US2310854A - Circuit breaker - Google Patents

Description

Feb. 9, 1943. T. LINDSTROM `vETAL CIRCUIT BREKER Filed July lO, 1941 vI5 Sheetsl-Sheet lA .lNvENToRS Twe mds/from and Jeff-ome Sandi/2.

ATTORN wlTNEssEs:

Patented Feb. 9, 1943 UNiTED STAT 35 PTNT GFFICE CIRCUIT BREAKER Ture Lindstrom, Edgewood, and Jerome Sandin, Forest Hills, Pa., assignors to Westinghouse Electric & Manufacturing Company,

East

12 Claims.

The invention relates to circuit breakers of the type embodying an operating mechanism which is manually operable to open and close the circuit and automatically operable to open the circuit in response to predetermined conditions. The present invention constitutes an improvement over the circuit breaker mechanism disclosed in Patent 2,083,304 issued to Ture Lindstrom, June 8, 1937, and assigned to the assignee of this invention.

An object of the invention is the provision of a manually and automatically operable circuit breaker with an improved means for preventing the holding of the circuit closed during the existence of an overload circuit condition.

Another object of the invention is the provision of a circuit breaker with an improved means for preventing reclosiug of the circuit by improper manipulation of the operating handle following an automatic opening operation of the circuit breaker.

Another object of the invention is the provision of a manually and automatically operable circuit breaker with an improved means for preventing reclosing movement of the contacts when the handle is held in closed position during and following an automatic opening operation of the breaker.

Another object of the invention is the provision of a manually and automatically operable circuit breaker with an improved latching means for holding the contacts in open position after automatic opening thereof until the operating handle has been properly operated to reset and reclose the circuit breaker.

Another object of the invention is the provision of a circuit breaker with an improved holding, or latching means as previously described and wherein the latching means is jointly controllable by the circuit breaker operating mechanism and the handle.

Another object of the invention is the provision of a manually and automatically operable circuit breaker with a pair of latches disposed side by side and engageable with the same element of the mechanism, one serving to hold the contacts in full open position after automatic opening thereof until the handle is properly operated to reset and reclose the breaker and the other to hold the contacts in open position until the main operating spring has been given a maximum operating stress and at this point to release the mechanism so that the contacts will be closed quickly and positively.

Another object of the invention is the pro- Vision of a circuit breaker as previously described that is simple, compact, reliable in operation, and inexpensive to manufacture.

rI'he novel features that are considered characteristic of the invention are set forth in particular in the appended claims, the invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure l is a front elevational view of a threepole circuit breaker embodying the principal elements of the invention. The cover has been partly broken away to more clearly show some of the parts of the circuit breaker;

Fig. 2 is a vertical sectional view of the circuit breaker taken substantially on line II-Il of Fig. 1 and looking in the direction of the arrows;

Fig. 3 is an enlarged detail View, partly in section, of the circuit breaker mechanism and the contact structure in the closed position thereof. Some of the parts have been broken away more clearly to show the structure;

Fig. 4 is an enlarged detail View similar to Fig. 3, showing, the breaker mechanism and the contact structure in the tripped open position;

Fig. 5 is an enlarged detail View similar to Fig. 3, showing the circuit breaker mechanism and the contact structure in the manually opened position;

Fig. 6 is an enlarged detail View similar to Fig. 3 showing the circuit breaker mechanism and the Contact structure in the tripped open position but with the operating handle held in closed position;

Fig. 'l is a perspective View of the circuit breaker operating mechanism and a part of the contact structure;

Fig. 8 is a front elevational view of a part of the latching mechanism; and

Fig. 9 is a detail view of a part of the operating mechanism showing a modied form of one of the latches.

Referring to the drawings, a base l of moulded insulating material has mounted thereon six terminals 3 and 5, a trip device l, an operating mechanism 9 with its associated assemblage of switch members Il, the arc extinguisher i3, and three stationary Contact assemblages l5. The movable Contact assemblages Il and the three stationary contact assemblages i5 combine to form a plurality of poles. Each of the poles is insulated from the adjacent pole by means of insulating barriers I'I (Figs. 1 and 2) moulded integral with the base I. These barriers are in alignment with similar barriers 2| in a cover I9 also made cf insulating material. An operating member 23 is provided with a handle 25 and is pivotally supported on the frame 4I of the operating mechanism 9. A suitable opening is provided in the cover I3 for the operating handle. The trip device 'I is secured in position by screws 3| and 33 which also serve to connect terminals and 37 of the trip device, respectively, to flexible shunt conductors 39 and the terminals 5.

The electrical circuit for each of the poles is substantially the same and extends from the terminal 3 through the main stationary contact assemblage I5, the cooperating movable contact assemblage II, the flexible shunt conductor 39, terminal 35, trip device 'I to the terminal 5.

The assemblage of switch-members II is pivoted to the frame 4I of the operating mechanism 9 by means of a pin 42. A metal tie-bar 43 rigidly connects the three switch assemblages II so that they pivot as a unit about the pin 42. Each of the switch members I I is secured to the tie-:bar 43 by means of a clamp 45 and a bolt 4'I. In order to prevent short circuiting the several poles the switch members I I are insulated from the tie-bar 43 by an insulating tube 48 surrounding the tiebar 43.

Each of the movable contact assemblages I includes a pair of contact members 52 supported on a pivot 53 carried by inwardly extending projections 55 of the clamp member 45. The contact members 52 are biased into engagement with contacts 56 of the stationary contact assemblage by springs 55. Projections 6I on rearwardly extending portions 69 of the contact members 52 are adapted to engage the projections 54 of the clamp member 45 to limit the counter-clockwise movement of the members 52 about their pivot 53.

The third contact member 49 (Figs. 2, 3, 4, 5 and 6) of the movable contact assemblage II is disposed between the outer contacts 52 and includes an arcing contact 59, a body portion 62 provided with a slot 93 (Figs. 3, 4, 5 and 6) and an intermediate contact 5 I. A rearwardly extending portion 64 of the body 62 is pivoted on the pin 53 and is conductively joined to the central portion cf a flexible shunt conductor 39. The outer portions of the shunt conductor 39 are connected to the main contact members 52. A spring 66 compressed between the top of the portion 62 and a Y projection 61 of the clamp 45 provides the contact pressure for the contacts 59 and 5I which are adapted to engage cooperating contacts of the stationary contact means I5. A spring guide 68 passes through an opening in the projection 61 and has its lower end curved to lie within the slot rotate about the common pivot 42 is dened by the engagement of a portion of the central clamp member 45 with portions 82 of the side walls of the frame 4I (see Figs. 4 and 5).

VThe arc extinguishers I3 may be of the spaced plate type and are disposed adjacent the arc path, the plates being provided with slots of substantially the same outline as the moving contacts. The arc is moved into the spaces between the plates where it is rotated by a suitable means until it is cooled and extinguished. Patent 1,896,764, issued to M. W. Brainard on February 7, 1933, fully discloses and describes the structural features and operation of an arc extinguisher of this type.

The frame 4I, which is secured to the base I by screws 99 and 9|, supports the breaker operating mechanism 9. This mechanism includes pairs of toggle links 33 and 54, pivotally connected by a knee pin 94. The toggle link 83 comprises a pair of parallel links rigidly connected by a yoke 92, and the toggle link 94 also comprises a pair of parallel links rigidly connected by a yoke 95. The yoke of the toggle link 84 is disposed to engage the underside of the yoke 92 of the toggle link 83 to limit the outward motion of the knee of the toggle.

The toggle link 83 is pivotally connected by means of a pin 93 to the portion 'I5 of the central clamp member 35 and thus to the three switch members I I. The ends of the parallel links forming the toggle link 84 are rounded as indicated at |94 (Fig. '7) to form bearings which engage suitable recesses in the upwardly extending arms of a bell crank carrier |95 which is pivoted at its apex to the frame 4I by means of a pin |99. Retainer plates |96 (only one being shown) are secured to the outer faces of the bell crank lever |95 to prevent lateral displacement of the toggle link 84. These plates |96 are provided with openings into which project studs I9? 'in the bearing portions |94 of the toggle links 84 to prevent longitudinal displacement of the bearings from the bell crank |95. An overcenter spring 99 is tensioned between the knee pin 94 of the toggle and the operating member 23, the spring being threaded at one end onto a member 9'I which is pivotally connected to the member 23 by a pin |99. At its opposite end, the spring 99 is threaded onto a member 98 pivoted on the knee pin 94 of the operating toggle. The spring 99 at all times exerts a tension force between the knee of the toggle 83-34 and the operating member 23.

The bell crank carrier lever |95 comprises a pair of parallel bell cranks |95 joined at their left hand ends (Fig. 3) by a cross bar or yoke |98. A latch member III comprising a pair of substantially parallel members pivoted to the frame 4I by means of a pin ||5 has a yoke |I2 joining the two members substantially above the pivot pin ||5. In the normal position of the parts, the yoke I I2 lies directly above and in the path of travel of the yoke I 98 thus normally preventing clockwise travel of the bell crank carrier |95 under the inuence of the spring 99. The latch member III is releasably retained in its normal latching position by a latch II 4 of the trip device 'I and is provided with a latch engaging element II'I pivotally mounted on a yoke II3 joining the free ends of the latch members III.

The latch member I I is normally restrained in latching position by the trip device I which is responsive to predetermined overload conditions in the circuit of any of the poles of the breaker to release the member III and thereby cause automatic opening of the circuit breaker. The instant invention is not particularly concerned with the details of the trip device I as any suitable device possessing the proper characteristics may be used, for instance, a trip device such as is disclosed in United States Patent 2,043,306, granted June 9, 1936 to Jerome Sandin and which is assigned to the assignee of the instant invention. Such a trip device includes a current responsive bimetal trip element and an electromagnetically responsive trip element electrically connected in each pole of the breaker, and a common trip bar operable by any one of the thermally or magnetically responsive trip elements to eiTect release of the circuit breaker latching lever` III.

Upon the occurrence of an overload of predetermined value in any one of the poles of the breaker, the current responsive bimetal element acts to trip the breaker mechanism after a predetermined time interval. Ii the overload in the circuit of any one of the poles is greater than a predetermined magnitude or is a short circuit, the electromagnetically responsive element in that pole acts to immediately trip the operating mechanism and open all the circuit breaker contacts substantially instantaneously. Suitable means are provided to restore all the parts of the trip device to operative condition following an operation.

The latch II9 (Figs. 3, d, 5, 6 and 7) is provided to prevent the overcenter spring 99 from closing the switch member I I until the operating handle has reached a predetermined point during the closing operation, that is, until the operating handle has been moved almost to the fully closed position so that the operating spring will be stretched substantially to the maximum length before the latch releases the switch member II. This insures that the contacts will be closed quickly and positively. This latch comprises a pair of parallel members I I9 (see Fig. 8) pivotally mounted by means of a pin I2I on the frame 4I, and the latch is biased in a clockwise direction by a spring |25 having one end anchored to the latch and the other fast to a pin projecting from the frame 4|. A roller |23 (Figs. 6 and 7) rotatably supported on a pin I2l1 connecting the members |I9 is adapted t0 cooperate with the toggle pin 93 when the breaker mechanism is in the open position. The projecting free end |26 of the latch I|9 engages the pin 93 of the toggle link 83 to limit clockwise movement of the latch. The latch is released by the engagement of a shoulder |21 (Fig. 4) on the underside of the operating member 23 with a tail |28 of the latch II9.

Another latch comprising a bifurcated member |29 is also pivoted on the stud I2I. The purpose of this latch is to prevent the spring 99 from partially closing the switch member II and thus prevent any rebound of the contacts from the open position in the event vthat the handle 25 is held in the closed position when the breaker mechanism is tripped open by an overload current. The latch |29 is biased in a counter-clockwise direction toward latching position by a spring Iiil (see Fig. 8) having one end anchored on a pin |33 on the latch and the other end secured to a pin on the frame 4|. A cam face |30 on the upper fork of the latch |29 is adapted to cooperate with the operating member 23 and the lower fork is shouldered as at |36 (Fig. Ll) to engage the toggle pin 93 in a manner to be more fully described later in connection With the description of the operation of the breaker.

When the breaker contacts ar-e in their fully closed position (Fig. 3) and an overload or short circuit occurs in the circuit controlled by any one of the poles, the latch lever I I I is released by the trip device l.. The latch lever III then moves counter-clockwise (Fig. 3) about its pivot I|5 under the influence of a spring |49 and also by a component of the force of the operating spring 99, one end of the spring |49 bearing on a projection I5I of the latch lever III. At this movement of the latch lever, the yoke II2 thereof is moved out of restraining relation with the yoke |08 of the carrier lever freeing the latter for movement by the operating spring 99 which, acting through the toggle link 84, immediately rocks the carrier lever |65 clockwise about its pivot |09. In this action, thc spring 99 is assisted by the contact springs 55 and 66 acting through the switch members and the toggle 33-84, During the opening Operation, the line of action of the operating spring 99 moves from a position above the center of the pivot pin S9 for the operating member 23 to a position below the pin 80. This biases the operating member 23 in a clockwise direction about the pin Si) and immediately moves the operating member until it is Iarrested by engagement of rollers |31 with the surfaces |39 on the carrier member |55. The parts are shown in this position in Fig. 4. This position of the operating handle provides a convenient means for indicating that the breaker has been automatically tripped open.

When the parts are in their fully closed positions (Fig. 3) a small clearance exists between a projection IM on the switch arm 'I6 (seen in Figs. 4, 5 and 6) and the yoke 92 of the toggle link 83. Soon after the latch lever |II frees the carrier lever and the parts start their opening movement, the contact members Il close this clearance and the projection |41 comes into contact with the yoke 92. This causes clockwise movement of the knee pin 911 about the pivot pin 42 and changes the line of action of the resultant force exerted by the operating spring 99 so that the spring will tend to bias the knee or" the toggle inward toward collapsed position if the operating member 23 is permitted to move to the intermediate position shown in Fig. 4. When the toggle collapses, the parts are moved to the positions in which they appear in Figure 4 in which the contacts are in the fully opened position.

To effect manual opening of the contacts the operating handle 25 (Fig. 3) is moved clockwise about the pivot 89. Shortly after the beginning of the clockwise movement, a projection |45 on the operating member 23 engages the yoke $2 of the toggle link 83 and upon continued movement of the handle positively moves the toggle 83-84 in the direction to cause collapse. At the same time, the movement of the operating member 23 moves the overcenter spring 99 across the center line of the toggle link 84 whereupon it exerts a downward pull on the knee pin 94 causing complete collapse of the toggle. This causes the contacts to open with a snap action. The parts are shown in their manually opened position in Fig. 5.

The latch ||9 (Figs. 3, 4, 5 and 6) is effective to latch the movable switch members II in the open position whether the breaker is operated manually or tripped under the influence of an overload circuit condition. As soon as the pivot pin 93 of the toggle link 83 passes to the right of the roller |23 of the latch ||9, the spring |25 rocks the latch clockwise into the path of the pin 93 to latch the movable contacts in the open position. Y

Following each opening of the circuitbreaker in response to an overload circuit condition, itis necessary to restore the operating mechanism and the trip device to an operative condition. This is accomplished by moving the handle 25 from the position in which it is shown in Fig. 4 to the full open position in which it appears in Fig. 5. During this movement the rollers |31 on the operating member 23 engage the carrier |65 and move it counter-clockwise. As Vthe carrier |95 nears the end of its counter-clockwise travel, the yoke |98 on the free end thereof engages a projection |55 (Fig. 3) forming a part of the yoke H2 of the latch lever |H and rocks this lever clockwise. Near the end of the clockwise movement of the latch lever the latch element H1 thereof reengages the latch H4 of the trip device 1 and at the same time the latch yoke H2 resumes its latching position in the path of the yoke 198.

When the breaker mechanism is in the open and reset position shown in Fig. 5, the line of action of the spring 99 is below the center line 91E-|91 and as a result the spring 99 restrains the toggle 83-85 in its collapsed position (Figs. 4 and 5), the clockwise or opening movement of the movable contact assemblage being limited by the central clamp member 45 striking thil frame 4|. In this position there is a slight clearance between the toggle pin 93 and the roller |23 of the latch l I9.

To close the circuit breaker the handle is rocked counter-clockwise to the closed positionthe pin 93 and the latch roller |23, and since the latch H9 occupies a latching position in the path of the toggle pin 93 the movable contacts are held in the open position while the counterclockwise movement of the operating member 23 increases the tension of the spring 99. Near the end of the counter-clockwise travel of the handle 25, the shoulder |21 on the operating member 23 strikes the tail |23 and rocks the latch I9 counter-clockwise out of the path of the pin 93 Vwhereupon the spring 99 acts to straighten the toggle {i3-39, thus closing the contacts with a snap action.

When the contacts have been opened manually the latch H has not been tripped and the handle 25 occupies the position shown in Fig. 5. In this case the contacts may be closed by moving the handle 25 from the position in Fig. 5 to that shown in Fig. 3. The latch H9 functions in the above described manner to retain the parts in the open po-sition and to release the movable contact means near the end of the closing movement of the handle 25.

Should an attempt be made to close the breaker against an overload or a short circuit condition, the latch lever will again be released in the above described manner, after a predetermined time delay or instantaneously, depending on the magnitude of the overload current. The carrier lever |95 will also be released and will cause the mechanism to again break the toggle 83-84 and open the contacts. It is not possible, therefore, to hold the breaker against an overload circuit condition.

When the operating mechanism 23 is in the A, closed position, the previously mentioned cam Cil -face |39 of the latch |29 is disposed justbelow-a recess |35 in the operating member'23 and is held infunlatched position by the toggle pin 93 in the fork of the latch. When the lbreaker is opened either manually or automatically, the pin 93 is withdrawn from the fork of the latch |29 to the position shown in Figs. 4 and 5. At the same time, the clockwise movement of the operating member 23 has moved the recess |35 toward the right from above the cam face |30, and a projection |68 on the underside of the member 23 holds the latch |29 in its lower or ineiective position.

At the beginning of the counter-clockwise or closing movement of the operating member 23, the toggle pin 93, under the influence of the spring 99 moves toward the left into contact with the roller |23 on the latch H9 where it is restrained until near the end of the manual closing operation of the operating member when the shoulder |21 strikes the tail |28 and disengages the latch H9. Since the shouldered portion |35 of the latch l|29 is longer than the latch H9, it can -be seen that the latch |29 will be held out of the path of the pin 93 and will not be elective to restrain the operating mechanism on normal operations.

Referring now to Fig. 6, if the breaker should be automatically tripped while the handle 25 and the operating member 23 are held in the closed position, the latch l I9, due to the engagement of the shoulder |21 with the tail |28, is held in its ineffective or unlatched position. However, as soon as the toggle 33-84 collapses and moves the toggle pin 93 clear of the shoulder |36, the latch spring |3| rocks the latch |29 counter-clockwise interposing the shoulder |36 in the path of the toggle pin 93, thus preventing rebound of the contact arm 16 from the open position toward closed position. At this movement of the latch |29, the cam portion |30 enters the recess |35. Without the latch 29 the spring 99 would tend to move the contacts towards closed position should the handle be held in closed position when the breaker trips, as can be seen in Fig. 6 since in this position the line of action of the spring is above the pivot |91.

The parts will remain in the position shown in Fig. 6 until the handle is released and moves clockwise to its Fig. 4 position. During the early part of the clockwise movement of the handle the shoulder |21 on the operating member 23 moves away from the tail |28, permitting the spring |25 to rock the latch H9 into the path of the toggle pin 93. Slightly later in the clockwise movement of the handle, the projection |48 engages the cam portion |39 and rocks the latch 29 clockwise, moving the shoulder |36 out of the path of the toggle pin 93.

Y The manual clockwise movement of the handle 25 from its Fig. 4 position to its Fig. 5 position resets the operating mechanism and reengages the latch member H1 with the trip device as previously described. The handle 25 is then moved counter-clockwise to its closed position, the shoulder |21, near the end of its travel, rocking the latch H9 to permit the spring 99 to reclose the contacts. Y

Should the handle 25 be moved from the tripped open position (Fig. 4) to the closed position (Fig. 3) without first moving the handle to the open position (Fig. 5) to reset the mechanism, the latch |9 would be moved to its unlatched position when the shoulder |21 strikes the'tail |28 of the latch. The latch |29 is ineffective to restrain the contacts in open position until the handle is near its closed position, consequently the contacts will be moved to partly closed position since the center of action of the spring 39 is moved about the center line 94-1 01 upon movement of the handle tc closed position.

In order to prevent this partial closing of the contacts by improper operation of the handle, a modified form of the invention comprising a latch |53 (Fig. 9) is provided in place of the latch |29 of the original embodiment. The latch is pivoted on the pivot l 2| and a spring |5'1 urges the latch |53 in a counter-clockwise direction about its pivot to l-atching position. With the contacts and the operating handle in the closed circuit position the latch |53 is restrained in its ineffective position by the toggle pin 93, which thus assumes a position above the latch at a point indicated at |51 (Fig. 9). When the breaker is automatically tripped in response to an overload current in one of the poles, the toggle collapses as previously described and the pin 93 moves to the position in which it is shown in Fig. 9. As the pin clears the shoulder of the latch |53, the spring |54 rocks said latch counter-clockwise to the latching position shown wherein it is effective to prevent movement of the movable contact assemblage toward closed position.

Since the latch |53 is not under the direct control of the handle 25 and the operating member 23, movement of these parts to closed position will not displace the latch |53 from its effective position. When the handle 25 and the operating member 23 are moved to the open position (Fig. to reset the mechanism, the carrier |05 is rocked counter-clockwise to the position shown in Fig. 5, moving the toggle 83-84 to its completely collapsed position. At this movement the toggle link 33 rocks clockwise about the pin 93 from the position shown in Fig. 9 to that in which it appears in Fig. 5. During this movement a member |56 (Fig. 9) secured to the inner face of the yoke S2 of the toggle link 83 engages a projection |59 on the latch |53 and rocks the latch clockwise to its ineffective or unlatched position. When the operating member 23 is now moved to the closed position to close the contacts, the spring 99 moves above the center line S34-|31 and attempts to straighten the toggle 233-84. Since the latch ||9 at this time is in its latching position the movement of the toggle will be arrested by the pin 93 striking the roller |23. During the first part of the closing movement of the handle, the spring 99 moves the toggle `a slight distance to take up the clearance between the pin 93 and the latch I I9, and since the latch |53 is longer than the latch H3 the pin 93 passes above the latch |53 onto the surface |51 thereof so that the latter is held in its unlatched position and does not now prevent closing the breaker. The movable contacts will be released for closinT movement by the spring 59 as previously disclosed, by the shoulder i2? moving the latch H9 to rits ineffective position as the operating member 23 approaches its closed position. The spring 33 then closes the contacts as previously set forth.

From the above description it is clear that the latch |53 of the modification has the additional function of holding the movable contacts in full open position until the handle has been properly operated to reset and reclose the breaker.

Having disclosed several embodiments of the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details disclosed without departing from some of the essential features of the invention. It is, therefore, desired that the invention be interpreted as broadly as the prior art permits, and that it is limited only by what is expressly stated in the following claims.

We claim as our invention:

l. A circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to open and to close said contacts, a member movable in response to predetermined abnormal conditions in the circuit to cause automatic opening of the contacts irrespective of the position of said operating member, said mechanism being resettable following automatic opening of said contacts, and latch means pivoted on a fixed support and operable to lock said contacts open upon automatic opening thereof while the operating member is held in closed position and until after said mechanism has been reset.

2. A circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to open and to close the contacts, means releasable to cause automatic opening of the contacts, said means being resettable by a predetermined movement of the operating member, and latch means pivoted on a fixed support and operable to lock the contacts open upon automatic opening thereof while the operating member is held in closed position and until after the mechanism has been reset.

3. A circuit breaker comprising relatively movable contacts, a resettable operating mechanism therefor including an operating member movable to open and to close the contacts, an operating toggle, an overcenter spring connecting said operating member and said toggle, means supporting one end of the toggle and release-bly to cause automatic opening of the contacts, and latch means pivoted on a fixed support and operable to engage a part of said toggle to lock the contacts open upon automatic opening thereof while the operating member is held in closed position and until after the mechanism has been reset.

4. A circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to open and to close the contacts, a member movable in response to predetermined abnormal conditions in the circuit to cause automatic opening of the contacts irrespective of the position of said operating member, said mechanism being resettable following automatic opening of the contacts, latch means pivoted on a fixed support and operable to lock the contacts open upon automatic opening thereof while the operating member is held in closed position and until after the mechanism has been reset, and another latch means operable to lock the contacts open upon opening thereof and until the operating member is moved a predetermined distance in a closing direction.

5. A circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to cause opening or closing of said contacts and including a member movable from one position to a second position in response to predetermined conditions to cause automatic opening of the contacts irrespective cf the position of the operating member, said mechanism being resettable by a predetermined movement of said operating member following automatic opening of said contacts, means mounted for movement independently of said mechanismandengageable with a part movable with the Ycontacts for automatically locking said contacts in open position upon automatic openinglthereof while the operating member is held in closed position, and until said mechanism has been reset. Y

6. A circuit breaker comprising relatively movable contacts, operating mechanism therefor including anA operating member movable to open and closed positions to cause opening and closing ofthe contacts, a member movable from one position toV a second position in response to predetermined conditions to cause automatic opening of the contacts irrespective of the position of the operating member, and means mounted for movement independently of said mechanism and engageable With a part movable with the contacts for locking said contacts open upon automatic opening'thereof while the operating member is held in closed position and until the operating member is moved a predetermined amount toward open position.

71 'A circuit breaker comprising relatively movable contacts, operating mechanism therefor ins Aof the contacts, a member movable from one position to a second position in response to predetermined condition to cause automatic opening ofthe contacts irrespective of the position of the operating lmember, and means mounted for movement independently of said mechanism and engageable with a part movable with the contacts for locking the contacts open upon automatic opening thereof While said Yoperating member is held in closed position and until the operating member is moved to its full open position.

8. A' circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to open and closed positions to cause opening and closing ofthe contacts,.a member movablefrom one position to a second position in response to predetermined conditions to cause automatic openingof the contacts irrespective'of the position of the'operating member, and means mounted for movement independently of said mechanism and engageable with a part movable with the contacts for locking said contacts in open position upon automatic opening of said contacts as long as the operating member is within -a predetermined distance of the closed position.

9. Acircuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating member movable to open and close Vthe contacts, a. member movable in response to predetermined abnormal conditions in theicircuit to cause automatic opening of the contacts irrespective of the position of said operating member, said mechanism being resettable by a predetermined movement of said operating member after automatic opening of said contacts,v

and a pair of coaXially pivoted latch members engageable with a part movable with the movable contacts, one of said latch members being operable to automatically lock the contacts open upon automatic opening thereof and until said operating member is moved a predetermined amount in an opening direction, the other of said latch members being operable to lock the contactsl open upon automatic opening thereof until the operating member is moved a predetermined distance in a closing direction.

l0. A circuit breaker comprisingV relatively movable contacts, operating mechanism therefor including an operating member movable to cause opening or closing of said contacts and including a member movable from one position to a second position in response to predetermined conditions to cause automatic opening of said contacts, and a latch movable independently of said mechanism and engageable with a part movable with the contacts for automatically locking said contacts in full open position upon automatic opening thereof, said latch being eiective to lock said contacts open as long as said operating member remains in closed position or in proximity to closedposition after automatic opening of said contacts.V

1l. lA circuit breaker comprising relatively movable contacts, operating mechanism therefor including an operating handle movable to an open position and to a closed position to open and close said contacts, and a member movable in response to predetermined abnormal circuit conditions to cause automatic opening of the contacts irrespective of the position of the operating handle, said operating mechanism being resettable followingl automatic opening of the contacts, and latch means pivoted on a xed support and operable to lock said contacts open upon automatic operation thereof while the handle is held in closed position.

i2. A circuit breaker comprising relatively movable contacts, operating mechanism for said contacts including an operating handle movable to open and closed positions to cause opening and closing of the contacts, a member movable from one position to a second position in response to predetermined conditions to cause automatic opening of the contacts irrespective of the position of the operating handle, and means mounted for movement independently of said mechanism and engageable with a part movable with the contacts for locking the contacts open upon automatic opening thereof While the handle is held in closed position. TURE LINDSTROM. JEROME SANDIN.

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