Abstract:
A manual sharpener for sharpening either right or left-handed blades of scissors or shears comprises a support structure with an attached hand holding arrangement. A magnetic device holds at least one adhesive pad on the supporting structure. One or more precision angle blade guides are mountable on the structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based on provisional application Ser. No. 60/494,680, filed Aug. 13, 2003. 

   FIELD OF INVENTION 
   This invention relates to an improved versatile manual scissor sharpener for sharpening a wide variety of either right or left handed scissors, shears, and similar cutting tools. 
   BACKGROUND OF THE INVENTION 
   Manual scissor sharpeners previously available have proven unsuccessful because of a lack of reliability, precision and versatility. They have lacked the means to provide either the correct sharpening angle, the angle for presharpening the edge or the range of precision angle guides necessary for different types of scissors. Consequently the user commonly damages his scissors and becomes extremely frustrated. There are many distinctly different types of scissors that complicates the task of sharpening them correctly. To sharpen scissors successfully requires identification of the type scissors and selection of the correct and precise angle guides for sharpening (honing) and presharpening the various types. Sharpening scissors improperly can render the scissors totally ineffective. 
   SUMMARY OF INVENTION 
   This invention describes an improved manual scissor sharpener that provides means to readily select and interchange easily precision angular guides set at appropriate sharpening angles for different types of scissors and the means to easily change the sharpening abrasive or the size of abrasive grit necessary for each sharpening step. In the subject sharpener, more efficient abrasives are used to speed up the sharpening process and means are provided to minimize the amount of metal that need be removed to create a superb edge quickly and with minimum manual effort. All of these elements are necessary for successful manual scissor sharpening. Sharpening scissors by hand is very labor intensive. The process of metal removal from a scissors edge by hand is consequently slow and time consuming, providing every opportunity to make damaging sharpening strokes at the wrong angle. Without appropriate equipment it is virtually impossible to hold manually the same angle stroke after stroke. Scissors and knives are distinctly different and must be sharpened at radically different angles. Knife edges are sharpened at highly acute total angles commonly 25 to 50 total degrees at the edge. Knives cut by the process of severing through the material at these relatively small angles. 
   Scissors are constructed with a pair of mating blades where the cutting facet on each blade is most commonly sharpened or honed at an angle of about 70° relative to the mating surface of the blades. The cutting process depends upon a shearing process between the two blades. As scissor blades are closed, the material to be cut is pinched between the blades and if the corner “edge” on the facet of each blade adjacent their mating surfaces is precisely honed, the meeting blades will cut the material as it is pinched by the blades. If the corner “edges” are rounded even slightly the blades will not cut but only pinch the material and jam. Consequently for scissors to cut rather than pinch the material the corner “edges” along each facet must be precisely sharpened (honed)—that is the cutting corner of each blade facet must be formed accurately by a precise honing step using very fine abrasive grit. 

   
     THE DRAWINGS 
       FIG. 1  is a side elevational view of a pair of opened scissor blades; 
       FIG. 2  is a side elevational view of a scissor blade facet; 
       FIG. 3  is a side elevational view partly in section of a manual scissor sharpener in accordance with this invention; 
       FIG. 4  is a perspective view of a manual scissor sharpener in accordance with this invention arranged for right handed operation; 
       FIG. 5  is a top plan view of the sharpener shown in  FIG. 4 ; 
       FIG. 6A  is a side elevational view of the sharpener shown in  FIG. 4 ; 
       FIG. 6B  is a view similar to  FIG. 6A  of a sharpener having multiple angle guides; 
       FIG. 6C  is a view similar to  FIGS. 6A and 6B  of a sharpener arranged for left handed operation; 
       FIG. 7  is a bottom plan view of the sharpener shown in  FIG. 4 ; 
       FIG. 8  is a perspective view of a guide which can be used with the sharpener shown in  FIGS. 4–7 ; 
       FIG. 9  is a front elevational view of the guide shown in  FIG. 8 ; 
       FIG. 10  is a side elevational view of the guide shown in  FIGS. 9–10 ; 
       FIG. 11  is a bottom plan view of a sharpener in accordance with this invention showing a closed storage compartment; 
       FIG. 12A  is a bottom plan view of the sharpener shown in  FIG. 11  with the storage compartment open; and 
       FIG. 12B  is a top plan view showing the hatch cover used in the sharpener of  FIGS. 11 and 12A . 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a typical pair of opened scissor blades  1  and  3 . The cutting facets  9  and  11  must be precisely honed at chosen angles A and B especially near the edge, in order to leave a sharp edge at corners  5  and  7 . At the very edge itself the corners  5  and  7  must be geometrically perfect with an accuracy of about 5/10,000 of an inch or less if the blades are to cut well. The exact magnitude of angles A and B are less critical than the perfection with which the cutting “edge” is formed. The most popular scissor blades are commonly ground and honed at an angle on the order of 70° but the specialized so called knife edge scissor blades will have an angle as low as 50°. Clearly these two types of scissors are very different and need to be presharpened, sharpened and honed at very different yet precise angles. 
   The cutting “edge” must be honed precisely and with a relatively fine abrasive grit in order to obtain a truly sharp “edge” with geometric imperfections less than 5/10,000 inch. The inventor has shown that the creation of exceptionally sharp edges on scissors with a manual means depends upon using a highly accurate guide for the scissors and a very fine abrasive grit to hone and create the final “edge”. But clearly an attempt to hone by hand the entire cutting edge facet with a fine grit is a tedious and time consuming effort. The sharpening process can, as explained herein, be shortened greatly by creating a corner “edge” on a small secondary facet honed immediately adjacent to the edge. In that manner a much more precise corner “edge” can be created and formed very quickly with less manual effort. None of the manual sharpeners known to this inventor have been designed to provide a means of sufficient accuracy to create readily such precise corner “edges” using a dual angle guide system—one angle guide for presharpening the entire facet and a second angel guide for honing a small corner facet using the appropriate abrasive grit means. 
   Prior art manual scissor sharpeners such as described in U.S. Pat. No. 371,689 have been difficult to use, tediously slow, and the performance of the scissors after sharpening has been far inferior to the edges that can be created by professional scissor sharpeners. The lack of versatility and precision of such manual sharpeners have been overcome by this inventor by employing sets of easily interchangeable precisely angled guides and sets of interchangeable diamond abrasives of appropriate grit size to permit and optimize the honing and presharpening (relieving) steps necessary to create edges of professional precision and hence sharpness. 
   The novel sharpening apparatus described here provides sets of precision sharpening angle guides, sets of abrasives including fine, abrasive grit pads necessary to hone precision honed corner edges and coarser abrasive grit pads needed to subsequently presharpen/relieve the entire blade face when the finer honing grit is no longer effective at the honing angle. The coarser grit is necessary to remove substantial metal in a reasonable time period from the cutting facet at a lesser angle relative to the mating face of the blade. The angle used for honing is optimally only a few degrees larger than the relief (presharpening) angle ground onto the blade face with the coarser grit. The novel apparatus described here incorporates a magnetic means to make it convenient to rapidly and easily interchange abrasive pads. Diamond abrasives are preferred to minimize the time needed to sharpen the blades. Importantly the physical design of the sharpener structure described here and the angle guides allows the guides to be manually attached and removed slidingly, enabling the angle guides to be used readily for sharpening either left or right handed scissors by either right or left handed individuals. 
     FIG. 2  shows a scissor blade facet  9  ground with coarse grit at smaller angle A 1  and honed at larger angle A 2 . It has become clear that sharpening scissors by a manual means is impractically laborious if one attempts to sharpen and resharpen by removing metal each time from the entire facet  9 . It is remarkably easier to resharpen by creating a small facet at an angle A 2  which is a few degrees larger than angle A 1 ,  FIG. 2 . It is evident that if the entire facet is first presharpened at a smaller angle A 1 , very little metal needs to be removed in order to form the small facet at larger angle A 2 . Because less metal need be removed at angle A 2  an exceedingly fine abrasive can be used to create a more perfect facet, angle and edge and it can be done quickly. It is also evident that the presharpening (relieving) of the entire facet can be done with a coarser more aggressive abrasive grit that reduces the time required to establish manually that larger facet area. It was found that with diamond abrasive of about 100 to 200 grit the entire facet of many scissors can be presharpened (relieved) in just a few minutes while it would take up to 30 minutes if the grit were 600 or 1200. While the presharpening/relieving can be done reasonably fast by using the coarser grit, that same grit would be too coarse for honing the final edge; that coarser grit would be incapable of creating a precisely formed corner edge. So by creating a smaller area facet at a slightly larger angle, for example 2° to 5° larger, it is possible to use an exceedingly fine grit to finely hone that facet and the final sharpening edge in less than one minute. This example illustrates the advantage of honing a small secondary facet at just a few degrees larger than the angle of the primary large blade facet and illustrates the advantages of designing a sharpener with ability to select rapidly and conveniently a separate presharpening (relief) angle and a slightly larger angle to hone the small facet and the corner edge. This selection of the appropriate angle for each of the presharpening and honing steps can be accomplished by using separate precision guides or by providing an adjustable angle guide that can be set conveniently either for presharpening the blade facet or for honing the final small facet at a somewhat larger angle. 
     FIG. 3  illustrates one mechanism  13  for setting precisely the presharpening angle and the honing angle of a scissor blade with a single adjustable guide. Angle guide  15  is supported thru linkage  17  by post  19 . Adjustment screws  21  secure link  17  to the post  19  and the angle guide  15 . The adjustment screws can be loosened and tightened while adjusting the angle A 1  or A 2 . The angle guide  15  can be set at a A 1  for presharpening and at A 2  for honing the final facet. The scissor blade  1  shown in cross section can be moved back and forth across abrasive surface  23  to create the appropriate facets on the blade. The mating face  2  of the scissor blade must be held in intimate contact with face  15  of the angle guide 
   It has proven convenient, reliable, and uniquely versatile to employ interchangeable angle control guides  27 , such as shown in  FIG. 4 , that can be readily interchanged and can longitudinally slip slidingly onto such a sharpener structure and be held without the need for fasteners. It has proven highly effective to slip off a guide and to replace it with another at a different angle that is also held slidingly yet securely mounted to the sharpener structure in a manner that makes it easily applied, held, and removed. 
   Because the most common scissors as purchased have a blade facet of about 72°, it is convenient to set the honing angle guide at 75° to 77° and the presharpening angle guide at 72°. A very fine or ultrafine abrasive, preferably diamonds of about 600–1200 grit, is then used for honing at say 75° to create a small facet angled 3° greater than the original 72° facet. After many resharpenings when the honed facet becomes substantially larger in area and takes too long to sharpen with fine grit, the 75° honing guide is removed, the 600 or 1200 grit pad is removed and the 72° presharpening guide and a coarser diamond pad, about 100–300 grit is mounted on the sharpener. The entire blade facet is then presharpened with the coarser grit. If the scissor blade as purchased is angled at greater than 72° it is best to presharpen the blade first with the 72° guide and coarse grit in order to insure that the original angle is less than the honing angle. In that manner one is always assured that the honing angle will be larger and the fine grit abrasive can create easily and quickly a precise small facet at the edge, leaving the edge very sharp and durable. 
   A scissor sharpener  25  made in accordance with this invention is designed with elongated abrasive pads  29 , as shown in  FIGS. 4 ,  5  and  6  where the angle guides  27  are attached slidingly. The angle guides hold securely on the body  34  of the sharpener  25  but will slide easily allowing the user to presharpen or hone the blade facet anywhere along the length of the abrasive pad  29 . Diamond abrasives on pad  29  are preferred not only because the diamond crystals are harder and sharpen and remove metal more efficiently, but because they do not “load-up” with sharpening debris (unlike other common abrasives) and because they do not wear significantly with use. The incorporation of diamond abrasives significantly enhances the effectiveness of this manual sharpener. 
   A magnetic pad-like structure or sheet  31 , such as shown in the break away portion of  FIG. 7  located below pad  29 , proved to be a particularly convenient means to hold a ferromagnetic metal backed abrasive coated pad  29  securely on top of the sharpener  25 , shown in  FIGS. 5 ,  6 A,  6 B,  6 C and  7 . This magnetic sheet  31  attached or adhered to the body  34  of sharpener  25  makes it extremely easy to interchange pads  29  of the different abrasive grits as needed for the presharpening and honing steps, without fasteners. A recess  24  ( FIGS. 5 and 7 ) in body  34  located near pad  29  permits the user to lift pad  29  from body  34  to remove the pad. Thus,  FIGS. 5 and 7  illustrate two different pads, with the fine grit pad having a central longitudinal groove shown in  FIG. 5  and the ungrooved coarse grit pad shown in  FIG. 7 . 
   The unique design of this sharpener allows it to be used easily by either left or right handed individuals and with either left or right handed scissors. For the sharpener  25  shown in  FIG. 6A , a right handed person can hold the handle  33  with his left hand and hold the scissor blade with his right hand to sharpen. If the scissors are right handed the angle guide  27  can be positioned slidingly with the open angle A, as shown facing to the user&#39;s right. If the scissors are left handed or for a left handed person, the user can simply reverse the sharpener 180°, and the open guide angle A will be facing to his left as shown in  FIG. 6C . Alternatively for a left handed scissors and a left handed user, the guide  27  can be completely removed, rotated 180° and mounted back on the sharpener with the guide plane angled toward the handle  33 . The user would have to position the guide away from the handle a sufficient distance to expose the abrasive pad  29  below the guide plane and by using the fingers of the hand holding the sharpener, the user would maintain the guide at that position. Preferably, however, for a left handed user or left handed scissors the sharpener itself is simply reversed 180° from the position shown in  FIG. 6A  to the position shown in  FIG. 6C . This reversibility of both the sharpener and the guides  27  uniquely permits either handed person to hold the sharpener comfortably and to sharpen either handed scissor. 
   The versatility of this design allows the user to place simultaneously and conveniently (See  FIGS. 5 and 6 ) use more than one appropriately angled precision angle guides  27  on the sharpener structure  25 , as shown in  FIG. 6B . 
   In the preferred practice of this invention the sharpener  25  would be placed adjacent to the edge of a table or other support surface. The user would hold the sharpener by grasping the handle  33 . The guide  27  would be located so that its guide surface  37  extends away from handle  33 . An advantageous feature of the invention is the ability to use essentially the entire length of abrasive pad  29  in sharpening the blade facet. For example, in one extreme position illustrated in  FIGS. 6A and 6C  the guide  27  is located against a shoulder  22  on body  34 . In this position the guide surface  37  is over the abrasive pad  29  at its closest position toward handle  33 . The user can place his fingers on the sleeve portion of guide  27  and slide guide  27  further away from handle  33  and then use the fingers to hold the guide  27  at the position when performing a different sharpening operation. This technique of the user holding the handle  33  and placing the fingers on the sleeve portion of guide  27  to position the guide  27  at different locations along the length of abrasive pad  29  thereby permits an increased area of pad  29  to be used during different sharpening operations so that use of the abrasive pad  29  will not be limited to one location and be prematurely worn out. 
     FIGS. 8 ,  9  and  10  show three views of a typical guide  27  which can be removably attached slidingly onto the sharpener structure  25 . Such guides can be contoured in the sleeve portion  39  to hold firmly to the sharpener body and slide over the metal backed abrasive pad  29  which is attached securely magnetically to the magnet  31  of  FIG. 7 . The guides  27  are shown with holes (windows)  28  through guide surface  37  to its junction with sleeve  39  so that the scissor blade can be easily viewed when its face is aligned against the guiding surface  37 , as in  FIG. 6A . The abrasive pads  29  are sufficiently long that two or more such guides  27  can be mounted simultaneously for presharpening at angle A 1  or alternately for honing irregular scissor blades (at angle A 2 , about 72°) and then honing knife-edge blades commonly at angle B, about 53°, as shown in  FIG. 6B . The sharpener can be provided with angle guides with the appropriate angle for any scissor. Knife-edge scissors are generally thinner and the facets are sufficiently small that a single angle guide at the honing angle is usually sufficient. There is less need for a presharpening (relief) angle guide as the honing grit generally will be sufficiently fast on the smaller facet area. 
   As best shown in  FIGS. 8 and 9 , the side walls  30  of the main body or sleeve  39  of the generally inverted U-shaped guide  27  are shaped to generally conform to the upper and side walls of body  34  of sharpener  25 . Side walls  30  may be resilient to snugly slidably fit against body  34 . Each wall  30  has an inwardly directed flange  32  to fit under the bottom wall of body  34  to assure the proper mounting of each guide  27  on body  34 . 
   Each guide  27  may be removed from the body  34  by simply sliding the guide  27  completely off body  34 . Alternatively, where the side walls  30  of guide  27  are resilient, the side walls could be spread apart sufficiently to remove the guide  27 . Where the removal is by sliding the guide  27  off body  34 , the side walls  30  need not be resilient. Thus the guide  27  may longitudinally slide on body  34  and may also be removed and then again mounted on body  34  when changing from one guide to another. 
   As shown in  FIGS. 8 and 10  the guide surface  37  is a surface on a plate-like upward extension of the main body or sleeve  39  of guide  27  and would be inclined at the desired angle. 
   This unique sharpener design as shown in  FIGS. 11 ,  12 A and  12 B incorporates a convenient storage compartment  35  under the sharpening area large enough for storage of an assortment of abrasive pads  29 . FIG  11  is a bottom view of the sharpener  25  with the compartment closed by a hatch cover  36 . As shown in  FIG. 12B , cover  36  includes a spring clamp closure  44  and tabs  38  similar to the type of removable locking structure conventionally used for battery compartments of various electrical control members, toys, etc. Any other type of detachable locking structure could also be used for hatch cover  36 .  FIG. 12A  is a bottom view of sharpener  25  showing the exposed compartment  35  when cover  36  has been removed. As shown therein, sharpener  25  includes complementary structure  40  for engagement by clamp closure  44  and holes  42  for receiving tabs  38 . 
   As shown in  FIG. 11  guide flanges  32  terminate at or inwardly of cover  36  so as not to interfere with the removal of cover  36 . 
   This disclosure describes a uniquely versatile manual scissor sharpener capable for the first time of creating professional quality cutting edges quickly and easily on a wide variety of scissors.