WO2007118924A1

WO2007118924A1 - Independently movable device with electric drive

Info

Publication number: WO2007118924A1
Application number: PCT/FI2007/000096
Authority: WO
Inventors: Mauno Keski-Luopa
Original assignee: Actioneco Oy
Priority date: 2006-04-13
Filing date: 2007-04-13
Publication date: 2007-10-25
Also published as: FI20060362A0; FI20060362L

Abstract

The invention relates to an electrically driven independently movable device (1) that comprises a frame (4); at least three bearing wheels (3; 31, 32, 33), of which at least one wheel (33) is turnably fastened to the frame; a drive motor unit (5) arranged in connection with at least one wheel (3; 31, 31, 32), including an electric motor, the outlet axis (20) of said drive motor unit (5) being connected to the hub of a wheel (3); a battery unit (6) and an electric control unit (11), by intermediation of which the user controls and adjusts the operation of the device. According to the invention, the device frame (4) is realized as a self-supporting structure made of thin plate-like material, which frame (4) comprises a basin-like basic frame (41) open at the top, inside which basic frame there is arranged a space for batteries (6) and for the control unit (11), an at least partly detachable top part (44) that is arranged to cover the basin-like basic frame, and an end part connected to the basic frame (41), particularly a front part (42) that is formed as a fork comprising two branches (42a, 42b); and in said device a pair of wheels (3; 31, 32) together with their drive motor units (5; 51, 52) is fastened to the fork of the end part of the frame (4), at least of the front part (42), and that both drive motor units (5; 51, 52) are connected to the frame (4) by means of an installation tube (17; 171, 172), so that the drive motor unit is fitted and locked in place in the installation tube. The electric motor of the drive motor unit (5) is realized as a servo motor (5a), preferably an AC servo motor, the operation of which is controlled by the control unit.

Description

Independently movable device with electric drive

The invention relates to an independently movable device with electric drive according to the preamble of claim 1.

In the prior art there is known, from the patent publication US-5,794,422, an independently moved and driven electric drive device for cutting grass, which device is provided with wheel-operating one or several electric motors. The operating time of the device is extended and the charging of the batteries made easier by providing the device with a combustion motor and a connected generator for charging the batteries. In addition, the mower includes alternative hydraulic systems. The electric control unit is realized by means of a microprocessor.

The problem is that the weight and frame measures of the mower are increased when it is provided with a combustion motor, its fuel tank and a generator. Another problem is caused by the noise created by a running combustion motor. Yet another problem is that the mower uses both fuel and possibly hydraulic fluid which are substances dangerous or at least hazardous for the environment.

Yet another problem results in that the electric motors and gears operating the wheels are mainly separate units that must be fitted together in order to ensure a reliable operation. In addition, AC-current electric motors and frequency modulators must be provided with suitable sensors in order to obtain sufficiently accurate information of the rotation speed and its fluctuations in order to give reliable speed instructions.

In said publication, a fixed seat is arranged for the user of the device on top of the device frame, and in the vicinity thereof there is provided a control support arm fastened to the frame, said arm including a steering wheel for steering the device. A foot deck provided with drive and brake pedals is arranged below, in front of the frame seat. Thus the control and operation arrangements are realized in a traditional fashion. The problem is poor ergonomy. It means that for instance sitting down on the seat and rising up again is cumbersome, because particularly the fixed control support arm forms an obstacle both when rising up from the seat and when sitting down.

The object of the invention is to eliminate the drawbacks connected to the above described the electrically driven and independently movable device. Another object of the invention is to realize a new electrically driven and independently movable device that is suited to be used as the chassis in particular for light machinery such as arrangements meant for the care and maintenance of lawns and courtyard areas.

The electrically driven and independently movable device according to the invention is characterized by what is set forth in claim 1. The dependent claims represent preferred embodiments of the invention.

The electrically driven and independently movable device according to the invention comprises a frame; at least three bearing wheels, at least one of which is turnably fastened to the frame; in connection with at least one wheel, there is provided a drive motor unit including an electric motor, the output axis of which drive motor unit is connected to the hub of the wheel; a battery unit and an electric control unit, by intermediation of which the user controls and adjusts the operation of the device. According to invention, in the device

- the frame is realized as a self-supporting structure made of a thin plate-like material, said frame comprising a basin-like basic frame that is open at the top, inside which frame there is arranged a space for the batteries and the control unit, an at least partly detachable top part that is arranged to cover the basin-like basic frame, and an end element connected to the basic frame, particularly a front element that is formed as a fork having two branches,

and in which device

- a pair of wheels together with their drive motor units is fastened to in connection with the fork of an end part of the frame, at least the fork of the front part, and that both drive motor units are connected to the frame by means of an installation tube, so that the drive motor unit is fitted and locked in place in the installation tube.

According to the invention, the frame is realized as a self-supporting structure made of a thin, plate-like material. The frame can be made of a thin steel plate, carbon or glass fiber or the like. The advantage of the self-supporting frame structure is lightness and easy modifiability.

In addition, a frame according to the invention comprises a basin-like basic frame that is open at the top, inside which basic frame there is arranged a space for batteries and a control unit, and at least a partly detachable top part that is arranged to cover the basin-like basic frame. The advantage is that owing to its simple basic structure, the frame is suited in various different targets of usage of the device. Yet another advantage is that there is provided a large space inside the basic frame, in which particularly the battery unit with a sufficient capacity can be fitted.

It is an advantage of the invention that in comparison with corresponding known devices, such as lawn mowers, the weight of the device is made remarkably smaller. This also affects the power consumption of the device as well as the effective time of usage of the batteries, which is extended. Particularly the new frame of the device can be realized as a light, torque and impact resistant structure, the measures of which can also be optimized with respect to its principal use.

A frame according to the invention also comprises an end part, particularly a front part, connected to the basic frame, said part being formed as a fork having two branches. The advantage is that at the frame end, in between the branches, there is thus formed a cavity, in which there can be placed auxiliary aids that are essential both for the use of the device and for the tools connected thereto. In this cavity, there can be fitted for instance a collecting tank for clippings, which clippings are shifted, by an air current, from the cutting units to the collecting tank, as is described in the Finnish patent application FI 20060364 " Arrangement for handling clippings" by the same applicant. A corresponding tank fitted in the cavity can be used for collecting sand and pebbles from the surroundings by means of a reel-like brush and connected vacuum that are provided in connection with the device.

In a device according to the invention, a pair of wheels together with their drive motor units is fastened in connection with the fork of the end part of the frame, at least the front part fork, and the drive motor unit is connected by a frame installation tube so that the drive motor unit is fitted and locked in place in the installation tube. The advantage is that the drive motor units are easily connectable by the installation tubes serving as fastening elements to the desired points of the frame in connection with the end parts, at least the front part, particularly at the sides of the frame and/or below the frame. Owing to the installation tube, in the most advantageous embodiment of the invention the drive motor unit can be connected directly to the frame, particularly in the installation tube opening arranged in the side wall thereof. As an alternative, the drive motor unit can be connected, by the installation tube and the fastening element arranged in connection thereof, even below the frame. In addition, the batteries are simply fitted in a separate battery space reserved in the frame, said battery space being located essentially on the level of the wheels. Likewise, the fitting of the control unit inside the frame does not require any special arrangements. In a device according to the invention, the advantage of the applied installation tubes is, in addition to the easy and simple fastening and connecting features of the drive motor units, that they protect the drive motor units and also reinforce the structures. It is a further advantage that owing to the installation tubes, the drive motor units are easy to maintain, the drive motor units are readily accessible, detachable by simple procedures and replaced by a new drive motor unit.

Owing to the installation tube according to the invention, the device does not include nor need any particular axis arrangements that are typical for four-wheel vehicles.

An advantage of the invention is that the drive motor unit, particularly its rotatable outlet axis, is placed in the immediate vicinity of the employed wheel.

An advantage of the invention is that the center of gravity of the device is obtained near the ground surface. This is due to the fact that the drive motor units are mainly located in the bottom part of the frame and/or below the frame, and that the battery space is located in the frame, preferably on the level of the wheels.

In a most advantageous embodiment of the invention, the electric motor of the drive motor unit is realized as a servo motor. All electric connections are typical servo motor interfaces and easily detachable and connectable to the batteries and the control unit. It is pointed out that it is not necessary to apply any separate external sensors in the drive motor unit, but all necessary and essential sensors belong as an essential part in an electric servo motor.

An advantage of the invention is that the servo motor of the drive motor unit has a high efficiency. Particularly with an AC servo motor, the efficiency rises even up to 95%. This is significant, because the device is battery driven and thus the effective working time obtained between the battery charging sessions is long.

It is another advantage of the invention that the electric servo motor of the drive motor unit is easily and effectively adjustable. Drive motor units are adjusted by means of an electric control unit that is realized preferably as a digitally programmed unit, such as a control unit based on logic circuits and/or a microprocessor. In that case, from the control unit there is for instance directly given an electric speed guideline value for one or several drive motor units, the outcome of which is followed directly from the measurement circuit of the servo motor feedback sensor. In an electric servo motor, particularly an AC servo motor, there is generally integrated the electric motor proper as well as its feedback sensor, such as a pulse sensor, a resolver or a tachometer. On the basis of the measurement data obtained from the feedback sensor, the angle position and rotation speed of the motor axis are known. It is pointed out that earlier electric servo motors are generally used for instance in industrial robots or similar applications, where the servo motors are used for adjusting for instance the position of swinging arms, such as their slewing angle or location.

It is a particular advantage of the invention that the electric servo motor also serves as a brake device when the motional speed of the device should be reduced and/or the device should be kept in place. The features of a servo motor, particularly an AC servo motor, include that with zero speed, the motor has a high torque, by which it keeps even a large load, in this case the device, in place. Also with low velocities the servo motor has a high torque, in which case the starting of the rotation of the drive motor units and hence the start-up of the device as well as the reaching and maintaining of the desired guideline speed are carried out without unreasonably stressing the electric motors, even if the weight and load of the device were comparatively large.

An advantage of the invention is that all drive motor units can be adjusted monitored separately in order to realize the desired motional speed and even motional orientation.

An advantage of the invention is that the anti-slip function for the wheels is realized by electric servo motors

An advantage of the invention is that the adjusting and control arrangements can be optimized and modified depending for instance on the applications in question, such as the tasks of the device. By utilizing the adjusting features of the drive motor units, the efficiency and motional capacities of the device can be further optimized and improved. The rotary direction of the outlet axis of the drive motor units can be selected, and it can easily be changed. Thus the device can, by means of the drive motor units, be easily moved both backward and forward.

It is a particular advantage of the invention that the electric servo motors of the drive motor units can be adjusted and controlled separately. The driving motors of the pair of wheels of the device can be controlled so that in the pair of wheels, the wheel driven by one drive motor unit rotates forwards in one direction, and the wheel driven by the other, parallel drive motor unit rotates backwards in the other direction. Thus the wheels in said pair of wheels rotate in different directions, in which case the device can be turned essentially on the same spot. In order to realize the operation described above, the drive motor units are adjusted by control commands obtained from the operation and control devices, which commands are transmitted and interpreted in the control unit to be in suitable form for the drive motor units. Now for example an instruction for turning the wheels at a relatively steep angle, surpassing the preset guideline value and given as a control command, makes the wheels of the pair of wheels in question rotate in different directions, and hence the device turns practically on the spot. In that case the turning radius of the device is minimal.

An advantage of the invention is that owing to the electric servo motors employed in the motor units, the device has versatile driving features, and thus they remarkably improve the controllability of the device.

Another invention of the invention is that the drive motor unit is quiet and pollution-free. The drive motor unit is electrically driven, and all moving, i.e. rotating parts are preferably arranged inside a uniform drive motor unit. Any exhaust gases emissions do not occur, as is the case with combustion motor driven machinery. Likewise, there is no danger of hydraulic fluids leaking to the ground, because the device does not include hydraulic cylinders or motors.

It is a particular advantage of the invention is that owing to the electric servo motor, the drive motor unit can be realized as a tight, compact structure. Now the drive motor unit can be fitted and fastened in the device frame by simple fastening elements and preferably so that it does not take up space inside the frame.

In a preferred embodiment of the invention, the drive motor unit is made as a uniform entity, such as a module that includes, apart from an electric servo motor, also a gear, particularly a reduction gear, such as a planetary gear or a cogged gear. The advantage is that the rotation speed of the outlet axis can thus be dropped for instance to 1/5 - 1/30 of the rotation speed of the servo motor, and the wheel rotation speed can be adjusted to be suitable for the device. An advantage of the planetary gear is a higher efficiency in comparison with a cogged gear, in which case the total efficiency of the drive motor unit is further improved. The efficiency of the planetary gear can be even 95%.

It is an advantage that this kind of drive motor unit realized as a uniform entity can be installed largely inside the wheel rim, i.e. it takes up little space in the device frame. This results in that the space left between the wheels in the self-supporting frame, particularly in the end portion of the frame, can be utilized, and the frame can be made short; also the driving qualities of the device are improved.

In a preferred embodiment of the invention in the frame, preferably in the front portion of the frame, there are arranged fastening elements for the tools, in which a tool from the group of several different tools can be detachably fastened. It is an advantage that the device is thus arranged as a movable chassis, in which there can be fitted various tools, such as a lawn cutting unit, a cleaning broom and a snow plough, according to the needs of the situation.

In a preferred embodiment of the invention, the device also comprises a seat device for the user, said seat being arranged on top of the frame, and operation and control devices by which the user controls and adjusts the operation of the device by intermediation of the control unit. In this embodiment, the operation and control devices are arranged in a control bracket arranged in the vicinity of the seat. The advantage is that there are not needed any foot-operated drive and control devices, but all control operations are realized manually.

Preferably the control bracket is connected to the seat. The advantage is that the control bracket is integrated effectively in the seat structures, so that the operation and control devices can be easily reached and operated by one hand.

In a preferred embodiment of the invention, the seat is pivoted turnably in the horizontal direction to the top part of the frame. The slewing angle of the seat is at least 90 degrees, preferably within the range 90 - 270 degrees. The advantage is that a device provided with this kind of seat is easy and safe to move both forward and backward; the seat is simply turned for 180 degrees, and the driving direction from the point of the user is always forwards. Another advantage is that in the intermediate position of the seat, it is easy to climb in the device and to step down therefrom.

The invention and its further advantages are described in more detail below, with reference to the appended drawing where

Figure 1 is a perspective illustration of a light, electrically driven and independently movable device, particularly a device for cutting lawns,

Figure 2 is a top-view illustration of the device of Figure 1, of which the top part of the frame part is removed; Figure 3 shows the device in partial cross-section B - B at the front wheels;

Figure 4 illustrates an alternative fastening arrangement for a drive motor unit;

Figure 5 shows the device in partial cross-section C - C at the vertical axis of the rear wheel;

Figure 6 is a side-view illustration of the rear portion of the frame and the rear wheel with its fastening arrangements, seen in partial cross-section;

Figure 7 is a top- view illustration of the rear portion of the frame and devices connected to controlling the rear wheel;

Figure 8A and 8B illustrate two alternatives for fitting the drive motor unit, the frame or a support connected to the frame and the wheel together;

Figure 9 is a top- view illustration of a device with a turnable seat; and

Figure 10 is a block diagram illustrating the control arrangements of the device, particularly as regards the controlling of the drive motor units.

Like numbers for like parts are used in the drawings.

A light, electrically driven device 1 according to the invention is illustrated in Figures 1 - 3. The device is mainly designed for maintenance, repair and/or cleaning tasks carried out mainly in yard areas or the like, but it is also suited in other corresponding light machinery tasks. In this case the device in question is device 1, in connection with which there are arranged means 2 for cutting the lawn. The device 1 represents an example of light electric independently movable machinery.

The device 1 comprises a frame 4 provided with at least three wheels 3; 31, 32, 33. The frame 4 rests against the ground supported by the wheels 3. The device 1 is provided with a number of drive motor units 5 connected to the wheels for moving the device 1. The drive motor unit 5; 51, 52 is preferably arranged in connection with at least two wheels 3; 31, 32. Each drive motor unit 5 is provided with an electric motor 5a. The operation of the drive motor units 5; 51, 52 is adjusted by a device control unit 11. The device includes a battery unit 6 composed of a number of electrically interconnected batteries and providing electric energy for running the drive motor units 5, for example. In the described embodiment, the device includes a seat 7 for the 1 user of the device, arranged in the frame 4, particularly in the top part 44 of the frame. In the vicinity of the seat 7 and simultaneously in the vicinity of the user, there are arranged operation and control devices 9 for adjusting and maintaining the movements and functions of the device.

The frame 4 of the device 1 according to the invention is realized as a self- supporting structure. Now the frame 4 is in itself a rigid structure that keeps its shape without particular support structures. The frame 4 is realized of a relatively thin plate-like material, such as metal plate, particularly steel plate, by injection molding, or as an alternative it is realized of carbon fiber or glass fiber reinforced plastic.

In its basic shape, the frame 4 is an elongate straight prism with a bottom and top part that are mainly rectangular (or modified therefrom), the side walls and ends of which constitute a solid frame structure around the bottom part. Inside the frame 4, there is arranged a space that is divided between the different functional units and preferably separated into suitable sub-spaces by light and rigid division walls and/or lids or corresponding case structures. Now the control unit 11 is arranged in a case arranged in connection with the device frame, or in a similar protected control unit space 13 that can be locked. The batteries for storing electric energy are collected in the battery unit 6 that is respectively arranged in the battery space 12.

In a preferred embodiment of the invention, the frame 4 comprises the basic frame 41 proper, the front and rear portions 42, 43 permanently connected thereto, and an at least partly detachable top part 44.

In the direction of the lengthwise axis A - A of the frame, the basic frame 41 is an elongate basin-like space that is open at the top. In geometrical form, the cross- section of the basic frame 41 is advantageously a rectangle or preferably a modified rectangle, its width being larger than its height. The sides of the basic frame 41 are preferably designed to be in the vertical direction outwardly curved side walls 411, 412. The basic frame 41 is covered by the frame top part 44. The battery space 12 and the control unit space 13 are arranged in the interior of the basic frame 41. The pair of wheels 3; 31, 32 is connected to the front part 42 of the frame arranged in connection with the basic frame 41a, on the opposite sides thereof, and they constitute the front wheels of the device. The end portion of the frame, particularly the front part 42, is formed as a fork. This fork comprises two brackets or branches 42a, 42b provided as extensions of each long side of the frame 4, particularly of the basic frame 41, and the space left in between said brackets or branches forms a cavity 46 in the end of the frame. In the top part of the frame front portion 42, and simultaneously in between the branches 42a, 42b, there is arranged a plate-like lid element 42c. This is preferably realized as a perforated, plate-like element. By means of the lid element 42c, the branches 42a, 42b are interconnected, and at the same time the cavity 46 is covered. The bottom of the cavity 46 is preferably left open, but it can be also be provided with a bottom plate, preferably a detachable bottom plate.

In the front part of the frame 42, in this case in connection with the branches 42a, 42b, in the vicinity of the front edge of the lid element 42c, there also are arranged fastening elements 27 for the tools. By means of these, the tools used in the device, such as the cutting units 2a of the cutting device in Figures 1 and 2, are attached in place in the device by the support frame 2b.

The rear portion 43 of the frame is connected to the rear end 41b of the basic frame 41. In this embodiment, the rear portion 43 of the frame is made as a support structure for a third wheel 3; 33 i.e. a rear wheel. When seen from above, the rear portion 43 is advantageously curved at its outer edge, constituting a preferably semicircular element, the top surface of which is mainly straight and planar, that is expanded to the width of the basic frame 41 and forms a frame element that is seamlessly integrated in said basic frame. At the bottom surface, the rear portion 43 conforms, with respect to vertical plane passing via the lengthwise axis A - A, at least partly to the shape of the wheel 33, being for instance curved (and/or a folded polygon). The rear wheel 33 is fastened to the rear wheel support 18 turnable with respect to the vertical axis D - D, so that the vertical axis passes through the rear wheel hub 3b (cf. Figure 5).

As an alternative, the frame 4 can be realized so that the rear portion 43 of the frame is similar to the front portion 42 of the frame. Alternatively, the rear portion 43 can be a plate-like wall that is connected to the other end of the basic frame 41 and is placed, with respect to the vertical plane passing through the lengthwise axis A - A, for instance essentially vertically, at a steep oblique angle (for instance 70 - 80 degrees) and/or curved in similar fashion as the side walls 411, 412 of the basic frame 41. The second pair of wheels is, instead of one rear wheel 33, easily connectable to this alternative frame, and particularly to the rear end 41b of the basic frame 41 on its opposite sides near the frame rear portion 43, in which case they constitute the rear wheels of the device.

The frame 4 also comprises a top part 44 that is preferably detachable from the frame 4. In a preferred embodiment of the invention, the top part 44 is arranged to cover the basin-like basic frame 41 of the frame, i.e. the center part of the frame 4. The top part 44 extends from the front end 41a of the basic frame 41 to its rear end 41b. In structure, the top part 44 is a rigid, plate-like and essentially rectangular element. At its long sides, the top part 44 is fitted for instance in the cavity arranged at the top edge of both side walls 411, 412 of the basic frame 41 and fastened in place by screws or other suitable fastening elements that can be opened and respectively closed. As an alternative, the top part 44 is at one edge provided with hinge elements that fasten it turnably to the frame 4. Now the top part 44 is fastened partly detachably to the frame 4.

In a preferred embodiment of the invention, in connection with the frame 4, advantageously on top of the top part 44, there is arranged a seat 7 for the user of the device. In the device according to the drawings, the lid element 42c is arranged to serve as a foot rest for the person sitting in on the seat 7 of the device.

In the embodiment according to the drawings, the frame 4 is provided with a footboard 15; 151, 152 that is arranged on the side of at least one frame 4; 41, preferably on both sides of the basic frame 41. The advantage with footboards is, first of all, that they make climbing on the seat 7 of the device and respectively getting down therefrom easier for the user, and secondly they reinforce the basic frame 41. In addition, the wheels 3, and in the described embodiment particularly the front wheels 31, 32, are provided with wheel protections 16; 161, 162. These cover the top part of the front wheel and protect both the wheels and the device user. In the described embodiment of the invention, the rear portion 43 of the frame also serves as protection for the rear wheel 33, because the wheel is fitted underneath the rear portion. In an alternative embodiment of the invention, the device is provided with two rear wheels instead of one.

In a preferred embodiment of the invention, an independently movable device with electric drive is provided with at least three bearing wheels 3; 31, 32, 33, of which one pair of wheels 31, 32 is located in the front end of the device frame 4, in this case the basic frame 41, on opposite sides thereof, and one wheel 33 is located at the opposite end of the frame in relation to this pair of wheels. As an alternative, the device includes four wheels 3, which are arranged in pairs at the front and rear ends of the device.

In the embodiment of the invention according to the drawings, the drive motor unit 5; 51, 52 is arranged in connection with both wheels 31, 32 of the pair of wheels 3. The device user controls and adjusts the operation of the drive motor units 5; 51, 52 by means of the control unit 11, by using the operation and control devices 9 provided in the control bracket 8 of the device.

The drive motor unit 5; 51, 52 comprises an electric motor 5a, the rotatable outlet axis of which is connected to the hub 3 a of the wheel 3; 31, 32. In another preferred embodiment, the drive motor unit 5; 51, 52 includes, apart from the electric motor, also a gear 5b, particularly a reduction gear, for dropping the rotation speed of the electric motor to be suitable for the device. Now the rotatable outlet axis of the electric motor is connected to the inlet axis of the reduction gear, and its outlet axis further to the hub 3 a of the wheel 3. Thus the drive motor unit 5 is realized as a solid, compact structure that can be provided in connection with the hub 3 a of the wheel 3.

The electric motor 5 a is realized as a servo motor, preferably an AC servo motor or as an alternative a DC servo motor. The desired guideline values, such as the speed guideline value, can be directly fed into the control unit 11 of the servo motor for adjusting said servo motor, and there can be directly obtained the position data of the servo motor (or if necessary) of the axis, as well as the rotation speed data to the electronic control unit 11. The AC servo motor is advantageously realized as a permanent magnet synchronous motor, the rotor of which is made of permanent magnets.

An advantage of an AC servo motor is that it works with a high efficiency, particularly within that power range that is well suited for the device according to the invention. Another advantage is that it is small in size, light in weight and economical in expenses. Yet another advantage is that its rotation speed is easily adjustable. Yet another advantage is its high torque at zero speed and immediately at the beginning of the rotary motion, as well as with low rotation speeds, too.

In a preferred embodiment of the invention, the drive motor unit 5; 51, 52 is formed as a module (cf. for instance Figure 8A), including a servo motor, particularly AC servo motor 5a and a gear 5b, particularly a rotation speed reduction gear. In a preferred embodiment, this module is realized so that the AC servo motor 5a and the gear, particularly a planetary gear, 5b are mutually fitted with drive shafts coaxially in succession. As an alternative, in another preferred embodiment of the invention, the AC servo motor 5a and the gear, particularly a gear drive, are realized so that their outlet axis and the motor drive shaft are preferably located in parallel, but at a distance from each other, and mutually connected by said gear drive. However, it is pointed out that also other AC servo motor and gear combinations can be applied in the device according to the invention.

The rotatable outlet axis of the drive motor unit 5; 51, 52 is connected to the hub 3a of the wheel 3; 31, 32, as was explained above. The fastening elements for the drive motor units 5; 51, 52 are arranged in connection with the frame 4. The fastening elements are realized as an installation tube or sleeve 17; 171, 172. The installation tube has a straight, preferably cylindrical casing.

In the embodiment illustrated in the drawings (cf. Figure 3), the installation tube 17; 171, 172 is arranged to proceed through the front part 42 of the frame 4 and particularly through openings 180 arranged in both branches 42a, 42b and simultaneously in the extensions of both side walls 411, 412 of the basic frame, near the bottom plane of the frame. In length, the drive motor units 5; 51, 52 and likewise the installation tubes 17; 171, 172 are relatively short, which means that they do not remarkably narrow the available space between the branches 42a, 42b. In length, the installation tube 17; 171, 172 is preferably essentially as long as the drive motor unit 5; 51, 52, but it can also be somewhat shorter than it (or even longer).

The rotatable power transmission axis of the drive motor unit 5; 51, 52, i.e. the outlet axis 20, is pivoted by a suitable bearing 19 to the installation tube 17 at its outer end 17a. The wheel 3; 31, 32 is in turn detachably fastened at the rim 3d to the outlet axis 20 (cf. Figure 8A). As an alternative, there is applied neither bearing 19 nor pivoting the outlet axis 20 to the installation tube 17, but the own bearings of the outlet axis of the drive motor unit 5; 51, 52 are sufficient (cf. Figure 8B). Also in this case, the wheel 3 is fastened at the rim 3d to the outlet axis 20 of the drive motor unit.

The installation tube 17 is arranged to extend outwardly from the frame 4; 42a, 42b, transversally and at an angle of essentially 90 degrees. The installation tube 17 also is placed partly inside the frame 4; 42a, 42b. The installation tube 17 is supported against the frame at least at the installation tube opening 180, but advantageously also inside the frame by suitable support elements, such as fastening plates 18 and/or rails. The installation tube 17 is preferably welded to the installation tube opening 180 when the frame is realized of steel plate. The other end and outer end 17a of the installation tube extend to such a distance d from the frame 4; 42a, 42b, that corresponds to a share, in this case roughly half, of the width of the wheel 3 and also of the width of the tire 3 c, added by a suitable clearance left between the wheel and the frame. In that case the rim 3d of the wheel 3 is arranged in the center of the wheel, when seen from above. As an alternative, the distance d is larger than half of the tire width, in which case also the rim 3d is arranged nearer to the outer edge of the wheel than in the alternative described above. The outer end 17a of the installation tube 17 is provided with an opening 17b, in which there is fitted a bearing 19, and through said bearing, the outlet axis 20 of the drive motor unit 5 (cf. Figure 8A). As an alternative, the outer end 17a of the installation tube 17 is open or provided with such an opening through which the outlet axis of the drive motor unit 5 has free access to proceed (cf. Figure 8B). The wheel 3 is fastened at the rim 3d, particularly at its hub 3 a, detachably by bolts 202 to a fastening flange 201, which in turn is fastened to the free end of the outlet axis 20 extending from the bearing 19.

In the installation step the drive motor unit 5; 51, 52 is mounted in place in the installation tube 17, preferably inside the tube, at the inner end thereof, through the inside of the frame 4, in this case through the cavity 46 of the branches 42a, 42b. The drive motor unit 5; 51, 52 is pushed, at least partly, into the installation tube 17; 171, 172, so that its outlet axis 20 is properly located at the outer end 17a. The diameter of the drive motor unit 5 preferably corresponds to the inner diameter of the installation tube 17, so that the drive motor unit 5 can be without problems fitted in place in the installation tube. The drive motor unit 5 is locked, for instance by one or several screws or other suitable fastening elements, in place in the installation tube 17 .

The drive motor unit 5 can be fastened in the frame 4; 41 by another, alternative fastening arrangement (cf. Figure 4) different from the one described above. Now the drive motor unit 5 can be connected underneath the frame by the installation tube 17 and the fastening element 39 arranged in connection thereto. Advantageously the fastening element 39 is an L-shaped support, preferably a metal plate that is fastened to the bottom part 45 of the frame 4; 41, in the vicinity of the side wall 411, 412. The first branch 391 of the L-shaped support is fastened to the bottom part 45, underneath the frame, and the second branch 392 is arranged to extend in the vertical direction downwardly from the frame 4; 41. The installation tube 17 is arranged to proceed through the second branch 392 and supported against it. The drive motor unit 5 is fitted in the installation tube 17 in similar fashion as in the above described first fastening arrangement. The advantage in this second fastening arrangement is that the ground clearance, i.e. the distance between the frame bottom 45 and the ground surface can thus be increased in a simple fashion. In principle, the L-shaped support can be realized as a similar element as the wheel support 21 in connection with one rear wheel 3; 33, which shall be dealt with below.

Among the advantages of the fastening of the drive motor unit 7 performed by means of the installation tube 17, let us point out the following. The installation tube provides a good protection for the drive motor units, particularly against possible external impacts, dust and moisture. Another advantage is that the installation tube reinforces the structures, particularly the frame, but it keeps its form also as the fastening element of the drive motor unit. The maintenance of the drive motor unit is easy: the wheel is removed, the drive motor unit is detached and removed from the installation tube, and a replacing motor unit is set in place. Owing to the installation tube, there are not needed any particular wheel axis arrangements.

The front part 42 of the frame 4 is made as a fork having two branches 42a, 42b, in connection with the pair of wheels 31, 32 and their drive motor units 51, 52 are attached, as was already pointed out above. In between the branches 42a, 42b in the front part 42 of the frame, there is formed a cavity 46 for storing auxiliary aids that are essential for the use of the device 1 and for the tools to be connected thereto. In said cavity 46, there can preferably be fitted a tank 47, for instance a collecting tank for clippings. Said tank is preferably provided with inlet and outlet apertures. The inlet aperture is located at the front end of the tank, near the tip of the front part 42 of the frame, and respectively the outlet is located at the opposite end of the tank, i.e. in the rear portion, and particularly at the bottom edge of the tank. Now the cutting units 2a can be provided with means by which, by making use of circulating air, the clippings are shifted from the cutting units to the collecting tank through said inlet, and when the tank is full, they are removed through the outlet by making use of circulating air, in a way that is described in the Finnish patent application "Arrangement for handling clippings" by the same applicant. A similar tank 47 fitted in the cavity can also be used for collecting sand and small trash from the surroundings by means of the reel-like brush and connected vacuum provided in the device. It is pointed out that the making of the space between the branches 42a, 42b of the front portion 42 sufficiently wide both in width and in depth, when observed in the direction of the lengthwise axis A - A of the device, is possible only because there is left ample free space in between the wheels, particularly the front wheels 31, 32, even if a drive motor unit 51, 52 is axially connected to both wheels.

In a preferred embodiment of the invention, in the device frame 4, particularly in the frame rear portion 43, there is arranged a wheel that is turnable in relation to the vertical axis D — D, or as an alternative a turning wheel 3; 33. in case the rear wheel 3; 33 is realized as a turnable wheel, by turning it the device can be guided in the desired direction when moving it. The wheel 3; 33 is connected, by intermediation of the wheel support 21, to the frame 4, particularly to the frame rear portion 43 (cf. Figures 5, 6 and 7). The turning device 22 is connected to the wheel support, and thereby the wheel support together with the wheels can be turned, within the desired angle range, on both sides of the lengthwise axis A - A. As an alternative, the wheel 3; 33 is freely turnable in relation to the vertical axis, in which case the device is controlled by suitably driving the pair of wheels, i.e. in this the front wheels 31, 33, for instance at different velocities.

The wheel support 21 is advantageously realized as an L-shaped element that is preferably bent of metal plate, such as steel plate. The first branch 211 of the wheel support 21 is attached to the rear portion 43, so that it is positioned essentially horizontally. In that case the second branch 212 of the wheel support 21 is directed downwards, essentially at an angle of 90 degrees with respect to the first branches 211. The installation tube 17; 173 is fitted in the aperture passing through the second branch 212 and supported against the branch. The drive motor unit 5; 53 is fitted in the installation tube 17; 173 in similar fashion as in the above described fastening arrangement of the drive motor units 5; 51, 52 of the pair of wheels. The rear wheel 3; 33 also is respectively fastened to the installation tube 17; 173 and in connection with the drive motor unit 5; 53.

The wheel support 21 is fastened by an axle stub 23 parallel with the vertical axis B - B and by connected vertical bearings 24 turnably at the first branch 211, underneath the rear portion 43, and in the middle region thereof. In this embodiment, the turning device 22 comprises a first and second idler wheel 221, 222, a cogged belt 223 (or a corresponding endless power transmission means, such as a belt or a chain) connecting their circumferences, and a slewing motor 225 (cf. Figures 6 and 7). The first idler wheel 221 is connected to the axle stub 23 and the second idler wheel 222 is connected on the same level, at a distance from the first. The cogged belt 223 passes around both idler wheels 221, 222. In connection with the cogged belt 223, it also is advantageous to use a belt tightener 224. The slewing motor 225 is arranged on the axis of the second idler wheel 222 and fastened to the frame 4; 41, 43. The slewing motor 225 is an electric motor, particularly a servo motor, such as an AC servo motor, the operation of which is controlled by the operation and control devices 9 arranged in the control bracket 8 of the device. The advantage with the above described embodiment is that the rear wheel is rear wheel 3; 33 is realized as the wheel driving the device. Thus the device is realized as a vehicle with four wheel drive. In that case the device has good features for traversing the ground. Another advantage is that the installation of the drive motor unit 5; 53 as such is stationary and similar to the other drive motor units 5; 51, 52 provided in the device.

In a preferred embodiment of the invention, the seat 7 provided for the device user is arranged on top of the frame 4, particularly on top of the frame top part 44. In this embodiment, the device control bracket 8 is arranged at the reach of the user in the vicinity of the seat 7, and in this case the control bracket 8 is fastened to the seat 7. The control bracket 8 comprises operation and control devices 9, including in this case at least a control stick 9a for controlling the device and for adjusting the functions. The control bracket 8 resembles an arm rest and extends essentially 40 -

50 cm forwards fro the back rest 7b of the seat 7, on the side of the bottom part 7a.

When the user is sitting on the seat 7 with his back against the back rest 7b, his hand advantageously rests on the control bracket 8, and particularly reaches as far as the control stick 9a.

In an embodiment of the invention, the seat 7 is fastened to a frame 4; 44 so that it can be moved for a short distance in the direction of the lengthwise axis A — A of the frame along suitable rails or the like.

In a preferred embodiment of the invention, the seat 7 is turnably fastened to the frame 4, particularly to the frame top part 44 (cf. Figures 5 and 9). The seat 7 is advantageously realized so that it is pivoted at the lower and middle regions of the seat bottom part 7a to the frame top part 44 or to a counterpart attached thereto, so that the seat 7 can be turned around its vertical axis (in the direction of the arrow

70) on the horizontal level in relation to the frame 4; 44. In addition, in connection with said vertical bearing, there are provided locking and release elements 27, by means of which the seat 7 is locked in a given turning position and respectively released therefrom for turning.

The seat 7 is turnable with respect to the bearing axis and simultaneously the vertical axis, at least for the magnitude of the angle α = 90 degrees, preferably within the range 90 - 270 degrees. In the first functional position of the device, the seat 7 is oriented directly forwards, i.e. in parallel with the frame lengthwise axis A — A towards the front part 42 of the frame and locked in this position. When the locking is released, the seat 7 can be turned from the first functional position α = 90 degrees (either clockwise or counterclockwise) of the device to the rest position, in which case it opens directly to the side of the device (illustrated by dotted lines in Figure 9), and the seat can be locked in place. Now both the rising from the seat as well as sitting down on it are performed easily. When the locking of the seat 7 again is released, it can be turned from the rest position either back to the first functional position or, as an alternative, to the opposite direction, and to the second functional position, which is at an angle β = 180 degrees with respect to the first functional position and opens towards the frame rear portion 43, in which it can be locked. In respective fashion, the seat can be turned further as far as the angle β = 270 degrees.

The advantage of the above described embodiment of the invention is that the device can be used with various positions of the seat, at least in the first and second functional positions. This makes the possibilities to use the device all the more versatile, when also taking into account that the device can be completed by with various tools that can be typically tools that are pushed and/or pulled.

As was already pointed out above, in a preferred embodiment of the invention a drive motor unit 5; 51, 52 is arranged in connection with at least one pair of wheels 3; 31, 32. As an alternative, drive motor units 5; 51, 52, 53 are arranged in connection with all wheels 3 of the device, also the rear wheel 33 or pair of rear wheels. The user of the device 1 controls and adjusts the operation of each drive motor unit 5; 51, 52, 53 by means of the control unit 11, by the operation and control devices 9 provided in the control bracket 8. The control system is illustrated as a block diagram in Figure 10.

The operation and control devices 9 comprise a control stick 9a or a similar control device, the position of which is mechanically adjustable, controlled by one hand, by which device 1 the motions and speed of the device are adjusted. The operation and control devices 9 also comprise a suitable display device and a keypad/selecting keys 9b that are advantageously located in the immediate vicinity of the control stick 9a. The display device can be a touch-sensitive screen, in which case any separate keys, switches and/or selecting keys are not needed, or at least their number can be kept moderately small.

In the most advantageous embodiment of the invention, an essential part of the drive motor unit 5 is the AC servo motor 5a. The electric power required by the drive motor units 5 is obtained from the battery unit 6 arranged in connection with the device 1, which unit is advantageously realized by suitably collecting the batteries. Preferably the battery unit 6 of the device is realized of lithium-ion batteries. With these batteries, the potential energy content per weight unit is clearly larger than with ordinary lead batteries. Another remarkable advantage is that the selection of lithium-ion batteries as the source of electricity for the device further reduces the weight of the device in comparison with a situation that ordinary lead batteries were used.

The output voltage obtained from the batteries of the battery unit 6 is direct voltage. This direct voltage can be for instance within the range 24 - 100 V, which can be raised, when necessary, to a higher level, for instance to 220 - 400V, by a suitable DC/DC converter 30. The direct voltage obtained from said converter is used for feeding in each driving motor combination 5; 51, 52, 53, the servo controller 31 provided in connection with the AC servo motor 5 a, including a frequency converter. It is pointed out that particularly in the intermediate circuit of the servo controller 31 , direct voltage is converted to alternating voltage required by the AC servo motor 5a. The servo controller 31 is used for adjusting and controlling the AC servo motor 5 a the control unit 11 by the operation and control devices 9, particularly the control stick 9a, on the basis of the obtained control messages. From each AC servo motor 5 a, there is collected measurement data, such as the outlet axis rotation speed and torque, for realizing feedback based on one or several difference signals to said motor.

The orientation data of the controlled wheels, such as the rear wheel 3; 33, is obtained from the position sensor 32 arranged in connection with the wheels. As an alternative, the slewing motor 225, preferably realized as a servo motor, such as an AC servo motor, is employed as the position sensor. In that case the position data of the swiveling axis, obtained from the servo motor, are monitored and used for defining the angle of the rear wheel 3; 33 in relation to the device lengthwise axis A - A. Said angle data is advantageously presented as a suitable figurative or numerical data on the screen 9b of the operation and control devices 9. The advantage is that the position of the directionally adjustable wheels, such as the rear wheel 3; 33, is known, and thus the motional direction of the device is known already at the start and can be immediately corrected when necessary.

The drive motor unit 5 based on an AC servo motor is particularly well suited in a device according to the invention, because the required wheel specific power is of the order 1 - 3 kW. Another advantage is that the AC servo motor is small in size, light in weight and economical in expenses. In addition, the AC servo motor speed range is wide and the torque large at zero speed and with low rotation speeds.

Yet another advantage of the invention is that the drive motor units 5 are easily and effectively adjustable. Advantageously the drive motor units 5; 51, 52, 53 are adjusted by such a control unit 11, that is realized as a digitally programmed unit, preferably a control unit based on a microprocessor unit. In that case the adjusting and control arrangements are optimized and modified for instance depending on the applications, such as the tasks of the device. The rotation direction of the outlet axis of the drive motor units 5; 51, 52, 53 can be freely selected and easily changed. Owing to the drive motor units 5, the device has versatile driving features, which remarkably improves the controllability of the device. All drive motor units 5 can be separately adjusted and monitored for realizing a desired motional speed and even orientation.

It is a particular advantage of the invention that the drive motor unit 5; 51, 52, 53 is a solid, compact structure that is arranged in connection with the hub 3 a, 3b of the wheel 3; 31, 32, 33. In the most preferred embodiment, the drive motor unit 5 includes, apart from an AC current electric motor 5a, also a gear 5b, particularly a reduction gear, preferably a planetary gear. By means of the reduction gear 5b, the rotation speed of the outlet axis of the drive motor unit 5 is dropped for instance to 1/25 of the rotation speed of the AC servo motor. In addition, the torque generated by the drive motor unit 5 is high immediately at the start. Thus the driving features of the device, particularly control features, are improved with respect to a drive motor unit provided with an AC servo motor only. It is pointed out that a fairly low traveling speed is required of the device; in working usage, and provided with means 2 suited for cutting lawn, it is of the order 5 km/h, and the transfer speed of the device for instance from one work site to another is of the order 10 — 15 km/h. Also the total efficiency of the drive motor unit 5 is high, particularly when used in connection with a planetary gear.

The invention is not restricted to the above described embodiment only, but many modifications are possible within the inventive idea defined in the appended claims.

Claims

1. An independently movable device with electric drive (1), comprising a frame (4); at least three bearing wheels (3; 31, 32, 33), at least one wheel (33) of which is turnably fastened to the frame; a drive motor unit (5) provided in connection with at least one wheel (3; 31, 31, 32), said unit (5) comprising an electric motor, the outlet axis (20) of said drive motor unit (5) being connected to the hub of the wheel (3); a battery unit (6) and an electric control unit (11), by intermediation of which the user controls and adjusts the operation of the device, characterized in that in the device

- the frame (4) is realized as a self-supporting structure made of a thin plate-like material, said frame (4) comprising a basin-like basic frame (41) open at the top, inside which basic frame there is arranged a space for batteries (6) and a control unit (11); an at least partly detachable top part (44) arranged to cover the basin-like basic frame, and an end portion, particularly a front portion (42) connected to the basic frame (41) that is formed as a fork comprising two branches (42a, 42b);

and in which device

- a pair of wheels (3; 31, 32) with their drive motor units (5; 51, 52) is fastened in connection with fork of the end portion of the frame (4), at least the fork of the front portion (42), and both drive motor units (5; 51, 52) are connected to the frame (4) by means of an installation tube (17; 171, 172), so that the drive motor unit is fitted and locked in place in the installation tube.

2. An independently movable device with electric drive, according to claim 1, characterized in that the installation tube (17; 171, 172) is arranged to extend outwardly from the frame (4), at least from the branch (42a, 42b) of the front portion, transversally at an angle of essentially 90 degrees, and so that the installation tube (17) also is partly inside the frame (4; 42a, 42b) and supported against the frame, at least in the installation tube opening (180).

3. An independently movable device with electric drive, according to claim 1 or 2, characterized in that the length of the installation tube (17; 171, 172) is essentially equal to the length of the drive motor unit (5; 51, 52).

4. An independently movable device with electric drive, according to claim 1, 2 or 3, characterized in that the electric motor of the drive motor unit (5) is realized as a servo motor (5a), preferably an AC servo motor, the operation of which is controlled by the control unit (11).

5. An independently movable device with electric drive, according to claim 4, characterized in that the drive motor unit (5; 51, 52, 53) is formed as a module comprising, in addition to a servo motor (5a), also a gear (5b), particularly a reduction gear.

6. An independently movable device with electric drive according to any of the preceding claims, also comprising a seat (7) for the device user, said seat being arranged on top of the frame, as well as operation and control devices (9), by means of which the user controls and adjusts the operation of the device unit by intermediation of the control unit (11), characterized in that the seat (7) is arranged in the top part (44) of the frame (49), and that the operation and control devices (9) are arranged in a control bracket (8) fitted in the vicinity of the seat (7).

7. An independently movable device with electric drive, according to claim 6, characterized in that the seat (7) is pivoted horizontally turnably in the top part (4; 44) of the frame.

8. An independently movable device with electric drive, according to claim 7, characterized in that the slewing angle (α, β) of the seat (7) is at least 90 degrees, preferably within the range 180 - 270 degrees.

9. An independently movable device with electric drive, according to claim 6, 7 or 8, characterized in that the control bracket (8) is connected to the seat (7).

10. An independently movable device with electric drive, according to any of the preceding claims, characterized in that in the device frame (4), particularly in the rear portion (43) of the frame, there is arranged a swiveling wheel (3; 33) provided with a drive motor unit (5; 53) that is fastened by means of an installation tube (17; 173) to the wheel support (21).

11. An independently movable device with electric drive according to any of the preceding claims, characterized in that in the cavity (46) arranged in between the branches (42a, 42b) provided in the end part of the frame (4), particularly the front part (42), there is fitted a tank (47), for instance a collecting tank for collecting clippings.

12. An independently movable device with electric drive according to any of the preceding claims, characterized in that in the front part (42) of the frame (4), there are arranged fastening elements (27) for tools, in which a tool (2; 35) from a group of several tools can be detachably fastened.