Abstract:
A device for abrading and finishing excess cured filler material from a bullnose outside cornerbead connected between immediately adjacent sheets of drywall. The device includes an elongated rigid body having a generally concave-shaped central longitudinal portion which replaceably receives a highly compressible elongated abrasive member which is substantially coextensive with, and arcuately formable to match against the bullnose cornerbead convex contours. A guide runner extends along either longitudinal side margin of the central longitudinal portion. These guide runners substantially match and glide along the outside angle between the adjacent drywall sheets when there is substantial compression in thickness of the abrasive member firmly engaged against the bullnose cornerbead.

Description:
BACKGROUND OF THE INVENTION 
     1. Scope of Invention 
     This invention relates generally to devices for sanding and finishing drywall installations, and more particularly to a device for cleaning and finishing outside bullnose joints between adjacent sheets of drywall. 
     2. Prior Art 
     There are a number of prior art devices used for finishing drywall installation corners and surfaces. Some of these devices known to applicants are directed to the application of cementious drywall filler compound; the majority of these devices, however, are directed to the sanding, scraping or finishing of the cured drywall compound prior to painting or wallpapering the finished drywall surfaces. 
     The following U.S. patents are known to applicant which generally fit into this category of prior art devices: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 U.S. Pat. No. 5,544,384 
                 Forselius, et al. 
               
               
                   
                 U.S. Pat. No. 3,878,581 
                 Perna 
               
               
                   
                 U.S. Pat. No. 5,545,287 
                 Carlson 
               
               
                   
                 U.S. Pat. No. 4,907,955 
                 Snipes 
               
               
                   
                 U.S. Pat. No. 4,946,360 
                 Brown 
               
               
                   
                 U.S. Pat. No. 5,069,610 
                 Milburn 
               
               
                   
                 U.S. Pat. No. 4,619,013 
                 Yon 
               
               
                   
                 U.S. Pat. No. 4,230,441 
                 Heronema 
               
               
                   
                   
               
             
          
         
       
     
     U.S. Pat. No. 5,368,461 Murphy 
     All of these above prior art devices are either adapted to fill or finish flat drywall surfaces or inside or outside drywall joint areas which have sharp or crisp inside or outside corners, respectively. 
     A recently introduced feature for drywall outside corner joints is typically referred to as a “bullnose” cornerbead or joint. These outside radiused cornerbeads are formed of elongated metal strips which define an arcuate or radiused quarter circle sector or other similar sector cylindrical surface and are attached to the adjacent aligned edges of drywall panels. 
     The invention disclosed in U.S. Pat. No. 5,638,570 invented by Gruner teaches a drywall bullnose cleaner tool which scrapes excess filler compound from the radiused surfaces of an outside bullnose cornerbead of such a drywall installation. However, scraping action may not be rest suited for optimal smooth finishing of the bullnose cornerbead. Another device for the scraping, cleaning and finishing of bullnose cornerbeads is disclosed by Stolzfus in U.S. Pat. No. 392,484. Again, the scraping of the cylindrical bullnose surface is not fully effective in producing ha smooth, high quality finished surface ready for painting. 
     I was recently co-inventor of two U.S. patent, U.S. 5,993,306 and U.S. Des. 411,672. These devices generally teach a cleaning and finishing device for bullnose cornerbeads or joints which more gently and uniformly abrades away excess cured or hardened drywall filler compound without concern for overly abrading or grooving the drywall filler compound immediately adjacent the side margins of the metal bullnose cornerbead. Further, by including a somewhat resilient or compliant abrasive fibrous pad which accomplishes the cleaning and finishing action, any non-uniformity of the bullnose joint is easily accommodated. 
     The following additional prior art references are known to applicant as follows: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 U.S. Pat. No. 1,927,574 
                 Parks 
               
               
                   
                 U.S. Pat. No. 2,402,069 
                 Minnick, et al. 
               
               
                   
                 U.S. Pat. No. 5,690,547 
                 Holland, Jr., et al. 
               
               
                   
                 U.S. Pat. No. 4,923,316 
                 Fattal 
               
               
                   
                 DE 3808138A1 
                 Lazar 
               
               
                   
                 U.S. Pat. No. 5,954,571 
                 Case 
               
               
                   
                 U.S. Pat. No. 5,947,803 
                 Gruner 
               
               
                   
                 U.S. Pat. No. 5,895,316 
                 Williams 
               
               
                   
                   
               
             
          
         
       
     
     The later three of these references are also directed to the sanding of rounded bullnose cornerbeads as is intended for the present invention. However, all have structural features and limitations which render them generally ineffective and even damaging to the filler plaster immediately adjacent to the hard typically metallic surface of the bullnose cornerbead. 
     Additionally, as disclosed in my prior &#39;306 patent, the preferred abrasive medium was in the form of an open non-woven fibrous abrasive material such as that known as SCOTCH-BRITE by the 3M Company. Although this abrasive medium has offered a substantial improvement over conventional sanding paper against a hard radius or arcuate support surface, nonetheless the compressibility of the SCOTCH-BRITE material has not been ideal for the intended objective of removing all excess filler material from the bullnose corner without abrading the adjacent filler material. 
     The present invention provides still further improvement and sanding accuracy in cleaning excess material from bullnose cornerbeads while avoiding the excess abrasion and grooving of the drywall filler compound immediately adjacent the margins of the bullnose cornerbead. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention is directed to a device for abrading and finishing excess cured filler material from a bullnose cornerbead which forms an outside corner joint between immediately adjacent sheets of drywall. The device includes an elongated rigid body having a generally concave-shaped central longitudinal portion which receives a highly compressible thick foam-backed adhesive member which is preferably substantially coextensive with, and arcuately compressibly formable to match the radiused bullnose joint contour. Two spaced parallel guide rails extend longitudinally of the device adjacent each side margin of the central longitudinal portion which, in cooperation with the compressible abrasive member is mateingly engageable against the bullnose corner to substantially match the outside corner angle between the adjacent drywall sheets when the device is pressed firmly against the bullnose corner. 
     It is therefore an object of this invention to provide an improved sanding and cleaning device for removing and finishing bullnose cornerbead joints of drywall installations. 
     It is another object of this invention to provide a device for sanding and cleaning excess drywall filler or fairing compound from metal strips which form radiused bullnose joints between adjacent drywall panels. 
     It is still another object of this invention to provide a device for sanding and cleaning bullnose joints of drywall installations which readily accommodate any irregularity in the metallic strip forming these bullnose joints. 
     It is a further object of this invention to provide a device for sanding and cleaning excess drywall filler compounds from bullnose corner joints which include a replaceable elongated highly compressible abrasive pad or member. 
     In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the invention absent the replaceable abrasive member. 
     FIG. 2 is side elevation view of FIG.  1 . 
     FIG. 3 is a bottom plan view of FIG.  1 . 
     FIG. 4 is an end elevation view of FIG.  1 . 
     FIG. 5 is an end elevation view of FIG. 1 showing the replaceable abrasive member attached thereto. 
     FIG. 6 is a perspective view of the invention shown in FIG. 1 in use in the removal of excess drywall filling compound from a typical bullnose corner joint. 
     FIG. 7A is an enlarged end elevation view of the prior device of U.S. Pat. No. 5,993,306 showing a typical bullnose corner joint in section for reference. 
     FIG. 7B is a view similar to FIG. 7A showing the present invention in functional engagement with the bullnose corner joint. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and firstly to FIGS. 1 to  5 , the invention is shown generally at numeral  10 . This sanding and abrading device  10  includes an elongated molded plastic rigid body  12  having a handle  14  attached to the convex or back surface thereof which defines a hand-holding opening  16  for grasping by a user. Alternate holding means such as connection to an elongated sanding pole are envisioned. 
     As best seen in FIG. 3 and 4, the inner or facing surface  17  of the molded body  12  is generally concaved and circular and cylindrical in nature having a radius R. Spaced, parallel longitudinally extending flat guide runners or rails  18  and  20  extend along and adjacent the longitudinal side margins  38  and  40  of the body  12  and define an angle A as seen in FIG. 4 which is substantially equal to the outside angular orientation between adjacent drywall sheets B and C as shown in FIGS. 6,  7 A and  7 B. Although drywall corners are typically orthogonal, the invention is easily adapted to any broad range of outside angles such as 60°, 120° and the like as called for by architectural design choice. 
     As best seen in FIGS. 6,  7 A and  7 B, the bullnose cornerbead D is attached by its longitudinal mounting flanges K and L to the supporting drywall sheets B and C as by nailing therethrough. Thus, the exposed rounded cylindrical outer surface of the bullnose cornerbead D will ultimately have to be finish sanded before painting. A layer of cementious-type drywall filler compound is first applied along F and G so as to fair or feather in the longitudinal edges H and J of exposed central portion of the bullnose cornerbead D. When the cementious material is applied, typically the radiused or contoured rounded portions of the bullnose cornerbead D are also inadvertently covered with this cementious filler material as at E in FIG.  6 . When cured, it must be removed and smoothly finished to receive paint or other coating materials thereafter. Note that the invention  10  is intended to substantially avoid contact with these faired filler portions F and G as that is left to other drywall sanding implements of a more suitable, generally flat nature. 
     The present invention  10  includes several distinctive features which have afforded enhanced operability of the device  10  for its intended purpose. The facing surface  17 , having a radius R, terminates at  26  and  28  to define alignment recesses or edges for accurate placement and adhesive attachment of the abrasive member  22  as best seen in FIGS. 4 and 5. Moreover, each of the guide runners  18  and  20  have been enlarged and, by the lengthening of arcuate concave relief surfaces  30  and  32 , which allow debris to drop downwardly and be cleared from between the device  10  and the cornerbead D, extend further from the bullnose cornerbead D as best seen in FIG. 7B as described herebelow. The leading edges  42  and  44  are substantially rounded to provide smooth, free gliding movement of the device  10  against the filler material F as the device  10  is moved longitudinally in the direction of the arrows in FIG.  6 . 
     The adhesive pad or member  22  is formed of 2# density open-cell polyester foam material of a highly compressible nature. As best seen in FIG. 5, each replaceable abrasive member  22  includes an adhered abrasive layer  25  which typically has a fabric-reinforced sanding surface of 80 to 120 grit, preferably  80  aluminum oxide grit with PSA backing. The opposite surface  24  is adhesively coated as with double-sided adhesive tape and covered with a protective backing prior to use (not shown). 
     The generally rectangular cross section of the abrasive member  22  shown in phantom, become slightly compressed at the side margins  22   a  and  22   b  when adhesively attached to arcuate facing surface  17 . Note in FIG. 5 the small spacing between the alignment recesses  26  and  28  which assist in precise alignment of the abrasive member  22 . These recesses  26  and  28  are preferably formed by inward offset of arcuate relief surfaces  30  and  32 . 
     As best seen in FIG. 6, the device  10  in use is firmly pressed against the bullnose cornerbead D and then moved longitudinally thereof in the direction of the arrows along the length of the bullnose joint D to abrasively remove the cured excess filler material E and to finish sand the exposed radiused portions of each bullnose cornerbead D. Again, the guide runners  18  and  20 , in cooperation with the concaved contour of the abrasive member  22 , substantially match or mate with the transverse cross section of the bullnose cornerbead D and adjacent drywall panels as best described in FIG. 7B below. 
     Referring now to FIG. 7A, my prior patented device is there shown generally at numeral  10 ′. This prior device  10 ′ also includes an elongated molded plastic rigid body  12 ′ having a handle  14 ′ attached to the convex or back surface thereof which defines a hand-holding opening (not there shown) for grasping by the user. The central longitudinally extending inner or facing surface  17 ′ of the molded body  12 ′ is also generally concaved and cylindrically circular in cross section. An abrasive layer  22 ′ formed of open non-woven fibrous abrasive material, namely SCOTCH-BRITE by 3M Company, is attached by an adhesive layer  24 ′ in longitudinally coextensive position with the central facing surface  17 ′. Note that the width of each abrasive layer  22 ′ is such that the side margin  22   a ′ and  22   b ′ substantially coincide with the longitudinal edges H and J of the Unexposed rounded central portion of the bullnose cornerbead D in the in-use position shown. Note further that the abrasive pad  22 ′ requires relatively little compression in order for the guide rails  18 ′ and  20 ′ to make contact against the filler surfaces F and G. 
     Still referring to  7 A, with respect to the radius M of the cornerbead D, the guide rails  18 ′ and  20 ′ are somewhat close to the edges H and J of the cornerbead D and, for spacial reference, are oriented within a sector angle Q starting at an angle P forwardly of imaginary line N which is drawn perpendicular to a central plane O passing longitudinally through the device  10 ′. Moreover, the angle Q representing the angular or sector width of the contact surfaces of the guide rails  18 ′ and  20 ′ is about ten degrees. Note that the included sector angle of the bullnose cornerbead D is 90° as shown about the center of radius M. 
     Referring now to FIG. 7B, improvements in the present invention are there more clearly shown and may be better understood. Initially, to cause the guide runners or rails  18  and  20  to make contact against the filler material F and G, a firm force against handle  14  in the direction of arrow S is required to compress the abrasive pad  22  sufficiently. That is to say that, in referring to FIG. 5 as well, the central portion of the abrasive member  22  compresses from numeral  50  in FIG. 5 to numeral  54  in FIG. 7B, while the side margins  22   a  and  22   b  compress from  52  in FIG. 5 down to  56  in FIG.  7 B. Numerically in preferred embodiment, a uniform thickness of each abrasive member  22  is approximately ½ inch. However, when in use as seen in FIG. 7B, the central portion compresses down at  54  to approximately 0.2″ or down to about 40% of its initial thickness while the side margins  22   a  and  22   b , compress down to approximately 0.28″ or about 56% of their relaxed thickness of ½″. 
     To greatly increase compression required of each abrasive member  22  in order to make surface contact of the guide runners  18  and  20  against the filler material F and G has shown to be extremely effective in allowing the abrasive layer or surface  25  to accomplish its intended task more easily and uniformly across the entire width and length of the outer surface of the bullnose corner D. The overall width of each abrasive member  22  is slightly increased so that the side margins  62  and  64  of the abrasive layer  25  extend very slightly beyond the side margins of the bullnose corner D. This slight overhang has shown to more effectively blend the filler material F and G to the side margins H and J of the bullnose corner D. 
     Still referring to FIG. 7B, the invention  10  is further enhanced in sanding effectiveness and stability by very slightly enlarging and extending the reach of each of the guide runners  18  and  20  with respect to the cornerbead D. Shown graphically, the guide runners  18  and  20  are increased in width about ⅛″ or less and moved further from the side margins H and J and the center of the radius M of the cornerbead D. The sector angle  60  is oriented rearwardly at an angle  58  with respect to a plane N which is orthogonal to the central plane O of the cornerbead D and the device  10  when properly positioned as shown. The guide runner width is thus broadened through a sector angle  60  of approximately 15°. When compared to the same graphic analysis of the &#39;306 device in FIG. 7A, the benefit of enhanced accuracy and stability of the present invention  10  as the guide runners  18  and  20  glide along the filler surfaces F and G should now be quite apparent. 
     While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be afforded the full scope of the claims so as to embrace any and all equivalent apparatus and articles.