US2057902A - Relay - Google Patents

Description

Oct. 20, 1936. H. MOREAU 2,057,902

RELAY Fi 1 ed Jan. 18, 1953 2 Sheets-Sheeh 1 lz'gj.

UNITED STATES PATENT OFFICE RELAY Henri Moreau, Paris, France Application January 18, 1933, Serial No. 652,400 In France January 26, 1932 2 Claims.

Relays responsive to weak currents (such for instance as contact galvanometers) do not allow the use of powerful returning springs or other powerful resilient returning members.

The condition of sensitiveness requires, in fact,

that the movable unit should be able to move under the action of a very reduced amount of energy. The returning spring must therefore be so much the more weaker as the required sensitiveness is greater.

On the other hand,

the necessity of an electric contact as satisfactory as possible leads to giving the contacts a very small common section, in order that the unitary contact pressure should not be too reduced. It results therefrom that the zone of contact is practically punctform.

In these conditions, it sometimes happens that the contacts no longer separate, even when the circuit of the relay is open, as the returning spring is sometimes too weak for overcoming the adherence of punctiform contacts.

The main object of the invention is to avoid this inconvenience and to sitive relays of the type indicated as safe and render the operation of sencertain as that of ordinary relays.

The accompanying drawings illustrate, by way of example only, some forms of carrying the invention into practice.

Fig. 1 is a diagram relating to a rst form of construction.

Fig. 2 is a diagram in which the energization of the relays takes place from currents circulating between the variable potential apices of a Wheatstone bridge.

Fig. 4 is a diagram tion.

Fig. 3 is a diagram of an installation for the control of temperatures.

of constructional modificawhole is so adjusted passes between the points 5 and 6 between which the winding I oi a sensitive relay is arranged. In other words, the rectifiers I and 2 form with the that, normally, no current resistances 3 and 4 a closed circuit wherein a constant current circulates permanently; the resistances 3 and 4 are selected so that the points 5 and 6 of the said closed circuit are of the same potential under normal circumstances.

However,

for instance, the resistance 4 is sensitive to the variations of temperature; it is therefore only at a predetermined temperature, for instance, 20 degrecs centigrade, that the points 5 and 6 are of the same potential.

The relay controls the closing of the circuit of apparatus such as a time switch device 8. A resistance 9 is arranged in the supply circuit of the rectier 2, for the purpose hereinafter described.

I1' the temperature decreases, the resistance 4 5 also decreases. Consequently, the potential at the point 6 becomes lower than that at the point 5 and a current, first of low intensity, passes through the sensitive relay 1, the movable unit 'Ia of which closes a contact at 1b, and a current flows in the circuit of 8. But the said circuit is in shunt with the terminals of the resistance 9. Consequently the difference of potential at the terminals of the primary of the transformer, which feeds the rectiiier 2, increases. The difference of potential at the terminals of the secondary therefore also increases so that the potential at the point 5 increases, this determining a rapid increase of the current in 'I and the positive closing of the contact.

The time switch 8 controls, the energization of an electromagnet I0, and thereby, the inversion of a rocking mercury contact having a double tube and adjusted in such a manner that the tube II iirst causes the opening of the circuit of the time switch 8, and thereafter the circuit of the relay 'l 25 is opened by the tube I2.

The time-switch device is of any known type comprising a relay which when it is energized, acts upon a movable armature which closes a contact, r and is then released after a predetermined time by 30 a clockwork movement. The relay I0 remains energized as long as the clockwork mechanism has not released the armature for breaking the contact of the energizing circuit of the said relay.

In the diagram of Fig. 2, a Wheatstone bridge is provided with groups of resistances I3, I4, I5, and I6; a relay I9 is arranged between the points I 'I and IB which are normally at the same potential during normal conditions, no current passes through this relay. 40

f The armature of the relay I9 is arranged for closing the circuit of an electromagnet 23 when the said relay I9 is energized and this circuit electromagnet 23 is shunted at 2I and 22 on the resistances I3 and I4. The electromagnet 23 is similar to4 the electromagnet I0 of the preceding example and the resistance I5, for instance, is similar to the resistance 4, that is to say it is sensitive to the variations of temperature. If the temperature decreases, the resistance I5 decreases. The potential at the point I8 increases and a current circulates from I8 to Il while exciting the relay I9 which attracts its armature 20, thus closing the circuit of the electromagnet 23. It is obvious that as the closing of the contact causes the passage of a current in the shunted circuit of 23, this determines a greater unbalancing of the Wheatstone bridge and an increase of the current passing through the relay I9; the closing of the contact is therefore accelerated.

The Value of the accelerating effect can be controlled. In fact, a suitable ratio can be established between the distances 2||1 and |1-22, and the direction of the current in the shunted circuit at the same time a's its strength can thus be controlled.

The contacts 1a (Fig. 1) and 20 (Fig. 2) are resilient so as to bend when the excitation of the relays 1 (Fig. 1) and I9 (Fig. 2) is increased.v

When these relays are de-energized, the resilient contacts 1 and 20 relax suddenly, thereby ensuring a perfect separation of the said contacts.

In the description of Fig. 3, the application of the invention to the control of the temperature of a hot source is considered.

It is assumed that the temperature of the latter is controlled by two relays, which are not shown, but the circuits of which are indicated at 24 and at 25, respectively.

This temperature is applied, for instance, to one of the variable resistances of a Wheatstone bridge supplied at points 26 with current by a source of current 21. The adjustment is such that, at the temperature to be maintained, there is no difference of potential between the apices 28 and 28a of the Wheatstone bridge. The variation of this difference of potential, when it appears, takes place in the same direction as the temperature rise or fall.

A movable member is constituted by a rod 29, pivoted at 30 and carrying a soft iron armature 3l which can be pulled by either of the two electromagnets 32 and 33. The rod 29 carries mercury contacts or their equivalents 34, 35, 36, the function of which will be explained later on.

The sensitive relay has an armature 31 provided with a contact piece 38 which can come ln engagement with a fixed terminal 39, and two windings 40 and 4|, the first energized from currents generated ln the Wheatstone bridge 26, the second energized by an independent source of current 42.

'I'he relay 4IJ-4 |-31 is made after the manner of a galvanometer, that is to say the armature 31 is displaced in one or the other direction according to the direction of the exciting current.

The operation is as follows:

The movable member 29 is in the position illustrated in the drawings and closes the circuit 24. If the temperature rises and exceeds the `value to be maintained, a current is generated between the apices 28a and 28 of the bridge 26 through the following circuit: apex 28, terminal 43 of the switch 36, mercury, terminal 2|, wire 45, wire 45, winding 40 `of the sensitive relay wire 46, wire 41, terminal 48 of the switch 35, mercury, terminal 49, and apex 28 of the bridge 26. The direction of this current is such that the armature 31 of the sensitive relay moves its contact piece 38 in contact with the terminal 39 for closing a circuit as follows: one of the poles of the source of current 42, wire 50, electromagnet 33, wire 5|, terminal 52 of the switch 34. mercury, terminal 53, wire 54, contact 39-38, armature 31, winding 4|, to the other pole of the source of current 42.

The energization of the winding 4| ensures the engagement of the contact 39-38, with resilient distortion lof the armature 31, and the electromagnet 33 being energized, draws the movable member 29 in a position symmetrical to that it occupies in the drawings. During the displacement of the movable member 29, the contact; terminal 53, mercury, terminal 52, is broken at the switch 34 and the contact 2 l-mercury 43-is also broken so that at the windings 4|) and 4| are deenergized, and the resilient reaction of the index 4| suddenly breaks the contact 39-38.

When the movable member has reached the position symmetrical to that it occupies in the drawings, the circuit 24 is broken, and the circuit is closed. The temperature of the hot source begins to lower and becomes nearer the adjusting value. The armature 31 remains well away from the contact piece 39, because a current of reverse direction to thepreceding one passes through the winding 40, through the following circuit: apex 28u of the bridge, terminal 43 of the switch 36, mercury, terminal 55, wire 46, winding 4D, wire 45a, wire 56, terminal 51 of the switch 35, mercury, terminal 49, and apex 28 of the bridge.

The conditions remain the same as long as the temperature at the hot source does not fall below its adjusting value.

But when this temperature decreases below the adjusting value, a diiference of potential appears between the apices 28 and 28a of the bridge 26, this difference of potential is evidently inverse to that of the preceding case and produces a current through the following circuit: apex 28, terminal 49 of the switch 35, mercury, terminal 51, wire 56, wire 45, winding 40, wire 46, terminal 55 of the switch 36, mercury, terminal 43, and apex 28a of the bridge. The direction of this current in the winding 40 is, as can be seen, that causing the armature 31 to move towards the contact piece 39. As soon as the contact 39-38 takes place, a circuit is closed as follows: one of the poles of the source of current 42, wire 58, electromagnet 32, terminal 59 of the switch 34, mercury, terminal 53, wire 54, contact 38-39, winding 4|, to the other pole of the source of current 42. The winding 4| is energized by a current of the same direction as that considered for the position of the movable member 29, position indicated in the drawing. The electromagnet 32 being energized, it restores the movable member 29 in the same position and everything is as it was initially.

Instead of a Wheatstone bridge, it is possible, in certain cases, to use photo-generating cells mounted as shown in Fig. 4, that is to say substantially as the sources of current and 2 of Fig. 1. The cell 6U is lighted by a source of light of constant intensity, and the cell 6| is lighted with variable intensity according to the production of phenomena the eifects of which are to be controlled (heat, temperature, light, etc.). For a definite illumination of the cell 6|, no current circulates between the points 28 and 28"1 which are connected to the points 28 and 28a of Fig. 3, when the bridge 26 has been done away with. For a smaller or greater illumination, a current in one direction or the other circulates between the points 28 and 28a, from which current the effects already described can be obtained, with an installation such as that of Fig. 3, the sun can be caused to intervene in the automatic regulation of central heating plants.

The commercial application of the galvanometric contacts, improved as just stated, to the control of relays for effecting various functions allows to obtain accuracy unknown up to this day. Thus, the invention applied to the thermal regulation of furnaces, ovens etc. allows the control plant to be responsive to differences of temperature inferior to one-tenth of a degree. In fact, it is obvious that the invention allows to derive profit from the entire sensitiveness of galvanometers the index of which is responsive to currents of the order of 50 thousandths of a milliampere. These currents are those which occur in Wheatstone bridges having resistances variable with the temperature and when the latter varies to the extent of one-tenth of a degree, or with photogenerating cells, thermo-electric couples, etc.

What I claim as my invention and desire to secure by Letters Patent is:

1. In a relay, a winding, a movable armature adapted to be displaced when the relay is energized, a fixed contact, a movable contact, means for operatively associating the movable contact with the armature and for pressing said movable contact against the fixed contact when the relay is energized, a Wheatstone bridge, a variable resistance placed in one of the arms of the bridge, a source of electric current connected to two opposite apices of the bridge, the winding of the relay being connected to the two other apices, a service circuit comprising the contacts of the relay and shunting a part of two adjacent arms of the bridge.

2. In a relay, a winding, a movable armature adapted to be displaced when the relay is energized, a xed contact, a resiliently distortable movable contact, means for operatively associating the movable contact with the armature and for pressing the movable contact against the xed contact when the relay is energized, a Wheatstone bridge, a Variable resistance placed in one of the arms of the bridge, a source of electric current connected to two opposite apices of the bridge, the winding of the relay being connected to the two apices, a service circuit comprising the contacts of the relay and shunting a part of two adjacent arms of the bridge.

HENRI MOREAU.

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