Patent ID: 6393338
Filing Date: 2002-05-21
Classification: F04B,G05D

Abstract:
In a rotary peristaltic filling machine of the type including a rotary peristaltic dispenser having a motor-driven dispense rotor mounted in parallel relation to a plurality of circumferentially disposed rollers, a plurality of flexible product transfer tubes including discharge nozzles, a dispenser chamber for containing said dispense rotor and further including a curved backing plate wherein said transfer tubes are disposed in operative relation around said rollers and compressed against said backing plate along the length of said tubes to dispense a quantity of a product contained therein through said discharge nozzles into collection containers, said filling machine further including a computer processor having associated circuitry and components for providing digitally controlled rotation of said rotor to dispense said product, a method of compensating for the nonlinear, pulsating flow rate characteristic of said peristaltic dispenser, said method comprising the steps of:sampling one pulse cycle of said flow rate characteristic of said dispenser based upon predetermined position increments of said rollers by weighing the amount of said product at each of said position increments of said rollers; calculating the flow rate at each of said position increments of said rollers by dividing the weight of the dispensed product by the angular rotation of said rollers which generated said dispensed product; generating a flow rate characteristic look-up table to store the values derived from said sampling step linking said flow rates and said position increments of said rollers; monitoring the position of said dispenser using sensing means prior to dispensing a quantity of said product; locating the current position of said dispenser on said look-up table including a corresponding flow rate characteristic; integrating said flow rate characteristic based on said look-up table starting from a current position of said dispenser and increasing rotation one angular position increment at a time to calculate a target position of said rollers; determining a subtotal of the weight of said product delivered; comparing said weight of said product delivered to a calibrated set point corresponding to a desired fill weight; repeating said step of integrating until said desired fill weight is attained; and advancing said rollers to said target position to attain said desired fill weight.