Harvesters – Motorized harvester – Including cutter yieldably mounted on its drive means
Reexamination Certificate
2003-03-18
2004-06-08
Will, Thomas B. (Department: 3671)
Harvesters
Motorized harvester
Including cutter yieldably mounted on its drive means
C056S017200
Reexamination Certificate
active
06745549
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to grass trimmer attachments, and in particular to a grass trimmer attachment that reduces operator strain caused by prolonged trimmer use while not interfering with the ability of an operator to easily extend trimmer line during operation.
Weed trimmers are in common use throughout the United States and many other countries today. The cutting action of these devices is typically provided by the high speed rotation of one or more lengths of monofilament polymer trimming line. The primary use for these devices is the cutting of grass and weeds in areas where the large size and limited maneuverability of traditional lawn mowers may render such machines impractical. Many weed trimmers may also be used for lawn edging, either by the employment of special attachments or the rotation of the grip used to hold the trimmer. Weed trimmers typically consist of a motor unit, which may Include either a gasoline-driven or electric motor; a support shaft; and a trimmer head at the opposite end of the support shaft from the motor unit. A drive connection passing through the shaft allows the motor unit to drive the trimmer head. The support shaft may be straight or curved, and may include a handle part-way along its length by which the owner may control the movement of the trimmer head. The trimmer head is comprised of a rotating disc from which a length of trimming line extends, which during operation spins to form a circular cutting pattern. A guard is often mounted above the trimmer head to protect the operator from accidentally placing a hand or foot in the arc of the spinning trimmer line. In addition, many weed trimmers include a mechanism within the trimmer head that extends line automatically when the trimmer head Is tapped against a surface such as the ground. In such devices, trimming line is stored within the spinning trimmer head on a spool, and is extended by depressing a spring-loaded button extending from the bottom of the trimmer head. This line extension mechanism is of great convenience to the operator, as It allows the operator to extend additional line while continuing the operation of the trimmer. The line typically used in such trimmers is lightweight and easily broken if it strikes rocks, concrete, edging materials, and other common yard obstacles, and thus line extension is periodically required during operation.
Muscle strain, aches, and numbness are common complaints of those persons who use weed trimmers for prolonged periods. Most of these devices are intended to be supported by the operator during use, which increases the maneuverability of the device. While some weed trimmers include slings that are placed across the operators shoulders, many are intended to be supported by simply holding the device with both hands. It is believed that the symptoms experienced by weed trimmer operators arise partly due to the fact that the weed trimmer head, which forms a significant portion of the weed trimmer weight, is cantilevered far out on the end of the support shaft, away from the operator. This weighted portion must of course be turned and repositioned constantly during operation so that trimmer line may be applied to the appropriate areas where vegetation is to be cut. Furthermore, the operator must periodically tap the trimmer head onto the ground in order to feed additional line, which increases operator strain. It is also believed that the vibration common to all weed trimmers, which results from the rotational operation of the motor, is largely responsible for the numbness often experienced by weed trimmer operators. This vibration may be transmitted directly to the operators hands and arms through the weed trimmer's rigidly attached handles.
One potential remedy for the muscle strain caused by the prolonged use of weed trimmers is to provide a wheeled carriage or support mechanism. The use of wheeled carriage assemblies in order to support grass trimmers is known in the art. For example, U.S. Pat. No. 6,009,694 to Moore et al. teaches a wheeled carriage assembly for supporting a grass trimmer that includes a large rear wheel and a pair of front wheels mounted on a rigid assembly, with a pair of handlebars extending rearwardly from the weed trimmer motor unit U.S. Pat. No. 5,970,692 to Foster teaches a weed trimmer carriage with a single, large support wheel mounted rigidly to the weed trimmer support shaft, with a control bar extending upwardly from the carriage mounting point. U.S. Pat. No. 5,829,236 to Ballard et al. teaches a wheeled carrier for a grass trimmer comprising a rigid frame and three ground-engaging wheels. The frame of the Ballard et al. device mounts to the shaft of the weed trimmer just below the motor unit and just below a handle that is mounted approximately half-way down the shaft to the trimmer head. U.S. Pat. No. 5,095,687 to Andrew et al. teaches a weed trimmer wheel assembly with a single ground-engaging wheel that mounts to the weed trimmer at two points, namely, the weed trimmer support shaft and the rearward portion of the guard extending rearwardly from the weed trimmer head assembly.
Each of the prior art devices in this field provide wheeled support for a weed trimmer in an attempt to relief some of the strain experienced by weed trimmer operators. None of these prior art devices, however, provide a means of significantly reducing the motor vibration transmitted to the operator's hands and arms while holding a weed trimmer. The rigid frames and mounting assemblies used by the prior art devices simply transmit this vibration to the user directly, or at best do nothing to dampen this vibration. In fact, some of these devices may in fact worsen the effects of vibration because the operator's grip is repositioned further from the source of the vibration, thereby increasing the perceived vibration amplitude at the point where the operator grips the carriage or attachment.
In addition, none of the prior art devices are mounted to the weed trimmer in such a manner as not to interfere with the extension of additional line from the weed trimmer head by tapping of the weed trimmer head upon the ground. For those devices that use both front and rear wheels, it would seem impossible to tap the head of the weed trimmer during operation without removing the rear set of wheels from the ground. This would defeat the purposes for which the carriage or attachment is provided, and may create a dangerous condition in which the weed trimmer and carriage unit may tip over, exposing the rotating trimmer head. For those weed trimmer carriages or attachments with only a single wheel, or a single set of wheels set on an axis perpendicular to that of the support shaft of the weed trimmer, tapping of the trimmer head to extend line would also be awkward. In order to perform this operation, the operator would be required to pivot the motor unit end of the weed trimmer in a large arc about the axis of the wheels. The difficulty of this maneuver would increase as the wheel axis is moved closer to the trimmer head and further from the motor unit. Even if this maneuver would be possible, the trimmer head would not be striking the ground with its face parallel to the ground surface. If the angle between the hub and ground is too great, the button on the trimmer head would not be sufficiently depressed, and the trimmer head would not release more line. Even if this angle is not too great to prevent operation of the hub line-release mechanism, greater force would be required for this operation when the hub is not parallel to the ground, which would increase strain upon the operator and would likely reduce the operational life of the trimmer head.
What is desired then is a weed trimmer wheeled attachment that relieves both stress and vibration experienced by the operator, but does not interfere with the normal operation of the weed trimmer, including the extension of additional line from the trimmer head by tapping the head of the trimmer upon the ground. The limitations of the prior art in this reg
Dougherty J. Charles
Petravick Meredith
Will Thomas B.
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