Abstract:
A sharpening device for a carpenter&#39;s pencil. A housing has a pivotable guide with a cruciform passage to receive the pencil in either of two positions. A pair of oppositely directed blades are mounted on opposed walls within the housing. The pencil is pivoted while sliding it through the guide to obtain a selected sharpened profile on the end of the pencil.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to sharpening device, and more particularly to a sharpening device for an elongated object with non-circular cross section, such as a carpenter&#39;s pencil. 
   Most pencil sharpening devices currently in use are designed for making round tapered points on pencils having cross-sections, which are either circular or in the shape of a regular polygon, generally hexagonal. This typical geometry, such as round or hexagonal, is not compatible with the rectangular lead pencils used by many professionals, including the well-known carpenter&#39;s pencil. It is desirable that carpenter&#39;s pencils be sharpened to create a selected profile rather than a point. The wooden sheath around the pencil lead is also non-circular, e.g., rectangular, with narrow edges and wide edges oriented at right angles to one another. 
   Existing pencil sharpening devices which are suitable for circular or hexagonal cross-sections are usually constructed to require a rotational movement of blades around the axis of the pencil being sharpened. This type of mechanical action will not create the desired profile for a carpenter&#39;s pencil. As a consequence, the user is reduced to manually shaving or scrapping the carpenter&#39;s pencil to provide the desired profile. 
   A number of authors have suggested sharpening devices especially designed for pencils of rectangular or non-circular cross-sections. These are listed as follows: 
   
     
       
             
             
             
             
           
         
             
                 
             
             
               U.S. Pat. 
                 
                 
                 
             
             
               No. 
               Inventor 
               Issue Date 
               Title 
             
             
                 
             
           
           
             
               4,081,010 
               Galli 
               Mar. 28, 1978 
               Pencil Sharpener for Non-circular 
             
             
                 
                 
                 
               Section Pencils 
             
             
               4,759,129 
               Alpha 
               Jul. 26, 1988 
               Pencil Sharpener 
             
             
               4,918,816 
               Alpha 
               Apr. 24, 1990 
               Pencil Sharpener 
             
             
               4,961,451 
               Bucci 
               Oct. 09, 1990 
               Sharpener for Rectangular Pencils 
             
             
               5,077,903 
               Creim 
               Jan. 7, 1992 
               Carpenter&#39;s Pencil Sharpener 
             
             
                 
             
           
        
       
     
   
   The foregoing devices generally require rotary cutter assemblies which are mounted or manipulated so as to accommodate the irregular cross-section of the carpenter&#39;s pencil. They involve complicated and expensive mechanisms. 
   A commercial pencil sharpener for a carpenter&#39;s pencil is manufactured by Penshar LLC, which is manually rotated. However, this sharpener puts a conical end on the carpenter&#39;s pencil. 
   It would be desirable to have a sharpening device which will sharpen or shape wooden or similar non-metallic elongated objects having radially non-symmetrical cross-sections. It would also be desirable to have a low cost sharpening device especially adapted to sharpen a carpenter&#39;s pencil and provide a selected profile. It would also be desirable to have a low cost manually operated sharpening device for carpenter&#39;s pencils. 
   Accordingly, one object of the present invention is to provide a low cost sharpening device for carpenter&#39;s pencils. 
   Another object of the invention is to provide a sharpening device for lead pencils of non-circular cross-sections or similar elongated objects which will sharpen or shape one end of the object to a desired profile. 
   SUMMARY OF THE INVENTION 
   Briefly stated the invention comprises apparatus for sharpening an elongated object so as to obtain a selected projected profile on one end of the elongated object, the elongated object having a uniform cross section along an object axis. The apparatus comprises a housing defining a recess having an opening and having a pair of convergent walls within the recess, a guide member pivotably mounted on the housing about a pivoting axis, the guide member defining a passage therethrough. The passage is shaped and dimensioned to receive the elongated object and to guide the object for longitudinal motion along the object axis between the convergent walls when manually actuated by a user, and at least one blade having a cutting edge and disposed on at least one of the opposed walls with the cutting edge extending into the recess, whereby the elongated object may be pushed through the passage of the guide toward the convergent walls while the elongated object is also being used to pivot the guide member to move the end of the elongated object past the cutting edge of the blade, so as to sharpen the elongated object to obtain the selected profile. 
   Preferably the convergent walls define an arcuate recess, the arcuate recess being defined by a generatrix having the shape of the selected projected profile moving with a fixed radius from the pivoting axis. 

   
     DRAWINGS 
     These and many other objects of the invention will be better understood by reference to the following description, taken in connection with the accompanying drawing, in which: 
       FIG. 1  is a front elevation view of a sharpened carpenter&#39;s pencil, 
       FIG. 2  is a side elevational view of the sharpened carpenter&#39;s pencil, and 
       FIG. 3  is an enlarged top plan view of the carpenter&#39;s pencil of  FIGS. 1 and 2 , 
       FIG. 4  is a top plan view of a sharpening device according to the present invention, 
       FIG. 5  is a front elevational view of the sharpening device, 
       FIG. 6  is a side elevational view of the sharpening device, 
       FIG. 7  is a front elevational view of the sharpening device, partly in cross section, taken along lines VII—VII of  FIG. 6 , 
       FIG. 8  is a side elevational view, partly in cross section, taken along lines VIII—VIII of  FIG. 5 , 
       FIGS. 9-13  depict the same views of the same sharpening device of FIG.  4  through  FIG. 8  respectively, except that an elongated object is added shown in one rotated position in the process of being sharpened, 
       FIGS. 14 through 18  show the same views of the same sharpening device of FIG.  4  through  FIG. 8  respectively, except that the same elongated object has been added in a different rotated position in the process of being sharpened. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 ,  2  and  3  illustrate a carpenter&#39;s pencil  10  sharpened on one end to achieve a selected profile. While the invention is primarily intended to provide a sharpened end on a carpenter&#39;s pencil, the invention may be utilized with any elongated object of material capable of being sharpened with a blade and having a uniform cross section along an object axis  12 . As shown in  FIG. 3 , the carpenter&#39;s pencil comprises a wooden sheath  14  around a lead core  16  of substantially rectangular cross section. As seen in  FIG. 3 , the carpenter&#39;s pencil  10  has a non-circular cross section with oppositely disposed wide sides  18  and oppositely disposed narrow sides  20  separated by chamfered surfaces  22 . The desired profile, viewed looking at the wide side in  FIG. 1  is an isosceles trapezoid  24 . The desired profile viewing the narrow side  20  in  FIG. 2  is either a narrow isosceles trapezoid or an isosceles triangle  26 . 
   Referring to  FIGS. 4-8  of the drawing, the sharpening device, according to the preferred embodiment of the invention comprises a housing shown generally as  28 , which is preferably, but not necessarily, made up of two identical joining halves  28   a ,  28   b . As seen in  FIG. 7 , the housing half  28   b  is roughly in the shape of one-quarter of a circle with an arcuate flange  30  formed about a pivoting axis  32  and an adjacent sloping interior wall  34 . The other housing half  28   a , as seen in the cross-section view of  FIG. 8 , is identical and also has a circular flange  31  and an adjacent sloping wall  35 . The two adjacent halves are assembled by means of screws  36 ,  38 ,  40  passing through the flanges  30 ,  31  to join the housing halves together. When the two halves are joined, they define a recess in housing  28  with an opening  42  at the top. The interior walls  34 ,  35  are convergent toward one another reaching their narrowest distance apart at flanges  30 ,  31 . It is not necessary that walls  34 ,  35  intersect one another; they approach until they almost intersect. 
   A guide member  44  is rotatably mounted in the housing  28  on pins  45  in bearing journals  46   a ,  46   b  in the respective halves  28   a ,  28   b . Guide member  44  is arranged to pivot in the housing about the pivoting axis  32 . Guide member  44  defines a passage  48  through the guide member  44 . Preferably passage  48  is of a cruciform cross section, with a portion  48   a  extending at right angle to a portion  48   b , so that it will accept the carpenter&#39;s pencil  10  in either of two rotated positions. However, the shape of passage  48  is immaterial so long as it is of uniform cross section permitting the elongated object to slide through the passage  48  toward the convergent walls  34 ,  35 . 
   Each of the housing halves  28   a ,  28   b  have a blade opening through the wall. This opening is shown generally as  50  on the half  28   a . Blade opening  50  leads from a wide rectangular entrance  50   a  on the outside, leading to a narrow rectangular exit  50   b  in the inside wall into the recess. A sharpening blade  52  is mounted on the sloped surface between  50   a ,  50   b  with its cutting edge  52   a  extending slightly into the recess. Blade  52  may be secured by any suitable means such as screw  54 . 
   Referring to  FIG. 7 , the corresponding exit  51   b  is seen with a blade cutting edge  52   b  protruding into the recess beyond the convergent wall  34 . 
   OPERATION 
   The operation of the invention will best be understood by reference to  FIGS. 9-13  showing the carpenter&#39;s pencil  10  being sharpened in one rotated position, and  FIGS. 14-18  showing the carpenter&#39;s pencil  10  being sharpened when it is positioned in the other rotated position. The reference numbers in  FIGS. 9-13  and  14 - 18  correspond to those in  FIGS. 4-8 . 
   In  FIGS. 9-13 , the pencil  10  is placed in portion  48   a  of cruciform passage  48 . Pencil  10  is grasped by a user and used to pivot the guide member  44  back and forth around the pivoting axis  32 , while also maintaining pushing pressure to cause the pencil  10  to slide toward the convergent walls  34 ,  35  as material is removed. Reference to  FIG. 12  shows the guide member  44  being pivoted in a counterclockwise direction so that the cutting edge  52   b  removes material to achieve the selected profile on the end of pencil  10 . When the pencil  10  is pivoted in the opposite direction, material is removed on the other side of the pencil by the cutting edge  52   a  of blade  52  (FIG.  10 ). 
   In a similar manner, referring to  FIGS. 14-18 , the pencil  10  is placed in portion  48   b  of cruciform passage  48 . Pencil  10  is now disposed in a position rotated about its axis with the narrow sides of the pencil facing the convergent walls. The guide member  44  is pivoted back and forth by means of pencil  10  while pressure is maintained.  FIG. 17  illustrates material being removed from pencil  10  as it is pivoted in a counterclockwise direction. When it is pivoted in the opposite direction, material is removed from the other side of the pencil by the cutting edge  52   a  (FIG.  15 ). 
   While the blade opening  50  and blade  52  are disposed in a radial direction from the pivoting axis  32 , the blade and opening may also be disposed at an angle to a radial direction to achieve different cutting characteristics. 
   It will be observed that the portion of the recess between convergent walls  34 ,  35  where the cutting action takes place is arcuate and generated by a generatrix in the shape of an isosceles triangle moving with a fixed radius about the pivoting axis. The blade edges are straight and extend into the recess in opposite directions, so that material is removed from one side of the elongated object as it is pivoted in one direction and removed from the other side of the object as it is pivoted in the opposite direction. During this time, the object slides through the passage of the guide member, until the desired profile is achieved.