US1809275A - Circuit breaker - Google Patents

Description

June 9,` 1931.'.

o. s. JENNIN'Gs CIRCUIT BREAKER Filed Nov. 14

WITNESSES:

ATTORNEY Patented June 9, 193.1` v

UNIT-ED STATES PATENT OFFICE p OLIVER S. JENNINGS, OF v WILKINS-BURG, PENNSYLVANIA., ASSIGN'OB T0 WESTTNG HOUSE ELECTRIC .AND MANUFACTURING COMPANY, .A CORPORATION F PENNSYL- VANIA CIRCUIT BREAKER Application led November 14, 1925. Serial N'o. 69,030.

My invention relates to electric switches .and particularly to motor-starting switches having means for protecting the circuit and apparatus therem against overload and short-circuit conditions.`

An object of my invention is to provide a ,motor-starting switch having a manually operated member that is automatically tripped to open position in response to overload conditions of the circuit after a predetermined period and instantly tripped in response to short-circuit or predetermined overload conditions.

In a co-pending a plication, of Hubert K. Krantz, Serial No. 52,336, filed November 26, 1924, which became Patent No. 1,726,233 on August 27, 1929, and assigned to the Westinghouse Electric and Manufacturing Company, a motor-starting switch is disclosed that is trip-free of the handle and is controlled by a bi-metal thermal element which releases the switch to open position in response to a predetermined duration of overload conditions. It is an object of my invention to render a switch, havin the characteristics embodied inthe swltch mechanism disclosed in the above noted application, instantaneously responsive to short-circuit or predetermined overload conditions.

These and other objects that will be made apparent throughout the, further description of my invention are attained by the switch mechanism hereinafter described and illustrated in the accompanying drawings, where- 1n Figure 1 is an elevational view of a switch mechanism yembodying features of my invention showing the switch arm in open position. A

Fig. 2 is a similar elevational view showing the switch arm in its tripped-open posilOIl.

- Fig. 3 is a transverse sectional view taken on the line III- III of Fig. 2 and illustrating a part of the switch mechanism-in end elevation, and

Fig. 4 is a diagrammatic isometric view of the apparatus, illustrating the manner nlland closed positions without interfering with which it is connected in an electric circuit.

Referring to the drawings, theswitch mechanism includes an insulating base 6 that and upon which the switch apparatus is mounted. Stationary contact members 7 and 8 are mounted upon an insulating projection 9 and are disposed on opposite sides of an insulating barrier 10. The contact members 7 and 8 constitute terminals of a circuit that is to be closed by a bridging switch member 11 that comprises a metal plate having two projecting contact arms 12 and 13 provided with contact members 14 and 15 which respectively engage the stationary contact members 7 and 8 when the switch member 11 is moved into the closed position. y

The switch member 11 is secured to an insulating switch arm 16 by means of rivets, and the switch arm 16 is pivotally mounted for oscillation upon a metal support member 18 that is, in turn, pivotally mounted for oscillation on a shaft 19 that is secured to the base 6. The supporting member 18 and the switch arm 16 may be considered as an articulated switch member, one portion of which is oscillated for opening and closing the switch for normal operations and both portions of which are movable to open the switch automatically in response to predetermined current conditions in the circuit controlled by the switch.

The supporting member 18 is stamped from a sheet-metal plate and is so formed that two similar portions, 21 and 22 (Fig. 3) are provided that are 'oined at their upper ends and have deep note es 23 of V-shape for receiving the switch arm 16 that is pivotally mounte for oscillation in the notches about a pivot point 20, as indicated in Figs. 1,2 and 3. The lower end of the supporting member is provided with otf-set cross-braces 24 which serve to prevent lateral displacement of the switch arm 16 with respect to the su port member 18. The switch arm 16 is provi ed with'a perforation 25 for receiving one end of an operating spring 26 and the switch arm is also provided with' a clearance slot 27 for permitting the switch arm to oscillate between open the spring.

The ot er'end of the spring 26 1s attached to an operating handle`28 that is pivotally mounted on the base 6 by means of a shaft 29. The operating handle 28 is provided with an free end of the thermal element 32 engages,

under normal operatingv conditions, a metal stop member 34 that is carried by, and insulated from, the support member 18, the stop member 34 and fastening means therefor be- 0 ing separated from the support member by a suitable insulating plate 35. The bi-metallic thermal element comprises a flat member made of two thin metal strips 36 and 37 (Fig. 1) that are welded together, the strip 36 having a greater co-etlicient of expansion than the strip 37, thereby causing the free end of the elementl 32 to move outwardly or away from the stop member 34 when the temperature of the elementfis raised to a predeter- 0 mined degree by an overload condition in the circuit.

Adjustment of the end of the thermal element 32 with respect to the stop member 34 for varying the time required for release of the support member 18 under overload condition may be'madeby loosening the screws 33 -and 40 and adjusting the angular position of the element.

During the normal operation ofthe switch,

current flows,.therefore, through the ther-y mal element and through the switch contact member ,ll'and contact members 7 and 8 to complete the circuit controlled by the switch.

The contact arm 11 is normally held in en *4 gagement with the contact members 7 and 8 bythe over-center spring 26, which contin- -ues to hold it in closed contact until the operating handle has moved the spring connected end of the bracket 31 beyond a central line traversing the points of engagement of the spring 26 with the arm 416 andthe pivot point 20, about which thel switch arm 16 oscillates.

The instant that the spring pivot point of thebracket 31 passes 'the said central line, the' over-center spring 26 causes the switch arm 16 to be moved to the open position shown in Fig;` 1 with a snap actiona vA return movement ofthe operatinghandle causes the-switch arm 16 to be moved, 0 with a snap action, to closed position after the spring pivot point of the bracket 31 has passed the line traversing the pivot points previously referred to. The movement of the handle is limited by the stop faces 46 and 47 provided in the insulating base 6,- Normal opening and closing operations of theA switch are accomplished by simply moving the opthat the free end thereof will-be moved out of engagement with the stop member 34 on the support member 18 after a predetermined duration of the overload. Thespring 26, irrespective of its position, exerts a pressure on the support member 18, tending tomove it to its inoperative or open position shown in Fig. 2. The instant that the stop member 34 clears the end of the thermal element 32, the support-member 18 is moved downwardly by the spring 26 connected to the switch arm 16.

During the downward movement of the support member 18,'the direction of application of force of the spring 26 on the switch arm 16 is shifted to move the arm to its extreme open position with respect to the support 'member 18, as shown in Fig. 2. This combined bodily and angular movement of the switch arm and the angular movement of the support member 18 causes a separation of the switch contact members 14 and 15 from .separation being greater, under such conditions, than the normal separation when the switch isactua-ted manually without movement of thel support member.

` The opening movement of the support member 18 is entirely independent of the positionof the 'operating handle, and, consequently, the circuit will be interrupted in response to overload conditions even though the handle be held in its closed position by the hand ofthe operator. The switch, therefore, is trip-free of the operating handle, and the operator can, in no manner, interfere with the automatic opening 'of the switch.

After the switch has been tripped to open position automatically, it may be restored or reset to normal operating position by moving the operating handle to open position, as shown in Fig. 1. The bracket 31 on the operating handle 28' engages an extension 48 on the portion 22 of the support member 18 and causes the supportmember to be'moved into lits operative position, as shown in Fig. 1, when the handle is moved to open position. The'bracket 31 also serves to limit the movement of the support member 18 when the member is moved to its inoperative position as shown, in Fig. 2.

' By reason of the construction above described, a single spring lserves to open, the switch under overload conditions or when the switch is actuated manually,`and the device is rendered trip-free of the handle withoiitthe necessity vof providing latches and triggers for connecting the operating handle to the switch member.

In order to cause the switch to instantaneously tri to open position, under short-circuit pre etermined overload conditions, the bi-metallic thermal element 32 is provided with an iron larmature 49 that is disposed adjacent to the core member 45 of the electromagnet 44 which, as indicated in Fig. 4, is connected in series with the thermal element 32 and the switch member 11. Slight overload current, such as the normal starting current, will not attract the armature to release the switch to open position but a short-circuit surge or a predetermined overload of greater value than the starting overload will cause the armature to be instantly attracted to the core and the switch will thus be tripped to open position. By placing the armature on the bi-metal member, that member is rendered vboth thermally and magnetically responsive to current conditions in the circuit.

As indicated in Fig. 4, the thermal element 32, electromagnet coil 44 and bridging'switch 11 are connected in series to the 'circuit 5, current passing from the conductor 4 of the circuit through the terminal screw 33, bi-metal strip 82, terminal screw 40, coil 44, conductor 41 terminal screw 43, contact member 8, bridgin switch 11, contact member 7, and termina screw 42, to conductor 5 of the circuit.

The electromagnet coil is so wound that it docs not effect movement of the armature except When overload conditions exceed those normally encountered in starting or normal operation of the machine operated by the motor, or when a short-circuit occurs. 'Over-V loads below the predetermined maximum value for which the coil is wound may endure for a predetermined time, determined by the characteristics of the bi-metal'element, before the circuit is interrupted by movement of the bi-metal element due to the heating thereof.

Consequently, starting overloads or overloads of short and harmless duration will not .cause the circuit to be interrupted, but the circuit will be interrupted instantly when the overload exceeds a predetermined maximum value or when a short circuit occurs.

While I have shown the electromagnet. and thermal element carryin an armature, associated with a switchin evice, such as illustrated and described, 1t is obvious that the combined thermal element and electroma net may function toecause tripping of any orm of switch or circuit-breaker mechanism. Y

-While I have illustratedv but one embodiment of my invention, it will be apparent o those skilled in the art that various changes modifications, f substitutions, additions an omissions ma be made in the apparatus illustrated witli'out departing from the spirit and scope of my invention, as set forth in the ap nded claims.

claim as my, invention:

1. The combination with a switch and a current-carrying thermalv responsive v element having one end movable for controlling'the switch and connected in series therewith and an armature on the movable end of the element, of an electromagnet connected in the circuit with the switch for actuating the thermal element under predetermined current conditions.v Y

2. The combination with a switch, of controlling means therefor comprising a composite unitary current-carrying element responsive to heating and magnetic characteristics of the current in the circuit controlled by the switch, the said element being affected thermally to initiate opening movement of the switch in response to an overload of predetermined duration and being affected magnetically to initiate instantaneous opening movement of the switch in response to a shortcircuit-current surge. l

3. The combination with a 'switch and a thermal element connected in' series therewith and having one endmovable in response to temperature changes thereof, of an armature carried by-the movable end ofthe thermal element, and an electromagnet connected in series with the thermal element for actuating the armature andthermal element.

4. A circuit breaker ycomprising a movable switch member and La current-responsive means for releasably retaining the circuit breaker in closed position comprising a bimetal thermal strip connected in series with the switch member and having one end movable and provided with an armature, and an electromagnet connected in series with the said thermal strip and the switch member for Vactuating the thermal-strip armature,

5. The combination with a quick-breakswitch, of a thermally-bendable element for latching said switch in closed position and a magnetically operable release device having a coil in -an electrical circuit with said element and having an armature directly associated with said element a'nd cooperating therewith to release said switch on excessive overload in the circuit. 6. The combination of a nick-break switch, abendable bimetallic lato normally holding the switch parts in closed-circuit positions andan electromagnet coil in series with the bimetallic latch for automatically bending said latchto release the switch on an excessive overload. f i

7. The combination with a quick-break switch, of a'bimetallic thermally-'operable latch, a magnetically-operable release means directly cooperatin therewith and a manu-V ally-operable switc member adapted also to move the vquiclr-breakswitch to latched'position.

8. The combination with a quick-break "switch, of a tli-ermally-bcndable latch, a niagiictically-operable release means for opertherewith for bending said latch gradually or instantaneously, depending upon the overloa-ds. l

10. A spring-pressed switch, element, a 'bendable member for latching said switch element in closed circuit-position, thermal means for bending said member to release the said switch element, and electromagnetically operated means in series with said thermal means for bending said member to release the said switch element.

11. A spring-pressed switch element, a bendablc latch for holding said switch-element in closed-circuit position, thermal means for bending said latch, electromagnetically-operated means for bending said latch and manually-'operable means for relatching said yswitch element, saidthermal means being operable lindependently of the resistance of said electroinagnetically-operated means.

- 12. A quick-.break switch construction including va spring-operated movable switch member, a thermally-bendable latch for holdy ing said switch member in closed position and for releasing said member under predetermined overload conditions, and an electromagnet having a coil in series with saidlatch and adapted to bend said latch to release said switch member on excessive overload in the circuit, regardless ofthe thermal condition of said latch.

13. A quick-break switch construction including a movable switch member, avbimetallic' latch for holding said switch member in closed` position under normal circuit conditions and for releasingsaid switch member onordinary overload conditions, and an electromagnet having a coil in series with said latch and having a 'direct operable connection to said latch to bend it and release said switch,

member on excessive overload conditions.

llfAquick-break switch construction iii-v A cluding a movable switch member, a thermally-bendable latch for holding said switch member'in closed position,` and an electromagnetvpositioned immediately adjacent said latch and having a coil,` in serieswith it and adapted to bend it to release said switch inemb er'on excessive overload conditions in the circuit, regardless of the thermalv action of said latch.

15. A quick-break switch construction including a spring-pressed switch member, a thermally-operable latch in the electrical eircuit for holgding said member in closed position under normal circuit conditionsand for unlatcliing said member under ordinary overloadconditions, and an electromagnetdirectly associated with said latch for bending it to unlatchsaid member in the event of a sudden excessive surge in the circuit:

16. An enclosed-switch construction including a movable switch member, a beiidable latch for holding said member in closed position, thermally-operable means for bending said latch to release said switch member, electromagiietically-operable means for bending said latch to release said switch member, and an externally-operable member servingas the only means for resetting said latch.

17. An automatic-Switch construct-ion including a spring-pressed movable switch member, a latch ffor holding said member in closed position, thermal means in the electrical circuit lfor slowly bending said latchv to release said switch, and electromagnetic x means for instantly bending said latch to release vsaid switch in response to a sudden excessive surge in the circuit.

18. An automatic-switch construction including a movable switch member, a thermally bendable latch for holding said member in closed-circuit position under 'normal lcircuit' conditions 'and for releasing said switch member on ordinary overload conditions, an armature carried by said latch, and an electromagnet cooperating with said armature to bend said latch to release said switch under excessive overload conditions.

19. An automatic-switch construction including a movable switch member, a bimetallic thermally-bend'able latch in the electrical circuit for normally holding said member inl closed-circuit position and having a free end, and an electromagnet adapted to bend the free end of said latch to release said switch member in the event of .a short circuit or sudden excessive overload in thecircuit.

20. An enclosed-switch construction including a box, a switch within the boxand an external operating handle for said switch, the said switch including a. movable contact member, a thermally-bendable latch for holding said contact member in closed position iio under normal circuit conditions and to re-l lease said contact member under other predetermined circuit conditions, and an electromagnetadapted to bend said latch to re! lease said cont-act member in response to a sudden excessive overloading of the circuit controlled by said contact member.

21. In an electric switch, an insulating body, a switch member pivotally mounted thereon, a spring for moving vsaid switch.

member to open-circuit position, a bimetallic thermostatic latch member supported by said body and having one end engaging said switch' member to hold the same in closedf circuit position, ,the other end of said thern mostatic latch member being bifnrcated, an electromagnet coil having two terminals, one yof which is directly connected electricall t0 f one part of said thermostatic latch mem r,

a circuit terminal, and a stationary contact electrically connected to the other terminal of said coll. i i lo 22. The combination, in a nick-break switch, of a springressed switc 4`member, a movable bimetal ic thermostatic latch therefor, and an electromagnet coil in series with said thermostatic latch, said latch being releasable from closed position by leither thermostatic action or by magnetic action.

23. The combination, in a quick-break switch, of a s ring-pressed switch member, a bimetallic t ermostatic spring latch for 2o holding said switch member in closed position, and an electromagnet in series with said switch member and with said'latch, said latch being operable both thermally and magnetically. I

24. The combination of an automaticallyoperable switch member, a thermostatic element for latching said member, and electromagnetic means for releasing said latclng element, a manually-operable switch member, and means of connection between said switch members whereby said automatically-operable switch member may be reset b a circuitopening movement of the manu y-operable switch member. Y

In testimony whereof, I have`hereunto subciied my name `this 11th day of November,

OLIVER S. JENNINGS.'

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