Abstract:
A system for ventilating and venting containers containing a fluid volume, such as gearboxes containing an oil filling, has a line system connecting the container to the atmosphere. Upon changes in the volumes in the container due to temperature changes, pressure is equalized. The line system contains a separating housing ( 12 ) in which a separating medium ( 46 ) having oleophobic and hydrophobic properties separates a first space ( 42 ) connected to the container from a second space ( 44 ) connected to the atmosphere. Line connections ( 10, 14 ) on the separating housing ( 12 ) are provided such that liquid-phase substances on opposite sides of the separating medium ( 46 ) can flow out of the first space ( 42 ) to the container and can drain out of the second space ( 44 ) to the atmosphere.

Description:
FIELD OF THE INVENTION 
     The invention relates to a system for ventilating and venting containers containing a fluid volume, such as gearboxes containing an oil filling. A line system connects the pertinent container to the atmosphere. Upon changes in the fluid volumes located in the container due to temperature changes, pressure equalization is enabled. 
     BACKGROUND OF THE INVENTION 
     Venting and ventilation systems are known in the prior art. Containers located in technical systems and which are filled with operating fluids, for example, an oil-filled gearbox, above the oil surface contain a certain air volume. The air volume, among other things, is used for compensation of volume changes of the oil filling caused by temperature changes. The line system leading from the container, for example, a gearbox, to the atmosphere prevents pressure differences from building up that could lead to leaks on the sealing system, for example, on housing passages. In systems operated over a large temperature range, such as, for example, in gearboxes, where a large temperature span exists between the cold start and the operating temperature, in operation, considerable volumetric flows of air result within the line system for pressure equalization. In particular, the risk exists that a discharge of oil or oil condensate to the atmosphere with the volumetric flow may occur or an entry of foreign materials from the atmosphere may take place. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved ventilating and venting system having an increased amount of operating reliability with respect to preventing the discharge of liquid phase substances and the entry of foreign substance from the atmosphere. 
     According to the invention, this object is basically achieved by a ventilating and venting system having a line system containing a separating housing in which a separating medium with oleophobic and hydrophobic properties separates a first space connected to the container from a second space connected to the atmosphere. On the separating housing, line connections are arranged such that liquid phase substances on opposite sides of the separating medium can drain out of the first space to the container and out of the second space to the atmosphere. The oleophobic property of the separating medium prevents an overflow of oil to the atmosphere side within the separating housing. At the same time, the hydrophobic property of the separating medium prevents the possibility of an entry of polar fluids, for example water, up to a material-specific pressure difference from the vicinity. Pressure equalization is possible in the form of the air volume without loading with liquid phase substances for a surface not completely wetted with liquid. The protection offered by the system according to the invention against ingress of water from the vicinity is especially important and advantageous when the system is used in containers of systems operated in a wet environment. 
     Especially in containers, such as gearboxes in automotive engineering where during operation of the vehicles under wet conditions or cleaning of the vehicles in car washes or when washing by hand, the entry of water could be a concern if the protective action offered according to the invention were not present. 
     Especially advantageously, the separating medium can be formed by a filter medium having oleophobic and hydrophobic properties. In this way, the separating medium separates not only water that may enter, but also offers protection against ingress of solid particles. Especially, when used in automotive engineering, this arrangement prevents road dust or other dirt particles from being able to travel into the gearbox in operation. 
     Especially advantageously, a mount can fix the separating housing such that in its operating position it lies at a height above the container, and such that the first space borders the underlying bottom of the separating housing on which the first line connection leading to the container discharges. This mount ensures that liquid phase substances, such as oil or oil condensate from a gearbox, that have been separated on the separating medium can easily drain completely out of the first space by the action of gravity. 
     Also especially advantageously, the separating housing can form a hollow cylinder surrounding the first and second spaces. The hollow cylinder axis in the operating position can extend horizontally, so that the underlying region of the inner wall of the hollow cylinder forms the bottom bordering the first space and on which the first line connection discharges. 
     In this case, the separating housing can have one closed end and one open end that can be closed by a housing cover. The first line connection can be located on the closed end on the radially outer edge of the hollow cylinder. 
     With respect to the structural configuration of the separating medium, a cartridge-like filter insert can be inserted from the open end of the separating housing and can have the filter medium forming the separating medium. The filter insert forms an inner cylinder that borders the second space and that is open on the end of the separating housing that can be closed by the housing cover. Due to the fluid connection of the second space to the housing cover formed in this way, the second line connection leading to the atmosphere on the housing cover can be directly provided on this housing cover. 
     In this respect, the housing cover can have a central cavity connected flush to the open end of the inner cylinder that forms the second space in the closed position which seals the separating housing. The second line connection on the housing cover forms a drain channel extending away from the cavity in the radial direction. 
     Further especially advantageously, between the housing cover and separating housing, a connecting device can fix the housing cover in the closed position such that the second line connection forms a drain channel pointed downward for liquid phase substances from the cavity of the housing cover. 
     Also especially advantageously, the connecting device is made in the form of a snap safety having elastic retaining fingers on the housing cover and latch bodies that can be engaged to them by latching on the separating housing. Guide parts interact with the retaining fingers on the separating housing for the closed position of the housing cover dictating a rotary position with the underlying second line connection. Thus, liquid phase substances, for example, water, that has penetrated as far as the filter medium, can flow back again to the atmosphere by the action of gravity. 
     Especially preferred, a bushing of elastomer material can be slipped onto the separating housing such that it forms a snap ring keeping the retaining fingers latched. The bushing can be clipped with an annular groove located in its periphery to a carrier part of the mount so that the bushing, in addition to its securing function, forms a flexible support of the separating housing. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure: 
         FIG. 1  is a broken-away, schematically simplified perspective view of one part of a motor vehicle drive axle with a gearbox provided with a ventilation and venting system according to an exemplary embodiment of the invention; 
         FIG. 2  is a perspective view of the separately shown ventilation and venting system of  FIG. 1 , shown enlarged compared to  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of only the separating housing of the ventilation and venting system of  FIG. 1 , shown slightly reduced in size relative to the practical exemplary embodiment; and 
         FIG. 4  is a side elevational view in section of the separating housing of the ventilation and venting system of  FIG. 1  drawn enlarged about 1.5 times compared to a practical exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is explained below using an example in which the container that can be ventilated and vented by the system according to the invention is the gearbox  2  of the drive axle  4  of a commercial vehicle. The axle is only partially and schematically suggested. In the manner which is conventional in this apparatus, the gearbox  2  is filled with oil. Above the oil surface, a certain air volume is provided. For pressure equalization over the entire operating temperature range of the drive axle  4  at a site on the gearbox  2 , located at the highest level in the normal installation position of the gearbox  2  is a ventilation and venting connection  6 . The connection  6  is connected to a first line connection  10  of a separating housing  12  via a first hose line  8  that forms a first section of a line system. The separating housing has a second line connection  14  from which a hose line  16  forming a second section of a line system leads to the atmosphere. A mount  18  screwed to the gearbox cover  20  fixes the separating housing  12  in its operating position such that the ventilating and venting connection  6  is located on the gearbox  2  at a higher level than the gearbox  2 . The hose line  8  then forms a gradient section over which fluid drainage from the separating housing  12  to the gearbox  2  can take place by the action of gravity. 
       FIG. 2  shows details of the mount  18  with a screw clip  22  for screwing to the gearbox housing cover  20  and with a carrier part  24  extending at an angle upward from the clip  22  and forming the actual support for the separating housing  12 . The second hose line  16  leading from the second line connection  14  of the separating housing  12  to the atmosphere extends from the second line connection  14  a considerable distance downward as far as the hose end  26 , which hose end is beveled. This arrangement facilitates the flexible hose being able to elude, for example, the water jet of a washer when the associated vehicle is cleaned. At a distance from the hose end  26 , the hose line  16  is held by an elastic hose support  28  clipped in a shoulder  30  forming the lower end of the mount  18 . 
       FIGS. 3 and 4  show details of the separating housing  12 . As is apparent, the separating housing  12 , made substantially cylindrical, forms in the interior a hollow cylinder  32  with one closed end  34  and one open end  36 . On the closed end  34 , the first line connection  10  is positioned such that the inlet and drain channel  38  into the hollow cylinder  32  discharges on its lowermost region in the normal operating position. This region is farthest underneath the longitudinal axis  40  of the hollow cylinder  32  and forms the first space  42  bordering the inside wall of the hollow cylinder  32 . This first space  42  is separated by the separating medium located in the separating housing  12  from the second space  44  of the atmosphere side. 
     In this example, the separating medium is formed by a filter medium  46  having oleophobic and hydrophobic properties and being part of a cartridge-like filter insert  48 . In the exploded drawing from  FIG. 3 , filter insert  48  is separately visible and can be inserted into the hollow cylinder  32  from the open end  36  in the direction of the arrow  50 . The filter medium  46  forms an inner cylinder  74  within a support structure  52  that has been injected molded from plastic with one closed end  54  and one open end  56 . With the filter insert  48  installed, open end  56  is flush with the open end  36  of the hollow cylinder  42 . In the region of the open end  56 , the support structure  52  is sealed by an O-ring  58  relative to the inner wall of the hollow cylinder  32 . Within the hollow cylinder  32 , the first space  42  and the second space  44  are completely separated from one another by the filter medium  46  that is used as the separating medium in terms of an overflow of liquid phase substances in the form of oil or oil condensate from the first line connection  10  or of water from the second line connection  14 , while a volumetric flow of air is enabled for pressure equalization between the spaces  42  and  44 . 
     The support structure  52  has webs  60  extending lengthwise and webs  62  extending crosswise. Not all webs are visible in  FIGS. 3 and 4 , and not all webs have the same material cross section. Thus, in the installation position shown in  FIG. 4 , the web  60  at the top in  FIG. 4  has a larger material cross section and adjoins the inside of the hollow cylinder  32 . Conversely, according to the drawing on the underlying, lower inner wall region of the hollow cylinder  32  no strip adjoins it and extends lengthwise, so that between the filter insert  48  with its altogether three support strips and the inner wall of the hollow cylinder  32 , an open space forms the first space  42 . The spacer for preserving this open space is a button-like projection  64  that projects slightly radially on the strip  62  extending crosswise and that is not visible in  FIGS. 3 and 4 . The projection  64  adjoins the inner wall of the hollow cylinder  32  on the bottom of the first space  42  in the installation position shown in  FIG. 4 . When the filter insert  48  and the separating housing  12  are joined, as is suggested in  FIG. 3  by the motion arrow  50 , the filter insert  48  is inserted in the corresponding position. This position is maintained in operation since the O-ring  58  on the open end  56  of the support structure  42  with sealing pretensioning adjoins the inner wall of an edge depression  66  in the end section of the separating housing  12 . 
     The separating housing  12  on the open end  36  can be closed by a housing cover  70  shown in  FIG. 3 . Cover  70  has a central cavity  72  that, in the closed position shown in  FIG. 4 , borders the open end  76  of the inner cylinder  74  formed by the filter medium  46  and contains the second space  44 . From the cavity  72  of the cover  70 , which cavity is connected to the second space  46 , the second line connection  14  extends in the radial direction downward forming a drain channel  73 ,  73 ′. A connecting device in the form of a snap safety attaches the cover  70  to the separating housing  12 . For this purpose, the cover  70  has axially extending retaining fingers  78  and  80  peripherally distributed and having openings  82 . When the retaining fingers  78  and  80  are slipped onto the cylinder jacket  84 , fingers  78 ,  80  latch to latching bodies  86 . To ensure that the cover  70  can be moved into the closed position, i.e., into a snap connection, only when the rotary position shown in  FIGS. 3 and 4  prevails, in which the second line connection  14  extends vertically downward, on the separating housing  12  guide bodies  88  are formed between the latch bodies  86 . Free distances of varied size are between the guide bodies  88 . Matched to those free distances, the retaining fingers  78  and  80  have a different width so that the cover  70  and the separating housing  12  can be moved together only in one desired rotary position such that the snap connection forms. 
     A bushing  92  of elastomer material shown separately in  FIG. 3  and is illustrated in  FIG. 4  in the active position. In the slipped-on active position, bushing  92  forms a snap ring that overlaps the retaining finger  78 ,  80  and ensures the latch engagement. The bushing  92  has a peripheral annular groove  94  with which it can be clipped into a segment  96  on the carrier part  24  of the mount  18  so that the bushing  92  has an additional function of forming an elastic support of the separating housing  12 . 
     For effective protection against ingress of dust or dirt particles from the atmosphere, the filter medium  46  can have a corresponding filter fineness. In this design of the filter medium  46 , oleophobic and hydrophobic properties can be implemented with simultaneous permeability to a degree necessary for pressure equalization. 
     While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.