GB2239299A

GB2239299A - Spigot for air-conditioning system

Info

Publication number: GB2239299A
Application number: GB9027266A
Authority: GB
Inventors: Paul Neil James Barsby
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-12-19
Filing date: 1990-12-17
Publication date: 1991-06-26
Also published as: AU6818890A; GB9027266D0

Abstract

A spigot (2) for connecting flexible ducting to a main duct (7), e.g. for use in air-conditioning or ventilation systems, comprises a bell-mouth section (3) of greatest diameter at one end; a middle section (4) of intermediate diameter; and an end section (5) of least diameter at the other end and means for securing said spigot over a hole in the duct, e.g. a series of labs (6) spaced around the periphery of said bell-mouth portion. The spigot may comprise two parts (Fig. 3, not shown) held together by dimples (10). The spigot may be formed by rolling a strip, spot welding along a seam, forming the bell-mouth (3) and end section (5) by pressing or spinning and punching the tabs (6). <IMAGE>

Description

IMPROVED SPIGOT FOR AIR-CONDITIONING SYSTEM The present invention relates to an improved spigot for use in air-conditioning or ventilation or similar systems, for connecting flexible ducting to a main duct. Flexible ducting generally comprises a helical skeleton of wire covered with an impervious flexible skin, and the end of the flexible ducting is push-fitted into the spigot and the joint sealed with tape.

The main duct generally is made of flat sheet metal (typically galvanised steel) and the spigot is secured to the duct by cutting a hole in one face of the duct and securing the spigot to the edges of the hole.

Hitherto, such spigots generally have been made from spun aluminium, but these spigots have to be secured to the main duct by pop-riveting (which is time-consuming) and often have problems of electrolytic corrosion of those parts of the spigot which are in contact with the main duct.

It is therefore an object of the present to provide a method of making a spigot of the above type which can be used for a variety of metals (e.g. mild steel, galvanisad steel) and is not restricted to metals which can be spun (e.g. aluminium).

A further object of the present invention is the provision of a spigot which can be quickly and easily connected and disconnected to and from the main duct.

The present invention provides a method of making a spigot, comprising: rolling a strip of material to make a spigot blank of the required cross-sectional shape; securing said strip along the seam; forming a bell-mouth portion at one end of said blank; forming a portion of reduced diameter at the other end of said blank.

Said bell-mouth portion and said reduced-diameter portion may be formed by pressing or by spinning said blank on a support and pressing the surface of said blank with a forming tool, to the required profile.

Typically the cross-section of said spigot will be circular or elliptical.

The present invention also provides a spigot comprising: a bell-mouth portion of greatest diameter at one end; a middle port'iron of intermediate diameter, and an end portion of least diameter at the other end, all three portions being formed integrally: and means for securing said spigot over a hole in duct.

Preferably said securing means comprises a plurality of spaced tabs provided around said bell-mouth portion; each of said tabs providing a portion adjacent the rim of said bell-mouth portion secured to the remainder of said portion at its inner edge but having its free outer edge depressed below the plane of the bell-mouth. Preferably, said tabs are formed integrally with said bell-mouth portion.

By way of example e only, a preferred embodiment of the present invention is described in detail with reference to the accompanying drawings, in which: Fig. 1 is an exploded perspective view of part of a main duct and a spigot in accordance with the present invention; Fig. 2 is a side view of the spigot of Fig. 3., on a larger scale; and Fig. 3 is a sectional exploded view of a modified form of the invention.

Referring to the drawings, a spigot 2 comprises a circular cros's-section tube having sections to three different diameters: a bell-mouth portion 3 of greatest diameter, a middle portion 4 of intermediate diameter, and an end portion 5 of least diameter. All three portions are formed integrally.

The outer edge of the bell-mouth portion is formed with a plurality (e.g. 4) of equidistantly spaced tabs 6, each of which provides a flat surface the inner edge of which is secured to the bell-mouth portion and the free outer edge of which is depressed below the plane of the bell-mouth. Preferably, the tabs 6 are formed integrally with the rest of the spigot 2.

As shown in Fig. 1, a main duct 7 is formed with a hole 8 to which the bell-mouth portion of the spigot 2 is connected.

The edge of the hole 8 is formed with a slot 9, and to connect the spigot to the main duct, one tab 6 is passed through the slot 9, and the spigot is rotated as indicated by arrow A to pass each tab 6 in turn through the slot 9, so that finally the spigot lies with the bell-mouth 3 pressed against the outer surface of the main duct adjacent the hole 8, and the tabs are pressed against the inner surface of the main duct adjacent the hole 8, fastening the spigot tightly over the hole 8.

Flexible ducting may then be secured to the spigot 2 by pushing the end of the ducting over the end portion 5 of the spigot, to rest against the shoulder Sa between portions 4 and 5. The ducting is sealed to the spigot by sealing tape, in known manner.

The above-described spigot preferably is made as follows to a strip of galvanised steel is formed into a cylinder having the same diameter as the middle portion 4; the seam of the cylinder is secured by spot-welding. The spot-welds are equidistantly spaced along the length of the seam: for reinforcement, a pair of spot-welds is used at each end of the seam. The line of welds stops short of one end of the seam, to allow the formation of the bell-mouth portion, as hereinafter deseribQd The bell-mouth portion 3 of the end portion 5 may be formed by pressing (it is believed that slow hydraulic pressing would be most suitable).Alternatively, the portions 3 and 5 may be formed by supporting the seamed cylinder on a cylindrical support, which is rotated at high speed to spin the cylinder, and a forming tool is pressed against the inner surface of said one end of the cylinder, to press that end outwards to form a bell-mouth. The portion 5 is formed in a similar manner, except that the forming tool is pressed on the outer surface of the other end of the cylinder, to press that end inwards, The tabs 6 are formed by punching into the rim of the bellmouth portion 3 a series of pairs of slits (one pair for each tab) and depressing the portion of the rim between each pair of slits. The number of tabs formed depends upon the diameter of the spigot and upon the weight of the spigot.

The above-described method may also be used to form spigots which are elliptical in cross-section; in this case, the spigot is formed from an elliptical-cross-section blank, and if formed by the spinning process, the support also is elliptical in cross-section. Tabs are formed in the same manner, but are pressed further, so as to extend at 90 degrees to the plane of the bell-mouth. An elliptical cross-section spigot is connected to a corresponding elliptical hole in the main duct by passing the tabs through the hole, and then bending the tabs back into the lane . of the bell-mouth, to secure the spigot in place.

In some applications, it is advantageous to cover the main duct with fibreglass, for heat insulation and/or to reduce noise. In this case, the construction shown in Fig. 3 may be used: the spigot 2 is formed with inwardly-protruding dimples 10 and a collar 11 is press-fitted over the hole in the main duct and the fibreglass mat 12, and is resiliently held in place by the dimples 10. The collar 11 comprises a bell-mouth.

portion 13, and a second portion 14; the portion 13 is dimensioned to extend over the edges of the hole, giving a smooth contour to the edges of the hole (and hence reducing turbulence in the gas flow through the hole) and the portion 14 is dimensioned to be a tight fit within the portion 4 of the spigot. Since the portion 14 extends beyond the bellmouth portion of the spigot 2, said bell-mouth portion may be formed as a flat flange (as shown in Fig. 3) rather than the curved portion shown in Fig. 1 and 2.

Claims

WHAT I CL#TX IS:

1. A method of making a spigot for connecting flexible ducting to a main duct, said method including: rolling a strip of sheet material to make a spigot blank of a predetermined cross-sectional shape; securing said blank along its seam; forming a bell-mouth portion of greatest diameter at one end of said blank; and forming a reduced-diameter portion to the other end of said blank, with a middle section of intermediate diameter between said bell-mouth and said reduced-diameter portions

2.The method as claimed in claim 1 wherein said bell-mouth portion and said reduced-diameter portion are formed by pressing

3. The method as claimed in claim 1 wherein said bell-mouth portion and said reduced-diameter portion are formed by: mounting said blank upon a support of slightly smaller size but similar cross-sectional shape; rotating said blank and support together at high speed; pressing a forming tool against the inner surface of the blank adjacent one end thereof and the outer surface of the blank adjacent to other end thereof, to form the bell-mouth and reduced-diameter portions respectively,

4. The method as claimed in any preceding claim further including cutting a series of spaced pairs of slots around the edge of the bell-mouth portions and bending inwards the portions between said slots of each pair, to form tabs.

5. The method as claimed in any preceding claim wherein said blank is secured along its seam by spot-welding.

6. The method as claimed in any preceding claim wherein the cross-section of the blank is circular.

7. The method as claimed in any one of claims 1-5 wherein the cross-section of the blank is elliptical.

8. A spigot for connecting flexible ducting to a main duct, made by the method as claimed in any one of claim 1-7.

9. A spigot for connecting flexible ducting to a main duct, said spigot comprising: a bell-mouth section of greatest diameter to one end: a middle section of intermediate diameter; and an end section of least diameter at the other end, all three sections being formed integrally; and means for securing said spigot over a hole in the duct.

10. The spigot as claimed in claim 9 wherein said means for securing said spigot over said hole comprise a series of tabs spaced around the periphery of said bell-mouth portion.

11. The spigot as claimed in claim 10 wherein each said tab provides a portion adjacent the rim of said bell-mouth portion secured to the remainder of said portion at its inner edge and having its free outer edge depressed below the plane of the bell-mouth.

12. The spigot as claimed in any one of claims 9-11 wherein a shoulder is formed on the exterior of said spigot, between the bell-mouth section and the middle section.

13. The spigot as claimed in any one of claims 9-12 wherein the spigot is circular in cross-section.

14. The spigot as claimed in any one of claim 9-12 wherein the spigot is elliptical in cross-section.

15. The spigot as claimed in any one of claims 9-14 wherein said means for securing said spigot over said hole comprises: a collar one end of which has a periphery larger than the periphery of said hole, and the other end of which has the same cross-sectional shape and size of periphery as the interior of the middle section of the spigot; and inwardlyprojecting dimples on said middle section such that said collar can be resiliently press-fitted inside said spigot, engaged with said dimples, with said one end of the collar engaged with the internal surface of the duct, to retain the spigot tightly around the hole.

16. A method of making a spigot substantially as hereinbefore described with reference to Fig. 1 and 2 or Fig. 3 of the accompanying drawings.

17. A spigot substantially as hereinbefore described with reference to Fig. 1 and 2 or Fig. 3 of the accompanying drawings.