TECHNICAL FIELD

The present invention relates to a robotic lawnmower. The lawnmower comprises, inter alia, a chassis with drive means, a body which is movably fitted to the chassis by means of at least one suspension and at least one collision sensor which is configured to detect an obstacle as the robotic lawnmower traverses over a surface area by sensing a movement of the body relative to the chassis when the lawnmower collides with an obstacle, and to provide one or more sensor signals indicative thereof for bringing the lawnmower to respond, e.g. stop or change traversing direction. The suspension comprises a joystick element by means of which the body is fitted to the chassis. The suspension also comprises a resilient positioning member which is configured to hold the joystick element in a neutral position. The resilient positioning member is also configured to permit movement of the joystick element when the lawnmower collides with an obstacle and the body moves relative to the chassis, and to return the joystick element to the neutral position after the collision. BACKGROUND OF THE INVENTION

For obstacle detection, the body is, as indicated above, elastically fitted to the chassis so they can move independently. For quality feel as well as robustness in detecting obstacles, the body position needs to be precisely aligned to the chassis, but still be able to deflect easily. According to prior art, this has been achieved e.g. by means of a plastic joystick element which is held in position by a rubber gaiter. A good quality feel for the movement of the joystick element is thereby achieved, but some compromises regarding the precision have been made because of the irregular material properties of the rubber.

SUMMARY OF THE INVENTION

The primary object of the device according to the present invention is to eliminate the above mentioned drawbacks and provide a positioning member without the uncertainties of the rubber material as well as provide a positioning member with a precise time and wear independent setup

The above object is achieved according to the present invention by providing the resilient positioning member of the suspension in the form of a spring element of a time and wear resistant material.

In a particular embodiment of the present invention, the spring element of a time and wear resistant material is a metal compression spring.

By using e.g. a metal compression spring instead of a rubber gaiter, it is possible to greatly improve the stability and precision of the joystick element position. For more flexibility, it is possible to attach the body to the chassis by using two joystick elements with metal compression springs and two other joystick elements with conventional rubber gaiters, thereby giving the system a smooth feel and good precision.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below by way of example only and with reference to the accompanying drawings, in which

Fig. 1 is a schematic side view of a robotic lawnmower according to the present invention in normal operation;

Fig. 2 is a schematic side view of the robotic lawnmower according to the present invention at a collision with an obstacle;

Fig. 3a is a schematic side view, partly in section, of a first embodiment of a suspension for a body in the lawnmower according to the present invention, illustrating the suspension in normal operation;

Fig. 3b is a schematic side view, partly in section, of a first embodiment of a suspension for a body in the lawnmower according to the present invention, illustrating the suspension at a collision with an obstacle; Fig. 4a is a schematic side view, partly in section, of a second embodiment of a suspension for a body in the lawnmower according to the present invention, illustrating the suspension in normal operation and at a collision with an obstacle; and Fig. 4b is a schematic side view, partly in section, of a second embodiment of a suspension for a body in the lawnmower according to the present invention, illustrating the suspension at a collision with an obstacle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As already mentioned above, the present invention relates to a robotic lawnmower of which one embodiment is schematically illustrated in fig. 1 and 2. It should be understood however, that the present invention can be incorporated into any suitable type of robotic outdoor equipment. The robotic lawnmower 1 may be a conventional-type robotic lawnmower, comprising, inter alia, a chassis 2 with drive means (front and rear wheels 3 and 4 respectively) for traversing over a surface area and with cutting means 5 for cutting vegetation within said surface area. The robotic lawnmower 1 may be powered by a main power source (not shown in the drawings), e.g. an electric motor which may be driven by one or more rechargeable batteries, a pneumatic or hydraulic drive, a fuel cell etc. The rechargeable batteries may be charged by electrical energy using a charger, solar energy via a solar panel or a combination thereof. The robotic lawnmower also comprises a control device (not shown in the drawings) with a processor; a memory etc., for maneuvering the lawnmower 1 within the surface area such that cutting is performed without supervision. The surface area may be limited in different ways e.g. by a physical fence or be demarcated by a perimeter wire of a suitable type.

Furthermore, the robotic lawnmower 1 comprises a body 6 which is movably fitted to the chassis 2 by means of at least one suspension. In case the body 6 is movably fitted to the chassis 2 by means of one suspension only, this suspension may then be located centrally in the lawnmower 1. Two or more centrally located suspensions may also be provided for movably fitting the body 6 to the chassis 2. The body 6 may be movably fitted to the chassis 2 also by means of at least one front suspension and at least one rear suspension, e.g. one front suspension and two rear suspensions or two front suspensions and one rear suspension. Furthermore, one or more front suspensions and one or more rear suspensions may be completed by one or more centrally located suspensions. At the illustrated embodiment of fig. 1 and 2, the body 6 is movably fitted to the chassis 2 by means of front and rear suspensions 7 and 8 respectively. There are in the illustrated embodiment two front suspensions 7 and two rear suspensions 8, although only one of each is schematically shown in fig. 1 and 2.

As indicated above, the robotic lawnmower also comprises at least one collision sensor 9. The collision sensor 9 is configured to detect an obstacle (not shown in the drawings) as the robotic lawnmower 1 during cutting or when it moves to a charging station traverses over said limited surface area. Detection is achieved by sensing a movement of the body 6 relative to the chassis 2 when the robotic lawnmower 1 collides with the obstacle. At the illustrated embodiment of fig. 1 and 2, the collision sensor 9 comprises a magnet 10 which is mounted on the body 6 and a sensor member 1 1 which is mounted on the chassis 2. The sensor member 1 1 senses a movement of the magnet 10 when the body 6 moves relative to the chassis 2. The collision sensor 9 provides thereby one or more sensor signals indicative of the detection of the obstacle and these sensor signals are fed to the control device for bringing the robotic lawnmower 1 to respond, e.g., send an alarm, stop or to change the traversing direction of the lawnmower during cutting or during movement to a charging station.

The body 6 is fitted to the chassis 2 by means of joystick elements 12, i.e. each of the front and rear suspensions 7, 8 at the illustrated embodiment of fig. 1 and 2 comprises a joystick element, of which one end 12a is in contact with the body 6 whereas the opposite "inner" end 12b or adjacent parts of the joystick element cooperate or are in contact with the chassis 2. A joystick element may in this connection be defined as a shaft with a return-to-center feature when moved from a center position. Accordingly, each of the front and rear suspensions 7, 8 further comprises a resilient positioning member 13 which is configured to hold the joystick element 12 in a neutral position N (see fig. 1 , 2, 3a and 4a). The resilient positioning member 13 is also configured to permit movement of the joystick element 12 (to another position I, different from the neutral position) when the lawnmower 1 collides with the obstacle and the body 6 moves relative to the chassis 2 (see fig. 2, 3b and 4b), and to return the joystick element to the neutral position N after the collision. According to the present invention, the resilient positioning member 13 comprises a spring element of a time and wear resistant material, and this spring element of a time and wear resistant material is at the illustrated embodiments of the invention a metal compression spring 14, i.e. the resilient positioning member 13 of either the front suspensions 7 or the rear suspension 8 or both, is at the illustrated embodiments of fig. 3a and 3b and 4a and 4b respectively, a metal compression spring. Thus, with the metal compression springs 14, the stability and precision of the joystick element position is greatly improved.

Alternatively, the resilient positioning member 13 may comprise a spring element of plastic, carbon fiber or any other suitable time and wear resistant material with the proper elastic and flexible properties. Leaf springs of metal or any other suitable material may also be used as resilient positioning members 13. Two suitable embodiments for obtaining stability and precision of the joystick element position by providing optimum seats for the joystick element 12 and the metal

compression spring 14 are described in the following and illustrated in fig. 3a and 3b and 4a and 4b. At the embodiment of fig. 3a and 3b, the joystick element 12 is at the inner end 12b thereof configured or provided with a member 15 which is configured to define a first seat 16 for the metal compression spring 14. This member 15 may be a separate member which in a suitable manner has been attached to the joystick element 12 or may constitute an integral part of said joystick element. Furthermore, the joystick element 12 is at a distance from its inner end 12b configured (see below) such that it is movably seated in a lead-through 17 in the chassis 2, i.e. the chassis defines a seat 18 for the joystick element in the lead-through. In other words, the joystick element 12 is "hanging" in the seat 18 in the lead-through 17 in the chassis 2. To permit movement of the joystick element 12, the side 17a defining the lead-through 17 is converging such that said lead-through is tapering conically from an "outer" side 2a of the chassis 2, facing the body 6, to an "inner" side 2b thereof, facing away from said body. The seat 18 for the joystick element 12 is provided in the part of the conically tapering lead-through 17 having the smallest diameter, close to the inner side 2b of the chassis 2. The chassis 2 also defines a second seat 19 for the metal compression spring 14 at the lead-through 17. Accordingly, the spring 14 is mounted between said first spring seat 16 and the second spring seat 19 at the lead-through 17. The spring 14 thereby pulls the joystick element 12 down against the seat 18, bringing the joystick element to hold its neutral position N. However, the spring 14 is also configured to permit movement of the joystick element 12 from the neutral position N, which here is substantially perpendicular to the chassis 2 at the lead-through 17, to said other position, here an inclined position I relative to said chassis, when the lawnmower 1 collides with an obstacle, and to return the joystick element to the substantially perpendicular position after the collision by pulling the joystick element towards and against its seat 18 in the lead-through 17 in the chassis 2. As illustrated in fig. 3a and 3b, the metal compression spring 14 is mounted surrounding the portion 12c of the joystick element 12 extending between the first spring seat 16 in the member 15 defining said first spring seat and the second spring seat 19 at the lead- through 17 in the chassis 2. The seat 18 for the joystick element 12 at the lead-through 17 in the chassis 2 is defined by an annular surface in the lead-through 17. The second seat 19 for the metal compression spring 14 at the lead-through 17 is defined by an annular flange 20 surrounding said lead-through on the inner side 2b of the chassis 2. Accordingly, the spring 14 is at the lead-through 17 seated against the inner side 2b of the chassis 2 around the annular flange 20 and is held in position by said annular flange. For engagement with the annular surface in the lead-through 17 defining the seat 18 for the joystick element 12, the joystick element is configured with an annular flange 21. At the illustrated embodiment according to fig. 3a and 3b, the annular surface in the lead-through 17 defining the seat 18 for the joystick element 12, is defined by a bottom surface of the annular flange 20 surrounding said lead-through, i.e. the annular flange 20 defines the seat 18 for the joystick element 12 as well as the second seat 19 for the spring 14.

At the embodiment of fig. 4a and 4b, the joystick element 12 is at the inner end 12b thereof, opposite to the end 12a in contact with the body 6, configured such that it is movably seated in a first member 22 of the chassis 2 and at a distance from said inner end configured such that it passes through a lead-through 23 in a second member 24 of the chassis adjacent to said first member thereof. Thus, said first member 22 defines a seat 25 for the joystick element. In other words, the joystick element 12 is "resting" in the seat 25 in said first member 22 of the chassis 2.

To permit movement of the joystick element 12 and to provide space for the metal compression spring 14, which in the embodiment of fig. 4a and 4b is conical, said first member 22 is configured with a hole 26, the side 26a of which diverges such that said hole expands conically towards said second member 24 of the chassis and which at the bottom thereof, having the smallest diameter, defines said seat 25 for the joystick element. To permit movement of the joystick element 12 and to provide space for the conical spring 14, said second member 24 is sufficiently large and configured with a sufficiently large lead-through 23. At the embodiment of fig. 4a and 4b, the lead-through 23 has substantially the same diameter in its extension through said second member 24, from an "outer" side 24a thereof, facing the body 6, to an "inner" side 24b thereof, facing said first member 22. Said first and second members 22, 24 may be separate members which have been attached to the chassis 2 in any suitable manner or may constitute integral parts of said chassis. The metal compression spring 14 is mounted between a first spring seat 27 on the joystick element 12 at the inner end 12b thereof, i.e. in said first member 22 of the chassis, and a second spring seat 28 in said second member 24. The spring 14 presses the joystick element 12 against its seat 25 in said first member 22, bringing the joystick element to hold its neutral position N. As in the embodiment of fig. 3a and 3b, the spring 14 is further configured to permit movement of the joystick element 12 from the neutral position N, i.e. from the position substantially perpendicular to the chassis 2, or to said second member 24 thereof, at the lead-through 23, to said other position, i.e. the inclined position I relative to said chassis, when the lawnmower collides with an obstacle, and to return the joystick element to the substantially perpendicular position after the collision by pushing the joy-stick down towards and against its seat 25 in said first member 22 of the chassis 2. As illustrated in fig. 4a and 4b, the metal compression spring 14 is mounted surrounding the portion 12c of the joystick element 12 extending between the first spring seat 27 at the inner end 12b of the joystick element and the second spring seat 28 in said second member 24 of the chassis 2, i.e. in the member with the lead-through 23. The second seat 28 for the metal compression spring 14 in the member 24 with the lead- through 23 for the joystick element 12, i.e. said second member, is defined by an annular flange 29 in said lead-through, surrounding the opening of said lead-through in the side 24a of said second member facing the body 6. Accordingly, the spring 14 is in the lead- through 23 seated against the side 23a defining said lead-through and seated around the annular flange 29 and held in position by said annular flange. The first seat 27 for the spring 14 at the inner end of the joystick element 12 is defined by an annular flange 30 on said inner end. This annular flange 30 on the inner end of the joystick element 12 also defines a surface for engagement with the seat 25 for the joystick element in said first member 22. Thus, the first seat 27 for the spring 14 and the surface for engagement with the seat 25 for the joystick element 12 in said first member 22 are defined by opposite surfaces of the annular flange 30 on the inner end of the joystick element. The seat 25 for the joystick element 12 is defined by an annular surface in said first member 22.

It will be evident to a skilled person that the robotic lawnmower according to the present invention can be modified and altered within the scope of the subsequent claims without departing from the idea and purpose of the invention. Thus, the shape, size and location of the metal compression spring 14 or any other spring element may vary based on its intended application, and so may the members associated therewith, e.g. the joystick element 12, the member 15 at the inner end 12b of the joystick element or the first and second members 22, 24 of the chassis 2 provided for the joystick element and the spring. As indicated, the metal compression spring 14 and any other spring element may in some applications be partly replaced by resilient positioning members of any conventional type, e.g. rubber gaiters. Replacements may be found in the front suspensions 7 or in the rear suspensions 8 or diagonally or in any other suitable arrangement.