Abstract:
The invention relates to an assembly comprising at least one hydraulic control valve and a body for receiving said hydraulic control valve, the hydraulic control valve including flow orifices and flow control means for putting the flow orifices selectively into hydraulic communication with one another. The hydraulic control valve is in the form of an oblong cartridge, the body includes an open housing adapted to receive the hydraulic control valve in removable manner such that when the hydraulic control valve is in place in the housing, the hydraulic control valve and the housing together define isolated hydraulic chambers into which the flow orifices of the hydraulic control valve open out.

Description:
[0001]    The invention relates to a hydraulic control valve in the form of a cartridge that is designed to be inserted in particular in a hydraulic manifold. 
       BACKGROUND OF THE INVENTION 
       [0002]    Hydraulic control valves are known, in particular in the field of aviation, that comprise inlet and outlet ports, and flow control means for putting the inlet ports selectively into communication with the outlet ports via at least two connection circuits. 
         [0003]    Such hydraulic control valves are used in particular for controlling the lowering and raising of landing gear, in a determined sequence. 
         [0004]    In general, hydraulic control valves are inserted in control valve manifolds that are received on separate support plates, in turn connected by associated piping to the hydraulic circuit of the aircraft and including mechanical and hydraulic interface means with the control valve manifolds. 
         [0005]    In the event of a hydraulic control valve manifold failing, it is traditionally considered as being a line replaceable unit (LRU) that is suitable for being removed by ground maintenance personnel and replaced by a good control valve manifold. 
         [0006]    In order to perform the function of lowering and raising landing gear, it is found that the number of hydraulic control valves can be large. Proposals have indeed between made to group together all of the separate support plates so as to constitute a single support plate that receives all of the hydraulic control valve manifolds, but such a solution is difficult to implement. Proposals have also been made to integrate the hydraulic control valves completely in a single hydraulic manifold, but without it being possible to perform line replacement of the hydraulic control valve. Although that solution is technically feasible, it is not compatible with economic operation of an aircraft. The failure of a single hydraulic control valve would require the entire hydraulic manifold to be replaced, and that is not very satisfactory. 
       OBJECT OF THE INVENTION 
       [0007]    There is therefore a need for hydraulic components that enable the hydraulic architecture to be compact and lightweight, but that nevertheless allow maintenance to be performed on the aircraft. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In order to achieve this object, the invention provides an assembly comprising at the least one hydraulic control valve and a body for receiving the hydraulic control valve, the hydraulic control valve including flow orifices and flow control means for putting the flow orifices selectively into hydraulic communication with one another, in which the hydraulic control valve is in the form of an oblong cartridge, the body including an open housing adapted to receive the hydraulic control valve in removable manner such that when the hydraulic control valve is in place in the housing, the hydraulic control valve and the housing together define isolated hydraulic chambers into which the flow orifices of the hydraulic control valve open out. 
         [0009]    It suffices to provide the body with hydraulic ports that open out into the chambers in order to obtain a hydraulic control assembly that is adapted to connect the hydraulic ports to one another selectively. 
         [0010]    The control valve is thus integrated in the body while remaining easily removable: it suffices to remove it from the housing, without it being necessary to make any hydraulic disconnection. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention can be better understood in the light of the following description given with reference to the figures of the accompanying drawings, in which: 
           [0012]      FIG. 1  is a perspective view of a hydraulic manifold receiving at least one hydraulic control valve of the invention; 
           [0013]      FIG. 2  is a longitudinal section view of the hydraulic control valve of  FIG. 1 , in place in its protective case; 
           [0014]      FIG. 3  is a longitudinal section view of the  FIG. 1  hydraulic control valve, on being put into place in the hydraulic manifold; 
           [0015]      FIG. 4  is a view analogous to that of  FIG. 3 , showing a later step in the installation of the hydraulic control valve in the hydraulic manifold; and 
           [0016]      FIG. 5  is a view analogous to  FIGS. 3 and 4  showing the hydraulic control valve in place in the hydraulic manifold. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    With reference to  FIG. 1 , the invention is illustrated herein in its application to a hydraulic manifold  1  used for controlling the extension and the retraction of landing gear in an aircraft. The hydraulic manifold  1  has a plurality of hydraulic ports  2 , including inlet ports and outlet ports. 
         [0018]    The hydraulic manifold  1  shown has a plurality of hydraulic control valves for selectively putting certain inlet ports into communication with certain outlet ports. At the top of the hydraulic manifold  1 , there can be seen a conventional hydraulic control valve  3 , having its own hydraulic ports, and connected to the hydraulic manifold  1  via a hydraulic manifold  4  constituting a support plate that is fitted onto the hydraulic manifold  1 . This control valve of known type acts as a safety valve for connecting the hydraulic manifold to the return in the event of an incident during the sequence of maneuvering the landing gear. 
         [0019]    The invention relates to hydraulic control valve  5  (one being shown extracted from the hydraulic manifold  1 ), that is in the form of an oblong cartridge designed to be received in an open blind housing  6  in the hydraulic manifold  1 . In this example, the hydraulic manifold  1  has a plurality of hydraulic control cartridge values  5 . 
         [0020]    As can be seen in  FIG. 2 , where the hydraulic control cartridge valve  5  is shown in its protective case  7 , the hydraulic control cartridge valve  5  comprises a jacket  10  having a first end carrying a blind fastener nut  11  provided with an outside thread  25 . The nut  11  is secured to the jacket  10  by a ring  12  leaving the nut  11  free to rotate relative to the jacket  10 . The jacket  10  has a second end forming a centering bearing surface  13 . 
         [0021]    Between its two ends, the jacket  10  carries a plurality of sealing gaskets  14  that are longitudinally spaced apart on its outside surface, the gaskets being of diameters that decrease going from the first end towards the second end of the jacket  10 . The jacket  10  includes a certain number of orifices  15  formed between the sealing gaskets  14 . 
         [0022]    A spool  16  is mounted to slide in the jacket  10  and it is held in the neutral position (as shown) by a resilient positioning member  17  such as a pair of springs. The axial displacement of the spool  16  against the resilient positioning member  17  on either side of the neutral position serves to put orifices  15  extending on either side of the sealing gaskets  14  selectively into communication with one another. The resilient positioning member  17  bears at one end against the end of the jacket  10  and at its other end against a shoulder on the nut  11 . 
         [0023]    Installing the hydraulic control valve  5  in the housing  6  of the hydraulic manifold  1  is described below in greater detail with reference to  FIGS. 3 to 5 . 
         [0024]    The housing  6  defines a certain number of sealing bearing surfaces  31  designed to co-operate with the sealing gaskets  14 . The bearing surfaces  31  are of diameter that decreases going from the inlet of the housing  6  towards the end wall thereof, such that the bearing surfaces  31  are stepped. The end wall of the housing  6  presents a centering bearing surface  32  for co-operating with the centering bearing surface  13  of the jacket  10 , and of diameter that is smaller than the diameter of the sealing bearing surfaces  31 . 
         [0025]    The hydraulic control cartridge valve  5  is engaged in the housing  6  until the centering bearing surface  13  of the jacket  10  co-operates with the complementary centering bearing surface  32  of the housing  6 . In so doing, some of the sealing gaskets  14  pass through some of the sealing bearing surfaces  31 . The stepped nature of the bearing surfaces  31  serves to avoid the sealing gaskets  14  being damaged as they pass through those bearing surfaces  31  that are of greater diameter. 
         [0026]    Thereafter, guided by the co-operation between the centering bearing surfaces  13  and  32 , the hydraulic control cartridge valve  5  continues to be pushed in until the thread of the nut  11  comes into abutment against the entry to complementary tapping  33  formed at the inlet of the housing  6 , but without yet being engaged therein, as shown in  FIG. 3 . It should be observed that in this position, none of the sealing gaskets  14  is yet engaged within the bearing surface  31  with which it is to co-operate. 
         [0027]    Thereafter, the nut  11  is tightened. Screw-tightening serves to move the hydraulic control cartridge valve  5  progressively into the housing  6 , causing the gaskets  14  to become engaged within the bearing surface  31 . Once the sealing gaskets  14  come into contact with the bearing surfaces  31 , the nut  11  is already engaged sufficiently to be able to exert the force required for engaging said gaskets against their respective bearing surfaces. In  FIG. 4 , there can be seen the position of the hydraulic control cartridge valve  5  in which the sealing gaskets  14  have just begun to be engaged against the bearing surfaces  31 . 
         [0028]    The force required for engagement can be considerable, because of the large number of sealing gaskets  14  (six gaskets  14  in the example shown plus an additional gasket  20  associated with the nut  11 ). Exerting such an engagement force is made easier by the reduction provided by the helical connection between the nut  11  of the hydraulic control cartridge valve  5  and the hydraulic manifold  1 , such that reasonable screw-tightening torque enables a large engagement force to be exerted. For this purpose, the ring  12  allows the nut  11  to turn while the jacket  10  remains stationary in rotation, thereby facilitating engagement of the gaskets  14  against the bearing surfaces  31  and avoiding damaging said gaskets by rotation. 
         [0029]    As shown in  FIG. 5 , screw-tightening is continued until an abutment collar  18  of the jacket  10  comes into abutment against an associated shoulder  36  of the housing  6  and becomes pinched between said shoulder  36  and the nut  11 . In this position, the sealing gaskets  14  extend against their respective bearing surfaces  31 , thereby defining between the control valve and the housing a set of chambers  35  that are hydraulically isolated from one another by the sealing gaskets  14 . Each of these chambers  35  has ducts  37  opening out therein (referenced in  FIG. 4 ) that connect said chambers to the hydraulic ports  2  of the hydraulic manifold  1 . The chambers  35 , and thus the associated hydraulic ports, are put selectively into hydraulic communication by means of a hydraulic path that extends within the hydraulic control cartridge valve  5  between the orifices  15  that open out into one or another of the chambers  35 . 
         [0030]    It should be observed that the sealing gasket  14  that is closest to the second end of the jacket  10  co-operates with the centering bearing surface  32  such that it too acts as a sealing bearing surface. 
         [0031]    According to a particular aspect of the invention, and as can be seen in  FIG. 5 , the sealing gaskets  14  closest to the ends of the jacket  10  define in the hydraulic manifold  1 : 
         [0032]    a first pilot chamber  41  in the end of the housing  6  into which there opens out a duct connected to a pilot hydraulic port for moving the spool  16  against the resilient positioning member  17 . For this purpose, the end of the jacket  10  is open so that the pressure that exists in the first pilot chamber  41  acts directly on the piston-forming end of the spool  16 ; and 
         [0033]    a second pilot chamber  42  connected to a pilot hydraulic port for moving the spool  16  against the resilient positioning member  17  in an opposite direction. For this purpose, the pressure that exists in the second pilot chamber  42  is transmitted to the inside of the nut  11  via orifices  19  to act directly on the other piston-forming end of the spool  16 . The second pilot chamber  42  is sealed by a sealing gasket  20  disposed in the vicinity of the thread of the nut  11 , in this example behind it, and co-operating with a complementary bearing surface  20 ′ provided at the inlet to the housing  6 . 
         [0034]    In order to remove the hydraulic control cartridge valve  5 , it suffices to unscrew it and take it out of the housing. Thus, the hydraulic control cartridge valve of the invention can be put into place and removed without making any hydraulic disconnection, nor does it require any special tooling. 
         [0035]    According to a particular aspect of the invention, the hydraulic control cartridge  5 , while not installed in a hydraulic manifold, is stored in a protective case  7 , as shown in  FIG. 2 . The protective case defines a housing with tapping at its inlet for co-operating with the thread of the nut  11 . 
         [0036]    The protective case  7  is partially filled with hydraulic fluid, and like the housing  6  in the hydraulic manifold  1 , it includes sealing bearing surfaces  21  for co-operating with the sealing gaskets  14  when the hydraulic control cartridge valve  5  is in place in the protective case  7 . Thus, the sealing gaskets  14  are pre-compressed by the bearing surfaces of the protective case  7 , but that when the hydraulic control cartridge valve  5  is extracted from the protective case  7  in order to put into place in the housing  6  of the hydraulic manifold  1 , the sealing gaskets  14  do not have enough time to return to their initial shape, thereby making it easier to engage said sealing gaskets against the sealing bearing surfaces  31  of the housing  6 . 
         [0037]    According to another aspect of the invention, it can be seen in  FIG. 1  that the hydraulic ports  2  extend in a first direction X in line with the associated ducts  37  (which can be seen opening out into the chambers  35  in  FIGS. 3 to 5 ), while the hydraulic control cartridge valves  5  and the associated housings  6  extend along a direction Y that is perpendicular to the direction X, thereby considerably facilitating design of the hydraulic manifold. 
         [0038]    The invention is not limited to the above description, but on the contrary covers any variant coming within the ambit defined by the claims. 
         [0039]    In particular, although the description above relates to a control valve having sliding spool type control means, the invention is applicable to other types of control valves, such as poppet valves. 
         [0040]    Although the control valve and the hydraulic manifold described define two pilot chambers, it is possible to make a control valve that has only one pilot chamber. 
         [0041]    More generally, although it is stated that the hydraulic control cartridge valve is designed to be received in the housing of a hydraulic manifold or of a protective case, it is possible to put the control valve in place into any body that includes a suitable housing.