Reciprocating water pump

Abstract

A reciprocating jetting water pump primarily for use on a vacuum truck is disclosed. The jetting water pump includes a pair of reciprocating pistons that are each movable within an outer cylinder mounted to a center block. The outer surface of each of the pistons includes a polymer surface that is closely spaced to the inner surface of the outer cylinder. The outer surface includes a pair of spaced polymer strips separated by a seal to enhance the seal between the piston and the outer cylinder. Each of the outer cylinders is mounted to the center block by a threaded connection. A control system mounted to the vacuum truck senses the pressure of water leaving the jetting water pump and controls the supply of pressurized hydraulic fluid to the jetting water pump to maintain the water pressure at an operator selected value.

We claim: 
     
         1 . A reciprocating water pump, comprising:
 a center block;   a first outer cylinder connected to the center block and having an inner surface having a constant inner diameter;   a second outer cylinder connected to the center block and having an inner surface having a constant inner diameter;   a first piston movably positioned within the first outer cylinder, the first piston having a main body and a polymeric outer surface having an outer diameter that closely corresponds to the inner diameter of the first outer cylinder;   a second piston movably positioned within the second outer cylinder, the second piston having a main body and a polymeric outer surface having an outer diameter that closely corresponds with the inner diameter of the second outer cylinder; and   a connecting rod extending through the center block and connected to both the first piston and the second piston.   
     
     
         2 . The reciprocating water pump of  claim 1  wherein the outer surface of both the first piston and the second piston include a pair of spaced polymer strips. 
     
     
         3 . The reciprocating water pump of  claim 2  further comprising a resilient ring positioned between the polymer strips along the outer surface of the pistons, wherein the resilient ring engages the inner diameter of the respective first or second outer cylinder. 
     
     
         4 . The reciprocating water pump of  claim 2  wherein the body of each of the pistons is formed from a metallic material and the pair of polymer snips are mounted to the body. 
     
     
         5 . The reciprocating water pump of  claim 1  wherein each of the first and second outer cylinders includes a threaded portion near an inner end of the cylinder, wherein the threaded portion is received along one of a pair of attachment threads Rimed on the center block. 
     
     
         6 . The reciprocating water pump of  claim 5  wherein each of the first and second outer cylinders includes an alignment guide and the center block includes a corresponding alignment guide, wherein each of the first and second outer cylinders are threaded onto the center block until the alignments guides are aligned with each other to align the first and second outer cylinders on the center block. 
     
     
         7 . The reciprocating water pump of  claim 1  wherein the first outer cylinder includes at least one drain port. 
     
     
         8 . The reciprocating water pump of  claim 7  wherein the drain port is formed at a vertically lowest point of the first outer cylinder. 
     
     
         9 . The reciprocating water pump of  claim 1  wherein one or both of the first and second outer cylinders are formed from a carburized heat treated metallic material. 
     
     
         10 . The reciprocating water pump of  claim 1  further comprising an end cap welded to an outer end of a cylindrical tube of each of the first and second outer cylinders, wherein the end cap includes a recessed clearance area formed in an attachment portion aligned with an outer end of the cylindrical tube. 
     
     
         11 . The reciprocation water pump of  claim 1  further comprising an end cap received on an outer end of a cylinder tube that includes the inner surface of each of the first and second outer cylinders, wherein the end cap is sized to create an interference fit with the inner surface. 
     
     
         12 . A control system for a jetting water pump that creates an output flow of water from a vacuum truck, comprising:
 a control unit;   a user input device coupled to the control unit to allow an operator to adjust the operational settings of the jetting water pump within the control unit;   a water pressure sensor positioned to determine the water pressure of the output flow of water, wherein the water pressure sensor is in communication with the control unit; and   a hydraulic pressure control valve in communication with the control unit and operable to selectively control the pressure of hydraulic fluid to the jetting water pump,   wherein the control unit selectively activates the hydraulic pressure control valve to control the water pressure from the jetting water pump.   
     
     
         13 . The control system of  claim 12  further comprising a linear velocity and displacement transducer positioned within the jetting water pump and in communication with the control unit, wherein the linear velocity and displacement transducer is positioned to sense the movement of a piston within the jetting water pump. 
     
     
         14 . The control system of  claim 12  further comprising a display coupled to the control unit such that the control unit can visually display the sensed water pressure. 
     
     
         15 . A truck operable to dispense water, comprising:
 a jetting water pump operable to create a supply of water from the track; and   a control system coupled to the jetting water pump to determine the water pressure from the jetting water pump and control the supply of hydraulic fluid to the jetting water pump to control the water pressure from the jetting water pump.   
     
     
         16 . The truck of  claim 15  wherein the control system further comprises:
 a control unit; 
 a user input device coupled to the control unit to allow an operator to adjust e operational settings of the jetting water pump within the control unit; 
 a water pressure sensor positioned to determine the water pressure of the output flow of water, wherein the water pressure sensor is in communication with the control unit; and 
 a hydraulic pressure control valve in communication with the control unit and operable to selectively control the pressure of hydraulic fluid to the jetting water pump. 
 
     
     
         17 . The truck of  claim 15  wherein the jetting water pump comprises:
 a center block; 
 a first outer cylinder connected to the center block and having an inner surface having a constant inner diameter; 
 a second outer cylinder connected to the center block and having an inner surface having a constant inner diameter; 
 a first piston movably positioned within the first outer cylinder, the first piston haying a main body and a polymeric outer surface having an outer diameter that closely corresponds to the inner diameter of the first outer cylinder; 
 a second piston movably positioned within the second outer cylinder, the second piston having a main body and a polymeric outer surface having an outer diameter that closely corresponds with the inner diameter of the second outer cylinder; and 
 a connecting rod extending through the center block and connected to both the first piston and the second piston. 
 
     
     
         18 . The truck of  claim 15  wherein the outer surface of both the first piston a Id the second piston include a pair of spaced polymer strips. 
     
     
         19 . The truck of  claim 15  wherein both of the first and second outer cylinders are attached to the center block through a threaded connection. 
     
     
         20 . The truck of  claim 17  further comprising an end cap welded to an outer end of a cylindrical tube of each of the first and second outer cylinders, wherein the end cap includes a recessed clearance area formed in an attachment portion aligned with an outer end of the cylindrical tube. 
     
     
         21 . A reciprocating water pump for use with a sewer cleaning truck, comprising:
 a center block;   a first outer cylinder connected to the center block and haying an inner surface having a constant inner diameter;   a second outer cylinder connected to the center block and haying an inner surface having a constant inner diameter;   a first piston movably positioned within the first outer cylinder, the first piston having a main body and a cap-seal extending around an outer surface of the main body, wherein the cap-seal engages the inner surface of the first outer cylinder;   a second piston movably positioned within the second outer cylinder, the second piston having a main body and a cap-seal extending around an outer surface of the main body, wherein the cap-seal engages the inner surface of the second outer cylinder; and   a connecting rod extending through the center block and connected to both the first piston and the second piston.