Harvesters – Cutting – Rotating-cutting-disk type
Reexamination Certificate
2000-06-02
2001-08-07
Pezzuto, Robert E. (Department: 3671)
Harvesters
Cutting
Rotating-cutting-disk type
C056S320200
Reexamination Certificate
active
06269621
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a rotary lawnmower and more specifically to a rotor assembly for lawn mowing having a rotor, which operates at a plurality of cutting levels, and a rotary lawnmower having such a rotor assembly.
BACKGROUND OF THE INVENTION
A traditional rotary lawnmower cuts grass at a pre-set cutting level. The cut grass normally stays on the fresh-cut lawn and will then be visible in a distinct and often unpleasant manner. For this reason, the grass is often collected and carried away from the lawn. This collection can be performed, for instance, by the cut grass being directly brought into a collecting container or by the cut grass being raked together after the cutting of the lawn. This is, however, disadvantageous since nourishment is removed from the lawn.
To solve this problem systems for disintegrating the grass have been developed. Hence the grass can be restored to the lawn in a way that is appealing to the eye since the disintegrated grass can penetrate into the lawn and thus become less noticeable. In addition, the cut grass degrades faster when it is cut into pieces.
One type of such rotary lawnmowers maintains the cut grass in the cover of the rotor and causes chopping knives to chop it, after which the small pieces fall down on the lawn. According to a second type of rotary lawnmower, the cut grass is put on the lawn, after which the knives of the rotary lawnmower engage the cut grass once again and chop it into small pieces. The problem of these types is that the cutting quality depends on the cutting conditions. In many cases, the grass which is cut from the lawn is only beaten around by the chopping knives without being hit and thus chopped, and if the grass should happen to be wet, the cut grass tends to be rubbed rather than chopped by the rotor knives.
A third type of rotary lawnmower, which solves the above problems, comprises a rotor which theoretically operates at a plurality of cutting levels. In this case, the rotor is arranged so as to first operate at the highest cutting level, and then successively down to the lowest. The grass is thus cut by steps, only a small piece of each blade of grass being cut in each step. Examples of such rotary lawnmowers are disclosed in FR 2,468,289, U.S. Pat. No. 4,351,144 and WO 96/29853. Since the grass is cut successively down to the desired height, so-called topping, the above-mentioned “beating” problem is eliminated. There is, however, a disadvantage of this type of lawnmower as well. It has appeared in practical application that the rotor does not operate in the intended manner. If the grass is high, the parts of the rotor which operate at the higher cutting levels will not be able to top the grass because when the lawnmower is travelling, the grass is first applied against the cover of the rotor, whereby the grass is bent forwards. Subsequently, when the grass thus bent forwards enters the rotor, this bending forwards of the grass is maintained and enhanced by the flow of air caused by the rotor. Consequently, at these higher cutting levels the grass escapes being hit and thus being cut by the rotor. Hence, it is only the intermediate and low parts of the rotor that cut the grass in a fairly efficient manner, which implies that a large piece of each blade of grass will be cut off. This results in the inconvenience of having an unpleasant accumulation of cut grass on the fresh-cut lawn.
The object of the present invention is to provide a rotor assembly and a rotary lawnmower of the above-mentioned second type, which secure a satisfactory disintegration of the grass, even if the grass is high.
SUMMARY OF THE INVENTION
The object is achieved by a rotor assembly comprising at least one rotor operating at a plurality of levels, the rotor assembly having an abutment structure which is arranged at least at the upper cutting levels and has supporting points adjacent to the rotor to keep grass upright while being cut by the rotor.
As a result, a rotor assembly is provided which yields an improved disintegration of grass when cutting the same, even if it is high. The improved disintegration is secured by the abutment structure, whose supporting points prevent the grass from bending owing to the flow of air caused by the rotor. Thus, the grass will be cut at all the levels at which the rotor operates, whereby the desired disintegration of the grass is achieved.
Preferably, the abutment structure is arranged outside the rotor.
According to a preferred embodiment, the abutment structure is arranged directly adjacent to the rotor.
Hence a scissors cutting action can be provided to secure an excellent cutting quality.
According to another embodiment, the position of the abutment structure is adjustable in relation to the rotor.
This makes it possible to adjust the cutting quality. If a better cutting quality is desired, the position of the abutment structure is adjusted so that it is arranged directly adjacent to the knives of the rotor.
Preferably, the abutment structure constitutes a part of or a part intended for a cover of the rotor, the abutment structure being arranged at a portion of the cover which is the front portion seen in the travelling direction of the rotor assembly.
By the abutment structure being arranged at the front side of the rotor assembly, it is secured that the abutment structure holds up grass which is unaffected by the rotor.
Preferably, the supporting points are evenly distributed along the front portion of the cover and the rotor is arranged to apply grass to the supporting points by its rotation, whereby the grass is cut when the rotor passes the respective supporting points.
Preferably, the abutment structure comprises apertures permitting grass to pass through to the rotor.
By the abutment structure being provided with apertures, the grass is permitted to pass through to the rotor at the same time as the grass is kept upright by the supporting points of the abutment structure as the lawnmower travels.
Preferably, the supporting points are formed of side edges of the apertures.
Preferably, the apertures are arranged in vertical planes, which are parallel with the travelling direction of the rotor assembly. Alternatively, the apertures can be arranged in vertical planes extending radially to the rotational axis of the rotor.
Preferably, the abutment structure comprises lifting means extending from the rotor assembly in its travelling direction to raise lying grass while advancing the rotor assembly.
According to one embodiment of the invention, the rotor comprises a knife means extending radially to or away from a rotor centre, the knife means being formed in such manner that a radially outer portion operates at a high cutting level and a radially inner portion operates at a low cutting level.
The knife means can be so formed that its cutting level decreases in an infinitely variable manner or by steps from the outer portion to the inner portion.
According to yet another embodiment of the invention, the rotor comprises, at a radially outermost portion, a knife means, which is formed in such manner as to operate at the different cutting levels, a first part of the knife means, which first part operates at a high cutting level, being arranged in front of a second part of the knife means, seen in the rotational direction of the rotor, which second part operates at a low cutting level.
This secures that all the operating parts of the knife means operate with the same cutting width while at the same time the topping function of the rotor is secured.
Further, the invention relates to a rotary lawnmower comprising at least one rotor assembly according to that stated above.
This results in a rotary lawnmower, which secures a satisfactory cutting of grass, even if the grass is high.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way
Fischier Mats
Larsson Sture
Birch & Stewart Kolasch & Birch, LLP
Mats Fischier i Båstad AB
Pezzuto Robert E.
LandOfFree
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