EP0302568A2 - Herstellungsverfahren für eine gekapselte Sicherung und eine derart hergestellte Sicherung - Google Patents

Herstellungsverfahren für eine gekapselte Sicherung und eine derart hergestellte Sicherung Download PDF

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Publication number
EP0302568A2
EP0302568A2 EP88201669A EP88201669A EP0302568A2 EP 0302568 A2 EP0302568 A2 EP 0302568A2 EP 88201669 A EP88201669 A EP 88201669A EP 88201669 A EP88201669 A EP 88201669A EP 0302568 A2 EP0302568 A2 EP 0302568A2
Authority
EP
European Patent Office
Prior art keywords
fuse
housing
terminal means
subassemblies
inner housing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP88201669A
Other languages
English (en)
French (fr)
Other versions
EP0302568A3 (de
Inventor
William Sexton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Littelfuse BV
Original Assignee
Littelfuse Tracor BV
Littelfuse BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Littelfuse Tracor BV, Littelfuse BV filed Critical Littelfuse Tracor BV
Publication of EP0302568A2 publication Critical patent/EP0302568A2/de
Publication of EP0302568A3 publication Critical patent/EP0302568A3/de
Withdrawn legal-status Critical Current

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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
    • H01H85/165—Casings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H69/00—Apparatus or processes for the manufacture of emergency protective devices
    • H01H69/02—Manufacture of fuses
    • 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
    • H01H85/17—Casings characterised by the casing material

Definitions

  • the present invention relates to improvement in electrical fuses, particularly to miniature cartridge fuses where, typically, the fuse blowing conditions have heretofore required ceramic fuse housings to prevent the fuse from blowing up under severe high overload conditions. More specifically, the invention is an improvement in the miniature fuse disclosed in U.S. Patent No. 4,460,887, granted July 17, 1984, and which, in its most useful form, can have an overall diameter of as little as about 0.1 and a housing length as short as about one quarter inch, even for rated current of as much as 15 amps. The invention has also been used on 100 amp fuses with a diameter of about .250 inches and a length of about 0.4 inches.
  • Cartridge type electrical fuses having axial lead have been long known in the fuse art.
  • the fuse element in such a fuse is typically a fusible wire supported within a cylindrical open-ended insulating housing for the fuse and closed by metal end caps carrying outwardly axially extending leads.
  • the fuse wire must not touch the interior wall of the housing along the portion of its length which can affect its fuse blowing characteristics; hence, the ends of the fuse wire are supported in such a manner as to prevent such contact.
  • the fuse element extends diagonally across the sleeve ends.
  • the lead carrying end caps having solder therein are used to capture the fuse wire ends folded over the outside of the sleeve ends.
  • the final mechanical assembly consists of press fitting the end caps over the folded-­over ends of the fuse wire followed by momentary heating of the solder to obtain good electrical connection between the fuse wire and the end caps.
  • the fuse was a miniature fuse having a housing typically made of ceramics material which cannot be solder bonded without adding a metal coating
  • the only substantial opposition to the separation of the end caps from the sleeve was derived from the pressure fitting of the end caps overs the outer surface of the housing.
  • Such fuse structures were generally weak in tension, and were prone to mechanical failure on a pull test applied to the end leads.
  • An alternative construction was to solder bond the end caps to the housing ends, which requires an expensive local outer metallization of the housing ends.
  • Such structures are prone to humidity induced corrosion problems because of the exposed metal end caps and the lack of any hermetic sealing thereof.
  • the resulting structure was still not adequately strong, in that a moderate pull on the leads can still sometimes shift the end caps to break the fuse wire.
  • the shrink tube fitted fuse as described also was more costly to manufacture than desired. Also, because the fuse housing was made of an opaque ceramic material, the fuse wire was not visible even when the shrink tubing was transparent.
  • the epoxy insulating coating was formed by initially applying epoxy powder to a rotated fuse which had been preheated to fuse the epoxy powder. Because of the temperatures involved, it was discovered that blow holes developed in the epoxy encapsulating body because of out-gassing caused by the heating of the fuse to the epoxy powder fusing temperature. When these fuses were subject to severe high current overload circuit tests, it was found that the blow holes undesirably reduced the insulation resistance of the encapsulating body. Also, the epoxy material was a translucent material so that the fuse wire was not visible, even if the housing were to be made of a transparent material.
  • Another object of the invention is to provide a method of making a sealed miniature fuse where the fuse is a unique, more reliable one than that produced by the method just described, and, most desirably, where the fuse wire is visible from the outside of the fuse so that a blown fuse condition can be visibly determined.
  • the encapsulating body used to seal the fuse to impart an increased terminal pull strength is made of material and is formed in a manner where it also serves as the main support structure for the entire fuse, making it possible to form the fuse housing of a relatively weak transparent glass housing.
  • the fuse withstands high terminal pulling forces and the high pressure-producing conditions caused by high overload fuse blowing conditions and no arcing occurs between the fuse terminals.
  • the encapsulating material can be a transparent material so that the condition of the fuse wire can be readily visibly determined.
  • Another aspect of the present invention is the unique method for making the fuse. While molding techniques have been heretofore used to form a fuse housing around a fuse wire, it is believed unique to mold a relatively strong encapsulation body around a pre-assembled fuse already having a relatively weak glass or glass-like housing to encapsulate an inner fuse housing, end terminals, and the innermost portions of the connecting leads extending from the end terminals.
  • Another aspect of the invention is the unique manner in which the molding operation is carried out.
  • the leads of the fuse subassemblies are secured between a pair of adhesive carrier strips wound up with the subassemblies into a roll supported on a rotatable supply reel.
  • the roll is unwound from the supply reel in a step-by-step fashion and delivered to a molding station which can mold an encapsulating body simultaneously around a large number of fuse subassemblies.
  • the fuse 1 of the present invention comprising a main fuse sub-assembly A encapsulated by a transparent encapsulating body B.
  • the subassembly comprises a length of fuse wire 7 held captive at the ends of an initially open ended cylindrical inner glass housing 2 by means of a pair of cup-shaped metal terminal end caps 3-3 having cylindrical interior recesses receiving the ends of the housing 2 with a pressure fit.
  • a body of solder 4 in each end cap 3 is heated to wet the fuse wire and secure it to the end caps 3-­3. Shouldered connecting leads 5-5 pass through the center of the caps 3-3 and are secured by staking prior to assembly of the fuse structure.
  • the encapsulating body B provides improved structural strength and a complete sealing of the housing 2 and end caps 3-3.
  • the resulting structure is substantially hermetically sealed and, thus, requires no plating of the end caps 3 for corrosion protection, thus resulting in a cost economy in manufacture.
  • the encapsulating body covers the outer exposed surfaces of the housing 2, end caps 3-3, and portions of the lead 5-5 adjacent to the end caps to form a reinforced sealed body which greatly increases the insulation resistance and pull strength of the fuse.
  • the fuse rating 9 may be imprinted at one or both end portions of the encapsulating body B where the subassembly end caps 3-3 are located, to avoid interfering with th view of the fuse wire 1 visible through the transparent walls of the encapsulating body B and inner housing 2.
  • the encapsulating body B may be a polypropylene or other suitable moldable synthetic plastic material, such as Rynite or Nylon. It is preferred that a thermoplastic material be used which can be quickly injection molded with water cooled molding equipment of the kind to be described.
  • the fuse subassembly is not preheated as in the epoxy encapsulating process disclosed in U.S. Patent NO. 4,460,887, and so no out-gassing occurs to form blow holes which decreased the insulation resistance of the fuse exterior of the sealed fuse disclosed in the previously mentioned patent. Also, because the epoxy powder application process disclosed in this patent required rotation of the fuse subassembly during application of epoxy powder, the encapsulation process could not be as easily and quickly carried out as in the encapsulation process now to be described.
  • FIG. 4-6 for a disclosure of the most preferred method for molding the encapsulating body B around each of the fuse subassemblies.
  • two adjacent lines of fuse subassemblies A which are fed through a mold assembly 18 which can simultaneously mold a large number of encapsulation bodies B, such as 25 per line.
  • a mold assembly 18 which can simultaneously mold a large number of encapsulation bodies B, such as 25 per line.
  • Each line of fuse subassemblies A are supported preferably in a horizontal orientation and at longitudinally spaced points along a pair of horizontally spaced adhesive strips 10-10.
  • the leads 5-5 are shown removably secured to the adhesive coated sides of the strips 10-10.
  • the strips 10-10 are preferably horizontally oriented so that the adhesive coated sides are horizontal co-planar surfaces of the strips.
  • the supply reel assembly 12 includes a shaft 14 having fuse lead positioning flanges 16-16 between which the outer ends of the fuse assembly leads 5-5 are retained.
  • the roll 11 of carrier strips are fuse subassemblies are unwound from the supply assembly reel 12 and moved to the mold assembly 18.
  • the encapsulation bodies B are molded around the fuse subassemblies A.
  • the encapsulated fuse body assemblies and the carrier strips to which the leads thereof are attached are then moved to a take-up reel assembly 12′ having lead-confining flanges 16′-16 ⁇ similar to the flanges 16-16 on the supply reel assembly 12.
  • the carrier strips 10-10 are rolled upon the shaft 14′ of the reel assembly 12.
  • the take-up reel shaft 14′ is connected to a suitable stepping motor 20′.
  • a similar stepping motor 20 is connected to the supply reel assembly shaft 14.
  • the motors 20 and 20′ are fed stepping pulses from a controller 21 intermittently to move the 25 fuse subassemblies A of each line on the associated carrier strips 10-10 to the mold assembly 18, as a like number of encapsulated fuse subassemblies are moved from the mold assembly 18 toward the take-up reel assembly 12′.
  • Figure 5 is a transverse cross sectional view through the mold assembly 18, showing two mold cavities 22-22, one for each line of fuses being processed.
  • Each cavity 22 is formed by upper and lower semi-cylindrical recesses 22A and 22B ( Figure 6) formed in the upper and lower faces of upper and lower mold assembly parts 18A and 18B. These parts are water cooled by the passage of water through passageways 20A-­20B in the upper mold assembly part 18A.
  • the referred to upper and lower mold assembly part 18A and 18B are each made up of an assembly of parts, all of which will not be individually described. These parts are carried on movable elements (not shown) which bodily move these parts vertically between spaced and contiguous positions.
  • the mold assembly parts 18A and 18B are separated to avoid interference with the movement of these subassemblies.
  • the subassemblies come to rest within the mold assembly, the mold assembly parts are then moved into confronting relationship where the mold cavities are formed therebetween and the molding material fed thereto.
  • the molding material immediately hardens and the mold assembly parts are then separated to permit the molded subassemblies to move on to the take-up reel assembly to enable the subassemblies not yet encapsulated to be moved to the mold assembly.
  • a nozzle 24 Communicating with each upper recess 22A in the mold assembly part 18A is a nozzle 24 defining a molding material inlet passageway 24.
  • the nozzle is formed by a metal body having an insulating sleeve 26 which retains heat generated in the interior thereof.
  • the nozzle body illustrated has a pair of molding material feeding passageways 28-28 communicating with the inlet passageway 24.
  • a heating element 30 in the center of the nozzle body generates heat within the nozzle body to keep the thermoplastic molding material involved in a plastic state within the inlet passageway 24.
  • the passageways 28-­28 in each nozzle body communicates with a main feed passageway 28′ in turn fed from one or more molding material inlet ports 31 provided at the tope of the mold assembly part 18A.
  • the ports 31 communicate with a source of molding material which can be fed by a feed screw (not shown) which is intermittently rotated to feed a fixed predetermined amount of molding material from passageway 24 into the associated mold cavity 22 after the mold assembly parts 18A-18B are brought together.
  • a feed screw not shown
  • the upper mold assembly part also has heating elements 30′ to keep the molten material in the passageway 28′ in a molten state at all times.
  • a power and thermocouple mold plug 34 is provided which controls current flow from a suitable current source to the heating elements 30 and 30′ contained in the upper mold assembly part 18A. Because substantially the entire surface area of the mold cavity defined by the recesses 22A-22B are cooled surfaces, the encapsulating bodies B are quickly formed in a hardened state. When the mold assembly parts 18A and 18B are then separated, the hardened encapsulating body B is cleanly separated from the still molten material in each passageway 24. The entire surface area of the encapsulating body B is a smooth cylindrical surface when the molded cavity-forming parts are separated.
  • a fuse made in accordance with the present invention having a 15 amp rating and a glass housing length of .228 inches, a housing outer diameter of .055 inches, a housing wall thickness of .013 inches, an end cap outer diameter of .073 inches, an encapsulating body outer diameter of .095 inches, a lead diameter of .024 inches, and a lead pull strength of well above 10 pounds.
  • the present invention thus provides a high speed, reliable and effective method for making the unique encapsulated fuses of the present invention.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Fuses (AREA)
EP88201669A 1987-08-03 1988-08-02 Herstellungsverfahren für eine gekapselte Sicherung und eine derart hergestellte Sicherung Withdrawn EP0302568A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US80799 1987-08-03
US8079987A 1987-08-08 1987-08-08

Publications (2)

Publication Number Publication Date
EP0302568A2 true EP0302568A2 (de) 1989-02-08
EP0302568A3 EP0302568A3 (de) 1990-08-01

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP88201669A Withdrawn EP0302568A3 (de) 1987-08-03 1988-08-02 Herstellungsverfahren für eine gekapselte Sicherung und eine derart hergestellte Sicherung

Country Status (4)

Country Link
EP (1) EP0302568A3 (de)
JP (1) JPS6459734A (de)
KR (1) KR890004370A (de)
BR (1) BR8803833A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994002890A1 (en) * 1992-07-16 1994-02-03 Terberg Benschop B.V. Automatic guided vehicle and control system therefor
CN1034892C (zh) * 1994-10-28 1997-05-14 佘秀月 保险丝组装机
WO2000060629A1 (en) * 1999-04-02 2000-10-12 Littelfuse, Inc. Fuse having improved fuse housing
EP4322194A1 (de) * 2022-08-12 2024-02-14 Suzhou Littelfuse OVS Co., Ltd. Neues dichtungsdesign zum umspritzen einer sammelschiene

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0526686Y2 (de) * 1988-08-26 1993-07-06
JPH0677434B2 (ja) * 1989-07-19 1994-09-28 株式会社長沢電機製作所 超小型リード線付ヒューズ

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1672394U (de) * 1953-12-28 1954-02-25 Lehner Fernsprech Signal Elektrisches geraet fuer schlagwetter- oder explosionsgefaehrdete betriebe.
US4282504A (en) * 1979-09-10 1981-08-04 S&C Electric Company Fault limiter having a one-piece enclosure of glass-reinforced resin
US4460887A (en) * 1981-03-19 1984-07-17 Littelfuse, Inc. Electrical fuse
DE8704621U1 (de) * 1987-03-28 1987-07-02 Wickmann-Werke GmbH, 5810 Witten Elektrische Sicherung

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3728775A1 (de) * 1987-03-27 1988-11-03 Cooper Ind Inc Elektrische sicherung, insbesondere axiale kleinstsicherung mit kunststoffformkoerper, sowie verfahren zur herstellung einer sicherung

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1672394U (de) * 1953-12-28 1954-02-25 Lehner Fernsprech Signal Elektrisches geraet fuer schlagwetter- oder explosionsgefaehrdete betriebe.
US4282504A (en) * 1979-09-10 1981-08-04 S&C Electric Company Fault limiter having a one-piece enclosure of glass-reinforced resin
US4460887A (en) * 1981-03-19 1984-07-17 Littelfuse, Inc. Electrical fuse
DE8704621U1 (de) * 1987-03-28 1987-07-02 Wickmann-Werke GmbH, 5810 Witten Elektrische Sicherung

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994002890A1 (en) * 1992-07-16 1994-02-03 Terberg Benschop B.V. Automatic guided vehicle and control system therefor
CN1034892C (zh) * 1994-10-28 1997-05-14 佘秀月 保险丝组装机
WO2000060629A1 (en) * 1999-04-02 2000-10-12 Littelfuse, Inc. Fuse having improved fuse housing
US6577222B1 (en) 1999-04-02 2003-06-10 Littelfuse, Inc. Fuse having improved fuse housing
EP4322194A1 (de) * 2022-08-12 2024-02-14 Suzhou Littelfuse OVS Co., Ltd. Neues dichtungsdesign zum umspritzen einer sammelschiene

Also Published As

Publication number Publication date
KR890004370A (ko) 1989-04-21
JPS6459734A (en) 1989-03-07
BR8803833A (pt) 1989-02-21
EP0302568A3 (de) 1990-08-01

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