US2574401A - Electric switch - Google Patents

Description

Nov. 6, 1951 w C, LESHER 2,574,401

ELECTRIC SWITCH Original Filed Aug. l, 1947 2 SHEETS-SHEET l Invenol WiHiClm'C. Leher1 bi1 His Aormj W. C. LESHER ELECTRIC SWITCH 2 SHEETS-SHEET 2 Original Filed Aug, l, 1947 w e MM, uw e WL P .fm il@ C D@ +1 w im U5 THQ i. m, m WH b the insulator and thence to the insulator Patented Nov. 6, 1951 ELECTRIC SWITCH William C. Lcsher, General Electric New York Original application August 1,

Pittseld, Mass., assigner to Company, a corporation or 1947, serial No.

765,369. Divided and this application Deceufra ber 29, 1948, Serial No. 68,016

1 claim. (ci. 2do-114i My invention relates to improvements in electric switches intended primarily for outdoor installation on distribution systems and more par ticularly to improvements in disconnecting switches and especially fuse disconnecting switches of the open dropout type.

This application is a division of my copending application for Electric Switch, Serial No. 765,369, iiled August l, 1947 and assigned to the same assignee as the instant application.

Fuse disconnecting switches of the open dropf out type, with which I am familiar, have been subject to false operations in consequence of animals such as birds, squirrels, etc., getting on the exposed metal parts and causing short circuits. 'I'hese false operations result in interruptions to the much desired continuity of service. To avoid such interruptions, the terminal por; tions at the ends of the supporting insulator have been mounted outwardly from the insulator at distances from each other and from the possibly grounded metallic band support which are suilicient to provide the dielectric strike and creepage values required to meet the basic insulation level o1' the voltage classification for which thel switches are designed.

In fuse disconnecting switches of the type having an expulsion tube sealed at one end and open at the other end, the expulsion effect of the blowout action tends to move the fuse tube and the parts connected thereto in a direction away from the open end so forcibly as to produce material shock which has to be absorbed and transmitted through the attachment of the parts to mounting. In prior art fuse disconnecting switches of the open type embodying the metallic band support, the eiiect of this expulsion force has been magniied many times by leverage, since the expulsion tube is mounted at considerable distance from the insulator in order to provide suiiicient dielectric strike distance from the metallic band support to the fuse in the expulsion tube or to the uninsulated solid disconnecting blade it is customary to furnish as an alternative to the fused expulsion tube. These magnified forces result in application to the insulator of stresses such as bending for which the usually employed ceramic structure ill adapted. In order to meet even current interrupting abilities required on normal distribution circuits without breaking the porcelain insulator or bending theterminals or supporting members so they are no longer usable, it has been proposed to have both ends of the expulsion tube open. However, the expulsion of hot ionized conducting arc gases from the energized end of the tube creates a hazard from arcover to nearby grounded parts or even between associated, electrically energized overhead lines or apparatus terminals. In view of this hazard, various methods have been proposed to limit the range of currents at which expulsion action occurs at both ends or to direct the expelling of the gas away from associated lines or apparatus. Each of these expedients only slightly lessons the hazard. 'I'he only positive corrective measure is to seal the end of the expulsion tube which remains energized after the arc is extinguished in the tube since tests have shown that the hot conducting arc gases expelled from the tube can cause flashover to ground members. or those excited at a. diiierent potential, even when located from iive to six feet from the terminal on the energized end of the expulsion tube whereas no iiashover will occur to such grounded or energized members even when located only six inches from the end of thel tube which is deenergized by the arc extinguish? ing action oi the tube.

An object of my invention is to provide an improved electric switch structure, particularly of the open fuse type, such that the possibility oi short circuits and false operations in consequence oi birds and other wild life getting across the exposed energized metal parts of the switch is so materially reduced as to be practically eliminated. Another object of my invention is to provide an improved electric switch structure, especially of the open fuse type, with the insulator supporting member so secured to the insulator as to permit positioning the expulsion tube in such a way that the stresses on the support caused byv the expulsion or blowout eiect are not magniiied by extended supporting arms or terminals. Also an object of my invention is to provide an improved electric swltchstructure, particularly of the open type, which is compact, sturdy, and of pleasing appearance.

My invention will be better understood from the following description when considered in connection with the accompanying drawings, and its scope will be pointed out in appended claim.

In the accompanying drawing, Fig. 1 is a side elevation of a fused disconnecting switch of the open dropout type embodying my invention and shown in the circuit closed position; Fig. 2 is an enlarged view similar to Fig. l with some parts broken away for clearness of illustration and in ,addition showing in broken lines some intermediate positions of the movable parts; Fig. 3 `is a front elevation of the switch shown in Fig. 2 with the `switch shown in the full open position; Fig. 4 is a view similar to Fig. 1 illustrating the switch with the parts in position just prior to dropout and also showing in broken lin\e`the fuse tube in an intermediate position following the blowout of the fuse and in its extreme open position; Fig. is an enlarged sectional view taken on the line 5 5 of Fig. 1 illustrating the upper switch terminal structure and its mounting; and Fig. 6 illustrates a modification of my invention wherein the switch is purely a disconnecting switch without a fuse and without dropout action.

For the purpose of illustrating my invention, I have shown in Figs. 1 to 4, inclusive, a fuse disconnecting switch of the open dropout type wherein the line terminals Ifand 2 and associated contact structures are mounted adjacent the ends of a suitable substantially cylindrical insulator 3. In order to have a compact structural arrangement whereby to avoid multiplying the expulsion recoil forces as they stress the porcelain and supporting member and also to Aavoid false operations in consequence of short circuits produced when birds and other wild life contact conducting parts of a switch, such as the terminals, for example,

' of the contact means' I0. At the other or lower the insulator supporting arm4 is mounted so a portion near one end thereof is within the cylindrical surface of the insulator 3 at the rear thereof and approximately midway of the ends of the insulator. With the supporting arm 4 thus extending directly from the insulator in a direction opposite to the contact structure hereinafter described, a more eifective strike-over distance to the fuse I9 in tube 2| or to the metallictube 92 shown in Fig. 6, when substituted for the tube 2 I, is insured with the tubes 2| or 62 located closer to the insulator .3 thanhas been possible with the heretofore used metallic band support around the outside of the middle portion of the insulator. Thus, in my construction, I combine mounting of lthe support 4 in the insulator 3 at the rear thereof and the location of the tube 2| or 62 closer to the insulator 3. This provides a more economical construction for open type switches and insures not only an interrupting ability comparable with that of switches of the enclosed type -but also, with minor modifications of the expulsion tube 2| and associated parts comprising current conducting means I8, a device with an interrupting ability end of the insulator 3, there is mounted on the bearing member I I a second relatively stationary contact means I3 in current conducting relationship with the terminal 2.V For completing a conducting -path between the stationary contact means I0 and I3 and consequently the terminals I and 2, I provide a hinge element I4 havingV trunnions I5 adapted to be inserted in the hooks I6 of the bearing element II and carrying a contact I'I movable into and out of engagement with the lower contact means I3 upon rotation of the hinge element. Also, I provide current conducting means indicated generally by I8 and carried by the hinge element I4 and rotatable therewith counterclockwise, as viewed in the drawings, about its bearing axis I2 to the circuit closed position to establish the conducting path between the lower and upper contact means I0 and I3.

As shown'in Figs. 1 to 4, inclusive, the current conducting means is of the expulsion fuse type comprising a conductor I9 having a portion 29 fusible at a predetermined value of current and an explusion tube 2| having a conducting cap 22 connected to one end of the conductor and engageable with the upper stationary contact means Ill. The fusibleportion 20 of the conductor I9 is mounted within a cylindrical casing 23 of insulating material and is connected to the cap 22 through a stud 24 which carries the casing 23 and a button head, not shown, engageable by the cap 22, as is well known to the art, when sealing the fuse tube 2| is practical in the light of the required interrupting duty. As shown, the tube 2| is pivotally mounted at 26 on the hinge elenearly double that of the normal interrupting ability and with theend of the tube 2|, which is normally energized after arc extinguishing, sealed by the cap 22 so as to prevent strike-over to 'associated lines of apparatus. As illustrated in Figs. 1 and 2, arm 4 is secured to a support such as a pole-mounted bracket 5 by suitable fastening means shown as a bolt 6 provided with a nut 1, a bearing washer 8 and a lockwasher 9.

Adjacent one end of the insulator 3 and supported therefrom in conductive relation with the terminal I and so as to extend transversely of the insulator in a direction oppositely to that of the support 4 is a first relatively stationary contact means III. Inasmuch as the tube 2| can be located closer to insulator 3, as hereinbefore described, the stationary' contact means I0 is relatively shorter than heretofore possible in devices of the prior art thus decreasing the leverage which multiplies the recoil forces from expulsion action. Supported from the other or lower end of the insulator 3, in line with the longitudinal axis thereof is a hinge means comprising a hook type bearing member Il, the bearing axis l2 of which is substantially perpendicular to the longiment I4 constituting therewith a toggle which is held in the rigid condition shown in Figs. i and 2 by tightening the conductor I9 around a thumb screw 21 in the hinge element I4 and then clamping the conductor between the element and a locked-against-turning nut 28. When the toggle is thus held rigid, the switch can be closed by inserting a switch hook in an operating eye member 23 mounted on the fuse tube 2|.

i For maintaining the switch in the closed circuit position after turning the rigid toggle counterclockwise, as viewed in the drawings, to the closed circuit position shown in Figs. 1 and 2, there is provided a holding means which, as illustrated, comprises a U-shaped resilient member 39, the outer ends of the legs of which are bent inwardly and then outwardly to provide, in V- shaped formation, ared ends which yield suiciently to permit entrance of the cap 22 and thereupon close over the cap to prevent reverse movement except when enough pull is exerted on the eye member 29 to expand the'legs of the U-shaped member 30 suiilciently for exit of the cap.

In order to reduce static interference of radio equipments and the like, a coiled spring-like conductor 3| is placed around the fuse tube 2| between the eye member 29 and the bottom of a threaded sleeve 3| onto whichthe cap 22 is threaded whereby to have the eye member at the same potential as the terminal I.

Referring now more particularly to other` features of the heretofore described structure, the upper stationary contact means comprises in addition to the leaf contact spring I0 a leaf backing spring I0. Both of these springs, as shown more clearly in Fig. 2, are carried by a bracket 32 extending outwardly from the insulator 3 and `hooks I6 to those of normal low cost supported therefrom on a stud 33 mounted in the insulator. For simplicity in mounting, the contact structure I0, I' is secured to the bracket 32 by the terminal bolt I which is provided ywith a shouldered cylindrical nut 34 having a ridged periphery. The smaller diameter portion of the nut 34 fits into a hole in the spring member I3" and clamps the spring contact I0 against theA bracket 32, as shown in both Figs. 2 and 5, thereby establishing electrical contact with the spring contact I0. The inner end of the spring I0 is notched and curved upwardly to engage the stud 33 whereby to prevent turning movement. The inner end ofthe backing spring IIl' bears on the curved portion of the contact spring II), and the smaller diameter portion of the nut 34 is somewhat longer than the thickness of the backing spring I IJ so as to provide greater freedom of movement of the backing spring Also, the front end of the bracket is bent .downwardly so that the contact spring II) can follow the/cap 22 during the first part of the dropout action of the switch, as shown in Fig. 4, whereby to maintain continuity of contact'until the expulsion action of the fuse and arc interruption in the tube 2| have occurred. The extreme end of the bracket 32 is further curved downwardly at 35 to provide a support for the U-shaped holding member 30, the base of which is secured to the bracket by suitable means such as a bolt 36 provided with a shock-absorbing head 3'I of suitable resilient material to absorb the closing impact. As the switch opens during the dropdown action of the fuse tube, particularly under small currents which effect vslow melting of the fuse and weak expulsion action, the cap 22 remains in conducting engagement with the holding member 30. This provides some delay without circuit interruption at the top whereby to insure arc clearing in the tube 2 I.

The fuse tube 2| is supported in a clamp 38 which is pivotally secured to the hinge element I4 at 26. For lateral stability relatively to this element, the lower end of the tube 2| is held between side arms 39 on the element. In order that the toggle comprising the hinge element I4 and the tube 2| may, when held rigid, swing in substantially a true plane and thus align the cap 22 with a relatively narrow entrance of the holding member 30 so as to be suitable for covering with a hood 52, the hinge element is provided with bearing shoulders 40 which ride against the inside surfaces of the hooks I6 and from which the trunnions I protrude outwardly since Ithis structure is mechanically simple to machine. Also, in order to increase the manufacturing limits for this simple machine operation and for the manufacture, the bearing member II is provided with flared wing guides 4I with which cooperates a relatively close fitting flange 42 on a supporting leg 43 of the hinge element. The relatively large distances between the trunnions I5 and between the guides 4I makes a more positive guide for directing the cap 22 into the relatively narrow entrance of the holding member 3|! than has been achieved in prior art constructions with which I am familiar. To limit the angular movement of the tube 2| relatively to the hinge element I4 during the dropout action, the upper end of thesupporting leg 43 is provided with an extension 44 which bears against a clamping screw 38' after a predetermined amount of dropout movement has occurred. Thehinge element I4 is also provided with an eye member 45 by which ported on a stud the element and the tube 2| can be removed' when in the open or vertically down position for inspection, fuse replacement, etc., with the aid l of the usual switch hook.

As shown, the lower stationary leaf spring contact Ilfis supported on a bracket 46 which is suitably secured to the outside of the rear wall 41 of the bearing member I I. For holding the contact on the bracket 46, the terminal bolt 2 extends through the outstanding leg of the bracket and is provided with a cylinidrical clamping nut 48 which has a ridged periphery and which bears against the contact I3. The contact I3 extends through an opening' in the rear` wall of thebearing member II so as to be engaged by the contact I'I on the hinge element I4 when the switch is closed. Ihe bearing member II is sup'' 49 extending axially downward from the lower end ofthe insulator 3 substan-l tially in line with the axis thereof and lalso substantially inline with the point of engagement of the contacts I3 and II. Shock-absorbing means is provided and positioned adjacent the lower end of the insulator and yieldable substantially in the direction of the axis of the insulator for absorbing the effect of the expulsion force transmitted to the hinge element I4 and thence through study 49 and insulator 3 to supporting arm 4 so the insulator 3 is essentially in compression substantially along the axis thereof upon rupture of the conductor I9 as at the fusible portion 2|) thereof. As illustrated, this means comprises a helical compression spring 50 which is positioned around a reduced diameter portion 5I of the stud 49 and between the inside of the upper wall of the bearing zrember II and the upper surface of the contact I3.

Also a resilient bumper 50', of rubber or the like, is inserted inside the spring 50 and arranged so as to be compressed between the stud 5| and the upper surface of the contact I3 after the spring 56 has been compressed a predetermined amount. The length of the reduced portion of the stud 49 and the resilient bumper 50' is such that, even though the hinge element is forcibly lifted by the expulsion shock, the contact I3 will strike and compress the bumper 50' a predetermined amount against the end of the stud 49 so as to cushion the impact and stop the upward movement before the trunnions I5 are raised far enough to be movable-out of the hooks I6, and also before the upward movement of the tube 2| under the action of therecoil forces has overstressed the terminal I and acting through said terminal has imposed a slightly amplified bending stress on the insulator 3.

Since the bearing axis I2 of the hinge elemeni I4 is to the left of theaxis of the insulator 3. the line of action of the force exerted on the hinge element by the compression spring 50 through the contact spring I3 and the contact I I is such that this force tends to maintain a high contact pressure between the contacts I3 and I 1. Also, because of the "direction of application of this force, it tends to move the hinge element I4 to the circuit open position whereby to accelerate the opening action when'the conductor I9 is ruptured. Also, in order to protect the parts associated with the terminal 2 from the elements, the bearing member 'II is preferably in the form of a hood with only""`the` front and lower sides open. 'In order toli mit the angular opening movement of the hinge element under the expulsion action, the rear wall' 41 of the bearing member II extends downwardly into the path of movement of the eye portion 45 of the hinge ele-- ment, as more clearly indicated by the broken line position X in Fig. 4.

- For sheltering the upper contact structure against the elements and also to make this contact structure practically inaccessible tol wild life, I provide an improved hood structure which is readily and simply attachable to and detachable from the switch. As shown, this structure comprises a hood 52 preferably of insulating material which may be formed by molding or otherwise. For ease in mounting, the bottom of the hood is open and also the front in order to allow passage of the cap 22 to and from the circuit closed position. Also for simplicity in mounting, the rear wall of the hood 52 is notched at 53 to fit over the stud 33 between the insulator 3 and the fixed end of the bracket 32, and the top wall 54 is provided with an opening just large enough to slip over and register with the periphery of the cylindrically headed nut 34 on the terminal bolt I. In order to prevent turning of the hood 52 about the head of the nut 34 the interior of the hood is arranged to engage the bracket 32. For clamping the hood in place and also keeping water from enteringthe hood, I provide a clamping nut 55 and a cupped spring washer 5t, as shown more clearly in Figs. l and 5. In order to avoid bending strains on the top wall of the hood 52 under the clamping action, the inside of the top wall is provided adjacent the hole in the wall with transversely extending thick bearing portions 57 which seat on the bracket 32, as shown most clearly in Fig. 5. These portions take in compression the clamping force consequent on tightening the nut E. Also the hood 52 may be provided with internal stiffening ribs 58, as shown. For securing line conductors to the terminals I and 2, each is provided with a wire clamp 59, a lock washer 60 and a nut 5I, as shown.

From the foregoing, it will be apparent that in consequence of having the supporting arm 4 extend outwardly from the insulator oppositely to the contact structure without the use of a band surrounding the middle of the insulator, it is possible to bring the contact structure in closer to the insulator without danger of wild life eecting short circuits between the contact structure and the supporting arm 4, which is often grounded. Also, because of the compact structure, less room is available for perching birds and the like to alight on the switch and have any material freedom of move ent without having to take oil'. This practically eliminates the possibility 'of two birds alighting on the switch at the same time and g-hting with each other with resultant possibility of a short circuit across the line. Likewise, the probably of a bird being able to perch on the contact structure and reach around to the supporting arm 4 is greatly minimized. Also, with the contact structure closer into the insulator, the construction is materially stronger and less stress is placed on the insulator due to the decrease in the lever arms. Also, the compactness of structure provides a more pleasing appearance which is further enhanced by the use of the protecting hood 52.

It will be observed that the expulsion type circuit interrupter, comprising the tube 2| and the conductor I9, in the closed position bridges the upper and lower stationary contacts I0 and I3 in a. direction forming a relatively small acute angle within a range of l0 to 30 degrees with the longitudinal axis of the insulator 3. The expulsion force on interruption is thus applied to the tion, as shown in Figs. 1 and 2, with the toggle comprising the tube 2I and the hinge element I4 held in the rigid condition against the bias of the contact springs, the helical spring 5B and gravity by the conductor I9, then if sufiicient current flows through the switch to melt the fusible portion 20 of this conductor, the toggle is free to collapse under its bias as soon asS the iuse parts. When this occurs, the parts assume the full line condition shown in Fig. 4 with the fuse tube initially being urged downwardly by the resilient action of the contact means I0, ID' and i3 and thedheiical spring 50. The cap 22 at the upper end of ,the fuse tube, however, rides downwardly inside of the holding means 3U until the conductor i9 is blown from the :fuse tube 2i whereupon the tube assumes the position Y shown in broken lines in Fig. 4 and also in Fig. 2. Under the force of gravity and the biasing impulse initially imparted to the tube, the hinge element id and the parts associated therewith move in a. clockwise direction until the eye d5 of the hinge element contacts the rear wall di of the bearing member, as indicated by the broken line position X in Fig. 4 and then nally swing back to a vertical position below the insulator under the eiect of gravity.

When it is desired to re-fuse the switch, the" hinge element I4 is lifted out of the bearing member Ii by using a switch hook or the like in the eye 45. A new fusible element is inserted in the tube 2i after rst removing the cap 22 and then restoring it to lock the fuse head at the top of the tube as is well known to the art. The new fused conductor I9 is then inserted around the clamping bolt 2l and this bolt tightened to lock the fuse so as to hold the toggle rigid. The tube with a new fused conductor I9 in the toggle retaining position is shown in broken lines in Fig. 2 in the position Z just after restoring the hinge element I4 in the bearing member I I. The switch may then be closed by inserting a switch hook' in the eye 29 and moving the rigid toggle about the bearing axis I2 into the position shown in full lines in Fig. 2 where the switch is maintained by the holding means 30 as`long as the toggle is held rigid.

The embodiment of my invention shown inl Fig. 8 is an adaptation of thefuse dropout switch shown in Figs. 1 to 5, inclusive, for use as a dis-f connecting switch nonresponsive to current conditions or for use as a'non-dropout type of fuse disconnecting switch by fastening the fuse tube 2| to the hinge element I4 by a screw 63 as shown in Fig. 6. In the case of a disconnectingswitch, as shown in Fig. 6, the fuse tube 2l is replaced by a tubular conducting member 62 which is attached to the hinge element I4 in a manner similar to the arrangement shown in the other igures4 except that, since no relative movement. is to take place between the hinge element and the conducting tube 62, the lower end of the tube is also secured to the hinge element to preventmovement about the'fpivot 26. For this purpose'.

any suitable means such as a screw 63 projecting the insulator 3 through rela-'t through the tube I and threaded into the hinge element may be used. To prevent any twisting action oi the tube 62, the tube may be notched at 64 so as to seat one of the clamping bolts, not shown, oi the clamping means 38. In this modiiication of my invention, of course, both the circuit opening and circuit closing movements are to be performed manually by means of a switch hook slipped in the eye, not shown, on the tubular member 62.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claim all those modifications that fall within the true spirit and scope of my invention.

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

An electric switch comprising a substantially cylindrical insulator any cross section of which normal to the longitudinal axis thereof is circular in shape, a rst contact means mounted on said insulator adjacent one end thereof and extending transversely of the insulator, a second contact means mounted on the other end of said insulator, circuit interrupting means including an expulsion tube and a rupturable fusible element mounted Within said tube for electrically interconnecting said rst and second contact means and positioned in spaced relationship with said insulator, means for maintaining said insulator on a supporting structure comprising a supporting arm in engagement with said insulator intermediate said two contact means and at a point diametrically opposite the point of mounting of said first contact means, and means axially positioned adjacent said other end of said insulator to transmit the expulsion force upon rupture of said fusible element to said insulator as a compressive stress in the portion thereof between said other end and said supporting arm, said supporting arm extending in a direction diametrically opposite to that of said transversely extending contact means and having one end thereof and a portion adjacent thereto mounted directly within the cylindrical surface of said insulator whereby said compressive stress is transmitted to said arm with practically no bending of said in sulator. f

WILLIAM C. LESHERU REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,925,624 Boll Sept. 5, 1933 2,088,415 Heinrich July 27, 1937 2,264,203 Fry Nov. 25, 1941 2,324,888 Strobel July 20, 1943 2,361,240 Rawlins Oct. 24, 1944 2,446,676 Yonkers Aug. 10, 1948

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