US959171A - Electric-circuit breaker. - Google Patents

Description

W. H. SCOTT. ELECTRIC CIRCUIT BREAKER.

APPLIOATIOII FILED DEO.23,1907.'

Patented May 24, 1910.

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Patented May 24, 1910.

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0 9 1 3 2 0 E D D E L I F N 0 I T A C I L P P A WITNE$$E$ ATTOR N EYS W. H. SCOTT. ELECTRIC CIRCUIT BREAKER. APPLICATION FILED DEO,.23,1907.

Patented May 24, 1910.

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ELECTRIC CIRCUIT BREAKER.

APPLICATION FILED DE'O.23,1907.

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Patented May 24, 11910 W. H. SCOTT. ELECTRIC CIRCUIT BREAKER, APPLICATION FILED 1): :o.23,19o7..v

Patented May 24, 1910.

5 sums-sum 5" ATTORNEYS W ILLIAM HARDING SCOTT, OF NORWICH, ENGLAND.

ELECTRIG-GIRCUIT BREAKER.

Specification of Letters Batent.

Patented May 24, 1910.

Application filed December 23, 1907. Serial No. 407,830.

To all whom it may concern:-

Be it known that I, WILLIAM Hsnnnvo $0011, a subject of the King of Great Britain and Ireland, of Gothic Works, Norwich, in

the county of Norfolk, England, electrical engineer, and whose post-oiiice address is Gothic Works, Norwich aforesaid, have invented new and useful Improvements in Connection with Electric-Circuit Breakers,

of which the following is a specification.

This invention relates to relay electric circuit breakers in which the main circuit is made by means of an electro-magnetically operated switch, the circuit being broken by the opening of the relay circuit.

I will describe my invention with reference to theaccompanying drawings,

Figure 1 is an elevation; Fig. 2 is a section on the line 1, 2, Fig.*1; Fig. 3 is a plan of Fig. 1; Fig. 4 shows the arrangement of the circuits; Figs. 5 and 6 are an elevation and vertical section respectively, of the dash pot; Figs. 7 and 8 show in plan and elevation respectively, a quick breaking modification ashereinafter described; and Figs. 9 to 13' represent modifications in the overload device for breaking the relay circuit and thus breaking the main circuit, the movable member being shown in different positions in Figs. 9 and 11.

I arrange the two switches A and B at opposite ends of an electro-magnet C. The switch contacts themselves I prefer to arrange as shown in Fig. 1, the actual circuit being broken principally at the top contact, which is provided with a magnetic blow-out with sparking contacts as shown. The lower end 0 each switch remains practically always in contact. When the upper end is away, the lower end may just leave; it does not matter whether it does or not, but on the switch being closed the motion at the lower end of course is very much smaller than at the up er end, as is apparent from the loca tion of the pivots. These brushes have very considerable springiness, and the small motion of the lower part is entirely, or almost entirely, taken up by this springiness.

I prefer the electro-inagnet C to be an ironclad solenoid with plungers c, c to which the switch frames sc, 2 are hinged, which plungers are attracted toward each other in the middle of the solenoid, although this electromagnetic arrangcn'ient may be of any other suitable description. 1 prefer to conmeet the two frames 1;, 23 by links D to make l i i the switches work simultaneously. This arrangement enables the two switches (which of course have full voltage between them) to be arranged at a maximum distance apart,

a and also enables the breaking portions of the switch to be arranged in separate compartnients Y, Y in accordance with my concurrent divisional application for a patent.

The iron-clad solenoid C, or its equivalent,

is Wound with fine wire in shunt to the mains, or it may be across a separate circuit as may be most convenient.

The overload operating device is shown in the drawings above the iron-clad solenoid C, and it consists of a device for producing a movable magnetic field in which the main current, passing through fixed conductors,

can flow. .ln the dra\\-'ing these conductors are shown on lheir respective poles F and G, the movable magnetic fields being at H, H and being induced by the electro-inagnet K, this elcctro-magnct being supported, on the ball-bearings Z, or their equivalent, in standards L. The coil of this electromagnet K maybe excited in any convenient way, though I prefer generally to put it in series with the switch-operating solenoid C. The magnetic fields H, H can, if desired, be produced by permanent magnets swung on anti-friction bearings. In the example illustrated, attached to part of this magnetic, or electromagnetic, system, is a bar it on the end of which 1s a pm If engaging a nected by a pin m to the end of a steel-yard P on which is a sliding weight 7) for setting the overload, and in connection with this steel-yard P, at its other end, is a circuit-breaking device R arranged primarily for breaking the circuit of the operating solenoid C. This circuit-breaking device preferably takes the form of a quick-break switch. The quick break may be effected follows: The end of the steel-yard P is connected by a pin 7% to a bracket Q and provided with a link 79 carrying a roller 7; acting on a forklcver r centered at r to. a bracket r on the pole F, the quick-break action being obtained by means of a spring 1' pulling beyond the center 9*. The last named details are, omitted from Fig. 2.

lVhen an excessive current flows through the conductors at F and G, or one of them, so that the force produced by the. magnetic fields, or field, at EH, H is sufficient to overcome the weight on the steel-yard P, then the circuit is broken at the lower end co of R, and the two main switches A and B are opened.

The link N underneath the pin k is connccted with a dash-pot S, which constitutes the time element, or retarding device. This I prefer to be a vacuum dash-pot of the type shown, comprising the dash-pot proper or cylinder S working "ver a plunger 8. The link N through which the cylinder is lifted. is provided with a valve head 8 which automatically closes the port in the head of the cylinder when the link N is actuated. In order to relieve the vacuum which results as the cylinder moves over the plunger, I arrange an opening 8 in the cylinder which permits the entry of air as soon as itcomes opposite the recess 8 in the plunger. This recess is cut at an angle to the axial plane of the cylinder, and thus afiiords means, by mounting the plunger on a pivot, for controlling the time of the dash-pot action, since by turning the plunger, the relative positions of the angular recess a and the opening 8 may be varied at will. Owing to the retarding action of the dash-pot, a suddenkick of overload, unless excessive, does not open the circuit breaker. The greater the overload, the less is the time lag. This overload arrangement forms an operating device which gives a force which is proportional to the current flowing at any point in the travel, the force increasing and decreasmg exactly with the main current. Wlth the ordinary solenoidal' overload device, as the plunger, or its equivalent, rises, the force exerted by a given number of amperes is very much increased, so that when ,once motion is started, the current has to drop down to a very large extent before this motion is arrested, and the consequence is that a sudden excess load may start the motion of the overload device, and this, b the time this very excessive load is remove has got into such a position that a comparatively small current will maintain suiiicient pull on the retarding device to make the circuit breaker go in a few extra seconds, any solenoidal arran ement of circuit breaker with a vacuum dasi-potretarder being open to the objection that it will, after it had once been started with a heavy momentary overload, or overload of short duration, only require a much smaller current than the normal to make it act. In the arrangement according to this invention, this de ect is overcome. and the magnet turning on its center will return to its right off position directly the current has dropped below the current at which it ought to start in motion. To assist this return, the vacuum d-ash-pot is fitted with a valve 8* which only retards in the one direction.

In the case of failure of voltage, of course,

.the circuit breaker comes out of itself, but

dead short from becoming very great.

With this object I arrange the iron pieces T, T T, T for the frames carrying the con tact brushes A and B (which are held in the iron frames a], 032 by means of clamping pieces of brass, or other non-magnetic metal ac so that when a very heavy current passes along these brushes, the projecting pairs of side pieces 2, 2 of the frames become magnetized. and. in'the case of very excessive current, there is powerful attraction between these projections .2 2", 2 and the pieces T, T T. T so that the switches are forcibly opened. Thisswitch obviously can be operated from a distance by means of the circuit of the operating solenoid C.

Referring to the diagram Fig. t the at tion of the relay circuits is as follows 2- The opening press-button w is normally closed so that there is a circuit from the main it through resistance V by the contact 7. through the coils C and K, then through the opening press-button w to the contact 10 which also is normally closed, on to the branch circuit a But as shown in the diagram, there is not a complete circuit right through from w to u. The break is at switch A. Now if this break be bridged momentarily by the closing press-button 10 the whole of this relay circuit is closed and a current flows in itsuliicient to so energize the magnetic plungers 0 and 0 as to close the switches A and 'B. Directly the closing of the large switch A is accomplished, the press-button w becomes unnecessary because it is short-circuilcd by A and press-button w can be released. The switch then keeps closed as long as there is a. certain voltagebetween w and u.

To open the circuit the opening pressbutton 10 is pressed momentarily. This breaks the whole relay circuit and switches A antl B open because there-is no current flowing in the coil C. This pressing ofthe opening-button to only requires to be momentary, because the switches A and B come out instantly, and when w is closedagain the relay circuit remains broken at the large switch A and cannot be closed again until the press-button w? is closed.

The ovei-loa .l-ope1'ate(l switch 10 acts in exactly the same way as the opening pressbutton at. It is in fact an opening pressbutton operated by the overload device.

The resistance V and the contact 4; are not really necessary parts of the apparatus; they are only utilized to economize the current used in the relay circuit. When the switch B is completely open, the contact a is closed, and theresistance V is short-circuited, so, that a current of a certain amperage flows through the coils C and K and the plungers 0 and 0 are powerfully attract-- ed, or ulled in toward one anotherin this articu ar construction. A smaller current. 'owever, is required for holding these switches in than for startingthem in, because the two plungers when they are home are closer together. The resistance V' is inserted, thereby reducing amperage of the relay current that is used.

Referring to the modification shown in Figs. 7 and 8, in place of the quick break arrangement hereinbefore described, I may employ a short-circuiting, or attracting,

iece of magnetic material, such as soft iron, in such'a position that it comes into ope ation, or exercises its influence, when the moving magnet is swung around to nearly its position of maximum deflection, the said moving magnet, except toward the end of its travel, being out of the range of influence of the said short-circuiting, or attracting,piece, but just before the said moving magnet attains the position to break the relay circuit, it comes under the influence of the said short-circuiting, or attracting, piece,

which causes it to make a sudden and definite jump, thus giving a quick break to the relay circuit.

, K is the shunt-wound electro-magnet, H, H, are themovable magnetic fields, and

F, G, the-conductors, as hereinbefore described.

H is a piece of soft iron secured in such a position that it beginsto exercise its influence on the movable magnet when near its maximum of deflection so as to cause the said magnet to make a sudden and definite jump and' quickly break the relay circuit by tact R".

pieces, being c'arried by a any suitable device, such, for instance, as an arm 72 secured to the magnet and provided with a piece ofinsulating materi'albearing on the spring arm .R carrying the con- The piece of soft iron H may be arranged in any other suitable position, such, for instance, as above the field H instead of below the field H or below one field and above the other.

In place of the arrangement hereinbefore described to break the relay circuit, I may use a U-shaped magnetic piece, or Ushaped magnetic pieces, which W1 1 embrace the conductor, or each conductor, this )iece, or these lever, or the equivalent, which will move when the U- shaped piece is, or U-shaped pieces are. at-

tracted by the-current in the conductor, or

conductors, and cause the breaking of the relay circuit. The following are suitable arrangements Figs. 9 and 10 are elevations at right anglcs to each other, and Fig. 11 is a vertical .ing-in catches.

section of a modification of the overload device for breaking the relay circuit with the movable member in a ditl'erentposition. The -relaybreaking switch is not. shown, but the breaking is plcsnmed to be e'tt'ected by the bell-crank lever p. The circuit-breaking device consists of two U-shaped magnetic pieces ll of soft iron connected to the opposite arms of a three-armed lever 71. capable of swinging on a center If mounted on a bar f secured to the conductor (1: so that when excess of current passes through the said con (luctor, the said U-shaped pieces pass over the conductor from opposite sides and the bell-cranklever is operated to, break the circuit. The third arm of the lever is con nected to a (lash-pot S which may be of the kind hercinbetore described. The movementof the lever is resisted by a coiled spring l, the tension of which can be altered as required by the nuts p through the intervention of the piece p (to which one entl ot' the spring is connected) being adjusted and fixed in llic slot f in the bar j", the other end of the spring being connected to the lever/z.

Fig. 12 shows, in elevation and transverse section, a similar arrangement but with a steel-yard l and adjustable weight thereon in place of a coiled spring. in this figure the projection ,r on the lever it directly acts on the contact maker lever It to break the relay circuit.

in Figs. 9 to 1;. l have shown a piece of soft iron ll" to bring the U-shaped pieces over quickly hcreinbetiore described with regard to Figs. 7 and 8.

The arrangements described can be used generally for causing the breaking of electric circuits, for example by releasing hold- I do not limit myself to the precise arrangements described, for example, the U-shaped pieces may embrace conductors on opposite sides after the manner in which they are en'ibraced by the arrangement, Fig. 1.

.I claim as my invention:

1. In a relay circuit breaker, a switch member, a relay circuit. controlling the same, means for :uilomatically breaking the relay circuit upon the occurrence of excessive current and electromagnetic means in connection with the movable switch member and said excessive current, for forcibly opening the main switch, substantially asdescribed.

2. in a relay circuit breaker, a relay circuit controlling .the switch member, means for automatically b -aking said relay circuit upon the occurrence of excessive current, a movable switch member of magnetic material-and means in connwtion with the magnetic licld produced when said excessive current flows through said switch member for forcibly opening the main switch, substantially as described.

'3. In a relay circuit breaker, a switch member and a relay controlling the same, means for automatically breaking the relay circuit, comprising a pivoted ,member and electromagnetic means for actuating the same upon "the occurrence of excessive current, and a contact member subject to the movement of said pivoted member, together with a piece of magnetic metal so arranged with relation to said pivoted member that its magnetic attraction for the latter comes into etlective action after said pivoted member has been partially actuated, to increase its movement and thereby effect a quick break or" the contact, substantially as described.

t. in a relay circuit breaker, a movable main switch i'nember, a relay circuit controlling the same and means for breaking the relay circuit upon the occurrence of cessive current whereby the main switch is opened, in combination with a magnetic member moving with the main switch memher and cooperating stationary magnetic members, said magnetic members being mutually attracted upon the passage of excessive current through said main switch membot whereby the switch is-torcibly opened, substantially as described.

in a relay circuit breaker, a movable main switch member, a relay circuit controlling the same, and a stationary magnetic member arranged within the magnetic field produced when an excessive current fiows in the main switch member, whereby the switch is forcibly openedupon the occurrence of excessiwc current. V

6. In a relay circuit breaker, means for automatically breaking the relay circa magnetic means for actuating the upon the occurrence of excessive current, and a contact member subject to the mov ment of said pivoted member, said eiectrcriagnetic means comprising a U-shaped piece of magnetic metal carried by said pivoted member and a stationary current carrying member embraced thereby upon the oscillation of said pivoted member, whereby the magnetic attraction for the latter is increased after said pivoted member has been partially actuated and a quick break of the contact efected, substantially as described.

In testimony whereof I have signed this specificatmn in the presence of two subscribing Witnesses.

ii itnesses P. Tr-rotmnss, RICHARD "-iortms.

i ARDING "0

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