WO1988002212A1

WO1988002212A1 - Lawn mower

Info

Publication number: WO1988002212A1
Application number: PCT/FI1987/000130
Authority: WO
Inventors: Jaakko Tapani HYVÖNEN; Heikki Tapio Salo
Original assignee: DESTEM Oy
Current assignee: DESTEM Oy
Priority date: 1986-09-26
Filing date: 1987-09-24
Publication date: 1988-04-07
Anticipated expiration: 1989-03-26
Also published as: AU8031087A; FI863902A0; FI863902A7

Abstract

Motor-operated grass cutter, which is provided with a base (11) supported by the wheels (30, 32) and with a cutting blade (13) rotating substantially horizontally inside a downwards open blade case (34). The axis (19) of the cutting blade has been laterally displaced from the motor shaft (20) so that the power transmission from the motor (12) to the cutting blade (13) has been arranged with the aid of a separate endless power transmission member (22). The wheels (30, 32) of the grass cutter (10) have been adjusted inside the cutting area of the cutting blade (13) and the front of the hem of the blade case (35) has been formed to substantially correspond to the shape of the circumference of the cutting blade (13). The auxiliary wheels (32) at the front of the grass cutter (10) have been arranged inside the circumference of the cutting blade (13). The supporting rear wheels (30), on the other hand, have been accommodated substantially beneath the motor (12) and transversely at a distance from each other, which distance is substantially smaller than the diameter of the circumference of the cutting blade (13).

Description

LAWN MOWER

The object of the invention is a motor-driven grass cutter, which is provided with a base supported by the wheels and with a cutting blade rotating substantially horizontally inside a downwards open blade case.

Motor-driven grass cutters are traditionally drum cutters or horizontally operating cutters. The horizontally operating cutters are usually fuimished with four wheels in the corners of the case and the grass cutter blade has been attached cLirectly to the vertical shaft of the motor. The drawback in these traditional grass cutters is that their supporting wheels are situated outside the curring area of the cutter blade, as a result of which the wheels prevent access to the vicinity of obstacles, such as walls, trees, shrubs and gardening arrangements. For this reason a cutting carried out with a traditional grass cutter often has to be finished manually or in some other way. Handling a grass cutting of a traditional type is clumsy and strenuous. Also the cutting height is difficult to adjust technically, because in a cutter height of all four wheels has to be adjusted. In a traditional grass cutter, the blade has been hung directly on motor shaft, as explained earlier and from this follows that, for example, in hitting an obstacle, the blade breaks down easily, this being an essential hazard, because from the broken blade the pieces may be harmful to the grass cutter user. Also in a drum cutter there are wheels next to both blades and they restrict σitting near obstacles.

The present invention brings about a considerable improvement ccaroared with the traditional cutters and at the same time it is possible to avoid the drawbacks related to the traditional grass cutters. In order to achieve this the present invention is mainly characterized in that the axis of the cutting blade has been laterally displaced from the motor shaft so that the power transmission from the motor to the blade has been arranged with the aid of a separate endless power transmission member, and that the wheels of the grass cutter have at least in the running direction of the cutter been adjusted inside the cutting area of the cutting blade so that the hem of the blade case has in the front been formed to substantially correspond to the shape of the circumference of the rotating cutting blade.

The present invention provides several advantages compared with grass cutters of prior art of which advantages the following examples can be given. The front hem of the blade case of the invention can be designed in the form of the rotating blade area and nade to comply with the terrain! Thanks to this it is possible to use the grass cutter according to the invention to cut the grass immediately beside obstacles, wherefore the normal postcutting finishing work can be omitted entirely. In the grass cutter according to the present in- vention the supporting rear wheels have been placed in the runningdirection inside the cutting area and, in addition, the front wheels have been placed entirely inside the cutting area, wherefore the wheels do not prevent running the cutter so close to the obstacle that the cutter touches it. In the grass cutter in question the motor is so located that the gravitation point is longitudinally immediately in the vicinity of the rear wheels, as a result of which the handling of the grass cutter is light and enables a better compliance with the terrain even at steeple places and when changing the direction. Since in the grass cutter according to the present invention the cutting blade has not been positioned directly on the motor shaft, the power being transmitted to the cutting blade with a separate power transmission member, the regulation of cutting height has been made very simple. The cutting height can be adjusted by adjusting the blade height or by changing the location of the rear wheels. Thanks to the power transmission mechanism the desired transmission ratio from motor shaft to cutting blade shaft can be chosen at will. Because of the above mentioned power transmission member it is also easy as part of power transmission to cause a gliding when the blade hits an obstacle or something like that, the blade not braking down as easily as before when hitting the obstacle. It is furthermore easy to furnish the power transmission with a dummy coupling, with which the cutting blade can be stepped, for example, when the user looses his grip from the operating handle. Thanks to the power transmission the grass cutter according to the present invention can also be by simple means made self-driven and runnable from top.

The invention is described in the following by way of examples with reference to the figures of the accompanying drawing.

Fig. 1 presents schematically the grass cutter according to the invention seen from side as a vertical cut.

Fig. 2 presents schematically the grass cutter depicted in Fig. 1, seen from the bottom.

Fig. 3 presents an alternative esnbodiment of the grass cutter according to the invention, made self-driven and dfivable.

Fig. 4 presents another embodiment of the grass cutter according to the invention, made self-driven and drivable.

In Figs 1 and 2 the grass cutter according to the invention has been generally marked with the reference number 10. Grass cutter 10 comprises a base 11 with the motor on top of it, the power from the motor having been transmitted essentially at the horizontal level to a rotating cutting blade 13. The base of the grass cutter has been located in the rear on supportive wheels 30 and in front at cutting blade 13 on auxiliary wheels 32. The motor 12 of the grass cutter is a so-called vertical shaft motor and from the vertical shaft 20 of the motor 12 power has been transmitted to the cutting blade with the aid of a separate power transmission member 22 such as a belt, chain or similar.

The cutting blade 13 includes the nave of the cutting blade 15, which has been fastened on the base of the grass cutter 11 with bearings 17 in such a way that the middle shaft of the cutting blade 19 is essentially vertical. On the nave 15 of the cutting blade the cutting blade pieces 14 have been fastened with attachment means 16 favourably so that the blade pieces 14 are detachable and can be replaced when necessary. Power from the motor shaft 20 to the cutting blade 13 has been transmitted so that on the motor shaft there is accommodated a drive wheel 21 and correspondingly at the nave 15 a driven wheel 18, whereby power from the drive wheel 21 to the driven wheel 18 is transmitted with a power transmission member 22 conducted around the wheels, such as a belt, chain or similar. If, for example, a V-belt or sσmsthing similar is used, it is a simple task to furnish power transmission, for example, with a dummy coupling 23 loaded with a spring 24 seen in Fig. 2, whereby the spring is ccsmpressed while hitting an obstacle and the dummy coupling 23 allows the loosening of the power transmission member 22, the cutting blade 13 then being loose from the power transmission. The dummy coupling 23 can be loaded with a spring 24 reversely so that the dummy coupling is installed to keep the cutting blade 13 detached from power transmission. In this embodiment the dummy coupling 23 has been attached, for example, with the aid of a drawing mamber 25, such as a wire, to the operating switch located on the handle of the grass cutter, whereby when the user pushes the operating switch 26 against the handle 27 the power transmission organ 22 is tight and the power transmission coupled, while when the operating switch 26 is released, the dummy coupling 23 has been adjusted so that owing to the functioning of the spring 24 it loosens the power transmission member 22 and detaches the cutting blade 13 frcm power transmission. In addition, the driven wheel 18 may be attached to the cutting blade nave 15 so that when the cutting blade 13 hits an obstacle, the driven wheel 19 has been arranged to glide on the nave, whereby the cutting blade 13 may step.

As is shown in Figs 1 and 2, the supporting wheels 30 of the grass cutter 10 have been placed at the rear of the grass cutter base so that the motor 12 of the grass cutter is located substantially on the shaft of the supporting wheels 31. This arrangement has resulted in a good manipulativeness and easy turning abilities for the grass cutter 10. Figs 1 and 2 further show that the front wheels or auxiliary wheels 32 have been located immediately underneath. the cutting blade 13 between the cutting blade's separate pieces 14. The said auxiliary wheels 32 have been arranged turnable and for this purpose they have been coupled to a substantially vertical turning shaft 33. For the turning shaft 33 a hole has been made through the nave 15 of the cutting blade and the turning shaft 33 of the auxiliary wheels 32 has been placed in the said hole and furnished with bearings so as to make it turn accessibly with the aid, for example, of a sleeve attached on the base of the grass cutter (not depicted). The auxiliary wheels 32 are entirely located inside the blade case 34 and they do not prevent cutting grass with the grass cutter 10 near walls, trees, bushes and similar obstacles. According to Figs 1 and 2 the hem of the blade case 35 has been designed at front so that it by its form corresponds to the form of the circumference of the rotating cutting blade 13. The rear supporting wheels 30 of the grass cutter 10 have been placed at such distance from each other that the width of the rotating cutting blade 13 is greater than the distance between the blade case 34 and the diameter of the circumference of the rotating cutting blade 13 is greater than the distance between the said supporting wheels 30, measured from the outer side of the said supporting wheels 30. The supporting rear wheels 30 are thus situated inside the cutting area in the running direction of the grass cutter 10, whereby these wheels are not either restrictive as regards the use of the grass cutter 10 in the vicinity of obstacles. In the grass cutter 10 according to the invention the regulation of the cutting height can be carried out in two simple ways. First, the cutting blade 13 can be adjustable by its height, whereby in adjusting the cutting height the hem of the blade case 35 remains at an unchanged distance from the ground. Second, the regulation of the cutting height can be arranged so that the turning shaft 33 of the auxiliary wheels 32 has been arranged adjustable in altitude. This can be arranged in a simple manner with the aid of adjustment nuts, for example, present on the turning shaft 33. According to Fig. 2 the grass cutter 10 has two auxiliary wheels 32, which have been placed symmetrically in relation to the turning shaft 33. Naturally only one auxiliary wheel 32 can be used instead of two, if the lower end of the turning shaft 33 has been furnished with a fork structure, to which said one auxiliary wheel has been attached. For purposes of stability and wheel supportability it must be, however, considered that the embodiment using two auxiliary wheels 32 according to Fig. 2 is better.

Another embodiment of the grass cutter according to the invention, which has been generally marked with the reference number 40, has been shown in Fig. 3. Grass cutter 40 according to Fig. 3 otherwise corresponds fully to the grass cutter shown in Figs 1 and 2, except that it has been made self-driven. For this reason, a drive has been arranged from the grass cutter motor 48 with the aid of appropriate power transmission means (not depicted) to the supporting rear wheels 41. The grass cutter 40 may in this case be made larger, while it at the same time provides a good manipulability. Beside being self- driven, the grass cutter 40 according to Fig. 3 comprises a bogie 44 provided with wheels 45, whereby the grass cutter 40 has been made drivable. The bogie 44 has been attached to the grass cutter base 43 with a frame joint 47, as a result of which the grass cutter 40 and the bogie 44 can be turned in relation to each other. The bogie 44 has been additionally provided with a seat 46 and sitting on it the user may manipulate the grass cutter-bogie combination by turning the grass cutter handle.

Fig. 4 shews a further embodiment of the grass cutter according to the invention, which has been generally given the reference number 50. The grass cutter 50, shown in Fig. 4, has been made self-driven, as the grass cutter 40 in Fig. 3, and in addition the grass cutter so has been made drivable from top. For this purpose a drive has been arranged for the supporting rear wheels 53 of the grass cutter 50 from the motor 52 of the grass cutter with the intermediation of appropriate power transmission means (not depicted) and additionally the auxiliary wheels 54 in front of the grass cutter have been made steerable and furthermore the grass cutter 50 is provided with a user seat 58, which in the embodiment indicated in Fig. 4 has been accommodated on top of the grass cutter motor. For the steering of the grass cutter the turning shaft 55 of the auxiliary wheels has been provided with a steering gear 56, and for steering, a steering wheel 57 or the similar has been attached to it. With a view to driving grass cutter 50, it has not been necessary to attach a separate bogie to it, as in the embodiment indicated by Fig. 3, but the grass cutter 50 according to Fig. 4 is by its size such that the user drives the grass cutter 50 being immediately on the top of the grass cutter base 51.

The invention has been described above taking examples with reference to the figures of the accompanying drawing. This has not, however, been done to limit the scope of the invention only for the examples presented in the figures, but many changes are possible within the scope of the principles of the invention set forth in the following claims.

Claims

1. A motor-driven grass cutter, which is provided with a base (11; 43;51) supported by the wheels (30,32;41,45;53,54) and with a cutting blade (13) rotating substantially horizontally inside a downwards open blade case (34), characterized in that the axis (19) of the cutting blade has been laterally displaced from the motor shaft (20) so that the power transmission from the motor (12) to the cutting blade (13) has been arranged with the aid of a separate endless power transmission member (22) and that the wheels (30,32;41,45;53,54) of the grass cutter (10;40;50) have at least in the running direction of the grass cutter been adjusted inside the cutting area of the cutting blade (13) so that the hem of the blade case (35) has in the front been formed to substantially correspond to the shape of the circumference of the rotating cutting blade (13).

2. A grass cutter according to claim 1, characterized in that the auxiliary wheel/auxiliary wheels (32;41;54) at the front of the grass cutter (10;40;50) have been arranged inside the circumference of the cutting blade (13) and the supporting rear wheels (30;45;53) of the grass cutter have been accommodated substantially beneath the motor (12;48;52) and transversely at a distance from each other which is substantially smaller than the diameter of the circumference of the cutting blade (13).

3. A grass cutter according to claim 1 or 2, characterized in that the auxiliary wheel/auxiliary wheels (32;41;54) in front of the grass cutter (10;40;50) are supported to the base (11;43;51) with a vertical shaft (33), which is turnably journalled on the base (11; 43;51).

4. A grass cutter according to claim 3, characterized in that a through hole has been made on the nave (15) of the cutting blade (13), through which hole the turning shaft (33) of the auxiliary wheels (32;41;54) has been adjusted.

5. A grass cutter according to any preceding claim, characterized in that the cutting height of the grass cutter (10;40;50) has been made adjustable by adjusting the height position of the auxiliary wheels (32;41;54) in relation to the base (11;43;51).

6. A grass cutter according to any one of the claims 1-4, characterized in that the cutting height of the grass cutter (10;40;50) has been made adjustable by regulating the height of the cutting blade (13).

7. a grass cutter according to any preceding claim, characterized in that a driven wheel (18) operated by an endless power transmission member (22) placed on the nave (15) has been made to allow a glide, while torsional loading of the cutting blade (13) increases suddenly and substantially, when the cutting blade (13) hits a solid obstacle or something similar.

8. A grass cutter according to any preceding claim, characterized in that a spring-loaded (24) dummy coupling device (23) has been accommodated in connection with the endless power transmission member (22), providing for manual (25,26) switching on of the power transmission between the motor (12;48;52) and the cutting blade (13).

9. A grass cutter according to any preceding claim, characterized in that the grass cutter (10;40;50) has been made self-driven in such a way that the supporting rear wheels (30;41;53) have been coupled to the motor (12;48;52) with the intermediation of power transmission.

10. A grass cutter according to claim 9, characterized in that the grass cutter (40;50) has been made drivable.

11. A grass cutter according to claim 10, characterized in that a bogie (44) provided with wheels (45) and a seat (46) has been attached to the grass cutter (40) through a turning frame joint (47).

12. A grass cutter according to claim 10, characterized in that the auxiliary wheels (54) at the front of the grass cutter (50) have been made steerable with the intermediation of the steering gear (56) and a steering wheel (57) or something similar and that the grass cutter (50) has been provided with a seat (58).