US2303442A

US2303442A - Electrical relay

Info

Publication number: US2303442A
Application number: US302937A
Authority: US
Inventors: Draper Thomas
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1939-11-04
Filing date: 1939-11-04
Publication date: 1942-12-01
Anticipated expiration: 1959-12-01

Description

Dec. 1, 1942. I T. DRAPER 2,303,442

ELECTRICAL RELAY F'iied Nov. 4, 1939 2 Sheets-Sheet 1 INVENTOR 772820905 Draper.

42 %TgNEY WITNESSES:

Dec. 1, 1942. S r 1-. DRAPER 7 2,303,442

ELECTRICAL RELAY Filed Nov. 4, 1939 2 Sheets-Sheet 2 WITNESSES:

INVENTOR mamas-Draper;

Patented Dec. 1, 1942 ELECTRICAL RELAY Thomas Draper, Millington, N. J., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 4, 1939, Serial No. 302,937

13 Claims.

This invention relates to relays and it has particular, relation to voltage and current relays o. the solenoid type. 1

Although voltage and current relays have an extremely large field of application, prior art relays of this type have not been entirely satisfactory. One of the principal objections found in prior art relays is a susceptibility to oscillate, especially when energized by low frequency alternating currents, such as 25 cycles. Such oscillations often reach a magnitude that cause intermittent contact and sometimes violent operation of the relay. Often it is desirable that a relay perform a control function over an appreciable range of voltages or currents. Since the tendency to oscillate increases as the current or voltage which energizes the relay increases, it is diilicult and sometimes impossible to obtain reliable operation of a prior art relay over an adequate range, Moreover oscillation is objectionable because of the increased wear on the parts of the relays and because of the noise accompanying such oscillation.

A number of additional factors must be taken into consideration in designing suitable voltage and current relays. Preferably the design adopted should be substantially the same for both current and voltage operation in order to reduce the number of parts required and the number and complexity of manufacturing operations. Moreover it is desirable that such relays have adjustments which permit one or a small number of relaysto cover a large range of operating conditions and this without consuming excessive power or volt amperes. should indicate the particular operating values for which the relay is adjusted.

Many applications of voltage and current relays require a high, consistent ratio or dropout to pickup. When this characteristic was obtained in prior art relays the resulting design was unsatisfactory in other respects.

It is also desirable in such relays that the voltage or current necessary to initiate operation of the relay be substantially the same as that necessary to complete the movement of the relay.

In accordance with my invention these desiderata are provided in a novel relay design. The relay including a magnetic armature or solenoid plunger and a shunt for diverting magnetic flux from the armature or plunger. By varying the adjustment of the shunt, it is possible to cover a wide range of voltage and current conditions with a limited number of relays. In order to ob- Preferably the adjustment tain either a high ratio'or' a low ratio of dropout to pickup over an appreciable range without oscillation and noise, I provide a magnetic core assembly which divides magnetic flux passing through the solenoid plunger into a horizontal component and a vertical component. These components vary in their relationship to each other during travel of the plunger to provide the desired characteristics. Further structural details which contribute to the improved performance of the relay will be pointed out below.

It is, therefore, an object of my invention to provide a solenoid type relay of improved construction.

It is a further object of my invention to provide a solenoid relay having a large range of adjustment.

It is another object of my invention to provide a solenoid relay having a high, consistent ratio of dropout to pickup.

It is also an object of my invention to provide an adjustable relay having a uniform, low ratio of dropout to pickup over a substantial range of pickup adjustment.

It is a further object of my invention to provide a solenoid relay having an actuating force which is automatically controlled during the travel of the solenoid plunger to provide desired characteristics,

It is a further object of my invention to provide a solenoid relay having a shunt for varying the adjustment of the relay.

It is an additional object of my invention to provide an adjustable solenoid relay having an indicator for indicating the value for which the relay is adjusted.

It is a still further object of my invention to provide a solenoid relay substantially free from noise and oscillation.

Other objects of my invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view in cross section of a voltage relay embodying my invention; the dimensions of this figure are substantially in correct proportion for a model of a voltage relay constructed in accordance with my invention;

Fig. 2 is an enlarged view in cross section of a shunt suitable for use in the relay of Fig. 1;

Fig. 3 is a View in top plan of the shunt illustrated in Fig. 2;

Fig. 4 is a View in sectional elevation of a solenoid assembly for a current relay embodying my invention;

Fig. is a view in bottom plan of certain details of the solenoid assembly illustrated in Fig. 4;

Fig. 6 is a detailed view in section of a modified shunt construction suitable for use in the solenoid assembly illustrated in Fig. 4; and

Fig. '7 is a detail view in front plan of a relay scale suitable for a relay embodying my invention.

Referring to the drawings, Figure 1 shows a voltage relay mounted on a base I. This base may be of suitable insulating material such as a phenol formaldehyde resin. On one face of this base a bracket or frame 2 of magnetic material is mounted by means of screws 3. Additional screws 3' may be threaded into the same bushings provided for the screws 3 in order to facilitate mounting of the relay on a switchboard or elsewhere.

The frame 2 includes two parallel legs 4 and 5 which are connected at one end by a vertical portion 6 of the frame. Between the legs 4 and 5 a voltage coil I is inserted for energization in accordance with the voltage to which the relay is to respond. Electrical circuits for the relay may be conducted through the base I through a plurality of terminals 8.

When the coil 1 is energized a magnetic field is established which is directed vertically as viewed in Fig. 1. Because of the position of the frame 2 a portion of the frame 2 will serve as a magnetic path for this magnetic field. That is, magnetic flux produced by the coil 1 will pass through portions of the legs 4 and 5 and through the vertical portion 6 of the frame 2.

In order to complete a magnetic path for the magnetic flux produced by the coil 1 an upper magnetic core 9 and a lower magnetic core in are inserted between the legs 4 and 5. In the specific embodiment illustrated in Fig. l, the cores 9 and I9 are rigidly united by a tubular nonmagnetic connector II. This connector has a portion at each end of reduced thickness which is spun into a groove l2 or [3 provided in the respective cores. A slip [4 on the core 9 and an additional lip l5 on the core ID are spun over the ends of the connector H to form a rigid core assembly made up of the cores 9 and I0 and the connector H. Although a specific method of connecting the elements has been described and illustrated, it is to be understood that other suitable methods of connection may be employed. The entire core assembly is attached to the frame 2 by means of a threaded extension i6 which passes through an opening provided in the leg 4 of the frame and which is secured thereto by means of a nut II.

In order to reduce the conductance of the core assembly to eddy currents produced by alternating current supplied to the coil '1 a slot l8 may be provided in the core assembly. This slot extends axially through a wall thickness of all three elements 9, l0 and H of the core assembly, and may have, for example, a thickness of With the magnetic path thus far described, it will be obvious that magnetic flux produced by the coil 7 will pass, for example, from the magsteel or ingot iron. For direct current work a material having a low residual induction preferably is employed. The frame 2 may be constructed of material similar to that employed for the magnetic cores. Non-magnetic parts may be constructed from materials such as brass or bronze.

The magnetic flux passing through the air gap between the cores 9 and I0 is employed for operating a magnetic plunger l9 which is designed to reciprocate in a vertical direction as viewed in Fig. 1. To this end the plunger I9 is mounted in a plunger guide 20 which is provided with a threaded portion for engaging threads provided in the lower magnetic core lil. Assembly of the guide 26 in the core assembly is effected merely by inserting the guide and threading it into the lower core IE. The upper end of the guide as illustrated is positioned in a bevel or conical surface 21 provided on the upper core 9. As the guide is screwed into the lower core Hi, the upper end of the guide contacts the conical surface 2| and centers itself therein. After insertion of the guide a portion of the threads at the junction between the guide and the core member In may be punched or deformed to prevent withdrawal of the guide from the core assembly.

The materials employed for the plunger 19 and the guide 20 should be such that good bearing surfaces are provided thereby. In addition the material selected for the plunger [9 should have good magnetic properties and should be non-corrosive under service conditions. Although the plunger may be formed of cold rolled steel such material is somewhat objectionable because of the possibility of corrosion. Stainless steel is somewhat better in this respect. I have found that a desirable material for the plunger is a high nickel content iron-nickel alloy similar to that disclosed in Patent No. 1,807,021 and marketed under the trade-mark Hipernik. In some cases it may be possible to employ substances such as cold rolled steel provided with an electroplated coating such as nickel or chromium.

The guide 20 is constructed from a material which is non-magnetic, and non-corrosive, and which cooperates with that employed for the plunger to provide a minimum of friction. To this end the guide 20 may be formed of a bearing material such as bearing bronze. This with a plunger constructed of Hipernik provides a satisfactory bearing for the plunger.

Reciprocation of the plunger in its guide is employed for actuating electrical contacts. For this purpose the plunger 19 is provided with a shaft 22 which is threaded into the plunger until a collar 23 formed on the shaft engages the plunger. In order to prevent subsequent movement of the shaft relative to the plunger an end 24 of the shaft may be split and spread. Preferably the shaft assembly is reduced in weight as much as is practicable to reduce the energy required to raise the plunger assembly. For example, the shaft 22 may be formed of aluminum or other similar light weight materials.

Under some circumstances the collar 23 is employed as a stop to restrict the upward travel of the plunger assembly. The maximum upward travel possible is provided when the collar 23 abuts the upper inner surface of the core 9. In order to prevent mushrooming of the collar 23 under repeated impacts against the core 9, a. washer 25 of harder material such as bronze may be placed on the collar.

A contact assembly is attached to the shaft 22 between a sleeve 26 which is fitted over a portion of the shaft of reduced diameter and a nut 21 which may be secured upon a threaded end of the shaft. This contact assembly includes a panel 28 of insulating material such as one of the well known phenol formaldehyde resins. The panel 28 carries one or more electrical contacts 29 as shown more clearly in Fig. 4. Each contact 29 may be formed by riveting an electro-conductive material in an opening provided in the panel, washers 30 being placed on each face of the panel for protective purposes. Each of the contacts 29 may be connected in an electrical circuit by means of a flexible electrical conductor 31.

. Engagement of the sleeve 26 with the extene sion I6 serves as a stop for the downward travel of the plunger assembly.

It should be noted that either end-of each contact 29 may be employed for contact making purposes. In Fig. 1 the contact 29 may be employed for engaging a fixed contact 32 when the plunger assembly rises. The contact 32 is mounted upon a resilient member 33 which is attached to a bracket 34 and spaced therefrom by means of a spacer 35. A relatively strong backup spring 353 may be employed for restricting deflection of the contact 32 away from the contact 29 when the latter suddenly stops. The

condition may occur when the Washer 25 strikes the core 9 in response to a sudden surge. In order to decrease inertia of the contact 32 and the effects of overtravel and rebound thereof the spring 33 preferably is made as Weak as possible, and the contact 32 is constructed with as light a weight as possible. The deflection of the contact .32 is held to a minimum by proper location of the bracket 34 relative to the movable contact 29. The spring 39 is slightly deflected when the washer 25 is against the core 9.

Rotation of the panel 28 and the shaft assembly is prevented by a guide rod 31 which passes through a slot 38 provided in the panel. The rod 37 may be attached to the frame 2.

As shown in Fig. 4 the contacts 29 also may be employed for engaging fixed contacts 39 positioned beneath the movable contacts. When contacts similar to the contact 39 are employed energization of the relay coil actuates the plunger assembly upwardly to break the electrical contact between the fixed contact 39 and a movable contact 29.

It should be noted that the shaft 22 passses freely through the core 9. The only sliding contact between the plunger assembly and the fixed parts of the relay is that between the plunger [9 and the guide 20. In analyzing the operation of the relay the friction developed between the panel 23 and the rod 31 may be disregarded.

When the coil 7 of the construction shown in Fig. 1 is energized magnetic flux is produced which passes between the cores 9 and I0 through the plunger it. When the force exerted by this magnetic flux reaches a value sufficient to overcome the weight of the moving assembly associated with the plunger [9, the plunger rises upwardly into the bore of the upper core 9. Because of the reduction of the magnetic reluctance between the cores 9 and In as the plunger rises, the total magnetic flux passing through the plunger tends to increase as the plunger rises. The reduction in magnetic reluctance is the result of the bridging action of the magnetic plunger l9 between the cores 9 and In. If the increase in magnetic flux were effective to assist 75 in raising the plunger IS, the force exerted on the plunger would increase as the plunger rises. In many cases such operation is objectionable.

In order to control the force exerted on the plunger the increase in magnetic flux is diverted in a horizontal direction through the plunger is. This may be accomplished by suitable design of the bevel or conical surface 2|. It will be noted that as the plunger rises, more and more flux passes in a horizontal direction from the magnetic core 9 to theplunger 19. The taper of conical surface 21 is so selected that this increase in the horizontal component of the magnetic flux maintains the verticalcomponent substantially constant as the plunger rises. Consequently a high ratio of dropout to pickup may be obtained. That is, a small departure of the voltage above or below a predetermined value actuates the contacts into or out of engagement. If the vertical component were to be maintained exactly constant the surface 2| would follow a complex curved shape which would be somewhat difficult to machine. I have found, however, that a straight conical surface is satisfactory from a practical standpoint. As

an example of a conical surface found suitable for a voltage relay the angle of inclination of the conical surfac relative to the axis of the core 9 may be of the order of 25.

Another factor controlling the total magnetic flux passing through the plunger is the reduction in current through the coil 1 caused by the increase in inductance of the coil as the plunger i5] rises. The reduction in current passing through the coil results in a lower magnetic flux than would be expected if the inductance of the coil were to be maintained constant. The incline tion of the conical surface 2| is designed to compensate for this variation in inductance and to maintain the vertical component substantially constant throughout the travel of the plunger. By suitable formation of the surface 21 the proportion of magnetic fluxpassed in a horizontal direction from the core 9 to the magnetic plungeriil may be controlled to produce various effects.

For example, if the relay is designed to provide a ratio of horizontal flux to vertical flux which increases as the plunger rises, the voltage required for relay actuation must increase as the plunger rises in order to maintain an adequate value of the vertical flux component.

By having the horizontal component of flux vary at one rate during a first portion. of the plunger travel and at a different rate during a second portion of the plunger travel, the operatic-n of a relay may be modified for various applications. As a typical application of such a relay, the

contacts

29 and 39 may open in reponse to a predetermined voltage, but because of v the increase in the horizontal flux component the plunger would fail to complete its travel. At a higher voltage, the plunger would complete its travel to close the

contacts

29 and 32.

Removal of the bevel from the upper core tends to lower the ratio of dropout to pickup. For example, this ratio may be lowered from a range of 0.90 to 1.00 to a range of 0.45 to 0.70. Preferably a sufiicient depth of bevel is retained to center the guide tube 29. Removal of the bevel shortens the upper core 9 and the connector H may be correspondingly lengthened. With this construction a predetermined voltage is required to pick up the plunger assembly. As the plunger rises, the horizontalfiux component increases at a relatively slow rate and the vertical flux component increases at a relatively great rate. Before the plunger assembly can drop, the voltage must decrease sufficiently to compensate for the increase in the vertical component. Consequently a low ratio of dropout voltage to pickup voltage is provided.

The height to which the plunger l9 rises is controlled by a number of factors. When the voltage on the coil 1 increases slowly, a value is reached at which the plunger starts to rise. A small increase in voltage in a high ratio relay or no increase in a low ratio relay carries the plunger to a, floating position in which the

contacts

32 and 29 are engaged and the washer 25 is close to the end of the bore in the core 9. The air gap between the plunger l9 and the upper core 9 is small. For example, this air gap may be one-half to one-third the air gap between the plunger and the lower core It]. Because of these relationships a further movement of the plunger above its normal floating position would produce a rapid increase in the horizonta. flux component. If the voltage is not further increased, a position of the plunger is reached in which the vertical component of flux is just sufficient to support the plunger assembly. Since further movement of the plunger is accompanied by a sharp increase in the proportion of the horizontal flux component and a corresponding decrease in the vertical flux component, it follows that a position is soon reached in which the resultant vertical force does not increase regardless of the increase in voltage or current applied to the coil. The various dimensions, such as plunger length, and thickness of the collar 23 and washer 25 are designed to leave a small space between the washer 25 and the end of the bore of the core 9 in this position of the plunger. This space should be small enough to prevent excessive overtravel of the plunger under the influence of the kinetic energy produced by suddenly applied excessive voltages or currents, and it should be large enough to prevent unnecessary noise and oscillation during normal operation. In a practicable relay, the plunger may travel 5 of an inch during normal pickup. A space 8% of an inch is left for overtravel. Half of this space cares for overtravel caused by abnormal energization of the relay. The remainder of the space permits a slight overtravel under the influence of kinetic energy.

For mechanical reasons it is desirable that the plunger |9 be as long as possible in order to provide adequate bearing surfaces. For magnetic reasons the plunger l9 should have a restricted length in order to decrease overtravel of the plunger and the weight thereof. These conflicting requirements may be satisfied by providing a skirt 40 on the plunger having an extremely thin wall section. Although this skirt provides adequate bearing support for the plunger it does not appreciably modify the magnetic characteristics of the plunger. If the effective solid part of the plunger is too short, a considerable magnetic force acting downwardly on the plunger may exist by the time the plunger reaches its mechanical stop. This may be effective for setting up undesirable oscillation of the plunger.

It is possible to lower the ratio of the relay by increasing the pickup value without substantially affecting the dropout value for the relay. This may be accomplished by lengthening the skirt 40 of the plunger, or by dropping the 7 plunger further from the sleeve 26. Since these modifications increase the energy required for pickup, the range over which the modified relays can be operated continuously is reduced.

The ratio of the relay is directly varied by altering the angle of the conical surface 2|. An increase or decrease in the angle may be employed for lowering the ratio.

The structure thus far described operates satisfactorily but is provided with no convenient adjustment for varying the pickup of the relay. In order to provide a suitable adjustment a tubular magnetic shunt 4| is provided which is attached to a nut 42 conveniently formed of brass. The nut 42 is provided with threads which engage a threaded portion of the guide 20 so that rotation of the nut raises or lowers the shunt 4| relative to the magnetic cores 9 and I0. As will be noted from the drawings, the shunt 4| surrounds the cylindrical cores 9 and ID in its raised position and provides a path for magnetic flux therebetween. It is clear that magnetic flux passing through the shunt 4| is diverted away from the magnetic plunger l9 and is not effective for lifting the plunger |9. The amount of magnetic flux diverted away from the plunger |9 is controlled not only by the relative position of the shunt 4| with respect to the cores 9 and II] but also by the configuration of the shunt itself. A satisfactory design for the shunt, as illustrated in Figs. 1, 2 and 3, includes a main tubular portion 43 and an upper portion 44 of reduced wall section. The section of the portion 44 may vary appreciably in accordance with the particular effects desired. I have found that this section may be tapered slightly with good results, a taper of approximately 1 in an axial direction being illustrated for the shunt of Figs. 1, 2 and 3.

The shunt 4| may be guided in any suitable manner. Usually the magnetic core structure and the hole in the leg 5 of the frame generally sufifice for this purpose. The coil 1 may have a supporting tube 45 of insulating material having an inside diameter sufficient for permitting entrance of the shunt.

A reduction in the paths offered to eddy currents by the magnetic shunt 4| may be efiected by providing the shunt with a slot 46 which extends axially for substantially the full length of the shunt. As illustrated, the slot terminates at a point adjacent the nut.

It will be noted that the position of the shunt determines the shunting effect thereof. That is, in the position illustrated in Fig. 1 a minimum amount of magnetic flux is shunted away from the magnetic flux member 9 by the magnetic shunt. If the shunt is rotated and raised, the amount of magnetic flux shunted therethrough increases. For this reason the position of the magnetic shunt determines the voltage for a voltage relay or the current for a current relay at which the plunger goes through its full pickup travel. The values of the voltage or current within the range of the relay may be marked on an adjacent scale 47. A groove 48 formed on the lower end of the magnetic shunt indicates on the scale 4'! the particular value for which the relay is adjusted. To facilitate rotation of the shunt 4| the portion of the shunt surrounding the nut 42 may be knurled.

If an exactly uniform scale is desired the con figuration of a vertical section of the portion 44 of the shunt 4| should have a complex curved shape. However, satisfactory operation may be obtained with simple shapes of the type illustrated. If the thin section of the magnetic shunt were lengthened without changing its thickness or the length of the thick section thereof, the result would be an increase in pickup value for low pickup settings of the shunt and a decrease in the range of adjustment of the relay. If for a given shunt length the thick section were made shorter an air gap would be introduced between the lower core I and the frame for low pickup settings of the shunt. The result would be a non-uniform scale and a reduced range for the relay. An increase in the taper of the thin section for a given thickness at its upper end increases the range. For a given taper and total shunt length, decreasing the length of the thin section increases the range of the relay and decreases the scale uniformity. An increase in the thickness of the thin wall section increases the volt-ampere and watt consumption of the relay.

Operation of the relay may be indicated in any conventional manner. As illustrated, an operation indicator is provided which includes a lever 49 pivoted on a bracket50 attached to the frame 2. An end of the lever 49 rests against the panel 28 and is so Weighted or biased that the lever tends to rotate in a clockwise direction as viewed in Fig. 1. A spring strip is biased against the left-hand end of the lever 49 as viewed in Fig. 1 and is provided with a window or slot 52 sufliciently large to allow the end of the lever 49 to project therethrough. When the plunger assembly is actuated upwardly the lever 49 is rotated in a counterclockwise direction until its end becomes aligned with the window 52 and projects therethrough. A stop 53 may be provided on the strip 5| to prevent overtravel of the lever 49.

In order to reset the operation indicator a sleeve 54 may be attached to the vertical portion 6 of the frame. A rod 55 is slidably mounted in the sleeve 54 and is provided with a pin 56 which projects through slots 51 in the sleeve. After an operation of the operation indicator the rod 55 is pulled outwardly or to the left as viewed in Fig. 1 to carry the pin 55 against the strip 5| and to move the strip 5! sufficiently to permit the return of the lever 49 to the position indicated in Fig. 1.

A suitable cover may be provided for the I relay. As illustrated a glass cover 58 is provided which has a cup shape and which, when in position abuts a gasket 59 positioned on the base I. The cover may be held in place by a sleeve 99 having a headed portion 9! which engages a washer 52 and a gasket 53 positioned adjacent the cover. The sleeve 59 extends through the cover and is provided with threads which cooperate with threads provided in the sleeve 54 for detachably holding the cover in position.

It is believed that the operation of the structure shown in Fig. 1 is apparent from the foregoing description. When the coil 7 is connected to be energized in accordance with the voltage of a circuit a magnetic flux is produced which passes from the core 9 through the magnetic plunger IS, the core I9, the shunt 4|, the leg 5 of the frame, the vertical portion 6 and the leg 4 of the frame and which normally does not produce movement of the plunger [9. When the voltage increases until the current passing through the coil I produces a magnetic flux that is suflicient to overcome the weight of the plunger assembly, the plunger rises in its guide 20 to perform any desired operation, such as to make or break electrical contacts.

As the plunger rises in its guide the total flux produced by the coil 1 increases because of the decreased reluctance of the magnetic circuit. As above explained for the high ratio relays the vertical component of this flux is maintained substantially constant by passing an increasing portion of the magnetic flux in a horizontal direction between the conical surface 2| of the core and the magnetic plunger. As the magnetic plunger is about to enter the cylindrical portion 9a of the magnetic core 9 the horizontal flux component starts to increase rapidly, and the vertical flux component starts to decrease to provide a stopping point for the plunger.

At the same time the panel 28 actuates the lever 49 in a counterclockwise direction until the lever 49 protrudes through the window 52 to indicate an operation of the relay. After the completion of an operation the rod 55 may be grasped and pulled outwardly to reset the operation indicator. Such movement of the rod 55 moves the strip 51 outwardly to free the lever 49 and permit it to return to the position indicated in Fig. 1. The outer portion of the rod 55 may be knurled to facilitate operation thereof.

If the relay is to be adjusted for operation at a different value of voltage the shunt M is rotated in order to raise or lower the shunt on the guide 20 until the proper setting is indicated on the scale 41. This setting is shown by the position of the groove 48 relative to the scale 41.

The relay illustrated in Fig. 1 is substantially free from oscillation. Some of the reasons for this freedom have been set forth above. For example, the tendency to stop the plunger magnetically in its overtravel region is kept low for preventing a certain amount of oscillation. Moreover it will be noted that the shunt 4| and the cores 9 and I9 are slotted so that a slight dis'symmetry exists in these members. This, together with the decentering permitted by the clearance required for the moving parts and manufacturing tolerances results in a side thrust on the plunger during actuation which tends to prevent oscillation. This side thrust is insignificant when the plunger is in the position illustrated in Fig. 1 but as the plunger rises the flux passing therethrough increases and the horizontal component of this flux increases with a resulting increase in the side thrust of the plunger against its guide. Consequently the maximum friction, though not excessive, is exerted between the plunger and its guide at the time it is most needed in order to prevent undesired oscillation of the plunger assembly.

A still further reduction in oscillation is obtained because of the resiliency of the frame 2 coupled with the inertia of the coil 1. It should be noted that the coil 1 is positioned freely between the legs 4 and 5 of the frame. Since the period of the legs 4 and 5 will differ from that of the plunger assembly and since the coil 1 tends to absorb the vibration of the legs 4 and 5, a still further control of oscillation is provided.

Another factor contributing to the successful application of the relay illustrated in Fig. 1 is that the ratio of dropout to pickup remains substantially constant for all positions of the shunt 4|.

Although my invention has been described thus far with reference to a voltage relay it is applicable also to current relays. For example, in Fig. 4 I have illustrated a current relay designed in accordance with my invention. In Fig. 4 a coil 1, rame 2, plunger l9, shaft 22, and a guide 26 correspond to the similar parts designated by unprimed reference characters in Fig. 1. It will be understood that the coil 1' is proportioned for current excitation instead of excitation from a voltage source as well understood in the art.

If the exact construction illustrated in Fig. 1 were to be employed for a current relay except for the substitution of a current coil for the voltage coil 7 satisfactory operation may be obtained, but the range of operation may be smaller than that desired, and the scale distribution may be unsatisfactory. For this reason certain parts of the relay are modified as set forth below.

In Fig. 4 an upper core 9' is employed which is considerably shorter than the corresponding core in Fig. 1. The purpose of this is to provide an air gap between the lower end of the core assembly and the frame 2. The upper core 9' is attached by a connector H to a lower core In which corresponds to the core ID of Fig. 1. The increased gap between the lower end of the core Ill and the lower leg 5 of the frame 2 is apparent from an inspection of the drawings. Another distinction between the upp r cores 9 and 9 may be found in the conical tapers provided therein. Because of the variation in inductance of the coil 1 during operation of the relay of Fig. l the conical surface 2| is given a taper such as 25. In a current relay the current passing through the coil 1' is substantially independent of the inductance of the relay. Consequently, the upper core 9' may be provided with a conical surface 2| which has a taper of the order of 18.

In order to extend the range of the current relay a shunt 4| of modified construction is employed therefor. As illustrated in Fig. 4 the shunt 4| has a magnetic portion 64 which is considerably shorter than the magnetic portion of the shunt 4| employed for a voltage relay. The magnetic portion 64 is attached to a nut 42' by means of a non-magnetic connecting sleeve 65 which may be constructed of brass. The connection between the sleeve and the magnetic portion 64 may be effected in any desired manner. As illustrated, however, the connection is similar to that employed between the connector H and the cores 9 and It. It will be noted from Fig. 4 that the magnetic portion 64 is divided into a lower portion of appreciable thickness and an upper portion of reduced thickness. Relationships between the design of the current relay and its characteristics are similar to those discussed in connection with Fig. 1. However, no taper need be employed for the thin section of the shunt 4| for the current relay. This is for the reason that over a suitable range the scale distribution is sufiiciently uniform when employing the shunt 4| illustrated in Fig. 4.

With the proportions illustrated in Fig, 4, as the shunt 4| is raised upwardly by rotation thereof on the guide 28' an air gap is introduced between the magnetic portion 64 and the leg 5. The effect of this gap is to increase the reluctance of the magnetic circuit for the coil 1' and consequently to reduce the force exerted on the plunger l9. As the shunt 4| continues to rise the air gap not only increases but the magnetic portion 64 begins to bridge the cores 9' and Hi. This bridging action tends further to decrease the magnetic flux passing through the plunger it by diverting a portion of flux in the cores 9 and I0 through the shunt. These two effects, namely; the air gap increase and the shunting action; overlap to some extent in order to provide a smooth and gradual increase in. the value of current for which the relay operates as the shunt 4| is raised. By this combined control of the magnetic flux a satisfactory range of operation of the relay illustrated in Fig. 4 is obtained.

The operation of the relay of Fig. 4 is substantially similar to that of the relay of Fig. 1 except for the energization of the coil '1 in accordance with the current flowing in a circuit instead of the voltage across the circuit. It is believed that this operation will be apparent from the description of the operation of the relay of Fig. 1.

There is a possibility that the adjustment of the shunt 4| of Fig. 1 or the shunt 4| may vary because of vibration of the relay or for other reasons. In order to preclude this possibility a locking device is provided for securing each shunt in the position to which it is adjusted. This locking device is illustrated most clearly in Figs. 4 and 5 and includes a plunger 66 preferably of relatively soft material, such as aluminum, for engaging the shunt 4|. The plunger is biased into engagement with the shunt 4| by means of a spring 61 which engages one end of a lever 68 pivoted for rotation by means of ascrew 69. A protuberance 68' may be provided on the lever for engaging the screw 69 as a pivoting point. The plunger 66 is guided in a block 78 which may be attached to the relay frame 2 and which contains a recess for the spring 61. The block I!) also may be employed for supporting the scale 41 which indicates the operating value for which the shunt 4| is adjusted. If desired the end of the plunger in contact with the shunt may be of reduced cross-section, or it may carry a friction pad 66 for engaging the shunt.

When the shunt is to be adjusted the lever 58 is moved in a counterclockwise direction as viewed in Fig. 5 in order to release the plunger 65. With the plunger released the shunt ll may be rotated to any desired position. When the lever 68 is released the spring 6'! again biases the lever against the plunger 55 and forces the plunger into locking engagement with the shunt 4|. If desired, the plunger 66 may have a projecting pin 1| which passes through an opening 12 in the lever 68 to assist in. positioning the lever.

In Fig. 6 a modified shunt construction is illustrated. In this figure, the upper end of a shunt 13 is provided with a uniform taper instead of an abrupt reduction in cross-section. The increased amount of magnetic material in this construction permits an increased amount of magnetic flux to be shunted from the plunger with a resulting increase in the operating range for the relay. A further decrease in the angle of the taper does not increase the range, but may reduce the uniformity of the relay scale.

It is to be understood that the shunt 4| is slotted in the same manner and for the same reason as the shunt 4| of Fig. 1. The range of the relay of Fig. 4 may be increased somewhat by omitting the slot from the sleeve and by constructing the sleeve from copper. This is effective only on alternating current relays, and the increase in range varies with frequency. Consequently a differently calibrated scale would be required for each frequency and for direct current.

The operation of the relays shown in Figs. 1 and 4 differs somewhat on direct current. Since the steady-state current in a direct current relay coil is proportional to the voltage across the coil, and this relationship is not influenced by reactance variations in the 0011, a relay designed as a current relay also may be employed as a voltage relay provided a proper coil is provided in each case. If the same relay design is employed for alternating and direct currents, it will be found that the ratio of the relay is slightly lower for direct current operation and the scale calibration difiers slightly. For most applications of the relay the differences are so small that they may be ignored. Obviously, diiierent scales may be provided for alternating and direct current operation.

Although I have described my invention with reference to certain specific embodiments thereof, it is obvious that numerous modifications thereof are possible, therefore I do not wish my invention to be restricted except as required by the appended claims when interpreted in view of the prior art.

I claim as my invention:

1. In a relay device, a magnetic structure including a pair of axially spaced. cylindrical magnetic cores having o enings therein, means for producing magnetic flux in said magnetic structure. a magnetic plunger movable in said ope. ings in response to magnetic flux in said marrnetic structure, a non-magnetic guide for said plunger, a tubular magnetic shunt surroundin said magnetic cores, and means mounting said magnetic shunt for adjustment across the space between said magnetic cores for adjustably diverting magnetic flux from said magnetic plunger.

2. In a relay device, a magnetic structure including a pair of axially spaced, cylindrical mag-v netic cores having axially aligned cylindrical openings therein, means for producing magnetic flux in said magnetic structure, a magnetic plunger movable in said openings in response to magnetic flux in said magnetic structure, a nonmagnetic guide for said plunger, said non-magnetic guide comprising a tube positioned within one of said openings and extending towards the other of said openings, a tubular magnetic shunt surrounding said magnetic cores, and means mounting said magnetic shunt for adjustment across the space between said magnetic cores for adjustably diverting magnetic flux from said 5 magnetic plunger.

3. In a relay device, a magnetic structure including a pair of spaced, cylindrical, axially aligned magnetic cores each having an axial opening therein, a non-magnetic tube positioned in the opening of a first one of said magnetic cores and extending towards the opening in a second one of said magnetic cores, said second magnetic core having a beveled face surrounding its opening within which said non-magnetic tube is seated, a magnetic plunger reciprocable in said non-magnetic tube, a tubular magnetic shunt proportioned to surround said magnetic cores. cooperating screw means associated with said tubular magnetic shunt and said non-magnetic tube for urging said magnetic shunt axially relative to said magnetic cores for adjustably shunt ing magnetic flux away from said magnetic plunger, and means for producing magnetic flux in said magnetic structure.

4. In a relay device, a magnetic structure including a pair of spaced, cylindrical, axially aligned magnetic cores each having an axial opening therein, a non-magnetic tube positioned in the opening of a first one of said magnetic cores and extending towards the opening in a second one of said magnetic cores, said second magnetic core having a beveled face surrounding its opening within which said non-magnetic tube is seated, a magnetic plunger reciprocable in said non-magnetic tube, a tubular magnetic shunt proportioned to surround said magnetic cores. cooperating screw means associated with said tubular magnetic shunt and said non-magnetic tube for urging said magnetic shunt axially relative to said magnetic cores for adjustably shunting magnetic flux away from said magnetic plunger, a stop for said magnetic plunger, said stop having a slight clearance from said magnetic plunger in the greatest displacement which the magnetic plunger attains in response to a steady state magnetic flux, and means for producing magnetic flux in said magnetic structure.

5. In a relay device, a magnetic core assembly comprising a pair of spaced, axially aligned, cylindrical magnetic cores, said magnetic cores having an opening extending through one of said magnetic cores into the other of said magnetic cores, and a tubular non-magnetic member connecting said magnetic cores, a tubular magnetic shunt embracing said magnetic core assembly. said magnetic shunt being adjustable along said magnetic core assembly for controlling magnetic flux passing therethrough, and a magnetic plunger positioned in said opening for movement therethrough in response to magnetization of said magnetic core assembly.

6. In a relay device, a tubular magnetic core assembly comprising a pair of tubular, axially spaced magnetic cores, a non-magnetic spacer element between said magnetic cores, a magnetic plunger positioned within said magnetic core assembly for movement relative thereto in response to magnetization of said core assembly, a tubular magnetic shunt embracing said magnetic core assembly, said magnetic shunt being adjustable along said magnetic core assembly for controlling magnetic flux passing therethrough, and a magnetic structure for directing magnetic flux into said magnetic core assembly through said magnetic shunt, said magnetic shunt having a relatively thick cross-section in the path of said last-named magnetic flux, and having a relatively thin cross-section movable between said magnetic cores.

7. In a relay device, a cylindrical magnetic core assembly comprising a pair of axially spaced. magnetic cores, said magnetic core assembly having an axial opening therein, a magnetic plunger positioned in said opening for movement axially therethrough in response to magnetic flux passing between said magnetic cores, means for magnetizing said magnetic core assembly, a magnetic shunt surrounding said magnetic core assembly, and means mounting said magnetic shunt for movement from a position surrounding substantially only a first one of said magnetic cores to a position substantially surrounding the gap between said magnetic cores.

8. In a relay device, a cylindrical magnetic core assembly comprising a pair of axially spaced magnetic cores, said magnetic core assembly having an axial opening therein, a non-magnetic tube positioned in said opening and extending through a first one of said magnetic cores into a second one of said magnetic cores, the opening in said second one of said magnetic cores having a tapering configuration dimensioned to center said tube accurately in said opening, a magnetic plunger positioned in said tube for movement axially therethrough in response to magnetic flux passing between said magnetic cores, means for magnetizing said magnetic core assembly, a magnetic shunt surrounding said magnetic core assembly, and means mounting said magnetic shunt for movement from a position surrounding substantially only a first one of said magnetic cores to a position substantially surrounding the gap between said magnetic cores.

9. In a relay device, a cylindrical magnetic core assembly comprising a pair of axially spaced magnetic cores, said magnetic core assembly having an axial opening therein, a magnetic plunger positioned in said opening for movement axially therethrough in response to magnetic fiux passing between said magnetic cores, means for magnetizing said magnetic core assembly, a tubular magnetic shunt surrounding said magnetic core assembly, and means mounting said magnetic shunt for movement from a position rounding substantially only a first one of said magnetic cores to a position substantially surrounding the gap between said magnetic cores, said shunt having a first portion engaging said first one of said magnetic cores, and having an end dimensioned for movement over, but spaced from, the second of said magnetic cores.

10. In a relay device, a cylindrical magnetic core assembly comprising a pair of axially spaced magnetic cores and a non-magnetic connector for said magnetic cores, said magnetic core assembly having an axial opening therein, a magnetic plunger positioned in said opening for movement axially therethrough in response to magnetic flux passing between said magnetic cores, means for magnetizing said magnetic core assembly, a tubular magnetic shunt surrounding said magnetic core assembly, said magnetic shunt having a first thick portion of predetermined internal diameter for slidably engaging a first one of said magnetic cores, and having a second thin portion substantially larger in internal diameter than the external diameter of the remaining one of said magnetic cores, and means mounting said magnetic shunt for movement from a position wherein said shunt substantially surrounds only said first one of said magnetic cores to a position wherein said thick portion substantially surrounds said first one of said magnetic cores, and said thin portion surrounds a substantial part of the resurw til to said cylindrical core by operation of said threaded portions, and non-magnetic connecting means for said magnetic cores, a tubular magnetic shunt surrounding said magnetic core assembly, said magnetic shunt having a portion in threaded engagement with said non-magnetic tube, whereby rotation of said magnetic shunt relative to said tube advances said magnetic shunt over the gap between said magnetic cores and retracts said magnetic shunt from said gap, a magnetic plunger positioned in said tube for movement therethrough, and means for magnetizing said magnetic core assembly.

12. In a relay device, a non-magnetic tube having a threaded portion, a cylindrical magnetic core assembly comprising an annular magnetic core surrounding said non-magnetic tube, said annular magnetic core having a portion in threaded engagement with a portion of the threads on said tube, a cylindrical magnetic core having an axially positioned beveled recess for receiving one end of said tube, said beveled recess being proportioned to receive and center the end of said tube as said tube is advanced relative to said cylindrical core by operation of said threaded portions, and non-magnetic connecting means for said magnetic cores, a tubular magnetic shunt surrounding said magnetic core assembly, said magnetic shunt having a first portion slidably engaging a first one of said magnetic cores, and a second portion surrounding, but spaced from, a second one of said magnetic cores, means establishing a threaded engagement between said magnetic shunt and said tube for urging said magnetic shunt away from said second one of said magnetic cores as said magnetic shunt is rotated relative to said tube, and means for magnetizing said magnetic core assembly, said magnetizing means including a magnetic structure having a portion positioned adjacent said magnetic shunt, whereby said magnetic shunt completes a magnetic path between said magnetic structure and said first one of said magnetic cores.

13. In a relay device, a cylindrical magnetic core assembly comprising a pair of axially spaced magnetic cores, said magnetic core assembly having an axial opening therein, a magnetic plunger positioned in said opening for movement axially therethrough in response to magnetic flux passing between said magnetic cores, a magnetic shunt surrounding said magnetic core assembly, means mounting said magnetic shunt for movement from a position surrounding substantially only a first one of said magnetic cores to a position substantially surrounding the gap between said magnetic cores, and means for magnetizin said magnetic core assembly, said last-named means comprising a magnetic structure having a portion positioned adjacent said magnetic shunt, whereby said magnetic shunt is positioned in a path extending between said magnetic structure and said first one of said magnetic cores, said magnetic shunt having zones differing in magnetic reluctance positioned for successive movement into, and out of, said path as said magnetic shunt is moved.

THOMAS DRAPER.