Abstract:
An improved diaphragm type chemical dosing pumps can be designed as both a variable displacement accurate dosing pump and a fixed displacement accurate dosing pump. The improved dosing pump provides a required supply of pressurized fluid, to be called hereafter as process fluid, to an injection point against varying gas or liquid pressures. By eliminating the use of elastomeric sealing, the failing of the pump due to seal wear is eliminated. An internal pressure relief valve protects the pump mechanicals from premature failure. Use of a spring assisted suction assists positive suction for very accurate dosing. The working fluid is a driver fluid that is used to lubricate working components of the pump. The angled ports minimize friction losses to further improve pump efficiency and also eliminate building up of air pockets.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application asserts priority from provisional application 61/400,392, filed on Jul. 27, 2010 which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to dosing pumps. More specifically, the present invention relates to diaphragm actuated dosing pumps, and particularly variable displacement dosing pumps, which use less energy and/or are subject to reduced cavitation problems compared to many conventional designs. The pump employs a vertical design as opposed to conventional horizontal design which positively influences the refill and depressurization of the driver fluid and thus makes the pump more efficient wherein vertical movement of the piston creates uniform pathways for the lubricating driver fluid around the piston to thereby enhance pump life. Further, the piston never touches the bore so there will be no wear, and the diaphragm is pre-energized so it maintains constant NPSHR which is independent of the positive suction caused by the piston. 
       BACKGROUND OF THE INVENTION 
       [0003]    Dosing pumps are well known and are used in a wide variety of applications. Dosing pumps have commonly been employed in industrial applications where very accurate dosing is expected. Traditionally piston pumps were used in gas field applications which were powered by compressed air or pressurized sour gas. They are not very precise or energy efficient and moreover, the vented sour gas is an environmental hazard. 
         [0004]    However, while this type of dosing pump, and in particular diaphragm actuated pump, can provide several advantages over piston type pumps or other pumps, they do suffer from some disadvantages. In particular, diaphragm dosing pumps can break down if a suction or discharge port is blocked during operation and/or can suffer from cavitation effects which, over time can damage components of the pump and especially the diaphragm. 
         [0005]    This prompted an invention of a pump powered by renewable energy which can work efficiently for months without having to be repaired or requiring replacement of the seal. This also prevents over pumping of the process fluid and thus saves costly chemicals and also avoids polluting the land where it is pumped into. 
         [0006]    It is an object of the present invention to provide a novel dosing pump which obviates or mitigates at least one disadvantage of the prior art. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first aspect of the present invention, a dosing pump is provided for pressurizing a driver fluid, comprising: a pump housing with a pumping chamber and having an inlet port and an outlet port in fluid communication with a pump head on the pump process side; a piston reliably mounted within the pump chamber and having an eccentric cam rotating inside the pump chamber and being mounted concentrically with respect to the pump chamber such that the rotation of the cam pushes the piston in and out of the pumping chamber causing the diaphragm to successively move forward and reverse inside the pump to cause the process liquid to enter the inlet port of the process side head and be expelled through the outlet port as the motor rotates. The motor operates to rotate the cam and in turn reversibly pushes or drives the piston to pressurize the driver fluid which drives a balanced diaphragm to thereby pressurize the process fluid by means of the balanced diaphragm. 
         [0008]    The pump includes a refill port, relief port and a pumping chamber wherein the refill, relief and the pumping chamber are connected which eliminates the need for multiple areas for supply and storage of operating fluid. 
         [0009]    The present invention provides a novel and useful improvement to dosing pumps, both variable displacement dosing pumps and fixed displacement dosing pumps, by providing a means of pressure equalization and refill from the same port. Pressure relief is against the gravity and gravity assisted refill further increases the efficiency of the pump. 
         [0010]    Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached figures, wherein: 
           [0012]      FIG. 1  is a side cross sectional view of a dosing pump of the invention. 
           [0013]      FIG. 2  is a perspective view thereof. 
           [0014]      FIG. 3  is an enlarged cross-sectional of the motor-cam unit. 
           [0015]      FIG. 4  is an enlarged cross-sectional view of the pump chamber. 
           [0016]      FIG. 5  is a partial perspective view thereof. 
           [0017]      FIG. 6  is an end view of a bearing-cam assembly. 
           [0018]      FIG. 7  is a side cross-sectional view as taken along section line  8 -A of  FIG. 6 . 
           [0019]      FIG. 8  is a side view of a liner sleeve sub-assembly for the diaphragm pump. 
           [0020]      FIG. 9  is a cross-sectional view thereof as taken along line B-B of  FIG. 8 . 
           [0021]      FIG. 10  is a connecting rod sub-assembly. 
           [0022]      FIG. 11  is an end view of the connecting rod sub-assembly. 
           [0023]      FIG. 12  is an end view of a front bearing holder sub-assembly. 
           [0024]      FIG. 13  is a side cross-sectional view as taken along line  13 - 13  of  FIG. 12 . 
           [0025]      FIG. 14  is an end view of a head sub-assembly. 
           [0026]      FIG. 15  is a side cross-sectional view of the head sub-assembly as taken along line  15 - 15  of  FIG. 14 . 
       
    
    
       [0027]    Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Before describing the present invention, prior art variable displacement dosing pumps generally have included a closed housing with a cam rotated by a drive shaft causing a reciprocating movement of the piston in the pumping chamber causing a driver fluid to be pressurized and depressurized and thus creating movement of a diaphragm. These known diagraph pumps work horizontally causing inefficient refill and piston lubrication. 
         [0029]    Generally, as to the present invention,  FIG. 1  illustrates an inventive diaphragm pump  10  which includes a motor “M”  11  that rotatably drives a cam  12  at a desired speed to move piston “PT”  14  vertically downwardly and upwardly inside the piston bore “PB”  16 . A driver fluid “F”  17  is provided in a driver fluid chamber or reservoir  18  so as to communicate with a pump chamber “PC”  19  of the piston bore  16 , wherein the driver fluid  17  enters through a refill port  20  that opens sidewardly or radially into the piston bore  16  to supply driver fluid  17  into the pump chamber  19 . With continuing descent of the piston “P”  14  during motor operation, trapped driver fluid  17 , which is located in the pump chamber  19  in front of the piston “PT”  14 , is pressurized and thereby pressurizes an energized diaphragm “D”  22  movably supported in a pump head  23 . Pressurized diaphragm “D”  22  moves forward into a process fluid chamber  24  and pushes out the process fluid  25  through a discharge port “DP”  26 . 
         [0030]    During the upward return stroke of the piston “PT”  14 , the pressurized driver fluid  17  is depressurized when the piston  14  clears the refill port “R”  20 . The diaphragm “D”  22  moves back to its original position by an attached spring  28  and a precise amount of process fluid  25  is filled inside the process chamber through the suction port “SP”  30 . The discharge port  26  and suction port  30  are controlled by check valves so that process fluid flow is from the suction port  30  through to the discharge port  26 . 
         [0031]    In case of accidental overpressure of the driver fluid  17  behind the energized diaphragm “D”  22 , a pressure relief port “P”  34  is provided which is controlled by a spring-biased pressure relief valve  35  that opens when overpressure is encountered to allow the excess driver fluid  17  to flow there through causing excess pressure to be expelled out into the driver fluid chamber  18  which is in fluid communication with the relief port  34 . 
         [0032]    In more detail as to  FIG. 1 , the pump  10  comprises a generally U-shaped base plate  36  that is mountable to any suitable support surface by mounting flanges  37 . The base plate  36  also includes a plate-like pump support  38  defining an upward-facing support surface  39 . The pump  10  further comprises a housing unit  40  which comprises a main housing  41  that is directly mounted to the pump support  38 . The top of the main housing  40  supports an intermediate housing body  42  which in turn supports an upper housing body  43 . One side of the main housing  40  also supports the pump head  23  as will be described further. 
         [0033]    First as to the main housing  40 , as seen in  FIGS. 1 ,  2  and  4 , the main housing has a bottom end formed with a first chamber or pocket  45 , and a second chamber or pocket  46 . The first chamber  45  provides an air space between the base  36  and the portion of the main housing  40  that is disposed next to the piston bore  16  and pump chamber  19  which helps insulate these cavities from the surrounding environment. Similarly, the second chamber  46  is located next to the pump head  23  and provides additional thermal separation between the pump head  23  and the remaining portions of the main housing  40 . 
         [0034]    The main housing  40  includes an outer housing wall  48  and an inner chamber wall  49  which is radially spaced inwardly from the outer wall  48  to define the driver fluid reservoir  18  radially therebetween. The fluid reservoir  18  thereby has an annular shape surrounding the inner chamber wall  49 . The outer wall  48  also includes a bore  51  which normally is closed by a set screw  52  ( FIG. 1 ) but is removable to help indicate the level of the driver fluid  17  within the reservoir  18 . 
         [0035]    The inner wall  49  further defines an open-ended central bore  53  ( FIG. 4 ) which opens vertically upwardly into the intermediate housing body  42  and opens downwardly into a transverse fluid passage  54  that allows the driver fluid  18  to flow transversely from the pump chamber  19  to the diaphragm  22  for operation thereof by reciprocation of the piston  14 . 
         [0036]    The transverse fluid passage  54  therefore has an inner end  55  receiving driver fluid  17  from the pump chamber  19 , and an outer end  56  that widens into a secondary passage  55  so as to open into and fluidly communicate with the pump head  23  as will be described further hereinafter. Since the fluid passage  54  receives pressurized driver fluid  17 , this fluid  17  is then able to communicate with the diaphragm  22  through communication with the secondary fluid passage  55 . 
         [0037]    If the fluid is over-pressurized, the aforementioned relief port  34  is provided that opens radially through the outer housing wall  48 . In particular, the outer housing wall  48  includes an enlarged valve section  56  that is provided with a vertically elongate passageway  57  comprising a valve seat  58  that receives the tapered or pointed valve body  35 A ( FIGS. 4 and 5 ) of the relief valve  35  therein. This passageway  57  has a tapered inner end  59  that cooperates with the tapered end of the relief valve  35  so as to selectively block fluid flow therethrough. The passageway  57  at this location further communicates with a relief passage  60  that opens radially downwardly into the secondary fluid passage  55  described above. During over-pressurization, the driver fluid  17  is able to enter the relief passage  60  to unseat or move the relief valve body  35 A upwardly away from the tapered passage end  59  and allow the driver fluid  18  to flow into the passageway  57 , into the relief port  34  and then into the driver fluid reservoir  18  described above. Normally, the valve body  35 A is maintained in a closed position by a spring  61  which allows the relief valve  35  to selectively open and close while automatically returning the valve  35  to the normally closed position. The spring force also sets the maximum pressure of the driver fluid  17  before pressure is released. 
         [0038]    The passageway  57  is enclosed by a valve cap or closure  62  which prevents leakage of the driver fluid  17  from the passageway  57 . As such, the relief valve  35  allows excess driver fluid  17  to be automatically returned to the reservoir  18  without affecting the desired operating pressure of the driver fluid  17  when operating the diaphragm  22 . Once the operating pressure is returned to the desired operating level, the valve  35  would automatically close in response to the spring  61  or other biasing or closing means. 
         [0039]    For the pumping operation, the inner chamber wall  49  is provided with a plurality of the refill ports  20  which are circumferentially spaced apart and open radially through the entire thickness of the inner wall  48 . 
         [0040]    To define the pump chamber  19  and piston bore  16 , the inventive pump  10  includes a liner sleeve sub-assembly  65  ( FIGS. 4 ,  8  and  9 ) which slidably fits downwardly into the central bore  53 . The liner sleeve assembly  65  comprises a cylindrical holder  66  having an upper mounting flange  67 , which includes a fastener bore  68  that allows for secure engagement to the inner chamber wall  49 . The outer surface of the holder  66  includes circumferential grooves  69  that receive seals like O-rings therein to seal the holder  66  relative to the inside surface of the central bore  53 . The holder  66  includes a long cylindrical liner or sleeve  71  which is preferably formed of steel and defines the pump chamber  19  at the bottom end  72  thereof and the piston bore  16  at the upper end  73  thereof. To allow for entry of the driver fluid  18  through the refill ports  20  into the pump chamber  19 , respective liner ports  75  and holder ports  76  are provided on diametrically opposite sides of the liner  71  and holder  66  so as to thereby align with the refill ports  20  and essentially define radial extensions of the refill ports  20 . Hence, reference to the refill ports  20  herein comprises the actual ports  20  formed in the inner chamber wall  49  as well as the port extensions defined by the liner ports  75  and holder ports  76  which together define continuous radial passages between the reservoir  18  and the pump chamber  19 . 
         [0041]    As seen in  FIG. 4 , piston  14  at the top end of stroke clears the refill ports  20  at least partially so as to allow a balanced level of the driver fluid  17  which can flow into the pump chamber  19  if necessary through the refill ports  20 . During downward travel during the pump stroke, the bottom end of the piston  14  extends into the pump chamber  19  as diagrammatically represented by reference line  78  which thereby causes the piston  14  to close the refill ports  20  and drive the fluid  17  out of the pump chamber  19  and into the transverse fluid passage  54  for driving operation of the diaphragm  22 . As the piston  14  travels upwardly through its return stroke, the bottom end of the piston  14  eventually clears the refill ports  20  at least partially to then release any fluid pressure in the pumped or driven fluid and allow the driver fluid  18  to refill the pump chamber  19  for subsequent pumping. Reciprocating operation of the piston  14  thereby causes the driver fluid  18  to reciprocatingly drive the diaphragm  22  as will be described further herein. All of the refill ports  20 , pump chamber  19  and pressure relief port  34  are in common communication with the reservoir  18  so that separate systems are not required to accommodate the separate functions of refilling the pump chamber  19 , driving the driver fluid  17  with the piston  14 , and releasing over-pressurization through the relief valve  35 . Further, it is not necessary to seal the driver fluid  17  within this fluid system so that wear-susceptible seals between the piston  14  and the liner  71  are avoided, which avoids any wear problems or leakage of fluid which might occur if a piston were to require elastomeric seals or other types of seals to prevent leakage of a driven fluid. 
         [0042]    To effect driving of the piston  14 , the motor  11  is provided with a cam assembly  79  ( FIG. 3 ) which connects a rotatable drive shaft  80  of the motor  11  with the piston  14 . More particularly as to  FIGS. 10 and 11 , the piston  14  is formed as part of a piston sub-assembly  81  which comprises a piston rod  82  that mounts within a support bracket  83 . The support bracket  83  includes a connector pin  84  that pivotally joins the support bracket  83  to a drive collar  85  having a central cam-receiving bore  86  extending there through. 
         [0043]    Referring to  FIGS. 3 and 4 , the motor drive shaft  80  is supported by a first bearing  88  that provides support to the shaft  80  on the upper end of the upper housing body  43 . The bearing  88  is supported within a motor flange  89  that in turns mounts with the motor  11  to the housing body  43  by mounting plate assembly  90 . The inboard free end of the motor shaft  80  supports a cam sub-assembly ( FIGS. 3 ,  6  and  7 ) for driving operation of the piston assembly  81 . In particular, the cam assembly  79  has a cam body  91  through which passes a central axis  92  that defines a rotation axis  93  for the cam assembly  79  during shaft rotation. The motor-driven end of the axle  92  includes a shaft-receiving bore  94  that receives the motor shaft  80  therein ( FIG. 3 ) which is then secured therein by a set screw  95 . This end of the axle  92  has the bearing  98  mounted thereon to support such end, while the axle  92  has a free end  97  opposite the driven end  96  which is configured to receive an additional bearing  98  thereon. 
         [0044]    To drive the piston assembly  81 , the cam body  91  is formed with an outer, radially-projecting hub  99  that has a circular outer surface which extends about a center hub axis that is positioned eccentric to the rotation axis  93 . As such, the hub  99  is formed eccentrically relative to the shaft axis  93  so that the hub  99  effectively works as a cam. The circular hub  99  is rotatably fitted within the circular bore  86  of the drive collar  85  so that rotation of the cam body  91  causes reciprocating vertical motion of the piston assembly  81  during rotation of the motor shaft  80 . 
         [0045]    Referring to  FIGS. 3 ,  12  and  13 , the axle end  97  is supported by a bearing sub-assembly  101  which comprises a mounting cover  102  formed with a shallow bearing seat  103  for receiving the aforementioned bearing  98  therein. The bearing seat  103  includes a spring  104  to ensure proper axial positioning of the bearing  98 . The cover  102  has an outer mounting flange  105  formed with holes for receiving fasteners there through that secure to the upper housing body  43 . 
         [0046]    Next as to  FIG. 3 , the upper housing body  43  also includes a removable top cap  106  that allows for the driver fluid  17  to be poured into the open vertical column or passageway defined internally by the intermediate housing body  42  and upper housing body  43 . Preferably, the driver fluid  17  is any suitable type of oil or other working fluid which can be poured through the top cap  106  to appropriately fill the reservoir  18  to the appropriate level indicated by the set screw  52 . Other types of fluids are suitable. Since this fluid is able to flow freely into and around the various components including the piston  14  itself, the driver fluid  17  not only serves as a pump driver for the diaphragm  22 , but also serves as a lubricant that lubricates the movable components including the piston  14  as it moves relative to the opposing interior surface of the steel liner  71  and the interior liner surface which forms the piston bore  16  and pump chamber  19 . 
         [0047]    Next as to the pump head  23 , said pump head  23  is best illustrated in  FIGS. 5 ,  14  and  15 . The pump head  23  comprises an inner head body  110  and an outer head body  111  which define opposing interior faces  112  and  113  defining an interface therebetween. The surfaces  112  and  113  have central cavities which face in opposing relation and define a circular, thin cavity that defines the process fluid chamber  24 . The fluid chamber  24  on the outboard side communicates with the discharge port  26  and suction port  30  by angled ports  114  and  115 , wherein the angled ports minimize friction loss so as to further improve pump efficiency and also eliminate build-up of air pockets. The inner and outer head bodies  110  and  111  are joined together by fasteners  117  extending through fastener bores  118 . The outer head body  111  also includes an indicator  119  showing the flow direction which would be dictated by the check valves in the discharge port  26  and suction port  30 . 
         [0048]    The diaphragm  22  preferably comprises a flexible, circular disk  121  which is formed from elastomeric Teflon and has an outer rib  122  that seats within opposing grooves formed in the head body faces  112  and  113 . The rib  122  is sandwiched or compressed between the interface of the inner and outer head bodies  110  and  110  and defines a fluid-tight seal therebetween. The disk  121  thereby sealingly separates the process fluid chamber  24 , which is on the outboard side of the diaphragm  22 , from an inner driver fluid chamber  123 , which is on the inboard side of the diaphragm  22 , such that axial flexing of the diaphragm disk  121  effects variations, i.e. increases and decreases in the volume of the pump chamber  24  and thereby effects pumping operation of the process fluid  25  that passes through the angled ports  114  and  115  into and out of the process fluid chamber  24 . 
         [0049]    The diaphragm  122  includes a stainless steel drive head  125  on the driven fluid side which drive head  125  has a connector collar  126  that is threadedly engaged with the shaft  126  of a bolt  127 . The head  128  of the bolt  127  has a spring  129  disposed in compression between the bolt head  128  and a divider wall  130  to normally bias the diaphragm  122  axially rightwardly in  FIG. 15 . This divider wall  130  includes passages  131  ( FIG. 5 ) which allows for driver fluid to flow into the driver fluid chamber  123  adjacent the inboard side of the diaphragm  22 . 
         [0050]    To mount the pump head  23  to the main housing body  41 , the inner head body  110  has an inboard flange  135  which fits in sealed engagement into a corresponding cavity in the main housing body  41  ( FIG. 2 ). The flange  135  defines a fluid passage  136  which aligns with and opens into the corresponding fluid passage  55  of  FIG. 4 . As such, the driver fluid  17  during pump operation is driven through the passages  54 ,  55 ,  136  and  131 , and into the pump chamber  123  so as to pressurize the inboard side of the diaphragm  22  and effect axial displacement or deformation of the central portion of the diaphragm  122  leftwardly in  FIG. 15  during the pumping stroke of the piston  14 . During the return stroke of the piston  14 , the driver fluid  17  can then flow out of these passages so that the spring-energized diaphragm  22  is then driven rightwardly by the aforementioned spring  129 . The diaphragm  22  therefore is energized to provide for spring-assisted suction of the process fluid into the process fluid chamber  24  during the return stroke which provides for positive suction and very accurate dosing of the process fluid. 
         [0051]    Hence, reciprocating upward and downward movement of the piston  14  causes a corresponding reciprocating horizontal movement of the diaphragm  22  to effect pumping of the process fluid. The improved dosing pump  10  provides a required supply of pressurized process fluid  25  to an injection point even against varying gas or liquid pressures. This pump  10  eliminates the use of elastomeric sealing within the piston configuration, and eliminates failing of the pump due to seal wear. Further the internal pressure release valve  35  protects the pump structures from premature failure, and providing the driver fluids  17  as a lubricant thereby lubricates the working components of the pump. 
         [0052]    The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.