Patent GB-420557-A (GB)
Title: Improvements in or relating to electric bells
IPC: G10K1/064
Filed: 1934-01-19
Abstract: 420,557. Reciprocating motors. DUNGEY, J. W., 97, Casino Avenue, Herne Hill, London. Jan. 19, 1934, No. 1905. [Class 35] Mechanism for producing an oscillatory movement by electrical means, for use more particularly as an electric bell, comprises a single coil and moving core in combination with a frictionally held make and break device which is operated during a portion only of the movement of the core for the purpose of producing an oscillating movement of the latter, the said mechanism being brought to a set position when at rest by a weight or spring. Mechanism is also described for operating a rocking bar linking piece in an oscillatory manner by electrical means comprising two solenoid coils and plungers in combination with a frictionally held make and break device which is operated during a portion only of the movement of the moving parts. Fig. 1 shows a construction of electric bell comprising a solenoid coil a in which is adapted to oscillate a plunger b having a preferably non-magnetic neck d<1> and striking head d. A switch arm e, arranged between the plunger b and head d and adapted to engage with contact f, is frictionally pivoted at c. In operation, when the circuit is completed through coil a, the plunger b moves upwards so that its head d strikes the gong h. When in this position the shoulder b<1> of the plunger has moved switch arm e away from contact f thus breaking the circuit and causing the plunger to return by its weight or spring z and strike the gong in its resting position. The arm e has in the meantime and during the main portion of the plunger's return been frictionally held at the off position and is only moved into contact with f by the underside of head d near the end of the plunger's return stroke. The circuit being again completed, a repeat sequence takes place which causes a rapid oscillation of the plunger so long as the outside circuit is closed. Fig. 3 shows a modified construction in which the striking head d is secured to a metal stem l and insulated extension m adapted to move freely in a recess at the end of the plunger b<3>, a pair of contact springs I, K being in frictional contact with the part l. On closing the circuit, the plunger is drawn upwards causing the head d<3> to strike the gong h<3> in which position the insulated portion m of the stem comes between the springs I, K and disconnects the circuit. The plunger then falls but the portion m is frictionally held between the springs I, K until near the end of the plunger's return stroke when the spun over end of the wall n of the plunger engages and pulls on the end projection of m. Fig. 4 shows a construction employing two coils R<1>, R<2> and a pair of plungers V<1>, V<2> carried by a centrally pivoted bar t. A centrally pivoted switch arm o is in frictional contact with a bearing spring W and is adapted alternately to engage a pair of contacts P, Q so as to effect the alternate energization of the coils R', R<2> and impart a rocking movement to the bar t so that the hammers x, y carried thereby alternately strike the gongs u, the arm o being frictionally held in engagement with one of the contacts P, Q during the greater part of the travel of the plungers V<1>, V<2>. When one coil is energized, the other coil may either be disconnected or as shown, short-circuited.