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plug segment permitting the flange to conform to the surface about the part opening and permitting the pull plug to be withdrawn through the part opening in the same direction as inserted thereby avoiding damage to the applied coating material.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.

1 . In a reusable pull plug for masking a part opening defined by at least one part wall, the plug having a plug body, first and second ends, a body axis, an axial length between the first and second ends, a plug segment adjacent the first end and a tail segment between the plug segment and plug second end, the improvement wherein: 
 the plug body is elastomeric and has a durometer of between about 30-45 on the Shore A scale;    the plug body includes a flange along the first end adjacent a plug segment first end, the flange and plug segment first end each have a cross-sectional shape and area transverse to the body axis and the flange cross-sectional area is greater than the plug segment cross-sectional area; and    the plug body includes a first end surface defining a void volume along the first end, said void volume facilitating radially-inward deformation of the flange and plug body segment to facilitate conformation of the plug to the at least one part wall defining the part opening.    
     
     
         2 . The pull plug of  claim 1  wherein the plug body further includes a tapered transition segment between the plug segment and the tail segment.  
     
     
         3 . The pull plug of  claim 2  wherein the plug segment further includes a second end adjacent the transition segment having a cross-sectional shape and area transverse to the body axis, an axial length between the plug segment first and second ends and the plug segment first end cross-sectional area is substantially the same as the plug segment second end cross-sectional area.  
     
     
         4 . The pull plug of  claim 3  wherein each cross-section transverse to the body axis between the plug segment first and second ends has substantially the same shape and area.  
     
     
         5 . The pull plug of  claim 4  wherein each cross-sectional shape is circular.  
     
     
         6 . The pull plug of  claim 3  wherein the transition segment includes a first end adjacent the plug segment second end having a cross-sectional shape and area transverse to the body axis, a second end having a cross-sectional shape and area transverse to the body axis, an axial length between the transition segment first and second ends and the transition segment first end cross-sectional area is greater than the transition segment second end cross-sectional area.  
     
     
         7 . The pull plug of  claim 6  wherein each transition segment first and second end cross-sectional shape is circular.  
     
     
         8 . The pull plug of  claim 6  wherein the tail segment includes a first end adjacent the transition segment second end having a cross-sectional shape and area transverse to the body axis, a second end at the body second end having a cross-sectional shape and area transverse to the body axis, an axial length between the tail segment first and second ends and the tail segment first end cross-sectional area is substantially the same as the tail segment second end cross-sectional area.  
     
     
         9 . The pull plug of  claim 8  wherein each cross-section transverse to the body axis between the tail segment first and second ends has substantially the same shape and area.  
     
     
         10 . The pull plug of  claim 9  wherein each cross-sectional shape is circular.  
     
     
         11 . The pull plug of  claim 8  wherein the plug segment first and second end cross-sectional areas are greater than the tail segment first and second end cross-sectional areas.  
     
     
         12 . The pull plug of  claim 8  wherein the plug segment and tail segment axial lengths are substantially the same.  
     
     
         13 . The pull plug of  claim 1  wherein the body is a unitary element.  
     
     
         14 . The pull plug of  claim 13  wherein the plug body is made of a material selected from the group consisting of ethylene propylene, butadiene acrylonitrile, styrene butadiene, fluorinated hydrocarbons, polychloroprene and conductive silicone.  
     
     
         15 . The pull plug of  claim 14  wherein the plug body has a durometer of between about 35-45 on the Shore A scale.  
     
     
         16 . The pull plug of  claim 1  wherein the flange has an axial length between the plug first end and a spaced apart flange edge surface, the void volume has an axial length between the plug first end and the plug first end surface and the void volume axial length is between about 0.7 to 2.0 times the flange axial length.  
     
     
         17 . The pull plug of  claim 1  wherein the void volume is a dimple.  
     
     
         18 . The pull plug of  claim 17  wherein the dimple has a hemispherical geometry  
     
     
         19 . The pull plug of  claim 18  wherein the hemispherical dimple has a circular cross-sectional shape and area transverse to the body axis at the plug first end and a diameter.  
     
     
         20 . The pull plug of  claim 19  wherein the flange cross-sectional shape is circular and the flange has a diameter and the dimple diameter is between about 0.20-0.60 of the flange diameter.  
     
     
         21 . The pull plug of  claim 1  wherein the flange is deformable at an angle of between about 90-180° to the body axis.  
     
     
         22 . A reusable pull plug for masking a part opening defined by at least one part wall comprising: 
 a unitary plug body having an outer surface, a body axis, first and second ends and an axial length between the first and second ends, said body being made of an elastomeric material having a durometer between 30-45 on the Shore A scale;    a cylindrically-shaped flange formed in the body first end coaxially aligned with the body axis, said flange having an axial length between the body first end and a spaced apart flange edge surface and a flange diameter;    a cylindrically-shaped plug segment formed in the body coaxially aligned with the body axis, said plug segment having a first end adjacent the flange, a second end, an axial length between the plug segment first and second ends;    a tapered transition segment formed in the body coaxially aligned with the body axis, said transition segment having a first end adjacent the plug segment second end, a second end and an axial length between the transition segment first and second ends;    a cylindrically-shaped tail segment formed in the body coaxially aligned with the body axis, said tail segment having a first end adjacent the transition segment second end, a second end at the body second end and an axial length between the tail segment first and second ends; and    a first end surface along the body first end forming a dimple coaxially aligned with the body axis, said dimple having a diameter between about 0.20-0.60 of the flange diameter;    whereby the pull plug flange and plug segment are deformable to facilitate conformation of the plug outer surface to the at least one part wall defining the part opening.    
     
     
         23 . The pull plug of  claim 21  wherein the dimple has an axial length between the plug first end and the first end surface and the dimple axial length is between about 0.7-2.0 times the flange axial length.  
     
     
         24 . The pull plug of  claim 23  wherein the plug segment has a volume, the tail segment has a volume which is less than the plug segment volume and the plug segment and tail segment axial lengths are substantially the same.  
     
     
         25 . The pull plug of  claim 24  wherein the plug body has a durometer of between about 35-45 on the Shore A scale.  
     
     
         26 . The pull plug of  claim 25  wherein the plug body is made of a material selected from the group consisting of ethylene propylene, butadiene acrylonitrile, styrene butadiene, fluorinated hydrocarbons, polychloroprene and conductive silicone.  
     
     
         27 . The pull plug of  claim 26  wherein the flange is deformable at an angle of between about 90-180° to the body axis.