The present invention relates to a system for metering and dispensing, at a low flow rate, a high viscosity fluid, such as oil, and a method of metering and dispensing that high viscosity fluid.
Motor oil that is used in automobiles, trucks, boats and other machinery has a very high viscosity. As used herein, the term "high viscosity" refers to fluids having a viscosity of in the range of 100 to 3,000 s.s.u., that is second say-bolt units. Currently, persons seeking to purchase quantities of oil would buy the oil in small units such as quarts or possibly single gallons. The oil is customarily sold in cans or quart containers (or gallon containers). This method of selling oil differs considerably from the sale of other petroleum products such as gasoline. In contrast, gasoline has a very low viscosity (approximately 30-40 s.s.u.) as compared with oil. As a reference, water has a viscosity of 30 s.s.u. Because of the compression problem when the oil includes air and because of the slippage problem when the oil flows through mechanical metering device, an oil dispensing system that meets government standards to controllably deliver set quantities of oil has not been commercially developed prior to the present invention.
One prior art device utilized a suction pump and an air eliminator but did not include an electronic calibration circuit that corrects for imperfections or characteristics in the oil dispensing system. In practice, it is necessary to calibrate to legal units of measure all government approved fluid dispensing systems that dispense fluid as a saleable product to the public. For example, the sale of gasoline to the public involves calibrating the pump, meter and the various system items. Since gasoline is a low viscosity and high flow rate product, compressibility of the fluid is not critical nor is slippage of the fluid through the system lines a problem. In contrast, a high viscosity fluid, such as oil has a high degree of slippage. Therefore, it is very difficult to design and manufacture a calibratable system to ensure that a customer receives a full legal quart of oil when a quart is purchased. The present invention overcomes these difficulties.