Note: Descriptions are shown in the official language in which they were submitted.
Field of tne Invention
The present inven-tion relates to a hydraulic control
apparatus for a plurality of parallel-connected double-acting
hydraulic cylinders enabling the pistons working in the
cylinders to extend and retract toge-ther substantially
uniformly. The hydraulic control apparatus of this invention
is par-ticularly adapted for use with a soil-working implement
having a number of soil-working tools spaced along the
implement. The height of each tool above the ground is
regulated by a piston working in a hydraulic cylinder
associated with the tool. In order to maintain uniform the
soil penetration of all the tools, a uniform lowering and
raising of all oE the tools moun-ted on the implement is
desirable, and this may be achieved within acceptable lim.its,
by rneans of hydraulic control apparatus constructed accordin~
to the inven-tion.
Prior Art
A conventional method Eor achieving the uniorm
e~tension and re-traction of the pistons of a plurality of
hydraulic cylinders has been to employ a master-slave
arrangement wherein -the return fluid :From the master cylinder
is used as -the source of pressurized fluid to drive a first
slave cylinder. Similarly, the return fluid from the first
slave cylinder is used as the source of pressurized Eluid for
the second slave cylinder, and so on. The return fluid from
the last slave cylinder is connected to the main hydraulic
fluid return supply line. In such an arrangement dephasiny
(i.e. moving out of step) of one of the piston-cylinders is a
common problem, and when such dephasiny occurs, it makes the
whole system inoperative and can even damage the equipment.
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Correction of the out-of-phase cylinder is of-ten a complex and
time-consuming operation. When such dephasing is due -to a
leaky cylincler, detec-tion of -the location of the leaky cylinder
requires an individual check of hydraulic cylinders in the
system un-til the faulty cylinder is located. Finally, in a
master-slave arrangement, the job of interconnection of
cylinders in modular extensions is cumbersome.
Summary of the Invention
According to the invention, there is provided a
hydraulic control apparatus for a plurality of double-acting
hydraulic cylinders. Each piston within a cylinder is movable
from a retracted position with respect to that cylinder to an
extended position, in response -to flow of hydraulic fluid under
pressure into and ou-t of the cylinder. A pair of hydraulic
fluid connecting lines are connected to each cylinder for
conducting the fluid into and out of the cylinder.
If bo-th uniform retraction and extension of each
piston is required, a pair of flow control valves are installed
in the hydraulic fluid lines for each cylinder for controlling
flow of fluid into and out of the cylinder during both
extension and retraction of -the piston working in the cylinder.
A "flow control valve", as the term is used herein, has the
property of maintaining a cons-tan-t flow of fluid in a forward
direc-tion therethrough whils-t permitting a substan-tially free
flow of fluid in a reverse direction therethrough. If -the flow
control valves are parallel-connected (i.e. one such valve is
connected to one end of the cylinder and the other valve to the
o-ther end), then each such valve is connected in the same
orienta-tion. If for example, -the forward direction of one of
the two valves is into -the cylinder and -the reverse direction
is out oE the cylinder, then -the other oE the two valves mus-t
be connected in the same sense. Since -the two valves control
flow to opposi-te sides of the piston working in the cylinder,
both extension and re-traction of the piston are regulated.
Alterna-tively, the two :Elow control valves may be
connected in series in mutually opposed orientation to one end
o -the cyl:inder ~one side of the piston), in which case -the
fluid connecting line to the other end of the cylinder i5
unimpeded.
If uniform extension is important but uniform
retraction unimportant, a single flow eontrol valve for each
cylinder will suffice; similarly if only uniform re-traetion is
important. OE eourse, the orientation o:E -the valves must be
selected so that the valves eooperate to afEord uniform
extension or retraction, as the case may be.
Hydraulic gating means such as a conventional pilo-t
lock valve is conneeted between eaeh cylinder and hydrau:Lic
fluid supply and return lines for controllably applying
pressurized hydraulie fluid into ancl eondue-ting return f:Luid
away from the assoeiated eylinder. The hydraulie fluid gating
means also preferably eontrollably bloeks flow of hyclrau:Lie
fluid into and out of its associated cylinder. The foregoing
arrangement enables a subs-tantially uniform amount of
extension and retraction of each piston with respec-t -to its
eylinder, assuming a pair of Elow control valves per cylinder
as just described/ and assuming tha-t the flow control valves
have generally the same flow control charaeteristies (an
assumption underlying the use of the -term "flow eontrol valve"
herein)~ If preeise uniformity is desired, the flow eontrol
valves may be selected as a matched set for any given
application.
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In another aspect o E the inven tion, there is provided
a soil-working implemen-t such as a soil-tillage implement of
the -type adap-ted for use behind a trac-tor. Such implement may
be comprised of a Erame, a plurali-ty oE soil-worlci n~ -tools
mounted on the frame, and a corresponding plurali-ty of double-
acting cylinders also mounted on -the frame. The pistons
working in the cylinders effect a reversible movement of the
soil-working tools between working (e.g. soil-engaging)
positions and non-working (e.g. non soil engaging) positions in
response to flow of hydraulic fluid in-to and out o:E the
cylinders. A hydraulic control apparatus as previously
described enables a substantially uniform ex-tension or
retraction (as the case may be) of each piston to be obtained.
Thus when the pistons rnove Erom an extended to a retracted
position (say), the soil-working tools are substantially
uniformly lowered to penetrate the ground frorn a non soil
engaging position to a preselected degree of penetration of the
soil. This may conveniently be effected by having the
hydraulic cylinders control the position relative to the frame
of a plurality of ground engaging wheels extensibly mounted to
the frame (as, for example, by mearls of a pivotal arm
connection). Thus when the pistons move from an extended to a
retracted position, the wheels a:Lso retract relative to the
frame, whereby the frame is lowered relative to the ground so
that the tools move from a non-soil engaging posit:ion to a
preselected soil engaging position. Alternative arrangements
are of course possible - for example, each soil-working tool
could be pivotally attached -to the frame and its associated
hydraulic cylinder could govern i-ts position relative to the
frame.
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The foregoing arrangemen-t -facilitates modular inter-
connection of soil-worlcing -tools, each rnodule having an
associa-ted sub-frame and hydraulic cylinder. Each module is
further provided with a pilot lock valve (or o-ther suitable
gating device) and a pair oE Elow control valves coupled to the
hydraulic Eluid connec-ting lines for the cylinder as previously
described. All that is required is a coupling of module
hydraulic lines to the main supply and return lines and a
mechanical sub-frame-to-frame in-terconnection.
Flow control valves which have been found suitable
are those manufactured by the ~a-terrnan Hydraulics Corporation
of Illinois, U.S.A., and marketed by the latter company as
'fixed flow pressure compensated valves'. It is possible to
obtain valves marketed by the latter Corporation synchronized
to within -~ 2~ for a dif:Eerential pressure range of Erom 70 -to
3000 psi. Suitable pilot lock valves are also rnarketed by the
Wa-terman ~Iydraulics Corporation. These consist basically of
two pilot opera-ted check valves arranged in a single housing.
Surnmary of the Drawings
Figure 1 is a schematic block diagram of a preferred
embodiment of the hydraulic control apparatus according to -the
invention, illustrating an exemplary six parallel-connected
hydraulic cylinders.
Figure 2 is a perspective view illustrating the
mechanical assembly associated with Figure 1.
E'igure 3 is a perspec-tive view of a chisel plow
havinc~ a cen-tral frame module with two additional modules added
to one side of the central module, and incorporatin~ the
preferred embodiment of hydraulic con-trol apparatus according
to the invention.
Figure 4 is an explodecl view of a portion of the farm
chisel plow of Figure 3, showing the interconnection of the
hydraulic cylinder with various parts of the frame structure of
the implement.
Figure 5 is a schematic block cliagram of an
alternative flow control valve arrangement that may be
substituted for the flow control valve arrangement of
Figure 1.
Detailed Description of Preferred Embodiment
In the following description words such as "upper",
"lower", "upwardly" and "downwardly" are used in a relative
sense rather than in an absolute sense. In the different
figures of the drawings, like par-ts are denoted by the same
reference numbers.
Referring to Figure 1, a plurality (six being
illustrated by way of example) of hydraulic cylinders 10 each
having a piston 11 movable therein are couple-l by means of
hydraulic fluid connecting lines 18 to hydraulic fluid supply
and return lines 16. The hydraulic fluid supply and return
lines 16, in turn, are coupled to a set of conventional main
supply and return lines 14 which connect to an external
conventional supply of pressurized hydraulic fluid (not shown).
A pair of Elow control valves 12 for each cylinder 10 are
coupled into the connecting lines 18 so that each operates in a
reverse (free-flow) direction when conducting fluid out of the
cylinder 10 and in a forward (controlled flow) direction when
conducting fluid into the cylinder 10. The connecting lines 18
for each cylinder 10 are also coupled to suitable hydraulic
fluid gating means, which as illustrated in Figure 1, is a
conventional pilot lock valve 13, located between the flow
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con-trol valves 12 ancl -the hydraulic fluid supply lines 16.
The use oE -the flow control valves L2 facilita-tes
unlform ex-tension and re-trac-tion of the pistons. Irnproved
uniEormity can be obtained by selecting the Elow control valves
as a matched set. Where uniformity oE ex-tension bu-t no-t
retraction (or vice versa) is required, a set of flow control
valves each operating on only the extension line for the
cylinder ~or only the re-trac-tion line, as the case may be) can
be used instead of the pair of flow con-trol valves illustrated
per cylinder. In -the tillage implement example -to be
described, uniformity of extension bu-t not necessarily of
retraction is desirable.
Figure 2 illustrates a hydraulic assembly
corresponding to the schematic arrangment oE Figure 1. As
illustrated, the hydraulic cylinders 10 each have an end plate
22 which is used as a stop to limit retraction of -the piston by
abutting against a hexagonal nut 20 threaded onto the
associated rod. By varying the position of nut 20 on the
piston the limit of retraction of the piston can be adjusted.
This feature will be discussed further below in the context of
a soil-working implement. Conventional hydraulic TEE fittings
15 are employed -throughou-t to interconnect the hydraulic fluid
lines 14, and 16.
Figure 3 illustrates an assembled farm tillage
implement incorporating the hydraulic control apparatus herein.
In this figure, only a few selected hydraulic-cylinder units
have been depicted, for the sake of clarity. A central frame
module 70 is attachable by means of an A-frarne 78 and locking
pin receptacle 76 -to -the rear end of a -tractor (not shown).
The central frame module 70 is pivotally attached by pivotal
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connections 80, ~2, ~4 and 86 to a first side :Erame rnoclule 72.
hydraulic cylinder unit 96 is rnoun-tecl on a vertical support
post 97 fixed to -the :Erarne structure of central frarne rnodule 70
and pivotally coupled by pivo-tal connection 86 -to a ]ink arm 87
pivotally at-tached to lever arm 85 fixed to module 72. Link
arm 87 is arcuately slo-tted a-t 81 to receive a pin 83 rnounted
in lever arm 85. Upon re-traction of -the piston rod gl, link
arm 87 pivots counterclockwise (as seen in Figure 3) un-til the
right-hand interior face of the slot 81 contacts pin 83.
Further retrac-tion of piston rod 91 forces counterclockwise
pivoting of module 72 about pivot connections ~0, 82, 8~ and 86
upwardly into a "winged" posi-tion for transporting the
implement. In field operation, -the piston rod 91 is positioned
so that pin 83 lies about midway along slot 81. This, permits
slight pivotal movemen-t oE module 72 relat.ive to module 70 to
accommodate ground irregulari-ties without requiring change o~
the position of piston rod 91 in the cylinder 96.
Similarly, a second side frame module 74 is pivotally
attached to first side frame module 72 by pivotal connections
88, 90, 92 and 94. Cylinder 98 is affixed at one end to an
upright support post 99 on module 72 and its piston rod :L01 is
pivotally attached by means of pivotal connection 9~ to a link
arm 102 pivotally mounted on lever arm 91 :Ei~ed to second side
frame element 74. Full retraction of piston rod 101 withi.n its
cylinder 98 causes frame module 74 to pivot about the aforesaid
pivotal connections to a "winged" position with respect to
frame module 72.
The s-tructure shcwn in Figure 3 may have an
additional two side modules (no-t shown) equivalent to side
frame modules 72 and 74 on the opposite side of central frame
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module 70. Generally the implement will be used so that a
symme-trical or balanced configuration of modules is employed.
Thus, the assembly shown in Figure 3 is capable of operating
with central frame module 70 alone, wi-th frame module 72 and
with a side frame module e~uivalent to side modu:Le 72 on the
opposite side of central frame module 70, or wi-th a total of
five separate frame modules. The coupling of each side Erame
module is accomplished simply by pivotally attaching that frame
module as shown and coupling the corresponding hydraulic fluid
supply and return lines 16 from one side frame module into the
supply and return lines 16 of either the cen-tral frame module
70 or an attached side frame rnodule.
Affixed to each of ~he frame modules are a plurality
of soil tilling tools such as chisel plow sweeps 100, a
representative few of which are shown mounted to the assembly
illustrated in Figure 3. Each sweep 100 is mounted into the
frame of an associated module by means of a trip assembly 103
which permits the chisel plow sweep to swing upwardly when
encountering a heavy obstacle such as a rock.
The hydraulic assembly of Figure 2 is distributed
throughout the soil-working implement of Figure 3 as follows:
Main supply and return lines 14 on central frame module 70
interconnect with distributed supply and return lines 16 which
branch out to adjacent modules as re~uired. Each module i9
provided Witll one of the hydraulic cylinders 10 and control
apparatus comprising an associated pilot lock valve 13 and flow
control valves 12 connec-ted between the associa-ted cylinder ]0
and lines 16 by means of connec-ting lines 18.
Details of the mechanical assembly to which each of
the pis-tons 10 is connected are shown in exploded form in
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Figure 4. A yoke 24 at the end oE the piston rod of the
cylinder 10 is pivotally affixed to an overhead S-arm 28
through a pin hole 26 therein. The overhead 5-arm 28 is
coupled at one end by means of flanged brackets 34 clamped to a
transverse member 26 of the frame structure. The opposite end
of arm 28 is bolted to a pair of elongated arms 30. The arms
3Q, in turn, are affixed to a second transverse frame member 38
by means of a pair of flanged brackets 32 clamped thereto. The
lower end of the cylinder 10 is mounted by means of a yoke 40
on-to a lug 42 affixed to a curved pivotal arm 44. The upper
end of the curved pivotal arm 44 is pivotally rnounted to the
*rame member 38 by means of a pair of brackets 48 which support
a pair of bushings 46 inserted into cylindrical end section 45
at the end of curved arm 44. The lower end of the curved arm
44 has a transverse cylindrical section 49 which is moun-ted by
means of a pair of bushings 50 (only one of which is shown)
inserted into respective ends of upright sections of a bracket
54. A bearing 58 is inserted, in turn, into the bushings 50
to provide support therefor. Bracket 54 is thus pivotally
connected to the curved arm 44 and is rigidly affixed to a
bogey arm 56. The bogey arm 56 has a transverse spindle arm 60
secured to either end thereof. To the extended portion of each
spindle arm 60 is affixed a rotatable wheel-receiving assembly
62 for rèceiving wheels 61 (shown in Figure 3, not shown in
Figure 4). (Note that for simplicity only one of the pair of
wheel assemblies for central module 70 is illustrated in
Figure 3). Also affixed to the upper surface of curved arm 44
are a pair of lugs 68 which can be pinned to the lower end of a
transpor-t arm 64. The upper end of the transport arm 64 as
shown has affixed thereto a right~angle bracket 66 for snugly
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supportably receiving a pair of perpendicular surfaces of the
transverse frame member 36. ~s previously mentioned in
referring -to Figure 2, a hexagonal nut 20 is -threaded onto a
portlon of the pis-ton arm of the pis-ton of cylinder 10 and
with the piston arm in a retracted position abuts against an
end plate 22 affixed -to the cylinder 10.
In operation, when the hydraulic cylinder 10 has i-ts
piston in an extended position, the curved arm ~4 is in a
downwardly-extended posi-tion. In the latter position the frame
structure, (of which only transverse member 36 and 38 are
shown) is in a raised position relative to wheels 61 affixed to
the wheel receiving assembly 62. In the extended position of
the cylinder 10, the frame structure is accordingly elevated
with respect to the ground and the chisel plow sweeps 100 are
in non-working position out of con-tact with -the ground.
Retraction of the piston rod of cylinder 10 causes curved arm
~4 to pivot upwardly toward the frame structure, thereby
bringing sweeps 100 into a soil-engagin~ position. The piston
of each cylinder 10 may continue to re-tract until -the
respective hexagonal nut 20 abuts against respective plate 22
at the top end of -the housing of the associated cylinder 10.
In the latter position, sweeps 100 penetrate the soil to
maximum permitted depth. The maximum permitted depth is
governed by the position of hex nut 20 relative to the piston
rod on-to which it is threaded. In Figure 3, the presence of a
plurality of wheels on the frame if full maximum penetration is
not desired, then the pistons of each of the cylinders 10 must
retract uniformly -to the same exten-t in order to ensure that
each sweep 100 penetrates the ground to substantially the same
depth (ignoring local irregularities in the ground). This is
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accomplished by providing hydraulic control apparatus according
to the i.nvention.
~ len the sweeps 100 are working in rnaximum-
soil-pene-tration mode, stresses on the plows are absorbed by
the abutment of hex nu-t 20 against cylinder end plate 22. If
-the sweeps lO0 are working at less than maxirnurn soil
penetration depth, these stresses must be borne by the check
valves within pilot lock valves 13.
In cases where the frame assembly is to be
transported, the transpor-t arm 64 is placed underneath the
transverse frame member 36 to engage the same, and the piston
of the associated hydraulic cylinder lO is caused to retract
slightly so tha-t the frame member 36 rests on the transport arrn
64 thereby relieving stress upon the hydraulic system. Pr.ior
to transporting the assembly, piston rods 91, lOl of hydraulic
cylinders 96 and 98 illustrated in Figure 3, are retrac-ted to
"wing up" frame modules 72 and 74 in order to minimize the
width of the overall assembly.
It is obvious that in an equivalent arrangement, the
tools 100 could be directly operated by the individual
hydraulic cylinders, keeping the wheels of -the frame assembly
Eixed in elevation relative to the latter, and all of -the
irnplements moved relative to the frame. A single suppor-t wheel
per module instead of the two illustrated could also be used.
~odifications of the flow con-trol valve arrangement are also
possible. For example, Figure 5 shows a series-connected flow
control valve arrangement which is equivalent to the
parallel-connected flow control valve arrangement of Figure 1.
~ote that flow control valve 12a of Figure 5 is oriented in the
same sense as flow control valves 12 in Figure 1, but flow
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control valve 12b is oriented in the reverse sense relative to
flow con-trol valve 12a. Thus valve 12a con-trols -the rate oE
ex-tension of piston lL (valve 12b operating in free-flow state
duriny extension of piston 11) whilst valve 12b controls the
rate of retraction of piston 11 (valve 12a operatiny in
free-flow state during retraction of piston 11). If a single
flow control valve were available which controlled flow in both
direc-tions of flow (instead of opera-ting in free-flow condition
in one direction, as described herein), it is apparent that
such single valve could be substituted for the pair of valves
illus~rated in Figure 5. These and other modifications,
variations and departures which are within the scope and spirit
of the invention as defined in -the appended claims will be
obvious to those skilled in the art.
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