EP0000303B1 - Automatic hydraulic valve - Google Patents

Automatic hydraulic valve Download PDF

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Publication number
EP0000303B1
EP0000303B1 EP78400021A EP78400021A EP0000303B1 EP 0000303 B1 EP0000303 B1 EP 0000303B1 EP 78400021 A EP78400021 A EP 78400021A EP 78400021 A EP78400021 A EP 78400021A EP 0000303 B1 EP0000303 B1 EP 0000303B1
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EP
European Patent Office
Prior art keywords
compartment
piston
pressure
valve
passage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP78400021A
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German (de)
French (fr)
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EP0000303A1 (en
Inventor
Gilbert Kervagoret
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DBA SA
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DBA SA
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Publication date
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Publication of EP0000303A1 publication Critical patent/EP0000303A1/en
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Publication of EP0000303B1 publication Critical patent/EP0000303B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F15B1/027—Installations or systems with accumulators having accumulator charging devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/2496—Self-proportioning or correlating systems
    • Y10T137/2559—Self-controlled branched flow systems
    • Y10T137/265—Plural outflows
    • Y10T137/2663—Pressure responsive

Definitions

  • the invention relates to a hydraulic circuit breaker intended for charging a pressurized fluid accumulator from a hydraulic pump.
  • a pressurized fluid accumulator is used in as an auxiliary pressure source. If the accumulator is used, the pressure prevailing in its pressure chamber decreases and is likely to reach a value lower than the minimum tolerable value. It is then necessary to recharge the accumulator from the pump with a substantially constant volumetric flow rate of the hydraulic circuit via such a contactor-circuit breaker. In normal operation, that is to say outside the period of charging the accumulator and the implementation of the power steering, the pump with substantially constant volumetric flow delivers fluid under a low pressure close to 2 to 3 bars.
  • the pressure at the pump outlet can reach significantly higher values. This results in the establishment of transient regimes at the beginning and at the end of the accumulator charge period, during which the variations in the fluid pressure delivered by the pump are particularly significant. If these pressure variations are too rapid, this results in pressure surges which can cause deterioration of the pump members.
  • the object of the present invention is to propose a contactor-circuit breaker which reduces these drawbacks and which makes it possible to spread out over time these pressure variations, during the transient regimes of rise or fall of the pump pressure, during the accumulator charge.
  • the invention provides a hydraulic circuit breaker of the type comprising a housing with an inlet port intended to be connected to the output of a hydraulic pump, a first outlet port intended to be connected to the pressure of a hydraulic pressure accumulator, and a second outlet orifice intended to be connected to an open-center hydraulic circuit, a stepped bore formed in the casing of this circuit-breaker receiving a differential type piston mounted to slide in leaktight manner in said bore and defining with the latter an inlet chamber in communication with the inlet orifice and a control chamber, the pressures in the inlet and control chambers acting respectively on the faces of small and large sections of the differential piston, a throttle orifice with variable section depending on the position of the differential piston being disposed between the inlet chamber and the second outlet orifice, ladi the inlet chamber being in communication with the control chamber via a first passage comprising a first restriction and being further connected to the first outlet orifice by a connection comprising a non-return valve, contactor-circuit breaker having this
  • the elastic capacity of the contactor-circuit breaker consists of a second bore formed in the housing, inside which a second piston is slidably mounted in leaktight manner to separate the second bore into a first compartment defining the variable volume compartment, and in a second compartment, said second piston being biased towards the end of the first compartment by elastic means arranged in the second compartment, an axial passage intended to put the two compartments in communication being provided in the second piston and opening towards the first compartment to define a valve seat cooperating with a valve element elastically biased against said seat, a pusher element fixed relative to the housing being disposed in the axial passage of the second piston, said element pusher being capable of lifting the fo element from its seat rmant valve to allow the flow of fluid in the leakage passage when the second piston has moved a given distance which corresponds to the first predetermined value of the pressure in said first compartment, the leakage passage then being constituted by the annular space defined between the pusher element and the axial passage, and said second compartment being in communication
  • a hydraulic circuit breaker shown in the rest position. It comprises a housing 12 having an inlet port (not shown), a first outlet port 14 and a second outlet port 16.
  • the inlet port (not shown) is connected to a hydraulic pump 18 with volumetric flow substantially constant, by a pipe 19.
  • the first outlet orifice 14 is connected, by a pipe 20, to the pressure chamber of an accumulator 22 intended for example to supply pressurized fluid to an assistance circuit of the type to closed center 24, such as a hydraulic brake booster.
  • the second outlet 16 is connected, by a pipe 26, to a power steering valve 28 connected from known manner to a hydraulic fluid reservoir 30 and comprising two working orifices connected to the respective chambers of an assistance cylinder 32.
  • the housing 12 has a first stepped bore 34 which comprises a small diameter portion and a large diameter portion arranged so as to define a shoulder 36.
  • the large diameter portion of the bore 34 opens into a control chamber 38 coaxial with the latter, while the small diameter portion of the bore 34 opens towards the first outlet orifice 14.
  • a differential piston 40 is slidably mounted in the bore 34. It has a large diameter portion which projects into the chamber 38, and a small diameter portion which slides in the small diameter portion of the bore 34 and the end of which is subjected to the pressure prevailing in the first outlet orifice 14.
  • the differential piston 40 cooperates with the large diameter portion of the bore 34 and with the shoulder 36 so as to define an annular chamber 42 which is in permanent communication with the pump 18 via the inlet port mentioned above ence (not shown).
  • An annular seal 44 is mounted on the large diameter portion of the differential piston 40, so that the passage of fluid between the chambers 42 and 38 can only take place through a restriction 56 provided in a passage which will be defined later.
  • the piston 40 also has longitudinal grooves 46, preferably obtained by milling and which are formed in its portion of small diameter.
  • the grooves 46 are intended to put the annular chamber 42 into communication with a radial passage 48, itself connected to the second outlet orifice 16.
  • the depth of the grooves 46 increases as one moves away from the shoulder of the differential piston 40.
  • the grooves 46 are intended to cooperate with the shoulder 36 to constitute a throttle orifice 50 disposed on the fluid flow path between the pump 18 and the power steering valve 28, this throttle orifice having a variable section as a function of the position of the stepped piston 40.
  • the stepped piston 40 also has an axial passage 52 connected to the annular chamber 42 by a radial passage 54.
  • the axial passage 52 communicates with the control chamber 38 via the restriction 56, which is formed in the embodiment represented by a stack of crimped pierced pellets.
  • the passages 52 and 54 ensure communication between the annular chamber 42 and the outlet orifice 14.
  • a non-return valve constituted by a ball 58 cooperates with a seat 59 defined at the end of the axial passage 52 on the side of the small face. diameter of the differential piston 40.
  • a spring 60 is arranged in the control chamber 38 to elastically bias the piston 40 at the against the action of the pressure prevailing in the annular chamber 42 on the one hand, and of the pressure of the accumulator 22 which acts on the small diameter end of the piston, on the other hand.
  • a stop 62 disposed in the control chamber 38 and intended to limit the penetration of the differential piston 40 in said chamber.
  • the hydraulic circuit breaker 10 also has an elastic capacity with variable volume generally designated by the reference 70.
  • This elastic capacity consists of a second bore 72 formed in the housing 12 and inside which is arranged a piston 74 sliding in leaktight manner.
  • This piston 74 divides the bore 72 into a first compartment 76 which communicates with the control chamber 38 by a passage 78, and into a second compartment 80 closed at its lower part by a plug 82.
  • the piston 74 is urged against the end of compartment 76 by an elastic assembly 84 disposed in the second compartment between the piston 74 and the plug 82.
  • the elastic assembly 84 is constituted, by way of nonlimiting example , by stacking elastic washers.
  • the second compartment 80 is in communication with the second outlet orifice 16, via a radial passage 86, the stepped bore 34 and the passage 48.
  • the piston 74 has an axial passage 88 intended to put the two compartments 76 and 80 into communication.
  • This passage opens into the first compartment 76 and defines a valve seat 90 cooperating with a valve element 92 (here constituted by a ball) urged elastically against said seat by a light spring 94.
  • a valve element 92 here constituted by a ball
  • a pusher 96 Inside the axial passage 88 is disposed a pusher 96 fixed relative to the housing and terminated by a finger 98. The axial position of the pusher 96 is capable of being adjusted by the plug 82. In the rest position shown in the single figure, the piston 74 is urged as far as possible towards the first compartment by the elastic assembly 84.
  • the end of the finger 98 is set back relative to the plane of the valve seat 90, and the ball 92 is held against the seat under the influence of spring 94.
  • Another spring 100 is disposed in the passage 88, bearing against the pusher 96, so as to surround the finger 98. At rest, the spring 100 has a length greater by a distance X than the finger length 98, but which is insufficient to urge the ball 92. The advantage of such a characteristic will be explained in the following description.
  • the pusher 96 is mounted in the axial passage 88 so as to allow restricted fluid communication between the first compartment 76 and the second compartment 80 via the annular space defined between the pusher 96 and the internal wall of the axial passage 88, when the ball 92 is kept away from its seat 90.
  • the differential piston 40 is moved by the spring 60, so as to cause a reduction in the cross section of the throttle 50 defined by the cooperation of the shoulder 36 and the grooves 46.
  • the flow rate delivered by the pump 18 remains substantially constant, the pressure in the annular chamber 42 increases, which has the effect of establishing a flow of fluid from the chamber 42 to the chamber 38, by means of the restriction 56. This results in a progressive charge of the capacity 70 via the passage 78. The action of this load on the operation of the capacity 70 will be explained later.
  • the increase in pressure in the control chamber 38 is progressive over time and causes an additional displacement of the differential piston which has the effect of further restricting the section of the constriction 50 located on the fluid flow path between outlet of the pump 18 and the power steering valve 28.
  • the piston 40 continues thus to descend as the pressure from the pump 18 increases. This pressure increase continues gradually until the moment when the pump pressure reaches the conjunction value (defined above) . From this moment, the ball 58 is lifted from its seat, against the pressure prevailing in the accumulator, and part of the pressurized fluid from the pump 18 is directed towards said accumulator which begins to recharge. From this point on, the pressure from the pump continues to increase, but with a more reduced rate of pressure increase.
  • variable volume capacity The action of variable volume capacity will now be explained in detail.
  • the piston 74 is permanently subjected to the same pressure as that prevailing in the control chamber 38. An increase in this pressure corresponds to a displacement of said piston 74 against the elastic assembly 84.
  • a first phase during which the compartments 76 and 80 do not communicate, the piston 74 and the ball 92 applied on its seat are integral in displacement relative to the pusher 96, so that the ball 92 comes first in contact with the free end of spring 100 to compress the latter during its subsequent movement down the figure.
  • the end of the first phase corresponds to the instant when the ball 92 comes into contact with the finger 98.
  • the opening pressure corresponds to a given pressure value in the annular chamber 42.
  • the variable volume capacity is provided in such a way that the valve formed by the ball 92 and its seat 90 opens when the pressure in the annular chamber 42 reaches a value corresponding to the cut-out pressure of the accumulator, this is ie the maximum pressure to which it must be reloaded. In other words, the valve of the variable volume capacity opens at the moment when the accumulator 22 is recharged.
  • the valve of the variable volume capacity remains open until the piston 74 has retreated by a distance equal to X of so that seat 90 resumes contact with the ball 92.
  • the valve is closed again and the communication of fluid between the compartments 76 and 80 is interrupted.
  • the distance X is calculated so that the interruption of the communication of fluid between the compartments 76 and 80 occurs when the pressure in the compartment 76 has decreased by a given quantity AP, to reach a so-called closing value.
  • This closing value is fixed so that the pressure prevailing in the annular chamber 42 has become lower than the pressure prevailing in the control chamber 38 and in the compartment 76 at the moment when the seat 90 comes back into contact. with the ball 92.
  • the third phase occurs from the moment the variable volume capacity valve is closed again.
  • the hydraulic fluid flows from the compartment 76 and the control chamber 38 to the pump, via the restriction 56, the axial passage 52, the radial passage 54 and the chamber 42, until the capacity is completely discharged.
  • leakage passage shown in the figure establishes a communication between the compartment 76 and the outlet orifice 16 connected to the power steering valve 28, it is very conceivable that the leakage passage is directly connected to a reservoir of hydraulic fluid, without departing from the scope of the present invention.

Description

L'invention concerne un conjoncteur-disjoncteur hydraulique destiné en particulier à charger un accumulateur de fluide sous pression à partir d'une pompe hydraulique.The invention relates to a hydraulic circuit breaker intended for charging a pressurized fluid accumulator from a hydraulic pump.

Dans un circuit hydraulique de véhicule automobile comportant un circuit hydraulique à centre ouvert, tel que par exemple un circuit de direction assistée, et un circuit hydraulique à centre fermé du type circuit d'assistance de freinage, un accumulateur de fluide sous pression est utilisé en tant que source auxiliaire de pression. Dans le cas où l'accumulateur est sollicité, la pression qui règne dans sa chambre de pression diminue et est susceptible d'atteindre une valeur inférieure à la valeur minimale tolérable. Il est alors nécessaire de recharger l'accumulateur à partir de la pompe à débit volumétrique sensiblement constant du circuit hydraulique par l'intermédiaire d'un tel conjoncteur-disjoncteur. En fonctionnement normal, c'est-à-dire en dehors de la période de charge de l'accumulateur et de la mise en oeuvre de la direction assistée, la pompe à débit volumétrique sensiblement constant, délivre du fluide sous une pression faible voisine de 2 à 3 bars. En période de charge, la pression à la sortie de la pompe peut atteindre des valeurs nettement plus grandes. Il en résulte l'établissement de régimes transitoires au début et à la fin de la période de charge de l'accumila- teur, au cours desquels les variations de la pression de fluide délivrée par la pompe sont particulièrement importantes. Si ces variations de pression sont trop rapides, il en résulte des coups de bélier de pression susceptibles de provoquer la détérioration des organes de la pompe.In a hydraulic circuit of a motor vehicle comprising an open center hydraulic circuit, such as for example a power steering circuit, and a closed center hydraulic circuit of the brake assist circuit type, a pressurized fluid accumulator is used in as an auxiliary pressure source. If the accumulator is used, the pressure prevailing in its pressure chamber decreases and is likely to reach a value lower than the minimum tolerable value. It is then necessary to recharge the accumulator from the pump with a substantially constant volumetric flow rate of the hydraulic circuit via such a contactor-circuit breaker. In normal operation, that is to say outside the period of charging the accumulator and the implementation of the power steering, the pump with substantially constant volumetric flow delivers fluid under a low pressure close to 2 to 3 bars. During charging, the pressure at the pump outlet can reach significantly higher values. This results in the establishment of transient regimes at the beginning and at the end of the accumulator charge period, during which the variations in the fluid pressure delivered by the pump are particularly significant. If these pressure variations are too rapid, this results in pressure surges which can cause deterioration of the pump members.

Le but de la présente invention est de proposer un conjoncteur-disjoncteur qui réduit ces inconvénients et qui permet d'étaler dans le temps ces variations de pression, au cours des régimes transitoires de montée ou de baisse de la pression de la pompe, pendant la charge de l'accumulateur.The object of the present invention is to propose a contactor-circuit breaker which reduces these drawbacks and which makes it possible to spread out over time these pressure variations, during the transient regimes of rise or fall of the pump pressure, during the accumulator charge.

A cet effet, l'invention propose un conjoncteur-disjoncteur hydraulique du type comportant un boîtier avec un orifice d'entrée destiné à être relié à la sortie d'une pompe hydraulique, un premier orifice de sortie destiné à être relié à la chambre de pression d'un accumulateur hydraulique de pression, et un second orifice de sortie destiné à être relié à un circuit hydraulique à centre ouvert, un alésage étagé formé dans le boîtier de ce conjoncteur-disjoncteur recevant un piston de type différentiel monté coulissant de façon étanche dans ledit alésage et définissant avec ce dernier une chambre d'entrée en communication avec l'orifice d'entrée et une chambre de contrôle, les pressions dans les chambres d'entrée et de contrôle agissant respectivement sur les faces de petite et grande sections du piston différentiel, un orifice d'étranglement à section variable en fonction de la position du piston différentiel étant disposé entre la chambre d'entrée et le deuxième orifice de sortie, ladite chambre d'entrée étant en communication avec la chambre de contrôle par l'intermédiaire d'un premier passage comportant une première restriction et étant en outre reliée au premier orifice de sortie par une connexion comprenant un clapet antiretour, conjoncteur-disjoncteur présentant ceci de particulier qu'il comprend en outre une capacité élastique ayant un compartiment à volume variable qui est relié à la chambre de contrôle, ladite capacité étant prévue pour mettre en communication ledit compartiment avec un deuxième passage de fuite formant restriction lorsque la pression dans ledit compartiment atteint une première valeur prédéterminée, et ladite communication avec le passage de fuite étant interrompue lorsque la valeur de la pression dans le compartiment retombe en dessous d'une deuxième valeur prédéterminée.To this end, the invention provides a hydraulic circuit breaker of the type comprising a housing with an inlet port intended to be connected to the output of a hydraulic pump, a first outlet port intended to be connected to the pressure of a hydraulic pressure accumulator, and a second outlet orifice intended to be connected to an open-center hydraulic circuit, a stepped bore formed in the casing of this circuit-breaker receiving a differential type piston mounted to slide in leaktight manner in said bore and defining with the latter an inlet chamber in communication with the inlet orifice and a control chamber, the pressures in the inlet and control chambers acting respectively on the faces of small and large sections of the differential piston, a throttle orifice with variable section depending on the position of the differential piston being disposed between the inlet chamber and the second outlet orifice, ladi the inlet chamber being in communication with the control chamber via a first passage comprising a first restriction and being further connected to the first outlet orifice by a connection comprising a non-return valve, contactor-circuit breaker having this of particular that it further comprises an elastic capacity having a variable volume compartment which is connected to the control chamber, said capacity being provided to put said compartment in communication with a second leakage passage forming a restriction when the pressure in said compartment reaches a first predetermined value, and said communication with the leakage passage being interrupted when the value of the pressure in the compartment falls below a second predetermined value.

Selon une forme de réalisation préférentielle, la capacité élastique de conjoncteur-disjoncteur selon l'invention est constituée par un deuxième alésage formé dans le boîtier, à l'intérieur duquel un deuxième piston est monté coulissant de façon étanche pour séparer le deuxième alésage en un premier compartiment définissant le compartiment à volume variable, et en un deuxième compartiment, ledit deuxième piston étant sollicité vers l'extrémité du premier compartiment par des moyens élastiques disposés dans le second compartiment, un passage axial destiné à mettre en communication les deux compartiments étant prévu dans le deuxième piston et ouvrant vers le premier compartiment pour définir un siège de valve coopérant avec un élément formant clapet sollicité élastiquement contre ledit siège, un élément formant poussoir fixe par rapport au boîtier étant disposé dans le passage axial du deuxième piston, ledit élément formant poussoir étant susceptible de soulever de son siège l'élément formant clapet pour autoriser l'écoulement de fluide dans le passage de fuite lorsque le second piston s'est déplacé d'une distance donnée qui correspond à la première valeur prédéterminée de la pression dans ledit premier compartiment, le passage de fuite étant alors constitué par l'espace annulaire défini entre l'élément formant poussoir et le passage axial, et ledit deuxième compartiment étant en communication avec le deuxième orifice de sortie.According to a preferred embodiment, the elastic capacity of the contactor-circuit breaker according to the invention consists of a second bore formed in the housing, inside which a second piston is slidably mounted in leaktight manner to separate the second bore into a first compartment defining the variable volume compartment, and in a second compartment, said second piston being biased towards the end of the first compartment by elastic means arranged in the second compartment, an axial passage intended to put the two compartments in communication being provided in the second piston and opening towards the first compartment to define a valve seat cooperating with a valve element elastically biased against said seat, a pusher element fixed relative to the housing being disposed in the axial passage of the second piston, said element pusher being capable of lifting the fo element from its seat rmant valve to allow the flow of fluid in the leakage passage when the second piston has moved a given distance which corresponds to the first predetermined value of the pressure in said first compartment, the leakage passage then being constituted by the annular space defined between the pusher element and the axial passage, and said second compartment being in communication with the second outlet orifice.

L'invention sera maintenant décrite en se référant à la figure unique de dessin annexé qui représente une vue en coupe d'un conjoncteur-disjoncteur hydraulique selon l'invention, associé à titre d'exemple non limitatif à un circuit hydraulique de véhicule automobile.The invention will now be described with reference to the single figure of the accompanying drawing which represents a sectional view of a hydraulic circuit breaker according to the invention, associated by way of nonlimiting example with a hydraulic circuit of a motor vehicle.

Sur cette figure unique, est désigné de façon générale par la référence numérique 10 un conjoncteur-disjoncteur hydraulique représenté en position de repos. Il comporte un boîtier 12 ayant un orifice d'entrée (non représenté), un premier orifice de sortie 14 et un deuxième orifice de sortie 16. L'orifice d'entrée (non représenté) est relié à une pompe hydraulique 18 à débit volumétrique sensiblement constant, par une canalisation 19. Le premier orifice de sortie 14 est relié, par une canalisation 20, à la chambre de pression d'un accumulateur 22 destiné par exemple à fournir du fluide sous pression à un circuit d'assistance du type à centre fermé 24, tel qu'un amplificateur hydraulique de freinage. Le deuxième orifice de sortie 16 est relié, par une canalisation 26, à une valve de direction assistée 28 reliée de façon connue à un réservoir de fluide hydraulique 30 et comportant deux orifices de travail reliés aux chambres respectives d'un vérin d'assistance 32.In this single figure, is generally designated by the reference numeral 10 a hydraulic circuit breaker shown in the rest position. It comprises a housing 12 having an inlet port (not shown), a first outlet port 14 and a second outlet port 16. The inlet port (not shown) is connected to a hydraulic pump 18 with volumetric flow substantially constant, by a pipe 19. The first outlet orifice 14 is connected, by a pipe 20, to the pressure chamber of an accumulator 22 intended for example to supply pressurized fluid to an assistance circuit of the type to closed center 24, such as a hydraulic brake booster. The second outlet 16 is connected, by a pipe 26, to a power steering valve 28 connected from known manner to a hydraulic fluid reservoir 30 and comprising two working orifices connected to the respective chambers of an assistance cylinder 32.

Le boîtier 12 comporte un premier alésage 34 étagé qui comprend une portion de petit diamètre et une portion de grand diamètre disposées de manière à définir un épaulement 36. La portion de grand diamètre de l'alésage 34 débouche dans une chambre de contrôle 38 coaxiale à ce dernier, tandis que la portion de petit diamètre de l'alésage 34 débouche vers le premier orifice de sortie 14. Un piston différentiel 40 est monté coulissant dans l'alésage 34. Il comporte une portion de grand diamètre qui fait saillie dans la chambre de contrôle 38, et une portion de petit diamètre qui coulisse dans la portion de petit diamètre de l'alésage 34 et dont l'extrémité est soumise à la pression qui règne dans le premier orifice de sortie 14. Le piston différentiel 40 coopère avec la portion de grand diamètre de l'alésage 34 et avec l'épaulement 36 de manière à définir une chambre annulaire 42 qui est en communication permanente avec la pompe 18 par l'intermédiaire de l'orifice d'entrée mentionné précédemment (non représenté). Un joint annulaire 44 est monté sur la portion de grand diamètre du piston différentiel 40, pour que le passage de fluide entre les chambres 42 et 38 ne puisse se faire qu'à travers une restriction 56 prévue dans un passage qui sera défini ultérieurement.The housing 12 has a first stepped bore 34 which comprises a small diameter portion and a large diameter portion arranged so as to define a shoulder 36. The large diameter portion of the bore 34 opens into a control chamber 38 coaxial with the latter, while the small diameter portion of the bore 34 opens towards the first outlet orifice 14. A differential piston 40 is slidably mounted in the bore 34. It has a large diameter portion which projects into the chamber 38, and a small diameter portion which slides in the small diameter portion of the bore 34 and the end of which is subjected to the pressure prevailing in the first outlet orifice 14. The differential piston 40 cooperates with the large diameter portion of the bore 34 and with the shoulder 36 so as to define an annular chamber 42 which is in permanent communication with the pump 18 via the inlet port mentioned above emment (not shown). An annular seal 44 is mounted on the large diameter portion of the differential piston 40, so that the passage of fluid between the chambers 42 and 38 can only take place through a restriction 56 provided in a passage which will be defined later.

Le piston 40 comporte également des rainures longitudinales 46, obtenues de préférence par fraisage et qui sont pratiquées dans sa portion de petit diamètre. Les rainures 46 sont destinées à mettre en communication la chambre annulaire 42 avec un passage radial 48, lui-même relié au deuxième orifice de sortie 16. La profondeur des rainures 46 est croissante au fur et à mesure que l'on s'éloigne de l'épaulement du piston différentiel 40. Ainsi les rainures 46 sont destinées à coopérer avec l'épaulement 36 pour constituer un orifice d'étranglement 50 disposé sur le chemin d'écoulement de fluide entre la pompe 18 et la valve de direction assistée 28, cet orifice d'étranglement ayant une section variable en fonction de la position du piston étagé 40.The piston 40 also has longitudinal grooves 46, preferably obtained by milling and which are formed in its portion of small diameter. The grooves 46 are intended to put the annular chamber 42 into communication with a radial passage 48, itself connected to the second outlet orifice 16. The depth of the grooves 46 increases as one moves away from the shoulder of the differential piston 40. Thus the grooves 46 are intended to cooperate with the shoulder 36 to constitute a throttle orifice 50 disposed on the fluid flow path between the pump 18 and the power steering valve 28, this throttle orifice having a variable section as a function of the position of the stepped piston 40.

Le piston étagé 40 comporte également un passage axial 52 relié à la chambre annulaire 42 par un passage radial 54. Le passage axial 52 communique avec la chambre de contrôle 38 par l'intermédiaire de la restriction 56, qui est constituée dans la forme de réalisation représentée par un empilage de pastilles serties percées. Les passages 52 et 54 assurent la communication entre la chambre annulaire 42 et l'orifice de sortie 14. Un clapet antiretour constitué par une bille 58 coopère avec un siège 59 défini à l'extrémité du passage axial 52 du côté de la face de petit diamètre du piston différentiel 40. Pour terminer la description relative à l'agencement du piston différentiel 40 dans le boîtier 12, on notera qu'un ressort 60 est disposé dans la chambre de contrôle 38 pour solliciter de façon élastique le piston 40 à l'encontre de l'action de la pression qui règne dans la chambre annulaire 42 d'une part, et de la pression de l'accumulateur 22 qui agit sur l'extrémité de petit diamètre du piston, d'autre part. En outre, il est prévu une butée 62 disposée dans la chambre de contrôle 38 et destinée à limiter la pénétration du piston différentiel 40 dans ladite chambre.The stepped piston 40 also has an axial passage 52 connected to the annular chamber 42 by a radial passage 54. The axial passage 52 communicates with the control chamber 38 via the restriction 56, which is formed in the embodiment represented by a stack of crimped pierced pellets. The passages 52 and 54 ensure communication between the annular chamber 42 and the outlet orifice 14. A non-return valve constituted by a ball 58 cooperates with a seat 59 defined at the end of the axial passage 52 on the side of the small face. diameter of the differential piston 40. To complete the description relating to the arrangement of the differential piston 40 in the housing 12, it will be noted that a spring 60 is arranged in the control chamber 38 to elastically bias the piston 40 at the against the action of the pressure prevailing in the annular chamber 42 on the one hand, and of the pressure of the accumulator 22 which acts on the small diameter end of the piston, on the other hand. In addition, there is provided a stop 62 disposed in the control chamber 38 and intended to limit the penetration of the differential piston 40 in said chamber.

Conformément à l'invention, la conjoncteur-disjoncteur hydraulique 10 comporte également une capacité élastique à volume variable désignée de façon générale par la référence numérique 70. Cette capacité élastique est constituée par un deuxième alésage 72 formé dans le boîtier 12 et à l'intérieur duquel est disposé un piston 74 coulissant de façon étanche. Ce piston 74 divise l'alésage 72 en un premier compartiment 76 qui communique avec la chambre de contrôle 38 par un passage 78, et en un deuxième compartiment 80 fermé à sa partie inférieure par un bouchon 82. En position de repos, le piston 74 est sollicité contre l'extrémité du compartiment 76 par un ensemble élastique 84 disposé dans le deuxième compartiment entre le piston 74 et le bouchon 82. Dans la forme de réalisation décrite, l'ensemble élastique 84 est constitué, à titre d'exemple non limitatif, par un empilage de rondelles élastiques. En outre, on notera que le deuxième compartiment 80 est en communication avec le deuxième orifice de sortie 16, par l'intermédiaire d'un passage radial 86, de l'alésage étagé 34 et du passage 48.According to the invention, the hydraulic circuit breaker 10 also has an elastic capacity with variable volume generally designated by the reference 70. This elastic capacity consists of a second bore 72 formed in the housing 12 and inside which is arranged a piston 74 sliding in leaktight manner. This piston 74 divides the bore 72 into a first compartment 76 which communicates with the control chamber 38 by a passage 78, and into a second compartment 80 closed at its lower part by a plug 82. In the rest position, the piston 74 is urged against the end of compartment 76 by an elastic assembly 84 disposed in the second compartment between the piston 74 and the plug 82. In the embodiment described, the elastic assembly 84 is constituted, by way of nonlimiting example , by stacking elastic washers. Furthermore, it will be noted that the second compartment 80 is in communication with the second outlet orifice 16, via a radial passage 86, the stepped bore 34 and the passage 48.

Le piston 74 comporte un passage axial 88 destiné à mettre en communication les deux compartiments 76 et 80. Ce passage débouche dans le premier compartiment 76 et définit un siège de valve 90 coopérant avec un élément formant clapet 92 (constitué ici par une bille) sollicité élastiquement contre ledit siège par un léger ressort 94. A l'intérieur du passage axial 88 est disposé un poussoir 96 fixe par rapport au boîtier et terminé par un doigt 98. La position axiale du poussoir 96 est susceptible d'être réglée par le bouchon 82. Dans la position de repos représentée sur la figure unique, le piston 74 est sollicité au maximum vers le premier compartiment par l'ensemble élastique 84. L'extrémité du doigt 98 est en retrait par rapport au plan du siège de valve 90, et la bille 92 est maintenue contre le siège sous l'influence de ressort 94. Un autre ressort 100 est disposé dans le passage 88, en appui contre le poussoir 96, de manière à entourer le doigt 98. Au repos, le ressort 100 a une longueur supérieure d'une distance X à la longueur de doigt 98, mais qui est insuffisante pour solliciter la bille 92. L'intérêt d'une telle caractéristique sera expliqué dans la suite de la description.The piston 74 has an axial passage 88 intended to put the two compartments 76 and 80 into communication. This passage opens into the first compartment 76 and defines a valve seat 90 cooperating with a valve element 92 (here constituted by a ball) urged elastically against said seat by a light spring 94. Inside the axial passage 88 is disposed a pusher 96 fixed relative to the housing and terminated by a finger 98. The axial position of the pusher 96 is capable of being adjusted by the plug 82. In the rest position shown in the single figure, the piston 74 is urged as far as possible towards the first compartment by the elastic assembly 84. The end of the finger 98 is set back relative to the plane of the valve seat 90, and the ball 92 is held against the seat under the influence of spring 94. Another spring 100 is disposed in the passage 88, bearing against the pusher 96, so as to surround the finger 98. At rest, the spring 100 has a length greater by a distance X than the finger length 98, but which is insufficient to urge the ball 92. The advantage of such a characteristic will be explained in the following description.

Pour terminer la description de la capacité élastique, on remarquera que le poussoir 96 est monté dans le passage axial 88 de manière à permettre une communication de fluide restreinte entre le premier compartiment 76 et le deuxième compartiment 80 par l'intermédiaire de l'espace annulaire défini entre le poussoir 96 et la paroi interne du passage axial 88, lorsque la bille 92 est maintenue éloignée de son siège 90.To complete the description of the elastic capacity, it will be noted that the pusher 96 is mounted in the axial passage 88 so as to allow restricted fluid communication between the first compartment 76 and the second compartment 80 via the annular space defined between the pusher 96 and the internal wall of the axial passage 88, when the ball 92 is kept away from its seat 90.

Le conjoncteur-disjoncteur hydraulique qui vient d'être décrit fonctionne de la manière suivante:

  • Dans la position de repos illustrée sur la figure, l'accumulateur 22 est chargé. La pression à l'orifice de sortie 14 maintient la bille 58 contre son siège 59, et sollicite le piston différentiel 40 vers le haut de la figure, de manière à permettre un écoulement normal de fluide entre la pompe 18 et la valve de direction assistée 28. La capacité élastique occupe la position illustrée sur la figure et la bille 92 est sollicitée contre son siège 90 par le ressort 94. Le fluide débité par la pompe est alors entièrement dirigé vers la valve de direction assistée.
The hydraulic circuit breaker which has just been described operates as follows:
  • In the rest position illustrated in the figure, the accumulator 22 is charged. The pressure at the outlet orifice 14 keeps the ball 58 against its seat 59, and urges the differential piston 40 upwards in the figure, so as to allow a normal flow of fluid between the pump 18 and the power steering valve 28. The elastic capacity occupies the position illustrated in the figure and the ball 92 is urged against its seat 90 by the spring 94. The fluid delivered by the pump is then entirely directed towards the power steering valve.

Si l'on suppose maintenant que l'accumulateur 22 a été sollicité de telle sorte que la pression dans sa chambre de pression chute en dessous de la pression de conjonction, c'est-à-dire de la pression minimale à laquelle il est prévu de l'utiliser, le piston différentiel 40 est déplacé par le ressort 60, de manière à provoquer une diminution de la section de l'étranglement 50 défini par la coopération de l'épaulement 36 et des rainures 46. Le débit délivré par la pompe 18 restant sensiblement constant, la pression dans la chambre annulaire 42 augmente, ce qui a pour conséquence d'établir un écoulement de fluide de la chambre 42 vers la chambre 38, par l'intermédiaire de la restriction 56. Il en résulte une charge progressive de la capacité 70 par l'intermédiaire du passage 78. L'action de cette charge sur le fonctionnement de la capacité 70 sera expliquée ultérieurement.If we now assume that the accumulator 22 has been stressed so that the pressure in its pressure chamber drops below the conjunction pressure, i.e. the minimum pressure at which it is intended to use it, the differential piston 40 is moved by the spring 60, so as to cause a reduction in the cross section of the throttle 50 defined by the cooperation of the shoulder 36 and the grooves 46. The flow rate delivered by the pump 18 remains substantially constant, the pressure in the annular chamber 42 increases, which has the effect of establishing a flow of fluid from the chamber 42 to the chamber 38, by means of the restriction 56. This results in a progressive charge of the capacity 70 via the passage 78. The action of this load on the operation of the capacity 70 will be explained later.

L'augmentation de pression dans la chambre de contrôle 38 est progressive dans le temps et provoque un déplacement supplémentaire du piston différentiel qui a pour effet de restreindre davantage la section de l'étranglement 50 situé sur le chemin d'écoulement de fluide entre de sortie de la pompe 18 et la valve de direction assistée 28. Il en résulte une augmentation progressive de la pression dans la chambre annulaire 42, qui a pour conséquence une nouvelle augmentation de la pression qui règne dans la chambre de contrôle 38. Le piston 40 continue ainsi de descendre au fur à mesure de l'augmentation de la pression en provenance de la pompe 18. Cette augmentation de la pression se poursuit progressivement jus-qu'à l'instant où la pression pompe atteint la valeur de conjonction (définie précédemment). A partir de cet instant, la bille 58 est soulevée de son siège, à l'encontre de la pression qui règne dans l'accumulateur, et une partie du fluide sous pression en provenance de la pompe 18 est dirigée vers ledit accumuiateur qui commence à se recharger. A partir de cet instant, la pression en provenance de la pompe continue de croître, mais avec un taux plus réduit d'augmentation de la pression.The increase in pressure in the control chamber 38 is progressive over time and causes an additional displacement of the differential piston which has the effect of further restricting the section of the constriction 50 located on the fluid flow path between outlet of the pump 18 and the power steering valve 28. This results in a progressive increase in the pressure in the annular chamber 42, which results in a further increase in the pressure prevailing in the control chamber 38. The piston 40 continues thus to descend as the pressure from the pump 18 increases. This pressure increase continues gradually until the moment when the pump pressure reaches the conjunction value (defined above) . From this moment, the ball 58 is lifted from its seat, against the pressure prevailing in the accumulator, and part of the pressurized fluid from the pump 18 is directed towards said accumulator which begins to recharge. From this point on, the pressure from the pump continues to increase, but with a more reduced rate of pressure increase.

L'action de la capacité à volume variable sera maintenant expliquée en détail. Le piston 74 est en permanence soumis à la même pression que celle régnant dans la chambre de contrôle 38. A une augmentation de cette pression correspond un déplacement dudit piston 74 à l'encontre de l'ensemble élastique 84.The action of variable volume capacity will now be explained in detail. The piston 74 is permanently subjected to the same pressure as that prevailing in the control chamber 38. An increase in this pressure corresponds to a displacement of said piston 74 against the elastic assembly 84.

Dans une première phase au cours de laquelle les compartiments 76 et 80 ne communiquent pas, le piston 74 et la bille 92 appliquée sur son siège sont solidaires en déplacement par rapport au poussoir 96, de telle sorte que la bille 92 vient d'abord en contact avec l'extrémité libre de ressort 100 pour comprimer ce dernier au cours de son déplacement ultérieur vers le bas de la figure. La fin de la première phase correspond à l'instant où la bille 92 entre en contact avec le doigt 98.In a first phase during which the compartments 76 and 80 do not communicate, the piston 74 and the ball 92 applied on its seat are integral in displacement relative to the pusher 96, so that the ball 92 comes first in contact with the free end of spring 100 to compress the latter during its subsequent movement down the figure. The end of the first phase corresponds to the instant when the ball 92 comes into contact with the finger 98.

Au début de la seconde phase, un léger déplacement supplémentaire du piston 74 a pour conséquence d'écarter la bille 92 de son siège 90, de telle sorte qu'il s'établit une pression identique sur chaque face de ladite bille. Cette dernière s'écarte alors franchement de l'extrémité du doigt 98 et du siège 90 sous l'action du ressort 100 qui se détend. L'ensemble élastique 84 et la longueur du poussoir 96, 98 peuvent être choisis de manière à ce que l'ouverture du clapet formé par la bille 92 se produise pour un déplacement donné du piston 74 correspondant à une valeur prédéterminée de la pression dans le compartiment 76 et la chambre de contrôle 38. Cette valeur prédéterminée de la pression sera appelée »pression d'ouverture«. Etant donné que le rapport des pressions dans la chambre annulaire 42 et la chambre de contrôle 38 est constant et fonction du rapport des surfaces efficaces du piston différentiel 40, la pression d'ouverture correspond à une valeur de pression donnée dans la chambre annulaire 42. La capacité à volume variable est prévue de telle sorte que le clapet formé par le bille 92 et son siège 90 s'ouvre lorsque la pression dans la chambre annulaire 42 atteint une valeur correspondant à la pression de disjonction de l'accumulateur, c'est-à-dire la pression maximale à laquelle il doit être rechargé. En d'autres termes, le clapet de la capacité à volume variable s'ouvre à l'instant où l'accumulateur 22 est rechargé.At the start of the second phase, a slight additional movement of the piston 74 has the consequence of spreading the ball 92 from its seat 90, so that an identical pressure is established on each face of said ball. The latter then deviates frankly from the end of the finger 98 and the seat 90 under the action of the spring 100 which relaxes. The elastic assembly 84 and the length of the pusher 96, 98 can be chosen so that the opening of the valve formed by the ball 92 occurs for a given displacement of the piston 74 corresponding to a predetermined value of the pressure in the compartment 76 and the control chamber 38. This predetermined pressure value will be called "opening pressure". Since the pressure ratio in the annular chamber 42 and the control chamber 38 is constant and a function of the ratio of the effective surfaces of the differential piston 40, the opening pressure corresponds to a given pressure value in the annular chamber 42. The variable volume capacity is provided in such a way that the valve formed by the ball 92 and its seat 90 opens when the pressure in the annular chamber 42 reaches a value corresponding to the cut-out pressure of the accumulator, this is ie the maximum pressure to which it must be reloaded. In other words, the valve of the variable volume capacity opens at the moment when the accumulator 22 is recharged.

Dès l'ouverture du clapet, il se produit un écoulement laminaire de fluide vers le deuxième orifice de sortie, par l'intermédiaire du passage de fuite précé- dement défini et des passages 86 et 48. On obtient ainsi une réduction progressive de la pression dans le compartiment 76 et la chambre de contrôle 38. En conséquence, il se produit un recul du piston différentiel 40 à l'encontre de l'action du ressort 60, qui a pour effet d'augmenter la section de l'étranglement 50, et de provoquer ainsi une diminution progressive de la pression qui règne dans la chambre annulaire 42. La baisse de pression dans le compartiment 76 provoque un retour progressif du piston 74 vers sa position de repos sous l'influence de l'ensemble élastique 84. Etant donné que le ressort 100 au repos a une longueur supérieure au doigt 98 d'une longueur X, le clapet de la capacité à volume variable reste ouvert jusqu'à l'instant où le piston 74 a reculé d'une distance égale à X de telle sorte que le siège 90 reprenne contact avec la bille 92. Le clapet est de nouveau fermé et la communication de fluide entre les compartiments 76 et 80 est interrompue. La distance X est calculée pour que l'interruption de la communication de fluide entre les compartiments 76 et 80 intervienne lorsque la pression dans le compartiment 76 a diminué d'une quantité AP donnée, pour atteindre une valeur dite de fermeture. Cette valeur de fermeture est fixée de manière à ce que la pression qui règne dans la chambre annulaire 42 soit devenue inférieure à la pression qui règne dans la chambre de contrôle 38 et dans le compartiment 76 à l'instant où le siège 90 revient en contact avec la bille 92. En effet, si la fermeture du clapet intervient avant que la pression dans le compartiment 76 et la chambre de contrôle 38 ait atteint une telle valeur de fermeture, la pression dans la chambre annulaire 42 n'a pas encore chuté en dessous de la pression qui règne dans la chambre de contrôle 38, et la dernière phase de chute de pression ne peut intervenir. Il est apparu que la pression de fermeture doit avoir une valeur inférieure à la plage de conjonction-disjonction de l'accumulateur.As soon as the valve is opened, a laminar flow of fluid takes place towards the second outlet orifice, via the previously defined leakage passage and passages 86 and 48. A progressive reduction of the pressure is thus obtained. in the compartment 76 and the control chamber 38. Consequently, there is a recoil of the differential piston 40 against the action of the spring 60, which has the effect of increasing the section of the throttle 50, and thus to cause a gradual decrease in the pressure prevailing in the annular chamber 42. The drop in pressure in the compartment 76 causes a gradual return of the piston 74 to its rest position under the influence of the elastic assembly 84. Being given that the spring 100 at rest has a length greater than the finger 98 by a length X, the valve of the variable volume capacity remains open until the piston 74 has retreated by a distance equal to X of so that seat 90 resumes contact with the ball 92. The valve is closed again and the communication of fluid between the compartments 76 and 80 is interrupted. The distance X is calculated so that the interruption of the communication of fluid between the compartments 76 and 80 occurs when the pressure in the compartment 76 has decreased by a given quantity AP, to reach a so-called closing value. This closing value is fixed so that the pressure prevailing in the annular chamber 42 has become lower than the pressure prevailing in the control chamber 38 and in the compartment 76 at the moment when the seat 90 comes back into contact. with the ball 92. In fact, if the valve closes before the pressure in the compartment 76 and the control chamber 38 has reached such a closure value, the pressure in the annular chamber 42 has not yet dropped in below the pressure prevailing in the control chamber 38, and the last phase of pressure drop cannot occur. It is It appeared that the closing pressure must have a value lower than the range of conjunction-disjunction of the accumulator.

La troisième phase se produit à partir de l'instant où le clapet de la capacité à volume variable est de nouveau fermé. Le fluide hydraulique s'écoule depuis le compartiment 76 et la chambre de contrôle 38 jusqu'à la pompe, par l'intermédiaire de la restriction 56, du passage axial 52, du passage radial 54 et de la chambre 42, jusqu'à ce que la capacité soit complètement déchargée.The third phase occurs from the moment the variable volume capacity valve is closed again. The hydraulic fluid flows from the compartment 76 and the control chamber 38 to the pump, via the restriction 56, the axial passage 52, the radial passage 54 and the chamber 42, until the capacity is completely discharged.

Bien que le passage de fuite représenté sur la figure établisse une communication entre le compartiment 76 et l'orifice de sortie 16 relié à la valve de direction assistée 28, on peut très bien concevoir que le passage de fuite soit directement relié à un réservoir de fluide hydraulique, sans pour cela sortir du cadre de la présente invention.Although the leakage passage shown in the figure establishes a communication between the compartment 76 and the outlet orifice 16 connected to the power steering valve 28, it is very conceivable that the leakage passage is directly connected to a reservoir of hydraulic fluid, without departing from the scope of the present invention.

Claims (5)

1. A hydraulic circuit breaker comprising a housing with an inlet orifice connectable to the outlet of a hydraulic pump, a first outlet orifice connectable to the pressure chamber of a hydraulic pressure accumulator, and a second outlet orifice connectable to an opencentre hydraulic circuit, a stepped bore in said housing, a piston of the differential type slidable in a fluid-tight manner in said bore and defining therewith an inlet chamber communicating with the inlet orifice and a control chamber, the pressures in said inlet chamber and control chamber acting respectively on those faces of the differential piston having the smaller and larger cross-sections, a constriction orifice whose cross-section is variable according to the position of the differential piston being provided between the inlet chamber and the second outlet orifice, said inlet chamber communicating with said control chamber through a first passage comprising a first restriction and being also connected to the first outlet orifice by a connection comprising a non-return valve, characterized in that this circuit breaker further comprises a resilient vessel (70) having a variable-volume compartment (76) connected to said control chamber (38), said vessel being adapted to connect said compartment to a second leakage passage forming a restriction when the pressure in said compartment reaches a first predetermined value, and to interrupt said connection to said leakage passage when the pressure in said compartment falls below a second predetermined value.
2. A hydraulic circuit breaker according to claim 1, characterized in that the resilient vessel consists of a second bore (72) defined in the housing, within which a second piston (74) is slidable in a fluid-tight manner so as to divide said second bore into a first compartment (76) defining said variable-volume compartment and into a second compartment (80), the second piston being urged towards the end of said first compartment by resilient means (84) located in said second compartment, an axial passage (88) intended to connect the two compartments being provided in said second piston and opening into the first compartment to define a valve seat (90) cooperating with a valve forming element (92) resiliently urged onto the seat, a valve lifter forming element (96, 98) fixed relative to the housing being provided in said axial passage of the second piston, said valve lifter forming element being adapted to lift said valve forming element off its seat to permit the fluid to flow in the leakage passage when the second piston has moved a given distance which corresponds to said first predetermined value for the pressure in the first compartment, the leakage passage then comprising the space defined between said valve lifter forming element and said axial passage, and the second compartment being connected to the second outlet orifice (16).
3. A hydraulic circuit breaker according to claim 2, characterized in that a spring (100) is mounted in said axial passage (88) in the second piston (74) between said valve lifter forming element and said valve forming element in order to move the latter away its seat after lifting of said valve and to keep said in its open position until the second piston has retracted a certain distance after a given pressure reduction in the first compartment (76).
4. A hydraulic circuit breaker according to any of claims 1 to 3, characterized in that the open-centre hydraulic circuit comprises a power steering valve.
5. A hydraulic circuit breaker according to any of claims 1 to 3, characterized in that the leakage passage communicates with a reservoir.
EP78400021A 1977-06-21 1978-06-14 Automatic hydraulic valve Expired EP0000303B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7718951 1977-06-21
FR7718951A FR2395442A1 (en) 1977-06-21 1977-06-21 HYDRAULIC CIRCUIT BREAKER

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EP0000303A1 EP0000303A1 (en) 1979-01-10
EP0000303B1 true EP0000303B1 (en) 1980-01-09

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DE (1) DE2857514D1 (en)
FR (1) FR2395442A1 (en)
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IT1096475B (en) 1985-08-26
IT7824676A0 (en) 1978-06-19
EP0000303A1 (en) 1979-01-10
US4223694A (en) 1980-09-23
DE2857514D1 (en) 1980-02-14
FR2395442A1 (en) 1979-01-19
FR2395442B1 (en) 1982-03-12

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