Patent Application
20080092977
The improved cap and plug of the present invention will be described in connection with the Figures.
The cap and plug 1 shown in the Figures is a molded tubular member comprised of a resilient material and having a closed end 3 and an open end 5, and having a sidewall therebetween.
The sidewall has an interior surface 9 which has an inwardly-directed ridge 7 extending circumferentially along at least a centrally-disposed portion of the interior surface of the sidewall. The inwardly-directed ridge 7 is shown in
The closed end comprises a centrally-positioned hollow dome portion 11. The dome portion is defined by an inwardly-extending open-ended annular recess 13. The annular recess defines a sidewall 15 spaced from the interior surface 9 of the sidewall of the tubular member.
The sidewall 15 defined by the annular recess contains at least one gas vent groove 17 extending along the longitudinal extent of the sidewall from an upper portion of the sidewall toward and to a lowermost portion of the sidewall. While two vent grooves are depicted in
The sidewall 15 defined by the annular recess 13 is spaced from the interior surface 9 of the sidewall of the tubular member a distance greater than the height of the inwardly-directed ridge. Preferably, the uppermost extent of the inwardly-directed ridge is spaced longitudinally from the lowermost extent of the open-ended annular recess. Such spacing enhances the ability of the cap and plug to snugly engage with an inserted pipe or tube.
The particular configuration of the end surface of the annular recess is not critical to practice of the present invention. For instance,
During use, the cap and plug of the present invention is employed with advantage during the coating of tubes or pipes, whereby an end portion of the tube or pipe is required to be masked during the coating process. Such pipes or tubes are generally hollow and open-ended at one end. For instance, during powder coating of a metal tube or pipe, the cap and plug of the present invention, when inserted onto the end of the tube or pipe, serves to mask the covered portion of the tube or pipe during the coating process. The design of the cap and plug also provides additional advantages. Prior to being coated, it is frequently necessary to wash the exterior surface of the tube or pipe to prepare the surface for coating. It is desirable to seal the end of the tube or pipe during the washing process to prevent entry of wash liquid or contaminants from entering the interior of the hollow tube or pipe. The presence of the cap and plug of the present invention accordingly serves to seal the end of the tube or pipe.
Further, after the coating step, it is generally necessary to cure the coating on the surface of the tube or pipe which involves subjecting the coated tube or pipe to elevated temperatures sufficient to cure the coating. The exposure of the capped tube or pipe to elevated temperatures causes gas (such as air) trapped in the capped tube or pipe to expand. Absent some means to permit such expanded gas to escape, the cap and plug may be blown off the end of the tube or pipe.
The present invention addresses this issue by providing a cap and plug comprised of a material which becomes sufficiently flexible at the elevated curing temperature such that, as the internally-trapped gas begins to expand, the walls of the cap and plug are caused to expand to an extent sufficient to permit the expanding gas to escape without the cap and plug being blown off the pipe or tube. The presence of the gas vent grooves 17 also serves to assist the internally-trapped gas to escape toward the top portion of the cap and plug. The presence of the dome portion permits heated gas to also expand therein which flexes the adjacent inner surfaces away from the end of the pipe or tube to assist in venting gas.
The plug body can be formed from any conventional polymeric material which provides the requisite balance of physical stability and flexibility during use. Any conventional moldable polymer such as flexible polymeric materials can be used as the raw material for the plug body of the present invention. Thermoplastic rubber or elastomeric materials are preferred to permit adequate flexibility when being inserted into a cavity for sealing, while maintaining desired resilience for purposes of sealing. The material chosen shall be both dimensionally stable at ambient and those elevated temperatures used for curing any coating applied to the pipe or tube. Such materials are well known in the art and one of ordinary skill in the art can readily select an appropriate material for use in the present invention.
The plug may be made by any conventional molding process, with the method of manufacture being well within the skill of the practitioner in the art. For instance, the cap and plug may be formed by injection molding processes known to those skilled in the art. In such a process, a polymeric material such as polyethylene or polypropylene material may be used that yields a cap body sufficiently elastic or conformable to permit the body to snugly engage the end of a pipe or tube while retaining sufficient stability and exhibiting the desired flexibility at curing temperatures. Accidental disengagement of the cap body is thus avoided.
