US2288265A - Automatic keying device - Google Patents

Description

Patented June 30, 1942 AUTOMATIC KEYING DEVICE Irving F. Byrnes, Riverdale, N. Y., assignor to Radio Corporation of America, a corporation .of Delaware Application February 14, 1941, Serial No. 378,881

2 Claims. (Cl. 17866) This invention relates to keying devices and more particularly to an arrangement for automatically keying a radio transmitter which is used to send out distress signals. The invention, however, has other applications which may readil suggest themselves to those skilled in the art.

It is an object of my invention to provide a system and a method for utilizing a direct current source to produce a periodic keying action consisting of circuit closures for definite periods of time separated by open circuit conditions for other definite periods of time.

It is another object of my invention to provide apparatus including a direct current source, a converter for deriving an alternating current from said direct current source, a synchronous or other constant speed motor, and a keying device operable by said motor for alternately closing and opening a circuit during periodically recurring time intervals.

It is conventional practice in radio marine signaling systems to send out a series of dash signals separated by spaces for the purpose of transmitting a distress call. Certain automatic alarm responsive devices are now standardized which will answer to a distress call consisting of at least four dash signals of four seconds duration separated by spacing signals of one second duration. Certain tolerances are made, however, in the durations of the dashes and the spaces respectively so that manual keying of the radio transmitter may be permissible. It is advantageous, however, to provide an automatic keying device which will more accurately determine the time intervals for the successive dashes and spaces in distress calls. Such a keying device is contemplated in the improvements herein disclosed.

On ship board it would be desirable to use alternating current and a synchronous motor driven thereby for timing the dash and space intervals of the distress call. The usual power supply system on board ship is not, however, one of alternating current but of direct current. Furthermore, it frequently happens that when a ship is in distress its entire power supply system is disabled. This, condition makes it desirable to operate any radio or auxiliary apparatus by means of storage batteries, or batteries of other types. It is, therefore, a further object of my invention to provide means for automatically keying a radio transmitter in accordance with the requirements of international distress calls, using only the power supply which is available from a battery.

Other objects and advantages of my invention will be appreciated upon review of .the following detailed description in which the accompanying drawing is referred to. In the drawing the sole figure represents diagrammatically a circuit arrangement and component elements in combination for producing certain new results.

The keying circuits I and la. may lead to the normal keying circuits of one or more radio transmitters. These circuits are closeable by means of a relay 2. The relay in turn is actuated by contact members 3 consisting preferably of a pair of contact springs one of which is substantialiy stationary, while the other is actuated by a rotating cam 4. The periphery of this cam is designed to open the contacts during one-fifth of a revolution, that is, for one second, and to close the contacts during the remaining fourfifths of a revolution, or four seconds. The preferred rotational speed of the cam 4 is determined by a reducing gear 5 and the speed of the synchronous motor 6.

Means are provided for converting the direct current from the battery source 1 into alternating current, consisting of a vibrator 8 of more or less conventional type. This vibrator is provided with a winding 9 in circuit between one terminal of the battery I and a self-interrupting contact arrangement shown at Ill, the other side of which leads back to the battery. The armature of the vibrator 8 is mounted on a spring I! in such manner as to have a definite vibration rate. When the winding 9 is unenergized, a circuit is closed from the battery I through the back contact which takes current from the spring I and feeds it to one of the windings in the synchronous motor 6. When the vibrator Winding 9 is energized, the current from battery I is diverted through the front contact which then engages with the spring H and is thence fed to another winding of the synchronous motor 6. The periodicity of the vibrations in the spring 9 is such as to set up periodic impulses alternately directed into different windings of the synchronous motor 6. This motor may be provided with means for automatically starting the same, or it may be provided with a knob on the end of its shaft for manually spinning it into synchronous speed.

In shunt with the self-interrupting contacts I0 I preferably provide a capacitor l2 for reducing the are on breaking the contacts ID. A doublepole single-throw switch 13 may be provided for starting the keying device when it is to be put in service. Fuses l4 may also be provided as amatter of protection against the possibility of short circuits.

In the operation of my improved keying device it will be clear that it is only necessary to close the switch I3, see that the vibrator 8 starts humming, see that the synchronous motor 6 goes into operation and finally to note that the keying operation itself is being properly efiected. This last step in the operation may be noted by the flashing of a pilot light I6 which is in parallel with the relay winding 2'.

The invention is to be understood as not necessarily limited to the precise details of the circuit arrangement and the combination elements as herein shown and described. On the contrary, the scope of the invention is limited only in accordance with the claims.

I claim:

1. In an automatic keying device for radiant energy transmission of distress signals, a source of direct current, a fixed frequency vibrator of the electro-magnetic type operable from said source, said vibrator having contact members arranged to alternately close two circuit paths from one terminal of said source, an alternating current motor having windings connected to said circuit paths and to the other terminal of said source, a reducing gear constituted by a worm driven by said motor and a gear driven by said worm, a cam rotatable by said reducing gear at a relatively slow angular velocity, said cam having a one-to-four ratio between the angles subtended by its maximum radius and its lesser radii, contact elements operable to an open-cit" cuit position by the cam periphery of maximum radius, and keying means including a relay energizable by periodic closure of said contact elements, during the relatively long periods of such closure as compared with the open-circuit periods.

2. In a device of the class described, a source of direct current, a substantially constant frequency vibrator operable by current from said source to produce a double-path output of discrete current pulses, a constant speed alternating current motor operable by said current pulses, cam controlled switching means for keying at least one circuit on and off during predetermineo marking and spacing intervals respectively, said cam being of suitable shape to produce marking intervals substantially four times as long as the spacing intervals, and a reducing gear through which the cam of said switching means is driven by said motor, said gear having a ratio such that the periodicity of said marking and spacing intervals is of the order of several seconds per cycle compared with an interrupting frequency of said vibrator amounting to many current pulses per second.

IRVING F. BYRNES.

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