US2980778A - Plunger type mercury switch - Google Patents

Description

April 18, 1961 K. HUNCIKER 2,980,778

PLUNGER TYPE MERCURY SWITCH Filed Aug. 1, 1958 2 Sheets-Sheet 1 27 IN V EN TOR.

KARL HUNG/KER April 18, 1961 K. HUNCIKER PLUNGER TYPE MERCURY SWITCH Filed Aug. 1, 1958 2 Sheets-Sheet 2 FIG. 5

Fig-6 INVENTOR. KARL HL/NCIK ER PLUNGER TYPE MERCURY SWITCH Karl Hunciker, Chicago, Ill., assignor to The Mercoid sgrgoratlon, Ch cago, 11]., a corporation of Dela- Filed Aug. 1, 1958, Ser. No. 752,463

Claims. (Cl. 200-112) The invention relates to mercury relays of the fluid flow, plunger type which produce a mercury to mercury make and break and has reference more particularly to improvements in the construction and mode of operation of such relays wherein definite periods of operation can be obtained therefrom at maximum rated values without deterioration and with low contact resistance and low internal heating.

As heretofore constructed, such relays have been characterized by a magnetizable plunger which normally floats in a main body of mercury contained within a closed tube of glass generally having a uniform diameter throughout its length. When the solenoid is energized to depress the plunger the main body of mercury is displaced and the same rises in the tube to unite with a second body of mercury contained in a ceramic cup, thereby closing an electric circuit through electrodes, respectively, immersed in each body of mercury at all times. To protect the glass tube from the are caused by the make and break of'the electric circuit, a tubular are resistant shield is employed and the said shield thus presents a concentrated area for the accumulation of dross which in time will cause defective operation of the said relay. Also the floating plunger will assume different depths of submersion with magnetizing voltages which may vary as much as twenty percent. At low voltages less mercuryis displaced to reduce the amount present at contact level below that desired for the maximum rated current capacity of the device. Thus upon initial closure aminimum of mercury may be presented for contact al though the current loadmay be close to a maximum.

Accordingly, the present invention has for its principal object to provide a device which will overcome the defects and limitations of the relay switches as heretofore manufactured, which will be rugged in construction; dependable in operation; and which will have a high electrical rating.

Other objects of the invention are to provide an improved fluid flow, plunger type relay wherein the various partsthereof will be so arranged and proportioned that the are resistant shield can be eliminated, thereby simplifying. the structure; to provide a relay as described which will have low contact resistance and low internal heating; and to provide a relay wherein the contacting surfaces of the mercury are maintained clean and free of dross, thus prolonging the useful life of the relay and assuring the best performance obtainable with clean mer- A more specific object is to provide a relay characterized by a lower section of tubular glass for containing the main body of mercury and the floating plunger, and by an upper glass section of enlarged diameter within which is located a ceramic cup containing the second body of mercury. The upper glass section thus provides a large surface area at the mercury contact level and also the glass walls are sufficiently spaced from the arcing area to be adequately protected from the damaging effects of the arcs.

atent O! ice Another object resides in the provision of a relay wherein the ceramic cup has its outer periphery at the top open end bevelled at an angle of approximately forty-five degrees. This bevelled edge, where the two bodies of mercury separate upon opening of the electric circuit, directs the arc at an angle to the walls of the container, thus increasing the arcing distance.

Another object resides in the provision of a mercury relay of the plunger type having secondary magnetic means for assisting the solenoid in depressing the plunger, thereby assuring uniformity in operation and the main tenance of current capacity throughout the fluctuations encountered in normal commercial voltages.

\Vith these and various other objects in view, the invention may consist of certain novel features of construction and operation, as will be more fully described and particularly pointed out in the specification, drawings and claims appended thereto.

In the drawings which illustrate an embodiment of the invention, and wherein like reference characters are used to designate like parts Figure 1 is a vertical sectional view taken through a relay of the fluid flow, plunger type, and which embodies the various improved features of the present invention, the parts thereof being shown in open circuit position;

Figure 2 is a vertical sectional view similar to Figure 1 but showing the parts of the relay in closed circuit position;

Figure 3 is a transverse sectional view taken substantially along line 33 of Figure 1;

Figure 4 is an exploded view of the magnetizable plunger showing the same as including the magnetic iron jacket, the core, and the ceramic cup;

Figure 5 is a fragmentary sectional view showing a modification of the invention wherein a metal ring is employed at the mercury contact level for reducing the contact resistance of the relay to the lowest possible minimum; and

Figure 6 is a fragmentary sectional'view similar to Figure 5 but showing the parts of the relay in closed circuit position.

Referring to the drawings and in particular to Figures 1 and 2, the container for the relay 10 consists of two sections, namely, 11 and 12, each comprising tubular bore-silicate glass, with the upper section 12 having a diameter which is larger than the diameter of the lower section 11 and wherein the lower section is open at its upper end only. The sectional container is completed by the preformed metal ring 14 and by the metal cap 15. Each glass section is fused to the metal ring 14 to thus unite the sections of the container and provide a continuous chamber therein and which is closed by the metal cap 15, fused to the top section 12. The ring 14 serves as one of the electrodes of the relay and accordingly the ring has the terminal 16 electrically connected thereto. The other electrode 17 is electrically connected to the cap 15 as by welding at 18, and the electrode depends from the cap, as shown in Figures 1 and 2. The terminal 19 has electrical connection with the cap and thus with the electrode 17.

The plunger 20 of the relay, which may be generally termed a floating body, is located within the lower glass section 11 which also contains the main body of mercury 21. Said floating body includes the magnetizable iron jacket 22, Figure 4, the ceramic core 23 and the ceramic cup 24. The iron jacket is slotted at 26 to reduce eddy current losses when operating on alternating current and as a result the heating effect of the current is likewise reduced. The iron jacket 22 is additionally pro vided at each end with the core retainers 27 for retaining the core 23 within the jacket. The fingers 28, which project upwardly from the iron jacket, are spring tensioned and grooved as at 30 for gripping and supporting the ceramic cup in spaced relation above the top of the jacket and core. The said cup is thereby securely attached to the plunger 20 and since the said'cup is formed of ceramic material it is well insulated from both the plunger and the main body of mercury. As previously explained, the ceramic cup 24 contains the second body of mercury 31 which has electrical contact with the electrode 17. It will be observed that the electrode 17 is irnmersed at all times in the second body of mercury and that the electrode is of such length that it remains within the ceramic cup for all positions of the plunger, and, further, that the electrode limits the floating position of the plunger, as is evident from Figure 1. The cap 15 is provided with a hole in the top center thereof through which the container can be exhausted following assembly of all the parts within the same. Following the exhausting operation, the container may be supplied with a gas such as hydrogen to suppress arcing, whereupon the container is filled with the desired amount of mercury andthen sealed closed to complete the assembly.

During operation of the relay it will be understood that the plunger 20 is alternately submerged and then allowed to rise and float on the mercury pool 21. To reduce the frictional engagement of the jacket 22 with the walls of the lower section, the said jacket is provided with a number of small knobs 32 so as to minimize contact of the jacket with the glass walls of the lower section. The ceramic cup 24 at the open top end thereof has its outer periphery chamfered at an angle of approximately fortyfive degrees. The bevelled edge, identified by numeral 33, is thus located at the make and break level for the relay and the are is thereby directed at an angle to the walls of the upper glass section to thus increase the arcing distance. With the upper section 12 of appropriate diameter the arcing distance is sufiicient to prevent the are from damaging the wall of the section.

The lower section 11 is located within the center opening of the solenoid 34. A supporting collar 35 also surrounds the lower section 11 above the solenoid 34 to provide a support for the relay and the mounting bracket 36 is secured at 37 to the support and at 38 to the iron cylinder 40. The iron cylinder is thereby retained within the center opening of the solenoid, being located below the glass section 11. The iron cylinder 40 provides secondary magnetic means for supplementing the magnetic forces produced by the solenoid for depressing the plunger 20. The iron cylinder is magnetized by the solenoid when the latter is energized and as a result the plunger is attracted, or, in other words, the plunger is pulled down into the main body of mercury within the lower section. As the plunger enters the magnetic field produced by cylinder 40 it is subjected to the attraction thereof, which assists the solenoid in depressing the plunger to its full extent, that is, until the shock absorber 41, in the form of a bent strip of spring metal, contacts the bottom wall of section 11. This secondary magnetic force is beneficial in several ways. It assures complete submersion of the plunger to the degree necessary to provide sufiicient mercury contact for satisfactory operation to the limit of its rated electrical capacity. This is accomplished throughout normal variations in commercial line voltages down to the lowest operating voltages. The secondary magnetic force furthermore assures permanency of suflicient mercury for contact following initial closure in the event such low voltage conditions occur. Thus dependability is assured at rated current values throughout commercial line voltage variations.

Low contact resistance is obtained by virtue of the shortest path existing between the electrodes for the flow of the electric current during the closed circuit position of the plunger. As is evident from Figure 2, current flow takes place through the mercury between the metal I 4 ring 14 and electrode 17. This short flow path for the electric current through the mercury reduces the internal heating of the relay which is a factor in establishing its electrical capacity. In the modification of the invention, as shown in Figures 5 and 6, the flow path for the electric current is even further reduced by the provision of the low resistance conductor 42 which is suitably welded or otherwise electrically connected to the metal ring so as to project upwardly therefrom. The conductor 42 partly or otherwise surrounds the ceramic cup 24 in relatively close relation thereto and thus when the plunger is in closed circuit position, as shown in Figure 6, the

current flows through the mercury between the top end j the container where it remains.

of the conductor 42 andthe electrode 17. The close proximity of the electrodes to each other reduces the contact resistance to the lowest possible minimum.

Although not fully explainable, the elimination of dross from the contact surfaces of the mercury in the present relay, is a proven fact. Dross which consists of scum and waste matter, produced by the action of the arcs on the center electrode and ceramic cup, is a factor in contaminating the mercury and if allowed to accumulate will bring about defective operation of the device. In the present relay the relative diameters of the ceramic cup and the upper glass section creates a trough of mercury from which dross disappears with repeated reciprocations of the plunger. During operation, the dross deposited on the surface of the mercury is washed or carried to the outer walls of the container as'the mercury is disturbed by the pumping action of the plunger as it floats and is depressed in the mercury. Collecting on the wall, the dross is washed down to the bottom of Should dross from the bottom be restored to the contact surface such as by shaking the container of mercury, it will again disappear upon righting the relay and subjecting it to a series of operations. Accordingly, the present relay operates with a substantially dross-free surface at contact level, thus prolonging the useful life of the relay and assuring the best performance possible with clean mercury. The size of the upper chamber, undoubtedly contributes to the clean mercury results obtainable with the present relay. The relatively large diameter of the upper section of the container permits the arc to blow dross to the far walls, and thus the dross doesnot accumulate upon the mercury adjacent the cup. With clean mercury the arc is reduced in temperature and little or no arcing occurs upon making contact. Borosilicate glass is preferred for the sectional container and ceramic material is desired for the core and the cup. However, the several elements are not limited thereto as other materials of an insulating nature could be substituted therefor. The plunger and solenoid have been described as coacting in a manner to form a normally open switch. It should be understood that the features and objectives of this invention can be obtained and not impaired by such modifications of the elements or their relationship to each other as would be made to provide a normally closed switch.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. A mercury switch comprising a two-section container wherein the lower and upper sections thereof are substantially cylindrical with the upper section being larger in diameter than the lower section, a metal ring located between the sections for joining and sealing the same, a main body of mercury contained within the container and extending normally to a level above the metal ring, a magnetizable plunger within the lower section and normally floating in the mercury contained by the lower section, a cap sealed to the upper section to close the container. an electrode depending from the cap, a ceramic cup supported by the plunger above the same whereby the cup is normally located within the upper section, a second body of mercury in the cup, said cup being so positioned that the electrode extends into the second body of mercury to be partly immersed therein for all positions of the plunger, a solenoid for magnetizing the plunger to effect downward movement thereof within the lower section for displacing the mercury there in and causing the same to rise and unite with the mercury in the cup, thereby providing a contact level for said bodies of mercury, and an upstanding conductor electrically connected to and supported by the metal ring, said conductor extending within the upper section in relatively close relation to the ceramic cup and within the main body of mercury, whereby the flow path for the electric current through the mercury from the electrode to the conductor is reduced to a minimum.

2. A mercury switch comprising a sectional container of non-conducting material including a lower cylindrical, closed bottom section and an upper section of tubular form and having a diameter greater than that of the lower section, a metal ring located between the sections and being hermetically sealed thereto for joining the sections, a magnetizable plunger having location within the lower section and normally floating in a body of mercury within the container, a vessel of insulating material supported by the plunger at its upper end to thus locate the vessel within the upper section, a second body of mercury within the vessel, an electrode extending into the vessel and into the second body of mercury for all positions of the plunger, means for actuating the plunger to cause downward movement of the plunger to displace the mercury in the lower section and cause the same to unite with the mercury in the vessel, thereby providing a contact level for said bodies of mercury closely adjacent the metal ring so that the electrode is electrically connected to the metal ring, the diameter of the upper section being such as to present a large surface area of mercury at the contact level and whereby the walls of the upper section are sufficiently spaced from the arcing area to be adequately protected from the damaging effects of the arcs, thus eliminating the need for a protective barrier in the upper section.

3. A mercury switch comprising a two-section glass container wherein the lower and upper sections thereof are joined and sealed by a metal ring, the upper section having a diameter greater than the lower section, a terminal member electrically connected to the metal ring whereby the same forms one electrode of the switch, a main body of mercury contained within the lower section of the container and extending normally to a level above the metal ring to maintain the metal ring immersed in the mercury at all times, a magnetizable plunger within the lower section and normally floating in the mercury contained by the lower section, means sealed to the upper section to close the container, a second electrode depending from said means, a vessel of insulating material supported by the plunger above the same to thus locate the vessel within the upper section at all times, a second body of mercury in the vessel, said vessel being so positioned that the second electrode extends into the for all positions of the plunger, means for magnetizing the plunger to attract the same downwardly within the lower section of the container and to displace the mercury therein causing the same to rise and unite with the mercury in the vessel, thereby providing a contact level within the upper section for said bodies of mercury and which results in electrically connecting the second electrode to the metal ring, said metal ring also having a location with respect to the contact level to provide a current path of approximately minimum length in the closed circuit position of the plunger, said plunger including an iron jacket in surrounding relation with a ceramic core and which is slotted longitudinally to reduce eddy current losses, and said iron jacket having small rounded projections on the outer surface thereof to minimize contact of the plunger with the walls of the lower section.

4. A mercury switch adapted to make and break an electric circuit by uniting and separating two bodies of mercury comprising, an hermetically sealed glass container having upper and lower cylindrical sections joined together by an intermediate metal ring constituting one electrode of the switch, the upper section being larger in diameter than the lower section to thus remove the walls thereof from the damaging effects of the switch are made within that area and which thus eliminates the need for a protective barrier and creates a large surface of mercury at make and break level, a magnetizable plunger having location within the lower section and movable to displace a body of mercury contained in the lower section, a vessel of insulating material supported by the plunger at its upper end to thus locate the vessel within the upper section, a second body of mercury within the vessel, a second electrode extending into the vessel and into the second body of mercury for all positions of the plunger, means for actuating the plunger to displace the mercury in the lower section and cause the same to unite with the second body of mercury at a contact level in the upper section, whereby said make and break level is in close proximity to the metal ring to provide a short conducting path of mercury over a large area between the two electrodes, and whereby said barrier free gap between the electrodes at the contact level permits the switch arc to blow dross towards the outer walls of the upper container to establish clean mercury at the contact area and also at the separation area of the mercury bodies.

5. A mercury switch as defined by claim 4, wherein the upper section of the container in creating a large surface of mercury at make and break level establishes a meniscus of mercury over which dross is washed to the outer walls of the upper section and down the walls thereof upon repeated agitation of the mercury as the plunger is actuated.

References Cited in the file of this patent UNITED STATES PATENTS 1,294,466 Housekeeper Feb. 18, 1919 2,147,506 Stoner Feb. 14, 1939 2,417,763 Larson Mar. 18, 1947 2,501,292 Russell et al. Mar. 21, 1950 2,506,763 Babler May 9, 1950 2,826,659 Raftree Mar. 11, 1958

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