Abstract:
A pump includes a housing with a pumping chamber, first and second check valves, and an inlet and an outlet in fluid communication with the pumping chamber through the check valves. The housing also includes a linear actuator with a pumping element located in the pumping chamber wherein actuation of the linear actuator induces the pumping element to move in the pumping chamber between the first and second check valves between a first position wherein the pump element moves toward the first check valve and generates a positive pressure in the pumping chamber with the positive pressure maintaining said first check valve closed and opening the second check valve to allow the fluid in the pumping chamber to flow to the outlet, and a second position wherein the pumping element moves away from the first check valve and reduces the pressure in the pumping chamber to allow the first check valve to open and draw in fluid from the inlet into the pumping chamber to thereby pump fluid from the pump.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. patent application Ser. No. 60/855,528, filed Oct. 31, 2006, entitled PUMP WITH LINEAR ACTUATOR, which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a pump and, more particularly, to a miniature pump that is particularly suitable for battery or fuel cell applications and medical applications and other applications where the volume of the fluid being delivered is relatively small. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention provides a miniature pump that can be used in a wide variety of applications, including medical applications, battery or fuel cell applications, such as a fuel cell for a computer. 
         [0004]    In one form of the invention, a pump includes a housing with a pumping chamber, first and second check valves, and an inlet and an outlet in selective fluid communication with each other through the pumping chamber. The second check valve includes a lip seal. In addition, the housing includes a linear actuator that includes a pumping element that is positioned in the pumping chamber and which is moved between the two checks valves between two positions—one position in which the pumping element applies pressure in the pumping chamber, which opens the second check valve to allow the fluid in the pumping chamber to be pumped through the outlet and further apply pressure against the first check valve, which is located at the inlet side of the pumping chamber, to thereby close off fluid communication between the inlet and the pumping chamber, and a second position where the pumping element is moved away from the first check valve to create a vacuum in the pumping chamber and to allow the first check valve to open and therefore allow fluid to enter the pumping chamber from the inlet. 
         [0005]    In one aspect, the linear actuator comprises an electrically operated solenoid. For example, the solenoid includes a stem and an armature mounted to the stem and an electromagnetic field generator, such as a coil, which extends around the armature. The pumping element is mounted or otherwise formed on the stem. When the electromagnetic field generator is energized and generates an electromagnetic field, the electromagnetic field urges the armature to move axially through the electromagnetic field generator and move the stem such that the pumping element is moved toward the first check valve and to increase pressure in the pumping chamber to close the first check valve. 
         [0006]    In yet another aspect, each check valve is formed from a lip seal. For example, the lip seals may be formed from an elastomeric seal member with a pair of lips or may be formed from two elastomeric bodies, each with a lip seal. The first lip seal forms an inner annular lip, which forms the first check valve, which opens and closes communication between the inlet and the pumping chamber. The second lip seal forms the check valve between the pumping chamber and the outlet. 
         [0007]    In another aspect, the solenoid includes a biasing member, such as a spring, which is mounted about the stem, to apply a biasing force to urge the pumping element to its second position away and spaced from the first check valve. As noted above, when the pumping element is moved away from the first check valve, the vacuum is generated in the pumping chamber which is then followed by the opening of the first check valve, which allows the fluid from the inlet to flow into the pumping chamber. When the electromagnetic field generator is powered and generates an electromagnetic field, a force is generated which is sufficient to overcome the biasing force and to urge the pumping element to move toward the first check valve, which increases the pressure in the pumping chamber to close the first check valve but open the second check to allow the fluid to flow to the outlet from the pumping chamber. When the electromagnetic field generator is de-energized, the biasing member then returns the pumping element to its second position which starts another pump cycle. 
         [0008]    It can be appreciated from the foregoing that a pump is provided that can be configured as a miniature pump that has a wide variety of applications where relatively low flows are desired. 
         [0009]    These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings. 
     
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a solenoid pump of the present invention; 
           [0011]      FIG. 2  is a top plan view of the pump of  FIG. 1 ; 
           [0012]      FIG. 3  is a cross-section taken along line III-III of  FIG. 2 ; 
           [0013]      FIG. 4  is an exploded perspective view of the valve assembly of  FIG. 1 ; 
           [0014]      FIG. 5  is an enlarged partial cross-section of the pump housing; 
           [0015]      FIG. 6  is an enlarged partial cross-section of the solenoid housing; 
           [0016]      FIG. 7  is an enlarged view similar to  FIG. 5  illustrating another embodiment of the pumping element shown in its first position applying pressure to the first check valve; 
           [0017]      FIG. 8  is a view similar to  FIG. 7  illustrating the pumping element in its second position moved away from the first check valve; 
           [0018]      FIG. 9  is a similar view to  FIG. 5  illustrating another embodiment of the stem with the first check valve sealing against the stem; and 
           [0019]      FIG. 10  is an exploded perspective view of the pump of  FIG. 9 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to  FIG. 1 , the numeral  10  generally designates a pump of the present invention. Pump  10  comprises a miniature pump that incorporates one or more lip seal check valves, which is particularly suitable for battery operation, including fuel cells, and medical applications. 
         [0021]    As best seen in  FIGS. 3 and 4 , pump  10  includes a housing  12 , which in the illustrated embodiment is formed from an actuator housing  14  and a pump housing  16 . Further, in the illustrated embodiment housings  14  and  16  are separate housings that are mounted together using conventional means, such as fasteners  16   a  and  16   b  ( FIG. 4 ), or the like. Alternately, housings  14  and  16  may be formed as a unitary housing, and like the separate housings, may be formed from metal or a plastic material. Housing  12  includes a pumping chamber  18  and an inlet  12   a  and outlet  12   b , which are in selective fluid communication with each other through pumping chamber  18 . Pumping chamber  18  includes first and second check valves  20  and  22 , which will be more fully described below. 
         [0022]    Positioned in housing  14  is a linear actuator  24 . In the illustrated embodiment, linear actuator  24  comprises a solenoid. However, it should be understood that other types of linear actuators may be used including a linear motor, a voice coil, or even a manual actuator. However, for ease of reference, the linear actuator will be described in reference to a solenoid application. 
         [0023]    As best seen in  FIGS. 3 and 4 , solenoid  24  includes a stem  26  with a pumping element  28 , which is located in pumping chamber  18 . Solenoid  24  also includes an armature  30 , an electromagnetic field generator  32 , and a center post  33 . Armature  30  and center post  33  are formed from a magnetic material, such as low carbon steel. Center post  33 , which extends into one end of housing  14  on one end and extends into housing  16  at its opposed end, provides a bridge or connector between the two housings and further provides a guide for stem  26  and for the biasing member noted below. In addition, the center post  33  provides a stop  35   a  ( FIGS. 3 and 5 ) for the armature, as will be more fully described below. A stop  35   b  for the pumping element is provided by housing  16  ( FIGS. 3 and 5 ). 
         [0024]    Armature  30  is mounted to the end of stem  26  by a threaded connection, with center post  33  spaced from armature  30  by an air gap when the coil is de-energized. In order to increase the air gap when the coil is energized/actuated, the end of armature  30  includes a recessed portion  30   b , which includes a removable plastic or other non-magnetic washer. The washer provides a stop or seat in the activated position. As would be understood, if the washer is removed the air gap is decreased. 
         [0025]    In the illustrated embodiment, electromagnetic field generator  32  comprises a coil  32   a , which is mounted about the armature  30  on a spool  34 . Solenoid  24  operates in a conventional manner in that when a current is applied to coil  32   a , coil  32   a  generates an electromagnetic field or a magnetic flux, which urges armature  30 , and hence stem  26 , to move axially through coil  32   a  and through passage  33   a  to close the air gap between the armature and the center post  33 . Further, when stem  26  moves, pumping element  28 , which in the illustrated embodiment is formed by an enlarged end of stem  26 , moves through pumping chamber  18  to pump fluid from inlet  12   a  through pumping chamber  18  to outlet  12   b , more fully described below. 
         [0026]    Spool  34  preferably comprises a non-magnetic bobbin, such as a glass filled plastic bobbin, and includes a sleeve portion  34   a  and upper and lower flanges  34   b  and  34   c . Extending around sleeve portion  34   a  and captured between flanges  34   b  and  34   c  is a wire, which forms coil  32   a . Spool  34  is supported in housing  12  by a frame  36 , which is preferably a magnetic frame, such as a low carbon steel frame, and includes a pair of outwardly projecting conductive leads  36   a  and  36   b  ( FIGS. 1 ,  2 , and  3 ) which project through housing  12  ( FIG. 2 ) for coupling to an external power supply. Coil  32   a  is coupled to conductive leads  36   a  and  36   b  and when energized controls the movement of stem  26  through housing  12  to control the movement of the pump element between the first and second check valves. 
         [0027]    As noted, armature  30  comprises a magnetic material, such as nickel plated steel, and is piloted to frame  36  on one end by non-magnetic bushing  30   a  and mounted to stem  26  for limited axial movement in the passage formed in housing  12 . Stem  26  extends through a central passage  33   a  of center post  33  to extend into pumping chamber  18  of pump housing  16  so that pump element  28  moves between a first position in which pump element  28  increases the pressure in pumping chamber  18 , which applies pressure against check valve  20  to close fluid communication between inlet  12   a  and the pumping chamber, and a second position in which pump element  28  is moved away from first check valve  20  against housing  16  at stop  35   b . When pumping element  28  is moved away from check valve  20 , a vacuum pressure is generated in pumping chamber  18 , which opens check valve  20  to allow fluid to flow into pumping chamber  18  from inlet  12   a . When pump element  28  is then pushed back into pumping chamber  18 , the pressure in the pumping chamber increases further and check valve  22  then opens to allow fluid to flow from pumping chamber  18  to outlet  12   b.    
         [0028]    In operation, therefore, when coil  32   a  is energized and current flows through coil  32   a , coil  32   a  generates an electromagnetic field around armature  30  which urges armature  30  to the right as viewed in  FIG. 3 . The magnetic field between the armature and the center post will then urge pump element  28  toward the right and stop when armature  30  contacts stop  35   a . As pump element  28  moves forward toward valve  20 , the pressure in the pumping chamber  18  increases and is applied against valve  20  to thereby close valve  20 , as noted above. The strength of the magnetic flux or the magnetic field depends on the wire size, the amount of current flowing, and the number of turns of the wire. As the number of turns or loops and current increases, so too does the magnetic flux. 
         [0029]    When coil  32   a  is de-energized, however, stem  26  and armature  30  are returned by a biasing member  40 , such as a spring, so that pump element  28  moves away from valve  20  until it contacts stop  35   b  which then generates the vacuum in the chamber to open fluid communication between the inlet and pumping chamber  18 . In addition to providing a guide for stem  26 , center post  33  also provides the bearing surface for spring  40 , which extends into the open end of center post  33 , and which is compressed when stem  26  is moved by the electromagnetic field to the right (as viewed in  FIG. 3 ). 
         [0030]    Referring again to  FIGS. 3 and 4 , pump element  28  includes a cylindrical body  42  and a flange  44 , which together form the pumping element. As best seen in  FIG. 3 , check valve  20  is formed from a first sealing member  52   a , and check valve  22  is formed from a second sealing member  52   b . Sealing member  52   a ,  52   b  comprises lip seals formed from an elastomeric material. In the illustrated embodiment, lip seals  52   a ,  52   b  are formed on a unitary seal member  50 . However, it should be understood that lip seals  52   a ,  52   b  may be formed as separate components that are in a juxtaposed position to provide the same or similar annular arrangement. Further, check valve  20  may be formed from another type of check valve, including a ball and seat check valve or a duck bill. 
         [0031]    In the illustrated embodiment, seal member  50  includes an annular portion  52  with a pair of inwardly projecting flanges that form lip seals  52   a  and  52   b , with lip seal  52   a  forming check valve  20  and lip seal  52   b  forming check valve  22 . Seal member  50  is mounted in housing  16  on a cover  54 , which includes inlet  12   a  and to which the inlet fixture is mounted. Further, cover  54  includes an inwardly projecting, stationary shaft or pin  54   a  about which seal member  50  is mounted, with lip seal  52   a  sealing against shaft  54   a . Though lip seal  52   a  is shown sealing on a stationary shaft, it could also be mounted on a part of the stem as will be more fully described below in reference to  FIG. 9 . 
         [0032]    Referring again to  FIG. 5 , lips  52   a  and  52   b  define therebetween the pumping chamber  18 , which is in fluid communication with inlet  12   a  through a passage  54   b  and which is shut off from fluid communication with outlet  12   b  when the pumping element ( 28 ) is moved to its first position toward lip seal  52   a  where it increases the pressure in chamber  18 . 
         [0033]    To seal stem  26  in pump housing  16  an optional second sealing member  56  is provided on stem  26  adjacent stop  35   b . Sealing member  56  is located in the passage  16   a  of pump housing  16  and provides a seal about stem  26  as well as a seal between center post  33  and housing  16 . 
         [0034]    Referring again to  FIG. 3 , sealing member  56  similarly comprises an annular seal member with a first cylindrical portion  62   a , which is mounted about stem  26  adjacent an enlarged portion  26   a  of stem  26 , which forms a stop for the sealing member. Sealing member  56  further includes a second cylindrical portion  62   b , which provides a seal between center post  58  and pump housing  16 . Cylindrical portions  62   a  and  62   b  are interconnected by a diaphragm  62   c  to thereby form a boot to accommodate the axial movement of stem  26  in housing  12 . 
         [0035]    Referring to  FIGS. 7 and 8 , the numeral  128  designates another embodiment of the pumping element of the present invention. Pumping element  128  is of similar construction to pumping element  28  but includes an annular projection  128   a  at the side facing sealing member  150 . Projection  128   a  projects into the pumping chamber  118  to reduce the volume of the pumping chamber, which facilitates self-priming of the pump. This results in an increased compression ratio and, subsequently, creates suction at the inlet. For further details of pump housing  116  and stem  126  and the linear actuator, reference is made to the first embodiment. 
         [0036]    As noted above, the sealing member may be mounted on the stem of the actuator. Referring to  FIG. 9 , pump  210  includes a pumping element  228  with an extended shaft  228   a  which extends through lip seal  252   a . Pumping element  228  operates in a similar manner as pumping elements  28  and  128  described in reference to the previous embodiments; therefore, for further details of the solenoid and the operation of pumping element  228 , reference is made to the previous embodiments. 
         [0037]    As noted above, the housing for the pump may be formed from separate housing components, such as the solenoid housing and the pump housing described above, or may be formed from a unitary housing. In addition, the housing may be configured as a cartridge so that it may be simply plugged into a manifold. For example, the housing may include external annular seals as is commonly used in valve cartridges. 
         [0038]    Accordingly, the pump of the present invention can be assembled as a miniature pump to consume less space than a conventional pump and further to consume less energy. 
         [0039]    While several forms of the invention has been shown and described, modifications will be apparent to those skilled in the art. For example, a portion of the housing may be formed from a magnetic material to form the frame and center post. In this case the unitary frame and center post may include a slot to accommodate the wire termination for the coil. Further as noted, housings  14  and  16  may be formed as a unitary housing. Additionally, the pumping element and the lip seals may be varied to adjust the compression ratio of the pump. The embodiments described herein are only exemplary and not intended to limit the scope of the invention, which is, instead, defined by the claims that follow.