Micro-sized fluid metering pump

Abstract

A motor-driven fluid pump has a positive displacement rotary pumping element with a circular rotating cam carried outwardly of the element that is rotated with the pumping element by contact with pistons carried radially by the pumping element. The pump maintains a constant mass flow rate for a given input command by adjusting for fluid type, for measured fluid operating temperature, and for changing motor speed according to a pre-set algorithm. The motor-driven fluid pump also has the capability to maintain a constant flow output over the life of the pump by adjusting for internal wear and having the capability to predict its remaining life by comparing its current motor speed against the maximum allowable motor speed.

I claim as my invention: 
     
         1 . A motor-driven fluid pump having a fixed manifold connected into a fluid flow system, the pump comprising:
 a positive displacement rotary pumping element driven by said motor;   a circular, rotating cam carried radially outwardly of the pumping element and eccentrically thereto, and having a circular inner surface;   an electronic motor control module that receives a flow demand input signal from the fluid flow system, and wherein   the cam rotates on bearings carried on said manifold, and   the cam is rotated with the pumping element solely by contact with outer ends of a plurality of pistons carried radially by the pumping element and bearing against the inner surface of the cam.   
     
     
         2 . A motor-driven pump as defined in  claim 1 , wherein the pump further comprises
 a microprocessor chip having means in said chip for receiving a fluid type signal from an external device and sensing at least one of fluid flow, fluid pressure, and fluid temperature.   
     
     
         3 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor is programmed to operate the motor at a selected speed based upon the fluid density and a viscosity algorithm of the fluid type being pumped. 
     
     
         4 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor is programmed to set the speed of the motor to provide both the minimum and the maximum required flow conditions during a calibration check. 
     
     
         5 . A motor-driven pump as defined in  claim 4 , wherein the minimum and maximum flow rates are set in accordance with two variables in the microprocessor programming code. 
     
     
         6 . A motor-driven pump as defined in  claim 4 , wherein the minimum and maximum flow rates are set in accordance with a pulse modulation signal sent from the microprocessor to the motor. 
     
     
         7 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor sets proper motor speed using an algorithm based on fluid density and viscosity. 
     
     
         8 . A motor-driven pump as defined in  claim 2 , wherein the pump temperature sensor measures the fluid temperature and generates and transmits a corresponding electrical signal to the microprocessor which then sets proper motor speed using the fluid density and viscosity algorithm. 
     
     
         9 . A motor driven pump as defined in  claim 1 , further comprising means for transmitting a measure of the pump's remaining life to an external device. 
     
     
         10 . A motor-driven pump as defined in  claim 2 , further comprising means for comparing at least one of the measured output flow volume and pressure with an expected value in the microprocessor code for a given input command for a particular fluid type and temperature. 
     
     
         11 . A motor-driven pump as defined in  claim 10 , wherein the microprocessor increases motor speed if at least one of measured flow and pressure is lower than the expected value stored in the microprocessor code. 
     
     
         12 . A motor-driven pump as defined in  claim 11 , wherein the motor speed is increased by increasing the pulse width modulation duty cycle. 
     
     
         13 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor has programmed in it an algorithm for calculating remaining pump life by comparing required motor speed against maximum permissible motor speed. 
     
     
         14 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor is programmed to store the expected life of the pump in hours. 
     
     
         15 . A micro-sized fluid-metering pump, the pump comprising a plurality of radially-oriented pistons carried in a rotor, a rotating circular cam carried about said rotor on a bearing eccentric of the rotor, for radially moving the pistons as the assembly of the rotor and cam rotate about their respective axes. 
     
     
         16 . A micro-sized fluid-metering pump as defined in  claim 15 , wherein the rotating eccentric cam is driven to rotate substantially with the pistons and rotor by physical contact between the pistons and an interior surface of the cam caused by centrifugal and hydraulic forces exerted on the pistons as the rotor spins. 
     
     
         17 . A rotating device comprising
 a rotor mounted for rotating about a first axis,   a plurality of pistons carried in the rotor for rotational movement therewith and for radial movement therein between inward and outward locations in said rotor,   a circular cam carried rotatably on said device and outwardly of said rotor and outwardly of said pistons but about a second axis spaced by a distance from the first axis,   whereby as the rotor, pistons, and cam spin about the first and second axes, the distance between the axes and the centrifugal and hydraulic forces on the pistons cause the pistons to move outwardly and inwardly with respect to the rotor as the rotor, pistons, and cam rotate substantially together about their offset axes but with minimal movement between each piston and the interior surface of the cam apart from start-up, shut-down, and other rotational speed changes of the rotor.   
     
     
         18 . A rotating device as defined in  claim 17 , wherein the device is a pump and the rotor further comprises a fixed manifold dividing a hollow center of the rotor into an inlet side and an outlet side, wherein the offset of the rotor and cam lies along an axis of the manifold that also is normal to the axes of the rotor and the cam.