WO2004031661A1

WO2004031661A1 - Injection head especially for stables with variable injection opening

Info

Publication number: WO2004031661A1
Application number: PCT/DK2003/000649
Authority: WO
Inventors: John L. Christensen
Original assignee: Skov A/S
Priority date: 2002-10-02
Filing date: 2003-10-02
Publication date: 2004-04-15
Also published as: AU2003269838A1; PL376406A1; DK200500577A; RU2005113290A

Abstract

The invention concerns an injection head for use in a ventilation system, including particularly for use in ventilation systems in stables for animal production. The injection head is peculiar in that the opening between the outlet funnel and the bottom plate constitutes the injection opening, and that the size of the injection opening can be varied by continuously variable adjustment of the bottom plate in relation to the outlet funnel. By thus being able to vary the injection opening in size, one may control the air volume drawn in but also control the thickess of the air jet.

Description

Injection head especially for stables with variable injection opening

The present invention concerns an injection head for use in a ventilation system, including particularly for use in ventilation systems in stables for animal production.

By all modern forms of animal production it is necessary to control all parameters to which the livestock are exposed, being temperature, humidity, water, feed mixture, feed amount and ventilation. Speaking of ventilation, it is very important to provide sufficient fresh air in so that the climate in the stable becomes optimal as well as to ensure that the airspeed in the stable, particularly in the living zone of the animals, does not become so great that the animals are exposed to draught with associated health complications.

In a modern stable, the ventilation is typically provided by ventilation openings ar- ranged in the side walls, end walls, or in ceiling and air vents in the roof of the stable.

By means of usually mechanical means there is created a subpressure in the stable so that fresh air is sucked out through an air vent, e.g. arranged in the ceiling. By being able to regulate the amount of air that is sucked out of the stable, it is possible relatively precisely to control the air volume that is replaced in the stable per hour. Par- ticularly in large stables with many animals, including particularly pigs and poultry, it is a problem to get the air renewed quickly enough without the airspeed around the animals becoming too high.

A typical air intake taking in the air over the roof consists of a roof chimney arranged upon the roof and connected via a pipe to an injection head which is disposed under the ceiling inside the stable. The injection heads are typically circular with a diameter of about 1 meter and designed with manually adjustable nozzles in various numbers.

In some cases, the injection head is designed so that a controllable slotted opening discharges the air as a radial jet. A prior art system is based on guiding in the air via a controllable louvre damper that utilises the Coanda effect by small outputs and thereby directs the air along the ceiling. By large outputs, the air is directed down towards the living zone of the animals. For all prior art systems with injection head, there is, however, quite fundamental problems, implying a number of disadvantages with this kind of ventilation.

Manually controllable nozzles provide an unsuitable procedure in animal production. The systems that have a controllable radial slot opening are only regulating with one plate and with mechanical principles that do not ensure the same opening all the way round, as well there is only regulated up to maximum about 150 mm slot opening, realising that the air is discharged at the same maximum level due the angular turning of the air from vertical movement through chimney and pipe into horizontal move- ment at the discharge through the inj ection head as radial j et.

The result is that small air volumes are coming differently out into the stable room with cold downwards draught as a consequence. Large air volumes are coming out from the injection head with so great airspeed that the airspeed in the living zone of the animals becomes so great that it detracts from the comfort of the animals and thereby the production. Another problem is that a circular injection unit is also ventilating a circular area. As stable buildings are preferably four-sided/rectangular, for this part of the stable interior is aimed at a injection head ventilating a square area. By and large this is impossible in practice if the desired air outputs and actual stable geometry is to be accounted for. In practice, various geometries of rectangles are ventilated, resulting in too great airspeeds across and too poor ventilation lengthwise.

A further problem with prior art ventilation systems is that the external wind actions may provide an air intake situation where air only comes out of one side of the injec- tion head, a phenomenon which is particularly distinct at small outputs where there is only slight air resistance in the opening of the injection head. The incoming air collects itself and is discharged at one side of the injection head (in the wind direction), with poor ventilation as a consequence.

Apart from the airspeed at the animals, i.e. in the living zone of the animals, it is also important that the temperature around the animals is kept relatively constant, and this means that it is necessary to minimise temperature variations. This is particularly a problem if e.g. there is +30°C inside the stable and -30°C outside the stable. When fresh air is used right from outside, it will be sucked into the stable at -30°C. Then it is heated inside the stable to about +30°C before reaching down into the living zone of the animals. This is to occur at the same time as a relatively large volume of air is to be replaced each hour.

Thus it is the purpose of the present invention to provide an injection head that provides for the conditions described above, namely providing for suitably low airspeed in the living zone of the animals simultaneously with a required large volume of air is ventilated each hour and relieving the disadvantages of the prior art ventilation ar- rangements.

The present invention thus provides an injection head for use in a ventilation system, where the injection head includes an outlet funnel and a bottom plate. This type of injection heads are particularly used for stable ventilation with animal production.

In connection with the present invention, the application will mainly be provided in connection with stables and animal production, but the invention is just as suited for other spaces, e.g. open-plan offices or other places where the need for ventilation exists.

According to the present invention, this is achieved with an injection head which is peculiar in that a gap between the outlet funnel and the bottom plate constitutes an injection opening, and that the size of the injection opening may vary by continuously variable adjustment of the bottom plate relative to the outlet funnel. For thus being able to vary the injection opening in size, one may control the volume of air drawn in, but also control the thickness of the air jet.

When the fresh air moves down through the chimney and on to the injection head, the cold fresh air will be conducted out into the warmer stable air as a kind of waterfall. The greater the injection opening, the lower the airspeed in the injection opening will be, but conversely the fresh air will only reach a limited distance from the injection opening into the stable space. By reducing the injection opening, the cold air jet will be thinner and attain greater speed in the injection opening itself, whereby the fresh air jet may get farther into the stable space. Thus it is of great interest to be able to control the air flow in the injection head.

In a further embodiment, one or more distributor plates are arranged in a plane in par- allel with the plane of the bottom plate, and where the distributor plates are arranged in the injection opening. Hereby, division of the incoming fresh air stream into several separate air streams is achieved. Experiments have shown that this feature reduces the airspeed in the injection opening, whereby considerably greater volumes of air may be brought into the stable, without the airspeed in the living zone of the animals being increased.

Many experiments with optimisation of the airspeed in the living zone of the animals have shown that the optimal airspeed in the living zone of the animals is between about 0.2 m/s and 0.3 m/s by optimal temperature conditions.

According to a further advantageous embodiment of the invention, each distributor plate is designed as a circular ring. Typically, the outer diameter of the circular ring will correspond to the outer diameter of the outlet funnel and corresponding outer diameter of the bottom plate. The inner diameter of the circular ring will typically be about half of that. By shaping the distributor plats as circular rings it is achieved that the air stream coming down through outlet funnel will be distributed on the different distributor plates, and thereby a number of air streams corresponding to the number of distributor plates plus the bottom plat appear. As each air stream becomes thinner, it may reach relatively shorter out in the stable space, whereby each ventilation injection head may introduce a greater volume of air in the stable simultaneously with the air volume becoming more optimally distributed in the stable space, thereby achieving the desired low airspeeds in the living zone of the animals.

In a further embodiment, there is arranged a cone where a top of the cone is pointing towards the outlet funnel. Hereby is achieved that the air drawn into the stable is conducted in a soft course on to the injection opening between the bottom plate and the outlet funnel, or alternatively between the bottom plate and the lowermost distributor plate. Hereby turbulence in the air flow is reduced, whereby the air streams out of the injection head become more laminar, whereby better ventilation is achieved.

In an advantageous embodiment of the invention, the continuously variable adjustment of the injection opening may be effected by means of a wire drive, where three or more separate wires are fastened to the bottom plate. Each wire is then passed around associated pulleys with horizontal axis, where the pulleys are mounted on the outlet funnel. Then all the wire ends are passed via further pulleys to a common tension wire or tension rod that is connected to a controllable tension unit. The common tension wire is typically to be moved between 300 and 500 mm for opening or closing the ven- tilation opening, respectively. The ventilation opening is closed by pulling the wires until the bottom plate has contact with the outlet funnel. Experiments have shown that a typical construction according to the invention will have a tensile force demand of about 15 kg per unit for the above mentioned length of pulling movement.

In an alternative embodiment according to the invention, the wires connected to the bottom plate are connected with a single tension wire which via pulleys is passed around the injection head. In that way is ensured that by pulling only one horizontal wire, the tension is transmitted via pulleys to the three or more vertical wires that are connected to the bottom plate. Hereby is achieved a 100% parallel displacement of the bottom plate, as all vertical wires are subjected to the same movement, namely the pulling action in the horizontal wire.

In order to further optimise the air stream out of the injection head at the passage of the distributor plates, one or more distributor plates may be designed so that the in- nermost part of the circular ring is curving upwards relative to the plane of the distributor plate. This construction provides several advantages, as the air stream, when passing the outlet funnel, becomes deflected on the distributor plate due to the upwards curving innermost part, so that turbulence in the air stream in the transition from vertical to horizontal, namely from intake through the chimney pipe and the out- let funnel and the transition via the distributor plate to a largely horizontal flow into the stable, is diminished. Furthermore, this provides the possibility that more distributor plates may be arranged in the injection opening, as the cone, which is arranged on the bottom plate with upwards directed point, may fit into the upward bent shape of the one or more distributor plates. Hereby, the diameter of the innermost ring on the distributor plate may be reduced, so that a greater volume of air may be delivered on the lowermost distributor plate.

When more than one distributor plate is used, the plates will typically have different geometry. Distributor plates with larger inner openings in the circular ring will be arranged uppermost, for in that way to allow air streams to be distributed to all distributor plates and the bottom plate. By so varying the inner opening on the various distributor plates, the volume of air distributed on each plate may be determined.

In general, the innermost diameter, i.e. the opening in the circular ring on the distributor plates, is determining how large part of the air volume that is drawn into the stable becomes distributed in the air stream corresponding to the individual distributor plate. The less internal diameter on each distributor plate, the greater part of the total volume of air is injected in that particular air stream. By combining distributor plates with different geometry and different internal diameter, the injection characteristic of the injection head may be optimised, so that the injection air supply is optimised simultaneously with the airspeed aimed at in the living zone of the animals is maintained at the optimal level.

The bottom plate, as well as the distributor plates, may as described above have varying geometry. In the most simple embodiments, bottom and distributor plates may be entirely plane, and in more advanced embodiments, there may be provided upwards curving inner as well as outer edges, for cutting off a laminar air stream of the incom- ing air stream supplied through the chimney and for delivering and discharging the air stream into the indicated space with a desired angle, respectively. This angle may be varied, depending on the conditions and the type of chimney. In some applications it is desirable to achieve a adhering effect for the air stream along the ceiling, whereas in other cases it is desirable to provide a narrow free air jet that is carried out into space.

In a further, advantageous embodiment of the invention, there is arranged one or more adjustable air directing plates in immediate vicinity of the injection opening in a plane largely perpendicular to the bottom plate. Hereby is achieved that the horizontal air streams that are blown out between outlet funnel and the bottom plate, and in some embodiments between the distributor plates, may be controlled so that a greater or lesser part of the airstream may be directed towards a certain point in the stable. This is interesting as most stables are four-sided, and particularly rectangular. This means that in order to achieve optimal ventilation in the living zone of the animals, it is necessary not only to direct the air radially out from the injection head, but also to control the ventilation so that largely the same ventilation is achieved in all areas of the stable, i.e. the same volume of fresh air is aimed at being supplied everywhere in the stable.

In a particularly advantageous embodiment, 12 pairs of air directing plates are arranged in the injection opening, so that the total ventilation airflow can be differentiated in up to 12 separate adjustable and controllable air jets.

In a further variant of the injection head according to the invention, a ventilator may be arranged in the bottom plate and which may draw the injection air down through the chimney and thereby conduct the air to the outlet funnel and the different distributor plates and the bottom plate. Alternatively, a ventilator may be placed in or before the outlet funnel, whereby air is pressed down through the injection head.

In a further embodiment of the injection head according to the invention, a ventilator may be arranged in the bottom plate, sucking up warm air from the stable floor and distributing it around the bottom plate. Hereby is achieved that a so-called carrier layer is created, whereby possible cold downdraught due to the incoming cooler outside air is hindered, so that the air deflected in the distributor plate and the bottom plate is car- ried a distance out from the injection head on the warm air stream provided by using a ventilator.

By furthermore providing a screen in the shape of largely vertical and in one direction parallel guide members, e.g. in the form of plate pairs, the air stream may be aligned so that the fresh air will be carried farther away from the injection head along the parallel guide members. The effect of ventilating rectangular spaces is thereby enhanced, and at the same time fewer injection heads may be used for achieving a high degree of ventilation. The distributor plates are suspended separately in relation to the continuously adjustable bottom plate. Besides, the distributor plates may be provided with means for preventing that they are brought to oscillate during operation. These means may e.g. be in the form of guide rails that are arranged vertically and in displaceable engagement with the distributor plates and the outlet funnel.

The outlet funnel may in principle be made of all types of suitable materials, but in a preferred embodiment it is made of a double-shell, glass-fibre reinforced polyester, which is smooth and cleaning friendly while at the same time forming a good insula- tion against formation of condensation. Alternatively, it may be made of a plastic or a thermosetting plastic.

With regard to the continuously variable adjustment of the bottom plate, pulleys may either be made as an integrated part of the outlet funnel or as separate plastic or light alloy metal parts that may be fastened to the outlet funnel. All pulleys and fittings are typically made of an injection moulded and imperishable plastic material or of a rustproof metal material.

The bottom plate is typically made of a double-shell, glass-fibre reinforced polyester like the outlet funnel, for also here to achieve a smooth and cleaning friendly surface and likewise to achieve a good insulation ability so that formation of condensation is prevented.

The distributor plates may also be made of glass-fibre reinforced polyester. For all components on distributor plates, bottom plates and outlet funnel, other materials, such as glass-fibre, various other plastic materials, thermosetting plastic materials, or other different suitable metal materials may be used.

For some applications, the colour of injection head and chimney is of less importance and may thus be selected freely, e.g. the material of manufacture may stand untreated.

In other applications, it is however desirable e.g. to limit light influx through the chimney and injection head. In these cases, the components may advantageously be coloured e.g. black, grey or the like. For aesthetical reasons it may furthermore be desirable to colour the components so that these either do not appear dominating in the interior, or for other reasons.

With regard to cleaning and service it is important that bottom plate and distributor plate may be lowered and thereby become accessible for the staff. In a particularly advantageous embodiment, both bottom plate and distributor plate may be detached from their respective suspension in order that they will hang down largely vertically, facilitating access but also cleaning. Where ventilators are installed in or in connection with the bottom plate, this is also mounted so that it may easily be loosened and taken out for efficient cleaning.

In some situations, the temperature difference between the injected air and the air in the space may be so that condensation is formed on mainly the outer side of the chimney pipe.

In order to control the condensation water, the outlet funnel may be provided with a drop point. Particularly in those cases, where the diameter of the outlet funnel is greater than the diameter of the bottom plate, it is hereby prevented that condensation moisture/water ends up on the bottom plate where there may be provided a ventilator or something else.

In cases where the injection air is below the freezing point, ice may be formed, e.g. in the shape of icicles along the periphery of the outlet funnel, where a drop point may be provided. The icicles will grow with continued supply of cool air until they have reached a size where the air in the space will cause melting corresponding to the ice formation. Formation of icicles may be disadvantageous in connection with regulation of the airstreams, particularly where the regulation is performed by adjusting the distance/height of the discharged air jets. When the plates are moved together, the icicles and/or other ice formation will prevent closing. Depending on how strong the tension in the wire is, one or more plates may be damaged. In a further embodiment is therefore provided a device so that the plates cannot be brought more together than to an adjustable slot width. If ice or similar gets caught, the suspension fitting, i.e. the fittings guiding the wires, is made with a pre-stressed spring that only yields when the force is clearly exceeding the "normal", i.e. predefined, force requirement. If the maximum functional force is 15 kg, the spring will be adjusted to 20 kg, and may then allow the wire move further, about 4 cm, even if the plate is not entirely closed, missing maybe up to 4 cm before being entirely closed due to ice or similar.

In a further, preferred embodiment of the invention, inserts are placed in the outlet funnel in such a way that the airstream is screened along two parallel, straight sides. The airstream is hereby controlled so that the sucked in air is largely prevented from expanding against the two inserts, whereas there is unlimited injection in two opposite directions, so that thereby an oblong air jet is formed. Hereby, there is possibility of distributing the air in the stable space so that an oblong area can be efficiently ventilated, whereby a better climate is achieved in all living zones for the animals. The inserts arranged in the outlet funnel are to be adapted according to the dimensions of the injection head so that optimal ventilation is attained under all conditions.

The invention will now be explained in detail with reference to the accompanying drawings, wherein:

Fig. 1 shows a schematic drawing of the injection head; Fig. 2 shows a schematic drawing of the injection head with air directing plates mounted thereon;

Fig. 3a shows airspeed profile in injection head without distributor plates;

Fig. 3b shows airspeed profile in injection head with two distributor plates;

Fig. 4 shows a diagram of airspeeds in the stable; and Figs. 5- 8 show various installation alternatives.

Fig. 1 shows a schematic drawing of an injection head according to the invention. The outlet funnel 1 is mounted in continuation of a chimney pipe 2. In this example, wires 3 connect the bottom plate with an adjustment device 4 mounted on the outlet funnel 1. Hereby is achieved that the bottom plate is hanging in a plane in parallel with the plane of the outlet funnel, so that the injection opening 5 may be adjusted continuously. In the injection opening there is arranged two distributor plates 6, 7. On the bottom plate 8 itself there is arranged a cone 9, which in the present example protrude up through the innermost opening in the circular ring on the distributor plate 7. In this way, the air stream drawn in through the chimney pipe 2, is guided further through the outlet funnel 1 onward to the distributor plates 6, 7 and the bottom plate 8, where the airstream is turned from a vertical, downwards going airstream into a horizontal, out- wards going airstream on the individual plates 6, 7, 8 at the encounter with the distributor plates and the bottom plate.

The continuously variable bottom plate 8 is shown in this example as suspended in four wires 3 that run over an adjusting device 4 in the shape of pulleys. The wires from the bottom plate are connected to a horizontally running wire 10 so that horizontal pull in the wire 10 causes the vertical wires 3 to be displaced a corresponding distance. In that way one may ensure 100% parallel motion between the four suspension wires 3 for the bottom plate. This relatively simple mechanical system is distinguished by being capable of regulating the bottom plate and the distributor plates as far down as the distance between the horizontally disposed pulleys, typically up to a little less than one meter. Furthermore, an entirely uniformly regulating slotted opening is achieved all the way round, as all inelastic wires are connected to one wire that is largely inelastic also.

In Fig. 2 is shown a further embodiment of the invention, where besides distributor plates there may be fitted air directing plates 11 in the injection opening 5.

In Fig. 2 is shown a division of the injection opening with a number of air directing plates 11, whereby the injected air is divided into e.g. twelve separate airstreams which may be controlled individually and adjusted by means of the air directing plates, so that all the areas of the stable may be supplied with a desired air volume. This is particularly applicable in connection with four-sided and particularly rectangular stables, as the radial ejecting of air may provide a circular injection configuration in its undisturbed form, whereas by adjusting with air directing plates one may approxi- mately achieved the same air volume supplied to all corners of the stable.

In Fig. 3a is shown measurements performed on an injection head without distributor plates, where the speed profile in the intake is illustrated with a "tongue" 21. In Fig. 3b, corresponding speed profiles in the intake are illustrated for an injection head in which there are arranged two distributor plates 6, 7 and a cone 9 on the bottom plate 8. Here, the Figure shows division of the airstream into three tongues 12, 13, 14.

The centre of the annular distributor plates may have different hole diameter so that identical air volumes are led out on each of the horizontally disposed plates which then provide the same number of uniform radial air jets as the number of plates. This results in a substantially reduced airspeed out of the injection head, enabling attaining the lower airspeed desired in the living zone of the animals. By furthermore making all distributor plates with the same discharge angle, i.e. the angle relative to horizontal of the outermost part of the plate, typically with a discharge angle of about 20° and above, an increased length of throw of air by free jets as well as better possibility of sure adhering effect at the ceiling are ensured. By furtheπnore making a suspension of intermediate plates in a suspended cord, the unit can be closed more or less by elevat- ing the bottom plate and carrying with the lowermost plate firstly and subsequently the other plates up so that at last only a small slot opening is left between the uppermost intermediate plate/distributor plate and the outlet funnel, so that a small air volume can be distributed in an even radial jet and with so great speed in the opening that it does not give any cold downdraught in case of large temperature differences.

Measurements in the laboratory has shown that the airspeed in the injection area on an injection head according to the invention mounted with two distributor plates is about 3 m/s at 12,000 m³ per hour. The corresponding speed in an injection head without the distributor plates was measured to about 9 m/s at a yield of only 8,500 m air per hour. Thus it is clear that the distributor plates and the inventive design of the injection head according to the invention provides a far greater air supply in the stable at a lower speed than the traditional injection heads. A part of the explanation of the increased effect at lower speed is that the distributor plates are splitting the total airstream up into two or more separate jets which thereby are substantially slowed in the injection opening, whereby an increased air volume can pass through the same injection head.

In Fig. 4 is illustrated measurements made on the speed profile of the injected air from an injection head according to the invention. The speed is measured at 1.8 m apart from the injection opening as a function of the level above the floor. It clearly appears from the Figure that the speed in the living zone of the animals, i.e. between 0 and 1 m above the floor, is considerably lower than the desired requirements for a maximum airspeed of between 0.2 and 0.3 m/s.

By an injection head according to the invention is thus achieved a ventilating injection head where a substantially lower airspeed in the living zone of the animals is achieved with a considerably greater air volume.

Besides improving the growth conditions of the animals in the living zone, one also achieves a substantial energy saving, as an injection head according to the invention at a usual subpressure of about 40 Pa may provide 12,000 m per hour without using ventilator, compared with a tradition injection head with the same physical conditions where 5,500 m per hour is discharged. A traditional injection head cannot supply a corresponding air volume. By installing a ventilator in a traditional injection head with the same dimensions, one may attain about 8,500 m³/h before the airspeed becomes too high in the living zone of the animals. Using a ventilator corresponds to a power consumption of about 3000 kWh per year, and in addition there is acquisition of extra injection heads for providing the required ventilation supply. This means that the in- jection head according to the invention without ventilator provides an annual saving of about 3,000 kWh.

In Figs. 5 - 8 are illustrated different installations, where the stable room 15 is ventilated by means of an injection head according to the invention. The injection head 16 is arranged in Fig. 5 together with means for mechanical ventilation 17. The ventilator

17 produces subpressure in the stable 15 so that fresh air is drawn in through the injection head 16.

In Fig. 6 is illustrated a corresponding arrangement, but where the stable is made with pitch so that the connecting pipe between the roof chimney and the injection head is considerably longer.

In Fig. 7 is illustrated an example of how the injection head receives the air from the space between the roof and the ceiling over the stable space, so that fresh air is sucked into the ceiling compartment, whereafter it is led down in the edge and out of the injection head due to the mechanical ventilation 17.

Finally, in Fig. 8 is illustrated a system with injection head directly connected to ambient surroundings via the chimney. Besides that the means for mechanical ventilation

17 provide subpressure inside the stable 15 itself, it may be necessary in this situation to supplement the injection head 16 with a recirculation ventilator 18. The ventilator

18 produces a carrier airflow of warm air illustrated by the arrow 19, carrying the fresh, cold air illustrated by the arrow 20 so that the radial jet from the injection head

16 can reach farther out. This may be necessary in a stable space where injection is performed at a certain distance from the ceiling, as no adhering effect can be achieved here like e.g. in the examples illustrated in Figs. 5, 6 and 7. In order thereby to achieve that the fresh air becomes evenly distributed in the entire space and does not end as cold downdraught, by means of the recirculation ventilator 18 there is thus provided a radial carrier air jet.

In the above the ventilation system and particularly the injection head have been explained with reference to a stable for animal production. However, it is to be under- lined that the injection head and its distributor plates, which are providing a very large fresh air volume with relatively lower airspeed in the living zone, are also suited for installation in workshops, halls, sports centres and similar places where there may be need for frequent air change in order to achieve and provide for the indoor climate.

Claims

1. Injection head for use in a ventilation system, where the injection head includes a outlet funnel and a bottom plate, characterised in that a gap between the outlet fun- nel and the bottom plate constitutes an injection opening, and that the size of the injection opening may vary by continuously variable adjustment of the bottom plate relative to the outlet funnel.

2. Injection head according to claim 1, characterised in that one or more distributor plates are arranged in a plane in parallel with the plane of the bottom plate, and that the distributor plates are arranged in the injection opening.

3. Injection head according to claim 1 or 2, characterised in that each distributor plate is designed as a circular ring.

4. Injection head according to one or more of the preceding claims, characterised in that a cone is arranged on the bottom plate, where a top of the cone is pointing towards the outlet funnel.

5. Injection head according to one or more of the preceding claims, characterised in that the continuously variable adjustment of the injection opening is effected by means of a wire drive, where three or more separate wires are fastened to the bottom plate, and each wire is passed around associated pulleys with a horizontal axis mounted on the outlet funnel, and that all wires are connected to a common tension wire or tension rod, and that the common tension wire or tension rod is connected to a controllable tension unit.

6. Injection head according to claim 3, characterised in that the one or more distributor plates are designed so that the innermost part of the circular ring is curving up- wards in relation to the plane of the distributor plate.

7. Injection head according to one or more of the preceding claims, characterised in that one or more adjustable air directing plates are arranged in immediate vicinity of the injection opening in a plane largely perpendicular to the bottom plate.

8. Injection head according to claim 7, characterised in that air directing plates are arranged in pairs, e.g. 12 pairs, whereby the injection air is divided into 12 separate controllable jets.

9. Injection head according to one or more of the preceding claims, characterised in that an insert is disposed in the outlet funnel in such a way that the air stream is screened along two parallel, straight sides.

10. Injection head according to one or more of the preceding claims, characterised in that a ventilator is arranged in or immediately under the bottom plate and or a ventilator in front of the outlet funnel.

11. Injection head according to claim 10, characterised in that guide members are arranged along two parallel sides around the ventilator, e.g. in the form of plate elements, for more or less aligning the air stream in direction in parallel with the guide members.