GB2158337A - Rotary lawnmowers - Google Patents

Abstract

A vertical axis rotary lawnmower has a cutter assembly (16) mounted on the drive shaft (13) of a motor for rotation about the vertical axis, and means for locating the cutter assembly on the drive shaft in a selected one of at least two alternative axially displaced positions to provide different heights-of- cut. The locating means includes a first component (18) rotatable with the drive shaft, a second component (29) carried by the cutter assembly, and means (70) for releasably engaging the two components with one another in the selected position. Further means are provided which prevent separation of the two components whenever the selected engagement between them is released. <IMAGE>

Description

SPECIFICATION Rotary lawnmowers A well known problem when designing electri cally powered vertical axis rotary lawn mowers is that of providing adjustment for the heightof-cut. In many cases adjusting the height-ofcut involves removal of the cutter assembly and the fitting of spacers on the motor drive shaft. This is not only a tedious operation but generally involves touching parts of the mower, such as the motor drive shaft, which are not electrically double insulated.

According to one aspect of the present invention there is provided a vertical axis rotary lawn mower comprising a cutter assembly mounted on the drive shaft of a motor for rotation about the said axis, means for locating the cutter assembly on the drive shaft in a selected one of at leaast two alternative axially displaced positions to provide different heights-of-cut, the locating means including a first component rotatable with the drive shaft, a second component carried by the cutter assembly, means for releasably engaging the two components with one another in the selected position, and further means resisting separation of the two components whenever the said engagement between the components is released.

By resisting complete separation of the two components when the normal engagement between them is otherwise released, there is a substantialiy reduced risk of the user touching parts of the mower which are not electrically double insulated.

According to an alternative aspect of the present invention there is provided a vertical axis rotary lawnmower having a cutter assembly mounted on the drive shaft of a motor for rotation about the said axis, and further comprising means for locating the cutter assembly on the drive shaft in a selected one of at least two alternative angularly spaced positions providing different heights-of-cut.

In a preferred embodiment of the invention one of the locating components includes angularly spaced axially extending guide walls for guiding corresponding locating members on the other component to the selected location, the guide walls terminating at respective axially displaced steps defining the different heights-of-cut.

The two components are preferably held together by a locking member having a screw threaded spindle in screw threaded engagement with the drive shaft of the motor, the member having an insulating head which is retained against the underside of a cutter disc forming part of the cutter assembly.

Moreover, further means are provided for retaining the two locating components loosely coupled to one another when the locking member is disengaged from the drive shaft, the loosely coupled components substantially enclosing the drive shaft above the cutter disc so that the drive shaft is never accessible to the fingers of the user without forcibly separating the two components from one another.

The first locating component may comprise a socket having a central hub rotatable with the drive shaft, the periphery of the hub being selectively recessed to provide the angularly spaced axially extending guide walls and the corresponding steps defining the different heights-of-cut. The second component may then comprise a plug for inserting in the socket, the plug consisting of a sleeve upstanding from the cutter disc, the diameter of the sleeve being slightly greater than the diameter of the hub, and the inside diameter of the sleeve including angularly spaced projections which selectively engage the guide walls of the hub according to the relative angular positions of the plug and socket.

The socket may also include a sleeve surrounding the hub and having a diameter slightly greater than the sleeve upstanding from the cutter disc. The respective rims of the two sleeves may then include angularly spaced ramped lips or projections which prevent the two sleeves being separated once the projections on the cutter sleeve have been forced over the projections on the hub sleeve when the components are first assembled.

A further labyrinth seal to prevent the coupled components becoming clogged with grass is then provided by a further concentric sleeve around the outside of each sleeve on the respective components, the outer sleeve of the first component being of slightly greater diameter than that of the outer sleeve of the second component.

For an air-cushion mower, the central hub of the first locating component may lie within a hub portion of the centrigual fan which generates the air cushion and which is mounted on the drive shaft via an adaptor.

For a ground-supported mower, on the other hand, the central hub of the first locating component may itself form part of an adaptor for mounting on the drive shaft.

By way of example only, an embodiment of the invention is illustrated in the accompanying drawing in which: Figure 1 is a side view, partly sectioned, of the lower portion of a hovermower showing the assembly of a cutter disc and a fan on the motor drive shaft, the cutter disc being in the lower of two alternative axially displaced positions providing different heights-of-cut.

Figure 2 is a plan view on the underside of the fan; Figure 3 is a sectional view on line C-C of Figure 2; Figure 4 is a plan view of the cutter disc, and Figure 5 is a sectional view on line W-W of Figure 4.

Referring to these drawings, the mower comprises an electric motor supported on a generally dome-shaped deck 11 and enclosed within a protective housing 1 2. The motor has an output shaft 1 3 passing through a central opening 14 in the deck and driving a fan 1 5 and a cutter assembly 16.

The fan consists of a circular disc 20 having angularly spaced upstanding blades 1 7 which draw in lift air through an opening 74 in the deck when the motor is energised.

The curved fan blades 1 7 on the disc 20 radiate from an upstanding central hub assembly 18 which engages an adaptor 35 fitted to the drive shaft 1 3. The periphery of the generally tubular adaptor 35 includes angularly spaced cut-away sections which receive corresponding projections 36 on the hub assembly to provide a driving engage ment. The bottom end of the drive shaft 1 3 also includes a flat section which cooperates with a corresponding flat within the bore of the tubular adaptor to prevent rotation of the adaptor on the shaft. The entire fan assembly is then retained against axial displacement on the drive shaft by means of a ratchet plate 1 9 fitted at the bottom end of the shaft.

The underside of the hub assembly 18 forms a socket for locating an upstanding plug 29 of the cutter assembly 16. The cutter assembly further comprises a circular disc 22 with a radially extending flange 31 having a hole 30 for receiving a pivot pin (not shown) to which an elongate cutting element (not shown) is pivotally connected. The cutting element may for example, comprise a plastic -blade having a keyhole opening which snap fits over an enlarged head of the pivot pin as more fully described in our copending Application 8418383 The 'socket' of the fan hub assembly 1 8 essentially comprises two concentric sleeves 40,41 surrounding a central hub 42.The 'plug' 29 of the cutter assembly 16 then consists of corresponding concentric sleeves 43,44 which respectively lie within the sleeves 40, 41 when the two components are coupled to one another. The outer sleeves 40,43 provide a labyrinth seal around the inner coupling to prevent the coupling becom ing clogged with grass.

The inner coupling consists of angularly spaced axially extending guide walls 45 produced by cutting away predetermined sectors of the central hub 42, and corresponding angularly spaced axially extending projections 46 located on the inside diameter of the sleeve 44. The guide walls 45 include first walls 45a which extend upwardly from the bottom of the hub and terminate at respective steps 47, and second walls 45b which termi nate at steps 48, the steps 48 being axially displaced from the steps 47 and being closer to the bottom of the hub. In addition, intermediate guide walls 45c extend axially from the steps 48 to the steps 47.

Accordingly different heights-of-cut can be selected by aligning the projections 46 of the cutter assembly 'plug' with either the steps 47 or the steps 48 in the socket of the hub assembly, and then inserting the 'plug' into the 'socket'. Should the projections not be correctly aligned with steps 48, relative axial displacement will cause ramps 49 at the top of each projection 46 to cooperate with corresponding ramped projections 50 projecting from the hub 42 such that the cutter assembly is rotated into 30 a position in which the projections 46 are aligned with the steps 47 providing the greater height-of-cut. The cooperating ramps 49, 50 also prevent rotation of the projections 46 away from the shorter length guide walls 45b when in the lower height-of-cut position.In the upper heightof-cut position, the projections 46 are, of course, located between the longer guide walls 45a and the intermediate guide walls 45c. The three equispaced steps 45 in either height-of-cut position ensure that the cutter disc 22 is located square to the hub assembly.

With the fan assembly mounted on the drive shaft 1 3 and retained by the ratchet plate 19, the cutter assembly is connected to the fan by axially inserting the 'plug' 29 into the socket 18, thereby forcing three angularly spaced outwardly projecting angled lips 60 at the rim of the cutter sleeve 44 over corresponding inwardly projecting angled lips 61 at the rim of the hub sleeve 41, the lips being angled so that the cutter assembly cannot separate from the fan once the two components have been assembled.

The combined cutter and fan assembly is then clamped in its selected position by a screw-threaded bolt 70 passing through a central hole in the cutter disc 22 and engaging a threaded bore 34 in the drive shaft 1 3 of the motor. The bolt 70 has an enlarged insulated head 71 which is retained against the underneath surface of the cutter disc 22 by means of a second ratchet plate 72 even when the bolt is disengaged from the drive shaft. Accordingly, since the cooperating lips 60,61 prevent the 'plug' 29 being withdrawn from the socket, and the ratchet plate 1 9 prevents the fan assembly being withdrawn from the drive shaft, the drive shaft and the metal parts of the bolt are never accessible to the fingers of the user when adjusting the height-of-cut.

Claims (16)

1. A vertical axis rotary lawn mower comprising a cutter assembly mounted on the drive shaft of a motor for rotation about the said axis, means for locating the cutter assembly on the drive shaft in a selected one of at least two alternative axially displaced positions to provide different heights-of-cut, the locating means including a first component rotatable with the drive shaft, a second component carried by the cutter assembly, means for releasably engaging the two components with one another in the selected position, and further means resisting separation of the two components whenever the said engagement between the components is released.

2. A mower according to claim 1 in which the alternative axially displaced positions are angularly spaced from one another.

3. A mower according to claim 2 in which one of the components includes angularly spaced axially extending guide walls for guid ing corresponding locating members on the other component to a selected location, the guide walls terminating at respective axially displaced steps defining the different heights- of-cut.

4. A mower according to any one of the preceding claims in which the means for releasably engaging the two components comprises a locking member in screw threaded engagement with the drive shaft of the motor.

5. A mower according to claim 4 in which the further means resisting separation of the two components is operative when the locking member is released from its screw threaded engagement with the drive shaft.

6. A mower according to claim 5 or claim 6 further comprising means for retaining an insulated head of the locking member against the underside of the cutter assembly.

7. A mower according to claim 6 in which the head retaining means is carried by a screw threaded spindle of the locking member, the spindle passing through the centre of the cutter assembly to engage the drive shaft.

8. A mower according to any one of the preceding claims in which the two components include respective co-operating concentric sleeves of different diameter which overlap one another in each of the selected positions and surround the drive shaft.

9. A mower according to claim 8 in which the further means for resisting separation of the two components comprises means offering minimum resistance to insertion of the smaller sleeve within the larger sleeve but substantially preventing to subsequent separation of the two sleeves.

10. A mower according to any one of claims 2 to 9 in which the two components are releasably engageable in first and second angularly spaced axially displaced positions, and in which means responsive to relative axial displacement between the two components urges the second component into a first of the two positions from a position of partial engagement lying between the two positions.

11. A mower according to claim 10 in which the urging means includes co-operating ramp surfaces on the first and second components.

12. A mower according to claim 8 as dependent on claim 3 in which the first com ponent comprises a socket having a central hub disposed within the respective sleeve, the outside diameter of the hub being selectively recessed to provide the angularly spaced axially extending guide walls and the axially displaced steps.

13. A mower according to claim 8in which the two components include an additional pair of co-operating sleeves which fit within one another to provide a labyrinth seal surrounding the first pair of sleeves.

14. A vertical axis rotary lawn mower comprising a cutter assembly mounted on the drive shaft of a motor for rotation about the said axis, means for locating the cutter assembly on the drive shaft in a selected one of at least two alternative axially displaced positions to provide different heights-of-cut, the locating means including a first component rotatable with the drive shaft, a second component carried by the cutter assembly, and means for releasably engaging the two components with one another in the selected position, the two components overlapping one another to enclose the drive shaft in each selected position, and further means for retaining an overlap between the two components when the engagement between the components is otherwise released.

1 5. A vertical axis rotary lawn mower having a cutter assembly mounted on the drive shaft of a motor for rotation about the said axis and further comprising means for locating the cutter assembly on the drive shaft in a selected one of at least two alternative angularly spaced positions providing different heightsof-cut.

16. A mower according to claim 15 in which the locating means comprising a first component rotatable with the drive shaft, a second component carried by the cutter assembly, and means for releasably engaging the two components with one another in the selected position.

1 7. A vertical axis rotary lawnmower substantially as herein described with reference to the accompanying drawings.