Apparatus and method for a metering system

Abstract

An apparatus and method for a fluid metering system that employs a high resolution position sensor and electronics to very accurately control the amount of fluid dispensed. This sensor may be an optical sensor which translates the movement of a positive displacement pump into electrical signal pulses that are serially fed into a counter which converts them to parallel binary or binary-coded decimal form. The optical sensor uses a light-sensitive transducer to convert light rays to electrical pulses, a light source, and two graticule frames therebetween. One graticule frame moves relative to the other graticule. Each of the graticules has a large number of equally-spaced light-transmitting areas. Preset counts in the counter compensate for time lags in the system operation such as the lag due to the movement of the dispensing valve and the solenoid valve in an actuating piston. These preset counts are added to the serial counts from the sensor, and then an electrical signal from the counter is sent to a comparator which compares the sum with a programmable number. This programmable number directly relates to the amount of fluid it is desired to dispense. When it and the sum from the counter are equal, the comparator sends a second signal to actuate the solenoid valve which results in the fluid flow being stopped. The programmable number may be manually inputted or may be determined by any measurable characteristic of an object, like its weight, or any fixed relationship relating to the object, for example, a percentage of its weight. In a modification to the basic system, provision is also made to control the position of the object fluid is being dispensed into relative to the dispenser. Positioning is obtained by utilizing a control circuit and an hydraulic-linear actuator to move the object. This latter operation may be positionally controlled by a signal directly proportional to the object's weight, for example, the weight of a fowl that is being injected with a fluid additive.

I claim: 
     
       1. A fluid metering system comprising: a positive displacement pump having a movable .Iadd.and reciprocable .Iaddend.piston;   a high resolution sensing means for sensing piston movement during a finite time interval and sending a series of first electrical signals in response to said movement;   a preset counting means operatively associated with said sensing means to receive and count the number of first signals in said time interval and add to them a preset number of counts to obtain a total;   a comparator means for receiving and comparing the total signals in said counter means with a programmable number and emitting a second electrical signal when their values are equal; and   means to control piston movement in response to said second signal from said comparator; and   a dispensing means with a valve, operatively associated with said control means and pump for dispensing a predetermined volume of fluid in response to said control means.   
     
     
       2. The system of claim 1 wherein said sensing means comprises a light-sensitive element to sense linear movement of said piston. 
     
     
       3. The system of claim 1 wherein said first electrical serial signals are changed to parallel binary-coded numbers within said counting means; and said preset number is also binary-coded and has its value determined by taking into consideration time lags that occur during the system operation.   
     
     
       4. The system of claim 1 wherein said dispensing valve is a normally closed valve and said preset counter value takes into consideration the time lag caused by said valve operation by adding a time equivalent number of signals to the signal number which corresponds to the total number of first signals emitted by said sensing device. 
     
     
       5. The system claim 1 claim wherein said first electrical serial signals are changed to parallel binary-coded decimal numbers within said counting means; and said preset number is also binary-coded decimal numbers and has its value determined by taking into consideration time lags that occur during the system operation.   
     
     
       6. The system of claim 1 wherein the sensing means comprises: a light-sensitive transducer to receive light rays and convert them to electrical signals;   a digital position sensor movable with said piston movement and having a plurality of equally-spaced light-transmitting areas; and   a source of light to transmit light rays through said digital sensor to said transducer to cause said first signals to be emitted seriatim as light rays are transmitted through said areas.   
     
     
       7. The system of claim 6 wherein there are at least 40 light-transmitting areas per inch. 
     
     
       8. The system of claim 1 wherein said high resolution sensing means can sense piston incremental movements of less than 0.1 inch and said preset counting means can count at least 1000 counts per second. 
     
     
       9. The system of claim 1 wherein said control means comprises a solenoid actuated valve. 
     
     
       10. A fluid metering system comprising: a characteristic measuring apparatus with means to indicate a measurable characteristic of an object of sending an electrical-indicating signal corresponding thereto;   a positive displacement pump having a movable piston;   a high resolution sensing means for sensing piston movement during a finite time interval and sending a series of first electrical signals in response to said movement;   a preset counting means operatively associated with said sensing means to receive and count the number of first signals in said time interval and add to said total number of first signals a preset number of counts to obtain a total;   a comparator means for receiving and comparing the total number of signals in said counter means with said electrical-indicating signal and emitting a second electrical signal when their values are equal; means to control piston movement in response to said second signal from said comparator; and   a dispensing means with a valve, operatively associated with said control means and pump for dispensing a predetermined volume of fluid in response to said control means.   
     
     
       11. The system of claim 10 wherein said characteristic measuring apparatus is a scale and said electrical indicating signal corresponds to the weight of an object on said scale. 
     
     
       12. The system of claim 10 wherein said sensing means comprises a light-sensitive element to sense linear movement of said piston. 
     
     
       13. The system of claim 10 wherein said first electrical serial signals are changed to parallel binary-coded numbers within said counting means; and said preset number is also binary-coded and has its value determined by taking into consideration time lags that occur during the system operation.   
     
     
       14. The system of claim 10 wherein said dispensing valve is a normally closed valve and said preset counter value takes into consideration the time lag caused by said valve operation by adding a time equivalent number of signals to the signal number which corresponds to the total number of first signals emitted by said sensing device. 
     
     
       15. The system of claim 10 wherein said first electrical serial signals are changed to parallel binary-coded decimal numbers within said counting means; and said preset number is also binary-coded decimal numbers and has its value determined by taking into consideration time lags that occur during the system operation.   
     
     
       16. The system of claim 10 wherein the sensing means comprises: a light-sensitive transducer to receive light rays and convert them to electrical signals;   a digital position sensor movable with said piston movement and having a plurality of equally-spaced light-transmitting areas; and a source of light to transmit light rays through said digital sensor to said transducer to cause said first signals to be emitted seriatim as light rays are transmitted through said areas.   
     
     
       17. The system of claim 16 wherein there are at least 40 light-transmitting areas per inch. 
     
     
       18. The system of claim 10 wherein said highly resolution sensing means can sense piston incremental movements of less than 0.1 inch and said preset counting means can count at least 1000 counts per second. 
     
     
       19. The system of claim 10 including means to position said object with respect to said dispensing means based upon said indicating signal. 
     
     
       20. The system of claim 11 wherein the object on said scale is a fowl to be injected with liquid additive, in which said dispensing means is an injector, and in which said system is employed to control the amount of liquid additive injected into the fowl in accordance with the weight of the fowl. 
     
     
       21. The system of claim 20 including means to position the fowl with respect to the injector based upon said indicating signal. 
     
     
       22. The system of claim 10 wherein said control means comprises a solenoid actuated valve. 
     
     
       23. A method of operating a fluid-metering system comprising the step of: sensing incremental movement of a positive displacement pump piston and coverting said movement into electrical serial pulses;   counting the number of serial pulses received during a finite time interval and adding to this total a preset number of counts to compensate for delays within the system;   comparing the total number of serial and preset counts with a programmable number and generating an equality pulse if they are equal; and   .[.acutating.]. .Iadd.actuating .Iaddend.a valve within a dispensing means in response to said equality pulse.   
     
     
       24. The method of claim 23 including the step of converting the total number of serial pulses and preset counts into a binary-coded number before the comparing step. 
     
     
       25. The method of claim 23 including the step of converting the total number of serial pulses and preset counts into a binary-coded decimal number before the comparing step. 
     
     
       26. The method of claim 23 including the step of measuring a characteristic of an object and generating an electrical pulse in response thereto to act as the programmable number. 
     
     
       27. The method of claim 26 including the step of positioning an object relative to a dispenser outlet in response to the same electrical pulse generated by the measuring characteristic step. 
     
     
       28. The method of claim 23 wherein the sensing step includes the step of moving a light-transmitting area relative to a light-sensitive transducer to obtain said electrical serial pulses.