Pipes and tubular conduits – With closures and plugs
Reexamination Certificate
1999-08-04
2001-01-09
Hook, James (Department: 3752)
Pipes and tubular conduits
With closures and plugs
C138S089400, C138S104000, C215S230000, C215S256000, C215S258000, C220S268000, C220S276000
Reexamination Certificate
active
06170529
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to end plugs for pipes and, more particularly, to polymeric plugs of the type that are cemented into the ends of plastic pipe for use in leak testing.
2. Description of Related Art
Pipe end plugs are frequently used for leak testing of plastic pipe installations and to keep debris out of plastic pipes during construction. The plugs are typically injection molded from a thermoplastic material such as polystyrene and have annular flanges that are cemented in place on the end of a section of plastic pipe. Once the pipe has been filled with a fluid and the flow system has been tested for leaks, a circular “knockout” disc in the plug is removed to permit the passage of fluid through the end of the pipe into other fittings or flow lines to which the pipe end is subsequently connected.
Conventional plastic pipe end plugs comprise a knockout disc that traverses the pipe bore at a point recessed slightly inside the end of the pipe. The knockout disc is typically molded as a unitary part of the plug and is connected to the inside annular flange of the plug by a continuous, circumferentially extending web having a reduced thickness as compared to the thickness of either the disc or flange portions of the plug. The thinned plastic web is designed to be strong enough to withstand the anticipated test pressure, but thin enough to facilitate removal from the plug flange by the application of force such as a hammer blow when it is time for the knockout plug to be removed.
One disadvantage commonly experienced in using conventional plastic pipe end plugs is that the knockout disc falls into the pipe when removed from the plug. Similarly, If the disc shatters instead of breaking away cleanly when struck with a tool such as a hammer, pliers or screwdriver, the blow can drive plastic fragments further into the bore. A pipe plug is therefore needed that comprises an easily removable disc which cannot fall into the pipe upon removal.
Another disadvantage commonly experienced in using conventional pipe end plugs is that the plug and disc are opaque. This opacity precludes the user from observing whether or not the test fluid, typically water, has sufficiently filled the piping system to reach and fully contact the plugged pipe end. In the past, users have often drilled through or otherwise punctured the end plug during a leak test in order to determine whether the underside was wetted. A pipe end plug is therefore needed that will permit the user to determine by visual inspection whether or not the underside of the knockout disc is wetted by a contained fluid.
SUMMARY OF THE INVENTION
Disclosed herein is a plastic end plug for use with plastic pipe, the end plug having a knock-off disc with dimensions that prevent the entire disc, when separated from the remainder of the plug, from entering the pipe bore. The knock-off disc of the plastic end plug is removable by a force applied to the disc in a direction substantially perpendicular to the longitudinal axis through the pipe bore, and desirably includes an optical indicator observable by the user to determine whether or not the underside of the knock-off disc is wetted by a fluid contained in the pipe segment.
According to one preferred embodiment of the invention, an end plug is provided for use with plastic pipe, the plug comprising a knock-off disc having a cross-sectional dimension that, when the disc is separated from the annular flange of the pipe, is too great to permit the disc to fall through the plug flange and into the pipe bore. The pipe end plug of the invention preferably includes a knock-off disc that extends slightly beyond the end of the plastic pipe section on which it is installed, has a diameter slightly greater than the inside diameter of the annular flange of the plug, and is removable from the annular flange of the plug by the application of a blow in a direction substantially perpendicular to the longitudinal axis through the pipe bore.
According to another embodiment of the invention, a pipe end plug is disclosed that comprises means for visually determining whether the underside of the plug is wetted by a contained fluid. One preferred pipe end plug comprises a clear plastic knock-off disc. Another preferred pipe end plug comprises a knock-off disc with an underside that appears “frosted” or has a visible symbol or legend when dry, but that appears transparent or without any visible symbol or legend when wetted by a fluid contained inside the pipe.
REFERENCES:
patent: 743269 (1903-11-01), Godin
patent: 3633586 (1972-01-01), Sheridan
patent: 3646980 (1972-03-01), Peterson
patent: 3996966 (1976-12-01), Princell
patent: 4678097 (1987-07-01), Crute
patent: 4899903 (1990-02-01), Miyasaka et al.
patent: 4936350 (1990-06-01), Huber
patent: 5033510 (1991-07-01), Huber
patent: 5706860 (1998-01-01), Gonyea
patent: 6032515 (2000-03-01), Huber
Specialty Products Catalog, p. 3, published at least as early as Oct. 15, 1998.
Hook James
Locke Liddell & Sapp LLP
LSP Products Group, Inc.
Ross Monty L.
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