US3869848A

US3869848A - Rotary mower having quiet cutter blade

Info

Publication number: US3869848A
Application number: US380294A
Authority: US
Inventors: Robert T Larsen
Original assignee: Outboard Marine Corp
Current assignee: Toro Co
Priority date: 1973-07-18
Filing date: 1973-07-18
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11
Also published as: CA993200A

Abstract

Disclosed herein is a rotary mower including a blade housing having a generally annular wall which depends vertically from a top deck and a generally flat, elongated cutter blade including diametrically opposed tip portions, each having a radially outer tip which terminates in closely spaced relation to the annular wall. Each tip portion includes a leading cutting edge and a trailing lift tab or vane which is spaced radially inwardly from the outer tip so as to provide a generally flat section between the outer tip and the lift tab or vane. The lift tabs or vanes preferably are arranged with a minimum vertical height and have a concave, longitudinal contour.

Description

Larsen 1 Mar. 11, 1975 l l ROTARY MOWER HAVING QUIET CUTTER BLADE [75] Inventor: Robert T. Larsen, Menomonee [21] Appl. No.2 380,294

[52] US. Cl. 56/295 [51] Int. Cl A01d 55/18 [58] Field of Search 56/295, 320.1, 320.2, 255, 56/175,134

[56] References Cited UNITED STATES PATENTS 2,663,984 12/1953 Clark 56/l3.7

2,969,634 1/1961 Lannert 2,983,096 5/1961 Phelps 3.191.371 6/1965 Brewer 56/295 lill l lg lllllllll Ill-Ill! minimum 1/1973 Knipc 56/295 Primary Examiner-Russell R. Kinsey Attorney, Agent, or Firm-Michael, Best & Freidrich [57] ABSTRACT Disclosed herein is a rotary mower including a blade housing having a generally annular wall which depends vertically from a top deck and a generally flat, elongated cutter blade including diametrically 0pposed tip portions, each having a radially outer tip which terminates in closely spaced relation to the annular wall. Each tip portion includes a leading cutting edge and a trailing lift tab or vane which is spaced radially inwardly from the outer tip so as to provide a generally flat section between the outer tip and the lift tab or vane. The lift tabs or vanes preferably are arranged with a minimum vertical height and have a concave, longitudinal contour.

7 Claims, Drawing Figures 5/1973 Dahl et al. 56/3202 ROTARY MOWER HAVING QUIET CUTTER BLADE BACKGROUND'OF THE INVENTION This invention relates to rotary lawnmowers and, more particularly, to rotary lawnmowers having a cutter blade which operates at reduced noise levels.

It is generally recognized that the rapidly rotating cutter blade of a rotary mower is one source of noise generation. The lift tabs or vanes carried on outer end portions of prior rotary cutter blades produce air vortices inside the blade housing, which vortices generate a wind-like noise. Such noise generation is, of course, undesirable.

Examples of prior art cutter blade constructions are disclosed in the Weiland U.S. Pat. No. 3,3 67,091 issued Feb. 6, 1968 and the Blume U.S. Pat. No. 2,990,666, issued July 4, 1961. Filed herewith with the Patent Oflice is a copy of a drawing illustrating a prior cutter blade construction manufactured by the assignee of this application.

SUMMARY OF THE INVENTION The invention provides a rotary mower including a blade housing having a generally annular wall depending vertically from a top deck and a cutter blade which is supported for rotary movement in a horizontal plane within the housing and which is arranged in a manner to minimize air vortices produced thereby within the interior of the blade housing. More specifically, the invention provides a generally flat cutter blade including diametrically opposed tip portions, each having a radially outer tip which terminates in closely spaced relation to the annular wall. Each tip portion includes a leading cutting edge which extends radially inwardly from the outer tip and a trailing lift tab or vane which is spaced radially inwardly from the outer tip so as to provide a generally flat section of predetermined radial length between the outer tip and the lift tab or vane. Provision of such a flat section on the outermost portion of the cutter blade minimizes the air vortices produced by the rotating cutter blade in the region adjacent the annular wall and thereby reduces the noise generated by the cutter blade.

Preferably, the distance which the lift tabs or vanes extend vertically above the horizontal plane of the cutter blade is kept to a minimum so as to minimize air vortices produced in the region adjacent the trailing edge of the rotating cutter blade and thereby further reduce the noise generated by the cutter blade. The spacing between the cutter blade outer tip and the annular wall is also kept to a minimum. To further reduce the air vortices produced in the region of the trailing edge of the cutter blade, the lift tabs or vanes can be provided with a generally concave longitudinal contour.

The principal feature of the invention is the provision of the rotary mower including a cutter blade which is designed to generate a reduced level of noise.

Another feature of the invention is the provision of a rotary mower including a blade housing having an annular wall and a cutter blade which is arranged so that, during rotation, the air vortices produced thereby in the region adjacent the annular wall are minimized.

A further feature of the invention is the provision of a rotary mower including a blade housing having an annular wall and a cutter blade having lift tabs or vanes which are arranged so that the air vortices produced in the region adjacent the trailing edge of the rotating cutter blade are minimized.

A still further feature of this invention is the provi sion of a rotary mower including a blade housing having an annular wall and a cutter blade which is designed so that the air vortices produced thereby in the region adjacent the annular wall and trailing edge of the cutter blade are minimized without substantially reducing the air flow for discharging grass clippings from the interior of the blade housing.

Other features and advantages of the invention will become apparent upon reviewing the following detailed description, drawing and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom plan view of the rotary mower in accordance with the invention.

FIG. 2 is an enlarged fragmentary top view, with parts broken away, of the rotary mower shown in FIG. 1.

FIG. 3 is an enlarged fragmentary side view, with parts broken away, corresponding to the view shown in FIG. 2.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawing. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purposes of description and should not be regarded as limiting.

Shown in the drawing is a rotary lawn mower 10 including a blade housing 12 which is supported in spaced relation above the ground 13 and for travel along the ground by a plurality of ground-engaging wheels 14. The blade housing 12 supports a prime mower (not shown) which can be an internal combustion engine and which includes a drive shaft 16 carrying an elongated cutter blade 18 for rotation through or in a generally horizontal plane within the blade housing 12 in the direction shown by the arrow 20. The cutter blade 18 is preferably in the form of a generally flat bar and has diametrically opposed tip portions 22. Each tip portion 22 includes a leading cutting edge 24 which extends radially inwardly a predetermined distance from the radially outer tip 25 for cutting the grass, and a trailing lift tab or vane 26 which serves as an impeller for drawing air into and circulating it about the interior of the blade housing upon rotation of the cutter blade 18.

The blade housing 12 includes a horizontally extending upper or top deck 28 located above the cutter blade 18. Depending from the top deck 28 is a generally annular, vertically extending, substantially continuous wall 30 which generally surrounds the periphery of the path of the cutter blade 18. The annular wall 30 includes a lower edge 31 adjacent to or slightly below the horizontal plane of the cutter blade 18 and a discharge opening 32 which extends between about 12 oclock and about 3 oclo'cktas viewed in FIG. 1, whenl2'oclock is in the front) and thro'ughwhich the grass clippings are discharged from the interior of the blade housing 12. Extending outwardly from the blade housing and in communication with the discharge opening 32 is a discharge chute 34 to which acollec-tion bag (not shown) can be re-movably attached in the usual manner for collecting the grass clippings.

As thus far described, the construction of the rotary mower is conventional.

In accordance with one of the features of the invention and in order to reduce the noise generated by the rapidly rotating cutter blade 18, each cutter blade vane 26 is spaced radially inwardly a predetermined distance from the respective outer tip so as to provide a generally flat, radially extending section 36 between the 'outer tip 25 and the vane 26. While other arrangements can be used, in the specific construction illustrated, the horizontal dimension of the flat section 36 between the outermost extremity of the outer tip 25 and the respective vane 26 is about 1/2 inch to about 1 inch. Conventional cutter blades having vanes which extends radially inwardly from the outer tip of the cutter blade produce air vortices in the region adjacent the blade housing annular wall 30. The so-called tip vortices produced by such vanes are one source of the wind-like noise typically generated by cutter blades of conventional design. With the generally flat section 36 provided by the invention, the magnitude of these tip vortices is significantly reduced with a resultant reduction in the level of the wind-like noise produced by the rotating cutter blade 18.

Another source of the wind-like noise typically generated by a cutter blade of conventional design is the socalled trailing vortices produced by the generally upstanding vanes. In accordance with another feature of the invention and in order to further reduce the windlike noise generated by the cutter blade 18, each vane 26 is arranged with a relatively small vertical height which is substantially less than that of vanes for conventional cutter blades. That is, the vertical distance which the vanes 26 extend above the bottom surface 38 of the cutter blade 18, designated by reference numeral 40 in FIG. 3, is kept to a minimum consistent with the requirement for generating a sufficient air flow inside the blade housing to discharge the grass clippings outwardly from the interior of the blade housing and through the discharge chute 34. A reduction in the vertical height of the vanes 26 usually results in a corresponding loss of pressure generated by the cutter blade 18 inside the blade housing 12. In order to compensate for this loss of pressure and thereby insure that the grass clippings are properly discharged through the discharge chute34, the spacing between the outer tip 25 of the cutter blade 18 and the annular wall is kept to a minimum. This tip clearance is minimized by providing the outer tip 25 with an arcuate outermost extremity havinga radius which closely coincides with the inside radius of the annular wall 30 and by manufacturing the annular wall to be as circular as possible.

The provision of a minimum clearance between the cutter blade tip 25 and the annular wall 30 results in a minimum pressure leakage therebetween and the net pressure produced inside the blade housing 12 by the rotating cutter blade 18, even though the vertical height of the vanes 26 is reduced, is sufficient to discharge the grass clippings outwardly through the discharge chute 34. While other arrangements can be used, in the specific construction illustrated, the spacing between the tip 25 and the annular wall 30 can be about l/l6 inch to about 3/16 inch and the vanes 26 can extend vertically above the bottom surface 38 of the cutter blade 18 a maximum distance of about inch to about /2 inch. The reduced vertical height of the vanes, in addition to reducing the trailing vortices and thus reducing the wind-like noise generated by the cutter blade, also reduces the power required to operate the cutter blade.

As best shown in FIGS. 3 and 4, the vanes 26 are preferably formed integrally from respective tip p0rtions 22 and the tip portion 22 includes a flat surface web section 42 extending laterally between the cutting edge 24 and the leading portion 44 of the vanes 26. Also, the vanes 26 preferably (See FIG. 4) have an arcuate lateral contour, i.e., curve arcuately rearwardly and upwardly from the leading portion 44 when seen from the outer blade extremity, and a generally downwardly concave longitudinal contour when seen from the rear (See FIG. 3) including a vertically raised central portion 46 and opposite end portions 48 which respectively curve gradually upwardly from the horizontal plane of the cutter blade 18 towards the raised central portion 46.

Various other features are set forth in the following claims.

What is claimed is:

l. A rotary mower comprising a blade housing including a top deck, a plurality of ground-engaging wheels mounted on said blade housing for supporting said blade housing for travel in spaced relation above the ground, a generally vertically extending, annular wall depending from said top deck, a generally flat and elongated cutter blade supported by said housing for rotary movement through a horizontal plane within said housing, diametrically opposed tip portions on said cutter blade each having an outer radial extremity which terminates in closely spaced relationship to said annular wall, each of said tip portions including a leading cutting edge extending radially inwardly from said outer extremity, a trailing edge extending radially inwardly from said outer extremity rearwardly of said leading cutting edge, and an upstanding vane extending forwardly from said trailing edge and having a radially outermost portion spaced radially inwardly a predetermined distance from said outer extremity so as to provide a generally flat section therebetween.

2. A rotary mower according to claim 1 wherein said cutter blade includes a top surface, and said vanes are formed integrally from said cutter blade and include a contoured edge means for reducing the air vortices produced in the region adjacent the trailing edges of said blade tip portions during rotation of said cutter blade.

3. A rotary mower according to claim 1 wherein said vanes are elongated in the direction of the longitudinal axis of said cutter blade and have a generally downwardly concave longitudinal contour when viewed from the rear.

4. A rotary mower according to claim 1 wherein each of said tip portions include an arcuate outermost extremity having a radius which closely coincides with the radius of said annular wall.

5. A rotary mower according to claim 1 wherein each of said tip portions includes an upper surface including a flat portion extending rearwardly from said cutting edge and arearward portion which extends arcuately upwardly from said flat portion.

6. A rotary mower according to claim 1 wherein said trailinge'dge includes a portion which is spaced inwardly of saidouter extremity and-which is rearwardly concave.

7. A rotary mower comprising a blade housing including a top deck, a plurality of ground-engaging wheels mounted on said blade housing for supporting said blade housing for travel in spaced relation above the ground, a generally vertically extending, annular wall depending from said top deck, a generally flat and elongated cutter blade supported by said housing for rotary movement through a horizontal plane within said housing, diametrically opposed tip portions on said cutter blade each having an outer radial extremity which terminates in closely spaced relationship to said annularwall, a trailing edge extending radially inwardly from said outer extremity rearwardly of said leading cutting edge and including a portion which is spaced inwardly from said outer extremity and which is slightly rearwardly concave, and an upstanding vane extending forwardly from said trailing edge portion and terminating forwardly in spaced relation rearwardly from said cutting edge, said vane being elongated in the direction of the longitudinal axis of said cutter blade and having a generally downwardly concave longitudinal contour when viewed from the rear and having an upper surface portion which is upwardly concave.

Claims

1. A rotary mower comprising a blade housing including a top deck, a plurality of ground-engaging wheels mounted on said blade housing for supporting said blade housing for travel in spaced relation above the ground, a generally vertically extending, annular wall depending from said top deck, a generally flat and elongated cutter blade supported by said housing for rotary movement through a horizontal plane within said housing, diametrically opposed tip portions on said cutter blade each having an outer radial extremity which terminates in closely spaced relationship to said annular wall, each of said tip portions including a leading cutting edge extending radially inwardly from said outer extremity, a trailing edge extending radially inwardly from said outer extremity rearwardly of said leading cutting edge, and an upstanding vane extending forwardly from said trailing edge and having a radially outermost portion spaced radially inwardly a predetermined distance from said outer extremity so as to provide a generally flat section therebetween.

5. A rotary mower according to claim 1 wherein each of said tip portions includes an upper surface including a flat portion extending rearwardly from said cutting edge and a rearward portion which extends arcuately upwardly from said flat portion.

6. A rotary mower according to claim 1 wherein said trailing edge includes a portion which is spaced inwardly of said outer extremity and which is rearwardly concave.