US2101101A - Liquid contact circuit closer - Google Patents

Description

Dec. 7, 1937. R: FLsAMBLEsoN LIQUID CONTACT CIRCUIT CLOSER Filed Jan. 14, 1937 Inventor: Robert F'. Sambleson, bld

His 'ttor*ney.

Patented Dec. 7, 1937 s PATENT OFFICE LIQUID CONTACT omcmr CLOSER Robert F. Sambleson, to General Electric New York Bridgeport, Conn., assignor Company, a corpora-tion of Application January 14, 1937, Serial No. 120,546

6 Claims.

The present invention relates to liquid contact circuit closers of the type having an envelope containing ,a small quantity of mercury which is arranged to complete and. interrupt a circuit between the terminals of the circuit closer. The present invention is particularly concerned with circuit closers of the type in which the terminals comprise the major portion of the envelope, and in which the enclosureof the envelope 'is completed by a relatively small part of glassarranged -between the terminals and having a glass-tometal seal with the edges of the terminals.

The object of my invention is to provide an improved Construction and arrangement in liquid contact circuit closers of this type, and for a consideration of what I believe to be novel and. my invention, attention is directed to the accompanying description and the claims appended thereto.

In the accompanying drawing, Fig. 1 is a sectional elevation of a liquid contact circuit closer embodying my invention; Fig. 2 is a sectional View taken on line 2-2 of Fg. 1; Fig. 3 is a sectional elevation of a modification, and Fg 4 is a sectional elevation of a prior art Construction.

Each of the circuit closers illustrated has an envelope l containing a limited quantity of mercury 2. r The major portion of the envelope comprises. opposed cup-shaped metal terminals 3.

Between the terminals is a diaphragm .4 of insulating material having an 'opening 5 therein through which the mercury flows in order to complete a circuit between the terminals' When the circuit closers are in the position il1ustrated, the circuit between r the terminals is v completed. 5 When the circuit closers are rotated about the axes of the terminals a few degrees from the position illustrated, the opening 5 is raised clear of the mercury and the circuit between the terminals is broken by separation of the mercury within the opening as it flows 'from each end theof. In this position, thediaphragm separates the mercury into two pools. When the circuit closer is returned to the 'position illustrated, the circuit between the terminals is completed by 45 the joining of mercury flowinginto the opening 5 from each end thereof. The diaphragm 4 is sealed to the edges of the terminals and the seal completes the enclosure of the envelope. Hydrogen at a. pressure of one or more atmospheres is 50 sealed within the envelope to increase the interrupting capacity of the circuit closer.

V In the construction illustrated in Figs. 1 and 2, the diaphragm 4 is of glass having a coemcient of expansion which' very closely matches the coei- 5 cient of expansion of the metal terminals and the seal between the terminals and the diaphragm is 'eflected by' heating the rim of the diaphragm until the glass has softened and -by pressing the edges S of the terminals into the softened glass.

00 Due to the shape of the edges 6, they will be somewhat flexible and accordingly a minimum of strain will be placed on' the seal due to' differences in the exp-ansion of the glass and metal. In the Construction shown in Fig. 3, the diaphragm 4 is also of glass having a coeificient of expansion closely matching the metal of, the terminals. In this construction, the terminals are provided with outwardly extending fianges 'I which fit in annular grooves 8 around the rim of 'the diaphragm. I

The seal between the diaphragm and the terrninals is completed by a head or fillet 9 of glass of the same composition as' the glass of the diaphragm which is fused to the flanges 'I and to the outer periphery of the diaphragm. The Construction shown in Fig. 4 is that shown in application Serial No. '159,527, filed December 28, 1934. It is similar to the Construction shown in Fig. 3 except that the diaphragm is a ceramic instead of glass. In the operation of circuit closers of this type arcing is producedvwithin the mercury both duringthe completing and the interrupting of the circuit between the terminals. Due to the surface tension of' the mercury, the arcing during the 'joining of the mercury to complete the circuit is more troublesome` than the arcing during the separation of the mercury to interrupt the circuit. The wearing away of the material in the opening 5 of the diaphragm during arcing is due to two factors, heat shock and erosion. Heat shock, which is due to high local temperatures produced in the vicinity of the arc, tends to cause chipping or fiakng. Chipping due to heat shock is particularly pronounced in the case of glass. The wear due to erosionis particularly great when the material in the opening 5 is porous It is due to .the seepage of partcle's of mercury into the interstices of the material and to subsequent arcing to these particles which causes the particles of mercury to be forced out of the interstices of the material with an explosive effect. It has been found that ceramics, such as porcelains, are in general the most satisfactory materials for the opening in the diaphragm' The wearing of ceramics is mainly due to erosion. Mate'rials, such as glass. while not porous, and accordingly not subject to the erosive action, are brittle and are chipped away by the`heat shock due to the are.

Another requirement for the material of the diaphragm is that' the 'daphragm be substantially non-porous. Glass admirably fills this characteristic, while ceramics are all porous' to some extent. The porosity of the diaphragm in time may cause sufii'cient absorption of th mercury to short-circuit the circuit closer or to lower the liquid level in the circuit closer so that the quantity of free mercury remaining in the circgit closer is insuflicient for satisfactory operation. Also, a porous material would tend to have expesive wear due to erosion as described above.

One of the first efiects of decreasing the quantity of free mercury wouldwbe to change the angle of turning of the circuit closer necessary to make and break the circuit. Since the mechanisms with which this circuit closer is used are in general designed for a fixed angle of turning, it is obvious that a change in the necessary angle of turning is undesirable.

A further requirement for the diaphragm is that its coefiicient of expansion closely match the coeficient of expansion of the metal of the terminals and also that it closely match the co efiicient of expansion of the' glass used in the seal between the terminals and the diaphragm.

This is necessary if the seal is to remain tight enough to prevent the outward leakage of hydrogen and the inward leakage of air. In the prior art construction shown in Fig. 4 in which the diaphragm is made of a ceramic it has been very difiicult to find a material for the diaphragm which will be satisfactory from the point of view of resistance to wear caused by arcing, will be sufiiciently non-porous, and will also have a coefificient of expansion which will closely match the coefiicient of expansion of the metal terminals and of the glass seal since these properties are not related in that if one of the properties of a material is ideal, the other properties will be somewhat undesirable. The coeflicient of expansion of the material of the diaphragm is the controlling property, since if it is such as to cause leakage of the seal, the circuit closer quickly becomes utterly useless due to oxidation of the mercury. In the prior art Construction shown in Fig. 4, it has therefore been necessary to select materials for the' diaphragm which were somewhat deficient in arc resistance and were somewhat porous in order to' secure a material having the proper coefiicient of expansion. This problem has been further increased by the fact 'that the diaphragm, the seal, and the terminals have different rates 'of heating and therefore assume different temperatures so that even if the coefiicients of expansion were matched very closely, the strains in the seal and the resultant possibility of leakage would not be eliminated.

Summing up, a satisfactory circuit closer'of this type requires a diaphragm which is nonporous, an opening in the diaphragm the surface of which is resistant to wear under the infiuence of an electric arc, and a seal which will prevent leakage of air into the envelope. The oxygen in the air would quickly oxidize the mercury, and render the circuit closer useless. With the prior art designsfor the circuit closers, it has been found difiicult to secure commercially practicable materials which would satisfy all of these requirements.

The circuit closers embodying the present inventionhave been designed to remove many of the limitations which have been previously placed upon the selection of materials for the diaphragm and the seal,. The diaphragm is made of glass which has a 'coefi'icient of expansion very closely matching the coefiicient of expansion of the metal of the terminals.` Such glasses are well known and have been` used commercially with good success. The diaphragm may be made by casting from molten glass or it may be made by mixing powdered glasses, at least one of which is a low melting point glass, pressing the mxture together to the desired shape, and then subjecting it to heat to fuse the low melting point glass. Either of these methods of manufacture result in a diaphragm which has the desired coefficient of expansion and which is non-porous and therefore impervious to mercury. In the opening 5 is a bushing I of a' ceramicwhich is highly resistant to wearing by either erosion or chipping under the influence of an electric arc. The bushing is suitably cemented to the glass, for example, by casting it in the glass. The joint between the bushing and the glass presents no problemsince it is only required that this joint be mercury-tight. This is a much simpler problem than making such a joint hydrogen or airtight. The material for the bushing may be chosen almost wholly for its arc-resisting properties and with little regard for the matching of its coefficient of expansion with the coefiicient of expansion of the glass of the diaphragm. This makes possible the use of a much larger number of materials and further removes the necessity for closeness of control of the composition, constituents and manufacture of the ceramic. The manufacturing advantages are obvious. In the present construction, instead of selecting the material for the diaphragm from one of the limited number of ceramics which are both resistant to wear under the conditions of an electric arc and which have a coeflicient of expansion closely matching the coefiicients of expansion of the metal and of the glass' seal, the diaphragm is made from the same glass as the seal, and the portion of the diaphragm which must be arcresisting is made from a separate material chosen expressly for this characteristic. This obviously greatly increases the number of materials which can be used in constructing the circuit closers and further makes possible the use of a material having greater arc'resistance which will result in a circuit closer having a longer life and more satisfactory Operating characteristics. The present Construction also makes possible a greater variety of methods for affecting the seal between the terminals. The seal shown in Fi g. 1 has been used commercially with great success in other constructions. It'obviously could not be used if the circuit closer were made as shown in Fig. 4 with a ceramic diaphragm. The seal of the type shown in Fig. 4: is also adapted for use'in the present invention, a circuit closer having such a seal being shown in Fig. 3. In this seal the diaphragm 4 and the glass bead 9 are of the same material. There is, therefore, no diiference in the coefficients of expansion which would place any strain on the seal and the diaphragm 4 and the bead 9 can, in eifect, be considered a single part. The seals shown in Figs. 1, 2 and 3 are, therefore, in efiect two-part glass-to-metal seals, which are well known in the art, and present no unsolved production dificulties. This -contrasts with the seal shown in Fig. 4 in which the diaphragm, a ceramic, must be chosen from a limited number of materials which are both resistant to wear under the influence of an electric arc and which have a satisfactory coeflicient 'of expansion. In this seal astrain which will result in fracture thereof may be produced by a difference in expansion between the glass bead 9 and the metal terminals 3 and also by a diiference in expansion between the glass bead 9 and the ceramic diaphragm 4. The seal shown in Fig. 4

is, in effect, a three-part seal; glass-to-metal and glass-to-ceramic; and there are accordingly much greater production diificulties in producing a successful seal.

With the present invention, each of the materials is chosen from the point of view of a single requirement. The material of the diaphragm is aromen chosen solely as a suitable material for a glassto-metal seal and the material of the bushing is chosen solely for its arc`-resisting properties. Since materials having these properties are well known and easily obtainable, the circuit closer is easier to manufacture. Also, it will have a longer life and more uniform Operating characteristics.

This contrasts with the prior art Construction shown in Fig. 4 where the choice of the material for the diaphragm must be a compromise between its arc-resistance, its porosity; and the matching of its coemcient of expansion with the coeflicients of expansion of the glass bead and oi'- the metal terminals and where the choice of the glass for the scaling bead must be with reference to its coefficient of expansion compared to the coeflicients of expansion of the diaphragm and of the metal terminals.

What I claim as new and desire to secure by V the mercury in another position of the circuit closer whereby the circuit between the terminals is completed through the mercury, said open'- ing being arranged so" that the circuit between the terminals is completed and interrupted in the mercury within said opening as the circuit closer is moved between said positions, and a' lining for the opening of insulating material resis'tant to wear under the influence of an electric arc.

2. In a liquid contact circuit closer, an' envelope containing a quantity of mercury, the' major portion of said envelope comprising opposed metal terminals provided with flexible edges, a diaphragm of glass 'therebetween having the flexible edges of the terminals sealed and embedded therein for completing the enclosure of the envelope, said diaphragm being adapted to separate the mercury into two pools in one position of the circuit closer whereby the circuit between the terminals is interrupted and having an opening therein arranged to be submerged in the mercury in another position of the circuit closer whereby the circuit between the terminals is completed through the mercury, said opening being arranged so that. the circuit between the terminals is completed and interrupted in the mercury within said opening as the circuit closer is moved between said positions, and a linin'g for the opening of insulating material resistant to wear under the influence of an electric arc.

3. In a'llquidcontact'circuit closer, an envelope containing a quantity of mercury, the major portion of said envelope comprising opposed metal jterminals, 'a diaphragm of glass between said terminals. flanges on said terminals abutting said diaph'agm, and a seal comprising a fillet of glass fused to said diaphragm and said flanges, said diaphragm being adapted to separate the mercury into two poolsin one position of the circuit closer whereby the circuit between the terminals is interrupted, and said diaphragm having 'an opening therein arranged to be submerged in the mercury in another position of the circuit closer whereby the circuit between the terminals is completed through the mercury, said opening being arranged so that the circuit between the terminals is completed and interrupted in the mercury within said opening as the circuit closer is moved between said positions, and a lining for the a' r opening of insulatng material resstant to wear under the, influence of an electric arc.

4. In a liquid contact circuit closer an-envelope containingta quantity of mercury, the major .portion of said envelope comprising opposed metal terminals, a member of glass between said terminals, said member having a glass-to-metal seal with the edges of said terminals for completing the enclosure of the envelope, said member being adapted to-separate the mercury into two pools in one position of the circuit closer 'whereby the circuit between the terminals is interrupted and being 'arranged to have the pools of mercury unite over an edge thereof in another :position of the circuit closer whereby the circuit between the terminals is completed through the mercury, said member being constructed and arranged so that the arcing between the pools of the mercury takes place adjacent said edge, and

` a member of insulating material resistant to wear under the influence of an electric arc sealed to said member providing an arc resistant surface for said edge. v

5. Inva liquid contact circuit closer, an envelope containing a quantity of mercury, the major portion of said envelope comprising opposed metal terminals, a diaphragm of glass therebetween having a glass-to-metal seal with the edges of said terminals for completing the enclosure of the envelope, said diaphragm being adapted'to separate the mercury into two pools in one position of the circuit closer whereby the circuit. be-

tween the terminals is interrupted and having an opening therein arranged to be submerged in the mercury in another position of the circuit closer whereby the circuit between the terminals is completed through the mercury, said opening being arranged so that the circuit between the terminals is completed and interrupted in the mercury within said opening as the circuit closer is moved between said positions, and a bushing of ceramic material sealed in said opening providing an arc resistant surface therefor.

6. In a liquid contact circuit closer, anenvelope containing a quantity ofmercury, the major portion' of said envelope comprising opposed metal terminals provided with flexible edges. a

diaphragm of glass therebetween having the flexible edges of the terminals sealed and embedded therein for completing the enclosure of the envelope, said diaphragm being adapted to separate v the mercury into two pools in one position of the circuit closer whereby the circuit between the teri minals is interrupted and having 'an opening therein arranged to be submerged in the mercury in another position of the circuit closer whereby the circuit between the terminals is completed through 'the mercury, said opening being arranged so that the circuit between the terminals is completed and interrupted in the mercury within said opening as the circuit closer is moved between said positions, and a bushing of ceramic material sealed in said opening providing an arc resstant surface therefor.

IROIERT F. SAMBLESN.

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