US2278971A - Electromagnetic apparatus - Google Patents

Description

April 7,' 1942. a. w. BOEHNE 2,278,971

' V ELECTROMAGNETIC APPARATUS Filed DQ O 31, 1938 v 3 Sheets-Sheet l LEVEL 7 Inve'hEQTT; Eugene W. Boehne,

' His Attorney.

April 1942M E. w. BOEHNE I 2,278,971

ELECTROMAGNETIC APPARATUS Filed Dec. :51, 1958 3- Sheets-sheaf, 2

A\\ 'IIIIIIIIIIIIIIIIIII- CLOSED TI ME a I 11IIIII/IIII/II/III/IIII/fl I VIIIIIIIII/IIIIIII Eugene W. Boehne,

' Hus Attorn ey,

A rilz 1942.-

Fil ed Dec. 31, 1938 3 Sheets-Sheet 3 48 Figfia.

I 3000 n SOLENOID O v 2.000% o H- LIODD 62 a I z u TRAV L INSULATION 0R HONMAGNETIG MATFRML msuunou on Now manure MATERIAL Ihventbw-z Eugene W. Boehne,

Hi ,AttoT-ney.

Patented Apr. 7, 1942 ELECTROMAGNETIC APPARATUS Eugene W. Boehne, Drexel Hill, Pa., assignor to General Electric Company, a corporation of New York Application December 31, 1938, Serial No. 248,783

9 Claims..

My invention relates to electromagnetic apparatus, and more particularly to high speed operating apparatus having electromagnetic means for effecting an energy storing operation in combination with a magnetic release.

In a conventional form of operating mechanism for reciprocally operable apparatus such as a circuit breaker, for example, a spring is arranged to be stressed by a cam or the like for storing energy for a working stroke. The energy is released by suitable latching and tripping mechanism that is responsive in turn to an electromagnetic tripping impulse. Accordingly, it will be apparent that this type of mechanism is not only complicated but also involves a certain time lag due to inertia and lost motion after initiation of the tripping impulse.

A principal object of the present invention is the provision of an improved high speed operating mechanism of the electromagnetic type that is simple and compact in construction and capable of releasing without delay a large operating force. In accordance with my invention electromagnetic means, such as a solenoid, is employed to effect an energy storing operation on a spring, for example, and the spring is held under tension at the completion of said operation by permanent magnet structure having a large magnetomotive force. The spring energy is subsequently released for the desired working stroke by a releasing flux tending to counteract the holding effect of the permanent magnet flux. In this arrangement no intermediate elements are involved to impede the release of the spring energy which in the present case can be of considerable magnitude.

My invention will be more fully set forth in the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawings, Fig. 1 is a sectional view in elevation of an electromagnetic device embodying the present invention as applied to an. electric circuit breaker; Fig. 1a is a partial view of the apparatus shown by Fig. 1 in the closed magnetic circuit position prior to tripping; Fig. 2 is a similar view illustrating a modified form of the magnetic structure shown in Fig. 1; Fig. 3 is a sectional view in elevation of another form of my invention also applied to a circuit breaker of the reclosing type; Fig. 4 is a graphical illustration of the reclosing characteristics of the apparatus shown by Fig. 3; Fig. 5 is a sectional view of another form of my invention that is capable of free-release operation; Figs. 5a, 5b and 5c illustrate diagrammatically the various operating positions of the apparatus shown by Fig. 5. Fig. 6 is a sectional view in elevation of another form of free-release apparatus as applied to a circuit breaker of the fluid blast type; Fig 6a is a graphical illustration of forces involved in Fig. 6; Fig. '7 is a sectional view of a modified form of the magnet holding surfaces for increasing the effectiveness of the holding flux; and Fig. 8 is a perspective view illustrating a modification of the magnetic circuit arrangement shown by Fig. 7 for obtaining calibration of the holding force.

The electromagnetic device illustrated by Fig. 1 comprises a solenoid arrangement including an energizing coil 1 and magnetic structure for completing a magnetic circuit for the coil flux including a pair of disc-like pole pieces 2 and 3. The pole piece 3, which comprises a disk composed of magnetic material, such as iron or steel, is provided with a central hub portion 3' extending part way within the coil l for coacting with a movable armature 4 that is reciprocally guided within the opposite pol'e piece 2. The armature 4 is provided with a flange 4' arranged to engage the pole piece 2 coincident with engagement of the lower end of armature 4 and pole piece 3. The armature 4' is also provided with an insulating or non-magnetic rod 5 for coacting with a spring 6 so that the armature is biased toward the open magnetic circuit position shown. The spring 6 is seated between a fixed tubular extension 1 secured to the lower pole piece 3 and a flange 8 secured to the insulating rod. Accordingly, when the armature 4 is drawn within the solenoid in response to energization thereof, the spring 6 is stressed and an energy storing operation is thereby performed.

For the purpose of holding the spring 6 under tension when the solenoid I is deenergized, there is provided a permanent magnet M comprising in the present instance a cylindrical member 9 composed of a precipitation-hardened permanent magnet alloy of the character described and claimed in Ruder Patents 1,947,274 and 1,968,569. This permanent magnet material has a very large magnetomotive force, the closed circuit flux output being of the order of 25 kilolines per square inch. This magnetomotive force is suflicient, even in the case of a small cylinder a few inches in diameter to maintain charged a comparatively powerful spring after the armature holding surfaces 2-4', and 34 have been brought into engagement. The above arrangement can be suitably assembled by mounting the coil I within the cylinder 9 and clamping the cylinder be tween the pole plates 2 and 3 by through bolts ID or the like. With this arrangement the energizing coil and permanent magnet use the same magnetic circuit.

It will be noted that the movable armature provides two separate holding surfaces, viz: that at the lower side of the flange 4 and at the lower end of the plunger 4. These surfaces are normal to the direction of motion of the plunger, thereby insuring double use of the entire permanent magnet holding flux, and also a corresponding increase in the holding power.

Another expedient for increasing the holding power of the permanent magnet lies in designing the aforesaid holding surfaces for optimum area, that is, relating the holding area to the total holding flux so that a maximum holding power results. Also the two air gaps at the aforesaid holding surfaces and pole pieces respectively are related so that as the gaps are closed simultaneously the armature 4 is seated with considerable impact. In other words, the movable armature delivers a hammer blow simultaneously to each pol piece 2 and 3 so that the impact is transmitted to the permanent magnet M. This hammer blow has the effect of increasing the magnetomotive force of the permanent magnet in the presence of the magnetizing flux of the main solenoid I.

Assuming now that the armature 4 is in closed magnetic circuit position and is being held solely against the bias of spring 6 by the perma-- nent magnet, th armature can be released by suitable electromagnetic means arranged to establish a flux opposing that of the holding magnet at one or both of the holding surfaces. Al though this can be accomplished by momentary energization of the coil l at reverse polarity, improved high speed operation results, if a small releasing coil II is disposed closely adjacent to one of the holding surfaces so as to build up a releasing flux at very high speed. Such a coil would be specially designed for high speed release and would preferably be of the character disclosed and claimed in my copending application Ser. No. 94,220, filed Aug. 4, 1936, for High 1 speed tripping system, which became Patent No. 2,130,871 on September 20, 1938. In the above system the number of coil turns is an optimum for the rate of increase of the releasing flux.

The releasing coil I I can b compactl mounted within an insulated annular pocket in the coil I as illustrated or can be suitably interleaved with the turns of the coil I at that location. In any event, the arrangement is preferably such that the releasing flux path through armature plunger 4 and th holding surfaces at 2 and 4' is of minimum length, in order to insure a maximum releasing speed. It will be noted that in the present instance the releasing flux threads both holding surfaces to oppose the magnet holding flux although the main releasing flux acts at 4. In view of the fact that the holding power varies as the square of the flux density, the effectiv holding flux need be reduced only about 10 or 12 per cent in order to release the comparatively larg spring force.

In order further to insure maximum speed of release of the spring energy, it is essential that the permanent magnet holding force decrease at a very rapid rate at the instant of separation of the holding surfaces. This is accomplished in th present instanc by shunting most of the holding flux at the instant of separation so that it has minimum holding force. It is well known that it is less difficult to slide the keeper of a magnet across the holding surface by a shearing motion than it is to pull the keeper directly away from the holding surface. In the present construction this characteristic is utilized by providing a thin insulating spacer, such as a fiber cylinder I2, A in thickness, for example, between the pole piece 2 and the plunger portion of the armature 4. Accordingly, when the holding surfaces at 2 and 4 start to separate the holding flux is progressively shunted directly across the insulating gap defined by the fiber spacer l2. This flux, however, is in a direction normal to the direction of motion of the plunger and therefore has minimum holding effect. The spring 5 therefore is effective to accelerate the movable armature very rapidly after this initial separation of the holding surfaces.

In the arrangement above described a fiber spacer in thickness permits the reluctance of the path from the upper pole piece 2 to the plunger 4 through the insulating gap at the fiber spacer to equal the reluctance across the upper holding surfaces between 2 and 4 when the plunger is less than away from its holding surfaces. Hence, as the plunger moves from direct contact to stroke, the holding flux shifts from a direction parallel to the plunger motion where it has a maximum restraining force to a direction which is normal to the line of motion and henc has no force component restraining the plunger against the bias of spring 6.

The relation of the releasing flux to the holding flux is diagrammatically illustrated by Fig. 1a which illustrates the armature 4 in th closed magnetic circuit position where it is held solely by the permanent magnet flux indicated by the solid line arrows at H. As previously pointed out the main charging coil or solenoid I is deenergized at the completion of the charging stroke. When the high speed working stroke under infiuence of the spring 6 is to be performed, the releasing coil II is energized so as to establish an opposing or releasing flux indicated by the chain arrows at T for decreasing the effectiveness of the holding flux H. As illustrated, the flux H normally takes a path through the holding surfaces at 24' and 43 normal to the direction of motion of the plunger, returning by way of the source of magnetomotive force, i. e., the permanent magnet M. Th releasing flux T tends to shunt the holding flux H around the releasing coil as indicated by the dotted line path, and to this end the coil H is comparatively short and compactly arranged adjacent to the holding sur faces at 24, so that the reluctance of the aforesaid shunt path for the flux H need not be greater than necessary. This compact arrangement of the releasing coil II with respect to a holding surface of the magnetic circuit results in high releasing speed by reason of the short iron path for the releasing flux and the short shunt path for the deflected holding flux.

The modification illustrated by Fig. 2 is designed further to increase the releasing speed. In this case the releasing coil II is provided with a cup-like magnetic shell ll suitably secured to the fixed pole piece extension 3' for decreasing the reluctance of the path for the releasing flux. In the closed position of the annature 4 the magnetic circuit for the releasing flux is complete, except for the essential gap at the point I3. It will also be noted that the magnetic shell or cup I I within which the releasing coil is mounted also serves to decrease the reluctance of the shunt path for the flux H during the releasing operation as illustrated in Fig. 1a. The cross-section of the core II is small so as to saturate quickly in the presence of the closing ampere turns. By energizing the releasing coil reversed in parallel with coil I, both can aid in closing the device.

The releasing flux path is further shortened at the upper holding surfaces by countersinking the flange 4' of the plunger armature with respect to the pole piece 2. That is, the length of the flux path from the pole piece 2 to the plunger 4 is now decreased substantially by the thickness of the pole piece 2'. A further advantage of this arrangement is that the'stroke of the plunger can be decreased and thereby the size and weight thereof decreased accordingly, so that the inertia of the moving element is reduced. This inertia is even further reduced in the present arrangement by arranging the charging spring 6 above the solenoid so that a short connecting rod I4, as compared with the rod 5 of Fig. 1 which extends through the lower pole piece 3, can be used. The spring 6, as in the previous instance, normally biases the plunger 4 toward open magnetic circuit position and is seated between a fixed bracket support I5 mounted on the pole piece 2 and a disk I6 secured to the rod I4. The means to be actuated is suitably related to the member I6.

As previously stated the present invention is applicable to reciprocally operated apparatus such as circuit breakers, but it should be understood that the invention is not limited thereto and may, for example, have general application as a thrust-transmitting mechanism.

Referring again to Fig. 1, the device is illustrated as applied to a specific form of oil circuit breakerof the fluid blast type. The circuit breaker obviously may be of any suitable type and, in the present instance, comprises a cylindrical casing I'I depending from the lower pole piece 3 and partly filled with oil to a level indicated. The circuit breaker structure comprises a pair of relatively movable contacts, such as a fixed contact l8 suitably mounted in the bottom of the casing and connected to a circuit terminal I9, and a movable contact 20 connected to the lower end of the plunger rod 5 and also suitably connected through conductors 2I and 22 to the other circuit terminal 23. The movable contact rod is also provided with a piston 24 operable within an insulating cylinder 25 having an opening at 26 for the movable contact. The cylinder 25 is also provided with a port 21 communicating with the main oil body. A oneway valve 28 is likewise mounted in the cylinder 25 for preventing retardation of the piston during the opening stroke.

When the device is released to open the breakerthe spring 6, resets the device with respect to the permanent magnet holding flux, and recharges the permanent magnet.

Under certain operating conditions it is highly desirable that a circuit breaker be adapted to reclose within a very short time after. interrupting a fault current. The reclosing speed should not appreciably exceed the time required for interrupting the fault current and therefore must be of the order of a few cycles of commercial frequency. An important characteristic of the electromagnetic device above described resides in high speed reclosing ability.

In the arrangements shown by Figs. 1 and 2 the releasing coil II is not necessarily used for the reclosing cycle. The charging coil I can be simply energized at reverse polarity as indicated at S (Fig. 1) to open the breaker and to effect the high speed reclosing operation as graphically illustrated by Fig. 4. As the coil current starts to build up at reverse polarity, the device operates as in the previous instance by the flux-shifting or flux-opposing principle, since the holding flux H is now directly opposed by the flux of the charging coil. Accordingly, the spring 6 functions to open the mechanism even before the coil current has increased to its normal value. However, as the coil current continues to build up, the permanent magnet is charged with reverse polarity, and the movable plunger 4 is immediately retracted again to close the magnetic circuit and also the circuit breaker. The charging coil circuit is then interrupted and the permanent magnet functions as before to maintain the spring charged until another releasing operation is performed.

The operation can be clearly understood by reference to the graphs of Fig. 4. In the closed position, the permanent magnet has, for example, a holding force of approximately 1500 pounds. Assuming that the opposing spring force is 1200 lbs., a releasing flux equivalent to but 300 lbs. is necessary. This flux is indicated as corresponding approximately to 10 amps. in the solenoid circuit, at which point release occurs as shown at t by the Travel graph. As the solenoid current continues to increase the polarity of the holding magnet is reversed and the holding force is reduced to zero. Further increase in the solenoid current causes the reclosing force to build up as clearly shown by the Force graph. When the reclosing force reaches a predetermined amount, the inertia of the moving structure is overcome and reversal or reclosing thereof is initiated at r as shown by the Travel graph. After reclosure the solenoid current is interrupted and simultaneously the solenoid force is replaced by the holding force of the permanent magnet. The apparatus is then in condition for another reclosing cycle that is started by energizing the solenoid with reversed polarity.

A subsequent reclosing operation is performed by simply again reversing the polarity of the charging coil and the above cycle is repeated. It will be apparent, of course, that where the releasing coil II is also used in this arrangement for normal release the polarity of the coil would automatically be reversed in accordance with reversal of the polarity of the coil I, in order to maintain a proper relation of the interacting fluxes.

By way of example, I have found that a device which has a 2 stroke and a maximum charge spring pressure of 1500 pounds can be reclosed by the above method in 0.25 second. This is considered to be excellent reclosing time since an in crease in the speed might in certain cases be undesirable due to possible incomplete clearance of the fault and the presence of ionized gas.

It will also be apparent that reclosing can be accomplished simply by energizing the releasing coil I l and thereupon immediately energizing the coil I at normal polarity. This method is also comparatively fast, the reclosing time for a specific device being but one cycle slower than by the reverse polarity method above described.

The main charging coil I is, in the present instance, composed of a single coil energized from a direct current source. However, where a direct current source is not available, the solenoid can comprise two separate coils interleaved and operated from a source of alternating current through a full wave rectifier. Where two coils are used, a series connection is employed for 250 volt operation and a parallel connection for 125 volt operation. In case of parallel operation the two coils must have the same characteristics, and to this end the coils are interleaved so as to have the closest possible coupling. By providing the two windings with difierent resistances, it is possible by parallel connection to make the device close and remain closed as long as current passes through the two windings in parallel. When the total current is interrupted the device will open because a complete circuit still remains in the parallel connection whereby the difierence in the two coil currents is a reverse component in one coil producing releasing action. However, when the two coil currents are interrupted separately, the device remains closed under influence of the permanent magnet flux until a releasing flux is established in the manner above described.

The present invention is not primarily concerned with the remote control system for energizing the charging and releasing coils, and it will be apparent that the energizing circuits can be controlled by simple manual switching means, or by the usual relay system for automatic operation. Also, both methods of control may be combined in a well known manner as in the case of automatic circuit breakers.

Fig. 3 illustrates a modified form of the invention wherein the permanent magnet M comprises a disk 3| secured as at 32 between the upper pole piece 2 and a steel disk 33. The magnetic circuit is completed by a magnetic cylinder 34 and the lower pole piece 3 through which the movable plunger armature 4 operates. As in the previous instance, the armature 4 is designed to make simultaneous butt contact at the pole piece 3 and disk 33. A fiber spacer 35 serves to maintain the proper flux insulating gap between the plunger and the pole piece 3, along the side parallel to the direction of motion.

For the purpose of facilitating the releasing operation, two separate releasing coils 36 and 31 are compactly arranged adjacent to the two holding surfaces at 3 and 33. Accordingly, when the device is to release the coils 36 and 31 can be energized, either separately or simultaneously, to establish an opposing flux at the holding surfaces for permitting immediate opening of the armature under the influence of spring 6.

The present arrangement shown as applied to a simple form of circuit breaker comprises a pair of fixed contacts 39 and 39 and a coacting bridging contact 49. The insulating operating rod 4| of the circuit breaker is in effect a continuation of the plunger rod and has affixed thereon a piston 42 operable within a fixed cylinder 43 depending from the lower pole piece 3. The

spring 6 is seated between a fixed shoulder 44 in the cylinder 43 and the movable piston 42 so as to bias the plunger 4 and the bridging contact 40 toward the open position. The piston 42 in opening the breaker functions also as a blast producing device, the conduits indicated at 45 at the lower end of the cylinder being utilized in any suitable manner for directing an arc-extinguishing fiuid into the arcs. Although the action of the piston 42 on the fluid at the lower part of the cylinder 43 serves to cushion the latter part of the opening stroke, a rubber buffer 46 seated on the shoulder 44 can also be provided for this purpose.

As in the case of the cylindrical form of permanent magnet, the disk form of magnet in Fig. 3 is fully recharged on each energization of the solenoid I, and this charging action is intensified by the closing impact due to the plunger 4. By way of example, I have found that a device constructed according to Fig. 3 and provided with a disk magnet 5 in diameter and 1" thick of precipitation--hardened permanent magnet alloy has a holding force of approximately 1500 pounds that is efiective to control 1200 pounds of stored spring energy. It will therefore be apparent that such a device is capable of initiating within a small fraction of a second a powerful high speed working stroke notwithstanding the small simple compact structure involved.

It will be apparent that the device above described is also capable of operating through a high speed reclosing cycle, the reverse polarity method previously described being preferred. Fig. 4 also illustrates graphically the reclosing performance of this device.

In Fig. 5 there is illustrated a modification of my invention particularly applicable to circuit breakers where the so-called free-release action is desired. That is, when the circuit breaker is closed on a fault the breaker is immediately released from the closing force notwithstanding continued energization of the closing mechanism. Referring more particularly to Fig. 5, the permanent magnet M in the form of a cylinder 9 is provided as in the case of Fig. l with upper and lower pole pieces 2 and 3 and a main springcharging coil I. In the present case, however, the magnet is provided with two separate armatures 48 and 49 arranged to coact with the pole pieces 2 and 3 respectively. A stationary iron core 50 is mounted centrally of the coil I for completing the magnetic circuit. The armatures 48 and 49 are normally biased in opposite directions by a spring 5 I, and to this end the armature 48 is provided with an operating rod 52 terminating in a piston member 53 which serves as a seat for the upper end of the spring 5|, and the armature 49 is provided with a suitable extension 54 serving as a seat for the lower end of the spring. will therefore be noted that when the spring is compressed the armatures are biased in opposite directions.

In the position illustrated the device is in the open position, the upper or anchor armature 43 being seated on the pole piece 2, so that when the coil is energized the energizing flux serves, together with magnet M, to hold the anchor armature in such position. As the lower armature 49 is drawn into the solenoid toward the fixed armature 50, the spring 5I is compressed against the fixed piston 53 of the anchor armature. Accordingly, when the armature 49 makes contact at 3 and 50, the magnetic circuit is completed so that the coil I can be deenergized and the two armatures held against the respective pole pieces against the bias of spring by the .permanen magnet flux. I

:Assumi-ng now that the device is in closed position andis to open in the normal manner, a releasing coil 55 disposed adjacent to the holding surfaces at the pole .piece 3 and armature 49 is energized to establish a flux opposing the holding flux. The spring Si is thereupon effective to return the apparatus to the position shown. If new free-release operation is desired, a second releasing coil 56 disposed adjacent to the holding surfaces of the pole piece 2 and anchor armature 48 is energized during the normal closing stroke above described so 'as' to release the anchor armature. When this takes place the upper end-of the spring at 53 is no longer restrained with the result that the spring cannot be recharged even though the armature 49 is moved by the closing coil to its fully closed position. Where the operating force of the coil 1 is comparatively large it may be desirable to energize both re leasing coils 55 and 56 for the free-release operation above described.

For the purpose of diagrammatically illustrating the application of the above device to a circuit breaker, reference is had to Figs. 5a, 5b and 50 which illustrate the open, closed and freerelease positions respectively of the device. The circuit-controlling contacts are indicated at 51 and 58 and are connected to the anchor armature 48 and the lower or charging armature 49 respectively. Fig. 5a illustrates the circuit breaker in open position with the anchorv armature in the holding position. In Fig. 5b the charging coil has raised the armature 49 so as to close the contacts. Normal opening is accomplished simply by releasing the armature 49 so that the contact 58 again drops to the position shown in Fig. 5a. In Fig. 50, however, the an.- chor armature is released for free-release operation during closing with the result that this time contact 51 moves upward to break the circuit. Resetting of the device to the position shown in Fig. 5a takes place under the influence of gravity when charging coil is deen'ergized so that the two armatures are released.

In case the normal releasing by one coil, it may be advantageous to provide a positive flux in the other coil so as to assist in maintaining in .position the armature which is functioning as the anchor.

The device shown by Fig. 6 is similar in principle to that disclosed by Fig- 5 and provides for normal closing, high speed releasing, free-release operation during any part of the closing stroke and high speed reclosing. The device is shown as applied to a circuit breaker of the fluid blast type, and as in the previous instance comprises a main spring-charging coil I, an anchor armature 48 and a spring-charging armature 49. The permanent magnet structure, however, in the present instance is of the disk type and comprises two separate magnet disks M1 and M2 suitably assembled With respect to a steel spacing .plate and fixed "steel "pieces 1H, and 62. The upper and lower pole .pieces 2 and 3 are spaced as in the case of Fig. 3 by a steel cylinder 63 for completing the magnetic circuit. I

Accordingly, when the anchor armature 49 is locked in position by the holding flux of magnet M1, energizing of the charging coil l is effective to raise the armature 49 and compress the spring 6 in the manner described in Fig. 5. As inthe previous instance the anchor armature 48 is provided with an operating rod 64 slidably guided in the permanent magnet structure and armature 49. Secured to the rod 64 is a piston comprising a seat for the upper end of the spring 6. The lower end of the spring seats at -65 in a cylnder 61 carried by the armature 49.

The circuit breaker structure operatively connected to the armatures 48 and 49 respectively comprises a pair of relatively. movable contacts 69 and 69 arranged for circuit-controlling movement in the manner diagrammatically illustrated in Figs. 5a, 5b and 50. In the present instance, the anchor armature rod 64 is secured to a tubular member 10. The tubular member 10 is provided with a port 10' located above the piston 65 so that upward movement of the piston is effective to drive fluid from the cylinder 61 downward through the tubular member 10 and the tubular contact 68, that forms therewith a continuous fluid passage. The contact 68 can be suitably insulated from the magnet structure by means of an insulating coupling II. The coacting contact 69 is suitably carried by the armature 49 by means of insulating supports 12 constituting in effect a frame depending from the cylinder 61. The contacts can be connected to the external circuit at the terminal 68 and 69' respectively.

It is believed that the circuit-controlling operation is apparent from the previous description. In the open-circuit position shown, the anchor armature 48 is held fast by the flux of the permanent magnet M1 and the apparatus is in readiness forthe closing operation which is effected by the charging coil l. During the charging operation the piston 65 remains fixed and the armature 49 is raised to compress the spring 6.

If the breaker is being closed on a fault, the releasing coil 36 immediately establishes a releasing flux at the anchor armature 48. The spring 6 is now effective to drive the piston 65 upward as the anchor armature is released with the result that a high velocity blast of fluid is directed through the tubular contact 58 and into the arc path between the separating contacts 68 and 59. This action can be concurrent with continued upward movement of the armature plunger 49 to closed position. It will be noted that the above-described blast action takes place, either in case of free-release operation, or during normal high speed opening, since in both cases there is relative movement between the piston 65 and cylinder 61 tending to drive fluid through the contact 68. As in the case of Fig. 5 the releasing coil 31, located adjacent to the holding surface of armature 49, is also provided for releasing the aforesaid armature for normal opening. It will be apparent, of course, that normal releasing can be accomplished by releasing either armature 48 or 49 by suitable energization of the coils 36 or 31 respectively.

In order that the charging flux of the coil I shall be more'efiective to assist the magnet M1 in holding fast the anchor armature 48, the steel spacer '69 can be notched at 69, as illustrated to provide a more saturable path, so that the charging flux will not be mainly shunted through that part of the magnetic circuit. During the aforesaid charging operation the magnet M2 being in series with the main charging flux is charged for the subsequent holding duty. In order to insure proper charging of the'magnet M1 a separate coil 73 can be provided for this purpose.

Fig. 6a illustrates diagrammatically the forcetravel relation between the spring 6 and the with two concentrically arranged ringlike members l and 16 of magnetic material spaced at 11 to form an annular insulating gap. The members 15 and 16 are assembled with respect to the armature operating rod 19 by means of an insulating plate 18. The pole piece 2 is likewise provided with an annular insulating gap 80 arranged staggered with respect to the gap 11 of armature H, so that the flux from the permanent magnet M threads the armature and pole pieces as illustrated at four separate holding surfaces. The area of these holding surfaces is of course designed so that it is an optimum with respect to the holding flux produced by the magnet M. The above arrangement, although increasing somewhat the reluctance of the magnetic circuit, increases by several times the total holding force produced by the magnet flux. The releasing flux of the coil II is effective to cause release of the armature in the manner above described by reducing the holding force at the adjacent holding surfaces below the opposing force of the spring. That is, the loss of holding power at the innermost holding surfaces adjacent to the releasing coil is sufficient to cause release, since as previously pointed out release can be accomplished by a reduction of but approximately 10% of the holding flux.

For the purpose of calibration where a comparatively sensitive and arcuate device is required, the armature l4 and coacting pole piece can be designed so that simply by rotating the armature 14 the holding force can be varied bei tween wide limits. To this end the ring 16 of the armature, instead of being a continuous steel member, is formed as alternate sections of nonmagnetic material or insulation 8|, and steel 82 as illustrated by Fig. 8. For coacting with the armature "M the inner part of the pole piece at 83 is similiarly constituted of alternating insulating and steel sections 84 and 85 respectively.

It will therefore be apparent, referring again to Fig. 7, that the path for the total holding flux can include in series either a high reluctance or a low reluctance section simply by rotating the armature 14 with respect to the fixed pole piece 2 so that the insulating and magnetic sections are either in alinement or staggered to the degree desired.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Operating mechanism of the high speed magnet release type comprising magnetic struc ture including a permanent magnet having a large magnetomotive force and a relatively movable armature arranged to complete a magnetic circuit, and spring means for biasing said armature toward an open magnetic circuit position to effect a positive working stroke, said armature having a holding surface disposed substantially normal to the direction of motion thereof for coacting with a similar holding surface on said structure, said coacting holding surfaces being adapted to abut in the holding position thereof, and a surface substantially parallel to said direction of motion, said parallel surface being non-holding and closely spaced with respect to the coacting normal holding surfaces of said magnetic structure and armature so that comparatively slight initial movement of said armature from said closed magnetic circuit position under influence of said spring bias effects transfer of the holding flux to said non-holding parallel surface for facilitating high acceleration of the armature opening movement.

2. Operating mechanism of the quick release type comprising a permanent magnet having a large magnetomotive force, magnetic structure including a reciprocally movable plunger arranged to form a magnetic circuit with said magnet, said plunger having a holding surface extending normal to the direction of motion of said plunger and arranged to make butt contact with said magnetic structure, a spring for biasing said plunger toward an open magnetic circuit position for effecting a working stroke, an energizing coil also coacting with said magnetic circuit for attracting said plunger to close the magnetic circuit against the bias of said spring, said permanent magnet thereby being effective solely to hold said plunger in said closed magnetic circuit position against said spring bias, and means for establishing an opposing flux in said magnetic circuit at said hOlding surface tending to weaken the holding flux, said magnetic structure adjacent said normal holding surface being spaced by an insulating gap of the order of onesixteenth of an inch from a surface of said plunger that is parallel to the direction of motion thereof whereby slight initial movement of said plunger under influence of the spring bias effects shifting of the holding flux from said normal surface to said parallel surface for insuring high acceleration of said working stroke.

3. Operating mechanism of the quick release type comprising magnetic structure including a source of magnetomotive force and a reciprocally movable plunger arranged to complete a magnetic circuit, said plunger having an annular flangelike portion at one end adapted for butt contact with said structure to form a holding surface, said plunger also adapted to make butt contact at its opposite end to form a second holding surface with said magnetic structure, a spring for biasing said plunger toward an open magnetic circuit position for effecting a working stroke, an energizing coil also coacting with said magnetic circuit for attracting said plunger to close the magnetic circuit against the bias of said spring, the aforesaid holding surfaces of said plunger engaging said magnetic structure substantially simultaneously, an electromagnetic means for establishing an opposing flux in said magnetic circuit at one of said holding surfaces tending to weaken the holding flux, said plunger being spaced by a very small insulating gap from said magnetic structure throughout longitudinal movement thereof so that slight initial movement of said plunger under influence of the spring bias effects shifting of the holding flux from said normal holding surface to the parallel plunger surface for insuring high acceleration of said working troke.

4. Operating mechanism of the quick release type comprising a permanent magnet having a large magnetomotive force, magnetic structure including a reciprocally movable plunger arranged to form a magnetic circuit with said magnet, said plunger having an annular flange arranged to seat in a corresponding recess in said magnetic structure so as to form holding surfaces both normal and parallel to the direction of motion of said plunger, a spring for biasing said plunger toward an open magnetic circuit position for efiecting a working stroke, an energizing coil also related to said magnetic structure for attracting said plunger to close the magnetic circuit against the bias of said spring, said permanent magnet being thereby effective solely to hold said plunger in said position against said bias, and a releasing coil positioned closely adjacent said fiange at a point of substantially minimum length of flux path through said holding surfaces for establishing an opposing flux at said surfaces.

5. An operating mechanism adapted for freerelease operation comprising magnetic structure including pole pieces, a pair of armatures coacting with said pole pieces, a source of magnetomotive force for establishing a holding flux for said armatures, circuit controlling contact structure connected to each of said armatures, a

spring operatively interconnecting said armatures tending to bias the same in opposite directions for opening said contact structure, and an energizing coil for actuating one of said arma- 1 tures and charging said spring against the holding force at the other of said armatures for closing said contact structure, and means for establishing a releasing flux at either of said armatures.

6. An operating mechanism adapted for freerelease operation comprising permanent magnet structure, magnetic pole pieces fixed with respect thereto, a pair of movable armatures coacting with said pole pieces, circuit controlling contacts connected to both said armatures respectively, a spring interconnecting said armatures so as to bias said contacts toward open circuit position, flux of said permanent magnet structure being effective to hold one of said armatures against said spring bias, an energizing coil for attracting the other of said armatures so as to compress said spring against said permanent magnet holding force, and a releasing coil for establishing a flux opposing said holding flux for permitting a free-release operation of said contacts during said closing stroke.

7. An operating mechanism adapted for freerelease operation comprising a solenoid, a movable armature coacting with said solenoid, a permanent magnet, an anchor armature coacting with said magnet, a spring operatively interconnecting said armatures and arranged to be stressed when said anchor armature is held closed by said permanent magnet coincident with actuation of said first-named armature by said solenoid, and electromagnetic means for establishing an opposing flux at said anchor armature for releasing the same irrespective of energization of said solenoid.

8. An operating mechanism adapted for freerelease operation comprising a solenoid, a movable armature coacting with said solenoid, a permanent magnet, an anchor armature coacting with said magnet, a spring operatively interconnecting said armatures and arranged to be stressed when said anchor armature is held closed by said permanent magnet coincident with actuation of said first-named armature by said solenoid, electromagnetic means for establishing an opposing flux at said anchor armature for releasing the same irrespective of energization of said solenoid, said solenoid normally establishing a flux tending to aid said permanent magnet holding flux at said anchor armature, and a releasing coil also arranged to establish a flux opposing that of said solenoid at said first-named armature.

9. A circuit breaker of the free-release type comprising a solenoid having a movable armature, a circuit controlling contact operatively connected to said armature, a permanent magnet for holding said movable armature in closed magnetic circuit position, a second permanent magnet, an anchor armature coacting with said magnet, a second circuit controlling contact coacting with said first-named contact operatively connected to said anchor armature, a spring operatively interconnecting said armatures arranged to be stressed when said anchor armature is held in its closed position coincident with actuation of said movable armature by said solenoid, a releasing coil for establishing an opposing fiux sufiicient to release said anchor armature at any time for opening said second contact in free-release operation, and a second releasing coil for establishing a separate opposing flux for releasing said movable armature at said first-named permanent magnet for normal releasing operation, both of said operations being under influence of said spring.

EUGENE W. BOEHNE.

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