Additive injection device

Abstract

A reciprocating drive system that utilizes energy available from pressure changes in flowing fluid systems, said drive used for the injection of additives into pipelines. The reciprocating drive includes a hydraulic accumulator having a gas chamber connected to a gas pipeline to contain said gas, whereby variation in the elevated pressure of the pipeline is reflected in the pressure applied to an incompressible fluid in a hydraulic conduit. The drive is capable of recycling gas used to drive the system back into pipelines.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
     
         1 . A reciprocating drive for use with a gas pipe line carrying gas at an elevated pressure, said drive comprising a drive rod, a pair of fluid motors each having a reactive surface acting on said rod to move said rod in opposite directions upon application of fluid pressure thereto, a valve connected between said pipeline and said motors and operable to direct gas from said pipeline to one or other of said motors, a reversing mechanism acting on said valve to change periodically the setting of said valve and reverse direction of movement of said rod, and a speed control device to control the rate of movement of said drive rod, said speed control device comprising a body of incompressible fluid disposed in a pair of chambers interconnected by a hydraulic conduit, each of said chambers including a cylinder and a piston moveable within the cylinder upon movement of said rod to vary the volume of said chamber, said chambers being arranged relative to one another such that a decrease in the volume of said chambers causes a corresponding increase in the volume of the other of said chambers, said speed control valve further comprising a flow control valve located in said conduit and a hydraulic accumulator connected to said conduit, said accumulator having a first chamber in communication with said conduit to contain said incompressible fluid and a second chamber connected to said gas pipeline to contain said gas, whereby variations in said elevated pressure of said pipeline are reflected in the pressure applied to said incompressible fluid in said conduit.  
     
     
         2 . A device according to  claim 1  wherein a pair of flow control valves are located in said conduit and said accumulator is connected between said valves.  
     
     
         3 . A drive according to  claim 1  wherein said flow control valve is adjustable.  
     
     
         4 . A drive according to  claim 1  wherein said valve includes a return line connected to said gas pipeline to return gas vented from said motors.  
     
     
         5 . A drive according to  claim 4  wherein said reversing mechanism is carried by said rod and is adjustable relative thereto to vary the stroke of said drive rod.  
     
     
         6 . A drive according to  claim 1  wherein said drive motors comprise a diaphragm device having a housing and an internal diaphragm or piston to define each of the drive motors, said rod being connected to said diaphragm from movement therewith.  
     
     
         7 . A drive according to  claim 6  wherein said valve is connected to said pipeline at spaced location to establish a pressure differential between gas supplied to said motors and gas vented by said motors.  
     
     
         8 . A drive according to  claim 1  wherein said drive motors each include a piston to provide said reactive surface and a cylinder in which said piston is moveable.  
     
     
         9 . A drive according to  claim 8  wherein said piston is secured to said rod.  
     
     
         10 . A drive according to  claim 9  wherein said drive and chamber are located in a common actuator with said cylinder disposed on one side of a common piston and a chamber disposed on the opposite side of said common piston.  
     
     
         11 . A drive according to  claim 1  wherein said reversing mechanism includes a bistable actuator acting between said valve and said rod.  
     
     
         12 . A drive according to  claim 1  wherein said bistable actuator is connected to said rod through a lost motion mechanism.  
     
     
         13 . A drive according to  claim 12  wherein said bistable actuator includes a carrier and a valve actuator, each moveable of which is moveable between a respective pair of abutments, interconnected by a bistable element operable in each of two positions to bias said carrier and valve actuator against a respective pair of said abutments and hold said valve in one of two positions.  
     
     
         14 . A drive according to  claim 13  wherein said bistable element is a conical spring element.  
     
     
         15 . A drive according to  claim 13  wherein said valve includes a land having radial sealing surfaces and a moveable within a chamber between a pair of sealing faces.  
     
     
         16 . A drive according to  claim 15  wherein said faces provide abutments of said actuator.  
     
     
         17 . A reciprocating drive comprising a drive rod, a pair of fluid motors each having a reactive surface acting on said rod to move said rod in opposite directions upon application of fluid pressure thereto, a valve to control flow of fluid to said motors and a reversing mechanism acting on said valve to change periodically the setting thereof and reverse the direction of movement of said rod, said reversing mechanism including a bistable actuator acting between said valve and said rod.  
     
     
         18 . A drive according to  claim 17  wherein said bistable actuator is connected to said rod through a lost motion mechanism.  
     
     
         19 . A drive according to  claim 18  wherein said bistable actuator includes a carrier and a valve actuator, each moveable of which is moveable between a respective pair of abutments, interconnected by a bistable element operable in each of two positions to bias said carrier and valve actuator against a respective pair of said abutments and hold said valve in one of two positions.  
     
     
         20 . A drive according to  claim 19  wherein said bistable element is a conical spring element.  
     
     
         21 . A drive according to  claim 19  wherein said valve includes a land having radial sealing surfaces and a moveable within a chamber between a pair of sealing faces.  
     
     
         22 . A drive according to  claim 21  wherein said faces provide abutments of said actuator.