Abstract:
A corner sander base including a sanding surface, the corner sander base for sanding proximate interior wallboard corners, the corner sander base including a first member and a second member connected together at a longitudinally oriented juncture where they form a tip, one side of the members defining a sanding surface. Each member further includes a planar forward section which in the radial direction originates at the juncture and terminates at a longitudinally oriented transition wherein a forward angle is the angle subtended between the planar forward sections in the radial plane. Each member further includes a planar rear section originating at the transition and connected to the forward section at the transition wherein a rear angle is the angle subtended between the planar rear sections in the radial plane and wherein the forward and rear angles selected to more aggressively sand the areas at the rear sections and less aggressively sand the area at the tip and forward section.

Description:
This application claims priority from previously filed U.S. provisional application 61/041,263 filed Apr. 1, 2008 under the title “Corner Sander” by John Lamers. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to sanding devices and in particular relates to corner sanding devices used for sanding of internal corners wherein the walls are covered with wallboard and/or drywall. 
     BACKGROUND OF THE INVENTION 
     Presently walls in residential and commercial structures are finished using wall board which is generally screwed or nailed to vertical wooden and/or metal studs, the gaps between the individual boards are covered with a joint reinforcement which is either a paper and/or a mesh and thereafter a drywall compound is applied thereon. In this patent application the words wallboard and/or drywall are used interchangeably to mean the same thing, namely gypsum board which is covered with paper and used for creation of walls prior to drywall compound being applied. 
     Of particular importance is the finishing of internal corners which are created at the juncture of two wallboards coming together at a corner location. 
     Presently a gap usually exists between the two wall boards which abut each other at the corner. In order to bridge this gap to prevent future cracking of the drywall compound a layer of paper and/or mesh is applied into the corner and thereafter the drywall compound is liberally applied for subsequent sanding. 
     The present device relates to the tool and mechanism used for sanding of the drywall compound after the joint paper and the drywall compound has been applied and dried. 
     There are a number of prior art devices and in particular U.S. Pat. No. 6,325,708 by Jody W. Miles filed on Sep. 28, 2000 and issued on Dec. 4, 2001 titled Device for Sanding a Drywall Corner describes and teaches a corner sander including a base made up of left and right planar wall members which meet at a juncture and/or as in our case at the tip and form a generally v-shape support for the abrasive media to be placed there upon. The V-shaped support is so designed that the sanding pad more aggressively sands the areas in and around the juncture (the tip) of the base and less aggressively sands the areas of the corner away or outwardly from the juncture or the tip. They further explain in the specification and also in the claims that in order to achieve this function the opposed first left and right members which are called “walls” preferably assume angles of slightly less than 90 degrees. 
     There device and geometry is best shown in FIG. 4 of the U.S. Pat. No. 6,325,708 specification and is schematically reproduced in our  FIG. 2  in which it is apparent that the corner of the sanding base aggressively impinges into the wallboard corner and the left wall and right wall of the base creates a large gap on one side of the corner and a smaller gap on the other side of the corner due to the angular relationship between the left wall and right wall being less than 90 degrees. 
     Referring to  FIG. 3  the resulting sanding profile after the tool has been used to smoothly sand away the drywall compound may result in either paper thinning as depicted in  FIG. 3  on one side and/or ridges and/or valleys occurring on the other side. 
     Those trained to finish wall board, wall surfaces and corners will know that it is undesirable to impinge upon the paper since this produces a rough surface finish which is not aesthetically pleasing to the end user. 
     In addition, it is desirable to have a smooth corner transition and surface free of ridges and valleys and free of paper thinning as depicted in  FIG. 3 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example only with reference to the following drawings in which: 
         FIG. 1  is a schematic cross sectional view of an inside wall board corner showing paper as well as drywall compound having been applied. 
         FIG. 2  is a schematic cross sectional view showing the sanding tool described in the prior art deployed in an inside wall board corner of a wall. 
         FIG. 3  is a cross sectional schematic view of an inside wall board corner showing the finished surface after sanding has occurred with the prior art unit shown in  FIG. 2 . 
         FIG. 4  is a schematic cross sectional view of an inside wall board corner showing the finished outer wall surface together with the remaining paper and drywall compound in the corner after sanding has occurred with the presently described device. 
         FIG. 5  is a schematic cross sectional view of an inside wallboard corner showing the presently described device, a corner sander positioned or deployed against the corner. 
         FIG. 6  is a cross sectional schematic view of the presently described device a corner sander base  200  showing the various geometries of the first and second opposed members which make up the base. 
         FIG. 7  is a schematic cross sectional view of the presently described device a corner sander base  200  showing the base together with abrasive material attached thereto and the first and second opposed members and their geometries. 
         FIG. 8  is an upright perspective schematic view of the entire corner sander  201  showing the corner sander base  200  connected to a handle. 
         FIG. 9  is an upright schematic perspective view of corner sander  203  wherein the corner sander base  200  is shown connected to a fine and pole attachment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1 ,  2  and  3  are Figures explaining the prior art and in particular explain and show the potential results of using the prior art unit described in U.S. Pat. No. 6,325,708 by Jody W. Miles patented on Dec. 4, 2001 under the title DEVICE FOR SANDING A DRYWALL CORNER. 
       FIG. 1  shows schematically an inside wall board corner  102  which includes two wallboards  104  which abut each other at joint gap  106  to form wallboard corner  108 . Normally a paper and/or mesh screening and/or some reinforcements means is placed in corner  108  such as paper  110  as shown in  FIG. 1  in order to reinforce joint gap  106 . Paper  110  as well as the entire joint is then covered with drywall compound  112  as shown schematically in  FIG. 1 . Once drywall compound  112  is dried, it is then ready for sanding into a smooth corner joint. 
       FIG. 2  shows schematically the Miles device U.S. Pat. No. 6,325,708 namely sanding tool  103  deployed into a inside wallboard corner  102  wherein a left wall  120  and a right wall  122  of sanding tool  103  subtends an angle of less than 90 degrees in accordance with the prior art discussion and teaching in U.S. Pat. No. 6,325,708. Left wall  120  and right wall  122  together form base  124  which has an outer sanding surface  126 . One will note from the diagram that due to the fact that most interior corners in residential and commercial construction are more or less at 90 degrees, the smaller angle subtended by left wall  120  and right wall  122  creates a large gap  130  on one side and smaller gap  132  on the other side of sanding tool  103  as shown in  FIG. 2 . This gap results purely out of the fact that the angular relationship between left wall  120  and right wall  122  is less than 90 degrees and is also depicted in FIG. 4 of U.S. Pat. No. 6,325,708. In this manner the sanding tool  103  more aggressively sands in the wall board corner  108  and less aggressively sands away from the corner namely in the area of large gap  130  as shown in  FIG. 2 . This is what is described in the prior art and claimed to the be the inventive feature of the patented device in U.S. Pat. No. 6,325,708. 
     Referring now to  FIG. 3  using the prior art depicted in  FIG. 2  and described in U.S. Pat. No. 6,325,708 may result in a finished corner contour as schematically depicted in  FIG. 3 .  FIGS. 3 and 4  show schematically in exaggerated fashion the corner geometry after sanding. 
     One side of the sanding tool  103  may create or cause paper thinning  144  as shown in  FIG. 3  and due to the fact that the left wall  120  and right wall  122  do not impinge with equal pressure on either side of the wall, one would tend to get ridges  140  forming which run vertically up and down the wall near the corner and/or valleys  142  near the drywall compound corner  109  which again run vertically up and down along the wall parallel to the corner. These ridges  140 , valleys  142  and paper thinning  144  is highly undesirable in that the contractor and the manufacturers of the finished walls preferably would like to have a very smooth and unnoticeable transition between the two adjacent wall boards and a very smooth corner joint. 
     The reader will also note that the gap or the distance between the wallboard corner  108  and the drywall compound corner  109  which is depicted is roughly the thickness of the paper  110  results in impingement of the sanding tool  103  onto the paper  110 . Sanding of the paper is undesired in that it creates a very rough and non-uniform surface. 
     Preferably one would like to leave a uniformly even film of drywall compound in and around corner  108  which provides for a smooth transition from the corner to the outward portions of each of the wallboards. 
       FIG. 4  is a schematic cross sectional view of an inside wallboard corner showing the results of sanding with the presently described device namely corner sander base  200  and/or corner sander  201  and/or corner sander  203 . The reader will note that two wallboards  104  abut each other in perpendicular arrangement thereby producing the 90 degree inside corner as is normally the case in residential or commercial construction. There usually is a small joint gap  106  created between the wallboards  104  where they intersect at wallboard corner  108  which is the corner in behind paper  110 . 
     As previously discussed normally paper  110  is placed into wallboard corner  108  to cover up joint gap  106  and thereafter drywall compound  112  is applied. Once it has been applied and sanded one ends up with finished corner as shown in  FIG. 4 . In this case the corner configuration shown would be created using the presently described device namely corner sander base  200  and/or corner sander  201  or  203  described later on herein. 
     The reader will note that there is a substantial amount of drywall compound and/or thickness between wallboard corner  108  and drywall compound corner  113 . The amount of drywall compound feathers uniformly away as one moves away from wallboard corner  108 . In other words the thickness of the drywall compound is greatest at drywall compound corner  113  and becomes subsequently thinner and tapers away to nothing as one moves away from wallboard corner  108 . 
     Ideally this will ensure that there is no damage of paper  110  or impingement of the abrasive and/or sandpaper onto paper  110  and that there is a uniform amount of drywall compound left in drywall compound corner  113  and a smooth transition away until one only sees outer wall surface  111  of each of wallboards  104 . 
     Preferably there is a smooth transition area shown as  115  where the drywall compound ends and the outer wall surface  111  begins. This smooth transition will almost be invisible to the naked eye due to the very subtle feathering and transitioning from drywall compound corner  113  away from the corner. 
     Now referring to  FIG. 5  which is a schematic cross sectional view of an inside wallboard corner  102  together with the presently described device namely corner sander base  200  shown deployed against each of the wall boards. 
       FIG. 5  shows two wallboards  104  abutting at approximately perpendicular angles to each other at wallboard corner  108  together with corner sander base  200  shown deployed against each of the wallboards  104 . Referring now to  FIG. 6  as well corner sander base  200  preferably includes a tip  216 , a sanding surface  210 , a forward section  220 , a transition section  222  and a rear section  224 . Corner sander base  200  is comprised of a first member  230  and a second member  232  which are joined at a juncture  291  where they form a tip  216 . 
       FIG. 5  shows that there is a very small right gap  214  and left gap  212 , both of these gaps being roughly the same amount. In practice however, there likely will be little or no gap on either the left side or the right side due to the fact that the rear section  224  of both of the first member  230  and the second member  232  subtend an angle of approximately 90 degrees which is equivalent to the angle of the corner as constructed. 
     The reader will note that there is a substantial tool gap  217  between tip  216  and wallboard corner  108  which is purposely introduced to allow for a predetermined amount of drywall compound  112  to be left behind thereby ensuring that paper  110  which is placed in the corner is not damaged due to the sanding process. 
     Referring now to  FIG. 6  which shows corner sander base  200  in cross sectional view which preferably includes a tip  216 , a first member  230  which is connected to a second member  232  at tip  216  or juncture  291  to form a V shaped corner base  200 . Both first member  230  and second member  232  include a forward section  220  a transition area  222  and a rear section  224 . The two members joined together form a V shaped corner sander base  200  which defines an outer sanding surface  210  and a base inner surface  262 . 
     The reader will note that the two forward sections of both first member  230  and second member  232  subtends a forward angle  382  greater than 90 degrees and preferably between 91 and 95 degrees and more preferably at approximately 93 degrees. Beyond the transition moving away from tip  216 , the rear sections  224  of each of first member  230  and second member  232  subtends a rear angle  384  of approximately 90 degrees as shown in  FIG. 6 . The relationship between forward angle  382  and rear angle  384  being such that a tool gap  217  is maintained. In other words the angular relationship is dimensioned to ensure that tip  216  does not contact wallboard corner  108  but rather has a standoff shown as tool gap  217 . The transition portion is oriented along the longitudinal direction  292  and defines the portion of the first member and second member which joins together the forward and rear. It is preferably a smooth curved transition when viewed in cross section through the radial direction as shown in  FIG. 7  but may also be a well defined longitudinally running edge as depicted in  FIG. 5  or  6  for example. 
     The transition section would preferably be smoothed out so that it is barely noticeable to the eye and sanding will not leave a noticeable line or ridge on the wall in the vertical longitudinal direction parallel to the corner. 
     Referring now to  FIG. 7  which shows in cross section corner sander base  200  together with a frame portion  277 . First member  230  and second member  232  defines a sanding surface  210  which can be covered with abrasive material  272 . The abrasive material can be attached to corner sander base  200  using gluing and/or any other conventional means including hook and loop type fasteners. 
     Furthermore, preferably the distal ends furthest away from tip  216  of first member  230  and second members  232  include a small rear flair  270  such that the members taper away from the wallboard when it is positioned into a corner. This provides for a smooth transition of the corner sander base  200  away from the wall and ensures that there are no vertical streaks and/or ridges which form as a result of sanding. 
       FIGS. 8 and 9  show the corner sander base connected to a handle  300  as shown in  FIG. 8  and/or a frame  302  and a pole attachment  304  as shown in  FIG. 9 . The handle  300  and pole attachment  304  are well known devices in the art of corner sanders. 
     The diagrams define the longitudinal direction  292  which is normally a direction which the corner sander  201  is urged in, in order to effect sanding, namely up and down vertically along the corner of the inside wall board corner. 
     Radial direction  260  is shown in  FIG. 8 . First member  230  and second member  232  are shown in cross section in the radial plane in  FIG. 6  and  FIG. 7 . Sanding surface  210  is the outer surface defined by the first and second members  230  and  232  as shown in  FIG. 8 . Sanding surface  210  includes portion of the outer surfaces defined by forward section  220 , transition section  222  and rear section  224  as shown. 
     As shown in  FIG. 9  alternatively the corner sander base  200  could be attached to a frame  302  which in turn is attached to a pole attachment  304  for use as a pole sander into the corner. 
     It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.