Abstract:
A dosing pump includes a dosing chamber ( 14 ), a suction channel ( 32 ) communicating with the dosing chamber ( 14 ) and a pressure channel ( 20 ) communicating with the dosing chamber ( 14 ). Features for popping gas bubbles are arranged in the suction channel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a United States National Phase application of International Application PCT/EP2011/000724 and claims the benefit of priority under 35 U.S.C. §119 of European Patent Application EP 10 001 641.9 filed Feb. 18, 2010, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a metering pump with a dosing chamber, an intake channel connected with the dosing chamber, and a pressure chamber ( 20 ) connected with the dosing chamber. 
       BACKGROUND OF THE INVENTION 
       [0003]    Metering pumps are usually designed as positive-displacement pumps, and as a positive-displacement body have a piston or membrane that is moved by a drive motor. The positive-displacement body displaces the volume inside the dosing chamber by a predetermined amount, so that this volume is conveyed out of the dosing chamber. The dosing chamber normally has two ports, a pressure channel and an intake channel, wherein the pressure channel usually extends perpendicularly upward, and the intake channel proceeds from the dosing chamber, extending perpendicularly downward. 
         [0004]    Problems during the metering process are caused by degassing substances, such as hydrogen peroxide. Gas can in this case form in the dosing chamber not just in the metering process, but also during intervals when the pump is not metering. However, gas bubbles in the dosing chamber result in the volume of liquid prescribed by the dosing chamber not being metered. For this reason, it is desirable to divert gas bubbles entering through the intake channel and present in the dosing chamber away from the dosing chamber as quickly as possible. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of this difficulty, an object of the invention is to optimize a metering pump in such a way as to quickly and reliably divert from the dosing chamber gas bubbles that might be present or enter through the intake channel 
         [0006]    The metering pump according to the invention has a known dosing chamber, which is connected with an intake channel, through which the medium to be conveyed, in particular the liquid to be convened, enters the dosing chamber. The dosing chamber is further connected with a pressure channel, through which the medium conveyed by the metering pump exits the dosing chamber. The conveying or pumping action is achieved in a conventional manner by means of a positive-displacement body, which is arranged on or in the dosing chamber. The positive-displacement body can consist of a membrane or piston, for example. 
         [0007]    According to the invention, the intake channel incorporates a means for breaking up gas bubbles, or the intake channel is designed in such a way that the gas bubbles entering it through the intake channel can be broken down into smaller gas bubbles. When large gas bubbles enter through the intake channel, the danger is that these large gas bubbles will adhere to the walls of the intake channel, and hence remain in the intake channel or dosing chamber. The advantage to breaking the gas bubbles up into smaller gas bubbles is that it reduces the risk of adhesion to the walls of the intake channel, allowing these smaller gas bubbles to rise up through the intake channel and further through the dosing chamber into the pressure channel more quickly. It is preferred that gas bubbles situated downstream from a valve in the intake channel in the dosing chamber rise quickly enough to reach the outlet end of the dosing chamber after 80% of the overall stroke time (period between the intake stroke and ensuing pressure stroke), i.e., the pressure channel and in particular an outlet valve lying in the pressure channel, so that they can then be expelled from the dosing chamber toward the end of the pressure stroke. The means for breaking up the gas bubbles can be arranged as additional elements, for example projections, ribs or the like, in the intake channel, preferably downstream from a valve or inlet valve in the intake channel As an alternative, gas bubbles can be broken up or torn away by making changes to the cross section of the intake channel, thereby causing larger gas bubbles to split up into smaller gas bubbles. 
         [0008]    To this end, it is further preferred that the means for breaking up the gas bubbles in the intake channel are designed like an expanded cross section, wherein this expansion in cross section additionally preferably is sudden, i.e., taking the form of a step or shoulder. The larger, i.e., expanded cross section of the intake channel in this case preferably abuts the dosing chamber. The cross section of this expanded intake channel is preferably greater than the cross section of the intake channels of conventional metering pumps. This means that the cross section selected for the intake channel is intentionally larger than would be required for the normal operation of the metering pump, so as to improve the removal of gas bubbles. As a result of the cross sectional expansion, rising gas bubbles are torn away. Larger gas bubbles will initially adhere to the wall(s) of the intake channel viewed in the direction of flow, before the expanded cross section. This means that the gas bubbles initially stick to the walls in this narrower portion of the intake channel However, the flow during the intake stroke and buoyant force tear parts of the gas bubbles away at the expanded cross section, and the latter then quickly rise in the dosing chamber as smaller gas bubbles, and exit through the latter to the pressure channel. 
         [0009]    It is especially preferred that the cross section of the intake channel expand from a first, smaller cross section to a second, larger cross section, wherein the surface area of the first cross section is between 0.3 and 0.8 times the surface area of the second cross section. It is in this case preferable that the first narrower cross section is selected such that it essentially correspond to the cross section, in particular the smallest cross section, of an intake channel of a conventional metering pump. This means that the expanded section adjoining downstream is expanded relative to the cross sectional size of the intake channel of a known metering pump. 
         [0010]    It is further preferred that the smaller cross section is defined by the outlet of a valve, i.e., the inlet valve in the intake channel This outlet represents the narrowest point in the intake channel In this regard, gas bubbles first get caught in this constriction, and are then torn away at the outlet end of the constriction, i.e., at the expanded cross section, and thereby broken up into smaller gas bubbles. 
         [0011]    It is further preferred that the valve exhibit a valve body held in a cage, in particular a valve ball, and that the smaller cross section is defined by the free spaces lying between the ribs or webs of the cage and the valve body. The cage or ball cage exhibits webs or ribs extending in the direction of flow, between which the valve body runs. At the downstream end, these webs or ribs project radially inward, thereby forming an axial stop there for the valve body. The liquid to be conveyed flows through the free spaces between the webs and ribs. The shared cross section of these free spaces defines the smaller cross section in front of the expanded cross section. Three or four such ribs or webs forming the cage are preferably provided. 
         [0012]    The pressure channel preferably extends in a first section, which borders the dosing chamber, upwardly at an inclination relative to the vertical, away from the dosing chamber. As a result of the inclined configuration of this pressure channel, i.e., outlet channel, which is situated at the vertical upper end of the dosing chamber, there are essentially no horizontally extending upper boundary surfaces in the area of the pressure channel on which gas bubbles might agglomerate. The inclined progression yields upper boundary surfaces extending at an inclination relative to the vertical, along which gas bubbles rise. The inclined upward progression causes the gas bubbles to continue rising upward along these surfaces, and hence automatically enter the pressure channel and rise therein. This ensures that gas bubbles in the dosing chamber that accumulate at the upper end of the dosing chamber due to buoyancy reliably enter the pressure channel, and are conveyed through the latter out of the dosing chamber as quickly as possible. 
         [0013]    It is further preferred that a second section extending in the vertical direction adjoin the first section of the pressure channel downstream. As a result, gas bubbles can also rise unimpeded and cannot agglomerate in this section either. This produces a pressure channel having no horizontally running sections or walls on which gas bubbles might accumulate and adhere. 
         [0014]    It is preferred that a valve is situated in the second section of the pressure channel This valve can be a check valve, which is usually arranged at the outlet side of the dosing chamber in such metering pumps. During the intake stroke of the positive-displacement body in the dosing chamber, this valve prevents a reflux of the medium to be conveyed through the pressure channel into the dosing chamber. This valve is situated in the vertical section of the pressure channel, so that there are preferably essentially no horizontal surfaces either, on which larger gas bubbles might agglomerate. In addition, this arrangement is advantageous, since such valves normally close under the force of gravity. 
         [0015]    It is further preferred that the intake channel emptying into the dosing chamber also is configured in a corresponding way, so that the intake channel in a first section bordering the dosing chamber extends downward at an inclination to the vertical, away from the dosing chamber. As a result, this section of the intake channel incorporates essentially no horizontally running upper surfaces on which gas bubbles might agglomerate. Rather, the inclined progression of the gas bubbles in the intake channel allows them to rise along the inclined upper wall of the intake channel, and enter the dosing chamber. They can there continue to rise and then enter the pressure channel, as described above. 
         [0016]    It is further preferred that a second section extending in a vertical direction adjoins the first section of the intake channel upstream. As a result, this section also has no horizontal surfaces on which gas bubbles might agglomerate. 
         [0017]    However, the inclined first sections of the pressure channel and possibly the intake channel in this case also make it possible, as in the hitherto known channels, extending horizontally away from the dosing chamber, to arrange the ports and possibly the valves of the intake and pressure channels horizontally offset relative to the middle of the dosing chamber or to the side of the dosing chamber. This is most often desirable for constructional reasons, in order to provide enough installation space for the ports and valves, since a positive-displacement body, such as a membrane, along with its drive, is usually arranged directly on the dosing chamber with one side, limiting the space available for incorporating ports and valves. In addition, these ports and valves usually have a diameter greater than the width of the dosing chamber, in particular viewed in the stroke direction of the positive-displacement body. In this regard, it is necessary that these components extend laterally over the boundaries of the dosing chamber. 
         [0018]    It is further preferred that a valve is situated in the second section of the intake channel, i.e., in the vertically extending section of the intake channel This valve can be a check valve of the kind known for conventional metering pumps. This check valve closes during a pressure stroke, thereby preventing the medium to be conveyed from flowing back into the intake channel instead of into the pressure channel Such a valve is usually designed to close under gravitational force, making it especially favorable to be accommodated in a vertical channel section. 
         [0019]    With respect to the arrangement of a valve in the pressure channel and possibly the intake channel, it must be understood that several valves can also be arranged there in series. 
         [0020]    It is further preferred that the first section of the pressure channel and/or the first section of the intake channel is inclined in a direction relative to the vertical that faces away from the positive-displacement body of the metering pump. As a result, the ports for the intake and pressure channel that connect the metering pump with external line systems, and particularly the inlet and outlet valves or check valves, can be laterally offset relative to the dosing chamber. These components can in this case be offset toward a side facing away from the positive-displacement body and its drive, where there is sufficient space available for installing these components, in particular for the valves. 
         [0021]    It is further preferred that the pressure channel and/or intake channel is connected with the dosing chamber in the area of its outer periphery. The dosing chamber preferably has a circular cross section around the horizontal axis, preferably the stroke axis of the positive-displacement body. The intake channel and pressure channel in this case preferably extend away from the outer periphery of the dosing chamber at the lowest and highest point of the dosing chamber, so that no upper horizontal surfaces on which gas bubbles might accumulate form there. As a result of the circular outer periphery of the dosing chamber, the surfaces adjoining the inlet opening of the pressure channel are also curved, ascending to the highest point, so that gas bubbles that accumulate there can continue rising all the way up to the inlet opening of the pressure channel, where they can then continue rising in the adjoining first inclined section and the possibly adjoining second vertical section, and exit the dosing chamber. 
         [0022]    The first inclined section of the pressure channel and possibly the intake channel preferably extend at an angle of between 20 and 70 degrees, more preferably at an angle of between 10 and 60 degrees, and particularly at an angle of between 10 and 60 degrees, relative to the vertical. 
         [0023]    In order to improve the passage for gas bubbles, the first section of the pressure channel and/or the first section of the intake channel preferably have a diameter greater than 4 mm, more preferably greater than 5 mm, and particularly greater than 6 mm, e.g., 6.5 mm. A large channel diameter of this kind ensures that larger gas bubbles can also quickly traverse the channel, and will not become lodged in the channel 
         [0024]    It is further preferred that the pressure channel has a larger diameter or cross section upstream from a valve body situated in the pressure channel than downstream from the valve body. As a result of this configuration, gas bubbles can be routed through the valve in the pressure channel as quickly as possible, thereby keeping the dosing chamber as devoid of gas bubbles as possible. The line cross section can then be reduced to the usual size again downstream from the valve. 
         [0025]    It is further preferred that the vertical distance between the valve in the pressure channel and a valve in the intake channel, i.e., the conventional check valve, is as small as possible. This means that the valves are situated as close as possible to the dosing chamber, in order to minimize the size of the channels bordering the dosing chambers and the total volume and path of the medium to be conveyed between the two valves. Reducing the distance between the valves in the pressure channel and in the intake channel shortens the rise time for gas bubbles from the valve in the intake channel to the valve in the pressure channel, thereby preferably making it possible to achieve a rise time of less than 80% of the overall stroke time of the intake and pressure stroke. 
         [0026]    It is preferred that the vertical distance between a valve in the pressure channel and a valve in the intake channel is equal to or less than 2.5 times, and preferably equal to or less than two times, the maximum diameter of the dosing chamber transverse to the horizontal axis. This configuration yields a similarly small distance between the valves. 
         [0027]    In another preferred embodiment, the vertical distance between a valve in the pressure channel and a valve in the intake channel, i.e., in particular between the check valves bordering the dosing chamber, is equal to or less than the outer diameter of a membrane comprising the positive-displacement body. The membrane usually extends a certain distance beyond the outer diameter of the dosing chamber, since it is sealed and fixated in this area. Because the distance between the valves is equal to or less than the outer diameter of this membrane, this yields an overall very compact construction of the metering head of the metering pump, and in particular keeps the volume lying between the valves as low as possible, accompanied by the positive effects described above. 
         [0028]    The invention will be described below based on the attached figures by way of example. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    In the drawings: 
           [0030]      FIG. 1  is a sectional view of a metering pump unit according to the invention; and 
           [0031]      FIG. 2  is an enlarged sectional view of the pump head of the metering pump unit according to  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Referring to the drawings in particular, the metering pump unit has a known motor housing  2  with a pump head  4  placed thereupon. The motor housing  2  incorporates a drive motor  6 , which drives a connecting rod  10 , so that it moves the middle area of a membrane  12  linearly forward and backward. 
         [0033]    The membrane  12  comprises the positive-displacement body on a dosing chamber  14  in the pump head  4 . The dosing chamber  14  forms a defined volume, which can be decreased and increased by the motion of the membrane  12 , as a result of which the pump conveys a defined volume via the dosing chamber  14  during each stroke of the membrane  12 . 
         [0034]    The pump head  4  is arranged in such a way that its upper end accommodates a pressure port  16 , and its lower end accommodates an intake port  18 . The medium to be conveyed or the liquid to be conveyed is sucked via the intake port  18 . The conveyed or metered liquid is released via the pressure port  18 . The pressure port  16  and intake port  18  are provided to be joined with connection lines. 
         [0035]    The pressure port  16  is connected with the dosing chamber  14  via a pressure channel  20 . The pressure channel  20  here has a first section  22 , and a second section  24  that adjoins it downstream. The first section  22  of the pressure channel  20  extends with its longitudinal axis A inclined relative to the vertical X, upward from the dosing chamber  14 . This first section  22  of the pressure channel  20  here ends at the upper end of the dosing chamber  14 , which is circular in cross section relative to the horizontal axis Y. At the same time, the first section of the pressure channel  22  extends in a curved manner in a direction away from the dosing chamber  14 , which faces away from the positive-displacement chamber in the form of the membrane  12  or the motor housing  2 . In the example shown, the longitudinal axis A of the first section  22  of the pressure channel  20  extends at an angle of 45 degrees relative to the vertical X and the horizontal Y. However, it is to be understood that another angle can be selected, preferably an angle of between 15 and 70 degrees. The advantage to the inclined arrangement of the first section of the pressure channel  22  on the one hand is that the vertical second section  24  of the pressure channel  20  can be offset laterally, i.e., toward he horizontal axis Y, from the dosing chamber  14  in the direction facing away from the membrane  12 . This provides enough space to accommodate the pressure port  16  and the two valves  26  and  28  lying in the pressure channel in the pump head  4 , without having to place them in proximity to the motor housing  2 . At the same time, the advantage to the inclined progression of the first section  22  of the pressure channel toward to a horizontal progression lies in the fact that any existing gas bubbles in the dosing chamber  14  can rise in the inclined first section of the pressure channel  22 . As a result, there are no larger horizontal surfaces on the upper side of the dosing chamber on which gas bubbles can accumulate. Because of its circular configuration, the remaining peripheral wall of the dosing chamber  14  is shaped in such a way that it allows gas bubbles to rise unimpeded up toward the inlet or branch of the pressure channel  20 . 
         [0036]    In addition, the cross section of the first section  22  of the pressure channel  20  is provided with large enough dimensions, i.e., the cross section in this example has a diameter greater than 5 mm, allowing even larger gas bubbles to pass unobstructed. The first section  22  is adjoined downstream by a vertical section  24  that accommodates the two check valves  26 ,  28 , which are connected in series. The perpendicular progression of the second section  24  also allows gas bubbles in the latter to rise unimpeded. In addition, the valves  26  and  28  can also be closed by gravitational force. 
         [0037]    The pressure channel  20  branches away from the dosing chamber  14  at its highest point. The intake channel  32  empties into the dosing chamber  14  vertically opposite, i.e., at the lower end. The intake channel  32  has a first section  34  adjoined downstream by a second section  36 . Just as the first section of the pressure channel  20 , the first section  34  of the intake channel  32  extends with its longitudinal axis B horizontally downward at an inclination to the vertical X and horizontal Y. In the example shown here, the angle of the longitudinal axis B relative to the horizontal Y and vertical X also measures 45 degrees, but a different angle could also be selected, preferably in the 15 to 70 degree range. The important factor is that the first section  34  of the intake channel  32  does not extend horizontally, as the first section  22  of the pressure channel  20  is also not to extend horizontally according to the invention. As a result of the inclined progression of the first section  34  of the intake channel  32 , gas bubbles in the intake channel  32  can rise upward unimpeded in this section. They will glide along the upper wall of the section  34  and enter the dosing chamber  14 , where they will then rise to the first section  22  of the pressure channel  20  and be conveyed away through the latter to the pressure port  16 . Therefore, the intake channel  32  also essentially has no horizontally progressing upper boundary surfaces on which gas bubbles might agglomerate. As a result of the inclined progression of the first section  34  of the intake channel  32  in a direction facing away from the membrane  12  and the motor housing  2 , the intake port  18  with the valves  30  and  38  in the intake channel  32  can be formed in a horizontal direction, laterally offset from the dosing chamber  14  in the pump head  4 , so that these components do not collide with the membrane arrangement. 
         [0038]    A second section  36  extending in the vertical direction X, in which two valves  30  and  38  are arranged in series, adjoins the first section  34  of the intake channel  32  upstream. The valves  30  and  38  also represent two known check valves that close under gravitational force. 
         [0039]    In addition, the intake channel  32  incorporates a means for breaking up gas bubbles in the entering liquid stream. In this case, the means for breaking up gas bubbles is realized in the form of an expanded cross section. The valve  30  is formed by a valve ball, which is held in a ball cage  31 . The ball cage is comprised of ribs or webs extending parallel to the vertical X, wherein the free spaces  33  between these webs define the flow paths through the valve. The free spaces  33  in the periphery of the ball and between the webs of the ball cage  31  together define a first smaller cross section, which is smaller than the cross section in the intake channel  32  adjoining downstream. In other words, the outlet end of the free spaces  33  has an expanded cross section. The expanded cross section is designed in such a way that the overall cross sectional surface of the free spaces  33  preferably lies between 0.3 and 0.8 times the cross sectional surface of the intake channel  32  adjoining downstream. As a result of this configuration, gas bubbles that enter through the intake port  18  adhere to the walls in the free spaces  33  and then are torn off as individual, smaller bubbles at the expanded cross section toward the intake channel  32  adjoining downstream, so that larger gas bubbles are here broken up into smaller gas bubbles, and the smaller gas bubbles can then quickly rise through the intake channel  32 , dosing chamber  14  and pressure chamber  20 . 
         [0040]    In addition, the lateral offset of the vertical sections  24  and  36  of the pressure channel  20  or intake channel  32  makes it possible to arrange the first valve  26  on the pressure side, and the first valve  30  on the intake side, in close proximity to each other in a vertical direction X, in order to minimize the overall volume and distance between these two valves  26  and  30 , in particular the distance between these valves outside the dosing chamber  14 , i.e., essentially the length of the pressure channel  20  upstream from the valve  26  and the length of the intake channel  32  downstream from the valve  30 . Another advantage to the above is that the volume of the medium to be conveyed or the liquid to be conveyed is as low as possible given a shutdown of the pump, so that only a smaller quantity of gas can be released in the event of a degassing medium, keeping the quantity and size of the gas bubbles accumulating in this area as small as possible. The distance a between the outlet side of the valve  30  and the inlet side of the valve  26  is equal to the outer diameter of the membrane  12  in the example shown. Such an arrangement, in which the distance a is essentially equal to or less than the outer diameter of the membrane  12 , exhibits this kind of expedient small vertical distance between the valves  62  and  30 . In addition, this distance a has a magnitude equal to or less than 2.5 times, more preferably less than two times, the maximum diameter d of the dosing chamber  14 . 
         [0041]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.