GB2311453A

GB2311453A - Rotary lawnmower

Info

Publication number: GB2311453A
Application number: GB9606499A
Authority: GB
Inventors: Roger Thomas
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 1996-03-28
Filing date: 1996-03-28
Publication date: 1997-10-01
Anticipated expiration: 2016-03-28
Also published as: GB2311453B; GB9606499D0

Description

A Rotary Lawnmower with Improved Cutter Assembly The present invention relates to a rotary lawnmower having an improved cutting assembly, in particular a cutter assembly having means for adjusting the height-of-cut.

In GB 2 158 337 there is disclosed a rotary lawnmower which is adapted to provide different heights-of-cut. The lawnmower comprises a first component rotatable with a drive shaft of a motor, a second component carried on a cutter assembly and means for releasably engaging the two components one with the other in one of two axially displaced positions so as to raise or lower the cutter assembly towards or away from vegetation growth.

However, such a lawnmower has a disadvantage in that adjustment of component engagement between the first axially displaced position and the second axially displaced position requires loosening of a screw threaded bolt which clamps the components in the selected position.

An alternative solution to the problem of adjusting the height-of-cut involves the fitting of spacers on the motor drive shaft.

However, such an operation is impractical for general use since it requires removal of the cutter assembly prior to fitting of the spacers.

This operation is time consuming and cumbersome, and is not attractive to a user of the lawnmower.

It is also known to have cutting blades fixed to a support disc such that the blades are angled downwardly relative to a horizontal plane. When the height of cut is to be raised, the disc is inverted such that the blades are angled upwardly. When the higher cut height is chosen, however, it is not the ends of the blades which tend to cut the vegetation but the portions of the blades closer to the support disc. As a result, poor cutting can occur and additional strain is put on the drive motor.

It is desirable, therefore, to provide a cutter assembly having means for adjusting the height-of-cut which is not cumbersome and which can be quickly operated without resulting in a reduction in the quality or efficiency of cut.

According to the present invention, there is provided a rotary lawnmower comprising a rotatably driven blade carrier disc, at leat one connecting means for releasably securing an associated blade to the carrier disc adjacent to an edge of the carrier disc, the or each connecting means being adapted to releasably secure the associated blade in a selected one of a first location and a second location, the second location being spaced from the first location such that the height-of-cut of the lawnmower can be adjusted by moving the or each blade between the first and the second locations.

Preferably the first location is above the carrier disc and the second location is below the carrier disc.

In a preferred embodiment the connecting means includes a double headed rivet.

Preferably, the connecting means includes a keyhole aperture located adjacent an end of the or each blade, the keyhole aperture being adapted to receive and engage a portion of reduced diameter of the associated double headed rivet.

In a preferred embodiment the carrier disc is substantially cone shaped.

Additionally, a flat portion of the carrier disc may subtend an angle of substantially 95" to the rotational axis of the disc.

The carrier disc may be provided with two double headed rivets, both rivets of which are provided with an associated blade securable thereto.

A specific embodiment of the present invention is now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sectional side view of a lower portion of a rotary hover lawnmower including a cutter assembly in accordance with the present invention; Figure 2 is a plan view of a blade, and Figure 3 is a plan view of the blade shown in Figure 2 secured to a carrier disc.

Referring now to the Figures, there is shown a lower portion 10 of a hovermower. However, the present invention could equally be applied to a wheel supported rotary lawnmower. The mower comprises a mower deck 11 and a cutting assembly 12, the cutting assembly 12 being attached to a drive shaft 13 of a motor (not shown) for effecting rotation of the cutting assembly 12 about a longitudinal axis of the drive shaft 13. An end of the drive shaft 13 is provided with an externally screw threaded portion 14 for receiving a corresponding internally screw threaded portion of the cutting assembly 12.

The cutting assembly 12 comprises a carrier disc 18 having a hub 19 integral with a substantially cone shaped web 20.

The web 20 includes a flat surface 21, which subtends an angle of approximately 95" to the axis of rotation of the cutting assembly 12, and a plurality of double headed rivets 22 (two of which are shown) located adjacent an edge of the carrier disc 18, the rivets 22 being riveted to the web 20 such that a substantially equal portion of each rivet 22 extends from both sides of the web 20. Each of the rivets 22 is provided with an upper enlarged head portion 23, a lower enlarged head portion 24, an upper portion of reduced diameter 25 and a lower portion of reduced diameter 26.

Each rivet 22 accommodates a blade 27 of plastics material. Each blade 27 comprises a cutting tip 28 and a keyhole aperture 29 located adjacent an end of the blade 27 spaced from the cutting tip 28. The keyhole aperture 29 is formed of a first larger portion 30 and a second smaller portion 31, the first portion 30 being located closer to the tip 28 than the second portion 31.

The blades 27 are connected to the carrier disc 18 by locating the first larger position 30 ofthe keyhole aperture 29 over an upper or lower head portion 23, 24 of a rivet 22 and urging the blade in an outward radial direction so that the second smaller portion 31 of the keyhole aperture 29 locates between the upper or lower head portion 23, 24 and the disc 18. Since the second smaller portion 31 of the keyhole aperture 29 is smaller in diameter than the upper and lower head portions 23, 24, the blade 27 remains in connection with the carrier disc 18 when the carrier disc 18 rotates.

With the blade 27 connected to a rivet 22 upwardly of the carrier disc 18, the cutter assembly 12 will effect a height-of-cut which is greater that the height-of-cut which would be effected with the blade 27 connected to a rivet 22 downwardly of the carrier disc 18.

It will be appreciated that because the surface 21 of the carrier disc 18 is angled downwardly at an angle of approximately 5 to the horizontal, thus the blades are similarly andgled down and so cut at their tips 28 rather than farther up the blades. As a result, efficient and neat cutting of vegetation occurs.

Although the rivets 22 described herein extend from both sides of the disc 18, in theory shorter rivets could be used which simply have a head 23, 24 on either end of a stub shaft. The rivet may then by biased either upwards or downwards to expose a portion of the stub shaft above or below the carrier disc 18 to receive a blade 27.

Alternatively, the two locations for the connection of the blades can be located either with both locations below the blade carrier disc or with both locations above the blade carrier disc. The connection means could include a double rivet with two areas of reduced cross section above the blade carrier disc or with two areas of reduced cross section below the blade carrier disc.

It should also be appreciated that where more than two heights of cut are required each connecting means could include three or more locations at which the associated blade could be mounted. For example a tripple rivet having three regions of reduced cross section could be used so that the blade mounted on that rivet could be mounted at any one of theose three regions at three different heights.

Claims

CLAIMS:

1. A rotary lawnmower comprising a rotatably driven blade carrier disc, at least one connecting means for releasably securing an associated blade to the carrier disc adjacent an edge of the carrier disc, the or each connecting means being adapted to releasably secure a blade in a selected one of a first location and a second location, the second location being spaced from the first such that the height-of-cut of the lawnmower is adjusted by moving the or each blade between the first and the second location.

2. A rotary lawnmower according to claim 1, wherein the first location is above the carrier disc and the second location is below the carrier disc.

3. A rotary lawnmower as claimed in claim 1 or claim 2, wherein the connecting means includes a double headed rivet.

4. A rotary lawnmower as claimed in claim 3, wherein the connecting means includes a keyhole aperture located adjacent an end of the associated blade, the keyhole aperture being adapted to receive and engage a portion of reduced diameter of the double headed rivet.

5. A rotary lawnmower as claimed in any one of the preceding claims, wherein the carrier disc is substantially cone shaped.

6. A rotary lawnmower as claimed in claim 5, wherein the carrier disc has a flat circumferential portion which subtends an angle of between ? and ? (95 ) to the rotational axis of the disc so that the blades when mounted on the disc are downwardly inclined.

7. A rotary lawnmower as claimed in any one of the preceding claims, wherein the carrier disc is provided with two double headed rivets, each of which is provided with a blade securable thereto.

8. A rotary lawnmower substantially as hereinbefore described with reference to and as shown in the accompanying drawings.