US946220A - Circuit-breaker. - Google Patents

Description

UNITED STATES PATENT OFFICE.

ED WARD M. HEWLETT, OF SCHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NET-V YORK.

: CIRCUIT-BREAKER.

Specification of Letters Patent. Patented J an, 11 191() Applicationfiled-Uuly 29, 1907. Serial No. 386,052.

To all "whomit may concern:

Be it known thatI, EDWARD M. HEWLETT, a citizen of the United States, raiding at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Circuit-Breakers, of which the following is aspecification.

My invention relates to circuit breakers which open automatically upon the occurrence of abnormal current, and more par ticularly to circuit breakers provided with time limit tripping mechanism which opens the circuit breaker only when the abnormal current persists for a predetermined length of time.

In many systems of electrical distribution and particularly in railway systems, it is desirable to have the circuit breakers open in case a moderate overload persists for a predetermined length of time, and to open instantly when a very severe 'overload, as a short circuit, occurs, while the circuit breakers should be capable of being immediately reset after they have been tripped automatically. Various types of time limit mechanism giving a predetermined time lag have been-devised and applied to circuit breakers, but those which permit the immediate resetting of the circuit breaker are usually complicated and expensive. A thermal expansion device, such as an expansion strip heated by the passa e of current through it, is a very simple an efficient type of time limit device not heretofore available for use'on circuit breakers, because when heated by abnormal current it trips the latching mechanism of the circuit breaker, and will not permit the return of said mechanism to position to hold the'circuit breaker closed until the thermal device has cooled down to its normal temperature, and this'interferes with the service of a supply station.

The object of my inventionis to provide a time limit tripping mechanism having a predetermined time lag arranged to permit the circuit breaker to be immediately reset after having been automatically tripped, re-

gardless of the type or position of device. used to secure the time lag, and which will instantly open'the circuit breaker in case a predetermined, highly abnormal current flows in the circuit.

In carrying out my invention, the circuit breaker is opened by a time limit trip mechanism, having a predetermined time lag and so related to the circuit breaker that when the current in the circuit is normal, the tripping mechanism is unable to have any efiect whatever upon the circuit breaker, while cooperating mechanism quickly responding to .the amount of current in the circuit is arranged to maintain the trip mechanism in operative relation to the circuit breaker only while the current is abnormal. As soon as the circuit is opened, or the current drops to the normal amount, the tripping mechanism instantly becomes inefiective, and the circuit breaker may be immediately reset and will stay closed. The mechanism which instantly responds to current is also so arranged that it will respond to current beyond a predetermined amount and trip the circuit breaker directly and instantly of a well known type to which my tripping mechanism is applied; Fig. 2 a view oft-lie device for rendering the tripping mechanism efiective and for also instantly tripping the circuit breaker; and Fig. 3 a sectional viewon the line 3, 3, of Fig. 2.

My improved tripplng mechanism is capa l r I ble of many uses, and I have shown it applied to a well known form of circult breaker carried upon any suitable base or support 1, and comprising fixed studs or icontacts 2 and 3, between which the circuit is closed by means of a bridging contact 4 and shunt cdntacts 5. The bridging contact is carried upon a pivoted arm 6 actuated by an operating handle 7 which is pivoted to the arm 6, and also to a link 8 pivotally secured to the base 1 to form a toggle, by

means of which the bridging contact 1S forced into engagement with the studs 2 and 3'. The circuit breaker is held closed by latching means consisting of a lug 9 on the operating handle 7 engaged by a latch 10 pivoted on the arm 6.

The time limit tripping mechanism for,

the circuit breaker may assume various forms, and in the form shown in the drawings the latch 10 has a movable member or link 11 pivoted to one end thereof and connected by means of a rod 12 to any suitable form of actuating means having a predetermined time lag. The simplest is a thermal expansion device, and I have shown in the drawing an expansion bar 13 connected in series in the circuit between the stud 3 and a stud 1 1 connected to one of the leads of the circuit. The rod 12 is adjustably connected to the expansion bar 13 by means of an adjustable connection 15. The parts are so proportioned that when the current is normal, the parts are in the position shown in Fig. 1, while an abnormal current causes the bar 13 to expand and swing the member 11 to the left. This movement of the member 11 will not actuate the latching mechanism and open the circuit-breaker unless the free end of said member engages with a relatively stationary lug or button, which will cause the swing of said member to exert an upward thrust tending to turn the latch 10.

The tripping mechanism is normally in inoperative relation to the circuit breaker, since the expansion bar 13 can affect the latch 10 only through the pivoted arm 11, and to render the time limit mechanism capable of actuating the latch 10, there must be provided a device instantly responsive to current, and so set that when the current becomes abnormal, the movement of the arm 11 is effective to shift the latch 10 and open the circuit breaker. Any suitable means may be used for this purpose, but the device which I prefer is shown in Fig. 2, and comprises a yoke 16 surrounding the stud 3 and forming an electromagnet having a pivoted armature 17 adjustably held with relation to the yoke 16 by a calibrating screw 18 carried in a lug l9, and instantly responsive to the current in the circuit. The device is so calibrated that when the current is normal, the armature is in the position shown in full lines, and has no influence on the relation of the trip mechanism to the circuit breaker, while when the current becomes abnormal, the armature is lifted into the position shown in dotted lines, where it renders the actuating means or expansion bar 13 able to operate the trip mechanism and thereby trip the circuit breaker. When the armature reaches the position shown in dotted lines it encounters a yielding stop, shown as a pin 20, slidably mounted in the lugs 19 and 21, and held in normal position by a spring 22 of such strength that an abnormal current of moderate amount cannot cause the armature to move the pin 20 against the spring 22, while an abnormal current of excessive amount causes the armature 17 to be attracted so strongly that it compresses the spring 22 and moves into' engagement with the lug 19.

In order to render the time limit device or actuating means 13 effective to move the latch-10 when an abnormal current is flowing in the circuit, the armature 17 is provided with a lugs23 having an inclined surface 24 arranged to cooperate, when the armatureis in the position shown by dotted lines, with a corresponding inclined surface 25 on the arm 11. As the arm 11 is moved to the left by the expansion of the time limit actuating device 13, the inclined surfaces 24 and 25 engage, with the result that the arm 11 is moved upward, thereby turning the latch 10 until the lug 9 is released, whereupon ,the circuit breaker'opens. The time lag, or length of, time which lapses between the occurrence of the abnormal current, which brings the armature to the position shown in dotted lines, and the release of the lug 9 by the latch 10, depends upon the rate of expansion of the bar 13. As soon as the circuit is opened or the current becomes normal, the armature 17 drops back to the posi-.

tion shown in full lines, and the trip mechanism is in inoperative relation to the circuit breaker and no longer able to have any effect upon the position of the latch 10, which thereupon returns to the normal position shown in Fig. 1 and is ready to hold the circuit breaker closed as soon as the breaker is reset.

In order to open the circuit breaker instantly, in case an-excessive abnormal current of predetermined amount flows through the circuit, the arm 11 is provided with a surface 26 arranged to cooperate with a lug 27 on the armature 17, and also to cooperate with asurface 28 on the lug 23. If the expansion device 13 is cool and the arm 11 is in the position shown in Figs. 1 and 3, an excessive abnormal current will cause the armature 17 to move upward, compressing the spring 22 and bringing the lug 27 into engagement with the'surface 26 of the arm 11, thereby directly and positively moving the latch 10 to open the circuit breaker. If the circuit breaker has been tripped as a result of the expansion of the bar 13, and the bar is still hot, the arm 11 will have been swung to the left to such an extent that the surface 26 is more or less in line with the surface 28 of the lug 23. If the circuit breaker is reset, therefore, immediately after having been tripped by the action of the time limit device, and another overload occurs before the expansion bar 13 has cooled down to normal temperature, the arm 17 will be attracted, the surface 28 of the lug 23 will engage the arm 11, and therebythe armature 17 will positively move the latch 10 to release the breaker to open the circuit breaker.

In a circuit breaker constructed in accordance with my invention, the trip mechanism can affect the circuit breaker only during the period the current is abnormal, and is rendered ineffective the instant the current ceases or is reduced to normal. When the current is normal, the circuit breaker can be closed without regard to the position of the time limit mechanism, and where a thermal device, such as an expansion bar, is used to obtain the time lag, the breaker can be reset while the expansion device is hot, with the result that while the expans ion device remains hot, the circuit breaker will open on any overload without any time lag, because the arm 11 is held in extreme ,position to the left by the heated expansion bar 13, and as soon as the armature 17 moves into the position shown in dotted lines, it will engage the arm 11 and open the circuit breaker. As long as the expansion bar 13 is cool, however, the circuit' breaker will trip with a predetermined time lag on abnormal current; and will trip instantly when the abnormal current exceeds a redetermined amount; while it can always e immediately reset after having been tripped automatically either by the time limit mechanism or by the armature 17 My invention may be embodied in many other forms than that shown and described, and I, therefore, do not wish to be restricted to the precise form disclosed, but intend to cover by the appended claims all changes and modifications within the spirit and scope of my invention.

What I claim as new and desireto secure by Letters Patent of the United States, is,-

' 1. In a circuit breaker, the combination with tripping mechanism controlled by athermostatic device, of means responsive to abnormal current of predetermined amount for actuating said mechanism instantly and for cooperating with said thermostatic device in response to abnormal current of less amount to cause said device to actuate said mechanism and to permit the circuit breaker to be reset immediately after having been tripped by said thermostatic device.

2. In a circuit breaker, the combination with tripping means controlled by a thermostatic device, of means for. actuating said mechanism instantly in response to current which exceeds in amount-a predetermined limit and for cooperating with said device in response to current between said predetermined limit and a lower limit to cause said device to actuate said mechanism and toof a tripping mechanism comprising an element slowly movable in response to excess current and normally without effect on sa d tripping mechanism when moved, and a second element quickly movable in response to excess current into a position to cooperate with said first element and cause the movement thereof to trip the circuit-breaker dur ing excess current.

4. In a circuit breaker, the combination with a latch for locking the circuit breaker closed, of a thermostatic deviceresponsive to current and amagnetic device for actuating said latch instantly in response to abnormal current of a predetermined amount and for cooperating with said device in response to current of less amount to cause said device to actuate the latch and to permit resetting of the circuitbreaker irrespective of said thermostatic device. I

5. The combination. with an automatic circuit-breaker comprising a latch, of a latch actuating member normally movable without effect on said latch, a time limit device responsive to current for moving said member, and an overload device arranged to cooperate withsaid member on one degree of overload to cause said member to actuate the latch and thereby trip the circuit breaker, said overload device being arranged to positively move said latch to open said circuit-breaker instantly on another degree of overload.

6. In a circuit-breaker the combination with a trip mechanism, of actuating means therefor movable with a predetermined time lag in response to variations of current and normally without effect on said trip mechanism, and means instantly responsive to variations of current for causing the movement of said actuating mechanism to actuate said trip mechanism when the current exceeds a predetermined amount, said means being arranged to positively trip the circuit-breaker when the, current exceeds another predetermined amount.

7. In a circuit-breaker the combination with a trip mechanism for the circuitbreaker, of actuating means therefor movable with a redetermined time lag in response to variations of current and normally without effect on said trip mechanism. and

a member moved by abnormal current to cause said actuating mechanism to operate said trip mechanism, said member being arranged to permit the circuit-breaker to be instantly reset irrespective of said actuating mechanism after the circuit breaker opens.

8. In a circuit-breaker the combination with a latching mechanism, of actuating .means for the latching mechanism responsive with a predetermined lag to variations of current and normally without effect on said mechanism, a member movable into a predetermined position to render said actuating means operative upon said latching mechanism, and means responsive to current for moving said member into said position.

9. In a circuit-breaker the combination with a latching mechanism, of actuating means for the latching mechanism responsive with a predetermined time lag to variations of current, connections whereby said actuating means is normally responsive to current Without efi'ect on said latching mechanism, a member arranged to cooperate with said connections to render said actuating means operative to move said latching mechanism while said member is in a predetermined position, and an electromagnet energized by abnormal current to move said member into said position.

10. In a circuit-breaker the combination with a trip mechanism, a current'responsive actuating means normally movable without effect upon said trip mechanism, a movable member for rendering said actuating mechanism effective to move said trip mechanism when in one predetermined position and for positively tripping the circuit-breaker when in another predetermined position, yielding restraining means for stopping said member in the first position, and means responsive to variations in current for moving said member.

11. In a circuit-breaker the combination 'with a trip mechanism, of current responsive actuating mechanism normally movable without effect on said trip mechanism, a movable member arranged to render said actuating mechanism operative to move said trip mechanism when said member is in one predetermined position, said member being arranged to positively trip the circuitbreaker in another position, a yielding stop in engagement with said member to hold it I in the first position, and means exerting a force proportional to the current for moving said member.

12. In a circuit-breaker the combination with a latching mechanism, of a current responsive thermostat for controlling said mechanism'and normally out of operative relation to said mechanism, whereby expansion of said thermostat. is without effect on said mechanism, and means for actuating said latching mechanism instantly in response to current which exceeds a predetermined limit and for maintaining the thermostat in operative relation to the latching mechanism only while abnormal current which does not exceed said predetermined limit is flowing in the circuit, whereby the circuit-breaker may be latched closed when the current is normal and while the thermostat is heated.

'13. In a circuit breaker, the combination with a latch, of a normally ineffective op-' with a latch, of a thermal device responsive to current, normally ineffective actuating mechanism for the latch comprising a member connected thereto and controlled by the thermal device, a second member movable into position to be engaged by said first member to render it effective to move the latch, and an electromagnetic device responsive to abnormal current for moving said second member.

15. In a circuit breaker, the combination with a latch, of an arm pivoted to the latch, a thermostat responsive to current connected to said arm to swing it about the pivot, an armature adapted to be engaged in a predetermined position by the end of said arm to actuate the latch, a stop for holding the armature in said position, and an electromagnet for holding said armature in engagement with said stop when an abnormal current is flowing.

16. In a circuit breaker, the combination with a latch, of a movable arm for actuating the latch, a thermal device responsive to current for moving said arm, an overload device comprising an armature for cooperating in one position with the arm to enable it to actuate the latch and for directly cooperating in another position with the latch to move it, a yielding stop engaged by the armature to hold it in the first position, and an electromagnetic device for moving the armature into engagement with the stop upon the occurrence of a predetermined excess of current andinto engagement with the latch upon the occurrence of a different predetermined excess of current.

17. In a circuit breaker, the combination with latching means for holding the circuit breaker closed, of athermostatic device for tripping the circuit breaker normally in inoperative relation to said means, an electromagnetic device responsive to one predetermined excess of current to maintain the thermostat in operative relation to the latching means and to a different predetermined excess of current to positively actuate the latching means.

18. In a circuit breaker, the combination with a latching means for holding the circuit breaker closed, of a thermostatic device normally'in ino erative relation to the latching means, an means for maintaining the thermostatic device in operative relation to the latching means during a predetermined excess of current and for actuating said latching means instantly in response to a greater excess of current.

In witness whereof, I have hereunto set my hand this 22nd day of July, 1907.

EDWARD M. HEWLETT.

Witnesses BENJAMIN "B. HULL, HELEN ORFORD.

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