US2838638A - Load interrupter switch - Google Patents

Description

June 10, 1958 K. H. DATE LOAD INTERRUPTER SWITCH 3 Sheets-Sheet 1 Filed May 28, 195

INVEN TOR. ifizuo Henry Date Md W flbt'arnqy' June 10, 1958 K. H. DATE LOAD INTERRUPTER SWITCH 3 Sheets-Sheet 2 Filed May 28, 1956 IN V EN TOR. k'azua fie/27y Date June 10, 1958 K. H. DATE 2,333,638

LOAD INTERRUPTER SWITCH Filed May 28, 1956 5 Sheets-Sheet 3 IIHIIHI IN VEN TOR. Kazua Henry .Date

flttorney United States Patent LGAD INTERRUPTER SWITCH Kazuo Henry Date, South Milwaukee, Wis., assignor to McGraw-Edison Company, a corporation of Delaware Application May 28, 1956, Serial No. 587,873

2 Claims. ((31. 200-146) This invention relates to a high voltage air disconnect switch in combination with an auxiliary path load current interrupter.

It is common practice to use air disconnect switches for sectionalizing power distribution systems but it is usually necessary to back them up with a circuit breaker capable of interrupting load current so that the sectionalizing switches may be opened while not conducting electricity. If the air disconnect switches are opened without previously de-energizing the circuit, a destructive arc may be drawn between the switch blade and its cooperating jaw contact. Because under modern con ditions very important electric loads may be connected to the system, it is seldom practical to de-energize the whole circuit when it is desired to sectionalize a portion thereof and for this reason it has become desirable to adapt air disconnect switches for interrupting their rated load current. it is becoming more common to do this by attaching an auxiliary device which confines the arc, incident to opening the switch, to an enclosed arcing chamber which takes on the status of a preferred current path while the switch is being opened.

Although such load interrupters are obviously desirable, their use has not become as extensive as might be expected because of the diiiiculty of adapting them to pro-existing switches and because they have heretofore been comparatively expensive.

Accordingly, it is a general object of this invention to provide an economical, compact, easily installed and effective load interrupter for coaction with an air disconnect switch.

A further object is to provide a load interrupter that is versatile in the respect that it is adaptable to currently manufactured switches or to a variety of switches already installed in power distribution systems.

. A further object is the provision of a switch and auxiliary load interrupter combination which acts positively, that is, which asstues that the auxiliary load interrupter will close and open only in accordance with a desired corresponding full opening and closing of the cooperating disconnect switch.

Another important object is to provide an assembly of the above indicated type which obviates drawing of damaging arcs between parts of the disconnect switch while interrupting its rated current.

Yet another object is to provide an auxiliary interrupter and disconnect switch combination which is unaffected by weather, requires a minimum of attention and operates reliably and positively under adverse conditions such as when heavily coated with ice.

Attainment of the atoregoing and other objects will become apparent throughout the course of the ensuing specification.

In general terms, a preferred form of the instant invention is characterized by its including an air-disconnect switch having a blade which rotates on its longitudinal axis while swinging on its transverse axis to an open position. The movable blades engagement with 2,838,638 Patented June 10, 1958 a stationary contact jaw constitutes a main current carrying path of the air disconnect switch.

In parallel with the air gap created by separation of the movable blades from the stationary contact jaw, is an auxiliary path including interrupting contacts in series with a bypass rod which maintains circuit continuity while the main blade is being operated toward open position and assures a by-pass circuit before the main blade is closed. Suitable quick acting mechanism is also provided for actuating the interrupting contacts when the main blade has swung to a predetermined position where the latter acts on the interrupter trip arm and thus opens the circuit through the by-pass rod. Further swinging movement of the main switch blade causes it to carry the by-pass rod into isolating spaced relation from the interrupter, allowing visual determination of whether the switch is in full open position.

A more detailed explanation of the invention will be set forth in connection with the drawing in which:

Fig. 1 is a side elevation, partly in section, of the air disconnect switch and auxiliary load interrupter combination, both the switch and interrupter being shown in closed circuit position;

Fig. 2 is a view similar to Fig. 1, but showing the switch and interrupter in open circuit position;

Fig. 3 is a fragmentary sectional view, showing parts of the interrupter, taken on a line corresponding with 3--3 in Fig. 1; and,

Fig. 4 is a left side elevational view, partly in section, taken on a line 4-4 of Fig. 1 and with parts broken away.

A typical three insulator, rotating and twisting blade, vertical break, air disconnect switch, designated generally by the reference numeral 1, is shown in Fig. 1 in combination with an auxiliary interrupter generally designated 2.

Switch 1 comprises a stationary contact jaw 3 mounted on a cast metal terminal adapter 4 supported on a stationary insulator 5. When switch 1 is closed as in Fig. 1, jaw 3 receives a movable, swinging and axially twisting blade 6 in high pressure electrical engagement. Blade 6 is adapted to swing into open position on a transverse axis coincident with that of a pair of hexagon headed trunnion pins 7 While it twists in a blade guide 8 about its longitudinal axis. This action is brought about by axial rotation of a center insulator 9 which carries a crank arm 10 terminating in a universal connection 11. Force from crank 10 is transmitted to blade 6 through a link 12 clamped to the blade by a blade carriage 13 having an extension journalled in blade guide 8. It is evident that blade 6 Will be disconnected from jaw contact 3 in Fig. 1 while being twisted and swung to its position in Fig. 2, when insulator 9 is rotated axially.

Trunnions 7 are partially threaded and screw into the spaced yoke arms 14 of a fixed metallic frame 15 which is journalled with respect to insulator 9 but anchored on a third insulator 20. A power line may be connected to the frame 15 on a casting extension 21. Frame 15 also supports a fixed contact jaw 22 which is in line with blade 6 and electrically engages the hinge end of the blade when the switch is closed as in Fig. l, wh reas the blade swings free from jaw 22 when the switch is open as in Fig. 2.

The auxiliary path load interrupter 2 which cooperates with air disconnect switch 1 is mounted on a conductive base casting 24 bolted at 25 to contact jaw terminal adapter 4. Base 24 has a portion 26 for connecting an incoming line wire, not shown. it is evident from the description thus far that the normal, main current path to disconnect switch 1 commences at incoming adapter portion 26, extends through blade 6 to contact jaw 22 and terminates in outgoing adapter 21 forming part of frame 15.

A more detailed description of the air disconnect switch 1 is set forth in the copending application of T. A. Fjellstedt, S. N. 449,129, filed August 11, 1954 and assigned to the instant assignee.

Having described the principal current path through the air disconnect switch 1, attention is now invited to he auxiliary path load interrupter 2 and by-pass rod 28 which together constitute a parallel preferential path when the main switch 1 is being opened under load.

Load interrupter 2 includes a hollow porcelain bushing 29 which is filled with oil to'the dashed line 3%} and houses an arcing chamber 31. A removable fluid measuring rod 19 projects beneath the fiuid to determine its depth. An oil filled interrupter is preferable for the duty here involved because it inherently maintains its dielectric strength so that an arc is not prematurely struck when the movable contact approaches the stationary contact during closing of the interrupter. An air or gas filled interrupter is more inclined toward prestriking an are before the contacts are fully closed and therefore necessitates higher contact speeds in order to minimize arc duration and energy and to overcome the tendency for the contacts to blow open due to the pressure of hot gases incident to arcing. The are extinguishing structure housed by porcelain bushing 29 is described in detail in a copending application of A. Van Ryan, S. N. 563,014 filed February 2, 1956, and assigned to the instant assignee. For understanding the present invention, however, it is suflicie nt to realize that the arc extinguishing chamber 31 includes near its bottom a fixed contact, not shown, but in electrical connection with conductive base 24 and which cooperates with a movable contact rod 32 to open and close a circuit through interrupter 2. Movable contact rod 32 is adapted to execute a straight line movement centrally of bushing 29 and to project into a metal housing 33 which encloses contact moving mechanism designated generally by the reference numeral 34. Current is interchanged directly from movable rod 32 to housing 33 by conventional wiping contact fingers, not shown, attached to the bottom of the housing 33 within the upper end of arcing chamber 31.

Movable contact 32 is indirectly actuated by main blade 6 oscillating an external trip arm 35 journalled in spaced sleeve bearings 36 which fit tightly into the sides of metal housing 33. Trip arm 35 is actually a double arm member supported on each side on short coaxial transverse shafts 37 disposed through sleeve bearings 36, see Fig. 3. Arm 35 is attached to shafts 37 through the agency of caps 38 by staking or other means, the caps being pinned to the shafts. Shafts 37 are sealed by tightly interposing an O-ring 27 between arm 35 and a radial flange on sleeve bearing 36.

The sides of trip arm 35 are bridged exteriorly of the interrupter housing 33 by means of a pair'of cross rods 39 and 40 spaced circumferentially from each other. It will be noted that when main blade 6 swings about its transverse axis '7 that a blade extension 45, carried by blade 6, projects positively into driving engagement with the trip arm between the two cross rods 39 and 40. This is also true when main blade 6 is swinging from its open position in Fig. 2 toward closed position. Blade extension 45 always engages trip arm 35 between cross rods 39, 40 so that if main blade 6 is opened sufiiciently to strike cross rod 39 and then reversed and brought back into closed switch position, trip arm 35 will always follow the blade 6, thereby assuring that the interrupter 2 circuit is closed when the switch 1 is closed and that the interrupter opens only when the main switch opens.

The mechanism 34 located'within housing 33for opening the circuit to interrupter 2 by accelerating movable contact 32 axially, is a quick acting, spring loaded toggle arrangement which does not begin to move contact rod 32 until a. predetermined toggle position is reached,

whereupon all of the spring energy is suddenly applied to opening the interrupter. The toggle mechanism is, of course, actuated in accordance with positions of trip arm 35. Referring particularly to Figs. 1 and 3, the toggle linkage comprises a pair of parallel spring loading levers 46 secured to shaft 57 by staking at ii or by other suitable means. A cross pin 48 joins levers 46 and is surrounded by a loose sleeve 49 to which an end of each toggle spring 559 is attached. Swinging of lovers 4-6 by changing the angular position of trip arm 35 tends to stretch and load spring 53, as will be more apparent hereinafter.

Movable interrupting contact rod 32 is carried by a pair of parallel links 51 which are pivotally connected to parallel levers 52 ata pivot joint 53. The other end of levers 52 is pivoted for swinging about a fixed pin 54 spanning spaced upright flat posts Springs 5t? are stretched between pivot 53 and cross sleeve 48 so that when the interrupter is either closed as in Fig. l or open as in Fig. 2 there is tension in the spring which holds rod 32 in a positive up or down position, respectively. It will be observed that the line of action of springs 50 is below fixed pivot 54 when the movable contact 32 is down as in Fig. l and the line of action is above pivot 54 in Fig. 2 where the interrupter 2 is shown in opened position. Accordingly, when trip arm 35 is swung to an intermediate position, causing the line of action of springs 50 to coincide with a straight line between pivot 53 and 54, the mechanism is in toggle position whereupon further movement in one direction or another will cause contact rod 32 to be projected axially with a snap action.

One end of contact carrying link 53 is pivoted to a compensating link 56 pivoting on an anchor post 57 attached to the bottom of housing 33 by screw means. Link 56 executes an oscillatory movement which compensates for the circular displacement of the other pivots during operation of the mechanism and allows contact rod 32 to follow an unrestrained straight line movement.

Link 51 pivotally attaches to a trunnioned thimble 58 connected with contact rod 32. When contact rod 32 reaches its lowermost position, thimble 58 strikes a shock absorbing ring made up in laminar form of metal and rubber washers. Upward movement of rod 32 is arrested when thimble 58 strikes a similarly constructed shock absorber 6t? screwed onto the top of housing 33 as shown.

In order to avoid arcing when blade 6 is separated from its cooperating contact jaw 3 under load, a parallel path must be maintained through the interrupter to the hinge end of main switch 1. This is achieved by means of a by-pass rod 23 which forms a bridge between a V-slotted rod stop contact 65, secured to the top of metallic housing 33 and a hinge end of blade 6. It is preferable to make by-pass rod 23 of highly conductive material such as Phosphor bronze having some rigidity but enough resilience to augment electrical contact pressure with the rod stop when blade 6 is in closed position. Note that by-pass rod 28 bows slightly when the main switch 1 is closed as in Fig. l in order to enhance pressure on rod stop 65.

By-pass rod 28 is supported for rotation on trunnion 7 at the hinge end of the main switch 1 on spaced members as in the nature of a pair of bell cranks. The bell crank members 66 are spanned by tubular stringers 67 and 63 which are each drilled radially for passing by-pass rod 28 therethrough. Tubular stringers 67, 68 are also drilled at right angles to the rod 28 for receiving rod clamping set screws 69 and 70. Set screw 70 may be a socket head type. It is preferable, however, that set screw 69 extend beyond the margin of bell crank arm 66 and to provide the former with a jam nut 71 for fixing the adjustment of the screw with respect to blade guide 8- which strikes screw 63 when the 'by-pass rod 28 is carried back as in Fig. 2. V

Trunnions 7 are each surrounded, on an unthreaded portion, by a torsion spring 72 having one end bearing exerting a normally counterclockwise force on the-hook shaped short pressure arm 66' of bell crank member 66. It is evident that torsion spring 72 will supplement contact pressure between by-pass rod 28 and its cooperating rod stop contact 65 on the interrupter housing 33. The primary contact pressure for by-pass rod 28, however, is derived from a force transmitted to the short end 66 of bell crank member 66 by means of a stud pin 74 anchored in blade guide 8 and extending radially therefrom. The configuration of one stud pin 74 is clearly evident in Fig. 4 where its companion on the right hand side of that view is broken away. When main switch 1 is in closed position, an appreciable force from the switch closing mechanism is transmitted to the relatively stiff by-pass rod by means of stud 74 so that the rod 28 will make positive connection with rod stops 65 despite the presence of ice or any other contaminants which tend to increase contact resistance.

It is evident that when opening movement of main blade 6 is initiated, torsion spring 72 will maintain bypass rod 28 in good contact relation with rod stop contact 65 even though stud 74 will at that time begin to depart from the short end 66' of bell crank lever 66. When main blade 6 has swung through a predetermined angle, blade guide 8 strikes adjustable screw 69 and thereby positively carries by-pass rod 28 through a visibly open position as in Fig. 2.

Observe in Fig. 2 that stud pin 74 is free of short end 66' of the bell crank member 66 when the switch is fully opened. When closing switch 1, however, the angular spacing of the elements just mentioned is such that stud 74 will begin to increase the bearing pressure on by-pass rod 28 after it has been arrested by stop contact 65 on the interrupter but before trip arm 35 has been moved sufiiciently by blade extension 45 to close the interrupter. Hence, rod 28 makes high pressure engagement with stop contact 65 before the rod begins conducting during closing of switch 1.

An electric circuit may be interrupted under full load conditions by a novel structure just described in the following manner: Insulator 9 is rotated to initiate twisting and angular swinging movement of main switch blade 6, causing free end of blade 6 to separate from stationary contact jaw 3 and create an air gap therebetween, whereupon the main load current passes through the auxiliary load interrupter 2 and continues to the hinge end of main switch 1 through the agency of by-pass rod 28. As swinging movement of blade 6 is continued, blade extension rod 45 passes between cross rods 39 and 40 and strikes 39 carried by the interrupter trip arm. Continued swinging movement of blade 6 causes trip arm 35 to rotate in a counterclockwise direction while simultaneously stretching toggle spring 51) interiorly of housing 33. During this interval by-pass rod 28 remains stationary and in conductive relation with rod contact 65. As rotation of main blade 6 continues, spring 50 reaches its over-center position whereupon it exerts its full vertical component of force upon movable interrupting contact rod 32, thereby opening the latter with a snap action. All arcing takes place within the arcing chamber 31 because during this time circuit continuity in parallel with the gap created by opening switch blade 6 is maintained by by-pass rod 28.

After interrupter 2 has tripped, blade guide 8 continues its radial swing along with blade 6 until the guide strikes adjustable screw 69 driving the by-pass rod out of contact engagement with stop 65 and completely opening the circuit through the interrupter. This action proceeds until blade 6 has swung to more than 100, whereupon the maximum air gap is established between the interrupter, and blade 6 and by-pass rod 28.

Reclosing of main switch 1 is again accomplished by rotation of insulator 9 in an opposite direction about its axis. This causes blade extension 45 to precede by-pass rod 28 in a counterclockwise direction until extension 45 strikes the lowermost cross rod 40 of trip arm 35 as shown Fig. 2. Continued closing of the main switch rotates trip arm 35 in a clockwise direction and by-pass rod 28 comes down and makes contact with rod stop 65 before auxiliary interrupter 2 closes its circuit. Trip arm 35 closes interrupter 2 prior to the engagement of main blade 6 with its cooperating stationary contact jaw 3 so that the current takes the auxiliary path to load interrupter 2 before circuit continuity is established through main switch 1.

It is an important feature of the present invention that main switch blade 6 cannot be swung to a partially open position where it inadvertently trips the circuit interrupter open and then be restored to engagement with stationary contact jaw 3 while the interrupter 2 is open. This is so because blade extension rod 45 only engages trip arm 35 between one or the other of cross rods 39 and 40, so that once engagement with either of the cross rods is effected, trip arm 35 must positively follow the direction established by rotation of main blade 6. Accordingly, if main blade 6 is partially opened it can only be reclosed subsequent to reclosure of the parallel path through auxiliary load interrupter 2 and it is impossible to draw an are between blade 6 and stationary jaw 3 whether the switch is being opened or closed.

Although a preferred arrangement of the load interrupter has been described in conjunction with a particular form of air disconnect switch, it is to be appreciated that the interrupter may take alternative forms and that it is readily adaptable to a variety of prior art air disconnect switches of the rotating and twisting blade types. It is further apparent that the supporting base casting 24, for tubular porcelain bushing 29, may be easily bolted to any form of terminal adapter such as 4 here serving as an illustrative example. Likewise, the bell crank supporting member 66 for by-pass rod 28 may be conveniently adapted to any switch having a transverse axis of rotation for its main blade and by-pass rod 28 may also be mounted directly on a blade such as 6.

The hereinabove described preferred embodiment of the invention is not to be construed as limiting the invention for it may be variously embodied and is to be interpreted as claimed.

It is claimed:

1. The combination of an air disconnect switch and a load interrupter, said switch including a stationary jaw means and a cooperable switch blade, blade guide means in which said blade is journalled for rotation on its longitudinal axis, said guide means being pivoted on an axis transverse to the blade axis for swinging the blade through angular positions into and out of engagement with the jaw means, a load interrupter having its lower end in conductive relation with the jaw means and extending generally along the swinging path of the blade, a trip arm operatively and pivotally connected to said load interrupter near its upper end, said trip arm extending into the blade path for being engaged by the blade when the latter is in intermediate angular positions, a by-pass rod means releasably engageable with a portion of said interrupter more remote from the jaw than said trip arm, crank means pivotally supporting said by-pass rod means for swinging in the direction of the blade means about said transverse axis, said crank means including an extension arm means, driving pin means carried by the blade guide means in the path of said extension arm means and angularly spaced therefrom when said switch blade is angularly remote from said jaw, said driving pin means engaging said extension arm means for positively increasing pressure on said by-pass rod means when said blade means is between its intermediate angular position and engagement with said jaw.

2. The combination of an air disconnect switch and a load interrupter, said switch comprising a pair of spaced terminals, a jaw on one terminal, a blade hingedly mounted on an axis on the other terminal transverse to its own longitudinal axis for swinging the blade through angular positions into and out of engagement with said jaw, a load interrupter disposed outside the swinging path of said' blade, said interrupter having spaced terminals one of which is connected to said jaw and the other of which is remote from said jaw, a movable contact adapted to bridge said interrupter terminals, means for operating said movable contact including a trip arm extending pivvotally from said upper interrupter terminal into the path of said blade, a bypass rod means pivotally mounted on said other switch terminal, said rod means being biased for swinging with said blade toward engagement with said other interrupter terminal when said blade is in angular positions between engagement with said trip arm and said jaw, crank means pivotally supporting said by-pass rod, and driving means swingable with the blade" but in lost motion relation with the crank means when:

References Qited in the file of this patent UNITED STATES PATENTS Howe Jan. 7, 1941 Lingal Oct. 30, 1956

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