Patent Application
20150258651
Initial research on the process of sharpening ceramic knives as disclosed in U.S. Pat. No. 8,585,462, ('462 Patent), concluded that due to the fracturing of the brittle and fragile ceramic knife edge, to properly develop a factory quality edge, it would require a minimum of three (3) progressive sharpening stages. All of the details of the '462 Patent are incorporated herein by reference thereto.
The (diamond) abrasives grit size would successively be smaller as the ceramic knife is sharpened in stage 1 followed by stage 2 and finished in stage 3. By reducing the grit size of the abrasives in stage 1 and 2 the sizes of the chips in the knife edge would be reduced sufficiently so that the very fine abrasive in stage 3 would be able to remove the remaining small chips and provide a chip free edge.
To further reduce the size of the chips developed in stages 1 and 2, the research concluded that the sharpening process in those two stages should be done by the abrasive moving into the edge, thereby removing ceramic material under compression. By this process the very fine abrasive in stage 3 could remove the small chips. However, to develop a sharp, chip free edge, the direction of the final, finishing stage abrasive would need to move in the opposite direction from stages 1 and 2, thereby moving away from the edge.
Although excellent results could be obtained by this method it provides some drawbacks. First, the requirement to change the direction of the rotation of the abrasive discs presented additional cost, making the manufacture of this sharpener more expensive. Second, the requirement to have at least 3 stages to accomplish the ceramic knife sharpening task, further exacerbated the manufacturing cost. And finally, because of the very small grit size abrasives required in all stages to minimize the chipping process, this sharpener would not be able to sharpen in a reasonably acceptable time, steel knives, which are much more prevalent in homes and stores.
A concern with knife sharpeners, whether for ceramic blades or metal blades, is the difficulty in cleaning or removing swarf created during sharpening from the guide surfaces in the various stages of a sharpener, particularly in the finishing stage.
An object of this invention is to provide a sharpener for knives and other cutting instruments which overcomes the above drawbacks.
A further object of this invention is to provide such a sharpener wherein a ceramic knife blade could be sharpened in only two stages.
A still further object of this invention is to provide such a sharpener which could also sharpen metallic blades.
A yet further object of this invention is to provide a blade guide which can be moved from its guiding position when sharpening the blade of a cutting instrument to a non-use position which is accessible for cleaning the guide surfaces.
Further research, to overcome the drawbacks of the '462 Patent discovered a surprising fact. A new abrasive system that combined a flexible abrasive matrix on a rigid support was able to overcome all of the problems faced by the previously mentioned development described in the '462 Patent.
Central to this new abrasive system is the sharpener's finishing stage abrasive, which combines the functions of both sharpening and polishing. This sharpening/polishing disc constructed with an overall rigid/low-flex reinforcing structure supports a soft, resilient polymer matrix containing ultra-hard abrasive particles. The sharpening/polishing disc's rigid support structure could be manufactured with use of a separate rigid backing plate, an over-molded rigid hub, or by using a substantially thick abrasive matrix material resulting in significant overall rigidity/low-flex of the overall disc structure while preserving the soft, resilient surface of the abrasive matrix. The rigid/low-flex support structure limits the displacement of the overall disc component during sharpening/polishing which affords very precise matching of a blade's edge facets by the matrix abrasive. The soft, resilient abrasive matrix surface allows very gentle polishing of the blade edge while the simultaneous machining of the facet is occurring.
The physical characteristics, specifically the resilience of the polymer matrix, incorporated in the finishing stage (stage 3) of this sharpener were measured using a modified Wilson Rockwell Hardness test, as more fully described in U.S. Pat. Nos. 5,611,762 and 6,012,971. All of the details of these patents are incorporated herein by reference thereto. As described in U.S. Pat. Nos. 5,611,762 and 6,012,971 the Rockwell Hardness test was conducted with a primary load of 60 Kg and recovery load of 10 Kg using a ⅞″ diameter steel compressor ball. Experiments were conducted with a variety of loading factors. The measured recovery ranged from 38% to 48%, with the optimal recovery in the range of 40% to 45%.
The abrasive particles used in the abrasive matrix are typically harder than the hardness of ceramic. Best results were obtained using diamond abrasive, but other very hard abrasive particles such as tungsten carbide, silicon carbide, boron carbide, and synthetic rubies or combinations thereof could also be used. Effective grit sizes were found in the range from 230 grit size to 2000 grit size. Best results were achieved using 600 grit size to 1200 grit size.
What this new abrasive system accomplished:
Stage 1, as noted, is particularly designed for pre-sharpening metal blades. Preferably the discs in stage 1 have a metal backing and an abrasive surface wherein the abrasive particles are in the range of 100-600 grit size. Where stage 1 is used for sharpening metal knives, the overall included angle of the facet is preferably 240-50° with the guide surface on each side of its disc thereby being at an angle of 120-25°. More preferably, the total included angle formed in stage 10 is 30° with each guide surface being at an angle of 15°. The spring force against the discs in stage 1 is preferably 0.2-1.5 pounds.
In the ceramic sharpener of the '462 patent all of the abrasives in the pre-sharpening stage(s) were too fine to effectively pre-sharpen a metal blade in a reasonable time. In the '462 patent the pre-sharpening stage(s) for ceramic knives required a very fine diamond size to prepare the edge facet for the final stage stropping without causing too much damage. The final stropping stage could not repair the large chips created if large abrasives were used in the pre-sharpening stage(s). This forced the use of very fine diamonds in the pre-sharpening stage(s). The fine diamonds were needed to prepare the ceramic edge facet without causing significantly large chip outs edge prior to moving on to the stropping stage.
With the sharpener 10 of this invention stage 3 is so effective that it can remove fairly significant chips from the ceramic edge. As a result, with this invention only one pre-sharpening stage is needed to prepare the edge for the final facet formation and polishing that occurs in stage 3. With this invention it is possible to use larger diamond grit sizes in one or two pre-sharpening stages without worrying too much about the larger chips that are created. Now that only one pre-sharpening stage is mandatory for ceramic blades, an extra stage is thereby available (within, for example, a total of 3) to tailor especially for metal blades. Thus, metal pre-sharpening stage 1 can be accommodated in the same sharpener 10 that is designed for sharpening ceramic blades. With this invention the new final stage disc can create a final facet with high polish on the metal blade coming out of this single pre-sharpening stage.
Stage 2 is designed for pre-sharpening ceramic blades. Preferably, the discs in stage 2 use abrasives having a grit size of 200-1200. The facet total included angle formed in stage 2 is preferably 240-420 which is achieved by having each guide surface at 120-210 and more preferably at 280 (guide angle 14°). The spring force against the disc in stage 2 is preferably the same as in stage 1.
In the '462 patent, pre-sharpening a ceramic knife required two stages both containing very fine abrasives. Both of these pre-sharpening stages require the use of very small abrasive sizes rotating into the edge to best reduce the chip out size at the edge. As long as the edge chips (leftover from the pre-sharpening stages) were small enough the old stropping disc technology could effectively remove these very small chips resulting in satisfactory final edge sharpness.
The third stage of the present invention is so effective at cutting a facet and also polishing it simultaneously that it is possible to use a larger grit size in the pre-sharpening stage for ceramic knives. Even though the larger abrasive particles (used in the pre-sharpening stage) create larger edge chip outs the stage 3 disc can remove them easily. Preferably, the abrasives in stage 3 are in the range of 180-2,000 grit size. The overall angle in stage 3 is preferably 280-50° (14°-25° for each guide surface) and more preferably 34° (17° for the guide surface). The spring force against the discs in stage 3 is preferably 0.2-2.0 pounds and more preferably 0.4-1.1 pounds.
Where stage 1 is used for pre-sharpening traditional European and American metal knives, generally characterized at an angle of about 380-40°, the angle of the finishing stage would be appropriately adjusted. This could be done by having the stage 3 guides adjustable in the angle of their guide surfaces to accommodate various style knives. Alternatively, a separate finishing stage could be provided for each style knife.
The new finishing (sharpening/polishing) stage 3 of this invention is so effective that the invention can be practiced with a single stage sharpener/polishing tool as a maintenance sharpener for ceramic blades. Thus, in a broad sense a sharpener of this invention might be a single stage sharpener which does not require a pre-sharpening stage in that it is used as a maintenance sharpener for ceramic knives or other cutting instruments.
Typically, knife sharpeners are designed with a maximum of three stages. The present invention, however, can be practiced with more than three stages, such as four or five stages that could incorporate some of the old technology that would sharpen both metal and ceramic knives or other cutting instruments, although this would add to the expense and size.
In the present invention super hard plating technology is used for the pre-sharpening stages to improve the durability and life of the pre-sharpening discs. This is especially helpful when sharpening the hard ceramic materials.
As is apparent, the present invention can be practiced using only a single stage sharpener which would incorporate the unique sharpening/polishing stage illustrated in the drawings as stage 3. The invention could also be practiced using only two stages, exclusively for ceramic blades wherein the two stages would correspond to stage 2 and stage 3 of sharpener 10. Similarly, the invention could be practiced with the three stage sharpener described above. Further the invention could be practiced with more than three stages as also described above.
As illustrated in
It is to be understood that the invention can be practiced where all of the discs in all of the stages are mounted on a single shaft eliminating the need for belt and pulley. All of the stages could be on the same side of the motor.
In
The combination rigid support and flexible abrasive matrix may take other forms. Instead of a two layer combination, such as in
An advantage of the combination rigid support and flexible abrasive matrix is that, as the abrasive surface wears away or ablates, fresh abrasive is exposed.
Although the sharpener 10 is shown and described as having a disc sharpening member, other forms of sharpening members such as sharpening structures using drums or using abrasive belts, etc. could be used.
When combining the function of sharpening both metallic and ceramic blades in a sharpener as envisioned in this invention, it became clear that the swarf created by sharpening the ceramic blades may abrade the blade surface of metallic knives, when they share sharpening stages, as for example the common finishing stage. This would occur because ceramic swarf is much harder than the metal alloy used for the typical steel blades. Therefore if a metal blade were to come in contact with the guide surfaces of the finishing stage, subsequent to a ceramic blade having been sharpened in that stage, the possibility exists that the surface of the metal blade could be slightly abraded.
To minimize that possibility, the inventors designed a removable guide to permit the cleaning of the guide surfaces in order to remove ceramic or any other swarf from the guide surfaces.
The cleaning of the guide surfaces could be accomplished with a vacuum device, a moist cloth, adhesive tape or other similar methods or combinations of methods.
One version of this removable guide is shown in
Although this invention can be most effectively used in the finishing stage, which is typically shared by metallic and ceramic blades, it could be used in all stages of the sharpener.
The benefits of this invention span beyond just the ability to clean the guide surfaces. For example, alternate guides could be developed with capabilities to sharpen a wider variety and geometries of blades, including but not limited to very thick blades, very thin blades, hollow ground blades and others. These alternate guides could be provided as accessories to the sharpener of this invention.
Another benefit is the application of this concept to the repair and maintenance of the sharpener. Since these guide surfaces are high wear areas, consumers that damage these guides by excessive use can easily purchase and replace these guides, without the need to return the sharpener to the manufacturer for repair.
Although this invention has focused on the use of this removable blade guide for the dual use sharpener for metallic and ceramic blades, it can similarly be applied to a sharpener designed exclusively for metal knives or other cutting instruments. Since metal alloys vary in hardness based on the components of the alloy and how it was heat treated, the swarf generated by sharpening harder metal blades, could abrade the surface of softer metal blades that are subsequently sharpened in the sharpener.
As shown in
As illustrated spring 22 is attached to post 48 in any suitable manner, such as by fasteners 62. Spring member 50 includes two outwardly extending projections. One of these projections at the free end of spring member 50 is a release button 56. Another projection below release button 56 is locking button 64. As best shown in
Although the inventors have focused on the specific construction of this removable guide, alternative methods of a removable guide could be envisioned. For example, instead of a molded in plastic spring release, an alternate device could use a metal spring release.
Alternatively, an external screw could hold the guide post in place, and the user could release or replace the guide by loosening or tightening the screw.
Other alternatives could be a slide type system where the guide 22 slides into a post by a “dovetail” arrangement. Further attaching/detaching alternatives for the guide include magnets and Velcro (hook/loop).
A further alternative could be one where the guide 22 is flipped, using a hinge arrangement away from its position to permit cleaning of the guide surfaces.
This application is based on provisional application Ser. No. 61/952,210, filed Mar. 13, 2014, all of the details of which are incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 61952210 | Mar 2014 | US |
