Patent Application
20180160622
The present invention concerns a mower such as a lawn mower or a brush mower. It concerns more specifically a mower with more than one blade. It may in particular be a mower with two or three blades.
In other respects, the invention concerns mowers with an electric cutting unit, which is to say mowers with blades driven by an electric motor.
The invention finds applications in the technical field of walk-behind lawnmowers, of riding lawnmowers, remotely controlled mowers and in the field of autonomous robotic mowers.
Although not referring to mowers with an electric cutting unit, an illustration of the state of the art of multi-blade mowers is given for example by the following documents:
Mowers with multiple rotary blades of the type illustrated by these documents are generally mowers of considerable size. Also, and because of the number of blades they are equipped with, these lawnmowers are generally provided with powerful thermal engines. With the exception of towed mowers, the thermal engine serves to drive the blades and to propel the mower.
The invention proposes to take advantage of new generations of high capacity batteries for the production of multi-blade mowers with electric motors.
Equipping multi-blade mowers with an electric motor does not mean to simply replace a thermal engine with an electric motor.
In effect, and in conformance with the invention, utilization of an electric motor goes together with measures which favor a significant reduction in the overall space requirement and the mass of the mower. Furthermore, using batteries goes generally together with achieving high energy yields to obtain the greatest operating autonomy possible. These measures permit utilization of a multi-blade mower in applications comparable to those of lightweight single-blade mowers while affording greater cutting widths. Cutting widths of 60 cm or more can be obtained with a multi-blade mower, whereas a cutting width of an electric mower with a single blade is generally in a range below 50 cm.
One aim of the invention is to propose an especially compact and manageable mower in spite of its considerable cutting width and permitting its configuration as a riding mower, walk-behind mower, remotely controlled mower or even an autonomous robotic mower. These latter configurations are generally impractical for known multi-blade mowers due to their size and weight.
One aim of the invention is also to propose a lightweight mower that is easy to clean and maintain.
Still another aim is to propose an electric mower with a limited number of electrical wires and connections.
Finally, another aim of the invention is to propose a mower that is especially reliable and durable.
To achieve these aims, the invention proposes an electric mower comprising a cutting unit with:
In accordance with the invention, the electric motor is installed in the casing between the cutting plate and the blade synchronization mechanism.
The characteristic of the invention according to which the electric motor for driving the blades is located between the cutting blade and the blade synchronization mechanism allows for an especially compact and efficient design of the cutting unit.
In the following description, reference is made primarily to a single electric motor. It should however be noted that one electric motor may be associated to each blade. In this case all motors used for driving the blades are located in the casing between the cutting plate and the synchronization mechanism.
The electric motor is preferably so positioned that its rotary axis is perpendicular to the cutting plane in which the cutting blades rotate. In an operating position of the mower the motor axis is therefore essentially vertical.
The motor axis may correspond to the axis of a shaft of the cutting blade. This aspect is described in greater detail in the text below.
The cutting unit preferably comprises several vertically superposed stages or levels. A first level which is near the ground in a working position of the mower corresponds to the cutting plate. It includes the cutting blades. The blades are mounted for rotation on blade shafts extending along axes essentially perpendicular to a cutting plane. The blades thus extend along a plane that is essentially parallel to the ground. To each blade corresponds a circular working area situated in the cutting plane The working areas of the different blades may present one or several overlapping areas that are covered by two adjacent blades respectively. In the case where the blades have the same length, this means that the blade shafts are apart by a dimension that is inferior to the length of a blade.
Above the first blade level, a second level receives a casing comprising the blade drive motor. The second level also extends along a plane essentially parallel to the ground, in a working position of the mower.
Above the second level, a third level holds the blade synchronization mechanism. Preferably, the elements of the synchronization mechanism are also fitted into the casing and in a plane essentially parallel to the ground.
A possibly present fourth level, above and in proximity to the third level may hold an electronic control unit for the mower and in particular of the electric motor. Preferably, the forth level constitutes the high portion of the casing and may consist of a casing cover containing the electronic control unit of the mower.
Finally, a possibly present fifth level, above the fourth level, or at the place of the fourth level, may hold one or several batteries for the power supply to the motor. The battery, however, is not necessarily part of the cutting unit and may be located elsewhere on the mower. Preferably, the levels one to four constituting the cutting unit and in particular the cutting plate, the casing and the casing cover are rigidly integral with each other.
The synchronization mechanism may have several functions. One major function is the mechanical synchronization of the blades. Synchronization of the blades enables the blades to rotate in concert, at the same rotation speed and while keeping a constant angular clearance between the angular positions of the adjacent blades.
A constant clearance between the angular positions of the adjacent blades in their working areas prevents the blades from colliding with each other, especially when the working ranges present an area where they mutually overlap. The angular clearance of adjacent blades is preferably in the order of 90°, and in any case sufficient to prevent the blades from coming into collision with each other during rotation or from squeezing the vegetation to be cut.
The mower may feature an electronic control unit of the blade drive motor(s). In case of a plurality of blade drive motors, the electronic control unit is also configured for synchronizing the rotation of the electric motors associated to the various cutting blades.
In this case the blades benefit from dual mechanical and electrical synchronization. A second function of the synchronization mechanism of the blades may be to transmit the movement of the electric motor to all the blades of the cutting unit. The synchronization mechanism then constitutes a transmission. The transmission function is important when the cutting unit comprises only one single electric blade drive motor the movement of which needs to be distributed to the various blades.
According to a particular implementation of the mower, it may feature a frame forming a chassis. The frame is preferably a tubular frame extending along a plane essentially horizontal in an operating position of the mower. In this case, a part of the cutting unit including the electric motor and the synchronization mechanism, and in particular the second, third and fourth levels of the cutting unit, may be configured to extend across the tubular frame, so as to protrude above the tubular frame. The first level, as far as it is concerned, remains below the plane of the frame.
Such a layout allows for a particularly compact and manageable design of the mower.
The cutting unit may be mounted in mobile fashion on the frame with a possibility of displacement along an axis perpendicular to the plane of the frame. Displacement of the cutting unit therefore occurs essentially in a direction perpendicular to the ground, in an operating position of the mower.
Thus, the height of the cutting unit relative to the plane of the frame is variable. By modifying the height of the cutting unit relative to the frame, it is possible to adjust the distance between the cutting blades and the ground on which the mower rests, and thus to set a desired cutting height.
The possibility of directly setting the cutting height by means of the mobility of the cutting unit allows the use of wheels that are at a fixed height relative to the frame. The wheels may also be mounted on the frame. This measure serves to increase the sturdiness of the wheel fastening and facilitates any wheel replacement during a maintenance operation.
The cutting unit may be mounted on the chassis of the mower by means of a mounting in form of a parallelogram, ramp or sliders, or in another appropriate manner so as to enable its height adjustment. Height adjustment is feasible while mowing, and without stopping the machine.
Furthermore, the mower may feature at least one electric jack for displacing the cutting unit relative to the frame. Using an electric jack facilitates modifying the cutting height during the mowing operation. It even permits continuous adaptation of the cutting height, if necessary.
As stated earlier, the cutting unit features a casing fastened on the cutting plate. The casing may enclose the motor, the blade synchronization mechanism and a control unit of the mower. The casing is fixed rigidly on the cutting plate and preferably on a protective skirt of the blades of the cutting plate, so as to form a monolithic unit.
The fact that the cutting plate is attached to the casing rather than being formed of a single piece with the casing makes it possible to replace the cutting plate, and in particular the blade protection skirt should it become damaged.
Advantageously, a part of the casing which forms the housing for the electric motor may be configured to extend partially into the cutting plate. In particular, when the cutting plate includes a blade protection skirt, the part of the casing which forms the housing for the motor may present journals which traverse the skirt.
The fact that a part of the casing extends into the cutting plate makes it possible to bring this part closer to the cutting blades and thus to cool the casing and the elements contained in it by an air flow generated by the cutting blades. In particular the air from the cutting blades can advantageously be used to cool the motor and the control unit housed in the casing.
The casing is preferably made of aluminum or a light aluminum-based or magnesium-based alloy. Such material is both solid and a good heat conductor. Thereby it promotes cooling of the elements contained in the casing and constitutes a dust-tight casing thus preventing the electric motor from becoming soiled.
The casing may also be made of a plastic material which is more economical but its heat-conducting capacity is not as good.
According to a particularly advantageous layout of the cutting unit, the control unit includes an electronic motor control card placed just above the synchronization mechanism. The electronic card is provided with a magnetic sensor, for example a magneto-resistive sensor or a Hall-effect sensor cooperating with a magnet integral with either a cutting blade shaft, an electric motor shaft or a shaft of the synchronization mechanism. Preferably the magnet is directly integral with the shaft of the electric motor.
The magnetic sensor allows measuring the angular position of the magnet. The electronic card uses the measure of the magnetic sensor to determine, among other things, the angular position of the motor rotor and to control the power supply of the motor. Such a controlled power supply is primarily used for brushless electric motors.
Locating the control unit and the electronic card just above the synchronization mechanism allows mounting the magnetic sensor directly on the electronic card. Thereby a wire connection between the sensor and the electronic card can be avoided, thus improving the compactness of the cutting unit. Reliability of the motor control is also greatly improved.
The signal of the magnetic sensor can also be used to determine other parameters such as effective rotation speed of the cutting blades, or blocking of the blades, for example.
Furthermore, according to an advantageous layout of the cutting unit, the casing may be provided with a removable cover providing access to the control unit and the synchronization mechanism. The cover greatly facilitates maintenance operations and in particular lubrication of the rotating parts of the cutting unit.
The cutting blades are mounted on rotary shafts resting on bearings. In conformance with a particular embodiment of the cutting unit, the bearings may be mounted in the casing. The stresses of the blades are thus transmitted to the frame forming a chassis through the intermediary of the casing of the cutting unit.
In a particular embodiment of the cutting unit, the blade shafts present respectively a first end for the installation of a cutting blade and a second end, opposite the first end, being connected to the synchronization mechanism, so as to maintain a constant angular distance between the cutting blades in the manner indicated above.
The synchronization mechanism may be a notched belt mechanism. In this case, the second end of the blade shafts is respectively connected to a toothed pulley cooperating with the notched belt.
The synchronization mechanism may also be a geared mechanism. In this case, the second end of the blade shafts is respectively connected to a toothed wheel cooperating with the gear.
The synchronization mechanism may also be a mixed mechanism with gear and notched belt. In this case, the second end of the blade shafts is respectively connected to a toothed pulley cooperating with a notched belt connected to an intermediary assembly with toothed pulley and gear.
In a configuration of the cutting unit with a single motor, a first cutting blade may be mounted on a blade drive shaft rigidly integral in rotation with a rotor of the electric motor, and at least one second cutting blade may be mounted respectively on at least one secondary blade shaft coupled to the drive shaft through the intermediary of the synchronization mechanism. In this case, and as indicated previously, the synchronization mechanism forms a transmission between the drive shaft and the secondary shaft(s).
The electric motor thus presents an output shaft which is the blade drive shaft.
In a particular implementation of a mower in accordance to the invention, the cutting plate may feature two counter-rotating blades and a blade projection skirt provided with a central ejection channel. The rotary movement of the blades is used for mowing and also for the ejection of the grass clippings through the central ejection channel.
Utilization of the counter-rotating blades and a central ejection channel contributes to the compactness of the mower.
The mower may, incidentally, be equipped with a removable collection bag, connected to the central ejection channel.
In order to facilitate its assembly and in the interest of compactness, the grass collection container may be fastened on the cutting unit. The collection container is then vertically removable relative to the frame together with the cutting unit.
The mower may be equipped with driven rear wheels coupled to the electric motor so as to ensure the forward movement of the mower. The coupling may be done in the classic manner over a transmission box.
The mower may also be equipped with driven rear wheels coupled to at least one electric motor separate from the electric motor driving the cutting blades. In particular, each wheel may be coupled to its own drive motor.
Other characteristics and advantages of the invention become clearer in the following description in reference to the numbers on the drawings. This description is given for purely illustrative purposes and is not limiting.
In the following description identical, similar or equivalent parts of the various figures are identified with the same reference numbers so as to be able to refer from one figure to the next.
Incidentally, the terms “horizontal”, “vertical”, “high”, “low”, “superior”, “inferior”, “above” and “below”, “front” and “rear” are used in reference to a position and a normal utilization of the walk-behind mower on a flat and horizontal terrain, corresponding to
The mower 10 comprises a frame 12 forming the chassis on which are fitted various elements. The frame extends essentially in the horizontal plane. It is preferably weldless, with tubing elements assembled with screws and by adapted sleeves. The frame holds essentially an articulated handlebar 14, rear driving wheelsl6, freely swiveling front wheels 18, a cutting unit 20 and a battery 22 located above the cutting unit 20.
The swiveling front wheels 18 are mounted on the frame with vertical pivoting range of 360°. These are dual wheels in the example shown. The rear drive wheels 16 are each provided with an electric motor 61 for propelling the mower forward.
The cutting unit 20 includes a cutting plate 24. The term cutting plate applies to an assembly including essentially the cutting blades, not visible in the figure, and a blade protection skirt 26. In the example shown, the cutting plate 24 is a plate with two counter-rotating blades. The term counter-rotating blades applies to blades that rotate in the opposite direction to each other. The opposite movement of the blades is used to evacuate the grass clippings.
The cutting plate extends in effect, behind the blades, in the form of an ejection channel 28 for the grass clippings with a removable collecting bin 30 for the clippings connected to it. In the example shown the bin 30 is attached to the cutting unit.
A casing 32 of the cutting unit 20, made of a light alloy, constitutes an upper part of the cutting unit 20. The casing 32 is above the cutting plate 24 and extends through the tubular frame 12. The cutting unit is located under a bridge frame 34, mounted on the tubular frame 12, provided for installation of the battery 22. The battery 22 is provided for the power supply to the motor of the cutting unit and to the motors 61 of the rear wheels.
At the front of the mower, one can observe an electric jack 36 provided for a vertical movement of the cutting unit relative to the frame 12. Operation of the jack can be controlled by a guiding unit of the mower or through the intermediary of a manual control interface 38 attached to the top of the handlebar 14.
The blade protection skirt 26 is rigidly attached to the casing 32, by means of screws 48 and it protects the inside face of the casing turned towards the blades. The skirt is preferably made of aluminum, a light alloy based on aluminum or magnesium, or of plastic material. It can be replaced when it is deteriorated.
The casing 32 presents, above each blade, a journal 50, 52 for passage of the shaft the low end of which traverses the skirt 26. The journals are provided at their low ends respectively with a bearing 54 for maintaining the blade shaft. The upper end of the journals is topped respectively by a cover 56, also provided with a bearing 58 for maintaining the blade shafts in their upper part.
In the example of implementation shown in
Above the journals and the motor 60 is a synchronization mechanism 70. The synchronization mechanism has a dual function in the example of implementation described in reference to
A cover 80 closes the upper part of the casing 32. The cover holds a control unit 82 of the mower. The control unit 82 comprises electronic cards 84 for the control of the drive motors of the driven rear wheels and, if applicable, electronic cards controlling the displacement of the mower according to a robotic autonomous mode of progression. The control unit 82 also includes an electronic card 86 for the control of the electric motor driving the blades. The electronic card 86 includes in particular field effect transistors for the commutation of the supply currents of the electric motor 60.
In the example of implementation described in reference to
The electronic card 86 includes for this effect a magnetic sensor 88, such as a magneto-resistive sensor or a Hall-effect sensor, directly welded on the card and maintained by the card opposite a small magnet 90 seated in a boring of the upper end of the motor blade shaft 42. The sensor retained in the described solution is a Hall-effect sensor. The magnet 90 is driven in rotation by the motor blade shaft 42 and thus reflects the angular position of the rotor. In effect, and as indicated previously, the rotor of the electric motor 60 is integral with the motor blade shaft 42. The rotation of the magnet 90 in front of the Hall-effect sensor 80 thus generates a directly exploitable electric signal to determine the supply currents of the motor.
The signal of the Hall-effect sensor can also be exploited by the electronic card 86 in order to determine supplementary parameters for controlling the mower such as blade rotation speed, blade blocking or a motor overload.
When the cutting unit is provided with two motors, one for each blade, the electronic motor control card can also be configured for electronic synchronization of the motors. Electronic synchronization makes it possible to relieve the synchronization mechanism and reduce any loss of energy in this mechanism.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1557162 | Jul 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2016/051540 | 6/23/2016 | WO | 00 |
