Deformable pull plug

Abstract

A reusable pull plug for masking part openings in parts to be coated or otherwise worked upon. The pull plug has particular utility in masking irregular surface portions about the part opening including, without limitation threaded, chamfered, stepped and spot faced surfaces. The pull plug is comprised of a deformable, segmented body including plug, transition and tail body segments. A flange and void volume, or "dimple," are formed in one plug body end adjacent the plug segment. The pull plug is pulled into the part opening by the tail segment and the plug segment forms a frictional fit with the deformable body tightly sealing the part opening. The flange covers the first thread in threaded part openings and further covers chamfered, stepped and spot faced surfaces protecting those surfaces from contact by the coating or other materials. The void volume facilitates deformation of the flange and plug segment permitting the flange to conform to the surface about the part opening and permitting the pull plug to be withdrawn through the part opening in the same direction as inserted thereby avoiding damage to the applied coating material. The novel design reduces stresses on the pull plug and enables the plug to be reused through repeated coating or operation cycles.

Description

[0001] This invention is related generally to masking apparatus and, more specifically, to masking apparatus for covering openings in parts during coating and other operations.[0002] Many types of manufactured parts, such as parts used in fabrication, aerospace and final assemblies must be coated with various materials and substances to adapt those parts for their intended end use. Such coatings are typically selected to impart desired characteristics to the coated part. For example, the coating may impart corrosion resistance to the part or may be selected to impart a selected surface finish or cosmetic appearance to the part.[0003] As is known, many different types of materials can be applied to the parts during coating operations. These materials include, for example, nylons, polycarbonates, metals and other known materials.[0004] There are many coating technologies available and the specific coating procedure can be selected based on the specific application. Modern coating oper...

AI Technical Summary

Benefits of technology

"The invention is a pull plug that solves problems with previous pull plugs by improving their design. The pull plug has a body with segmented parts that can deform to conform to the shape of the part opening. It can mask a range of part openings and is simple and easy to use. The pull plug can be removed in the same direction as inserted and is reusable. The technical effects of this invention include improved pull plug performance, simplified use, and prevention of damage to coatings or other materials."

Problems solved by technology

Depending on the specific application for the part, contact between the coating and the internal surface portions of the part can be undesirable and can severely damage the part.

These threads about the part opening pose a particular problem with respect to limiting the migration of coating material into the interior portions of the part.

More specifically, the protruding threads interfere with the operator's ability to form a complete seal over the part opening blocking the flow of coating material into the part.

Yet another complication involving threaded openings relates to the fact that the first thread of the threaded opening is typically chamfered and is not flat or smooth.

The chamfered edge further interferes with the ability to form a complete seal over the opening.

Failure to fully mask the first thread of the chamfered opening may permit coating materials to contact and build up on the threads damaging the threads and preventing engagement with the fastener or other part following completing of the coating or other work process.

Unwanted application of coating to the threads can result in costly re-working expenses or loss of the part.

The different surface geometries about the part opening present an obstacle to forming a complete mask over such surfaces.

As will be readily understood by those of skill in the art, serious contamination of a threaded part opening tapped directly into the part could potentially result in loss of the entire part.

During manufacturing of the product, flux and metal contaminants from welding operations near the weld nut can undesirably become attached to the weld nut in or near the weld nut threaded opening.

Any such contamination may require costly cleaning or re-working of the threaded opening in the weld nut or may even require removal of the weld nut.

Yet a further factor complicating coating and manufacturing processes is the fact that there is an almost infinite variation in the types of part openings that may be encountered.

Each different type of part opening potentially represents a unique set of problems with respect to masking of the opening.

Because thousands of masking devices may be required for a large production run, the operator is required to maintain a large inventory of plugs.

While conventional plugs are very effective in masking typical part openings, such plugs are less than fully effective in masking specialized part openings such as threaded openings, countersunk openings and other openings having more unique configurations.

A less than complete seal may be formed because the more rigid material typically used to make these plugs does not fully seal the helical passageway formed by the threads.

By way of further example, conventional plugs, including pull plugs, lack structure to shield the chamfered edge of the threaded opening from contact with coating material or contaminants.

The higher durometer material used in the washer flanges limits the capability of the plug to conform to the irregular surfaces about the part opening.

A further disadvantage of washer plugs involves the fact that such plugs must be removed from the part opening in a direction opposite to the direction in which the plug was inserted.

Removal of the washer plug in the direction opposite to the direction of insertion can result in an irregular tearing of the applied coating material around the location of the plug damaging the coated part.

As a further example, conventional plugs, including pull plugs, are also ineffective in masking countersunk portions about the part opening, such as the tapered annular portions located about the annulus of a part opening.

Such conventional plugs are not effective in masking the countersunk portion because the plug body is sized to approximate the opening and is not sized sufficiently to mask the larger countersunk region surrounding the opening.

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