Patent Publication Number: US-2005142012-A1

Title: Rodder pump

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
      This application claims the benefit of U.S. Provisional Patent Application No. 60/525,349, filed Nov. 26, 2003, the entire disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION  
      This invention relates in general to a reciprocating pump driven by pressurized fluid from a hydraulic pump and more particularly to a closed-loop, hydraulically-driven rodder pump.  
     BACKGROUND OF THE INVENTION  
      Heretofore vacuum cleaning of catch basins and flushing of sewer pipes has required the use of at least two separate vehicles. A first vehicle with a hose reel mounted on the rear end thereof was positioned at the manhole and a high pressure hose fitted with a jet nozzle was introduced into the sewer. Water from a tank on the vehicle was pumped through the hose at pressures at about 1,000 pounds per square inch to drive the hose through the pipe against the water flow. Pressure drops along the hose length were considerable and at 400 feet, available pressures were only about 600 to 800 pounds per square inch. Debris flushed from the sewer pipe was then sucked out of the catch basin by a second follow-up vehicle. This multiple vehicle system duplicated personnel and the rear mounted hose reel exposed the personnel to traffic hazards.  
      A single vehicle for vacuum cleaning of catch basins and flushing of sewer pipes with water surged through a hose and nozzle at pressures of about 2,000-3,000 pounds per square inch is known, an example being disclosed and described in U.S. Pat. No. 3,658,589, entitled, “Catch Basin And Sewer Pipe Cleaner.” Such a vehicle is typically provided with a pump to deliver water at operating pressure for cleaning the catch basins and sewer pipes. An engine-driven oil pump, located either on the vehicle or remotely therefrom, can hydraulically drive the pump.  
     SUMMARY OF THE INVENTION  
      The invention provides a closed-loop, hydraulically-driven rodder pump. The pump of the present invention seeks to improve upon the piston pump shown and described in U.S. Pat. No. 3,700,360, entitled, “Double-Acting Tandem Piston Pump,” which is incorporated herein by this reference in its entirety.  
      The present invention can be used in a vehicle for cleaning sewer pipes and catch basins by the use of water pressure and the carrying power of moving air. In one embodiment, a combined catch basin and sewer pipe cleaning vehicle includes a large debris collecting dump body from which air is continuously pulled by an engine driven fan on the vehicle and easily opened for dumping. The vehicle also has a separate water tank, a reciprocating water pump driven by pressurized oil from a vehicle engine-driven hydraulic pump, and a reeled high pressure hose with a self-propelling jet nozzle receiving surges of high pressure water from the water pump, which can be in the form of a closed-loop, hydraulically-driven rodder pump. In other embodiments, the rodder pump of the present invention can be used in other vehicles, such as, hydroexcavaters, for example.  
      In one aspect of the invention, a pair of single cylinder reciprocating rodder pumps can be provided in a closed loop system. In yet another embodiment, a single rodder pump having a dual-acting cylinder assembly can be provided in a closed loop system.  
      These and other features of the present invention will become apparent to one of ordinary skill in the art upon reading the detailed description, in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of an embodiment of a pump according to the present invention.  
       FIG. 2  is a front elevational view of the pump of  FIG. 1 .  
       FIG. 3  is an enlarged detailed view taken from  FIG. 2  of the pump of  FIG. 1 .  
       FIG. 4  is an enlarged detailed view taken from  FIG. 2  of the pump of  FIG. 1 .  
       FIG. 5  is an enlarged detailed view taken from  FIG. 2  of the pump of  FIG. 1 .  
       FIG. 6  is a first end view of the pump of  FIG. 1 .  
       FIG. 7  is a second end view of the pump of  FIG. 1 .  
       FIG. 8  is a diagrammatic view of an input circuit for a pair of pumps as shown in  FIG. 1 , which is configured as a deintensifier circuit.  
       FIG. 9  is a perspective view of another embodiment of a pump according to the present invention.  
       FIG. 10  is a perspective view of a cylinder assembly of the pump of  FIG. 9 .  
       FIG. 11  is a front side elevational view, partially in section, of the pump of  FIG. 9 .  
       FIG. 12  is a fragmentary top view of the pump of  FIG. 9 .  
       FIG. 13  is an enlarged detailed view taken from  FIG. 11  of the pump of  FIG. 9 .  
       FIG. 14  is a bottom view, partially in section, of the pump of  FIG. 9 .  
       FIG. 15  is an enlarged detailed view taken from  FIG. 14  of the pump of  FIG. 9 .  
       FIG. 16  is an end view of the pump of  FIG. 9 .  
       FIG. 17  is a cross-sectional view taken along line  17 - 17  in  FIG. 11  of the pump of  FIG. 9 .  
       FIG. 18  is a cross-sectional view taken along line  18 - 18  in  FIG. 14  of the pump of  FIG. 9 .  
       FIG. 19  is a cross-sectional view taken along line  19 - 19  in  FIG. 14  of the pump of  FIG. 9 .  
       FIG. 20  is a cross-sectional view taken along line  20 - 20  in  FIG. 14  of the pump of  FIG. 9 .  
       FIG. 21  is a cross-sectional view of a check valve suitable for use with the pump of the present invention.  
       FIG. 22  is a diagrammatic view of an input circuit which includes the pump of  FIG. 9 .  
       FIG. 23  is a side elevational view of a vehicle for cleaning sewer pipes and catch basins that includes a pump according to the present invention.  
       FIG. 24  is a somewhat schematic perspective view, partially in section, of another embodiment of a rodder pump according to the present invention having a dual-acting cylinder. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION  
      Referring to  FIGS. 1-7 , an embodiment of a pump  50  according to the present invention is shown that includes a single acting cylinder  52  (see  FIG. 2 ). Referring to  FIG. 1 , the pump  50  includes first and second tube assemblies  54 ,  56 . The first tube assembly  54  has a butt fitting  58  mounted thereto at a first end  59  thereof. The butt fitting  58  can include a first hydraulic port  60 . Disposed at the other end  61  of the first tube assembly  54  is a gland assembly  62 . The second tube assembly  56  can have a pair of flanges  64 ,  65  disposed at the respective ends thereof. The first and second tube assemblies  54 ,  56  can be mounted together by a tie rod assembly  68 , which can comprise a plurality of tie rods  69  extending through the butt fitting  58 , the gland assembly  62 , and the first flange  64  of the second tube assembly  56  and a plurality of bolts  70  threadedly engaged with the tie rods  69  to retain the first and second tube assemblies  54 ,  56  in substantially fixed relationship relative to each other.  
      The first tube assembly  54  can include a second hydraulic port  78  disposed adjacent the second end  61  thereof and a pair of sensor ports  82 ,  83  disposed respectively adjacent the first and second ends  59 ,  61  of the first tube assembly  54 . The sensor ports  82 ,  83  can each be sized to respectively accommodate a sensor configured to detect the presence of the cylinder when it is in proximity thereto. The first hydraulic port  60  can be configured as a No. 16 SAE port, for example, and the second hydraulic port  78  can be configured as a No. 8 SAE port, for example. The second tube assembly  56  can include a fluid port  86  in the second flange  65  disposed in axial alignment with the tube portion thereof.  
      Referring to  FIG. 2 , the cylinder assembly  52  is disposed within the first tube assembly  54  and is reciprocally movable over a discharge stroke, when moving in a discharge direction  88 , and over a suction stroke, when moving in a charge direction  89 . The cylinder assembly  52  can include a plunger  90  having a large diameter section  92  and a small diameter section  94 , a piston portion  96  mounted to the plunger  90  via a lock nut  98  which is threadedly engaged with the small diameter section  94  of the plunger  90 . The cylinder assembly  52  is shown in  FIG. 2  in a discharge or power position wherein the cylinder assembly is ready to discharge fluid from the fluid port  86  through a pressure stroke. The piston portion  96  is in sealing contact with an interior surface  99  of the first tube  54 . The plunger  90  extends through an opening  100  defined by the gland  62  and the first flange  64  such that at least a portion of the plunger  92  is disposed within the second tube assembly  56 . The plunger  90  is in sealing contact with the gland  62 .  
      Referring to  FIG. 3 , the first port  60  is in fluid communication with the interior of the first tube assembly  54 . The butt fitting  58  can include a circumferential groove  104  which can receive a back-up washer  106  and an O-ring seal  108  to provide a sealed connection between the butt fitting  58  and the first tube.  
      Referring to  FIG. 4 , the first sensor port  82  can be configured to receive a suitable sensor therein, such as a Hall effect sensor, for detecting the position of the cylinder assembly. The sensor port  82  can include a back-up washer  110  and an O-ring seal  112  therein for sealingly engaging the sensor  109  inserted therein. The sensor can detect when the piston portion  96  is proximate the first sensor port and send a control signal to a controller to operate various valves in response to the position of the cylinder assembly. The sensor can be electrically connected to the controller via an electrical wire, for example. When the piston portion  96  is proximate the first sensor port  82 , the cylinder assembly is in a discharge position and is ready to undergo the pressure stroke. In some embodiments, the sensor can be a magnetic field sensor, such as one commercially available from Balluf Inc. of Florence, Ky., including one of the sensors designated under the series BMF 32M, including, for example, the sensor referenced with part number BMF-32M-PS-C-2-S49, for example.  
      Referring to  FIG. 2 , the second sensor port  83  can sealingly house a similar sensor. The second sensor port  83  is disposed such that it can detect when the cylinder assembly is in a charge position and is ready to undergo the suction stroke by moving in the charge direction  89 .  
      Referring to  FIG. 4 , the piston assembly  96  can include a wear ring  118  and a seal  120  made from any suitable material, such as, any suitable fluoropolymer resin sold under the Teflon® brand by E. I. duPont de Nemours and Company, for example. The wear ring  118  and the seal  120  are disposed circumferentially around the piston  96  in a pair of grooves  122 ,  124 , respectively. An O-ring  126  can be provided that is in sealing engagement with the piston assembly  96  and the small diameter section  94  of the plunger  90 , as shown in  FIG. 2 .  
      Referring to  FIG. 5 , the gland assembly  62  can include a breather  130  which communicates with the interior of the first tube assembly  54 . The gland assembly  62  can include a back-up washer  132  and an O-ring seal  134  disposed in a circumferential groove  136 . A Z-seal  140  can extend around the breather  130  and be in contacting relationship with the plunger  90 . A wiper  142  can extend from the gland assembly such that it is in contacting relationship with the plunger  90 . An O-ring seal  146  can be disposed between the gland assembly  62  and the first flange  64  of the second tube assembly.  
      Referring to  FIG. 6 , the butt fitting  58  is shown. Referring to  FIG. 7 , the second flange  65  of the second tube assembly is shown. The fluid port  86  can have a chamfered perimeter  148 . The second flange  65  can include a plurality of mounting bores  149 .  
      Referring to  FIG. 2 , to move the cylinder assembly  52  in the discharge direction  88 , hydraulic fluid can be conveyed through the first hydraulic port  60  such that it acts upon the piston portion  96  of the cylinder  52 , thereby driving the large diameter section  92  of the plunger  90  into the second tube assembly  56 . Once the piston assembly  96  is disposed adjacent the second sensor port  83 , the sensor disposed therein can detect the presence of the piston assembly and, in turn, signal the controller to cease the flow of hydraulic fluid through the first hydraulic port  60  and to initiate the flow of hydraulic fluid through the second hydraulic port  78 . The hydraulic fluid flowing through the second hydraulic port  78  can act upon the piston assembly  96  of the cylinder assembly  52 , thereby driving the cylinder assembly  52  in the charged direction to move the cylinder assembly through the section stroke. Once the piston assembly  96  is adjacent the first sensor port  82 , the sensor disposed therein can signal the controller to cease the flow of hydraulic fluid through the second hydraulic port  78  and to initiate the flow of hydraulic fluid through the first hydraulic port  60 , thereby sending the cylinder  52  in the discharge direction to travel over the pressure stroke yet again. The pump  50  can continue to operate in this sequence, reciprocating between the pressure stroke and the suction stroke.  
      Any suitable valving can be used to allow fluid, such as water, for example, to selectively enter the second tube assembly  56  via the fluid port  86  where the plunger can act upon the fluid during the pressure stroke so that pressurized fluid can exit the fluid port  86 . In some embodiments, the second tube assembly can include a pair of fluid ports, with one port for receiving fluid therethrough for delivering fluid to the pump to be acted upon by the cylinder assembly, and the other port for discharging pressurized fluid from the pump. The fluid entering the second tube assembly can be pressurized to an initial level by any suitable pump before the cylinder assembly acts upon it.  
      Referring to  FIG. 8 , an embodiment of a closed loop pump circuit  170  is shown. The pump circuit  170  is configured to have a 1:1 ratio between input and output. The pump circuit  170  can include a pair of pumps  50 ,  51  that are both similar to the pump shown in  FIG. 1 . The pumps  50 ,  51  can be fluidly connected to each other via a connecting line  172  connecting the first hydraulic ports  60  to each other. The pump circuit  170  can also include a valve package  180  and a pump and tank assembly  182 .  
      The valve package  180  can be connected to the second hydraulic ports  78  of the pumps  50 ,  51  by first and second drive lines A, B, respectively. The valve package  180  can be operated to selectively deliver hydraulic fluid to the pumps  50 ,  51  based upon the valve condition of the valve package. The valve package  180  and the sensors disposed in the first and second pumps  50 ,  51  can be electrically connected to a controller to allow the valve package to change its valve condition in response to the position of the cylinders  52  within the pumps  50 ,  51 , which positions can be communicated to the controller by the sensors. The valve package  180  can be operated to selectively drive the pumps  50 ,  51  such that the pumps operate in tandem with the cylinder assemblies  52  operating in alternating sequence. The first pump  50  can be moving through a pressure stroke while the second pump is undergoing a suction stroke and vice versa. The sensors can communicate with the valve package  180  via the controller to yield the desired operation.  
      The valve package  180  can include a directional valve  184  to direct the hydraulic fluid through one of the drive lines A, B, a pilot valve  186  connected to the directional valve  184  and to the controller, a relief valve  188 , and first and second control valves  190 ,  191  and check valves  192 ,  193  interposed between the pilot valve  186  and the directional valve  184 . The pilot valve  186  is provided to operate the directional valve  184  based upon the signals the pilot valve  186  receives from the controller. The pilot valve  186  can operate to selectively change the condition of the directional valve  184  to produce the desired operation of the pumps  50 ,  51 .  
      The pump and tank assembly  182  can include a pump  196  and a tank  198  and can include a plurality of filters.  
      In operation, hydraulic fluid can be delivered through the second drive line B to the second hydraulic port  78  of the second pump  51  whose cylinder assembly  52  moves in response thereto in the charge direction  89 . The cylinder forces hydraulic fluid in the second pump  51  out of the first port  60  thereof through the line  172  and into the first port  60  of the first pump  50 . The hydraulic fluid entering the first pump  50  acts upon the cylinder assembly  52  therein, moving the cylinder  52  in the discharge direction  88 . The cylinder assembly  52  of the first pump  50  can act upon fluid disposed in the second tube assembly thereof to drive the fluid out of the first pump  50  in a pressurized condition. When the cylinder assembly  52  of the first pump  50  reaches the end of the pressure stroke, the second sensor can sense that the piston is proximal thereto and send a signal to the controller to that effect. The controller can communicate with the pilot valve  186  to redirect the drive flow through the directional valve  184  so that hydraulic fluid runs through the first drive line A into the second port  78  of the first pump to reverse the sequence described above.  
      In another embodiment, the closed loop circuit can be arranged to be an intensifier circuit by running a connecting line  173  between the second hydraulic ports  78  of the pumps  50 ,  51  and running first and second drive lines A′, B′ to the first hydraulic ports  60  of the pumps  50 ,  51 . The intensifier ratio can be based upon the surface area of the end of the plunger in relation to the surface area of the annulus defined by the part of the piston portion of the cylinder assembly which extends radially beyond the plunger. In one embodiment, the ratio of the area of the end of the plunger to the area of the annulus of the piston is about 2:1. In yet other embodiments the intensifier ratio can be varied by changing the diameters of the annulus and/or the end surface of the plunger.  
      Referring to  FIGS. 9-20 , another embodiment of a pump  250  according to the present invention is shown. The pump  250  includes a dual-acting cylinder  252  (see  FIG. 10 ). Referring to  FIG. 9 , the pump  250  include three tube assemblies  254 ,  255 ,  256  which define a first pressure chamber, a hydraulic chamber, and a second pressure chamber, respectively. The second tube assembly  255  is disposed between the first and third tube assemblies  254 ,  256 . The first and third tube assemblies  254 ,  256  each have a butt fitting  258  mounted thereto. The second tube assembly  255  can have a gland assembly  261 ,  262  mounted at each end thereof. A tie rod assembly  268 , which includes a plurality of tie rods  269  and a plurality of bolts  270  threadedly engaged therewith, can be provided to connect the various components together. The pump  250  is a dual acting pump in that the cylinder can movably reciprocate within the tubes under the influence of a hydraulic fluid selectively entering first and second hydraulic ports  260 ,  278  in fluid communication with the hydraulic chamber defined by the second tube assembly  255  to alternatingly discharge pressurized fluid from the first and third tubes  254 ,  256 .  
      Referring to  FIG. 9 , the pump  250  can include a first sensor port  282  and a second sensor port  283 . The sensor ports  282 ,  283  can be configured to respectively accommodate a sensor that is configured to detect when the piston portion  296  is in proximity therewith. The sensors disposed in the first and second sensor ports  282 ,  283  can be electrically connected to a controller, as described above in connection with the pump  50  of  FIG. 1 , to selectively control the flow of hydraulic fluid through the first and second hydraulic ports  260 ,  278  to reciprocally move the dual-acting cylinder  252  to alternatingly discharge pressurized fluid from the first and third tubes  254 ,  256  through the butt fittings  258  mounted thereto.  
      Referring to  FIG. 10 , the cylinder assembly  252  can include first and second plungers  290 ,  291  and a piston portion  296  interposed between the plungers. Each plunger  290 ,  291  can be similar to the plunger  90  of the pump  50  shown in  FIGS. 1-7  and as described above. The piston portion  296  can be similar to the piston portion  96  of the pump  50  of  FIGS. 1-7  as described above.  
      Referring to  FIGS. 12 and 13 , the first sensor port  282  is shown. The first sensor port  282  can be similar to the first sensor port  82  of the pump  50  of  FIG. 1 . The second sensor port  283 , shown in  FIG. 9 , can be similar to the first sensor port  282 .  
      Referring to  FIGS. 14 and 15 , the first gland assembly  261  is in sealing relationship with the first plunger  290 . The second gland assembly  262  is in sealing contact with the second plunger  291 . The first and second gland assemblies  261 ,  262  can each be similar to the gland assembly  62  of the pump  50  of  FIG. 1 . The piston portion  296  has a larger diameter than either of the plungers  290 ,  291  and is disposed within the hydraulic tube  255 . The piston  296  is configured such that it can reciprocate within the hydraulic tube  255  but cannot enter either of the pressure tubes  254 ,  256 . The first and second plungers  290 ,  291  are configured such that they can enter the first and second pressure tubes  254 ,  256 , respectively. The entire cylinder assembly  252  can reciprocate within the tube assemblies such that the first plunger  290  is undergoing a charge stroke while the second plunger  291  is undergoing a discharge stroke and vice versa.  
      Referring to  FIG. 16 , one of the butt fittings  258  is shown. In practice, the butt fitting may be rotated about the longitudinal axis of the pump  250  over a predetermined angle  297 , such as 21°, for example, from the position shown in  FIG. 11 . Referring to  FIG. 17 , an integrated dual check valve or a suction and discharge valve cartridge  352  can be disposed within a cavity  354  of each butt fitting  258 . The valve cartridge assembly  57  as shown and described in U.S. Pat. No. 4,878,815 to Stachowiak, which is incorporated in its entirety herein by this reference, and the Uni-Valve cartridge assembly sold by Jetstream of Houston LLP are exemplary valves for use as the valve cartridge  352 . The butt fitting  258  can have an inlet port  356  for admitting fluid to be pressurized within the pressure tube  254  to which the butt fitting  258  is mounted and an outlet port  357  for allowing pressurized fluid to leave the pressure tube  254  for use downstream of the pump. The valve cartridge  352  is disposed between the inlet and outlet ports  356 ,  357  and the pressure tube to selectively allow and prevent fluid flow therethrough such that fluid can flow from the inlet port to the tube, but not to the outlet port, and fluid can flow from the tube to the outlet port, but not to the inlet port.  
      Referring to  FIG. 18 , the butt fitting  258  is shown with the valve cartridge  352  removed therefrom. The inlet port  356  is in communication with the cavity  354 . The cavity  354  includes a weep hole  258  to provide an indicator in the event the valve cartridge fails. The cavity  354  includes a stepped configuration to retain the valve cartridge therein.  
      Referring to  FIG. 19 , the first plunger  290  closely conforms to the first tube  254 . Referring to  FIG. 20 , the second plunger  291  is relatively smaller than the hydraulic tube  255 . The second plunger  291  can closely conform to the second pressure tube.  
      Referring to  FIG. 21 , in other embodiments of the pump, a check valve  353  can be paired with another similar check valve in lieu of the integrated dual check valve  352  shown in  FIG. 17 . The check valve  353  shown in  FIG. 21  is an example of a suitable check valve for use with the pump and is similar to the valve which has been commercialized by National Oil Well and is similar to the valve shown and described in U.S. Pat. No. 4,667,697, entitled “Unitized Check Valve,” which is incorporated in its entirety herein by this reference.  
      Referring to  FIG. 21 , another embodiment of a closed loop pump circuit  370  is shown. The circuit  370  can include a charge pump  376 , an electrical control package  378  including a plurality of proportional solenoids  379 , a swash plate  381  configured to change position in response to the movement of the solenoids  379 , a relief valve  383  for the charge pump  376 , a hot oil shuttle  385  hydraulically connected to the charge pump  376 , and a dual acting pump  250 , as shown in  FIG. 9 , hydraulically connected to the charge pump  376 . The sensors of the pump  250  can be electrically connected to the control package  378  to position the swash plate  381  such that the charge pump  376  is feeding hydraulic fluid to the low side of the loop in order to reciprocate the cylinder assembly  252  within the pump  250  such that pressurized fluid is alternatingly discharged from the first and second pressure tubes  254 ,  256 .  
      In yet other embodiments of a closed loop circuit, the rodder pump  250  can be used in a de-intensifier circuit wherein the pressure of the hydraulic fluid used to reciprocate the pump  250  is higher than the pressure of the fluid alternately discharged from the first and second pressure chambers. For example, the hydraulic fluid can be at a pressure of about 5 kpsi and the water discharged from the first and second pressure chambers can be at a pressure of about 3 kpsi. In such a situation, a relatively smaller amount of hydraulic fluid can be used than the amount of water that can be discharged from the pump.  
      In some embodiments of the dual-acting pump, four sensor ports and four corresponding sensors can be provided. Two of the four sensors can be disposed in sensor ports disposed as shown in  FIG. 9  to monitor the location of the piston assembly of the cylinder. The other two sensor ports, and accompanying sensors, can be respectively disposed adjacent the butt fittings  258  such that they detect the presence of the distal end of the first and second plungers, respectively. The third and fourth sensors can detect when the first and second plungers are disposed at the end of their respective discharge stroke and can help to keep the pump in phase. The sensors can also be used to monitor the amount of time it takes for each plunger to travel over its discharge stroke, for example. By disposing the sensors a predetermined amount away from each other, the speed of the plunger can be determined once the time of stroke travel is known. With the pressure tubes being configured to have a predetermined area, the flow rate of fluid from the pump can be computed. This information, along with a cycle count, can be displayed via an LCD, for example, that is electrically connected to the controller.  
      In yet other embodiments of the pump, the external sensors can be replaced by an inductive sensor system, such as a linear variable differential transformer (LVDT) system or a linear velocity transducer (LVT) system, for example, with the inductive sensor comprising a plurality of coils and a core, one of which being mounted to or comprising the plunger of the cylinder of the pump and the other of which mounted to or comprising a portion of the tube assembly within which the plunger is disposed. The inductive sensor system can include an extension rod made of a non-ferrous material, such as non-magnetic stainless steel, for example. For embodiments having a rodder pump with the dual-acting cylinder, a pair of inductive sensor systems can be provided for each plunger and tube combination.  
      The inductive sensor can detect the location of the plunger or plungers over the entire stroke of the cylinder and transmit that information to a controller via an electrical connection therewith. The inductive sensor can provide data to the controller relating to the instant position of the cylinder within the tube assembly such that the controller can provide an output of the instantaneous flow rate developed by the pump.  
      The inductive sensor system can be electrically connected to a controller that is configured to provide a buffered transition when the cylinder changes direction. The controller can be configured to change the flow of hydraulic fluid to the hydraulic ports over a time gradient based on the location of the cylinder as detected by the inductive sensor system such that the velocity of the cylinder gradually decreases until the cylinder changes direction, which also can be detected by the inductive sensor system. Any suitable LVDT system or LVT system can be used as the inductive sensor system with the rodder pump of the present invention.  
      Referring to  FIG. 23 , a vehicle  400  for cleaning sewer pipes and/or catch basins is shown. The vehicle  400  can include a debris-collecting dump body  402 , a vacuum hose  404  connected thereto, and a vacuum operably connected to the vacuum hose line  404  such that debris can be collected via the vacuum hose  404  and collected in the body  402 . The vehicle  400  can also include a multi-stage blower filtration system  406 , disposed between the vacuum and the vacuum hose  404 , that can act to prevent debris from entering the vacuum blower. The filtration system  406  can include a centrifugal cyclone  408  and a stainless steel screen strainer  410  for filtering debris from the vacuum. The screen strainer  410  can act to remove particles as small as  10  microns, for example. The vacuum hose  404  can be mounted to a hydraulic boom  412  that is pivotally connected to the vehicle chassis. The boom  412  can also be extendable up to a predetermined amount.  
      The vehicle  400  can also include a cleaning system  420  that comprises a front-mounted hose reel  422  that includes a predetermined length of water hose wound thereon, a control panel  424  disposed adjacent the reel  422  for use by an operator to operate the cleaning system  420 , a pair of water tanks  424 , respectively disposed on either side of the vehicle  400 , a hydraulically driven water pump  426  in fluid communication with the water. tanks  424 , and a rodder pump  250 , as shown in  FIG. 9 , in fluid communication with the water pump  426  by any suitable water lines. The water lines can connect the butt fittings of the rodder pump to the water pump  426  to allow water to be alternately pumped into the first and second pressure chambers of the rodder pump  250  from the water tanks during the suction stroke of the first and second plungers, respectively. Each of the butt fittings of the pump  250  can also be fluidly connected, via a common feed line, for example, to the length of hose wound on the hose reel  422  such that pressurized water can alternately exit the butt fittings during the discharge stroke of the first and second plungers, respectively. The pressurized water can move through the common feed line to the water hose, and ultimately exit the distal free end of the length of hose. The first and second hydraulic ports of the pump  250  can be hydraulically connected to a hydraulic supply of the vehicle to reciprocally move the cylinder. The distal end of the hose can also support any of a number of tools to facilitate the cleaning of the sewer, such as, a self-propelling jet nozzle, for example. The dual-acting pump  250  can be disposed at the rear end of the vehicle  400 . The pump  250  can be arranged in any suitable fluid circuit, such as any described herein above.  
      The water hose can be unwound from the reel  422  and fed into a sewer, for example. The operator can use the control panel  424  to control the unwinding of the water hose from the reel  422 . The operator can activate the water pump and the hydraulic supply such that the water pump operates to pump water to the rodder pump  250  and the hydraulic supply selectively feeds hydraulic fluid to the first and second hydraulic ports of the rodder pump  250  to reciprocally move the dual-acting cylinder to generate pressurized water which, in turn, can be dispensed from the water hose to clean the sewer.  
      The vehicle  400  can be any suitable vehicle, such as the Vactor® 2100 Series positive displacement sewer cleaner sold by Vactor Manufacturing, Inc. of Streator, Ill. In yet other embodiments, the pump according to the present invention can be used as part of a water excavator. Other suitable vehicles, and components thereof, are shown and described in U.S. Pat. Nos. 3,658,589; RE34,585; and 6,792,646, the entire disclosures thereof being incorporated herein in their entireties by this reference.  
      Referring to  FIG. 24 , another embodiment of a rodder pump  550  according to the present invention is shown. The rodder pump  550  includes a dual-acting cylinder  552  and is similar to the rodder pump  250  shown in  FIG. 9  and described above. The rodder pump include three tube assemblies  554 ,  555 ,  556  that respectively define a first pressure chamber, a hydraulic chamber, and a second pressure chamber. The rodder pump  550  includes first and second blocks  572 ,  573  disposed at the distal ends of the first and third tube assemblies  554 ,  556 .  
      Each block  572 ,  573  includes appropriate valving to allow fluid to alternatingly enter the first and second pressure chambers, respectively, via an inlet port  574 . Water can be drawn into a particular pressure chamber when the plunger of the cylinder  552  that is disposed in the particular pressure chamber is undergoing a suction stroke. The inlet ports  574  can be fluidly connected to a vehicle-mounted water pump that is operable to pump water stored in tanks of the vehicle to the rodder pump  550  to provide the supply of fluid to the rodder pump  550 .  
      Each block  572 ,  573  includes appropriate valving to allow fluid to alternatingly discharge from the first and second pressure chambers, respectively, via an outlet port  575 . Water can be discharged from a particular pressure chamber when the plunger of the cylinder  552  that is disposed in the particular pressure chamber is undergoing a discharge stroke. The outlet ports  575  can be fluidly connected to a common feed  576  that is operably connected to a vehicle-mounted water hose line to deliver pressurized water for sewer cleaning applications, for example.  
      All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.  
      The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.  
      Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.