NZ198816A - Elongated plastics strip for forming spirally wound tubing incorporating interlocking edges with sealing flap - Google Patents

Description

1 9881 & Priority Date(s): . lr>.. 1 t Complete Specification Filed: . i\Ciass: f:l A fl '// 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 circumferentially clinching the spiral tube with a differential movement within the confines where changes of diameter are required.

All these configurations can be carried out 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 v More specifically, to facilitate sliding along the joint, the multiple barbs of the locking device of Menzel, U.S. Patent No. 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 ccmponents of the looking device are provided with increased clearance space to further facilitate the sliding movement necessary to allow changing of the diameter of the tube. However, the increased clearance space correspondingly increases the likelihood of fluid leakage through the joint, and to seal the joint, the sealing marfoer, namely the sealing flap referred to above, can be employed.

In order, however, to enable the nature of the invention to be more folly appreciated, but without necessarily limiting the invention to the form illustrated, embodiments are shown in the accompanying drawing in which: Brief Description of the Drawings FIG. 1 is a portion of a tube in cross section showing the two edges of the strip which interlock to form a spiral seam.

FIG. 2 shows a further embodiment 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 cn it, each of which have webs or enlarged end portions 4 of preferably a "tee" configuration. That is, webs 2 198816 _4_ ccmprise the upstanding portion 3 and the enlarged end portion 4. The functions of these webs are more fully set forth in the above-referenced U.S. Patent No. 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 8 to engage, when 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 above-referenced patent.

An extended tapering sealing flap 15 is provided on the edge 5 of the strip and outwardly beyond the shorter locking rib 6. The sealing flap 15 is arranged to engage a mating surface 16 on the second edge 11 of the strip body portion 1 can the side of the body portion 1 opposite socket 12 when pressure is exerted on the inside of the tube. The relatively thin and resilient sealing flap 15 is forced against the mating surface IS to increase the fluid-tight seal in the manner of a hydraulic cup washer.

An optional feature of the invention is the provision of a second resilient sealing flap 151 which is integral with the lock-web 13 and which projects axially frcm the base of the lock-web 13. With the strip joined together in a tubular form, the sealing flap 15' resiliently engages a corresponding mating surface 161 on the cuter 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 formed with a strip which is identical to the strip shown in FIG. 1 in all respects not shown car described herein. However, portions of the tube and the strip of FIG. 2 corresponding to those shown in FIG. I are designated by corresponding reference characters preceeded by the numeral 2. Here, the first edge 25 of the body portion 21 of the strip includes sealing flap 215 which further includes a hook-like edge portion 217. Also, 198816 flap 215 differs frcm sealing flap 15 of FIG. 1 in that flap 215 also includes an elongated central portion 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 portion 21 includes a mating surface 216 ccmprising 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 opposite direction frcm that shown in FIG. 1. Although the operation is essentially identical, the corresponding ridge 29 of the extension 210 preferably is spaced from ridge 28 in 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 of the mating surface 216 has a further advantage in assuring alignment and mating of flap 215 with surface 216.

The slight clearance between ridges 28 and 29 permit a slight displacement of edge 211 relative to edge 25 of the strip in order to facilitate rapid changes in the diameter of the tube formed thereby.

This slight radial displacement, either brought on by the operation of the above-referenced machine (via the application of the differential force as the spiral seam is formed) or by subsequent manipulation of the strip in the tube form, has little or no effect on the sealing function provided by the sealing flap 215 and mating surface 216. It will be realized from the foregoing that, so far as longitudinal movement of the one edge 5 or 25 of the strip in relation to the other edge 11, 211 of the strip is concerned, the arrangement is such that the one edge of the strip can move in relation to the other interengaging edge of the strip to allow the changes in diameter to be effected as opposed to the more rigid form of interlocking disclosed in U.S. Patent No. 4,209,043. In this patent, the differential movement existed primarily for the purpose of forcing the joint together and for maintaining a 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 twisting moment during winding of the 198816 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 frcm the strip to be 5 increased or decreased as desired. The sealing flap 15 cooperates with the mating surface 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 operation of the disclosed inven-10 tion. Indeed, a relatively snug fit between the locking rib 6 or 26 and the socket 12 or 212 respectively can be tolerated and in sctne cases desired, 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 PTFE, each of which have 15 vastly different frictional co-efficients) , and whether the tube to be formed frcm the strip is to have a relatively constant diameter or a diameter 'which rapidly changes. What is most significant is that the provision of a sealing flap as disclosed permits these interlocking features on the edges to be designed to fulfill a mechanical inter-20 locking function without regard to whether their ultimate design would result in an adequate fluid seal. This fluid seal function, of course, is entirely or at least mostly fulfilled by the separately provided sealing flap and mating surface. Due to the relatively flexible and/or resilient nature of the sealing flap, its sealing engagement with the 25 corresponding mating surface would effect only minimally the operation of the remainder of the seam structure.

The sealing flaps 15, 151, 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 30 material of a softer characteristic than the rest of the strip could be extruded onto mating surfaces 16, 16', or 216, or sealing flaps 15, 15', or 215 by known techniques to aid in sealing at these mutually mating surfaces. Also, sealing flaps 15, 15', and 215 could be initially formed so as to be mechanically deflected by their respective 35 mating surfaces 16 and 16' when interengaged in the tube forming process, thus forming a continuous seal which is biased closed. FIG. 2 shows sealing flap 215 in phantom in its position as initially formed 198816 -7— and prior to engaging mating surfaces 216. The final sealing position is as shown.

In one embodiment of the invention, a strip of un-plasticized PVC having longitudinal edges as in FIG. 2 had a total width frcm the 5 outer edge of lock-web 213 to the feathered edge 218 of sealing flap 215 of about 20 an. The total thickness of the strip was about 2.5 an and the body portion 21 had a thickness of about .5 an. The thickness of the elongated central portion of sealing flap 215 was about one-half the thickness of body portion 21 or about .25 cm. This sealing flap 10 extended outwardly past the headed rib 26 away frcm the rest of the strip about 1.8 cm. The hook portion 217 had a maximum thickness of about .381 an. Tubes and pipes made from this strip were vound on the machine described supra. The tubes could be made to have a constant diameter ranging frcm about 45 cm to about 122 cm, and could be made to 15 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.

I98S16

Claims (4)

1. WHAT WE CLAIM IS: 1. In an elongated strip of plastics material for forming articles by spiral winding said strip to overlap and interlock the two longitudinal edges of the body portion of the strip to form a continuous spiral seam, a first of said longitudinal edges having a locking rib upstanding from said body portion and a second of said longitudinal edges including a longitudinally extending socket for receiving said rib such that said spiral seam 1s formed, the improvement comprising one of said longitudinal edges includes a relatively resilient sealing flap extending laterally from and generally parallel to said body portion and the other of said longitudinal edges Includes a mating surface for mating with said sealing flap, said strip having a plurality of upstanding webs, each of said webs Including an enlarged end, and with the other of said longitudinal edges further Including a lock-web, said lock-web being dimensioned to extend between a first of said upstanding webs adjacent said headed rib and said socket when said rib 1s engaged within said socket.

2. A strip as set forth in Claim 1 wherein said one of said longitudinal edges 1s said first longitudinal edge, and said sealing flap extends outwardly from said body portion beyond said rib.

3. A strip as set forth 1n Claim 1 wherein said rib 1s headed and Includes a ridge extending along one side and wherein said socket Includes a corresponding ridge for engaging said ridge on 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 1s engaged 1n said socket, a clearance exists between said ridge and said corresponding ridge. 1S8816 -9- 6. An elongated strip as set forth in Claim 1 wherein said mating surface comprises a longitudinally extending recess in said body portion. 7. An elongated strip as set forth in any one 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 set forth in any one of the preceding claims wherein said upstanding webs are generally T-shaped in cross section and wherein said longitudinally extending socket further includes an expanded end portion dimensionally corresponding t\ the upper ends of said upstanding webs. 9. In a tube comprising an elongated strip having a body portion with two longitudinal edges, the strip being spirally wound to overlap and interlock said two longitudinal edges, a first of said longitudinal edges including a lock rib and a second of said longitudinal edges including a longitudinal socket sized to mechanically receive and engage said lock rib, the improvement comprising one of said longitudinal edges has a sealing flap extending laterally from 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 on said body portion shaped to engage a surface of said sealing flap when said longitudinal edge portions are interlocked, whereby said tube includes an helically extending, fluid-tight seam and wherein said has a plurality of upstanding webs, each of said webs including an enlarged end and one of said longitudinal edges further includes a lock-web, said lock-web being dimensioned to extend between a first of said upstanding webs adjacent said heade rib and said socket when said rib is engaged within said socket. 188816 -10- 10. A strip as claimed in any one of claims 1 to 8 substantially as hereinbefore described with reference to any of the accompanying drawings. 11. A tube as claimed in claim 9 substantially as hereinbefore described with reference to any of the accompanying drawings. DATED THISY~7*k DAY OF A. J. PARK & SON AGENTS FOR THE APPLICANTS