Corrugated plastic pipe sections having flanged ends and structurally tight joints thereof

Abstract

Corrugated plastic pipe sections having a flanged end formed by a circumferential portion of an end corrugation or section of the pipe liner and a method and kit for joining flanged end corrugated plastic pipe sections are described in a system in which a portion of the end corrugation or pipe liner forms a flange and a peripheral flange clamp straddles flanges and draws the flanges together to provide a structurally sound joint. A gasket may be interposed between flanges or the flange periphery and the clamp. The invention achieves a cost effective tight joint, allows field cuts of the corrugated plastic pipe and the fabrication of fittings from corrugated pipe sections and provides a selectable pipe size reducer coupling for corrugated plastic pipe.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001] This application is a continuation-in-part of my co-pending applications "Joint and Seal for Large Diameter Corrugated Plastic Pipe and Method for Joining Plastic Pipe Sections," Ser. No. 09 / 597,338 filed on Jun. 19, 2000; "Water tight Joint and Method of Sealing Drainage and Sanitary Sewer Pipe Sections," Ser. No. 09 / 788,913 filed on Feb. 19, 2001; and "Method and Joint Design for Infield Water Tight Sealing of Dual Wall Corrugated Plastic Pipe Sections," Ser. No. 09 / 794,638 filed on Feb. 27, 2001.BACKGROUND OF THE INVENTION[0002] Large diameter corrugated plastic (typically formed from polyethylene) pipe sections are known products. Past and present attempts to design water tight joints for corrugated plastic pipe to expand the use of the pipe to drainage and sanitary sewer applications typically involve radial compression of a gasket (molded or extruded and spliced) that occurs when an end section of the pipe formed as a spigot is ins...

AI Technical Summary

Benefits of technology

[0006] The invention comprises corrugated plastic pipe sections having a flanged end formed by a circumferential portion of an end corrugation or the pipe liner and a method and kit for joining corrugated plastic pipe sections to create a structurally sound joint that may be adapted for applications where soil and water tight joint properties are required. In the system of the invention, a portion of the end corrugation or pipe liner forms a flange at the end of each pipe to be joined; a clamp straddles the outside lateral surfaces of the two flanges and draws the flanges together. A joint is thereby formed. An annular elastomeric gasket may be inserted contacting the facing surfaces of the pipe flange and a second flange at the end of another pipe or fitting, or the radially peripheral side edges of the flanges. The invention achieves a cost effective structurally sound joint, allows field cuts of the corrugated plastic pipe and the fabrication of pipe fittings and connectors from corrugated pipe sections with limited modification to the molding process.

[0007] An object of the invention is to provide a tight joint by providing a flange at the end of the corrugated plastic pipe from a circumferential portion of the end corrugation, thereby avoiding the need and expense associated with molding separate bell and spigot or dual bell couplers. It is a further object of the invention to provide a section of corrugated plastic pipe having a flange at its end formed from a section of a corrugation, the liner and / or from both the liner and the corrugation. It is also an object of this invention to provide a section of corrugated plastic pipe joined to an abutting section of corrugated plastic pipe or a fitting having a flange at its end by inserting a gasket between the abutting flanges and utilizing a clamp to axially compress a gasket to form a water tight seal. An external rigid clamp supports the relatively weak flange eliminating the need to stiffen the end of the corrugated pipe by injecting rigid foam into the end corrugations.

[0008] The present application also discloses a kit for providing a water tight seal between adjacent (abutting) sections of corrugated plastic pipe or fittings comprising a gasket and a flange clamp adapted to form the joint. In a further object, the invention comprises a design for and method of using fabricated fittings to join flanges on the end sections of corrugated pipe that are formed from circumferential portions of the pipe corrugations and / or liner. Presently fabricated fittings typically require pipe ends that have bell shapes or spigot shapes and may require dual bell couplers. The present invention eliminates the need for specially formed ends and couplings and allows corrugated pipe to be manufactured without introducing coupling molds into the forming process, thus saving the money associated with utilizing specially molded bells and spigots for fittings. The invention eliminates the need for bell and spigot ends on sections of corrugated plastic pipe and fittings and eliminates the need for internal and external dual bell couplers.

[0010] The enhanced joint design and method of fabricating soil tight and water tight joints disclosed is cost effective, allows field cuts of corrugated plastic pipe, and simplifies in-plant fabrication of flanged end fittings from sections of corrugated pipe. A clamp is utilized to compress the annular gasket by drawing the two flanges together. This invention utilizes a portion of the end corrugation or liner to provide an interior surface to compress a rubber gasket and an exterior surface against which the clamp radially pushes inwardly.

Problems solved by technology

The motion of pushing the gasket on the spigot in an axial direction and the frictional force on the interior lateral surface of the bell may cause the gasket to un-seat, twist and roll.

In addition, circumferential tensile stresses on the interior of the bell, required to maintain gasket compression, decrease the stress crack resistance of the plastic pipe.

In the prior case the stiffness of the corrugation is not sufficient to withstand the hydrostatic water pressure required to prevent water leaks.

Both solutions add considerable cost obtain a reliable water tight joint.

A further disadvantage of joints that utilize radial compressed gaskets is that the joints are subject to failure, leaking water under pressure, as a result of rolling and twisting of the gasket or by stress cracking of the bell.

However, the gasket transfers stress to the plastic inner wall or liner and to the corrugations.

Both the corrugations and the liner are relatively low in stiffness and have difficulty maintaining the radial compression of the gasket.

The high creep behavior of semi-crystalline polymers such as high-density polyethylene is responsible for increased leaking due to aging.

It may also be difficult to assemble a joint as described by Hattori when the pipe sections to be joined are located in an open trench.

Another disadvantage is the relatively high cost associated with an extended cylindrical gasket and a metal clamp.

Bell and spigot type joints have an additional disadvantage insofar as field cuts of sections of corrugated pipe are not possible.

The locating seat (transverse ridge) on the end corrugation has a disadvantage in that formation of the spigot requires a thermoforming mold to be introduced in the corrugation process and the other end of the corrugated plastic pipe either requires a molded bell at the end or necessitates the use of a dual bell coupler.

This approach suffers from the weakness of the walls the corrugation supporting the crown of the corrugation and the gasket plus the cost associated with manufacturing in-line bell and spigot couplers.

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