Classifications

• • 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
  • H01H85/055—Fusible members
  • H01H85/06—Fusible members characterised by the fusible material
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C13/00—Alloys based on tin
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H37/00—Thermally-actuated switches
  • H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
  • H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
  • H01H2037/768—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material characterised by the composition of the fusible material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H37/00—Thermally-actuated switches
  • H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
  • H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
  • H01H37/761—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material with a fusible element forming part of the switched circuit

Definitions

• This invention relates to fusible or low melting point alloys and, more particularly, to a ternary alloy suitable for use in the manufacture of thermal protective devices for electrical circuitry.
• fusible link comprising a length of a suitable low-melting alloy.
• Such links are subject to stringent temperature-time standards or, in other words, must be capable of melting rapidly at a specified temperature in order to drop out of and disrupt a circuit when critical conditions arise.
• a fusible link or the alloy from which it is made, to be suitable in every respect, must be characterized by rapid and substantially isothermal phase transition from solid to liquid.
• the alloy must possess satisfactory mechanical strength and good resistance to the formation of surface films (occurring primarily through the agency of oxidation), such that the desired response to critical temperature changes remains unimpaired.
• an alloy in order to be satisfactory in use as a fusible link, must remain substantially solid with limited expansion or contraction until the temperature in its operative environment reaches a predetermined point. At that time, the alloy must transform rapidly and substantially isothermally to the liquid phase, dropping out of circuit and thus disrupting the latter.
• the temperature range over which an alloy melts may be termed a function of the variation as between the crystallization rates of the components elements, while the phase transition time may be stated as a function of the various crystallization rates considered together with the latent heat of fusion of the particular composition.
• the melting point of an alloy bears no apparent relationship to the individual melting points of its components and, similarly, it is extremely difiicult to predict, with any accuracy, the numerical value of latent heat of fusion of an alloy merely by reference to the characteristics of the individual elements involved.
• Copper was found to provide a definite decrease in melting point while silver has an even more desirable effect.
• metallographic examination of a sample of the new alloy revealed a substantially homogenous structure over the entire cross-section, indicative of a eutectic or near-eutectic composition.
• the true eutectic is the most preferred composition when one considers the desirability of a pure isothermal transition, but observation has established that for the purpose in question, the alloy may be comprised within the approximate composition given and still melt at a temperature in the prescribed area.
• a fusible link manufactured from the novel material proved to have satisfactory mechanical strength for its purpose and exhibited good resistance to surface film formation (oxidation).
• the new ternary alloy of In- Sn-Ag is eminently suitable for use in the manufacture of fusible links while additions of about 0.17% copper to the In-Sn eutectic result in an alloy suitable for use under present regulations, having an M.P. of 1l7.6 C. :1" C.
• the ternary fusible alloy according to the present invention can be processed to any desired configuration for use as a fusible link.
• any desired configuration for use as a fusible link.
• such use is not intended as being exhaustive of the overall utility of the alloy.
• Pat. No. 3,354,282 reveals a thermal fuse with capillary action in which the molten fusible link will separate reliably and completely under any practical service conditions, in any position, and after long, useful life.
• a tubular sleeve Enclosed within a tubular sleeve is a fusible link and a means attached to each end of the fusible link for providing capillary action on the molten fuse link so that when the fusible link melts upon increase of the environmental temperature beyond its melting point, the molten material is withdrawn into the capillary means thus en suring that the current flow in the electrical lead is entirely interrupted.
• a ternary fusible alloy comprising a substantially eutectic composition of ln-Sn with the balance made up of silver.
• a ternary fusible alloy having a composition of about 51.4% In, 47.3% Sn, and 1.3% Ag, characterized by a melting point of 113.811 C.
• a ternary fusible alloy as recited in claim 1, wherein the composition is chosen to have the lowest possible melting point, which is approximately 114 C.
• a ternary fusible alloy as recited in claim 1, wherein a sufiicient amount of silver is added to the ln-Sn to lower its melting point below the 117 C. minimum melting point of an In-Sn eutectic.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Fuses (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=4083945

Family Applications (1)

Country Status (6)

Cited By (9)

Families Citing this family (1)

• 1967
  • 1967-12-16 CA CA868830A patent/CA868830A/en not_active Expired
• 1968
  • 1968-12-10 FR FR1594275D patent/FR1594275A/fr not_active Expired
  • 1968-12-12 DE DE19681814107 patent/DE1814107A1/de active Pending
  • 1968-12-13 US US783764A patent/US3627517A/en not_active Expired - Lifetime
  • 1968-12-13 NO NO4993/68A patent/NO120655B/no unknown
  • 1968-12-16 GB GB59666/68A patent/GB1244186A/en not_active Expired

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