NZ196800A - Rotary lawn mower with fan to assist cut grass discharge - Google Patents

Description

196800 No.: Date: NEW ZEALAND PATENTS ACT, 1953 196800 13 April 1981 COMPLETE SPECIFICATION "Improvements in or relating to Rotary Mowers" I/We, MASON PORTER LIMITED a company duly incorporated under the laws of New Zealand of Mt. Wellington Highway, Mt. Wellington, Auckland, New Zealand. hereby declare the invention for which I / we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - l<?6goO This invention relates to rotary mowers.

It is an object of the present invention to provide a rotary mower which will at least provide the public with a useful choice.

Accordingly the invention consists in a rotary mower including a body having a cut grass exit and a wall the inner surface of which defines an outer boundary of a cutting chamber, a blade mounted in said body so as to be rotatable in use on a substantially vertical axis and 10 a centrifugal fan impeller concentrically mounted with said blade and above it in use, said body having an air inlet concentric with and adjacent to the axis of said impeller and having a shroud which encircles said fan impeller except for an air exit therefrom, the outer surface 15 of said shroud defining an inner boundary of said cutting chamber, said blade having cutting edges extending outwardly beyond said shroud so that said cutting edges operate to cut grass within said cutting chamber, the construction 3 SEP t^SS / and arrangement being such that in use air is drawn into 20>" said body by said impeller and discharged through said air exit in a manner such as to assist in discharging cut grass from said cutting chamber.

To those skilled in the art to which this invention relates many changes in construction and widely differing embodiments 25 and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and it is not our intention to limit the scope of the invention by those disclosures 30 and descriptions, or otherwise, than by the terms of the 196800 appended claims.

On preferred form of the invention will now be described with reference to the accompanying drawings in which : Figure 1 is a transverse cross section through a rotary mower constructed according to the invention.

JQGSOD Referring to the drawings, in the preferred form of the invention a rotary lawn mower is made and comprises a body, linium/alloy body 1, such body z Demg separaieu Dy a space from an inner short cylinder or shroud 4. The short cylinder provides a shroud for an air impeller 5 and to provide an inlet to the air impeller 5, the upper part of the body has an opening 6 therein, The opening 6 is concentric with the shaft 7 of a motor 8 and to provide access to ambient atmosphere the motor 8 is mounted on spacers 9 by bolts 10 thus providing an annular passageway between the top 12 of the casing 1 and the lower edge 13 of the motor mounting 14. The impeller 5 preferably comprises a plastics moulding, e.g. a nylon moulding, having a plurality of radial fan blades 20 mounted on a disc or dished member 21, the dished member 21 being positioned lowermost in use and the fan blades upstanding from that body. Each blade may be of an outer rectangular formation with a triangular formation reaching in some cases down to a rib 22 which reinforces the dished member 21. The dished member 21 is preferably dished so that the central part of the dished member is higher than the outer edges of the disc.

The shroud 4 is provided with an air exit 15 which directs air towards a grass cuttings outlet in the body preferably with a rearward component of velocity and the air exit spans between 60°-90° and preferably 75°-85° commencing on or near a line approximately transverse of the mower across the centre of rotation of the blade and finishing on or near a line approximately centrally longitudinally disposed the outer wall 3 of the chamber - X - 196800 of the mower. The body has a baffle adjacent the part of the shroud towards which the impeller turns. This is to inhibit the recirculation of grass in the cutting chamber.

The grass cutting chamber increases in height from adjacent the aforementioned baffle towards the grass cuttings outlet, the rate of increase being greater towards the exit than at the commencement of the increase in height.

In accordance with usual practice, the body 1 is mounted on wheels and a suitable e.g. lever operated height adjustment is provided.

A cutting blade 25 is mounted below the centrifugal impeller 5 and this blade has a channelled portion 26 with slightly twisted (10°-15°) cutting ends 27. The blade 25 and impeller 5 are driven by a bar 28 welded to a boss 29 keyed with a Woodruff key 30 to the shaft 7. The blade 25 and impeller 5 are bolted to the bar 28 by bolts 31. Alternatively the bar 28 may be shorter and the impeller 5 bolted direct to the blade 25 with the bar clamped between them. The blade ends 27 are sloped downwardly relative to the channelled portion 26.

Sharpened cutting edges are provided on the blade by bevelling the blade on that upper side and as stated the rear outer ends of the blades are upturned at an angle of 10°-15° so that some fan effect will be provided by such upturned ends.

A catcher is mounted on the mower attached in any convenient way and such catcher preferably comprises a substantially rigid frame of metal and an open weave fabric portion on the two vertical sides and substantially vertical rear thereof and across the top. The bottom panel is 196800 preferably of impermeable metal or plastics. The fabric and the bottom panel are preferably fixed to the frame of the catcher by providing one or more plastics C shaped members one edge of the mouth of the C being fixed e.g. by an adhesive or stitching or both to the fabric or bottom panel and such member is then clipped over the frame to hold the fabric and bottom panel in position.

An operating handle is of course provided on the mower.

The use of the construction is as follows: The motor 8 is started and the cutting height of the blade 25 adjusted by raising and lowering the body in the known way. The centrifugal impeller 5 draws air in through the opening 6 in the central upper part of the body, and such air is then passed downwardly and driven by the impeller through the air exit 15 and through the cut grass exit from the mower into the catcher. The upturned portions of the blades will assist in carrying cut grass until such cut grass is caught up by the stream of air passing to the rear of the mower.

The advantage of this arrangement at least in the preferred form is that because the mower blade does not have to provide any material flow of air the mower is quieter in operation than present mowers.

Additionally because a more efficient air impeller means is used the blade may be run more slowly again giving a noise reduction and requiring less energy to give the required cutting actions. lo - X -

Claims (12)

WHAT WE CLAIM IS: J96&00

1. A rotary mower including a body having a cut grass exit and a wall the inner surface of which defines an outer boundary of a cutting chamber, a blade mounted in 5 said body so as to be rotatable in use on a substantially vertical axis and a centrifugal fan impeller concentrically mounted with said blade and above it in use, said body having an air inlet concentric with and adjacent to the axis of said impeller and having a shroud which encircles 10 said fan impeller except for an air exit therefrom, the outer surface of said shroud defining an inner boundary of said cutting chamber, said blade having cutting edges extending outwardly beyond said shroud so that said cutting edges operate to cut grass within said cutting chamber, 15 the construction and arrangement being such that in use air is drawn into said body by said impeller and discharged c " through said air exit in a manner such as to assist in discharging cut grass from said cutting chamber.

2. A rotary mower as claimed in Claim 1 wherein said impeller shroud comprises a short hollow cylinder slightly larger in diameter than said impeller, said cylinder having a portion removed to provide said air exit.

3. A rotary mower as claimed in Claim 2 wherein said shroud has said air exit disposed over 60° to 90° of arc 25 positioned so that air is discharged with a rearwardly directed component of velocity to discharge air to said cut grass exit.

4. A rotary mower as claimed in Claim 3 wherein said air exit extends over 70° to 85° of arc. - 7 19&200

5. A rotary mower as claimed in any one of the preceding claims wherein said cutting chamber increases in height in the direction of rotation of said blade from the rear of the body towards said cut grass exit. 5

6. A rotary mower as claimed in any one of the preceding claims wherein said mower blade is of substantially flat outline but having a twist of 10° - 15° at the rear of the cutting edges of the blade to assist in lifting grass.

7. A rotary mower as claimed in any one of the preceding 10 claims wherein said blade and said impeller are driven by being clamped or bolted to a bar having a boss keyed to a driving motor shaft.

8. A rotary mower as claimed in Claim 7 wherein said blade has a central channelled portion in which said bar 15 fits.

9. A rotary mower as claimed in any one of the preceding claims wherein said mower is fitted with a catcher part of the walls of which are of open weave textile material.

10. A rotary mower as claimed in Claim 9 wherein said textile material is removably attached to a catcher frame by split tubular means fixed to said fabric, said split V- '.1 .i ^ c'(; tubular means fixed to said fabric, said split tubular ~ 3 SEP 1985 !j / means fitting over said catcher frame.

A rotary mower as claimed in Claim 9 or Claim 10 25 wherein a lower panel of impermeable metal or plastics is provided on said catcher attached to the catcher frame by split tubular means fitting over the panel and the frame.

12. A rotary mower when constructed arranged and operable 30 substantially as herein described with reference to the accompanying drawings . D/lT:ID THIS X DAY OF S a. J. pa;ik a sou <y f • *