US1951161A - Mercury switch - Google Patents

Description

March I 13, 1934. F. MOOS 1,951,161

MERCURY SWITCH Filed Feb. 20, 1950 1 g, INVE2T%W B I I ms ATTORNEY.

Patented Mar. 13,

UNITED STATES PATENT OFFICE 1,951,161 A MERCURY swrrcn Application February 20, 1930, Serial No; 429,861 3 Claims. (01. 200-152) The present invention relates to electric switches of the fluid flow type, and particularly to switches having soft glass envelopes.

. The invention consists in a new method and in 5 a new and novel combination of parts as hereinafter set forth and claimed.

A particular object of the invention is to pro duce a fluid flow switch having a soft glass en velope which will not only be inexpensive but reliable and which will have a long useful life. Another object of the invention is to provide an inlead for such a switch'whichwill be'relatively simple and inexpensive. Still another object of the invention is to provide a switch which will be sensitive to slight changes in the fluid level therein. Other objects and advantages of the invention will appear from the following detailed specification, or from an inspection of the accompanying drawing.

From the manufacturing standpoint the use of soft glass for the envelopes of mercury or other fluid flow switches is highly desirable, since it is relatively inexpensive and is easily worked. Several factors have, however, tended to mini mize the use of this material. One of these has been the fact that no simple, inexpensive inlead construction has heretofore been possible, especially where appreciable currents were to be interrupted. Platinum is too expensive for inleads having any appreciable current capacity; dumet is somewhat expensive and has the further dis-= advantage that in switches containing mercury it has been found expedient in some instances to either weld it to an electrode of different metal or else remove the copper sheath from the portion extending within the envelope; while other metals, such as tungsten, which have heretofore been used for inleads could not be conveniently sealed into soft glass. Furthermore, the life of such a switch has been uncertain since any areing in the switch in proximity to the soft glass wall is apt to completely destroy the switch. Certain remedial measures, some involving the use of shields of hard glass, fused silica, or the like, have heretofore been adopted, particularly in switches in which the circuit was made and broken between liquid electrodes, but the added expense has been a limiting factor in their use. Ihave discovered that both of these difliculties may be overcome by the use of chrome-iron inleads, suitably placed in the envelope, whereby a relatively cheap fluid switch of great reliability and having a long useful life is produced. The

chrome-iron alloy which is used for the inlead material is sealed into the soft glass envelope in a cury switch of t e tilting type in a closed circuit novel'manner of my invention, the inleads being so disposed within the envelope that a fluid pool always shields the adjacent portion of the soft glass envelope from the arcing which may occur when the circuit is either closed or interrupted. The method of sealing the chrome-iron inleads into the soft glass envelope according to my invention is extremely-simple, in that the inlead may be sealed directly into a lime glass envelope, or where the envelope is of lead glass the inlead need only have a lime glass, instead of the usual lead glass, head or ring fused thereto before sealing into said envelope. My new ar-= rangement of elements, which consists in placing at least one of the electrodes at some distance to from the end of the envelope and some distance from the bottom thereof, in a switch of the tilting type, is contrary to what has been considered the best practice in mercury switches, since it requires the use of more mercury, but I have found iii that this new arrangement is very effective in protecting the envelope. In mercury switches the use of chrome-iron inleads, due to the fact that the mercury does not tend to amalgamate there= with or adhere thereto, permits the construction tilt of a switch of this type which will be extremely sensitive to small changes in mercury level, a result which is impossible with other known inlead materials without rendering the protection of the walls by the mercury uncertain.

For the purpose of illustrating my invention I have shown one embodiment thereof in the accompanying drawing, in which Fig. l is a longitudinal cross section of a merposition,

Fig. 2 is a similar view of the same switch at the instant of opening, and

Fig. 3 is a longitudinal cross-section showing a detail of the inlead seal used in this switch.

In the drawing a tubular soft glass envelope 1, which is preferably filled with hydrogen or the like, has inleads 2 and 3 of suitable material, such as chrome-iron alloy, sealed through the top thereof toward one end of said envelope.

I have found the chrome-iron alloy which is sold by the Crucible. Steel Co. of America under the trade name of Stainless Iron 23/30 Chrome Annealed to be especially suitable for these electrodes, although other similar alloys having a coeflicient of expansion not materially greater than that of soft glass and having the property of not amalgamating with mercury can be used in place thereof.

A body of mercury 4 in said envelope 1 is adapted 110 to close the circuit between said electrodes when the envelope 1 is in the position indicated in Fig. 1. The inlead 2 is located at an appreciable distance, of say atleast the radius of the envelope 1, from the end of said envelope and while it extends downwardly toward the bottom of said envelope, terminates at a considerable distance thereabove. The inlead 3 is located at any suitable distance from the inlead 2, and extends substantially to the bottom of the envelope 1, the lower end thereof preferably being pointed or flattened'so as not to impede the free flow of the mercury 4 thereby. The position of the inlead 3 may be varied considerably, however, so long as it makes contact before inlead 2, and maintains contact longer, with the mercury 4 when the switch is tilted between the positions of Figs. 1 and 2.

As shown in Fig. 3, the seal between envelope 1 and the inleads 2 and 3, when said envelope is of lead glass and said inleads are of chrome-iron, is effected by fusing a bead 5 of lime glass to said inleads, and then fusing said envelope to said head.

In the use and operation of the switch, the switch being in the position shown in Fig. 1 a circuit will be completed by the mercury 4 between the inleads 2 and 3. As the switch is tilted toward the position shown in Fig. 2 the mercury 4 will decrease in depth until it finally opens the circuit at inlead 2. At this moment the mercury 4 still extends to the adjacent end of the envelope 1, hence the bottom of said envelope, which is the only part thereof in proximity to the arc of rupture, is completely shielded thereby from thearc. Since the arc can thus have no deleterious eflect on the envelope 1, it follows that the switch has an extremely long useful life. This result may also be achieved when inleads which are wet by mercury after amalgamation therewith are used, but only by considerable sacrifice in the sensitivity of the switch.

While I have shown and described a specific embodiment of my invention it is obvious that my invention is not limited thereto. It is further to be understood that various changes, omissions and substitutions may be made therein without departing from the spirit of my invention.

What is claimed is:

'1. In an electric fluid flow switch of the tilting type, an elongated tubular sealed vitreous envelope, a conducting fluid therein, and inleads to which mercury will not adhere sealed into said envelope and extending into said fluid when said switch is in a closed circuit position, one of said inleads being at a distance from the end of said envelope which is at least equal to the distance from the side walls of said envelope, and terminating at an appreciable distance from the bottom of said envelope, and another inlead so located as to be in contact with said fluid before said circuit is made and after it is broken at first said electrode, said fluid being suflicient in quantity to form a shield between arcs at first said electrode and the bottom of said envelope.

2. In an electric fluid flow switch of the tilting type, an elongated tubular sealed vitreous envelope, mercury therein, and inleads of a chrome iron alloy which is not wetted by mercury sealed into said envelope and extending into said fluid when said switch is' in a closed circuit position, one of said inleads being at a distance from the end of said envelope which is at least equal to the distance from the side walls of said envelope, and terminating at an appreciable distance from the bottom of said envelope, and another inlead so located as to be in contact with said fluid before said circuit is made and after it is broken at first said electrode, said fluid forming a shield between arcs at first said electrode and the bottom of said envelope.

3. In an electric fluid flow switch of the tilting type, an elongated-tubular sealed vitreous envelope of soft glass, mercury therein, and inleads of a chrome-iron alloy which is not wetted by 110 mercury sealed into said envelope and extending into said fluid when said switch is in a closed circuit position, one of said inleads being at a distance from the end of said envelope which is at least equal to the distance from the side walls of 115 said envelope, and terminating at an appreciable distance from the bottom of said envelope, said inlead having a smooth surface to which mercury will not adhere, and another inlead so located as to be in contact with said fluid before said 120 circuit is made and after it is broken at first said electrode, fluid being suflicient in said quantity to form a shield between arcs at first said electrode and the bottom of said envelope.

FRANK MOOS.

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