Fixing structure of supporting bottom plate and atomic layer deposition equipment

Abstract

The utility model provides a fixing structure of a supporting bottom plate and atomic layer deposition equipment, and the fixing structure of the supporting bottom plate comprises an outer cavity door plate; the inner cavity door plate is located on one side of the outer cavity door plate, a gap is formed between the inner cavity door plate and the outer cavity door plate, and the inner cavity door plate comprises a first through hole; the bottom supporting plate is located on the side, away from the outer cavity door plate, of the inner cavity door plate, and one end of the bottom supporting plate penetrates through the first through hole and is connected with the outer cavity door plate; and the sealing pipe sleeves one end, connected with the outer cavity door plate, of the bottom supporting plate, one end of the sealing pipe is connected with the outer cavity door plate, and the other end of the sealing pipe covers one end of the first through hole and is fixedly connected with the inner cavity door plate. According to the fixing structure of the bottom supporting plate, the weight of the bottom supporting plate can be transferred to the outer cavity door plate, deformation of the inner cavity door plate is avoided, and process gas leakage is avoided.

Description

Technical Field

[0001] The present application belongs to the technical field of atomic layer deposition, and more specifically, relates to a fixing structure of a supporting base plate and an atomic layer deposition device. Background Art

[0002] In photovoltaic equipment, currently in the atomic layer deposition equipment for coating the surface of solar cell silicon wafers, the carrying boat enters the reaction chamber mainly by being sent to the reaction chamber by the bottom support plate. In the related technology, the reaction chamber is provided with two layers, inner and outer, and the inner cavity door plate and the outer cavity door plate are provided correspondingly to respectively seal the inner and outer layers of the reaction chamber. The bottom support plate is fixed to the inner cavity door plate. During the atomic deposition reaction in the furnace, the bottom support plate and the carrying boat are both in the reaction chamber, and the weight of the carrying boat is placed on the bottom support plate, so that there is a large downward pressure on the inner cavity door plate, which can easily cause slight deformation of the inner cavity door plate and may not be closed tightly, thereby causing the process gas to leak into the outer chamber, affecting the process. Utility Model Content

[0003] The embodiment of the present application provides a fixing structure of a bottom support plate to prevent deformation of an inner cavity door plate and leakage of process gases.

[0004] The technical solution adopted in the embodiment of the present application is: to provide a fixing structure of a bottom support plate, including:

[0005] External cavity door panel;

[0006] An inner cavity door panel, located at one side of the outer cavity door panel and spaced apart from the outer cavity door panel, wherein the inner cavity door panel comprises a first through hole;

[0007] A bottom supporting plate, located at a side of the inner cavity door plate facing away from the outer cavity door plate, one end of the bottom supporting plate passes through the first through hole and is connected to the outer cavity door plate; and

[0008] A sealing tube is sleeved on one end of the support plate connected to the outer cavity door plate. One end of the sealing tube is connected to the outer cavity door plate, and the other end covers one end of the first through hole and is connected and fixed to the inner cavity door plate.

[0009] Furthermore, the bottom support plate includes a connecting rod and a bottom support main board, the connecting rod includes a rod body and a connecting block fixed at one end of the rod body, the connecting block is located between the outer cavity door plate and the inner cavity door plate and connected to the outer cavity door plate, and the rod body passes through the first through hole to be connected to the bottom support main board.

[0010] Furthermore, one end of the rod body close to the bottom supporting main board is provided with a slot matching the thickness of the bottom supporting main board, and the slot horizontally penetrates the rod body in a radial direction;

[0011] One end of the bottom supporting mainboard is inserted into the slot and fixed.

[0012] Furthermore, the outer surface of one end of the rod body provided with the slot is provided with two locking planes which are away from each other, the locking plane is provided with a penetrating connecting hole, the bottom supporting main board is provided with a through hole corresponding to the connecting hole, a connecting piece passes through the through hole and the through hole to connect and fix the rod body to the bottom supporting main board, and the upper and lower ends of the connecting piece are pressed against the locking plane.

[0013] Furthermore, the bottom supporting plate also includes reinforcing ribs arranged on both sides of the bottom supporting main plate along the length direction.

[0014] Furthermore, the fixing structure of the bottom support plate also includes a telescopic mechanism, which is arranged on the outer cavity door plate and connected to the inner cavity door plate, and the telescopic mechanism is used to adjust the distance, and the sealing tube is a first corrugated tube.

[0015] Furthermore, the first bellows includes a first flange, a bellows body, and a second flange which are connected in sequence, the connecting block is connected to the first flange, and the second flange is connected to the inner cavity door panel.

[0016] Furthermore, the outer cavity door panel further includes a second through hole;

[0017] The telescopic mechanism includes a telescopic drive and a second bellows. The telescopic drive is fixed on the side of the outer cavity door panel facing away from the inner cavity door panel. The output end of the telescopic drive passes through the second through hole and is connected to the inner cavity door panel. The second bellows is sleeved on the output end. One end of the second bellows is connected to the outer cavity door panel, and the other end covers one end of the second through hole and is connected and fixed to the inner cavity door panel.

[0018] Furthermore, the telescopic mechanism also includes a shielding cover and a guide rod, one end of the guide rod is connected to the inner cavity door panel, and the other end extends through the outer cavity door panel, the outer cavity door panel is correspondingly provided with a guide hole for the guide rod to pass through, the shielding cover is fixed to the side of the outer cavity door panel away from the inner cavity door panel and covers the guide hole, and the depth of the shielding cover is greater than the sliding stroke of the guide rod in the guide hole.

[0019] An embodiment of the present application also provides an atomic layer deposition device, including the fixing structure of the bottom support plate as described above.

[0020] The beneficial effect of the fixing structure of the bottom support plate provided in the embodiment of the present application is that: in the fixing structure of the bottom support plate in the embodiment of the present application, a first through hole is set on the inner cavity door plate, one end of the bottom support plate is connected to the outer cavity door plate through the first through hole, and a sealing tube is also set to cover the first through hole to prevent the process gas from leaking from the first through hole, thereby transferring the weight of the bottom support plate from the inner cavity door plate to the outer cavity door plate, thereby preventing the leakage of process gas caused by deformation of the inner cavity door plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 A schematic diagram of the three-dimensional structure of the fixing structure of the bottom support plate provided in an embodiment of the present application;

[0023] Figure 2 A side view of the fixing structure of the bottom support plate provided in an embodiment of the present application;

[0024] Figure 3 An exploded schematic diagram of a fixing structure of a bottom support plate provided in an embodiment of the present application;

[0025] Figure 4 A schematic diagram of the structure of a sealing tube of a fixing structure of a supporting bottom plate provided in an embodiment of the present application;

[0026] Figure 5 A schematic diagram of the telescopic mechanism of the fixing structure of the bottom support plate provided in an embodiment of the present application.

[0027] Among them, the reference numerals in the figure are:

[0028] 10. outer cavity door panel; 11. second through hole; 12. guide hole;

[0029] 20. Inner cavity door panel; 21. First through hole;

[0030] 30, bottom support plate; 31, connecting rod; 311, rod body; 3111, slot; 3112, connecting hole; 3113, locking plane; 312, connecting block; 32, bottom support main board; 321, perforation; 3211, reinforcing rib;

[0031] 40. Sealing tube; 41. First flange; 42. Bellows body; 43. Second flange;

[0032] 50. Telescopic mechanism; 51. Telescopic driver; 52. Second bellows; 53. Shielding cover; 54. Guide rod. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0035] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] See also Figure 1 and Figure 2 The fixing structure of the bottom support plate 30 provided in the embodiment of the present application is now described. The fixing structure of the bottom support plate 30 provided in the embodiment of the present application comprises an outer cavity door plate 10, an inner cavity door plate 20, a bottom support plate 30 and a sealing tube 40.

[0038] The reaction chamber of the atomic layer deposition equipment is divided into two layers, the outer chamber door plate 10 is used to close the outer layer of the reaction chamber, and the inner chamber door plate 20 is used to close the inner layer of the reaction chamber. It can be understood that the outer chamber door plate 10 matches the door of the outer layer of the reaction chamber, and the inner chamber door plate 20 matches the door of the inner layer of the reaction chamber.

[0039] Reference Figure 1 and Figure 2The inner cavity door plate 20 is located on one side of the outer cavity door plate 10 and has a spacing with the outer cavity door plate 10, and the inner cavity door plate 20 includes a first through hole 21. Specifically, the inner cavity door plate 20 is located on the inner side of the outer cavity door plate 10, and the spacing between the inner cavity door plate 20 and the outer cavity door plate 10 is used to match the spacing between the inner and outer layers of the reaction chamber. In addition, the spacing between the inner cavity door plate 20 and the outer cavity door plate 10 can also be used to install a heating plate to heat the inner cavity from the inner cavity door plate 20. The first through hole 21 is provided for the bottom support plate 30 to pass through.

[0040] Reference Figure 1 and Figure 2 , the bottom support plate 30 is located on the side of the inner cavity door plate 20 away from the outer cavity door plate 10, and one end of the bottom support plate 30 passes through the first through hole 21 and is connected to the outer cavity door plate 10. The bottom support plate 30 is mainly on the inner side of the inner cavity door plate 20, and a part of the bottom support plate 30 passes through the first through hole 21 and is connected to the outer cavity door plate 10, rather than being connected to the inner cavity door plate 20. When the carrying boat enters the reaction chamber, the weight of the carrying boat is supported by the bottom support plate 30 and eventually transferred to the outer cavity door plate 10, so as not to cause deformation of the inner cavity door plate 20 and avoid leakage of process gas. The structure of the outer cavity door plate 10 is thicker and more stable than that of the inner cavity door plate 20, and is fully capable of bearing the weight of the carrying boat and the bottom support plate 30 without deformation, thereby preventing the external atmosphere from entering the reaction outer chamber.

[0041] Reference Figure 1 and Figure 2 The sealing tube 40 is sleeved on one end of the supporting plate 30 connected to the outer cavity door plate 10. One end of the sealing tube 40 is connected to the outer cavity door plate 10, and the other end covers one end of the first through hole 21 and is fixedly connected to the inner cavity door plate 20. Since the first through hole 21 is opened on the inner cavity door plate 20, in order to seal the first through hole 21 and prevent the process gas in the inner layer reaction chamber from leaking from the first through hole 21, a sealing tube 40 is provided. The sealing tube 40 is sleeved on the supporting plate 30 and the two ends are respectively connected to the outer cavity door plate 10 and the inner cavity door plate 20, so that the sealing tube 40 can seal the first through hole 21 and prevent the process gas from leaking from the inner layer reaction chamber through the first through hole 21 to the inner layer reaction chamber.

[0042] Reference Figure 2 and Figure 3The bottom support plate 30 includes a connecting rod 31 and a bottom support main board 32. The connecting rod 31 includes a rod body 311 and a connecting block 312 fixed at one end of the rod body 311. The connecting block 312 is located between the outer cavity door plate 10 and the inner cavity door plate 20 and connected to the outer cavity door plate 10. The rod body 311 passes through the first through hole 21 and is connected to the bottom support main board 32. That is, the connecting rod 31 is fixed to the outer cavity door plate 10 through the connecting block 312, and the rod body 311 of the connecting rod passes through the first through hole 21 and is fixed to the bottom support main board 32, so that the bottom support main board 32 is suspended on the outer cavity door plate 10, and the weight of the bottom support main board 32 is transferred to the outer cavity door plate 10 through the connecting rod 31. The connecting block 312 and the outer cavity door plate 10 can be connected by screws, and the thickness of the outer cavity door plate 10 can allow the screws to be screwed in without penetrating the outer cavity door plate 10, thereby preventing the external atmosphere from entering the reaction outer cavity. Of course, the connection block 312 can also be fixed to the outer door panel 10 by welding.

[0043] In the bottom support plate 30 , the number of the connecting rods 31 may be one, two, three or even more, and the number of the first through holes 21 and the sealing tubes 40 also corresponds to the number of the connecting rods 31 one by one.

[0044] Reference Figure 2 and Figure 3 , the end of the rod body 311 close to the bottom support main board 32 is provided with a slot 3111 matching the thickness of the bottom support main board 32, and the slot 3111 runs through the rod body 311 horizontally in the radial direction; one end of the bottom support main board 32 is inserted into the slot 3111 and fixed. It is understandable that a slot running through the left and right can be opened on the end of the rod body 311 in the axial direction, so that the slot forms three notches, that is, one notch on the end face and two notches on both sides of the cylindrical surface. The bottom support main board 32 is inserted into the slot of the rod body 311, and then fixedly connected. The bottom support main board 32 is supported and limited by the upper and lower walls of the slot, so as to ensure that the bottom support main board 32 is more firmly connected and fixed to the connecting rod 31. It is understandable that after the bottom support main board 32 is inserted into the slot 3111, it can be fixedly connected by screws or bolts, or fixed by welding.

[0045] Reference Figure 2 and Figure 3The outer circumferential surface of one end of the rod body 311 provided with the slot 3111 is provided with two locking planes 3113 which are away from each other, the locking plane 3113 is provided with a connecting hole 3112 which penetrates through it, the bottom supporting main board 32 is provided with a through hole 321 which corresponds to the connecting hole 3112, a connecting piece passes through the through hole and the through hole 321 to connect and fix the rod body 311 with the bottom supporting main board 32, and the upper and lower ends of the connecting piece are pressed against the locking plane 3113. The connecting piece passes through the connecting hole 3112 and the through hole 321 to restrict and fix the bottom supporting main board 32 inserted into the slot 3111, and then the upper and lower ends are pressed against the locking plane 3113 to fix the connecting piece to prevent the connecting piece from loosening. Specifically, the connecting piece is a bolt. If the rod body 311 is not provided with the locking plane 3113, but the outer side is a circumferential surface, the locking of the bolt is not stable enough. After the locking plane 3113 is provided, the nut and the screw nut in the bolt can both tightly abut against the locking plane 3113 after being locked, so that the locking of the bolt is more stable.

[0046] Reference Figure 2 and Figure 3 The bottom supporting plate 30 further includes reinforcing ribs 3211 disposed on both sides of the bottom supporting main board 32 along the length direction. Since only one end of the bottom supporting main board 32 is connected and fixed to the connecting rod 31, and since the bottom supporting main board 32 is relatively long, it is easy to bend downward under the action of gravity. Therefore, reinforcing ribs 3211 are disposed to strengthen the bottom supporting main board 32 in the length direction to prevent it from being deformed and bent downward.

[0047] In actual use, the outer door panel 10 needs to be closed first, and then the inner door panel 20 is closed to ensure that both doors are tightly closed. Therefore, the inner door panel 20 needs to be able to move relative to the outer door panel 10. Based on this, the embodiment of the present application makes the following designs:

[0048] Reference Figure 2 and Figure 5 The fixing structure of the bottom support plate 30 further includes a telescopic mechanism 50, which is arranged on the outer cavity door plate 10 and connected to the inner cavity door plate 20. The telescopic mechanism 50 is used to adjust the spacing, and the sealing tube 40 is a first corrugated tube. That is, the telescopic mechanism 50 arranged on the outer cavity door plate 10 can drive the inner cavity door plate 20 to move relative to the outer cavity door plate 10 to change the spacing between the two. Specifically, when the outer cavity door plate 10 is closed, the telescopic mechanism 50 drives the inner cavity door plate 20 away from the outer cavity door plate 10, so that the inner cavity door plate 20 closes the inner layer reaction chamber.

[0049] Reference Figure 4The first bellows includes a first flange 41, a bellows body 42, and a second flange 43 connected in sequence, the connection block 312 is connected to the first flange 41, and the second flange 43 is connected to the inner cavity door plate 20. After the first flange 41 is connected to the connection block 312, one end of the first bellows is closed, and after the second flange 43 is connected to the inner cavity door plate 20, the other end of the second bellows 52 is closed, and the first through hole 21 is connected to the inside of the first bellows, but the process gas coming out of the first through hole 21 cannot be discharged from the first bellows, thereby ensuring that the process gas will not leak. The bellows body 42 of the first bellows is retractable and can adapt to the extension and contraction of the telescopic mechanism 50, and will not pull or crush the first bellows to cause leakage.

[0050] Furthermore, the outer cavity door panel 10 also includes a second through hole 11; the telescopic mechanism 50 includes a telescopic driver 51 and a second bellows 52, the telescopic driver 51 is fixed on the side of the outer cavity door panel 10 facing away from the inner cavity door panel 20, the output end of the telescopic driver 51 passes through the second through hole 11 and is connected to the inner cavity door panel 20, the second bellows 52 is sleeved on the output end, one end of the second bellows 52 is connected to the outer cavity door panel 10, and the other end covers one end of the second through hole 11 and is connected and fixed to the inner cavity door panel 20.

[0051] In actual work, the outer layer reaction cavity is heated to increase the temperature in the inner layer reaction cavity. If the telescopic driver 51 is directly set in the outer layer reaction cavity, the high temperature in the outer layer reaction cavity will directly damage the telescopic driver 51. Therefore, in the embodiment of the present application, the telescopic driver 51 of the telescopic mechanism 50 is set outside the outer layer reaction cavity, and its output end passes through the outer cavity door panel 10 and is connected to the inner cavity door panel 20. In this way, the high temperature in the outer layer reaction cavity can be prevented from damaging the telescopic driver 51.

[0052] In order to allow the output end to pass through the outer cavity door plate 10, a second through hole 11 is provided on the outer cavity door plate 10. In order to prevent the external atmosphere from entering the outer reaction chamber from the second through hole 11, a second bellows 52 is provided and sleeved on the output end. The two ends of the second bellows 52 are respectively connected to the inner cavity door plate 20 and the outer cavity door plate 10, and cover the second through hole 11, thereby sealing the second through hole 11. The second bellows 52 can be extended and retracted to adapt to the change in the distance between the outer cavity door plate 10 and the inner cavity door plate 20.

[0053] Specifically, the first bellows and / or the second bellows 52 are welded bellows.

[0054] Reference Figure 5The telescopic mechanism 50 further includes a shielding cover 53 and a guide rod 54. One end of the guide rod 54 is connected to the inner cavity door plate 20, and the other end extends through the outer cavity door plate 10. The outer cavity door plate 10 is correspondingly provided with a guide hole 12 for the guide rod 54 to pass through. The shielding cover 53 is fixed to the side of the outer cavity door plate 10 away from the inner cavity door plate 20 and covers the guide hole 12. The depth of the shielding cover 53 is greater than the sliding stroke of the guide rod 54 in the guide hole 12. That is, by setting the cooperation of the guide rod 54 and the guide hole 12, the telescopic actuator 51 is guided to be telescopic, so that the telescopic actuator 51 is more stable. The setting of the shielding cover 53 can prevent the external atmosphere from entering the outer layer reaction chamber from the guide hole 12. The depth of the shielding cover 53 is greater than the sliding stroke of the guide rod 54 in the guide hole 12, which can prevent the guide rod from moving too far when sliding and colliding with the shielding cover 53 to cause leakage. It can be understood that the axis of the guide hole 12 is parallel to the telescopic direction of the output end of the telescopic driver 51 .

[0055] Preferably, a linear bearing may be installed in the guide hole 12 to make the telescopic sliding of the guide rod 54 in the guide hole 12 smoother.

[0056] An embodiment of the present application further provides an atomic layer deposition device, comprising a fixing structure of the bottom support plate 30 in any of the above embodiments.

[0057] The atomic layer deposition device of the embodiment of the present application includes the fixing structure of the bottom support plate 30 in any of the above embodiments, and thus has the beneficial effects brought by the fixing structure of the bottom support plate 30 in any of the above embodiments, which will not be elaborated here.

[0058] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A fixing structure of a bottom support plate, characterized in that: include: External cavity door panel; An inner cavity door panel, located at one side of the outer cavity door panel and spaced apart from the outer cavity door panel, wherein the inner cavity door panel comprises a first through hole; A bottom supporting plate, located at a side of the inner cavity door plate away from the outer cavity door plate, one end of the bottom supporting plate passes through the first through hole and is connected to the outer cavity door plate; as well as A sealing tube is sleeved on one end of the support plate connected to the outer cavity door plate. One end of the sealing tube is connected to the outer cavity door plate, and the other end covers one end of the first through hole and is connected and fixed to the inner cavity door plate.

2. The fixing structure of the bottom support plate according to claim 1, characterized in that: The bottom support plate includes a connecting rod and a bottom support main board, the connecting rod includes a rod body and a connecting block fixed at one end of the rod body, the connecting block is located between the outer cavity door plate and the inner cavity door plate and connected to the outer cavity door plate, and the rod body passes through the first through hole to be connected to the bottom support main board.

3. The fixing structure of the bottom support plate according to claim 2, characterized in that: An end of the rod body close to the bottom supporting main board is provided with a slot matching the thickness of the bottom supporting main board, and the slot horizontally penetrates the rod body in a radial direction; One end of the bottom supporting mainboard is inserted into the slot and fixed.

4. The fixing structure of the bottom support plate according to claim 3, characterized in that: The outer surface of one end of the rod body provided with the slot is provided with two locking planes which are away from each other, the locking plane is provided with a penetrating connecting hole, the bottom supporting main board is provided with a through hole corresponding to the connecting hole, a connecting piece passes through the through hole and the through hole to connect and fix the rod body to the bottom supporting main board, and the upper and lower ends of the connecting piece are pressed against the locking plane.

5. The fixing structure of the bottom support plate according to claim 2, characterized in that: The bottom supporting plate also includes reinforcing ribs arranged on both sides of the bottom supporting main plate along the length direction.

6. The fixing structure of the bottom support plate according to claim 2, characterized in that: The fixing structure of the bottom support plate also includes a telescopic mechanism, which is arranged on the outer cavity door plate and connected to the inner cavity door plate. The telescopic mechanism is used to adjust the distance, and the sealing tube is a first corrugated tube.

7. The fixing structure of the bottom support plate according to claim 6, characterized in that: The first bellows comprises a first flange, a bellows body and a second flange which are connected in sequence, the connection block is connected to the first flange, and the second flange is connected to the inner cavity door panel.

8. The fixing structure of the bottom support plate according to claim 6, characterized in that: The outer cavity door panel also includes a second through hole; The telescopic mechanism includes a telescopic drive and a second bellows. The telescopic drive is fixed on the side of the outer cavity door panel facing away from the inner cavity door panel. The output end of the telescopic drive passes through the second through hole and is connected to the inner cavity door panel. The second bellows is sleeved on the output end. One end of the second bellows is connected to the outer cavity door panel, and the other end covers one end of the second through hole and is connected and fixed to the inner cavity door panel.

9. The fixing structure of the bottom support plate according to claim 6, characterized in that: The telescopic mechanism also includes a shielding cover and a guide rod, one end of the guide rod is connected to the inner cavity door panel, and the other end extends through the outer cavity door panel, the outer cavity door panel is correspondingly provided with a guide hole for the guide rod to pass through, the shielding cover is fixed to the side of the outer cavity door panel away from the inner cavity door panel and covers the guide hole, and the depth of the shielding cover is greater than the sliding stroke of the guide rod in the guide hole.

10. An atomic layer deposition device, characterized in that: The invention comprises a fixing structure for a bottom supporting plate as claimed in any one of claims 1 to 9.

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