AU2020200508B2

AU2020200508B2 - Duct segment

Info

Publication number: AU2020200508B2
Application number: AU2020200508A
Authority: AU
Inventors: Anthony Paul Wigg
Original assignee: Ac Ind Nominees Pty Ltd
Current assignee: Ac Industries Nominees Pty Ltd
Priority date: 2019-01-23
Filing date: 2020-01-23
Publication date: 2025-09-18
Anticipated expiration: 2040-01-23
Also published as: AU2020200508A1

Abstract

#$%^&*AU2020200508B220250918.pdf##### Abstract There is provided a duct segment (10) comprising first and second opposing duct wall portions (100, 200), and a valve member (300) disposed between the first and second duct wall portions (100, 200). The valve member (300) comprises a leading edge (302) and a trailing edge (304), the trailing edge (304) being attached to the first duct wall portion (100). The valve member (300) is moveable between an open position in which the leading edge (302) is positioned substantially adjacent the first duct wall portion (100) to allow airflow through the duct segment (10), and a closed position in which the leading edge (302) is positioned substantially adjacent the second duct wall portion (200) to restrict airflow through the duct segment (10). Abstract2020 There is provided a duct segment (10) comprising first and second opposing duct wall portions (100, 200), and a valve member (300) disposed between the first and second duct 2020200508 23 Jan wall portions (100, 200). The valve member (300) comprises a leading edge (302) and a trailing edge (304), the trailing edge (304) being attached to the first duct wall portion (100). The valve member (300) is moveable between an open position in which the leading edge (302) is positioned substantially adjacent the first duct wall portion (100) to allow airflow through the duct segment (10), and a closed position in which the leading edge (302) is positioned substantially adjacent the second duct wall portion (200) to restrict airflow through the duct segment (10). 1/2 Fig. 1 Fig. 2 10 10 100 200 300 102 202 104 204 106 206 108 110 110 210 208 210 100 200 300 20 30 302 304 306 308 A A 500 500 112 212 302 20 20 20 05 08 2 3 Ja n 20 20 Fig. 2 2110OII oz808 2001000 00£ 212112 302 206901 90E 00E 208801 OI I 204104 0E VV 00S302 000 304 20001001 2110OII 2020200508 23 Jan 2020 202102OI 1/2

Description

1/2 1/2

2020200508 23 Jan 2020 23 Jan 2020

10 OI 102 102 202 202

110 OII 210 2110

100 1001 200 2000 2020200508

304 304

300 000

302 302 500 00S

A A V V

30 0E

104 104 204 204

Fig. I1 10 OI 108 801 208 208 300 00E 306 90E 106 901 206 206 302 302 112 112 212 212 500 00£

100 1000 200 200 308 808 20 oz

110 OII 210 2110

Fig. 22 Fig.

DUCT SEGMENT 11 Aug 2025

Technical Field

[0001] The present disclosure relates to a duct segment. The duct segment is of the kind typically used for providing air supply in underground mining and tunnelling operations. 2020200508

Background

[0002] Ducting for underground mining and tunnelling operations is known. Ducting is typically formed by coupling duct segments together end-to-end. The duct segments are hollow so as to allow airflow therethrough. The duct segments may be arranged to form various lengths and configurations depending on mining and tunnelling needs.

[0003] In some instances, it may be desirable to close certain sections of the mine ducting where air supply is not needed. Typically, a rope is tied around a particular duct segment and the rope is pulled tight to constrict the duct segment thereby closing the duct segment. A disadvantage with this method is that it may be difficult, time-consuming and cumbersome to fit a rope around a duct segment, particularly with larger scale mines. Another disadvantage with this method is that the rope may be fitted in a haphazard manner, which may result in the duct segment being damaged. A further disadvantage with this method is that the rope may not provide a tight enough seal to adequately constrict the duct segment thus leading to air leakage through the constricted duct segment.

Object

[0004] It is an object of the present disclosure to substantially overcome or ameliorate one or more of the above disadvantages.

Summary

[0005] In accordance with an aspect of the present disclosure, there is provided a duct segment, comprising: first and second opposing duct wall portions, wherein the first and second duct wall portions are each formed from a sheet of flexible plastics material; and

2

Jan 2020 a valve a valve member disposedbetween member disposed between thethe firstand first andsecond second duct duct wall wall portions,the portions, thevalve valve membercomprising member comprising a leading a leading edge edge andand a trailingedge, a trailing edge,the thetrailing trailing edge edge being being attached attached to to the the first first duct duct wall portion, wall portion,

whereinthe wherein the valve valve member memberis ismoveable moveable between between an open an open position position in which in which the the 2020200508 23

leadingedge leading edgeis ispositioned positioned substantially substantially adjacent adjacent the duct the first first wall ducttowall to airflow allow allow airflow through through the duct the ductsegment, segment,andand a closed a closed position position in which in which the leading the leading edge is positioned edge is positioned substantially substantially

adjacentthe adjacent thesecond second duct duct wallwall to restrict to restrict airflow airflow through through thesegment. the duct duct segment.

[0006] TheThe

[0006] valve valve member member may further may further comprise comprise one orone or reinforcing more more reinforcing members members at or at or adjacent the adjacent the leading leading edge. edge. In In some embodiments,thetheone some embodiments, oneorormore more reinforcingmembers reinforcing members may may be formed be froma afibreglass formed from fibreglass material. material.

[0007] InInsome

[0007] some embodiments, embodiments, the trailing the trailing edge edge maymay be attached be attached to the to the first first ductwall duct wallportion portion by thermally by thermally welded weldedseams. seams.InInalternative alternative embodiments, embodiments,thethe trailingedge trailing edgemay maybebe sewn sewn onto onto

the first the first duct wallportion. duct wall portion.

[0008] InInsome

[0008] some embodiments, embodiments, the valve the valve member member and and the the first first duct duct wall wall portion portion may may be be integrally formed. integrally formed.

[0009] TheThe

[0009] firstduct first ductwall wallportion portion may maycomprise comprise firstopposing first opposingedge edge portions portions and and thethe second second

duct wall duct wall portion may comprisesecond may comprise second opposing opposing edge edge portions, portions,

whereinthe wherein the valve valve member membermaymay comprise comprise third third opposing opposing edge edge portions, portions, and and whereinthe wherein the third third opposing edgeportions opposing edge portions of ofthe the valve valve member membermaymay be be attached attached

betweenthe between the first first and and second opposingedge second opposing edgeportions portionsofofthe the first first and and second second duct wall

portions. portions.

[0010] TheThe

[0010] duct duct segment segment may may further further comprising comprising a tether. a tether. The The tether tether maymaybe coupled be coupled to to the the valve member valve memberatatororadjacent adjacentthe the leading leading edge. edge. In In some someembodiments, embodiments,thethe tethermay tether may be be in in thethe

formofofa arope, form rope,a acord, cord, or or thethe like.In In like. alternative alternative embodiments, embodiments, the may the tether tether may be be webbing. webbing.

[0011] TheThe

[0011] duct duct segment segment may may further further comprise comprise an actuator an actuator configured configured to move to move the valve the valve

memberbetween member between thethe open open andand closed closed positions. positions. In In some some embodiments, embodiments, the actuator the actuator may may comprise aa winch comprise winchcoupled coupledtotothe thetether, tether, and and aa motor for driving motor for driving the the winch. winch.

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Jan 2020

[0012] TheThe

[0012] firstduct first ductwall wallportion portion may mayhave havea first a first aperture aperture and and the the second second duct duct wall wall portion portion mayhave may havea asecond secondaperture, aperture, whereinthe wherein the leading leading edge edge ofofthe the valve valve member membermaymay be be positioned positioned adjacent adjacent thethe first first

aperture in the open position, and aperture in the open position, and 2020200508 23

whereinthe wherein the leading leading edge edge ofofthe the valve valve member membermaymay be be positioned positioned adjacent adjacent thethe second second

aperture in the closed position. aperture in the closed position.

[0013] TheThe

[0013] firstand first andsecond secondapertures aperturesmay maybe configured be configured to to allow allow thethe tethertotopass tether pass therethrough. therethrough.

[0014] Each

[0014] Each of of thethefirst first and andsecond secondduct ductwall wallportions portionsmay maybe formed be formed from from a flexible a flexible

material. In material. In one one embodiment, eachofofthe embodiment, each the first first and and second duct wall second duct wall portions portions may beformed may be formed from from a asheet sheetofofflexible flexibleplastics plastics material. material.

[0015] TheThe

[0015] valve valve member member maybe may be formedformed from afrom a flexible flexible material. material. In oneIn embodiment, one embodiment, the the valve member valve membermaymay be be formed formed fromfrom a sheet a sheet of flexible of flexible plasticsmaterial. plastics material.

Brief Description Brief of Drawings Description of Drawings

[0016] AnAn

[0016] embodiment embodiment of present of the the present disclosure disclosure willwill now now be described be described hereinafter, hereinafter, byway by way

of example of only, with example only, with reference reference to to the the accompanying drawings, accompanying drawings, in in which: which:

[0017] Fig.

[0017] Fig.1 1isis aa cross-sectional cross-sectional top top view of an view of an embodiment embodiment ofof a aduct ductsegment, segment,with witha valve a valve memberininthe member theopen openposition; position;

[0018] Fig.

[0018] Fig.2 2isis aa sectional sectional view of the view of the duct duct segment of Fig. segment of Fig. 11 along along section section A-A; A-A;

[0019] Fig. 3 is a cross-sectional top view of the duct segment of Fig. 1, with the valve

memberininthe member theclosed closedposition; position; and and

[0020] Fig.

[0020] Fig.4 4isis aa sectional sectional view of the view of the duct duct segment of Fig. segment of Fig. 33 along along section section B-B. B-B.

4

2020 Description of Description of Embodiments Embodiments

2020200508 23 Jan [0021] Figs.

[0021] Figs.1 1toto44show showa aduct ductsegment segment10 10 according according to to an an embodiment embodiment of present of the the present disclosure. The disclosure. The duct segment 10comprises segment 10 comprisesfirst first and and second secondopposing opposingduct duct wallportions wall portions100, 100, 200 and 200 and aa valve valve member member300300 disposed disposed between between the the first first andand second second ductduct wall wall portions portions 100, 100,

200. 200.

[0022]Referring

[0022] Referring to Figs. to Figs. 1 and 12,and the 2, the first first ductportion duct wall wall portion 100 comprises 100 comprises a first end a102, firsta end 102, a second end second end104, 104,ananinner inner surface surface 106, 106, and and first first opposing edge portions opposing edge portions 108, 108, 110. 110. Similarly, Similarly, the second the duct wall second duct wall portion portion 200 200 comprises comprisesa afirst first end end 202, a second end 204, second end 204, an an inner inner surface surface 206, and 206, and second second opposing opposingedge edge portions208, portions 208,210. 210.AsAs best best shown shown in Fig in Fig 2, 2, thethefirst first opposing opposing edgeportions edge portions108, 108, 110 110 of first of the the first ductduct wall wall portion portion 100 100 are are coupled coupled to theopposing to the second second opposing edgeportions edge portions208, 208, 210210 of second of the the second ductportion duct wall wall portion 200, respectively. 200, respectively. Thesecond The first and first and second duct wall duct wallportions portions 100, 100, 200 200 are each are each formed formed from of from a sheet a sheet of plastics flexible flexible material plasticsand, material and, whencoupled when coupledtogether togetherand andexpanded expanded in in use,forms use, forms a duct a duct wall wall 2020 generally generally circularinincross- circular cross section and section and has a diameter ranging from diameter ranging from 300 300mmmm to to 2400 2400 mm.mm. Air Air flows flows through through the duct the duct

segment1010inin aa direction segment direction 30 30 from the second from the second ends ends104, 104,204 204ofofthe thefirst first and and second duct wall second duct wall portions100, portions 100,200200 to to thethe first first ends ends 102,102, 202theoffirst 202 of the first and second and second duct duct wall wall portions portions 100, 100, 200. 200.

[0023] TheThe

[0023] valve valve member member 300 comprises 300 comprises a leading a leading edge a302, edge 302, a trailing trailing edge edge 304, 304, and third and third

opposing edge opposing edgeportions portions306, 306,308. 308.The Thethird thirdopposing opposingedge edge portions306, portions 306,308 308 of of thevalve the valve member300300 member areare attachedbetween attached between thethe firstand first andsecond secondopposing opposing edge edge portions portions 108,108, 110,110, 208, 208,

210ofofthe 210 thefirst first and andsecond secondductduct wallwall portions portions 100,Further, 100, 200. 200. Further, the trailing the trailing edge 304edge of the304 of the valvemember valve member300 300 is attached is attached to thetoinner the inner surfacesurface 106first 106 of the of the first duct wallduct wall100. portion portion In 100. In one embodiment, one embodiment,thethetrailing trailing edge edge304 304may maybe be sewn sewn onto onto thethe inner inner surface surface 106106 of of thethe first first

duct wall duct wall portion portion 100. 100. In In another another embodiment, thetrailing embodiment, the trailing edge 304 may edge 304 maybebeattached attachedtotothe the inner surface surface 106 106 of the thefirst firstduct wall duct portion wall 100100bybythermally portion thermallywelded welded seams. seams. The valve The valve

member300300 member is isformed formed from from a flexiblematerial. a flexible material.InInone oneembodiment, embodiment,thethe valve valve member member 300 300 is is formed form formed form a sheet a sheet of flexible of flexible plastics plastics material. material.

[0024] TheThe

[0024] valve valve member member 300 also 300 also comprises comprises one one or or more more reinforcing reinforcing members members (not (not shown) shown) at or at or adjacent theleading adjacent the leadingedge edge 302.302. The reinforcing The reinforcing membersmembers are configured are configured to add to add rigidity to rigidity to the leading edge the 302 of edge 302 of the the valve valve member 300.The member 300. The reinforcingmembers reinforcing members are are in the in the form form of of

5

Jan 2020 thin strips thin strips that that extend extendsubstantially substantially along along the the length length ofleading of the the leading edge edge 302. The302. The reinforcing reinforcing

membersareareformed members formed from from a fibreglassmaterial a fibreglass materialororthe thelike. like.

[0025] InInuse,

[0025] use,the thevalve valvemember member300300 is moveable is moveable between between an open an open position position (Figs. (Figs. 1 and1 2) and 2) 2020200508 23

andaaclosed and closedposition position (Figs. (Figs. 3 and 3 and 4). the 4). In In open the open position, position, the leading the leading edge 302edge 302 of the of the valve valve member member 300 300 is positioned is positioned substantially substantially adjacent adjacent thesurface the inner inner 106 surface of the106 ofduct first the first wall duct wall portion100 portion 100to toallow allow airflow airflow through through thesegment the duct duct segment 10, in 10, as shown as Fig. shown in the 2. In Fig.closed 2. In the closed position, the position, the leading leading edge edge 302 302 of of the the valve valve member 300isis displaced member 300 displaced from fromthe theinner innersurface surface 106 ofofthe 106 thefirst first duct ductwall wallportion portion 100100 and and is positioned is positioned substantially substantially adjacent adjacent the the inner inner surface surface 206 of 206 of the the second duct wall second duct wall portion portion 200, 200, as as best best shown in Fig. shown in Fig. 4. 4. The The valve valve member 300andand member 300

the inner the innersurface surface106106 of of thethe first first duct duct wall wall portion portion 100 define 100 define a cavity a cavity 400,terminates 400, which which terminates at the at the trailing trailingedge edge304 304of ofthe valve the member valve 300. The member 300. The trailing trailing edge edge 304 of the 304 of the valve valve member member

300restricts 300 restricts airflow airflowthrough through the the ductduct segment segment 10. 10.

[0026] TheThe

[0026] duct duct segment segment 10 also 10 also comprises comprises a tether a tether 500500 in the in the form form of of a rope,a cord, a rope, a cord,ororthe the like. InInother like. otherembodiments, the tether embodiments, the tether 500 500 may be webbing. may be webbing.The Thetether tether500 500isiscoupled coupledtotothe the valve member valve member300 300 at at ororadjacent adjacentthe theleading leadingedge edge302, 302,and andextends extendsthrough through firstand first andsecond second apertures112, apertures 112,212212 in in thethe first first andand second second duct duct wall portions wall portions 100, 100, 200, 200, respectively. respectively. In the In the openposition, open position,thetheleading leading edgeedge 302 302 of theof the valve valve member member 300 is positioned 300 is positioned adjacent theadjacent first the first aperture112, aperture 112,asasshown shown in Fig. in Fig. 2. In2.the In closed the closed position, position, the leading the leading edge 302edge 302 of the of valve the valve member300300 member is ispositioned positionedadjacent adjacentthe thesecond secondaperture aperture212, 212,asasshown shownin in Fig.4.4.The Fig. Thefirst first and and second apertures second apertures 112, 112, 212 212 are are configured configured toto allow allow the the tether tether 500 to pass 500 to pass therethrough. therethrough. In In some some

embodiments, eyeletsororguides embodiments, eyelets guides(not (notshown) shown)may may be be provided provided in the in the firstand first andsecond secondapertures apertures 112, 212totofacilitate 112, 212 facilitatepassage passageof of thethe tether tether 502 502 therethrough. therethrough.

[0027] InInsome

[0027] some embodiments, embodiments, onemore one or or more support support members members (not shown) (not shown) may be attached may be attached to to the first the first and secondduct and second duct wall wall portions portions 100, 100, 200 adjacent 200 adjacent theand the first first and apertures second second apertures 112, 112, 212. The 212. Thesupport support members members are configured are configured to add and to add strength strength and support structural structural support to the first to the first and second and second apertures apertures 112, 112, 212. 212. For Forexample, example,the theone oneorormore moresupport support members members may may be inbe in the the formofofa aplate form platehaving having an aperture an aperture that that is configured is configured to the to allow allow the 500 tether tether 500 to pass to pass therethrough. The therethrough. The support support members membersmaymay be formed be formed from from a plastics a plastics material material or the or the like. like.

[0028] InInsome

[0028] some embodiments, embodiments, the duct the duct segment segment may comprise may also also comprise an actuator an actuator (not shown) (not shown)

configured to configured to move movethe thevalve valvemember member300300 between between the open the open and closed and closed positions. positions. The The

6

23 Jan 2020

actuator may actuator comprisea awinch may comprise winch(not (notshown) shown) coupled coupled to to thethe tether500, tether anda amotor 500,and motor (not (not

shown)for shown) for driving driving the the winch. winch.

[0029] ToTo

[0029] closethetheduct close ductsegment segment 10 10 to to airflow,thethetether airflow, tether 500 500isis pulled pulled outwardly outwardlythrough through the second the aperture 212 second aperture 212 to to move movethe theleading leadingedge edge302 302ofofthe thevalve valvemember member300300 toward toward the the inner surface inner surface 206 206 of of the the second second duct duct wall wall portion portion 200. 200. The airflow catches The airflow catches the the leading leading edge edge

2020200508 302 of 302 of the the valve valve member 300andand member 300 assiststotourge assists urgeand andretain retain the the valve valve member member300300 in in the the

closed position. Air pressure within the cavity 400 forces the reinforcing members of the closed position. Air pressure within the cavity 400 forces the reinforcing members of the

valve member valve member300300 towards towards thethe inner inner surface206206 surface of of thethesecond second duct duct wall wall portion portion 200,which 200, which provides a tight seal between the inner surface 206 of the second duct wall portion 200 and provides a tight seal between the inner surface 206 of the second duct wall portion 200 and

the leading the leading edge 302. edge 302.

[0030] ToTo

[0030] open open thethe duct duct segment segment 10 airflow, 10 to to airflow, thethe tether500 tether 500isispulled pulledoutwardly outwardlythrough through the first the firstaperture aperture112 112totomove move the theleading leadingedge edge 302 302 of of the the valve valvemember 300toward member 300 towardthetheinner inner surface 106 of the first duct wall portion 100. The airflow again catches the leading edge 302 surface 106 of the first duct wall portion 100. The airflow again catches the leading edge 302

of the of the valve valve member 300and member 300 andassists assiststoto urge urge and andretain retain the the valve valve member 300against member 300 againstthe theinner inner surface 106 of the first duct wall portion 100 in the open position. Air pressure within the duct surface 106 of the first duct wall portion 100 in the open position. Air pressure within the duct

segment1010forces segment forces the the reinforcing reinforcing members membersofofthe thevalve valvemember member300 300 towards towards the inner the inner

surface 106 of the first duct wall portion 100, which provides a tight seal between the inner surface 106 of the first duct wall portion 100, which provides a tight seal between the inner

surface 106 of the first duct wall portion 100 and the leading edge 302. surface 106 of the first duct wall portion 100 and the leading edge 302.

[0031] InInother

[0031] otherembodiments, embodiments,the the valve valve member member 300the 300 and andfirst the first ductduct wallwall portion portion 100 100 may may be integrally formed. In this regard, the first end 102 of the first duct wall portion 100 may be be integrally formed. In this regard, the first end 102 of the first duct wall portion 100 may be

folded through folded through 180°, 180°, for for example. example. The Thefolded foldedportion portionofofthe the first first duct ductwall wallportion portion100 100 may may

then be sewn onto the inner surface 106 of the first duct wall portion 100 or attached thereto then be sewn onto the inner surface 106 of the first duct wall portion 100 or attached thereto

by thermally by thermally welded weldedseams. seams.

[0032] InInfurther

[0032] furtheralternative alternative embodiments, embodiments,thetheduct ductsegment segment 10 10 maymay comprise comprise a single a single ductduct

wall. wall.

[0033] TheThe

[0033] duct duct segment segment 10 described 10 described above above has numerous has numerous advantages. advantages. Firstly, Firstly, the valve the valve

member300300 member provides provides a tightseal a tight sealthat that prevents prevents air air leakage leakage through the duct through the duct segment segment 1010when when in the in the closed closed position. position.Secondly, Secondly, operation operation of ofthe thevalve valvemember 300 between member 300 betweenthe theopen openandand closed positions is relatively quick and simple and thus does not require specialised training. closed positions is relatively quick and simple and thus does not require specialised training.

7

Thirdly, the the tether tether500 500 provides provides easy easy access access for formoving the valve valve member member300 300 between the the 2020200508 23 Jan 2020

Thirdly, moving the between

openand open andclosed closed positions. positions. Fourthly, Fourthly, the segment the duct duct segment 10 is relatively 10 is relatively easy to manufacture, easy to manufacture,

thus reducing thus manufacturingcosts. reducing manufacturing costs.

[0034]It will

[0034] It will be be appreciated appreciated by persons by persons skilled skilled in the in the art thatart that numerous numerous variations variations and/or and/or modifications maybebemade modifications may madeto to theabove-described the above-described embodiments, embodiments, without without departing departing from from the the

broad general broad general scope scope of of the the present present disclosure. disclosure. The The present present embodiments are,therefore, embodiments are, therefore, to to be be

consideredin inallallrespects considered respects as as illustrative illustrative andand not not restrictive. restrictive.

Claims

CLAIMS: 11 Aug 2025

1. A duct segment, comprising: first and second opposing duct wall portions, wherein the first and second duct wall portions are each formed from a sheet of flexible plastics material; and a valve member disposed between the first and second duct wall portions, the valve member comprising a leading edge and a trailing edge, the trailing edge being attached to the 2020200508

first duct wall portion, wherein the valve member is moveable between an open position in which the leading edge is positioned substantially adjacent the first duct wall portion to allow airflow through the duct segment, and a closed position in which the leading edge is positioned substantially adjacent the second duct wall portion to restrict airflow through the duct segment.

2. The duct segment of claim 1, wherein the valve member further comprises one or more reinforcing members at or adjacent the leading edge.

3. The duct segment of claim 2, wherein the one or more reinforcing members are formed from a fibreglass material.

4. The duct segment of any one of the preceding claims, wherein the trailing edge is attached to the first duct wall portion by thermally welded seams.

5. The duct segment of any one of claims 1 to 3, wherein the trailing edge is sewn onto the first duct wall portion.

6. The duct segment of any one of the preceding claims, wherein the valve member and the first duct wall portion are integrally formed.

7. The duct segment of any one of the preceding claims, wherein the first duct wall portion comprises first opposing edge portions and the second duct wall portion comprises second opposing edge portions, wherein the valve member comprises third opposing edge portions, and wherein the third opposing edge portions of the valve member are attached between the first and second opposing edge portions of the first and second duct wall portions.

8. The duct segment of any one of the preceding claims, further comprising a tether. 11 Aug 2025

9. The duct segment of claim 8, wherein the tether is coupled to the valve member at or adjacent the leading edge.

10. The duct segment of claim 8 or 9, wherein the tether is in the form of a rope, a cord, or the like. 2020200508

11. The duct segment of claim 8 or 9, wherein the tether is webbing.

12. The duct segment of any one of claims 8 to 11, further comprising an actuator configured to move the valve member between the open and closed positions.

13. The duct segment of claim 12, wherein the actuator comprising a winch coupled to the tether, and a motor for driving the winch.

14. The duct segment of any one of claims 8 to 13, wherein the first duct wall portion has a first aperture and the second duct wall portion has a second aperture, wherein the leading edge of the valve member is positioned adjacent the first aperture in the open position, and wherein the leading edge of the valve member is positioned adjacent the second aperture in the closed position.

15. The duct segment of claim 14, wherein the first and second apertures are configured to allow the tether to pass therethrough.

16. The duct segment of any one of the preceding claims, wherein the valve member is formed from a flexible material.

17. The duct segment of claim 16, wherein the valve member is formed from a sheet of flexible plastics material.