US3401244A - Spring and shunt assembly for circuit interrupters - Google Patents

Description

P 10, 1958 c. c. PATTERSON 3,401,244

SPRING AND SHUNT ASSEMBLY FOR CIRCUIT INTERRUPTERS Filed Aug. 24, 1967 58 D: l I

United States PatentO 3,401,244 SPRING AND SHUNT ASSEMBLY FOR CIRCUIT INTERRUPTERS Calvin C. Patterson, Bethel Park, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 24, 1967, Ser. No. 663,021 8 Claims. (Cl. 337-178) ABSTRACT OF THE DISCLOSURE Background of invention In the construction of circuit interrupters for higher voltage, such as power fuses of the dropout type which include a conducting rod that is movable through an arcextinguishing means, such as a body of gas evolving material, a problem arises in providing a reliable means for actuating the movement of the conducting rod during arc interruption and a reliable means for actuating the dropout action of the circuit interrupter following arc interruption. In certain known interrupter structures of the type described, the movement of the conducting rod is actuated by an associated biasing spring and to initiate dropout action of the interrupter, the conducting rod includes an extension which is rigidly mounted on the conducting rod for movement therewith and which is actuated to move through at least a portion of the turns of the associated biasing spring to actuate the dropout action of the interrupter. It has been found in such known interrupter structures, the movement of the conducting rod which is required for both are interruption and for actuating the dropout action of the overall interrupter may be prevented by the jamming of the extension of the conducting rod with either the turns or the associated biasing spring or with flexible conductors which may be provided as part of a current path extending through the turns of the biasing spring. It has also been found that the turns of the biasing spring in known structures of the type described may tend to overlap during an interruption operation of the circuit interrupter to prevent proper operation of the interrupter or to cause damage to the turns of the spring to thereby prevent repetitive operations with the same biasing spring. It is therefore desirable to provide an improved circuit interrupter of the type described which includes a more reliable means for both actuating the movement of a conducting rod during an interrupting operation and to actuate the dropout action of the overall interrupter following arc interruption. It is also desirable to provide an improved circuit interrupter construction of the type described which may be either of the dropout or non-dropout type in which overlapping of the turns of the bias ing spring along 'with the consequent damage to'the spring is prevented during an interrupting operation.

Summary of invention In order to actuate the movement of the elongated conducting member, a helically coiled tension spring is connected between one end of the elongated conducting member and a movable spring seat which is slidably 3,401,244 Patented Sept. 10, 1968 mounted on a relatively stationary conducting member at one end of the casing and which is coupled to a separate tripping rod mounted inside of a tubular portion of the stationary conducting member. When the fusible means blows or fuses, the spring collapses at least partially to actuate the elongated conducting member during arc interruption and collapses fullyto actuate the movable spring seat and the tripping rod to thereby actuate dropout movement of the interrupter. Another feature of the invention relates to a circuit interrupter construetion of the dropout or non-dropout type including a spring having turns of a rectangular cross-section to prevent overlapping ofthe turns and damage to the spring during an interrupting operation.

It is an object of this invention to provide a new and improved high-voltage circuit interrupter construction.

Another object of this invention is to provide an improved means for actuating the dropout action of a power fuse.

A more specific object of this invention is to provide a common means for actuating movement of the conducting parts of the circuit interrupter during arc interruption and the release of a releasable latch means for a power fuse following arc interruption.

.A further object of this invention is to provide an improved means for preventing overlapping and consequent damage to the turns of the spring which actuates the movement of the conducting parts in a circuit interrupter during an interrupting operation.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a side elevational view of a high-voltage power fuse structure which embodies the principles of the present invention and which is shown in the normally closed operating condition;

FIG. 2 is an enlarged, longitudinal, sectional view of a fuse unit of the dropout type which forms part of the fuse structure shown in FIGURE 1 with portions of the end fittings of the fuse unit omitted; and

FIG. 3 is an enlarged, longitudinal, sectional view of a portion of a fuse unit of the non-dropout type which embodies certain features of the invention.

Referring now to the drawings, and FIGURE 1 in particular, the structure shown comprises a power fuse structure of the high voltage, dropout type, the general arrangement of which is set forth more fully in copending application Ser. No. 663,020 filed Aug. 24, 1967. By R. E. Frink and C. T. Walker which is assigned to the same assignee as the present application.

As illustrated in FIG. 1, the fuse structure 10 includes a base (not shown) formed of sheet metal and a pair of outwardly extending insulator supports 272 and 282. The upper insulator support 272 fixedly supports in position a latching assembly 250 which includes a break contact 252, as described in greater detail in the copending application just mentioned. A lower insulator support 282 supports a hinge assembly 260 which pivotally supports a fuse unit and which includes a hinge contact 262 which is mounted in a relatively stationary position on the lower insulator support 282, as described in the copending application just mentioned. As illustrated in FIG. 1, the fuse unit 100 serves to electrically bridge the break contact 252 and the hinge contact 262 so that electric current will normally pass therebetween by way of terminal pads (not shown) to which an external electrical circuit may be connected.

The fuse unit 100 includes a generally tubular fuse holder which is formed from a suitable weatherproof,

electrically insulating material, such as a filament wound glass epoxy material or the like, and a pair of upper and lower end fittings or terminals 34 and 36, respectively, which are disposed at the opposite ends of the holder 32 and which are formed from an electrically conducting material. The upper and lower end fittings or terminals 34 and 36, respectively, are securely fastened to the opposite ends of the associated holder or tube 32 by suitable means, such as cement and a plurality of pins which may pass transversely through both the end fittings 34 and 36 and the associated holder 32. As illustrated, the fuse unit 100 also includes a hook-eye 274 which is pivotally mounted on a laterally projecting portion 34A on the upper end fitting 34 and which may be utilized for effecting opening and closing movements of the fuse unit 100 by means of a conventional hook-stick. The lower end fitting 36 includes a hinge lifting eye 284 which may be formed integrally with the lower end fitting 36 and which may be employed in conjunction with a conventional hook-stick' to effect physical removal of the fuse unit 100 from the hinge assembly 260 for replacement of the fuse unit 100. The lower end fitting or terminal 36 also includes an inwardly projecting flange portion 36B against which the lower end of the holder 32 bears, as shown in FIG. 2.

The fuse unit 100 further includes a removable or refillable unit 20 which is mounted within the holder structure which includes the outer tube 32 and the upper and lower end fittings or terminals 34 and 36 respectively. The removable unit 20 includes its own supporting tube for insulating casing 108 which is formed from a suitable elec trically insulating material having sufiicient strength to withstand the internal gas pressures and intense heat which result during an interrupting operation of the fuse unit 100, such as a filament wound glass epoxy material. A body of gas evolving material, such as boric acid, which may include a plurality of generally annular blocks 122, 124, 126 and 128 is disposed inside the tube 108 and spaced from the ends thereof. Each of the blocks 122, 124, 126 and 128 include a relatively larger central opening and a relatively smaller opening at one side thereof, both of which extend axially through the individual blocks. When the blocks 122, 124, 126 and 128 are axially stacked in end-to end relation, as shown in FIG. 2, with the respective larger and smaller openings thereof substantially aligned, a main bore 130 is formed through the body of gas evolving or arc-extinguishing material which includes said blocks and a relatively small auxiliary bore 192 is formed through the body of gas evolving material.

In order to prevent the travel of ionized gases between the main bore 130 and the auxiliary bore 192 during an interrupting operation of the fuse unit 100 as described in greater detail in copending application Ser. No. 663,018, filed Aug. 24, 1967 by C. W. Upton, Jr. and J. A. Sensue, which is assigned to the same assignee as the present application, the meeting surfaces of the blocks 122, 124, 126 and 128 are structurally joined to one another around the relatively smaller openings of said blocks which form the auxiliary bore 192 by a sealing and bonding material having a relatively high dielectric strength, such as an epoxy resin. More specifically, as explained in the copending application just mentioned, the meeting surfaces of the blocks 122, 124, 126 and 128 each includes a groove or recess which extends substantially around and is spaced from the relatively smaller opening in each of said blocks and forms with the corresponding recess in the end of the adjacent blocks a larger passageway which is substantially filled with the sealing and bonding material, as indicated at 132 in FIG. 2. It is to be noted that the manner in which the blocks 122, 124, 126 and 128 are bonded to one another around the auxiliary bore 192 substantially prevents the entrance of the sealing and bonding material employed into either the auxiliary bore 192 or into the main bore 130.

In order to limit the gas pressures which result during an interrupting operation of the fuse unit 100 inside the tube 108 to a value within the rupture strength of the tube 100, as disclosed in greater detail in copending application Ser. No. 663,126, filed Aug. 24, 1967 by C. C. Patterson, which is assigned to the same assignee as the present application, each of the blocks 126 and 128 includes a generally C-shaped recess, as indicated at 129 in FIG. 2, which extends axially from one end of each of said blocks to a point which is adjacent to and axially spaced from the other end of the respective blocks, with each of the recesses terminating peripherally short of the portion of each of said blocks which includes the relatively smaller openings which form part of the auxiliary bore 192. Each of the blocks 126 and 128 therefore includes around a major portion of its inner periphery a frangible inner wall, as indicated at 126A and 128A, respectively, which is arranged to disintegrate when the fuse unit is called upon to interrupt relatively large currents and when the intense heat results within the main bore 130 and the gas pressure within the main bore 130 exceeds a predetermined value. During such an interrupting operation, the size or cross-section of the main bore 130 through the blocks 126 and 128 is effectively increased by the distintegration of the inner walls 126A and 128A of the blocks 126 and 128, respectively, to thereby 0 increase the size of the gas passageway and decrease or limit the gas pressure which would otherwise result.

In order to retain the blocks 122, 124, 126 and 128 in assembled relationship with the associated tube 108 as shown in FIG. 2, the outer surfaces of said blocks may be coated with a suitable cement or bonding material, such as an epoxy bonding material prior to assembly of the blocks inside the tube 108. In addition, a generally tubular or annular retaining member or plug 189 may be disposed at the upper end of the blocks 122, 124, 126 and 128 with the major portion of the retaining member 189 extending axially inside the tube 108. The retaining member 189 may be formed or molded from a suitable electrically insulating material having sufiicient strength to assist in retaining the blocks 122, 124, 126 and 12.8 in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, such as a glass polyester material. A washer 183 formed from similar material may be disposed between the retaining member 189 and the uppermost block 122, as shown in FIG. 2, and may be employed during the preassembly and bonding of the blocks 122, 124, 126 and 128 together prior to the assembly of said blocks inside the tube 108. It is to be noted that the retaining member 189, as well as the washer 183, includes a relatively larger central opening which forms an extension of the main bore 130 and a relatively smaller opening which forms an extension of the auxiliary bore 192.

In order to assist in retaining the member 189 in assembled relation with the associated tube 108 during an interrupting operation of the fuse unit 100, the outer surface of the retaining member 189 and the inner surface of the tube 108 at the upper end of the tube 108 include adjacent helical grooves which together form a passageway in which a helical wire 181 is disposed to firmly secure the retaining member 189 in assembled relation with the tube 108. The retaining member 189 may be assembled with the upper end of the tube 108 by first assembling the helical wire 181 in the helical groove around the outer surface of the retaining member 189 and then screwing the retaining member 189 into the upper end of the tube 108 to the final position shown in FIG. 2. It is to be noted that the outer surface of the retaining member 189 may also be coated with a suitable cement or bonding material, such as an epoxy bonding material to additionally secure the retaining member 189 to the tube 108.

In order to substantially prevent the escape of ionized gases from the upper end of the refillable or renewable unit 20 around the elongated conducting member 83 which extends through the main bore 130, a generally tubular member 185 is disposed in concentric or nested relation with the retaining member 189, as shown in FIG. 2, and is preferably formed from an electrically insulating material having a relatively low coefficient of friction, such as polytetrafiuoroethylene which is sold under the trademark Teflon. A shoulder portion 185A is provided at the upper end of the tubular member 185 and includes a central opening of reduced cross-section or size through which the conducting member passes and which forms a substantially gastight seal with the conducting member 83 during an interrupting operation of the fuse unit 100 when the conducting member 83 is actuated to move axially upwardly, as viewed in FIG. 2. The tubular member 185 also acts as a bearing to guide the axial movement of the conducting member 83. In order to prevent the tubular member 185 from being blown out of the upper end of the tube 198 during an interrupting operation of the fuse unit 100, the retaining member 189 includes an inner shoulder portion against which the upper end of the tubular member 185 bears as shown in FIG. 2. The escape of ionized gases from the upper end of the renewable unit 20 from the auxiliary bore 192 may be adequately prevented by reducing the size of the relatively smaller opening through the retaining member 189 through which the auxiliary conduc or 182 passes so that the cross-section of the auxiliary conductor 182 substantially fills the relatively smaller opening through the retaining member 189.

In order to further assist in retaining the blocks 122, 124, 126 and 128 in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, a generally tubular or annular retaining member 142 is disposed inside the tube 108 at the lower end of the blocks 122, 124, 126 and 128, as shown in FIG. 2, and is formed or molded from an electrically insulating material having sufiicient strength to assist in retaining the blocks 122, 124, 126 and 128 inside the tube 108 during such an interrupting operation, such as a glass polyester material. The outer surface of the retaining member 142 is preferably coated with a suitable cement or bonding material, such as an epoxy bonding material, prior to the assembly of the retaining member 142 inside the tube 108. This bonding material serves to secure the retaining member 142 to the inside of the tube 108. The retaining member 142 includes a relatively larger opening 142A which extends axially therethrough, into which the lower end of the main bore 130 opens and which may serve as an exhaust passageway for high pressure gases which result during the operation of the fuse unit 100. The opening 142 may also serve as ,a chamber in which the fusible means 160 is disposed. The retaining member 142 also includes a relatively smaller opening 142B which extends axially therethrough. The lower end of the auxiliary bore 192 opens into the opening 142B and the lower end of the auxiliary conductor 182 projects into the same opening. The insulating wall or partition 142C which is formed integrally with the retaining member 142 around the relatively smaller opening 142B through the retaining member 142 assists in preventing certain are products which may result during the operation of the fuse unit 100 in the relatively smaller opening 142B from being deflected into the relatively larger opening 142A of the retaining member 142 and impinging on parts of the fusible means 160. The retaining :member 142 also includes an up wardly projecting tubular portion 142D adjacent to the relatively smaller opening 1428 through the retaining member 142 with the projecting portion 142D being joined to the adjacent block 120A around a recess in the block 128 which is adapted to receive the projecting portion 142D by a flexible bonding material, such as silicone rubber. This joint between the retaining member 142 and the block 128 around the auxiliary bore 192 assists in preventing the travel or escape of ionized gases between the auxiliary bore 192 and the main bore 130 and between the auxiliary bore 192 and the relatively larger opening 142B through the retaining member 142 during an interrupting operation of the fuse at 100.

The elongated conducting member or rod 83 of the refillable unit 20 is normally disposed as shown in FIG. 2 to extend through the main bore with the upper end of the conducting rod 83 projecting axially beyond the upper end of the tube 108 and with the upper portion of the conducting rod 83 being externally threaded, as indicated at 83A. The conducting rod 83 is normally held in the position shown in FIG. 2 by a connection through the fusible means 160 to the generally annular or tubular lower conducting member or contact 150.

More specifically, the fusible means 160 comprises a strain element 162 and a fusible element or link 164. The upper end of the strain element 162 is secured by suitable means, such as brazing, to the lower end of the conducting rod 83, while the other end of the strain element 162 is secured by suitable means, such as brazing, to the connecting conductor or terminal 156 which is of the flat strip type. The connecting conductor 156 is secured, in turn, to the lower contact adjacent to the upper end of the lower contact 150 such as brazing. Similarly, the upper end of the fusible element or link 164 is secured to the lower end of the conducting rod 83 by suitable means, such as brazing, while the lower end of the fusible element or link is secured to the lower contact 150 adjacent to the upper end of the lower contact 159 by suitable means, such as brazing. It is to be noted that the strain element 162 and the fusible element 164 areelectrically connected in parallel between the lower end of the conducting rod 83 and the lower contact 150 of the removable unit 20.

Similarly, the auxiliary conductor 182 which is of a relatively smaller cross section or size compared with that of the conducting rod 83 normally extends through the auxiliary bore 192 with the upper end of the auxiliary conductor 182 extending axially beyond the'upper end of the auxiliary bore 192 and being both mechanically and electrically connected to the upper portion of the conducting rod 83 by a transversely extending spring pin 184. The pin 184 is disposed in a transversely extending recess or opening provided at the upper end of the retaining member 189 to prevent rotation of the conducting rod 83 after assembly of the rod 83 into the renewable unit 20. The upper end of the auxiliary conductor 182 may be formed as a loop which is assembled over the conducting spring pin 184 and retained thereon by the head 186 of the spring pin 184. The lower end of the auxiliary conductor 182 extends or projects into the relatively smaller opening 142B of the retaining member 142, as shown in FIG. 2, and is electrically connected through a helical conducting wire of reduced cross section as indicated at 194 to an angle-shaped auxiliary stationary terminal 157 which is secured to the tubular conducting member or contact 150 adjacent to the upper end of the member 150 by suitable means, such as brazing. The upper end of the helical wire 194 which is disposed inside the relatively smaller opening 142B is secured to the lower end of the auxiliary conductor 182 by suitable means, such as brazing, and the lower end of the helical wire 194 is secured to the auxiliary terminal 157 by suitable means, such as crimping or brazing, as disclosed in greater detail in copending application Ser. No. 663,127, filed Aug. 24, 1967 by C. W. Upton, Jr., C. C. Patterson and F. L. Cameron which is assigned to the same assignee as the present application.

The lower contact or conducting member 150 also includes an elongated arcing terminal 158 as disclosed in the copending application just mentioned which projects upwardly from the upper end of the contact 150 into the relatively smaller opening 1428 of the retaining member 142 to axially overlap the lower end of the auxiliary conducting member 182 with the lower portion of the arcing terminal 158 being disposed adjacent to and generally parallel to the axis of the helical wire 194. The arcing terminal 158 is electrically insulated along its length by a coating or film of electrically insulating material, such as an insulating enamel, which is provided on the arcing terminal 158 to prevent the electrical shorting out of the helical wire 194. The arcing terminal 158 which is formed from an electrically conducting material may be structurally secured to the upper end of the lower contact 150 at the inner periphery thereof by suitable means, such as brazing, or may be formed integrally therewith in a particular application. It is to be noted that the auxiliary current path which extends from the upper portion of the conducting rod 83, through the cross pin 184, the auxiliary conductor 182 and the helical wire 194 to the auxiliary terminal 157 on the lower contact 150 is also electrically connected in parallel with the conducting paths which include, respectively, the strain element 162 and the fusible element 164.

In order to assist in retaining the blocks 122, 124, 126 and 128 and the retaining member 142 in assembled relationship outside the tube 108, as well as for another important purpose, during an interrupting operation of the fuse unit 100, the lower tubular conducting member or contact 150 includes a main portion 152 which extends axially inwardly from the lower end of the tube 108 to bear against the lower end of the retaining member 142. The lower contact 150 also includes a flange portion 154 at the lower end thereof against which the lower end of the tube 108 bears when the conducting member 150 is assembled with the fuse tube 108.

In order to retain the lower contact 150, as well as other parts of the renewable unit 20, in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, a generally tubular external terminal member or ferrule 172 is disposed to telescope or extend axially over the lower end of the tube 108 In order to firmly secure the external terminal member 172 to the lower end of the tube 108, the internal surface of the external terminal member 172 and the external surface of the portion of the tube 108 adjacent to the member 172 include adjacent helical grooves which, when the parts are assembled, form a helical passageway in which a helical wire 173 is disposed. In the assembly of the external terminal member 172 on the lower end of the tube 108, the helical wire 173 may be first assembled in the helical groove on the lower end of the tube 108 and the external terminal member 172 may then be screwed onto the lower end of the tube 108 until the parts reach their final positions as shown in FIG. 2. In order to additionally assist in retaining the external terminal member 17 2 on the lower end of the tube 108, the outer surface of the tube 108 and the inner surface of the external terminal member 172 may be coated with a cement or bonding material, such as an epoxy bonding material, prior to the assembly of the external terminal member 172 on the lower end of the tube 108. It should be noted that the external terminal member 172 also includes an inwardly projecting flange portion 172A around a central opening 172 which bears against the adjacent flange portion 154 of the tubular conducting member 150 to assist in retaining the tubular conducting member 150 in assembled relation with the other parts of the renewable unit 20.

In order to form a current conducting path which extends between the lower end fitting 36 and the lower contact 150 of the renewable unit 20, the external terminal member 172 also includes an external flange portion 172C which bears against the inwardly projecting flange portion 36B at the shoulder 36C of the lower end fitting 36. The electrically conducting path thus formed extends to the lower contact 150 through the inwardly projecting flange portion 172A of the external terminal 172 and through the externally projecting flange portion 172C to the inwardly projecting flange portion 36B of the lower end fitting 36. The area of the current transfer path between the external terminal 172 of the removable unit 20 and the lower end fitting 36 may also be augmented by the contact ring 195 which may be formed of electrically conducting material and which is disposed to threadedly engage the internally threaded opening provided at the lower end of the end fitting 36 and to bear against the external terminal member 172 of the renewable unit 20 as shown in FIG. 2.

It is important to note that in order to prevent the concentration of relatively high potential stresses adjacent to the external terminal member 172 during an interrupting operation of the fuse at relatively high voltages, the upper end of the lower contact extends axially beyond the upper end of the external terminal member 172 toward the other end of the tube 108 a minimum distance to prevent such a concentration of relatively high potential stresses externally of the tube 108 adjacent to the external terminal member 172 as disclosed in greater detail in copending application Ser. No. 663,029 filed Aug. 24, 1967, by F. L. Cameron which is assigned to the same assignee as the present application.

In order to actuate the axial movement of the conducting rod 83, as well as that of the auxiliary conductor 182, during an interrupting operation of the fuse unit 100 and to electrically connect the renewable or refillable unit 20 just described to the upper end fitting or terminal 34, a spring and cable assembly 30 is disposed inside the outer holder or tube 32 between the renewable unit 20 and the upper end fitting 34. The spring and cable assembly 30 includes at its lower end a generally tubular conducting member or socket 84 having an internally threaded central opening, as indicated at 84A, to receive the upper threaded end 83A of the conducting rod 83. A lower spring seat member 86 which is also generally tubular in configuration includes a helically threaded outer surface and is fixedly mounted on the socket 84 for movement therewith by assembling the spring seat 86 over the outer surface of the socket 84 with the lower end of the spring seat 86 bearing against a shoulder provided on the outer surface of the socket 84 and with the upper end of the spring seat 86 being engaged by a plurality of portions of the socket 84 at the upper end of the socket 84 which serve to stake or secure the spring seat 86 on the socket 84. The spring and cable assembly 30 also includes a generally tubular upper spring seat 74 which includes a helically threaded outer surface and which is slidably disposed over the lower portion 60A of a generally cylindrical conducting member 60. As shown in FIG. 2, the lower portion 60A of the conducting member 60 projects axially inside the upper end of the outer holder 32. The integral upper portion 60B of the conducting member 60 extends axially through an opening 34B in the upper end fitting 34 and is externally threaded at the upper end thereof, as indicated at 60C. As illustrated, the generally cylindrical conducting member 60 may be secured to the upper end fitting 34 by an internally threaded end cap 44 which may be screwed down on the upper threaded portion 600 of the conducting member 60 until the flange portion 44A of the end cap 44 bears against the upper end fitting 34 around a flange or shoulder portion, as indicated at 34C in FIG. 2. A helically coiled tension spring 76 is secured at its upper end to the external, helically threaded portion of the upper spring seat 74 while the lower end of the spring 76 is secured to the external, helically threaded portion of the lower spring seat 86 to bias the conducting rod 83, as well as the auxiliary conductor 182, in a generally upward direction, as viewed in FIG. 2, away from the lower contact 150. It is important to note that each of the turns of the spring 76 is generally rectangular or square in cross-section to substantially prevent any overlapping of the turns of the spring 76 and the consequent damage to the spring 76 that might otherwise result during an interrupting operation of the fuse unit 100 and otherwise prevent the repetitive use of the spring 76. Since the turns of the spring 76 are not required to conduct electrical current during the operation of l the fuse 100, the turns of the spring 76 may be formed from a material having a greater mechanical strength and higher electrical resistance, such as stainless steel.

In order to electrically connect the renewable unit 20 and more specifically the conducting rod 83 of the renewable unit 20 to the upper end fitting 34 both prior to and during an interrupting operation of the fuse unit 100, a plurality of helically coiled flexible cables or conductors 82 are electrically and structurally connected at the bottom ends thereof to the conducting socket 84 into separate openings (not shown) provided in the socket 84 by suitable means, such as brazing or by staking, and at the.

upper end thereof are electrically and structurally connected to the conducting member 60 in separate openings provided in the lower portions 60A of the conducting member 60 by suitable means, such as brazing or staking. In order to increase the effective current transfer area between the conducting member 60 and the upper end fitting 34, a washer 54 formed of electrically conducting material may be disposed between the shoulder which is formed at the intersection of the upper and lower portions 60A and 60B, respectively, of the conducting member 60 and the shoulder which is formed inside the upper end fittings 34, as indicated at 34D, around the central opening 34B of the upper end fitting 34. Since the electrical resistance of the flexible conductors 82 is relatively much less than that of the spring 76, substantially all of the current which flows between the conducting rod 83 and the upper end fitting 34 both prior to and during an interrupting operation of the fuse unit 100 will flow through the flexible conductors 82 without producing any thermal stress in the turns of the spring 76. It is also to be noted that the flexible conductors 82 which are helically coiled will maintain a continuous electrically conducting path between the conducting rod 83 and the conducting member 60 during an interrupting operation of the fuse unit 100 substantially without any retarding effect on the rate of movement of the turns of the spring 7 6.

34E provided in the upper end fitting 34 as shown in FIG. 2.

In order to actuate the release of the latching assembly 250 shown in FIG. 1 following an interrupting operation by the fuse unit 100, a tripping rod or member having a generally cylindrical, elongated shape is slidably disposed inside a central opening or passageway 72 which is internally threaded at its upper end and which extends axially from a point which is axially spaced from the lower-end of a conducting member 60 to-the other end of the conducting member 60, as shown in FIG. 2. The upper end of the tripping rod 52 is normally positioned below the top of the end cap 44, as shown in FIG. 2. The lower end of the tripping rod 52 is fixedly coupled to the upper spring seat 74 for axial movement therewith by the cross-pin 56. The cross pin 56 passes laterally through aligned transverse openings provided in the tripping rod 52 and the upper spring seat 74 and through a pair of elongated slots 62 which are provided at the opposite sides of' the lower portion 60A of the conducting member 60 and which open into the central passageway or opening 72. The cross pin 56 is normally positioned at the lower ends of the slots 62, as shown in FIG. 2. In order to permit the axial movement of the tripping rod 52 upwardly through the end cap 44 following an interrupting operation of the fuse unit 100, the top of the end cap 44 includes a central opening 46 through which the tripping rod may pass to actuate therelease of the latching assembly 250 shown in FIG. 1. When the latching assembly 250 is released by the movement of the tripping rod 52, the upper end of the fuse unit 100 will be actuated to rotate in a clockwise direction, as viewed in FIG. 1, about the lower hinge assembly 260 to thereby provide an electrically insulating gap between the upper break contact 252 and the lower stationary hinge contact 262 by such dropout action.

In order to assemble the renewable unit 20 and the associated spring and cable assembly 30 into the outer holder 32, the threaded end of the conducting rod 83 is first screwed into the socket 84 at the lower end of the spring and cable assembly 30. A refill fusing tool (not shown) is then screwed into the internally threaded central opening or passageway 72 at the other end of the spring and cable assembly 30. The spring and cable assembly 30 is then inserted into the outer holder 32 with the upper end of the spring and cable assembly 30 being inserted first into the lower end of the outer holder 32, as viewed in FIG. 2, until the refill fusing tool (not shown) passes through the central opening 34B of the upper end fitting 34. By use of the refill fusing tool, the spring 76 is stretched and placed in tension until the cross pins 58 mounted at the sides of the upper portion 603 of the conducting member 60 are drawn upwardly through a pair of radial slots (not shown) provided in the upper end fitting 34 around the central opening 34B. The upper conducting member 60 and the spring and cable assembly 30 are then rotated until the pins 58 rest on the shoulder provided at the bottom of the enlarged opening 34E in the upper end fitting 34. The end cap 44 may then be screwed down on the upper threaded portions 60C of the conducting member 60 to further stretch the spring 76 to the final charged condition or position shown in FIG. 2 in which the cross pins 58 are drawn upwardly away from the shoulder in the upper end pin 34 at the bottom of the enlarged opening 34E. It is to be noted that when the spring and cable assembly 30 and the renewable unit 20 are assembled inside the outer holder 32 as just described, the cross pin 56 which couples the upper spring seat 74 to the tripping rod 52 to insure that the tripping rod 52 move axially with the upper spring seat 74 during an interrupting operation of the fuse unit is disposed at the bottom of the slots 62 at the opposite sides of the conducting member 60 to permit limited upward travel of the upper spring seat 74 along with the cross pin 56 and the tripping rod 52 to a final position of the tripping rod 52 in which the tripping rod 52 projects axially beyond the end cap 44 to release the latching assembly 250, as previously mentioned. The washer 54 also acts as a stop surface against which the upper end of the spring seat 72 bears to limit the upward travel of the tripping rod 52, the cross pin 56 and the spring seat 74.

In considering the operation of the fuse unit 100, it is to be noted first that the current paths which include, respectively, the strain element 162, the fusible element 164, and the helical wire 194, which is connected in series with the auxiliary conductor 182, are all electrically connected in parallel between the upper end of the conducting rod 83 and the lower contact at the lower end of the renewable unit 20. The resistance of the cur which includes the strain element 162 is relatively greater' than that of the path which includes the fusible element 164, the resistance of the path which includes the strain element 162 is relatively less than that of the path which includes the helical wire 194 so that when the fusible element 164 melts or blows, most of the current which was formerly carried by the fusible element 164 is then transferred to the strain element 162. In other words, when the current which is flowing through the fuse unit 100 increases to a value which is of suflicient magnitude and duration to melt or blow the fuse element 164, most l 1 of the current of which is flowing through the fuse unit 100 then transfers to the strain element 162. When the current which is transferred to the strain element 162 after the melting of the fusible element 164 is suflicient to melt or blow the strain element 162, the current which was previously carried by the strain element 162 is finally transferred to the current path through the auxiliary bore 192 which includes the auxiliary conductor 183 and the helical wire 194. When the strain element 162 melts or blows the conducting rod 83 is no longer restrained from upward movement under the influence of the biasing spring 76 and the conducting rod 83 and the auxiliary conductor 182 will start to move upwardly under the influence of the spring 76 to thereby stretch the helical wire 194 which is electrically connected to the bottom of the auxiliary conductor 182. It is to be noted that the stretching of the helical wire 194 permits limited travel of both the conducting rod 83 and the auxiliary conductor 182 while maintaining a continuous electric circuit or path through the auxiliary bore 192 and that as long as the current path which includes the auxiliary conductor 182 and the helical conductor 194 is intact, no arcing will take place in either the main bore 130 or an auxiliary bore 192. In other words, stretching of the helical Wire 194 during the initial movement of the conducting rod 83 and the auxiliary conductor 182 following the melting or blowing of the fusible element 164 and the strain element 162 will permit the formation of an electrically insulating gap in the main bore 130 while initially delaying the formation of a significant insulating gap in the auxiliary bore 192.

After the strain element 162 melts or blows as just described, and the conducting rod 83 and the auxiliary conductor 182 begin to move upwardly to thereby stretch the helical wire 194, the helical wire 194 will either fracture mechanically when stretched to its limit or the current transferred to the current path which includes the helical wire 194 and the auxiliary conductor 182 will be sufiicient to melt or blow the helical wire 194 which is of reduced cross-section compared to that of the auxiliary conductor or rod 182. After the helical wire 194 is melted or otherwise b roken, an arc will be initiated between the retreating end of either the broken helical wire 194 or the auxiliary conductor 182 and the terminal 157 or the arcing terminal 158, which axially overlaps the lower end of the auxiliary conductor 18 2, to thereby burn through the electrical insulation on the arcing terminal 158. Even after the wire 194 melts or is broken, the formation of a significant electrically insulating gap in the auxiliary bore 192 is further delayed by the overlapping of the auxiliary conductor 182 by the arcing termfinal 158 until the retreating free end of either the wire 194 or the conductor 182 passes the upper end of the arcing terminal 158 whose insulation will have burned through by this time. It is important to note that the insulating gap in the main bore 130 between the separated ends of the conducting parts will increase at a faster rate than the formation of an insulating gap in the auxiliary bore 192 due to both the delay in the formation of an arc in the auxiliary bore 192 because of the presence of the helical wire 194 and due to the overlapping of the auxiliary conductor 182 by the arcing terminal 158. "It is also important to note that the arcing which takes place in the fuse unit 100 during an interrupting operation will always take place initially in the auxiliary bore 192 as just explained. When the retreating end of either the helical wire 194 or the auxiliary conductor 182 passes the upper end of the arcing terminal 158, the arcing which takes place initially in the auxiliary bore 192 will cause gases to be evolved from the gas evolving material around the auxiliary bore 192 which will be un-ionized.

When the current to be interrupted by the fuse unit 100 is relatively low, such as 1000 amperes or less, and when the gas pressure of the evolved gases in the auxiliary bore 192 increases to thereby increase the corresponding 12" dielectric strength in the auxiliary bore 192, the insulating gap which is formed in the auxiliary bore 192 along with the corresponding increased dielectric strength, will be suflic'ient to interrupt the alternating current being interrupted following a particularly current zero in the auxiliary bore 192. The insulating gap which is formed simultaneously in the main bore 130 of the fuse unit at a relatively faster rate will have suflicient dielectric strength considering theinstantaneous potential difference between the separating conducting parts in the main bore of the fuse unit 100 to prevent a restrike of the arc in the main bore 130 for such relatively low fault currents. In other words, when any fault current is interrupted by the fuse unit 100, as just described, arcing will always be initiated in the auxiliary bore 192 and for relatively smaller fault currents, the arcing which results will be finallyinterrupted in the auxiliary bore 192. One important reason for this is that the dielectric strength of the main bore 130 at the time that the arc is finally interrupted in the auxiliary bore 192 will be relatively higher than that in the auxiliary bore 192 to prevent a restrike or breakdown of the :main bore 130 due to the instantaneous potential difference which exists or results between the separated conducting parts in the main bore 130 at the time of arc interruption in the auxiliary bore 192.

For relatively higher fault currents, the arcing which is initiated in the fuse unit 100 will still be initiated in the auxiliary bore 192 in the manner just described. For such relatively higher current faults, however, the gas pressure which builds up in the auxiliary bore 192 during an interrupting operation and the burning back of the separating conducting parts in the auxiliary bore 192 will result in a relatively higher dielectric strength in the auxiliary bore 192 compared with that in the main bore 130 between the separated conducting .parts in the main bore 130. If the instantaneous potential difference between the separate ends of the conducting parts in the main bore 130 is sutficient when the dielectric strength of the main bore 130 becomes relatively less than that of the auxiliary bore 192, the arc will restrike in the main bore 130 to thereby cause the evolution of un-ionized gases in the main bore 130 to thereby increase the gas pressure in the main bore 130, as well as the corresponding dielectric strength in the main bore 130. The are which restrikes the main bore 130 will be elognated both by the upward movement of the conducting rod 83 and by the burning back of the separated conducting parts in the main bore 130 to thereby increase the quantity of un-ionized gases evolved from the gas evolving material disposed around the main bore 130. The are in the main bore 130 will be finally interrupted following a particular current zero in the alternating current which is being interrupted when the insulating gap and the corresponding dielectric strength in the main bore 130 is sufficient to withstand the instantaneous potential difference between the separated conducting parts in the main bore 130. If the fault current which is being interrupted is of a relatively still higher magnitude, the gas pressure in the main bore 130 along with the intense heat which results may be sufiicient to disintegrate the inner walls of the blocks 126 and 128 to thereby limit the gas pressure of the evolved gases to a value within the rupture strength of the tube 108 as previously explained. It is to be noted that when the arc is interrupted in the main bore 130 as just described to thereby cause the evolution of gas from the gas evolving material in the blocks 122, 124, 126 and 128 which surround the main bore 130, the upward movement of the conducting rod 130 along with the upward movement of the auxiliary conductor 182 will he additionally accelerated by the force of the gas pressure of such evolved gases in the main bore 130 along with the force exerted on the conducting rod 83 by the biasing force of the spring 76.

During an interrupting operation of the fuse unit 100 as just described, when the con-ducting rod 83 is released and moved upwardly under the influence of the spring 76 or under the influence of both the spring 76 and the gas pressure of the evolved gases inside the renewable unit 20, the turns of the spring 76 which are normally held in tension will-tend to collapse toward a fully compressed condition but after the turns of the spring 76 partially collapse, the upper spring seat 74 will begin to slide axially on the lower portion 60A of the conducting member 60. The upper spring seat 74 will continue to slide axially on the'lower portion 60A of the conducting member 60 until the upper end of the spring seat 74 impacts or bears against the'washer 54 and the turns of the spring 76 reach a fully compressed or fully collapsed condition. During the initial partial collapse of the spring 76, the conducting rod 83 and the auxiliary conductor 182 will be actuated upwardly to finally interrupt the are which is formed either in the main bore 130' or in the auxiliary bore 192, as previously described. During the final collapse of the turns of the spring 76 and the axial movement of the upper spring seat 74 until the upper end of the spring seat 74 impacts against the washer 54, the tripping rod 52 will be actuated from the position shown in FIG. 2 until the upper end of the tripping rod 52 projects axially beyond the upper end of the end cap 44 to actuate the release of the latching means 250, as described in the copending application previously mentioned and in US. Patent 2,403,121 which issued July 2, 1946 to H. L. Rawlins et al. It is to be noted that a common spring 76 is employed in a sequential operation to first actuate the movement of the conducting rod 83 and the auxiliary conductor 182 which is required to accomplish arc interruption either in the main bore 130 or in the auxiliary bore 192 and then after arc interruption is accomplished to actuate the tripping rod 52 to thereby actuate the release of the latching means 250 and the dropout action of the fuse structure 10. It is also to be noted that the upward movement of the conducting rod 83 and the auxiliary conductor 182 will establish the electrically insulating gaps previously described between the separated ends of the conducting parts inside the renewable unit 20 during an interrupting operation. In addition, the fuse unit 100 will be actuated by the release of the latching means 250 by the tripping rod 52 to rotate in a clockwise direction about the lower hinge assembly 260 in a dropout movement to establish a larger electrically insulating gap between the break contact 252 and the lower stationary hinge "contact 262 of the fuse structure 10.

Referring now to FIG. 3 there is illustrated a modified fuse unit structure'300 which is intended for use in a nondropout application rather than in a dropoutapplica'tion' as 'is the fuse unit 100 previously described. In general the construction of the 'fuse unit 300 is similar to the fuse unit 100 previously described except that the fuse unit 300 does not include any means, such as the tripping rod 52, for actuating the release of a latching mechanism at the upper end of thefuse unit. Since-the lower portion of the fuse unit 300 is identical to the corresponding portion of the fuse unit 100 previously described in detail, only the upper portion of the fuse unit 300 will be described.

More specifically the fuse unit 300 includes a spring and cable assembly 330 which is disposed inside an outer holder 332 between a renewable unit which is identical to the renewable unit 20 previously described and the upper end fitting 334 of the fuse unit 300. The spring and cable assembly 330 includes -a spring 376 which is structurally identical to the spring 76 previously described with the lower end of the spring 376 being secured to a lower spring seat (not shown) which is identical to the spring seat 86 previously described. The upper end of the spring 376 is in the spring seat 374 and the lower portion 360A of the conducting member 360. The conducting member 360 in: cludes an upper portion 360B which passes through a central opening 334B in the upper end fitting 334 with the upper end of the upper portion 360B being externally threaded, as indicated at 360C. In order to secure the conducting member 360 to the upper end fitting 334, an internally threaded end cap 344 may be screwed down on the upper portion 360B of the conducting member 360 until a shoulder portion 344A of the end cap 344 engages a shoulder portion 334C of the upper end fitting 334. A pair of spring pins 358 may be disposed in associated openings provided in the upper portion 360B of the conducting member 360 to project laterally and to aid in the assembly of the renewable unit and the associated spring and cable assembly of the fuse unit 300' in the outer holder 332, as explained in detail in connection with the fuse unit 100. A washer 334 may be disposed between the shoulder which is formed at the intersection of the upper and lower portions 360B and 360A, respectively, of the conducting member 360 and the inwardly projecting flange portion of the upper end fitting 334, as indicated at 334D in FIG. 3.

In order to electrically connect the renewable unit (not shown) of the fuse unit 300 and the conducting member 360, a plurality of helically coiled flexible conductors 382 may be electrically and structurally connected at the lower end to openings provided in a conducting socket (not shown) which would be structurally identical to the socket 84 of the fuse unit while the upper end of the flexible conductors 382 may be electrically and structurally connected to associated openings (not shown) provided at the lower end of the lower portion 360A of the conducting member 362 by suitable means, such as brazing. It is important to note that the turns of the spring 376 are substantially rectangular or square in cross section to prevent overlapping of the turns of the spring 376 during an interrupting operation and the consequent damage that would otherwise result and prevent repetitive use of the spring 376.

The operation of the fuse unit 300 is similar to that of the fuse unit 100 previously described in detail except that during an interrupting operation the turns of the spring 376 would simply collapse or compress during an interrupting operation to actuate the movement of the conducting rod and the auxiliary conductor in the associated renewable unit which has a structure identical to the renewable unit 20 previously described without the spring 376 actuating the tripping rod, such as the tripping rod 52 which is provided as part of the fuse unit 100. In other words, the upper spring seat 374 would be fixed in a relatively stationary position during an interrupting operation and the turns of the spring 376 would simply fully collapse against the washer 354 during an interrupting operation. It is to be noted that the end cap 334 is fully closed in the fuse unit 100 since the central opening is not required to permit the passage of a tripping rod therethrough as in the fuse unit 100. It is also to be noted that the spring 376 in the fuse unit 300 similarly to the spring 76 of the fuse unit 100 carries only a negligible amount of current since the resistance of the flexible conductors 382 is relatively much less than the resistance of the material from which the spring 376 is formed which may have a higher mechanical strength and a relatively higher electrical resistance, such as stainless steel.

It is to be understood that the teachings of the applicants invention may be applied to power fuses for high voltage applications which do not include a tubular conducting member or shield, such as the lower contact shown in FIG. 2, but which instead employed a lower contact ring of the type disclosed in copending application Ser. No. 663,127 previously mentioned. It is also to be understood that a releasable end closure cap may be provided at the lower end of either the fuse unit 100 or the fuse unit 300.

The apparatus embodying the teachings of this invention has several advantages. For example, in the applicants construction, a common spring actuates both the movement of the conducting rod which is required for are interruption and also actuates a separate tripping rod to release an associated latching mechanism to accomplish dropout operation without requiring an extension of a conducting rod to move axially through the turns of an associated actuating spring, In addition, the turns of the actuating spring in the applicants construction are not required to conduct substantial current either before or during an interrupting operation of the associated fuse unit. A positive and continuous electric circuit is maintained between the conducting rod and the end fitting or terminal at the other end of the fuse unit by the helically coiled flexible conductors which permits substantially unhampered movement of the associated actuating spring and spring seat in the appllcants construction. A further advantage is that the applicants construction substantially prevents the entrance of moisture or other contaminating materials into the fuse unit at the upper end of the fuse unit where the release of the associated latching means is actuated by the tripping rod in the applicants construction. In one embodiment of the applicants invention, overlapping of the turns of the actuating spring is substantially prevented, along with the consequent damage the spring that might otherwise result and prevent repetitive operations of the actuating spring which is required for certain applications. Finally if the fault current which the disclosed fuse unit is called upon to interrupt exceeds the rating for which the fuse unit is designed, the dropout action will be initiated by the release of the tripping rod independently of arc interruption in the renewable unit of the fuse unit. In other words, an insulating gap will be established by the dropout action of the fuse unit independently of the magnitude of the fault current and even if the fault current which is involved is greater than the rating of the particular fuse unit to substantially prevent any internal arcing which might otherwise continue in the fuse unit.

Since numerous changes may be made in the abovedescribed apparatus, different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material disposed inside of and spaced from the ends of the holder and including at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the conducting member and one of the terminal means, -a generally cylindrical conducting member secured to the other terminal means and having a main portion projecting axially into the holder, a generally tubular'member slidably disposed on the main portion of the cylindrical conducting member, a spring connected between the other end of the elongated conducting member and the tubular member, a plurality of flexible, helically coiled conductors connected between the main portion of the cylindrical conducting member and the other end of the elongated conducting member, and means movably mounted on the cylindrical conducting member and coupled to the tubular member to be actuated by said spring when the fusible means blows for projecting axially beyond the other terminal means.

2. The combination as claimed in claim 1 wherein the cylindrical conducting member includes a central passageway which extends axially from a point which is spaced from the end of the cylindrical member which projects into the holder to the other end of the cylindrical member and a pair of axially extending slots at the opposite sides thereof which open into the central passageway, and the last-mentioned means comprises an elongated tripping rod disposed in the central passageway and coupled to the tubular member through the slots for movement with the tubular member under the influence of the spring when the fusible means blows.

3. The combination as claimed in claim 1 wherein the spring comprises a plurality of helically coiled turns and the plurality of coiled conductors are disposed inside the turns of the spring.

4. The combination as claimed in claim 2 wherein the spring comprises a plurality of helically coiled turns and the plurality of coiled conductors are disposed inside the turns of the spring.

5. The combination as claimed in claim 2 wherein a pair of vertically spaced, relatively stationary contacts is provided, means is provided for pivotally supporting the holder adjacent one end near the lower of the contacts to permit movement of said other terminal means into and out of engagement with the other contact, and a latch means is disposed adjacent to the other contact for releasably maintaining the holder in a closed circuit position with both of said contacts until actuated by said tripping rod to release the holder.

6. The combination as claimed in claim 5 wherein the spring comprises a plurality of helically coiled turns and the plurality of coiled conductors are disposed inside the turns of the spring.

7. The high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material inside of and spaced from the ends of the holder and in: cluding at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the elongated conducting member and one end of the terminal means, a helically coiled spring connected between the other end of the elongated conducting member and the other terminal means to actuate the movement of the elongated conducting member away from said one of the terminal means upon the fusion of the fusible means, said spring including a plurality of turns each having a rectangular cross-section.

8. The combination as claimed in claim 7 wherein the turns of the spring are each substantially square in crosssection.

References Cited UNITED STATES PATENTS 2,183,728 12/1939 Triplett 200- XR 2,247,704 7/ 1941 Triplett 200120 XR 2,403,121 7/1946 Rawlins et al 2001l7 2,502,992 4/1950 Rawlins et al. 200-120 XR 2,752,458 6/1956 Baker et a1 280-120 XR 2,976,381 3/1961 Lindell 200-120 3,184,568 5/1965 Fahnde 200120 BERNARD A. GILHEANY, Primary Examiner. H. B. GILSON, Assistant Examiner.

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