US2809252A - Circuit interrupters - Google Patents

Description

Oct. 8, 1957 H. J. LINGAL ET AL 2,809,252

CIRCUIT INTERRUPTERS Filed May 23 1955 2 Sheets-Sheet 2 United States Patent CIRCUIT INTERRUPTERS Harry J. Lingal, Penn Township, Allegheny County, and Jerome Sandin and Richard Hauser, Forest Hills, Pa. assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 23, 1955, Serial No. 510,094

Claims. (Cl. 200-108) This invention relates to circuit interrupters and, more particularly, to circuit interrupters of the type used to control light to moderate power distribution circuits.

An object of the invention is to provide a circuit interrupter embodying a novel time delay trip device of the fluid dashpot type wherein separate magnetic circuits are provided for operating the time delay and for controlling the operation of the time delay.

Another object of the invention is to provide a circuit interrupter embodying a time delay device of the fluid dashpot type wherein different amounts of time delay are provided by operation of one or more control valves to admit fluid to the dashpot at difierent rates, separate electromagnets being provided for operating the time delay and the control valve.

Another object of the invention is to provide a circuit interrupter embodying a trip device having a fluid dashpot time delay device in which separate magnetic means is provided for operating the time delay device and for controlling the operation of the time delay device, each of said separate magnetic means surrounding the main circuit through the interrupter to provide a single turn energizing coil.

Another object of the invention is to provide a circuit interrupter embodying a trip device having time delay means, means for controlling the time delay means, and electromagnetic means for actuating the time delay means and the control means, the magnetic circuits for said electromagnetic means being separate to provide improved calibration of the trip device.

The invention, 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 drawing.

In said drawing:

Figure 1 is a vertical sectional view taken through the center pole of a three-pole circuit interrupter embodying the principles of the invention.

Fig. 2 is an enlarged sectional view through the trip device for one of the poles of the interrupter.

Fig. 3 is a sectional view of a portion of the time delay device shown in Fig. 2, showing the short time delay control means.

Referring to Fig. l of the drawing, the circuit interrupter includes a plurality of pole units, each comprising a separable contact structure indicated generally at 11, and an overcurrent trip device indicated generally at 13. The contact structure and trip device for each pole of the circuit interrupter are mounted on separate insulating bases 15 which are rigidly secured to a metal panel 17 by means of screws 19. Since the pole units are alike, only one will be described herein.

The contact structure comprises stationary main contacts 23 and a stationary arcing contact 25 all supported on the inner end of a U-shaped terminal conductor 27 (Fig. 1), the legs of which extend through suitable open- Patented Oct. 8, 1957 ICC . ings in the base 15 and panel 17. Cooperating with the stationary main contacts 23 and the stationary arcing contact 25, respectively, are movable main contacts 29 and a movable arcing contact 31. The movable main contacts 29 are rigidly mounted on a channel-shaped main switch arm 33 pivotally mounted at its lower end on a pin 35 supported in a bracket 37 which is rigidly mounted by means of bolts 39 (only one being shown) on a lower U-shaped terminal conductor 41. The movable arcing contact 31 is mounted on a contact carrying member 43 rigidly mounted on the upper or free end of an arcing contact arm 47 which is also pivoted on the pin 35. A flexible conductor 49 has its upper end secured to the movable arcing contact and its lower end secured to the upper end of the main contact arm 33.

The main stationary contacts 23 (Fig. 2) are pivotally supported in bearing openings in an extension 55 of the terminal 27, and are biased by means of a common spring 57 into engagement with the movable main contacts 29 in the closed position of the circuit interrupter. The stationary arcing contact 25 is pivotally supported on a bracket 60 secured to the terminal extension 55, and is biased by means of a spring 64 into engagement with the movable arcing contact 31.

The movable contact structure is normally maintained in the closed position by an operating mechanism indicated generally at 61 (Fig. I) mounted in a U-shaped frame 63. The frame 63 comprises spaced side members 65 and a connecting cross member 67 and is supported on a platform 69 which forms a cross member of a main bracket comprising a pair of spaced side members 71 joined at their outer ends by the cross member or platform 69. The platform extends substantially across the width of the circuit interrupter, and the side members 71 are rigidly secured to the panel 17 on the outer sides of the two outer pole units.

The operating mechanism includes a lever 73 pivotally mounted on a pivot pin 75 supported in the side members 65 of the frame 63. The lever 73 comprises a pair of spaced levers rigidly joined by an angle member 77 which extends across all of the poles of the interrupter. The angle member 77 is operatively connected to the main movable switch arm 33 by means of an insulating connecting member 81 and a pivot pin 79 in the main switch arm. The other end of the connecting member 81 is pivotally connected to the angle members 77 by means of a pivot pin and a bracket 82 rigid with the angle member 77. There is a connecting member 81 for each pole of the circuit interrupter connecting the angle members 77 to the main moving contact member 33 for each pole unit so that, upon operation of the lever 73, the movable contact structure for all these poles move in unison.

An operating linkage comprising toggle links 83, 85 and 87 is provided to hold the lever 73 and, consequently, the movable contacts in the closed position and to operate the movable contacts to open and closed positions. The toggle link 83 is pivotally connected to lever 73 by a pivot pin 89, and the toggle link 85 is connected by a knee pivot pin 91 to the toggle link 83 and by a knee pivot pin 93 to the toggle link 87. The toggle link 8; is pivotally mounted on a fixed pivot 97 in the frame 6 mally slightly underset above a line drawn through the centers of the pivot pins 89, 93 and the closing toggle 85, 87 is normally slightly underset below a line drawn through the centers of the pivot pins 91, 97.

.The tripping toggle 83, 85 is normally biased in a'" 3 direction to cause its collapse by components of the springs 57 and 64 and springs '98 (only one being shown) which bias the moving main contact structure for the severalpoles of the interrupter in opening direction and bias the connecting members 81 toward' the lefttFig. 1). The tripping toggle 83, 85 is normallyprevented'from collapsing by means of a main' latch member 99 pivoted on a pin'100 and connected by a link 101 to the knee pin 91 of the tripping toggle, the link 101 being connected to the latch member 99 by a pin 103.

The main latch'99 is'held in latching position by an intermediate latch lever 1'05 pivoted on a'pin'107 in' the frame 63. The latch lever 1 'car'ries a latch roller 111 which normally engages'themain'latch 99 to releasably hold the latter 'in'holding position. The latchlever'I05 at its lower end carries 'a latch'member 113 which normally engages a latchmember 115 on a light-load latch member'117' pivoted on a 'pin'119 in the frame-63. The latch lever 105 and the member 117 are 'bias'ed'to their latching positions by a spring 121'tensioned between the parts. Rigidly mounted on the right hand end of member11'7 is a trip bar 123 which extends across all of the poles of the-interrupter and has secured thereto an insulating bracket-125 (Figs. 1 and 2) for each pole of the interrupter cooperating with the trip'device 13forthe corresponding pole unit.

As long as the main latch 99 is held in'latching' position by the latching mechanism just described, the tripping toggle 83, 85 will, through the link 101, be held in the position shown in which the interrupter contacts are held in closed position. The closing'toggle85, '87 is normally prevented from collapsing by a shouldered support member 131 pivoted on the pin 107 and biased bya spring 133 into supporting engagement with the knee pin 93 of the closing toggle.

The circuit interrupter is tripped open by operation of the trip device 13, to be described later, for any pole of the interrupter. Operation of the trip device actuates the trip bar 123 to effect release of the latch lever 105 which, in turn, releases the main latch 99. When the main latch 99 is released, the force of the springs 57 and 98 biasing the main movable switch arm 33in opening direction and which is transmitted through the connecting members 81 to the lever 73, causes-the tripping toggle 83, 85 to collapse upwardly and effects opening movement of the-movable main switch arms 33 for a'll of the poles. of the breaker.

The closing toggle 85, 87 does not immediately collapse following release of the latchmechariism, since it is held by thesupport member 13. During the unlatching movement of the main latch 99, a cam (not shown) thereon engages the tail of the support member '133 and moves this member in a clockwise direction about its'piv- 0t 107 to disengage the shoulder thereon from beneath the pin 93, whereupon the closingtoggle 85, 87,being no longer supported, collapses downwardly under its own weight and the weight of the moving armature of the closing solenoid which will be described later. Collapse of the closing toggle 85, 87 causes the tripping toggle 83, 85 to be reset to thrust transmitting position and also effects resetting of the latch mechanism to'latching position. The operating mechanism is now in condition for a closing operation.

Means is provided to hold the movable arcing contact arm 47 stationary with full contact pressure until the movablemain contacts have separated a predetermined distance from the stationary main contacts. This means comprises a cam member 135 (Figs. land 3) rigidly securedto themoving arcing contact arm 47. Cooperating with a .cam surface 137 on the cam member- 135 is a roller 139. rotatable on'thepin80 whichpivotally connects the lever 73 to the connecting member 81. .-It will be remembered that the connecting member 81 is connected by the pin 79 to the moving main contact arm 33. .Inorder to openthe contacts the lever 73 moves in a counterclockwise direction about the pivot moving the roller along the cam surface 137. The configuration of the cam surface 137 is such that during the early part of the opening movement and until the roller 139 reaches a point A on the cam member 135, the roller 139 holds the cam member and, hence,-the movable arcing contact arm 47 stationary in'thefully closed position. During this early movement, the counterclockwise movement of the lever 73 and the leftward movement of the connecting'member 81 moves the moving main contact arm 33 in opening direction until the pin 79 engages the arcing contact arm 47. At this time, the roller 139 is at the point A. Thereafter, during the opening movement it moves along an arcuate surface'141 of the cam member which, it will be noted, is struck around the center of the pin 79 with the pin in contact with the arcing contact arm 47 By this means, the two moving contact arms 33 and 47 are locked together for unitary movement during the rest of the opening operation.

During opening and closing operations and in the closed position, good electrical contact is provided at the pivoted end of themovable main contact arm 33 by means of spring biased contact members 143 (Figs. 1 and 2)which arepivoted on the bracket 37 adjacent the terminal conductor 41 and biased into engagement with opposed arcuate surfaces 145 'on the contact arm 33 by a spring 147.

The main current path through the interrupter is from the upper'terminal 27,'through the main stationary contacts 23, the main moving contacts 29, the main contact arm "33 and'through the contact members 143 to the lower terminal 41. A parallel current path is formed from the upper terminal 27 through the stationary arcing contact 25, the'moving arcing contact 31, through the flexible conductor 49, the main moving contact arm 33 and the contact members 143 to the lower terminal '41. The magnetic effect of the current loop through the arcing contacts in the closed contact position tends to blow the arcing contacts on, thus permitting the interrupter to carry its rated interrupting current for the duration of the short time delay provided by the short time delay means of the trip device13.

The circuit interrupter is closed automatically by energiz-ation of a closing solenoid 149 (Fig. l) which is effected either manually or by automatic means. The closing solenoid '149 comprises a fixed'magnet yoke'151 and a fixedcore member 153 mounted on the underside of the platform 69. A movable armature 155 is attached to the lowerend of an operating rod 157 which extends upwardly and has its upper end pivotally connected to the knee pin 93 of the closing toggle 85, 87. An energizing coil 159 is'supported on the lower end'of a supporting bracket 161 having its upper end fastened to the platform 69.

In the closed position of the interrupter, the armature 187 is held in itsraised position (Fig. 1). When the breaker is tripped open, the closing toggle 85, 87 collapses downwardly permitting the armature 155 to assume its lower or unattracted position. Thereafter, upon cnergization of the coil 159, the armature 155 is attracted upwardly and acts through the rod 157 to straighten the closing toggle 85, 87 and close the contacts.

The action of the contact structure during a closing operation is the reverse of that of the opening operation.

The trip device 13 includes a tripping electromagnet indicated generally at 163 (Figs. 1 and 2) and a time delay device indicated generally at 165. The tripping magnet 163 comprises a U-shaped magnet yoke '167 (Fig. 2) rigidly secured to the base '15 of its corresponding pole unit by means of bolts 169 (only one being shown). The legs 171 of the magnet yoke 167'extend downwardly on opposite sides of the main current carrying switch arm 33 and'terminate'in pole faces 173. Also mounted on the'base IS by'means'ofthe bolts 169 and acne-zeobetween the legs 171 of the yoke 167 is a separate U- shaped magnet yoke 175, the legs 177 of which extend toward the left (Fig. 2) on opposite sides of the main movable switch arm 33 and terminate in pole faces 179. The electromagnet comprising the magnet yokes 167 and 175 is energized by the current flow in the switch arm 33, which forms a single turn energizing coil passing through the U of both of the magnet yokes. The legs 171 and 177 respectively of the magnet yokes 167 and 175 are spaced from each other.

The time delay device 155 and the elements of the trip device, other than the magnet yokes, are supported in a U-shaped frame indicated generally at 131 (Fig. 2). The frame 181 comprises spaced side members 183 (only one being shown) integrally joined by a cross member 185. The lower portion of each of the side members 183 are rigidly supported on the base by means of a belt 187, and the upper end of each of the side members 183 is rigidly secured to the adjacent downwardly extending leg 171 of the magnet yoke 167 by means of a bolt 189 which threadedly engages a bracket 191 riveted to the leg 171.

The trip device is actuated by a moving armature 193 mounted on a pair of spaced arms 195 (only one being shown) joined by a cross member 197 and pivotally supported on pins 199 in the side members 183. Upon energization of the electromagnet in response to overcurrents, the armature 193 is attracted to the pole faces 17 3 and actuates a trip rod 201 to effect tripping of the interrupter. The trip rod 201 engages a roller 203 mounted on one end of a bell-crank lever 205 pivoted on a pin supported in the frame 181 and rotates the lever 205 counterclockwise. During this movement of the bell crank 205, the other end thereof engages a pin 207 in one end of a bell crank 208 and rotates the latter in a clockwise direction. The bell crank 208 is mounted on a pin 209 in the frame 181 and, when actuated, the other end 210 thereof engages a screw 211 threaded into the bracket 125 (Figs. 1 and 2), and actuates the previously described trip 123 and the latch mechanism to trip the interrupter.

The trip rod 201 is moved upwardly to trip the interrupter under the control of the time delay device 165 which comprises, enerally, a flexible diaphragm 213 (Fig. 2) attached to the lower end of the trip rod and valve elements for controlling the admission of air to the space below the diaphragm at various rates to provide difi'erent amounts of time delay. The flexible diaphragm 213 is disposed in a chamber 215 formed in an upper housing member 217 and a lower housing member 219, both of the housing members being of molded insulating material. The outer edge of the diaphragm 213 is clamped between the housing members 217 and 219, together with a sealing gasket 221 to form an airtight seal. The housing members are secured together and rigidly secured to a cross member 222 of the frame 181 by means of bolts 223 (Figs. 1 and 2). The central portion of the diaphragm 213 is suitably clamped between upper and lower clamp members 225 and 227, respectively, to form an air-tight seal. The clamp members are rigidly secured to the lower end of the trip rod 201. Disposed above the upper clamp member 225 and surrounding the trip rod 201 is a cylindrical member 229 having spaced flanges 231 at its upper end between them forming an annular groove 233 which is engaged by opposed ears 228 (only one being shown) on the cross member 197 of the armature lever 195. The cylindrical member 229 has a bore 230 therein in the upper end of which is disposed a collar 232 fastened to the trip rod 201. A coil spring 234 is disposed in the cylinder bore 230 and is compressed betweeen the collar 232 and the bottom of the bore 230.

Since the spaces above and below the diaphragm 213 are completely sealed off from each other and the space above the is at atmospheric pressure, any

6 force tending to raise the trip rod 201 will be restrained by the partial vacuum below the diaphragm. In order to control the rate of tripping movement of the trip rod 201, valve devices are provided to admit air to the space below the diaphragm. The valve devices comprise a long time delay valve indicated generally at 235 (Fig. 2), and a short time delay valve indicated generally at 237 (Fig. 3

The long time delay device will be described first. The central bottom portion of the lower housing memher 219 is molded to form a valve seat 241 in the shape of an inverted truncated cone. Surrounding the valve seat 241 is a tubular metallic member 243 molded into the housing member 219 and threaded internally to receive a valve 245 having a conical opening therein for cooperating with the valve seat 241. The valve 245 is provided with a flange 247 for supporting a knurled adjusting knob 249 of molded insulating material which is biased thereagainst by a spring 251. An air passage 259 in the form of a groove is provided along the threaded portion of the valve 245, and a passage 261 is provided axially through the valve seat 241. The flow of air into the chamber below the diaphragm is through a filter 257, the passage 259, the orifice defined by the valve 245 and the valve seat 241 and through the passage 26]..

The inner surface of the knob 249 is provided with serrations which engage corresponding serrations on the valve 245, whereby rotation of the knob 249 rotates the valve 245 which, due to its threaded engagement with the fixed tubular members 243, moves the valve axially of the valve seat 241 to thereby vary the rate of admission of air to the space below the diaphragm 213 and, hence, varies the amount of time delay in the operation of the trip device.

The valve device 235 is calibrated by pushing upwardly on the knob 249 to disengage it from the valve member 245. The knob 249 is then set to zero and the valve member 245 rotated to the closed position. Thereafter, the knob 249 is released and restored to engagement with the valve by the spring 251. The knob 249, together with the valve 245 is then rotated to the position to provide the required amount of time delay.

The short time delay valve device 237 (Fig. 3) controls a passage for admitting air from the chamber 215 above the diaphragm 213 to the space below the diaphragm at a rate to provide tripping with a very short time delay in the order of alternating current cycles. The valve device 237 comprises a tubular valve element 273 (Fig. 3) disposed in an opening 275 in the upper housing member 217. The valve element 273 is provided with an enlarged head portion 277 seated in an opening 279 in the bottom housing member 219. The valve element is also provided with a valve 281, slidably disposed in the tubular valve element 273, and which normally cooperates with a valve seat to close a communication with the opposite sides of the diaphragm 213. The valve element 273 is provided with an axial passage in which is disposed a tapered projection 285 of the valve 281 and which is normally closed by the valve 281. The head 277 of the valve element 273 is provided with horizontal passages 287. A passage 289 in the housing member 217 communicates the chamber 215 above the diaphragm 213 to the opening 275 above the valve seat, and a passage 291 in the housing member 219 communicates the chamber 215 below the diaphragm 213 with the passages 287.

It will be seen that upward movement of the valve 281 will open the passage comprising the passages 289, 287, and 291 and establish a communication from the upper side to the lower side of the diaphragm.

The valve 281 (Fig. 3) is actuated to the open position by means of an armature 292 (Fig. 2) rigidly mounted on one end of a lever 293 which is pivoted on the pin 209. The other end of the lever 293 is connected by a link 294 to a lever 295 pivotally mounted at 296 on the housing 217. The link 294 is guided in its movement by a pin 297 and slot 298 and has a pin and slot connection 299-30i9 with a bracket 301 rigidly mounted on the lever 295. A bracket 393 (Fig. 3) secured to the lever 295 engages in a notch 305 in the upper end of the valve 231, so that upon actuation of the lever 295 by the armature 292 acting through the lever 293 and link 294, the valve 281 is moved upwardly to the open position. This opens the previously described communication permitting air to pass from the chamber 215 above the diaphragm 213 to the space below the diaphragm to control the rate of tripping movement of the trip rod 201.

The amount of opening of the valve and, hence, the rate of flow of air to the space below the diaphragm is controlled by an adjustable S-shaped stop member 337 (Fig. 3). The upper portion of the stop member 307 is disposed in the path of tripping movement of the upturned end of the lever 295 to be engaged thereby and thus limit the extent of opening of the valve 281.

The stop member is adjustable to vary the amount of short time delay by means of an adjusting screw 3 59 which threadedly engages the center cross bar 311 of the S-shaped member 307. The adjusting screw 309 is rotatably mounted in an insulating cross bar 313 supported on the underside of the housing member 217 by means of screws 315 only one of which is shown. A knurled knob 317 is mounted on the lower end of the screw 309 below the cross bar 313, whereby the adjusting screw 309 may be rotated to provide the proper setting of the stop 367.

A portion 319 of the screw 309 also engages a pointer 321, one end of which projects outward through a slot in a scale plate 323 to give an indication of the setting of the adjustable stop 307 for the short time delay valve 281.

The pick-up point; that is, the magnitude of overload current required to actuate the armatures 193 and 292 (Fig. 2) may be varied by varying the tension respectively, of springs 325 and 327. The spring 325 has one end attached to a yoke 329 which has its legs pivotally supported in spaced grooved studs 331 (only one being shown) supported in the housing member 217. The right-hand end of the yoke 329 is provided with inwardly extending projections 333 which engage in an annular groove 335 in the cylindrical member 229. The other end of the spring 325 is attached to a pointer 337 which is threadedly engaged by an adjusting screw 339 rotatably mounted in the cross bar 313 and which is provided with an adjusting knob 341 on the end thereof below the cross bar. Rotation of the screw 339 varies the tension of the spring 325 to thereby vary the pick-up point of the armature 193. The tension of the spring 327 for the armature 292 is similarly adjusted by means of a screw and pointer (not shown) but which are like the adjusting means for the spring 325.

The legs of the magnetic yokes 167 and 175 are spaced from each other in order that operation of armature 193, upon energization of its magnet yoke 167, will not shunt part of the flux from the magnet yoke 175 as would be the case if the yokes 167 and 175 formed a single magnet yoke. This prevents disturbing the calibration of the short time delay armature 292 when the armature 193 is attracted to its pole faces 173.

The trip device functions with time delays of different durations in response to overload currents of different magnitudes. For instance, the device may function with a relatively long time delay in the order of seconds, in response to overload currents up to approximately ten times normal rated current and with a relative short time delay in the order of alternating current cycles.

Assuming an overload current flow ten times normal rated current, the tripping electromagnet becomes enerev gized by the current flow through the switch arm 33 sufficiently to attract the armature 193 upwardly. The armature 193 acts through the lever 195, cylindrical member 2-29, and the spring 234 to produce an upward thrust on the trip rod 201, the movement of the trip rod being retarded by the partial vacuum below the diaphragm 213. The trip rod 201 moves slowly upwardly in tripping direction as air is drawn into the space below the diaphragm through the long time delay valve 235. The slow upward movement of the trip rod 201 acts through the roller 203 to slowly rotate the bell crank -35 in a counterclockwise direction. The upper end of the bell crank 205 acts through the pin 207 to rotate the bell crank 208 in a clockwise direction until eventually the end 210 of the bell crank 238 engages the screw 211 and actuates the trip bar 123 and eifects release of the latch mechanism and opening of the interrupter in the previously described manner.

As soon as the interrupter contacts have opened the tripping electromagnet is deenergized and the armature 193, the cylindrical member 229, and the trip rod 201 are restored to their normal positions by the spring 325. A spring biased reset or bypass valve 343 (Fig. 2) controls a passage through the diaphragm 213 to provide quick dumping of the air in the space below the diaphragm and quick restoration of the parts.

Energization of the electromagnet in response to overload currents above ten times normal rated current attracts the short time delay armature 292 which acts through the link 294 to move the lever 295 upwardly against the stop 307 opening the short time delay valve 237 an amount determined by the adjustment of the stop 307. This admits air to the space below the diaphragm 213 at a higher rate than the long time delay valve 235 alone and provides a short time delay in the order of cycles in the tripping operation of the device.

The trip device may be arranged to trip the interrupter after a relatively long time delay and instantaneously by omitting the short time delay valve 237 and omitting the slot 345 in the lever 293 which carries the armature 292, as shown in Fig. 1. The armature 292 in response to an overload current above a predetermined value will act through the pin 207 to instantaneously trip the interrupter.

The invention provides a trip device for a circuit interrupter having a time delay device and control means for the time delay device in which the electromagnetic means for operating the time delay device and the control means therefor are separate to prevent disturbing the calibration of one electromagnet upon operation of the other electromagnet. The magnet yokes of each of the electromagnets surround the main current carrying path through the interrupter to provide single time energizing coils for the electromagnets.

Having described the invention in accordance with the provisions of the patent statutes, it is to be understood that various changes and modifications may be made in the structural details and combinations of elements disclosed without departing from the spirit of the invention.

We claim as our invention:

1. In a circuit interrupter having a main current carrying circuit therethrough, an electromagnetic trip device comprising a fixed magnet yoke surrounding said main current circuit to be energized by currents therein, a trip rod operable to effect automatic operation of said interrupter, an armature operable by energization of said magnet yoke in response to overload currents of certain value to positively actuate said trip rod, time delay means retarding tripping movement of said trip rod comprising a fluid dashpot connected to said trip rod, a plurality of valve means admitting fluid to said dashpot at different rates, separate electromagnetic means operable in response to overload currents of certain other value to positively operate one of said valve means to increase the rate of admission of fluid to said dashpot, said separate electromagnetic means comprising a separate fixed magnet yoke surrounding said main current carrying circuit and an armature connected to operate said one valve means.

2. in a circuit interrupter having a main current path therethrough, a tripping electromagnet comprising a fixed U-shaped magnet yoke, said main current path extending through said magnet yoke to form a single turn energizing coil, a tripod movable to effect automatic operation of said interrupter, an armature operable by energization of said electromagnet in response to certain overload currents to positively actuate said trip rod, time delay means retarding tripping movement of said trip rod, a plurality of valve means admitting fluid to said dishpot at different rates, a second electromagnet operable in response to certain other overload currents in said main circuit to positively operate one of said valve means to increase the rate of admission of fluid to said dashpot, said second electromagnet comprising a U-shaped yoke through which the main circuit extends to form a single turn energizing coil and an armature connected to operate said one valve means.

3. In a circuit interrupter having relatively movable contacts, a main current path through said interrupter including said contacts, a trip member operable to effect automatic opening of said contacts, a trip device com-- prising a magnetic circuit surrounding said main current path and including an armature operable in response to overload currents to positively actuate said trip member, a time delay device retarding tripping operation of said trip member comprising a fluid dashpot, a plurality of valves admitting fluid to said dashpot at different rates, one of said valves being operable to increase the rate of admission of fluid to said dashpot, and electromagnetic means comprising a separate magnetic circuit surrounding said main current path and responsive to other overload currents, said separate magnetic circuit including an armature movable to positively operate said one valve.

4. In a circuit interrupter having a main current path through said interrupter including relatively movable contact means, a trip member operable to effect automatic opening of said contact means, a time delay means effecting a time delay in the operation of said trip member, a control element for controlling said time delay means to effect a predetermined time delay in the operation of said trip member, electromagnetic means operable to actuate said trip member and said control element comprising separate magnetic circuits surrounding said main current path and responsive to overload currents of different values, each of said magnetic circuits including an armature operated by energization of said magnetic circuits in response to overload currents of different values, one of said armatures being connected to positively actuate said trip member and the other of said armatures being connected to positively actuate said control element.

5. In a circuit interrupter having a main current carrying circuit including a switch arm movable to open and closed positions, a trip member operable to eflect automatic opening of said switch arm, time delay means pro-- viding a time delay in the operation of said trip member, a control element operable to decrease the time delay provided by said time delay means, electromagnetic means comprising separate magnetic circuits surrounding said switch arm whereby said switch arm provides a single turn energizing coil for energizing said separate magnetic circuits in response to overload currents of different values, each of said magnetic circuits including a movable armature, one of said armatures being operable when its magnetic circuit is energized in response to overload currents below a predetermined value to positively actuate said trip member, and the other of said armatures being operable when its magnetic circuit is energized in response to overload currents above said predetermined value to positively actuate said control element.

References Cited in the file of this patent UNITED STATES PATENTS 754,505 Scott Mar. 15, 1904 2,000,442 Healis May 7, 1935 2,144,501 Lingal Jan. 17, 1939 2,340,973 May et al Feb. 8, 1944 2,669,623 MacNeill et al Feb. 16, 1954 2,700,082 Lingal Jan. 18, 1955 FOREIGN PATENTS 282,642 Great Britain Nov. 25, 1927

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