Abstract:
A magnetic reciprocating pump includes a tube having ends defining intake and discharge ports, first and second magnetic plungers axially aligned within the tube of corresponding cross section for reciprocation therewithin, and a plurality of longitudinally spaced coils circumscribing the tube for driving the plungers axially when electrically energized. A gap is defined between the plungers so that the first plunger is slidable between one tube end and the second plunger and the second plunger is slidable between the other tube end and the first plunger. The first plunger closes one port when moved thereagainst and has a peripheral flow path permitting flow when moved away. The second plunger closes the other port when moved thereagainst and has an outer peripheral flow path and a communicating inner axial flow path permitting flow when moved away. The plungers when moved together close the second plunger axial flow path.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a pump and, more particularly, to a reciprocating electromagnetic type pump. 
     2. Background Art 
     Typically, electrically driven reciprocating pumps include an electric motor, a motion translation means, and a pumping element of some kind. To make the motor work, a magnetic field is generated by the motor coils and this magnetic field creates tangential forces to turn the motor&#39;s rotor. 
     There have been many attempts in the past to eliminate the electric motor by applying magnetic forces to drive a pump plunger directly. Examples of these designs are shown in Hirabayashi et al. U.S. Pat. No. 5,472,323 issued Dec. 5, 1995 and Olson U.S. Pat. No. 7,288,085 issued Oct. 30, 2007. By employing such designs, many mechanical components can be eliminated from the pump system, including bearings, sliding seals, and rotors. 
     While having direct plunger drive capability, these past pump designs did not take full advantage of the direct magnetic drive. They were still complex mechanisms, they still required check valves to prevent backflow, and they were difficult to disassemble if they required cleaning or maintenance. Check valves are an especially troublesome component, since they have a tendency to leak or sometimes stick after a long idle period. In addition, check valves are usually not reversible, allowing fluid to flow in only one direction. In addition, the material from which check valves are constructed, namely, springs, balls, and the like, are incompatible with many fluids that are being moved through the pump. 
     While many of the prior art devices may be sufficient for their intended function, other constructions may provide features that may be more desirable to a user. It might be more advantageous to provide a pump that does not employ check valves or wearable seals, that is reversible, that is simple and easy to disassemble, that is made with materials compatible with the fluids being pumped, and that is scalable for use in small and large volume applications. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to overcoming one or more of the problems as set forth above. 
     It is a feature of the present invention to provide a pump that has a minimum of parts and may be easily disassembled to clean or repair and reassembled. 
     It is also a feature of the present invention to provide a pump having parts that have minimal physical and chemical interaction with fluids being pumped though it. 
     It is another feature of the present invention to provide a pump without check valves or springs. 
     It is yet another feature of the present invention to provide a pump that it is driven by means external of the fluid flow path. 
     It is a further feature of the present invention to provide a pump that is reversible and self-priming and can handle many different fluids, including liquids and gases. 
     It is a still further feature of the present invention to provide a pump that can be constructed in many different sizes and can deliver a predetermined measure of fluid. 
     It is yet a further feature of the present invention to provide a pump that does not require seals that reciprocate or rotate and wear by frictionally engaging an opposed surface. 
     In an exemplary embodiment of the present invention, a pump includes a tube with end caps defining a pump chamber with inlet and outlet ports, a pair of magnetic plungers separately slidable within the tube, and magnetic drive means to effect reciprocation of the plungers in the pump chamber. 
     In one aspect of the present invention, the plungers define a first work space when moved from one tube end, define a second work space when moved apart, and define a third work space when moved from the other tube end. 
     In another aspect of the present invention, the plungers are provided with radially arranged passageways so that the plungers selectively close communication of the pump chamber with the inlet and outlet ports and also selectively enable and disable flow fluid past the plungers themselves. As fluid flows longitudinally through the pump, the position of the plungers effects fluid flow alternately between the center and the periphery of the pump chamber. 
     In another aspect of the present invention, the end ports are closed by the ends of the plungers and the passageways include peripheral grooves on the sides of the plungers and a bore radially inward of the periphery of one plunger communicating with the grooves. 
     In still another aspect of the invention, the magnetic drive means includes coils circumscribing the tube that are energized with directionally selectable current or de-energized in programmed sequence to move the plungers to appropriate axial position within the tube to effect pumping of fluids in a selected direction. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The details of construction and operation of the invention are more fully described with reference to the accompanying drawings which form a part hereof and in which like reference numerals refer to like parts throughout. 
       In the drawings: 
         FIG. 1  is a cross-sectional view of an exemplary embodiment of a pump constructed in accordance with the present invention; 
         FIG. 2   a  is a perspective view of one of the plungers shown in  FIG. 1 ; 
         FIG. 2   b  is an enlarged cross-sectional view of the plunger shown in  FIG. 2   a;    
         FIG. 3   a  is a perspective view of the other plunger shown in  FIG. 1 ; 
         FIG. 3   b  is an enlarged cross-sectional view of the plunger shown in  FIG. 3   a;    
         FIG. 4   a  is a diagram showing the operating stages of the pump shown in  FIG. 1  when run in forward mode; 
         FIG. 4   b  is a diagram showing the operating stages of the pump shown in  FIG. 1  when run in reverse mode; 
         FIG. 5   a  is a timing diagram indicating current flow to the coils when the pump shown in  FIG. 1  is run in forward mode for about 2 cycles; 
         FIG. 5   b  is a timing diagram indicating current flow to the coils when the pump shown in  FIG. 1  is run in reverse mode for about 2 cycles; 
         FIG. 6  is a cross-sectional view of another exemplary embodiment of a pump constructed in accordance with the present invention; and, 
         FIG. 7  is a timing diagram indicating current flow to the coils when the pump shown in  FIG. 6  is run in forward mode. 
     
    
    
     All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. 
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     Referring to the drawings in greater detail,  FIG. 1  shows an exemplary embodiment of a magnetic reciprocating pump, generally designated  10 , constructed in accordance with the teachings of the present invention. The magnetic pump is seen to include an elongate tube  12 , a pair of sliding, generally cylindrical, magnetic armatures or plungers  14  and  15  positioned end-to-end within the tube  12 , and a pair of coils  1  and  2 . 
     The tube  12  includes a side wall  20  with a relatively smooth inner surface  21 , an outer surface  22 , and upper and lower ends  23  and  24 . Upper and lower end caps  26  and  27  releasably secured by well-known means having respective O-ring seals  29  and  30  located in annular grooves (not numbered) close off each end of the tube  12  to define a constant diameter cylindrical internal pump chamber  32  extending along a longitudinal axis. Upper and lower ports  34  and  35  defined in the respective end caps  26  and  27  centered along the pump axis provide fluid communication to the tube exterior. 
     While the upper tube end  23  is described herein for convenience as a downstream end with an outlet discharge port  34  and the lower tube end  24  as an upstream end with an inlet intake port  35 , it is understood that the pump described herein is bi-directional and that that upstream and downstream directions can be reversed such that the inlet becomes an outlet and an outlet becomes an inlet. 
     Each of the elongate plungers  14  and  15  respectively includes a pair of adjacent internal permanent magnets  37   a,b  and  38   a,b  enclosed by an outer layer of encapsulating material  40 . The magnets  37   a,b  and  38   a,b  are preferably rare earth magnets and are positioned with their south (S) poles axially facing each other and their non-facing north (N) poles facing outward. It is noted that this face-to-face orientation of the south poles may be reversed to place the north poles face-to-face while maintaining functionality. 
     The plungers  14  and  15  have a cylindrical shape with an outer diameter corresponding to the inner diameter of the tube  12  so as to permit reciprocating sliding movement therein and to provide a relatively close fit between the tube  12  and the plungers  14  and  15 . It is understood that the plungers  14  and  15  may spin or rotate freely about the longitudinal axis as they are reciprocated. 
     The tube  12  and encapsulating plunger layers  40  are both made from a durable, non-magnetic, chemically non-reactive and non-corrosive material with a relatively low co-efficient of friction. Preferably, the material is a high-density plastic, ceramic, glass, stainless steel, or the like, the material being selected to minimize friction, wear, pitting, corrosion, contamination, and the like. 
     The plungers  14  and  15  include passageways described hereafter that extend longitudinally in a radially inward center region or in a radially outward peripheral region. These passageways or flow paths permit fluid flow around or through the plungers  14  and  15  from one end to the other. Radial separation of the passageways allows communication between center and peripheral passageways to be closed when pump parts are moved into longitudinal contact with one another. For reasons that will be apparent, the peripheral regions should not overlap the center region even though the plungers may spin. 
     Each of the reciprocating plungers  14  and  15  is movable to two discrete positions between their respective tube ends and the opposing end of the other plunger. The plungers  14  and  15  are separably slidable within the tube  12  and as seen in  FIGS. 4   a  and  4   b  at various stages of operation, the plungers travel between three relative positions, namely, (1) both plungers  14  and  15  at an upper position to define a lower work space  45  wherein the upper port  34  is sealed from the pump chamber  32 , (2) the plungers  14  and  15  separated with the upper plunger  14  at an upper position and the lower plunger  15  at a lower position to define an intermediate work space  46  wherein both ports  34  and  35  are sealed from the pump chamber  32 , and (3) both plungers  14  and  15  at a lower position to define an upper work space  47  wherein the lower port  35  is sealed from the pump chamber  32 . It can also be seen that when the plungers  14  and  15  are together, no fluid can move past the plungers  14  and  15  from one work space to another. 
     As best seen in  FIGS. 2   a  and  2   b , the upper plunger  14  has longitudinally spaced inner and outer end surfaces  50  and  51  and a cylindrical side wall surface  52  extending therebetween. The outer end surface  51  carries an annular resilient element  54  within a circular cavity (not numbered) defined therein. The upper plunger  14  has a plurality of longitudinally extending, circumferentially spaced grooves, collectively numbered  55 , defined in a peripheral region along its side surface  52  extending between its inner and outer end surfaces  50  and  51 . The grooves  55  permit fluid flow between the side wall  52  and the tube side wall  20  past the upper plunger  14  to provide fluid communication between the upper port  34  and the space between the plungers  14  and  15 . When the upper plunger  14  is moved axially outward against the upper end cap  26 , the annular resilient element  54  closes off fluid communication between the upper port  34  and the upper work space  47  at port inner opening  34   a.    
     As best seen in  FIGS. 3   a  and  3   b , the lower plunger  15  has outer and inner portions  58  and  59 , respectively, separated by an annular circumferential groove  61  defined by spaced outer and inner shoulders  62  and  63 . The outer portion  58  has a cylindrical side wall surface  65  extending from an outer end surface  66  to the outer shoulder  62  and has a longitudinal length similar to the length of the upper plunger  14 . The inner portion  59  has a cylindrical side wall surface  68  extending from the inner shoulder  63  to an inner end surface  69  and has a length that is shorter than the outer portion  58 . The outer portion  58  carries an annular resilient element  71  within a circular cavity (not numbered) defined in outer end surface  66  and has a plurality of longitudinally extending, circumferentially spaced grooves, collectively designated  72 , defined in a peripheral region along its side wall  68  permitting fluid flow between its side wall  68  and the tube side wall  20  past the outer portion  58  to provide fluid communication between the lower port  35  and the annular groove  61 . When the lower plunger  15  is moved axially outward against the lower end cap  27 , the annular resilient element  71  closes off fluid communication between the lower port  35  and the lower work space  45  at port inner opening  35   a.    
     An axial bore  73  extends from the center of the inner end surface  69  of the plunger inner portion  59  and communicates with a transverse bore  74  axially located between the shoulders  62  and  63  providing communication with the annular groove  61 . The plunger inner portion  59  carries an annular resilient element  76  within a circular cavity (not numbered) defined in inner end surface  69  and when moved against the upper plunger  14  closes off fluid communication between the axial bore  73  and the intermediate work space  46  at bore inner opening  73   a.    
     The axial flow paths  34 ,  35  and  73  are located within a center circular region on or near the longitudinal axis of the pump  10 . The peripheral flow paths  55  and  72  are located within a peripheral region on or near the periphery of the plungers  14  and  15 . The annular resilient elements  54 ,  71  and  76  are radially disposed within the boundary region between the center and peripheral regions to function as seals and close off fluid flow between axial and peripheral flow paths when adjacent parts are closed together. The annular resilient elements  54 ,  71  and  76 , which may be made of rubber, soft plastic, or other suitable materials, also act as bumpers permitting moving plungers to stop quickly without excessive noise. It is understood that the plungers  14  and  15  are adapted to function as pistons and as valves closing the openings  34   a ,  35   a  and  73   a.    
     While it is preferred that the axial passageways and ports be centered on the longitudinal axis and that the longitudinally extending peripheral grooves be located on the side surfaces of the plungers  14  and  15 , it is understood that they need not be so located as long as a seal can be provided and maintained between axial and peripheral passageways even though there may be relative rotation of the parts about the longitudinal axis. Herein, the respective annular resilient elements surround the axial passageways  34 ,  35  and  73  and lie radially inward of the peripheral passageways  55  and  72  to effect separation of the axial and peripheral passageways when required. 
     The longitudinally spaced coils  1  and  2  circumscribe the outside of the tube  12  and are coaxial therewith. The coils  1  and  2  when energized establish a magnetic field within the tube chamber  32  to effect movement of the magnetic plungers  14  and  15  which are pulled into the coil&#39;s field, the direction of the applied current determining the polarity of the magnetic fields and, hence, the direction of axial pull. Each of the coils  1  and  2  is provided with leads  78  for connection to a suitable power source. The coils  1  and  2 , have side walls  81  and  82 , respectively, made of soft metallic material that shield the coils to focus magnetic flux in the coil gap  83  and the interior of the tube  12 . After either magnetic plunger  14  or  15  has been pulled a plunger to either of its discrete positions, the plunger will remain in that position without any additional electrical current being applied due to the attraction of the permanent magnets latching with the respective metallic coil side walls  81  and  82 . 
     Preferably, the width of the coil gap  83  should be less than half the length of the magnet pair  37   a,b  or  38   a,b  within the plungers. The stroke of the plungers, which is limited by the size of the empty work space, should be less than the width of the coil gap. Thus, the plungers do not move beyond the effect of the magnetic field that is established by the coils and each plunger can then be attracted to one side of its respective coil or the other. 
     Operation of the pump  10  in a forward mode is best understood by describing the operating positions shown in  FIG. 4   a  in view of the timing diagram shown in  FIG. 5   a . Beginning with no drive current to the coils as indicated at time point t 0  in  FIG. 5   a , the upper and lower plungers  14  and  15  are at their upper positions with the lower plunger  15  up against the upper plunger  14 . The fluid to be pumped from the lower port  35  is located in the lower work space  45  of the pump chamber  32  as seen at  86  in  FIG. 4   a.    
     At time point t 1 , the lower coil  2  is negatively energized to drive the lower plunger  15  downward toward the lower end of the pump chamber  32 . Downward movement of the lower plunger  15  forces fluid flow from the lower work space  45  upward around and through the lower plunger  15  into the intermediate work space  46  as indicated by the arrows at  87  in  FIG. 4   a.    
     At time point t 2 , the lower coil  2  is de-energized with the lower plunger  15  at the lower end of the pump chamber  32  with the upper plunger  14  remaining at the upper end of the pump chamber  32 . Fluid has been moved from the lower work space  45  upward into the intermediate work space  46  as seen at  88  in  FIG. 4   a.    
     At time point t 3 , the upper coil  1  is negatively energized to drive the upper plunger  14  downward toward the lower plunger  15  with the lower plunger  15  remaining at the lower end of the pump chamber  32 . Downward movement of the upper plunger  14  forces fluid flow from the intermediate work space  46  upward around the upper plunger  14  into the upper work space  47  as indicated by the arrows at  89  in  FIG. 4   a.    
     At time point t 4 , the upper coil  1  is de-energized so that both upper and lower plungers  14  and  15  are at their lower positions with the upper plunger  14  against the lower plunger  15 . Fluid has been moved from the intermediate work space  46  upward into the upper work space  47  as seen at  90  in  FIG. 4   a.    
     At time point t 5 , the upper and lower coils  1  and  2  are positively energized to drive both upper and lower plungers  14  and  15  upwardly together toward the upper end of the pump chamber  32 . Upward movement of the upper plunger  14  forces fluid from the upper work space  47  upward through the upper port  34  and upward movement of the lower plunger  15  draws fluid from the lower port  35  upward into the lower work space  45  as seen at  91  in  FIG. 4   a.    
     At time point t 6 , the upper and lower coils  1  and  2  are de-energized with the upper and lower plungers  14  and  15  returned to their upper positions as they were at time point t 0 , and the process is begun again to pump more fluid through the pump  10  from bottom to top. 
     Operation of the pump  10  in a reverse mode is best understood by describing the operating positions shown in  FIG. 4   b  in view of the timing diagram shown in  FIG. 5   b . Beginning with no drive current to the coils  1  and  2  as indicated at time point t 0  in  FIG. 5   b , the top and bottom plungers  14  and  15  are at their lower positions with the upper plunger  14  down against the lower plunger  15 . The fluid to be pumped from the upper port  34  is located in the upper work space  47  of the pump chamber  32  as seen at  93  in  FIG. 4   b.    
     At time point t 1 , the upper coil  1  is positively energized to drive the upper plunger  14  upward toward the upper end of the pump chamber  32 . Upward movement of the upper plunger  32  forces fluid flow from the upper work space  47  downward around the upper plunger  14  into the intermediate work space  46  as indicated by the arrows at  94  in  FIG. 4   b.    
     At time point t 2 , the upper coil  1  is de-energized with the upper plunger  14  at the upper end of the pump chamber  32  and the lower plunger  15  remaining at the lower end of the pump chamber  32 . Fluid has been moved from the upper work space  47  downward into the intermediate work space  46  as seen at  95  in  FIG. 4   b.    
     At time point t 3 , the lower coil  2  is positively energized to drive the lower plunger  15  upward toward the upper plunger  14 . Upward movement of the lower plunger  15  forces fluid from the intermediate work space  46  downward through and around the lower plunger  15  into the lower work space  45  as seen by the arrows at  96  in  FIG. 4   b.    
     At time point t 4 , the lower coil  2  is de-energized so that both upper and lower plungers  14  and  15  are at their upper positions with the lower plunger  15  against the upper plunger  14 . Fluid has been moved from the intermediate work space  46  downward into the lower work space  45  as seen at  97  in  FIG. 4   b.    
     At time point t 5 , the upper and lower coils  1  and  2  are negatively energized to drive both upper and lower plungers  14  and  15  downward together toward the lower end of the pump chamber  32 . Downward movement of the lower plunger  15  forces fluid from the lower work space  45  downward through the lower port  35  and downward movement of the upper plunger  14  draws fluid from the upper port  34  downward into the upper work space  47  as seen at  98  in  FIG. 4   b.    
     At time point t 6 , the upper and lower coils  1  and  2  are de-energized with the upper and lower plungers  14  and  15  returned to their lower positions as they were at time point t 0 , and the process is begun again to pump more fluid through the pump  10  from top to bottom. 
     In another exemplary embodiment of the invention shown in  FIG. 6 , a magnetic reciprocating pump, generally designated  100 , includes two pairs of coils  1   a , 1   b  and  2   a , 2   b  that are employed to move and hold the plungers  14  and  15  in discrete position. Herein, there is no requirement that the polarity of the electric current be reversed, only that current be turned off. Coils  1   a  and  1   b  making up the upper coil pair are positively energized one at a time to selectively pull the upper magnetic plunger  14  upward or downward. Similarly, coils  2   a  and  2   b  making up the lower coil pair are positively energized one at a time to selectively pull the lower magnetic plunger  15  upward or downward. 
     The operating stages of the pump embodiment shown in  FIG. 6  in a forward mode is best described by viewing  FIG. 4   a  in view of the timing diagram of  FIG. 7 . Beginning with time point t 0  in  FIG. 7 , coils  1   a  and  2   a  are energized and coils  1   b  and  2   b  are de-energized so that both upper and lower plungers  14  and  15  are at their upper positions with the lower plunger  15  up against the upper plunger  14 . The fluid to be pumped from the lower port  35  is located within the lower work space  45  of the pump chamber  32  as seen at  86  in  FIG. 4   a.    
     At time point t 1 , coil  2   a  is de-energized and coil  2   b  is energized to pull the lower plunger  15  downward toward the lower end of the pump chamber  32  with the upper plunger  14  remaining at the upper end of the pump chamber  32 . Downward movement of the lower plunger  15  forces fluid flow from the lower work space  45  upward around and through the lower plunger  15  into the immediate work space  46  as indicated by the arrows at  87  in  FIG. 4   a.    
     At time point t 2 , coils  1   b  and  2   a  remain de-energized and coils  1   a  and  2   b  remain energized holding the plungers  14  and  15  in fully spaced relation, each at their respective ends of the pump chamber  32 . Fluid has been moved from the lower work space  45  upward into the intermediate work space  46  as seen at  88  in  FIG. 4   a.    
     At time point t 3 , coil  1   a  is de-energized and coil  1   b  is energized to pull the upper plunger  14  downward toward the lower plunger  15  with the lower plunger  15  remaining at the lower end of the pump chamber  32 . Downward movement of the upper plunger  14  forces fluid flow from the intermediate work space  46  upward around the upper plunger  14  into the upper work space  47  as indicated by the arrows at  89  in  FIG. 4   a.    
     At time point t 4 , coils  1   b  and  2   b  remain energized and coils  1   a  and  2   a  remain de-energized so that both upper and lower plungers  14  and  15  are at their lower positions with the upper plunger  14  against the lower plunger  15 . Fluid has been moved from the intermediate work space  46  upward into the upper work space  47  as seen at  90  in  FIG. 4   a.    
     At time point t 5 , coils  1   b  and  2   b  are de-energized and coils  1   a  and  2   a  are energized to pull the upper and lower plungers  14  and  15  upward together toward the upper end of the pump chamber  32 . Upward movement of the upper plunger  14  forces fluid from the upper work space  47  upward through the upper port  34  and upward movement of the lower plunger  15  draws fluid from the lower port  35  upward into the lower work space  45  as seen at  91  in  FIG. 4   a.    
     At time point t 6 , coils  1   a  and  2   a  remain energized with the upper and lower plungers  14  and  15  returned to their upper positions as they were at time point t 0 , and the process is begun again to pump more fluid through the pump  10  from bottom to top. 
     Technical Use 
     In the pump embodiment shown herein, the plungers have an outside diameter of about ¼ inch and are moved through a complete pumping operation at a rate of about 1/10 to 10 cycles per second. Because the pump has a fixed stroke, the pumping of fluids can be controlled to obtain measured volumes. The magnetic pump described herein can be used advantageously in laboratory applications, but its size can be scaled upwardly or downwardly for any particular application. For any given pump, the operating speed can be easily modified by adjusting the cycle time and the pump pressure can be modified by changing the cycle volume or the number of windings in the coil. 
     INDUSTRIAL APPLICABILITY 
     It should be apparent the pump described herein is a simple, functional unit that is effective and easily constructed and operated. 
     Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims. 
     It should be understood that the terms “top,” “bottom,” “front,” “back,” “forward,” “rear,” “first,” “second,” “upper,” “lower,” “height,” “width,” “length,” “end,” “side,” “horizontal,” “vertical,” and similar terms as used herein, have reference only to the structure shown in the drawings and are utilized only to facilitate describing the invention. The terms and expressions employed herein have been used as terms of description and not of limitation. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. While specific embodiments of the invention have been disclosed, one of ordinary skill in the art will recognize that one can modify the dimensions and particulars of the embodiments without straying from the inventive concept.