely to make the patent claims easier to understand.

[0044] BRIEF DESCRIPTION OF THE CHARACTERS

[0045] In the following, the invention is further explained and described with reference to preferred embodiments shown in the figures.

[0046] Fig. 1 is a perspective view of an embodiment of an actuator according to the invention.

[0047] Fig. 2 is a perspective view of another embodiment of an actuator according to the invention.

[0048] Fig. 3 is a view basically corresponding to Fig. 2, in which some turns of a shape memory alloy wire are omitted to show an internal structure of a contraction element of the actuator of Fig. 2.

[0049] Fig. 4 is a perspective view of the actuator according to Figs. 2 and 3, in which a connector of the actuator is omitted to show an adjustment device of the actuator.

[0050] Fig. 5 is a perspective view of the actuator according to Figs. 2 to 4 from a similar viewing direction as in Fig. 4, but showing its two connecting pieces. Fig. 6 is an exploded view of the actuator according to Figs. 2 to 5, viewed from the same viewing direction as Figs. 2 and 3.

[0051] Fig. 7 is a perspective view of another embodiment of an actuator according to the invention.

[0052] Fig. 8 is a view basically corresponding to Fig. 7, in which some turns of a wire and a shape memory alloy tension wire are omitted to show an internal structure of a contraction element and a biasing assembly of the actuator according to Fig. 7.

[0053] Fig. 9 is a view generally corresponding to Figs. 7 and 8, with all turns of the wire and the shape memory alloy tension wire omitted to show the internal structure of the contraction element and the biasing assembly of the actuator according to Figs. 7 and 8.

[0054] Fig. 10 is an exploded view of the actuator according to Figs. 7 to 9 with the same viewing direction as that of Figs. 7 to 9.

[0055] Fig. 11 is an axial sectional view of an embodiment of another actuator according to the invention.

[0056] Fig. 12 is an external perspective view of the embodiment of the other actuator according to the invention shown in Fig. 11; and

[0057] Fig. 13 is an axial sectional view of a friction spring of the embodiment of the other actuator according to the invention shown in Figs. 11 and 12.

[0058] FIGURE DESCRIPTION

[0059] The actuator 1 shown in Fig. 1 has two connecting pieces 3 and 4 spaced apart from one another in the direction of a main actuator axis 2. The connecting pieces 3 and 4 are dimensionally stable, solid plates with square outlines 34 defined by pairs of parallel sides 35 and 36, a central opening 5 on the main actuator axis 2 and three threaded holes 6 in each of their four side surfaces for receiving fastening screws 7. Two band-shaped contraction elements 8 run along and here also parallel to the main actuator axis 2 between the connecting pieces 3 and 4. The band-shaped contraction elements 8 are fixed to opposite side surfaces of the connecting pieces 3 and 4 across their entire widths. For this purpose, what is shown in Fig.1 is not shown, fastening screws 7 with their threaded shafts pass through holding elements 9 and the contraction elements 8 into the threaded holes 6 in the respective side surface and are supported by their screw heads on the holding elements 9. The contraction elements 8 are formed on the basis of a shape memory alloy and can be controlled to shorten their lengths between the connecting pieces 3 and 4 by heating the shape memory alloy above its transition temperature. In the opposite direction along the main actuator axis 2, the connecting pieces 3 and 4 are pressed apart by a compression spring 10 with an engagement protection sleeve of a pretensioning device 26. The compression spring 10 is supported on the connecting piece 3 via a support plate 11. The compression spring 10 is supported on the connecting piece 4 via a further support plate 12, wherein it is guided in a guide sleeve 13 fastened to this support plate 12.The compression spring 10 is dimensioned and preloaded between the connecting pieces 3 and 4 such that it lengthens the contraction elements 8 again when their shape memory alloy has cooled below its transition temperature. Alternatively or additionally, it is a two-way shape memory alloy, so that the contraction elements 8 automatically return to their original length when the temperature falls below the transition temperature. The band-shaped contraction elements 8 each extend in or parallel to a main extension plane, wherein a width 14 of the contraction elements 8 in a virtual reference plane, to which the actuator main axis 2 is a surface normal, is not only the same size as the side lengths 37 of the sides 35 of the plan views 34 of the connecting pieces 3, 4, but also approximately the same size as a free length 15 of the contraction elements between the connecting pieces 3 and 4.This results in a dimensional rigidity of the contraction elements 8, which suppresses not only relative tilting of the connecting pieces 3 and 4, but also relative displacements of the connecting pieces 3 and 4 transverse to the main actuator axis 2, at least in the direction of the width 14.

[0060] The contraction elements 8 can each have a layered structure consisting of one or more strips or one or more plates made of the shape memory alloy and one or more sheet-like heating elements, which are glued together and / or embedded together in a plastic matrix. The plastic matrix not only holds the layered structure together but also thermally insulates it from the outside, so that heat input by the heating element is largely used to increase the temperature of the strips or plates made of the shape memory alloy in order to exceed their transition temperature. Alternatively or additionally, wires made of the shape memory alloy running along the main actuator axis 2 can also be embedded in such a plastic matrix together with one or more heating elements. Furthermore, the plastic matrix can be reinforced by embedded, preferably non-electrically conductive reinforcing fibers.These reinforcing fibers can be aligned crosswise diagonally to the width 14 and the free length 15.

[0061] A tensioning element (not shown in Fig. 1) can extend from one of the connecting pieces 3 and 4 through the adjacent pressure plate 11 or 12 and the compression spring 10 as well as the opening 5 in the other connecting piece 3 or 4 in order to tension a structural element or a stack of structural elements between the other connecting piece 3 or 4 and an anchor element fastened to the tensioning element and to release it selectively by controlling the contraction elements 8 to shorten their lengths 15 between the connecting pieces.

[0062] This application possibility also exists for the actuator 1 shown in the following figures. Fig. 2 shows that the connecting pieces 3 and 4 of this actuator 1 are each H-shaped within their rectangular footprints 34, with deflecting bodies 16 mounted in the free ends of their legs. Wires 17 made of the shape memory alloy 18 of the contraction elements 8 run around the deflecting bodies 16. Each of the four wires 17 here is wound in a plurality of turns around the two deflecting bodies 16 on corresponding sides of the connecting pieces 3 and 4, with lengths 19 of the wire 17 made of the shape memory alloy 18 running between the connecting pieces 3 and 4 and being distributed across the width 14 of the respective contraction element 8. Each of the four wires 17 according to Fig. 2 accordingly has a plurality of successive lengths 19.The width 14 of the contraction elements 8 is also approximately the same size as their free length 15 between the connecting pieces, which is the free length of the longitudinal sections 19 between the deflecting bodies 16. At the same time, the width 14 here makes up approximately two-thirds of the side length 37 of the sides 35 of the plan views 34, which are somewhat longer here than the other sides 36. Fig. 3, in which one of the wires 17 is omitted, shows that the deflecting bodies 16 each have an insulating body 20, which is guided on a bolt 21 and is provided with grooves 22 on its outer circumference. The grooves 22 guide the windings of the respective wire 17, so that its individual longitudinal sections 19 run at defined lateral distances from one another.For direct resistive heating of the wire 17, in which the lengths 19 are connected in series, the wire 17 can be used without additional insulation because the lengths 19 do not come into electrical contact with each other except via their ends and thus do not electrically short-circuit any part of the respective wire 17.

[0063] Fig. 4 shows, by omitting the connecting piece 3 of the actuator 1 according to Figs. 3 and 4 and from a different angle, an abutment 38 for the compression spring 10, which is formed with free ends of three adjusting screws 24 and whose relative position relative to the connecting piece 3 omitted in Fig. 4 can be adjusted by turning the three adjusting screws 24 arranged rotationally symmetrically around the actuator main axis 2. This adjustability allows both a displacement of the abutment 38 in the direction of the actuator main axis 2 and an angular alignment of the abutment 38 relative to the actuator main axis 2.

[0064] Specifically, the adjusting screws 24 engage in internal threads in a perforated disc 23, which is supported in the direction of the main actuator axis 2 on the connecting piece 3 (not shown here).

[0065] Fig. 5 shows the actuator 1 with the lower connecting piece 3 from a similar perspective as in Fig. 4. The heads of the adjusting screws 24 with their tool engagement surfaces are accessible through holes in the connecting piece 3. By turning the adjusting screws 24, not only can the preload of the compression spring 10 be varied, but the compression spring 10 can also be relieved to such an extent that it can be replaced without further disassembly of the actuator 1.

[0066] The exploded view according to Fig. 6 shows an annular channel 25 in the lower connecting piece 3, in which the compression spring 10, supported by the free ends of the adjusting screws 24, is laterally guided. Furthermore, Fig. 6 shows that the connecting pieces 3 and 4 have tubular extensions that telescopically engage with each other within the compression spring 10 and whose lumens are aligned with the opening 5.

[0067] In the embodiment of the actuator 1 shown in Figs. 7 to 10, the two contraction elements 8 are each divided into two partial contraction elements 27, which are arranged next to one another in the direction of the width of the respective contraction element 8. Partial widths 14' and 14" of the partial contraction elements 27 add up to the width 14 of the contraction elements 8. By subdividing the contraction elements 8, it is possible to support the bolts 21, on which the insulating bodies 20 are guided, even between the partial contraction elements 27. In addition, outriggers 32 and 33 are attached to both connecting pieces 3 and 4. Even taking the outriggers 32 and 33 into account, the widths 14 of the contraction elements 8 are greater than 50% of the side lengths 37 of the sides 35 of the plan views 34 of the connecting pieces 3 and 4.The arms 32 and 33 extend and overlap along the main actuator axis 2, so that further connecting pieces 30 and 31 at the free ends of the arms 32 and 33 have a reverse order along the main actuator axis 2 compared to the connecting pieces 3 and 4 rigidly connected to them. Sections of a tension wire 28 made of a superelastic shape memory alloy 29 run between the further connecting pieces 30 and 31. The tension wire 28 is wound directly around bolts 21, which are each supported not only at their ends but also in their centers on the further connecting pieces 30 and 31. The tension wire 28 is prestressed to such an extent that it is in a superelastic state and thus applies a prestress force that is largely independent of the distance between the connecting pieces 3 and 4 or the further connections 30 and 31, i.e., essentially constant.The preload arrangement 26 of this embodiment of the actuator 1 applies a comparatively small preload force between the connecting pieces 3 and 4, which is distributed evenly over the sides 36 of the further connecting pieces 30 and 31.

[0068] In the other actuator 1 according to the invention shown in Figs. 11 and 12, the connecting pieces 3 and 4 are circular disk-shaped and have a diameter that is only slightly larger than an outer diameter of the compression spring 10 of the pretensioning arrangement 26, which presses the connecting pieces 3 and 4 apart. The compression spring 10 is designed here as a friction spring 39, the internal structure of which is not shown in Figs. 11 and 12. However, Fig. 13 shows that the friction spring 39 is designed with interlocking ring elements 40 to 42 that support one another via complementary conical surfaces 48 and 49. The contraction elements 8, which are designed here as bolt-shaped contraction elements 43, are arranged inside the cylinder-jacket-shaped compression spring 10. The bolt-shaped contraction elements 43 are screwed into the lower connecting piece 3 and are supported on the upper side of the upper connecting piece 4 via screwed-on clamping nuts 8.Between the connecting pieces 3 and 4, the bolt-shaped contraction elements 43 are provided with a heating wire winding 44. Annular projections 46 and 47 of the connecting pieces 3 and 4 serve to radially guide the cylinder-shaped compression spring 10.

[0069] LIST OF REFERENCE SYMBOLS

[0070] Actuator

[0071] Actuator main axis

[0072] connector

[0073] connector

[0074] opening

[0075] threaded hole

[0076] Fixing screw

[0077] Contraction element

[0078] Holding elements

[0079] compression spring

[0080] Backing plate

[0081] Backing plate

[0082] Guide sleeve

[0083] Width ' Partial width

[0084] Partial width

[0085] length

[0086] deflection element

[0087] wire

[0088] Shape memory alloy

[0089] Length section

[0090] Insulating body

[0091] bolt

[0092] groove

[0093] Perforated disc

[0094] Adjusting screw

[0095] Ring canal

[0096] Preload arrangement

[0097] Partial contraction element

[0098] Tension wire superelastic shape memory alloy additional connecting piece additional connecting piece boom

[0099] boom

[0100] Floor plan

[0101] Page

[0102] Page

[0103] Page length

[0104] abutment

[0105] Friction spring

[0106] Ring element

[0107] Ring element

[0108] Ring element bolt-shaped contraction element

[0109] Heating wire wrapping

[0110] clamping nut

[0111] projection

[0112] projection

[0113] Conical surface

[0114] Conical surface

Claims

PATENT CLAIMS 1. Actuator (1) with two connecting pieces (3, 4) spaced apart in the direction of an actuator main axis (2), a preload arrangement (26) which applies a preload force pressing the connecting pieces (3, 4) apart in the direction of the actuator main axis (2), and two contraction elements (8) running along the actuator main axis (2) between the connecting pieces (3, 4), which are formed on the basis of a shape memory alloy (18) and can be controlled to shorten their free lengths (15) between the connecting pieces (3, 4), wherein the contraction elements (8) running between the connecting pieces (3, 4) are arranged axially and / or rotationally symmetrically to one another with respect to the actuator main axis (2) and run at equal angles to a reference plane to which the actuator main axis (2) is a surface normal, characterized in that the connecting pieces (3, 4) are parallel to the reference plane have rectangular floor plans (34),that the contraction elements (8) are band-shaped, each extend parallel to a main extension plane and have widths (14) running parallel to the reference plane, and that the two contraction elements (8) are fixed to the connecting pieces (3, 4) across their widths (14) on two mutually parallel sides (35) of the outlines (34) of the connecting pieces (3, 4), wherein the widths (14) of the contraction elements (8) amount to at least 50% of side lengths (37) of the two mutually parallel sides (35) of the outlines (34) of the connecting pieces (3, 4).

2. Actuator (1) according to claim 1, characterized in that the pretensioning arrangement (26) has a compression spring (10) which is supported on one of the connecting pieces (3, 4) via an abutment (38), the relative position of which relative to one of the connecting pieces (3, 4) is adjustable in the direction of the actuator main axis (2), wherein the relative position of the abutment (38) can optionally be adjusted by means of three longitudinally aligned and rotationally symmetrical about the actuator main axis (2) Adjusting screws (24) arranged around the main actuator axis (2) are adjustable relative to one of the connecting pieces (3, 4).

3. Actuator (1) according to claim 1 or 2, characterized in that the pretensioning arrangement (26) has a friction spring (39) which optionally has ring elements (40 to 42) which engage in one another and are supported on one another via conical surfaces (48, 49).

4. Actuator (1) according to one of the preceding claims, characterized in that the pretensioning arrangement (26) has tensioning wires (28) running along the actuator main axis (2) between two further connecting pieces (30, 31), wherein the two further connecting pieces (30, 31) are arranged on two arms which each extend away from one of the connecting pieces (3, 4) along the actuator main axis (2) and cross each other along the actuator main axis (2).

5. Actuator (1) according to claim 4, characterized in that the tension wires (28) are formed from a superelastic shape memory alloy (29).

6. Actuator (1) according to one of the preceding claims, characterized in that the widths (14) of the contraction elements (8) are at least 60% or 75% or 90% of the side lengths (37) of the two mutually parallel sides (35) of the outlines (34) of the connecting pieces (3, 4).

7. Actuator (1) according to one of the preceding claims, characterized in that radial distances of the contraction elements (8) to the actuator main axis (2) are not more than 100% or 80% or 60% and / or not less than 20% or 30% or 40% of their widths (14).

8. Actuator (1) according to one of the preceding claims, characterized in that the outlines (34) of the connecting pieces (3, 4) are square.

9. Actuator (1) according to one of the preceding claims, characterized in that the equal angles of the contraction elements (8) to the reference plane are 90°.

10. Actuator (1) according to one of the preceding claims, characterized in that each contraction element (8) is divided in the direction of its width (14) into partial contraction elements (27), the partial widths (14', 14") of which add up to the width (14) of the respective contraction element (8).

11. Actuator (1) according to one of the preceding claims, characterized in that each contraction element (8) has a band made of the shape memory alloy (18) which runs between the connecting pieces (3, 4) and is clamped to the connecting pieces (3, 4), the band width of which is at least 90% or 95% of the width (14) of the contraction element (8).

12. Actuator (1) according to one of the preceding claims, characterized in that each contraction element (8) has at least 8 or 16 or 32 length sections (19) of a wire (17) made of the shape memory alloy (18), which run between the connecting pieces (3, 4) and which are distributed over at least 90% or 95% of the width (14) of the contraction element (8).

13. Actuator (1) according to claim 12, characterized in that at least 4 or 8 or 16 length sections (19) of the wire (17) made of the shape memory alloy (18) are connected.

14. Actuator (1) according to claim 13, characterized in that the connected length sections (19) are guided around the ends of the respective band-shaped contraction element (8) via deflecting bodies (16), wherein the deflecting bodies (16) run across the width (14) of the respective band-shaped contraction element (8) and are formed on their circumference from a thermally and electrically insulating material.

15. Actuator (1) according to one of the preceding claims, characterized in that each contraction element (8) has a plastic matrix in which reinforcing fibers are optionally embedded.

16. Actuator (1) according to one of the preceding claims, characterized in that each contraction element (8) is arranged adjacent to the shape memory alloy (18). Heating element which can be controlled to increase the temperature by applying an electrical voltage between its ends.

17. Actuator (1) according to one of the preceding claims, characterized in that the shape memory alloy (18) reduces the length of the contraction elements (8) between the connecting pieces (3, 4) when the temperature increases.

18. Actuator (1) according to claim 13, characterized in that the prestressing force is dimensioned such that it lengthens the contraction elements (8) again as soon as the shape memory alloy (18) cools down again below its transition temperature.

19. Actuator (1) according to one of the preceding claims, characterized in that a tensioning element which is rigid in compression and / or tension in the direction of the actuator main axis (2) extends from one of the connecting pieces (3, 4) along the actuator main axis (2) through the other of the connecting pieces (3, 4), wherein an anchor element is fastened or can be fastened to the free end of the tensioning element on the side of the other of the connecting pieces (3, 4) facing away from the other of the connecting pieces (3, 4).

20. Actuator (1) with two connecting pieces (3, 4) spaced apart in the direction of an actuator main axis (2), a preloading arrangement (26) which applies a preload force pressing the connecting pieces (3, 4) apart in the direction of the actuator main axis (2), and contraction elements (8) extending along the actuator main axis (2) between the connecting pieces (3, 4), which are formed on the basis of a shape memory alloy (18) and can be controlled to shorten their free lengths (15) between the connecting pieces (3, 4), wherein the contraction elements (8) extending between the connecting pieces (3, 4) are arranged axially and / or rotationally symmetrically to one another with respect to the actuator main axis (2) and extend at equal angles to a reference plane to which the actuator main axis (2) is a surface normal, characterized in that the preloading arrangement (26) comprises a friction spring (39) has.

21. Actuator (1) according to claim 20, characterized in that the friction spring (39) has ring elements (40 to 42) which engage in one another and are supported on one another via conical surfaces (48, 49).

22. Actuator (1) according to claim 21, characterized in that the contraction elements (8) run between the connecting pieces (3, 4) within the friction spring (39).

23. Actuator (1) according to claim 22, characterized in that the contraction elements (8) are bolt-shaped contraction elements (43) made of the shape memory alloy (18) which are wrapped with heating wires, heating bands or heating foils.

24. Actuator (1) with two connecting pieces (3, 4) spaced apart in the direction of an actuator main axis (2), a pretensioning arrangement (26) which applies a pretensioning force pressing the connecting pieces (3, 4) apart in the direction of the actuator main axis (2) and which has a compression spring (10) in the shape of a cylinder jacket section, and contraction elements (8) which run along the actuator main axis (2) between the connecting pieces (3, 4), which are formed on the basis of a shape memory alloy (18) and can be controlled to shorten their free lengths (15) between the connecting pieces (3, 4), wherein the contraction elements (8) running between the connecting pieces (3, 4) are arranged axially and / or rotationally symmetrically to one another with respect to the actuator main axis (2) and run at equal angles to a reference plane to which the actuator main axis (2) is a surface normal, characterized in that Contraction elements (8) between the connecting pieces (3,4) extend within the cylinder jacket section-shaped compression spring (10)., 25. Actuator (1) according to claim 24, characterized in that the contraction elements (8) are bolt-shaped contraction elements (39) made of the shape memory alloy (18) which are wrapped with heating wires, heating bands or heating foils.

26. Actuator (1) according to claim 24 or 25, characterized in that the compression spring (10) has a friction spring (39) with ring elements (40 to 42) which engage in one another and are supported on one another via conical surfaces (48, 49).

27. Device for clamping and releasing a bolt with a clamping sleeve for receiving a portion of the bolt and an actuator (1) according to one of the preceding claims, which is arranged so that the clamping sleeve is relieved when its contraction elements (8) are controlled to shorten their lengths (14) between the connecting pieces (3, 4).

Images