GB2085997A - Repairing flexible ducting - Google Patents

Abstract

Flexible ducting formed of helically reinforced air-impermeable material is repaired by putting a sleeve 20, also of flexible material, over part of the length of ducting and securing the ends of the sleeve to the ducting by welding to the material of the ducting on the outer or inner surfaces thereof or by the use of a coupling band 30, Fig. 4 to effect an airtight seal. One or more suspension bands 40 are secured around the sleeve and extend completely around the ducting. Each suspension band has at least one attachment means such as an eyelet for suspension of the ducting from a support. To effect an airtight seal the right hand side of Fig. 4 shows the sleeve 20 welded to the ducting. The left hand side of Fig. 4 shows the sleeve 20 tucked around into the inside of the ducting and the seal being formed merely by tightening the coupling band around the sleeve and ducting. <IMAGE>

Description

SPECIFICATION Helically reinforced ventilation ducting This invention relates to helically reinforced ventilation ducting.

It is common practice to make ventilation ducts, particularly ducting for use in mines, in relatively short lengths which have to be joined.

For forced ventilation, it is nowadays the common practice to use flexible or collapsible ducts made for example of plastics or reinforced plastics material or fabric. If a suction or reversible ventilating system is employed however then it is not possible to use such collapsible ducts. It was a common practice to use rigid ventilation ducts, for example wooden or metal ducts for such purposes. In recent years however widespread use has been made of ducts made of plastics or reinforced plastics material or fabric, the duct incorporating a helical reinforcing member, conveniently a resilient metal element, which extends continuously along each length of ducting. The ducting is made in lengths which are joined together by coupling devices.Typically the coupling device is an endless band which is put around the abutting ends of two lengths of ducting, the coupling either being secured e.g. by welding or heat sealing, to the end of one length of the ducting and secured to the other length by a tensioning fastening device or having two such tensioning and fastening devices for tightening around the respective abutting ends of the ducting. The helical reinforcing member in the length of ducting prevents the ducting from collapsing inwardly when suction is applied.

Such ducting, particularly in mines, is subjected to severe wear and exposure to abrasive particles and to mechanical damage and can develop leaks.

The present invention is concerned more particularly with the repair of lengths of ducting which have become leaky. The conventional method heretofore of repairing ducting of plastics or reinforced plastics material has been to apply patches over the leaks. It is often a timeconsuming job to discover leaks which may be of pin-hole size and then to repair each leak. It is an object of the present invention to provide an improved method of repairing such reinforced flexible ducting.

According to one aspect of the present invention, a method of repairing a length of flexible ducting formed of helically-reinforced airimpermeable material comprises the steps of putting a sleeve of flexible plastics material around the length of ducting, securing the two ends of the sleeve to the ducting to form an airtight seal and securing around the sleeve one or more suspension bands to hold the sleeve against the ducting, the or each suspension band extending completely around the ducting and having at least one attachment means for suspension of the ducting from a support.The sleeve may be secured at its ends to the ducting by welding the sleeve to the ducting or, if, as is usually the case, the ducting has a resilient end ring, tucking the sleeve around the end ring and into the inside of the duct so that it may be sealed against the surface of the ducting when a coupling is tightened around that end of the ducting. This coupling would normally be the coupling required to join adjacent lengths of ducting. In some cases it may be preferable to seal the sleeve, by welding, to the ducting at one end of the ducting and, at the other end, to tuck the sleeve around the end ring for securing by the coupling member.This latter technique is convenient where the lengths of ducting each have a male and female end, with a coupling permanently secured on the female end; in this case the sleeve is conveniently welded to the ducting at the female end and is tucked around a resilient end ring on the male end so that it is secured in an airtight manner to the ducting when that male end is put in the coupling of the female end of an adjacent length of duct.

It will be seen that this technique of putting a sleeve over a length of ducting and then putting normal bands around to provide suspension means enables a leaky length of ducting to be repaired very simply and easily. There is no need to determine the exact location of the leaks. This sleeve may be of the same material as that used for the ducting but, since the helically reinforced ducting provides the mechanical strength, the sleeve may be thinner than that used for the ducting. The sleeve may be preformed from a sheet into a tube by seam welding before being applied over the ducting or the sheet may be wrapped around the ducting and then seam welded along its length to form a continuous tube.

According to another aspect of the present invention, a ventilation duct comprises a length of flexible ducting of air-impermeable material which is helically reinforced, a sleeve of flexible impermeable plastics material around said length of flexible ducting with the ends of the sleeve secured to the ducting and one or more suspension bands extending around the ducting and sleeve, each suspension band having at least one attachment means for suspending the duct from a support. The attachment means may be an eyelet or hook secured on or to or in said band.

As previously explained, the sleeve may be secured at one end or at each end to the length of ducting by welding to form an airtight seal.

Alternatively it may be secured to the ducting by tucking the sleeve around a resilient ring at the end of the ducting and then inserting that end into a coupler which extends over and is tightened around said resilient end ring.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawings in which.~ Figure 1 is a view in side elevation of part of a ventilation duct; Figure 2 is a detailed scrap section at A in Figure 1; Figure 3 is a detail scrap section at B in Figure 1 showing the attachment of the sleeve to the ducting; Figure 4 is a part section through a coupling band coupling two lengths of ducting; Figure 5 is a plan view of a suspension band laid out flat before putting around a duct; Figure 6 is a side elevation of the band of Figure 5; Figure 7 is an end view of the band of Figures 5 and 6 as in position around the ducting, this figure having the details of the ducting omitted; and Figure 8 is a view similar to Figure 7 of an alternative form of suspension band.

Referring to Figure 1 there is shown part of a length of helically reinforced ducting of polyvinylchloride material 10 formed into a tube, the helical reinforcement being shown at 11.

Referring to Figure 2 this helical reinforcement is constituted by a helical wire 12 which is encapsulated within a polyvinylchloride strip 13, this strip being welded onto the sheet material 10 which constitutes the impermeable layer of the ducting. The ducting is formed in length which are secured together by coupling bands in the known way. The material 10 extends continuously along each length of the ducting which length is terminated at each end by an end ring 15 (Figure 3) formed of resilient metal which normally holds the end of the ducting to a circular shape.

This end ring is enclosed within a cuff 18 formed from the end portion of the sheet material 10.

Similar end rings are formed at each end of the length of ducting.

The ducting comprising the sheet material 10 with the helical reinforcement and end rings is normally used without the outer sleeve to be described later. In that case, the ducting is supported by means of suspension attachments which are secured on the strip 13. The present invention is concerned more particularly with the repair of a length of such ducting in the event that it develops a leak or leaks. This repair is effected by putting around the length of ducting an outer envelope or sleeve 20 of polyvinylchloride or reinforced polyvinylchloride. This sleeve is constituted by a sheet which is seam-welded to form a tube, the seam-welding being effected either before the sleeve is drawn over the length of ducting or after wrapping the sheet around the length of ducting. The seam weld extends along the whole length of the sheet to form a continuous airtight seal.The sheet forming the sleeve 20 may be of similar material to that used for the sheet 10 forming the ducting. It may be preferred however to use thinner material since the helically reinforced ducting provides the mechanical strength of the structure.

After the sleeve 20 has been put in position over the ducting, it is secured at its ends to the ducting. It may be welded to the material in the ducting adjacent to one of the end rings or, as shown in Figure 3, the material of a cuff 22 enclosing the end ring 15 of resilient metal. In Figure 3 the weld is shown on the outside of the ducting. Alternatively the material of the sleeve 20 may be taken beyond the end ring and tucked around into the inside of the ducting and welded to the material 10 of the ducting on the inner surface thereof.

Lengths of ducting of this type are commonly secured together by coupling units. One such coupling unit is shown in cross-section in Figure 4 and comprises essentially an endless band 30 which extends completely around the abutting ends of two lengths of ducting lying over end rings 32, 33. Embedded in cuffs 34, 35 formed on the two peripheral edges of the band 30 are steel wires 35, 36. In this particular embodiment these wires are enclosed within PVC tubes 37. For each of the steel wires, the two ends are secured on the shaft of a capstan enabling the wire to be wound up so as to tighten the peripheral edge of the band to a smaller diameter. This diameter is less than the diameter of the two end rings and hence the coupling band can be tightened to secure two lengths of ducting together.

As shown at the right-hand side of Figure 4, the sleeve material 20 may be welded to the ducting.

At the left-hand side of Figure 4 an alternative arrangement is shown in which the sleeve material is tucked around into the inside of the ducting and the required airtight seal is formed merely by tightening the coupling band around the sleeve and ducting.

In some cases the coupling band may be permanently secured onto one end of a length of ducting and, in this case, it is convenient to secure the sleeve by welding at that end of that length of ducting.

After the sleeve has been put around the length of ducting, one or more suspension bands 40 formed of polyvinylchloride are put around the sleeve and ducting. One form of suspension band is shown in Figures 5, 6 and 7, comprising a length of polyvinylchloride material. Eyelets 46, 47 are formed in the two ends of the band and these eyelets may be secured together to secure the band around the ducting. Preferably however the suspension band is tack-welded to the sleeve.

It will be appreciated that these welds are merely to hold the band in position; the weight of the ducting is supported by the loop formed by the band. Commonly the ducting is suspended from a suspension wire 50 as shown in Figure 1.

Suspension hooks 52 may be put on this wire to hook through the aforementioned eyelet to support the ducting. In some cases, it is desired to form side supports and in the band shown in Figures 5, 6 and 7, such a side support is formed by a fold 58 in the band with eyelets passing through the two parts of the fold.

Figure 8 illustrates another form of suspension band. In this figure, the band 60 extends continuously around the ducting and a side support is formed on a tail 61 extending from one end of the band.

A length of ducting that has developed a leak or leaks may readily be repaired by putting a sleeve over it and bands around it as described above.

This repair can be effected without any need to identify the exact locations of any leaks in that length of ducting. This technique thus provides a simple, quick and economic way of repairing helically reinforced ventilation ducting.

Claims (17)

1. A method of repairing a length of flexible ducting formed of helically-reinforced airimpermeable material comprising the steps of putting a sleeve of flexible plastics material around the length of ducting, securing the two ends of the sleeve to the ducting to form an airtight seal and securing around the sleeve one or more suspension bands to hold the sleeve against the ducting, the or each suspension band extending completely around the ducting and having at least one attachment means for suspension of the ducting from a support.

2. A method as claimed in claim 1 wherein the sleeve is secured at its ends to the ducting by welding the sleeve to the ducting.

3. A method as claimed in claim 1 wherein the ducting has a resilient end ring at one or at each end and wherein the sleeve is tucked around the end ring and into the inside of the ducting at one end or at each end of the ducting so that the sleeve is sealed against the surface of the ducting when a coupling is tightened around that end of the ducting.

4. A method as claimed in claim 3 wherein the sleeve at one end is welded to the ducting and is secured by a coupling at the other end.

5. A method as claimed in any of the preceding claims wherein the sleeve is of the same material as that used for the ducting.

6. A method as claimed in any of the preceding claims wherein the sleeve is of thinner sheet material than that used for the ducting.

7. A method as claimed in any of the preceding claims wherein the sleeve is preformed from a sheet into a tube by seam welding before being applied over the ducting.

8. A method as claimed in any of claims 1 to 6 wherein the sleeve is formed of a sheet wrapped around the ducting and then seam welded along its length to form a continuous tube.

9. A ventilation duct comprising a length of flexible ducting of air-impermeable material which is helically reinforced, a sleeve of flexible impermeable plastics material around said length of flexible ducting with the ends of the sleeve secured to the ducting and one or more suspension bands extending around the ducting and sleeve, each suspension band having at least one attachment means for suspending the duct from a support.

10. A ventilation duct as claimed in claim 9 wherein the attachment means is an eyelet or hook secured on or to or in said band.

11. A ventilation duct as claimed in either claim 9 or claim 10 wherein the sleeve is secured at one end or at each end to the length of ducting by welding to form an airtight seal.

12. A ventilation duct as claimed in either claim 9 or claim 10 wherein the sleeve is secured to the ducting at at least one end thereof by tucking the sleeve around a resilient ring at the end of the ducting and then inserting that end into a coupler which extends over and is tightened around said resilient end ring.

13. A ventilation duct as claimed in any of claims 9 to 12 wherein the sleeve is of the same material as the ducting.

14. A ventilation duct as claimed in any of claims 9 to 13 wherein the sleeve is thinner than the material of the ducting.

15. A method of repairing a length of helically reinforced ducting substantially as hereinbefore described with reference to the accompanying drawings.

16. A ventilation duct repaired by the method of any of claims 1 to 8 or claim 15.

17. A ventilation duct substantially as hereinbefore described with reference to the accompanying drawings.