US3307455A - Hydraulic equipment raising and stresscontrol devices for farming tractors - Google Patents

Description

March 7, 1967 L. PERAS 3,307,455

HYDRAULIC EQUIPMENT RAISING AND STRESS-CONTROL DEVICES FOR FARMING TRACTORS Filed March- 2, 1964 3 Sheets-Sheet 1 Invenlor Lucien e -'65 8 fm, MM W W/MM gifzowneyg.

March 7, 1967 PE 7 HYDRAULIC EQUIPMENT RAISING AND STRESS'CONTROL DEVICES FOR FARMING TRACTORS Filed March 2, 1964 5 Sheets-Sheet 2 Im/ehZ w Lac fen pe ma 8 14 iorne y I r I March 7, 1967 L. PERAS 3,307,455

HYDRAULIC EQUIPMENT RAISING AND STRESS-CONTROL DEVICES FOR FARMING TRAGTORS Filed March 2, 1964 3 Sheets-Sheet 5 D P 180 v 173 Imus/i140! Lucien aras United States Patent 3,307,455 HYDRAULIC EQUIPMENT RAISING AND STRESS- CONTROL DEVICES FOR FARMING TRACTORS Lucien Peras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France, a French works Filed Mar. 2, 1964, Ser. No. 348,540 Claims priority, application France, Mar. 4, 1963, 926,788, Patent 1,363,918; Sept. 16, 1963, 947,625, Patent 1,37 6,690

14 Claims. (Cl. 91-367) This invention relates to hydraulic devices adapted to raise the equipment or tool carried by farming tractors, to transfer the equipment load to the tractor, and to control the tractive effort exerted on the equipment. It applies notably to tractors of the type comprising a singleacting hydraulic equipment-raising cylinder controlling one or a plurality of lifting arms having their ends connected through links to the traction rods carrying the equipment, tool or implement of the tractor.

This invention relates more particularly to a device comprising in combination a preselector-type control in the form of a preselector handlever adjustable as a function of the desired vertical or depth position of the equipment, and another control of the tractive-effort type, i.e. responsive to the resistant stress produced by the equipment during the ploughing or other soil-working operation, this last-named control being adapted to limit this stress to a preselected value by acting upon the tool operation depth, that is, upon the raising device proper, so that the tractor will operate with a predetermined constant or maximum tractive effort.

It is an object of this invention to provide a specific form of embodiment of a dual-control device of the type broadly set forth hereinabove, which is characterized by a greatly simplified construction and by a considerable degree of manoeuverabiiity, the operator having furthermore the choice of using only one of the two control means available in the device.

Generally, two solutions may be resorted to for controlling either the tractive eifort of the tractor vehicle or the resistant effort of the equipment during its operation:

(a) The first solution consists in creating in the equipment raising cylinder pressure values determined beforehand as a function of the type of work to be performed, these pressure values being obtained whenever the tractive effort rises to certain predetermined corresponding values;

This first solution requires a nearly constant throttling of the hydraulic fluid, as a rule oil, in an open-center hydraulic circuit, i.e. a circuit wherein a distributor having at least three ports or ways provides a continuous fluid flow from the first port to the second and/ or third ports.

(b) The second solution consists in causing automatically a slight upward movement of the equipment each time the resistant effort increases by a predetermined value in order to decrease this resistant effort and therefore reduce to zero the equipment-raising control action in conjunction with the stabilization of the working depth of the equipment at a value consistent with or corresponding to a given tractive effort.

Conversely, when the tractive effort decreases, the effort detecting device will control automatically the means for lowering the equipment in order to increase the working depth of the equipment until the preselected tractive effort is restored.

This second solution is advantageous in that the feed pump operates only during the equipment raising periods for altering the working depth, without requiring a constant throttling of the fluid.

In the device according to the present invention, which ice is based on this second solution, the equipment raising cylinder is connected to a distributor comprising a slidevalve for controlling the delivery of hydraulic fluid from a source of fluid under pressure such as a pump either to said raising cylinder through an inlet valve in a first position of the movable member of said slide valve or from said equipment raising cylinder through an exhaust valve to an exhaust duct connected to the reservoir feeding said source in the second position of said slide valve in which the movable member of the slide valve is urged by spring means, or directly to said exhaust valve in the intermediate position of the aforesaid movable member of the slide valve. Moreover, this movable member of the slide valve may assume other intermediate positions in which, instead of causing the complete closing or opening of the ports concerned, it produces a more or less pronounced throttling thereof.

The desired position of the equipment raising arm is obtained by means of a preselector control arrangement incorporating a preselector handlever and interconnected through suitable linkage means with this handlever, the slide valve and the raising arm.

An effort control system co-operates with the slide valve and is connected to the draw-gear or coupling system incorporating resilient means responsive to the tractive effort when the latter exceeds a predetermined value. This effort control system comprises a first pivoting bearing member so arranged that the draw-gear may exert therethrough a certain force on the slide valve in the direction of the first position thereof. The permissible movement of said bearing member in the direction of this force is limited by an adjustable stop member provided on an adjustment handlever.

The linkage means comprise a second pivoting bearing member also adapted to act upon the slide valve.

The operative connections between said first pivoting bearing member and the draw-gear, on the one hand, the between said second pivoting bearing member, said raising arm and said preselector handlever, on the other hand, are so designed that a tractive effort exerted on the draw-gear which has a force sufficient to overcome the resistance of the resilient means, the movement of said preselector handle in one direction as Well as the lowering of the raising arm, are capable of causing the slide valve member to move in the direction of its first position. Conversely, if this tractive effort decreases to a value sulficient to render the tractive eifort exerted by said resilient means preponderant, a displacement of the preselector handlever in the opposite direction, a displacement of the adjustment handlever in the direction to enable its stop member to exert a pressure against the first pivoting bearing member and an upward movement of the raising arm, will cause .the slide valve to move toward its second position.

This invention is also concerned with a distributor device of which the slide valve is responsive to the various mechanical control elements set forth hereinabove.

This distributor device comprises essentially inlet and exhaust valves, a cock adapted to connect the source of hydraulic fluid under pressure directly to the feed reservoir of said source, a controlled relief valve and a distributor proper.

The cock is controlled from a double-acting cylinder the inner space of which is divided by its piston into a closing chamber containing a spring urging said piston in the cock closing direction and an opening chamber connected to said source of hydraulic fluid under pressure, whereby the application of this pressure in this opening chamber will drive said piston in the cock opening direction.

Said relief valve comprises a piston-like shutter opening with one end into a cavity into which a sliding valve seat is also adapted to open. This sliding seat communicates with the exhaust duct and is urged by spring means toward said shutter of which the other end opens into a control chamber adapted to be connected either to the source of hydraulic fluid under pressure or to said discharge duct.

The distributor proper comprises around its slide valve member a first chamber communicating with the source of hydraulic fluid under pressure, a second chamber communicating with the raising cylinder through said inlet valve, with the closing chamber of said cock and with the cavity of said relief valve, and a third chamber communicating with said control chamber of said relief valve and with said discharge duct. These three chambers disposed around the slide valve are separated from each other by two partitions disposed the one between said first and second chambers, and the other between said second and third chambers.

The slide valve incorporating said valve shutter disposed in said second chamber is adapted to close an orifice formed through said first partition and is connected through an axial stem to a piston-type shutter disposed at the level of saidthird chamber ar d adapted to close either a passage formed through said second partition or a passage leading to the discharge duct. The distance between the seat of the valve shutter and the edge of the port into which said seat opens into said third chamber and the distance between the shutters are so calculated that in the first position the slide valve will free the passage between said three chambers, that in the second position it will prevent the communication between these chambers and that in the intermediate position it will free only the passage between the first chamber and the second chamber. The duct connecting the equipment raising cylinder to the inlet valve communicates with the discharge duct through the medium of the exhaust valve the opening of which is controlled mechanically by the slide valve member when it is moved to its second position.

Two typical forms of embodiment of the hydraulic raising device according to this invention are described hereinafter by way of example with reference to the accompanying drawings. Other features and advantages of the invention will appear as the description proceeds. In the drawings:

FIGURE 1 illustrates diagrammatically in section an equipment raising mechanism constructed according to the teachings of this invention;

FIGURE 2 is a diagrammatic sectional view showing the rear portion of a tractor of which the left-hand wheel has been removed, with the carried equipment consisting in this case of a plough;

FIGURE 3 is a diagrammatic section showing on a larger scale a relief valve incorporated in the distributor device of this invention;

FIGURE 4 to 6 illustrate diagrammatically three different positions of the distributor slide valve;

FIGURE 7 is another diagrammatic sectional view showing an alternate form of embodiment of the equipment raising device of this invention;

FIGURE 8 illustrates diagrammatically a modified mounting of the raising device of FIGURE 7, at the rear of a tractor; and I FIGURE 9 is a detail view showing an alternate form of embodiment of the distributor slide valve.

The device of this invention is comprised of an assembly of mechanical component elements illustrated in the right-hand portion of FIGURES l and 2, which assembly is adapted to act upon a single control member of the distributor shown in the left-hand portion of FIG- URE 1, this control member being sunk more or less in the distributor body during the operation of the assembly.

The traction rods 1 permitting the rigid mounting of a farming equipment such as a plough are pivotally mounted by means of their pivot pins 2 on the crank-pins 3 of a crankarm 4 adapted to rotate about a mainshaft 5 mounted in the casing of the final drive of the tractor. The traction rods 1 are suspended from a lifting link 6 pivoted on the end of a lifting arm 7 rigid with a control lever 8 pivotally mounted on a spindle 9 also carried by said casing. An equipment raising cylinder 10 of which the movable element or piston bears through the medium of a thrust rod 11 against the end of one of the arms of said lever 8 exerts on the lifting arm 7 and raising link 6 a stress counter-acting the force tending to lower the equipment.

The c-rankarm 4 is rigid with another lever 12 of which the permissible angular amplitude is limited by stop members 13 and 14. A traction spring 15 constantly urges the lever 12 towards the stop 13, i.e. in a direction opposite to the direction in which this lever is urged by the tractive force exerted by the equipment.

A first bearing member 16 in the form of a bell-crank lever pivoted on the end of lever 12 by mean-s of a pivot pin 17 and adapted to pivot in the same directions as this lever, has its free end registering with the control member or push-rod 18, another tension spring 19 urging this free end for engagement with the aforesaid push-rod, as shown. The permissible angular movements of this first bearing member 16 is restricted, in the direction in which it is urged by the spring 19, due to the provision of an adjustable stop 20, consisting for example of the loosed bottom of an axial blind bore of a tube 21 pivoted on a lever 22 rigid with a control handlever 23 pivotally mounted on a fixed pivot pin 24, this blind bore being engaged by a rod 25 pivotally mounted on said first bearing member 16.

A cam 26 of which the operative contour registers likewise with said push-rod 18 is pivotally mounted on a fixed pivot pin 27. A first rod 28 is pivoted at one end on a point of said cam which is spaced from its axis of rotation and at its other end on an intermediate point of another rod 29 also pivoted at one end on the arm of control lever 8 which is opposite to that engaged by the thrust rod 11. The other end of rod 29 is connected through a third pivoted rod 30 to one end of a lever 31 rigid with a preselector control handlever 32 pivoted about a fixed pivot pin 33.

In order better to distinguish the movable pivot points from the fixed pivot points on the tractor or its final drive casing, these pins are shown in the form of shaded discs in FIGURE 2.

The form of embodiment of the distributor device according to this invention which is illustrated in FIGURES l and 3 to 6 consists of a unitary block in which are incorporated the inlet and exhaust valves 34 and 35, respectively, the cock 36 adapted to connect the delivery duct 37 of a pump 38 directly to the reservoir 39 filled with hydraulic fluid such as oil, the relief valve 40 and the distributor proper 41. This distributor device communicates with the reservoir 39 through a discharge duct 42 and with the cylinder 10 through a pipe line 43.

The member controlled directly by the mechanical control members illustrated in the right-hand side of FIG- URE 1 is the slide valve member 44 constantly urged against the aforesaid push-rod 18 by a spring 45.

The slide valve 44 is slidably mounted in the distributor 41 shown on a larger scale in FIGURE 4. This distributor comprises around its slide valve member and from the end adjacent to push-rod 18 three chambers 46, 47 and 48 in axial alignment. The first chamber 46 is separated from the second chamber 47 by a partition through which an orifice 49 is formed, and the second chamber 47 is separated from the third chamber 48 by another partition in which a passage 50 is formed, this third chamber 48 being separated in turn from a cavity 51 by'a partition formed'with a passage 52.

The slide valve member 44 is a one-piece member projecting from the distributor 41 with a cylindrical end portion 53 engaged by the push-rod 18. Any fluid leaking between this cylindrical end portion 53 and the surrounding bore in the distributor wall is collected by a cavity 54 communicating through a passage 55 with the discharge duct 42.

As seen from its cylindrical end 53 the slide valve member 44 comprises a frustoconical valve portion 56 disposed in the second chamber 47 and adapted to close the orifice 49, a piston-type shutter 57 disposed in the plane of the third chamber 48 and adapted to close either passage 50 or passage 52, and finally a cam portion 58 disposed in the cavity 51 and adapted to hold the shutter 59 of exhaust valve 35 open or unseated by means of a ball 60 and a control rod 61. A passage 62 formed in the slide valve body connects the cavity 51 to the discharge duct 42. The distances between the valve shutter 56, piston shutter 57 and cam 58, on the one hand, and between the seat of valve shutter 56 in orifice 49, the edges by which passage 50 and cavity 51 open into the third chamber 48 and the ball 60, on the other hand are so calculated that the communication between the first, second and third chambers is established, that between the third chamber 48 and cavity 51 is discontinued and exhaust valve 35 is closed when the slide valve member has completed its stroke to the -left, as shown in FIG- URE 4, and that the slide valve member closes the passage between the chambers, frees the passage between the third chamber 48 and cavity 51 and the discharge duct 42, and causes the opening of the exhaust valve 35 when it attains its endmost position to the right (FIG- URE 6). In an intermediate position (see FIGURE 5) the slide valve member frees only the passage from the first chamber to the second chamber. Of course, the slide valve member may occupy intermediate positions in which the different passages are more or less throttled.

The cock 36 comprises a cylindrical chamber 63 connected to the delivery duct 37, and through a duct 64 to the first chamber 46 of distributor 41 and through a passage 65 do the discharge duct 42. Slidably fitted in the cylindrical chamber 63 is a first piston 66 which carries, aligned on one side and in this order, a valve shutter 67 and another, smaller piston 68 sliding in a closed cylinder 69. A duct 70 formed in the valve shutter 67 and the second piston 68 maintains a permanent communication between the delivery duct 37 and the space formed between the second piston 68 and the bottom of the closed cylinder 69. On the other side of said first piston 66 a spring 71 housed in a closed chamber 72 exerts a resilient force on the first piston 66 so that the valve shutter be urged against the seat-forming passage 65. The closed chamber 72 communicates with the second chamber 47 of distributor 41.

The relief valve 40 of which one portion is illustrated on a larger scale in FIGURE 3 comprises a piston-type 1 shutter 73 sliding in a cylinder 74. This shutter 73 opens with one of its ends into a cavity 75 communicating with the closed chamber 72 of cock 36, a sliding seat 76 opening likewise into this chamber, as shown. This sliding seat communicates with the discharge duct 42 and is urged by a spring 77 in the direction of shutter 73. How ever, its stroke is limited in this direction by a shoulder 78. The other end of shutter 73 opens into a control chamber 79 communicating with the aforesaid third chamber 48 of distributor 41. The diameter 80 of said sliding seat 76 engageable by said shutter is smaller than either the diameter 81 of cylinder 74 or the diameter 82 of the passage in which the seat 76 is slidably fitted (see FIGURE 3).

Finally, the pipe line 43 connected to the raising cylinder communicates on the one hand with the second chamber 47 of distributor 41 through the medium of the inlet valve 34 permitting the flow of hydraulic fluid from this chamber to the cylinder and on the other hand with the discharge duct 42 through the intermediary of the aforesaid exhaust valve 35. Throttling devices such as an adjustable needle valve 83 interposed in the duct 64 connecting the cylindrical chamber 63 of cock 36 to the first chamber 46 of distributor 41 and another adjustable needle valve 84 mounted immediately upstream of the exhaust valve 35 permit a proper limitation of the equipment raising and lowering speeds.

A throttling device 85 may also be provided in the duct connecting the closed chamber 72 of cook 36 to the second chamber 47 of the distributor, the function of this device being explained presently.

Finally, another cook 86, for example a three-way cock, which may be interposed in the pipe line 43 connecting the raising cylinder 10 to the distributor device permits of closing this line and to connect other apparatus operated by the hydraulic fluid under pressure than the raising cylinder 10 to the distributor device.

The equipment-raising device described hereinabove by way of example operates as follows:

(1) Efiort control device.-The tractive effort exerted in the linkage in the direction of the arrow shown on the traction rod 1 of FIGURE 1 varies as a function of the type of work to be performed by the equipment and varies also during the Work performed by a given equipment as a function of the changes arising inevitably in the nature of the soil as the tractor and equipment unit is operated.

As long as the tractive effort remains below a predetermined value the spring 15 holds the arm 12 stationary against the stop 13. When this effort rises above this value the arm 12 moves to the left and elongates the spring 15 until the spring force balances the tractive effort through the medium of the arms of lever 12 and crankshaft 4.

Thus, for each value of the tractive effort which lies within the adjustment range contemplated by construction, the lever 12 will occupy a position between stop 13 and stop 14.

During its movements this lever 12, through the intermediary of pivot pin 17, carries along the first bearing member 16. Thus, this bearing member 16 is caused to occupy different positions as a function of the variations in the tractive effort and therefore, as a function of these positions, to engage the push-rod 18 and to move same more or less to the left.

Moreover, it is possible to vary the position of the first bearing member 16 in relation to this lever 12 by means of the handle 23, lever 22, stop 20 and rod 25.

As a result, different positions of push-rod 18 can be obtained for a same position of lever 12, thus permitting the proper adjustment of presetting of the beginning of the upward pulse given to the equipment-raising means in relation to the value of the tractive effort.

Thus, with the first bearing member 16 adjusted for maximum sensitivity, it will contact the push-rod 18 and cause the hydraulic fluid pressure in the equipmentraising cylinder to increase when the lever 12 ceases from hearing against the stop member 13. On the other hand, if the first bearing member 16 is adjusted for minimum sensitivity corresponding to the higher range of tractive efforts it will be necessary that lever 12 attains a position relatively remote from stop member 13 (which corresponds to a substantial value of the tractive effort) before the first bearing member 16 causes a pressure increase by depressing the push-rod 18.

When the first bearing member 16 is in its endmost position to the left (FIGURE 4) abutting against the push-rod 18 and while lever 12 continues its leftward movement, the first bearing member 16 tilts due to the sliding movement of rod 25 in its tube 21 and thereby causes elongation of spring 19.

(2.) Equipment raising controL-The second bearing member, that is, cam 26, acts upon the push-rod 18 in conjunction with, but independently from, the first bearing member 16.

Starting from the neutral Position of the slide 44 when the lever 32 is moved towards the right in the drawing, the link 30 is pulled towards the left by the small lever 31 rigidly connected with the lever 32. The link 29 turns around its pivot point on the lever 8 in clockwise direction and forces the link (28) to move towards the left and therefore to turn the cam 26 in counter-clockwise direction. This causes the displacement of the slide 44 towards the left and the feeding of the jack.

The feeding of the jack causes the lever 8 to turn around the pin 9 and the lever 32 being then fixed, this has the effect of returning the link 28 to the right, carrying along the cam 26 in clockwise direction. The movement stops when the slide 44 has returned, under the action of the spring 45, into neutral position.

For control of descent, the procedure is the same but the lever 32 is in this case moved towards the left.

(3) Conjugate action of the equipment-raising control and of the stress control means.-When cam 26 is in its neutral position, the first bearing member 16 cannot act upon push-rod 18 save for moving same to the left to its initial neutral position, that is, only for controlling a pressure increase and therefore an upward movement of the equipment.

When the first bearing member 16 moves to the right from the neutral position of push-rod 18, the latter remains in engagement with cam 26 and therefore no control of a downward movement below the position preselected by means of the preselector control handlever 32 can take place.

With this arrangement it is possible to combine the position preselection with the stress control, whereby the maximum working depth of the equipment is determined in an unchanging manner by the preselection, and the stress control is effective for producing a load transfer followed by a gradual upward movement of the equipment immediately when the tractive effort equals or exceeds a predetermined value.

When it is desired that the position of the equipment be determined only by the effort control device, the position preselector control handlever 32 must be so placed that cam 26 be positioned somewhat backwards in relation to the neutral position of push-rod 18.

From the intermediate position of slide valve 44 in which the raising arm 7 is kept in a predetermined position the distributor device permits of controlling either the upward movement of the equipment by moving the slide valve to the left, or the downward movement of the equipment by moving said slide valve to the right.

In the intermediate or neutral position of slide valve 44 (see FIGURE the hydraulic fluid is allowed to flow from the first chamber 46 to the second chamber 47, and from the third chamber 48 to the exhaust duct 42 through cavity 51 and passages 62. Since the control chamber 79 of relief valve 40 is connected to the discharge duct 42 through the third chamber 48, the fluid delivered by pump 38 and flowing freely into the cavity 75 of relief valve 40 through the circuit comprising the delivery duct 37, cylindrical chamber 63 of valve 36, duct 64, first and second chambers 46, 47 and throttling device 85, unseats the shutter 73 due to the pressure exerted on the relevant annular portion corresponding to the difference between diameters 80 and 81 (see FIGURE 3). Therefore, this hydraulic fluid may flow freely through the sliding seat 76 to the discharge duct 42 without exerting any control pressure in the closing chamber 72 of valve 36. Under these conditions, the oil delivery pressure prevailing in the cylindrical chamber 63 of valve 36 acts upon the first piston 66 and through duct 70 upon the second piston 68 thereof, these pistons compressing the coil spring 71 and unseating the shutter 67 to free the passage 65 through which the major portion of the oil is returned directly to the reservoir 39 through the discharge duct 42. The throttling device 85 assists in conjunction with the adjustable needle valve 83 in establishing in the cylindrical chamber 63 of valve 36 the fluid pressure necessary for opening this valve.

The upward movement of the equipment (see FIG- URE 4) is controlled by moving the slide valve 44 left wards; it has been explained hereinabove that this movement could be caused either by the cam 26 or by the first bearing member 16 transmitting the reactions of the equipment during the work.

During its movement the slide valve 44 frees the passage betWeen chambers 46, 47 and 48, while closing the passage 52 between the third chamber 48 and cavity 51. The moderate oil pressure prevailing in this case in the second chamber 47 is transmitted to control chamber 79 of relief valve 40 wherein it applies the shutter 73 against its sliding seat 76.

As the return of oil to the reservoir 39 through the sliding seat 76 is discontinued the pressure becomes substantially equal to that prevailing in the closing chamber 72 and in the cylindrical chamber 63 of valve 36; in other words, this pressure becomes equal on either side of pistons 66 and 68. Therefore, spring 71 will seat the valve shutter 67.

Since the fluid cannot flow freely through the passage 65 and since the sliding seat 76 of relief valve 40 is fully closed, this fluid is forced into the raising cylinder by flowing along duct 64, first and second chambers 46, 47 around the unseated ball 34 of the inlet valve, and finally through the pipe line 43.

It will be noted that the quantity of oil discharged through passage 65 is determined by the pressure differential obtaining between the cylindrical chamber 63 and the closing chamber 72, irrespective of the value of the pressures prevailing in these chambers. Now this pressure differential varies as a function of the throttling actions produced in the circuit downstream of valve 36. The throttling action produced by the adjustable needlevalve 83 may be adjusted permanently with a view to reduce under all circumstances the maximum feed rate of the cylinder, the throttling action of orifice 49 which is caused by the valve shutter 56 varying on the other hand as a function of each slide valve movement. Thus, it will be seen that when a relatively short slide valve movement takes place as the orific 49 is throttled considerably the fluid output to the cyinder will be very small, whereas a longer slide valve stroke will practically elimimate the throttling action so that the feed rate of the cylinder can attain its maximum value determined by the adjustment of needle valve 83.

The throttling device 85 is designed to permit a rapid pressure drop in closing chamber 72 when shutter 73 begins to move away from its sliding seat 76 in order to ensure a clean return of valve shutter 67 of valve 36 to its open position.

The downward movement of the equipment (see FIG- URE 6) is controlled by a movement of slide valve 44 to the right.

When the cam 26 is moved away from the distributor body the coil spring 45 moves the slide valve member 44 to the right, thus holding it in contact with the cam. As it completes its stroke (i.e. after having cut off the passage between the three chamber 46, 47 and 48) the slide valve member 44 unseats by means of its cam 58 the ball 60 which unseats in turn the shutter 59 of exhaust valve 35 through the medium of the control push-rod 61. This shutter 59 is hydraulically balanced and seated only by the spring 86 (FIGURE 1). The oil contained in the cylinder is thus discharged to the reservoir through pipe line 43, needle valve 84 and discharge duct 42.

Finally, one of the component elements of the distributor device, the relief valve 40, is also adapted to operate as a pressure limiting device. The shutter 73 of this valve comprises a stop member limiting its stroke in the direction of its sliding seat 76.

When the shutter 73 under the influence of the pressure build up-in chamber 79 is abutting it also bears against its sliding seat 76 which has moved and partially compressed spring 77 (see FIGURE 3). If the pressure in cavity 75, (which applies to the annular section of sliding seat 76 corresponding to the difference existing between the diameter 82 of the bore in which said seat is slidably mounted and the diameter 80 engaged by the shutter on this seat) exceeds the value corresponding to the calibration of spring 77, the sliding seat 76 by compressing to a greater extent the spring 77 will move away from shutter 73 and open the passage leading to discharge duct 42. Under these conditions, the pressure decreases immediately in the closing chamber 72 of valve 36, due to the throttling device 85 limiting the permissible re-feeding of said closing chamber, thus opening valve 36 and discharging the oil through passage 65 to the discharge duct 42.

A modified form of embodiment of the raising device of this invention will now be described with reference to FIGURES 7 and 9.

In this alternate form of embodiment the preselector handlever is provided with a stop member co-acting unidirectionally with the second bearing member pivoting in the direction permitting the positive displacement of this member and of the slide valve for producing the equipment raising movement. slide valve in the opposite direction tends to keep the second bearing member in contact with said stop member. The pivoted linkage of the preselector control system comprises an element co-acting undirectionally with the raising arm provided with a stop member, said element being urged by said spring for engagement with this stop member. The stop member of the adjustment handlever is so disposed thereon that it acts as a counter-stop to said first pivoting bearing member in order to adjust according to its position the setting into operation of the slide valve in the equipment raising direction when the tractive effort exceeds a predetermined value.

As shown in FIGURE 8 the tractor 101 of this modified arrangement comprises a three-point equipment coupling system comprising as in conventional systems of this character two lateral traction rods 102 pivoted on the rear part of the tractor frame and raising links 103 connected on the other hand on the end of a raising arm 104 pivoted on the tractor frame structure by means of a pivot pin 105.

The equipment illustrated in this case is also a plough pivotally connected to the rods 102 at 106 and to another link 107 at a third point 108.

As shown in FIGURE 7, co-a-cting with the raising arm 104 is a single-acting cylinder 109 having its cylinder body 110 rigid with the tractor and its piston 111 connected through a thrust rod 112 to the aforesaid arm 104.

Connected through a pipe line 113 is a hydraulic device 114 for distributing fluid under pressure from the reservoir 115 through the medium of a pump 116 and a delivery duct 117, a discharge duct 118 connecting the distributor device 114 to the reservoir 115, as shown.

This distributor device comprises a slide valve member 119 slidably fitted in the distributor body forming a plurality of spaced annular chambers adapted to be isolated from one another by means of slide-valve shutters, notably chambers 120, 121 separable by a valve shutter 122 and chamber 123 separable from chamber 121 by means of a piston shutter 124.

The pump delivery duct 117 is connected to a duct 125 of the distributor device which communicates permanently with the aforesaid chamber 120, this duct 125 having inserted therein a valve 126 having its valve shutter adapted to engage a seat 127 to control the fluid flow to another duct 128 connected to the discharge duct 118. The valve shutter of valve 126 is in the form of a sliding piston having a closing control chamber 129 containing a coil spring 130 and connected to the aforesaid chamber 121 by means of a duct 131 in which a relief valve or pilot valve 132 of valve 126 is inserted. This valve 132 is The spring urging the' also of the sliding piston type formed at one end with a shutter adapted to engage a seat 133 through which the duct 131 communicates with another duct 134 constantly connected to the discharge duct 128.

At the other end of valve 132 a control chamber 135 constantly connected to chamber 123 is provided.

Chamber 121 is connected through an inlet valve 136 to a duct 137 communicating normally through a cock 138 with a duct 139 leading to the aforesaid pipe line 113. This duct 139 is also constantly communicating with a duct 140 in which a needle valve 141 is inserted, this duct 140 having in addition with a duct 142 connected to the discharge duct 128 a communication controlled by an exhaust valve 143 of the balanced type which is urged to its seated position by a spring 144. This valve 143 is controlled by means of a ball 145 engaged by a cam face or ramp 146 (see FIGURE 9) formed on the sliding member 119 cf the distributor slide valve.

On the other hand a safety valve 150 is connected to the control chamber 129 of valve 126. This safety valve 150 consists of a piston-like member slidably mounted in a bore 151 and carrying a shutter 152 adapted to engage a seat 153 opening int-o the chamber 129. This shutter 152 forms with the valve bore and the piston an annular chamber 154 constantly communicating with a duct 155 which a rotary cock 156 is adapted to either isolate from, or connect through its inner passages 157 with, a duct 158 connected in turn to the discharge duct 142. On the side opposite to the shutter 152 the valve 150 is urged by a spring 159 housed in a chamber 160 having a diameter somewhat greater than that of bore 151, and the piston sliding in this bore is formed with at least one flat side face 161 forming in the bore 151 a passage permitting the communication between the annular chamber 154 and the chamber 160 after a certain compression of spring 159 which corresponds to a backward movement of shutter 152, said chamber 160 communicating permanently with the duct 158 through a duct 161 and the passage of cock 156.

The slide valve member 119 of the distributor has one end urged against a control push-rod 162 by one end of a compression spring 163 bearing against the distributor body with its other end.

At the ends of the slide valve member a pair of chambers 164 and 165 are provided which communicate respectively with the discharge ducts 142 and 128, chamber 164 communicating in addition through a passage 166 formed in slide valve member 119 with an annular space 167 formed between this member 119 and the surrounding cavity, this passage 166 being adapted to communicate or not with chamber 123 according to the position of the piston shutter 124 of the slide valve in relation to the slide valve member 119.

In this form of embodiment the push-rod 162 is springloaded and consists of'two members 162 162 slidably mounted in each other with a spring 168 interposed therebetween, their relative expansion being limited by a pin 169. Spring 168 is tightened with a force greater than that of spring 163 in its maximum compressed position, whereby the push-rod 162 acts norm-ally as a rigid memher with respect to spring 163. This push-rod 162 carries a pin 170 on which are pivoted intermediate their ends the second pivoting bearing member and the first pivoting bearing member, in the form of a lever 172, of a tractive effort control system.

The second pivoting bearing member 171 is an integral part of a linkage interposed between an adjustable preselector handlever 173 and the raising arm 104. The preselector handlever 173 is provided with a stop 174 co-acting unidirectionally with one end of the other bearing member 171 having its opposite end connected to a link 175 pivoted on the other hand intermediate the ends of lever 176, this lever 176 having one end pivoted on a fixed pin 177 of the tractor and the other end coacting unidirectionally with a stop member 178 carried by said raising arm 104. This linkage is so designed that the aforesaid spring 163 of slide valve 119 constantly urges through push-rod 162 the second bearing member 171 and lever 176 in contact with stop members 174 and 178.

The first bearing member 172 is an integral part of a linkage interposed between an effort-control adjustment lever 180 and the equipment coupling system comprising resilient means responsive to the tractive effort, which means in this example consists of a compression spring 181. This spring 181 is interposed between the tractor frame structure and a guide push-member 182 responsive to the action of a lever 183 forming an integral part of a crankshaft pivoted on a fixed pivot pin 184 and provided, on the other hand, with crankpins 185 on which the aforesaid traction rods 102 are pivoted as at 186. Lever 183 bears against the tractor frame structure as illustrated in FIGURE 7 for a given degree of prestress of spring 181 which is determined as a function of the range of tractive efforts to which the spring is required to react by deformation.

The adjustment lever 180 is formed with a stop member 187 adapted to engage unidirectionally one end of the first pivoting bearing member 172 of which the other end is connected to a link 188 which, by means of a bell-crank lever 189 pivoted on pin 177, co-acts with another link 190 connected in turn to the lever 183 of said crankshaft.

The control handlevers 173 and 180 are mounted on a common fixed pin 191 and can be locked in relation thereto in any desired angular position by means of any known and convenient device designed for control means of this character, this locking system being no part of the present invention.

It will be seen firstly that the preselector control system implies that to each selected angular position of the preselector handlever 173 there corresponds a predetermined angular position of the equipment raising arm 104 in which as both elements 171 and 176 bear against stop elements 174 and 178, the distributor slide valve member 119 is in its intermediate or neutral position which is the position shown in FIGURE 7.

In this position, the oil delivered by pump 116 into the delivery duct 125 is returned to the reservoir through thevalv'e 126, the shutter of this valve being unseated by the fact that the oil delivery pressure exceeds the force of spring 130since no pressure exists in the closing chamber 129; stress may be laid on the fact that in spite of a possible flow of fluid from chamber 120 to chamber 121 in the neutral position of the slide valve the duct 131 is then connected to the reservoir through the seat of pilot valve element 132 of valve 126.

To produce the upward movement of arm 104 and therefore of the equipment carried thereby, the operator moves the preselector handlever 173 in the direction of the arrow M. In this case the push-rod 162 moves the slide valve member 119 to the left, thus disposing the valve shutter 122 and piston shutter 124 of the slide valve in such positions that the annular chambers 120, 121 and 123 communicate with one another, chamber 123 being isolated from the reservoir 115. As a result, the shutter member of pilot valve 132 is responsive to a preponderant pressure in control chamber 135 which urges said member to its closed position against seat 133, this pressure preponderance being due notably to the presence of a throttled passage 192 formed in the duct 131 and to the preliminary opening of the seat 133 of this valve.

Under these conditions the pressure built up in the closing chamber 129 of valve 126 attains a value tending to equal the oil delivery pressure toward the reservoir through this valve, whereby the shutter thereof will then be urged to its closed position by the spring 130. Under these conditions the oil pressure rises in the circuit involved and the cylinder 109 is then fed through the inlet valve 136. This produces an upward movement of arm 104 and therefore of the equipment, simultaneously with a movement to the right (as seen in the drawing) of the stop member 178, so that the linkage 176, 175, 171, push-rod 162 and slide valve member 119 move back to the right as seen in the drawing until they are stopped in a stable position when the slide valve member 119 has resumed its neutral position.

In fact, it will be noted that as slide valve member 119 resumes its neutral position the piston shutter 124 thereof simultaneously separates chambers 121 and 123 from each other and restores the communication between this chamber 123 and control chamber 135, on the one hand, and reservoir 115, on the other hand, thus causing the opening of seat 133 of pilot valve 132 and a pressure drop in closing chamber 129 of valve 126, whereby the oil pressure exerted against this valve 126 becomes again preponderant in relation to the action of spring and causes the opening of seat 127 to restore the communication between the pump and the reservoir. During this return movement of the slide valve member to its intermediate or neutral position the throttled passage 192 permits a rapid pressure drop in closing chamber 129 immediately as the seat 133 is re-opened, thus causing a clean return of valve shutter 126 to its open position.

To obtain a downward movement of arm 104 the preselector handlever 173 must be moved in the direction of the arrow D. In this case the spring 163 urges the slide valve member 119 and push-rod 162 to the right, as seen in the figures, together with the second pivoting bearing member 171 due to the clearing of stop member 174 in relation thereto, and in addition the movement of slide valve member 119, while maintaining the circuit in the by-pass condition, will open by means of the cam face or ramp 146 the exhaust valve 143 to vent the cylinder 109. This venting of cylinder 109 takes place through needle valve 141, whereby the rate of downward movement of the equipment can be adjusted at will. This involves a downward movement, toward the left-hand side of the figures, of stop member 178, whereby the linkage system comprising 176, 175, 171, pushrod 162 and slide valve 119 resumes a stable position corresponding to the intermediate or neutral position of slide valve member 119 in which position this member 119 permits the re-closing of exhaust valve 143.

If it is required to raise the equipment, the preselector control handlever 173 may be moved in the direction M 1n such a manner that it involves a movement of pin of slide valve member 119 which is greater than the permissible stroke of this member 119 toward the left-hand side of the figures, for when the slide valve member abuts in the distributor body while compressing home the spring 163, the spring-loaded member 162 retracts to permit a complementary movement of pin 170.

Of course the push-rod 162 could also consist of a rigid member but in this case the operation, in the case of raising movements of relatively great amplitude, should accompany the preselector handlever 173 to the desired position as the equipment is actually raised.

It will be noted that the interaction between this preselector control and the effort control means produces through the pivot pin 170 a displacement of the first pivoting bearing member 172 of this last-named control means of which the movement takes place with-out any interference whatsoever in case of equipment raising movement and must be assured, to permit the above-described operation in case of downward movement, by the provision of a minimum play e between the stop member 187 of adjustment handlever 180 and the element 172 of the effort control, this play e being such as to permit the movement of pin 170 to the extent necessary for actuating the exhaust valve 143.

The above-described tractive effort control device operates as follows:

The effort required for pulling the equipment or tool during the work (for example the ploughing of a soil), which corresponds to the resistant effort exerted in the direction of the arrow F on the traction rods 102, varies as a function of the type of work performed and during a same type of work according to changes intervening in the quality of the soil.

As long as this effort F transmitted to the spring 181 in the manner described hereinabove exerts on this spring a force inferior to the prestress force of said spring, the

lever 183 remains in abutment against the frame structure of the tractor and the effort control system is inoperative in relation to the preselector control by which the desired working depth of the equipment was preset.

When this effort F increases until the spring 181 is compressed to a condition of equilibrium depending on the effort involved, the lever 183 is raised and through the elements 190, 189 and 188 the first pivoting bearing member 172 is caused to move angularly about the pivot pin 170 directed toward the abutment 187 of adjustment handlever 180.

From the moment the first pivoting bearing member 172 engages the stop member 187, the movement of this member 172. is changed to a pivoting movement, during which said stop'member 187 serves as a fulcrum, thus causing the translation of pivot pin 170 of push-rod 162 to the left, as seen in the figures, and moving consequently the slide valve member 119 in the direction to release the hydraulic feed of cylinder 109 and cause the upward movement of the tractor equipment under the conditions 'already set forth. The thus initiated raising movement of the equipment causes the effort F exerted on the tracti-on rods 102 to decrease, whereby the spring 181 is somewhat allowed to expand. When as a consequence of the foregoing the linkage 183, 190, 189, 188 and 172 resumes its preceding position in which the first bearing member 172 engaged the stop member 187, the pivot pin 170 has resumed the position corresponding to the neutral position of slide valve member 119 in which the distributor is again in its by-pass condition, as already explained. Thus, the overstepping of a predetermined tractive effort involved automatically the application of a raising impulse to the equipment which tends to regularize the necessary tractor hauling effort.

It may also be noted that when the slide valve member 119-has resumed its neutral position, with the first pivoting bearing member 172 engaging the stop member 187 under the conditions set forth hereinabove, the linkage system of the preselector control assembly has a certain play in relation to the stop members 174, 178 due to the equipment-raising impulse which has just been controlled by the effort control system.

If in this case the tractive effort dropped below the value having caused the first bearing member 172 to contact stop member 187, spring 181 will expand further and slide valve member 119 will then be caused to move to the right, as seen in the figures, in the direction to operate the exhaust valve 143 of the cylinder, as permitted by the aforementioned play stored by the preselector control. Under these conditions, the equipment will be lowered to a greater working depth, thus tending to compensate the aforesaid reduction in tractive effort and therefore to regularize this reduction.

It will be noted that if under these conditions the tractive effort continues to decrease, the downward movement of the equipment can be limited when the aforementioned play given to the preselector control has been taken up, for this control will then become operative to return the slide valve and the control elements associated therewith to their initial neutral positions shown in the drawing.

It is clear that this dual-control device permits of combining the preselector control means with the effort control means, so that the maximum working depth of the equipment be determined by the preselector control means whereas the effort control means are effective to limit the tractive effort to a predetermined maximum value.

Of course, the maximum working depth may be selected by means of the preselector control and set to such a value that the effort control becomes preponderant during the operation, if desired.

More particularly, it will be noted that the tractive effort value above which the effort control becomes operative is simply determined by the position of stop member 187 and therefore of the adjustment handlever 180 located within easy reach of the operator. The displacement of the adjustment handlever 180 in the direction P (FIG- URE 7) will cause notably the compression stroke of spring 181 to increase, thus incrementing the effort value at which the effort control becomes operative, whereby this adjustment handlever 180 enables the operator to select the desired sensitivity of the effort control as a function of the type of work to be or being performed.

On the other hand, any overload in the feed circuit of cylinder 109 is safety avoided due to the provision of the safety or relief valve in the distributor body, this valve co-acting with the valve 126 under the following conditions:

When the control lever ofcock 156 is so positioned that chamber 154 of valve 150 is connected through a passage thereof with the discharge duct 142, the maximum value of the circuit pressure is that above which the shutter 152 is lifted off its seat 153, thus connecting the closing chamber 129 of valve 126 to the exhaust and causing the immediate opening of the seat 127 of this valve so as to connect the pump with the reservoir.

' latter compresses the spring 159 until the fiat face 161 of the piston, by receding, opens the communication between chambers 154 and 160. As this last-named chamber 160 is constantly communicating with the reservoir, as already explained the closing chamber 129 of valve 126 is exhausted, whereby the maximum pressure is limited by the opening of this valve. In this case the safety pressure may be selected to have a lower value than in the preceding case, the use of two safety pressure values depending if desired on specific working conditions, and may notably be useful in case the distributor were used for feeding load other or auxiliary apparatus outside the equipment raising cylinder 109, which are adapted to be connected to the distributor through the duct 139 and fed by means of the three-way cock 138 so as to isolate the raising cylinder 109 in this case.

Although the present invention has been described notably in conjunction with two preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope type, comprising a single-acting raising cylinder co-acting with at least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulic distributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the reservoir feeding said source, or, furthermore, in an intermediate position of said slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are permitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort control system co-acting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effort control system comprising a first pivoting bearing member a-buttingly engaged with said slide valve member and so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force on said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last-named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member abuttingly engaged with said slide valve member and also adapted to act upon said slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that atractive effort exerted on said coupling system and of a value sufficient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort which causes the effort exerted by said resilient means to become preponderant as well as a displacement of said preselector handlever in the opposite direction, a displacement of said adjustment handlever in the direction to enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said second position.

2. Hydraulic equipment raising device as set forth in claim 1, characterized in that said second bearing member consists of a cam.

3. Hydraulic equipment raising device as set forth in claim 1, characterized in that said pivoting bearing members act upon said slide valve member through the medium of a push-rod guided in the body of said distributor device.

4. Hydraulic equipment-raising and tractive-effort control device for farming tractors of the carried equipment type, comprising a single acting raising cylinder coacting with at least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulic distributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward 15 which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the'reservoir feeding said source, or, furthermore, in an intermediate position of said'slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are permitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort. control system coacting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effortcontrol system comprising a first pivoting bearing member so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force of said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member also adapted to act upon said-slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that a tractive effort exerted on said coupling system and of a value sufficient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort which causes the effort exerted by said resilient means to become preponderant as well as a displacement of said preselector handlever in the opposite direction, a displacement of said adjustment handlever in the direction to enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said second position, characterizedin that said first bearing member is a lever having one end so disposed as to be capable of exerting upon one of the ends of said slide valve member an effort in the axial direction of said slide valve member, the other end of said lever being subjected to the action ofa spring so that said first end may exert a force upon said slide valve member in the direction of said first position of said slide valve member.

5. Hydraulic equipment raising device as set forth in claim 4, characterized in that said second bearing member consists of a cam.

6. Hydraulic equipment raising device as set forth in claim 5, characterized in that the movable member of said hydraulic cylinder bears against one arm of a control lever solid with the lifting arm, said coupling system comprising a first link having one end pivoted on said second bearing member and the other end pivoted on one point of another link pivoted in turn'by means of a third link on a lever arm rigid with said preselector control handlever.

7. Hydraulic equipment raising device as set forth in claim 4, characterized in that the movable member of said hydraulic cylinder bears against one arm of'a control lever solid with the lifting arm, said coupling system comprising a first link having one end pivoted on said second bearing member and the other end pivoted on one point of another link pivoted in turn by means of a third link on a lever arm rigid with said preselector control handlever.

8. Hydraulic equipment-raising and tractive-effort control device for farming tractors of the carried equipment type, comprising a single acting raising cylinder coacting with a least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulic distributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the reservoir feeding said source, or, furthermore, in an intermediate position of said slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are permitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort control system coacting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effort control system comprising a first pivoting bearing member so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force on said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member also adapted to act 'upon said slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that a tractive effort exerted on said coupling system and of a value suflicient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort which causes the effort exerted by said resilient means to become preponderant as well as a displacement of said preselector handlever in the opposite direction, a displacement of said adjustment handlever in the direction to enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of caus ing the displacement of said slide valve member in the direction of said second position, characterized in that the movable member of said hydraulic cylinder bears against one arm of a control lever solid with the lifting arm, said coupling system comprising a first link having one end pivoted on said second bearing member and the other end pivoted on one point of another link pivoted in turn by means of a third link on a lever arm rigid with said preselector control handlever.

9. Hydraulic equipment-raising and tractive-effort control device for farming tractors of the carried equipment type, comprising a single acting raising cylinder coating with at least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulic distributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the reservoir feeding said source, or, furthermore, in an intermediate position of said slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are permitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort control sys tem co-acting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effort control system comprising a first pivoting bearing member so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force on said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member also adapted to act upon said slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that a tractive effort exerted on said coupling system and of a value sufiicient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort which causes the effort exerted by said resilient means to become preponderant as well as a displacement of said preselector handlever in the opposite direction, a displacement of said adjustment handlever in the direction to enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said second position, said second bearing member consisting of a 'cam, characterized in that the movable member of said hydraulic cylinder bears against one arm of a control lever solid with the lifting arm, said coupling system comprising a first link having one end pivoted on said second bearing member and the other end pivoted on one point of another link pivoted in turn by means of a third link on a lever armrigid with said preselector control handlever.

10. Hydraulic equipment-raising and tractive-effort control device for farming tractors of the carried equipment type, comprising a single acting raising cylinder coacting with at least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulicdistributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the reservoir feeding said source, or, furthermore, in an intermediate position of said slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are permitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort control system coacting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effort control system comprising a first pivoting bearing member so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force on said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member also adapted to act upon said slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that a tractive effort exerted on said coupling system and of a value sufficient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort which causes the effort exerted by said resilient means to become preponderant as well as a displacement of said preselector handlever in the opposite direction, a displacement of said adjustment handlever in the direction to enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said second position, characterized in that said first pivoting bearing member and said second pivoting bearing member are pivoted at their fulcrums on a common pivot pin controlling the displacement of said slide valve member of said distributor device, said preselector handlever being provided with stop means co-acting unidirectionally with said second pivoting bearing member in the direction to permit the positive displacement of said second pivoting bearing member and said slide valve member to obtain a lifting, said spring which urges said slide valve member in the opposite direction tending to keep said second pivoting bearing member in contact with said stop member, said linkage system of said preselector control comprising a member co-acting unidirectionally with said lifting arm formed with a stop against which said last-named member is urged by said spring, said stop member of said adjustment handlever being so disposed thereon that it acts as a counterbearing stop means to said first pivoting bearing member in order to adjust as a function of its position the operation of said slide valve member in the equipment-raising direction from a predetermined value of the tractive effort transmitted from the equipment.

11. Hydraulic equipment-raising device as set forth in claim 10, characterized in that said movable member of said hydraulic cylinder bears against one of the arms of a control lever solid with said lifting arm, the member which co-acts unidirectionally with said lifting arm consisting of an inter-resistant lever or a lever of the second order of which the free end is caused to engage said stop member disposed on said other arm of said control lever, while said second pivoting bearing member consists of a lever having on one side of its fulcrum an arm kept in contact with said stop member of said preselector handlever and on the other side of said fulcrum another arm connected through a link to the point of application of the resistant effort of said inter-resistant lever or lever of the second order.

12. Hydraulic equipment raising device as set forth in claim 10, characterized in that said distributor device comprises the following component element: a valve adapted to connect said source of hydraulic fluid under pressure directly to said reservoir feeding said source, said valve being controlled by a double-acting cylinder having its inner space divided by a piston into a closing chamber containing a compression spring urging said piston in the direction to close said valve, and an opening chamber connected to said source of hydraulic fluid under pressure and in which the fluid pressure urges said piston in the valve opening direction, a controlled relief valve of which a piston-forming shutter opens with one end into a cavity into which opens likewise a valve seat communicating with the discharge duct and with the opposite end into a control chamber, a distributor comprising about said slide valve member a first chamber communicating with said source of hydraulic fluid under pressure, a second chamber communicating with said equipment raising cylinder through the medium of said inlet valve, with said closing chamber of said valve and with the cavity of said relief valve, a third chamber communicating with said control chamber and with said discharge duct, said first, second and third chambers being separated by a first partition disposed between said first and second chambers and by a second partition disposed between said second and third chambers, said slide valve member comprising a valve-type shutter disposed in said second chamber and adapted to close an orifice formed in said first partition and connected through an axial rod to a pistontype shutter disposed at the level of said third chamber and adapted to close either a passage formed in said second partition or another passage leading to said discharge duct, the space left between the seat of said valve-shutter and the edge of said passage leading into said third chamber, on the one hand, and the distance between said shutters, on the other hand, being such that in its first position said slide valve member frees the passage between said three chambers and that in its second position it prevents the communication between said chambers and that in the intermediate position it frees only the passage between said first chamber to said second chamber while the duct connecting said equipment raising cylinder to said inlet valve communicates with said discharge duct through said exhaust valve the opening of which is controlled mechanically by said slide valve member when the latter is moved to its second position.

13-. Hydraulic equipment-raising device as set forth in claim 12, wherein devices for reducing the cross-sectional area are provided in the duct connecting said second chamber to said cavity of said relief valve, in the duct connecting said raising cylinder to said exhaust valve, and possibly in the duct connecting said first chamber to said source of fluid under pressure.

14. Hydraulic equipment-raising and tractive-effort control device for farming tractors of the carried equipment type, comprising a single acting raising cylinder coacting with at least one equipment lifting arm, an equipment coupling system to which said lifting arm is connected and comprising traction links, a source of hydraulic fluid under pressure, a hydraulic distributor device comprising a movable slide valve member for distributing the hydraulic fluid delivered from said source of fluid under pressure either, in a first position of said slide valve member, to said raising cylinder through an inlet valve, or, in a second position of said slide valve member toward which said valve member is urged by a spring, from said raising cylinder through an exhaust valve to a discharge duct connected to the reservoir feeding said source, or, furthermore, in an intermediate position of said slide valve member, directly to said discharge duct, it being understood that other intermediate positions and actions of said slide valve member are per mitted, a preselector control comprising a handlever for preselecting the desired position of said lifting arm and a linkage system interconnecting said preselector handlever, said slide valve member and said lifting arm, an effort control system coacting with said slide valve member and connected to said coupling system incorporating resilient means responsive to the tractive effort above a predetermined value of said effort, said effort control system comprising a first pivoting bearing member so designed and mounted that said coupling system is capable, through the medium of said bearing member, of exerting a certain force on said slide valve member in the direction of said first position thereof and of which the permissible movement in the direction of said last named force is limited by an adjustable stop provided on an adjustment handlever, said linkage system comprising a second pivoting bearing member also adapted to act upon said slide valve member while the connections between said first pivoting bearing member and said coupling system, on the one hand, and between said second pivoting bearing member, said lifting arm and said preselector handlever, on the other hand, are so designed and arranged that a tractive effort exerted on said coupling system and of a value sufficient to overcome the force of said resilient means, the displacement of said preselector handlever in one direction as well as the lowering of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said first position, and that a reduction in the tractive effort 20 enable its adjustable stop to exert a pressure on the first pivoting bearing member and an upward movement of said lifting arm be capable of causing the displacement of said slide valve member in the direction of said second position, characterized in that said coupling system is adapted to exert a force on said slide valve member through a traction rod pivoted on a crankpin of a crankshaft movable about an axis fixed on said tractor, said crankshaft being solid with a one-arm lever retained by a spring acting against the force to which it is subjected by the equipment during the work, said one-arm lever being connected through said effort control system to said first bearing member.

References Cited by the Examiner UNITED STATES PATENTS 7/1951 Newgen 91-367 2/1961 Hershman 91-367

Claims (1)

1. HYDRAULIC EQUIPMENT-RAISING AND TRACTIVE-EFFECT CONTROL DEVICE FOR FARMING TRACTORS OF THE CARRIED EQUIPMENT TYPE, COMPRISING A SINGLE-ACTING RAISING CYLINDER CO-ACTING WITH AT LEAST ONE EQUIPMENT LIFTING ARM, AN EQUIPMENT COUPLING SYSTEM TO WHICH SAID LIFTING ARM IS CONNECTED AND COMPRISING TRACTION LINKS, A SOURCE OF HYDRAULIC FLUID UNDER PRESSURE, A HYDRAULIC DISTRIBUTOR DEVICE COMPRISING A MOVABLE SLIDE VALVE MEMBER FOR DISTRIBUTING THE HYDRAULIC FLUID DELIVERED FROM SAID SOURCE OF FLUID UNDER PRESSURE EITHER, IN A FIRST POSITION OF SAID SLIDE VALVE MEMBER, TO SAID RAISING CYLINDER THROUGH AN INLET VALVE, OR, IN A SECOND POSITION OF SAID SLIDE VALVE MEMBER TOWARD WHICH SAID VALVE MEMBER IS URGED BY A SPRING, FROM SAID RAISING CYLINDER THROUGH AN EXHAUST VALVE TO A DISCHARGE DUCT CONNECTED TO THE RESERVOIR FEEDING SAID SOURCE, OR, FURTHERMORE, IN AN INTERMEDIATE POSITION OF SAID SLIDE VALVE MEMBER, DIRECTLY TO SAID DISCHARGE DUCT, IT BEING UNDERSTOOD THAT OTHER INTERMEDIATE POSITIONS AND ACTIONS OF SAID SLIDE VALVE MEMBER ARE PERMITTED, A PRESELECTOR CONTROL COMPRISING A HANDLEVER FOR PRESELECTING THE DESIRED POSITION OF SAID LIFTING ARM AND A LINKAGE SYSTEM INTERCONNECTING SAID PRESELECTOR HANDLEVER, SAID SLIDE VALVE MEMBER AND SAID LIFTING ARM, AN EFFORT CONTROL SYSTEM CO-ACTING WITH SAID SLIDE VALVE MEMBER AND CONNECTED TO SAID COUPLING SYSTEM INCORPORATING RESILIENT MEANS RESPONSIVE TO THE TRACTIVE EFFORT ABOVE A PREDETERMINED VALUE OF SAID EFFORT, SAID EFFORT CONTROL SYSTEM COMPRISING A FIRST PIVOTING BEARING MEMBER ABUTTINGLY ENGAGED WITH SAID SLIDE VALVE MEMBER AND SO DESIGNED AND MOUNTED THAT SAID COUPLING SYSTEM IS CAPABLE, THROUGH THE MEDIUM OF SAID BEARING MEMBER, OF EXERTING A CERTAIN FORCE ON SAID SLIDE VALVE MEMBER IN THE DIRECTION OF SAID FIRST POSITION THEREOF AND OF WHICH THE PERMISSIBLE MOVEMENT IN THE DIRECTION OF SAID LAST-NAMED FORCE IS LIMITED BY AN ADJUSTABLE STOP PROVIDED ON AN ADJUSTMENT HANDLEVER, SAID LINKAGE SYSTEM COMPRISING A SECOND PIVOTING BEARING MEMBER ABUTTINGLY ENGAGED WITH SAID SLIDE VALVE MEMBER AND ALSO ADAPTED TO ACT UPON SAID SLIDE VALVE MEMBER WHILE THE CONNECTIONS BETWEEN SAID FIRST PIVOTING BEARING MEMBER AND SAID COUPLING SYSTEM, ON THE ONE HAND, AND BETWEEN SAID SECOND PIVOTING BEARING MEMBER, SAID LIFTING ARM AND SAID PRESELECTOR HANDLEVER, ON THE OTHER HAND, ARE SO DESIGNED AND ARRANGED THAT A TRACTIVE EFFORT EXERTED ON SAID COUPLING SYSTEM AND OF A VALUE SUFFICIENT TO OVERCOME THE FORCE OF SAID RESILIENT MEANS, THE DISPLACEMENT OF SAID PRESELECTOR HANDLEVER IN ONE DIRECTION AS WELL AS THE LOWERING OF SAID LIFTING ARM BE CAPABLE OF CAUSING THE DISPLACEMENT OF SAID SLIDE VALVE MEMBER IN THE DIRECTION OF SAID FIRST POSITION, AND THAT A REDUCTION IN THE TRACTIVE EFFORT WHICH CAUSES THE EFFORT EXERTED BY SAID RESILIENT MEANS TO BECOME PREPONDERANT AS WELL AS A DISPLACEMENT OF SAID PRESELECTOR HANDLEVER IN THE OPPOSITE DIRECTION, A DISPLACEMENT OF SAID ADJUSTMENT HANDLEVER IN THE DIRECTION TO ENABLE ITS ADJUSTABLE STOP TO EXERT A PRESSURE ON THE FIRST PIVOTING BEARING MEMBER AND AN UPWARD MOVEMENT OF SAID LIFTING ARM BE CAPABLE OF CAUSING THE DISPLACEMENT OF SAID SLIDE VALVE MEMBER IN THE DIRECTION OF SAID SECOND POSITION.

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