Harvesters – Cutting – Cutter members
Patent
1989-08-03
1991-07-23
Melius, Terry Lee
Harvesters
Cutting
Cutter members
56255, 56DIG17, A01D 3482
Patent
active
050332597
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a blade for rotary lawnmowers and the like.
Rotary lawnmowers, in which a blade revolves at high speed about a vertical axis, have been used for many years. More recently this blade arrangement has been widely used in hovering lawnmowers, in which the mower is supported by a downdraught of air instead of being mounted on wheels. Such mowers are easy to maintain and convenient to use, and have proved very popular. However the growth in their use has been accompanied by numerous accidents in which, for example, the blade has cut into the operator's foot or, if the mower is electrically powered, its power cable, when the mower has been carelessly used.
Accidents such as these have led to several attempts to develop a safer cutting system for rotary lawnmowers, by replacing the standard substantially rigid metal blade with a blade whose edges will not so readily cut through obstacles such as shoes or cables. However these safety blades have until now been unable to match the standard blade for its combination of wear resistance, cutting efficiency, simplicity and ease of manufacture.
Therefore an object of this invention is to provide a safety blade for a rotary lawnmower which can replace, or be supplied instead of, a standard blade without seriously detracting from the mower's performance and ease of use.
SUMMARY OF THE INVENTION
According to this invention, a rotary blade for lawnmowers, brush cutters, trimmers and the like comprises a plurality of flexible and resilient, outwardly extending blade members angularly spaced in fixed relation about a central hub portion.
In preferred embodiments, the inner, root portion of each blade member merges smoothly into the hub portion and into the root portion of adjacent blade members, so as to encourage obstacles to be thrown clear rather than cut. Advantageously, each blade member incorporates one or more points of weakness to ensure that it breaks off rather than applying sufficient force to cut into an obstacle.
In some embodiments, intended primarily for use in grass-collecting machines, each blade member has an upturned vane at its tip to create an updraft as the blade rotates in use. The blade members may incorporate a step to position their cutting edges at a different height to the mower spindle. It is preferred that the blade of this invention is suitable for fitment to any of a variety of different machines, and to this end the hub portion may have a range of attachment points arranged to correspond with the attachment points of common existing machines. The blade is suitably made of a plastic, plastic composite or composite material and each blade member may be provided with two cutting edges, one on either side, to facilitate use of the blade in different machines whose spindles rotate in different senses. There are preferably four blade members, although any number may be used if appropriate. In an embodiment which is particularly suitable for use in machines powered by reciprocating engines, the outer ends of each blade member are weighted to enhance the flywheel properties of the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a first embodiment of the present invention having wing end turned out of the plane of the blade.
FIG. 2 is a schematic perspective view of a second embodiment of the present invention having vanes on the wing ends.
FIG. 3 is a schematic perspective view of another embodiment of the present invention in which the wings are substantially flat and have cutting edges on both edges of each wing.
FIG. 4 is a schematic perspective view of the blade of FIG. 2 having wings downturned out of the plane of the hub.
FIG. 5 is a schematic perspective view of the blade of FIG. 3 having wings downturned out of the plane of the hub.
FIG. 6 is a schematic perspective view of a fourth embodiment of the present invention having a step and vane in each wing.
FIG. 7 is a schematic perspective view of a fifth embodiment of the present invention having a st
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