Note: Descriptions are shown in the official language in which they were submitted.
TITLE
MULTIPLE- SPEED TRAN SMI S S ION FOP~
SELF-PROPELLED LAWN MOWERS AND THE LIKE
INVENTOR
Eugene H. Schlapper
BACKGROUND OF THE INVENTION
This invention relates to multiple-speed trans-
missions for self-propelled devices and, more particularly
to multiple-speed transmission for sel-propelled lawn mowers.
Self-propelled lawn mowers typically are driven by
a transmission connected to the cutter blade drive shaft.
Consequently, for mowers powered by an internal combustion
engine, the mower speed can be varied only by adjustment o~
the engine throttle. In some situations, such as cut~ing
heavy weeds or grass or mulching leaves, high cutter blade
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speed and lower mower travel speed may be desired. If the
engine speed is reduced to accomplish the desired slower mower
speed, the blade speed is reduced and, in some cases, the
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reduced power of the engine at the lower speed may be
insufficient to accomplish the desired cutting. In other
situations, it may be desired to operate the mower at high
blade and mower speeds, low blade and mower speeds, or low
blade speed and high mower speed.
United States Shaw Patent 2,947,132, issued August 2,
1960, discloses a transmission for a power mower or the like
including a drive shaft which is drivingly connected to a prime
; mover and is selectively movable into frictional engagement
with the outer periphery of a pair of the mower wheels to drive
the mower. The present invention is directed to an improvement
for such a transmission whereby the mower speed can be -
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selectively varied independently of the engine speed.
The United States Jepson Patent 2,962,85~, issued
December 6, 1960, discloses a transmission including a two-
speed drive gear having concentric rings of gear teeth and
a driven gear which is connected to a wheel-engagable drive
shaft and can be moved axially to mesh with either of the
drive gear rings or varying the mower speed.
SUM~RY OF THE INVENTION
The invention provides a self-propelled lawn mower
including a frame supported on a plurality of wheels for move-
ment over the ground, at least one of which is adapted to serve
as a drive wheel, a prime mover supported on the frame, a drive
shaft rotatably moun~ed on the frame in parallel relationship
to the drive wheel axis, means drivingly connecting the prime
mover to the drive shaft, and drive means on the drive shaft
for selectively driving the drive wheel at two different speeds.
The drive means includes a first or low-speed drive member
mounted on the drive shaft for common rotation therewith and
having a first generally circular drive surface for riction-
ally engaging the outer periphery of the drive wheel and a
second or high-speed drive member including a second generally
circular drive surface having an outer diameter greater than
the outer diameter of the drive surface on the low-speed drive
member. The high-speed drive member is mounted on the drive
shaft for common rotation therewith and for axial movement
relative to the low-speed drive member between a first position
wherein the high-speed drive member is axially spaced ~o~ the
drive wheel and the drive surface on the low-speed drive member
is exposed for engagement with the outer periphery of the drive
wheel and a second position wherein the drive surface on the :~
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high~speed drive member is located for engagement with the
outer periphery of the drive wheel. The drive means further
includes means for moving the drive shaft and the drive wheel
relative to each other between a drive position wherein either
the low-speed or the high-speed drive member is in driving
engagement with the drive wheel and a non-driving position
wherein both of the drive members are disengaged from the
drive wheel.
In one embodiment, the mower includes a pair of
wheels mounted on a common axle and individual drive means are
provided on each of the opposite end portions of the drive-
shaft for driving each of these wheels.
In one embodiment, the mower includes shift means
operably connected to the high-speed drive member(s) for
selectively moving the high-speed drive member(s) between the
first and second positions. :
In one embodiment, this shift means includes a
movable control lever on the mower guiding handle, a shift
member operably connected to each high-speed drive member for
af~ecting axial movement of the high-speed drive members in
response to axial movement of the shift members while permitting
rotary movement of each high-speed drive member relative to
the respective shift member, and means connecting the control
lever to the shift members for affecting axial movement of the -
shift members in response to movement of the control lever. -~
In one embodiment, the low-speed drive member
includes a pair of radially outwardly extending, annular
shoulders disposed adjacent the opposite ends of the first
drive surface, each shoulder having a plurallty of circum-
ferentially-spaced, axially extending external splines, and ~ -
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the high-speed drive member includes a central bore having
a plurality of circumferentiall~-spaced, axially extending
internal splines for receiving the splined shoulders on the
low-speed drive member.
One of the principal features of the invention is
the provision of a multi-speed transmission for a self-propelled
lawn mower or the like.
Another of the principal features of the invention
is the provision of such a transmission which is capable of
selectively changing the mower speed independently of the
speed of the mower prime mover.
A further of the principal features of the invention
is the provision of a self-propelled lawn mower including a
drive mechanism which is arranged to selectively drivingly
engage the outer periphery of one or more of the mower wheels
and which includes selectively operable drive members of
different size for propelling the drive wheel, and thus the
mower, at different speeds.
Other features and advantages of the embodiments
of the invention will become apparent to those skilled in the
art upon reviewing the following detailed description, the
dra~ings and the appended claims. ~-
BRIEF DESCRIPTION OF THE DRAWINGS ~::
Fig. 1 is a side elevational view of a self-propelled
lawn mower embodying various of the features of the invention.
Fig. 2 is an enlarged, fragmentary, top plan view ;
of the mower in Fig. 1 with the drive means shown in the low-
speed position.
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Fig. 3 is a sectional view taken generally along
line 3-3 in Fig. 2.
Fig. 4 is a sectional view taken generally along
line ~-4 in Fig. 3.
Fig. 5 is an enlarged fragmentary top view of the
righthand portion of the mower in Fig. 3 with the drive means
shown in the high-speed position.
Fig. 6 is a fragmentary view taken generally along
line 6-6 of Fig. 2.
Before explaining at least one embodiment of the
invention in detail, it is to be understood that the invention
is not limited in its application to the details of construc-
tion and the arrangements of the components set forth in the
following description or illustrated in the drawing. The
invention is capable of other embodiments and of being
practiced and carried out in various ways. Also, it is to be
understood that ~he phraseology and terminology employed
herein is for the purposes of description and should not be
regarded as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in the drawing is a sel~-propelled
lawn mower 10 including a prime mover 12, such as an internal
combustion engine or an electric mo~or, partially covered by
a shroud 14 and supported on a frame including a blade housing
16. Drivingly connected to the prime mover 12 is an engine
drive shaft 17 which drives a rotary cutter blade 18 located
inside the blade housing 16. The mower 10 is supported for
travel along the ground by a pair of front wheels 20 (one shown)
and a pair of rear wheels 21 and 22 carried on an a~le 24
rotatably supported rearwardly of the blade housing 16 as
described in more detail below. The mower 10 is guided by a
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handle 26 connected to and extending rearwardly from the blade
housing 16.
The mower 10 is powered by a drive mechanism or
transmission which is operable to selectively connect the prime
mover 12 in driving engagement with at least one of the w'neels.
In the specific construction illustrated, the transmission is
generally arranged in the manner disclosed in the above-
identified United States Shaw patent. ~ore specifically,
the transmission includes (Figs. 2 and 3) a drive shaft 28
disposed in parallel relationship to the rear axle 24 and
rotatably supported in bearings 30 (one shown in Fig. 3) carried
by fixed support brackets 32. The drive shaft 28 is drivingly
connected to the prime mover 12 by a suitable drive arrangement,
such as a pulley 34 driven by the engine drive shaft 17 via a
belt 36 and a beveled gear 38 on the pulley 34 meshing with and `
driving a beveled gear 40 fixedly mounted on the drive shaft 28.
Located on at least one end portion of the drive
shaft 28 is a drive means 41 for selectively engaging the ~
outer periphery of the respective rear wheel and driving the -
mower 10 at two different speeds. In the specific construc-
tion îllustrated, a drive means 41 is provided on each of the
opposite end portions of the drive shaft 28; however, a drive
means 41 on only one end portion of the drive shaft 28 may be
adequate in some-applications. In that case, the rear wheels
21 and 22 preferably are fixedly mounted on the axle 24 so
that rotation of one wheel acting as the drive wheel also
rotates the other wheel, thereby maximizing traction. -~
The drive means 41 (Fig. 3) includes a first or -
low-speed drive member 42 fixedly mounted, by a drive pin 43
or the like, on the drive shaft 28 for common rotation therewith.
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The low-speed drive mem~er 42 has a first generally circular
drive surface 44 for frictionally engaging the outer peripheral
surface o~ the rear wheel 22 and driving the wheel in response
to rotation of the drive shaft 28. The drive means 41 further
includes a second or high-speed drive member 46 having a second
generally circular drive surface 48 which has an outer diameter
greater than the outer diameter of the first drive surface 44.
The high-speed drive member 46 is mounted for
common rotation with the drive shaft 28 and for axial movement
relative to the low-speed drive member 42 between a first or
low-speed position shown in Fig. 3 wherein the second drive
member 46 is axially spaced from the wheel 22 and the first ; ~ :
drive surface 44 of the low-speed drive member is exposed for
engagement with the outer periphery of the wheel and a second
or high-speed position shown in Fig. 5 wherein the second drive ~ :
surface 48 is located for engagement with the outer periphery
of the wheel. The first and second driving surfaces 44 and 48
are serrated, kmlrled or ctherwise roughened to enhance the
traction of the drive members 42 and 46 with the wheels 21 and
22.
Provided on the low-speed drive member 42 adjacent the
opposite ends of the first drive surface 44 are a pair of
radially extending annular shoulders 50 which have an outside
diameter somewhat greater than the outside diameter of the first
drive surface 44 and a plurality of circumferentially-spaced, ~-
axially extending external splines 51. The high-speed drive
member 46 has a central bore 52 including a plurality of cir-
cumferentially-spaced, axially extending internal splines 53
which mesh with the external splines 51 on the shoulders 50 and
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permit axial movement of the high-speed drive member 46
relative to the low-speed drive member 42 while providing
common rotation of the low-speed and the high-speed drive
members 42 and 46. The inner end of the high-speed drive
member 46 is supported by a pressed-in bushing 54 slidably
and rotatably mounted on the drive shaft 28. Thus, the
drive members 42 and 46 are rotating any ~ime theprime
mover 12 is operating. t~
Shift means are provided for moving the high-speed
drive member 46 between the high-speed and the low-speed
positions. While various arrangements can be used, in the
specific construc~ion illustrated, such means (Figs. 3 and 4)
includes a pair of shift members or yokes 56, each having a
pair of diametrically opposed arms or legs 58 which are
slidably received in an annular guideway 59 provided in the
inner end portion of the high-speed drive member 46. Each
yoke 56 is pivotally connected to a lever 60 which is pivotally
connected to a rocker arm 61. The rocker arm 61 pivots at
62 and is operatively connected, via a push-pull element 64
~r the like, to a control lever 66 mounted on the mower handle
26 for oscillatory movement. Oscillatory movement of the control
lever 66 causes axial movement of the high-speed drive members
46, via the push-pull element 64, the rocker arm 61, the levers
60, and the yokes 56, between the high and low-speed positions
and the guideway 59 permits rotary movement of the high-speed
drive member 46 relative to the yoke 56.
Means are provided for moving the drive shaft 28
and the rear wheels 22 relative to each other between a drive
position wherein either the high-speed drive members 46 or the
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low-speed drive members ~2 (depending on the position of the
control lever 66) frictionally engages the outer periphery of
the rear wheels 21 and 22 and a non-driving position wherein
either of the drive members are disengaged from the rear wheels.
While various arrangements can be used, in the specific con-
s~rUction illustrated, such means is generally arranged in
the ~anner disclosed in the above U.S. Shaw Patent No. 2,9~7,132.
The construction and operation of the means for moving the
drive shaft 28 and the rear wheels 22 relative to each other
will be briefly summarized and reference càn be made to the Shaw
patent for a more detailed description.
The rear wheels 22 are rotatable relative to the
rear axle 24 which is carried by links or levers 68 and 70
pivotally mounted on arms 72 and 74 of a yoke 76. The yoke
arms 72 and 74 are suitably supported from the blade housing
16 at 7S for pivotal movement relative to the blade housing 16.
The levers 68 and 70 project upwardly from the yoke to
accommodate fore and aft movement of the axle 24 and the rear
wheels 21 and 22 relative to ~he drive shaft 28 for respectively
engaging the rear wheels with the drive shaft 28 and dis-
engaging the rear wheels 21 and 22 from the drive sha~t 28.
A tension spring (not shown) connected between the lever 68
and the yoke arm 72 urges the rear wheels 21 and 22 toward
the disengagedposition.
Movement of the rear wheels 22 between the drive or
engaged position and the non-driving or disengaged position
is effected by a control handle S0 mounted on themower handle
26 for oscillatory movement and an actuator link 82. The
actuator link 82 is operatively connected at the upper end
to the control handle 80 and is connected at the lower end
to the wheel axle 24 through a linkage arrangement including
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a lever 84 pivotally connected to the actuator link 82 and
pivotally connected at 86 to another lever 88 which is
pivotally mounted on the wheel axle 24.
When the control handle 80 is moved to the drive
position (i.e., to the forward position shown in Fig.l), the
actuator link 82 is moved downwardly and moves the linkage
arrangement to the position shown in Fig. 5 wherein the
axle 24 is advanced to engage the wheels 22 with whichever
of the drive members 42 and 46 is in the driving position.
When the control handle 80 is moved to a neutral or non-
driving position (i.e., moved rearwardly from the position
shown in Fig. 1), the actuator link 82 is moved upwardly and
moves the linkage arrangement to a position wherein the
wheel axle 24 is retracted to disengage the rear wheels 21 and
22 ~rom the drive members 42 and 46.
While the invention has been described in connection
with a rotary lawn mower, it can be readily adapted for use
on lawn mowers engaging reel-type cutter blades.
Various of the features of the invention are set
:~0 forth in the follow-ing claims:
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