DE19958375A1 - System for transferring force, especially in aircraft construction, consists of tubes connected by coaxial sleeve, first tube being glued to sleeve and gap between second tube and sleeve containing pressure medium - Google Patents

Abstract

System for transferring force consists of tubes (10, 20) connected by a coaxial sleeve (30). The first tube (10) is glued to the sleeve and there is a gap (50) between the second tube (20) and the sleeve. This contains a pressure medium. An Independent claim is included for a method for producing the system.

Description

The invention relates to an improved device for applying force with a Connection of two elements made of materials that are inadequate have a frictional connection, e.g. B. with different thermal expansion behavior, and a method for connecting such incompatible Materials.

A resilient and permanent connection of two elements or joints partners from incompatible materials is a big problem different thermal expansion behavior and the resulting Common glue connections are critical, for example under Permanent loads or when there is heat from outside or this heat is caused by stress.

An example of such an incompatible pairing of materials is the mate rialien carbon fiber reinforced plastic and aluminum. These two works However, fabrics are now due to their excellent weight-specific properties are well suited for highly resilient lightweight structures.

EP 0 841 490 A2 describes a device for applying force with a Ver binding of two elements made of incompatible materials, such as B. coal fiber-reinforced plastic and aluminum, described that despite use extension of these incompatible materials to a greater durability or loading resilience leads.

The device for force introduction described there has a connection of two elements made of materials that are insufficiently interconnected Allow frictional connection, i.e. with different thermal expansion behavior, with a third surrounding the connection area internally Element is provided, the first element and the second element with each other  are positively connected, and the first element and the third element are connected to each other by means of a frictional adhesive connection.

The first element described there can be a fiber composite act tube into which a metallic element, for. B. a Ge winch element is inserted. In the connection area between power line element and tubular rod is a third element a slotted carbon fiber reinforced plastic sleeve with the force application element form inserted conclusively, the sleeve, d. H. the third element, with the staff wall, d. H. with the first element, so that between the in compatible joining partners "metallic force introduction element" and "sleeve carbon fiber reinforced plastic "is a positive connection and the two compatible joining partner "sleeve made of carbon fiber reinforced plastic" and "Pipe wall made of carbon fiber reinforced plastic" non-positively ver are bound.

However, it has been shown that the frictional adhesive connection between Sleeve (3rd element) and pipe wall (1st element) not always with the required Lichen reproducibility can be produced because z. B. in each other the joining partner push the pasty adhesive applied to the sleeve can be partially stripped and thus an uneven and unde finished adhesive application leads.

For many industrial applications, especially for high-precision devices such as they z. B. will be used in the aerospace and automotive industries, however a defined and reproducible bond is required.

Attempts have been made to ensure adequate bonding by using the adhesive oversized fabric was applied. This process is not just un economical, but results in the application of pressure and temperature that for curing adhesive films are required to escape from shot adhesive from the adhesive surface and to contaminate the adhesive area surrounding areas. The necessary cleaning of these areas  Excess adhesive is complex and time-consuming and therefore undesirable.

It was therefore an object of the present invention to provide a device for power introduction with a connection of two elements from an incompatible work fabrics such as z. B. described in the aforementioned EP 0 841 490 A2 will be available to provide the above problems shows. In particular, the frictional adhesive connection between the first element, e.g. B. the tubular rod, and the third element, for. B. the slotted sleeve, reproducible.

This problem is solved by a device for applying force with a Connection of two elements, one connecting area internally surrounding third element is provided, the first element and the second Element are positively connected to each other, the first element and the third element connected by a frictional adhesive connection are characterized in that between the second element and the third element a space for receiving at least one type pressure medium is provided.

In addition, the invention relates to a method for producing such a pre direction.

With the device for applying force according to the invention, in particular especially connect two elements that are incompatible are and are difficult to connect with each other, such as e.g. B. elements made of different materials with different Haf behavior or elements with different thermal expansion behavior.

The structure and design of the device is essentially analog the structure and design of the device as described in EP 0 841 490 A2 is described, to which full reference is made here.  

It is particularly preferred if the first and third elements are made of a fiber-reinforced plastic and the second element made of a metal, in particular made of aluminum.

The first element is the actual fiber composite structure, the second Element the preferably metallic element, via which the force in from the outside this fiber composite structure is to be introduced.

The different elements can differ with paragraphs support, which we do especially with rod or tubular connections is kissing. In the case of rod or tubular connections, these are from sentences designed essentially ring-shaped.

The third element consists of one with the material of the first element compatible material, preferably made of the same material as the first element is the easiest way to ensure that both materials have the same thermal expansion behavior or adhesion possess behavior.

The first element and the third are for the device according to the invention Element frictionally connected to each other via an adhesive connection.

To form the connection between the first element and the force introductory second element is a recess in the first element seen, in which the second element is inserted form-fitting.

To securely connect the incompatible joining partners, i.e. H. of the first and of the second element, is located in the connection area between the first and second elements a third element. This third element is connected to the first element via a frictional adhesive connection.  

To produce the second element together with the third element in inserted the recess of the first element and the third element with the first element glued.

On the surface of the third element is used for gluing before the one insert an adhesive into the recess of the first element.

The diameter of the recess in the first element becomes somewhat larger chosen as the total diameter of the second element and the third Element, so that the second and third element without further ado, in particular which are inserted into the recess without stripping the adhesive can. Due to the difference in diameter, there is a gap or gap between the second element and the third element after these have been inserted into the recess.

In this space or gap pressure means are provided that the third element can press against the inner wall of the first element, so that the pressure required for a secure bond is generated.

Essential to the present invention are one or more pressure means, which are provided in the space or gap, which due to the un different diameter of the recess in the first element and the second and third element arises. These pressure media ensure that necessary pressure, which is necessary to ensure a secure gluing of the first and to ensure third element. In the following the term "pressure medium "used in the singular, but it does not refer to a single one Pressure means, but depending on the embodiment, can also be multiple pressure include means.

Depending on the embodiment, the pressure medium can be in the The space or gap remains or is removed from it. Example an expanding resin can be chosen as the pressure medium. In In this case, the pressure medium remains in the gap after gluing.  

The expanding substance can be a pasty or foaming epoxy resin also be an adhesive film. With the increased required for the gluing Temperature begins to expand and creates the expanding substance a pressure that presses the third element against the first element. Further can be used as pressure medium spring elements or resilient steel strips be seen, which are inserted into the gap. The number of Federele elements depends on the dimensions of the device or the gap. Preferably at least three spring elements are used to create one to ensure as even a pressure as possible. The shot in the gap benen spring elements can be a tape measure similar in the transverse direction be bent elastically and thus press the third element against the first Element. After the adhesive has hardened to bond the third ele mentes with the first element, the spring elements again from the Gap are pulled out.

Preferably, the remaining space or gap is retrofitted, e.g. B. filled with a thin laminate or liquid resin, so that the second Element can not move in the gap under attacking transverse forces.

The third element is preferably a fiber composite sleeve, in particular a slotted tube element made of carbon fiber reinforced plastics with preferably predominantly unidirectional fiber orientation such as, for example are known from DE 44 19 691 C1.

As an additional measure for improvement, especially with internal force cables, it has proven itself when it comes to the connection area with the first Element, the second element and the third element a ring winding is placed. This outer ring winding achieves a higher strength against Tensile and compressive forces because they are expanding the rod or tubular Counteracts elements and thus supports the adhesion.

It is particularly preferred if the ring winding has a thickness of we has less than 0.2 mm, in particular less than 0.1 mm. This minor  Thickness is minimal in terms of weight and thus load, at the same time it already is achieved a very efficient prevention of expansion.

It is also possible to provide this ring winding in annular slots and such an additional thickening to the outside of the entire structure avoid. However, a free ring winding is also possible and takes that Tensile stresses occurring.

The ring winding can consist of endless fibers in annular grooves run.  

The present invention is explained below with reference to figures. It demonstrate:

Fig. 1 shows a section through a first embodiment of an apparatus according to EP 0841490 A2;

Fig. 2 shows a section through a second embodiment of the apparatus according to EP 0841490 A2;

Fig. 3 shows a section through a first embodiment of the invention; and

Fig. 4 shows a section through a second embodiment of the invention.

Fig. 1 shows a first generic embodiment according to the prior art, as it is also used in principle for the present invention. It is a fiber composite rod with an internal connection for force transmission.

A first element 10 can be seen , here a rod-shaped fiber composite structure made of a carbon fiber reinforced plastic. This is cylindrical, the central axis 11 is also the central axis of the other components. The first element 10 can extend far to the left outside of the drawings.

A second element 20 is connected to this first element in such a way that force can be applied. The second element 20 is made of aluminum and has an internal thread 21 , in which then engage from outside, not shown, directions that exert the force.

The second element 20 has a cylindrical central part 22 (also be shaft), an annular shoulder 23 which closes the element to the left in the drawing, for example in the form of a collar, and a further annular shoulder 24 which is on the opposite side of the cylindrical middle part 22 is arranged and this also projects radially outwards.

The third element 30 is arranged around the cylindrical middle part 22 . This element 30 is a sleeve that is relatively short and also consists of a carbon fiber-reinforced plastic, entirely from the same material as the first element 10 . The sleeve is slotted and corresponds, for example, to sleeves from DE 44 19 691 C1. In the illustrated embodiment, it is inserted with a precise fit between the two annular shoulders 23 and 24 around the cylindrical member 22 of the second element.

In the embodiment according to the prior art, the wall thickness of the sleeve or of the third element 30 and the central part 22 of the second element corresponds to the heel height of the left-hand paragraph 23 in the illustration; the ring-shaped shoulder 23 and the third element 30 thus form a common outside without jumping. The third element 30 is in the illustrated embodiment from the two paragraphs 23 and 24 immovably inserted when it is laid around and the slot is closed in a suitable manner.

In the embodiment shown in FIG. 1, a fourth element 40 , a longer sleeve, is provided to improve the quality of the adhesive. This sleeve may have specifications similar to elements 10 and 30 and is preferably also made of carbon fiber reinforced plastic. The fourth element 40 is glued on its outside to the inside of the first rod-shaped element 10 and with its inside to the outside of the third element 30 . It is relevant for this embodiment that the end of the sleeve of the fourth element 40 ends with the end of the fiber composite structure of the element 10 and the end of the third element 30 .

Fig. 2 shows a second embodiment according to EP 0,841,490, for which the present invention is also applicable in principle.

The embodiment shown here shows a force introduction into a sand wichplatte, which forms the first element 10 . The sandwich plate 10 has a core 15 and a cover layer 16 and has a through-hole. The cover layer 16 has been defined and drilled cleanly with a certain diameter. In the sandwich core 15 z. B. with a cylindrical milling cutter (not shown) produces a back milling, the diameter of which is greater than the drilling in the cover layer 16 , in order to accommodate the third element 30 , for. B. a sleeve to create.

The core 15 of the sandwich panel can be foamed, it can also have a honeycomb structure.

To apply force, a metallic element 20 is used, here a Ge threaded element with a cylindrical middle part 22 and two outer shoulders 23 and 24 . The shoulder 23 protrudes into the bore, the annular shoulder 24 engages over the cover layer 16 and lies on this with the interposition of a reinforcement of the first element 10 in this area with its cover layer 16 before local reinforcement 17th

The third element 30 is in turn a relatively short sleeve which has been inserted with a precise fit between the two annular shoulders 23 and 24 and is made of carbon fiber reinforced plastic. The direct contact between the element 30 and the shoulder 23 is again essential. As in the embodiment shown in FIG. 1, a fourth element 40 is provided to improve the adhesive quality. The fourth element 40 is a relatively long sleeve made of carbon fiber reinforced plastic, the length of which corresponds to the thickness of the sandwich core 15 .

The size of the bore in the cover layer 16 is selected such that the cylindrical central part 22 of the second element 20 can be pushed through with the short fiber composite sleeve of the third element 30 inserted into it.

The long sleeve or the fourth element 40 is in the finished Verbindungsvor direction over the short and therefore abuts from the inside against both cover layers th 16 of the first element 10 .

Fig. 3 shows a first embodiment of the present invention. The embodiment shown corresponds essentially to the device according to the prior art shown in FIG. 1. In contrast to the device according to the prior art, the invention provides an intermediate space or gap 50 between the sleeve, the third element 30 , and the cylindrical middle part 22 of the second element 20 . The space 50 is essential to the invention for receiving the pressure means.

Analogously to FIG. 1, the wall thickness of the third element 30 and the diameter of the gap 50 can also be selected so that they correspond to the heel height of the heel 23 .

A fourth element 40 used in accordance with the prior art according to FIGS. 1 and 2 to improve the adhesive quality is not required per se according to the invention, since sufficient and reproducible bonding is brought about due to the pressure means.

However, it is understood that if necessary, e.g. B. a particularly high adhesive to achieve performance, such a fourth element used for the invention can be.

In the embodiment shown here, the contact pressure means can be special an expanding substance can advantageously be used.

Preferably, the element 30 should rest against the inner shoulder 23 of the second element 20 without play, so that the introduction of force without hysteresis is possible. As shown, this can be achieved in that the element 30 is fitted exactly between the two paragraphs 23 and 24 of the two-th element. However, this requires a very precise and therefore complex processing of the third element.

According to the invention, it is now possible to manufacture the sleeve, the third element 30 , with a certain undersize in length, the sleeve being pressed against the shoulder 23 without play, in that the expanding substance is also applied in a targeted manner between the sleeve end face and the outer stop 24 . If the expanding substance then expands during the adhesive bonding, the pressure which arises between the face of the sleeve and the stop 24 ensures that the sleeve rests against the inner stop 23 without play .

The embodiment according to the invention shown in FIG. 4 is particularly suitable for receiving spring elements as pressure means.

In Fig. 4, the tubular rod end of a fiber composite structure as the first element 10 , a second element 20 with an internal thread 21 , cylindrical middle part 22 (shaft) and an inner shoulder 23 (on stroke 23 ).

A suitable for this embodiment second element 20 , a threaded set, z. B. made of aluminum, Fig. 4.3.

Instead of the outer shoulder 24 shown in FIG. 3, the embodiment shown here has a pressure plate 25 which, as shown in FIG. 4.2, is designed as a stepped disk with a bore. The pressure plate can be made of aluminum.

To avoid undesirable tensile stress when force is applied, it is particularly advantageous to carry out the bore in the pressure plate 25 without a thread.

As already mentioned, this embodiment is particularly suitable for taking on spring elements as a pressure means. These spring elements (not shown) are inserted from the front into the annular space 50 , ie the space between the sleeve and the threaded element. Resilient steel strips can be used as spring elements, which are elastically bent in the transverse direction similar to a tape measure and thus press the sleeve 30 against the rod wall. The resulting pressure ensures that the rod wall is well bonded to the sleeve 30 .

After the adhesive has hardened, the spring elements can be pulled out of the gap 50 again. The gap 50 is preferably after gluing and removing the spring elements with a suitable filling material, for. B. filled with a thin laminate or by liquid resin to prevent the threaded element from moving under the application of transverse forces in the annular gap 50 . With a correspondingly closely tolerated bore, the transverse force can be taken up alternatively or additionally via the stepped washer 25 .

In this embodiment, it is particularly advantageous that both the sleeve 30 and the rod, ie the first element 10 , can have an excess length in relation to the thread element, ie the second element 20 . These protrusions can be ground to the desired size after gluing.

The device for applying force according to the invention, as shown by way of example in FIGS. 3 and 4, can be assembled in a simple manner by placing the sleeve 30 around the central part 22 of the threaded element and applying a suitable adhesive to the outer wall of the sleeve 30 is, and these are inserted together into the recess or bore provided for the first element 10 , z. B. - as shown in FIGS. 3 and 4 - in the connection area of the rod-shaped or tubular fiber composite structures 10 .

It is essential for the invention that the overall diameter of the middle part 22 and the sleeve wall are chosen such that, together with the adhesive film applied, they are slightly smaller in diameter than the inside diameter of the bore or recess provided for receiving in the first element (optionally including Wall thickness of a fourth element). This measure ensures that the threaded element with sleeve and adhesive film can be inserted into the first element without damaging the adhesive layer. After inserting the threaded element prepared in this way, the connection area is exposed to the temperature required for the bonding. The necessary pressure arises from the pressure medium, for. B. the expanding substance or the spring elements.

The present invention enables a safe and reproducible connection formation of joining partners made of incompatible materials. In particular, the Safe installation of heavy-duty, usually metallic, power transmission tion elements in fiber composite structures. So a reprodu connectable connection between such incompatible material pairings how carbon fiber reinforced plastic and aluminum are produced which because of their excellent weight-specific properties particularly suitable for heavy-duty lightweight structures.  

Reference list

10th

first element

11

axis

15

Sandwich core

16

Top layer

17th

local reinforcement

18th

Adhesive filling compound

20th

second element

21

thread

22

Middle part (shaft)

23

Paragraph (stop)

24th

Paragraph (stop)

25th

Disc with hole

27

Ring winding

30th

third element

40

fourth element

50

Space (gap)

Claims (19)

1. Device for applying force with a connection of two ele ments ( 10 , 20 ), wherein a connecting area internally surrounding third element ( 30 ) is provided, the first element ( 10 ) and the second element ( 20 ) are positively connected to each other , The first element ( 10 ) and the third element ( 30 ) are connected to one another by an adhesive connection, characterized in that between the second element ( 20 ) and the third element ( 30 ) there is an intermediate space ( 50 ) for receiving at least one pressure medium is provided. 2. Device according to claim 1, characterized in that the first element ( 10 ) and the third element ( 30 ) each made of a carbon fiber reinforced plastic and the second element ( 20 ) made of a metal, in particular aluminum. 3. Device according to one of the preceding claims, characterized in that the second element ( 20 ) has a thread ( 21 ) for power transmission. 4. Device according to one of the preceding claims, characterized in that the elements ( 10 , 20 , 30 ) are essentially coaxial tubes made of different materials. 5. Device according to one of the preceding claims, characterized in that the third element ( 30 ) is a sleeve which surrounds the central part ( 22 ) of the second element ( 20 ). 6. The device according to claim 5, characterized, that the sleeve is a slotted tubular element from a is carbon fiber reinforced plastic, preferably with predominantly unidirectional fiber alignment. 7. Device according to one of the preceding claims, characterized in that an expanding substance or spring element are provided in the intermediate space ( 50 ) as pressure means. 8. The device according to claim 7, characterized, that as an expanding substance on a paste or an adhesive film Epoxy base is used. 9. Device according to one of the preceding claims, characterized in that the intermediate space ( 50 ) contains the pressure means or a filling material. 10. Device according to one of the preceding claims, characterized in that
that the force is introduced into a rod-shaped fiber composite structure by a threaded element ( 21 ) arranged in the rod-shaped fiber composite structure,
that the threaded element is the second element ( 20 ) made of the preferably metallic material,
that the threaded element ( 21 ) has a substantially cylindrical central part ( 22 ) and the third element ( 30 ) is a slotted sleeve which surrounds the substantially cylindrical central part ( 22 ) and an annular space ( 50 ) between the sleeve and in essential cylin drical middle part ( 22 ) forms for receiving the pressure medium. 11. The device according to claim 10, characterized in that the threaded element ( 21 ) at the ends has outwardly projecting annular shoulders ( 23 , 24 ) and the third element ( 30 ) is inserted between the annular shoulders ( 23 , 24 ), wherein the third element ( 30 ) lies against the inner shoulder ( 23 ) without play. 12. Device according to one of claims 10 or 11, characterized in that the outer shoulder ( 24 ) is designed as a stepped disc ( 25 ) with a bore, in particular made of aluminum. 13. Device according to one of the preceding claims, characterized in that a ring winding ( 27 ) is placed around the connection area with the first element ( 10 ), the second element ( 20 ) and the third element ( 30 ). 14. A method for producing a device for applying force with a connection of two elements ( 10 , 20 ), characterized in that a surrounding third element ( 30 ) is provided internally in the connection area, the first element ( 10 ) and the second element ( 20 ) are positively connected to one another, the first element ( 10 ) and the third element ( 30 ) are connected to one another by an adhesive connection, the adhesive connection being effected by at least one between the second element ( 20 ) and the third element ( 30 ) Pressure means is provided. 15. The method according to claim 14, characterized, that an expanding substance is chosen as the pressure medium. 16. The method according to claim 15, characterized, that the expanding substance is a paste or an adhesive film Is based on epoxy. 17. The method according to claim 15 characterized, that the pressure medium has a suitable number of spring elements are provided. 18. The method according to claim 17, characterized, that the spring elements are removed after the adhesive connection has been made. 19. The method according to claim 18, characterized in that the space ( 50 ) provided for receiving the spring elements is filled after removal of the spring elements.