Patent GB-371330-A (GB)
Title: Improvements in electro magnets which may be associated with electrical contacts or otherwise, applicable more particularly to electric clocks
IPC: G04C3/00
Filed: 1930-10-17
Abstract: 371,330. Electric clocks. SOC. ANON. DES ETABLISSEMENTS L. HATOT, 12, Rue du Faubourg St. Honore, Paris. Oct. 17, 1930, No. 31212. Convention date, Oct. 17, 1929. Void [Published under Sect. 91 of the Acts]. [Class 139.] A polarized electromagnet particularly for driving clocks comprises a coil-carrying core N with sheet metal polepieces B movable in the field of a permanent magnet A, a number of iron posts P being mounted parallel to the axis of the coil and connected magnetically to the poles of the permanent magnet by sheet metal member E having a certain amount of elasticity and bent to allow space for the flexible connections to the coil. The permanent magnet A is preferably of cobalt steel and other parts of the magnetic circuit may be of electrolytic iron, or alloys of nickel or silicon. In the form shown in Fig. 1 the coil is in two parts and the pivot passes through the core ; alternatively, a single coil is employed and the pivots are carried by two brass brackets screwed to the polepieces B. The polepieces B are shaped in various ways depending upon the sensitivity required. The coil may be supplied with alternating current or continuous current, the return movement in the last mentioned case being effected by a spring. The movable core and the polepieces may be integral with each other as shown in Fig. 19 or stampings may be used both for the movable core and stationary poles as shown in Fig. 17. Fig. 18 shows a form in which the coil is concentric with the axis of rotation. The polarized magnet is constructed to occupy the smallest possible space, so that when used in connection with clocks having translucent dials illuminated from the back, the shadow mark is small. Fig. 11 shows a suitable arrangement in which the coil oscillates about a pivot O<1> and drives the hour and minute hands through a ratchet and pawl and toothed gearing. If the coil length is greater than the radius of the clock casing, the arrangement shown in Fig. 15 may be adopted. If a continuous oscillation is required as for example in clock winding mechanism, a mercury or other interrupter may be employed. Fig. 7 shows an interrupter comprising a contact pin 11 fixed on the oscillatory coil and co-operating with a pivoted member 12 formed of magnetic metal and having conducting and non-conducting parts. The edges of the member 12 are so shaped that movement to one side or the other inaugurated by the pin 11 is completed by the attraction of one of the fixed polepieces P, and contact between the pin 11 and the conducting portion of the member 12 occurs during a part of the movement in one direction, the return movement of the coil being effected by a spring. Fig. 10 shows a watch case in which a modified interrupter switch is applied to watch spring winding mechanism. The coil carries a pin 11<1> which imparts movement to a member partly conducting and partly non-conducting upon which rubs a brush b. A magnetic screen t shields delicate members of the watch from the strong magnetic field. The use of the described contacts in a two-position motor for remote control and the application to time distribution are referred to. Modifications are described in which the polepieces P and the resilient members E are dispensed with, the coils have the pivot at one end, and the coils are fixed and co-operate with movable permanent magnets or unwound cores. Fig. 25 shows means for obtaining unidirectional rotation from the oscillating coil. In one direction of movement of the coil the pinions z carried by arms b jam on the wheel R but rotate freely when moved in the opposite direction. The pinions z may be replaced by cams acting on a non-toothed wheel. In a modification, movement is transmitted through a clutch controlled by the alternating current supplying the oscillating coil.