EP0589006B1 - Dispositif hydraulique d'entrainement a verin - Google Patents

Dispositif hydraulique d'entrainement a verin Download PDF

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Publication number
EP0589006B1
EP0589006B1 EP93906521A EP93906521A EP0589006B1 EP 0589006 B1 EP0589006 B1 EP 0589006B1 EP 93906521 A EP93906521 A EP 93906521A EP 93906521 A EP93906521 A EP 93906521A EP 0589006 B1 EP0589006 B1 EP 0589006B1
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EP
European Patent Office
Prior art keywords
hydraulic drive
seal
drive apparatus
cylinder head
valve
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 - Lifetime
Application number
EP93906521A
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German (de)
English (en)
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EP0589006A1 (fr
Inventor
Otmar KRÄMER
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Bosch Rexroth AG
Original Assignee
Mannesmann Rexroth AG
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Publication of EP0589006A1 publication Critical patent/EP0589006A1/fr
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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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/149—Fluid interconnections, e.g. fluid connectors, passages
    • 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
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/1423—Component parts; Constructional details
    • F15B15/1433—End caps

Definitions

  • the invention relates to a hydraulic drive device which has the features from the preamble of claim 1.
  • Such a hydraulic drive device is already known from DE 3026877A1.
  • a hydraulic cylinder with a piston rod the implementation of which is sealed by the cylinder head with the help of two seals.
  • the primary seal which is closer to the piston working space, is a ring made of metal or another dimensionally stable material, e.g. plastic with the corresponding properties.
  • This primary seal is wear-resistant but not leak-free. Therefore, there is a collecting ring groove between it and the secondary seal for the leakage oil that is not retained by the primary seal and that can drain through a leakage oil line starting from the collecting ring groove.
  • the secondary seal is therefore not the system or. Load holding pressure exposed. Their wear is therefore only slight.
  • a disadvantage of the known hydraulic drive device is the permanent loss of leakage oil, which does not allow a load to be held at a specific point when the pump is switched off. The piston would slowly move out of position so that the load also changes position.
  • the invention has for its object to develop a hydraulic drive device with the features from the preamble of claim 1 so that the cylinder can hold its position even when the pump is switched off.
  • the firm contact with the stationary piston rod does not lead to wear on the secondary seal which affects the service life of the cylinder.
  • the leakage oil line can be connected to the tank via the valve, so that the secondary seal is not subjected to the system pressure and there is a slight tension on the sealing surfaces, which is sufficient to pass the piston rod through to seal the cylinder head leak-free, which is, however, also so small that the movement of the piston rod leads to little wear on the secondary gasket.
  • the valve that is to be switched over in order to apply load holding pressure to the leakage oil line is particularly simple in construction if the leakage oil line can be shut off by switching over the valve.
  • the load holding pressure before the secondary seal then builds up along the piston rod. If the pressure builds up very quickly, it appears favorable if the leak oil line can be connected via the valve to the pressure chamber of the cylinder on the piston rod side.
  • the pressure chambers on both sides of the piston can be alternately connected to a pump and a tank via a directional valve. If one wants to keep the number of individual structural components low in a hydraulic drive device according to the invention, it seems expedient that, according to claim 4, the leakage oil line is connected to the directional control valve and can be acted upon by load switching pressure by switching it over. However, the construction of the directional control valve, which must then have five connections, can be complicated. In the preferred embodiment according to claim 5, the leak oil line is therefore connected to an additional valve and can be acted upon by switching this additional valve with load holding pressure.
  • the valve to which the leak oil line is connected is preferably designed such that it can be switched from a starting position into a switching position, in particular by a lifting magnet against the force of a return spring. It may therefore be held in the starting position by the return spring in connection with a second return spring. If the time in which the piston and the piston rod of the cylinder are moved is shorter than the time in which they are to be held in a rest position against a load, then the leakage oil line is can advantageously be loaded with load holding pressure in the initial position of the valve. The time in which the solenoid, which can also belong to a pilot stage of the valve, must be supplied with voltage is then limited to the time in which the piston and the piston rod move.
  • the secondary seal is already in contact with the piston rod and the cylinder head with a certain preload when the leak oil can flow freely through the leak oil line.
  • This preload can be achieved by coordinating the dimensions of the piston rod, the seal and the mounting of the seal in the cylinder head, i.e. the inner diameter of the seal is slightly smaller than the diameter of the piston rod and / or the outer diameter of the seal is slightly larger than that Select the diameter of the mount in the cylinder head.
  • the seal can then be called self-biased.
  • the secondary seal can be installed more easily if it can be externally pre-tensioned to the smallest axial dimension using a support ring that can be placed on a shoulder of the cylinder head. If the support ring rests on the shoulder, this smallest axial dimension of the secondary seal is reached. Before the support ring rests on the shoulder, the preload of the secondary seal can be set to different values. In particular, the preload can also be readjusted while the cylinder is in use. It is considered to be particularly advantageous if the support ring according to claim 10 has a hydraulically actuated, axially up to the shoulder of the cylinder head slidable piston is biased.
  • the preload can be changed by changing the pressure exerted on the piston. It is easy to see that such variability in the preload of the seal is advantageous even when there is no primary seal and no leakage oil line are. can adjust the preload of the seal regardless of its tolerances and adjust it during the life of the cylinder.
  • the cylinder head has two parts, the first part being the secondary seal and the drain line and a second part containing the working connection to the pressure chamber of the cylinder on the piston rod side. It is then easily possible to plunge ring grooves open radially inward and axially on one side on the first and / or second part in order to create receptacles for additional parts into which these additional parts can easily be inserted.
  • These additional parts can be the primary seal, which can be arranged on the second part of the cylinder head, but which, according to claim 16, is advantageously arranged on the first part of the cylinder head like the secondary seal.
  • a guide bush for the piston rod is advantageously arranged in the cylinder head between the primary seal and a working connection to the piston rod-side pressure chamber, so that good lubrication between the piston rod and guide bush is ensured.
  • the various exemplary embodiments of a hydraulic drive device according to the invention shown in the figures comprise a cylinder 10 with a cylinder head 11, a cylinder base 12 and a cylinder tube 13 extending between the cylinder head 11 and the cylinder base 12.
  • a flange 14 is screwed onto both ends of the cylinder tube 13 , on which, as can be seen in FIG. 2, the cylinder head 11 or the cylinder base 12 are fastened with axially extending machine screws 15.
  • a piston 16 is displaceable, which is seated on a piston rod 17, which emerges through a central passage 18 in the cylinder head 11.
  • This passage 18 is sealed with two seals, a primary seal 19 and a secondary seal 20, leak-free to the outside.
  • the primary seal is arranged closer to the piston rod-side pressure chamber 21 than the secondary seal 20 and is not leak-free.
  • Annular groove 22 is screwed in, which serves as a collecting space for the leakage oil passing through the primary seal and from which a radial bore 23 leads to the outside of the cylinder head 11.
  • the radial bore 23 is part of a leakage oil line, which is provided with the reference number 24 and is connected to the single outlet A of a 3/2-way valve 25.
  • the directional control valve 25 also has two inputs T and P, the input T being connected to a tank 26.
  • a working connection 30 which leads into the pressure chamber 21 on the piston rod side and which is connected via a line 29 to the outlet A of a 4/2-way valve 31.
  • a line 32 connects the outlet B of the directional control valve 31 to a working connection 33 in the cylinder base 12, which leads into the piston-side pressure chamber 34 of the cylinder 10.
  • the inlet P of the directional valve 31 is connected to a pump 40 via a check valve 35 and the inlet T of the directional valve 31 to the tank 26.
  • the directional control valve 31 serves to reverse the direction of movement of the piston 16 of the cylinder 10.
  • the input P of the directional control valve 25 is connected to the line 29 leading from the output A of the directional control valve 31 to the working connection 30 of the cylinder 10. In the shown rest position of the valve 25, which it assumes due to the spring 38, the inlet P is blocked and the leak oil can flow to the tank 26.
  • the leakage oil line 24 is connected to the input P and thus to the line 29, the working connection 30 of the cylinder 10 and finally to the pressure chamber 21.
  • Fig. 1 the valves 25 and 31 are shown in the rest position determined by the springs 38 and 36.
  • the pump 40 is running.
  • the piston 16 and the piston rod 17 are located shortly before the end of their return stroke to the right.
  • leakage oil that has passed through the primary seal 19 has flowed to the tank 26 via the valve 25.
  • the secondary seal is not exposed to the system pressure prevailing in the pressure chamber 21 and is pressed against the piston rod 17 with a predetermined low tension, which prevents oil from escaping at the end face of the cylinder head 11, but still keeps the wear low.
  • the pump 36 is switched off.
  • the lifting magnet 39 moves the valve into the other switching position, in which the leak oil line 24 is connected to the pressure chamber 21.
  • FIG. 2 shows more details of the construction of the cylinder 10, which is only shown in principle in FIG. 1.
  • the flange 14 can be seen, which is screwed onto the cylinder tube 13.
  • the cylinder head 11 held with screws 15 on the flange 14 has a first cylinder head part 45 and a second cylinder head part 46, which lie essentially axially one behind the other and of which the cylinder head part 46 is seated on the cylinder tube 13. Close to this cylinder tube 13 there is the working connection 30 in the cylinder head part 46, which is connected to the pressure chamber 21 on the piston rod side.
  • a guide bushing 47 is introduced into the cylinder head part 46 with a sliding seat, which is provided at one end with an outer collar 48 and thus engages in an annular groove 49 of the cylinder head part 46 that is open on the end side toward the cylinder head part 45.
  • the axial dimension of the outer collar 48 is equal to the axial dimension of the annular groove 49.
  • a first annular groove 55 which is open to the piston rod 17 and to one end face, and a second annular groove 56, which is likewise open to the piston rod 17 and the other end face of the cylinder head part 45, are introduced into the first cylinder head part 45.
  • the two ring grooves 55 and 56 are spaced apart. Between them is the annular groove 22 serving as a leakage oil collecting space, from which the radial bore 23 extends to the outside.
  • annular groove 55 In the annular groove 55 is the primary seal 19 and in the annular groove 56 Secondary seal 20 inserted.
  • a roof collar seal set known per se is provided, in which one or more sealing rings 57 are framed by a pressure ring 58 and a support ring 59. With axial pressure, the sealing rings spread and lie more or less firmly on the piston rod 17 and on the cylinder head part 45.
  • the sealing rings 57 normally consist of a rubber / fabric combination. However, only rubber boot seals are known.
  • the annular groove 56 is closed by a sealing flange 60 which is clamped onto a shoulder 62 of the cylinder head part 45 with screws 61 and projects into the annular groove 56 with a collar. The dimensions of the sealing set 20 and the remaining length of the annular groove 56 determine the tension of the seal 20.
  • a seal set which is known per se, is also used as the primary seal 19.
  • the sealing set contains four metallic piston rings 63 which bear radially against the piston rod 17 due to their own spring force.
  • a spacer ring 64 is located behind each piston ring 63.
  • a piston ring and the spacer ring 64 located behind it are each separated from the adjacent piston ring and adjacent spacer ring by a cover ring 65, the last ring on each side of the sealing set also being a cover ring 65.
  • the axial depth of the annular groove 55 corresponds to the total thickness of the sealing set 19, so that the one cover ring 65 is aligned with the end face of the cylinder head part 45 facing the cylinder head part 46 and bears against the collar 48 of the guide bush 47, which closes the annular groove 55.
  • the outer collar 48 of the guide bush 47 extends radially beyond the annular groove 55, so that it can be received between the first cylinder head part 45 and the second cylinder head part 46 and the guide bush 47 maintains a fixed position in the axial direction, without exerting pressure on the primary seal 19.
  • FIG. 3 is similar to that according to FIG. 2. Only the means with which the pretensioning of the secondary seal 20, which in turn is designed as a roof seal set, is generated.
  • an annular piston 71 is located in an annular space 70 formed by the first cylinder head part 45 and the sealing flange 60, which engages with an offset to the piston rod 17 and acts on the support ring 59 of the seal 20.
  • a closed pressure chamber is delimited by the first cylinder head part 45, the sealing flange 60 and the annular piston 71, from which a bore 73 leads radially outwards through the first cylinder head part.
  • the bore 73 can be connected to the working connection 30 of the cylinder head 11 with a line 74, into which a pressure reducing valve 75 can also be inserted.
  • the secondary seal 20 is prestressed to a specific dimension that can be set via the pressure reducing valve 75. If one also wants to have this pretension in the opposite direction of movement of the piston rod 17, the line 74 can be included of the pressure reducing valve 75 also connect directly to the pressure connection of the pump.
  • the prestressability of the seal 20 is limited in that the annular piston 71 abuts the shoulder 62 of the cylinder head part 45 after a certain distance.
  • a 4/3-way valve 31 is used to control the direction of movement of piston 16 and piston rod 17, the four ports P, T, A and B of which are blocked in the central position.
  • the leakage oil line 24 is connected to a 2/2-way valve 25, which in turn is held in the rest position by a spring 38 and can be switched to a second switching position by a solenoid 39. In the rest position, the two connections are blocked, in the second switch position, the leak oil can flow to the tank. 1, the leak oil line 24 can only be shut off here, but not connected to the line 29 between the outlet A of the directional control valve 31 and the working connection 30 of the cylinder 10. The load holding pressure in the leakage oil collecting chamber 22 therefore builds up here only via the primary seal 19.
  • the directional control valve 31 of the embodiment according to FIG. 4 is again used.
  • the valve 25 has the same connections as that according to FIG. 1.
  • the line connections are the same as in the embodiment according to FIG. 1.
  • the magnet 39 only has to be excited as long as the pump 40 is running.
  • Switch 81 are controlled in parallel to an electric motor 82 driving the pump 40.
  • a second contact bridge 83 of the same electrical switch 81 either a magnet 84 or a magnet 85 of the directional control valve 31 is also switched on. Both contact bridges can be operated via the same handle 86.
  • the leak oil line 24 is connected to an outlet B of a 5/3-way valve 31, which controls the direction of movement of the piston 16 and piston rod 17 and additionally fulfills the function of the valve 25 from the previously described embodiments.
  • the connection A is connected to the working connection 30 in the cylinder head 10 and the connection C to the working connection 33 in the cylinder base 12.
  • the ports P, T and C are blocked.
  • the connections A and B can also be blocked against one another. This alternative then corresponds to the embodiment according to FIG. 4, in which the leakage oil line 24 is only shut off in the rest position of the valve 25.
  • connections A and B can also be internally connected to one another in the rest position of the valve 31, as is indicated in FIG. 7 by a dashed line. Then the leakage oil line 24 is connected in the rest position of the valve 31 to the working connection 30 of the cylinder 10.
  • This alternative therefore corresponds to the embodiment according to FIG. 5. However, one valve less is used in each case.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)

Claims (19)

  1. Tout système d'entraînement hydraulique comprenant un vérin (10), lequel est doté d'un piston (16) mobile dans une chambre de travail, d'une tige de piston (17) menée vers l'extérieur au travers d'une tête de vérin (11), d'un joint d'étanchéité primaire (19) résistant à l'usure et d'un joint d'étanchéité secondaire (20) sans fuite d'huile, lesquels tous deux agissent entre la tête de vérin (11) et la tige de piston (17) cependant que le joint d'étanchéité primaire (19) est plus rapproché de la chambre de travail que le joint d'étanchéité secondaire (20), ainsi que d'une tuyauterie de fuite (24) située entre le joint d'étanchéité primaire (19) et le joint d'étanchéité secondaire (20), caractérisé en ce que la tuyauterie de fuite (24) est soumise à une pression de retenue de charge lorsqu'un distributeur (25 ; 31) commute.
  2. Tout système d'entraînement hydraulique selon la revendication n°1, caractérisé en ce que la tuyauterie de fuite (24) peut être fermée par la commutation d'un distributeur (25 ; 31).
  3. Tout système d'entraînement hydraulique selon la revendication n°1, caractérisé en ce que la tuyauterie de fuite (24) peut être connectée à la chambre soumise à la pression (21) côté tige du vérin (10) au travers du distributeur (25 ; 31).
  4. Tout système d'entraînement hydraulique selon les revendications nos 1, 2 ou 3, caractérisé en ce que les chambres soumises à la pression (21 ; 34) des deux côtés du piston du vérin (16) peuvent être connectées alternativement avec une pompe (40) et avec un réservoir (26) au travers d'un distributeur (31), et que la tuyauterie de fuite (24) est connectée à ce distributeur (31) et peut être soumise à une pression de retenue de charge par commutation de celui-ci.
  5. Tout système d'entraînement hydraulique selon les revendications nos 1, 2 ou 3, caractérisé en ce que les chambres soumises à la pression (21 ; 34) des deux côtés du piston du vérin (16) peuvent être connectées alternativement avec une pompe (40) et avec un réservoir (26) au travers d'un distributeur (31), et que la tuyauterie de fuite (24) est connectée à un distributeur (25) supplémentaire et peut être soumise à une pression de retenue de charge par commutation de ce distributeur (25) supplémentaire.
  6. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce que le distributeur (25 ; 31) auquel est connectée la tuyauterie de fuite (24) peut être commuté à partir de sa position initiale, en surmontant la force exercée par un ressort de rappel (38), en particulier à l'aide d'un electro-aimant (39), et que la tuyauterie de fuite (24) peut être soumise à une pression de retenue de charge lorsque le distributeur (25 ; 31) détient sa position initiale.
  7. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce qu'une cavité annulaire (22) de ramassage d'huile de fuite est contenue dans la tête de vérin (11) entre les joints d'étanchéité primaire et secondaire (19 ; 20) et sert de base à la tuyauterie de fuite (24).
  8. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce que le joint d'étanchéité secondaire (20) est soumis à une précontrainte due à ses dimensions et à la cavité d'insertion qui lui est donnée.
  9. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce que le joint d'étanchéité secondaire (20) peut être précontraint jusqu'à une dimension minimale dans le sens axial au travers d'une bride (60), laquelle de préférence aura pour butée une épaule (62) de la tête de vérin (11).
  10. Tout système d'entraînement hydraulique selon la revendication n°9, caractérisé en ce que le joint d'étanchéité secondaire (20) peut être précontraint par un piston (71), qui est coulissant dans le sens de l'axe, qui est déplacé par voie hydraulique et qui de préférence aura pour butée une épaule (62) de la tête de vérin (11).
  11. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce que le joint d'étanchéité primaire (19) est un joint d'étanchéité séparé, positionné dans la tête de vérin (11).
  12. Tout système d'entraînement hydraulique selon une des revendications précédentes, caractérisé en ce que le joint d'étanchéité primaire (19) comprend une bague d'étanchéité (63) qui est constituée d'une matière rigide à la flexion, en particulier d'un métal ou d'un alliage métallique.
  13. Tout système d'entraînement hydraulique selon la revendication n°12, caractérisé en ce que le joint d'étanchéité primaire (19) comprend plusieurs bagues d'étanchéité (63), au moins une bague d'obturation (65) qui sépare deux bagues d'étanchéité (63) l'une de l'autre, et derrière chaque bague d'étanchéité (63) une bague de séparation (64), dont l'épaisseur dans le sens de l'axe est égale ou supérieure à l'épaisseur correspondante de la bague d'étanchéité (63) respective.
  14. Tout système d'entraînement hydraulique selon une des revendications nos 11 à 13, caractérisé en ce que un élément de la tête de vérin (45) est munie de deux rainures (55 ; 56) qui sont ouvertes dans des faces en vis-à-vis, l'une contenant un joint d'étanchéité primaire (19), l'autre un joint d'étanchéité secondaire (20), et sont fermées par des brides (60 ; 71 ; 48).
  15. Tout système d'entraînement hydraulique selon une des revendications nos 11 à 14, caractérisé en ce que la tête de vérin (11) comprend deux éléments (45; 46), qu'un premier élément (45) contient le joint d'étanchéité secondaire (20) et la tuyauterie de fuite (24) et qu'un deuxième élément (46) contient la connexion de travail (30) avec la chambre soumise à la pression (21) côté tige de piston.
  16. Tout système d'entraînement hydraulique selon la revendication n° 15, caractérisé en ce que le joint d'étanchéité primaire (19) est solidaire du premier élément (45) de la tête de vérin (11).
  17. Tout système d'entraînement hydraulique selon une des revendications nos 11 à 16, caractérisé en ce que une douille de guidage (47) pour la tige de piston (17) est disposée dans la tête de vérin (11) entre le joint d'étanchéité primaire (19) et une connexion de travail (30) avec la chambre soumise à la pression (21) côté tige du vérin.
  18. Tout système d'entraînement hydraulique selon la revendication n° 17, caractérisé en ce que le joint d'étanchéité primaire (19) est accolé à un collet externe (48) de la douille de guidage (47).
  19. Tout système d'entraînement hydraulique selon la revendication n° 18, caractérisé en ce que le collet externe (48) de la douille de guidage (47) dépasse, dans le sens radial, le joint d'étanchéité primaire (19) et va s'insérer entre le premier et le deuxième élément (45 ; 46) de la tête de vérin (11).
EP93906521A 1992-03-20 1993-03-13 Dispositif hydraulique d'entrainement a verin Expired - Lifetime EP0589006B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4208980A DE4208980A1 (de) 1992-03-20 1992-03-20 Hydraulische antriebsvorrichtung mit einem zylinder
DE4208980 1992-03-20
PCT/EP1993/000583 WO1993019301A1 (fr) 1992-03-20 1993-03-13 Dispositif hydraulique d'entrainement a verin

Publications (2)

Publication Number Publication Date
EP0589006A1 EP0589006A1 (fr) 1994-03-30
EP0589006B1 true EP0589006B1 (fr) 1996-05-08

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EP93906521A Expired - Lifetime EP0589006B1 (fr) 1992-03-20 1993-03-13 Dispositif hydraulique d'entrainement a verin

Country Status (5)

Country Link
US (1) US5469704A (fr)
EP (1) EP0589006B1 (fr)
AT (1) ATE137842T1 (fr)
DE (1) DE4208980A1 (fr)
WO (1) WO1993019301A1 (fr)

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CN102852900A (zh) * 2012-09-11 2013-01-02 苏州同大机械有限公司 塑料制品成型机械用的油缸的泄漏油收集装置
WO2016008151A1 (fr) * 2014-07-18 2016-01-21 Norgren, Inc. Cylindre de moulage par soufflage avec étirage et procédé associé
GB2536980B (en) * 2015-06-30 2017-05-24 Anglia Hydraulics Holdings Ltd Hydraulic device
DE202020104630U1 (de) 2020-08-11 2021-11-12 Woco Industrietechnik Gmbh Tandemdichtungssystem und hydraulischer Stellantrieb
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CN104043973B (zh) * 2014-06-04 2016-08-17 洛阳利维科技有限公司 一种倍力式同心活塞杆油缸移动大负荷工作台的装置

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DE4208980A1 (de) 1993-09-23
ATE137842T1 (de) 1996-05-15
WO1993019301A1 (fr) 1993-09-30
EP0589006A1 (fr) 1994-03-30
US5469704A (en) 1995-11-28

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