Aquatic animal counting
This invention relates to the counting of aquatic animals such as fish, and also relates to the grading or sorting of such animals. 
     The need for an effective device for counting aquatic animals such as fish has existed for a long time. Many different devices have been proposed, from the very simple to the very sophisticated, and it is believed that none has proved to be satisfactory to any great degree. The result is that most fish counting today is believed to be done manually by the tedious task of counting and weighing samples, and then weighing the entire group of fish. This method not only is slow but it is inaccurate. 
     Accordingly, it is an object of this invention to provide a fast, reliable, accurate and labor-saving device and method for counting aquatic animals. It is another object of the invention to provide such a device which is reliable in operation and relatively inexpensive to produce. 
     The foregoing objects are met, in accordance with the present invention, by the provision of a device and method which combines the counting operation with sorting or grading of the fish as to size, thus utilizing the same labor to grade the animals and to count them. 
     A grading barrier is provided with a plurality of openings. The fish are urged toward the openings. A detector near each opening detects each fish and produces an electrical signal which is counted by an electronic counter. The openings are of a size to pass only animals smaller than a pre-determined minimum size. The remaining fish can be counted, if desired, by enlarging the openings. The grading barrier can be used horizontally, either in the water or out of the water. In this case, gravity assists in urging the animals towards the barrier. The barrier also can be placed vertically between two containers for the animals, with the animals being herded toward the barrier to urge them through it. 
     Preferably, the detector at each opening consists of an electrode which normally contacts a contact member to form a closed switch. The passage of the animal through the hole opens the switch and creates a signal which is stored in a memory. The memory is sampled subsequently in a sequential manner and the signals are read out of the memory into a counter which counts them. 
     The foregoing and other objects and advantages of the invention will be set forth in or apparent from the following description and drawings. 
    
    
     In the drawings: 
     FIG. 1 is a perspective, partially broken-away and partially schematic view of a counter-sorter constructed in accordance with the present invention; 
     FIG. 2 is a cross-sectional, partially broken away view taken along line 2--2 of FIG. 1; 
     FIG. 3 is a cross-sectional schematic view of another embodiment of the invention; 
     FIG. 4 is a partially broken-away, partially schematic view of the underside of the grading barrier of the device of FIG. 1, together with electronic detecting and counting circuitry; 
     FIG. 5 is a schematic circuit diagram of another embodiment of the invention; and 
     FIG. 6 is a schematic plan view of another embodiment of the invention. 
     GENERAL DESCRIPTION 
     FIG. 1 shows a counter-sorter device 10 constructed in accordance with the present invention. The device 10 includes an upper hopper portion having end-walls 12 and 14 and side-walls 16 and 18. In the bottom of the device 10 is a grading barrier 28. The grading barrier 28 has holes 30 of a size selected to allow only fish smaller than a pre-determined size to pass through. Each hole has an electrical switch 27 which is used as a detector which is operated when a fish passes through. A counting device 32 counts the fish by counting the number of operations of the switches. Thus, both grading and counting of the fish can be done in one operation. 
     Immediately above the grading barrier is a grading bar assembly 20 with parallel grading bars 21 which are spaced from one another so as to allow only fish smaller than a given size to pass through. These bars protect the switches 27 from false actuation by fish too large to pass through the holes 30. 
     Now considering the counter-sorter device 10 in greater detail, the walls 12 and 14 of the device 10 preferably are hollow and filled with a foam material such as polystyrene in order to cause the device 10 to float on water. The water level when the device 10 is floating is indicated at 19. A housing assembly 22 is provided beneath the grader bar assembly. The assembly 22 includes a skirt 24 forming a housing, and the grading barrier 28. The skirt 24 has a hinged end-wall 26, and guides 38 and 40 (see FIG. 2) so that the panel 28 can be moved in and out of the unit 22 by lifting the hinged end-wall 26 and sliding the panel 28 along the guides 38 and 40. 
     Referring now to FIG. 2, which is a cross-sectional view taken along line 2--2 of FIG. 1, the holes 30 in the grading barrier 28 are spaced so that there is one row of holes for every pair of grader bars 21. The Diameter D of each hole is the same as or slightly larger than the spacing C between adjacent bars 21. The height H between the grading barrier and the bars 21 is sufficient to prevent fish too large to pass between the bars 21 from activating the switches in the holes 30 as they writhe and swing their bodies about. 
     Referring again to FIG. 2, the fish being counted, such as the fish 42, swim between the grading bars 21 and downwardly towards one of the holes 30. As the fish passes through the hole, it bends the thin, flexible contact member 34 which is attached across the hole and opens the switch 27. The opening of the switch is used to develop an electrical signal. Such signals are counted by the electronic counting device 32, which indicates the total number of fish passing through. 
     In order to regulate the flow of fish through the holes 30, frustro-conical guides 44 (shown in dashed outline in FIG. 2) can be provided. In effect, these guides form funnels leading to each hole 30 and help to keep fish from becoming trapped between the bars 21 and barrier 28, as well as guiding the fish towards the holes. 
     It also should be understood that the holes can be more or less numerous relative to the grader bars 21 than indicated in FIG. 2, if desired. 
     Although the device has been described as operating while immersed in water, a form which is preferred for some fish species such as channel catfish, the device then also can be operated in the open air with certain other species such as trout and salmon. In either case, the barrier is horizontal so that gravity assists in the operation. 
     The device 10 also can be operated as a vertical barrier between two adjacent bodies of water as is illustrated in FIG. 3. FIG. 3 shows the grading barrier 28 aligned vertically, as are the grader bars 21. The barrier 28 separates two adjacent bodies of water 120 and 122, for example, in a raceway. Large fish 124 cannot pass through the grading barrier, but small fish 126 can. They are counted then in the same way as in the other embodiments described herein. 
     ELECTRICAL DETECTION CIRCUITRY 
     Returning now to FIG. 2, each electrode 34 of each switch 27 is a thin stainless steel wire which is secured to one end to a mounting post 36. The wire 34 is resilient and normally makes electrical contact with a metallic contact member 58 on the opposite edge of the hole which the electrode 34 bridges. When the fish 42 passes through, it breaks the contact by moving the wire 34, thus providing a substantial change in the electrical impedance through the switch. This changes is used to provide an electrical signal which is detected by the electronic circuitry to be described below. One advantage of the invention lies in the fact that the operation of the switch provides a substantial impedance change and, therefore, a reliable indication, regardless of whether the device 10 is immersed in water (even salt water) or is used in the open air. 
     FIG. 4 shows the counter mechanism 32, together with a portion of the underside of the barrier 28. The holes 30 are arranged in rows and columns. Two rows 52 and 53 and three columns 46, 48 and 50 of holes are shown in FIG. 4. Each of the binding posts 36 is connected through the insulating material of the barrier 28 to a metal bar or strip 60, 62 or 64 associated with each of the three columns of holes. Each of these strips preferably is applied to the board 28 by conventional printed circuit technology, and is coated with a protective material, such as epoxy resin, except at points where electrical contact is made. The strips 60, 62 and 64 are on the upper or opposite surface of the sheet 28. They are not shown in FIG. 1 for the sake of clarity in the drawings. 
     On the underside of the board 28 are printed-circuit conductors leading to the contacts 58, 56 and 54. The electrodes 34 make contact with the conductors 54, 56 and 58. 
     Connected as shown to the conductors leading to the contacts 54, 56 and 58 are external conductors 66, 68 and 70. Similar conductors 67, 69 and 71 are connected to the conductors leading to the contacts for the other row 53 of holes. 
     The conductors 66-71 are connected to an electronic memory shown in dashed outline at 72. The memory 72 preferably consists of several latching circuits 74, 76, 78, 80, 82 and 84, each of whose function is to store the signal it receives on its upper input lead and then to deliver a corresponding signal over its lower output lead 94 when enabled by a signal delivered over a line 96. A conventional shift register 86 driven by high-frequency signals from a clock source 88 is provided as a scanner. The shift register applies an output pulse on each of its output leads 94 in sequence, and automatically repeats this operation over and over again. The shift register thus scans the latches and reads the stored signals out sequentially to a conventional electronic counter 90. The counter 90 can be reset by means of a conventional reset switch 92. 
     From the above description it can be seen that each of the electrodes 34 and its corresponding contacts 36, 58, etc. forms a switch which is normally closed. If the shift register 86 enables one of the latches 74, 76 etc. while the associated switch is closed, a signal is not delivered by the latch, and a count is not registered in the counter 90. If, however, the switch has been opened by the passage of an aquatic animal through one of the holes 30, then the latch stores a signal. Actually, the latch is a flip-flop which is switched to a new state by the opening of the switch, and is reset by the shift register. When the sampling signal comes from the shift register, a signal is delivered to the counter 90 which counts it, and the latch is reset to await another signal. 
     Preferably, the clock rate (output frequency) of the clock 88 is much higher than the frequency with which fish pass through the grading barrier so that the sequential sampling of the latches and the storage of the signal until the sampling is done enables fish to pass through various holes simultaneously without any fish being missed. 
     FIG. 5 shows an alternative embodiment of the invention in which the vertical conductors 60, 62 and 64 of FIG. 4 are arranged with horizontal conductors 106, one for each row of holes, to form a matrix. Each of the electrodes 34 is connected between one of the vertical conductors 60, 62 or 64 and one of the horizontal conductors associated with the row of holes to which the electrode 34 belongs. A clock source 104 drives a first shift register 100 which sequentially enables each of the horizontal lines 106, and then repeats the cycle. A second shift register 102 enables one of the vertical lines 60, 62 or 64. At the end of each cycle, the shift register 100 develops a signal on line 101 which shifts the second shift register 102 and thus changes the selected one of the vertical lines 60, 62 and 64. In this manner, selected ones of the vertical lines and the horizontal lines are enabled so that the condition of each switch can be determined uniquely. The information regarding the condition of each switch is read out by sending the shift register pulses through interface circuits 108 and 110 to a random access memory 112 in which the condition of each separate switch is stored at a unique location in the memory. The information stored in the memory 112 then is read out (preferably under the control of the clock source 104) to the counter 90, which indicates the total number of fish counted. 
     The circuit shown in FIG. 5 has the advantage, compared with the circuit in FIG. 4, that it does not require as many individual conductors leading from the board 28 to external circuitry. This leaves more space on the boards for holes and reduces the complexity and cost of the board. 
     In accordance with another aspect of the present invention, safety features are provided to ensure that an opening of the switch is caused by a fish passing through. It is known that fish or other species of aquatic animals with which the device is used will require a certain amount of time to pass through the hole 30. A shift register can complete many cycles in the time it takes for a fish to pass through one of the holes. Therefore, preferably, when a signal is received from one of the switches indicating that it is open, this is not taken as the indication of a fish passing through until such time as the signal has endured during each of several successive sampling cycles. This is accomplished by using a counter at each location in the memory to count up to a count of three or four before a signal is stored. If, for example, less than four signals are received before a switch is closed again, then no signal is stored in memory, the counter at that memory location is reset to zero, and the counter does not count. This feature of the invention discriminates against and minimizes the counting of spurious switch openings due to water currents and other extraneous causes. 
     It is preferred that the random-access memory 112 be of the MOS FET type, in which each memory cell consists of a semi-conductor flip-flop circuit. In such a memory, successive cells (e.g. 113, 115 in FIG. 5) can be connected together in series to form a counter with a minimum of extra circuitry. 
     VARIATIONS 
     If desired, all of the fish in a batch can be counted in one counting operation without sorting them. This can be done simply by selecting holes 30 and openings between grader bars 21 large enough so that all of the fish in the batch will pass through. 
     Alternatively, the counting and sorting operation can be done in two or more different steps, the first one for sorting out small fish from the larger ones, with one size of hole 30, and the second step with larger holes to count the remaining fish. It may be easiest to simply change the grading barrier 28 in order to change the size of the holes. Alternatively, the structure of FIG. 6 can be used to change the size of the holes. The structure in FIG. 6 includes a pair of side-rails 130 and 132 which can slide along the longitudinal edges of the panel 28, and the bars 134 and 136 attached to the bars 130 and 132. By sliding the structure along the board, the holes 30 can by covered and uncovered as desired to enlarge or constrict the holes 30. Other structures are known for performing the same function. 
     The above description of the invention is intended to be illustrative and not limiting. Various changes or modifications in the embodiments described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention.