1. Field of the Invention
This invention pertains to normalizing the ejection rate of fungible products progressing through multiple channels of a color sorting machine, or even through multiple channels of multiple machines, to a common master channel by the use of trip level adjustments.
2. Description of Prior Art
A typical sorting machine used for sorting fungible products, such as for sorting acceptable quality food products from non-acceptable quality food products, generally comprises for each channel through which the products to be sorted pass, one or more lighting illumination sources; optical viewing and detection stations including suitable detectors and discrimination electronics; various electronic circuits for amplifying, conditioning and classifying signals into acceptable and unacceptable occurrences; and ejector mechanisms for removing the unacceptable products from the acceptable products, which may move through the machine by gravity feed or by being belt or conveyor fed. A machine typically includes multiple parallel channels of products moving at the same speed. Moreover, multiple machines are often employed in parallel sorting, each with multiple channels.
In any sorting machine that is comprised of more than one photo detector, typically, photosensitive silicon or germanium or other element pickup devices, there is an inherent problem in using a common control, conveniently referred to as a "trip level" in defining a point at which all offending material (i.e., non-acceptable products) should be ejected. Regardless of the effort expended in fabricating, assembling, testing, and "tweaking" of signals to seek conformity from one pickup device, or one view, to another, actual signals that should be the same coming off the devices will likely all be different after a short period of time. This is because of such factors as light bulb aging, dust accumulation, mechanical vibrations and variations in the surface treatment of channels, to name a few of the causes.
Many approaches have been used to minimize the problems discussed above. Compensating circuits, such as the patented auto-null system described in U.S. Pat. No. 4,626,677, "Continuous Normalizer for an Electronic Circuit that Compensates for External and Internal Drift Factors", Edward M. Browne, issued Dec. 2, 1986, helps insure that a signal, once amplified to a particular level, is constantly corrected. This technique does assist in removing the ill effects of electronic "drift" and dust accumulation. Mechanical and pneumatic cleaning systems also are useful in keeping the equipment relatively free of dust from the environment and products being sorted, at least for short periods of use. None of these approaches, however, completely remove the problems associated with the primary signals from various pickup devices being different in relative amplitude and direction after a period of equipment operation. So long as different signal generating devices are employed, there will exist a problem of conforming the signals.
One of the most successful approaches in ensuring that the above described variables are reduced, if not eliminated, is the approach disclosed in U.S. Pat. No. 4,774,718, "Automatic Ejector Rate Normalizer" George A. Zivley, et al., issued Sep. 27, 1988, commonly assigned, which is incorporated herein for all purposes. In a monochromatic sorting machine, this patent discloses the use of a trip level value that is a result of the rate of rejection in a master channel. The master channel rejection rate is compared to a standard value and when there is a deviation, a so-called distributed trip level is adjusted. This same procedure is followed for each of the other or slave channels, but the comparison is made not to its own independent trip level value, but to an adjusted trip level value that is the distributed trip level value times a multiplier. The multiplying factor is produced as controlled by an up/down counter, in turn controlled up or down by whether the slave channel counter output or the master channel counter output arrives first. The multiplier makes the adjusted trip level value higher or lower to change the sensitivity of the slave channel to keep it operating at the same rate as the operation of the master channel.
Although the above scheme is readily suited for monochromatic sorting using analog components, the scheme is not practical for bichromatic sorting machines, for the flexible selection of which channel is designated as "master" or to the interconnecting of multiple sorting machines for operating at a uniform rate of rejection.
Therefore, it is a feature of the present invention to provide an improved automatic ejector rate normalizer for monochromatic sorting machines, and to extend the concept for bichromatic sorting machines having multiple channels and for multiple sorting machines operating at the same time to the same rate of rejection.
It is another feature of the present invention to provide improved automatic rejector rate normalizing for multiple channel bichromatic sorting machines and such multiple machines, wherein sorting can be readily normalized to the rate of any channel as the master.
It is still another feature of the present invention to provide improved automatic ejector rate normalizing with respect to adjustable trip levels of a selectable one of multiple channels of a bichromatic sorting machine or of ganged sorting machines.