Diaphragm pump motor driven by a pulse width modulator circuit and activated by a pressure switch

Abstract

A pump assembly that has a control circuit and a pressure switch which control the operation of a pump motor. The motor drives a positive displacement pump that is coupled to a fluid system. The control circuit includes a pulse width modulator circuit. The control circuit is activated when a pressure switch senses that a line pressure of the fluid system is below a threshold value. The control circuit can either operate in a continuous mode to provide a constant signal to the motor, or a pulse regulating mode to provide a series of pulses to the motor. The pulses begin with a minimum width and gradually increase until a predetermined current limit has been attained, or the motor reaches a full speed with the control circuit in a continuous on state. The speed of the motor will then correspond to the flow demanded by the fluid system. The energy provided by the pulses is varied as a function of changes in peak current drawn by the motor. The peak current is sensed and used to determine the pulse width. Changing the pulse energy varies the speed of the motor.

What is claimed is:  
     
         1 . A pump assembly, comprising: 
 a positive displacement pump that can create an output pressure;    a motor that drives said pump;    a pulse width modulating circuit that creates a plurality of pulses that provide energy to said motor; and,    a pressure switch that is coupled to said pulse width modulating circuit and which can sense the output pressure, said pressure switch activating said pulse width modulating circuit when output pressure is less than a threshold value.    
     
     
         2 . The pump assembly of  claim 1 , further comprising a current sensing circuit that varies the pulse energy as a function of the current drawn by said motor.  
     
     
         3 . The pump assembly of  claim 1 , further comprising a thermal breaker coupled to said pulse width modulating circuit.  
     
     
         4 . The pump assembly of  claim 2 , wherein said pulse width modulating circuit can provide a minimum pulse width.  
     
     
         5 . The pump assembly of  claim 1 , wherein said pulse width modulating circuit includes an amplifier that receives a Varef input signal and Vsense input signal and provides an output signal to an input of a comparator, said comparator receiving a Vcref input signal and generates an output signal that creates the plurality of pulses.  
     
     
         6 . The pump assembly of  claim 1 , wherein said a pulse width modulating circuit and said pressure switch are located within said positive displacement pump.  
     
     
         7 . The pump assembly of  claim 1 , wherein said pulse width modulating circuit is located in a first cavity and said pressure switch is located in a second cavity of said positive displacement pump.  
     
     
         8 . A pump assembly, comprising: 
 a pump that can create an output pressure;    a motor that draws a current and drives said pump;    a pulse width modulating circuit that creates a series of pulses that provide energy to said motor; and,    a current sensing circuit that varies the pulse energy as a function of the current drawn by said motor.    
     
     
         9 . The pump assembly of  claim 8 , further comprising a thermal breaker coupled to said pulse width modulating circuit.  
     
     
         10 . The pump assembly of  claim 8 , wherein said pulse width modulating circuit can provide a minimum pulse width.  
     
     
         11 . The pump assembly of  claim 8 , wherein said pulse width modulating circuit includes an amplifier that receives a Varef input signal and Vsense input signal and provides an output signal to an input of a comparator, said comparator receiving a Vcref input signal and generates an output signal that creates a plurality of pulses that power said motor.  
     
     
         12 . The pump assembly of  claim 8 , wherein said a pulse width modulating circuit and said current sensing circuit are located within said pump.  
     
     
         13 . A pump assembly, comprising: 
 a pump that can create an output pressure;    a motor that drives said pump;    a motor control circuit that can activate and then gradually increase a speed of said motor.    
     
     
         14 . The pump assembly of  claim 13 , wherein said control circuit includes a pulse width modulator circuit that creates a series of pulses that provide energy to said motor.  
     
     
         15 . The pump assembly of  claim 14 , wherein said pulse width modulating circuit varies the width of each pulse.  
     
     
         16 . The pump assembly of  claim 15 , wherein said pulse width modulating circuit can provide a minimum pulse width.  
     
     
         17 . The pump assembly of  claim 14 , wherein said pulse width modulating circuit includes an amplifier that receives a Varef input signal and Vsense input signal and provides an output signal to an input of a comparator, said comparator receiving a Vcref input signal and generates an output signal that creates the plurality of pulses.  
     
     
         18 . The pump assembly of  claim 13 , wherein said motor control circuit varies said pulse energy as a function of the current drawn by said motor.  
     
     
         19 . A method for operating a pump, comprising: 
 generating a plurality of pulses that drive a motor and a pump; and,    varying an energy of the pulses until the motor reaches a constant speed.    
     
     
         20 . The method of claim, 19 , further comprising sensing a variation in a current drawn by the motor and varying the energy provided by the pulses as a function of the varying current.  
     
     
         21 . The method of  claim 19 , further comprising sensing a temperature of a control circuit and terminating the generation of pulses when the temperature exceeds a threshold value.  
     
     
         22 . The method of  claim 19 , wherein the pulses are generated by a pressure switch that senses when an output pressure exceeds a threshold value.  
     
     
         23 . A method for operating a pump, comprising: 
 generating a plurality of pulses that drive a motor and a pump, said pulses providing an energy to the motor;    sensing a variation in a current drawn by the motor; and,    varying the pulse energy as a function of the variation in the current.    
     
     
         24 . The method of  claim 23 , further comprising sensing a temperature of a control circuit and terminating the generation of pulses when the temperature exceeds a threshold value.  
     
     
         25 . A method for operating a pump, comprising: 
 generating a plurality of pulses that drive a motor and a pump;    sensing a temperature of a control circuit; and,    terminating the generation of pulses when the temperature exceeds a threshold value.    
     
     
         26 . A pump assembly, comprising: 
 a motor;    a wobble plate coupled to said motor;    a diaphragm coupled to said wobble plate;    a piston coupled to said diaphragm;    a pump housing coupled to said piston, said diaphragm and said wobble plate, said pump housing having an outlet port;    a control circuit that is located within said pump housing and coupled to said motor; and,    a pressure switch that is located within said pump housing adjacent to said output port, and is coupled to said control circuit.    
     
     
         27 . The assembly of  claim 26 , wherein said control circuit is located within a first cavity of said pump housing and said pressure switch is located within a separate second cavity of said pump housing.  
     
     
         28 . The assembly of  claim 26 , further comprising a set screw located within said pump housing and adjustable to vary a threshold setting of said pressure switch.  
     
     
         29 . The assembly of  claim 27 , wherein said pump housing includes a third cavity located between said first and second cavities.  
     
     
         30 . The assembly of  claim 27 , wherein said control circuit is podded into said first cavity.  
     
     
         31 . A pump assembly, comprising: 
 a pump that can create an output pressure;    a motor that draws a current and drives said pump; and,    a control circuit that creates a continuous signal to said motor when the current drawn by the motor is less than a threshold value, and switches to a pulsating regulation mode to provide a series of pulses to said motor when the current drawn by the motor exceeds the threshold value.    
     
     
         32 . The assembly of  claim 31 , further comprising a diode coupled to said motor to allow a flow of current due to a back emf voltage of said motor.  
     
     
         33 . The assembly of  claim 31 , wherein the threshold value is adjustable.