US2974211A - Electric switches - Google Patents

Description

March 7, 1961 E. F. BREDE ELECTRIC SWITCHES Filed March 23, 1959 INVENTOR.

ERWIN F. BREDE 1.1 1 l a I United States Patent The object of this invention is to provide a low cost momentary push button switch capable of perpetual service without functional breakdown, and which will operate reliably in any possible position whatsoever in which it is placed; e.g., its operation must not be limited to table or wall mounting and it must be capable of operating upside down or in any angular position; and also, which will be capable of operating in the absence of the influence of gravity if need be, and must not be subject to failure due to inertia effects if used on a vehicle or machine. 1

. The characteristic purpose of my invention is to effect better reliability of operation in electric single pole momentary push button switches of the type which are normally on open circuit. This purpose applies to the above mentioned class of push button switches in general, but more especially to door bell push button switches in particular in order to prevent bothersome breakdowns due to dirty contacts of the butting type or to fissuring or breaking of flexible metal parts or a membranous part in a mercury type of switch.

- Heretofore mercury has been used as a medium for closing and opening the circuit in a push button type of switch in which a relatively large quantity of mercury in a membranous sack, or chamber in which one wall is of a material membranous in character, is used and compressed by a flat spring, or other means, in articulation with the membranous part and the push button when the button is pressed so as to raise the level of the mercury and bridge two contact points in the upper part of the mercury housing and thus close the circuit. But such a system of parts, aside from being redundant, is liable to breakdown eventually due to repeated flexing, or deterioration of the membranous part. One such type of switch will not operate automatically in all of the possible positions in which it may be placed due to the influence of gravity on the quantity of mercury required for its operation. Another such type of switch overcomes the impracticability which could be caused by the influence of gravity but the amount of mercury required to make it function properly is far in excess of the minimum amount required to conduct the whole current that is to be controlled. Still a third such type of switch, besides requiring a quantity of mercury far in excess of the minimum amount required to conduct the whole current, requires a supplementary mechanism, built into the switch, to accommodate the condition caused by expansion and contraction of the mercury due to temperature changes.

-None of these three cited switches would be reliable if used in a situation where there is excessive turbulence of the mercury; as for example, on some vehicles or on a machine which does gyrations or the like in its cycle of operations.

My invention is an improvement over customary electric push button switches for the following reasons: It embodies only a few parts none of which are liable to deterioration or breakdown due to repeated use since none of them are flexible except a single compression spring connector which lasts continually. The mercury ice 2 a component is contained in a tubular part of a small'tubu lar capsule; constructed of hard insulator which must, however, be inert to the chemical effects of mercury; in

such manner that the mercury lies in the tube between a fixed electric contact that hermetically seals the base of the tube, and a movable electric plunger contact that keeps the other end of the tube closed at all times, and so as to close the circuit through the mercury only when the distance between the two contacts is shortened Sllffif ciently by the plunger contact moving toward the fixed contact in the tube and pushing the globuleof mercury until these three elements are-in electrical contact when the button is pressed sufliciently; and the electric circuit is automatically opened by the compression spring when the pressure on the button is released sufiiciently. It is reliable in any possible position in which it is placed since neither the influence of gravity nor the lack of it can by itself cause themercury to bridge the two contacts. It closes the circuit through a mercury component the whole volume of which need be no larger than the minimum amount required to safely conduct the whole current that is to be controlled; as for example, if used to control an electric door bell circuit the volume of the mercury component need not be over .0002 cubic inch. Since the quantity of mercury it requires, which is relatively small,

is contained in a space whose cubical measurement when the switch is normally open is over twice that of the mercury any expansion or contraction of the mercury is negligible and there is no need for additional mechanism to accommodate the condition caused by temperature changes. It would be practical even in the absence of the influence of gravity; as for example, at a point in outer space where the gravitation of the earth and that of the moon are equal, except in this instance in situations where there are inertia effects the size of the globule of mercury must be limited in order to prevent lessening of the cross sectional area of the mercury; otherwise it is also reliable where there is excessive turbulence of the mercury; as for example, inertia effects on the mercury that could be caused if it, were used on a vehicle subject to either rapid acceleration or rapid negative acceleration or to vertical movements caused by a rough road or the like, or inertia effects on the mercury that could be caused if it were used on a machine that does gyrations or the like in its cycle of operations.

Referring to the drawings:

Figure 1 is a plan view of the electric push button switch as assembled in unmodified form ready for fastening with two fasteners to a surface.

Figure 2 is a vertical sectional view except with portions thereof in elevation, taken on line 2-2 of Figure 1.

a Figure 3 is a horizontal sectional view taken on 33 of Figure 2.

Referring to the drawings for a detailed description; in Figure 1 the push button, which is constructed of hard insulator, is 1 and it also appears in Figure 2; 2, which also appears in Figures 2 and 3, is the cover and it can be constructed of either rust proof metal-or hard plastic insulator; 3 and 4, which also appear in Figure 3, are two screws, each passing through holes of appropriate size through the same diameter and through the outer flange of the cover 2 and the base 5, shown in Figures 2 and;3,- and their purpose is to secure the assembled push button switch to a surface.

In Figure 2 the base, mentioned above and also shown. in Figure 3, is 5 and it is constructed of hard insulator and carries all of the electrical parts in such manner as 2,974,211 Patented Mar. 7',-

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plug having a flange on the under side and serves doubly as a fixed electric contact and as a means of securing the tubular capsule 9, shown in vertical section in Figure 2 and horizontal section in Figure 3, to the copper strip 7, also shown in Figure 3, and'to the base 5; and the flange serves to prevent the base 5 from buckling inthe event of any excessive pressure on the button since the flange occupies a space between the under side of the base and the surface on which the assembled push button switch is mounted. This contactplug 6 secures the tubular capsule fast to the copper strip,7 and'to the base 5 by virtue of a tight forced fit into the tubeiofthe, tubular capsule. 7, shown sectionally in-Figure 2 and full in Figure 3, is an electric connector in the formofa thin flat copper strip extendingfrom under the flange of 6, to which it is soldered by 8, to under 'the rust proof metal machine screw of binding post 16, also shown in Figure 3. 8 is solder. 9, shown in vertical section in Figure 2 and in horizontal section in Figure 3, is a tubular capsulewhose function has been describedjin the summary, of my invention herein preceding the description of the figures. It is constructed of hard insulator, either clear or opaque; which must, however, be inert to the chemical effects of mercury. It houses the fixed contact plug 6 hermetically sealing the inner end of the tube; the globule of mercury 10 which occupies less than half of the space in the tube of the assembled capsule when there is no pressure applied to the button, but which has suflicient volume to adequately make contact with the plunger contact 11 when the button is pressed sufliciently to make the plunger contact travel toward the mercurythe maximum distance provided by the tube; and the movable plunger contact 11 which keeps the end of the tube into which it fits closed at all times. The diameter of the tube is such as to insure a snug fit between the rod portion of the plunger contact but-at the same time only large enough to avoid friction enough to render the electric compression spring connector 12, also shown sectionally in Figure 3, capable of moving the plunger and push button to their original open circuit position after pressure on the button is completely released. The diameter of the tube for any given application of this invention is determined from the size of the current to be controlled, the diameter being a function of the size of the current. 10, shown sectionally in this figure but full in Figure 3, is a globule of mercury described in the foregoing herein and it is the medium through which the circut is closed when the button is pressed sufficiently to move the plunger contact 11 until it compresses the mercury between the two contacts thus closing the circuit. The quantity of mercury used is such that it will completely occupy the space remaining in the tube when theplunger hastraveled toward the mercury until stopped by the plunger flange striking the outer end of the tubular capsule. The mercury when being thus compressed begins to lose its globular form and finally completely occupies the remaining space and remains so until pressure on the button is released whereupon it begins to assume the globular form again. 11, shown in elevation and whose function has been described in the foregoing herein, is a rust proof solid metal electric contact plunger whose head is a thin flat round flange which is in articulation with the base of the push button 1 and whose opposite extremity is the contact surface that pushes the mercury when the button is pressed sufliciently. The portion of this electric plunger contact that travels in the tube of the tubular capsule is a rod of such diameter asto insure a snug fit between this rod and the tube into which it fits, at the same time however, being just loose enough to render the compression spring portion of the electric compression spring connector 12 capable of movingthe plunger and push button to their original opencircuit position after pressure on the button is completely released. The plunger contact is so designed that when the button is pressed sufficiently the plunger will travel until its flange strikes the outer end of the capsule and in the tube there is a space left which is completely occupied by the mercury. 12, mentioned above and shown in vertical section in this figure but in horizontal section in Figure 3, is a specially constructed combination of a Phosphor bronze or brass compression spring and electric connector. Its function is to automatically move the plunger and push button toward their original open circuit position when pressure on the button is released, and also to make a permanent electrical connection between the plunger 11, to-which it is soldered by 13, and the binding post,14, also shown in Figure 3, to which it is electrically connected and held secure under a rust proof metal washer 15, shown sectionally in this figure but full in Figure 3, by means of a hexagon rust proof metal machine screw nut on binding post 14. It also serves to keep the switch circuit open when the button is not being used. The inside diameter of the compression spring portion of this component is about ,4 of an inch larger than the outside diameter of the tubular capsule 9 in order to avoid any friction between these two components. 13 is solder. 14, which also appears in Figure 3, is a binding post consisting of a rust proof metal machine screw, a rust proof metal washer 15 mentioned above, and two hexagon rust proof metal machine screw nuts. One of the nuts secures the combination compression spring connector 12 and the washer 15, as described above, and the binding post itself to the base 5. The other nut is for the purpose of connecting to this binding post one of the terminal wires 17, shown sectionally in this figure and full in Figure 3, of the circuit which is to be controlled by the push button switch. 15, shown sectionally in this figure andfull in Figure 3, is a rust proof metal washer used as described above. 16, which also appears in Figure 3, is a binding post consisting of a rust proofmetal machine screw and twohexagon rustproof metal machine screw nuts. One of the nuts secures this binding post in electrical contact with the copper strip 7, as described in the foregoing herein, and to the base 5. The other nut is for the purpose of connecting to this binding post the other terminal wire 18, shown full in this figure before it enters the push button switch and sectionally where it is fastened under the nut and full in Figure 3, of the circuit which is to be controlled by the push button switch. 17 and 18, as described above, are the two terminal wires of the circuit which is to be controlled by the push button switch. 19 is a coat of electrical insulating varnish over the bottom parts only of the entire recess on the under side of the base 5. The insulating varnish prevents electrical leakage which otherwise might be caused by moist atmosphere or the like.

In Figure 3 the cover, shown in horizontal section, is 2.

It can be constructed of rust proof metal or hard plastic and together with the push button 1 serves to cover the insulator and it is completely described in the detailed description of Figure 2. 9 is a horizontal sectional view of the tubular capsule which is constructed of hard insulator, either clear or opaque; which, however, must be chemically inert to the chemical action of mercury. The function of the tubular capsule 9 is described in the summary of my invention preceding the description of the figures herein and a complete description of the physical aspects of the tubular capsule is given in the detailed description of Figure 2 so further explanation of it here should not be necessary. whichis described in the detailed description of Figure 2 and'reference is also made to the fact that the volume of the mercury required for any given application of my invention need be no larger than such volume as will safely carry the specified current. In my invention only 10 is a globule of mercury the safe current carrying capacity of mercury indicates the volume of mercury to be used for a given current. In other words the volume of the mercury to be used is commensurate to the maximum specified current to be controlled and the mechanism of my invention is not dependent on a superfluous volume of mercury. 12, shown in horizontal section, is a specially constructed combination of a Phosphor bronze, or brass, compression spring and electric connector. It and its function are described in the detailed description of Figure 2 and should not need any further explanation here. 14 and 16 are two binding posts and they also are described in the detailed description of Figure 2. Their ultimate purpose is to provide a means for connecting the two terminal wires 17 and 18, respectively, of the circuit to be controlled by the push button switch. is a rust proof metal washer whose purpose has been described in the detailed descriptionof Figure 2. 17 and 18 are the two terminal wires of the circuit to be controlled and they pass from without through two identical holes 20 and 21, respectively, in the base 5 and are connected to the binding posts 14 and 16, respectively. 20 and 21 are two holes of such diameter as to snugly accommodate the terminal wires 17 and 18, respectively, through the base 5. They are located symmetrically on a diameter of the base, close. to the binding posts 14 and 16, respectively, and directly under the bell shaped part of the cover 2. Their purpose is to provide openings for the terminal wires 17 and 18, respectively, to facilitate their connection to the binding posts 14 and 16, respectively.

It should be noted that in this specification the volume of mercury is referred to as a globule whose volume is a function of the size of current to be controlled, and it f0llows that in designing this push button switch to control a specified current, it should be taken into account that the maximum current that my invention can control is limited to such current as that which the largest possible globule of mercury will safely conduct because, except in the absence of gravity, when a volume of mercury originally globular in shape is increased beyond a certain limit in a space that is always larger than the volume of the mercury it loses its globular shape and assumes a different shape on account of the weight of the mercury overcoming the surface tension of the globule of mercury, and the scope of my claim following herein does not include the use of mercury in any physical shape other than globular shape.

I claim: In a push button electric switch an improvement in the compactness and durable qualities of the switch by the elimination of all flexible solid parts, including membranous parts, other than a single compression spring portion, and elimination of all electric contact points of the butting or sliding type that close the circuit exclusively through a solid state medium; with the result that there is no component part subject to the destructive efiects of repeated flexure that could cause breakdown and failure of the switch: accomplished by means of a tubular capsule constructed of hard insulator inert to the chemical effects of mercury and which houses three component parts; a fixed electric contact plug which hermetically seals the inner end of the tube and secures the capsule to the top of the base and, in electrical contact, to a flat copper strip connecting it on the under side of the base to a binding post fastener; a globule of mercury that by volume is less than one half the internal space left in the tube when the capsule is assembled and no pressure is applied to the button; an electric plunger contact whose shank is a rod which fits into the outer end of the tube and keeps it closed at all times and whose head is a thin round flange which is in articulation with the button and is electrically connected to an electric compression spring connector serving to connect the plunger contact to the other binding post on the top side of the base and to keep the switch circuit open when no pressure is applied to the button; assembled in such manner that when the button is pressed sufliciently the plunger contact moves in the tube toward the mercury, pushes it, and finally compresses it against the contact plug that seals the inner end of the tube thus closing the circuit and coming to rest as the head of the plunger contact strikes the outer end of the tubular capsule at the same time that the mercury completely occupies the space remaining in the tube, and that when pressure on the button isreleased sufliciently the compression spring portion of the compression spring connector returns the button and plunger contact to their original open circuit position.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,493 Harrison et a1. July 1, 1941

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