Abstract:
The invention relates to a pump comprising a housing ( 2 ), comprising at least one pump chamber ( 15 ), comprising an inlet valve ( 30 ) that has a valve element ( 30   a ) which controls an inlet opening ( 30   c ), comprising an outlet valve ( 33 ) that has a valve element ( 33   a ) which controls an outlet opening ( 33   c ), comprising a pressure relief valve ( 43 ) that has a valve element ( 43   a ) which controls a pressure relief opening ( 43   c ) and on which a spring element ( 48 ) acts in the closing direction ( 31 ), and comprising a spring chamber ( 49 ) that receives the spring element. A stop element ( 51 ) which can be accessed from the housing outer face and which can be adjusted in the closing direction ( 31 ) is arranged in the spring chamber ( 49 ), the spring element ( 48 ) end that faces away from the closing direction resting against the stop element.

Description:
RELATED APPLICATION 
     This application is a continuation of patent application Ser. No. 14/123,998, filed Dec. 5, 2013, which is a US Nationalization of PCT/EP2012/067126 having a filing date of Sep. 3, 2012, which claims filing benefit of German Patent Application DE102011082105.8 having a filing date of Sep. 2, 2011, which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The invention refers to a pump, in particular to a pneumatic pump. 
     BACKGROUND 
     Pneumatic pumps are used in the automotive sector, for example, for filling the seat bladders with air to change the contour of the seat&#39;s sitting and backrest areas. A pump used for the purpose named above, for example, has at least one pump chamber. By enlarging and reducing the chamber volume with the help of a drive unit, surrounding air is suctioned into the pump chamber during volume enlargement and air is driven out from the pump chamber during volume reduction. To control the corresponding air flows, the pump is equipped with an inlet valve that has a valve element for controlling the inlet opening. The inlet valve opens autonomously when the pump chamber enlarges and air flows into it from the surroundings. An outlet valve serves for controlling the outgoing airflow. It is likewise equipped with a valve element, but it controls an outlet opening which opens when air is driven out of the pump chamber. 
     A pump of the type described above is additionally equipped with a pressure relief valve used especially when a vehicle&#39;s seat bladders are being filled because they can leak under an excess pressure load. The pressure relief valve, in turn, has a valve element that closes a pressure relief opening and in closing direction rests on a spring element arranged in a spring space. When the pressure in the pump chamber exceeds a preset value, the excess pressure valve opens when there is a limit pressure set by the spring element. With regard to the respectively permissible maximum pressure of the pneumatic system or of a designed part thereof, the limit pressure can vary depending on the application. So far, the approach has been to use springs of various strengths in the assembly of the pump, but this entails a corresponding logistical and technical assembly effort. Additionally, there is the risk of that the wrong springs could be fit into the pump during assembly. 
     SUMMARY 
     The task of the invention is to suggest a pump of the type described above to remedy this situation. 
     This task is solved according to the present disclosure by arranging a stop element accessible from the external side of the housing and movable in closing direction on which the spring element can rest with its end pointing towards the closing direction. In this way, the required limit pressure can be easily adjusted during assembly by building in a spring element in the spring space that can be universally used for limiting the pressure range. Afterwards, the stop element is brought into the spring space and—while a pressure corresponding to the limit pressure is applied on the pump—is positioned with regard to its distance to the valve element in such a way that the desired limit pressure is reached. When doing so, deviations from limit pressure resulting from manufacturing tolerances can be compensated. 
     In an especially preferred design variant (particularly advantageous in pump housings made of plastic) it is foreseen for the inner wall of the spring space to have a regulating area extending along the closing direction by holding the excessively dimensioned stop element in a clamped way with regard to the regulating area, whereby the spring space has an actuating opening through which the stop element advancing in closing direction is accessible with a tappet or the like, for example. In this case, the clamping force can be chosen through corresponding dimensional ratios in such a way that the stop element impinged on by the spring element against the closing direction is reliably held in the intended position in the adjustment area. Depending on the chosen excess of the stop element, a more or less elastic and/or plastic deformation of the stop element takes place and/or of a housing wall that circumscribes the spring space. Particularly in the case of housings made of soft materials such as plastic, a stop element made of a material harder than the one used for the pump&#39;s housing or for the housing wall that circumscribes the spring space is advantageous. Here, the stop element is pressed into the material of a housing wall that circumscribes the spring space. A metallic stop element is preferably used. 
     Seen in top view in closing direction, the stop element has a complementary shape to the inner transversal shape of the adjustment area. One result of this is the accomplishment of a sealing of the spring space towards the surroundings and another result is a higher clamping effect. Penetration of humidity into the spring space, for example, is thereby prevented. 
     Preferably, a stop element executed as a sphere is used, in which case the adjustment area that acts together with the stop element is circularly cylindrical, i.e. forms the surface shell of a circular cylinder. This design rules out a wrong assembly caused by erroneously positioning the stop element in the spring space, for example in a wrong turning position with regard to an axis running parallel to the closing direction. 
     When pressure relief valves of the type used here open, this is accompanied most of the time by the generation of noise. In at least one design variant independent from the spring space and stop element designs, noise reduction is achieved by having the lower-pressure side of the pressure relief valve end in the spring space. With regard to its surroundings, the spring space can be fully closed so there is no fluid connection to the atmosphere and therefore the propagation of an airborne noise generated inside the spring space is prevented from reaching the exterior. Even if the spring space is connected to the surroundings through a bore hole to allow pressure to equalize between spring space and surroundings—as is the case in a design variant—if excess pressure occurs, this bore hole can have a very small flow cross-section. It is different with the inlet opening, whose flow cross-section cannot be reduced at will so that an airborne noise generated in the pressure relief valve can propagate almost unhindered into the surroundings. 
     The pressure-equalizing bore hole that connects the spring space to the surroundings mentioned above can be done completely without if the spring space is connected to the inlet opening, in which case its end located upstream (i.e. its entrance opening) does not end directly in the surroundings but in a housing space of the pump in which one drive unit for actuating the pump is arranged. In doing so, the drive unit acts like the insulating material in a sound absorber to eliminate the noise. However, in conventional pumps of the type presented here, the inlet opening is separated by a duct wall of the other housing spaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in more detail with the help of the enclosed drawings, which show: 
         FIG. 1 : A perspective lateral view of a pump with a housing encompassing one upper part of the housing, one lower part of the housing, an upper and a lower support, and a motor, 
         FIG. 2 : An exploded view of the pump shown in  FIG. 1 , 
         FIG. 3 : A perspective view of the housing&#39;s upper part, 
         FIG. 4 : A perspective view of a valve membrane arranged between the upper part of the housing and the upper support, 
         FIG. 5 : A perspective view of the upper support, 
         FIG. 6 : A longitudinal cut through the pump housing with a cutting line corresponding to line VI-VI in  FIGS. 4 &amp; 5 , 
         FIG. 7 : A longitudinal cut through the pump housing with a cutting line corresponding to line in  FIGS. 4 &amp; 5 , 
         FIG. 8 : A longitudinal cut through the pump housing with a cutting line corresponding to line VIII-VIII in  FIGS. 4 &amp; 5 , 
         FIG. 9 : A partial sectional view of another embodiment of a pump, in which the spring space is connected to the surroundings via a bore hole; 
         FIG. 10 : A sectional view of the pump of  FIG. 9 , but shown from another angle. 
     
    
    
     DETAILED DESCRIPTION 
     To explain the invention, exemplary reference is made to a pneumatic pump, in which case the designs described also apply to pumps for fluids. The pump  1  shown in the illustrations is intended to be installed in a vehicle seat and serves for filling seat bladders to change the contour of a vehicle seat in the sitting or backrest area, for example. The pump  1  comprises a housing  2  (especially made of plastic) on which an outlet connection piece  3  has been form-fitted. The side of the housing  2  supporting the outlet connection piece  3  will also be referred to as upper side  4  below. A motor  6 , especially an electric motor, has been flanged onto the lower side  5  of the housing  2 . The housing  2  comprises an upper part  7  and a lower part  8 , in which case the upper part  7  supports the connection piece  3  and forms the upper side  4 . Two plate-shaped supports—namely an upper support  9  and a lower support  10 —are clamped sandwich-like between the upper part  7  and the lower part  8 . Between the upper support  9  and the upper part of the housing  7 , a plate-shaped valve membrane  13  made of an elastic material (e.g. a rubbery polymer) has been clamped in. Four pot-shaped depressions that create pump chambers  15  have been form-fitted in the pump membrane. In its upper border, the pump membrane  14  has a circumferential bulge  16  clamped between the upper support  9  and the lower support  10 . On the upper part of the housing, peripheral arms  18  extending downwards have been form-fitted along the middle longitudinal axis  17  of the pump. On the free end of two diametrically opposing arms  18 , a rear grip element  18  has been fixed or form-fitted that, by creating an axially effective positive-locking fit, grips an opposing element  20  on the lower part of the housing  8  from behind. As a result of this, the valve membrane  13 , the upper support  9 , the pump membrane  14  and the lower support  10  are axially tensed between the upper part of the housing  7  and the lower part of the housing  8 . In the lower part of the housing  9 , there is a turnstile  23  obliquely positioned with respect to the middle longitudinal axis  17  that has been mounted on an eccentric  25  with an axis  24  protruding from its underside. The eccentric  25 , in turn, is connected in a fixed rotary way to a drive shaft  26  of the motor  6 . The pump membrane  14  has on the underside, in the area of the pump chambers  15 , a tappet-shaped extension  27  with a head-shaped end  28  fixed in a recess  29  of the turnstile. 
     Each pump chamber  15  is assigned to an inlet valve  30  and an outlet valve  33 . The outlet valves  33  are arranged in an outlet port  34  that extends inwards from the pump chamber  15  all the way to the inlet connection piece  3  and finally ends in the surroundings (i.e., the environment). The inlet valves  30  are arranged in an inlet port  35  in which—with respect to the inflow direction  36 —suctioned air flows towards the pump chamber, the end  37  located upstream ends in a housing space  38 , in which a drive unit  39  for actuating the pump chambers  15  (i.e. for enlarging and reducing them), in this case the turnstile  23  and the eccentric  25 , are arranged. The inlet valves  30  and the outlet valves  33  have in each case a valve element  30   a  that is freely cut as tongue-shaped parts from a valve membrane  13  forming an entire membrane and that in each case controls an inlet opening  30  and an outlet opening  33   c  located in the upper support  9 . Each one of the valve elements  30   a  acts with a seal seat  30   b  protruding from the underside of the upper part of the housing  7  ( FIGS. 3 &amp; 6 ). The seal seats  30   b  are sections of a ring-shaped closed seal seat  32  that separates the lower pressure side of the pump  1  from its pressurized side. The valve seats  33   b  assigned to the outlet valves  33  protrude from the upper side of the upper support  9 . In the situation shown in  FIG. 7 , the valve element  33   a  lies on top of the valve seat  33   b  that encompasses the outlet opening  33   c.    
     On the upper side of the valve membrane  13 , all inlet ports  35  end in a collecting space  41  (located above the valve membrane  13 ) arranged centrally on the pump in the direction of the arrow  40  in  FIG. 1  in the top view. The collecting space  45  is circumscribed towards the top by the upper part of the housing  7  and towards the bottom by a central area of the valve membrane  13  that comprises the valve elements  30   a  of the inlet valves  30 . 
     Apart from the inlet and outlet vales  30 ,  33 , the pump  1  is equipped with a pressure relief valve  43  developed between a central area of the valve membrane  13  that forms a valve element  43   a  and a seal seat  43   b  of the upper support  9 . The valve element  43   b  is centrally arranged in the collecting space  41  and interfused by a central connection opening  44 . Thus, the valve element  43   a  is the peripheral area of the valve membrane  13  that circumscribes the connection opening. The valve element  43   a  lies on a ring-shaped seal seat  43   b  of the upper support  9  that circumscribes the pressure relief opening  43   c . To increase the sealing effect, the peripheral area mentioned above has a sealing lip  45  on its underside. An opening  42   a  interfused with the pump membrane  14  is located centrally in the latter. Below the opening  45 , the central area of the pump membrane  14  surrounded by the pump chambers  15  is supported by an area  42  of the lower support  8  that bulges out upwards, in which case it is also interfused with an opening  46 . Thus, the section of the inlet port  35  extending away from the valve element  30   a  of the inlet valves  30  against the inflow direction  36  is created by the collecting space, the connection opening  44  and subsequent openings  44 ,  43   c ,  42   a  and  46 , in which case the inlet port  35  ends with the opening  46  in the housing space  38 , which is circumscribed by the lower support  10  and the lower part of the housing  8 . 
     A largely cylindrical connection piece  47  open towards the upper side of the housing  4  juts out from a central position of the upper part of the housing  7 . The interior of the connection piece creates a spring space  49  for receiving a spring element  48 , namely a threaded compression spring. On its front side facing away from the upper part of the housing  7 , the connection piece  47  has an assembly opening  50  over which the spring element  48  can be inserted into the spring space  49 . The spring element  49  supports itself with its lower end on the valve element  43   a  of the pressure relief valve  43  by means of an intermediate layer of a supporting ring  52 , thus impinging on the former in closing direction  31 . The other end of the spring element  48 , on the other hand, supports itself on a stop element  51  arranged on a fixed axis (with respect to the medium longitudinal axis  17 , inside an adjustment area  53  formed by a longitudinal section of the inner wall  54  of the spring space  49 ). The axially fixed fixation of the stop element  51  is accomplished by making its dimension transversal to the medium longitudinal axis  17  slightly larger than the inside diameter of the adjustment area  53 . In the examples shown in the drawings, the inner wall  54  of the adjustment area is cylindrical or extends on the outer surface of a cylinder and has an inside width or diameter  55  that is smaller than the dimension of the stop element  51  in a direction running transversally to the medium longitudinal axis  17 . The stop element  51  is preferably a metallic sphere with a diameter  56  slightly larger than the inner diameter  55  of the adjustment area  53 . Owing to the dimensions mentioned above and the connection piece&#39;s softer plastic material compared to the metallic sphere, the stop element  51  digs itself into the contact area  57  by forming a ring-shaped cavity  58  in the inner wall  54  of the connection piece  47 . The dimension relationships mentioned above have been chosen in this case so that the clamping force with which the stop element  51  is held in the adjustment area  53  is larger than the force exerted by the spring element  48  in axial direction. To set a certain limit pressure (i.e. a pump chamber pressure) to which the pressure relief valve  43  should react, the stop element  51  is inserted into the spring space  49  through the assembly opening  50  while the pump is being assembled and moved in closing direction  31  until the spring force exerted by the threaded compression spring  48  correlates with the desired limit pressure. 
     In the design variant shown in  FIGS. 9 &amp; 10 , the spring space  49 ′ is not connected to an inlet port. Here, the pressure between the spring space and the surroundings is compensated through a connection opening  59  interfused with the wall of the connection piece  47 . As in the design variant described above, the valve element  43   a  lies on a ring-shaped seal seat  43   b ′, though it does not border an opening but merely a recess  60  dosed towards the bottom. The inlet port (not shown) is therefore not connected to the spring space  49 . 
     The way the pump works will now be explained: When the air from the surroundings or from the housing space  38  is suctioned, it enlarges the pump chambers  15  by moving the extensions  27  of the pump membrane  14  downwards. The air [flows] through the openings  46 ,  42   a ,  43   c  and  44  into the collecting space  41  (arrows  63 ) and from there through the inlet valves  30  to the pump chambers  15  ( FIG. 6 ). When this occurs, the valve element  30   a  is elastically deformed and moved downwards (arrow  64 ) and as this happens, it lifts off the seal seat  30   b . The valve elements  30   a  and the valve elements  33   a  of the outlet valves  33  are not as thick as the remaining valve membrane  13 , so that in each case a free space is created above and below the valve elements that allows the valve elements to be lifted from the respective valve seat. 
     If the extensions  27  move upwards, the pump chambers  15  are made smaller and air is driven out of them. The air that was driven out flows through the outlet openings  33   c  in accordance with arrow  66  in  FIG. 7  and reaches a pressure space (see also  FIG. 3 ) bordered by the valve membrane  13 , the upper part of the housing  7  and the seal seat  32 . The pressure space is connected to the outlet port  34  of the outlet connection piece  3 . 
     If excess pressure exceeds the limit pressure, the pressure relief valve  43  reacts. When this occurs, the valve element  43   a  is lifted off the valve seat  43   b ,  43   b ′, so air can reach the spring space through the connection opening  44  available in the valve element  43   a  (see arrow  70  in  FIG. 8 ). In the design variant shown in  FIGS. 9 and 10 , pressure is compensated with the surroundings through the connection opening  59 , otherwise via the inlet port  35 . The impingement of the valve element  43   a  with excess pressure takes place through another pressure space  68  arranged below the valve membrane and bordered by it and the upper support  9 . The pressure space  67  mentioned above arranged above the valve membrane is connected to the pressure space  68  arranged below the valve membrane through openings  69 .