Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Patent
1998-09-03
1999-11-30
Picard, Leo P.
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
337228, 337231, 337252, H01H 85157, H01H 85143, H01H 8518
Patent
active
059949945
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fuse. More particularly, the present invention relates to a reliable fuse which facilitates automation of the process.
BACKGROUND OF THE INVENTION
There is a tubular fuse as a safety device for protecting an electric circuit from an excess current. As shown in FIG. 11, a generally-used tubular fuse 1 is made up of a glass tube 2, a fuse element 3 arranged in the glass tube 2 along an axial line of the glass tube 2, and a pair of cap terminals 4 (only one side is shown) fitted on both ends of the glass tube 2. Both ends of the fuse element 3 protrude and are soldered to the outside of the glass tube 2 through element insertion holes 4a formed to the respective cap terminals 4. This causes the fuse element 3 to be directly supported in the center of the glass tube 2 by each cap terminal 4 with a predetermined gap between the fuse element 3 and the glass tube 2. It is to be noted that both end portions 3a (indicated by a two-dot long and two short dashes line in the drawing) of the fuse element 3 protruding from solder 5 after soldering are shaved off by using a knife or the like.
In this tubular fuse 1, however, the solder 5 is piled up on the surface of the cap terminal 4 to fix the cap terminal 4 and the fuse element 3 protruding from the element insertion hole 4a, which makes it difficult to automate the process and leads to the deteriorated productivity. That is, in case of external soldering, an advanced technique is required for soldering for maintaining the quality of the fuse. For example, if the solder is overflowed from the bottom to the outer peripheral surface of the cap, this can cause an imperfect contact with the fuse holder. Further, in order to obtain the sufficient strength, the soldering must be applied on the entire bottom surface of the cap around the element insertion hole 4a of the cap terminal 4 without making any unsoldered part. Furthermore, when the soldering is not finished in one time and a soldering iron is again put to cover the unsoldered or insufficient part, the hardened solder may be melted to loosen the fuse element 3. Only a skilled operator can, therefore, carry out the soldering and the automation is not realized so far. However, the soldering causes the poor working environment that may cause a flux or the like to be generated, leading to the shortage of operators.
In addition, since the soldering is so applied as to cover the element insertion hole 4a of the cap terminal 4, the melted solder may bring the air therein and a cavity may be generated inside the solder 5 and above the element insertion hole 4a in particular, thereby preventing a desired strength from being obtained. Detection of this cavity is hard by the visual test, and hence it does not give a serious question to fusion of the fuse caused by the usual excess current if such a cavity exists. However, if a short-circuit or the like occurs near the fuse and a large current flows to cause interruption, the element may explode to blow the solder into pieces and to cause jet of an arc flame or gas or emission of metal powder.
Moreover, since the soldering is performed with the glass tube 2 being erected in such a manner that the solder 5 is piled up from the top, the melted solder may run down from the element insertion hole 4a before being hardened to wrap the fuse element 3 therein, and the length of the exposed part of the fuse element 3, i.e., the fuse length may become unequal to give the irregularity to the pre-arcing time/current characteristic.
Additionally, as a tubular fuse enabling the automation of manufacture, there is one shown in FIG. 12. In this tubular fuse 6, both end portions of the fuse element 3 are externally bent along the edges of the glass tube 2 and sandwiched between the glass tube 2 and a cap terminal 7 to be fixed. According to this fuse structure, the fuse element 3 can be temporarily fixed by only fitting the cap terminal 7 and, if the solder 5 is piled up inside the cap terminal 7 in advance, the soldering can be eff
REFERENCES:
patent: 961891 (1910-06-01), Orelli
patent: 1121876 (1914-12-01), Schipper
patent: 1502881 (1924-07-01), Sandin
patent: 2168153 (1939-08-01), Brown
patent: 2929900 (1960-03-01), White
patent: 3275772 (1966-09-01), Neff
patent: 4346362 (1982-08-01), Feenan et al.
Ito Hideo
Shinzawa Tomohiro
Kabushiki Kaisha Sinzetto
Picard Leo P.
Vortman Anatoly
LandOfFree
Fuse does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuse, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuse will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1678235