Abstract:
Presented is a blade sharpener, resurfacer, and planer, for sharpening flat or beveled blades of a linear edged tool, such as a drywall finishing tool and other tools edges, such as concrete trowel blades. The device of the invention makes using a file for such tasks much more precise, and much safer.

Description:
PRIORITY 
   This document claims priority from the provisional application filed on Dec. 17, 2001 with a Ser. No. 60/339,770 of the same title. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to sharpening tools, and more particularly relates to a sharpening tool that will resurface, plane, and sharpen tools such as drywall tools, drywall knives, trowels, and other tools. This repairs and prolongs tool life. 
   2. Background Information 
   It is often desirable to thoroughly or selectively smooth the surface of rigid walls or other working surfaces. A surface smoothing treatment can be performed to alter the shape of the wall, remove unwanted material from the wall, and/or improve the adherence and appearance of preliminary and final coatings on the wall. For example, in preparing the joints of drywall in preparation for texturing or painting, a worker may wish to smooth drywall joints, and to imperfections and screw depressions by applying a coat of drywall compound using a drywall knife or blade. 
   One step in preparing a drywall surface is to uniformly smooth or scrape all portions of the surface without removing too much material from any one portion. This is done by smoothing over the wall and drywall joints with a flat or planar surfaced tool in a single smooth motion with the tool. Further, it is desirable to maintain a sharp scraping edge on such a tool, which can he quickly and easily resurfaced to remove nicks. Many times the screws used in securing drywall to the studs of a building are not sufficiently countersunk, and contact with the drywall surfacing tool causing nicks or scratches in the blade of the drywall tool. Drywall flashing material will also scratch or mar the working surface of a drywall knife or blade. These nicks, scratches, and gouges will leave lines or grooves in the surface being worked, which renders the tool useless for further work. At present, there is no practical method of resurfacing the working edge of such a tool, and thus a new tool may have to be purchased. Additionally, certain have a linear working surface like a drywall tool, but tools do not require a flat edge for scraping. Such tools require a beveled edge for their particular use. As with the edge of a drywall tool, there is not a practical way to sharpen such a linear edged on the jobsite. 
   Thus, there exists a need for a portable device for resurfacing the working edge of a linear edged tool, such as a drywall knife, concrete working trowels, or other tools that have a linear edge. Some of these edges would have a flat edge with two 90 degree corners, and others might require a single edge formed by a bevel. Such a resurfacing device needs to be safe and easy to use, and portable so that it can easily be brought to a jobsite and made available for workers to use on the site. Such a device would need to be designed to allow a linear edge to be sharpened so that it is perfectly straight, which is impossible to do when using a tool such as a file alone worked against the edge of a blade by hand. In such a case, the edge of the blade would be left with high and low spots, and would no longer serve its function. Those having ordinary skill in the art will appreciate that these and other needs are not provided by devices available to craftsmen, and are met by the present invention. Drywall knives and concrete trowels tend to become worn and rounded with use. This device makes such blade edges flat, straight, and true again, prolonging tool life. 
   It is therefore an object of the present invention to provide an inexpensive planing or sharpening tool that provides a range of light to heavy duty shaving action from the edge of a linear blade. It is also an object of the invention to provide such a device that can utilize commonly available files that may be changed as required. 
   Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
   SUMMARY OF THE INVENTION 
   The above objects and others not specifically recited are realized in the blade sharpener of the invention. The blade sharpener of the invention includes a sharpener body in which is defined a file cavity and a blade slot. The file cavity is sized to hold a file, which can be a standard hand file or one specifically made for the device. The blade slot is a slot in which the blade to be sharpened is inserted, and through which the blade may contact the file held securing in the file cavity. A file securing means is used to hold the file in the file cavity. This can be set screws, a friction grip, or other securing means that releasably secure the file. The blade sharpener may be moved back and force against a stationary blade to be sharpened, or the blade sharpener may remain stationary and the blade to be sharpened can be moved back and forth, so that the file removes nicks, makes the blade linear, and to the desired angle. For instance, one embodiment of the device utilizes a blade cavity that presents the blade to be sharpened at a 90 degree angle to the file. When finished, such a device results in a blade that has two 90 degree angles and flat edge. Other embodiments of the device can have the blade slot at a different angle from the blade, such as 30 degrees or 45 degrees. When used with a blade, these result in a blade with a linear sharp edge, with a bevel of 30 degrees or 45 degrees. Other angles would also be possible. 
   One embodiment of the present invention utilizes a sharpener body made from one piece. This might be made from plastic, wood, or a suitable metal such as aluminum, steel or brass. Another embodiment of the invention has a sharpener body that is made in three pieces. In this embodiment, a first and second shoulder piece attach to the base section and thereby define one or more blade slots and the file cavity for holding the file. The first and second shoulder sections would typically be attached by shoulder screws, but other means of attachment would also be suitable. One version of the device has multiple blade slots each at different angles, so that tools can be sharpened at different angles. One embodiment of the device has a blade slot that is much wider than the width of the blade. This allows this embodiment of the blade sharpener to be utilized to create a flat edge in which the edges of the working surface of the blade are at 90 degree angles, and the edge of the blade is flat. A beveled blade can also be sharpened in this device by placing the blade to be sharpened at an angle, so that it is touching the top edge of one side of the blade slot and the bottom edge of the other side of the blade, resulting in a beveled, linear edge. 
   Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiment are to be regarded as illustrative in nature, and not as restrictive in nature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the device of the invention. 
       FIG. 2  is an end, cutaway view of an embodiment of the present invention in which the sharpener body is made of more than one piece. 
       FIG. 3  is an end, cutaway view of another embodiment of the device. 
       FIG. 4  is a perspective view of an embodiment of the device that presents multiple angled slots for sharpening blades at different angles. 
       FIG. 5  is a perspective view of an embodiment of the device in which the upper portions can be removed, leaving a file surface for other uses. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While the invention is susceptible of various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims. 
     FIGS. 1-5  show some of the preferred embodiments of the blade sharpener of the invention.  FIG. 1  shows an embodiment of the invention in which the sharpener body  12  is made from one piece. This could be made from any type of plastic, of a suitable metal, or wood. The sharpener body  12  defines a file cavity  16  in which a file  14  is placed and secured in the sharpener body  12  with a file securing means  20 , which in this case are several set screws  22 . The sharpener body  12  also defines a blade slot  18  through which a blade  32  can be inserted for sharpening by contact with the file  14 . Although this sharpener would work with a number of different types of blades, it is particularly useful for the blade of a drywall finishing tool. The blade slot  18  of this particular embodiment of the device is wide enough so that the blade  32  can be placed in contact with the file  14  parallel with a side wall of the blade slot, as shown in  FIG. 1 , for a flat edge. The blade  32  can also be placed at an angle with its leading edge touching the file, and the upper part of the blade resting against the corner of the opposite side wall of the blade slot. When the blade is held in a vertical position, the blade is sharpened to have perfect two 90 degree edges and to have a flat end surface. When the blade is held at an angle, which is also shown in  FIG. 1 , the blade is sharpened to have a sharp edge and a bevel. It is advantageous for the embodiment with a wider blade slot to include a gap between the working surface of the file and the upper surface of the file slot. This gap prevents the blade from binding as it is being sharpened, and is visible in FIG.  1 . 
   The blade sharpener  10  can be configured so that the file  14  is a standard hand file that is inserted into the sharpener body  12 . A specially constructed file can also be used with the device. 
     FIG. 2  shows another embodiment of the blade sharpener of the blade sharpener  10 . This embodiment of the blade sharpener is made in more than one piece, in this case three pieces. This device includes a base section  24 , a first shoulder section  26 , and a second shoulder section  28 . These are joined together by shoulder screws  30 . Set screws  22  hold the file in place in the file cavity  16 . In this particular embodiment, the blade slot  18  is narrower than that shown in  FIG. 1 , and holds a blade in a vertical position against the file, which results in a flat surface with two 90 degree edges on the tip of the blade. 
     FIG. 3  shows another preferred embodiment of the present invention, one in which the access cavity  18  is at an angle, which will result in a blade being sharpened with an edge and a bevel. This embodiment could be made with the sharpener block  12  being made from one piece, as shown, or it could also be constructed in more than one piece as shown in FIG.  2 . 
     FIG. 4  shows another embodiment of the blade sharpener  10 . In this embodiment, there are multiple access cavities  18 , each with a different angle. In the example shown in  FIG. 4 , the middle blade slot would be for sharpening a blade at a 90 degree angle, to have a flat edge. The other two would be at other angles such as 30 degrees and 45 degrees. As with the other designs, the sharpener body  12  could be made from one piece or from several pieces. A file securing means would also be incorporated into the design. 
     FIG. 5  shows an embodiment of the design in which the first shoulder section  26  and the second shoulder section  28  can be removed. The file can then be secured in place, such as by the horizontal set screws shown in  FIG. 5 , or by other means. This allows the file to be used for other tasks such as sharpening other tools. 
   While there is shown and described the present preferred embodiment of the invention, it is to be distinctly understood that this invention is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the invention as defined by the following claims.