US2859337A - Power transformer shield for radio receiver - Google Patents

Description

Nov. 4, 1958 E D 2,859,337

POWER TRANSFORMER SHIELD FOR RADIO RECEIVER Filed March 15, 1954 IN VEN TOR JAN JOO ST RIETVELD AGENT United States Patent POWER TRANSFORMER SHIELD FOR RADIO RECEIVER Jan Joost Rietveld, Eindhoven, Netherlands, assignor, by

mesue assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware The present invention relates to radio receiving apparatus. More particularly, the invention relates to a radio receiving apparatus comprising a frame aerial structurally united with the apparatus, more particularly, an incorporated aerial. The component parts of a radio receiver are, in general, housed in a rectangular cabinet of wood or other insulating material. It is often desired to unite the aerial, in the form of a frame, directly with the apparatus. For this purpose the frame is preferably arranged inside the cabinet in a vertical diagonal plane in order to obtain a maximum surface. Since in this case the directional effect of the frame frequently gives rise to interference, use is often made of two frame aerials each arranged in a different diagonal plane. These aerials are used separately or in conjunction, for example, in series combination, for the reception.

A receiver comprising such an aerial, which is structurally united with the apparatus, provides the best results, if it is fed directly from the power supply, for example, an alternating-current power source or a directcurrent power source via a rectifier. Feeding by means of a supply transformer gives rise to interference which is suppressed only with difiiculty by electro-statically shielding the windings.

The invention has for its object to suppress this interference in a simple manner.

It must be assumed that the said interference is due to magnetic couplings between the frame and the windings of the supply transformer and that across these windings, parts of which may function as high-frequency resonant circuits, undue high-frequency currents may occur, producing interference in the reception.

The invention consists in that use is made of a supply transformer provided with a magnetic shield. This shield may comprise a closed winding of one or more turns, completely surrounding the transformer. The plane of the winding is parallel to the plane of the turns of the transformer windings. The shield is preferably constructed in the form of an electrically closed tape surrounding the transformer at the area of the windings.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein:

Fig. 1 is a schematic diagram of an embodiment of radio receiving apparatus viewed from the rear;

Fig. 2 is a schematic diagram of the transformer 6, 7 of the embodiment of Fig. I, viewed from the top; and

Fig. 3 is a schematic diagram of the transformer 6, 7 of the embodiment of Fig. 1, viewed from the rear.

Referring to Fig. 1, reference numeral 1 designates 2,859,337.- Patented Nov. 4, 1958 the cabinet of the receiving apparatus, made of wood or other insulating material. In the interior of the cabinet, in vertical diagonal planes, provision is made of two frame windings 2 and 3, each of which comprises one or more turns and which operate as receiving aerials. These windings may be included separately or in conjunction in the input circuit of the first tube of the receiver. The cabinet comprises, moreover, a chassis 4, in which and on which the various parts of the apparatus, for example, the tubes 5, are mounted.

It is assumed that the receiver is fed from an alternating-current power source and that provision is made of a supply transformer, constructed in this case as a shell transformer, the central core of which supports the windings. The magnetic circuit 6 of the transformer is, as usual, laminated, and the windings 7 of the transformer are arranged coaxially about the central core. It has been found to be difiicult to arrange the transformer in a manner such that it does not produce interference.

According to the invention, a magnetic shield in the form of a closed tape 8 is provided to surround the entire transformer, i. e. the windings and the cores. The tape 8 may be made of material of good conductivity, preferably of copper and the ends may be united by soldering at 9 in a manner such that an electrically good conducting circuit is formed. The width of the tape may be equal to the length of the coil or it may be smaller.

It has been found that the said undue magnetic couplings may thus be suppressed to such an extent that substantially no interference occurs.

The frame aerial or aerials may, as an alternative, be arranged in a different manner in or on the cabinet.

While the invention has been described by means of a specific example and in a specific embodiment; I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

A radio receiver comprising a radio signal processing assembly including an alternating current supply transformer for energizing said signal processing assembly and a frame aerial comprising a plurality of turns of conductive material arranged in a plurality of given planes and structurally united with said assembly and in close proximity thereto, said supply transformer comprising a plurality of windings positioned substantially within said turns and having a common axis and a magnetic shielding member comprising a closed winding of copper tape looped over the windings of said transformer and interposed between the said windings of said transformer and said aerial, said closed winding of tape being arranged with its axis substantially perpendicular to said planes.

References Cited in the file of this patent UNITED STATES PATENTS 1,775,276 Ferguson et al. Sept. 9, 1930 2,228,174 Miller Ian. 7, 1941 2,388,848 Howe Nov. 13, 1945 2,515,333 Buflington' July 18, 1950 2,520,984 Williams et al. Sept. 5, 1950 2,552,816 Root May 15, 1951

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