Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BAC~GROUND OF THE INVENTION
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1. Field of the Invention
This invention relates generally to rotary lawn
mowers and more particularly is directed towards a new and
improved satety attachment for rotary lawn mowers.
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2. Descrlption of the Prior Art
Rotary lawn mowers are becoming increasingly more
popular as compared to reel type lawn mowers ~rimarily for the
reason that rotary lawn mowers are mechanically simpler,
generally less expensive, lighter and easier to service than
a reel type lawn mower~ Despite the many advantages of the
rotary type lawn mower, it i~ somewhat dangerous to use because
the cutting blade rotates at a high speed and serious injuries
frequently occur as the result of persons accidentally or
negligently getting their foot or hand in under the lawn
mower while it is operating. The high speed blade can easily
sever a finger or toe even through work shoes.
~Jhile various devices have been developed heretofore
to prevent injuries of this type by rotary lawn mowers, none
of them has been entirely satisfactory from the standpoint of
effectiveness, simplicity, ease of maintenance and other
factors.
Accordingly, it is an object of the present invention
to provide a new and improved safety attachment for rotary
; 20 lawn mowers. Another objec~ of this invention is to provide a
simple, low-cost safety attachment for lawn mowers which is
; quickly and easily installed and may be provided as original
equipment or as an attachment for existing lawn mowers. Another
; object of this invention is to provide a safety cutter assembly
for a rotary lawn mower in which a single cutting bar may provide
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fresh cutting edges by simply changing the position of the bar.
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SUMMARY OF THE INVENTION
This invention features a safety attachment for
rotary type lawn mowers comprising an annular disc mountable
to the lower end of the drive shaft of the mower motor and a
cutter bar having a length substantially equal to the diameter
of the disc mounted flush against the disc diametrically across
the underside thereof. In one embodiment the disc is provided
with slots adjacent the leading edges of the cutter bar and
air scoops are provided on the upper side of the disc proximate
to the slots to discharge grass cuttings from the side of the
machine. The cutter bar is rectangular in cross section and
has four cutting edges which may be brought to bear by changing
the position of the bar.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a view in perspective of a safety attachment
for a rotary type lawn mower made according to the invention,
Fig 2 is a cross-sectional view taken along the lines
`~ 2-2 of Fig. 1,
Fig. 3 is a sectional view in side elevation showing
the attachment mounted to a standard rotary lawn mower,
Fig. 4 is a view in perspective, partially broken away,
of a lawn mower equipped with the attachment,
- Fig. 5 is a view in perspective showing a modification
of the attachment,
Fig. 6 is a cross-sectional view taken along the lines
6-6 of Fig. 5,
Fig. 7 is a bottom plan view showing a further modi-
fication of the invention~
Fig. g is an exploded perspective view showing yet
another modification of the invention,
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Fig. 9 is a view in side elevation thereof,
Fig. 10 is an exploded perspective view showing still
another modification o~ the invention,
Fig. 11 is a bottom plan view thereof, and,
Fig. 12 is a view in side elevation thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, the refexence
character 10 generally indicates a rotary lawn mower comprised
of a housing 12 mounted on wheels 14 and directed by a handle 16.
A motor 18, either gasoline or electric, is mounted on top of
the housing, and its drive shaft 20 extends down through the top
of the housing to rotate a safety cutter attachment 22 at a
high speed about a vertical axis. The housing 12 is entirely
open across its bottom and the grass is cut by the rotating cutter
attachment 22 to a height determined by the position of the
wheels 14.
The safety cutter attachment 22, according to the
invention, is comprised of an annular disc 24 mounted coaxially
to the lower end of the drive shaft 20 and a cutter bar 26
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mounted diametrically across the lower face of the disc 24.
~ The diameter of the disc 24 should no-t be less than the length
;~ of the cutter bar and preferably the disc diameter and cutter
; bar length are substantially equal so that the peripheral
edge of the disc 24 is substantially even with the ends of the
cutter bar 26.
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The disc 24 is relatively stiff and may be fa~ricated
from a variety of materials, such as aluminum, fiberglass,
sui~able high impact plastics, or other materials which are
relatively stiff, tough and will not shatter. The diameter
of the disc is made to match the length of the cutter bar
which the mower housing is designed to accommodate. By way
of example, for a standard size 18" rotary lawn mower, a
disc 18" in diameter is employed. The disc may have a thick-
ness of perhaps 1/4" if fabricated from aluminum, magnesium
or the like, or may be thinner if fabricated from steel. The
cutter bar 26 has a length of 18" and is fastened diametrically
across the lower face of the disc as by 3/4" bolts 28 threaded
into nuts 30 and spaced diametrically across the disc. Typically~
four such nuts and bolts are suf ficient to hold the cutter bar 26
flat against the face of the disc. The disc, together with the
cutter bar, commonly are mounted to the drive shaft 20 by
means of a nut 32 engaging the threaded lower end of the drive
shaft.
Preferably, the cutter bar is made of steel to
~; 20 provide a long lasting cutting edge.~ Typically the cutter bar
may be perhaps 2" wide by 1/4" thic~, although these dimensions
- obviously may be varied. While the forward and leading edges
of the cutter bar may be tapered to provide an acute angle
cutting edge, it has been found that the cutter bar works
effectively if the cutter bar is a true rectangle in cross-
section so that the leading and trailing edges are perpendicular
to the upper and lower faces of the cutter bar. Using a cutter
bar of rectangular cross-section, it is possible to use the bar
for a much longer period between sharpenings than would other-
wise be the case. Since only the leading lower corners of the
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cutter bar become worn when the lawn mower is in uset it is
possible to detach the cutter bar from the disc and by turning
the bar appropriately and remounting it, a fresh, sharp cutting
edye may be brought to bear. All four corners of the cutter
bar may thus be put to use before it becomes necessary to remove
the cutter bar and sharpen it. In practice, the outer ends
of the cutter bar should be slightly rounded, particularly at
the corners,to reduce the risk of serious injury by that portion
of the attachment in the event that a person comes in contact
with the device.
~Ihile it has been found that a flatj imperforate disc
and cutter bar assembly will cut grass, the cutting action is
greatly improved by ~orming slots 34 through the di5c directly
above and in advance of the leading edge of the cutter bar. The
; 15 slots typically may be 1/~" wide and 7" in length and serve
to provide an air flow up through the disc. This air flow helps
to raise the blades of grass so that they will be trimmed to the
same height by the cutter bar as it rotates with the disc.
; The air flow is further enhanced and the discharge of
the grass out through the side of the mower is aided by means
of fan blades 36 on top of the disc extending lengthwise of
the slots 34 behind the trailing edges thereof. The blades
preferably are in the form of concave, semi-cylindrical segments
which may be formed integral with the disc as by stamping the
segments out of the disc to form the slots. Alternatively,
the blades may be formed by tubing sectors 38, as suggested in
Figs. 5 and 6, and mounted diametrically along the top of the
disc by means of the same nuts and bolts that mount the cutter
bar. The width of the blades might be on the order of perhaps
l/2" or so and provide sufficient fanning action to discharge
the cut grass out the side chute of the mower.
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In order to reduce the weight of the disc and aid in
the air flowy the disc may be formed with a number of perfora-
tions 40 which might be arranged in radial array as shown in
Fig. 1.
Referring now to Fig. 7 of the drawings, there is
illustrated a further modification of the invention and in this
embodiment cutter bars 42 and 44 are arranged in a cross at
right angles to one another. The cutter bars thus provide four
active cutting edges to improve the cutting action of the attach-
ment. Each of the cutter bars is adapted to be inverted and
reversed so that a fresh cutting edge may be brought to bear
four times for each cutter bar before it becomes necessary to
sharpen the cutters. As before, the cutters are mounted to the
bottom face of the di.sc 46, the diameter of which corresponds
with the lengths of the cutters. As before, the disc is formed
with slots 48 directly above t:he leading edges of the cutter
: bars. Fan blades similar to t.hose described in conjunction
with the principal embodiment may also be employed on the
~ upper face of the disc.
;~ 20 Referring now to Figs. 8 and 9 of the drawings, there
is illustrated another modification of the invention and in this
embodiment a straight, standard cutter bar 50 is secured to the
: underside of a disc 52 by means of a standard.bolt 54. The disc
52 has a diameter substantially corresponding to the length of
the cutter bar and is formed with a diametrical groove 56 of a
width corresponding to the width of the cutter bar and of a depth
somewhat less than the thickness of the cutter bar so that the
bar, when mounted in the groove and fastened to the drive shaft
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of the motor, will appear as is shown in Fig. 9 with its
lea~ing cutting edge 5% extending below the bottom surface
o~ the disc. By forming a groove in the disc and locating
the cutter bar within the groove, there will be no relative
movement between the cutter bar and the disc when the machine
is operated.
In this embodiment the disc may be solid through-
out, with the exception of a central opening 60 through
which the bolt passes. The assembly provides a good cutting
action and a simple means for locking the blade to the disc.
It has been found that it is not necessary for the grass to
extend up above the cutting edge in order to produce a
cutting action and, in practice, the device of Figs. 8 and
9 works well in mowing wet grass and high weeds and tends
'i` 15 to keep itself in a very clean condition. Because of the
solid nature o~ the disc, the mower continues at substantially
the same speed and does not hesitate even in the thickest of
grass or high weeds. In a conventional rotary mower, on the
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- other hand, deep grass must be cut very slowly to preventstalling the machine,and using the solid disc,- the grass tends
to lay down somewhat and then is cut. Since the grass does not
extend up across the full face of the cutter bar, it has also
been found that the cutting edge tends to remain much sharper
for longer periods of time than a conventional blade.
Re~erring now to Figs. 10, 11 and 12, there is
illustrated yet another modification of the invention, and
in this embodiment a straight cutter bar 62 is connected to a
solid disc 64 by means of a bolt 66 passing through the center
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Of the cutter bar and the disc. The cutter bar and disc
are locked against relative movement by means o~ a pair of
spaced studs 6~ and 70 extending from the bottom face of the
disc and engaging the cutter bar 62 through keyhole openings
72 and 74 formed near opposite ends of the cutter bar. The
cutter bar is connected to the disc by placing the bar so that
the heads of the studs pass through the larger ends of the key-
hole openings, in which position the bar will be slightly of~-
set. The bax is then placed flush against the surface o~ the
disc and slipped siaewise so that the smaller portions of the
~eyhole openings pass in under the heads of the studs with the
~ center opening 76 of the cutter bar and the center opening 78; of the disc now in alignment. The bolt 66 is then installed
and connected to the drive shaft of the mower. The assembly
has operating characteristics similar to the device of
~ Figs 8 and 9, and the disc is easily separated ~rom the cutter
; bar to periodically service the bar or replace it as required.
In the event that a person, such as the operator pushing
the lawn mower, accidentally places his foot under the housing
he will not be seriously injured by the attachment by virtue
of the disc preventing the foot from coming into the full path
of the cutters. It has been found that, in such cases where the
foot does accidentally move in under the mower, some scuffing
of the shoe occurs but no serious injury is done to the foot.
While the invention has been described with particular
reference to the illustrated embodiments, numerous modifications
thereto will appear to those skilled in the art.
Having thus described the invention, what I claim and
desire to ~btain by Letters Patent of the United States is:
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