GB2216212A - Duct jointing devices - Google Patents

Abstract

Conventional duct-jointing apparatus comprising a plurality of hollow flanges 2 and corner-pieces 1 having angularly spaced legs 6 is improved by providing inner faces of the flanges and the outer faces of the legs of the corner-pieces with rows of tooth-like projection which inter-engage in ratchet fashion when the legs are inserted in the flanges. This reduces the chances of the corner-pieces falling out of the flanges before the latter can be attached to the ducts. Duct ends are subsequently joined together by bolts passing through holes 7 at each corner. <IMAGE>

Description

Duct Jointing Devices The invention relates to duct jointing devices comprising hollow flanges and corner pieces and more particularly relates to the securing of such flanges to such corner pieces.

It has long been recognised that an effective and, if necessary, essentially 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.

The corner pieces are located in correct angular position relative to the flanges essentially by ensuring that the cross section of the arms of the corner pieces corresponds with the internal cross section of the hollow of the flange.

However, it is also desirable to ensure that the corner pieces do not slip longitudinally within the flanges, and this requirement has hitherto been provided by the use of screws, bolts, rivets or welding. These techniques however require the use of tools and represent an additional and time consuming constructional step which it is the object of the invention to avoid.

According to the invention there is provided apparatus for use in the joining of two polygonal ducts and comprising a hollow flange and a corner piece having at least one arm slidable lengthwise into said flange with at least one external surface of the arm in sliding contact with an internal surface of the flange, characterised in that one of said surfaces is provided with a row of projections and the other of said surfaces is provided with at least one projection whereby the projections of the respective surfaces engage with one another ratchet wise as the arm is slid inwardly of the flange.

Preferably the said other of said surfaces is provided with a plurality of projections arranged in a row parallel to the direction of said lengthwise movement of the arm. Rows of the projections parallel to said direction may be provided on opposed surfaces of the arm and of the flange, being surfaces which are in sliding contact with one another as the arm is slid inwardly of the flange. The said surfaces are preferably in a plane transverse to the ducts at their ends. The projections are preferably elongate transversely to said direction.

The projections may be of saw-tooth form in a plane perpendicular to the surface from which they project, each comprising leading and trailing faces relative to the direction of relative movement of the surfaces during said inward sliding movement, said leading face being inclined at an angle to the surface from which it projects less than or equal to the corresponding angle of inclination of the trailing edge. Preferably said first-mentioned angle is not greater than 450 and it is even more preferable that said angle be not greater than 300.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, of which: Fig. 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; Fig. 2 is a perspective view of a hollow duct flange, shown partly cut away; Fig. 3 is a plan view of a corner piece for co-operating with the hollow flange of Fig. 2; Fig. 4 is a section (exaggerated) of assembled securing means; and Fig. 5 is a section (exaggerated) of assembly of securing means of alternative embodiment.

The invention relates to means for securing together the ends of sheet metal ducts, such as the square duct shown in Fig.

1, though the invention is applicable to any polygonalsectioned duct. The figure also shows, in part, means conventionally employed for securing the ends of ducts together, those means comprising a flat corner piece 1, and a pair of hollow flanges 2.

Each of the flanges 2 comprises a strip of sheet metal somewhat shorter than the width of the duct and folded through 1800 widthwise to form an open loop 3 and also through 900 to provide upper 4 and lower 5 duct-engaging limbs. The flanges are attached to the ducts by sliding them onto the walls of the ducts at their ends with the limb 5 on the inner side of the wall and the limb 4 exterior of the wall as shown in Fig. 1, and then- securing the flange to the wall in any conventional manner.

If a flange piece is so attached, not just to the two sides as shown in Fig. 1 but to all sides, the end of the duct presents a plurality of projecting hollow flanges, each terminating at both ends in an opening 3. In order to complete the securing together of the duct ends, the legs 6 of the corner piece 1 are introduced into the open loop 3 of adjacent flange pieces, and similar corner pieces are introduced into the ends of the flanges at each other corner.

The legs of the corner pieces are of thickness and width corresponding to the interior dimensions of the loops 3 so that the combination of flange pieces and corner pieces, when fully assembled, constitutes a rigid frame attached as already described to the duct. If a matching duct end is similarly provided with a framework comprising flange pieces and corner pieces, the respective ends can be secured to one another by aligning the corner pieces of the respective frames and securing them together by, for example, the bolts passing through holes corresponding to hole 7 shown in the corner piece of Fig. 1.

It will be appreciated from a consideration of Fig. 1 that, in practice, it will generally be necessary to insert the leg 6 of the corner pieces 1 into the ends of the flange pieces before the said flange pieces are fitted onto the duct ends, and this requirement means that a framework of corner and flange pieces has to be carried to the site of the end of the duct, and during this operation there is a danger of some legs, especially those arranged vertically, slipping out of their corresponding flanges.

Fig. 2 shows in perspective view, and partly cut away, a length of hollow flange corresponding to reference 2 in Fig.

1, and it will be understood that in use an edge of a duct wall will be introduced between the lower plate 5 and the upper plate 4, whilst a leg of a corner piece, corresponding to reference 6 in Fig. 1 will be introduced between the spaced vertical walls 10, 11. The wall 10 is shown cut away in order to show, on the inner face of the wall 11, a row. 12 of notches or serrations 13. The row itself is parallel to the top 14 of the flange piece, whilst the notches are transverse to the length of the row and are equally spaced from one another.

Turning now to Fig. 3, there is shown a corner piece 1 having extending legs 6 and a bolt hole 7 at the junction of the legs. One of the legs is shown to have a lengthwise row 15 of transverse notches or serrations 16, spaced equally with the spacing of notches 13 of the flange piece. The arrangement of the notches 16 is such that when the leg 6 bearing the notches is introduced into the flange of Fig. 2 in the direction of arrow 17, the notches 16 engage in a ratchet-like manner with the notches 13 on the inner face of wall 11 of the flange piece so as to inhibit relative movement of the leg in the direction opposite to arrow 17.

Although not shown in the figures, each of the legs of each corner piece, and the interior of each flange piece at each end, will similarly be provided in practice with serrations as here described.

In a preferred embodiment a similar row of nothces 13 will be formed on the inner face of the wall 10 of the flange piece, and a corresponding row of notches 16 will be formed on the reverse face of the leg 6, the arrangement again being that when the leg 6 is introduced into the flange piece in the direction of arrow 17 the nothces of the other rows, respectively on the inner face of wall 10 and the reverse face of leg 6 will inter-engage in a ratchet-like manner to restrain relative output movement of the leg.

As shown in the figures the rows of notches extend respectively to the free end of the leg 6 and to the opening of a flange piece where the leg is intended to enter, but in some circumstances it may be sufficient for the rows to stop short of the respective end and opening always providing that during at least one part of the movement of the leg into the flange in the direction of arrow 17, there is interengagement between at least one of the grooves 16 with at least one of the grooves 13.

For maximum grip between the corner piece leg and the walls 10, 11 of the flange piece, the serrations may be formed with leading slopes 18 (see Fig. 4) of relatively small angles relative to the direction of movement 17 and opposed slopes 19 of greater angle - even up to 900 - in order that the leg may be introduced with relative ease but be fast against removal. However, it may be that symmetrical serrations, having leading and reverse slopes of equal angle, may be adequate in most cases and easier to produce.

The serrations in the corner piece may be formed by a pressing operation and conveniently during the forming of the piece itself. Those in the flange piece may be formed in the sheet metal strip before folding to the form shown in Fig. 2.

Whilst the serrations have been described in terms of projections, it will be understood that they can equally be regarded as spaced grooves, the lands between the grooves representing relative projections.

It will be understood that the gripping of the leg 6 between the walls 10, 11 depends on there existing a tight fit between the elements and a certain resilience in one or other of the elements, but the former is a requirement of the previous art and the latter is assured by most materials of construction.

The above consideration leads to the construction of Fig. 5 wherein the inner faces of the flange walls 10, 11 are provided with spaced, and even staggered, rounded grooves whilst the free end of leg 6 is provided with a round bead 20 of such size as to be accommodated in one or other of the grooves.

Claims (5)

1. Apparatus for use in the joining of two polygonal ducts and comprising a hollow flange and a corner piece having at least one arm slidable lengthwise into said flange with at least one external surface of the arm in sliding contact with an internal surface of the flange, characterised in that one of said surfaces is provided with a row of projections and the other of said surfaces is provided with at least one projection whereby the projections of the respective surfaces engage with one another ratchet wise as the arm is slid inwardly of the flange.

2. Apparatus according to Claim 1 wherein the said other of said surfaces is provided with a plurality of projections arranged in a row parallel to the direction of said lengthwise movement of the arm.

3. Apparatus according to Claim 2, wherein rows of projections parallel to said direction are provided on opposed surfaces of the arm and of the flange, being surfaces which are in sliding contact with one another as the arm is slid inwardly of the flange.

4. Apparatus according to any one of the preceding claims, wherein each of the projections is elongate transversely to said direction.

5. Apparatus according to any one of the preceding claims, wherein the projections are of saw-tooth form in a plane perpendicular to the surface from which it projects each comprising leading and trailing faces relative to the direction of relative movement of the surfaces during said inward sliding movement, said leading face being inclined at an angle to the surface from which it projects less than or equal to the corresponding angle of inclination of the trailing edge. Preferably said first-mentioned angle is not greater than 450 and it is even more preferable that said angle be not greater than 300.