Patent Publication Number: US-2006018776-A1

Title: Piston pump

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Application No. 60/583,097 filed on Jun. 25, 2004. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to piston pumps. More specifically, this invention relates to piston pumps for use in removing subterraneous liquids, from the ground such as landfill and ground water clean-up sites.  
     BACKGROUND OF THE INVENTION  
      Increased monitoring of environmental quality has resulted in a substantial rise in the number of identified sites of contaminated ground water. Accompanying this trend has been an increased effort to clean up these sites. In response, there is a need for improved below ground pumping systems to assist in these clean up efforts.  
      Ideally, below ground pumping systems used for these purposes will have a number of desired characteristics. Because of the large number of pumping systems required, it is desirable to minimize the cost of each pump and each installation. Accordingly, such pumps should be relatively simple and inexpensive and should fit in a small diameter well due to the increased cost of drilling large diameter wells. To minimize maintenance and repair costs, the pumps should have a minimum of moving parts and should have high reliability. Also, such pumps should be able to withstand corrosive fluid streams without failure.  
      In addition to the problems with the actuating mechanism, the pneumatic valve used to control the flow of compressed air into these pumps, have often proved unreliable. Spool type valves incorporating sliding seals are generally used in prior art pumps of this nature. The force necessary to move these sliding seals to actuate spool type valves are one source of the excess actuating force requiring the above mentioned large and heavy floats. In addition, spool type valves result in high maintenance and repair costs due to their tendency to freeze or to leak.  
      There are a number of causes of the difficulties with sliding seals. These include debris entering the seals from the source of compressed air; contamination of the seals from the liquid being pumped (especially where highly corrosive waste products are pumped); loss of lubrication in the seals; and compression set of the elastomeric seals if they remain inactive for an extended period of time.  
      Another difficulty with sliding seals results from their use to provide a detent action between the discharge and refill cycles of the valve. As the sliding seals wear, the ability of these sliding seals to provide a detent action will be lost. The sliding seals are normally comprised of o-rings and the wear of these o-rings will result in short and erratic pump cycles unless the o-rings are replaced.  
      Thus, it would be desirable to provide an underground pneumatic piston driven pumping system which overcomes some or all of the above mentioned difficulties.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the present invention to provide a piston pump having a reversing air cylinder driving piston pump, for use at landfills and ground water contamination clean-up sites utilizing internal reversing components in place of multiple external industrial control valves and connecting tubing, all subject to weather damage.  
      Another object of the present invention is to provide a piston pump having a reversing air valve with controlled rate descent of the drive-rod, wherein the internal air valving in the air cylinder reversing assembly is sized so that the piston descends more slowly preventing excess wear and damage.  
      A further object of the present invention is to provide a piston pump having an epoxy piston drive-rod resin versus polyester, yielding longer service life because it is less prone to splintering and fracture than conventionally used fiberglass-reinforced polyester rods.  
      A further object of the present invention is to provide a piston pump having a poly-coated drive rod for friction and wear reduction, instead of the conventional uncoated fiberglass-reinforced polyester rods used in other piston pump designs. The lubricity and resistance to abrasion of the coating, such as ultra-high molecular weight polyethylene (UHMW) or polypropylene, is superior to the uncoated fiberglass-reinforced polyester in terms of less wear and damage on the surrounding pump casing.  
      The lower friction coating also causes less resistance to movement and therefore lower loads on the pump rod drive mechanism, especially in wells not straight and/or vertical. The coating also prevents the onset of drive rod splintering initiated by surface abrasion.  
      A further object of the present invention is to provide a piston pump having long drive rod connector which distributes the gripping load over a much greater rod area. This provides a stronger grip less likely to pull out or to fracture or damage the rod surface. The standard, short ferrule compression nut fittings conventionally used concentrate the ferrule contact in a very small area, and have been prone to failure, especially with the higher drive rod loads found in deeper wells.  
      Another object of the present invention is to provide a piston pump having replaceable check valve seats and balls in the piston and foot valves, constructed of metal (preferably stainless steel) instead of plastic.  
      A further object of the present invention is to provide a piston pump having a special wobble-connection joint used in the piston rod drive mechanism to allow slight sidewards movement between two rigid sections of the drive mechanism. The freedom to allow slight sidewards movement avoids having the entire drive shaft being a rigid assembly, which is hard to align perfectly with all of the bushings and air and liquid seal elements along such a drive shaft. The slight flexure in the shaft thereby allowed greatly reduces the wear and leakage in critical bushings and seals otherwise caused by non-linearities along an extended length rigid drive shaft assembly.  
      Another object of the present invention is to provide a piston pump having a piston seal arrangement including a downward facing scraper element at the bottom of the piston, to exclude grit and abrasive solids at the bottom of the pump casing from migrating upward and prematurely wearing out the upward facing piston seals. The scraper is similar to a seal but is constructed of more abrasion-resistant materials such as HDPE than most seals, and is not intended to serve as a leak prevention seal keeping the pumped liquid from moving downward past the piston.  
      Finally, it is an object of the present invention is to provide a piston pump having an all-metal or all plastic piston without elastomeric seals. Such pistons can provide a much longer service life between pump maintenance events compared to that of pistons with elastomeric seals, especially when abrasive solids are present in the pumped liquids.  
      These objects and others are achieved in a piston pump comprising generally of a piston and a foot valve. A pneumatic driver slides the piston assembly up and down inside the foot valve assembly, which is connected to the driver by means of a drive shaft coupled to the piston assembly by means of a polypropylene coated epoxy resin based rod. On the upward stroke the foot valve opens and lets water enter the volume below the piston assembly and the piston assembly check valve is closed and lifts the column of water. On the down stroke the foot valve closes, holding the column of water and the piston check valve opens, allowing the water to pass through to recharge the cylinder for the next lift cycle.  
      Leakage of the pumped liquid downward past the piston is prevented by the tight diametral clearance between the piston and the cylinder it operates within, such as less than 0.010 inches total diametral clearance. Oil well piston pumps use this feature but it has not been applied to piston pumps used at landfills and ground water clean-up sites, because the longer service life advantages of the all-metal pistons and plastic pistons without seals have not been understood or appreciated, and an economical design for providing a close diametrical clearance had not been developed.  
      Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
       FIG. 1A  is a disassembled side view of the piston pump assembly;  
       FIG. 1B  is a side view of the lower elements of the piston pump assembly of the present invention;  
       FIG. 1C  is a cross-sectional side view of the piston pump assembly of  FIG. 1B  taken along Line  1 C;  
       FIG. 1D  is a disassembled side view of the piston pump assembly of  FIGS. 1B and 1C ;  
       FIG. 2A  is a side view of the foot valve and piston housing of the piston pump assembly of the present invention;  
       FIG. 2B  is a cross-sectional side view of the foot valve and piston housing of  FIG. 2A  taken along Line  2 B;  
       FIG. 2C  is a disassembled side view of the foot valve and piston housing of  FIGS. 2A and 2B ;  
       FIG. 3A  is a side view of the piston of the piston pump assembly of the present invention;  
       FIG. 3B  is a cross-sectional side view of the piston of  FIG. 3A  taken along line  3 B;  
       FIG. 3C  is a disassembled side view of the piston of  FIGS. 3A and 3B ;  
       FIG. 4  is an exploded perspective view of the piston driver assembly of the piston pump of the present invention;  
       FIG. 5A  is a side view of the piston driver assembly extended housing of the piston pump assembly;  
       FIG. 5B  is a cross-sectional side view of the piston driver assembly extended housing of  FIG. 5A  taken along line  5 B;  
       FIG. 5C  is a disassembled side view of the piston driver assembly extended housing of  FIGS. 5A and 5B ;  
       FIG. 6A  is a side view of the lower termination fitting of the piston pump assembly of the present invention;  
       FIG. 6B  is a cross-sectional side view of the lower termination fitting of  FIG. 6A  taken along line  6 B;  
       FIG. 6C  is a disassembled side view of the lower termination fitting of  FIGS. 6A and 6B ;  
       FIG. 7A  is a side view of the air cylinder reversing assembly of the present invention;  
       FIG. 7B  is a cross-sectional side view of the air cylinder reversing assembly of  FIG. 7A  taken along line  7 B; and  
       FIG. 7C  is a disassembled side view of the air cylinder reversing assembly of  FIGS. 7A and 7B . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. The piston pump of the present invention consists of a piston and a foot valve. In a preferred embodiment the piston is manufactured to have a outside diameter of 1 and ¾ inches, but the scope of the present invention is intended to cover a piston pump having a piston of any reasonable diameter.  
      A pneumatic driver slides the piston assembly up and down inside the foot valve assembly, which is connected to the driver by means of a stationary length of pipe. The drive shaft of the pneumatic driver is connected to the piston assembly by means of a polypropylene coated epoxy resin based rod. On the upward stroke the foot valve opens and lets water enter the volume below the piston assembly and the piston assembly check valve is closed and lifts the column of water. On the down stroke the foot valve closes holding the column of water and the piston check valve open, and allows the water to pass through to recharge the cylinder for the next lift cycle.  
      Referring now to the drawings,  FIG. 1A  shows a general illustration of the piston pump assembly  10  components. Specifically, and discussed individually hereon, the pump assembly  10  comprises a reversing pneumatic valve assembly  130  attached to a piston shaft inside the air cylinder body  120 . Sealed at a upper end by the air cylinder cap  103 , and reinforced by a plurality of threaded rods  106 . A lower termination fitting  110  is positioned below the cylinder body  120 , and attaches journally to the drive shaft housing  121 . The piston shaft attaches to a driveshaft  118  by means of a wobble joint  117 , and the lower end of the driveshaft  118  attaches to a male adapter  119  which is received by the piston assembly described and illustrated in the latter figures.  
      Illustrated in  FIGS. 1B-1D , the lower assemblage of the piston pump assembly  10  is shown. Shown in  FIGS. 1B and 1C , the lower portion of piston pump assembly  10  comprises a foot valve assembly  30 , a slotted screen  20 , and a piston assembly  40 . As previously stated, the preferred embodiment of the present invention is manufactured in two sizes, but can be applied to a piston pump having variable diameter pistons, and since the manufacture and assembly process of the different sized piston pump assemblies is identical, for the purpose of simplification, it will herein simply be referred to as piston pump assembly  10 .  
      The foot valve assembly  30 , and slotted screen  20  are manufactured out of PVC or any suitable material wherein the piston assembly  40  may be manufactured either out of PVC or of corrosion resistant stainless steel, though the scope of the present invention is intended to cover other suitable manufacturing materials known in the art.  
       FIGS. 2A-2C  show a more detailed illustration of the foot valve assembly  30 , having a cylindrical body  31 , with an upper pump attaching coupler  33  and a lower foot valve housing  35  shown attached there to. Resilient o-rings  34  are disposed between the cylindrical body  31  and the upper pump attaching coupler  33  as well as between the cylindrical body  31  and the lower foot valve housing  35 , there by sealing the assembly from leakage. A stainless steel inner sleeve  32  is received within the cylindrical body, for support of the piston assembly  40  shown in detail in  FIGS. 3A-3C .  
      The lower foot valve housing  35  is generally cylindrical in shape and comprises an inner bore for containing a stainless steel ball  36 , which provides the valve actuating means against valve seat  38  when in operation. An additional resilient o-ring seal  37  is positioned around the valve seat  38  for sealing the valve housing  35  to the subsequently attached screen adapter  39 , which provides a connecting means for attaching the slotted screen  20  of  FIGS. 1B-1D  to the foot valve assembly  30 , for preventing large particulate latter from entering the pump assembly during operation.  
      Referring now to  FIGS. 3A-3C , the piston assembly  40  is shown. As mentioned, the piston assembly  40  may be manufactured out of either stainless steel or PVC, and is slidably received within the inner sleeve  32  of the foot valve assembly  30  as shown in illustration  1 C. The inner sleeve  32  is electroless nickel plated to improve wear characteristics. The piston assembly  40  comprises a generally hollow cylindrical piston body  41  having a passage there through for allowing the pumped fluid to migrate from a position below the piston assembly  40  during an up-stroke of the pump assembly  10  to a position above the piston assembly  40  during a down-stroke by way of the piston head  47  when the check valve ball  45  is in a bypass position relative to the valve seat  43 . Resilient o-ring  44  is disposed in a annular groove around valve seat  43  providing a seal between the piston body  41  and the piston head  47 .  
      The piston head  47  is generally hollow, having an inner bore for slidably receiving the check valve ball  45  there within, and further comprises a plurality of radial fluid passages for allowing the pumped fluid to migrate from the passage within the piston body  41  around the check valve ball  45  to within the valve assembly  30  above the piston assembly  40 . A stainless steel threaded fastener  46  is threaded through an aperture in the upper end of the piston head  47  and receives jam nut  48 , and piston rod adapter  49 , which in turn attaches to and receives piston rod connector  50 . The check valve ball  45  is limited in its longitudinal movement within the piston head  47  by the valve seat  43  and threaded fastener  46 .  
      A plurality of resilient cup seals  42 , are received in corresponding circumfrential annular grooves disposed on the outer diameter of the piston body  41 , for sealing the piston assembly  40  against the inner sleeve  32  of the foot valve assembly as shown in  FIG. 1C . Alternatively, the piston assembly  40  is manufactured to a diametral clearance of less than 0.010 inches with the inside diameter of the inner sleeve  32 , thereby eliminating the need for additional seals. A distal scraper seal  51  is disposed at the lower end of the piston body  41  before the plug  52  is threadably received within a corresponding threaded bore in the distal end of the piston body  41 .  
      Turning now to  FIG. 4 , an exploded view of the piston driver  100  of the piston pump assembly  10  is shown. The piston driver  100  provides the pneumatic force upon the piston assembly  40  described above by means of the piston shaft  111  which extends downward through the lower termination fitting  110  where it connects by means of a wobble joint at end  113  to a drive shaft not shown having a specific length dependant upon the pumping application which in turn connects with the piston rod connector  50  shown in  FIG. 3C .  
      In addition to the above elements, The piston drive pump comprises an air cylinder body  120  which slidably contains the reversing pneumatic valve assembly  130  attached to the upper end of the piston shaft  111  there within and forms a sealable air chamber when sealingly adjoined at the lower end of the cylinder with the lower termination fitting  110 , and sealingly adjoined at the upper end of the cylinder to the air cylinder cap  103 . The air cylinder cap  103  has a limiting cone spring  104  attached to the inner surface to prevent damage in the event of over extension of the valve assembly  130 . A plurality of threaded rods  106  spaced around the outside of the air cylinder body  120 , and running the length there of are threaded at one end into corresponding threaded, receiving apertures on the lower termination fitting  110  and threaded through corresponding apertures in the air cylinder cap  103  and secured using threaded fasteners  101  and washers  102 , thereby securing the piston driver  100  assembly together.  
      The reversing pneumatic valve assembly  130  acts to control the compressed air for the upward or downward stroke, and attached to an upper surface there of is a counter magnet  108 , attached to the valve assembly  130  by means of fasteners  109 . This magnet activates the stroke counter  105  attached to the outside of the air cylinder body  120  by means of clamp  107  at a specified position along the cylinder&#39;s length. The counter  105  tabulates the number of strokes the valve assembly makes within the cylinder by means of the counter magnet  108  attached thereto.  
      Referring to  FIG. 5A-5C , the driveshaft housing  121  is shown in detail. The driveshaft housing provides support and protection for the driveshaft connected to the piston shaft  111  through the wobble joint which allows slight sideways movement between the two rigid sections of the drive mechanism. The freedom to allow slight sidewards movement avoids having the entire driveshaft assembly to be a single rigid piece, which makes perfect alignment with the plurality of bushings air seals and liquid seals along the length of the driveshaft very difficult. By utilizing a wobble joint, slight flexure in the shaft is allowed which greatly reduces the wear and leakage in critical bushings and seals otherwise caused by nonlinearities along an extended length rigid drive shaft assembly.  
      The seals of particular concern with otherwise rigid driveshaft assemblies can be seen in detail in  FIG. 5C , comprising a stainless steel spacer  123 , a resilient o-ring  124 , a U-cup seal  125 , followed by a drive shaft bushing  122 , Installed in the inner bore of the upper end of the drive shaft housing. At the lower end of the housing  121  a similar assembly is located, comprising a second drive shaft bushing  122 , U-cup seal  125 , o-ring  124 , U-cup seal holder  126 , a third U-cup seal  125 , o-ring  128 , end cap  127 , and urethane scraper seal  129 , all through which the drive shaft penetrates, to seal and support it through it&#39;s pumping oscillations.  
      The scraper seal  129  is unique in this aspect, in that it is embodied to exclude grit and abrasive solids which may be present adjacent the pump assembly from migrating upward and prematurely wearing out the seals. The scraper seal  129  is constructed of a more abrasion-resistant material than the other shaft seals such as HDPE and is not intended to serve as a leak prevention seal.  
       FIGS. 6A through 6C  illustrate the lower termination fitting  110  shown in  FIG. 4 . The lower termination fitting  110  comprises a generally cylindrical tube with having an upper end for journally attaching to the air cylinder body  120 , a lower end for journally attaching to the driveshaft housing  121 , and a through bore there between. The lower end of the through bore attached to the drive shaft by means of the flexible mechanical wobble joint described above, but not shown in  FIGS. 6A through 6C . At the upper end of the housing  110 , a compression spring  116 , housing spacer  115  piston shaft bushing  114  and U-cup seal  117  are positioned within the through bore for sealing and supporting the piston shaft, while a o-ring  112  is positioned in an annular grove around the upper end of the housing  110 , forming a seal when journally connected to the air cylinder body  120 .  
      Referring now to  FIGS. 7A through 7C , the reversing pneumatic valve assembly  130  is shown. This valve assembly  130  controls the compressed air used to drive the pump system for the upwards or downwards stroke, and contains a combination of poppet style pneumatic valves and springs. This further provides for a controlled rate decent of the drive rod, prolonging piston and seal wear.  FIG. 7C  illustrates a detailed assembly of the reversing air valve assembly  130 , comprising the connecter reversing pinion  131 , having a connector washer  132  and o-ring seal  133  disposed annularly around the lower connecting portion thereof. Positioned on the upper end of pinion  131 , an additional o-ring  135 , followed by the impactor  134 , formed of stainless steel. The impactor  134  has a plurality of spaced threaded apertures positioned concentrically around the center, for receiving assembly screws  142  threaded through the standoff sleeves  140  and o-rings  139  holding the entire assembly together.  
      Positioned between the valve assembly poppet cap  141 , and the impactor  134 , is a wear ring  138 , the actual piston  136 , and plural cup seals  137  positioned around the piston for sealing the piston  136  of the valve assembly within the air cylinder body  120 .  
      The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.