Cutlery – Cutting tools – With blade moving means
Reexamination Certificate
1999-06-08
2001-07-17
Ashley, Boyer (Department: 3724)
Cutlery
Cutting tools
With blade moving means
C030S347000, C172S041000
Reexamination Certificate
active
06260278
ABSTRACT:
This invention relates to hand-held lawn and brush trimmers and in particular a lawn and brush trimmer that includes mechanical adjustments for selectively changing the attitude and orientation of the cutting plane of the trimmer head in relation to the trimmer's boom arm.
BACKGROUND OF THE INVENTION
Hand-held trimmers for cutting grass, brush and weeds are well known. Most hand held trimmers include a type of portable motor, a trimmer head having a rotating cutting component, such as a nylon cord or metal and plastic blades and a long boom arm. The trimmer head is connected at an angle to the distal end of the boom arm. In operation, a user typically grasps the boom arm or a handle part mounted to the boom at approximately the user's waist height and directs the rotating cutting component of the trimmer head at the distal end of the boom arm over the terrain. The length and angular orientation of the boom arm allows the operator to work the trimmer head directly over the terrain surface in a natural upright stance and without bending over. The angular orientation of the trimmer head with respect to the boom arm also positions the cutting plane of the rotating cutting component to be parallel to level terrain.
Many trimmer designs have been developed. Some trimmer designs incorporate the drive motor directly into the trimmer head, however, trimmers of this design are more difficult to manipulate and fatiguing to the operator because most of the trimmer's weight is located at one end of the boom arm. Consequently, most conventional trimmer designs locate the drive motors at opposite ends of the boom arms to provide more balanced and ergonomic operation. Since the motor and trimmer head are located at opposite ends of the boom arm, a drive shaft is rotatably disposed in the boom arm to transfer the rotational motion from the motor to the cutting component in the trimmer head.
Heretofore, lawn and brush trimmers that use a drive motor and trimmer head located at opposite ends of a boom arm have cutting planes that are fixed at permanent angular orientation with respect to the longitudinal axis of the boom arm. The angular orientation between the cutting plane and the boom arm is fixed due to the mechanical constraints of the drive shaft, which extends through the boom arm and connects the motor to the cutting components. The fixed angular orientation between the cutting plane and the boom arm make trimming difficult for persons of other than about average height. In addition, the fixed angular relationship can also make the trimmer difficult to use on uneven and sloping terrain. Consequently, in operation over un-level sloped terrain, an operator must hold and manipulate the trimmer to alter the natural balanced orientation of the boom arm in order to achieve a cutting plane parallel to the un-level sloped terrain. On upward sloping terrain, an operator must hold and manipulate the trimmer so that the trimmer head is raised and the boom arm is more parallel. On a downward sloping terrain, the operator must manipulate the trimmer so that the trimmer head is closer to the operator's feet and the boom arm is lowered at a more acute angle and the trimmer head is closer to the operators feet. Manipulating the trimmer outside of its natural balanced operating orientation makes the operation of the trimmer more fatiguing to the operator and may lead to unsafe use of the trimmer. Some lawn and brush trimmers have been developed that have boom arms that are adjustably connected to the trimmer heads, but these trimmers all locate the drive motor and trimmer heads at the distal end of the boom arms, which again creates an unbalanced tool for operation. Consequently, a balanced lawn and brush trimmer including an adjustment, which allows the attitude and orientation of the cutting plane of the trimmer head without changing the angular orientation of the boom arm from its normal balanced position is desirable.
SUMMARY OF THE INVENTION
The invention in one form thereof, provides a lawn and brush trimmer including a motor assembly and trimmer head mounted on opposite ends of a tubular boom arm and two manual adjustment mechanisms, which allow the attitude and orientation of the trimmer head to be adjusted with respect to the boom arm. The two adjustment mechanisms allow the trimmer head to pivot and rotate about two different axis in relation to the boom arm between several discrete adjustment positions. The adjustment mechanisms allow an operator to manually change the attitude and orientation of the trimmer's cutting plane to conform to the slope and contour of the terrain without the operator altering the natural balanced operating position of the trimmer or his body posture and while maintaining the natural balanced orientation of the boom arm with respect to the operator and not the terrain being worked. One adjustment mechanism (the pivot adjustment) allows the trimmer head to pivot in relationship to the boom arm between a number of manually selectable angular positions. Another adjustment mechanism (the swivel adjustment) allows the trimmer head to swivel 360° about the longitudinal axis of the trimmer head's neck and lock into one of several fixed positions. Both adjustment mechanisms work independently thereby providing different combinations of angular adjustments for the trimmer head about two separate axis of rotation while allowing the drive shaft to transfer rotational movement from the motor to the cutting components of the trimmer head. The invention in one form incorporates the adjustment mechanisms directly into the design of a hand-held lawn and brush trimmer, but in alternative forms, the adjustments can be incorporated as a modification to conventional trimmers.
The trimmer head pivot adjustment is connected to the trimmer's boom arm and includes a pivot selection assembly and a pivot joint assembly connected by a long rod. The joint assembly includes an upper housing part connected to the boom arm and a lower housing part connected to the trimmer head. The upper and lower housing parts form an enclosed cylindrical inner chamber for enclosing an universal joint. The pivot assembly divides the trimmer's drive shaft into two segments, connected by the universal joint. The upper housing part is shiftably disposed within the lower housing part for pivotal movement about a lateral axis. The selector assembly includes a disc shaped selector plate, a mounting clamp, a rotatable C-shaped selector handle, a coil spring and a C-shaped release lever. When the release lever is depressed, the handle can be rotated between seven discrete trimmer head positions. Rotating the handle moves the rod, which pivots the lower joint housing about the upper joint housing lifting or lowering the trimmer head in relation to the boom arm. When the lever is released, a spring forces the lever against the inner surface of the selector plate and seats two detents in one pair of several opposed bores in the selector plate, which locks the trimmer head in one of several discrete positions.
The trimmer head swivel assembly includes an inner collar part connected to the joint housing, an outer collar connected to the neck of the trimmer head and a spring tensioned release button. The inner collar is retained within the outer collar for rotatable concentric movement about its longitudinal axis. The inner collar can be secured in one of eight discrete positions by the lock button that extends into one of several radial bores formed in the inner collar. The lock button can be manually withdrawn from a bore to allow the inner collar to rotate within the outer collar. When manually released, a tension spring forces the lock button into another bore to lock the trimmer head in a set position.
Accordingly, an advantage of this invention is that the lawn and brush trimmer can be quickly and readily adjusted by a user for operation on terrains of different slopes and contours.
Another advantage of this invention is that the trimmer head can be pivoted and rotated about two a
Ashley Boyer
Crump R. Tracy
LandOfFree
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