Note: Descriptions are shown in the official language in which they were submitted.
2~7~ ?~
FLUID CYLINDER MECHANISM
I Backqround of the Invention
¦ 1. Field of the Invention:
The invention relates to hydraulic cylinder mechanisms
used for raising and lowering implements carried by powered
vehicles.
2. Description of the Related Art:
U. S. Patent 4,920,732 illustrates a mowing vehicle
having a mower deck coupled to a vehicle via a hydraulic
cylinder assembly. Conventional cylinders have rods rigidly
fixed to pistons within the cylinder, and can be actuated to
selectively transfer the weight of the deck to the vehicle to
enhance the vehicle's traction and stability during operation.
These cylinders can also be actuated by the operators to lift
the deck over curbs or other obstructions during transport.
During operation, the mower deck shown in 4,920,732 will
roll over ground contours. The deck will rise up as it
encounters a bump, and will therefore press upwardly on the
rod to cause the piston to shift upwardly within the cylinder.
Fluid will be drawn into the rod end of the cylinder in
response to the piston shifting upwardly. The piston tends to
shift upward rapidly, since the ground and deck press the rod
and piston upwardly against the large weight of the vehicle.
Fluid therefore enters the rod end of the cylinder quickly and
does not undesirably slow the shifting of the piston.
Once the deck passes over the crest of a bump the front
of the deck must tilt downwardly to remain in contact with the
ground for continued mowing operations. To accomplish this,
the weight of the deck ac~s to shift the piston downwardly
within the cylinder. Fluid must be forced out of the rod end
of the cylinder by the piston as it shifts downwardly. The
small size of the opening in the cylinder and the pressure in
the hydraulic circuit tend to resist the displacement of fluid
from the cylinder. Since the weight of the deck, which is
small compared to the weight of the vehicle, is the only force
acting to shift the piston downwardly and force the fluid out
of the cylinder, the downward shifting of the piston and deck
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thereattached is relatively slow. Therefore, once the deck
has passed over the crest of a bump, the slow downward
shifting of the deck may cause an area of vegetation to be
left uncut by the mower.
Therefore, it would be desirable to provide a fluid
cylinder assembly that can be selectively actuated for weight
transferral or lifting of the implement, and that allows the
implement to follow the contours of the ground. It would be
desirable to provide such a cylinder with a mechanism that
allows the deck to rapidly shift downwardly to remain in
contact with the ground after ground undulations have been
encountered such that little or no areas of grass are left
uncut. It would also be desirable ~or such a mechanism to be
internally provided by the workings of the cylinder.
Summary of the Invention
A fluid cylinder mechanism is provided for coupling a
first structure or vehicle to a second structure or implement.
A cylinder means is provided having a base end coupled to the
vehicle, and a rod end opposite the base end. A piston means
is slidably received by the cylinder means and defines a
piston opening. A rod means is slidably received within the
piston opening to allow the piston means to float on the rod
means. The rod means is also received in the rod end of the
cylinder. The rod means is coupled to the implement and is
shiftable vertically within the piston means and rod end of
the cylinder means in response to the implement encountering
undulations in ground conditions. A hydraulic circuit is
coupled with the cylinder means, and can be controlled for
forcing additional fluid into a rod end chamber of the
cylinder means to thereby force the piston means upwardly
along the rod means and against a snap ring coupled to the end
of the rod means. The snap ring, rod means, and implement are
thereby lifted for transport over obstructions such as curbs.
~he hydraulic circuit can also be controlled for transferring
a portion of the weight of the implement to the vehicle via
the fluid cylinder mechanism for enhancing traction and
stability during operation.
2 ~
Brief Description of the Drawinqs
Figure 1 illustrates the present invention as used to
¦ couple an implement to a vehicle, and a schematic of a
hydraulic circuit for controlling the fluid cylinder
mechanism.
Figure 2 illustrates the preferred embodiment of the
present invention when used with a hydraulic circuit as shown
schematically in Figure 8, the fluid cylinder mechanism being
shown in operation over level terrain.
Figure 3 illustrates the preferred embodiment of the
fluid cylinder mechanism when used with the hydraulic circuit
depicted in Figure 1 and as the implement encounters an
upslope in ground conditions.
Figure 4 shows the fluid cylinder mechanism as used with
the hydraulic circuit shown in Figure 1 when the implement
encounters a downslope in ground conditions.
Figure 5 shows the fluid cylinder mechanism as used with
the hydraulic circuit depicted in Figure 1 and with the
implement operating on level ground.
Figure 6 shows the fluid cylinder mechanism when used
with the hydraulic circuit depicted in Figure 1 and with the
variable orifice valve closed by the operator to thereby lift
the implement for transport over an obstruction.
Figure 7 shows the fluid cylinder mechanism having a
spring for biasing the piston means toward the rod end of the
cylinder means, the fluid cylinder mechanism being shown in
operation on level ground.
Figure 8 schematically illustrates a hydraulic circuit
that maintains a higher pressure in the base end chamber of
the cylinder mechanism than the rod end chamber during normal
operation.
Description of the Preferred Embodiment
Referring now to Figure 1, there is shown a vehicle 10
adapted for carrying an implement 12 such as a mower deck or
snow blower. A cylinder mechanism 14 according to the
preferred embodiment acts to couple the implement 12 to the
vehicle 10, and allows the implement 12 to ride over
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undulations in ground conditions. The cylinder mechanism 14
I is coupled to a hydraulic circuit 16 such as the one shown
I schematically in Figure 1. A pump 18 is provided for
directing pressurized fluid through the circuit 16. Other
mechanisms, such as a hydraulic steering mechanism, may also
be powered by the pump 18. A weight transfer valve 20 having
a variable orifice is provided in the circuit 16 that can be
selectively controlled to raise the implement 12 for transport
over obstructions such as curbs. The hydraulic circuit 16 and
valve 20 are also controllable by the operator for selectively
transferring the weight of the implement 12 to the vehicle 10
during implement operation to thereby enhance the vehicle's
operating traction and stability.
Referring now to Figures 2 - 6, there is shown the fluid
cylinder mechanism 14 according to the preferred embodiment of
the present invention for coupling an implement 12 to a
- vehicle 10. A cylinder means 22 having a base end 24 and a
rod end 26 is pivotally coupled to the vehicle 10. A base end
port 28 and a rod end port 30 are provided in the cylinder
means 22, and each accommodates the flow of hydraulic fluid
into and out of the cylinder means 22. A rod means 32 having
first and second end portions 34, 36 is pivotally coupled to
the implement 12 and is clidably received by the rod end 26 of
the cylinder means 22. A seal 38 and wiper 40 are positioned
between the rod means 32 and the cylinder means 22. The rod
means 32 is also slidably received by a piston means 42 having
a central opening 44, and is therefore capable of shifting
relative to the piston means 42. Seals 46 are carried by the
piston means 42 and are positioned between the piston means 42
and rod means 32, and between the piston means 42 and cylinder
walls. The piston means 42 and cylinder means 22 define a
pair of chambers 48, 50 that are filled with fluid during
operation. On one side of the piston means 42 is a base end
chamber 48, and on the opposite side is a rod end chamber 50.
An abutment means or snap ring 52 is carried by the rod mPans
32 for abutting the piston means 42 as the piston means 42
shifts on the rod means 32 in response to fluid being
I selectively forced into the rod end chamber 50.
I Next the operation of the preferred embodiment will be
discussed. First, the weight transfer and lifting operation
will be addressed. Figure 5 is believed to illustrate the
cylinder mechanism 14 in its neutral operating position. The
snap ring 52 coupled to the rod means 32 is positioned as
shown near the middle of the cylinder means 22 when the mower
deck 12 is operating on level ground. The piston means 42 as
shown is positioned against the snap ring 52 due to the fluid
in the rod end chamber 50 being at a slightly higher pressure
than the fluid in the base end chamber 48. This pressure
differential is caused in part by the weight transfer valve
20, which causes the fluid flowing therethrough to experience
a pressure drop of approximately 28 psi when the valve is
fully opened. This 28 psi pressure drop causes the pressures
upstream of the weight transfer valve 20 to be higher than the
downstream pressures. Therefore, the fluid in the rod end
chamber 50, which is upstream of the weight transfer valve 20,
will normally be at a higher pressure than the fluid in the
base end chamber 48, which is downstream of the weight
transfer valve 20. This pressure differential causes the
piston means 42 to be forced upwardly on the rod means 32 and
toward the snap rlng 52 during normal operation, however the
pressure differential is not great enough to lift the
implement 12.
To initiate the weight transfer or lift operation, the
operator actuates the valve 20 to restrict the passage of
fluid through the weight transfer valve 20, thereby forcing
more fluid to pass through the rod end port 30 and enter the
rod end chamber 50. The pressure in the rod end chamber S0 is
thereby increased, which causes the piston means 42 to press
upwardly on the snap ring 52. As the piston means 42 presses
upwardly on the snap ring 52 a portion of the weight of the
implement 12 is transferred to the vehicle 10 via the cylinder
mechanism 14. Therefore, the operator can transfer a portion
of the implement's weight to the vehicle 10 during operation
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2:04pm
for increasing the vehicle traction by manipulating the
restriction in the valve 20.
¦ To lift the implement 12 off the ground, the operator
further restricts or closes the variable orifice of the weight
transfer valve 20, which forces more fluid into the rod end
chamber 50. The increased pressure in rod end ~hA her 50
causes the piston means 42 to raise the snap ring 52, the rod
means 32 and implement 12 thereattached (See Figure 6). The
implement 12 is thereby lifted for transport over obstacles
such as curbs.
When the operator wishes to lower the implement 12 for
operation, he opens the variable orifice of the weight
transfer valve 20. The pressure in the rod end chamber 50
will therefore decrease, and the weight of the implement 12
will act on the rod means 32, snap ring 52 and piston means
42, causing them to move downwardly within the cylinder means
22. Fluid will be displaced from the rod end chamber 50 and
into the hydraulic circuit 16 as the piston means 42 shifts
toward the rod end 26 of the cylinder means 22. Fluid will be
2~ drawn in from the circuit 16 to the base end chamber 48 as the
piston means 42 shifts downwardly. The implement 12 will
eventually come to rest on the ground again, and the cylinder
mechanism 14 will then be in the configuration as shown in
Figure 5. At this point the rod means 32 will stop traveling
downwardly, since the implement 12 has come to rest on the
ground. The piston means 42 will also stop traveling
downwardly, and will remain in abutment with the snap ring 52
as shown in Figure 5 due to the pressure in the rod end
chamber 50 being at a higher pressure than the base end
chamber 48.
Next, the operation of the preferred embodiment will be
described as the implement 12 is being utilized on undulating
terrain with the weight transfer and li~t mechanisms
unactuated. Figure 5 illustrates one configuration of the
cylinder means 22, piston means 42 and rod means 32 when the
implement 12 is operating on level ground. When the implement
12 encounters a rise in the surface of the ground, the
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implement 12 will shift upwardly to ride over the bump. This
will cause the rod means 32 coupled to the implement 12 to
I shift upwardly within the cylinder means 22 to a position
similar to that shown in Figure 3. Since the rod means 32 is
slidably received within the opening 44 in the piston means
42, the piston means 42 need not necessarily shift upwardly
with the rod means 32. As the rod means 32 shifts upwardly
into the base end chamber 48, the fluid pressure in the base
end chamber 4~ will increase. This increase in pressure can
cause fluid to exit the base end chamber 48 through the base
end port 2~, and can cause the piston means 42 to shift
further downwardly on the rod means 32 within the cylinder
means 22. Since the rod means 32 is driven upwardly within
the cylinder means 22 against the relatively large weight of
the vehicle 10, the rod means 32 can shift upward relatively
rapidly.
As the implement 12 rides over the crest of the bump, the
implement 12 will tend to fall to the ground again under its
own weight. The rod means 32 therefsre shifts downwardly from
the position shown in Figure 3 to the position shown in Figure
5. As the rod shifts downwardly from the position shown in
Figure 3, the volume previously occupied by the rod means 32
within the base end chamber 48 must be filled. This volume is
filled by fluid flowing into the base end chamber 48, or by
the piston means 42 shifting upwardly on the rod means 32.
The weight of the implement 12 i5 small compared to the
vehicle 10, and therefore the force acting to draw fluid into
the base end chamber 48 as the implement 12 shifts downwardly
is relatively small. ~owever, the amount of fluid that must
be drawn into the base end chamber 48 is believed to be less
than the amount displaced by prior art mechanisms during
similar downward shifting of the implement 12. The amount of
fluid displaced is smaller because the rod means 32 is allowed
to shift within the piston means 42 as the implement 12 drops.
The cross sectional area of the rod means 32 as it shifts
within the base end chamber 4~ is less than the cross
sectional area of prior art pistons and rods rigidly coupled
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together, and therefore the volume of fluid that is required
I to be displaced within the cylinder is decreased. Because the
I amount of fluid drawn in is less than if the piston means 42
were fixed to the rod means 32, the downward shifting of the
implement 12 as it passes over the crest of the bump will
occur more rapidly. Also, the shifting of the piston means 42
within the cylinder means 22 to fill the volume within the
base end chamber 48 vacated by the shifting rod means 32 tends
to decrease the amount of fluid required to be displaced.
Therefore, the implement 12 will tilt downwardly toward the
ground under its own weight more rapidly to continue
operation.
The preferred embodiment shown in Figure 1 is coupled
between a vehicle 10 and a mower deck implement 12. As the
lS deck 12 passes over a bump's crest, the deck 12 will tilt
downwardly more quickly under its own weight since a smaller
amount of fluid is required to be displaced. Therefore,
little or no area of grass is left uncut when the deck 12
encounters a downslope.
When the implement 12 is operating on level ground and
then encounters a dip, the implement 12 must shift downwardly
under its own weight to stay in contact with the ground for
optimum performance. When this occurs, the rod means 32 and
piston means 42 shift downwardly from the neutral position
shown in Figure 5 to the position shown in Figure 4. As the
rod means 32 and piston means 42 shift downwardly within the
cylinder means 22, fluid will be forced out of the rod end
chamber 50 and into the hydraulic circuit 16~ At the same
time, fluid from the circuit 16 will flow into the base end
chamber 48 to occupy the space vacated by the rod means 32 and
piston means 42.
The preferred embodiment of the present invention is
described above as used with a hydraulic circuit 16 that
causes the fluid in the rod end chamber 50 to be at a pressure
sliqhtly higher than the fluid in the ~ase end chamber 48
during normal operating conditions. Therefore the piston
means 42 utilized in the above described environment will
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normally be positioned against the snap ring 52 when operating
on level ground. However, the cylinder mechanism 14 according
I to the present invention could also be used with a hydraulic
circuit, such as the one shown in Figure 8, that creates a
slightly higher pressure in the base end chamber 48 than the
rod end chamber 50 during normal operation. This would cause
the piston means 42 to shift downwardly with respect to the
rod means 32 and thereby be positioned adjacent the rod end 26
of the cylinder means 22 during operation on level ground, as
shown in Figure 2. A space or clearance would therefore exist
between the snap ring 52 and the piston means 42. When the
implement 12 would encounter a depression in the ground
conditions, the rod means 32 and snap ring 52 would then shift
downwardly due to the weight of the implement 12 without
abutting the piston means 42 or shifting the piston means 42
downwardly. Therefore, it is believed that less fluid would
need to be displaced, and the downward shifting of the
implement 12 would occur more rapidly.
The alternate hydraulic circuit 56 shown schematically in
Figure 8 depicts a three position valve 58. The valve is
configured in the first position during normal operation of
the implement. The first position allows the piston means 42
to float on the rod means 32, and creates a slightly higher
pressure in the base end chamber 48 than the rod end chamber
50, since the rod end chamber 50 is downstream of the weight
transfer valve 20. The second position of the valve 58 is
utilized when the weight transfer valve 20 is actuated for
transfering the weight of the implement 12 to the vehicle 10.
The third position is utilized when the implement 12 is being
raised for transport.
The preferred embodiment illustrated in the attached
drawings shows the cylinder mechanism 1~ having the base end
portion 24 of the cylinder means 22 coupled to the vehicle 10,
and the rod means 32 coupled to the implement or deck 12. In
this configuration the rod means 32 is positioned beneath the
cylinder means 22, thereby generally preventing debris from
accumulating in the vicinity where the rod means 32 passes
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through the base end 24 of the cylinder means 22. The rod
means 32 therefore remains cleaner, and fewer contaminants are
¦ introduced into the cylinder chambers 48, 50. ~owever, it is
apparent that the cylinder mechanism 14 according to the
present invention could also be employed by coupling the base
end portion 24 of the cylinder means 22 to the implement 12,
and coupling the rod 32 to the vehicle 10.
Referring now to Figure 7, there is shown an alternative
embodiment of the present invention utilizing a single acting
cylinder. The base end chamber 48 of the alternative
embodiment shown in Figure 7 does not contain hydraulic fluid,
but rather is provided with a biasing means or spring 54 for
biasing the piston means 42 to shift toward the rod end 26 of
the cylinder means 22. The base end port 28 allows the
passage of air into and out of the base end chamber 48, and is
sized large enough that the flow of air is not significantly
- restricted as the rod means 32 shifts upwardly due to ground
undulations. However, the rod end chamber 50 is coupled
during operation to a hydraulic circuit as shown in U.S.
Patent 4,920,320, and allows fluid to be selectively forced
into the cylinder means 22 when the operator actuates a
control to restrict the variable orifice. When the orifice is
restricted, fluid is forced into the rod end chamber 50 to
shift the piston means 42 upward against the biasing force of
the spring 54. The piston means 42 can thus be forced
upwardly against the snap ring 52 for transferring the weight
of the implement 12 to the vehicle 10, or can be shifted
further upwardly to lift the implement 12. The sprin~ 54 of
the alternative embodiment acts to bias the piston means 42
toward the rod end 26 of the cylinder means 22, and thereby
create a space or clearance between the snap ring 52 and
piston means 42 during operation on level ground, such that
the rod means 32 can shift either up or down as bumps or dips
are encountered without abutting the piston means 42. In this
way less fluid is displaced and the shifting of the implement
12 is quickened.
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