US1924686A - Electromagnetic device - Google Patents

Description

Aug. 2'9, 1933.

H. C. GRAVES, JR., ET AL ELECTROMAGNET I C DEVICE .Filed OCT,

4 Sheets-Sheet l A TTORNE Y Aug 29, 1933- H. c. GRAVES, JR., ETA. 1,924,686

ELECTROMAGNETIC DEVICE 11, lso

4 Sheets-Sheet 2 Filed Oct.

ATTORNEY H. c. GRAVES, JR., ET AL 1,924,686

Aug. 29, 1933.

ELECTROMAGNETIC DEVICE Filed Oct. 11, 1930 4 Sheets-Sheet 3 IVNR gm; ATTORNEY Aug. 29, 1933. H. c. GRAVES, JR.'v ET AL 1,924,685

ELECTROMAGNETIC DEVICE Filed dot. 11, 1930 4 Sheets-Sheet 4 INVENToRs M.; )A

ATTORNEY.

Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE Chester County,

and Henry J. Schmid,

Philadelphia, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of New Jersey Application October 1l, 1930. Serial No. 487,978

39 Claims.

Our invention relates to electromagnetic devices, and particularly to tripping apparatus associated with automatic circuit breaker mechanism adapted specifically to control the circuits of electric motors. v

In accordance with our invention, the time interval after which actuation of the tripping mechanism is eifected under high current conditions, as during starting of a motor, is increased with little or no effect upon the time interval alter which the trip is actuated under lower current conditions, by providing in shunt to the movable armature of retarded action tripping mechanism a magnetic leakage path which is of relatively low reluctance at high current values and of relatively high reluctance at comparatively low current values.

More particularly, the shunt path includes a second movable armature which in addition to increasing the holding time of the first armature is eiiective instantaneously to actuate the tripping mechanism upon occurrence of excessively high current conditions.

Preferably both armatures are adjustable, and more particularly are so related that they are simultaneously adjustable, the reluctance or" the retarded action armature circuit or path changing more rapidly than the reluctance of the instantaneous trip armature circuit.

More specifically, our invention relates to improvements in that 'form of tripping mechanism embodying a single tripping coil employed to actuate two separate armatures, or equivalent, under respectively different circuit conditions, as

` exemplified in copending Scott application, Serial No. 354.480, led April 12, 1929, patented June 20, 1933, No. 1,914,582.

Our invention further resides in the features of construction and arrangement hereinafter described and claimed.

For an understanding of our invention, and for illustration of some of the various forms it may take, reference is to be had to the accompanying drawings, in which:

Fig-.41S a detail View disclosing modified armature structure.

Fig. is a side elevational view of another modification.

(Cl. G- 109) Fig. 6 is a side elevational view of a further modication.

Referring to Fig. 1, the laminated core 1, suitably secured to and extending perpendicularly from the panel l?, is provided with the pole pieces G0 2 and 3, the latter having the auxiliary pole extensions 4 extending therefrom, the lower faces of the pole pieces and pole extensions lying substantially in the same horizontal plane. The coil 6F L) 21 encircles the core 1, and is ordinarily traversed by current flowing in the circuit to be controlled as hereinafter described.

The supports 20, 20, secured on opposite sides of the rear pole piece 2, project downwardly therefrom. The pin 6, extending between the supports, just below the pole piece 2, carries a laminated armature 5, which is of such length as substantially to cover the outer pole piece when in its upper position, the upper surface of the armature then lying in the plane of the magnet pole faces.

The weight of the armature is normally supported by a link 10 fitted into a recess in the bottom of the armature and hinged thereto by a pin 9, the link passing through an opening in the top 11 of the casing 12, and at its lower end being hinged to the adhesive plate or sucker disc 14 by the pin 13. The disc 14, and the bottom of the housing 12, with oil within casing 12 comprise a start-delaying device well known in the art, for the armature 5. Briefly, for currents through coil 21 in excess of a predetermined value, the armature 5 will be released after a time interval whose duration is inversely related to the current, that is the time interval becomes shorter as the current increases.

The yoke 7 of non-magnetic material, as brass, embraces the movable armature 5 and is pivotally mounted upon the pin 8 extending between the supports-20 substantially more remote from the pole piece 2 than the pin 6 which carries the armature 5 so that the air gap between pole piece 2 and armature 1S is relatively large compared to the air gap between pole piece 2 and armature 5. An armature 18 is secured to the inside of each leg of the yoke in such position that when the yoke is in its upper position the armatures 18 lie in the plane of the magnetic pole faces. The armature 5 and the armature system comprising the yoke 'l and armatures 18 move between their upper and lower positions Without mechanical interference with the other.

The outer end of the armature 5, as it approaches the pole piece S, strikes the end 24 of the tripping member 25, which'is slidably held in a groove by the support 16. The plate 26, shown more clearly in Fig. 3, which is mounted upon the pin 27 extending outwardly from the tripping member 25, is adapted to be engaged by the yoke 7 as it approaches or reaches the upper limit of its travel. The plate 26 floats or is freely pivoted on pin 27 and is normally held in a substantially horizontal position by the shoulder 16a of the support 16. If for any reason, as slight inaccuracy of manufacture or Wear, the plate 26 is engaged by one arm of yoke 7 before the other, it rocks upon pin 27 until both arms engage it, whereupon further movement of the yoke is transmitted to the reciprocal member 25, avoiding any binding of the latter in lits guideway.

The construction and operation of the apparatus actuated by the tripping member 25 form, per se, no part of the present invention, though one form is described and illustrated to make clear the operation and advantages of our invention. When the tripping member 25 moves upwardly, it engages the under side of the setting lever 28, causing it to rotate about the pivot 29 and breaking the toggle formed by lever 28 and the link member 30 pivoted thereto at 31. Upon collapse of the toggle, the contact supporting member 32, connected to the other end of link 30, rotates in clockwise direction, as viewed inl Fig. 1, to move the contact member 83 out of engagement with the stationary contacts 34, 34 supported by the panel 17, breaking the circuit which includes the coil 21.

For large circuit breakers, it may be necessary or desirable to interpose between the tripping member 25 and the locking mechanism of the breaker, a suitable mechanical relay in order that the force utilized may be sufficiently great positively to eect opening of the breaker.

The armature 5 and the yoke 7 with its attached armatures 18 are both normally held down by gravity, the former being supported by the link 10, as above described, and the yoke 7 resting on a projection or stop 15 secured to or integral with the casing 12. This projection may be filed for calibration adjustment. A vertical adjustment of the position of the housing 12, which is notched or grooved partially vto surround the support 16 to prevent rotation as it is moved -along the support by the knob 22, which normally clamps it thereto, simultaneously adjusts the armature 5 and yoke 7 As the distance between the pivot 6 of the armature 5 and its link pin 9 is much less than the distance between the pivot 8 of the yoke 7 and its point of engagement with the lug 15, the relative positions of the armature 5 and the yoke 7 change as the casing is moved or adjusted in a vertical direction, the air gap between armature 5 and the pole piece 3 changing more than the air gap between the pole piece 3 and the armatures 18 for any given increment of adjustment of casing 12.

When current ows through the coil 21, a. magneto motive force exists between the poles 2 and 3 which produces a ux between the poles traveling in several paths. There is direct leakage flux from pole 2 to pole'3 through the air; a leak age path from the pole 2 into Ythe armature 5 and thence to pole piece 3; a leakage path from the pole piece 2 into armature 5, thence to armatures 18 and therefrom to the pole piece 3 and extensions 4; and the side leakage path from the sides of the pole piece 3 directly to the armatures 18. The distribution of the total flux depends upon the relative positions and masses of the armatures and the flux densities. 'Ihe armatures 5 and 18 form parallel magnetic paths between the pole pieces 2 and 3. Since the permeability of the several air gaps is constant, while the permeability of the iron of the armatures is constantly decreasing as the flux density increases, the relative ilux values in the several paths above mentioned will change as the current changes. For example, with increased current flow the relative value of the lux from the pole piece 2 into the armature 5 and thence into pole piece 3 will decrease and the flux through the shunt paths relatively increase. The armatures 18, therefore, exert a shading or diverting eiect on the armature 5 which is insubstantial or slight for low current values and of increasing effect at high current values. The armatures 18 for all positions of yoke 7 are substantially spaced from the pole piece 2 to insure that the major part'of the flux traveling from the pole piece 2, which reaches the armatures 18, first passes through armature 5. Most of the flux which enters armatures 18 from armature 5 enters across an air gap which is substantially of uniform length and approximately constant area. As a result the magnetic pull on the armatures is substantially independent of their relative positions under pole piece 2, and largely dependent upon their relative positions to pole piece 3 and pole piece extension 4.

By constructing the armature 5 so that it will be saturated under heavy current conditions, a definite ratio between the current values of instantaneous tripping and the setting of armature 5 may be obtained. Alternatively, it is possible to obtain a constant instantaneous tripping point for all positions of the retarded armature or to obtain any desired relation by suitable design and position of the armatures.

The circuit breaker described utilizing this tripping mechanism is particularly adapted for use in motor starting systems in which, for example', the motor is connected directly across the line without the introduction of starting resistances, or the like. Initially, upon closing of the motor circuit by moving lever 28 to the position in Fig. 1, there is a rush of current through the coil 1 which is many times the normal or running current. In the absence of armatures 18, or equivalent, and particularly if the motors are starting under load, the armature 5 may be attracted, tripping the circuit breaker and interruping the desired starting operation. If the armature 5 is adjusted to a higher tripping point, as by changing the position of the casing 12, to prevent this unnecessary tripping during starting, there is danger that under running conditions the breaker will not open except after a prolonged interval of overload, damaging the motor and circuit-breaker windings.

When the current values are normal, as under running conditions, the flux density'in armature 5 does not approach the saturation point, and the reluctance of the armature will be relatively low with respect to the reluctance of the path through armatures 18 which have longer air gaps and usually less cross-sectional area than armature 5, so that a small amount only of the total flux produced by the current in the coil 21 ows through armatures 18 under normal conditions. When the current increases to very high or abnormal values, however, this causes an increasingly high ux density in armature 5, and the reluctance of armature 5 increases as the ilux density increases, so that an increasing percentage of the total flux will now through armatures 18. When the armatures 18 are utilized as above described, they afford, under starting conditions, a path in shunt to the armature 5 which is of relatively low reluctance since its flux density is low at this time, With the eiect that the pull exerted by the magnet on armature 5 is decreased by the presence of armatures 18, and therefore the time interval in which the tripping system comprising the armature 5 and the time-delay device 14 may act is considerably increased which permits the motor to start, even when under load, Without tripping of the breaker. As the motor comes up to speed, the current drops due to the relatively higher counter electro-motiveforce, and the current through the coil drops to the normal running value. Under normal running conditions the force exerted upon the armatures 5 and 18 is not suflicient to attract. For a range of current values corresponding to ordinary overloads, the armature 5 affords a path of low reluctance compared to the path formed by armature 18, so that the normal operation of the tripping system comprising the armature 5 and the retarding device connected thereto is notv substantially'aiected by the presence of the armatures 18. Upon occurrence of excessively high current through the coil 21, as occasioned,

for example, by short circuits, the armatures 18 are instantaneously attracted to trip the circuit breaker, independently of armature 5.

If the instantaneous trip is not required, and only the increased holding time during-starting is desired, stationary iron vanes may be disposed adjacent armature 5 to promote high ux leakage, in substitution for the armatures 18. By adjusting these vanes toward or away from poles 2 and 3, the time-delay of armature 5 may be increased or decreased at will. The retarded action feature may be dispensed with, if desired, by disconnecting armature 5 from the suckerdisk, or by omitting the latter and its appurtenances. The current value at which the armature 5 is attracted may be predetermined by adjusting magnetizable structure forming a magnetic path in shunt thereto, for example armatures 18, or normally stationary but adjustable vanes.

While it is convenient, it is not necessary to pivot the yoke 7 and the armature 5 at diierent points. For example, as in Fig. 4 both the yoke 7 and armature 5 may be supported by the Asingle pin 6. However, the yoke 7 does not extend parallel toarmature 5, but lis provided with an offset portion 36 adjacent the pivot pin 6` of such length that the remainder of the yoke yand the armatures 18 bear substantially the same relation to armature 5 and pole pieces 2 and 3, as in Fig. 1, when the modied yoke 7' is in its lower position, f

A further modication of our invention is disclosed in Fig. 5. The armature 18 is pivotally mounted on pin 8', the position of the armature with respect to the additional pole 37 having the pole face 4' being determined by the stop 38, which, as indicated, may be adjustable. The eld structure 37 and armature 18 form a leakage path in shunt to armature 5, as in the prior modications, which is so designed that its reluctance for high current values corresponding in range to the starting currents, is low compared to the reluctance of the path including the armature 5, with the result that there is afforded an increased time for starting. For currents in excess of normal running currents the armature 5 and the associated retarding mechanism, Which may be identical to that previously described, provides normal delayed tripping protection, the armature 5 engaging the tripping member 25 to raise lever 28 which eiects counterclockwise movement vof lever 28 to release circuit breaker mechanism, interrupting the circuit including the coil 21 and apparatus sought to be protected. When the current values are excessively high, the armature 18 instantly effects tripping by engaging the projection 39 of member 25 effecting its movement to trip or release the circuit breaker, or equivalent.

It will be understood that the construction may differ from the examples shown or described, without departure from our invention. For example, the armatures 5 and 18, or equivalents, may be of the plunger type for cooperation with a solenoid, which is comprehended by the term coil as used in the claims. More specically, the plungers may be concentric. For example, referring to Fig. 6, the plunger armature 5a adapted to reciprocate axially of the solenoid 21a is connected to the suction disk 14 of the startdelaying device 12. Preferably, the skirt member 37 threaded or otherwise suitably connected to the lower end of the armature 5a is provided to cooperate with the plate 11 to guide the armature 5a when moving in response to the attraction of solenoid 21a. The interior of this armature which is hollow is preferably provided with a lining 38 of non-magnetic material to prevent sticking thereto of the second plunger armature 18a which nests within armature 5a and normally rests upon the bottom of lining 38. The purpose and operation of the two armatures correspond to that of the armatures 5 and 18 of the preceding modications and is not repeated in full.

Briefly, for current values that are excessively high, the armature 18a is moved independently of armature 5a, moving the tripping member 25a, which may, as indicated, project therefrom through the pole piece 3a with which it cooperates to guide the armature, into engagement with the projecting part 28h of the switch arm 28a, breaking the toggle holding the movable switch contacts 33 in engagement with the fixed contacts 34. For currants less than those necessary to operate armature 18a, but in excess of normal values, the armature 5a and the start-delaying device 12 provide normal delay tripping operation, the armature 5, upon upward movement, carrying with it the armature 18a which through tripping member 25a, opens the switch or circuit breaker. During starting, the relative reluctances of the paths formed by the armatures between the poles 2a and 3a, are such that the time-current characteristic of armature 5a and start-delaying device 12 is modified, to avoid tripping by the momentary surge of current when the circuit breaker or switch is rst closed, as in the starting of a motor.

As in the preceding modifications, both armatures are simultaneously adjustable by the knob 22, or equivalent, which clamps the iixed or pot member of the start-delaying device 12, against the frame 16a..

While the magnetic device has been specically illustrated and described as a tripping device for a circuit breaker which must be reset, it may be utilized as a relay by mounting a contact member for direct actuation by the member 25, for example, so that a circuit will be made or broken when armature structure is actuated by the coil 2l, or equivalent, and broken or made when the coil is de-energized.

What We claim is:

l. An electromagnetic tripping device comprising a coil, a tripping system comprising a movable armature and time-delay structure associated therewith responsive to passage through said coil of current of magnitudes lying within a predetermined range, and means for increasing the lag of said tripping system when the magnitude of said current lies in the upper portion of said range comprising magnetizable structure forming a path in shunt to said armature when said current is of said last-named magnitude.

2. An electromagnetic tripping device comprising a coil, a tripping system comprising a movable armature and time-delay structure associated therewith responsive to passage through said coil of current of magnitudes lying within a predetermined range, and a second armature normally stationary in predetermined position to provide a path in shunt to said movable armature, of relatively low reluctance when the magnitude of said current lies in the portion of said range to increase the time delay of said system and movable instantaneously to eiect tripping when the current through said coil is of a magnitude substantially in excess of the greatest magnitude of the range aforesaid.

3. An electromagnetic device comprising a coil, stationary core structure therefor having pole pieces, an armature movable substantially to complete the magnetic path between said pole pieces, a retarding device connected to said .movable armature, and masses of magnetic material on both sides of the path of movement of said armature providing between said pole pieces a magnetic path of relatively low reluctance for high values of current traversing said coil to decrease the pull exerted upon said movable armature thereby to increase the time-delay afforded by said retarding device.

4. An electromagnetic device comprising a coil, stationary core structure therefor having pole pieces, an armature movable substantially to complete the magnetic path between said pole pieces, a retarding device connected to said movable armature, and a second movable armature forming a magnetic path in shunt to said rst armature so disposed that for all positions thereof a substantial air gap exists between said second armature and one of said pole pieces..

5. An electromagnetic tripping device comprising a coil, stationary core structure therefor having pole pieces, an armature pivoted adjacent one of said pole pieces and movable substantially to complete the magnetic path between them, a retarding device connected to said armature, and a second movable armature plvoted more remotely from said one of said pole pieces for effecting instantaneous tripping for excessively high currents.

6.\ An electromagnetic device comprising a coil, stationary core structure therefor having pole pieces, an armature pivoted adjacent one of said pole' pieces and movable substantially to complete the magnetic path between them, a retarding device connected to said armature, a second movable armature pivoted -more remotely from said one of said pole pieces, and means for varying the position of the ,armatures with respect to each other and to said pole pieces.

'7. An electromagnetic tripping device for a circuit breaker adapted to control a motor circuit comprising a coil traversed by the motor current, a tripping system comprising a movable armature and time-delay structure associated therewith effecting opening of said breaker upon occurrence of overload during running of said motor, and means for modifying the characteristic of said system during starting of said motor comprising magnetizable structure affording a path in shunt to said armature of relatively low reluctance under high current conditions of starting.

8. An electromagnetic tripping device for a circuit breaker adapted to control a motor circuit comprising a coil traversed by the motor current, a tripping system comprising a movable armature and time-delay structure associated therewith effecting opening of said breaker upon occurrence of overload during running of said motor, and a second armature unattracted lor current values no greater than those of starting for providing a magnetic path in shunt to said armature of low reluctance under high current conditions of starting to avoid unnecessary tripping of said breaker and of relatively high reluctance for materially less current values to permit normal operation of said system under running conditions, and attracted instantaneously to trip said breaker upon existence at any time of current values in excess of starting values.

9. An electromagnetic tripping device for a circuit-breaker comprising a current coil, a tripping system comprising a movable armature and a retarding device connected thereto affording an inverse time-current characteristic throughout a range oi current values, and means for retarding the action of said system for current values above said range comprising magnetizable structure providing in shunt to said armature a path of relatively low reluctance for current values above said range and of relatively high reluctance throughout said range.

10. An electromagnetictripping device for a circuit breaker comprising a current coil, a tripping system comprising a movable armature and a retarding device connected thereto affording an inverse time-current characteristic throughout a range of current values, and a second armature, unattracted throughout said range and a higher range of current values, for providing a path of relatively low reluctance in shunt to said first armature for said higher range to increase the interval before tripping throughout said higher range with insubstantial effect throughout said lower range, and attracted for current values in excess of the higher range to effect substantially instantaneous tripping of said circuit-breaker independently of said first armature.

11. An electromagnetic device comprising a coil, core structure therefor having pole pieces, an armature movable substantially to complete the magnetic path between said pole pieces,y a start-retarding device connected to said armature, and magnetizable structure on either side of said armature affording magnetic paths in shunt to said armature with relatively large air gaps between said structures and one of said pole pieces.

12. An electromagnetic device comprising a coil, core structure therefor having pole pieces, a pivoted armature movable substantially to complete the magnetic path between said pole pieces, a start-retarding device connectedto said armature, and a pivoted support carrying magnetizable structure on either side of said armature affording magnetic paths in shunt to said armature with relatively large air gaps between said structures and the pole piece adjacent the pivoted end of said support.

13. An electromagnetic tripping device for a circuit-breaker comprising a coil, core structure therefor having pole pieces, an armature pivoted adjacent one of said pole pieces, a pivoted yoke embracing said armature carrying a magnetizable member on each side of said armature affording magnetic paths in shunt thereto with large air gaps between said members and the pole piece adjacent the pivoted ends of said armature and yoke, and means for varying the air gap between said members and the other of said pole pieces,

and to greater extent the air gap between said armature and said other pole piece while insubstantially varying said large air gaps.

14. An electromagnetic device comprising a coil, stationary core structure therefor having pole pieces, a movable armature pivoted adjacent one of said pole pieces, a start-retarding device connected to said armature, and magnetizable structure forming a magnetic path in shunt to said armature so disposed that the reluctance of the air gap between said structure and the pole piece adjacent the pivoted end of said armature is greater than the reluctance of the air gap between said structure and said movable armature.

15. An electromagnetic device .comprising a coil, stationary core structure therefor having pole pieces, a movable armature pivoted adjacent one of said pole pieces, means to adjust the free end of said armature toward and away from the other pole piece, a start-retarding device connected to said armature, and magnetizable structure forming a magnetic path in shunt to said armature so disposed that for all positions of said armature the reluctance of the airl gap between said structure and said armature is substantially constant and less than the reluctance of the air gap between said structure and the pole piece adjacent the pivoted end of said armature.

16. An electromagnetic tripping device comprising a coil, stationary core structure therefore having pole pieces, an armature pivoted adjacent one of said pole pieces and movable substantially to complete the magnetic path between them, a retarding device connected to said armature, and a second movable armature pivoted more remotely from said one of said pole pieces for providing in shunt to said first armature a magnetic path of relatively low reluctance for high values of current through said coil and for effecting instantaneous tripping for excessively high currents.

17. An` electromagnetic device comprising a coil, stationary core structure therefor having pole pieces, an armature pivoted adjacent one or" said pole pieces and movable substantially to complete the magnetic path between them, a retarding device connected to said armature, a second movable armature pivoted more remotely from said one of said pole pieces for providing in shunt to said rst armature a magnetic path of relatively low reluctance for high values of current through said coil, and means for varying the position of the armatures with respect to each other and to said pole pieces.

18. An electromagnetic device comprising a coil, a system comprising an armature and timedelay structure associated therewith, and means for increasing or decreasing the retarded action of said system comprising adjustable magnetic structure forming a magnetic path in shunt to said armature.

19. An electromagnetic device comprising a coil, a system comprising an armature and timedelay structure associated therewith, magnetizable structure forming a path in shunt to said armature, and means for adjusting said armature and said magnetizable structure to effect a predetermined time-current characteristic of said system.

20. An electromagnetic circuit controlling device comprising a coil, a contact system, an armature and time delay mechanism associated therewith responsive to passage through said coil of current of magnitudes lying within a predetermined range for actuating said contact system, and a second armature adjustable relative to said iirst armature to effect a predetermined timecurrent characteristic of the controlling device and movable instantaneously to effect actuation of said contact system upon passages through said coil of current of a magnitude substantially in excess of the greatest magnitude of the range aforesaid.

21. An electromagnetic device comprising a coil, a pivoted armature, a time-delay device connected thereto, a second pivoted armature, and a reciprocable element selectively actuatable by said armatures.

22. An electromagnetic circuit-controlling device comprising a coil, a pivoted armature, a timedelay device connected thereto, a second pivoted armature, and a reciprocable contact-actuating member selectively actuatable by said armatures.

23. An electromagnetic device comprising a coil, pivoted armature structure comprising a yoke, a reciprocable member, and a pivoted element disposed in the path of movement of the arms of said yoke for transmitting movement thereof to said reciprocable member.

24. An electromagnetic device comprising a coil, telescoping plunger armatures therefor, one of said armatures adapted for instantaneous movement, and the other armature having startdelaying means associated therewith.

25. An electromagnetic device comprising a coil, a hollow plunger armature in the field thereof, a second plunger armature normally within said rst armature adapted for instantaneous movement, and start-delaying means associated with said iirst armature.

26. An electromagnetic tripping device comprising a coil, a hollow plunger armature in the iield thereof, a second plunger armaturx normally within said rst armature and supported thereby, start-delaying means associated with said first armature, and holding mechanism tripped directly by the second armature under certain current conditions and through the second armature by said first armature under other current conditions.

lll5

27. An electromagnetic tripping device comprising a solenoid, a pair of concentric plungers reciprocable axially of said solenoid,l start-delaying mechanism connected to only one of said plungers, and tripping structure actuable upon movement of either of said plungers.

28. An electromagnetic circuit controlling device comprising a contact system, a coil, and a multiplicity of armatures reciprocable axially oi said coil to operate said contact system, each of said armatures adapted to be actuated by said coil upon occurrence of respectively diiferent current conditions, and at least one of said armatures being associated with a time-delay device.

29. An electromagnetic tripping device for a circuit breaker comprising a coil, pivoted armature structure comprising a yoke, a tripping member, a guideway therefor, and a plate pivotally.

connected to, and extending from said member on both sides thereof in the path of movement of the arms of said yoke for transmitting movement of said yoke to said tripping member.

30. An electromagnetic device comprising a coil, a pivoted armature, a member in the path of movement of said armature, pivoted armature structure comprising a yoke embracing said rst armature, and an element pivotally connected to and extending from said member on both sides thereof i n the path of movement of the arms of said yoke.

31. Electromagnetic tripping mechanism including a coil, an armature movable in the field of said coil in response to passage therethrough of current of magnitudes lying Within a predetermined range, means associated with said armature for delaying its action, and further means for substantially delaying the time at which said armature acts when the magnitude of said current lies in the upper portion of said range comprising means for diverting from said armature part of the total magnetic flux produced by said coil when said current is of said last-named magnitude.

32. Electromagnetic tripping mechanism including a coil, an armature movable in the field of said coil in response to passage therethrough of current of magnitudes lying within a predetermined range, means associated with said armature for delaying its action, and further means for substantially delaying the time at which said armature acts when the magnitude of said current lies in the upper portion of said range comprising means for diverting from said armature part of the total magnetic ilux produced by said coil when said current is of said last-named magnitude, said last-named means comprising a second armature controlling tripping in response to current through said coil when of a magnitude substantially in excess of the greatest magnitude of Vthe range aforesaid.

33.l Electromagnetic tripping mechanism in cluding a coil, an armature movable in the field of said coil in response to passage of current therethrough, means associated with said armature for delaying its action, and further means for substantially delaying the time at which said armature acts comprising means for diverting from said armature part of the total magnetic ux produced by said coil.

34. Electromagnetic tripping mechanism including a coil, an armature movable in the field of said coil in response to passage of current l therethrough, means associated with said armature for delaying its action, and further means for substantially delaying the time at which said armature acts comprising means for diverting from said armature part of the total magnetic ilux produced by said coil, said last-named means comprising a second armature controlling tripping upon attainment of magnitude of current in said coil substantially in excess of the magnitude of current which normally sufiices to cause action of said first-named armature.

35. An electromagnetic device comprising a coil, an armature, a time-delay device connected thereto, a second pivoted armature, and a reciprocable contact-controlling member selectively actuable by said armatures.

36. Electromagnetic tripping mechanism including a coil, an armature movable in the eld of said coil in response to passage therethrough of current of magnitudes lying within a prede termined range, means associated with said armature for delaying its action, further means for substantially delaying the time at which said armature acts when the magnitude of said current lies in the upper portion of said range comprising means for diverting from said armature part of the total magnetic ilux produced by said coil when said current is of said last-named magnitude, and means for adjusting said fluxdiverting means to vary the delay effect of saidr` second time-delay means.

37. Electromagnetic tripping mechanism including a coil, an armature movable in the field. of said coil in response to passage therethrough of current of magnitudes lying within a predetermined range, means associated with said armature for delaying its action, further means for substantially delaying the time at which said armature acts when the magnitude of said current lies in the upper portion of said range comprising means for diverting from said armature part of the total magnetic flux produced by said coil when said current is of said last-named magnitude, said last-named means comprising a second armature controlling tripping in response to current through said coil when of a magnitude substantially in excess of the greatest magnitude of the range aforesaid, and means for adjusting the second armature to vary its ldelay effect upon said rst armature for said higher current values of said range.

38. Electromagnetic tripping mechanism including a coil, an armature movable in the field to vary the'delay`r effect of the second armature .125

upon said first armature.

39. Electromagnetic tripping mechanism infcluding a coil, an armature movable in the fieldV` of said coil in response to passage of current'- therethrough, means associated with said armature for delaying its action, further means for substantially delaying the time at which said armature acts comprising means for diverting from said armature part of the total magnetic flux produced by said coil, said last-named means comprising a second armature controlling tripping upon attainment of magnitude of current in said coil substantially in excess of the magnitude of current which normally suices to cause action of said rst-named armature, and means for adjusting the relative positions of said armatures to vary the delay eiect of the second armature upon the first armature and the value of current required to actuate said second armature.

HERBERT C. GRAVES, JR. HENRY J. SCHMID.

CERTIETCATE 0F CORRECTION.

Patent No. 1,924,686. August 29, 1933.

HERBERT c. GRAVES, JR., ET AL.,

it is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3. line 123, for "cui-rants" read currents; page 4, line 24, claim 2, before "portion" insert the word upper; and page 5. line 97, claim 20, for "passages" read passage; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of November, A. D. 1933.

F. M. Hopkins (Seal) Acting Commissioner of Patents.

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