US2905785A - Electric switch - Google Patents

Description

F. R. QUINN ELECTRIC SWITCH Sept. 22, 1959 2 Sheets-Sheet 1 Filed July 8, 1957 n n mm w HR 5 s. n F .l n

United States Patent ELECTRIC SWITCH} Frederic R. Quinn, Red Hook, N3.

Application July 8,1957, Serial No. 670,435

7- Claims: (or. 200-8 7) invention relates to electric switches, and more especially torelay-operated toggle typeswitches and. other snap action switches operating. ona. similar principle, and-has for itsprincipal object a substantial reduction in the weight and volume of the device for a given switching duty, or alternatively, asubstantial increase inswitching capability for a given weight and volume. Other objects are increased life and reliability of the switch, and still others will be apparent from the following description and explanations. Although the invention was developed. for air-borne equipment, its desirability in other fields also will be evident.

The basic duty of an electric switch is to close and: to open anelectric circuit, the latter duty being ingeneral the more difficult one. In an air-break: switch, the device performs this circuit opening; duty by breaking the electrical continuity of the circuit by physically separating two terminals of the circuit sufficiently far apart to introduce an air-gap capable of withstanding the circuit voltage without break down. As'metallic contact is broken, an are or spark generally follows the break and tends to bridge the air-gap that is forming. In successful switch. operation, this are or spark is extinguished very promptly by the air gap. Failing this, the parting contacts are burnt and damaged.

As alternating current passes through zero twice each cycle; these zero-current instants'afford favorable movements for the extinguishing of the are or spark. However, this. causes the full circuit voltage to appear across the developing gap, tending to; restrike the are or, spark; It

will be. appreciated then that the speed with which the developing gap reaches its full design length may have a great deal to do with the: success or failure of opening the circuit.

Toggle type and. allied. snap switches are favored in small applications because they are: relatively simple, their contacts are stable and under pressurein their continuously operative positions, and can not. stay in an 'inbetwe'en position'partially open, partially closed. Al-

though theoretically there is a neutral in-between': positionat'which there is no force accelerating: the movable contact to one or to the other end position, yet this neut'ral position is highly unstable like a pencil, balanced on its point, and the movable contact generally moves into one or the other stable end position by the momentum acquired'while approaching that neutral position.

It may be appreciated on reflection that: the desirable characteristics of a toggle switch are obtained. at a considerable price, seeing that, in the neighborhood of that neut'ral point, the movable contact is not accelerated and gains no speed to shorten the opening time.

It is an object of the present invention therefore: to provide auxiliary means to furnish a substantial positive force to accelerate the movable contact in the neighborhood of the neutral position characteristic of atoggle type switch, and a preferred construction for this purpo'se' will now" be described.

2,905,785 Patented Sept. 22, 1959 e CC For an understanding of the invention principles, referenceis made to the following description and the accompanying drawings in which:

Fig; l is a magnified perspective view of a preferred embodying of the invention in a small unit, with the cover plate of one side removed. to expose to viewthe mechanism inside;

Fig. 2 is a cross-sectional view taken on the line 2-2 of Fig. 1;

Figs. 3 and 4 are plan views of the two members of the toggle mechanism;

Figs. 5, 6 and 7 are sectional elevation views illustrat; ing three important operating positions of the toggle mechanism and other parts of the switch; and

Fig. 8 isa horizontal sectional view illustrating the construction and disposition of the shading coil.

Referring now to Figures 1 and 2 together, 10 is a relay coil that initiates the operation of the switch; and 11a, 11b and 11c are the three legs of a three-legged laminated elcctromagnet core around the middle leg of which the relay coil is positioned. Part 12 is the movable armature of the electromagnet and is hinged on legllc of the core, being held there by means of spring 12a, while 13 is a fixed magnetic extension of leg 11a and overlaps the free end of armature 12 over the middle leg of the core. Part 15 is a magnetic extension of leg to assist in conveying the magnetic flux of this leg toarmature 12 and also to provide a pivoting groove for armature 12. A movable pin 14 runs through an axial hole in the middle leg of the core, projecting both above and below the core, so that when the relay coil 10 is energized, magnetizing the core, the armature 12 is pulled down over the middle leg and presses down on this pin. Below the core, this pin projects into a chamber formed by container 16 and there rests on a strip spring 17 which is shaped as shown and pivoted at its end 17a in a recess formed by the end 18a of a fixed conductive strip 18 set at the bottom of the chamber and, made fast to a supporting and insulating foundation layer 18d by means of a. rivet or screw 18c. The other end, 18b, of the strip 18 is shaped as shown so as to engage the portions 20a and 20b of element 20 which is one of the two toggle members. A plan of this member is to be seen in Figure 3. Part 21 is the other member of the toggle mechanism, shown in plan view in Figure 4. Portion 17b of the strip spring 17 is recessed to engage portion 21c (Fig. 4) of this toggle member. The two loops 21a and 21b (Fig. 4) of the toggle member 21 engage. the portions 20:: and 20 (Fig. 3) respectively of the toggle member 20 to form a toggle joint.

Part 22 is the fixed terminal of a circuit having the external lead 22a, and 23 is the fixed terminal of another circuit havingthe external lead 23a, both to be controlled by the switch; and it will be seen that portion 200 of part 20 (Fig. 1) is adapted to make contact with'either terminal 22 or 23 to close their respective circuits. Current flowing into 20c from either 22 or 23 isconducted to 18b (Fig. l) and thence to 18c (Fig. 2.) as. the common return circuit for the leads 22a and 23a.

The operation of the switch is as follows. Whenthe relay coil is not energized, or weakly energized. below a. predetermined value, the. movable terminal 200 rests against terminal 23 (Figs. 1, 2 and 5), and therefore the circuit of 23 is closed, and that of 22 is open. If the relay coil is energized above that predetermined value, the core becomes sutficiently magnetized to pull down. the armature 12 with sufiicient pressure on pin 14' to depress the spring 17 downward, as. seen in. Figures. 6 and, 7.

In Figure 5, part 21 diverges. upwardly from: part- 20; in Figure 7, part 21 extends downwardly beyond part 20; andin Figure 6, the two parts (20. and 21). are substantially parallel and coplanar. The set of the spring 17 is such that, in the position shown in Figure 5, part 17b is pushing part 210 to the right. As this force has a downward component with respect to part 20, part 23 is pushed downward by loops 21a and 21b (Figs. 4, 5), and end 200 is held in contact with contact 23 under some pressure.

When spring 17 is depressed (Fig. 6), this component of force acting to the right is diminished; and when parts 20 and 21 are in parallelism, loops 21a and 21b exert no force on part 20 upwards or downwards. The axial forces on parts 21 and 26 are actually greater in Figure 6 than in Figure 5, but they have no transverse com ponent to rotate parts 2% or 21 at either pivot line 17b or 18b. This is the theoretical unstable neutral equilibrium position alluded to above. As spring 17 is depressed lower, and part 21 points below part 25} (Fig. 7), the large axial force exerted by part 21 on part 20 acquires an upward component, raising the toggle joint and toggle members upward, thus bring end 200 into contact with contact 22 under some pressure.

The structure and operation of the switch described so far are those of its toggle type structure, and now the additional and particularly novel features will be described.

Part 20 has an extension 20d (Fig. 3) shown in Figures 1 and 5 as in close proximity to portion 17d of the spring 17 but not under pressure from it. However, when spring 17 is depressed by pin 14 (Fig. 6), simultaneously with the changed action of spring part 17b on 21, and through it on member 20, an action is started also by spring portion 17d on member extension 20d, presssing extension 20d downward and, bearing against portion 18b as a fulcrum, pushing the right hand portion of 20 (and hence member 280) upward. In Fig. 6, part 17b develops only an axial force on members 21 and 20, with no transverse component; but part 17d does, and this force is not only a component force but the full total force exerted by part 17d. Additionally, as the movement of member 20 and its portion 200 under this force is rotational in nature, portion 20c moves upward faster than portion Ztld moves downward in the ratio of the lever arms (2tlc20b) :(20b2ld). Thus, when breaking contact between portion 200 and contact 23, in the neighborhood of the position of end 200 shown in Fig ure 6, the total accelerating force is not zero or very small but very substantial on account of the direct switching force exerted by spring end 17d, and the moving contact 200 is accelerated with an increased force over a larger percentage of its travel. When end contact 200 arrives at 22, the new electrical contact is held under the joint pressure from spring parts 17d and 17b.

When switching back from the circuit of 22 to that of 23, the relaxation of pressure from pin 14 on spring 17 reduces both forces simultaneously, and as part 17 moves upward, end 210 also moves upward, and soon part 21 develops suflicient downward component of force to carry the mechanism into the position shown in Figure 5.

It may be observed that the supplemental force exerted by spring end 17d is particularly beneficial in breaking the contact at 23; and therefore in all those cases in which the current interrupting duty demanded by the circuits of contact 22 and 23 are unequalwhich is frequently the casethe circuit demanding the higher duty should be connected to terminal 23.

It may be pointed out also that, during the position of parallelism between members 20 and 21 (Fig. 6), the movable contact 200 need not be half way between 22 and 23, but may be designed closer to one than the other depending on the relative switching duties involved.

Two further structural features of the invention that improve its performance are associated with the relay portion of the device and improve the operating force developed by the armature 12.

To consider the first, at any given moment when the relay coil is energized, the magnetic flux developed in the core may be thought of as flowing up in the two outside legs, 11a and 110, of the core (Fig. 2), then through part 13 and armature 12 respectively towards the middle leg, and then down through the middle leg. Thus the two outside legs of the core are of one polarity and the middle leg of opposite polarity. To further clarify this important matter, it may be pointed out that parts 12 and 13 cannot act as magnetic return to each other because both are of the same polarity. This then leads to the conclusion that there must be repulsion between the two as like poles, and as armature 12 is pulled down from below by the middle leg 11b, it will be pushed down from above by the magnetic pole 13. As the initial gap between armature 12 and pole 13 is negligible, and the final gap between armature 12 and leg 11b is negligible, it follows that the force of repulsion starts with its maximum value, and as it gets weaker with increasing upper gap, the pull from below increases with the diminishing lower gap; and thus, armature 12 is accelerated downward and held there with a more uniform resultant force than by either component force.

The second feature of novelty associated with the relay portion of the device and improving its performance is the structure of the short-circuited coil 10a (Figs. 2 and 8), generally called a shading coil, surrounding the middle leg of a group of the laminations. The function of a shading coil is ordinarily spoken of as prevention of chatter caused by the alternations of the magnetic flux, and it is constructed as a single short-circuited turn around a portion of a pole face. Current in this short circuit is limited by the high reactance of the turn.

Contrasted with the foregoing theory and structure of shading coils, the function here aimed at is the development of a two-phase flux so as to exert on the armature a steady force more akin to that produced by direct current. It is further recognized here that twophase flux will not be produced if the current in the shading coil is limited by reactance, making it a zero or near-zero lagging power factor current: the shading coil current must be of high power factor to develop a quadrature phase flux in the portion of the core which it surrounds. This is accomplished in the present invention by making the shading coil a long thin cylinder enclosing the full length of the core leg which it surrounds; thin, to secure the desired high resistance; and long full coverage, to secure the desired low reactance.

Although the most extensive use of the present switch is likely to be in combination with a relay, as illustrated and described above, yet it is not limited to such use, as it can be used also in combination with any other device that can exert pressure on pin or button 14 in response to a predetermined situation, such as temperature responsive bimetallic strips, pressure responsive bellows and other pneumatic and hydraulic devices, and the multitude of other well-known control devices and transducers.

The invention having been explained fully, clearly and concisely with the help of an embodiment thereof that is now preferred as particularly suitable for small units, various modifications thereof can be made without departure from the spirit of the invention and the scope of the appended claims.

I claim:

1. The switching device comprising in combination a toggle mechanism adapted to open and close an electric circuit, said toggle mechanism having two operating positions and a neutral position between said two operating positions at which said mechanism is free from an accelcrating force towards either one of said operating positions; a relay device adapted to actuate said toggle mechanism; and auxiliary linkage between said relay device and said toggle mechanism and adapted to exert an accelerating force on said toggle mechanism towards one of said operating positions when said toggle mechanism is in the neighborhood of said neutral position; said relay device having a magnetic core with a winding leg, a relay coil surrounding said leg, a magnetic armature member movably positioned to be subject to attraction from said leg and adapted to actuate said toggle mechanism, said core comprising a plurality of magnetic laminations in parallel, and a low-reactance closed electrical circuit surrounding said winding leg of a fractional group of said laminations for substantially the full length of said winding leg; said core being three-legged and comprising a stack of two groups of E-shaped magnetic laminations, said relay coil surrounding the middle leg of said stack, said closed circuit surrounding the middle leg of one of said two groups of laminations, one end of said armature being hinged and resting over one end leg of said core, the other and free end of said armature facing said middle leg of said core and subject to attraction by said middle leg, the other end leg of said core having an extension that reaches and overlaps said free end of said armature to repel said free end towards said middle leg when said core is magnetized.

2. The switching device of claim 1, said winding leg having an axial hole, and a movable pin in said hole, said pin projecting beyond said core at each end and subject to axial pressure at one end from said movable armature when said armature is attracted by said winding leg, said pin being adapted to exert pressure at its other end on said toggle mechanism to operate said mechanism.

3. The switching device of claim 2, said pin exerting pressure on said mechanism through two linkages, one of said linkages transmitting to said toggle members a predominantly axial force, and said second linkage transmitting to said toggle members a predominantly transverse accelerating force.

4. A toggle switch mechanism comprising, in combination, a first relatively elongated contact member having a circuit controlling end normally engaged with a first contact; a second relatively elongated member pivotally connected at one end to said first member intermediate the ends of the latter and normally diverging from said first member; a first spring element engaged with said first member; and a second spring element having an end engaged with said first element and a movable end engaged with the free end of said second member; said spring elements biasing said members in opposed longitudinal directions with said second member exerting a force on said first member in a downward direction; the movable end of said second element being movable downwardly to move the free end of said second member downwardly below said first member to snap the circuit controlling end of said first member upwardly to engage a second contact; and operating means engaged with said second spring element selectively operable to move its movable end downwardly.

5. A toggle switch mechanism comprising, in combination, a first relatively elongated contact member having a circuit controlling end normally engaged with a first contact; a second relatively elongated member pivotally connected at one end to said first member intermediate the ends of the latter and normally diverging from said first member; a first spring element engaged with said first member; and a second spring element having an end engaged with said first element and a movable end engaged with the free end of said second member; said spring elements biasing said members in opposed longitudinal directions with said second member exerting a force on said first member in a downward direction; the movable end of said second element being movable downwardly to move the free end of said second member downwardly below said first member to snap the circuit controlling end of said first member upwardly to engage a second contact; and operating means engaged with said second spring element selectively operable to move its movable end downwardly; said second element having a portion bearing against the opposite end of said first member during downward movement of said movable end and moving said opposite end downwardly to augment the upward movement of said circuit controlling end.

6. A toggle switch mechanism as claimed in claim 4, in which said first member is a wire loop having transverse portions intermediate its ends pivotally connected to said second member.

7. A toggle switch mechanism as claimed in claim 6 in which said second member is a U-shape wire having loops at its ends embracing said transverse portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,292,650 Rippl Jan. 28, 1919 1,485,750 Wolfe et al. Mar. 4, 1924 2,444,352 Hoffman June 29, 1948 2,486,061 Ransome Oct. 25, 1949 2,702,841 Bernstein Feb. 22, 1955 2,728,826 Lauder Dec. 27, 1955 2,743,331 Lauder Apr. 24, 1956 2,782,278 Peters Feb. 19, 1957 2,800,546 Reitler July 23, 1957 2,821,587 Cherry, Jr. Jan. 28, 1958 2,825,013 Krenke Feb. 25, 1958

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