[0002] A sprinkler of the type described above is known from pub- lished international patent no. WO 95/31252. This known sprinkler is of a type, in which all its nozzles spray an extinguishing medium when the sprinkler transfers from its standby state, in which the temperature-activated means (ampoule) is intact, to its active state after the temperature-activated means breaks due to heat. After the temperature-activated means breaks, all the noz- zles continue spraying as long as the extinguishing medium is fed into the inlet of the sprinkler.

[0003] The use of this known sprinkler in a fire extinguishing appa- ratus is normally problem-free. However, if this known sprinkler is used in ap- plications, in which it is possible that hot combustible gases move far from the fire site because of airflows, the sprinklers transfer in the normal manner to said active state after the temperature-activated means has broken. The dan- ger then exists that a great deal of the fire-extinguishing medium is sprayed on locations that do not need it. This unnecessarily sprayed extinguishing medium decreases the output of the spray nozzles close to the fire site, because the pressure of the extinguishing medium decreases below the design pressure of the fire extinguishing apparatus and/or the extinguisher fluid tank is emptied quicker than designed. Examples of such applications are tunnels, such as tunnels for vehicles. When sprinklers that are far from the fire site spray, the

actual fire site does not receive the full output and there is a danger that the fire fighting fails or is inefficient with unfortunate results.

BRIEF DESCRIPTION OF THE INVENTION [0004] It is an object of the invention to provide a sprinkler that eliminates or at least reduces substantially the above-mentioned drawback. To achieve this, the sprinkler of the invention is characterized in that the spindle means comprises a first spindle part which, when it is in a first position, is ar- ranged to keep the second channel closed while the sprinkler is in its standby state, which first spindle part comprises a first action surface area that is ex- posed to the pressure of the medium after the temperature-activated means of the sprinkler is triggered and while the sprinkler is in its active state, and which first spindle part, when the temperature-activated means of the sprinkler is trig- gered, is arranged to move against the spring-back force of a spring from the first position to a second position in such a manner that it opens the second channel as a result of the medium directing to the first action surface area at least a first pressure, and that the first spindle part comprises an additional surface area that is exposed to said at least first pressure of the medium when the first spindle part moves from its first position to its second position, the size of the additional surface area being selected so that it, as a result of the pres- sure of the medium, keeps the first spindle part in said second position when the pressure of the medium is above a second pressure, which second pres- sure is substantially lower than the first pressure, whereby after the tempera- ture-activated means is triggered, the sprinkler is in a first active state when the first spindle part is in its second position and in a second active state when the first spindle part is in its first position. The first pressure can be called an opening pressure. If, when the temperature-activated means is triggered, a pressure lower than the first pressure is directed to the first action surface area, the first spindle part does not move, but the first channel opens and the medium flows to the central nozzle only and the sprinkler is in its second active state. The sprinkler then sprays at a reduced output, and as a result of this, the sprinklers that are close to the fire site and in the first active state are able to continue spraying at a high power even if the pressure had decreased to a relatively low level.

[0005] When the first pressure is selected to be relatively high, for instance 50 bar, the triggering of the temperature-activated means in the sprin- klers that are far from the fire site causes in practice that in these sprinklers-

assuming that the pressure of the fire extinguishing apparatus has already due to the triggered sprinklers decreased to a level below 50 bar-only the central nozzles spray. The sizes of the first action surface area and the additional sur- face area and the force of the spring are selected to obtain the desired opera- tion of the sprinkler.

[0006] When the size of the additional surface area is selected in such a manner that the second pressure is substantially lower than the first pressure (typically at most half of the first pressure), the sprinkler that is al- ready in its first active state continues to spray with all its nozzles, even though the pressure of the extinguishing medium, for instance as a result of the trig- gering of the rest of the sprinklers, is significantly lower.

[0007] Preferred embodiments of the sprinkler of the invention are described in the attached claims 2 to 13.

[0008] The greatest advantage of the sprinkler of the invention is that by means of it, it is possible to provide a fire fighting apparatus that pro- duces a great extinguishing power even if hot combustible gases were spread far from the fire site to cause the triggering of the sprinklers far from the fire site.

BRIEF DESCRIPTION OF THE FIGURES [0009] The invention will now be described in greater detail by means of a preferred embodiment and with reference to the attached drawing illustrating an embodiment of the sprinkler of the invention, in which Figure 1 shows the sprinkler in its standby state, Figure 2 shows a triggered sprinkler in its first active state, Figure 3 shows a triggered sprinkler in its second active state, Figure 4 is a view from the top of the spindle part of the sprinkler in the axial direction of the spindle means.

DETAILED DESCRIPTION OF THE INVENTION [0010] The sprinkler shown in Figure 1 comprises a housing 2 with an inlet 3 for a medium, a central nozzle 4, four side nozzles 5a, 5b (only two shown in the figure), and a temperature-activated means in the form of a glass ampoule 1. Instead of the glass ampoule 1, the temperature-activated means can be some other heat-activating means, such as a metal that melts at a low temperature.

[0011] Reference numeral 8 generally marks a spindle means that is arranged to move in a housing channel 14 in the housing. The movement of the spindle means 8 will be described later. The spindle means 8 comprises a first spindle part 8a and a second spindle part 8b moving in relation thereto.

The first spindle part 8a is arranged loaded by a spring 10 inside a spindle channel 15 in the second spindle part 8b. The spindle channel 15 comprises a narrower section marked with reference numeral 9 and having a diameter that is smaller than that of the top of the first spindle part 8a. When the sprinkler is in its standby state, the top of the first spindle part 8a closes the spindle chan- nel 15 in such a manner that the spindle channel is not open to the housing channel 14. The wall of the second spindle part 8b has openings 17 through which the spindle channel 15 is connected to the housing channel 14 when the sprinkler is in the active state shown in Figure 2. A sleeve-like part 16 at the top of the second spindle part 8b is arranged to close the inlet 3 when the sprinkler is in the standby state shown in Figure 1, in which the glass ampoule 1 is intact. The top of the sleeve-like part 16 is closed with a plug 18 and the diameter of the sleeve-like part in the housing channel 14 remains the same or nearly the same on both sides of the inlet 3 in such a manner that the pressure of the medium in the inlet does not cause the spindle means 8 to cause a force directed towards the ampoule 1-or causes at most a small force directed to- wards the ampoule. Instead of the plug 18, the housing may be closed at its top in an integrated manner. The plug 18 provides the advantage that it makes the structure of the sprinkler relatively simple and the assembly of the sprinkler easy.

[0012] From the inlet 3 of the sprinkler, there is a channel 9-15-6- 12-13 to the central nozzle 4 and channels 9-15-17-14-7a and 9-15-17-14-7b to the side nozzles 5a, 5b. The channel mentioned first can be called the first channel and the ones mentioned second the second channels.

[0013] When the ampoule 1 of the sprinkler in Figure 1 is triggered, the spindle means 8 moves downward due to gravity. If the sprinkler is not ver- tical in the position of the figure, said movement of the spindle means 8 can be provided by cup springs 20 arranged at the top of the spindle means and/or by making the geometry of the spindle means such that it comprises a sufficiently large projection surface area susceptible to the pressure of the medium that under the effect of the medium produces to the spindle means a force directed towards the ampoule 1. The projection surface area is in the direction of travel

of the spindle means 8 the projected area that is perpendicular to the direction of travel of the spindle means.

[0014] When the sprinkler is triggered, it transfers depending on the size of the pressure of the medium either to the first active state shown in Fig- ure 3, in which only the central nozzle 4 sprays, or to the second active state shown in Figure 2, in which all nozzles 4,5a, 5b spray. The transfers of the sprinkler are described in more detail in the following.

[0015] When the sprinkler is triggered, the spindle means 8 drops to the position in Figure 3 and the pressure of the medium in the inlet 3 directs a pressure to a projected circular action surface area A1 (the area inside the dashed line in Figure 4) of the first spindle part 8a and through a middle chan- nel 6 of the first spindle part to an annular action surface area A3. In Figure 4 that shows a top view of the first spindle part 8a, the action surface area A1 is the section inside the dashed line. The pressure causes opposing force com- ponents to the action surface areas A1 and A3, so the action surface area A3 partly compensates for the force caused by the action surface area A1. The action surface area A1 is selected to be larger than the action surface area A3.

If, when the ampoule 1 is triggered, all nozzles 4,5a, 5b of the sprinkler are to start spraying when the pressure of the medium exceeds a certain first pres- sure, for instance 50 bar, the action surface area A1 should be selected to be so much bigger than the action surface area A3 that the force that the first pressure directs to the action surface area A1 is greater than the force that the medium directs to the action surface area A3 added by the force caused by the spring 10. The first spindle part 8a then moves to the position in Figure 2.

When moving in relation to the second spindle part 8b, a circular additional surface area A2 at the top of the first spindle part 8a comes under the pressure of the medium. The additional surface area A2 is the section remaining outside the dashed line in Figure 4 and causes to the first spindle part 8a a force that is parallel with the force of the action surface area A1, which is the area inside the dashed line. The dashed line shows the point, where the top of the first spindle part 8a is sealed against a shoulder 19 of the second spindle part 8b in the situations in Figures 1 and 3. Owing to this, the first spindle part 8a re- mains in the position of Figure 2 even though the pressure of the medium drops to the second pressure that is significantly lower than the first pressure (50 bar). The size of the additional surface area A2 is selected to be such, for instance, that the channels 9-15-17-14-7a and 9-15-17-14-7b remain open if

the pressure is at least 5 bars. The size of the additional surface area A2 is selected in such a manner that the second pressure is substantially lower than the first pressure, and is typically at most half and preferably at most 0.2 times the first pressure, which provides a good result for most applications. If the second pressure is too close in size to the first pressure, the side nozzles 5a, 5b close too early for an efficient fire extinguishing. Therefore, if the second pressure is more than 0.8 times the first pressure, the tendency of the side nozzles to close too soon is great. Figure 2 shows that the shoulder 20 in the spindle channel 15 of the second spindle means 8b covers a considerable part of the action surface area A3 when the sprinkler is in the first active state shown in Figure 2. Therefore, quite low a pressure and quite a small additional surface area A2 are sufficient to keep the first spindle part 8a in the lower posi- tion shown in the figure.

[0016] If the pressure is lower than the first pressure (50 bar) when the sprinkler is triggered, the pressure of the medium is not sufficient to move the sprinkler to the position of Figure 2, but it moves to or stays in the position of Figure 3, in which only the channel 9-15-6-12-13 to the central nozzle 4 is open. The sprinkler works in the position of Figure 3 even though the pressure is very low, for instance 2 bar.

[0017] The first spindle part 8a comprises a throttle 12 that is lo- cated after the action surface area A3 in the flow direction. Owing to the throt- tle 12, when the sprinkler is triggered, the medium directs a greater force to the action surface area A3 than if no throttle existed, which means that the spring- back force of the spring 10 does not need to be great to keep the first spindle part 8a in its upper position. The significance of the throttle 12 is emphasized depending on the size of the initial pressure designed for the sprinkler : if the initial pressure is low, the throttle is not necessarily needed.

[0018] The figures show that a helical spring 10 arranged around the first spindle means 8a forms a spiral route 13 for the medium. In the posi- tion of Figure 2, the route 13 is smaller than in Figure 3 and gives a higher speed for the flowing medium. A spiral (helical) route 13 provides efficient spraying.

[0019] The invention is above described by means of only one ex- ample and, therefore, it should be noted that the invention may differ in detail in many ways within the scope of the attached claims. The spindle means of the sprinkler need not comprise two spindle parts movable in relation to each

other, but the spindle means can be a one-piece component, in which case it is loaded by a spring from below (the direction of the ampoule). However, the two-piece structure of the spindle means makes the sprinkler structure practi- cal. The spindle means need not keep the inlet closed when the sprinkler is in its standby position, but in high-pressure solutions, this is recommended, be- cause great forces that load the sprinkler in its standby position are then not generated. Instead of a helical spring, the spindle means can, in principle, be loaded by any spring means, which means that the term'spring'in claim 1 re- fers to any spring means suitable for the purpose, including elastomer mem- bers. The surface areas A1, A2 and A3 need not necessarily be circular or an- nular, even though these forms are highly recommended in view of manufac- turing.