NO116714B - - Google Patents

Description

Control system for tractors.

This invention relates to tractors

of the type having a power lift connected to a linkage system by means of which any of a number of agricultural implements and other types of apparatus can be connected to and carried by the tractor.

For tractors of the specified type, the power lifter is put into operation and adjusted under the control of the tractor driver. In addition, the power lifter, during operation with a tillage implement, is under the control of automatic devices which are mainly concerned with maintaining a practically uniform working depth.

In the following description, different expressions will be used which will now be explained, namely: "Drag regulation". It is a method of regulating the working depth, well known from considerable use in connection with Ferguson tractors, according to which the pull in the longitudinal axis which the soil reaction against the work of the implement transmits through the coupling joint system of the tractor, is kept constant by automatic devices. If the draft is constant, the working depth will be practically constant as long as the soil structure is uniform. It is important to note that when traction regulation takes place over undulating ground, the tractor and implement rise and fall, each relative to the other, as there is a pivoting connection between each of them and the linkage system. "Controller". The connecting link system includes a link, which is a single top link through which a control force is transferred from the tool to a control valve in a hydraulic system that includes the power lifter.

"Control spring". The tractor, which has an automatic traction control device, uses a powerful spring as an intermediate link to counteract and balance the force transmitted through the control link.

"Position control". This is a previously proposed way of regulating or controlling power lifters' height. With this regulation method, the driver raises or lowers a control weight arm which is connected to the regulation valve and the power lifter follows and comes to rest in a position - which, with regard to level or height - corresponds exactly to the position of the weight arm. This involves two mutually opposing effects: firstly, the control valve at the driver-actuated weight arm is moved in one direction or another from a closed setting to raise or lower the power lifter, and secondly, the power lifter itself acts on the valve to move it back to its closed setting in which the power lifter is hydraulically locked. This method of regulation is thus also known to include a "subsequent" effect. It is important to note that during position control while the control weight arm is stationary, an implement or device, which is connected to the tractor, is held down rigidly with the tractor, i.e. no downward rotation can occur as during "traction control". When it comes to a tillage implement under position control, the working depth can thus be constant without the surface being level, as it will be seen that if the tractor "rocks", i.e. tilts in the longitudinal direction

over waves or elevations, the implement will be raised and lowered in relation to the surface of the substrate.

It will be obvious that position control is well suited for implements or devices that are carried or carried above the earth's surface.

"Transport position". When a tractor must carry a tillage implement, e.g. from the farm and out. in the field, the power lifter is brought to its top position, which is called the "transport position".

The present invention is a control system for tractors of the specified type, including a steering part influenced by the driver, device movable by this steering part, to start the movement of the power lifter towards a position corresponding to the position in which the steering part is moved, devices that react for tensile load on the connecting link system for taking control of the power lifter and effecting corrective movements thereof in a direction to restore a predetermined value of the tensile load, another driver-actuated control part and means operable by this other control part to set the value of the tensile load at which the device reacting to the tensile load takes over control. The tractor is running, one can thus set the aforementioned second steering part in a position that corresponds to a tensile load that will be produced by the implement when it works at a desired depth in the soil, and by lowering the first mentioned steering part, he will cause the implement to be lowered to the selected depth, which follows from the fact that the devices that react to tensile load will automatically take over control and keep the implement practically at this depth.

In the control system, the articulated system is lowered by draining hydraulic fluid from the power lifter through an outflow passage, and a device that can be influenced by the driver may be arranged to vary the outflow rate through the passage to regulate the sensitivity of the device that reacts to the traction load, namely the traction regulating device.

The control system includes a valve to regulate the action of the power lifter, the traction control device being adapted to automatically move this control valve during changes in the traction load caused by an implement connected to the tractor. The arrangement can be such that the valve is moved, under normal load increase, to a position in which hydraulic fluid admitted through a supply passage is pumped to the power lifter, and also such that the valve is automatically advanced under a predetermined increased draft overload to empty the hydraulic fluid out through the same passage.

The control system may include a control valve comprising a control valve housing, two rings arranged axially in line with each other in the housing to define opposite ends of a hydraulic chamber, a third ring placed in the housing substantially axially in line with said two rings and separated from a of them to define the opposite end of another hydraulic chamber, one of the rings being supported to be susceptible of limited trans-axial movement, and a valve piston slidably axially through the rings and having passages which can be aligned with the said chambers for the flow of hydraulic fluid to and from them.

The invention shall be described as an example with reference to the drawings, where fig. 1 is a side view of a tractor with an implement connected thereto, fig. 2 is a longitudinal section of the tractor housing, fig. 3 is a section along the line 3-3 in fig. 2, fig. 4 is part of a section of the tractor housing in a transverse vertical plane, fig. 5 is a section of the position control device along the lines 5-5 in fig. 4, fig. 6 is a view corresponding to fig. 5 with the parts in transport position, fig. 7 is a section of the traction control device along the line 7-7 in fig. 4, fig. 7a and 7b are perspective views of two elements of this control system, fig. 8 is a longitudinal section of the control valve, fig. 9 is a section along the line 9—9 in fig. 8 which shows the pump in the tractor's hydraulic system, fig. 10 is a view corresponding to fig. 5 and 6, but showing the position control device in a different position, fig. 11 is a section of the valve in the overloaded release position, fig. 12 is part of a plan of the connection between the control link of the connecting link system and the tractor, fig.

13 is part of a plan of the dumbbell arms

which form elements of the position and traction control devices, and fig. 14, 15 and 16 are drawings illustrating different states of the regulating spring assembly.

In fig. 1 and 2, the tractor on which the control system according to the invention is arranged is a "Ferguson" tractor. The tractor includes the usual middle housing 12 which contains the engine-driven transmission shaft 13 which drives the rear axles 14. The tractor has the usual rear three-link connection system, consisting of two lower draw links 15 and a single upper link 16 which is the system's control link. A plow 17 is shown as a typical tillage implement coupled to the tractor. The ends of a transverse crankshaft 18 on the plow axle are rotatably connected to the rear ends of the draw links 15. An upright frame 19 on the plow axle has a rotatable connection with the control link 16.

The traction links 15 are rotatably connected to the housing 12 at 20. The control link is rotatably connected to a control piston 22 by a pivot pin 21. This forms an effective connection between the link 16 and the tractor's traction control device. The rotatable connection at 21 has a suspended support consisting of a rocker 25 which is rotatably connected by a short pin 24 between two claws 26b on a rear extension 26a of a cover plate 26 on the housing 12. The rocker 25 is U-shaped, which best seen in fig. 12, and also has two hanging legs 25a, one on each side of the joint 16, and these are by bushings (not shown), rotatably connected to a crosshead 27 with a screw-threaded part 27a in which the piston is fixed in a set position by a locking pin 22a . At the front end of the piston there is a head 22b with a flange 22c which is slidable in a cup 28. The control link 16 can be easily connected to and released from the rocker 25 and the crosshead 27 by the pin 21 which is passed through the link and the aforementioned bushings . When connected, the front end of the joint is simply dropped into the opening between the legs 25a, and the pin 21 is inserted through the aligned holes in the rocker, crosshead and joint. Disconnecting is just as easy and is done simply by pulling out the pin and lifting the link 16. The feature that the link can be lowered into or lifted out of position simplifies connecting and disconnecting the tool.

The tension control control spring is indicated at 29. This is a strong coil spring that surrounds the piston 22. The spring rests with its front end against a lip on the cup 28, which lip can rest against the flange 22c. A collar 30 which is threaded into the cover extension 26a is adapted to act as a seat for the rear end of the spring. The cup 28 is slidable in a bore 31 in the cover 26. A plate 31a which comes against an annular shoulder at the front end of the bore 31 serves as a closure for the extension 26a in which the regulating spring is placed. The rear end of this extension is closed by a cup-shaped flexible rubber sealing ring 32 between the collar 30 and the crosshead 27.

The hydraulic power lifter comprises the usual pressure piston whose cylinder 36 is attached to the cover plate 26 and the piston 37 (fig. 6) has a rod 38 placed on an arm 39 on a rocker shaft 40. Opposite ends of this shaft have crank arms 41 from which hangs a drop link 42 which is connected to the draw links 15. When hydraulic pressure - liquid (e.g. oil) is supplied to the cylinder 36, the piston 37 is driven backwards to tilt the arms 41 upwards and thereby lift the draw links 15. When liquid is drained from the cylinder, the piston is drawn 37 back into the cylinder under the weight of the joints 15 and the tool carried by them so that the joints swing downwards.

The oil is supplied from a pump 45 (fig. 2, 8 and 9). The lower part of the housing 26 contains the oil and forms a sump for the hydraulic system. Oil enters the pump through an intake channel 47 (fig. 8) and flows out of the pump through a line 48 leading to the cylinder 36. A spring-loaded safety valve 45 a (fig. 2) relieves the pump if excessive pressure is reached. The pump is driven from the tractor's engine through a shaft 46 independently of the general drive box by which the transmission shaft 13 is driven.

The hydraulic power lifter control valve is indicated by V and is best shown in fig. 8. The valve is placed near the bottom of the housing 26. The valve is arranged to avoid

that it is tied or fixed in such a way that one

a highly reliable effect will be ensured under even the most difficult field conditions.

The valve itself comprises an axially sliding piston 55. That is. tubular with an internal dividing wall through which an axial opening with a square cross-section passes. The piston can be machined from a bar blank and suitably hardened. The piston can be machined from a bar blank and suitably hardened. The piston is slidable through bearings formed as hardened, matched steel rings 63, 65, which define the opposite ends of a high pressure chamber 62. A third bearing is formed by a ring 64 which cooperates with the center ring 63 to define the opposite ends of a low pressure intake chamber 61. However, this third ring 64 is free

to flow transaxially inside an outer ring

68. The nose of the piston 55 which adjoins

the ring 64 is conical so that it can freely enter the ring and thereby centers it. As a result, exact concentricity in assembly is only required for the two rings 63, 65 and not for all three rings, which would be difficult.

As shown, by using rings as bearings that close the opposite ends of the chambers, the propensity of the valve piston 55 to stick is reduced. The contact areas of the ring with the piston are axially short and can be formed with greater accuracy (with a tolerance of a few hundredths of a millimeter) than a relatively long sleeve drilled to fit the piston.

Spacer sleeves 66, 67 are inserted between rings 64, 63 and 63, 65 respectively. As they are completely out of contact with the piston 55, the bores in these sleeves do not have to be exact with respect to size or straightness. The sleeve 66 has large openings 71 for the free passage of oil from the chamber 61 to the annular space that surrounds the sleeve and from there into the pump's intake channel 47. In a similar way, the other sleeve 67 has large openings 72 for the unimpeded flow of oil into the high-pressure chamber 62 from the pump's outflow passage 49. This passage runs through the pump housing and is connected to the line 48.

The rings 63, 64, 65 with their intermediate spacer sleeves 66, 67 are held together in a bore in the pump housing by a cover plate 69 which is bolted to this. Sealing at the ends of the high-pressure chamber 62 is ensured by elastic rings 70 which are inserted between the flanged ends of the sleeve 67 and the adjacent sides of the steel rings 63, 65. The assembly is pressed by the cover plate 69 against a shoulder 60 at the inner end of the bore.

In the neutral position of the valve piston 55, unbroken parts of its surface extend between the two rings 63, 65 and the two rings 63, 64. That is. that in the neutral position the control valve is closed, and as a result both the entry of oil into the intake chamber 61 and the outflow of oil from the high-pressure chamber 62 are prevented. Consequently, the oil is locked in the system and thus also the pressure piston 37 remains stationary.

When the piston 55 is shifted axially backwards (towards the left in Fig. 8) from the neutral position, a gradual uncovering of the outflow channels formed as two narrow, axial slits 74 takes place. When these slits continue to pass under the ring 65, a gradually increasing slit area is opened from the high-pressure chamber 62. As soon as these slots begin to open, high-pressure oil accordingly flows through them from the chamber 62 by means of the interior of the piston and a passage 58a in the pump housing into the sump. Such an outflow of oil from the system allows the pressure piston 37 to retract into the cylinder 36, the tension links 15 thereby being lowered.

The rate at which the joints are lowered depends on the rate at which oil can flow to the sump. By using long narrow slots 74, the speed can be regulated with accuracy.

Another pair of adjacent slits 75, shorter and wider than the slits 74, are also

arranged in the piston 55. When the piston is moved so far back that these slots 75 also begin to open, the speed of the oil outflow suddenly increases. Rapid descent • of the links 15 and the tool carried by it is ensured. By providing precisely controlled lowering and rapid descent, the control mechanism fits well with the requirements of the various implements which will be explained later. The slots 74, 75 can be called "fall gates", as it can be seen that the valve piston opens them to cause the draw links 15 to lower.

A stop collar 76 (placed in a circumferential groove in the middle part of the piston) limits, by abutting against the central ring 63, the backward movement of the piston. This limit position is one in which the piston is still guided in the precisely fitted front ring 65. Similarly, the stop collar 76 abuts against the ring 65 to limit the travel of the piston in the forward direction. In this forward limit position (see fig.

11) the piston has left the ring 64 but can

easily again fed into this ring because it can be moved across the axis.

As the piston is moved forward from its neutral position, the high pressure chamber 62 remains closed. Access channels shaped as a pair of very wide slits 73 at the rear end of the piston pass under the ring 64 and open the oil intake to the pump. When these slits 73 are uncovered, oil from the sump passes through them into the chamber 61 from where the oil continues through the large ports 71 to the intake passage 47. This oil is delivered by the pump under hydraulic pressure to the cylinder 36 so that the draw links 15 are lifted.

In the example, the valve piston is driven springily back towards its "fall" position by a compression spring 77 which acts between a fixed device and a head 78 on a push rod 79 which is connected to the piston. The connection is provided by a head 80 with a truncated pyramidal shape which fits in the square passage in the middle partition wall 56 of the piston.

In order to displace the valve piston 55 against the pressure of the spring 77, a push rod 81 with a hemispherical head 82 is arranged which engages in a conical holder 83 at the rear end of the dividing wall 56. The push rod 81 is rotatably connected by a pin 84 to the lower end of a valve rocker arm 85 which acts as the control valve actuator portion of the control mechanism. The weight arm 85 is rotatable at 86 on a support part 87, which in the example shown is a rod which extends backwards from the pump body. A nut 88 on the rod serves to set the pivot point in the longitudinal direction.

Provision is made for continuous oscillation of the valve piston 55 about its longitudinal axis to ensure smooth and easy sliding. The spring 77 is arranged in a housing in the form of a cylinder 89 which occupies the square head 78 (fig. 9) of the push rod 79. Four grooves in the cylinder occupy the corners of the head 78 so that it can slide freely in the longitudinal direction of the cylinder but is nevertheless forced to swing the cylinder about its axis. Limited clearance remains between the edges of the head 78 and the cylinder through which oil can flow to produce a vibration dampening effect on the piston, i.e. the movement of the piston is dampened. The head 80 provides a rotating drive connection whereby the valve piston 55 is pivoted with the push rod when the cylinder is pivoted. A spring 90 in the cylinder forms a stop for the spring 77. Another spring 90a at the rear end of the cylinder prevents the square head 78 from leaving the cylinder during assembly of the parts.

As shown in fig. 8 and 9, the cylinder 89 is rotatably supported at one end in a recess 91 in the pump body concentric with the valve bore 57. At its other end, the cylinder is similarly rotatably supported in a bore 92 in a hub 93 which may be part of the pump body or a part of a carrier that is rigidly attached to the same. A spring 94 in the bore 92 absorbs the reaction of the cylinder 89 to the pressure of the spring 77. Between the ring 94 and the end of the cylinder a disk 94a is inserted. This disc closes the cylinder end so that it can act as a hydraulic shock absorber as mentioned above.

The cylinder 89 and the parts connected thereto are swung or oscillated in controlled relationship with the pump by means of an arm 95 which has an extended end which encloses the cylinder and is attached to it by a locking screw 96. At its other end, the arm 95 rotatably connected with a connecting rod 97 which has • a ring portion that encloses an eccentric 98 on the pump shaft 99. When the pump shaft is turned, the eccentric acts through the connecting rod to swing the arm 95 and the cylinder 89, and such oscillations are transmitted by the push rod 79 to valve piston 55.

It will be seen in fig. 8 that the valve piston 55 has a not insignificant length. A factor contributing to this is the necessity to remove the bearing rings 63' and 64 far apart to provide a so-called "overload release effect", to be described below, which induces or requires travel of the opening 73 forward past the intermediate ring 63, and this long travel requires a corresponding length between the rings 63 and 65 for the stopper 76. This length between the rings 63 also includes a part which. allows travel for features none of the long narrow slots 74. It is because of the appreciably long length of the piston that one of the three rings, namely the ring 64, can move freely across the axis.

The hydraulic pump used in the example is shown in fig. 9, but as the construction of the pump does not form any part of the invention, it will not be described here.

The control system's position control device includes as part of its driver-influenced device a main steering part, formed as a hand weight arm 100 (fig. 4 and 5) which can be called a quadrant weight arm. This weight arm is fixed on a shaft 101 stored in a hollow support arm 102 (fig. 4) which is anchored in a recess in the cover plate 26 by a locking screw 103. A slotted sheet metal quadrant 104 serves as a guide for the weight arm 100. Bolts 105a and 105b are provided as presettable stops at the ends of the quadrant slot. A stopper with a rifled. knob 105 can be adjusted along the slot. The position control device includes as its "follower" device a cam 120 which is attached to the rocker shaft 40 and is therefore always positioned in exact accordance with the power lifter's moving parts 37-42. It will be seen that it is at parts 100 and 120 that the hydraulic control valve V is operated under the "position control" conditions.

The control system's draft regulation device includes, as part of its control-driven device, a control part which can be called a "deep still" which is indicated generally 141. This includes an additional hand weight arm 141b (Fig. 7A) which is attached to a rotatable shaft 140 stored in the arm 102. best shown in fig. 7 is an additional quadrant 142 slotted at 144, arranged next to the main quadrant 104. The still 141 is controlled by the quadrant 142. The still includes a finger piece 141a (Fig. 7B). The finger piece is integrally formed with an inverted T-shaped slide 141c with two spaced ears 141d and is guided by the slot 144. A bolt with a knurled nut 141 engages the slide and extends through the slot 144. The nut 143 can be set to fixing the slide 141c in any selected position to which it is guided by its finger piece 141a. A bolt 141f maintains a frictional relationship between the quadrant 142, the slide 141c and the weight arm 141b. This bolt 141f passes through the following parts, namely: the slot 144, an arcuate slot 141g in the slide 141c, suitable friction discs 141h, a hole 141j in the weight arm 141b and a coil spring (not shown). To use the depth adjuster, the operator loosens knob 143, grasps finger piece 141a and weight arm 141b and pushes them to a position corresponding to the working depth he requires for the implement. The knob 143 is then fixed again. Should he wish to make some short-term adjustments in the field, he grabs the weight arm 141b alone, and pushes it up or down as needed (see fig. 14). To then bring the weight arm to its previous setting he has only to bring it back into line with the finger piece 141a.

The draft regulation device includes as a part that can be moved by the connection joint system a push rod 131. This is movable in association with the regulation piston 22 as it is controlled through the extension 26a and the closing plate 31a. It will be noted that it is at parts 141b and 131 that the hydraulic control valve V is operated under the conditions of "draft control".

Considering the mechanical connection between the valve V and its manual and mechanical drive sources, it is expedient to first describe the connection from the quadrant weight arm 100 and the follower cam 120 by which the position control is carried out.

The main weight arm's shaft 101 (see fig. 4, 5 and 6) has a radially projecting arm 106 with an eccentric roller 107. This is placed between two jaws 108 and 109 formed at the end of a cam weight arm 110 which at 111 is rotatably connected to the upper end of an intermediate valve-acting weight arm 112 which is the end part of the position-controlling device. The bent-down front end of the weight arm 110 is crouched over an eccentric 122 fixed in a set position on the weight arm 112 by a locking nut 122a. The weight arm 112 is rotatable on a normally stationary pivot 113 and has its lower end positioned in the path of a roller 114 on the upper end of the valve-operating weight arm 85. The weight arm 112 is guided in a slot 111' (see also Fig. 3) formed in a rib 112 which forms part of a support member 113' connected to and hanging down from one side of the pressure cylinder 36. The action of the spring 77 which drives the valve piston 55 backwards, namely in a direction to swing the weight arm 85 clockwise as seen in the drawing, seeks to tilt the weight arm 112 clockwise and thereby exert a backward force on the cam weight arm 110. The lower edge of the cam weight arm crank 108 has an inclined cam surface 115 adapted to cooperate with a roller 116 carried by a rocker 117. This is mounted to rotate on a pivot shaft 118 which is supported in and extends transversely across the upper part of the cover 26. Another roller 119 on the rocker 117 removed rearward from the roller 116 acts as a cam roller on the follower cam 120. This is shaped like that d one swings the rocker forward when the coupling links are lowered and allows the rocker to swing backwards when the links are raised.

Assuming that the joints 15 are initially in a lowered position, then the cam 120 will hold the rocker 117 forward, fig. 5. Movement of the main weight arm 100 to its upper position, as shown in fig. 6, the cam weight arm 110 swings in a counter-clockwise direction. The cam 115, which is guided on the roller 116, will move the cam weight arm 110 forward. The weight arm 112 will be turned clockwise and the valve weight arm 85 counter-clockwise, and the valve piston 55 will be moved forward to the "lift" position. The hydraulic power lifter will consequently lift the draw links 15. When the links 15 rise, the cam 120 is turned at the same time and thereby the rocker 117 and the cam weight arm 110 will be moved back. As a result, the valve piston is returned to its neutral position by its spring 77. The valve will reach its neutral position when the pull links reach their upper position, namely the "transport position".

To lower the draw links, the driver leads the weight arm 100 downwards from the one in fig. 6 shown position. This lifts the rear end of the cam weight arm 110 and allows the cam 115 to slide rearward on the roller 116. Such rearward transfer of the cam weight arm and the consequent tilting of the weight arms 112 and 85 allows the valve piston 55 to be moved rearward to the "fall" position. Oil is thus led out of the pressure cylinder 36 and allows the draw links to lower. When the links are lowered, the cam 120 returns the cam weight arm and associated parts, including the valve piston 55, slightly towards the neutral position. If one now ignores the effects of the earth reaction on the tool if it goes into the earth, the neutral position will be reached and the oil outflow stopped (thereby the oil inside the pressure cylinder 36 is closed) at the moment when the draw links come into a position corresponding to the position to which the control weight arm 100 has been moved. Full lowering is provided when the weight arm 100 is approximated in the one in fig. 5 Displayed position. It will thus be seen that the links 15 can be raised and lowered by swinging the control weight arm 100 through the upper part of its range. The joints precisely follow the movements of the weight arm 100 and come to rest in a position corresponding to the position of the weight arm 100 so that the driver can stop the joints at any desired position and they will automatically be held in this position. When it is seen that the movement of the links 15 returns the valve to the neutral position, it follows that the driver can regulate the speed of lifting and falling. If he moves the weight arm 100 slowly, the valve will not be moved far from the neutral position and the speed of movement will thus be slow. If the driver moves the handle 100 quickly down from the one in fig. 6 to that in fig. 5 shown position, the opening 75 for rapid fall will come into operation to provide a rapid fall.

It will be noted that the mechanical connection between the follower cam 120 and the valve piston 55 acts as a joint system whose length is variable by adjusting the cam 115 in relation to the roller 116. This relationship between the cam and the roller affects subsequent action on the valve by the cam 120. During the action, the driver-maneuvered control part 100 is a device for setting the length of the joint system between the automatically driven cam 120 and the valve V.

The connections from the extra weight arm 141 and the push rod 131 by which the tension regulation is carried out will now be described with reference mainly to fig. 2 and 7. As shown, the draft control device includes a rocker 130 mounted for pivoting on the pivot shaft 118 at one side of the rocker 117. The push rod 131 is rotatably connected to the rocker 130 by a pin 132. The forward movement of the push rod 131 under the action of the tensile load on the control link 16 therefore swings the wiper forward.

On the pin 132 of the rocker 130 is stored a cam roller 133, adapted to be guided over a cam 134 on a weight arm 135. This cam weight arm is rotatably connected at its front end, at 135a, to the upper end of a weight arm 136 which between its ends is rotatable on a normally stationary pivot pin 145a. The weight arm 136 is arranged along the side of the position control weight arm 112 and has its lower end guided in the slot 111', the end extending through this slot and cooperating with the roller 14 on the weight arm 85 which drives the valve. The spring action on the weight arm 85 (at the valve spring 77) drives the weight arm 136 counter-clockwise and thus drives the cam weight arm 135 backwards.

The cam weight arm 135 has a backward-protruding finger 137 which, on the underside, forms a cam 138 arranged above and placed at an angle with the cam 134. With the upper cam 138, an eccentric roller 139 cooperates which is carried by an arm on the shaft 140 for the depth adjuster 141. Turning of the shaft 140 at the depth adjuster 141 will vary the position of the cam 134 in relation to the roller 133. As a result, the position in which the weight arm 136 will catch the valve weight arm 85 can be varied as desired by setting the depth adjuster 141 to swing the cam weight arm 135 on its pivot. This setting thus determines the inwardly offset position of the control rod 131 required to return the control valve piston 55 to the neutral position or, in other words, the tensile load to be maintained by the implement.

It will be noted that the mechanical connection between the regulating piston 22 and the valve piston 55 is in effect a joint system whose length is variable by setting the cam 134 in relation to the roller 133. This relationship between the cam and the roller affects subsequent action on the valve by the regulating piston 22. I in its effect, the control part 141 operated by the driver is a device for setting the length of the joint system between the automatically driven regulating piston 22 and the valve V.

Provision has been made to protect the control system from damage in the event that the main weight arm 100 is violently lifted faster than the pressure piston 36, 37 can cause the connecting link system and the connected tool to follow. To this end, the pivot extension 113, on which the weight arm 112 is rotatable, is carried by a slidably supported rod 125 which is carried by separate flanges

126 on the carrier part 113'. A compression spring 127 interposed between a flange and the extension holds the rod and its pivot spring back in the FIG. 5 shown position. If the weight arm 100 is lifted too quickly, the spring allows forward movement of the rod for what is called an "interruption". When the pressure cylinder lifts the tension links 15, the rod 125 is gradually returned to its normal position. In a similar way, the pivot pin 145a is arranged on a rod 145 which is slidably supported by the flanges 126. A compression spring 146 drives the rod to the one in fig. 5 shown position, but allows it to move forward when necessary, namely by violent forward pressure applied to the weight arm 135, the rod returns to its normal position when the pressure is released.

Different implements have different effects on the draft regulation device. For example if the draft regulation device . is sensitive enough to react correctly to. a light cultivator, it will overregulate so badly for a heavy plow that it causes irregular and poor work. Conversely, if the draft regulation device is suitable for a heavy tool, a light one will practically not be able to produce any regulation effect. Heavy-weight implements with a light pull and lightweight implements with a heavy pull extend the problem. The problem also becomes more acute with larger tractors, because with them an increasingly large range of implement sizes can be used.

These problems are solved in the present system by inserting a positive stop to adjustably limit displacement of the valve V in the "fall" direction and to regulate the rate at which oil can be emptied from the pressure cylinder 36.

As previously explained, the main weight arm 100 is brought down to the position in fig. 5 for full lowering of the connecting links 15. When pushed further down, the weight arm 100 serves to progressively reduce the "fall" movement allowed to the valve piston. If the driver therefore finds that a heavy towing implement is over-regulated, he pushes the weight-. arm 100 a little further down until the irregular effect ceases. He then adjusts the knob 105 so that he can easily bring the weight arm back to this optimal setting if he had to lift the weight arm again.

The effect that occurs is the following: when the main weight arm 100 is moved downwards from the position in fig. 5, it will lift the cam surface 115 from the path of the roller 116 and thereby break the connection between the cam 120 and the valve driving joint system. The hook-like element 121 will engage against the adjustable eccentric 122 on the weight arm 122 when the cam weight arm 110 swings past it in fig. 5 shown position. After this engagement, the weight arms 110 and 112 form a rigid unit and they will rotate together about the pivot point 113 in a clockwise direction during any subsequent downward movement of the weight arm 100. Such movement sets the lower end of the weight arm 112 backwards so that it now serves as a stop which limits the movement of the valve piston towards the full "fall" position. Maximum restriction of oil outflow through the control valve V is consequently obtained when the weight arm 100 is brought to its lowest position and thereby blocks the movement of the valve piston 55 past a position in which only small portions of the slots 74 are exposed to the valve's pressure chamber 62. Minimal restriction of the outflow can be obtained only when the parts 121 and 122 come into contact (as in Fig. 5) for

in this position the valve piston 55 can be moved

backwards to its full outflow position.

For any implement, the driver can thus change the outflow speed through the outflow passage.

For a heavy plough, the weight arm 100 is set low so that at most only a small portion of the narrow slots 74 can be exposed when the traction control device requires a corrective lowering of the implement. Because of this, even if the implement is very heavy and oil is driven out under high pressure, the draft control device will not over-regulate, i.e. will not allow the implement to dig in too deeply before the corrective lowering can be stopped. With a lighter tool, the weight arm 100 is adjusted to allow a greater travel of the valve piston 55 so that more of the length of the slits 74 can be uncovered, if desired some of the area of the slits 75 can also be uncovered. For that reason, even if the lighter tool exerts less pressure per unit on the oil in the system (and therefore will not cause oil to be expelled during "fall" at the same rate through an equal channel area as the heavier tool) the expansion of the available drop opening area is compensated. The volumetric rate at which oil is emptied for "fall" can thus be made practically the same for all implements regardless of their weight and the earth's downward "suction" on them.

With regard to raising an implement under draft regulation by means of the hydraulic power lifter, the system's response appears to be practically uniform despite changes in the load on the draft links 15. The pump's delivery rate for a given opening of the inlet slots 73 is practically unaffected by changes in oil pressure caused by differences in the tool's weight. Therefore, there is no reason to have an adjustable limitation of the valve's travel in the "lift" direction.

With reference to the control spring 29 and the push rod 131 with which it is connected, the valve spring 77 acts through the system of weight arms 85, 136 and 135 to drive the push rod backwards into contact with the control piston head 22b as shown in fig. 2 and 8. Accordingly, when the piston 22 is moved forwards or backwards, under load supplied from the connecting joint system, the push rod 131 will follow its movement and transfer it to the rocker 130 for the already described purpose.

The control mechanism is arranged to be suitable for a large range of implements including implements overhanging backwards, the pull of which is insufficient to balance the overhanging weight, and therefore a known per se "double-acting" spring is used. That is when a heavy, backward-hanging, easily pulled implement is used, the control link 16 will be under tension so that the rocker 25 seeks to swing backwards and pull the piston 22 and the cap 28 backwards so that the spring 29 is pressed together between the cup 28 and the collar 30, as shown in fig. 14. However, when a tool is used which exerts a tensile load greater than its overhanging weight on the joint system, compression is applied to the joint 16, the rocker 25 seeks to swing forward and also push the piston 22 forward so that the spring 29 is compressed between the head 27a and the rear end of the cup 28 (since the latter now abuts the plate 31a) as shown in fig. 15.

When mounting the spring mechanism, the cup 28 and the spring 29 are slid onto the piston 22. The collar 30 is pulled onto the crosshead. The piston is then screwed into the head 27a and is tightened just enough to eliminate end play. When it has been tightened in this way, the locking pin 22a is introduced. The assembled parts are then fed into the housing 26a and the collar 30 is screwed into place just enough to eliminate end play. A set screw (not shown) is screwed in to lock the collar 30. During the screwing of the collar 30, the weight arm 141 for depth adjustment takes its lowest position in which the push rod is free from the action of the valve spring 77.

Provision has been made for a so-called "overload release", i.e. for immediate release of the pressure in the hydraulic system whenever a stone, tree root or other obstacle is caught by the tool. By releasing the pressure in this way, the implement's support at the pressure pistons 36, 37 is retracted and consequently the load imposed on the tractor is now no longer effective. Such a sudden release of weight allows the tractor's rear wheels to spin so that traction and the possibility of destruction is reduced.

The present overload release device is designed to release the pressure in the hydraulic system whenever there is a predetermined increase in draft, e.g. 906 kg, above the value for which the traction control weight arm 141 is set.

In fig. 11 it will be seen that when the valve piston 55 is brought through its "lift" position to the front limit, the wide slots 73, which ordinarily act as intake ports, are now past the middle ring 63 and open into the high pressure chamber 62. Consequently, in this position the oil in the pressure cylinder 36 is drained out through the slots 73 to the sump. That is the pressure cylinder is released from hydraulic pressure and by the effect of the width of the slots 73 immediate overload release is provided.

It will be obvious that if the tensile load on the control link 16, the piston 22 and the spring 29 is exceeded by any predetermined increase in the setting of the depth setting weight arm 141, such a movement of the valve piston 55 will occur. Change in the position of the weight arm 141 changes the extent of the displacement of the rod 131 - which is necessary to displace the piston 55 to the neutral position, and from now on varies the draft or depth at which the implement will work. However, when it is seen that during operation the valve is normally in the neutral position, regardless of whether the system is set for light or heavy draft, it will be understood that a predetermined excess of valve movement or excess of load will trigger the release device in case of overload.

Furthermore, the overload protection is always available even if the system is working under position control at the time. For example if the position control weight arm 100 is set so high relative to the depth setting weight arm 141 that no draft control action occurs, if an obstacle meets the implement, the resulting oscillation of the draft control weight arm 136

(fig. 7) clockwise drive the valve-acting weight arm 85 from the position-controlling weight arm 112 and bring the valve V to the overload relieving position according to fig. 11.

Fig. 3 shows that the slot for the traction control weight arm 136 is made longer than the slot for the position control weight arm 112 in order to accommodate it in case of overload releasing movement. The slot for the weight arm 112 is the shortest and this weight arm cannot move the valve piston 55 to the position that releases in case of overload, so the danger of it doing this is avoided when the main weight arm 100 is swung upwards faster than the system can keep up with. Under such conditions, the spring 127 will allow the pivot pin 113 of the weight arm 112 to move

forward during the breakout effect described above.

It will be clear that due to the overload-releasing effect, the regulating spring 29 will be much more compressed than necessary to keep the valve V in the neutral position. For example the spring can be compressed to an extent that corresponds to an overload of approx. 900 kg. This contraction is transferred to the valve piston part 55 and hence the previously mentioned necessity for a long piston and widely spaced bearing rings 63 and 64.

The following procedure can be followed for mounting and initial setting of the position and traction control device.

With respect to the position control device, the first step is to set the weight arm 100 at the end of its lowering range, fig. 5. The hydraulic power lifting arm 41 is placed in a similar manner in its fully lowered position. Then the nut 125a (Fig. 6) is set on the rod 125 just clear of the right end of the slot 111' against a force equal to that applied to it by the valve spring 77, which is a force that can be easily measured, especially since the ratio of the weight arm 85 is practically 1 to 1. The eccentric 122 is then turned into firm contact with the hook-shaped nose of the cam 110 and the locking nut 122a is then tightened.

To set the draft control weight arm 136, the depth adjustment weight arm 141 is set in a low position (preferably at a mark on the quadrant 142) intended to delineate the desired area for tension control on the control piston 22 (above the mark) and the desired area for compression (below the mark ). A position such as that in fig. 7 shown is appropriate. The nut 145b (fig. 4) is then adjusted to set the pivot pin 145a so that the weight arm 136 is kept just clear of the front end of the slot 111' against a force equal to that supplied to it by the valve spring "77.

The preceding settings can most easily be carried out before the cover plate 26 and the regulating elements carried by it are mounted in the tractor. After assembly, the self-locking nut 88 is adjusted to position the valve driving weight arm 85 so that the roller 114 rests lightly against the lower ends of the weight arms 112 and 136 with the valve V at full outflow, as shown in fig. 8.

With the sump supplied with oil and the tractor engine running, adjustments can now be made to establish the "transport position" and to determine the point at which the valve V will begin to empty the pressure cylinder. Accordingly, the weight arm 100 for position control is moved upwards until the power lifting arms 41 reach the desired conveyor position. The stop bolt 105a is then guided backwards towards the weight arm 100 and locked in place. This indicates "transport position".

The weight arm 100 is moved downwards past its position control area, i.e. below the position in fig. 5 to the lowest possible position, thereby leading the valve piston 55 to a limited intake position. The tension links 15 will now rise (due to the action of the pump 45). With the links in an intermediate position and loaded with a prescribed weight, the weight arm 100 is moved upwards until the slots 73 forming the inlet channels are closed and the outflow slots 74 are opened just enough to allow the weight-loaded links 15 to sink very slowly. The adjustable stopper 105 is brought into contact with the edge of the counterweight arm and the stopper bolt 105b is brought against the stopper 105 and then locked in position as shown in fig. 10.

With regard to the transport position of the drawbars, a double-acting regulating spring has so far caused difficulties because the overhanging weight of an implement carried in transport inadvertently bends such a regulating spring down by tensioning the regulating link. This tension effect sought to bring the control valve to a position in which the continuously running hydraulic pump accidentally resumed pumping, and this tendency became more noticeable when the tractor was driven over bumpy ground which caused the implement to swing up and down.

In contrast to this, the present arrangement is such that a transported tool is suspended by the regulating spring itself and there is no tendency to bring the pump to start again. This comes from the fact that the load which is transferred to the regulating valve 29 has no effect until the load exceeds the value determined by the depth setting weight arm 141. When. the main weight arm 100 is lifted to raise a tool in the transport position, the valve is moved to the neutral position when the draw links 15 reach the height corresponding to the setting of this weight arm. The weight arm 141 is set low so that only a strongly compressive load on the control joint can move the valve V (at the draft control device) for supply to the pump. A voltage load on the control joint cannot thus cause the pump 45 to resume pumping.

In such cases, the system is not only immune to false restarts, but the regulation spring 29 itself serves an additional purpose, i.e. the spring becomes a support part for the transportable tool. This smoothes or dampens the tractor's ride and counteracts the tendency of a heavy implement to lift the tractor's front end. The hydraulic system is also in other respects protected by spring supporting a transported implement, because, in a system lacking such a spring suspension, the pounding of a heavy implement over uneven ground exerts shock loads on the oil column in the pressure cylinder with a corresponding impact in it normal release valve and possible damage to it.

The hydraulic system is well suited for use as a source of hydraulic fluid for operating auxiliary mechanisms including cylinder and piston drive parts or other hydraulic devices.

To supply such an auxiliary device from the hydraulic pump 45, a supply line can easily be connected to the pipe 48 or to a cross passage 51a (fig. 2) in the tractor cover 26 under a removable plate 50 which is bolted to the upper side of the cover. This plate with its internal passage 51 is removable so that it can be replaced, if desired, by any of various other plates with valves or more passages for connection with various auxiliary devices. Instead: a connection can be made directly with one or each end of the passage 51a by screwing in. a suitable coupling. The hydraulic system is particularly useful for implements that have a working part that must be lowered quickly. For this purpose. the "fall" openings formed at slots 74 and 75 provide such a large liquid outflow area that rapid lowering of even a light, empty fork is practically possible.

In addition, the control mechanism facilitates the operation of an auxiliary device. With a saw connected to the passage 51a, the driver can first place the main weight arm 100 at the lower end of its normal setting range (as in Fig. 5). The valve piston 55 is then brought to the full "fall" position and the pull links 15 fall loose. The driver then lifts the weight arm 141 for depth setting and as a result the valve piston is moved to the "lift" position. The pump is then started and delivers oil under hydraulic pressure to the auxiliary device. This delivery of oil will cause lifting either of the main pressure cylinder 36 and then of the cylinder for the auxiliary device, or vice versa, as the one that is moved first is the lightest loaded as the two are connected "in parallel" in the hydraulic circuit. If the draw links 15 are not loaded, i.e. not carrying any tools at the time, the main pressure cylinder 36 will be driven first so that the links are lifted until finally their lifting is stopped by the pressure piston hitting the inner top part of the tractor housing. The auxiliary drive is then operated. When this has completed its working stroke, the driver returns the weight arm 141 for the depth setting downwards. This causes the valve piston 55 to move from the "lift" to the "fall" position, so that the return stroke of the auxiliary actuator occurs. It will be seen that the return stroke of the auxiliary drive part takes place by oil being drained out through the passage 51a, the pipe 48 and the valve V and no special return pipe is required.

To take advantage of a maximum area of the piston 55 drop port, the weight arm 100 is set at the lower end of its controlling setting range (Fig. 5) as just described above. The fastest retraction of the auxiliary drive is provided by this setting. An auxiliary drive may also be actuated with the weight arm 100 at any part of its range above its lower position control setting. In such a case, the weight arm 141 for depth setting can be used as previously described and the same operating cycle is carried out except that the return stroke of the auxiliary drive part takes place at a lower speed.

In order for the operation of the control system to be more easily understood, a cycle of normal work operations shall be described as an illustration.

It is assumed that a tillage tool is connected to the three-link suspension 15, 15, 16 and that the tractor engine and the hydraulic pump are running.

To transport the implement to the field, the driver raises the main weight arm 100

(from the setting in Fig. 5). This causes the cam weight arm 110 to move forward, the position control weight arm 112 to rotate clockwise, the valve actuated weight arm 85 to rotate counterclockwise and the valve piston 55 to move forward to open the inlet ports 73. The pump thus begins to operate and delivers pressure oil to pressure - the pistons 36, 37 so that the pull links 15 lift the tool. This brings the follower cam 120 into action as it rotates clockwise and strives to bring the weight arms 110, 112 and 85 back with the valve piston to the neutral position. Finally, the neutral position is reached and the lifting of the tool is stopped at a height which corresponds to the setting of the weight arm 100. This setting can be the one shown in fig. 6.

When cultivation or other work is about to begin, the operator sets the depth setting weight arm 141 approximately in accordance with the draft — and therefore the depth

— at which the tool will work. Furthermore, he lowers the main weight arm 100, e.g. to the position in fig. 5. As a result of this, the cam weight arm 110 is driven backwards, and turns the weight arm 112 anti-clockwise and the weight arm 85 clockwise so that the valve V is moved backwards to its "fall" position. Oil is thus emptied from the pressure pistons 36, 36 and thereby the tool is lowered towards and

down into the earth. The follower cam 120 again comes into action and strives to bring the weight arms 110, 112 and 85 and the valve V back to the neutral position.

It is assumed that the tool is a heavy overhanging, easily pulled tool which will exert a tension load of about 450 kg on the control link 16. In this case, the setting of the weight arm 141 will be approximately as high as shown with full lines in fig. 14 and indicated by B. While the musher, as mentioned above, lowers the main weight arm 100, he guards the tool when it goes down into the ground and he sets the depth adjuster 141 to get the depth he wants. He then pulls knob 143 to set this optimal setting. At this stage, the control spring 29 will be compressed backwards under the tension which is transferred from the control link 16 and the piston 22 to the movable 'cup 28 which is displaced backwards along the length b, fig. 14. In a practical example, the length b which corresponds to a tensile stress of 453 kg is equal to 3.3 mm. In this balanced state of the spring construction, the valve V will be in the neutral position. That is the valve pressure pistons 36, 37 will be supported and held at the depth reached.

If instead it is assumed that the implement is heavy both in weight and draft, the setting of the depth adjuster 141 will be approximately as low as that in fig. 14 with C indicated position. In this case, a control spring 29 will be compressed forward by the compressive traction force which is transmitted through the joint 16 to the piston crosshead 27, as shown in fig. 15. The length of the compression is c. In a practical example, the size of c corresponding to a compression pull of 1360 kg is equal to 10 mm. In this balanced state of the spring assembly, the valve V will be in the neutral position.

Suppose, in order to fit an implement, that the driver sets the depth adjuster 141 at the intermediate height indicated by A in fig. 14, and that the tool is lowered into the ground as already described. When the spring assembly reaches a balanced state, with the valve V in the neutral position, the spring will be compressed forwards under a compressive tensile force corresponding to the length a in fig. 16.

We return to the cycle of operation in which the step had been reached where the implement had sunk into the earth and had reached a depth selected by the driver by setting the depth setter 141. During this work the automatic parts of the control device for position and draft operate as follows: While the implement is lowered above ground level, only the position control device is active as already described. That is the lowering weight arm 100 acts to keep the valve's drop ports 74, 75 open while the follower cam 120 seeks to close them. Should no other effect intervene, this position control effect would continue until the tool came to rest at a height corresponding to the final setting of the main weight arm 100. However, a new effect occurs as soon as the tool enters the earth, namely tensile load. The best illustration of what attracts is obtained from a heavy drawn implement, such as a plough. When the draft load is created, the push rod 131 is driven forward and acts through the cam weight arm 135 to turn the draft regulator's weight arm 136 clockwise. That is the weight arm 136 begins to follow the position control weight arm 112 which has meanwhile been returned clockwise by the follower cam 120, the valve V still being at the "fall" end of its range of motion. However, the control mechanism is shaped so that the tension control weight arm 136 will rotate faster than the position control weight arm 112, so much so that the weight arm 136 will catch up with the weight arm 112 and will take over the work of bringing the weight arm 85 and the valve V to the neutral position in which the lowering of the tool stops. It is therefore important to note that, due to the intervention of the traction control device, the implement is stopped at a height higher than that at which the position control device would have stopped if there had been pure position control conditions. Accordingly, for all working depths deeper than the depth at which the draft control weight arm 136 intervenes by catching up with the position control weight arm 112 and influencing the valve V through the weight arm 85, the position control device is out of operation and the draft control device is the only control.

During the continued operation of the tractor, when the draft varies under varying soil conditions, the draft will sometimes increase and sometimes decrease. Under increasing pressure, the pressure rod 131 will be driven forward and turn the weight arm 85 clockwise and move the valve V forward to its "lift" position. Oil will thus be given access through the ports 73 and pumped into the pressure cylinders 36, 37 and the power lifter 39-42 lifts the draw links 15 which carry the tool. The tool will thus work shallower so that the draft will decrease, until the moment it reaches the "normal" value, namely the value for which the depth adjuster 141 is set, at which moment the valve V will have returned to the neutral position and the pumping will have stopped. Conversely, if the pull decreases, the pushrod 131 will move rearward and the valve V will also move rearward to its "fall" position, in which oil will be discharged from the pressure cylinder. The tool will thus work deeper until the moment normal draft is reached again when the valve is brought to neutral position.

In summary, the position control device will take over the entire control, both with regard to lowering and lifting the tool above a height in the ground, while the traction control device will take over the entire control below this height. The driver must set the depth adjuster 141 so that the normal working depth is to a reasonable degree deeper than the aforementioned height and thereby give the traction control device a working margin for its correction work under temporarily reduced traction conditions.

In the foregoing, the operating cycle is described in connection with an implement that is heavy to pull. The same cycle will occur with implements in general provided the driver sets the depth adjuster 141 correctly.

It is assumed that the driver feels that the mechanism is too sensitive, i.e. it over-controls or over-corrects. This undesirable condition is indicated by vibration of the hydraulic power lifter and the seat he sits on. He therefore turns the main weight arm 100 downwards, during the setting in fig. 5, until the vibration stops. Such vibration is usually due to too rapid implement lowering during the corrective setting of its depth by the draft control mechanism. The heavier the implement, the further down he has to turn the weight arm 100. When he has obtained a satisfactory setting, this is marked with the knob 105. By turning the weight arm downwards, as described, he brings the hook end 121 and the eccentric 122 into action on the weight arm 112 and turns it to an adjustable stopper for the valve weight arm 85, which stopper's function is to limit the "fall" limit for the rearward movement of the valve piston 55, and it thus reduces the maximum gate opening obtained by the narrow slots 74 with or without the wider ones slots 75.

At the end of each furrow or driving length across the field, the driver lifts the weight arm 100 and thus lifts the implement, and steers the tractor to the next starting point. Now he lowers the weight arm 100 again to the position already determined by the knob 105. He leaves the depth adjuster 141 unaffected. As a result, the tool is lowered to the previously selected working depth.

During the tractor's work, it will appear that the implement goes wherever the driver lowers or lifts it with the weight arm 100 under position control. If, however, the following position control system was really the ruling one, the working depth, whenever the tractor tilted while driving over the field, would become very irregular because the implement would rise and fall with the tractor, seeing that the implement would be rigidly attached to the tractor with respect to relative downward movement.

What has happened, however, is that the draft control device has automatically intervened and taken over the command as soon as the implement is properly in the ground, and the draft control device automatically maintains uniform draft and therefore a practically even working depth despite the uneven ground contour. The tractor and implement are not rigid, instead the implement has complete freedom to turn, not only upwards, but also downwards in relation to the tractor in the loosely coupled manner that is characteristic of proper traction control.

The tool used can be a so-called drainage tool, i.e. a tool that cuts a channel below the soil surface, e.g. for drainage or to accommodate drainage pipes, an electric cable or similar wires. A characteristic feature of this type of implement is that it exerts a very large pull but is relatively light in weight. In order to cause the implement to sink quickly into the ground, despite its light weight, the driver lowers the weight arm 100 quickly to bring the drawbars 15 forward, although no further than the end of its position control range, fig. 5, to get the "fall" ports 74, 75 temporarily wide open to get rapid penetration. The operator then slowly moves the weight arm further down to reduce the sensitivity of the control mechanism after the implement is at full depth, by which time the downward "suction" of the implement will have caused a heavy load to be placed on the tractor. Should the tractor carry a crane or a loading device on the draw links, these will be devices that work above the ground surface and the driver can raise or lower the device simply by maneuvering the weight arm 100. The device will accurately follow the movement of this weight arm under correct position control. The driver's ability to open the valve V strongly for rapid outflow of oil during such operations ensures quick reaction despite the fact that the valve will release oil completely gradually if the driver moves the weight arm slowly.

Claims (33)

1. Control system for a tractor which has a valve-controlled hydraulic power lifter with a connection joint system for an agricultural implement and which also has a position control mechanism and automatic draft regulation mechanism which can both be used with the valve dg where the draft regulation mechanism comprises a joint system which is under the unified control of firstly, a weight arm influenced by the driver, which is movable to any selected position within a range of positions, and secondly, by a piston which is moved automatically in accordance with changes in the draft, characterized in that the position control mechanism comprises another weight arm (100, 101) which can be influenced by the driver, which is movable independently of the traction control weight arm (141) to any selected position within a range of positions, and by a known in and of itself follower device (120) which is movable by and in accordance with with the power lifter (36—42) and a mechanical joint system (111, 112, 117) so m is continuously under the unified control of this weight arm and follower arrangement and in that the two mechanical joint systems 111, 112, 117 and 135, 136 and 131) of the position control and traction regulation mechanisms are each continuously available to take over control of the valve (55) by movement of the associated weight arm that can be influenced by the driver. 2. Control system according to claim 1, characterized in that the position control mechanism includes a one-way connection (115, 116) which enables the driver, when maneuvering the position control weight arm (100), can withdraw the position control mechanical joint system (111, 112, 117) from its normally operative connection with the follower device (120, Fig. 10). 3. Control system according to claim 1, characterized by the combination of the position control device including a part (112) which is movable in one direction by a main device (100-107) operated by the driver and in the return direction by a follower device (120) in the power lifter (36) —42), traction control device including another part (136) movable by a driver-operated auxiliary device (138-141) and by the connection joint system (16), and a valve with the position control part (112) and with the traction control part (136) to regulate the flow of hydraulic fluid to and from the power lifter, as the valve is movable at these parts, alternatively such that the driver can initiate position control - the arrangement for bringing a connected tillage tool (17) to be lowered to and lifted from a working depth in the soil which is determined by his setting of the auxiliary device (138-141) and also so that with the tool at this depth the traction control device automatically takes over the control of the powerlifter. 4. Control system according to claim 1 or 2, characterized in that the two devices operated by the driver both include control parts consisting of separate hand-weight arms (100 and 141). 5. Regulation system according to claim 4, characterized in that one of the dumbbell arms is connected to a guide quadrant (142) and to a setting device (141å) which can be adjusted to any of a range of positions on the quadrant and has stops (141d) "which limit the movement of the dumbbell arm (141) in relation to the position device. 6. Regulation system according to claim 5, characterized in that the positioning device (i41a) has a device (143) to be fixed in any chosen position on the quadrant (142) and in that a friction device (141 f, h, k) maintains the hand weight arm (141) springing in relation to the quadrant (142). 7. Regulation system according to claim 3 or 4, characterized in that the traction regulation device includes a control spring (29) arranged to be compressed under both compression and tension loads which are supplied through the control joint (16) and in that the position control control part (100) when it is lifted to transport position (Fig. 6) acts through the position control device (110, 112) to keep the valve actuator (85) in its neutral position against inadvertent "dropping" action from the tension control device under tensile loads and also to keep said actuator separate from inadvertent "lifting" » effect from the traction control device under compressive loads. 8. Control system according to claim 3, 4 or 7, characterized in that the control part (141) for the draft regulation, when it is lifted while the position control device (100, 110, 112) is in the transport position, acts through the draft regulation device (135, 136) to take over the control off the valve (55) and keep the valve open in that position to add fluid to the hydraulic system.' 9. Control system according to one of the preceding claims, including a control piston arranged to be pushed and pulled by the control link of the connecting link system, characterized by a rocker (25) having a hanging pivotable connection (24) with the tractor and a hanging part ( 25a) under the aforementioned rotatable connection, which part is connected to the control piston (22) and to the control joint (16) by a common axis of rotation. 10. Control system according to one of the preceding claims with a control spring assembly, characterized in that the tractor housing for the hydraulic power unit (36, 37) has an upper opening closed by a cover (26) which includes a housing (26a) for the spring assembly ( 22, 29) as the cover and assembly form a detachable unit. 11. Control system according to claim 10, characterized in that the cover (26) has that separate jaws (26b) for rotatably attaching a rocker (25) provided as a support device for a connection (21) between the piston (22) for the spring assembly and the regulating link (16) of the joint system. 12. Control mechanism according to claim 9 or 11, characterized in that the rocker (25) is formed double-limbed as the limbs (25a) are separated to fit between them the interconnected ends of the control piston and the control joint. 13. Control system for a tractor which has a traction control mechanism, and/or a position control mechanism according to one of the preceding claims, characterized in that the connection joint system is lowered by the release of hydraulic fluid from the power lifter (36-42) through an outflow opening (49) and in that a driver-operated device (100, 55) is arranged to vary the speed of the outflow through the outlet passage in order to regulate the sensitivity of the control device (131-136). 14. Control system according to claim 13, characterized by draft regulation devices (22, 29, 131-136) are arranged to automatically lead a valve (55) as determined by draft load imposed by a tool connected to the tractor to bring hydraulic fluid to to be pumped to the power lifter or to be discharged from it, an outflow passage (49) regulated by the valve and driver operated means (100, 110, 112) to limit the movement of the valve relative to the outflow passage thereby enabling driving -re to regulate the sensitivity of the traction control device in accordance with the nature of the tool. 15. Control system according to claim 13 or 14, characterized in that the valve comprises a housing (67) and a movable piston (55) and that the outflow passage (49) leads through a constricted port (74) whose effect tive area can be varied by movement aV the piston. 16. Control system according to claim 15, characterized in that the constricted gate (74) is a long narrow slot in the piston (55), the slot being progressively closable by a bearing ring (65) through which the piston is movable. 17. Control system according to one of the claims 13 to 16, also including position control device, characterized in that the control part (100) for the position control is movable through part of its area to start the power lifter (36-41) and is movable through another part of its area to vary the outflow rate of the hydraulic fluid from the power lifter through the outflow passage (49). 18. Control system according to claim 17, characterized in that the control part (100) for the position control when it is in the aforementioned second part of its area (Fig. 5) forms a positive connection with a stop (112) which forms a boundary for the outflow area from the outflow passage (49) and where movement of the control part gradually reduces the outflow area. 19. Control system according to claims 13-16, with both a position control device and a traction control device, characterized in that the position control device includes a control part (100) and a mechanism to optionally determine the speed of the joint system (15) lowering during the operation of the traction control device. 20. Control system according to one of claims 13-19, characterized by a valve-operating mechanism including a first weight arm (112) rotatable between its ends and with an operative connection at one end with the valve (55) to be operated, a second weight arm (110) rotatable between its ends on the other end (111) of said first weight arm, which second weight arm has an extension (121) which can cooperate with a stop (122) on the first weight arm when the second weight arm is turned to a predetermined position, which extension cooperates with said stop to cause said weight arms to rotate as a unit when the second weight arm is rotated past said predetermined position. 21. Control system according to claims 13-20, characterized in that the narrowed port (74) is connected to a larger port (75) and in that the control part (100) can be manipulated to move the valve (55) to a position in which the largest port is uncovered so that the hydraulic fluid flows out without obstacles and the joint system (15) is lowered quickly. 22. Control system according to one of the preceding claims with draft control device or position control device or both parts and also with a mechanical joint system that extends from an automatic drive part to a control valve, characterized in that the joint system includes a cam weight arm (135, 110) with an inclined cam ( 134, 115) which is affected by a drivable connection (135a, 111) with the cam weight arm and is operatively connected to the valve (55), and further characterized by a driver-maneuvered device (139, 107) which is arranged to turn the cam weight arm about its pivot joint to vary the effective length of the joint system by selecting the part of the cam affected by the drive part. 23. Control system according to claim 22, characterized by a traction control joint system including a weight arm (136) which has a drive connection with the control valve (55) and a pivot connection (135a) with the cam weight arm (135) and a pusher (131, 133) which is exposed to the effect of the tensile load and is placed on the cam (134), the length of the joint system being variable between the pusher and the pivoting connection when turning the cam weight arm about this connection. 24. Control system according to claim 22, characterized by a joint system for position control including a weight arm (112) which has a drive connection with the control valve (55) and a rotary connection (111) with the cam weight arm (110), and a follower cam (120) which has a drive connection (117) with the cam weight arm as the length of the joint system is variable between the follower cam and the pivoting connection when turning the cam weight arm about this connection. 25. Control system according to one of the preceding claims including a valve for controlling the operation of the power lift and the traction control device arranged to automatically move the valve under normal increase of traction load imposed by an implement coupled to the tractor to a position in which hydraulic fluid is pumped to the power lift through a wide supply channel, characterized in that the draft regulation device (22, 131, 135, 136) is also arranged to automatically advance the valve (55) during a predetermined increase in draft overload in order to discharge hydraulic fluid through the same channel (73). 26. Control system according to claim 25, characterized in that the channel (73) is a port in the valve (55) and cooperates with separate bearings (64, 63) through which the valve is movable, which bearings delimit the ends of the pump inlet (61) and the power lifter outlet (62) respectively and where the said port opens the inlet, with or without the outlet, when the valve is properly routed through the bearings. 27. Control system according to claim 25 or 26, characterized by a valve comprising a housing (58) with a long cylindrical bore (57) divided into two axially aligned chambers (61, 62), a tubular valve part (55 ) slidably axially through the bore, which valve part has slots (73, 74) at opposite ends sufficiently spaced apart for the valve part to close both chambers when placed in the center position, a stop (76) on the valve part cooperating with stops (63, 65 ) in the valve bore to delimit the end positions of the part to both sides of the middle position, which part in one of its end positions opens the slots (74) at one of its ends to one of the aforementioned chambers to ventilate it while the other chamber is held closed, and in the other end position of the part it exposes the slits (73) at its other end to both chambers to ventilate them simultaneously. 28. Control system according to claim 27, characterized in that three thin rings (63-65) separated from each other in the bore (57) delimit the two valve chambers and serve as bearings through which the valve part (55) is slidable and which cooperates with the slots (73, 74). 29. Control valve according to one of the preceding claims, with draft control device or position control device or both, characterized by a control valve housing (58) two axially aligned rings (63, 65) placed in the housing to define opposite ends of a hydraulic chamber (62), a third ring (64) placed in said housing substantially axially in line with said two rings and separated from one of them to define the opposite end of another hydraulic chamber (61), one of the rings is supported so that it can perform a limited movement across the axis, and a valve piston (55) which is slidable axially through the rings and which has passages (73-75) which can be brought into line with the chamber one for the flow of hydraulic fluid to and from them. 30. Control valve according to claim 29, characterized in that the two chambers (61, 62) are respectively low-pressure and high-pressure chambers, and that the movable ring (64) delimits the end of the low-pressure chamber which is farthest from the high-pressure chamber. 31. Control system according to one of claims 25-30, with a control valve housing, characterized by three bearings (63-65) axially removed from each other in said housing to divide the housing into two hydraulic chambers (61, 62), a low-pressure - and the second high-pressure chamber, a valve piston (55) slidable axially through said bearings, a long narrow passage (74) and a short wider passage (75) in the piston at one end to cooperate with the bearing (65) at the adjacent end of the high-pressure chamber, and a passage (73) in the piston at the opposite end to cooperate with at least the bearing (64) at the adjacent end of the low-pressure chamber, the piston being movable from a neutral position in which it closes both chambers, in one direction to open the low-pressure chamber (61) for conveying hydraulic fluid and in the other direction to open the high pressure chamber (62) for discharge at a progressively variable limited speed by means of the long narrow passages (74) or at a practically unobstructed speed by means of the added wider passages (75 ). 32. Control valve according to claim 31, characterized in that the bearings (63-65) are thin rings through which the piston (55) has a sliding fit. 33. Control valve according to claim 29, 30 or 32, characterized in that the valve piston is a tube which is open at the ends and which has an intermediate partition (56), the ends of the tube being equipped with ports for interaction with the rings (63-65). Cited publications: