Fire extinguishers – Fusible connections
Patent
1984-07-06
1986-12-09
Kashnikow, Andres
Fire extinguishers
Fusible connections
49 7, 1262875, 137 72, E05F 100
Patent
active
046274987
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a fuse design for tripping fire limiters or other safety appliances in ventilation installations, comprising a fuse body part and a fuse material, the fuse material being disposed, when in solid state, to maintain the parts of the fuse in a certain position relative to each other and when in liquid state, to permit the parts of the fuse to move with reference to each other.
It would be highly welcome in fire limiters if one fuse could be used more often than just once. It would be of importance that subsequent to false or test tripping for reasons other than fire, which occurs frequently in the case of fire limiters, the same fuse could be immediately used for resetting. It is also important that the operability of a fire limiter could be checked in a simple and convenient manner regarding the structure other than the fuse, by tripping and resetting the closing member, e.g. the flap or louvre pack, once or several times. Convenient detachability and replaceability of the fuse are also advantages.
SUMMARY OF THE INVENTION
The currently most well known and most used design is a strip fuse, in this structure two metal strips being soldered together with the aid of fuse material having desired melting point. When the temperature of the fuse material rises to a pre-determined limit value, that is to the melting temperature, the strips become detached from each other. A drawback of a structure of this kind is however that the same fuse cannot be reused after false or test tripping. A strip fuse is also quite likely to suffer damage or to break. There is also the problem of the long-term strength of the fuse material and the difficult control of the soldering process.
Another fuse design known in the art is the so-called glass ball fuse in which between two latches are placed a glass ball filled with a liquid with powerful thermal expansion, and which breaks when the liquid expands. The set-up of the latches relative to each other is such that when the glass ball bursts as the temperature reaches its given limit value they get free from each other. A drawback of this design is its single-use, expensive and inconvenient construction.
At present, reuse of the fuses proper is not possible, although it is true that triggers based on thermal expansion are known in the art, for instance a tripping mechanism wherein a stack assembled of bimetal strips expands as it is heated and detaches a pin, connected to the structure, from a locking hole, whereby tripping can take place. A drawback of the structure has been found to be that the bimetal strips react slowly to temperature increase, and moreover the design is expensive; it is rather susceptible to interference, easily damaged, sensitive to corrosion, and in case of fault awkward to repair.
The object of the present invention is to provide an improvement in fuse designs known in the art. A more detailed object of the invention is to provide a fuse design based on the melting of a substance and which is durable, reliable in operation, resistant to corrosion, easy to test, favourable as to its manufacturing cost, easy to detach or replace, and which permits repeated use of the fuse.
In the German publicizing print No. 2 261 153 is disclosed a fuse design in which the fuse plate is subject to pressure. After the fuse material has melted, the molten substance flows off in uncontrolled manner, and therefore reuse is not possible as a rule. In addition, the design requires an ample amount of fuse material. The softening of the fuse material at temperature below the melting point may also cause failure of the locking in this type of fuse because in it a harmful creep is possible, which is a phenomenon typical of fuse materials.
The objects of the invention are attained with the aid of a fuse design which is mainly characterized in that the fuse material has been arranged in molten state to flow through a narrow flow path arranged in the fuse design under action of the internal pressure caused in the fuse material b
REFERENCES:
patent: 1924869 (1933-08-01), Lovekin et al.
patent: 2523029 (1950-09-01), Kramer
patent: 2635718 (1953-04-01), Birkemeier
patent: 2764025 (1956-09-01), Otto
patent: 3283691 (1966-11-01), Reiter
patent: 3543439 (1968-10-01), Pantland
patent: 3896835 (1975-07-01), Wicke
patent: 4221231 (1980-09-01), Harvey et al.
patent: 4366830 (1983-01-01), Becelaere
Aalto Erkki
Hasa Juhani
Saukkonen Harri
Halton Oy
Kashnikow Andres
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