CA1097713A - Puffer circuit interrupter with fluorocarbon liner - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A single barrel puffer circuit interrupter is taught which has a thin fluorocarbon plastic liner for the single insulating barrel. The fluorocarbon plastic liner is polytetrafluorethylene (TFE) sold under the trademark TEFLON. The fluorocarbon plastic material is disposed in the form of a wound overlapped thin film. The film is etched so that an epoxy resin adhesive may be used for binding successive layers of the overlapping film one to the other and for binding the film to an outer sheel of fiber-glass which forms the remainder of the band. The fluori-nated plastic is generally resistive to the detrimental effects of the presence of an electric arc within the barrel of the circuit interrupter. Such effects include the heat of an electric arc, the current of the electric arc or the arc products which are formed by the use of sulfur hexa-fluoride gas in the puffer operation in the presence of the arc.

Description

CROSS-REFERENCE TO RELATED APPLICATION AND PATENT
This invention is related to those disclo~ed in U.S. Patent 4,144,426 issued March 13, 1979 and Canadian Application Serlal No. 295,977 filed January 31, 1978 both assigned to the assignee of the present application.
BACKGROUND OF THE INVENTION
Field of the Invention:
The sub~ect matter of this invention relates gen-erally to puffer circuit interrupters and relates more particularly to single barrel puffer circuit interrupters ~k ..

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~, lQ97713 46,910 with protective linings.
Description of the Prior_Art:
The use of double or multiple barrel puffer cir-cuit interrupters is well known. Such apparatus is des-cribed in U.S. Patent 3,659,065, issued April 25, 1972, to R. M. Roidt et al and entitled "Fluid Blast Circuit Inter-rupter With Delayed Moving Contact Travel", and U.S. Patent 3,814,883, issued June 4, 1974, to S. A. Milianowicz and entitled "Gas Blast Circuit Interrupter With Insulating Arc Shield". Both of the latter mentioned United States patents are assigned to the assignee of the present invention. In both cases two barrels are utilized in the puffer operation described therein. The first barrel is the main insulating and support barrel which generally encloses and protects the other barrel. The other barrel is a necessary part of a piston operated puffer mechanism. Because of the presence of an electrical arc during an interrupting opera~ion and the exposure of the electrical arc to a puffer gas such as sulfur hexafluoride, the opportunity for exposure of either of the barrels to the heat of the electrical arc, the arc products or the current of the electrical arc is relatively high. In addition, because of the presence of the sulfur hexafluoride gas within the main barrel of the circuit breaker interrupter and the presence of evolved gas during the arcing operation, the main or outer shell must be able to withstand relatively high gas pressure without rupturing.
It would be advantageous if a single shell puffer circuit breaker apparatus could be provided. In this case, the single shell would serve the dual purpose of support and electrical insulation on the one hand and be an integral 1 O g 7 7 1 3 46,910 part of the puffer apparatus on the other hand. In order for this to be effective however, the single barrel must have many favorable characteristics. It must act as a basic support member for the entire circuit breaker apparatus, it must act as an insulating member for spaced high voltage terminals, it must be relatively smooth on the inside there-of so that the piston action during the puffing operation is relatively friction-free, and it must resist the deleterious effects of arcing, especially the phenomenon known as "track-ing". Tracking is the well-known phenomenon of burning or charring certain insulating material during an exposure to an electrical arc which tends to lead to subsequent cata-strophic electrical breakdown or structuring weakening of the insulating substance. In the tracking phenomenon, carbon tracks are formed in an insulator, which tracks are potential paths for high voltage electrical breakdown. It was thought that a tube liner or shell constructed of fibrous materials, which was impregnated with resin and wound upon a mandrel until a satisfactory thickness had been obtained, and then overwound with impregnated fiberglass to form a relatively rigid tubular body would be appropriate for the above-mentioned purposes. It is known to form a single fiberglass reinforced tube, although this is not taught in an electrical circuit interrupter environment. Such a tube is described in U.S. Patent 3,733,228, which was patented May 15, 1973, by L. W. Heidelberg. It has been found though, that a fiberglass-resin tube without an internal shield is not sufficiently resistive to the deleterious effects of electrical arcing in the presence of sulfur hexafluoride gas. A corrosion resistant, glass reinforced plastic pipe 10977~3 46,910 liner is taught in U.S. Patent 3,939,873, issued February 24, 1976, to J. W. Rinker et al. However, the Rinker patent teaches the use of a relatively porous layer as the inner-most portion of the tube. This porous layer not only in-creases the friction of the puffer circuit breaker apparatus, but also is taught exclusively for the purpose of resisting the effect of corrosive materials. Utilization in an elec-trical environment is not taught. Polytetrafluoroethylene linings are taught in U.S. Patent 3,050,786, issued August 28, 1962, to A. N. T. St. John et al and entitled "Methods Of Lining And Jacketing Tubular Members With Prestressed Polytetrafluoroethylene", U.S. Patent 2,907,103, issued October 6, 1959, to D. R. Lewis et al and entitled "Method Of Making An Internally Lined Pipe" and the publication "The Journal Of Teflon", January-April, 1971, published by the Tr~) DuPont Company. All teach the utilization of "Teflon"~as a liner for an electrically conducting pipe. However, as was mentioned previously, an electrically conducting pipe would be wholly unsuitable in a circuit breaker environment where 20 an insulating support member is necessary. Furthermore, none of the latter-mentioned items teach the use of Teflon in the environment of a circuit breaker apparatus. A seam-less plastic inner lining for a flexible hose is taught in U.S. Patent 3,599,677, issued August 17, 1971 to P. W.
O'Brian. However, the basic structural material for the flexible hose is rubber material which, because of its inherent flexibility, would be wholly unacceptable as a structural support member for circuit breaker apparatus and which, because of its relative lack of strength, when com-30 pared to fiberglass, would be highly likely to rupture under 46,910 ~0~77i3 the presence of even moderate gas pressures. A plastic lined conduit is taught in U.S. Patent 3,369,426, which issued February 20, 1968, to A. S. Matz. The plastic lined conduit, however, is completely fllled with a mechanical control cable and it is obviously not intended to resist the effects of an electrical arc or gas pressure. Once again, none of the previously mentioned patents referred to utili-zation in a circuit breaker apparatus. Pipes are taught in U.S. Patent 3,002,534, issued October 3, 1961, to R. L.
Noland, and U.S. Patent 3,718,161, issued February 27, 1973, to C. W. Woodson. In general, both of the aforementioned patents teach some form of inner construction for an elongated pipe where the inner construction has substantial thickness when compared with the overall thickness of the pipe. In general, none of the aforementioned patents teach the utili-zation of electrical circuit breaker apparatus. Finally, the concept of utilizing a relatively thin layer of poly-tetrafluoroethylene material on the inner portion of a reinforced pipe is taught in U.S. Patent 2,783,173, issued February 26, 1957 to B. M. Walker et al, U.S. Patent 2,888,042, issued May 26, 1959 to A. N. T. St. John et al and U.S.
Patent 2,991,808, issued July 11, 1961 to H. A. Siegmann et al. All of the above-mentioned, though, are in the form of pipes for carrying or storing corrosive chemically active or solvent materials or the like. None of the above-mentioned patents teaches the utilization of a circuit breaker appar-atus. It would be advantageous, therefore, if puffer circuit breaker apparatus having a single barrel, which barrel serves the multiple purposes of providing a low function 30 internal surface, of providing electrical insulation between 46, glo terminals, of providing structural support and of being relatively unaffected by the presence of an electrical arc, arc products, or the heat of the electrical arc, could be provided.
SUMMARY OF THE INVENTION
In accordance with the invention, puffer circuit interrupter apparatus is taught which includes separable contact means for controlling the status of an electrical circuit and terminal means which are electrically intercon-nected with the contact means and the electrical circuit. Apuffer means is taught for providing arc extinguishing gas to the separable contact means during a circuit interruption operation for extinguishing, cooling or otherwise affecting the arc. Operating means are taught for causing the opera-tion of the puffer. A generally rigid, electrically insulat-ing vessel means having a relatively thin protective film of fluorocarbon plastic material on an interior wall thereof, is also taught. The latter vessel means withstands the pressure of the gas while the film resists electrical track-ing due to the current of the arc, or the hea~ of the arc orthe gaseous products caused by the arc. The fluorocarbon plastic material may comprise polytetrafluoroethylene (TFE).
A resin may be used as an adhesive for the film and its surrounding fiberglass support body. The resin may comprise a base of b~sphenol-A/epichlorohydrin in one embodiment of the invention or may comprise cycloaliphatic diepoxide in another embodiment of the invention.

` -46,719 46,910 10~7713 BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding Or the invention, reference may be had to the preferred embodiments thereof shown in the accompanying drawings, in which:
Figure 1 shows a pufrer circuit breaker apparatus partially in section, partlally broken away, and partially in block diagram form; and Figure 2 shows a broken away section Or a portion Or the interior wall Or the support and insulating cylinder for the circuit breaker apparatus Or Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and Figure 1 in particular, a single tube puffer ~ircuit interrupter 10 is shown. The pufrer circuit interrupter or circuit breaker 10 may include a hollow cylindrical insulating support tube 12, the purpose Or which will be described in more detail here-inafter. Support tube 12 has an electrically conducting terminal 14 on the left portion thereof and has an operating mechanism 16 on the right portion thereof as viewed in Figure 1. The insulating support tube 12 may be radially symmetrical about a centerline CL. A hollow, generally cylindrical electrical conductor 18 is shown in the left portion Or circuit breaker apparatus 10. The hollow con-ductor 18 is interconnected electrically with the termlnal 14 through a conducting cooler tube TUl, the purpose of which will be described in detail hereinafter. At the right end of the hollow electrical conductor 18 is an arcing contact piece 19 which may comprlse any suitable electri-cally con~uctive material which will withstand repeated 3~ arcing for a relatively long period of time for many opera-lQ97713 46,719 46,910 tions. Flexible main conducting fingers 20 are also con-nected to terminal 14 by way of cooler tube TUl. Inter-connected with the operating mechanism 16, shown schema-tically to the right of Figure 1, is a movable connecting rod 22, the use of which will be described more fully here-inafter. Disposed on either side (top and bottom as viewed in Figure 1) of the electrically insulating support tube 12 may be electrically conductive terminals 24. Each electri-cally conductive terminal 24 may be seated and sealed in an appropriate groove or seat 25 in the insulating support member 12. A portion of the electrically conductive ter-minal 24 protrudes through the insulating support tube 12 and is threaded into an internal connector and support piece 26 for securing the terminal 24 against the inside wall of the insulating support tube 12 in electrically conducting relationship with the internal conductor 26. Disposed on the internal conducting member 26 may be a plurality of electrically conducting flexible fingers 28 and at least one unidirectional gas valve 30. The use of the latter two elements will be described more fully hereinafter. Also disposed on the internal conducting member 25 may be a neoprene seal 32 or the like. The use of the neoprene seal 32 will be described more fully hereinafter with respect to other portions of the apparatus. A cooler tube TU2 is interlocked against the inside wall of the support tube 12 at 26a on the support piece 26. The use of tube 12 will be described more fully hereinafter.
There is provided a movable electrical contact assembly 34 which includes a generally cylindrical hollow electrically conducting tube member 36. The electrically -46,719 46,910 10~7713 conducting tube member 36 may be radially disposed symmetri-cally about the previously-described centerline CL. Dis-posed at the left end of the electrically conducting movable tube member 36 ls a conducting flange 38 having an extended electrically conducting portion 39 which is adapted to make sliding electrical contact with the previously described main contact fingers 20 when the puffer circuit breaker 10 is closed. Also disposed on the left portion of the hollow conductive tube member 36 may be flexible contact fingers ~0 which are complementary to the contact piece 19 described previously. On the right portion of the electrically con-ducting hollow cylindrical tube 36 is disposed a yoke 42 which is mechanically interconnected with the connecting rod 22 such that movement of the connecting rod 22 in the direc-tion 70 in response to an appropriate action in the oper-ating mechanism 16 will cause the entire body of the hollow conducting tube member 36 to move to the left to thus place the arcing contact fingers 40 in a disposition of overlap-ping electrical contact with the arcing contact 19 and to place the extended portion 39 of the conducting flange 38 in a disposition of electrical contact with the main contact fingers 20. It is to be noted that in this particular embodiment of the invention the relative longitudinal dis-position of the contact fingers 20, the extended portion 39, the contact piece 19, and the contact fingers 40 is such that electrical contact is made during a circuit breaker closing operation between the contact piece 19 and the contact fingers 40 before electrical contact is made between the contact fingers 20 and the extended portion 39. Like-wise5 in an opening operation, the contact fingers 20 and _g_ 46,719 46,910 ~097713 the extended portion 39 separate before the contact piece 19and the contact fingers 40 separate. The amount of overlap between fingers 40 and contact 19 is represented by D. The flngers 40 are joined at the roots thereof so that the inner regions of tubes 18 and 36 are sealed off from chamber 52 when the circuit breaker 10 is in the closed state. There is provided a neoprene seal 44 on the outer portion of the contact flange 38. The seal operates against the inner surface of the insulating support tJube 12 to thus locally isolate two gas pressure regions whlch will be described hereinafter. In a like manner, the previously described seal 32 operates against the hollow conducting tube 36 to locally isolate one of the previously described gas pressure regions from a third gas pressure region.
There may be disposed to the right of the elec-trically conducting cylinder 36 an opening 43 which provides communication between the internal portion of the hollow conducting tube 36 and the reglon surrounding the external portion of the hollow conducting tube member 36 to the right of the seal 32.
There is provided an arc nozzle 46, the right portion of which is disposed on the previously described conducting flange 38. Nozzle 46 is supported at the left portion thereof in sealed but movable relationship against the outer surface of the previously described hollow con-ductor 18. The seal 48 cooperates with the previously described-seal 44 to provide the first two previously des-cribed regions of different gas pressure during the opera-tion of the circuit interrupter apparatus 10. In a pre-30 ferred embodiment of the invention, nozzle 46 always remains 46,719 46,910 ~ 9 ~ i 3 in sealed relationship with tube 18 thus providing an arcshield between the arcing contacts 19 and 40 and the inner surface Or wall 12 during an arcing operation. On the lnternal portion of the arc noz~le 46 may be disposed a corrugated or ridged region 50 which provides high arc tracking resistance during the circuit breaker opening operation.
mere is provided a first gas pressure region 52 which may exlst between the seals 32 and the comblned eals 44 and 48. Gas pressure iæ built up in the region 52 during a circuit breaker opening operation as will be described more fully hereinafter. A second gas pressure region 53 may exist between the left end of the circuit breaker apparatus 10 and the combined seals 44 and 48. Openings 5~ disposed ln the coollng tube TUl provide paths Or communication between the latter region 53 and the internal portion Or the hollow conductor 18. A third gas pressure region may exist in the right portion of the circuit breaker apparatus between the seal 32 and the right side of tlle circuit breaker apparatus 10. The previously described open~ng 43 provides a path of gas communication between the internal portion of the hollow conducting tube 36 and the region 54.
.All of the latter described gas pressure regions contain gas of relatively different pressure during certain portions of the operating cycle of the circuit brea~er 10. The pressure in each case is related to the relative sizes of openings 51 and 43 for example. The relative gas pressures in the latter-named regions 52, 53 and 54 during opening and closing of the circuit brea~er apparatus provide the puffer action which will be described hereinafter. There is 46,719 46,910 ~0~ 3 provided in the conducting flange 38 an opening 56 which communicates with the previously described region 52 and with the internal portions of both of the hollow conducting members 18 and 36. The communicating path previously described is conveniently located such that the contact fingers 40 and the contact piece 19 are disposed therein during a circuit breaker opening or closing operation. The previously described flexible fingers 28 provide a path of electrical conduction between the movable hollow conductive tube 36 and the internal conductor 26. A source of elec-trical power S may be serially or otherwise connected with a load LD which is to be protected by the circuit breaker apparatus 10. Such an arrangement is shown schematically in Figure 1. The serial arrangement is interconnected with the terminal 14 and the terminal 24. Cooling tube TUl encloses a cooling mesh Ml through which hot gas following path 62 may exhaust radially into region ~3 by way of openings 51.
Likewise, cooling tube TU2 encloses a cooling mesh M2 through which hot gas following path 60 may be diffused laterally by way of opening 43. In the latter case, a deflector 22a is positioned on rod 22 to aid in channeling a portion of the gas in path 60 into the mesh M2 for lateral diffusion therethrough.

OPERATION OF THE PUFFER CIRCUIT

During the closing operation of the circuit breaker apparatus 10, the connecting rod 22 forces the hollow conducting tube 36 to the left as viewed in Figure 1.
Electrical continuity is maintained between the terminals 24 and the mo~ing conducting cylinder 36 by way of the internal 46,719 ~6,910 lQ"7713 conductor or connector 26 and the f~ngers 28. As the cylin-der 36 moves-to the left, the flange 38, the nozzle 46 and the contact flngers 40 also move to the left. me movement Or the flange 38 to the left causes the volume of the region 52 to enlarge, thus creating a local short term pressure differential between region 52 and regions 53 and 54 such that gas from region 54 moves through valve 30 by way of a channel 55 along the path 72 to region 52. Gas from regions ~3 and 54 may move into region 52 by way of opening 56 until portion 41 Or fingers 40 overlaps cor,tact 19 thus closing off orifice 56 from regions 53 and 54. This charges region 52 with puffer gas (SF6 for example) during the circuit breaker closing operation, it being understood that the unidirectional valve 30 opens to pass gas only in the direction 72 and closes to prevent gas from passing therethrough in the opposite direction. As the movable contact assembly 34 continues movement to the left, a posi-tion is reached where the contact fingers 40 make electrical contact with the contact piece 19 on the hollow conductor 18. A short time thereafter the extended contact region 39 makes electrical contact with the main contact fingers 20.
In this position the circuit which includes the load ~D and the source S is closed through the puffer circuit breaker 10 .
In a contact opening operation the contact rod 22 moves in the direction 57, thus causing the hollow conduc-tive tube 36 of the movable contact assembly 34 to move to the right. me main contact fingers 20 and the extended contact region 39 of the conducting flange 38 disengage first. Movement o~ the flang~ 38 and nozzle 46 ln the direction 57 through the distance D forces the trapped gas in the region 52 to become pressured by the reduction in volume in region 52. The latter movement through the region D is sometimes referred to as "lost motion" movement.
Eventually a point is reached during the contact opening cycle where the contact piece 19 of the generally stationary hollow conductor 1~ and the contact fingers 40 of the mov-able contact assembly 34 disengage under load or overload current or the like, thus generating an arc A. The pres-surized gas in region 52 follows path 5~ through opening 56 and is puffed or forced into the region of the arc A for quenching and cooling the arc A and for blowing the arc A
out from between the contact piece 19 and the contact fin-gers 40. The heated gas may then follow path 62 into the hollow conductor 1~, radially through the cooling mesh Ml, through the openings 51 of the tube TUl and into the region 53. Alternatively or concurrently the heated gas may follow the path 60 through the internal portion of the cylinder 36 and out through the holes 43 to be diffused laterally of the centerline CL through the mesh M2 and into the reg~on 54.
The relationship between the diameter of the orifice through the contact 19, the internal diameter of the tube 12, and the velocity of the piston 3~ are chosen so that the volume of space 53 increases appreciably faster than gas can flow into the space through the central orifice of the contact piece 19. The resu.lt is a reduction in gas pressure in the space 53 and an increase in the pressure drop across the central orifice of the contact 19, which increases inter-rupting ability.

After the arc A has been extinguished, the movable - 14 _ 10~7'713 contact assembly 34 continues movement to the right in the direction 57 until a stable opened position is reached. The puffer circuit breaker apparatus 10 is in this position ready for a closing or reclosing operation. After a time the pressures in the three gas regions 52, 53, 54 becomes equalized if such has not occurred earlier in the opening cycle. It is to be noted with respect to the arc A that the openings 56 in the conducting flange 3a provide a path whereby the arc current A may impinge upon the inner surface of the insulating support tube 12. In a like manner, the heat of the arc A may follow the same path and raise the temperature of the inner surface of the insulating support tube 12. Furthermore, the arc products produced by the interaction of sulfur hexafluoride gas for example and the electrical arc A may contact the inner surface of the insul-ating support member 12. These arc products may be carried along the path 62 or along the path 60 to the regions 53 and 54, respectively. The latter regions are adjacent to the inner surface of the insulating support tube 12. It is to be noted that direct radial exposure of the inner wall of tube 12 to arc A is prevented by the presence of the cone 46. In a like manner, since the gases are likely to be hot, the residual heat of the arc A even after cooling by the cooling meshes Ml and M2 may raise the temperature in the regions 53 and 54. It is also to be understood that the pressure of the accumulated gas within the interior of the insulating support tube 12 may increase, at least for a short time, during the arcing process because of the pres-ence of the arc products, for example. It is therefore desirous that the insulating support tube be relatively unaffected by the direct impinge_ 46,719 46,910 1 0 ~ ~ 1 3 ment of electrical current such as may exist in the arc A orby the presence of arc products or by the presence of the heat of the arc or by the presence of relatively high pres-sure gas for at least a short period of time.
Because of the unitary, i.e. single shell concept, the insulating support tube 12 must not only support most of the portlons of the circuit breaker apparatus 10, but must also act as an electrical insulator between terminals 24 and 14. The tube 12 must also act as a gas containing vessel heat shield and corrosion resistive vessel. Generally, it has been found that if the inner wall of the insulating support tube 12 becomes carbonized, blistering and flaking of the inner wall surface interferes with the mechanical functions of the interrupter, which of course is undesir-able. It has been found that a fiberglass tube alone will not resist carbonizing and the well-known tracking phenom-enon associated therewith. It has been found that the use of a thin polytetrafluoroethylene (TFE) liner for a fiber-glass main tube body resists tracking in the presence of the electrical arc, resists decomposition under the heat of the electrical arc, and resists decomposition under the influ-ence of the arc products of the electrical arc. In addl-tion, the substantial outer fiberglass support body resists rupture under the presence of the pressure of the various gases which are present either before or after the arcing operation.
It has been found that fluorinated polymers or fluoroplastic materials such as TFE work well in the pre-viously described circuit breaker apparatus. TFE lined tubes are constructed by first coating a steel mandrel with 46,719 46,910 1~13 either of two resin systems which will be discussed herein-after. At this point a five mll (.005 in.) TFE film, such as may be sold under the trademark CHEMPLAST, may be utilized.
The film ls etched on both sides to permit resin bonding. A
sodium based etching solution may be used for the etching purpose. The etched thin film is wound on the wet mandrel employing, for example, a 50% overlap to provide a two-ply liner. While the film is being wound, it is also being continuously coated with one of the two resin systems to be discussed hereinafter. The resin systems act as a bonding agent between the plies. In the preferred embodiment of the invention the total thickness of the completed liner is .010 inch.
By referring to Figure 2, in addition to Figure 1, it can be seen that the relatively thin layer of TFE film 64 forms the inner liner for the insulating support tube 12.
The remalning portion 66 (not shown to its full dimenslon relative to the thin film 64 in Figure 2) may comprlse type 30-E glass which is filament wound. The glass roving is wet wound using one of the previously described reslns over the TFE liner. A 60 helical winding pattern may be used in a - preferred embodiment of the invention. The layers of glass are built up until a wall thickness of 7/16 of an inch is achieved in a preferred embodiment of the invention. At this point the tube is gelled and cured, then after cooling, stripped from the winding mandrel.
As was mentioned previously, two resin systems have been found for use with the TFE lined, filament wound tube previously discussed. One of the resins is sold under the trademark DER 330. It is a bisphenol-A/epichlorohydrin 46,719 46,91Q
1 0 ~ ~ 1 3 base epoxy resin. Its desirable characteristics include hardness, toughness, and resistance to chemical attack. It also possesses high tensile and compressive strength, good chemical properties, and it adheres tenaciously to most ~aterials including etched TFE. It is also favorably suited to structural laminates, such as filament wound pipes and vessels. The formulation and cure schedule is shown below:
DER 330 - 70 parts by weight Diglycidylether of Neopentyl Glycol (DGENPG) -30 parts by weight p,p'-Methylenedianiline (MDA) - 27 parts by weight Gel 2 hours at 175F
Cure 2 hours at 212F plus 4 hours at 300F.
Another resin system which was found to be useful is sold under the trademark CY-179. This is a general purpose cycloaliphatic-diepoxide. When anhydride cured it features good electrical loss properties, arc and track resistance, and high heat deflection temperature. Another very desirable feature is its good resistance to weathering.
Even if the puffer interrupter is'to be protected from weather, in some instances dust and moisture may deposit on the outside surface of the single insulating tube 12 and electrical flashover between electrodes 24 and 14, for example, may occur. In these cases the cycloaliphatic resin is a distinct advantage because of its superior non-tracking performance. Formulation and cure schedules follow:
CY 179 - 100 parts by weight Hexahydrophthalic Anhydride (HHPA) -105 parts by weight Accelerator 065 (Ciba-Geigy) - 12 parts by weight 46,719 46,910 10~7~3 Gel 2 hours at 175F
Cure 4 hours at 300F.
The TFE lining, polytetrafluoroethylene, plays a number of important functions in the interrupter 10. The thermal stability of TFE is well known. The polymer does not melt, but rather cold flows at 620F and can be used ~2 7L"nC e ~/oos~ e 0~
~J continuously at 500F. Short timc~ at temperatures higher than 700F can be tolerated without the occurrence of car-bonization. TFE has good arc resistance qualities. Carbon tracks are not formed. The surface friction of TFE is low and its static friction is lower than its dynamic friction.
This is useful because the piston, i.e. seal 44, of the puffer rides against the inner wall of the tube 12. The latter piston comprises the conducting flange 38 with its seal 44. The products of arced sulfur hexafluoride do not react with TFE.
It is to be understood with respect to the embodi-ments of the invention that the relative thin lining of the tube 12 may be larger or smaller than 10/1000 inch as was cited in the illustrative example. The relatively thin film is necessary as a protective coating for the inner surface of the insulating support tube 12. It is also to be under-stood that the cylindrical relationships of the elements is not necessary. The tube 12 may be non-cylindrical or even angular in cross-section in other embodiments of the inven-tion. It is also to be understood that the basic operating characteristics of the circuit breaker are not limiting except to the extent that the single tube is utilized in close proximity to an arc, or to the heat of the arc, or the products or the arc, or the pressure caused by the arc in 46,719 46,910 ~097713 the presence of gas. It is also to be understood that the arrangement of the terminals of the apparatus is not limiting.
It is to be understood that the cooling materials Ml and M2 arC
may comprise wound copper mesh, but ~ not limited thereto in either material of geometry.

~0~7713 46, glo The apparatus taught with respect to the embodi-ments of this invention have many advantages. One advantage lies in the fact that the unique properties of TFE makes possible the single tube concept for this type of circuit interrupter. With the geometry and spacing of the inter-rupter as now extablished, a TFE lined tube appears to be the only practical material which can be used. All other materials tested have been found to be damaged by the arc energy. Damage from the arc energy could be avoided by making the tube much larger in diameter and thus removing the interior part of the tube from the region of highest arc energy, but this would result in a larger, more costly and more cumbersome device, which is undesirable.

Claims (9)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. Puffer circuit interrupter apparatus comprising separable contact means, terminal means electrically inter-connected with said separable contact means for placing said contact means in electrical circuit relationship with a cir-cuit, arc extinguishing gas, puffer means operable in con-junction with said separable contact means for controlling an electrical arc drawn on separation of said separable contact means during operation thereof by providing said arc exting-uishing gas to the region of said arc, operating means for causing operation of said separable contact means and said puffer means, and rigid electrically insulating vessel means having a thin film of fluorocarbon plastic material on an interior wall portion thereof, said separable contact means and said puffer means and said operating means and said gas being disposed within said vessel, said terminal means being disposed on said vessel, said puffer means cooperating with said vessel means during said operation of said contact means to provide said gas to said contact means, said interior wall portion being exposable to the electrical current of said arc and to the heat of said electrical arc and to said arc products and to the gas pressure of the combination of said gas and said evolved arc products, said fluorocarbon plastic material reducing friction between said puffer means and said interior wall, said fluorocarbon plastic material resisting electrical tracking therein in the presence of said heat of said arc and in the presence of said arc products and in the presence of said arc current, said vessel means containing the pressure of the combination of said gas and said arc products without rupturing, said fluorocarbon plastic material shielding the remainder of said vessel from said arc products and from said arc current and from a portion of the heat of said arc.

2. Circuit interrupter as claimed in claim 1 wherein said fluorocarbon plastic material chemically com-prises polytetrafluoroethylene (TFE).

3. Circuit interrupter as claimed in claim 2 wherein said fluorocarbon plastic material structurally comprises wound overlapping film.

4. Circuit interrupter as claimed in claim 3 wherein said film is etched and coated with thermosetting resin material for bonding said overlapping layers together.

5. Circuit interrupter as claimed in claim 4 wherein said thermosetting resin material comprises epoxy resin.

6. Circuit interrupter as claimed in claim 4 wherein said thermosetting resin material comprises diepoxy resin.

7. Circuit interrupter as claimed in claim 5 wherein said epoxy resin material is bisphenol-A/epichloro-hydrin based.

8. Circuit interrupter as claimed in claim 5 wherein said epoxy resin material is cycloaliphatic diepoxide.

9. A circuit interrupter as claimed in any one of claims 1, 2 or 3, in which insulating vessel means comprising an insulating tube means having first and second spaced external electrical terminal means thereon, said external terminal means communicating with the internal portion of said tube means, said insulating tube having the thin film of protective fluorocarbon plastic material on the interior wall thereof to protect said tube from arc effects, the first electrical contact means disposed within said tube means in electrical contact with said first external terminal means, the second movable contact means disposed within said tube means in electrical contact with said second external terminal means, said second contact means being movable into and out of contact with said first contact means, piston means fixedly disposed upon said second control means for movement therewith to compress puffer gas in a gas compression region, said piston means having an opening therein which communicates with an arc region between said first and second contacts, said puffer gas flowing through said opening into said arc region as said contacts open to effect an arc between said first and second contacts, and nozzle means fixedly disposed upon said second contact means and movably disposed upon said first contact means, said nozzle means at all times being radially interposed between said arc region and said interior wall of said insulating tube means to further protect said insulating tube means from arc effects.