referring now to fig1 there is shown a top plan view of one particular mulching attachment 10 structured in accord with the principles of the present invention . the mulching attachment 10 of fig1 includes a generally planar disc - shaped member 12 which has a plurality of fan vanes 14 radially disposed thereupon . the mulching attachment 10 further includes a mulcher blade assembly 16 disposed about the circumference of the disc - shaped member 12 and including a number of mulching blades 18 thereupon . as depicted , the mulcher blade assembly 16 is fabricated as a separate member which is affixed to the disc - shaped member 12 by bolts 20 . it will also be noted that the mulcher attachment 10 includes a central opening 15 configured to mount the attachment onto the drive shaft of a lawn mower . in operation , the entire mulching attachment 10 is rotated as a unit by the lawn mower motor and the fan vanes 14 provide a radial flow of air across the disk . it should be noted that by &# 34 ; radial flow of air &# 34 ; is meant a flow of air which passes across the face of the disc - shaped member 12 to the outer circumference thereof . it should also be noted that while the fan vanes 14 of the fig1 embodiment are shown as being generally disposed along the radii of the disc 12 , it may be advantageous in some instances to dispose the vanes in other orientations , as for example at angles to the radii . it will also be appreciated that other fan means , such as a propeller type fan or a squirrel cage fan , may be similarly employed in the present invention provided that the proper radial flow of air is established . the fan vanes 14 , in this embodiment , are formed by captive tabs partially cut from the disc - shaped member 12 and bent out of the plane thereof . this is a simple method for providing fan vanes although it will be appreciated that in some instances the fan may be fabricated as a separate member which is affixed to the disc - shaped member . the radial flow of air carries grass clippings , leaves and other plant waste to the mulching blades 18 which serve to finely chop or macerate the plant material . the blades 18 , as will be explained in greater detail hereinbelow , define a plurality of relatively small openings therebetween and these openings constrain plant material within the mulcher 10 until such time as it is finely chopped . in the depicted embodiment , the mulcher blades 18 are shown as being inclined into the interior of the mulching attachment , although it will be appreciated that various other blades , designs and dispositions may be similarly employed . referring now to fig2 there is shown a cross - sectional view of the mulcher attachment 10 of fig1 taken along lines ii -- ii . the fig2 illustration better shows the fan vanes 14 and the manner in which they project from the disc - shaped member 12 . the fig . also illustrates clearly , a portion of the mulcher blade assembly 16 , showing one of the mulcher blades 18 and a bolt 20 which mounts a flange portion 22 of the mulcher blade assembly 16 to the disc - shaped member 12 . it will be appreciated that means other than a bolt , such as rivets , clamps , clips , welds and the like may be similarly employed . it will also be appreciated that in some instances , the disc - shaped member 12 and mulcher blade assembly 16 may be fabricated as a single unitary unit ; although , it has been found that by manufacturing the mulcher attachment as a two component item , replacement of the mulcher blades 18 is greatly facilitated . referring now to fig3 there is shown a portion of a mulcher blade assembly 16 structured in accord with the principles of the present invention . this assembly is configured as a generally cylindrical member having a plurality of mulcher blades 18 and also including a mounting flange 22 for attachment of the assembly 16 to the disc - shaped member , as noted hereinabove . in the fig3 embodiment , the mulcher blades 18 are fabricated by cutting captive tabs from the cylindrical wall and turning these tabs inward . optionally , the leading edges of the tabs may be sharpened and / or hardened . it will also be noted that in the illustrated embodiment , the tabs are cut so as to extend along the entire length of the cylindrical wall down to the flange 22 . in other embodiments , the tabs may be formed from only a portion of the wall so as to leave a top and / or a bottom , reinforcement rail on the assembly 16 . it should be noted that the configuration of the blade assembly 16 of fig3 provides a number of open spaces between the blades and these spaces permit egress of chopped vegetable debris . it has been found that , to some degree , the size of these openings will influence the degree of fineness with which the vegetation is chopped . relatively large openings will permit coarsely chopped materials to exit whereas relatively small openings will cause vegetation to be retained longer and hence chopped finer . referring now to fig4 there is shown a cut - away view of one configuration of rotary lawn mower including the mulcher attachment of the present invention therein . the fig4 mower includes a mower blade 28 disposed within a blade housing 30 and rotated by a drive shaft 32 which is turned by a motor , ( not shown ). in the fig4 embodiment , the mulcher attachment 16 is disposed within a particularly configured upper portion of the mower blade housing and in general it is anticipated that this particular embodiment will be a factory - manufactured item . as is shown in the fig ., the mulcher attachment 16 includes fan vanes 14 and mulcher blades 18 supported by a disc - shaped member 12 . the mulcher attachment 16 is mounted in a top portion of the funnel - shaped housing so as to create a suction which will draw grass clippings and leaves upwards into the housing and radially convey those clippings to the mulcher blade 18 . the discharge chute 34 of the mower is placed so that all clippings must pass through the mulcher attachment 16 before exit . referring now to fig5 there is shown another embodiment of the present invention wherein the mulching attachment 16 of the present invention is disposed upon a preexisting rotary - type lawn mower . in such mounting , the mower blade housing 36 is not specifically configured to accommodate the attachment . since it is desirable that substantially all of the grass clippings and other debris be passed through the mulching attachment ; and since in the fig5 embodiment the housing is not funnel - shaped , it is necessary that the mulching attachment be of a diameter corresponding to that of the mower blade 28 . in this embodiment , the mulching attachment 16 is generally similar to that previously described but for diameter . the mulching attachment 16 , in the fig5 embodiment , creates a radial flow of air across the disc - shaped member 12 thereof , which flow of air carries grass clippings and other debris to the mulching blades 18 , from which they exit to the discharge chute 34 as in the previous embodiment . in order to retrofit an existing lawn mower with the mulching attachment 16 of the present invention , it may be necessary to include a mounting collar or similar item of hardware for purposes of retaining the mulching attachment 16 on the motor shaft 32 of the mower . fig5 a depicts one such mounting collar 38 , which is configured to include a central socket 40 adapted to receive the motor shaft 32 and further including a set screw 42 for locking the collar 38 against the shaft 32 . the mounting collar 38 is either fabricated to be integral with the mulching attachment or may be keyed so as to engage the central aperture thereof and prevent the attachment from slipping on the shaft . obviously , various other attachment means will be readily apparent to one of skill in the art and may be adapted for the present invention . in particular embodiments , the mulching attachment of the present invention may be fabricated from metal stock such as steel or non - ferrous metals . ideally , the material from which the mulching attachment is fabricated should be relatively durable , easy to shape and fairly light in weight . also , the mulcher blades should be fairly hard so as to resist damage by twigs , stones and like material . if the mulching attachment is fabricated as a dual - membered unit having a separate disc and blade assembly , it is possible to employ a relatively hard material such as hardened steel and the like for the mulching blades while utilizing a lower cost and / or easier to fabricate material such as mild steel for the disc - shaped member and fan blades . obviously , many other materials , including high strength polymers such as glass - filled polyamides and the like may be employed to fabricate all or part of the assembly . obviously , many variations of the present invention may be prepared in accord with the teachings herein . for example , while the blade assembly is shown as a right cylindrical member extending at approximately 90 degree angles to the disc - shaped member , the blade assembly may in some instances be inclined at an angle greater or less than 90 degrees to the plane of the disc - shaped member and for this reason it is to be understood that the &# 34 ; generally cylindrical &# 34 ; mulcher blade assembly is meant to include all such variants wherein the mulcher blade assembly is disposed at some angle to the disc - shaped member . it is also to be understood that the mulcher blades themselves may be configured other than is exactly shown herein . for example , the leading edges of the blades may be serrated , saw - toothed or otherwise configured and the blade assembly may include blades of various sizes and / or blades disposed in staggered relationship . all such embodiments are considered within the general scope of the present invention insofar as they include a plurality of blades disposed about the circumferential periphery of a generally planar member and operative in cooperation with fan means to mulch vegetable waste . in light of the foregoing , it is apparent that the preceding drawings , discussion and description are merely meant to be illustrative of particular embodiments of the present invention and are not meant to be limitations upon the practice thereof . it is the following claims , including all equivalents , which define the scope of the invention .
a mulching attachment for a lawn mower includes a disc - like base having a fan associated therewith for establishing a radial flow of air thereacross . the mulching attachment further includes a cylindrical blade assembly disposed around the periphery of the disc and including a number of spaced apart blades operative to finely chop vegetation into mulch and to discharge the mulch through openings between the blades . the mulching attachment may be factory installed or retrofitted onto existing lawn mowers .