Patent GB-1132143-A (GB)
Title: Automatic flushing system
IPC: E03D5/10
Filed: 1966-07-12
Abstract: 1,132,143. Capacitative proximity detectors. TUNG-SOL ELECTRIC Inc. July 12, 1966 [July 21, 1965], No.31311/66. Heading G1N. An automatic flushing system for a water closet or urinal is controlled by the change of capacity to earth of an antenna 2, Fig. 1, on the water closet or urinal, see also Fig. 3 (not shown), as a person approaches it. This change in capacity causes a capacitor 60 to be charged and subsequently discharged through the windings 50 of a relay 52 when the person leaves the vicinity, which energized relay causes the operation of a flush valve. Means is also provided in the circuit to prevent operation of the relay if the capacitor has not been charged to a predetermined level. In the embodiment, the antenna 2, e. g. a metal plate forming the front of an enclosure (3), Fig.3  (not shown), mounted on the urinal, is connected to an oscillator 18, which in the absence of a person transmits a low signal to an amplifier 24. The output of the amplifier is connected through a capacitor 26 to the base of a PNPN switching device 28, normally in its off state as the output from the oscillator is insufficient to overcome the positive bias on the gate of the device. When a person approaches, the oscillator transmits larger pulses through the amplifier to the device 28, which are sufficiently negative to cause it to conduct. A normally energized relay 38, in parallel with the switching device 28 is thus deenergized, causing its armature 44 to engage a contact 54. This connects the capacitor 60 to the positive terminal 6 of the A. C. energizing supply, by which the capacitor is charged for as long as the person remains in the vicinity of the antenna 2. If a sufficiently long time has elapsed, the charge on the capacitor will exceed the break down voltage of a neon tube 62, which then conducts causing a transistor 48, normally in its conductive state, to be switched off. Under these circumstances, when the person moves away from the antenna 2, and the relay 38 is de-energized resulting in the disconnection of the capacitor 60 from its charging supply, the capacitor 60 discharges through the windings 50 of the relay 52, and not through the transistor 48. The energization of relay 52 causes its armature 74 to engage a terminal 78 connecting a solenoid 80, controlling the operation of the flush valve, to the terminal 6. Simultaneously the terminal 6 is applied through a diode 82 and a resistor 84 to the windings of the relay 38 to keep it energized, in order to prevent intermittent energization of relay 52, by the intermittent de-energization of relay 38 with resulting chattering of the flush valve. In the event that the person does not remain in position for sufficiently long time to ensure the full charging of capacitor 60 with resultant breakdown of the neon tube 62, the transistor 48 remains conducting, so that when the relay 38 becomes de-energized, as the person moves away from the antenna 2, the capacitor 60 discharges through the transistor 48 to earth without the energization of relay 52 and resultant operation of the flush valve. In a modification, the switching device 28 may be replaced by two transistors (130), Fig. 2 (not shown), of PNP type and one (132) of NPN type connected as a regenerative loop having the same mode of operation as the device 28. The electromagnetic relays 38 and 52 may be replaced by solid state switching devices. The capacitor 60, connected between the antenna 2 and its charging circuit, could be omitted and the two neon tubes 88, 90 in the oscillator 18 could be replaced by a single tube. The oscillator may be replaced by that shown in Specification 1, 009, 854.