Field of the Invention
The present invention relates to a wheel-mounted lawnmower
or the like of the type comprising a cutting device which is connected to a motor
for performing a cutting function, the lawnmower being operated by an operating
means. The invention also relates to an insulator arranged on a lawnmower or the
like. The invention also concerns use of a lawnmower or the like.
Lawnmowers and the like relate to motor-driven devices
which in the first place perform a cutting operation. Examples of such lawnmowers
are manual rotary lawnmowers, cylinder lawnmowers and, in some cases, chopper mowers.
Not only lawnmowers but also wheel-mounted and motor-driven vertical cutters and
moss cutters are concerned. Other conceivable examples are wheel-mounted aerators,
peat cutters, rotary cultivators and trimmers.
The motor-driven devices of the type mentioned above, however,
result in vibrations from, for instance, motor and rotating tools being transmitted
to the handle and then on to the user.
This vibration problem may cause problems for the user,
especially in daily and frequent use, in the form of vibration injuries in arms
and hands. A common vibration injury is the white finger syndrome which means that
the blood flow to the fingers is reduced, resulting in tingling and numbness.
Due to the vibrations, also components of the lawnmower
may be damaged and/or come loose.
EP 0 268 571 B1 (Claesson
) discloses a lawnmower with vibration damping, see Fig. 1. The lawnmower
has vibration-insulating means arranged between the chassis and the attachment of
the motor. The solution described results in a reduction of the vibrations from
the motor to the other parts, such as a handle, of the lawnmower. However, a remaining
problem is that the motor in this case is subjected to high vibration levels, which
in turn may result in motor wear and a reduced motor life. Moreover, the cutting
casing must on the underside be made slightly larger than usual so as not to collide
with the cutting unit owing to vibration movements originating from the motor. The
enlarged dimension of the cutting casing may thus cause deteriorated aerodynamic
properties, which has an adverse effect on the cutting performance.
Another prior-art technique of reducing the vibration transmission
to the handle is that the handle rod is separated in its longitudinal extent by
an intermediate uniting spring. This solution results merely in a certain reduction
of the vibration problem since only a small mass is available on the vibration insulated
side of the system while at the same time the vibration insulator cannot be made
particularly weak so as not to lose at the same time the handleability of the machine.
Moreover this solution results in reduced handleability of the lawnmower, especially
when the user, for instance, wants to slightly change the travelling direction of
the lawnmower by the user pressing the handle towards the base and moving the handle
sideways relative to the travelling direction, whereby the front portion of the
lawnmower is moved in an opposite lateral direction relative to the preceding travelling
direction. This results in considerable moment strain for this type of resilient
There is currently also a directive within the EU for,
inter alia, lawnmowers in professional use that stipulates that the average vibration
levels should not exceed 2.5 m/s2 hand-arm vibration during an 8-hour
It is also desirable to provide a lawnmower with lower
vibration levels which is not too expensive.
It is also preferred for the lawnmower to have good handleability.
Thus there is a need to satisfy the above requirements
and to provide a solution to the above problems. Document
discloses a wheel-mounted lawnmower.
Summary of the Invention
Therefore the object of the present invention is to provide
a lawnmower or the like which results in an improvement relative to prior art in
one or more of the above aspects.
The above object is achieved by a lawnmower as stated by
way of introduction, in which the lawnmower has a first unit which is provided with
said cutting device and said motor. A second unit has at least two rotatable wheels
for moving the lawnmower relative to a base, a wheel frame for arranging the wheels
and for arranging said operating means on said wheel frame. An insulator is arranged
to at least partly mutually connect said first and second unit to reduce any vibrations
between said units.
This construction makes it possible to reduce the vibrations
from the motor as well as from the cutting device, so that the operating means will
have a reduced vibration level. Furthermore, the vibration levels of the motor will
be reduced by the mass of the other parts of the first unit counteracting the movements
of the motor. This also allows the distance between the cutting device and the first
unit to be kept constant.
The above object is also achieved by an insulator arranged
on a lawnmower or the like as described above.
Preferably said insulator is adapted to reduce any vibrations
in said first unit to be transmitted to said second unit which is connected to said
Said first unit comprises preferably a frame for attaching
said cutting device and said motor. Further said first unit suitably has a protective
cover which at least partially surrounds said cutting device. The protective cover
performs a protecting function and is also suitably adapted to produce convenient
currents of air when the lawnmower is in operation, thus facilitating the cutting
function. Moreover, a body is suitably included in said first unit. The above-mentioned
components increase the total mass of the first unit, which thus counteracts the
movements and vibrations of the motor.
Said operating means is alternatively in its longitudinal
direction divided into at least two pieces which are connected at least partially
by a damping element to reduce any vibrations from said second unit to the handle
portion of the operating means. In this manner, the remaining vibrations to the
user may be reduced.
The operating means advantageously constitutes part of
said wheel frame. Moreover the operating means is suitably L-shaped with a first
end having an operating handle and a second end to be connected to the wheels of
Alternatively the operating means is at least one operating
rod which is connected to said wheel frame.
Additional features and advantages of the present invention
will be evident from the following description of special embodiments of the invention
with reference to the accompanying drawings.
Brief Description of the Drawings
Description of Preferred Embodiments
- Fig. 1 illustrates a lawnmower according to prior art.
- Fig. 2 illustrates schematically a lawnmower according to a first embodiment
of the invention.
- Fig. 3a shows a first unit of the lawnmower according to Fig. 2.
- Fig. 3b shows a second unit of the lawnmower according to Fig. 2.
- Fig. 4 illustrates schematically a lawnmower with a an operating means according
to a second embodiment of the invention.
- Fig. 5a illustrates schematically a lawnmower according to a third embodiment
of the invention.
- Fig. 5b shows the lawnmower according to Fig. 5a in an assembled state.
- Fig. 6 is an enlarged section seen from the front according Fig. 5a.
- Fig. 7a illustrates schematically a lawnmower according to a fourth embodiment
of the invention.
- Fig. 7b is an enlarged section seen from the front according to Fig. 7a.
- Fig. 8a illustrates an insulator according to Fig. 7b.
- Fig. 8b shows an alternative insulator according to Fig. 7b.
Fig. 1 illustrates a lawnmower according to prior art.
The prior-art lawnmower is provided with rubber blocks 30 which are fixed between
a motor and a chassis 31. Fig. 1 illustrates an example where there is a risk of
the motor being subjected to high vibration levels, as described above.
Fig. 2 shows a non-self-propelled rotary lawnmower 1 according
to a first embodiment of the invention of the type where the user steers and walks
preferably behind the lawnmower (relative to the main direction of movement). The
lawnmower 1 comprises a cutting device 2 which is driven by a motor 3 connected
thereto. The cutting device 2 and the motor 3 are according to the first embodiment
mounted on a frame 10 for attachment, and the frame 10 also constitutes a hood-shaped
protective cover 11 for the cutting device 2. The lawnmower is operated by an operating
means 4 which is connected to the lawnmower 1. The operating means 4, which in the
first embodiment is U-shaped seen from above and L-shaped seen from the side, consists
of two operating rods 18 (directed to the far end in the Figure) with a connecting
handle portion 14 at a first end 15 of the operating means 4. The lawnmower 1 is
also provided with four rotatable wheels 7 to be able to move the lawnmower relative
to a base.
Fig. 3a shows a first unit 5 of the lawnmower 1 according
to the first embodiment. The first unit comprises in this case suitably the hood-shaped
frame 10 for stable attachment of the motor 3 and the cutting device 2. The hood-shaped
frame 10 with its protective cover 10 surrounds, peripherally and above, a rotatable
blade 19 of the cutting device 2. The protective cover 11 has an opening for the
blade (directed towards the base of the lawnmower) to perform the cutting function
of the lawnmower. The hood-shaped frame 10 is preferably cast in one piece which
is made of metal such as steel or aluminium or alternatively pressed metal sheet
or a rigid plastic material. As is evident from Fig. 3a, the rectangular frame 10
has in each corner portion a first fixing portion 20 for an insulator 9. The upper
portions of the first unit can be seen as a body 12, which may of course comprise
a plurality of adjusted protective hoods for, for instance, the motor 3.
Fig. 3b shows a second unit 6 of the lawnmower according
to the first embodiment. The second unit 6 comprises a rectangular wheel frame 8
supporting the four wheels 7. It is evident from Fig. 3b that the front and rear
wheels 7 are arranged on a wheel axle 22 each. The operating means 4 is at its second
end 16 attached to the wheel frame 8 at the two rear wheels (seen at the far end
in the Figure) of the lawnmower. The wheel frame 8 in Fig. 3 has four further fixing
portions 21 for the insulator 9 located at the lateral portions of the wheel frame
With reference once more to Figs 3a and 3b, the insulators
9 are in the first embodiment pressure springs which are positioned between the
first 20 and the second 21 fixing portions. Furthermore the insulator 9 preferably
is made of a rigid material which is suited for springs, such as steel.
Of course, the insulator 9 may consist of other vibration-damping
elements in terms of shapes as well as material which is adapted to reduce vibrations,
for instance a piece of foamed polymer, such as polyurethane. Further examples are
rubber and other suitable elastomers.
The function of the lawnmower will now be described. With
reference once more to Figs 2, 3a and 3b, when the spring 9 is mounted in the intended
place, the spring will be slightly compressed as a result of the mass of the first
unit 5. When the motor 3 and the cutting device 2 are in operation, the vibrations
will be propagated within the first unit 5 which also comprises the hood-shaped
The vibrations of the motor will thus be distributed within
the first unit 5. In this way, the total mass of the first unit 5 counteracts the
vibrations of the motor 3 and the cutting device 2. The first unit 5 has preferably
only contact with second unit 6 by means of the insulators 9. The vibrations from
the first unit 5 can thus essentially be transmitted merely via the insulators 9.
In this way the vibrations from the first unit 5 to the
second unit 6 are reduced, and the user of the lawnmower avoids high vibration levels
through the handle portion 14.
Any remaining vibrations will be distributed within the
second unit 6 which comprises the wheel frame 8, the wheels 7 and the operating
means 4. However, it should be noted that the wheels in normal use of the lawnmower
have contact with a supporting and usually damping base.
The main vibrations which should be reduced originate mainly
from the imbalance and accelerating forces of the motor and also from any imbalance
in the cutting unit. The vibrations occur essentially in the radial direction, but
since the centre of gravity of the lawnmower does not coincide with the plane in
which the forces occur, also axial vibrations occur.
In the same way as described above, any vibrations from
the second unit 6 to the first unit 5 can be damped.
With reference once more to Fig. 2, the lawnmower is provided
with a control handle 23 for adjusting the height of the cutting device relative
to its base (the lawn). However, it should be noted that the distance in the vertical
direction between the cutting blade and the first unit 5 is constant. Fig. 3 also
shows a regulator 24 for adjusting, for instance, the speed of the motor 3 of the
Fig. 4 shows a lawnmower with an operating means 4', according
to a second embodiment of the invention. In the second embodiment, the operating
means 4' has two operating rods 18' which are each divided into two elongate pieces.
Each divided operating rod 18' is connected by a damping element 13' which in this
embodiment is a coil spring, but which may of course consist of other suitable vibration
damping means. This damping element 13' can thus reduce any remaining vibrations
from the second unit 6 to reach the handle portion 14' and, thus, also the user.
Fig. 5a shows a lawnmower according to a third embodiment
of the invention. The lawnmower is provided with insulators 9" which are fixed to
the protective cover 11 in a clamp 17" and in the wheel frame 8 at each wheel 7.
The insulators 9" are preferably arranged so as to be longitudinally compressed
owing to the weight of the first unit 5, but may of course be arranged so as to
be subjected to tractive forces instead. It goes without saying that the insulators
9" can be arranged in some other way so as to be subjected to a combination of tractive
and compressive forces and/or shear forces.
The insulators 9" according to the third embodiment are
made, for instance, of foamed polyurethane or other suitable materials that exhibit
properties according to the intentions of the invention.
Any stress that exceeds normal use is suitably relieved
by limit stops (not shown) to prevent the insulators from being subjected to excessive
stress levels which may cause a reduction of the life of the insulators.
Fig. 5b, which shows the invention according to the third
embodiment in an assembled state, has the parts of the wheel frame 8 parallel to
the travelling direction arranged on the upper side of the protective cover 11.
Fig. 6, which is an enlarged section seen from the front
of the invention according to the third embodiment, is provided with said clamp
17". The insulator 9" is at its upper end fixed to the clamp 17" and at its lower
end to a connecting plate 25" of the wheel frame 8. The protective cover 11 and/or
the connecting plate 25" are provided with a damping means 26" for preventing the
connecting plate 25" and the protective cover 11 from coming into direct contact
with each other, thus reducing any vibrations.
With reference to Fig. 7a, a fourth embodiment of the present
invention will be described. The definitions, components, functions and variations
of the previously described embodiments, which are not directly mentioned below
in connection with the fourth embodiment, are similar to the other embodiments,
and therefore the description thereof will be omitted with reference to the above
Fig. 7a illustrates an alternative of the previous third
embodiment, in which a respective insulator 9"' is arranged under the protective
cover 11 adjacent to a respective connecting plate 25"'.
Fig. 7b illustrates the connecting plate 25"', which is
fixed to the wheel frame 8, for instance by a welded joint. The connecting plate
25"' has a through hole for holding a fixing means 32"', for instance a screw means.
The fixing means 32"' is attached to the connecting plate 25"', for example by a
welded joint. As shown in Fig. 7b, the connecting plate 25"' has a sleeve-like damping
means 26"' which is mounted on the underside of the connecting plate 25'''.
Fig. 7b also shows a portion of the protective cover 11,
which portion may consist of another suitable part of the first unit 5. The protective
cover 11 has a recess 35"' which is adapted to be diametrically slightly larger
than the fixing means 32"', for instance as illustrated in Fig. 7b. An insulator
9"' is mounted on the underside of the protective cover 11. The insulator 9"' is
preferably sleeve-shaped with an inner cylindrical cavity and a through hole 36"'
which is adjusted to the fixing means 32"'. Fig. 8a shows an insulator 9"' with
a cylindrical peripheral shape. Fig. 8b shows another example of an insulator 9""
which has a square peripheral shape. Of course, the insulator 9"'; 9"" can be designed
in many different ways and still perform a similar damping function according to
the intentions of the invention. According to the fourth embodiment in Fig. 7b,
a washer 34"' and a nut 33"' are arranged on the threaded fixing means 32"' at the
through hole 36"' of the insulator.
With reference once more to Fig. 7b, the fixing means 32
"' will thus in the mounted state of use be subjected to essentially axial tractive
forces caused by forces of gravity and any other forces from the unit 5 acting downwards.
The wheel frame 8 thus supports these forces by means of the insulator 9"'; 9"",
and any vibrations may be effectively reduced as described above. Thus, the insulator
9"', 9"" is slightly compressed in the normal mounted state. Furthermore, an air
gap each is shown between the damping means 26"' and the protective cover 11 and
also between the damping means 26"' and the recess 35"'. In case of stress in addition
to normal stress, this is absorbed by the damping means 26"' which acts as a limit
stop. Moreover, the fourth embodiment gives an advantage since the fixing means
32"' can easily be adjusted. It will be appreciated that the above-described embodiments
of the invention can be modified, combined and varied by a person skilled in the
art without departing from the inventive idea as defined in the claims. For instance,
the above-described lawnmower can with relatively simple means be adjusted to be
arranged with at least two driven wheels 7 of the lawnmower. The lawnmower can also
be adjusted to be without wheels, referred to as hoover mower, where in this case
the second unit 6 without wheels can be arranged with the fastening of insulators
to the first unit, so that the desired corresponding vibration-damping effect is
The lawnmower and the like may, of course, comprise several
working units, such as two rotatable cutting units.
The operating means 4 and the wheel frame 8 may, of course,
also consist of a single stable unit, which, for instance, is welded together.
Furthermore, the lawnmower 1 can be adjusted to insulators
9 which, among other things, are subjected to forces in a pulling direction, the
second fixing portion 21 being positioned above the first fixing portion 20. In
this case; the insulators 9 may be, for example, tension springs which are extended
due to the mass of the first unit 5 and which may thus give a corresponding vibration-damping
effect. The insulators 9 can also be fixed to the wheel frame 8 at the wheels 7
or, alternatively, to the axles 22 of the wheels.
Moreover the insulators 9 can be fixed to the first fixing
portions 20 and the second fixing portions 21, respectively, by welded joints, glue
or rivet joints or alternatively screw joints, splines, key joints, mechanical joints,
press and shrink fits.