US2144475A

US2144475A - Circuit breaker

Info

Publication number: US2144475A
Application number: US164142A
Authority: US
Inventors: Wulsten Kurt
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1936-09-12
Filing date: 1937-09-16
Publication date: 1939-01-17
Anticipated expiration: 1956-01-17
Also published as: DE714597C; US2150307A; NL54265C; FR826604A; DE702993C; DE712051C; DE706843C; NL49967C; DE701870C; DE708012C; GB490721A; NL56886C

Description

Jam 17, 1939. K. WULSTEN 2,144,475

CIRCUIT BREAKER Filed Sept. 16, 1957 3 Sheets-Sheet 1 WITNESSES: j INVENTOR Jan. 17, 1939. K. WULSTEN 2,144,475

CIRCUIT BREAKER Filed sept. 16, 1937 5 sheets-sheet 2 INVENTOR WITNESSES:

i l. Kurt Wulsen. y :if w/d/f,

K, WULSTEN CIRCUIT BREAKER qgan., 37, 1939.

. Filed Sept. 16, 1937 5 Sheets-Sheet 3 INVENTOR hur Wahre/1.

WITNESSES: yf MM Patented Jah. 17, 1939 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Application September 16, 1937, Serial No. 164,142 In Germany September 11, 1936 18 Claims.

The invention relates to electrical circuit controlling devices, in general, and'more particularly, to circuit breakers of the type which are manually operable to open and to close the circuit and automatically operable to open the circuit in response to predetermined overload or fault conditions, and which are used for controlling lighting and moderate power industrial feeder circuits.

Due to the inter-connection of a large number of circuits in such applications, a considerable burden is placed on the individual circuit breakers since very large amounts of power may be fed into a short circuit or other fault condition. The circuit breaker involved must be capable of interrupting large amounts of power in the shortest possible' time. AHeretofore reliance has been placed on snap-acting operating mechanisms land arc extinguishing means to shorten the time of circuit interruption following occurrence oi the fault condition. In most instances, however, the necessary contact pressure in the closed position of the breaker has been obtained by the resilient mounting of at least one of the contacts, and this arrangement has the inherent disadvantage that the time required to relax the resilient means before the contacts separate materially increases the time required for circuit interruption. Furthermore, as the contact pressure approaches zero value, the contacts may become welded together, thus preventing opening of the circuit.

It is accordingly an object of the invention to provide an improved circuit breaker which is operable to effect circuit interruption in a shorter period of time than has heretofore been achieved.

Another object of the invention is the provision of a circuit breaker embodying an improved actuating and coacting tripping means for effecting a very rapid circuit interruption.

The general arrangement for carrying out this feature of the invention consists in providing a spring directly engaging the switch member for biasing the same toppen position, an actuating means for opening and closing the switch member which includes a spring means for securing pressure engagement of the contacts when the breaker is closed, and a trip member normally connecting the actuating and contact pressure securing spring means to the switch member, which is operable in response to predetermined conditions to disconnect the actuating and contact pressure securing spring means from the switch member to permit opening of the same by its biasing spring. In addition, an improved arc-extinguishing structure is provided for quick- 1y extinguishing the arc drawn between the contacts.

In addition to the previously mentioned requirements, for a circuit breaker to be commercially successful, it must be safe in operation, compact in structure, inexpensiveV to manufacture and its parts readily accessible for servicing.

Another `object of the invention is the provision of an improved circuit breaker which will satisfactorily meet all of the previously mentioned requirements.

Another object of the invention is the provision of a circuit breaker embodying an improved arcextinguishing structure.

Another object of the invention is the provision of a circuit breaker in which the operating mechanism and contact means are assembled as a unit, removably mounted on the breaker base, and readily accessible for servicing.

Another object of the invention is the provision of a circuit breaker in which the insulating base for supporting the breaker is formed to provide an enclosed interrupting chamber for the contacts, thus eliminating the necessity of a separate structure for this purpose.

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

Figure 1 is a side View, partly in section and partly in elevation, of the circuit breaker embodying the features of the invention;

Fig. 2 is a vertical sectional view of the circuit breaker illustrated in Fig. 1;

Fig. 3 is a plan view of the circuit breaker with the cover removed;

Fig. 4 is an end View partly in elevation and partly in section, of the circuit breaker;

Fig. 5 is a plan View of the base of the circuit breaker;

Fig. 6 is a plan view of one of the arc-extinguishing plates;

Fig. '7 is a plan view of the winding spool for vthe electromagnetic blowout and trip means;

Fig. 8 is a diagrammatic view illustrating the electrical connection of the windings of the aforementioned electromagnetic means to the contacts of the breaker;

Fig. 9 is a schematic view of a modification of the invention; y

Fig. 10 is a schematic view showing the contact means and actuating means of the embodiment shown in Fig. 1 in the manually open position of the breaker;

Fig. 11 is a view similar to Fig. 10 showing the contact means and actuating means in the manually closed position of the breaker;

Fig. 12 is a view similar to Fig. 10 showing the position of the parts immediately following release of the trip latch during a tripping operation of the breaker; and

Fig. 13 is a horizontal sectional view of the circuit breaker taken substantially on the line XIII- XIII of Fig. 2.

Referring to the drawings, particularly Figs. 1 through 4 thereof, the circuit breaker illustrated comprises, in general, relatively movable contact means indicated generally at I5, actuating means therefor indicated generally at I1, a trip latch member I9, which serves to releasably connect the actuating means to the contact means, an electromagnetic means indicated generally at l2| for blowing out the arc formed during circuit interruption and for actuating the latch member I9 to trip the breaker open in response to predetermined conditions, and a thermal trip element 23 which is also operable to actuate the latch member I9 to trip the breaker. The aforementioned elements are all assembled together and to a main frame 25 of inverted U-shape, to form a unitary breaker assemblage which is adapted to be removably mounted on a base 21 of insulating material. A cover 29 also of insulating material is provided for enclosing and protecting the unitary breaker assemblage, the cover being secured to the assemblage by means of a screw 3| which engages a threaded opening provided therefor in the upper portion of the frame 25.

The contact means of the breaker, as shown in Figs. 2 and 10 to 12, comprises a pair of spaced stationary contacts 33 and a movable bridging contact 35. The stationary contacts 33 are carried by bolts 31 which engage internally threaded conducting sleeves 38 embedded in an insulating body 39 which forms a winding spool for the windings of the electromagnetic means. 'I'he movable bridging contact 35 is secured to the lower end of an operating rod 4I which is mounted for vertical sliding movement in a vertical opening provided therefor in the insulating body 39. The upper end of the operating rod 4I is pivotally connected by means of a pin 43 to a contact lever 45 which is pivotally mounted on a main pivot pin 41 carried by the frame 25. TThe operating rod 4I and movable bridging contact 35 carried thereby are biased in a downward direction to open position by means of a coil compression spring 49 surrounding the rod 4I. The upper end of the spring engages a vertical insulating sleeve 42 provided in the core of the electromagnetic means, while the lower end thereof engages an insulating sleeve 5I mounted on the lower portion of the rod 4I.

'Ihe actuating means for the breaker comprises, in general a manually operable handle 53, a pair of

toggle links

55 and 51, a pair of pivoted bell crank levers 59 anda spring means 6I for securing a pressure engagement of the contacts in the closed position of the switch. The operating handle is pivotally mounted on the main pivot pin 41 and is biased in a clockwise direction by a spring 54. The handle 53 is provided with an operating knob 63 which projects through a Suitable opening 65 provided therefor in the cover 29. The toggle link 55, which is U-shaped, is also pivotally mounted at one end on the main pivot pin 41 and its legs are provided with angular extensions 61 which carry a transverse pin 69. The pin 69 extends through a slotted opening 1I formed in the handle 53, the slotted opening 1I and the pin 69 forming a lost motion coupling means between the handle 53 and the toggle link 55. The lower toggle link 51 which is U- shaped, is pivoted at its upper end to the lower end of the toggle link 55 by means of a knee pivot pin 13. The two bell crank levers 59 which are mounted on opposite sides of the frame 25, are pivoted to the side walls of the main frame by means of the pivot screws 15 (Fig. 1). The right-hand arms of the bell crank levers 59 are secured for movement together by a transverse pivot pin 11 and this pin 11 engages slotted openings 19 provided therefor in the legs of the lower toggle link 51. The bell crank levers 59 are Vthus coupled at their one ends to the lower toggle link 51.

The contact pressure securing spring means BI consists of a coil tension spring, the upper end of which is secured to the transverse pivot pin 11,

the lowers end thereof b'eing secured to the bight portion or lower end of the toggle link 51, as shown in Fig. 6.

The actuating means ofthe circuit breaker is adapted to be releasably connected to the contact means and operating rod 4I by means of the floating trip latch member I9. The latch member I9 comprises a plate 8| of magnetic material to which is secured a transverse pin 83 'and a latch plate 85. The opposite ends of the transverse pin 83 engage vertical slots 81 provided therefor in the side walls of the frame 25 so that the latch member I9 is mounted for vertical movement. The left-hand ends of the bell crank levers 59 are provided with horizontal slots 89 in which the extended end portions of the transverse pin 83 engage to couple the bell crank levers 59 to the latch member I9. The latch member I9 is biased in a clockwise direction about the pivot pin 83 by means of the weight and position of the latch plate 85 and/or a suitable spring means (not shown) and the free end of the lever 45 is adapted to normally engage the upper edge of the latch plate 85 as shown in Fig. 2. be seen that the latch member I9 normally couples the actuating means I1 to the contact operating lever 45 and operating rod Il. The magnetic portion of the latch member I9 cooperates with the electromagnetic means 2| so that when a high magnitude overload or short circuit condition occurs in the circuit controlled by the breaker, the latch member I9 is rotated in a counter-clockwise direction, as viewed in Fig. 2, to release the contact lever 45 and permit opening of the contact means by the biasing spring.

49,l as will'be hereinafter described.

Forl effecting automatic opening of the contact means of the breaker in response to lower magnitude overloads of predetermined duration, there is provided the thermally responsive trip element 23 which consists of a strip of bimetallic material secured at its upper end to the frame 25 and connected in circuit with the contact means of the breaker. The lower free end of the trip element 23 is provided with an adjustable screw 88 for engaging and moving the lower' end of the latch member I9 when the trip element is heated a predetermined amount in response to an overload condition. The trip element 23 is adapted It will thus to flex toward the actuating mechanism when heated by overloads of predetermined magnitude and duration to engage and move the latch member I9 in a counter-clockwise direction to effect release of the contact lever 45 and opening of the contact means of the breaker.

'I'he electromagnetic means for blowing out the arc drawn between the contacts during circuit interruption and for actuating the trip member |9 in response to high| magnitude overloads and short circuit conditions comprises a core of magnetic material, a pair of spaced pole pieces 9| and a pair of separate windings 93 only one winding being shown in Fig. 2. The core member 90 is mounted within and extends through a hollow hub portion (Figs. 7 and 13) of the insulating body 39 and its ends are s'ecured to the pole pieces 9| which are disposed on opposite sides of the body 39. The insulating body 39 is provided with a central portion 91 and a pair of end discs 99. mentioned, the central portion 91 of the insulating body 39 is provided with a vertical opening |0| for accommodating the operating rod 4|. The core member 90 is also provided with a vertical opening aligned with the opening IDI for' receiving the operating Irod 4|, the vertical insulating sleeve 42 being mounted in the opening in the core 90 for insulating the rod 4| from the core. The two windings 93 are wound upon the hub portion 95 of the body 39 on opposite sides of the central portion 91 and between the end discs 99. l

The two pole pieces 9| are of inverted L-shape and extend downwardly on opposite sides'of the

contacts

33 and 35, and are secured to the opposite ends of the core 90 outside the discs 99. The lower ends of the pole pieces 9| are centrally notched, as indicated at |03, in Figs. l and 2, to provide a pair of pole shoes |05 on the opposite side of each stationary contact 33 and the path of movement of the contact portions of the movable bridging contact 35. This structure of the lower end of the pole pieces concentrates and increases the flux density across the interrupting gaps so as to increase the force which acts to move the arcs outwardly. The angular extensions 92 of the upper ends of the pole pieces 9| form pole shoes for cooperating with the lower end of the magnetic plate 8| of the trip member I9 so as to attract the same and move the trip member in a. counter-clockwise direction as viewed in Fig. 2 when a high. magnitudeoverload or short circuit condition occurs in the circuit controlled by the breaker to trip the breaker.

'Ihe blowout action of the electromagnetic means is briey as follows. The current flows in opposite directions in the two arcs drawn between the stationary contacts 33 and the movable contact 35, and since the magnetic fields between the two pairs of pole shoes |05 are in the same direction across the arc path, the

arcs are moved in opposite directions away from one another by the magnetic fields.

It will also be noted that the path taken by the current during circuit interruption is substantially U-shaped, due to the structure of the contacts, so that the magnetic field produced by the current flow through this path. also tends to move the two arcs outwardly in opposite directions from one another.

It will be observed from Fig. 8' that the windings 93 are each separately connected to one of the stationary contacts 33 so that the two gaps As has previously been` 'biasing influence of the opening spring are located between the windings 93. The end of one of the windings 93 is adapted to be connected to one of the end terminals of the breaker, while the end of the other winding 93 is adapted to be connected in series circuit with the thermally responsive bimetallic trip element 23 and to the opposite end terminal of the breaker through suitable connecting means.

The operation of the circuit breaker as thus far described is briefly as follows. With the breaker in the closed position as shown in Figs. 2 and ll, let it be assumed that it is desired to manually open the contact means. The operating handle 53 is moved in a counter-clockwise direction about its pivot axis 41. When the lost motion between the operating handle and the toggle link 55 is taken up by this movement, that is, when the lower edge of the slot 1| engages the transverse pin 69, the continued movement of the operating handle causes rotation of the upper toggle link 55 in a counter-clockwise direction about the pivot axis 41 to effect a collapse of the toggle links 55 and 51. As soon as the knee pivot pin 13 of the toggle crosses the line joining the pivot axis 41 and the pivot pin 11, the force exerted by the opening spring 49 acts through

levers

45 and 59 to quicklyvmove the toggle links to their collapsed position independently of the movement of the operating handle. The movement of the toggle links to the collapsed position as shown in Fig. l0 effects a counter-clockwise movement of the bell crank levers 59 about their pivot axes 15 from the position shown in Fig. l1 to the position shown in Fig. 10. This movement of the bell crank levers 59 allows the trip latch member |9 to be moved downwardly in the slots 81 to permit downward movement of the lever 45 and operating rod 4| under the 49. Downward movement of the operating rod 4| under the influence of the spring 49 moves the movable bridging contact 35 to the open-circuit position, as shown in Fig. 10. It will be noted that in this position of the parts the trip latch member I9 still connects the actuating means with the contact lever 45 and operating rod 4|.

To manually close the contact means of the breaker the operating handle 53 is moved in a clockwise direction about its pivot axis 41. Since the transverse pin 59 is in engagement with the upper end of the slot 1| in the operating handle, this movement of the operating handle causes clockwise rotation of the upper toggle link 55 to effect movement of the toggle links 55 and 51 from their collapsed positions, as shown in Fig. 2, to their extended or overset position against a stop, shown 'in Fig. ll. The movement of the toggle links from collapsed to extended position by the operating handle 53 causes the contact pressure spring 6| to move the bell crank levers 59 in a clockwise direction about their pivot axes 15. 'Ihis clockwise movement of the bell crank levers moves the trip latch member I9 upwardly in its guide slots 31, and since the free end of the contact lever 45 engages the latch plate 85 of the trip latch member, the contact lever 45 and the operating rod 4|, which carries the movable bridging contact 35, are moved upwardly to effect closing of the contact means. It will be noted that in the closed position of the breaker, as shown in Figs. 2 and l1, the toggle links 55 and 51 are overset and held against further movement by a suitable stop means so that the breaker is maintained in closed circuit position. The contact pressure spring 6I exerts a downward force on the transverse connecting pin 11 carried by the bell crank lever 59, and this force is transmitted to the movable bridging contact through the agency of the trip latch member I9, contact lever 45 and operating rod 4| to effect a pressure engagement of the movable bridging contact 35 with the stationary contacts 33. v

If an overload of low magnitude and sufficient duration occurs in the circuit controlled by the breaker, the bimetallic trip element 23 is heated a suiicient amount to ilex and move the trip latch member I 9 in a counter-clockwise direction about its pivot axis 83. This movement of the trip latch member releases the contact lever 45 or disconnects it from the actuating means of the breaker so as to permit movement of the contact lever 45, operating rod 4| and movable bridging contact 35 to open circuit position under the influence of the opening spring 49, as shown in Fig. l2.

Following the above-described tripping operation, the bell crank levers 59 are moved in a clockwise direction about their pivot axes 15 by the spring 6| until the transverse pin 83 of the trip latch member I9 reaches the upper end of its guide slots 81. 'I'his movement of the bell crank levers causes a breaking of the toggle links 55 and 51 and the force exerted by the contact pres sure spring 6| then moves the toggle links toward collapsed position to reset the trip latch member I9 into operative or latching engagement with I the contact lever 45. This movement may be aided by the mass of the latch member I9 and left-hand arms of the bell crank levers 59 or by a light spring (not shown) acting on the `bell crank levers 59 to move them counter-clockwise. The parts of the breaker are now in the position shown in Fig. 10 andare ready for a subsequent manual closing operation.

If a high magnitude overload or short-circuit condition occurs in the circuit controlled by the breaker, the lower end of the armature portion 8| of' the trip latch member I9 is moved to attracted position against the pole shoes 92 by the pull of the electromagnetic means to eiect counter-clockwise movement of the trip latch member I9 about its pivoty axis 83. This movement of the trip latch member by the electromagnetic means eft'ects release of the contact lever 45, or disconnectionof that member from the actuating means to permit the opening spring 49 to open the contacts in the manner previously described in connection with a thermal tripping operation. 'Following the magnetic tripping operation, the parts of thebreaker are automatically reset in the manner previously described vso that the breaker is ready for a subsequent manual closing operation.

An important advantage of the previously described structure is that it provides a considerable decrease in .the total time required for circuit .since it permits ready access to be had to the actuating means and contact means.

The base 21 of the circuit breaker is of ceramic insulating material and is provided with recesses at each end for accommodating the end terminal bolts |01, which are secured in the base by the fastening nuts ||5. If desired, the base may be composed of molded insulating material instead of ceramic material. The terminal bolts |01, together with the cooperating terminal nuts |09, form a means for mounting terminal lugs III, as shown in Fig. 2; or to connect switchboard studs ||3 to the breaker, as shown in Figs. 1 and 4. The inner ends of the terminal lugs I I I are bifurcated, as indicated in Fig. 2, to engage the-bolts |01, and are adapted to be secured rmly against the fastening nuts I I5, by means of the terminal nuts |09.

In the case of the switchboard studs H3, their upper ends are attened and bent angularly as shown in Fig. 4. The angularly-bentportions I|1 are perforated for engaging the bolts |01 and are firmly clamped against the fastening nuts I I5 by means of the terminal nuts |09. It will thus be seen that the terminal structure of the circuit breaker lends itself readily to either of the two types of connections for connecting the breaker in an external circuit.

' The base 21 of the breaker is provided with a relatively deep main recess I I9 (Fig. 5) the centrol portion of which forms an interrupting chamber for thecontact means as shown in Fig. 2. The base 21 is also provided with a pair of pole shoe receiving recesses |2| disposed on opposite sides of the central portion of the main recess I I9 and separated therefrom. The recesses |2| serve to receive the pole shoes |05 of the electromagnetic means, as best shown in Fig. 4.

The previously described breaker unit assemblage is adapted to be removably mounted on the base 21 so that the contact means is disposed in the main interrupting recess or chamber |I9v and the pole shoes |05 in the pole receiving recesses |2I. For securing the breaker unit assemblage in mounted position on thebase 21, there are provided a pair of bolts |23 (Figs. 1 and 4) which extend upwardly through suitable openings provided therefor in the base member. The upper ends of the boltsr |23 extend through suitable restricted openings |25 provided therefor in the pole pieces 9| between the pole shoes |05. Recesses |21 are provided in the pole pieces 9| for receiving astening nuts |29 into which the bolts |23 are crewed. The recesses |21 may be of irregular or square shape so as to prevent the fastening nuts |29 from turning when the screws |23 are turned. It will thus be seen that it is a relatively simple matter to remove the unitary breaker assemblage from the base 21 for adjustment or repair purposes.

f n Suitable closure plates |3| (Fig. 2) are provided for closing the open side of the interrupting chamber |I9. The plates |3| are secured to the unitary breaker assemblage by means of the bolts 31 and the stationary contacts 33, so that when the unitary breaker assemblage is mounted in position on the base 21 the plates |3| serve to close the interrupting chamber.- The plates |3| are provided With a suitable opening for receiving the operating rod 4| and this opening is substantially closed to the passage of gases generated in the interrupting chamber by means of the spacer sleeve 5|, the opening spring 49 and the electromagnetic core 90. v

The provision of the closed chamber about the contact means of the breaker aids in extinguishing the arc drawn between'the contacts during circuit interruption, the pressure developed by the arc tending to quench the same.

Additional arc-extinguishing means are provided in the chamber ||9. The additional arcextinguishing means comprises a plurality of spaced and insulated arc-extinguishing plates |33 disposed in the opposite ends of the interrupting chamber H9. These plates may be of metal or other suitable type of arc-extinguishing material. The electromagnetic means 2| moves the arcs drawn between the stationary contacts 33 and the movable bridging contact 35 in opposite directions into the spaces between the plates |33 to split the arcs up into a series of short arcs which are quickly cooled and extinguished by the arc-extinguishing plates |33.

Additional recesses or chambers |35 (Fig. 5) are provided opposite the ends of the arc-extinguishing plates |33 and these chambers are open to the main interrupting chamber ||9 through the spaces between the plates. Since these chambers |35 are closed or substantially closed, the air or gas Within the same is compressed during circuit interruption by the rise in pressure within the main interrupting chamber ||9, so that the arc and hot gases are caused to penetrate deeply within the spaces between the arc-extinguishing plates |33 and are maintained therein until the arc is extinguished. Where extremely large amounts of power are required to be interrupted it may be expedient to provide vents or openings to allow escape of the gas from the interrupting chamber. In such cases the vents or openings would be positioned at and joining the chambers |35 so that the gases would be required to first pass by the arc-extinguishing plates I 33, where they would be considerably cooled before exit.

The provision of the interrupting chamber within the base of the circuit breaker considerably reduces the overall size of the breaker and eliminates the necessity of any additional arc chamber structure.

'I'he operation of this form of the invention is briey as follows. To open the contact means |31 and |39, the operating handle |41 is moved in a counterclockwise direction, as viewed in Fig. 9. This movement of the operating handle effects collapse of the toggle formed by the lower portion of the handle |41 and the link |5|. The collapse of this toggle allows the switch arm |4| to be moved to open-circuit position under the influence of the opening spring |45. To close the contact means |31 and |39 the operating handle |41 is moved in a clockwise direction about its pivot axis |43 to effect movement of the toggle formed by the lower portion of the handle and the link |5| to the over-set or made position as shown in Fig. 9. This movement of the toggle to the over-setl position effects clockwise movement of the spring |55 about its pivot axis |59 and downward movement of the trip latch member |6| to cause movement of the switch member |4| to closed circuit position. The resiliency of the spring |55 provides the necessary contact pressure between the stationary contact |31 and the movable contact |39.

When the electromagnet |61 is energized asumcient amount, the plunger engages and moves the trip latch member |5| in a counter-clockwise direction to effect a disconnection of the switch arm |4| from the actuating means and the contact pressure securing spring |55 to permit the switch arm to be moved to its open position under the influence of the opening spring |45. 'I'his form of the invention possesses the same desirable advantage as described in connection with the original embodiment, namely, a decrease in the overall time required for circuit interruption. This results from the fact that the trip means is operable to effect immediate disconnection of the switch arm or movable contact from both the actuating means and the contact pressure securing means.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable construction possible in the light of the prior art.

I claim as my invention:

1. In a circuit breaker, a stationary contact, va cooperating contact movable to open and to closed position, means biasing said movable contact to open position, actuating means for eiecting movement of the movable contact to open and tof closed position, means for securing a pressure engagement of said contacts in the closed position of said movable contact, and trip means operable to immediately release said contacts from said contact pressure securing means and said actuating means to cause opening of said contacts independently of the influence of said actuating means and said contact pressure securing means.

2. In a circuit interrupter, a pair of rigidly mounted separable contacts, an operating member, connecting means for moving one of said contacts upon movement of said operating member, means applying a biasing force to said connecting means adjacent said movable'contact for moving it to open position, means applying a biasing force to said connecting means remote from said movable contact for supplying contact pressure, and electro-responsive releasable means in soI said connecting means intermediate said two biasing means.

3. In a circuit breaker, relatively movable contacts, a switch member movable to open and to closed position to open and to close said contacts, means biasing said switch member to open position to quickly open said contacts, actuating means for moving the switch member to open and to closed position including a toggle and a means for securing pressure engagement of the contacts in the closed position of the contacts, trip means for immediately freeing said switch member from the influence of said actuating means and pressure securing means to cause separation and opening of said contacts independently of the position of said actuating means and pressure securing means.

4 In a circuit breaker, a fixed contact, a cooperating movable contact movable to open and to closed position, means biasing said movable contact to open position, actuating means for moving said movable contact to open and to closed position including a spring means for securing a pressure engagement of said contacts in the closed position of said movable contact, trip means for freeing said movable contact from the influence of said actuating means and from said spring means to permit movement of said movable contact to open position independently of the iniiuence of said actuating means and spring means.

5. In a circuit breaker, a fixed contact and a cooperating movable contact movable to open and to closed position, means biasing said movable contact to open position, actuating means for moving said movable contact to open and to closed position including a spring means for securing a pressure engagement between said contacts in the closed position of said movable contact, a latch member normally and releasably eiecting operative connection of said actuating means and spring means to said movable contact, and trip means for moving said latch member to release said movable contact from its operative connection to said actuating means and said spring means.

6. In a circuit breaker, a fixed contact and a cooperating movable contact movable to open and to closed position, means biasing said movable contact to open position, actuating means for moving said movable contact to open and to closed position including a spring means for securing a pressure engagement between said contacts in the closed position of said movable contact, a latch member normally and releasably effecting operative connection of said actuating means and spring means to said movable contact, and electroresponsive trip means operable in response to predetermined conditions for moving said latch member to release said movable contact from its operative connection to said actuating means and said spring means.

7. In a circuit breaker, relatively movable contacts, a switch member movable to open and to closed position to open and to close said contacts, means biasing said switch member to open position to open said contacts, actuating means for eiecting movement of the switch member to open and to'closed position including a spring means for securing a pressure engagement of said contacts in the closed position of the switch member, and means normally effecting an operative connection of said actuating means and spring means to the switch member including a latch member movable from a normal connecting position to a released position to release said switch member from operative connection to said actuating means and pressure securing means to permit opening of the switch member by its biasing means free from any influence of said actuating means and pressure securing means.

8. In a circuit breaker, relatively movable contacts, a switch member movable to open and to closed position to open and to close said contacts, means biasing said switch member to open position, actuating means for eiecting movement of the switch member to open and to closed position including a toggle, and a spring means for connection to said switch member, said spring means providing a pressure engagement of said contacts when the breaker is closed, and a releasable latch member normally effecting an operative connection of said toggle and spring means to said switch member, said latch member being movable to release said switch member from operative connection to said spring means to permit opening of the switch member by its biasing means free of any iniiuence by said spring means and toggle.

9. In a circuit breaker, relatively movable contacts, a switch member movable to open and to closed position to open and to close said contacts, means biasing said switch member to open position, actuating means for effecting movement of the switch member to open and to closed position including a toggle and a spring means for connection to said switch member, said spring means providing a pressure engagement of said contacts when the breaker is closed, and a releasable latch member normally effecting an operative connection of said toggle and spring means to said switch member, said latch member being movable to release said switch member from operative connection tosaid toggle and spring means to permit opening of the switch member by its biasing means free of any inuence by said spring means and toggle, said latch member being bodily shiftable by said actuating means during normal operation of said breaker.

10. In a circuit breaker, relatively movable contacts, a switch member movable to open and to closed position to open and to close said contacts, means biasing said switch member to open position, actuating means for eiecting movement of the switch member to open and to closed position including a toggle and a spring means for connection to said switch member, said spring means providing a pressure engagement of said contacts when the breaker is closed, and a releasable latch member normally effecting an operative connection of said spring means to said switch member, said latch member being movable to disconnect said toggle and spring means from said switch member to permit opening of the switch member by its biasing means free oi any influence by said spring means and toggle, said latch member being bodily shiftable by said actuating means during normal operation of said 1 breaker, and current responsive means operable supporting said contacts and said actuating means and said trip means to form a unit, means for removably mounting said unit on said base, said base being provided with a recess forming an interrupting chamber for receiving said contacts and pole pieces, and closure means for closing the interrupting chamber.

12. In a circuit breaker, a base, relatively movable contacts, actuating means manually operable to open and close said contacts, trip means operable to cause opening of said contacts including an electromagnet, said electromagnet being provided with pole pieces adjacent said contacts for aiding in extinguishing the arc formed during circuit interruption, a frame for supporting said contacts and said actuating'means and said trip means to form a unit, means for removably mounting ysaid unit on said base, said base being provided with a recess forming an interrupting chamber for receiving said contacts and pole pieces; and a closure means carried by said unit for covering said interrupting chamber when the unit is in mounted position.

13. In a circuit breaker, a fixed contact and a cooperating movable contact movable to open and to closed position, means biasing said movable contact to open position, actuating means for moving said movable contact to open and to closed position including a spring means for securing a pressure engagement between said contacts in the closed position of said movable contact, a latch member normally and releasably effecting an operative connection oi said actuating means and spring means to said movable contact, an electromagnetic and a thermally responsive trip means, each operable in response to predetermined conditions to move said latch member to release said movable contact from operative connection to said actuating means and said spring means.

14. In a circuit breaker, a base of insulating terrupting chamber, relatively movable contacts disposed in said chamber, actuating means for said contacts mounted on said base outside said chamber, means closing the open side of said chamber, a plurality of spaced and insulated arc-extinguishing plates disposed in said chamber, and means for moving the arc drawn between ysaid contacts during circuit interruption into said plates to extinguish the same, said base being provided with at least one auxiliary chamber disposed opposite said plates and joining the interrupting chamber throughv the spaces between the plates for providing a back pressure to cause the arc to penetrate deep into the spaces between the plates and remain there until extinguished.

15. In an air circuit breaker, a pair of spaced stationary contacts and a cooperating movable bridging contact, means forming a relatively small closed pressure chamber about said contacts, a plurality of spaced arc-extinguishing plates disposed in said chamber adjacent each stationary contact means for moving the arcs drawn between said bridging contact and the stationary contacts in opposite directions into said plates for extinguishing the same, and means for actuating said bridging contact from outside saidl chamber.

16. In a circuit breaker, a base of insulating material therefor provided with a recess forming an interrupting chamber, a breaker unit including a pair of spaced stationary contacts, a movable bridging contact, actuating means for the bridging contact, electromagnetic means having a pair of pole pieces disposed on opposite sides of the contacts and path of movement of the bridging contact for moving the arcs drawn between said bridging contact and stationary contacts outwardly in opposite directions, means removably mounting said breaker unit on saidy base so that said contact means and pole pieces are disposed in said recess, means closing said interrupting chamber, and a plurality of spaced and insulated arc-extinguishing plates disposed in said chamber adjacent each stationary contact into which the arcs are moved by said electromagnetic means.

17. In a circuit breaker, a fixed contact and a cooperating movable contact movable to open and to closed circuit position, means biasing said movablecontact to open circuit position, actuating means normally connected to said movable contact for moving said movable contact to open and closed circuit position including resilient means for securing a pressure engagement be- 'tween said contacts in the closed position of said movable contact, trip means for disconnecting said actuating means and said resilient contact x pressure securing means from said movable conmaterial provided with a recess forming an inf' tact to permit said biasing means to quickly move said movable contact to open circuit position.

18. In a circuit breaker, a xed stationary contact, -a cooperating contact movable to open and to closed circuit position, means biasing said movable contact to open circuit position, actating means for effecting movement of said movable contact to open and to closed circuit position including a means for securing a pressure engagement of said contacts in the closed circuit position of said movable contact, and trip means operable to immediately render said actuating means and contact pressure securing means incapable of exerting any force on said movable contact opposing movement thereof to open position by its biasing means.

KURT W'ULSTEN.