Abstract: A connector includes a cube, a first cylinder and a second cylinder. The cube includes first, second, third, fourth, fifth and sixth faces. The cube includes a first bore therein, the first bore having a first longitudinal axis. The first cylinder extends from the first face; the first cylinder includes a first hole therein, the first hole having a second longitudinal axis. The second cylinder extends from the second face; the second cylinder includes a second hole therein, the second hole having a third longitudinal axis. The first, second and third longitudinal axes are parallel to each other. In another aspect, a vent element includes a first piece and a second piece that is a mirror image of the first piece, each of the pieces having upper, middle and lower portions. In yet another aspect, a system is configured for removable attachment of an elongated tube to a surface.

Abstract: A sun tracking solar energy collection system can include torque tubes that can be configured to allow the cylindrical body of one torque tube to nest with projections extending from an adjacent torque tube. The torque tubes can be formed with a plurality of rotatable shafts connected to each other in an end to end fashion. The torque tubes may be connected with coupling flanges, shaped with a plurality of radially extending lobes. The coupling flanges can include a plurality of concave portions disposed between adjacent lobes. The rotatable shafts can be round and the concave portions can be curved with a radius of curvature that is about the same as a radius of curvature of outer surface of the rotatable shafts. The torque tubes can also have saddle mounts which can include a concave portion configured to nest with an adjacent torque tube.

Abstract: Hydraulic flange connectors connect two flange components together, and hydraulic pressure applied to ports in connector holes of one of the flanges tension the flange studs and crush the gasket between the flange components. Each connector has a piston that disposes in the connector hole and can move therein when hydraulic pressure is applied through the port by a pump. A first stud connected to the piston extends beyond one open end of the hole for connection to a first nut, while a second stud connected to the piston extending beyond another open end of the to the second flange component for connection to a second nut. A retainer having seals threads in this other open end of the hole and seals between the hole and the second stud.

Abstract: A cooling tube includes a tube member extending from a first end to a second end through an intermediate portion having an outer surface and an inner surface. The outer surface has an outside diameter. A flange is mounted at one of the first and second ends of the tube member. The flange includes a flange body extending from a first end portion to a second end portion through an intermediate section having an outer surface and an inner surface. The inner surface defines an inside diameter. The outside diameter of the tube member is between about 0.010-inch (0.0254-cm) and about 0.030-inch (0.0762-cm) smaller than the inside diameter of the flange.

Abstract: A connecting block includes a first member having a flow header extending from a sealing surface, a planar end face oppositely directed with respect to the sealing surface, and a perimeter wall angularly oriented with respect to the sealing surface. A second member is slidably received within the perimeter wall of the first member and has a flow member receiving bore axially aligned with the flow header. A bonding zone is created by heating both the first and second members until the planar end face and the planar interior face join together to create a physical connection between the first and second members. A material of the second member is corrosively sacrificial with respect to a material of the first member.

Abstract: Hydraulic flange connectors connect two flange components together, and hydraulic pressure applied to ports in connector holes of one of the flanges tension the flange studs and crush the gasket between the flange components. Each connector has a piston that dispose in the connector hole and can move therein when hydraulic pressure is applied through the port by a pump. A first stud connected to the piston extends beyond one open end of the hole for connection to a first nut, while a second stud connected to the piston extending beyond another open end of the to the second flange component for connection to a second nut. A retainer having seals threads in this other open end of the hole and seals between the hole and the second stud.

Abstract: A coupling flange assembly for connecting steel pipes including coupling flanges having stiffening plates located on the front side of the flange plate along axial directions of the steel pipes towards a coupling surface of the steel pipe to be connected. Equilibrium contact surfaces are set up on front end surfaces of the stiffening plates. Two abutting coupling flange assemblies may be used to connect two steel pipes, and when the two steel pipes are connected, the equilibrium contact surfaces of each stiffening plate of the coupling flange assemblies will be in contact with each other on a one-to-one basis.

Abstract: A method is disclosed. The method includes obtaining a tubular structure having a passageway and comprising a fiber reinforced plastic material, and then attaching a flange structure comprising an aperture coupled to the tubular structure using an attachment element.

Abstract: A spigot for a line-stopping sheath assembly includes a flange including a flange plate and a flange barrel. The flange barrel includes a wall extending from the flange plate, with an end of the wall of the flange barrel opposing the flange plate having a projection defining a periphery of a socket area for receiving an end of a pipe. The spigot also includes a pipe having an end disposed within the periphery of the socket area defined by the projection of the flange barrel.

Abstract: A manifold for mounting on the cylinder head of internal combustion engines includes a manifold housing, a pipe connecting flange, and, for each cylinder, an individual flange with a fastener. To make handling easier, adjacent individual flanges are joined by an expansion arch.

Abstract: A self-aligning flange includes a flange member, a collar member and a stop member. An inner perimeter of the collar member is sized to receive an outer perimeter of a pipe. The flange member extends outward from an outer perimeter of the collar member. The stop member extends inward from the inner perimeter of the collar member. A large diameter extruded pipe includes a continuous cross section of at least six inches in diameter. It is preferable to weld a flange to one end of the large diameter extruded pipe. Immediately after the large diameter extruded pipe has been formed in an extrusion press, it is sprayed with a coolant to increase the surface hardness thereof.

Abstract: A coupling for joining socket ends of multilayer tubing through electrofusion including a central body having opposing male ends. A core at least partially surrounds the central body and an outer layer encloses the core and central body. The outer layer defines a flange protruding radially outwardly from the central body, wherein the core includes a portion that extends radially outwardly through the flange and out of the flange so that the core can be directly heated by an external heating element.

Abstract: A housing for an exhaust gas purification component encloses an interior space in which at least one receptacle is formed by the housing at the outside. An exhaust system includes at least one first exhaust line section and the housing having the exhaust gas purification component. The first exhaust line section is in engagement with the receptacle, and the first exhaust line section and the receptacle are connected to one another in a materially integral manner. A motor vehicle having the exhaust system is also provided.

Abstract: Couplers for coupling or joining metal tubing are provided which develop the full-strength structural connection between two sections of the metal tubing. In this manner, the full capacity of the adjacent tubes is developed in compression, tension and bending. A first coupler includes a half-shell, central portion surrounding and welded to approximately half of an outside dimension (in the case of a round tube, the circumference) of a first tube, and a pair of outwardly extending flanges. The first coupler is mounted on a first side of the first tube such that it extends beyond the end of the first metal tube. A second coupler is mounted on an opposing side of the second metal tube in a similar manner. The first coupler and the second coupler are then bolted together by joining the lengths of the flanges to thereby connect the first tube with the second tube. Each coupler may be seam welded to its tube at a proximal portion of its flanges.

Abstract: A method of connecting pipe ends of two subsea pipes using a jumper includes raising two separate ends of two separate pipelines from an initial position of each of the two separate ends; creating a jumper pipe; welding a flange with a landing saddle to each pipeline end; disposing a predetermined number of cylinders at a predetermined interval offset with respect to each of the cylinders; connecting a cylinder end to a first leg of the jumper pipe; connecting a rod end to a second leg of the jumper pipe; using the cylinders to contract the jumper in a predetermined plane so that the flanges clear the pipe ends but not the flange saddles; supporting the jumper by a spreader bar; lowering the jumper over the pipeline such that the flange saddles rest on the pipeline ends; relaxing at least one of the cylinders so the jumper expands in the predetermined plane, driving the flanges onto the pipeline ends; releasing the spreader bar; and lowering the pipeline ends and jumper to a predetermined position.

Abstract: A method and a device for connecting a plastic line part in a plastic socket. A head end (9) of the line part (6) is heated contactlessly all the way round until the end curls over to a diameter that is greater than the inside diameter of the socket (5). The line part is then pushed into the socket without using a mandrel or insert, so that the head end (9) forms a liquid-tight fused connection of high tensile strength with molten wall material of the socket (5).

Abstract: A housing for an exhaust gas purification component encloses an interior space in which at least one receptacle is formed by the housing at the outside. An exhaust system includes at least one first exhaust line section and the housing having the exhaust gas purification component. The first exhaust line section is in engagement with the receptacle, and the first exhaust line section and the receptacle are connected to one another in a materially integral manner. A motor vehicle having the exhaust system is also provided.

Abstract: A method of attaching a self-aligning flange to a vacuum pipe includes a flange member, a collar member and a stop member. An inner perimeter of the collar member is sized to receive an outer perimeter of a pipe. The flange member extends outward from an outer perimeter of the collar member. The stop member extends inward from the inner perimeter of the collar member. A method of forming a large diameter extruded pipe includes a continuous cross section of at least six inches in diameter. It is preferable to weld a flange to one end of the large diameter extruded pipe. Immediately after the large diameter extruded pipe has been formed in an extrusion press, it is sprayed with a coolant to increase the surface hardness thereof.

Abstract: In order to attach a fuel system component such as a pipe nipple to a fuel tank having a polyethylene outer layer, the fuel system component is made from a first material which may have desirable characteristics such as resistance to creep, but which may not be easily weldable to the polyethylene outer layer of the tank. The flange member is used for attachment to the body portion of the fuel system component by welding and for attachment to the polyethylene layer of the tank. To inhibit hydrocarbon vapour flow through through the flange member, the flange member includes a barrier layer which extends from one side of the flange to the other and which surrounds the central aperture. In another embodiment of the invention, the flange member is made from a material which has the necessary barrier properties.

Abstract: A first half part includes a second raised portion and a third raised portion respectively on the inner side of the hollow body and on the outer side of the hollow body with respect to a first raised portion, the second raised portion and the third raised portion being separated from the first raised portion with a spacing and being lower than the first raised portion. A second half part includes a third raised portion on the outer side of the hollow body with respect to a first raised portion, the third raised portion being separated from the first raised portion with a spacing and being lower than the first raised portion. An internal member includes a second raised portion on the inner side of the hollow body with respect to a first raised portion, the second raised portion being separated from the first raised portion with a spacing and being lower than the first raised portion. As a result, there is provided a high quality hollow body that can be provided at low cost and is cosmetically appealing.

Abstract: A method for forming and attaching a clamping collar to a pipe configured for forming a pipe section in a concrete pumping line for carrying of fluid concrete includes the steps of placing a sleeve on the pipe to provide a heat transfer limit area between the sleeve and the pipe; welding the sleeve to the pipe; heat treating the pipe; and assembling a collar to the sleeve and welding the collar to the sleeve.

Abstract: A flange (20) for connection between an axial compressor and high-pressure rotor disc unit (14) in a gas turbine (10), wherein the flange (20) has a body (22) with a frusto-conical shape which is joined to a shaft (12) of the axial compressor by means of a hub (24) which has a cylindrical shape and which, at the larger base of the frustum of the cone of the body (22) is connected to the rotor disc unit (14) by means of an extension (26) of the hub in the form of a circular ring, a circumferential recess (28) provided in a surface (29) of the extension (26) which faces the rotor disc unit (14) being connected by interference with a projection, which is complementary to the recess and is provided on the rotor disc unit (14); the body (22) has an outer generatrix which is inclined relative to the direction at right-angles to the axis (X) by an angle &agr;1 of between 25° and 35° and an inner generatrix which is inclined by an angle &agr;2 of between 12° and 18°.

Abstract: An erosion resistant pipe flange assembly for preventing erosion of metal pipe flanges connecting two joints of pipe. The erosion resistant pipe flange assembly includes a flange section, a reducer section integrally formed with said flange section, and a replaceable liner for preventing erosion and abrasion of the interior of said pipe flange assembly.

Abstract: An arcuate double-layer pipe for a pipeline for fluidic transport of abrasive solids, includes an inner pipe portion made of wear-resistant material, and an outer pipe portion of weldable steel in surrounding relationship to the inner pipe portion. A pair of coupling collars made of weldable steel is placed on opposite ends of the inner pipe portion, with each coupling collar having a ring-shaped insert of wear-resistant material and a rim-like projection so that the inner pipe portion extends between the ring-shaped inserts in the coupling collars and is overlapped on the opposite ends by the rim-like projections of the coupling collars. The rim-like projections of the coupling collars engage interiorly into opposite ends of the outer pipe portion for centering the outer pipe portion, with the opposite ends of the outer pipe portion being welded to the coupling collars.

Abstract: An expansion section for expanding the distance between longitudinal side surfaces of an opening of a tube when being inserted a predetermined depth into the opening is formed an expansion wedge body, and guide protuberances are protrusively formed on the respective longitudinal sides of the expansion section. The guide protuberances are inserted into the spaces provided on the respective sides of the opening of the tube, thereby guiding the expansion section into the opening.

Abstract: A sweat flange, piping system utilizing the same, and method of installing a circulator to a copper pipe. The sweat flange includes a base portion having a predetermined shape and at least two bolt openings dimensioned to accept at least two mounting bolts. A shoulder portion extends from the base portion and includes a substantially circular pipe opening that extends through the base portion and the shoulder portion. The pipe opening includes a first portion dimensioned to accept the pipe and a second portion of decreased diameter in order to limit the travel of the pipe through the opening. The sweat flange is attached to the pipe by inserting the pipe into the pipe opening of the flange and soldering the two together using art recognized soldering techniques. The piping system includes at least one pipe, a sweat, a pair of mounting bolts and a circulator or other pump.

Abstract: A perimeter weld flange comprising an inner and external perimeter wall surface and a perimeter weld lip on said flange for welding said flange onto a receiving surface. The perimeter weld flange herein is particularly suitable for weldable metal-gasketed ultra-high vacuum joints, and is also conveniently welded onto tubes, cones, ellipsoids, plates and other shapes, including even irregular shapes, in addition to spheres.

Abstract: An exhaust manifold flange for an internal combustion engine, for sealably connecting at least one stub pipe of an exhaust manifold to a wall of the engine, the flange has a basic part made of sheet steel provided with a bead which extends substantially around the entire outer contour of the basic part, at least one receiving hole with another bead therearound for securely receiving the at least one stub pipe in the manifold which has holes which are arranged for attaching the exhaust manifold flange to the wall of the internal combustion engine.

Abstract: A pipe for conveying solids provided at least at one end thereof with a circumferential radially extending coupling flange and an axially extending annular portion connected to the coupling flange. An annular insert of a material having a greater resistance to wear as compared to the material of the pipe is arranged in a chamber formed by the coupling flange and the annular portion. The coupling flange and the annular portion are formed by a chipless deformation from a tubular steel cylinder.

Abstract: A method for installing a flange on the end of a tubular member lined with a thermoplastic liner is provided. The flange is formed with a groove having extrusion openings extending from the front to the rear surface of the flange, the groove for receiving the reformed end of the liner which is forced into the extrusion openings and extends above the front surface of the flange to provide a surface for securing with a corresponding flange.

Abstract: A conveying pipe for hydraulically transporting solids, such as sand, gravel or also concrete is composed of a straight or curved pipe portion and of coupling flanges at the ends of the pipe portion, wherein the coupling flanges protrude radially above the outer surface of the pipe portion. The outer end faces of the coupling flanges which face away from each other are each located in the transverse planes of the end faces of the conveying pipe. The coupling flange located at the end of the conveying pipe on the inlet side has a greater width than the coupling flange arranged at the end on the outlet side.

Abstract: A dual seal is provided for establishing fluid tight engagement between conduits subjected to both internal and external pressure. The dual seal comprises four seal portions disposed between an inner and an outer cylindrical surface.

Abstract: A tapping sleeve assembly for direct connection to a gate valve. The assembly includes a tapping sleeve attached to a main pipe. An outlet conduit formed integrally with and extend outwardly from the tapping sleeve terminates in a distal end outlet. A retaining ring is attached to the outer surface of the outlet conduit and is located between the tapping sleeve and the distal end outlet. Opposed, longitudinally facing annular surfaces are formed on the retaining ring with one of the annular surfaces facing the tapping sleeve and the other facing the distal end outlet. The annular surface facing the tapping sleeve is inclined. A gland telescopes over the outlet conduit. The gland has a collar with an annular surface engaged with an annular surface of the retaining ring. A gate valve has a socket facing the outlet conduit, a gasket is positioned in the socket and a mechanical joint flange surrounds the socket. Bolts and nuts attach the gland to the mechanical joint flange of the gate valve.

Abstract: Improved convoluted flanges including one embodiment having a metal inset in a polymer casing in which the inset has a convoluted configuration similar to the outer convoluted configuration of the casing and another embodiment of a convoluted, slip-on, welding flange for welding to a pipe having a cross sectional, convoluted contour that is configured using stress analysis to shift the effective loading of connecting bolts from the centerline of the bolt holes in the flange to a locus closer to the pipe to which the flange is welded.

Abstract: An erosion resistant pipe flange assembly and a method for preventing erosion of metal pipe flanges connecting larger diameter pipe to smaller diameter pipe. The erosion resistant pipe flange assembly includes a flange section, a reducer section integrally formed with said flange section, and a replaceable liner for preventing erosion and abrasion of the interior of said pipe flange assembly.

Abstract: A pipe for conveying solids, particularly for conveying concrete, includes a cylindrical middle portion and a welding neck with a coupling ring flange. The welding neck has an inner layer and an outer layer, wherein the inner layer is of a material which has a greater resistance to wear than the outer layer. The inner layer and the outer layer have end faces which extend in a common transverse plane. The inner layer is of ceramic material or of cast material resistant to wear by impacts, such as, Ni-hard IV, and the entire surface of the inner layer is glued into an internal groove of the coupling ring flange.

Abstract: A pipe coupling for sealing a joint between pipes in a pipeline by compressing annular gasket members against the pipes around the joint, the pipe coupling comprising an annular coupling member having end members and spaced annular protrusions forming gasket channels between the annular protrusions and respective end members for receiving the annular gasket members and a central channel between the gasket channels for accommodating some offset, deflection, or out-of-roundness in the pipes. In one embodiment, the coupling further comprises an outer set of annular protrusions for forming expansion channels outside of the gasket channels. The expansion channels allow retaining rings fixed to the pipe ends to reciprocate within the expansion channels during expansion or contraction of the pipe ends. The protrusions also restrain the degree of expansion or contraction of the pipes and protect the gasket. In another embodiment, an interior pipe coupling with a spreader bolt assembly is provided.

Abstract: A connector assembly is provided for connecting two pipes of dissimilar material. In particular, an assembly is provided for connecting a first end portion of a first pipe to a second end portion of a second pipe formed as a bell housing having a larger inside diameter than an outside diameter of the first end portion and which second end portion overlaps the first end portion. The connector assembly includes a mandrill for attachment to the first end portion, which is formed as a flange extending radially from an outside circumference of the first end portion to face at least a portion of an end face of the bell housing, and an axial tubular extension extending from the flange so as to, upon assembly, reach a point approximately equal to an axial end point of the first pipe, and reside within the second end portion creating an annular space therebetween.

Abstract: A sump adaptor is provided which includes first and second flanges having respective first and second openings, each having a respective first and second axis which axes are in coaxial relationship to each other when the flanges are assembled. A plurality of apertures are formed in a first of the flange and a plurality of threaded bolts which are welded to the second flanges pass through holes in annular seals which sandwich therebetween a bottom wall of a tank sump. The threaded bolts pass through the apertures of the second flange and nuts threaded to the threaded bolts coupled the flanges together. The first flange opening is unthreaded and receives a tubular portion having an exterior thread. A weld secures the tubular portion to the first flange. The opening of the second flange has interior threads into which are threaded exterior threads for releasably securing thereto a sump-associated element.

Abstract: An improved all-metal coupler for coupling vacuum components. The coupler comprises a hollow tube terminating at each end in a flange. At least one of the flanged ends comprises a plurality of radially outwardly extending tabs or lugs for accommodating the bolt holes. In a preferred embodiment of the invention, the coupler is machined from a unitary piece of metal.

Abstract: A fluid-tight joint formed by a pair of annular rings, each attached to the end of a tubular fluid-conducting conduit. The rings are similar, each having one side with a channel with a frusto-conical wall and the other side having a ridge with a frusto-conical wall receivable in the channel of a similarly-shaped ring. Threaded fastener means engage the two sealing rings to form a fluid-tight joint in the area of contact between the two frusto-conical walls.

Abstract: A flexible joint for an automobile exhaust system includes a flexible bellows for sealing the communication between the engine and the tail pipe with first and second flanges fixed to the respective members and interconnected by coupling shafts that are fixed at one end to one of the flanges and passed loosely through the other flange whereby compression springs that surround the coupling shafts serve together with the bellows to provide support capable of accommodating relative axial and angular deflections between the members. One of the flanges is so configured and disposed with respect to the bellows as to limit the amount of angular deflection imposed on the bellows. Damping sleeves composed of compressed wire mesh material operate to dampen vibrations imposed on the joint.

Abstract: A fluid conduit connection includes in combination a cast or molded connecting member; a connecting socket affixed to the connecting member and comprising a standarized sheet metal press fitting having one end thereof attached to the connecting member and comprising a substantially cylindrically portion and, at the other end thereof, an annular groove for housing a sealing member. The press fitting is dimensioned for receiving a substantially cylindrical conduit to be inserted therein and for non-releasably crimping the fitting around the conduit.

Abstract: A convoluted flange ring for a flange coupler in a piping system the flange ring having an annular bolting disk with an outer rim and an inner rim forming a U-shaped cross section, with the bolting disk having a transitional thickness for improved stress management, the thickness of the bolting disk increasing from the outer rim to the inner rim.

Abstract: A double-layer pipe bend for a pipeline includes an inner pipe of cast steel, an outer pipe of weldable steel surrounding the inner pipe, and connecting flanges at the ends of the pipe bend. The connecting flanges are welded to the outer pipe. The inner pipe and the outer pipe are formed such that a pressure-compensating layer can be formed by the transported medium between the pipes. Another pressure-compensating layer can form between an inner wearing ring and an outer coupling ring of each connecting flange. The wearing ring and, thus, the inner pipe, is axially secured by a groove in the wearing ring and a radial collar in the coupling ring.

Abstract: An article for joining in end-to-end relationship two or more tubular articles such as pipe sections, and particularly pipe sections coated on their inner and outer surfaces with an electroless metal such as nickel and adapted for passing corrosive liquids and solids includes a ring-shaped member having a meltable coating, on its surfaces intended to engage the ends of the tubular articles and the inner surface of the tubular articles at their junction, and having a flange on its outer circumference that is of a shape and size adapted to engage and seat upon the inner surfaces of the tubular articles to be joined in end-to-end relationship. Welding material is placed in a chamfered region formed at the outer edge of two tubular articles at their ends, joining the two tubular articles in end-to-end relationship with the ring-shaped member between them, and melting the coating into the junction between those ends, and into the interface between the flange surface and the inner surfaces of the tubular articles.

Abstract: An expansion joint is disclosed for connection between fluid flow conduits for permitting the expansion and contraction of the conduits while sealing same. The joint includes telescoping cylindrical members each connectable to a conduit and having a rolling seal or membrane connected therebetween to prevent leakage of fluid out of the joint. One of the members includes an inwardly turned, annular shoulder formed so as to closely surround the other member during full relative movement between the members to prevent the seal from coming in contact with foreign matter. The expansion joint is provided with a plurality of guide rods which are arranged circumferentially around the pipe joint and serve to lock the rolling seal in operative position with one member and to guide the movement of the other member during movement of members relative to each other.

Abstract: A self-aligned flanged coupling for a pair of product transport pipes comprising a male member, a female member disposable in coupling relation to the male member, a clamping assembly mating with the male and female members for releasably securing the members, and an O-ring for disposed between the male and female members, wherein the male member comprises a first pipe, an annular flange for receiving the O-ring extending outwardly and circumferentially about the outer diameter of the first pipe and secured to the pipe having a recess disposed therein to receive the O-ring, wherein the pipe extends beyond the annular flange, wherein the female member comprises a second pipe, a support extending outwardly and circumferentially about the outer diameter of the second pipe, wherein the support extends beyond the second pipe, and a flanged portion extending outwardly from the second pipe and secured to the support having an orifice therein also adapted to receive the O-ring, wherein the O-ring is disposed within t

Abstract: In a construction for joining a copper tube (20) to a steel body (10) which may be part of a device such as an accumulator used in an air conditioning system, the copper tube is passed into an opening (14) in a wall (12) of the steel body. The opening in the steel body is bounded by a neck projection (18) which extends outward therefrom. A copper collar (24) includes a first portion (26) which accepts neck projection (18) of the steel body. A second portion (28) of the copper collar (24) accepts the copper tube. A mass (34) of brazing material is positioned in the collar in a tapered transitional portion (30) between the first and second portions of the collar. When the body, tube and collar are assembled and placed in a brazing furnace, the brazing material melts and flows by capillary action between the first portion of the collar and the outside of the neck projection of the steel body. The brazing material also flows between the second portion of the collar and the tube.

Abstract: A pipe for conveying solid matter, particularly for conveying concrete. The pipe has a cylindrical middle portion and a double-layer welding neck with annular coupling flange at each end of the middle portion. The inner layer is replaceably clamped in the outer layer in a positively locking and frictionally engaging manner. This is accomplished by a roof-like bevel of the inner layer which is engaged by a corresponding inner groove of the outer layer which is of limited elasticity. The inner diameter of the inner layer may be smaller than the inner diameter of the cylindrical middle portion.