AU2002300296B2

AU2002300296B2 - Ventilation duct

Info

Publication number: AU2002300296B2
Application number: AU2002300296A
Authority: AU
Inventors: George Antonopolos
Original assignee: PLASTICOAT Pty Ltd
Current assignee: PLASTICOAT Pty Ltd
Priority date: 2001-07-31
Filing date: 2002-07-26
Publication date: 2006-12-07
Anticipated expiration: 2022-07-26

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Ventilation duct The following statement is a full description of this invention, including the best method of performing it known to us: 1-reenhlls~ Uarte Smt M oun\04050 rntd26Jl 20 pg reehias Carter Smith Beadle Melbourne\004108500 Printed 26 July 2002 (9:09) page 2 The present invention relates to ventilation ducting and more particularly to ventilation ducting of the kind typically used in mines to provide air supply to remote locations underground.

Such ducting is traditionally formed from polyethylene woven fabric having a polyethylene coating and has one or more longitudinal seams extending over the length of each duct section. Most commonly there are two longitudinal seams since the duct is formed from two elongate strips of the fabric each of which forms half the circular duct section with the seams joining the two strips together. In small diameter ducting a single strip of the fabric may be used to form the tubular duct section in which case only one seam would be necessary.

The joins or seams along the duct sections are conventionally formed by stitching or heat welding the two adjoining edges together. A problem that arises with a stitched seam is that air leakage occurs through the stitch holes whereas with a welded seam delamination of the fabric can occur and furthermore, the integrity of the weld is not evident over the entire length of a duct section.

In locations where a poor welding occurs air leakage again constitutes a problem and the duct may also delaminate in the vicinity of the location. Thus existing mine ventilation ducting suffers from problems or disadvantages which generally necessitate the use of more and larger fans to deliver the required air flow to the remote location because of leakage that occurs along the length of the ducting, which ducting may be several kilometres in length.

Accordingly it is an object of this invention to provide improved ventilation ducting of the kind in question which overcomes or at least reduces the aforementioned problems of existing ducting.

One form of the invention provides a ventilation duct formed from elongate flat polyethylene woven fabric, or the like, and having a like plastics coating thereon, said duct being formed into tubular section duct having a seam extending along the length thereof for the purpose of joining two longitudinal edges of said flat fabric together to form said tubular section, characterised in that, said seam is formed by abutting the inner surfaces of the duct at the seam and forming said join by a combination of stitching and heat welding, and subsequently heat welding a Melbourne\004107849 Printed 25 July 2002 (12:51) separate cuff over said join to enclose said seam.

In order that the invention may be more readily understood a particular embodiment will now be described with reference to the accompanying drawings wherein: FIGURE 1 is a schematic side elevation of portion of a ventilation duct according to the invention; FIGURE 2 is a schematic sectional view on the line 2-2 of FIGURE 1; FIGURE 3 is an enlarged view of the seam enclosed by the broken line "B" of FIGURE 2; and FIGURE 4 is an enlarged view of the seam enclosed by the broken line "A" of FIGURE 2.

The ventilation duct 10 is formed from polyethylene woven fabric having a polyethylene coating. The duct 10 is tubular in cross-section although this is not evident in the drawings as it is manufactured from continuous strips of flat polyethylene fabric. The respective strips 11 and 12 are evident in FIGURES 2, 3 and 4 and are joined at diametrically opposed points to form seams 13 and 14 which extend longitudinally of the duct The seam 13 in use is at the bottom of the duct and is of less width than the seam 14 which in use is at the top of the duct. As shown more clearly in FIGURE 4, the seam 13 is formed by abutting two surfaces of the strips 11 and 12 against each other along adjacent edges of the strips 11 and 12 in a manner such that the surfaces which form the inside of the tubular duct are mated. Two rows of stitching 15 and 16, respectively, are sewn along the length of the duct parallel to the outer edge of the seam 13. The stitching secures the two strips 11 and 12 together along an edge but would be subject to leaking of air through the stitch holes in the absence of anything else. In order to prevent such leakage a cuff 17 formed of the same fabric is heat welded over the seam continuously along the length of the duct and covers both rows of stitching 15 and 16. It should be apparent that the cuff 17 provides additional strength to the seam and prevents any leakage of air.

Referring now to FIGURE 3, the other seam 14 is shown more clearly and is Melbourne\004107849 Printed 25 July 2002 (12:51) -4similar to the seam 13 of FIGURE 4 except that it is wider in order to make provision for eyelets 18 which are spaced along the length of the duct. Furthermore, the seam 14 is formed by firstly internally welding the two strips 11 and 12 together along the mating longitudinal edges. Once the internal heat weld is completed two rows of stitching 19 and 20 are applied similar to the rows of stitching 15 and 16. It should be noted that the stitching row 20 is through the part of the seam that is internally heat welded whereas the stitching row 19 is spaced away from the portion which is internally heat welded. This avoids the possibility of delamination of the fabric which could occur when the duct is under pressure due to the strips 11 and 12 being forced apart at the seam. The portion of the seam which is internally welded is represented by the hatched lines 21.

In order to manufacture ventilation duct according to this invention, apparatus (not shown) is provided to automatically perform the necessary procedures. Firstly, the polyethylene fabric is fed from two separate roles in continuous strips which are superposed and aligned for processing via automatic machine steps.

Next, heat is applied to the mating surfaces along the side which comprises the seam 14 in order to internally weld the two edges of the respective strips 11 and 12 together. After this processing step stitching is applied in two rows along each of the seams 13 and 14 in the positions shown in FIGURES 3 and 4. Finally, heat is applied externally on the respective seams and a cuff 17 is applied over each seam and thereby heat welded over the seams as shown in the drawings. The cuff or cover strip is also heated in this process. Nip rollers (not shown) are used to force the surfaces together once heat is applied in order to complete the welding process.

As a further optional step markings 22 are applied to the ventilation duct at one meter intervals adjacent the lower seam to facilitate measuring off a length of duct at the outset and when it is necessary to replace a length of duct in a mine, for example. In other words, it is a simple task to merely count the number of meter marks in order to determine a particular length of duct.

The ventilation duct is generally manufactured in diameters ranging from 500 mm to 1600 mm and in lengths between 20 meters and 100 meters.

Melbourne\004107849 Printed 25 July 2002 (12:51) It should be evident to those skilled in the art that the invention is not limited to the particular embodiment described hereinabove. For example, different materials may be used in manufacturing the duct and the number of rows of stitching can be varied to suit different applications. Furthermore, whilst internal welding is necessary on the seam containing the eyelets 18 to prevent leakage of air at the eyelets, such internal welding could, if desired, be applied to the other seam although this would be for strength purposes only as no leakage of air can occur at this seam as there is no eyelet present. According to a further optional feature hooks or clips may be installed in the eyelets 18 during the manufacturing process to enable the duct to be easily hung from the roof of a mine without the need to insert eyelet hangers on site.

It should also be apparent that the ventilation duct according to this invention is superior in strength to existing ventilation ducts and avoids any leakage of air along the length of the duct. This means that fans for blowing air down a mine shaft need not be as powerful and any boost fans along the length of the duct can also be smaller in size and thus more efficient.

Melboume\004107849 Printed 25 July 2002 (12:51)

Claims

1. A ventilation duct formed from elongate flat polyethylene woven fabric, or the like, and having a like plastics coating thereon, said duct being formed into tubular section duct having a seam extending along the length thereof for the purpose of joining two longitudinal edges of said flat fabric together to form said tubular section, characterised in that, said seam is formed by abutting the inner surfaces of the duct at the seam and forming said join by a combination of stitching and heat welding, and subsequently heat welding a separate cuff over said join to enclose said seam.

2. A ventilation duct according to claim 1, characterised in that, said seam comprises two spaced rows of said stitching and said heat welding includes an internal weld to join said abutting surfaces together prior to stitching, one said row of stitching being over a portion of said seam which is internally welded and the other said row being spaced inwardly towards the tubular portion of said duct from said internal weld.

3. A ventilation duct according to claim 2, characterised in that, said duct is formed from two separate strips of said elongate flat fabric which are superposed and joined at respective seams along the adjacent edges to form said tube.

4. A ventilation duct according to claim 3, characterised in that, one said seam is wider than the other said seam and includes spaced eyelets therealong enabling said duct to be suspended, said eyelets being located between the outermost row of stitching and the outer or free edge of said seam.

A ventilation duct according to claim 4, characterised in that, the other said seam is absent of said internal welding.

6. A ventilation duct substantially as hereinbefore described with reference to the accompanying drawings. Dated: 26 July 2002 FREEHILLS CARTER SMITH BEADLE Patent Attorneys for the Applicant: PLASTICOAT PTY. LTD. Melbourne\004107849 Printed 25 July 2002 (12:51)