GB2061437A - Joining Lengths of Flexible Ducting - Google Patents

Abstract

For joining helically reinforced flexible ventilation ducting, the lengths of ducting 10, 11 are formed with male and female ends, each female end having a band 20 secured along one of its side peripheries around the ducting inwardly from an end ring 17. The band 20 fits over the male end and has a peripheral cuff 22 containing a steel wire 23 which can be tightened by a capstan 26 (Figure 4) to tighten the cuff 22 behind an end ring 16 on the male member. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to the Joining of Lengths of Flexible Ducting This invention relates to the joining of lengths of flexible ducting.

Particularly in mines and the like, it is a common practice to make ventilation ducts in relatively short lengths which have to be joined.

The method of jointing has to be substantially airtight but more particularly has to be simple so that joints can readily be made in possibly difficult working conditions. For forced ventilation, it is nowadays the common practice to use flexible or collapsible ducts made for example of a plastics or reinforced plastics material or fabric. These commonly have end rings which are resilient, one ring being fitted at each end of the length of ducting, the two rings being of the same diameter, this diameter being very slightly less than the diameter of the duct between the rings.

It is then possible, by deforming one ring for example into an elliptical form, to insert that ring together with a length of duct into the end of an adjacent duct and then to pull the two ducts apart in the longitudinal direction so that the firstmentioned ring, when it has reassumed in circular form, is held by the end ring of the other length of duct. This provides a very simple and convenient method of joining lengths of duct which are formed of flexible material such as may be used for forced ventilation.

If a suction or reversible ventilating system is employed, then it is not possible to use such collapsible ducts. It was a common practice in these circumstances to use rigid ventilation ducts, such as for example wooden or metal ducts. 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 helical reinforcing member prevents the ducting from collapsing inwardly when suction is applied.

This helically reinforced ducting cannot be joined by the simple technique of interlocking the end rings as described above because of the presence of the helical reinforcing element. For this reason, lengths of such helically reinforced ducting are commonly joined by a coupling, such as is described for example, in Specification No 1050871, having an endless flexible band which is put around the abutting ends of two lengths of ducting, the coupling having a tensioning and fastening device for tightening a flexible element extending along each edge of the band whereby the flexible band may be deformed to be of channel section between the edges, the channel section fitting over and gripping end bands or end flanges or end rings on the two lengths of ducting.

This arrangement however requires couplings which are separate from the lengths of ducting.

The present invention is directed to an improved coupling arrangement which is particularly applicable for coupling lengths of helically reinforced flexible ducting but which may also be used for other flexible ducting having end rings.

According to the present invention, in a length of flexible ducting of air-impermeable material having male and female ends, whereby a male end on one length may be joined to a female end on another length by insertion thereinto, the male end has an end ring and the female end has an end portion of larger diameter than said end ring with a flexible wire or other tensioning element around its periphery and with tightening and locking means whereby the female end may be tightened over the male end after the part with the tensioning element has been put over the male end beyond said end ring. As indicated above, the invention is particularly applicable to helically reinforced ducting.

The invention further includes a length of flexible ducting having male and female ends, the ducting being formed of flexible air-impermeable material with a helical reinforcement along its length of resilient material with the male end having an end stiffening ring, and the female end having a stiffening ring of the same diameter as said end ring at the male end, with an end portion of flexible material terminating the length of ducting, the end portion being of larger diameter than said end ring and being terminated with a tensioning and fastening device comprising a flexible wire or other tensioning element around the periphery of the end portion with tightening and locking means whereby the end portion on a female end can be secured over a male portion on an adjacent length of ducting with the tensioning element tightened behind the end ring on the male end.

With this construction, there is no separate coupling device as in the arrangement of No 1050871. The male element at one end of a length of ducting can be put directly in the end portion on the female end of the next adjacent length and the tensioning means operated to secure the two lengths together with the two stiffening rings close together.

Conveniently the wire or other flexible tensioning element is arranged in a tube formed on or embedded within the periphery of said end portion.

The tensioning device preferably comprises a capstan secured on said end portion with the axis of the capstan generally normal to the surface of the end portion in the region at which it is located.

The axis of the capstan is thus generally radial with respect to the duct. This arrangement of the capstan is more convenient for operation than a windlass type of tensioning device such as is described in the aforementioned Specification No 1050871. The capstan can readily be operated by means of a lever extending through the capstan at right angles to the axis thereof; the lever may be fixed or it may, for example, be slidable in a bore through the capstan.

The capstan may be mounted on a base secured to the aforementioned end portion and this base may include or carry an upstanding part spaced away from the capstan and with a recess to receive the aforementioned lever arranged so that the lever may be engaged in said recess whereby the upstanding element prevents rotation of the capstan in the unwinding direction.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawings in which.~ Figure 1 illustrates diagrammatically adjacent end portions of two lengths of helically reinforced flexible ducting to be connected together; Figure 2 is a cross-section through part of the - adjacent end of the two lengths of ducting of Figure 1 before these lengths have been coupled together; Figure 3 is a view similar to Figure 2 but showing adjacent ends of the two lengths of ducting of Figure 1 when coupled; Figure 4 is an exploded perspective diagram of a capstan tightening device for use in the construction of Figures 1, 2 and 3; Figure 5 is a side elevation of the capstan tightening device of Figure 4 shown in position on a length of ducting;; Figure 6 is a scrap section showing the construction of helical reinforcement for the ducting.

Referring to Figure 1 there is shown a male end of a first length of ducting 10 and an adjacent female end of a second length of ducting 11. Each of these lengths of ducting, over the major portion of its length, comprises flexible air-impermeable sheet material 12, typically a plastics or reinforced plastics material, such as polyvinyl chloride. The lengths of ducting are each reinforced by a member 13 including helical reinforcement as shown in further detail in Figure 6. In this particular construction, the reinforcing member comprises a metal element 14 in the form of a resilient steel wire embedded in or secured under strips 1 5 of plastics material, which strips are welded to the material 12 along the two edges of the strip. On each length of ducting the strip 15 extends in a continuous length as a helix from one end to the other of the duct.

The male end of the length of ducting has a separate end ring 16 (Figures 2 and 3) formed of resilient metal which normally holds the end to a circular shape. This end ring is enclosed within a cuff 1 7 formed of the plastics sheet material 12 by turning the edge of the sheet material 12 over to extend back around the ring thereby forming the cuff 17. A similar ring 18 is provided on the female end of the ducting. These two rings 1 6, 18 are of the same diameter. The female end however has an end portion 19 which extends beyond the ring 18. This end portion is formed of a separate band 20 of flexible plastics material secured to the sheet material 12 by welding, sewing or other convenient way.This end portion 19 is of slightly larger diameter than the rings 16, 18 so that normally this end portion 19 can slip freely over the ring 16 and cuff 17 at the end of the male portion. The band 20 forming this end portion 19 at one peripheral edge 21 is secured by welding in the embodiment illustrated, to the material 12 of the ducting behind (that is inwardly from the end) the ring 18. At the other peripheral edge of this band 20 of material forming the end portion 19, a cuff 22 is formed by welding or glueing or stitching, the cuff enclosing a flexible steel wire 23. In the embodiment illustrated, this steel wire 23 is enclosed within a polyvinyl chloride tube 24 housed within the cuff 22.

The two ends of this steel wire 23 are secured in a shaft 25 of a capstan 26 (Figures 4 and 5), this capstan shaft 25 being rotatably mounted in a frame 27 resting on the band 20. The ends of the wire 23 conveniently are secured in the capstan shaft by passing each of the ends through a transverse hole 28 in the shaft 25 and then securing the passed-through portions against withdrawal. Rotation of the capstan shaft 25 is effected by means of a lever arm 30 fixed or slidably mounted in a transverse bore 31 at the upper end of the rotatable capstan shaft 25.

Rotation of this shaft 25 causes the two ends of the wire 23 to be wound up on the shaft 25 of the capstan and thereby tightening the peripheral edge of the end portion 1 9 to a smaller diameter.

In the untightened condition, this peripheral edge is of such size that it will pass freely over the cuff 17 and ring 1 6 on a male end of the length of ducting. When two lengths of ducting are to be joined together, the male end of one length is inserted in the female end portion 19 and the capstan shaft 25 turned to tighten the ring constituted by the wire 23 around the male end behind the ring 17 thereby preventing separation of the two lengths of ducting in the axial direction.

To hold the capstan against rotation, an upstanding portion 32 provided on or carried on the capstan base has a recess 33 in which the aforementioned lever arm 30 may engage, the recess 33 being so shaped that it prevents rotation of the lever arm 30 in a direction in which tension in the wire 23 is released.

Claims (10)

Claims

1. A length of flexible ducting of airimpermeable material, having male and female ends, whereby a male end on one length may be joined to a female end on another length by insertion thereinto, wherein the male end has an end ring and the female end has an end portion of larger diameter than said end ring with a flexible wire or other tensioning element around its periphery and with tightening and locking means whereby the female end may be tightened over the male end after the part with the tensioning element has been put over the male end beyond said end ring.

2. A length of flexible ducting as claimed in claim 1 and having a helical resilient reinforcement.

3. A length of flexible ducting having male and female ends, the ducting being formed of flexible air-impermeable material with a helical reinforcement along its length of resilient material with the male end having an end stiffening ring, and the female end having a stiffening ring of the same diameter as said end ring at the male end, with an end portion of flexible material terminating the length of ducting, the end portion being of larger diameter than said end ring and being terminated with a tensioning and fastening device comprising a flexible wire or other tensioning element around the periphery of the end portion with tightening and locking means whereby the end portion on a female end can be secured over a male portion on an adjacent length of ducting with the tensioning element tightened behind the end ring on the male end.

4. A length of flexible ducting as claimed in any of the preceding claims wherein the wire or other flexible tensioning element is arranged in a tube formed on or embedded within the periphery of said end portion.

5. A length of flexible ducting as claimed in any of the preceding claims wherein the tensioning device comprises a capstan secured on said end portion with the axis of the capstan generally normal to the surface of the end portion in the region at which it is located.

6. A length of flexible ducting as claimed in claim 5 wherein the capstan has a lever extending through the capstan at right angles to the axis thereof.

7. A length of flexible ducting as claimed in claim 6 wherein the lever is slidable in a bore through the capstan.

8. A length of flexible ducting as claimed in either claim 6 or claim 7 wherein the capstan is mounted on a base resting on said end portion and wherein the base includes or carries an upstanding part spaced away from the capstan and with a recess to receive said lever, the recess being arranged so that the lever is engageable in said recess whereby the upstanding element prevents rotation of the capstan in the unwinding direction.

9. A length of flexible ducting as claimed in any of the preceding claims wherein the helical reinforcement comprises a metal wire embedded in or carried by plastics material, which plastics material is sealed to the outer surface of said flexible air-impermeable material.

10. A length of flexible ducting substantially as hereinbefore described with reference to the accompanying drawings.