US2282865A - Electric switch - Google Patents

Description

Patented May 12, 1942 2,282,865

UNlTED STATES PATENT OFFICE ELECTRIC SWITCH Robert W. Gofi, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 4, 1941, Serial No. 386,928

6 Claims. (Cl. 200-97) My invention relates to electric switches and 3 is a sectional view of the cutout switch of Figs.

particularly to cutout switches for use in con- 1 and 2 taken along the line 3-3 of Fig. 2 looking nection with the operating coil of plunger type in the direction of the arrows; Fig. 4 is a side electromagnets. elevation partly in section of a modified form of In direct current plunger type electromag 5 cutout switch embodying my invention, the elecnets where a relatively high pick-up force is retromagnet being indicated in dotted outline; Fig.

quired in comparison to the magnitude of the 5 is a plan view of the cutout switch of Fig. 4; necessary holding-in force it is known to.change and Figs. 6 and 7 are simplified circuit diagrams the operatingcoil connections after the plunger of connections for the electromagnet actuating has completed its pick-up stroke. This may be 10 coil illustrating respectively the use of normally done either by using only a portion of the operclosed and normally open cutout switch contacts. ating coil acros the full voltage for pick-up and Referring now to the drawing, and particuthereafter connecting in series the remainder of larly to Fig 1, I have shown an electromagnet the coil, or by using a high resistance portion of comprising a magnetic frame It, a T-shaped the coil to pick up the plunger and thereafter l5 movable plunger II, and an actuating coil I2. As connecting a low resistance portion of the coil shown in Fig. 2, the laminated iron structure I3 in parallel therewith. In either case it is necesof the magnetic frame I!) is riveted together besary to provide a cutout switch preferably opertween a p ir of flanged end plat s 4 and I5. ated directly by the solenoid plunger. The end plates I4 and I5. are provided with Accordingly, it is an object ofmy invention to flanges on all four sides thereof to provide for provide a simple and durable and efflcient device convenient mounting of the solenoid to other of this character consisting of a minimum numapparatus and for convenient mounting of the bar of parts and adapted for inexpensive manucutout switch to the solenoid. The electromagnet facture upon a large scale basis. is fully described and claimed in my copending According to my invention the switch operating '25 application, Serial No. 395,077, filed May 24, 1941, member of a solenoid cutout switch is made of and assigned to the same assignee as the inresilient material to obtain a time delay in switch stant application.

opening operation by utilizing the inertia and Mounted upon one side of the flanged end resilience of the contact carrying end of the plates I4 and I5 is a cutout switch 20 comprising switch member, The time delay thus obtained a base plate 2|, a pair of fixed contacts 22 insures that the switch contacts will remain mounted upon the base plate,apivotally mounted closed until the electromagnet lunger has commov ble switch member 23 carrying a bridging pleted its pick-up stroke To prevent reclosing contact 24, and a damping buffer positioned of the switch contacts due to oscillations of the closely adj ce t t actuated Position 0! the resilient switch operating member after it has movable switch member 23. The buffer 25 may,

been actuated, I provide damping means cooperbut preferably does not, act as a stop for deterating with the free end of the switch operating mining the actuated position of the switch memmember to interrupt vibrations at natural freher. The actuated position of the switch memquency due to switch actuating operation. since her 23 is predetermined by separate means, as devices of the character described are frequently 40 will more clearly appear hereinafter.

installed upon rapidly moving parts of controlled The base plate 2| for the cutout switch preferapparatus, my damping means is also useful in ably consists of a metal plate having flanges at preventing vibrations of the switch operating its upper and lower extremities for supporting a. member induced by vibrations of the controlled cover 26. Attached to the base 2! is a fixed suptu port 21 carrying a pair of stationary contacts 22. My invention itself will be better understood The base P te is slotted at 28 and bent inand its objects and advantages further apprewardly to provide a piv t l pport for the ciated by referring now to the following detailed operating member 23.

specification taken in connection with the acr The operating member 23 comprises a switch companying drawing in which Fig. 1 is a side elearm of rubber or other resilient material mounted vation of a plunger type of electromagnet having between a pair of metallic supporting plates 23 connected thereto a cutout switch embodying my and 30. The suppo t g plate 29 is bent transinvention, the cutout switch cover being shown ver ely to provide a knife edge Sea f r in in section; Fig. 2 is an end view of the device of the pivot point 28 0f the cutout switch base. As

' Fig. 1 with the cutout switch cover removed; Fig. clearly indicated at Figs. 1 and 3, one end of th supporting plate 29 extends through the cutout switch base plate 21 to provide a striker for engaging an actuating bar mounted upon the electromagnet plunger ll. At its free end the rubber switch arm 23 carries the bridging contact 24.

As shown at Fig. 2, the rubber switch operating member 23 is apertured at and the supporting plate 30 is correspondingly apertured at 4| to receive a biasing spring 42 which holds the switch operating member 23 in a normal position. As shown in the drawing the switch contacts are closed in the normal position of the switch member. The spring 42 is mounted upon a pin 43 which passes through apertures in the base 2| and the supporting plate 23 and carries at one end a stop 44 engaging one end of the biasing spring 42. The other end of the spring 42 engages the supporting plate 23 to hold the switch operating member 23 in position. The pin 43 is also provided with a head 45 engaging the switch base 2| and with a threaded portion 46 arranged to aid in mounting the switch cover 23 as shown in Fig. 1.

In operation, when the actuating coil l2 of the solenoid is energized to pick up the plunger II the bar 35 strikes the projecting end of the supporting plate 29 to move the switch operating member 23 to its switch opening or actuated position. The actuated position of the switch member 23 is preferably not determined by the bufler 25, but rather the projecting end oi the supporting plate 23 is so positioned that the plunger II will move the switch member 23 only so far that it is closely adjacent the buffer 25. I, therefore, wish to have it understood that, while the switch member 23 in its actuated position may actually engage the buffer, it is sumcient and in fact preferable that the buffer 25 be only sufllciently near the actuated position of the switch member to engage the contact carrying end whenever that end begins to vibrate, thereby to interrupt violent oscillations at natural frequency.

As shown in Fig. 6, opening of the switch contacts 22 and 24 results in inserting a high resistance holding portion I. of the actuating coll l2 in series with a low resistance pick-up portion 5| of the coil. The switch contacts, however, cannot be separated until the plunger II has completed its pick-up stroke due to the fact that an earlier diminution in the operating current would permit the plunger to drop out before completing its pick-up stroke. On the other hand, after the plunger has completed its stroke it no longer has any movement which may be used to open the switch contacts. For this reason the switch operating member 23 is made of rubber to introduce a time delay between the engagement of the actuating bar 35 with the switch member 23 and the opening of the switch contacts. Such time delay is introduced by the resilience of the rubber operating member 23 which permits the contact carrying end of the operating member to remain in switch closing position due to its inertia while the lower end of the operating member begins its movement under the influence of the actuating bar 35. By actual test it has been found that the contacts 22 and 24 do not separate untfl the plunger H has fully completed its pick-up stroke. After completion of the plunger pick-up the resilient operating member 23 opens the switch contacts to insert the holding portion 50 of the operating coil in series with the pick-up portion 5|. It has also been found that the rubber member 23 is much better able to withstand the repeated and sudden shocks to which a switch of this type is subjected. A metallic or other rigid switch member has proven unsatisfactory.

To prevent violent oscillation of the upper end of the rubber operating member 23 at its natural frequency after the switch opening operation the bufler member 25 is positioned sufliciently close to the upper end of the operating member 23 in its switch opening position to engage the member 23 and interrupt any substantial vibration of its resilient upper end. As shown in Figs. 1 and 2 the oscillation damping bufier 25 is attached to a depending metallic arm 52 mounted upon a rubber support 53 which is attached to the cutout switch base 2|.

By actual test it has been found that, while without the damping buffer 25 the oscillations of the upper end of the switch operating member 23 are sufllciently violent to cause intermittent closing of the switch contact and ultimate buming out of the pick-up portion 5! of the coil as well as rupture of the rubber armature above the supporting plates 23 and 33, the vibrations of the switch operating member 23 are almost imperceptible when the buffer is used. In addition to its function in damping oscillations due to switch opening movement of the operating member 23, the buffer 25, which preferably consists of a block of resilient material, is also useful in preventing oscillation of the switch operating member 23 due to vibrations of moving machinery upon which the cutout switch and magnet are sometimes mounted.

It will be understood, of course, that by supporting the stationary contacts in a position to be engaged by the bridging contact 24 when the operating member 23 is in its actuated position,

the switch may be converted to a normally open type. The switch which I have disclosed may be so connected without any permanent structural change by merely detaching the bridging contact 24 and connecting it to the opposite face of the extending end of the rubber switch arm 23.

As shown in the circuit diagram of Fig. 'l the normally open switch mechanism may be employed to connect a plurality of portions of the actuating winding in multiple circuit relation upon operation of the plunger II to the attracted position. With the connection as shown in Fig. 7 only the pick-up portion 54 of the actuating winding I2 is energized initially and serves to supply the attractive force necessary to effect operation of the plunger II to the attracted position. Preferably the portion 54 of the actuating winding i2 is formed of a large number of turns and consequently has a relatively high resistance, while the remaining portion 55 of the winding is formed of a relatively few turns having a relatively low resistance. With the phmger II in the attracted position a very much reduced attractive force is sufllcient to maintain the plunger picked up. Thus the switch contact 24 is arranged to connect the portion 55 of the actuating winding in parallel circuit relation with the portion 54. With the portion 55 of the actuating winding of relatively few turns and relatively low resistance, the major portion of the current in the series circuit will flow through the portion 55 while the portion 54 of the actuating winding will be energized in accordance with the voltage drop across the portion 55. In this way the eiIective ampere turns of the actuating winding may be materially reduced with a corresponding reduction in the watts input.

At Figs. 4 and 5 I have illustrated a modified form of my invention in which the damping buffer consists of a pair of U-shaped members 60 and 6| fixedly attached to the electromagnet or cutout switch frame in position to nearly engage the bridging contact 24 in the actuated position of the switch member 23. As shown at Fig. 4 the switch operating member 23 comprises an apertured rubber arm mounted between two supporting plates in a manner generally similar to the construction shown in Fig. 3. To illustrate another means for mounting the operating member of the cutout switch the supporting plate 29 of Fig. 4 is shown bent to form a pivoted striker portion 63 apertured at 64 to receive the shank of the T-shaped plunger II.. The striker portion 63 is provided with a flange 65 at either side thereof for pivotal connection to the electromagnetframe as by pivot pins 66.

The damping bufiers 60 and SI of Figs. 4 and5 are preferably formed of a molded insulating material in order to avoid metallic connection between the electromagnet frame and the bridging contact 24. It will be understood, of course, that if desired the U-shaped buffers 60 and GI may be metallic and provided with insulating means at their point of contact with the bridging contact 24.

While I have described and illustrated only certain preferred embodiments of my invention, by way of example, many other modifications will occur to those skilled in the art and I, therefore, wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A delayed action electric control switch comprising a support, cooperating switch contacts, a resilient switch member having one end movably mounted upon said support and carrying at its free end one of said contacts, means for biasing said switch member to a normal position, quick-acting actuating means for moving said switch member to an actuated position spaced from said normal position, the resilience of said switch member and the inertia of its free end being sufilcient to delay movement of said free end from said normal position until said actuating means has substantially completed its movement, and means mounted upon said support ad-' jacent said actuated position of said switch member to engage and damp oscillations of said free end of said switch member after movement thereof to its actuated position.

2. A delayed action electric control switch comprising a support, a fixed contact mounted upon said support, a movable switch member of resilient material pivotally mounted at one end upon said support and carrying at its free end a movable contact for cooperation with said fixed contact, means for biasing said switch member to a normal position, electromagnetic actuating means for suddenly moving the pivoted end of said switch member to an actuated position spaced from said normal position, the resilience of said switch member and the inertia of said free end being sufiicient to delay movement of said free end until said actuating means has submember intermittently to engage said free end and damp oscillations produced by its actuation.

3. A delayed action electric control switch comprising a support, a fixed contact mounted upon said support, a movable switch member comprising a switch arm of resilient material mounted between and extending beyond a pair of rigid supporting plates, means for pivotally mounting one of said plates upon said support, a movable contact mounted upon the extending end of said switch arm, spring means for biasing said switch member to a normal position, magnetically movable actuating means for moving said supporting plates suddenly to an actuated position spaced from said normal position, the resilience of said extending end of said switch arm and its inertia being such that said movable contact remains in said normal position until said actuating means has substantially completed its movement, and a buffer mounted upon said support closely adjacent and spaced from the free end of said resilient switch arm when said switch arm is in its actuated position thereby to engage said arm and damp oscillation thereof.

4. In a delayed action cutout switch for controlling the actuating coil of a plunger type electromagnet, the combination with said plunger of a support, a fixed contact mounted upon said support, a movable switch member comprising a rubber switch arm supported between and extending at one end beyond a pair of rigid supporting plates, a movable contact mounted upon the extending end of said switch arm for cooperation with said fixed contact, means including one of said supporting plates for pivotally mounting said movable switch member at its other end upon said support, a spring for biasing said movable switch member to a normal position, actuating means connected to said plunger for engaging at least one of said supporting plates thereby to move said plates suddenly to an actuated position spaced from said normal position, the resilience of said rubber switch arm and the inertia of its extending end being suflicient to delay movement of said movable contact until said plunger has substantially completed its'actuating stroke, and a damping buffer connected to said support and positioned in closely spaced relation to the extending end of said rubber switch arm in its actuated position thereby to engage said arm and to damp oscillations thereof.

5. In a delayed action cutout switch for controlling the actuating coil of a plunger type electromagnet, the combination with said plunger of a support, a fixed contact mounted upon said support, a movable switch member comprising a flexible arm supported between and extending at one end beyond a pair of rigid supporting plates, a movable contact mounted upon the extending end of said arm for cooperation with said fixed contact, one of said supporting plates being bent stantially completed its movement, and stop' transversely and extending through an aperture in said support to provide a pivot seat at the other end of said switch member and a striker bar for operating said switch member, knife edge means associated with said support for pivotally mounting said movable switch member upon said pivot seat, spring means engaging said support and said switch member for biasing said switch member to a normal position, actuating means connected to said plunger for engaging said striker bar upon energization of said electromagnet thereby to move said switch member from said normal position to an actuated position of said switch arm and the inertia of its extending end being suiiicient to delay movement of said movable contact until said plunger has substantially completed its stroke, and a damping buffer of resilient material connected to said support and positioned in closely spaced relation to the extending end of said flexible switch arm in the actuated position of said switch member thereby to engage said am and damp oscillations thereof.

6. In a delayed action cutout switch for controlling the actuating coil of a plunger type electromagnet, the combination with said plunger of a support, a fixed contact mounted upon said support, a movable switch member comprising a flexible arm supported between and extending at one end beyond a pair of rigid supporting plates, a movable contact mounted upon the extending end of said flexible arm for cooperation with said fixed contact, one of said supporting plates being spaced from said normal position, the resilience bent transversely to provide a striker member for moving said switch member, flange means associated with said striker member for pivotally mounting said movable switch member upon said support, spring means engaging said support and said movable switch member for biasing said switch member to a normal position, means associated with said plunger for engaging said striker member to move said movable switch member to an actuated position spaced from said normal position, the resilience of said flexible switch arm and the inertia of its extending end being suiiicient to delay the movement of said movable contact until said plunger has substantially completed its stroke, and a rigid bufler member having a leg positioned in closely spaced relation to said bridging contact in the actuating position of said switch member thereby to engage said contact and to damp oscillations of said switch arm.

ROBERT W. GOFF'.

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