Note: Descriptions are shown in the official language in which they were submitted.
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HYDRAULIC LIFT ASSIST FOR TRACTOR TOWED EARTH MOVING
APPARATUS
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application No.
60/661,703, filed March 15, 2005, which is incorporated herein by reference in
its entirety.
TECHNICAL FIELD
The present invention relates generally to hydraulic systems for lifting a
load. More specifically, the present invention relates to hydraulic systems
that
allow the selection of a secondary source of hydraulic power to lift a load.
BACKGROUND
Certain kinds of earth moving equipment use a single power source for
multiple purposes. For instance, a tractor may use its internal combustion
engine to
not only provide locomotion, but to also operate a high pressure hydraulic
pump.
While the tractor engine is typically able to provide sufficient horsepower
for all
needs, there may arise situations where the tractor engine is under powered.
One example might include a tractor being used to pull an earth moving
apparatus. As the tractor pulls the earth moving apparatus, it fills with
earth thereby
increasing the resistance to the tractor pull. In order to compensate for this
increased resistance, the operator of the tractor may gradually lift the frame
of the
earth moving apparatus, and, thereby the cutting blade, as the apparatus fills
with
earth. This lifting of the cutting blade, using the tractor's hydraulic
system,
decreases the resistance to the tractor's pull as the blade cuts less deeply
into the
earth. However, because the earthmoving apparatus' hydraulic system is powered
by the tractor's engine, the horsepower of the engine must now be split
between the
simultaneous pulling of the earth moving apparatus and the lifting of the
cutting
blade. If the tractor is in a heavy pull, operating the hydraulics to lift the
cutting
blade may put enough extra drag on the engine to cause it to stall.
Many hydraulic systems for lifting loads, such as an earth moving apparatus
frame and/or cutting blade, are known. Such hydraulic systems typically use
hydraulic pressure to actuate a hydraulic cylinder in such a way that a load
is lifted.
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However, if the primary source of pressurized hydraulic fluid fails or is
unable to provide sufficient hydraulic pressure, the system will be unable to
lift the
load.
A number of systems exist to provide hydraulic pressure given the absence,
or failure, of a primary source of pressurized hydraulic fluid. Representative
examples include, without limitation, the hydraulic systems disclosed in U.S.
Patents 5,313,795, 5,090,495, 3,965,587, 4,360,187, 5,037,368, 5,516,070,
5,806,838, 3,945,685, and 3,945,691, the disclosures of each which are hereby
incorporated by reference. These systems typically use a hydraulic accumulator
to
store hydraulic pressure to be used in the absence or failure of another power
source. Systems of this type are typically constantly engaged to the active
hydraulic
system with the accumulator being 'inline' between the sources of pressurized
hydraulic fluid and the ultimate use. Such systems can be said to be
'constantly
engaged' as the operator of the system has no means of selecting when the
pressure
stored in the accumulator is not to be used, i.e. no means of disconnecting
the
accumulator from the hydraulic system. As such, the constant engagement of
such
systems do not allow the operator or designer of the hydraulic system to
select
whether the primary source of pressurized hydraulic fluid or the reserve
hydraulic
pressure in the accumulator is to be used for a given purpose. The reserve
pressure
is always available regardless of the operator's wishes. However, the
hydraulic
systems typical of earth moving machinery are designed so as to not be under
significant pressure unless they are being used. Thus, a'constantly engaged'
accumulator would provide hydraulic pressure to the system every time the
primary
source is not in use, even when the operator desires that there be relatively
little
hydraulic pressure in the system.
Other systems for selectively engaging an accumulator with a hydraulic
system only engage when the hydraulic pressure in the system falls below a
predetermined level. Representative examples include, without limitation, the
hydraulic systems disclosed in U.S. Patents 4,736,991, and 4,792,192, the
disclosures of each which are hereby incorporated by reference. However, such
selective engagement systems are of little aid in selectively raising an earth
moving
apparatus frame, bucket, or cutting blade. This is because the hydraulic
systems
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typical of earth moving machinery are not under significant pressure unless
they
are being used. Thus, an accumulator under a pressure sensitive control
provides
hydraulic pressure to the system every time the primary source is not in use,
precisely when the operator desires that there be relatively little hydraulic
pressure
in the system.
Lastly, accumulator systems that engage when a certain back pressure has
been reached are also known. A representative example includes, without
limitation, the hydraulic system disclosed in U.S. Patent 2,846,187, the
disclosure of
which is hereby incorporated by reference. In such a system, the hydraulic
pressure
in an accumulator is released into a hydraulic system when the pressure in the
hydraulic system rises to a predetermined level. Such systems increase the
hydraulic flow, allowing the hydraulic system to actuate more quickly, but
would be
of little use where the primary source of hydraulic power is unable to provide
that
predetermined hydraulic pressure. Further, such systems do not allow the
operator
or designer of the hydraulic system to select whether the primary source of
pressurized hydraulic fluid or the reserve hydraulic pressure in the
accumulator is
used.
As such, an improved hydraulic system that allows the selective introduction
of a reserve source of pressurized hydraulic fluid to lift a load would be an
improvement in the art.
SUMMARY
The present invention includes hydraulic systems designed to allow the
selection of a source of pressurized hydraulic fluid to lift a load. In one
illustrative
embodiment, a hydraulic system in accordance with the present invention
comprises
a hydraulic accumulator that may be selected as a source of pressurized
hydraulic
fluid to lift a load. Such a hydraulic system may or may not be part of a
cushion
ride system.
The present invention also includes methods for selecting a source of
pressurized hydraulic fluid to lift a load. In one illustrative embodiment, a
source of
pressurized hydraulic fluid is used to charge an accumulator. The hydraulic
pressure in the accumulator is then used to lift the load when selected to do
so.
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A further illustrative embodiment of the present invention includes a
hydraulic system comprising a hydraulic accumulator that may be selected as a
source of pressurized hydraulic fluid to lift a load into earth moving or
ground
leveling apparatus. The load lifted in the eartli moving apparatus may be the
earth
moving or ground leveling apparatus frame, wheels, apron, cutting blade or
other
portion of the earth moving or ground leveling apparatus or its cargo. Such a
hydraulic system may or may not be part of a cushion ride system incorporated
into
the earth moving or ground leveling apparatus.
DESCRIPTION OF THE DRAWINGS
It will be appreciated by those of ordinary skill in the art that the elements
depicted in the various drawings are not to scale, but are for illustrative
purposes
only. The nature of the present invention, as well as other embodiments of the
present invention may be more clearly understood by reference to the following
detailed description of the invention, to the appended claims, and to the
several
drawings attached hereto.
FIG. 1 is a schematic diagram of an illustrative embodiment of a hydraulic
system for selectively regulating the flow of a hydraulic fluid into and out
of a
hydraulic accumulator.
FIG. 2 is a schematic diagram of a second illustrative embodiment of a
hydraulic system for selectively regulating the flow of hydraulic fluid
between a
source of pressurized hydraulic fluid, a hydraulic accumulator, a hydraulic
cylinder,
and a cushion ride system.
FIG. 3 illustrates a further embodiment of an earth moving apparatus on to
which the hydraulic system of the present invention may be incorporated.
DETAILED DESCRIPTION
It will be appreciated that the embodiments described herein, while
illustrative, are not intended to so limit the invention or the scope of the
appended
claims. Those of ordinary skill in the art will understand that various
combinations
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or modifications of the embodiments presented herein maybe made without
departing from the scope of the present invention.
Referring now to drawing FIG. 1, there is illustrated a schematic view of a
hydraulic system in accordance with the present invention generally at 100. As
illustrated, the hydraulic system 100 comprises a source of pressurized
hydraulic
fluid generally at 102. The source of pressurized hydraulic fluid generally at
102
includes, as illustrated, a hydraulic pump 104, a reservoir of hydraulic fluid
106, a
selector valve 108, and an engine 109 for driving hydraulic pump 104. A non-
limiting example of a source of pressurized hydraulic fluid generally at 102
would
be the engine and high pressure hydraulic system present on a prime mover.
Examples of prime movers include, but are not limited to, tractors, trucks,
and
various other self-propelled vehicles. Hydraulic system 100 further comprises
hydraulic lines 110a and 110b, which may be used to carry hydraulic fluid to
and
from hydraulic cylinders 112a and 112b. Branching from hydraulic line 110a is
a
lift assist system generally at 114. The lift assist system generally at 114
includes
an accumulator 116, a check valve 118, a valve 120, and a check valve 122. As
shown, the directional force of the load on hydraulic cylinder 112a is as
indicated by
arrow 124.
Although not illustrated, the hydraulic system 100 may also be used to
operate multiple hydraulic cylinders which can be single or double acting.
Such
additional cylinders may include, for example, but are not limited to,
cylinders for
raising or lowering a scraper bucket, opening or closing a scraper apron,
operating a
load ejector, operating a brake system, or providing pilot pressure for other
hydraulic valves. These other operative hydraulic systems are as illustrated
and
disclosed in 4,383,380, 4,388,769, 4,398,363, 4,553,608, and 6,347,670 to
Miskin
which are incorporated herein by reference.
During normal operation, valve 120 remains closed. As hydraulic cylinders
112a and 112b are actuated during normal operation, hydraulic oil under
pressure
will pass through check valve 118 to be stored in accumulator 116. If the
operator
desires, or if a certain predetermined condition or conditions are sensed,
valve 120
may be caused to open allowing the stored hydraulic oil under pressured to
pass
through valve 120 and check valve 122 and into hydraulic line 110a. If the
stored
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hydraulic pressure in accumulator 116 is sufficient, hydraulic cylinders 112a
and
112b will actuate to lift the load. When actuating the hydraulic cylinder
causes the
lifting of a load comprising the frame of an earth moving apparatus, bucket,
and/or
cutting blade, the demands on engine 109 may be tliereby reduced, allowing the
source of pressurized hydraulic fluid generally at 102 to further lift the
load without
assistance of the hydraulic pressure stored in the accumulator.
It will be appreciated by one of skill in the art that various types of valve
120
may be used. In one exemplary embodiment, valve 120 may comprise an
electrically-controlled, solenoid-type valve that may be controlled by a
control
switch (not shown) that may be located in the cab of the prime mover used to
pull
the apparatus to which hydraulic system 100 is mounted, or, if the apparatus
on
which hydraulic system 100 is self-propelled, the control switch (not shown)
may be
located in the control area of the self-propelled apparatus. In other
embodiments,
valve 120 may be any type of hydraulic valve and controlled in any manner
known
in the art, such as by mechanical systems and the like. Other types of valves
that
may be used with hydraulic system 100 of the present invention include,
without
limitation, sandwich valves, hydraulic control valves, electro-hydraulic
valves,
remote control valves, mobile valves, directional control valves, check
valves, glove
valves, gate valves, and other types of manual control valves. Types of
control
systems that may be used to control valve 120 of the present invention
include,
without limitation, pressure controlled systems, pneumatic systems, vacuum
systems, electronically controlled systems, automatically controlled systems,
manually controlled systems, remote control systems, and mechanically linked
systems.
As would be apparent to one of skill in the art, a load comprises the force of
gravity acting on a particular mass so as to drive the actuation of a piston
rod of a
hydraulic cylinder. In one exemplary embodiment, the load may be the weight of
the frame of an earth moving apparatus. The lifting of a load comprises the
actuation of a hydraulic cylinder causing a load to move against the force of
gravity.
Referring now to drawing FIG. 2, there is illustrated a schematic view of a
hydraulic system in accordance with the present invention generally at 200. As
illustrated, the hydraulic system 200 includes a cushion ride system generally
at 210
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in place of check valve 118. When actuated, the cushion ride system utilizes
the accumulator 116 as a shock absorber when the hydraulic system 200 is
mounted
on a veliicle such as an earth moving or ground leveling apparatus. Examples
of
using an accumulator as a shock absorber can be found in U.S. Patents
6,382,326
and 6,749,035, both of which are incorporated herein by reference. As
illustrated,
cusliion ride system generally at 210 may comprise check valves 212 and 214,
valves 216 and 220, and restrictor 218. Also depicted is valve 222. During
normal
operation, valve 222 remains open. However, if it desired to charge
accumulator
116 without actuating hydraulic cylinders 112a and 112b, valve 222 may be
closed,
thereby diverting the flow of pressurized hydraulic away from hydraulic
cylinders
112a and 112b.
Hydraulic system 200 further includes sensor 224 for sensing the flow of
hydraulic fluid in hydraulic line 110a. As shown, sensor 224 may be
operatively
connected to valves 120 and 220 so as to control the position of valves 120
and 220
in response to predetermined sensor inputs. It will be appreciated by one of
skill in
the art that the position and type of sensor 224 described is merely exemplary
and
that any number of sensors inputs may be used to determine when valves 120 and
220 are opened. Such sensors or inputs include, but are not limited to,
operator
decision, a system for sensing a failure of movement of hydraulic cylinders
112a
and 112b when selector valve 108 is actuated so as to lift the load, a speed
sensor
for sensing the speed of the prime mover, a system for sensing the engine
speed of a
prime mover, a system for sensing which gear the transmission of the prime
mover
is currently in, or a system for sensing a lack of hydraulic fluid flow in
hydraulic
line 110a when selector valve 108 is actuated so as to lift the load.
At the beginning of normal operation, valves 120 and 220 are opened and
valve 222 closed so that hydraulic fluid under pressure from the source of
pressurized hydraulic fluid generally at 102 can pass through valves 216 and
220 as
well as check valve 212 and/or restrictor 218 to be stored in accumulator 116.
Once
the accumulator 116 is charged, valves 120 and 220 are closed and valve 222 is
opened. If, at any time, the stored pressurized hydraulic fluid in accumulator
116 is
selected to actuate hydraulic cylinders 112a and 112b, valves 120 and 220 will
be
opened and the hydraulic fluid will pass through restrictor 218 as well as
valves 120
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and 220 and into hydraulic line 110a. If the stored hydraulic pressure in
hydraulic
accumulator 116 is sufficient, hydraulic cylinders 112a and 112b will be
actuated to
lift the load. To recharge accumulator 116, valve 222 may again be closed
while
valves 120 and 220 remain open to allow hydraulic fluid under pressure from
the
source of pressurized hydraulic fluid generally at 102 to pass into the
accumulator.
In the alternative, the accumulator may be recharged when piston rod 318
reaches
its maximum extension while valves 120 and 220 remain open. To operate the
cushion ride system, the operator interrupts the connection between hydraulic
lines
110a and 110b and hydraulic pump 114 using selector valve 108. Valves 216 and
220 are then opened. Any forces on hydraulic cylinders 112a and 112b are then
dampened by the entry and release of hydraulic fluid from accumulator 116.
Referring now to drawing FIG. 3, which is a side view of an earth moving
apparatus generally at 300. Scrapers and earthmoving apparatuses of the
general
type to which earth moving apparatus 300 relate are generally known.
Representative examples of earthmoving apparatuses include, without
limitation,
the scrapers disclosed in U.S. Patents No. 4,383,380, 4,388,769, 4,398,363,
4,553,608, and 6,347,670 to Miskin, the disclosures of which are herein
incorporated by reference. A typical earth moving apparatus includes a bucket
for
holding earth. The bucket includes a floor, a rear wall, two upstanding
opposing
side walls, an open front, and an open top. An apron, or gate, is located
opposite the
rear wall of the bucket and can swing closed to hold the soil in the bucket
during
transport. In a scraper device, a blade is located adjacent the front edge of
the floor
of the bucket and cuts the eat.-th to a predetermined depth as the earth
moving
apparatus is moved forward over the earth's surface. The soil cut from the
earth by
the blade is collected in the bucket. When the bucket is full of soil, the
earth
moving apparatus is transported to another location where the soil is
deposited.
Other examples of earth moving apparatuses having a bucket include, but are
not
limited to, dump trucks, backhoes, and front end loaders.
More specifically, the depicted exemplary earth moving apparatus generally
at 300 includes a frame 302, a cutting blade 304, a bucket 306, an apron 308 a
tongue 310 and at least two ground engaging wheels 312. An actuator, such as
hydraulic cylinder 112a has a first end 314 and a second end 316. When a
piston
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rod 318 of the hydraulic cylinder 112a is extended (as shown), the frame 302
is
effectively raised. The imposed weight of frame 302 thus applies pressure upon
the
piston rod of hydraulic cylinder 112a. According the present invention, the
pressure
stored in accumulator 116 (not shown) may be used extend piston rod 318 of the
hydraulic cylinder to effectively raise the frame 302 and therefore the bucket
306
and the cutting blade 304.
When beginning an earth scraping operation using an earth moving
apparatus such as the an earth moving apparatus geilerally at 300, the
operator first
lifts the frame 302 by supplying hydraulic pressure to hydraulic cylinders
112a and
1 12b through hydraulic line 110a by the selection of the proper setting of
selector
valve 108. The charging of the hydraulic accumulator 116 would occur
automatically when the piston rod 318 is fully extended, if the hydraulic
system is
equipped with a check valve 118, or, if the earth moving apparatus 300 is
equipped
with a cushion ride system, such as the cushion ride system generally at 210,
the
accumulator can be charged when piston rod 318 reaches its maximum extension
and valves 120 and 220 are opened or when valve 222 is closed and valves 120
and
220 are opened.
During normal operation, as the bucket 306 fills with earth, the resistance to
the pull of the prime mover will increase. To mitigate this increased
resistance, the
operator or a sensor input may select to raise the frame 302, and thereby
bucket 306
and cutting blade 304. However, if the tractor is in a heavy pull, engine 109
may
not have enough power to both pull earth moving apparatus 300 and provide
sufficient hydraulic pressure via hydraulic pump 104 to lift frame 302, and
thereby
bucket 306 and cutting blade 304. To provide sufficient hydraulic pressure,
the
operator or a sensor input from as sensor such as sensor 224 causes valves 120
and
220 to open releasing the hydraulic pressure stored in hydraulic accumulator
116,
through valves 120 and 220, and into hydraulic line 110a. If the hydraulic
pressure
stored in hydraulic accumulator is sufficient, piston rod 318 of hydraulic
cylinder
112a will be extended, raising the frame 302, and thereby bucket 306 and
cutting
blade 304. The resistance to the pull of the prime mover will be thereby
decreased
allowing the engine 109 to provide enough power to both pull earth moving
apparatus 300 and provide sufficient further hydraulic pressure via hydraulic
pump
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104 to lift frame 302, and thereby bucket 306 and cutting blade 304. If the
hydraulic system is equipped with a check valve 118 the accumulator 116 will
be
recharged when piston rod 318 reaches its maximum extension, or, if the earth
moving apparatus 300 is equipped with a cushion ride system, such as the
cushion
ride system generally at 210, the accumulator may be recharged wlien piston
rod
318 reaches its maximum extension and valves 120 and 220 are opened or when
valve 222 is closed and valves 120 and 220 are opened.
It will be appreciated by those of ordinary skill in the art that the
embodiments described herein are not intended to limit the scope of the
present
invention. Various combinations and modifications of the embodiments described
herein may be made without departing from the scope of the present invention
and
all modifications are meant to be included within the scope of the present
invention.
Thus, while certain exemplary embodiments and details have been described for
purposes of describing the invention, it will be apparent to those of ordinary
skill in
the art that various changes in the invention described herein may be made
without
departing from the scope of the present invention, which is defined in the
appended
claims.
