Micro-Sized Fluid Metering Pump

Abstract

A motor-driven fluid pump has a positive displacement rotary pumping element with an offset circular cam carried outwardly of the element, the cam being rotated with the pumping element by contact with pistons carried radially by the pumping element. Ends of the pistons are spherical and bear directly on the cam's inner surface. During breaking in of each pump, the piston ends wear a single concave groove in the inner surface of the cam, which helps to stabilize the pistons. The pump maintains a constant mass flow rate for a given input command by adjusting for fluid type, measured fluid operating temperature, and changing motor speed. The pump also maintains a constant flow output for its life by adjusting for internal wear; it also predicts its remaining life by comparing its current motor speed for a given flow 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 control system which generates a flow demand signal, the pump comprising:
 a positive displacement rotary pumping element driven by said motor;   a plurality of pistons carried radially within the pumping element;   a rotating cam carried radially outwardly of the pumping element and eccentrically thereto, and having a concave radius portion within a circular inner surface;   an electronic motor control module connected to receive said flow demand signal from the fluid flow control system, and wherein   
       the cam rotates on rolling element bearings carried on said manifold, and 
       the cam is rotated with the pumping element solely by contact with outer ends of the plurality of pistons, said spherical ends bearing against the concave inner surface portion 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 remote fluid type signal from the fluid flow control system and for 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 chip is programmed to set the speed of the motor to provide the required fluid flow control system range for a given fluid type. 
     
     
         4 . A motor-driven pump as defined in  claim 3 , wherein the fluid flow control system range is set by entering two numerical values in the microprocessor programming code, the values corresponding to motor speed set via a graphical user interface. 
     
     
         5 . A motor-driven pump as defined in  claim 4 , wherein the minimum fluid flow is set by a value equating to the minimum flow input demand signal and the maximum fluid flow is set by another value equating to the maximum flow input demand signal. 
     
     
         6 . A motor driven pump as defined in  claim 1 , further comprising means for transmitting a measure of the pump's remaining useful life to a fluid flow control system. 
     
     
         7 . A motor-driven pump as defined in  claim 2 , wherein the microprocessor has programmed in it a means for calculating remaining useful pump life by comparing required motor speed against maximum permissible motor speed. 
     
     
         8 . A motor-driven pump as defined in  claim 1 , wherein the pump delivers flow over the entire fluid flow control system range by having said electronic motor control module receiving a proportional flow demand input signal. 
     
     
         9 . A motor-driven pump as defined in  claim 1 , wherein the pistons are fabricated from a higher hardness material than that of the rotating eccentric cam 
     
     
         10 . A motor-driven pump as defined in  claim 9 , wherein the pistons generate a concave groove in the inner surface portion of the cam conforming to said pistons' spherical ends 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 during said motor-driven pump's break-in procedure. 
     
     
         11 . A motor-driven pump as defined in  claim 10 , wherein the depth of concave groove in the inner surface portion of the cam is determined by a Hertzian contact stress between said pistons and the cam interior surface. 
     
     
         12 . A motor driven pump as defined in  claim 11 , wherein outer ends of said pistons fit into and operate within said concave groove in said cam inner surface.