Circuit board blade fuse

Information

  • Patent Grant
  • 6272000
  • Patent Number
    6,272,000
  • Date Filed
    Wednesday, March 29, 2000
    24 years ago
  • Date Issued
    Tuesday, August 7, 2001
    23 years ago
Abstract
A fuse includes a housing and terminal blades extending therefrom. Each terminal blade includes a stop face, a stop brace, a hold face, and a hold brace. The stop face and stop brace prevent over insertion of the terminal blade through a circuit board and separate the fuse housing from the circuit board. The stop brace and hold brace position the housing relative to the board and prevent dislodging of the blades from the board during soldering operations.
Description




BACKGROUND OF THE INVENTION




This invention relates generally to blade-type fuses and, more particularly, to blade-type fuses for being secured to circuit boards.




Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. One type of fuse for personal computer power supplies is a blade-type fuse. The blade-type fuse includes a plastic housing, two electrical conducting terminal blades extending from the housing, and a fusible link connected between the terminal blades within the housing. The terminal blades are inserted through openings in a printed circuit board and soldered to the board to complete an electrical connection through the fusible link. In operation, when the current approaches unacceptable limits, the link melts and opens the circuit to prevent electrical component damage.




Fuses and other components are typically secured to a circuit board by soldering. Wave soldering is one known soldering technique that is simple and reliable. With wave soldering, the electrical components are stuffed onto a printed circuit board, a solder flux is applied to the board, the board is preheated, and the board is transported across one or several solder waves.




Proper location of a fuse on the circuit board is important to provide a desired electrical connection. For example, if the fuse housing contacts the board when terminal blades are inserted through the board, solder wicking and the creation of an electric path around the fuse may result. Also, a portion of the blade terminal that extends, or protrudes, from a bottom of the board typically must be trimmed after soldering to prevent undesired electrical contacts between the terminals and other components.




Accordingly, it would be desirable to provide a blade-type fuse that facilitates the proper location of a fuse with respect to a circuit board to prevent the fuse housing from resting on a surface of the board and that eliminates a need to trim the terminals after soldering.




BRIEF SUMMARY OF THE INVENTION




In an exemplary embodiment of the invention, terminal blades extending from a housing of a fuse include stop portions and hold portions to facilitate properly locating a fuse with respect to a circuit board. Particularly, and in the exemplary embodiment, the blades have opposite flat faces and include stop portions configured to prevent the blades from being inserted through a printed circuit board for more than a predetermined distance. The hold portions are configured to hold the fuse housing in a separated position from the surface of the board during soldering.




More particularly, and in the exemplary embodiment, the stop portion of each blade includes a projection configured to extend from at least one of the flat faces of the blades. The stop portion is dimensioned so that the blade and projection together have a cross-sectional area greater than the area of the blade terminal opening in a circuit board so that the blade cannot be inserted through the circuit board opening beyond the stop portion. By locating the stop portion a selected distance from the bottom of the blade housing along a longitudinal axis of the blade, the stop portion prevents the blade fuse housing from resting on a surface of the board.




The hold portion also includes a projection configured to extend from at least one flat face of the blades. The hold portion projection is separated from the stop portion projection and has a cross sectional area smaller than the stop portion projection so that the hold portion projection and blade may be inserted through the blade terminal opening in a printed circuit board. The hold portion is positioned at a distal end of the blade, and facilitates maintaining the blade terminals in place during handling and soldering of the boards.




The above-described stop portion prevents the fuse housing from contacting the board surface as the terminal blades are inserted into the circuit board. Therefore, solder wicking and the creation of electrical paths around the fuse are avoided. In addition, the stop and hold portions maintain the fuse in place during handling and soldering operations, thereby preventing the terminals from dislodging from the circuit board during handling and/or soldering. The stop and hold portions also eliminate trimming of the terminal blades, providing further cost savings and reducing manufacturing time.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a front elevational view of a first embodiment of a fuse;





FIG. 2

is a side elevational view of the fuse of

FIG. 1

;





FIG. 3

is an enlarged view of a portion of the fuse of

FIG. 1

connected to a circuit board;





FIG. 4

is a side elevational view of a second embodiment of a fuse;





FIG. 5

is an end view of the fuse shown in

FIG. 4

; and





FIG. 6

is a view similar to

FIG. 3

but illustrating a third embodiment of a fuse connected to a circuit board.











DETAILED DESCRIPTION OF THE INVENTION





FIG. 1

is a front elevational view of a fuse


10


including a housing


12


and two blades


14


extending therefrom. Each blade


14


includes a stop portion


16


and a hold portion


18


to prevent blade insertion through a printed circuit board (not shown in

FIG. 1

) beyond a predetermined point and to hold blades


14


to the board during soldering operations.




The printed circuit board is made of a dielectric substrate or substrates. Circuitry is chemically formed on the substrates, and fuses


10


are connected to the circuits to protect the circuits from damaging overcurrents. There are generally four types of circuit boards, namely, single side, double side, flex, and multilayer. Single mount boards have circuitry on one side of the board, and may or may not include openings drilled through the board for mounting of components. Double sided boards have circuitry on both sides of the board, drilled openings in the board for the mounting of electrical components, and electroplated walls to allow for electrical continuity between the sides of the board. Flex boards have multilayered circuitry overcoated with a flexible film. Electrical continuity of flex boards is commonly achieved in a manner similar to double sided boards. Multilayer boards are similar to double sided boards but are bonded together in a stack. Fuse


10


may be used in connection with many different types of circuit boards, including the types of boards described above.




Fuse housing


12


is a molded plastic construction that encapsulates terminal blades


14


and a fusible link (not shown) electrically connecting blades


14


. Terminal blades


14


extend from a bottom


20


of housing


12


. Housing


12


is dimensioned to facilitate insertion of terminal blades


14


into the circuit board and protects the fusible link from severance or disconnection during handling of fuse


10


.




Terminal blades


14


extend from within housing


12


and include distal ends


22


. Distal ends


22


include chamfers


24


to guide blades


14


into proper position as blades


14


are inserted through openings in the circuit board. Terminal blades


14


are fabricated from an electrically conductive material and are configured in accordance with the desired voltage and current rating of fuse


10


. Each blade


14


also includes a stop portion


16


and a hold portion


18


. In one embodiment, stop portion


16


and hold portion


18


are punched or sheared from blades


14


on three sides and the free end bent upwardly with respect to flat portions


28


,


30


of blades


14


. In alternative embodiments, stop portion


16


and hold portion


18


are formed using other known fabrication methods, including but not limited to die casting, skiving, and machining of blades


14


with stop and hold portions


16


,


18


.




In the illustrated embodiment, stop portion


16


and hold portion


18


partially span a width of each blade


14


and are approximately centered between a pair of side edges


26


of blade


14


. In an alternative embodiment, stop portion


16


and hold portion


18


are located on one blade only. In another alternative embodiment, both stop portion


16


and hold portion


18


are located on one blade


14


, and only one of stop portion


16


and hold portion


18


is located on the other blade


14


. In yet another embodiment, only stop portion


16


or hold portion


18


is provided on each blade


14


.





FIG. 2

is a side view of fuse


10


. Blades


14


have a first flat face


28


and a second flat face


30


. Stop portion


16


is separated from bottom


20


of housing


12


along longitudinal axis


32


of blade


14


and extends from first blade face


28


. Hold portion


18


is separated from stop portion


16


along longitudinal axis


32


and also extends from first blade face


28


. Thus, a gap


34


between stop portion


16


and hold portion


18


is created that, in a particular embodiment, is less than the thickness of a circuit board (not shown). Hold portion


18


is positioned adjacent distal end


22


of said blade


14


. In an alternative embodiment, stop portion


16


and hold portion


18


are connected to different faces


28


,


30


of blade


14


.





FIG. 3

is an enlarged view of a portion of fuse


10


connected to a printed circuit board


36


. Stop portion


16


includes a stop face


38


and a stop brace


40


. Stop face


38


is substantially flat and extends obliquely to first face


28


of blade


14


. Stop face


38


is substantially rectangular, and is dimensioned so that the thickness of blade


14


and stop face


38


is larger than a blade terminal opening


42


in circuit board


36


. Stop brace


40


extends from stop face


38


and includes a top surface


44


that is sloped toward blade first face


28


, and stop portion


16


is separated from bottom


20


of fuse housing


12


along longitudinal axis


32


of blade


14


.




Hold portion


18


includes a hold face


46


and a hold brace


48


. Hold face


46


is substantially flat and extends obliquely to first blade face


28


. Hold face


46


is substantially rectangular and dimensioned so that the thickness of blade


14


and hold face


46


is smaller than a thickness of blade


14


and stop face


38


. In alternative embodiments, other shapes of faces


38


,


46


and braces


40


,


48


are employed for stop portions


16


and hold portions


18


. For instance, stop face and hold face may extend substantially perpendicularly to blade first face


28


so that stop portion


16


and hold portion


18


are substantially triangular in profile.




Hold face


46


extends obliquely to stop face


38


and is separated from stop face


38


by gap


34


. Hold brace


48


extends from hold face


46


and includes a top surface


50


that is sloped toward first blade face


28


. Thus, hold portion


18


is substantially triangular. Hold brace


48


and blade face


28


converge adjacent distal end


22


of blade


14


.




When fuse


10


is inserted into circuit board


36


, terminal blades


14


are inserted through blade terminal opening


42


in circuit board


36


until stop face


38


contacts a first side


52


of circuit board


36


and cooperates with stop brace


40


to prevent further insertion of blade


14


. Hold face


48


is dimensioned to engage circuit board blade terminal opening


42


with an interference fit to prevent terminal blades


14


from dislodging from circuit board


36


during wave soldering. The relative position of stop portion


16


and hold portion


18


with respect to blade distal end


22


determines the blade length that protrudes through circuit board


36


after blade


14


is inserted. Thus, excess terminal length protruding through second side


54


, i.e., the bottom of circuit board


36


, is eliminated and the costs of trimming the terminals saved.




The separation of the stop portion


16


and fuse housing


12


along longitudinal axis


32


of blade


14


prevents housing


12


from contacting the surface of the board. Solder wicking and the creation of electrical paths around the fuse are therefore avoided.





FIG. 4

is a side view of a second embodiment of a fuse


60


including a housing


62


and a pair of terminal blades


64


extending therefrom. Each blade includes a first flat face


66


and an opposed second flat face


68


. A hold portion


70


is located adjacent distal ends


72


of each terminal blade


64


and extends from first face


66


and second face


68


, respectively, of each blade


64


. A stop portion


74


is located a distance from hold portion


70


on each terminal blade


64


and extends from first face


66


and second face


68


, respectively, of each blade


64


to form a gap


76


between a stop portion stop face


80


and a hold portion hold face


82


of each blade


64


. Hold face


82


of each blade


64


is dimensioned to allow insertion of hold portion


70


through an opening (not shown in

FIG. 4

) of a printed circuit board (not shown in

FIG. 4

) while stop face


80


is dimensioned to prevent insertion of stop portion


74


through the opening of the printed circuit board. Therefore, when terminal blades


64


are inserted into the circuit board, stop face


80


contacts a top surface (not shown) of the printed circuit board and prevents a bottom


84


of housing


62


from contacting the top surface of the printed circuit board.




While in the illustrated embodiment, stop portions


74


and hold portions


70


are dimensioned approximately equally on each blade


64


, in alternative embodiments stop face


80


and hold face


82


of each blade


64


are dimensioned differently so that fuse


60


may be installed into the printed circuit board only in a pre-selected orientation determined by the dimensions of openings in the printed circuit board.





FIG. 5

is an end view of fuse


60


illustrating terminal blades


64


with opposed first and second faces


66


,


68


, and stop and hold portions


74


,


70


of one blade


64


extending from first face


66


while stop and hold portions


74


,


70


of the other blade


64


extend from second face


68


. In the illustrated embodiment, stop and hold portions


74


,


70


are substantially centered and span only a portion of a width of each blade


64


, while in alternative embodiments stop and hold portions


74


,


70


may be off-centered and/or span substantially the entire width of terminal blades


64


. Distal ends


72


of terminal blades


64


include chamfers


86


to guide insertion of terminal blades


64


into a printed circuit board (not shown in FIG.


5


).




When inserted into the printed circuit board, stop portion


74


and hold portion


70


of each blade


64


is positioned substantially as illustrated and described in relation to FIG.


3


. Therefore, prevention of solder wicking and creation of electrical paths around fuse


60


is accomplished, and the cost of trimming blade terminals


64


is saved.





FIG. 6

is an enlarged view of a portion of a third embodiment of a fuse


100


including a hold portion


102


of a terminal blade


104


inserted completely through a circuit board


106


so that a hold face


108


contacts a second surface


110


of circuit board


106


. Thus, circuit board


106


is retained between a stop portion


112


contacting a first surface


114


of circuit board


106


and stop face


116


contacting circuit board second surface


110


. In other words, a gap


118


between stop portion


112


and hold portion


102


is dimensioned approximately equal to the thickness of circuit board


106


.




While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.



Claims
  • 1. A fuse for a circuit board, the circuit board including a first surface and a plurality of openings therethrough, said fuse comprising:a housing; and first and second blades extending from the housing, at least one of said first and second blades comprising a pair of side edges and a flat face extending therebetween, and a first stop portion upwardly sloped from said flat face to prevent insertion of said blade through the opening beyond a predetermined point when said blades are inserted through the openings.
  • 2. A fuse in accordance claim 1 wherein said at least one blade comprises a distal end, said first stop portion extending from said flat face toward said distal end.
  • 3. A fuse in accordance with claim 2 wherein said first stop portion comprises a stop face.
  • 4. A fuse in accordance with claim 3 wherein said stop face is oblique to said flat face.
  • 5. A fuse in accordance with claim 2 wherein said first blade comprises a first face and said second blade comprises a second face opposed to said first face, said first stop portion extending from said first face, said fuse further comprising a second stop portion extending from said second face.
  • 6. A fuse in accordance with claim 2 wherein said at least one blade further comprises a hold portion separated from said first stop portion and configured to engage one of the circuit board openings.
  • 7. A fuse in accordance with claim 1 wherein at least one of said blades is further configured to prevent said blades from disconnecting with the circuit board after being inserted through the board a predetermined amount.
  • 8. A fuse in accordance claim 7 wherein said at least one blade configured to prevent disconnection comprises a flat portion and a first hold portion.
  • 9. A fuse in accordance with claim 8 wherein each of said first and second blades comprises a first face and an opposed second face, said first hold portion extending from said first face of said first blade, said fuse further comprising a second hold portion extending from said second face of said second blade.
  • 10. A fuse in accordance with claim 8 wherein said first hold portion comprises a hold face, said hold face extending obliquely to said flat portion.
  • 11. A fuse in accordance with claim 10 wherein said first hold portion is configured to prevent said blade from disconnecting with the circuit board after said at least one blade is inserted through the board a predetermined amount.
  • 12. A fuse in accordance with claim 11 wherein said at least one blade configured to prevent disconnection further comprises said first stop portion separated from said first hold portion and preventing insertion of said blade into a circuit board beyond said first stop portion.
  • 13. A circuit board assembly comprising:a circuit board comprising at least a first surface, a second surface and a plurality of openings therethrough: a fuse housing; and a first blade and a second blade extending from said housing, each of said first blade and second blade comprising a distal end and a stop portion upwardly sloped toward said distal end for contacting said first surface of said board and a hold portion engaging said circuit board when said blades are inserted through said openings.
  • 14. A circuit board assembly in accordance with claim 13 wherein said stop portion comprises a stop face extending from each said blade, said hold portion comprising a hold face extending from each said blade, said stop face separated from said hold face on each blade.
  • 15. A circuit board assembly in accordance with claim 14 wherein each said blade comprises a first surface and an opposed second surface, said stop face of said first blade extending from said first surface, said stop face of said second blade extending from said second surface.
  • 16. A circuit board assembly in accordance with claim 15 wherein said stop face and said hold face are substantially parallel to one another.
  • 17. A circuit board assembly in accordance with claim 14 wherein said stop portion further comprises a stop brace including a top surface, said hold portion comprises a hold brace including a top surface, said stop brace top surface and said hold face top surface are oblique to said stop face and said hold face.
  • 18. A circuit board assembly in accordance with claim 17 wherein said blades further include distal ends, said stop brace top surface extending toward said distal end of said blade.
  • 19. A circuit board assembly in accordance with claim 17 wherein said top surface of said stop brace extends to said blade, said stop brace top surface separated from said housing.
  • 20. A circuit board assembly in accordance with claim 14 wherein said hold face contacts said second surface when said blades are inserted through said openings.
  • 21. A fuse for a circuit board, the circuit board including a first surface and a plurality of openings therethrough, said fuse comprising:a housing; and first and second blades extending from the housing, each of said first and second blades comprising a distal end, first and second lateral sides, and a flat face extending between said lateral sides to said distal end, at least one of said first and second blades comprising a sloped stop portion substantially centered between said lateral sides and configured to contact the first surface of the board and prevent insertion of said blade through the opening beyond a predetermined point when said blades are inserted through the openings.
  • 22. A fuse for a circuit board, the circuit board including a first surface and a plurality of openings therethrough, said fuse comprising:a housing; first and second blade terminals extending from said housing, each of first and second blade terminals comprising opposed flat faces extending between lateral sides, at least one of said flat faces comprising a sloped stop portion configured to prevent insertion of said first and second blade terminals through the openings beyond a predetermined point, and at least one of said flat faces comprising a hold portion configured to secure said blade terminal to the opening of the board with an interference fit.
CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/130,354, filed Apr. 21, 1999.

US Referenced Citations (3)
Number Name Date Kind
3786402 Horecky Jan 1974
4343530 Leger Aug 1982
4612539 Gurevich et al. Sep 1986
Provisional Applications (1)
Number Date Country
60/130354 Apr 1999 US