GB1460143A - Water heaters - Google Patents

Abstract

1460143 Electrode boiler D G TATE and R P WOODS 17 Dec 1973 [19 Sept 1972] 43344/72 Heading H5H [Also in Division F4] A water heater comprises a container 1 e.g. a pipe, a neutral plate electrode 2 within the container, a live plate electrode 3 located within an aperture in the neutral electrode and spaced therefrom by a uniform gap 4, and an insulating layer 7 e.g. of P.T.FE between the container wall and the electrodes. The neutral plate electrode 2 is cylindrical and the live electrode 3 is arcuate, having the same curvature as the neutral electrode and being centred on the same axis. A control electrode 12 may be provided to vary the heating effect. When the earthed electrode 12 is adjacent the electrode gap 4 it increases the number of current paths between electrodes 2, 3 and thus the heating effect. When water is first passed through a pipe 1, the control electrode 12 is adjacent gap 4 and rapid heating ensues. As the water temperature rises a thermal bellows 14 expands raising the electrode 12 and thus reducing the heating effect. A flow sensitive device may actuate the heater for a timed period. The heater may be formed as a waste trap sterilizer unit, one arm of the U trap containing the heating electrodes and the other arm containing a flow sensitive switch which is arranged to actuate a magnetic reed or microswitch controlling the heater. Fig. 4, shows a printed circuit form of electrodes, the outer neutral one 25 containing four live electrodes 22 in separate apertures. The live and neutral electrodes have interdigitated extensions 23, 24 as shown. The electrodes may be formed on rigid or insulating boards, which may be flat or curved. The heater may be controlled electronically by a sensing electrode which produces a control pulse when water flows. The pulse is sensed by an operational amplifier (Fig. 5A, not shown), which passes the signal to a timer, or by an electronic timer direct (Fig. 5B, not shown). The timers connect the heater electrodes to a supply by means of a triac and a reed relay for a time change the state of the output from I3 and the circuit output 32 switches to its other state to turn on transistor N2 and turn off transistor P2 thus further reducing the impedance of path 1, 16 and increasing that of 1, 14. When E approaches +V, transistor P1 turns off. As E falls the reverse action takes place until I3 again switches, this time at a point where V1 has risen + V/2. The two switching points are thus determined by the relative impedances of the transistors in the two paths 1, 14 and 1, 16 and not by their absolute magnitudes. In a modification, Fig. 3 (not shown), the transistors P3, N3 are replaced by two transistors (P3a, N3a) connected in parallel between the junction of P1, N1 and the junction of P2, N2. This alternative form is used in a NAND circuit arrangement Fig. 5 (not shown).