Description:

Nuts and bolts are mechanical fasteners that are widely used for assembly purposes. The two parts are almost always used in conjunction with each other. The nut is a threaded female part (or hole) and the bolt is a threaded male part (or shaft). Upon assembly the nut is placed around the bolt, or the bolt inside the nut, and the nut is tightened to the bolt by rotating the nut and/or the bolt. Once properly tightened, the two parts are kept together by a combination of their threads' friction (with slight elastic deformation), a slight stretching of the bolt, and compression of the components to be held together.

WO 2015/015224 discloses a fixing member, which can be adhered to a substrate, whereby the fixing member comprises a fixed part. In WO 2015/015224 a dual mode of fixing is used, at first the fixing member fixes a fixed part and the fixing member is adhered to a substrate. Both modes of fixing are permanent.

EP 2 778 309 discloses a method of forming adhesive connections, which is able to adhere a spider point glazing system to optically transparent substrates. Also the spider point glazing system has a dual mode of fixing, firstly connector(s) are adhered to the optically transparent substrates and secondly the connector are fixed to a body portion. Both modes of fixing are permanent.

US 4,822,224 discloses a wire harness retainer stud. This retainer stud comprises a bolt, which can be adhesively bonded at the head of the bolt to an automobile body panel. Also in this case a dual mode of fixing is obtained by tighten the wire harness retainer stud to the bolt, and the adhesive bonding of the bolt to an automobile body panel. Both modes of fixing are also permanent.

During the tightening procedure it is important that one of the two parts is kept in place while the other part is being rotated. Whether the nut or bolt is kept in place highly depends on the assembly procedure. Often one of the parts is manually kept in place, however, this is not always possible. As for example in highly automated production lines or difficult to reach places. A common solution for this is the use of weld nuts or weld bolts. These parts are kept in place by welding them onto a substrate. The nut or bolt is kept in place by the weld and no manual fixing is required during tightening of the counter-part. This is for example used in the automotive industry where weld-nut and weld-bolts are welded onto a chassis. This method has some restrictions as welding can only be done with a limited amount of materials such as carbon steel. Welding is not possible with polymer based materials (e.g. fiber-reinforced plastics, polyethylene or polyurethanes), ceramics (e.g. glass), coated components (e.g. paints, corrosion protection layers) and quite some metals (e.g. high strength steel). This limits the applicability of this technique.

An alternative solution has been proposed in GB2388172 and JP19980061531. These documents teach a method for fixing a nut or bolt to a workpiece by using a self-adhesive membrane. The self-adhesive membrane is a rubber or plastic material which has double sided self-stick properties. The self-adhesive membrane is placed over the full contact area of the bolt or nut and pressed onto the workpiece thus effectively fixing the part to the workpiece. This technique can be used to fix nuts and bolts to a broad range of substrates. However, during the tightening procedure a lot of clamping pressure will be applied to the self-adhesive membrane. This force will over time cause the self-stick membrane to deform (i.e. by polymer creep) which reduces the clamping pressure and thus effectively loosening the nut/bolt assembly.

Another solution is proposed in US5051049. This document teaches a method for fixing a nut or bolt to a substrate by using an adhesive ring and a lock nut that has a star-washer in unitary assembly therewith. The adhesive ring is used to fix the lock nut, which comprises the star-washer, to a substrate. During the tightening procedure, the star-washer penetrates through the adhesive ring gripping itself into the substrate. After tightening there thus is a direct contact between the nut (via the star-washer which is an integral part of the nut) to the substrate. This creates a stronger connection to maintain the clamping force over time. However, the springy construction of the star-washer makes it an unsuitable element for maintaining the clamping force and in particular for high clamping forces. Furthermore, the design of the nut that comprises the start-washer is not easy to manufacture via common cold- forging techniques used for making bolts and nuts.

Also, JP04254011 teaches a method to join a nut and a bolt while the nut is not held by a spanner or the like. In a three-step tightening procedure the nut and bold are clamped to fix the substrates. First the nut is adhered to a substrate, second the nut is locked into position by using a guide bolt that upon tightening forces the sharp edge on the outer periphery of the nut into the substrate. In a final step the guide nut is removed and replaced by another bolt, which is tightened to the nut with the desired clamp force. This three-step procedure is required because the force required to fix the nut into the substrate (by forcing the sharp edge on the outer periphery of the nut into the substrate) is different from the desired clamp force. This makes this method rather complex. The object of the present invention is to provide a connecting assembly, which overcomes the problems of the prior art.

The connecting assembly according to the present invention comprises a first part and a second part, whereby the first part is connectable with the second part via a form-fit and/or a material-locking connection and whereby the connecting assembly comprises an adhesive material for an adhesive connection from the first part and/or the second part to a third part, characterized in that the first part and/or the second part comprises at least one cavity on a surface area Atotai of the first part and/or the second part, whereby the at least one cavity is located between the first part and the second part, and the adhesive material is located in the at least one cavity on a cavity surface area Ac and substantially fills the entire cavity and the cavity surface area Ac of the at least one cavity is less than 95% of the surface area Atotai of the first part and/or the second part.

For purpose of clarity the following is defined and is used during the description.

The surface area Atotai is to be understood as the surfaces of the first and/or second part, which does not be a part of a form-fit connection of the first part and the second part, does not lay in the longitudinal plane of the connecting assembly and is faced to the third part.

For illustration, e.g. the surface area Atotai is to be understood as the non-threaded surface of a nut and/or a bolt, which is faced to the third part. Thereby, the surface area Atotai comprises a bearing surface area Ab and a cavity surface area Ac. The bearing surface area Ab is to be understood as a part of the surface area Atotai of the first part and/or the second part, which is in direct contact with the third part after tightening process of the connecting assembly.

The cavity surface area Ac is to be understood as a part of the surface area Atotai of the first part and/or the second part which is faced to the third part, is in direct contact with an adhesive material and is not in direct contact to the third part.

The third part of the connecting assembly, which can be clamped by the first part and/or second part, can be one work piece or more than one work piece. In case the third part is more than one work piece, the work pieces can be clamped together by the first part and/or second part.

The part, e.g. the first part and/or second part, that comprises the adhesive material can be adhered to the third part (Figure 2, a). The adhesive material, which substantially fills the entire cavity of the first and/or the second part and preferably exceeds the surface area Atotai of the first and/or the second part, keeps the part in position during handling of the third part and prevents rotation of said part upon tightening the first/ second part construction (Figure 2, b). During the tightening procedure, the adhesive material is compressed inside the cavity, and maybe squeezed out of the cavity, creating a direct contact between the bearing surface area Ab of the part and the third part (Figure 2, c). This direct contact creates frictional forces that prevent the part from rotating during further tightening and prevent losing clamp force after assembly.

This means that the adhesive in the cavity of the first part and/or second part accomplishes only for a short period of time the adhesion of the first part and/or second part to the third part and keeps the first part and/or second part in place. After tightening of the connecting assembly, firstly the friction forces between the first part and/or second part and the third part overtakes keeping the first part and/or second part in place, and secondly the clamping pressure of the connecting assembly overtakes fixing of the first part and/or second part to the third part and vice versa.

In addition, by assembling a part comprising the adhesive material with pressure onto a third part, a partial vacuum can occur which also prevents the part from rotating during the tightening process. After the first part and second part are tightened and clamping the third part no adhesive is between the bearing surface Ab and the third part. Therefore, the absence of the adhesive between the bearing surface Ab and the third part causes that the clamping pressure between the first part and/or second part and the third part is remained over a long period of time.

The at least one cavity can be located on the surface area Atotai of both the first part (Figure 3) and/or the second part (Figure 4). The at least one cavity can in principle have any geometry and can for example have circular shape positioned concentrically around the central rotational axis of the first part and/or the second part. This circular at least one cavity can be placed on the inside of the surface area Atotai (close to central rotation axis), at the outside of the surface area Atotai (at outer edge of the first part and/or the second part) or anywhere in between. Another shape of the at least one cavity suitable for carrying out the invention is a cavity that radially extends from the inside of the surface area Atotai to the outside. Also, an embodiment is that the first and/or the second part comprises more than one cavity on the surface area Atotai, so that the surface area Atotai comprises several cavity surface areas Ad , A _C 2 ... . Flowever, also in this preferred embodiment the sum of the cavity surface areas Ad , A _C 2 ... is less than 95% of the surface area Atotai of the first part and/or the second part. These cavities can form following pattern: linear cavities which are extending from the center to the outer i.e. a cross, a circular ring comprising smaller circular rings, an island in the sea pattern, a single linear cavity crossing the surface area Atotai, a stripe pattern where at least two linear cavities are parallel to each other on the surface area Atotai, a mesh structure, wherein at least two linear cavities, which are parallel to each other, have an angle of >0° and < 90° in view of at least one further linear cavity and combination of the above mentioned patterns.

The at least one cavity can have any depth, but preferably the depth of the at least one cavity is less than 2 mm, more preferably the depth is less than 1 mm, even more preferably the depth is less than 0.6 mm, most preferably the depth is less than 0.3 mm and especially most preferably the depth is less than 0.1 mm. If more than one cavity is used, the different cavities may have the same depth or different depths. It is common to a person skilled in the art, that the depth of the at least one cavity has to be selected, such that the first part and/or second part is not destroyed by the upcoming clamping pressure, e.g. the at least one cavity is not acting as a predetermined breaking point.

Regardless of the shape of the at least one cavity, it is important to carry out the invention that the cavity is located on only a part of the surface area Atotai and does not extend over its complete surface. Preferably the at least one cavity is located on less than 95% of the surface area Atotai, more preferably less than 90% and even more preferably less than 80%, most preferably less than 70 % and especially most preferably less than 60% of the surface area Atotai .

The first and/or the second part according to the invention can be made from any material such as any metal, any metal alloy, steel, carbon steel, aluminum, titanium, carbon reinforced plastic, glass fiber reinforced plastic, or any polymer.

The first and/or the second part according to the invention can also be coated or even comprise multiple coatings. This is one particular advantage of the invention in comparison to for example welt nuts/bolts. Welt nuts/bolts cannot be coated since the coating would affect the quality of the welt. Examples of coatings that can be used are corrosion protection coatings such Zn or Zn/Ni coatings, passivation layers and sealers. When using multiple coatings, it is in particular the top coating that should be selected carefully to obtain a proper bond with the adhesive. Good results are for example obtained by using a sealants of the type Enseal 135 and Hydroclad SC40.

The adhesive material can in principle be any kind of material that can be located inside the at least one cavity and does have at least adhesive properties on its two main surfaces when the first and/or the second part is applied to the third part. In a preferred embodiment the adhesive material is a pressure sensitive adhesive such as acrylic foam tape. In another preferred embodiment, the adhesive material is a three- layer system wherein the central layer is made of a thermoplastic foam (e.g. PE), thermoharder-foam (e.g. XPE) or rubber and the outer layers are pressure sensitive adhesives. In yet another preferred embodiment the adhesive material comprises of a hot-melt material like ethylvinylacetate (EVA), polyolefins, polyurethanes or polyvinylbutyral (PVB). Also, the use of liquid adhesives would be possible as an adhesive material to carry out the invention, although in view of takt time and handling this would be less preferred. If more than one cavity is used, the different cavities may be filled with the same or different adhesive material.

In case different cavities are filled with the same adhesive material, it can have the effect that the adhesion is enhanced. Further, in case different cavities are filled with different adhesive materials, the adhesive materials can be customized to the materials of the different parts, hence, also this can enhance the adhesion.

In a preferred embodiment the bearing surface area Ab of the first and/or the second part does further comprise features that improve the friction to the third part. Such features can for example be a micro-texture or a coating. Suitable micro-textures could be for example arrays of random-, pyramidal or groove shaped relief textures.

To improve the adhesion of the adhesive material to the workpiece and or the adhesion to the first and/or the second part it is possible to apply a primer layer to these surfaces. Alternatively, a corona or plasma treatment is preferred.

The first and/or the second part can in principle be used on any workpiece made from any material. This is also a particular advantage of this invention since for example welt nuts/bolts can only be used on a limited amount of the materials. The third part can be from materials like steel, carbon steel, aluminum, high-strength steel, carbon- fiber-reinforced plastic, glass-fiber-reinforced plastic, various plastics or ceramics.

In a preferred embodiment the first part and/or the second part comprises a washer. A washer is a thin plate, typically disk-shaped, with a hole, typically in the middle, that is normally used to distribute the load of a threaded fastener, such as the first part and/or the second part. The first part and/or the second part might comprise said washer, wherein the washer can be characterized in terms of material and surface construction as outlined above with respect to the first part and/or the second part.

The washer and the first or the second part can be one-piece or made of different pieces. One-piece means, the washer and the first or the second part is one piece and made from one piece. Preferably, no connecting means are used for connecting the washer with the first or the second part if the washer and the first part or the second part is one-piece. For the sake of clarity and as already mentioned above - all embodiments of the first and/or the second part are also applicable for the washer. This means (for example) also the washer may have friction increaser or undergone a treatment.

In one embodiment the washer can comprise teeth on its surface area.

In a preferred embodiment the first part is a nut and the second part is a bolt.

In one embodiment, the washer might comprises an adhesive material placed inside a cavity located on one or both of said washer main surfaces. Accordingly, the main surface of the washer which comprises the cavity is the surface area Atotai which comprises also a cavity surface area Ac and a bearing surface Ab with characteristics as explained above.

Thereby, the washer is further characterized by that said cavity comprises less than 95 % of the surface area Atotai of the washer. In this embodiment it might not be necessary to have an adhesive material inside the at least one cavity on the first part and/or the second part.

The object of the present invention is also to provide a connecting assembly, comprising a first part and a second part, whereby the first part is connectable with the second part via a form-fit and/or a material-locking connection and whereby the connecting assembly comprises an adhesive material for an adhesive connection from a third part to the first part and/or second part, characterized in that the third part comprises at least one cavity on a surface area Atotai of the third part, whereby the adhesive material is located in the at least one cavity on a cavity surface area Ac and substantially fills the entire cavity and the cavity surface area Ac of the at least one cavity is less than 95% of the surface area Atotai of the third part.

For the sake of clarity and as already mentioned above - all embodiments of the first and/or the second part are also applicable for the third part. This means (for example) also the third part may have friction increaser or undergone a treatment.

For clarity reasons, the surface area Atotai of the third part is corresponding to the surface area Atotai of the first part and/or second part. This means, the surface area Atotai of the third part is the surface area of the third part, which is covered by the first part and/or second part, if the first part and second part is tightened and clamping the third part. Therefore, the surface area Atotai of the third part has the same value as the surface area Atotai of the first part and/or second part.

The third part has two sides, where the first and/or second part can be clamped on. After clamping a first side of the third part is faced to the first part and a second side of the third part is faced to the second part. As the first part and/or second part can have different surface area values Atotai, the surface area Atotai of the first side of the third part and the surface area Atotai of the third part can have different values.

The connecting assembly according to the invention can be used in the automotive industry, train industry, aerospace industry or construction industry.

The invention is described by figures 1 to 5.

Description of the Figures 1 to 5:

Figure 1 : a) schematically shows a cross section view of a nut 001 as a first part with a single cavity 005. b) schematically shows a cross section view of a nut as a first part, as shown in Figure 1a, with an applied adhesive material 002.

Figure 2: a) schematically shows a cross section view of a nut 001 as a first part with an adhesive material 002 adhered to a third part 004. b) schematically shows a cross section view with the same parts as in Figure 2a. In addition a bolt 003 as a second part is schematically shown, which is screwed. c) schematically shows a cross section view of the tightened parts Figure 2b.

Figure 3: a) schematically shows a nut 001 as a first part on a third part

004 with a cavity 005 located on the inner side of the nut 001. b) schematically shows a nut and a third part as in Figure 3a with a cavity 005 on the outer side of the nut. c) schematically shows a nut 001 as a first part on a third part 004 with a cavity 005 located on the inner side of the third part 004. d) schematically shows a nut and a third part as in Figure 3c with a cavity 005 located on the outer side of the third part.

Figure 4: a) schematically shows a bolt 003 as a second part on a third part 004 with a cavity 005 located on the inner side of the bolt. b) schematically shows a bolt and a third part as in Figure 4a with a cavity 005 located on the outer side of the bolt. c) schematically shows a bolt 003 as a second part on a third part 004 with a cavity 005 located on the inner side of the third part. d) schematically shows a bolt and a third part as in Figure 4c with a cavity 005 located on the outer side of the bolt

Figure 5: a) schematically shows a nut as a first part with an alternative pattern of the cavity surface area with an adhesive material 002 by a top view. b) schematically shows a nut as a first part with an alternative pattern of the cavity surface area with an adhesive material by a side view.

In Figure 1a a nut 001 as a first part with a cavity 005 is shown. Thereby, the surface area Atotai the bearing surface area Ab and the cavity surface area Ac are indicated. In Figure 1 b a nut as a first part with an applied adhesive material 002 is shown. In Figure 2a is a preferred embodiment of a nut 001 as a first part which is adhered on a third part 004 which can be for example a sheet of metal by an applied adhesive material 002 inside a cavity. In the following figure 2b the bolt 003 as a second part is screwed into position. After the bolt and the nut is tightened to the third part (Figure 2c) the adhesive material is squeezed out of the cavity.

In figure 3a an embodiment of a nut 001 as a first part with a cavity 005 in the inner side of the nut 001 on a third part 004 is shown. Further, an embodiment is shown in Figure 3b where a nut as a first part on a third part comprises a cavity 005 on the outer side of the first part.

As an embodiment the cavity 005 can also be located on the inner side of the third part 004 (Fig. 3c) or on the outer side of the third part 004 (Fig. 3d). The cavities 005 can be filled with an adhesive 002 (not shown), such that a nut 001 can be attached to the third part 004.

One embodiment is shown in Figure 4a, wherein a bolt 003 as a second part on a third part 004 comprises a cavity 005 at the outer side of the bolt 003. Further, an embodiment is shown in Figure 4b where a bolt as a second part on a third part comprises a cavity 005 on the inner side of the bolt.

As an embodiment the cavity 005 can also be located on the inner side of the third part 004 (Fig. 4c) or on the outer side of the third part 004 (Fig. 4d). The cavity 005 can be filled with an adhesive 002 (not shown) such that a bolt 003 can be attached to the third part 004.

In Figure 5a and 5b an embodiment of a nut as a first part is shown, wherein the nut comprises an alternative pattern of the cavity surface area with an adhesive material 002.