Rotary blade sharpener

A rotary blade sharpener is comprised of a motorized platen positioned in a housing with a surrounding wall and an open top. An abrasive sheet with an adhesive bottom surface is adhered to a disc, which is tightened to the platen by a knob. The disc is color coded to indicate the grit of the abrasive sheet. An adjustable support rack is hinged to the housing above the platen. A jig is positioned on the rack and arranged to slide side to side thereon. The jig is arranged to receive and securely hold a blade and position it against the abrasive sheet. The rack is adjustable to position a beveled front end of the blade flat on the abrasive sheet. A lubricant container with a drip tube is attached to the housing. A cutout in the surrounding wall is arranged to enable grinding a flat side of the blade.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention broadly relates to grinders and sharpeners for blades and chisels.

2. Prior Art

A wood working blade, such as a chisel blade or a plane blade, includes a beveled front end and a flat back which must both be perfectly flat. The flatness of the beveled front end is particularly important for a plane blade, because even a slightly curved surface will prevent the sharp edge from making full contact with the work piece. The back must also be perfectly flat at least at the front end to cooperate with the beveled front end to make a straight cutting surface.

Woodworking blades are often sharpened with the rim of a grinding wheel. However, the grinding wheel makes a concave cutting edge which weakens the edge. Therefore, Japanese tools should never be sharpened with a grinding wheel. Another type of grinding platen provides a flat side for grinding. However, the high rotation rate of several hundred r.p.m. may heat the blade enough to lose its temper. Also, it is very difficult to hold the blade by hand at the correct angle to grind a perfectly flat surface. Any wobbling will result in a curved surface on the blade. Further, lubricant used on the platen may be flung outward towards the user and the surrounding area.

BRIEF SUMMARY OF THE INVENTION

Objects of the present rotary blade sharpener are to:sharpen various types of blades, particularly plane and chisel blades;support the blade at an adjustable angle for grinding a perfectly flat surface on the blade;provide interchangeable abrasive discs of different grades;provide interchangeable abrasive discs which are color coded to indicate their grade;enable the blade to move across the surface of the abrasive disc for evening wearing the abrasive disc;automatically dispense lubricant onto the abrasive disc;prevent the lubricant from flinging outside the sharpener;enable grinding the back side of the blade; and abrade other objects.

The rotary blade sharpener is comprised of a rotatable platen positioned in a housing with a surrounding wall and an open top. The platen is driven by a motor under the housing to rotate about a vertical axis. An abrasive sheet with an adhesive bottom surface is adhered to a disc, which is tightened to the platen by a knob. The disc is color coded to indicate the grit of the abrasive sheet. An adjustable support rack has a bottom end hinged to the housing at a position above the platen, and a top end supported by a vertical rod movably positioned through a clamp attached to the housing. A jig is positioned on the rack and arranged to slide side to side thereon. The jig is arranged to receive a blade and position it against the abrasive sheet. The rack is adjustable to position the blade at a desired angle on the abrasive sheet. A lubricant container is attached to the housing. A tube extending from the container is positioned to dispense lubricant onto the abrasive sheet. A cutout in the surrounding wall is arranged to enable grinding the flat side of the blade.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of a rotary blade sharpener10shown inFIG. 1is comprised of a platen11positioned in a housing12. A right angled motor13controlled by a foot switch14is attached under housing12. Motor13is connected to platen11for rotating it about a vertical axis at about 100 to 200 revolutions per minute. A detachable disc15with a center hole16is for being tightened to an axle17on top of platen11by a knurled disc knob18. An abrasive sheet19has a pressure sensitive adhesive bottom surface20for sticking on top of disc15, which is color coded to indicate the grit of sheet19. Disc15is slightly larger than platen11to enhanced grip during removal. Different abrasive sheets of different grits and abrasive materials may be provided. Alternatively, abrasive sheet19may be adhered directly to platen111without disc15.

A lubricant container21is attached to housing12. A tube22extending from container21is positioned to drip lubricant onto abrasive disc15at a rate controlled by a valve23. Housing12includes a bottom24, a surrounding wall25extending above platen11, an open top26, and a support assembly27. Surrounding wall25is arranged to completely surround platen11for catching lubricant flung from abrasive disc15.

A blade holder assembly48is positioned over platen11for holding a blade (not shown), and is comprised of an adjustable support rack28and a jig33. Adjustable support rack28includes a bottom end hinged to housing12at a position directly over platen11, and a top end supported by a vertical rod29movably positioned through a clamp30attached to housing12. Rack28is comprised of sides31connected by transverse rails32. A jig33is for being positioned on rack28, and includes a hook34on its bottom for hooking onto a selected rail32. Additional jigs of different sizes may be provided for holding different size blades, and are arranged for hooking onto different rails. For example, a larger jig is hooked onto the lowest rail and rests on the highest rail, and a smaller jig is hooked onto the lowest rail and rests on the middle rail.

Jig33is comprised of a plate35with a flat portion36for supporting the blade, a cutout37for providing clearance for a handle of the blade, and a clamp49on a top side comprising a frame38with blade knobs39for tightening the blade. Jig33is arranged for sliding side to side on rack28. Jig33is for positioning the beveled front end of the chisel blade against abrasive sheet19with the blade perpendicular to a radius of platen11. Rack28is adjustable in tilt to position the blade on abrasive sheet19at the angle of the beveled front end. Platen11is arranged to rotate away from the blade. In this example, platen11is arranged to rotate counterclockwise. A molding40of a collapsible material in a cutout41in surrounding wall25may be depressed to enable grinding the back of the blade.

InFIG. 2, abrasive sheet19is attached on top of disc15, which is attached to platen11and secured with knob18. Jig33is positioned on rack28.

InFIG. 3, a chisel42is positioned in jig33wherein a blade43thereof is positioned with a beveled side44against flat portion36of plate35and a flat side45facing up. A handle46of chisel42is positioned in cutout37of plate35. Blade43is positioned with its beveled front end47against abrasive sheet19, and rack28is adjusted in tilt by sliding rod29in clamp30to position beveled front end47flat against abrasive disc15. Chisel42is tightened with knobs39.

Platen is arranged to rotate at about 100–200 rpm to avoid overheating blade43which may otherwise alter its temper. Platen11is arranged to rotate away from blade43to automatically pull it downward against abrasive sheet19to eliminate the need for the user to press it down manually. Jig33may be manually moved side to side in rack28for evenly wearing abrasive sheet19.

Valve23on lubricant container21is opened to dispense a lubricant onto abrasive sheet19. Lubricant flung outward by platen11is caught by surrounding wall25.

InFIG. 4, the cover on cutout41is removed to allow back45of blade43to be placed flat on abrasive sheet19for grinding, wherein handle42is positioned through cutout41.

Although the foregoing description is specific, it should not be considered as a limitation on the scope of the invention, but only as an example of the preferred embodiment. Many variations are possible within the teachings of the invention. For example, the sharpener may be used to sharpen different types of blades in addition to chisel blades. The relative positions of the elements can vary, and the shapes of the elements can vary. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents, not by the examples given.