Pipe joints or couplings – Flexible joint – rigid members – Concrete – clay – or masonry pipe
Reexamination Certificate
1998-07-02
2001-05-29
Luu, Teri Pham (Department: 3629)
Pipe joints or couplings
Flexible joint, rigid members
Concrete, clay, or masonry pipe
C292S231000, C277S625000, C277S944000
Reexamination Certificate
active
06237966
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to pipe joints having flexible fluid-type seals.
2. Description of Related Art
Storm and sanitary sewer pipes are generally made of plastic, metal, concrete, or other suitable materials fabricated in configurations and sizes to meet particular requirements or specifications. It is known in the art to form grooves or provide recesses in ribbed or corrugated types of pipe. Spigots (i.e., male pipe sections) are the dominant method performed for manufacturing sewer pipe, although grooves can be formed in bells (i.e., female pipe sections). Resilient seals are typically provided by polymeric gasket elements. O-ring type gaskets are one type of resilient seal that is frequently employed. An O-ring can be mounted on the spigot and then the spigot pushed into the bell.
It is known in the art that O-rings may distort non-uniformly, resulting in weak seals or voids through which liquids can flow. Thus, spigots are often provided with a circumferential groove or a single or double offset shoulder to keep the O-ring from rolling as the pipes are interconnected. Nevertheless, if the diameter of the O-ring and its radial cross-section are greater than the depth of the groove or shoulder, the ring may still roll over the inside edge of the groove, become snagged, or shear off segments of the O-ring as the spigot enters the bell. Various gasket profiles have been used or suggested to overcome these deficiencies.
One conventional pipe joint has an outer pipe and an inner pipe inserted into the outer pipe wherein one of the outer and inner pipe comprises an annular groove. A gasket is positioned within the annular groove and is adapted to provide a seal between the outer pipe and the inner pipe. The gasket comprises an annular gasket body of resilient material. A protrusion extending radially away from the gasket body is located on the gasket body and is bisected by a centerline thereof. An annular bore extends through in the gasket body. The gasket is used between a first pipe and a second pipe, and is placed with its body essentially filling a U-shaped groove in one of the pipes. A number of compression points are provided that are in contact with respective surfaces of the first pipe and the second pipe, including surfaces of the groove. When compressed, a sealing contact is established between a first compression point and an inner surface of the pipe not having the groove, and sealing contacts are established via contact of several additional compression points with the walls of the groove. Thus, except for a small aperture through the base of the gasket, it is the case both before and after compression that the gasket essentially completely fills a groove in one of the pipes.
In view of the large number of pipe joints that may be installed in a typical sewer system, conventional gaskets require more gasket material then is economical. In addition, because their requires them to essentially fill a groove to function properly, such gaskets are impracticable for use in pipe joints in which suitable grooves are not provided.
SUMMARY OF THE INVENTION
It would be advantageous to provide a pipe joint and gasket with a grooved pipe in which the groove holds the gasket in place but is essentially void of gasket material, thus reducing the cost of the gasket without compromising its sealing function. It would further be advantageous to provide a grooved pipe joint having a gasket that is also suitable for use with pipe joints not employing discrete grooves, thus reducing the number of types of gaskets required in inventory when both grooved and ungrooved pipe joints are required.
It is an object of the present invention to provide a gasket that provides a sealing function, yet does so without requiring as much gasket material as is needed with prior art gaskets.
It is yet a further object of the present invention to provide a pipe joint having a co-extruded gasket.
It is another object of the present invention to provide an improved pipe joint having a pipe section with a groove for holding a gasket in place, yet having a gasket that provides a sealing function with less gasket material than prior art gaskets.
It is still another object of the present invention to provide an improved pipe joint that requires substantially reduced gasket material from that required by comparable prior art pipe joints.
It is yet another object of the present invention to provide a pipe joint having a groove for a gasket, but employing a gasket that can be fitted to pipe joints without grooves, so that an inventory of gaskets can be reduced from that which might otherwise be required.
It is still another object of the present invention to provide a method of making a pipe joint in which one of the pipe joints has a groove for a gasket, wherein the method requires substantially less gasket material that is required by comparable methods of making pipe joints.
It is yet another object of the present invention to provide a method of making a pipe joint in which one of the pipes has a groove for a gasket the method using a gasket that may be used in joints with or without grooves, so that an inventory of gaskets may be reduced.
According to the present invention, there is therefore provided a pipe joint comprising: a first pipe section; a second pipe section operatively connected to the first pipe section; a gasket sealingly engaging the first pipe section and the second pipe section for resisting fluid leakage therebetween, the gasket having a first portion having a first durometer hardness and a second portion having a second durometer hardness, the first durometer hardness being different from the second durometer hardness. Advantageously, the first portion and the second portion of the gasket may be co-extruded, and the first portion made of a relatively soft, thermoplastic elastomer material. The first portion of the gasket can comprise an annular tongue affixed to an annular substrate of a relatively harder, plastic material. Preferably, the substrate comprises an inward-facing portion relative to the tongue of the gasket, with the tongue extending in an outward radial direction from the substrate. The substrate may have stiffening ribs on either side of the affixed tongue, and ridges on a side of the substrate opposite the tongue to hold the gasket in a groove of one of the pipe sections without filling the groove. The ridges may comprise a portion of a softer material than the substrate, and may comprise a material of the same composition as the tongue. This softer material allows the gasket to be used in applications where no groove is present by having the ridges themselves form a seal with a surface of a pipe section.
Also in accordance with the invention, there is provided a method of sealing a pipe joint, the pipe joint comprising a first pipe section and a second pipe section, the method comprising: co-extruding a first material and a second material to form a co-extrusion having a first portion of a first durometer hardness and a second portion of a second durometer hardness; forming a gasket from the co-extrusion; and sealingly engaging the pipes with the gasket. The co-extrusion step may advantageously comprise co-extruding a thermoplastic elastomer as the first material, and a second material such as polypropylene, the first material being relatively softer than the second material. The co-extrusion step may advantageously co-extrude a tongue as the first portion and a substrate as the second portion. Stiffening ribs generally on opposite sides of the tongue may be formed in the substrate in the co-extrusion step. Also, a plurality of ridges may also be co-extruded on a side of the substrate opposite to that of the tongue, and a recess in a groove in one of the pipe sections may be bridged without filling the groove. The ridges may be formed of the same material as the softer, first portion and co-extruded therewith.
The manner of realizing each of the objects of the invention will become apparent to one skilled in t
Bidco Plastic Extrusion, Inc.
Howell & Haferkamp L.C.
Luu Teri Pham
LandOfFree
Co-extruded dual durometer hardness pipe gasket does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Co-extruded dual durometer hardness pipe gasket, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Co-extruded dual durometer hardness pipe gasket will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2568152