EP0330575A1 - Hydraulic circuit comprising a safety valve for a hydraulic actuator - Google Patents

Abstract

Safety valve for a hydraulic circuit supplying a hydraulic receiver having an inlet and an outlet connected to the receiver which includes between the inlet and the outlet a non-return module which has a non-return valve and a selectively operable valve having an unoperated position in which the non-return valve prevents any reverse flow of fluid from the outlet to the inlet and an operated position in which such reverse flow is made possible. A control inlet is provided for applying control pressure to the selectively operable valve. A pressure relief valve is provided between the outlet and the control inlet which is adapted to enable flow from the outlet to the control inlet from a predetermined pressure threshold.

Description

The present invention relates to a safety valve intended to equip a hydraulic circuit of the kind used to control a machine, a machine tool, a public works machine, in the 'aviation, or on various vehicles. Such a circuit is generally controlled by at least one hydraulic distributor.

It is known that a hydraulic circuit of the aforementioned kind most often includes flexible pipes ensuring the control of jacks or the like, for example for handling a load. A safety problem arises in the event of a rupture of a pipe ensuring the supply of a jack.

The present invention aims to solve this problem by ensuring the safety of users, even in the event of a broken pipe in a circuit controlling the handling of a load. In the case of load handling, it aims in particular to allow the load to be immobilized during the lifting phase and, during the descent phase, the normal continuation of its movement and / or its stopping on order.

To this end, it offers a permanent standby safety valve normally allowing a flow of fluid only in one direction between its inlet and outlet ports, a flow of fluid in the other direction requiring the application of a pilot pressure which is normally applied by the pilot but which, in the event of a pipe rupture, may appear due to the exceeding of a pressure threshold at the outlet orifice.

To this end, the invention proposes a safety valve for a hydraulic circuit supplying a hydraulic receiver, comprising an inlet orifice and an outlet orifice connected to said receiver, characterized in that it comprises: - between the inlet and outlet ports, a non-return module comprising a non-return valve and a controlled valve admitting a rest position in which the non-return valve prevents any backflow of fluid from the outlet orifice to the 'inlet port, and an active position in which such reflux is made possible, a pilot port being provided to bring pilot pressure to this controlled valve; and
- a pressure relief valve interposed between the outlet orifice and the pilot orifice adapted to allow a flow from the outlet orifice to the pilot orifice beyond a predetermined pressure threshold.

It will be appreciated that such a valve makes it possible, for example, to control fluid flows under approximately 400 bars with pilot pressures less than or equal to only 25 bars.

According to other preferred arrangements of the invention which may be combined: - a nozzle is provided near the pilot orifice to ensure that, in the event of overpressure, the exhaust flow is mainly applied to the non-return module as the piloting;
- the controlled valve is provided with a leakage drain, leading to a leakage orifice, allowing, in particular, to apply to the pilot pressure a backpressure resulting from an overpressure and thus allow, in the event of a plurality of receivers used simultaneously and provided with such a safety valve, to synchronize their behavior by the application of appropriate counter pressures;
- The controlled valve admits a plurality of intermediate positions between its rest and active positions, admitting a reflux flow lower than the flow admitted in the active position; this allows progressiveness the reflux flow with the amplitude of the pilot pressure;
- the non-return valve is part of the controlled valve; or
- the non-return valve is arranged in a circuit parallel to that in which the controlled valve is interposed;
- The controlled valve includes a sliding sleeve forming a drawer, the movement of which is controlled by a valve itself controlled by the rod of a piston subjected to piloting pressure.

The invention also relates to a hydraulic circuit comprising such a valve fixed to this receiver and the distributor of which can be controlled by the overpressure from the pilot orifice.

• - la figure 1 est un schéma d'un récepteur hydraulique équipé d'une valve de sécurité conforme à l'invention et de son circuit hydraulique de commande ;
• - la figure 1A est un schéma d'une variante de cette valve de sécurité ;
• - la figure 2 est une vue en coupe, selon la ligne II-II de la figure 3, d'une autre variante de valve de sécurité ;
• - la figure 3 en est une vue en bout selon la flèche III de la figure 2 ;
• - la figure 4 en est une vue en coupe selon la ligne IV-IV de la figure 2 ; et
• la figure 5 est une vue partielle en coupe d'une valve de sécurité conforme à la figure 1A.

Objects, characteristics and advantages of the invention appear from the description which follows, given by way of nonlimiting example, with reference to the appended drawings in which:

• - Figure 1 is a diagram of a hydraulic receiver equipped with a safety valve according to the invention and its hydraulic control circuit;
• - Figure 1A is a diagram of a variant of this safety valve;
• - Figure 2 is a sectional view, along the line II-II of Figure 3, of another variant of the safety valve;
• - Figure 3 is an end view along arrow III of Figure 2;
• - Figure 4 is a sectional view along the line IV-IV of Figure 2; and
• Figure 5 is a partial sectional view of a safety valve according to Figure 1A.

Figure 1 illustrates a hydraulic receiver 1 consisting of a double-acting cylinder whose chambers 1A and 1B are connected by lines 2 and 3 to a pressure source 4, here constituted by a pump, and at a pressure well 5 by a controlled distribution-switching valve 6. The pipes 2 and 3, for example made up of flexible pipes, are fitted with pressure relief valves 7 and 8 ; similarly, a pressure relief valve 9 is interposed between the pressure source and the controlled valve 6.

The controlled valve 6 has three positions corresponding respectively to the pressurization of one or the other, or none of the chambers 1A and 1B of the jack.

This valve is controlled by a manipulator 10 connected, to a pressure source 11 by a pipe 12 equipped with a pressure relief valve 13, and to a pressure well 14.

At least one of the pipes 2 and 3, here the pipe 2, is fitted with a safety valve 15 which protects the corresponding jack chamber (1A).

This safety valve 15 has three inputs A, B and Z respectively connected to the pipe 2, to the chamber 1A and to a pilot pipe 16 connected, on the one hand, to the manipulator 10 and, on the other hand, to the controlled distribution-switching valve 6.

Between the inputs A and B is provided a controlled valve 17 with two positions chosen according to the pilot pressure applied to the input Z. One of the positions (rest) corresponds to the interposition between A and B d ' a non-return valve preventing any movement from B to A while the other position (in the event of non-zero pilot pressure) allows free movement between B and A. This valve advantageously admits intermediate positions between these extreme positions allowing a flow from B to A which increases with the pilot pressure.

Between the inputs B and Z is interposed a calibrated pressure relief valve 18 which allows circulation from B to Z beyond a limit pressure threshold in chamber 1A. A nozzle 19 is interposed between this pressure relief valve as well as the controlled valve 17, and the inlet Z.

In the absence of pilot pressure, the chamber 1A can be pressurized via the pipe 2.

Emptying this chamber requires the application of pilot pressure to bring the valve 17 to its other position. In normal operating conditions, this pilot pressure is controlled by the manipulator.

In the event of an accidental drop in the pressure in the pipe 2 during a phase of pressurizing the chamber 1A, as a result for example of a rupture of this pipe, the safety valve 15 ensures that the load is maintained this chamber as long as no pilot pressure is applied at Z. This makes it possible to avoid any accident for a possible load that the jack is handling and for people in the vicinity.

In addition, the presence of the pressure relief valve 18 prevents any exaggerated increase in the pressure in the chamber 1A. Indeed, as soon as this pressure exceeds the threshold associated with this valve, the latter authorizes a flow of fluid which, due to the fact that its flow to the manipulator 10 is limited by the nozzle 19, induces a pilot pressure on the controlled valve 17 whose amplitude controls a more or less significant flow from B to A until the pressure in the chamber 1A returns below the above-mentioned threshold, which brings the pressure relief valve 18 back to the blocked state. This results in a slow and limited emptying of the chamber 1A.

It should be noted that the exhaust flow through port Z, in the event of an accidental drop in pressure (see above), in the absence of any action on the manipulator 10, automatically controls a movement of the controlled valve 6 towards its neutral position which stops any injection of hydraulic fluid in the pipe 2.

In FIG. 1A is shown, by way of isolation, an alternative embodiment 15 ′ of the safety valve of FIG. 1.

This second valve is distinguished from the first by the presence of a leakage drain 50 communicating a backpressure chamber associated with the controlled valve 17 with a leakage orifice Y. A non-return valve with adjustable threshold 51 is advantageously provided on this drain. By adjusting this threshold, the counter-pressure opposite to the pilot pressure is acted on to control the controlled valve. This facilitates coordinated control of several safety valves. In addition, the control chamber of the valve 17 is controlled by an element 52 adapted to be exclusively traversed by a pilot fluid coming from the valve 18 or from the orifice Z.

FIGS. 2 to 4 illustrate an embodiment of the safety valve 15.

This valve is formed from a block of several elements in which various conduits are formed connecting orifices 20, 21 and 22 corresponding respectively to the orifices A, B and Z of FIG. 1.

The inlet orifice 20 is connected to a main conduit 23 terminating in a pressure chamber 24 in free communication with the outlet orifice 22 by channels 25 located above and below the section plane of the figure 2. A non-return valve 26 applied to its seat by a spring 26A is interposed in this circuit 23 between the inlet orifice 20 and the pressure chamber 24. In this valve 26 is provided a balancing channel 26B putting the chamber of the spring 26A in communication with the chamber 24.

The conduit 23 also leads to a chamber 27 in which slides a sleeve 28 forming a drawer integral with a valve 29 preventing, in the closed position, any reflux of fluid from the chamber 24 towards the chamber 27. This sleeve 28 is guided in sliding, in a sealed manner, by bearing surfaces 30 and 31 framing the communication of the main conduit 23 with the chamber 27. In the wall of this sleeve, holes 28A are provided near the valve part 29 and, near its opposite end, holes 28B. Advantageously, a ring of orifices 28 C smaller than the orifices 28 B is formed near the latter, on the side of the orifices 28A. Normally, these various orifices do not communicate with the main conduit 23.

In the valve 29, integral with the sleeve 28, there is provided a channel closed by a control and pressure balancing valve 32, subjected to the action of a spring 32A, normally preventing any flow from 24 to 27.

The pressure chamber 24 also communicates, via a conduit 33, with a control chamber 34 in communication, through a nozzle 22A, with the control orifice 22. The flow from 24 to 34 is normally prevented by a valve 35 subjected to a calibration spring 35A.

This pilot chamber 34 is also in communication, through a pilot channel 36, with an operating chamber 37 in which slides a piston 38 provided with a rod 39 forming a pusher and subjected to a restoring force by a spring 40. This rod 39 extends into the chamber 27 and its end is near and in the extension of the valve 32 for controlling the sleeve-drawer 28. After having forced the opening of the valve 32, the rod 39 is adapted to come wear directly on the valve 29 of the drawer 28 and thus check its position in chamber 27.

Opposite the valve 32, the piston rod is slidably mounted in a cap 41 in which it defines a balancing chamber with variable volume 42 placed in communication with the chamber 27 of the sleeve by a balancing duct 43 formed longitudinally in the stem.

The elements 26, 28, 32, 38 and 39 generally constitute the controlled valve 17 of FIG. 1, except that the non-return valve 26 is here independent of the controlled drawer. In a variant not shown, this valve 26 and the section of conduit which contains it can be omitted if the orifices 28B or 28B ′ normally open out between the bearing surfaces 30 and 31.

The elements 33, 35, 35A and 36 generally constitute the pressure relief valve 18 of FIG. 1.

The nozzle 22A corresponds to that marked 19 in FIG. 1.

• a) la fonction alimentation : passage de 20 vers 21 à travers le clapet anti-retour 26 ;
• b) la fonction maintien de charge : en absence de pression de pilotage sur l'orifice 22, les clapets 26, 29 et 32 sont en appui sur leur siège respectif et interdisent le passage de 20 vers 21 ;
• c) la fonction limiteur de pression : en cas de surpression dans la chambre protégée 1A du vérin 1, le clapet taré 35 s'ouvre, un débit s'établit entre cette chambre de vérin et la chambre de pilotage 37 à travers le jeu entre le siège et la jupe de guidage du clapet 35 et par franchissement de l'ouverture de ce dernier. Ce débit subit au passage du gicleur 22A une perte de charge variable en fonction de celui-ci. Le montée en pression dans la chambre 35 provoque l'ouverture des clapets 29 et 32 par l'intermédiaire du piston 38 et du poussoir 39 : cela autorise le passage de 21 vers 20 d'où le fluide est ensuite évacué, soit à travers le distributeur d'alimentation 6, soit à travers sa soupape de surpression 7.
• d) la fonction régulation : à une pression de pilotage donnée, reçue du manipulateur 10, le poussoir 29 produit l'ouverture du clapet 32, ce qui a pour effet d'équilibrer entièrement sur la pression le clapet 29 du tiroir de distributeur 28. Il en résulte une section de passage vers le conduit 23, variable avec le déplacement du clapet 29 en fonction du nombre d'orifices de progressivité 28B, 28B′ dégagés en tout ou partie. La pression dans la chambre 27 ne modifie pas la loi d'ouverture du clapet 29. En effet, le poussoir 39 est équilibré sur cette pression à travers le conduit d'équilibrage 43.

This device advantageously performs a quadruple function:

• a) the power supply function: passage from 20 to 21 through the non-return valve 26;
• b) the load maintenance function: in the absence of pilot pressure on the orifice 22, the valves 26, 29 and 32 are supported on their respective seats and prohibit the passage from 20 to 21;
• c) the pressure limiter function: in the event of overpressure in the protected chamber 1A of the jack 1, the calibrated valve 35 opens, a flow rate is established between this jack chamber and the piloting chamber 37 through the clearance between the seat and the guide skirt of the valve 35 and by crossing the opening of the latter. This flow undergoes, as the nozzle 22A passes, a variable pressure drop as a function of the latter. The increase in pressure in the chamber 35 causes the valves 29 to open and 32 via the piston 38 and the pusher 39: this authorizes the passage from 21 to 20 from which the fluid is then evacuated, either through the feed distributor 6 or through its pressure relief valve 7.
• d) the regulation function: at a given pilot pressure, received from the manipulator 10, the pusher 29 produces the opening of the valve 32, which has the effect of completely balancing the valve 29 of the distributor slide 28 on the pressure. This results in a passage section towards the conduit 23, variable with the movement of the valve 29 as a function of the number of progressive openings 28B, 28B ′ released in whole or in part. The pressure in the chamber 27 does not modify the law for opening the valve 29. In fact, the pusher 39 is balanced on this pressure through the balancing duct 43.

This device makes it possible, when an earthmoving machine is used to handle loads, to ensure the safety of people and equipment.

In the event of the supply hose in the protected section of the cylinder breaking, the operator can continue to deposit the load he was handling, without danger to him and the people accompanying him. In addition to this safety function, the device maintains the load in position, thanks to the flap closures.

According to an alternative embodiment shown in Figure 5, corresponding to the diagram in Figure 1A, the valve 15 'is similar to that shown in Figures 2 to 4, except that the chamber 37' where the piston 38 'moves communicates , by a conduit 60 opening into the part of this chamber where the pusher spring 40 ′ is located, with a leakage orifice 61 corresponding to the orifice Y of FIG. 1A provided with a calibrated valve 62 corresponding to that marked 51 in this figure 1A.

It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention.

Thus, for example, the shape and distribution of the orifices 28B and 28B 'can easily be optimized to obtain better progressiveness.

Claims (11)

1. Safety valve for hydraulic circuit supplying a hydraulic receiver (1), comprising an inlet orifice (A, 20) and an outlet orifice (B, 21) connected to said receiver, characterized in that it comprises: - between the inlet (A, 20) and outlet (B, 21) orifices a non-return module (17; 26-32, 37-42) comprising a non-return valve and a controlled valve admitting a rest position in which the non-return valve prevents any backflow of fluid from the outlet orifice to the inlet orifice, and an active position in which such a backward flow is made possible, a pilot orifice (Z, 22) being provided to bring a pilot pressure to this controlled valve; and
- a pressure relief valve (18; 34-36) interposed between the outlet orifice (B, 21) and the pilot orifice (Z, 22) adapted to allow flow from the outlet orifice to the orifice piloting beyond a predetermined pressure threshold. 2. Safety valve according to claim 1, characterized in that a nozzle (19, 22A) is interposed between the pilot orifice and the outlet of the pressure relief valve, on the one hand, and the controlled valve, of somewhere else. 3. Safety valve according to claim 1 Or claim 2, characterized in that the controlled valve is provided with a drain (50, 60) leading to a leakage orifice (Y, 61) in communication with a backpressure chamber (37 ′) of this controlled valve (17; 38-40; 38′-40). 4. Safety valve according to any one of claims 1 to 3, characterized in that the controlled valve admits at least one intermediate position for which a reflux is made possible with a flow lower than that allowed by the active position of this controlled valve, thus ensuring an adjustable reflux flow. 5. Safety valve according to any one of claims 1 to 4, characterized in that the non-return valve is part of the controlled valve (17). 6. Safety valve according to any one of claims 1 to 4, characterized in that the non-return valve (26), independent of the controlled valve, is disposed in a conduit parallel to that in which said valve is interposed. 7. Safety valve according to any one of claims 1 to 6, characterized in that the controlled valve comprises a sliding sleeve forming a drawer (28) interposed between the inlet (21) and outlet (22) orifices, admitting a closed position and at least one position in which orifices (28A, 28B, 28B ′) allow a flow between these orifices, the movement of this drawer being controlled by a pusher (38, 39) subjected to a piloting pressure opposite to an elastic restoring force. 8. Safety valve according to claim 7, characterized in that the drawer (28) comprises a pressure balancing valve (32) adapted to be opened by the pusher before any movement of said drawer. 9. Safety valve according to claim 7 or claim 8, characterized in that the pusher comprises a rod in which is formed a channel (43) pressure balancing adapted to put in communication separate chambers (27, 42) in which are engaged the ends of this rod. 10. Hydraulic circuit comprising a hydraulic receiver (1), a power distributor (6) and supply lines (2, 3) further comprising a safety valve (15, 15 ′) according to any one of Claims 1 to 9, which is integral with the receiver. 11. Circuit according to claim 10, characterized in that the pilot orifice (Z, 22) of the valve is connected to a control orifice of the distributor (6).

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