CA1150137A - Hydraulic control system for controlling level of cultivators, chisel plows and like machines - Google Patents

Abstract

ABSTRACT

Hydraulic control apparatus for parallel-connected double-acting cylinders enables the associated pistons to extend and retract together substantially uniformly. Mounted in a soil working implement such as an agricultural cultivator having a spaced array of soil-working tools whose working position is controlled by parallel-connected cylinders, the hydraulic control apparatus enables substantially uniform depth of soil penetration by all the tools in the array. A flow control valve for each cylinder is connected in one of the hydraulic fluid connecting lines to the cylinder. The flow control valves for all the cylinders are oriented so that uniform extension or retraction, as the case may be, of the associated pistons is obtained. If both extension and retraction are to be controlled, a pair of flow control valves is provided for each cylinder, one controlling extension and the other retraction. The invention also includes an implement such as a soil-working implement provided with such hydraulic control apparatus.

Description

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.

~ 4 -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 3 :~ 3 ~

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 3~

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 _ g _ 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 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 3'~

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 ;3t~
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 3~7 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.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A soil-working implement comprising:
(a) a frame;
(b) a plurality of soil-working tools mounted on said frames and spaced therealong for cooperative working;
(c) a plurality of ground engaging wheels mounted for extensible movement relative to said frame;
(d) a plurality of double-acting hydraulic cylinders mounted on said frame, each cylinder having a piston coupled to an associated one or more of more of said wheels for reversibly moving same between an extended position and a retracted position relative to said frame in response to flow of hydraulic fluid into and out of the cylinder;
(e) hydraulic fluid connecting lines individually connected to the cylinders for conducting hydraulic fluid into and out of the cylinders;
(f) for each cylinder, hydraulic fluid gating means for controllably reversibly applying pressurized hydraulic fluid to and conducting return hydraulic fluid away from each of said cylinders through said associated hydraulic fluid connecting lines, said hydraulic fluid gating means couplable to hydraulic fluid supply and return lines;
(g) each said hydraulic fluid gating means being a pilot lock valve coupled to an associated pair of said hydraulic fluid connecting lines whereby such pilot lock - Page 1 of Claims -valve is operable controllably to lock hydraulic fluid in its associated cylinder and to apply pressurized hydraulic fluid to either hydraulic fluid connecting line of the associated pair of said hydraulic fluid connecting lines connected to the associated cylinder whilst permitting return flow from the cylinder through the other of said pair of hydraulic fluid connecting lines; and (h) a flow control valve in at least one of said hydraulic fluid connecting lines for each cylinder for maintaining a substantially constant flow of fluid into and out of the associated cylinder when fluid flows in the forward direction through the flow control valve; the orientation of the flow control valves for all the cylinders being selected so that a substantially uniform amount of extension of each said piston is obtained, and when said pistons move from a fully extended to a preselected retracted position, said frame is lowered relative to the ground so that said tools move from a non-working position to a preselected soil-working position.

2. A soil-working implement as defined in claim 1, wherein each piston is provided with a stop which is adjustably positioned on an extended portion of the piston and, upon retraction of the piston, abuts a casing end wall of said cylinder when the frame is in said preselected working position, whereby stresses on the working elements are absorbed by - Page 2 of Claims -the cylinder casing by the abutment of the stop thereagainst, thereby relieving associated hydraulic valves of the burden of said stresses.

3. A soil-working implement as defined in claim 1, wherein each said tool is connected to an adjustably positionable stop which abuts the frame when the tool is in said preselected working position, whereby stresses on the working element in its operating position are absorbed by the frame by the abutment of the associated stop thereagainst, thereby relieving associated hydraulic valves of the burden of said stresses.

4. A soil-working implement as defined in claim 1, 2 or 3, constructed in modular fashion whereby at least one of said tools, its associated cylinder, associated pair of hydraulic fluid connecting line or lines, associated flow control valve or valves, associated wheel, and associated pilot lock valve are mounted on a sub-frame detachably connected to the rest of the implement.

5. A soil-working implement as defined in claim 1, 2 or 3, wherein there are a pair of flow control valves connected to each cylinder, one for controlling piston extension and the other for controlling piston retraction.

6. A soil-working implement as defined in claim 1, 2 or 3, wherein there are a pair of flow control valves connected to each cylinder, one for controlling piston extension - Page 3 of Claims -and the other for controlling piston retraction, and wherein the implement is constructed in modular fashion whereby at least one of said tools, its associated cylinder, associated pair of hydraulic fluid connecting lines, associated pair of flow control valves, associated wheel, and associated pilot lock valve are mounted on a sub-frame detachably connected to the rest of the implement.

7. An implement comprising (a) a frame;
(b) a plurality of tools mounted on said frame and spaced therealong for cooperative working;
(c) a plurality of double-acting hydraulic cylinders mounted on said frame for effecting reversible movement of said tools between a working and a non-working position thereof in response to a flow of hydraulic fluid into and out of said cylinders;
(d) for each cylinder, a pair of hydraulic fluid connecting lines individually connected to the cylinders for conducting hydraulic fluid into and out of the cylinders;
(e) hydraulic fluid gating means for each cylinder for controllably reversibly applying pressurized hydraulic fluid to and conducting return hydraulic fluid away from each of said cylinders through said associated hydraulic fluid connecting lines and for controllably locking hydraulic fluid in each of said cylinders, said hydraulic fluid gating means couplable to hydraulic fluid supply and return lines;

- Page 4 of Claims -(f) a pair of flow control valves in at least one of said hydraulic fluid connecting lines for each cylinder for maintaining a substantially constant flow of fluid into the associated cylinder when fluid flows in the forward direction through the flow control valves; the orientation of the flow control valves for all the cylinders being selected so that substantially uniform extension or retraction, as the case may be, of each piston with respect to its cylinder is obtained; one of said flow control valves for each cylinder being for controlling piston extension and the other being for controlling piston retraction.