A JOINTING SYSTEM WHICH JOINS TWO SHEET MATERIAL COMPONENTS AT JUXTAPOSED EDGES THEREOF AND DUCTWORK INCORPORATING SUCH A JOINTING SYSTEM

Abstract: Two sheets (38 and 39) having externally visible surfaces are joined together at their juxtaposed edges by a joining member (18) which is secured to their inner surfaces and which straddles the juxtaposed edges. The joining member (18) is formed with a groove (35) which extends along and is concave to the juxtaposed edges. The sheets (38 and 39) are turned down at the juxtaposed edges, the turned down portions (43 and 44) extending inwardly away from the externally visible surfaces and into the hollow formed by the groove (35). Externally visible bend radii are formed where each turned down portion (43, 44) meets its respective externally visible surface.

Description: "A JQIHTINS SYSTEM WHICH JOINS TWO SHEET MATERIAL COMPONENTS AT JUXTAPOSED EDGES THEREOF AND DUCTWORK INCORPORATING SUCH A JOINTING SYSTEM" This invention relates to a jointing system which joins two sheet material components at juxtaposed edges thereof, each of the sheet material components having an externally visible surface. More particularly, although not exclusively, this invention relates to a jointing system which is suitable for joining ventilation ductwork end to end in an exposed location and to ductwork incorporating such a jointing system. If sheet material components which have an externally visible surface are joined together at juxtaposed edges with those edges in abutment, by a joining member which is secured to the inner surfaces of the sheet material components so that it straddles the abutting edges, the resultant joint is unattractive from an aesthetic viewpoint because the edges exhibit sharp corners. This is so if the components that are joined are large ducts, such as ventilation ducts and the joining member is an inner joining ring. An alternative method of joining ducts end to end is by bolting together external flanges which are formed at the juxtaposed ends of the ducts, but that is unattractive as well. It has often been thought necessary to paint the external surfaces' or to cover them with a cladding which is more visually acceptable. Such cladding may comprise thin gauge (say 20 or 22 SWG) aluminium sheet laid on a layer of mineral wool insulation. Such painting or cladding leads to an increase in cost and/or weight. US-A-3791681 discloses a jointing system for joining two cylindrical sheet metal conduit elements together at juxtaposed edges, each of the sheet metal elements having an externally visible surface and an inner surface. The marginal portions of the sheet metal elements, that is to say the portions of those element that form the respective ones of the juxtaposed edges at the joint, are bent outwards. A connecting strip having a U-shaped cross-section is snap-fitted over the radially-outwardly bent marginal portions of the sheet metal elements so as to urge the latter into sealing engagement with a sealing strip of elastomeric material which is between them. The end result is that the gap between the juxtaposed edges of the cylindrical sheet metal elements is concealed from view by the connecting strip. An object of this invention is to provide a jointing system which will be acceptable from both the structural and aesthetic standpoint and which will not incur cost and/or weight penalties such as are referred to above. By this invention a joining member is secured to the inner surfaces of the two components so that it straddles the juxtaposed edges of the two components and it is formed with a groove which extends along and is concave to those edges, and the sheet material components are turned down at those edges, the turned down edge portions extending inwardly, away from said externally visible surfaces and into the hollow formed by the groove, an externally visible bend radius being formed where each turned down portion meets its respective externally visible surface. Hence, according to one aspect of this invention there is provided a jointing system as claimed in claim 1. Preferred features of such a jointing system are claimed in claims 2 to 12. This invention is applicable to any industrially formed product which includes a joint between two sheet material components which have externally visible surfaces and which might otherwise be painted or clad for aesthetic purposes. A preferred application however is to joining end to end large ducts, such as ventilation ducts, which may have a cross-section which is circular or 'half-oval', that is to say opposed semi-circular portions interconnected by substantially parallel straight portions. According to another aspect of this invention there is provided ductwork as claimed in claim 13. A feature of this invention comprises using a cable to support ductwork which incorporates a jointing system which embodies this invention, the supporting cable running in the hollow formed by the groove that runs circumferentially between a juxtaposed pair of tubular sections of such ductwork. The support cable would be of an appropriate diameter (e.g. 5 roil) and preferably would be Stainless Steel or galvanised steel cable. The cable and other elements of the support system in which this invention is embodied are virtually invisible to an observer standing at or below or at the side of the supported duct. Preferred features of this aspect of the invention are claimed by claims 14 and 15. The ductwork may be supported horizontally or vertically. Above horizontally supported ductwork, in a space through which the cables run to overhead support structure, standard turnbuckles and clevises may be used. A system in which this invention is embodied may be used to support single horizontal ducts which may be circular or 'flat-oval' and can be adapted to incorporate the additional support for cable trays and/or other services in the blind spot between the duct and overhead support structure ( e.g. a ceiling). In another form, the invention may be used to support single or multiple ducts. The cables extend from a suitable cable bracket which will cradle the ducts with the tensioned cable acting as the retaining mechanism. In practice, the bracket is mounted on an adjacent surface, typically vertical. In another form, the cable support system can be used to hold one or more ducts in a horizontal position. In this form, the cables pass below the duct and may hold the duct against a crescent shaped cradle support. Several embodiments of this invention will be described now by way of example with reference to the accompanying drawings, of which :- Figure 1 is a schematic in plan of part of a twin duct ventilation system which embodies this invention; Figure 2 is an isometric view of a ventilation system splitter box which embodies this invention; Figure 3 is a view of the structure of the splitter box shown in Figure 2 with the external aluminium sheeting removed; Figure 4 is a sectioned fragment of the splitter box shown in Figure 2, the section being on the line IV-IV in Figure 2; Figure 5 is a sectioned fragment of the splitter box shown in Figure 2, the section being on the line V-V in Figure 2; Figures 6 to ' 11 are views similar to Figures 4 and 5 of different embodiments of the invention; Figure 12 is a section on the line XII-XII in Figure 1 showing one form of suspension of the ducts shown in Figure 1; Figure 13 is a view in perspective on arrow A in Figure 12 of a support arrangement for a juxtaposed pair of vertical ducts of the system shown in Figure 1; Figure 14 is view similar to Figure 12 of a single duct which embodies this invention; Figure 15 illustrates installation of a 'flat-oval' ventilation duct in a confined space; and Figure 16 is a section on the line XVI-XVI in Figure 15 of the mechanism shown in Figure 15. Figure 1 shows a ventilation ductwork system which comprises two long ventilation ducts 10 and 11 which are supported horizontally, side by side from a roof 12 by a suspension system at spaced intervals along the ducts 10 and 11. Figure 2 shows a splitter box 14 which provides a junction between the two longitudinally extending, parallel ducts 10 and 11 and two laterally extending branch ducts 15 and 16 which are circular as well. Like the ducts 10 and 11, the splitter box 14 and the ducts 15 and 16 are formed of a number of 18 SWG rigidised aluminium sheets which are joined at their edges. The ventilation system, including the ducts 10 and 11 and the splitter box 14 is suspended from the roof of a large hall or similar enclosure so that it is exposed to view from below. At least those joints between juxtaposed aluminium sheets of the splitter box 14 and of the ducts 10 and 11, which are visible from below, as well as those of the branch ducts 15 and 16 are joined by a jointing system which embodies this invention. Figures 4 and 5 show such joints which each comprise an inner joining member 17, 18 secured to the sheets by rivets 19. However any suitable securing means such as screws or an adhesive could be used. Figure 2 shows that the splitter box 14 has a so- called 'flat oval' cross-section, comprising semi¬ circular side walls 21 and 22 which are interconnected by flat walls 23 and 24 at its top and its bottom, and which is closed by flat walls 25 and 26 at either end. Two circular apertures 27 and 28, 29 and 31 are formed in each end wall 25,26, each being substantially coaxially aligned with one of the apertures 27-29,31 in the other end wall 25,26. Each of these apertures 27- 29,31 is for connection into a respective one of the longitudinally extending ventilation ducts 10 and 11. Two circular apertures 32 and 33 are formed in one, 22 of the semi-circular side walls 21 and 22 and are for connection to the laterally extending ducts 15 and 16. The inner joining members (including the joining members 17 and 18 shown in Figures 4 and 5) are part of an inner framework 34 which reinforces the aluminium sheeting at the joints and which is shown in Figure 3. Each duct 10,11,15,16 comprises lengths of the rigidised aluminium sheet which are rolled into tubes. Juxtaposed tubes are joined together end to end by a jointing system which embodies this invention. The joining member is an inner joining ring which is secured to the inner surfaces of the tubes it joins and which conveniently is as is illustrated at 18 in Figure 5. The ducts are large, having a diameter of at least 2 metres. The joining member 17 shown in Figure 4 has a top hat section. It is formed of aluminium , conveniently 14 or 16 SWG. It is suitable for joining flat sheets at their edges. It may be an extrusion or it may be a pressing. It is not limited in its application to joining flat sheets. It could be arcuate in form. Indeed it could formed as a ring as has been described for the ducts. The joining member 18 shown in Figure 5 is arcuate, being either semi-circular as shown in Figures 2 and 3, or being a ring as has been described for the ducts 10,11,15 and 16. Figure 5 shows it has a deep arcuate groove 35 formed in it. The groove 35 is formed by swaging. It may be formed from 14 or 16 SWG aluminium strip, or it may be formed of titanium, stainless steel, a plastics material or a composite. In addition to the joining member 17, 18, the jointing system comprises each of the sheets 36 and 37, 38 and 39 to be joined being turned down at its edge to be joined. The turned down edge portions extend into the groove formed by the joining member (see 41 and 42 in Figure 4 and 43 and 44 in Figure 5). There is a bend radius rather than a sharp edge at the corner between each turned down portion 41 to 44 and the externally visible surface of the respective sheet 36 to 39. The turned down portions 41 to 44 are shown to be as far apart as they can be in Figures 4 and 5. Figures 6 and 7 show they may be closer together, although still spaced apart. The resultant gap between the pair of turned down portions 41 and 42, 43 and 44 and the base of the respective groove visible between them, as shown in Figures 4 to 7, forms what is known in architectural terms as a "shadow gap" which is aesthetically pleasing. The concave surface of the groove may be darkened by painting or coating in order to enhance the "shadow gap" effect. The groove formed by the joining member 17, 18 should be as deep as possible without the joining member 17, 18 projecting into the interior of the splitter box 14 or duct 10, II, 15, 16 so as to disturb flow through the splitter box 14 or duct 10, 11, 15, 16. Any voids between the turned down portions 41 to 44 and the concave surface of the groove in the joining member 17,18 may be filled with a synthetic mastic material 45 (see Figures 5 to 9) to enhance the rigidity of the joint. Figures 8 to 11 illustrate alternative forms of the jointing system in which the turned down portions 46 and 47 about one another. In these cases the aesthetic effect is provided by the radiused edges of the sheets between the turned down portions and the externally visible surfaces. The junction arrangements described above have the advantage that the aesthetic appeal from the exterior of the splitter box or joined ducts is such that external painting or cladding is not required. Also, the weight of the ducting is greatly reduced. A further advantage is that the use of a joining member with a smooth groove reduces the likelihood of turbulence in fluid flow in the ducts. The jointing system described herein may be used for joining ducts which are to be used in a ductwork support system, as described in my co-pending International patent application no. PCT/GB96 which designates the priority of my British Patent application no. 9506814.4 filed 01 April 1995. Figure 12 shows another form of suspension system for the ducts 10 and 11 which uses a feature of the jointing system that embodies this invention. The suspension system 13 shown in figure 12 comprises a support bracket 48 which is mounted on the roof 12. A crescent-shaped support cradle 49,51 for each duct 10,11 is supported below the bracket 48 by a respective arm 52,53 which depends from the bracket 48 to which it is rigidly secured. Each crescent-shaped support cradle 59,51 receives the respective duct 10,11 in its concave surface which bridges a 'shadow gap' between juxtaposed tubular lengths 10A and 10B, 11A and 11B of the respective duct 10,11. Each duct 10,11 is held engaged in the respective downwardly-facing concave surface of the respective support cradle 49,51 by a respective cable 54,55 which is secured at one end to the support bracket 48, which extends into the space between the ducts 10 and 11, passing over the respective end portion of the respective crescent-shaped support cradle 49,51 and into the groove 35 of the internal ring 18 that joins together the juxtaposed pair of tubular lengths 10A and 10B, 11A and 11B, and forms the 'shadow gap' therebetween, and which runs around that groove 35 on the diametrically opposite side of the duct 10,11 from the respective crescent-shaped support cradle 49,51 to the other end of the support cradle 49,51 to which it is secured. A suitable tensioning mechanism 56,57, such as a turnbuckle, is fitted into each cable 54,55 by which the latter is tensioned. Each cable 54,55 is preferably a Stainless Steel cable or a galvanised steel cable. Separate cable trays may be suspended from the roof 12, one on either side of the support bracket 48 and each above a respective one of the lengths of duct 10,11. A spacer device 58 is provided in the space between the ducts 10 and 11 and connected at either end to a respective one of the crescent-shaped cradles 49 and 51. Figure 13 shows that the vertical branch ducts 15 and 16 are supported by a system which is similar to the system 13 just described with reference to Figure 12. The differences are that the arms 52A and 53A are pivoted onto the support' bracket 48A and extend horizontally therefrom to the crescent-shaped support cradles 49A and 51A which are also horizontal. Figure 14 shows a single duct 61 supported by a Stainless Steel cable 62 which runs in a 'shadow gap' formed in the duct 61 and which is suspended by its ends from support structure 63. A clevis 64,65 at either end of the cable 62 is pivotably connected to a respective angle bracket 66,67 of the support structure 63. Each of the angle brackets 63 and 67 is fitted by one of its arms onto a screw 68 and they are fixed in position on the screw 68 by locknuts 69 so that the tension of the cable 62 which is tensioned by the weight of the duct can be adjusted by adjusting the relative locations of the angle brackets 66 and 67 on the screw 68. Figure 14 shows the angle brackets 66 and 67 spaced apart by a distance which is less than the diameter of the duct 61. Each angle bracket 66,67 is supported from a roof 71 overhead by a respective screw-threaded rod 72,73 which depends from a respective mounting bracket 74,75 which is mounted on the roof 71. Each screw-threaded rod 72,73 extends through a respective aperture 76,77 in the other arm of the respective angle bracket 66,67 and through a respective aperture 78,79 in the respective mounting bracket 74,75, those apertures 76-79 allowing lateral displacement of the rods 72 and 73 relative to the respective angle and mounting brackets 66,67 and 74,75. A cable tray 80 runs above the two angle brackets 66 and 67 on which it is supported. There are various possible alternatives to the particular arrangement just described with reference to Figure 14 for supporting a single duct 61 by a cable 62 which runs in a 'shadow gap' formed in the duct. Instead of being fixed to angle brackets 66 and 67, the ends of the cable may be connected to a fitting at the lower end of the respective depending screw-threaded rod 72,73, the fittings being spaced apart by a screw in a similar manner to the angle brackets 66 and 67 and that spacing may be substantially equal to the diameter of the duct 61. The locknut and screw arrangement 68 and 69 for spacing apart the clevises 64 and 65 at the ends of the cable 62 and for supporting a cable tray 80 may be suspended from the roof 71 cables instead of the depending screw-threaded rods 72 and 73. In such an arrangement the supporting cables may depend from support brackets on the roof that are spaced apart by a distance that is greater than the spacing of the ends of the cable that runs around the 'shadow gap' in the duct. Indeed the distance between those support brackets on the roof may be substantially equal to the diameter of the duct. Figures 15 and 16 illustrate installation of a 'flat-oval' ventilation duct in a confined space which is particularly suitable for use where weight and space are at a premium, such as in marine platforms, high-speed hydrofoils etc. The 'flat-oval' duct 81 is suspended from two spaced wall-mounted brackets 82,83 by a Stainless Steel cable 84 which runs under the duct 81 in a 'shadow gap' . A clevis 85,86 at either end of the cable 84 is pivotably connected to a respective nut member 87,88. The latter is interengaged with a respective vertical setscrew 89,91 which is supported in a respective one of the wall- mounted brackets 82,83 with its head at its lower end so that it is accessible from below. Also each nut member 87,88 is held against rotation by being fitted into a slot 92 which is formed by the respective bracket 82,83 as is shown in Figure 16. This arrangement allows the 'flat-oval' duct 81 to be mounted with its top close to a roof 93 overhead and with its sides close to the walls on which the brackets 82 and 83 are mounted, it being possible to use a long screw driver 94 to turn either of the setscrews 89 and 91 as is shown at 94 in Figure 15.

Claims: CLAIMS: 1. A jointing system which joins two sheet material components at juxtaposed edges thereof, each of the sheet material components having an externally visible surface and an inner surface and being joined by a joining member which is secured to the two components and which straddles said edges, wherein the joining member is formed with a groove which extends along and is concave to said edges, and the sheet material components are turned down at said edges, characterised in that, the joining member is secured to the inner surfaces of the two components and the turned down portions extend inwardly, away from said externally visible surfaces and into the hollow formed by said groove, an externally visible bend radius being formed where each turned down portion meets its respective externally visible surface. 2. A jointing system according to claim 1, wherein the two sheet material components are large ducts which are joined together end to end by the jointing system. 3. A jointing system according to claim 2, wherein the ducts are ventilation ducts. 4. A jointing system according to claim 2 or claim 3, wherein the ducts have a circular cross-section. 5. A jointing system according to claim 2 or claim 3 wherein the ducts have a cross-section which is 'flat' oval, comprising opposed semi-circular portions interconnected by substantially parallel straight portions. 6. A jointing system according to any one of claims 2 to 5, wherein the ducts are formed of rigidised aluminium sheet material. 7. A jointing system according to any one of claims 1 to 6 wherein the turned down edges of the two sheet material components are spaced apart. 8. A jointing system according to any one of claims 1 to 6, wherein the turned down edges of the two sheet material components abut one another. 9. A jointing system according to any one of claims 1 to 8, wherein the joining member is made from sheet material. 10. A jointing system according to any one of claims 2 to 6, or any one of claims 7 to 9 when appended to claim 2, wherein the joining member is an inner joining ring. 11. A jointing system according to claim 10, wherein the groove is formed in a metal inner joining ring by swagin . 12. A jointing system according to any one of claims 1 to 11 wherein any void between each turned down edge and the joining member is filled with a synthetic mastic material. 13. Ductwork comprising tubular sections of sheet material jointed together end to end, each juxtaposed pair of tubular sections being joined together by an internal ring which is fitted into and secured to each of them, each ring being formed with an annular groove which runs between the juxtaposed ends of the respective pair of tubular sections, and the sheet material of each tubular section being turned down at its ends, the turned down portions extending inwardly, away from the external surface of the respective tubular section and into the hollow formed by the groove , and a bend radius being formed where each turned down portion meets its respective external surface. 14. Ductwork according to claim 13, wherein a support arrangement is provided for supporting the ductwork in a situation where it is visible, the support arrangement comprising an elongate tensile load bearing member which is substantially inextensible longitudinally whilst being laterally flexible, which runs in the hollow formed by the internal joining ring between a juxtaposed pair of tubular sections so that it is substantially unobtrusive, which is anchored at either end and which is tensioned whereby to locate the ductwork. 15. Ductwork according to claim 14, wherein said elongate tensile load bearing member runs around the ring whereby to hold the respective pair of tubular sections that are joined by the ring, against a crescent-shaped cradle support.

Inventors: HACLIN GRAHAM JOHN, HACLIN, GRAHAM, JOHN
Applicants: HACLIN GRAHAM JOHN, HACLIN, GRAHAM, JOHN
Application year: 1996
Main classification: F24F13
IPC codes: F16L13, F24F13