Abstract: A combination rubber/composite hose comprising an inner composite hose section and a surrounding outer rubber textile reinforced hose section sealingly fastened together at their ends, but free to shift longitudinally and bend with respect to each other.

Abstract: A pipe formed from a continuous, cold rolled, lock seam quality, sheet steel, having a spiral rib. The pipe may be protected by an abrasion or corrosion resistant coating. The pipe is normally used for storm drains, culverts, sewer lines or HVAC. A closed spiral rib formed in the pipe wall adds strength to the wall, while maintaining a smooth inner wall that promotes exceptionally good fluid flow. The pipe has a smooth interior surface with outwardly projecting structural ribs of helical configuration throughout the length of the pipe.

Abstract: A highly flexible and hydrolysis and burst resistant, coolant conduit comprising a plurality of layers of different polymer compatible with one another at the contact surfaces of the layers, the conduit being at least partially corrugated and at least some of the individual adjacent corrugations being connected to each other by at least one crossbar or rib.

Abstract: A flexible lamp tube includes an elongated foam member, a metal wire, and an accordion plastic pipe. The foam member has a central bore extending through the length of the foam member. The metal wire extends through the central bore of the foam member. The accordion plastic pipe is sleeved around the foam member.

Abstract: Heat-reflective and protective sleeving is provided which has both an interior and an exterior convoluted profile. The sleeving includes layers of polymeric material, insulative material and reflective material which is assembled together into the convoluted profiles. A method and apparatus are provided for manufacturing the convoluted sleeving by wrapping a fabric-backed foil over a convoluted polymeric tubing while pushing the laminate into the grooves and over the crests of the convoluted profile of the polymeric tubing. In the preferred arrangement which is shown, this procedure is facilitated by the use of a plurality of worm gears that rotate substantially in unison in order to pull the convoluted polymeric tubing through an area defined by the worm gears, while simultaneously forming the convolutions in the laminate at the same time that the laminate is engaged with the external convoluted surface of the polymeric tubing.

Abstract: A flexible hose assembly for conveying gas comprising an inner tube member having a reinforcing spring coil that selectively functions as an electric heater engaging the inner surface and an outer flexible tube member having its head and outlet ends closed upon those of the inner member. A second reinforcing spring coil surrounds the outer surface of the outer member such that a dead air space or insulating chamber is formed between the two flexible tubes. Superior insulation, flexibility, energy consumption, weight and strength characteristics are achieved. A temperature responsive electrical device can be mounted near the outlet end of the inside wall of the inner tube with leads extending through the hose exiting the head end for connection to a controller for controlling an external heating or cooling system or for controlling electric power applied to the inner spring coil for directly heating the flowing gas for delivering temperature controlled heated gas to the end user system.

Abstract: A system for conveying a fluid through an under-the-ground location and method of making the same are provided, the system comprising a primary flexible conduit for conveying the fluid therethrough and having an outer peripheral surface and an inner peripheral surface, and an outer secondary conduit having at least a portion of the primary conduit removably disposed therein and having an inner peripheral surface and an outer peripheral surface that engages the ground in the under-the-ground location thereof, the secondary conduit having the inner peripheral surface thereof comprising a helically disposed and inwardly directed projection thereof that engages the outer peripheral surface of the primary conduit in a spiral manner and cooperates therewith to define a helically disposed passage that extends therebetween throughout substantially the entire engagement area thereof.

Abstract: A pressure-resistant helical corrugated pipe comprises a helical corrugated pipe wall formed by a top portion, opposite side wall portions and a bottom portion; and a continuous thin metal belt plate disposed at least in the top portion or the bottom portion and also in part or the whole of the opposite side wall portions. The metal belt plate serves as a constitent element for the pipe wall. A portion of the metal belt plate disposed at the top portion or the bottom portion has one or more reinforcement ribs and a connective portion for the metal belt plate is integrally formed of a synthetic resin material or rubber material.

Abstract: A system for conveying a fluid through an under-the-ground location and method of making the same are provided, the system comprising a primary flexible conduit for conveying the fluid therethrough and having an outer peripheral surface and an inner peripheral surface, and an outer secondary conduit having at least a portion of the primary conduit removably disposed therein and having an inner peripheral surface and an outer peripheral surface that engages the ground in the under-the-ground location thereof, the secondary conduit having the inner peripheral surface thereof comprising a helically disposed and inwardly directed projection thereof that engages the outer peripheral surface of the primary conduit in a spiral manner and cooperates therewith to define a helically disposed passage that extends therebetween throughout substantially the entire engagement area thereof.

Abstract: A system for conveying a fluid through an under-the-ground location and method of making the same are provided, the system comprising a primary flexible conduit for conveying the fluid therethrough and having an outer peripheral surface and an inner peripheral surface, and an outer secondary conduit having at least a portion of the primary conduit removably disposed therein and having an inner peripheral surface and an outer peripheral surface that engages the ground in the under-the-ground location thereof, the secondary conduit having the inner peripheral surface thereof comprising a helically disposed and inwardly directed projection thereof that engages the outer peripheral surface of the primary conduit in a spiral manner and cooperates therewith to define a helically disposed passage that extends therebetween throughout substantially the entire engagement area thereof.

Abstract: A flexible hose construction and method of making the same are provided, the flexible hose construction comprising an inner corrugated hose made of polymeric material and having a plurality of outwardly convex projections with recesses therebetween and extending from one end thereof to the other end thereof, an outer sleeve of reinforcing material disposed in telescoping relation on the inner hose, and a tube of polymeric material disposed between the sleeve of reinforcing material and the inner hose and extending in a generally straight-line manner from projection to projection of the inner hose so as to tend to prevent the sleeve of reinforcing material from entering into the recesses of the inner hose an amount that would tend to substantially reduce the flexibility characteristics of the inner hose.

Abstract: In order to obtain optimum absorption and compensation of relative movements in an exhaust gas system while at the same time avoiding a transmission of movement and the occurrence of a resonance phenomena, a conduit element is proposed having a bellows and a metallic braided or knit jacket. The bellows is fashioned as a highly flexible bellows with an all around absorption of movement. The jacket is applied to the bellows so that the jacket solely follows substantially the wave crests of the bellows.

Abstract: A hydraulically efficient metal pipe particularly adapted for use in storm drain and sanitary sewer applications which is adapted for use with a self-supporting interior inert protective lining. The pipe has a channeled wall defining a plurality of outwardly projecting structural ribs and a hydraulically smooth interior surface. The ribs are preferably of a helical configuration and the channels which are formed interiorly thereof are generally either square or rectangular in cross-section and are open along the interior surface of the pipe. The walls defining the ribs can be tapered inwardly to form triangular-shaped channels so as to define an anchor throughout the length of the pipe for securing thereto a smooth interior lining of corrosion-resistant protective material.

Abstract: A leaching chamber for burial in the ground includes non-symmetrical corrugations extending laterally across the leaching chamber. Each corrugation has a ridge and a shoulder with the ridge being higher than the shoulder and sloping down from the ridge to the shoulder. Additionally, the ridge of each corrugation is also wider than the shoulder. The corrugations are oriented relative to each other such that the ridge of each corrugation is adjacent to the shoulder of an adjoining corrugation.

Abstract: A hose including a number of circumferential corrugations substantially parallel to one another when the hose is unbent, separated by grooves, and connected in a longitudinal direction by ribs, so that each corrugation is connected to at least one adjacent corrugation. The ribs form at least two groups of angularly-offset ribs, and the ribs in the first group alternate with the ribs in the second group.

Abstract: A pressure-withstanding synthetic resin pipe includes an inner wall of a synthetic resin and an outer wall of a synthetic resin. A metallic reinforcement belt plate having an inverted U-shaped sectional contour and a flat, metallic belt plate having ends bent to form engagement portions and adapted to be engaged with open end portions of the metallic reinforcement belt plate are disposed between the inner wall and a protruded corrugation portion of the outer wall.

Abstract: Soil/metal supporting structures commonly include panel sections having a short radius of curvature in the range of 750 mm to 2,500 mm. In such soil metal supporting structures the panels are of heavy gauge in the range of 2 mm to 10 mm thickness. Usually, expensive tooling and forming techniques are required to cold form the heavy gauge material into a curved shaped having such short radius. Such expensive techniques have been eliminated by this invention by virtue of the improvements comprising:a) the panels have a high degree of ductility before being cold formed, such high degree of ductility being determined by a ratio of specified minimum yield strength to specified minimum tensile strength equal to or less than 0.

Abstract: A system for conveying a fluid through an under-the-ground location and method of making the same are provided, the system comprising a primary flexible conduit for conveying the fluid therethrough and having an outer peripheral surface and an inner peripheral surface, and an outer secondary conduit having at least a portion of the primary conduit removably disposed therein and having an inner peripheral surface and an outer peripheral surface that engages the ground in the under-the-ground location thereof, the secondary conduit having the inner peripheral surface thereof comprising a helically disposed and inwardly directed projection thereof that engages the outer peripheral surface of the primary conduit in a spiral manner and cooperates therewith to define a helically disposed passage that extends therebetween throughout substantially the entire engagement area thereof.

Abstract: A flexible hose particularly suitable for use with automatically operated swimming pool cleaners, the hose being blow moulded from suitable plastics material such that separate lengths can be cut with each length having an integral coupling component at each end. Preferably there will be a male component at one end and a female component at the other end.

Abstract: A flexible air duct is connected to a dishwashing unit for conducting hot moist air therefrom. Opposite ends of the duct communicate with the dishwashing unit for conducting condensed water back thereto, while hot air is discharged through an air outlet disposed intermediate the ends of the duct. The duct is of oblong cross-section and includes cooling fins on one side.

Abstract: An air duct is disclosed which includes a tubular member formed from a metal sheet. A paper is disposed around an outer periphery of the tubular member for preventing condensation droplets condensed on the tubular member from dripping, and an adhesive is interposed between the tubular member and the paper to adhesively secure the tubular member and the paper. Furthermore, a paper for an air duct, adapted to be secured to an outer periphery of the air duct, is disclosed. The paper is produced from a material including a papermaking pulp and is characterized by the following: a wet strength of at least 0.3 kgf/15 mm, a critical value for dripping of water droplets of at least 45 g/m.sup.2, and a basis weight of 40 to 5000 g/m.sup.2.

Abstract: A pressure-resistant helical corrugated pipe comprises a helical corrugated pipe wall formed by a top portion, opposite side wall portions and a bottom portion; and a continuous thin metal belt plate disposed at least in the top portion or the bottom portion and also in part or the whole of the opposite side wall portions. The metal belt plate serves as a constituent element for the pipe wall. A portion of the metal belt plate disposed at the top portion or the bottom portion has one or more reinforcement ribs and a connective portion for the metal belt plate is integrally formed of a synthetic resin material or rubber material.

Abstract: Flexible hose or tube comprises a hose body and a plurality of ribs extending radially outwardly from the outer periphery of the hose body. The ribs are of annular shape and are axially spaced with respect to each other. The hose body wall is of relatively small thickness as compared to the thickness of the ribs. The hose may be integrally made from a thermoplastic caoutschuc or rubber and exhibits a high degree of flexibility due to its relative softness, while the shape and structure of the ribs provide a high degree of resistance against lateral bending or buckling of the tube.

Abstract: An avionic tray is fixed to a shelf and comprises a base plate, side rails and a back plate. At least a forward end of the base plate of the tray is reinforced by a reinforcing plate fixed to the upper surface of the base plate. The part of the base plate carrying the reinforcing plate is stepped downwards so that the upper surface of the reinforcing plate is level with the surface of the base plate to the rear of the reinforcing plate. Fixing holes are provided in the reinforcing plate and the base plate for fixing the tray to the shelf by means of screws whose heads are housed in housings in the reinforcing plate.

Abstract: A method and apparatus for preventing casing damage due to high axial loading in a well as a result of compaction of the surrounding earth formations. The method consists of providing specially sized and located grooves on both the inside and outside diameters of a section of well casing. The grooves are designed and spacers may be used in some grooves to ensure symmetrical deformation of the casing when subjected to a compressive loading.

Abstract: An arrow and its shaft wherein the shaft has a longitudinal axis extending between the arrowhead and the arrow nock. Flight feathers are disposed on the shaft near the nock to guide and rotate the arrow during flight. The shaft is hollow having longitudinally extended flutes to strengthen and stiffen the shaft. Strengthening and stiffening the shaft permits a smaller diameter shaft with a thinner wall thickness to be used to lighten the shaft and arrow without sacrificing the strength and stiffness of the arrow.

Abstract: A dust seal connector for accommodating the relative movement between the enclosed, moving screen box of a screening machine, and a fixed particle inlet or outlet conduit connected to the screen box. The relative movement occurs as sliding motion between a suspended flat slide plate and a wear ring below the slide plate, with which the plate is facially engaged. The plate is connected upwardly by an enclosed particle passage to the conduit or box member from which it is suspended, and communicates downwardly with an opening in the ring for the flow of particles. In a preferred embodiment the particles flow through an axially compressed corrugated sleeve which connects the plate to the member from which it is suspended, compression of the sleeve biasing the ring and plate together to maintain a sliding dust seal between them.

Abstract: Method for producing a composite pipe made of material which is resistant to an internal and/or external environment at a specific internal and/or external temperature and a specific internal and/or external pressure, the pipe being provided with a reinforcement made of material which at very high temperatures is resistant to compressive and tensile forces occurring during the use of the composite pipe, which reinforcement is provided with a diffusion barrier, wherein the reinforcement provided with a diffusion barrier is applied by welding or fusing to the outside of the pipe.

Abstract: A pressure-resistant helical corrugated pipe comprises a helical corrugated pipe wall having a top portion, opposite side wall portions and a bottom portion; a continuous thin metal belt plate of a generally U-shaped transverse cross-section which is disposed in one of the top portion and the bottom portion and also in at least part of the opposite side wall portions extending from the one of the top portion and the bottom portion; another metal belt plate of a flat configuration being disposed in the other of the top portion and the bottom portion and disposed out of contact with the thin metal belt plate; and connective belt regions provided between the two metal belt plates in which the metal belt plates are absent, the connective belt regions being made of a synthetic resin or rubber to interconnect the two metal belt plates.

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 method and apparatus for preventing casing damage due to high axial loading in a well as a result of compaction of the surrounding earth formations. The method consists of providing specially sized and located grooves on both the inside and outside diameters of a section of well casing. The grooves are designed and spacers may be used in some grooves to ensure symmetrical deformation of the casing when subjected to a compressive loading.

Abstract: A coupling including a first hollow section having longitudinal corrugations and a second section having an aperture therein. The coupling is made according to the method including the steps of inserting the first hollow section having longitudinal corrugations into the aperture in the second section so that at least a portion thereof including the corrugations extends into and beyond the aperture, the first hollow section being selected so that its cross-sectional length exceeds the perimeter of the aperture. At least the portion of said first hollow section beyond said aperture is then expanded so as to smooth the corrugations, while avoiding stretching the wall of the first hollow section whereby the exterior size of the hollow section exceeds the entire perimeter of the aperture and the cross-sectional length remains unchanged.

Abstract: A corrugated cardboard structure for use in wrapping of goods during shipment. A core cardboard of wave shape is glued to at least one cardboard surface sheet at crests of the waves of the core cardboard, with at least one non-glued portion of the cardboard surface sheet adjacent to one of the crests being between two glued portions. The corrugated cardboard structure of the invention can be formed into an open-ended hollow tubular configuration for placement around goods during shipment of the goods. Alternatively, the cardboard structure can be formed into a rectangular box for containment of goods during shipment or storage of the goods.

Abstract: A pressure-resistant helical corrugated pipe comprises a helical corrugated pipe wall having a top portion, opposite side wall portions and a bottom portion; a continuous thin metal belt plate of a generally U-shaped transverse cross-section which is disposed in one of the top portion and the bottom portion and also in at least part of the opposite side wall portions extending from the one of the top portion and the bottom portion; another metal belt plate of a flat configuration being disposed in the other of the top portion and the bottom portion and disposed out of contact with the thin metal belt plate; and connective belt regions provided between the two metal belt plates in which the metal belt plates are absent, the connective belt regions being made of a synthetic resin or rubber to interconnect the two metal belt plates.

Abstract: Insulating the exhaust pipe of an internal combustion exhaust system by sliding a flexible insulated tube over the exhaust pipe. The tube comprises concentrically arranged inner and outer corrugated stainless steel tubes, with the annulus between the corrugated tubes filled with refractory fiber insulation. The wall thickness of the corrugated tubes is in the range of 0.002 inch and 0.004 inch, which provides the insulated tube with sufficient flexibility to be trained over the angled portions of the exhaust pipe. The contact between the corrugations and the pipe assists in holding the insulated tube in place. The inner tube may extend beyond the outer tube and be flared back to the outer tube to enclose the insulation and facilitate movement of the insulated tube over the exhaust pipe. Alternatively, the insulation may also be sealed by end caps.

Abstract: A rectangular, flexible duct serves as an alternative to galvanized sheet metal duct work installed in homes by utilizing corrugated semi-rigid top and bottom walls with relatively flexible connecting side walls so that the duct may be easily rolled and stored. But when unrolled, it is fastened, for example, between floor joists of a home by use of an overhanging flange formed by one of the top or bottom walls. The duct walls are made of heat resistant plastic suitable for heating and ventilating. Rigidity is provided in the top and bottom walls by corrugations or ribs formed in the plastic.

Abstract: A rollformed tubular vehicle bumper beam is fabricated of ultra-high strength steel and has a plan view sweep value of more than 10. The bumper beam has a cross-sectional configuration comprising an upper wall, a lower wall, an outer wall, and an inner wall. Inner portions of the upper and lower walls are angled, respectively, downwardly and upwardly. This configuration permits fabrication of the bumper beam by rollforming without stretching the outer wall to a point where it would be damaged.

Abstract: The wall (5) of the encasing tube (1) includes spiralling protrusions (3, 4). First protrusions (3) and second protrusions (4) run either in different directions or in the same direction but at different pitches. The encasing tube is used for enclosing tensioning cable (2) in concrete structures. By means of the particular arrangement of the protrusions, the flow properties of the grout are improved, air bubbles are virtually eliminated during injection, and the bonding properties of tensioning cables are improved by means of large bonding zones while respecting the required high fatigue strength.

Abstract: An inner duct is disclosed which can fit inside a duct and extend along a length thereof for receiving communication cable, particularly a light-guide cable. The inner duct has a continuous side wall with protruding ribs on the inside and outside surfaces to maintain an effective supply of lubricant during the installation of the inner duct and cable in the inner duct. The ribs on the inside surface of the inner duct guide the cable during the placement operation. It is preferred to install a plurality of inner ducts into a duct during which the ribs on the inner duct interlock with one another to prevent spiraling. The ribs also facilitate the dissipation of heat due to friction and ambient sources of heat.

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 flat strip-like metallic material having both surfaces coated with a first synthetic resin layer is passed between plural pairs of upper and lower rollers so that a U-shaped recess is formed at the central portion in the longitudinal direction of the strip material and ring-like projection at both edges of the strip material. Then, the strip material is bent into a spiral form. The spirally wound strip material is passed to a transferring means and first, second and third extruders to extrude molten resin and first, second and third pressing rollers operating in association with the repsective extruders, whereby a second synthetic resin layer is formed at the outer circumferential portion of the adjoining edges of the sprially wound strip material, a third synthetic resin layer is formed on the back side of the recess portion of the same, and a fourth synthetic resin layer is formed on the outer circumferential surface of the recess portion and the adjoining edges of the spirally wound strip material.

Abstract: A shape retention hose contruction and method of making the same are provided, the hose construction comprising a length of flexible tubular hose formed mainly of polymeric material and having opposite end portions and an intermediate body portion that defines internal and external peripheral surfaces of said hose, and a shape retention unit carried by the hose and being adapted to generally retain the shape of the hose construction when the hose and its carried shape retention unit are jointly bent into a particular shape, the shape retention unit comprising a deformable tubular member having opposed ends and a continuous sidewall between the ends that defines an internal and external peripheral surface of the tubular member, the hose and tubular member being telescoped together with the surfaces of the tubular member being disposed closely adjacent the surfaces of the hose.

Abstract: Disclosed herein is a hydraulically efficient metal pipe particularly adapted for use in storm drain and sanitary sewer applications which is adapted for use with a self-supporting interior inert protective lining. The pipe has a channeled wall defining a plurality of outwardly projecting structural ribs and a hydraulically smooth interior surface. The ribs are preferably of a helical configuration and the channels which are formed interiorly thereof are generally either square or rectangular in cross-section and are open along the interior surface of the pipe. The walls defining the ribs can be tapered inwardly to form triangular-shaped channels so as to define an anchor throughout the length of the pipe for securing thereto a smooth interior lining of corrosion-resistant protective material.

Abstract: Strips for use in forming flexible hoses from helically wound convolutions of the strip are disclosed, in which the strip has a substantially U-shaped body including a pair of radially projecting, spaced-apart walls connected by a transverse wall, and in which the body is produced from a polymeric material having a predetermined Young's modulus, and substantially the entire surface of the body is composed of that polymeric material, so that adjacent portions of the body can be directly bonded together to form a flexible hose upon the helical winding of the strip. Furthermore, supports are embedded in the pair of walls in order to reinforce the walls and permit the body to substantially retain its shape upon the application of external forces thereto. Methods for making flexible hoses from these strips are also disclosed.

Abstract: Strips for use in forming flexible hoses from helically wound convolutions of the strip are disclosed, in which the strip has a substantially U-shaped body including a pair of radially projecting, spaced-apart walls connected by a transverse wall, and in which the body is produced from a polymeric material having a predetermined Young's modulus, and substantially the entire surface of the body is composed of that polymeric material, so that adjacent portions of the body can be directly bonded together to form a flexible hose upon the helical winding of the strip. Furthermore, supports are embedded in the pair of walls in order to reinforce the walls and permit the body to substantially retain its shape upon the application of external forces thereto. Methods for making flexible hoses from these strips are also disclosed.

Abstract: A pipe connecting element serves to connect pipes, which consist essentially of a continuous inner pipe and connected with it, extending radially outwards, projections, which serve to stiffen the pipe. To make such a pipe connecting element suitable to the light construction concept of double walled pipes or corrugated pipes on the one hand and achieve high load capacity in the direction of the pipe axis and good hydraulic properties on the other, the pipe connecting element consists of connected with each other sections, which are constructed by a core pipe and a jacket pipe. Adjacent sections are connected on their butt joint surfaces in such a manner that the core pipes and the jacket pipes each of these adjacent sections are connected with each other. Additionally, the core pipe and the jacket pipe of each section are firmly connected with each other.

Abstract: A method for producing a laminated composite structure is provided, the structure including a tubular reinforcement braid, of which the wall is folded over to form corrugations of wrinkles which constitute layers of fibrous material superposed in axial direction, each layer extending from the inside surface to the outside surface of the structure.

Abstract: A flexible hard pipe in which over a soft inner pipe wall a hard belt-like member is helically wound. The belt-like member has a double-hook shape in which a flat inner surface is fused to the inner pipe wall. A raised hook portion overlaps a hook portion of the fused portion of a neighboring wrap.

Abstract: A spirally wound corrugated pipe of sheet steel or the like is provided with outwardly convex corrugations which are spaced apart, with a flat portion of single wall thickness between adjacent corrugations. In one embodiment, the corrugation have a pitch of five inches and a height of one-half inch; in another embodiment, the pitch is six inches and the height is one inch.

Abstract: Proximal end connector units, by which medico-surgical tubes may be attached to breathing circuits or like fluid flow devices in a manner that mitigates interference with operations being performed on patients intubated with the MS tubes, comprising a straight, rigid, cylindrical distal end portion, a straight, rigid, cylindrical proximal end portion, a central tubular portion joining the distal end portion to the proximal end portion, the central tubular portion being bendable in an arc of at least 180.degree. without diminution of its effective lumen, such proximal end portion, distal end portion and central tubular portion all being integral and formed of the same thin, plastic material, the central tubular portion comprising a plurality of circumferential, angular segments each consisting of a pair of sides that are of unequal length, the central tubular portion being compressed lengthwise by having the shorter side in each segment folded back under its longer side.