US1484707A - Relay and circuits therefor - Google Patents

Description

Feb. 26 1924.

D. K. GANNETT RELAY AND CIRCUITS THEREFOR Filed Dec. 18. 1922 INVENTOR. a5 G ZZIZ/IMZZ ATTORNEY Patented Feb. 26, 1924.

UNITED STATES,

PATENT OFFICE.

nmron'rn x. GANNETT, or ELMHURST, NEW YORK, ASSIGNOR To AMERICAN TELE- rnozm am: TELEGRAPHCOMPANY, A coaroaa'rron or NEW YORK.

RELAY AND cmcurr's' mum-R;

Application filed December 18, 1922. Serial at. 607,873.

To all whom it may concern Be it known that I, DANFORTH K. GAN- NETT, residing at Elmhurst, in-the county of Queens and State. of New York, have invented certain Improvementsin Rela s and- Circuits Therefor, of which the fol owing is a specification.

This invention relates to relays of the vibrating armature type, and more particularly to arrangements for causing such relays to operate with minimum bias effects.

\Vhile relays of this character are capable of a wide variety of uses, one. of the methods of employing the vibrating relay-of this invention is for the purpose of generating telegraph reversals. Such reversals consist of a steady train of impulses or dots, the succeeding impulses being usually of opposite signs, and currents of this character may be utilized for testing purposes in connection with telegraph apparatuses, repeater sets, etc.

operate with a minimum amount of bias, or,

in other words, that the reversals or sucmeans of these reversals, any liability of error due to the bias of the testing current itself will be eliminated. Such bias is exemplified in a periodically reversing current by either a longer resistance or a greater amplitude of the current pulses of one polarity. It is, in general, the object of the invention to provide arrangements for a vibrating relay whichwill cause the relay to be very stable with respect to bias so that imperfect adjustment of the relay or other variable factor will not introduce perceptible bias into the generated reversals.

The invention may be more fully understood from the following description when read in connection with the accompanying drawing in which Fig. 1 is a schematic circuit diagram of a the invention.

Figures 2 and 3 are graphic illustrations of the operation of the device ofthe present invention under different conditions, Figi l illustrates a form of testing circuit to which the vibrating relay arrangement of the When used for such purposes, it is extremely desirable that the vibrating relay 7 the same direction.

preferred embodiment of.

present invention may be applied, Fig. 5 illustrates a modification of the arrangement shown in Fig. 1, in which thewinding for correctingbias of the relay is'independent of the operating winding of'therelay and Fig. 6 illustrates a still further. modification in which the correcting function of one rela is controlled by the. operation of another re ay. h

Referring to Fig. 1, a polar relay having windings 1 and 2 and an armature 3 is illustrated, the armature 3 being adapted to vibrate between fixed contacts 4zand 5, one

of which is connected to positive battery and the'other-of which is connected to negative battery, the other terminals of these'batteries being connected to ground. A suitable 'inductance. 6, which preferably has a high time constant, is connected in circuit with the winding 2, and a resistance 7 is included in circuit with the winding 1, the circuits of both windings being arranged in parallel and connected to ground at 8.

The windings 1 and '2 are so constructed that: a circulatingcurrentflowing through.

the windings in' series produces and additive effect, that is, both windings under these circumstances tend to shift the armature in The current flowing through the two windings in parallel to or from the mid-point, however, willrproduce opposing effects upon the armature. The circuit arrangement is such that, when the armature is resting upon one contact, the current flowing throughthe winding-2 and the inductance 6 will be in such a direction as to tend to shiftthe armature to the opposite contact, while the current flowing through the winding land the resistance! will be in such a direction as tohold' the These cur-.

armature against the contact. rents will hereinafter be referred to as operatingand holding currents respectively, and the windings 2 and 1 will likewise be referred to as'oper'ating and holding windings respectively.

The operation is as follows:

Let us suppose that the armature 3 is resting against one of the contacts, for example, the contact'4, and that a positive potential with respect to ground is suddenly. applied.

to the contact4,.by*closingaswitch, for

example. A current is immediately established through the holding winding 1 and the resistance 7, tending to lock the armature against the contact 4. It will be observed that the full battery potential is applied to the terminals 3 and 8 of the circuit including the winding 1, so that the current flowing through the winding 1 will be independent of the resistance or inductance of the circuit including the winding 2. Consequently, the current which immediately flows through the holding winding 1 maintains a steady value so long as the armature 3 remains against the contact 4:.

As soon as the battery potential is applied to the contact l, however, a current starts to build up in the circuit including the winding 2, but, due to the time constant of the inductance 6, it takes an appreciable time for this current to build up. As soon as this operating current reaches a value sufficient to overcome the effect or" the holding current flowing through the winding 1, the armature 3 leaves the contact a. The instant this occurs the holding current through the winding 1 ceases, and a circulating current due to the discharge or the energy stored in the magnetic field in the inductance 6 flows through said inductance, through the resistance 7 and through the windings 1 and 2 in series. This current flows through the winding 2 in the same direction as the current originally flowing from the contact 4, but it flows through the winding 1 in a direction opposite to that of the holding current, so that the winding 1 now aids the winding 2 to sharply kick the armature over against the negative contact 5. As soon as the armature rests against the contact 5, the holding current flows through the winding 1 in the same direction as the circulating current, but in a direction opposite to that of the previous holding current, so that the winding 1 tends to hold the armature against the contact 5. The potential now applied to the winding 2 is in a direction opposite to that of the previous operating potential, so that the current built up in the inductance 6 begins to decay until it falls to zero and then begins to build up in the opposite direction. When the current builds up in the opposite direction through the winding 2 to a value sufiicient to overcome the holding current flowing through the winding 1, the armature 3 leaves the contact 5 and a circulatng current flows through windings 1 and 2 in series in such a direction that winding 1 assists the winding 2 to sharply shift the armature to contact 4:.

If reference is now had to the graphic showin of Fig. 2 in which the dashed line L, represents the holding current and the dotted line I represents the operating current, it will be seen that it took a longer time for the current in the operating winding to build up in a direction to shift the armature from contact 5 to contact 4 than it did for the operating current to build up to shift the armature originally from contact 1 to contact 5. This is for the reason that dur- 1g the first seinicycle the operating current only had to build up from zero, while during the second semicycle a suflicient time must elapse for the current to decay from the built-up value to zero and then build up to an operating current in the opposite direction. At the end of the second semicycle when the operating current through the winding 2 has reached a sullicient value to again shift the armature from contact 4 to contact 5, the holding current through the winding 1 will hold the armature 3 against the contact 5 as before. The operating current through the winding 2, however, begins to decay until it becomes zero and builds up in the opposite direction to a value sutlicient to again shift the armature. Since the current builds up to the same value during each semicycle (although in the opposite direction), the same length of time now clapses between the shifting of the armature to the contact 5 and the shifting of the armature back to the contact a as elapsed during the preceding semicycle. A steady state has now been reached, and the armautre will continue to automatically shift back and forth at equal intervals, as will be apparent from the curve of Fig. 2, in which the effective current operating upon the armature (that is, a current equal to the algebraic sum of the operating and holding currents) is indicated by the full line curve, this curve commencing in the diagram at the point where the steady state conditions begins. T is frequency of vibration of the armature may be easily adjusted by means of the resistance 7 which controls the value of I The larger 1,, is made the longer will be the time interval before I builds up to a value sufficient to overcome T The curves in Fig. 2 were plotted from the calculations made in accordance *ith formulae which will be given hereinafter. In making these calculations, and hence in plotting the curves, the time of travel of the relay arn'iature was neglected, the constants of the relay windings were neglected, and it was assumed that the relay shifted its armature just wh n the opcratin g current reached a value equal to that of the holding current, but in the opposite direction. These assumptions involve only a very slight error, and hence the curves of Fig. 3 substantially represent the operation of the relay.

It will be seen that a relay such as illustrated in Fig. 1 and operating as indicated in Fig. 2 will be subject to bias to a very small extent only, as the force tending to pull the armature away from the contact is roughly proportional to the length of time that the armature has remained on said contact. In other words, the longer the armature rests upon a given'contact the greater becomes the value to which the operating current builds up, and hence the greater becomes the force tending to shift the armature from the position in which it is resting. In order to more fully understand the correctingaction against bias effects, let us suppose that, instead ofpermitting the relay to operate automatically as above de scribed, thearmature of the relay be forcibly operated at the same speed as its free vibrations, but with a 20% bias, that is, with the armature resting upon the positive contact, a time only eight-tenths as long as indicated in the curve of Fig. 2 and on the negative contact a time one and two-tenths as lon as indicated in Fig. 2. The currents will then take the form indicated by the curvesof Fjig.

Referring to Fig. 3, it will be observed that when the positive potential is applied to the armature of the relay the operating current begins to build upin the negative direction and continues to so build up for eighttenths of a semicycle. As this period is much longer than the first semicycle shown in Fig 2, the operating current builds up to a much greater value than that necessary to overcome the holding current before the armature shifts. As soon as the armature shifts. the operating current begins to decay and to build up in the opposite direction, this 'operation continuing for one and two-thirds semicycles. Owing to the great value in the negative direction to which the operating current has been built up, this time, while greater than that of the previous reversal, does not permit the operating current to build up in the positive direction to a value equal to the negative operating current when the next reversal takes place at the point marked 3. The current now begins to decay and build up in the opposite direction until the reversal at the point marked 4: takes place. The'operatingcurrent does not in this instance build up to as great a value as at the point marked 2. For each succeeding cycle, theoperating current builds up to a greater positive value but builds up to a smaller negative value until a steady condition is reached, as indicated at the point marked 9, at which point the operating current attains its greatest positive value. At the point designated 10, the operating cur rent has not been permitted to decay sufficiently to reach zero, before the armature is again shifted. From this point on the operating current passes through the same riations for each succeeding cycle.

It will be observed that after the steady state condition is reached at the point- 9 the axis of the operating current is shifted in a positive direction a distance marked D This represents an effective direct current through the operating winding upon which direct current an alternating current is su perposed. This direct current component is in such a direction as to tend to counteract the bias. The holding current, on theother hand, has shifted in a negative direction to the extent indicated by the horizontal line marked axis of I This axisis drawn so that the area included within the dashed line 'curve corresponding to a negative semicycle will be equal to the area circumscribed above said line by the dashed lines of the positive semicycle. The shifting of the axis of I represents the effective bias due to the prolongation of the negative semicycle. and it will be apparent that the shifting of the axis of I in the positive direction is much greater thanis necessary to overcome the negative shifting of the axis of I The resultant current operating upon the armature is indicated by the full line curve, and its axis has shiftedin a positive direction a distance marked D. This represents the effective restoring current which tends to oppose the force that produces the bias. For the conditions and circumstances assumed in the drawing, the effective restoring current is about equal to the maximum normal current through either winding. The restoring current increases rapidly in amplitude with the magnitude of the forces tending to produce bias. This results in very stable operation of the relay. In practice, the constants of the circuit should preferably be chosen so that the relay core is not saturated by the operating flux.

The presence of the restoring force represented by D may be explained physically by noting that as the relay armature 3 vibrates, a. periodically reversing E. M. F. is

impressed across the circuit 3-2-6-8. If the operation of the relay is slightly biased, the armature 3 resting longer on one contact than on the other, the Fourier series repre senting the E. M. F wave would possess a small D. C. voltage component. The D. C. impedance of winding 2- and inductance 6, however, is small compared with the A. C. impedance at the frequency of vibration of the relay and therefore the current which flows will possess a relatively large D. C. component notwithstanding that the D. C. voltage is small. This D. C. component is represented by D in Fig. 4: and as noted above is in such a direction as to strongly oppose the forces which tend to bias the operation of the relay.

As has already been stated, the curves of Figs. 2 and 3 were computed from formulae. The formuiae are derived as follows:

Given inductance L and resistance R in series with source of voltage which applies constants of inductance 6 in Fig. 1. Taking 25:0 when the voltage changes from e to +6, the current is 6 where I I IS the current in the cmcuit when :0, w equals and E is the in base oi the rlaperian logarithms. T T

Let it as s is reversed when t t Let the alue of i when zf t tbe lc,I. 20 Then The extreme values of current are k I and ia I. The location of an axis half way between these values is given by very approxnn piy equal to the distance to the axis so .ced that the areas of the curve each side of it are equal. In other words it very closely represents the value of the D. G. component of the current which flows.

when 6 :5 D 0. For this condition,

expression gives the amplitude of cat peaks in inductive circuit 3 l i e consisting of periodic unnased rever are is applied.

mple o'r the manner in which 3 i; ent of Fig. 1 may be attention is called to the telegraph 'cstng circuit illustrated in Fig. 4. The reconprising the winnings 1 and 2 and 8 vibrating between contacts 4 and o tance 6 connected in series with the w :16 g 2 and resistances 7 and '11" in series with the windin 1. The ground connection 8 extending from the terminals of the resistance and inductance legs passes over a normally open contact of the jack J, so that when the plug P is inserted in the jack, the contact is closed, thereby completing the operating circuit. As the armature 3 is directed against one of the contacts, the full battery potential to ground is applied to the windings of the relay and the relay commences to operate as already described. The armature 3 has a connection 12 extending through a contact of a jack J and through the windings of polar relays PR PR PR etc, to ground, so that successive positive and negative impulses pass over the contact 3 of the master relay and through the condenser and. resistance 1 1 and through the windings of the relays PR PR PR etc. These relays transmit successive unbiased pulses over the jacks such as J to suitable testing circuits. The condenser and resistance arrangement 14 are for the purpose of causing a large momentary current to flow through the windings of relays PR PR PR etc, at each instant of transfer of armature 3 from contact 4 to 5 or from contact 5 to 4, so that relays PR PR PR etc, will be very positively operated and will not introduce any bias of their own. The frequency at which the master relay vibrates will de pend upon the resistance in series with the winding 1. This resistance may be varied by operating a key K which controls the circuit of relay 13 adapted to remove a short circuit from about the resistance 7, thereby increasing the efiective resistance in series with the winding 1. \Vhen the key K is operated and the short circuit is removed from about resistance 7 the frequency of the master relay will be increased. A suitable milliammeter 14 may be plugged into the jack J by means of the plug P in order to check up the action of the master relay by means of the reading of the milliammeter.

In the arrangement of Fig. 1, the relay winding 2 performs a double function of acting as an operating winding and also as a correcting winding. As an operating winding, its function is to shift the armature from the contact upon which it is at the moment resting to the opposite contact as soon as the operating current has built up to a value greater than the holding current through the winding 1. As a correcting winding, its function is to apply a force to the armature tending to overcome any biasing forces acting upon the armature. These functions may, however, be separated and performed by different windings. The arrangement shown in Fig. 5 illustrates one method of separating the functions.

In Fig. 5, winding 1 is the holding winding and winding 2 is the operating winding. A resistance 9 is connected in series with the operating winding and a capacity 10 and I in the opposite direction.

small resistance 11 are connected in series with the holding winding. The operation of the circuit thus far described will be as follows. Assuming that the armature 3 rests against the positive contact 4 and that the circuit is closed by a suitable switch for example, a positive current of full normal value at once flows throughthe operating winding 2 and the resistance 9. This current is independent of the conditions of the circuit through the winding 1, as the full battery potential is applied across the terminals of the circuit 2-9-8. At the same instant, however, a holding current flows through the winding 1 and charges up the capacity 10. The value of this current will be greatest at the instant of closing the circuit and, as the capacity charges up, the current through the winding 1 will decrease. The holding current, at the instant of closing the circuit, is greaterthan the operating current through the winding 2, but when it decreases to a value slightly less than the operating current through the winding 2, the operating winding acts to shift the armature to the opposite contact 5. An operating current now flows through the winding 2 in the opposite direction and a holding current also flows through the winding 1 The holding current again tends to hold the armature against the contact 5 until it becomes less in value than the operating current, whereupon the operating Winding shifts the armature back to the contact 4 and this process continues indefinitely.

The circuit thus far described has no effect to overcome bias for the reason that the impedance of the circuit 2-98 is practically the same for the alternating current components as it is for the directcurrent component which results from bias. In order to overcome the efi'ect of bias, a third winding 2' is provided, which is so connected as to be energized over the contacts 4 or 5, as the case may be. This winding is so poled that when the armature is resting upon a given contact the current flowing through the winding tends to shift the armature away from the contact. An inductance 6 is included in circuit with the correcting winding 2. This inductance makes the impedance of the circuit of the winding 2 very high for the alternating current components resulting from the shifting of the armature between the contacts 4 and 5. Its resistance to direct current, however, is quite' low. In the normal operation of the relay, if there is no bias tending to hold the contact against one armature longer than the other, there will be no direct current component and consequently the effect of the winding 2 u on the operation of the circuit is inapprecia le. As soon as the operation of the relay bethe direction of this component is such that the winding creates a constant pull upon the armature in a direction opposite to the bias ing effect.

his not even necessary that the correcting winding be energized over the armature j of the vibrating relay, as illustrated in Fig. 5, but this winding may be energized over the armature of any other relay in a system of relays controlled by the vibrating relay. For example, Fig. 6 shows in simplified form how the circuit arrangement of Fig. 4 may be modified to permit of controlling the correcting winding 2 from one of the polar relays PR PR or PR,. In the case illustrated, the relay PR which in the circuit of Fig. 4 supplies current reversals to a testing circuit, for example, is utilized for controlling the winding 2. To this end, the winding 2, instead of being connected to the armature 3 of the master relay, is connected to the armature of the polar relay PR and the contacts of said polar relay are connected to positive and negative sources of potential respectively. Consequently, if, for any reason, the operation of the master relay becomes biased and its armature rests longer upon one contact than the other, the polar relay PR will so operate that its armature rests longer upon the corresponding contact than the other contact. As a result, a direct current component flows through the winding 2' in such a direction as to oppose the biasing effect upon the armature 3. The inductance 6 is provided in circuit with the winding 2 as before so that the winding is practically unaffected by alternating current components owing to its high impedance thereto, while its resistance is quite low to direct current components.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely difierent from those illustrated without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. A vibrating relay system including a polar relay having an operating winding. a holding winding and an armature adapted to rest upon either of two contacts connected to opposite potentials, means whereby when the armature rests upon either of the contacts a steady current flows through the holding winding tending to hold the armature against that contact and means whereby a gradually increasing operating current is built up through the operating winding to shift the armature against the opposite contact.

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