Composite Sealing Gasket and Process for Belling Plastic Pipe

Abstract

An sealing gasket is shown for use in forming joints of plastic pipe. The gasket is formed as a composite elastomeric body with a leading region formed of a thermoplastic elastomer material and with a trailing region formed of a synthetic plastic material. The gasket body has an outer circumferential region provided with a series of recessed pocket which give it a scallop-like appearance. The relatively harder plastic region of the gasket body deforms the associated pipe socket end during manufacture of the pipe end, whereby the gasket is integrally locked within an internal pipe groove in the pipe socket end upon completion of the pipe belling operation.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates generally to sealing systems for thermoplastic pipes and, more specifically, to an improved pipe gasket and to an improved belling process for installing a gasket in a socket end of a thermoplastic pipe.[0003]2. Description of the Prior Art[0004]Pipes formed from thermoplastic materials including polyethylene and PVC are used in a variety of industries. In forming a joint between sections of pipe, the spigot or male pipe end is inserted within the female or socket pipe end. An annular, elastomeric ring or gasket is typically seated within a groove formed in the socket end of the thermoplastic pipe. As the spigot is inserted within the socket, the gasket provides the major seal capacity for the joint. It is critical, during the installation process, that the gasket not be able to twist, flip or be displaced, since a displaced or dislocated gasket will adversely affect the ultimate sealing ca...

AI Technical Summary

Benefits of technology

[0015]The present invention has as its object to provide an improved sealing gasket, an improved pipe belling process, and an improved pipe assembly method, all of which meet the needs described in the prior art and which meet the previous objectives. The belling process and pipe joint of the invention uses a special “scallop” design in a hard polymer region of the gasket body to integrate the gasket and the pipe wall. As compared to the previously described Rieber and Forsheda processes, the pipe wall and the trailing region (ramp) interface of the gasket body is no longer two smooth mating surfaces. Now the pipe wall is formed over the gasket at a temperature above its glass transition temperature. Then, either using vacuum or pressure, the pipe wall is forced to flow into cavities formed by the scalloped regions of the gasket. Now integrated with the pipe wall, the hard polymer component of the subject gasket is no longer required to act as the discrete structural member seen in the previous gasket designs described in the prior art. The structural integration apparent in the new design provides for optimal design of the trailing region of the gasket body.

Problems solved by technology

It is critical, during the installation process, that the gasket not be able to twist, flip or be displaced, since a displaced or dislocated gasket will adversely affect the ultimate sealing capacity of the joint.

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