US3414695A - Multi-break interrupter assembly - Google Patents

Description

5 Shets-Sheet l INVENTOKS J. R. MCCLOUD ET Al- MULTI-BREAK INTERRUPTER ASSEMBLY 17o w20 wam w Dec. 3, 196s J, R, MCCLOLJD ET AL 3,414,695

MULT I BREAK INTERRUPTER AS SEMBLY Filed June- 2?, 1965 5 Sheets-Sheet 3 df/vf a. mma/mezz Dec. s, 196s J,R,MC1 OU ET AL 3,414,695

MULTI-BREAK INTERRUPTER ASSEMBLY Filed June 21, 1965 v 5 sheets-,sheet 4 Dec. 3, 1968 J. R. MCCLOUD ET AL MULTI-BREAK INTERRUPTER ASSEMBLY 5 Sheets-Sheet 5 Filed lJune 2B, 1965 United States Patent O MULTI-BREAK INTERRUPTER ASSEMBLY James R. McCloud, Burbank, and Lorne D. McConnell, Sierra Madre, Calif., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed June 21, 1965, Ser. No. 465,530 8 Claims. (Cl. 200-150) ABSTRACT OF THE DISCLOSURE An oil circuit breaker interrupter structure having two series-connected breaks and a series disconnect where the interrupter structure carries axially-spaced fixed contacts which each consist of two pluralities of contact segments which are biased toward contact with respective elongated movable contacts. The movable contacts are carried on the rungs of a movable ladder which terminates in a disconnect contact segment. Interrupter plates within the interrupter chamber enclose the contact breaks formed between the stationary contacts and their cooperating movable contact. A movable disconnect contact carried on the end of a cross bar engages the disconnect contact on the bottom of the movable ladder and moves the ladder upward against the force of biasing springs to close the ladder contacts.

This invention relates to oil circuit breakers, and more specically relates to a novel multiple-break circuit interrupter.

In particular, the novel circuit intrrupter of the present invention provides two interrupter plate assemblies spaced from one another which vent in opposite directions frorn one another.

The present invention provides a novel support and alignment structure for these interrupter plate assemblies to permit easy 'access thereto for maintenance and inspection.

In a preferred embodiment of the invention, two interrupting sets of contacts are connected in series with a disconnect set of contacts. The interrupting contacts include an upper contact assembly and a central contact assembly wherein the contact assemblies are supported and aligned in a novel and simplified manner.

Moreover, `and in accordance with the invention, a ladder-type movable contact assembly is provided which is supported and guided in a novel manner, and is biased toward an open position by a novel spring arrangement.

Another novel feature of t-he present invention involves the construction of the piston whereby a piston which provides pressure during interruption conditions is prevented from being forced backwardly, thus preventing the formation of a low pressure area within the interrupter chamber during interruption conditions.

More particularly, a novel check valve arrangement is provided which forces at least equalization of pressure on, both sides of the piston during high pressure conditions lwithin the interrupter tube, while still permitting the easy closing of the contacts which moves the piston upwardly during non-arcing conditions.

Accordingly, a primary object of this invention is to provide a novel multiple-break interrupter assembly.

Another object of this invention is to simplify the support and alignment of the interrupter plate assemblies of a multiple-break interrupter assembly.

A further object of this invention is to simplify the support and alignment of the center contact structure of a multiple-break interrupter assembly.

Fpice Yet a further object of this invention is to provide a simple structure for assembling and supporting and guiding the motion of the movable contacts of a multiplebreak interrupter assembly.

A still 4further object of this invention is to provide a novel opening spring assembly for the movable contact bridge of a multi-break interrupter assembly.

Another object of this invention is to provide a novel valve arrangement for a pressure generating piston of an interrupter assembly.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 schematically shows a top view of a circuit breaker illustrating the location of the interrupters in the tank.

FIGURE 2 is a partial cross-sectional view of the interrupter of FIGURE 1 taken across the lines 2 2 in FIGURE 1.

FIGURE 3 is a partial sectional view of the interrupter of FIGURE 1 taken across the lines 3 3 in FIG- URE l.

FIGURE 4 is a bottom view of the adapter casting of FIGURES 2 and 3.

FIGURE 5 is a plan view of the contact bridge for the interrupters of FIGURES 1, 2 and 3.

FIGURE 6 is a top plan view of the bridge of FIG- URE 5. l

FIGURE 7 is a bottom view of the upper contact of FIGURES 2 and 3.

FIGURE 8 shows an exploded perspective view of a contact housing and its respective pressure screws and a typical contact.

FIGURE 9 is a schematic cross-sectional view of FIGURE 2 taken across the lines 9 9 in FIGURE 2.

FIGURE l0 is a top plan view of the upper interrupter plate assemblies of FIGURES 2 and 3.

FIGURE 11 is a cross-sectional view of FIGURE 10 taken across lines 11 11 in FIGURE 10.

FIGURE 12 is a front view of the assembly of FIG- URE 10.

FIGURE 13 is a cross-sectional view of FIGURE 2 taken across the lines 13 13 in FIGURE 2.

FIGURE 14 shows -a cross-sectional view of a second embodiment of the invention using a modied piston structure having a check valve arrangement therefor with the novel piston being used in a structure of the type shown in FIGURES 1 and 2, and the piston in its upper or extended position.

FIGURE 15 is similar to FIGURE 14 and illustrates the piston in its contact open and extended position.

FIGURE 1 schematically shows `an oil circuit breaker tank 20 cut away to show series connected interrupter structures 21 and 22 which have respective parallel connected resistors 23 and 24 connected thereto, and are immersed in oil contained by tank 20. An insulation lift rod 25 connected to a suitable operation mechanism then carries conductive cross bars 26 and 27 which are connected to suitable contacts which enter the interrupter structures 21 and 22 in the usual manner. As will be more fully described, interrupters 21 and 22 and their resistors are of identical design and have -a first series of upper venting ports on one side thereof and a second series of lower venting ports on their other side. However, interrupters 21 and 22 are mounted rotated 180 from one another so that the upper ports of interrupter 21 and lower ports of interrupter 22 face the same direction (toward the top of `the drawing in FIGURE l). while the lower ports of interrupter 21 and top ports of interrupter 22 similarly face in the same direction (toward the bottom of the drawing in FIGURE 1).

Referring now to FIGURES 2 and 3 which are different partial cross-sectional drawings of identical units 21 and 22 of FIGURE 2 and, therefore, will be described as drawings of a single unit, the interrupters are supported within the tank of FIGURE 1 by the usual insulator bushings (not shown) which enter the tank and connect to adapter casting 30. Thus, adapter casting 30, which is of a suitable conductive material, serves to both mechanically and electrically connect the interrupter to its bushing.

As shown in FIGURES 2, 3 and 4, the adapter casting has an outer tiange which has a plurality of openings 31 through 36 therein (FIGURE 4) for receiving bolts such as bolts 39, of FIGURE 2 (through openings 33 and 32, respectively, in FIGURE 4), and bolts 41, 42 of FIGURE 3 (through openings 31 and 36, respectively, in FIGURE 4). Adapter casting 30 further has a circular opening 43 therein which acts as a cylinder for piston 44 (FIGURES 2 and 3). The top of the opening 43 then has a threaded opening 45 which receives a guide rod 46 of any suitable material and serves as a guide for the concentric compression springs 47 and 48 which are captured at the closed bottom of piston 44.

Adapter casting 30 is further provided with cavities 49 and 50 (FIGURES 3 and 4) which receive the conductive bridge guide members 51 and 52 of bridge 53 of FIG- URES 5 and 6, as shown for bridge guide section 51 and cavity 49 in FIGURE 3. The bridge guide sections 51 and 52 are hollow, as shown in FIGURES 3 and 6, and receive respective guide bolts such as bolt 54 of FIGURE 3 which is threaded into a suitable tapped opening 55 in cavity 49 (FIGURE 4). A similar tapped opening 56 is formed in cavity 50 in FIGURE 4 for receiving its respective guide bolt. Each guide bolt secured to openings 55 and 56 then receive compression springs such as compression spring 47 in FIGURE 3 which is carried on guide bolt 57 and within bridge guide 51. Thus, the complete contact bridge 53 is biased downward. In a similar manner, the springs 47 and 48 bias piston 44 downward, the piston movement being guided and limited by ring stop 60 which is secured to the bottom of adapter casting 30.

Adapter casting 30 is further provided with through passages 61, 62 (FIGURE 2) and 63 (FIGURE 3) to provide a circulation path for oil, as will be later described. A cast corona shield 64, as best shown in FIG- URES 2 and 3, then has suitable extending bosses such as bosses 65 through 68 (FIGURE 2) which receive bolts such as bolt 69 of FIGURE 2 which are threaded into suitable tapped openings in adapter casting 30.

The next important function of adapter casting 30 is to support the upper stationary contact 70 and interrupter tube 71. Thus, the upper stationary contact 70 has a ange 72 (FIGURES 2, 3, and 7) which has a plurality of openings 73 through 78 therein (FIGURE 7) which receive suitable bolts such as bolt 79, shown in FIGURE 2, which bolt contact 70 to adapter casting 30. A further opening (FIGURE 7) is provided in the upper surface of flange 72 to receive keying pin 81 from the bottom surface of casting 30 to properly align the contact 70 and casting 30. Contact 70 is then provided with two extending legs 82 and 83 which straddle the conductive bridge 84 (FIGURES 2, 3 and 7) of bridge 53 which abuts against the bottom of piston 44, as shown in FIGURE 2. Each of legs 82 and 83 terminate in a bolting flange such as flange 85 for leg 82 (FIGURES 2 and 7) and flange 86 for leg 83 (FIGURE 7).

Each of flanges 85 and 86 then have arcuate contact housings 86a and 87, respectively, bolted thereto as by bolts such as bolts 88, 89 and 90 of FIGURE 2. The arcuate contact housings 86a and 87 threadably receive pressure screws such as pressure screws 91, 92 and 93 for housing 86a and pressure screws 94, 95 and 96 for housing 87. As shown in FIGURES 2 and 8 for pressure screws 91 to 93, they are preferably provided with hex l heads and have threaded shank portions 97, 98 and 99 which are threadably received by threaded openings 100, 101 and 102, respectively, in housing 82. They then have extending guide rod portions 103, 104 and 105, respectively, which extend into respective pressure springs such as springs 196 and 107 for rods 103 and 104, respectively. Each of the pressure springs such as springs 196 and 107 are then carried in insulation cups such as cups 108 and 109, respectively, which prevent the formation of a current path through the springs which would adversely affect the spring characteristics.

Each of the insulation cups are then carried in a respective contact inger of Contact fingers 110, 111 and 112 carried on leg 82 and contact fingers 113, 114 and 115 carried on leg 83 (FIGURES 2, 3, 7 and 8). Note that contact fingers 110 and 112 through 115 are identical to one another while contact finger 111 has an extending arcing portion 116 which serves to position the arc drawn therefrom, as will be described later. Each of the contact fingers are then provided with a conductive jumper such as jumpers 117 and 118 (FIGURES 2 and 3) connected to their respective contact leg 82 or 83 to provide a good electrical connection to the contact body 70.

The contacts 110 through 115, therefore, define a circular cluster of contacts which act to receive the upper end of contact 120 carried on bridge 53 (FIGURES 2, 3 and 5). Contact 120 extends from a conductive cross member 121 which may be cast therewith (FIGURES 2, 3 and 5) which is, in turn, connected to insulation rods 12,2 and 123 at one end and insulation rods 124 and 125 at its other end, as shown in FIGURES 3 and 4. Note that rod sections 51, 122 and 123 define a first solid coaxial rod section while rod sections 52, 124 and 125 define a second coaxial rod section. The insulation rods ' f 122 and 124 serve to insulate bridge 84 and contact 120.

Insulation rods 123 and 125 serve to insulate contact 120 from further contacts 126 and 127 carried on a conductivebridge 128 connected to Ithe ends of rods 123 and as by bolts 129 and 130, respectively (FIGURES 2, 3 and 5).

The adapter casting 30 finally carries the interrupter tube 71 by means of a bolt ring 140. More specifically, tube 71 has an extending head portion 141 which is captured by a suitable tapered surface on the interior of i ringk 140. The bolts such as bolts 39 through 42 which pass through the flange in the adapter casting 30 then extend into ring to connect tube 71 to casting 30. Note that a suitable key 142 (FIGURE 2) extends from ring'l 140l to casting 30 to prelocate these members and to .insure the proper location of upper ports 143 and lower "i ports 144 in tube 71 (FIGURE 2) with respect to the contact 70. Moreover, note that arcing contact finger section 116 is aligned adjacent to upper por-ts 143 as by suitablekeying pins which align the arcing contact finger k with its support assembly.

Al centrally located support contact assembly is then provided which includes a main casing body 151. As best shown in FIGURES 2 and 9, a pair of insulation supports 152 and 153 are secured to casing body 151 by bolts such as bolts 154 and `155 (FIGURE 2) some of which have extending heads extending into openings, such as openings 156 and 157, in the tube 71. The casing 151 also has extending central flange sections 158 and 159 which are carried in suitable slots in supports 152 and 153, as shown in FIGURES 2 and 9. The upper half of casing body 151 then has extending first and second contact holder segments 160 and 161 which respectively carry three contact fingers 162, 163, 164 and 165, 166, 167. Each of contact fingers 162 through 167 are then mounted by a pair of springs and respective pressure screws similar to those shown in FIGURE 8. For example, as shown in FIGURE 2, contact nger 163 carries two springs 170 and 171 in suitable insulation cups, and pressure screws 172 and 173 press the upper and lower portions of contact finger 163 toward high pressure engagement with the lower portion of contact 120 and the upper portion of casing 150, respectively. Note that there will always be only sliding contact between contact ngers 162-167 and contact 120 so that jumpers such as those used for the contact fingers in the upper contact are not needed to provide a current path during possible contact bouncing.

The lower portion of the casing 151 in then provided with opposing sets of contact fingers such as lingers 180, 181 (FIGURE 2) and 182, 183 (FIGURE 3) which are identical in construction and mounting to fingers 110-115 of FIGURE 7. These lower contacts such as contacts 180-183 are engageable by movable contact 126, as shown in FIGURES 2 and 3.

Contact 126 of FIGURES 2, 3 and 5 is integral with contact 127. As best shown in FIGURE 3, the contact 127 is engageable by a cooperating tulip clip type contact 190 which includes biased contact segments such as segments 191 and 192 which are biased toward engagement with contact rod 127 by springs such as springs 193- 194 and 195-196, respectively. The bottom of contact 190 is filled by a threaded plug 197 which carries a conductive rod contact 198 which is threadably received by a slotted conductive cross-bar 199 and clamped by bolts through openings 199a and 19911. Contact 198 also serves as a dashpot during closing operation. Thus, as the crossbar closes, contact rod 127 enters the contact assembly and the oil in the assembly is forced out through the top hole of the shield 190. This provides a cushion action between contacts 127 and 128 before metallic contact is made, and reduces shock on the ladder assembly and lother mechanical parts of the system.

This complete bottom contact assembly is then substantially enclosed by a corona shield 200 which is suitably bolted to a conductive bottom plate 201 as by bolts 202 and 203 of FIGURE 2. Clearly, the shield 200 has a suitable slot therein to accommodate vertical translation of cross bar 199.

From the foregoing description, it will be understood that a current path is formed, when the interrupter is in the closed position shown, which extends from adapter casting 30, extending contact legs 82 and 83, contact fingers 110-115, contact 120, contact fingers 162-167, casting 150, contact fingers such as fingers 180-183, contact rod 126, contact rod 127, tulip contact 190, and cross bar 199. To open the interrupter, -cross-bar 199 is moved downward whereby springs such as compressing spring 57 in b- ridge sections 51 and 52 move the entire bridge 53 of FIGURE 5 downwardly. This causes disconnection betwen contact rod 120 and contact fingers 110 through 115. It also causes disconnection of a series gap between contact rod 126 and contact fingers such as fingers 180 through 184. Moreover, once bridge 53 moves completely down to where the bottom of bridge section 128 engages plate 201 and thereby is stopped, cross-bar 199 continues to move down until contact 190 disconnects from contact rod 127 thereby defining a disconnect gap.

It should be further noted that bridge section 128 has an enlarged rod section 210 which enters depression 211 in plate 201 to provide a dashpot effect in stopping the downward lmovement of bridge 53.

As pointed out above, two series interruptions take place in the current path of the apparatus of FIGURES 2 and 3. Two identical interrupter plate assemblies 220 and 221 are provided to receive the arcs drawn by these gaps and to direct the arc products and oil toward ports 143 and 144, respectively.

The lower plate assembly 221 is held in position between insulation cylinder 230 which'is seated on plate 201 and the bottom of supports 152 and 153, as shown in FIGURES 2 and 3. Note that support 153 has a pair of projecting fingers such as fingers 231 (FIGURE 2) and 231:1 (FIGURE 9) which straddle 'and position assembly 221 so that its venting ports face ports 144, as will be later described.

The upper plate assembly 220 is then held between the top of supports 152 and 153 and the spacing insulation cylinder 232, as shown in FIGURES 2 and 3. FIGURE 2 further shows finger 233 extending from support 153 which aids in connection with a similar finger (not shown) to position assembly 220 with its venting ports facing ports 143, The top of ring 232 is received by the clamping ring 233 which is suitably secured to the interior of tube 71 as by threading. A cork ring 234 is contained in the area betwen ring 233 and the inner diameter of tube 71 to provide a downward compression on all the interior structure and, in effect, hold it in position. This provides means to compensate for the build-up of tolerances used in the various parts of the structure.

Each of plate assemblies 220 and 221 are substantially identical to one another and assembly 220 is typically shown in FIGURES 10, 11 and 12.

Referring to FIGURES 10, 1l and 12, assembly 220 is formed of upper and lower insulation plates 240 and 241, a central spacer plate 242, and two identical arc splitter plates 243 and 244. Upper plate 240l has a keyhole type opening 245 where the extending portion 245a of opening 245 receives the extending arcing contact fingers 116 of the upper contact assembly in FIGURE 2. Note that the lower contact assembly in FIGURE 2 also has an extending arcing contact finger 246 which extends into the portion 245a of the top plate of its respective interrupter plate assembly 221.

Spacer plate 242 then has a circular opening 247 therein which is aligned with opening 245 for receiving contact rod 120. The splitter plates 243 and 244 have openings 248 and 249, respectively, therethrough having the shape shown in dotted lines in FIGURE l0. These openings 248 and 249 define oil pockets 250 and 251, respectively, which communicate with venting channels 252-253 and 254-255, respectively, which are formed between the shaped surfaces of splitter plates 243 and 244 and the adjacent plates 240, 241 and 242. Note that the ends of channels 252, 253, 254 and 255 will be disposed immediately adjacent the respective ports 143a, 143b, 143C and 143d of ports 143 in FIGURE 2.

The assembly of plates is then held together by four pins 260, 261, 262 and 263 which are force fitted or otherwise suitably secured in plates 240 and 241.

The interrupter assembly of FIGURES 1 and 2 is then provided with a resistor assembly 270, as best shown in FIGURES 2 and 3, which is composed of an insulation housing 271 which is terminated by upper and lower conductive castings 272 and 273, respectively, which are shaped to define corona shields. The resistor assembly 270 can be formed in the manner previously disclosed in copending application Serial No. 439,304, filed March 12, 1965, entitled Interrupter Structure Having Contoured Arc Splitter Plates and Separately Housed Resistor Contacts and Resistor Structure Therefor, in the name of Earl B. Rietz et al., and assigned to the assignee of the present application.

As shown best in FIGURE 3, the upper conductive housing 272 is directly bolted to the conductive ring 140 as by bolt 274. Therefore, the resistor 275 is connected in parallel with the gap created between contact rod 120 and the upper contact assembly.

The bottom housing 273 of resistor 270 is bolted directly into the conductive plate or plug 201 as by bolt 2735i. The plug, in turn, as best shown in FIGURE 13, carries a plurality of contacts such as contacts 300, 301, 302 and 303 which surround contact rod 127 and are biased toward engagement with contact rod 127 by respective biasing springs 304, 305, 306 and 307, respectively. It is noted that the separate contacts 300 through 303 and their respective biasing springs are carried in slotted portions in the lower surface of plug 201. They are retained in these slotted positions by a suitable retaining plate, shown as plate 310 in FIGURES 2 and 3, which is secured to plug 201 as by screws such as screws 311 and 312 in FIGURES 2 and 13.

This arrangement of contacts can specifically be of the type generally indicated, or, if desired, can lbe of the type described in copending application Ser. No. 439,304. Whichever type of sliding contact arrangement is used, it will be clear that the bottom of resistor portion 276 is electrically connected to contact rod 127 and thus, contact rod 126. Accordingly, resistor portion 276 will be conected in parallel with the contact gap formed between the central contact asembly in contact rod 126.

Note that after interruption the resistive current iiowing through resistor portions 275 and 276 will be interrupted by disengagement between the bottom of contact rod 127 and the contact assembly 190.

Referring again to FIGURE 13 and FIGURE 3, the figures further show that the upper surface of plate or plug 201 has depressions 320 and 32,1 therein which receive nuts 129 and 130 to further act as a dashpot restraining means along with enlarged section 210 and opening 211 in plate 201.

FIGURES l and 13 illustrate that the bottom plug 201 has a plurality of openings therethrough such as openings 325 and 326. A washer valve 327, best shown in FIGURE 2, is then carried on a bolt 328 which is threaded into plate 201 and secured thereto as by nut 329. The bolt 328 then carries a spring 330 which biases washer 327 upwardly, thus exposing openings 325 and 326. These openings then serve as an oil passage to permit the normal circulation of oil through the interrupter tube. However, under interruption conditions when high pressure is generated Within the tube, the high pressure will drive washer 327 downwardly to close ofr" openings 325 and 326.

As indicated previously, it is possible for the piston 44, shown in FIGURES 2 and 3, during moderate to high current arcs, to be moved upward, due to the internal pressure generated within the interrupter tube. This could permit the formation of a void or low pressure area within the chamber which could allow an arc to wander from its proper location.

The embodiment of FIGURES 14 and l5 provide a modified piston arrangement wherein piston blow-back during interruption of moderate to heavy current arcs is prevented. Notwithstanding this, the piston in FIGURES 14 and 15 can be moved freely in an upward direction during the closing operation, and will still deliver oil into the interrupter with proper pressure and volume during low current arc interruption.

Turning now to FIGURES 14 and 15, we have illustrated therein the piston 44 where, however, the piston 44 has a movable end valve surface section 400. The end section 400 serves as an annular valve which seats upon an annular opening 401 in the bottom of piston 44, and is carried upon a rod 402 which is, for example, threadably secured to a threaded opening passing through member 400. The rod 402 is then received in a central opening 403 of guide rod 404, the outer surface of which serves to guide the spring 47 in the manner of guide rod 54 of FIGURES 2 and 3. Note that the top of opening 403 is plugged by plug 403a to prevent oil from escaping out ofthe interior of casting 30.

The upper conductive casting is then provided with an opening 405 therein which has a check valve 406 connected thereto. The check valve 406 more particularly includes a tubular body 407 which communicates with the opening 405 and has a ball 408 captured therein between insert shoulder 409 and shoulder 410.

A pin 41.1 passing through body 407 then prevents the motion of ball 408 into sealing engagement with shoulder 410 whereby the ball 408 can never move to the left to seal at shoulder 410. When, however, the ball moves to the right it will seal against shoulder 409 to prevent the passage of oil through body 406 from the interior of the device to the exterior of the device.

During opening operation under moderate to high current fault conditions and in a manner identical to that previously described, the spring such as spring 47 which now seats upon the valve member 400, will drive the valve 400 and its piston 44 downwardly from the position of FIGURE 14 to the position of FIGURE 15. This biasing action will force valve 400 against the opening in piston 44, thereby sealing off the normally open channel 412 (FIGURE 14) which exists between valve 400 and piston 44.

At the same time, oil will flow into the region above piston 44 from areas external of the interrupter structure and past ball 408 to ill the volume left by the downward stroke of piston 44. As this action continues, and arcing occurs within the interrupter, the pressure generated by the arc tends to force the piston 44 upward which would decrease the pressure in the interrupter plate assembly. However, this pressure forces valve 400 to form the opening 412 of FIGURE 14, thereby causing the ball 408 to seat into shoulder 409. This causes the pressure on both sides of the piston to be equal, whereupon piston blowback is checked and the pressure inside the interrupter is stabilized.

During closing operation, the valve 400 will be forced upwardly (at this moment ball 408 not being seated against shoulder 409 due to the force of gravity). This permits sufficient oil to escape from the upper side of piston 44 to allow the valve 400 to move upwardly with respect to piston 44, thus vdefining the opening 412 of FIGURE 14. The subsequent upward movement of conductive bridge 84 which initially contacted valve 400 will now pick up piston 44 to carry the piston upwardly. Oil from the upper side of piston 44 will then pass through the open valve structure 406, and as soon as the upper part of piston 44 passes opening 405, the opening 405 is closed.

The operation of the system for low current arc interruption is similar to that described above for high current fault conditions, except that the pressure generated by the arc will not reach a value suicient to retard the travel of piston 44. Therefore, the piston delivers moderate pressure oil into the interrupter during the complete opening stroke.

Although we have described our invention with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and we prefer, therefore, that the scope of the invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An interrupter structure comprising a main conductive casting, a hollow insulation tube having one end thereof secured to one surface of said casting, first and second interrupter plate means secured within said insulation tube and axially spaced from one another along the axis of said insulation tube, first and second stationary contact means positioned within said insulation tube and spaced from one another along the axis of said insulation tube; said lirst stationary contact means secured to said main conductive casting; said second stationary contact means secured to said insulation tube, a ladder-type movable contact movable within said insulation tube along the axis of said insulation tube and comprising first and second elongated spaced side members and first and second transverse conductive members connected between said first and second side members; said first and second transverse conductive members axially spaced from one another along the axis of said insulation tube; said irst and second transverse conductive members movable into and out of electrical engagement with said first and second stationary contact means respectively responsive to axial movement of said ladder-type movable contact within said insulation tube; said main conductive casting having first and second parallel spaced openings formed therein extending parallel to the axis of said insulation tube; said first and second elongated spaced side members having hollow end portions slidably received in said first and second spaced openings in said main casting; said first and second spaced openings closely surrounding said end portions along substantially their entire length, thereby to limit transverse movement of said end portions; and biasing spring means received in said first and second spaced openings and terminating at one end at the respective bottoms of said first and second spaced openings; said biasing springs extending into the said hollow end portions of said side members and terminating at the other ends thereof on the bottom of said hollow end portions respectively.

2. The device substantially as set forth in claim 1 which further includes first and second guide posts; said first and second guide posts connected to said bottoms of said openings in said main conductive casting and extending parallel to the axis of said biasing spring means in each of said openings.

3. The device substantially as set forth in claim 1 which further includes piston means; said main casting having a central opening therein defining a cylinder receiving said piston means and further spring biasing means extending from the bottom of said central opening to the bottom of said piston for biasing said piston downwardly and away from said main conductive casting.

4. The device substantially as set forth in claim 3 which includes a further guide post means extending from said bottom of said central opening and coaxially with said further spring biasing means.

5. The device substantially as set forth in claim 3 which further includes a piston operating cross bar connected between said spaced elongated side members; said cross bar engaging the bottom of said piston and holding said piston in said central opening when said first and second contact means are engaged and permitting the downward movement of said piston when said ladder-type structure is moved downwardly andsaid rst and second contact means are disengaged.

6. The device substantially as set forth in claim 5 wherein said piston includes a separable bottom portion and a wall portion; said separable bottom portion being biased toward sealed engagement with said wall portion by said further biasing means; and a one-way check valve in said cylinder defined in said main casting.

7. The device substantially as set forth in claim 1 wherein at least said first stationary contact means comprises a generally curved support plate having a plurality of threaded openings therethrough, a plurality of contact segments having openings formed therein; a retaining surface means for loosely retaining said contact segments between said curved support plate land said retaining surface means, a plurality of biasing springs, and a plurality of guide screws; each of said plurality of guide screws having a threaded section and an extending section extending beyond said threaded section; each of said guide screws being threaded into a respective opening of said plurality of threaded openings with said extending sections extending beyond the surface of said curved support plate; each of said biasing springs surrounding the said extending section of a respective guide screw and being received in said opening of a respective Contact segment of said plurality of contact segments; said biasing springs biasing their said respective contact segments toward said retaining surface means.

8. The structure substantially as set forth in claim 7 which further includes a plurality of cup means disposed in respective openings in said contact segments for receiving said respective biasing means.

References Cited UNITED STATES PATENTS 1,673,676 6/1928 Hilliard ZOO-150 2,790,880 4/1957 Florschutz et al. 20G-150K 3,284,603 ll/1966 Rietz et al 200-150 FOREIGN PATENTS 422,292 l/ 1935 Great Britain.

ROBERT S. MACON, Primary Examiner.

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