Abrading – Rigid tool – Stationary
Utility Patent
1999-11-18
2001-01-02
Eley, Timothy V. (Department: 3723)
Abrading
Rigid tool
Stationary
C451S371000
Utility Patent
active
06168509
ABSTRACT:
FIELD OF INVENTION
This invention relates to knife sharpening devices.
BACKGROUND OF THE INVENTION
In order to sharpen a knife, the blade has to be drawn across the surface of and in contact with a sharpening stone while maintaining a desired angle between the stone and the blade. Maintaining the desired angle while the blade is drawn across the stone by hand with no mechanical assistance has been the most difficult part of the task.
Currently there are several devices which use mechanical assistance to sharpen knifes. U.S. Pat. No. 4,216,627 to Westrom (1980) and U.S. Pat. No. 4,320,892 to Longbrake (1982) describe devices for sharpening a knife blade that keep the blade stationary as a sharpening stone is drawn across the blade at a predetermined angle. Once the stone is drawn from the base to the tip of the blade, the blade has to be rotated 180° so the stone can be drawn across the opposite side of the blade, again, at the pre-determined angle. The process is repeated until it produces a sharp blade at a precise angle. Unfortunately, repeating this action the number of times necessary to obtain a sharp edge is time consuming and the process is cumbersome.
U.S. Pat. No, 4,602,531 to Korhonen (1986) teaches a system that mounts the apparatus that holds the knife upon a surface. The apparatus that holds the sharpening stones is mounted to a different surface opposite to and in proximity of the knife holding apparatus. To operate the device, the stones are positioned at a selected elevation. The knife blade is then positioned until one side of the blade edge comes in contact with one of the stones. The knife blade is then drawn across the stone at a constant elevation. All operations are done with pistons. Positioning the stones and the blade, and drawing the blade across the stones are all separate, sequential steps requiring the use of the pistons. Operation is intricate and done with instruments and controls. Pressurized hydraulics or pneumatics is required and the device has to be permanently mounted to two opposing surfaces.
U.S. Pat. No. 4,530,188 to Graves (1985) describes the use a base designed to receive one end of sharpening sticks inserted into holes formed in the base at a predetermined angle. The user draws the knife across the stick while attempting to maintain a specific angle between the blade and the sticks. It is difficult to hold the angle manually. In addition, stones that are held in place by inserting one end of the stone into holes formed in a base create a cantilever beam. Upon use, the slots become enlarged which changes the predetermined angle at which the sticks are held. In some cases, the hole becomes so enlarged that the stones can not be held in place or the stone brakes at the point of contact with the base.
U.S. Pat. No. 3,874,120 to Dalton (1975), U.S. Pat. No. 3,883,995 to Ohashi (1975), U.S. Pat. No. 4,528,777to Bernstein (1985), U.S. Pat. No. 4,567,693 to Magnuson (1986) and U.S. Pat. No. 4,627,194 to Friel all describe the use gears and motors to control the process. They are all external power supply dependent and require numerous alignments prior to use.
Thus there remains a need for an effective way to sharpen a knife manually.
SUMMARY OF THE INVENTION
According to its major aspects and briefly recited, the present invention is a knife sharpener where the knife's orientation with respect to a pair of sharpening stones when drawn across the stones is fixed at a predetermined angle. The knife is free to be drawn across and down the surface of the stones, one side of the blade at a time, but remains at the predetermined angle throughout the sharpening process, even as the curved tip of a blade is drawn across the stones.
The device comprises a base supporting a frame that holds the stones at the preselected angle, and a guide rod held by the frame and which supports a knife clamp. The combination of the clamp, the guide rod and the frame enables the knife to move between the stones, forward and backward, and up and down but not about any axis through the knife itself. Therefore, the knife is prevented from rolling or yawing but can otherwise be moved freely within the range of motion dictated by the stones to the side and the length of the connection between the clamp and the guide rod. The predetermined angle between the stones and the blade of the knife can be adjusted and the device broken down for easy portability.
The sharpening stones are preferably formed to have a triangular cross section where the apexes of the angles are rounded. Each apex, or comer, has a different radius of curvature so that knives with serrations of different radii of curvature can be sharpened.
Finally, in an alternate preferred embodiment, the present knife sharpener can be hung from the underside of cabinetry in either a folded configuration for storage or an unfolded configuration for use.
An important feature of the present sharpener is the combination of the guide rod and the clamp that holds the knife to be sharpened. This combination allows a knife of almost any size to be moved against the sharpening stones and drawn across and down their faces but without the knife rotating about any axis through the knife; that is, the knife will not roll or yaw with respect to the stones. Thus, the angle between the knife and the stones' faces is held constant. Furthermore, control of the knife is a significant safety advantage.
Another important feature of the present invention is that the stones are free to swivel about their major axis while being held rigidly at the preselected angle by the frame. This allows the faces of the stones to remain engaged with the knife blade as the tip of the blade is pulled across the face because the stones rotate into the curve of the blade tip.
Still another feature of the present invention is that the stones are preferably formed to have triangular cross sections (although stones having any cross section can be used), thus creating three “corners” each of which is rounded and preferably with a different radius of curvature. By selecting the appropriate corner, serrations on a wide variety of different serrated knives can be sharpened.
Another important feature of the present invention is the alternative preferred embodiment that allows the present sharpener to be mounted to the underside of cabinetry in a foldable form so that it can be unfolded for use and refolded for storage. Also, the primary embodiment may conveniently be disassembled for storage or transportation. Thus the present invention is convenient as well as an effective sharpening tool for knives.
The present sharpener is also adjustable, in that the angle between the knife and stones may be changed and may be conveniently used by either a left handed or right handed person.
Other features and their advantages will be readily apparent to those skilled in the art of knife sharpeners from a careful reading of the Detailed Description of Preferred Embodiments accompanied by the following Drawings.
REFERENCES:
patent: 3874120 (1975-04-01), Dalton et al.
patent: 3883995 (1975-05-01), Ohashi
patent: 4216627 (1980-08-01), Westrom
patent: 4231194 (1980-11-01), Glesser
patent: 4259815 (1981-04-01), Kuban
patent: 4320892 (1982-03-01), Longbrake
patent: 4450653 (1984-05-01), Fletcher
patent: 4528777 (1985-07-01), Bernstein et al.
patent: 4530188 (1985-07-01), Graves
patent: 4567693 (1986-02-01), Magnuson
patent: 4602531 (1986-07-01), Korhonen
patent: 4627194 (1986-12-01), Friel
patent: 4640058 (1987-02-01), Glesser
patent: 4719722 (1988-01-01), Washburn
patent: 4759153 (1988-07-01), Cohen
Eley Timothy V.
Mann Michael
Nguyen Dung Van
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