US2322161A - Overload relay switch - Google Patents

Description

June 15, 1943. H. E. scHLlcl-IER OVERLOAD RELAY SWITCH Filed June 14, 1940 HIM IMQ fm INAMI 2 Sheets-Sheet 1 /7 ,20 m92 fi- 22 20 77 m Invenar HAROLD E. SCHLEICHER y hr's aorneys June 15,1943. n H, E SCHLElCHER 2,322,161

OVERLOAD RELAY SWITCH n Filed June 14, 1940 l 2 Sheets-Sheet 2 Resa? pas Z'Zz'an/ @u a maz:

resetting manual resezn f :/S J0 `60 Ef/l/ InvenZ-or 66 HAROLD E. scHLElcHER BREAKERS,

Patented June 15, 1943 OVERLOAD RELAY SWITCH Harold E. Schleicher, West Hartford, Conn., as-

signor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation oi Connecticut Application June 14, 1940, Serial No. 340,587

24 Claims.

' This invention relates to switch mechanism.I iMore particularly, it relates to a snap switch! imechanism which is operable in response to over:

load conditions to automatically move into operi .',circuit position, and vcan also be set either t automatically reset itself, or to require manua resetting from open circuit position.

It is an object of my invention to provide an;

. improved form of automatically operable switchjLx -in which the contacts separate upon the oc' in currence of an overload current and reclose.l

when the load-responsive means resumes its nor-l mal position.

Another object of my invention is to provide ,`an improved form of automatically operable (switch having means for resetting or reclosing lfby hand.

Another object of my invention is to provide an automatically opening and reclosing switch having means for reclosing by hand, with settable means for determining when the switch shall be reclosed by hand or shall reclose automatically.

Another object of my invention is to provide .a mechanism of the above type with an overicenter snapping mechanism in which the movable contact will be moving toward open circuit )position at the instant of disengagement from the fixed contact.

Another object of my invention is to provide means to protect the operating mechanism and the bi-metallic element of an automatically operable switch mechanism from the deleterious action of the heater element when the heater element is excessively loaded or burns up.

Another object of my invention is to provide, lin an automatically operable switch having protection for the operating mechanism and bimetal from the heater element, improvements in said operating mechanism to increase its sensitivity in order to enable the use of the same caliber bi-metal as in devices that have no protection for the bi-metal and operating mechanism from the heater element.

Another object is to provide a mechanism of the above type with means which will store energy as the switch parts move into their positions and will release that energy when the mechanism is operated whereby to obtain increased sensitivity of the mechanism.

Other objects and advantages of my invention will become apparent as it is described in connection with the accompanying drawings.

In the drawings- Fig. 1 is a plan view of a device embodying the principles of my invention.

Fig. 2 is a bottom view with the bottom plate removed of the device shown in Fig. 1.

Fig. 3 is a longitudinal section view taken along line 3--3 of Fig. 1.

Fig. 4 is a view similar to Fig. 3 but showing the parts in open circuit position when the device is set for automatic reclosing.

Fig. 5 is a transverse section view taken along line 5 5 of Fig. 1.

Fig. 6 is a view similaito Fig. 3, but showing the parts in open circuit position when the device is set to require reclosing by hand.

Figs. 7, 8 and 9 are diagrammatic views of the operating parts showing, in Fig. 7, the parts in closed circuit section position, and in Figs. 8 and 9, in open circuit position. In Fig. 8, the parts are set for automative reclosing and in Fig. 9, the parts are set to require manual reclosing of the circuit.

In the drawings, the parts are mounted in a base I0 of molded insulating material. The base is of generally rectangular form having a longitudinal, horizontal, dividing wall I2 in the mid-portion of the base to separate the switch mechanism from the load-responsive elements of the device, the switch mechanism being located below the dividing wall i2 and the load-responsive elements comprising a heater coil i4 and bimetal strip I6 being located above the dividing wall. The dividing wall i2 minimizes the transmission of heat from the heater to the operating parts of the switch. The enclosure formed by the dividing wall cooperating with the side walls of the casing makes the operating parts substantially dust-proof and tamper-proof, assuring clean contacts at all times and protecting the moving parts from foreign substances that could create troublesome friction.

The heater I4 may be in the form of a coil of wire having the proper characteristics of resistance for the current to be regulated. The ends of the coil preferably are secured by screws l1 to terminal plates I8 which, in turn, are screwed to the top of the base by screws 20.

It is difficult, in devices of the type herein described, to design a heater element that will not develop too high a temperature and will not be destroyed under the required short circuit test conditions. If a protective insulating barrier is introduced between the bi-metal and heater, the effective heat acting on the bi-metal is reduced. Attempts to overcome the lessened heat transmittal by using a heater of higher resistance are objectionable because of the danger of the element burning out at reasonable overcurrent values. Also, it develops too high ambient temperature for the switch parts. Also, it prevents rapid cooling of the bi-metal.

The piesent invention overcomes the foregoing objections by shielding the bi-metal from the heater I4 with a ash plate 22 which extends below the heater I4 from one end of the base toward the other, and is attached at one end to one terminal element l8. Two right angle bends offset the main portion of the flash plate from its anchored end, so as to position the main portion close to the bi-metal and also close to the bottom side of the heater. The attachment of the flash plate and terminal may be accomplished by soldering, welding or securing screwsl as may be most convenient. The unattached end of the flash plate is arranged to lie in contact with the upper surface of the anchored end of the bimetal. This enhances the thermal action of the bi-metal through conduction of heat to it from the ash plate.

Near the unattached end of the flash plate, there is pressed out of the upper surface thereof in position directly beneath the last convolution of the heating coil, a bump or protuberance 24. The ash plate serves to protect the bi-metal strip I6 in two ways: first, it acts as a barrier between the heating coil and the bi-metal; and second, the bump 24 may engage with the last convolution of the coil I4 under excessive heat conditions, causing the plate to act as a shunt and minimize the amount of current passing l through the coil, thus keeping it from burning excessively. The bump also serves to localize the burning point and it prevents a larger area from becoming involved.

The bi-metal I6 is secured at one end (the right end, as viewed in Figs, 3, 4, 6 and 7) to a terminal plate 26 of L-shape. One or more securing bolts 28 may pass through the dividing wall I2 to secure the terminal 26 upon the upper surface of the end of the bi-metal I6 and thus hold the bi-metal in position. The opposite end of the bi-metal will be free to bend as the effect of the heat from the coil I4 raises the temperature of the bi-metal. For the purpose of adjusting the position of the bi-metal, there is provided an adjustment bolt 30 in a downwardly bent leg of the terminal plate 26. This bolt abuts one arm of a bell crank lever 32 which is pivoted upon a pin 34 journalled in the base. By turning the adjustment bolt 30, its end will cause rotation of the bell crank lever 32 and will cause one arm of that lever to engage the undersurface of the bi-metal and set it in various positions, as may be desired.

As the bi-metal bends upon the generation of heat by the heater I4, the free end of the bimetal engages a roller whose axle 42 (which is integral with the roller) is guided for vertical movement in vertical slots 44 in the walls of the base. The base at this point is pierced from top to bottom by a passage for the purpose of accommodating and allowing movement of the roller 40 and a pair of insulating bars 46 in whose upper ends the oppositely extending ends of the roller axle 42 are rotatively mounted. The insulating bars 46 (only one is visible) are connected at their lower Aends by a transverse pin 48 to one end of an operating lever 50. Movements of this operating lever 50 cause the operation of the switch mechanism, which will now be described.

For the purpose of facilitating understanding of the operation of the invention, Fig. 'l diagrammatically shows the position of the parts of the device as they are in Fig. 3. Fig. 8, in a similar manner, diagrammatically shows the position of the parts as they are in Fig. 4. Fig. 9 diagrammatically shows the position of the parts as they are in Fig, 6. In these diagrammatic views, the movement of the parts has been exaggerated to clearly indicate the principle of operation. Similar reference characters are applied to similarly functioning parts of the actual mechanism.

The operating lever 58 is a stamped sheet-metal part extending in a vertical plane centrally in the base I0, and is pivoted about a pin 52 that is journalled transversely in the parallel side plates 53L1 of a U-bent metallic switch frame 53. This frame fits within the casing I0 and has the bottom edges of the side plates connected near one end by the transverse portion 53h, The operating lever 50 moves between the sides of the frame and is pressed in clockwise direction (see Fig. 3) by a restoring spring 54 which is wound about the pin 52 and has one end pressing upon the back of the operating lever 5l) and the other end pressing against a wall of the casing. The left end (see Fig. 3) of the operating lever has the insulating bar 46 connected thereto, as hereinbefore mentioned, while the right end has a hook formation to receive a loop on one end of a coiled, tensioned, over-center switch spring 56. The other end of this spring 56 is attached to a movable contact member 58 near one end thereof This movable contact member is preferably of U- shape, with the parallel side arms thereof notched at one end to receive coaxial pivot pins 60 that extend in from the side plates 53n of the frame 53. At the opposite end of the side arms of the movable contact member 58 from the pivot, there is a transverse portion connecting the bottom edges of said arms. On this transverse portion there is mounted a downwardly facing Contact button 64 in position to engage and disengage a contact button 66. The movable Contact member 58 is adapted to oscillate about the pin 60 under the influence of the over-center spring 56, as the line of action of that spring moves across the axis of the pivot pins 60.

The contact button 66 is mounted upon a xedly mounted contact member comprising a U- bent strip of resilient sheet metal 68. The resilient strip 68 absorbs and stores energy from the movable contact member as the xed and movable contacts engage for a purpose hereinafter to be more fully explained. One end of the strip 68 is secured by a screw to a terminal plate l0 which extends transversely through a slot in the side wall of the switch casing and has a connecting portion 1I extending lengthwise along the outside wall of the casing to a wire terminal portion 12 by means of which the terminal may be conveniently connected in an electric circuit. Ordinarily the heater coil will be connected in series with a main line of a circuit to be controlled and will be responsive to variations in the main line current. However, the invention is not limited to such use, which is only mentioned as one example of a use of the invention.

For the purpose of connecting the other side of the circuit to the device, there is provided aterminal having a flat plate portion 14 with a binding screw therein at the opposite end of the casing from the terminal 12. Connecting with tion extending along the outside wall of the casing and connecting at its end with a narrow plate 16 extending through a slot in the side wall of the casing. Screws 11 mount this terminal plate 16 in the lower part of the casing.

From the foregoing, it will be apparent that movement of the switching member 56 is accomplished with a snap by the movement of the line of action of the switch spring 56 across the axis of the pivot 60. When the spring moves downwardly across the axis, the movable contact member engages with the fixed contact member; when the spring moves upwardly across the axis, the movable contact member disengages the fixed contact member.

The amount of upward travel of the movable contact member is limited by a stop pin 90 which extends transversely of the casing from a vertically reciprocative resetting plunger 92. This plunger may slide within grooves 93 provided in one of the side walls of the switch casing and may be acted upon by a compression spring 94 which presses against the lower end of the plunger and against a plate 95 covering the bottom of the switch casing. For the purpose of determining the amount of upward movement of the resetting plunger and its pin 90, there is provided an adjustment device comprising a vertically movable piston 96 having a radial finger 91 mounted on its upper end and a head 98 on its lower end. Upon the top surface of the head 98 presses a coil spring 99 that is wound around the lower end of the piston. The upper end of the coil spring presses against a portion of the switch casing so as to normally urge the adjustment piston into its lowermost position. The piston 96 is located in the opposite side wall of the casing from the resetting plunger, and it slides in a vertical boring which terminates in an upwardly open notch, the floor of which has two levels providing lower and upper shoulders |00, |02 (see Figs. 1 and 5). In its lowermost position, the finger 91 will be in the dotted position shown in Fig. l wherein the lever will rest upon a lower shoulder |00. If the plunger 96 be pulled upwardly against the action of the spring 99 and the finger 91 be turned to its full line position of Fig. 1, the lever 91 will rest upon the upper shoulder |02. When the adjustment finger 91 is set in the full line position of Fig. 1, the device is then set to require manual resetting after overload operation of the device. It may thus be seen that by manipulation of the finger 91, the location of the head 98 of the adjustment piston may be varied and similar variation of the location of the stop pin 90 will result.

In order to absorb and store energy during the upward stroke of the movable contact member 58, a narrow bowed leaf spring |04 is placed along the under side of the stop pin 90 and is secured in that position by having one end anchored in the resetting plunger 92. As the movable contact member strikes this bowed leaf spring |04, the energy will be absorbed and stored by the spring.

It will be understood that the strength of the spring 99 of the adjustment piston will be too great to be affected by the throw of this movable contact member, since the strength of this spring 99 must be greater than the strength of the fairly strong spring 94 of the resetting plunger 92, or else the piston would not be able to adjust the position of the pin 90.

Use of the flash plate 22 to protect the bi-metal retards the action of the heater on the bi-metal this terminal portion 14 is a connecting bar por-` and slows up the cooling-off and restorationof the bi-metal to normal because the flash plate insulates the bi-metal, to some extent, from the heater and the cool air. (This is a serious handicap where suitable short time reset is desired in the automatic resetting.) To offset this handicap, the fixed contact 66 is mounted on the spring 68, and the absorption spring |04 is provided. Each spring exerts a force tending to move the switch from the position it is occupying when that particular spring is stressed. Hence, when the main switch spring 56 approaches dead center and the tangential component of its force upon the switch arm 50 approaches zero, the spring strip 68 or the absorption spring |04, as the case may be, will act to start the switch arm moving across dead center before the switch spring 56 is in dead center position. The movement will start as soon as the tangential component becomes less than the force of the spring |04 or spring strip 60, as the case may be. Therefore, the spring |04 and spring strip 68 act to reduce the time required by the switch to change positions, since they reduce the amount of movement required of the switch arm. In this manner, the disadvantage of thermal retardation that results from the use of the flash plate is overcome and the switch is made more sensitive as well as quick-acting.

The absorption spring |04 will have the maximum allowable strength permissible to allow the movable contact 58 to come to rest in automatic resettable position.

Operation The tripping orf action is the same, whether the device is set for manual or automatic resetting. As the bi-metal I6 becomes heated by the excess current passing through the heating coil |4, the bi-metal will bend down until its end presses upon the rollers 4 0, causing the insulating bars 46 to act on the operating lever 50 to rotate that lever counter-clockwise (referring to Figs. 3 and '1). As the switch spring- 56 moves upwardly across the axis of the pivot pin B0, that over-center movement will cause the movable contact member 50 to move in clockwise direction lin Fig. 3) into the position shown in Figs. 4 and 8. During the first part of this movement, the contact buttons of the movable and fixed contact members will remain engaged by reason of the spring arm 68 causing its contact to follow the movable contact 58. Thus the movable cont-act will be moving quite rapidly at the time that the shank of the movable contact member 68 strikes against and is stopped in its movement by the terminal plate 10. By this means, an instantaneous break is accomplished and the relatively long interval of low pressure between the fixed and movable contacts, which normally occurs in slow activated over-center snap mechanisms, is eliminated. Concomitantiy, the snap over-center takes place with less bi-metal deflection and less heat than would otherwise be required. These are valuable characteristics of the invention.

When the adjustment finger 91 is placed in the dotted position of Fig. l for automatic reclosing, and the bi-metal has operated to cause separation of the switch contacts, the parts will have moved from the positions of Figs. 3 and 7 into the positions of Figs. 4 and 8. In this position, the contacts are separated the minimum distance for safe are interruption. The torque exerted by the return spring 54 constantly urges the operating member 50 into the position of Figs. 3 and 'i (shown dotted in Figs. 8 and 9). This urge is overcome while the bi-metal remains hot. As soon as the bi-metal cools and straightens itself, the spring 54 will move the operating member 50 in clockwise direction to the dotted position in Fig. 8, thus carrying the line of action of the switch spring 56 across the axis of the pivot 60 (as shown in dot-and-dash lines in Fig. 8), resulting in the arm '58 moving its contact; button into engagement with the button on fixed contact 68. The movement of arm 58 is assisted at the start by absorption spring IM, as hereinbefore described.

If the adjustment linger 91 is elevated into the full line position of Fig. 1 for manual operation, the parts take the position shown in Figs. 6 and 9, when the bi-metal heats up and bends. In this position, the switch arm is at a greater angle to the horizontal than in Fig. 8, so that as the bi-metal cools and the operating arm 50 is moved into the dotted line position by return spring 54 carrying the line of action of the switch spring 56 to the dot-and-dash line position, the line of action of the switch spring will remain above the pivot of arm 58, and the switch parts will remain in the position of Figs. 6 and 9, in spite of the straightening of the bi-metal. In order to reset the device and reengage the contacts, it will be necessary to press down upon the resetting plunger 92, which will positively start the movement of the movable contact member 58 into engagement with the xed contact member 68.

From the foregoing description and drawings, it will be seen that I have provided a switch mechanism which is responsive to overload conditions and is particularly adapted to operation by the thermal effect of an overload current. The invention provides protection for the bi-metal and operating parts of the switch from the heat of the thermal element. The invention possesses the advantage that it can be adjusted for either automatic or manual reclosing of the contacts. The invention also possesses the advantage that the movable contact is rapidly moving at the instant of contact separation, thus avoiding the relatively long period of zero or very low contact resistance which occurs in most over-center switch mechanisms. The invention is particularly adapted for use as a sensitive relay switching device whose operation controls other devices such as solenoids of electromagnetic main line switches, which carry full line current. The principles of the invention, however, are adaptable to switches of all types.

Many modifications within the scope of my invention will occur to those skilled in the art. Therefore, I do not limit the invention to the specic embodiment described.

What I claim is:

l. In an electric switch device, relatively movable contacts, snap action mechanism for moving said contacts relatively to one another, means for operating said mechanism, means exerting a force in an engaged position of said contacts tending to move one of said contacts and said mechanism into disengaged position, said lastmentioned means causing said contacts to remain engaged until that point, over-center, is reached where the snap action mechanism causes rapid separation of the contacts to occur.

2. In an electric switch device, relatively movable contacts, snap action mechanism for moving said contacts relatively to one another, means for operating said mechanism, means for storing energy as said snap mechanism comes to rest in one position, said energy being released during movement of said mechanism toward the other position to impart initial movement to one of said contact members before its quick-action motion by said snap mechanism starts.

3. In an electric switch, an insulating base having a cavity, switch operating means in said cavity, a current-carrying thermal device mounted on said base, and a metal plate fitting into said cavity between said device and said means, shielding said means form said thermal device.

4. In an electric switch, a hollowed insulating casing, switch operating means in said cavity, a current-carrying heater coil mounted on said casing and a metal plate between said coil and means shielding said means from said coil, and means on said plate in closer proximity to the coil than the main portion of said plate tending to localize coil failure thereat.

5. In an electric switch, a hollowed insulating casing, switch operating means in said cavity, a current-carrying heater coil mounted on said casing and a metal plate between said coil and said means to shield said means from said coil, said plate being electrically connected with one end of said coil, and means adjacent the other end of said plate more proximate to the coil than is the main portion of said plate, said means tending to localize failure of said coil and slaid plate acting as a shunt in case of coil failre, thereby to protect said coil.

6. In an electric switch device, relatively movable contacts, snap action mechanism for moving said contacts relative to one another, means for operating said mechanism, manually adjustable means to vary one of the positions of rest of said snap mechanism, means to automatically return said snap mechanism to its opposite position when said adjustable means is set in a certain position, said automatic returning means being inefective in another position of said adjustable means, and means exerting a force in an engaged position of said contacts tending to move one of said contacts into its disengaged position, said last-mentioned means causing said contacts to remain engaged during the initial movement of said contacts toward separated position, whereby one of said contacts is rapidly moving at the instant that contact separation occurs.

7. In an electric switch device, relatively movable contacts, snap action mechanism for moving said contacts relative to one another, means for operating said mechanism, means to automatically actuate said operating means, manually adjustable means to vary one of the positions of rest of said snap mechanism, means to automatically return said snap mechanism to its opposite position when said adjustable means is set in a certain position, said automatic returning means being ineffective in another position of said adjustable means, means manually operable to reset said snap mechanism in said op posite position of said snap mechanism when said adjustable means is in its said other position, and means exerting a force in an engaged position of said contacts tending to move one of said contacts into its disengaged position, said last-mentioned means causing said contacts to remain engaged during the initial movement of said contacts toward separated position, whereby one of said contacts is rapidly moving at the instant that contact separation occurs.

8. In an electric switch device, relatively movable contacts, an over-center snap mechanism for moving said contacts relatively to one another, means for operating said mechanism, manually adjustable means to vary the travel of the contact-moving portion of said over-center mechanism in one direction, means to automatically move said over-center mechanism in the opposite direction when said adjustable means is set in the position permitting short travel, said automatic means being ineifective when said adjustable means is set in position permitting long travel of said snap mechanism.

9. In an electric switch device, relatively movable contacts, an over-center snap mechanism for moving said contacts relatively to one another, lever means for operating said mechanism, manually adjustable means to vary the travel of said over-center mechanism in one direction, means to automatically move said overcenter mechanism in the opposite direction when said adjustable means is set in the position permitting short travel, said automatic means being ineffective when said adjustable means is set in position permitting long travel of said snap mechanism, means exerting a force in an engaged position of said contacts tending to move one of said contacts into its disengaged position, said last-mentioned means causing said contacts to remain engaged during the initial movement of said contacts toward separated position, whereby one of the contacts is rapidly moving at the instant that contact separation occurs.

10. In an electric switch, an insulating base, relatively movable contacts mounted for movement within said base, mechanism for engaging and disengaging said contacts, a bi-metallic member for operating said mechanism, heater means to cause bending of said bi-metal, insulating barrier means shielding said bi-metal member from said mechanism. and metallic barrier means shielding said bi-metal member from said heater.

l1. In an electric switch, an insulating base, relatively movable contacts mounted for movement within said base, mechanism for engaging and disengaging said contacts, a bi-metallic member for operating said mechanism, heater means to cause bending of said bi-metal, and barrier means separating said bi-metal from said heater and said mechanism, whereby destruction of the parts of either the switch circuit or the heater circuit will not harm the bi-metal.

12. In a thermal current operated device, an insulating base, a member bendable in response to temperature changes, heater means to cause bending of said member, a thermally and electrically conductive shield between said member and said heater means, said shield serving to shunt excess current around said heater means under certain conditions and permitting the passage of heat from said heater means to said member.

13. In a thermal current operated device, an insulating base, a member bendable in response to temperature changes, heater means to cause bending of said member, a thermally and electrically conductive shield between said member and said heater means, one end of said heater means and said lshield being in thermal and electrical contact, whereby said shield receives heat by radiation and conduction from said heater for transmission to said member, and said shield serving to shunt excess current around said heater means under abnormal conditions.

14. In an electric switch device, relatively movable contacts, snap action mechanism for moving said contacts relatively to one another, spring means for mounting one of said contacts and exerting a force in engaged position of said contacts in opposition to said mechanism, said force acting to move said contact in contact separating direction before the start of snap action movement of said snap mechanism and serving to shorten the amount of motion and time required by said mechanism to cause contact separation.

15. In an electric switch device, relatively movable contacts, over-center snap action mechanism, spring means for mounting one of said contacts and exerting a force in engaged position of said contacts tending to separate said contacts and to operate said mechanism into open circuit position and opposing said over-center mechanism, said spring means being constructed and arranged to travel while holding the xed contact in engagement with the movable contact until said movable contact is moving under the eiort of said over-center mechanism toward contact-disengaged position and then to stop abruptly whereby an instantaneous break is efr fected, said spring acting on said movable contact as said mechanism approaches dead center to decrease the time for movement through dead center position.

16. In an electric switch device, relatively movable contacts, over-center snap mechanism for moving said contacts relatively to one another, spring means to absorb and store energy as said movable Contact comes into one position of rest, said spring means being constructed and arranged to release its energy to move said movable contact toward dead-center position as said overcenter mechanism is moved toward dead center, whereby to shorten the amount of motion and time required by said mechanism for movement through dead center position.

17. In an electric switch device, relatively movable contacts, one of which is movable into three positions of rest, means adjustable for determining into which of two of said positions said movable contact shall come to rest, lever means, spring means tending at all times to move said lever into a certain position, means cooperating with said lever means and operable to automatically move said movable contact into the third position when said movable contact occupies one of said two positions and said lever means moves into said certain position, said contact-moving means operating to hold said movable contact in the other of said two positions when the movable contact comes to rest therein.

18. In an electric switch device as set forth in claim 17, manually operable means for moving said adjustable means to move said movable contact into said third position from said other position.

19. In an electric switch device, relatively movable contacts, snap action mechanism including a contact moving member for moving said contacts relative to one another, operating means for operating said mechanism, manually adjustable means to determine into which of two positions the contact-moving member of said snap mechanism shall corne to rest following movement in one direction, resetting means operable when said adjustable means is set in a certain position to move said snap mechanism automatically in the other direction when said operating means permits, said automatic returning means being ineffective in another position of said adjustable means.

420. An electric switch device as set forth in claim 19, provided with means responsive to overload conditions in an electric circuit for actuating said operating means, and means operable manually to move said snap mechanism in said other direction to reset it when said adjustable means is in said. other position.

21. An electric switch device as set forth in claim 19, provided with means to automatically actuate said operating means, and means operable manually to move said snap mechanism in said other direction to reset it when said adjustable means is in said other position.

22. An electric switch device having relatively movable contacts, snap acting mechanism for moving said contacts relative to one another, means for operating said mechanism automatically, and means for storing energy as said mechanism comes to rest in one position. said energy being released proportionately during movement in contact opening direction, in cooperation with the actuating energy that is applied to said operating means, to cause snap action of the switch mechanism and to decrease the time lag in operation of said mechanism.

23. An electric switch having relatively movable contacts, mechanism for moving said con tacts relative to one another comprising operating means and a contact-moving member and an over-center spring for moving said contactmoving member with a snap motion as said spring is moved through the line oi' action of said contact-moving member, means to limit the movement of said operating means in one direction, and manually-adjustable means to determine the location of said line of action whereby in one position of said adjustable means said spring cannot be moved through the line of action of said contact-moving means within the limits of possible movement of said operating means, while in the other position of said adjustable means said spring can move across the line of action of said contact-moving member to cause movement of the latter for resetting the the device.

24. In an electric switch, relatively movable contacts, over-center snap acting mechanism movable over-center and thereupon acting with a snap motion independently of the actuating force to separate said contacts, spring means for mounting one of said contacts and exerting a force in engaged position of said contacts tending to move said mechanism across center, said force acting to move said contacts in contact separating direction before the over-center position is reached and serving to shorten the time required by said mechanism to cause said device to operate.

y HAROLD E. SCHLEICHER.

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