WO2005092596A1

WO2005092596A1 - Threaded joint

Info

Publication number: WO2005092596A1
Application number: PCT/EP2005/002838
Authority: WO
Inventors: Stephan Kramb; Karl-Heinz Schuller
Original assignee: Daimlerchrysler Ag
Priority date: 2004-03-23
Filing date: 2005-03-17
Publication date: 2005-10-06
Also published as: DE102004014055A1

Abstract

The invention relates to a threaded joint (1) comprising at least one screw (4) and at least one dowel (5) for fastening an add-on piece (2) to a support piece (3). The invention is characterized in that the support piece (3) is provided with a foam structure while the dowel (5) is formed from a thermoplastic material which plastically deforms into the foam structure of the support piece (3) when the threaded joint is put in place, thereby being non-positively and positively connected to said foam structure.

Description

screw

The present invention relates to a screw connection for fastening an add-on part to a support part according to the preamble of claim 1.

DE 101 39 261 C2 discloses a screw connection for fastening an attachment, for example a wall element and / or insulation, to a support part, for example masonry, with at least one screw and at least one dowel. The add-on part has a foamed structure and is penetrated by bushings perpendicular to its element plane. A dowel is guided through these bushings, which is anchored in the masonry behind when the screw is screwed in. In addition, a holding element is arranged in the feedthrough, which has a collar-like widening on its side facing away from the masonry and thereby causes a non-positive connection to a screw head when the screw is screwed in.

From DE 41 31 779 AI a screw fastening for covers or front panels of devices or systems is known. To increase the radial play at a fastening point, a neck screw of the screw fastening is screwed axially through a threaded hole washer, which is mounted in a radially floating and captive manner in a radial extension on a bushing that is firmly connected to the cover or front plate. As a result, a greater tolerance compensation for hole patterns with large hole spacing to a reference hole or enables a more economical production of such hole patterns with larger tolerances.

From DE 197 18 062 AI an impact protector made of rigid foam is known, in which fastening devices are foamed. Foaming leads to an intimate connection of foam and fastening device without the use of additional glue.

The present invention is concerned with the problem of specifying an improved embodiment for a screw connection of the type mentioned at the outset, which in particular enables improved fastening in a porous material.

According to the invention, this problem is solved by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of providing a dowel made of thermoplastic material for a screw connection for fastening an add-on part to a support part having a foam structure, which dowel is plastically deformed into the foam structure of the support part when the screw connection is produced, and is thereby connected to the latter in a force-fitting and positive manner.

Fastening in foam structures is often problematic because conventional dowels or conventional screws cannot be used due to the high porosity of the foam. In particular, the screwing in of conventional screws in foam structures does not lead to the desired load-bearing connection, but only to the local displacement of the foam structure in the screw-in area. By using a A dowel made of thermoplastic material can penetrate the porous structure of the foam by softening, in particular by partially melting, the dowel and thereby effecting a non-positive and positive connection. In particular, there can be a fine branching of the plastically deformed dowel within the foam structure, which increases a toothing effect between the dowel and the foam structure. Such a toothing effect is achieved in conventional dowels in solid structures by a simple clamping effect.

According to an advantageous embodiment of the invention, the dowel is made of a thermoplastic. Thermoplastic materials are today inexpensive and easy to manufacture in almost any color, density, temperature sensitivity, etc. Modern injection molding technology enables extremely low unit costs to be achieved with high quality requirements, which means that a high competitive advantage can be achieved.

According to a preferred embodiment, the dowel is designed such that the deformation temperature required to deform the dowel occurs when the screw is screwed in due to the frictional heat that occurs. The dowel is inserted into a hole predrilled in the foam structure, essentially with a precise fit, and softens or partially melts only as a result of the frictional heat that occurs when the screw is screwed in. This offers the advantage that, in the screw connection produced, the plastically deformed dowel on the one hand penetrates into the foam structure in a non-positive or positive manner and on the other hand is also non-positively or positively connected to the threads of the screw. Using modern screwing tools, high torques can be introduced into the screw and thereby the deformation temperature required for the deformation are easily generated. In particular, this solution offers the advantage that the dowel to be placed can be arranged at any point at which a hole was previously made, for example drilled, in the foam structure.

In a further embodiment, the dowel is designed such that the deformation temperature required to deform the dowel occurs when the dowel is pressed into the foam structure. As in the aforementioned example, the dowel can also be placed at any, if accessible, location and pressed into the foam structure using a suitable tool. The pressure is so high that the dowel plastically deforms and a non-positive or positive connection with the foam structure is created. The screw can be subsequently screwed into the dowel that is already connected to the foam structure, with the screwing causing further local compression of the foam structure in the area of the thread of the screw, and the load-bearing capacity of the screw connection can thereby be increased further. If necessary, a set hole can first be drilled in the foam structure, into which the dowel is then pressed or the dowel is directly, i.e. without pre-drilling a hole, pressed into the foam structure.

According to a further preferred embodiment of the solution according to the invention, the dowel is foamed into the foam structure and is designed such that the deformation temperature required to deform the dowel occurs when the foam structure is foamed. In this embodiment, a subsequent arrangement of the dowel is not possible compared to the two previously mentioned, since the setting of the dowel and thus the location of the screw connection already done when foaming the supporting part. Foaming the dowel into the foam structure and plastically deforming the dowel during the foaming process ensures a particularly intimate and therefore particularly stable connection between the dowel and the foam structure. Similar to the two aforementioned variants, screwing into the dowel leads to local compression of the foam structure in the area of the thread of the screw and thus to particularly effective interlocking between screw and dowel or dowel and foam structure.

In a further advantageous embodiment, the support part is made of aluminum or steel foam. By using such foam materials, a reduced weight compared to a solid material can be achieved. For this reason, metallic foams of this type are being used increasingly, for example in the construction industry or in automobile construction. Due to the porous structure of the foam materials, an insulation property can be significantly increased compared to a full profile of the same material.

Further important features and advantages of the invention emerge from the subclaims, from the drawing and from the associated figure description with reference to the drawing.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention.

A preferred embodiment of the invention is shown in the drawing and is explained in more detail in the following description. The only FIG. 1 shows a section through a screw connection according to the invention.

1, a screw connection 1 for attaching an attachment 2 to a support part 3 has at least one screw 4 and at least one dowel 5. Here, the support part 3 is designed as a porous foam structure, whereas the add-on part 2, for example a mounting element, can have a full structure.

The dowel 5, which extends essentially orthogonally to a surface of the supporting part 3, is arranged in the supporting part 3. The dowel 5 consists of a thermoplastic material, preferably a thermoplastic material, which plastically deforms into the foam structure of the support part 3 when the screw connection 1 is produced, and is thereby connected to the latter in a force-fitting and form-fitting manner.

In order to bring about the non-positive and positive connection between the dowel 5 and the foam structure, the dowel 5 is heated to the required deformation temperature, so that it plastically deforms into the cavities or pores of the foam structure and thereby interlocks with it. In principle, several different methods for producing the non-positive or positive connection between dowel 5 and support part 3 are conceivable. Four of these are to be explained in more detail below:

In a first method, the deformation temperature required for deforming the thermoplastic dowel 5 is generated when the screw 4 is screwed into the dowel 5 due to the frictional heat that occurs in the process. First, a hole is made in the foam structure of the support at the desired partially drilled 3 and the dowel 5 sunk in the initial state, ie with an essentially hollow cylindrical shape in the drilled hole substantially free of play. Then the screw 4, whose outer diameter in the area of its thread 6 is larger than an inner diameter of the plug 5 in the initial state or larger than an outer diameter of the plug 5 in the initial state or larger than an inner diameter of a bore in the foam structure for inserting the plug 5 screwed into the dowel 5 in the initial state. The originally hollow cylindrical dowel 5 (hatched dowel cut surface in the initial state) then deforms in accordance with the respective thread 6 of the screw 4 under the frictional heat introduced by the rotary movement. The frictional heat also causes the dowel 5 to deform into the cavities in the foam structure, thereby producing a non-positive or positive ramification 7 or connection to the supporting part 3. The screw 4 is screwed into the dowel 5 by means of a high-torque screwdriver in order to generate the deformation temperature required for the deformation. The plastic deformation of the dowel 5 can be more or less pronounced depending on the level of the temperature generated by the friction and can range from a slight deformation to a strong ramification 7 with a correspondingly high frictional heat.

In a further method for producing the screw connection 1 according to the invention, the deformation temperature required for deforming the thermoplastic dowel 5 is generated when the dowel 5 is pressed into the foam structure. It is conceivable that the dowel 5 is first pressed into its prepared state, ie with an essentially hollow cylindrical shape, either into a prepared recess in the support part 3 or directly into the support part 3. During the pressing process, for example, due to high pressure and / or frictional heat reaches or exceeds the deformation temperature of the plug 5 and thus causes the same to be deformed into the porous foam structure of the support part 3. The screw 4 is then screwed into the already deformed dowel 5 by means of a screwdriver. Alternatively, it is also conceivable that after the deformation during the pressing-in process when the screw 4 is screwed in, a deformation is again brought about due to the frictional heat generated by the screwing in. Thus, each of the two methods presented can be used separately from one another, and a combination of the two methods can also be imagined.

In another method for producing the screw connection 1 according to the invention, the dowel 5 is foamed into the foam structure and the deformation temperature required to deform the thermoplastic dowel 5 is generated during the foaming of the foam structure. In contrast to the methods described above, a positive or non-positive connection of the dowel 5 to the porous foam structure of the support part 3 is thus already produced during the manufacturing process of the support part 3. The screw 4 can then be screwed into the dowel 5, which is already interlocked with the supporting part 3, using a conventional screwdriver. It is also conceivable here that the frictional heat introduced into the dowel 5 when the screw 4 is screwed in leads to a renewed deformation and can thus be used to increase the load-bearing capacity of the dowel 5.

In a further method variant, it is conceivable that the dowel 5 is heated before insertion and is inserted into the prepared hole in a soft state. The screw 4 is then screwed in and the dowel 5 is deformed into the pores of the foam structure. All four explained methods have in common that the dowel 5 is heated or heated from an initial state to the deformation temperature, which can be, for example, above a softening point and close to a melting point of the thermoplastic dowel 5, so that a tooth-like and thus non-positive and positive connection can be created with the porous hollow structure of the support part 3.

Metallic foams, such as aluminum or steel foams, as well as other foams suitable for the respective application are considered as foam structures for the supporting part 3. It is also conceivable that the dowel 5 is made of a thermoplastic metal, which must then be coordinated with regard to the foam of the supporting part 3 used with regard to a possible tendency to corrode (contact corrosion) between the metallic dowel 5 and the metallic foam of the supporting part 3.

Commercially available screws can be considered as usable screws 4 for producing the screw connection 1 according to the invention, wherein a thread profile of the screw 4 used can be, for example, semicircular or semi-elliptical. Such a rather blunt design of the thread supports an intensive deformation of the dowel 5 when the screw 4 is inserted and prevents the thread 6 from cutting too much, as a result of which a cutting of the dowel 5 and thus a considerable reduction in the load-bearing effect of the screw connection 1 can be avoided.

In summary, the essential features of the solution according to the invention can be characterized as follows: The invention provides a screw connection 1 with at least one screw 4 and at least one dowel 5 for fastening an attachment 2 to a support part 3. The support part 3 has a foam structure in which the dowel 5, which is made of a thermoplastic material, is plastically deformed when the screw connection 1 is produced, and is thereby connected to the latter in a force-fitting or positive manner.

As a result of the heating or heating of the dowel 5 up to its deformation temperature, the dowel 5 becomes soft or flowable and can easily deform or branch into the cavities of the foam structure of the support part 3 in this state. This results in an effective interlocking between the dowel 5 and the foam structure and thus a good load-bearing capacity between the two.

Claims

claims

Screw connection (1) for fastening an add-on part (2) to a support part (3) with at least one screw (4) and at least one dowel (5), characterized in that

- That the supporting part (3) has a foam structure, that the dowel (5) is formed from a thermoplastic material which, when the screw connection (1) is produced, plastically deforms into the foam structure of the supporting part (3) and is thereby connected to the latter in a force-fitting and positive manner is.

Screw connection according to claim 1, characterized in that the dowel (5) is formed from a thermoplastic.

Screw connection according to claim 1 or 2, characterized in that an outer diameter of the screw (4) in the region of its thread (6) is larger than an inner diameter of the dowel (5) in the initial state or larger than an outer diameter of the dowel (5) in the initial state or is larger than an inner diameter of a bore in the foam structure for inserting the dowel (5) in the initial state.

4. Screw connection according to one of claims 1 to 3, characterized in that the dowel (5) is designed such that the deformation temperature required for the deformation of the dowel (5) occurs when the screw (4) is screwed in due to the frictional heat occurring in the process ,

5. Screw connection according to one of claims 1 to 4, characterized in that the dowel (5) is foamed into the foam structure and is designed such that the deformation temperature required for the deformation of the dowel (5) occurs when the foam structure is foamed.

6. Screw connection according to one of claims 1 to 4, characterized in that the dowel (5) is designed such that the deformation temperature required for the deformation of the dowel (5) occurs when the dowel (5) is pressed into the foam structure.

7. Screw connection according to one of claims 1 to 6, characterized in that the supporting part (3) is made of aluminum or steel foam.

8. Screw connection according to one of claims 3 to 7, characterized in that the thread profile of the screw (4) is semicircular or semi-elliptical.

9. The method for producing a screw connection according to one of claims 1 to 8, wherein the deformation temperature required for deforming the thermoplastic dowel (5) when screwing in Screw (4) in the dowel (5) is generated due to the resulting frictional heat.

10. A method for producing a screw connection according to one of claims 1 to 8, wherein the dowel (5) is foamed into the foam structure and the deformation temperature required to deform the thermoplastic dowel (5) is generated when the foam structure is foamed.

11. A method for producing a screw connection according to one of claims 1 to 8, wherein the deformation temperature required for deforming the thermoplastic dowel (5) is generated when the dowel (5) is pressed into the foam structure.