GB2136664A - A lawnmower - Google Patents

Abstract

In a lawnmower of the type having a wheel-mounted or roller-mounted frame carrying a horizontal cutter bar under a bladed rotor for cutting grass between them, the rotor consists of a number of spaced rotor plates (11,12) coaxially mounted on a shaft, each plate having a circular peripheral series of pitched blades (13) which, as the rotor is driven, move sequentially from front to rear over the cutter bar. The blades of each rotor plate are angularly displaced relative to the corresponding blades of the next, and the paths of the blades of successive rotor plates overlap. The blades of the two halves of the rotor may be oppositely pitched for impelling grass clippings from both ends towards the middle. <IMAGE>

Description

SPECIFICATION A lawnmower (1) Field ofthe invention This Invention relates to a lawnmower.

(2) Brief description of the prior art In mowing a fine lawn, such as, for example, a bowling green or a golf green, it is usual to use a cylinder type lawn mower, that is to say a lawnmower having an assembly of helical blades mounted in equally spaced arrangement about an axial shaft, the outer edges of the blades being a uniform distance from the shaft which is motor-driven so that the blades of the advancing mower, sweeping in sequence over a transverse cutter bar, cut the grass between the blades and the bar. The grass clippings are swept, by the rotating cylinder, upwardly and forwardly against a fixed delfector plate and thrown into a grass catcher mounted in front of the cylinder.

The cutter bar, advancing at a low level, is likely to push some of the grass under it, particularly if the grass is fairly long, pressing it towards the ground to bring about the undesirable effect known as "thatching", which is a well-known problem to green keepers and professional golfers. A further disadvantage of the cylinder-type mowers is their tendency to tear at grass blades momentarily held between the advancing cutter bar and the blades sweeping over it.

Summary of the present invention The present invention has been devised with the general object of providing a lawnmower cutting assembly which is particularly efficient in operation.

Other objects achieved in preferred embodiments of the invention are to provide such an assembly which may be readily installed in an existing mower in replacement for its conventional cylinder cutter, which is simple and economical to manufacture and to maintain, and is sturdy, durable and trouble-free in use.

With the foregoing and other objects in view, the invention resides broadly in a lawnmower of the type having a wheel-mounted or roller-mounted frame, a transverse cutter bar on the frame, a bladed rotor mounted above the cutter bar and means for driving the rotor as the mower is advanced to cause grass to be cut between the rotor blades and the cutter bar; wherein the rotor includes a plurality of spaced rotor plates mounted coaxially on a rotor shaft, each of the rotor plates having a circular peripheral series of piched blades, which as the rotor is driven, are brought sequentially from front to rear over the front of the cutter bar. The path of the blades of each rotor plate preferably overlaps the path of the blades of each adjacent rotor plate.The rotor plates are preferably in two series, the blades of each series being pitched similarly, and oppositely to the blades of the other series, the blades of the two series being so pitched as to be adapted to impel grass clippings from both sides towards the middle.

Other features of the invention will become apparent from the following description.

Brief description of the views of the drawings In order that a preferred embodiment of the invention may be readily understood and carried into practical effect, reference is now made to the accompanying drawings, wherein: Figure 1 is a front elevational view of a rotor assembly according to the invention applied to a lawn mower, part of which is indicated in broken outline, and Figure2 is a sectional view taken along line 2-2 in Figure 1.

Detailed description of the preferred embodiments The rotor assembly, which is applicable to a conventional motor-driven lawnmower in substitution for its normal helically bladed rotor or cutting cylinder includes a shaft 10 on which there are coaxially mounted, in equally spaced arrangement, a series of bladed rotor plate 11, and a further series of bladed rotor plates 12.

Each of the rotor plates 11 and 12 may be formed of fairly heavy gauge sheet metal, being initially in the form of a centrally apertured disc with a number of equally spaced wedge-shaped excisions extending radially in from its periphery to leave, between the excised sections, a series of equally spaced and similar blades 13. These blades 13 of each rotor plate are similarly twisted by any suitable method and means to impart pitch. Extending into the central aperture of each of the rotor members 11 and 12 is a projection or key 14.

The bladed rotor members 11 of the first series differ from the bladed rotor members 12 of the second series in that their blades 13 are oppositely pitched, as shown particularly in Figure 1.

The rotor shaft 10 is formed with an integral circumferential stop flange 15 near to one end, and near to its other end it is formed with a threaded portion (not shown) on which a locking nut 17 may be screwed. The end portions of the shaft are reduced in diameter for engagement in bearings at 18 mounted on the side plates 19 of the mower. The shaft 10 is formed with two longitudinal keyways 20 and 21 either one of which will accept the keys 14 of the rotor members 11. In assembling the rotor, the first rotor plate 11 is engaged on the shaft 10, its key being engaged in the keyway 20, the plate being brought against the stop flange 15. A spacer sleeve 22 is then fitted on the shaft 10, against the first rotor plate, followed by a second rotor plate 11, its key 14 being engaged in the other keyway 21.When all of the rotor plates 11 have been so assembled on the shaft 10, their keys 14 engaging alternately in the keyways 20 and 21, and with interposed spacer sleeves 22, a further spacer sleeve is added followed by the first of the oppositely pitched rotor plates 12, a spacer sleeve 22 and so on. Finally, a washer 23 is fitted on the shaft 10 against the last of the bladed rotor plates 12, and the locking nut 17 is screwed tightly onto the shaft to hold the assembly of rotor plates and spacer sleeves firmly together. The shaft 10 is then engaged in the bearings 18 and, within the mower's chain case 24, is connected to a drive (not shown) from the motor mower (not shown).

The angular displacement of the two keyways 20 and 21 is such that, by engaging the rotor plate keys 14 alternately in one and the other, the blades of succeeding rotor plate are displaced by similar angles; by 30" in the embodiment illustrated, in which each of the rotor plates 11 and 12 has six blades at 60" spacing. It will be seen from Figure 1 that the path of the outer edges of the blades of each of the rotor plates slightly overlaps the path of the blades of the adjacent rotor plates.

When the rotor is driven in the direction indicated by an arrow in Figure 2,the blades 13 of the rotor plates 11 and 12 sweep from front to rear over the leading edge portion of the mower's cutter bar 26.

The blades 13 thus sever any grass against which the cutter bar 26 is brought as the mower advances. The blades also impel the grass clippings over the inside face of the arcuately curved deflector plate 27 of the mower, so that the clippings are ejected forwardly, above the rotor, and into the grass catcher (not shown) carried removably in front of the mower. The oppositely pitched blades 13 of the two series of rotor plates 11 and 12 tend to impel the grass clippings from both sides towards the middle, for more efficient grass collection.

The mower may be adjustably raised or lowered relative to its front wheels 28 and rear roller 29 to alter the height of the cut, and the cutter bar 26 may be adjusted by any suitable means (not shown) to compenate for wear.

Lawnmowers according to the invention will be found to be very efficient in operation, and the cutting assemblies may be made and assembled simple and economically. Any of the rotor plates that may become damaged may be easily and conveniently removed for repair or replaced.

While a conventional mower, with a series of continuous helical blades from end to end of the rotor, tends to push long grass over in front of it, a mower according to the present invention with its series of bladed rotor plates will efficiently cut long grass not previously or recently mown. Hitherto, it has been found necessary to use a rotary slasher type of mowerto cut long grass preparatoryto mowing with a cylinder type mower; but mowers according to the invention are usable both for the preliminary cutting of very long grass and also for mowing the lawn after it has been nurtured to a good class turf.

The particular embodiment of the invention herein described and illustrated may be subject to many minor modifications of constructional detail and design, which will be readily apparent to persons skilled in the art, without departing from the scope of the invention hereinafter claimed.

Claims (6)

1. A lawnmower of the type having a wheelmounted or roller-mounted frame, a transverse cutter bar on the frame, a bladed rotor mounted above the cutter bar and means for driving the rotor as the mower advances to cause grass to be cut between the rotor blades and the cutter bar, wherein: the rotor includes a plurality of spaced rotor blades mounted coaxially on a rotor shaft, each of the rotor plates having a circular peripheral series of pitched blades which, as the rotor is driven, are brought sequentially from front to rear over the front of the cutter bar.

2. A lawnmower according to Claim 1 wherein: the blades of the rotor plates are in staggered arrangement, those of each rotor plate being angularly displaced relative to those of each adjacent rotor plate.

3. A lawnmower according to Claim 2 wherein the path of the blades of each rotor plate overpass the path of the blades of each adjacent rotor plate.

4. A lawnmower according to any one of the preceding claims wherein: the rotor plate are mounted on the rotor shaft in two series, the blades of the rotor plates of each series being pitched similarly, and oppositely to the blades of the rotor plates ofthe other series, the blades of the rotor plates of the two series being pitched to impel grass clippings from both sides towards the middle of the rotor.

5. A Iawnmowe.according to any one of the preceding claims wherein: each rotor plate is formed with a central aperture to receive the rotor shaft, and a key extending into the said aperture, and the rotor shaft is formed with two longitudinal keyways, each accepting keys of alternate rotor plates.

6. A lawnmower substantially as herein described with reference to the accompanying drawings.