The present invention relates to fire fighting equipment comprising a release means arranged to be activated at a predetermined temperature. The release means may be e.g. a glass ampoule or a fuse, which breaks or melts, respectively, at a predetermined temperature and thereby releases, i.e. activates a spray head to spray extinguishing liquid. The nominal release temperature may be e.g. about 70°C. Usual release elements are, however, heated up to the release temperature rather slowly; at a fire e.g. in a hotel room or in a ship cabin the temperature in the room has time to rise to even some 300°C - 400°C before release takes place, in conventional sprinkler installations.

Recent so-called fast response sprinklers are in similar situations capable of release at a temperature of about 200°C - 250°C. As a measure of the release rate is generally used a so-called Response Time Index (RTI). Conventional sprinklers have a Response Time Index of about 300, the "fast" sprinklers mentioned above have a Response Time Index of about 50.

The object of the present invention is to provide new fire fighting equipment which is released considerably faster than earlier known designs.

The fire fighting equipment according to the invention is mainly characterized in that immediately close to the release means is provided an element of memory metal arranged to at a predetermined temperature, by changing shape, close an electric circuit for heating the memory metal element, and thereby the release means, in order to effect a fast release action. The element of memory metal is preferably made as a wire helically laid around the release means.

The memory metal can preferably be a NiTi-alloy with a memory temperature of about 70°C.

The wire of memory metal has the property to at a certain predeterminable temperature take a previously "taught" shape; at lower temperatures the wire can be deformed practically at will without mentionable mechanical resistance.

Thus, a helical spring can be made to "remember" a certain length at a temperature of about 70°C, whereafter the spring at e.g. room temperature can be compressed to another ^* length which remains until the temperature of the spring rises to the memory temperature, whereat the spring returns to its

"taught" length. In the present invention this property is utilized for closing an electric circuit at a predetermined raised temperature, preferably by making contact to suitable metal parts of a sprinkler included in the electric circuit. The wire of memory metal can be made thin, with a diameter of e . g. 0 .3 mm, whereby it is rapidly heated by surrounding hot smoke gases . When a conducting connection has been established, the memory metal wire is immediately heated up and conveys its heat to the release means formed e . g . by a conventional glass ampoule which is broken in about two seconds .

Thanks to the invention, a Response Time Index of less than 10 can be achieved, which in the fire situations earlier referred to results in extinguish release already at a temperature less than 100°C. This means that fires can be fought already in their initial stage and the generation of poisonous smoke gases can be decisively restricted. In the following the invention will be described with reference to the attached drawing which, by way

of example, shows a preferred embodiment.

Figure 1 shows a section of a sprinkler with a helical spring of memory metal around the release means, at normal temperature. Figure 2 shows an initial stage at a raised temperature.

Figure 3 shows the sprinkler in activated state. In the drawing, reference numeral 1 generally indicates a sprinkler the housing of which is indicated by 2. The sprinkler has a liquid inlet 3 and a number of nozzles 4.

In a central bore in the housing 2 , starting from the inlet 3, is arranged a spindle 5 which under the influence of a spring 6 supported by a shoulder in the housing 2 is pressed against a release means 7, e.g. a conventional glass ampoule.

At normal temperature the ampoule 7 withstands the mechanical load exerted by the spring 6 through the spindle 5, whereat the upper end (in the drawing) of the spindle closes connection from the inlet 3 to the nozzles 4, as shown in figure 1.

At a raised temperature, generally about 70°C, the ampoule 7 is demolished and allows the spring 6 to axially push the spindle to the position shown in figure 3, with open connection from the liquid inlet 3 to the nozzles 4.

Around the ampoule 7 is laid a spiral 8 of memory metal. At normal temperature, figure 1, the spiral 8 is compressed, whereat there is a gap of e.g 2-5 mm between the upper end (in the drawing) of the spiral 8 and the adjacent lower end of the spindle 5. The lower end of the spiral 8 is in contact with an electrically conducting support 9 for the ampoule 7, said support 9 being connected to one terminal 10 of an electric circuit having a voltage of preferably about 24 Volt. The second terminal 11 of the circuit

is connected to the housing 2 of the sprinkler 1. An insulation piece 12 is provided between the support 9 and a usually metallic casing 13 surrounding the ampoule 7 and having a number of apertures 14. If a fire breaks out within the area monitored by the sprinkler, the spiral 8 is rapidly heated by surrounding smoke gases and upon reaching the memory' temperature, e.g. about 70°C, the spiral 8 immediately straightens out to a preset, "taught" length which is so chosen that the spiral 8 is pressed into contact against the adjacent end of the spindle 5 thus closing the electric circuit 10 - 9 - 8 - 5 - (6) - 2 - 11, figure 2. The spiral 8 no ^* */ acts as a heating coil and rapidly heats the ampoule 7 to release temperature. A current of about one ampere through the spiral 8 is capable of releasing the ampoule 7 in about two seconds. At normal temperature the spiral 8 need not be in contact with the support 9; there can be a gap between. A wire of a NiTi-alloy and having a diameter of e.g. 0.3 mm is of advantage in that it has a favourable electric resistance; those parts of the spray head which are included in the electric circuit have practically no resistance.

The drawing shows a sprinkler intended for a high operating pressure and with nozzles arranged in such a way, that they can produce a continuous fog spray with a good penetration power, preferably as presented in the international . patent applications PCT/FI92/00060 and PCT/FI92/00155, respectively, but the invention can naturally be used for other types of sprinklers, as well as for other temperature activating elements.

As will appear from the drawing, the sprinkler 1 preferably comprises a spindle structure with an axially movable spindle 5 loaded by a spring 6 against the release ampoule 7 and having an axial channel 20

leading to an annular chamber 21 with an end face 22 which balances the liquid pressure force acting through the inlet 3 on the spindle end; the end face 22 has an area equal to the one of the spindle end at the inlet 3.

In figure 1, the sprinkler is inactive, i.e. the ampoule 7 is intact and there is no connection from the inlet 3 to the nozzles 4. In figure 3, the ampoule 7 has been broken, the spring 6 has pressed the spindle 5 downwards to make free a connection from the inlet 3 to respective side channels leading to the nozzles 4.

When the release means is an ampoule like the one shown in the drawing, a surrounding spiral is preferable, but if the release means is e.g. a fuse intended to melt the element of memory metal may be of another shape suitable for each case, respectively.

An additional advantage of the equipment according to the invention is that it can be used as a heat detector e.g. for fire alarm. As the electric circuit closes, an electric signal can conveniently be obtained for that purpose. Separate heat detectors are no longer necessary.