Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to an improved device in the form of a
rotar~ head or attachment to the lo~er end of the driving shaft of the
motor (elec~ric or internal combustion~ of a conventional rotary lawn mower,
edger, tri~ner or the like, and principally readily portable hand-held type
lalYn mowing and edging tools.
Up until the past fe~ years, the rotary head, or cutting blade, of
rotary lawn mo~ers, edgers, and the like, have comprised a rotating metal
bar or the like, usually ~ith sharpened edges, which is rotated at sufficient
speeds to effect cutting of grass, ~eeds, or the like. However, such ro-
tating metal bars create and project dangerous missiles ~hich may strike theoperator or persons, or animals, adjacent the machine.
Because of the dangerous conditions created by the rotating head,
most la~Yn edging and trimning around trecs and the like, ~hich uould other-
~ise be damaged by the metal blades, must be done manually; and this is both
laborious and time consuming.
I am aware of certain developments ~hich include lawn mowing or
trimming devices comprising a disc-like head member arranged to be rotated
by a suitable prime mower and containing a spool ~hich is housed therein in
coaxial alignment with the shaft of the motor. A length of flexible non-
metallic line, usually monofilament fishing line, is coiled about the spool,hereby a free traveling end ~Yill be s~ung arcuately about to cut adjacent
vegetation in the manner of a flaii.
Certain of the prior art devices ~hich u~ilize monofilament fish-
ing line ~ill cut or trim grass and other light vegetation ~ith reasonable
effectiveness, and posses the additional advantage that they are much safer
to use than the more conventional metal-bar cutting blades in that they do
; not cause stones or other solid objects to be discharged in the dangerous
` manner earlier described, and are almost completely incapable of causing any
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significant injury to persons or pets struch by the flailing cutting string.
- On the other hand, the devices referred to immediately herein-
before are su~ject to certain disadvantages o~ a magnitude which severely
limit their practical value. In the first place~ they are largely effective
only to cut standing light-weight vegetation, being practically useless for
any other purpose. Secondly, they will only cut such vegetation if growing
relatively sparsely, and cannot effectively handle even light-w3ight vege-
:~ tation if it is in a rank condition.
The light-weight plastic cutting lines of the prior art devices
referred to are of relatively small diameter, and therefore are relatively
incapable of cutting any but the lightest and sparsest vegetation, which
prevents such deviGes from possessing much commercial value.
The disadvantages of th~ prior art, and especially the aforemen-
tioned devices which utilize monofilament fishing line can be overcome by
the present invention, and commercially acceptable embodiments of a vege-
tation cutter and the like are herein described which are not only fully cap-
; able of cutting vegetation under most operating co-nditions, but which are
also fully capable of other tasks completely beyond the capabilities of the
prior art devices of the same general type: such as cleaning dead leaves,
~O trash and other such debris from along fences, walls, and the trunks or stems
of trees and bushes. More importantly, however, is the fact that the em-
bodiments of the present invention are capable of operation with a much
lower brea~age rate for their cutting strings, ~ithout any sacrifice whatso-
ever of the safety features and the cutting advantages which will be more
f~llly described hereinafter.
Various attempts have been made to overcome the aforementioned
I~azardous conditions created with rotating rigid-type metal cutting blades,
most of which involved the utilization of some type of flexible flail ~h.ich
will have sufficient resiliency so as not to propel objects which are struck
at high velocities.
Resiliency itself is not sufficient to insure that the dangerous
conditions will not be created when rotation is effected at necessary cutting
speeds.
Another and great disadvantage of prior art cutting elements of the
type described, is that they are usually not provided with means for easy
replaceability in the event of wearing out, and they are usually quite time-
consuming to replace.
The present invention provides an attachment for the drive shaft of
a rotary lawn mower comprising, in combination, a rigid cylindrical sleeve,
an adjustably lengthwise compressible spool of slightly greater length disposed
in said rigid cylindrical sleeve, a supply of filament-type cu~ting line carried
by said spool, said rigid cylindrical sleeve having at least one aperture in the
sidewall thereof, and a tube communicating with and projecting externally from
the aforementioned aperture, whereby the outer end of said line may be threaded
through and made to adjustably project from the outer end of said tube.
The invention also provides an attachment for the vertically-extending
drive shaft of a rotary lawn mower, edger or trimmer comprising, in combination
(a) a centrally apertured, flexible and longitudinally compressible
spool;
~b) a rigid cylindrical housing of shorter length for said spool;
(c) upper and lower centrally apertured washers for contacting the
corresponding ends of said spool and said rigid cylindrical housing;
(d) an elongated centrally disposed adjustable bolt extending through
said spool, housing and washers and adapted for screw-threaded reception in a
screw-threaded recess in the lower end of the drive shaft; and
(e) a heavy-duty filament-type cutting strand wrapped around the
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-` spool so as to provide at least two free-travelling ends which extend outwardly
through relatively short radially disposed tubes which are mounted on the
periphery of said rigid cylindrical housing and in evenly spaced alignment with
communicating apertures in the sidewall of said rigid cylindrical housing;
(f) the diameter and composition oE said cen-trally apertured,
flexible and longitudinally compressible spool being such as to permit the
adjustment of said bolt and washers to preclude rotative movement between said
spool and said rigid cylindrical housing.
The difficulties which were experienced with the devices of the prior
art as described herein can be overcome by providing a relatively simple device
which very efficiently performs the desired cutting operation, is quickly and
easily adjustable, and which may be quickly and easily substituted for the usual
horizontally-extending metallic cutting bar of a conventional rotary lawn mower.
Preferably the attachment is durable in service and may be easily and inexpensive-
ly manufactured.
The foregoing and other advantages will become more readily understood
from the following description and annexed drawings wherein like reference
numerals designate like elements and wherein:
Figure 1 is an elevational view partly in section, which illustrates
the device of the invention as substituted for the horizontally extending blade
member of an otherwise conventional rotary lawn mower.
Figure 2 is &n enlarged view, partly in section, which has been taken
on the line 2-2 of Figure 1.
Figure 3 is a sectional view taken on the line 3-3 of Figure 2.
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Figure 4 is an exploded view of the centr~l elements of the showing
fFigure 2, as ~ill ~e more fully described hereinafter.
Figure 5 is a view which is similar in nature to that of Figure 2,
but illustrating a modification in the form of a dual-spool arrangement
which provides for increased storage of monofilament line.
Figure 6 is a sectional view taken along the line 6-6 of Figure 5.
Figure 7 is a perspective illustrating in further detail the dual-
spool arrangement of Figure 5,
and
Figure 8 is a perspective of a further embodiment.
As shown in Figure 1 of the drawings, the numeral 1 designates the
lower end of the vertically disposed driven shaft of an in~ernal combustion
engine or electric motor of a rotary mower 3 which may be entirely conven-
tional in design. As usual, the housing 4 of the rotary mower 3 is pro-
vided with an elevated opening or oulet 6 for discharging the cuttings of
the mower, frequently into a bag which is connected thereto
As in the case of practically all of the popular makes of rotary
mower 3, the lower extremity of the drivenshaft 1 is provided with a screw-
threaded recess 8 which is adapted to receive a relatively short bolt which
secures the usual horizontally-extending metallic cutting bar in place
~neither of which is shown herein).
According to the teachings of the present invention, the screw-
threaded recess 8 in the lower extremity of the driven shaft 1 of the rotary
mo~er receives, instead, the upper and screw-threaded end of an elongated
bolt 12 or holding in place the novel spool which is to be substituted for
the transversely extending metallic cutting bar of the earlier prior art
described hereinhefore.
More specifically, the spool assembly of the present invention com-
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prises an outer cyllndrical body 15 of suitable rigid or inflexible material.
This outer cylindrical body 15 comprises centrally-apertured flat-
tened ends 16; and the interior thereof is hollow and serves as a housing
for a line-receiving cone-shaped ~lexible spool 17, the sidewall o~ which is
continuously concave, as indicated at 18. As shown, the concavity 18 is on
a single and unvarying radius.
A flexible tube 20 extends through the rigid outer cylindrical body
15 adjacent its lower end and communicates with the correspondingly adjacent
portion of the continuously concave sidewall 18 of the flexible line-receiv-
ing spool 17. Another flexible tube 20 may be disposed directly opposite
on the cylindrical body 15; and the top of the rigid outer cylindrical body
15 of the novel spool assembly is shown as provided with a flat washer 2~
which contacts the lowermost extremity of the driven shaft 1 of the motor
and is provided with a central aperture through which the elongated bolt
12 extends, the upper end of the latter being screw-threaded, as earlier
described, to be received in the screw-threaded recess 8 in the motor shaft.
In so doing, the elongated bolt 12 extends axially through the
earlier described flexible line-receiving spool 17.
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A similar flat washer 25 contacts the bottom of the rigid outer
cylindrical body 15, and is provided with a central aperture through which
the lower end of the elongated bolt 12 extends.
The lowermost extremity of the elongated bolt 12 is provided with
the usual bolt-head 27 which permits upward pressure against the bottom of
the lower flat washer 25.
Nhen the bolt-head 27 is tightened, and the bottom flat washer 25
is moved against the bottom of the rigid outer inflexible cylindrical body
15 and the bottom of the cone-shaped flexible line-receiving spool 17. When
this is done the monofilament fishing line X passes through the flexible
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tube 20, and with the reduced friction effected thereby, the line will not
receive excessive friction at this point o-f stress while the mower or trim-
ming apparatus is in use.
As indicated in Figures S and 6, the flexible tube 20 may be con-
structed of two separable parts in the manner of a valve stem for tubeless
tires for automotive vehicles.
As the outer ends of the non-metallic line wear, replacement of
those portions thereof is necessitated; and this has long been a very big
problem ~ith the prior art line-receiving spools of which I am presently
aware; all of which require troublesome and time-consuming adjustment. In
addition, the line-receiving spools of the prior art are unnecessarily com-
plex and the cost of manufacture thereof unnecessarily high.
Due to the simplicity of the device of the present invention, when
-`` more line is needed, because of wear, etc., it is only nccessary to slightly
loosen the bolt-head 27, which will enable the rigid outer cylindrical body
.;~ 15 to become loose enough to similarly loosen the cone-shaped flexible spool
17, and permit the line X to be manually pulled through the latter to the
extent desired.
After this, the bolt-head 27 is again tightened and the device is
; ready for immediate reuse.
It has been found that ~ith the relatively small diameter of the
rigid outer cylindrical body 15, which is actually very little larger than
that of the driven shaft 1 of the motor, ~here is not as much air to drive
the clippings from the device and out of the elevated opening or outlet 6
in the housing of the rotary mower as is desirable.
In improving this situation I have found it highly successful to
dispose a series of equally spaced substantially vertically ex~ending air-
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agitating vanes 30 on the exterior of the rigid outer cylindrical body 15.
These air vanes 30 are shown as tapering from top to bottom, and
are preferably disposed at an angle to the axis of the rigid outer cylin-
drical body 15; for example 22.5 degrees, although this may be increased or
decreased as desired, and depending to some extent on the interior design
of the housing of the rotary mower.
As earlier indicated, the device of the invention, as described
herein, and shown in the drawings, is not only highly efficient and durable
` in service, but is so simple as to lend itself to ease and inexpensiveness
of manufacture, whereby it can find a ready market for application to exist-
ing rotary mowers or trimmers, as well as comprîse part o the original
equipment if such is desired.
In Figures 5, 6 and 7 a modified form of the inventlon is shown as
;~ comprising a somewhat vertically elongated rigid outer cylindrical body
15' with correspondingly dimensioned elements which are disposed therewithin.
The previously described cone-shaped flexible spool 17 is replaced by a pair
of such spools 17' in vertical alignment, in which case the flexible line
X may be paid-out from the two spools 17' simultaneously, as indicated in
Figure 7 and threaded through two opposed flexible tubes 20.
Just by tipping the lawn mower on its side twenty degrees will
enable this line to be inserted within the flexible tube. This enables all
line to be in use to conserve waste and also enables the device to wor~ in
an efficient malmer. Referring to Figure 5 and Figure 6 the flexible stems
20 being in two separable parts, as previously mentioned, is helpful because
whenever the operator runs out of line coming from the spool the construction
will enable the extension to be unscrewed from the flexible stem. Then a
knotted short piece of line inse~ted int'o the extension shown as at X is
then screwed back into the ~lexible stem or continued cutting. The knotted
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end enables the line to be permanently inserted therein until replacement
is in need.
In Figures 6 and 8 the rigid outer cylindrical body 15' is shown as
- provided with but two opposed air vanes 30' which are of somewhat modified
design.
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