WEIGHT CONTROL SYSTEM

• US 3,828,869 A
• Filed: 08/30/1972
• Issued: 08/13/1974
• Est. Priority Date: 08/30/1972
• Status: Expired due to Term

• Current Assignee: Kenneth W. Sellers
• Original Assignee: Kenneth W. Sellers
• Inventors: Sellers, Kenneth W.
• Primary Examiner(s): Wilkinson, Richard B.
• Assistant Examiner(s): Miska, Vit W.
• Application Number:
  US05/284,708
• Time in Patent Office: 713 Days
• Field of Search: 177/1,6.75,15,25,26,50,60,63,64,80,81,116-123,45,164,210,DIG.1,DIG.3,DIG.11 235/157.1,158.53
• US Class Current: 177/50
• CPC Class Codes: G01G 13/003 Details; specially adapted accessories details of weighing apparatus in general G01G21/00; auxiliary devices for weighing apparatus in general G01G23/00
• CPC Class Codes: G01G 13/2954 wherein the main feed is effected by mechanical conveying means, e.g. by belt conveyors, by vibratory conveyors
• CPC Class Codes: G01G 13/2958 Arrangements for the determination of, or compensation for, the tare weight of an unloaded container, e.g. a disposable container
• CPC Class Codes: G01G 15/006 using electrical, electromechanical, or electronic means not covered by G01G15/001, G01G15/02, G01G15/04

Abstract

A weight control system is disclosed for accurately dispensing a preselected quantity of material. The system include a circuit for generating an optimum weight profile curve which represents the desired quantity of material in terms of net weight to be dispensed with respect to time. The curve is an exponentially increasing function of time having a rate of increase that progressively decreases so that the curve approaches an asymptotic level which represents the total net weight of the material to be dispensed. The curve is segmented into small time intervals, and at each interval the weight of the material dispensed is compared with the optimum weight defined by the curve. Depending on whether the accumulated weight of the material dispensed at each time interval is greater or less than the optimum weight, a circuit is enabled for conducting current to one or more material feeders which in turn dispense the material into a charge hopper. A circuit is provided which detects a change in the tare weight of a scale due to the accumulation of foreign materials on the scale. The circuit automatically compensates for these accumulations which would otherwise cause an undesirable variance in the weight of the charge of material.

Claims

1. A weight control system comprising means for continuously weighing a charge of material as said charge is being formed and generating an output proportional to the instantaneous measured weight of said charge, means for generating a weight profile curve, said curve representing the optimum desired weight of said charge with respect to time as said charge is being formed, means for comparing periodically during the time of formation of said charge points of optimum weight on said weight profile curve with said generated output proportional to the instantaneous weight of said charge and producing a signal indicative of the difference thereof, means for dispensing material to form said charge, and means activated by said signal for energizing said material dispensing means each time said measured weight of said charge is less than the optimum weight represented by said weight profile curve to thereby increase the weight of said charge.

2. The weight control system of claim 1 wherein said means for generating said weight profile curve comprises means for generating a progressively increasing signal having an asymptote which corresponds to the desired end weight of said charge, and means for storing the value of said signal at predetermined time intervals.

3. The weight control system of claim 1 further coMprising means for compensating said measured weight of said charge for error in the net charge weight measured by said weighing means.

4. The weight control system of claim 3 wherein said compensating means includes means for periodically measuring and storing a signal representing the error in the output of said weighing means due to a non-zero charge weight measurement and adder means for subtracting said signal representing the error in the output of said weighing means from said measured weight of said material, the resulting signal representing the net weight of the material in said charge.

5. The weight control system of claim 2 further comprising means for progressively decreasing the level of energization of said dispensing means as said charge is formed.

6. The weight control system of claim 2 wherein said material dispensing means comprises at least one feeder, said feeder dispensing material therefrom when vibrated and wherein said material dispenser energizing means comprises an SCR between a vibrator and a source of current, said SCR being enabled when the weight of said charge is less than the weight represented by said optimum weight profile curve.

7. A package weight control system comprising means for weighing a package as said package is being filled and generating an output proportional to the instantaneous measured weight to said package, means for generating a package weight profile curve, said curve representing the optimum desired weight of said package with respect to time as said package is being filled, means for comparing periodically during the time of filling of said package points of optimum weight on said package weight curve with said generated output proportional to the instantaneous weight of said package and producing a signal indicative of the difference thereof, a material dispenser for filling said package, and means activated by said signal for energizing said material dispenser when said measured weight of said package is less than the optimum weight represented by said package weight profile curve to thereby increase the weight of said package.

8. A weight control system comprising means for continuously weighing a charge of material as said charge is being formed, means for generating a weight profile curve comprising means for generating a progressively increasing signal having an asymptote which corresponds to the desired end weight of said charge, means for progressively decreasing the level of energization of said dispensing means as said charge is formed, and means for storing the value of said signal at predetermined time intervals, said curve representing the optimum weight of said charge with respect to time as said charge is being formed, means for comparing said weight profile curve with said measured weight of said charge, means for dispensing material to form said charge comprising at least one feeder, said feeder dispensing material therefrom when vibrated and wherein said material dispenser energizing means comprises an SCR between a vibrator and a source of current, said SCR being enabled when the weight of said charge is less than the weight represented by said optimum weight profile curve, means for energizing said material dispensing means each time said measured weight is less than the weight represented by said weight profile curve, and means for compensating said measured weight of said charge for error in the net charge weight measured by said weighing means, said compensating means comprising a second means for weighing the charge of material after said charge has been formed, means for storing the values of the measured weight of a plurality of formed charges, means for calculating the difference between the average final charge weight and a desired charge weight, means for generating a compensating signal when said difference is greater than a predetermined amount, and means for substracting said compensating signal from said signal representing the weight of the charge being formed.