EP0772752A1

EP0772752A1 - Sealing apparatus

Info

Publication number: EP0772752A1
Application number: EP95927031A
Authority: EP
Inventors: Alain Wambeke
Original assignee: Raychem NV SA
Current assignee: Commscope Connectivity Belgium BVBA
Priority date: 1994-07-29
Filing date: 1995-07-27
Publication date: 1997-05-14
Also published as: PE8196A1; AU3119695A; WO1996004504A1

Abstract

Apparatus that can form a seal in a hollow article, comprises: (a) an inflatable sealing member which can be spirally coiled and inflated in the hollow article to seal the article; and (b) a retaining member; wherein the retaining member has an opening preferably a slot, through which the sealing member can extend and/or the sealing member has an opening through which the retaining member can extend, when the sealing member is so coiled and inflated in the article in use, thereby impeding helical uncoiling of the inflated sealing member.

Description

Scaling Apparatus

The present invention relates to apparatus for forming a seal in a hollow article, for example a duct.

A variety of different systems have been proposed for sealing ducts (which term includes 'feedthroughs'). One highly successful system is disclosed in International Patent Application No. WO92/19034, which comprises a flexible hollow sealing member that can be inflated to seal a gap between first and second articles (e.g. between a duct and one or more cables extending through the duct). The sealing member has a hole directly through a wall or between walls thereof through which hole a probe can be inserted to introduce a pressurizing medium into the member, and means by which the hole is automatically sealed on withdrawal of the probe. The sealing member may, for example, be coiled around one or more cables or pipes extending through the duct and then inflated to form a seal between the cables and the wall of the duct. The entire disclosure of WO92/ 19034 is incorporated herein by reference.

Although the inflatable sealing member disclosed in W092/ 19034 generally performs excellently, it has been found that in a small proportion of cases when the sealing member is required to seal relatively large diameter ducts (e.g. 6 inches (150mm) or greater) which are empty (i.e. there are no cables or pipes extending through the duct), there is a risk that the seal might be difficult to install reliably. Possible failure of the seal on incorrect installation might occur, due to a combination of the large diameters of the ducts involved, the fact that the ducts are empty, and a relatively high external pressure (e.g. 50 or 70 KPa) to which the seals may be subjected.

It has been found that these failures of incorrectly installed inflatable seals can happen by a particular mechanism of uncoiling of the inflatable sealing member. For example, due to excess pressure exerted against one side of the sealing member relative to the other side, the coils of the inflated sealing member may elongate in a manner similar to the lengthening of a collapsible telescope, until the sealing member becomes uncoiled and the seal fails. This uncoiling mechanism in the form of 'telescopic elongation' is referred to herein as 'helical uncoiling'. The present invention provides a solution to the problem of helical uncoiling of spirally coiled inflated (which term includes partially inflated) sealing members and can therefore substantially reduce the risk of failure of such sealing members, particularly when installed in empty ducts. The invention may also, advantageously, substantially prevent an inflated sealing member from being forced along a duct or the like, for example due to excess pressure on one side of the sealing member (the so-called 'piston effect'). The invention may often be used with advantage even when the duct or the like contains one or more elongate objects (e.g. pipes and / or cables).

According to a first aspect of the present invention, there is provided apparatus that can form a seal in a hollow article, comprising:

(a) an inflatable sealing member which can be spirally coiled and inflated in the hollow article to seal the article; and

(b) a retaining member;

wherein the retaining member has an opening through which the sealing member can extend and / or the sealing member has an opening through which the retaining member can extend, when the sealing member is so coiled and inflated in the article in use, thereby impeding helical uncoiling of the inflated sealing member.

The invention is based on the discovery that helical uncoiling of an inflatable sealing member may be substantially prevented merely by passing part of the sealing member, e.g. one or more coils of the sealing member, through an opening extending through a member (called a 'retaining member' herein) which is provided in addition to, or as part of, the sealing member, and / or by passing a retaining member (which may or may not have an opening extending through it) through an opening extending through the sealing member. It is preferred, for most applications, to use a retaining member having an opening through which the sealing member can extend, rather than a sealing member having an opening through which the retaining member can extend. It is surprising that any resistance to inflation caused by the retaining member is generally not detrimental to the sealing ability of the sealing member. It is particularly surprising that, according to preferred embodiments of the invention, it is necessary (and preferred) only to pass one coil (as opposed to two or more coils) of the sealing member through the operiing in the retaining member substantially to prevent helical uncoiling of the sealing member. Alternatively, however, in some preferred embodiments of the invention, the retaining member can retain two or more coils of the sealing member together, thereby impeding helical uncoiling of the sealing member.

The scope of the invention is not limited by any suggested explanations for its success, but one or more of a variety of explanations may be postulated. One possible explanation is that the extension of the sealing member through the opening in the retaining member (and / or the extension of the retaining member through the opening, where present, in the sealing member) substantially prevents rotation of the coils of the sealing member with respect to each other, and since such coil rotation is normally necessary in order for helical uncoiling to take place, helical uncoiling of die sealing member is substantially prevented. Another possible explanation, for those embodiments of the invention in which the retaining member is longer than the axial length of the sealing member when coiled and inflated, is that if the retaining member is fixed to a coil of the sealing member, any helical uncoiling of the sealing member would normally force the retaining member to rotate about an axis peφendicular to its length, and this rotation of the retaining member would normally be restricted either by the presence of the sealing member or by the end(s) of the retaining member contacting the internal wall of the hollow article, thereby at least hindering, or preferably preventing, helical uncoiling of the sealing member. Accordingly, in a preferred embodiment of the invention, the retaining member is longer than the axial length of the sealing member when coiled and inflated in use, such that rotation of the retaining member about an axis peφendicular to its length is impeded, in use, by the interior of the hollow article or by the sealing member, thereby impeding helical uncoiling of the inflated sealing member.

Preferably, the retaining member comprises a rod, and the opening preferably comprises a slot extending through the rod. This preferred embodiment has a number of advantages which will be described below, but one advantage which may be mentioned here is that because the retaining member is in the form of a rod (as opposed to a flexible strap or band, for example) it may provide a relatively, or preferably substantially, rigid article around which the sealing member may be coiled and inflated, and hence the inflated sealing member may in effect be trapped between the rod and the hollow article (e.g. a duct). It is to be understood however that the retaining member may, in some embodiments of the invention, be sμbstantially rigid without being in the form of a rod. The retaining member may advantageously be formed from a plastics material, e.g. a polyamide material, and / or metal.

The term 'rod' as used herein means any generally or approximately rod-like article, including articles which in appearance would not normally be considered to be rods as such. For example, the rod may comprise a substantially rigid elongate band; an article formed from two or more parts which when joined together form an opening of substantially closed cross-section; and/or an article in which the opening is not completely closed in cross-section. The rod of preferred embodiments of the invention is substantially rigid, but in some embodiments the rod may advantageously have some flexibility, e.g. so that it may bend to fit into different shapes of duct. Preferably, the rod is generally curved in cross-section (at least in those parts of the rod not having the opening), but the rod may have any of a range of cross-sections, e.g. it may be polygonal in cross-section. The rod may advantageously be substantially solid in those parts not containing the opening, or alternatively it may be hollow, for example. The rod may have one or more enlarged end-pieces, e.g. in the form of flanges. Advantageously, the retaining member may have one or more gripping protrusions on one or more surfaces thereof, e.g. to aid in impeding uncoiling of the sealing member. For example, the retaining member may have one or more gripping protrusions on its external surface and/or inside the opening (e.g. the slot) extending through the rod. Additionally or alternatively, the retaining member may have an outer diameter which varies along the length of the retaining member. For example, the retaining member (especially when in the form of a rod) may have a relatively narrow central portion and two relatively wide end portions on either side of the central portion, e.g. so that the member has a generally 'dog-bone-like' shape. The gripping protrusions and/or the varying diameter of the retaining member may, for example, help to prevent the sealing member from sliding off the retaining member (e.g. rod) longitudinally.

According to a particularly preferred embodiment of the invention, the retaining member further comprises one or more gripping members to grip the inside of the hollow article, e.g. the inner wall of a duct. The gripping member(s) may, for example, substantially prevent, or at least hinder, unwanted movement of the sealing member along the inside of the hollow article (e.g. a duct), e.g. due to excess pressure on one side of the sealing member (the piston effect). When the retaining member comprises a rod, the gripping members) preferably extend laterally with respect to the rod. The gripping members) may be formed integrally with the retaining member, but preferably it is/they are attached to the retaining member during the installation of the apparatus in the hollow article. The gripping member(s) may, for example, be screwed to the retaining member. Preferably, the gripping members) are located, in use, at at least one end, and more preferably at both ends, of the retaining member. The gripping member(s) may advantageously have one or more blades or other gripping device(s) (e.g. teeth) to penetrate the inner wall of the hollow article. A particularly preferred embodiment is one in which the or each gripping member can expand (e.g. extend) to grip the interior of the hollow article. This expansion may, for example, comprise the lengthening of an elongate gripping member, e.g. by screwing one or more (preferably two) threaded portions of the gripping member outwardly with respect to a substantially non-expansible or non-extensible portion thereof. It is preferred that the gripping member(s) is/are provided in embodiments in which the retaining member comprises a rod.

Preferred embodiments of the invention may include a protection plate located at one end, or preferably at both ends, of the sealing member installed in the hollow article in use. Preferably, therefore, the sealing member is "sandwiched", in use between at least two protection plates longitudinally spaced apart in the hollow article. The protection plate(s) may, for example, provide protection of the inflatable sealing member from fire and/or animals, e.g. insects or rodents. The, or at least one of the, protection plate(s) may advantageously be integrally formed with the retaining member, preferably however, the protection plate(s) is/are attached to the retaining member during the installation of the apparatus in the hollow article. The protection plate(s) may, for example, be screwed to the retaining member. Preferably, the protection plate(s) substantially completely shield the sealing member from access by rodents and/or fire inside the hollow article. It is particularly preferred that the protection plate(s) is/are provided in embodiments of the invention in which the retaining member comprises a rod. Advantageously, for example, the protection plate(s) may be attached to, or formed integrally with, one or both ends of the rod.

For many applications of the invention, the retaining member preferably comprises a rod. However, for other applications of the invention, the retaining member may advantageously comprise a flexible band which can extend around at least one coil of the sealing member thereby forming the opening through which the part of the sealing member extends. The flexible band may, for example, comprise a component of the apparatus which is distinct from the sealing member and which is installed around one or more coil(s) of the sealing member during the installation of the apparatus in the hollow article. Alternatively, the flexible band may comprise part of the sealing member and may, for example, be integrally formed with the sealing member. In either form of the flexible band, the band may advantageously be closed in cross-section (e.g. in the form of a ring) so that it has to be slid onto a free end of the sealing member which is then coiled within the hollow article. Alternatively, in either form of the flexible band, the band may be wraparound. By 'wraparound' is meant that the flexible band is open in cross section so that it may be positioned around one or more of d e coils of the sealing member without having to slide the band onto a free end of the sealing member. If the flexible band is wraparound, it is preferably provided with means for joining its free ends together, e.g. clasp means or an adhesive, especially a pressure sensitive adhesive.

It was mentioned above that in some preferred embodiments of the first aspect of the invention, the retaining member further comprises one or more gripping members to grip the inside of the hollow article (e.g. the inner wall of a duct). However, I have discovered that such gripping members may advantageously be used without the retaining member according to the first aspect of the invention, to hinder, or preferably to prevent, the sealing member from being forced out of the hollow article or forced out of position in the hollow article, for example due to excess pressure on one side of the sealing member (often referred to as the 'piston effect'). I have further discovered that such gripping members can often impede helical uncoiling of the sealing member.

Consequently, according to a second aspect of the invention, there is provided apparatus that can form a seal in a hollow article, comprising:

(b) at least one gripping member which can be situated next to the sealing member in use, and which can expand to grip the interior (e.g. an inner wall) of the hollow article, thereby impeding axial movement of the sealing member with respect to the hollow article when so coiled and inflated therein in use. The axial movement of the sealing member with respect to the hollow article which the gripping member(s) impede may comprise piston movement (i.e. movement of the sealing member as a whole along, or out of, the hollow article) and/or helical uncoiling of the sealing member.

Preferably, the gripping member(s) of the second aspect of the invention is/are elongate and can be lengthened, or comprise one or more elongate portions which can be lengthened, to grip the interior of the hollow article. More preferably, this lengthening can be achieved by moving one or more extending portions with respect to one or more substantially non-extensible portions. The or each extending portion preferably comprises a threaded portion which can be screwed outwardly with respect to the or each substantially non-extensible portion of the gripping member. Particularly preferred embodiments are those in which the or each extending portion is screwed into a female screw thread in a non-extensible portion

Other designs of gripping member may be used, for example gripping members which can expand by means of one or more slidable portions which can be slid outwardly to grip the interior of the hollow article. In one design, the or each gripping member may be slidably mounted to a substantially non-extensible portion which may, for example, comprise a protection plate as described above. In another design, the gripping members comprise a plurality of (e.g. six) segments of a protection plate which are each movably (e.g. slidably) mounted on a central part and which may be moved outwardly so as to increase the cross-sectional area of the plate and to grip the inner wall of a hollow article. This design has the advantage of providing the gripping members and a protection plate in one.

The gripping member(s) of the second aspect of the invention may, for example, be secured, in use, next to the sealing member inside a hollow article merely by means of its/their grip on the interior of the hollow article. Alternatively, however, the gripping member(s) may be attached, in use, to one or more other members which may, advantageously help to maintain the gripping members in position. Preferably, this other member (where present), comprises at least one member which extends, in use, between parts of the sealing member and/or between the sealing member and the hollow article. The other member is preferably elongate. It is particularly preferred that the other member comprise the retaining member of the first aspect of the invention.

The inflatable sealing member of the apparatus according to the invention may, in the broadest aspect of the invention, comprise any inflatable sealing member which can be coiled and inflated in a hollow article. Generally any inflating medium may be used, but a preferred medium is gas and a particularly preferred medium is air.

A particularly preferred inflatable sealing member is that disclosed in International Patent Application No. WO92/19034, namely a flexible hollow sealing member (preferably having substantially non-stretchable walls) that can be inflated to form a seal in a hollow article (e.g. a duct) and that has a hole directly through a wall or between walls thereof through which hole a probe can be inserted (and from which it can preferably be removed by mere pulling) to introduce a pressurizing medium into the sealing member, and means by which the hole is automatically sealed on witiidrawal of the probe. The inflatable sealing member may be supplied with the probe inserted through the hole. Furthermore, insertion of the probe may be part of the manufacturing process of the sealing member.

The specific design of the inflatable sealing member will normally be chosen according to the requirements of each application of the invention. However, designs which incoφorate one or both of the following features are generally preferred.

Firstly, an internal flap may, for example, be provided across the hole in or between the walls of the inflatable sealing member. The flap may seal in response to pressure within the member. The flap preferably comprises a flexible polymeric sheet fixed to a wall of the member such that the probe can pass through the hole and displace the flap, the probe preferably passing between the flap and the wall substantially in the plane of the wall (say at less than 45° to that plane). A sealing material, for example a gel or a mastic, may be provided between the flap and the wall, for example as a coating on the flap. The flap may be bonded or welded to the wall along two lines separated by a small gap (say 5-20 mm), such that the probe can be inserted through the hole in the wall and between the wall and the flap generally along the axis of the channel formed between the two bond or weld lines.

The second design is particularly appropriate where the hole is between overlapping walls of a lap join. (The lap join may arise in formation of the member by forming a tube from a sheet of material). The hole, which extends the width of the lap join, may decrease in cross-sectional size toward the outside of the sealing member. The hole may therefore have a funnel, or flattened funnel, shape. A sealing material (preferably a mastic or a gel) may be provided within this funnel-or-other- shaped hole, such that the sealing material is driven by internal pressure to block the hole. The size of the hole and the physical properties and amount of the sealing material may be chosen such that the material does not creep out of the hole to an unacceptable extent. A flap as mentioned above may be used in conjunction with this type of hole.

In preferred embodiments of the invention, the inflatable sealing member has sealing material on one or more external surface(s) thereof. The sealing material may, for example, comprise mastic or gel. In some embodiments the sealing material may comprise mastic and gel in combination.

The gel may, for example, comprise silicone gel, urea gel, urethane gel, thermoplastic gel or any suitable gel or gelloid sealing material. Preferred gels comprise an oil - extended polymer composition. Preferably the gel has a hardness at room temperature as determined using a Stevens- Volland Texture Analyser of greater than 45g, particularly greater than 50g especially greater than 55g, e.g. between 55g and 60g. It preferably has a stress-relaxation of less than 12%, particularly less than 10% and especially less than 8%. Ultimate elongation, also at room temperature, is preferably greater than 60%, especially greater than 1000%, particularly greater than 1400%, as determined according to ASTM D638. Tensile modulus at 100% strain is preferably at least 1.8 MPa more preferably at least 2.2 MPa. In general compression set will be less than 35%, especially less than 25%. Preferably, the gel has a cone penetration as measured by ASTM D217 of at least 50 (10'1 mm), more preferably at least 100 (10^*1 mm), even more preferably at least 200 (10"* mm) and preferably no greater than 400 (10"* mm), especially no greater than 350 (10"1 mm).

The polymer composition of the gel, particularly when comprising a thermoplastic gel, may for example comprise an elastomer, or a block copolymer having relatively hard blocks and relatively elastomeric blocks. Examples of such copolymers include styrene-diene block copolymers, for example styrene-butadiene or styrene-isoprene diblock or triblock copolymers, or styrene-ethylene-butylene-styrene triblock copolymers as disclosed in international patent publication number WO88/00603. Preferably, however, the polymer composition comprises one or more styrene-ethylene-propylene-styrene block copolymers, for example as sold under the Trade Mark 'Septon' by Kuraray of Japan. The extender liquids employed in the gel preferably comprise one or more oils. The oils may be hydrocarbon oils, for example paraffinic or naphthenic oils, synthectic oils for example polybutene or polypropene oils, and mixtures thereof. The preferred oils are mixtures of non-aromatic paraffins and naphthenic hydrocarbon oils. The gel may contain additives such as moisture scavengers (eg. Benzoyl chloride), antioxidants, pigments and fungicides.

Inflation of the sealing member may, for example, be carried out by attaching a probe to a source of pressurizing fluid and (if it is not supplied in place) inserting the probe into the sealing member. Generally any suitable pressurizing means may be used to inflate the sealing member, for example, a hand pump, an electric pump, or a pressurized gas cylinder. The invention will now be described, by way of example, with reference to the accompanying drawings, of which:

Figure 1 shows an inflatable sealing member of the apparatus according to the invention;

Figure 2 shows, schematically, in sequence, an inflatable sealing member uncoiling and helical uncoiling out of a duct;

Figure 3 shows, in perspective, three different forms of retaining member according to the invention, and a side view of one of these forms of retaining member;

Figure 4 shows some perspective views of a preferred form of apparatus according to the invention;

Figure 5 shows another form of apparatus according to the invention;

Figure 6 shows a further form of apparatus according to the invention;

Figure 7 shows a gripping member according to the invention;

Figure 8 shows, schematically, two alternative shapes of gripping member of the invention;

Figure 9 shows two forms of attachment means for attaching a gripping member to another member; and

Figure 10 shows a sealing member and a gripping member according to the invention installed in a duct or other hollow article. Figure 1 shows a preferred form of inflatable sealing member 1 of the apparatus according to the invention, comprising an inflatable bag 3 and sealing material 5 which preferably comprises mastic.

Figures 2a, 2b and 2c show schematically and in sequence a problem which is solved by the invention, namely helical uncoiling of an inflated sealing member out of a hollow article. Figure 2a shows a sealing member 1 which has been coiled and inflated inside a hollow article 7, which may, for example, comprise a duct. The arrow A shows the direction in which the sealing member 1 is being urged (i.e. out of the hollow article 7) due, for example, to a higher pressure of gas or liquid inside the duct behind the sealing member than outside the duct in front of the sealing member. Figure 2b shows the innermost part of the coiled sealing member beginning to uncoil helically out of the duct in the direction of the arrow A, and Figure 2c shows the sealing member almost entirely forced out of the duct.

Figures 3a, 3b and 3c show, in perspective, three different types of retaining member in the form of a rod. The retaining member 9 shown in Figure 3a comprises a simple right cylindrical rod having a slot 11 extending through it. Each end of the rod has a screw thread 13 (only one of which is shown) to enable a protection plate and/or a gripping member to be attached to it. The rod 15 shown in Figure 3 b is substantially identical to the rod 9, except that it has a plurality of gripping protrusions on its external curved surface, to aid in preventing an inflated sealing member sliding longitudinally off the rod, in use. The rod 19 shown in figure 3c is similar to the rod 9 shown in figure 3a, except that its external diameter varies along its length. The rod 19 has a relatively narrow central portion 21 and two relatively wide end portions 23 on either side of the central portion, giving the rod a generally 'dog-bone-like' appearance. This 'dog-bone' shape can help to prevent an inflated sealing member which is coiled around the central portion 21 of the rod from sliding longitudinally off the rod. The rods 15 and 19 each have a slot 11 extending through them and screw tfireads 13 at each end, similarly to the rod 9 of Figure 3a. Figure 3d shows a side view of the rod 9 of Figure 3 a. The inter-relation of the retaining member of the apparatus when it is in the form of a rod with a slot and the inflatable sealing member of the apparatus, is illustrated in Figures 4a, 4b and 4c. An inflatable sealing member 1 , prior to inflation, is shown in a partially coiled configuration in Figure 4a. The sealing material 5 (mastic) and the inflatable bag 3 are indicated. A retaining member in the form of a rod 9 substantially the same as that shown in Figure 3 a is illustrated in Figure 4b. The slot 11 and the screw thread 13 are indicated. Figure 4c shows part of the sealing member 1 having been passed through the slot 11 of the rod 9, so that part of one coil of the sealing member extends through the slot. In order to install the sealing member 1 and rod 9 into a hollow article (e.g. a duct), the sealing member is subsequently coiled around the rod, and the coiled sealing member and the rod are inserted into the article. The sealing member may then be inflated to seal the hollow article. Uncoiling of the inflated sealing member (and in particular, helical uncoiling of the sealing member out of the article) is substantially prevented by the presence of the rod and the fact that part of the sealing member extends through the rod. Two or more coils of the sealing member may, in some embodiments, be passed through the slot in the rod, or through separate slots in a rod, or through respective slots in two or more rods, and this may enhance the ability of the rod(s) to prevent helical uncoiling, but it has been found that this is not necessary for many applications.

Also shown in Figure 4c are two protection plates 25, each of which may be attached to an end of the rod, for example, by means of bolts screwed into screw threads 13. The protection plates 25, when attached to the rod, are each therefore located at one end of the sealing member 1, so that the sealing member is 'sandwiched' between the protection plates. The protection plates 25 may, for example, protect the inflated sealing member from fire and/or rodents. The protection plate(s) may have one or more slots (not shown in the drawings) to enable eccentric positioning of the rod, for example for situations in which it would be inconvenient or impossible for the rod to extend between the centres of the plates. Figures 5 and 6 illustrate an alternative form of the retaining member of the invention. Figure 5a shows a retaining member in the form of a flexible band 27. In Figure 5b, the band 27 is shown extending around part of two coils of a sealmg member 1 (which sealing member is substantially identical to that shown in Figure 1 ). When the retaining member is in the form of a flexible band, it preferably extends around at least two coils of the sealing member in order to maximise its ability to prevent helical uncoiling of the coiled sealing member in use. However, for some embodiments of the invention, the band may impede uncoiling of the sealing member even if it extends around only one coil of the sealing member. Also shown in Figure 5b is a probe 29 which may be used to inflate the sealing member.

Figures 6a and 6b show another embodiment of the invention, in which the retaining member is in the form of a flexible band 31, but in this embodiment the band (which in this case may be described as a strap) comprises part of the sealing member 33. The strap is in two parts, each of which has been integrally formed with the inflatable bag 35 of the sealing member 33, each part of the strap being located at opposite ends of the sealing member. Figure 6b shows the sealing member 33 coiled partially around itself and part of the strap folded over a coil of the sealing member. In this embodiment, therefore, part of the sealing member acts as part of the retaining member, so that the retaining member extends around a coil of the sealing member partly in the form of a strap and partly in the form of the sealing member itself. The two parts of the strap may be joined together, for example by means of pressure sensitive adhesive 37. A probe 29 is also shown.

Figures 7a and 7b show a gripping member (according to the first or preferably the second aspect of the invention), in the form of an elongate member comprising a substantially non-extensible portion 39 and two extending portions 41. Portion 39 comprises a rod having female screw threads 43 in each end, and portions 41 comprise threaded bolts which, in use, are located in the female threaded ends of the rod 39. In order to expand the gripping member, one or both of the bolts 41 are screwed outwardly. The extending portions (bolts) 41 preferably have gripping means at their gripping ends, e.g. comprising teeth or other protrusions which may penetrate the inner wall of a duct or other hollow article.

Figure 8 shows, schematically, two other shapes of gripping member which may be used, namely a 'Y' shape 45 and a cruciform shape 47, having elongate portions 49, each of which may have female threads, for example. Other shapes of gripping member may be used, and in particular shapes having greater numbers of elongate portions,e.g. five, six, or more. Shapes of gripping members having greater numbers of elongate portions are generally particularly effective at preventing helical uncoiling of the sealing member.

Figure 9 shows attachment members 51 and 53 (e.g. in the form of brackets) which may be used to attach a gripping member to another member, e.g. a retaining member according to the first aspect of the invention. The brackets may be attached to the other member by means of a screw 55, for example.

Figure 10 shows a sealing member 57 of the invention installed in a duct or other hollow article 59. A gripping member in the form of a substantially non- extensible portion 39 and two extending portions 41 is positioned next to the sealing member, and this gripping member is attached, by means of a bracket 51 to the end of a retaining member 61 according to the first aspect of the invention. The extending portions 41 of the gripping member (in the form of bolts) have been screwed outwardly into gripping engagement with the inner wall of the hollow article 59.

Claims

1. Apparatus that can form a seal in a hollow article, comprising:

(b) a retaining member;

2. Apparatus according to claim 1, in which the retaining member is longer than the axial length of the sealing member when coiled and inflated in use, such that rotation of the retaining member about an axis peφendicular to its length is impeded, in use, by the interior of the hollow article or by the sealing member, thereby impeding helical uncoiling of the inflated sealing member.

3. Apparatus according to claim 1 or claim 2, in which the retaining member can retain two or more coils of the sealing member together, thereby impeding helical uncoiling of the sealing member.

4. Apparatus according to any preceding claim, in which the retaining member is substantially rigid.

5. Apparatus according to any preceding claim, in which the retaining member comprises a rod, and the opening comprises a slot extending through the rod.

6. Apparatus according to any one of claims 1 to 3, in which the retaining member comprises a flexible band which can extend around at least one coil of die sealing member thereby forming the opening through which the part of the sealing member extends.

7. Apparatus according to any preceding claim, in which the retaining member has one or more gripping protrusions on one or more surfaces thereof.

8. Apparatus according to any preceding claim, in which the retaining member has an outer diameter which varies along the length of the retaining member.

9. Apparatus according to any preceding claim, in which the retaining member further comprises one or more gripping members to grip the inside of the hollow article.

10. Apparatus according to any preceding claim, which further comprises at least one protection plate, which can be located at at least one end of the sealing member when it is coiled and inflated in the hollow article in use.

11. Apparatus that can form a seal in a hollow article, comprising:

(b) at least one gripping member which can be situated next to the sealing member in use, and which can expand to grip the interior of the hollow article, hereby impeding axial movement of the sealing member with respect to the hollow article when so coiled and inflated therein in use.

12. Apparatus according to claim 1 1, in which the gripping member(s) is/are elongate and can be lengthened, or comprise(s) one or more elongate portions which can be lengthened, to grip the interior of the hollow article.

13. Apparatus according to claim 12, in which the lengthening of the gripping member(s) can be achieved by moving one or more extending portions widi respect to one or more substantially non-extensible portions thereof.

14. Apparatus according to claim 13, in which the or each extending portion comprises a threaded portion which can be screwed outwardly with respect to the or each substabtially non-extensible portion of the gripping member.

15. Apparatus according to any one of claims 11 to 14, further comprising an elongate member which extends, in use, between parts of the sealing member and/or between the sealing member and the hollow article, the or each gripping member being attached to the elongate member.

16. Apparatus substantially as described herein with reference to, and as shown in, the accompanying drawings.