US2262386A - Electrical switch - Google Patents

Description

Nov. 1-1, 1941. H CRAB S 2,262,386

ELECTRICAL SWITCH Filed-Dec. 31, 1937 WITNESSES: INVENTOR Her e12 J Crabfis far/2M" WW Patented Nov. 11, 1941 UNlTED STATES PATENT OFFICE ELECTRICAL SWITCH pany, East Pittsburgh, Pennsylvania Pa., a corporation of Application December 31, 1937, Serial No. 182,754

8 Claims.

The invention relates in general .to electrical switches and more particularly to air break switches for opening and closing electrical circuits and for extinguishing the are formed during circuit interruption.

An object of the invention is the provision of an improved electrical switch that is operable to open the circuit and quickly extinguish the arc and which in the open position provides an air gap in the circuit capable of withstanding high 10 voltages.

Another object of the invention is the provision of an electrical switch embodying an improved contact means and associated arc extinguishing means.

Another object of the invention is the provision of an electrical switch embodying a stationary' contact and a movable switch means comprising a movable contact and a, movable arc extinguishing structure both of which are mounted for movement together toward and away from the stationary contact,*and in which the movable contact is movable a limited amount relative to the arc extinguishing structure.

Another object of the invention is the provision of an electrical switch as described embodying an improved actuating means that is operable during a circuit opening operation to first separate the movable contact from the stationary contact, and to then move both the movable contact and the 39 are extinguishing structure together away from the stationary-contact to opemcircuit position. I

Another object of the invention is the provision of electrical switch as described above in which all of the parts are mounted on a single insulating support and arranged so as to occupy a small amount of space.

Another object of the invention is the provision of an electrical switch embodying an improved switch means for opening and closing the 40 circuit and for extinguishing the are, and an improved actuating mechanism that is automaticallyoperable to cause the switch means to open the circuit and to reclose the circuit following interruption thereof. 1

Another object of the invention is the provision of an automatic electric switch as described which also embodies electro-responsive means including a thermal trip element and a magnetic trip element each of which is operable in response to to predetermined overload conditions to cause auto- 1 matic operation of the actuating mechanism to effect opening and reclosing of the switch means.

Another object of the invention is the provision or an automatic switch embodying an improved spring driven actuating mechanism for automatically opening-and reclosing the switch means and for holding the switch means in open circuit position after a predetermined number of opening and closing operations.

Another object of the invention is the provision of an improved automatic switch as described above, that is entirely self-contained, all of the parts being mounted within an enclosing casing.

Another object of the invention is the provision of an improved electrical switch which is simple, safe and reliable in operation, which 00- cupies a small amount of space, and which can be manufactured at a relatively low cost.

' The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from the following detailed description of several embodiments thereof when read in connection: with the accompanying drawing, in which:

Figure 1 is a vertical sectional view of the electrical switch constructed in accordance with the invention, the switch means being shown in the closed circuit position,

Fig. 2 is a view similar to Fig. 1, showing the switch means in open circuit position during an automatic opening and reclosing operation,

Fig. 3 is a side elevational view of a modification of the invention, the switch illustrated being shown in the closedcircuit position, and

Fig. 4 is a View similar to Fig. 3, showing the switch in open circuit position. 7

Referring to Figs. 1 and 2 of the drawing, the

automatic switch illustrated comprises, in general, a casing I, a stationary contact 9, a movable switch means indicated generally at H for opening and closing the circuit and for extinguishing the are formed during circuit interruption, an actuating mechanism indicated generally at I3 for opening and reclosing the switch means, and electro-responsive means indicated generally at l5 for causing operation of the actuating mechanism in response to predetermined overload conditions.

The casing I which is formed of insulating material is cylindrical in shape and has an end wall I! and a cover (not shown) which is removably mounted on the casing to close the open end thereof. The switch is entirely self-contained, all of the parts thereof being mounted I within and protected by the insulating casing 1.

a pair of conductors It and 2 I, which form a part of the circuit controlled by the switch and which are adapted to be connected to the terminals of the switch, extend into the casing I through a pair of lead-in bushings 23 which are formed integral with the casing 1. After the conductors I9 and 2| have been inserted through the openings in the bushings 23 and connected to the terminals of the switch, the openings may be sealed in any suitable manner-in order to prevent the entrance of moisture in the casing.

The stationary contact 9 which is rigidly secured to a terminal member 25 mounted within the casing, consists of a curved rod of conducting material. The terminal 25 is provided with a terminal lug 21 for receiving the end of the conductor |9 to electrically connect the conductor to the terminal 25 and stationary contact 9.

The movable switch means II for opening and closing the circuit and for extinguishing the arc formed during circuit interruption comprises a pair of arms 29 and 3| which are mounted for swinging movement together toward and away from the stationary contact 9 by means of a centrally located pivot stud 33 secured to the end wall I! of the casing. The arm 29 which is preferably formed of insulating material is pivotally mounted at one end on the stud .33 and carries at its outer end a curved arc extinguishing tube 35. The stationary contact 9 and the tube 35 have the same curvature, the center of which coincides with the center of the pivot stud 33. The tube 35 is provided with a bore 31 for receiving the stationary contact 9, and the length of the tube is such that it encloses the major portion of the stationary contact 9 in the closed circuit position of the switch means, as is shown in Fig. 1. The tube 35 is formed of a suitable insulating material which acts to extinguish the are formed during circuit interruption. A material known as horn fiber, may be used for the composition of the tube. If desired, the tube 35 may be composed of molded insulating material -or a refractory insulating material and the bore 31' thereof lined with an arc extinguishing material such as horn fibre, boric acid compound or other material which gives off a gas when acted on by the arc. The tube functions as an expulsion arc extinguishing device utilizing a blast of gas through the arc to extinguish the outer end of the arm 3| carries a yoke'shaped movable contact 43 which is adapted to engage the lower end portion of the stationary contact 9. The arm 3| is connected to the insulating arm 29 for swinging movement therewith by means of aguide bracket 45 carried by the arm 29, the guide bracket 45 being provided with an opening through which the arm 3| extends.

The bell crank lever 4| forms a part of the actuating mechanism to be hereinafter'described and this lever is rotatable on the pivot stud 33 a limited amount relative to the insulating arm 29. The arm of the bell crank lever 4| is provided with. a projection 49 which engages a projection 5| carried by the insulating arm 29 to limit "counter-clockwise movement of the bell crank lever relative to the insulating arm 29. For limiting clockwise rotation of the bell crank lever 4| relative to the insulating arm 29, there is provided a projection 53 carried by the insulating arm 29 which is adapted to be engaged by the arm 39 of the bell crank lever 4 The bell crank lever 4| is biased to the counter-clockwise limit of its movement relative to the insulating arm 29 by means of a spring 55 which is connected in tension between the arm 41 of the bell crank lever 4| and the insulating arm 29.

When the switch means H is in the closed circuit position, as shown in Fig. 1, and the bell crank lever 4| is rotated in a counter-clockwise direction about the pivot stud 33 by the actuating mechanism, the bell crank lever 4| first rotates counter-clockwise relative to the insulating arm 29 which remains stationary. This relative rotation of the bell crank lever 4| moves the contact carrying arm 3| longitudinally relative to the insulating arm 29 to separate the movable contact 43 from the lower end of the stationary contact 9. During this movement an arc is drawn between the movable contact 43 and the end of the stationary contact 9. Continued counter-clockwise movement of the bell crank lever 4| after the projection 49 engages the projection 5|, causes counter-clockwise movement of the insulatingarm 29 and the contact carrying arm 3| about the pivot stud 33 as an axis to the open circuit position shown in Fig. 2. During this movement of the switch means H to open circuit position, the arc extinguishing tube 35 is withdrawn from the stationary contact and the arc is drawn inside, of the bore 31 of the tube where it is deionized and extinguished in a well known manner.

When the switch means is in the open circuit position shown in Fig. 2 and the bell crank lever 4| is rotated in a clockwise direction by the actuating mechanism to close the switch, the insulating arm 29 is moved from the open circuit position shown in Fig. 2 to the closed circuit position shown in Fig. 1, the contact carrying arm 3| being carried along with the insulating arm 29 by reason of the bracket 45 which connects the two arms. During this movement, the spring 55 maintains the projection 49 of the bell crank lever 4| in engagement with the projection 5| carried by the insulating arm 29. After the arc extinguishing tube 35 engages the terminal member 25, the continued clockwise movement of.the bell crank lever 4| causes the contact carrying arm 3| to be moved longitudinally relative to the insulating arm 29 to effect engagement of the movable contact 43 with the lower end of the stationary contact 9.

The switch means is adapted to be releasably held in closed position by a pivoted latch member 51 which engages a latch pin 59 carried by the bell crank lever 4|.

The actuating mechanism indicated generally at |3 for opening and reclosing the switch means ll comprises a rotatable crank arm 5|, 9. link 53 which connects the free end of the crank arm 5| with the bell crank lever 4| and a spiral spring 55 for driving the crank arm. The crank arm 5| is secured to a barrel 56 which is ro'tatably mounted on a shaft 61 mounted within the casing, and the free end of the crank arm is pivotally connected to the upper end of the link 53 by means of a pivot'pin 59. The lower end of the connecting link 53 is pivotally connected to the end of the arm 41 of the bell crank lever 4| by means of a pivot pin 1|. One end of the driving spring 55 is secured to the barrel 55 and the opposite end thereof is rigidly secured to the casing 1 by means of a stud 13. The spring 55 is adapted to be wound up by a suitable key, not shown,

crank arm 8| in a counter-clockwise direction about the shaft 61 when the mechanism I3 is released. The crank arm 6| and the link 63 form a toggle linkage which assumes approximately one dead center position when the switch is closed, as shown in Fig. .1, and approximately the opposite or extended dead center position when the switch means is in the open circuit position. The actuating mechanism is releasably held in inoperative position by means of the pivoted latch member 51 which in its latching position engages the pin 59 carried by the bell crank lever 4|. The latch member 51 thus serves to releasably hold the switch means H in closed circuit position and the actuating mechanism in an inoperative condition.

When the latch member 51 is moved to its released position by the electro-responsive means |5 to release the bell crank lever 4|, the spring 65 drives the crank arm 6| in a counter-clockwise direction about the shaft 61. The counter-clockwise movement of the crank arm during the first 180 of its travel causes the bell crank lever 4|, which is connected thereto by the link 63, to rotate in a counter-clockwise direction. This rotation of the bell crank lever 4| effects movement of the switch means H to open circuit position in the manner previously described. The con tinued rotation of the crank arm 6| through the next 180 of its movement after the switch means II has moved to the open circuit position shown in Fig. 2, causes the bell crank lever 4| to be rotated in a reverse or clockwise direction to automatically effect reclosing of the switch means H in the manner previously described. When the switch means reaches closed circuit position, the pin 59 of the bell crank lever is reengaged by the latch member 51 to hold the switch means in closed circuit position and the actuating mechanism in the position shown in Fig. 1, if the overload condition which caused movement of the latch member 51to its releasing position no longer exists. the crank arm 6| and the link 63 provides a certain amount of time delay as it passes through its extended dead center position, reducing the speed of rotation of the bell crank lever 4|, thus permitting the fault condition to be cleared if it is of a transitory nature before the switch is reclosed. If desired, the reclosing movement of the switch means may be further retarded in any well known manner to provide a longer time delay prior to reclosing of the circuit.

A lock-out means is provided for preventing reclosure of the switch means after a predetermined number of opening and closing operations have occurred. The lock-out means comprises the reduction gear which is driven by a pinion gear 11 which is secured to the crank arm 6| for rotation therewith. The gear 15 carries a stop pin 19 which engages the right hand side of a stop member 8| carried by the casing 1 after a predetermined number of opening and reclosing operations have occurred, The stop member 8| is manually movable out of the way of the pin 19 to permit reclosing of the switch means after the fault condition has been cleared.

The lock-out means prevents the spring 65 from being unwound more than a predetermined amount so that sufficient reserve spring effort is provided for the final reclosing operation after the stop member 8| has been moved to an inoperative position.

The toggle formed by The electro-responsive means for moving the latch member 51 to releasing position to cause operation of the actuating mechanism 3 comprises, in general, a thermal trip means in the form of a bimetallic strip 83, and an electromagnetic trip means consisting of an armature and a stationary core 81. The stationary core 81 and the bimetallic trip element 83 are mounted on a bracket 88 secured to the end wall |1 oi the casing 1. The core 81 is U-shaped and is adapted to cooperate with the armature 85 which is secured to one leg 90 of the latch member 51; the latch member being pivotally mounted on a pivot stud extending from the end wall H of the casing 1. The latch member 51 is also provided with a leg 89 which extends on the other side of the pivot axis of the latch member from the leg 98 which carries the armature 85. The leg 89 of the latch member 51 is adapted to be engaged by the projection 9| carried by the free end of the bimetallic trip element 83. Thelatch member 51 is biased to latching position by means of a spring 93 connected at oneend to the leg 89 of the latch member and having its other end secured to a stud carried by a casing 1.

The bimetallic trip element 83 and the electromagnetic trip means comprising the armature 85 and the core 81 are each energized in response to the current flowing in the circuit by means of a heater strip 95. The heater strip 95 is secured at one end to the bracket 88 and at its opposite end to a bracket 91 which supports a terminal lug 99. A portion of the heater strip extends between the legs of the U-shaped core and for a considerable portion of the length of the bimetallic trip element 83. One end of the heater strip 95 is electrically connected to the terminal lug 99 which receives the conductor 2|,

and the other end of the heater strip is electrically connected to the contact carrying arms 3| by means of a flexible shunt conductor IN.

The circuit through the switch extends from the left-hand terminal 25 through the stationary contact 9, movable contact 43, contact carrying 7 arm 3|, flexible shunt conductor |0| and through the heater strip 95 to the right-hand terminal lug 99.

The operation of the switch is briefly as follows. When an overload of predetermined magnitude and duration occurs in the circuit controlled by the switch, the bimetallic trip element 83 is heated a sufficient amount to flex in the direction of the latch member 51. This flexing of the bimetallictrip element moves the latch member 51 to released position, as shown in Fig. 2, to effect release of the switch means H and the actuating mechanism l3. When the actuating mechanism I3 is released the crank arm 6| is driven by the spiral spring 65 in a counterclockwise direction to effect counter-clockwise movement of the bell crank lever 4|. The count-er-clockwise movement of the bell crank lever 4| effects separation of the movable contact 43 from the stationary contact 9 and then causes counter-clockwise movement of the switch means comprising the arms 29 and 3| to the open circuit position shown in Fig. 2. During this movement of the switch means-l to open circuit position, the arc is extinguished by means of the arc extinguishing tube 35. The continued counter-clockwise movement of the crank arm 6| after the switch means has reached full open position, as shown in Fig. 2, causes reverse or clockwise rotation of the bell crank lever 4| to effect reclosing of the switch means H and. cir- 4 1 Fig. 1.

-a yoke shaped actuating member I31.

cuit. If the overload condition which causes re-' lease of the latch member 51 no longer exists, the latch member reengages the pin 59 carried by the bell crank lever M to hold the switch means II in closed circuit position and the actuating means in the inoperative position as shown in If the overload condition still exists, the spring 65 continues to drive the crank arm 6| to cause another opening and reclosing operation of the switch means' After a predetermined number of opening and reclosing operations have occurred, the lock-out means comprising the pin 19 and the top member 9| operate to prevent reclosure of the switch means II.

When an overload of higher'magnitude or a short circuit occurs in the circuit, the electromagnetic means comprising the core 81 and the armature 85 is energized a sufiicient amount to move the armature 85 to attracted position. This e'fiects release of the latch member 51. The release of the latch member 51 by the electromagnetic means causes the actuating mechanism I3 to eflect automatic opening and reclosing of the switch means II in the manner prev-i ously described in connection with the tripping by the bimetallic trip element.

A modification of the invention is illustrated in Figs. 3 and 4 of the drawing. In this modification the switch means and are extinguishing means are substantially similar to the correspending means described in the original embodiment. The modified form of switch comprises,

in general, an insulating support I05; a station-- my contact I01, switch means indicated generally at I09 and an actuating means for the switch means indicated generally at III. The insulating support I05 consists of a column formed of vitreous insulating material such as porcelain having a mounting bracket II3 secured thereto intermediate its ends. The bracket H3 is provided with a clamp means II5 for mounting the switch on a cross arm of a pole, tower or other form of support. A pair of terminal members I I1 and II9 are rigidly secured to the opposite ends of the column I05 and each of the terminal members is provided with a terminal lug I2I for connecting the switch in an electrical circuit.

The stationary contact I01 consists of a curved rod of conducting material secured at one end to the terminal member II1.

The switch means I09 comprises a pair of arms I23 and I24 mounted for swinging movement together toward and away from the stationary contact I01. Thearm I23 is of insulating material and is pivotally mounted on a pivot pin I 21 carried by a bracket J29 secured to the lower end of the column I05. The upper end of the insulating arm I23 carries a curved arc extinguish-- ing tube I3I. The curvature of the tube I3I and the stationary contact member I01 are the same, the'center of which curvature-coincides with the center of the pivot pin I21. The tube I3I ./is composed of suitable insulating material similar to the material of the tube described in connection with the original embodiment of the invention. The tube I3I is provided with a bore I33 for receiving and enclosing a major portion of the stationary contact I01 in the closed circuit position of the switch means. The arm I24 which is of the conducting material is pivotally connected at its lower end to a pivot pin I35 which extends transversely between the legs of The actuating member, in turn, is pivotally mounted at of the arm I24 carries a yoke shapedmovable I contact I39 which is adapted to engage the outer end portion of the stationary contact I01 in the closed circuit position of the switch. The contact carrying arm I24 is electrically connected at its lower end to the terminal member II9 by means of a flexible shunt conductor MI.

The actuating member I31 which forms the actuating means for the switch is provided with an operating eye. I43 adapted to be engaged by a hook stick for operating the switch means I09 to open or to closed circuit position.

A cover or shroud I 45 is mounted on the upper end of the column I05 for protecting the hook stick in the operating eye I43 of the actuating member I31 and exerts a downward pull on the actuating member-to cause that member. to

rotate in a counterclockwise direction about the pivot axis I21.- During the first portion of the counterclockwise movement of the actuating member I31, the contact carrying arm I24 is moved longitudinally downwardly relative to the insulating arm I 23 to separate the'movable contact I39 from the end of the stationary contact I01. ,The continued counterclockwise movement of the actuating member I31 swings both the arms I23 and I 24 in a counterclockwise direction about the pivot axis I21 to the open circuit position shown in Fig. 4. During this movement, the arc is drawn into the bore I33 of the arc extinguishing tube I3I and quickly extinguished in a well known manner. It will be noted that in the open circuit position of the switch a large air gap is provided between the, movable contact I39 and the stationary contact I01, that is capable of withstanding high voltages.

To reclose the switch the actuating member I31 is moved by the hook stick from the position shown in Fig. 4 in a clockwise direction about the pivot axis I 21 to the position shown in Fig. 3. This movement of the actuating member swings the connected arms I 23 and I24 in a clockwise direction. After the arc extinguishing tube I3I engages the terminal member II1, the continued movement of the actuating member I31 causes upward longitudinal movement of the contact carrying arm I24 relative to the insulating arm I23 to efiect engagement of the movable contact I39 with theouter end of the stationary contact I 01. The invention in both of the embodiments disclosed provides an electrical switch that is simple, safe and reliable in operation, compact so that it occupies a small amount of space, and that can be manufactured at a relatively 'low cost.-

All of the operative parts of the switch are supported on a single insulating support. The movement of both the movable contact and the arc extinguishing structure away from the stationary contact provides a relatively large air gap between the movable contact and the stationary contact which is capable of withstanding high voltages.

The original embodiment of the invention-illustrated in Figs. 1 and 2 and described in connection therewith provides an automatic switch that is operable to open the circuit either in response to a lower magnitude overload of prolonged nature, or a heavy overload or short circuit condition. The switch means is automatically reclosed following extinguishment of the arc so as to assure continuity of service in the event that the overload condition is of a transitory nature. The switch embodies a very simple and effective actuating mechanism that is spring driven for opening and reclosing the switch means, thus eliminating the necessity of any auxiliary apparatus and control circuits. The automatic switch is entirely self-contained and enclosed.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various omissions, substitutions and changes may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest construction permissible in view of the prior art.

I claim as my invention:

1. In an electrical switch, a stationary'contact member, switch means movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the are formed during circuit interruption comprising a movable contact member and a, movable arc extinguishing device mounted for movement together away from and toward said stationary contact, said movable contact member being movable a limited amount relative to said arc extinguishing device.

2. In an electrical switch, a stationary contact member, switch means movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the are formed during circuit interruption comprising a movable contact member and an arc extinguishing device mounted for swinging movement together away from and toward said stationary contact, said movable contact member being movable a limited amount relative to said arc extinguishing device; and a single insulating support on which said stationary contact and switch means are mounted.

3. In an electric switch, a stationary contact member, switch means movable to open and to closed circuit position for opening and for closing the circuit and for extinguishing the are formed during circuit interruption, said switch means comprising an arm carrying a movable contact and a second arm carrying an are extinguishing device, both of said arms being mounted for swinging movement together toward and away from said stationary contact, said movable contact being movable a limited amount relative to said second arm.

4. In an electrical switch, a stationary contact, switch means movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the arc formed during circuit interruption comprising a movable contact member and a movable arc extinguishing device, and actuating means operable during a circuit opening operation to first separate said movable contact member from said stationary contact While said are extinguishing device remains stationary, and to then move said arc extinguishing device and movable contact member together to open circuit position away from said stationary contact.

5. In an electric switch, a stationary contact member, switchmeans movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the arc formed during circuit interruption comprising an arm carrying a movable contact and a second arm carrying an arc extinguishing device, both of said arms being mounted for swinging movement together toward and away from said stationary contact and said contact carrying arm having limited movement relative to said second arm. and actuating means operable during a circuit opening operation to first move said contact carrying arm relative to said second arm to separate said movable contact from said stationary contact, and to then move both said arms together to open circuit position away from said stationary contact. v

6. In an electrical switch, a stationary contact member, switch means movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the arc formed during circuit interruption comprising a movable contact and a movable arc extinguishing tube within which said stationary contact member extends in the closed circuit position of the switch means, said movable contact member and tube being mounted for movement together toward and away from said stationary contact, and said movable contact member being movable a limited amount relative to said arc extinguishing tube.

'7. In. an electric switch, a stationary contact member, switch means movable to open and to closed circuit position for opening and for closing the circuit and for extinguishing the arc formed during circuit interruption comprising an arm carrying a movable contact and a second arm carrying an arc extinguishing tube within which said stationary contact member extends in the closed circuit position of the switch means, said arms being mounted for swinging movement together toward and away from said stationary contact and said contact carrying am being movable longitudinally relative to said second arm to separate said movable contact from said stationary contact, and actuating means operable during a circuit opening operation to first eflect longitudinal movement of said contact carrying arm relative to said second arm to separate said movable contact from said stationary con tact, and to then swing both said arms away from said stationary contact to open circuit position.

8. In an electrical switch, a-stationary contact, switch means movable to open and to closed circuit position for opening and closing the circuit and for extinguishing the arc formed during circuit interruption comprising a movable contact member and a movable arc extinguishing device. and actuating means operable during a circuit opening operation to first separate-said movable contact member from said stationary contact while said are extinguishing device remains stationary, and to then move said arc extinguishing device and movable contact member together to open circuit position away from said stationary contact, and an enclosed protecting casing within which said stationary contact, switch means, and actuating means are mounted.

HERBERT J. CRABBS.

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