(19)
(11)EP 3 328 773 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 15784453.1

(22)Date of filing:  27.07.2015
(51)Int. Cl.: 
B66B 5/28  (2006.01)
B66B 7/02  (2006.01)
(86)International application number:
PCT/IB2015/001307
(87)International publication number:
WO 2017/017486 (02.02.2017 Gazette  2017/05)

(54)

ABSORBER FOR ELEVATOR SYSTEM RAIL

ABSORBER FÜR SCHIENE EINES AUFZUGSSYSTEMS

ABSORBEUR POUR RAIL DE SYSTÈME D'ASCENSEUR


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
06.06.2018 Bulletin 2018/23

(73)Proprietor: Otis Elevator Company
Farmington CT 06032 (US)

(72)Inventor:
  • FAUCONNET, Aurélien
    F-45500 Gien (FR)

(74)Representative: Dehns 
St. Bride's House 10 Salisbury Square
London EC4Y 8JD
London EC4Y 8JD (GB)


(56)References cited: : 
WO-A1-2011/095493
JP-A- 2001 106 455
WO-A2-2007/070208
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND



    [0001] The subject matter disclosed herein relates to elevator systems. More particularly, the present disclosure relates to guide rail structures and support for elevator systems.

    [0002] In current, typical elevator systems, guide rails secured in the hoistway are utilized to guide elevator cars and/or counterweights along the hoistway. The guide rails are secured to the hoistway wall via guide rail brackets. The guide rails are sized to withstand loads from normal elevator system operation, from safety brake actuation at car or counterweight rail, from building settling and the like. In the case of building settling, the guide rails must remain supported by the guide rail brackets while not buckling during the settling. Recent changes in elevator systems standards by governing bodies have introduced new requirements requiring that, in elevator systems having a rise of 40 meters or higher, push through forces at all brackets along the guide rail length, as opposed to at a single guide rail bracket, must be taken into account when sizing the guide rails. This would have the effect of increasing the necessary rail size in the elevator systems, which also increases cost. Thus a solution to meet the necessary standard requirements while not significantly increasing rail size or system cost is desired.

    [0003] WO 2007/070208 A1 discloses a shock absorber positioned on a pit floor between a car guide rail and the pit floor and/or between the car or counterweight and the pit floor. WO 2011/095493 A1 discloses a shock absorber positioned on a pit floor between a guide rail and the pit floor.

    [0004] JP 2001 106455 A discloses an absorber according to the preamble of claim 1.

    BRIEF SUMMARY



    [0005] From a first aspect, the invention provides an absorber for an elevator system guide rail as claimed in claim 1.

    [0006] In this or other embodiments a pressure relief valve may periodically release fluid from the housing chamber, thereby reducing a stroke of the absorber piston in the absorber housing.

    [0007] In this or other embodiments a fluid collector may be operably connected to the pressure relief valve to collect the fluid released from the housing chamber via the pressure relief valve.

    [0008] In this or other embodiments the pressure relief valve may release fluid from the housing chamber when a fluid pressure in the housing chamber exceeds a selected threshold.

    [0009] in this or other embodiments the absorber piston may include a recess in the piston upper surface receptive of the guide rail.

    [0010] From a further aspect, the invention provides an elevator system as claimed in claim 6.

    [0011] In this or other embodiments the one or more guide rails may be at least two guide rails.

    [0012] In this or other embodiments the one or more elevator system components may include an elevator car and/or an elevator system counterweight.

    [0013] From a further aspect, the invention provides a method of supporting a guide rail of an elevator system as claimed in claim 9.

    [0014] In this or other embodiments fluid may be periodically released from the housing chamber via opening of a pressure relief valve, and a stroke of the absorber piston in the absorber housing is thereby reduced.

    [0015] In this or other embodiments the fluid may be released from the housing chamber via opening of the pressure relief valve when a fluid pressure in the housing chamber exceeds a first threshold.

    [0016] In this or other embodiments the pressure relief valve may be closed when the fluid pressure in the housing chamber falls below a second threshold.

    [0017] In this or other embodiments the first threshold may be substantially equal to the second threshold.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0018] The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

    FIG. 1 is a schematic view of an embodiment of an elevator system;

    FIG. 2 is a perspective view of a portion of a hoistway of an embodiment of an elevator system;

    FIG. 3 is a perspective view of an embodiment of an absorber for an elevator system;

    FIG. 4 is a cross-sectional view of an embodiment of an absorber for an elevator system; and

    FIG. 5 is a graphical representation of operation of an absorber for an elevator system.


    DETAILED DESCRIPTION



    [0019] Shown in FIG. 1 is a schematic of an exemplary elevator system 10. The elevator system 10 includes an elevator car 12 operatively suspended or supported in a hoistway 14 with one or more suspension members 16, such as ropes or belts. The one or more suspension members 16 interact with one or more sheaves 18 to be routed around various components of the elevator system 10. The one or more sheaves 18 could also be connected to a counterweight 22, which is used to help balance the elevator system 10 and reduce the difference in suspension member 16 tension on both sides of a traction sheave 24 during operation.

    [0020] The elevator system 10 further includes one or more car guide rails 28 to guide the elevator car 12 along the hoistway 14. The elevator car 12 includes one or more guide shoes or rollers 30 interactive with the car guide rails 28 to guide the elevator car 12. The elevator car 12 also may include safeties 32 interactive with the car guide rail 28 to slow and/or stop motion of the elevator car 12 under certain conditions, such as an overspeed condition. Further, the elevator system 10 includes one or more counterweight guide rails 34 to guide the counterweight 22 along the hoistway 14. Car guide rails 28 and counterweight guide rails 34 are installed to hoistway walls 36 using a plurality of guide rail brackets 38, which in some embodiments are located along the hoistway walls 36 at intervals of about 3 meters between guide rail brackets 38.

    [0021] The hoistway 14 includes one or more landing floors 40 at which the elevator car 12 stops to allow ingress and/or egress of passengers from the elevator car 12 through elevator car doors (not shown). Below the lowest landing floor 40 of the hoistway 14, the hoistway 14 terminates in a pit 42, including a pit floor 44. After construction of the building and installation of the elevator system 10, some settling or vertical compression of the building typically occurs, especially in buildings having a larger rise. The settling can result in undesired effects on the guide rails of the elevator system 10, such as shifting or buckling due to relative movement of the guide rail brackets 38 and guide rails 28, 34. Further, the settling imparts forces on the guide rails 28, 34 at the guide rail brackets 38 which dictate sizing of the guide rails 28, 34 to withstand such forces.

    [0022] Referring now to FIG. 2, to alleviate forces acting on the guide rails 28, 34, and the guide rail brackets 38, each guide rail 28, 34 terminates at an absorber 46 located at the pit floor 44. The absorber 46 is configured to absorb the effect of building settling, allowing the guide rails 28, 34 to reposition themselves downwardly relative to the pit floor 44 as the building settles, so that in effect, the guide rails 28, 34 move with the guide rail brackets 38 fixed to the hoistway walls 36. This reduces the relative forces between the guide rails 28, 34 and the guide rail brackets 38.

    [0023] Referring now to FIGs. 3 and 4, an embodiment of an absorber 46 is illustrated. The absorber 46 includes an absorber housing 48 with a movable absorber piston 50 located in the absorber housing 48 and movable along a stroke axis 52. As shown in FIG. 3, the guide rail 28, 34 rests at an upper piston surface 54. In some embodiments, as shown in FIG. 4, the absorber piston 50 includes a rail recess 56 in which the guide rail 28, 34 may be positioned. The absorber housing 48 and absorber piston 50 define a housing chamber 58 in the absorber housing 48. The housing chamber 58 is pressurized with a volume of oil or other fluid medium. A pressure relief valve 60 and an oil collector tank 62 are fluidly connected to the housing chamber 58.

    [0024] At initial installation, the absorber piston 50 is positioned at its maximum position along the stroke axis 52, maximizing the housing chamber 58 volume. As the building settles, the guide rail 28, 34 imparts a downward force on the upper piston surface 54, thus increasing a pressure on the fluid in the housing chamber 58. Once the fluid pressure builds to a first threshold, the pressure relief valve 60 opens, releasing a volume of fluid from the housing chamber 58 into the oil collector tank 62 and allowing the absorber piston 50 to travel downwardly along the stroke axis 52. Once a sufficient volume of fluid is released from the housing chamber 58 such that the fluid pressure is reduced to below a second threshold, the pressure relief valve 60 closes, thus stopping travel of the absorber piston 50. In some embodiments, the first threshold is substantially equal to the second threshold. In some embodiments, the pressure relief valve 60 has a time delay feature in order to not retract the absorber piston 50 during elevator car 12 or counterweight 22 safety actuation. These events may also increase fluid pressure in the housing chamber 58, but are very short time duration events compared to building settling.

    [0025] As illustrated in FIG. 5, this operation is repeated over time as the building settles further, in some instances over about the first ten years after building construction. As the building settles, represented by curve 64, fluid pressure 66 in the housing chamber 58 increases until pressure relief valve 60 is opened at point 68, dropping the fluid pressure and retracting the absorber piston 50, shown at 70. With each periodic opening of the pressure relief valve 60, the absorber piston 50 is retracted further, until it reaches a minimum stroke point 72, at which a safety switch 74 (shown in FIG. 3, 4) is triggered stopping operation of the absorber 46 and will alert to service people to readjust the guide rails 28, 34 and reset the absorbers 46.

    [0026] Utilizing the absorbers 46 absorbs forces that would typically be transferred into the guide rails 28, 34 during building settling. This allows for the guide rail 28, 34 configuration to be constrained by other factors such as loads during safety operations, not loads from building settling. Thus, the guide rails 28, 34 can often be formed of more lightweight materials, at a considerable cost savings. Further, the absorbers 46 reduce the risk of guide rail buckling or other deformation to the guide rails 28, 34 and/or guide rail brackets 38.

    [0027] While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.


    Claims

    1. An absorber (46) for an elevator system guide rail (28, 34) comprising:

    an absorber housing (48);

    an absorber piston (50) disposed in the absorber housing (48), together with the absorber housing (48) defining a housing chamber (58) containing a volume of fluid,

    characterized in

    the absorber piston (50) including a piston upper surface (54) configured to interact with a guide rail (28, 34) of an elevator system;

    wherein the absorber (46) is configured such that, when the absorber (46) is disposed at a hoistway pit (42) and supportive of a guide rail (28, 34) of an elevator system in such a way that the piston upper surface (54) is interactive with the guide rail (28, 34), relative motion of the guide rail (28; 34) relative to a hoistway pit floor (44) increases fluid pressure in the housing chamber (58), the absorber (46) configured to absorb loads imparted to the guide rail (28, 34) due to vertical translation and/or compression of a hoistway (14) of the elevator system.


     
    2. The absorber (46) of Claim 1, further comprising a pressure relief valve (60) to periodically release fluid from the housing chamber (58), thereby reducing a stroke of the absorber piston (50) in the absorber housing (48).
     
    3. The absorber (46) of Claim 2, further comprising a fluid collector operably connected to the pressure relief valve (60) to collect the fluid released from the housing chamber (58) via the pressure relief valve (60).
     
    4. The absorber (46) of Claim 2 or 3, wherein the pressure relief valve (60) releases fluid from the housing chamber (58) when a fluid pressure in the housing chamber (58) exceeds a selected threshold.
     
    5. The absorber (46) of any of Claims 1-4, wherein the absorber piston (50) includes a recess (56) in the piston upper surface (54) receptive of the guide rail (28, 34).
     
    6. An elevator system (10) comprising:

    a hoistway (14), the hoistway (14) having a plurality of landing floors (40) each landing floor having a landing floor door;

    one or more guide rails (28, 34) disposed in the hoistway (14) to guide one or more elevator system components along the hoistway (14); and

    an absorber (46) as claimed in any of claims 1-5, the absorber (46) disposed at a hoistway pit (42) and supportive of a guide rail (28, 34) of the one or more guide rails (28, 34), the absorber (46) configured to absorb loads imparted to the guide rail (28, 34) due to vertical translation and/or compression of the hoistway (14).


     
    7. The elevator system (10) of Claim 6, wherein the one or more guide rails (28, 34) are at least two guide rails.
     
    8. The elevator system (10) of Claim 6 or 7, wherein the one or more elevator system components include an elevator car (12) and/or an elevator system counterweight (22).
     
    9. A method of supporting a guide rail (28, 34) of an elevator system (10) comprising:

    locating an absorber (46) in an elevator hoistway (14) in operable communication with a guide rail (28, 34) of an elevator system (10) such that the absorber (46) is disposed at a hoistway pit (42) and supportive of the guide rail (28, 34), the absorber (46) including an absorber housing (48), an absorber piston (50) located in the absorber housing (48) defining a housing chamber (58) containing a volume of fluid; and

    transmitting vertically-acting loads from the guide rail (28, 34) to the absorber (46) via the absorber piston (50) thereby increasing a fluid pressure in the housing chamber (58).


     
    10. The method of Claim 9, further comprising:

    periodically release fluid from the housing chamber (58) via opening of a pressure relief valve (60); and

    thereby reducing a stroke of the absorber piston (50) in the absorber housing (48).


     
    11. The method of Claim 10, wherein the fluid is released from the housing chamber (58) via opening of the pressure relief valve (60) when a fluid pressure in the housing chamber (58) exceeds a first threshold.
     
    12. The method of Claim 11, wherein the pressure relief valve (60) is closed when the fluid pressure in the housing chamber (58) falls below a second threshold.
     
    13. The method of Claim 12, wherein the first threshold is substantially equal to the second threshold.
     


    Ansprüche

    1. Absorber (46) für eine Führungsschiene (28, 34) eines Aufzugssystems, umfassend:

    ein Absorbergehäuse (48);

    einen Absorberkolben (50), der in dem Absorbergehäuse (48) angeordnet ist und zusammen mit dem Absorbergehäuse (48) eine Gehäusekammer (58) definiert, die ein Fluidvolumen enthält, dadurch gekennzeichnet, dass der Absorberkolben (50) eine obere Kolbenfläche (54) einschließt, die konfiguriert ist, um mit einer Führungsschiene (28, 34) eines Aufzugssystems zu interagieren;

    wobei der Absorber (46) so konfiguriert ist, dass, wenn der Absorber (46) an einer Aufzugschachtgrube (42) angeordnet ist und eine Führungsschiene (28, 34) eines Aufzugssystems stützt, sodass die obere Kolbenfläche (54) mit der Führungsschiene (28, 34) interagiert, eine entsprechende Bewegung der Führungsschiene (28, 34) in Bezug auf den Boden (44) einer Aufzugschachtgrube den Fluiddruck in der Gehäusekammer (58) erhöht, wobei der Absorber (46) konfiguriert ist, um Lasten zu absorbieren, die aufgrund einer vertikalen Verschiebung und/oder Verdichtung eines Schachts (14) des Aufzugssystems auf die Führungsschiene (28, 34) übertragen werden.


     
    2. Absorber (46) nach Anspruch 1, ferner umfassend ein Überdruckventil (60), um regelmäßig Fluid aus der Gehäusekammer (58) abzugeben, wodurch ein Hub des Absorberkolbens (50) in dem Absorbergehäuse (48) verringert wird.
     
    3. Absorber (46) nach Anspruch 2, ferner umfassend einen Fluidsammler, der mit dem Überdruckventil (60) wirkverbunden ist, um das Fluid zu sammeln, das aus der Gehäusekammer (58) über das Überdruckventil (60) abgegeben wird.
     
    4. Absorber (46) nach Anspruch 2 oder 3, wobei das Überdruckventil (60) Fluid aus der Gehäusekammer (58) abgibt, wenn ein Fluiddruck in der Gehäusekammer (58) einen ausgewählten Schwellenwert übersteigt.
     
    5. Absorber (46) nach einem der Ansprüche 1-4, wobei der Absorberkolben (50) eine Aussparung (56) in der oberen Kolbenfläche (54) einschließt, welche die Führungsschiene (28, 34) aufnimmt.
     
    6. Aufzugssystem (10), umfassend:

    einen Schacht (14), wobei der Schacht (14) eine Vielzahl von Etagenabsätzen (40) aufweist, wobei jeder Etagenabsatz eine Etagenabsatztür aufweist;

    eine oder mehrere Führungsschienen (28, 34), die in dem Schacht (14) angeordnet sind, um eine oder mehrere des Aufzugssystemkomponenten entlang des Schachts (14) zu führen; und

    einen Absorber (46) nach einem der Ansprüche 1-5, wobei der Absorber (46) an einer Aufzugschachtgrube (42) angeordnet ist und eine Führungsschiene (28, 34) der einen oder mehreren Führungsschienen (28, 34) stützt, wobei der Absorber (46) konfiguriert ist, um Lasten zu absorbieren, die aufgrund einer vertikalen Verschiebung und/oder Verdichtung des Schachts (14) auf die Führungsschiene (28, 34) übertragen werden.


     
    7. Aufzugssystem (10) nach Anspruch 6, wobei die eine oder die mehreren Führungsschienen (28, 34) mindestens zwei Führungsschienen entsprechen.
     
    8. Aufzugssystem (10) nach Anspruch 6 oder 7, wobei die eine oder die mehreren Aufzugssystemkomponenten eine Aufzugskabine (12) und/oder ein Aufzugssystemgegengewicht (22) einschließen.
     
    9. Verfahren zum Stützen einer Führungsschiene (28, 34) eines Aufgzugssystems (10), umfassend:

    Platzieren eines Absorbers (46) in einem Aufzugsschacht (14) in Wirkverbindung mit einer Führungsschiene (28, 34) eines Aufzugssystems (10), sodass der Absorber (46) an einer Aufzugschachtgrube (42) angeordnet ist und die Führungsschiene (28, 34) stützt, wobei der Absorber (46) ein Absorbergehäuse (48) einschließt, wobei sich ein Absorberkolben (50) in dem Absorbergehäuse (48) befindet, definierend eine Gehäusekammer (58), die ein Fluidvolumen enthält; und

    Übertragen von vertikal wirkenden Lasten von der Führungsschiene (28, 34) auf den Absorber (46) über den Absorberkolben (50), wodurch ein Fluiddruck in der Gehäusekammer (58) erhöht wird.


     
    10. Verfahren nach Anspruch 9, ferner umfassend:

    regelmäßiges Abgeben von Fluid aus der Gehäusekammer (58) über das Öffnen eines Überdruckventils (60); und

    wodurch ein Hub des Absorberkolbens (50) in dem Absorbergehäuse (48) verringert wird.


     
    11. Verfahren nach Anspruch 10, wobei das Fluid aus der Gehäusekammer (58) über das Öffnen des Überdruckventils (60) abgegeben wird, wenn ein Fluiddruck in der Gehäusekammer (58) einen ersten Schwellenwert übersteigt.
     
    12. Verfahren nach Anspruch 11, wobei das Überdruckventil (60) geschlossen ist, wenn der Fluiddruck in der Gehäusekammer (58) unter einen zweiten Schwellenwert fällt.
     
    13. Verfahren nach Anspruch 12, wobei der erste Schwellenwert im Wesentlichen dem zweiten Schwellenwert entspricht.
     


    Revendications

    1. Absorbeur (46) pour rail de guidage de système d'ascenseur (28, 34), comprenant :

    un logement d'absorbeur (48) ;

    un piston d'absorbeur (50) disposé dans le logement d'absorbeur (48), conjointement avec le logement d'absorbeur (48) définissant une chambre de logement (58) contenant un volume de fluide, caractérisé en ce que

    le piston d'absorbeur (50) comprend une surface supérieure de piston (54) configurée pour interagir avec un rail de guidage (28, 34) d'un système d'ascenseur ;

    dans lequel l'absorbeur (46) est configuré de sorte que, lorsque l'absorbeur (46) est disposé dans une fosse de cage (42) et soutient un rail de guidage (28, 34) d'un système d'ascenseur de telle manière que la surface supérieure de piston (54) interagit avec le rail de guidage (28, 34), le mouvement relatif du rail de guidage (28; 34) par rapport au plancher d'une fosse de cage (44) augmente la pression de fluide dans la chambre de logement (58), l'absorbeur (46) étant configuré pour absorber les charges communiquées au rail de guidage (28, 34) résultant de la translation verticale et/ou de la compression de la cage (14) du système d'ascenseur.


     
    2. Absorbeur (46) selon la revendication 1, comprenant en outre une soupape de surpression (60) pour libérer périodiquement du fluide de la chambre de logement (58), en réduisant ainsi une course du piston d'absorbeur (50) dans le logement d'absorbeur (48).
     
    3. Absorbeur (46) selon la revendication 2, comprenant en outre un collecteur de fluide connecté fonctionnellement à la soupape de surpression (60) pour collecter le fluide libéré de la chambre de logement (58) via la soupape de surpression (60).
     
    4. Absorbeur (46) selon la revendication 2 ou 3, dans lequel la soupape de surpression (60) libère du fluide de la chambre de logement (58) lorsqu'une pression de fluide dans la chambre de logement (58) dépasse un seuil sélectionné.
     
    5. Absorbeur (46) selon l'une quelconque des revendications 1 à 4, dans lequel le piston d'absorbeur (50) comprend un évidement (56) dans la surface supérieure de piston (54), qui reçoit le rail de guidage (28, 34).
     
    6. Système d'ascenseur (10) comprenant :

    une cage (14), la cage (14) ayant une pluralité de paliers (40), chaque palier ayant une porte de palier ;

    un ou plusieurs rails de guidage (28, 34) disposés dans la cage (14) pour guider un ou plusieurs composants du système d'ascenseur le long de la cage (14) ; et

    un absorbeur (46) selon l'une quelconque des revendications 1 à 5, l'absorbeur (46) étant disposé dans une fosse de cage (42) et soutenant un rail de guidage (28, 34) des un ou plusieurs rails de guidage (28, 34), l'absorbeur (46) étant configuré pour absorber les charges communiquées au rail de guidage (28, 34) résultant de la translation verticale et/ou de la compression de la cage (14).


     
    7. Système d'ascenseur (10) selon la revendication 6, dans lequel les un ou plusieurs rails de guidage (28, 34) sont au moins deux rails de guidage.
     
    8. Système d'ascenseur (10) selon la revendication 6 ou 7, dans lequel les un ou plusieurs composants du système d'ascenseur comprennent une cabine d'ascenseur (12) et/ou un contrepoids de système d'ascenseur (22).
     
    9. Procédé pour soutenir un rail de guidage (28, 34) d'un système d'ascenseur (10), comprenant :

    le placement d'un absorbeur (46) dans une cage d'ascenseur (14) en communication fonctionnelle avec un rail de guidage (28, 34) d'un système d'ascenseur (10) de sorte que l'absorbeur (46) est disposé au niveau d'une fosse de cage (42) et soutient le rail de guidage (28, 34), l'absorbeur (46) comprenant un logement d'absorbeur (48), un piston d'absorbeur (50) situé dans le logement d'absorbeur (48) définissant une chambre de logement (58) contenant un volume de fluide ; et

    la transmission de charges à action verticale depuis le rail de guidage (28, 34) à l'absorbeur (46) par l'intermédiaire du piston d'absorbeur (50), en augmentant ainsi une pression de fluide dans la chambre de logement (58).


     
    10. Procédé selon la revendication 9, comprenant en outre :

    la libération périodique de fluide de la chambre de logement (58) par l'ouverture d'une soupape de surpression (60) ; et

    la réduction en conséquence d'une course du piston d'absorbeur (50) dans le logement d'absorbeur (48).


     
    11. Procédé selon la revendication 10, dans lequel le fluide est libéré de la chambre de logement (58) par l'ouverture de la soupape de surpression (60) lorsqu'une pression de fluide dans la chambre de logement (58) dépasse un premier seuil.
     
    12. Procédé selon la revendication 11, dans lequel la soupape de surpression (60) est fermée lorsque la pression de fluide dans la chambre de logement (58) tombe en dessous d'un second seuil.
     
    13. Procédé selon la revendication 12, dans lequel le premier seuil est sensiblement égal au second seuil.
     




    Drawing


















    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description