Abstract:
The invention relates to a vacuum pump, in particular a vane cell pump, having a housing in which a suction space is provided, and a housing passage opening into the suction space, wherein a suction non-return valve opening to the outside or into an external vacuum space is arranged in the housing passage, said valve being accommodated in a crucible-shaped housing and the crucible-shaped housing having a housing jacket, wherein the suction non-return valve can be latched in the pump housing passage.

Description:
This application is the national stage of PCT/EP2009/059539 filed on Jul. 24, 2009 and claims Paris Convention Priority to DE 10 2008 059 227.7 filed Nov. 20, 2008. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a vacuum pump, in particular a vane cell pump, having a pump housing in which a suction chamber is provided, and a pump housing opening which opens into the suction chamber, wherein a suction check valve opening to the outside or into an external vacuum chamber is arranged in the pump housing opening and is accommodated in a pot-shaped valve housing, the pot-shaped valve housing having a housing jacket. 
     WO 2008/009251 A1 discloses a vacuum pump having a construction of this type. This vacuum pump extracts air from a vacuum chamber, e.g. a power brake unit, wherein the suction chamber is formed by vane cells inside the vacuum pump. In order to prevent backflow, the vacuum pump has a suction check valve which is disposed in a pump housing opening. This suction check valve is designed like a sleeve and has a pot-shaped valve housing with a housing jacket and a housing bottom, wherein the housing bottom is inserted into the pump housing of the vacuum pump. A suction hose is e.g. pushed onto the free end of the suction check valve which projects out of the pump housing of the vacuum pump. The suction check valve is sealed in the pump housing opening e.g. using sealing elements, for example O-rings. The suction check valve of the above-mentioned conventional vacuum pump is held on the pump housing and in the pump housing opening in that the edge of the pump housing opening overlaps a flange of the suction check valve such that the free end of the edge can be flanged or caulked and the flange is fixed in the pump housing opening. Mounting of the suction check valve therefore requires an additional work step and additional tools. The pump housing is moreover deformed. It must therefore be made from a plastically deformable material and must not be brittle. 
     It is regarded as disadvantageous that the suction check valve must be fixed to the pump housing in a separate work step. Moreover, the pump housing must consist of a plastically deformable material. 
     It is therefore the object of the invention to provide a vacuum pump which facilitates fixing the suction check valve thereto. 
     SUMMARY OF THE INVENTION 
     This object is achieved in accordance with the invention with a vacuum pump of the above-mentioned type in that the suction check valve can be locked in the pump housing opening. 
     The suction check valve of the inventive vacuum pump is not only inserted into the pump housing opening but is thereby also locked to the pump housing. No additional work step is required for permanently fixing the suction check valve to the pump housing. In particular, neither the suction check valve nor the housing of the vacuum pump must be deformed or modified in any other fashion for fixing the suction check valve. Nor are bonding agents, such as adhesive or the like, required for mounting. Mounting of the suction check valve to the pump housing can therefore not only be facilitated and performed within less time but also performed by machines. 
     In a further development of the invention, the suction check valve and/or the pump housing opening has/have at least one undercut. This undercut is used to receive a latching means as soon as this latching means engages the undercut. The latching means is designed in such a fashion that it is not automatically released from the undercut and therefore prevents the suction check valve from being pulled out. 
     In accordance with the invention, the suction check valve and/or the pump housing opening is/are provided with at least one latching hook. This latching hook is disposed in such a fashion that the suction check valve can be easily inserted into the pump housing opening, thereby deflecting the latching hook. When the suction check valve has been completely inserted into the pump housing opening, the latching hook moves to the area of the undercut and engages therein. This undercut is formed in such a fashion that it engages behind the latching hook and blocks or retains it. The suction check valve is thereby prevented from being pulled out of the pump housing opening. 
     In a further development of the invention, the latching hook is disposed radially outside of the housing jacket. The housing jacket forms the fluid-tight connection e.g. between a suction hose, which is disposed outside of the vacuum pump, and the suction chamber, and the latching hook is only used for locking fixation of the suction check valve to the pump housing. It is advantageously disposed in such a fashion that it can no longer be accessed from the outside after insertion of the suction check valve into the pump housing opening. The suction check valve can only be removed from the pump housing by destroying the suction check valve. 
     In a preferred variant, the latching hook has a latching finger which can be radially pivoted with respect to the housing jacket of the suction check valve and has a terminal latch. The latch projects in a radial direction, in particular, past the outer contour of the housing jacket such that the latch is initially radially displaced during insertion of the suction check valve and, upon complete insertion of the suction check valve into the pump housing opening, radially snaps out into a receptacle provided for this purpose, in particular into an undercut. 
     In a further development, the suction check valve and/or the housing opening has/have a circumferential groove. This circumferential groove of the pump housing opening is designed in the form of an inner circumferential groove and that of the suction check valve is designed in the form of an outer circumferential groove, the circumferential groove being used to receive a latching element of the latching hook. The circumferential groove may thereby be designed to extend along the overall circumference such that rotation of the inserted locking suction check valve is not impeded. 
     The circumferential groove may also only extend over a partial area of the circumference, such that the suction check valve is not only fixed in an axial direction, i.e. in the insertion or removal direction, but also in the direction of rotation. Rotation of the suction check valve within the pump housing opening is thereby prevented. 
     In one variant of the invention, the undercut is formed by at least one opening in the pump housing. The latches of the latching fingers are locked in this opening. The suction check valve is then not only reliably fixed to the pump housing but also secured against rotation. 
     The suction check valve is removed by inserting a tool from the outside into the opening for lifting the latch out of the opening. 
     In another variant for removing the suction check valve, an inner circumferential groove is provided in the pump housing, which extends in a radial direction, at least in sections, parallel, next to and, in the insertion direction of the suction check valve, behind the opening, and terminates in the peripheral direction in the inner circumference of the pump housing opening. When the suction check valve, which is locked with the pump housing, is further inserted into the pump housing, the inclined latches slide out of the opening and move to the inner circumferential groove. The suction check valve can then be rotated, thereby lifting the latches out of the inner circumferential groove such that they abut the non-recessed inner circumferential surface of the pump housing opening. The suction check valve can then be removed. A support spring, which acts on the front side of the suction check valve and is pretensioned during insertion of the suction check valve, ensures reliable retention of the suction check valve in the pump housing. Locking is realized in the manner of bayonet locking. 
     Further advantages, features and details of the invention can be extracted from the dependent claims and the following description which describes in detail a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and recited in the description and the claims may be essential to the invention either individually or in arbitrary combination. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the drawing: 
         FIG. 1  shows a longitudinal section I-I in accordance with  FIG. 2  through a suction check valve that is inserted into a pump housing; 
         FIG. 2  shows a side view of the suction check valve; 
         FIG. 3  shows a longitudinal section through a suction check valve inserted in a pump housing in accordance with a second embodiment; 
         FIG. 4  shows a cross-section IV-IV in accordance with  FIG. 3 ; 
         FIG. 5  shows the view in accordance with  FIG. 3  with inserted tools for releasing the locking; and 
         FIG. 6  shows a cross-section VI-VI in accordance with  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  schematically shows a section of a pump housing of a vacuum pump  12 , which is designated in total with  10 , wherein  14  designates the inner circumferential surface of a suction chamber  16 . A channel  18  of a pump housing opening  20  opens into this suction chamber  16  and opens to the outside  22 . A suction check valve  24  is inserted into this pump housing opening  20 , onto the free end  26  of which a suction hose (not shown) may be pushed. The suction check valve  24 , which is shown in a longitudinal section, has a valve housing  28  having a pot-shaped design and being substantially formed by a housing jacket  30  and a housing bottom  32 . The housing jacket  30  extends past the housing bottom  32  to an edge  34  which projects past the housing bottom  32  on its opposing side. The valve housing  28  has a circumferential groove  36  into which a sealing ring  38 , in particular an O-ring, is inserted for fluid-tight reception of the suction check valve  24  in the pump housing opening  20 . 
       FIG. 1  clearly shows that the edge  34  of the suction check valve  24  is inserted into the pump housing opening  20  with tight fit in a radial direction. The housing jacket  30  also abuts the free end  40  of the pump housing opening  20  such that the suction check valve  24  is seated in the pump housing opening  20  without play in the radial direction. 
     Both  FIG. 1  and  FIG. 2  show that the suction check valve  24  has a latching means  42  which is designed as a latching hook  44  which substantially extends along the outer side of the housing jacket  30  in the axial direction, and one end of which is formed in one piece on the housing jacket  30  and the other free end  46  of which radially projects past the outer circumference or the outer contour of the housing jacket  30 . The free end  46  of the latching hook  44  is designed like a latch  48  and engages in an undercut  50  which is provided on the inner circumferential surface in the area of the free end  40  of the pump housing opening  20 . The undercut  50  is designed as an inner circumferential groove  52 . 
     It should also be emphasized that the diameter of the pump housing opening  20  in the area of the sealing ring  38  has a recess  54 , i.e. the diameter of the pump housing opening  20  is reduced in the insertion direction. The sealing ring  38  therefore abuts the recessed edge  54 , which is advantageous in that the sealing effect of the recessed edge  54  is improved compared to the case in which the sealing ring  38  flatly abuts the inner surface of the pump housing opening  20 . The sealing ring  38  is moreover not only used as a sealing means for fluid-tight sealing of the suction check valve  24  in the pump housing opening  20  but is also used as a pretensioning means such that the suction check valve  24  is pretensioned in the direction in which it is pushed out when the sealing ring  38  abuts the recessed edge  54 . This ensures that the latches  48  engage (as viewed in the axial direction) without play in the inner circumferential groove  52  and thereby fix the suction check valve  24  without play in the axial direction in the pump housing opening  20 . 
       FIG. 3  shows a variant in which two opposing openings  56  are undercut. Each opening extends over approximately 30° in the circumferential direction slightly below the free end  40  of the pump housing  10  as is illustrated in  FIG. 4 . The latches  49  of the latching fingers engage in this opening  56  when the suction check valve  24  is inserted. One can also see that a coiled spring  58  abuts the front side of the suction check valve  24 , which is compressed at the bottom of the pump housing opening  20  upon insertion of the suction check valve  24 . 
     As is clearly visible in  FIG. 4 , the width of the latch  48  corresponds to the width of the opening  56 . This prevents rotation of the suction check valve  24  when the suction check valve  24  is locked. 
     The locking is released by means of a tool  60  which is radially inserted from the outside into the (in each) opening  56  ( FIG. 5 ). The latches  48  are radially pushed into and out of the opening  56  by means of this tool  60  such that the free end  40  of the pump housing  10  no longer overlaps them. The suction check valve  24  can then be removed or the suction check valve  24  is pushed out of the pump housing opening  20  by means of the coiled spring  58 . 
     In another variant for releasing the locking, an inner circumferential groove  62  ( FIGS. 3 and 6 ) is provided which, in the insertion direction of the suction check valve  24 , directly adjoins the opening  56  or generally adjoins the undercut  50  and has a larger diameter than the diameter of the free end  40  of the pump housing  10  or the pump housing opening  20 . The inner circumferential groove extends over part of the inner circumference and terminates at the diameter of the pump housing opening  20 . When the suction check valve  24  is inserted, the latches  48  gain entrance to the inner circumferential groove  62 . When the suction check valve  24  is then turned e.g. through  30 , the latches  48  are lifted out of the inner circumferential groove  62  and abut the inner surface of the pump housing opening  20  (see  FIG. 6 ). The suction check valve  24  can then be removed. 
     It is also possible to design the latches  48  without inclination  64  but in a cuboid shape. It is then no longer possible to insert the suction check valve  24  into the pump housing opening  20  without the tool  60 . The free end  40  of the pump housing  10  is then provided with a funnel-shaped insertion inclination. In simple embodiments, it is also possible to completely omit the inner circumferential wall  62 .