Description of the Related Art Inflatable bladders are commonly used to repair breaks or cracks in underground pipes such as sewers. The inflatable bladder typically includes a leading and trailing conduit that is used to pull the bladder within the sewer and position it adjacent the failure in the sewer pipe. A patch material, typically comprising activated styrene, is temporarily affixed to the exterior of the bladder prior to positioning the bladder within the sewer. Once the bladder is properly positioned so that the patch is aligned with the pipe failure, the bladder is inflated through one or both of the leading and trailing hoses to press the patch against the failure in the pipe.

The patch material is heated to a temperature great enough to affix/cure the patch to the pipe and seal the failure.

Current bladders typically comprise a laminate of opposing layers of air- impermeable material, preferably fluorosilicone, fluorocarbon, or other fluorinated elasomet, between which is positioned a carbon fiber mesh, commonly referred to as a carbon fiber sock, which is electrically conductive. The inflatable bladder terminates in opposing tapered ends on which are mounted end caps that close the ends of the bladder and couple the conduits to the sock. The end caps include an inner and outer cone. The inner cone is positioned on the interior of the bladder at the outer edge of the tapered end and couples with the sock. The outer cone slides over the outer edge of the bladder and the inner cone to compressively retain the bladder between the cones. Electrical conductors, usually entrained about, forming part of, or contained within the conduits, electrically couple to the inner cone to electrically couple the carbon fiber sock to a source of electrical power. The application of electrical power to the carbon fiber sock generates heat, which heats the air-impermeable layers,

resulting in a transfer of the heat to the patch to cure the patch to the sewer pipe. U. S.

Patent Nos. 5,451,651; 5,648,137 ; and 5,656,231 all disclose conventional inflatable bladders for patching an underground pipe as described above.

A disadvantage of the current inflatable bladders is that, during the heating process where electricity is supplied to the carbon fiber sock, part of the heat generated by the resistance of the sock is retained in the inner and outer cones, especially the inner cone. The inner cone can be heated to such an extent that it can revert the inner air-impermeable layer of the laminate. The inner air-impermeable layer is typically a rubber material and the heat turns the rubber into a gum like consistency, destroying the useful characteristics of the rubber.

It is desirable to have an inflatable bladder in which the heat does not build up to a sufficient extent to destroy the functionality of the inner air-impermeable layer. It is further desirable to have an inflatable bladder the removes the heat at the portions of the bladder corresponding to the cones.

SUMMARY OF THE INVENTION The invention relates to an inflatable bladder for use in repairing a failure in a pipe. The inflatable bladder includes an elongated tubular body portion defining a hollow interior of a first dimension and having open ends. An expandable end portion closes one of the tubular body open ends, and extends from a proximal edge, near the one of the tubular body portion ends, to an opposing distal edge, with a tapered cross section that reduces in area from the proximal edge to the distal edge, which has a second dimension that is less than the first dimension. The distal edge is expandable a sufficient amount such that the cross-sectional area at the distal edge is expandable an amount substantially equal to the cross sectional edge of the body.

Preferably, the expandable end portions are made from a laminate comprising an air-impermeable layer and the electrically conductive layer. The air-impermeable layer comprises a laminate of an air-impermeable material and a backing material.

The air-impermeable material can be made from flourosilicone, fluorocarbon, or other fluorinated elastomer, and the backing material can be made from a knit fabric.

The expandable end portion can include a cuff extending from the distal end toward the proximal end. Preferably, the cuff portion is made from the air- impermeable material with the backing material facing the exterior of the inflatable bladder and the air-impermeable material facing the interior of the inflatable bladder.

The remainder of the expandable end portion excluding the cuff is made from the air- impermeable material with the expandable backing material facing the interior of the inflatable bladder and the air-impermeable material facing the exterior of the inflatable bladder.

In another aspect of the invention, the inflatable bladder comprises an elongated, tubular body portion defining a hollow interior and having open ends. First and second end portions each close one of the tubular body open ends at a proximal edge and extend to a distal edge. At least one of the tubular body portion, first end portion, and second end portion is made from a laminate comprising air-impermeable layer and an electrically conductive layer. One of the first and second end portions has a heat sink for dissipating heat generated when the electrically conductive layer is energized.

Preferably, the heat sink comprises a laminate of an air-impermeable material and a backing material wherein the backing material faces away from the bladder interior. The backing material is preferably fabric. The air-impermeable material forming the heat sink also forms a portion of the air-impermeable layer.

In yet another aspect, the invention relates to a method of making an inflatable bladder on a form having an elongated body section and a tapered end section, comprising the steps of : forming the conductive layer by positioning a conductive material on the form, and forming the air-impermeable layer by positioning an expandable air-impermeable material over the conductive layer substantially along the form tapered end section and positioning an air-impermeable material over the conductive material along the remainder of the form.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 illustrates a side view of an inflatable bladder with a heat sink cuff according to the invention; FIG. 2 is a left end view of the inflatable bladder of FIG. 1 illustrating the heat sink cuff ; FIG. 3 is a sectional view taken along line 3-3 of FIG. 2; FIG. 4 is an enlarged view of the left end of the bladder of FIG. 4 to more clearly illustrate the heat sink cuff and coupler; FIG. 5 is a schematic view of the build-up of the inner air-impermeable layer on a mandrel or tool; FIG. 6 is a schematic view illustrating the build-up of a conductive layer over the first air-impermeable layer of FIG. 5; FIG. 7 is a schematic view of the build-up of the heat sink cuff on the tool as part of forming a portion of an outer air-impermeable layer of the inflatable bladder; FIG. 8 is a schematic view illustrating the build-up of the remainder of the outer air-impermeable layer; and FIG. 9 is a schematic view illustrating the completion of the build-up of the second air-impermeable layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates an inflatable bladder 10 that can be conceptually divided into a generally constant diameter middle portion 12 and opposing concentrically tapered end portions 14,16. Each of the end portions extend between a distal edge 19,21 and a proximal edge 23,25, terminating in an opening 18,20 at the distal edge 19,21 (FIG. 4) sized to receive a conduit 22,24, respectively. Couplers 26,28 close off the openings 18,20 and connect the corresponding conduit 22,24 to the appropriate end 14,16.

Referring to FIGS. 3 and 4, the inflatable bladder 10 is made from a laminate comprising inner and outer air-impermeable layers 30,32 between which is positioned an electrically conductive layer 34. Preferably, the inner and outer air-impermeable layers are made from rubber, such as fluorosilicone and/or fluorocarbon rubber. In the

preferred form the inner air-impermeable layer 30 is a single layer of fluorosilicone.

The outer air-impermeable layer 32 comprises two layers, the first of which is a laminate 32a of an air-impermeable material, preferably fluorosilicone, and an expandable fabric backing. The second is a single layer of fluorocarbon 32b, which generally only extends across the middle portion of the 12 of the bladder, leaving the laminate 32a exposed on the cuff. The inner layer 30 forms the body 12 and the ends 14,16 (Fig. 1). The fluorocarbon is generally less expandable than the fluorosilicone but is more abrasion resistant. The conductive layer 34 preferably is made from carbon fiber, specifically, a sock or cylinder of a carbon fiber mesh.

During manufacturing, the ends of the carbon fiber sock extend beyond the ends of the air-impermeable layers 30,32. The exposed portions of the carbon fiber sock extending beyond the ends of the air-impermeable layers 30,32 are used to electrically couple the sock to an electrical conduit by the couplers 26,28. Each of the couplers 26,28 includes an inner cone 36 and an outer cone 38. The inner cone 36 has an axial through opening 40, a clamping surface 42, and an annular angled shoulder 44. A retaining ring 45 has an angled surface 46 complementary to the angled shoulder 44 and is sized to be received within the shoulder 44. The outer cone comprises a clamping surface 48 sized to receive the inner cone clamping surface and the bladder therebetween.

The inner cone 36 is received within the opening 18 and the exposed portions of the carbon fiber sock are wrapped around and over the shoulder 44 and inserted into the axial opening 40. The retaining ring 45 is positioned against the inner cone 36 so that the sock is trapped between the retaining ring angled surface 46 and the angled shoulder 44. Preferably the retaining ring is fastened to the inner cone by mechanical fasteners.

The outer cone 38 receives the inner cone 36 so that the clamping surfaces 42, o-ring 43, and 48 compressively trap a portion of the bladder therebetween. The conduit 22 is coupled to the outer cone 38 in the traditional manner so that it supplies pressurized air to the bladder through the inner and outer cones as well as electrically coupling the inner cone and/or the conductive layer to a supply of electrical power.

The electric power is preferablysupplied by a positive wire 74, and a negative conductive wire, 76, that travel internally to the coupler on the opposite end, 28.

A heat sink 50 is formed at the ends 14,16, preferably at a longitudinal position corresponding to the couplers 26,28, which for the preferred embodiment is adjacent the openings 18,20. The heat sink 50 is formed by a portion of the outer air- impermeable layer being oriented so that the fabric backing faces away from the interior of the bladder, or, in other words, faces away from the inner cone 36. In this orientation, the fabric backing is exposed to the external air surrounding the bladder 10. The fabric backing transfers the heat from the air-impermeable material, preferably fluorosilicone, to the atmosphere to function as a heat sink for the bladder.

The manufacture of the inflatable bladder 10 with a heat sink 50 according to the invention is illustrated in FIGS. 5-8. FIG. 5 illustrates the build-up of the inner air impermeable layer 30, which is preferably created by wrapping a strip 52 of air- impermeable material about a mandrel or tool 54 along a portion of the end 14. The tool 54 has an exterior shape corresponding to the desired finished exterior shape of the inflatable bladder 10. For example, the tool 54 has a substantially constant diameter middle portion 56 with concentrically tapered ends 58,60, from which extend projections 62,64, which form the end of openings 18,20 in the inflatable bladder. The inner air-impermeable layer is preferably made from fluorosilicone, fluorocarbon, or other fluorinated elastomer, and forms part of the body 12 and ends 14,16 of the bladder 10.

Referring to FIG. 6, once the inner air-impermeable layer 30 is built-up on the tool 54, the conductive layer 34 is then built on the tool on top of the inner air- impermeable layer 30. The conductive layer 34 is preferably built-up on the tool by taking a cylindrical tube or sock 65 of conductive material and sliding it over the strips of air-impermeable material 52 built-up on the tool. Preferably, the sock 65 is of such a length that the ends of the sock extend slightly beyond the ends of the air- impermeable material 52. The sock 65 can be made from a conductive material that is capable of radial stretching or expansion to provide a snug fit relative to the inner air- impermeable layer 30 as the sock 65 is slid over the tool 54.

Referring to FIG. 7, after the creation of the conductive layer 34, the heat sink cuff 50 is built-up on the tool 54. The heat sink cuff is preferably formed by wrapping a strip of air-impermeable material 66 having a fabric backing about the tool in such a manner that the fabric backing faces away from the sock 65 or is reversed wrapped in other words.

It should be noted that the reverse wrapping of the air-impermeable material strip 52 preferably extends only along the portion where the inner cone is to be mounted. It is within the scope of the invention for the reverse wrapping to comprise a greater portion of the bladder, for example all of the bladder end, the bladder end and body, or the entire bladder. The greater the portion of the reverse wrapping, the greater will be the cooling effect of the heat sink. Preferably, the reverse wrapping is only done at spot locations where the heat can rise to a temperature that will damage the bladder. Otherwise, any other areas of reverse wrapping will diminish the heat needed to cure the patch.

Referring to FIG. 8 once the heat sink is created by building up a reversed wrapped portion of the air-impermeable material, the outer air-impermeable layer 32a is completed by wrapping a strip of air-impermeable material from the reversed wrapper portion across the rest of the tool. The air-impermeable material used to complete the outer air-impermeable layer is preferable the same material as used for the heat sink, but the material is wrapped in the traditional manner with the fabric backing facing the interior of the bladder. The strips of air-impermeable material 66 are preferably wrapped in a helical-type fashion.

Referring to FIG. 8, after the outer air-impermeable layer 32a is completed, the outer air-impermeable layer 32b is built-up on the tool 54. As with the first outer air- impermeable layer 32a, the second outer air-impermeable layer 32b is built-up by wrapping a strip of air-impermeable material 70 about the tool 54 on the exterior of the air impermeable layer 32a. The strip of air-impermeable material 70 is preferably made from a durable material, such a fluorocabon. The air-impermeable material 70 can be fiber-backed, but it is not necessary as the main function of the layer 32b is for

abrasion resistance. The strip of air-impermeable material 70 is wrapped in the same manner as the strip 52, preferably in a helical fashion.

In the invention, it is preferred that the heat sink cuff be formed as part of the outer air-impermeable layer 32, namely as part of the air-impermeable layer 32a with the layer 32b for protection. The outer layer 32 could comprise only the layer 32a with the heat sink formed by the reversed wrapped portion and the remainder of the outer layer formed by a regularly wrapped portion. The regularly wrapped portion does not necessarily need to be made from the same material as the heat sink cuff and could be made from a fluorinated elastomer material with or without a fabric backing.

Upon the completion of the build-up of the outer air-impermeable layer 32, the build-up inner and outer air-impermeable layers 30,32 and the conductive layer 34 are subjected to a curing process, typically heat, for the fluorocarbon and fluorosilicone rubber.

The cured bladder 10 is removed from the tool by blowing air into one or more of the openings 18,20 of the ends 14,16 of the bladder 10. The pressurized air helps to lift the bladder 10 off the tool and permit the bladder to be slid off of the tool. A lubricant can also be used alone or in combination with the pressurized air to enhance the sliding of the bladder off the tool. The inner and outer air-impermeable layers 30, 32 and the conductive layer 34 typically can stretch a sufficient amount to permit the sliding removal of the bladder from the tool 54.