US1925954A - Electric relay - Google Patents

Description

Sept. 5, '1933.

H. J. J. M. DE REGNAULD DE BELLESCIZE ELECTRIC RELAY- Filed Nov. 50, 1929 2 Shoots-Sheet 1 ma n m M to e Z Va r flu t M M W af M w w Sept. 5, 1933.

1,925,954 H. J. J. M. DE REGNAULD DE BELLESCIZE ELECTRIC RELAY Filed Nov. 30, 1929 2 Sheets-Sheet 2 Henri Jqn crase q Marie 42 Patented Sept. 5, 1933 ELECTRIC RELAY Henri Jean Joseph Marie de Regnanld de' Bellesciae, Neuilly; France Application November 8 Claims.

relates to electrical relays and to sensitive high speed relays responsive to minute current signals.

An object of my invention is to provide a sensitive relay whose armature stroke and contact pressure for a fixed operating current is increased over previous relays.

A further object of my invention is to provide a high speed sensitive relay in which the armature space from its engaging contact is increased to a value exceeding the diameter of the particles which are torn off when operating.

still a further object of my invention is to provide a high speed sensitive relay having novel relationship, between the positioning of the parts.

A still further object of my invention is to provide a sensitive high speed inexpensive relay operating in response to small amounts of current for industrial use and reliable for precise control and which will not require periodic inspection in order to maintain its properties indefinitely.

There are other objects of my invention which, together with the foregoing, will appear in the detailed description which follows in connection with the drawings, in which;

Figures 1 and 2 are side elevational views of preferred forms of my invention.

Figure 3 is a curve showing the relation between the airgap and the magnetic and spring tension in accordance with which my relays are constructed and adjusted.

Figure 4 is a curve showing the relation between the biasing current of my relay and the deflection of the armature of the relay.

Figure 5 shows the principle of hysteresis curves applied to my invention.

Figures 6 and 7 are cross-sectional views showing details, dealing with methods of overcoming effects of thermal expansion of my relays;

And Figure 8 is a diagrammatic view of the preferred form of my relay in operation.

In Figure 1 the relay is shown with a magnetic circuit having legs 1 and 3 connected to a core 2 in conjunction with an armature 4 screwed My invention more particularly fast to leg 3 by screw 14 and a pole piece 1'7 formed.

to thread into' leg 1; all being of suitable magnetic material hereinafter to be described. Ar mature 4 exerts an elastic force due to cantilever action. Its free end is confined in movement by the screws 9 and 10 threaded through suitably insulated blocks 23 and 23. Leads are indicated from the contact screws -9 and 10 for circuits to be operated by the relay. The armature 4, of

and in France December 12,

30, 1929, Serial No.

course, is grounded to the magnetic circuit, as

shown in Figure 8.

Two sets of terminals 5-5 and 18-18, 1, are wound around the core mined fixed biasing current supplied tery, as shown in Figure 8,

windings, each having its own as shown in Figure 2. A predeterby a batfiows through one of the windings, such as through terminals 18-18,

and the signalling current to sponds in the manner through the second winding over which I shall refer signalling circuit.

which the relay reto be described flows terminals 5, to in the following as the In Figure 2 is an alternative arrangement for the armature. Here a stiff member 4 pivoted on a knife edge; as shown, and having bearing upon it a spring 6 as shown, acts as an armature.

Three distinct and independent mechanically variable parts are provided for bringing the vato be hereinrious characteristics of the relay,

after described, into proper cooperation for use. These are the aforementioned threaded pole piece 17 and stopping and contacting screws 9 and 10.

magnetic force actions on armature 4 and between the same airgap and the spring tension force must first be explained in connection with Figure 8.

In Figure 3,

the abscissa represents the length of the airgap. The positive ordinate (upwards) represents the force of the magnetic attraction tending to bring the armature 4 toward the movable polepiece 17; the

negative ordinate represents the elastic resistance of the spring acting in a contrary direction; the curves 35, 22

each for a constant magnetic energizing flux,

show the relations between the magnetic force and the airgap acting on armature 4. As shown,

the magnetic force increases rapidly with the decrease in first slowly and then the airgap. Lines 24 and 25 show the relation between the elastic force and the airgap. As shown,theseare straight line relations whose inclinations depend on the stiffness of the spring, inasmuch as the elastic resistance of the spring is practically propor- 5 tional to the deflection. does not exceed a few This deflection usually tenths of a millimeter.

For an initial airgap 0 -27, the elastic resistance as a function of the airgap is represented by the straight line 24. For an initial airgap 0-26. the 1 elastic resistance is represented by a parallel line 25 If the airgap is so placed that an initial airgap 0-27 is obtained (with no current) and then a current is caused to flow through one of the windings of such a value that the magnetic attraction versus airgap characteristic will be represented by the curve 22, the armature will be attracted by the magnetic force; but this attraction will be impeded by the elastic force of the spring. When these two forces are in equilibrium, the armature will come to rest. These two There is, however, an important distinction between these two points where the forces are equal and opposite. In the first case a decrease of the airgap makes the elastic force predominate and thus tends to keep the airgap from decreasing beyond the equilibrium point. Also, an increase in the airgap makes the magnetic force predominate and thus tends to further decrease the airgap and cause the moving away from equilibrium. Also in the second case an increase in the airgap makes the elastic force predominate, and the airgap is thus further increased until the first point of equilibrium 29 is reached, and thus tends to cause the moving away from equilibrium point 30. In the first case we have a stable form of equilibrium. In the second case we have an unstable form of equilibrium.

In the present day adjustment of relays which are biased, the practice is to adjust by chance until the person in charge in the field is satisfied. No step by step procedure based upon the characteristic of the individual elements comprising the relay is practised. I Accordingly, when a relay was adjusted and biased, a condition similar to that in accordance to curve 35 and line 28 was obtained. A back stop for similar purpose as that of screw 10 was placed in a position to make the airgap less than 035 in order to insure a positive pressure upon the back-stop by the armature. An increase of the'magnetic force due to any cause, such as by energizing of the signal circuit, caused a shift from curve 35 to some other magnetic force curve above 35, such as curve 22. As shown before, the point of stable equilibrium is now at point 29. This allows at most a movement of the relay armature a distance 36 to 31. 'In practice, a stop and contacts, such as. 9'and 10 in the case of my invention for stopping and making contact with the armature in operation, must be placed at a greater distance from the pole face than 0-31 and at less distance from poleface than 0-36 to give positive contact pressure. 7

I have discovered that by adjusting the spacing of pole piece 17 from armature 4 to such a distance' that the line of elastic resistance becomes practically tangent to the curve representing magnetic force for a biased state not energized by a signal component, the operation of relays al- 30', and at this point the magnetic f and spring tension forces are also equal and opposite.

vfly to the pole piece 17 lows, for the same change iii-signalling, current, a much greater displacement than in the case of the prior art. This greater displacement is equivalent to an increased sensitivity. This in turn, in conjunction with details to be hereinafter disclosed, allows me to set and seal relays permanently at the manufactory, thus giving a sensitive yet rugged devicewhich needs noskilled technician in the field for its care.

The analysis of the method of my invention will now be described in detail. The screws 9 and 10, being open and with no magnetizing flux operating, let us assume that pole piece 17 is in such a position as to give an initial airgap 0-27. Any change in position ofv the armature will have a correspondence in the elastic-force versus airgap characteristic along-line 24, whose image is line 28. By turning pole piece 17, the elastic force versus airgap line can be shifted parallel to line 24, and correspondingly its image parallel to 28. The biasing coil is now energized with a fixed current, thus giving the magnetic circuit of. the relay a fixed magnetic fiux bias, which bias gives rise to a magnetic force versus airgap characteristic curve. such as 22. The turning of pole piece 17 causes a shift of stable equilibrium points from 29 along the curve until point 34, which is the point of tangency to curve 22 of a line parallel toline 28. The same operation also causes a shift of the unstable equilibrium point 30 to point 34. Hence, when point 34 is reached, we are at a point of indifferent equilibrium; that is, where an increase of airgap causes a stable equilibrium, and a decrease of airgap, an unstable equilibrium. Decrease of the airgap distance the least bit further by turning pole 17 causes the armature to and this serves as the important indication of the proper spacing of the pole piece 17 from the armature 4 according to my invention. Here the line of elastic force will lie entirely below the curve 22.

A change in magnetizing flux, the same as hereinbefore disclosed; namely from curve 22 to curve 35 or vice versa, causes a shift in the equilibrium point the distance of 3440, much greater than distance 36-31 as hereinbefore described. Thus for an equal change in signal power, I obtain a greater range of deflection than in the prior art. This in turn allows the contacts 9 and 10 which, as stated before, must lie within the range of deflection, to bespaced further apart than in prior practice, thus allowing, as far as the magnetic and elastic characteristics are concerned, a spacing great enough to avoid tacts due to dust and metallic particles tom 01! of the relay contacts. 1

As can be seen from Figure 3, the resultant force on the armature in the region of indifferent equilibrium is very small for a considerable range of airgap; that is, in this region the elastic force line and magnetic force line are close to each other. This allows the employment of a very small change in magnetizing. fiux to produce a given change in the position of the armature. And because of this I make this range a working range for my relay. Since operation of the relay in the unstable region, to the left of 34, makes it unfit for many purposes in practice, generally although not necessarily,-the armature 4 is confined to move to the right of the point of tangency. This function is performed by the screw 9, which also serves as means of electrical contact with armature 4 as hereinbefore mentioned.

A further aid to understanding of the relative 7 1,925,954 positioning of the parts. hereinafter to be described is given by the diagram shown in Figure 4.- This curve was obtained by means of a relay of actual construction. The abscissa give the successive values of the operating current in 'milliamperes, and the ordinates the corresponding displacementof the armature for a given' spacing of pole piece 1'7. The data for the curve is obtained as follows: The current is cut off, and the contact screw 10 is brought against the armature 4. This position is readily found by the use. of a voltmeter and a source of current. A circuit is formed through the voltmeter and source of current connected at one end to the armature and at the other to the contact screw 10. The magnetizing current is now supplied to the relay, and it is increased by known successive steps. Each time the angle, through which the screw 10 must be turned in order to bring it into contact with the armature 4, is observed by watching for a deflection of the voltmeter. The pitch of the screw being known, such angles correspond to the calculable linear displacements, which displacements are-plotted as ordinates as a function of the magnetizing current. For any point, such as M, the sensitiveness of the relay is measured. by the trigonometrical tangent of the angle on since a variation Mm of the operating current will cause a displacement mn. of the armature. This sensitiveness has an infinite value'fo'r the exact adjustment Mo corresponding to the indifferent equilibrium mentioned here- I before. With the relay herein employed, this equilibrium is obtained with a current of five milliamperes and a deflection of the armature of 0.28 millimeters. A. departing from the adjustment such as a: of a few hundredths of a millimeter, if produced in thedirection shown in Figure 4, will yield a decreased sensitivity but which is still much greater than that at point M, and if produced in the other direction, it will bring the armature into the region of unstable equilibrium situated above the ordinate e0. As stated before, this region is generally to be avoided. I use the region just below and as near as possible to point 80.

.Figure 4 supplies data for two purposes; one, the limits of position to be fixed during manufacture so as to maintain a degree of accuracy within 0.01 millimeter or thereabout; and second, the margin of safety necessary to allow such that all incompletely corrected errors (hysteresis, thermal expansion, or the like) will not cause the -unstable equilibriumof the armature in the future use of the relay. Details of construction dealing with these last matters will hereinafter be described.

In practical application use can be made of the above disclosed features in cooperation with certain constructional details to be hereinafter described in the following manner. The adjustment of pole piece 17 to bring the image of the elasticforce versus airgap line tangent to the magnetic force versus airgap curve for a constant biasing magnetic flux is performed in the hereinbefore described manner, by watching for the clicking of armature 4 against pole piece 17. As soon as this has occurred, the biasing flux is released, the armature 4 being then freed from the pole piece 17. A biasing current less than that used before is now used to furnish a magnetizing fiux. In practice, I use 995/1000 of the original biasing current in coil 18 to insure that I am on the side of stability. This close value can be maintained in view of constructional details tobe described meter.

the contact pieces 9 and 10 and to the movable hereinafter. Screw 9 is now set to come into contact with armature 4. When in this definite position, screw 9 is set fast. The contact screw 10 is now screwed so as to bring the three parts 10, 4, and 9 into short-circuit, and then starting from this definite position, the contact screw 10 is moved to the rear by a quantity equal to the proper stroke to be given to the armature, as determined from the curve 4; that is, 0.03 milli- The contact screw 10 is now in its definite position. The relay can be sealed, marketed, and put into permanent use for the biasing current last described, without further mechanical changes.

The configuration of elements as described above may be attained in other ways and 'I by no means limit myself to this one means of accomplishing my end. Essentially, as has been borne out by the disclosure so far, I place emphasis on operation in the range of indifferent stability. A means has been disclosed for locating this suitable range.

In Figure 8 I have illustrated one specific system by which my relay is used. As shown, the terminals 18 are connected to a biasing battery, terminals 5 to a signalling line, contact 10 is connected through a battery to a device 25 to be operated by the relay in accordance to signals received over line 5. Contact 9 is shown connected to a battery in the reverse direction to device 25 and to a device 26. Thus the relay is here adapted to operate as a polarized relay.

Further special precautions should be taken in constructing the magnet in accordance with my invention. The variations of the magnetic state of the metal due to hysteresis, as well as the ex pansion effects due to temperature variations tend to separate its parts from the elative positions corresponding to the indifferent equilibrium.

To control these factors within the desired limits of operation, the relay must be so constructed as to minimize these sources of variation.

The mechanical deformations are counteracted by: the use of fine pitched threads on screws 9 and 10 and on pole piece 1'7 which threads fit 120 snugly without play into their respective nuts: the use of strong construction, such as a heavy base 13, leg 3 of large sections: the lowering of the armature and contact screws as near the bases as possible. 125

With regard to temperature variations, there are two kinds of deformation resulting from the unequal expansion of parts, one of which is linear and the other angular. The linear deformations which are less important, are reduced by disposingthe assembling screws 21, 23, 23' etc. as close as possible to the plane containing the armature. The angular deformations, as shown in practice, are due to a defective method of securing the parts, as represented in Figure 6, where the bolt 14, the armature 4, the core 3, and the shoulder of the non-magnetic base 13 will expand unequally, and hence where the compression due to the assembling bolt will vary, and where there-- fore inasmuch as the surfaces of the pieces assembled cannot be made mathematically plane, such variations in pressure will cause an angular deformation of thearmature, whose outer end will be circularly displaced with reference to pole piece 17. The lack of precision which results may attain 4/ 1000'per degree centrigrade. To obviate this defect, the armature is secured by means of members having the same .coeflicient of thermal expansion, and preferably consisting of 159 the same metal, if possible. This can be effected by the method of assembling shown in Figure '7, in which the core, the armature, and the bolt consist of such metal.

With regard to the defects due to hysteresis, a discussion follows. It is necessary to employ the same attraction and hence the same magnetic induction, to bring the armature against one of the contact pieces. However, due to the size of the hysteresis curve, Figure 5, a uniform induction such as 0-43 can be obtained for a range of values of ampere turns, as in this case between 41 and 42. Each value depends upon the previous state of the metal and upon the direction of the hysteresis curve. Hence the hysteresis will vary the value of the current which brings the armature upon one of the contact pieces. To reduce these variations, it is necessary to employ metals having a high maximum permeability and a small hysteresis curve, which is the smaller as the term JLL is greater is the maximum permeability and no the initial permeability). It can be shown by a complete calculation that for a part of the magnetic circuit whose cross section is s and length is l, the effect of the hysteresis will be less according as the term is greater. In the practical construction of the relay, I thus employ for the magnetic members of small cross-section, such as the armature, only metals corresponding to the condition #m the current required to bring the armature upon the contact screw 9 will vary by 32 percent according as the eflect took place by increasing or decreasing values. For this reason, such a relay cannot be used in practice.

Additional disclosure concerning the construction of an armature under my conditions of operation will now be given. The magnetic circuit.

outside of the airgap has a very low reluctance, and therefore, as an approximation, we can assume that the total reluctance resides in the air- .gap. When this is done it can be shown that the deflection of the armature from initial airgap position will, when in indifferent equilibrium,

be equal to one-third of the initial airgap, Or stated in other words, in Figure 3 the segment 34--36 is one-third of the segment 026. This particular property of the relay serves to calculate the dimensions of the elastic armature, when used as a cantilever. g

The same principles can be employed for the constructions of relays which are somewhat different, such as those in which the armature consists of a piston or plunger, or the like, or any other apparatus employing the attraction of an armature by an electromagnet.

It is to be finally stated that the sealing up of the relay constitutes not only an advantage, but also a practical necessity, for in order to operate satisfactorily and for a long time, a sensitive apparatus of this kind must be protected against any operations on the part of the persons occupied with the apparatus, who have not the proper means for keeping the apparatus in order. In placing upon the market a sensitive and reliable relay which is constructed, set, and sealed according to my invention, I am insuring a guaranty of proper service.

Having now particularly described and ascertained the nature of my invention and in what manner the same is to be performed I declare that what I claim is:

1. In a relay, a tensioned armature having two positions, a magnetic core having a pole piece, said armature and core forming a magnetic path, an air-gap between said armature and pole piece in said magnetic path varying in length as said armature moves from one position to its alternate position, the relation of the magnetic reluctance of the magnetic path, the spring tension on the armature .and the magneto motor force in the path being such that the curve showing the relation between the armature spring tension and the distance of said air gap is substantially tangential to the curve showing the relation between the magnetic force and the air-gap distance.

2. In a relay, a tensioned armature having two positions, a magnetic core having a pole piece, said armature and core forming a magnetic path, an air-gap between said armature and pole piece in said magnetic path varying in length as said armature moves from one position to its alternate position, means for producing a biasing flux in said path to normally maintain said armature in one position and means for producing an opposing flux to move said armature to its opposite position, the relation of the magnetic reluctance of the magnetic path, the spring being such that the curve showing the relation between the armature spring tension and the distance of said air gap is substantially tangential to the curve show- 1 ing the relation between the magnetic force and the air-gap distance.

3. In a relay, a tensioned armature having two positions, a magnetic core having a pole piece, said armature and core forming a magnetic path, an air-gap between said armature and pole piece in said magnetic path varying in length as said armature moves from one position to its alternate position, the method of adjusting the relay which comprises inducing a predetermined flux in the magnetic circuit, adjusting the air-gap until a state of unstable equilibrium between spring tension and magnetic force is produced and thereafter further adjusting the air gap just enough to produce a stable equilibrium between the magnetic force and spring tension.

4. In a relay, a tensioned armature having two positions, a magnetic core having a pole piece, said armature and core forming a magnetic path, an air-gap between said armature and pole piece in said magnetic path varying in length as said armature moves from one position to its alternate position, the methodoi adjusting the relay which comprises inducing a predetermined flux in the magnetic circuit, adjusting the air-gap until a state of unstable equilibrium between spring tension and magnetic force is produced and thereafter decreasing the air gap just suflicient to move the armature to its alternate position.

5. In a relay, a tensioned armature having two positions controlled by front and back stops, a magnetic core having a pole piece, said armature and core forming a magnetic path, an air-gap, between said armature and pole piece in said magnetic path varying in length as said armature moves from one position to'its alternate position,

the method of adjusting the relay which comprises inducing a predetermined flux in the magnetic circuit adjusting the air-gap until a state of unstable equilibrium between spring tension and magnetic force is produced and thereafter decreasing the air-gap just sufiicient to move the armature to its alternate position, discontinuing the predetermined flux to release the armature inducing a biasing flux slightly less than the predetermined flux, adjusting one armature position controlling contact to engage the armature, moving the second contact stop to engage the armature and thereafter moving the second contact a. predetermined distance to produce a predetermined armature movement. 1

6. In a relay, a magnetic circuit comprising a spring tensioned armature, air-gap, pole face and core, means for generating a. predetermined magneto motor force in said magnetic circuit for inducing a flux to act on said armature against said spring tension, the reluctance of said magnetic circuit being such that any increase in said magneto motor force tends to cause said armature to move into contact with said pole face and a contact for preventing said armature from responding to said change.

'7. In a relay, a magnetic circuit comprising a spring tensioned armature, air-gap, pole face and core, means for generating a predetermined magneto motor force in said magnetic circuit for inducing a flux to act on said armature against said spring tension, the reluctance of said magnetic circuit being such that any increase in said ma neto motor force tends to cause said armature to move into contact with said pole face, a contact for preventing said armature from responding to said change, a second contact and means for inducing a further magneto motive force for opposing said predetermined magneto motive force to permit said armature to move to said second contact.

8. A relay comprising a pair of core members having opposite pole faces spaced by an initial gap to form a magnetic path, said pole faces being adapted to move into engagement with each other, restoring means acting on said core members tending to restore the same to said initial gap position, means for producing in said path a steady magnetic flux close to the value of flux under the condition of indifierent equilibrium in which said fiux exercises in said gap a force slightly different than the restoring force and upon slight increase of the flux overpowers said restoring force and causes said pole faces to move into contact with each other and means for actuating the relay by inducing an additional flux in said path.

HENRI JEAN JOSEPH MARIE DE REGNAULD DE BELLESCIZE.

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