Plates to provide a hydrodynamic seal and hydrostatic support for plants performing the pickling and/or chemical treatment and/or cleaning of metallic strip

Abstract

 Plates to provide a hydrodynamic seal and hydrostatic support for plants performing the pickling and/or chemical treatment and/or cleaning of metallic strip, the plates cooperating at least with the inlet and outlet of the dip tanks (11) in which the metallic strip (12) is fed straight without diversions within the dip tank (11), the plates comprising a first lower sealing plate (15a) and a second upper sealing plate (15b), the first (15a) and second (15b) plates being distanced from each other vertically to define a feed gap (16) for the feed of the metallic strip (12), a plurality of holes (17) for injection of the chemical solution under pressure being contained in the two opposed surfaces (18) of the first plate (15a) and second plate (15b), these injection holes (17) being oriented towards the inside of the tank (11), at least one of the plates (15a-15b) being moved vertically so as to alter as desired the height of the feed gap (16).

Description

[0001] This invention concerns plates to provide a hydrodynamic seal and hydrostatic support for plants performing the pickling and/or chemical treatment and/or electrochemical treatment and/or cleaning of metallic strip, as set forth in the main claim.

[0002] The hydrodynamic sealing plates according to the invention are fitted to dip tanks using a low level, or low head, of a liquid and employed for the treatment of metallic strip passing through in a straight line.

[0003] The process of pickling has the purpose of removing from the surface of steel the non-metallic particles and, in particular, the oxides which form on that surface.

[0004] Pickling is carried out by making the surface of the steel cooperate with inorganic acids or salts that attack more or less strongly the surface of the steel to be treated.

[0005] Plants for the pickling or chemical cleaning of metallic strip, as described in this invention, are continuous dipping plants and comprise at least one tank filled with a solution containing the required acid or salt, in which the strip is dipped and fed at the desired speed.

[0006] For practical reasons the dip tanks through which the strip is fed substantially straight and horizontally are filled only to a modest height, which can also be defined as a head, with the acid solution.

[0007] So as to ensure that the whole surface of the strip is lapped by the pickling action, it is necessary to ensure that the strip is fully immersed in the solution.

[0008] For this purpose the technologies of the state of the art have used tanks in which the strip is made to cooperate with the lower surface of immersion rolls, which are at least partly sunk in the solution. These immersion rolls thus ensure that the whole surface of the strip is dipped in the pickling solution.

[0009] In another type of disclosed embodiment the strip is deflected to form a catenary, thereby entailing an increase of the volume of the dip tank.

[0010] So as to obviate problems linked to the drawing action which such deflection of the strip might involve, and to enable tanks of a modest volume to be used, straight pickling plants have been disclosed in which the strip slides substantially horizontally in the acid pickling tanks, electrolytic acid pickling tanks or neutral electrolytic pickling tanks.

[0011] So as to ensure that the upper surface too of the strip is affected by the pickling action, the strip is caused to cooperate at both the initial and final parts of the dip tank with sealing means, which ensure that the pickling solution is kept at a level higher than the plane of sliding of the strip.

[0012] At the same time the sealing means have to contain solution above the strip and to enable the strip to be fed without any scraping which might lead to scratching of the strip.

[0013] An embodiment has been disclosed in which the sealing means consist of two pairs of rolls acting as dykes and arranged respectively at the beginning and end of the pickling tanks. Each pair of these "dyke" rolls includes a lower dyke roll and an upper dyke roll, which are superimposed on each other in contact respectively with the lower surface and upper surface of the strip being fed.

[0014] While the lower dyke roll is fully immersed in the pickling solution, the upper dyke roll acts to retain the pickling solution present above the strip being fed and at all times ensures a minimum level of liquid above the strip.

[0015] In both the first and second embodiments disclosed in the state of the art at least one surface of the strip to be pickled is in contact with a roll. This creates problems of technical difficulties in operations of maintenance and seal engagement, problems linked to friction and also problems linked to the quality of the surface of the outgoing strip due to the condition of the surface of the rolls.

[0016] GB-A-2.031.036 and US-A-4,162,955 disclose plates providing a hydrodynamic seal and positioned opposite to each other at the inlet and at the outlet of the dip tank; these plates providing a hydrodynamic seal include a plurality of nozzles directed towards the strip being fed.

[0017] These nozzles are generally directed in such a way as to provide a countercurrent to the strip being fed and form an angle less than 90°, but advantageously between 10° and 30°, with the strip being fed.

[0018] These plates are positioned above and below the plane of feed of the strip so as to define a feed gap of a constant determined height with which the strip being fed cooperates.

[0019] So as to enable these tanks to be used with a wide range of strip, the height of the gap has to be high enough, thus entailing a great loss of fluid which leaves through these hydrodynamic sealing plates when the strip to be processed has a relatively small thickness.

[0020] As a result, the efficiency of the seal which can be achieved with these plates depends also on the thickness of the strip to be processed.

[0021] Moreover, the angle of the positioning of the nozzles is stationary and cannot be changed to suit the thickness of the strip being fed and/or to suit other operating factors.

[0022] Furthermore, the force exerted to support the moving strip by the flows of liquid leaving the nozzles can be adjusted only by changing, if possible, the pressure of the means that feed the fluid to these hydrodynamic sealing plates.

[0023] Besides so as to improve the hydrodynamic seal of these plates, these patents include the use of air blowoff means arranged respectively upstream of the pair of inlet plates and downstream of the pair of outlet plates, these blowoff means blowing air under pressure against the two opposite faces of the strip being fed.

[0024] This air creates problems of oxidation of the strip and, in electrolytic pickling processes and other electrolytic processes, this air acting as an insulation reduces considerably the efficiency of the process.

[0025] Moreover, where the air pressure is such as to cause the air to enter the inside of the treatment tank, the air bubbles reduce considerably the pickling capacity of the solution.

[0026] Furthermore, the air delivered by these blowoff means increases very greatly the volume of the gases which have to be treated before they can be discharged to the outer environment, and this situation increases the costs of the plant and of the working of the plant that treats the gaseous discharges.

[0027] Besides, these jets of air under pressure are in contrast with the fact that the treatment tank is generally kept under a slight negative pressure so as to reduce the volume of the gases to be treated.

[0028] US-A-4,928,717 discloses a device for the surface treatment of a moving strip, the device including a tank having two openings at its ends for the feed of the strip; this tank includes at its inlet opening one plate and at its outlet opening two plates of the above type, which have the task of providing a hydrodynamic seal together with the problems described above.

[0029] Moreover, the inclusion of only one plate at the inlet opening of the tank cannot fully ensure a satisfactory seal.

[0030] JP-A-63.270.486 discloses a device for the surface treatment of strip, in which are included two pairs of superimposed cylindrical plates containing a plurality of inclined holes to inject a fluid onto the surface of the strip being fed; these cylindrical plates do not have the task of providing a hydrodynamic seal and are fitted so as to be stationary both vertically and rotatably.

[0031] The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art and to achieve further advantages.

[0032] The invention is set forth and characterised in the main claim, while the dependent claims describe variants of the idea of the main embodiment.

[0033] The purpose of this invention is to provide a sealing system fitted to the dip tanks of a plant for the pickling and/or chemical treatment and/or cleaning of metallic strip, the system lessening or eliminating the possibility of contact and/or sliding of the strip to be cleaned against surfaces which might scratch the strip or become worn.

[0034] This invention comprises at least two pairs of sealing plates, each pair of which is fitted within the dip tank containing the solution in which the strip has to be dipped.

[0035] These pairs of sealing plates are located respectively at the inlet (pair of initial plates) and at the outlet (pair of final plates) of the pickling tank.

[0036] Each pair comprises a first lower sealing plate and a second upper sealing plate placed substantially vertically above the first lower sealing plate; the sealing plates extend across the whole width of the dip tank.

[0037] The sealing plates have the tasks of manifolds for the solution to be injected into the tank and of providing a seal.

[0038] The lower sealing plate is fitted to provide a seal engagement together with the bottom of the dip tank and acts as a lower wall to contain the solution.

[0039] The sealing plates are suitably distanced vertically from each other to define a feed gap with which the strip being fed cooperates.

[0040] In the invention at least one of the plates of each pair of superimposed plates is fitted so as to be able to move vertically in such a way as to adjust fully or partly the height of the feed gap, for instance according to the thickness and relative levelness of the strip to be treated.

[0041] According to a variant at least one of the plates can be moved in the direction of feed of the metallic strip.

[0042] The respective initial and final pairs of sealing plates determine an intermediate dipping zone and retain the pickling solution, which is kept at a level higher than the horizontal plane of sliding of the strip.

[0043] According to a particular embodiment the surfaces of the plates defining the feed gap are parallel to each other and the feed gap has a lengthwise section of a constant height.

[0044] According to a variant the surfaces of the plates defining the feed gap have developments that diverge at least partly from each other in the direction towards the intermediate zone of the tank so as to define a feed gap having a lengthwise section of an increasing height at least in its portion towards the intermediate part of the tank.

[0045] The respective zones upstream of the initial pair of sealing plates and downstream of the final pair of sealing plates are discharge zones for collection of the pickling solution leaving the intermediate dipping zone through the feed gap; this solution thus leaving is in a quantity less than the rate of flow of solution into the tank.

[0046] The pickling solution is discharged by gravity from the discharge zones and is possibly re-circulated after a suitable treatment.

[0047] The strip in these respective discharge zones upstream of the initial pair of sealing plates and downstream of the final pair of sealing plates is caused to cooperate with supporting and drawing means.

[0048] Each sealing plate contains an inner chamber into which the pickling solution is fed under pressure.

[0049] A plurality of gauged injection holes through which the pickling solution leaves under pressure and at speed is included in the wall of the sealing plates which defines the inner chamber and which faces the sliding strip.

[0050] According to a first embodiment the gauged injection holes have their axis substantially perpendicular to the plane of sliding of the strip.

[0051] According to a variant the gauged injection holes have their axis suitably inclined to the line perpendicular to that plane of sliding; this inclination is oriented towards the intermediate dipping zone defined by the pairs of sealing plates, so that the solution leaving under pressure and at speed acts also as a sealing means to retain the solution in the intermediate zone.

[0052] According to yet another variant the gauged injection holes in the sealing plates can be arranged along a plurality of lines and be inclined differently from each other.

[0053] For instance, there may be a plurality of lines of gauged holes staggered in relation to each other.

[0054] A particular embodiment of the invention includes at least two rows of gauged holes; a first row consists of first gauged holes having their axis substantially perpendicular to the plane of feed of the strip, whereas a second row consists of second gauged holes which have their axis advantageously inclined towards the inside of the intermediate part of the tank.

[0055] The first gauged holes have the tasks of hydrostatic supporting of the strip and of detaching the particles on the surface of the strip.

[0056] The second gauged holes have the task of holding and retaining the solution within the intermediate zone so as to enable a head to be created in the intermediate zone of the tank; this head has a height between 50 and 300 mm. depending on the pressure with which the fluid is fed to the gauged holes.

[0057] Moreover, the inclined gauged holes of the pair of final plates have the purpose of opposing the outgoing of the solution which the strip being fed tends to draw with itself.

[0058] Where there is a plurality of gauged holes, the latter can be fed with differentiated pressures and/or rates of flow.

[0059] According to a particular form of embodiment the plates can be moved advantageously by being rotated about their own lengthwise axis so as to change the inclination with which the jets of solution leaving the gauged holes strike the surface of the strip being fed.

[0060] The pressure and rate of flow of the jet of solution delivered through the gauged injection holes are such as to ensure a constant action on the whole surface of the strip.

[0061] As we said above, the pressure and rate of flow of the jet of solution are such as to provide a hydrodynamic seal for the solution held in the intermediate zone.

[0062] Furthermore, the pressure and rate of flow of the jet of the pickling solution are such as to create a fluid bed to support and position the strip being pickled.

[0063] To be more exact, the hydrodynamic pressure due to the kinetic energy of the jets leaving the gauged injection holes opposes, to the extent of at least balancing, the hydrostatic pressure due to the greater level of the solution in the intermediate dipping zone.

[0064] These localised jets of solution striking the surface of the strip being fed have the further task of causing occurrences of local turbulence, which apply a mechanical action to the surface of the strip and increase the efficiency of the pickling treatment and chemical cleaning.

[0065] Partition elements which are associated with the sealing plates and which have the purpose of obtaining well defined sectors in the row or rows of the gauged holes may be included to ensure a uniform supporting action along the whole strip being pickled.

[0066] According to a first embodiment the partition elements are of a lengthwise type and are arranged with their axis parallel to the direction of feed of the strip.

[0067] According to another embodiment the partition elements are of a transverse type and are arranged with their axis at a right angle to the direction of feed of the strip; in this case they together with the associated lengthwise partition elements define closed sectors separated from each other, each sector being affected only by the gauged holes contained therein.

[0068] Thus a level of solution such as will cover the strip fully is ensured within the intermediate zone and also ensures an intense, widespread action of uniform pickling of the upper and lower surfaces of the strip.

[0069] Where there are tanks of a great length or a plurality of tanks in series, means for intermediate supporting of the strip being fed may be included. These intermediate supporting means may consist of a lower supporting roll or of a pair of respective lower and upper rolls, which are opposite to each other or are staggered in relation to each other.

[0070] Where there is only one intermediate supporting roll or one pair of intermediate supporting rolls, the roll or rolls can be of an idling type or be powered.

[0071] The attached figures are given as a non-restrictive example and show some preferred embodiments of the invention as follows:

Fig.1

is a diagram of the lengthwise section of a single dipping tank for chemical treatment of strip, the tank including plates to provide hydrodynamic sealing according to the invention;

Fig.2

shows the detail A of Fig.1 in an enlarged scale;

Fig.3

shows a section along the line B-B of Fig. 2;

Fig.4

is a diagram of a lengthwise section of a multiple tank for chemical treatment of strip, the tank including the hydrodynamic sealing plates according to the invention;

Fig.5

shows the detail C of Fig.4 in an enlarged scale;

Fig.6

shows a variant of the detail of Fig.5;

Figs.7a, 7b and 7c

show diagrams of some possible cross-sections of a sealing plate of the initial pair of plates:

Fig.8

shows a cross-section of an initial pair of sealing plates comprising two separate inner chambers;

Fig.9

shows a cross-section of a pair of initial sealing plates of a rotary type;

Fig.10

shows part of a lengthwise section along the line D-D of the pair of sealing plates of a rotary type of Fig.9.

[0072] The reference number 10 in the attached figures denotes generally a sealing system according to the invention as applied to a dip tank 11 of a chemical treatment plant to clean metallic strip 12.

[0073] The sealing system 10 according to the invention includes sealing means 13 installed at both the initial part and final part of the dip tank 11.

[0074] These sealing means 13, which are initial sealing means 13a and final sealing means 13b respectively, define an intermediate zone 14 in which a chemical solution is contained.

[0075] The sealing means 13 define also two discharge zones 21, which are an initial discharge zone 21a and a final discharge zone 21b respectively and are located upstream of the initial sealing means 13a and downstream of the final sealing means 13b.

[0076] In this case two pairs of guiding and supporting rolls 22 with which the strip 12 being fed cooperates are included in the discharge zones 21.

[0077] The sealing means 13 comprise a pair of vertically superimposed and facing sealing plates 15, which are a lower sealing plate 15a and an upper sealing plate 15b.

[0078] The sealing plates 15 extend transversely across the tank 11 and the upper sealing plate 15b is raised from the lower sealing plate 15a so as to define a feed gap 16 with which the strip 12 being fed cooperates.

[0079] According to an advantageous form of embodiment shown in Fig.2 the feed gap 16 includes in its length a narrowed portion 24 in the direction towards the discharge zones 21 so as to oppose the outward departure of the pickling solution held in the intermediate zone 14.

[0080] According to a particular form of embodiment (Fig.7a), surfaces 18 of the sealing plates 15a-15b defining the feed gap 16 are parallel to each other and the feed gap 16 has a lengthwise section of a constant height.

[0081] According to a variant (Figs.7b and 7c) the surface 18 of at least one sealing plate 15 defining the feed gap 16 has a development diverging at least partly in the direction towards the intermediate zone 14 of the tank 11.

[0082] Thus the feed gap 16 defined by the pair of initial sealing plates 15 has a lengthwise section with a height increasing at least in the part facing towards the intermediate zone 14 of the tank 11, whereas the feed gap 16 defined by the pair of final sealing plates 15 has a development decreasing towards the final discharge zone 21b.

[0083] This progressively variable development has the purpose of reducing the flow of solution tending to leave the intermediate zone 14 through the feed gaps 16 towards the discharge zones 21, thus enabling a head of solution of a desired height to be ensured in the intermediate zone 14.

[0084] The lower sealing plate 15a is fitted with a seal engagement to the bottom of the dip tank 11 and acts as a lower retaining wall for the solution.

[0085] According to a particular form of embodiment the upper sealing plate 15b can be moved vertically to enable the height of the feed gap 16 to be adjusted, for instance, according to the thickness of the strip 12 to be processed.

[0086] Each sealing plate 15 contains a plurality of gauged holes 17 arranged evenly on the surface 18 of the sealing plate 15 facing the strip being fed.

[0087] These gauged holes 17 permit intercommunication between an inner chamber 19 within the sealing plates 15 and the feed gap 16. The inner chamber 19 acts as a manifold to feed the solution, and is continuously supplied with the chemical solution under pressure through a feeder conduit 20.

[0088] According to a variant, partition elements 25 shown with lines of dashes in Fig.3 may be provided on the surfaces 18 of the sealing plates 15 in which the gauged holes 17 are made; these partition elements 25 have the purpose of defining well defined sectors 26 in the row or rows of gauged holes 17.

[0089] According to a first embodiment the partition elements 25 are of a lengthwise type 25a and arranged with their axis parallel to the direction of feed of the strip 12 so as to form open sectors 26 upstream and downstream.

[0090] According to another embodiment the lengthwise partition elements 25a are associated with transverse partition elements 25b arranged with their axis perpendicular to the direction of feed of the strip 12 so as to define closed sectors 26 separated from each other.

[0091] The inclusion of the partition elements 25 ensures a more uniform treatment of the whole surface of the strip 12 being fed and a more uniform supporting of the strip 12.

[0092] In the case of Fig.2 each gauged hole 17 has its axis inclined to the horizontal so as to be directed towards the inside of the intermediate zone 14 and so as to define together with the direction of feed of the strip 12 an angle of incidence "a" between 30° and 60°, but advantageously 45°.

[0093] According to a variant which is not shown here, the gauged injection holes 17 have their axis substantially at a right angle to the plane of feed of the strip 12.

[0094] According to still another variant the gauged injection holes 17 in the sealing plates 15 may be arranged in a plurality of lines. According to the variant shown in Fig.8 for example, two rows of gauged holes 17 on the same axis as each other or offset from each other may be provided with different inclinations, namely first holes 17b and second holes 17a respectively.

[0095] The particular form of embodiment of the invention as shown in Fig.8 includes two rows 17a and 17b respectively of gauged holes 17, of which a first row consists of first gauged holes 17b with their axis substantially perpendicular to the plane of feed of the strip 12, whereas the second row consists of second gauged holes 17a which have their axis advantageously inclined towards the inside of the intermediate zone 14 of the tank 11.

[0096] The first row of gauged holes 17b has mainly the task of the hydrostatic supporting of the strip 12 and the removal of the particles on the surface of the strip 12 being fed.

[0097] The second row of gauged holes 17a has the task of obstructing and retaining the solution so as to enable a head of acid solution to be created in the intermediate zone 14 of the tank 11; this head will have a height between 50 and 300 mm., depending on the pressure and speed with which the acid solution is fed to the gauged holes 17b-17a.

[0098] The second row of holes 17a is especially advantageous in the pair of the final sealing plates 15 inasmuch as it acts to oppose the departure of the solution which the moving strip 12 tends to draw with it.

[0099] Where there is a plurality of rows of gauged holes 17, the sealing plate 15 may have its inner chamber 19 divided into a first inner chamber 19b and second inner chamber 19a respectively, which communicate with the first row of gauged holes 17b and the second row of gauged holes 17a respectively.

[0100] In this case (Fig. 8) it is possible to feed the first inner chamber 19b and second inner chamber 19a with fluid at differentiated pressures and therefore to feed the first gauged holes 17b and second gauged holes 17a respectively with differentiated pressures.

[0101] The rate of flow and pressure of the flow of solution leaving each gauged hole 17 can be adjusted advantageously by the machine operator according to factors such as, for instance, the speed of feed of the strip 12 and the height of the desired head of solution in the intermediate dipping zone 14.

[0102] The hydrodynamic pressure generated by the kinematic energy possessed by the jet of solution leaving the gauged holes 17 is such as will resist and balance the static pressure of the head of solution in the intermediate zone 14 of the dip tank 11.

[0103] The chemical solution leaving the intermediate dipping zone 14 through the feed gap 16 is collected in the discharge zones 21, whence it is discharged through discharge conduits 23.

[0104] In this way the sealing system 10 according to the invention ensures full immersion of the strip 12 and therefore a correct surface treatment of all the surfaces of the strip 12 and reduces to a minimum the contacts with, and sliding on, rolls or other guiding and supporting elements in the pickling bath 11.

[0105] According to a particular form of embodiment shown in Figs.9 and 10 the two sealing plates 15, namely a lower plate 15a and an upper plate 15b respectively, have a cylindrical conformation and include gauged injection holes 17 arranged in two rows, a first row 17b and a second row 17a respectively.

[0106] These plates 15 can be rotated about their lengthwise axis so as to change, as required, the inclination with which the jets of solution leaving the gauged injection holes 17 strike the strip 12 being fed.

[0107] According to the embodiment shown in Fig.4 the dip tank 11 is of a modular type and a plurality of these tanks 11 is placed end to end so as to form a multiple dip tank 111 when a longer stay time of the strip 12 in the chemical treatment station is required.

[0108] Where there is a tank 11 of a great length or a multiple tank 111, intermediate supporting and guiding means 27 may be included to prevent the strip 12 bending along its length.

[0109] In the situation of Fig.4 these intermediate supporting and guiding means 27 consist of the supporting plates 15 themselves, advantageously of a double type, in which the gauged holes 17 face towards the inside of the intermediate zone 14 with which they cooperate (Fig.5).

[0110] In the case of Fig.6 the intermediate supporting and guiding means 27 consist of an auxiliary supporting roll 28 placed below the strip 12 being fed in an intermediate position between two pairs of sealing plates 15. This auxiliary supporting roll 28 can be of an idler type or be powered.

[0111] According to a variant shown with lines of dashes in Fig.6, the intermediate supporting and guiding means 27 consist of a pair of opposed auxiliary supporting rolls 28-128 positioned respectively below and above the strip 12 being fed.

Claims

1. Plates to provide a hydrodynamic seal and hydrostatic support for plants performing the pickling and/or chemical treatment and/or cleaning of metallic strip, the plates cooperating at least with the inlet and outlet of the dip tanks (11) in which the metallic strip (12) is fed straight without diversions within the dip tank (11), the plates comprising a first lower sealing plate (15a) and a second upper sealing plate (15b), the first (15a) and second (15b) plates being distanced from each other vertically to define a feed gap (16) for the feed of the metallic strip (12), a plurality of holes (17) for injection of the chemical solution under pressure being contained in the two opposed surfaces (18) of the first plate (15a) and second plate (15b), these injection holes (17) being oriented towards the inside of the tank (11), the plates (15) being characterized in that at least one of the plates (15a-15b) can be moved vertically so as to alter as desired the height of the feed gap (16).

2. Hydrodynamic sealing plates as in Claim 1, in which the lengthwise section of the feed gap (16) defined by the pair of initial sealing plates (15a-15b) in the direction of feed of the strip (12) diverges at least partly.

3. Hydrodynamic sealing plates as in Claim 1 or 2, in which the lengthwise section of the feed gap (16) defined by the pair of final sealing plates (15a-15b) in the direction of feed of the strip (12) converges at least partly.

4. Hydrodynamic sealing plates as in any claim hereinbefore, in which the injection holes are gauged injection holes (17) and are arranged in at least two rows (17a-17b).

5. Hydrodynamic sealing plates as in any claim hereinbefore, in which at least part of the gauged injection holes (17) have an axis perpendicular or substantially perpendicular to the plane of the metallic strip (12).

6. Hydrodynamic sealing plates as in Claim 4, in which at least the first row of gauged injection holes (17b) and at least the second row of gauged injection holes (17a) are fed with differentiated pressures.

7. Hydrodynamic sealing plates as in any claim hereinbefore, in which at least one sealing plate (15a-15b) can be moved by being rotated about its lengthwise axis.

8. Hydrodynamic sealing plates as in any claim hereinbefore, which include lengthwise partition elements (25a), in the direction of feed of the strip (12), which define open sectors (26) upstream and downstream.

9. Hydrodynamic sealing plates as in Claim 8, which include transverse partition elements (25b) perpendicular to the lengthwise partition elements (25a) so as to define closed sectors (26) containing a determined number of gauged injection holes (17).

Drawing