GB2296108A

GB2296108A - Control system for a machine hitched to an agricultural tractor

Info

Publication number: GB2296108A
Application number: GB9525318A
Authority: GB
Inventors: Christophe Godreau; Gerard Lucas
Original assignee: Lucas G SA
Current assignee: Lucas G SA
Priority date: 1994-12-13
Filing date: 1995-12-12
Publication date: 1996-06-19
Anticipated expiration: 2015-12-12
Also published as: GB9525318D0; GB2296108B; FR2727821A1; DE19546201A1; DE19546201C2; FR2727821B1

Description

i 2296108 CONTROL SYSTEM FOR A MACHINE EQUIPPED WITH SEVERAL HYDRAULIC

DRIVE MEMBERS, THIS MACHINE BEING HITCHED TO AN AGRICULTURAL TRACTOR The present invention relates to a control system for a machine temporarily hitched to an agricultural tractor in particular and more particularly a machine which includes several hydraulic members of the type comprising cylinders and motors, which can be actuated separately or together.

For some, relatively simple, machines provided with a small number of hydraulic members, the control of the said members may be accomplished directly from the tractor. Hoses convey the hydraulic fluid between the control system and the machine, the number of hoses is depending on the number of members on the machine.

For more complicated machines, that is to say those provided with a large number of hydraulic members, it is common practice to fit a control box on the machine, this being placed on the latter so as to be accessible by the operator from the cabin of the tractor.

A device of this kind is especially described in document PR-A-2,652,706.

This position of the box means that the operator has to keep a cabin open and adopt a position which very quickly becomes uncomfortable.

In addition, this control system includes, for complicated machines, a multitude of levers which actuate, via valves, each of the various hydraulic m emb era of the machine. Each lever operates a hydraulic cylinder or member, for example of the drive type. The operator must memorize the function of each of these levers.

The present invention provides a control system which makes it possible to dispense with the multitude of levers, thus preventing the operator from having to memorize, for each type of machine, the function of each lever.

The control system according to the invention also enables the operator to remain seated on his seat, without having to perform contortions or to adopt dangerous positions. This system also has the advantage of being easily f itted to various types of machines or to the presence of options on these machines.

According to the invention, the control system is fitted to a machine temporarily hitched to an agricultural tractor in particular, which machine comprises hydraulic members of the kind comprising cylinders and motors, the functions of which make it possible to set up various tasks, such as, for example in the case of a silage unloader- distributer, filling the skip, mixing products in the skip and distributing these products; this control system comprises:

- means which are attached to the machine, in the is operator's sight, in the form of a synoptical screen or panel on which are suitably represented and illustrated, grouped into modules according to the tasks to be carried out, all the said operational and controllable hydraulic members of the machine; - means, at the said operator's disposal, in the form of a selection device, for selecting on the said panel, the hydraulic member or members to be operated for the purpose of accomplishing a tank, which selection device is equipped with at least two selection contactors operating in a closed cycle of the scrolling-menu kind, one of the contactors allowing selection of the appropriate module and the other contactor allowing selection, within the chosen module, of a function in order to carry out, by means of a hydraulic member, the task or tasks attached to the said chosen module; - electronic means fitted onto the machine and connected to the selection device in order, on the one hand, to display on the said panel tasks and functions selected and, on the other hand, to control the electro- hydraulic component or components which are brought together into a hydraulic directional control unit and which are responsible for supplying the hydraulic member or members selected for accomplishment of the said tasks and functions; 3 - - means located on the tractor, at the operator's disposal, for operating the hydraulic member or members selected, that is to say for supplying them with pressurized f luid.

According to a preferred arrangement of the invention, the selection device consists of a multipurpose handle which is associated, on the tractor, with means for operating the member or members selected, which operating means consist of a lever used to control a double-acting directional control valve situated downstream of a hydraulic power unit, either on the tractor or on the machine, which directional control valve is interposed between the said power unit and the solenoid-operated hydraulic components assembled in the is hydraulic directional control unit located on the machine.

Still according to the invention, the electronic means consist, for example, of a microprocessor associated with a program which is adapted to the machine and, in particular to the various functions which can be performed on this machine, which electronic means receive and process, depending on the program, the pulses coming especially from the multipurpose handle.

Still according to the invention, the double- acting directional control valve is placed either on the tractor, connected by means of hoses to the hydraulic directional control unit situated on the machine, or directly to the machine, connected to the control lever via appropriate means and supplied by the hydraulic power unit of the tractor or that of the machine.

By using the hydraulic power unit of the tractor and the double-acting directional control valve which quite often forms part of the standard equipment, the control system does not require any expensive equipment to be fitted onto the tractor; all that is required to be fitted is a multipurpose handle, which is associated with the lever of the said directional control valve, and an electrical connection.

still according to the invention, the multipurpose handle includes one or two additional contactors which make it possible to actuate or vary parameters on some members, like the speed of rotation of a hydraulic motor for example.

According to another arrangement of the invention, the control system comprises a console fitted onto the machine, enabling the operator to carry out particular operations once fitted onto the said machine which console is activated beforehand by means of the multipurpose handle located on the tractor and is displayed on the synoptical control panel, which control panel also displays the various operations carried out from the said console; which console allows operation of the hydraulic members selected by acting directly on the is hydraulic directional control unit which is supplied with pressurized fluid by means of the double-acting directional control valve which is blocked by appropriate means in one or other of its active positions.

Still according to the invention, the hydraulic directional control unit preferably comprises a unit called the flow- diverting unit which groups together solenoid valves, and it may also comprise, depending on the type of machine, a bypass unit interposed between the double-acting directional control valve and the said flow-diverting unit, which bypass unit makes it possible to operate two members of the machine simultaneously using the single control lever of the double-acting directional control valve.

Still according to the invention, the bypass unit allowing simultaneous supply of a particular member includes means interposed between the inlet of the double-acting directional control valve and a second double-acting directional control valve situated upstream of the flow-diverting assembly and, moreover, a solenoid- operated directional control valve of the 4/2 type which makes it possible, in the rest position, to establish a return circuit for the various members supplied by the flow-diverting unit and, in the active position, on the one hand to close the simultaneous-supply circuit and on the other hand to bring the two double-acting directional control valves into communication.

According to another arrangement of the invention, the simultaneoussupply circuit includes a motoroperated flow regulator which enables, for example, the speed of rotation of a member of the hydraulic motor type to be varied at will, which regulator is mounted in parallel with a check valve which allows operation of the said motor in one direction with speed regulation and in 10 the other direction without speed regulation.

The invention will be explained in more detail with the aid of the following description and of the appended drawings given by way of indication, and in which:

- Figure 1 represents, in diagrammatic form, all the means which may be involved in the control system according to the invention; - Figure 2 represents a model of a synoptical or pictogram control panel; Figure 3 represents, diagrammatically, the components involved in the hydraulic directional control unit; - Figure 4 represents, in a diagrammatic way, the electronic unit and its various connections.

Figure 1 is divided into two areas: a first area, Identified by 1, which symbolizes the part specific to the tractor and a second area, identified by 2, which symbolizes the part corresponding to the machine.

This machine 2 may include several hydraulic members 3 such as, for example, single-acting or doubleacting cylinders 4, or one or more hydraulic motors 5, etc.

These various members are connected to a hydraulic unit 6 by means of hoses 7 for the single- acting cylinder, hoses 8 for the double-acting cylinder, hoses 9 for the hydraulic motor 5 and hoses 10 for the supply of other members, depending on the type of machine.

This hydraulic unit, explained in detail later in Figure 3, contains hydraulic components. It Is connected to a double-acting directional control valve 17 which is, in Figure 1, located on the tractor 1. This directional control- valve 17 is itself supplied by the hydraulic power unit of the tractor, this unit including especially the pump 18.

The double-acting hydraulic directional control valve Is connected to the hydraulic directional control unit 6 by means of two hoses 19 and 20, each of which include a coupling 21 situated on the tractor, for example on a panel, not shown, located at the rear of the said tractor.

The double-acting directional control valve 17 may also be located on the machine 2, supplied either by the hydraulic power unit 18 of the tractor or by means of a hydraulic power unit situated on the said machine.

The double-acting directional control valve 17 is controlled, wherever it is situated, by means of a lever 22 which in on the tractor 1, in the cabin, within the operator's reach. An appropriate connection, whether mechanical, electrical or of another type, is interposed between this lover 22 and the double-acting directional control valve.

In its upper part, this lever 22 includes a handle 23 of the multipurpose type, which groups together contactors 24. This handle 23 in fixed to the lever 22 by any appropriate means.

Moving the lever 22 forwards by the handle 23, as shown by the arrow F, or rearwards, as shown by the arrow R, makes it possible to operate the double-acting direc tional control valve 17 and to send the hydraulic fluid in one direction or the other, towards the directional control unit 6. This directional control unit 6 supplies the various members 3, thereby enabling, for example, cylinders to be operated in one direction or the other and to cause the motor 5 to rotate in one direction or the other.

The hydraulic directional control unit 6 is also connected, via an electronic unit 26, to the multipurpose 7 - handle 23.

The various contactors 24 located on the handle 23 control, by means of the electronic unit 26, the directional control unit 6 in order to activate the solenoid- operated hydraulic component or components which will enable at least one of the members 3 to be supplied and operated by means of the directional control valve 17.

This selection of the members 3 is made by means of the contactors 24 which will be explained in detail later in conjunction with the other figures.

The electronic unit 26 is connected to the handle 23 by means of a conductor 27 which is equipped with a connector 28 located, for example, on the rear panel of is the tractor 1. This connector 28 may include, on the tractor aide, a conductor 29 connected to the storage battery 30 of the tractor in order to power the elec tronic unit 26.

The electronic unit 26, explained in detail later in Figure 4, serves as interface between the handle 23 and a control panel 31 preferably situated on the machine, but possibly, depending on the case, situated on the tractor. It also serves as interface between the multipurpose handle 23 and the hydraulic directional control unit 6 by means of a conductor 32.

The control panel 31 is a synoptical control panel, or pictogram; it provides the operator with all the information about the machine and the members of this machine by means of indicator lamps or other signalling devices. This control panel is shown in more detail in Figure 2.

Thus, in order to operate the machine 2 from the tractor 1, the operator uses a multipurpose handle 23 from which, by means of the contactors 24, he may select the hydraulic member or members to be operated in order to perform a particular task. The operator selects the member or members on the control panel 31 by means of the contactors 24 on the handle 23, using a conventional scrolling-menu technique.

- a - Having made his selection, the operator controls the lever 22 by means of the handle 23, in the direction of the arrow P of R, in order to operate the member 2 selected.

In order to select other members, the operator must act on the contactors 24 on the handle 23 and then move the lever 22 forwards or rearwards.

The handle 23 and the control panel 31 are geographically or physically separate from each other.

The control panel 31 is attached to the machine 2; it enables the operator to have an overall view of the operating members of the machine, thus monitoring the execution of the operations.

Figure 1 also shows a control console 35, present here in the form of an option. This console 35 is connected via a conductor 36 to the electronic unit 26. This console 35 is fitted onto the machine 2; it enables the operator to act on the machine in order to carry out particular operations. This console 35 is switched on or off by means of the handle 23. It forms part of the selection which is displayed on the control panel 31. This console 35 is a substitute for the handle 23 in order to control certain hydraulic members of the machine. In order to allow supply of the hydraulic directional control unit 6, the lever 22 is locked in one of its positions, according to the arrow F or R, and fluid is distributed by means of the unit 6, controlled from the console 35.

Figure 2 shows a model of the synoptical control panel 31 which may be found on an agricultural machine used, for example, for feeding cattle. This machine, which is like that described in the document FR-A 2,671,460, enables several types of operation or task to be carried out, such as silage -unloading operations, that is to say the removal of products from a silo in order to load the skip of the machine, and product-mixing operations, in order to homogenize the products put into the skip and/or to mix them with supplementary feeds. This machine also carries out feed distribution operations.

The control panel 31 groups together, in the form of pictograms, these various operations which are grouped into modules. Thus, there is a module 37 corresponding to the product distribution module. This module is contained in a square in the top right of the panel 31. Below this distribution module 37 is a module 38 which corresponds to the operation of loading the skip or of silage unloading.

Below this module 38 is a third module 39 which corresponds to special operations carried out on the machine such as, for example, the orientation of an ejection chute 40, the raising or lowering of the skip 41, the selection of an ejection or recycling operation and the selection of a product-mixing operation.

The loading module 38 includes several functions:

a function which enables the scoop 42 to be tilted forwards or rearwards and a function which enables this scoop to be raised or lowered. This module 38 may also include other functions.

The distribution module 37 illustrates the operation of the apron conveyor 43 lying in the bottom of the skip 41 and which allows the products lying in the latter to be moved forwards. This apron conveyor 43 rotates continuously in order to move the products forwards, by means of the hydraulic motor 5 for example.

The speed of this apron conveyor may be adjusted in order to advance the products in the skip more quickly or more slowly. This function of adjusting the speed of advance is illustrated by means of the hare and the tortoise.

Still within this distribution module 37 may be seen the chute 40, the orientation of which may be varied depending on the place where the products have to be deposited. There is also a mixing function which makes it possible especially to put supplementary feeds of the granule or other type into the skip via a hopper 44.

This control panel 31 includes, for example, indicator lamps consisting of LEDs which indicate to the operator the module selected and, within this module, the function or functions selected. This selection is made by means of the multipurpose handle 23 also shown diagrammatically on the control panel 31. The contactor 51 situated on the top of the handle 23, as shown also in Figure 1 in perspective, enables the control system to be switched on and this switched-on status to be displayed on the control panel 31 by means of the indicator lamp 52. Further pressure on the contactor 51 makes it possible to select, according to a known scrolling-menu procedure, one of the modules 37, 38 or 39, which move past in a closed loop manner. When the module anticipated has been selected, the contactor 53 located on the handle 23 enables functions within the module to be selected.

The contactor 51 also serves to switch of f the control system by maintaining contact for a few seconds.

The operator therefore has one hand on the multipurpose handle 23 and both eyes on the control panel 31 in order to make his choice. Thus, by way of example, the selection of the module 37 is identified by the indicator 54 lighting up, signalling in fact the selection of the apron conveyor 43 advance function. The operation of moving the apron conveyor, in one direction or the other, results from the movement of the handle 23, and of the lever 22 on which it is mounted, in the direction of the arrows P or R.

In order to speed up or slow down the movement of the apron conveyor 43 during distribution, the operator can select the speed-of-advance adjustment function within the module 37 by means of the contactor 53 which, still according to the scrolling-menu procedure, will light up the indicator 55 and initiate this function.

The speed is varied by means of the contactors 56 and 57 situated on the handle 23. These contactors make it possible either to increase or to decrease the speed of rotation of the hydraulic motor 5 and to adjust the rate of distribution of the machine, by acting on a motor-operated flow regulator situated in the hydraulic directional control unit 6, this regulator being discussed later in conjunction with Figure 3.

- 11 Likewise, it is possible to select the ejection chute 40 adjustment/orientation function by means of the contactor 53. This function is indicated by the indicator lamp 58- The chute 40 is adjusted, like the adjustment of the speed of advance of the apron conveyor 43, by means of the contactors 56 and 57, acting on its control cylinder.

Still within this module 37, it is also possible to select the mixing function which makes it possible to put in supplementary feeds. This function is selected by means of the contactor 53 and is indicated by the indicator lamp 59.

In this distribution module 37, it is pointed out that the functions of advancing the apron conveyor 43, with the adjustment of its speed or the orientation of the chute 40 or the additional mixing operation are performed simultaneously.

These operations are possible by means of the hydraulic directional control unit 6 explained in detail in Figure 3. This simultaneous nature of the functions within one module is not found in the modules 38 and 39 where each function is exclusive.

In the loading module 38 for example, the contactor 53 makes it possible to select the tilting movement of the scoop 42, indicated by the indicator lamp 60, or the raising or lowering movement of this scoop, which is indicated by the indicator lamp 61.

When the lamp 60 is lit, the operator can pivot the scoop 42 forwards or rearwards, by acting on the handle 23 and the lever 22 in the direction of the arrows P or R.

When the indicator lamp 61 is lit, the operator, still using the lever 22, can either raise the scoop 42 or lower it. The same principle is found in the module 39 which groups together the various functions explained in detail previously.

It should also be pointed out that there is an indicator lamp 62 on the control panel 31, which lamp indicates to the operator that something is wrong with the control system.

Thus flashing of the indicator lamp 62 may Indicate too low an electrical voltage. This reduction in voltage-may run the risk of malfunction in the hydraulic directional control unit 6 and, in particular, in the solenoid valves. This indicator lamp may also indicate a complete stoppage of the control system in the event of a major drop in voltage leading to a general malfunction.

Figure 3 shows the hydraulic directional control unit 6 which is supplied with hydraulic fluid by the double-acting directional control valve 17 and powered electrically by the electronic unit 26 by means of the conductor 32. This unit 6 consists of a bypass assembly or unit 65 and a flow-diverting assembly or unit 66. The bypass unit 65 comprises hydraulic components which enable the functions to be performed simultaneously, as explained in detail above for the description of the distribution module 37. 20 The flow-diverting unit 66 consists of electrohydraulic components of the type consisting of solenoid valves, solenoid-operated directional control valves or, more simply, a flow diverter, responsible for supplying the members 4. These solenoid valves 67 are assigned to the cylinders for example and are controlled by coils 68 which are excited by the electronic unit 26. The bypass unit 65 comprises a double-acting directional control valve 70 interposed between the flow- diverting unit 66 and the double-acting directional control valve 17. This double-acting directional control valve 70 has coils 71 and 72 which are excited by means of the electronic unit 26, depending on the functions to be performed.

Upstream of this double-acting directional control valve is a solenoid valve 73 of the 4/2 type which, in the rest position as shown in Figure 3, enables the hydraulic motor 5 and the cylinders 4 to be operated simultaneously.

When the solenoid valve 73 is at rest, the double-acting directional control valve 70 enables the movements of the cylinders 4, which are supplied via the flow-diverting unit 66, to be reversed.

When the solenoid valve 73 in activated through the action of its coil 74, which is excited by the electronic unit 26, the hydraulic motor 5 is blocked and the flow-diverting unit 66 is supplied normally through the double-acting directional control valve 70.

This possibility of simultaneously controlling several hydraulic members is most especially advantageous for the distribution module 37. The reason for this is that distribution requires the hydraulic motor 5 to be put into operation in order to advance the apron conveyor 43. This operation results from operating the lever 22 and the directional control valve 17. Another member, such as the cylinder for adjusting the orientation of the chute 40 for example, can be operated only by using the hydraulic power assigned to the hydraulic motor 5. This chute-adjusting cylinder is operated by means of the double-acting directional control valve 70 in one direc tion or the other, without affecting the operation of the motor 5, by acting on the contactors 56 or 57 on the handle 23.

The direction of rotation of the motor 5 is obtained by operating the double-acting directional control valve 17 by means of the lever 22, by moving this lever in the direction of the arrows F or R. It should be pointed out, in the hydraulic diagram, that the speed of rotation of the hydraulic motor in one direction can be controlled by means of a flow regulator 75 located in the line 76 supplying the motor 5. This flow regulator 75 operates in one direction in this supply line 76. In the other direction of rotation of the motor, the regulator 75 is short-circuited by a valve 77 which allows the return of the fluid coming from the motor supplied by the line 78 coming from the solenoid valve 73 when it is in the rest position.

It should be pointed out that, between the two 14 - double-acting directional control valves 17 and 70, there is a direct line 79 and a line 80 which passes through the solenoid valve 73. Between the solenoid valve 73 and the double-acting directional control valve 70, in this line 80, it should be pointed out that there is a valve 81 which prevents circulation of the fluid in the direction going from the said solenoid valve 73 to the doubleacting directional control valve 70 so as to enable the hydraulic motor 5 to be supplied via the line 78 with return via the line 76 and the valve 77.

The speed of the hydraulic motor 5 is adjusted when it is supplied via the line 79 with return via the line 80.

When the solenoid valve 73 is actuated, it establishes the direct line 80 between the two doubleacting directional control valves 17 and 70 and it closes the line 78 extending between the motor 5 and the solenoid valve 73. Thus, when the modules 38 and 39 on the control panel 31 are selected, the motor 5 is stopped.

Figure 4 shows, diagrammatically, the electronic unit 26. This electronic unit 26 comprises, for example, a microprocessor or microcontroller of the RMotorola 68 HC11" type.

This microcontroller 81 is equipped with a program 82 which contains the characteristics of several types of machine.

The electronic unit 26 includes a connection box 83 which receives the conductor 27 coming from the multipurpose handle 23 and, at the same time, the neces- sary electrical power, by means of a socket 84 which is associated with the connector 28. This connection unit 83 also receives optionally the conductor 36 coming from the console 35.

It may also receive conductors 85 connected to various sensors 86, such as position sensors associated with certain items of equipment on the machine for example.

The electronic unit 26 is connected to the control panel 31 via a conductor 87. It may also be built - is - into the control panel, forming a compact assembly fixed to the machine.

This electronic unit 26 also includes a power stage 88 which supplies power by means of the conductor 32 to the electrohydraulic components of the directional control unit 6.

In order to allow the control system to be fitted to any type of tractor, the electronic unit 26 may also include a selection stage 89 which takes into account the type of hydraulic power unit of the tractor, such as a hydraulic power unit of the open-centre or closed-centre type for example. This selection stage consists of a contactor 90 which allows the information to be input to the microprocessor in order consequently to use the is components of the hydraulic directional control unit 6.

Given the great variety of machines, the electronic unit 26 also includes an option selection stage. This selection stage 91 includes, for example,microswitches which enable the programmed options to be input or modified.

This control system in suitable for any type of machine, from the simplest machine to the complicated machine, that is to say comprising a large number of hydraulic members to be controlled separately or together.

When the hydraulic members of the machine are used separately, in an exclusive manner, the directional control unit 6 may only include the flow-diverting unit 66 which is supplied directly via the double-acting directional control valve 17.

In the same way, for some machines such as, for example machines mounted directly by the tractor, the presence of the console 35 is not absolutely necessary. The reason for this console 35 is mainly for use on machines of the semi-mounted type in which it is more practical to carry out the operation of loading the skip from the machine because of better visibility.

When this loading operation is carried out from the console 35, the solenoid valve 73 is actuated in order to supply the double-acting directional control valve 70. This double-acting directional control valve 70 serves t o reverse the movements of the various cylinders used to carry out the loading operation.

It should be pointed out that the double-acting directional control valve 17, which is controlled by the lever 22 and the handle 23, may, in certain cases be a substitute for the solenoid-operated directional control valve 70 of the bypass unit.65.

In the attached claims, reference numerals have been included merely for assisting in understanding the claims and are in no way intended to be limiting.

1

Claims

1. Control system for a machine temporarily hitched to an agricultural tractor in particular, which machine comprises hydraulic members (3) of the kind comprising cylinders (4) and motors (5), the functions of which make it possible to set up various tasks, such as, for example in the case of a silage unloader-distributer, filling the skip, mixing products in the skip and distributing these products, characterized in that this system comprises:

- means which are attached to the machine, in the operator's sight, in the form of a synoptical screen or control panel (31) on which are suitably represented and illustrated, grouped into modules (37, 38, 39) according to the tasks to be carried out, all the said operational is and controllable hydraulic members (3) of the machine; - means, at the said operator's disposal, in the form of a selection device (23), for selecting on the said control panel (31), the hydraulic member or members (3) to be operated for the purpose of accomplishing a task, which selection device (23) is equipped with at least two selection contactors (24) operating in a closed cycle of the scrolling-menu kind, one of the contactors allowing selection of the appropriate module (37, 38, 39) and the other contactor allowing selection, within the chosen module, of a function in order to carry out, by means of a hydraulic member. the task or tasks attached to the said chosen module; - electronic means fitted onto the machine and connected to the selection device (23) in order, on the one hand, to display on the said control panel (31) the tasks and functions selected and, on the other hand, to control the electro-hydraulic component or components which are brought together in a hydraulic directional control unit (6) and which are responsible for supplying the hydraulic member or members (3) selected; - means located on the tractor, at the operator's dis posal, for operating the hydraulic member or members (3) selected, that is to say for supplying them with pressur ized fluid.

2. Control system for a machine hitched to a tractor, according to Claim 1, characterized in that the selection device consists of a multipurpose handle (23), which handle is associated with the means for operating the member or members selected, which means consist of the lever (22) used to control a double-acting hydraulic directional control valve (17) which is interposed between a hydraulic power unit (18) and the hydraulic directional control unit (6) on the tractor or the machine.

3. Control system for a machine hitched to a tractor, according to either of Claims 1 and 2, characterized in that the electronic means consist of a unit (26) comprising, for example, a microprocessor (81) and a program (82) adapted to the various types of machine and, in particular, to the various functions which can be carried out on the machine, the said microprocessor receives and processes, depending on the said program, the pulses coming especially from the multipurpose handle (23) in order to display on the synoptical control panel (31) the function or functions selected and, simultaneously, to actuate the various hydraulic components (solenoid valve, etc.) of the hydraulic directional control unit (6).

4. Control system for a machine hitched to an agricultural tractor according to Claim 2, characterized in that it includes a double-acting directional control valve (17) placed on the tractor and supplied directly via the hydraulic power unit (18) of the said tractor, which tractor includes a connection panel which enables the hydraulic directional control unit (6) of the machine to be supplied by means of hoses.

5. Control system for a machine hitched to an agricultural tractor according to Claim 2, characterized in that it includes a double-acting directional control valve (17) placed on the machine, which directional control valve (17) is associated with the directional control unit (6) and is supplied by means of either a hydraulic power unit (18) fitted to the tractor or a - 19 hydraulic power unit fitted to the machine, which doubleacting directional control valve is remotely controlled via an appropriate means by the lever (22) located on the tractor.

6. Control system for a machine hitched to an agricultural tractor according to any one of Claims 1 to 5, characterized in that the selection device in the form of a multipurpose control handle (23) includes one or two additional contactors (56, 57) which make it possible to actuate or vary the parameters of the hydraulic members like, for example, the speed of rotation of a hydraulic motor.

7.

Control system for a machine hitched to an agricultural tractor according to Claim 6, characterized in that it comprises a control console (35), fitted to the machine, enabling the operator to carry out specific operations directly from the machine, which console (35) is activated beforehand by means of the multipurpose handle (23) located on the tractor, which handle further- more makes it possible to display on.the control panel (31) the selection from the control console (35) which console operates the appropriate hydraulic members by means of an solenoid-operated directional control valve (70) built into the directional control unit (6) and by means of solenoid valves associated with the said members, which solenoid- operated directional control valve (70) is supplied via the double-acting directional control valve (17) blocked in any way whatsoever in the active positive, for example by means of its lever (22).

8. Control system for a machine hitched to a tractor, according to any one of Claims 1 to 7, characterized in that the hydraulic directional control unit (6) consists of a flow-diverting assembly or unit (66), enabling each hydraulic member of the machine to be supplied individually, and, depending on the machine, a bypass assembly or unit (65) enabling two functions of the machine to be performed simultaneously.

9. Control system for a machine hitched to a tractor according to Claim 8, characterized in that the bypass unit (65) Includes means which enable several members of the machine to be operated simultaneously, which unit comprises, interposed between the inlet of the doubleacting directional control valve (17) and a double- acting solenoid-operated directional control valve (70) supplying the flow-diverting unit (66), a solenoidoperated directional control valve (73) which makes it possible, in the rest position, to establish a return circuit for the various members of the machine, as well as the supply of a member capable of operating simultaneously with one of the other members of the machine, and, in the active position, on the one hand to close the simultaneous -supply circuit and on the other hand to bring the two double-acting directional control valves (17 and 70) into communication.

10. Control system for a machine hitched to a tractor according to Claim 9, characterized in that the bypass unit (65) includes, on the supply circuit for the additional member (hydraulic motor driving the apron conveyor), a motor-operated flow regulator (75) which enables the speed of rotation of the said member to be varied at will, which flow regulator in mounted in parallel with a check valve (77) which allows operation of the said motor in one direction with speed regulation and in the other without speed regulation, which circuit is designed so as to allow, simultaneously with the speed regulation, supply of other members of the machine which are capable of being selected simultaneously with the said member subjected to the speed regulation.

11. Control system for a machine temporarily hitched to an agricultural tractor, substantially as hereinbefore described with reference to the accompanying drawings.