US2424909A - Circuit interrupting device - Google Patents

Description

July 29, 1947. F. a. ADAM ETAL 2,424,909

' CIRCUIT INTERRUPTING DEVICE Fil-ed Dec. 30.' 1942 4 Sheets-Sheet 1 522 52 98" o zo /7 A 24 /I/ r, 2 60 58 22 22 1s A 24 Inl/[Alfani Ersten/cx Auw /oya .5. Gauw Haw/w M .Sr/561.112

me. agn'rry July 29,1947.- F, B ADAM ETAL f 2,424,909

CIRCUIT INTERRUPTING DEVICE Fnednec. so, 1942 4 sneetssneet 2 l @TRE ,sa/5# Fla/.52 55' 550m/cx AMM fiom GREEN HE/var M r/fcL/Tz lJuly 29,1947. F, B, ADAM Em z,4z .4,sm9`

CIRCUIT INTERRUPTING DBVIE Filed DW. 30. 1942 4 Sheets-Sheet 3 Bunaxblw me July 29, 1947. F. a. ADAM Erm. 2,424,909

' cmcul'r In'rnnnur'rme Dnvrc Filed Dec. 50, 1942 4 Sheets-Sheet 4 y Y/ 4 I u Wren/rana Ernia/ck AMM BYQMMM-Arr'x Patented July 29., 1.947

CIRCUIT IN'IVEBBUPTING DEVICE dreamer n. Aam, st. Louis county. and Floyd S. Green and Henry M. Stieglitz, St. Louis, Mo., assignors to Frank Adam iilectric Company, St. Louis, Mo., a corporation o! Missouri Application December so, 1942, serial No. 410,680

This invention relates to improvements in circuit interrupting devices oi' a .type shown in the patent to Frederick B. Adam and Henry M. Stieglitz, No. 2,328,767, dated Sept. 7, 1943.

It is an object of this invention to provide an improved enclosed switch or circuit breaker.

The circuit breaker of this invention is shown equipped with a iioating type contact which is self-cleaning and will not freeze or stick.

Provision is also made for a magnetic type arc quencher with pole pieces properly positioned to aid in extinguishing the arc formed by the opening of the contacts.

The invention also provides means for the escape of gases from the bottom of the circuit breaker enclosure where a specially formed .piece of nbre prevents the ame o! the arc from escaping outside of the enclosure, but nevertheless permits gas pressure relief.

Further improvements for protecting the thermal element against excessive heat of the arc are also shown.

The circuit breaker of this invention provides a method of utilizing the. magnetic eld created by short-circuit currents to aid the thermal element in quicker tripping of the breaker.

Other objects and advantages of the invention will become apparent'from the following detailed description and the accompanying drawings. Several preferred forms of the invention are shown in the accompanying drawings and hereinafter described, but it is understood that the drawings land accompanying description do not limit the invention to the' forms there shown and here described, but that the invention will be dened by the appended claim.v

In the accompanying drawings:

Figure 1 is a longitudinal sectional view of a circuit breaker embodying this invention. The

s breaker is in the "on" position.

- views of the bottom oi the circuit breaker, showing the paths provided for the escape of gases, Figure 19 showing the normal pomtion of parts 1 cuan. (ci. zoo-ss) 2 and Figure 20 the change in position of parts to allow the escape of gases.

Figure 21 is a bottom plan view of the circuit breaker, y

Figure 22 is a longitudinal sectional view of the circuit breaker with the breaker in the "tripped" position.

Figure 23 is a longitudinal sectional view oi' the circuit breaker provided with an alternative form of enclosure. The breaker is here shown in the on position.

Figure 24 is the same view as Figure 23 with the breaker in the manual oil position.

Figure 25 is the same view as Figure 19 with the breaker in the tripped position.

Referring now to the drawings, 20 is `a housing or enclosure which is formed of molded plastic or other suitable material. The material is formed to provide walls 2l surrounding cavities 22 in which the operating parts are positioned. A contact carrier 28 is guided and maintained in position for sliding movement in adirection longitudinal `of the housing, by the inner walls 23. The housing as shown is formed of two substantlally identical half sections. The contact carrier is provided with a transverse bar 28. The transverse bar may be pivotally supported for rotation about a pivot 30. A cam surface 32 is provided on one end of the transverse bar and on the other end a projection 34 may be provided. An operating handle 36, which may be formed of a molded insulating material, is provided with openings 31 which are journaled on pivots 39 formed on the housing. The molded handle is provided with a portion 38 which acts as a follower in co-operating with the cam surface 32 of the transverse bar. A bump or projection 35 is provided on the handle for a, purpose later to be described. The contacts I9 and il are the make and "break contacts of the device. The contact 40 is the movable contact and iscarried by the contact carrier 26.

An optional form of handle 3| is shown in Figure 9. In this form of handle a slot 33 replaces the bump 35. on handle 36. Either the bump or slot in co-operation with the cam surface 32 provides snap operation and aids in holding the handle in position.

The contact 4U is part of an assembly shown in detail in Figure 17, consisting of the bimet'allic element 42, a strip ol' fibre or insulating material M, a mounting piece 46 and a soit-iron U-shaped member 46. The libre strip I4 is not always necessary and may be omitted if desired. A dowel pin |02 may extend through the member 48 and bimetal 42 and serves to locate them properly while they are welded together. The copper braid 41 may then be welded to the assembly in the position shown. The assembly shown in Fig. 17 is mounted between the two half sections of insulating material of the contact carrier to form the completed contact carrier shown in Fig. 18. The rivet 52 extends through the hole shown in member 46 and the slot 50 positions member 44. The thermal element 42 extends along the outside of the insulating half sections as can be seen in Fig, 1. The contact carrier is biased in the open position by a spring 54 secured to the contact carrier at one end and to the housing at the other end by slipping it over a projection 56 which is formed integral with the housing.

Copper braid 41 electrically connects the thermal element with a terminal piece 49 shown in detail in Figure l5. Figure 16 shows an optional form of terminal piece which may replace that shown in Figure 15, provided with a screw 5l which co-operates with a cavity 53 formed in the terminal piece to clamp a wire therein.

The terminal piece shown in Fig. l5 has a cable receiving portion 55 provided with a screw 51 to clamp a cable or wire in an opening passing through the cable receiving portion under the screw 51. The construction of the braker makes it possible to substitute one type of terminal for another without changing the relation of the other parts, thus the terminal shown in Fig. 16 is easily used instead of that shown in Figure 15.

Formations 58 are provided (Figs. 1 and 5) in the insulating material to receive and position the terminal piece 49 which may be easily slid into position when the circuit breaker is assembled.

A soft iron armature 60 is positioned in a recess or slot 62 formed in the housing. The iron piece 60 serves as an armature for the magnet 48 on the transverse bar as shown in Fig. 5, whereupon it projects through the opening and is visible from the front face of the circuit breaker. 'I'he indicator is formed of a colored plastic.

The contact 4l is secured to a floating contact strip 10 which is guided and maintained in position by projections of ythe insulating material of the housing (see Fig. 5). The strip 10 is pivoted on a projection 12 of the housing and is biased towards the on position and away from the bottom of the housing by a spring 14. The projections 16 and 11 limit the upward movement of the strip 10. A piece of copper braid connects the contact strip 10 with a terminal member 80. The terminal member 8U may be any one of a number of types depending on the particular application of the circuit breaker.

A detailed View of the floating contact strip 10 is shown in Fig, 10. The notches 92 co-operate with projections or walls 94 (see Fig 5) to hold the strip in proper operating position. The projection 12 acts as a pivot point `so that the contact strip 10 moves in an arc rather than rectilinearly. This is done for the purpose of providing a sliding self-cleaning Contact between the movable contact 40 and the contact 4l. As the contact 40 moves rectilinearly and the contact 4| can move only in an arc, then a sliding action must take place between them.

c In Figures 6, 7, and 8 are shown various substitutes for the terminal member 8l) shown in Fig. 6. In Fig. 6 the terminal member 80 is provided with an integral clip portion 62 which makes it possible for the individual circuit breakers of an assembly to be connected with the line bus bar by merely clipping them onto the bus bar. In Fig. 7 is shown a. terminal equipped with a wire or cable connector 84 which is provided with a screw 86 which clamps a wire when inserted in the opening 86 shown in dotted lines. In Fig. 8 is shown a terminal equipped with a screw B9 which co-operates with a concave portion 90 of the terminal to secure a wire therein.

A straight spring 96 projects into the recess 98 of the handle at one end and at the other end is held in a recess |00 formed in the insulating material. This spring biases the handle in the off position. Because it is diilicult to mold a narrow slot in the housing the recess |00 was formed as shown, of two relatively wide recesses offset from one another. This in effect provides a narrow slot at the oil'set.

Manually, the circuit breaker operates essentially as that described in the prior patent referred to above. On short-circuit however, the automatic tripl action is considerably improved.

The handle 36 is normally used to open and close the circuit. This is accomplished by the follower portion 36 on the handle engaging the inclined portion 32 of the transverse bar and thus forcing the bar to the on" position against the bias of the spring 54. The contact 40 engages the contact 4I by means of a sliding engagement as previously described, which insures that the contacts will not stick or freeze When the handle is moved in the opposite direction the contacts are separated by the spring 54. It can be seen that the indicator 64 is raised from the face of the circuit breaker housing whenever the Contact carrier 26 is in the open position as shown in Fig. 5.

Should the current through the breaker become excessive, then the circuit breaker is tripped by action yet to be described and the parts assume the position shown in Fig. 22. The path of current is normally through the terminal 8D, the copper braid 1B to the contact strip 'l0 and contact 4|, thence to the movable contact 40 and bimetal 42, copper braid 41 and terminal 49.

The tripping of the circuit breaker may be brought about by either one of two causes or by a combination of these two causes. Thus, if the bimetallic element 42 is heated by a high abnormal current for a short time, or by a lower abnormal current for a longer period of time, it

will be distorted int'o the position shown in Fig. 22 and allow the projection 34 of the transverse bar to slip out from under the member 48 and allow the contact carrier 26 to move to the open circuit position.

Should a. short circuit occur, the heavy rush of current which flows through the bimetal and braid will create a strong magnetic field which will magnetize the soft iron magnet piece 48,` and the fixed member B0, causing them to be attracted to each other. be pulled 01T of the projection 34 which will allow the circuit breaker to open.

The magnetic trip action will operate the breaker faster in case of a short circuit than the thermal element alone and hence is desirable in operating the circuit breaker on short circuits.

It can thus be seen that the magneticl action accelerates the thermal action on short-circuits. While the thermal element is becoming distorted because of the temperature rise the magnetic ac- This will cause the member 48 to ing which may tion due to thel short-circuit currents accelerates the distortion of the thermal element and the breaker opens. O n ordinary overloads themagnetic action has little or no effect and the breaker operates as an ordinary thermal breaker.

Details of the magnetic member 48 vare shown in Fig. 12 and the armature 60 in Fis. 13.

The contact `4| is effectually inclosed bythe walls of the insulating rhousing which surrounds it, as can be seen from Figures 1 and 5. Under this contact however, there is provided an opening in the housing (see Fig. 21.) This opening is closed by a piece of fibre identified in these iigures by numeral |05. This piece of fibre fits in` slots |01 at the bottom of the housing. Thus after an arc is formed on the breaking of a short circuit, the gases may escape by following the path shown in Fig. 20 to the outside. Their contact with the fibrous material helps c`ool them and subdue them so that they do not reach to the outside at a high temperature. By inspection of Figures 19 and 20 the'action of the gas pressure in forcing the fibre piece downto allow exit of the gases may be followed.

It can be seen that the terminal member 49 is mounted in a sloping lposition and enclosed on each side by a portion of the plastic housing. The sloping of the terminal makes it easier for the wireman to connect Fig. 18) will not interfere therewith when it is in the closed circuit position.

vIt can thus be seen thatfa. circuit breaker is provided which will have an improved operating characteristic on short circuits. A magnetic trip action has been added to aid and accelerate the action of the thermal element on short circuit and yet not interfere with the action of the V v thermal element on prolonged overloads.

An arc quencher is provided to limit the extent of the arc and to reduce the peak current reached before the breaker opens.

A self-cleaning contact insures against failure because of frozen contacts.

Figures 23,24 and 25 show ,on, "manual ot!" and tripped positions of another forrm of the circuit breaker of this invention. rThe breaker here shown is arranged more compactly in a housbe introduced into the ordinary This makes it possible for ordinary be replaced by switches embodyswitch box. wall switches to the wire to this terminall when it is enclosed on the other sides as this.

ing circuit breaker protection. The samenumerals are used with this embodiment as the operation of the breaker is identical. The position of the terminal 80 is slightly diierent.

We claim:

In an automatic circuit breaker of the enclosed type, a housing of insulating material, a contact positioned in said housing, a contact carrier mounted for sliding longitudinal movement in the housing, a contact aiil'xed to the contact carrier, a transverse bar pivoted to the contact carrier for rotary-movement relative to said contact, means biasing the contact carrier to open circuit position, manual means for depressing one end of the transverse bar to move the contact carrier to closed circuit position, a thermal element carried by ing the other end of the transverse bar to hold it against rotation relativefto said contact, said thermal element being adapted to warp when the current through the circuit breaker exceeds a predetermined value and allow the release of the end,

Y of the transverse bar to permit the contact car- Fig. 11. It is formed of magrier to move to theopen circuit position independently of the manual operating means, magnetic means arranged to move the thermal element in the same direction as it warps, when the current through the circuit breaker exceeds a second predetermined value, said magnetic means consisting of a magnetizable yokemounted on said thermal element and a stationary magnetizable member mounted on said housing in proximity to the position of said yoke when the circuit breaker is in closed circuit position but remote therefrom when the circuit breaker is in open circuitposition, and a flexible conductor partially surrounding said stationary magnetizable member and connected at onel end to said thermal element and at the other end to a stationary part.

FREDERICK B. ADAM..

FLOYD S. GREEN.

HENRY M. STIEGLITZ.

REFERENCES CITED The following references are of record in the ille of this patent:

UNrrED STATES PATENTS the contact carrier and latch-

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