The present invention relates to a sprinkler which in stand-by mode comprises a heat-sensitive releasing device in close contact with a spindle. More specifically, the invention relates to a sprinkler comprising a body provided with at least one nozzle, a liquid inlet and a passage for supplying extinguishing medium to at least one nozzle, the sprinkler in stand-by mode comprising a heat-sensitive releasing device in close contact with a spindle displaceably mounted in a liquid passage with an inlet and outlet to said nozzle.

The releasing device can be, for example, a glass ampoule which breaks at an elevated temperature. In order to ensure rapid release, it is desirable to make the ampoule as thin as possible. Even a thin ampoule resists a sufficiently heavy mechanical load if the load is exerted directly on the end of the ampoule and is even. SE 501 267 discloses a sprinkler of this kind.

However, the known sprinkler does not allow a high liquid pressure to prevail in the liquid inlet when the sprinkler is in stand-by mode, and therefore rapid release of the sprinkler is not possible. In this known sprinkler, a high liquid pressure would exert such a great force on the releasing device that the releasing device would break or. In order to avoid breakage, the releasing device should have a special construction.

The object of the present invention is to provide a new sprinkler which ensures even and straight load on the releasing device; the load is not so heavy that the releasing device can break merely by the action of the liquid pressure when the sprinkler is in stand-by mode.

The sprinkler according to the invention is characterized in that the liquid passage consists of a channel against whose wall the spindle bears slidably or almost slidably, said spindle and channel extending to both sides of the inlet of the channel for at least partial balancing of the liquid pressure at the inlet when the sprinkler is in stand-by mode, and that a nozzle centrally directed in relation to the obliquely positioned nozzles is provided at that end of the spindle which faces the releasing device. Preferred embodiments of the sprinkler are disclosed in appended claims 2 to 4.

In the following, the invention will be described in greater detail with reference to an embodi- ment shown in the accompanying drawings, in which

Figure 1 is a longitudinal section of an embodiment of the invention in stand-by mode,

Figure 2 shows the sprinkler of Figure 1 in released mode, Figure 3 is an end view of the sprinkler, seen from below.

In Figures 1 and 2, reference numeral 1 denotes a sprinkler. The sprinkler comprises a housing 2, which is secured to a ceiling 4 by a plurality of screws 3; the housing 2 is provided with a liquid inlet 5, which extends through the ceiling 4 and continues as a central channel 6. The sprinkler is further provided with an insert 7 comprising a housing 8 which is attached to the sprinkler housing 2, for instance, by means of a head 9 screwed in the central channel 6 and tightened against it.

The head 9 of the insert housing 8 comprises a plurality of inlet openings 10 which are connected through a filter 11 to the liquid inlet 5 and which lead to a central channel 12 in the head 9. The central

channel 12 branches off through branchings 13 to a plurality of obliquely positioned nozzles 14. A spindle 15 is slidably mounted in the central channel 12 of the insert housing 8. When the sprinkler is in stand-by mode, as shown in Figure 1, the spindle 15 is sealed against the head 9 by means of a sealing 16 below the liquid inlet openings 10. The central channel 12 extends to both sides of the liquid inlet openings 10 to prevent the liquid pressure from exerting too great a downward force on the spindle 15 when the sprinkler is in stand¬ by mode.

The spindle 15 is also provided with a central channel 17 (hereafter: spindle channel) which below the spindle sealing 16 is connected via openings 18 to the central channel 12 of the head 9 and therefrom via the branchings 13 to the nozzles 14.

A holder 19 for a releasing device 20, e.g. an ampoule of a heat-sensitive glass-like material which softens and/or melts at an elevated temperature, is mounted on the bottom of the insert housing 8. The inner end of the ampoule 20 is fitted into the outer end portion 21 of the spindle 15, through which it is loaded by a spring 22 provided in the central channel of the spindle. The end of the spring 22 that faces the ampoule 20 bears against the bottom of the spindle channel 17 at a shoulder 33, whereas its opposite end bears against a plug 24 which is mounted in the head and sealed against the inside of the spindle channel 17 by means of an annular sealing 25. Alternatively, the shoulder 33 can be positioned higher in the spindle channel 17, and an adjustable stopper can be used instead of the plug 24.

The force of the spring 22 and the (typically very small) annular area of the sealing 16, on which the liquid pressure acts at the inlet openings 10, are

dimensioned in such a manner that they do not break the ampoule 20 when its temperature is normal in stand-by mode as shown in Figure 1. If the part of the spindle 15 that is located above the sealing 16 is in close contact with the surrounding wall of the head 9 on both sides of the inlet openings 10, the liquid pressure is in complete balance; only the spring 22 presses the spindle.

In stand-by mode illustrated in Figure 1, there is, because of sealing 25, no liquid connection from the inlet openings 10 through the upper end of the spindle channel 17 to the nozzles 14; the direct connection is closed by sealing 16.

If the ampoule 20 breaks or at least softens because of hot gases or active heating by means of a heating coil (not shown) and yields under the force of the spring 22, as shown in Figure 2, the spindle 15 strikes down until a shoulder 23 provided on said spindle interlocks tightly with a shoulder 26 provided in the insert housing 8. The spindle 15 moves a suffi¬ ciently long way to provide a connection for the liquid from the inlet openings 10 through the channel 12 in the head 9 past the sealing 25 to the spindle channel 17 and further to the nozzles 14 via openings 18 in the spindle 15. The nozzles 14 are preferably of such a type that they operate under high pressure and spray penetrating extinguishing liquid in the form of liquid fog in accordance with, for example, patent application PCT/FI92/00155. Before the insert 7 is mounted, the ampoule 20 and the spindle construction 15, including the spring 22, are positioned in the insert housing 8. Thereafter the insert 7 is mounted in its entirety. It is thus easy to carry out careful mounting without damaging the ampoule, which is sensitive to shocks and uneven load.

The outer end portion 21 of the spindle 15, i.e. the end which faces the ampoule 20, is provided with a nozzle 27 having preferably the same basic con¬ struction as the nozzles 14 with a coil spring 28 around a nozzle pin 29. In the released position shown in Figure 2, the liquid, in addition to flowing out through the nozzles 14, also flows from the spindle channel 17 through openings 30 in between and along the spirals of the spring 28 through a nozzle opening 31 and spreads through oblique spread surfaces 32 provided at the outer end of the holder 19.

The central nozzle 27 at the end of the spindle 15 ensures that there is no "hole" in the liquid fog produced by the sprinkler.