Rotary Cutting Assembly

Rotary cutting assemblies for cutting growing vegetation with whirling filament, and especially intended for household lawn trimming, are generally alluded to in the prior art including, inter alia U.S. Pat. Nos. 3,708,967 and 3,826,068. However, these and other related prior art vegetation cutting devices suffer from several noteworthy disadvantages and deficiencies. Many of the prior art devices are too cumbersome to permit convenient, comfortable and trouble-free use by the typical householder. Others are mechanically unreliable and difficult, if not impossible, to repair. Most are too expensive for the average householder to purchase by virtue of requiring a integrally incorporated special power plant, such as an electric motor designed exclusively for the rotary cutting assembly.

It is accordingly the general objective of the present invention to provide an improved and economical rotary cutting assembly of the whirling filament type and which overcomes many of the disadvantages and deficiencies of prior art structures. An important ancillary objective is to provide a rotary cutting assembly which does not require an elaborate specially-designed powering means, but rather can be simply powered as by a conventional portable powered drill chuck which is already possessed by the householder for other purposes, e.g. a household drill, etc.

With the above and other objects and advantages in view, which will become apparent as this description proceeds, the vegetation rotary cutting assembly herein generally comprises: an elongate lineal shaft extending along a longitudinal vertical-axis, the shaft having a bottom-end and also a top-end for removable insertion into a portable-held powered chuck for rapidly rotating the shaft around its vertical-axis; a disc-like base-plate co-rotatably associated with the shaft nearer its bottom-end and having a peripheral-edge remotely surrounding the shaft and lying within a horizontal plane; a convolutely coiled supply of cutting filament located adjacent the base-plate and surrounding the shaft vertical-axis; at least one retainer means attached to the base-plate for removably securing successive leadward portions of the wearable filament radially outwardly from the vertical-axis and base-plate peripheral edge and in cutting relationship to growing vegetation; axial confinement means for maintaining the coiled stored filament longitudinally confined toward the base-plate; and gravimetric balancing means to ensure that the center-of-mass for the assembly head portion (e.g. combination of base-plate, confinement means, filament, and retainer means) is located substantially at the vertical-axis.

In the drawing, wherein like characters refer to like parts in the several views, and in which:

FIG. 1 is a elevational view of a representative embodiment of the rotary cutting assembly of the present invention;

FIG. 2 is a detail elevational view of FIG. 1;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a sectional plan view taken along line 4-4 of FIG. 2;

FIG. 5 is a top plan view of a preferred embodiment base-plate component;

FIG. 6 is a bottom plan view of a preferred embodiment for the axial confinement means component; and

FIG. 7 is a detail elevational view in section showing the FIGS. 5 and 6 components in assembled relationship at the assembly head end.

As is indicated in the FIGS. 1 and 2 elevational views, the rotary cutting assembly "R" generally comprises an elongate lineal shaft 10 extending along a vertical-axis 9. The longitudinally extending shaft 10 has a top-end 11 for removable insertion into a portable operator-held powered chuck "C", such as typified by a powered conventional hand-drill "B", whereby the shaft 10 is rapidly powerably rotatable about its vertical-axis 9. Co-rotatably associated with shaft 10 near its bottom-end 12 is a disc-like base-plate 20 which has adjacent thereto a convolutely coiled supply of tough flexible filament 50. Successive leadward portions 52-53 of filament 50 are extendable radially outwardly of axis 9 and base-plate 20 to cut growing vegetation at the earth's surface "G" as shaft 10 and base-plate 20 together rotate upwards of 1800 rpm about vertical-axis 9. Preferably, the length of shaft 10 is within the range of some 12 to 18 inches so that the standing operator (holding powering means "B") may be able to accomplish the vegetation cutting task in comfortable non-stooping posture. However, because of the lengthy distance from powering plant "B" to the rapidly whirling cutting head (e.g. 20,30,50), apparatus "R" requires gravimetric balancing means to ensure that the cutting head center-of-mass is located substantially at axis 9. In this vein, base-plate 20 and axial confinement means 30 are each geometrically symmetrical about axis 9. As the vegetation cutting proceeds over extended time periods, leadward portions of the wearing filament need to be periodically fed radially outwardly from supply 50 which is coiled about axis 9, each successive filament leadward portion 52-53 being removably secured to base-plate 20 with suitable retainer means e.g. 25. Thus, the typical householder might utilize an electrically ("P") powered handdrill "B" having chuck "C" for powering assembly "R" which cuts growing vegetation at "G" with expendably wearable tough whirling filament 52-53.

Elongate lineal shaft 10 extending longitudinally lengthily along vertical-axis 9 is preferably of non-circular cross-sectional shape, including near top-end 11 and bottom-end 12 to promote secure co-rotatable engagement with rotating chuck "C" and with the downwardly remote cutting head (e.g. 20,30). Uniform polygonal shapes and sizes are preferred for the shaft cross-section, such as the hexagonal shape seen in FIG. 4.

Disc-like base-plate 20 is co-rotatably associated with shaft 10 nearer bottom-end 12 and substantially perpendicular to axis 9. Base-plate 20 includes a peripheral-edge 20A lying within a horizontal plane, periphery 20A being herein of circular geometric shape with axis 9 at the geometric center. The base-plate includes a pair of surfaces extending transversely of axis 9, including a lower-surface 22 (herein of frusto-spheroidal shape) and an uppersurface 21 (herein defining a horizontal plane perpendicular to axis 9).

Attached to the base-plate and extending upwardly from that surface nearer the coiled filament supply 50 is suitable retainer means (e.g. 25) for removably securing a filament leadward portion 52 to the base plate, the retainer means being located nearer the base-plate peripheral-edge 20A than to vertical-axis 9. Desireably, there is a plurality of retainer means and (consistent with gravimetric balancing means) spaced at substantially equal intervals about and like distances radially from vertical-axis 9, whereby alternate positions for the filament leadward portions 52-53 are possible as indicated in FIG. 4 phantom line.

The preferred type base-plate component 20, depicted alone in FIG. 5, comprises a central circular hub 23 surrounding axis 9 with a plurality of radial horizontal ribs 23A (spaced at equal angles about axis 9) extending outwardly from hub 23 toward annular periphery 20A. Ribs 23A and hub 23 are located above frustro-spheroidal lower-surface 22 and together are herein co-planar at base-plate upper-surface 21. Base-plate 20 is centrally perforate (22A) along axis 9, hole 22A being surrounded by hub 23. The horizontal base of hub 23 above lower-surface 22 is provided with a horizontally transversely slotted portion 24 which registers with hole 22A. Preferably, the base-plate and the retainer means (25) are together singularly constructed of a hard resinous structural material. For example, each retainer means herein desireably comprises an L-shaped boss 26 and lug 27 each upstanding from plane 21, the horizontal distance between boss 26 and lug 27 being sufficiently close to permit a tight frictional manually-pressed fit therebetween for successive filament radial leadward portions 52.

There are axial confinement means (30-31) for maintaining the stored filament (which is coiled about axis 9) longitudinally confined toward the rotating base-plate 20, and herein at its upper-surface 21. Moreover, the axial confinement means is co-rotatable with the shaft (10) and the base-plate (20). Herein, the preferred confinement means comprises a singly-flanged (31) spool 30 having its upright collar 35 surrounding axis 9. The periphery of horizontal flange 31 surrounds axis 9 and collar 35, but not base-plate edge 20A. Consistent with gravimetric balancing, the periphery of flange 31 is herein geometrically symmetric about axis 9 such as circular with axis 9 at the geometric center. The coiled stored portion of filment 50 surrounds circular collar 35 whereby transverse flange 31 provides axial confinement means of coil 50 toward base-plate 20. The filament knotted trail portion 51 passes downwardly through flange aperture 39. Spool 30 is herein provided with an axial bore 31A of non-circular cross-sectional shape, such as hexagonal to match shaft 10, to provide a co-rotatable relationship therewith.

In order to provide the necessary co-rotatable relationship between the flange and base-plate, it would be possible inter alia to integrally fabricate spool 30 with base-plate 20. However, as indicated in FIG. 7, for embodiment "R" shaft 10 does itself extend downwardly into base-plate 20. Rather, the lower-end of spool collar 35 is provided with a horizontally extending upright shoulder 34 which extends mateably downwardly into base-plate slot 24. A threaded fastener, such as screw 40, passes upwardly through baseplate hole 22A, and thence along axis 9 into removable threaded engagement with the shaft bottom-end 12 thereby removably and securely holding spool shoulder 34 within base-plate slot 24. Accordingly, when so removably assembled for cutting vegetation at 53, base-plate 20 and spool 30 are rendered co-rotatable with shaft 10. After the entire filament coil 50 has become expended after having radially withdrawn therefrom numerous successive leads 52-53 for cutting vegetation, a fresh coiled filament supply is installed between the confinement flange 31 and base-plate 20 simply by temporarily removing screw 40.

From the foregoing, the construction and operation of the rotary cutting assembly will be readily understood and further explanation is believed to be unnecessary. However, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction shown, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the appended claims.