Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to farming implements and in particular to
the hydraulic system for selectively raising and lowering a farming implement
such as a cultivator. More specifically, the invention is directed to a master-
slave cylinder system used for such purpose and preferably so disposed and
5 arranged that the contracting of the hydraulic cylinders of the system resultsin the lowering of the implement, while the extending of the cylinders serves
the purpose of raising the implement.
The known master/slave cylinder systems, provide many advantages
among which the most important are relative structural simplicity and
10 reliability. On the other hand, the system is also known to give rise to several
problems.
For instance, the hoses interconnecting the cylinders of the system,
while providing the desired flexibility and thus reliability of the hydraulic
connection, give rise to a phenomenon which is known as "rebound". Rebound
15 occurs as a consequence of a sudden interruption of the flow of hydraulic fluid
from a master cylinder of the system on lowering of the implement. The
sudden interruption of the flow of hydraulic fluid from the master cylinder is
caused by a poppet valve actuated by an adjustable mechanism at a point of
a predetermined contraction of the piston rod of the master cylinder. The
20 sudden interruption of the flow of hydraulic fluid through the master cylinder
results in a surge of pressure at the opposed end of the series of the cylinderswhich results in an expansion of the hoses of the system bringing the slave
cylinders out of alignment which may be significant particularly from the
standpoint of modern cultivators combined with air seeders wherein the
25 tolerances of the depth of penetration of the soil are relatively small. If, for
instance, the operator runs a cultivator over a soft ground condition, he has toraise the implement slightly so as to maintain the depth at the set value. The
only way this can be done from the tractor is to manipulate the control valve.
The changes caused by the manipulation in the system give rise to the
30 misalignment described .
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Attempts have been made to resolve this problem by limiting the pressure
causing the lowering of the implement by way of a pressure reducing valve
interposed between the pump of the system (on an associated tractor) and the
last cylinder of the system.
Another problem encountered with the known systems is the chatter of
the hydraulic system on lowering of the implement with the resulting impacts
which give rise to further inaccuracies of the operation. The chatter is caused
by a number of factors including the inherent pressure in the system caused
by the weight of the implement in combination with the action of check valves
employed to prevent leaking of the pressurized oil from the slave system back
to the tractor control valve and to the hydraulic fluid tank of the system.
Attempts have been made to improve the operation of the master/slave
systems. For instance, the device disclosed in US Patent 4,825,655 (Buchl et
al.) discloses a master/slave system wherein a pressure reducing valve is used
to avoid pressure surges in the system. The system disclosed and claimed
does not provide efficient check of the leakage of the pressurized fluid from the
master/slave system back to the control valve of the tractor and therethrough
to the tank of the system.
It is an object of the present invention to further advance the art of
master/slave systems used in farming implements by providing a system which
would (a) have virtually no back leakage to the control valve at the tractor, (b)
in which the rebound would be eliminated and (c) which would also eliminate
the chatter upon lowering.
In general terms, the invention provides a master/slave cylinder hydraulic
system for use in selectively raising or lowering a farming implement, said
system comprising, in combination: a plurality of hydraulic cylinders disposed
in cylinder series, each cylinder of the cylinder series having a first port at a
first end of the respective cylinder, and a second port at a second end thereof,the first and second ports being alternate inlet or discharge ports of the
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respective cylinder, each port communicating with one of two cylinder
chambers disposed one to each sides of a piston of the respective cylinder;
a depth stop valve operatively associated with the first port of a first cylinder
of said series to block the flow of hydraulic fluid through said first cylinder
when a predetermined extent of lowering of the farming implement is reached;
raise line means and lower line means for alternately supplying or discharging
hydraulic fluid to or from the series of cylinders, and connecting means for
connecting said line means to respective portions of an operator control valve,
said lower line means being that line which is pressurized when the implement
is lowered, and said raise line means being that line which is pressurized when
the implement is raised;
said raise line means hydraulically communicating with said depth stop valve,
said lower line means hydraulically communicating with the second port of a
last cylinder in said cylinder series;
pressure reducing means operatively associated with said lower line means and
interposed in that part of the lower line means which is upstream of the last
cylinder when the implement is being lowered, said lowerline means being
arranged to reduce the pressure of the hydraulic fluid at the second port of thelast cylinder to a fraction of fluid pressure supplied to the pressure reducing
means from the control valve; and
releasable first pressure arresting means and second pressure arresting means
operatively associated with the first and lower line means, respectively, and
interposed between the cylinder series and each of said line means for
releasably arresting pressure within the cylinder series.
The invention will be described by way of a preferred, exemplary
embodiment, with reference to the attached drawings. In the drawings:
Figure 1 is a diagrammatic representation of a slave cylinder depth control
system according to the present invention;
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Figure 2 is a simplified, explanatory cross sectional view of the poppet
valve used in the system, with the poppet valve shown in closed
state;
Figure 3 is a view similar to that of Fig. 2 but showing the poppet valve
open; and
Figure 4 is an enlarged view of the valve system of the present invention.
Reference numeral 10 generally designates a master/slave hydraulic
system of a farming implement, in this case a cultivator. The system includes
four hydraulic cylinders 11, 12, 13, 14, disposed in series as is well known in
the art. Each cylinder 11 - 14 has a piston 15, 16, 17 and 18 connected to the
respective piston rod 19, 20, 21 and 22, respectively. The free end of each
piston rod 19 - 22, which, in the embodiment shown, is the lower end, is
provided with a yoke 23, 24, 25 and 26, while a similar mounting bracket 27,
28, 29 and 30 is fixedly secured to the cylinder body of the respective cylinder11 - 14.
As is well known, the brackets 27-30 and the yokes 23-26 are secured
to the respective mechanism of the cultivator (the mechanism not shown)
which raises or lowers the ground wheels of the implement relative to its frame
to lower or raise, respectively, the frame with respect to the ground. As
mentioned, the cylinders 11-14 are disposed in series. This means, that they
are interconnected with each other such that they perform the same function
with respect to the implement - i.e. they all either raise or lower the implement.
More specifically and preferably, they all either extend or contract to perform
the desired function. In the embodiment shown, simultaneous extension of
piston rods 19-22 of cylinders 11-15 raises the implement and the contraction
lowers same. This is achieved by hydraulically connecting the cylinders 11-15
in series: the piston rod end or chamber 31 of the "master" cylinder 11
communicates with the bottom end or chamber 32 of the next cylinder 12, its
piston rod end 31 with the bottom end 32 of cylinder 13. The piston rod end
and the bottom end can also be referred to as a "first" and "second" end or
port, respectively, it being understood that the terms "first" and "second"
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could have the reversed meaning designating the bottom end and the piston
rod end or port, respectively. The piston rod end 32, of cylinder 13, in turn,
communicates with the bottom end 32 of the last cylinder 14. The piston rod
end 31 of the last cylinder 14 of the series is provided with a hydraulic fluid
5 supply line which is referred to as a lower line 33 because the line is
pressurized when it is desired to lower the implement. The line 33 and its
associated parts which will be described later, are also generally referred to as
a "lower line means".
The bottom end 32 of the master cylinder 11 communicates via a depth
10 stop valve, in the embodiment shown, a poppet valve 34 whose housing
slidably receives a lifting rod 35. The top end of the rod 35 faces the stem 36
of a poppet 37. The port 38 of the poppet valve 34 communicates with the
cylinder 11, the port 39 with a hydraulic fluid supply line, referred to as a raise
line 40 as, in the embodiment shown, it is pressurized when the implement is
15 to be raised as will be explained later. The line 40 and its associated parts to
be described as this disclosure proceeds, is also generally referred to as a
"raise line means." The lower end of rod 35 faces a lifting plate 41 fixedly
secured to the piston rod 19 at a selected location to secure the closing of theport 39 by poppet 37 (Fig. 2) when the contraction of piston rod 19 reaches
20 a position at which the plate 41 lifts the rod 35 and with it the poppet 37. The
position of plate 41 is adjustable to allow adjustment of the lowermost positionof the implement which corresponds to the desired depth of penetration of the
soil by the tools of the implement, e.g. the sweeps of a cultivator.
The master/slave cylinder system described above is known in the art
25 and therefore does not need a more detailed description. It will suffice to say
that it is powered by hydraulic fluid coming from a hydraulic pump 42 of
hydraulic system of an associated tractor. The tractor system also includes a
manually operated control valve 43, to which valve both lines 33 and 40 are
hydraulically connected by suitable connecting means, and a tank 44. Suction
30 line 45 communicates the pump 42 with the tank 44, while a drain line section46 extends between the control valve 43 and the tank 44. The pressure side
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of pump 42 communicates with the control valve 43 by a pressure line 47. The
tractor system, likewise, is known in the art and therefore does not have to be
described in greater detail.
The implement side of the control valve 43 is provided with what
5 functions as an extension of the lower line 33 and the raise line 40 already
mentioned .
It should be borne in mind that the term "raise line" and "lower line" was
selected for convenience, reference being made to the operation of the two.
As already mentioned, when the "raise" line is pressurized by fluid coming from
10 valve 43, the associated implement is raised. When the "lower" line is
pressurized, it is lowered.
Interposed within the system of the raise and lower lines 40, 33 is
double line lock pressure reducing valve system 50 according to the present
invention. The inventive valve system will now be described in detail.
Its pump side has two ports generally designated as V1 for the pump
side port of raise line 40, while V2 is the pump side port of the lower line 33.The implement side ports of the valve system 50 is correspondingly designated
as port C1 for the raise line 40 and C2 for the lower line 33.
The valve system 50 comprises three interactive valve cartridges which
20 are generally referred to as cartridges A, B, and C. Proceeding firstly from the
port V2, the line 33 branches off to one end of a first pilot line 51 at point 52.
It then enters the cartridge B which is in effect a pilot operated pressure
arresting means, i.e. a check valve 53 connected to one end of a second pilot
line 54. The line 33 then proceeds to the cartridge A which is an adjustable
25 pressure reducing valve 55. The valve 55 presents a preferred embodiment of
what is also referred to as "pressure reducing means". It should be noted that
the valve 55 could also be an adjustable pressure reducing/relieving valve. A
third pilot line 56 communicates the valve with an implement side point 57 of
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the line 33. The valve 55 is further connected to one end of a drain line 58.
The line 33 then continues through port C2 to the cylinder 14 as described.
Turning now to the implement side port C1, the line 40 enters the valve
system 50 and enters the cartridge C. The cartridge C includes another
5 pressure arresting means or check valve element 59 which presents a preferred
embodiment of what is generally referred to as "second pressure arresting
means". The second pressure arresting means 59 is arranged in a branch 40a
of line 40. Note that this indication is diagrammatic only and is to indicate
operative capability of the cartridge rather than its physical arrangement. The
10 branch 40a thus could also be merely a portion of the line 40. At an implement
side point 61, the line 40 communicates with one end of a fourth pilot line 62.
The other end of pilot line 62 is connected to a counterbalance valve element
63. The valve element 63 also receives the second end of the pilot line 51. At
the pump side of the valve system 50, the second end of the second pilot line
15 54 communicates with the line 40. The second end of the drain line 58 is alsoconnected to the line 40 at the pump side of the cartridge C. The raise line is
then connected to the implement side of the control valve 43 as best seen in
Fig. 1.
It should be noted that cartridges A, B and C are commercially available
20 valving units. In the embodiment shown, the cartridge A is marketed as
"PRESSURE REDUCING or PRESSURE REDUCING/RELIEVING VALVE. Cartridge
B is known as PILOT-TO-OPEN CHECK VALVE and Cartridge C bears
designation COUNTER BALANCE VALVE. Each of the cartridges of the
embodiment described is commercially available, for instance from Sun
25 Hydraulic Corporation of Sarasota, Fla., U.S.A..
In operation, let it first be assumed that the system is shown in a
"neutral" position. That is to say, the pump 42 is running and the control valve43 is in a neutral position causing the hydraulic fluid to circulate from tank 44,
via line 45, pump 42, valve 43 and drain line section 46 back to the tank 44.
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If it is now desired to raise the implement, for instance, at a turn, the
control valve is manipulated to connect line 47 with line 40 and line 46 with
line 33. The pressurized hydraulic fluid passes through line 40 and enters the
valve system 50 (Fig. 4). The drain line 58 is also pressurized at this stage,
5 which internally pressurizes cartridge A and allows full reverse flow from C2
to V2. The second pilot line 54 transmits the fluid pressure of about 1800 psi
to the valve 53 and causes its opening allowing passage of fluid down the
lower line 33 to the tank 44. The pressurized fluid opens the check valve
element 59 and then flows, at the implement side of the valve system 50,
10 through line 40 and via poppet valve 39, into the bottom end 32 of the mastercylinder 11, causing the piston 15 to extend the piston rod 19, raising the
implement. The remaining cylinders 12-14 act in the same way and
simultaneously, as is well known in master/slave systems.
The operation of the cylinders 11 -14 results in the flow of hydraulic fluid
15 from the piston rod end 31 of cylinder 14, via line 33, to valve 55 and valve53 (maintained open by pilot line 54 as mentioned), control valve 43 and line
46 into the tank 44.
If it is now desired to stop the raising movement at any point, the
control valve 43 is manipulated back in the neutral position. The fluid now
20 circulates between the pump 42, valve 43 and tank 44. At this point some
residual pressure is held at V1 until it bleeds off. The valve element 59 closesalso. The valve element 63 is also closed due to a low pressure active at its
pilot input where pilot lines 51 and 62 enter the valve element 63.
On lowering of the implement, the pressure from pump 42 causes the
25 flow of fluid to the pump side of line 33. The pressurized fluid enters the valve
system 50 at V2. Its pressure is transmitted by pilot line 51 to the valve
element 63. The pressure, combined with the already existing pressure coming
via pilot line 62 and caused by the locked in fluid subjected to the weight of
the implement frame, opens the valve element 63 to allow passage of fluid
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from C1 to V1 and valve 43 to tank 44. Note that valve element 59 is now
closed.
At the implement side of the valve 53, the pressurized fluid enters the
pressure reduction valve 55. Typically, the pressure upstream of valve 55 is
5 about 2400 psi and is reduced, at the implement side of valve 55, to the
predetermined value of, say,650 psi. The excess fluid is drained from valve 55
via drain line 58, bypassing the cartridge C, to the pump side of the valve
system 50 and thence to the tank 44 as described.
The implement is now lowered to its operating position. Eventually, the
10 plate 41 engages the lifting rod 35 to push the poppet 37 to a closed position.
When the poppet valve is so closed, the flow out of the slave system is shut
off instantly, creating a surge of pressure at V2 of about 2400 psi. Without thepressure reducing valve 55, this would cause expansion of connecting hoses
of the system, bringing cylinder 14 out of phase with the other cylinders in the15 system. It will be most out of phase with cylinder 11, second most with
cylinder 12 and third most with cylinder 13. However, since the pressure
reducing valve 55 is provided, this out-of-phase condition is held to a
minimum.
One of the important improvements of the present invention is in the
20 elimination of the chattering effect upon lowering of the implement. The
chattering also disrupts accuracy of the lowering and thus has undesirable
effect on the overall operation. In accordance with the invention, the chattering
is avoided by utilizing pressure generated by the weight of the implement in
combination with the pilot pressure from the lower line. Pressure is always
25 present at C1, regardless of the stage of operation, even during the loweringof the implement. This is achieved by providing the valve 63 with two pilot lineinputs - one, 51, coming from the lower line 33 at the pump side of the valve
system 50, the other, 62, from the point 61 at the implement side of the valve
system 50. The arrangement shown is such that the pressure actuating valve
30 63 to open is always a sum of pressure generated by the two pilot lines 54,
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61. In other words, the pressure generated by pilot line 54 alone, or the
pressure generated solely by the weight of the implement, is not capable of
opening valve 63. There must be a combination of the two pressures to open
the valve 63. As is indicated in Figs. 1 and 4, the valve 63 is adjustable to set
5 the pressure required for opening the valve.
It follows from the above that the arrangement described has a
compensating effect when the implement is lowered. It secures that the valve
63 can only be opened if pressure at the implement port C 1 is at a
predetermined positive value which is greater than the pressure inherent in this10 line due to the weight of the implement. This prevents chatter in the system
and contributes to the accuracy of the lowering operation. The required
pressure is maintained by the locking action of valve element 59 and valve 53.
The valve 53 is also referred to as "releasable pressure arresting means".
Those skilled in the art will appreciate that many modifications may exist
15 which depart to a greater or lesser degree from the embodiment disclosed,
without departing from the combination of the present invention. Accordingly,
we wish to protect by letters patent which may issue on this application all
such embodiments as properly fall within the scope of our contribution to the
art.
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