Patent Description:
Inflatable devices such as inflatable bags have found use in stopping flow in pipes such as gas or water pipes, to allow repair and maintenance procedures to be carried out.

For example two such inflatables can allow isolation of a short section of damaged pipe, with one inflatable bag to either side of the damaged section. This avoids having to depressurise, isolate or even drain a long section of pipe to allow safe access for repair or replacement. For further example long sections of pipework can be isolated, <NUM> or more, by using inflatable bags. This can be done where replacement or abandonment of an extensive system, such as a gas main, is being undertaken.

In some procedures an isolated section of pipe can be bypassed to allow flow to continue via a bypass loop of pipe that connects to either end of the isolated section. The isolated section of pipe may then be depressurised and work undertaken.

As an alternative approach, use of a stent may be considered when repairing, maintaining or remediating pipework. A stent generally has a passage through to allow flow to continue, whilst at the same time supporting or even isolating a section of pipe that is damaged; weakened or even has failed, causing leakage. Thus a stent can bridge across a damaged length of a pipe (from the inside); from an undamaged section, past the damage, to an undamaged section on the other side; to provide a safe passage through for a fluid flow, even a pressurised fluid flow.

Stent operations can include isolation of damaged or failed lengths of a pipe system; sealing of leakage at pipe joints or damaged pipe walls; maintenance, repair or replacement of pipe components such as valves or pipe sections; and temporary or permanent repair of damaged pipe walls.

There is a need for improved stents and systems for use. In particular, to allow the use of an inflatable stent in relatively harsh environments such as in gas, oil and water systems, including at high pressure, for example mains water pipe systems.

Similarly there is a need for improved stents and systems of use in medical applications, where speed, ease of use and confidence of successful deployment are of great importance.

<CIT> discloses an improved drain plug device. The device includes an elongated, hollow, flexible, resilient, unitary, self-supporting tubular member having a central passageway extending all the way therethrough to the exits in the opposite ends of the member. The member has a rear bulbous inlet portion, a middle very flexible portion to allow the member to bend around curves in drain lines, and a front bulbous outlet portion. The inlet and outlet portions have the same sidewall thickness while that of the middle portion is preferably somewhat thicker. Preferably, the middle portion is narrower in diameter than the other portions of the member. The outlet portion has a higher Shore hardness than the inlet portion and therefore expands radially under internal fluid pressure more slowly than the inlet portion but collapses, after removal of such pressure, at a faster rate, thus assuring that water in the tubular member during use thereof will not back up and out the inlet exit. The inlet is fitted with a pressure hose connector and the outlet with a pressure relief valve. The method includes molding the tubular member after supplying a mold with two different rubberlike moldable compositions so that, when set, the three portions of the member will exhibit their separate characteristic properties. The method also includes fitting the member with the connector and relief valve.

<CIT> discloses a medical device consisting of a dual lumen catheter with three intra-connecting balloons comprising a balloon stent. The adjustable tissue approximation using negative pressure exerted between device and mucosa of stomach/esophagus/colon with improved injury site isolation via adjustable balloon stent and added potential of negative pressure application to injury site for active healing process and distal feeding potential.

<CIT> discloses a method and apparatus for installing a liner material into a host conduit such as, e.g., a sewer pipe, hydrocarbon pipeline, gas line, water line, industrial chemical pipe, or a saltwater line. The liner material may include a compression liner and/or a preliner that is attached to the inner wall of the host conduit to repair or reinforce the host conduit or separate the host conduit from materials transported within the new liner formed from the liner material. Curable resin, slurry, or cement can be placed between the liner material and the host conduit to affix the liner material into place. Before and during curing, a fluid such as air or water can be used to inflate the compression liner outwardly toward the host conduit. Spacers positioned between at least a portion of the liner material and the host conduit may be used to (i) calibrate the thickness of the liner material and curable material that is cured to form the new liner, and (ii) form communication channels adapted to house devices such as wire, cable, fiber optic cable, telephone lines, power lines, etc. The spacers and channels can be selectively inflatable to various sizes to allow calibration of the liner thickness and to form communication channels having a selected width or height. Additionally, the liner material may be formed into a one-piece, tubular lining member having an inflatable enclosure defined between an inner and an outer layer of the lining member. The enclosure can be selectively inflated to (i) calibrate the resulting thickness of the cured liner material, and (ii) form communication channels running along the length of the host conduit.

The present invention provides an inflatable stent comprising an inflatable portion that comprises:.

The pipe or lumen engaging portion may be a portion, for example a ring, of a resiliently flexible material. For example, of a foam, a rubber or a gel (that may be provided in a bag) or combinations thereof. Advantageously the pipe or lumen engaging portions are inflatable. Typically they are inflatable and of a flexible sheet material.

In the description of the invention described herein the term lumen is employed for the inside space of a generally tubular structure within the human or animal body. The term pipe refers to any other type of generally tubular conduit.

The inflatable portion may be provided with a plurality of the inflatable pipe or lumen engaging portions.

The inner and outer membranes are formed of a flexible sheet material. The end caps are also typically of a flexible sheet material to aid in providing a stent that (when in the collapsed state) can be compact and readily manoeuvred into position through a route that may be convoluted. The stent can then be inflated. In use the stent may be deployed along a pipe that is under pressure, for example a water mains pipe. Such a deployment may be carried out by using equipment of the known types for deployment of conventional inflatable bags into an under pressure pipe system. Thus the stent may be deployed into a pipe system via existing access points such as a branch including a valve, or by means of system specifically designed for access (and typically also egress) into an under pressure pipe system. For example, a system whereby access to a pipe is obtained by fitting a saddle and a pressure containing fitment to the pipe. The saddle and fitment allow cutting into the pipe whilst holding in the pressure. The stent is then deployed via the pressure containing fitment.

The passage may be generally cylindrical in form, having a generally cylindrical inner membrane defining it, when the stent is inflated. Other forms of passage may be provided, for example generally frusto conical, with a narrower diameter at one of the ends than at the other. Typically the inner and the outer membrane are both generally cylindrical in form when inflated. However, other shapes of inner and/or outer membrane structure may be employed. For example if a pipe is of a square cross section then an outer membrane that takes a square or substantially square form when inflated can find use. The inner membrane may take the same general form as the outer, or it may be different. The inflatable portion may take the form of a bend (when inflated) for some applications. This may allow better sealing to the inner walls of a pipe or lumen, when the stent is deployed in a curved section of pipe or lumen.

The inner membrane defines first and second ends of the inflatable portion. The outer membrane is disposed about the inner membrane and so may have corresponding first and second ends i.e. may have substantially the same, or the same, length. For example when inflated the inner and outer membranes and the first and second end caps may take the form of a cylindrical or substantially cylindrical pipe with end faces defined by the end caps. The end caps may provide flat or substantially flat end faces to the inflatable portion. Alternatively the end caps may be profiled, having a shape that projects outwardly, in generally the axial direction, from the first and second ends. For example an end cap, when viewed in cross section may present an outwards projecting curved surface towards the direction of flow. This surface may aid in reducing the turbulence and/or pressure experienced by the inflatable portion in use, avoiding the stent being dislodges due to pressure of fluid flow through it.

The connecting members may be a plurality of cords or wires that may each extend outwards from the inner membrane to the outer membrane when the stent is inflated, (a so called "dropped thread" arrangement).

The connecting members may be membrane portions (sheet portions), that may be of a flexible sheet material. The connecting member membrane portions may each extend outwards (typically radially outwards) from the inner membrane to the outer membrane and run along the axial length of the inflatable portion of the stent, i.e. in the direction from the first to the second end. Connecting membrane portions may run axially along substantially the whole length, or along the whole length of the inner membrane. Optionally there may be a gap or gaps dividing a connecting member portion that runs axially along substantially the whole length, or along the whole length of the inner membrane into sub portions. Connecting membranes running along the length of the inner membrane may be continuous, or they may be interrupted, for example by an aperture that allows fluid communication between.

Such membrane portions may divide the annular space into a series of axially extending cells around its circumference.

As an alternative membrane portions may extend outwards (typically radially outwards) from the inner membrane to the outer membrane, but run circumferentially around the annular space, between inner and outer membrane. A plurality of such membranes may be provided, one after the other along the axial length of the inflatable portion. This divides the annular space into a series of circumferentially extending cells, one after another along the axial length.

The cells may all be in fluid communication with each other. Alternatively, a selected group of cells may be in fluid communication with each other and another selected group of cells may be separately in communication one with each other. One or more cells or groups of cells may be selectively inflatable.

For example, where the membrane portions divide the annular space into a series of axially extending cells around its circumference, every second cell around the circumference of the annular space may be in fluid communication with each other and the remaining cells in fluid communication with each other but not with the second cells. This provides two groups of cells. It is then possible to inflate one group of cells without inflating the other. This can be useful, when it is desired to partially inflate the stent to provide it with some shape and/or rigidity to aid deployment along a path before fully inflating in use.

The cells may be sealed one from the other, except where fluid communication is provided.

Fluid communication between cells may be provided in a number of ways. In general openings or passageways may be provided between cells. On inflation communicating parts of the stent will be inflated by the same inflating action.

At least one end cap may define a circumferential space at an end of the stent that is in fluid communication with all of the cells. This can allow inflation of the annular space from one port that supplies inflating fluid (gas or liquid). The port for inflating may be in the end cap.

When membrane portions are employed to divide the annular space into a series of axially extending cells around its circumference they may each be a separate, typically rectangular, portion of flexible sheet material, bonding to the inner and outer membranes. Alternatively, a number of the membrane portions or all of the membrane portions may be made from a single sheet of flexible sheet material connecting alternately along the axial length of the inner membrane and then along the axial length of the outer membrane in a zig-zag arrangement dividing the annular space into axially extending cells.

With such a zig zag arrangement the cells, when viewed from an end of the stent may be generally triangular in form (cross section). Alternatively, cells may be formed to have a generally trapezoidal form. This can be achieved if the single sheet is bonded circumferentially along a portion of the inner membrane before extending radially to the outer membrane where again it is bonded circumferentially along a portion before returning to the inner membrane, and so on. This is illustrated hereafter with reference to a particular embodiment.

The use of a plurality of connecting members between the inner and outer membranes can provide relative rigidity to the inflated inflatable portion of stent as the inner and outer membranes are constrained in a fixed relationship, following inflation, avoiding or at least reducing bulging or 'ballooning' of the flexible sheet material of the inner and outer membranes. Where the connecting members are membrane portions that divide the annular space into a series of axially extending cells around its circumference, a notably stiff arrangement can be provided. For example sufficiently rigid to deal with the forces applied when a substantial flow rate of water or other fluid runs through the passage in use of the stent. Where the connecting members divide the annular space into a series of circumferentially extending cells similar benefits in stiffness may be contemplated.

The inflatable portion of the stent is further provided with at least one or a plurality of pipe or lumen engaging portions of flexible sheet material that define a second, larger, diameter of the stent, when inflated. Typically the pipe or lumen engaging portion or portions provide the second diameter along only a part or parts of the length of the inflatable portion. These inflatable pipe or lumen engaging portions allow the stent to be installed in pipes or lumens of differing diameter (larger than the first diameter) and yet still firmly engage with the pipe or lumen walls. The engagement can provide a seal with the pipe or lumen walls. At the same time the inner and outer membrane arrangement can be fully inflated, to achieve the relatively rigid structure of the inner and outer membranes connected by the end caps and the connecting members. The passage between the first end and the second end, defined by the inner membrane is relatively rigid and robust for use e.g. where a turbulent and/or solids containing flow through of a fluid is anticipated in use of the stent.

A yet further advantage of the plurality of pipe or lumen engaging portions is that, when the stent is employed in a pipe or lumen of larger diameter than the first diameter, an external annular space may be defined between the inside of the pipe or lumen, the pipe or lumen engaging portions, and the outer surface of the outer membrane.

This external annular space can be accessed, for example to obtain samples, to allow in situ pressure testing or control, to view the interior surface of the pipe or lumen (e.g. by a camera or a fibre optic cable directing light to a camera), or even to allow repair of the pipe or lumen (e.g. by injection of a filler material that sets). To that end the stent may be provided with a port providing fluid communication from the passage through the annular space and out of the outer membrane, at a location between pipe or lumen engaging portions.

Furthermore when the stent is installed in a section of pipe or lumen that is damaged, contact between the outer membrane and the damaged part of the pipe or lumen wall may be avoided, reducing the risk of further damage being caused on inflation of the stent.

Pipe or lumen engaging portions may be provided one at (or near) each end of the inflatable portion of the stent. Pipe or lumen engaging portions may be provided at other locations along the length of the inflatable portion of the stent. Additional portions, for example one or several, at intervals along the length of the stent, may provide more secure engagement to pipe or lumen walls. The arrangement may aid in gripping the pipe or lumen wall, and/or providing more effective sealing to prevent fluid flow past the stent (between the stent and the pipe or lumen wall).

The pipe or lumen engaging portions may be provided in various ways. The pipe or lumen engaging portions may be larger diameter (when inflated) parts of the outer membrane. They may be larger diameter parts of the outer membrane that connect to the respective end cap.

The pipe or lumen engaging portions may be formed as separate chambers which may be separately inflatable or may be in fluid communication with the annular space and inflate when the annular space, or a part of the annular space, (such as a cell formed by the connecting members and inner and outer membranes), is inflated.

More generally inflation of the inflatable portion of the stent occurs when the annular space is filled with an inflating fluid and the pipe or lumen engaging portions are also inflated with an inflating fluid. The inflating fluid may be a gas (e.g. air or a non-flammable gas such as nitrogen), a liquid (such as water), a fluid that sets as a solid (such as a curable resin composition) or even a foam, such as a foam composition that sets as a solid foam. The inflating fluid may be supplied to different inflatable parts of the stent via appropriate ports or manifolds. Conveniently and as discussed above, different parts of the inflatable portion of the stent are in fluid communication (have apertures or passageways connecting between) so as to reduce the number of locations where inflating fluid is applied to inflate the stent as a whole.

As the stent is typically deployed along a pipe or a lumen before inflation, it is convenient for the stent to be inflatable by supplying inflating fluid from only one end. For example, by having an inflation port or ports, or an inflation manifold or manifolds, for feeding inflating fluid into the inflatable portion on one of the end caps. Alternatively, port(s) or manifold(s) may be located at or near one end of the stent.

The stent has an inflatable portion. For some uses there will be a single inflatable portion, which may constitute the main body of the stent. However, as an alternative, the stent may have two inflatable portions, typically of the same form as discussed above. Each may have the same or different optional features. The two inflatable portions may connect to each other via a tubular portion of flexible sheet material, to provide flow through the stent as a whole. The tubular portion of flexible sheet material may be e.g. cylindrical but other shapes are contemplated. The tubular portion of sheet material can provide a sealing engagement between the two inflatable portions.

Thus when deployed and inflated, with both inflatable portions in sealing engagement with the walls of a pipe or lumen , the stent provides a passage for through flow of fluid that extends through the first inflatable portion, the tubular portion of flexible sheet material and the second inflatable portion.

The tubular portion of flexible sheet material may be of the same type of material as the membrane sheets of the inflatable portions. However, to allow containment of pressure the tubular portion of flexible sheet material may be of a different material and/or may be reinforced; for example with a braided reinforcement or layers of reinforcement such as found in pressure hoses and the like.

Also contemplated is a stent including three or even more inflatable portions, typically with a tubular portion of flexible sheet material between each pair of inflatable portions, along the length of the stent.

Arrangements with two or more inflatable portions can have advantages. Tubular portion of membrane sheet material connecting the relatively stiff or rigid inflatable portions (when they are inflated) may more easily accommodate imperfections, and/or bends or even radial displacement between ends (following breakage) in a pipe or lumen. Relatively less material is employed where the stent is not inflatable along its whole length, which may aid in deployment through a narrow opening. The use of tubular portions of membrane sheet material can make accessing the external annular space easier as passage through only a single membrane can provide it.

Inflating fluid can be supplied by means of a suitable tube, or tubes, advantageously connecting at one end of the stent. A suitably stiff inflating tube may be employed as a deployment rod connecting to one end of the stent and enabling the uninflated stent to be moved along a path to the location where in may be inflated.

More generally the stent may be deployed by using a deployment rod. Alternatively deployment by a robotic device (tethered or untethered by umbilical) may be used. The deployment rod may generally be resiliently deformable to allow control of the stent but also to allow bending around the contours of a deployment path, such as through valves and around bends. A deployment rod is convenient when the stent is deployed into a pressurised pipe system using under pressure deployment equipment. The rod can pass through a gland in the deployment system for advancing and/or withdrawing the stent in the same manner as employed for advancing or withdrawing inflatable bags employed in prior art pipe sealing systems.

Conveniently a deployment rod for deploying the stent may pass through the passage and connect to the stent at the end distal to that of a user deploying the stent. Thus the end of the deployment rod connecting to the stent pulls rather than pushes the stent along a path e.g. along the inside of a pipe or lumen. Alternatively or additionally the deployment rod may connect to the proximal end of the stent to allow pushing of the stent on insertion along a pipe or lumen. When withdrawing the stent a proximal connection allows the stent to be pulled from the pipe or lumen. The deployment rod may carry or may be an inflation tube for the stent. The deployment rod may include other apparatus. For example the deployment rod may mount at least one camera and optionally at least one light. This allows viewing of the path (e.g. pipe) along which the stent is being deployed. Conveniently where a camera or camera and light are employed they are mounted towards or at an end of the deployment rod, forwards of the end of the stent. Thus the camera can provide a view of the path ahead for an operator deploying the stent. Other optional equipment that may be provided with stents and may conveniently be included in or on a deployment rod includes one or more of a microphone, hydrophone, and a sonde sensor or other device to allow location of the stent from above ground/outside the pipe or lumen. The front end of a deployment rod may include a formation such as a ball or cone shape to facilitate guiding the apparatus along a pipe or lumen.

A deployment rod may be releasably detachable from the stent. For example where the rod includes or is an inflating tube, the connection to an inflation port may be via a non-return valve fitted to the port, to prevent deflation on detachment of the deployment rod. Thus a remotely detachable inflating tube and/or deployment rod combined with a self-closing valve or valves, is convenient where the stent is to be left in places for an extended period of time.

When withdrawing the stent it may be convenient for the deployment rod to connect to the proximal end of the stent (i.e. the end of the stent nearer a user who will be manipulating the deployment rod). When the stent is being withdrawn from a location (after deflation or partial deflation) this connection can allow the rod to pull the stent back out from the pipe or lumen where it has been deployed. Conveniently, (especially where making use of a deployment rod that connects to the stent at the end distal to that of a user) the proximal connection can be by one or more, (typically a plurality) of cords or straps that connect from the deployment rod to an inflatable portion of the stent. The cords or straps may connect to the outer membrane for example.

The cords or straps may extend, when the inflatable portion is inflated, from a connection point or points on the deployment rod, to the proximal end of the stent. The connection point on the deployment rod may conveniently be at a location closer to the user than the proximal end of the stent.

The inner membrane defines a passage from the first end to the second end of the inflatable portion. Typically such passages through the inflatable portions and connecting tubular membrane portions (if employed) may provide fluid communication from one end of the stent to the other, allowing flow through a pipe or lumen to continue, after installation (and inflation). This is typical for a stent used in medical applications.

Alternatively the passage through the stent can be blocked e.g. by an end cap, or a sealing membrane part way along the passage, if through flow is to be prevented in a particular use.

For example the stent may be provided with one or more sealing membranes part way along the passage. This can allow fluid flow and/or venting of the passage at one end of the stent, or at an intermediate portion of the stent, to be separated from fluid flow and/or venting at the other end of the stent. Venting or fluid flow can be out through a suitable port in the wall of the stent (inner and outer membranes).

Conveniently for some applications one end of the stent may be provided with an end that is tubular, has sealing engagement to the passage through the stent and reduces in size, to connect to; or be connectable to; a tubular. For example a generally conical end can be connected to or connectable to a pipe or hose for the passage of fluid.

At least the inner and outer membranes and the pipe or lumen engaging portions are of a flexible sheet material. They may be of polymeric or rubber type materials and may be reinforced by fibres or woven fabric. For example rubber, polyurethane, fabric (that may be rubber or polyurethane coated) may be employed. The flexible sheet material may be of different thicknesses and the flexible sheet material may include portions comprising laminated together flexible sheet materials. The flexible sheet material may be reinforced. For example, by metal wire or by plastic members of a material that is relatively stronger and/or stiffer than the flexible sheet material.

The stent may be manufactured in various ways, for example by bonding e.g. bonding with adhesive or RF welding, of plastic sheet material pieces together. Stitching may be employed to attach components one to another. Alternatively, extrusion can be used to extrude the inner and outer membrane, and membrane portions in between, as a one piece unit. The end caps and any other parts required can then be added to the extrusion. Vacuum forming, moulding, casting, or even 3D printing type methods of manufacture are also contemplated.

The present invention also provides a method of by-passing a section of pipe or a lumen, the method comprising:.

The access locations may be existing connections to the pipe such as a branch including a valve, or by means of system specifically designed for access (and typically also egress) into an under pressure pipe system.

The method may further include providing a third inflatable stent and deploying it through one of the access locations in the direction of the by-passed section of pipe. This can allow venting and or inspection of the by-passed section via a fluid communication such as a pipe that may vent, for example, via the corresponding access pipe. As an alternative third and fourth inflatable stents may be provided, one deployed through each access location, allowing venting or inspection via either or both stents and access locations.

The route of fluid communication from upstream to downstream is generally substantially sealed to avoid loss of fluid; as is usual for by-pass work. For example one end of each stent may be provided with an end that is tubular, has sealing engagement to the passage through the stent and reduces in size; and is connected to the by-pass pipe.

<FIG> shows in schematic perspective view an inflatable stent <NUM>, without the pipe or lumen engaging portions of a stent of the invention (see <FIG>, <FIG> and <FIG> and the description below for these).

The stent <NUM> is shown in its inflated state and is cylindrical. The stent <NUM> has an inner membrane <NUM> defining first and second ends <NUM>, <NUM> and a passage <NUM> allowing through flow of fluid. In <FIG> as follows the stent has only one inflatable portion <NUM>. <FIG> (discussed below) shows an alternative arrangement with two inflatable portions. Outer membrane <NUM> is spaced apart from inner membrane <NUM> and defines a first diameter D1 of the stent (<FIG>). Also visible in <FIG> is a port or valve <NUM> located in in one of the end caps <NUM>, <NUM> provided at either end of the stent. Port <NUM> has been used to inflate the stent by filling it with inflation fluid.

Cross section view <FIG> (at dashed line A) shows the annular space <NUM> between membranes <NUM> and <NUM>. Annular space <NUM> is divided, by connecting members <NUM> into a series of cells <NUM> that are axially extending (i.e. running in the direction from the first to the second ends). These can be more clearly seen in magnified view (<FIG>) of part B in <FIG> and further in <FIG> as discussed below.

The connecting members <NUM> take the form of portions of membrane sheet ("membrane portions"). The membrane portions <NUM> extend from the first end <NUM> to or towards the second end <NUM>. They connect the inner and outer membranes <NUM>, <NUM> and are joined in sealing engagement with them. <FIG> shows the same perspective view as <FIG> but with the inner membrane absent, to allow viewing of the connecting members <NUM> (membrane portions <NUM>) which take the form of rectangular portions of flexible membrane sheet that run spaced apart and parallel between the ends <NUM>,<NUM> in this example. The extreme ends <NUM> of membrane portions <NUM> do not extend to meet and seal to end cap <NUM>. Thus when inflating the device through inflation port <NUM>, all the cells <NUM> are in fluid communication via the space between the extreme ends <NUM> and the end cap <NUM>. A similar arrangement may be provided at the other end <NUM> of the stent <NUM>, which may aid in even and reproducible inflation from a deflated state.

<FIG> shows, in a cross section view like that of <FIG>, an alternative arrangement of connecting members <NUM>. In this arrangement connecting members <NUM> also take the form of membrane portions <NUM> extending and connecting between the inner and outer membranes <NUM>, <NUM>. In contrast to <FIG>, the membrane portions <NUM> do not each extend along a radius. In <FIG> the cells <NUM> are generally trapezoidal in cross section but they alternate in location of the base <NUM> of each trapezoid around the circumference of the stent (see magnified view of part B in <FIG>). The arrangement in <FIG> may be formed by use of a single sheet of membrane material running circumferentially in a zig zag fashion in the annular space <NUM> with alternate bonding to the inner <NUM> and then the outer <NUM> membrane.

<FIG> shows in schematic perspective a stent <NUM> of the same general construction as those of <FIG> or <FIG> with like parts numbered the same. The stent of <FIG> also includes two inflatable pipe or lumen engaging portions <NUM>. The pipe or lumen engaging portions <NUM> are spaced apart and attached to the outer membrane <NUM> they define a second, larger, diameter D2 of the stent, as indicated in end view <FIG>. In this example both portions <NUM> define the same diameter D2. In other examples where the stent may not be a regular cylinder and/or the pipe or lumen engaging portions may have different sizes, the second diameter D2 may be defined as the largest provided.

<FIG> shows the stent <NUM> of <FIG> in elevation. As can be seen in this view the pipe or lumen engaging portions <NUM> each have a largest diameter in the middle part (indicated on the figure by centre line <NUM>) and relatively broad edges <NUM> where sheet material pieces are joined together. Dashed circles indicate the location of passages <NUM> communicating with the annular space to allow inflation. The structure is also shown in schematic cross section <FIG> taken through line X - X of <FIG>.

As can be seen in <FIG> the inflated pipe or lumen engaging portion <NUM> is attached to the outer membrane <NUM> at two regions <NUM> of bonding (e.g. RF welding). The two regions of bonding <NUM> run circumferentially around the diameter of outer membrane <NUM>. In this example gap <NUM> between edges <NUM> of connecting member sub portions <NUM>, <NUM> of connecting member membrane portion <NUM> allows access to make the circumferential bonds at the bonding regions <NUM> during the manufacturing process. Gap <NUM> also provides fluid communication between cells <NUM> (see <FIG>) defined by connecting members <NUM>. In this example pipe or lumen engaging portion <NUM> is otherwise free from attachment to the rest of the stent and so can readily inflate radially outwards in direction Y. This may aid in making more positive (e.g. sealing) engagement with the wall of a pipe or lumen in use, for example if the pipe or lumen has some variance in diameter or is oval rather than a perfect circle in diameter.

<FIG> shows the same stent <NUM> as is shown in the other <FIG>; but with only one of the two pipe or lumen engaging portions <NUM> shown. This allows viewing of the passages <NUM> that communicate with the annular space to allow inflation of the pipe or lumen engaging portion. In this example passages <NUM> are spaced circumferentially about outer membrane <NUM> and in alignment with the largest diameter part (indicated on the figure by centre line <NUM>) of the pipe or lumen engaging portions <NUM>.

<FIG> shows in a detail similar to <FIG> and <FIG> a method of bonding membrane portions <NUM> to inner and outer membranes <NUM>, <NUM>. In this example end parts <NUM> of the membrane <NUM> illustrated are fused by RF welding to the inner and outer membranes.

<FIG> and <FIG> show schematically some alternative arrangements that may be employed in inflatable stents.

In <FIG> a part of an inflatable portion <NUM> of a stent <NUM> is shown in part elevation view with the outer membrane <NUM> removed (position suggested by dashed lines 10a) to allow viewing of membrane portions <NUM>. In this example they extend circumferentially in alignment with end cap <NUM> to divide the annular space <NUM> into cells <NUM> that each extend circumferentially with one cell <NUM> after another along the length of the inflatable portion.

In <FIG> an inflatable portion <NUM> of a stent <NUM> is shown in partial cross-section elevation view. End cap <NUM> has a profile projecting from the end <NUM> of inner membrane <NUM>. This may serve to reduce pressure from a fluid flow suggested by arrow F acting to displace the inflatable portion from its selected location in a pipe or lumen.

In <FIG> a stent <NUM> having an inflatable portion <NUM> is shown. in elevation. In this example the stent <NUM> is fitted with a deployment rod <NUM> that extends through the passage <NUM> of inflatable portion <NUM>. The deployment rod <NUM> includes within it an inflating tube <NUM> that emerges from the rod <NUM> and connects to the valve <NUM> at the distal end (<NUM> in this example) of the stent <NUM>. When the stent <NUM> (typically in a deflated state rather than inflated as shown in the figure) is being inserted along a pipe or lumen by pushing the rod <NUM> in the direction of arrow I, then the connection of the inflating tube <NUM> to valve <NUM> results in the stent being pulled into position by rod <NUM>.

At the proximal end <NUM> of the stent a number of cords <NUM> attach to the circumference of the outer membrane <NUM> and to a more proximal (to a user) connection point <NUM> on the connecting rod. After use, when a user withdraws the stent by pulling in the direction W (typically after deflating or partially deflating) then the cords <NUM> allow the inflating portion <NUM> to be pulled from end <NUM> back out of the pipe or lumen.

Also included in this example is a camera and light assembly <NUM>, which may also include other components such as gas sensors. The assembly <NUM> allows viewing of a pipe or lumen ahead of the stent <NUM>.

<FIG> shows a stent <NUM> including two inflating portions <NUM> that are connected by a tube of reinforced flexible sheet material <NUM>. The inflating portions are of the same general form as those shown in <FIG>, but only one inflatable pipe or lumen engaging portions <NUM> is provided on each portion <NUM>. A port <NUM> can provide access to the passage <NUM>, via end <NUM> or end <NUM> if required. For example; by a sensor or camera for inspection; for a delivery tube for filler material to reinforce or repair a pipe, or to allow purging and/ or venting and/or monitoring of the external space between the inflatable portions <NUM>.

<FIG> shows schematically a prior art arrangement for by-passing a pipe <NUM>, such as a mains gas or water pipe. In this example access to pipe <NUM> has been made via flanged `tee' connections <NUM> leading to hydrant valves <NUM>, onto which an under pressure delivery system casing <NUM>, for inflatable stopper bags <NUM>, has been fitted. In <FIG> the bypass system is shown in use. Inflatable bags <NUM> have been inserted with the assistance of a delivery tube <NUM> that includes a 'nose' or stop <NUM> at its lower end. This nose <NUM> aids in delivery of the bags <NUM>, and also, in the position shown, can aid in preventing inflating bags <NUM> being displaced by pressure and flow of fluid in the pipe <NUM>.

Inflatable bags <NUM> have been inflated by inflating fluid delivered via ports <NUM> and appropriate inflating tubes (inflating tubes and other small details not shown in this schematic view). In some prior art systems the inflating fluid for bags <NUM> can be the fluid of the pipe <NUM>, typically extracted at ports <NUM> and fed via a pump into ports <NUM>.

Bags <NUM> are provided with pipes <NUM> that connect through casing <NUM> to bypass pipe <NUM>. Thus the flow along pipe <NUM> is diverted via by pass pipe <NUM> as indicated by arrows F, to allow work to be carried out in the bypassed pipe section <NUM>. It will be understood that the flow direction may be reversed from that shown or there may be no flow, depending on the usage of the fluid in the pipe.

<FIG> shows an alternative by-pass making use of inflatable stents of the invention, shown in cross-section and generally of the form shown in <FIG>. Two inflatable stents <NUM> are allowing the by-pass flow F and each has an end <NUM> connecting from passage <NUM> to give sealed fluid communication to tube <NUM>; and hence to by-pass pipe <NUM>. In this example the ends <NUM> reduce in size from the larger diameter of passage <NUM> to the smaller diameter of tube <NUM>. Thus section of <NUM> of pipe <NUM>, between tee connections <NUM> is by passed. This arrangement allows secure placement of the stents <NUM> in pipe <NUM>. Passages <NUM> and ends <NUM> can aid in providing good flow through in the by-pass via tubes <NUM>. Furthermore the stents <NUM> are relatively low (inflated) volume devices that can readily be inflated to higher pressures, such as are required for higher pressure pipe systems.

<FIG> also shows optional inflatable stents <NUM>, shown in cross-section and generally of the form shown in <FIG>. Each is placed via the respective delivery system through connections <NUM> as used for stents <NUM>, but in the direction of the by-passed (isolated) section <NUM> of pipe <NUM>, These stents <NUM> include an end <NUM> connecting from passage <NUM> to allow venting along a tubing connecting through and out of casing <NUM> as suggested by arrows V (venting tubes and other small details not shown in this schematic view). In this example the ends <NUM> reduce in size from the larger diameter of passage <NUM> to the smaller diameter of a vent tube. The section <NUM> can thus be vented if desired. Inspection by camera or other sensors through stents <NUM> can also be contemplated. In an alternative arrangement only one stent <NUM> may be employed, with venting and/or inspection available from the respective side of section <NUM>.

Claim 1:
An inflatable stent (<NUM>) comprising an inflatable portion (<NUM>) that comprises:
an inner membrane (<NUM>) of a flexible sheet material defining a first end (<NUM>) and a second end (<NUM>) of the inflatable portion (<NUM>), and a passage (<NUM>) there between when inflated; and
an outer membrane (<NUM>) of a flexible sheet material disposed about the inner membrane (<NUM>), the outer membrane (<NUM>) defining a first diameter (D1) of the stent (<NUM>) when inflated;
wherein, when inflated, the inner (<NUM>) and outer (<NUM>) membranes are radially spaced apart to define an annular space (<NUM>) there between;
the inner (<NUM>) and outer (<NUM>) membranes are connected by a plurality of connecting members (<NUM>) in the annular space (<NUM>), and by first (<NUM>) and second (<NUM>) end caps that connect the membranes (<NUM>, <NUM>) at the respective first and second ends (<NUM>, <NUM>) of the inner membrane (<NUM>); and
wherein the inflatable portion (<NUM>) is further provided with at least one inflatable pipe or lumen engaging portion (<NUM>) that defines a second, larger diameter (D2) of the stent (<NUM>), when the inflatable portion (<NUM>) is inflated.