Abstract:
A suction pump, in particular a breast pump, comprises a bleed valve with a bleed opening, a bleed body which seals the bleed opening and an operating means for operating the bleed body. The bleed body may be operated such that upon opening the valve initially only a partial region of the bleed opening is released and subsequently a greater part thereof or the whole bleed opening is released. The suction pump provides a large functionality with the smallest size and, furthermore, is cheap to produce and easily assembled.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a divisional application of U.S. application Ser. No. 13/936,064 filed Jul. 5, 2013, which is a continuation application of U.S. application Ser. No. 11/662,683 filed Mar. 12, 2007, which claims the benefit of Swiss Patent Application No. 1541/04 filed Sep. 20, 2004, the contents of which are fully incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a suction pump with a safety valve. 
       BACKGROUND 
       [0003]    Suction pumps are known for a wide variety of applications. However, they can preferably be used in breast pump devices for pumping off breast milk, or as drainage pumps for suctioning off body fluids. 
         [0004]    There are suction pumps in closed systems which at all times move the same air within the pump chamber. However, open pump systems are also known with an air release valve which can be opened cyclically via an electromagnet. 
         [0005]    The requirements placed on these suction pumps, in particular when they are used as breast pumps, are quite high. They should be as powerful as possible but, at the same time, relatively small. Particularly in their use as breast pumps, they should be able to operate with minimum maintenance and should be easy to clean. 
       SUMMARY 
       [0006]    It is an object of the invention to make available a suction pump which has a safety valve and which cannot be inactivated by liquid, in particular milk, that has been sucked into the pump and has accumulated there. 
         [0007]    The suction pump according to the invention has a safety valve with a first stage which opens at a first underpressure, and with a second stage which opens at a second underpressure. The first underpressure is quantitatively lower than the second. 
         [0008]    This two-stage design of the safety valve ensures that milk cannot get as far as the second stage. Since the first stage opens even in the event of a very slight deviation from the ideal underpressure, it will still open, in the event of clogging, when the underpressure is at a higher level, that is to say in an emergency situation. The second valve prevents the entire safety valve from opening at too small a deviation, but it still opens reliably in an emergency situation. 
         [0009]    This two-stage safety valve can also be used in a pump that does not have an air release valve as mentioned below or a modular construction as mentioned below. 
         [0010]    In preferred embodiments the suction pump permits the smallest possible design of the pump yet at the same time allowing short pump cycles. 
         [0011]    In a method according to a preferred variant of the invention, an air release body, which closes an air release opening of the air release valve, is at first only partially lifted. In this way, a smaller force is needed than if the whole air release opening is freed in a single step. 
         [0012]    The means for actuating, in particular for lifting, the air release body can therefore be less powerful and can thus be made smaller. If an electromagnet is used as such a means, a relatively low-power type can be used. The reason is that, when pulling up or lifting the air release body, the electromagnet can at first apply less force than it does at the end of the movement. This initially available lower force, however, is sufficient to free a relatively small opening. It is therefore possible to use a relatively small and thus also inexpensive electromagnet. Moreover, the air release opening can be made relatively large. This ensures a rapid cancellation of the underpressure and, therefore, the desired functionality of the pump. 
         [0013]    The pump easily reaches 120 cycles per minute. However, it can also operate optimally at a cycle rate of 50-72 cycles per minute. The first cycle rate is particularly suitable for stimulation, the second one for expression of breast milk. 
         [0014]    In a preferred variant of a method according to the invention, only an edge area of the air release body is at first removed from the air release opening. A minimal amount of force is needed if this edge area coincides with a corner of the air release body. 
         [0015]    The air release body is preferably a membrane. The lifting of its edge area is made easier if the lifted edge area is less thick than the rest of the membrane. The air release opening is preferably polygonal, in particular square or triangular. The membrane too is preferably polygonal, preferably square or triangular. 
         [0016]    To permit easier lifting of the membrane, a connecting pin can be secured to it or integrally formed on it, and this connecting pin is connected to an armature of the lifting magnet. This connecting pin is preferably situated in the edge area of the membrane that covers the air release opening. However, the membrane can also be designed with a raised flange, in which case the connecting pin is not arranged over the air release opening but instead on this raised flange. 
         [0017]    If the connecting pin is designed so as to be movable relative to the membrane, it is possible to overcome any production-related or assembly-related tolerances. Errors in the angle of the electromagnet can also be compensated. Good results were achieved using a connecting pin which is formed integrally on an air release membrane made of silicone and which, by means of suitable thickening of the material, has sufficient stiffness. It can be formed thereon in a hinged manner. However, in a simple embodiment, the elasticity of the material of the connecting pin suffices to make it movable about its point of attachment. 
         [0018]    In another embodiment, the air release body has a first subsidiary body and a second subsidiary body. A first subsidiary body closes the air release opening only partially, since it has an air release channel which creates a connection from the air release opening to the outside. This first subsidiary body including the air release channel can be closed by a second subsidiary body. When air is released, only the first subsidiary body is at first lifted, or distanced from the air release channel, such that only part of the air release opening is freed. The second subsidiary body can then also be distanced from it, such that the whole air release opening is now freed. In this second stage, the second subsidiary body can preferably be actuated jointly with the first subsidiary body. 
         [0019]    Compared to this embodiment, the first embodiment mentioned, with the air release membrane that can be actuated in an edge area, has the advantage that it ensures leaktightness and thus, particularly when used in a breast pump, ensures there is no leakage of the pumped-off milk. 
         [0020]    A further advantage of the abovementioned embodiments, particularly as regards the use of the membrane, is that no springs are needed, and the number of individual parts required can therefore be reduced. Since no spring has to be fitted, the work involved in assembling the pump is also reduced. 
         [0021]    In preferred embodiments of the invention, the suction pump can be put together as easily as possible. 
         [0022]    The suction pump according to a preferred embodiment of the invention has an air release valve with an air release membrane, and this air release membrane and a vacuum membrane used to generate the vacuum are designed integrally in the form of a common membrane plate. 
         [0023]    Arranging the air release valve and the vacuum membrane on the same plate means that these elements are less expensive to produce and are easier to assemble. 
         [0024]    In a preferred embodiment, the pump comprises an upper housing part, a middle housing part and a lower housing part, with a membrane plate and a valve plate being arranged between the housing parts. This division means that several elements can be formed on the same structural part. In particular, the vacuum membrane needed to generate the underpressure, and the air release membrane needed to rapidly cancel the underpressure, can be formed integrally on the same structural part. Control flaps and valve flaps can also be formed integrally on a common structural part. Electric motor and electromagnet can be secured in the same housing part. By dividing the pump into several levels, preferably five levels, the number of individual parts can be reduced to a minimum without having to give up the complexity of the pump assembly. This not only reduces the outer dimensions of the pump assembly, but also minimizes the production and assembly costs. 
         [0025]    A further advantage of this modular construction with several levels is that the pump can be cleaned by simple flushing, without having to be dismantled into its individual parts. By virtue of the exhaust leading to the outside, no sponge is needed. Such sponges are used in the prior art to absorb milk that has been sucked into the pump and also to attenuate noise. However, they take up space in the pump and tend to give rise to unpleasant odor. 
         [0026]    This modular construction can also be used in a pump that does not have the abovementioned air release valve. 
         [0027]    The suction pump according to some embodiments of the invention can reduce the vacuum in a relatively short time and without too much force. The pump according to the invention is suitable for a wide variety of applications. It is suitable in particular as a breast pump for suctioning off breast milk and as a drainage pump for suctioning off body fluids. The pump assembly according to the invention is suitable in particular for use in a portable breast pump, as is described in particular in still to be published PCT/CH 2004/000061. 
         [0028]    Further advantageous embodiments are set forth in the attached patent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The subject matter of the invention is explained below on the basis of preferred illustrative embodiments depicted in the attached drawings, in which: 
           [0030]      FIG. 1  shows a perspective view of the suction pump according to the invention without outer housing; 
           [0031]      FIG. 2  shows a view of the suction pump according to  FIG. 1  from below; 
           [0032]      FIG. 3  shows a longitudinal section through the suction pump according to  FIG. 1 ; 
           [0033]      FIG. 4  shows an exploded view of the suction pump according to  FIG. 1 ; 
           [0034]      FIG. 5  shows a perspective view of a lower housing part of the suction pump according to  FIG. 1 ; 
           [0035]      FIG. 6  shows a view of a membrane plate of the suction pump according to  FIG. 1  from above; 
           [0036]      FIG. 7  shows a longitudinal section through the membrane plate according to  FIG. 6 ; 
           [0037]      FIG. 8  shows an enlarged detail of the membrane plate according to  FIG. 7 ; 
           [0038]      FIG. 9  shows a view into a part of the upper housing part from above; 
           [0039]      FIG. 10  shows a view of a membrane plate of the suction pump according to a second embodiment from above; 
           [0040]      FIG. 11  shows a longitudinal section through the membrane plate according to  FIG. 10 ; 
           [0041]      FIG. 12  shows an enlarged detail of the membrane plate according to  FIG. 11 , and 
           [0042]      FIG. 13  shows a longitudinal section through an air release unit according to the invention in a third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]      FIG. 1  shows a suction pump according to the invention, such as is suitable in particular for a breast pump device for pumping off human breast milk. However, the pump is also suitable for other applications, for example for drainage pumps for suctioning off body fluids. 
         [0044]    Only the actual pump assembly is shown. This assembly is usually arranged in an outer housing. The figure does not show this outer housing and the electronics needed for actuating the pump, or any energy storage means, for example an accumulator or battery. 
         [0045]    The pump has an extremely compact structure. One of its largest elements is an electric motor  1 . It also has an upper housing part  2 , a middle housing part  4  and a lower housing part  6 , which can be plugged together. An attachment part  7  is also provided which is a component part of these housing parts or, as is the case here, is plugged onto them. 
         [0046]    On the attachment part  7 , there is at least one breast shield attachment piece  70  on which a connecting tube to a breast shield can be plugged. The attachment part  7  also comprises an exhaust  71 . This exhaust  71  also leads out of the outer housing. An air release channel  72 , also protruding from the outer housing, and spacer elements  73  are also present. The spacer elements  73  brace the pump assembly in relation to an outer housing in such a way that vibrations cannot be transmitted and a sufficient sound insulation is ensured. 
         [0047]    It will be seen from  FIG. 2  how the individual attachments  70 ,  71 ,  72  are connected via individual channels to the individual areas of the pump. 
         [0048]    The longitudinal section shown in  FIG. 3  through the pump, now without motor  1 , shows that the pump, despite its compact design, is divided into three clearly distinguishable function areas: a pump unit P, an air release unit V and, arranged between these, a safety unit S. The structure of the pump can best be seen from an overview of  FIGS. 3 and 4 . 
         [0049]    The pump unit P comprises a vacuum membrane  31  and inlet and outlet control flaps  51 ,  52  which, together with inlet and outlet openings  62 ,  63  and with a pump chamber opening  43 ′, create a connection between a pump chamber  43  and a vacuum channel  69 . The vacuum membrane  31  is connected to a drive shaft  10  of the electric motor  1  via a connecting rod  11 , coupling piece  12 , for example a ball bearing, and eccentric  13  and, by means of this motor  1 , it can be lifted and lowered according to a predetermined rhythm or pump curve or according to a rhythm or pump curve that can be freely selected via a control system. 
         [0050]    The air release unit V comprises an air release valve with an air release membrane  32 , and an air release opening which can be closed tightly by the latter and is in the form of an air release membrane seat  44 . The chamber  44 ′ surrounding the air release membrane seat  44  is connected via an air release attachment  45  to the air release channel  72 . The air release membrane seat  44  is open at the bottom, that is to say on the side directed away from the air release membrane  32 , and adjoins a first air release opening  54  of the valve plate  5  and a second air release opening  67  of the lower housing part  6 . This second air release opening  67  is connected via the vacuum channel  69  to a safety valve chamber  68  and to the inlet opening  62 . 
         [0051]    The air release membrane  32  is connected via a connecting pin  33  to an armature  80  of a lifting magnet or electromagnet  8 . The electromagnet  8  lifts the air release membrane  32  and thus frees the air release membrane seat  44 . By this means, air passes through the air release channel  72  and through the first and second air release openings  54 ,  67  into the vacuum channel  69 , and the underpressure in the latter is reduced. This lifting and lowering of the air release membrane  32  also takes place according to a predetermined function or according to a function that can be freely selected via a control system, and which function is coordinated with the movement of the vacuum membrane  31 . The movements of the vacuum membrane  31  and of the air release membrane  32  are preferably coordinated in such a way that a pump curve is obtained which is as described in WO 01/47577 and which is adapted to the needs of mother and child or imitates the natural sucking rhythm of a baby. The assembly functions in all positions, that is to say, for example, when it is lying or standing on a table or being carried. The vacuum generated is largely independent of how the assembly is spatially arranged. 
         [0052]    The safety unit S comprises a safety valve. In the event of a malfunction or failure of the control electronics that coordinate the movement of the vacuum membrane  31  and of the air release membrane  32 , this safety valve ensures that the level of the underpressure in the pump does not become too great and injure the mother&#39;s breast. 
         [0053]    According to the invention, the safety unit S is designed with two stages. The first stage consists of a first safety membrane  55  and of a semispherical safety valve closure  46  which has a small lateral opening  46 ′ and which presses on the first safety membrane  55 . This first stage opens even at a low underpressure of about 120 mmHg. 
         [0054]    The second stage comprises a second safety membrane  35  which is closed by means of an adjusting screw  9 . Its limit value, at which it opens, can be modified by adjustment of the adjusting screw  9 . According to the invention, it opens at a higher underpressure than the first stage, for example at about 290 mmHg. 
         [0055]    If milk or another suctioned fluid accidentally gets into the pump, it settles in the area of the first stage and cannot pass through to the second stage via the chamber lying in between. At the very most, therefore, it can cover the first safety membrane  55 . In this covered state, the latter possibly no longer opens at the preset value, but it always opens early enough to permit release. The second membrane always opens only when the limit value is actually exceeded and the pump has to be relieved. Since the second stage cannot be soiled, it always opens reliably. 
         [0056]    The individual parts of the pump can best be seen in  FIG. 4 . This exploded view shows that the pump is divided into several levels I, II, III, IV and V, where parts of the pump unit P, of the safety unit S and of the air release unit V are arranged on common levels. 
         [0057]    A first level I, which usually, but not necessarily, forms the uppermost level in the operating position, comprises the upper housing part  2 , the aforementioned motor  1 , and the electromagnet  8 . The motor  1  is secured by fastening screws  21  onto a motor plate  20  of the upper housing part  2 . The motor can be screwed onto the motor plate  20  and can likewise be plugged onto the pump assembly. The housing part  2  comprises a connecting rod chamber  23  which is used to receive the connecting rod  11 , the ball bearing  12  connected thereto, and an eccentric with counterweight  13 . The counterweight  13  does not necessarily have to be present. The upper housing part  2  also comprises a magnet chamber  24  which is separate from the connecting rod chamber  23  and in which the electromagnet  8  is secured. At its lower end, the upper housing part  2  has upper locking clips  22  which protrude downward. 
         [0058]    The adjusting screw  9  for the second stage of the safety valve is also arranged adjustably in the upper housing part  2 . 
         [0059]    The second level II is defined by a membrane plate  3  which extends at least approximately across the whole base surface of the upper housing part  2  and thus of the pump assembly. The membrane plate  3  is made of a flexible material, in particular silicone, and is relatively thin. It has centering holes  30  in its edge areas, and upper and lower sealing lips  34 ,  34 ′,  34 ″ which ensure an airtight and liquid-tight connection to the upper housing part  2  and middle housing part  4 , respectively. The lower sealing lips can be seen in  FIG. 7 . The membrane plate  3  comprises the air release membrane  32 , which is designed in the shape of a triangle. As can be seen in  FIG. 6 , the air release membrane  32  has a triangular basic shape. This triangle is divided into two subsidiary areas, where a first subsidiary area  32 ′ again forms a triangle, and the second subsidiary area  32 ″ is formed by the remaining part of the membrane and thus has a trapezoid shape. A first corner of the first subsidiary area  32 ′ coincides with a corner of the air release membrane  32 . An opposite side of the first subsidiary area  32 ′ extends parallel to an opposite side of the air release membrane  32 , and the two other sides of the triangle of the first subsidiary area  32 ′ extend congruently with respect to the sides of the triangle of the air release membrane  32 . The triangular first subsidiary area  32 ′ is less thick than the second subsidiary area  32 ″, as can be seen in  FIGS. 7 and 8 . 
         [0060]    The connecting pin  33  is formed integrally on the free corner of the first subsidiary area  32 ′. As can also be seen from  FIGS. 7 and 8 , it projects upward at least approximately perpendicular to the plane of the membrane and is fixedly connected to the armature  80 . The air release membrane  32  is surrounded by a first sealing lip  34 . 
         [0061]    The membrane plate  3  further comprises the vacuum membrane  31 , which is connected to the connecting rod  11 . The connecting rod  11  can be formed integrally on the vacuum membrane  31  by material thickening and can be composed of a two-component material. It can also be produced separately, however, and be connected to the membrane  31  during assembly. The vacuum membrane is sealed off from the upper and middle housing parts  2 ,  4  by means of a second sealing lip  34 ′. 
         [0062]    The membrane plate  3  further comprises the second membrane  35  of the safety valve. The latter, as can best be seen in  FIG. 7 , has a v-shaped opening that widens toward the bottom and is sealed off from the upper and middle housing parts  2 ,  4  by means of a third sealing lip  34 ″ that surrounds it. 
         [0063]    The third level III is formed by the middle housing part  4 . Like the upper and lower housing parts  2 ,  6 , it is preferably made of a solid plastic material, for example POM (polyoxymethylene). The middle housing part  4  is panel-shaped and has a plane upper face and a plane lower face. On its side faces, it is provided with upwardly and downwardly directed catches  40 ,  41 , respectively, the upper catches  40  engaging into the upper locking clips  22  of the upper housing part  2 , and the lower catches  41  engaging into lower locking clips  60  of the lower housing part  6 . Centering holes  42  are also present which are in alignment with the centering holes  30  of the membrane plate  3 . 
         [0064]    Two recesses, closed at the bottom and with small lateral connecting openings, are present in the middle housing part  4 . One of these recesses forms the vacuum membrane seat  43  for the vacuum membrane and thus defines the pump chamber. A second of these recesses forms a safety closure  46  of the first safety stage. The chamber  44 ′, with the membrane seat  44  arranged therein for the air release membrane  32 , is also present in the middle housing part  4 . This seat  44  has a triangular shape in this example. The chamber  44 ′ is a recessed, h-shaped trough, the latter being connected to the air release attachment  45 . 
         [0065]    The fourth level IV in turn comprises a flexible plate, preferably of silicone. It is formed by a valve plate  5 . This too has centering holes  50 , at least one pair of these centering holes  50  being in alignment with the centering holes of the middle housing part  4  and of the membrane plate  3 . 
         [0066]    The valve plate  5  comprises a first control flap  51 , which forms an inlet for the vacuum chamber. It further comprises a second control flap  52 , which forms an outlet for the vacuum chamber. Leading away from the second control flap  52 , there is a double sealing lip  53  which surrounds an upwardly open connecting channel  64  arranged in the lower housing part  6  and seals this connecting channel  64  at the top. 
         [0067]    The first membrane  55  of the safety valve is also formed integrally in the valve plate  5 . The latter also comprises the first air release opening  54 , which ensures a connection between the air release membrane seat  44  and a second air release opening  67 , which is arranged in the lower housing part  6 . The individual elements of the valve plate  5  are in turn provided with upper and lower sealing lips to seal them relative to the middle and lower housing parts  4 ,  6 . All the elements of the valve plate  5  are preferably produced integrally with the latter. 
         [0068]    The fifth level V comprises the lower housing part  6  and the attachment part  7 . These two parts can be formed by a single common part, or, as is shown here, they can be coupled to one another by plug connections. 
         [0069]    The lower housing part  6  is shown in  FIG. 4 , and in another perspective view in  FIG. 5 . It also has a plate-shaped design, its underside forming the base of the pump assembly. The lower locking clips  60  project upward at the sides, such that the lower catches  41  of the middle housing part  4  can lock into them. Centering pins  61  are also present which also project upward and can be guided through the centering holes  30 ,  42 ,  50  of the membrane plate  3 , of the middle housing part  4  and of the valve plate  5 . These centering pins and centering holes make it easier to stack the individual levels on one another and thus permit rapid assembly. 
         [0070]    The lower housing part  6  further comprises a first circular recess with central elevation, which forms an inlet opening  62 . A second circular recess forms an outlet opening  63 . This inlet opening  62  is connected to the vacuum channel  69  extending in the inside of the lower housing part  6 . This channel  69  first passes through the safety valve opening  68  which is likewise designed as a trough and over which the safety membrane  55  of the first stage is arranged. 
         [0071]    The connecting channel  64 , open at the top and sealed off by the sealing lip  53 , extends in the lower housing part  6  and opens into the outlet opening  63 . This connecting channel  64  is connected to the second air release opening  67  present in the lower housing part  6 . 
         [0072]    As can be seen in  FIG. 5 , the connecting channel  64  ends in an exhaust attachment  66  which can be plugged into the exhaust  71 . The second air release opening  67  leads to a breast shield attachment part  65 , which is connected to the breast shield attachment piece  70 . 
         [0073]    This construction permits simple cleaning of the pump. If milk or another suctioned liquid gets into the pump, the latter can simply be flushed with water or air, the cleaning medium being pressed or blown in through the beast pump attachment piece  70  and leaving the pump again by way of the air release channel  72  and the exhaust  71 . 
         [0074]      FIG. 9  shows a partial view from above into the upper housing part  2 . As can be seen here, the adjusting screw  9  of the safety valve S is designed with a round cross section but is screwed into a square thread opening  25 . This means that a sufficient passage of air is at all times ensured. 
         [0075]      FIGS. 10 to 12  show a second embodiment. This embodiment differs from the one described above in the area of the air release valve. The other parts are of the same design and are therefore not described again here. In this example, the air release membrane  32  is not triangular, but square. However, it can also be hexagonal or octagonal or of any desired polygonal shape. It has been found in practice, however, that the square shape closes and opens more reliably compared to the triangular shape. The air release membrane is once again divided into thick and thin subsidiary areas  32 ′,  32 ″, the connecting pin  33  being arranged on the thin subsidiary area  32 ′. The two subsidiary areas  32 ′,  32 ″ are also substantially square, the connecting pin  33  being arranged on a long side of the thin subsidiary area  32 ′ directed away from the thick subsidiary area  32 ″. It is now no longer secured in a corner, but approximately midway along this long side, as can be seen in  FIG. 10 . It has also been found that the functionality is better ensured if the connecting pin is integrally formed on the side wall  44 ″ of the chamber  44 ′, as is shown in  FIG. 12 . However, the opening lying below this, that is to say the air release membrane seat  44 , is preferably triangular as before. In this case, the connecting pin  33  is preferably arranged exactly over the corner of the triangular hole  44 . 
         [0076]      FIG. 13  shows a further embodiment of the air release valve according to some embodiments of the invention. The rest of the pump can be designed the same way as described above and is therefore not shown again here. The air release body is not a membrane here, but instead is formed by first and second air release blocks  320 ,  321 . 
         [0077]    The first air release block  320  is fixedly connected to the armature  80  of the lifting magnet  8 . It is connected to the second air release block  321  via a first, soft spring element  322  and a retaining clip  323 . The retaining clip  323  is secured, via a second, harder spring element  324 , on a base body  325  surrounding the air release body. The base body  325 , the first air release block  320 , the retaining clip  323  and the two spring elements  322 ,  324  are preferably made of plastic and are all designed together in one piece. 
         [0078]    The second air release block  321  has a first air release channel  326 , which can be closed by the first air release block  320 . The second air release block  321  closes a second air release channel  327 , which is connected to the vacuum channel  69 . The second air release channel  327  has a greater diameter than the first air release channel  326 . 
         [0079]    If the armature  80  of the magnet  8  is now lifted, the soft spring element  322  means that only the first air release block  320  is lifted at first and the first air release channel  326  is freed. If the armature  80  is lifted further, the magnet is then more powerful and, despite the harder spring element  324 , is able to lift the second air release block  321  and thus free the second air release channel  327 . A connection is thereby created now between the first air release channel  326  and the vacuum channel  69 , and the underpressure in the pump is reduced. As an alternative or in addition to the springs of different strength, abutment elements can be provided which limit the travel of the first and second springs. 
         [0080]    Therefore, in this embodiment too, the air release body is lifted such that it at first only frees part of the air release opening, with the result that less force is needed at the beginning of the lifting movement than at the end of the movement. 
         [0081]    The suction pump according to the invention therefore affords several advantages. It provides wide-ranging functionality within a very small space and can also be produced inexpensively and is easy to assemble.