Connecting device

Abstract

Connecting device for establishing a mechanical connection between a first body (11) and at least one second body (12), comprising a first connecting element (20) and a second connecting element (22) cooperating therewith, wherein the second connecting element (22) has an engagement portion (27) for a coupling portion (28) of the first connecting element (20), and wherein the first connecting element (20) and the second connecting element (22) are designed to form a positive connection when connected to one another, characterized in that the engagement portion (27) is formed on a holding component (29) which is connected to a core of the second connecting element (22), wherein the holding component (29) and / or the second connecting element (22) consists of or comprises a thermoplastic material, and in that at least one spring (3) is provided,which applies a force which repels the two connecting elements (20, 22) and / or the two bodies (11, 12) from each other and moves the two connecting elements (20, 22) away from each other above a predetermined temperature threshold (T1).

Description

[0001] The invention relates to a connecting device according to the preamble of patent claim 1. It further relates to a space object having at least two structural components which are connected to one another by means of at least one such connecting device.

[0002] Space objects, such as satellites, space stations, or parts thereof, are usually put into orbit around the Earth at the end of their service life. This leads to re-entry into the Earth's atmosphere, where the high temperatures encountered during re-entry cause the space object to burn up. For particularly large space objects, however, the time during re-entry during which the space object is exposed to the high temperatures may not be sufficient to completely burn up the space object. The result is that debris remains and falls to the Earth's surface. The aim is therefore for a space object re-entering the Earth's atmosphere to break up into individual pieces.

[0003] Satellite primary structures are connected by connecting elements, such as screws, which are typically made of metallic materials and therefore have high melting points. Various concepts have been developed to achieve a targeted increase in the breakup height of the primary structure during re-entry into the Earth's atmosphere. However, such technologies have little to no commercial application. Failure to comply with existing regulations will result in costly controlled re-entries into the Earth's atmosphere. The technologies being researched are intended to enable more efficient burnup of the critical components inside the satellite. The following methods have been developed to date: • non-explosive devices in which a screw fails at a predetermined breaking point due to targeted active heating of a shape memory actuator; • Washers made of a metallic material with a reduced melting temperature compared to the other fasteners; • Sandwich structure inserts made of thermoplastic material.

[0004] From TW 201627202 A, a passive device for facilitating the disintegration of a space system upon re-entry into the Earth's atmosphere is known, in which the connecting elements have threaded connections and may use detonator assemblies that resemble seals and in which detonators are provided in screw holes as actuators.

[0005] From US 5 695 306 A a fusible link with a fusible alloy is known, which comprises an alloy with a low melting temperature, such as bismuth-lead or bismuth-tin.

[0006] DE 10 2016 205 326 A1 shows and describes a thermally detachable fastening device comprising a screw consisting of a shaft and a head connected by means of a solder material having a lower melting temperature than those temperatures occurring during re-entry into the atmosphere.

[0007] DE 10 2016 212 582 A1 shows and describes a connection arrangement for a satellite with thermally controlled fracture behavior, which includes an actuator element resting on a coupling element. The actuator element and the coupling element have different thermal expansion properties. As a result, when a certain temperature is reached, the actuator element acts on the coupling element with a force sufficient to break through a predetermined fracture point.

[0008] DE 697 02 395 T2 shows and describes two variants of a device for temporarily blocking a relative movement between two bodies which, in the locked state, are firmly connected to one another by means of a tie rod. The first variant serves to decouple and separate the two bodies from one another, and the second variant serves to bring the two bodies closer together until they stop. In the first variant, the tie rod has a predetermined breaking point and is surrounded by a heatable sleeve made of a shape memory material that stretches in the axial direction when heated. When the sleeve stretches axially in this way, axial forces are applied to the tie rod, which lead to a failure of the predetermined breaking point and thus to a severing of the tie rod shaft, thereby decoupled from one another.

[0009] From DE 602 06 835 T2 and US 6 661 331 B2, a thermally controlled unlocking mechanism is known which separates two axially interlocking components when heated.

[0010] A disadvantage of these known devices is that the respective threshold temperature, which causes a connection to melt or an actuator to be triggered and leads to a failure of the main structures of conventional satellites and thus to a breakup of the satellite, is only reached some time after the start of the re-entry phase.

[0011] This shortens the time in which the individual parts created after the breakup can still burn.

[0012] The object of the present invention is to provide a connecting device that leads to early structural disruption of a space object upon re-entry into the Earth's atmosphere. Furthermore, a space object is to be provided that disintegrates at an early stage upon re-entry into the Earth's atmosphere.

[0013] The part of the problem directed to the connecting device is solved with the features of patent claim 1.

[0014] A connecting device for establishing a mechanical connection between a first body and at least one second body, comprising a first connecting element and a second connecting element cooperating therewith, wherein the second connecting element has an engagement portion for a coupling portion of the first connecting element and wherein the first connecting element and the second connecting element are designed to form a positive connection when connected to one another, wherein the engagement portion is formed on a holding component which is connected to a core of the second connecting element, is characterized according to the invention in that the holding component and / or the second connecting element consists of or comprises a thermoplastic material, and in that at least one spring is provided,which applies a force that repels the two connecting elements and / or the two bodies from each other, which moves the two connecting elements away from each other above a predetermined temperature threshold.

[0015] The provision of at least one spring in conjunction with the holding component made of a thermoplastic material causes the connecting device to break apart at an early stage during the thermally induced softening of the thermoplastic material, i.e. already in the initial phase of a re-entry, since the spring force generated when the temperature threshold, i.e. the threshold temperature, is reached causes the structure of the thermoplastic material, which has already softened but has not yet completely dissolved, to break up.

[0016] Further preferred and advantageous design features of the connecting device according to the invention are the subject of subclaims 2 to 12.

[0017] Preferably, the spring only exerts its repulsive force above the specified temperature threshold. This design has the advantage that during regular operation, for example, of a satellite, i.e., before the temperature threshold is reached, no spring forces act on the connecting device, and thus it is not subjected to any stress.

[0018] It is further advantageous if the spring consists of or has a high-temperature shape memory alloy and if the spring only applies the repulsive force in a shape memory state above the specified temperature threshold.

[0019] Preferably, the predetermined temperature threshold is in the range of the melting temperature or in the range of the glass transition temperature of the thermoplastic material.

[0020] It is particularly advantageous if the threshold temperature of the spring's high-temperature shape memory alloy, at which the spring regains or enhances its resilient properties, is lower than the melting temperature or the glass transition temperature of the thermoplastic material. If the spring force then exceeds the maximum tensile strength of the thermoplastic material, which has softened due to the temperature, the thermoplastic support component tears, and the bond between the two bodies is broken. For semi-crystalline thermoplastic material, the term "melting temperature" applies; for amorphous thermoplastic material, however, the glass transition temperature is the relevant value, at which the strength, especially the tensile strength, of the thermoplastic material decreases drastically.

[0021] An advantageous embodiment is one in which the at least one spring acts between the first connecting element and the first body. The spring is supported – directly or indirectly – on the first body and the connecting element, pushing the latter away from the first body and out of the connection with the second body.

[0022] Alternatively, the at least one spring can act between the first connecting element and the second body and be supported on these two components - directly or indirectly.

[0023] Finally, in a further alternative embodiment, the at least one spring can act between the first body and the second body and can be supported on these two bodies - directly or indirectly.

[0024] It is particularly advantageous if the spring is a compression spring. Thanks to the high-temperature shape memory alloy, this spring only builds up its compressive force or increases an initially existing compression spring force when a material-specific threshold temperature is reached, which lies in the range of the melting temperature or the glass transition temperature.

[0025] In a preferred embodiment, which can be combined with other embodiments, it is provided that the thermoplastic material has a melting point or a glass transition point which lies in a range between 150 °C and 300 °C, preferably between 200 °C and 250 °C.

[0026] Particularly preferred is also an embodiment which can be combined with other embodiments and in which the temperature threshold of the high-temperature shape memory alloy lies in a range between 150 °C and 300 °C, preferably between 200 °C and 250 °C.

[0027] A particularly advantageous embodiment is one in which the engagement section and the coupling section form a threaded pair. When the thermoplastic material softens and the spring force builds up essentially simultaneously, the thermoplastic material in the finely structured threads fails at a particularly early point in time, so that the connection between the two bodies determined by the connecting device breaks prematurely and the bodies decouple.

[0028] It is particularly advantageous if the first connecting element is a screw and the second connecting element is a nut or an internal thread insert.

[0029] The part of the problem directed at the space object is solved according to claim 10 by a space object with at least two structural components that are connected to one another by means of at least one connecting device according to the invention. A space object designed in this way disintegrates into smaller individual components during the initial phase of re-entry, each of which can quickly and almost completely burn up in the high-temperature plasma generated during re-entry into the atmosphere.

[0030] Preferred embodiments of the invention with additional design details and further advantages are described and explained in more detail below with reference to the accompanying drawings.

[0031] It shows: Fig. 1 a schematic representation of a space object consisting of several individual components which are connected to one another by means of connecting devices according to the invention, and Fig. 2 a sectional drawing through a connecting device according to the invention in a space object.

[0032] Fig. 1 schematically shows a space object 1 in the form of a satellite, which consists of several bodies 11, 12, 13, 14 forming individual components, which are connected to each other by means of several connecting devices 2 and of which one is described below with reference to the Fig. 2 is described by way of example. In the example shown, the space object 1 has four structural components, each of which is assigned to one of the bodies 11, 12, 13, 14, namely a satellite fuselage structure 11', a battery pack structure 12', a first solar panel structure 13' and a second solar panel structure 14'. These structural components are each connected to one another by means of the associated connecting devices 2, of which Fig. 1 only two connecting devices 2 are shown symbolically.

[0033] The Fig. The connecting device 2 shown in Figure 2 is shown by way of example as a screw connection with a threaded pair; however, the invention can also be implemented in any other mechanical connection by means of a connecting element, for example in a connection by means of rivets, pins or the like, in which part of the connecting element consists of a thermoplastic material.

[0034] Fig. 2 shows one of the connecting devices 2 according to the invention for establishing a mechanical connection, for example between the first body 11 and the second body 12. The connecting devices between the other bodies are essentially identical and the following description also applies in this regard.

[0035] The connecting device 2 consists of a first connecting element 20 and a second connecting element 22 cooperating with the first connecting element. The first connecting element 20 is formed by a screw 24 provided with an external thread 23. The second connecting element 22 is provided with an internal thread 25, which is formed on a holding component 29 designed as an internal thread insert 26. The internal thread 25 forms an engagement section 27 for a coupling section 28 of the first connecting element 20 formed by the external thread 23; the engagement section 27 and the coupling section 28 thus form an internal threaded connection. Thus, the first connecting element 20 and the second connecting element 22 are designed to form a positive connection when connected to one another.

[0036] The internal thread insert 26 is connected to a core 22' of the second connecting element 22, which core consists of or comprises a thermoplastic material; in the example shown, it is screwed into the core 22' by means of an external threaded connection 21. Alternatively or additionally, the retaining component 29 can consist of or comprise a thermoplastic material.

[0037] Furthermore, a spring 3 designed as a compression spring 30 is provided, which preferably consists of or comprises a high-temperature shape memory alloy and exerts a repulsive force on the two connecting elements 20, 22 and / or the two bodies 11, 12, so that the spring 3, in the example shown, acts indirectly between the first connecting element 20 and the first body 11. Advantageously, the spring 3 only exerts its spring force above a predetermined temperature threshold T1, for example, in a shape memory state released by heating above the predetermined temperature threshold T1.

[0038] For the purpose of applying the spring force, the first body 11 is provided with a sleeve 4 having a stepped through-bore 40 through which the screw 24 passes. The head 24' of the screw 24 is received in a pot-shaped insert 42 which is inserted into the through-bore 40 of the sleeve 4 at a first end 41 of the sleeve 4 and which is provided with a first inner annular step 43 which forms a washer for the screw 24. The spring 3, designed as a compression spring 30, is supported with its first end 31 on the side of the first inner annular step 43 facing away from the head 24' of the screw 24. At the second end 44 of the sleeve 4, a further inner annular step 45 is formed, which narrows the inner diameter of the through-bore 40 and against which the spring 3 is supported with its second end 32.The spring force of the spring 3 designed as a compression spring 30 thus acts between the sleeve 4 inserted into the first body 11 and the pot-shaped insert 42, thus on the head 24' of the screw 24 in a force direction that pushes the screw 24 out of the sleeve 4.

[0039] If the connecting device 2 is heated—for example, upon re-entry into the Earth's atmosphere—the thermoplastic material of the internal thread insert 26 softens, and the spring 3 regains its shape-memory resilient properties. The resulting spring force pushes the screw 24 out of the softened internal thread insert 26, and the positive and non-positive connection between the first body 11 and the second body 12 is released.

[0040] The invention is not limited to the above embodiment, which merely serves to generally explain the core concept of the invention. Within the scope of protection, the device according to the invention may also take on embodiments other than those described above. In particular, the device may have features that represent a combination of the respective individual features of the claims.

[0041] Reference symbols in the claims, the description and the drawings serve only to improve the understanding of the invention and are not intended to limit the scope of protection. List of reference symbols 1 space object 2 connecting device 3 springs 4 sleeve 11 first body 11' satellite fuselage structure 12 second body 12' battery pack structure 13 third body 13' first solar panel structure 14 fourth body 14' second solar panel structure 20 first connecting element 21 external thread connection 22 second connecting element 22' Core of the second connecting element 22 23 external threads 24 screw 24' head of screw 24 25 internal threads 26 internal thread insert 27 intervention section 28 Coupling section 29 Bracket component 30 compression spring 31 first end of the compression spring 30 32 second end of the compression spring 30 40 through hole 41 first end of sleeve 4 42 pot-shaped insert 43 first inner ring stage 44 second end of sleeve 4 45 second inner ring stage T1 temperature threshold

Claims

[1] Connecting device for establishing a mechanical connection between a first body (11) and at least one second body (12), comprising a first connecting element (20) and a second connecting element (22) cooperating therewith, wherein the second connecting element (22) has an engagement portion (27) for a coupling portion (28) of the first connecting element (20) and wherein the first connecting element (20) and the second connecting element (22) are designed to form a positive connection when connected to one another, wherein the engagement portion (27) is formed on a holding component (29) which is connected to a core of the second connecting element (22), characterized by , that the holding component (29) and / or the second connecting element (22) consists of or comprises a thermoplastic material, and that at least one spring (3) is provided which applies a force which repels the two connecting elements (20, 22) and / or the two bodies (11, 12) from one another and which moves the two connecting elements (20, 22) away from one another above a predetermined temperature threshold (T1). [2] Connecting device according to claim 1, characterized by that the spring (3) only develops its repulsive force above the specified temperature threshold (T1). [3] Connecting device according to claim 2, characterized by that the spring (3) consists of or comprises a high-temperature shape memory alloy and that the spring (3) applies the repulsive force in a shape memory state above the predetermined temperature threshold (T1). [4] Connecting device according to one of claims 1 to 3, characterized bythat the specified temperature threshold (T1) is in the range of the melting temperature or in the range of the glass transition temperature of the thermoplastic material. [5] Connecting device according to one of the preceding claims, characterized by that the at least one spring (3) acts between the first connecting element (20) and the first body (11). [6] Connecting device according to one of claims 1 to 4, characterized by that the at least one spring (3) acts between the first connecting element (20) and the second body (12). [7] Connecting device according to one of claims 1 to 4, characterized by that the at least one spring (3) acts between the first body (11) and the second body (12). [8] Connecting device according to one of the preceding claims, characterized by that the spring (3) is a compression spring (30). [9] Connecting device according to one of the preceding claims, characterized bythat the thermoplastic material has a melting point or a glass transition point which lies in a range between 150 °C and 300 °C, preferably between 200 °C and 250 °C. [10] Connecting device according to one of the preceding claims, characterized by that the temperature threshold (T1) of the high-temperature shape memory alloy is in a range between 150 °C and 300 °C, preferably between 200 °C and 250 °C. [11] Connecting device according to one of the preceding claims, characterized by that the engagement portion (27) and the coupling portion (28) form a thread pair. [12] Connecting device according to claim 11, characterized by that the first connecting element (20) is a screw (24) and the second connecting element (22) is a nut or an internal thread insert (26). [13] Space object with at least two structural components (11, 12, 13, 14) which are connected to one another by means of at least one connecting device (2) according to one of the preceding claims.

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