Patent GB-676989-A (GB)
Title: Improvements relating to a gravity sorter
IPC: B07C5/342
Filed: 1949-11-22
Abstract: 676,989. Sorting photo-electrically. ELECTRIC SORTING MACHINE CO. Nov. 22, 1949 [Dec. 13, 1948], No. 29946/49. Class 40 (iii). General operation, Fig. 1.-Freely falling objects to be sorted photo-electrically pass through a lamp housing comprising closed side walls around a vertical axis within which are situated devices for directing light reflected from the object toward a photo-cell and associated focusing arrangements situated at one side of the housing. As shown, lemons, for example, are fed at equal intervals by a spiral conveyer 25 and rest on an upper gate 27 of the hexagonal housing 16. Shortly after the gate is opened by a timing shaft and cam mechanism geared to the conveyer and the lemon falls vertically through the housing. As it falls it receives indirect light from lamps situated in recesses 41, 42 at the top and bottom of the housing. Screens 50 and 145 shield the lemons from direct light. The light reflected by the fruit is directed by mirrors (not shown in Fig. 1) to a focusing arrangement 17 and a photo-cell 18. If the fruit, as compared with standard surfaces in the housing, is abnormally light, the photo-cell releases a lower gate 51 which hangs in the vertical position and the fruit passes to a light bin. If not, the gate deflects the fruit to a different bin. The two gates are closed by cam mechanism on the timing shaft which also carries a drum switch 79 for resetting circuits associated with the photo-cell. Housing details.-Each wall of the hexagonal housing, a plan sectional view of which is shown in Fig. 4, is provided with an opening. Three of these openings receive comparison surfaces 97. Another two carry mirrors 91, 92 and in the other is mounted the focusing arrangement 17 and the photo-cell 98. Three separate light tubes 93, 94 and 105 are in housing 17, each being equipped with lens to focus the light on the cell and a transparent dust cover 100. The central tube receives light direct from a comparison plate or the lemon when present; the others receive light either from a plate or the lemon but via one of mirrors 91, 92. Details of gates (Fig. 11). The upper gate comprises a number of pivoted sectors 53, each joined to a lever 55 through the slotted ends of which a ring 57 passes. Raising of the ring by a lever 62 and a cam 64 on the timing shaft pivots the sectors and opens the gate. The lower gate comprises a number of wires joined to a plate which is spring-loaded to pivot to rotate the wires out of the path of the lemon when a latch normally holding the gate closed is released by the photo-cell. Circuit details, Fig. 13.-Photo-cell 98, which may be connected by a triple pole switch 129 for " light trip " or dark trip " feeds a pentode 99 with a large anode load 102 (2 Megohms). The pentode is directly coupled to the grid of a cathode follower 109 which is in turn coupled through a very large condenser 108 (2 microfarads) to a further cathode follower 111 feeding the grid of a thyratron 101 which releases the latch on the lower gate, by a coil in its anode circuit. Condenser 108 and cathode follower 111 are intended to constitute a coupling circuit with a very high time-constant. Cathode follower 109 avoids the necessity for the charging current to flow through the anode load, while cathode follower 111 enables the thyratron bias voltage to be derived from a high potential source. Once per revolution of the timing shaft 15 a drum switch 79 breaks the anode circuit of the thyratron and connects the negative plate of condenser 108 to a reference potential derived from cathode follower 112 and the grid of tube 111 to leak resistors 121, 122. Photo-cells may be situated in alternate walls of the housing, each feeding its own amplifier and thyratron. The common anode circuit of all the thyratrons is broken by the same drum switch, however.