Method for processing a gummed paper sleeve core

Abstract

The application discloses a processing method of a glue-impregnated paper sleeve core body, which comprises the following steps: taking a metal tube as a center shaft, winding insulating paper on the metal tube to form a coiled core; placing the coiled core into a mold, meanwhile, placing a partitioning piece into the mold, and making the partitioning piece contact with the end of the insulating paper; pouring liquid epoxy resin into the mold, so that the coiled core and the partitioning piece are completely impregnated in the epoxy resin, and a blank body is formed after the epoxy resin is solidified; and cutting the pure glue layer body and the partitioning layer body in the blank body according to preset requirements to form the core body. After the epoxy resin is solidified, the partitioning layer body separates the pure glue layer body from the core body, the partitioning layer body can block the cracks generated on the pure glue layer body, and can also disperse the extending direction of the cracks, so that the cracks are prevented from extending to the core body, the integrity of the core body is ensured, and the qualified rate of the core body is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage insulation sleeve, in particular to a processing method of a rubber-impregnated paper sleeve core. BACKGROUND

[0002] With the rapid development of the national economy, the rapid growth of electricity demand, thus the problem of energy transportation and electricity supply tends to be nervous. At present, the whole power system transmission pressure, resulting in 500kV AC and ± 500kV DC system as the backbone of the transmission network can not meet the needs of the development of the national economy. In order to solve this problem, China has accelerated the construction of UHV power grid, in 2010, the world's first ± 800kV UHV DC transmission project. Among them, the UHV DC sleeve is one of the important electrical equipment of UHV DC transmission project, which can insulate the current under high voltage and the grounding position, and can also provide mechanical support.

[0003] At present, the DC sleeve mainly includes oil paper sleeve and rubber-impregnated paper sleeve. Among them, the oil paper sleeve has the risk of explosion and fire, therefore, the rubber-impregnated paper sleeve is often used to replace the oil paper sleeve. However, the main insulation core of the rubber-impregnated paper sleeve in the industry is integrally cast, especially the UHV product, because the core of the rubber-impregnated paper sleeve is long in length, large in diameter and thin in wall thickness, therefore, the core is easy to crack and damage during forming, so that the core production qualified rate is very low, the cost is high, and there is a high safety risk when used. SUMMARY

[0004] Therefore, it is necessary to provide a processing method of a rubber-impregnated paper sleeve core, which can effectively avoid cracks in the production process of the core.

[0005] A processing method of a rubber-impregnated paper sleeve core, comprising: taking a metal pipe as a center axis, winding insulation paper on the metal pipe to form a coiled core; placing the coiled core into a mold, at the same time, placing a partitioning member in the mold, and making the partitioning member contact the end of the insulation paper; pouring liquid epoxy resin into the mold, so that the coiled core and the partitioning member are completely immersed in the epoxy resin and form a blank after the epoxy resin is cured; according to the preset requirement, cutting the pure glue layer and the partitioning layer in the blank to form a core.

[0006] In the processing method, when the winding core is put into the mold, the partition member can contact the end of the insulating paper, and after the liquid epoxy resin is poured into the mold, the winding core and the partition member can be soaked in the epoxy resin. After the epoxy resin is cured, the partition layer separates the pure glue layer from the core, and the partition layer can block the cracks generated on the pure glue layer and disperse the extension direction of the cracks, so as to avoid the cracks extending to the core and ensure the integrity of the core and improve the qualified rate of the core.

[0007] The technical solutions are further described as follows:

[0008] In one of the embodiments, before the step of pouring the liquid epoxy resin into the mold, the method further comprises: removing the moisture in the insulating paper in the winding core.

[0009] In one of the embodiments, along the axial direction of the winding core, the length of the metal pipe is greater than the winding length of the insulating paper on the metal pipe, and the two ends of the metal pipe are not wound with the insulating paper.

[0010] In one of the embodiments, in the step of putting the partition member into the mold and contacting the end of the insulating paper, the step specifically comprises: the partition member is provided with two, and the two partition members are put into the mold and contact the ends of the insulating paper respectively.

[0011] In one of the embodiments, in the step of forming the blank after the epoxy resin is cured, the step specifically comprises: vacuumizing the mold to maintain the vacuum state inside the mold; heating the mold, and the heating temperature is higher than the temperature required for the curing reaction of the epoxy resin, until the liquid epoxy resin is completely cured in the mold.

[0012] In one of the embodiments, the blank comprises the core, two partition layers and two pure glue layers, the two partition layers are respectively located at the two ends of the core, the pure glue layer corresponds to the partition layer one by one, and the pure glue layer is located at the end of the partition layer away from the core. In the step of cutting the pure glue layer and the partition layer in the blank to form the core, the step specifically comprises: radially cutting the blank along the axial direction of the blank to cut the two partition layers and the two pure glue layers.

[0013] In one embodiment, the step of winding the insulating paper around the metal tube to form a wound core specifically includes: increasing the width of the insulating paper so that the winding length of the insulating paper on the metal tube increases, wherein the width of one end of the insulating paper increases by 30mm to 70mm along the axial direction of the metal tube, and the width of the other end of the insulating paper increases by 80mm to 120mm.

[0014] In one embodiment, the width of the insulating paper at one end increases by 50 mm along the axial direction of the metal tube, and the width of the insulating paper at the other end increases by 100 mm.

[0015] In one embodiment, the step of cutting the pure adhesive layer and the partition layer within the preform to form the core further includes: cutting the portion of the insulating paper that has increased in width to form the core.

[0016] In one embodiment, the partition is a polyurethane material board, a phenolic material board, or an insulating paper material board;

[0017] And / or, the insulating paper is crepe paper;

[0018] And / or, the metal tube is a copper tube or an aluminum tube. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Furthermore, the accompanying drawings are not drawn to a 1:1 scale, and the relative dimensions of the various components are shown as examples only and not necessarily to scale. In the accompanying drawings:

[0022] Figure 1 This is a flowchart of a method for processing a paper-impregnated sleeve core according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the wound core in one embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the embryo's structure in one embodiment of the present invention;

[0025] Figure 4 for Figure 3 A cross-sectional view of plane AA.

[0026] The components in the diagram are labeled as follows:

[0027] 10. Embryo body; 110. Core body; 111. Rolled core; 1111. Metal tube; 1112. Insulating paper; 120. Partition layer; 130. Pure adhesive layer; 20. Support platform. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] The impregnated paper sleeve is mainly composed of metal parts, outer insulation, core 110, flange, equalizing ball, and other components. The core 110 is generally manufactured by first using a metal tube 1111 as the central guide tube, and then winding insulating paper 1112 around the metal tube 1111 until the designed diameter is reached; then the wound insulating paper 1112 and the metal tube 1111 are placed together into a mold for impregnation with epoxy resin; finally, after the epoxy resin cures, the core 110 is formed.

[0030] Specifically, during the manufacturing of the core 110 of the impregnated paper sleeve, the volume of the epoxy resin in the mold shrinks as it cures. To ensure that the insulating paper 1112 wound around the metal tube 1111 is fully impregnated with epoxy resin in the mold and to ensure the molding quality of the core 110, a certain space is reserved between the two ends of the insulating paper 1112 and the mold along the axial direction of the metal tube 1111 to store excess liquid epoxy resin. As the epoxy resin gradually cures, the epoxy resin at both ends of the insulating paper 1112 can compensate for the shrinkage of the epoxy resin volume on the insulating paper 1112, thus enabling the core 110 to be molded normally. However, after the epoxy resin is completely cured, cracks are prone to occur in the pure adhesive layer 130 formed at both ends of the core 110. The cracks will extend along the axial direction of the metal tube 1111, causing cracks in the core 110, which will damage the core 110.

[0031] It should be noted that the pure adhesive layer 130 in this embodiment refers to the molded body formed by curing epoxy resin other than insulating paper 1112 in the mold along the axial direction of the mold.

[0032] To overcome the above problems, please refer to Figures 1 to 4One embodiment of this application provides a method for processing a paper-impregnated sleeve core 110, comprising:

[0033] With the metal tube 1111 as the central axis, the insulating paper 1112 is wound around the metal tube 1111 to form a wound core 111;

[0034] The rolled core 111 is placed into the mold, and a partition is placed into the mold, with the partition in contact with the end of the insulating paper 1112.

[0035] Liquid epoxy resin is poured into the mold so that the rolled core 111 and the partition are completely immersed in the epoxy resin and form a preform 10 after the epoxy resin is cured.

[0036] According to preset requirements, the pure rubber layer 130 and the partition layer 120 in the embryo 10 are cut to form the core 110.

[0037] In the above processing method, when the rolled core 111 is placed into the mold, the partition can contact the end of the insulating paper 1112. After liquid epoxy resin is poured into the mold, both the rolled core 111 and the partition can be immersed in the epoxy resin. After the epoxy resin cures, since the partition layer 120 separates the pure adhesive layer 130 from the core 110, the partition layer 120 can block the cracks generated on the pure adhesive layer 130, and at the same time disperse the direction of crack extension, preventing cracks from extending to the core 110, ensuring the integrity of the core 110, and improving the yield of the core 110.

[0038] It should be noted that, in this embodiment, the partition layer 120 refers to a partition component covered with solid epoxy resin after the epoxy resin has been cured.

[0039] It should be noted that the pure adhesive layer 130 in this embodiment refers to the molded body formed by curing epoxy resin other than the insulating paper 1112 and the partition in the mold along the axial direction of the mold.

[0040] Specifically, the insulating paper 1112 is wound around the metal tube 1111 in a loop, and the winding stops when the diameter of the wound core 111 meets the set requirements. In other words, the winding stops when the thickness of the insulating paper 1112 wound around the metal tube 1111 meets the set requirements to form a wound core 111 that meets the requirements.

[0041] Typically, the core 110 used in ultra-high voltage environments is relatively large. Therefore, when winding insulating paper 1112 onto the metal tube 1111 to form a wound core 111, multiple rolls of insulating paper 1112 are usually arranged sequentially along the axial direction of the metal tube 1111. During winding, the multiple rolls of insulating paper 1112 are simultaneously wound circumferentially along the outer wall of the metal tube 1111. Specifically, each roll of insulating paper 1112 must be evenly wound onto the outer wall of the metal tube 1111 during the winding process until the diameter of the formed wound core 111 meets the requirements. Once the diameter requirement of the wound core 111 is met, the outermost layer of insulating paper 1112 is fixed to prevent loosening.

[0042] It should be noted that "core 110 dimensions" refers to the diameter and length of core 110.

[0043] Specifically, in this embodiment, the insulating paper 1112 is crepe paper.

[0044] Specifically, in this embodiment, the metal tube 1111 is a copper tube or an aluminum tube.

[0045] Based on the above embodiments, in one embodiment, the partition is a polyurethane material board, a phenolic material board, or an insulating paper material board.

[0046] Optionally, in other embodiments, the partitions may be pre-positioned at both ends of the insulating paper 1112. When the wound core 111 is placed into the mold, the partitions enter the mold together with the wound core 111.

[0047] To improve the insulation performance of the core 110 and ensure its safe use, based on the above embodiments, in one embodiment, before the step of pouring liquid epoxy resin into the mold, the following steps are further included:

[0048] Remove moisture from the insulating paper 1112 in the wound core 111.

[0049] Specifically, in this embodiment, the water removal operation is carried out inside the mold using a pressure difference method.

[0050] Specifically, after the rolled core 111 is placed into the mold, the inside of the mold is sealed. A vacuum pump is used to evacuate the inside of the mold, and at the same time, the mold is heated to remove moisture from the insulating paper 1112.

[0051] To ensure the moisture content of the insulating paper inside the mold is maintained

[0052] Alternatively, in another embodiment, the moisture in the insulating paper 1112 of the wound core 111 can be removed by other equipment.

[0053] Because epoxy resin undergoes exothermic and volume shrinkage changes during its transformation from liquid to solid, measures are taken to prevent the epoxy resin impregnated on the insulating paper 1112 from shrinking during curing and affecting the normal molding of the core 110. Please refer to [link to relevant documentation]. Figure 2 Based on the above embodiments, in one embodiment, along the axial direction of the wound core 111, the length of the metal tube 1111 is greater than the winding length of the insulating paper 1112 on the metal tube 1111, and the two ends of the metal tube 1111 are not wrapped with the insulating paper 1112. Thus, when the wound core 111 is placed in the mold and epoxy resin is poured, the two ends of the metal tube 1111, i.e., the parts without the insulating paper 1112, are immersed in the epoxy resin. As the epoxy resin gradually cures, the epoxy resin in the insulating paper 1112 shrinks in volume due to curing, and the epoxy resin at both ends of the metal tube 1111 replenishes it, so that the core 110 can be formed normally. When the epoxy resin in the mold is completely cured, a pure adhesive layer 130 is formed at the two ends of the metal tube 1111, i.e., the parts without the insulating paper 1112.

[0054] Specifically, in this embodiment, the mold has a cylindrical structure, and the diameter of the mold is adapted to the diameter of the insulating paper 1112 wound around the metal tube 1111.

[0055] To improve the stability of the rolled core 111 placed within the mold, slots are further provided at both the top and bottom of the mold. For example... Figure 3 As shown, the metal tube 1111 has support platforms 20 at both ends. During installation, the support platforms 20 can be directly inserted into the corresponding slots in the mold.

[0056] Please see Figure 2 and Figure 3 Based on the above embodiments, in one embodiment, the step of placing a partition member inside the mold and bringing the partition member into contact with the end of the insulating paper 1112 specifically includes:

[0057] Two partitions are provided, and both partitions are placed inside the mold so that the two partitions are in contact with the ends of the insulating paper 1112 respectively.

[0058] It should be noted that the ends of the insulating paper 1112 refer to both ends of the insulating paper 1112 along the axial direction of the rolled core 111.

[0059] Inside the mold, there are spacers in contact with both ends of the insulating paper 1112 along the axial direction of the rolled core 111. This can prevent the pure rubber layer 130 at both ends of the metal tube 1111 from cracking and causing cracks in the core 110.

[0060] Based on the above embodiments, in one embodiment, the step of forming the preform 10 after the epoxy resin has cured specifically includes:

[0061] The mold is evacuated to maintain a vacuum inside the mold;

[0062] The mold is heated to a temperature higher than that required for the curing reaction of the epoxy resin until the liquid epoxy resin is completely cured inside the mold.

[0063] Alternatively, in one embodiment, a vacuum pump or other air-drawing device may be used to evacuate the air inside the mold.

[0064] Specifically, in this embodiment, such as Figure 3 As shown, the embryo 10 includes a core 110, two partition layers 120, and two pure adhesive layers 130. The two partition layers 120 are located at opposite ends of the core 110. Each pure adhesive layer 130 corresponds to one of the partition layers 120, and the pure adhesive layer 130 is located at the end of the partition layer 120 away from the core 110.

[0065] Based on the above embodiments, in one embodiment, the step of cutting the pure rubber layer 130 and the partition layer 120 within the embryo 10 to form the core 110 specifically includes:

[0066] The embryo 10 is radially cut along its axial direction to sever the two partition layers 120 and the two pure rubber layers 130.

[0067] To further reduce the damage caused by cracks to the core 110, based on the above embodiments, in one embodiment, the step of winding the insulating paper 1112 around the metal tube 1111 to form the wound core 111 specifically includes:

[0068] The width of the insulating paper 1112 is increased so that the winding length of the insulating paper 1112 on the metal tube 1111 is increased. The width of the insulating paper 1112 at one end along the axial direction of the metal tube 1111 is increased by 30mm to 70mm, and the width of the insulating paper 1112 at the other end is increased by 80mm to 120mm.

[0069] Specifically, the width of one end of the insulating paper 1112 increases by 30mm, 50mm, or 70mm along the axial direction of the metal tube 1111.

[0070] Specifically, the width of the insulating paper 1112 at the other end increases by 80mm, 100mm, or 120mm along the axial direction of the metal tube 1111.

[0071] Because the width of the insulating paper 1112 wrapped around the metal tube 1111 is increased, when a crack appears in the pure adhesive layer 130 and the crack extends longitudinally to the portion of the insulating paper 1112, the increased portion of the insulating paper 1112 can absorb the spread of the crack, ensuring that the original width of the insulating paper 1112 is not affected by the crack. Therefore, appropriately increasing the width of the insulating paper 1112 can reduce the degree of damage to the original width of the insulating paper 1112 caused by subsequent cracks in the pure adhesive layer 130.

[0072] Based on the above embodiments, in one embodiment, the step of cutting the pure rubber layer 130 and the partition layer 120 within the embryo 10 to form the core 110 further includes:

[0073] The portion of the insulating paper 1112 with increased width is cut to form the core 110.

[0074] Specifically, when the preform 10 is cut, the additional width portion of the insulating paper 1112 is cut together with the partition layer 120 and the pure adhesive layer 130.

[0075] Specifically, in this embodiment, the width of one end of the insulating paper 1112 increases by 50 mm along the axial direction of the metal tube 1111, and the width of the other end of the insulating paper 1112 increases by 100 mm.

[0076] In this embodiment, before winding the insulating paper 1112, the width of the insulating paper 1112 can be appropriately increased as needed, thus increasing the length of the insulating paper 1112 wound around the metal tube 1111. The wound core 111 and two spacers are placed together into the mold, wherein the two spacers are located at both ends of the insulating paper 1112 along the axial direction of the metal tube 1111 and are in contact with the insulating paper 1112. The moisture in the insulating paper 1112 in the mold is removed using a pressure difference method. When the moisture content in the insulating paper 1112 meets the requirements, liquid epoxy resin is poured into the mold, so that the wound core 111 and the spacers are both immersed in the epoxy resin.

[0077] Further, the mold is vacuumed again and heated until the liquid epoxy resin is completely cured inside the mold to form a preform 10. This preform 10 includes a resin-impregnated rolled core 111 (core 110), resin-impregnated separators (septum layers 120), and a pure epoxy layer 130 (cured epoxy resin on both ends of the metal tube 1111). Finally, after the mold has cooled naturally to room temperature, the preform 10 is removed from the mold, and radially cut along its axial direction to separate the two separator layers 120, the two pure epoxy layers 130, and the increased width of the insulating paper 1112 from the core 110.

[0078] In this embodiment, the partition layer 120 can effectively block or disperse cracks generated in the pure adhesive layer 130. In addition, appropriately increasing the width at both ends of the insulating paper 1112 can reduce the degree of damage to the core 110 caused by cracks.

[0079] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0080] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0081] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0082] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for processing a paper-impregnated sleeve core, characterized in that, include: With the metal tube as the central axis, insulating paper is wound around the metal tube to form a wound core; The rolled core is placed into the mold, and a partition is placed into the mold, with the partition in contact with the end of the insulating paper. Liquid epoxy resin is poured into the mold, so that the rolled core and the partition are completely immersed in the epoxy resin and form a preform after the epoxy resin is cured. According to the preset requirements, the pure rubber layer and the partition layer in the embryo are cut to form the core. Specifically, the step of winding the insulating paper around the metal tube to form a wound core includes: increasing the width of the insulating paper so that the winding length of the insulating paper around the metal tube is increased; The step of cutting the pure rubber layer and the partition layer in the preform to form the core further includes: cutting the portion of the insulating paper that has increased width to form the core.

2. The processing method of the resin-impregnated paper sleeve core according to claim 1, characterized in that, Before the step of pouring liquid epoxy resin into the mold, the method further includes: Remove moisture from the insulating paper in the wound core.

3. The processing method of the resin-impregnated paper sleeve core according to claim 1, characterized in that, Along the axial direction of the wound core, the length of the metal tube is greater than the length of the insulating paper wound on the metal tube, and the two ends of the metal tube are not wrapped with the insulating paper.

4. The processing method of the resin-impregnated paper sleeve core according to claim 3, characterized in that, The step of placing the partition member inside the mold and bringing the partition member into contact with the end of the insulating paper specifically includes: Two partitions are provided, and both partitions are placed inside the mold so that the two partitions are in contact with the ends of the insulating paper.

5. The processing method of the resin-impregnated paper sleeve core according to claim 4, characterized in that, The step of forming a preform after the epoxy resin has cured specifically includes: The mold is evacuated to maintain a vacuum inside the mold; The mold is heated to a temperature higher than that required for the curing reaction of the epoxy resin until the liquid epoxy resin is completely cured inside the mold.

6. The processing method of the resin-impregnated paper sleeve core according to claim 5, characterized in that, The preform includes the core, two partition layers, and two pure rubber layers. The two partition layers are located at both ends of the core, and the pure rubber layers correspond one-to-one with the partition layers, with the pure rubber layers located at the ends of the partition layers away from the core. The step of cutting the pure rubber layers and partition layers within the preform to form the core specifically includes: The embryo is radially cut along its axial direction to sever the two partition layers and the two pure rubber layers.

7. The processing method of the resin-impregnated paper sleeve core according to claim 1, characterized in that, The step of increasing the width of the insulating paper to increase the winding length of the insulating paper on the metal tube specifically includes: The width of the insulating paper increases by 30mm to 70mm at one end along the axial direction of the metal tube, and the width of the insulating paper increases by 80mm to 120mm at the other end.

8. The processing method of the resin-impregnated paper sleeve core according to claim 7, characterized in that, The width of the insulating paper increases by 50 mm at one end along the axial direction of the metal tube, and the width of the insulating paper increases by 100 mm at the other end.

9. The method for processing the impregnated paper sleeve core according to any one of claims 1-8, characterized in that, The partition is a polyurethane material board, a phenolic material board, or an insulating paper material board; And / or, the insulating paper is crepe paper; And / or, the metal tube is a copper tube or an aluminum tube.

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