Abstract:
A diaphragm pump ( 1 ) having a diaphragm ( 11 ), a solenoid with a movable magnetic armature ( 8 ) as a drive element for the diaphragm ( 11 ), and a stop element ( 9 ) for adjusting the stroke for the drive element ( 8 ). The diaphragm pump includes at least one elastic damper ( 36 ) between the drive element ( 8 ) and the stop element ( 9 ), which elastic damper ( 36 ) has at least one compression chamber ( 26 ) which is surrounded and formed by at least one elastic boundary wall and by at least one rigid boundary wall of the drive element ( 8 ) and/or stop element ( 9 ).

Description:
BACKGROUND 
     The invention relates to a diaphragm pump comprising a diaphragm, a solenoid with a movable magnetic armature as the drive element for the diaphragms, and a stop element for adjusting the stroke of the drive element, with at least one elastic damper being provided between the drive element and the stop element. 
     Diaphragm pumps of this type are known from prior art, for example from the U.S. Pat. No. 6,568,926 B1 or U.S. Pat. No. 4,143,998, and are widely used. Additionally, FR 2 485 108 A and U.S. Pat. No. 6,758,657 B1 also disclose such diaphragm pumps. Depending on their design, the noise developed by such pumps is rather high. 
     SUMMARY 
     The object of the invention is to provide a diaphragm pump of the type mentioned at the outset, with its operating noise being considerably reduced. 
     This object is attained according to the invention in the elastic damper comprising at least one compression chamber, which is enclosed and formed by at least one elastic limiting wall and by at least one stiff wall of the drive element and/or the stop element. 
     In a preferred embodiment of the invention the elastic limiting wall is formed by a ring made from an elastic material. 
     The elastic ring acts as a first damper in the downward motion of the drive element. A compression chamber is formed inside the ring by the ring contacting the opposite limiting wall, ensuring an additional slowing of the motion of the drive elements. The compression of the air in the compression chamber causes a progressive dampening characteristic such that the dampening increases with the distance becoming shorter. By the time the drive element contacts the stop element it has slowed to such an extent that only low noise develops. The damper with the compression chamber therefore acts as a pneumatic spring. By the air cushion in the compression chamber braking the motion, the elastic ring is relieved and thus its life is extended. 
     For operation, the elastic damper is dimensioned such that during each stroke executed by the drive element the drive element contacts the stop element. This results in the drive element performing a defined stroke and the pump conveys a precisely defined volume, which remains constant even in case of the damper failing. 
     It is particularly beneficial for the elastic ring to be inserted into a groove or onto a shoulder of the drive element and/or stop element. This way the assembly of the ring is facilitated and it is prevented that the ring slips or becomes damaged during operation. Here, the ring projects beyond the respective limiting wall, allowing it to influence the dampening by its projection. 
     In another advantageous embodiment of the invention at least one recess is arranged inside the elastic ring in at least one stiff limiting wall of the drive element and/or the stop element, increasing the air volume of the compression chamber and thus also influencing the dampening characteristic. Another advantage of this arrangement is the fact that the recess is effectively enlarged on a small area of the compression volume such that the operating gap between the drive element and the stop element can be selected narrower without having to waive any additional dampening. Due to the short distance, the resistance for the magnetic flux, formed by the operating gap between the drive element and the stop element, is reduced and the pump can therefore build up a greater pressure with a reduced stroke. 
     Another embodiment of the invention with an improved magnetic flux provides that the stiff limiting wall ends flush with or projects from the elastic ring inserted into the groove or placed upon the shoulder and that a ring is provided on the opposite stiff limiting wall, impinging the circumferential circular flange in the stop position. 
     In all embodiments, the elastic ring is not limited to a circular shape. Rather arbitrary, closed shapes are possible, conditional to allowing a volume to be formed inside by covering the planar sides. 
     Advantageous further embodiments are discernible from the drawings as well as the dependent claims and by combining several features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, preferred embodiments of the diaphragm pump according to the invention are explained in greater detail using the drawings. They show: 
         FIG. 1  is a cross-sectional view of a diaphragm pump according to the invention, 
         FIG. 1   a  is a detailed view of a part of the diaphragm pump according to the invention, 
         FIG. 1B  is a view of the diaphragm pump of  FIG. 1  with the armature in a bottom position contacting the stop element, 
         FIG. 1C  is a view of the diaphragm pump of  FIGS. 1 and 1B  shown with the axial position of the stop element adjusted from the position shown in  FIG. 1B  to adjust the maximum stroke. 
         FIGS. 2A and 2B  are enlarged views of a diaphragm pump in the region of the elastic damper, and 
         FIGS. 3-7  are views of additional embodiments of elastic dampers. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a diaphragm pump marked  1  in its entirety. The pump  1  essentially comprises a drive part  2  and a pump part  3 . 
     The drive part  2  has a solenoid with a magnetic coil  5 , which is surrounded by a yoke  6 , held in the drive housing  7  and forming the stator of the drive. 
     Inside the magnetic coil  5 , an armature  8  can be moved back and forth as a drive element, connected via a drive sheath  10  to the diaphragm  11 . The armature  8  is impinged by a compression spring  30  in the direction of the operating stroke (arrow Pf  1 ) such that the armature  8  with the diaphragm  11  is moved towards the diaphragm chamber  37 . When the magnetic coil  5  is subjected to a current feed, the armature  8  is moved inversely in the direction of the intake stroke, opposite the arrow direction Pf  1 . 
     The face of the armature  8  facing away from the diaphragm  11  faces a stop element  9  comprising a ferromagnetic material, connected to a sheath  4  in a torque-proof fashion. The sheath  4  projects beyond the stop element  9 , with the armature  8  being guided inside the sheath  4 . At the end facing the pump head the sheath  4  is screw connected via a thread  14  to the pump housing  29 . The compression spring  30  is supported on a shoulder of the sheath  4 . 
     The axial position of the stop element  9  can be changed by rotating the stop element  9  in the thread  14  and thus the operating gap  28  between the armature  8  and the stop element  9 . Compare  FIGS. 1B and 1C . The operating gap  28  is equivalent to the maximum stroke of the armature  8  and thus determines the volume conveyed per stroke. 
     At its exterior end section, the stop element  9  is subjected to tensile stress towards the outside by a disk spring  18 . 
     A circular gap  17  is formed between the sheath  4  and the armature  8  such that the armature is guided smooth-running in the sheath  4 . 
     Additionally, the circular gap  17  forms a ventilation channel, via which the air can exit, which is displaced from the operating gap  28  by the armature  8  when approaching the stop element  9 . 
     In  FIG. 1   a  the pump part  3  of the diaphragm pump  1  is shown enlarged for a better illustration. At its exterior perimeter the circular diaphragm  11  contacts the edge of the pump housing  29  and is here clamped by the diaphragm cover  12 . At the interior perimeter of the diaphragm  11 , a suspension member  32  is engaged, which is pulled by the tensile screw  33  towards the diaphragm cover  12  and thus clamps the diaphragm  11 . 
     Together with the diaphragm cover  12 , the diaphragm  11  limits the diaphragm chamber  37  and thus the actual operating volume. The inlet valve  22  and the outlet valves  19  are located in the diaphragm cover  12  and the pump lid  13  positioned thereupon and are each connected to the diaphragm chamber  37  and on the other side to the inlet connectors  21  and the outlet connectors  20  of the pump. 
     During operation, the armature  8  with the diaphragm  11  performs an upward and downward motion, which is limited on the one side by the diaphragm cover  12  and on the other side by the stop element  9 . 
     According to the invention, in the bottom dead center area an elastic damper  36  is provided between the armature  8  and the stop element  9 , comprising an elastic ring  15  inserted into a circular groove  31  of the lower wall face of the armature  8 , shown in detail in  FIG. 2A , which forms a limiting wall. 
     The elastic ring  15  can also be placed upon a shoulder  31   a , as indicated in  FIG. 2B . When feeding a current to the magnetic coil  5 , the downward motion of the armature  8  is dampened when the elastic ring  15  contacts the limiting wall of the stop element  9 . As discernible from  FIG. 2 , when the ring  15  contacts the face of the stop element  9  in the interior space of the ring between the limiting walls of the armature  8  and the stop element  9 , a compression chamber  26  forms enclosing an air volume. 
     A dampening effect by compressing the air is achieved in addition to the elastic deformation of the ring  15 , which is the greater the further the two limiting walls approach each other. The compression volume can be enlarged by an additional recess  16  ( FIG. 2A ) and adjusted to the respective application. 
     The remaining exterior operating gap  28  is ventilated via the circular gap  17  and thus has no influence on the dampening. This ensures a defined dampening, largely independent from the environmental conditions. 
     In the upper dead center position, the motion of the armature  8  is slowed and dampened by the elastic diaphragm  11 . In the pump area another dampening can be provided according to the principle of the compression chamber, as discernible in  FIG. 1   a . For this purpose, circumferential sealing rims  23 ,  23   a  are arranged at the mouth openings of the valve connection channels  39  in the diaphragm cover  12 , extending into the diaphragm chamber  37 . When the diaphragm  11  contacts the sealing edges  23 ,  23   a  the diaphragm chamber  37 , then sealed towards the outside, forms a compression chamber  37  and dampens the stroking motion near the upper dead center. 
       FIG. 3  shows another embodiment of the elastic damper  36 . Deviating from the embodiment shown in  FIG. 2 , the elastic ring  15  is inserted into a groove  31  in the limiting facial wall of the stop element  9 . This way, the ring  15  is not subject to any acceleration forces during operation and therefore the position in the groove  31  is secured. 
     In this exemplary embodiment, in order to ventilate the operating gap  28  a lateral opening  27  is provided in the sheath  4  such that the air displaced by the armature  8  can exit faster and has no slowing effect upon the motion of the armature. 
     Another variant of the elastic damper  36  is shown in  FIG. 4 . Another elastic ring  35  in the stop element  9  is here allocated to the ring  15  in the armature  8  such that during operation, the compression volume is formed between the two rings. Due to the “rubber on rubber” contract, on the one side, the operating noise is further reduced and, on the other side, potential wear and tear by friction against the stiff limiting wall is eliminated. 
     In the embodiment of an elastic damper  36  according to  FIG. 5 , the elastic ring  15   a  is embodied as a flat ring. For example, such flat rings can be punched or cut out of an elastic sheet material. The ring can be produced in arbitrary dimensions in a simple fashion, so that a fine adjustment of the dampening is possible. Due to the greater, flat contact area the dampening is also considerably harder and allows a great dampening effect even at short distances. In this way, the dampening can occur over a very short distance and accordingly the operating gap  28  can be kept narrow for high pump pressures. 
       FIG. 6  shows another embodiment of the elastic damper  36 , in which the facial limiting wall of the armature  8  projects beyond the elastic ring  15  located in the groove  31 . 
     At the opposite limiting wall of the stop element  9 , a circular flange  24  is provided, impinging the ring  15  in the contact position, which limits the compression chamber when contacting the ring  15 . Due to the fact that the ring  15  is arranged entirely inserted in the groove  31 , the ring  15  is held particularly securely. 
     In the embodiment shown in  FIG. 7 , the elastic damper  36  is essentially formed by a cup-shaped formed part, comprising a plate  25  with a ring  15   b , formed in one piece at the outside perimeter, and comprising an elastic material. The cup-shaped formed part is inserted into a recess  31   b  of the armature  8 . 
     It is also possible to insert only the plate-shaped part  25  without any connected elastic ring  15   b  formed on it, however, in connection with a recess  16 , for example shown in  FIG. 2 , or also into the plate  25  itself. 
     It should also be mentioned that several compression chambers  26  may be provided when appropriate space is available. For example, instead of a central ring  15 , as shown in  FIG. 1 , several, for example three, rings  15  may be provided side-by-side at the bottom face of the armature  8  and accordingly form three compression chambers in connection with the face of the stop element  9 .