JP4744399B2 - Synthetic resin pipe - Google Patents

Description

  The present invention is embedded in the ground or piped outside the building on the ground, and a cable such as an electric wire, telephone line or optical cable is inserted into the pipe to form a protective pipe, or used as a drain pipe or a culvert pipe The present invention relates to a synthetic resin tube suitable for the above.

  Conventionally, a synthetic resin corrugated pipe in which the shape of the pipe wall is formed into an annular or spiral corrugated wave shape has been widely known. Such synthetic resin pipes are already widely used as cable protection pipes and drain pipes.

  Such a conventional tube body has a circular uneven corrugated shape, so that it is not stable at the time of piping, it is difficult to make adjacent pipes in parallel, and in the case of underground piping, each tube body There is a problem that earth and sand get in between and the straightness is easily disturbed, the stability is poor even when multi-layered piping is used, the resistance tends to increase when inserting cables such as electric wires, and the resistance of the fluid tends to increase. I had it.

  Therefore, as a tubular structure that can solve the problems of the conventional circular concavo-convex corrugated tube, as shown in the attached FIGS. 19 to 21, a cylindrical portion having a substantially square cross-sectional shape. A tubular body P1 having a structure in which 2 and the cylindrical portion 3 having a substantially circular cross section are alternately arranged in the axial direction of the tubular body has been developed (see Patent Document 1).

  Since the tubular portion 2 having a substantially square cross-sectional shape is sequentially arranged in the axial direction, the tubular body thus configured has good stability at the time of piping, and can be easily placed adjacent and parallel to each other. Even in the case, earth and sand get into the pipe body and the directity is less disturbed, and it is easy to stably laminate the pipes in multiple stages, and when inserting cables such as electric wires, work can be done with less resistance, In addition, there is an advantage that resistance to fluid movement can be reduced.

  However, in order to mass-produce this tubular body, various experiments were conducted with respect to various production means. As a result, the tubular body P1 having such a structure has a cylindrical section with a circular cross section as shown in FIG. 3 is formed to have a uniform thickness, the thickness of each corner 2a in the rectangular tube portion 2 is thinner than the thickness C of the central portion 2b of each side. In other words, as shown in an enlarged manner in FIG. 21, that is, in the cross section indicated by the line FF in FIG. 14, both corner portions B of the corner portions 2a. , B has become extremely thin, and it has been found that the thinned portion is extremely inferior in pressure-resistant deformation and easily damaged as compared with other portions.

  Therefore, as means for surely solving this problem, the corner portions 2a of the rectangular cylindrical portion 2 that are weak in pressure resistance and easily cause damage, particularly both axial directions of the corner portions 2a. A tube body in which the corner portions B and B are strengthened to such an extent that they have the required pressure-resistant deformation strength without locally weakening has been developed and already proposed.

That is, as the technical solution, the present applicant, as shown in the attached FIGS. 22 to 24, the resin tube (parison) T that forms the tube body, and the thickness T1 is changed at four locations in the circumferential direction. The resin tube (FIG. 16) having a non-uniform thickness formed partially thicker than the thickness T2 of this portion, and the thick thickness T1... Each of the corner portions 2a of the rectangular tube portion 2 is formed, and each of the corner portions 2a, in particular, the tubular body P2 in which the axial corner portions B and B of the corner portion 2a are reinforced. It was developed (see Patent Document 2).
JP-A-8-219333 Japanese Patent Laid-Open No. 10-325490

  This tubular body P2 has a rectangular tubular portion 2 as compared with the tubular body P1 of Patent Document 1 having the problem that the corner 2a of the former rectangular tubular portion 2 is poor in pressure-resistant deformation and easily causes damage. The strength of the corner 2a, particularly the strength of both corners B, B, is provided with a required pressure deformation strength without locally weakening, and is a tube that has been strengthened to the extent that it is difficult to damage. It is excellent in practicality and is a preferable tube in industry.

  However, in the case of this tubular body P2, since it is necessary to use the non-uniformly thick resin tube T in which a portion where the thickness is thickened is partially formed as described above, the former Patent Document 1 is used. Compared with the pipe body P1 described in 1., the weight of the pipe body is heavy, a large amount of resin material is required for forming the pipe, and there is a new problem that cannot be overlooked that leads to an increase in the cost of the product. It was a thing.

  Therefore, the present invention does not require a large amount of resin material as described above, and does not increase in weight as compared with the former tube described in Patent Document 1, leading to an increase in product cost. However, the strength of the corners of the rectangular tube portion, particularly the strength of both corner portions, which the tube described in Patent Document 2 possesses, is not required. The purpose of the present invention is to obtain a tubular body having a required pressure-resistant deformation strength and a strength that is difficult to damage without weakening, and the production efficiency is not reduced in the above-mentioned Patent Document 1. -It aims at providing the synthetic resin tubular body which can be manufactured efficiently similarly to the tubular body of 2.

  The first configuration of the synthetic resin pipe according to the present invention taken to solve this problem is that the cylindrical portion 2 having a substantially square cross section and the cylindrical portion 3 having a substantially circular cross section are alternately arranged in the tube axis direction. A tubular body P having at least a part of the tubular wall 1 and having a shape in which each corner portion 2a of the rectangular tube portion 2 becomes narrower in the tube axis direction toward the corner apex portion t. It is set as the structure currently formed in this.

  Further, the second configuration is a tubular body P including a tube wall 1 in which a cylindrical portion 2 having a substantially square cross section and a cylindrical portion 3 having a substantially circular cross section are arranged alternately in the tube axis direction. Each corner 2a in the cylindrical portion 2 is formed in a circular arc shape in cross section, and the width in the tube axis direction becomes narrower toward the corner apex t.

  The invention described in claim 1 according to the present invention is a synthetic resin tube in which a tube portion having a substantially square cross section and a substantially circular tube portion are alternately arranged in the tube axis direction. In addition, the structure of each corner portion in the rectangular tube portion is formed in such a shape that the width in the tube axis direction becomes narrower as it reaches the direction of the apex portion t. Since the corner apex does not expand greatly in the direction of the tube axis, it is possible to prevent the occurrence of thinning phenomenon at each corner apex of the rectangular tube portion. A tube in which the strength is locally weakened and the required pressure-resistant deformation strength cannot be maintained, and the defect of being easily damaged by an external force can be reliably compensated, and the strength of the corner portions B and B is reliably enhanced. The body is obtained by a resin tube with a uniform wall thickness in the circumferential direction. Remarkable effect that can be led to be obtained.

  Therefore, there is no need to use a non-uniformly thick resin tube that is partially thickened at four locations in the circumferential direction, which increases the weight of the tube or tube formation. The effect of being able to solve the problem of requiring a lot of resin materials and increasing the cost of the product can also be expected.

  Further, in the invention described in claim 2, it is assumed that the shape of each corner portion in the rectangular tube portion is formed in a circular arc shape in cross section, and further, the width in the tube axis direction increases toward the corner apex portion t. Since it is formed into a narrow shape, it is possible to obtain a tubular body in which the strength of each corner of the rectangular tube portion, particularly the strength of both corners B and B in the tube axis direction, is further reinforced. The effect that can be expected.

  As the synthetic resin material for forming the tubular body according to the present invention, polyolefin resins such as polyethylene and polypropylene are preferable in that they are excellent in weather resistance and durability, are easily available, and are harmless to the human body. However, since there is no advantage in specifying the resin material, it goes without saying that, for example, polyvinyl chloride or any other synthetic resin material may be selectively used.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are views showing a tube body according to a first embodiment of the present invention. FIGS. 1 and 2 are views showing the external shape of the tube P, FIGS. 3 and 4 are front views showing the shapes of the cut end face sides of the substantially rectangular tube section and the substantially circular tube section, and FIG. 2 is an enlarged view of a section of the circular cylinder portion along the line DD in FIG. 2 and a part of the rectangular cylinder portion, and FIG. 6 is a cross section cut in the longitudinal direction of the tube body along the line EE in FIG. FIG.

  In the tubular body P shown in the embodiment, as shown in FIG. 1, the outer surface shape of the tube wall 1 is configured such that the cross-sectional square tube portion 2 and the cross-sectional circular tube portion 3 are alternately arranged in the tube axis direction. It is a synthetic resin tube formed in a state. Thus, as shown in FIGS. 1, 2 and 6, the tubular body P is formed by forming the four sides 2b of the rectangular tube portion 2 on a flat surface having a width in the tube axis direction. The shape of the corner 2a is formed in a shape in which the width in the tube axis direction becomes gradually smaller toward the corner apex t.

  By doing in this way, as shown in the cross-sectional shape in the lower half of FIG. 5 and FIG. 6, the thickness at the circular cylindrical portion 3 does not become extremely thin even at the apex portion t. The wall thickness is such that the wall thickness is slightly thinner than w and does not differ from the wall thickness of the bulging base a.

  As one of means for forming such a tubular body P, there is a molding method by a generally known blow molding means. In the case of this blow molding method, although the drawing is omitted, a resin tube having a uniform wall thickness is extruded from the resin extrusion port of the resin extrusion apparatus, and this resin tube is introduced into the blow molding die. It can be molded by adopting a molding method in which it is applied to the inner surface of the mold by applying an internal pressure and expanding in the circumferential direction.

  FIGS. 7 to 9 show a tubular body of the second embodiment. The tubular body P shown in the embodiment is configured such that the corner apex t of each corner 2a of the rectangular tube portion 2 is inclined. The shape is cut. By doing so, it is possible to prevent the occurrence of a local thinning phenomenon without bulging up to the topmost end of the imaginary corner apex t, and the cross section referred to in the present invention. This shows an example in which the uniform thickness by narrowing the width in the tube axis direction as each corner 2a of the rectangular tube portion 2 reaches the corner apex t is more effective. About another point, it is set as the structure according to the said 1st Example.

  FIGS. 10 to 12 show the third embodiment, and the tubular body P shown in the embodiment has each corner portion 2a in the rectangular tube portion 2 having a circular arc section in the corner apex portion t. Thus, in the example of the embodiment, as seen in FIG. 12, along the concentric curve S1 with the circular cylindrical portion 3, from the same concentric curve S2 inside, the apex t side The cross section is formed in an arc shape so that the width in the tube axis direction becomes narrower. The other points are the same as the structure of the tubular body P shown in the first embodiment.

  Attached sheets FIGS. 13 to 18 show the external shape and side surface shape of the tube P in the fourth, fifth, and sixth embodiments. Thus, the pipe body P of the fourth embodiment shown in FIGS. 13 and 14 is in the direction of the pipe axis reaching each corner 2a of each rectangular tube section 2 in the pipe body P shown in the first embodiment. The narrow shape is formed into a shape that is gradually inclined from the circular cylindrical portion 3 toward the respective corners 2a in a side view.

  That is, in the tubular body P of the first embodiment, the circular cylindrical portion 3 exists in a short cylindrical state, and the side wall in the tube axial direction forming the rectangular cylindrical portion 2 rises in the vertical direction from both ends of the tubular axial direction. In addition, the vertical wall is formed in a shape that becomes narrow in the tube axis direction at each corner 2a, but the tubular body P of the fourth embodiment has each corner in each square tube 2 The portion of the circular cylindrical portion 3 facing the corner 2a is narrowed in the tube axis direction at an appropriate angle from the circular cylindrical portion 3 toward the corner 2a immediately without using the vertical wall. It becomes the shape which becomes. The other points are the same as the structure of the tubular body P of the first embodiment.

  The pipe P of the fifth embodiment shown in FIGS. 15 and 16 is the same as the pipe P of the second embodiment shown in FIGS. 8 to 10 and the sixth embodiment shown in FIGS. When compared with the tubular body P of the third embodiment shown in FIG. 11 to FIG. 13, the tubular body P of the example has a rectangular shape similar to the shape of the circular cylindrical portion 3 described in the fourth embodiment. In the structure in which the circular cylindrical portion 3 existing in the portion facing each corner 2a in the cylindrical portion 2 is narrowed in the tube axis direction toward the corner 2a of the rectangular tube 2 without a vertical wall. Formed. The other points are formed in the same manner as the tubular body P of the second embodiment and the third embodiment.

  By adopting such a structure, the synthetic resin tubular body referred to in the present invention is thinned at each corner 2a of the rectangular tube portion 2, and is particularly localized at both corners in the tube axis direction. Thinning and the accompanying weakening can be prevented efficiently and reliably. The curve S <b> 1 of the apex portion t here does not need to be a concentric curve with the circular cylindrical portion 3 as described above. However, if the concentric circular curves are used, the bulging rate from the circular cylindrical portion 3 of all the curved portions of the curve S1 can be made the same, and the thickness of the apex t is uniform. can do. In addition, the curve S1 here is not restricted to a concentric curve with the circular cylinder part 3, It can also form on a straight line.

  The synthetic resin material for forming the pipe body P referred to in the present invention includes a synthetic rubber material. Moreover, since it is necessary to change the hardness of a pipe body according to the magnitude | size of a pipe body to manufacture, a use place, etc., the resin raw material to be used should just select and use the thing of arbitrary hardness. However, in the case of a pipe that is used by being buried in the ground, it is necessary to take into account the external pressure applied to the pipe wall 1 and to make it a thick pipe body having sufficient flat pressure strength. The tubular body P shown in each of the above-described embodiments includes a cylindrical portion 2 having a substantially square cross section and a cylindrical portion 3 having a substantially circular cross section, one by one in the tube axis direction, and one over the entire tube. Although shown as being formed, the cylindrical portions 2 and 3 do not have to be alternately arranged one by one, and are formed not on the entire tube but on a part of the tube. It may be.

  The representative embodiments of the present invention have been described above. However, the present invention is not necessarily limited only to the structures of these embodiments, and has the above-described constituent features according to the present invention and the object of the present invention. Can be implemented with appropriate modifications within the range having the above-mentioned effects.

  Since the tubular body referred to in the present invention has a square cylindrical portion with a substantially square cross section arranged in the direction of the tube axis, it is possible to stabilize the posture during piping, but there is no localized weak portion. Moreover, since the weight of the tube does not increase and a large amount of material is not required, it is expected to be used and used greatly in the market.

The perspective view which shows the tubular body of 1st Example. The side view of the pipe. The right front view of the same pipe. The left front view of the pipe. FIG. 3 is an enlarged cross-sectional view taken along line D-D in FIG. Sectional drawing along the EE line of FIG. The perspective view which shows the pipe body of 2nd Example. The side view of the same tubular body. The left front view of the tube. The perspective view which shows the pipe body of 3rd Example. The side view of the same tubular body. The left front view of the tube. The perspective view which shows the tubular body of 4th Example. The side view of the same tubular body. The perspective view which shows the pipe body of 5th Example. The side view of the same tubular body. The perspective view which shows the pipe body of 6th Example. The side view of the same tubular body. The perspective view which shows the tubular body of a prior art example. Sectional drawing which fractured | ruptured some square cylinder parts by the left side enlarged front view of the same pipe body. The expanded sectional view which cut | disconnected the corner | angular corner part of the same pipe body along the FF line of the pipe-axis direction FIG. The perspective view of the tube which forms the tubular body which shows a comparative example. FIG. 6 is an enlarged cross-sectional view of a portion corresponding to FIG. 5 of the tube. Sectional drawing of FIG. 6 equivalent part of the same tubular body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tube wall 2 Rectangular cylinder part 2a Corner | angular corner part 2b Side part t Corner | angular apex part 3 Circular cylinder part w Thickness of a circular cylinder part P Tube

Claims (2)

A tubular body provided with at least a part of a tubular wall (1) in which a tubular section (2) having a substantially square cross section (2) and a tubular section (3) having a substantially circular cross section are arranged alternately in the tube axis direction ( P), a synthetic resin pipe that is formed in a shape in which each corner (2a) in the rectangular tube portion (2) has a narrower width in the tube axis direction as it reaches the apex (t). A tubular body (P) having a tubular wall (1) in which a tubular section (2) having a substantially square cross section (2) and a tubular section (3) having a substantially circular cross section are arranged alternately in the tube axis direction, Each corner (2a) in the cylindrical part (2) is formed in a circular arc shape in cross section, and the synthetic resin pipe is formed in such a shape that the width in the tube axis direction becomes narrower toward the direction of the corner apex (t). .

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