US3080003A - Control for hydraulic system - Google Patents

Description

March 5, 1963 c. H. DENKER CONTROL FOR HYDRAULIC SYSTEM 4 Sheets-Sheet 1 Filed May 3, 1960 March 5, 1963 c. H. DENKER CONTROL FOR HYDRAULIC SYSTEM 4 Sheets-Sheet 2 Filed May 3, 1960 a w k l/bkorhug March 5, 1963 cfi-l. DENKER 3,080,003

CONTROL FOR HYDRAULIC SYSTEM 'IYIIIIIIIIIII Emma . Man}! 5, 1963 c. H. DENKER 3,080,003

CONTROL FOR HYDRAULIC SYSTEM Filed May 3, 1960 4 Sheets-Sheet 4 3,089,903 CQNTRGL BOB HYDRAEHJIC SYSTEM Chester H. Banker, fapiilion, Nebrn, assignor to sun- Chalmers Manufacturing Company, Milwaukee, Wis. Filed May 3, 196%, der. No. 26,574 4 Qlaims. (Ci. 1'729) This invention relates to hydraulic systems for tractors and is more particularly concerned with the control mechanism for such systems.

Heretofore, implements have been lifted by hydraulic actuators under the selective control of an operator upon movement of a control valve to apply pressure to the hydraulic actuator. Also heretofore a load sensitive hydraulic control mechanism has been employed wherein the hydraulic actuator employed to lift a towed implement is subjected to increased iiuid pressure upon increase in implement draft load. Previous systems have employed an unloading valve whereby the major portion of the pressure fluid is diverted to sump upon the pressure in the actuator reaching a predetermined value. Once the unloading valve opens, fluid at a lower pressure will maintain the unloading valve open so that fluid flows to sump at a lower pressure than was required to open the unloading valve.

Heretofore a spring loaded dashpot has been employed at one end of the control valve. Such a motion retarding device prevents rapid movement of the control valve. Heretofore a positive hand control linkage has been utilized to move the main control valve to an implement raising position against the biasing action of the dashpot. If the operator moved the control valve too rapidly to a full lift position, the pressure surges would sometimes be so great the unloading valve would open. Once opened the unloading valve would remain open until a rather low closing pressure was reached.

Also the operator often desires to quickly place the lift and lower hand control in an implement raising position so as to free his hand so employed for steering or other functions. If he must keep his hand on the hand control lever and slowly move the control lever to an implement raising position, it can be appreciated that the operator is inconvenienced in not having the hand available during such time for other operations. Often the operator is at the end of the field and must operate the hand throttle to reduce speed and turn the steering wheel at approximatcly the same time as he operates the lift and lower control lever. Further, it has been found that the dashpot offers an undesira le feeling of resistance to the operator with the heretofore employed positive lift and lower hand control linkage.

Another problem heretofore existing in relation to the lift and lower hand control was that of providing suitable indexing for a restricted lowering of the implement. Manufacturing tolerances made it difficult to coordinate a predetermined position of the valve for lowering the implement with a predetermined position of the hand control lever. Further, it was difiicult to provide an accurate setting of the separate lowering valve for the different weights of implements that might be mounted on the tractor. It can be ap reciated that a different weight of implement would produce difierent rates of lowering when the check valve for lowering the implement is placed in a predetermined position of fluid restriction. Accordingly,

v it has been desired to provide adjusting means for allowing, for instance, the same rate of lowering for a heavy and light implement or different rates of lowering for "implements of the same weight. For instance, it is usually desirable to lower a cultivator quickly into the ground, whereas a planter should be lowered slowly so as to avoid clogging of the seed channeling spout.

are atet Heretofore it was thought desirable to allow free flow of fluid through the check valve controlling fluid flow from the lift ram when the tractor hydraulic system was adjusted for automatic weight transfer operations. However, it was found that upon traversing short lengths of low draft, such as when traversing a few feet of loose sandy soil in an otherwise packed type soil, the control valve would permit rapid draining of fluid from the ram through the check valve permitting the implement to lower excessively and then when the tool encountered a packed section of earth the ram would lift the tool excessively. This caused what is known in the art as a hunting action which resulted in an undesirable undulating of the bottom depth of penetration of the soil by the tool. The bottom of a plowed furrow, for instance, would have a wavy or washboard contour.

It has been found that this undulating or hunting of the tool can be satisfactorily minimized by placing the check valve controlling flow from the lift mm in a flow restricting position. Accurate positioning of the lowering valve was found to be desirable to effectively combat the hunting tendency of the previous automatic weight transfer system. It was found that the restricted lowering rate for lowering the implement to the ground was a satisfactory restriction to fluid flow from the lift ram during automatic weight transfer operation of the tractor and implement.

Also by use of the restricted fiow position of the lowerring valve during weight transfer the pressure in the lift ram will not suddenly diminish when a slippery spot is encountered. When a slippery spot is traversed weight transfer from the implement to the tractor driving wheels is desired. The slippery condition however causes loss of traction and thereby loss of drawbar pull. Upon reduction of drawbar pull the weight transfer linkage permits the control valve to move to an implement lowering position thereby reducing pressure in the lift ram. However, with a restricted lowering position of the lowering valve, ram pressure is slowly reduced and usually sufficient lifting force is exerted on the implement to transfer enough weight to the rear wheels of the tractor to enable the tractor to successfully pull the implement through short distances of poor traction.

It is an object of this invention to provide an improved lift-lower linkage for a hydraulic control system for a tractor which avoids the hereinbefore described difliculties.

It is a further object of this invention to provide a resilient connection in the control linkage whereby the hand control member may be quickly placed in its lift position without suddenly overcoming the resistance offered by the dashpot on the control valve.

it is a further object of this invention to provide an improved hand control linkage for the lift and lower function of the hydraulic system wherein the main control is assured of a gradual opening from its implement lowering position to a full implement lifting position so as to avoid sudden surges of oil which would result in unloading the system and in dropping the implement rather than raising it.

It is a further object of this invention to provide a resilient member in the hand control lift and lower linkage which will prevent distortion or breakage of the linkage due to the operator using rute force to move the hand control lever quickly against the biasing action of the dashpot employed on the main control valve.

t is a further object of this invention to permit the operator to quickly place the lift and lower lever in an implement lift position without causing the unloading valve to open.

It is a further object of this invention to provide an scribed system wherein a restricted rate of 'loweringcan' beefiected during weight transfer operatiouthereby preventing undulating depth of said working. and. loss'of weight transfer during short intervals of 'poor'tra'ctlon.

It-is a further object of'this invention to provide a'lift and lower linkage for a tractor hydraulic control system ofthe automaticweight transfer type whichlias a; resilient connection which isselectively adjustable to effect alde sired rate of implement lowering.

Theseandother objects and advanta'ge's of this iiiven'a tion will become apparent to technicians in the art when the following description is read ini conjuncuonwith the drawings in which:

FIG. 1 is a side view of a farm tractor a'ndmouiited' plowin which this" invention is incorporated;

FIG. ZiS a'Ver ticalsectionI takehlongitudinallyof the" tractor;

FIG FIG. 2; 1

FIG. 4' is'a sectiont'ak'en' along"the"lines'IV-"IV of FIG. 5 is a view t'ak'en'along the lines V-V in FIG. 3;

FIG; 6 is a section view taken alongthe linesVI-VI" in FIG. 5;

FIG. 7 is a view taken along the section line VII -VII FIG. 8 is ase'ction vie'w'take n'along the'lines VIII'- VIII of FIG. 7; and

FIG. 9" is a section taken" alongjth'e lines IX--I X of FIG. 2 with the'unloadin'gvalve' shown schematically;

Referrin'g t'o FIGS. 1, land 3 a farm tractor'll has a hydraulic system 12'includingi control valve means 11 for-controlling men-ow of fluid supplied by pumps 16', 17, 18 19 to the'hy'draulic actuator in the form of a ram 21 pivotally connected to the interior of the rear transmission housing '22; andforcontrolling flow of fluid from/the ram 21 tothe' sump 23,1which is the'lower' part of the torque't'ube 242 r p p A plow 26 is con'nectedthrough a pairof lift links 27 to'crahk arms28'which'are'secured'for rotation with a' rock shaft 29 to which an arm 31 is secured on the interior of the rear casing 32. The arm 31 is pivotally. connectedto the r'od' end'of the ram 21; The draft bar 33 oftheplow'is pivotallyconnected to a draw bar 34 which is pivotally connected at its upper end to the housing 22; The lower end of drawbar" 34 is pivotally connected to the'automatic weight transfer linkage36. The weight transfer linkage36 adjusts the position of a' control valve which controls the pressure in ram 21. A link 37 is connected to lever arm 38which is 'nonrotatably connected toa shaft 39 which is in turn pivotally supported onia' bottom cover 40. An arm 41' is nonrotatably secured to the shaft'39' within the cover 40. A lever 42 is pivotallysupported on a shaft 43 mounted on the cover 40' and has a camming face in abutmentvwith a camming faceofarm 41; A rod 44 is biased. by spring 46 and has an inverted U-portion'within which a roller on the upper end of lever 42 fits. A lever 49 is pivotally connected at one end to rod de'by a pin51 andis pivotally connected at its central portion to an adjusting'member 52 by a pivot pin 53 so that upon counterclockwise movement about the pivot pin 53, as viewed from the top, the other end of lever 49 will move the control-valve spool'54.

Referring now to'FIGS. 2, 3" and 9, when the valve spool 54 is moved to the left, as viewed in FIG. 9, by the lever 49 uponincreases in' di'af't load, a sequence of events occurs. First the port 55 in the bore 56 is closed by a land 57 on the spool '54. Thus fluid pumped by small plunger pump 19 will'not return to the sump through pas- 3 is a sectiontakeri alongthe lines III- 111 of 4.. sage 58 but instead it is forced to pass through the check valve 59 and conduit 61 to the ram 21. Upon further movement of the spool 54 to the left a land 62 will block the port 63 in the bore 56 thereby causing the pump 18 to supply fluid through itscheck valve 64 to the pressure manifold 66. As draft load'b'ecomes even greater, the valve spool 54 is moved further to the left, causing'the land'68 to close port 69 in the valve bore 56 and-this causes pump'17 to supply oil through its check valve 71 to the pressure manifold 66. Upon'further increases in draft thevalvespool 54 moves even further to the left and land 72.blocks port 73in thevalve bore 56' thereby causing the fiuidpumped'b'y pump 16 to be supplied through. check valve 74 to the pressure manifold'fifii Pressure fluid inthe manifold 66 flows through the" check valveF. to passage 77' thence through check valve 59" tothe ram supply conduit 61'.

If excessive pressure develop in the pressure manifold 66, anunloadirlg valve mountedo-n' the ti'actorwill' dimanifold -66l 91,;passa'ge' 92in the spool 87 thence through an annular groove 93 to exhaust passage 94, which is open to sump; Passage 96 is also open to sump.

The lowering control valve in the form of check valve;

59is employed to control thefiow of fluid from the ram 21 to sump, The check valve 59 includes a ballseating member 97 having a cylindrical bore 98 and a frustoconical seating surface 99 atone endof the bore 98. A

ball 101 has a loose fit in bore 98' permitting; fluid to fiow'f with restriction between the ball 101 and the bore98l When the ball is near its seat' 99 the coaction of the spherical surface of the ball 10 1 and the seat 99'willbe to efiect a second area of restriction to.-the flow offluid" from the ram to sump; Aplunger 162 is movableby a; lever 103. secured for rotation with a rod 104. The

other end of lever 103i is engag'eable with the spool: 54*

independently of the weight transfer linkage lever 49.

The position of the ball 101 as shown in FIG. 9 rnay be considered the position of. minimum restriction of iiuidflow from the ram to sump, thus giving a slow implement descent. As the ball is permitted to move. to the right by movement of lever 103, the restriction to fluid flow from the ram 21 tosump increases. When the ball 101 reaches a position nearly seating on its seat 99 the restriction to flow will be very great and a very, slow rate of implement descent is available. Although a tapered bore, in. place of cylindrical bore 98, would give satisfactory results; it has been found that a cylindrical bore such as illustrated together with. the restricltion'afiorded by coactio-n of the ball. and theseat99'provide a satisfactory range of restriction for various rates" of descent of implements.

Referring to FIGS. 1, 2, 3, 4, 7 and 8, thecontrol linkage for the hydraulic system will be described. A djacent the steering wheel 1% a quadrant 107 is welded to the steering column 1&8. This quadrant107' pivotall'y carries a pair of rods 109 and 111. Spring biased hand control levers 112 and 113 are secured to the rods 109 and 111, respectively. Control rod 111 is rotatably supported by a fiange 142 secured to a brace mounted on torque tube 24. As shown in'FIGS. 7 and 8, the levers are pivotally connected by pins 114 and 116 to the rods 11 and 111, respectively. As shown in FIG. 8, lever 113 has a spring 117 with-one end connected to a hook formed on the lever and its other end connected to a cotter pin extending [through a rod 111. This spring 117 bimes the lever 113 upwardly so that it will be in abutment with the quadrant if the pin 113 carried by the lever 113 is in one of the windows 119 or 121. When the lever 113 is moved to its lift position, the pin 118 engages window 121 in the quadrant 107 and the control valve is moved to an implement raising position.

The control lever 112 operates the adiustlng member 52 through the rod 1%9 which is universally connected to a rod 122 to which the adjusting member is nonrotatably connected.

The lift and lower lever 113 constitutes a part of a manually operable control linkage for selectively moving the control valve from its implement lowering to its implement raising position through pivotal swinging movement of the lever 103 connected to rod 104. Referring to FIGS. 2, 3, 4, 5 and 6, rod 194 and rod 111 have a connection providing positive movement in one direction of pivotal rotation and a resilient connection in the other direction of pivotal rotation. The connection includes a positive force transmitting member in the form of a link 123 pivoted at one end to an arm 1Z4 nonroatably secured to? rod 104. The other end of the link 123 passes through a pivot member 126 carried by a pair of arms 127. The arms 127 are nonrotatably secured to rod 111.

A nut 128 is secured to the threaded end of link 123 to vary the effective length thereof. The nut 123 has an internally threaded part 129 which carries a nylon locking washer 131. The rod 123 has a loose fit with a bore 132 in pin 126. A coil spring 133, which constitutes a resilient member, has an end abutting against a washer 134 which is held in place by a cotter pin 13%. The other end of coil spring 133, which surrounds the rod 123, abuts a recessed llat surface 137 of pin 125. A hole 138 is provided in side panel 139 and this hole is in horizontal alignment with the nut 128 as shown in FIG. 1. The hole 138 is so positioned as to permit a screw driver to be inserted through the hole into the slot 14-1 in the head of the nut 128 to turn it to adjust the effective length of link 123.

The operation of the manual control linkage for lifting and lowering of the implement will now be described. When the operator approaches the end or the field in a plowing or other soil working operation, he desires to place the lift lever in a raising position prior to turning the tractor at the end of the furrow. it is desirable to place the lift lever quickly to the full lift position and heretofore this has caused high pressure to develop due to the sudden engaging of the pumps 1d, 17 and 18 to supply fluid to the ram 21. Heretofore, the pressure surge is often great enough to exceed the predetermined pressure necessary to open the unloading valve thereby dumping the fluid to sump. Thus, instead of lifting the implement the operator would find that the pressure has dropped in the ram sufilcien-tly that ther would be no lifting action at all. Then the operator would have to move the lift and lower lever 113 to implement lowering position to reduce the pressure in the pressure manifold 66 sufiiciently to cause the unloading valve 81 to close. Once the unloading valve 81 was closed the operator then moved the lift lever 113 to the raised position. The use of a resilient member in the form of coil spring 133 eliminates this undesirable unloading occurring upon sudden movement of the lift and lower lever to the lift position. The spring 153 interposed between rod parts 111 and 122 of the manual control permits the lever 193 to slowly move the spool 54 to the left, as shown in FIG. 9, against the biasing action of the dashpot 146 at the left end of the valve spool 54. The dashpot 146 is biased against the spool 54 by a coil spring 149. The fluid level in the reservoir is above the small opening 148. Also by having the spring 133 in the lift lower linkage, damage to the lift and lower control linkage is avoided. Heretofo-re, the lift and lower linkage could be distorted by the brute the to force of the operator if he attempted to move the lever faster than permitted by the control valve dashpot 146.

When the automatic weight transfer linkage is employed the pressure of the fluid in the ram 21 will increase and decrease in correspondence to draft load and it has been found desirable to place the lift and lower lever 113 in a restricted lowered position during weight transfer operation. The restricted lower position of the lift and lower lever ll?) is shown in FIG. 7 and in that position the pin 118 is abutting one edge of the window 119. By providing an adjustable link 123 it is possible to select the desired position oi the check valve ltll to correspond with a setting of the control lever 113 in its restricted lowered position as shown in FIG. 7. Thus the provision of an adjustable link in the lift and lower control linkage markedly improves the weight transfer system hereinbefore described.

Also it is desired to provide means for lowering the implements at different rates. For one rate of restricted lowering the ball 101 may occupy a position similar to that shown in PEG. 9 where the only restriction to return the fluid from the ram would be that imposed by the spacing of the ball 191 and the bore $8, however, if slower lowering is desired, such as in the case of lowering a corn planter into the ground, the nut is turned by a screw driver to change the length of link 23 so as to position the ball 1.91 more closely to the seat 99' when the lever pin 118 is in the upper part of window 1. 3, thereby presenting two areas or restriction to fluid ilow from the return conduit 63 to the passage '77. The double restriction offered by the ball 1%1 fitting in here 93 and the spherical surface of the ball 1% adjacent seat 99 efiects a slow lowering rate.

When the operator has lowered an earth working tool by holding the lift and lower lever in its lowering position, he need merely release the lever and it will automatically move upwardly until pin 113 engages the upper edge of the window 119 in bracket 197. The pressure exerted by the fluid on the ram side of the ball 101 during moments of decreasing draft load will urge the ball toward its seat 99 thereby urging the pin 118 against the upper edge of window 119.

It is to be understood that although only one embodiment of the invention has been shown and described in detail, it is not intended to limit the patent granted hereon otherwise than is necessitated by the scope of the appended claims.

What is claimed is:

1. In a hydraulic control system for a tractor of the type including a source of hydraulic pressure fluid and a hydraulic actuator for r ising and lowering an implement connected in draft relation to said tractor, the combina t-ion comprising: a control valve on said tractor for controlling the flow of fluid to and from said actuator having an implement raising position and an implement lowering position, a dashpot yieldingly resisting movement of said control valve toward its implement raising position, a manually operable control linkage On said tractor for selectively moving said valve from its implement lowering position to its implement raising position including first and second rotatable parts, said second part having a portion engageable with said control valve, and a motion transmitting connection between said parts including positive and yieldable force transmitting members providing positive engagement between said parts upon rotation of said first part in a d' ection permitting said valve to move toward its implement lowering position and providing a yieldable connection between said parts when said first part is rotated in the opposite direction urging said valve to move against said dashpot toward its implement raising position.

2. The structure set forth in claim 1 in which said means includes arms formed on said parts, said positive force transmitting member is a link pivotally connected at one of its ends to one of said arms, and slidably connected at its other end to the other arm with means for limiting'slidingwmovement of saidlink in onedirection and :saidtyieldableforce transmitting member is a spring interposed between said'parts biasing said link in said one direction. a

3. In: a hydraulic system for attractor and draft connested implement: ahydraulic actuator for raising and lowering said implement; a first valve shiftable between implement raising and loweringpositionga second valve for controlling fluid flow from said actuator interposed betweensaid first valve and said actuator, said valve being shiftablettoa position afliording a slow implement lowering rate; automatic weight transfer linkage'between-said firstvalve andsaid' implementfor varying fluid pressure in: said actuator in response to variationsin implement draft; a controlilinkage-for openatingsaidvalves'includ ing a. hand operated member shiftable; between ai lowerv and raise position connected to a first part-thereofaa second partthavingportions:tbereofengageable with said first-and second'valves; and adjustableconnectingmeans;

8 implement raising and lowering positions, a dasnpot for urging said first valve-toward its lowering position, a second valvefor controlling fluid flow from said actuator interposed between said first .valve and said actuaton said valve being shiftable to increase or decrease said rate of} flow from said actuator, automatic weight transferlinlrage between saidfirst valve and said implementffor varying fluid pressure in-said'actuator in response to variations'in implement draft, :a control linkage for operating said valves including a hand operated member shiftable be tween a lower andlift position, said linkage including afirst and-second par-t having an' adjustable connection v 'therebetween, said second part having portions thereof v engageable with saidvalves, said'sec'ond valve beingeni gageable by saidfsecond'part when-said hand operated member is shifted to said 'lowenpositiont References Cited' in the tile of this patent' UNITED STATES PATENTS

Claims (1)

1. IN A HYDRAULIC CONTROL SYSTEM FOR A TRACTOR OF THE TYPE INCLUDING A SOURCE OF HYDRAULIC PRESSURE FLUID AND A HYDRAULIC ACTUATOR FOR RAISING AND LOWERING AN IMPLEMENT CONNECTED IN DRAFT RELATION TO SAID TRACTOR, THE COMBINATION COMPRISING: A CONTROL VALVE ON SAID TRACTOR FOR CONTROLLING THE FLOW OF FLUID TO AND FROM SAID ACTUATOR HAVING AN IMPLEMENT RAISING POSITION AND AN IMPLEMENT LOWERING POSITION, A DASHPOT YIELDINGLY RESISTING MOVEMENT OF SAID CONTROL VALVE TOWARD ITS IMPLEMENT RAISING POSITION, A MANUALLY OPERABLE CONTROL LINKAGE ON SAID TRACTOR FOR SELECTIVELY MOVING SAID VALVE FROM ITS IMPLEMENT LOWERING POSITION TO ITS IMPLEMENT RAISING POSITION

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