Control device of the piston stroke of a dosing pump for high performance automatic flow regulation

Abstract

A device for controlling the stroke of a piston 3 of a metering pump comprising an electromagnet 1 formed by a fixed part and a mobile part fixed with respect to said piston 3 in such a way that at each displacement of the piston there corresponds a different value of inductance of the electromagnet 1 and hence of the piston stroke itself.

1 . A device for controlling the stroke of a piston ( 3 ) of a metering pump, the device comprising an electromagnet ( 1 ) and being characterized in that the pumping part is managed by means of measurement and control of the electromagnet ( 1 ) in such a way that the pumping element is simultaneously sensor and actuator, for this purpose said electromagnet ( 1 ) being equipped with a fixed plate and a mobile plate ( 2 ) fixed with respect to said piston ( 3 ) in such a way that to each displacement of the piston there corresponds a different distance between said plates and hence a different value of the impedance of the electromagnet itself; said electromagnet being connected to a microcontroller electronic card, which is designed to detect, in real time, the position of the piston ( 3 ), through the variations of the values of impedance of the electromagnet caused by the variations of inductance, which depends only upon the geometrical/constructional characteristics of the electromagnet ( 1 ) and not upon functional or environmental parameters. 
     
     
         2 . The control device according to  claim 1 , characterized in that, in order to program the microcontroller in such a way that associated to each variation of inductance of the electromagnet is a piston stroke and consequently a different capacity of the metering pump, it is envisaged to apply across the electromagnet ( 1 ) a pulse train, which generates an intermittent magnetic field that attracts and releases a plate ( 2 ), which, since it is fixed with respect to the piston ( 3 ), which is in turn fixed to the diaphragm ( 4 ), displaces the latter inside the pump body ( 5 ), and consequently a liquid agent is pumped into the system on which the pump is installed; thus obtaining that to each value of inductance detected by the microcontroller there corresponds a precise piston stroke, the value of which is stored in the memory of the microcontroller itself. 
     
     
         3 . The device according to  claim 1 , characterized in that in order to keep the capacity of the metering pump constant, the electronic card sends a pulse for measuring the inductance upon first turning-on of the pump itself in order to correlate the piston stroke to the inductance itself of the electromagnet; said first pulse being designed to cause the piston ( 3 ) to perform an entire stroke, in such a way that the microcontroller can measure the current in the electromagnet ( 1 ) at intervals of one millisecond, storing in its own internal memory said values together with the piston stroke, simultaneously obtaining the impedance of the electromagnet. 
     
     
         4 . The device according to  claim 1 , characterized in that the microcontroller is designed to regulate the piston stroke ( 3 ) by modulating the impulsive current at a fixed frequency on the electromagnet on the basis of the values detected of the inductance as compared with those contained in the internal memory of the microcontroller that relate them to the piston stroke. 
     
     
         5 . The device according to  claim 1 , characterized in that said microcontroller is designed to regulate the piston stroke ( 3 ) by modulating the current that is required for the electromagnet ( 1 ) in order to displace the piston ( 3 ). 
     
     
         6 . The device according to  claim 1 , characterized in that said microcontroller is designed to verify and evaluate the rate of displacement of the piston ( 3 ) in order to detect the state of UNDERLOAD, i.e., detect the absence of additive inside the pump body during normal operation of the device. 
     
     
         7 . The control device according to  claim 1 , characterized in that said electronic device is designed to verify and evaluate the rate of displacement of the piston ( 3 ) in order to detect the state of OVERLOAD, i.e., detect a possible obstruction or over-pressure of the delivery line of the pump during normal operation of the device. 
     
     
         8 . A metering pump comprising a device for controlling the piston stroke ( 3 ) according to  claim 1 . 
     
     
         9 . The metering pump according to  claim 8 , characterized in that it is equipped with a serial port for connection to a computer or other similar electronic device for remote acquisition of the information gathered by the microcontroller and/or intervention on operation of the pump itself. 
     
     
         10 . The control device according to  claim 1 , characterized in that, albeit envisaging a measurement of the current that uses for the calculation the impedance, it is not limited to intercepting the point of arrival of the plate ( 2 ) and hence the end-of-travel, but said microcontroller electronic card is designed to set in relation the value of the inductance with the position assumed by the piston ( 3 ) during its stroke and to determine, on the basis of the settings made by the user, in which position to block the piston stroke; thus obtaining the possibility of controlling with centesimal precision the piston stroke ( 3 ) and hence the capacity of the pump for each single injection of additive. 
     
     
         11 . The control device according to  claim 1 , characterized in that said microcontroller electronic card controls the current on the electromagnet ( 1 ) in order to prevent any useless waste of energy and activates the solenoid thereof with a precise amount of current, controlling the advance through the calculation of the impedance and determining blocking thereof in a precisely defined position that can be set through calibration of the electronic circuit, without any mechanical system for controlling the pump capacity. 
     
     
         12 . The control device according to  claim 1 , characterized in that in order to control the piston stroke ( 3 ) so as to modify instantaneously the injection volume of the metering pump, said microcontroller electronic card determines whether the pre-set end-of-travel has been reached and controls, in real time, what occurs in the electromagnet ( 1 ) calculating the impedance and determining the exact point at which the piston stroke ( 3 ) must cease; thus obtaining that the solenoid of the electromagnet ( 1 ), in addition to performing the function of actuator, functions also as sensor. 
     
     
         13 . The metering pump according to  claim 8 , characterized in that it is basically constituted by three fundamental elements: an electronic card, an electromagnet ( 1 ), and a pump body with piston ( 3 ), wherein said electromagnet ( 1 ), appropriately actuated by the electronic card and recalled by a spring, actuates the piston ( 3 ) in a pulsed mode in a range preferably comprised between 0 and 360 pulses per minute. 
     
     
         14 . The metering pump according to  claim 13 , characterized in that said electronic card actuates the electromagnet ( 1 ) gradually with small increments of voltage whilst it simultaneously measures the current that traverses the solenoid of said electromagnet in order to obtain therefrom the corresponding value of impedance, which is directly associated to the position of the piston ( 3 ) along the maximum stroke envisaged; through a potentiometric or digital regulation, that can be set directly by the operator via the interface of the electronic card, it being possible to select with centesimal precision the exact point of arrest of the piston, i.e., its maximum stroke, it thus being possible to vary with extreme precision the amount of additive injected for each single actuation of the electromagnet, without the aid of particular and costly mechanical regulations or of further sensors and electronic feedback. 
     
     
         15 . The metering pump according to  claim 9 , characterized in that it is basically constituted by three fundamental elements: an electronic card, an electromagnet ( 1 ), and a pump body with piston ( 3 ), wherein said electromagnet ( 1 ), appropriately actuated by the electronic card and recalled by a spring, actuates the piston ( 3 ) in a pulsed mode in a range preferably comprised between 0 and 360 pulses per minute. 
     
     
         16 . The metering pump according to  claim 15 , characterized in that said electronic card actuates the electromagnet ( 1 ) gradually with small increments of voltage whilst it simultaneously measures the current that traverses the solenoid of said electromagnet in order to obtain therefrom the corresponding value of impedance, which is directly associated to the position of the piston ( 3 ) along the maximum stroke envisaged; through a potentiometric or digital regulation, that can be set directly by the operator via the interface of the electronic card, it being possible to select with centesimal precision the exact point of arrest of the piston, i.e., its maximum stroke, it thus being possible to vary with extreme precision the amount of additive injected for each single actuation of the electromagnet, without the aid of particular and costly mechanical regulations or of further sensors and electronic feedback.