US2115865A - Electromagnetic relay - Google Patents

Description

0. LU H N ELECTROMAGNETIC RELAY May 3, 1938.

Filed Aug. :51, 19:55 ZSheets-Sheet 1 fawn zar o. LUHN ELECTROMAGNETIC RELAY Filed Mg. '31, 19:55

2 Sheets-Sheet 2' In van for.-

Patented May 3, 1938 UNITED STATES PATENT OFFICE Germany Application August 81, 1935, No. 38,797 In Germany April 12, 1935 8 Claims. (Cl. 115-320) 7 It is wellknown that, in the electric control of recording devices, lighting systems and the like by means of capacity variations, an amplifier must be employed if the controlling device is to m operate satisfactorily. Amplification is also necessary if the controlling device operates by means of a photo-electric cell. It is also known that contacts with small directing force, such as thermal elements and moving coil contacts, produce 10 sparkling which tends to destroy the contacts. The tendency of the contacts to stick is also a cause of failure of the controlling device, to act satisfactorily. I

The usually employed amplifiers, operating with or without thermionic valves,'moving coil relays, and the like, while generally too expensive, are not suificiently reliable for ensuring a satisfactory operation of the controlling devices. The known employment of a moving coil galvanometer has proved unsuitable on account of its tendency to act under the influence of the slightest mechanical vibration.

The object of the present invention is to obtain a relay which, without being affected by mechanical vibrations, is readily responsive to capacity vibrations, and which will operate without amplifying ,devices and with contacts, such as thermal elements, moving coil contacts and the like having very small directing force.

a With this object in view, the invention consists essentially in the combination with an electro-magnetic relay of a variable resistor of particular construction which is responsive to the smallest pulsations of current and which can be I operated by means of a' capacity diaphragm or other contact with very small directing force.

The variable resistor has the property of lowering its resistance under the influence oi weak pulsations of current and thus allowing a local,

40 normally inactive electric source to operate the relay.

. Fig. 1 of the accomp nying drawings represents a diagram of one form of the relay,

Fig. 2 is a sectional view of the variable re- 45 slstor,

Figs. 3 and 4 are views showing different modifications of the operating device,

Fig. 5 is a diagramof a modified form of relay,

Fig. 6 is a diagram of a iurther modification,

60 Fig. '1 is a sectional view of a modified form. of

resistance, a Fig. 8 is a detail view .of the resistor, and

Fig. 9 is a diagram of electric connection of the In order to start the tongue 2i vibrating under resistance. i i The relay shown in, Fig. l'comorisea an electromagnet i; a shorting armature 2; a switchoperating armature 3; a variable resistor 4 carried by the armature 3; an interrupter comprising a contact spring II which is operated by the armature I and which co-operates with a rigid a contact i2; and a rotary switch comprising a cam l which is operated by means of a ratchet wheel 6 and a pawl 5, the latter being mounted on the armature 3. The cam 1 co-operates with two contact springs I1 and II which close and break 10',

circuits by co-operation with contacts is and 20. The circuit of the electro-magnetic relay contains the winding of the electro-magneti one end of which is connected through the interrupter with the positive pole of an electric source 16 ii, the other 'end-of the winding being connected through contacts i6, 9 and 8, through the variable resistor 4, through the armature I and through the armature-controlling spring ll with the negative pole of the source II. 20

The internal resistance of the element 4 is very high so long as the element is not affected by pulsations of current, and the direct current from the source I5 will not flow through it to the extent of operating the readily responsive armature 2. v

The resistor 4 comprisu, as shown in Fig. 3, a pair of dished stampings 31 and 38 which are filled with tinsel 48 and connected together over an insulating frame 39 to form a casing. The latter contains a pair of oscillatory electrodes 40 and 42 which are connected by means of blade, springs 4| and binding posts 44 and 45 to the two parts 31 and 38, one to each. Any weak pulsations of current to which the electrodes are exposed will, as is usual in coherers, reduce the resistance of the tinsel to the potential imposed on it by the source ii. The two masses of tinsel separated by the presence of the insulating frame ll, may be interconnected by means of a lead containing two coils 48 and 41 embedded in the tinsel. This arrangement, which somewhat reduces the resistance of the resister 4 to the current from the source II, will not be required except in the case of relays desired to be especially sensitive.

The relay comprises in addition a transformer 21 the primary 0! which is connected to the mains, the secondary being connected on the one hand to the mains and on the other hand, 50 through a capacitor 2: and through the contact spring i1 and contact is, to a vibratory tongue 2! which can be adjusted by means of a screw 24.

the influence of a capacitor variation, a metal plate 22 is provided which is slightly spaced from the tongue. The diaphragm formed by the tongue 2| and the metal plate 22, serves the purpose of setting the tongue 2| into vibrations whenever the plate 22 is influenced by hand or body capacity. The tongue, on being vibrated, makes contact with the plate 22 and thus sets up weak pulsations of current. When a metallic conductor approaches or contacts with a pole subjected to a static electric charge, sparks are produced which in their turn set up pulsations of current, and it therefore follows that such pulsations will be obtained by the contact of the tongue 2| with-the plate 22. In order to enable the pulsations of current to actuate the variable resistor 4, the lead from the transformer 21 to the contact springs l! is connected to the resistor through capacitors 25 and I8.

When, with the arrangement shown in Fig. 1, the metallic plate 22, which may be arranged behind a glass plate 23, is subjected to a capacity variation, the tongue 2| begins to vibrate, and as it touches the plate 22 impulses of current will be set up which are transmitted through the capacitor 25 to the variable resistor 4. The internal resistance of the latter then sinks and allows direct current from the source l5 to pass through the winding of the electro-magnet I, the circuit being traced through |2||--||84- 3--|3|5. The shorting armature 2 will then be attracted by the magnet and placed against the contact I6, thereby cutting out the resistance from the circuit which is traced through |2,- ||,-|-|62|3--|5. The magnet will then be suiliciently energized for attracting the armature 3 which lifts the spring II from the contact |2 and thus breaks the circuit of the relay. At the same time the armature 2 leaves the contact |6 under the influence of the spring l3, and the armature 3 is also restored by the spring I4 to its normal position. The return movement of the armature 3 brings about a rotation of the cam I so that the contactspring II will be separated from the contact I8, while the contact spring I8 will be brought into contact with the contact 28, thereby connecting a retarding device 33 to an electric source 36. Since, owing to the altered positionof the cam the connection of the relay with the tongue 2| is broken, further operation of the relay by capacity variations is temporarily impossible. The restoration of the device to operative position is 'eiTected after a predetermined time by means of the retarding device 33. This is eifected by means of an armature 3| which, after a given lapse of time, is momentarily attracted by a magnet 38, thereby discharging through the contact 32 the tension imposed on the armature through the capacitors 26, 25, and 28 and producing sparking at the contact 32.. The circuit is traced through earth, 21, 26, 25, 28, 3|, 32, 28, I8 and earth. As the armature is connected through 28, 8 and 8 with the resistor 4, the latter will be affected by impulses of current due to the sparking, andthe relay will once more be operated for restoringthe cam and the springs I1 and I8 to their normal positions. Thereupon the relay is again ready for operation.

The operation of the relay through capacity variations can alternatively be eilected by means of the tube shown in Fig. 3 which contains two electrodes 58 and 5|. A capacitor formed by a plate 53 is tuned by a capacity 52 arranged across the electrodes, so that no sparking will take place between the latter except when the plate 53 is capacitively influenced.

Electricimp'ulses by hand or body capacity can also be setup by means of the device shown in Fig. 4. I This device comprises a star electrode 68 which is mounted on a supporting disc 54 so as tov be easily rotatable. The four limbs of the illustrated electrode 58 co-operate with the rigid electrodes 55, 56, 51 and 58 secured to the disc 54. The distance between the cooperating electrodes is regulated by means oi. a screw 68. A coil 6 connects the star electrode with the contact I8. When the disc 54, which is insulated from the electrode 58, is influenced by hand or body capacity, the star electrode will be attracted by the rigid electrode, and pulsations of current will be set up by the contact between them.

The retarding device connected to the contacts l8 and 28 in Fig. 1, may be of any suitable known type. For instance it may be fitted with a clock movement which is released when the current from the source 36 passes through the terminals 35 and which, after a predetermined time, operates a switch for energizing the magnet 38. Lamps 34 or other indicating devicesmay be included in the circuit of the contacts I8 and 28.

illumination of a selenium cell 86 for shifting the needle from the contact 83 onto the contact 84. The slightest contact of the needle with the contact 84 will cause pulsations of current to be set up which reach the variable resistor 65 through a capacitor 89, whereupon first the armature 63 and then the armature 64 will be operated. After the armature 64 has been operated, the circuit of the source 16 is interrupted by the contact spring 12 which leaves the contact 13, thereby restoring the armatures 63 and 64 to their initial positions. The return movement of the armature 64 is brought about by a spring 15 and effects a rotation of the switch cam 68 through the medium of the pawl 66 and the ratchet wheel 61, whereupon the spring 18 leaves the contact 88 and makes contact with the contact 8|. When the illumination of the selenium cell is interrupted, the needle of the coil 82 returns to the contact 83, sparks and impulses of current being then again produced for renewed operation of the relay. This causes the spring 18 to be pressed against the contact 88, thus restoring the relay to its normal condition. The retarding device in Fig. 6 is only used in some cases for retarding the restoration of the relay to its normal condition. In this case the electric connection between the contact 83 and contact 8| is interrupted, so that the restoration oi the relay will be effected by means of the retarding device instead of by means of the moving coil needle. In order to nullify the suction effect on the needle due to the tension between the contacts 88 and 8|, capacitors 85 and 81 are placed in parallel with the contacts 88 and 8|. For instance, a suction effect would exist between the contact 84 and the needle in the absence of the capacitor 85. v

The relay shown in Fig. 6 also employs a moving coil galvanometer and can be used for the same purpose as the relay shown in Fig. 5. The

circuit comprises an electro-magnet |8|; an interrupter comprising a contact spring I and a contact II2; a source III of electric current;

avariable resistor Ill; and contacts Ill and Ill. The relay'difl'ers from that of Pig. 5 principally by the feature that one pole oi the source II! is connected to the variable resistor Ill through a coil I II, the other pole being connected to the resistance through contacts Ill and Ill according to the position of the spring I" relative to the contacts I22 and I21 01' I24 and I2l. The object of this arrangement is to-cause the variable resistor to be short-circuited at the moment of contact between the galvanometer needle and its contacts I21 and I 2l. Such a contact and the resulting pulsations of current, will be suflicient to influence the variable resistor and to allow the direct current from Hi to energize the electromagnet I III. The operation is substantially the same as before. the like, fed from a source 9, can be switched on and oil! by means or the'contacts Ill and I2I. The lead containing the capacity I2l may connect the resistor Ill with a source Ill or alternating current in order to render the relay more responsive. The relay may be controlled either by direct or alternating current according to the nature of the moving coil. The spark-quenching property ot-the variable resistor is very large, be-

cause the internal resistance thereof sinks con-.

siderably under the influence or the electromagnetic oscillations caused by the sparking. In

, order to achieve this eilect, the constructions shown-in Figs. 2 and 7 are of importance. The resistor shown in Fig. 8 consists of a casing the body portion I22 01' which is made or insulating material while the top and bottom portions Ill and Ill are adapted to serve as electrodes. The casing is filled with tinsel having the p rty of reducing the electric resistance under the influence of the pulsations of current. The tinsel content of the casing is divided by an insulating disc I into two separate portions. The shaft 'Ill on which the disc Ill is mounted is divided into two parts which are connected by insulating bosses Ill and Ill. The disc Ill serves as a compensating means' for restoring the normal positions by a rotary movement of the disc. The

rotation may be eitec'tedthrough the medium of an arm Ill which may for this purpose cooperate either with the armature Ill or with a magnet Illwhichisarrangedintherelaycircuitby means oi'leads I. v

Iclaim:

1,.An electro-masnetic relay ior operating switches and the like, comprising an electromagnet, a switch-operatingarmahire for said As an example, a lamp I20 or 2. The relay claimed in claim 1 in combination with an additional armature responsive to smaller currents than the switch-operating armature, and means controlled by said additional armature for cutting out the resistance from the circuit when attracted by the magnet.

3. The relay claimed in claim 1 in combination with a retarding device, and means operated by said device for restoring the relay to its initial condition.

4. A relay as claimed in claim 1 wherein the spark producer comprises a vibratory tongue connected to the source providing the static tension, and wherein the actuating means consists of a metal plate adapted to attract and make contact with said tongue under the influence or hand or body capacity.

5. A relay as claimed in claim 1 wherein the spark producer comprises an electrode tube having one electrode connected to the source providing the static tension, and wherein the actuating means consists of a plate connected to a second electrode in the tube so as to generate oscillations under the influence of hand or body capacity.

8. The relay as claimed in claim 1 in combination with a source of alternating current, a lead connecting said source with the resistor, and a condenser arranged in said lead.

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