US3243559A - Electric switch with novel arc cooling means - Google Patents

Description

E. B. HEFT March 29, 1966 ELECTRIC SWITCH WITH NOVEL ARC COOLING MEANS Filed July 1, 1963 2 Sheets-Sheet 1 nvv /vron.

ELDON B. HEFT,

8y ATTORNEY- March 29, 1966 E. B. HEFT 3,243,559

I ELECTRIC SWITCH WITH NOVEL ARC COOLING MEANS Filed July 1, 1965 J v 2 Sheets-Sheet 2 INVENTOR. ELDON B. HEFT,

BY WMISC AT TORNE).

United States Patent 3,243,559 ELECTRIC SWITCH WITH NOVEL ARC COOLING MEANS Eldon B. Heft, West Hartford, Conn., assignor to General Electric Company, a corporation of New York Filed July 1, 1963, Ser. No. 291,676 3 Claims. (Cl. 200-444) The present invention relates to electric switches and more particularly to electric switches of high interrupting capacity, and which are required to withstand high shortcircuit currents such for example as currents having peak values of 30,000 to 75,000 or more amperes.

More particularly, the invention relates to electric switches of the type including butt-type contacts operated by quickmake and break overcenter-spring operating mechanisms.

As is will known, electric switches of the type including separable butt-type contacts, operate to interrupt electric current by separating the contacts so as to draw an arc therebetween. Following creation of an are, various means are used to cause the voltage-drop existing through the arc to increase until it becomes greater than the applied voltage, causing the current to go to zero. The dielectric strength of the air between the separate contacts then prevents re-striking or futher arcing. Among the means used to increase the voltage-drop in such arcs are, (1) increasing the length of the are by physical separation of the contacts, and (2) cooling the are by various means such as by causing it to move into or against a stack of spaced metallic plates. In either case, there is a brief period between the incidence of arcing and the extinction of the arc, during which a substantial amount of metallic vapor and other are gases are generated and violently expelled from the immediate arcing area. The volume of the gas generated and the force of the expulsion of such gases are such that in the cases of prior art switches operated at high current interrupting duty, such, for example, as 10,000 a-mperes at 480 volts, the stream of such metallic vapor expelled from the Contact area sometimes forms a conductive path between one of the contacts and the other adjacent parts of difiering polarity, such as another phase of the circuit or a grounded member. Since such switches are commonly utilized within a metallic enclosure, such gases, if they do not strike an adjacent pole assembly, may strike any exposed part of the enclosure, causing a ground fault. If such gases strike the adjacent pole unit, a phaseto phase arcing short may be created, causing a violent explosion.

It is an object of the present invention to provide an electric switch of the butt-contact type having means for cooling arc gases in the immediate vicinity of the separable contacts, means for directing the arc gases away from the immediate contact area in a predetermined general direction, and means for causing the arc gases to be cooled by other parts of the switch operating mechanism in addition to the arc chute plates.

It is an object of the present invention to provide an electric switching'device of relatively high interrupting capacity having means for cooling arc gases and preventing the direct impingement of such are gases on either an adjacent pole unit or an adjacent surrounding member such as an enclosure.

It is another object of the invention to provide arc cooling and extinguishing means which will not only protect the device against accidental short circuits to another phase or to ground caused by arc lgases, but will assist in cooling such arc gases so as to cause more elficient interruption of the circuit.

In accordance with the invention in one form, an electric switching device is provided of the butt-contact type, including are cooling and extinguishing means com- 3,243,559 Patented Mar. 29, 1966 "ice prising a stack of spaced metallic plate-s surrounded on three sides by an enclosing and supporting wall. The plates have a central portion cut-away to provide a path through which the movable contact moves. In addition, each of the three outer sides of the arc plates have portions cut away so that when the plates are stacked in vertical alignment, the cut-away portions provide vertical passages of substantial size. These vertical passages permit the arc gases to pass into and between the arc chute plates, thereby being cooled, and also provide vertical passages through which the cooled arc gases can then pass upwardly, being deflected by a flat cover member back toward the operating mechanism of the switch. This prevents build-up of gas pressure within the arc chute which might prevent succeeding generated gas from entering the plates. The somewhat cooled arc gases are then directed through the switch operating mechanism, which includes operating springs, a metallic handle support, and associated supporting frame and pin members, all of which are at a relatively cooler temperature than the arc gases, and which help to further cool and denionize them.

In accordance with another aspect of the invention, the side walls of the arc chute assembly are extended to meet the side frame members of the operating mechanism, to provide substantially continuous side walls between which the arc gases are contained so as to prevent their escaping the adjacent sidewise pole units. In addition, the contact arm is constructed of fiat sheet metallic meterial having two sides bent downwardly to provide a generally channel-shaped construction and having its bight portion extended lengthwise directly over the mo-vable contact member and fitting closely within the cutaway part of the arc chute assembly to provide a deflector for are gases, tending to-keep them from escaping directly upwardly where they might strike the inner surface of an enclosure cover.

In the drawings:

FIGURE 1 is a perspective view of an electric switching device incorporating the invention, the arc plate assembly being shown in exploded relation;

FIGURE 2 is a side elevation view of the switching device of FIGURE 1, partly in section;

FIGURE 3 is a sectional view of the switching device of FIGURES '1 and 2, taken substantially on the line 3-3 of FIGURE 2, and

FIGURE 4 is a plan view of the arc chute assembly of the device of FIGURE 1.

Referring to FIGURE 1, the invention is shown as incorporated in an electric switching device including an insulating base 10 having a line terminal strap 11 mounted thereon by suitable means, such as by means of mounting screw 12 (see FIGURE 2). The line terminal strap 11 includes a tapped hole 13 for the purpose of connecting a suitable line conductor (not shown). The inner end of the terminal strap 11 carries a stationary contact 17.

A generally U-shaped arc runner plate 19 is also mounted on the inner end of the line terminal strap 11, being insulated therefrom throughout its major flat portion by a sheet of fiber type insulating material 20. The are runner plate 19 has its end portions connected to the line terminal strap 11 by suitable means such as by screws 21. The are runner plate 19 also has its center portion notched or cut-away as at 22. The construction of the arc runner plate 19 is substantially as shown and described in prior application Serial No. 209,418, filed July 12, 1962 by K. W. Klein et a1. and assigned to the same assignee as the present invention.

Arc cooling and extinguishing means is provided in accordance with the invention, as indicated generally at 23 in FIGURE 1 and comprises a series of generally U-shaped magnetic metallic plates 24 assembled in spaced vertically 1 .aligned relation by nieans of-a generally U-shaped fiber insulating sheet 25, the plates 24 having lug portions 26 projecting through the fiber piece 25. The arc chute plates 24 are each provided with cut-away portions or notches 24A at the back, and other cut-away portions or notches 24B, at each of the sides. A cover plate 28 is also provided, of insulating material.

The entire arc chute assembly is held in place by the in-terfitting relation of the assembly in the recess A of the base 10, being held therein by screws 27 which pass through holes 28A of the cover 28 and also through holes 29 in the base 10.

At the end of the insulating base 10 opposite from the line strap 11 a load connecting strap 31 is mounted by suitable means, not shown, and including a tapped hole 32 for receiving a suitable load connector, not shown.

A contact operating mechanism is mounted on the base 10 between the line strap 11 and the load strap 31, and includes a pair of mechanism side-frame pieces 33 having bent-over edge portions 34 rigidly mounted to the base 10 by suitable means such as by screws 35. The side-frames 33 each include a pivot pin 36 serving to pivotally support a generally inverted U-shaped handle member 37.

The handle member 37 is adapted to be rocked about the pivot pins 36 to open and close the switch contacts. It will be understood that suitable manually operable handle means, not shown, may be provided for operating the member 37, and also that two or more of the switch assemblies illustrated may be and commonly are ganged together for common operation, such as by rigidly attaching an insulating cross-piece to the handle support member 37. Such operating means have been omitted, however, for reasons of simplification and clarity.

Each of the side-frames 33 also supports an upper toggle link 38 on a suitable pivot pin 39. Each of the upper toggle links 38 includes a projecting pin 40 which extends into a window or opening 41 in the side portions of the handle member 37, for the purpose of positively initiating toggle-straightening and toggle-collapsing movements. The upper toggle links 38 are connected by means of,a toggle knee pin 42 (see FIGURE 2) to lower toggle links 43, which in turn are pivotally connected by means of pivot pin 44 to a generally channel-shaped rigid contact arm 45. The bight portion of the contact arm 45 has a pair of elongated slots (not shown) cut therein, through which the links 43 respectively extend. The side portions of the contact arm 45 are extended and are pivotally supported on the side-frames 33 by means of pivot pin 47. The bight portions of the contact arm 45 is extended forwardly at 48, and carries a contact-depression adjusting screw 49, which threadedly engages the movable contact member 50 which is also pivotally supported on the pivot pin 44.

The movable contact member 50 is constantly biased away from the contact arm extension 48 by means of a compression spring 51, which has one end abutting the extension 48 and which has its other end extending into a recess 52 in the contact 50.

For the purpose of flexibly connecting the movable contact member 50 to the load terminal strap 31, a pair of flexible conductors 53 are provided, which are connected at one end to the contact member 50 by suitable means such as by screws 54. The movable contact member 50 carries a movable contact 57, and has a sheet of insulating material 55 rigidly attached to the underside thereof by suitable means such as by rivets 56, to shield it from arc gases generated between the contacts.

The operating handle 37 is connected by means of a pair of operating springs 63 to the knee pins 42 of the toggle links 38-43. Movement of the operating handle 37 about its pivotal support 36 causes the operating springs 63 to move across the center line of the pivot pins 39, 42 (see FIGURE 2), until the toggle linkage is snapped from the collapsed condition as shown in FIGURES 1 and 2 to 4 straightened position, moving the contact arm 45 clockwise about its pivotal support 47 and bringing the movable contact 57 into contact with the stationary contact 17.

Movement of the handle member 37 in the opposite direction, likewise stresses the operating springs 63 until the line of action of the springs passes across the center line of the pivot pins 39-42, at which time the toggle linkage is snapped to collapsed position, moving the movable contact 57 to open circuit position.

In accordance with the invention, means is provided for preventing the metallic vapors and other gases generated during arcing betwen the contacts 17-57 from causing electrical breakdown between the switch unit and its surrounding metallic enclosure on the one hand, or between the switch unit and an adjacent switch unit on either side, on the other. For this purpose, the supporting member 25 for the plates 24 is provided with a solid back wall, thereby preventing the arc gases from being blown directly out the back of the switch or to the right as viewed.

In addition, the supporting member 25 for the arc plates 24 is extended at each side as indicated at 25A so that its edges abut against corresponding edges of the sides frames 33. This provides substantially continuous side walls for preventing direct side-wise escape of arc gases from the general arcing area.

In addition, means is provided for preventing the direct escape of arc gases in a direction vertically upward from the contact. For this purpose, the cover member 28 is provided, as previously described, and held in place by the screws 27. The cover member 28 is substantially continuous over the arcing area, and is provided with a cutaway portion 28B to provide clearance for the contact arm extension 48 in its open-circuit position. To further. reduce the possibility of arc gases escaping directly upward, the extension 48 of the contact arm 45 is made of a width to substantially completely cover the contact member 50 and the contact 57. Thus, as indicated particularly in FIGURE 3, the extension 48 is made of a width at least equal to the contact member 50, and the arc plate members 24 are provided with cut-out just wide enough to clear this member. Thus, when the contact arm is in open circuit position as shown in FIGURE 1, and the arc chute assembly is in position, the extension 48 of the contact arm 45 substantially completely fills the cut-out portion 28B of the cover member 28.

Although the possible escape of the arc gases from the arcing area is thus substantially completely prevented in all directions except one, it is nevertheless not desired that the arc gases should, on the other hand, be trapped within the arcing chamber. On the contrary, it is an object of applicants invention to permit the arc gases to move rapidly through the arc cooling plates 24. This would not be possible if there were no escape means for such gases at the outer edges of the cooling plates, since back-pressure would be generated adjacent the walls of the arcing chamber, which would prevent further movement of arc gases. For this reason, applicants arc plates 24 are provided with aligned cut-out portions 24A and 24B. (See FIGURE 2.) The aligned cut-out portions 24A provide a back vertical passage or chimney 60, and the cut-out portions 24B provide corresponding side vertical passages or chimneys 61 and 62 respectively. Referring to FIGURE 2, it will be seen that are gases generated between the contacts 17-57 are permitted to pass between plates 24 toward the back wall of the supporting member 25 and thence upwardly against the under surface of the cover member 28 and thence in the opposite direction over the contact arm 45 and through the operating mechanism, that is, between and around the operating springs 63, etc. I

In a similar manner, referring to FIGURE 3, are gases generated between the contacts 17-57 are permitted to pass between the side portions of the arc plates 24 to the vertical passages or chimneys 61, 62 and thence upwardly .5 against the under-surface of the cover member 28 and again through and over the operating mechanism.

The extra wide contact arm portion 48 directly over the contacts 17-57 helps to prevent the direct escape of arc gases upwardly, such as through the cut-out portion 28B of the cover 28. This is true even while the contact member 45 is in closed circuit position, such as the condition in which the contact member 45 remains while the switch is withstanding short-circuit currents which will be completely interrupted by a circuit protective device, such as a fuse in series with the circuit. Such a shortcircuit may be in the neighborhood of 75,000 amperes peak value, and its effect is to blow the contacts 17-57 apart a short distance against the compressive force of the contact spring 51, even though the contact arm 45 remains in the closed circuit position. This temporary parting of'the contacts 17-57 permits a substantial amount of arcing, with accompanying generation of metallic vapors and other'gaseous arc products. By permitting the arc gases and other arc products to pass through the assemblyof arc plates 24, a beneficial action is achieved, which quickly removes the ionized gases and metallic vapors from the immediate area of the contact while at the same time reducing the temperature of such gases. Further cooling of these gases is achieved by the fact that they pass over the switch operating mechanism, including the operating spring 63 andbetween the operating member sides 37.

In the switch and circuit breaker art, a generally recognized desirable objective has been to keep arc gases away from the operating mechanism because of the damage that was feared to the mechanism by such are products. Applicant has discovered, however, that by causing the arc gases to pass through the arc plates first, they may then be redirected to pass over and around the operating mechanism. This path of venting not only provides further cooling by exposing such arc products to the relatively cool metallic mass of the mechanism, but it provides a harmless path of escape for such gases which is not likely to cause any breakdown or short-circuit, since no parts of dilfering polarity lie in the path.

While the invention has been disclosed in one particular embodiment, it will be readily appreciated that many modifications thereof may readily be made, and it is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What'I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric switch comprising:

(a) a support;

(b) at least one stationary contact supported on said support;

(c) an elongated contact arm pivotally supported on said support;

((1) a movable contact carried by said contact arm and movable by said contact arm along a predetermined path between a closed circuit position in which it is in engagement with said stationary contact and an open circuit position in which it is out of engagement with said stationary contact;

(e) operating mechanism supported on said support substantially co-planar with and at one side of said stationary contact for moving said contact arm between said open and said closed circuit position said operating mechanism comprising at least an operating spring, means connecting said operating spring to said contact arm, and means connected to said operating spring for moving said operating spring between first and second positions to move said contact arm between open and closed circuit positions;

(f) a plurality of generally U-shaped spaced metallic arc chute plates disposed along said predetermined contact path;

(g) support means for said are chute plates comprising a pair of opposed side wall members;

(h) an insulating back wall member closing the space between said side wall members at the back of said plates and a cover member extending between said side wall portions at right angles to said back wall member;

(i) said side wall members said back wall member and said cover member all being substantially imperforate to prevent the passage of arc gases therethrough,

(j) each of said are chute plates having a portion adjacent said back wall cut-away and portions adjacent each of said side walls cut-away, said cut-away portions of said plates being in alignment when said plates are in vertical alignment, whereby to provide three vertical pasages at right angles to the general planes of said plates, whereby arc gases generated between said contacts may be blown between said plates and into said vertical passages thence upwardly against said cover member and thence outwardly in the direction of said operating mechanism.

2'. An electric switch comprising:

(a) a support;

(b) at least one stationary contact supported on said support;

(c) an enlongated contact arm pivotally supported on said support;

((1) a movable contact carried by said contact arm and movable by said contact arm along a predetermined path between a closed circuit position in which it is in engagement with said stationary contact and an open circuit position in which it is out of engagement with said stationary contact;

(e) operating mechanism supported on said support substantially co-planar with and at one side of said stationary contact for moving said contact arm between said open and said closed circuit positions;

(f) a plurality of generally U-shaped spaced metallic arc chute plates disposed along said predetermined contact path;

(g) support means for said arc chute plates comprising a pair of opposed side wall members;

(h) an insulating back wall member closing the space between said side wall members at the back of said plates and a cover member extending between said side wall portions at right angles to said back wall member;

(i) said side wall members, said back wall member and said cover member all being substantially imperforate to prevent the passage of arc gases therethrough;

(j) said arc chute plates having aligned openings therein to permit the flow of arc gases in a direction substantially perpendicular to the planes of said are chute plates;

(k) said operating mechanism including a pair of side frame members of sheet metallic material;

(1) said side wall members of said support means being extended to meet said side frame members of said operating mechanism;

(in) said side frame members of said mechanism and said side extensions of said are chute cooperating to confine arc gases generated between said contacts to the space above said support occupied by said operating mechanism.

3. An electric switch comprising:

(a) a support;

(b) at least one stationary contact supported on said support;

(0) an elongated contact arm pivotally supported on said support;

(d) a movable contact carried by said contact arm and movable by said contact arm along a predetermined path between a closed position in which it is in engagement with said stationary contact and an open position in which it is out of engagement with said stationary contact;

(e) operating mechanism supported on said support substantially co-planar with and at one side of said stationary contact for moving said contact arm between said open and said closed circuit positions said operating mechanism comprising at least an operating spring, means connecting said operating spring to said contact arm, and means connected to said opcrating spring for moving said operating spring between first and second positions to move said contact arm between said open and closed circuit positions;

(f) a plurality of generally U-shaped spaced metallic arc chute plates disposed along said predetermined path;

(g) support means for said arc chute plates comprising a pair of opposed side wall members;

(h) an insulating back wall member closing the space between saidside wall members at the back of said plates and a cover member extending between said side wall portions at right angles to said back wall member;

(i) said side wall members, said back wall member,

and said cover member all being substantially imperforate to prevent the passage of arc gases therethrough;

(j) each of said are chute plates having a portion adjacent said back wall cut-away and a portion adjacent each of said side walls cut away, said cut-away portions of said plates being in alignment when said plates are in vertical alignment, whereby to provide three vertical passages at right angles to the general' planes of said plates, whereby arc gases generated between said contacts may be blown between said plates and into said vertical passage thence upwardly against said cover member and thence outwardly in the direction of said operating mechanism, and

(k) said contact arm comprising a relatively wide thin flat member having its major plane extending sub-' stantially parallel to the major planes of said are chute plates and substantially completely filling the space enclosed by said U-shaped arc chute plates, whereby the flow of gases directly upwardly from said stationary contact is substantially impeded by said contact arm.

I References Cited by the Examiner UNITED STATES PATENTS 2,590,543 3/1952 Kalaway 200-144 3,043,939 '7/ 1962 Gryctko et al 200-144 25 KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT s. MACON, Examiner.

P. E. CRAWFORD, Assistant Examiner.

Claims (1)

1. AN ELECTRIC SWITCH COMPRISING: (A) A SUPPORT; (B) AT LEAST ONE STATIONARY CONTACT SUPPORTED ON SAID SUPPORT; (C) AN ELONGATED CONTACT ARM PIVOTALLY SUPPORTED ON SAID SUPPORT; (D) A MOVABLE CONTACT CARRIED BY SAID CONTACT ARM AND MOVABLE BY SAID CONTACT ARM ALONG A PREDETERMINED PATH BETWEEN A CLOSED CIRCUIT POSITION IN WHICH IT IS IN ENGAGEMENT WITH SAID STATIONARY CONTACT AND AN OPEN CIRCUIT POSITION IN WHICH IT IS OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACT; (E) OPERATING MECHANISM SUPPORTED ON SAID SUPPORT SUBSTANTIALLY CO-PLANAR WITH AND AT ONE SIDE OF SAID STATIONARY CONTACT FOR MOVING SAID CONTACT ARM BETWEEN SAID OPEN AND SAID CLOSED CIRCUIT POSITION SAID OPERATING MECHANISM COMPRISING AT LEAST AN OPERATING SPRING, MEANS CONNECTING SAID OPERATING SPRING TO SAID CONTACT ARM, AND MEANS CONNECTED TO SAID OPERATING SPRING FOR MOVING SAID OPERATING SPRING BETWEEN FIRST AND SECOND POSITIONS TO MOVE SAID CONTACT ARM BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS; (F) A PLURALITY OF GENERALLY U-SPACED METALLIC ARC CHUTE PLATES DISPOSED ALONG SAID PREDETERMINED CONTACT PATH; (G) SUPPORT MEANS FOR SAID ARC CHUTE PLATES COMPRISING A PAIR OF OPPOSED SIDE WALL MEMBERS; (H) AN INSULATING BACK WALL MEMBER CLOSING THE SPACE BETWEEN SAID SIDE SALL MEMBERS AT THE BACK OF SAID PLATES AND A COVER MEMBER EXTENDING BETWEEN SAID SIDE WALL PORTION AT RIGHT ANGLES TO SAID BACK WALL MEMBER; (I) SAID SIDE WALL MEMBERS SAID BACK WALL MEMBER AND SAID COVER MEMBER ALL BEING SUBSTANTIALLY IMPERFORATE TO PREVENT THE PASSAGE OF ARC GASES THERETHROUGH, (J) EACH OF SAID ARC CHUTE PLATES HAVING A PORTION ADJACENT SAID BACK WALL CUT-AWAY AND PORTIONS ADJACENT EACH OF SAID SIDE WALLS CUT-AWAY, SAID CUT-AWAY PORTIONS OF SAID PLATES BEING IN ALIGNMENT WHEN SAID PLATES ARE IN VERTICAL ALIGNMENT, WHEREBY TO PROVIDE THREE VERTICAL PASSAGES AT RIGHT ANGLES TO THE GENERAL PLANES OF SAID PLATES, WHEREBY ARC GASES GENERATED BETWEEN SAID CONTACTS MAY BE BLOWN BETWEEN SAID PLATES AND INTO SAID VERTICAL PASSAGES THENCE UPWARDLY AGAINST SAID COVER MEMBER AND THENCE OUTWARDLY IN THE DIRECTION OF SAID OPERATING MECHANISM.

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