This invention relates to a lawnmower, and in particular
to a so-called "wheeled rotary lawnmower" which includes a deck mounted on wheels,
a cutting chamber defined within the deck, a cutter blade or blades rotatably mounted
within the cutting chamber about a substantially vertical axis, and a grass collection
receptacle for collecting cut grass.
discloses a wheeled rotary lawnmower whose deck includes access means
in the form of an aperture or duct which leads cut grass to the grass collection
receptacle. A fan blows air through the cutting chamber and the access means into
the grass collection receptacle, sucks air from the receptacle for re-circulation.
While this type of lawnmower is effective, it is often necessary to direct the air
and cut grass around a curve or bend in order to take it from the cutting chamber
to the grass collection receptacle. This is of particular concern where the grass
collection receptacle is located above the deck, since the air and cut grass must
pass through a longer and tighter curve than if the receptacle is located outwardly
of (for example, behind) the deck. Where the grass collection receptacle is above
the deck, the cut grass is very difficult to re-direct, since it tends to drop out
of a curved stream of air and clog the lawnmower.
discloses a wheeled rotary lawnmower which attempts to overcome this problem
by positioning the grass collection receptacle substantially centrally within the
wheel base of the lawnmower, and by providing a secondary air stream which is directed
into the grass collection receptacle to complement the main air flow through the
receptacle, and to assist in deflecting the cut grass entrained in the main air
stream into the interior of the receptacle.
Although this lawnmower is an improvement on earlier wheeled
rotary lawnmowers, it does still suffer from problems in turning the grass and air
around the relatively long and tight curve between the cutting chamber and the interior
of the grass collection receptacle, particularly in wet conditions, when the cut
grass tends to stick to the wall of the curve, eventually causing a blockage, and
thereby preventing any further filling of the grass collection receptacle.
A mower according to the preamble of claim 1 is known from
US-A-4 932 194
The aim of the invention is to provide a wheeled rotary
lawnmower which has a reduced or eliminated clogging problem.
The present invention provides a lawnmower comprising a
deck defining a cutting chamber, the deck including an outlet for passage of cut
grass from the cutting chamber, a cutter blade rotatable within the cutting chamber
about a substantially vertical axis, and a grass collection receptacle including
an air-permeable region and an inlet for entry of the cut grass from the cutting
chamber, the deck being mounted on rotary members at forward and rearward positions,
wherein the inlet of the grass collection receptacle is provided in a front wall
of the receptacle, the outlet of the cutting chamber is aligned, in use, with the
inlet of the grass collection receptacle, and the grass collection receptacle is
positioned above the deck with the major part thereof within the wheelbase of the
lawnmower, and with its front wall above the cutting chamber characterised in that
the outlet of the cutting chamber is positioned substantially at a central, transverse
outer edge portion of the cutting chamber, and a substantially straight volute disposed
between the outlet of the cutting chamber and the inlet of the grass collection
Throughout this specification, the terms "forward" and
"rearward" should be taken to mean those positions remote from and adjacent to respectively
the user of the lawnmower when the lawnmower is being operated in the usual manner,
that is to say with the user pushing the lawnmower from "behind". Similarly, the
"front wall" of the grass collection receptacle is that wall remote from the user
when the lawnmower is being operated in the usual manner.
In a preferred embodiment, the volute rises from the outlet
of the cutting chamber to define a volute exit that extends over a substantial portion
of the height of the front wall of the receptacle. Advantageously, the volute exit
extends over substantially the entire height of the front wall of the receptacle.
Preferably, the inlet of the receptacle surrounds, in use, the volute exit.
The deck may support a housing, the housing enclosing the
grass collection receptacle, and the lawnmower may further comprise a motor positioned
within the housing, the motor being in drivable engagement with the cutter blade.
In a preferred embodiment, the grass collection receptacle
is an open-topped receptacle having at least one of its walls formed with air-permeable
Advantageously, the grass collection receptacle is provided
with a pair of handles positioned at the top of a pair of opposed wall portions.
Preferably, the housing is provided with an upwardly-open
aperture through which the grass collection receptacle can be inserted into, and
removed from, the housing, and wherein a cover is provided for closing said aperture
when the lawnmower is in use. Conveniently, the cover is pivotally mounted to the
housing for movement between a first position, in which the grass collection receptacle
can enter or leave the housing, and a second position in which the aperture is closed.
Preferably, when the cover is in the closed position, it
provides a substantially airtight seal against those portions of the housing defining
the upwardly-open aperture.
In a preferred embodiment, the rotary members are wheels.
Preferably, there are two wheels at the front of the deck and two wheels at the
rear of the deck. The lawnmower may further comprise a roller positioned between
the two rear wheels.
It will be appreciated that, where the rotary members are
not wheels, the term "wheelbase" should be taken to mean the distance between the
axis of rotation of the forward and rearward rotary members.
A wheeled rotary lawnmower constructed in accordance with
the invention will now be described in greater detail, by way of example, with reference
to the drawings, in which:-
- Figure 1 is a schematic, sectional side elevation of the lawnmower;
- Figure 2 is a perspective view of the lawnmower with its deck and upper portion
- Figure 3 is a plan view of the lawnmower with its upper portion removed.
Referring to the drawings, Figure 1 shows a lawnmower having
a base or deck 1, and a housing 2 mounted above the deck. The housing 2 defines
a large internal cavity bounded by a sloping front wall 3, a rear wall 4, side walls
5 and a top wall 6. The top wall 6 is apertured (as indicated by the edges 6a),
a cover 7 being pivotally attached to the top of the rear wall 4, so as to be movable
between a closed position (as seen in the drawings), in which it overlies the aperture,
and an open position which exposes the aperture. The deck 1 is supported by wheels
8 at the front and rear thereof, and a rear roller 9 is provided for generating
a "stripe" appearance on a cut lawn.
The housing 2 is constituted by two moulded parts 2a and
2b, the forward housing part 2a being formed with a rear wall 2c that separates
the two housing parts. The forward housing part 2a encloses a motor 10, which is
mounted above a cutting chamber 11 formed beneath the deck 1, and the rearward part
2b is open towards ground datum. A cutter blade 12 is rotatably mounted within the
cutting chamber 11 for rotation about a substantially vertical axis. The motor 10
has an output shaft 10a which is off-set from a shaft 12a of the cutter blade 12,
drive being transferred from the motor output shaft to the cutter blade shaft by
means of a drive belt 13. An impeller 14 is positioned above the cutter blade 12
on the shaft 12a for rotation therewith. The motor 10 is a self-cooled motor having
an internal fan (not shown) which results in improved motor durability, as cooling
is maintained when the motor is operating under load because the internal fan is
still moving large volumes of air. Thus, the motor 10 is protected from overheating,
even if the drive belt 13 fails, and cooling from the impeller 14 is lost. The belt
13 is of the V-belt type and co-operates with a matching pulley (not shown) on the
motor shaft 10a and with a plain/smooth pulley (not shown) which operates a braking
device (not shown) on the shaft 12a. Alternatively, the belt 13 is a toothed drive
belt which co-operates with toothed pulleys on the motor drive shaft 10a and the
shaft 12a. This type of drive belt is manufactured to tighter length tolerances
than "smooth" drive belts normally used in lawnmowers, so that the pulleys can be
mounted on fixed centres, resulting in improved reliability (there being substantially
no loss of belt tension during product life), and lower assembly costs. Moreover,
because of the toothed engagement of the belt 13 with the pulleys, there is reduced
noise at start-up, as there is no danger of the belt slipping.
A removable grass collection receptacle 15 is mounted within
the rearward part 2b of the housing 2, the receptacle being provided with a pair
of handles (not shown) for facilitating removal of the receptacle from the lawnmower
when the receptacle is to be emptied, and for returning the receptacle after emptying.
The handles are positioned at opposite sides of the receptacle 15 across the width
of the lawnmower. Alternatively, the handles could be positioned at the front and
back of the receptacle. In either case, the provision of the handles allows easy
removal of the receptacle 15 from the lawnmower, via the aperture 6a, by the operator
using both hands. The cover 7 is provided with a transparent panel 7a so that the
operator can see into the receptacle 15 to ascertain when it needs emptying. The
receptacle 15 is of the basket type with an open top, and has perforations (not
shown) in each of its side walls. Perforations may also be provided in the front
and rear walls and/or in the floor of the receptacle 15. Where the receptacle 15
has perforations in all sides and the base, improved grass compaction results. Thus,
air blown into the receptacle 15 by the cutter blade 12 and the impeller 14 can
easily vent through the perforations in the receptacle sides and base, that is to
say the flow of air is not obstructed as the receptacle fills. In addition, air
is continuously drawn by the impeller 14 through the perforations at the front side
of the receptacle 15 to aid compaction at the front, and then exhausts back into
the cutting chamber 11. In the closed position, the cover 7 rests against the portions
6a of the top wall 6 defining the aperture so that the housing 2 defines a substantially
airtight enclosure around the grass collection receptacle 15. The lawnmower incorporates
a safety switch (not shown) which operates automatically when the cover 7 is open,
thereby immobilising the motor and cutting off drive to the cutter blade 12.
The receptacle 15 is formed with an inlet aperture (not
shown) in its front wall 15a, the aperture surrounding an upwardly-inclined, short
and straight volute 11a leading from the cutting chamber 11, the volute having an
exit 11b which, in use, is positioned within the receptacle 15 adjacent to its front
wall 15a, the volute exit extending over substantially the entire height by the
receptacle front wall (see Figure 2). A handle 16 is provided for an operator to
control the lawnmower.
As will be apparent from Figure 1, the receptacle 15 is
positioned within the wheel base of the lawnmower, with its forward portion extending
partially over the cutting chamber 11. Moreover, as shown in Figure 2, the volute
11a leading from the cutting chamber 11 to the inlet to the receptacle 15 rises
sharply to lift cut grass into the receptacle, and to prevent it falling back within
the cutting chamber for re-circulation therein or dropping onto the lawn. The height
of the volute exit 11b reinforces the lifting of cut grass and the preventing of
it falling back into the cutting chamber 11. The position of the volute exit 11b
(see Figure 3) at a substantially central, transverse outer edge portion of the
cutting chamber 11 (the three o'clock position) permits the use of a receptacle
15 which extends partially over the cutting chamber 11, and so has potentially a
larger volume than receptacles of known lawnmowers of this type in which the receptacle
is positioned entirely behind the cutting chamber. This is a very important feature
of the lawnmower described above, as the receptacle 15 can hold substantially more
cut grass than known lawnmowers having the same overall configuration. Thus, the
user of this lawnmower needs to make fewer stops during mowing to empty the receptacle
15 than would be necessary with known lawnmowers of this type.
The volute exit 11b is a non-vertical plane surface, this
plane being radial from the centre of the volute 11a and being approximately normal
to the side wall of the mower.
The plane is inclined at an angle, with the top of the
exit 1 1b leaning towards the front of the mower. This helps with the removal and
fitting of the receptacle 15 when emptying it of cut grass.
To aid the passage of cut grass from the volute 11a into
the receptacle 15 through the volute exit 11b without the grass escaping into the
body of the mower, the receptacle entrance has a lip (not shown) on its outside
surface that overlaps the volute exit. This feature is on both the top and inner
vertical surfaces (closest to the motor baseplate). There is not room for such a
lip on the outer surface towards the outer wall of the mower body, as the two parts
butt together in this region to form a simpler seal.
In operation, the motor drives the cutter blade 12 and
the impeller which generate a low pressure within the cutting chamber 11, causing
air to be drawn in under the perimeter of the deck 1 from the high-pressure area
outside the deck. The air and entrained cut grass then pass from the cutting chamber
11 through the volute 11 a and into the receptacle 15. Because of its perforated
nature, air (but not grass) can pass from within the receptacle 15 outwardly and
then downwardly within the lawnmower body, finally exhausting through an opening
(not shown) in the base of the deck 1, and out to the atmosphere. This downward
exhaustion of air is assisted by the airtight fit between the cover 7 and the top
wall 6 of the housing 2.
Because the volute 11a is short and straight, there is
a substantially reduced chance that the passageway between the cutting chamber 11
and the receptacle 15 will clog, even with wet grass, in use. This lawnmower has
the advantage of having the grass collection receptacle 15 mounted within the wheelbase
of the mower, thereby ensuring that the weight of cut grass within the receptacle
is positioned generally over the centre of gravity of the machine. This facilitates
manoeuvrability of the lawnmower, even as the receptacle 15 fills with grass.
As the rearward part 2b of the lawnmower housing is open
to ground datum beneath the receptacle 15, air can readily escape from the receptacle
(via the perforations in its base and sides), resulting in a noise reduction from
the lawnmower. The easier escape of air also improves grass compaction. Moreover,
any grass entrained in the escaping air is deposited on the lawn, out of sight of
the user. Consequently, a reduction in the amount of grass "sprayed" out by the
lawnmower results. This also has the effect of keeping the lawnmower cleaner - in
a conventional lawnmower grass "sprays" out of perforations in the sides and rear
of the grass box, some of which will stick to the lawnmower and to the user's clothing.
As previously stated, cut grass travels from the cutting
chamber 11 into the receptacle 15 by the movement of air created by the blade 12
and the impeller 14. To improve the efficiency of the passage of grass, the lower
surface of the receptacle 15 at the interface of the volute exit 11b, and the receptacle
entrance are angled downwards towards the ground, but above the plane scribed by
the tip of the blade 12 to avoid damage by the blade. This makes it easier for the
grass to be collected off the blade 12, and more grass can be collected with less
grass being dropped by the mower. This lower surface of the receptacle 15 protrudes
through a "cheese/wedge" shaped hole 11c seen behind the volute exit 11b and in
the top surface of the main volute body 11a. Without the receptacle 15 in position,
the ground can be seen.
A major user benefit of the lawnmower described above is
the ease with which the grass collection receptacle 15 can be removed using both
hands. Thus, whilst on other types of lawnmower, the grass box has to be removed
for emptying using one hand to hold open a safety flap provided to close off access
to the cutting chamber, and the other to lift the grass box away from the lawnmower,
with the lawnmower described above, the cover 7 can first be raised and left in
an open position (for example resting against the handle 16), after which the receptacle
15 can be removed using both hands. In this connection, it should be noted that
this lawnmower does not need a safety flap to close off access to the cutting chamber
11, as the safety switch associated with the cover 7 is effective, together with
a braking arrangement (not shown) associated with the motor 10, to ensure that the
cutter blade 12 is stationary by the time that a user has removed the receptacle
15 for emptying. The receptacle 15 can then be inverted to empty out the cut grass.
The large, open area at the top of the receptacle 14 allows the grass to fall out
easily. This is to be contrasted with many traditional rear-mounted receptacles
which have a small opening for entry of cut grass from the mower, the small opening
acting also as an exit aperture through which the cut grass must be shaken or pulled
Another advantage of positioning the receptacle 15 within
the wheelbase of the lawnmower is improved safety. Thus, if a stone or other hard
object is thrown back by the cutter blade 12, the operator positioned behind the
receptacle 15 is protected by the two-walled construction (that is to say the rear
wall of the receptacle and the rear wall 4 of the housing 2) of the mower. Another
advantage is that the housing 2 constitutes a strong, rigid structure that is both
cost effective to manufacture and assemble. This structure may also contribute to
lower noise levels than with traditional lawnmowers where the grass bag or box is
mounted externally on the rear of the product.
A further advantage is that the handle 16 can be attached
to the housing 2 in a simple manner, leading both to lower manufacturing costs and
improved operating features.
The construction of the lawnmower having a smooth enclosed
shape defined by the housing 2 is less likely to become entangled in, or damage,
flowers, shrubs etc in flower beds adjacent to a lawn being cut. On a conventional
lawnmower, the grassbox is held on location features, typically provided at the
rear of the machine. In such a case, it is sometimes difficult for the user to locate
the grassbox properly, as the spring safety flap has to be held open by one hand,
whilst an attempt to locate the grassbox is made using the other hand. With the
lawnmower described above, however, as the receptacle 15 is located, in use, entirely
within the housing of the lawnmower, it is easily located in alignment with the
volute 11a by being dropped in.
Moreover, the rear of the grassbox of a conventional lawnmower
can be positioned so close to where the user grips the lawnmower's handle that,
in some instances, the user can inadvertently kick the grassbox and remove it from
engagement with the lawnmower. With the lawnmower described above, however, this
cannot happen, as the receptacle 15 is located within the housing of the lawnmower.
Yet another advantage is that the roller 9 is mounted at
the very rear of the lawnmower, thereby facilitating the provision of a superior
"striped" finish to a cut lawn. This is to be contrasted with many known types of
lawnmower, in which the roller is positioned between the cutting chamber and the
grass collection receptacle, thereby complicating the passage of air with entrained
grass into the receptacle. As the roller 9 is positioned behind the receptacle 15,
the path for passage of air and grass cuttings into the receptacle is simplified,
and, the action of the roller on a lawn is not affected by blown air and entrained
grass cuttings, thereby resulting in the improved "striped" effect referred to above.
The rear roller 9, which is used for producing a striped finish to a cut lawn, can
be positioned between the rear wheels 9. This allows the volute 11 a between the
cutting chamber 11 and the receptacle 15 to be reduced in length. This, in turn,
reduces the length of the lawnmower, and reduces the length of grass that can plug
the volute 11a. Moreover, if the volute 11a is so plugged, it is easier to clear,
as the plug will be smaller than with a conventional lawnmower.
It will be apparent that the lawnmower described above
could be modified in a number of ways. For example, air exiting the receptacle 15
could be drawn into the cutting chamber 11, thereby assisting with the compacting
of cut grass within the receptacle.
It would also be possible to replace the wheels 8 by other
forms of rotary member such as balls or rollers. The front wheels (or other forms
of rotary member) could be positioned some way from the front of the deck 1, provided
that the grass collection receptacle 15 remained within the wheelbase of the lawnmower.
Thus, the front wheels (rotary members) could be positioned at, or towards, the
rear of the cutting chamber 11, thereby enabling the mower to cut to the edge of
a lawn without the front wheels (rotary members) going over the edge of the lawn
which could cause the front of the mower to dip, leading to scuffing of the lawn
edge by the cutter blade 12. A recess could also be included in the base of the
receptacle 15 to act as an additional hand grip to assist in emptying the receptacle.
It would also be possible to mount the roller 9 at the very rear of the machine,
rather than between the rear wheels 8.
In another modified arrangement, a petrol engine could
be used instead of the electric motor 10.