AU608370B2 - Pultruded or filament wound synthetic resin fuse tube - Google Patents

Description

1116 1.8-111- ZAXMAn1SNldONW1NrIH0:J3GD0V 'Id 8 068L99I176L zAxMAnsbdouwplw I !6ja p: o ZAXMAfilSdONWlfIHE H0R0D9V 'Id 01 SIII 1. 1.8 Ill i I1.25 1 i 116i I I I i I AU-AI-23155/88 PCT WORLD INTELL A P ORNIZ INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 89/ 01697 He1Hn38 sH fa1,o 04 0697 H01H 85/38 H01H 85/54 Al (43) International Publication Date: 23 February 1989 (23.02.89) (21) International Application Number: PCT/US88/02824 (72) Inventor; and Inventor/Applicant (for US only) RINEHART, Willi- (22) International Filing Date: 17 August 1988 (17.08.88) am, M. [US/US]; 304 South Collier, Centralia, MO 65240 (US).

(31) Pri rity Application Number: 086,535 (74) Agents: WILLIAMS, Warren, N. et al.; Hovey, Williams, Timmons Collins, 1101 Walnut, Suite 1400, (32) Priority Date: 18 August 1987 (18.08.87) Kansas City, MO 64106 (US).

(33) Priority Country:

US

(81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (Euro- Parent Application or Grant pean patent), FR (European patent), GB, GB (Euro- (63) Related by Continuation pean patent), IT (European patent), KR, LU (Euro- US 086,535 (CIP) pean patent), NL (European patent), SE (European Filed on 18 August 1987 (18.08.87) patent), US.

(71) Applicant (for all designated States except US): A.B. Published CHANCE COMPANY [US/US]; 210 North Allen, With international search report.

Centralia, MO 65240 (US).

This document contains the amendments made under Section 49 and is correct for printing (54) Title: PULTRUDED OR FILAMENT WOUND SYNTHETIC RESIN FUSE TUBE (57) Abstract Improved arc-suppressing fuse tube of the type used in electrical cutouts is provided which includes a filled epoxy resin matrix core designed, upon experiencing high temperature arcing conditions, to generate sufficient moisture and arcsuppressing gases to safely and efficiently interrupt an arc. The fuse tubes of the invention completely eliminate the use of expensive and difficult to fabricate bone fiber conventionally used in fuse tubes of this type. The preferred fuse tube construction is an integrated, synthetic resin body having an outer tubular shell including an epoxy fiberglass-reinforced synthetic resin matrix, together with an inner tubular arc-suppressing core having an epoxy resin matrix with respective quantities of an organic fiber and an inorganic filler therein. An anhydride curing agent for the epoxy is incorporated at an anhydride to epoxide ratio from about 1.0 to 1.4:1. The filler, aluminum trihydrate, makes up 40 to 80 by weight of the inner core and is operable to generate copious amounts of molecular water under arcing conditions. The organic fiber, present in an amount of from 5 to 30 by volume of the core, is either polyester or polyester plus rayon and pro,,ides a degree of structural reinforcement for the core during manufacturing. The fiber also aids in arc-suppression through the evolution of gaseous products. The fuse tubes of the invention may b pultruded as integrated, joint-free bodies of any convenient length.

A.O.J.P. 27 APR 1989

AUSTRALIAN

9 MiAi 1989 PATENT OFFICE WO 89/01697 PCT/US88/02824

I

PULTRUDED OR FIL-.MENT WOUND SYNTHETIC RESIN FUSE TUBE Background of the Invention 1. Field of the Invention The present invention is broadly concerned with improved, relatively low cost, synthetic resinbased arc-quenching fuse link tubes adapted for use with electrical cutouts or other similar equipment and which serve, under fault current-induced arcing conditions when the fuse link melts, to suppress the arc and thereby clear the fault. More particularly, it is concerned with such improved arc-quenching fuse tubes which include an inner wall segment formed of arc-quenching material, preferably comprised of an epoxy synthetic aresin formulation, e.g.

bis-phenol epoxy (BPA) or cycloaliphatic epoxy impregnated with an inorganic filler which generates molecular water upon being subjected to arcing conditions. The epoxy matrix is reinforced by provision of an _rganic fiber such as polyester, rayon or mixtures thereof that supports the resin during cure and contributes to arc interruption. The synthetic resin-based fuse tubes in accordance with the invention completely eliminate the use of conventional bone fiber as a lining material for fuse tubes, while at the same time giving equivalent or even enhanced arc-quenching results, as compared with bone fiber.

2. Description of the Prior Art The use of so-called bone fiber as a lining material for expulsion fuse tubes is well-established. The arc-interrupting operation of bone WO 89/01697 PCT/US88/02824 2 1 fiber in this context results from the fact that the material is a high density, cellulosic, exceptionally strong, resilient material which becomes a charring ablator in the presence of an electric arc.

As bone fiber decomposes under the intense arc heat, a char of carbonaceous material is formed in the tube, along with simultaneous production of a number of insulating and cooling gases. The exceptionally low thermal conductivity of the char layer protects the virgin bone fiber from excessive ablation hence rendering the tube reusable. The bone fiber is also somewhat hydrophilic in nature and the adsorbed water is also subject to decomposition to provide gaseous arc-interrupting products. The presence of the evolved gases, along with their turbulent intermixing with the arc, usually leads to a successful circuit interruption. It has been reported that over 90% of the decomposition gases from bone fiber consist of hydrogen and carbon monoxide. These materials are formed by a highly endothermic reaction of carbon with the water present in the bone fiber. Hence, it will be appreciated that the water content of the bone fiber not only provides endothermic cooling by evaporation, but also reacts with carbon to form arc extinguishing gases in the form of carbon monoxide and hydrogen.

As noted, an important characteristic of bone fiber is its tendency to absorb water; however, if atmospheric conditions are either too dry or too humid, the interrupting capability of bone fiber may be adversely affected. Hence, bone fiber is subject to an inherent variability depending in large measure upon uncontrollable ambient conditions.

The carbonaceous char formed when bone fiber interrupts an arc also acts as a thermal bar- WO 89/01697 PCT/US88/02824 3 1 rier to prevent excessive ablation of the bone fiber surface. Such ablation is controlled to a certain extent by by the endothermic events associated with the presence of a significant quantity of water, evaporation and reaction with carbon. The carbonaceous char layer must not, however, be too heavy or it will cause a restrike. As the moisture content in bone fiber goes down, more of the arcing energy is available for char formation, and hence the probability of a restrike increases.

While the use and operational efficiency of bone fiber is thus well known, a number of severe problems remain. In the first place, bone fiber is in short supply; only two reliable remain in the market and how long they will continue to do so is unknown. The material is difficult and time-consuming to make, and therefore is costly. Furthermore, it is produced only in certain standard lengths, and this inevitably means that there is substantial wastage when the tube lengths are cut for tube fabrication purposes.

In addition, a completed fuse tube employing bone fiber typically comprises an outer synthetic resin reinforced shell with the bone fiber secured to the inner portions thereof as a liner.

25 It is sometimes very difficult to properly adhere the bone fiber to the outer shell, and in most cases a weak mechanical bond is the best that can be accomplished.

Finally, it has been established that the expulsion forces generated by bone fiber during an arc interruption are considerable, and this in turn requires that the fuse assembly hardware holding the tube be relatively massive and hence expensive.

WO 89/01697 PCT/US88/02824 4 All of these drawbacks have made it clear that there is a real need in the art for an adequate replacement for bone fiber in the construction of arc-quenching fuse tubes.

Although there have been prior efforts to provide synthetic resin substitutes for bone fiber fuse tubes, the solutions suggested have not found significant commercial acceptance.

Canadian General Electric Company Limited has addressed the problem as discussed in Mattuck and Conte U.S. Patent Nos. 4,373,555 and Bergh U.S.

Patent No. 4,373,556. Both patents describe a cutout fuse tube in which a cycloaliphatic epoxy core is reinforced with polyester fiber to aid in arcquenching. The polyester fiber content is described as being at least about 45% by weight. The outer shell is either a cycloaliphatic or BPA epoxy formulation. Mattuck, et al. suggest that heat treating the polyester fiber may improve the mechanical and electrical characteristics of a fuse tube. The '555 patent to Mattuck, et al. also indicates that the composition may contain aluminum trihydrate (ATH) as a flame retardant. The concentration of ATH is limited to no more than about 15% by weight based on the minimum resin and polyester constituents that 2 must be provided to satisfy the requirements of the patentees' system. Although described as a flame retardant, ATH at that concentration would have very limited flame suppression characteristics and would contribute very little, if any, to arc extinguishment.

Tobin in U.S. Patent No. 4,349,803 discusses a fuse tube made from a cycloaliphatic epoxy resin that incorporates a melamine or dicyandiamide as an arc-extinguishing filler. Also the patentee teaches reinforcing the interface between the core and shell glass cloth, mat or strands under conditions such that the core and shell agents are said to flow into the reinforcing material during pressure gelation.

Summary of the Invention The present invention provides an arc-quenching fuse tube comprising an elongated tubular body having at least the inner wall thereof formed of an arc-quenching material, said material comprising an epoxy resin matrix including an epoxy resin cured in the presence of an anhydride curing agent, the matrix having an anhydride to epoxide equivalent of from 1.2:1 to 1.4:1; from 5% to 30% by volume of an organic fiber dispersed in said resin matrix, said organic fiber supporting go S: the epoxy during formation of the tube therefrom, and having 9 the function of forming arc-suppressing gaseous products during arcing within the tube; and an inorganic filler making S up from 40% to 80% by weight of the material and capable of generating molecular water under high temperature arcing conditions within the tube for reaction with carbon produced by decomposition of the epoxy resin and the organic fiber by such arcing to release gaseous products which serve to interrupt the arc.

S

S

OS S

S

4A WO 89/01697 PCT/US88/02824 reinforcing the interface between the core andh-e glass cloth, mat or strands under c nd ions such that the core and shell agentzs/--e said to flow into the reinforcing mat ei-aT during pressure gelation.

ary of the Invention The present invention overcomes the heretofore unsolved problem of providing an epoxy resin based fuse tube which has enhanced arc-quenching properties while exhibiting superior resistance to 1I erosion during interruption. As a result, the synthetic resin fuse tube has a significantly longer interrupting cycle life than existing resin fuse tubes. The synthetic resin matrix making up che improved fuse tube of this invention also incorporates a higher proportion of aluminum trihydrate (ATH) than heretofore deemed desirable. The ATH serves the dual function of decreasing the cost of the fuse tube but more importantly contributes molecular water to the interruption process which not only provide gaseous products to assist in arcinterruption but also lowers the temperature of the interruption gases to decrease heat degradation of the tube wall which would adversely affect fuse tube longevity. An organic fiber in the nature of a' polyester or the like is added to the resin formulation not only for the purpose of supporting the base resin system until it cures to self-sustaining form, but also to furnish additional gaseous products which assist in the arc-extinguishing process.

When rayon is included as an organic fiber, the hydrophilic nature thereof contributes additional molecular water for arc-extinguishing enhancement.

The shell of the fuse tube as well as the core thereof may be fabricated of either cycloali-

.A

17' WO 89/01697 PCT/US88/02824 6 phatic or BPA epoxy resins, with the core and shell of different epoxy resins, or of the same type. The anhydride used to effect curing of the core resin should be higher than that normally recommended and preferably present in a concentration such that the anhydride to epoxy ratio on the basis of anhydride equivalents to epoxy equivalents is at least about to 1.4:1. The ATH filler incorporated in the resin making up the core should be in the range of about 40% to about 80% on a weight basis of the total weight of the composition. Best results are obtained when an additional additive such as rayon is added to the formulation with the ratio of polyester fiber to rayon fiber being about 2:1 on a weight basis.

1Advantageously, the fuse tubes of the invention are formed with an outer tubular shell including an epoxy resin matrix reinforced with a fiber such as fiberglass. The inner tubular core disposed within the shell defines the arc-suppress- S ing region of the tube. The core most preferably comprises a thermosetting synthetic resin matrix such as a cycloaliphatic or BPA epoxy with respective quantities of the organic fiber and the filler therein. During manufacture of the shell and core, the resins are at least partially intermixed and are interreacted and cured together. In this fashion, the completed tube presents a joint-free body with an intimate fusion between the shell and core portions. In practice, it is contemplated that the fuse tube will be manufactured using pultrusion 3O? techniques in order to give a continuous, joint-free structure. In this context, the organic fiber of the preferred core system holds the latter in place during curing. In the outer shell portion, inor- WO 89/01697 PCT/US88/02824 7 1 ganic fiberglass fiber is preferred for reasons of strength.

While pultrusion production is believed to be the most efficient from a commercial point of view, those skilled in the art will understand that fuse tubes in accordance with the invention can be produced by a variety of other methods, such as filament winding or casting.

Description of the Preferred Embodiments As indicated above, the fuse tubes of the present invention are in the form of elongated, tubular bodies each having an inner core section and an outer shell section. The core section is made up of an organic synthetic resin matrix selected from the group consisting of the cycloaliphatic and BPA epoxy resins and mixtures thereof. BPA epoxy is the most preferred core resin. The purpose of the resin in the core is to hold and bond to the reinforcing fiber and fillers preferably employed therein, to supply organic material which in turn will generate arc-quenching gases, and to mix and react with the resin of the shell portion in order to give a fused, integrated tubular body. In view of the fact that the core resin should be chemically similar to that used in the shell, it is apparent that inorganic or semiorganic silane resins are not preferred as the core resin matrix. These silanes are known for their heat resistance, and therefore it is believed that they would not be as effective for arc-suppression.

Reactive diluents may be used in the core resin system to lower the viscosity thereof and thereby allow h'gher filler loadings along with efficiei~ct organic fiber wetout. Such reactive WO 89/01697 PCT/US88/02824 1 are known. For example, in epoxy resin systems, diluents such as butyl glycidyl ether, neopentyl glycol diglycidyl ether, vinyl cyclohexene dioxide (VCD) are useful. Such diluents are generally present at a level of up to 20% by volume in the core matrix.

The core matrix also contains a substantial amount of aluminum trihydrate (ATH, i.e.

hydrated aluminum) filler which is capable of generating molecular water under arcing conditions within the tube. The filler is generally present at a level of from about 40% to about 80% by weight of the core resin system, more preferably about 45% to by weight, and usually present in an amount of about 55% to 60% by weight.

Hydrated alumina (ATH) is well suited as a water source in the core resin system. The water of hydration is sufficiently bound so as to not cause problems during normal curing temperatures 300 0 but is released when needed at relatively high arcing temperatures. The preferred ATH filler contains about 35% by weight of water which is not released until temperature conditions of at least about 300 0 C are reached.

It has also been found that improved results are obtained if a stoichiometric excess of the anhydride hardener is used for the core epoxy resin of the fuse tube. The anhydride to epoxy ratio may be expressed using the formulas below based on parts of anhydride by weight per hundred parts of resin: Grams of Anhydride Anhydride Equivalents Anhydride Equivalent Weight Grams of Epoxy Epoxy Equivalents Epoxy Equivalent Weight Anhydride Equivalents Anhydride/Epoxy Ratio Epoxy Equivalents WO 89/01697 PCT/US88/02824 9 1 When the preferred BPA epoxy resin is used for fabrication of the fuse tube core, best results are obtained when the anhydride to epoxy ratio is maintained at a level of at least about 1.2:1. The ratio may be somewhat lower, about 1.0 to 1.1:1 when the less preferred cycloaliphatic epoxy resin is employed as the core matrix material.

Epoxy groups react not only with the anhydride but with OH groups present in the epoxy molecule. As a consequence, it is generally recommended i0 that less than a theoretical stoichiometric amount of anhydride be used for hardening of the epoxy because of the internal reactions that are known to take place. It is contrary to general practice to use a 20% greater anhydride to epoxide ratio because to do so would normally result in a deterioration of the product. It is accepted thought that the greater the anhydride ratio, the poorer the properties of the resulting epoxy resin. This is attributable to the fact that each time an epoxy radical reacts with an anhydride, an ester group is formed. The ester group is known to be the weakest chemical group in organic chemistry. A molecule therefore breaks first at the ester linkage. Furthermore, an ester linkage can be broken by almost any kind of stress whether it be UV, heat, electrical, or chemical in nature. This is the reason polyesters are not as strong as epoxies; a polyester may have 20% to ester groups in its backbone whereas an epoxy contains only 7% to 8% esters in the backbone. How- 30 ever, the ester composition of an epoxy is increased 3O with a concomitant lessening of the ester linkage stress resistance of the epoxy when the anhydride equivalent to epoxide equivalent ratio exceeds the i; L. WO 89/01697 PCT/US88/02824 /0 1 minimum amount required to effect hardening of the resin.

However, in the present instance wherein there is a need to provide a core for a fuse tube which will rapidly and efficiently suppress an arc while at the same time be sufficiently resistant to erosion so as to have a long useful life, it has be-n found that the desired rasult can be obtai ied by using a greater than recommended amount of anhydride for curing of the epoxy, even though to do so increases the ester linkages in the core material.

The first reaction that occurs when the arc interrupts is depolymerization of the core organic material. It is preferred that the depolymerization take place primarily as small molecular groups rather than large molecular entities. It is believed that the size of the molecular groups that break away from the tube wall and enter the arc plasma is determined largely by the anhydride equivalent to epoxide equivalent ratio. The smaller the molecular groups resulting from the depolymerization, the more energetic they are in the arc interruption process because of the greater incorporation of such groups into the plasma and the faster such incorporation takes place. These molecular fragments subjected to decomposition by the heat of the arc plasma make carbon available for reaction with molecular water furnished by the filler and from water contained in hydrophilic fibers making up a part of the inner core. The water-carbon reaction which takes place necessarily causes erosion of the inner surface of the tube core. The promotion of smaller organic resin fragments and the assurance of adequate water to quickly react therewith causes the surface of the core material exposed to the arc to E01l" Pr-, WO 89/01697 PCT/US88/02824 /1 1 be more rapidly erodable than would otherwise be the case, thereby cutting down on the total amount of erosion.

This seemingly antithetical result is theorized to occur because of the fact that two distinct reactions are taking place at the same time. One is the depolymerization or decomposition of the epoxy polymer which produces proportionately smaller molecular fragments; the second reaction is water split off from the ATH and furnished by the i0 rayon fibers. Water reacting with carbon from the molecular fragments produces hydrogen gas and carbon monoxide under high pressures which expand rapidly and extinguish the arc. All of this occurs at a sufficiently rapid rate that the arc is extinguished so early in the event that overall erosion of the core material is significantly decreased. Consequently, a faster erosion rate cuts down the total amount of erosion.

The supplemental organic fiber added to the core resin system is selected from the group consisting of polyester, rayon, acrylic, nylon, cotton and mixtures thereof. The fiber is generally present at a level of from about 5% to 30% by volume in the core system, and most preferably at a level of about 13% by volume of fiber therein.

Although the purpose of the organic fiber in the core is principally to hold the uncured resin in place during the curing process, the fiber also provides a certain amount of carbon for reaction 30 with water during the arc-quenching function of the core. Typically, organic fibers in the core will be present at a level of from about 5% to 30% by volume of the core system, for tubes produced by filament winding or pultrusion processes. Furthermore, matec~ ~ii WO 89/01697 PCT/US88/02824 1 rials such as rayon and cotton are cellulosic in nature' and therefore are very hydrophilic. These adaitives, therefore, contribute water for reaction with carbon to form arc extinguishing gases.

Inorganic fibers such as fiberglass actually inhibit the arc-quenching function of the core, although it may be used in moderate amounts in the core in conjunction with other more efficient arc extinguishers. Glass fibers may be used in this context because of their relatively low cost and strength properties.

The epoxy resin of the shell portion of the fuse tubes of the invention serves to hold and bond to the reinforcing fiber of the shell and to form a composite with sufficient stiffness and burst 1 strength to withstand the forces of arc interruption. Also, it is very advantageous to select a shell resin system which forms an integrated, fused body with the resin system of the core. Epoxy resins are therefore well suited for use in the shell portions of the fuse tubes of the invention.

Cycloaliphatic and BPA epoxy resins available from a variety of suppliers are especially well suited for use in the shell portion and the fuse tubes of the invention. The anhydride cured epoxies are of particular interest because of their high strength, long pot life and moderate costs. In such shell systems, the anhydrides would normally be used at an anhydride/epoxide equivalent ratio of from about 0.85 to 1.0. Anhydrides such as hexahydropthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophtalic anhydride, methyltetrahydropthalic anhydride and various blends thereof are preferred.

To aid in the cure of these anhydride-epoxy systems, an accelerator may be added such as benzodimethyl-

SAUSTRALIAN

9 AiAR 1989 PATENT OFFICE WO 89/01697 PCT/US88/02824 /3 1 amine, 2,4,6-tris (dimethylamino methyl) phenol, the

BF

3 complexes or the like. The level of accelerator in the shell system varies with the accelerator type and the desired speed of cure.

Fiberglass roving is the material of choice for use in reinforcing the shell matrix system. Any one of a number of commercially available fiberglass fibers could be used in this context.

In a preferred embodiment of the invention, the outer diameter of the core is nominally 3/4 inch, the OD of the overall tube is about 1 inch and the internal passage therethrough is about 1/2 inch.

EXAMPLES

The following examples describe the construction and testing of a number of fuse tubes in accordance with the invention. -It is to be understood that these examples are presented by way of illustration only, and nothing therein should be taken as a limitation upon the overall scope of the invention.

A number of test fuse tubes were constructed in the laboratory. In each instance, a 1/2 inch diameter polished steel winding mandrel having the outer surface thereof coated with a release agent was employed, and respective inner core and outer shell portions of the completed tubes were wound on the mandrel. Specifically, in each case, a core fiber was first passed through a quantity of the selected core synthetic resin formulation, whereupon it was wound onto the mandrel. Thereafter, the shell fiber fiberglass) was passed through the shell synthetic resin formulation, and was then wound over the previously deposited, resin- .1 yj In*Lai L LU u expuision Iuse tubes is well-established. The arc-interrupting operation of bone WO 89/01697 PCT/US88/02824 impregnated core fiber. The doubly wound product was then cured at 300 0 F for a period of one hour in order to form a fused, integrated tubular body. The outer diameter of the core section in each case was about 0.78 inch, whereas the outer diameter of the finished product was about 1 inch.

The cured tubular fuse tubes were then removed from the mandrel and a conventional aluminum-bronze tubular fuse tube casting was inserted into the upper ends of the test tubes. At this point, 6 amp fuse links were installed by passing the same upwardly through the fuse tubes until the washer element carried by the links engaged the bottom open ends of the tubes. The upper ends of the tubes were then closed using a standard threaded fuse link cap which also served to secure the fuse links within the tubes.

The completed fuse assemblies were then tested by individually placing them in an inverted condition casting end down) and attaching them to a compression strain gauge. The fuse link in each case was then electrically coupled to a high amperage source, and the link was severed by passing a fault level current (5,000 amps AC) through the link. This resulted in creation of high temperature arcing conditions within the test tubes, and the arc-quenching characteristics of the respective tubes were measured by determ-'.iing the number of cycles required to achieve complete interruption.

Each test tube was then re-fused and retested for a total of three interruptions.

Example 1 In this Example, various organic fibers were employed in the cores of the test tubes in i, u~ WO 89/01697 PCT/US88/02824 1 order to determine the arc interrupting capability of the fibers. In each case, the core synthetic resin formulation contained 75 parts by weight Epon 828 BPA epoxy resin (Shell Chemical 25 parts by weight of neopentyl glycol diglycidyl ether reactive diluent commercialized under the designation WC-68 by Wilmington Chemical Co.; 92.7 parts by weight of methyl hexa, methyl tetra, tetra and hexahydrophthalic anhydride blend sold by the ArChem Company of Houston, Texas under the designation ECA 100h; 1.4 parts by weight of DMP-30 anhydride accelerator (2,4,6-tris (dimethylamino methyl) phenol) sold by Rohm Haas Chemical Co.; 4.0 parts by weight of gray paste coloring agent; 1.0 parts by weight of a air release agent sold by BYK Chemie USA under the designation Byk-070; and 243.3 parts by weight of hydrated alumina (AC-450 sold by Aluchem Inc.). These materials were mixed in the conventional fashion to obtain a flowable epoxy formulation which gave a 55% by weight hydrated alumina filled formulation with an anhydride to epoxide ratio of The selected core fiber for each test tube was then run through the above described core resin formulation, and hand wound onto the mandrel. The S core fibers employed were interlaced polyester (745 yards per pound), interlaced rayon (617 yards per pound), interlaced nylon (624 yards per pound), spun cotton (795 yards per pound), interlaced acrylic (636 yards per pound) and spun acrylic (1,486 yards per pound). These fibers were obtained from Coats Clark, Inc. of Toccoa, Georgia.

The shell portion of the test tubes was then applied directly over the resin-impregnated core fiber. In each instance, the shell resin ile i~11 WO 89/01697 PCT/US88/02824 /i 1 contained 100 parts by weight Epon 828; 80 parts by weight of ECA 100h; 1.2 parts by weight of accelerator; and 3.6 parts by weight of gray paste.

The shell fiber was standard fiberglass roving commercialized under the name Hybon 2063 by PPG Industries. As described previously, the fiberglass roving was first passed through the shell resin whereupon the impregnated roving was wound onto the mandrel atop the core portion.

The results from the interruption tests with each of the test tubes are set forth in the following table: Table I Sample Fiber Cycles to Interrupt Number In Core Shot 1 Shot 2 Shot 3 1 Nylon 1/2 1 2 Cotton 1/2 3 Acrylic 1 3 4 Rayon 1/2 1/2 1/2 Polyester 1-1/2 1/2 2 6 Glass Did not clear no interruption These results demonstrate that the use of the various organic fibers in conjunction with a hydrated alumina-filled core resin formulation give acceptable arc interruption. The use of fiberglass in the core, however, yields an unacceptable fuse tube. It is believed that the presence of the inorganic fiberglass in the core interferes with the generation of requisite quantities of arc-suppressing gases within the tube.

i WO 89/01697 PCT/US88/02824 /7 1 Example 2 In this Example, three' separate test tube constructions were fabricated, with a replicate being made in each case for a total of six test tubes. The core resin formulation with respect to Samples 7 and 7a included 75 parts by weight Epon 828; 25 parts by weigh; of WC-68; 92.7 parts by weight of ECA 100h; 1.4 parts by weight of parts by weight gray paste; 1.0 parts by weight of Byk 070; and 243.3 parts by weight of chemically modified hydrated alumina sold by Solem Industries of Norcross, Georgia under the designation SB-36CM.

The formulation had an anhydride to epoxide ratio of The core resin for Samples 8 and 8a included 75 parts by weight of Epon 828; 25 parts by weight of WC-68; 102.0 parts by weight of ECA 100h; parts by weight of DMP-30; 4.0 parts by weight gray paste; 1.0 parts by weight of Byk 070; and 254.8 parts by weight of AC-450 hydrated alumina.

The formulation had an anhydride to epoxide ratio of 1.1.

The core resin for Samples 9 and 9a included 75 parts by weight of Epon 828; 25 parts by weight of WC-68; 111.3 parts by weight of ECA 100h; 1.7 parts by weight of DMP-30; 4.0 parts by weight gray paste; 1.0 parts by weight of Byk 070; and 266.4 parts by weight of SB-36CM hydrated alumina.

The formulation had an anhydride to epoxide ratio of 1.2.

The core fiber in each case was a 2:1 ratio of polyester to rayon. Application of this ratio of core fiber was accomplished by employing two spools of polyester with one spool of rayon, passing the respective fiber leads through the I ~Y WO 89/01697 PCT/US88/02824 appropriate core resin formulation, and application of the impregnated fiber onto the mandrel.

The shell resin formulation and fiber materials were identical to those described in connection with Example 1, and the method of final fabrication was similarly identical.

The results of this series of tests is set forth in Table II: Table II Sample Anhydride/ Cycles to Interrupt Number Epoxide Shot 1 Shot 2 Shot 3 7 1.0 3 1/2 1 7a 1.0 1/2 3 1/2 8 1.1 1/2 1/2 1/2 8a 1.1 3 1/2 1/2 9 1.2 1/2 1/2 1/2 9a 1.2 1/2 1/2 1/2 The results of this test show that arc interrupting efficiency may be increased by increasing the anhydride content of the core resin.

Example 3 In this series of tests, three separate tubes were fabricated, with a replicate for each tube. The purpose of the test was to demonstrate the effect of a combination of organic fiber and glass fiber in the core portion of the tubes. All core resin formulations were identical and were exactly as set forth with respect to Samples 7 and 7A of Example 2. The fiber portion of the cores are ~L 1-- WO 89/01697 PCT/US88/02824 /9 1 as set forth in Table III, the rayon/fiberglass ratio was varied from 3:0 to 1:2.

The outer shell portions of the respective test tubes were likewise identical and were fabri- S cated as set forth in connection with Example 1.

The test results from this study are set forth in Table III.

Table III Sample Rayon/ Cycles to Interrupt Number Glass Shot 1 Shot 2 Shot 3 3/0 1/2 1/2 1/2 10a 3/0 1/2 1/2 1/2 11 2/1 1/2 1/2 1/2 lla 2/1 NI 1 2-1/2 NI 12 1/2 NI 1/2 NI 12a 1/2 1 NI 1/2 NI no interruption As can be seen from Table III, as the amount of glass is increased in the core portion, interrupting efficiency decreases.

Example 4 In this series of tests, four test samples were prepared containing 45% and 50% by weight of hydrated alumina In particular, Sample 13 had a core resin formulation including 80 parts by weight of Epon 828; 20 parts by weight of vinyl cyclohexene dioxide reactive diluent (VCD); 105 PQSrt .LU11' 11 Ior- WO 89/01697 PCT/US88/02824 a0 1 parts by weight of methylhexahydrophthalic anhydride (MHHA); 1.6 parts by weight of DMP-30; 4.0 parts by weight of gray paste; 173.1 parts by weight of hydrated alumina; and 1.0 parts by weight of Byk- 070. The resin formulation contained 45% by weight

HA.

Sample 14 contained 80 parts by weight of Epon 828; 20 parts by weight of VCD; 105 parts by weight of MHHA; 1.6 parts by weight of DMP-30; parts by weight of gray paste; and 260 parts by weight of hydrated alumina. This formulation contained 55.2% by weight HA.

Sample 15 contained 44.5 parts by weight of CY-184; 5.5 parts by weight of VCD; 96.4 parts by weight of MHHA; 1.6 parts by weight of DMP-30; parts by weight of gray paste; 166.1 parts by weight of hydrated alumina; and 1.0 parts by weight of Byk- 070. This formulation contained 45% by weight HA.

The core resin of Sample 16 contained 94.5 parts by weight of cycloaliphatic epoxy resin sold by the Ciba-Geigy Corporation under the designation CY-184; 5.5 parts by weight of VCD; 96.4 parts by weight of MHHA; 1.6 parts by weight of DMP-30; parts by weight of gray paste; 249 parts by weight of hydrated alumina; and 1.0 parts by weight of Byk- 070. This formulation contained 55.1% by weight HA.

The shell resin consisted of 100 parts by weight of Epon 828; 80 parts by weight of MHHA; 1.2 parts by weight of DMP-30; and 3.6 parts by weight of gray paste.

The core fiber in each case was acrylic, whereas the same glass fiber described in previous examples was used as the shell fiber.

The results of this test are set forth in Table IV.

i WO 89/01697 PCT/US88/02824 1 Table IV HA 55% HA Sample Number Anhydride Shot Shot HA 55% HA Epoxide 1 2 3 1 2 3 13 14 0.91 1/2 1/2 3 2 1/2 3 16 0.91 1 1/2 1/2 1/2 3-1/2 1-1/2 Example A particularly preferred fuse tube in accordance with the invention is constructed as set forth above, and the core resin system contained parts by weight of Epon 828; 25 parts by weight of WC-68; 112 parts by weight ECA 100h; 1.7 parts by weight of DMP-30; 4.0 parts by weight of gray paste; 270 parts by weight of SB-36CM hydrated alumina; and parts by weight of Byk-070. This core resin matrix therefore includes 55.2% by weight hydrated alumina. The preferred organic fiber used with the above described core resin formulation is a 2:1 ratio mixture of polyester and rayon fibers.

The shell resin system used in this example contains 100 parts by weight of Epon 828; parts by weight ECA 100h; 1.2 parts by weight of S DMP-30; and 3.6 parts by weight of gray paste. The shell fiber preferred for use with this shell matrix formulation-is Hybon 2063 fiberglass fiber described previously.

Example 6 Effect of Anhydride/Epoxide Ratio and Polyester/Rayon Ratio on Cycles to Interrupt and Erosion Rate A series of fuse tubes were evaluated at 7.8kV and 5000 amps for the number of cycles to WO 89/01697 PCT/US88/02824 22 1 interrupt the arc and erosion rate. For these series of tests, the core was formulated with a BPA resin where anhydride/epoxide equivalent ratio in the core was varied from 1.0 to 1.2 and the ratio of polyester fiber to rayon fiber was varied from to 0/3.

The results obtained are tabulated in the table below. In this table, the following notations were used: An/EP Anhydride/Epoxide Equivalent Ratio in Core PE/R Volume Ratio of Polyester Fiber to Rayon Fiber NI Did not interrupt the arc TABLE VI The Effect of Anhydride/Epoxide Ratio Reactive Diluent WC-68 ATH Filler 55% WT. SB-36 0 ample 58A 58B 64A 64B 67A 67B An/EP PE/R 1.0 3/0 1.0 3/0 1.1 3/0 1.1 3/0 1.2 3/0 1.2 3/0 Cycles Shot 1

NI

1 1

NI

1/2 1/2 to Interrupt Shot Shot 2 3 1/2 1/2 1/2 Erosion Mils Per 1/2 Cycle 4.4 4.3 3.7 2.8 5.1 59A 1.0 2/1 3 1/2 1 4.6 59B 1.0 2/1 1/2 3 1/2 4.8 1.1 2/1 1/2 1/2 1/2 4.2 1.1 2/1 1 1/2 1/2 3.8 68A 1.2 2/1 1/2 1/2 1/2 4.3 68B 1.2 2/1 1/2 1/2 1/2 WO 89/01697 PCT/US88/02824 1 60A 1.0 1/2 NI 1/2 NI 1.0 1/2 1/2 1/2 1-1/2 4.6 66A 1.1 1/2 1/2 1/2 1/2 5.7 66B 1.1 1/2 1/2 1/2 NI 4.2 69A 1.2 1/2 1/2 1/2 1/2 69B 1.2 1/2 1/2 1/2 1/2 4.2 71A 1.0 0/3 1/2 1/2 1/2 9.8 71A 1.0 0/3 1/2 1/2 1/2 9.8 71B 1.0 0/3 1/2 1/2 1/2 12.8 Samples 58, 64 and 67 were made with only polyester fiber in the core. Although there were successful interruptions (within 1/2 cycle), these samples failed to interrupt in every shot tried. It was demonstrated that successful interruptions occurred as required when an excess amount of anhydride was used (An/EP 1.2:1).

Samples 59, 65 and 68 were made with a polyester fiber/rayon fiber ratio of 2/1. These samples were more effective at interrupting the arc.

Again, the samples with an anhydride/epoxide ratio of 1.2:1 performed the best, i.e. all interruptions were successful.

0 Samples 60, 66 and 69 were made with a polyester fiber/rayon fiber ratio of 1/2. These samples were all successful except for two interruptions at a normal 1:1 anhydride/epoxide ratio.

Sample 71 was made with all rayon fiber in the core and an anhydride/epoxide ratio of 11. All interruptions were successful; however, the erosion rate was quite high compared with the other samples, 9.8 to 12.8 versus 2.8 to 5.7 mils of erosion per 1/2 cycle.

C

WO 89/01697 PCT/US88/02824 1 In view of the higher cost of rayon fiber as compared with polyester, there is an economic advantage to maintain the rayon fiber content as low as possible. With cost as an important factor, the preferred formulation is sample 68 where the polyester fiber/rayon fiber was 2:1 and the anhydride/epoxide ratio was 1.2:1.

Claims (11)

1. An arc-quenching fuse tube comprising an elongated tubular body having at least the inner wall thereof formed of an arc-quenching material, said material comprising an epoxy resin matrix including an epoxy resin cured in the presence of an anhydride curing agent, the matrix having an anhydride to epoxide equivalent of from 1.2:1 to 1.4:1; from 5% to by volume of an organic fiber dispersed in said resin matrix, said organic fiber supporting the epoxy during formation of the tube therefrom, and having the function of forming arc-suppressing gaseous products during arcing within the tube; and an inorganic filler making up ~:om 40% to 80% by weight of the material and capable of generating molecular water under high temperature arcing conditions within the tube for reaction with carbon produced by decomposition of the epoxy resin and the organic fiber by such arcing to S release gaseous products which serve to interrupt the arc. S

2. The fuse tube of claim 1, said matrix being selected S from the group consisting of cycloaliphatic, bis-phenol A. epoxy, and mixtures thereof.

3. The fuse tube of claim 1 or claim 2, said organic fiber being selected from the group consisting of fibers of polyester, rayon, acrylic, nylon, cotton and mixtures thereof.

4. The fuse tube of zny one of claims 1 to 3, said inner wall having about 13% by volume of fiber therein.

The fuse tube of any one of claims 1 to 4, said filler Scomprising aluminum trihydrate.

6. The fuse tube of any one of claims 1 to 4, said filler S being hydrated alumina present in said matrix at a level of 0 about 45% to 70% by weight.

7. The fuse tube of any one of claims 1 to 4, said filler being hydrated alumina present in said matrix at a level of about 55% to 60% by weight.

8. The fuse tube of any one c claims 1 to 7, said epoxy resin having dispersed therein a reactive diluent, sa' diluent being selected from the group consisting of butyl glycidyl ether, neopentyl glycol iiglycidyl ether, vinyl cyclohexene dioxide and mixtures thereof. 39

9. The fuse tube of claim 8, said diluent being present at go0 0 0 be 0 0 a s C 25 a level of up to 20% by volume in said matrix.

The fuse tube of any one of claims 1 to 9, said organic fiber being a mixture of polyester and rayon fibers.

11. The fuse tube of claim 1, substantially as herein described in relation to any one of the Examples. DATED: 27 December, 1990. PHILLIPS ORMONDE FITZPATRICK ATTORNEYS FOR:- A.B. CHANCE COMPANY 5626i S *9 9* 9 9* 39 26 r 1411LX INTERNATIONAL SEARCH REPORT International Aoolication No PCT/US 88/0 2 8 2 4 1. CLASSIFICATION OF SUBJECT MATTER several classificaion symools apply, indicate all) 3 According to International Patent Classification (IPC) or to both National Classification and IPC IPC(4)HO1H 85/38 11 HO1H 85/54 U.S. CL: 337/186, 246, 273, 414 II. FIELDS SEARCHED Minimum Documentation Searched Classification System Cl n ymbols 428/36 138/140 337/142, 186, 246, 273, 414, 415 Documentation Searched other than Minimum Documentation to the Extent that such Documents are Included in the Fields Searched III. DOCUMENTS CONSIDERED TO BE RELEVANT 14 Category Citation of Document, I with indication, where appropriate, of the relevant oassages Relevant to Claim No. i1 A US, A, 3,979,709 (HEALEY) 07 SEPTEMBER 1976 1-17 (NOTE ENTIRE DOCUMENT). A US, A, 4,074,220 (SANTILLI) 14 FEBRUARY 1978 1 1-17 (NOTE ENTIRE DOCUMENT). A US, A, 4,312,100 (SCHMUNK) 26 JANUARY 1982 1-17 (NOTE ENTIRE DOCUMENT). A US, A, 4,373,555 (MATTUCK) 15 FEBRUARY 1983 1-17 (NOTE ENTIRE DOCUMENT). A US, A, 4,520,337 (CAMERON) 28 MAY 1985 1-17 (NOTE ENTIRE DOCUMENT). A,P US, A, 4,709,222 (MORITAL) 24 NOVEMBER 1987 1-17 (NOTE ENTIRE DOCUMENT). A US, A, 4,713,645 (RAZAVI) 15 DECEMBER 1971 1-17 (NOTE ENTIRE DOCUMENT). SSpecial categories of cited documents: 1 later document published after the international filing date "A doument definingthe eneral state of the art htch is not or priority date and not in conflict with the application but document de ofnin the gnerl stere oflv the ar ,htc not cited to understand the principle or theory underlying the considered to be of paicular relevance invention earlier document but published on or after the international document of particular relevance: the claimed invention iling date cannot be considered novel or cannot be considered to document which may throw doubts on priority claim(s) or involve an inventive step which is cited to establish the publication date of another document of particular relevance; the claimed invention citation or other special reason (as sDecified) cannot be considered to involve an inventive step when the document referring to an oral disclosure, use, exhibition or document is combined with one or more other such docu- other means ments, such combination being obvious to a person skilled document published prior to the International filing date but in the art. later than the priority date claimed document member of the same patent family IV. CERTIFICATION Date of the Actual Completlon of the International Search 3 Date of Mailing of this International Search Report s SEPTEMBER 1988 2 9NOV 1988 International Searching Authority I Signature of Au6orlzed Officer *o ISA/US D. J. LONE Form PCT/ISA/210 (second shet) (May 1986)