1. Technical Field
This invention relates generally to bell and spigot pipe, and more particularly to a new and improved seal construction for such a pipe.
2. Background Information
Bell and spigot pipe is fabricated in generally rigid, cylindrically shaped sections. A bell portion of a section flares outwardly to the bell end in a bell shape, while a spigot end remains relatively straight in a configuration adapted to be inserted into the bell portion of another section to form a joint. Construction crews can join practically any number of sections in this way, and they often do so with large sections composed of pipe materials such as concrete, plastics, asbestos cement, steel, cast iron, or ceramics and the like, to construct any of various types of pipelines, such as those used in water supply, sewage systems, and drainage systems.
However, such pipelines often require adequately sealed joints between adjoining pipe sections, and existing bell and spigot pipe has certain drawbacks in this respect that need to be overcome. For example, some existing seal constructions employ a bell portion that is cast over part of an annular gasket or sealing ring so that the bell portion is formed with the sealing ring embedded in place, facing radially inwardly. When the spigot portion of another section is inserted in the bell portion, it bears against the sealing ring in sealing engagement.
This technique produces a sealing ring that is permanently affixed to the pipe section at the time of fabrication. One reason for doing this is that the sealing ring may otherwise become dislodged from or displaced as the spigot portion is inserted. In other words, as the spigot portion bears against the sealing ring, the sealing ring may loop or roll out of proper alignment, and the permanently affixed sealing ring is intended to overcome this problem. However, existing methods of fabricating a permanently affixed sealing ring may require complicated casting forms with components that can not be reused. Thus, the fabrication is more costly and inconvenient. Consequently, it is desirable to have a seal construction that overcomes this concern.
In addition, a permanently affixed sealing ring may deteriorate prior to use when the pipe section is stored in an unregulated environment, such as out of doors, from exposure to sun, ozone, and other environmental conditions. Since such a sealing ring is not conveniently replaced, the whole section of pipe may have to be replaced. Consequently, it is desirable to have a new and improved seal construction that overcomes this concern also.
Furthermore, the pressure distribution created as the spigot portion is forced into the bell portion against the sealing ring sometimes results in the bell portion fracturing. When the fracture is noticed, the section of pipe must be replaced. When unnoticed, a leaky joint may result, and this may occur long after construction has been completed to further compound the cost of remedial action. Consequently, it is desirable to have a new and improved seal construction that reduces the forces acting on the bell to thereby reduce the occurrences of bell fracturing, and it is desirable to do so with a seal construction fabrication method that is more convenient and less costly to perform.