GB2059237A

GB2059237A - Lawn-mower

Info

Publication number: GB2059237A
Application number: GB8032143A
Authority: GB
Original assignee: LAA K
Current assignee: LAA K
Priority date: 1979-10-05
Filing date: 1980-10-06
Publication date: 1981-04-23
Also published as: IT1133665B; SE444377B; FR2466180A3; AT366542B; GB2059237B; BE885511A; CH649192A5; SE8006918L; ATA651179A; IT8025085A0; FR2466180B3

Abstract

A mobile lawn-mower has a carriage 1 and a pressurized air drive carried by the carriage 1 for driving the cutting blades 33, the pressurized air drive being designed as a pressurized air motor 5 and being supplied with pressurized air from a pressurized air reservoir 8 carried by the carriage 1. For regulating the pressurized air motor 5, an adjustable pressure regulator 10 connected to the pressurized air reservoir 8 and a valve 13 provided with a manually actuable member 14 are arranged on the carriage, said valve 13 being located in the pressurized air conduct 6 leading from the pressure regulator 10 to the pressurized air motor 5. The pressurized air motor 5 is designed as a lamellae motor, and on the elongated output shaft 28 thereof are put the cutting blades 33. <IMAGE>

Description

SPECIFICATION Lawn mower The present invention refers to a lawn-mower comprising a mobile carriage on which at least one cutting blade is movably supported and comprising a pressurized air drive means, carried by the carriage, for said cutting blade, noting that at least one pressurized air reservoir and a manually operable control means for the pressurized air drive means is provided on said carriage.

Lawn-mowers up till now suffer from drawbacks which have its origin in the type of the drive means.

Frequently, the lawn-mowers are driven by petrol engines, but some types of lawnmowers are driven by Diesel-engines or driven electrically. Two-stroke engines produce much noise whereas four-stroke motors indeed produce less noise but are positiondependent in operation. All petrol engines and Diesel-engines need continuous servicing, for example change of lubricant oil, exchange of springs and adjustment of valves, and are frequently in need of spare parts, for example of the silencer. Electrically driven lawn-mowers are indeed free of these drawbacks, but require a cable for being connected to the wall-socket nearest at hand, which represents a hindrance when using such lawn-mowers.There are known, however, electrically driven lawnmowers being energized by batteries, but such lawn-mowers are equally position-dependent and for example not operable on strongly inclinated slopes, because the acid flows out of the battery container. Furthermore, battery-operated machines have only a limited power, which is valid also for mowers driven by dry batteries; such lawn-mowers are expensive and also expensive in operation.

There is also known a lawn-mower in which the cutting blades are driven by back-thrust devices comprising pressurized air nozzles. The shaft for the cutting blade as well as the arms carrying the cutting blades are hollow and are in connection with the pressurized air container arranged on the lawn mower. Such a back-thrust drive requires a complicated construction of the cutting blade shaft and of the cutting blade arms. The pressurized air nozzles are in need of continuous maintainance to avoid any irregularities of rotation. Therefore, such a construction has not succeeded in practice.

The present invention has an object to improve a lawn-mower of the initially defined type such that, on the one hand, the construction is simplified and, on the other hand, the safety in operation is increased. This task is, according to the invention, solved in that the pressurized air drive means is designed as pressurized air motor to which is, as control means arranged on the carriage, coordinated an adjustable pressure regulator connected to the pressurized air reservoir and a valve comprising a manually operable dosing member, noting that said valve is located in the pressurized air conduit leading from the pressure regulator to the pressurized air motor.By using a pressurized air motor, the construction is substantially more space-saving and more light-weighted as compared with a back-thrust drive, and this particularly if the pressurized air motor is directly driving the cutting blade shaft, i.e. if the cutting blades are mounted on the output-shaft of the pressurized air motor, The pressure regulator allows to correctly adjust the pressure of the pressurized air supplied to the pressurized air motor independent from the pressure prevailing within the pressurized air reservoirs so that, on the one hand, the most favourable motor power can be selected and, on the other hand, iceing up of the motor on behalf of too high pressure is avoided.Furthermore, the pressure regulator has the advantage of representing a security means for the motor, fittings and hoses so that these constructional parts are reliably prevented from becoming damaged by excess pressure. The dosing member can interrupt air supply if the lawn-mower shall be stopped. Furthermore, this dosing member represents an additionally manually operable control means so that the lawn-mower can also be operated with a lower speed, if desired.

A lawn-mower according to the invention can be operated with nearly no noise production and with nearly no maintainence work and can be used also on slopes of strong inclination. There are no problems of starting the lawn-mower and the lawnmower can also be operated in a simple manner, because it is only necessary to actuate the dosing member to start or stop the lawn-mower. Suitable pressurized air motors are available on the market and there result particularly favourable conditions with respect to a space-saving and a light-weighted construction if, according to the invention, the pressurized air motor is formed of a lamellae motor.

The dosing member could be an adjusting screw, however, it is more favourable to give the dosing member the shape of a dosing lever which simplifies operation particularly in those cases where the dosing lever is arranged on a handle upstanding from the carriage.

According to a preferred embodiment of the invention, two identical pressurized airflasks are arranged on the carriage at both sides of the longitudinal axis of the carriage and of the pressurized air motor. This provides the possibility to centrically arrange the pressurized air motor on the carriage without unilaterally loading the carriage of the lawn-mower which would be the case if the pressurized air flask would be eccentrically arranged. The stability of the lawn-mower against tilting is thus increased.

The drawing schematically shows an embodiment of the invention.

Figure 1 shows a top plan view of the lawn-mower, Figure 2 shows a side view of this lawn-mower and Figure 3 shows a section through the pressurized air motor.

The lawn-mower has a mobile carriage 1 provided with four wheels 2. The carriage 1 carries a housing 3 in which the shaft 28 of the cutting blade 33 is rotatably supported. The carriage can manually be moved by means of a hoop-like handle 4 obliquely extending in upward direction. For driving the cutting blades 33, a pressurized air motor 5 designed as lamellae motor is centrically arranged on the car riage 1 with respect to the housing 3, the pressurized air motor 5 being supplied with pressurized air via a pressurized air conduit 6. The pressurized air is taken from two pressurized air flasks 7 forming the pressurized air reservoir 8. The pressurized air flasks 7 are supported on the housing 3 and on the carriage 1, respectively, on both sides of the pressurized air motor 5 so that the carriage 1 is approximately symmetrically loaded with respect to its longitudinal axis.To each of the pressurized air flasks 7 an outlet conduit is connected, said two outlet conduits leading to a common, manually operable closure valve 9 to which a pressure regulator 10 is connected which opens into the pressurized air conduit 6. The pressure regulator 10 is provided with two pressure gauges 11 which indicate the air pressure in the pressurized air flasks 7, on the one hand, and the working pressure for the pressurized air motor 5 as delivered by the pressurized air regulator 10, on the other hand. As is shown in Figure 1, the pressurized air conduit 6 runs along the hoop-like handle 4 and is fixed thereto by clamps 12. At the area of a bent portion of the handle 4, a valve 13 is interconnected in the pressurized air conduit 6, said valve 13 being opened or closed, respectively, by means of a manually actuable dosing lever 14.

Figure 3 shows a pressurized air motor 5 for driving the lawn-mower in an enlarged scale and in a longitudinal section. The pressurized air motor has a housing 15 being closed by a connecting socket 16 having two threaded bores 17, 18 for connecting the conduits serving for supplying and, respectively, venting pressurized air. A cylinder 22 is fixed within the housin 15 by means of cylindrical discs 23 closing both front ends of said cylinder 2, the shaft 20 of the rotor 19 being rotatably supported within said cylindrical discs 23 by means of ball bearings 21. The rotor has a plurality of lamellae 24 which are supported within the rotor 19 such that they can move in direction to the axis of the shaft 20 and in opposite direction thereto.These lamellae 24 are sliding along the wall of the cylindrical space 25 which is delimited by the surface ofthe rotor 19, the bore of the cylinder 22 and the mentioned both cylindrical discs 23. The shaft 20 is in connection with a planetary gear 26 which transmits the rotational movement of the rotor 19 to the output shaft 28 rotatably supported within the housing 75 by means of a ball bearing 27, noting that the cutting blades 33 of the lawn-mower are put onto this output shaft 28 of elongated construction.The pressurized air supplied via the pressurized air conduit 6 connected to the threaded bore 17 flows in direction of the arrows 29 and enters, via an air inlet opening 30 of the cylindrical disc 23, into the cylindrical space 25 and is exterting a pressing force on the lamellae 24 for effecting rotation of the rotor 79. Because of the centrifugal force, the lamellae are pressed against the cylindrical wall of the cylindrical space. Then, the air is flowing through air outlet openings 32 within the wall of the cylinder 22 and via a noise damping insert 31 into the threaded bore 18 and then into atmosphere via a conduit connected to said bore. On starting the lawn-mower and with low numbers of revolutions, pressurized air flows below the lamellae 24 moving upwardly. During the remaining portion of one revolution of the rotor 19, the space below the lamellae is vented via the air outlet opening 32 so that the lamellae 24 can again be shifted into the slots, accommodating said lamellae, of the rotor.

Lamellae motors of this type are known per se.

Claims

1. A lawn-mower comprising a mobile carriage on which at least one cutting blade is movably supported and comprising a pressurized air drive means, carried by said carriage, for said cutting blade, noting that at least one pressurized air reservoid and a manually operable control means for the pressurized air drive means is provided on said carriage, characterized in that the pressurized air drive means is designed as pressurized air motor (5), to which is, as control means arranged on the carriage (1), coordinated an adjustable pressure regulator (10) connected to the pressurized air reservoir (8) and a valve (13) having a manually operable dosing member (14), noting that said valve (13) is located in the pressurized air conduit (6) leading from the pressure regulator (10) to the pressurized air motor (5).

2. Lawn-mower as claimed in claim 1, characterized in that the cutting blades (33) are put onto the output shaft (28) of the pressurized air motor (5).

3. Lawn-mower as claimed in claim 1 or 2, characterized in that the pressurized air motor (5) is a lamellae motor.

4. Lawn-mower as claimed in any of claims 1 to 3, characterized in that the dosing member (4) is a dosing lever.

5. Lawn-mower as claimed in claim 4, characterized in that the dosing lever is arranged on an upstanding handle of the carriage (Ij.

6. Lawn-mower as claimed in any of claims 1 to 5, characterized in that two identical pressurized air flasks (7) are arranged on the carriage (1) at both sides of the longitudinal axis of the carriage (1) and of the pressurized air motor (5).

7. A lawn-mower substantially as described in the specification.