Lawn Mower Rasenmaher Tondeuse a Gazon
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Patentamt Europaisches || || 1 1| || || || || 1 1| || || || || (19) J European Patent Office Office europeen des brevets (11) EP 0 481 655 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publicationation and mention (51) |nt. CI.6: A01 D 34/70 of the grant of the patent: 17.09.1997 Bulletin 1997/38 (21) Application number: 91309223.5 (22) Date of filing: 08.10.1991 (54) Lawn mower Rasenmaher Tondeuse a gazon (84) Designated Contracting States: • Bone, Daniel BE DE FR GB IT NL SE Langley Moor, County Durham DH7 8LW (GB) (30) Priority: 18.10.1990 GB 9022636 (74) Representative: Stagg, Diana Christine et al Emhart Patents Department (43) Date of publication of application: Emhart International Ltd. 22.04.1992 Bulletin 1992/17 177 Walsall Road Birmingham B42 1 BP (GB) (73) Proprietor: Black & Decker Inc. Newark Delaware 19711 (US) (56) References cited: EP-A- 0 037 871 EP-A- 0 045 177 (72) Inventors: WO-A-91/02449 GB-A- 2 017 475 • Stones, Kevin GB-A-2127 665 US-A- 3 838 558 Bishop Auckland, County Durham DL14 6AE (GB) CO 10 10 CO CO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in o a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q_ 99(1) European Patent Convention). LU Printed by Rank Xerox (UK) Business Services 2.14.14/3.4 1 EP 0 481 655 B1 2 Description a grass collection receptacle. It is an object of the present invention to provide a This invention relates to a lawn mower of the type lawn mower of the "hover" type with improved grass col- which in operation is supported by a cushion of air and lection. which comprises a motor-driven blade rotatable about a s It is an object of the present invention to provide a substantially vertical axis and a fan rotatable about the lawn mower of the type which in operation is supported same axis, the blade and fan being surrounded by a by a cushion of air and has a knife rotatable about a ver- hood having one or more inlets for air to form the cush- tical axis, a first fan adapted to generate a first air ion of air. Such lawn mowers are known as "hover" stream, a second fan adapted to generate a second air mowers. to stream and barrier means preventing said second air The first hover mowers left the cut grass, normally stream from contributing to said first air stream, charac- in a finely divided state, on the ground. Users could then terised in that said cushion of air is provided by said first either leave the cut grass on the ground, for example as air stream generated by the first fan and cut grass is a mulch, or they could pick the cut grass up in a second- transported by suction into collecting means by the sec- ary operation. In due course attempts were made to is ond air stream generated by the second fan. design mowers of the hover type which picked the grass The two air streams are caused by two separate up as they went along. Examples of such mowers are fans driven by one or two motors. Thus, separate described in Patent Specifications GB-A-2,01 7,475 and motors each driving a fan may be used to produce the EP-B-0,037,871. In the construction described in the two air streams, one of the motors also carrying the former, cut grass is blown by the air forming the air 20 rotating grass-cutting blade. Alternatively, the two fans cushion through an outlet in the hood surrounding the may be driven by a single motor. cutting blade and into a grass collecting container In a preferred embodiment of the invention, the first attached to the rear of the mower. The efficient opera- and second air streams are created by respective fans tion of this mower requires a specially-shaped hood. In mounted on opposite ends of the motor driving the cut- the construction disclosed in Specification EP-B- 25 ting blade. 0,037,871 , the cut grass is effectively sucked up by the Two embodiments of the invention will now be air stream which then forms the air cushion on which the described, with reference to the accompanying draw- mower hovers. Thus, the air stream to the fan wheel ings, in which forming the hover air cushion, before reaching the fan wheel, is used to pick up cut grass and transport it into 30 Figures 1 and 2 are longitudinal vertical sections a grass collecting chamber in the mower. through the two mowers. Corresponding parts of A disadvantage of the former type of grass-collect- the two mowers are given the same reference ing mower, i.e. that which uses the hover air to blow cut numerals. grass into the grass bag, is that it requires a fairly com- plicated hood configuration. A disadvantage of the latter 35 Referring to Figure 1 , a lawn mower of the hover type of mower, i.e. that which uses the air forming the air type comprises a body 1, suitably injection moulded cushion to suck up cut grass, is that as the grass collect- from a thermoplastics material, the body comprising a ing chamber fills up, it becomes heavier and the filter housing 2 mounted on an outwardly-directed hood 3 ter- tends to become blocked. Thus air is prevented from minating in an upwardly-directed peripheral rim 4. An reaching the fan, and the cushion of air cannot be main- 40 electric motor 5 is seated on an annular flange 6 of a tained at a level which will enable effective grass cutting. stepped collar 7 attached to the inside wall of housing 2. WO-A-91 02449 relates both to lawn mowers and to Extending from the lower end of motor 5 is an out- vacuum cleaners. Insofar as it relates to lawn mowers, it put shaft 8 on which is mounted a fan 9 and a cutting is principally directed towards single impeller rotary blade 10. The upper end 11 of output shaft 8 extends mowers of the air-supported type, in which a plate mem- 45 upwardly from the upper end of motor 5, and penetrates ber is provided to control air flow within the housing of a barrier wall 1 2 mounted at the upper end of housing 2, the mower, in order to provide improved support for the and thereabove mounts a second fan 13. mower and to support and direct out grass into a dis- Fan 13 is contained in a chamber formed by the charge duct. Figure 5 shows a mower with a dual impel- barrier wall 1 2 and an apertured cover 1 4. Cover 1 4 has ler, and this dual impeller is a two stage single impeller, so a central opening 15, covered by a wire mesh or other both stages of which co-operate to provide an air flow to air-permeable material 16, and a series of circumferen- lift the mower. tial apertures 1 7. The air flows generated by both stages of the impel- Housing 2 is provided with air inlets 20 and 21 . ler discharge into the chamber defined by the plate Mounted on the lawn mower is a grass collecting member and a platform, where they mix. The cutting ss box 22, comprising a collecting chamber 23 and a filter blade does not define a base to this chamber. As is comprising an apertured plate 24. The front end of the stated in the description, the air pressure generated is grass box 22 is fitted around the opening 15. more than sufficient to lift the mower and some of the In use, the fans 9 and 13 produce separate air excess air is bled off into an air pod adaptor to support streams, that produced by fan 9 providing the air cush- 2 3 EP 0 481 655 B1 4 ion on which the mower hovers, and that provided by fan generate a first air stream, a second fan (13) 1 3 sucking the cut grass into the box 22. adapted to generate a second air stream and bar- More specifically, fan 9 draws air into the housing 2 rier means (12) preventing said second air stream from to said first air character- through air inlets 21 , the air then passing into the hood contributing stream, 3 to form the air cushion. Air is also passed into the 5 ised in that said cushion of air is provided by said upper part of the housing 2 through air inlets 20, this air first air stream generated by the first fan (9) and cut passing into the annular air passage between the motor grass is transported by suction into collecting 5 and the collar 7 and through the motor to cool the means(22) by the second air stream generated by motor. This motor-cooling air can then join the air enter- the second fan (13). ing through the inlets 21 to form the hover cushion. 10 Quite separately, the fan 13 causes air to enter the 2. A lawn mower according to Claim 1 , characterised grass box 22 through an aperture 26, such air entraining in that said first and second air streams are pro- cut grass, leaves and similar debris.