US1896819A - Method and means for reducing radio interference - Google Patents

Description

Feb. 7, 1933. E. N, HYDE 1,896,819

METHOD AND MEANS FOR REDUCING RADIO INTERFERENCE Filed May 5, 1931 Patented Feb. 7, 1933 PATENT OFFICE ERNEST N. HYDE, OF PHILADELPHIA, PENNSYLVANIA METHOD AND MEANS FOR REDUCING RADIO INTERFERENCE Application filed May 5,

This invention relates to a method and means for reducing to the extent of practical elimination radio interference caused by the making and breaking of an electric circuit,

which making or breaking may be complete or only partial, as in the case of thermally operated flashers for signs or the like.

In cases where circuits carrying currents for power purposes are opened or closed,

either partially or completely, there are propagated disturbances of high frequency which produce audible cracks or noises, depending upon the frequency of such breaks, in radio receivers. Such making or breaking is particularly annoying when it occurs in connection with the operation of a motor provided with a commutator since in such cases the disturbances follow each other in rapid succession producing a continuous noise.

It is the object of the present invention to provide both a method and means for carrying out the method which are both of general application for the elimination of interference of the type mentioned above, occurring because of the use of motors, sign flashers,

switches, or the like.

Detailed objects of the invention relating particularly to preferred constructions will be apparent from the following description read in conjunction with the accompanying drawing in which:

Fig. 1 is a wiring diagram showing one preferred form of the invention; and

Fig. 2 is a wiring diagram showing a modii fication.

Referring first to the modification illustrated in Fig. 1, 2 and 4 represent currentcarrying wires which may lead from an alternating or direct current source to a load.

It will be understood that these wires may be considered to be parts of the wiring of a motor. Located in series with one of these wires is a suitable capacity indicated as a condenser 6. While in the preferred embodiment the capacity consists of a separate condenser, it may under certain circumstances be provided by the distributed capacity of the coil 8 which, in Fig. 1, is shown as shunted across the condenser 6 in series with the contacts 10. The contacts are also merely dia- 1931. Serial No. 535,119.

grammatically illustrated and may be of any i K of the usual circuit making or breaking forms. For example, they may be switch contacts or the contacts of a thermal flasher, in which case a circuit is not completely open because the contacts remain shunted by the high resistance heater wire. Or the contacts here diagrammatically illustrated may consist of the circuit interrupting arrangement provided by the brushes and commutator of a direct or alternating current motor.

In any case, the essence of the invention comprises the location of the contacts, this word being used in a broad sense, within the electromagnetic field of coil 8, the contacts being preferably located at the point of maximum intensity of this electromagnetic field which, in the case of a solenoid, would be its geometrical center.

As a specific instance of one device which is found to be very effective in producing substantially an entire elimination of interference, there may be cited a case in which a lamp load was supplied, being provided with the arrangement of Fig. 1, the condenser 6 having a capacity of approximately .400 mfd. and the coil 8 comprising 72 turns of #22 copper wire wound as a solenoid having a diameter of about 4.5 inches. In this case the breaker consisted of a mercury switch, the load being approximately 260 watts. It is found, however, that very large variations may be made in the constants of the circuit. For example, the condenser may be from .0006 mfd. up to .500 mfd., or even larger Likewise, the inductance of the coil may vary widely as will be brought out more particu larly in connection with the second modification.

In the modification illustrated in Fig. 2 there is again provided a condenser 6 in series with the line while shunted across this condenser are the coil 12 and contacts 16 in series with each other. In this case the coil 12 consists of iron wire wound upon a wooden support 14, the contacts 16 being located in the geometrical center of the form. In this case. of course the electromagnetic field at the contacts is substantially equivalent to that produced by a single turn. However, the inductance of the coil is quite large, particularly because of the magnetic material of which the coil is made. As an alternative arrangement a magnetic core may be used upon which copper wire could be wound or parallel to which the wire convolutions may lie, Whereby again a relatively high inductance would result. Comparing the arrangement in Fig. 2 with that in Fig. 1, both of which are found to be satisfactory, it will be seen that the inductance as well as the capacity may vary within wide limits, the inductance in Fig. 2,

being considerably larger than that in Fig. 1. If the core of the arrangement of Fig. 2 is metallic it may form part of the circuit, that is, the contacts, core and coil may all be in series shunted across the condenser.

Both the coil and condenser may, of course,

. take various forms depending'upon conditions, and, in the case of the coil, the required current carrying capacity, since the coil preferably carries the full load. Alternatively, of course, the coil may, in the case of large loads, be shunted by a lower resistance path so that it carries only a fraction of the total the contacts being located substantially at the position of maximum intensity of the electromagne'tic field of the coil, and a capacity shunting the coil and contacts, the coil and capacity forming a circuit having a high natural frequency.

In testimony of which invention, I have hereunto 'set my hand, at Philadelphia, Pennsylvania, on this 1st day of May, 1931.

ERNEST N. HYDE.

current. Of course, in certain arrangements several coils arranged in series or parallel may be used, the contacts being located in their combined fields or in the fields of any one of them. 7 V 7 It is'found that interferencemay be substantially eliminated even though the contacts may not be in series with the coil in whose field they lie providing that this coil is supplied with the same type of current as that interrupted by the contacts and both are.

in synchronism with each other. For example, if 60 cycle alternating current is being interrupted then it is found thatthe contacts in such circuit may be located in the field of a coil shunted by a condenser carrying 60 cycle current even though the current thereto may not be interrupted by the movement of the contacts.

Still more 'efiectiveness may be given to the device in certain instances by shielding the coil and contact points by their location within a conductive container and this shielding container .may be grounded. In certain cases where the current density is very high, the whole device may be immersed in oil or other liquids to suppress arcing, or they may be enclosed in sealed or unsealed glass or quartz or metalcontainers or shields.

What I claim and desire to protect by Letters Patent is i i 1. An arrangement for reducing electromagnetic radiations due to the openingor closing of contacts in a circuit, including a coil arranged tocarry current, the contacts being located in the field of the coil, and a capacity in parallel with the coil, the coil and capacity forming a circuit having a high natural frequency.

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