US3300608A - High power fuse with ceramic casing - Google Patents

High power fuse with ceramic casing Download PDF

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Publication number
US3300608A
US3300608A US495592A US49559265A US3300608A US 3300608 A US3300608 A US 3300608A US 495592 A US495592 A US 495592A US 49559265 A US49559265 A US 49559265A US 3300608 A US3300608 A US 3300608A
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United States
Prior art keywords
casing
fuse
cordierite
fuses
fissures
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Expired - Lifetime
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US495592A
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English (en)
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Rath Erich Werner
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Individual
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Individual
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Publication of US3300608A publication Critical patent/US3300608A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/04—Fuses, i.e. expendable parts of the protective device, e.g. cartridges
    • H01H85/05—Component parts thereof
    • H01H85/165—Casings

Definitions

  • the fuse When a fuse has passed maximum rated current for a long period of time, then, upon occurrence of a su-bstantial'overload or a short circuit, the fuse may heat to such an extent that a fuse body which already does have heat fissures ruptures and the now hot quartz sand flows out requiring bothersome cleaning. Removal of the remaining parts of the fuse body from the fuse holder, particularly if the parts are still hot, is very difiicult.
  • a fuse which has a casing which will not rupture even under the most severe operating or test condition, by forming the ceramic casing essentially entirely of sintered cordierite.
  • the cordierite should be dense, and, for certain applications, is preferably coated with a glazing, for
  • cordierite although it has only about half the tensile strength of steatite or other customarily used ceramic materials, has unusual and particular advantages as housings for fuses. Contrary to the prevailing view, that such housings must be formed of a material having the highest possible tensile strength, for example steatite, it has been found that the use of the cordierite as a material for the housing for casing of the fuse entirely avoids heat fissures in the body of the casing, and thus avoids the predisposition to rupture under operating, or test conditions.
  • Fuses having casings formed of steatite and sub jected to a test current for 30 minutes were found to fissure, even before thermal equilibrium has been reached; in contrast thereto, and with identical test conditions, fuses having housings formed of cordierite remained free of fissures long after thermal equilibrium has been 3,3btifi08 Patented Jan. 24, 1967 reached.
  • the substantially greater ability of cordierite housings to endure rapid temperature rises due to internal heating of the fusible link, without fissuring or rupturing, is equally advantageous in comparison with porcelain based fuses. It is thus no longer necessary to accept fuses with heat fissures even though they may meet some official test standards.
  • the cordierite substance of the fuse casing may consist of the known three or four component systems MgO-Al O -SiO and, if desired, further containing an alkali oxide additive as fourth component, to provide for self-glazing.
  • Fuse casings formed from cordierite which is compression sintered, so that it will not absorb moisture in its structure which might reduce the insulating properties, are particularly useful. Further, it has been found that the thermal resistivity is particularly high if the insulating material is sintered, that is fired, until glazing just about commences.
  • the four component system that is utilizing for example K 0 or Na O; MgO; A1 0 SiO for the casing of the fuse in accordance with the present invention, then it is preferably fireduntil self-glazing be gins.
  • the insulating body then has a smooth, glazed, glossy external coating. It does not require a separate glaze coating and a second firing is avoided.
  • FIG. 1 is an illustrative embodiment of a fuse having knife blade contacts
  • FIG. 2 is a longitudinal section through the ceramic casing of the fuse of FIG. 1;
  • FIG. 3 is a top view of the ceramic casing
  • FIG. 4 illustrates the fusible link without the casing in front view
  • 5 FIG. 5 is an end view of the link of FIG. 4.
  • Fusible link 5, illustrated in FIGURES 4 and 5 (FIG- UR'E 5 showing the link after rupture) is inserted in the housing as well known in the art, surrounded, if desired by quartz sand.
  • Metal covers 6 are secured to link 5 and assembled to casing 4, preferably by means of an intervening asbestos gasket 3.
  • Contact blades 1 are preferably welded to metal covers 6.
  • the entire assembly, that is metal covers 6, fusible link 5 and casing 4 are secured together by screws 2.
  • the usual length of the fuse casing 4 is between 2 and 3 inches.
  • cordierite casings for fuses are better than cases made of 'steatite; and that cordierite casings having a self-glaze outer coating are substantially superior to the unglazed cordierite casings.
  • Use of the self-glaze has the additional advantage that the smooth glazed surface represents a high surface resistance even in dirty or contaminated surroundings, without even requiring a further ad ditional step in the process of manufacture, mainly an additional glazing step.
  • the preferred self glazinlg cordierite material approximately within the following limits:
  • Example 1 Percent SiO 40 to 70 A1 20 to so .MgO 3 to 30 K 0 or a O 2 to 20
  • the material has the following composition:
  • Example 3 Percent SiO .52 A1 0 40 MgO 8
  • the firing temperature is the sameas for the self-glaze above, that is 1300 to 1340 C.
  • raw materials are used toproyide the supply of silicic acid, alumina, magnesia and alkali.
  • ka-olian, clay, steatite and talc are suitable, although the components may be added inthe form of oxide as for example salts which form, oxides during firing (for example chlorides and sulphates, etc.), hy-
  • the alkali is entirely or largely introduced as feldspar; alkali containing .fr-i'ts, or the like may also be used.
  • a similar favorable effect can be obtained, as is known, with four component'imaterials if the magnesium oxide is wholly or partly replaced by zinc oxide or beryllium oxide, or a mixture of the two.
  • Themagnesium oxide may also be replaced in part by calcium oxide, strontium oxide or barium oxide.
  • the firing and dense sintering or c0mpression sintering, up to theforrnation of the self glaze on the surface on the body, if desired, is done in accordance with known ceramic methods, in which the firing temperature, firing time, and oven atmosphere is controlled in accordance with the desired materials, so that, when glazing is desired, the glazing will form before the work pieces' begin to soften, or the expansion introduces diificulties.
  • Simple preliminary experiments in accordance with known ceramic techniques readily will show the correct conditions for various sizes and compositions of material.
  • An electrical fuse comprising a tubular casing; a pair of cover means, each, closing a respective end of said casing; a pair of terminal elements, each element extending from a respective end of said casing and beyond a respectivecover meansyfusible strip means inside said casing conductively connecting said terminal elements; said casing enveloping and being spaced from said fusible strip means; said casing being-composed essentially' of cordierite to withstand overload heating without developing cracks.
  • cordierite material is based on the composition including MgO A1 0 SiO 4.
  • saidcordierite material further includes an alkali oxide additive to provide for surface glazing.
  • cordierite material has the following composition:

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  • Compositions Of Oxide Ceramics (AREA)
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US495592A 1965-06-15 1965-10-13 High power fuse with ceramic casing Expired - Lifetime US3300608A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEST023980 1965-06-15

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US495592A Expired - Lifetime US3300608A (en) 1965-06-15 1965-10-13 High power fuse with ceramic casing

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US (1) US3300608A (enrdf_load_stackoverflow)
DE (1) DE1287682B (enrdf_load_stackoverflow)
GB (1) GB1077270A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5270679A (en) * 1993-02-08 1993-12-14 Gould Inc. Split end plate fuse assembly

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3228763C2 (de) * 1982-08-02 1993-10-07 Mueller Jean Ohg Elektrotech Hochspannungs-Hochleistungs-Sicherung

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE19449E (en) * 1935-02-05 Fuse box
US1991918A (en) * 1932-07-09 1935-02-19 Berchtold Margit Method of manufacturing blue glazed ceramic articles
US2302820A (en) * 1938-09-01 1942-11-24 Hartford Nat Bank & Trust Co Safety fuse for electric circuits
US2327972A (en) * 1939-01-17 1943-08-24 Lapp Insulator Company Inc High strength ceramic surface
US2337691A (en) * 1942-04-29 1943-12-28 Lapp Insulator Company Inc Method of making high strength ceramic surfaces
US3024303A (en) * 1960-03-09 1962-03-06 Ohio Brass Co Glazed insulator which comprises a ceramic body and a primary coat under the glaze which has a lower coefficient of thermal expansion than the ceramic body

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE19449E (en) * 1935-02-05 Fuse box
US1991918A (en) * 1932-07-09 1935-02-19 Berchtold Margit Method of manufacturing blue glazed ceramic articles
US2302820A (en) * 1938-09-01 1942-11-24 Hartford Nat Bank & Trust Co Safety fuse for electric circuits
US2327972A (en) * 1939-01-17 1943-08-24 Lapp Insulator Company Inc High strength ceramic surface
US2337691A (en) * 1942-04-29 1943-12-28 Lapp Insulator Company Inc Method of making high strength ceramic surfaces
US3024303A (en) * 1960-03-09 1962-03-06 Ohio Brass Co Glazed insulator which comprises a ceramic body and a primary coat under the glaze which has a lower coefficient of thermal expansion than the ceramic body

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5270679A (en) * 1993-02-08 1993-12-14 Gould Inc. Split end plate fuse assembly

Also Published As

Publication number Publication date
DE1287682B (enrdf_load_stackoverflow) 1969-01-23
GB1077270A (en) 1967-07-26

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