Patent Application
20100139227
The present document relates to a drive arrangement for a walk behind lawnmower. In particular, the present document relates to a drive arrangement as defined by the appended independent claim.
Conventional walk behind lawn mowers comprise a chassis, an engine, a cutting blade, wheels and a handle.
The rotating cutting blade is generally arranged at the middle of the chassis, and is, for grass collection and security reasons, covered by a a cutting deck.
The engine may be arranged at the cutting deck, above the cutting blade, so as to transmit the fast rotation of the engine shaft directly to the cutting blade.
The engine power is also used for driving the lawn mower drive wheels at the front or back of the chassis. For this purpose, a lawn mower powertrain may be provided, comprising a belt transmission and a gear box arranged between the engine output shaft and an axle driving the drive wheels.
The belt transmission may comprise an engine pulley connected to the engine shaft and an input pulley connected to a gearbox input shaft.
The purpose of the gear box is to reduce and redirect the fast rotation of the vertical engine shaft into a suitable rotational speed of the horizontal axis driving the wheels.
U.S. Pat. No. 4,907,401 discloses a gear box casing, which is rotatably mounted about the wheel axle for providing a main clutch which is engaged and disengaged by a selective tightening and loosening of an input belt for the casing by rotational displacement of the casing.
It is also known from recent lawn mower types to provide a disengageable and/or speed regulating drive function of a lawnmower with a clutch-less powertrain, by controlling a degree of slipping of the belt transmission. This may be done by rotating the gear arrangement, and thus the input pulley, about an axle connected to the drive wheels. Such arrangements can be manufactured at low cost. They can also be made relatively simple and space-efficient.
The rotation of the gear arrangement is usually carried out by the user manoeuvring a wire extending from the handle bar of the lawn mower.
However, such drive arrangements require a manoeuvring force which, for some users, may be difficult, or uncomfortable, to provide.
It may further be difficult for the user to adjust the speed of such drive arrangements.
In view of the above, it is an objective of the present disclosure to provide an alternative and/or improved drive arrangement. In particular, an objective is to provide a drive arrangement which requires less manoeuvring force to be applied by the user. It is an additional object to decrease the load on the wire. It is also an additional object to provide a compact solution that takes up little space when mounted on a lawn mower.
According to a first aspect of the present solution, there is provided a disengageable drive arrangement for a lawn mower, said arrangement comprising a gear box assembly having at least one input shaft, a housing, and at least one output shaft, wherein said output shaft is drivingly connectable to a propulsion member, such as a drive wheel, disposed to be in contact with the ground during operation of the lawn mower, said gear box assembly being mountable for rotation about a first axis under the action of a rotational force acting at a point of application on the gear box assembly, wherein a rotational position of said gear box assembly about said first axis is controllable by a cable force applied by a cable, and wherein the cable is connected to the gear box assembly via a force transmission arrangement such that the rotational force applied on the gear box assembly at said point of application is greater than the cable force applied by the cable.
By “point of application” is understood the established meaning of the expression, that is the centre of the force application as used by those skilled in the art when performing force calculations. However, the physical connection between the force transmission arrangement and the gear box assembly is not necessarily limited to a point.
By “cable” is understood any suitable wire, cable or rod known in the art. The cable may be of the same material and/or stiffness along its entire length, or be of variable stiffness and/or comprise several materials.
The solution results in a reduction of the requisite manoeuvring force, and thus of a more comfortable manoeuvring of the lawn mower.
It also reduces the force exerted on the cable, and thus the demands on the cable construction.
Moreover, the drive arrangement is well suited for providing a variable speed function, since the force transmission arrangement results in a longer cable stroke that makes it easier for the user to adjust the speed by manoeuvring the cable.
The drive arrangement may further comprise return spring means for biasing the rotational position of said gear box assembly.
The drive arrangement may further comprise cable overload protection spring means.
The cable overload protection spring means may be arranged between the cable and its connection to said gear box assembly.
The purpose of the cable overload protection spring means is to unload the cable, thus reducing strain and risk of damage on the cable.
The return spring means and the cable overload protection spring means may be any suitable spring means known in the art, such as for example a coil spring.
The transmission arrangement may comprise a lever. Levers are well-tested and low-complexity components well known in the art.
The lever may comprise a cable connecting portion, wherein the cable is connected, and an abutment portion.
The lever may be rotatably connected to the gearbox assembly about a second axis, which is positioned between said connecting portion and said abutment portion.
A point of action of the cable at the lever may be at a distance from the axis.
The second axis may be pivotable about the first axis in response to the cable force.
The second axis may be a geometrical axis. By “pivotable about” is understood how the axis is movable relative to the first axis, and it does not imply that the second axis has a point of connection to the first axis.
The abutment portion may be adapted for sliding engagement with a support.
The abutment portion may be adapted for rotating engagement with a support.
The rotating force may be applied to the gear box assembly at the second axis.
The abutment portion provides a compact solution, since it results in a relatively short lever being capable of transmitting a desired rotational force to the gear box assembly.
The transmission arrangement may comprise a guide element arranged for deflecting the cable.
The deflection results in a force transmission that produces a rotational force with greater magnitude than the applied cable force, without the need of separate supports.
Thus, a guide element may be mounted entirely on the gear box assembly. This allows displacement of the gear box assembly, which may be useful for adjustment of a powertrain belt transmission connected to the gear box assembly.
The cable may be displaceable about the guide element in response to the cable force.
The rotating force may be applied to the gear box assembly at its connection to the guide element.
The guide element may be adapted for mainly sliding engagement with the cable.
The guide element may be substantially fixed relative to the gear box assembly.
The guide element may be rotatable about a second axis.
The guide element may comprise sheave.
According to a second aspect of the present solution a lawn mower is provided, comprising a drive arrangement according to the present solution.
The drive arrangement may further comprise an input belt pulley for engagement with a transmission belt.
A relative motion between the transmission belt and the input belt pulley may be controllable by the rotational position of the gear box assembly.
The relative motion between the transmission belt and the input belt pulley may be arranged to provide a speed regulating function for the lawn mower.
The rotational position of the gear box assembly, and the associated relative motion between the transmission belt and the input belt pulley may provide the only clutch function of the drive arrangement, and/or of the gear box assembly.
The cable may be connected to a control device of said lawn mower.
It may be a one-hand or a two-hand control device. The control device may be a handle. The complexity of the control device arrangement may depend on the intended use. If, for example, the lawn mower is intended for single speed drive, the control device may be a low-complexity handle with two-handed grip. If the intended use is variable speed drive, a handle with a one-handed grip may be more suitable.
The lawn mower may further comprise a support for the abutment portion.
The abutment portion may be displaceable along the support in a longitudinal direction of the lawn mower.
This allows adjustment of the powertrain by displacement of the gear box assembly, and thus of the output shaft of the gear box assembly, in a horizontal direction substantially perpendicular to the length direction of the output shaft of the gear box assembly.
Other objectives, features and advantages of the present solution will be better understood through the following illustrative and non-limiting detailed description of embodiments of the present solution, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:
Referring to
Referring to
In
It should be noted that the exact rotating force may be chosen according to what is found to be suitable.
The support may form part of the lawn mower chassis.
In an alternative embodiment, the cable 7 may be at least partially stiff.
In another embodiment, the support 13 may be in the form of a link arrangement connected to the lever 9 so as to provide a support while allowing the necessary displacement of the lever.
The lever 9 may be resilient and/or flexible, in which case it may, but does not need to, be rotatably connected to the gear box assembly 2.
The cable connecting portion 10 may or may not be at an end of said lever 9.
The lever's connection to the gear box assembly 2 may be arranged at any suitable distance from said cable connecting portion 10 and said abutment portion 12, according to the desired transmission ratio.
The abutment portion 12 may be curved.
The spring means 15, 16 may be any suitable spring means known in the art.
The support 13 may be sufficiently long to allow displacement of the gear box assembly 2 in a direction perpendicular to the length direction of the axis A1, which allows adjustment of the powertrain by displacement of the axis A1 driven by the gear box assembly 2.
The axis A1 may or may not be directly connectable to the drive wheels, and may or may not be a wheel axle.
The support may form an integrated part of the chassis, or be provided on a separate part.
The guide element 9′ may be formed in one piece with said gear box assembly 2.
The guide element may or may not be pivotaly connected to the gear box assembly.
The solution has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE07/00298 | 3/29/2007 | WO | 00 | 1/5/2010 |
