US2543410A - Circuit breaker time-delay device - Google Patents

Description

Feb. 27,1951

0. JENSEN CIRCUIT BREAKER TIME DELAY DEVICE Filed April 19, 1945 5 Sheets-Sheet l TYPICAL AIR ClRCUKT BREAKER A. CURVE 1 100 AMP. wn'u ispooA INTER. 1 CURVE 2 600 me wm4 25 m nurse. 2 cuavs 3 I200 AMP WITH Q W x cuevc 4 2000 AME wm4 7:,oooA mm:

Q Ia CL, Fa yfll .06 .04

mtoo looolooo 400 CURRENT IN AMPEQES Fig Z Iqcoc qweeopoo INVENTOR.

B OTTO JENSEN Y A T TORNE Y6 Feb. 27, 1951 0, JENSEN 2,543,410

CIRCUIT BREAKER TIME DELAY DEVICE Filed April 19, 1945 5 Sheets-Sheet 2 2 0 INVENTOR. I 0770. JENJ'EN Feb. 27, 1951 o. JENSEN 2,543,410

cmcun BREAKER TIME DELAY DEVICE Filed April 19, 1945 Sheets-Sheet 3 f V 4 4|\ 3.3 23 v 3 EI I B 1 3 4 F 5' INVENTOR. OTTO JENSEN Feb. 27, 1951 JENSEN 2,543,410

ciRcuI'r anmm TIIIE DELAY DEVICE Filed April 19, 1945 5 Sheets-Sheet 5 uwsurm 0170. JENSEN aM'lM v- ATTORNEYS Patented Feb. 27, 1951 CIRCUIT BREAKER TIME-DELAY DEVICE Otto Jensen. Malvern. Pa., assignor to I. T. E. Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application April 19,1945, Serial No. 589,170

3 Claims. (Cl. 200-97) My invention relates to circuit breakers and more specifically to novel tripp devices therefor adapted to be used in a system of circuit breakers arranged for sequential tripping over the entire protective range of the circuit breakers including the short circuit current ranges.

More specifically, my invention relates to a novel tripping device provided with direct acting overload elements and novel time delay means which may be adjusted to secure sequential or other appropriately timed tripping with respect to other breakers in the system.

A primary object 01' my invention is the provision or a novel tripping device for a circuit breaker which will be selectively responsive at diderent speeds to different types of overload and short circuit.

Another object o! my invention is the provision of a time delay device for a circuit breaker tripping mechanism wherein a single unitary time delay element may be provided with a plurality of independent adjustments for various time delays under diiferent loads.

Still another object of my invention is the provision of a novel time delay device for the tripping elements of a circuit breaker which will adapt the circuit breaker for use in a sequential tripping system.

Another object of my invention is the provi--- sion of a time delay device arranged to have characteristic curves for protecting normal overloads, such as starting current in motor circuits, while at the same time it has other characteristic curves for protection against various more excessive loads up to and including short circuits.

Another object of my invention is the provision of a novel time delay device for use in connection with tripping elements of circuit breakers arranged in a sequential tripping system in which both long time delay periods and quick trip op crating periods are obtainable.

In a preferred form of my invention, the time delay device comprises essentially a, dashpot having a plurality of passages between the charm bers thereof. Each of the passages is controlled by an independently set valve, which valve may be adjusted for a diflerent degree of overload; and the passage may be adjusted for a diilerent time delay. Thus, the first passage may have a valve which will permit the dashpot fluid to flow therethrough at an overload of say, from 2 to times normal and the passage controlled by that valve may permit a tripping operation to occur within a period of, for instance, 'I to 100 seconds.

The valve of the second e may be ad- 10 to 150 times normal and the passage may iniusted so that it will respond to currents of say.

terpose a time delay of the order of .1 second.

The third passage may have a valve adjusted to respond to short circuit currents instantaneously without any time delay at all. The various valve elements of each of the circuit breakers in the sequence may be adjusted to operate sequentially. Thus, when an overload less than a short circuit occurs, the armature will begin to move but will be restrained b the time delay de-- vice. When, however, one of the circuit breakers having a slightly faster operation is tripped, this circuit breaker efiects an opening of the system and the remaining armatures of the other circuit breakers in the system (each having been delayed by the device of my invention for slightly longer periods) will not yet have reached the tripping position.

Since the clearance of the fault by the circuit breaker will reduce the magnetic attraction ex erted by the cvercurrent magnet on the armature to the full load level or less, and since the arma ture is normally restrained by a spring having a somewhat greater force than that exerted by the magnet at full load even at the reduced air gap, the armature will return when reaching the tripping position.

Figure l is a schematic diagram of a group of circuit breakers in a typical distribution systern.

Figure 2 is a graph showing the tripping characteristics of each of the circuit breakers in the group.

.Figure 3 is a side view oi. a circuit interrupter which may be used in the system of Figure 1, the circuit breaker having a time delay device on its tripping armature.

Figure 4 is a schematic view of my novel time delay device showing the condition thereof when the armature is not attracted.

Figure 5 is a schematic view of the device of Figure 4 showing the operation for normaloverloads of, for instance, 2 to 10 times normal.

Figure 6 is a schematic view of the device of Figure 4 showing the operation for overloads above 10 times normal but less than short circuit.

i ure 7 is a schematic view of the device of Figure 4 showing the operation of the device for instantaneous tripping.

Figure 8 is a schematic view of the device of Figure 4 showing the manner in which the time delay device is reset after operation.

Figure 9 is a front view of a specific embodiment of the schematic time delay device of Figures 4 through 8, the view of Figure 9 being taken from line 9--9 of Figure 3 looking in the direction of the arrows.

Figure 10 is a view partly in cross-section of the time delay device of Figure 9 taken along line |--|0 of Figure 9 looking in the direction of the arrows.

Figure 11 is a cross-sectional view taken on line of Figure 10 looking in the direction of the arrows.

Figure 12 is a plan view partly in cross-section taken on line |2--|2 of Figure 11 looking in the direction of the arrows.

Figure 13 is a cross-sectional view taken on line |3-|3 of Figure 12 looking in the direction of the arrows.

Figure 14 is an expanded view of one of the valves of the device of Figures 10 to 13.

Referring now to Figures 1 and 2, I have here shown a typical distribution system having a plurality of circuit breakers together with a graph showing the tripping characteristics thereof. In this distribution system, the electrical energy is distributed at a utilization voltage of 440 volts, the various interrupting capacities for each of the breakers are shown in the curves.

The power enters the main plant by the circuit breaker 4, and then passes to a main distribution switchboard whence it is fed out on a number of feeder breakers 3. These feeders may each go to large loads. Some, or all, however, may go to additional distribution switchboards where they are again divided into a plurality of small distribution circuits to which energy is fed out over the circuit breakers 2. Each of these circuits may in turn go to load centers or power panels for distribution of the energy over the circuit breakers to a multiplicity of loads.

The optimum tripping characteristics are shown in the graph of Figure 2.

In Figure 4, time delay device 20 is shown, which comprises an oil dashpot having a lower chamber 2| and an upper chamber 22 with a suitable stationary diaphragm or wall 23 between. The lower chamber 2| is adapted to be compressed by the fiexible diaphragm 25 which is connected by the extension 25 and link 21 to the armature. Raising of the armature will result in raising the diaphragm 25 to compress the fluid within the lower chamber 2|. The fluid will then be driven up into the passages 3|, 32, 33, which are blocked respectively by valves 4|, 42, 43, urged into blocking arrangement by the springs 52, 53.

The passage 3|, valve 4|, and spring 5| give a time delay curve corresponding to section a of curve 2 of the graph of Figure 2. Passage 32, valve 42, and spring 52 provide a time delay corresponding to section 0 of curve 2 of Figure 2, while passage 33, valve 43 and spring 53 provide for instantaneous operation as shown at section d of curve 2 of Figure 2.

Passage 35, check valve 45 and spring 55 provide a return passage for the fluid on relaxation of tripping pressure. The passages 3|, 32 and 33 vary in cross-section in accordance with the degree of time delay which is desired, the longest time delay being obtained through the passage 3| which cooperates with valve 4| having the lightest spring 5|; intermediate time delay being obtained through the wider passage 32 which cooperates with valve 42 having a heavier spring 52, and the widest passage 33 being sufficient to permit instantaneous operation of the valve 43 having the heaviest spring 53.

Through calibration of the device, the width of the passages 3|, 32, 33 may be adjusted for various time delays and springs 5|, 52 and 53 may also be adjusted to respond to different loads in order to obtain various time delays for various purposes as determined by the position of the particular circuit breaker in the sequence and the particular load which the circuit breaker is to protect.

Figure 5 shows the operation of the device of Figure 4 along section a of curve 2 of Figure 2. That is, the diaphragm has been raised only with suflicient force to exert lifting pressure only on valve 4| and spring 5|. Accordingly the Figure 5 condition of the device of Figure 4 shows the normal overcurrent time delay condition of the time delay device. Restricted passage 3| provides for a long time delay.

Figure 6 shows the condition of the time delay device where in addition to valve 4 valve 42 and spring 52 have been raised by the pressure of the armature on the diaphragm and the condition of Figure 6 corresponds to section 0 of curve 2 of Figure 2. Accordingly when the time delay device is in the condition of Figure 6, the armature is being attracted by a high overload, which overload is, however, less than the short circuit current or less than the maximum interrupting capacity of the circuit breaker. A very much shorter time delay is obtained through wider passage 32 cooperating with passage 3|.

Figure 7 shows the condition of the time delay device when the overload condition attracting the armature corresponds to that of section (1, curve 2 of Figure 2, and in which the pressure on the diaphragm is at its maximum and is thus sufllcient to raise not only valves 4| and 42 but also valve 43 and its spring 53. The adjustment of valve 43 and spring 53 should be such that the condition of the time delay device of Figure 7 will occur either at short circuit currents or at the maximum interrupting capacity of the circuit breaker. The very wide passage 33, cooperating with passages 3| and 32 permit instantaneous tripping.

Figure 8 shows the condition of the time delay device after the circuit breaker has tripped or after the fault has been cleared so that the arma ture is no longer subject to overload. The diaphragm 25 is now restored to its original position and the fluid forced from chamber 2| up through passages 3| or 32 or 33 is returningthrough passage 35 and check valve 45. Accordingly my novel time delay dashpot serves accurately to control each of the circuit breakers which form part oi the protective mechanism in a sequential system.

It will be obvious that the adjustment of the various time delays for the various circuit breakers in the system in accordance with the principles set forth in connection with the description of Figures 1 and 2, will provide for appropriate sequential operation of the various circuit breakers to which the time delay device of Fig ures 4 through 8 is attached.

In Figure 3 I have shown a circuit breaker of a well known type having a time delay device 20 attached thereto, having the operating elements shown in Figures 4 through 8 and in Figures 9 through 14 I have shown a specific operative embodiment of the time delay device of Figures 4 through 8. Referring to Figure 3, there is here shown a circuit breaker I00 of the type generally described in Patents No. 2,348,228 and 2,338,715, which is mounted on a panel Illl. Current enters the circuit breaker through connection stud I02 to the main stationary contact I03 and then passes to the main movable contact I04 mounted on the contact arm I35, through the pigtail I03 to the lower terminal block I01, then through the series overload coil I03 to the lower back connection stud I03.

The series overload coil I" is arranged to energize a magnet III! which in turn cooperates with the balanced armature III to attract the same under predetermined overload conditions. Armature III is pivotally mounted on the stationary pivot H2 and is connected by the link III to the cross-bar II4 which in turn is connected by a pair of straps I I5 passing down on opposite sides of the time delay mechanism 20 to the lower cross-bar H8. The lower cross-bar H3 is provided with a central upwardly directed post III (see also Figure 11) engaging the diaphragm I II o! the time delay device 20.

Accordingly, any pull on the armature III exerted by magnet H will cause the armature III to rotate about its pivot H2 and pull up the link II3, thus pulling up the cross-bar H4 and the straps II5 thereby pulling up the cross-bar H6 and the upwardly directed post II1, thus tending to raise the diaphragm H8 of the time delay devices of Figures 9 through 14. Accordingly, any back pressure on the diaphragm exerted by the fluid in the time delay device will resist the movement of the armature III and thus delay the tripping operation of the circuit breaker.

The time delay device is supported by a bracket I22 secured to the panel IIII of the circuit breaker (Figure 3) which is connected by bolts I24 entering into the tapped openings I25, I25 (Figure 10) of the main block I28 of the time delay device 20.

Referring now to Figure 9 which is a front view of the time delay device 20 of Figure 3, the

device has a plurality of calibrating elements comprising passage opening calibrating discs I30 and i300 and valve spring calibrating discs I3I and I3Ia. The calibrating disc I301: changes the passage opening corresponding to passage 3| of Figure 4 and calibrating element I3Ia changes the spring tension of a spring hereinafter described corresponding to spring 5I of Figure 4. Members I300. and l3la comprise the setting for normal overloads.

Calibrating disc I30 changes a passage opening in the device of Figures 9 through 13 which corresponds to passage 32 of the schematic device of Figure 4 while the member I3I calibrates a spring corresponding to spring 52 of the schematic device of Figure 4. Members I33 and I3I are for calibration of the circuit breaker for heavy overloads less than short circuit or less than the capacity of the circuit breaker but more than normal overloads.

The instantaneous calibration is obtained by rotating the upper cover I35 of the dashpot I36 against the stationary index I31. This results in a change in the interior of the device corresponding to a change in the dimemion oi passage 33 of the schematic device of Figure 4, and a change in the tension of spring 53 thereof. The dashpot I35 as shown particularly in Figures 11 and 13 comprises a lower chamber 22! on the underside of block I23 and an upper chamber 222 on the upper side of block I28. The lower chamber 22I is closed at its bottom end by the diaphragm II3 which corresponds in operation to the diaphragm 25 of the schematic device of Figure 4. Chambers 222 and 22I are connected by a central cylindrical opening 250 through the principal supporting block I24. Opening 2" is closed at the upper end by the flanged tubular cylindrical insert member 23I.

The tubular member 23I has a diameter substantially less than the diameter or the central opening 230 but is provided with a plurality of ribs 232 spacing it evenly from the side walls or the opening 230 and centering the tube 25l within the opening 230. Tube 23I is provided at its upper end with the flange 243 which serves as a valve seating on the bottom wall 264 of the upper chamber 222 closing the upper chamber. Flange 243 is provided with a central opening 235 through which fluid may pass, which opening is, however, closed by the check valve 245 held against the lower end of the opening 235 by the compression spring 255 within the interior of the tube 23L Compression spring 255 for valve 245 is held in position by the tubular screw 253 which is threaded into the lower tapped end or the tube 23I. The screw 255 is provided with a counterbore 251 providing an appropriate seat and guide for the end oi. compression spring 255 which counterbore 251 communicates with the opening 253 in the lower end of the screw 256 to provide a complete passage from the upper chamber 222 to the lower chamber 22i when the check valve 245 is opened. The check valve 245 corresponds to the check valve oi the schematic view of Figure 4, and the spring 255 of check valve 245 corresponds to the spring 55 of the schematic device of Figure 4.

The entire tubular member 26I is pressed down so that its flange 243 bears against the base 264 oi chamber 222 and closes the opening 260 by the compression spring 253. Accordingly, the entire tube 26] with its flange 243 comprises a valve which is held closed by spring 253 and the flange 243 corresponds in function and in operation to the valve 43 of the schematic device of Figure 4 with the compression spring 253 for flange 243 corresponding to the spring 53 of the schematic device of Figure 4.

The tension of spring 253 is adjusted by means of the pin 210 which is flxed in the top wall I35 0! the dashpot I33. Pin 213 has an extension 2" with a helical thread 212 engaging nut 213 which bears against the upper end or compression spring 253. Rotation of top wall I35 and hence 01' pin 210 will result in rotation of the helix 212 vand in corresponding longitudinal movement of the nut 213 to change the compression of spring 253, and accordingly changethe pressure or the spring on the valve-flange 243. Nut 213 is prevented from rotation by engagement between the tines o1 the'forked member 215 which is secured in any'suitable manner, as by the rivet 21! to the side wall 218 of the dashpot I36.

The degree of compression of spring 253 obtained may be determined from an appropriate scale marked along the edge I35a of the top wall which may be read against the index member I31 also secured by the rivet 211 to the side wall 218. An appropriate stop 280 may be secured in the upper surface or the top wall I35 to bear against the cross-piece 2 3i and to limit the rotation of the top wall I35 over an angle of the order of The cross-piece 28I is secured in any suitable manner as, for instance, by the screws 232, 282 to the side straps 283, 283 which are rotatably mounted around the ends of plugs 284, 284. Cross-piece 23I is held in position by the setscrew 286 which may be screwed down against 7 the top wall 235. With the cross-piece 28| in position, adjustment of the compression spring 253 to vary the calibration of the instantaneous trip valve 243 is limited as determined by a rotational arc of the order of 170 of the top I35 of the dashpot I36.

Should any greater adjustment be desired, then the set-screw 286 may be loosened, cross-piece 28| swung aside on its straps 2B3 around the plugs 284, and the top I35 may then be freely rotated (over a full 360 and more) to an appropriate setting and then the cross-piece 28| may be restored to position to cooperate with the stop 280 to limit the adjustment within the narrow limits determined by the free movement allowed to the stop 280 (of the order of 170).

As previously pointed out, the valve 243 and the compression spring 253 correspond to the instantaneous setting shown schematically at 43-53 of Figure 4 and shown in operation in the schematic view of Figure '7. The normal overload setting and the heavy load (but not instantaneous) setting are shown more clearly in Figures and 13.

The passage 260 from the lower chamber 22I to the upper chamber 222 communicates with a cross-passage 300 in the block I25. The ends of the cross-passag 300 are sealed by the plugs 284, the outer ends of the plugs 284 furnishing a pivot for the straps 283 of the cross-piece 2-8I. The block I26 is also provided with a pair of passages 301, 302 emerging at the base 264 of the upper chamber 222 and combining with the valves hereinafter described to provide a through passage from the lower to the upper chamber in addition to th passage 260.

As will be seen from a comparison of Figures 12, 13 and 10, the passages and 302 do not extend in the same plane as the cross-passage 300 but are stepped toward the front of the time delay device. The block I26 is provided with another pair of passages 3| I and 3|2 bored from the front ofthe time delay unit into the body of the block I26 connecting with the cross-passage 300. The passages 30| and 302, as indicated in Figure 12, communicate with the bored passages or openings 3H and 3|2 respectively.

Accordingly the fluid under appropriate pressure will flow from the lower chamber 22I up into passage 260 on the outside of the tube 26| up to the cross-passage 300 which communicates with the opening 260. The fluid under pressure will divide, a portion of the fluid under pressure flowing back through the bore 3| I to passage 30I and up through passage 30| to the upper chamber 222. Another portion of the fluid in passage 300 will flow back through the bore 3|2 up through the passage 302 and into the upper chamber 222.

It will be obvious, of course, that a portion of the fluid forced up through the opening or passage 260 will not be divided along the transverse passage 300 but will be pushed up against the valve flange 243 for operations previously described.

Bores or openings 3 and 3|2 are provided with independently adjustable valve units and independently adjustable passage width regulators to control the flow of fluid up into the respzctive passages 30| and 302.

The two valve mechanisms for the bores 3H and 3|2 are the same in construction. Accordingly the description 01' valve mechanisms for the bor 3 and passage 30I will suflice for description of both valve elements.

One 01' the valves and its associated passage width regulator will be adjusted for a long time delay to take care of normal overcurrent surges while the other valve and its associated passage width regulator will be adjusted for heavy overloads which, however, are short of the maximum capacity of the circuit breaker or short circuit current.

In Figure 14 I have shown an expanded view of the valve mechanism utilized in each of the bores 3H and 3|2 and this expanded view corresponds to the mechanism shown in bore 3 of Figure 10. The end of bore 3 at the point of communication with the tranverse passage 300 is provided with a valve seat insert 3I5 which is pressed into the body of the block I26 and securely held in place to furnish appropriate means with which the valve hereinafter described may cooperate. The valve 3 forced against the valve seat 3|5 by the compression spring 35| closes off the passage previously defined from lower chamber 22I through opening 260 through passage 300 through bore 3|| through passage 30| to the upper chamber 222.

When valve 3 is opened by sufllcient upward pressure exerted by the diaphragm IIS on the fluid, then the fluid may flow through the passage above outlined, the volume, however, being regulated by the passage width regulating means associated with the valve mechanism and hereinafter described. Valve MI and its compression spring 35| are housed in a sleeve 320 also pressed into the body of the block I26. The sleeve 320 is continuous in the bore 3 across the base of passage 30| and thus would ordinarily close off this passage except for the fact that the sleeve 320 is provided with a slit 32| at the area where it crosses the lower opening of passage 30I.

An additional sleeve 325 is provided within the sleeve 320, the said sleeve 325 being rotatable with respect to the sleeve 320 and extending out beyond the front end of the time delay device 20. The calibrating disc |30a previously mentioned is secured to the outer end of the sleeve 325 and the sleeve 325 may be rotated by rotating the calibrating disc I30a. Sleeve 325 is also provided with a slit 326 registering in the same axial position as the slit 32| of stationary sleeve 320 so that the two slits match each other and cooperate to provide an opening from the interior of sleeve 320 to the passage 30L Rotation of the sleeve 325 by the calibrating disc |30a varies the portion of slit 326 which is in radial registration with slit 32I to vary the size of the opening between the interior of sleeve 320 and passage 30I.

Accordingly, the width of the passage from the lower chamber 22I to upper chamber 222 controlled by the valve 34| and its compression spring 35| may be varied by simple rotation of the calibrating disc I30a. In this device, therefore, valve MI and its spring 35| correspond to the valve 4| and spring 5| of the schematic device of Figure 4 while the complete passage as controlled by the radial position with respect to each other of slits 32| and 326 correspond to the passage 3| of the schematic device of Figure 4, the rotation of sleeve 325 with respect to the stationary sleeve 320 providing means for regulating the width of the passage for various purposes.

The sleeve 325 is provided with a flange 330 which bears against the annular ledge 33| in the bore 3, the said ledge "I being formed by a tapped counterbore in the bore 3| I; the cooperation between annular flange 336 of sleeve 326 and annular ledge 33| in the bore 3 positions the sleeve 325 accurately in the bore 3 and within the sleeve 320 so as to line up the slits 32| and 323 in appropriate registering relation,

A packing 333 is provided in front of the annular flange 336 to prevent escape of fluid and the packing is held in place by the threaded tubular plug 335.

The compression of spring "I may be regulated to regulate the pressure required to open valve 3 by rotating the handle |3|a mounted on the shaft 363. Shaft 36!! carries an enlarged extension "I having a helical groove 362 therein which receives a re-entrant extension 363 of the nut 334. The front end of compression spring 35| bears against the nut 364. Nut 364 has a pair of opposite extensions 365 engaging in opposite longitudinal slots 366 in the sleeve 325 so that the nut ma only move longitudinally with respect to the sleeve 326 but may not rotate with respect thereto.

Accordingly, rotation of handle l3 |a will rotate shaft 360 to rotate the extension 36L By reason of the registration of the re-entrant flange 363 of nut 364 in the helix 362 of extension 36L the nut 364 will be moved toward or away from the front of the time delay device in accordance with the direction of rotation and thus will vary the compression of spring 35| to vary the pressure required to open the valve 3.

A transverse wall 310 is provided within the rotatable tube 325 between the extension 36| of shaft 366 and the front of the time delay device, the shaft 356 passing through an appropriate opening in the transverse wall 310. A compression spring 312 at its rear end bears against the front surface of the transverse wall 310 and at its front end bears against the washer 315 which in turn bears against the handle |3|a of shaft 360, and thus creates sufllcient pressure on the handle member |3| a to prevent any vibration or jarring from changing the setting of handle |3|a or the position of nut 364 (which would thereby change the setting of valve 34 I) The gasket 333 is provided around the shaft 366 against the rear surface of the transverse wall 310 to prevent leakage of fluid from the interior'of tube 325 out through the opening in the transverse wall 310 through which the shaft 360 passes. It will now be clear that in order to change the valve setting, it will be necessary only to rotate the handle |3|a. This will operate the nut 364 to change the compression of spring 35| and change the pressure on valve 3 so that it will open under a selected pressure thereon.

The rate of flow from lower chamber 22| to upper chamber 222 through the valve 34| is regulated by rotating the calibrating disc |30a to rotate the entire tube 325 to vary the degree of registration of slits 32| and 326 with respect to each other. It will be clear, however, from an inspection of Figure that changing the rate of flow will not affect the setting of the valve 34| since the setting of valve 3 is controlled by the position of nut 364 with respect to the tube 325 and nut 364 does not rotate with respect to tube 325, but the entire assembly is rotated when tube 325 is rotated.

Similarly rotation of the handle I3 I a to change the setting of the valve 34! will not affect the setting for rate of flow through the passage since such variation in the compression of the slinging 3" is obtained without rotating, the tube Accordingly, the passage width and the pressure required to open the valve may be set independently of each other.

The entire arrangement of valve structure and passage width regulating structure is duplicated in the bore 3|2. In actual use, however, the settings for valve pressure and passage width in bore 3 I2 will be diiferent.

In the device in use, (1) the valve structure located in the bore 3 will have the lowest pressure setting and the smallest channel width as determined by the compression of spring 36! for the former and registration of slits MI and 326 for the latter; (2) the valve structure housed in the bore 3|2 will have its spring "I set for greater valve pressure and the slits 32| and 326 will be in greater radial registration to provide a larger passage for a larger rate of flow for the fluid; (3) the valve which is formed by flange 243 of Figure 11 will have the strongest compression spring 253 and the passage between tube 26| and the sides of the opening 260 will be larger in cross-section than that determined by registration of slits 32| and 326 for the other two valve structures.

Accordingly, (l) the valve structure in bore 3| I will have the function and operation previously described for valve 4| in passage 3| of the schematic structure of Figure 4; (2) the valve structure in bore 3| 2 will have the operation previously described in connection with the valve 42 in passage 32 of the schematic device of Figure 4; and (3) the valve 243 and the passage between tube 26| and the sides of opening 260 will have the operation previously described for valve 43 in passage 33 of the schematic device of Figure 4;

0n the occurrence of an overload of say, 2 to 10 times normal, the valve 3 in bore 3 will be opened but the passage width as determined by registration of slits MI and 326 will be so small as to require an extended interval of time before suflicient fluid can flow from the lower chamber 22| to the upper chamber 222 to permit a tripping of the circuit breaker. At 2 times overload it is obvious from Figure 2 that the tripping operation would take seconds while at 10 times overload the tripping operation will take about 7 seconds.

When a heavy overload less than short circuit 'or less than the maximum capacity of the circuit breaker is reached, then the upward pressure on the diaphragm I It! will be sufficient to actuate and open the valve in bore 3|2. The setting of slits 32| and 326 in this bore is such that a larger passage is provided for the flow of fluid from the lower to the upper chamber and accordingly the time delay interval will be less.

en the maximum capacity of the circuit breaker is reached or a short circuit current occurs, then valve 243 will be opened and the passage with this valve open is so large that a substantially instantaneous transfer of fluid from the lower chamber 22| to the uper chamber 222 will occur to permit substantially instantaneous upward movement of the diaphragm I I8 and substantially instantaneous tripping of the circuit breaker.

In the foregoing I have described my novel time delay device in connection with the sequential circuit breaker tripping operations which it is adapted to achieve. When the circuit breaker closest to the fault has suflicient capacity and speed to clear that fault, the next circuit breaker in sequence toward the line will be permitted to continue in operation without being itself tripped. This sequential operation is achieved by so regulating the time intervals of the successive circuit breakers in the sequence that the circuit breaker nearest the particular fault will respond more quickly to that fault than other circuit breakers in sequence between that circuit breaker and the last.

My invention provides a novel, quick-acting, accurate and definite means for providing sequential tripping operations in circuit breakers arranged in sequence (as in a cascade system) so that only those circuit breakers which are actually necessary to clear a particular fault will be tripped while the remainder of the system will continue in operation.

I have descibed my invention schematically and also in connection with a specific practical embodiment thereof. It is obvious, however, that many variations and modifications of my invention will now be clear to those skilled in the art. I prefer, therefore, to be bound not by the specific description herein but only by the appended claims.

I claim:

1. In a circuit breaker having a pair of cooperable contacts, tripping mechanism therefor and time delay mechanism includin a dashpot having an upper and a lower chamber, an armature responsive to current conditions in the circuit to be controlled, means for permitting instantaneous operation of said armature in response to a predetermined short circuit condition in the circuit being protected by said circuit breaker, means controlled by said armature for variably compressing said fluid in the lower chamber, in accordance with the current conditions in the circuit to be controlled, a plurality of passageways between said chambers, each of a cross-sectional dimension different than the other, valves in each passage, each having springs of individual strengths holding said passageways closed, each of said valves being responsive to predetermined fluid pressure to open its associated passageway.

2. In a circuit breaker having a pair of cooperable contacts, trippin mechanism therefor and time delay mechanism including a dashpot having an upper and a lower chamber, an armature responsive to current conditions in the circuit to be controlled, means for permitting instantaneous operation of said armature in response to a predetermined short circuit condition in the circuit being protected by said circuit breaker, means controlled by said armature for variably compressing said fluid in the lower chamber, in accordance with the current conditions in the circuit to be controlled, a plurality of passageways between said chambers, each of a cross-sectional dimension different than the other, valves in each passage, each having springs of individual strengths holding said passageways closed, each of said valves being responsive to predetermined fluid pressure to open its associated passageway, said armature being operative after a predetermined movement thereof for effecting a tripping operation of said tripping mechanism.

3. In a circuit breaker having a pair of cooperable contacts, a trip mechanism therefor and a time delay mechanism including a dash pot having a first chamber and a second chamber containing a fluid therein, an electro-magnet irrcluding an armature operable responsive to current conditions in the circuit to be controlled to engage and operate said trip mechanism, means controlled by said armature for applying variable pressure to said fluid in the second chamber in accordance with the current conditions in the circuit to be controlled, a plurality of passageways between said first and second chambers, each passageway having a cross sectional dimension different than the other, a valve in the larger of said passageways, a valve seat therefor having an open and a closed seated position, biasing means for normally maintaining said valve on said seat, said armature operating in response to predetermined overload current energization of said electro-magnet to force the fluid from said second to said first chamber through the smaller of said passageways to permit long time delayed movement of said armature mechanism to engage and operate said trip mechanism and said 7 armature operating in response to fault current said biasing means and forcin the fluid from said second to said first chambers through the larger of said passageways to permit short time delayed movement of said armature mechanism to engage and operate said trip mechanism.

OTTO JENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 885,446 Crocker Apr. 21, 1908 959,073 Richardson May 24, 1910 1,154,359 Basch Sept. 21, 1915 1,288,500 Burnham Dec. 24, 1918 2,029,137 Stevens Jan. 28, 1936 2,350,938 Sparrow June 6, 1944 2,414,305 Hurlburt Jan. 14, 1947

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