US2648737A - Fuse cutout - Google Patents

Description

Aug. 11, 1953 J. M. WALLACE sf AL 7 I FUSE CUTOUT Filed June 23 Insulation Fig,4.

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INVENTORS James M. Wallace and Andrew W. Edwards Patented Aug. 11, 1953 FUSE CUTOUT James M. Wallace and Andrew W. Edwards, East McKeesport, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 23, 1949, Serial No. 100,788

3 Claims.

This invention relates to electrical protective devices and more particularly to circuit interrupters of the open fuse type for power transmission.

. An object of this invention is the provision of a simple and practical open fuse cutout for an electric power transmission line, the cutout being 1 well suited for conducting the line current in an efiicient manner within load limits and for reliably opening the line upon encountering an overload current.

Another object of this invention is that of providing a strong and efficient open fuse cutout which affords physically stable support for the fuse link thereof and reliably gives a continuous current path, yet promptly and positively opens the current path when current limits are exceeded.

A further object of this invention is the provision of an inexpensive and practical open fuse cutout such as may be installed on power transmission line poles, towers, transformers, or the like.

A still further object of this invention is that of providing an open fuse cutout in which the fuse link thereof is reliably supported in tension and is effectively electrically connected.

' Another object of this invention is the provision of a strong and mechanically simple open fuse cutout which rigidly retains a circuit protective setting corresponding to normal current conditions and promptly snaps to circuit interrupting position upon encounterin a current overload.

As conducive to a clearer understanding of certain features of the present invention, it may be noted at this point that open fuse cutouts are intended to arrest the flow of current by spending a fusible electrically conductive or heat sensitive portion in response to overload current and thereupon open a related electrical line with a snap action. A variety of these cutouts employ contact arms which support the fuse and are electrically connected into the transmission line to form an electrically conductive portion thereof. In these cutouts the contact arms are biased in favor of pulling the leads of the fuse apart when fusion occurs, thus to achieve a further opening of the transmission line and decrease the danger of arcing. To restore the outout to electrically conductive condition relative to the power line, a replacement fuse of desired rating is inserted between the contact arms, and is supported in tension by the same until current overload releases the bias in favor of separation once more.

These electrical protective devices have come into demand in such important fields as the outdoor transmission of electrical power, and are often used on line towers, poles, transformers, or the like, thus to afford a component part of the power transmission system. Among these systems are those employed for rural electrification, which are mentioned here as an example illustrating certain conditions and economic levels of use. Thus, it will be appreciated that economy is a highly important factor in many installations where the demand exists for open fuse cutouts, considering too that the quantity of cutouts needed in a particular system or for an over-all plan for electrification, may be quite large.

A number of the heretofore known circuit interrupters or open fuse cutouts have been eliminated from possible use for any of a variety of their intended purposes by virtue of such considerations as failure to lend themselves readily to mass production techniques and yet give a strong, easily assembled, reliable product. More specifically, some of these cutouts have been particularly objectionable from the standpoint of being highly expensive to produce on the competitive market. There are others which, once installed, offer an extremely unfavorable aspect of upkeep. In this connection, it will be appreciated too that certain open fuse cutouts in the prior art are physically too weak because the precise character and arrangement of parts, or otherwise, they are very difficult to reset or service from a safe distance, as with a suitable tool, to replace a spent fuse.

Many of the heretofore known open fuse cutouts introduce a highly objectionable detriment to operating efficiency of the related electrical transmission line under normal current conditions. This fault often arises because of the very structural nature of the cutout contact arms and because small physical cross-sections exist at crucial points where the line current has to pass. Also, when attempts are made to overcome the detrimental effect of low current capacity, the necessary changes in the cutout structure often introduce production difliculties, such as reflected by expense of the product, or are not feasible at all,

A further object of this invention, accordingly, is the provision of a practical and reliable open fuse cutout which is easy to produce and simple to service and maintain.

A still further object of the present invention is that of providing a fuse cutout of the type described, which is strong and easy to assemble and has favorable current capacity under power transmitting conditions.

The preceding objects and other objects of this invention will become more apparent upon consideration of the following description of a preferred embodiment thereof, when taken in connection with the attached drawing, in which:

Figure 1 represents, in side elevation, an open fuse cutout having features in accordance with the invention;

Figure 2 is a fragmentary view, in plan, showing details of a contact arm hinge or pivot in the apparatus depicted in Figure 1;

Figure 3 is a view in side-elevation of that portion of the apparatus shown in Figure 2; and

Figure 4 is a fragmentary view, in plan, of the outer end of one of the contact arms of the open fuse'cutout apparatus just mentioned.

In the particular embodiment of the present invention disclosed in the accompanying drawing, there is provided an open fuse cutout H! which includes an electrical insulator H and relatively movable contact arms I2 and i3 supporting. a fuselink M which electrically interconnects these arms. The cutout comprises line terminals 16 and H individually corresponding to the contact arms I2 and I3 for connection of the cutout into a power line of an electrical transmission system. Terminals l6 and l! are in electrically conductive relation with each other through the fuse link l4 and a fusible portion 34 of" the latter, so long as the link'remains conductive. The relatively movable contact arms l2 and I3? serve to impose tension on the fuse link I4 and to separate the free ends of the fusible portion 34 when this is melted or softened by heat of overload current in thel I illustratively is oblong,.as for mounting with the major dimen sion. in upright position, and conveniently is round or" substantially circular in transverse sec.- tion. It is made of porcelain, glass, or of any other-suitable dielectric. The long dimension of the insulator advantageously gives more available length for spacing the terminals 16 and H, considering that an effective'spacing isdesired to keep the-v electricaltransmission line open after the fuse link isexpended due to overload current.

A bracket illustratively serves for mounting the insulator H as in an upright position on a pole, line tower or transformer casing, and preferably' is disposed at some point in the general vicinity of midlength of the insulator body; for example, at about half way between the terminals I6 and I7. The inner end of the bracket 25 preferably is ofa form which connects to only one side of the transverse periphery of the insulator body, this connection for. example being on M further the side opposite from those portions of the open fuse cutout [0 which are electrically conductive in the power transmission line. The bracket 25 illustratively is in the form of a metal strap or flat bar extending transversely from one side of the insulator l I and having one or more openings 25a therethrough, clear of the insulator body for receiving a screw, bolt, or the like to support the cutout [0 in useful position. The inner end of the strap conveniently is affixed to the insulator II by being embedded therein or seated in a transverse opening in the side of the insulator body and cemented in the seated position. It will, of course, be understood that a conventional collar or band of metal is at times employed to encircle the insulator body and thus affix the bracket, but this arrangement preferably is avoided for such reasons as often being susceptible to easy connection with the line to ground, as by birds roosting on the cutout Il By keeping the bracket 25 to one side of the insulator body and disposing the contact arms l2 and I3 on the opposite side so as to be remote from this bracket, danger of line to ground connection between the several elements is considerably reduced.

The contact arms !2 and I3 illustratively have supports lii'andv IQ, for respectively mounting the same to opposite end portions H17 and l [o of the insulator H. The support l8 preferably is a strap orv a flat bar fixed atone end to the side of lower end portion H!) as by being embeddedv therein or seated in a transverse opening in the insulator body and cemented in position. It is made ofelectrically conductive material such as copper-clad steel or a copper alloy such as of cobalt-beryllium-copper composition and affords a fixed terminal iii of the contact arm I2 for receiving an electrical lead for power supply. From the insulator end portion l lb, the strap of support l8 extends outward as ona sharp, straight-away longitudinal curve to a substantially parallel outer end position relative to the longitudinal axis of the insulator H. The shape of the strap may for example be that of a substantially right-angle piece having a leg l8b transverse to the longitudinal axis of the insulator H and a leg substantially parallel to the axis. There is a longitudinal slot l8a through. the curved strap portion of support l8 and following around the bend of the curve to points short of the respective ends of the strap. The outer end of the support l8 conveniently has an opening; 18d for receiving terminal it which.

illustratively includes a nut and bolt for clamping an. electrical lead to conductive position relative to the, strapv end and contact arm I2. If desired, this terminal may be integral with support l8 as by welding. Welding preferably is employed for increased electrical. capacity of the cutout l0.

Support [9 for the contact arm 13 conveniently may be of the same strap material as support [3. In this instance, however, the support I9 conveniently is a substantially straight piece having its inner endafflxed to end portion lie of the insulator I I such as by embedding or inserting into a transverse opening in the side of the insulator body and cemented in place. This support for the contact. arm [3 then extends transversely from the insulator side wall and terminates somedistance out from the point of anchoring. Usually, the supports I8 and I9 are afiixed to opposite ends of the insulator ll and on the side of the. body thereof opposite from the side where the bracket 25 is disposed. The contact arms I2'and I3 advantageously extend from their respective supports in a generally opposite direction from the bracket 25 so'as to be remote from the latter.

Contact, arm I2 preferably is made: of a substantially rigid strap or fiat bar, this of electrically conductive material such as copper-clad steel or copper alloy. A cobalt-beryllium-copper alloy is quite satisfactory for the strap composition. The contact arm strap advantageously has two opposed transverse notches I2a and I2b entering the opposite narrow edges thereof just short of the inner end and extending toward the longitudinal axis of the strap material, thus leaving a reduced section I20 slightly narrower across than the width of the slot I8a for the strap to fit in movable relation within the latter and yet receive lateral bracing by the adjacent portions of the support I8. Notches I2a and IZb'are'wide enough to clear the thickness 'of support I8 and also preferably are deep'enough' to receive the adjacent walls of support I8 when the inner end of arm I2 is inserted in the slot I8a and is subsequently rotated about its longitudinal axis.

This allows easy assembly of the contact arm l2 to pivotal relation with its support. In the assembled condition, the contact arm advantageously has the long dimension of its transverse cross-section substantially lateral to the fuse link for rigidity and ease of replacement of the link. The same holds true for the lateral cross-section of the contact arm support I8.

The notched construction of the inner end of contact arm I2 thus enables pivotal movement of this arm relative to the support I8. Further, by making the slot IBa .of the support sufiiciently lon the contact arm I2is easily mounted to the pivotal position. lhe lower end "of the slot I8a, as in the vertical leg IBc, conveniently affords a rest or pivot-a1 bearing for the reduced section I2c of the arm. Also, the width of the notches I2a and I2!) as measured longitudinally of the contact arm I2, and the proportionate thicknesstive to arrest longitudinal movement of the contact arm.

The pivoted contact arm I2 is biased bymeans of a spring so as to be urged to swing away from the contact arm I3 and accordingly in crease the separation of the outer ends of these arms. The spring 2!! illustratively is a torsion spring as of the spiral wire variety welded at its' inner end to the contact'arm support I8, and bearing at its outer end on contact arm I 2.

Spring 23 is made of an electrically conductive -material, as for example a' resilient copper alloy.

Thus, by employing an electrically conductive biasing spring, the pivotal connection between contact arm I2 and the arm support It is reliably shunted to assure better conductivity in the cutout Ill and greater electrical capacity in the vicinity of the pivot point.

The outer end of contact arm I2 conveniently is longitudinally split and the resulting portions turned or bent back to give integral hooks I2d and I2e on opposite sides thereof for holding the fuse link I4. These hooks are made, for example,

a highly satisfactory electrical path. Each of the hooks (Figure 4) preferably extends backward and diverges away from the main body of contact arm I2, thus forming an angle for effectively receiving and holding an' end of fuse link I4. An outer portion I21 of contact arm I2 and including these hooks, conveniently is inclined from the plane of a rearward portion IZg, toward the outer end of contact arm I 3 so as to enhance the receiving'and holding effect of the hooks. The several hooks advantageously are in substantially the same plane as the adjacent portion I21 of 'arm I2.

The contact arm I3 preferably is fixed to its corresponding support I9, as by riveting, welding or both. This contact arm, for example, also is made of electrically conductive strap material such as copper-clad steel or cobalt-beryllium-copper alloy. At the inner end the strap is bent away so as to extend substantially vertically above the support I9 and there conveniently has an opening I3a for'receiving the corresponding terminal II of the power line in which the cutout I0 is to serve. This terminal may be made integral with the corresponding contact arm I3 as by welding to increase the electrical capacity of the cutout III. At the outer end, the arm I3 is provided withmea-ns for receiving and holding the fuse link I4, such as hooks I3d (not shown) and I3e on portion I37 which is inclined from the plane of 'a rearward portion I3g, toward the outer end of contact arm I2, thus to enhance the receiving and holding of fuse link I4. Arm I3 preferably has the long dimension of its transverse cross-section substantially lateral to the link I4 for rigidity, and ease of replacement of the link. The same holds true for the lateral cross-section of arm support I9.

Fuse link I4 preferably includes an opposed pair of electrical conductors 32, made, for example, of copper wire, and which are provided at their outer ends with eyes 33. The inner end portions of the electrical conductors 32 are spaced apart to form a gap and located in this gap and connected to the conductors 32 is the fusible element 34 of relatively low melting point material. This fusible element 34 and the inner ends of conductors 32 preferably are enclosed within a tube 35 made, for example, of a weatherprotective material such as phenolic resin lined' with fiber capable of emitting an arc-suppressing gas due to proximity with the electric are formed coincident with'rupture of the fusible element 34 on overload current. The conductors 32 conveniently have stops 29, which for example are elec-'- tr'ically conductive washers, affixed thereto between the inner sides of eyes 33 and the ends of tube 35 as by welding or soldering.

In use of the cutout In, one of the opposed electrical conductors 32 of the fusible link I4 is' set into the hook I 201 or I 2e with the corresponding stop 29 on that side of the contact arm I2 which is remote from arm I3. For this, a conventional switch stick is useful to handle an appropriate one of the eyes 33. With further use of the switch stick or tool, conductor 32 at the opposite end of the link I4 is set into either hook I3d or I36 of fixed contact arm I3 with the corresponding stop 29 outside this arm. In this latter operation, the pivoted contact arm is pulled toward fixed arm I3, against the bias of spring 20. Stops 29 then engage the contact arms I2 and I3 while the link it is in tension under'the 7 bias; of arm 5.21 of the contact arms; in being inclined and sub stantially approaching each other, advantageduslymaintainthe-bottoms of the hooks 52d and l-2c1substantially' toward the bottoms ofv the op posed hooks F301! and. Me for positively receiving and holding the fuse link in the bight portions or. the; hooks; It should also be noted that while parts of conductors 32 may engage contact arms [2 and i3", stops 29will engage these respective arms at one point toachieve limited area contacts under pressure due tospring 20. Thenwith normal current conditions prevailing, the open fuse cutout Ill serves to maintain current fiow through the transmission line of which terminal 6; inclusive of support is, the shunt spring 20; contact arm l2, fusible link l4, contact arml:3and;terminal ll comprise-a part. If, however, overload currents pass through the electrically conductive portions just named, the fusible com-- ponenttd in. the link M ruptures. When that occurs; contact arm t2 pivots (clockwise in Figure 1) with a snap under the force of spring 20; quickly pulling apart the electrical conductors 32 oflink it. across-'the-cutou-t Ill,-but-can be restored, if safe transmission limits exist, by introducing another link Id having afusible component 3 ofappropriate current rating.

Where, for example, the'cutout Hl= is to be used for lending safety to a high voltage electrical transmission line, as is often the case, a considerablebenefit is had-by employing an insulator' it having a corrugated surface, such as a surface provided by aseries of raised annular portions Ila: spaced alongthe-length of the insulator body. This corrugated surface is illustratively achieved by molding the insulator to form inclusive ofthe corrugations-,- such as by pouring a desired dielectric composition: into a mold having suflicient dimensions to produce the entire insulator unit as a molded product. The corrugated surface tends to arrest discharge b'Et-WBSII the terminals 56 and llby increasing.

the creepage distance therebetween. The mounting bracket 25 conveniently is secured to the insulator H ata point intermediate thepluralityof raised annular portions Ha which then also protect this element against discharge. desired, the several end portions [lb and H0 of the insulator H, and also the intermediateport-ion where bracket 25 is affixed, may lee-made substantially cylindrical, in shape and in. axial alignment. Also, if desired, the. several raised annular portions Hamay be disposed between the cylindrical portions of the insulator and inaxial alignment withthese portions by integral relation achieved by molding the insulator body.

To further assist in the avoidance of free electrical discharge over the surface'of the insulator H, aswhere the insulator is to be used in the upright position, the bottom surface of at least some of theraised annular portions Ila preferably is substantially normal to the longitudinal axis of the insulator or is inclined in upward direction from the rim of the corresponding annular portion. The top surface of at leastv some of the raised annular portions llaadvan tageously slopes downward and outward from a sheltered position beneath the underneath surface of the annular portion Ha next above or from an undercut position relative to the top or intermediate cylindrical portion of the insulator, thus being protected against moisture.

Thus; it will be seen that in this invention there The outer portions I27" and. [3

Current flow thus no longer prevails Whenis provided: an openf use cutout in which. the

various. obj ects noted herein; together with manythorloughly practical advantages,- are successfully achievedz It will' bexseen that the cutout-is ple and efficient and is effectively biased in favor of Snapping to pen. circuit position upon overload currents being; encountered it will be' seen that thei cutout not only is effiec tively biased for' achieving. open circuit condi-- tion's upon overload, but very efliciently avoids" sacrifice of electrical? capacity in the vicinity of the pivoting means should normal current. cons-- ditionsiprevail. Then, too; it will be appreciatedthatthe cutout is highly effectiveand? conducive to safe electrical conditions.v

The features relating to? the structural mount ing arrangement f'orthet insulator H are'set out' and claimed. in U. patent application filed June- 10',- 19'49,. by James M1 Wallace and Earl-F; Beach; j

Serial No; 98,378, and'v assigned to the assignee of the instant application.

Having described a preferred embodiment: ofi:

the invention in accordance with the patent statutes, it. is desired that the invention be not limited to: this particular structure;v inasmuch as: it willbe obvious toperson's" skilled in the artlthats many modifications: and changes may be made inthis particular structure without departing from the-b'road'spirit and scope of this invention;

Weclaim aszour invention;

1'. An open fuse cutout comprising: anelectrical insulator; spaced electrically conductive; contact arms mounted on said insulator andibeing benttosubstantially approach each other" toward their outer ends to'maintain the bottoms of opposed.

integral hooks at the outer: ends. thereof inward for positively receiving and holding a fuse. link,

one of saidzar-ms being substantially fixed in posi tion' on: the insulator, aterminal fixed on'theiin sulator" for-the other arm, and. said other aim-- being: movably mounted at: its inner end relative armi andhaving anelongated' slot therein: and. a.

terminal on thebod-y thereof, a movable electrically conductive contact arm of strip form having at least one edge at the inner end thereof n otched'for receivinga side wall of said slot when the greatest cross-sectional dimension of the arm" issubstantially transverse of said slot and with said movable arm inpivotal engagement with anend of said slot to-form a pivot-withthe same for swingin away from saidsubstantially fixed contact arm; both of said arms being directed outward fromasaidinsulator, and a spring urging movement of the movable arm away from said substantially fixed arm while: biasing it into engagement with said-'endw-all of the slot.-

3; An openfuse cutout comprising an electrical insulator; an electrically conductive contact arm mountedon said insulator and having a substantially fixed position throughout; an electrically conductive support connected; to said insulator away from said. substantiallyfixedcontact;

arm and having an elongated slot therein anda terminal on the body thereof, a movable electrically conductive contact. arm of strip form;

, 9 having opposed edges at the inner end thereof notched for receiving opposite side walls of said slot when the greatest cross-sectional dimension of the arm is substantially transverse or" said slot and with said movable arm in pivotal engagement with an end of said slot to form a pivot with the same for swinging away from said substantially fixed contact arm, both of said arms being directed outward from said insulator, and a spring urging movement of the movable arm away from said substantially fixed arm while biasing it into engagement with said end wall of the slot.

JAMES M. WALLACE.

ANDREW W. EDWARDS.

Number Name Date Sherwood May 1, 1906 Steinmayer Jan. 21, 1936 Ramsey Feb. 15, 1933 McCluskey et al. Apr; 19, 1933 Cooley Sept. 17, 1940 Triplett et al. July 13; 1943 Steinmayer July 27, 1943 Steinmayer et all May 2, 1944 Fox et al. May 29, 1945 Hubbard July 3, 1951 Yonkers Oct. 30, 1951

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