Solenoid Pump Driver

Abstract

A method of driving a solenoid pump of the type comprising a metal shuttle urged by a solenoid against a spring with the spring providing the force for the pumping stroke of the shuttle is disclosed. The method comprises applying a periodic driving voltage to the solenoid. Each period of the driving voltage comprises a first portion during which the driving voltage increases from a minimum voltage to a maximum voltage to compress the spring, a second portion during which the driving voltage decreases from the maximum voltage to the minimum voltage to release the spring, and a third portion during which the driving voltage is maintained at the minimum voltage. The duration of the second portion is substantially less than the duration of the first portion and may be substantially instantaneous. The driving voltage increases from the minimum voltage to the maximum voltage substantially linearly during the first portion, such that the driving voltage has a sawtooth waveform.

1 . A method of driving a solenoid pump of the type comprising a metal shuttle urged by a solenoid against a spring with the spring providing the force for a pumping stroke of the shuttle, the method comprising applying a periodic driving voltage to the solenoid,
 wherein each period of the driving voltage comprises a first portion during which the driving voltage increases from a minimum voltage to a maximum voltage to compress the spring, a second portion during which the driving voltage decreases from the maximum voltage to the minimum voltage to release the spring, and a third portion during which the driving voltage is maintained at the minimum voltage, wherein the duration of the second portion is substantially less than the duration of the first portion.   
     
     
         2 . A method as claimed in  claim 1 , wherein the driving voltage decreases from the maximum voltage to the minimum voltage substantially instantaneously during the second portion. 
     
     
         3 . A method as claimed in  claim 1 , wherein the driving voltage increases from the minimum voltage to the maximum voltage substantially linearly during the first portion. 
     
     
         4 . A method as claimed in  claim 1 , wherein the driving voltage has a sawtooth waveform. 
     
     
         5 . A method as claimed in  claim 1  further comprising controlling the duration of the third portion to provide a required flow rate through the pump. 
     
     
         6 . A method as claimed in claim further comprising controlling the maximum voltage to provide a required flow rate through the pump. 
     
     
         7 . A method as claimed in  claim 1 , wherein the frequency of the driving voltage is different to the frequency of a supply voltage providing electrical power for the driving voltage. 
     
     
         8 . A method as claimed in  claim 1  further comprising controlling the frequency of the driving voltage to provide a required flow rate through the pump. 
     
     
         9 . A method as claimed in  claim 1 , wherein the minimum voltage is zero volts. 
     
     
         10 . A driver circuit for a solenoid pump, the driver circuit configured to generate a driving voltage in accordance with the method of  claim 1 . 
     
     
         11 . A solenoid pump in combination with the driver circuit of  claim 11 .