Background of the invention

The present invention relates to a joining device for connecting air

conditioning duct members to each other, the joining device having an essentially H-shaped cross-section, the grooves of the H opening in opposite directions being fitted to receive the walls of the duct members to be connected to each other end to end, and which joining device is provided with gripping means for locking the walls positioned in the grooves in place with respect to the joining device. The invention also relates to a method for fabricating such joining device. Connecting air conditioning duct members to each other with H-shaped joining devices is known as such. Such solutions are disclosed, for example, in the publications US 2 360 159 and EP 0 366 637. Both solutions show an H-shaped device which is fitted to receive the opposite walls of successive air conditioning duct members. Publication DE 3110405 also describes this type of an H-shaped joining device.

However, these earlier solutions involve a number of problems. Thus, in the solution described in the publication EP 0 366 637, the walls of the air conditioning duct members are supported with thick gaskets. Such gaskets allow for considerable elasticity of the joint, which in turn requires that a considerable number of duct supports must be used when mounting the air conditioning duct, whereby both the material costs and the labour costs increase. Since the walls of the air conditioning duct members remain supported on the gaskets when mounted, the joining does not provide any tensile strength. This type of joint withstands poorly, for example, test pressurization of the duct system, where an air pressure of up to 400 pascals is conducted into the flow space. The described joining solution is also problematic in the case of a fire, because the gasket at the joint would probably melt and break down in the case of a fire. In order for the mounting means according to the publication EP 0 366 637 to be usable, a separate edging must be made on the air conditioning duct members. Such additional work stages tend to increase the cost of the mounting work significantly. The workload is also increased by the need to seal each corner area of the air conditioning duct members separately, because the

connecting work must be carried out one side at a time, leaving the corner areas without mounting means.

The publication US 2 360 159 discloses a mounting means which is assembled of seven different parts with a number of fixing means, in this case with bolts and nuts, among others.

The publication DE 3110405 describes a solution in which the straight parts of a polygonal duct member are connected with separate joining devices and separately made corner pieces are used for the corners. Brief description of the invention

The aim of the present invention is to provide a joining device and a method for fabricating it so as to eliminate the above-mentioned disadvantages of the prior art. In this way, the mounting work of the air conditioning duct members is simplified, as is the structure of the joining devices used for this work, the space requirement of the mounting work and the joining devices is minimised and the durability of the mounting is secured also in case of a fire.

To achieve this aim, the joining device according to the invention is characterised in that the joining device is comprised of a uniform profiled strip which is cut or made to correspond directly to the length of the circumference of the duct member and bent to correspond to the shape of the circumference of the duct member in such a way that a joining device mounted in place only has one butt joint between its ends which are placed against one another parallel to its circumference.

The method according to the invention for fabricating a joining device is characterised in that, in the method, of at least one sheet blank is formed a uniform H-profiled strip by bending, which corresponds in length to at least the length of the circumference of the duct member, and that, if necessary, the H-profiled strip is cut to correspond to the length of the circumference of the duct member and bent to correspond to the shape of the circumference of the duct member.

The starting point of the invention has been to simplify the joining device used for the connecting work, however, securing at the same time the durability of the air conditioning duct in all conditions of use.

The H-profiled strip used in the invention can be formed by many work methods known as such, for example, by roll forming or bending of one or more sheet blanks and, if necessary, by joining different parts to each other, for example, by welding, riveting or gluing.

By means of the invention are obtained considerable advantages, such as a solid joint, the air conditioning duct members connected by which are unable to turn or move at all with respect to one another. A solid joint is ensured by locking claws made at the ends of the duct members which attach to a notch formed by the gripping means of the joining device. When the ends of opposite duct members are locked with the joining device, the result is an extremely solid joint which has to be broken if the duct members are to be disconnected. When used for polygonal duct members, the corners can be maintained intact, because the entire joint can be encircled circumferentially with one strip and thus only one butt seam to be sealed is formed between the ends of the joining device which are circumferentially against one another. The prior art solutions require the use of several parts in the joining device, which slows down mounting work and may complicate achieving a solid joint.

When fabricating and using the joining device of the invention, no special parts or machining of the air conditioning duct members is required. The employees do not, therefore, need to have knowledge of or carry out any new or additional work stages. Since also the joining device itself comprises significantly less parts than before, the material consumption resulting from its fabrication is lower. The fabrication of the joining device also requires a significantly lower work input of the employees. Most of the work can even be carried out mechanically in a factory environment. The solution thus lowers the cost of the joint considerably.

Since the connection of the air conditioning duct members can be achieved with a single strip-like joining device, by means of which the joining point of the duct member is encircled only once, also the time to be reserved for the mounting of the air conditioning duct members is significantly shorter than before. In the tests carried out, it has been possible to almost halve the mounting time. Due to the simple structure of the joining device, significantly fewer tools are also required for the mounting work than before. With the solution according to the invention the connection work is also completely sparkless, whereby this type of connection can be carried out also in highly inflammable conditions without expensive special arrangements.

The joining device according to the invention is equally applicable for use with air conditioning duct members having a polygonal cross-section as with those having a circular cross-section. Brief description of the figures

Some preferred embodiments of the invention are described in greater detail in the following, with reference to the accompanying drawing, in which:

Figure 1 shows the mounting of the joining device in conventional, simple air conditioning duct members,

Figure 2 shows the mounting of the joining device in insulated air

conditioning duct members,

Figure 3 shows a diagrammatic, axonometric cross-section of one

embodiment of the profiled strip forming the joining device, Figure 4 shows a cross-section of the profiled strip according to Figure 3 on the normal plane of its centreline,

Figure 5 shows a partial cross-section of the profiled strip according to

Figure 3 with the duct walls mounted to it, and

Figure 6 shows a diagrammatic cross-section of another embodiment of the profiled strip forming the joining device on the normal plane of its centreline. Detailed description of the preferred embodiments

In the present Figures, the joining device is not shown to scale, but the Figures are diagrammatic, demonstrating the structure and operation of the embodiments in principle. Thus, the structural parts indicated by reference numerals in the accompanying Figures correspond to the structural parts designated by reference numerals in this specification. Figures 1 and 2 show the use of the joining device when connecting, for example, air conditioning ducts 2 to each other. In the case shown in Figure 1, uninsulated ducts are being connected to each other, whereas in Figure 2, insulated ducts with an internal insulation 19 are being connected to each other.

Figures 3 and 4 show one preferred embodiment of the profiled strip used for forming the joining device 1 of the present invention. The profiled strip has been made essentially H-shaped, preferably of a sheet blank, such as a sheet-metal blank. As a sheet blank can be used a metal sheet suitable for that purpose, such as steel or aluminium. The sheet raw material may also consist of other material suitable for bending.

The profiled strip thus has an inner surface 3 forming one side of the H, which, when fitted in the air conditioning duct member 2, is located on the flow space 4 side of the duct member 2, for example, as shown in Figure 3. The profiled strip has an outer surface 5, which forms the other side of the H and is essentially parallel with the inner surface, whereupon the inner and outer surfaces are connected to each other by means of a joining wall 6 which forms the transverse branch of the H. In this way, two insertion grooves 7 opening in opposite directions, with mouths indicated by reference numeral 8, are formed in the profiled strip for receiving the walls 9 of the air conditioning duct members 2. In its preferred embodiment according to Figures 3 to 5, the profiled strip is made of a single uniform piece of sheet metal constituting a sheet blank by bending in accordance with Figure 4. The dimension of the profiled strip parallel with the longitudinal axis is mainly limited by the fabrication raw material available and the processability of the profiled strip. When mounted on an air conditioning duct member 2, the profiled strip is, if necessary, cut to a length corresponding to the dimension of the cross-sectional circumference of the air conditioning duct member. The profiled strip may obviously also be made to correspond directly to the circumferential length of a duct member of a certain size. In the embodiment of Figure 4, the profiled strip is made of a single sheet blank, in which case the inner surface 3 and the transverse branch 6 comprise two sheet metal layers and the outer surface 5 is formed as a single layer. Reference numeral 10 denotes essentially parallel outer edges at which the sheet is bent back towards the longitudinal centreline of the strip. The height of the insertion groove 7 is indicated with reference marking h.

On the outer surface 5 is formed a gripping means 12 directed at the insertion groove. Figures 3 to 5 show an edging which forms an essentially V-shaped gripping means. This type of projection may, however, also comprise a convex projection made on sheet metal or an edging which is other than V-shaped.

In the mouth 8 area, the outer surface 5 is bent further from the inner surface 3, thus providing a larger mouth, which in turn facilitates the guiding of the wall 9 of the air conditioning duct member 2 into the insertion groove 7.

By fitting a gasket 14 in the insertion groove 7, a good grip between the insertion groove and the wall 9 of the air conditioning duct member 2 guided into it can be ensured. The tightness of the joint is ensured at the same time. This type of gasket can be formed both with a rubber gasket fitted in connection with the transverse branch 6 at the bottom of the insertion groove and with a sealing compound. The gasket may likewise be formed as shown in Figures 3 to 5 by fitting a lip seal in a separate gasket groove 15 formed at the bottom 3. The gasket may also be fitted on the outer edge 16 of the wall of the air conditioning duct member in such a way that when this wall is guided into the insertion groove of the joining device, the gasket is pushed in the insertion groove at the same time.

Figure 6 in turn shows another embodiment of a profiled strip suitable for forming the joining device 1 of the invention. The same or corresponding parts as in the previous embodiment are marked with the same reference numerals. The profiled strip is comprised of at least two sheet blanks placed against one another, such as sheet-metal blank, which together form an essentially H-shaped profile. As a sheet blank can be used a metal sheet suitable for the purpose, such as one of steel or aluminium. The raw material of such a sheet may also be some other material suitable for bending.

In the embodiment of Figure 6, the profiled strip is provided by two sheet metal pieces forming a sheet blank, which are connected to each other mechanically in the area between the connecting walls. For such connection are used methods known as such, for example, welding, gluing, riveting or the like.

The joining device 1 according to this second embodiment can be made as follows. The inner surface 3 is comprised of an essentially straight uniform sheet blank to which can, if necessary, be formed gasket grooves 15. The outer surface 5 is similarly made of a single uniform sheet blank by making a fold in it, which forms the transverse branch of the H, which comprises transverse walls 6 and a neck 21 connecting them. The desired insertion groove height is achieved by adjusting the height of the walls 6. The choice of the joining method of the inner surface and the outer surface can be influenced by adjusting the length of the attachment neck 21. The finished sheet blanks are placed against one another and joined with each other at the attachment neck 21, whereby two insertion grooves 7 opening in opposite directions are formed in the joining device. By arranging the joining walls 6 connected to the outer surface 5 of the insertion groove 7 at a distance from one another, the bending resistance formed by them is reduced and the fitting of the joining device to its receiving air conditioning duct member 2 wall 9 is simplified. To maintain sufficient insertion rigidity it is, on the other hand, conceivable to make the inner surface 3 in this embodiment of a sheet blank, which has a greater thickness than the sheet blank which forms the outer surface 5.

It is also conceivable that when the profiled strip is fabricated, a difference in length between the inner 3 and outer surface 5 and parallel to the axial centreline of the joining device is obtained in such a way that the profiled strip assumes the shape of a round circle, the circumferential dimension of which corresponds directly to the desired circumferential dimension of a circular duct. The joining device 1 according to the invention is used for connecting air conditioning duct members 2 to each other as follows.

On the walls 9 of the opposite ends of two air conditioning duct members 2 mounted successively are by means of a pressing means made gripping claws 17 projecting from the surface of the air conditioning duct member. The direction of projection of the gripping claws is determined by the position of the gripping means 12 in the joining device 1. The joining device is cut to correspond to the dimension of the cross-sectional circumference of the air conditioning duct member and bent to conform to the geometry of the duct members 2. In order not to produce compressions hindering mounting work in the corners 18 formed in the joining device mounted in the polygonal air conditioning duct member, the upper surface is cut open at the corners up to the joining walls 6 and, if necessary, the joining wall up to the inner surface 3. After this, the walls 9 are guided into the opposite insertion grooves 7 in the joining device. The walls of the air conditioning duct member are pressed in the insertion groove when being guided against one or more gaskets 14 in it, thus sealing the joint, while the gripping claws previously formed in the walls are guided in connection with the gripping means, locking the air conditioning duct member to the joining device, for example, as shown in Figure 5.

The joining device solution according to the invention makes possible rapid and simple mounting work, where the number of parts mounted is small as well as the number of tools required at the mounting stage, which thus reduces labour costs significantly compared with present solutions.