EP0182927B1 - Hydraulic jack with limited travel - Google Patents

Hydraulic jack with limited travel Download PDF

Info

Publication number
EP0182927B1
EP0182927B1 EP19840114236 EP84114236A EP0182927B1 EP 0182927 B1 EP0182927 B1 EP 0182927B1 EP 19840114236 EP19840114236 EP 19840114236 EP 84114236 A EP84114236 A EP 84114236A EP 0182927 B1 EP0182927 B1 EP 0182927B1
Authority
EP
European Patent Office
Prior art keywords
piston
rod
cylinder
bearing
shoulder
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
EP19840114236
Other languages
German (de)
French (fr)
Other versions
EP0182927A1 (en
Inventor
Claude Pestourie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
F Rassant Sa Ets
Original Assignee
F Rassant Sa Ets
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by F Rassant Sa Ets filed Critical F Rassant Sa Ets
Priority to DE8484114236T priority Critical patent/DE3474134D1/en
Priority to EP19840114236 priority patent/EP0182927B1/en
Publication of EP0182927A1 publication Critical patent/EP0182927A1/en
Application granted granted Critical
Publication of EP0182927B1 publication Critical patent/EP0182927B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F3/00—Devices, e.g. jacks, adapted for uninterrupted lifting of loads
    • B66F3/24—Devices, e.g. jacks, adapted for uninterrupted lifting of loads fluid-pressure operated
    • B66F3/25—Constructional features
    • B66F3/32—Constructional features with means for avoiding excessive shocks on completion of movements
    • 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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/24—Other details, e.g. assembly with regulating devices for restricting the stroke

Definitions

  • the invention relates to hydraulic jacks, consisting of a vertical hydraulic cylinder surrounded by a reserve of coaxial oil and provided with a hand pump, sucking in the reserve and discharging into the base of the jack to ensure the rise, with in in addition to a tap or relief valve allowing the descent.
  • a first solution consists in providing the piston of the jack with a lip seal of a form derived from the classic pump leather, and in constituting the hydraulic stroke limiting device simply by a hole or a groove made in the wall of the cylinder of the jack, in the vicinity of the high point of its stroke, to make the interior of the cylinder communicate with the reserve when this hole or this groove is exposed by the lip of the seal of the piston.
  • Such a device is relatively effective but has the drawback that the seal lip is caught up in the pressure difference towards the inside of the hole, at the same time as its up and down movement occurs, so that the seal quickly deteriorates, especially if the seal is rubber.
  • a leather seal is more often used which is more expensive, less waterproof, and which is nevertheless caught in the hole; this results in the tearing of particles of leather which are then suspended in the oil, which alters the functioning of the entire jack, in particular at the level of the valves of the pump.
  • Another minor drawback of the device with a lateral hole is that an additional stroke must be provided at the end of the stroke which is substantially equal to the diameter of the hole in order to be sure of discharging.
  • the object of the invention is to eliminate the preceding drawback by producing a stroke limiting device of the preceding type, with a piston mounted axially movable and not leaktight in the central part on the end of its rod, but arranged for use. high pressures ensuring both perfect sealing in normal operation and sufficient leakage rate at the end of the stroke.
  • the jack 1 usually comprises a cylinder 2, closed at its lower end by the base 3 of the device and open at its upper end.
  • a piston 4 provided with a lip seal 5 and extended at its upper part by a rod 6 which passes through the seal in a sealed manner, using a seal 7 upper 8 of the jack screwed onto the upper end of the cylinder 2.
  • the upper end of the rod 6 of the jack may further end in the usual manner by a support piece 9 comprising a threaded lower rod 10 which is screwed freely in the rod 6 in order to allow manual adjustment of the initial height of the jack.
  • the pressureless oil reserve is located at 13 between the cylinder 2 and the casing 11.
  • a hand pump actuable by a lever not shown and consisting of a sliding plunger 14 in a bore 15 of the base, with in addition communication channels and suction and discharge valves, shown in FIG. 1 and not referenced, to allow the pump to draw the oil into the reserve 13 and to discharge it inside the cylinder 2 through the base thereof.
  • a tap or relief valve 16 controlled by hand to allow, with an adjustable pressure drop, the communication between the interior of the cylinder 2 and the reserve 13 in order to ensure the descent control at the desired speed, after the hand pump 14 has produced the rise of the rod 6.
  • the piston 4 instead of the lateral discharge hole usually provided in the wall 2, provision is made to mount the piston 4 on the rod 6 in a movable manner with a determined axial play.
  • the rod 6 can be extended by a reduced portion 17 on which the piston 4 threads, provided for this purpose with a central bore 18 with a diameter slightly larger than the outside diameter of 17 so to allow both a play and a passage of oil.
  • a summary stop constituted for example by a simple circlip 19 placed in a groove 20 near the end of the reduced part 17, makes it possible to prevent the piston 4 from completely detaching from its rod 6.
  • a flat seal 21 coming to bear directly on the flat shoulder 22 of the rod 6 around its reduced part 17.
  • a vulcanized fiber joint of sufficient hardness preferably 40 to 100 Rockwells, is used to maintain an operating pressure of 1800 to 2500 bars.
  • this seal 21 is preferably placed in a groove made in the piston 4 or in the shoulder 22, this groove naturally being of a depth less than the thickness of the uncompressed seal.
  • the device is arranged so that the screw connection between the upper bearing 8 and the upper end of the cylinder 2 is not sealed, for example by not screwing it to the end, as shown in FIG 2, so in providing an annular space 23, and in addition providing one or more orifices 24 for communication between this space 23 and the reserve 13.
  • the outside diameter of the rod 6, that is to say therefore the inside diameter of the bore 25 of the upper bearing 8, is slightly less than the outside diameter of the piston 4 and the bore inside 26 of cylinder 2, so that the piston 4 does not run the risk of passing through the bore 25.
  • the piston 4 reaches the top of its travel, as shown in FIG. 3, it abuts on the shoulder 27 of the upper bearing 8 surrounding the bore 25, which produces a slight increase in the pressure in the cylinder 2 in a ratio which is the square of the ratio of the diameters of the bore 26 and of the seal 21, whereby the rod 6 continues to rise with an extremely short stroke, just sufficient to allow the decompression of the seal 21 and the escape of the oil through the interval 28, greatly exaggerated in FIG.
  • the production of which is just as economical as the usual production, and even more, if you take into account the possibility of using a rubber seal 5 of the usual type, there is the advantage of a very long service life due to the absence of deterioration of the seals, and at the same time a high level of safety while using the entire stroke.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Structural Engineering (AREA)
  • Actuator (AREA)

Description

L'invention concerne les crics hydrauliques, constituée par un vérin hydraulique vertical entouré d'une réserve d'huile coaxiale et munis d'une pompe à main, aspirant dans la réserve et refoulant dans le base du vérin pour assurer la montée, avec en outre un robinet ou clapet de décharge permettant la descente.The invention relates to hydraulic jacks, consisting of a vertical hydraulic cylinder surrounded by a reserve of coaxial oil and provided with a hand pump, sucking in the reserve and discharging into the base of the jack to ensure the rise, with in in addition to a tap or relief valve allowing the descent.

La force développée par ce vérin peut atteindre des valeurs assez considérables, et pour des raisons de sécurité il est imposé de les munir d'un dispositif de limitation de course hydraulique assurant la décharge de la pression lorsque le piston du vérin arrive au point haut de sa course afin d'éviter toute rupture de pièce et effondrement de charge consécutif.The force developed by this jack can reach fairly considerable values, and for safety reasons it is necessary to provide them with a hydraulic stroke limiting device ensuring the discharge of the pressure when the piston of the jack reaches the high point of its stroke in order to avoid any part rupture and subsequent load collapse.

Une première solution, selon le documment US-A-4 077 608, consiste à munir le piston du vérin d'un joint à lèvre d'une forme dérivée du classique cuir de pompe, et à constituer le dispositif de limitation de course hydraulique simplement par un trou ou une rainure pratiqué dans la paroi du cylindre du vérin, au voisinage du point haut de sa course, pour faire communiquer l'intérieur du cylindre avec la réserve lorsque ce trou ou cette rainure se trouve démasqué par la lèvre du joint du piston.A first solution, according to the document US-A-4 077 608, consists in providing the piston of the jack with a lip seal of a form derived from the classic pump leather, and in constituting the hydraulic stroke limiting device simply by a hole or a groove made in the wall of the cylinder of the jack, in the vicinity of the high point of its stroke, to make the interior of the cylinder communicate with the reserve when this hole or this groove is exposed by the lip of the seal of the piston.

Un tel dispositif est relativement efficace mais présente l'inconvénient que la lèvre du joint se trouve happée par la différence de pression vers l'intérieur du trou, en même temps que se produit son mouvement de montée et de descente, de sorte que le joint se trouve rapidement détérioré, surtout si le joint est en caoutchouc. Pour y remédier en partie, on utilise le plus souvent un joint en cuir qui est plus onéreux, moins étanche, et qui se trouve néanmoins happé dans le trou; il en résulte l'arrachement de particules de cuir qui se trouvent ensuite en suspension dans l'huile, ce qui altère le fonctionnement de l'ensemble du cric, en particulier au niveau des clapets de la pompe. Un autre inconvénient mineur du dispositif à trou latéral est qu'il faut prévoir en fin de course un supplément de course sensiblement égal au diamètre du trou pour être sûr d'opérer la décharge.Such a device is relatively effective but has the drawback that the seal lip is caught up in the pressure difference towards the inside of the hole, at the same time as its up and down movement occurs, so that the seal quickly deteriorates, especially if the seal is rubber. To partially remedy this, a leather seal is more often used which is more expensive, less waterproof, and which is nevertheless caught in the hole; this results in the tearing of particles of leather which are then suspended in the oil, which alters the functioning of the entire jack, in particular at the level of the valves of the pump. Another minor drawback of the device with a lateral hole is that an additional stroke must be provided at the end of the stroke which is substantially equal to the diameter of the hole in order to be sure of discharging.

Une autre solution pour remédier au problème exposé consiste, selon le document US-A-3404 868, à utiliser un piston avec joints périphériques d'étanchéité, mais monté à l'extrémité de la tige de manière mobile axialement et non étanche en partie centrale, l'étanchéité de cette partie centrale étant réalisée de manière temporaire à un niveau supérieur par contact métallique directe entre des surfaces coniques du piston et de la tige, de manière que cette étanchéité soit rompue lorsque le piston entre en butée à l'extrémité supérieure de sa course.Another solution to remedy the problem presented consists, according to document US-A-3404 868, of using a piston with peripheral seals, but mounted at the end of the rod in an axially movable manner and not leaktight in the central part. , the sealing of this central part being made temporarily at an upper level by direct metallic contact between conical surfaces of the piston and of the rod, so that this sealing is broken when the piston comes into abutment at the upper end of its course.

Cependant une telle solution est mal adaptée à l'utilisation de hautes pressions par le fait qu'en fonctionnement normal, l'étanchéité métal sur métal est insuffisante, alors qu'en fin de course, lorsque doit se produire la fuite du débit de la pompe, depuis la partie centrale du piston vers l'écoulement prévu à la partie supérieure du cylindre, le contact de la périphérie du piston avec sa butée est au contraire trop étanche pour assurer ce débit.However, such a solution is ill-suited to the use of high pressures by the fact that in normal operation, the metal-to-metal seal is insufficient, whereas at the end of the race, when the flow of the flow from the pump, from the central part of the piston towards the flow provided at the upper part of the cylinder, the contact of the periphery of the piston with its stop is, on the contrary, too tight to ensure this flow.

Le but de l'invention est d'éliminer l'inconvénient précédent en réalisant un dispositif limiteur de course du type précédent, à piston monté mobile axialement et non étanche en partie centrale sur l'extrémité de sa tige, mais agencé pour l'utilisation de hautes pressions en assurant à la fois une parfaite étanchéité en fonctionnement normal, et un débit de fuite suffisant en fin de course.The object of the invention is to eliminate the preceding drawback by producing a stroke limiting device of the preceding type, with a piston mounted axially movable and not leaktight in the central part on the end of its rod, but arranged for use. high pressures ensuring both perfect sealing in normal operation and sufficient leakage rate at the end of the stroke.

Selon l'invention, ce résultat est atteint grâce au fait

  • a) qu'un joint plat (21) est disposé dans une gorge pratiquée dans une des deux surfaces en regard du piston (4) et de l'épaulement (22), et que ledit joint plat (21) est un joint d'une dureté suffisante pour tenir une pression élevée,
  • b) que ladite gorge a une profondeur à peine inférieure à l'épaisseur du joint plat (21) à l'état comprimé, et
  • c) que des encoches radiales (29) sont pratiquées entre cette gorge et la périphérie de l'organe correspondant (6 ou 4) (pour assurer le passage de l'huile entre le piston (4) et le palier d'extrémité (8) lorsque ladite périphérie vient buter sur le palier supérieur (8).
According to the invention, this result is achieved thanks to the fact
  • a) that a flat seal (21) is arranged in a groove formed in one of the two surfaces facing the piston (4) and the shoulder (22), and that said flat seal (21) is a seal of sufficient hardness to withstand high pressure,
  • b) that said groove has a depth barely less than the thickness of the flat seal (21) in the compressed state, and
  • c) that radial notches (29) are formed between this groove and the periphery of the corresponding member (6 or 4) (to ensure the passage of the oil between the piston (4) and the end bearing (8 ) when said periphery abuts on the upper bearing (8).

D'autres particularités de l'invention apparaîtront dans la description qui va suivre d'un mode de réalisation pris comme exemple et représenté sur le dessin annexé, sur lequel

  • la fig. 1 est une vue en coupe axiale de l'ensemble du vérin;
  • la fig. 2 est une coupe partielle à plus grande échelle au niveau du piston; et
  • la fig. 3 est une vue analogue à la fig. 2 montrant le piston arrivé en fin de course.
Other features of the invention will appear in the following description of an embodiment taken as an example and shown in the accompanying drawing, in which
  • fig. 1 is an axial sectional view of the entire cylinder;
  • fig. 2 is a partial section on a larger scale at the piston; and
  • fig. 3 is a view similar to FIG. 2 showing the piston reaching the end of the stroke.

Le cric 1 comprend d'une manière usuelle un cylindre de vérin 2, fermé à son extrémité inférieure par la base 3 de l'appareil et ouvert à son extrémité supérieure. Dans l'alésage intérieur 26 de ce cylindre peut coulisser de manière étanche un piston 4, muni d'un joint à lèvre 5 et prolongé à sa partie supérieure par une tige 6 qui traverse de manière étanche, grâce à un joint 7, le palier supérieur 8 du vérin vissé sur l'extrémité supérieure du cylindre 2. L'extrémité supérieure de la tige 6 du vérin peut en outre se terminer d'une manière usuelle par une pièce d'appui 9 comportant une tige inférieure filetée 10 qui se visse librement dans la tige 6 afin de permettre manuellement une adaptation de la hauteur initiale du cric.The jack 1 usually comprises a cylinder 2, closed at its lower end by the base 3 of the device and open at its upper end. In the inner bore 26 of this cylinder can slide in a sealed manner a piston 4, provided with a lip seal 5 and extended at its upper part by a rod 6 which passes through the seal in a sealed manner, using a seal 7 upper 8 of the jack screwed onto the upper end of the cylinder 2. The upper end of the rod 6 of the jack may further end in the usual manner by a support piece 9 comprising a threaded lower rod 10 which is screwed freely in the rod 6 in order to allow manual adjustment of the initial height of the jack.

Autour du cylindre principal 2 se trouve disposé concentriquement une enveloppe extérieure 11 qui se raccorde de manière étanche avec la base 3 et avec le palier supérieur 8 et qui comporte un bouchon 12 de niveau d'huile. En effet, la réserve d'huile sans pression est située en 13 entre le cylindre 2 et l'enveloppe 11.Around the main cylinder 2 is located concentrically an outer casing 11 which is tightly connected with the base 3 and with the upper bearing 8 and which comprises a plug 12 for the oil level. Indeed, the pressureless oil reserve is located at 13 between the cylinder 2 and the casing 11.

Dans la base 3 est prévue une pompe à main actionnable par un levier non représenté et constitué par un piston plongeur 14 coulissant dans un alésage 15 de la base, avec en outre des canaux de communication et des clapets d'aspiration et de refoulement, représentés sur la fig. 1 et non référencés, pour permettre à la pompe d'aspirer l'huile dans la réserve 13 et de la refouler à l'intérieur du cylindre 2 par la base de celui-ci. En outre, il est prévu un robinet ou clapet de décharge 16 commandé à la main pour permettre, avec une perte de charge réglable, la communication entre l'intérieur du cylindre 2 et la réserve 13 afin d'assurer la commande de descente à la vitesse voulue, après que la pompe à main 14 ait produit la montée de la tige 6.In the base 3 is provided a hand pump actuable by a lever not shown and consisting of a sliding plunger 14 in a bore 15 of the base, with in addition communication channels and suction and discharge valves, shown in FIG. 1 and not referenced, to allow the pump to draw the oil into the reserve 13 and to discharge it inside the cylinder 2 through the base thereof. In addition, there is a tap or relief valve 16 controlled by hand to allow, with an adjustable pressure drop, the communication between the interior of the cylinder 2 and the reserve 13 in order to ensure the descent control at the desired speed, after the hand pump 14 has produced the rise of the rod 6.

Comme exposé plus haut, avec un tel vérin il existe le danger qu'une fois que le piston 4 est arrivé à l'extrémité supérieure de la course il se produise, lorsqu'on force sur le piston 14, un accroissement important de la force développée qui puisse amener des ruptures de pièces ou de joints produisant l'effondrement de la charge soulevée par la tête 9. C'est pour cette raison qu'il est imposé un limiteur hydraulique de course.As explained above, with such a cylinder there is the danger that once the piston 4 has reached the upper end of the stroke, there will be produced, when the piston 14 is forced, a significant increase in the force developed which could lead to ruptures of parts or joints producing the collapse of the load lifted by the head 9. It is for this reason that a hydraulic stroke limiter is imposed.

Conformément à l'invention, à la place du trou latéral de décharge habituellement prévu dans la paroi 2, il est prévu de monter le piston 4 sur la tige 6 d'une manière mobile avec un jeu axial déterminé. Par exemple, la tige 6 peut se prolonger par une partie réduite 17 sur laquelle s'enfile le piston 4, muni à cet effet d'un alésage central 18 d'un diamètre légèrement plus grand que le diamètre de l'extérieur de 17 afin de permettre tout à la fois un jeu et un passage d'huile. Un arrêt sommaire, constitué par exemple par un simple circlip 19 placé dans une gorge 20 près de l'extrémité de la partie réduite 17, permet d'empêcher le piston 4 de se désolidariser complètement de sa tige 6.According to the invention, instead of the lateral discharge hole usually provided in the wall 2, provision is made to mount the piston 4 on the rod 6 in a movable manner with a determined axial play. For example, the rod 6 can be extended by a reduced portion 17 on which the piston 4 threads, provided for this purpose with a central bore 18 with a diameter slightly larger than the outside diameter of 17 so to allow both a play and a passage of oil. A summary stop, constituted for example by a simple circlip 19 placed in a groove 20 near the end of the reduced part 17, makes it possible to prevent the piston 4 from completely detaching from its rod 6.

En outre, conformément à l'invention, il est prévu dans la partie supérieure du piston 4 un joint plat 21 venant porter directement sur l'épaulement plan 22 de la tige 6 à l'entour de sa partie réduite 17. Pour éviter tout écrasement exagéré de ce joint 21, on utilise un joint en fibre vulcanisée d'une dureté suffisante, de préférence de 40 à 100 Rockwell pour tenir une pression de service de 1800 à 2500 bars. En outre, ce joint 21 se trouve de préférence placé dans une gorge pratiquée dans le piston 4 ou dans l'épaulement 22, cette gorge étant naturellement d'une profondeur inférieure à l'épaisseur du joint non comprimé.In addition, in accordance with the invention, there is provided in the upper part of the piston 4 a flat seal 21 coming to bear directly on the flat shoulder 22 of the rod 6 around its reduced part 17. To avoid any crushing exaggerated of this joint 21, a vulcanized fiber joint of sufficient hardness, preferably 40 to 100 Rockwells, is used to maintain an operating pressure of 1800 to 2500 bars. In addition, this seal 21 is preferably placed in a groove made in the piston 4 or in the shoulder 22, this groove naturally being of a depth less than the thickness of the uncompressed seal.

Enfin, le dispositif est agencé pour que le raccordement vissé entre le palier supérieur 8 et l'extrémité supérieure du cylindre 2 ne soit pas étanche, par exemple en ne le vissant pas jusqu'au bout, comme représenté sur la fig 2, de manière à ménager un espace annulaire 23, et en prévoyant en outre un ou plusieurs orifices 24 de communication entre cet espace 23 et la réserve 13.Finally, the device is arranged so that the screw connection between the upper bearing 8 and the upper end of the cylinder 2 is not sealed, for example by not screwing it to the end, as shown in FIG 2, so in providing an annular space 23, and in addition providing one or more orifices 24 for communication between this space 23 and the reserve 13.

Lorsqu'on actionne la pompe 14 pour mettre en pression l'intérieur du cylindre 2, le piston 4 appuie fortement sous l'épaulement 22 de la tige 6 ce qui assure par conséquent l'étanchéité entre le piston et la tige et assure l'ascension de la charge d'une manière habituelle.When the pump 14 is actuated to pressurize the interior of the cylinder 2, the piston 4 presses strongly under the shoulder 22 of the rod 6 which consequently ensures the seal between the piston and the rod and ensures the load as usual.

Comme à l'ordinaire, le diamètre extérieur de la tige 6, c'est-à-dire par conséquent le diamètre intérieur de l'alésage 25 du palier supérieur 8, est légèrement inférieur au diamètre extérieur du piston 4 et de l'alésage intérieur 26 du cylindre 2, de sorte que le piston 4 ne risque pas de passer à travers l'alésage 25. Au contraire de cela, lorsque le piston 4 arrive au sommet de sa course, comme représenté sur la fig. 3, il vient buter sur l'épaulement 27 du palier supérieur 8 entourant l'alésage 25, ce qui produit une légère augmentation de la pression dans le cylindre 2 dans un rapport qui est le carré du rapport des diamètres de l'alésage 26 et du joint 21, grâce à quoi la tige 6 continue à monter d'une course extrêmement faible, juste suffisante pour permettre la décompression du joint 21 et l'échappement de l'huile par l'intervalle 28, fortement exagéré sur la fig. 3, existant entre le joint 21 et l'épaulement 22. Par sécurité il est prévu également des encoches radiales 29 dans le dessus du piston 4 entre la gorge recevant le joint 21 et la périphérie du piston (ou de la tige) afin de permettre à l'échappement de l'huile par 28 à se continuer par les encoches 29, par la chambre annulaire 23, puis par les orifices 24 jusqu'à la réserve.As usual, the outside diameter of the rod 6, that is to say therefore the inside diameter of the bore 25 of the upper bearing 8, is slightly less than the outside diameter of the piston 4 and the bore inside 26 of cylinder 2, so that the piston 4 does not run the risk of passing through the bore 25. On the contrary, when the piston 4 reaches the top of its travel, as shown in FIG. 3, it abuts on the shoulder 27 of the upper bearing 8 surrounding the bore 25, which produces a slight increase in the pressure in the cylinder 2 in a ratio which is the square of the ratio of the diameters of the bore 26 and of the seal 21, whereby the rod 6 continues to rise with an extremely short stroke, just sufficient to allow the decompression of the seal 21 and the escape of the oil through the interval 28, greatly exaggerated in FIG. 3, existing between the seal 21 and the shoulder 22. For safety, there are also provided radial notches 29 in the top of the piston 4 between the groove receiving the seal 21 and the periphery of the piston (or of the rod) in order to allow when the oil escapes through 28, continue through the notches 29, through the annular chamber 23, then through the orifices 24 to the reserve.

On voit que cette décharge de la pression a lieu sans aucune détérioration possible du joint principal 5 ni du joint auxiliaire 21 qui ne rencontre jamais que des surfaces lisses et continues.It can be seen that this pressure relief takes place without any possible deterioration of the main seal 5 or of the auxiliary seal 21 which never meets anything other than smooth and continuous surfaces.

En réalité, naturellement cette décharge de la pression ne se produit jamais complètement tant que la charge demeure sur la tête 9, et seul l'excédent est évacué, comme c'est le cas habituellement, de manière à assurer la sécurité et en même temps le maintien de la charge en postion haute, la descente n'étant produite que par l'action manuelle sur la décharge 16. Ceci revient à dire qu'aucun supplément de course n'est nécessaire pour le piston 4, et que le supplément de course qui intervient seulement pour la tige 6 n'utilise qu'une fraction infime du jeu axial prévu pour le piston 4 sur la partie réduite 17, cette partie infime étant celle nécessaire pour assurer la décharge de la pression sur le grand diamètre du joint 21.In reality, of course, this pressure discharge never occurs completely as long as the charge remains on the head 9, and only the excess is evacuated, as is usually the case, so as to ensure safety and at the same time maintaining the load in the high position, the descent being produced only by manual action on the discharge 16. This amounts to saying that no additional stroke is necessary for the piston 4, and that the additional stroke which occurs only for the rod 6 uses only a tiny fraction of the axial clearance provided for the piston 4 on the reduced part 17, this tiny part being that necessary to ensure the discharge of the pressure over the large diameter of the seal 21 .

En effet, pour limiter le rapport d'augmentation de pression en fin de course à une valeur tolérée, on a intérêt à donner au diamètre du joint 21 une valeur aussi proche que possible du diamètre de l'alésage 26.In fact, to limit the ratio of pressure increase at the end of travel to a tolerated value, it is advantageous to give the diameter of the seal 21 a value as close as possible to the diameter of the bore 26.

Grâce à l'invention, dont la réalisation est tout aussi économique que la réalisation habituelle, et même davantage, si t'en tient compte de la possibilité d'utiliser un joint 5 en caoutchouc du type usuel, on a l'avantage d'une très grande longévité par absence de détérioration des joints, et en même temps une grande sécurité tout en utilisant la totalité de la course.Thanks to the invention, the production of which is just as economical as the usual production, and even more, if you take into account the possibility of using a rubber seal 5 of the usual type, there is the advantage of a very long service life due to the absence of deterioration of the seals, and at the same time a high level of safety while using the entire stroke.

Naturellement, l'invention s'applique à tous les types de crics hydrauliques à commande à main.Naturally, the invention applies to all types of hydraulic jacks with manual control.

Claims (4)

1. Hydraulic jack having a hand pump (14, 15) which sucks oil into a reserve (13) which is not under pressure to deliver it to a cylinder (2) in the bore (26) of which there slides a piston (4) provided with a rod (6) which passes through an upper bearing (8) in order to lift a load, moreover having a hydraulic travel limitation means ensuring that the pressure in the cylinder (2) is released when the piston (4) reaches the upper end of its travel, the said travel limiter is constructed by selecting the size of the piston (4) such that it can abut against the upper bearing (8) and by mounting it in non-sealed manner and with an axial play at the narrowed lower end (17) of the rod (6), the upper end of the piston (4) bearing against a shoulder (22) provided below the rod (6) around its narrowed end (17), communication passages (29, 23, 24) being provided to allow the flow towards the resetve (13) of the oil which escapes between the said shoulder (22) and the said upper end of the piston at the upper end of travel of the jack, characterized in that
a) a sheet gasket (21) is arranged in a groove made in one of the two opposing surfaces of the piston (4) and the shoulder (22), and in that the said sheet gasket (21) is a gasket of sufficient strength to support an elevated pressure,
b) the said groove has a depth barely less than the thickness of the sheet gasket (21) in the compressed state, and
c) radial notches (29) are made between this groove and the periphery of the corresponding element (6 or 4) to ensure passage of the oil between the piston (4) and the end bearing (8) when the said periphery abuts against the upper bearing (8).
2. Jack according to claim 1, characterized in that the upper end of the cylinder (2) does not abut against the shoulder (22) of the bearing (8) which the piston (4) meets, but on the contrary allows an annular recess (23) to remain, which communicates by means of at least one orifice (24) with the reserve (13) in order to constitute the said communication passages towards the reserve.
3. Jack according to one of the preceding claims, characterized in that the diameter of the auxiliary sheet gasket (21) is as close as possible to the diameter of the bore (26) of the cylinder (2).
4. Jack according to one of the preceding claims, characterized in that the narrowed part (17) of the rod (6) has a circlip (19) mounted in a groove (20) close to its lower end to prevent the separation of the piston (4) from this rod (6) and to ensure the said limited axial play.
EP19840114236 1984-11-26 1984-11-26 Hydraulic jack with limited travel Expired EP0182927B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE8484114236T DE3474134D1 (en) 1984-11-26 1984-11-26 Hydraulic jack with limited travel
EP19840114236 EP0182927B1 (en) 1984-11-26 1984-11-26 Hydraulic jack with limited travel

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19840114236 EP0182927B1 (en) 1984-11-26 1984-11-26 Hydraulic jack with limited travel

Publications (2)

Publication Number Publication Date
EP0182927A1 EP0182927A1 (en) 1986-06-04
EP0182927B1 true EP0182927B1 (en) 1988-09-21

Family

ID=8192308

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19840114236 Expired EP0182927B1 (en) 1984-11-26 1984-11-26 Hydraulic jack with limited travel

Country Status (2)

Country Link
EP (1) EP0182927B1 (en)
DE (1) DE3474134D1 (en)

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1720434A (en) * 1924-12-05 1929-07-09 Oil Jack Inc Fluid-operated jack
FR998545A (en) * 1945-10-25 1952-01-21 Improvement in hydraulic cylinders
US2520426A (en) * 1947-10-15 1950-08-29 Auto Specialties Mfg Co Hydraulic jack
FR1175430A (en) * 1957-02-05 1959-03-26 Saxby Ets Improvements in hydro-mechanical transmissions
US3311026A (en) * 1965-12-27 1967-03-28 Caterpillar Tractor Co Bypass valve for hydraulic jacks
US3404868A (en) * 1966-06-22 1968-10-08 Walker Mfg Co Hydraulic jack
GB1239648A (en) * 1969-07-04 1971-07-21
US3601011A (en) * 1969-07-22 1971-08-24 Tenneco Inc Diffusion ring for limiting hydraulic ram travel
US4077608A (en) * 1977-01-04 1978-03-07 Auto Specialties Manufacturing Company Hydraulic hand jack
FR2547290B1 (en) * 1983-06-07 1987-04-30 Rassant Sa Ets F HYDRAULIC JACK WITH IMPROVED TRAVEL LIMITER

Also Published As

Publication number Publication date
DE3474134D1 (en) 1988-10-27
EP0182927A1 (en) 1986-06-04

Similar Documents

Publication Publication Date Title
EP0235065B1 (en) Installation for filling containers by use of counter-pressure
EP2870516A1 (en) Pressure-reducing valve having a residual pressure function built into the reducing valve
WO1999056045A1 (en) Differential relief valve for flexible sea line
EP0227541B1 (en) Pressure relief valve with integrated pilot valve
FR2704478A3 (en) Press-driven tool module, particularly press-driven coining element.
EP0182927B1 (en) Hydraulic jack with limited travel
FR2658580A1 (en) PILOT PRESSURE CUT-OFF VALVE AND PILOTAGE VALVE.
FR3044572A1 (en) ROCK BRISE DEVICE
EP0287434B1 (en) Differential hydraulic jack, with a damping device, for operating electric breakers
FR2636379A1 (en) Anti-bounce safety valve for hydraulic jack or similar.
FR2547290A1 (en) Hydraulic jack with improved travel stop
EP1069355B1 (en) Safety valve for pressure vessel
EP3428740B1 (en) Safety valve for a watch
EP3051150A1 (en) Proximity sensor for aircraft provided with a hydraulic fuse
FR2681685A1 (en) LEVEL DETECTOR WITHIN A CONTAINER CONTAINING A GRANULAR MATERIAL, ESPECIALLY SAND, PARTICULARLY INSIDE A SANDBLASTER ASSOCIATED WITH A DRIVE WHEEL.
FR2878313A1 (en) Pressurized gas distribution assembly for bottle, has valve with control rod cooperating with operating rod which exerts thrust on former rod when main piston is in end position, to unhook auxiliary piston to open valve in filling direction
FR2576966A1 (en) ANNULAR SAFETY ASSEMBLY FOR OIL WELLS, PARTICULARLY WITH DOUBLE PRODUCTION AREA
FR2484029A1 (en) Double acting selector valve - has sliding cylinder moving across casing to connect operating cylinder to valve
EP0260166B1 (en) Bottle device forming a gas vessel under pressure
FR2609774A1 (en) SAFETY VALVE FOR HIGH PRESSURE FLUID AND ABRASIVE
FR2526778A1 (en) Double actuator hydraulic lifting device - has simple and sequential type non return valves
EP0133399A1 (en) Hydraulic security device for roll adjustment in rolling mills
EP0516528A1 (en) Safety valve for the ventilation of a fuel tank of a motor vehicle
EP1895378B1 (en) Pressurised gas flow or pressure regulation device
WO1990002899A1 (en) High pressure valve usable particularly in a fluid jet cutting tool

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE GB IT SE

17P Request for examination filed

Effective date: 19861201

17Q First examination report despatched

Effective date: 19870923

ITF It: translation for a ep patent filed

Owner name: SOCIETA' ITALIANA BREVETTI S.P.A.

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE GB IT SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19880921

REF Corresponds to:

Ref document number: 3474134

Country of ref document: DE

Date of ref document: 19881027

GBV Gb: ep patent (uk) treated as always having been void in accordance with gb section 77(7)/1977 [no translation filed]
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19921117

Year of fee payment: 9

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19931127

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19950130

Year of fee payment: 11

EUG Se: european patent has lapsed

Ref document number: 84114236.7

Effective date: 19940610

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19960801