Abstract:
A single sided, dual plunger pump is disclosed for use pumping difficult working fluids, including fluids with high particulate content. Each plunger operates in the opposite state as the other, such that when one plunger is filling with fluid, the other is discharging, and so forth. This creates discharge flow that is much more stable than a pump using only a single plunger, without requiring two individual pumps to be connected together.

Description:
FIELD 
       [0001]    This invention relates to the field of pumps and more particularly to a device for nearly continuous pumping of highly viscous or particulate laden fluids. 
       BACKGROUND 
       [0002]    Many pumps are inappropriate for pumping highly viscous fluids, or fluids that have a high particulate content. There are existing pumps that can handle such difficult working fluids but do so with drawbacks, namely limited pressure increase or intermittent fluid flow. 
         [0003]    Prior art pumps exist that can pump difficult fluids. For abrasive fluids, a diaphragm or membrane pump is often recommended. Such pumps operate by sharing a flexible wall between a fluid chamber containing a working fluid and a pressure chamber, the pressure chamber alternately pressured and depressurized. A check valve on the inlet and another on the outlet of the working fluid chamber prevents backflow. When the pressure chamber is depressurized, working fluid is drawn into the fluid chamber. When the pressure chamber is pressurized, the working fluid is pushed out of the fluid chamber. Alternating these two steps pumps fluid. But there are multiple drawbacks to a diaphragm pump. In a diaphragm pump, the discharge pressure of the working fluid cannot exceed that of the pressure source supplying the pressure chamber, commonly air. This is because the membrane area acted upon by the air pressure is the same membrane area acting upon the working fluid. Also, due to the intermittent nature of the pumping, the fluid is discharged in pulses. 
         [0004]    A plunger pump addresses some of the shortcomings of a diaphragm pump, specifically the limitation of low pressure differential. But similar to a diaphragm pump and a piston pump, the pumping of a plunger pump is intermittent, causing surging discharge pressure and flow. 
         [0005]    U.S. Pat. No. 4,029,442 to Schlosser discloses a high pressure plunger pump for use pumping heavy, highly viscous, and abrasive materials. The &#39;442 patent discloses the use of an elastomeric ring to form a seal between the wall that separates the high and low pressure chambers, and the outer wall of the piston. This elastomeric ring functions as a pressure barrier, preventing pressurized fluid from leaking backwards across the plunger. More importantly, the seal also acts as a wiper. The wiper cleans material from the plunger wall during each stroke, preventing aggregate suspended within the material from scratching the surface of the plunger. But the Schlosser device does not disclose the use of multiple plungers within a single enclosure, alternating between intake and discharge. 
         [0006]    What is needed is a system that will allow nearly continuous pumping of difficult working fluids, with the potential for significant pressure differentials between the inlet and outlet. 
       SUMMARY 
       [0007]    Described within is a pump apparatus comprising a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a shaft, the shaft located within the penetration and extending through a portion of the housing, a proximal plunger, the proximal plunger affixed to the shaft, a distal plunger, the distal plunger affixed to the shaft, a proximal chamber seal, the proximal chamber seal having an inner diameter and an outer diameter, the proximal chamber seal located at an interface of the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal having an inner diameter and an outer diameter, the distal chamber seal located at an interface of the distal low pressure chamber and the distal high pressure chamber, whereas when the proximal plunger moves toward the proximal high pressure chamber, and away from the proximal low pressure chamber, the distal plunger moves away from the distal high pressure chamber, and toward the distal low pressure chamber. 
         [0008]    Further disclosed is a pump apparatus comprising, a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a shaft, the shaft located within the penetration and extending through a portion of the housing, the shaft comprised of one or more pieces, a proximal plunger, the proximal plunger integral to at least one portion of the shaft, a distal plunger, the distal plunger integral to at least one piece of the shaft, a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber, whereas while the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber. 
         [0009]    Finally, disclosed is a pump apparatus comprising, a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a cylindrical shaft, the cylindrical shaft located within the penetration and extending through a portion of the housing, the cylindrical shaft comprised of one or more pieces, a proximal plunger, the proximal plunger integral to at least one portion of the cylindrical shaft, a distal plunger, the distal plunger integral to at least one piece of the cylindrical shaft, a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber, wherein the proximal low pressure chamber is near the proximal end of the housing, the proximal high pressure chamber is between a center of the housing and the proximal low pressure chamber, the distal high pressure chamber is between the center of the housing and the distal low pressure chamber, and the distal low pressure chamber is near the distal end of the housing; and as the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  illustrates a plan view of a single sided, dual plunger pump. 
           [0012]      FIG. 2  illustrates a cutaway view of the single sided, dual plunger pump. 
           [0013]      FIG. 3  illustrates a side plan view of the single sided, dual plunger pump. 
           [0014]      FIG. 4  illustrates another cutaway view of the single sided, dual plunger pump. 
           [0015]      FIG. 5  illustrates a close-up cutaway view of the shaft seals of the single sided, dual plunger pump. 
           [0016]      FIG. 6  illustrates a close-up cutaway view of the second cylinder and associated components of the single sided, dual plunger pump. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. 
         [0018]    Referring to  FIGS. 1 and 2 , the frontal view of a first embodiment of the dual piston, single sided plunger pump is shown. The pump is shown in a vertical orientation, but is used in any orientation. The driver attachment point  2  connects to a pump driver (not shown). This portion of the pump will be referred to as the proximal portion, the driver attachment point  2  used as a point of reference. The pump driver is most frequently a linear air motor (pneumatic motor) powered by a source of compressed air, but any source of oscillating force is anticipated to provide the power necessary for operation. A penetration  3  is present at the top of the pump housing  100  to allow the shaft components  126 / 124 / 123 / 10 / 60  to connect to an air motor (not shown). 
         [0019]    The optional surge chambers  6 / 8  are shown. This embodiment includes surge chambers  6 / 8  to smooth out pressure fluctuations that result from varying inlet conditions. In other embodiments the surge chambers are not present. 
         [0020]    Moving to the internal parts of the pump, four chambers are shown. Each of the two plungers  10 / 60  has a low pressure chamber  12 / 62  and a high pressure chamber  14 / 64 . The proximal plunger  10 , or plunger closest to the driver attachment point  2 , oscillates between a proximal low pressure chamber  12  and a proximal high pressure chamber  14 . The distal plunger  60 , or plunger furthest from the driver attachment point  2 , oscillates between a distal low pressure chamber  62  and a distal high pressure chamber  64 . 
         [0021]    The operation of the dual plunger pump  1  will be described. When there exists a fixed volume of space filled with fluid, and an additional volume is introduced into the space, the fluid pressure increases. In the dual plunger pump  1 , the high pressure chambers  14 / 64  have a fixed volume. As the plunger  10 / 60  moves into the high pressure chamber  14 / 64 , contacting the seal  40 / 90 , the space available to be occupied by the fluid decreases, pressure increases, and fluid exits, passing through the check valve  18 / 68 . This example contains discharge check valves  18 / 68 , but in other embodiments there are no discharge check valves  18 / 68 . The example shown uses ball check valves, but the use of other types of check valves is anticipated, including swing check valves, tilting disc check valves, dual plate check valves, and others as are known in the art. 
         [0022]    The manner in which the dual plunger pump  1  operates allows the seal  40 / 90  to clean the plunger  10 / 60  during operation. What follows is a description of a single cycle of one plunger, starting with the plunger  10 / 60  within the low pressure chamber  12 / 62 . 
         [0023]    When the plunger  10 / 60  is starting its stroke, it is within the low pressure chamber  12 / 62 . The walls of the plunger  10 / 60  are not in contact with the seal  40 / 90 . As the plunger  10 / 60  in the dual plunger pump  1  moves from the low pressure chamber  12 / 62  to the high pressure chamber  14 / 64 , the wall of the plunger  10 / 60  contacts the seal  40 / 90 . Each plunger  10 / 60  has a seal  40 / 90  positioned between the plunger  10 / 60  wall and the inner portion of the pump housing  100 . As the wall of the plunger  10 / 60  moves through the seal  40 / 90 , the seal  40 / 90  wipes any debris from the plunger  10 / 60  wall, returning it to the working fluid. The plunger  10 / 60  then returns to the low pressure chamber  12 / 62 , and the cycle begins again. As the plunger  10 / 60  returns to the low pressure chamber  12 / 62 , a vacuum is created in the high pressure chamber  14 / 64 . This vacuum draws new working fluid into the high pressure chamber  14 / 64 , preparing it for the next cycle. The plunger  10 / 60  is wiped during each stroke to prevent abrasive material from accumulating on the plunger  10 / 60  wall, instead pushing the abrasive material back into suspension, to be pumped through on the next stroke. 
         [0024]    The surge chambers  6 / 8 , when installed, work to buffer/decrease pressure fluctuations in the low pressure chambers  12 / 62 . When the plunger  10 / 60  is returning to the low pressure chamber  12 / 62 , working fluid must be displaced to make room for the volume of the plunger  10 / 60 . The working fluid will either move out one of the inlets  101 / 102 , or into the surge chambers  6 / 8 . Either way, when the plunger  10 / 60  moves out of the low pressure chamber  12 / 62 , the working fluid will be pulled into the low pressure chamber  12 / 62  to fill the space left by the plunger  10 / 60 . Whether or not surge chambers are appropriate for use depends on the service of the pump and the type/properties of working fluid. 
         [0025]    The pressurized fluid is discharged past valves  18 / 68  and through the discharge  106 . Plugs  120 / 121  are present to allow the check valves  18 / 68  to be cleaned out. 
         [0026]    Referring now to  FIGS. 3 and 4 , a side view of the pump is shown. The pump has multiple input locations that are selected based on service and orientation. The use of dual plungers created a filling problem, solved in the dual plunger pump  1  by the use of specific inlets for certain orientations. In  FIGS. 3 &amp; 4 , an alternative inlet  102  is shown. In this example, the pump is used in a vertical orientation. In other embodiments the vertical inlet  101  is used. In still other embodiments, inlets are present in other locations, such as the distal portion of the housing. 
         [0027]    When the pump is in a horizontal orientation, filling through the alternate inlet  102  provides fluid to both the low pressure chambers  12 / 62  equally. In contrast, when the pump is orientated vertically as shown in  FIG. 4 , using the alternative inlet  102  fills distal low pressure chamber  62  first, but traps air within the dual plunger pump  1 , preventing proximal low pressure chamber  12  from filling. Therefore, a vertical inlet  101  is provided for vertical orientations. To use the vertical inlet  101 , the alternative inlet  102  is plugged/blocked and the pump is filled through vertical inlet  101 . When in a vertical orientation, fluid is introduced through the vertical input location  101 , passing through the proximal low pressure chamber  12 , into the inlet jumper  104 , and finally into the distal low pressure chamber  62 . When the pump is then started, both low pressure chambers  12 / 62  are filled with fluid and pumping of the fluid starts immediately, rather than having only one low pressure chamber  12 / 62  pumping fluid and the other low pressure chamber  12 / 62  only partially full. Starting the dual plunger pump  1  with both chambers full minimizes the presence of air in the discharge. 
         [0028]    Referring now to  FIG. 5 , a larger view of the center seals is shown. There are two primary sets of seals  30 / 80 / 32 / 82 . One set of seals, the fluid seals  30 / 80  keeps the pressure from the high pressure chambers  14 / 64  from leaking into the area surrounding the bearing  110 , or from one chamber  14 / 64  to the other chamber  14 / 64 . Supporting the shaft center portion  123  is a bearing  110 . In this embodiment the bearing  110  is a plain bearing (friction bearing) lubricated with oil. Oil is provided by the oil reservoir  112 . The second set of seals is the oil seals  32 / 82  that prevent the oil from leaving the area surrounding the bearing  110 , thereby reducing oil use and contamination of the working fluid. 
         [0029]    In this example the seals  30 / 32 / 80 / 82  are U-shaped, with an internal spring, known as spring energized seals. The internal spring preloads the seals  30 / 32 / 80 / 82 , providing some level of sealing even in the absence of pressure. The open portion of the U shape of the seals  30 / 32 / 80 / 82  faces toward the high pressure side of the seal  30 / 32 / 80 / 82 . This allows the fluid pressure to press against the inside of the seals  30 / 32 / 80 / 82 , forcing the outside of the seals  30 / 32 / 80 / 82  against the adjacent surfaces, creating a tight seal that becomes even tighter as pressure increases. In other embodiments the seals  30 / 32 / 80 / 82  are dynamic o-rings, o-ring energized seals, or o-ring seals. 
         [0030]    The bearings are held in cartridges  36 / 86 , which are sealed to the pump housing by seals  34 / 84 . In this embodiment the seals  34 / 84  are static o-rings, but in other embodiments other types of seal are employed as known in the art. 
         [0031]    Dual plunger pump  1  is well suited for use with viscous fluids, such as epoxy resins. The Dual plunger pump  1  is also well suited for use with coatings that cure or have fillers that collect in crevices, making pump service and repair difficult. The use of such materials can lead to difficulties when the dual plunger pump  1  needs cleaning, seal replacement, or general maintenance. The cartridges  36 / 86  lay in the bottom of their respective high pressure chambers  14 / 64  and are sometimes difficult to remove. Alternate embodiments of the dual plunger pump  1  include a break in the pump housing  100  near the cartridges  36 / 86  to facilitate removal of cartridge  36 / 86 . In other embodiments, the portion of the housing  100  between the cartridges  36 / 86  is removable, allowing the cartridges  36 / 86  to be pushed out of the pump housing  100 , such as through use of a wooden block and a hammer. 
         [0032]    Referring now to  FIG. 6 , a close up of a single plunger  60  with its associated components is shown. The seal  90  is shown, next to the guide  92 . The plunger  60  is only supported on one end and the guide  92  serves as a centering device, helping the plunger  60  to meet the seal  90  while centered. The beveled sides of the guide  92  allow the plunger  60  to be pushed back toward center as part of the discharge stroke. In some embodiments, the guide  92  is missing, with the seal  90  being able to compensate for an off-center plunger  60  by either having sufficient stiffness to center the plunger  60  or sufficient flexibility to seal despite the plunger  60  being off-center. 
         [0033]    Referring now to  FIGS. 1-6 , the pump overall will be described. The dual plunger pump  1  provides almost a continuous flow of fluid by having two plungers  10 / 60  with associated low and high pressure chambers  12 / 62 / 14 / 64 . The arrangement of plungers  10 / 60  in the dual plunger pump  1  results in a need for additional seals  30 / 32 / 34 / 80 / 82 / 84 . The penetration  3  into the proximal low pressure chamber  12  is sealed with a bellows  130 . The center of the pump separates the two high pressure chambers  14 / 64  using cartridges  36 / 86  with seals  30 / 32 / 34 / 80 / 82 / 84 , as discussed above. 
         [0034]    The bellows  130  is a pressure barrier between the outside of the pump, assumed to be at atmospheric pressure (though there is no reason the pump could not operate surrounded by a higher or lower pressure), and the pressure within the low pressure chambers  12 / 62  varying, often below atmospheric pressure (i.e., a slight vacuum). When a transfer pump is used (such as to pull material out of a barrel) the pressure within the low pressure chambers  12 / 62  is greater, though generally no higher than 15 psig. The proximal end of the bellows  130  is sealed by compression between the upper sealing ring  5  and the pump housing  100 . The distal end of the bellows  130  is sealed by compression between the proximal shaft section  126  and proximal plunger  10 . The bellows  130  is sized to avoid rubbing against the proximal shaft section  126  or the sides of penetration  3  through pump housing  100 . The upper sealing ring  5  attaches to the pump housing  100  in numerous possible ways, including threading into the pump housing  100 , or by having a flanged connection and bolted to the pump housing  100 , or any other means of attachment as known in the art. 
         [0035]    Because the center of the shaft requires support to remain coaxial with the low and high pressure chambers  12 / 62 / 14 / 64 , a bearing  110  is included, with associated oil reservoir  112  and seals  32 / 82 . As discussed, the oil reservoir  112  provides oil to the bearing area, keeping the bearing  110  lubricated, as well as the shaft center portion  123 . The oiled portion extends away from the bearing in both directions, with oil being wiped from the shaft center portion  123  by the seals  32 / 82 . 
         [0036]    The dual plunger pump  1  has two modes of operation. In one mode both chambers  12 / 62  are fed the same fluid. In the other mode each chamber  12 / 62  is fed a different fluid. When both chambers are fed the same fluid, the output flow is substantially continuous, only ebbing when the shaft  123 / 124 / 126  changes direction. 
         [0037]    In the continuous discharge mode, the dual plunger pump  1  makes nearly continuous discharge possible by using two plungers, and opposing their strokes. When the proximal plunger  10  is filling with fluid, the distal plunger  60  is discharging fluid. The directions then reverse, with the distal plunger  60  filling with fluid and the proximal plunger  10  discharging fluid. There is a slight lag between the two motions as directions change and the plunger  10 / 60  about to pump approaches its seal  40 / 90 . But with the exception of this lag, this arrangement creates a nearly continuous discharge. 
         [0038]    When the dual plunger pump  1  is used to pump two different fluids, some changes are required from the current example. The inlet jumper  104  is removed and replaced with two individual connections, one to each low pressure chamber  12 / 62 . The discharge manifold  108  is removed and replaced with two individual discharge manifolds, each manifold including its own check valve  18 / 68  and discharge connection. 
         [0039]    While there are many benefits to the dual plunger pump  1 , specific benefits are seen in certain applications. In applications where there are two fluids, here called Fluid A and Fluid B, it is useful to use a single dual plunger pump  1  to pump Fluid A, and attach small pump to the opposite side of the driver. The small pump then pumps some percentage of Fluid B, resulting in the proper mix of the two fluids. Or for other applications where the mix ratio of Fluid A and Fluid B is  1 : 1 , a dual plunger pump  1  is installed on each side of a driver, allowing one driver to power two dual plunger pumps. 
         [0040]    Referring now to  FIGS. 1-6 , assembly of the dual plunger pump  1  will be described. The moving portion of the dual plunger pump  1  consists of the air motor attachment point  2 , proximal shaft section  126 , proximal plunger  10 , threaded rod  124 , shaft center portion  123 , and distal plunger  60 . In this embodiment the distal plunger  60  is held to the shaft center portion  123  by a threaded bolt  122 . Proximal shaft section  126  penetrates the proximal plunger  10 , compressing the proximal plunger  10  between proximal shaft section  126  and shaft center portion  123 . In some embodiments the shafts  126 / 124 / 123  are threaded into one another, and the plungers  10 / 60 . In other embodiments they are press fit (interference fit), or attached using any other means of attachment as known in the art. In still other embodiments, the plungers  10 / 60  and shafts  126 / 124 / 123  are machined as a single piece. 
         [0041]    The dual plunger pump  1  is shown with the low pressure chambers  12 / 62  near the ends, and the high pressure chambers  14 / 34  near the center. This is not a requirement; rather, the dual plunger pump  1  functions with the low pressure chambers  12 / 62  near the center and the high pressure chambers  14 / 64  near the ends. In this modified design, many associated parts are be relocated, as known in the art, as needed to accommodate the new locations. Notwithstanding, the modified dual plunger pump  1  operates as described above. 
         [0042]    Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
         [0043]    It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.