Note: Descriptions are shown in the official language in which they were submitted.
CA 02868130 2014-10-23
HIGH CLEARANCE MOWER HITCH
This disclosure relates to the field of rotary mowers and in particular a high
clearance
hitch for such a mower to facilitate passing over variable terrain and
obstacles such as
road approaches across ditches.
BACKGROUND
Typical rotary mowers have a horizontally oriented mower deck mounted on
wheels for
movement along the ground and a horizontally oriented rotating blade mounted
under the
deck. Wider rotary mowers typically include a center deck with right and left
wing decks
pivotally attached to the center deck about horizontal wing pivot axes
oriented
substantially in alignment with an operating travel direction of the mower.
For transport
the wings are pivoted up about the wing pivot axes to a generally vertical
transport
1 5 position. One or more rotating blades are mounted under each wing deck.
These wider rotary mowers are typically supported on front and rear wheels and
are
towed by a tractor connected to the front end of a hitch arm extending forward
from the
mower. The blades are commonly driven by the power take-off of the towing
tractor
. 20 connected by drives-hafts to gearboxes mounted on the tops of the
decks for example as
shown in United States Patent Numbers 7,775,024 and 6,854,250 to Boyko. It is
also
known to drive the blades with hydraulic motors powered by the tractor
hydraulic supply
or by a separate hydraulic pump mounted on the mower and driven by the
tractor's power
take offl for example as disclosed in United States Patent Number 1511,368 to
Kocher.
Such wider rotary mowers are often used for cutting on ditches alongside
roads. Such
ditches are sloped and are also are periodically crossed by approaches which
allow access
to the road across the ditch. To allow the towing tractor to drive on the road
surface with
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the mower pulled behind in an offset position on the sloped ditch surface, the
hitch arms
of the Boyko '024 and '250 mowers pivot with respect to the mower so the mower
trails
the tractor in the desired offset position. The Kocher mower can be operated
while
located in a variety of positions relative to the tractor as well.
Obstructions, such as road approaches in the ditches, can be quite steep and
sharply
sloped. The wider mowers usually used tbr ditch cutting have quite long hitch
members
extending forward from the mower to the tractor to provide for sufficient
offset. These
hitch arms often drag on these obstructions as the tractor moves sharply up
and down
relative to the mower. On both of .the Boyko '024 and '250 mowers, the hitch
extends
upward from the tractor attachment end and then rearward and down to the mower
providing a raised hitch that provides increased clearance thus reducing the
contact of the
hitch with approaches and the like.
SUMMARY OF THE INVENTION
The present disclosure provides a hitch apparatus for a rotary mower that
overcomes
problems in the prior art.
In a first embodiment the present disclosure provides a rotary mower apparatus
comprising a center mower deck mounted on Front and rear wheels for movement
along a
ground surface in an operating travel direction, and a hitch arm assembly
adapted at a
front end thereof for connection to a drawbar of a tractor. A hydraulic pump
is mounted
on the hitch arm assembly, and a pump driveshaft is adapted at a front end
thereof for
attachment to a power take-off of the tractor, and is connected at a rear end
thereof to the
hydraulic pump. A hydraulic motor mounted on the center mower deck is
connected to
rotate a blade under the center mower deck, and the hydraulic motor is
connected to
receive pressurized hydraulic fluid from the hydraulic pump. An upward arm
section of
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the hitch atm assembly extends upward from a front portion of the hitch arm
assembly to
provide a desired clearance distance between a middle ann section of the hitch
arm
assembly and the ground surface, and a downward arm section of the hitch arm
assembly
extends downward from the middle arm section to a rear end of the hitch arm
assembly.
The rear end of the hitch arm assembly is pivotally connected to the mower
deck about a
hitch pivot axis oriented substantially horizontally and perpendicular to the
operating
travel direction, and the hitch pivot axis is located at a vertical position
below top edges
of the front wheels.
In a second embodiment the present disclosure provides a rotary mower
apparatus
comprising a center mower deck mounted on front and rear wheels for movement
along a
ground surface in an operating travel direction. A drawbar assembly is adapted
at a front
end thereof for connection to a drawbar of a tractor in a substantially fixed
position with
respect to the drawbar, and a rear portion of the drawbar assembly is
pivotally attached to
a front end of a rigid hitch arm member about a substantially horizontal first
drawbar
pivot axis oriented substantially parallel to the operating travel direction,
and about a
substantially vertical second drawbar pivot axis. A hydraulic pump is mounted
on the
drawbar assembly, and a pump driveshaft adapted at a front end thereof for
attachment to
a power take-off of the tractor is connected at a rear end thereof to the
hydraulic pump.
A hydraulic motor mounted on the center mower deck is connected to rotate a
blade
under the mower deck, and is connected to receive pressurized hydraulic fluid
from the
hydraulic pump. A forward arm section of the hitch arm member extends upward
from
the front end of the hitch arm member to provide a desired clearance distance
between a
middle arm section of the hitch arm member and the ground surface, and a rear
arm
section of the hitch arm member extends downward from the middle section to a
rear end
of the hitch arm member. The rear end of the hitch arm member is pivotally
connected to
the mower deck about a hitch pivot axis oriented substantially horizontally
and
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perpendicular to the operating travel direction arid the hitch pivot axis is
located at a
vertical position below top edges of the front wheels.
The rotary mower apparatus of the present disclosure provides a high clearance
hitch
assembly with a low and forward pull point on the mower deck that reduces
downward
forces on the front wheels which tend to push the front wheels down into soft
ground. A
hydraulic drive system tbr the mower blades provides a low cost, low
maintenance drive
that transfers power simply from the power take-off of the towing tractor to
the mower
blades through several pivot axes.
DESCRIPTION OF THE DRAWINGS
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and .where:
Fig. 1 is a schematic side view of an embodiment of a rotary mower apparatus
of the
present disclosure;
Fig. 2 is a schematic top view of the embodiment of Fig. 1;
Fig. 3 is a schematic top view of the embodiment of Fig. 1 with the hitch arm
assembly
pivoted with respect to the mower deck to place the mower deck in an offset
position
with respect to the towing tractor;
Fig. 4 is a schematic top view of the embodiment of Fie. 1 showing the right
and left
wing decks, hydraulic reservoir, and hydraulic fluid cooling system;
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Fig. 5 is a schematic side view of a rotary mower apparatus of the prior art
with a high
clearance hitch assembly showing the forces exerted thereon in operation;
Fig. 6 is a side view of the apparatus of Fig. 5 with rear wheels moving up in
response
to torque exerted on the elevated hitch pivot axis;
Fig. 7 is a schematic side view of a different rotary mower apparatus of the
prior art
with a high clearance hitch assembly showing the forces exerted thereon in
operation;
Fig. 8 is a schematic side view of the embodiment of Fig. 1 showing the forces
exerted
thereon in operation.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Figs. I and 2 schematically illustrate an embodiment of a rotary mower
apparatus 1 of the
present disclosure. The apparatus 1 comprises a center mower deck 3 mounted on
front
and rear wheels 5, 7 tin- movement along a ground surface 9 in an operating
travel
direction T. A hitch arm assembly 11 is adapted at a front end thereof for
connection to a
drawbar 13 of a tractor 15. The left front wheel and the front wheel mounting
frame have
been removed in Fig. 1 to allow illustration of the connection of the hitch
arm assembly
11 to the mower deck 3. Similarly the pump driveshaft, hydraulic reservoir and
cooling
system, and the right and left wing decks have been removed from Fig. 2.
A hydraulic pump 17 is mounted on the hitch arm assembly 11, and a pump
drivcshaft 19
is adapted at a front end thereof for attachment to a power take-off 21 of the
tractor 15,
and is connected at a rear end thereof to the hydraulic pump. In the
illustrated apparatus
1, the pump driveshaft 19 is connected at the rear end thereof to the
hydraulic pump 17
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through a gearbox 23 such that the rotational speed of the pump 17 can be
increased if
necessary. The gearbox 23 is fixed to the rear drawbar section 37 at an
elevation
selected such that the pump driveshaft 19 is substantially horizontal when
connected to
the tractor power take-off 21, and the hydraulic pump 17 is then attached to
the gearbox
'-)3. =
A hydraulic motor 25 is mounted on the center mower deck 3 and is connected to
rotate a
blade 27 under the center mower deck 3. The hydraulic motor 25 is connected to
receive
pressurized hydraulic fluid from the hydraulic pump 17 through conduits (not
shown) as
is known in the art.
The hitch arm assembly 11 is configured to provide a desired clearance
distance CD
between the central portion of the hitch arm assembly it and the ground
surface 9 to
reduce the occurrence of the hitch arm assembly 11 contacting the ground, as
when
crossing road approaches when mowing road ditches. In the illustrated
apparatus 1 the
hitch arm assembly 11 comprises a drawbar assembly 31 at a front end thereof
pivotally
connected to a rigid hitch arin member 33 which in turn is pivotally connected
at a rear
end thereof to the mower deck 3 about a hitch pivot axis HPA oriented
substantially
horizontally and perpendicular to the operating travel direction T.
)0
The drawbar assembly 31 comprises a front drawbar section 35 adapted at a
front end
thereof for connection to the drawbar 13 in a substantially fixed position
with respect to
the drawbar 13. For example the drawbar 13 can slide into a sleeve in the
front drawbar
section 35, such that the front drawbar section 35 does not pivot with respect
to the
drawbar 13. The drawbar assembly 31 further comprises a rear drawbar section
37
pivotally connected at a front end thereof to the front drawbar section 35
about a
substantially horizontal first drawbar pivot axis DA1 oriented substantially
parallel to the
operating travel direction T. The rear drawbar section 37 is then pivotally
connected at a
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rear end thereof to the front end of a rigid hitch arm member 33 about a
substantially
vertical second drawbar pivot axis DA2.
Thus the rigid hitch arm member 33 can swing laterally about the second
drawbar pivot
axis DA2, and can also pivot with respect to the tractor 15 about the first
drawbar pivot
axis DAI to accommodate varying terrain. The rear drawbar section 37 pivots
with
respect to the tractor 15 only about the first drawbar pivot axis DA1, while
the front
drawbar section 35 is substantially fixed with respect to the tractor 15. The
first drawbar
pivot axis DA1 intersects the second drawbar pivot axis DA2 to align the
towing forces
on the drawbar 13.
The hitch arm member 33 comprises upward arm section 33A sloping up from the
front
end of the hitch arm member 33, a middle arm section 3313 extending generally
rearward
from the top end of the upward arm section 33A, and a downward arm section 33C
sloping downward from the rear end of the middle arm section 3313 to the
connection to
the mower deck 3 at the hitch pivot axis HPA. The hitch pivot axis HPA is
located at a
vertical position below top edges 5A of the front Wheels 5, and in the
illustrated
apparatus the hitch pivot axis HPA is located between the top edges 5A of the
front
wheels 5 and the rotational axis RA of the front wheels 5, and fbrward of the
rotational
axis RA of the front wheels.
In the illustrated apparatus 1, the rear end of the hitch arm assembly 11 at
the rear end of
the hitch arm member 33 is pivotally connected to the mower deck 3 by a pivot
plate 39.
The pivot plate 39 is pivotally connected to the mower deck 3 about the hitch
pivot axis
HPA and the rear end of the hitch arm member 33 is pivotally connected to the
pivot
plate 39 about a substantially vertical swing pivot axis SPA. An actuator,
such as a
hydraulic cylinder 41, is operative to pivot the hitch arm assembly 11 about
the swing
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pivot axis SPA to a desired offset position thr conveniently mowing ditches
and like
operations, as schematically illustrated in Fig. 3.
Thus in the apparatus 1, the front drawbar section 35 is fixed with respect to
the drawbar
13, and the rear drawbar section 37 can pivot only with respect to the drawbar
about the
first drawbar pivot axis DA1, a fairly small rocking motion in most terrain,
such that the
pump driveshaft 19 remains substantially level and aligned with the gearbox
23, reducing
strain on the universal joints 43 at the ends of the pump driveshaft 19. As
can be seen in
Fig. 3 the upward arm section 33A passes rearward of the hydraulic pump 17
when the
hitch arm member 33 pivots about the second drawbar pivot axis DA2, and the
pump 17
stays substantially aligned with the tractor power take-off 21.
Fig. 4 schematically illustrates the apparatus 1 with the typical right and
left wing mower
decks 3R, 3L pivotally attached to the center mower deck 3 about corresponding
right
and le-ft wing pivot axes WPA oriented substantially parallel to the operating
travel
direction T. Right and left hydraulic motors 25R, 25L are connected to receive
pressurized hydraulic fluid from the hydraulic pump 17 and drive blades 27R,
27L under
the corresponding right and left wing decks 3R, 3L.
A hydraulic fluid reservoir 45 is mounted on the center mower deck 3 and
connected to
supply hydraulic fluid to the hydraulic pump 17 through conventional conduits
which are
known in the art and not illustrated. A cooling system 47 is operative to cool
the
hydraulic fluid.
Figs. 5 and 6 schematically illustrate a rotary mower apparatus I of the prior
art with a
high clearance hitch. The hitch arm assembly ii is pivotally attached to the
mower
about hitch pivot axis HPA', at a location significantly elevated above the
front wheels 51
.
When the drag force DE on the front wheels 5' increases, such as when
encountering soft
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ground, the towing force IF is exerted at the hitch pivot axis HPA' and causes
the hitch
arm assembly 1.1 to pivot on the elevated hitch pivot axis HPA.' and exert a
torque
tending to rotate the hitch mount post 51' about the rotational axis RA' of
the front wheels
5'. This torque tends to raise the rear end of the mower deck 3', putting
added weight on
the front wheels 5', and sinking the front wheels 5' farther into the soft
ground.
Similarly Fig. 7 schematically illustrates a hitch arrangement of a different
type of rotary
mower apparatus 1" of the prior art with a high clearance hitch. Here the
hitch arm
assembly 11" is attached to the mower deck 3" about a hitch pivot axis HPA"
that is
above the center of the mower deck 3", such that the tow force TF essentially
pulls the
rear wheels 7" and pushes the front -Wheels 5" in the operating travel
direction T. This
arrangement tends to push the front wheels 5" downward in soft ground,
increasing the
drag forces DF.
[5 In contrast in the rotary mower apparatus 1 of the present invention,
shown in Fig. 8, the
towing force IF is exerted at the hitch pivot axis HPA which is very low and
forward of
the rotational axis RA of the front wheels 5. The mower deck 3 can pivot in
three
directions about axes HPA. DA1, and DA2 but the hitch arm member 33 of the
hitch arm
assembly 11 is rigid down to the hitch pivot axis HPA, locating the pull point
low and
forward where there is little torque about the rotational axis RA of the front
wheels that
would tend to drive the front wheels 5 down into soft ground.
The rotary mower apparatus I of the present disclosure pulls the mower from a
low point
to reduce downward forces on the front wheels 5 that tend to push the wheels
down into
soft ground and cause the mower to become stuck. The hitch arm assembly II
provides
high clearance to reduce the occurrence of contact between the hitch and the
ground
during travel over sharp vertical obstructions. The hydraulic drive system
avoids
complicated, expensive, and high maintenance mechanical drive lines with
multiple gear
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boxes that would be necessary to provide mechanical drive along the several
pivot axes
between the power take-off 21 of the tractor and the blades 27 of the
apparatus I.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
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