Electromagnetic apparatus



Feb. 12, 1924.- 1,483,682 J. A. ROSTRON ELECTROMAGNETIC APPARATUS Filed May 5. 1920 Ina/wilful" JOSEPH A R05 77? ON Patented Feb. 12, 1924. UNITED STATES JOSEPH A. ROSTRGN, F BOSTON, MASSACHUSETTS. ELECTROMAGNETIC APPARATUS. Application. filed May 3, 1820. To all whom it may 0071mm. Be it known that I, Josnrn A. Ros'rnoN, a citizen of Great Britain, residing at Boston, in the county of Suffolk and State of Massa chusetts, have invented certain new and useful Improvements in Electromagnetic Ap paratus, of which the following is a specification. The present invention relates to buzzers, so called, in the general class of electrd magnets and electromagnetic switches, adapted as rapid make and break contact apparatus to produce a vibration making a sound or ringing a bell, and to magnets for other uses. The object of the invention is to provide improved electromagnetic apparatus of this sort which shall be extremely simple in construction, economical to manufacture, compact, and efficient in operation. In particular it is an object to avoid the customary U-shape of magnet, which is rela tively expensive to construct, and to do this without loss of magnetic efiiciency; also to produce an armature of inexpensive but effective type, and to provide also for adjustments. According to the present invention an inexpensive, straight, fiat bar of iron is the core adapted to attract a sheet metal. armature. The sides of the end portions of the metal core constitute pole faces for the sides of the end portions of the armature. The coil is wound about the middle of the core. The armature is substantially parallel to the core at a little distance therefrom, but the sides of its end portions are offset toward the core so that the armature constitutes an iron path from one end to the other of the straight core, such path being bowed out around the Winding thereon. To obtain a buzzer effect the armature may have a sheet metal integral extension edgewise from its middle, long enough to have necessary flexibility for vibration when clamped at the extremity. The neck leading to this clamped end may make and break contact with a bit of sheetmetal constituting a stationary switch memher just beside it. A very simple and etfi cient device is thus provided that is procurable for a small fraction of the cost prevailing for similar articles today. The principle may however be applied in more expensive and larger apparatus with correspond ing advantages. Serial No. 378,476. In the accompanying drawings illustrating the invention: Figure 1 is a perspective view of one embodiment of the present invention showing the base in dot-and-d-ash lines and the armature in contact with the core; Figure 2 is a section on the line 22 of Fig. 1, looking in the direction of the arrows; Figure 3 shows the same as a bell. The electro-magnet of the present invention comprises a fiat, straight core 2, the sides of whose ends 4 and 6 constitute pole faces being in fact a simple section cut from a length of bar iron and an energizing winding 14 thereon. The armature 8 is preferably a stamping of thin sheet iron, set parallel therewith, the sides of whose end portions 10 and 12 are adapted to contact with the sides of the pole pieces 4.- and 6, respectively. The armature ends are ofiset towards the poles from the body portion of the armature, it being ordinarily less expensive to bend such thin sheet metal, and less expensive to wind the coil on a straight core. In the illustrated embodiment of the invention, the offset ends are thus shown upon the sheet metal armature, the ofisetting being effected by a die which blanks out the shape and then bends the ends, which may be all at one operation. The armature is a T-shaped piece, with the leg of the T constituting a flexible stem that holds the armature proper, whose poles are at the ends of the arms of the T. When the winding 14 is energized, the armature will be drawn to the core until their respective ends are in contact, thus closing a good magnetic circuit. As the winding is flat on account of flat shape of the core, the armature body can fairly be close to it and substantially parallel with it, with one side 18 of the coil lying in the bowed space 16 of the armature, whereby a very compact structure is obtained. In order to adapt the electro-magnet to switch purposes, the armature is made the movable member. The core is accordingly shown as stationary, supported upon the bottom 20 of an insulating base which may be a mere wooden cup with the bar iron core simply pressed in tight; although additional fastening may be employed if desired such as tacks driven into the wood. The extremity of the leg 22 of the T is fastened to the bottom 2% of a recess 26 in the side wall 28 of the base. The head of the T is mounted parallel to the core, so that its ends may be drawn to the poles, the somewhat springy sheet-metal leg 2-2 of the T bend1ng to permit such movement, and flying back immediately on the weakening of the magnet. When the armature occupies its normal open position, it contacts with a sheetmetal switchmember 30 which is fastened in the same recess 26, with the leg of the armature, and with the same single screw, being insulated therefrom at Thus a current is passed through the coil of the magnet. \Vhen the armature is attracted to the core, it breaks contact with the switch member, thereby opening the magnet circuit. Thereupon the armature springs back, away from the magnet. Contact between the armature and the switch member may thus be rapidly made and broken in accordance with rapid energization of the winding 14, to cause the operation of a buzzer or similar device in well known manner. Terminals 36 and 38 are conveniently made in the wooden wall 28 by screws passing through it. Of course more elaborate contacts and adjustments can be made at will, but it is one advantage of the invention that adjustments can be made in the simple form illustrated by merely bending the short contact piece 30 or the armature leg 22. To use the invention as a bell a hammer 40 may be attached to the armature and a bell 42 mounted on the base, as indicated in Figure 3. The base can be made of any other suitable material if found more desirable than the wood mentioned. It is intended that the patent shall cover by suitable expression in the following claims whatever patentable novelty is involved in the invention disclosed. I claim as my invention: 1. A vibrator comprising, in combination, a casing having fixed within it an electromagnet and one electrical contact; and an armature, secured in the casing between them and bearing the other electrical contact; the magnet core and said armature being flat metal sheets arranged with their broad surfaces parallel to each other; the said magnet sheet being relatively thick, constituting a straight bar and having the winding about its middle; and the said armature sheet being relatively thin, elastic and flexible, and having its end portion bent around the end portion of the said winding on the magnet, to proximity with the magnet core. for vibrating toward and from the broad side of said core. An electric vibrator having, in combination, a section of flat bar iron comprising a core, the sides of whose ends constitute pole faces and about whose middle is wound an energizing coil; and a T-shaped elastic sheet iron armature, the arms of the T being parallel to said bar, overlying the coil with their ends offset from the plane of the middle part toward the respective pole faces to co-operate closely therewith nothwithstanding the coil intervening between the straight armature and core; a base to which the leg of the T is secured; and a terminal for make and break contact with the said leg said leg and terminal having contacts for make and break of an electric current. In a vibrator, the combination of two fiat, broad strips of permeable material arranged with their broad surfaces parallel to each other; one of them being relatively thick and constituting an electro-magnet core, and the other relatively thin and constituting its armature: the said core strip being straight and having its energizing coil wound about its middle; and the said armature strip being relatively thin, elastic and flexible, and having its end portion bent around the end portion of the said winding to proximity with the magnet core, for vibrating toward and from the broad side of said core. 4. A make and break apparatus comprising in combination an electromagnet whose core is of straight bar iron whereon is wound medially an electric coil, the sides of the ends of the bar being exposed; an armature of sheet metal bowed around said coil with the sides of its ends against and parallel with the said sides of ends of the magnet; a tongue extension of the sheet metal comprising the armature, perpendicular thereto, supporting it and constituting part of the electrical circuit; and a base to which it is secured at a distance from the armature, thereby to vibrate to and from. the side of the bar. Signed at Boston, Massachusetts, this 15th day of April, 1920. JOSEPH A. ROSTRON.



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