Abstract: A method for manufacturing a double jacketed fire hose, and a double jacketed fire hose comprising an inner jacket and an outer jacket, the inner jacket being encapsulated with polyurethane, the inner jacket residing within the outer jacket, the inner and outer jacket having a controlled net twist.

Abstract: A multi-layer metal tube consists of a flat steel band having a soldering layer connected to at least one side of the steel band. The soldering layer consists of a copper alloy having a melting point below 1020.degree.. The tube is produced by deforming the flat steel band into a tubular shape by winding or cylindrically rolling and by subsequently soldering the steel band to form the multi-layer metal tube. The soldering step prevents leaks as well as corrosion. In the corresponding method for manufacturing the multi-layer tubes the steel band in a first step is electrolytically degreased and activated in a nickel flash bath or in a copper pickling bath. Subsequently, the steel band is coated with the copper alloy which contains tin, zinc, or silver in order to reduce the melting point. After completion of the winding step or rolling step, the multi-layer tube can be coated with an additional corrosion-preventing layer.

Abstract: A reinforced rubber hose having a layer of ethylene-propylene rubber outside or inside a fiber-reinforcing layer. The two layers are firmly bonded to each other by an extruded adhesive layer of butyl rubber which exhibits a high bond strength after vulcanization. This obviates the necessity of treating (usually by dipping) the fibrous reinforcement with an adhesive before its braiding or knitting.

Abstract: A composite material tube, withstanding the internal pressure, and comprising at least two layers of pressure reinforcement fibers, or pressure resistant layers, wound at an angle at least equal in absolute value to 70.degree., with respect to the center axis of the tube. The two layers both undergo radial expansion under an effect of the pressure, with one of these two layers being inside the other. A circumferential modulus of elasticity of the external layer is greater than the circumferential modulus of elasticity of the internal layer.

Abstract: A rectangular reinforcing cage is provided for a cast concrete structure having longitudinal registration tubes at each corner of the cage. An outer reinforcing cage surrounds the registration tubes and a coaxial inner reinforcing cage is supported from the outer cage by a plurality of spacers. Each reinforcing cage has a pair of facing C-shaped mats having straight mats overlapping and connected to the bent ends of the "C" to complete each reinforcing cage. Each end of the C-shaped mats have a smoothly curved transition bend joining a portion perpendicular to the main portion of the mat. Each mat has a layer of longitudinal wires connected to a layer of transverse wires. The longitudinal wires being more closely spaced near the end of each mat than in the remainder of the mat with no longitudinal wires in the transition bend of each C-shaped mat. The longitudinal wires are positioned inside each C-shaped mat and outside each straight mat when a reinforcing cage is assembled.

Abstract: Methods of producing electrically fusable sleeve connectors for connecting large diameter thermoplastic pipe sections and the sleeve connectors produced by such methods are provided. Methods of sealingly connecting adjacent ends of a pair of large diameter thermoplastic pipe sections by electric fusion are also provided. The methods of producing electrically fusable thermoplastic sleeve connectors broadly include the steps of winding a tape of molten thermoplastic material onto a large diameter core drum whereby adjacent windings are fused and upon being cooled a solid sleeve is formed, embedding an electric resistance heating wire in a surface of the sleeve while the thermoplastic material is still in the molten state and removing the sleeve after cooling with electric resistance heating wire embedded therein from the core drum.

Abstract: A concrete article having a mixture layer comprising concrete and a polysulfide-modified epoxy resin as an intermediate layer between a concrete body and a cured layer of a polysulfide-modified epoxy resin, which concrete article is excellent in corrosion resistance, durability and workability, and shows good adhesion to the concrete body and to the cured layer of the polysulfide-modified epoxy resin. This concrete article can be produced by applying a coating composition containing the polysulfide-modified epoxy resin to the concrete body in an uncured state.

Abstract: A porous fibrous sheet material for use in the manufacture of food casings and the like is pressed prior to bonding and is bonded with about 10% by weight or less of a non-viscose bonding agent. The pressed and bonded material can be used to form casings having characteristics of thinness and elasticity similar to the thinness and elasticity of viscose-bonded casings, without the environmental problems associated therewith. The non-viscose bonding agent will result in significantly less shrinkage in the base web than results from viscose bonding.

Abstract: A duct device for insulated delivery of temperature controlled air. The device comprises an elongated, tubular member configured as a conduit for delivery of air and having a tubular wall fabricated of non-load-bearing insulative material. This insulated material includes at least one continuous gap formed into the tubular wall and extending along the tubular member. This gap is filled with a rigid binder which bonds to the insulative material and is capable of reinforcing the structural strength of the tubular member. This binder filled gap operates as a strut, which may be positioned longitudinally along the tubular member, or in other patterns such as a helical configuration. Reinforcing structure is also disclosed for the end sections of the tubular member, along with interconnecting structure.

Abstract: Process for the manufacture of a flexible polymeric structure comprising a sealant barrier, consisting of a multilayer film a few microns thick, oriented longitudinally, in a continuous manner, whereby all of the components of said flexible structure are intimately bonded by a final heat treatment. Flexible polymeric structures manufactured according to this process. Application to the fields of the transport of all fluids and protection against external aggressive agents.

Abstract: Process for the manufacture of a flexible tubular structure comprising a sealant barrier, consisting of a monolayer film a few microns thick, oriented longitudinally, in a continuous manner, whereby all of the components of said flexible structure are intimately bonded by a final heat treatment. Flexible tubular structures realized according to this process. Application to the fields of the transport of all fluids and protection against external aggressive agents.

Abstract: A reinforced hose has an inner tube made of rubber, an inner reinforcing layer made of aromatic polyamide yarn formed on the inner tube, an intermediate layer made of rubber formed on the inner reinforcing layer, an outer reinforcing layer made of synthetic yarn formed on the intermediate layer which has a heat shrinkage ratio at dried condition of over about 0.5% due to the temperature of a curing process, and a covering layer made of rubber being formed on the outer reinforcing layer. By providing the inner reinforcing layer of aromatic polyamide yarn, the reinforced hose of the present invention has a high stretching strength. Furthermore, by making the outer reinforcing layer of synthetic yarn, which has a heat shrinkage ratio at dried condition of over about 0.5% due to the temperature of a curing process, the reinforced hose of the present invention can hardly be expanded by the pressure of inside fluid.

Abstract: A high pressure (up to 8000 psi service) hose assembly has an inner core made of "Teflon" PTFE, covered by a "Kevlar" aramid reinforcing braid. The PTFE can, but the aramid cannot, withstand the attack of oils and other fluids which may be conveyed through the hose. Therefore, the aramid is covered by PTFE tape and the end of the hose is sealed inside an end fitting. In one embodiment, when the end fitting is swaged or otherwise manipulated to capture the hose, the PTFE inner core extrudes to complete the sealing of the hose end.

Abstract: In a pipe clamp for tapping and closing off plastic supply pipelines, the clamp upper shell is constructed from plastic and provided with a one-piece pipe socket. The clamp upper shell can be welded to the desired position of the supply pipeline. In the pipe socket, a coaxial, tubular metal insert, with an internal thread accessible from the interior of the pipe, is provided. To facilitate the handling of the pipe clamp and to strengthen its plastic, it is proposed that the metal insert, although it is constructed in one piece, be organized in two axial sections, different in shape and action. Of these, only the lower axial section is anchored in the pipe socket, while the upper axial section protrudes freely out of the upper front end of the pipe socket and makes the inner thread conveniently available for connecting eligible functional parts.

Abstract: Extruded catheters and other flexible plastic tubing may be manufactured with improved rotational and/or longitudinal stiffness, compared with catheters made of more conventional plastics. A tubing of liquid crystal polymer plastic-containing material may be extruded through a tube extrusion die while rotating the inner and outer die walls to provide circumferential shear to the extruded tube. Thus the liquid crystal polymer is oriented in a helical manner to provide improved properties, including greater rotational stiffness.

Abstract: A new auxiliary injection tube concept is disclosed for injecting a fluid containing corrosion and/or deposit inhibiting agents into a well from the surface, without stopping working. The auxiliary injection tube includes a tube 10 conveying the injected agents. The tube is coated with a material 11 which is inert with respect to to the fluid collected by the well. Support cables 12, disposed about the tube 10 and also coated with material 11, provide both secondary protection of the tube 10 in the case of damage to coating 11 and the mechanical characteristics required for the injection tube, particularly during withdrawal from the well.

Abstract: A refrigerant-transport hose having an inner tube, an outer tube located radially outwardly of the inner tube, and a reinforcing fiber layer interposed between the inner and outer tubes, the reinforcing fiber layer and the inner and outer tubes providing an integral tubular body, and inner tube including a gas-impermeable resinous layer formed of a composition containing a polyamide resin produced by reaction of hexamethylene diamine and an aliphatic dicarboxylic acid having eight to sixteen carbon atoms.

Abstract: A double-wall composite pipe comprises a permeable annulus structure separating impermeable inner and outer walls. The permeable annulus structure has micro-fractures formed therein that function to reduce the flow rate and pressure of fluids leaking through the inner wall to thus inhibit fluid leakage. The annulus structure resists the stresses produced by internal fluid pressures and other service loads. The inner and outer walls will remain permanently impermeable while the pipe annulus structure undergoes stress-induced dimensional changes. A coupler assembly mechanically connects each longitudinally adjacent pair of pipes together and comprises two semi-cylindrical half-couplers, a compressible seal ring, a cylindrical retaining sleeve, and a flexible boot that encloses and seals the assembled half-couplers. A leak detecting sensor may be located at the coupler assembly. A preferred method and apparatus for making the pipe and coupler assembly are also taught.

Abstract: Better mechanical properties are achieved with tubes for shell and tube heat exchangers by providing a coating on the tubes which is formed of fibers and a fluorine-containing polymer covering the fibers. The tubes are formed of fluorine-containing polymers whose use in heat exchangers is normally limited by the comparatively small compressive strength and fatigue resistance of the tubes.

Abstract: A pressure-resistant helical corrugated pipe comprises a helical corrugated pipe wall having a top portion, opposite side wall portions extending from the top portion and a bottom portion extending from the side wall portions and disposed closed to the axis of the pipe; and belt plates which are formed separately from each other and made of a thin metal. The belt plates are disposed respectively at the side of the top portion and the side of the bottom portion as constituent elements for the pipe wall. The opposite edges of the two metal belt plates are disposed in abutted relation or in spaced opposed relation at the opposite side wall portions. The two metal belt plates are interconnected by connective portions which are made of a synthetic resin or rubber.

Abstract: A lining material for pipe lines, especially those buried in the ground and a process for providing pipe lines therewith are disclosed, which includes a flexible tubular film, a sheet covering the outer surface of the tubular film and a film capable of being split off covering the outer surface of the sheet, characterized in that the sheet includes a fabric and a mat of fibers of high tenacity impregnated with a thickened liquid thermohardenable resin to form a fabric-fiber-reinforced composite molding sheet having a sufficient length and a width greater than the inner circumferential length of a pipe line to be treated, and that both lateral end portions of the sheet are slidably overlapped with each other to form a tube around the tubular film, the outer circumferential length of the tube being shorter than the inner circumferential length of the pipe line.

Abstract: A composite hose comprising an inner helical core (1) made of metal, a plurality of layers of plastics material fibres and films (2, 2a, 2b, 2c) wound on the helical core (1), at least one layer of glass cloth (3) and at least one layer (4) of aluminium foil disposed adjacent one another and wound onto the layers of plastics material fibres and films (2) and an outer helical former (7) made of metallic material.In an alternative embodiment, at least one layer of ceramic fibres (5) is wound around the plastics material, which layer (5) is covered by at least one winding of a protective layer (6a; 6b).Such hoses are made by winding the layers successively one upon another on a rotating mandrel.

Abstract: A polyvinyl choride resin pipe serves as an inner lining material for the existing pipes. The resin pipe is formed of a resin composition which comprises as a main component either a polyvinyl chloride having a degree of polymerization DP of 600 to 1,050, or a mixture of 40 to 60% by weight of a polyvinyl chloride having a lower average degree of polymerization DP.sub.L of 400 to 600 and 60 to 40% by weight of another polyvinyl chloride having a higher average degree of polymerization DP.sub.H of 1,050 to 1,350. The resin composition further comprises 3 to 25 parts by weight of a modifying agent blended with 100 parts by weight of the main component. The modifying agent is composed of MMA- and/or MBS-modifiers.

Abstract: Hoses are disclosed for transporting refrigerant media and a 1,1,1,2-tetrafluoroethane gas in particular. An inner tube is formed of a rubber composition comprising a selected ethylene-propylene-diene rubber and having a specified permeation limit of the gas. Disposed around the inner tube are a reinforcing layer and then an outer cover. The resulting hose is highly impermeable to gas and to water, sufficiently resistant to heat and fully free from maintenance.

Abstract: Composite tube, which is a sandwich structure, comprising a plurality of fiber strata, each made of epoxy-saturated fibers, and at least one layer of a honeycomb material sandwiched between. The fiber strata and the honeycomb layers are in alternating sequence. Each fiber stratum may include a fiber web surrounded by a fiber cable, which consists essentially of a large number of twisted fibers arranged in the axial direction and parallel to each other. The composite tube of this invention is very light in weight, yet has tensile strength and other mechanical properties corresponding to those of conventional tubes made of steel. The tube of this invention is especially useful as a guide roller or an expansion shaft.

Abstract: A conduit including an inner tubular liner comprised of organic polymeric material, an outer case and an intermediate layer of metallic filaments extending alternatively in a first direction and then in a second opposite helical direction about the inner tubular liner. The method of making same comprises the steps of; providing an organic polymeric inner tubular liner, applying a single layer of filaments alternately in a first helical direction and then in a second opposite helical direction continuously about the inner liner, and applying an outer layer thereabout.

Abstract: A synthetic resin pipe intended for underground use is disclosed having both an improved strength and flexibility but reduced weight. An inner layer of the body of the pipe is formed of a synthetic resin, and a reinforcing layer is wound around the inner layer. The reinforcing layer is porous, and may be composed of a helically wound punched metal belt, mesh, or the like. An outer layer composed of a helically wound belt of synthetic resin having a high fusibility with the material of the inner layer is formed over the reinforcing layer. A reinforcing rib, forming the corrugations of the pipe, is wound around the outer layer. If desired, the reinforcing rib can be made integral with the belt of the outer layer.

Abstract: The molding has a body (3) of thermoplastic. A sound-muffling layer (4), which is affixed to the body (3) by the injection-molding process, consists of a thermoplastic elastomer. The body (3) protrudes at its end from the sound-muffling layer (4). Welding sleeves (2) are welded onto these unlayered areas (5) of the body (3). Molding (1) in the course of repair work can also be severed in the area of the sound-muffling layer (4) and joined by means of butt welding. The thickness of the sound-muffling layer (4) is comparatively small.

Abstract: Improved arc-suppressing fuse tubes of the type used in electrical cutouts is provided which includes a fluid epoxy resin matrix core designed, upon experiencing high temperature arcing conditions, to generate sufficient moisture and arc-suppressing gases to safely and efficiently interrupt an arc. The fuse tubes of the invention completely eliminate the use of expensive and difficult to fabricate bone fiber conventionally used in fuse tubes of this type. The preferred fuse tube construction is an integrated, synthetic resin body having an outer tubular shell including an epoxy fiberglass-reinforced synthetic resin matrix, together with an inner tubular arc-suppressing core having an epoxy resin matrix with respective quantities of an organic fiber and an inorganic filler therein. An anhydride curing agent for the epoxy is incorporated at an anhydride to epoxide ratio from about 1.0 to 1.4:1.

Abstract: A synthetic resin pipe intended for underground use having an increased strength but reduced wall thickness. In accordance with the invention, a reinforcing member, in the form of a perforated belt, is embedded in or fused to the resin material of the pipe and extends along top portions and at least portions of the side walls adjacent to the top portions of the corrugations of the pipe.

Abstract: A metallic outer sleeve 10 is provided which is capable of enveloping a hollow metallic inner member 12 having continuous reinforcing fibers 14 attached to the distal end thereof. Inner member 12 is then introduced into outer sleeve 10 until inner member 12 is completely enveloped by outer sleeve 10. A liquid matrix member 20 is then injected into space 22 between inner member 12 and outer sleeve 10. A pressurized heat transfer medium 23 is flowed through the inside of inner member 12, thereby forming a fiber reinforced matrix composite material 26. The wall thicknesses of both inner member 12 and outer sleeve 10 are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure 28 to the desired value.

Abstract: Disclosed is a prestressed tube and a method of its manufacture. The tube includes inner and outer walls with an intermediate nonadhering lamina layer. A pressure medium is fluidically injected through one of the walls to the interface between the nonadhering lamina layer and at least one of the walls so as to form a cavity therebetween for receiving the pressure medium. The medium is thereafter hardened to provide a prestress force to the tube. The method includes the step of fluidically injecting pressure medium between the walls to the intermediate lamina layer and the interface between that layer and at least one of the walls, so as to form a gap therebetween for receiving the pressure medium. During the step, one or both of the walls may be expanded so as to form an enlarged cavity for receiving the pressure medium. The method thereafter includes the step of hardening the pressure medium so as to provide a permanent leak-proof prestress force to the tube.

Abstract: In order to increase resistance to fatigue which is decreased by crack formation in at least one fiber layer of a torsion-stressed component part, an intermediate layer of a material which is soft relative to the fiber layers is arranged between individual fiber layers.

Abstract: The invention relates to a hose comprising an inner plastics tube (2) covered by at least one braiding of filaments disposed in helically crossed layers (5, 6) around the inner tube (2), characterized in that the filaments (7) are made of plastics and are so deformed in their right cross-section that the gap (8) between any two adjacent layers (6a, 6b) which extend in the same direction as one another is at least 100% filled. The invention also relates to a process for the production of the hose.

Abstract: A joint is provided for joining together two sections of a tube wherein the sections are prestressed by a surrounding pressure medium to press the sections together and to resist forces tending to separate the sections and the bursting pressure inside the tube. The pressure medium can be a resin which can be pressurized and subsequently cured or a fluid. The outside diameter of each section, at and near the end to be joined, is enlarged. A coupling means encircles the enlarged portions and couples the two sections together. One or more expandable pressure cavities located within said coupling means and/or within the enlarged portions have the general shape of a flared annuli. The pressure medium fills and expands the pressure cavities and, when pressurized, exerts stresses compressing both sections together at the joint and also applies relatively uniform radial stress in the vicinity of the end of each section.

Abstract: A fluid energy absorber device, such as a fluid spring or shock absorber, or a combination of both, having a composite casing of an outer cylinder of molded plastic around an inner high strength plastic cylinder having high strength fibers therein, the high strength fibers extending both longitudinally and circumferentially, with the circumferential fibers preferably being a high strength plastic which will permit the casing to expand radially. The inner cylinder may be a separate plastic cylinder containing the high strength fibers and to which the outer cylinder is bonded, or the inner cylinder may be formed by a matrix of plastic which is a continuation of the outer cylinder. The high strength cylinder may be located between inner and outer plastic cylinders which are fused to each other to encapsulate the high strength cylinder.

Abstract: The specification discloses a low-cost, simple, and efficient duct system for conveying heated and/or cooled air throughout a building. The system includes duct assemblies and transition components for interconnecting the duct assemblies. Each duct assembly includes an insulated duct having a rigid sleeve within at least one end. Each sleeve includes an abutment ring and orifices in the ring for permitting air to flow into the insulated layer to balloon the layer and improve its insulative effect. Each transition component includes a rigid external skeleton and a plurality of duct board panels fitted therein. After the sleeves are fitted within openings in the duct board panels, the tabs are deformed to retain the abutment rings in engagement with the panels.

Abstract: Filament wound pressure tube has layers of filaments wound helically. The filaments of each such layer are disposed at an angle to a line parallel to the longitudinal axis of said tube which angle is approximately equal to a respective angle .theta. to the line, such angle .theta. being chosen such that the ratio sin.sup.2 .theta./r is approximately the same for all layers, where r is the radial distance from said axis to the location of such layer.

Abstract: In the case of strand-shaped material, for instance corrugated tubes, electric cables or lines, there is provided on the surface of the material an armoring comprising a plurality of wires which are applied with a long length of lay and are held by a further armoring layer. The wires are applied to the material with changing direction of lay. The additional armoring layer is at least one wire applied with a short length of lay and which is applied with initial tension onto the first armoring layer.

Abstract: A tubular material based on a fabric reinforced resin, said material comprising layed up fabric layers, the inside and outside layers consisting of bidirectional braided sheaths, said latter two layers sandwiching an intermediate, unidirectional braid consisting primarily of parallel, longitudinal yarns at least 10% of which have a high tensile strength and the remainder of which are yarns of the same type as the yarns of said bidirectional braids. An application in the construction of a bicycle frame is described.

Abstract: To manufacture tubes having a wear-resistant inside coating, such as gun barrels, hard material layers are deposited on the barrel and the layers are strain-hardened in their surface area by at least the ratio of the area by which the surface area is reduced by compression divided by the surface area of 0.001 (.DELTA.F/F=1.10.sup.-3) or reducing the area of the layer by 0.1%.

Abstract: This invention is concerned with a hose construction particularly suitable for Freon service in refrigeration systems. The hose comprises (1) a core tube of polyamide covered by an elastomeric friction layer such as EPDM rubber having incorporated therein a calcium ion source and an adhesion system and a curative, (2) a layer of tensioned reinforcement strands, (3) an adhesive/barrier/friction layer such as an ethylene acrylic acid copolymer, (4) a second layer of tensioned reinforcement strands, and (5) a cover selected from chlorobutyl rubber or other suitable materials wherein the chlorobutyl rubber utilizes a bis-dienophile as a crosslinker.

Abstract: A hydraulic brake hose has an inner tube made of nylon, an isocyanate adhesive layer formed on the outer surface of the inner tube, a chloroprene-rubber adhesive layer formed on the outer surface of the isocyanate adhesive layer, a reinforcing fiber layer made of high polymeric material selected from the group consisting of rayon, polyester, polyamid and polyvinyl alcohol, impregnated with resorcinol formaldehyde latex containing chloroprene-rubber and formed on the outer surface of the chloroprene-rubber adhesive layer and an outer tube made of chloroprene-rubber and formed on the outer surface of the reinforcing fiber layer. The inner tube has the modulus of elasticity of 7,000 to 15,000 kg/cm.sup.2 and has an inner diameter of not less than 2.0 mm, an outer diameter of not more than 6.0 mm and a thickness of not less than 0.7 mm.

Abstract: A reinforced underground pipe made of a synthetic resin having an improved strength and reduced resin requirement. The reinforcement of the pipe is constituted by a helical rib formed on the outer surface of the main body of the pipe. At least side wall portions of the rib are corrugated. The rib may be U shaped or have a semicircular cross section. The corrugations may be rectangular, sinusoidal or triangular.

Abstract: Structures, such as pressure vessels or pipes, for the storage and transportation of fluids under pressure are wrapped with a composite material including a high-strength unidirectional filament material in a matrix of a flexibilized isophthalic polyester resin which has an elongation at least equal to the elongation of the material of the structure. The index of refraction of the resin is matched to the index of refraction of the filament material so that the pressure vessel is visible through the wrapping. The resin discolors when exposed to a heat above which the material of the structure weakens, thus acting as an indicator that the structure is unsuitable for use.

Abstract: A porous tube suitable for use as a vascular graft prosthesis is disclosed. It is reinforced by external ribs, integral with the tube wall. These ribs are generally transverse to the tube axis and less porous than the wall. Suitable tubing can be made from polymers exhibiting a significant degree of crystallinity, preferably polytetrafluoroethylene. Methods for making these ribbed, porous tubes are also disclosed.

Abstract: A rubber tube for dredging work embedded in and used in a pipe-line used for dredging work in the sea or river. This rubber tube has a tubular body made of rubber having a plurality of strengthening clothes embedded therein, and a plurality of metal rings axially arranged in a suitably spaced relation which are embedded in an inner peripheral surface of said tubular body and which inner peripheral surface forms a part of the inner peripheral surface of said tubular body. The metal rings have their joined surface with the tubular body placed in parallel to the axis and axial both ends thereof made thin in wall-thickness. Thereby, a contact area between the metal ring and the tubular body is increased to strengthen a bonding force and minimize a peeling off of the joined surface between both ends of the metal rings and the tubular body.

Abstract: According to the method of the invention there is wound, around a hollow body (1) and in substantially contiguous turns, a flexible strip (2), the latter strip being fixed onto the hollow body. The strip is of a material, the tensile limit of which is in excess of that of the material of which the hollow body (1) is made, and when wound around the hollow body, a tension is applied thereto which is sufficient for the stresses which may develop within the body and the winding of the strip (2) to reach their permissible maximum limits at substantially the same time, when the hollow body is used under pressure.

Abstract: Tube bundle heat exchanger of graphite, in which a multiplicity of graphite tubes are set into the tube sheets and are joined to the sheets by screw or cement joints, characterized by the feature that each tube is surrounded by at least one group of graphite fiber bundles, the latter are connected to the tube in a force-locking manner, and the distance of adjacent fiber bundles is five to ten times the diameter of the graphite fiber bundle.

Abstract: A one-piece metal wear sleeve, circumferentially homogeneous, is secured by epoxy to the outer periphery of a drill pipe. The inner diameter of the sleeve is less than the outer diameter of tool joints at the end of the drill pipe. The sleeve is centrifugally cast of two materials, including a tough, strong material such as an iron alloy at its inner portion and a hard non-abrasive wear resistant material such as alloy steel at its outer portion to resist wear on the sleeve, e.g. when it is run in open hole or in a cased hole. The outer portion is homogenous and has a smooth outer periphery so as to reduce wear on the casing when the pipe is run in cased hole.