US2462791A - Circuit interrupter - Google Patents

Description

Feb. 22, 1949. o, VON MEHREN 2,462,791

CIRCUIT INTERRUPTER Filed Feb. 13, 1945 3 Sheets-Sheet 1 II 4%} a WITNESSES: INVENTOR Oswa /0 Van Me/vren.

. BY a Feb. 22, 1949. 0. /ON MEHREN 2,462,791

CIRCUIT INTERRUPTER Filed Feb. l3, 1945 3 Sheets-Sheet 2 INVENTOR Osm/aVanMehren.

Feb. 22, 1949. o. VON MEHREN 2,462,791

CIRCUIT INTERRUPTER Filed Feb. l5, 1945 Y s Sheets-Sheet 5 Fig: 22.

WlTNESSES: 4/ INVENTOR ash ago 00 Meibren.

Patented Feb. 22, 1949 CIRCUIT INTERRUPTER Oswald von Mehren, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 13, 1945, Serial No. 577,637

This invention relates to circuit interrupters in general, and, more particularly, to are extinguishing structures therefor. More specifically, the invention relates to improved contact constructions.

It is common practice to provide the contact carrying elements of a circuit breaker with tips made of silver, or of a silver-tungsten or other alloy having better arc-resisting qualities than silver. The use of silver as a contact tip is advantageous due to the instability of the silver oxide produced by the arcing. This silver oxide has about as high a resistivity :as copper oxide, but while the latter is very stable at high temperature, the silver oxide instead breaks down under the very same heat of the are which forms it, and thus restores the conductive capacity of the contact tip. However, silver has the disadvantage that the low melting point of silver has produced many a case of fused or frozen contactshence the use of a tungsten-silver or other alloy which combines a high melting point with a high resistance to oxidation. These alloys, however, have a fairly high electrical resistivity due to the tungsten or other components. Consequently, contact tips made of such alloys have a relatively low current carrying capacity and,

if kept within normal size, are unable to carry temporary current surges which may reach a value several times the normal current flowing through the circuit.

The purpose of my invention is to provide means whereby the current carrying capacity of a circuit breaker using arc-resisting alloy contact tips may be increased, in its closed position, to a point where such current surges as mentioned above may be easily taken care of, this without aifecting the arc resisting quality of its circuit breaking elements.

Another object of my invention is to provide an improved circuit interrupter in which abutting oooperable contacts are spanned in the closedcircuit position by one or more bridging contacts. It is a more specific object to adapt such a contact construction to an interrupter of the type establishing both pressure-generating and interrupting arcs, and in which the pressure of fluid generated at the pressure-generating ar is directed toward the interrupting arc to effect the latters extinction.

Another object is to provide an improved contact construction in which one or more bridging contacts are utilized in the closed-circuit position to span the contacts, and in which improved biasing means are furnished to wedge the bridg-,

Claims. (Cl. 200-470) ing contacts against the cooperable contacts in the fully closed-circuit position of the interrupter.

Further objects and advantages will readily become apparent upon a reading of the following specifiction, taken in conjunction with the accompanying drawings, in which:

Figure 1 is an elevational view, partly in section, of a circuit interrupter embodying my in- Vention, and shown in the closed-circuit position;

Fig. 2 is an enlarged vertical sectional view through the left-hand arc extinguishing unit of Fig. 1, the contacts being shown in the closedcircuit position;

Fig. 3 is a vertical sectional View through the arc extinguishing unit of Fig. 2, taken at right angles to said View, but the contacts being shown in the fully open-circuit position;

Fig. 4 is a sectional view taken along the line IV-IV of Fig. 2;

Fig. 5 is a sectional view taken along the line VV of Fig. 2;

Fig. 6 is a, fragmentary enlarged view, taken in substantially vertical section, of the upper contact construction shown in Fig. 2, the contacts being shown in the closed-circuit position;

Fig. '7 is a fragmentary enlarged vertical sectional View through the lower contact construction of Fig. 2 modified to show two points of contact of the bridging member, the contacts also being shown in the closed-circuit position; and

Figs. 8 through 27 are detailed views of the contact elements employed in the improved contact constructions of my invention.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral l designates a tank filled to the level 2 with a suitable arc-extinguishing fluid 3, in this instance circuit breaker oil. Depending from the cover 4 of the tank I are two insulating bushings 5, 6, through which extend terminal studs (not shown). Threaded to the lower end of the terminal studs, and clamped thereto, are contact feet 7, 8 which rigidly support in place two identical arc-extinguishing units generally designated by the reference numeral 9.

The two units 9 are electricall interconnected in the closed-circuit position as shown in Fig. l by a conducting cross-bar Hi, which is operated reciprocally in a vertical direction by an insulating operating rod ll actuated by suitable mechanism (not shown) Rigidly secured to the outer extremities of the cross-bar it! are two movable contacts l2, l3,

which contact the intermediate contacts l4 of the interrupters in the closed circuit position thereof, as is more clearly shown in Fig. 2. The intermediate contact M in turn engages in abutting relation, a relatively stationary contact IS.

The separation between the relatively stationary contact !5 and the intermediate contact M during the opening operation takes place in a pressure-generating chamber, generally designated by the reference numeral IE, and in this instance being formed by side members [1, l8 cooperating with upstanding curved members L9 in a manner more clearly shown in Fig. 4.

Suitable plates properly configured are held in contiguous relation by insulating tie rods 20. The several plates collectively form two vertical flow passages, generally designated by the reference numeral 2i, which interconnect the pressure-generating chamber it with a plurality, in this instance four, inlet passages 22. Consequently, during th opening operation, fluid, in this instance oil, put under pressure by the pressure-generating arc established between the contacts id, l5, flows downwardly in the direction as indicated by the arrows in Fig. 2, inwardly through the inlet passages 22 to contact the interrupting arc, whence the fluid passes through orifices 23 provided by insulating orifice plates 2% to exhaust out of the unit 9 through exhaust passages 25, as more clearly shown in Fig. 3.

Certain features of the passages and inlets just described are set forth and broadly claimed in a patent application filed November 11, 1942, Serial No. i65,24., now United States Patent 2,406,- 469, issued August 27, 1946, by Leon R. Ludwi Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application.

The several plates have portions 26 removed therefrom to form a cylindrical cut-out portion in which is inserted an insulating tube 2]. Movable within the tube ET is a tubular member 23 having a flange portion 29 at its lower extremity, the flange portion being conically-shaped as indicated at 36. A compression spring 3| having its upper seat against a plate 32 serves to bias the tubular or cup-shaped member 28 in a downwardly direction.

The conically-shaped portion 33 serves as wedging means to bias a plurality, in this instance three, bridging contacts 33 radially inwardly against the contacts l2, i lin the closed circuit position, as shown in Fig. 2.

The individual bridging contacts 33 are more clearly shown in Figs. 20 and 21 of the drawings. Also, Figs. 17 and 18 collectively show more clearly the construction of the tubular member 28.

The three bridging contacts 33 are secured in position by a contact holder 34 shown more clearly in Figs. 25 through 27 of the drawings. A pin 35 having a roller 36 thereon extends loosely through apertures 31 provided in a bifurcated portion 33 of the bridging contact 33, as shown more clearly in Fig. 20. The roller 38 mounted on the pin 35 is positioned between the legs of the bifurcated portion 38 and bears against the conical portion 39 of the flange 29 in the closed circuit position as shown in Fig. 2.

A cup-shaped member 39, as shown more clearly in. Figs. 23, 24 of the drawings, is threaded into the contact holder 35 by a threaded connection at so. Th intermediate contact I i has an integrally formed flange portion il which engages a shoulder 52 of the cup-shaped member 39 during the closing stroke as shown in Fig. 2. A

compression spring 43 has its lower seat on the flange 4! and has its upper seat against a recess so formed in the tubular member 28, as shown more clearly in Fig. 18.

The drawings illustrate the working principle of my invention as applied to an arc-breaking grid as used in a 69 kv. oil circuit breaker. Referring to Fig. 2, which shows the contacts in [their closed circuit position, it will be observed that there are provided the regular three main elements of such a grid, namely, the moving contact E2, the intermediate contact i4 and the relatively stationary contact !5 which, through the shunts 45, is electrically connected to the contact foot 2 which is clamped to the current carrying terminal stud of the condenser bushing of the breaker. The contact making ends of the three elements are provided with tungsten-silver or other arc-resisting alloy tips 45, ii, 48 and 59. Considering the intermediate contact I4 first, it is noted that the contact is provided with a shoulder ii through Which it engages a cup 38 which is fastened to the contact holder or spider 34. The latter carries a series of contact bridges 33 so arranged as to form a bridge contact between the intermediate contact l4 and the movable contact i2 beyond the contact tips 48, 49, when in the position shown in Fig. 2. These contact bridges 33 are held in place by pins 35 positioned in suitably located clearance holes 31a in the corresponding faces of the spider 34. Through these clearance holes 3111, the said contact bridges 33 are allowed a limited but sufiicient radial motion. These contact bridges 33 are provided with rollers 35, through which they bear on the coneshaped cup 28, which is biased downwardly by the accelerating spring 3|. The other accelerating spring 43 biases the intermediate contact 14 in relation to the coned cup 28 as shown.

In the closed position shown in Figs. 2 and 7, the pressure exerted by the moving contact I2 upon the intermediate contact I l forces the rollers 35 to bear against the coned cup 28 and raise the latter upwardly against the spring 31. This forces the contact bridges 33 to close around the intermediate contact I i and the moving contact 12 so as to grip the two together and substantially increase the contact area between points of high conductivity beyond the tungsten silver alloy tips 48, 49.

The contact pressure of these bridges 33 is quite high due to the wedging or biasing action exerted by the cone 28. When the breaker has to be. opened, a release of the pressure from the moving contact 12 causes the whole assembly to travel downwardly as one unit under the influence of the compression spring 3| until the lower end of the cone 28 is stopped by the grid plate 58. At this instant, all. pressure on the contact bridges 33 ceases, and the latter together with the spider 35 separate themselves from the cone 28 and continue their downward travel until the spider 3 i is stopped by the grid plate 5!.

This extra travel of the spider 34 is just sufficient to establish a mechanical clearance between the rollers and the cone 28. The intermediate contact Hi continues its downward travel under the action of compression spring 43 until it reaches the position shown in Fig. 3. This position is determined by the shoulder l! hitting the spider 34. Up until now the moving and the intermediate contacts I2, I4 have remained in contact with each other and it is only at this instant that the separation between the two takes place. Thus, the arcing takes place only between the tungsten silver alloy contact tips 48, 49, well beyond the position of the contact bridges 33.

In closing the breaker, the moving contact l2 moves upwardly to first engage the intermediate contact |4, whence it moves the latter upwardly against the biasing action exerted by the sprin 43 until the shoulder 4| engages the cup 39. When this occurs, the contact plane common to the two contact tips 48, 49 has reached the position shown in Fig. 2, i.e. in the center of the contact bridges 33.

At this point the spider 34 is raised with the contacts l2, l4 and the rollers 36 are brought to bear against the cone 28, and thus the bridges 33 are forced to close around the contacts I2, |4 while the contact pressure of these bridges 33 increases with an increase in the compression of accelerating spring 3|. The springs 3| and 43 must be so proportioned that the final load of spring 43 is less than the initial load of the spring 3|.

It will be noticed here that the main characteristic of this device lies in the instantaneous release of the pressure on the contact bridges 33, as soon as the cone 28 is stopped in its downward motion, thus leaving the intermediate and moving contacts |2, |4 free to continue together their downward motion until their contact plane is well beyond the position of the bridge contacts 33, so that the actual arcing will take place only between the contact tips 48, 49 provided for this purpose.

In order to provide cooling of the contacts when the breaker is closed, the contact holder or spider 34 is provided with longitudinal passages 52, as more clearly shown in Fig. 2'7. These passages 52, together with perforations 53, 54 and 55, allow the oil to circulate around the contact I4, and thus the oil becomes a cooling medium.

During the opening operation after the tubular member 28 has struck and is stopped by the plate 50, inward biasing tension is released upon the rollers 36. However, even after the release of such tension the contact bridges 33 are still in engagement with the contacts l2, l4. Two forces now come into play to cause radial outward retraction of the contact bridges 33. One of these forces is the force of gravity which tends to cause rotation of the contact bridges 33 so that the pins 35 thereof will be moved outwardly within the apertures 31a of the contact holder 34. Also the sliding friction exerted by the intermediate contact |4 upon the contact bridges 33 tends to assist the force of gravity in causing rotation of the contact bridges 33 so that the pins 35 are forced outwardly. Consequently, these two forces, namely, the force of gravity and the sliding frictional force of the intermediate contact |4 tend to cause freeing outward retraction of the pins 35 to thereby result in radial outward movement of the contact bridges 33.

It will furthermore be noticed that the lower edges of the contact bridges 33, as viewed in Fig. 21, are rounded. This cooperates with the beveled surface of the arc resisting tip portion 49 of the movable contact l2 to prevent jamming of the contact surfaces during the closing stroke.

The circuit breaking device illustrated in the top section of the grid is in principle a duplication of the one just described. The only changes are those of a structural nature necessitated by the shape of the stationary contact which, in this case, has to be connected through 6 the shunts 45 to the current carrying foot 1 of the grid.

More specifically, the contact bridges 33 are secured in position in a contact holder or spider 56, shown more clearly in Figs. 14, 15, 16 and 22 of the drawings. It will be observed that the contact holder 56 has a pair of longitudinal slots 57 provided therein through which moves a pin 58. The pin 58 passes through the contact l5 having integrally formed therewith a cross-member 59 of rectangular configuration. The cross member 59 moves within a pair of slots 60, also provided in the contact holder 56.

The coned member for the upper contact construction is generally designated by the reference numeral 6|, and comprises three pieces, respectively designated by the reference numerals 62, 63, and 64. The member 62 has a configuration more clearly shown in Figs. 8 and 9 of the drawings; the member 63 has a configuration more clearly shown in Figs. 10 and 11 of the drawings; and member 64 has a configuration more clearly shown in Figs. 12 and 13 of the drawings.

In assembling, the threaded stop ring 64 is threadedly secured at 65 to the ring 63, the latter being secured by screws (not shown) to the member 62. A compression spring 66 serves the same function as the spring 3| in the lower contact construction, and a compression spring 61 serves the same function as the spring 43 in the lower contact construction. A screw 68 threaded into the contact foot 1 at 69 has its head HI serve as a stop for downward travel of the coned member 6|.

Consequently, during the initial opening travel from the position shown in Fig. 2, the entire unit moves downwardly under the influence of the compression spring 66 until the flange portion H of the member 62 strikes the head 10 of the screw 68. This substantially one-eighth inch travel furnishes the requisite contact pressure for the several contact gaps of the interrupter, the compression spring 66 thus furnishing the requisite contact pressure. However, after the shoulder strikes the head 10, downward movement of the member 62 ceases and thereafter the contact bridges 33, spider 56, relatively stationary contact I5 and intermediate contact |4 together move downwardly as a unit under the influence of spring 61 until the spider 56 strikes the stop ring 64, at which time there is sufficient mechanical clearance between the rollers 36 and the cone portion 30 so that the stationary contact l5 thereafter slides downwardly through the contact bridges 33 to a position as shown in Fig. 3.

After the stationary contact l5 has moved to the position shown in Fig. 3, the cross-bar 59 has struck the ring 63, thereby stopping the downward movement of the relatively stationary contact l5. Arcing then takes place between the contact l5 and the intermediate contact l4, but only after the contact l5 has reached the position shown in Fig. 3 where arcing takes place only between the contact tips 46, 4'! well out of reach of the bridging contacts 33.

During the closing stroke, the intermediate contact l4 moves upwardly to pick up the stationary contact l5, raising the latter until the pin 58 strikes the top of the slots 51, at which time the contact l5 carries the spider 56 upwardly therewith. However, the upward travel of the spider 56 brings the rollers 36 into engagement with the cone portion 36 of the wedging means 6| so that radial inward pressure is brought to 7 bear on the bridging contacts 33 to force them radially inwardly against the contacts l4, l5. Further, upward motion compresses the compression spring $6, thereby producing the requisite contact pressure.

From the foregoing description it will be apparent that I have provided an improved contact construction, in which abutting contacts are bridged in the closed circuit position to enable the contacts to carry high momentary current surges without destructive consequences. It will be noted that the bridging contacts are biased radially inwardly to firmly engage the abutting contacts and thereby provide requisite contact pressure between bridging contacts and abutting contacts. It will be noted that the relatively high resistant tungsten-silver alloy tips are bridged in the closed-circuit position, and that during the opening operation arcing takes place at a point beyond reach of the bridging contacts.

Although I have shown and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, a pair of contacts cooperable to estabiish an arc, and one or more independently laterally movable bridging contacts being Wholly laterally movable to span the pair in the closed circuit position with the terminal ends of each bridging contact engaging both the aforesaid contacts.

2. In a circuit interrupter, a pair of cooperable contacts which abut in the closed circuit position, an independently laterally movable bridging contact being wholly movable laterally which spans the pair or contacts in the closed circuit position with the terminal ends of the bridging contact engaging the aforesaid pair of contacts, and biasing means to bias the bridging contact toward the pair of contacts when the latter are in the closed position.

3. In a circuit interrupter, a pair of contacts cooperable to establish an are, a contact holder, a plurality of bridging contacts, the contact holder pivotally carrying the bridging contacts, and the bridging contacts spanning the pair in the closed circuit position so that the terminal ends of the bridging contacts engage the aforesaid pair of contacts.

4. In a circuit interrupter, a pair of contacts cooperable to establish an are, a contact holder, a' plurality of bridging contacts, the contact holder pivotally carrying the bridging contacts, the bridging contacts spanning the pair in the closed circuit position, and biasing means to bias the bridging contacts toward the pair of contacts in the closed circuit position so that the terminal portions of the bridging contacts are pressed against the aforesaid pair of contacts.

5. In a circuit interrupter, a pair of contacts cooperable to establish an arc, a contact holder, a plurality of bridging contacts, the contact holder pivotally carrying the bridging contacts, the bridging contacts spanning the pair in the closed circuit position, and biasing means to bias the bridging contacts radially inwardly toward the pair of contacts in the closed circuit position so that the terminal portions of the bridging contacts are pressed against the aforesaid pair of contacts.

6. In a circuit interrupter, a pair of contacts cooperable to establish an arc, a contact holder, a plurality of independently laterally movable bridging contacts carried by the contact holder being wholly movable laterally, and wedging means to bias the bridging contacts radially inwardly to span the pair of contacts in the closed circuit position of the interrupter with the terminal ends of each bridging contact engaging both the aforesaid contacts.

7. In a circuit interrupter, a pair of contacts cooperable to establish an are, a contact holder, a plurality of independently laterally movable bridging contacts carried by the contact holder being wholly movable laterally, and wedging means comprising an annular conically-shaped member to bias the bridging contacts radially inwardly to span the pair of contacts in the closed circuit position of the interrupter with the terminal ends of each bridging contact positively engaging both the aforesaid contacts.

3. In a circuit interrupter, a pair of cooperable contacts which abut in the closed circuit position, a contact holder, a plurality of independently laterally movable bridging contacts, means pivotally mounting the bridging contacts in the contact holder, and a tubular member having a flange portion, the flange portion being conical- 1y shaped to wedge the bridging contacts radially inwardly to span the contacts in the closed circuit position of the interrupter so that the terminal portions of the bridging contacts are pressed against the aforesaid pair of contacts.

9. In a circuit interrupter, a pair of cooperable contacts which abut in the closed circuit position, an independently laterally movable bridging contact to span the pair in the closed circuit position, means biasing the bridging contact into bridging relationship in the closed circuit position of the interrupter so that the terminal ends of the bridging contact are pressed against both aforesaid contacts, and means for releasing the tension of the biasing means prior to separation of the pair of contacts during the opening operation.

10. In a circuit interrupter, a pair of cooperable contacts which abut in the closed circuit position, a bridging contact to span the pair in the closed circuit position, means biasing the bridging contact into bridging relationship in the closed circuit position of the interrupter so that both terminal ends of the bridging contact are pressed against the two aforesaid contacts, means for releasing the tension of the biasing means prior to separation of the pair of contacts during the opening operation, and means permitting one of the contacts to slide past the bridging contact during the opening operation following release of tension of the biasing means so that are drawal takes place away from the bridging contact.

11. In a circuit interrupter, a pair of contacts one of which is rod-shaped cooperable to establish an arc, one or more bridging contacts adaptable to span the pair of contacts in the closed circuit position with the terminal ends of each bridging contact engaging both the aforesaid contacts, a coil spring surrounding said one contact, camming means to force the one or more bridging contacts into engagement with the pair of contacts, and the coil spring biasing the camming means into operative position in the closed circuit position of the interrupter.

12. In a circuit interrupting device, arod-shaped contact cooperable with another contact in abutting relation in the closed circuit position, bridging means adaptable to completely span the contacts in the closed circuit position, a cam to bias the bridging means against the contacts, and a coil spring encircling the rodshaped contact biasing the cam into operative relationship in the closed circuit position of the interrupter.

13. In a circuit interrupter, a pair of contacts one of which is rod-shaped cooperable to establish an arc, one or more bridging contacts adaptable to span the pair of contacts in the closed circuit position with the terminal ends of each bridging contact engaging both the aforesaid contacts, a coil spring surrounding said one contact, camming means to force the one or more bridging contacts into engagement with the pair of contacts, the coil spring biasing the camming means into operative position in the closed circuit position of the interrupter, and means for causing opening separating motion of the contacts to cause arc drawal at a place away from the one or more bridging contacts.

14. In a circuit interrupting device, a rodshaped contact cooperable with another contact in abutting relation in the closed circuit position, bridging means adaptable to completely span the contacts in the closed circuit position, a cam to bias the bridging means against the contacts, a coil spring encircling the rod-chaped contact biasing the cam into operative relationship in the closed circuit position of the interrupter, and means for causing opening separating motion of 10 the contacts to cause arc drawal at a place remote from the bridging means.

15. A circuit interrupter including a pair of contacts cooperable to establish an arc, one or more independently laterally movable bridging contacts being wholly laterally movable to span the pair in the closed circuit position with the terminal ends of each bridging contact engaging both the aforesaid contacts, and means causing the first said pair of contacts to remain in engagement and slide past the one or more bridging contacts during the opening operation and thereafter separate from each other so that are drawal takes place away from the one or more bridging contacts.

OSWALD VON MEHREN.

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

UNITED STATES PATENTS Number Name Date 1,601,314 Mahoney Sept. 28, 1926 1,796,217 Rankin Mar. 10, 1931 1,821,414 Allan Sept. 1, 1931 1,955,337 Leeds et a1. Apr. 17, 1934 2,069,641 Bold et a1. Feb. 2, 1937 2,235,171 Schilgen et a1 Mar. 18, 1941 FOREIGN PATENTS Number Country Date 376,300 Great Britain July 4, 1932

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