US1180805A - Oil-switch. - Google Patents

Description

R. TED-GER.

OIL SWITCH.

APPLICATION FILED OCT. 11. 1912.

1,180,805. Patented Apr. 25,1916.

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/, ATTORNEY.

RICHARD TROGER, OF CHARLOTTENBURG, GERMANY, ASSIGNOR '10 GENERAL ELECTRIC COMPANY, A CORPORATION OI NEW YORK.

OIL-SWITCH.

specification.

My invention relates to electric switches,

. and particularly to oil switches for con- 'tacts of trolling circuits carrying large amounts of energy. q

Experience has shown that when the cona switch are separated under oil, the are produced exerts an explosive effect and tends to throw the oil out of the switch, particularly if a large amount of current is flowing in the circuit when the contacts separate. Efforts have been made to prevent these explosions by strengthening the oil tank, or by inclosing the contacts in an insulated casing or chamber strong enough to resist the explosive action of the arc and protect the main body of the oil from the explosive action of the arc. In some types of switches, bafiies or perforated plates have been mounted near the fixed contacts to dampen the movement of the oil and keep it as near the contacts as possible. All of these expedients deal only with the explosive action of the arc itself. Experience has shown, however, that the explosive action of the arc is not the only reason for explosions in oil switches, but that explosions occur in cases where the arc is confined in various ways and where there has been no direct discharge between the contacts at the surface of the oil. Such explosions appear to be caused by the formation of bubbles of vapor of very high temperature in the im- These bubbles mediate-vicinity of the arc. of vapor tend'to rise through the oil and are still at a very high temperature when they reach the surface of the oilwhere they ignite explosively as soon as they come in 'contact withvthe oxygen of the air. It is also probable that the air at the surface of the oil is impregnated with oil vapor, and forms an explosive mixture which is ignited by the hot vapors from the arc. The various plans proposed for inclosing the are or ,limiting its direct action upon the oil have but little effect in preventing explosions due to the hot bubbles of vapor rising into the air space from the oil.

The-object of my invention is to prevent Specification of Letters Patent.

Patented Apr. 25, 1916.

Application filed October 11, 1912. Serial No. 725,172.

explosions of every kind in oil switches, even when the switches open circuits carrying very large amounts of energy. I accomplish the desired result by not only dampening and diminishing the direct explosive action of the arc, but also by preventing the access of hot vapor or partlcles to the air space above the surface of theoil. To this end, I provide means for so reducing the temperature of the vapor and particles from the are, that by the time they reach the surface of the oil they are at such a'low temperature that they will not cause explosions.

-My invention will best be understood by reference to the accompanying drawing, in which I have shown merely for purposes of illustration, one of the many forms in which the invention may be embodied, and in is provided with a suitable cover, in which there is mounted an insulator for carrying a stationary contact I) submerged in the oil in the tank. A cooperating movable contact 0 is mounted to move vertically into and out of engagement with the stationary contact and to move toward the bottom of the tank as the circuit is opened. 7

The are formed upon the separation of the contacts 6 and 0 tends'to'expand and throw the oil away from the contacts, and this action of the arc may be suflicient to throw the oil out of the tank. To prevent this direct explosive action of the are, and also to prevent access of the hot arc vapors and particles to the air space above the oil, I surround the contacts with some good heat conducting shell, which is preferably metallic andhas many perforations,so that thehot gases of the expanding arc must pass through this perforated v metal shell. Owing to the small perforations? and the inertia and viscosity of the oil in them, the arc encounters a great deal of resistance as it attempts to expand through the metal shell. In this way the direct explosive efiect of the arc is weakened. The are gases are furthermore sub-divided into many small jets and are very much cooled by passing through the metal shell. As

the perforated protecting these small jets enter the body of oil in the tank they are further cooled until any are gases or vapor bubbles which reach the surface of the oil are at such a low temperature that no ignition or explosion can occur.

One particular form ofheat conducting shell which I may use, is indicated in the drawing, which shows the contacts surrounded by a protecting shell or barrier d consisting of a series of parallel flat rings made of some suitable metal, such as copper. These copper rings are bent up slightly at their outer edge, and are spaced away from each other to a slight extent to leave between them, comparatively small passages through which the arc gases may pass out into the body of oil in the tank. The copper rings are insulated from one another in any suitable way, as by insulating spacers,"and are firmly held in proper relation to the contacts and to each other by bolts which extend thrpugh the plates. By insulating the individual parts or rings of body (Z, the are formed when the circuit is opened cannot use the protecting body 03 as a metallic bridge between the two contacts, but instead the protecting body breaks the arc up into a number of small arcs in series, which are more easily extinguished by the oil than one continuous arc of equal length.

As the contacts separate, the are formed between them tends to expand and the hot arc gases are driven out through the passages between the metal rings. As these passages are narrow and are scaled up with oil,

' the protecting body of acts to some extent like an inclosing chamber for the arc and very materially decreases the direct explosive action of the arc. The metal rlngs abstract a great deal of heat f'romthe arc gases flowing between them, and also compel the arc gases to emerge from the protecting shell in the form of thin sheets instead of in a compactbody. The oil in the tank exerts a much more marked cooling and extinguishing action upon the gases in the form of thin sheets than it would upon an equal amount of gas in a compact mass or bubble.

In the particular switch shown in the drawing, the protecting shell d extends downwardly nearly to a point that corresponds to the lowest position of the movable contact 0. 'In case there is any danger that the arc gases may be driven out of the lower end of the protecting shell 0! and then rise 'to the surface of the ,oil without suflicient cooling, the protecting shell may be made longer. In order to guard still further against the access of hot gases and heated particles to the airspace above the oil, protecting bodies of good heat conductlng material and provided with many perforations may be placed above the contacts or directly at the surface of the oil. For example, a perforated protecting body 6 may be placed above the protecting body (Z in any suitable position, which may be on the surface of the oil, or directly under or over it. The protecting body 6 may be made in any suitable manner, preferably of a thick perforated metal plate.

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

1. An electric switch comprising an oil vessel, relatively movable cooperating contacts mounted toseparate beneath the oil in said vessel, means for moving one of said contacts vertically away from the other to open the circuit, and a protecting bell shaped shell with a closed top and open at the bottom and mounted beneath the oil in said vessel with the open end down and with the upper one of saidcontacts alwa s Within said bell and near the upper c osed end thereof, said protecting shell having in its walls restricted vents ,to permit only slow escape of arc gases and to cool said escaping gases.

2. An electric switch comprising an oil vessel, a fixed contact mounted in said vessel beneath the oil, a cooperating movable 00111351013 mounted to move downwardly from said fixed contact to open the circuit, and aprotecting bell shaped shell closed at the top and open at the bottom and secured to sages to cool the escaping arc gases, and a vertically movable cooperating contact separable from said fixed contact within said bell to draw an are within said bell and be: neath the imperforate top ofsaid bell and thus compel the arc gases formed within .said bell to pass through said narrow passages,

In witness whereof, I have hereunto set myhand this eighteenth day of-September, 1912.

RICHARD TRfjGER.

Witnesses:

- JULIUs RUMLANDS,

ALFRED WOLF.

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