Horizontal vacuum multi-power extrusion device for casting rods

Abstract

The invention relates to the technical field of extrusion devices, and particularly discloses a horizontal vacuum multi-power extrusion device for casting rods, which comprises a mold, an extrusion container, an extruder body, an extrusion rod and a vacuum pumping system, the mold is arranged at the outlet end of the extrusion container, a main cylinder is arranged on the extruder body, a plurality of main return cylinders are arranged on the outer side of the main cylinder, and a plurality of auxiliary return cylinders are arranged on the outer side of the main return cylinders; the extrusion rod is fixedly arranged on the main cylinder, a first hydraulic rod is arranged on the outer side of the extrusion rod, one end of the first hydraulic rod is connected with the main return cylinder, the other end of the first hydraulic rod is connected with the extrusion barrel, the main cylinder pushes the extrusion rod to stretch into the extrusion barrel to push a casting rod to move, a vacuumizing channel is formed in the extrusion rod, and an inlet of the vacuumizing channel is formed in the outer wall of the extrusion rod. The extrusion rod is arranged close to the extrusion end of the extrusion rod. The extrusion rod in the extrusion device extrudes towards the direction of the mold, and while a casting rod is pushed to be formed, gas in the inner cavity of the lining layer is subjected to vacuum extraction through the vacuum extraction system, so that the product quality and performance are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of valve sealing, in particular to a horizontal vacuum multi-power extrusion device for casting rods. Background Art

[0002] Aluminum alloys have been widely used in automotive heat exchange systems, household air conditioning systems, etc. due to their low density, good corrosion resistance and good processing performance. Aluminum alloy hot extrusion is one of the main processes for aluminum alloy forming. The process is to put aluminum alloy castings of a certain length and diameter into an extrusion cylinder heated to a certain temperature, and pass through a certain shape of die under the extrusion of the extrusion rod to obtain a profile with the required cross-sectional shape;

[0003] In order to facilitate the loading of cast rods, the diameter of the cast rods is usually smaller than the inner diameter of the extrusion barrel. During the process of loading the cast rods into the extrusion barrel, there is a certain gap between the cast rods and the extrusion barrel. During the extrusion process, the air in this gap usually enters the product as the product is extruded, and is particularly prone to appear on the surface of the product, causing internal bubbles or surface bubbles to appear during the extrusion of the cast rods, seriously affecting the performance of the product. In the prior art, a vacuum suction channel is directly opened on the extrusion barrel, but this method can neither guarantee the sealing effect inside the extrusion barrel. Therefore, it is urgently necessary to design a horizontal vacuum multi-power extrusion device for cast rods to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a horizontal vacuum multi-power extrusion device for cast rods, which solves the problem that air easily enters the gap between the cast rods and the extrusion barrel, thereby causing internal bubbles or surface bubbles to appear during cast rod extrusion, seriously affecting product performance.

[0005] In order to solve the above technical problems, the present invention provides a horizontal vacuum multi-power extrusion device for cast rods, comprising a mold, an extrusion barrel, an extruder body, an extrusion rod and a vacuum exhaust system, wherein the mold is arranged at the outlet end of the extrusion barrel, the extruder body is provided with a main cylinder, a plurality of main return cylinders are provided on the outside of the main cylinder, the extrusion rod is fixedly arranged on the main cylinder, a first hydraulic rod is provided on the outside of the extrusion rod, one end of the first hydraulic rod is connected to the main return cylinder, and the other end is connected to the extrusion barrel, the main cylinder pushes the extrusion rod to extend into the extrusion barrel to push the cast rod to move,

[0006] A vacuum channel is provided in the extrusion rod, the inlet of the vacuum channel is opened on the outer wall of the extrusion rod and is arranged close to the extrusion end of the extrusion rod, the outlet of the vacuum channel is connected to the vacuum pumping system, and the vacuum pumping system extracts gas in the extrusion cylinder through the vacuum channel.

[0007] Furthermore, the vacuum channel includes an exhaust channel, a main channel and an air suction channel arranged in the extrusion rod, the exhaust channel and the air suction channel are respectively vertically arranged at both ends of the main channel, and the exhaust channel is arranged close to the extrusion cylinder, the vacuum exhaust system is connected to the air suction channel through an exhaust pipe, and the exhaust pipe and the air suction channel are fastened and sealed by a sealing member.

[0008] Furthermore, a mounting groove is provided at the extrusion end of the extrusion rod, an elastic member is placed in the mounting groove, and the extrusion pad is pressed on the outer side of the elastic member.

[0009] Furthermore, an extrusion pad is provided at the extrusion end of the extrusion rod, and the extrusion pad includes a cylindrical section and a conical section connected in sequence, a plurality of limit grooves are opened on the outer wall of the cylindrical section, the minimum diameter of the conical section is larger than the diameter of the cylindrical section, and a step surface is formed at the junction of the conical section and the cylindrical section, and a reserved gap is provided between the step surface and the extrusion end of the extrusion rod.

[0010] Furthermore, a plurality of limit bolts are provided on the outer wall of the extrusion rod, and the inner end of each limit bolt passes through the outer wall of the extrusion rod and extends into the corresponding limit groove. The length of the limit groove is greater than the diameter of the limit bolt, and the length of the limit groove is 5-10 mm.

[0011] Furthermore, an expansion ring is sleeved on the outer side of the compression pad, the inner and outer sides of the expansion ring are both conical, and the cone angle of the expansion ring is equal to the cone surface angle of the conical section.

[0012] Furthermore, a sealing plate is sleeved on the outer side of the extrusion rod, and the sealing plate is connected to the auxiliary cylinder of the extruder body through two second hydraulic rods. A sealing ring for sealing with the extrusion rod is embedded on the inner wall of the sealing plate.

[0013] Furthermore, the extrusion cylinder includes a lining layer, a heating layer and an outer layer arranged from the inside to the outside, the lining layer is cylindrical, a number of evenly distributed heating tubes are passed through the heating layer, bosses are provided at both ends of the outer side of the outer layer, the bosses are used to pass the first hydraulic rod, and the mold and the sealing plate are respectively provided with a first sealing ring and a second sealing ring that seals with the two ends of the outer layer.

[0014] Beneficial effects of the present invention: the extrusion horizontal vacuum multi-power extrusion device of the present invention seals both sides of the extrusion barrel through the mold and the sealing plate, and when the second hydraulic rod pushes the sealing plate to seal, the extrusion rod is simultaneously extruded toward the mold direction, so as to promote the casting rod to be formed, and at the same time, the inner cavity of the lining layer of the extrusion barrel can be sealed, and then the air in the inner cavity of the lining layer is vacuumed out by the vacuum exhaust system to prevent the problem of bubbles inside and on the surface of the profile, so that it can ensure the sealing inside the extrusion barrel and improve the quality and performance of the product;

[0015] The setting of the vacuum channel enables the extrusion rod to gradually move forward to uniformly extract the gas around the cast rod while extruding, effectively solving the problem that the gap between the extrusion rod and the extrusion barrel is small and the pipeline used by the vacuum exhaust system cannot be arranged, effectively saving the extrusion space, and at the same time solving the problem that the vacuum suction channel on the extrusion barrel cannot ensure the sealing effect inside the extrusion barrel;

[0016] The setting of the extrusion pad can make the extrusion pad contact with the cast rod when the extrusion rod is driven by the main cylinder of the extruder body. At the same time, the elastic part is forced to shrink, so that the extrusion rod can flexibly contact the cast rod when extruding the cast rod, so as to prevent the problem that the impact force of the extrusion rod is too large and the profile forming speed is affected. At the same time, it can also solve the problem that the product discharge amount is uneven due to the hard contact between the extrusion rod and the cast rod, resulting in poor profile quality or scrap; the intersection of the conical section and the cylindrical section of the extrusion pad forms a step surface, and a reserved gap is provided between the step surface and the extrusion end of the extrusion rod, so that the extrusion pad has a certain amount of movement, so as to improve the buffering effect of the extrusion pad;

[0017] The arrangement of several limit bolts on the extrusion rod can effectively prevent the extrusion pad from being affected by the elastic effect of the elastic member and popping out of the installation slot. In serious cases, it will bounce onto the product and be adsorbed on the casting rod at high temperature and extruded together with the casting rod, causing defects in the product.

[0018] The auxiliary cylinder of the extruder body is connected to the sealing plate through two second hydraulic rods, so that the auxiliary cylinder of the extruder body can push the sealing plate to seal with the extrusion barrel, and at the same time, the sealing plate and the extrusion rod are sealed by a sealing ring to prevent the gap between the sealing plate and the extrusion rod in the air from entering the extrusion barrel, thereby solving the problem that the existing extrusion barrel cannot ensure a fully closed state, so as to improve the sealing effect in the extrusion barrel;

[0019] The first hydraulic rod is connected to the main return cylinder to drive the extrusion cylinder to return, so that the extrusion cylinder can maintain the sealing inside when it is not in a working state, so as to ensure that the gas in the extrusion cylinder can be easily extracted when it is used next time, so as to improve the efficiency of gas extraction, and at the same time, it can also solve the problem that the single power of the existing extrusion device cannot meet the use requirements;

[0020] The mold and the sealing plate are respectively provided with a first sealing ring and a second sealing ring, and the design of sealing with both ends of the outer layer of the extrusion barrel respectively can effectively prevent air from entering the extrusion barrel when the extrusion rod extrude the cast rod, thereby causing the product to be damaged again. At the same time, it can also reduce the extraction volume of the vacuum exhaust system and reduce energy waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present invention, 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a partial cross-sectional view of a horizontal vacuum multi-power extrusion device for casting rods in an embodiment of the present invention;

[0023] Figure 2 It is a partial cross-sectional view of a horizontal vacuum multi-power extrusion device for extruding a valve seat rod in a cast rod embodiment of the present invention;

[0024] Figure 3 It is a right side view of a horizontal vacuum multi-power extrusion device for casting rods in an embodiment of the present invention after the mold is removed;

[0025] In the figure: 1-mold, 2-extrusion cylinder, 3-main cylinder, 4-vacuum exhaust system, 5-extrusion rod, 6-first hydraulic rod, 7-extrusion pad, 8-cast rod, 9-elastic member, 10-limiting bolt, 11-expansion ring, 12-sealing plate, 13-second hydraulic rod, 14-sealing ring, 15-heating tube, 16-first sealing ring, 17-second sealing ring, 21-bushing layer, 22-heating layer, 23-outer layer, 51-vacuum exhaust channel, 52-installation groove, 71-cylindrical section, 72-conical section, 231-boss, 511-exhaust channel, 512-main channel, 513-suction channel, 711-limiting groove. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings of the present invention specification to clearly and completely describe the technical solutions in the embodiments of the invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The following will be combined with a specific embodiment of the present invention and the attached Figure 1-3To explain in detail, a horizontal vacuum multi-power extrusion device for casting rods is specifically disclosed, including a mold 1, an extrusion barrel 2, an extruder body, an extrusion rod 5 and a vacuum exhaust system 4. The mold 1 is arranged at the outlet end of the extrusion barrel 2, and a main cylinder 3 is arranged on the extruder body. A plurality of main return cylinders are arranged on the outside of the main cylinder 3. The extrusion rod 5 is fixedly arranged on the main cylinder 3. A first hydraulic rod 6 is arranged on the outside of the extrusion rod 5. One end of the first hydraulic rod 6 is connected to the main return cylinder, and the other end is connected to the extrusion barrel 2. The main cylinder 3 pushes the extrusion rod 5 to extend into the extrusion barrel 2 to push the casting rod 8 to move. The setting of the first hydraulic rod 6 connected to the main return cylinder can drive the extrusion barrel 2 to return, so as to achieve the sealing of the inner cavity of the extrusion barrel 2 when it is not in a working state, so as to ensure that the gas in the extrusion barrel 2 is easily extracted when it is used next time, so as to improve the efficiency of extracting gas, and at the same time, it can also solve the problem that the single power of the existing extrusion device cannot meet the use requirements;

[0028] A vacuum channel 51 is provided in the extrusion rod 5. The inlet of the vacuum channel 51 is opened on the outer wall of the extrusion rod 5 and is arranged close to the extrusion end of the extrusion rod 5. The outlet of the vacuum channel 51 is connected to the vacuum pumping system 4. The vacuum pumping system 4 extracts the gas in the extrusion cylinder 2 through the vacuum channel 51.

[0029] The vacuum channel 51 includes an exhaust channel 511, a main channel 512 and an air suction channel 513 arranged in the extrusion rod 5. The exhaust channel 511 and the air suction channel 513 are respectively arranged vertically at the two ends of the main channel 512, and the exhaust channel 511 is arranged close to the extrusion cylinder 2. The vacuum exhaust system 4 is connected to the air suction channel 513 through the exhaust pipe 41, and the exhaust pipe 41 and the air suction channel 513 are tightly sealed by a sealing member.

[0030] The arrangement of the vacuum channel 51 enables the extrusion rod 5 to gradually and uniformly extract the gas around the cast rod 8 while extruding, effectively solving the problem that the gap between the extrusion rod 5 and the extrusion barrel 2 is too small to arrange the pipeline used by the vacuum exhaust system 4, effectively saving the extrusion space, and at the same time solving the problem that the vacuum suction channel on the extrusion barrel 2 cannot ensure the sealing effect inside the extrusion barrel 2;

[0031] The extrusion end of the extrusion rod 5 is provided with a mounting groove 52 , an elastic member 9 is placed in the mounting groove 52 , and the extrusion pad 7 is pressed on the outer side of the elastic member 9 .

[0032] An extrusion pad 7 is provided at the extrusion end of the extrusion rod 5, and the extrusion pad 7 includes a cylindrical section 71 and a conical section 72 connected in sequence. A plurality of limit grooves 711 are provided on the outer wall of the cylindrical section 71. The minimum diameter of the conical section 72 is greater than the diameter of the cylindrical section 71. A step surface is formed at the junction of the conical section 72 and the cylindrical section 71, and a reserved gap is provided between the step surface and the extrusion end of the extrusion rod 5.

[0033] A plurality of limiting bolts 10 are provided on the outer wall of the extrusion rod 5. The inner end of each limiting bolt 10 passes through the outer wall of the extrusion rod 5 and extends into the corresponding limiting groove 711. The length of the limiting groove 711 is greater than the diameter of the limiting bolt 10, and the length of the limiting groove 711 is 5-10 mm.

[0034] The arrangement of several limit bolts on the extrusion rod 5 can effectively prevent the extrusion pad 7 from being affected by the elastic action of the elastic member 9 and popping out of the mounting groove 52. In serious cases, it may bounce onto the product and be adsorbed on the casting rod 8 at high temperature and be extruded together with the casting rod 8, causing defects in the product.

[0035] An expansion ring 11 is sleeved on the outer side of the compression pad 7 . The inner and outer sides of the expansion ring 11 are both conical, and the cone angle of the expansion ring 11 is equal to the cone surface angle of the conical section 72 .

[0036] The setting of the extrusion pad 7 can make the extrusion pad 7 contact with the cast rod 8 when the extrusion rod 5 is driven by the main cylinder 3 of the extruder body. At the same time, the elastic member 9 is forced to contract, so that the extrusion rod 5 can flexibly contact the cast rod 8 when extruding the cast rod 8, so as to prevent the problem that the impact force of the extrusion rod 5 is too large and the profile forming speed is affected. At the same time, it can also solve the problem that the profile discharge amount is uneven due to the hard contact between the extrusion rod 5 and the cast rod 8, resulting in poor profile quality or scrap; the intersection of the conical section 72 and the cylindrical section 71 of the extrusion pad 7 forms a step surface, and a reserved gap is provided between the step surface and the extrusion end of the extrusion rod 5, so that the extrusion pad 7 has a certain amount of movement, so as to improve the buffering effect of the extrusion pad 7.

[0037] A sealing plate 12 is sleeved on the outer side of the extrusion rod 5, and the sealing plate 12 is connected to the auxiliary cylinder of the extruder body through two second hydraulic rods 13. A sealing ring 14 for sealing with the extrusion rod 5 is embedded on the inner wall of the sealing plate 12;

[0038] The auxiliary cylinder of the extruder body is connected to the sealing plate 12 through two second hydraulic rods 13, so that the auxiliary cylinder of the extruder body can push the sealing plate 12 to seal with the extrusion barrel 2, and at the same time, the sealing plate 12 and the extrusion rod 5 are sealed by the sealing ring 14 to prevent the gap between the sealing plate 12 and the extrusion rod 5 in the air from entering the extrusion barrel 2, so as to improve the sealing effect in the extrusion barrel 2;

[0039] The extrusion barrel 2 includes a lining layer 21, a heating layer 22 and an outer layer 23 arranged from the inside to the outside. The lining layer 21 is cylindrical. A number of evenly distributed heating tubes 15 are inserted into the heating layer 22. Bosses 231 are provided at both ends of the outer side of the outer layer 23. The bosses 231 are used to insert the first hydraulic rod 6. The mold 1 and the sealing plate 12 are respectively provided with a first sealing ring 16 and a second sealing ring 17 sealed at both ends of the outer layer 23. The mold 1 and the sealing plate 12 are respectively provided with a first sealing ring 16 and a second sealing ring 17, and the design of sealing at both ends of the outer layer 23 of the extrusion barrel 2 can effectively prevent air from entering the extrusion barrel 2 when the extrusion rod 5 extrude the cast rod 8, thereby causing the product to be damaged again. At the same time, it can also reduce the extraction amount of the vacuum exhaust system 4 and reduce energy waste.

[0040] The extrusion horizontal vacuum multi-power extrusion device of the present invention seals both sides of the extrusion cylinder 2 through the mold 1 and the sealing plate 12, and when the second hydraulic rod 13 pushes the sealing plate 12 for sealing, the extrusion rod 5 is simultaneously squeezed toward the mold 1 to push the cast rod 8 into shape, while also being able to seal the inner cavity of the lining layer 21 of the extrusion cylinder 2, and then the air in the inner cavity of the lining layer 21 is vacuumed out through the vacuum exhaust system to prevent the problem of bubbles inside and on the surface of the profile, so that it can ensure the sealing inside the extrusion cylinder 2 while also improving the quality and performance of the product.

[0041] The workflow of the present invention is:

[0042] Insert the cast rod 8 into the inner cavity of the lining layer 21 of the extrusion barrel 2, the main cylinder 3 of the extruder body drives the extrusion rod 5 to extend into the extrusion barrel 2, and at the same time, the auxiliary cylinder of the extruder body pushes the second hydraulic rod 13 and the sealing plate 12 to move toward the extrusion barrel 2, so that the sealing plate 12 is sealed with the inlet end of the extrusion barrel 2 through the second sealing ring 17, and the vacuum exhaust system 4 extracts the gas in the extrusion barrel 2, and the main cylinder 3 of the extruder body continues to push the extrusion rod 5 to continue to move toward the mold, and while pushing, the exhaust channel 511 on the extrusion rod 5 close to the extrusion end can gradually suck the gas remaining in the extrusion barrel 2 into the main channel 512, so as to further The gas in the extrusion cylinder 2 is extracted, and at the same time, the gas is transported from the suction channel 513 to the exhaust pipe 41 and then enters the vacuum exhaust system 4. When the conical section 72 of the extrusion pad 7 at the extrusion end of the extrusion rod 5 contacts the cast rod 8, the elastic member 9 is compressed by the reverse force of the cast rod 8, and the extrusion pad 7 moves toward the main cylinder 3 to increase the buffering force between the extrusion pad 7 and the cast rod 8, thereby avoiding the problem of uneven speed during profile extrusion caused by the impact force of the extrusion rod 5 and affecting the performance of the profile. After the cast rod 8 is subjected to the extrusion force of the extrusion rod 5, it passes through the die opening of the mold 1 and extrude a profile with the same shape as the die opening, thereby improving the extrusion forming rate of the profile.

[0043] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A horizontal vacuum multi-power extrusion device for casting rods, characterized in that: The invention comprises a mold (1), an extrusion barrel (2), an extruder body, an extrusion rod (5) and a vacuum exhaust system (4), wherein the mold (1) is arranged at the outlet end of the extrusion barrel (2), the extruder body is provided with a main cylinder (3), a plurality of main return cylinders are provided on the outside of the main cylinder (3), the extrusion rod (5) is fixedly arranged on the main cylinder (3), a first hydraulic rod (6) is provided on the outside of the extrusion rod (5), one end of the first hydraulic rod (6) is connected to the main return cylinder, and the other end is connected to the extrusion barrel (2), the main cylinder (3) pushes the extrusion rod (5) to extend into the extrusion barrel (2) to push the casting rod (8) to move, The extrusion rod (5) is provided with a vacuum channel (51), the inlet of the vacuum channel (51) is opened on the outer wall of the extrusion rod (5) and is arranged close to the extrusion end of the extrusion rod (5), the outlet of the vacuum channel (51) is connected to the vacuum pumping system (4), and the vacuum pumping system (4) extracts the gas in the extrusion cylinder (2) through the vacuum channel (51).

2. A horizontal vacuum multi-power extrusion device for cast rods according to claim 1, characterized in that: The vacuum extraction channel (51) comprises an exhaust channel (511), a main channel (512) and an air suction channel (513) arranged in the extrusion rod (5); the exhaust channel (511) and the air suction channel (513) are respectively arranged vertically at two ends of the main channel (512), and the exhaust channel (511) is arranged close to the extrusion cylinder (2); the vacuum exhaust system (4) is connected to the air suction channel (513) through an exhaust pipe (41), and the exhaust pipe (41) and the air suction channel (513) are tightly sealed by a sealing member.

3. A horizontal vacuum multi-power extrusion device for cast rods according to claim 1, characterized in that: The extrusion end of the extrusion rod (5) is provided with a mounting groove (52), an elastic member (9) is placed in the mounting groove (52), and the extrusion pad (7) is pressed on the outer side of the elastic member (9).

4. A horizontal vacuum multi-power extrusion device for cast rods according to claim 1, characterized in that: The extrusion end of the extrusion rod (5) is provided with an extrusion pad (7), the extrusion pad (7) comprising a cylindrical section (71) and a conical section (72) connected in sequence, a plurality of limit grooves (711) are provided on the outer wall of the cylindrical section (71), the minimum diameter of the conical section (72) is greater than the diameter of the cylindrical section (71), a step surface is formed at the intersection of the conical section (72) and the cylindrical section (71), and a reserved gap is provided between the step surface and the extrusion end of the extrusion rod (5).

5. A horizontal vacuum multi-power extrusion device for cast rods according to claim 4, characterized in that: A plurality of limiting bolts (10) are provided on the outer wall of the extrusion rod (5), and the inner end of each limiting bolt (10) passes through the outer wall of the extrusion rod (5) and extends into the corresponding limiting groove (711), and the length of the limiting groove (711) is greater than the diameter of the limiting bolt (10), and the length of the limiting groove (711) is 5-10 mm.

6. A horizontal vacuum multi-power extrusion device for cast rods according to claim 4, characterized in that: An expansion ring (11) is sleeved on the outer side of the compression pad (7), the inner and outer sides of the expansion ring (11) are both conical, and the cone angle of the expansion ring (11) is equal to the cone surface angle of the conical section (72).

7. A horizontal vacuum multi-power extrusion device for cast rods according to claim 1, characterized in that: The outer side of the extrusion rod (5) is sleeved with a sealing plate (12), and the sealing plate (12) is connected to the auxiliary cylinder of the extruder body through two second hydraulic rods (13). The inner wall of the sealing plate (12) is embedded with a sealing ring (14) for sealing with the extrusion rod (5).

8. A horizontal vacuum multi-power extrusion device for cast rods according to claim 7, characterized in that: The extrusion cylinder (2) comprises a lining layer (21), a heating layer (22) and an outer layer (23) arranged from the inside to the outside, the lining layer (21) is cylindrical, a plurality of evenly distributed heating tubes (15) are inserted into the heating layer (22), bosses (231) are provided at both ends of the outer side of the outer layer (23), and the bosses (231) are used to insert the first hydraulic rod (6), and the mold (1) and the sealing plate (12) are respectively provided with a first sealing ring (16) and a second sealing ring (17) that seal with both ends of the outer layer (23).

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