US1523349A - Movable coil for electrodynamic receivers - Google Patents

Description

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E. S. PRIDHAM ET AL.

MovABLE COIL FOR ELECTRODYNAMIC REGEIVERS FiledAlVIay l0, 1922 lll Patent dan., 13, 1925,

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EDWIN S. PRIDHAM AND PETER L. I'IilIiTSEIhL` OF OAKLAND, CALIFORNIA, ASSIGNORS T0 THE M AGNAVOX COMPANY, OF OAKLAND, CALIFORNIA, A CORPORATION OF ARIZONA.

MOVABLE COIL FOR ELECTRODYNAMIC RECEIVE-RS.

AppIication led May 10,

Z 1o all whom it may concern:

Be it known that we, EDWIN IDRIDHAM and PETER L. JENSEN, citizens of the United States, residing at Oakland, county of Alameda, and State of California, have invente-d new and useful Improvements in Movable Coils for Electrodynamic Receivers, of which the following is a specification.

This invention relates to movable coils for electro-dynamic receivers,

.il receiver of the type under consideration is illustrated and described in our application, Serial .No 377,354, filed April 28th, 1920, of which the present application .is a continuation and improvement.

The receiver comprises generally an electro-magnet havingconcentric pole pieces with a circular coil disposed in the annular space between the pole pieces, said coil bcing rigidly attached to the diaphragm of a sound box. The object of the present. inventionis to simplify and improve the construction, operation and assembly of a movable coil of this type.

One form which our invention may assume ,is exemplified in the following description and illustrated in the accompanying drawing, in Which- The figure' shows a central sectional View of the upper portion of af receiver embodying our invention'.

So much of the magnetic structure asis necessary to an understanding of the invention is shown herein and `includes an iron casing 10, a core 11 Within the casing and a winding 12 for the core. The core terminates in a pole piece 13 and a plate Mfitted upon the casing and provided with a circular opening to surround the pole piece 13 constitutes an outer pole piece. These. pole pieces should be carefully spaced so as to leave a true annular space for the reception of the movable coil.

This coil comprises a ring-shaped frame 15 of insulating material formed with a depression 16 to receive a winding 17. This winding consists of a large number of turns of very fine Wire, 'The coil is rigidly connected to a diaphragm 18 of a sound box by means` of abracket 19. This bracket is somewhat cone-shaped' in form With its sides cut away, vleaving three or more legs 20. The legs each have a small integral lug.

1922. Serial No. 559,751.

2l at their lower ends to enter a small opening 22 in the insulating frame of the coil for connecting the parts together. The apex or top portion 23 of the bracket is provided with a central openingl through which a ssrew 24 passes for connecting the saine to the diaphragm, the screw lbeing preferably provided with a nut 25.

Since the coil vibrates freely, it is important to bring the leads into the coil in such a way as to avoid breakage and this we accomplish by connecting the ends of the coil b v soldering or otherwise to flat metallic conducting strips 26, which are led along the legs of the bracketand across the lower face of the diaphragm to the outer edge thereof, where they connect with binding posts 27. The metallic strips are laid between twov adhesive tapes 28 and by means -of theseadhesive tapes the conducting strips are held in place on the bracket and diaphragm. Inasmuch as the vibration at the periphery of the diaphragm is comparatively small, the conducting strips are not subjected to the liability of breakage as they would be if they extended directly out from the movable coil to the stationary posts. 1

In assembling the coil, the bracket is connected to the frame thereof by slightly compressing the legs to bring them within the frame so that thelugs 21 enter the openings in the frame. Then the legs are spread and the lugs bent over to retain the parts together. The bracket is thereafter connected to the diaphragm and the latter is positioned on the sound box to bring the movable coil into proper' position Within the annular space bet-Ween the poles. IVe nd that a bracket, such as shown herein, having a somewhat conical shape affords the desired rigidity and, furthermore, the open sides are important, since an enclosed connecting member or bracket in this location would impair the value of the tones given oft' by the diaphragm.

Having thus described our invention, what We claim and desire to secure by Letters Patent is:

1. In an electro-dynamic receiver, an inner cylindrical pole piece, an outer pole piece having a cylindrical opening surrounding `and spaced from the innepole 1.iece, a circular coil positioned within .irannular lli) space between the pole pieces, said coil comprising an insulating frame having a large number' ot' turns oi' line Wire Wound upon its exterior, a flexible diaphragm and means for rigidly connecting said frame to the diaphragm, saidl connecting means comprising a conical member cut away at its sides to form legs, said legs fitting within the frame and each having an integral lug to enteran opening in the frame and means for connecting the apex of the bracket to the central portion oi' the diaphragm.

2. In an electro-dynamic receiver, an inner cylindrical pole piece, an outer pole piece having a circular opening surrounding and spaced from the inner pole piece, a circular coil positioned Within the annular space between the polepieces, said coil comprising an insulating frame having a large number of turns of fine Wire Wound upon its exterior, a diaphragm, abracl'ret having a plurality of legs extending from the insulating Jframe up to the diaphragm for rigidly connecting the coil thereto, and means for electrically connecting thecoil to the stationary binding posts comprising conducting strips ad?.

hesively secured to the legs of the bracket and to the under surface of the diaphragm.

3. In an electro-dynamic receiver, an inner cylindrical pole piece, having a circular opening surrounding and spaced from the inner pole piece, a circulaicoil positioned Within the annular space bef. tween the pole pieces, said coil comprising an insulating frame having a large number of turns ot' ine Wire Wound upon its eX- terior, a diaphragm, a bracket having a plurality of legs extending from, the insulating frame up to the diaphragm for rigidly connecting the coil thereto, and means for elec trically connecting the coil to the stationary binding posts, said means comprising a pair of adhesive strips for each end of the coil applied to the legs of the bracket and. to the under side of the diaphragm and a conductpr carried between each pair of adhesive strips.

lEDWiN s. PEIDHAM. PETER L. JENSEN.

an outer pole piece

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