US2824925A

US2824925A - Electromagnetic trip circuit interrupters

Info

Publication number: US2824925A
Application number: US233212A
Authority: US
Inventors: George G Grissinger; Sandin Jerome; Lindstrom Ture
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1951-06-23
Filing date: 1951-06-23
Publication date: 1958-02-25
Anticipated expiration: 1975-02-25

Description

Feb. 25, 1958 G. G. GRlssINGER ET AL 2,824,925

ELECIROMAGNETIC TRIP CIRCUIT INTERRUPIERS 2 Sheets-Sheet l m n T F|g.2.

Filed June 23, 1951 FIgI.

und Jerome Sondin. Oi 2l" f W ATTO EY G. G. GRISSINGER ET AL 2,824,925

ELECTROMAGNETIC TRIP CIRCUIT INTERRUPTERS Feb. 25, 1958 2 Sheets-Sheet 2 Filed June 23, 195] Fig.4.

Fig.5.

Insulation INVENTORS George G.Grissinger, Ture Lindstrom WITNESSES: T4

Jerome Sondin. Z ATTORN-EY United States Patent O ELECTROMA'GNETIC TRIP CIRCUIT IN TERRUPTERS George G.V Grissinger, Wilkinsburg, and `Ierome Sandin and Ture Lindstrom, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 23, 1951, Serial No. 233,212 18 Claims. (Cl. 200-109) This invention relates tol circuit interrupte'rs and more particularly totrip devices` for circuit interrupterswhich are operable tofinstantaneously trip the breakerv ony overload currents: above a predetermined value and after a time delay'on-lesser overload-currents.

An object` of the invention is to provide a circuit interrupter having, a current responsive trip device embodying adjusting means for selectively determining the minimum overload current atV which thel trip device. will instantaneously-trip the breaker.

Another object of the invention is to providev a circuit interrupter having an electromagnetic trip device comprising an armature operable to trip the interrupter and a fixed` core member for producing a differential pull on the armature and'manual means for adjustin-g the armaturev to vary the differential pullY on the armature..

Another object of` the invention is. to provide a circuit interrupter. having anelectromagnetic trip meansA including an armature` and embodying means for maintaining a substantially constant bias onA the armature during its entire travel.

Another object of. theV invention is. to provide ak circuit interrupter` having an electromagnetic trip device including an adjustable armature embodying means providing substantially the same spring bias on the armature. in each of the adjusted positions..

Another object` of the invention is to provide acircuit interrupter having an electromagnetic trip device including a movable armature embodying a movable pivot and biasingmeans adjacent the pivot whereby, upon deenergization of the magnet, an air gap is established at the pivot end of. the armature to etect quick retraction of the armature at the other end.

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

In said drawings:

Fig. 1 is a vertical sectional view of` acircuit interrupter embodyingthe invention.

Fig. 2 is an enlarged sectional view of the trip device.

Fig. 3 is a sectional view taken on line lII-lllof Fig. 2 showingv the tripping electromagnet.

Fig. 4- is.` a sectional view taken on line IV-IV of Fig; 3 showing the adjusting means for the armature;-

Fig.' 5 isa fragmentary view of a portion of. the enclosing casingv for the trip. device showing the graduations for setting theadjustablearmature.

Fig. 6 is a view similar to Fig. 3 but showing a modification ofthe electromagnetic trip device;

Fig. 7 isa top; view of Fig. 6; and

Fig. 8 isaztletailA view oa portion of Fig. 3 showing the meansfor adjusting kthe magnet core.

Referring. to Pig; 1. of. the;I drawings, the circuit interrupter operating mechanism illustrated is of the three-,pole

ICC

2,. type and' is ofV the same' general construction as fully described in Patent No. 2,083,304, issued June 8, 1937, to Tute Lindstrom and assigned to the assignee ofthe present invention. For a more detaileddescription of the construction and` operation of the circuit interrupter mechanism, reference may be had to the above-mentioned patent.

The circuit breaker comprises, in general, a` casing 11 and a removable cover 13 both of molded insulating material, stationary contact means 15, cooperating movable contact means 17, an operating mechanism 19 and a trip device 21.

Three sets of stationary and movable contact means 15 and 17 are provided forming the three poles of the breaker. The movable contact means 17 for the several poles are mounted on contact members 23 and the movable contact members-23 for the center pole are pivotally mounted on a movable switch member 25, and are biased towardl the stationary contact means 15 relative to the switch memberZSby. springs 22.

The switchmember 25 is pivotally mounted by means of a pivot pin. 29 ina U-shaped main frame 31l which also supports the. circuit interrupter operating mechanism 19. The switch members for the outer poles are connected to the center pole switch member 25 for simultaneous'l movementtherewith by means of a rigid tie bar 33 which-extends transversely across the three poles of thebreaker, eachof the switch members being-securely clamped to the tie bar and insulated therefrom.

The electrical circuits for the severall poles of the circuit interrupter are the same, for which reason only the circuit for the center pole will be described. This cir- ,cuit extends from an upper terminal 45 through a conductorV 47, the stationary andV movable contact means 15-17 aexible conductor 49, a conductor 51 and an energizing conductor 53 for the trip device 21 to alower terminal 55..

The operating mechanism 19 (Fig. 1). is mounted in the main frame 31. andl includes a toggle-r comprisingv a -pair of toggle.. links 57 and 59 having one end pivotally connected to thev center-pole switch member. 25, a carrier lever 61 for releasably restraining the other end of the toggleV 57.--59V in operative position,` a channelshaped operating member 63, an overcenter spring 65 for4 connecting the adjusting member 63 to theknee 67 of the toggle,y and an operating handle 69.

The mainframe 31-is disposed below the contact means and is rigidly secured.- to the base of the casing 11 by meansof screws- 71 and 73. The screw 73 extends throughI the conductor 51 and' serves tosecurel the conductor as welll asy the frame 31 to the casing. One end of the-toggle-link 57 is pivotally connected to the centerpole switch member 25 by a pivot pin 77- and the other end-ofA the toggle link 57 is pivotally connected by means of the knee pivot pin 67 to the toggle link 59'.

The lower end of the overcenter spring unit is pivotally connected to the lower end of theV operating member 63 by means of a pivot pin 81 and a pair of` supporting ears 83l projecting from the operating member 63. The operating member 63 isf pivotally supported on the main frame 31- by means of a pivot pin 85. The lower end of toggle link-59 is` pivotally connected to the carrier lever 61 by means of pivots 87only one of which isshown.'

The. carrier lever 61 is pivotally mounted in the main frame 31 by means of a pivot pin 89 at the apex ofthe bell crank levers. Clockwise movement of the carrier lever 61 is normally prevented by va latching lever 91 comprising av pair of spaced parallel levers which are joined by'integralyokes 93 and 95 and pivotally mounted on. av pivotpin97 supported in the main frame 31. The yoke93lofthe latching member 91 normally engagestlie upperendo'f-thecarrier levcrl and restrans the car- 3 rer lever in operative position. The free lower end of the latching lever 91 carries a pivoted latch engaging pawl 99 supported on the voke 95 of the latching lever. the pawl 99 andthe latching lever 91 being manually restrained bv the trio device 21.

When the trip device functions. the pawl 99 and the latching lever 91 are released thereby permitting counterclockwise movement of the latching lever under the biasing inuence of the overcenter sprint.7 65. This movement of the latching lever causes the yoke 93 to release the carrier lever 61 which is then moved clockwise about its pivot 89 by the overcenter spring 65 and the force exerted by the contact springs 27. This causes movement and collapse of the toggle 57-59 toward the base of the casing 11 and simultaneous opening of the contact for all of the poles of the breaker.

In order to reset the mechanism following an automatic opening'operation, the operating handle 69 is moved in a clockwise direction to the off position causing the operating member 63 to engage and reset the carrier lever 61 and the latching lever 91 to their latched positions. The contacts are then closed by moving the handle 69 in a counterclockwise direction to the on position.

The circuit interrupter is opened manually by movement of the operating handle 69 in a clockwise direction from its Fig. 1 position to the oli position. When the handle has been moved a short distance. a projection (not shown) on the operating member 63 engages the yoke 75 of the toggle link 57 and starts the knee 67 of the toggle 57-59 toward the base of the breaker. At the same time, the spring 65 moves across the center line of the toggle link 59 and now exerts a force in a direction to move the knee of the toggle toward the base. The movement of the several parts of the operating mechanism is now automatic and the contacts for all of the poles of the breaker are opened simultaneously with a snap action.

The contacts are closed following a manual opening operation by moving the operating handle counterclockwise back to the on" position. This movement carries the line of action of the spring 65 over the center line of the toggle link 59 whereupon the springs 65 exert a force biasing the knee of the toggle 57--59 outwardly away from the base, causing straightening of the toggle and closing of the contacts with a snap action.

The trip device 21 comprises a unitary structure, the several elements of which are mounted on a panel or base 101 (Figs. 1 and 2) of insulating material removably mounted on the base of the casing 11. The trip device is enclosed in a casing 102 and comprises generally a bimetal element 103 and an electromagnet 105 for each pole-of the breaker. The conductor 53 forms a loop 107 and is secured by means of rivets 111 to a bracket 109. The rivets 111 also serve to rigidly secure one end of the bimetal element 103 to the conductor 53. The bimetal element 103 extends substantially parallel to the upper leg of the loop 107 of the conductor 53 which serves as a heater element for the bimetal element. -T he bracket 109 is firmly secured to the panel 101 by means of rivets 113 thereby rigidly securing the conductor 53 and thebimetal element to the panel.

A trip bar 115 of insulating material is pivotally supported by means of brackets 117 (only one being shown) which are suitably secured to the panel 101. The trip bar extends across all of the poles of the breaker and is adapted to be operated by the thermal trip device on the electromagnetic trip device of any pole to eect release of the operating mechanism and opening of the contacts. Secured to the trip bar 115 is a latch member 119 which engages and restrains an intermediate latch 121. The latch 121 is pivotally mounted on a pin'123 in the bracket 117 and is provided with a latching portion which engages the pawl 99 and restrains the latching lever 91 and the operating mechanism in closed position. Also secured tothe trip bar 115 is an extension 125 with which an adjusting screw 127 on the free outer end ot the .bimetal 4 element 103 is adapted to cooperate to operate the trip bar.

Upon the occurrence of an overload current below a predetermined value of, for instance, from 300% to 1100% of normal rated current in the circuit of any pole of the breaker, the bimetal element 103 associated with the affected pole is heated by the flow of excessive current through the loop 107 of the conductor 53 and when heated a predetermined amount deects toward the trip bar and rotates the trip bar counterclockwise about its pivot. This movement of the trip bar releases the latch 121 whereupon the force of the operating springs 65 (Fig. 1) causes opening of the breaker contacts in the previously described manner.

The circuit breaker is tripped open instantaneously upon the occurrence of overload currents of from 300% to ll00% or more of normal rated current, or on shortcircuit currents by lmeans of the electromagnetic trip means 105. The electromagnet 105 comprises a iixed U-shaped core member 129 (Figs. 1 and 2) secured to the bracket 109 by means of

screws

130 and 132, and a pivoted armature 131. The armature 131 is pivotally supported by means of a pin 133 in the armature having its ends engaging in slightly elongated slots 135 in brackets 137 secured one on each side of one leg 136 of the core member 129. The armature 131 is biased to unattracted position by means of a compression spring 139 having one end seated in a spring seat 141 in the fixed core member 129 and the other end seated in a spring seat 143 in the armature 131 adjacent the pivoted end thereof. By placing vthe spring 139 close to the pivot 133, the biasing force of the spring is kept substantially constant throughout the travel of the armature and in each of the adjusted positions thereof. The other leg 145 of the U-shaped core member opposite the pivot for the armature forms an angular pole face 147 for cooperating with the angular free end of the armature to form a main magnetic air gap.

A differential pull is provided on the armature 131 vby means of a magnetic member 149 secured to the end of the leg 145 of the core member 129 and having a formed-over portion 151 cooperating with the back of the free end of the armature 131 to provide a limited path for at least a portion of the magnetic ilux to thereby provide a back pull on the armature 131. The core member 129 adjacent the leg 145 is provided with a slot 153 (Figs. 3 and 8) through which extends the screw 132 which secures the core member to the bracket 109. This permits adjustment Vof the entire electromagnet 105 relative to projection 155 of the trip bar 115 to effect calibration of the magnetic trip device. By loosening the

screws

132 and 130, the Vmagnet assembly 105 can be moved to a position relative to the projecting member 155 on the trip bar where actuation of the trip bar 115 by the armature 131 will just release the latch 121. Thev screws 130-132 are then tightened to hold the magnet in place. 1

The upper leg of the conductor loop 107 passes through the U of the core member 129 and serves as an energizing means for the electromagnet. Normal current owing in the circuit of the breaker including the conductor 53 energizes the electromagnet 105 but not suiciently to attract and operate the armature 131 against the force of the spring 139 and the back pull of the portion 151 of member 149. VUpon the occurrence of an Voverload current Vof 1000% or more. of normal rated current, or a` short-circuit current, the electromagnet is energized sutiicientlyto instantaneously -attract and move the armature to the pole face 147 of the xed core member 129. During this movement the armature 131 engages a projecting member 155 on the trip bar 115 and thereby actuates the trip bar to release the intermediate latch 121, causing an automatic opening operation of the breaker mechanism in the manner previouslycleB scribed.

'unattractedposition of the armature.

the breaker.

:3) movable relativeto the lleg 138 iof the UShapedcore member, a slightair gapislprovided at this Vpoint in the Upon energization of the electromagnet, the pivoted end of the armature 131 is moved against the poleface `of the leg 138 and the opposite or free end of the armature is attracted against the pole face 147-.to actuate the trip bar. The spring 139 is located close to the pivot .pin 133 of the armature 131 and is relatively strong so that it will always overcome .the residual liuxat the pivoted end of the armature and the armature will be moved away from the pole face 138the'pin 133 moving to the outer end of the slot 135 as ysoon as the current is interrupted by the opening operation ofthe circuit breaker. This slight motion of the pivoted end of the armature away from the pole face 138 increases `the reluctance of the remanent magnetic circuit, and the pull at the otherend of the magnet will .be decreased sufiiciently to allow the spring 139 to quickly move the armature .to its fullyunattracted position.

Means are provided to selectively vdetermine the minimum overload current required to instantaneously trip This is accomplished by adjusting the position of the armature 131 relative to thel pole face 147 of the fixed core member and the portion 151 of the magnetic member 149 to thereby vary the initial main and secondary air gaps. The means for adjusting the position of the armature 131 includes a member 157 of non-magnetic material suitably secured to the varmature 131. The member 157 is angular in shape asshown in Fig. 3 and .has an ear 159 formed on the end thereof. An adjusting screw 161 is mounted in the ear '159 and is locked in position by a lock nut 163. The inner end of the screw 161 is rounded and cooperates with a stepped `cam 165 secured to a shaft 167 for rotation therewith. The inner end of theshaft 167 passes through a clearance slot 169 in the member 157 and is rotatably seated in a cup-shaped bearing surface 171 (Fig. 4) in the vleg 145 of the core member 129. The shaft 167 extends outwardly substantially perpendicular to the plane of the core member 129 and at its outer end has secured thereto a member 175 of insulating material. The member 175 is provided with serrations 177 cooperating with formedout portions of a leaf spring 179 secured by means of a screw 131 to the panel or base 101of the trip device. The leaf spring 179 serves the dual purpose of retaining the shaft 167 and cam 165 in the adjusted position and biasing the inner end of the shaft 167 into the cupshaped bearing surface 171. The member 175 is provided with a reduced portion 183 extending through an opening in the leaf spring 179 to serve as a bearing for the outer end of the shaft 1'67. The outer end of the portion 183 is accessible from outside the casing 102 through an opening therein and is provided with a slot for receiving a tool whereby the shaft 167 and cam 16S can be rotated.

When the electromagnet 105 is deenergized and the relatively strong spring 139 moves the armature 131 to its unattracted position, the adjusting screw 161 strikes the cam 165. This blow, if struck against a solid stop, may be of suicient force to bend or kdeform the ear 159 in which the screw is mounted and thus destroy the calibration of the device. To avoid this, the side Wall of the cup-shaped bearing 171 is slanted so that when the screw 161 strikes the cam 165, the inner end of the shaft 167 slides up the side of the bearing surface 171camming the shaft axially outwardly against the bias of the leaf spring 179 thus resiliently .absorbing the blow. The leaf spring 179 then forces rthe-shaft 167 back to its normal position in the center ofthe bearing surface 171.

The `electromagnet is initially. calibratedby first loosening the screws v130 .and 132 and then, with the armature held :in attractedpositiomthe magnet is moved to the position where it 'causes the trip bar lto just releasethe latch 121 after whichthe screws '130'and 132 are tightened to securely hold the core member in position.

The cam 165 is then rotated to bring the -lowest point of its periphery into engagement with the adjusting screw 161 after which vthe screw 161 is adjusted so that the armature 131 almost touches the projecting member 155 (Figs..2.and 3) .on the trip bar 115 and the lock nut 163 is then tightened to lock the screw 161 in its adjusted position.

As shown in Fig. 3, the armature 131 is adjusted to vtrip the interrupter in response to overload currents of high value. ln this adjusted position, the armature 131, biased by the spring 139 against the cam 165, occupies the position of greatest retraction permissible by adjustment ofthe cam 165. This position of the armature 131 provides the greatest main air gap between the armature andthe pole face 147 and the smallest air gap between the armature 131 and the auxiliary pole face 151. This decreases the forward pull of the magnet for a given value of 'overload current and increases the value of current required to operate the trip magnet and trip the interrupter. Clockwise rotation of the cam 165 from the position in which it is shown in Fig. 3 moves the armature 13-1 clockwise about its pivot 133 thereby decreasing the main .air gap and increasing the secondary air gap. This has the effect of increasing the forward pull of the magnet on thearmature and of decreasing the back pull opposing tripping movement of the armature. When the device is adjusted toa position below the highest position to which it is capable of adjustment, the electromagnetic trip device will beactuatedin response to overload currents of lesser magnitude to trip the breaker.

By way of example, assuming thatthebreaker is rated to carry a normal load indefinitely without actuating the trip device, the birnetal 103 may be calibrated to trip the breaker with kan inverse time delay in response to overload `currents of, for instance, between and 300% of the normal rated current. The electromagnetic trip device may be calibrated and adjusted to instantaneously trip the breaker in response to overload currents of, for instancebetween 300% and 1.100% of rated current depending on the adjustment .of the armature 131. Assuming that the trip device is calibrated to the above arbitrary values,"then with the cam V165 adjusted so that the highest point of the cam 165 engages the adjusting screw 161, the armature 131 will be correspondingly moved closer to the pole face 147 and the electromagnet willopcrate to instantaneously trip the breaker in response to overload currents of 300% or more of rated current. If the cam 165 is rotated to bring the lowest point thereon into engagement with the adjusting screw, thearmature 131 will be moved away from the pole face 147, and the armature will not be attracted until the occurrence of an overload current of 1100% of normal. By adjusting the cam 165 to any point between the maximum and minimum settings, the magnet willfunction to instantaneously trip the breaker in response to an overload current of a minimum value corresponding to they particular setting of the device. Thus, the trip device may beset to cause instantaneous tripping of tne breaker in response to a minimum overload current of, for example, 300%, 500%, 700%, etc., up to approximately 1100% of Vnormal rated current. If the device is adjusted to instantaneously trip the breaker at a minimum overload current of,.for instance, 700% of normal, the bimetal element will function to trip the breaker after a time delay in response to overload currents of any value between 100% and 700%, or between 100% and the particular minimum current value between 300% and 1100% to which the magnet is adjusted.

Figure 6 illustratesia modified embodiment ofthe tripping electromagnet in which .the .armature is provided of the outer laminations 197 of the core member.

'connectedthereto and arranged so that the biasof the spring remains even more substantially constant throughout the armature travel than with the arrangement previously described. The electromagnet indicated generally at 184 in Fig. 6 includes a U-shaped laminated core 185 which is mounted on the bracket 109 in the trip device in the same manner as the magnet 105 shown in Figs. l and 2, by means of

screws

187 and 189. An armature 191 is provided with spaced knife-edge pivot members 193 seated in V-shaped bearing surfaces 195 formed in one leg 194 The inner laminations of the core member4 185 are cut off as shown at 199, and a pair of springs 201 having one end hooked over the screw 187 is disposed within the recess formed by the end of the laminations and the extension of the outer laminations 197. The other end of the springs 201 is attached to the armature 191 by means of inwardly bent ears 202 on the outer laminations at a point adjacent the pivoted end of the armature. The springs 201 apply a biasing force to the armature, biasing the armature to unattracted position with a very small moment arm.

The outer laminations 197 on the other leg 203 of the core member are bent at right angles and lie adjacent the ends of the other laminations of the fixed core members. Projections 205 of the outer laminations 197 extend toward the armature and are bent inwardly to form small auxiliary pole pieces 207 which, when the magnet is energized, exert a back pull on the armature 191. The auxiliary pole pieces 207 provide a limited path for at least a portion of the magnetic ux to thereby provide a diferential pull on the armature 191 which is varied according to the adjustment of the armature relative to the leg 203 of the core members and the auxiliary pole piece 207.

The armature is adjusted in the previously described manner by means of the cam 165 and shaft 167. The cam 165 engages the inner end of an adjusting screw 209, mounted in an ear 211 of a member 213 secured to `the Aarmature 191 and locked in adjusted position by means of a lock nut 215. The member 213 is provided with an arcuate clearance slot 217 through which the l shaft 167 extends, the shaft 167 having a bearing in one of the outer laminations 197.

The operation of the electromagnet 184 (Fig. 6) is similar to that of the electromagnet 105 (Fig. 3). The arrangement of the spring 201 relative to the pivot 193- 195 is such that as the armature 191 is operated toward the attracted position, the line of action of the spring moves toward the pivot point of the armature shortening the moment arm by which the force of the spring 201 is applied to the armature. As the armature 191 moves toward attracted position, the point 202 at which the springs 201 are attached thereto causes a slight tensioning of the springs but this increased tension is offset by the shortening of the moment arm of the springs. This results in a substantially constant bias on the armature throughout its travel. This also applies to the several positions to which the armature can be adjusted by means of the cam 165. That is, the armature will be biased by substantially the same force in each of its adjusted positions.

From the foregoing description, it will be seen that the invention provides a circuit breaker having an improved trip device embodying an electromagnetic trip device embodying an electromagnetic trip means in which a variable differential pull is produced on the armature to permit a wide range of adjustment of the minimum overload current value required to trip the breaker. The

invention provides means for quickly restoring the arma- Y ture to unattracted position and also for maintaining substantially constant biasing force on the armature.

-While the invention has been disclosed in accordance withV Athepro'visionsof thepatent statutes, it is to be unqderstood that various changes in theA structural details vand arrangement of parts thereof may be made without departing from some of the essential features of the invention. It is desired, therefore, that the language of the appended claims be given as reasonably broad interpretation as the prior art permits.

We claim as Vour invention:

1. A circuit interrupting device comprising an energ'izing winding, a U-shaped fixed core structure disposed to be energized by overload currents of predetermined value flowing in said winding, an armature pivotally supported ou one leg of said U-shaped core structure, biasing means disposed adjacent the pivot of said armature normally biasing said armature to unattracted position, nonmagnetic means mounted on said armature and having an angular portion extending from the armature and adjacent the other leg of said VU-shaped core structure, a rotatable cam member engaging said non-magnetic member and rotatable to adjust the position of said armature relative to said U-shaped core structure, manual means operatively related to said cam member for rotating said cam member, and adjusting means supported in said nonmagnetic member and adjustably engaging said cam member for varying the initial position of said armature.

2. A circuit interrupting device comprising an energizing winding, a U-shaped fixed core member disposed to be energized by overload current of predetermined value owing throughV said winding, an armature pivotally supported on one leg of said U-shaped core member, biasing means disposed adjacent the pivot of said armature for biasing said armature to unattracted position with a relatively small moment arm, a member of non-magnetic material secured to said armature and having an angular portion extending from said armature and adjacent the other leg of said .U-shaped core member, adjusting means mounted in said non-magnetic member and movable with said armature, a cam member engaging said adjusting means, means operatively related to said cam member for manually rotating said cam member to selectively position said armature relative to said core member to vary the minimum current required to operate said armature, and said adjusting means being adjustable to vary the initial position of said armature relative to said core member.

3. A circuit interrupting device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, an armature having one end pivotally supported on one leg of said U-shaped core member and the other end free, spring means disposed adjacent the pivot of said armature biasing said armature to a position whereby one side of said armature forms a main air gap with the other leg of said U- shaped core member for producing a forward pull on said armature, said other leg of said U-shaped core member having a member'of magnetic material extending around the free end of the pivoted armature to the opposite side of said -armature forming a secondary air gap with said armature for producing a back pull on said armature, a non-magnetic member secured to said armature and extending adjacent to said other leg of said U- shaped core member, a cam member engaging said noumagnetic member and movable to vary the position of said armature relative to said U-shaped core member and said magnetic member to vary said main air gap and said secondary air gap, and manual means for moving said cam member.

4. A circuit interrupting device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, a movable armature, means slidably and pivotally supporting one end of said armature on one leg of said U-shaped core member for pivotal movement and for sliding movement toward and away Afrom said one leg, spring means normally biasing both ends of 'said armature away from said core structure so that said armature forms a main air. gap with the other .ing winding,

9 legof saidfcore .member fand a'second air gap with` said one leg -ot said core memberysaid core member upon energizationthereof bysaid windingiattracting and slidyablymovingsaid oneY end of said armature to said core member and then pivotally moving said armature to close said main air gap, and vsaid spring means upon deenergization .of said winding slidably 'moving the plvoted endof .said armature away from said core member to cause quick pivotal movement of said armature to unattractedvposition irrespective of any residual magnetism ,in said corestructure.

Vends ofrsaid armature away from said core structure so .that said armature forms a main air gap with the kother legtof `said coremember and a second airgap with said yone leg-ofsaid core member,said core member upon energization thereof by said winding attracting and slidably moving said one end of said armature to .said core member and then pivotally moving said armature to close` said .main air gap, and said spring means upon deenergization of said winding slidably moving the pivoted end o't said armature away from said core member to cause quick pivotal movement of said armature to unattracted position irrespective of any residual magnetism in said core structure, and adjusting means for engaging and y positioning the armature relative to said 'core member to vary the main air gap and thereby Vary the minimum current required to operate said armature.

'6. A tripdevice for a circuit interrupter operable to effect opening of said interrupter comprising an electromagnet 4including anV armature lpivoted at one endand having 'the'otherend-freq a xed U-shaped core member disposed on `one sideof said armature tol operate said armature upon energization of saidelectromagnetin response to overload currents vof vpredetermined value, an

-auxiliary core vmember extending from lone leg of said U-shaped core structure around the free'end of the pivoted armature and disposed "on rktheother side offthe free end ofsaid armature to restrain-said armature against operation in response to roverload currents below said predetermined value, pivot means pivotally supporting the other end of said armature on Vthe other 'leg of said core structure, spring means disposed adjacent the pivotedfend of said armature andconnected to said armature `in 11a manner kto Vbias said armature to unattracted position l.with a relatively small moment arm, an extension of non-magnetic material on said armature, -manual means-comprising a rotatable cam for engaging said non- -magnetie extension and adjusting said armature relative to said xed core member and said auxiliary core member to vary the'minimum overload current required to operate saidvarmature.

7. A trip device fora circuit interrupter operablel to effect opening of said interrupter comprising an electromagnet including an armature pivoted at one end'and having the other end free, aiixed U-shaped core member disposed on one side of said armature to operatevsaid armature Vupon energization of said electromagnet in response tooverload currents of predetermined value, an.

auxiliary core member extending from one leg of said U-shaped core structure around the free end of the -pivoted armature and disposed on the other side of the free end of said armature to restrain said armature against operation in response to overload currents below said predetermined value, pivot means pivotally supporting the otherend of said armature on the other leg of said core structure, spring means disposed adjacent the pivoted .e'nd of said armature and connected to said armature in a manner to bias. said armature .to uuattracted position with-a relatively small moment arm, an extensionofnotmagnetic `material on said armature, manual means comprising .a rotatable cam for engaging said non-magnetic extension and adjusting said armature relative to said -ixed core member and said auxiliary core member tov .spaced knife-edge pivot means on-said armature enga ing VspaeedV-shaped :bearings in one leg of said core structure tofpivotally fsupport said armature on said one leg of said .U-shapedcorestructura adjustingrmeans comprising-asmanually .operable cam engaging a part movable .with saidrrarmatureafor adjusting the position of said yarmature relative towsaid xed core structure, spring means connectedtunder tension to said armature adjacent said vpivot meansandsto a` `iixed member applying a force biasing saidarmature to unattracted position with Va Apredetermined initial momentarm, said spring means lmovingbetween .said spaced pivot means when said armature is operated,isaid spring means being connected to .said armature so that `uponadjustment of said armature the Vline of action of said spring means is moved relative to said pivot means thereby changing the moment arm so as to cause the spring means to apply substantially the same biasinglforce to said armature in all of the adjusted positions of said armature.

. 9. A circuitinterrupting device comprising an energizing winding, a U.shaped fixed core member disposed to be energized by current of predetermined valueflowing through said winding, a pivoted armature, spaced,` pivot means on said armature engaging spaced V-shaped bearings on one leg ofV said core member pivotally supporting said armature on said one 4leg-of said U-shaped corefmember, biasing means connected under tension to said. armature adjacent toV said pivotl means biasing said armature with a predetermined moment arm, the line of action of said biasing means being disposed to be moved between said spaced pivotzme'ans .by operation of said armature to vary said moment arm and thereby cause .said biasing means to bias saidarmature with a substantially constant force during the operation of said armature, adjusting means comprising .a manually operablecam engaging a part movable with said armature for adjusting the position of said 'armature relative to said xed core member to vary the minimum current required to operate said armature, and adjustment of said armature causing said biasing means to apply 'substantially the same biasing force to said armature in each of the adjusted positions ot said armature.

10. A'trip device `for a circuit interrupter operable to eiect opening of said interrupter comprising an energizing winding, a U-shaped fixed core member ydisposed to 'be energized by 'currents of predetermined valueiin said winding, a pivoted armature, spaced pivotmeans on. said'armature pivotally supporting said armature on one leg of said U-shaped core member, a member of non-magnetic material secured to said armature and having'an `angular portion Aextending adjacent the other leg ofsaid U-shaped core member, a stepped cam membervengaging said angular portion of said non-magnetic member and movable to adjust said armature to al plurality of positions relative to said fixed-core member to thereby vary the 'minimum current required to operate said armature, spring means biasing said non-magnetic member into engagement with said cam member, said spring means `being connected under tension to said armature and to a `fixed member in a manner so that adjustment of said armature moves the line of action of said spring means relative to said ypivot means to thereby cause 'said spring means to bias said armature with substanan energizing winding, a U-shaped core member disposed to be energized by said winding, an armature pivotally supported on one leg of said core member and operable upon energization of said winding in response to overload currents of predetermined value to engage and actuate 'said trip member, said trip member extending between said core member and said armature, cam means operable to selectively position said armature relatively to said core member to vary the minimum overload current required to actuate said armature, and adjusting means for simultaneously adjusting the position of said ycore member and the position of said armature relative to said trip member while said armature remains in substantially the same position relative to the core member.

12. A circuit interrupting device comprising a trip member operable to effect opening of said interrupter, an energizing winding, a U-shaped core member disposed to be energized by said Winding,an armature pivotally supported on one leg of said core member and operable upon energization of said winding in response to overload currents of predetermined value to engage and actuate said trip member, said trip member extending between said core member and said armature, cam means operable to selectively position said armature relatively to said core member to vary the minimum overload current required to actuate said armature, adjusting means for engaging said cam means and adjusting the initial position of said armature relative to said cam means, and adjusting means for simultaneously adjusting the position of said core member and the position of said armature relative to said trip member.

13. A circuit interrupting device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, an armature pivotally supported on one leg of said U-shaped core member, a member of non-magnetic material secured to said armature and extending adjacent the other leg of said U-shaped core member, a cam member engaging said non-magnetic member and operable to selectively position said armature relative to said core member, a shaft supporting said cam member for rotation therewith, means defining a concave seat in the other leg of said U-shaped core member for receiving and supporting one end of said shaft, spring means having an opening therein for receiving and rotatably Vsupporting the other end of said shaft, biasing means for biasing said armature to unattracted position against said cam member and for returning said armature to said unattracted position upon opening of said interrupter, said one end of said shaft moving sideways in said convex seat to move said shaft axially against the bias of said spring means to resiliently absorb the blow of said armature when said armature is returned to unattracted position.

14. A circuit interrupting device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, an armature pivotally supported on one leg of said U-shaped core member, adjusting means comprising a member of non-magnetic material mounted on said armature, a cam member engaging said adjusting means, a shaft supporting said cam memlber for rotating said cam to selectively position said armature relative to said core member, means defining a conical seat in the other leg of said core member for receiving and pivotally supporting one end of said shaft, detent means on said shaft, spring means pivotally supporting the other end of said shaft and having means thereon engaging said detent means to resiliently hold said shaft and said cam member in the selected position, said spring means biasing said one end of said shaft into said conical seat, biasing means biasing said armature to unattracted position in which said adjusting means en- 12 gages said cam member, said shaft moving laterally on said conical seat and axially against the bias of said spring means to act as a resilient stop for said armature when said armature is moved to unattracted position, and said spring means then moving said one end of said shaft back to the center of said conical seat.

l5. A circuit interrupting device comprising an energizing winding, a U-shaped core member energized by said winding, a movable armature, slidable pivot means at one end of said armature supporting said one end 'of said armature on one leg of said U-shaped core member for sliding movement toward and away from said one leg of said core member, said armature being pivotally movable about said pivot means, spring means acting on said armature at a point between said pivot means 'at said one end of said armature and the other end of said armature biasing both ends of said armature away from said core member against fixed stop means to normally provide a relatively small air gap at the pivoted end of said armature and a larger main air gap at the other end of said armature, said core member when energized first slidably moving said pivot means and said pivoted end of said armature toward said core member to reduce the magnetic reluctance while said main air gap remains open and then pivotally moving said armature about said pivot means to attracted position to close said main air gap, and said spring means upon deenergization of said core members rst slidably moving said pivot means and said pivoted end of said armature away from said core member reestablishing said air gap at said pivoted end of said armature to increase the magnetic reluctance and then Ypivotally moving said armature about said pivot means to the unattracted position.

16. A circuit interrupting device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, a movable armature having a pivot in one end thereof, support members on one leg of said U-shaped core member having slots therein for receiving and slidably supporting said pivot to permit movement of said armature about said pivot and sliding movement of said pivoted end of said armature toward and away from said one leg of said core member, spaced fixed stop means at opposite ends of said armature,.a spring applying a force to said armature at a point between said pivot and the other end of said armature normally biasing the ends of said armature to the unattracted position against said spaced xed stop means to provide Y an air gap at each end of said armature, said core member when energized slidably moving said pivoted end of said armature toward said one leg of said core member to first close the air gap at said pivoted end of said armature while the air gap at the other end of said armature remains open and then pivotally moving said armature about said pivot to close the air gap at said other end of said armature, said spring upon deenergization of said core member first slidably moving said pivoted end of said armature away from said core member against one of said stop means and then pivotally moving said armature to unattracted position against another of said stop means.

17. A circuit interrupter comprising a U-shaped core member energized in response to abnormal conditions in the circuit of the interrupter, a movable armature, pivot means on one end of said armature, spaced support members onone leg of said lVJ-shaped core, said support members having slots'therein for receiving and supporting said pivot means for both pivotal movement and sliding move- Yment toward and-away from said one leg, spring means in said core member between said pivot means and the other end of said armature normally biasing said pivot lmeans away from said one leg to provide a relatively small air gap and biasing said armature away from the other leg of said core to provide a relatively large main air gap, Said core member when energized slidably moving said pivot means toward said one leg to reduce said small air gap while said relatively large air gap remains open and then pivotally moving said armature about said pivot means to close said main air gap, and said spring means upon deenergization of said core member rst slidingly moving said pivot away from said one leg to reestablish said relatively small air gap and then pivotally moving the armature about said pivot means to unattracted position.

18. A circuit interrupting device comprising a trip member operable to effect opening of said interrupter, an energizing winding, a U-shaped core member disposed to be energized by said winding, an armature pivotally supported on one leg of said core member and operable upon energization of said winding in response to overload currents of predetermined value to engage and actuate said trip member, said trip member extending between said core member and said armature, a shaft pivotally supported at one end on said core member, spring means supporting the other end of said shaft and biasing said shaft toward said core member, cam means on said shaft operable to selectively position said armature relative to said core member to vary the minimum overload current required to actuate said armature, and adjusting means 14 for simultaneously adjusting the position of said core member and the position of said armature relative to said trip member While said armature remains in substan tially the same position relative to the core member.

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