IMPROVED TUBULAR PLASTICS OBJECTS

Abstract: Formation of tubular objects by spirally winding and seaming a relatively rigid strip of plastics material. In the prior form of this rigid plastic strip, it was difficult to control and change the diameter of the resulting tube due to the forces required to overcome the extreme frictional engagement between the interlocking portions of that prior art strip. This invention provides a sealing flap (15, 215) along one longitudinal edge (5, 25) of the strip, and an engaging surface (16, 216) along the other edge (11, 211) positioned close to but separate from the interlocking portions (8 and 12, 28, 212) of these longitudinal edges. The provision of these sealing flaps and engaging surfaces permit the interlocking portions at the edges to be designed independent of the ability of the these interlocking portions to create a fluid seal. This results in optimum operation of these interlocking portions to, for example, permit relatively rapid changes in the diameter of the tube as it is formed, as well as subsequent to its formation.

Description: IMPROVED TUBUIAR PLASTICS OBJECT'S Background of the Invention In the past, generall , spirally wound tubes formed frστi plastics have teen made frαπ soft rubber-like plastics or rαn rigid plastics that have been heated and softened and then wound into a spiral tubular configuration. In U.S. Patent Nb. 4,209,043, Julian . Meπzel, a new approach is described according to which a unique ribbed ribbon is used. The ribbon is shaped so that a spirally wound tube can be prcduced with interlocking edges of the ribbon formed by the shape of the ribs en the ribbon itself. Also known is a πachine for spirally winding such a strip to produce an elongated tubular article. In the operation of this machine, a differential prsssure or fbrca is applied to the tarts of the strip being brought into contact with one .another for interlocking the edges of the ribbon to form ' spiral joint. These parts are fed under dif erential force so that the diameter of the tube can be controlled according to the extent of the difference in hs force applied to the two interengaging edges. Also, the method of iπterengaging the two edges of the tube which are to be locked together is such that the application of this differential- force forces these interengaging edges firmly together to give an effective joint. Ho e er, it is possible to wind such strip on a mandrel. But whether the machine described above is used to produce the tube, or whether a mandrel is used, it is only possible to maintain control over relatively vary minor changes in diameter that can- occur during the winding process. It is an cσject of the present invention to provide cartain improvements to the form of the strip - * hich will allow greater changes in diameter to occur during the actual winding of the strip into a tube, and such changes in diameter can be relatively rapid σr quite slow, to give approximately a range of frcm 1" of taper to 20° or rπore of tacer. C PI t is a further object of the invention to so construct the spiral joint -chat, even when made of a ery rigid plastic for ' a tube of considerable rigidity, either with ribs as an outer part of the configuration, or the ribs as an inner part of the configuration, or both, the strip can readily be spirally wound into a tube, yet have a spiral seam of such integrity that it will seal into a watertight joint with or without the need for using a sealing compound. This special feature is achieved by using a particular type of snap lock continuous joint which is so designed that when snapped into place, by means, for example by means of a pair of pinc rollers in cπe type of the above-described tube forming machines, the spiral joint will seal and yet still allow itself to be manipulated into a larger αr smaller diameter anywhere along the length of the tube by simply applying a circumferential twisting πc eπt, applied either within the confnes of the above-described machine wiich is winding the tube, cr even after the tube has been wound. .3rief Sumrπarv → of the Invention The invention comprises an improved elongated -strip which includes a member, namely a sealing flap, wiich is generally parallel and flush with the main body portion of the strip, " and thus the inner wall of the tube made thereby, extending substantially at right angles to the portion of the locking device, namely upstanding rib; which rib is generally of the type as described in the earlier referred to U.S. Patent Sb. 4,209,043. • Εis member or sealing flap extends across the actual spiral seam joint onto the adjacent wall ≤rcm which the opposite portion of the lock, namely the socket which receives the headed rib, is extended, and in this portion of the wall there is a recess equal to the dimensions of the aforesmeπticπed extended member or sealing flap, which is of such a configuration that its extreme edge can be feathered so that it .^n to be scmshat resilient even in a rigid plastics material, so that - * 2ιen internal pressure is applied to the finished spirally wound tube, this extended member or sealing flap, with its feathered edge, will increase the seal. However, in the case where external pressure is applied, the πating surfaces can be bonded together thus providing a relatively large continuous sealinσ surface. OMFI ytD_,.«n>' In addition, the extending member or " sealing flap can have locking protuberances en its upper ■ surface that can engage in the configuration created in the surface of the mating parts. This construction results in a locking device in which the joint can slide within itself, and as changes in diameter are required it is just a natter of circαπferentially clinching the spiral tube with a differential movement within -the confines where changes of diameter are required. All these configurations can be carried cut using a rigid plastic profile that is at ambient temperature,- which of course adds to the feature because of the spring-like tension imparted to the plastics profile έie wound into a tube allowing it to naturally take a circular configuration v#ιich of course is important in order that the sliding between the two parts of the joint can occur. More specifically, to facilitate sliding along the joint, the multiple barbs of the locking device of Menzel, U.S. Patent o. 4,209,043, are eliminated in favor of a single enlarged head or hook which is received within a mating recess or socket. In addition, the components of the locking device are provided with increased clearance space to norther facilitate the sliding movement necessary to allow changing of the diameter of the tube. Hswever, the increased clearance space correspondingly increases the likelihood of fluid leakage through the joint, and to seal the joint, the sealing member, namely the sealing flap referred to above, ' can be employed. " In order, however, to enable the nature of the invention to be more fully appreciated, but without necessarily limiting the invention to the form illustrated, embodiments are shewn in the ■ accompanying drawing in which: 3rief Description of the Drawings FIG. 1 is a portion of a tube in cross section shewing the two edges of the strip which interlock to form a spiral seam. FIG. 2 shews a further a_ribcdiment of the invention similar to that of FIG. 1. Detailed Description of the Invention In FIG. 1, the body portion 1 of the strip has a number of upstanding webs 2 i it, each of which have webs or enlarged end portions 4 of preferably a "z s" configuration. That is, webs 2 O ?l cαπprise the upstanding portion 3 and the enlarged end portion 4. The functions of these webs are more folly set forth in the above- referenced U.S. Patent 5Jb. 4,209,043, which patent, to the extent it is consistent with this disclosure, is hereby incorporated by reference. Also, as in this U.S. patent, a first longitudinal edge 5 of the strip has a shorter locking rib 6. However, in this invention this rib 6 is headed and is provided with a hook 7 at its top arranged to form a ridge 3 to engage, wien wound into tubular form, a corresponding ridge 9 of extension 10 at the second longitudinal edge 11 of the body portion 1 of the strip. The web portion 3 including a socket 12 which mechanically locks over the locking rib 6. lock-web 13 projects angularly upwardly so that this part 13 can have its extreme edge 14 engage beneath the enlarged end portion 4 of the first full web 3 at the first edge 5 of the strip such as more fully set forth in the ahcve- referenced patent. An extended tapering sealing flap 15 is provided on the edge 3 of the strip and outwardly beyond the shorter locking rib 6. The sealing flap 15 is arranged to engage a mating surface 16 en the second edge 11 of the strip body portion 1 en the side of the body portion 1 opposite socket 12 when pressure is exerted z the inside of the tube. The relatively thin and resilient sealing flap 15 is forced against the πating surface 16.to increase the fluid-tight seal in the manner of a hydraulic cup washer. An cptional feature ' of the invention is the provision of a second resilient sealing flap 15* which is integral with the ' lock-web 13 and projects axialiy from the base of the lock-web 13. "With the strip joined together in a tubular form, the sealing flap 15' resiliently engages a corresponding πating surface 16' n the outer surface of the body portion 1 to seal the tube against the ingress of fluids, such as water. FIG. 2 shows a portion of a tube which is farmed with a strip which is identical to the strip shown in FIG. 1 in all respects not shown αr described herein. However, portions of the tube and the s-crip of FIG. 2 corresponding to those shown in FIG. 1 are designated y corresponding reference characters p ceeded by the rurr≤ral 2. Here, e first edge 25 of the body portion 21 of the strip includes sealing flap 215 which further includes a hook-like edge cortion 217. Also, O FI flap 215 differs from sealing flap 15 of FIG. 1 in that flap 215 also includes an elongated central portiαi 218 of generally uniform thickness interconnecting the first portion of flap 215 connected to body portion .21 with the hook portion 217. The extreme edge of flap 215 is feathered as in FIG. 1. The other edge 211 of body portiαi 21 includes a mating surface 216 comprising a recess which is shaped to conform to the upper surface of sealing flap 215. Ridge 28 of hook 27 in this embodiment faces the eroosite direction from that shown in FIG. 1. Although the operation is essentially identical, the corresponding ridge 29 of the extension 210 preferably is spaced from ridge 23 i order to provide a slight clearance. As in the embodiment of FIG. 1, the strip and tube formed thereby of FIG. 2 employs the sealing flap 215 and the mating surface 216 to provide most, if not all, of the fluid sealing ' function. The addition of the -hook portion 217 and the corresponding portion cf the mating surface 216 has a further advantage in assuring alignment and mating of flap 215 with surface 216. The slight clearance between ridges 23 and 29 permit a slight displacement of edge 211 relative to edge 25 of the strip in order ta fecilitate rapid changes in the diameter of the tube formed thereby. This slight radial displacement, either brought en by the operation cf the above-referenced machine (via the application of the differential fores as the spiral seam is farmed) σr by subsequent manipulation of the strip in the tube form, has little or no effect on th sealing functiαi provided by -tzhe sealing flap 215 and mating surface 216. It will be realized frαπ the foregoing that, so far as longitudinal move- • ment of the cne edge 5 or 25 of the strip in relation to the ether edge 11, 211 of the strip is concerned, the arrangement is such that the cne edge of the strip can move in relation to the ether . interengagi g edge of the strip to allow the changes in diameter to be effected as opposed to the more rigid orm of interlocking disclosed in U.S. Patent H~Ό . 4,209,043. In this patent, the differential movement existed primarily for the purpose of forcing the joint together and for maintaining given constant diameter, but generally could not allow any significant sliding movement thereafter without the exertion of considerable force in the form of a circumferential f.visting moment during winding cf the tube. With this invention, " however, sufficient clearance is provided between the short rib 6 or 26 and the socket 12 or 215 to allow significant sliding movement between these interengaging portions to thereby allow the diameter of the tube formed firαti the strip to be increased or decreased as desirad. The sealing flap 15 cooperates with the mating surfaca 16 to seal the joint, notwithstanding the clearance space referred to above. Clearance between the locking rib and socket of the disclosed embodiments is not necessary to the cperatiαa of the disclosed iπven- ticn. Indeed, a relatively snug fit. between the locking rd_b 6 or 26 and the socket 12 σr 212 respectively can be tolerated and in seme cases desirad, depending en the structural characteristics of the strip itself (the stiffness, etc.) , the frictional characteristics of the material used (whether the material is PVC or FTFS, each of hich ave vastly different frictioπal co-efficients) , and v&iether the tube to be formed frσα the strip is to have a relatively constant diameter cr a dia etar which rapidly changes. Tihat is most significant is that th*a provision of a sealing flap as disclosed permits these interlocking features en the edges to be designed to fulfill a mechanical inter- locking function without ragard to vjiether their ultimate design would result in an adequate fluid seal. Ihis fluid seal function, of course, is eiitirely αr at least, mostly fulfilled by the separately provided sealing flap and mating surface. EXie to the relatively flexible am/or resilient nature of the sealing flap, its sealing engagement with the ■ corresponding mating surface would effect cnly minimally the operation of the remainder of the seam structure. The sealing flaps 15, 15' , and 215 can be longitudinally corrugated at the mating surface or otherwise formed to still further increase the sealing action. Also, for example, a thermoplastic material of a softer characteristic than the rast of the strip could be extruded onto mating surfaces 16, 16*, αr 216, or sealing flaps 15, 15' , αr 215 by known techniques to aid in seaii_ng at these mutually mating surfaces. Also, sealing flaps 15, 15', and 215 could be initially formed so as to be πechanically deflected by their respective mating surfaces 16 and 16' when intarangaged in the tube forming process, thus forming a continuous seal which is biased closed. FIG. 2 sh ws sealing flap 215 in phantom in its position as initial! formed and prior to engaging mating surfaces 216. - The final sealing position is as shown. In cne embodiment of the invention, a strip of un-plasticised FVC having longitudinal edges as in FIG. 2 had a total width frαn the outer edge of lock-web 213 to the feathered edge 213 of sealing flap 215 of about 20 cm. The total thickness of the strip was about 2.5 en and the body portion 21 had a thickness of about .5 on. The thickness of the elongated central portion of sealing flap 215 was about one-half the thickness of body portion 21 or about .25 en. This sealing- flap extended outwardly past the headed rib 26 away frαn the rest of the strip about 1.8 . on. The hook porticn 217 had a maximum thickness of about .381 on. Tubes and pipes made frαπ this strip were wound on the machine described supra. The tubes could be made " to have a constant diameter ranging frαπ about 45 cm to about 122 an, and could be made to have a rapidly changing diameter as the strip was spirally wound and the edges interengaged. A solvent cement was placed within the seam structure. The resulting seam was water-tight. OMPI ~

Claims: Clai s 1. In an elongated strip of plastics material for forming articles by spiral winding said strip to overlap and interlock the w lcngitudinal edges of the body portion of the strip to form a contirt- uαus spiral seam, a first of said longitudinal edges having a locking rib frαn said bcdy porticti and a second of said longitudinal edges including a longitudinally extending socket for receiving said rib such that said.spiral seam is formed, the improvement comprising ne αf said lcngitudinal edges includes a relatively resilient sealing flap extending laterally frαπ and generally parallel to said body portion and the other of said longitudinal edges includes a mating surface for mating with said sealing La ^ 2. A strip as set forth in Claim 1 wherein said one of said longitudinal edges is said first logitudinal edge, and said sealing flap extends outwardly frαn said body portion beyond said rib. 3. A strip as set forth in Claim 1 wherein said rib is headed and includes a ridge extending along cne side ' and wherein said socket includes a corresponding ridge for engaging said ridge en said rib. 4. A strip as set forth in Claim 3 wherein said headed rib and said socket are mutually dimensioned so that, when -said headed rib is engaged in said socket, a clearance exists between said ridge and said corresponding ridge. 5. A.strip as set forth in Claim 1 wherein said sealing flap - is feathered at its extreme edge. 6. ~ ~ ι elongated scrip as set forth in Claim 2 wherein said mating surface oαupri≤es a longitudinally extending recess in said body portion. 7. ~~x elongated strip as set forth in any cne of Claims 1 through 5 wherein said strip includes a plurality of upstanding webs, each of said webs including an enlarged end portion. 8. A strip as sat forth in Cairn 7 wherein cne of said longitudinal edges further includes a lock-web, said lock-wεb being dimensioned to extend between a first of said upstanding webs adjacent said headed rib and said socket when said rib is engaged within said socket. PI 9. A strip as set forth in Claim 7 wherein said upstanding webs are generally T-shaped in cross section and wherein said longitudinally extending socket further includes an expanded end portion diπiensionally corresponding to the upper ends of said upstanding webs. 10. In a tube σ πprising an elongated strip having a body portion with two longitudinal edges, the strip being spirally wound to overlap and interlock said wo longitudinal edges, a first of said longitudinal edges including a lcck rib and a second of said longi- tudinal edges including a longitudinal socket sised to mechanically receive and engage said lock rib, the improvement comprising cne of said longitudinal edges has a sealing flap extending laterally frαn and generally parallel to said body portion, said sealing flap being resilient relative to said body portion, the other of said longitudinal edges including a mating surface en said body portion shaped to engage a surface of said sealing flap said longitudinal edge portions, are interlocked, here said tube includes an helically extending, fluid- tight seam. OMPI

Inventors: MENZEL STANLEY W, MOMINEE DAVID E, VANCE GILBERT W
Applicants: JOHNS MANVILLE, JOHNS MANVILLE CORP
Application year: 1981
Main classification: F16L11
IPC codes: B29C53, B29C65, F16L9, F16L11