Mulching Deck Spillgate

This invention relates generally to the structure of lawn mower housings and to such housing constructions for discharge of grass clippings and is particularly directed to an improved lawn mower blade housing having a structure which enhances even distribution of grass clippings.

With the increasing need for mulching mowers which reduce grass clippings to a small particle size thereby permitting grass clippings to remain on and below the mowed grass without being bagged or otherwise disposed of, many types of lawn mowers having unique blade configurations have been developed. The housings within which such blades are used present a variety of problems, which problems are significantly increased when it is desired to use a plural blade lawn mower to produce a larger cutting width. The distribution of clippings from such a plural blade mulching mower presents problems whether or not those lawn mowers are of the riding type, walk behind, or tractor type. Most mulching mowers operate with one or more blades which endeavor to elevate and recut the grass clippings thereby creating smaller particles which can be distributed in the remaining "growing" grass without creating wind rows, clumps, or other difficulties and returning valuable nutrients to the soil.

It is a principle object of this invention to provide a housing for spaced multiple blade grass cutting apparatus providing improved grass clipping distribution.

It is a further object of this invention to provide a power driven lawn mower having at least two blades rotating in a substantially horizontal plane about spaced driven vertical shafts, the mower being suitable for user walk behind operation with improved grass clipping distribution and containment of most foreign materials ingested by the lawn mower.

It is an additional object of this invention to provide a walk behind, power driven lawn mower having at least two rotating mulching blades bout vertical axes in the housing, which housing has a rear spillgate to effect improved glass clipping distribution.

It is a still further object of the invention to provide a housing for spaced multiple blade grass cutting apparatus having a rearwardly extending downwardly facing spillgate to effect the improved grass distribution.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

A better understanding of this invention will be obtained from the following detailed description and accompanying drawings of illustrative applications of the invention.

A lawn mower housing is provided with two compartments to accommodate two rotating blades, the general shape of the compartments being inverted cup-shaped with cup side walls interrupted along a common chordal merger line to form a generally FIG. 8 configuration when viewed from the housing bottom. A cutting blade is supported in each compartment and the trailing edge housing portion extending from the merged area is constructed to extend rearwardly and outwardly to provide a rear projection having a top and side and rear ground-facing edges. The side and rear edges of the projection or spillgate are outwardly and downwardly sloped to provide improved distribution of grass cuttings and other materials ingested by the mower.

In the drawings:

FIG. 1 is a perspective view of a power driven riding lawn mower showing the typical environment of use of the present invention;

FIG. 2 is an exploded perspective view of a two blade housing illustrating a preferred embodiment of the invention and illustrating a typical blade drive mechanism;

FIG. 3 is a top plan view of a preferred embodiment of the housing; and

FIG. 4 is a cross section view taken generally along the lines 4-4 of FIG. 3 and showing a schematic side view of a blade.

Turning first to FIG. 1, it is seen that a typical rear engine, riding lawn mower generally identified by the numeral 10, has wheels 11, supporting a frame 12 on which is located a rear mounted engine 13, (partially shown) a seat 14, and a suitably supported steering wheel 15 for controlling the movement of the front wheels 11. In addition there are brake pedals, gear shifts, etc., all of which are environmental structure, well known in the prior art in which the present invention can be utilized.

FIG. 2 illustrates a housing or deck generally designated 20, having suitable support members 22, for attachment to the frame of a mower such as that of FIG. 1. There are two compartments in housing 20 generally designated 24 and 25. Housing 20 is typically fabricated from stamped and welded sheet metal but any suitable technique for construction such as casting is acceptable.

Each compartment 24, 25 supports a lawn cutting blade 27, (only one of which is shown in FIG. 2) which blade 27 is suitably secured by fastener 29 extending through blade aperture 30 to engage spindle 31. The support structure generally bracketed by the numeral 33 includes bearings, a mounting collar, and suitable fasteners extending through the housing, to securely affix and position a blade 27 within each housing compartment for rotary motion. The drive to each blade is provided by a toothed drive pulley or member 38, which is secured to shaft 31, by fastener 40. The same drive and blade mounting structure exists for compartment 25 and toothed drive pulley 41 is drivingly connected with pulley 38, by timing belt drive member 42. Additionally there is provided a pulley 43, which is secured to toothed drive pulley 41, which pulley 43 can be a standard V-belt pulley for connection to the engine and controls (not shown). For completeness in the description of FIG. 2, it is observed that a spillgate generally designated 45, is illustrated and is hereinafter described in greater detail.

By way of general information, the present mower deck is intended for principal usage in connection with so-called mulching blades such as partially shown in FIG. 2. When the grass is cut, the shape of the blade causes the clippings to experience an upward flow of air to be recut into smaller and smaller pieces in accordance with known mulching blade and housing technology. It is customary with such mulching blades to provide a somewhat dome shaped housing which assists in the requisite upward air flow as the clippings are cut and recut and such a dome shaped housing is also common in the prior art.

Considering FIGS. 3 and 4 together, it is noted that the housing 20 has a general "FIG. 8" shape and, as best seen in FIG. 4, is comprised of two inverted cup-shaped compartments 24 and 25, which overlap each other so as to merge their top and side walls together along a chord line 50, such that with appropriate weldments, the two compartments are secured together as a unitary housing structure 20. Such inverted generally cup-shaped compartments having side walls which merge along one portion of each cup to form a downwardly extending continuous housing skirt 52 having a lower rim extending about the housing which rim is generally designated 53.

A front web 55 provides a leading edge of movement and a rear spillgate 63 provides a trailing edge of movement. The front web 55 interconnects the open space between the compartments in the forward portion of the housing as determined by the direction of travel arrow 56. It is pointed out (as best seen in FIG. 4) that the front portion of rim 53 ends above the basic height of the plane of rotation of cutting blade 27 thereby to facilitate entry of grass into the two compartments to be cut.

In accordance with a primary feature of the present invention, there is provided a spillgate generally designated 45 which is formed by a web that interconnects open space between the rear walls (in the direction of travel) of the two inverted cup-shaped compartments and includes a generally flat roof portion 60, a pair of side wall portions 62, and a rear portion 63, all of the portions of the spillgate terminate in the downwardly facing rim 53. Rear spillgate portion 63 and side spillgate portions 62 extend downwardly and outwardly from roof 60 and, as seen in FIG. 4, rim 53 of the skin or spillgate (and a portion of the compartment sidewalls, as well) extend below the general plane of rotation of the blade 27. Hence, as the mower of FIG. 1 moves forward, the grass clippings are discharged through the spillgate and directed toward the ground. Because of the timing belt drive described in connection with FIG. 2, the blades in each compartment rotate in the same direction to cut and recut grass clippings in each compartment for discharge through spillgate. By providing a spillgate extending beyond the blade compartments in the rearwardly facing direction and by providing downwardly and outwardly tapering walls having their lower edges below the plane of rotation of each blade, the clippings and other materials such as leaves, etc., that are ingested into the lawn mower cutting compartments are distributed in a surprisingly even manner so as to bring the benefits of mulching mowing to a plural compartment tractor type or walk behind mower. This development is particularly useful in so called wide-cut mowers which endeavor to use plural blades in compartments rather than a single large rotary blade and by providing the spillgate structure for a conventional two bladed FIG. 8 compartment, significant improvement is obtained in the distribution of grass clippings thereby to substantially eliminate the need for clipping, bagging and the like for riding and walk behind mowers.

In the preferred embodiment of this invention, it has been found that significant improvement of performance is achieved when the length indicated at FIG. 4 (numeral 60) is between 12% and 15% of the length of one of the cutting blades 27. The width of the spillgate at 65 of FIG. 3 has been found to be particularly effective if it is approximately 90% of the length of one mower blade, and of course, positioned at the rear center of the housing.

Although this invention has been illustrated and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various changes, omissions and additions may be made without departing from the spirit and scope of the invention.