Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to lawn mowers, To date there have
been three common types of mowing machines, i,e. the "clipper", the "reel"
and "rotary" type mowers.
The present invention relates to an improved lawn mower which is
quite different in mechanism from those conventional lawn mowers. More
particularly, this invention relates to an improved lawn mower in which a
disc or rotor is rotatably mounted under the mower housing and a suitable
number of pairs of disc like blades is mounted on the rotary disc in such a
manner that each of the blades rotates about its own axis and revolves about
that of the disc in a planetary motion. Lawn mowing is performed by mutual
rotating and sliding contact between th0 blades of each pair.
A mower of this type is disclosed in applicant's Canadian Patent
Application 246,793, filed February 27, 1976. In that mower, the pairs of
blades are mounted on respective gear casings,containing gears coupling the
shafts of the blades for counter rotation~ The gear casing itself is pivot-
ally mounted on the disc so that it piYots outwardly upon rota~ion of the
disc. The blade shafts ar driven by centrifugal engagement of a roller
carried by one of them with a cylindrical flange mounted on the underside of
the mower housing. The present invention is concerned with the provision of
a lawn mower which uses no driving gears.
According to the present invention there is provided a lal~n mower
comprising: a housing having an open bottom; a ring member mounted within
the housing with its axis upright; a rotor within the housing, mounted on
rotation about the axis of the ring member; a support member pivotally mount-
ed on the rotor for rota~ion about an upri~ht axis; two blade shafts jou~nal-
led to the support member for independent rotation about respective upright
axes; two disc-like blades mounted on the lower ends of respective ones of
the blade shafts, beneath the suppor~ member, the blades having overlapping
cutting edges; a roller mounted on one of the blade shafts, at the level of -
the ring member; resilient mesns coupled to the other of the blade shafts to
bias its blade into engagement with the blade of the one blade shaft such that
rotation of the one blade shaft and its blade in one direction will cause a
rotation of the other blade in the opposite direction; and means for rotating
the rotor, the positioning of the ring member, the axis of the support member
and the blade shafts being such that upon rotation of the rotor, the support
~ember will pivot about its axis under the influence of centrifugal force un-
til the roller comes into engagement with the inside of the ring member to
cause rotation of the roller7 the one blade shaft and its blade about the
axis of the one blade shaft and, via engagement of the blades, rotation of
the other blade.
With this improved lawm mower, the support member is lighter in
weight; the magnitude of the centrifugal force on the support mem~er is re-
ducad; and both the impactive load at start up and the steady running load of
the blade driving roller on the inside surface of the ring member is reduced
so that roller wear is improved and the noise generated by the rotation of
the roller on-the ring member is reduced.
Another advantage of this structure is a reduction in cost of the
lawn mower by simplifying the structure of the support member and ~he rotary
shafts.
The accompanying drawings illustrate a preferred embodiment of the
la~m mower according to the invention in which:
Figure 1 is a bottom view, partly in section, of the embodimen~;
Figure 2 is a section along the line II-II of Figure 1, and;
Figure 3 is a plan view along the line III-III of Figure 2.
Referring to the drawings, the mower has a housing 1 with a flat
top wall, a square peripheral wall, a central cylindrical wall and an open
bottom. Four supporting wheels 2, 2 are mounted on the housing, adjacent the
respective corners. A motor 4 is mounted on the top wall of the housing. A
ring member in the form of a ~t~tionarycylindrical flange 5 is mounted within
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7~3
the housing on the underside of the top wall, concentrically with the central
cylindrical wall of the housing. A rotor or disk 3 is mounted on the motor
drive shaft, beneath the flange 5 and concentrically therewith.
A suitable number of support members 8, 8 are pivotally mounted on
the underside of disc 3 by means of respective shafts 9. Each shaft 9 is it-
self carried on disc 3 via a pillow block secured to a radial flange 17 depend-
ing from disc 3. In Figure 1, three support members are shown with an angu-
lar spacing of 120 . Each support member 8 has two blade shafts 10a and lOb
journalled to it for independent rotation about spaced apart axes parallel to
the motor shaft 6. The shafts lOa, 10b have mounted to their bottom ends,
respective disc cutter blades 7a, 7b. -~
Each support member 8 is a box shape and is mounted on the under-
side of disc 3 in such a manner that it can pivot outward with the shaft 9 as
a fulcrum, under the influence of the centrifugal force generated by rotation
of the disc 3. The shafts 10a and 10b are arranged such that when the support
member 8 pivots outward upon rotation of the disc 3 in the direction t, they
are aligned radially of the disc 3, so that the lawn to be mown can be taken
in between the two blades 7a3 7b.
The support member 8 can pi~ot in a direction opposite to the direc-
tion of rotation t of the disc 3. This is to enable the support member andthe blades to be pivoted inwardly when foreign objects such as stones or wood
in the lawn hit the support or blades, so as to prevent damage to the machine.
Each of the blades 7a, 7b has the shape of a flat disc or plate
with its periphery formed into a cutting edge 11a or 11b respecti~ely. These
blades are fixed to the shafts 10a, lOb in such a manner that the blades con-
tact and overlap each other so as to produce a scissors type of cutting action
when the two blades rotate in opposite directions.
Two shafts 10a and 10b are mounted to a support member 8 such that
. ~, ~ . .
they rotate independentlyO Also, a bias spring 13 is applied to shaft 10b so
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that the blade 7b mounted on this shaft is urged into engagement with the
other, 7a for effecting a relative sliding and a shearing motion so as to draw
in the grass between the blades and to cut it.
Shaft 10a extends upwardly from the support member 8 so as to pro-
ject throughi an arcuate slot 14 in the disc 3. A roller 15 is mounted on the -
upper end of shaft 10a. Roller 15 is rotated by contact with the inside sur-
face of the stationary flange 5 located under the housing 1. The other shaft
10b is mounted rotatably on the support member 8 as mentioned3 and because
of the downwards bias generated by pressing spring 13, blade 7b rotates in
contact with blade 7a.
As sho~m in the drawings, the rotary disc 3 is larger in diameter
than the flange 5. Consequently, shaft 10a projects through the arcuate slot
14 provided in the rotary disc 3. However, the disc 3 may in other embodiments
be smaller than the ring 5. For exampleg the disc ~ may be only of sufficient
size to mount the shafts 9 for the support members 8. In such a case, the `
arcuate slot 14 of the disc 3 is naturally not necessary.
.
~ he rotary roller 15 is made of metal material on which hard rubber
or synthetic resin is applied. It is fo~med in a ring shape and with a dia-
meter similar to or a bit smaller than that of the blades 7a, 7bo In order to
reduce the noise generated by the contact between the rotary roller 15 and
the stationary ring 5, it is preferable to provide a hollow tire type rotary
roller.
In the drawings, reference numeral 17 indicates a flange or fin
which extends in a radial direction under the disc 3. The fin 17 generates
an air flow within the housing 1 upon rotation of the disc 3, which flow
allows the mown lawn to be discharged from the discharge opening 18 from the
housing 1.
Operation of ~he lawn mower is as follows:
~`~ Motor 4 rotates disc 3 in a generally horizontal plane in direction
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t via drive shaft 6. The support member 8 mounted on the disc pivots outward---
ly about the shaft 9, under the influence of centrifugal force. Simultaneous-
ly with this movement, the rotary shaft lOa for the rotary blade 7a moves ;`
along the arcuate slot 14 in the disc 3 ancl roller 15, which is mounted on
the shaft lOa is pressed into engagement with the inside surface of the stat~
ionary ring 5.
Roller 15 rolls along the inside surface of the ring 5 so as torotate the shaft lOa. Consequently, the blade 7a rotates with shaft lOa
and revolves about the axis of shaft 6 in a planetary movement. Because of
the planetary movement of the blade 7a, ~he other blade 7b3 which is biased
into engagement with blade 7a by spring 13, rotates in a direction opposite
to that of blade 7a. Thus, through this mutual contact, a relative rotat-
ing and sliding motion is effected between the superposed blade edges of the
two rotary blades and lawn mowing is performed.
As described above, two parallel shafts lOa, lOb for respective
disc-like blades, 7a, 7b are mounted on a support member 8 such that the
shafts rotate independently. A biasing spring 13 is applied to one shaft, lOb, i~
so that the blade 7b mounted on that shact is pressed into engagement with
the other blade 7a for taking in and cutting the lawn. In this way~ since a ; -
pair of two rotary blades can be rotated in opposite directions, there is no
need to -provide a dri~ing gear as is-used in the prior apparatus and, thus,
the support member can be designed smaller and lighter than the prior one. `~
Therefore, the contrifugal force applied to the support member at
the time of starting the mower, is reduced. In additiong the shock and noise
generated at the moment when the roller 15 contacts the flange 5 is reduced.
Further, since the force applied by roller 15 on the flange 5 can be small
during operation of the mower, the roller can be used for long periods without
being worn out or damaged. In additiona the noise generated when the roller
rolls along the flange can be reduced.
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Also, since a driving gear is not used, the structure of the
support member and cutter shaft assembly is simplified and, therefore, the
machine, which has an excellent service life, can be produced a~ a low cost.
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