GB1575131A

GB1575131A - Tractor vehicle

Info

Publication number: GB1575131A
Application number: GB350277A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-02-10
Filing date: 1977-01-28
Publication date: 1980-09-17
Also published as: FR2376782B2; FR2376782A2; DE2705400C2; DE7740374U1; BE851294A; NL7701282A; IT1071785B; CA1076963A; JPS52118728A; DE2705400A1; JPS5922063U

Description

(54) IMPROVEMENT IN OR RELATING TO A TRACTOR VEHICLE (71) I, JACQUES BIDON, 51230 Velye/Vertus, France, a French Citizen, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a tractor vehicle and particularly but not exclusively to such a tractor vehicle for agricultural use.

These vehicles, which are well known in the rural world, usually comprise a chassis supported by two sets of driving and steering wheels, the chassis being surmounted by a driving cab in which the operator is placed. The chassis most often has, at the rear, a power take-off which is capable of being coupled to earth working tools, a "three point" coupling, and a hydraulic raising device. These various devices are sometimes located in the front of the machine when the latter does not have a towing function but a pushing function. This type of machine, which is well known to cultivators, has many drawbacks as concerns its design, its handling and its driving on the ground.

As concerns the developed power: The conventional tractor has only two driving wheels which are really adapted and capable of developing the power that the engine is capable of furnishing.

Sometimes a front driving axle is added to improve the efficiency of the tractor.

Generally, it might be said that tractors of more than 100 HP utilize very inefficiently the power of their engine. For high powers, tractors have a poor adherence to the ground. To overcome this it is necessary to render them considerably heavier (inflation of the wheels with water-provision of many weighting masses, etc.). The dimensions of the pneumatic tires are also increased (45 to 50 cm). The more they are widened the less they can be employed, principally for crops arranged in rows (beetroots, potatoes, treatment of cereals, etc.). They must be replaced by narrow equipments, most of the time coupled at the spacing of the crops.

The use of wide pneumatic tires presses down an excessively large area of earth which is sometimes difficult to work subsequently. The wear of these tires is greater and costs more than that of smaller tires.

The front driving axles are often imperfectly adapted. For certain work the equilibrium of the weight between the front driving axle and the rear driving axle is unsatisfactory in many cases. The front driving axles reduce the turning circles. The tractor becomes much less easy to handle and does not allow any skid-turning at the field ends.

The differential locking is only valid for straight-ahead travel. It is not always possible with front driving axles. It is difficult to achieve a transmission which is proportional to the travel with a driving axle which is located under a trailer vehicle (too many universal joints, which are difficult to use when turning, etc.).

As concerns the items of equipment: There is no front power take-off which'is really adapted for the purpose, whence the necessity to provide lay shafts leading from the rear power take-off. with the use of universal joints, speed reducing shafts, etc.

Which arrangement is hardly elegant from the mechanical point of view. There is no front lifting. This is mainly due to the fact that the tractors no longer have a chassis on which fixing means for multiple uses may be provided. There is no bearing platform on which there may be adapted different containers (fertilizers, seeds, treating products) or other adaptations (cranes, buckets).

As concerns the driving of the tractor: The gear-boxes are not all equipped with synchronized speeds. In any case it is very difficult to change speed when towing a heavy load on wet ground.

There is- no possibility of reversing the travel. Tractors are equipped in such manner that they can only be employed in one direction of travel, and it is up to the user to make the best of the situation. To do this, he must most of the time drive his tractor while looking at the tool located behind him.

There is no continuous speed variator from 0 to 27 km per hour. Most of the time no speed really corresponds to the envisaged work or to the equipment towed, coupled and used.

The speed, raising and steering controls are often very badly positioned and do not take into account that these machines are employed essentially for working the earth (the levers located between often soiled feet reduce the freedom of movement of the driver, etc.).

Poor visibility in front owing to the front driving axle and the engine, and at the rear owing to the fact that the driver must turn round for this purpose. Visibility is bad in many other applications since the cab is inserted between the two rear wheels of the machine.

Comfort is very often poor, since the tractor follows rather badly the contour of the ground. Without a forward driving axle the comfort is still worse.

The invention provides a tractor vehicle comprising a chassis having a longitudinal axis, at least a front pair of driving wheels and a rear pair of driving wheels supporting the chassis, a cab, means mounting the cab on the chassis and allowing the cab to travel from one end of the vehicle to an opposite end of the vehicle in a direction parallel to said longitudinal axis, an engine and power take-off means carried by the chassis, the power take-off means being for connection to tool means, substantially identical raising devices respectively mounted on the chassis at longitudinally opposed ends of the vehicle, first means for controlling the driving and steering of the vehicle and second means for controlling the raising devices, the first and second means being located inside the cab, two independent drive means, one of the drive means being drivingly connected to two of said wheels located on one lateral side of said longitudinal axis and the other of the drive means being drivingly connected to two of said wheels located on an opposite lateral side of said longitudinal axis, transmission means drivingly connecting the engine to the two drive means, means included in the two drive means to allow the engine to drive selectively either of the drive means, both of the drive means at the same time in a symmetrical manner, or both of the drive means at the same time in an unsymmetrical manner, means included in the two drive means for reversing the drive means so that the vehicle can be made to travel in two opposite directions a driving station located in the cab and mounted to pivot through at least 1800 about a vertical axis relative to the chassis, whereby irrespective of the direction of travel of the vehicle, the operator of the vehicle can face and be close to the stretch of ground to be treated.

According to a preferred embodiment, each of the two independent drives comprises a variable delivery and reversible hydraulic pump operating in a closed circuit, the two pumps being connected to two outputs of a coupling box which has a third output for a power take-off and an input for coupling to the crankshaft of an engine.

In this case, advantageously, each raising device is a hydraulic raising device and control means located in the cab are connected to control the hydraulic actuation of the raising device.

Conveniently, the tractor vehicle further comprises rails mounted on the chassis and extending in a direction parallel to said longitudinal axis and rollers carried by the cab and rollingly engaged on the rails, means for holding the cab in any chosen position on said rails, the size of the cab being such that positioning the cab at an end of the chassis makes available a loading platform.

Preferably, the cab is movable in translation and the connections between the different driving means of the vehicle are constituted by flexible and elastic pipes which are easily disassembled.

Conveniently, there are three pairs of wheels, the front and rear pairs of wheels forming driving and steerable wheels and the third pair of wheels being mounted on the chassis to remain parallel to said longitudinal axis when viewed in plan, each independent driving means driving all the wheels located on the corresponding side of the chassis.

Conveniently, the travelling speed of the tractor vehicle is proportional to the deliveries of the pumps.

Conveniently, means are provided whereby the front wheels can be declutched on the road.

Conveniently, the pumps are controlled electrically at the driving station by pedal means and a steering wheel and are reversible so as to cause the vehicle to travel in either direction, each wheel being connected to its respective pump through a double displacement hydraulic motor.

Conveniently, the third output of the coupling box is connected to a third hydraulic pump which drives at least one hydraulic motor actuating the power takeoff.

In this case a speed reducer may be interposed between the hydraulic motor actuating the power take-off and the power take-off.

Moreover, the third hydraulic pump may drive at least one hydraulic motor actuating a tool provided for the vehicle.

Preferably, the tractor vehicle comprises, in the vicinity of each of the front and rear pairs of wheels, a hydraulic raising device comprising two upper arms pivoted to the chassis and two lower arms, the upper arms being connected to the lower arms by stays, a position sensor combined with the upper arms, and a pressure sensor is inserted in a hydraulic supply circuit for hydraulic motors driving the driving wheels, said two sensors being connected to an electric control unit to which control unit position control means and force control means located in the cab are also connected.

In this case, the control unit may comprise a position amplifier and a force amplifier and the position control means and force control means each comprise a regulating potentiometer. Moreover, the tractor vehicle may comprise a hydraulic distributor valve actuated by the control unit, which distributor valve controls jacks actuating the raising device.

Conveniently, the chassis comprises, in the direction of said longitudinal axis, two chassis sections and pivot means interconnecting the two sections for pivoting about a vertical axis which is offset toward the front of the vehicle with respect to the middle of the length of the vehicle so that one chassis section is longer than the other chassis section, said means mounting the cab on the chassis being mounted on the longer chassis section and extending beyond the longer chassis section to overhang the shorter chassis section.

In this case the front section may be rotatable by means of at least one hydraulic jack secured to the rear section.

The invention will now be more particularly described with reference to the accompanying drawings, wherein: Fig. 1 is a side elevational view of one embodiment of a tractor vehicle according to the invention, Fig. 2 is a top plan view of the vehicle shown in Fig. 1, the cab and the front and rear raising devices having been removed; Fig. 3 is a diagrammatic and partial elevational view of a further embodiment of a tractor according to the invention; Fig. 4 is a diagrammatic and partial top plan view of the vehicle shown in Fig. 3; Fig. 5 is a sectional view, to an enlarged scale, of a hydraulic power take-off provided on this vehicle; Fig. 6 is a diagram of the hydraulic circuit driving the power take-offs, and Fig. 7 is a diagram of the electrohydraulic control circuit for the raising devices of the vehicle.

A vehicle, such as an agricultural machine is illustrated and, comprises in the known manner, a chassis 1 supported by at least two pairs of wheels, the chassis being provided with a driving cab 2 and substantially identical raising devices 3 at opposite ends to each of which a groundworking tool can be coupled. The tool may be inter alia a harrow or a plough.

Referring to Figures 1 & 2, the vehicle shown therein comprises three pairs of wheels 4a, 4b, 4c so that the load of the vehicle is distributed among six wheels, whereby it is possible to employ narrow rims for receiving pneumatic tires whose tread is such that the vehicle can pass freely between rows of plants which have even been spaced relatively close together. These narrow pneumatic tires are, moreover, much cheaper than those employed on conventional 'tractors. Furthermore, they require no interchanging when passing from one crop to another, so that the operator has no need to have a stock of tires of different widths and tread patterns.

The fact of employing six wheels not only enables the weight of the vehicle to be evenly distributed, it enables the energy which must be developed for driving the vehicle to be distributed in a symmetrical manner.

For this purpose, as can be seen in Fig. 2, the wheels 4a, 4b, 4c located on one side of the chassis are supplied with power by a drive independent of the drive driving the other wheels 4a, 4b, 4c on the other side of the chassis.

The power is uniformly distributed among the six wheels of equal size and is transmitted to these wheels by two pumps 5 and 6 which have a variable delivery or flow and are reversible. These pumps are of the barrel type and include in the conventional manner a booster pump and a protecting and exchanging unit.

Thus each pump drives three wheels located on each longitudinal side of the chassis, and each wheel is provided with a double-displacement hydraulic motor 7.

The pumps 5 and 6 are connected to a coupling box 8 through the centre of which box a power take-off shaft 9 extends, opposite ends of shaft 9 being connected to front or rear power take-off units 10 through elastically yieldable lug-type couplings 11.

The front power take-off 12 is rendered operative by a clutch 13 contained in the power take-off box, and this clutch cooperates with a speed reducer 14 and an electro-hydraulic distributor valve 15. This mechanical construction is of course also provided at the other end of the vehicle.

The power is furnished to the two pumps 5 and 6 by a Diesel engine 16 which also supplies the energy for the two power takeoffs 12, which latter may be rendered operative alternately or simultaneously.

The pumps are controlled electrically from the driving station and are fully independent of each other. By varying the delivery or flow of one pump with respect to the other, the vehicle can be skid-turned.

This utilization enables the turning circle of the machine to be reduced when the nature of the ground allows this. In the extreme case, it is possible to completely neutralize one pump so that the three wheels located on one side of the vehicle are locked, and then supply fluid to the other pump so as to achieve a complete skid-turn, on the spot, of the machine on the locked wheels.

The vehicle is made to travel by inclining the swashplates of the two pumps 5 and 6 at the same angle so as to obtain identical deliveries from the pumps. The travelling speed of the vehicle is therefore proportional to the delivery of the pumps, and the variation of the delivery of one pump with respect to the other enables the machine to be turned to the right or the left.

On the other hand, an identical variation of the deliveries of the two pumps enables the machine to be moved forwardly or rearwardly, or stopped. This arrangement provides a differential locking with no mechanical connection at the different travelling speeds of the wheels on opposite sides of the chassis. Furthermore, when stationary, a hydrostatic braking of each wheel is achieved.

The vehicle drive controls are footoperated from the driving cab. Under the right foot, there is a forward drive control of the vehicle whereas under the left foot there is a reverse drive control. These pedals actuate the control device of the delivery of the two pumps 5 and 6, and these controls are identical for the two pumps. The vehicle is steered by means of a steering member or wheel (referred to hereinafter as a steering wheel) which actuates the control of the deliveries of the two pumps; in this case, the two pumps are controlled differently.

Thus, when the vehicle is stationary, if the steering wheel is turned to the right through an angle a, the control device will maintain the delivery of the right pump null and produce a delivery of +dl of the left pump. This will skid-turn the machine on itself (the right wheels being locked). If in addition it is desired that the machine travel forward, the right pedal will be depressed and the control device will then produce a delivery of +d2 of the two pumps.

This therefore gives, for the right pump: D,=O+d2 and for the left pump: D1=dl +d2, the machine will therefore travel forward in turning to the right since the value D1 > Dr.

The front & rear wheels may be steered in conventional manner. Thus it is possible to turn the front steerable wheels, turn the rear steerable wheels, turn the front and rear steerable wheels simultaneously.

This choice is made by means of separate control circuits for the front steering and rear steering.

The steering wheel actuates the control device of the delivery of the hydraulic pumps, and also two step-by-step rotary distributor valves for steering, one of which is mounted on the front pair of wheels and the other on the rear axle. These rotary distributor valves are actuated by electric motor-speed reducer units controlled by steering control circuits fixed to the steering wheel. If the steering wheel is turned in a given direction, there will be achieved both a control of the deliveries of the pumps 5 and 6 and a control of electric motor-speed reducer units (not shown) actuating the rotary distributor valves so as to achieve a change in direction.

As the vehicle is capable of travelling in two opposite directions, it is obviously desirable that it be capable of operating indifferently for towing or pushing, irrespective of its direction of travel. For this purpose, the vehicle is provided with a raising device 3 in the front and at the rear, these two devices being identical.

The raising device comprises two lower arms 17 which are connected to two upper arms or links 18, pivoted at 19 to the chassis 1 of the vehicle, through the agency of two stays 20, so that this assembly forms, with the cross-members of the chassis, a deformable parallelogram structure which is subjected to the action of two jacks 21 whose pistons 22 are connected by lugs 23 to the upper raising arms or links 18.

The two lower raising arms 17 are connected, in the region of their pivotal mounting 24, to a flexion bar which is combined with a force sensor 25 whereas the upper arms 18 are combined with a position sensor 26 sensing the height of the raising device.

These two raising devices have an independent control and the required hydraulic power is provided by respective pumps 27 or 28 driven by the Diesel engine 16.

These pumps supply fluid either to the two outer jacks 21 of the front raising device or to those of the rear raising device by way of hydraulic electro-distributing valves.

The control of the position determined by the sensor 26 associated with the raising arms is ensured electrically from the driving station through an electric positioning control unit. This control unit is actuated, on one hand, by the position sensor 26 mounted between the raising arms or links, and, on the other hand, by signals coming from the value that the operator feeds into or sets on the position control selector in the cab. In this way, the operator feeds the required value into the position control sector and the electro-distributor valve (not shown) supplies fluid to the raising jacks 21.

When the latter reach the chosen position, the value of the signal produced by the position sensor 26 becomes such that the control unit produces the closure of the electro-distributor valve.

The force control device is also actuated electrically from the driving station through an electric control unit. This control unit is actuated, on one hand, by the signal of the force sensor 25 located on the flexion bar 24 interconnecting the two lower arms 17 and, on the other hand, by the signals coming from the value that the operator feeds into or sets on the force control selector in the cab.

The force control device operates as follows: A value E is fed into the force control sector in the cab. There corresponds to this value E a signal e which is fed to the control unit.

If the buckling in the flexion bar becomes great, so that the force sensor 25 connected thereto indicates a value el > e, this force control unit then produces the opening of the electro-distributor valve and thus raises the lower arms 17 so that the towing force is relieved.

When the value of el > e, this unit then produces the closure of the electrodistributor valve.

As the chosen position has been exceeded, the position control device takes over the regulation of the raising and returns the arms to the initial positions.

As the vehicle is capable of travelling in two opposite directions (reversibility of the pumps 5 and 6), a feature of the vehicle is to have a cab 2 which is movable in translation along upper longitudinal members 1, of the chassis 1. The base of this cab is mounted on a carriage 29 provided with rollers 30 which roll along section members 1, constituting the upper longitudinal members of the chassis.

This cab, movable in translation in opposite directions, may be held stationary in any position by locking means, such as pins, studs, spring-biased locks, screws or other means.

Preferably, this can is held stationary in the region of the two end faces of the vehicle so as to leave free a surface S which constitutes a platform for receiving various appliances such as sprayers, distributors, tanks, buckets, etc.

Further, in order to allow the operator to face always in the direction of the stretch of ground to be treated, the driving station 31 in this cab is mounted to be rotatable on a pivotal hub so that the whole of the station,, including the control means, can pivot through at least 1800.

The connections between the various driving means of the machine (Diesel engine, power take-off, pump coupling box) are achieved by elastic couplings allowing a disassembly of a single element of the transmission system in any region.

The illustrated machine is so designed as to be utilizable on any ground, including the road, since means are provided whereby the front set of wheels can be declutched, and its utilization is greatly facilitated by the two independent drives for the wheels located on each side of the chassis, since it is possible, by varying the deliveries of the pumps, to cause the vehicle to travel in one direction or the other or to obtain the locking of one series of wheels to obtain its skid-turning on the spot.

As concerns the steering, the wheels of the front and rear pairs of wheels 4a, 4c serve as both driving and steerable wheels whilst the wheels of the intermediate pairs of wheels 4b serve only as driving wheels.

The illustrated machine has the following advantages: the machine can travel in both directions at any speed between 0 and 27 km per hour owing to the hydrostatic transmission; the items of equipment are identical at the front and at the rear so that tools may be coupled both to the front and to the rear of the machine; the steering is effected on two axles, namely the front axle and rear axle, the center axle remaining fixed, with the result that there is an improved turning circle. The latter can be still further improved by skidturning the machine by means of the hydraulic pumps; there is a differential locking on all the wheels in all conditions of use in a straightahead travel and when turning; the cab, located completely above the wheels, improves the front visibility. The cab may be advanced or shifted back, depending on the work to be carried out, and the driver can choose the most suitable position the driving station inside the cab can turn through 0--180" and assume any intermediate position; the machine is much more easy to handle than conventional tractors, since the transmissions are hydraulic and not mechanical.

The vehicle shown in Figs. 3 and 4 comprises a chassis 101 supported by two pairs of driving wheels 102 and 103 which are controlled in the same manner as the front & rear wheels of the above described embodiment and on which there is fixed a driving cab 104 having there in vehicle drive control means and means controlling tools which may be coupled to two power takeoffs 105 and 106 disposed respectively in the front and at the rear of the chassis.

The chassis 101 comprises, in the longitudinal direction, two sections 101a and 101b which are interconnected to pivot with respect to each other about a vertical axis X-X which is offset toward the front of the vehicle with respect to the middle of the latter, that is to say, with respect to the transverse plane midway between the front and rear faces of the chassis.

The front section 101a of the chassis has a generally parallel-sided shape and is extended rearwardly by a portion 107a having a trapezoidal horizontal section, whereas the rear section 101b also has a generally parallel-sided shape and is extended forwardly by an upper portion and a lower portion 107b having a trapezoidal horizontal section. These portions 107b terminate in forks 108 between which there are engaged brackets 109 which are integral with the portion 107a. These forks and brackets are pivotally interconnected by shaft portions 110. Two jacks 111 are mounted on the front face of the parallelsided portion of the section 101b between the levels of the portions 107b so as to be disposed in the same horizontal plane and pivotable about vertical axes X-Y located on said face. The ends of their rods 112 are mounted in two forks 113, respectively fixed to each of the two sides of the chassis portion 107a, to pivot about vertical axes Z-Z. It should be noted that the general pivot axis X-X of the chassis is disposed in a transverse plane of the vehicle located practically at the rear of the front pair of wheels 102. The chassis 101 is completed by an upper platform 114 which covers the entire area of the rear section 101b and extends forwardly beyond this part in overhanging relation to above the middle of the front set of wheels 102, this overhanging part carrying the cab 104 in the position for normal travel of the vehicle.

Such a pivoted arrangement of the chassis permits reducing to the maximum extent the gap between the latter and the wheels, so that it is possible to locate therein devices which are larger than in a rigid chassis.

Indeed, a rigid chassis must provide a sufficient clearance between the wheels and the chassis to permit a suitable steering angle of the steering wheels. The gain as concerns the turning circle is between 20 and 30%. The offsetting of the pivotal connection in the direction of the front set of wheels above all permits a solution of the problem of the steerability of the machine in rows of plants. Indeed, the inclination of the front section of the chassis through a small angle, for example 10 on each side of the median axis, has practically no effect on the performance of the tools which may be coupled to the rear of the vehicle.

The pivotal connection of the chassis is distinctly simpler, from the structural point of view, than the complex pivotal connection of steering wheels. It very definitely simplifies the supply of fluid to the driving wheels, each of which, as mentioned hereinafter, are driven by a hydraulic motor 115, since these wheels become fixed in position on the chassis. This results in a considerable reduction in the cost of the vehicle and a most appreciable mechanical simplification.

In addition to the hydraulic motors 115 which are integral with the front wheels 102 and drive the latter, and the front power take-off 105, the front section 101a of the chassis carries two batteries 116 and a cooling device 117.

Likewise, apart from the hydraulic motors 115 integral with and driving the rear wheels 103 and the rear power take-off 106, the rear section 101b of the chassis carries a drive unit constituted by an internal combustion engine 118 whose crankshaft is coupled to the input of a coupling box 119 which has three outputs respectively connected to a variable delivery and reversible hydraulic pump 120 for driving the power take-offs and to two units each having a single driving shaft each unit being constituted by a variable delivery and reversible hydraulic pump 121a or 121b for driving the hydraulic motors 115, a booster pump 122, a hydraulic pump 123a or 123b for driving the raising devices described hereinafter and, on one side, a pump 124a driving the hydraulic motor of the fan of the cooling device and, on the other side, a pump 1 24b actuating the jacks 111.

As shown in more detail in Fig. 5, each of the hydraulic power take-offs 105 or 106 comprises a case 125 within which there is disposed a speed-reducing train of gears 126 the input of which is integral with the shaft of a hydraulic motor 127, whereas the output is constituted by a hollow which receives, in two coaxial stepped bores of different diameters, the central splined part of a power take-off shaft 129, the latter being fitted in corresponding splines of the associated bore, and one of the splined ends 129a of this shaft, the other splined end 129b of the latter projecting from the sleeve 128 for connection to a tool to be driven.

As shown in Fig. 6, the two outputs of the reversible pump 120 are connected by pipes 130a and 130b respectively to two inputs of the motors 127 for driving the power takeoffs, whereas the other two inputs of these motors are interconnected by a third pipe 130c, the assembly thereby constituting a closed pipe circuit. Two electrohydraulically actuated hydraulic distributor valves 131a and 131b are interposed, one, between the pipes 130a and 130c and, the other, between the pipes 130b and 130c so as to permit supplying fluid to one or the other of the motors 127 or to both at the same time.

The circuit further comprises two pipes 132a and l32b branch connected to the pipes 1 30b and 1 30c between the distributor valve 131b and the motor 127 and connected to the inputs of an auxiliary hydraulic motor 133 which is adapted to drive one of the tools 133a with which the vehicle is provided, these pipes 132a and 132b having check valves 134 which allow the passage of the fluid only in the direction of the motor.

Stop valves 135 are inserted in the pipes 130b and 130c between the motor 127 and the branch connections of the pipes 132a and 132b.

The pump 120 is supplied with oil, as are moreover the pumps 121a and 121b from an oil tank 136 which is fixed outside on one of the sides of the section 101b of the chassis in front of the rear wheel 103. A fuel tank 137 for supplying fuel to the engine 118 is disposed symmetrically on the other side of this section.

This circuit drives the front and rear power take-offs 105 and 106 either individually or simultaneously in one direction or tEe other and at a variable speed which may reach either of the aforementioned two values, the two power take-offs necessarily rotating at the same speed when they are employed simultaneously owing to the use of a hydraulic control circuit in series.

Such a power take-off driving circuit has the great interest of taking advantage of the presence of a central hydraulic drive for the vehicle constituted by the engine 118, the box 119, the pumps 121a amd 121b and the motors 115 so as to provide a hydraulic power transmission with no difficulty. Such an arrangement uses the same oil tank, the same cooling device and the same filtering means as those already existing in the vehicle drive device.

In addition to the simplicity of construction of this power take-off drive circuit, there is an excellent utilization of these power take-offs owing to the extreme flexibility of use of its component parts and in particular the variable delivery pump.

The vehicle further comprises at each of its two longitudinal ends a hydraulic raising device 138 or 139, two of these devices being provided at each end, one on the left side and the other on the right side. As shown in Figs. 3 and 4, each of these four devices is disposed in a vertical plane parallel to the longitudinal median plane of the vehicle and is constituted by a lower arm 141, an upper arm 140, a stay 142, and a jack 143. The two arms 140 and 141 are mounted at one of their ends on the front face of the section 101a of the chassis to pivot about horizontal transverse axes and respectively in the lower region and upper region of this front face.

The stay 142 is pivoted, on one hand, to the other end of the arm 140 and, on the other hand, to the lower arm 141 in the vicinity of the other end of the lower arm 141, this end being adapted for the fixing of a tool.

The jack 143 is pivoted in the lower region of the front face of the chassis and its upwardly extending rod is pivoted to the arm 140 in the vicinity of the end of the arm 140 which receives the stay 142.

As shown in Fig. 7, the device actuating such a raising device 138 or 139 comprises, on the one hand, a displacement sensor 144 disposed above the upper arm 140 and actuated by the latter in accordance with its displacement, and on the other hand, a pressure sensor 145 inserted in a pipe 146 which connects either of the pumps 121a and 121b to the hydraulic motors 115 of the wheels. The sensor 144 is connected to one of the inputs of an amplifier 147 controlling the position of the raising device, and the sensor 145 is connected to one of the two inputs of another amplifier 148 controlling the force applied to the tool, the other input of the amplifier 147 being connected to a slide of a potentiometer 149 controlling the position and the second input of the amplifier 148 being connected to the slide of a second potentiometer 150 controlling the force, these two potentiometers being disposed in the cab so as to allow the driver to regulate them.

The two outputs of the amplifiers 147 and 148 are connected to the electric control input of a hydraulic distributor valve 151 which is actuated electro-hydraulically and has an input connected to the corresponding raising pump 123a or l23b and two outputs, one of which outputs is connected to the fluid supply of the jack 143 and the other is connected to the oil tank 136.

The pressure sensor 145 delivers a voltage which is proportional to the pressure of the fluid fed to the motors 115 driving the wheels and therefore proportional to the force of resistance applied to these wheels on the part of the tools carried by the vehicle which are either pushed along, if they are secured to the front raising devices 138, or towed if they are secured to the rear raising devices 139. The value of this force is then compared in the amplifier 148 with the value that the driver fed into or set on the force control potentiometer 150. If the value given by the sensor is higher than that set by the driver, the control produces the opening of the distributor valve 151 so as to raise the arms and consequently relieve the towing or pushing force.

When the value given by the sensor once again reaches the control value, the control produces the closure of the distributor valve. As the position chosen for the raising device is thus reached, it is the position control device 149 and the displacement sensor 144 which permit a regulation of the raising by bringing the latter constantly to the previously-determined position. The operation is of course symmetrical in the case where the value given by the sensor 145 is lower than the value set by the driver.

Such a control of the raising devices has the great advantage of benefitting from the presence of a hydraulic drive for driving the driving wheels, in that the force applied to the tools is taken directly from the oil pressure prevailing in the oil supply circuit for the driving motors.

WHAT I CLAIM IS: 1. A tractor vehicle comprising a chassis having a longitudinal axis, at least a front pair of driving wheels and a rear pair of driving wheels supporting the chassis, a cab, means mounting the cab on the chassis and allowing the cab to travel from one end of the vehicle to an opposite end of the vehicle in a direction parallel to said longitudinal axis, an engine and power take-off means carried by the chassis, the power take-off means being for connection to tool means, substantially identical raising devices respectively mounted on the chassis at longitudinally opposed ends of the vehicle, first means for controlling the driving and steering of the vehicle and second means for controlling the raising devices, the first and second means being located inside the cab, two independent drive means, one of the drive means being drivingly connected to two of said wheels located on one lateral side of said longitudinal axis and the other of the drive means being drivingly connected to two of said wheels located on an opposite lateral side of said longitudinal axis, transmission means drivingly connecting the engine to the two drive means, means included in the two drive means to allow the engine to drive selectively either of the drive means, both of the drive means at the same time in a symmetrical manner, or both of the drive means at the same time in an unsymmetrical manner, means included in the two drive means for reversing the drive means so that the vehicle can be made to travel in two opposite directions, a driving station located in the cab and mounted to pivot through at least 1800 about a vertical axis relative to the chassis, whereby irrespective of the direction of travel of the vehicle, the operator of the vehicle can face and be close to the stretch of ground to be treated.

2. A tractor vehicle as claimed in claim 1, wherein each of the two independent drive means comprises a variable delivery and reversible hydraulic pump operating in a closed circuit, the two pumps being connected to two outputs of a coupling box which has a third output for a power takeoff and an input for coupling to the crankshaft of an engine.

3. A tractor vehicle as claimed in claim 2 wherein each raising device is a hydraulic raising device and control means located in the cab are connected to control the hydraulic actuation of the raising device.

4. A tractor vehicle as claimed in any one of the claims 1--3 comprising rails mounted on the chassis and extending in a direction parallel to said longitudinal axis and rollers carried by the cab and rollingly engaged on the rails, means for holding the cab in any chosen position on said rails, the size of the cab being such that positioning the cab at an end of the chassis makes available a loading platform.

5. A tractor vehicle as claimed in any one of claims 14, wherein the cab is movable in translation and the connections between the different driving means of the vehicle are constituted by flexible and elastic pipes which are easily disassembled.

6. A tractor vehicle as claimed in claim 1, wherein there are three pairs of wheels, the front and rear pairs of wheels forming driving and steerable wheels and the third pair of wheels being mounted on the chassis to remain parallel to said longitudinal axis when viewed in plan, each independent driving means driving all the wheels located on the corresponding side of the chassis.

7. A tractor vehicle as claimed in claim 2, wherein its travelling speed is proportional to the deliveries of the pumps.

8. A tractor vehicle as claimed in claim 2, wherein the means are provided whereby front wheels can be declutched on the road.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. connected to the fluid supply of the jack 143 and the other is connected to the oil tank 136. The pressure sensor 145 delivers a voltage which is proportional to the pressure of the fluid fed to the motors 115 driving the wheels and therefore proportional to the force of resistance applied to these wheels on the part of the tools carried by the vehicle which are either pushed along, if they are secured to the front raising devices 138, or towed if they are secured to the rear raising devices 139. The value of this force is then compared in the amplifier 148 with the value that the driver fed into or set on the force control potentiometer 150. If the value given by the sensor is higher than that set by the driver, the control produces the opening of the distributor valve 151 so as to raise the arms and consequently relieve the towing or pushing force. When the value given by the sensor once again reaches the control value, the control produces the closure of the distributor valve. As the position chosen for the raising device is thus reached, it is the position control device 149 and the displacement sensor 144 which permit a regulation of the raising by bringing the latter constantly to the previously-determined position. The operation is of course symmetrical in the case where the value given by the sensor 145 is lower than the value set by the driver. Such a control of the raising devices has the great advantage of benefitting from the presence of a hydraulic drive for driving the driving wheels, in that the force applied to the tools is taken directly from the oil pressure prevailing in the oil supply circuit for the driving motors. WHAT I CLAIM IS:

1. A tractor vehicle comprising a chassis having a longitudinal axis, at least a front pair of driving wheels and a rear pair of driving wheels supporting the chassis, a cab, means mounting the cab on the chassis and allowing the cab to travel from one end of the vehicle to an opposite end of the vehicle in a direction parallel to said longitudinal axis, an engine and power take-off means carried by the chassis, the power take-off means being for connection to tool means, substantially identical raising devices respectively mounted on the chassis at longitudinally opposed ends of the vehicle, first means for controlling the driving and steering of the vehicle and second means for controlling the raising devices, the first and second means being located inside the cab, two independent drive means, one of the drive means being drivingly connected to two of said wheels located on one lateral side of said longitudinal axis and the other of the drive means being drivingly connected to two of said wheels located on an opposite lateral side of said longitudinal axis, transmission means drivingly connecting the engine to the two drive means, means included in the two drive means to allow the engine to drive selectively either of the drive means, both of the drive means at the same time in a symmetrical manner, or both of the drive means at the same time in an unsymmetrical manner, means included in the two drive means for reversing the drive means so that the vehicle can be made to travel in two opposite directions, a driving station located in the cab and mounted to pivot through at least 1800 about a vertical axis relative to the chassis, whereby irrespective of the direction of travel of the vehicle, the operator of the vehicle can face and be close to the stretch of ground to be treated.

9. A tractor vehicle as claimed in claim 2,

wherein the pumps are controlled electrically at the driving station by pedal means and a steering wheel and are reversible so as to cause the vehicle to travel in either direction, each wheel being connected to its respective pump through a double displacement hydraulic motor.

10. A tractor vehicle as claimed in claim 2, wherein the third output of the coupling box is connected to a third hydraulic pump which drives at least one hydraulic motor actuating the power take-off.

11. A tractor vehicle as claimed in claim 10, wherein a speed reducer is interposed between the hydraulic motor actuating the power take-off and the power take-off.

12. A tractor vehicle as claimed in claim 10, wherein the third hydraulic pump drives at least one hydraulic motor actuating a tool provided for the vehicle.

13. A tractor vehicle as claimed in claim 2, wherein each wheel has a hydraulic motor combined therewith to drive the wheel, the hydraulic motor being inserted in said closed circuit of the corresponding independent drive means.

14. A tractor vehicle as claimed in claim 2 comprising, in the vicinity of each of the front and rear pairs of wheels, a hydraulic raising device comprising two upper arms pivoted to the chassis and two lower arms, the upper arms being connected to the lower arms by stays, a position sensor combined with the upper arms, and a pressure sensor is inserted in a hydraulic supply circuit for hydraulic motors driving the driving wheels, said two sensors being connected to an electric 'control unit to which control unit position control means and force control means located in the cab are also connected.

15. A tractor vehicle as claimed in claim 14, wherein the control unit comprises a position amplifier and a force amplifier and the position control means and force control means each comprise a regulating potentiometer.

16. A tractor vehicle as claimed in claim 14, comprising a hydraulic distributor valve actuated by the control unit, which distributor valve controls jacks actuating the raising device.

17. A tractor vehicle as claimed in claim 1, wherein the chassis comprises, in the direction of said longitudinal axis, two chassis sections and pivot means interconnecting the two sections for pivoting about a vertical axis which is offset toward the front of the vehicle with respect to the middle of the length of the vehicle so that one chassis section is longer than the other chassis section, said means mounting the cab on the chassis being mounted on the longer chassis section and extending beyond the longer chassis section to overhang the shorter chassis section.

18. A tractor vehicle as claimed in claim 17, wherein the front section is rotatable by means of at least one hydraulic jack secured to the rear section.

19. A tractor vehicle, substantially as hereinbefore described with reference to and as shown in Figs. 1 and 2 of the accompanying drawings.

20. A tractor vehicle, substantially as hereinbefore described with reference to and as shown in Figs. 3-7 of the accompanying drawings.