Measuring and testing – Volume or rate of flow – Tank type
Reexamination Certificate
2000-07-17
2002-12-24
Patel, Harshad (Department: 2855)
Measuring and testing
Volume or rate of flow
Tank type
C073S305000, C073S861570, C137S395000, C137S409000
Reexamination Certificate
active
06497143
ABSTRACT:
The present invention relates to apparatus for measuring liquid flow on a continuous “flow-through” basis, and more particularly, to a container of unique design which permits accurate measurement during the low flow rate periods, such as at the beginning and at the end of the flow cycle.
The invention is particularly well suited for the measurement of milk yield of individual cows in a dairy farm. It can be used in conjunction with automatic milking machines of conventional design.
At one time, milk yields from individual cows were measured only on an occasional basis because taking accurate measurements is time consuming and requires additional equipment, as well as skilled personnel to operate the equipment. However, the daily measurement and recording of the milk yield for each cow in a herd can enhance the overall milk production significantly. Monitoring daily milk yield facilitates, among other things, efficient culling (selling of inefficient milk producers for beef), feed allocation on a selected basis (group or individual) and calved cows problems (including due date). Further, it is useful in detecting cows in heat, mastitis and other health problems.
The data obtained from daily measurement of milk yield enables the owner of the herd to detect problems quickly and to react to them by taking the necessary steps to maintain the optimum milk yield for each animal, either by altering the feed mix, administering medication, or the like. In spite of the usefulness of this data, to be practical, measurements must be capable of being made without imposing additional work load on the personnel, who are already fully occupied by caring for the livestock.
Apparatus for the measurement of quantities of liquid, such as milk, on a batch basis, are known. One example of such apparatus is disclosed in U.S. Pat. No. 4,173,892, entitled “Apparatus For Measurement of Quantity of Liquid in Container” issued on Nov. 13, 1979 to Boris Khurgin. That apparatus is designed to generate an electrical signal proportioned to the total milk volume in a container of glass or similar non-conducting material. The container is provided, on its exterior surface, with a pair of spaced, opposed electrodes which operate like the plates of a capacitor, with the container and its contents acting as a dielectric. The capacitance of the container is sensed and a representative electrical signal is generated which can be used to calculate the total volume of the liquid in the container.
The apparatus of the above mentioned patent has been found to produce very accurate results. However, its use requires considerable extra work and time on the part of the dairy personnel because it is a batch-type process, where measurement can be made only after all of the milk from the cow is in the container.
Metering flow during milking is not possible with the batch type capacitance measuring system because liquid flowing into the container, and thus between the capacitor surfaces, interferes with the accurate measurement of the capacitance which is a result of the liquid in the container. Moreover, such containers, because of their dimensions, require containers which are relatively tall.
In order to reduce the time and effort associated with making accurate measurements of daily milk yields for each cow, a flow-through liquid measuring apparatus was developed. That apparatus, in its simplest form, comprises two concentric vertical tubes. The exterior surface of each tube is provided with a metallic coating which acts as an electrode. Each electrode is electrically isolated from the other, so as to form a capacitor. The inner of the two concentric tubes is connected at its upper end to a pipe conveying milk through an orifice. The size of the orifice is selected to maintain the liquid level in the tube above a restriction of known dimension, as long as milk flows through the apparatus. The inner tube and the outer tube communicate through openings in the inner tube wall adjacent the restriction, causing the liquid to rise to the same level in both tubes.
The capacitance between the plates changes in proportion to the liquid level in the space between the concentric tubes. The two electrodes are connected to an electronic circuit which generates a voltage output proportional to the capacitance. The milk level in the apparatus changes in proportion to the square of the milk flow rate through the restriction. The electronic circuit is designed to take the square root of the voltage output, in order to obtain a signal which is proportional to milk flow rate. This function is then integrated over the interval of time for the milking operation, so as to obtain the total milk yield.
For health reasons, milking machines and associated hardware designed to handle the flow of milk, must be capable of being sanitized and completely cleaned of all milk residue at regular intervals. Any equipment, such as that which measures the flow of milk, must also have this capability, so as to prevent contamination. Aside from high initial cost, one significant drawback of the double tube design is the difficulty inherent in keeping the apparatus clean and sterile.
Another drawback, which is common to all types of apparatus employing opposed capacitor surfaces separated by a liquid, is that milk, or any other liquid, when it is receding, forms a thin layer or coating which remains on the interior tube walls for a certain period of time. This residue causes the instruments to falsely detect a higher capacitance than which corresponds to the actual milk level. Although this error is relatively small, it nevertheless causes inaccurate final results of the milk yield and, thus, this type of apparatus may not be suitable in cases where extremely accurate results are required.
On Feb. 28, 1984, U.S. Pat. No. 4,433,577 entitled “Apparatus For Metering Liquid Flow” issued to Khurgin et al. That patent discloses apparatus for continuously measuring the rate of flow of a liquid from a source which overcomes the disadvantages of the flow-through capacitance type measuring system. The apparatus includes a container with an inlet tube connected to the liquid source. The container has an inlet port, connected to the inlet tube, through which liquid is supplied to the container. An orifice is situated at the bottom of the container to permit liquid to drain from the container at a known rate. An outlet tube is connected to the orifice. A conduit is provided to connect the container, at a point above the liquid therein, and the outlet tube, for equalizing the pressure therebetween. Means are provided for sensing the liquid level in the container and for generating a signal representative of the instantaneous rate of liquid flow through the container, in accordance with the sensed liquid level.
A bypass conduit connects the container and the outlet tube. This conduit permits liquid situated above a given level in the container to bypass the orifice and flow directly into the outlet tube. The pressure equalizing conduit and the bypass conduit may be embodied in a single conduit connecting the upper portion of the container and the outlet tube.
The apparatus is designed for use in conjunction with suction means which form a portion of an automatic milking machine. When so used, the suction means and the inlet tube are connected, such that milk is drawn through the tube and into the container by the suction action of the machine.
The signal generating means disclosed in the patent includes means for detecting the level of the liquid surface in the container, means for generating an analog signal representative of the detected surface level, and means for converting the analog signal into a digital signal representative of the liquid flow rate. Means are provided for integrating the digital signal over a given time period and for generating a signal representative of the total liquid volume flow through the container, during the time period.
One category of detecting means described in the patent is a plurality or array of sensors situated along the vertical sur
Epstein Robert L.
James Harold
James & Franklin LLP
Mack Corey D.
Patel Harshad
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