DUCT JOINTING DEVICES

Abstract: Duct jointing devices comprising two separate legs (6A, 6B) adapted to be assembled together to form a rigid L-shaped corner piece for associating with hollow flanges (2) wherein the two leg bodies (6A, 6B) overlap to form a corner body.

Description: DUCT JOINTING DEVICES The invention relates to duct jointing devices comprisin corner pieces for introduction into hollow flanges. It has long been recognised that an effective and, if necessary, essential air tight, joint between adjacent matching ends of polygonal sheet metal ducts can be provided by attaching to the end of each wall of each duct an elongate hollow flange, forming the flanges into rigid frames by introducing the respective arms of rigid L-shaped corner pieces endwise into the open ends of each pair of adjacent hollow flanges associated with each duct, and joining together adjacent pairs of corner pieces associated with the respective ducts. The corner pieces not only provide means for the securing of the respective ducts together but also ensure, by their rigid connection within the flanges, that the corners of the duct ends are maintained at their correct angles which are commonly, though not necessarily, right angles. With the corner pieces conventionally used in such devices, it is necessary to assemble the frame remotely from the end of the duct and then carry the frame to the duct end for attachment thereto. The transportation of frames to the attachment site presents difficulties particularly if the frame is of large dimensions, and it is an object of the present invention to alleviate this difficulty. According to the invention there are provided two separate legs adapted to be assembled together to form a rigid L- shaped corner piece for associating with hollow flanges to provide a duct jointing device. Each leg may be attachable, after location in a flange piece, to a separate corner body, but preferably the corner piece comprises two leg bodies overlapping at their ends to form a corner body. Preferably the two leg bodies comprising one corner piece are identical. The legs may be at least substantially planar and may be capable of assembly by movement perpendicular to said plane. Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings of which:- Figure 1 is a perspective view of one end of a rectangular duct partially equipped with means for securing that end to an end of a matching duct; Figure 2 is an isometric view of a whole duct flange; Figure 3 is an exploded isometric view of overlapping leg elements capable of assembly form a rigid L-section corner piece; Figure 4 is a plan view of the assembled corner piece; and Figure 5 is a side elevation on one of the leg elements of Figure 4. The invention relates to means for securing together the ends of sheet metal ducts, such as the square duct shown in Figur 1, though the invention is applicable to any polygonal sectioned duct. The Figure also shows, in part, mean conventionally employed for securing the ends of duct together, such means comprising a corner piece 1, and a pai of hollow flanges 2. Each of the flanges 2 comprises a strip of sheet meta somewhat shorter than the width of the duct and folde through 180° widthwise to form an open rectangular loop 3 an also through 90° to provide upper 4 and lower 5 duct-engagin limbs. The flanges are attached to the ducts by sliding the onto the walls of the ducts at their ends with the limb 5 o the inner side of the wall and the limb 4 exterior of th wall as shown in Figure 1, and then securing the flange t the wall in any conventional manner. The corner piece 1 conventionally comprises a corner portio from which legs 6 project at angles corresponding to th interior angles of the duct, in the example 90°. Each of the legs is of such dimensions that it may be introduced into the open loop 3 of a respective one of a pair of adjacent flange pieces, and to be a tight fit therein, so that the flange pieces are held together substantially rigidly at the angle of the corner piece. A complete duct jointing frame comprises a number of corner pieces and a number of flange pieces each corresponding to the number of sides to the duct. In the jointing devices hitherto described, it has been necessary to assemble together the corner pieces and the flange pieces into a closed and substantially rigid frame remote from the duct and to transport the frame to the duct for attachment thereto. This is because each leg is required to be introduced into the flange piece lengthwise of the leg, and this has necessitated relative movement between the corner piece and angularly disposed flange pieces, which movement could not be accommodated with the flange pieces already in situ as shown in Figure 1. As shown in Figures 3 and 4, however, the corner piece of the invention has separable leg elements 6A and 6B adapted to be joined together as a half-lap joint. To this end the leg element 6A is provided with a corner portion 7 having a terminal flange 8 and an opposed parallel shoulder 9 between which to accommodate, in face to face relationship, a corner portion 10 of the leg element 6B. Similarly, the corner portion 10 has a flange 11 and an opposed shoulder 12 fo engagement respectively with the edges 13 and 14 of the portion 7 when the respective corner pieces are brought together face to face. The edge 13 of leg element 6A and the corresponding edge 16 of leg element 6B are set back from the general lines 17, 18 of the leg elements in order t accommodate the terminal flanges. As will be appreciated from Figure 5, each leg elemen comprises material of substantially constant thickness an may be made, for example from sheet metal, with a single pressing operation. When assembled, the corner piece thus constitutes a corner body comprising the portions 7 and 10 i face to face relationship, and extending from the said body pair of legs, suitably oriented with respect to one another, and of half the thickness of the corner body. In order tha the two legs are co-planar in the assembled corner piece, each of the elements 6A and 6B has a curved portion 1 inclined in the opposite direction to the projection of it terminal flange. It is particularly advantageous if the two leg elements ar identical, rather than handed, so that both can b manufactured by the same pressing tool. The invention is capable of variation in that the securin together of the separate elements may be effected by mean other than the flanges 11, 8 and the shoulders 9, 12, and th alternative means may for example comprise one or mor upstanding pegs on one of the elements where they overlap an matching hole or holes in the other element. Again, th corner piece may comprise three elements, a separate corne body to which is attached separate legs, the proviso bei that the attachment is such that the corner piece can assembled without signficant movement of either l lengthwise thereof.

Claims: CLAIMS 1. A duct jointing device comprising two separate leg adapted to be assembled together to form a rigid L-shape corner piece for associating with hollow flanges. 2. A duct jointing device according to Claim 1, wherein eac leg is attachable after location in a flange piece, to separate corner body. 3. A duct jointing device according to Claim 1, wherein th corner piece comprises two leg bodies overlapping at thei ends to form a corner body. 4. A duct jointing device according to Claim 3, wherein eac leg body where it overlaps with the other leg body has channel rebate enabling the two leg bodies to overlap an interfit. 5. A duct jointing device according to Claim 3 or 4 wherei the two leg bodies comprising one corner piece are identical 6. A duct jointing device according to any one of th preceding claims wherein the legs are at least substantiall planar and are capable of assembly by movement perpendicula to said plane. 7. A duct jointing device substantially as herein describe with reference to the accompanying drawings. 8. A duct section wherein each end of each wall is equippe with a hollow flange and wherein adjacent flanges ar connected by duct jointing devices according to Claims 1 t 7. 9. A duct formed from at least two duct sections accordin to Claim 8, said sections being placed end to end with duc jointing devices of each section being connected to duc jointing devices of adjacent sections so that the section are joined to each other.

Inventors: FIRTH COLIN, FIRTH, COLIN
Applicants: FIRMAC LTD, FIRMAC LIMITED
Application year: 1989
Main classification: F16L23
IPC codes: F16L23