Patent Description:
Rotary mowers which employ a cutting deck to house multiple rotary cutting blades that rotate about vertical axes are well known for cutting grass. The deck is carried by a traction frame for propelling the deck over the ground and for powering the cutting blades. The traction frame may comprise a ride on unit which carries the operator in a sitting and/or standing position during operation of the mower. Alternatively, the traction frame may comprise a walk behind unit in which the operator walks on the ground behind the traction frame during operation of the mower. In some cases, the traction frame may be remotely controlled by an operator or may operate in an autonomous manner under the control of an electronic microprocessor based controller.

The cutting blades carried in the deck are typically staggered fore-and-aft relative to one another. This permits the orbits of the blades to avoid hitting one another but to be slightly overlapped with one another to allow the blades to collectively cut a swath of grass that is wider than the swath cut by any single blade. Alternatively, the blades may be arranged directly side-by-side relative to one another with the orbits of the blades slightly overlapping to again cut a swath of grass that is wider than the swath cut by any single blade. However, in this direct side-by-side arrangement of the blades, the rotation of the blades must be timed to prevent the blades from hitting one another as they rotate.

The grass clippings generated by the operation of the blades may be discharged from the cutting deck in various modes. For example, the side discharge mode throws the clippings laterally from the deck through a side discharge opening located in a side wall of the deck. The mulching mode comprises the discharge of the clippings downwardly into the cut grass swath through an open bottom face of the deck. Some decks may also include a rear discharge mode in which the clippings are thrown rearwardly through a rear discharge opening. One or more of these modes may be incorporated into any given deck as desired.

In known rotary cutting decks having multiple discharge modes, e.g., both side discharge and mulching modes, some structure is normally provided for blocking the side discharge opening when the user wishes to operate in the mulching mode. This structure varies but often includes a selectively pivotal plate or door that closes the side discharge opening during operation in the mulching mode. In some cases, a closure member must be manually installed in the side discharge opening as part of a mulching kit rather than using a pivotal plate or door. In other cases, the pivotal plate or door is permanently installed in the deck and is swung between open and closed positions by the operator using a manually operable mechanical linkage or an electric motor kit. Regardless of how one closes the side discharge opening, the need for some type of closure and the operation or installation of such closure increases the expense of manufacturing the deck. Moreover, when a mulching kit is used that must be manually installed to mulch and must then be manually removed for side discharge, the burden on the operator in shifting between the different modes is significant.

Rotary lawn mowers are e.g. known from <CIT> and <CIT>.

Accordingly, there is a need in the art to provide a rotary cutting deck that is optimized for operation in the side discharge and mulching modes with the operator having the ability to quickly and easily shift between the modes. This invention is directed to satisfying this need.

The invention relates to a rotary lawn mower which comprises a cutting deck comprising a top wall and a peripheral skirt extending downwardly from the top wall. The top wall and peripheral skirt form a cutting chamber having an open bottom face. The cutting chamber has a discharge opening located at least partially in the peripheral skirt of the deck for allowing grass clippings to exit from the cutting chamber. At least one cutting blade is located within the cutting chamber with the at least one blade being rotatable about a substantially vertical axis of rotation. Each end of the at least one blade comprises a front cutting edge and a rear cutting edge. A reversible blade drive system is provided for allowing a user to select either a discharge mode of operation in which the at least one blade rotates in a first direction about the axis of rotation with the front cutting edges being leading edges and the rear cutting edges being trailing edges or a mulching mode of operation in which the at least one blade rotates in a second opposite direction about the axis of rotation with the rear cutting edges being leading edges and the front cutting edges being trailing edges. The cutting chamber has a substantially vertical guide wall therein adjacent the discharge opening. The guide wall presents an outward side to grass clippings that have been generated in the discharge mode to direct such clippings outwardly through the discharge opening. The guide wall further presents an inward side to grass clippings that have been generated in the mulching mode to direct such clippings inwardly in the cutting chamber away from the discharge opening.

This invention will be described more fully in the following Detailed Description, when taken in conjunction with the following drawings, in which like reference numerals refer to like elements throughout.

<FIG> illustrates a rotary mower <NUM> equipped with one embodiment of a rotary cutting deck <NUM> according to this invention. Mower <NUM> has a traction frame <NUM> that is supported for rolling over the ground by a pair of front caster wheels <NUM> and by a pair of rear drive wheels <NUM>. A prime mover (not shown) or other source of power is carried on traction frame <NUM> to self-propel mower <NUM> by rotating drive wheels <NUM> and to provide power to rotate various rotary cutting blades <NUM> carried on deck <NUM>. Deck <NUM> is mounted to traction frame <NUM> in a manner well known in the art in a mid-mount position between front wheels <NUM> and rear wheels <NUM>.

Traction frame <NUM> preferably includes a seat <NUM> for carrying an operator in a seated position. Alternatively, traction frame <NUM> could be a stand-on type in which the operator is carried in a standing position on a rear foot platform provided on traction frame <NUM>. In addition, traction frame <NUM> may also be a walk behind frame, a remotely controlled frame, or an autonomous, self-guiding frame. Thus, the type of mower <NUM> to which deck <NUM> is attached is not important to this invention.

Referring now to <FIG>, deck <NUM> comprises a top wall <NUM> and a peripheral skirt <NUM> extending downwardly for a short distance from the outer edges of top wall <NUM>. Skirt <NUM> is substantially continuous except for a first side discharge opening <NUM> shown in <FIG> provided in one of the lateral side walls of skirt <NUM>. A typical side discharge chute <NUM> having a downwardly facing U-shape is attached to deck <NUM> and extends outwardly from first opening <NUM> to shield bystanders from the flow of grass clippings or any thrown objects which are being discharged from deck <NUM>. The bottom face of deck <NUM> is open towards the ground. Skirt <NUM> has a substantially linear front wall <NUM> which mounts a pair of laterally spaced anti-scalp wheels or rollers <NUM>.

As best shown in <FIG>, the underside of deck <NUM> carries two laterally spaced blades <NUM> beneath top wall <NUM> and within skirt <NUM> of deck <NUM>. Deck <NUM> has a scalloped rear wall having a pair of semicircular sections <NUM> which partially surround the rear portions of the orbits of blades <NUM>. In the embodiment shown herein, blades <NUM> are staggered fore-and-aft relative to one another with the inner portions of the orbits of blades <NUM> slightly overlapping one another. Thus, blades <NUM> will cut a single, unbroken swath of grass that is wider than the swath that would have been cut by either blade <NUM> alone. Alternatively, blades <NUM> could be arranged directly side-by-side with the inner portions of the orbits of blades <NUM> slightly overlapping one another. However, in this alternative blade arrangement, a timed drive system would be required to rotate blades <NUM> out of phase with one another to ensure that blades <NUM> never hit one another in the overlap region.

Preferably, blades <NUM> are powered by individual electric motors <NUM> which are powered by a source of electric power carried on traction frame <NUM>. Thus, motors <NUM> are reversible at the click of a switch to change the direction of rotation of blades <NUM> without there being any cost incurred other than for the switch. While electric motors are disclosed, hydraulic motors could also be used supplied by pressurized hydraulic oil generated by a hydraulic system on traction frame <NUM> along with a valve to reverse the direction of oil flow when so desired. In addition, a reversible belt and pulley drive system or some other reversible mechanical drive system could be used as well.

Referring now to <FIG>, each blade <NUM> has an elongated rectangular shape with opposite ends. Each blade <NUM> is identical. Thus, a description of one blade <NUM> will suffice to describe the other blade <NUM>.

Each end <NUM> of blade <NUM> is double edged with a sharpened cutting edge A located on a front face and a sharpened cutting edge B located on a rear face. The lengths of cutting edges A and B are substantially the same as one another and may comprise about two to four inches. Ends <NUM> of blades <NUM> are also inclined slightly downwardly. Thus, cutting edges A and B are not purely horizontal relative to the horizontal central section of blade <NUM>, but incline slightly downwardly relative to the central section <NUM> of blade <NUM> as they extend outwardly at an angle of about <NUM>°.

Blade <NUM> has an upwardly extending ridge <NUM> between cutting edges A and B. Ridge <NUM> has a crest <NUM> which is generally parallel to cutting edges A and B. However, ridge <NUM> is asymmetric relative to cutting edges A and B with crest <NUM> of ridge <NUM> being closer to cutting edge A than crest <NUM> is to cutting edge B. As a result, the sloped transition between cutting edge A and crest <NUM> necessarily forms a short and steeply inclined face C. Correspondingly, the sloped transition between cutting edge B and crest <NUM> forms a face D that is necessarily longer and substantially more gently inclined as a result.

In one embodiment of blade <NUM>, the angle α of inclination of face C is approximately <NUM>° at the tip <NUM> of blade <NUM> while the angle β of face D is approximately <NUM>° at blade tip <NUM>. In this embodiment, face C is approximately three times steeper than face D at blade tip <NUM> over the same rise of crest <NUM>. The rise of crest <NUM> gradually decreases as ridge <NUM> extends inwardly from blade tip <NUM> with ridge <NUM> disappearing at radial inner ends of cutting edges A and B.

Referring now to <FIG>, first opening <NUM> is of the general size and shape typically found on prior art rotary mowers for the passage of grass clippings in a side discharge mode of operation. However, in this invention, a flow director <NUM> is mounted within and remains within first opening <NUM> during operation of mower <NUM>. Flow director <NUM> is preferably molded as a single piece from a relatively hard and durable plastic material and is mounted in any suitable fashion, e.g. by threaded fasteners such as bolts or screws or by bungee cords or some other structure which does not require the use of tools, to the portions of deck <NUM> adjacent first opening <NUM>. This is done primarily for the sake of convenience and cost savings. However, the geometry and functions provided by flow director <NUM> could alternatively be designed as part of deck <NUM> and would thus be built as an integral part of deck <NUM> during the manufacture of deck <NUM>.

As further shown in <FIG> and <FIG>, flow director <NUM> provides a second side discharge opening <NUM> at a front end of flow director <NUM> which second opening effectively replaces first opening <NUM>. Second opening <NUM> is located at the exit or grass clippings discharge end of front wall <NUM> of deck <NUM> when deck <NUM> is operating in the side discharge mode. However, second opening <NUM> is reduced in height and length compared to first opening <NUM>.

The rest of flow director <NUM> downstream of second opening <NUM> is solid and fills in the rest of first opening <NUM> with downstream being taken with reference to the direction of rotation of the blade <NUM> adjacent flow director <NUM> when deck <NUM> is operating in the side discharge mode. As flow director <NUM> extends downstream away from second opening <NUM> when deck <NUM> is operating in the side discharge mode, it forms a generally L-shaped, curved baffle <NUM> having a substantially horizontal floor <NUM> and a substantially vertical, upwardly extending interior guide wall <NUM>. The curved guide wall <NUM> progressively decreases in height and floor <NUM> progressively decreases in width as flow director <NUM> extends downstream away from second opening <NUM> as best shown in <FIG>. Eventually, baffle <NUM> disappears adjacent a rear end of flow director <NUM> with the rear end of guide wall <NUM> being radially outboard of the front end of guide wall <NUM>. Blade <NUM> adjacent flow director <NUM> is positioned to rotate beneath floor <NUM> of baffle <NUM> with blade <NUM> never hitting or striking any portion of flow director <NUM>.

Referring now to <FIG> illustrating the side discharge mode of operation, second opening <NUM> in flow director <NUM> is always open to the passage of the grass clippings being generated by blades <NUM>. Each blade <NUM> is rotated in the same counter-clockwise direction CCW so that cutting edges A are cutting grass. The steeply inclined faces C behind cutting edges A act as effective sails or vanes for creating an air flow within deck <NUM> that is directed along the inside of front wall <NUM> of skirt <NUM> of deck <NUM> in the direction of the arrows E in <FIG>. This air flow E feeds substantially directly into second opening <NUM> provided by flow director <NUM>. Thus, the grass clippings generated by cutting edges A and B during the counter-clockwise CCW rotation of blades <NUM> are quickly and efficiently thrown through second opening <NUM>. Once the grass clippings pass through second opening <NUM>, the grass clippings flow along floor <NUM> and guide wall <NUM> of baffle <NUM> and are progressively forced and ejected to the side of deck <NUM> by the outward curvature of the outer face of guide wall <NUM> of baffle <NUM> as further shown by the arrow E in <FIG>.

Referring now to <FIG> and <FIG>, the same L-shaped baffle <NUM> described above in flow director <NUM> provides an opposite function in the mulching mode of operation. Now, the inner face of vertical guide wall <NUM> of baffle <NUM> provides an inwardly curved surface taken with respect to the direction the grass clippings are being circulated in the mulching mode of operation.

Deck <NUM> can be easily placed into its mulching mode of operation by reversing the direction of rotation of blades <NUM> so that blades <NUM> both rotate in a clockwise direction CW in <FIG>. In this direction, cutting edges B of blades <NUM> are the edges which are cutting the grass. The gently inclined slope of the face D that follows the edges B is also a relatively ineffective air flow generating sail. Moreover, the grass clippings entrained in the lessened air flow generated by the faces D, i.e., primarily the clippings from the blade <NUM> closest to flow director <NUM> as the clippings generated by the other blade <NUM> are not circulated near flow director <NUM>, are directed inwardly towards the middle of deck <NUM> by the increasingly inward protrusion of the curved inner face of guide wall <NUM> of baffle <NUM> as shown by the arrow F in <FIG> and <FIG>. In addition and as best shown in <FIG>, the curvature of the semi-circular portion <NUM> surrounding the other blade <NUM> also acts to direct clippings from such blade back towards the middle of deck <NUM> as shown by arrow G in <FIG>. Thus, with the reversal in direction of the bidirectional blades <NUM> to the clockwise CW direction in <FIG> required for mulching, the grass clippings will substantially be directed inwardly and drop out of deck <NUM> through the open bottom face of deck <NUM> due to reduced air flow near the center of blades <NUM>. Such grass clippings act as mulch in the cut grass swath rather than being thrown out through second opening <NUM> in flow director <NUM>.

Referring again to <FIG> and when side discharge is desired, the counter-clockwise direction CCW of rotation of blades <NUM> is selected. The grass clippings being generated by blades <NUM> are thrown along front wall <NUM> of skirt <NUM> and will pass through second opening <NUM> provided by flow director <NUM> and then be ejected laterally under discharge chute <NUM>. When mulching is desired, a clockwise CW direction of rotation of blades <NUM> in <FIG> is selected. The grass clippings then being generated by blades <NUM> will be recirculated within deck <NUM> until they are driven downwardly through the open bottom face of deck <NUM>. During mulching the clippings are simply not directed at second opening <NUM> provided by flow director <NUM> and thus do not enter in any significant number the side discharge path provided by flow director <NUM>.

Accordingly, switching between side discharge and mulching modes of operation is as easy as activating a switching device of some type to change the direction of rotation of the bidirectional, double edged blades. The convenience in which an operator can switch or toggle between side discharge and mulching modes of operation provides the operator with greater ease of operation. The operator no longer needs to manually install a mulching kit to use during mulching with the operator having to remove the mulching kit when side discharge is desired. In decks where structure is carried on deck <NUM>, such as pivotal doors or plates that can be swung to a closed position to block the side discharge opening to enter into the mulching mode, the operator no longer needs to activate the linkages that control such doors or plates. Moreover, such movable and separately activated blocking structure is no longer required.

Referring now to <FIG>, an alternative blade <NUM> is depicted which may be used in place of each blade <NUM> described herein. Like blade <NUM>, each blade <NUM> has an elongated rectangular shape with opposite ends. Each blade <NUM> is identical. Thus, a description of one blade <NUM> will suffice to describe the other blade <NUM>.

Each end <NUM> of blade <NUM> is double edged with a sharpened cutting edge A' located on a front face and a sharpened cutting edge B' located on a rear face. The lengths of cutting edges A' and B' are substantially the same as one another and may comprise about two to four inches. Ends <NUM> of blades <NUM> are also inclined slightly downwardly. Thus, cutting edges A' and B' are not purely horizontal relative to the horizontal central section of blade <NUM>, but incline slightly downwardly relative to the central section <NUM> of blade <NUM> as they extend outwardly at an angle of about <NUM>°. A mounting hole <NUM> or any other suitable mounting is provided in central section <NUM> of blade <NUM> to allow blade <NUM> to be bolted or otherwise secured to the vertical downwardly extending drive shaft of one of the drive motors <NUM>.

Each end <NUM> of blade <NUM> has a radial opening or slot <NUM> located between cutting edges A' and B'. Each slot <NUM> extends completely through the thickness of blade <NUM>. Each slot <NUM> also extends radially inwardly from the tip of each end of blade <NUM> for a length approximately equal to the length of cutting edges A' and B'.

An upwardly extending, airflow generating sloped face C' is formed in each end of blade <NUM> by an upwardly bent portion of blade <NUM> that is inboard of cutting edge A'. Similarly, an upwardly extending, airflow generating sloped face D' is formed in each end of blade <NUM> by an upwardly bent portion of blade <NUM> that is inboard of cutting edge B'. Sloped faces C' and D' are substantially identical to one another. For example, each sloped face C' or D' is inclined upwardly at the same angle Θ of approximately at least <NUM>° or more. In addition, each sloped face C' or D' has a constant height relative to its adjacent cutting edge A' or B' between a radially outer end of each sloped face C' or D' and a radially inner end of each sloped face C' or D'. Accordingly, sloped faces C' and D' are symmetrical relative to one another along opposite sides of radial slot <NUM>.

The Applicants currently believe that the radial slots <NUM> on each end of blade <NUM> extending as shown in <FIG> allow air to flow more easily through each end of blade <NUM>. This is believed to provide enhanced lift by sloped faces C' or D', each of which acts as an airflow generating sail, when cutting edge A' or B', respectively, is the leading edge of blade <NUM> taken with respect to the direction of rotation. While cutting blade <NUM> described earlier herein also provides better performance in this invention over standard blades known in the art, it is currently thought that cutting blade <NUM> may provide even better performance than cutting blade <NUM>. Rather than use a radial slot <NUM> on each end <NUM> of blade <NUM>, one or more openings or holes could be formed or drilled in each end <NUM> of blade <NUM> to permit the passage of air through each end <NUM> of blade <NUM>.

Various modifications of this invention will be apparent to those skilled in the within the scope of the claims.

For example, while the blade tip configurations for the tips of blades <NUM> or <NUM> and the flow director <NUM> are preferably used together in the same deck <NUM>, each could be used in deck <NUM> or other rotary cutting decks without using the other. Moreover, the blade tip configurations for the tips of blades <NUM> or <NUM> and the flow director <NUM> could be used together or individually in a rotary cutting deck having a single blade <NUM> or <NUM>, a rotary cutting deck having more than two blades <NUM> or <NUM>, and/or a rotary cutting deck having an additional third mode of operation comprising a rear discharge mode for throwing the grass clippings rearwardly from deck <NUM>.

Claim 1:
A rotary lawn mower (<NUM>), which comprises:
(a) a cutting deck (<NUM>) comprising a top wall (<NUM>) and a peripheral skirt (<NUM>) extending downwardly from the top wall (<NUM>), the top wall (<NUM>) and peripheral skirt (<NUM>) forming a cutting chamber having an open bottom face, the cutting chamber having a discharge opening (<NUM>) located at least partially in the peripheral skirt (<NUM>) of the cutting deck (<NUM>) for allowing grass clippings to exit from the cutting chamber;
(b) at least one cutting blade (<NUM>;<NUM>) located within the cutting chamber with the at least one cutting blade (<NUM>;<NUM>) being rotatable about a substantially vertical axis of rotation, each end of the at least one cutting blade (<NUM>;<NUM>) comprising a front cutting edge (A;A') and a rear cutting edge (B;B');
(c) a reversible blade drive for allowing a user to select either:
(i) a discharge mode of operation in which the at least one cutting blade (<NUM>;<NUM>) rotates in a first direction about the axis of rotation with the front cutting edges (A;A') being leading edges and the rear cutting edges (B;B') being trailing edges, or
(ii) a mulching mode of operation in which the at least one cutting blade (<NUM>;<NUM>) rotates in a second opposite direction about the axis of rotation with the rear cutting edges (B;B') being leading edges and the front cutting edges (A;A') being trailing edges;
the rotary lawn mower (<NUM>) being characterized in that the cutting chamber has a substantially vertical guide wall (<NUM>) therein adjacent the discharge opening, the vertical guide wall (<NUM>) presenting an outward side to grass clippings that have been generated in the discharge mode to direct such clippings outwardly through the discharge opening (<NUM>), and the vertical guide wall (<NUM>) further presenting an inward side to grass clippings that have been generated in the mulching mode to direct such clippings inwardly in the cutting chamber away from the discharge opening (<NUM>).