Field of the Invention

The present invention relates to connecting ducts and in particular to an apparatus and method for connecting ducts, particularly those used in heating and air conditioning systems.

Background of the Invention

Ducting is commonly used in large buildings such as factories, office blocks and apartment blocks for the transmission of air, which may be for the purposes of heating or cooling an environment in a building, or ventilating a building. Typically, such ducts are used to transport heated or cooled air and the ducts may be insulated as described in GB2423343.

Figure la illustrates a cross section through a prior art rectangular ductwork jointing system in which flange profiles 1, T are slid onto the end of duct sections 2, 2’. A sealing gasket 3 is inserted between the two flange profiles and the flange profiles 1, T are then clamped together using a clip or clamp 4. The flange profiles include two channels: a first channel 5 for receipt of the end of the duct section, and a second channel 6, used for the insertion of corner elements. Sealant 7 must be applied between the channels to attempt to prevent leakage of fluid from the duct via the flange profile. Fluid transfer between the two channels is only prevented by the sealant 7. The application of sealant to the flange profiles is time consuming and not fail-safe. Clamps can also bow or warp under pressure which can also compromise the seals.

EPl 995530 describes a rolled flange profile made from folded sheet metal. It comprises two separate channels and the folded joint between the two channels is made from four layers of metal which are pressed together and clinched or pinched together. In this design, the two channels are separated by the clinched metal joint. There is a risk of rupture of the clinched joint, particularly since 4 layers are involved, there is a risk that the joint may not be fully sealed.

EP0678696 describes a flange profile in which the outer edge of the flange profile is folded and the join between the two channels is located in-between these two folded outer layers. This flange profile is illustrated in Figure lb. Manufacturing of this profile would be complex, requiring a semi- circular channel 8 to be formed in one of the walls, and a hook-shaped edge strip 9 inserted into the semi-circular channel. It would be difficult to secure the hook-shaped edge strip within the channel by crimping or clinching due to the location and orientation of the join.

It would be desirable to provide an improved flange profile for the connection of duct sections.

Summary of the Invention

According to a first aspect of the invention there is provided a flange profile for attachment to a duct section, the duct section comprising a plurality of walls; wherein the flange profile comprises a plurality of folds of sheet metal and a central wall comprising two layers of folded sheet metal, the first layer folded to form a first channel into which a wall of a duct section may be inserted, and the second layer folded to form a second channel, wherein the second channel is separated from the first channel in an airtight manner and arranged at an angle thereto; wherein the second channel comprises a pair of spaced apart walls: a first, substantially flat outer wall and a second, inner wall, and the second layer of folded sheet metal is connected to the inner wall of the second channel; wherein the second channel includes a free edge of the sheet metal and the free edge is located in-between the two layers of folded sheet material forming the central wall; and wherein the second layer of the central wall comprises an upper wall portion and a lower wall portion and the lower wall portion lies in a different plane to the upper wall portion and wherein the free edge is substantially aligned with the upper wall portion and adjacent to the lower wall portion.

A second layer may be stepped such that a lower wall portion may lie in a different plane to an upper wall portion. For example a step between the lower wall portion and the upper wall portion may project at an angle of between 10 degrees and 90 degrees, or 20 degrees and 70 degrees, or 30 degrees and 60 degrees, or 40 degrees and 50 degrees, with respect to the longitudinal axis of the upper wall portion.

Other preferred features of the invention are set out in the Claims that depend from Claim 1 and the description herein. Brief Description of the Drawings

In the drawings, which illustrate the prior art, and a preferred embodiment of the apparatus of the invention, and are by way of example:

Figure la is an example of a prior art flange profile element;

Figure lb is a further example of a prior art flange profile element;

Figure 2a is a plan view of a connector assembly according to an aspect of the invention;

Figure 2b is a perspective view of the connector assembly of Figure 2a, in a partially assembled state;

Figure 3a is an end view of a flange profile section according to a further aspect of the invention, the flange profile section forming part of the connector assembly of Figure la;

Figure 3b is an end view of the flange profile section of Figure 3a attached to a duct wall;

Figure 3c is is a schematic end view of a flange profile section according to an aspect of the invention;

Figure 4 is a cross-section through an edge of a pair of ducts joined with the connector assembly of the invention;

Figure 5a is a perspective view of a part of the connector assembly of Figure 2a, prior to assembly; and

Figure 5b is a perspective view of a part of the connector assembly of Figure 2a, after assembly;

Figure 6 is an end view of a flange profile section according to a further aspect of the invention.

Figure 7a is a perspective view of a flange profile midway during fabrication, after clinching process.

Figure 7b is a perspective view of the flange profile of Figure 7a after fabrication of the flange is completed; Figure 8a is a schematic side view cross section of the flange profile of Figure 7a, taken through a clinch; and

Figure 8b is a schematic side view cross section of the flange profile of Figure 7b, taken through a clinch.

Detailed Description of the Preferred Embodiments

As shown in Figures 2a and 2b, a connector assembly for connecting together of duct sections, shown generally at 10, comprises four flange profile sections 12 joined together by four corner elements 14. The corner elements 14 are preferably right angled to provide for the attachment of rectangular or square duct sections.

Figures 3a and 3b illustrates a cross section through one of the flange profile sections 12. The flange profile is fabricated from folded sheet metal, preferably with a thickness of approximately 0.8mm, and the central wall 22 of the flange profile section 12 comprises two layers of folded sheet metal 24, 26. The first layer 24 is folded back on itself to form a first channel 16 shaped for receipt of a duct wall 20 (see Figure 3b). The first channel 16 has an end wall 17. The folded end of the central wall 22 is folded to form a lip 36 which is angled outwardly from the channel 16. The lip 36 adds strength to the flange profile as well as allowing easier insertion of a duct wall 20 into the channel 16. The outer wall 38 of the first channel 16 is resilient so that it can move outwards (anticlockwise) to allow the duct wall 20 to fit into the first channel 16. At rest, the outer wall 38 preferably lies at an angle of approximately 93 degrees to the adjacent end wall 17. The outer wall 38 of the first channel 16 may be provided with strengthening ribs 52. The first layer 24 of the central wall 22 is preferably not completely straight, as illustrated in the Figures. Preferably, the first end 24’ of the first layer of the central wall which is immediately adjacent to the end wall 17 is at an angle of substantially 90 degrees to the end wall 17, and the second end 24” of the first layer of the central wall which is immediately adjacent to the lip 36 is angled slightly towards the outer wall 38 of the first channel 16.

The second layer 26 of the central wall comprises an upper wall portion 28’ and a lower wall portion 28”. The second layer 26 is stepped such that the lower wall portion 28” lies in a different plane to the upper wall portion 28’. The upper wall portion 28’, immediately adjacent to the lip 36, is substantially parallel to, and aligned with, the first end 24’ of the first layer of the central wall. The second layer of folded sheet metal 26 is folded to form a second channel 18. The second channel 18 is at an angle to the first channel 16, typically approximately 90 degrees. The second channel 18 includes an inner wall 34 which extends from the lower wall portion 28” of the second layer of folded sheet metal 26. The stepped portion 27 of the second layer 26 preferably lies at an angle of approximately 134 degrees to the inner wall 34. The upper wall portion 28’ preferably lies at an angle of approximately 93 degrees to the inner wall 34. The inner wall 34 is folded back on itself to form a nose 30 and end wall 40. The angled portion of wall 29 forming the nose 30 is preferably at an angle of approximately 96 degrees to the inner wall 34. The formation of a nose 30 adds strength to the profile, and aids in the positioning of clips or clamps as shown in Figure 4. The sheet metal is folded again to form the outer wall 32, which is preferably substantially flat and preferably extends substantially perpendicular to the lower part of the central wall 22. The end 48 of the second layer of sheet material is then folded to form a second end wall 42, the free edge 48 of which is located in-between the two layers of folded sheet material 24, 26. The angle between the outer wall 32 and the second end wall 42 is preferably substantially 90 degrees, and the angle between the end wall 40 and the outer wall 32 is also preferably substantially 90 degrees. The free edge 48 lies in substantially the same plane as the upper wall portion 28’ of the second layer of sheet metal 26 and adjacent to the lower wall portion 28”. The second end wall 42 of the second channel 18, including the free edge 48, is parallel to, and aligned with the first end 24’ of the first layer 24 of the central wall 22, and the free edge 48 is parallel to the lower wall portion 28”, such that the free edge 48 is sandwiched in-between the the first end 24’ of the first layer 24 of the central wall, and the lower wall portion 28” of the second layer of folded sheet metal 26. The free edge 48 of the second end wall is then secured to the lower wall portion 28” of the outer layer 26, for example by clinching at intervals along the length of the profile or by spot welding. The spaced apart inner wall 34 and outer wall 32 of the second channel 18 may be parallel to each other, as illustrated. The inner wall 34 of the second channel 18 may be provided with strengthening ribs. Figure 4 illustrates a cross section through two flange sections 12, 12’ used to connect together two duct sections, 20, 20’. A sealing gasket 44 is located between the two flange sections. The nose portion 30, 30’ allow the sections to be clipped or clamped together, for example using a clip 44 as illustrated.

Figure 5a and 5b illustrate perspective views of the flange profile and show how duct walls 20 and a corner profiles 50 are inserted into the first and second channels 16, 18.

Figure 6 illustrates an alternative flange profile 54, which differs slightly from the previously described embodiment. This embodiment also includes a central wall 70 comprising two layers of folded sheet metal 64, 66, and the first layer 64 is folded back on itself to form a first channel 56 shaped for receipt of a duct wall. The second layer 66 of the central wall comprises an upper wall portion and a lower wall portion 62. The lower wall portion 62 is curved, rather than stepped, such that the lower wall portion 62 does not lie in the same plane as the upper wall portion. The second layer of folded sheet metal 66 is folded to form a second channel 58 in the same way as in the previous embodiment, with an inner wall 76, first end wall 78 and outer wall 74. The outer wall 74 of the second channel 58 is folded to form a second end wall 72, with the free edge 68 located in-between the two layers of folded sheet material, such that the free edge 68 is contact with the lower wall portion 62. The second end wall 72 is substantially aligned with the upper wall portion of the second layer of sheet metal 66 and is parallel to, and aligned with the first layer 64 of the central wall 70. In this embodiment the free edge 68 of the second end wall 72 is not further secured to the lower wall portion 62 of the outer layer 66. The spaced apart inner wall 34 and outer wall 32 of the second channel 18 may be parallel to each other, as illustrated. As with the previous embodiment, the outer wall 80 of the first channel and the inner wall 76 of the second channel may be provided with strengthening ribs 60.

As shown most clearly in Figures 3a and 6, the folded arrangement of the flange profiles provides a complete separation of the first channel 16, 56 and second channel 18, 58. There is no seal between the two channels that could fail. This means that any leakage from the duct between the duct wall 20 and the central wall 22, 70 of the flange profile 12, 54 cannot escape via the second channel 18, 58. The folded arrangement can also be fabricated using a far less complex process compared to the prior art, and, in relation to the first embodiment, the free edge 48 is easily secured using mechanical fastening techniques such as clinching or spot welding. Figures 7a, 7b, 8a and 8b illustrate formation of the flange profile and how the free edge 48 can be secured via a clinching process. As shown in Figure 7a, the central wall 36 is first folded, leaving the first layer 24 substantially flat. The second layer is then folded to form the second channel 18 and the free end 48 is folded around to sandwich between the two layers making up the central wall. Those three layers (24, 48 and 28”) are then fastened together, for example by a series of clinches 82 as illustrated. Spot welding could also be used to join the layers in a similar manner. After clinching or welding the first layer 24 is folded to form the first channel 16 as previously described.