WO2006133704A1

WO2006133704A1 - Process for creating an angle connection in a plane member

Info

Publication number: WO2006133704A1
Application number: PCT/DK2006/000335
Authority: WO
Inventors: Erik Jensen
Original assignee: Isic A/S
Priority date: 2005-06-13
Filing date: 2006-06-13
Publication date: 2006-12-21

Abstract

Process for creating an angle connection in a plane member, in particular an aluminium sheet wherein the following steps are performed: a substantially V-shaped groove is formed in the plane member where the angle is to be; an adhesive is applied, at least to the sides of the groove; the plane member is folded such that the two sides of the groove are forced together, but maintained at a distance.

Description

Process for creating an angle connection in a plane member

The present invention relates to a process for creating an angle connection in a plane member in particular in a metal sheet, more particularly in a sheet of aluminium. Fur- thermore, the invention relates to the use of such an angle connection in a computer or electronic cabinet or any other object where it may be desirable to apply this inventive principle.

When manufacturing traditional cabinets for computers, in particular personal com- puters as well as electronic equipment for example radios, VCRs and the like, the cabinet is traditionally made from a relatively thin piece of metal which is folded into the desired shape. In this manner, it is possible to fold up four sides whereas the connection between the first and fourth side may be done by other means which traditionally includes screws or the like. The M-panels are usually partly folded up and along the three edges, they are screwed into the cabinet.

For cabinets where it is desirable to have somewhat thicker wall thickness, it is not possible to fold the material in that along the fold, the material will be severely damaged. Depending on the type of metal, the cabinet is made from, the material on the outside may be stretched whereby cracks are induced, and on the inside, the material has a tendency to buckle which may have influence on the straightness of the fold all together. Visually, the cracks and the buckling may give the finished member a very unappealing presentation. Therefore, traditional cabinets of this type are made from single plane material sheets which are for example screwed together along the edges.

By these assembly methods, a number of drawbacks are present. Firstly, it is quite labour intensive to provide the holes for the screws necessary in order to assemble the two plate materials. Furthermore, these holes are usually countersunk which incorporates an extra work routine. Furthermore, where cabinets are used for electronic equipment, it is desirable to be able to fulfil certain requirements relating to EMC (Electro-Magnetic Compatibility). These requirements are usually raised in order to assure that interference from other electronic devices is minimised. This is becoming even more important with the expansion of wireless networks but also for computer, telephone or cable networks requiring cabling, the EMC "tightness", i.e. the EMC sensibility is a factor which is important when deciding which cabinet should be used, hi particular in application used in military equipment, the EMC requirements may be very stringent.

For the manufacture of cabinets using screw connections, there are certain standards which must be fulfilled relating to the number of screws, the distance between the screws and the packaging material placed between the two plates which are assembled by the screws. These requirements must be met in order to provide an EMC-certified cabinet. Generally, the EMC requirements may be stringent when the equipment is placed in very electronically sensible environments.

The present invention, consequently, addresses the drawbacks associated with assembling of prior art cabinets but additionally provides the possibility of manufacturing improved EMC tight cabinets.

The invention addresses this by providing a process for creating an angle connection in a plane member, in particular an aluminium sheet wherein the following steps are performed: - a substantially V-shaped groove is formed in the plane member where the angle is to be; an adhesive is applied, at least to the sides of the groove; the plane member is folded such that the two sides of the groove are forced together, but maintained at a distance. By creating the V-shaped groove, the material which would otherwise hinder folding of the sheet, and which material would create buckling and other distortions, has been removed. Hereby, it becomes possible to fold the sheet in a clean manner such that the angle connection will appear with a sharp edge. Furthermore, as the groove does not penetrate the sheet material, the material is unbroken whereby the EMC tightness is vastly improved such that for example cabinets manufactured by using the inventive process according to claim 1 will have an extremely high EMC rating. The choice of adhesive should obviously be an adhesive which is compatible with the material from which the plane member is made. A number of commercially available adhesive products are suitable, and which products are designed for specific purposes depending on the materials in question.

hi order to utilize the adhesive properties, the two sides of the groove should not be in contact over the entire area, once the angle connection of the plane member is finished. This is due to the fact that the adhesive materials usually require a certain minimum thickness in order to exhibit the required strength characteristics. Depending on the material characteristics of the adhesive, the optimal distance and thereby the thickness of the resulting adhesive layer is determined due to the length of the polymer chains created by the polymerisation of the adhesive material.

hi a further advantageous embodiment of the invention, the material of the plane member is aluminium, and the angle α of the V-shaped groove is between 65 and 125 degrees, preferably between 80 and 110 degrees, even more preferred between 85 and 100 degrees, and most preferred 90 degrees, hi particular for metals and in particular metals having a certain thickness, it has been difficult to bend/fold these without the effects of buckling and crack formation along the fold/bend line. For certain purposes, it is highly desirable to be able to make the cabinet or object from aluminium and in particular by creating the V-shaped groove having angles in the above-mentioned intervals, a wide variety of substantially rectangular cabinets or objects, may be created without necessarily having an angle between two adjacent planes of 90 degrees.

hi a still further advantageous embodiment, the depth of the groove into the plane member leaves 0.1 mm to 0.6 mm material thickness, more preferred 0.2 mm to 0.4 mm and most preferred 0.3 mm material thickness in the bottom of the groove. It has been found that most metal materials will be able to be bent without cracking or buckling or exhibiting any other detrimental effects along the bend line if a certain amount of material thickness is left.

The process in a further advantageous embodiment discloses that the adhesive is an epoxy based adhesive, optionally two component adhesive, and that the adhesive com- prises a carboxylic acid. Tests have indicated that the provision of carboxylic acid as a component in the two-component adhesive enlarges the surface area inside the groove by a factor 10 in that a certain corrosion due to the effect of the acid provides for a very large surface area and thereby for a very large bonding area between the two sides of the groove such that a very strong adhesive connection may be created by the two sides of the groove. This in turn results in a very strong and extremely rigid angle construction. In this context, it should be noted that although carboxylic acid is mentioned, other types of appropriate acids may be used depending on the material of the plane member and the adhesive.

hi particular for aluminium, the advantages of the carboxylic acid and in particular when the carboxylic acid is formic acid prove to exhibit excellent results.

hi a further advantageous embodiment, one or more notches are provided inside the groove on one or both side surfaces forming the groove, and that the one or more notches extends 0.1 mm to 0.5 mm from the plane of the side of the groove. The notches serve to assure that the distance between the two opposing sides of the groove when the plane member is folded are kept at a distance such that the optimum polymerisation of the adhesive may be assured. The distance is necessary in order to provide. enough space for the polymer components of the adhesive to establish the polymeric chains which create the adhesive effect.

In order to further advance this, the process a further advantageous embodiment provides that in the bottom of the groove, a plane section connecting the two side faces of the groove is provided, and that said plane section is between 0.1 mm and 0.5 mm, measured perpendicularly to the longitudinal extend of the groove. In this manner, the shape of the adhesive material between the two sides of the groove will not be triangular or wedge shaped but will have a substantially rectangular cross section such that optimum conditions are provided for the adhesive connection between the two sides of the groove.

In a further advantageous embodiment of the invention, the adhesive is allowed to cure up to 10 minutes, before the plane member is folded. This is particularly impor- tant where the adhesive material contains an acid in that the curing time allows the acid to react with the surfaces of the sides of the groove thereby creating an enlarged surface area due to the corrosion such that the extremely strong bonding provided by the adhesive materials may be effected.

The process may be used for creating a structure such as a computer or electronic cabinet or any other object, constructed by incorporating transitions between at least a number of plane surfaces of the cabinet or object, according to a process as described above, where a groove is arranged where the transition between two connecting plane surfaces is to be.

The invention will now be explained with reference to the accompanying drawing, wherein

Fig. 1 illustrates a plane material sheet,

Fig. 2 illustrates a plane material sheet wherein a groove is cut,

Fig. 3 illustrates a material sheet bend along the groove,

Fig. 4 illustrates a large cross section through a groove according to the invention, and Fig. 5 illustrates the cross section, cf. Fig. 4, when bend along the groove.

With reference to fig. 1, a plane material sheet is illustrated. The typical thickness T of the material may be between 2 and 10 mm depending on the material in question. For this specific example, reference will be made to a sheet of metal made from alumin- ium. At the place where it is desirable to bend/fold the material, a groove 1 is cut in the material sheet 2. In practice, the groove is formed by milling or grinding The sides of the groove 3 are cut such that the groove 1 does not go all the way through the material, but a certain material thickness 4 is left. Typically, the material thickness for aluminium is 0.3 mm. Furthermore, the angle α between the two sides 3 in the groove may be any desired bending angle, but in addition to the actual bending angle, a further few degrees should be added in order to provide for a groove thickness 5 as illustrated with respect to fig. 3. Turning back to fig. 2, the adhesive material (not illustrated) will be applied to the side of the groove 3 before the material 2 is bent into the desired angle. The adhesive material may be a 3M product, product code/type DP460 where formic acid HCOOH is added.

The formic acid will corrode the aluminium but will itself be neutralised after approximately 2 minutes by the presence of NaOH, without any detrimental effect on the adhesive as such.

By utilising an adhesive comprising in the case of an aluminium metal sheet a formic acid will corrode the surface of the sides of the groove 3 whereby the bonding area is typically enlarged by a factor 10. Therefore, when the sheet is folded as indicated in fig. 3, a very strong bond between the two sides of the groove will be created due to the adhesive properties of the adhesive material in cooperation with the extremely large surface provided by the formic acid as explained above.

In fig. 4, a close up view of a groove 1 according to a further embodiment of the invention is illustrated. The sides of the groove 3 are provided with notches 6 such that as the material sheet 2 is folded, the notches will meet and maintain a certain distance as illustrated with reference to fig. 5. This leaves space 7 in combination with a plane bottom section 8 of the groove such that a substantially rectangular space 7 is left for the adhesive material whereby the optimum size for achieving the high adhesive bonding due to the minimum distance for creating the polymerisation chains in the adhesive material is provided.

In this fashion, it is possible to create an angle in a plane sheet of material without breaking the material, and at the same time due to the characteristics of the adhesive and in particular the provision of an acid in the adhesive material which will corrode the sides of the groove create an extremely strong bond such that the resulting angle created by the process according to the invention will exhibit extremely stiff characteristics. Although the illustrated embodiment has been illustrated with reference to an arbitrary angle α and with reference to the material sheet being made from aluminium, any bending angle and in particular an angle resulting in a 90 degree bend may be elected which does not crack the material or create buckling, and furthermore, any suitable adhesive which is both suitable for being applied to the choice of material but also which is cooperative with the acid add-mixed to the adhesive may be selected.

Claims

1. Process for creating an angle connection in a plane member, in particular an aluminium sheet wherein the following steps are performed: - a substantially V-shaped groove is formed in the plane member where the angle is to be; an adhesive is applied, at least to the sides of the groove; the plane member is folded such that the two sides of the groove are forced together, but maintained at a distance.

2. Process according to claim 1 characterized in that the material of the plane member is aluminium, and that the angle α of the V-shaped groove is between 65 and 125 degrees, preferably between 80 and 110 degrees, even more preferred between 85 and 100 degrees, and most preferred 90 degrees.

3. Process according to claim 1 or 2 characterized in that the depth of the groove into the plane member leaves 0.1 mm to 0.6 mm material thickness, more preferred 0.2 mm to 0.4 mm and most preferred 0.3 mm material thickness in the bottom of the groove.

4. Process according to claim 1 characterized in that the adhesive is an epoxy based adhesive, optionally two component adhesive, and that the adhesive comprises a car- boxylic acid.

5. Process according to claim 4 characterized in that the carboxylic acid is formic acid.

6. Process according to claim 1 characterized in that one or more notches are provided inside the groove on one or both side surfaces forming the groove, and that the one or more notches extends 0.1 mm to 0.5 mm from the plane of the side of the groove.

7. Process according to claim 1 or claim 6 characterized in that in the bottom of the groove, a plane section connecting the two side faces of the groove is provided, and that said plane section is between 0.1 mm and 0.5 mm, measured perpendicularly to the longitudinal extend of the groove.

8. Process according to any preceding claim characterized in that the adhesive is allowed to cure up to 10 minutes, before the plane member is folded.

9. Structure, such as a computer or electronic cabinet or any other object, constructed by incorporating transitions between at least a number of plane surfaces of the cabinet or object, according to a process according to any of claims 1 to 8, where a groove is arranged where the transition between two connecting plane surfaces is to be.