Patent Application
20080271324
The present invention is related to the field of cutting nippers and more specifically to farrier nippers which have lightweight alloy handles biased with a torsion type spring, replaceable carbide blades, and ergonomically designed for users with small hands or to be used one-handedly.
The design for nippers to trim horse hooves predates the invention of horseshoes. Horse hooves, like human fingernails or other animal nails, grow constantly. Unlike wild horses who wear their hooves down by traveling many miles each day in search of food, domestic horses are confined and relatively sedentary. Because of this human caused confinement, it is necessary for humans to trim the horse hooves before they become too long and cause injury and separation of the hoof wall, typically every six weeks. Conventional available nippers, particularly those used to trim the hooves of horses or cattle were designed in the Middle Ages and have continued to this day relatively unchanged. Indeed, in some cases of modern nippers, they are still made by hand in a blacksmith forge. They are typically large and heavy and the handles are far apart making them unwieldy for small hands or one-handed use. The perpendicular cutting edges are of the same low carbon steel material as the handles and are therefore impossible to grind to a thin edge or to properly harden so that they stay sharp. Most conventional nippers also need to be resharpened by someone highly skilled, require disassembly to sharpen properly and are often outsourced for sharpening. The pivot point is a steel rivet which can rust and cause the nippers to bind. These nippers can fall unrestrictedly open during use necessitating the use of two hands at all times. Spring biased nippers designed for self opening typically have handles even further apart when open.
An improvement in the original nipper design was disclosed by G. P. Whiting (U.S. Pat. No. 532,509) where fastener affixed blades were shown. However, the described purpose of this disclosure is for the capability of adjusting the blades and makes no mention of using a different metal or for use in trimming hooves. A spring-biased nipper was disclosed by Jerry Mennicken (U.S. Pat. No. 5,214,854) where a helical spring is used to force the handles apart, and the handles are shown to be uncomfortably wide. This disclosure leaves the handles at their furthest opening and the nippers themselves are designed for parallel cutting rather than the perpendicular cutting which is required in hoof trimming. An improvement in nippers designed for cutting glass and tiles was disclosed by Bernd Siebenlist of Germany (U.S. Pat. No. 5,361,498) which shows replaceable cutting wheels of carbide. Although the disclosure of carbide steel for the wheel shaped blades is an improvement, the wheels will not work for hoof trimming and the nipper handles are very heavy, as required for tile cutting. An improvement in conventional farrier nippers was disclosed by John E. Swanstrom, Jr. (U.S. Pat. No. 5,987,752). This disclosure shows carbide blades attached to mild steel handles. In this disclosure the carbide blades are brazed into shelves, described in the disclosure for the purpose of reducing manufacturing cost. This would require someone skilled in the art of metal working to replace the blades at a workshop location using special tools and the handles are without spring bias, heavy and ergonomically wide. Currently, the state of the art of hoof trimming tooling remains the best reason for hiring someone else to trim. Many people, particularly women, who are doing horse hoof trimming have requested a new design that is lightweight, spring-biased with easily replaceable blades, and ergonomically designed for small hands or one-hand use.
The present invention describes nippers with ergonomically designed handles spaced narrowly apart for small hands or one-handed use. The invention also describes a torsion type spring biased means that assists in opening the nipper handles, but also holds them at a convenient distance apart rather than opening fully. The invention also describes the utilization of light weight alloy material for the nipper handles and of fastener affixed carbide blades for easy replacement and to further make cutting easier. The edges of these carbide blades, being much tougher than the conventional low carbon steel, can be ground thinner than the conventional steel cutting edges for easier cutting and can be replaced rather than resharpened. Also disclosed is the utilization of a friction reducing bushing at the pivot point. The invention will become more apparent from the following Detailed Description which proceeds with reference to the drawings.
The preferred embodiment of the disclosed nipper design shows the handle body forged to the shape in the drawings of aluminum alloy 7075 which is typically used in aircraft. The forged aluminum worked well, but cast aluminum broke in testing. The handles are close together and more so at the distal end for better leverage with smaller hands. The machining done on the aluminum alloy nipper body would comprise shelves for the carbide blades which are drilled and tapped to match the blade fastener holes. An accurate bushing hole for the bushing pivot would be drilled and reamed. A friction reducing material such as oil impregnated bronze would be installed in the pivot hole and a polymer washer installed around that bushing to further reduce wear and friction between the two handles. Recesses would be machined for the spring to be positioned inside the handle bodies. This protects the spring and reduces interference during use. Holes are drilled at the lower end of the recess in which the 90 degree leg of the spring is anchored. In addition would be drilling and tapping for a small set screw located in the lower adjoining contacting faces to allow for adjustment of the blade contact. The handles would be coated with a non-slip rubber for safety and convenience. The blades would be vanadium carbide tool steel such as Crucible Metals CPM S30V or CPM S90V. The blades would be hollow ground on the cutting edge to require the least pressure to trim hooves. This carbide steel also would not become dull very easily requiring ease of use and longevity. The carbide steel blades would be drilled for the fasteners, hollow ground and then heat treated to approximately 60 Rockwell. The blades would be mounted with countersunk or counterbored fasteners so they do not interfere with the cutting edge.
While the above description contains detailed specifications and instructions, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible, such as forming the handles of polymer material, or blades of ceramic. Accordingly, the scope of the invention should be determined not by the embodiment illustrated, but by the appended claims and their legal equivalents.
