The present invention relates to ^.ventilation plant, especially fior stables, being of the kind which comprises one or more roof mounted down blow pipes which at the lower end are fitted with a spreading nozzle spreading the down blown air over a larger floor building. This spreading of the air is essential to permit a plant to comprise as few down blow pipes as possible. By the use of fixed spreading nozzles it is,on the other side,difficult to optimize the spreading according to varying operation con- ditions because the in-blowof the air is regulated after demand, especially to maintain a suitable temperature within the building. In case of warm weather it may be necessary with a powerful in-blow and a correspondingly powerful spreading of the air from the nozzles, whereas in case of cold weather only a weak in-blow may occur, which by the passing through the same nozzles, would result in a rather ineffe- cient and unsufficient spreading of the air.

To make a good spreading of the air possible, also in case of weak in-blow, it is well known to attach a valve system to the spreading nozzles by means of which the speed of the air out through the nozzles can be kept accep¬ tably high, even when the in-blown amount of air is small. On the other side it is normally so, that the valves hereof,be¬ ing -concerned, only manually are adjustable, f.i. between operation during summer and during winter, as a possible automatic servo control of the valves would present a very costly solution to obtain an optimzing of the plant. A well known other and to some extend better solution is to use rotatable spreading nozzles which give an in-blow of air in form of a single or very few concentrated rays which by the rotation are brought to sweep over the area at the vicini¬ ty of the single down blow pipes; a rather good spreading effect even in case of a rather weak in-blow can be attai¬ ned but with the limitation that it is difficult obtain an even spreading of the air in case of respectively powerful and weak in-blow of air so that a manual valve adjustment

may be demanded for an optimization of the plant f.i. re¬ spectively to-operation during summer or during winter. The pupose of the present invention is to present a ventilation plant by means of which the in-blow of air through the spreading nozzles can take place in a simple way so that the speed of the air through the nozzles can be kept approximately constant irrespective of the volume speed of the air, that is, that the air undergoes a sprea¬ ding which is approximately even irrespective of the in— blow is powerful or is weak.

This is attained by means of the present invention in that a valve plate is positioned below the exit ope¬ ning of the single blow down pipes which valve plate in direction towards the exit opening of the down blow pipe is biased by a spring with a spring force which is adapted in such a way that the down-blown air influences upon the valveplate to be shiftedmore or less downwards away from said opening depending upon the volume speed of the in-blown air. In this way the size of the exit mouth slot existing between the exit mouth of the pipe and the valve plate automatically is augmented at increased ventilation and is diminished at more weak ventilation, in this way it has shown itself possible to obtain that the air speed of the radiated air from the valve plate is kept approximately constant irrespective of changes in the size- of the venti¬ lation, that is, that the spreading of air around the in- blow-nozzle automatically is kept approximately constant solely due to the spring biased valve plate.

The valve plate works especially satisfactory when the exit mouth of the down blow pipe possesses a projec¬ ting, rounding possessing rim which terminates in a mainly horizontal external ring shaped plate means which together with the valve plate forms an outwards radiating ring nozzle.

In practise it is to be wished that the in-blow nozz- le is kept completely closed during winter, when the venti¬ lation is shut o f, to prevent chilled air-intake from the

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down blow pipe. It is well known to use special tiltable closing valve means which automatically close when the down blow approaches zero, but according to the invention the applied valve plate in itself can be utilized to per- form this at zero closing of the down blow pipe, as the mentioned spring may be thus adjusted that it safeguards the attainment of a complete closing position of the valve plate when this plate not becomes affected by a blow down pressure. If wanted, the valve plate for this purpose might be biased a little in direction towards the exit mouth of the down blow pipe so that the plate not opens in case of casual occurence of varying pressure pulsations.

On the other side, during summer it might be wanted, that the valve plate not closes completely, even in case of shut off of the ventilation, as hereby a wanted minimum ventilation can be obtained without having the ventilation in operation. This want it is possible according to the present invention to fulfill in the simple way that the complete valve-plate-spring-biased-system is arranged height adjustable in which way the valve plate may be adjusted to obtain an upper positioning having a wanted spacing from the exit mouth of the pipe from which upper position the valve plate is movable further downwards against the influence from the spring. In case of a powerful in-blow of air it may be wanted, that the air blown outwards from the nozzle not only is radiated horizontally, as this might lead to a bad di¬ stribution of air at the floor, but to attain a better distribution is radiated as well horizontally as with a downwards directed component. This downwards directed com¬ ponent is according to the invention automatically ob¬ tained, in that, that the valve plate at a comparatively low pushed down position, corresponding to a powerful in- blow of air, opens the ring nozzle so much that not all down blow air reach to be directed horizontally out from the nozzle but that some part of the air only changes di-

rection to be directed into an oblique downwards directed radiation from the nozzle.

Preferably the said down blow pipe in well known manner comprises a built-in ventilation blower which in a non-step-manner is regulated according to the ventilation demand detected by means of temperature sensors.

Practical experiments utilising the invention have shown that the automatical control of the in-blowing nozzles lead to a significant reduction of the energy con- sumption required by the actual and demanded ventilation. As follows the invention is further explained with reference to the drawing which in cut-away-view illustra¬ tes a prefered embodiment of a down blow pipe for a plant according to the present invention. in the drawing a down blow pipe 2 is illustrated mounted in a roof 4. At the top the pipe 2 comprises a suck-in nozzle means 6 whereas inside the pipe a fan 8, which in a non-stepwise manner regulable by means of temperature sensors and possible moisture sensors within the room to e ventilated is driven by means of a motor TO, provides a downwards directed air flow. The lower and exit mouth end of the pipe 2 possesses a projecting rim 12 beneath which a valve plate 14 is arranged which plate in vertical direction may be moved up or down on a centrally positioned downwards protuding rod 18 which is mounted within the pipe 2 by means of radial support rods 16. The valve plate ^' 14 is supported on the upper end of a compression spring 20 which is positioned around the rod 18 and of which spring the lower end is supported by a bushing 22 which by means of a set or pinching screw 24 or by means of any other sqeezing means is permitted to be fixed to the rod 18 corresponding to any wanted height level positonings on the rod.

For the use during winter the carrying bushing 22 is positoned at such a height level on the rod 18 that the valve plate 14 just is closing against the projecting rim 12 of the down blow pipe with the ventilator 8, 10 being

shut off in which case the down blow pipe 2 is closed against lead-through of down-falling cold air from above. With the ventilator 8, 10 being started the valve plate 14 is pushed downwards against the influence from the spring 20 and a radiation of air in horizontal direction through the ring shaped slot 26 takes place,which ring shaped slot thus is formed between the outstanding rim 12 and the valve plate 14, ref. the illustrated arrow A. In case of powerful ventilation the valve plate 14 is pushed further downwards to the position shown in dotted line, at which position a part of the in-blown air due to the augmented size of the opening is blown outwards-downwards according to the arrow B shown in dotted line.

During summer the carrying bushing 22 is moved further downwards upon the rod 18 so that the exit mouth of the pipe not is completely closed at shut off ventilation, but elsethe automatically performed regulating of the size of the slot takes place during operation, just as earlier described. it is aforementioned, that the valve plate lends itself to be pushed downwards against the force from a spring, but it is to be understood that an alternate and useful embodi¬ ment is to be found by the use of a balance system employing a counter weight which system not seems to need a further and detailed description to be understood.