Manufacturing Method of Tank

Abstract

The present disclosure relates to a method for manufacturing a water tank. The method for manufacturing a water tank according to the present disclosure comprises the steps of manufacturing an upper tube of the water tank, manufacturing a lower cap of the water tank, welding the upper tube and the lower cap, a first polishing step using sandpaper of a first grit range, and a second polishing step using sandpaper of a second grit range with a grit larger than that of the first grit range.

Description

Technology Field

[0001] The present disclosure relates to a method for manufacturing a water tank, and more specifically, to a method for manufacturing a stainless steel water tank used in a humidifier. Background Technology

[0002] A humidifier is a device that generates humidified air using water. To extend the operating time of a humidifier, the size of the water tank where the water is stored must be increased.

[0003] If the size of the water tank increases, the weight of the tank may make it difficult for the user to transport. Additionally, if the tank is dropped during transport, it may easily become deformed or damaged, potentially preventing it from being installed inside the humidifier.

[0004] To increase the size of the tank, the vertical length of the tank can be increased. The deep dining method can be used to manufacture such a tank. However, with this deep dining method, if the vertical length of the tank is formed to be long, a problem arises in that the thickness of the tank cannot be maintained consistently.

[0005] In addition, since water is stored inside the tank, it must not corrode easily.

[0006] Domestic registered patent KR 10-2667526 B1 discloses a water tank used in a humidifier, but does not disclose a specific method for manufacturing it. The problem to be solved

[0007] The present disclosure aims to solve the aforementioned problems and other problems.

[0008] Another objective is to provide a method for manufacturing a water tank with a constant thickness.

[0009] Another objective is to provide a method for manufacturing a water tank with improved corrosion resistance.

[0010] Another objective is to provide a method for manufacturing a tank with ensured strength. means of solving the problem

[0011] To achieve the above objective, a method for manufacturing a water tank according to an embodiment of the present disclosure comprises the steps of manufacturing an upper tube of the water tank, manufacturing a lower cap of the water tank, welding the upper tube and the lower cap, a first polishing step using sandpaper of a first grit range, and a second polishing step using sandpaper of a second grit range with a grit larger than that of the first grit range.

[0012] The above-mentioned tank is formed of stainless steel.

[0013] The above first polishing step uses sandpaper with a grit of 100 to 150.

[0014] The above first polishing step changes the sandpaper in the direction of increasing the grit size of the sandpaper.

[0015] The above first polishing step removes the bead of the welded portion of the upper pass and the lower cap.

[0016] The above second polishing step changes the sandpaper in a direction where the grit size of the sandpaper increases.

[0017] The above second polishing step uses sandpaper with a grit of 150 to 240.

[0018] The method for manufacturing the water tank includes, in the above-mentioned second polishing step, a polishing process using fine sandpaper with a grit of 600 or more.

[0019] The method for manufacturing the tank further includes, after the second polishing step, an electrolytic polishing step in which the tank is immersed in an electrolyte solution and an electric current is passed through the electrolyte solution.

[0020] The method for manufacturing the water tank further includes, after the electrolytic polishing step, a hairline polishing step for forming fine stripes on the surface of the water tank.

[0021] Method for manufacturing a water tank.

[0022] The method of manufacturing the water tank further includes a first processing step of expanding the upper tube portion and trimming the upper part of the upper tube after the step of welding the upper tube and the lower cap.

[0023] The method of manufacturing the water tank further includes a second processing step of adding a bead shape to reinforce strength to the upper part of the upper tube after the first polishing step.

[0024] The step of manufacturing the lower cap includes a process of forming the lower surface of the lower cap.

[0025] The length of the upper tube is formed to be larger than the diameter of the lower cap.

[0026] The step of manufacturing the upper tube above involves rolling a stainless steel plate into a cylindrical pipe and welding the abutting parts.

[0027] Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0028] According to the method for manufacturing a water tank of the present disclosure, one or more of the following effects are provided.

[0029] First, by manufacturing the upper and lower parts of the tank separately and welding them together, there is an advantage in maintaining a consistent thickness of the tank.

[0030] Second, there is also the advantage of providing a water tank with ensured corrosion resistance through multiple polishing processes and electrolytic polishing during the manufacturing process.

[0031] Third, there is also the advantage of providing a tank in which strength is secured through a forming structure on the lower surface of the tank and a separate shape on the upper structure.

[0032] The effects of the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0034] FIG. 1 is a perspective view of a humidifier according to one embodiment of the present disclosure. Figure 2 is a plan view of Figure 1. Figure 3 is a cross-sectional view taken along III-III' of Figure 2. FIG. 4 is an exploded perspective view of an inner tank and an outer tank according to one embodiment of the present disclosure. FIG. 5 is a perspective view of an inner tank according to one embodiment of the present disclosure. FIG. 6 is a flowchart of a method for manufacturing an inner tank according to one embodiment of the present disclosure. Specific details for implementing the invention

[0035] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0036] Hereinafter, the present invention will be described with reference to drawings illustrating a method for manufacturing a humidifier and an inner water tank (or 'water tank') according to embodiments of the present invention.

[0037] The humidifier of the present invention can generate humidified air by ultrasonic vibration of water. The humidifier of the present invention can generate humidified air by heating water. The humidifier of the present invention can generate humidified air generated by ultrasonic vibration and humidified air generated by heating.

[0038] Referring to FIG. 1, the external appearance of the humidifier of the present invention will be described.

[0039] The humidifier includes a case (10) that forms an outer shape and has an inlet (24a) and an outlet (12a) formed therein.

[0040] The case (10) can have a cylindrical shape overall.

[0041] The case (10) may include an intake grille (24) forming an inlet (24a) into which air is introduced, and a discharge grille (12) forming an outlet (12a) into which air is discharged. The inlet (24a) may be formed on the circumferential surface of the case (10) having a cylindrical shape. The outlet (12a) may be formed on the upper surface of the case (10) having a cylindrical shape. The humidifier of the present invention may introduce air through the circumferential surface and discharge air through the upper surface.

[0042] A plurality of grilles (24b) extending in the vertical direction are arranged in the intake grille (24). The plurality of grilles (24b) may be spaced apart in the circumferential direction of the intake grille (24). A plurality of inlets (24a) may be formed between the plurality of grilles (24b).

[0043] The case (10) may include a tank cover (14) positioned on the upper side of the tank (100).

[0044] The humidifier may include a discharge grille (12) forming an outlet (12a) and a water tank cover (14) positioned on the upper side of the water tank (100).

[0045] The discharge grille (12) may have a structure that is separated upward from the outer shell (22) described below. The water tank cover (14) may have a structure that is separated from the discharge grille (12) or the water tank (100) described below.

[0046] The discharge grille (12) may include a plurality of ribs (12b) extending radially from the outer circumference of the water tank cover (14). The plurality of ribs (12b) disposed on the discharge grille (12) may be spaced apart in the circumferential direction from the outer circumference of the water tank cover (14).

[0047] The case (10) may include an outer shell (22) that guides air flowing inside to an outlet (12a).

[0048] The outer shell (22) includes an upper outer shell (22a) positioned below the discharge grille (12) and a lower outer shell (22b) positioned below the upper outer shell (22a). The lower outer shell (22b) may be formed of a transparent material.

[0049] The humidifier may include a base (28) that is positioned on the lower side of the case (10) and separates the case (10) from the ground at a certain distance. The upper part of the base (28) may be connected to the lower part of the case (10).

[0050] The upper part of the humidifier will be described below with reference to FIG. 2.

[0051] The water tank cover (14) may include a central cover (16) and a perimeter cover (18) arranged around the central cover (16). The central cover (16) may have a structure that is convex toward the upper side as it moves toward the center. A water supply hole (20) through which water flows into the water tank (100) may be formed between the perimeter cover (18) and the central cover (16).

[0052] A plurality of ribs (12b) and a plurality of outlets (12a) can be formed in the discharge grille (12).

[0053] Below, the internal configuration of the humidifier will be described with reference to FIG. 3.

[0054] The humidifier includes a filter device disposed inside the case (10) and filtering air introduced through the inlet (24a). The humidifier includes a blower (60) disposed inside the case (10) and flowing air inside the case (10) from the inlet (24a) to the outlet (12a). The humidifier includes a water tank (100) disposed inside the case (10) and storing water. The humidifier includes a humidification module that receives water from the water tank (100) and generates humidified air.

[0055] The humidifier may include a base (28). The base (28) may raise the case upward from the ground. The base (28) may be connected to the lower wall (26) of the case (10).

[0056] The case (10) may include a lower wall (26) that covers the lower side of the intake grille (24).

[0057] The upper part of the base (28) can be connected to the lower wall (26). The lower wall (26) is positioned to cover the lower surface of the humidifier, which is spaced upward from the ground by the base (28).

[0058] The intake grille (24) can cover the outer side of the filter (50) and the blower housing (68) to be described below. A plurality of inlets (24a) can be formed in the intake grille (24), which are formed in the vertical direction and spaced apart in the circumferential direction. The inlets (24a) can be formed around where the filter (50) is placed. The inlets (24a) can be formed at the bottom of the intake grille (24). The bottom of the intake grille (24) has the inlets (24a) formed therein, and the top of the intake grille (24) can be formed to be closed to protect the internal components of the humidifier.

[0059] An outer shell (22) may be placed on the upper part of the intake grille (24).

[0060] The filter device can filter the air introduced through the inlet (24a) via the filter (50). The filter device can allow the filtered air to flow upward.

[0061] The filter device includes a filter (50) that filters air flowing into the inlet (24a), and a filter mounting part that fixes the arrangement of the filter (50) inside the case (10).

[0062] The filter (50) may have a cylindrical shape. Accordingly, the filter (50) can filter air sucked in from the front, back, left, and right directions perpendicular to the vertical direction. Air introduced from the inlet (24a) can flow into the inner space of the filter (50). Air passing through the filter (50) can flow to a blower (60) positioned above the filter (50).

[0063] The filter mounting portion includes a lower plate (52) positioned on the lower side of the filter (50), an upper plate (54) positioned on the upper side of the filter (50), and a supporter (not shown) connecting the lower plate (52) and the upper plate (54).

[0064] The lower plate (52) is positioned below the filter (50). The lower plate (52) moves up and down and can detect whether the filter (50) is positioned. A fan sterilization device (53) that irradiates ultraviolet light upwards may be positioned at the center of the lower plate (52).

[0065] The fan sterilization device (53) can sterilize the inside of the blower fan (62) or filter (50) described below.

[0066] An orifice (56) is formed in the upper plate (54). The orifice (56) may be formed at the center of the upper plate (54). The orifice (56) can allow air flowing into the filter (50) to flow to the blower fan (62). The inner circumference of the upper plate (54) has a shape that is bent upward, so that air flowing upward from the internal space of the filter (50) can be guided to the blower fan (62).

[0067] The supporter (58) can connect the lower plate (52) and the upper plate (54). The supporter (58) can be spaced apart in the circumferential direction.

[0068] The blower device (60) includes a blower fan (62) that forms air flow inside the case (10) and a fan motor (64) that rotates the blower fan (62).

[0069] The blower fan (62) may form a fan intake port on one side facing the orifice (56) and a fan discharge port on the opposite side of the fan intake port. The blower fan (62) may use a centrifugal fan in which the fan discharge port faces the centrifugal direction opposite to the fan intake port. The blower fan (62) may include a hub connected to a fan motor (64), a shroud spaced apart from the hub at a certain distance and forming a fan intake port, and a blade extending radially to connect the hub and the shroud.

[0070] The blower fan (62) can send air from the lower side to the upper side by operating. The blower fan (62) can draw air toward the orifice (56) and discharge air toward the blower housing (68) where the diffuser (72) is placed.

[0071] The fan motor (64) can be positioned above the blower fan (62).

[0072] The blower device includes a motor cover (66) that covers the outside of a fan motor (64), and a blower housing (68) that is spaced radially outward from the motor cover (66) and guides the air flowing by the blower fan (62) upward.

[0073] Between the motor cover (66) and the blower housing (68), a blower passage (70) may be formed through which air flowing by the blower fan (62) flows upward. The blower passage (70) may extend to the area where the humidification module housing (410) and the flow passage housing (430) are formed.

[0074] An intake grille (24) may be placed on the outer side of the blower housing (68).

[0075] The blower device (60) includes a diffuser (72) that is positioned between the motor cover (66) and the blower housing (68) and reduces the rotational component of the air flowing upward by the blower fan (62). A plurality of diffusers (72) may be arranged spaced apart in the circumferential direction.

[0076] A control box (74) may be disposed on the upper side of the motor cover (66), forming a space in which a circuit board (76) is disposed inside. The control box (74) may be disposed spaced apart from the inside of the blower housing (68). Accordingly, a blower passage (70) may be formed in the space between the control box (74) and the blower housing (68).

[0077] A plurality of circuit boards (76) may be arranged inside the control box (74). The humidification module includes a first humidification tank (300) that heats water. The humidification module includes a second humidification tank (350) that generates humidified air from water. The humidification module may include a humidification module housing (410) that covers the perimeter of the first humidification tank (300) and the second humidification tank (350). A flow channel housing (430) may be arranged on the outer perimeter of the humidification module housing (410). A blower channel (70) may be formed between the humidification module housing (410) and the flow channel housing (430).

[0078] The humidifier includes a water tank (100) forming a space for storing water, an inner shell (180) forming a space for the water tank (100) to be placed, and a middle tray (200) placed below the inner shell (180).

[0079] The tank (100) may have an inner tank (102) positioned inside the outer tank (160). Accordingly, a connector (120) may be positioned through the through hole (164) of the outer tank (160).

[0080] The outer tank (160) can be placed on the upper side of the middle tray (200) while positioned inside the inner shell (180). The middle tray (200) may be a structure that supports the inner shell (180), the outer tank (160), and the inner tank (102). Thus, the load of the inner tank (102), the outer tank (160), and the inner shell (180) can be transferred to the middle tray (200).

[0081] The outer tank (160) is placed around the outer circumference of the inner tank (102).

[0082] The inner tank (102) can be positioned inside the outer tank (160). When the inner tank (102) is positioned inside the outer tank (160), the outer circumference surface of the inner tank (102) can be positioned to contact the inner circumference surface of the outer tank (160).

[0083] The humidifier includes a water softening device (140) placed inside the inner water tank (102).

[0084] The water softening device (140) is positioned inside the inner water tank (102). The water softening device (140) can be fixed in position by being connected to a connector (120) positioned inside the inner water tank (102).

[0085] The inner shell (180) is spaced apart from the outer tank (160). The inner shell (180) is spaced apart from the tank (100). A first discharge channel (32) through which humidified air flows is formed between the inner shell (180) and the outer tank (160).

[0086] A second discharge channel (34) is formed between the outer shell (22) and the inner shell (180).

[0087] The inner shell (180) and the outer shell (22) are spaced apart from each other to form a second discharge channel (34). Filtered clean air flowing through the second discharge channel (34) can flow through it via a blower (60).

[0088] The discharge grill (12) can be positioned above the first discharge channel (32) and the second discharge channel (34) described below.

[0089] The discharge grille (12) can form a constant height in the vertical direction. Accordingly, a mixing channel (13) can be formed between a plurality of ribs (12b) arranged on the discharge grille (12). In the mixing channel (13), the air flowing through the first discharge channel (32) can be mixed with the air flowing through the second discharge channel (34).

[0090] Each of the multiple ribs (12b) is formed such that the height of the outer end is higher than the height of the inner end. Accordingly, the air flowing through the first discharge channel (32) and the second discharge channel (34) can be guided radially inward.

[0091] A display (30) is placed on one side of the case (10). The display (30) allows the user to control the power or operation of the humidifier. A display that shows the operating status of the humidifier to the user may be placed on the display (30).

[0092] Referring to FIG. 4, the inner tank, the outer tank, and the connector will be described.

[0093] The water tank (100) includes an inner water tank (102) and an outer water tank (160) positioned outside the inner water tank. The inner water tank (102) forms a space in which water is stored. The outer water tank (160) forms a space in which the inner water tank (102) is accommodated.

[0094] A water tank sealer (115) is positioned at the upper part of the inner water tank (102). The water tank sealer (115) is positioned on the outer circumference of the inner water tank (102) and is positioned to be in contact with the inner circumference of the outer water tank (160).

[0095] The outer tank (160) has a through hole (164) formed on its lower surface through which the connector (120) passes.

[0096] The outer tank (160) includes a lower rim (166) that protrudes downward from the lower surface. The lower rim (166) has a structure that protrudes downward from the circumference of the through hole (164). The lower rim (166) may have a ring-shaped structure.

[0097] The inner tank (102) forms a space where water is stored. A handle (108) is placed on the upper part of the inner tank (102).

[0098] The humidifier includes a connector (120) that is fixedly positioned in the inner water tank (102) and connects the inner water tank (102) and the supply pipe (230). A portion of the connector (120) is positioned inside the inner water tank (102). The remainder of the connector (120) is positioned outside the inner water tank (102).

[0099] The connector (120) can send water stored in the inner water tank (102) to the humidification module. The connector (120) can send water stored in the inner water tank (102) to the humidification module through the supply pipe (230).

[0100] A connector holder (132) of the connector (120) and a part of the connector valve (130) may be positioned outside the inner tank (102). Each of the connector holder (132) and the connector valve (130) may be connected to an inlet port (232) of the supply pipe (230).

[0101] A portion of the connector holder (132) and the connector valve (130) may protrude to the lower side of the outer tank (160) through the through hole (164) of the outer tank (160).

[0102] When the inner tank (102) is accommodated in the outer tank (160), a connector holder (132) and a part of the connector valve (130) may be positioned on the lower side of the outer tank (160).

[0103] Referring to Fig. 5, the inner tank is described.

[0104] The inner tank (102) includes an upper tube (104) extending in the upward and downward directions, and a lower cap (105) connected to the lower part of the upper tube (104).

[0105] The upper tube (104) and the lower cap (105) can be joined together by welding. The upper tube (104) can be formed to be longer in the vertical direction than the lower cap (105). A lower hole (106) can be formed on the lower surface of the lower cap (105).

[0106] The upper tube (104) may be formed in a cylindrical shape that is open in the vertical direction. The upper tube (104) may be formed with a structure in which the internal diameter increases towards the top. A coupling groove (104a) is formed at the upper end of the upper tube (104) to be coupled with a handle (108).

[0107] A flange (104b) protruding outward can be formed on the top of the upper tube (104).

[0108] A bead shape (104c) with an inwardly recessed groove may be formed on the upper part of the upper tube (104).

[0109] A connecting groove (104a) is formed between the flange (104b) and the bead shape (104c).

[0110] On the lower surface of the lower cap (105), a forming (105c) that is recessed upward or downward may be formed to reinforce strength. The lower cap (105) includes a lower surface (105a) where a lower hole (106) is formed, and a bending surface (105b) that is bent toward the upper tube (104). The upper end of the bending surface (105b) is joined to the upper tube (104).

[0111] Referring to Fig. 6, a method for manufacturing an inner tank is described.

[0112] The inner tank (102) can be formed of stainless steel.

[0113] The inner tank (102) is formed by separately manufacturing the upper tube (104) and the lower cap (105) and then connecting them.

[0114] The step (S100) of manufacturing the upper tube (104) can be carried out.

[0115] The upper tube (104) can be manufactured in the step (S100) by rolling a stainless steel plate into a cylindrical pipe and welding the abutting parts.

[0116] That is, the upper tube can be manufactured through a pipe rolling process and a straight welding process. The upper tube (104) manufactured in the step (S100) of manufacturing the upper tube (104) may have a cylindrical shape that is open in the vertical direction. At this time, the upper tube (104) may be formed with the same internal diameter at the top and bottom.

[0117] The step (S200) of manufacturing the lower cap (105) can be carried out.

[0118] The lower cap (105) is formed with a structure that forms a lower surface (105a) and a bending surface (105b). The lower cap (105) can be manufactured using a deep dining method.

[0119] In the step (S200) of manufacturing the lower cap (105), the lower surface (105a) of the lower cap (105) can be formed.

[0120] The upper tube (104) and the lower cap (105) undergo a welding step (S300).

[0121] The lower part of the upper tube (104) and the upper part of the lower cap (105) are welded together. That is, the upper tube (104) and the lower cap (105) can be connected by a butt welding method.

[0122] In the following description, the state in which the upper tube (104) and the lower cap (105) are welded is referred to as the inner tank (102).

[0123] Afterwards, the step of processing or polishing the inner tank is performed.

[0124] Afterwards, the first processing step (S400) is performed.

[0125] In the first processing step (S400), the upper tube (104) can be expanded. That is, the upper tube (104) can be expanded so that its internal diameter increases from the bottom to the top. That is, a slope shape can be added to the inner circumference of the upper tube (104).

[0126] In the first processing step (S400), the upper part of the upper tube (104) can be cut. That is, the upper part can be cut to match the length of the area where the upper tube (104) is formed.

[0127] In addition, in the first processing step (S400), the upper part of the upper tube (104) can be compressed so that a flange (104b) formed on the upper part of the upper tube (104) is formed.

[0128] Afterwards, it undergoes a first polishing step (S500).

[0129] The first polishing step (S500) can remove the bead from the butt weld portion. Additionally, the first polishing step (S500) can flatten the surface of the outer surface of the inner tank (102).

[0130] In the first polishing step (S500), sandpaper of a first grit range may be used. The sandpaper of the first grit range may be sandpaper with a grit of 100 to 150.

[0131] In the first grinding step (S500), the sandpaper can be changed in a direction that increases the grit size of the sandpaper.

[0132] In one embodiment, 120-grit sandpaper may be used during the initial first polishing step (S500), and 150-grit sandpaper may be used during the later S500.

[0133] Afterwards, a secondary processing step (S600) is performed.

[0134] The second processing step (S600) involves processing to form a coupling groove (104a) on the upper part of the upper tube (104) that is coupled with the handle (108).

[0135] The second processing step (S600) involves processing to add a bead shape (104c) to the upper part of the upper tube (104). The bead shape (104c) can reinforce the strength of the inner tank (102).

[0136] The second processing step (S600) can perform a chamfering process to smooth the end of the flange (104b).

[0137] Afterwards, a second polishing step (S700) is performed.

[0138] For the second polishing step (S700), sandpaper with a larger grit than that used in the first polishing step (S500) may be used.

[0139] In the second polishing step (S700), sandpaper of a second grit range may be used. The second grit range may be larger than the first grit range. The second grit range may be sandpaper of 150 grit or higher.

[0140] The second polishing step (S700) may perform polishing using sandpaper with a grit of 150 to 240. Additionally, the second polishing step (S700) may include a polishing process using fine sandpaper with a grit of 600 or more.

[0141] The second polishing step (S700) may be a process of cleaning the surface of the inner tank (102). The second polishing step (S700) may homogenize the surface roughness of the inner tank. The second polishing step (S700) may change the sandpaper in a direction that increases the grit size of the sandpaper.

[0142] In one embodiment, 150-grit sandpaper may be used at the beginning of the second polishing step (S700), and 180-grit sandpaper may be used during the middle of the second polishing step (S700). Additionally, at the end of the second polishing step (S700), polishing work may be performed through a polishing process.

[0143] Afterwards, it undergoes an electrolytic polishing step (S800).

[0144] The electrolytic polishing step (S800) can be performed by immersing the inner tank (102) in an electrolyte solution and passing an electric current through the electrolyte solution.

[0145] The inner tank (102) that has undergone the electrolytic polishing step (S800) may have improved surface roughness or gloss. The inner tank (102) that has undergone the electrolytic polishing step (S800) may have improved corrosion resistance.

[0146] Afterwards, the hairline polishing step (S900) is performed.

[0147] The hairline polishing step (S900) can form continuous fine stripes on the surface of the inner tank (102).

[0148] Afterwards, a marking step (S1000) is performed. Necessary information can be marked on the outer perimeter or inner perimeter of the inner tank (102). A laser can be used for the marking step (S1000).

[0149] Although preferred embodiments of the present disclosure have been illustrated and described above, the present disclosure is not limited to the specific embodiments described above. Various modifications are possible by those skilled in the art without departing from the essence of the present disclosure as claimed in the claims, and such modifications should not be understood individually from the technical spirit or perspective of the present disclosure.

Claims

Claim 1 A method for manufacturing a water tank to be installed in a humidifier, comprising: a step of manufacturing an upper tube of the water tank by rolling a stainless steel plate to form a cylindrical pipe and welding the abutting parts; a step of manufacturing a lower cap by forming the lower surface of the lower cap of the water tank; a step of welding the upper tube and the lower cap; a first polishing step using sandpaper of a first grit range to remove the bead of the welded portion of the upper tube and the lower cap and flatten the surface; a second polishing step using sandpaper of a second grit range with a grit larger than that of the first grit range; and an electrolytic polishing step, after the second polishing step, in which the water tank is immersed in an electrolyte solution and an electric current is passed through the electrolyte solution. Claim 2 In claim 1, the method of manufacturing a water tank formed of stainless steel. Claim 3 In claim 1, the first polishing step is a method for manufacturing a water tank using sandpaper with a grit of 100 to 150. Claim 4 In claim 1, the first polishing step is a method for manufacturing a water tank that changes the sandpaper in a direction in which the grit size of the sandpaper increases. Claim 5 delete Claim 6 In claim 1, the second polishing step is a method for manufacturing a tank that changes the sandpaper in a direction in which the grit size of the sandpaper increases. Claim 7 In claim 1, the second polishing step is a method for manufacturing a water tank using sandpaper with a grit of 150 to 240. Claim 8 In claim 7, the second polishing step further comprises a polishing process using fine sandpaper with a grit of 600 or more, a method for manufacturing a water tank. Claim 9 delete Claim 10 A method for manufacturing a water tank according to claim 1, further comprising a hairline polishing step for forming fine stripes on the surface of the water tank after the electrolytic polishing step. Claim 11 A method for manufacturing a water tank according to claim 1, further comprising a first processing step of expanding the upper tube portion and trimming the upper part of the upper tube after the step of welding the upper tube and the lower cap. Claim 12 A method for manufacturing a water tank according to claim 1, further comprising a second processing step of adding a bead shape to reinforce strength to the upper part of the upper tube after the first polishing step. Claim 13 delete Claim 14 A method for manufacturing a water tank according to claim 1, wherein the length of the upper tube is formed to be larger than the diameter of the lower cap. Claim 15 delete

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