A method for the manufacture of helical pipes and an apparatus for the connection of strips

5 Technical Field

This invention relates to a method for the manufacture of helical pipes made of synthetic resin that are used in, for example, sewage pipes that have deteriorated with age.

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Background Art

The hu e pipes and the like of sewage pipes deteriorate with age as a result of the effects of corrosion by corrosive gases, pressure of the

^5 surrounding earth, and the like, giving rise to the. danger of cracks, breakage, leaking, and so on. For this reason, sewage pipes that have deteriorated with age are rehabilitated by the use of an inner pipe made of synthetic resin.

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As one method for the rehabilitation of such sewage pipes, the method has been used that uses a pipe-forming machine by which a helical pipe can be continuously manufactured by winding strips made of

25 synthetic resin into a helical shape. Vhlle the strips of synthetic resin are introduced into the pipe-forming machine to be wound in a helical fashion, one edge portion of a wound strip is fitted together to one edge portion of the next strip that is fed into the pipe-

3ø forming machine, resulting in a helical pipe. The method by which sewage pipes are rehabilitated by the use of such a pipe-forming machine is practised as follows. First, the pipe-forming machine is placed

within a manhole that communicates with one end of the sewage pipe to be rehabilitated, and a strip drum formed from the wound strips of synthetic resin is placed on the surface of the earth; next, from the said strip drum, the strips are fed into the pipe-forming machine provided in the manhole, and the spiral pipe formed by the said pipe-forming machine is introduced into the sewage pipe.

^he strips that are introduced into the pipe- forming machine are usually wound into a strip drum over a fixed length. When a helical pipe with a fixed length is installed inside a sewage pipe with a fixed length, the helical pipe is interrupted in one place, and the helical pipe that has been cut short remains on the helical drum. When a strip is paid out from the strip drum on which is wrapped a strip that does not have the necessary length, a helical pipe of the desired length cannot be obtained, and the helical pipe being formed must be discarded; it is necessary for another helical pipe to be formed with new strips on another strip drum. Thus, the short strip that has been left on the strip drum is discarded as scrap. Therefore, although it would be ideal to use all of the strip on the strip drum for the spiral pipe, it is not possible in practice to avoid the generation of leftover scraps of strip that cannot be used, because the length of sewage pipes is not uniform. Such leftover scraps can be as long as several hundreds of meters long, which means that the economical aspect of production are worsened.

This invention overcomes the above-discussed problems of the prior art, and one object of the invention is to provide a method for the manufacture of helical pipes that can be made to the desired length without the generation of scraps of strip in the process. Another object of the invention is to provide a method for the manufacture of helical pipes in which there is no danger of damage readily occurring at the places in which strips are connected with each other to form the helical pipe. Yet another object of this invention is to provide an apparatus for the connection of strips by which it is readily possible to connect strips to each other that are used for the manufacture of the helical pipe.

Disclosure of the Invention

The method for the manufacture of helical pipes of this invention comprises opposing the back- edge portion of the strip of synthetic resin that is introduced into the pipe-forming machine to form the helical pipe to the front-edge portion of the next strip of synthetic resin that is to be connected with the back-edge portion of the said first strip so that the said edges of the strips are fitted, heating these edges of the strips that have been opposed to each other so as to fuse them together, making contact of these two edges that have been fused by the application come together with the use of a certain amount of pressure to both edges, and the continuous feeding of the back-edge portion of one strip and the front-edge portion of the following strip into the pipe-forming machine, resulting in a helical pipe.

In a preferred embodiment, the back-edge portion of the leading strip and the front-edge portion of the next strip are opposed to each other so that they bend to face in the direction corresponding to the outside when the helical pipe is formed.

The apparatus for the connection of strips of this invention comprises a ixing means that fixes the back-edge portion of the leading strip that is introduced to a pipe-forming machine to form a helical pipe and the front-edge portion of the next strip that is to be connected with the back-edge portion of the said leading strip in such a way that the edge portions of the strips are opposed to each other; a pressure means for the application of a certain amount of pressure to the end surfaces of the individual strips that are fixed in the said fixing means; and a heating means for the application of heat to the ends of the individual strips, so as to fuse them.

In a preferred embodiment, the fixing means comprises a fixing stand for the leading strip on which and by which the back-edge portion of the leading strip is placed and fixed; a support stand for the leading strip on which and by which a portion of the leading strip adjacent to the back edge of the leading strip that is fixed in the said fixing stand for the leading strip is placed and supported; a fixing stand for the later strip on which and by which the front-edge portion of the later strip to be joined to the leading strip is placed and fixed; and a support stand for the later strip on which and by which a portion of the later strip adjacent to the front edge of the said

later strip that is fixed by the said fixing stand for the later strip is placed and supported.

In a preferred embodiment, the said fixing stand for the leading strip and the said fixing stand for the later strip each have a spacer that bends upwards the edges of the strips placed thereon.

In a preferred embodiment, the said fixing stand for the leading strip and the said fixing stand for the later strip are each provided with a position- regulating device that regulates the position of the strips placed thereon.

In a preferred embodiment, at least one of the two fixing stands, namely, the fixing stand for the leading strip and the fixing stand for the later strip, is provided with a position-adjustment device for regulating the position of the individual strips in the direction of their width.

In a preferred embodiment, the pressure means is a fixing-stand shifting device that can shift one of the two fixing stands, namely, the fixing stand for the leading strip and the fixing stand for the later strip, nearer to the other fixing stand.

In a preferred embodiment, the said fixing- stand shifting device is provided with a locking mechanism for the prevention of the movement of the shifted fixing stand after it has been shifted.

Thus, by the method for the manufacture of helical pipes of this invention, the back-edge portion of the strip that is formed into a helical pipe by the pipe-forming machine can be connected with the fron - edge portion of another strip, so that a helical pipe can be manufactured with no generation of leftover scraps of strip. Also, the back-edge portion of the leading strip and the front-edge portion of the next strip are bent outwardly when the said helical pipe is being formed, so when they are made into a helical pipe, the stress bearing on the connected portions is small, and there is no danger that the said connected portions will come apart.

In the apparatus for the connection of strips of this invention, strips to be formed into a helical pipe are accurately and continuously connected to each other by fitting together the edges of the strips, and there is no possibility of the waste of leftover scraps of strips. Moreover, the joined strips can be formed into a helical pipe without difficulty.

Brief Description of the Drawings

This invention may be better understood and its numerous objects and advantages will become appar¬ ent to those skilled in the art by reference to the accompanying drawings as follows:

Figure 1 is a diagram illustrating a method of this invention.

Figure 2 is a sectional view showing the strips shown in Figure 1.

Figure 3 is a perspective view showing an apparatus for the connection of strips of this invention.

Figure 4 is a sectional view taken along the line IV-IV of Figure 3.

Figure 5 is a side view showing the apparatus for the connection of strips in use.

Figure 6 is a sectional front view showing the main portion of another apparatus for the connection of strips of this invention.

Figure 7 is a sectional side view showing the apparatus of Figure 6.

Figure 8 is a sectional view taken along line VIII-VIII of Figure 6.

Figure 9 is a perspective view showing another apparatus for the connection of strips of this invention.

Figure 10 is a sectional view taken along line X-X of Figure 9.

Figure 11 is a sectional view taken along line XI-XI of Figure 9.

Figure 12 is a sectional view taken along line XII-XII of Figure 9.

Figure 13 is a side view showing the apparatus of Figure 9 in use.

Best Mode for Carrying Out the Invention Figure 1 shows a method for the manufacture of helical pipes of this invention, in which reference numeral 10 is a sewage pipe that is to be rehabili¬ tated, and there are two manholes, 21 and 22, that communicate with the said sewage pipe 10 placed with a certain difference in gradient between the two. In the manhole 21, there is placed a pipe-forming machine 30. The pipe- orming machine 30 winds into a helical shape a strip made of synthetic resin that is paid out from a strip drum that is provided on the surface of the ground in the vicinity of the opening 21a of the said manhole 21, while connecting one edge in the direction of the width of this wound strip with the adjacent edge in the direction of the width of the next strip that is introduced into the pipe-forming machine 30, .resulting i ⁿ a helical pipe 40. The helical pipe 40 that is formed by the said pipe-forming machine 30 is fed gradually into the sewage pipe 10, and it proceeds directly forward while being rotated inside the said sewage pipe 10.

In a case where a spiral pipe is forme in this way, when the back-edge portion of the strip 41 appears, the drive of the pipe-forming machine 30 is temporarily stopped. Then, the back-edge portion of the strip 41 is connected by fusion with the application of heat by, for example, an apparatus 5 for the connection of strips, to the front-edge portion of

the next strip 42 that is wound on another strip drum 43, and thereafter, the pipe-forming machine 30 has the connected strips fed into it continuously, and thus, the helical pipe 40 is continuously formed from the strips.

The pipe-forming machine 30 forms helical pipes by the use of strips 41 (42) with the cross- sectional structure shown in Figure 2, for example. The said strip 41 (42) has a sheet portion 41a (42a) with a smooth surface, and there are a plurality of projections 41b (42b) on the back of the said sheet portion 41a (42a) at fixed intervals, lined up in the direction of the width of the strip. The said strip 41a (42a) is wound so that the back portion of the said sheet portion 41a (42a) on which these projections 41b (42b) are provided faces outward, resulting in a helical pipe. Each projection 41b (42b) has a cross-section in the shape of a T. At one edge portion in the direction of the width of the surface of the sheet portion 41a, there are meshing projections 41c (42c) that have a ball-shaped tip, which are arranged in parallel with the other projections 41b (42b). At the tops of the projections 41b (42b) that are adjacent to the said meshing projections 41c (42c), stoppers 41d (42d) that bend toward the said meshing projections 41c (42c) are provided. The other edge portion in the direction of the width of the sheet portion 41a (42a) is arranged so that an indentation 41f (42f) that meshes with one edge portion 4le (42e) of the sheet portion 41a with the meshing projections 41c (42c) can be formed, and thus placed in the outward position with respect to the

surface of the sheet portion 41a by the thickness of the sheet portion 41a. This portion is formed with a meshing groove 41g (42g) that is curved and protrudes outwardly so that the meshing projection 41c (42c) can meshes with the said meshing groove 41g (42g). The curved area formed by this meshing groove 41g (42g) has a projection 41h (42h) that projects outwardly and that is T-shaped in cross-section. On the edge in the direction of the width of the sheet portion 41a with the said meshing groove 41g (42g), there is formed a rib 41i that extends slantingly to the outward. The said rib 41i (421) is formed so that its top will engage with the curved stopping portion 41d (42d) of the projection 41b (42b) that is adjacent to the meshing projection 41c (42c) when the ad acent meshing projection 41c (42c) and meshing groove 41g (42g) are fit together by winding of the said strip 41 (42) into a helical shape.

The apparatus 5 for the connection of strips of this invention has, as shown in Figure 3, a joining device 50 for the fitting together by the application of a certain amount of pressure of the end face of the back-edge portion of a strip 41 made, for example, of a synthetic resin such as vinyl chloride, which strip is the leading strip, and the end face of the front-edge portion of a strip 42 that is made of synthetic resin, which strip is the following strip, both of which have been fixed in a substantially horizontal position, and a heating device 80 for the heating and fusion of the end faces of these strip that have been fixed by the said joining device 50. The heating device 80 is a device that is separated from the joining apparatus 50.

The joining device 50 has a bridge 51 in the shape of a right-angled parallelepiped. The said bridge 51 has a width slightly larger than the width of the strips 41 and 42 that are to be joined, and its length is appropriately longer that the width. On one of the edge portions of the said bridge 51, there is a board-like support stand 53 for later strips provided so as to be substantially horizontal. The said support stand 53 for later strips is supported at each corner by blocks 52. The portion of the later strip 42 adjacent to the front edge of the said later strip 42 that is to be connected to the back edge of the leading strip 41 is put on this support stand 53 for later strips. The strip 42 is placed in such a way that the sheet portion 42a (Figure 2) thereof that will become the inner face when the helical pipe is formed faces downward. On the upper surface of the said support stand 53 for later strips, there is provided along the bridge 51 a position-regulating projection 53a that meshes with the above-mentioned meshing groove 42g of the strip 42. The strip 42 is held in a fixed position on the top of the said support stand 53 for later strips by means of the position-regulating projection 53a that is on the top surface of the said support stand 53 and that meshes with the meshing groove 42g.

The said support stand 53 for later strips has projections 53b at each corner projecting outward in the direction of the width of the bridge 51. On the top of the support stand 53 for later strips, there is a pair of fixing plates 54 that extend in the direction of the width of bridge 51. The plates are in the shape

of long slats. The fixing plates 54 are placed so that the edge portions of the fixing plates 54 correspond respectively to the projections 53b that are opposed to each other in the direction of width of the support stand 53, and each is fixed to the support stand 53 for later strips by the screws 55 at each end. When the portion adjacent to the front edge of the later strip 42 is placed on the top of the support stand 53 for later strips, the fixing plates 54 are each placed above the later strip 42, and by the fastening and tightening of the screws 55 into the projections 53b of the support stand 53 and into the individual edge portions of the fixing plates 54, .the portion adjacent to the front edge of the later strip 42 is fastened.

At a predetermined position at a fixed distance away from the support 53 toward the central part of the bridge 51, there is a fixing stand 56 for later strips shaped in the form of a slat that extends * ¹ "the direction of the width of the bridge 51, installed substantially horizontally. The said fixing stand 56 for later strips is supported at each end by the pair of blocks 57 on the bridge 51, and the height of its upper surface is equal to that of the upper surface of the support 53 for later strips. Over the fixing stand 56 for later strips, there is provided a slat-shaped fixing plate 58 similar to the fixing stand 56 for later strips. The said fixing plate 58 is fastened with screws 59 on each edge to the edges of the fixing stand 56 for later strips. Then, on the top of the fixing stand 56 for later strips, the front-edge portion of the later strip 42 is placed, and by the fastening and tightening of screws 59 on each edge of

the said fixing plate 58, the front-edge portion of the said strip 42 is fixed into place.

The fixing plate 58 is provided with guide 58a that projects upward and extends along the whole edge in the direction of the width of the said fixing plate 58. The said guide 58a is used as a guide for cutting along which the front-edge portion of the strip 42 that is supported by and placed between the fixing stand 56 and the fixing plate 58 when the stripe 42 is cut at right angles to its long direction with a cutter. When a cutter is moved along the said guide 58a, the cutter can cut so that the end face of the strip 42 is exactly at right angles to the long direction of the said strip 42.

In the central region of bridge 51, there is a rack .61 provided that extends in the long direction of the bridge 51. Also, above the bridge 51, and parallel to the said rack 61, a pair of guide posts 62 and 64 are provided. One of the guide posts, guide post 62, is supported by the block 52 that also supports one of the corners of the support 53 for later strips. The said guide post 62 pierces one of the blocks 57 that supports the fixing stand 56 for later strips, and is supported by the block 63a that is provided at the edge of the bridge 51. A block 63b is also provided on the edge of bridge 51 so that it will be opposed to the block 63a in the direction of the width of the bridge 51. The guide post 64 is provided between the block 63b and the block 57 that supports the fixing stand 56 for later strips as mentioned above.

The other guide post 62 pierces the two blocks 65 and 66 that are installed with a certain interval therebetween and that can move slidably along the said guide post. The block 66, which is installed at a position at some distance from the block 63a, is longer than the other block 65 in the long direction of the guide post 62. The other guide post 64 pierces blocks 67 and 68 (see Figure 6) of equal size installed with a fixed interval therebetween which can move slidably along the said guide post 64.

To the blocks 65-68, the support 69 for the leading strip that is in the shape of a board is attached in a substantially horizontal way. The said support 69 for the leading strip is supported at each corner by the blocks 65-68. The block 66, which is pierced by the guide post 62 and which extends in the long direction of the guide post 62 extends from the underneath of support stand 69 for the leading strip in the direction of the support 56 for later strips.

On the support stand 69 for leading strips, the adjacent portion to the back edge of the leading strip 41 that is being formed into a helical pipe by the pipe-forming machine 30 is placed. On the upper surface of the support stand 69 for leading strips, there is a position-regulating projection 69a that meshes with the meshing groove 41g of the strip that is in position; this position-regulating projection 69a is provided along the long direction of the bridge 51. The strip 41 placed on the top of said support stand 69 for leading strips is held in a fixed position on the

said support stand 69 for leading strips by the fitting together of the position- egulating projection 69a with the meshing groove 41g thereof.

The said support stand 69 has projections 69b projecting outward in the direction of width of the bridge 51 at each of its corners. Over the support stand 69, there are a pair of fixing plate 71 that are in the shape of slats that extend in the direction of the width of the bridge 51. Each fixing plate 71 is . fastened by the screws 72 at its edges to projections 69b that are paired up in the direction of width of the bridge 51. When the portion of the leading strip 41 adjacent to the back edge of the leading strip 41 is placed on the top of the said support stand 69, the said portion adjacent to the back edge of the leading strip- 41 is fixed onto the top of the said support stand 69 by the fastening and tightening of the screws 72 to the projections 69a of the support stand 69 at each end of these fixing plates 71.

By the sliding along the guide posts 62 and 64 of the blocks 65, 66, 67, and 68 that support the said support stand 69, it is possible to achieve nearness or distance of the said support stand 69 for leading strips to the said support stand 56 for later strips.

At a fixed distance from the support 69 for leading strips in the direction of the fixing stand for the later strips, there is provided in a substantially horizontal position the fixing stand 73 for leading

strips, which stand 73 is in the shape of a slat and which extends in the direction of the width of the bridge 51. The said fixing stand 73 for leading strips is supported at one of its edges by the block 66 by

5 _. which the support stand 69 for leading strips is also supported at one of its edges, and is supported at the other edge by block 74, which is pierced by the guide post 64 so that the block 74 can move slidably along the guide post 64. The upper surface of the fixing

10 stand 73 for leading strips is at a uniform height with the upper surface of the support 69 for leading strips and the upper surface of the support 56 for later strips. The said fixing stand 73 for leading strips and the said support stand 69 for leading strips are

15 connected to each other by a single block 66 therebetween, and because the support stand 69 for leading strips can slide along the guide post 62 and the guide post 64, the fixing stand 73 also can move following the support stand 69 for leading strips.

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On the top of the fixing stand 73 for the back edge, there is a slat-shaped fixing plate 75 that is similar to the fixing stand 73 for the back edge. The fixing plate 75 is fastened at each end to each

25 edge of the fixing stand 73 for leading strips with screws 76. After the back edge of the leading strip 41 is placed on the top of the fixing stand 73 for the back edge and the fixing plate 75 is placed on the back edge of the strip 41, the back edge of the strip 41 is

30 fastened to the fixing stand 73 for the back edge by fastening with screws onto the fixing stand 73 for the back edge.

The fixing plate 75 is provided with a projecting guide 75a for the cutter that cuts the back- edge portion of the strip 41 in the direction at right angles to the long direction of the strip 41, which is similar to the fixing plate 58 positioned over the fixing stand 56 for the leading edge.

On the undersurface of the support stand 69 for leading strips, as shown in Figure 4, there are provided fastening means 69c and 69d, and between these fastening means 69c and 69d, there is a single fastening rod 76 that bridges the gap. The said fastening rod 76 pierces the upper portion of slidable block 77 so that the sliding, block 77 can slide along the fastening rod 76. The said fastening rod 76 is fit into a push-screw 76a. The said push-screw 76a is positioned in the space between the said sl dable block 77 and the fastening means 69c. Thus, when the said slidable block 77 moves in the direction of the fixing stand 73 for leading strips, resisting the force exerted by the push-screw 76a, the push-screw 76a exerts pressure on the fastening means 69c, which brings the support 69 for leading strips nearer to the fixing stand 73 for later strips.

The guide posts 62 and 64 penetrate the slidable block 77 from one end to the other slidably. In the middle region of the slidable block 77 that is placed between the guide posts 62 and 64 and that corresponds to rack 61 arranged on the bridge 61 , a space extending to the rack 61 is formed. This space has a rotatable pinion gear 78 that meshes with the said rack 61. The said pinion gear 78 is attached to

the gear shaft 78a that extends in the direction at right angles to the fastening post 76. The said gear shaft 78a is supported rotatably by the slidable block 77; at one of its ends, it extends further than the slidable block 77, and the end that extends outward in this way has attached to it a handle 79 for the purpose of rotation of the said gear shaft 78a.

Therefore, when the said handle 79 is rotated, the gear shaft 78a is rotated in the direction shown by the arrow A in Figure 4; the pinion gear 78 also rotates in the same direction, and the said pinion gear 78 rotates in the direction of the fixing stand 73 for leading strips on the rack 61. In this way, the slidable block 77 moves in the same direction along the fastening post 76, and exerts pressure on the push- screw 76a. The result is that the fastening means.69c attached to the support 69 for the back edge is pushed by the push-screw 76a, to approach the fixing stand 73 for leading strips. In this case, the fixing stand 73 for leading strips, being connected via the block 66 so as to be integrated with the support stand 69 for leading strips, moves in the same direction following the support stand 69 for leading strips.

When the handle 79 is rotated in the opposite direction, the slidable block 77 also moves in the opposite direction. Then, the slidable block 77 is moved again in the same direction, and when the block 77 is brought into contact with the blocks 65 and 67 that support the support stand 69 for leading strips, the said slidable block 77 moves the support stand 69 for leading strips in the same direction.

The heating device 80, as shown in Figure 3, has a controlling means 81 that carries out the regulation of the degree of heat applied, the time of heating, and the like, a heating section 82 that is connected to the said controlling means 81 via a cable 84, and the pressure means 83. The heating section 82 is in the shape of a rod with a cross- section in the shape of a square; this surface conveys a fixed amount of heat as directed by the controlling means 81. The pressure means 83 has a pair of planes 83a that are arranged in parallel and a curved handle 83b in the shape of a U that connects the said pair of planes 83a with each other.

The rod-shaped heating section 82 that is heated to a certain temperature is positioned so that one surface of the heating section 82 is brought into contact with the end face of the front edge of the strip 42 that is fixed on the top of the fixing stand 56 for later strips, while the end face on the other side of the heating section 82 is brought into contact with the end face of the back edge of the leading strip that is fixed on the top of the fixing stand 73 for leading strips with the use of a certain amount of pressure. Thereafter, as shown in Figure 5, the planes 83a of the pressure means 83 are placed on the fixing plates 58 and 75, and each end face of both strips 41 and 42 is treated by heat, fusing the ends.

With an apparatus for connecting strips that has such a structure, connection of the strips to each other is carried out as follows:

First, the front edge of the later strip 42 that is to be connected to the leading strip 41 is placed on the top of the fixing stand 56 for later strips; its end is placed so as to extend slightly further out from the end of the fixing stand 56 for later strips toward the fixing stand 73 for leading strips while the portion of the strip 42 adjacent to the front edge of the said strip 42 is placed on top of the support stand 53 for later strips. In these circumstances, the meshing groove 42g of the strip 42 is fit together with the position-regulating projection 53a provided over the upper surface of the support stand 53 for later strips so that the position of the said strip 42 is decided.

Thereafter, the fixing plate 58 is placed on the top of the strip 42; each end of the said fixing plate 58 is fastened with screws 59 to the fixing stand 56 for later strips, followed by tightening of the screws 59. Then, the fixing plates 54 are placed on the top of the strip 42 to be fastened to the support stand 53 for later strips by the tightening of screws 55. In this way, the front edge portion of the strip 42 including its adjacent portion is fixed onto the support 53 for later strips and onto the fixing stand 56 for later strips.

In the same way, the back edge of the strip 41 that is previously formed into a helical pipe by the pipe-forming machine 30 in the manhole 21 is placed on top of the fixing stand 73 for leading strips and on the support 69 for leading strips, and then

fixed with the use of the fixing plates 75 and 71.

Then, the end of the later strip fixed onto the fixing stand 56 for later strips, which projects from the end of the said fixing stand 56 for later strips, is cut by a cutter, leaving a certain length of remaining portion on the said fixing stand 56 for later strips. In this case, the cutter moves along the guide 58a of the fixing plate 58 that is fixed on the fixing stand 56 for later strips so that the end of the strip 42 that is cut is at right angles to the long direction of the said strip 42. The strip 41 that is fixed on the top of the fixing stand 73 for later strips is cut in the same way by the cutter. The end of this strip 41 after being cut is also at right angles to the long direction of the strip 41.

Thereafter, the heating means 82 of the heating device 80 is placed on the guide rods 62 and 64 so as to be slightly separated from the leading end surface of the strip 42 that is fixed on the top of the fixing stand 56 for later strips. Then, by the rotation of the handle 79, the pinion gear 78 is brought to the top of the rack 61, and the slidable block 77 is brought nearer to the fixing stand 56 for later strips. When the slidable block 77 is brought nearer to the fixing stand 56 for the later strips, the push-screw 76a into which the fastening rod 76 is fit applies pressure to the support stand 69 for leading strips in the direction of the fixing stand 56 for later strips, and the said support stand 69 for leading strips is moved in the same direction. Together with this movement of the support stand 69 for leading

strips, the fixing stand 73 that is connected so as to be one piece with the said support stand 69 for leading strips by the block 66 is moved in the direction of the fixing stand 56 for later strips, and the end surface of the leading strip 41 that is fixed on the fixing stand 73 for leading strips is brought into contact with the heating portion 82. Then, by moving the end surface of the leading strip 41, the heating means 82 is moved to be brought into contact with the end surface of the later strip 42. When the handle 79 is rotated in the same direction, the slidable block 77 moves along the fastening rod 76 toward the fixing stand 56 for later strips, so that the said slidable block 77 applies pressure to the push-screw 76a. Then, by the force of the push-screw 76a, the end face of the back edge of the leading strip 41 is pressed to the heating means 82. By the placement of slidable block 77 at a fixed position designated by marking on the side surface of the support stand 69 for leading strips, the desired amount of pressure can generally be exerted on the end face of the back edge of the leading strip 41 and the heating means 82. In this way, the said heating means 82 is heated, and the end surfaces of the strips 41 and 42 are brought into contact with the said heating means 82 and then fused.

After the end surfaces of the strips 41 and 42 are heated by the heating means 82 for a fixed length of time, the ends of the strips 41 and 42 are separated from the heating means 82 by the slight rotation of the handle 79 in the reverse direction. Then, the pressure means 83 and the heating means 82 are removed from the apparatus 50 for the connection of

strips, and the handle 79 is immediately rotated so as to move the support stand 69 for leading strips and the fixing stand 73 for leading strips in the direction of the fixing stand 56 for later strips in the same way as described before. Then, the end surfaces that have been fused of the strips 41 and 42 are brought together correspondingly. As described above, by the use of markings on the side surface of the support 69 for leading strips, the handle 79 is rotated to move the fixing stand 73 for leading strips further in the direction of the fixing stand 56 for later strips, so that the desired amount of pressure can be exerted on both of the end surfaces of the strips 41 and 42. Thus, the end surfaces of the strips 41 and 42 are pressed together, and are joined by fusion.

In this way, by connecting the leading strip 41 and the later strip 42 with each other, the pipe-forming machine 30 in the manhole 21 is driven again to form a helical pipe. Then, another later strip can be continuously fed into the pipe-making machine 30 following the leading strip 41, and made into a helical pipe.

When the strips 41 and 42 are made of vinyl chloride, the degree of heating required for the fusion of their ends is around 230-270°C, and preferably about 240-260 C. The pressure used to make the fused end portions join to each other is preferably 2.0- 4.0 kg/cm . In winter or in a cold area, it is preferable to raise the temperature of the end portions of the strips to around 30-40 C, in advance.

When the ends of the strips 41 and 42 have been fused to each other by the addition of heat, there is the danger that fused beads may form in the meshing grooves 41g and 42g of the strips 41 and 42, ' respectively. It is necessary to remove the fused beads, or it will not be possible during the formation of the helical pipe to fit the meshing projections 41c and 42c into the meshing grooves 41g and 42g, respectively, which makes it impossible to form a helical pipe. Therefore, if fused beads arise in the meshing grooves 41g and 42g during fusion of these portions, a knife, a rasp, or the like is needed for removal of the beads.

It is troublesome to carry out the manual operation for the removal of this kind of fused beads, an in particular to carry out the manual operation for the removal of this kind of fused beads from the insides of the meshing groove 41g or 42g, so in order to make it unnecessary to carry out such a manual operation for the removal of fused beads, the apparatus 50 for the joining of the strips can be provided with a mechanism that does not permit the formation of fused beads inside the meshing groove 41g and/or 42g at the time of fusion of the strips 41 and 42. One example of such a mechanism is shown in Figure 6, in which block 56 is attached to the undersu face of the fixing stand 56 for later strips, and the said block 56c is penetrated slidably in the long direction of the strip 42 by the slidable shaft 56d, underneath the meshing groove 42g of the strip 42 that is fixed on the fixing stand 56 for later strips. Also, onto the undersurface of the support 53

for later strips, a block 53d is attached, and the said block 53d is penetrated slidably by the base end of the slidable shaft 56d.

The top of the slidable shaft 56d is provided with a meshing projection 56e that points upward. As shown in Figure 7 that is a partial cross section of the said apparatus, the upper portion of the said meshing projection 56e is formed so that it meshes with the meshing groove 42g of the later strip 42 that is fixed to the fixing stand 56 for later strips and fits tightly to the inside surfaces of the meshing groove 42g. This meshing projection 56e has an appropriate length in the long direction of the slidable shaft 56d. The length of the said meshing projection 56e in the long direction of the shaft is slightly shorter than the length from the fixing stand 56 for later strips to the end surface of the strip 42 that is fixed on the fixing stand 56 for later strips and that has been cut with the use of a cutter.

The slidable shaft 56d is fit into the push- spring 56f. The said push-spring 56f is placed in the space between the block 56σ that is attached to the undersurface of the fixing stand.56 for later strips and the block 53d that is attached to the undersurface of the support stand 53 for later strips. The said push-spring 56f applies pressure to the entire slidable shaft 56d so that the meshing projection 56e on the top of the slidable shaft 56d protrudes from the block 56c. The slidable shaft 56d is supplied with a stopper 56g that can prevent the removal of the said slidable shaft 56d from the said block 56c by catching on the

block 56c.

As shown in Figure 8, the block 56c is provided with a lever 56h that engages with the stopper 56g of the slidable shaft 56d so that the meshing projection 56e on the top of the slidable shaft 56d is held near the said block 56c. The said lever 56h engages with the stopper 56g when a cutter is used to cut the front edge of the later strip 42 that extends from the fixing stand 56 for later strips so that the meshing projection 56e is held near the block 56c.

In the same way as described above for the slidable shaft 56d, the fixing stand 73 for leading strips has a slidable shaft that has a meshing projection.

After the cutter is used to cut the front- edge portion of the later strip 42 that is fixed on the fixing stand 56 for later strips, the said slidable shaft 56d is moved until the meshing projection 56e on the tip of the slidable shaft 56d projects from the front edge of the strip 42 because of the removal of the stopping of the stopper 56g by means of lever 56h.

When the end face of the front edge of the strip 42 is brought into contact with the heating means 82, the said meshing projection 56e is pressed by the heating means 82 to move, resisting the force of the push- spring 56 . In this way, as shown by the double-dotted lines in Figure 6, the meshing groove 42g of the said strip 42 meshes with the top portion of the meshing projection 56e on the top of the slidable shaft 56f.

Then, the end surface of the strip 42 and the meshing projection 56e inside the meshing groove 42g of the strip 42 are brought into contact with the heating means 82.

Similarly, the meshing projection 56e is pressed by the heating means 82 and meshes with the inside of the meshing groove 41g of the leading strip 41 and then the end surface of the leading 0 strip 41 that is fixed on the fixing stand 73 for leading strips is pushed to come in contact with the heating means 82 .

In this way, the heating means 82 generates _5 heat, and the end faces of the strips 42 and 41 are fused. In this case, because the upper end portion of the meshing projection 56e is firmly in contact with the inside of the meshing groove 42f of the later strip 42 and a meshing projection is firmly in contact o with the inside of the meshing groove 41g of the other strip, there is no danger that fused beads will be formed in the meshing groove 42g or 41g.

After the heat treatment by use of the 5 heating means 82, the heating means 82 can be removed from the apparatus 50 for the joining of strips. Because the meshing projection 56e that is in contact with the heating means 82 is removed from contact with the heating means 82, its upper portion is slid into 0 the inside of the meshing groove 42g by the force of the push-screw 56f so that the said meshing projection 56e projects outward in one place from the end surface of the later strip 42. In this way, even

if fused beads are formed in the inside surfaces of the meshing groove 42g of the strip 42, it is possible to remove the fused beads with the upper portion of the meshing projection 56e that slides along the inside of the meshing groove 42g.

The meshing groove 41g of the leading strip 41 fixed on the top of the fixing stand 73 for leading strips can also have its heating means 82 removed, and the meshing projection that is fit into the meshing groove 41g slides along these inside portions, so that even if fused beads are formed inside the meshing groove 41g, the fused beads can be removed with the meshing projection.

In this way, the end surfaces of the strips 41 and 42, on which there are no fused beads formed inside the meshing grooves 41g and 42g, are joined to each other with the application of a certain amount of pressure. Because the upper part of the meshing projections are fit into the meshing grooves of the strips pressed together with the meshing projections abutting on each other, there is no occasion for the fused beads that arise from the pressure to enter the meshing grooves.

The slidable shaft 56d that has meshing projections 56e need not be used by this method alone, but can be used as follows: For example, when the end faces of the strips 41 and 42 are brought into contact with the heating means 82, the push-spring 56f is compressed, and the handle 56h engages with the stopper 56h as shown in Figure 8; in these

circumstances, fused beads are formed inside the meshing groove 42g of the strip 42, and immediately after the pressing together of the strips 41 and 42 to each other, the handle 56h is released from the stopper 56g, which causes the slidable shaft 56d to project outward from the block 56c with the force of the pushing spring 56f so that the fused beads formed inside the meshing groove 42g of the strip 42 are removed by the meshing projection 56e that slides along the inside portions of the meshing groove 42g. In the method described above in which the strips 41 and 42 are fused to each other with a meshing projection 56e positioned inside the meshing groove 42g,. the formation of the fused beads inside the meshing groove 42g are prevented by the meshing projection 56e, so that there is a danger that a large amount of fused beads will be piled up on the reverse side only and that the vicinity of the meshing groove 42g will be slightly deformed. However, if fused beads are formed temporarily inside the meshing groove 42g, and then removed by the sliding of the meshing projection 56e inside the meshing groove 42g by the use of this method, this danger can be avoided. It is preferable for the tip of the meshing projection 56e in the long direction to be in the shape of a knife. The mechanism that exerts pressure on the slidable shaft 56d is not limited to the pushing spring described above; it can also be an air cylinder, an oil cylinder, or the like.

In the example given above, apparatuses 50 for joining of strips have a structure in which the front-edge portion of later strips 42 is fixed while the back-edge portion of the leading strips 41 is

moved. However, the example is not limited to this structure, and it is possible to have a structure in which the front-edge portion of the later strips is moved while the back-edge portion of the leading strips 41 is fixed. Because the later strips 42 are wrapped around a strip drum 43, relatively free movement is possible.

Figure 9 shows another apparatus for the connection of strips of this invention, in which one part of the joining apparatus 50' has a structure different from the joining apparatus 50 described above. First of all, the position-adjustment device for regulating the front-edge portion of the strip 42 so that it will be in a desired position is provided on the support stand 53 for later strips, instead of the position-regulating projection 53a. The said device for the adjustment of the position of strips has, as shown in Figure 10, an adjustment block 91 that fits into the opening 53d that is installed in a fixed position of the support.stand 53 for later strips. The opening 53d on the support stand 53 for later strips is placed so as to face the meshing groove 42g of the later strip 42 that is placed on top. of the support 53 for later strips. The adjustment block 91 that fits into the said opening 53d can be moved within the opening 53d in the direction of the width of the strip 42 that is placed on the support stand 53 for later strips. The said adjustment block 91, so that it can fit into the interlocking indentation 42f that is provided on one side of the strip 42, projects upward from the opening 53d that is provided in the support stand 53 for the front-edge portion. The said

adjustment block 91 is formed with a slanting surface 91b that supports the interlocking rib 42i that is continuous with the interlocking indentation 42f of the strip 42; and also, a projection 91c that projects so that it can fit into the meshing groove 42g in the strip 42 is provided.

This adjustment block 91 is fixed on the top of the guide block 92. In the central part of the said guide block 92, there is a hole bored from end to end that is parallel to the direction of the width of the strip 42 placed on the top of the support 53.for later strips, and the inner surface of the said hole is provided with grooves for a screw. Under the support 53 for later strips, there is a screw rod 93 provided that can rotate and that can pass through the hole in the said guide block 92. The grooves for a screw that are provided on the outer surface of the said screw rod 93 engage with the grooves for a screw provided on the inner surface of the hole in the guide block 92.

As shown in Figure 11, the upper parts of the guide block 92 are provided with sliding parts 92a and 92a that extend in a direction at right angles to the screw rod 93. On the undersurface of the support stand 53 for later strips, there is attached a pair of guide rails 94 and 94 that can engage with the sliding parts 92a and 92a of the guide block 92, and the sliding parts 92a slide along the top of the corresponding guide rails 94 and 94, respectively.

Therefore, if the screw rod 93 is rotated clockwise and then counterclockwise, the guide block 92 is sent in the direction of the width of the strip 42 that is placed on the top of the support stand 53 for later strips. Then, the adjustment block 91 that is attached to the top of the guide block 92 moves together with the said block 92. The adjustment block 91 is moved with the projection 91c thereof being fit into the meshing groove 42g of the strip 42, so that the front-edge portion of the strip 42 on the support stand 53 for later strips is moved in the direction of the width of the strip 42.

As shown in Figure 10, one end of the screw rod 93 penetrates the support block 95 that is attached to the undersurface of the support 53 for later strips, and there is a handle 96 for use in the rotation of the screw rod 93 attached to the end of the screw rod 93 that penetrates this block. Also, the said support block 95 is provided with a locking mechanism 97. that stops the rotation of the said screw rod 93 by abutting on the screw rod 93 within the support block 95. The said locking mechanism 97 is composed of a screw bolt 97a that is screwed into the support block 95 and a handle 97b that can be used to rotate the said screw bolt 97a; when the handle 97b is rotated, the top of the bolt 97a comes into contact with the screw rod 93, and restrains the rotation of the said screw rod 93.

Also, on the top of the fixing stand 56 for later strips, there is attached a spacer 56a that is made of an elastic material, such as rubber or the like. The said spacer 56a is in the shape of a thin

plate about 3-5 mm thick, and as shown in Figure 11, the front-edge portion of the later strip 42 is placed on the top of the said spacer 56a, and the said front- edge portion is bent in the direction that corresponds to the outside when a helical pipe is formed from the strip, which direction is upward from the said spacer 56a. The front-edge portion of the later strip 42 is placed on the spacer 56a that is on the top of the said fixing stand 56 for the front edge, each end of the fixed plate 58 is fastened to the fixing stand 56 for later strips by means of screws, and the strip 42 is fixed on the fixing stand 56 for later strips with the front-edge portion of the said strip 42 being bent in the upward direction.

On the top of the fixing stand 73 for leading strips, there is also provided a spacer 73a that is made of an elastic material such as rubber or the like. The said spacer 73a is in the shape of a thin plate about 3-5 mm thick, and, as shown in Figure 12, the back-edge portion of the leading strip 41 is placed on the top of the said spacer 73a, and the said back-edge portion is bent in the direction that corresponds to the outside when a helical pipe is formed from the strip, which direction is upward from the spacer 73a. The back-edge portion of the leading strip 41 is placed on the said fixing stand 73 for the leading strip, each end of the fixing plate 75 is placed on the back-edge portion of the strip 41 and then fastened to the fixing stand 73 for leading strips by means of screws, and the back-edge portion of the said strip 41 is bent in the upward direction and fixed to the fixing stand 73 for leading strips.

The sliding block 77 that is attached underneath the support stand 69 for leading strips is provided with a locking mechanism that comes into contact with the gear shaft 78a inside the said sliding block 77 and that restrains the rotation of the said gear shaft 78a. The said locking mechanism 98 has a screw bolt that is screwed into the sliding block 77 and a handle that can be used to rotate the said screw bolt, and by the coming into contact of the screw bolt with the gear shaft 78a, the rotation of the gear shaft 78a is restrained.

Other structures for the joining apparatus 50' of this example are the same as those shown in Figure 3 for the joining apparatus 50, so their description is omitted here.

With the joining apparatus 50' of this example, the front-edge portion of the later strip 42 that is to be joined is placed on the top of the spacer 56a of the fixing stand 56 for later strips so that it extends slightly toward the direction of the fixing stand 73 for leading strips. In this way, the front-edge portion of the said strip 42 is bent upward.

At the same time, the vicinity of the said front edge is placed on the top of the support stand 53 for later strips. The projection 91c of the adjustment block 91 of the position-regulating mechanism that projects from the top surface of the support 53 for later strips is fit into the meshing groove 42g in the strip 42.

Then, the fixing plate 58 is placed on the top of the strip 42, and each end of the said fixing plate 58 is fixed by screws 59 to the fixing stand 56 for later strips, and the screws 59 are lightly fastened. Moreover, the fixing plates 54 and 54 are placed on the strip 42 and are fixed by screws 55 to the support 53 for later strips; then the screws 55 are lightly fastened. In this way, the front-edge portion of the strip 42 is fixed to the top of the fixing stand 56 for later strips and to the support stand 53 for later strips. The front-edge portion of the strip 42 placed at the spacer 56a on the fixing stand 56 for later strips is bent upward.

Similarly, the back-edge portion of the strip 41 that had been formed into a helical pipe previously by the pipe-forming machine 30 in the manhole 21 is placed on the spacer 73a on top of the fixing stand 73 for leading strips and on the support stand 69 for the leading strip, so as to be fixed by the fixing plate 75 and the fixing stand 73. The back- edge portion of the said leading strip 41 placed at the spacer 73a on the fixing stand 73 for leading strips is bent upward.

Thereafter, the end face of the back edge of the leading strip 41 that is bent upward and the end face of the front edge of the later strip 42 that is bent upward in the same way are brought together by the somewhat gentle tightening of the screws 55 and 59 that fasten the fixed plates 54 and 58, and by the rotation of the handle 96 of the position-regulating mechanism for strips, the front-edge portion of the later

strip 42 is moved in the direction of the width of the strip. Then, if the end face of said strip 42 has been brought together with the end face of the leading strip 41, the operation of the locking mechanism 97 restrains the rotation of the screw rod 93. In this way, the end face of the later strip 42 that is fixed on the support stand 53 for later strips is brought together with the end face of the leading strip 41.

Then, after the ends of the strips 41 and 42 are cut with a cutter, the surfaces are heated and fused by the heating means 82, so that they are fused together.

When the end face of the back edge of the leading strip 41 and the end face of the front edge of the later strip 42 are fused while, being held bent upwards, a helical pipe can be made by the pipe-forming machine 30 inside the manhole 21. The connected portion of the strips 41 and 42 that is fused together is made into a helical pipe by winding so that the connected portions will be bent outward. Thus, when the strips 41 and 42 are wrapped, the force exerted on the connected portion is small, and there is no danger of the breakage of the said connected portion because of force exerted on it.

The back-edge portion of the leading strip 41 and the front-edge portion of the later strip 42 can be bent to about 5-9 degrees. For that reason, the thickness of the spacers 56a and 73a to give this degree of bending is decided by the material from which the strips are made, on the measurements of the strips.

and so on. When the material from which the strips are made is vinyl chloride, depending on the measurements of the strips, the thickness of the spacers 56a and 73a is decided as shown in Table 1. Moreover, the thickness T, height H, and width W of the sheet portion of the strips shown in Table 1 have the measurements shown in Figure 2. The spacers 56a and 73a measure in their long dimension about the same as the width of the strips, and the width at right angles to the long

10 dimension is about 20 mm.

Table 1

It is understood that various other modifica¬ tions 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 pertain .