CN114011677A

CN114011677A - Tuyere assembly and coating oven

Info

Publication number: CN114011677A
Application number: CN202111264004.7A
Authority: CN
Inventors: 陈周龙
Original assignee: Sunwoda Electric Vehicle Battery Co Ltd
Current assignee: Sunwoda Electric Vehicle Battery Co Ltd
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2022-02-08

Abstract

The application relates to a tuyere assembly and a coating oven, and belongs to the technical field of drying equipment. Wherein, the tuyere assembly includes casing, guide plate and mechanism of keeping out the wind. The shell is internally provided with an air passing cavity for air circulation, and the shell is provided with an air outlet; the guide plate is arranged in the shell and divides the air passing cavity into a first cavity and a second cavity, the air outlet is communicated with the first cavity, the guide plate is provided with a plurality of air passing holes, and the air passing holes are communicated with the first cavity and the second cavity; the wind shielding mechanism is arranged on the guide plate and can open or close part of the air passing holes so as to adjust the air volume blown to the first chamber by the second chamber. The utility model provides a tuyere subassembly can prevent that the pole piece from receiving the overbaking, can effectually avoid the pole piece phenomenon that fracture and bulging appear.

Description

Tuyere assembly and coating oven

Technical Field

The invention relates to the technical field of drying equipment, in particular to an air nozzle assembly and a coating oven using the same.

Background

In the production process of the battery, the coating procedure is to coat the slurry after stirring on a current collector according to a preset process, and the electrode plates are dried by a coating oven in sequence. In the related technology, because the edge of the pole piece at the pole lug coating position has a thinning area, the thickness of the thinning area is generally 5-10um thinner than that of a normal area, and in the drying process of the pole piece, hot air blown to the pole piece by a nozzle is uniform, so that each area of the pole piece is heated in equal quantity, and the local position of the thinning area of the pole piece is easy to cause the unevenness of the pole piece due to overbaking, and further the pole piece is bulged and cracked.

Disclosure of Invention

Therefore, when the air nozzle uniformly blows air to the pole piece, unevenness is easily generated at the local position of the thinned area of the pole piece due to overbaking, and the problems of bulging and cracking of the pole piece are caused.

To achieve the above object, the present invention provides a nozzle assembly, including:

the air conditioner comprises a shell, wherein an air passing cavity for air circulation is formed in the shell, and an air outlet communicated with the air passing cavity is formed in the shell;

the guide plate is arranged in the shell and divides the air passing cavity into a first cavity and a second cavity, the air outlet is communicated with the first cavity, the guide plate is provided with a plurality of air passing holes, and the plurality of air passing holes are communicated with the first cavity and the second cavity; and

and the wind shielding mechanism is arranged on the guide plate and can open or close part of the wind passing holes so as to adjust the wind quantity blown to the first chamber by the second chamber.

Foretell tuyere assembly through set up the guide plate in the casing, makes the guide plate form first cavity and second cavity with the space separation in the casing, sets up a plurality of wind holes simultaneously on the guide plate for first cavity and second cavity can communicate through a plurality of wind holes, and tuyere assembly is blowing the in-process of drying like this, and hot-air can be blown to first cavity back by the second cavity through a plurality of wind holes, blows to the pole piece from the air outlet again. And through setting up the mechanism of keeping out the wind at the guide plate, make the mechanism of keeping out the wind open or close the air hole of part wherein, when utilizing the tuyere subassembly to blow the stoving towards the pole piece like this, can select to close the air hole that will correspond at the pole piece zone of weakening to blow to this regional amount of wind reduction in the casing, the corresponding is heated and also reduces, prevents that this region from receiving the overbaking, and then the effectual phenomenon of avoiding the pole piece fracture and bulging appears.

In one embodiment, the wind shielding mechanism comprises a wind shielding plate and a rotating shaft, the rotating shaft is rotatably connected to the wind shielding plate, and the wind shielding plate is connected to the rotating shaft and can drive the rotating shaft to open or close part of the wind passing holes.

In one embodiment, the air deflector has a length direction and a width direction, the air holes are arranged in a rectangular array along the length direction and the width direction, and the wind deflector is driven by the rotating shaft to open or close at least one row of air holes in the width direction.

In one embodiment, the number of the wind shielding mechanisms is the same as that of the wind passing holes, and one wind shielding mechanism is arranged at the edge of one corresponding wind passing hole to open or close the corresponding wind passing hole.

In one embodiment, two ends of the guide plate are further provided with adjusting mechanisms, and the adjusting mechanisms are connected to the shell to drive the guide plate to move close to or far away from the air outlet.

In one embodiment, the adjusting mechanism comprises an adjusting rod and a locking member, one end of the adjusting rod is connected to the guide plate, a movable groove is formed in the side wall of the shell, the other end of the adjusting rod penetrates through the movable groove and can move along the movable groove, and the locking member is movably connected to the adjusting rod and can fix the adjusting rod on the side wall of the shell.

In one embodiment, a gap is formed between the edge of the guide plate and the inner side wall of the shell, and the adjusting rod is rotatably arranged in the movable groove, so that the guide plate can turn around the adjusting rod in the shell.

In one embodiment, the casing includes a bottom casing and a cover that are detachably connected, the bottom casing and the cover enclose the air passing cavity, the cover is provided with the air outlet, and the wind shielding mechanism is connected to a side wall of the bottom casing.

In one embodiment, an air inlet is formed in one side of the bottom shell, which is away from the cover body, the air inlet is communicated with the second chamber, and a sealing gasket is further arranged on the edge of the bottom shell, which is located at the air inlet.

The invention also provides a coating oven, which comprises a box body, a guide roller and the air nozzle assembly, wherein the guide roller is installed in the box body and is used for conveying the pole piece, and the air nozzle assembly is installed in the box body and is arranged towards the surface of the pole piece so as to blow air to the surface of the pole piece.

Drawings

FIG. 1 is an exploded view of one embodiment of the tuyere assembly of the present invention;

FIG. 2 is an enlarged view of a portion of FIG. 1 at A;

FIG. 3 is a left side view of one embodiment of the tuyere assembly of the present invention;

FIG. 4 is a schematic structural view of an embodiment of a baffle of the present invention;

FIG. 5 is a partial enlarged view of the portion B in FIG. 4;

fig. 6 is a schematic structural diagram of one embodiment of the coating oven of the present invention.

The reference numbers illustrate:

10: a housing; 11: a bottom case; 111: a movable groove; 13: a cover body; 131: an air outlet;

10 a: a first chamber; 10 b: a second chamber; 20: a baffle; 21: air passing holes;

30: a wind shielding mechanism; 31: a wind deflector; 32: a rotating shaft; 40: an adjustment mechanism;

41: adjusting a rod; 42: a locking member; 50: a gasket; 100: a tuyere assembly; 200: a guide roller; 300: a box body; 400: pole pieces; 401: a thinned region; 1000: coating oven

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Referring to fig. 1 and 4 in combination, in an embodiment of the present invention, a nozzle assembly 100 includes a housing 10, a baffle 20, and a wind shielding mechanism 30. An air passing cavity for air circulation is formed in the shell 10, and an air outlet 131 communicated with the air passing cavity is formed in the shell 10; the air deflector 20 is installed in the housing 10, and divides the air passing cavity into a first cavity 10a and a second cavity 10b, the air outlet 131 is communicated with the first cavity 10a, the air deflector 20 is provided with a plurality of air passing holes 21, and the plurality of air passing holes 21 are communicated with the first cavity 10a and the second cavity 10 b; the wind shielding mechanism 30 is mounted on the baffle 20 and can open or close a part of the wind passing holes 21 to adjust the amount of wind blown from the second chamber 10b to the first chamber 10 a.

Specifically, the housing 10 may be made of a metal material that is heat-resistant, has a high structural strength, and is easy to machine. The shape of the housing 10 can be designed into various shapes, such as a rectangular parallelepiped shape, a cylindrical shape, or other reasonable and effective special shapes, and in the present embodiment, the rectangular parallelepiped shape is taken as an example for illustration.

In practical applications, referring to fig. 6, after passing through the air passing cavity in the casing 10, the hot air generated by the coating oven 1000 is blown to the pole piece 400 through the air outlet 131 to dry the pole piece 400, so that the casing 10 has an air guiding function. In order to uniformly blow out the hot air from the air passing cavity, in this embodiment, the number of the air outlets 131 may be multiple, and the multiple air outlets 131 are uniformly arranged along the length direction of the housing 10 at intervals, so that the hot air is uniformly dispersed. The shape, size and specific number of the air outlets 131 may be adaptively set according to the actual situation of the housing 10, which is not specifically limited in this application.

The shape of the baffle 20 may be rectangular to fit the shape of the housing 10, and the material of the baffle may be the same as that of the housing 10. In practical cases, when the guide plate 20 is horizontally arranged in the air passing cavity, the first cavity 10a and the second cavity 10b formed at this time are arranged up and down, and the air outlet 131 can be arranged opposite to the air passing hole 21 and arranged at the top of the casing 10, so that when the coating oven 1000 blows hot air through the air nozzle assembly 100, the air flow can sequentially pass through the second cavity 10b, the air passing hole 21, the first cavity 10a and the air outlet 131 from bottom to top, and the path through which the air flow circulates in the casing 10 is shorter, thereby greatly reducing heat loss and improving drying efficiency.

The wind shielding mechanism 30 may be installed on a surface of the deflector 20 facing the wind outlet 131, and it is understood that the wind shielding mechanism 30 may also be half shielded at the opening of the wind passing hole 21 when the wind shielding mechanism 30 opens or closes the wind passing hole 21, thereby adjusting the amount of wind passing through the wind passing hole 21.

Therefore, in the nozzle assembly 100 of the present invention, the baffle plate 20 is disposed in the housing 10, so that the baffle plate 20 separates the space in the housing 10 into the first chamber 10a and the second chamber 10b, and meanwhile, the baffle plate 20 is provided with the plurality of air passing holes 21, so that the first chamber 10a and the second chamber 10b can be communicated through the plurality of air passing holes 21, so that during the blowing and drying process of the nozzle assembly 100, hot air can be blown from the second chamber 10b to the first chamber 10a through the plurality of air passing holes 21, and then blown to the pole piece 400 from the air outlet 131. And through setting up mechanism 30 of keeping out the wind at guide plate 20, make mechanism 30 of keeping out the wind open and close some air holes 21 wherein, when utilizing tuyere subassembly 100 to blow dry towards pole piece 400 like this, can select to close air holes 21 that pass at pole piece 400 zone 401 that thins to make by the reduction of the amount of wind that blows to this region in the casing 10, the corresponding is heated and is also reduced, prevent that this region from receiving the overbaking, and then the effectual phenomenon of avoiding pole piece 400 fracture and bulging appears.

Referring to fig. 5, further, in an embodiment of the present application, the wind shielding mechanism 30 includes a wind shielding plate 31 and a rotating shaft 32, the rotating shaft 32 is rotatably connected to the flow guiding plate 20, the wind shielding plate 31 is connected to the rotating shaft 32, and can be driven by the rotating shaft 32 to open or close a portion of the air passing hole 21.

The wind deflector 31 may be a straight plate structure, the shape of the wind deflector 31 may be adapted to the shape of the aperture of the air passing hole 21, and the area of the wind deflector 31 should be slightly larger than the area of the aperture of the air passing hole 21 to ensure that the aperture of the air passing hole 21 can be covered. The axis of rotation 32 then can adopt the damping pivot, the damping effect through the damping pivot like this for when driving deep bead 31 and rotating, be favorable to controlling deep bead 31's the range that opens and shuts, make deep bead 31 can cover, partly cover and open completely and freely switch between the wind hole 21, freely adjust the size of the amount of wind, simultaneously, the operation that deep bead 31 opened and closed is also comparatively convenient, deep bead 31 can stably maintain on predetermined range that opens and shuts.

Further, as shown in fig. 4, in the present application, the air deflector 20 has a length direction and a width direction, the air holes 21 are arranged in a rectangular array along the length direction and the width direction, and the wind deflector 31 is driven by the rotating shaft 32 to open or close at least one row of air holes 21 in the width direction.

In this embodiment, the width direction of the deflector 20 is the same as the moving direction of the pole piece 400 in the coating oven 1000, so that the thinned area 401 of the surface of the pole piece 400 can always correspond to the air passing hole 21 in the width direction of the deflector 20 during the moving process. And open or close the one row of air holes 21 of guide plate 20 on the width direction through controlling the deep bead 31, can guarantee that pole piece 400 disappears the air holes 21 that the thin region 401 corresponds and is closed, and the air holes 21 that other regions on pole piece 400 correspond are then opened, have guaranteed that each regional of pole piece 400 is heated rationally, prevent that the phenomenon that overbaking or baking is not enough from appearing in pole piece 400 local position, the effectual quality of guaranteeing pole piece 400.

In an embodiment of the present application, the number of the wind shielding mechanisms 30 is the same as the number of the wind passing holes 21, and one wind shielding mechanism 30 is disposed at an edge of one corresponding wind passing hole 21 to open or close the corresponding wind passing hole 21.

In this embodiment, the wind shielding mechanisms 30 correspond to the wind passing holes 21 one by one, so that each wind passing hole 21 can be opened or closed by the corresponding wind shielding mechanism 30, and thus in practical application, a user can correspondingly adjust the number of the opened or closed wind passing holes 21 according to the specific drying condition of the pole piece 400, thereby realizing more refined wind volume control.

Based on the above-described embodiment, it is considered that the sealing performance may be deteriorated when each of the air passing holes 21 is subjected to the opening and closing control by the separate wind shielding mechanism 30. The deflector 20 is concavely provided with an installation groove (not marked) at one side edge of the air passing hole 21, the rotating shaft 32 is rotatably installed in the installation groove, the air passing hole 21 is closed by the wind deflector 31, and the surface of the wind deflector 31 facing the air outlet 131 and the surface of the deflector 20 facing the air outlet 131 are coplanar. So set up for in the embedded guide plate 20 of axis of rotation 32, thereby when wind hole 21 is closed to deep bead 31, can not produce the air gap between axis of rotation 32 and the deep bead 31, the control of being heated of pole piece 400 is better.

Of course, in another embodiment of the present application, the wind shielding mechanism 30 may not be in one-to-one correspondence with the air holes 21, for example, the wind shielding plate 31 of the wind shielding mechanism 30 opens or closes one or more rows of the air holes 21 on the wind guiding plate 20, so that the efficiency is higher in the process of opening and closing the air holes 21.

Because the pole piece 400 has the problem of inconsistent drying of the membrane area during the coating and drying processes, the pole piece 400 on the side close to the heating bag of the coating oven 1000 is dried first, while the pole piece 400 on the side far away from the heating bag is dried slowly. In order to make the pole piece 400 heated uniformly in the transverse direction (i.e. the width direction of the pole piece 400), in an embodiment of the present application, the two ends of the flow guide plate 20 are further provided with an adjusting mechanism 40, and the adjusting mechanism 40 is connected to the housing 10 to drive the flow guide plate 20 to move close to or away from the air outlet 131.

The adjusting mechanisms 40 may be respectively disposed at two ends of the length direction of the air deflector 20, and the heights of the two ends of the air deflector 20 may be respectively adjusted by the adjusting mechanisms 40, so that the sizes of the spaces of the second chamber 10b and the first chamber 10a formed may be correspondingly adjusted. For example, when the air outlet 131 is disposed at the top of the casing 10, and the air deflector 20 is disposed opposite to the top of the casing 10, the air deflector 20 at the side close to the heating pack is adjusted downward and away from the air outlet 131, so that the heating process of the air passing through the second chamber 10b by the heating pack is shorter, and the amount of heat blown out correspondingly is also smaller; the guide plate 20 far away from the heating bag side is adjusted to be close to the air outlet 131 upwards, so that the heating process of the air passing through the second chamber 10b by the heating bag is longer, the amount of heat correspondingly blown out is more, and the consistency of transverse heating of the pole piece 400 is ensured.

Referring to fig. 2 and 3, in an embodiment, the adjusting mechanism 40 includes an adjusting lever 41 and a locking member 42, one end of the adjusting lever 41 is connected to the baffle 20, a movable slot 111 is formed in a side wall of the housing 10, the other end of the adjusting lever 41 passes through the movable slot 111 and can move along the movable slot 111, and the locking member 42 is movably connected to the adjusting lever 41 and can fix the adjusting lever 41 to the side wall of the housing 10.

In this embodiment, the adjusting rod 41 may be a screw rod, the locking member 42 may be a locking nut sleeved on the screw rod, the locking member 42 is disposed on an outer side wall of the housing 10, and the movable groove 111 is a strip-shaped groove disposed on a side wall of the housing 10 and extends up and down along the side wall of the housing 10. In practical application, when the height of the guide plate 20 needs to be adjusted, the locking nut can be adjusted up and down after being loosened by the lead screw, and finally the locking nut is fastened again, so that the adjusting rod 41 is kept relatively fixed. In the structure mode, the guide plate 20 is moved and fixed by matching the locking piece 42 and the adjusting rod 41, so that on one hand, the guide plate 20 can be stably and fixedly kept, and the guide plate is ensured not to be easily loosened in the using process; on the other hand, when the height needs to be adjusted, the adjustment operation is also convenient. Of course, in another embodiment, the locking member 42 can be a magnetic member, and the adjusting rod 41 is a fixed rod, so that the adjusting rod 41 can be fixed to the sidewall of the housing 10 by a magnetic method.

Further, in an embodiment of the present application, the two sidewalls of the housing 10 provided with the movable groove 111 are disposed in an inclined manner, and the distance between the two sidewalls is gradually increased in a direction from the top to the bottom of the housing 10, that is, the outer contours of the two sidewalls of the housing 10 provided with the movable groove 111 form a "v" shape. It can be understood that the arrangement of the locking member 42 to fix the adjusting rod 41 to the side wall of the housing 10 can further increase the stability of locking fixation, and the locking member 42 is not easy to fall off. Meanwhile, the bottom of the second chamber 10b can be flared, so that air can form an air guide effect when entering the second chamber 10b, and the drying efficiency is better.

Further, a gap is formed between the edge of the flow guide plate 20 and the inner side wall of the housing 10, and the adjusting rod 41 is rotatably disposed in the movable groove 111, so that the flow guide plate 20 is turned inside the housing 10 around the adjusting rod 41.

When the deflector 20 needs to be turned over, the retaining member 42 can be released and the adjusting rod 41 can be rotated, so that the deflector 20 can be turned over in the air passing cavity. Through upset guide plate 20, can adjust and blow to the route and the angle of the air current of first cavity 10a by second cavity 10b, and then the angle of blowing of adjustable air outlet 131, the user can carry out the adaptability adjustment according to the pole piece 400 of difference, and it is more convenient to use.

With continued reference to fig. 1, in an embodiment of the present application, the casing 10 includes a bottom casing 11 and a cover 13 detachably connected to each other, the bottom casing 11 and the cover 13 enclose the air passing cavity, the air outlet 131 is opened in the cover 13, and the wind shielding mechanism 30 is connected to a side wall of the bottom casing 11.

The bottom case 11 and the cover 13 may be detachably fixed by a snap connection or a screw connection, wherein the air outlet 131 may be opened at the top of the cover 13, and the sidewall of the bottom case 11 is provided with the movable groove 111 for the guide plate 20 to move and mount. Therefore, the casing 10 is designed to be detachable and split, so that the wind shielding mechanism 30 can be conveniently opened and closed, and the casing 10 can be conveniently detached and assembled.

Further, an air inlet (not labeled) is disposed at a side of the bottom case 11 away from the cover 13, the air inlet is communicated with the second chamber 10b, and a sealing gasket 50 is further disposed at an edge of the air inlet of the bottom case 11.

Specifically, a side of the housing 10 facing away from the cover 13 is provided with an opening, and the opening is formed as an air inlet. The sealing pad 50 may be a heat-resistant and high-temperature-resistant rubber pad, for example, a rubber pad, and the sealing pad 50 may seal an air gap at the periphery of the air inlet, so that air flow enters through the air inlet with good air tightness and low heat loss. When the pole piece 400 is dried, the airflow can enter the second chamber 10b through the air inlet, selectively ventilate through the air deflector and the wind shielding mechanism 30 to enter the first chamber 10a, and then blow out from the air outlet 131, so that the drying efficiency is higher.

Referring to fig. 6, the present invention also provides a coating oven 1000, the coating oven 1000 including a case 300, a guide roller 200 installed in the case 300 and used to convey a pole piece 400, and a tuyere assembly 100 installed in the case 300 and disposed toward a surface of the pole piece 400 to blow air toward the surface of the pole piece 400. The specific structure of the tuyere assembly 100 refers to the above embodiments, and since the coating oven 1000 adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.

The surface of the pole piece 400 is formed with the above-mentioned thinned area 401, so when the tuyere assembly 100 blows air towards the surface of the pole piece 400 through the air outlet 131, the air quantity blown to the thinned area 401 can be adjusted through the wind shielding mechanism 30, and the pole piece 400 is prevented from being heated in the same amount at the positions with different thicknesses, so that the pole piece 400 is effectively prevented from being uneven, bulged and cracked.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A tuyere assembly, comprising:

2. The tuyere assembly of claim 1, wherein the wind shielding mechanism comprises a wind shielding plate and a rotation shaft, the rotation shaft is rotatably connected to the flow guiding plate, and the wind shielding plate is connected to the rotation shaft and can be driven by the rotation shaft to open or close a part of the air passing holes.

3. The tuyere assembly of claim 2, wherein the deflector has a length direction and a width direction, the plurality of air passing holes are arranged in a rectangular array along the length direction and the width direction, and the wind deflector is driven by the rotating shaft to open or close at least one row of air passing holes in the width direction.

4. The tuyere assembly of claim 1, wherein the number of the wind shielding mechanisms is the same as the number of the air passing holes, and one wind shielding mechanism is provided at an edge of one corresponding air passing hole to open or close the corresponding air passing hole.

5. The tuyere assembly of any one of claims 1 to 4, wherein both ends of the flow guiding plate are further provided with adjusting mechanisms, and the adjusting mechanisms are connected to the housing to drive the flow guiding plate to move close to or away from the air outlet.

6. The tuyere assembly of claim 5, wherein the adjusting mechanism comprises an adjusting rod and a locking member, one end of the adjusting rod is connected to the guide plate, a movable slot is formed in a side wall of the housing, the other end of the adjusting rod passes through the movable slot and can move along the movable slot, and the locking member is movably connected to the adjusting rod and can fix the adjusting rod to the side wall of the housing.

7. The tuyere assembly of claim 6, wherein a gap is formed between an edge of the baffle and an inner sidewall of the housing, and the adjustment bar is rotatably disposed in the movable groove to allow the baffle to be turned inside the housing around the adjustment bar.

8. The tuyere assembly of any one of claims 1 to 4, wherein the casing includes a bottom casing and a cover body detachably connected to each other, the bottom casing and the cover body enclose the air passing cavity, the cover body is opened with the air outlet, and the wind shielding mechanism is connected to a side wall of the bottom casing.

9. The tuyere assembly of claim 8, wherein an air inlet is formed in a side of the bottom casing facing away from the cover, the air inlet is communicated with the second chamber, and a gasket is further formed on an edge of the air inlet of the bottom casing.

10. A coating oven, characterized in that it comprises a box, guide rollers mounted in the box and intended to convey a pole piece, and a tuyere assembly according to any one of claims 1 to 9 mounted in the box and arranged towards the surface of the pole piece so as to blow air towards the surface of the pole piece.