EP0119884B1 - Processus and circuit for controlling a motor with a safety brake - Google Patents

Description

• ledit moteur,
• ledit frein, comprenant un vérin muni d'une chambre de défreinage, et, un ressort de freinage,
• une source principale de fluide sous pression,
• un distributeur principal de fluide, interposé entre le moteur et la source principale de fluide sous pression,
• au moins un organe de pilotage du distributeur principal de fluide, attelé à celui-ci, apte à placer le distributeur principal de fluide dans une position de mise en communication du moteur avec la source principale de fluide, à partir d'une position de non-alimentation du moteur en fluide,
• une source de fluide de pilotage,
• un distributeur de défreinage disposé sur une liaison reliant la source de fluide de pilotage à la chambre de défreinage du vérin du frein et apte à réaliser, soit la continuité, soit l'interruption de cette liaison et la mise en communication de la chambre de défreinage avec un échappement sans pression, et,
• un manipulateur disposé sur une liaison reliant une source de fluide de pilotage audit au moins un organe de pilotage, du distributeur principal.

In the field of power transmissions, there are already known control circuits for a pressurized fluid motor associated with a spring-loaded safety brake, the rest configuration of which is that of braking, consisting of:

• said motor,
• said brake, comprising a jack provided with a brake release chamber, and, a braking spring,
• a main source of pressurized fluid,
• a main fluid distributor, interposed between the engine and the main source of pressurized fluid,
• at least one control member of the main fluid distributor, coupled to it, capable of placing the main fluid distributor in a position for placing the engine in communication with the main source of fluid, from a position of no -feeding the engine with fluid,
• a source of pilot fluid,
• a brake release distributor arranged on a link connecting the source of control fluid to the brake release chamber of the brake jack and capable of producing either continuity or the interruption of this connection and the communication of the brake release chamber with an exhaust without pressure, and,
• a manipulator disposed on a link connecting a source of pilot fluid to said at least one pilot member of the main distributor.

These safety brakes are often emergency brakes, which have a relatively fragile constitution. It is therefore advisable to avoid commanding the starting of the engine before the release of the brake, which would be incapable of supporting without damage the driving forces of the engine.

What is observed with a hydraulic motor is moreover a more general phenomenon than that of hydraulic alone. This is why the invention relates firstly to a method of controlling an engine associated with a safety brake, the rest configuration of which is that of braking, according to which, on the one hand, the starting is controlled. on the other hand, the brake release, only ordering the engine to start as soon as possible when the brake release is ordered.

According to this method, when a new braking is ordered, this is carried out in a timed fashion after the engine has been stopped.

The advantageous arrangement below is also preferably adopted: when the motor is at variable speed and capable of being selectively placed in low and high speed configuration, by commanding a new braking, the selection is automatically controlled of the low engine speed.

The invention also relates to a fluid motor control circuit, such as that defined above and in which said link on which the manipulator is arranged comprises a conduit for supplying the manipulator with pilot fluid which is connected to the part of said connection on which the brake release distributor is disposed between this brake release distributor and the brake release cylinder.

• une restriction est disposée sur la partie de la liaison reliant le distributeur de défreinage à la chambre de défreinage du vérin de frein, cependant qu'un conduit de by-pass est raccordé à ladite partie de cette liaison de part et d'autre de la restriction, un clapet de non-retour étant placé sur ce conduit de by-pass et permettant le passage du fluide du distributeur de défreinage vers la chambre de défreinage;
• le moteur étant à cylindrée variable et muni d'un sélecteur à fluide de sa cylindrée susceptible de placer ledit moteur en configuration d'une grande et d'une petite cylindrées, en étant mis en communication avec un échappement sans pression lors du choix de ladite grande cylindrée, ledit sélecteur à fluide est relié par un conduit à la partie de ladite liaison sur laquelle est disposé le distributeur de défreinage comprise entre ce distributeur de défreinage et le vérin de défreinage.
• Les avantages des dispositions précédemment définies sont les suivants:
• on constate, tout d'abord, l'existence d'une séquence de commande qui ne permet la mise en marche du moteur, quel que soit son type, que lorsque le défreinage a été commandé; le risque de commander l'entraînement par le moteur alors que le frein est encore serré, a donc été supprimé;
• il est bien entendu nécessaire de protéger le frein lorsqu'à partir de la configuration «marche» du moteur, on en commande l'arrêt; la temporisation avantageusement prévue séparant le refrei- nage de la commande d'arrêt du moteur réalise cette protection;
• enfin, lorsque le moteur possède au moins une petite et une grande cylindrée, ou encore une grande et une petite vitesse d'entraînement, il est intéressant au moment de commander l'arrêt de ce moteur, de le replacer automatiquement sur sa petite vitesse d'entraînement ou sa grande cylindrée, respectivement, afin d'obtenir le couple de freinage maximal.

Advantageously:

• a restriction is placed on the part of the link connecting the brake release valve to the brake release chamber of the brake cylinder, while a by-pass duct is connected to said part of this link on either side of the restriction, a non-return valve being placed on this by-pass duct and allowing the passage of the fluid from the brake release valve to the brake release chamber;
• the engine being of variable displacement and provided with a fluid selector of its displacement capable of placing said engine in the configuration of a large and a small displacement, by being placed in communication with an exhaust without pressure when choosing said large displacement, said fluid selector is connected by a conduit to the part of said connection on which is arranged the brake release valve comprised between this brake release valve and the brake release cylinder.
• The advantages of the previously defined provisions are as follows:
• we note, first of all, the existence of a control sequence which does not allow the engine to start, whatever its type, until the brake release has been ordered; the risk of controlling the drive by the motor while the brake is still applied has therefore been eliminated;
• it is of course necessary to protect the brake when, from the "running" configuration of the engine, it is stopped; the advantageously provided time delay separating the braking from the engine stop command achieves this protection;
• Finally, when the motor has at least a small and a large displacement, or even a large and a small driving speed, it is advantageous when ordering the stopping of this motor, to automatically replace it on its low speed d drive or its large displacement, respectively, in order to obtain the maximum braking torque.

The invention will be better understood, and secondary characteristics and their advantages will appear during the description of an embodiment given below by way of example.

It is understood that the description and the drawings are given for information only and are not limiting.

• la fig. 1 constitue le schéma d'un circuit hydraulique conforme à l'invention, et,
• les fig. 2 et 3 définissent les constitutions schématiques détaillées de deux sous-ensembles de la fig. 1.

Reference will be made to the accompanying drawings, in which:

• fig. 1 constitutes the diagram of a hydraulic circuit according to the invention, and,
• fig. 2 and 3 define the detailed schematic constitutions of two subsets of FIG. 1.

• deux moteurs hydrauliques 1 et 2, réversibles, à chacun deux cylindrées distinctes, munis de sélecteurs 3, 4 de sélection de la cylindrée,
• deux pompes principales 5, 6,
• un réservoir de fluide 7,
• une pompe de fluide de pilotage 8,
• un ensemble 9 de deux manipulateurs,
• des freins de sécurité 10, 11, correspondant aux moteurs 1, 2, munis de vérins de défreinage 12, 13, ayant chacun un ressort de freinage 14, 15, et une chambre de défreinage 16, 17 susceptible de contenir un fluide d'effet antagoniste de celui des ressorts 14, 15, respectivement,
• un distributeur de fluide de défreinage 18, à deux positions, attelé à un électro-aimant 19 apte à le placer dans sa deuxième position, et à un ressort 20 d'effet antagoniste, le rappelant dans sa première position,
• un distributeur 21 de commande des cylindrées des deux moteurs, à deux positions, attelé à un électro-aimant 22 apte à le placer dans sa première position, et à un ressort 23 d'effet antagoniste, le rappelant dans sa deuxième position,
• deux distributeurs principaux de fluide 24, 25 à chacun trois positions attelés, le distributeur 24, à deux vérins 26, 27 de réglage de sa position, d'effets antagonistes, aptes à placer ce distributeur 24 dans ses première, respectivement troisième positions, et à des ressorts de rappel 28 aptes à rappeler le distributeur dans sa deuxième position, et, le distributeur 25, à deux vérins 29, 30 de réglage de sa position, d'effets antagonistes, aptes à placer ce distributeur 25 dans ses première, respectivement troisième positions, et à des ressorts de rappel 31 aptes à rappeler le distributeur dans sa deuxième position.

The circuit shown includes:

• two hydraulic motors 1 and 2, reversible, each with two separate displacements, provided with selectors 3, 4 for selecting the displacement,
• two main pumps 5, 6,
• a fluid reservoir 7,
• a pilot fluid pump 8,
• a set 9 of two manipulators,
• safety brakes 10, 11, corresponding to motors 1, 2, provided with brake release cylinders 12, 13, each having a brake spring 14, 15, and a brake release chamber 16, 17 capable of containing an effect fluid antagonist of that of the springs 14, 15, respectively,
• a brake release fluid distributor 18, with two positions, coupled to an electromagnet 19 able to place it in its second position, and to a spring 20 of antagonistic effect, returning it to its first position,
• a distributor 21 for controlling the displacement of the two motors, with two positions, coupled to an electromagnet 22 capable of placing it in its first position, and to a spring 23 of antagonistic effect, recalling it to its second position,
• two main fluid distributors 24, 25 at each three coupled positions, the distributor 24, with two jacks 26, 27 for adjusting its position, with antagonistic effects, capable of placing this distributor 24 in its first, respectively third positions, and to return springs 28 capable of returning the distributor to its second position, and, the distributor 25, to two jacks 29, 30 for adjusting its position, of antagonistic effects, capable of placing this distributor 25 in its first, respectively third positions, and return springs 31 capable of returning the dispenser to its second position.

• le conduit 32 d'aspiration de la pompe principale 5 relie cette pompe au réservoir 7,
• un conduit 33 relie ce distributeur principal 24 au réservoir 7,
• le conduit de refoulement 44 de la pompe 5 la relie au distributeur principal 24,
• deux conduits 34, 35 relient le distributeur principal 24 aux raccords principaux 36, 37 du moteur 1,
• le conduit 38 d'aspiration de la pompe principale 6 relie cette pompe au réservoir 7,
• un conduit 39 relie ce distributeur principal 25 au réservoir 7,
• le conduit de refoulement 45 de la pompe 6 la relie au distributeur principal 25,
• deux conduits 40, 41 relient le distributeur principal 25 aux raccords principaux 42, 43 du moteur 2,
• des conduits 46, 47, 48, 49 sont raccordés aux conduits 34, 35, 40, 41, respectivement, et sont eux-mêmes reliés au réservoir 7, les conduits 46 et 47, par l'intermédiaire de deux autres conduits 50 et 51, et, les conduits 48 et 49, par l'intermédiaire d'un conduit 52 et du conduit 51, cependant que des clapets de décharge tarés 53, 54, 55, 56 sont disposés sur lesdits conduits 46, 47, 48, 49, respectivement,
• le conduit d'aspiration 57 de la pompe 8 relie celle-ci au réservoir 7,
• le conduit de refoulement 58 de la pompe 8 relie celle-ci au distributeur 18,
• deux conduits 59, 60 relient les chambres de défreinage 16, 17, respectivement, à un même conduit 61, lui-même raccordé au distributeur 18, cependant qu'une restriction 64 est disposée sur le conduit 61, et qu'un conduit de by-pass 65 est raccordé au conduit 61 de part et d'autre de la restriction 64, un clapet de non-retour 66 étant placé sur le conduit de by-pass 65 et permettant le passage du fluide du distributeur 18 vers les conduits 59 et 60,
• un conduit 62 relie ce distributeur 18 au réservoir 7,
• un conduit 63 relie la partie du conduit 61 comprise entre le distributeur 18 et la restriction 64 au distributeur 21,
• deux conduits 67, 68 relient les sélecteurs de cylindrées 3, 4, respectivement, à un même conduit 69, lui-même relié au distributeur 21,
• un conduit 70 relie ce distributeur 21 au réservoir 7,
• un conduit 71 est raccordé à la partie du conduit 61 comprise entre le distributeur 18 et la restriction 64,
• deux conduits 72, 73 relient l'ensemble 9 de manipulateurs à ce conduit 71,
• un conduit général de retour 74 relie l'ensemble 9 de manipulateurs au réservoir 7,
• des conduits 75, 76, 77, 78 relient, respectivement, les vérins de pilotage 26, 27, 29, 30 audit ensemble 9 de manipulateurs.

These various elements are connected by the following conduits:

• the suction pipe 32 of the main pump 5 connects this pump to the tank 7,
• a duct 33 connects this main distributor 24 to the reservoir 7,
• the discharge duct 44 of the pump 5 connects it to the main distributor 24,
• two conduits 34, 35 connect the main distributor 24 to the main connections 36, 37 of the engine 1,
• the suction pipe 38 of the main pump 6 connects this pump to the tank 7,
• a conduit 39 connects this main distributor 25 to the reservoir 7,
• the discharge duct 45 of the pump 6 connects it to the main distributor 25,
• two conduits 40, 41 connect the main distributor 25 to the main connections 42, 43 of the engine 2,
• conduits 46, 47, 48, 49 are connected to conduits 34, 35, 40, 41, respectively, and are themselves connected to the reservoir 7, conduits 46 and 47, via two other conduits 50 and 51 , and, the conduits 48 and 49, via a conduit 52 and the conduit 51, while tared discharge valves 53, 54, 55, 56 are disposed on said conduits 46, 47, 48, 49, respectively,
• the suction duct 57 of the pump 8 connects the latter to the reservoir 7,
• the discharge conduit 58 of the pump 8 connects the latter to the distributor 18,
• two conduits 59, 60 connect the brake release chambers 16, 17, respectively, to the same conduit 61, itself connected to the distributor 18, while a restriction 64 is arranged on the conduit 61, and that a bypass conduit -pass 65 is connected to the conduit 61 on either side of the restriction 64, a non-return valve 66 being placed on the by-pass conduit 65 and allowing the passage of the fluid from the distributor 18 towards the conduits 59 and 60,
• a conduit 62 connects this distributor 18 to the reservoir 7,
• a conduit 63 connects the part of the conduit 61 between the distributor 18 and the restriction 64 to the distributor 21,
• two conduits 67, 68 connect the displacement selectors 3, 4, respectively, to the same conduit 69, itself connected to the distributor 21,
• a conduit 70 connects this distributor 21 to the reservoir 7,
• a conduit 71 is connected to the part of the conduit 61 between the distributor 18 and the restriction 64,
• two conduits 72, 73 connect the assembly 9 of manipulators to this conduit 71,
• a general return duct 74 connects the assembly 9 of manipulators to the reservoir 7,
• conduits 75, 76, 77, 78 connect, respectively, the control cylinders 26, 27, 29, 30 to said set 9 of manipulators.

Of course, the electromagnets 19, 22 are connected, by electrical connections 79, 80 on which are arranged control switches 81, 82 (or alternatively, manually operated selectors, respectively, to an energy source electric 83).

The detail of the assembly 9 of manipulators is shown diagrammatically in FIG. 2. This assembly comprises two groups 84, 85 of each two handling valves 86, 87 and 88, 89.

The valves 86, 87 are coupled, on the one hand, by springs 90 to the same control lever 91, pivotally mounted (92), on the other hand, to elements of effects antagonistic to those of the springs 90: it these are springs 93, and jacks 94, 95 connected, by conduits 96, 97 to conduits 75, 76, themselves connected to said valves 86, 87, respectively. Conduits 98, 99 connect the valves 86, 87 to the conduit 72, while the conduit 74 is connected to the valve 86 and that a conduit 100 connects the valve 87 to the conduit 74.

The valves 88, 89 are coupled, on the one hand, by springs 101 to the same control lever 102, pivotally mounted (103), on the other hand, to elements of effects antagonistic to those of the springs 101: it these are springs 104, and cylinders 105, 106 connected, by conduits 107, 108 to conduits 77, 78, themselves connected to said valves 88, 89, respectively. Conduits 109, 110 connect the valves 88, 89 to the conduit 73, while conduits 111, 112 connect these valves 88, 89 to the conduit 74, respectively.

Fig. 3 schematically represents the constitution of the reversible motor 1 with two separate displacements and of its selector 3 of displacements. This type of engine is known in itself, being described, for example in French patent n ° 1460752. It should also be noted that other embodiments exist such as in particular those of continuously variable displacement engines, of the type with axial pistons resting on an inclined plate with adjustable inclination. The motor 1 can be represented as being constituted by two motors 1 a, 1 b provided with main connections 36a, 37a and 36b, 37b. Conduits 113, 114 connect the conduit 34 to the connectors 36a, 36b, while conduits 115, 116 connect the conduit 35 to the connector 37a and to a two-position distributor 117, respectively. Two conduits 118, 119 connect the conduit 114 (and the connector 36b) and the connector 37b to the distributor 117. Furthermore, a pilot cylinder 120 is coupled to the distributor 117, as well as a return spring 121 of antagonistic effect, the conduit 67 being connected to the jack 120.

• la première position, aux mises en communication des conduits 44 et 34, et, des conduits 35 et 33;
• la deuxième position, à la mise en communication des conduits 44 et 33, et, à l'obturation des conduits 34 et 35; et,
• la troisième position, aux mises en communication des conduits 44 et 35, et, des conduits 34 et 33.

The three positions of the distributor 24 correspond:

• the first position, when the conduits 44 and 34 are put into communication, and, the conduits 35 and 33;
• the second position, when the conduits 44 and 33 are placed in communication, and when the conduits 34 and 35 are closed; and,
• the third position, at the connections between conduits 44 and 35, and, conduits 34 and 33.

• la première position, aux mises en communication des conduits 45 et 40, et, des conduits 41 et 39;
• la deuxième position, à la mise en communication des conduits 45 et 39, et, à l'obturation des conduits 40 et 41; et,
• la troisième position, aux mises en communication des conduits 45 et 41, et, des conduits 40 et 39.

The three positions of the distributor 25 correspond:

• the first position, when the conduits 45 and 40 are put into communication, and, conduits 41 and 39;
• the second position, when the conduits 45 and 39 are placed in communication, and when the conduits 40 and 41 are closed; and,
• the third position, at the connections between conduits 45 and 41, and, conduits 40 and 39.

• la première position, à la mise en communication des conduits 61 et 62, et, à l'obturation du conduit 58; et,
• la deuxième position, à la mise en communication des conduits 58 et 61, et, à l'obturation du conduit 62.

The two positions of the distributor 18 correspond:

• the first position, when the conduits 61 and 62 are put into communication, and when the conduit 58 is closed; and,
• the second position, when the conduits 58 and 61 are placed in communication, and, when the conduit 62 is closed.

• la première position, à la mise en communication des conduits 63 et 69, et, à l'obturation du conduit 70; et,
• la deuxième position, à la mise en communication des conduits 69 et 70, et, à l'obturation du conduit 63.

The two positions of the distributor 21 correspond:

• the first position, when the conduits 63 and 69 are placed in communication, and when the conduit 70 is closed; and,
• the second position, when the conduits 69 and 70 are placed in communication, and when the conduit 63 is closed.

• la première position, à la mise en communication des conduits 116 et 119; à l'obturation du conduit 118; à la prépondérance de l'effet du ressort 121; et, au branchement en parallèle des moteurs 1a et 1b, donc également au fonctionnement du moteur 1 avec sa plus grande cylindrée, donc à sa plus petite vitesse; et,
• la deuxième position, à la mise en communication des conduits 118 et 119; à l'obturation du conduit 116; à la prépondérance de l'effet du vérin 120; et, finalement à la mise en court-circuit du moteur 1 b; donc au fonctionnement du moteur 1 avec sa plus petite cylindrée; donc à sa plus grande vitesse.

The two positions of the distributor 117 correspond:

• the first position, when the conduits 116 and 119 are put into communication; closing the conduit 118; the preponderance of the effect of spring 121; and, in parallel connection of the motors 1a and 1b, therefore also in the operation of the motor 1 with its larger displacement, therefore at its lower speed; and,
• the second position, when the conduits 118 and 119 are put into communication; closing the conduit 116; the preponderance of the effect of the jack 120; and finally when the motor 1b is short-circuited; therefore when the engine 1 operates with its smallest displacement; so at its highest speed.

• dans sa première position, la valve 86 met en communication les conduits 75 et 98, et obture l'extrémité du conduit 74 qui y est raccordée; il lui correspond la deuxième position de la valve 87, qui réalise la mise en communication des conduits 76 et 100, et, l'obturation du conduit 99;
• l'absence d'action sur le levier 91 font se correspondre les deuxièmes positions des valves 86 et 87, la deuxième position de la valve 86 réalisant la mise en communication des conduits 75 et 74, et, l'obturation du conduit 98;
• la première position de la valve 87, qui réalise la mise en communication des conduits 99 et 76, et, l'obturation du conduit 100, est obtenu en même temps que la deuxième position, déjà définie, de la valve 86.

The valves 86 and 87 each have two positions which are obtained in combination with the single lever 91, and which correspond as follows:

• in its first position, the valve 86 communicates the conduits 75 and 98, and closes the end of the conduit 74 which is connected thereto; the second position of the valve 87 corresponds to it, which brings the conduits 76 and 100 into communication, and the obturation of the conduit 99;
• the absence of action on the lever 91 makes the second positions of the valves 86 and 87 correspond, the second position of the valve 86 bringing the conduits 75 and 74 into communication, and the obturation of the conduit 98;
• the first position of the valve 87, which brings the conduits 99 and 76 into communication, and the obturation of the conduit 100 is obtained at the same time as the second position, already defined, of the valve 86.

• dans sa première position, la valve 88 met en communication les conduits 77 et 109, et obture l'extrémité du conduit 111; il lui correspond la deuxième position de la valve 89, qui réalise la mise en communication des conduits 78 et 112, et l'obturation du conduit 110;
• l'absence d'action sur le levier 102 font se correspondre les deuxièmes positions des valves 88 et 89, la deuxième position de la valve 88 réalisant la mise en communication des conduits 77 et 111, et, l'obturation du conduit 109;
• la première position de la valve 89, qui réalise la mise en communication des conduits 110 et 78, et, l'obturation du conduit 112 est obtenue en même temps que la deuxième position, déjà définie, de la valve 88.

The valves 88 and 89 each have two positions which are obtained in combination with the single lever 102, and which correspond as follows:

• in its first position, the valve 88 connects the conduits 77 and 109, and closes the end of the conduit 111; it corresponds to it the second position of the valve 89, which realizes the communication of the conduits 78 and 112, and the obturation of the conduit 110;
• the absence of action on the lever 102 make the second positions of the valves 88 and 89 correspond, the second position of the valve 88 bringing the conduits 77 and 111 into communication, and the obturation of the conduit 109;
• the first position of the valve 89, which brings the conduits 110 and 78 into communication, and the obturation of the conduit 112 is obtained at the same time as the second position, already defined, of the valve 88.

The operation obtained will now be explained.

First, the first position of the distributor 18 is chosen. In this configuration, the brake release chambers 16 and 18 are placed in communication with the reservoir 7, by the conduits 59 and 60, 61 and 62. The brakes 10 and 11, under the effect of the springs 14, 15 are therefore tight. Furthermore, the conduits 75, 76, 77 and 78, which convey the fluid optionally supplying the pilot cylinders 26, 27, 29 and 30 contain a fluid at zero pressure. Indeed, either the valves 86, 87, 88 and 89 are placed in their second respective positions, and, said conduits 75, 76, 77 and 78 communicate with the reservoir by means of conduits 74, 100, 111 and 112, or well some of these valves are placed in their first respective positions, and those of the con lines 75, 76, 77 and 78 which are connected to it are in communication, via lines 98, 99, 72 and 71, or 109, 110, 73 and 71, with line 61 therefore, via line 62, with the reservoir 7. Under these conditions, the distributors 24 and 25 are placed in their second positions under the effect of the springs 28 and 31, so that the motors 1 and 2 are not supplied with pressurized fluid. Braked by brakes 10 and 11, these motors are kept stationary.

From this configuration, actuating one and / or the other of the levers 91 and 102, does nothing, because no pressurized fluid can reach the cylinders 26, 27, 29, 30 as long as the distributor 18 is placed in its first position, so as long as the brakes 10 and 11 are applied.

On the other hand, as soon as the distributor 18 is placed in its second position, by action on the switch 81, the pressurized fluid discharged by the pump 8 reaches the conduit 61, and consequently, also in the conduits 71, 72 and 73, and, in the conduit 63. It therefore becomes possible to control, by means of the assembly 9, the starting of one or both motors 24 and 25. It is noted however that, at the same time, by conduits 65, 59 and 60, the pressurized fluid has reached the brake release chambers 16 and 17 and has enabled the brakes 10 and 11 to be released. Thus, the motors 1 and 2 can be started, even while the brakes 10 and 11 are loose, and therefore do not risk being damaged by the drive of the motors.

The replacement of the valves 86, 87, 88 and 89, in their second positions, causes the interruption of the supply of the motors 1 and 2, with pressurized fluid, but not a new application of the brakes 10 and 11. That -This is only obtained by replacing the distributor 18 in its first position.

However, before allowing the brakes to be re-applied, motors 1 and 2 must be stopped completely. The brake release fluid contained in the chambers 16 and 17 does not return to the reservoir 7 via the conduits 59, 60, 61 and 62 until it escapes through the restriction 64, that is to say after a certain time. from the delivery of the distributor 18 in its first position. This period of time is, in fact, at least equal to that corresponding to the complete stopping of motors 1 and 2.

Finally, it should be noted that the user can choose the operating displacement of the motors 1 and 2. The chosen displacement is either the small or the large displacement, to which corresponds, on the one hand, the high or low speed. of the corresponding motor, on the other hand, a small or large motor torque, respectively.

When the engines operate with their large displacements, that is to say low speed, at the time of ordering their stopping, a hydrostatic resistant torque is developed by each engine and is a large torque.

When the motors operate with their small displacements, and the distributor 18 is returned to its first position to control the stopping of the motors, the resistive torque is initially small. However, the fluid contained in the selectors 3 and 4 and therefore, for example, in the control cylinder 120 of the distributor 117, automatically returns to the reservoir 7 through the conduits 67, 68, 69, 63 and 62. This has the effect to put the conduits 116 and 119 into communication; automatically return motor 1 (1a and 1b) to its large displacement configuration; and again to obtain a large hydrostatic braking torque.

This provision is important with regard to the operational safety obtained during the possible rupture of a conduit.

The invention is not limited to the embodiment described, but on the contrary covers all the variants which could be made to it without departing from its scope or its spirit.

Claims (4)

1. A circuit controlling a pressurized fluid motor (1) associated to safety spring brakes (10) whose rest configuration is the braking configuration, and constituted by:

said motor (1),

said brake (10) comprising a jack (12) with a brake-releasing chamber (16) and a braking spring (14),

one main source of pressurized fluid (5),

one main fluid distributor (24), placed between the motor and the main source of pressurized fluid,

at least one means (26, 27) of controlling the main fluid distributor, coupled to the latter and capable of moving said fluid distributor from a position where the motor (1) is not supplied to a position where said distributor communicates with the main source of fluid (5),

one source of controlling fluid (8),

one brake-releasing distributor (18) situated on a connection (58, 61, 59) joining the source of controlling fluid (8) with the brake-releasing chamber (16) of the brake jack (14), and designed either to ensure continuity of said connection or to interrupt it and to cause the brake-releasing chamber (16) to communicate (61, 62) with pressure-free exhaust (7), and,

one manipulateur (9) placed on a connection (71, 75, 76) joining a source of controlling fluid (8) to at least one means of controlling (26, 27) the main distributor, characterized in that the connection (71, 75, 76) on which is situated the manipulator (9) comprises a pipe (71) supplying controlling fluid to the manipulator, said pipe being connected to that part (61) of said connection (58, 61) on which is located the brake-releasing distributor (18), which part is situated between the brake-releasing distributor (18) and the brake-releasing jack (12).

2. A control circuit according to claim 1, characterized in that a constrictor (64) is placed on the part (61) of connection (58, 61) joining the brake-releasing distributor (18) to the brake-releasing chamber (16) of the brake jack, whereas a by-pass (65) is connected to said part (61) of said connection on either side of said constriction (64), a non- return valve (66) being placed on said by-pass pipe and allowing the fluid to flow from the brake-releasing distributor (18) towards the brake-releasing chamber (16).

3. A control circuit according to any one of claims 1 and 2, characterized in that the motor (1) being of variable cubic capacity and being provided with a fluid selector (3) of its cubic capacity adapted to place said motor in the configuration of a small or large cubic capacity, by being caused to communicate with a pressurefree exhaust (7) when the large cubic capacity is selected, said fluid selector (3) is connected via a pipe (67,69,63) to that part (61) of the connection (58, 61) on which is situated the brake - releasing distributor (18) and which is between said distributor (18) and the brake-releasing cylinder (12).

4. A method for controlling a motor (1) associated to a safety brake (10), whose rest configuration is the braking configuration, and consisting, on the one hand, in controlling the starting of the motor (9), and on the other hand, in releasing the brake (18), the motor being started only when the brake (81) is released, whereas every braking operation is timed to occur after the motor has been stopped, characterized in that the motor being a variable-speed motor adapted to be selectively placed in low or high speed configuration, the control (81) of another braking operation automatically (63-62) selects the low speed for the motor.

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