US2573458A - Fuseless circuit opening device - Google Patents

Description

1951 G. F. LINCKS ET AL 2,573,458

FUSELESS CIRCUIT OPENING DEVICE Filed July 18, 1947 1 :13.2. 32 ig.

Inventors Geore FLincKa; i x 63 63 si n R.Smith,Jr

b M W W y Their Airborne) Patented Oct. 30, 1951 UNITED STATES PATENT OFFICE 2,578,458 FUSELESS CIRCUIT OPENING DEVICE George F. Lincks field, Mass.,

and Sidney a. Smith, assignors to General Electric Com- Jr., Pittapany, a corporation of New York Application J nly 18, 1947, Serial No. 761,893 9 Claims. (01. 200-108) tus from the distribution system, more particularly transformers, and preferably those provided with overcurrent protective devices located in the secondary circuit.

In such distribution systems when a permanent heavy current fault or a short circuit occurs in a transformer or other apparatus, it is desirable to isolate that particular device from the system and permit service on the unaffected circuit to be continued. Heretofore, both fuses and automatic opening devices have been installed at transformer installations to serve this purpose. However, a fuse must be chosen with the proper time-current characteristic for coordination with the reclosing circuit interrupter and is liable to cause circuit interruption in the Ease of temporary lightning surges on the line. A fuse must also be replaced after it blows which economically involves the cost of a new fuse and some additional labor time required for actual replacement after each blowing over that required to close a switch and introduces a chance of error in installing the correct rating of fuse. On the other hand, the coordination between reclosing circuit interrupters and automatic opening devices is on the basis of mechanical operation not involving time-current characteristics and the automatic opening device is entirely free from causing circuit interruptions due to lightning surges on the line.

Obviously, the general substitution of such automatic opening devices for fuses in all circuits to transformers would be desirable and advantageous. Nevertheless, the higher initial cost of all such devices compared with the relatively low cost fuse has heretofore precluded such general substitution.

It is therefore an object of our invention to provide a new and improved circuit opening device which is so simple in construction compared with prior art devices that its initial cost will closely approach that of the conventional fuse.

It is another object of our invention to provide a circuit opening device in which a fault current both conditions the device for operation and also holds the contacts in engagement as long as the fault current exists in the circuit.

It is still another object of our invention to provide a circuit opening device which will be conditioned for operation by a fault current but whose contacts will be held in engagement until after the fault current has been interrupted by fuseless circuit opening device and more paranother device connected in series relationship therewith.

It is a further object of our invention to provide a new and improved fuseless circuit opening device which is simple and compact and which may be used in connection with the prior art holders for fuse cutouts.

In accordance with our invention we provide an improved circuit opening device in which the circuit completing contacts are normally held in engagement by a latching means which is released under surge conditions by a current responsive means which then holds the contacts in engagement as long as the surge conditions exist but subsequently permits the contacts after the surge interrupted by another device in the circuit.

Our invention will be better understood from the following description when taken in connection with the accompanying drawing and'the scope of our invention will be pointed out in the appended claims. In the drawing, Figure 1 is a schematic diagram illustrating a small section oi a distribution system employing the fuseless circuit opening device of our invention; Figure 2 is a side view partly in section of our improved circuit opening device in the normal closed circuit position; Figure 3 is a front view of Figure 1 with the cover or door partly broken away; Figure 4 is a sectional view similar to Figure 2 still in the closed circuit position but after a fault current has caused the device to be conditioned for opening; Figure 5 is a side sectional view of our device following its initial opening movement after the interruption of the fault by another device in the distribution circuit; Figure 6 is a partial side sectional view in the completed open position; Figure '7 is a detail view in perspective of the element which, when released, conditions our device for opening, and Figure 8 is a partial side view of our device illustrating a modification thereof.

Referring now to Fig. 2 of the drawing, we have illustrated our invention in connection with a housing In or porcelain or similar insulating material of the size and shape used in connection with the fuse cutouts of the prior art, such as is disclosed, for example, in United States Letters Patent 2,081,813 assigned to the same assignee as the present application. Housing l0 provided with an integrally formed electric creepage and gas barrier ll disposed between stationary line terminal contacts l2 and I3 carried by the housing. To the rear of the housing or casing It is secured a mounting bar H for the attachment of the casing to an electric line pole and cross-arm structure or the like. Conductors which are brought into the housing through holes in the housing side wall opposite each of the terminal contacts are adapted to be connected disengagement of current has been may be to contacts l2 and I3 by means of binding screws |5and |6, respectively. Upper contact i2 has a contact finger I! backed up by means of a spring strip l8 which serves to press the finger l'l downwardly and has also a pair of spaced resilient contact latching fingers l9, only one of which can be seen in the drawings.

A movable door or cover 20 preferably constructed of insulating material is provided for housing l0 and suitably supports a contact support tube 2| and our circuit opening elements to be described hereinafter and generally indicated by the numeral 22. Door support bracket 23 is formed by bending a metallic bar of conducting material at two points equidistant from the midpoint of its predetermined length to form, in plan, an open sided isosceles trapezoid the open side of which is closed by welding or otherwise suitably fixing the two free ends of the trapezoid to a metallic circular cylindrical tube having a length equal to the width of the bars as shown in the drawing and an inside diameter slightly larger than the outside diameter of the contact support tube. This bracket is rigidly fixed to the door by means of screws 24. Contact support tube 2| is of insulating material and is mounted on the cover adjacent its upper end by means of projection 25 of insulating material formed integrally with the cover and provided with an opening for accommodating the tube. The tube is supported adjacent its lower end by insertion into the cylindrical part of the door support bracket and is rigidly held therein by pivot pin 26 which engages an opening in the cylinder and passes through a groove in the wall of the tube perpendicular to its axis.

A metal lever 21 of conducting material supports cover 20 and is bifurcated at its upper end to form a fork, only one arm of which is visible in the drawing. The arms of the fork are pivotally connected to the cylindrical part of the door support bracket by means of pin 26. Lever 27 is provided at its lower end with a hook 28 which passes over a pivotal pin 29 secured in housing ill. Lever 21, prior to the final open circuit position, is electrically connected to the lower contact terminal |3 by means of a contact finger 30 which is pivotally connected between the forks of lever 21 at 3|. Contact finger 30 is biased in a clockwise direction to provide the desired contact pressure and also to urge cover 20 and its connected parts to the open position.

Contact cap 32 is threadedly mounted on the upper end of contact support tube 2| and when the door is closed as shown in Figures 2 and 4, this cap passes between the resilient contact latching fingers I9 and engages contact finger I1,

all of which are connected to upper contact terminal l2.

The circuit opening elements of our circuit opening device, indicated generally as 22, consists of an electromagnet 33 mounted on its frame 34 which is in turn rigidly mounted on cover 20 by means of screws 35, an armature 36, a latch 31 and an arm or second latch 38 rigidly fixed to and projecting from hooked-shaped lever 21. One end of the electro-m-agnet winding is electrically connected by flexible conductor 39 to cover support bracket 23 while the other end of the winding is connected to contact cap 32 by flexible conductor 40 which passes up through the contact support tube 2| and is electrically connected by solder or other suitable means to a button head. The button head, of the type conventionally used for fuse links, is fixed in good coli- 30. To assure the best conduction between coversupport bracket 23 and contact finger 38 these two elements may be interconnected by flexible conductor 4| shown in Fig. 5.

From the description thus far and an inspection of the drawing, it is obvious that the device as a whole, exclusive of the housing, is pivotally mounted on pin 29 and constitutes a toggle mechanism one arm of which consists of hookedshaped lever 27 and the other arm consists of cover support bracket 23, door 20 and the various elements hereinbefore described and mounted thereon. These two arms are interconnected at the knee of the toggle by the pin 26. When in the condition shown by Fig. 2, the toggle mechanism is in rigid position with movable contact cap 32 and contact finger 30 in electrical engagement with terminals l2 and I3, respectively. These contacts are held in engagement and the toggle maintained in rigid position by the engagement of a projection 42 on latch 31 with an aperture 43 in the projecting arm or latch 38 of hooked-shaped lever 21 as better illustrated by Fig. 7. Latch 37 is pivotally mounted at 44 on the frame 34 of the electro-magnet and is biased by spring 65 in a counterclockwise direction as viewed in Fig. 7. However, the biasing actions of contact IT on contact cap 32 and contact finger 36 urge projecting arm 38 in a counterclockwise direction, as viewed inFig. 2, about pivot pin 29 to maintain the latch 3'? and second latch or projecting arm 38 in engagement. The winding of our electro-magnet is wound on a spool the inside diameter of which is suficient to accommodate armature 36 for axial movement therein. Armature 36 is prevented from falling by gravity out of the magnet by the engagement of a suitable screw or pin 66 thereon with the magnet frame as better illustrated in Fig. 3 and is provided at the opposite end with an enlarged head 47: containing a ledge or lip 58, thereon.

Referring now to Fig. l, we have schematically illustrated in a one line diagram a distribution system comprising a substation 6|] supplying a plurality of branch distribution transformers 63 through a conventional automatic reclosing circuit breaker or a multi-shot fuse cutout 6| located in the main circuit near the substation and our opening device 62 located in each lead connection, before each transformer, to the main line. Fuse or breaker 64 is connected in the lines at the secondary terminals of transformers 63 to protect each transformer from faults on the secondary lines. Under normal current conditions, the door 20, the tube 2| and the circuit opening elements which are pivotally mounted on pin 29 for movement into and out of electrical conducting relation with terminals l2 and I3 will be held so the contact cap 32 is in contact with terminal contact I! and thus with terminal I 2 by the engagement of latch 31 with latch or projecting arm 38 and armature 36 will be in the lowermost position of its travel as indicated in Fig. 2. Upon the occurrence of a fault above a predetermined value in one of the transformers, the electromagnet in Qur circuit opening device 62 located in the lead connecting that transformer to the line will be sufilciently energized to attract armature 36 to the uppermost position of its travel as illustrated in Fig. 4. Since the free end of projecting arm 38 is positioned so as to be in the path of the upward travel of the lip or ledge 48 on the head 41 of the armature, the ledge will engage this end of the arm and raise it sufliciently to disengage the aperture 43 in the arm from projection 42 thereby releasing latch 31 for counterclockwise movement under biasing action of spring 45. Actually, the upward movement of arm 38 is a slight clockwise motion of the arm and toggle 21 about the hinge pin 29 which at the same time results in and is permitted by a slight additional upward movement of the entire cover assembly. The counterclockwise travel of latch 31 is limited by a screw or pin 49 mounted on the magnet frame and passing through a slot 50 in the latch as viewed best in Fig. 7. The relationship between this pin and slot is such that in its extreme released position the projec tion 42 on the latch is completely out from under the arm 38, as better shown by broken outline in Fig. 3, so that downward or counterclockwise motion of the arm about pin 29 will no longer be prevented by latch 37. However, upon the occurrence of a fault having sufficient current value to attract armature 36 to the position illustrated in Fig. 4 so as to trip latch 31, the toggle mechanism is nevertheless prevented from collapse and the contacts held in engagement, not by latch 31, but by the lip or ledge 48 on the head 47 of the armature continuing to engage the arm 38 as long as the fault current continues. The fault current which causes the attraction of the armature in our circuit opening device also, however, causes operation of automatic reclosing circuit breaker Bl which temporarily interrupts the circuit whereupon our electro-magnet is deenergized sufficiently to allow downward movement of armature 36, the freeing of projecting arm 38 for counterclockwise movement about pin 29 and collapse of the toggle mechanism as illustrated in Fig. 5 and finally disengagement of the contacts and opening of the door as illus trated in Fig. 6. Inasmuch as the fault in the transformer will thus be isolated by our circuit opening device during the momentary period breaker 6! is open, service will be restored on the remainder of the circuit following the next reclosin of the automatic recloser BI. It is to be noted that since the eventual opening of our device is contingent upon the interruption of a fault current by another device between it and the supply, interrupt any current. As a consequence, our device can be produced at a relatively low cost since the various elements therein need only to be designed to carry current, and no interrupting means need be provided. Obviously, our device will cooperate equally as well with a multishot fuse cutout as with an automatic recloser.

Following the removal of a fault in a transformer, the linesman need replace no parts in the device, and thus has no choice of a rating such as he would have in replacing a blown fuse link in a fuse cutout. All that is necessary to renew service to the transformer is to re-engage latch 31 with arm 38 and re-engage the contacts by pivoting door 20- and its associated parts about pin 29 to the closed position.

In addition to the engagement of latch 31 with projecting arm 38, the contacts are held in engagement and the door 20 is maintained closed,

our device is never called upon to during normal circuit conditions, by the engagement of the contact cap 32 with the pair of latching fingers l9.

Since some faults are not permanent but temporary in nature, it would be desirable to provide a circuit opening or sectionalizing'device incorporating our invention but which would not be conditioned for operation until such time as the recloser had opened and reclosed a suilicient number of times to indicate that the fault was relatively permanent in nature. Accordingly, in Fig. 8 we have illustrated a modification of our invention comprising a cylinder 5| mounted between the arms of cover bracket 23 on the frame of the electro-magnet and a piston 52 with piston rod 53 attached to the armature 36 by pin or screw 54. So as not to impair quick downward motion of armature 3B, piston 52 is provided with a. check or flapper valve 58 therein. In the head of the cylinder we have provided a small opening 55 and an adjustment 56 to vary the area of the opening. It should be recognized that the type of time delay mechanism described is only one of several types that might be adapted quite readily to our device, such as, for example, a flywheel retarding the upward thrust, a spring, or a gear train with escapement elements. This modification of our device is especially adapted for cooperation with prior art reclosers which, upon the occurrence of a fault, operates one or more times in quick succession to interrupt the circuit and then interrupts the circuit after a relatively longer time delay. When utilized in connection with such reclosers, the fault current above a predetermined value would attract our armature but its upward travel would be retarded or de layed by the piston which must remove practically all of the air from the cylinder through the relatively small opening 55 before the armature can reach a point sufliciently high to release latch 31. By properly adjusting the area of opening 55, this modification of our device can be delayed, following the occurrence of a fault, so that latch 31 will never be released before the quick or instantaneous interruptions of the recloser but the time involved between the delayed interruption and the prior closure of the recloser will be suflicient to permit the armature to release latch 31. Hence, upon the occurrence of the time delayed interruption of a recloser or the like, our armature will have been moved sufliciently' to condition our device so that the deenergization of our electro-magnet by the interruption will permit dropping of the armature and disengagement of the contacts as hereinbefore described.

The dropping of the armature will, of course, be

relatively rapid since flapper valve 58 will open on the downward stroke to allow escape of air trapped under the piston into the space above the piston. It will be apparent that this modification of our opening device may be used in cooperation with any type of interrupter so long as there is one or more interruptions of the circuit by the interrupter which are relatively fast with respect to a succeeding operation concerning which our device has been adjusted for coordination. In fact, the interrupter need operate after only one such delayed interruption without any relatively instantaneous interruption prior thereto. In this connection, our device will work equally as well with a multi-shot fuse device having the first fuse link or links to blow of lower rating or size than the last link to blow so as to provide the dual time-current characteristics hereinbefore described and to which our opener has been adjusted to cooperate. Itis to be understood, however, that the use of our circuit opening device in combination with the aforementioned prior art reclosers is not a part of our invention inasmuch as such combination in a distribution system is described and claimed in the copending application, Serial. No. 761,894 of Lincks filed July 18, 1947, and assigned to the same assignee as the present application.

While we have, in accordance with the patent statutes, shown and described a particular embodiment of our invention and a modification thereof mounted on a cover for use with prior art fuse cutout housings, we d not desire our invention to be limited to the construction shown and described for it will, of course, be evident to those skilled in the art that changes and modifications may be made without departing from our invention. For example, any electro-responsive means other than a magnet and various arrangements of latches and levers may be utilized. Moreover, these elements may be mounted for use with prior art open type fuse cutout supports as well as with prior art enclosing fuse housings. We, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope 'of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A circuit opening device comprising a stationary support. a contact mounted on said stationary support, a movable support, a contact mounted on said movable support and movable therewith. means engageable with said movable support to hold said contacts in engagement, a single magnetically actuated armature sep- 4 arate from said engageable means operable in ing one of said contacts out of engagement with the other when said armature is no longer efiective to hold said contacts in engagement.

2. A circuit opening device comprising a pair of cooperating contacts, one of said contacts being mounted on a stationary support and the other of said contacts being mounted on a movable support and movable therewith, means biasing one of said contacts out of engagement with the other contact, a mechanical latch releasably engageable with said movable support to hold said contacts in engagement against the bias of said biasing means, and a single magnetically actuated armature separate from said latch operable in response to and upon the occurrence of a current operating contacts one of said contacts being stationary and mounted on said insulator and the other of said contacts being mounted on said support and movable therewith, said contacts being in engagement when said toggle is in rigid position, means biasing said toggle to a collapsed position and said contacts out of engagement, latching means engageable with said hook member for maintaining said toggle in rigid condition and the contacts in the closed circuit position against said bias, holding means for maintaining said support unmovable and said contacts in engagement when said toggle is in rigid position, an electro-magnet having a winding connected in series relation with said contacts, an armature for said electro-magnet operative to the attracted position upon the occurrence of a current through the winding above a predetermined value to disengage said latching means from said hook member and thereafter hold the contacts in engagement as long as the current through the winding exceeds a predetermined value but subsequently operative to the unattracted position to permit collapse of the toggle and disengagement of the contacts as soon as the current through the winding falls below a. predetermined value.

4. In a circuit opening device, a supporting insulator, a toggle mechanism comprising a hook member pivotally mounted on said insulator and a movablesupport pivotally mounted on said hook member, a pair of relatively movable cooperating contacts, one of said contacts being stationary and mounted on said insulator and the other of said contacts being mounted on said support and movable therewith, said contacts being in engagement when said toggle is in rigid position, means biasing'said toggle to a collapsed position and said contacts out of engagement, latching means for normally maintaining said toggle in the rigid position and the contacts in the closed circuit position against said bias comprising a projecting arm on said hook member and a latch engageable therewith but biased to the releasing position, holding means on said latch engaging said projecting arm on said hook member for restraining the latch in latching position against the bias thereon, said holding means being releasable-by movement of said projecting arm, an electro-magnet mounted on said support having a winding connected in series relation with said contacts, an armature for said electromagnet operative to the attracted position upon the occurrence of a current-through the winding above a predetermined value to move said projecting arm and release said latch and to thereafter hold the toggle mechanism rigid and the contacts in engagement as long as the current through the winding exceeds a predetermined value but operative to the unattracted position to permit collapse of the toggle mechanism, movement of the support and disengagement of the contacts as soon as the current through the wind-.

ing falls below a predetermined value.

5. In a circuit opening device, an insulating housing, a toggle mechanism comprising a hook member pivotally mounted in said housing and a movable cover for closing an open side of said housing pivotally mounted on said hook member, a pair of relatively movable cooperating contacts, one of said contacts being stationary and mounted within said housing and the other of said contacts being mounted on saidcover and movable therewith, said contacts being in engagement when said toggle is in rigid position, means biasing said toggle to a collapsed position and contacts out of engagement, latching means for normally maintaining said toggle in the rigid position and the contacts in the closed circuit position against said bias comprising a projecting arm on said hook member and a latch engageable therewith but biased to the releasing position, a projection on said latch engaging the arm on said hook member for restraining the latch in latching position against the bias thereon, said projection being releasable by movement of said projecting arm, holding means for maintaining said cover closed and said contacts in engagement when said toggle is latched in rigid position, an electro-magnet mounted on said cover having a winding connected in series relation with said contacts, and an armature for said electro-magnet engageable with said projecting arm, said armature operative to the attracted position upon the occurrence of a current through the winding above a predetermined value to engage and to move said projecting arm and to remain in engagement therewith to maintain said toggle mechanism rigid and said contacts in the closed circuit position as long as the current exceeds said predetermined value and upon decrease in the current and movement to the unattracted position to permit collapse of the toggle whereby to eiiect disengagement of the contacts.

6. A circuit opening device comprising a pair or cooperating separable contacts, one of said contacts being mounted on a movable support and movable therewith, an arm movable away from one position to a second position to initiate separation of said contacts and movable to a third position to maintain said contacts in engagement, means biasing said arm to said second position, a latch engageable with said arm when in said one position to hold said contacts in engagement and releasable from said arm when in said third position, a single magnetically actuated armature separate from, independent of and directly engageable with said arm and operable in response to and upon the occurrence of a. current through said contacts exceeding a predetermined value to move said arm to said third position to release said latch and thereafter to hold by direct engagement with said arm said contacts in engagement until the current therethrough subsequently decreases below a predetermined value.

7. A circuit opening device comprising a pair of cooperating separable contacts, one of said contacts being mounted on a movable support and movable therewith, an arm movable away from one position to a second position to initiate separation of said contacts and movable to a third position to maintain said contacts in engagement, means biasing said arm to said second position, a latch engageable with said arm when in said one position to hold said contacts in engagement and releasable from said arm when in said third position, an electro-magnet having a winding connected in series relation with said contacts. a single armature for said electro-magnet separate from, independent of, and directly engageable with said arm and operable in response to thecurrent through said contacts exceeding a predetermined value to move said arm to said third position to release said latch and thereafter to hold by direct engagement with said arm said contacts in engagement until the current theremined 8. A circuit opening device comprising a pair of separable contacts, an arm movable away from one position to a second position to initiate separation of said contacts and movable to a third position to maintain said contacts in engagement, means biasing said arm to said second position, a latch engageable with said arm when in said one position to hold said contacts in engagement and releasable from said arm when in said third position, a single magnetically actuated armature separate from, independent of and directly engageable with said arm and operable upon the occurrence of a current impulse through said contacts exceeding a predetermined value to first move said arm from said one position to said third position to release said latch and then to hold by direct engagement with said arm said contacts in engagement until the current therethrough subsequently decreases below a predetermined value, time delay means operable to delay said current operable means from moving said arm to said third position until said current impulse continues above said predetermined value for a predetermined time.

9. In a circuit opening device, a supporting insulator, a first and second contact mounted on said supporting insulator adjacent opposite ends thereof, a bridging means movable into and out of engagement so as to electrically interconnect said first and second contacts, an arm movable away from one position to a second position to initiate disengagement of said bridging means from at least one of said contacts and movable to a third position to maintain engagement of said bridging means with said contacts, means biasing said arm to said second position, a latch engageable with said arm when in said one position to hold said bridging means in the contact engageable position and releasable from said arm when in said third position, a single magnetically actuated armature separate from, independent of and directly engageable with said arm and operable to move said arm to said third position to release said latch upon the occurrence of a current through said current responsive means above a predetermined value and thereafter to restrain movement by direct engagement with said arm of said bridging means out of the contact engageable position as long as the current through said current responsive means is above a predetermined value.

GEORGE F. HNCKS. SIDNEY R. BMITH, Jn.

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

UNITED STATES PATENTS 60 Number Name Date 835,025 Jackson Nov. 8, 1906 1,330,094 Simon Feb. 10, 1920 2,081,813 Hermann May 25, 1937 2,081,826 Lincks May 25, 1937 as 2,253,400 shoemaker et a1. Aug. 19, 1941 2,387,372 Watkins et al. Oct. 23, 1945 2,523,984 Edwards Sept. 26, 1950 FOREIGN PATENTS Number Country Date Great Britain Nov. 5, 1931 through subsequently decreases below a predetervalue.

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