STRIPS FOR THE FORMATION OF HELICAL PIPES

Abstract: A strip for the formation of helical pipes by winding said strip into a helical shape. The strip (1) has a narrow, long, flat body, and on one edge of said body, there is a joining rib (3) that is provided continuously in the longitudinal direction of the strip and that is perpendicular with respect to the strip; on the other edge of the body, there is provided a socket (4) into which said joining rib can be inserted. There is a slanting rib (5) that extends to the outside from the lower portion of said socket. When the joining rib is inserted into the socket, the connecting part (51) that connects the socket with the slanting rib and the part connecting with said joining rib of the body of the said strip form a space therebetween in which a soft and elastic packing (7, 8) is provided.

Description: STRIPS FOR THE FORMATION OF HELICAL PIPES Technical Field This invention relates to a strip that can be wound into a helical pipe. In particular, it relates to a strip that is suitable for the formation of a helical pipe that is inserted into a preexisting pipe for the purpose of rehabilitation of the aging preexisting pipe that has damaged. Background Art In recent years, in place of conventional synthetic resin pipes made by the extrusion method, a helical pipe that is made by winding a strip of synthetic resin into a helical form is used for ducts, transport, water supply, sewage, and the like. A method has been proposed for the rehabilitation of pipes in a sewer system in which the above-mentioned strip can be wound into a helical pipe within a manhole. The helical pipe is introduced steadily, and the space between the helical pipe and the pipes in the sewer system is filled with a backing agent such as mortar, etc. This kind of a helical pipe has the following advantages: (1) The strip that has been wound in the form of a coil can be transported to the construction place, and by the use of simple machinery for forming tubes (such as that disclosed in Japanese Laid-Open PCT Patent Application 55-61434, Japanese Laid-Open PCT Patent Application 57-501229, etc.), it can be formed into a helical pipe by simply winding it into a helical form at the construction place. Thus, transportation of the prepared pipe is not necessary, thereby attaining the minimization of transportation cost. (2) The production of a helical pipe of the desired diameter is easy. The strip that is used to form this kind of a helical pipe is disclosed by, for example, Japanese Laid-Open Patent Application 54-65780, in which the strip has, on one edge of its long, narrow, flat body, a joining rib that extends in the longitudinal direction of the strip, and it has on the other edge a socket that also extends in the longitudinal direction of the strip. There are a number of reinforcing ribs on the body, positioned between said joining rib and socket, which extend in the longitudinal direction of the strip. A flange is provided on the tip of each of these reinforcing ribs. This strip also has an auxiliary rib that extends outwards from the socket mentioned above. When this kind of a strip is formed into a helical pipe by being wound into helical form, there are methods such as those disclosed by Japanese Laid-Open PCT Patent Application 57-501229 in which the socket and the joining rib will be reliably joined, one of which methods (called the adhesion method) involves the application of a solvent-type adhesive to the surfaces of the joining rib immediately before the strip is formed into a helix, and then the joining rib is joined into the socket; and the other of which methods (called a fusion-adhesion method) involves the application of heat to the joining rib and the socket of a strip that is made of synthetic resin, and the fitting together of the joining rib and the socket in a fused condition. Moreover, Japanese Laid-Open Utility Model Application 61-35083 discloses a strip in which a packing made of a soft, flexible material is positioned either on the outer surface of the joining rib or on the inner surface of the socket in the longitudinal direction in a continuous way. However, in the above-mentioned adhesion method in which a solvent-type adhesive is applied, if the strip is made of, for example, rigid vinyl chloride resin, environmental stress cracking may arise because of the solvent that is included in the adhesive, which causes the disadvantage of decreased mechanical strength of the pipe. Moreover, because the adhesive does not harden instantaneously, the force that is exerted on the strip when it is being formed into a pipe causes the disadvantage that the diameter of the helical pipe will become greater. Also, when the safety of the workers and environmental hygiene are considered, it is necessary to provide for a container of the adhesive (such as a container that will not explode and that will be air-tight), which has the disadvantage of high cost for equipment. When the joining rib and the socket are fused together by the application of heat in the fusion-adhesion method, it is necessary to have a heating apparatus, which has the disadvantage of high cost for equipment. Besides, the parts of the strip to be heated are only the socket and the joining strip, so uneven stresses remain in the pipe wall of the helical pipe, which causes the disadvantage of decreasing the mechanical strength of the helical pipe. In addition, with either of the two methods, the adhesive method and the fusion-adhesion method, when the strip is wetted by sewage, etc., there are undesirable effects, and so when a strip is wound inside a manhole so as to form a helical pipe, it is necessary to prevent the flowing of sewage, etc., within the manhole at that time. With the packing method mentioned above, there is no undesirable effect even when the strip is wetted, so when manufacture of the helical pipe takes place in. a manhole, there is no need to prevent sewage from flowing through the manhole. However, the manufacture of the strip is difficult so that the packing will firmly adhere to both the outside surface of the joining rib and the inside surface of the socket. In addition, when the outside surface of the joining rib and the inside surface of the socket are being brought together, force is created to push the packing aside, and the packing may be peeled from the outer surface of the joining rib or from the inner surface of the socket, ending up in a position other than that in which it should be fixed, and this causes the disadvantage that the two parts will not readily come together. Further, when this kind of a strip is being formed into a helical pipe, the packing that is placed between the joining rib and the socket receives almost no pressure at all. For this reason, because of the force exerted on the strip when it is being formed into a pipe, the joining rib and the socket, when brought together, may slide relative to each other in the longitudinal direction of the strip. If the two slide relative to each other, the diameter of the spiral pipe that is being formed will become larger. Disclosure of Invention The strip for the formation of helical pipes of this invention, which overcomes the above-discussed and numerous other disadvantages and deficiencies of the prior art, comprises a long, narrow, flat body, a joining rib at one edge of said body that is perpendicular with respect to the strip and continuous in the longitudinal direction of said strip, a socket at the other edge of said body into which said joining rib is fitted, said socket being continuous in the longitudinal direction of said strip, a slanting rib that slants in the outside direction from the lower portion of said socket, said slanting rib being continuous in the longitudinal direction of said strip, and a soft and elastic packing that is disposed continuously in the longitudinal direction of said strip in such a manner that said packing is positioned in a space formed between the connecting part connecting said socket with said slanting rib and the part connecting to said joining rib of the body of said strip in the case where said strip is wound into a helical shape so as to fit said joining rib into the inside of the socket, so that said packing is compressed between the two parts. In a preferred embodiment, the packing is disposed on at least one of these two: said connecting part connecting the socket with the slanting rib and said part connecting with the joining rib of the body of said strip. In a preferred embodiment, the packing is disposed on one of these two: said connecting part connecting the socket with the slanting rib and said part connecting with the joining rib of the body of said strip t and one of said two parts has a rollette- processed surface thereon into which said packing is taken. In a preferred embodiment, at least one reinforcing rib that is perpendicular with respect to the body of said strip is continuously disposed in the longitudinal direction of said strip at a fixed distance from said joining rib, and when said joining rib is inserted into said socket, said slanting rib is engaged with said reinforcing rib in such a manner that said reinforcing rib stops said slanting rib. Thus r the invention disclosed herein makes possible the objectives of (1) providing a strip that can be used to manufacture helical pipes without the use of an adhesive and without the application of heat fusion to one part of the strip; (2) providing a strip that can be used to manufacture helical pipes even in a manhole in which there is something flowing, such as sewage, etc; and (3) providing a strip that can be used to manufacture helical pipes in which there is no danger of the joining rib and socket sliding with respect to each other at the time of the formation of the helical pipe because of the force that is exerted on the strip, so that a helical pipe of a uniform diameter can be readily manufactured. Brief Description of the Drawings This invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings as follows: Figure 1 is a perspective view of an outline of one part of a strip of this invention. Figure 2 is a perspective view of an outline of one part of another strip of this invention. Figure 3 is a front sectional view of the joined part of a helical pipe formed from a strip of this invention. Best Mode for Carrying Out the Invention Example As shown in Figure 1, a strip 1 of this invention is manufactured from a rigid synthetic resin such as rigid vinyl chloride, etc. The strip 1 has a long, flat, narrow body 2, and on one edge of the body 2, there is provided a continuous joining rib 3 in the longitudinal direction of the strip 1. On the other edge of the body 2, there is a continuous socket 4 that is perpendicular to the body 2 along the longitudinal direction. The joining rib 3 has a perpendicular part 31 that is perpendicular with respect to the body 2 of the strip 1, and a joining part 32 that is provided at the top of the said perpendicular part 31. The joining part 31 is circular in cross-section. The socket 4 is made in order to fit the joining rib 3 into the inside of the socket 4, and the inside surface of the said socket 4 is formed in order to correspond to the outside shape of the joining rib 3. The base of the socket 4 is provided with a connecting part 51 that is connected to a slanting rib 5, which extends slanting to the outside, and which is provided continuously in the longitudinal direction of the strip 1. In the space between the joining rib 3 and the socket 4 of the body 2, there are a number of reinforcing ribs 6 that are at a fixed distance from each other, and that are continuous in the longitudinal direction of the strip 1. Each reinforcing rib 6 is Tshaped in c-ross-section, and constituted by a perpendicular part 61 that is perpendicular with respect to the body 2 and a flange 62 placed on the top of each perpendicular part 61. When the body 2 is wound into a spiral so as to bring together the socket 4 and the joining rib 3, the top of the slanting rib 5 is stopped by the flange 62 of the reinforcing rib 6 that is positioned next to the joining rib 3. When the body 2 is wound into helical form and the joining rib 3 is fitted into the socket 4, the connecting part 51 connecting the said socket 4 to the slanting rib 5 faces the part 21 that connects to the joining rib 3 of the body 2. A packing 7 that is flat is attached to the said connecting part 51. A packing 8 that is also flat is attached with adhesive to the said connecting part 21. When the body 2 is wound into a helical form as mentioned above, the packings 7 and 8 are positioned in the space between the connecting part 51 and the part 21 of the body 2. It is not necessary that the packings 7 and 8 be flat as shown in Figure 1; for example, they can also be round, like a rubber string. It is acceptable for the packings 7 and 8 to be attached by means of an adhesive to these fixed locations, but it is also acceptable for the packings 7 and 8 to be made in one piece by the extrusion method in which rigid synthetic resin that is the material for the body 2 and rubber that are the material for packings 7 and 8 are extruded at the same time. The length (Q) of the above-mentioned slanting rib 5 and its angle (0) with respect to the body 2 of the strip 1 can be decided so that the tip of the slanting rib 5 can be stopped by the flange 62 of the reinforcing ribs 6. Then, when the flange 62 stops the top of slanting rib 5, the packings 7 and 8 are put under pressure. Packing need not be provided at both the connecting part 51 connecting the socket 4 with the slanting rib 5 and the connecting part 21 connecting with the joining rib 3 of the body 2; it is sufficient if packing is provided at either one of these locations. For example, as shown in Figure 2, when there is no packing 7 provided at the connecting part 51 positioned between the socket 4 and the slanting rib 5, then the surface 52 of the connecting part 51 that comes into contact with the packing 8 is processed into a rollette by means of a rollette processing means. The formation of this rolletteprocessed surface 52 takes place immediately after the extrusion formation of the strip 1. Figure 3 is a cross-sectional view of the joined portion of a helical pipe that was formed by winding the strip 1 shown in Figure 1 into a helical shape. By the stoppage of the slanting rib 5 at its tip by the reinforcing ribs 6, pressure that is directed in the directions indicated by arrow a and arrow b is applied to the slanting rib 5. The packings 7 and 8 are compressed by this pressure between the connecting part 51 connecting the socket 4 with the slanting rib 5 and the part 21 connecting with the joining rib 3 of the body 2, so that the space between the connecting part 51 and the part 21 is impervious to liquids, and also so that sliding between these parts can be prevented. When the strip 1 is wound into a helical shape so as to form a helical pipe, even if the said strip 1 receives propulsive force, the diameter of the helical pipe that is being formed does not increase. There is also no danger that the diameter of the resulting helical pipe will vary. When the strip 1 shown in Figure 2 is wound into a helical shape, the packing 8 will be taken into the rollette-processed surface 52, which makes still more sure the prevention of sliding between the connecting part 51 and the part 21 of the body 2. In this example, only one packing 8 is provided, but because this packing 8 is placed in order to be surrounded by the body 2, the joining rib 3, and the reinforcing rib 6, when the strip 1 is transported or stored, this packing 8 is not directly affected by outside pressure, and the said packing 8 is not torn from the body 2, nor is there any danger of the said packing 8 being damaged like this. It is understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty that reside in the present invention, including all features that would be treated as equivalents thereof by those skilled in the art to which this invention pertains.

Claims: Claims 1. A strip for the formation of helical pipes by helically winding said strip, which comprises a long, narrow, flat body, a joining rib at one edge of said body, which is perpendicular with respect to the strip and continuous in the longitudinal direction of said strip, a socket at the other edge of said body, into which said joining rib is fitted, said socket being continuous in the longitudinal direction of said strip, a slanting rib that slants in the outside direction from the lower portion of said socket, said slanting rib being continuous in the longitudinal direction of said strip, and a soft and elastic packing that is continuously disposed in the longitudinal direction of said strip in such a manner that said packing is positioned in a space formed between the connecting part that connects said socket with said slanting rib and the part connecting to said joining rib of the body of said strip in the case where said strip is wound into a helical shape so as to fit said joining rib into the inside of the socket, so that said packing is compressed between the two parts. 2. A strip according to claim 1, wherein said packing is disposed on at least one of these two: said connecting part connecting the socket with the slanting rib and said part connecting with the joining rib of the body of said strip. 3. A strip according to claim 1, wherein said packing is disposed on one of these two: said connecting part connecting the socket with the slanting rib and said part connecting with the joining rib of the body of said strip, and wherein one of said two parts has a rollette-processed surface thereon into which said packing is taken. 4. A strip according to claim 1, wherein at least one reinforcing rib that is perpendicular with respect to the body of said strip is continuously disposed in the longitudinal direction of said strip at a fixed distance from said joining rib, and when said joining rib is inserted into said socket, said slanting rib is engaged with said reinforcing rib in such a manner that said reinforcing rib stops said slanting rib.

Inventors: FUJII SHIGEKI, MORIKAWA KENICHI, FUJII, SHIGEKI, MORIKAWA, KENICHI
Applicants: SEIKISUI CHEMICAL CO LTD, SEKISUI KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: F16L11
IPC codes: F16L11