Low speed rotary mower

• US 4,149,358 A
• Filed: 03/10/1977
• Issued: 04/17/1979
• Est. Priority Date: 08/02/1974
• Status: Expired due to Term

• Current Assignee: Toro Company (Toro)
• Original Assignee: Toro Company (Toro)
• Inventors: Comer, Robert C.
• Primary Examiner(s): Eskovitz, Jay N.
• Application Number:
  US05/776,278
• Time in Patent Office: 768 Days
• Field of Search: 56/320.1, 56/320.2, 56/295, 56/255, 56/202, 56/13.4, 56/16.6
• US Class Current: 56/13.4
• CPC Class Codes: A01D 2101/00 Lawn-mowers
• CPC Class Codes: A01D 34/63 having cutters rotating about a vertical axis
• CPC Class Codes: A01D 34/71 with means for discharging mown material A01D57/26 - A01D57/30 take precedence; combined with means for gathering or loading mown material A01D43/06

Abstract

A rotary mower in which grass cutting and collection of cut grass particles is achieved with a relatively low blade tip speed. A cutting blade is mounted for rotation about a vertical axis within a symmetrical expansion type mower housing in which the expansion top wall has a substantial rise to a discharge opening vertically above the cutting blade. The housing has a continuous exterior side wall surrounding the cutting blades and extending above the sail portion thereof. The sail portions of the blade trailing the cutting edges have substantial inward and upward rake angles which result in mechanical throwing of the grass and a pumping effect results from the housing and blade configuration. In certain embodiments, the cutting edges may be swept back at an angle with respect to the blade center line and the blade diameter may be selected to aid in effective cleaning of cut grass particles from the blade.

Claims

1. Rotary mowing and bagging apparatus, comprising, in combination:

(a) a cutting blade mounted for rotation about a substantially vertical axis, said blade having a pair of cutting tips at opposite ends thereof, with each tip having a body including a leading cutting edge and a trailing sail portion having a front surface thereon, each of said front surfaces being substantially inwardly raked at an angle substantially in the range of ten degrees (10°

) to sixty degrees (60°

) with respect to the blade center line measured in the plane of rotation, said front surfaces being substantially upwardly raked at an upward rake angle substantially in the range of fifteen degrees (15°

) to fifty degrees (50°

), said upward rake angle being defined as the angle between said front surface and a line perpendicular to the body of said tips;

(b) a mower housing in which said blade is mounted, having an expansion portion with an expansion top wall with a substantial rise therein leading to a discharge opening, said housing also having a continuous exterior side wall surrounding said blade at the height thereof and extending above said cutting portions;

(c) means for rotatably driving said blade at a predetermined tip speed below 14,000 FPM, yet sufficient to cause the cutting edges of said blade to cleanly cut blades of grass, clear cut grass particles from the edges, and to impart sufficient momentum to the cut grass particles to allow collection thereof;

(d) front and rear wheels mounted on said housing to enable movement of said mower over a ground surface at a controlled height thereabove; and

(e) a grass-catching bag attached to said housing at said discharge opening.

2. The structure of claim 1 wherein said discharge opening is vertically spaced entirely above said sail portions and the top wall of said discharge opening is an extension of said expansion top wall.

3. The structure of claim 2 wherein said expansion top wall defines a circular helix in form having a vertical rise of at least six (6) inches in its extent about said housing.

4. The structure of claim 3 wherein said continuous exterior side wall defines essentially a circular cylinder in shape.

5. The structure of claim 4 wherein the vertical axis of rotation of said blade is rearwardly offset from the axis of said circular cylinder and the clearance between said blade tip and said housing in the rear two quadrants of blade rotation does not exceed three-sixteenths (3/16) inch.

6. The structure of claim 1 wherein said cutting edges are sweptback with respect to the blade center line measured in the plane of rotation at an angle of substantially twenty-five degrees (25°

) or less.

7. The structure of claim 1 wherein said cutting blade has a predetermined blade diameter which is sufficiently small so as to develop sufficient centrifugal force at the predetermined tip speed to achieve cleaning of severed grass filaments from said cutting edges.

8. The structure of claim 7 wherein said expansion top wall has an angular rise of at least twenty degrees (20°

) with respect to said cutting plane.

9. The structure of claim 7 wherein said cutting blade is mounted with respect to said front and rear wheels so that the clearance between said ground surface and said blade tips in the front two quadrants of blade rotation is less than the clearance in the rear two quadrants of blade rotation;

and each of said blade tips have a body portion between said cutting edge and said trailing sail portion, said body portions each being formed at an angle upward with respect to said cutting plane whereby repeated contact between said body portions and the tips of cut blades of grass may be avoided.

10. In combination with a rotary lawn mower:

(a) a mower housing having a cutting region thereof with a continuous closed vertical side wall, and a transport and discharge region spaced above said cutting region and defining a channel extending circumferentially about said housing, said channel having a top wall of progressively increasing height generally defining a circular helix in form and terminating at a discharge opening in said housing, said discharge opening being positioned entirely vertically above said cutting region;

(b) a cutting blade mounted for rotation about a nearly vertical axis within said cutting region, said blade having a pair of leading cutting edges thereon;

(c) mechanical throwing means defining impact surfaces trailing said cutting edges and rotating therewith to impact grass particles severed by said edges and direct said particles inward and upward into said transport and discharge region, said impact surfaces being located entirely within said cutting region and having substantial upward rake less than a right angle to the cutting plane defined by rotation of said cutting edges about said axis, also having substantial inward rake;

(d) means rotatably driving said blade at a tip speed less than 14,000 FPM, yet sufficient to cause the cutting edges of said blade to cleanly cut blades of grass, clear cut grass particles from the edges, and to impart sufficient momentum to the cut grass particles to allow collection thereof; and

(e) pumping means rotating with said blade and combining with said vertical side wall for drawing air inwardly around the bottom edge thereof and pumping said air circumferentially and axially to said discharge opening by means of said channel to aid in transport of said particles.

11. The structure of claim 10 wherein said mechanical throwing means and pumping means comprise a pair of sail portions trailing said cutting edges, said impact surfaces comprising front surfaces on each of said sail portions, said front surfaces being directed inwardly and upwardly to promote substantial upward flow of said air and grass particles with respect to said blade.

12. The structure of claim 10 wherein said front surfaces form an angle in range of substantially ten degrees (10°

) to sixty degrees (60°

) with respect to the blade center line measured in the plane of rotation.

13. The structure of claim 10 wherein the front surfaces of said sail portions are upwardly raked at an angle substantially in the range of fifteen degrees (15°

) to fifty degrees (50°

), the angle of upward rake being defined as the angle between said front surfaces and a line parallel to the blade axis of rotation.

14. The structure of claim 13 wherein said sail portions have front surfaces with a vertical height of at least one half inch.

15. Rotary mowing and bagging apparatus, comprising, in combination:

(a) a cutting blade mounted for rotation about a substantially vertical axis, said blade having a pair of cutting tips at opposite ends thereof, with each tip having a body including a leading cutting edge and a trailing sail portion having a front surface thereon, each of said front surfaces being substantially inwardly raked, said front surfaces each having substantial upward rake less than a right angle to the cutting plane defined by rotation of said cutting edges about said axis, said upward rake angle being defined as the angle between said front surface and a line perpendicular to the body of said tips;

(b) a mower housing in which said blade is mounted, having an expansion portion with an expansion top wall with a substantial rise therein leading to a discharge opening, said housing also having a continuous exterior side wall surrounding said blade at the height thereof and extending above said sail portions;

(c) means for rotatably driving said blade at a predetermined tip speed below 14,000 FPM, yet sufficient to cause the cutting edges of said blade to cleanly cut blades of grass, clear cut grass particles from the edges, and to impart sufficient momentum to the cut grass particles to allow collection thereof;

(d) said cutting edges having sufficient sweep back and said blade having a predetermined blade diameter which is sufficiently small so as to develop sufficient centrifugal force at the predetermined tip speed so as to achieve cleaning of severed grass filaments from said cutting edges;

(e) front and rear wheels mounted on said housing to enable movement of said mower over a ground surface at a controlled height thereabove; and

(f) a grass-catching bag attached to said housing at said discharge opening.

16. The structure of claim 15 wherein said cutting edges are swept back with respect to said blade center at an angle less than twenty-five degrees (25°

).

17. The structure of claim 15 wherein said predetermined speed is substantially 8,500 FPM or less, yet sufficient to cause the cutting edges of said blade to cleanly cut blades of grass, clear cut grass particles from the edges, and to impart sufficient momentum to the cut grass particles to allow collection thereof, and said sail portions have a vertical height above said body portions of at least one inch.