Plastic pipe coupling system

Details Plastic pipe coupling system Plastic pipe coupling system

2002-02-25

2004-01-13

Bagnell, David (Department: 3672)

Pipe joints or couplings

With means blocking release of holding means

Auxiliary latch

C285S255000, C285S382000

Reexamination Certificate

active

06676166

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention relates generally to plastic pipe systems or tubes of the type used particularly but not exclusively for irrigation systems, potable water, sewage, electrical power lines, and for any structures made from pipe or tube components which are assembled together.
Plastic pipe systems formed from polyvinyl chloride, chlorinated polyvinyl chloride, polyethylene and other plastic materials are widely used for a variety of applications at the present time. With the advent of plastic pipe materials a need has existed for connecting lengths of pipe together to form a string of pipes or a structure.
Currently there are several methods employed for joining plastic pipe or tubing strings. The most commonly used methods feature use of solvents and couplings, or specialized couplings, which include gaskets when a fluid seal is desired, or pipes with integral end connections.
In the first case, a solvent is applied to the free ends of two or more pipes and a coupling piece. The coupling piece can be integral to the pipe in the form of a bell end or can be a separate piece such as an elbow, a “T”, a “Y”, a cross or similar coupling. The solvent is used to join the pipe and coupling pieces together. In the case of fluid transport or electrical power lines, the solvent also provides a liquid seal.
There are numerous inherent liabilities when utilizing solvents to join pipe components:
(a) The solvents typically have a short working time typically about ten seconds. Once the solvent has set, relative motion of the parts is not possible.
(b) A solvent bond does not allow for any rotational or axial misalignment of the pipe joints. Misalignment can occur when assembling a pipe string that has an elbow, “T”, “Y” or other geometry which requires specific rotational alignment.
(c) Disassembly of the parts after the solvent has set requires destructive techniques. The fittings must be cut off and a new fitting added.
(d) The mating surfaces which are to be solvent welded need to be clean and dry before application of the solvent.
(e) Before testing the system for integrity of a sealed connection the solvent must be completely cured.
(f) The unused solvent hardens over time until it is no longer usable.
(g) Frequently, use of a primer is recommended further complicating the task.
(h) The solvent is difficult to use. The solvent and primer tend to get on surfaces beyond the desired surfaces such as clothing, hands, and other pipe components. The threaded caps on the solvent cans can be difficult to open particularly if any solvent has dripped onto the threaded surfaces. It is not unusual to spill the solvent can.
(i) Use of solvents for joining pipe components is unpleasant, and potentially hazardous. The fumes represent a health hazard and are unpleasant. The solvents can be extremely flammable and can cause damage to the environment.
Alternatively, as mentioned previously, lengths of pipe can be joined using couplings and gaskets. Listed below are two critical disadvantages in using couplings with gaskets to join pipes:
(a) Couplings that require a gasket for sealing are very expensive and hence are rarely used for residential irrigation.
(b) These couplings are dimensionally large making them difficult to incorporate in pipe or tube strings. The increase in diameter can make it difficult to put many pipe strings in an irrigation trench such as those for residential sprinkler systems that are typically limited in size.
Various types of connections have been devised which do not have coupling parts but instead have integral end connections. Several types of plastic pipe joining systems have been proposed—for example in the U.S. Pat. No. 5,918,914 to Morris (1999), U.S. Pat. No. 5,662,360 to Guzowski (1997), U.S. Pat. No. 5,078,430 to St. Onge (1992), U.S. Pat. No. 4,875,714 to Lee (1989), U.S. Pat. No. 4,779,902 to Lee (1988), U.S. Pat. No. 3,784,235 to Kessler (1974), and U.S. Pat. No. 3,217,400 to Illesy (1965). For all of these patents, repairs are very difficult, that is, in order to repair a broken section without the use of a coupling, the entire pipe must be replaced. Additionally these patents suffer from a combination of the following problems: requires a complex, integral end connection that can not accommodate custom lengths, requires a gasket or solvent for sealing, does not include a press fit outer ring for support of the coupling under bending loads, requires tight tolerancing. U.S. Pat. No. 5,918,914 and U.S. Pat. No. 5,662,360 have complex, integral end connections, require gaskets for sealing, and lack support for bending loads. U.S. Pat. No. 5,078,430 has a complex, preformed, integral end connection, can not accommodate custom lengths, and requires a gasket for sealing. U.S. Pat. No. 4,875,714 has a complex, preformed, integral end connection, requires tight tolerancing, can not be easily disassembled, and can not accommodate custom lengths. U.S. Pat. No. 4,779,902 and U.S. Pat. No. 3,784,235 require a gasket or adhesive for sealing, can not accommodate custom lengths, and can not be easily repaired without the use of a coupling. U.S. Pat. No. 3,217,400 can not be easily repaired or disassembled, and does not have an outer ring to support against bending loads. These devices and others which feature integral end connections without separate coupling parts have several disadvantages:
(a) Fabrication of the pipe or tubing is complicated. The pipe can not be simply extruded but requires additional machining or other laborious fabrication process.
(b) Key components can not be easily fabricated in the field so they are impractical for applications which require customized pipe lengths.
(c) The joint is mechanically weak in bending.
(d) Relatively tight tolerancing is required between the mating surfaces.
(e) The parts generally can not be easily disassembled.
(f) Repair of a broken section requires the replacement of the entire pipe.
Patents that feature couplings can be complex. U.S. Pat. No. 5,180,197 to Thompson Jr. (1993) features a coupling made from two different materials; a hard outer plastic shell encasing a gasket-like, soft, elastomeric material for sealing. U.S. Pat. No. 4,392,294 to Campbell (1983) requires an outer metallic support ring which is bolted together and requires that the pipe ends be butted together.
Many pipe string applications require that the pipes provide an effective, fluid-tight barrier between the contents of the pipe and the environment surrounding the pipe. For example, the piping may need to provide a shield for protecting electrical conductors or the pipes may contain sewage or caustic chemicals. What is needed is a simple, inexpensive pipe coupling system which can be easily used in the field for custom applications, allows for easy assembly and alignment of components, and maintains a fluid seal without the use of cements or solvents.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a system for joining lengths of plastic pipe using a coupling and an outer ring. A shallow groove is cut into the end of a pipe, a specialized coupling is snapped into the groove and an outer ring is added to provide additional mechanical strength. It is an object of the present invention to provide an interlocked restraint for a plastic pipe coupling system. This is accomplished by cutting a shallow groove into the end of a pipe using a basic cutting tool. Next a ring with an internal taper is slid over the free end of the pipe. The ring is designed such that the inside diameter of this ring is larger than the outside diameter of the pipe so the ring is free to slide over the pipe. A female coupling is slipped onto the pipe and snaps in place in the cut groove in the pipe. The ring is then manually installed over the coupling. The inside diameter of the tapered ring is smaller than the outside diameter of the coupling so th

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