US2229990A - Circuit breaker - Google Patents

Description

R E T A S G. M

Jan. 2s, 1941.

,R E K A E R B T I U C R I C Filed Nov. 2l, 1934 MTM INVENTOR WITNESSES:

ATTORN Patente# Jan. 28, 1941 PATENT OFFICE CIRCUIT BREAKER Manin c. stieren, west springfield, Mass., assignor to Westinghouse Electric t Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 21, 1934, serial 1go. 754,932

16 Claims.

My invention relates generally to circuit interrupters and particularly to electrical switching devices which utilize mercury for opening and for closing the electrical circuit therethrough.

The principal object of my invention is to provide an improved mercury switch which shall be more rugged in design, more reliable in operation, and less expensive to manufacture than the previously known devices of this type.

Heretofore, most oi the mercury switches which have been known to the art have utilized a glass tube or casing for enclosing the mercury and have .been provided with suitable actuating means for tilting this tube in order to operate the switch. There are numerous disadvantages in the use of glass casings, the most important of which, perhaps, is the frangibility of that substance. Despite this, however, glass closures have been widely used, particularly in those applications where it was found desirable toprovide a liquid or gaseous medium for aiding in extinguishing such arcs as may be formed during the operation of the switch.

It would appear that the most desirable form of mercury switch would include an unbreakable casing which might be made absolutely gas tight. One of the most likely materials for such a casing would, of course, be metal, but heretofore no satisfactory means has been found for providing a metal casing for mercury switches which could be made gas-tight without unreasonably large expense. And even in those switches which have utilized metallic casings, it has been found necessary to include a ceramic or other frangible insulating means for a portion of that casing in order to separate and insulate the switch electrodes from each other.

My invention, however, provides means whereby a metallic casing may be utilized for a mercury switch or similar device, in such manner that a substantially unbreakable structure is produced. It also provides means for completelyvsealing the casing of the switch in order that a gas or other medium may be introduced therein for aiding in D the extinction of such arcs as may be established during the normal operation of the switch.

The complete enclosing of the structure of my invention is rnade possible primarily through the provision of an improved seal which utilizes a means of resilient insulating material for insulating one of the electrodes from the metallic Vcasing and for providing a gas-tight seal between that electrode and the casing.

A further object of my invention is to provide a mercury switch which shall utilize a metallic (Cl. ZUG-152) casing for one of the electrodes, and which shall be provided with means of refractory material for aiding in the extinction of the arcs whichv are established during the operation thereof.

A still further object of my invention is to provide a mercury switch which shall be substantially shock-proof, and which may be manufactured without the use of"`any complicated apparatus.

These and other objects of my invention will be made more apparent n the following description ofa preferred embodiment of my invention. Referring to the single sheet of drawings:

Fig. 1 is a sectional view of a mercury switch constructed according to the principles of my invention;

Fig. 2 is a sectional view on the line II-II of Fis- 1;

' Fig. 3 is a sectional view on the line III-III of Fig. 1; ft

Fig. 4 is a sectional,- view on the line IV-IV of Fig. 1; and

Fig. 5 is a view partially in elevation and partially in section, illustrating a modified sealing means which may be used with the switch shown in the other figures of the drawing.

The switch illustrated in Figs. l` to 4 comprises, essentially, an outer shell".or casing I which is spun or otherwise formed from a single piece of metal and which is adapted to `serve as one of the electrodes of'the switch. A "second electrode 3 is disposed within this casing andis insulated therefromby a sealing means 5 which includes a member 1 of resilient insulating material. This member 1, in the complete device, has the further function of providing a gas-tight seal between the second electrode 3 and the casing I. An annular member 9 of refractory material, preferably porcelain, is positioned within the outer casing I and has a shoulder that provides an arc resistant surface upon which the arc incident to the opening of the electrical circuit through the switchfis established.

More specifically, the outer casing I comprises a pair of concentric tubular, members I0 and I2 which are of dissimilar diameters and which are joined together at one end so as to form a continuous passageway. The left-hand end of the smaller tube I0 ls closed at all times by an end portion II which is either formed integral therewith or is rigidly aiiixed thereon by any of the well known means to make the -tube ID a cupshaped member. The junction of the larger and the smaller tubes forms an annular shoulder I3 which is adapted to serve as aV support for the member 9 of refractory material, and, through I as the opening within that member, for the electrode and sealing means. A quantity of mercury, which separates into two pools Il and I6 when the switch is in the open circuit position, is contained within the casing I for effecting the opening and the closing of the electrical circuit through the switch.

The electrode 3 consists of a rod-like member or stein portion, preferably of steel, which terminates in an enlarged head portion I5 having substantially the same outer dimensions as the larger opening I1 within the annular member of refractory material. cut away in order to provide a pocket or recess I9 for retaining the smaller of the two pools of mercury and for facilitating the opening of the switch, the opening 20 within the annular member 9 being somewhat smaller than the cut away portion I9 in order to aid in retaining the smaller mercury pool I6 in the position shown.

The sealing member 1 has the formol a hollow cylinder of substantially the same outer diameter the larger of the two tubes, and in order to further facilitate the sealing operation the central opening therethrough has substantially the same cross sectional dimensions as the rod portion of the electrode 3. The left-hand surface of the sealing membe is adapted to abut against the right-hand surface of the enlarged portion I5 of the electrode and the right-hand surface of. the annular member 9, and a flat circular plate 2|, of a rigid, mechanically strong insulating material, is disposed at the right-hand surface of the main sealing member 1 in order that suiiicient force may be transmitted thereto to secure a gas-tight seal between the electrode and the casing.

During the assembling of the switch, the righthand end of the larger tube I2 is open. The annular member 9, the electrode 3, the sealing member 1, and the plate member are inserted through this opening, in the order named, following the placing of the mercury in the bottom of the casingl then the outer edges of the right-hand portion of the larger tube I2 are spun so as to subject the resilient sealing member 1 to a deforming stress of sufficient magnitude to provide a gastight seal. A space 22 is left between the casing and the electrode in order to avoid short circuiting of the switch. The resultant structure is substantially unbreakable and, if desired, it may, during the manufacturing operation, be lled with any suitable gas or fluid, at a pressure either less than or greater than atmospheric, the seal 5 assuring that no leaks shall occur during the normal operative life of the device. If desired, gaskets (such as those shown at 23 and 25) may be utilized for equalizing the stresses on the annular member 9.

In the preferred form of my invention, I utilize a body of synthetic rubber for the main sealing member 1. This substance has numerous advantages over the other known resilient insulating materials in that it is quite resistant to mercury vapor, and thus assures the maximum operative life of the switch. Ordinary rubber may also be used with reasonable success, as may certain other resilient insulating substances and compounds.

'I'he annular refractory member 9 is preferably constructed of porcelain chiefly because that material is comparatively inexpensive. Other refractory materials are equally suitable, and it is also possible, in some instances desirable, that the shape of this member be other than that shown in the drawing. For example, if it is desired to in- The inner end of this portion is crease the arc rupturing capacity of the switch, it may be desirable to provide a sleeve extension on to this refractory member which would extend into the smaller of the two tubes lor a greater or less distance.

Soft steel has been found particularly suitable for use in forming the casing of the switch, it being possible when using this material to spin the entire casing from a single sheet of metal. Other materialsv are, of course, suitable for this purpose, and itis not necessary or imperative that the entire casing be spun. l

It is also within the province of my invention that the deforming stress which is imparted to the sealing member 1 may be produced by means other than spinning over the outer edge of the tube. The spinning method is particularly preferable, however, because of its low cost.

In certain installations it is highly desirable that the switch be entirely water-proof, and my invention lends itself particularly to this form. As illustrated in Fig. 5, it is easily possible to vulcanize a body 21 of rubber or rubber compound over the main body of the casing and over the end thereof which is open following the spinning operation. This assures a water-proofing of the entire switch, and is, of course, of great value in certain applications.

For those installations wherein the gaseous medium contained within the main closure is at a pressure considerably above or below atmospheric, it may be desirable to vulcanize the sealing member 1 to the electrode 3 and the adjacent portions of the larger tubular member I2. If a steel casing and a steel electrode are employed it may be found necessary, for best results in this operation, to plate the surfaces which contact the member 1 with brass, this metal being capable of adhering particularly well to vulcanized sulphur-free rubber. A vulcanized seal is, a perfect seal than one which depends upon pressure for its efficacy, but its increased expense usually limits its use to certain special applications.

The switch is operated in a manner similar to other mercury switches, that is, by tilting the outer casing in order to cause the mercury to move from the open circuit position illustrated in Fig. 1 to a position where 4the two pools Il and I6 contact each other. No mounting or operating means has been shown, because numer-v ous arrangements of both types are well known in the art.

In order to aid in the extinction of such arcs as may be established within the device, I prefer to lll the space between the outer casing and the electrode with a low atomic weight gas which is chemically inert to mercury vapor. Hydrogen is particularly suitable when used under a pressure of about 11/2 atmospheres, this pressure assuring that existence of small leaks will not result in contamination of the arc extinguishing medium within less than a very considerable period of time. Helium is also suitable and certain other inert gases may be utilized with reasonable success.

From the foregoing, it will be seen that I have provided a mercury switch which has numerous advantages over the devices heretofore known in the art. My improved switch is practically unbreakable. It may be assembled by an ordinary mechanic without the use of any complicated glass-blowing or sealing equipment, and low in cost. Further, by

despite this it is very of course, more nearly A Cai may be made gasand liquid tight.

As a feature of my improved switch, I have' disclosed anew form of gas-tight seal which is applicable not only to mercury switches but to other devices generally. I have also shown how my improved seal may be utilized for insulating and positioning an electrode within a piece of electrical apparatus, thereby reducing the cost and simplifying the structure of that device.

While. in accordance with the patent statutes. I have disclosed lthe foregoing details of a preferred embodiment of my invention, it is to be understood that many of these details are merely illustrative and that variations of their precise form will be both possible and in some instances desirable. I desire. therefore. that the language of the 'accompanying claims shall be accorded the broadest reasonable construction. and that my invention shall be limited only by what is expressly stated therein and by the prior art.

I claim the following as my invention:

l. In a switch having a conducting fluid for completing the circuit. a metallic casing which serves as one of the electrodes of said switch, an opening formed in said casing, an electrode extending through said opening into said casing. means providing a stop for determining the point to which said electrode may extend into the casing, and` means for positioning said electrode within said opening against said stop means and for forming an insulating, gas-tight seal between saidv electrode and said casing. said l seal forming means including means of resilient insulating material and means for placingy said means of resilient material under a suitable deforming stress. l

2. In a switchQa metallic casing. an electrode extending into said casing, a body of conducting uid in the casing for completing the electric circuit through the switch, means of resilient insulating material between said casing and said electrode, a pair of spaced abutments extending inwardly from the wall of the casing and providing a force placing said means of resilient insulating material in compression, thereby providing a seal between said electrode and said casing. l

3. In a switch,`a metallic casing, an electrode extending into said casing, a body of conducting fluid in the casing for completing the electric circuit through the switch. meansl of resilient insulating material between said casing and said electrode, a pair of spaced abutments extending inwardlyl from the wall of the casing and providing a force placing said means of resilient insulating,Vj material in compression, and means for distributing said force over a major part of the area -of said means of resilient insulating material, thereby providingv a seal between said electrode4 annsaid casing.

4. A conducting fluid switch comprising a metallic casing which is 'provided with an opening formed therein, an electrode extendingv through said opening intdi` said casing, said casing serving as the other electrode, means of hard retractory insulating material for positioning and spacing said electrode within said casing, and a single member of relatively soft resilient insu lating material extending across and sealing said opening in said casing through which said electrode extends and positioning the means of refractory material in the casing.

5. A conducting-fluid switch comprising a. me-

tallic casing which serves as one of the electrodes of said switch and which is provided with an opening formed therein. an electrode extending through said opening into said casing, means of refractory insulating material disposed within said casing for positioning said electrode therein and for providing an arc resistant surface across which the arc incident to the circuit opening operation oi said switch is drawn, and a sealing member of a material which is composed, at least in part, of resilient rubber-like material for positioning said means oi refractory material in the casing. for insulating said electrode from said casing and for providing a seal extending between said electrode and said cas? ing.

5. A mercury switch comprising a metallic casing which serves as one ol the electrodes of Said switch and which is provided with an opening formed therein. an electrode extending through said opening into said casing, means of refractory insulating material disposed within said casing for positioning said electrode therein and for providing an arc resistant surface upon which the arc incident to the circuit opening operation of said switch is drawn, and `Vmeans for forming a gas-tight, insulating seal between said electrode and said casing. said seal forming means including means of resilient insulating material and spaced parts extending inwardly from the casing for exerting a force compressing said meansv of resilient insulating material at points close to said electrode.

7. In a switch having a conducting iluid for completing the circuit, a metallic casing, an opening formed in said casing, an electrode extending through said opening into said casing, an abutment in said casing, a member of resil-` ient insulating material disposed about at least a portion of said electrode adjacent said opening for insulating said electrode from said casing and for closing said opening, means adjacent said opening for forcing said resilient material toward said abutment and placing said resilient material under a suficient deforming stress to provide a gas-tight, insulating seal between said casing and said electrode.

8. In a mercury switch, a tubular metallic casing which serves as one of the electrodes of said switch, one end of said casing being normally closed at all times and the other end being open during the manufacturing of said switch, an electrode extending through said opening end into said casing, an abutment in said casing, and a member of resilient insulating material disposed about at least a portion of said second electrode adjacent said open end for insulating said electrode from said casing and for closing said opening, the outer edges of the open end of said tubular means being in-turned and forcing said number of resilient material toward said abutment and subjecting said member of resilient material to a suiiicient deiorming stress to provide a gas-tight. insulating seal between said casing and said electrode.

9. In a switch, a metallic casing, an electrode extending into said casing, a body of conductinguid in the casing for complet-ing the electric circuit through the switch, means of resilient insulating material between said casing and said electrode, a ridge on the inner wall of the placing said means of resilient insulating material and said electrode in compression between said ridge and said spun-over end, thereby procasing and a spun-over end on said casing for` viding a seal between said electrode and said casing.

10. In a switch, a metallic casing. an electrode extending into one end of said casing, a body of conducting fluid in the casing for completing the electric circuit through the switch, means on the inner wall of the casing providing a stop, means of relatively soft resilient insulating material in the space between said electrode and casing, means of relatively hard insulating material between said means of relatively soft insulating material and the end of the casing, and means on the end of the casing for applying a force to said means of relatively hard insulating material and thereby forcing said means of relatively soft insulating material toward said means providing a stop for deforming said means of relatively soft insulating material and providing a seal between said electrode and casing.

1l. In a mercury switch; a unitary metallic casing, having the substantial form of two concentric cylinders of differing internal diameters, which casing serves as one of the electrodes of said switch; the outer end of the smaller diameter portion of said casing being closed at all times, and the outer end of the larger diameter portion of said casing being open during the manufacture of said switch; an electrode extending through said open end into said casing; a hollow cylindrical member of resilient insulating material, having substantially the same diameter as the internal diameter of the larger portion of said casing, disposed about at least a portion of said electrode adjacent said open end, said member serving to position said electrode within said casing, to insulate said electrode from said casing, and to close said opening; and means for forcing said member of resilient material toward the smaller portion of the casing and thereby subjecting it to a suicient deforming stress during the manufacture of said switch to provide a gas-tight insulating seal between said electrode and said casing.

12. In a switch, a metallic casing having an opening therein, an electrode extending into said casing through said opening, said electrode having a terminal portion for making electrical connection to an electrical circuit, a body of conducting fluid in the casing for completing the electric circuit through the switch, means forming a seal between said electrode and said casing including a member of resilient'insulating material forced into tight engagement with said electrode and said casing, and a one-piece coating of an insulating rubber material vulcanized on said casing and on said terminal portion and covering at least said opening through which the .electrode extends and the portion of the casing adjacent thereto.

13. A mercury switch having a tubular metal shell comprising a main body portion closed at one end and a portion of larger diameter at the other end terminating in a beaded edge portion which extends radially inwardly to provide a retaining flange, a shoulder portion joining said main body portion and said portion of larger diameter, an insulator fitting within said portion of larger diameter and held endwise in one direction by said shoulder portion of the shell and in the other direction of said retaining iange,

an electrode mounted in said insulator, sealing means extending across the area between said electrode and said shell, said retaining flange applying a force compressing said sealing means and forcing it into sealing engagement with said electrode and causing it to expand radially into sealing engagement with said shell, and a body of mercury in said shell which connects the main body portion of the shell and the electrode across a portion of the insulator when the switch is tilted in one direction.

14. A mercury switch comprising a closed end tubular shell having an enlarged portion at the open end, an insert of insulation sealed in said enlarged portion, said enlarged portion having its margin beaded over inwardly, a central electrode carried by said insert and communicating at its inner end with the inside of the shell, a body of mercury in said shell, a yielding gasket member extending over the entire area between said central electrode and said shell, said yielding gasket member being compressed axially of said shell by said beaded-over margin so as to be forced into sealing engagement with said electrode and expanded radially into sealing engagement with said shell.

15. In a mercury switch, a metal shell comprislng a first main cylindrical portion and a second portion of larger diameter joined to the rst portion by a shoulder and having an inturned flange at its open end, a circular insulator disposed in said second portion of the shell and held against endwise displacement by said shoulder and said flange, an axially disposed electrode having a stem extending outside of .said

insulator, a body of mercury for making contact between the electrode and the shell, an annular member of yielding insulating material around said stem and extending into engagement with said shell, and an annular member of relatively rigid insulating material around said stem between said member of yielding material and said inturned flange for distributing the force applied by said inturned flange over substantially the entire area of said member of yielding material and forcing it into sealing engagement with both said electrode and said shell.

16. In an inclosed mercury switch, the combination of a tubular cup-shaped shell having an inturned flange at its open end, a body of insulation adjacent the open end of the shell and having a shouldered aperture, an electrode member carried in and closing the aperture in said body, said electrodelmember having a stern and a head provided with a recess therein, a body of mercury for making contact with said recessed head and a part of said mercury being normally retained in said recess by said shoulder, an annular member of yielding insulating material around said stem and extending into engagement with said shell, and an annular member of relatively rigid insulating material around said stem between said member of yielding material and said inturned flange for distributing the force applied by said inturned ange over substantially the entire area of said member of yielding material and forcing it into sealing engagement with both said electrode and said shell.

MARTIN G. SA'I'EREN.

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