Patent GB-274137-A (GB)
Title: Improvements in means for enabling electric supply mains to be utilised for operating wireless receiving apparatus or the like
IPC: H04B1/16
Filed: 1926-01-06
Abstract: 274,137. Urquhart, J. W-, and Dubilier Condenser Co. (1925), Ltd. Jan. 6, 1926. Charging and discharging batteries; voltage modifying a p p. a r a t u s.-The filament circuits of wireless receiving apparatus are supplied from a.c. or d.c. mains through two secondary batteries of equal and relatively small capacity which are intermittently interchanged between charging and discharging circuits by an electrically controlled commutator device, preferably an electromagnetic switch controlled automatically by two facsimile thermal switches. During periods of rest both batteries are in parallel equalizing their charges. Means for supplying the plate circuits may be included; the means described for a.c. mains is applicable to three different mains voltages. The apparatus may be embodied in a unitary structure. The electromagnetic switch C comprises two actuating coils G, Fig. 6, and an armature E pivoted at F and operating an arm H lying between, two sets of spring blades a, b, c and d, e. The blades normally lie against sets of contact screws a<1>, d<2> but by the oscillation of the armature E are alternately engaged! with sets of contacts a<2>, d<1>. The arrangement constitutes a two-pole change-over switch a, b, d, e for the batteries incorporated with a further switch c controlling the thermal switches. The moving system is slightly unbalanced so that it moves to one extreme position when both magnets are energized. The thermal switches each comprise a heating coil wound upon a mica strip K, Fig. 5, confined between relatively broad strips M, N of brass and steel respectively with intervening insulation, all being anchored to an insulating block P. The switching devices may be energized in parallel or in series with the battery charging circuit. Fig. 2 shows an arrangement for supplying filament and plate circuits from a.c. mains 1, 2, a double pole switch 5 controlling leads 8, 35 to the former and leads 45 to the latter. A filtering or smoothing circuit as described in Specifications 241,944 and 241,946, [both in Class 38 (ii), Electric currents, Converting &c.], is included in the latter circuit. The filament supply includes a variable resistance 9 regulating the battery charging current, a resistance 12 in shunt to the thermal switches L, L1, to regulate their time interval and a variable resistance 44 in parallel with the filament circuits to regulate the load on the discharging battery and prevent overcharging. The battery A is connected to the switch blades d, e and the battery B to the blades a, b whilst the output circuit is connected to the co-operating outer contacts of both and the input to their inner contacts; a condenser 38 of about 1 mfd. is in parallel with these input contacts. The blade c is connected to the common junction of the heating coils of the thermal switches and the contacts c<1>, c<2> respectively to their other ends so that each is short-circuited in turn by the movement of the arm H. The magnets 24, 25 and the switch C are in series with the thermal switch coils. Each magnet is in series with one thermal switch contact, these being closed when cold. The thermal switch contacts are shunted by condensers of about 1 mfd. High resistances may shunt these and the condenser 38. Fig. 3 shows an arrangement including a double plate thermionic rectifier 62 in the low tension supply circuit and a double filament thermionic rectifier 63 of the type described in Specifications 220,966 and 237,233, [both in Class 39 (i), Electric lamps, Arc &c.], in the high tension circuit, these being fed from two transformers 70, 71, each with three primary circuits adapted for various connections and wound for 110, 110 and 20 volts respectively. The thermal switch heaters are fed from a, separate secondary on the transformer 71. The coils of the electromagnetic switch are included in the charging circuit and a battery 61 under the control of a relay 60 is connected in parallel with these coils to prevent humming due to the rectified a.c. Specification 241,947, [Class 38 (ii), Electric currents, Converting &c.], also is referred to.