Earth working – With drive means for tool or cleaner – Tool driven about generally vertical axis
Reexamination Certificate
2002-06-14
2004-01-27
Batson, Victor (Department: 3671)
Earth working
With drive means for tool or cleaner
Tool driven about generally vertical axis
C172S041000, C056S017500, C056S249500, C030S276000
Reexamination Certificate
active
06681865
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the horticultural and/or lawn care arts. It is especially relevant to the selective cutting, trimming, or removal of unwanted weeds, overgrown grasses, and other vegetation or plants. It finds particular application in connection with power trimmers or weed whackers, and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications which employ a rotary cutting tool or device, e.g., lawn mowers, brush choppers and other landscaping and gardening equipment.
In the horticultural and/or lawn maintenance fields, a wide range of power-driven equipment for cutting or trimming unwanted growth is employed. For large area cutting such as for mowing lawns or fields, equipment such as, riding mowers, push or self-driven power mowers, brush choppers and the like, are commonly employed. This type of equipment is often wheel based such that it supported by and rolls across the area to be cut. It typically includes one or more rotating cutting tools (e.g., a sharpened blade of steel, or another hard metal) powered by a combustion engine, an electric motor, or another type of drive. The rotating cutting tool in much of this type of equipment is position at a selected height substantially horizontal to the surface of the area being cut. As the equipment traverses the area, e.g., on its wheels, the underlying grass or other vegetation is cut at a uniform height corresponding to the separation of the rotating cutting tool from the ground.
One piece of equipment, which is typically a hand-held and/or hand-operated power-driven cutting or trimming device, is known in the art as a power trimmer or weed whacker. Power trimmers are commonly used for selectively cutting or trimming unwanted vegetation in places or regions unsuited and/or inhospitable to the aforementioned large area cutting equipment, e.g., at lawn edges; near garden beds; around fences, trees or other obstacles; in tight or confined areas where larger equipment will not readily fit; in other areas where artificial fixtures or plants such as flowers or vegetables are desirably left unscathed; on uneven or heavily sloped terrain which is difficult to negotiated by equipment which rests on the ground; etc. In a typical embodiment, a weed whacker includes an elongated shaft having a handle or other grip disposed at a first end, and a rotary cutting element or device disposed at an opposite cutting end. A drive, such as a combustion engine, an electric motor or otherwise, is often arranged on the weed whacker to power the rotating cutting element via a drive shaft or other linkage.
In operation, a user holds the weed whacker by the handle or grip end (i.e., the operating end) and guides the cutting end into the overgrown grass, weeds, or other unwanted plant growth which is to be trimmed or cut. In a typical embodiment, the rotating cutting element includes a cutting tool which rotates rapidly under the influence of the operating motor and which strikes and cuts the targeted plant stems, branches, leaves, etc., in a rapid cutting motion which minimizes damage to the remaining uncut portion of the targeted plant. Optionally, the operating end also includes a trigger or other switch for selectively engaging the rotary cutting device or element, a throttle lever for controlling engine speed, and similar or other operating controls.
In some known power trimmer or weed whacker embodiments, the cutting tool is a blade made of steel or other hard material which is integrally attached to the rotating cutting element and radially extends outward therefrom. A blade has advantages in cutting strength and in durability. However, the blade edge wears down over time. When the blade edge becomes sufficiently dulled, it has to be re-sharpened or replaced. Due to its integral construction, replacement typically involves a replacement of the entire rotating cutting element or device. Sharpening also typically involves removal of the whole rotary cutting element. In either case, the detachment can involve tools such as a wrench which may not be readily available in the field. Detachment of the rotating cutting element can also be complicated by corrosion of the bolt or other fastener which secures it to the trimmer, e.g., due to extended exposure of the rotating cutting element to moisture and other contaminants. In any event, the removal of the entire rotary cutting device can be an inefficient and disadvantageously time consuming process. For commercial users especially, in addition to being a bother, the time expended in such efforts is lost time with respect to getting jobs completed. With heavy use, this lost time can add up quickly. Additionally, the “in service” to “down time” ratio for the trimmer is disadvantageously impacted to the extent maintenance time is increased by such inefficiencies.
Blade damage can be accelerated by inadvertent impacts with rocks, tree trunks, and other hard object. Such impacts can cause a catastrophic blade fracture or other failure. Because the cutting end is manually guided, such impacts are to be expected at least occasionally. The difficulty and expense in re-sharpening or replacing the blade typically dictates using a very hard, durable blade material such as steel. However, although any manually guided rotating cutting element presents a safety hazard, a rigidly attached steel blade can be especially dangerous. The steel blade is relatively inflexible and cannot bend around or flex to avoid or lessen the full impact with objects inadvertently struck. The inflexibility combined with the blade hardness tends to result in substantial injury or damage to the struck object or the blade.
In part, to avoid some of the aforementioned difficulties, in other known weed whacker embodiments the cutting tool is a length of nylon string or similarly tough but flexible material connected to the rotary cutting element. Under rapid rotation, an end of the nylon string is drawn radially out and away from the axis of rotation by centrifugal force to form an elongated whip suitable for the cutting tasks. In a typical arrangement, the rotating cutting element includes a reel of nylon thread which is selectively unreeled, e.g., in a stepped fashion, to provide a controlled length for cutting and/or replace length as the nylon thread disintegrates or otherwise shortens due to wear.
Flexible elongated elements such as nylon thread can bend around or flex to avoid or lessen the impact with an object, and can therefore be safer than a rigidly attached inflexible blade. However, the highly abrasive cutting can quickly disintegrate the comparatively soft nylon string, requiring inconvenient repeated operation of the unreeling mechanism to maintain a usable length. When all the string on the reel is used up, it typically has to be replaced. Hence, the same disadvantages previously described with respect to the integral blade cutting tool are encountered. Both the unreeling mechanism and the reel replacement can be complicated by grass clippings and other contaminants which can jam up the unreeling mechanism. Furthermore, the bending and flexing of the flexible string which beneficially improves safety also substantially limits cutting strength, so that nylon string weed whackers are usually limited in application to light duty cutting tasks. Further, the nylon string can tend to be come tangled which in turn demands further maintenance.
The present invention contemplates a new and improved rotary cutting device with quick-release blades and/or an associated method that overcomes the above-mentioned limitations and others.
BRIEF SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a rotary cutting device is provided. The rotary cutting device includes base having: a coupling region adapted for connection of the base with an associated drive that rotates the base; a slot at a periphery of the base; and, a hollow shaft in communication with the slot. A retain
Batson Victor
Fay Sharpe Fagan Minnich & McKee LLP
Warwood Products, Inc.
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