Abstract:
A liquid metering system is disclosed for pumping two components of an adhesive into a mixer. The liquid metering system uses gear pumps of certain dimensions to pump each component into a manifold which delivers the components to a mixer where the components become an adhesive. A fixed mass flow ratio related to the size of the gear pumps is automatically established because the gear pumps are driven by the same motor at a fixed speed ratio. The self-metering system eliminates the complexity of known adhesive pumping systems.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to pending U.S. Provisional Patent Application No. 60/976,888, filed Oct. 2, 2007 (pending), which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to liquid dispensing systems, and more particularly to a dual-component metering pump assembly driven by a single motor. 
       BACKGROUND 
       [0003]    Various types of pumps, such as piston pumps and gear pumps, have been used in liquid dispensing systems to facilitate the dispensing of liquid material. While the configurations of the pumps themselves is known, there is room for improvement in assembly designs using these pumps in various applications. 
         [0004]    In various fields such as the window glazing adhesive market, two or more components must be mixed together in a static mixer or similar device before application to a window. These two components must not interact before delivery to the static mixer, so separate pumps driven by separate motors have generally been used to deliver the two components to the mixer. These separate pumps may be piston pumps, reciprocating pumps, gear pumps, or any other kind of pump. Piston pumps have been very popular in these industries because a piston pump is easily and cheaply acquired in various sizes. The two components mixed in the dispensing system usually have a mix ratio that the pumps have to accurately meet. For example, adhesives used in the window glazing market are two component materials that need to be mixed in ratios of about 1:1 to 10:1, depending on the particular type of adhesive selected. While a mix ratio in the range of about 8:1 to 13:1 can provide acceptable results for the 10:1 adhesive, the more accurate the mix ratio the better the results. 
         [0005]    Using two motors to drive two separate component pumps requires some an additional metering mechanism to ensure the two components are being delivered at an acceptable ratio. With two motors, two pumps, and a metering mechanism all being used for this one function, an operator will have multiple controls to monitor, including the speed controls of the two motors. The increased complexity of these systems creates more demands on the operator. The potential for error increases because of this increased complexity. More equipment also increases the likelihood of failure of one particular component, thereby bringing the whole system down for repair. Consequently, there is a need for a dispensing system for accurately and efficiently mixing two-component adhesive materials which addresses these and other issues of prior systems. 
       SUMMARY 
       [0006]    In one illustrative embodiment, a liquid metering system in accordance with the present disclosure includes a first pump, a second pump, a manifold, and a motor. When pumping two-part adhesive, the first pump comprises a first inlet for receiving a first component of the two-part adhesive and a first outlet for delivering the first component to the manifold. The second pump similarly comprises a second inlet for receiving a second component of the two-part adhesive and a second outlet for delivering the second component to the manifold. The manifold communicates with the first and second outlet and includes two manifold outlets for dispensing each of the components into a mixing device such as a static mixer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention. 
           [0008]      FIG. 1A  is a side view of a first embodiment of a “double pump” assembly in accordance with the present disclosure. 
           [0009]      FIG. 1B  is a front view of the embodiment shown in  FIG. 1A . 
           [0010]      FIG. 1C  is a cross-sectional view of the “double pump” used in the embodiment shown in  FIG. 1A . 
           [0011]      FIG. 1D  is a front view of the embodiment shown in  FIG. 1A  with component supply lines shown. 
           [0012]      FIG. 1E  is a cross-sectional view of the “double pump” of  FIG. 1C , taken along line  1 E- 1 E. 
           [0013]      FIG. 1F  is a cross-sectional view of the “double pump” of  FIG. 1C , taken along line  1 F- 1 F. 
           [0014]      FIG. 2A  is a front view of a second embodiment of a pump assembly in accordance with the present disclosure. 
           [0015]      FIG. 2B  is a detail front view of the embodiment of  FIG. 2A , illustrating component flow into the pumps using hidden lines. 
           [0016]      FIG. 2C  is a detail front view of the embodiment of  FIG. 2A , illustrating component flow out of the pumps using hidden lines. 
           [0017]      FIG. 2D  is a view taken along line  2 D- 2 D of  FIG. 2C . 
           [0018]      FIG. 3  is a top view of a third embodiment of a pump assembly in accordance with the present disclosure, showing a belt or chain driving two separate gear pump driveshafts. 
           [0019]      FIG. 4  is a side view of a fourth embodiment of a pump assembly, similar to  FIG. 1A . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIGS. 1A-1F  depict an exemplary embodiment of a liquid metering system  10 , configured to meter and mix components of a two-part adhesive. The metering system  10  includes a first pump  12  and a second pump  14  contained within a double pump assembly  16 , a single motor  18  (such as a servo motor), and a manifold  20 . The manifold  20  communicates with an outlet  22  of the first pump  12  and an outlet  24  of the second pump  14  ( FIG. 1D ). The first pump  12  has an inlet  26 , and the second pump  14  has an inlet  28  ( FIG. 1B ). Inlets  26 ,  28  receive the components to be pumped from a source (not shown). The manifold  20  also includes a first manifold outlet  31  and a first passage  27  configured to carry the first component from the outlet  22  of the first pump  12  to the first manifold outlet  31  ( FIG. 1D ). Similarly, the manifold  20  includes a second manifold outlet  32  and a second passage  29  configured to carry the second component from the outlet  24  of the second pump  14  to the second manifold outlet  32 . Each manifold outlet  31 ,  32  communicates with a static mixer  30 , which may be part of a two-component gun  33 , such as a two-part dispensing gun, available from Nordson Corporation of Westlake, Ohio. The static mixer  30  combines the two components and dispenses the mixed adhesive through a nozzle tip  34 . The two-component gun  33  may include fittings  35   a,    35   b  for coupling the gun  33  to a pressurized air source for operating on/off valves within the gun  33 . 
         [0021]    The double pump assembly  16  used in this embodiment is shown in greater detail in  FIGS. 1C ,  1 E, and  1 F. In this embodiment, the first pump  12  and the second pump  14  are gear pumps. The first gear pump  12  includes a first gear train  40  which comprises a drive gear  42  and an idler gear  44 , mounted on a driveshaft  46  and an idler shaft  48 , respectively. The first gear pump  12  has a case thickness h 1  as shown in  FIG. 1C . The second gear pump  14  includes a second gear train  50  which comprises a drive gear  52  and an idler gear  54 , mounted on the same driveshaft  46  and idler shaft  48 , respectively, as the first gear train  40 . The second gear pump  14  has a case thickness h 2  as shown in  FIG. 1C . A plurality of plates  56  covers and seals the two gear pumps  12 ,  14  with respect to the outside environment and each other. 
         [0022]    Referring to  FIGS. 1A and 1F , when the motor  18  drives the driveshaft  46 , the first gear train  40  pumps a volume of the first component from the inlet  26  to the outlet  22  of the first gear pump  12 , while the second gear train  50  pumps a volume of the second component from the inlet  28  to the outlet  24  of the second gear pump  14 . The first component is then carried through the first passage  27  of the manifold  20  to a first manifold outlet  31  communicating with the static mixer  30 . Similarly, the second component is then carried through the second passage  29  of the manifold  20  to a second manifold outlet  32  communicating with the static mixer  30 . The static mixer  30  finally combines the two components to create the two-part adhesive. 
         [0023]    The relative sizes of the two gear trains  40 ,  50  determines a fixed speed ratio of the single motor double pump assembly  16 . When the drive gears  42 ,  52  and the idler gears  44 ,  54  have the same diameters as shown in  FIG. 1C , the ratio of case thickness h 2 /h 1  determines the volumetric flow ratio of the two components delivered by the double pump assembly  16 . Accordingly, the gear trains  40 ,  50  can be designed to deliver any desired volumetric ratio of the two components. 
         [0024]    The double pump assembly  16  of this embodiment also includes a case  36 , as shown in  FIGS. 1A-1D , holding the first gear pump  12  and the second gear pump  14  adjacent to each other. The case comprises the manifold  20  as a bottom portion, a top plate  37 , and a plurality of rods  39  coupled to the top plate  37  and the manifold  20 . The embodiment of  FIGS. 1A-1D  has the first gear pump  12  and the second gear pump  14  supported on the manifold  20 , or bottom portion of the case  36 , and the driveshaft  46  extending through the top plate  37  into the motor  18  located above the top plate  37 . One skilled in the art will recognize that the case  36  may alternatively comprise various other structure suitable for supporting metering system  10 . 
         [0025]      FIGS. 2A-2D  depict another embodiment of a liquid metering system  60  configured to meter and mix the components of a two-part adhesive. This embodiment differs from the embodiment of  FIG. 1A  in that the two pumps  62 ,  64  of this embodiment are not located adjacent to each other, but are spaced apart and positioned on opposite sides of the manifold  68 . Mechanically, the embodiments work in the same manner, but separating the pump bodies allows for easier replacement and modification of the two pumps  62 ,  64  when desired. The metering system  60  includes a first pump  62 , a second pump  64 , a single motor  66  (such as a servo motor), and a manifold  68 . The manifold  68  communicates with an outlet  70  of the first pump  62  and an outlet  72  of the second pump  64 . The first pump  62  has an inlet  74 , and the second gear pump  64  has an inlet  76 . The inlets  74 ,  76  receive the components from respective sources (not shown). The manifold  68  also includes a first manifold outlet  77  and a first passage  81  configured to carry the first component from the outlet  70  of the first pump  62  to the first manifold outlet  77 . Similarly the manifold  68  also includes a second manifold outlet  79  and a second passage  83  designed to carry the second component from the outlet  72  of the second pump  64  to the second manifold outlet  79 . Each manifold outlet  77 ,  79  communicates with a static mixer  78 , which may be part of a two-component gun  80 . The static mixer  78  combines the two components and dispenses the mixed adhesive at a nozzle tip  82 . 
         [0026]    In the embodiment shown in  FIGS. 2A-2D , the first and second pumps  62 ,  64  are again depicted as gear pumps, although it will be appreciated that various other types of pumps may alternatively be used. The first gear pump  62  includes a gear train  63  that comprises a drive gear  84  and an idler gear  86 , respectively mounted on a driveshaft  88  and an idler shaft  92 . The second gear pump  64  includes a gear train  65  comprising a drive gear  85  and an idler gear  67 , respectively mounted on the common driveshaft  88  and an idler shaft  93 . The two gear pumps  62 ,  64  are internally coupled in such a way to fix the speed ratio between the pumps  62 ,  64 , and this can be accomplished by driving both pumps  62 ,  64  with the common driveshaft  88 . 
         [0027]    The liquid metering system  60  further includes an outer case  90  similar to case  36  of  FIGS. 1A-1D . One skilled in the art will appreciate that the outer case  90  may alternatively comprise any casing suitable for supporting the pumps  62 ,  64  and other components of the liquid metering system  60 . As described above with respect to the embodiment of  FIGS. 1A-1F , the pumps  62 ,  64  operate at a fixed speed ratio in order to pump the components of a two-part adhesive at a desired volumetric flow ratio related to the size of the pumps  62 ,  64 . 
         [0028]    Another exemplary embodiment of a liquid metering system  150  is shown in  FIG. 3 . This embodiment contains all the major structural components of the previously-described embodiments: two gear pumps  100 ,  102 , one motor  104 , a manifold  106 , and a static mixer within a two-component gun  108 . Instead of driving both gear pumps  100 ,  102  via a common driveshaft, as in other disclosed embodiments, liquid metering system  150  includes separate driveshafts  110 ,  112  for respective gear pumps  100 ,  102 . Motor  104  drives the driveshafts  110 ,  112  with a belt or chain  114  as shown in  FIG. 3 . All other components have the same features and advantages as disclosed in previous embodiments. 
         [0029]    Liquid metering systems  10 ,  60 ,  150  as shown and described above may be used to mix two-component adhesives, while maintaining a fixed ratio of the two components. In an exemplary application, a liquid metering system  10 ,  60 ,  150  as described above may be used to mix adhesive used in window glazing applications. The two components in window glazing adhesive are a base component and a catalyst component. The metering system can then mix the base and catalyst components in any mass ratio desired, typically between a range of about 1:1 to about 10:1 in the window glazing field. Unlike known metering systems with two motors driving respective pumps, no adjustments are necessary due to motor fatigue or replacement because the mass metering of the base and catalyst components occurs automatically in this metering system. A liquid dispensing system in accordance with the present disclosure is therefore well-suited to the exemplary application, as well as various other applications where precise metering of two components is desired. 
         [0030]    While the embodiments discussed herein have been described with respect to maintaining a desired volumetric flow ratio, it will be appreciated that a mass flow ratio of the dispensed components may also be obtained, provided the temperature of the components can be controlled. To this end, a pump assembly in accordance with the present disclosure may include heating and/or cooling devices to maintain the components of the two-part adhesive within predetermined temperature ranges. Such devices may include heaters and/or chillers operatively coupled to one or more of manifold  20 , the first and second pumps  12 ,  14 ,  62 ,  64 ,  100 ,  102 , and the gun  33 . For example,  FIG. 4  depicts an exemplary liquid dispensing system  10   a,  similar to liquid dispensing system  10  discussed above, wherein heating elements  120   a,    120   b,    120   c,    120   d  are operatively associated with the manifold  20 , first pump  12 , second pump  14 , and gun  33 , respectively. Alternatively, the liquid metering system  10   a  may be fitted with a jacketing system for circulating heating and/or cooling fluid to one or more parts of the system  10   a  to maintain the temperature of the adhesive components. Various other structure and methods may alternatively be used to control the temperature of the adhesive components within desired ranges. 
         [0031]    The liquid metering system  10   a  may further include sensors  122   a,    122   b  for sensing temperatures associated with the adhesive components, and communicating with a controller  124  operable to adjust the temperature of the adhesive components to maintain the desired temperature. With the temperature being controlled, a desired mass flow ratio can be obtained by considering the specific gravities of the adhesive components. For example, a roughly 1:1 mass flow ratio could be achieved by setting the ratio of case thickness h 2 /h 1  equal to the ratio of specific gravity of the first component to the specific gravity of the second component. 
         [0032]    While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants&#39; general inventive concept. The scope of the invention itself should only be defined by the appended claims.