TWI787960B - Manufacturing method for can body and manufacturing line for the same - Google Patents

Abstract

There is provided a manufacturing method for a can body capable of manufacturing a can body having a curved end of its bottom on which a coating film is precisely formed, and a production line for a can body. The manufacturing method for a can body includes: a preform can shaping step of shaping a preform can by shaping a dome portion on a bottom of a bottomed cylindrical body, the dome portion becoming hollow inside the bottomed cylindrical body, and a circular leg portion projecting to a side opposite to the side in which the dome portion becomes hollow, an inner periphery of the leg portion inclining to a can axis direction from a grounded point of the leg portion when viewed in longitudinal section along the can axis direction; a coating step of coating at least one of an inner surface and an outer surface of the preform can; and a bottom reform step of shaping a shaped can having a curved end around the dome portion by pressing the inner surface of the dome portion of the preform can which has been coated by the coating step.

Description

Manufacturing method of tank body and production line of tank body

The invention relates to a manufacturing method of a tank body and a production line of the tank body.

Two-piece cans, bottles, and the like are known for cans that can hold contents such as beverages or food. These can systems thin the can body and lighten the weight of the container in order to reduce the raw materials used. Next, in order to obtain sufficient compressive strength for the thinned can container, various processing is required for the shape of the bottom.

The shape of the bottom of a tank body generally used to increase the compressive strength is known to have a domed top recessed inside the tank body and a ring-shaped foot arranged around the domed top.

In this tank body, the shapes of the domed top and the ring-shaped foot are appropriately designed in order to further increase the compressive strength. For example, Patent Document 1 has disclosed that the inner peripheral wall (inner peripheral portion) connected to the domed portion in the annular convex portion (foot portion) is formed with a first concave curved surface, and the first concave curved surface is longitudinally along the direction of the tank axis. The cross-section is viewed as a curved shape that is concave toward the outer side of the radial direction perpendicular to the tank axis, and forms a dome top and a second concave curved surface on the dome top. The dome top is located on the tank axis, and the second concave curved surface is It is connected with the outer side of the dome top in the radial direction and is a concave curve with a radius of curvature smaller than the dome top, and forms a tapered part on the outer edge of the dome. The tapered part is connected with the first concave surface and the second concave The curved surfaces are connected to each other and are in the shape of a straight line in contact with the first curved surface and the second curved surface.

[Prior Art Literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2016-43991.

In the technology described in this patent document 1, a roller is used to reshape the bottom of the tank on the inner peripheral wall (inner peripheral portion) of the annular convex portion (foot portion), thereby shaping the bottom of the tank (body) with the ground point as the base point. The curved end is inclined sideways.

In addition, in order to protect the contents from the material (metal surface) of the can, prevent the flavor of the contents from deteriorating, and prevent corrosion, a synthetic resin is sprayed on the surface (inner surface) of the above-mentioned can, such as epoxy acrylic copolymer and water-based The solvent-based paint composition is applied by spraying or the like, dried, and cured to form a paint film.

However, conventionally, as described in Patent Document 1, the inner peripheral wall of the leg portion before the tank bottom reshaping process is formed approximately perpendicular to the ground contact surface. Therefore, in the coating operation such as spraying, it is more difficult for the paint sprayed from the direction of the opening of the tank body to reach the inner surface of the inner peripheral wall of the foot than the dome or the inner surface of the outer peripheral wall of the foot. Therefore, if the necessary coating is to be applied to protect the inner surface of the inner peripheral wall of the foot, more than necessary coating film will be formed on the dome or the inner surface of the outer peripheral wall of the foot. In addition to wasting paint, the film thickness of the coating film will be uneven. . In addition, the same problem also arises when coating the outer surface (outer surface) of the bottom of the can body.

This invention was made in view of the said situation, and it aims at solving the said problem as one of the subjects. That is, one of the objects of the present invention is to provide a can body manufacturing method and a can body production line capable of manufacturing a can body in which a coating film is formed on the bent end portion of the bottom with high precision.

The manufacturing method of the can body of the present invention includes the following steps in sequence: the preformed can forming step is to form a domed top and a foot at the bottom of a cylindrical body with a bottom, thereby forming a preformed can, the aforesaid domed top is connected to the aforementioned The inner side of the bottomed cylinder is concave, and the aforementioned leg is a ring-shaped leg that protrudes toward the opposite side of the concave side of the aforementioned domed top. In the longitudinal section along the direction of the tank axis, the inner periphery of the aforementioned leg is defined by the aforementioned leg The grounding point is the base point inclined to the direction of the aforementioned tank axis; the coating step is to coat at least one side of the inner surface and the outer side of the aforementioned preformed tank; and the tank bottom reshaping step is to carry out the Pressing the inner surface of the aforementioned dome in the aforementioned preformed tank to be coated, thereby forming a formed tank having a curved end around the aforementioned dome; wherein, in the aforementioned coating step, relative to the inner surface of the aforementioned preformed tank Coating by spraying; wherein, the aforementioned preformed tank formed in the aforementioned preformed tank forming step satisfies: the maximum height BS1 of the aforementioned preformed tank from the grounding surface to the aforementioned domed top is greater than that of the aforementioned shaped tank after molding. The maximum height BS2 from the grounding surface to the aforementioned round top, that is, BS2<BS1, in the longitudinal section view along the axis of the aforementioned tank, the length N of the inner peripheral portion of the aforementioned leg portion is greater than the aforementioned circle in the aforementioned formed tank after molding The length X of the above-mentioned curved end formed around the top, that is, X<N; wherein, in the above-mentioned can bottom reshaping step, a molding device with a pressing body and a molding die is used to press the aforementioned pressing body on the aforementioned the inner surface of the dome, whereby the aforementioned curved end portion of the aforementioned forming die is formed around the aforementioned dome, the aforementioned pressing system is inserted into the interior of the aforementioned preformed tank and abuts against the inner surface of the aforementioned dome, and the aforementioned forming die is formed by means of the aforementioned The above-mentioned curved end is formed by pressing the pressing body; wherein, the distance between the two ground points passing through the tank shaft of the aforementioned preformed tank is used as the grounding diameter φ 1, and the tank shaft of the aforementioned formed tank passing through the molding is The distance between the two grounding points is used as the grounding diameter φ 2, and the grounding diameter φ 2 is smaller than the grounding diameter φ 1; wherein, the inner peripheral portion of the aforementioned foot portion in the aforementioned preformed tank has a straight-line reduced diameter portion, the The linear narrowing portion is length L when viewed in longitudinal section along the axis of the tank, and the distance between the grounded surface of the preformed tank or a surface parallel to the grounding surface and the linear narrowing portion is on the side of the tank axis. When the angle of inclination is θ , the radius of curvature R1=0.8mm~2.2mm, the aforementioned length L=4.0mm~7.0mm, and the angle of inclination θ =70°~85°; wherein, the aforementioned preforming before forming the aforementioned curved end In the tank, and at the front end of the aforementioned leg portion on the straight line E1 formed by the aforementioned leg portion and a part of the aforementioned dome portion, the approximate arc length of the aforementioned radius of curvature R1 formed by it is MR1, where X<MR1+L.

The production line of the can body of the present invention includes the following steps in sequence: forming a domed top and a foot at the bottom of a bottomed cylinder to form a preformed can, the domed top is sunken toward the inside of the bottomed cylinder, The aforementioned leg is an annular leg that protrudes toward the side opposite to the concave side of the aforementioned domed top, and the inner peripheral portion of the aforementioned leg is directed toward the aforementioned tank with the grounding point of the aforementioned leg as the base point when viewed in a longitudinal section along the direction of the tank axis. inclination in the axial direction; painting on at least one side of the inner surface and the outer surface of the aforementioned preformed tank; and reshaping the bottom of the tank by pressing the inner surface of the aforementioned dome in the aforementioned preformed tank to be coated, Thereby forming a shaped tank having a curved end around the aforementioned domed top; wherein, in the aforementioned coating step, the inner surface of the aforementioned preformed tank is painted by spraying; wherein, the aforementioned preformed tank formed in the step of forming The aforementioned preformed tank satisfies: the maximum height BS1 from the ground plane to the aforementioned dome in the aforementioned preformed tank is greater than the maximum height BS2 from the ground plane to the aforementioned dome in the aforementioned molded tank after molding, that is, BS2<BS1, along the In the view of the longitudinal section in the axial direction of the tank, the length N of the inner peripheral portion of the leg is greater than the length X of the curved end formed around the dome in the formed tank after molding, that is, X<N ; Wherein, in the above-mentioned can bottom remolding step, a molding device with a pressing body and a molding die is used, and the aforementioned pressing body is pressed against the inner surface of the aforementioned dome, thereby molding around the aforementioned dome to correspond to the shape of the aforementioned molding mould. The aforementioned curved end, the aforementioned pressing system is inserted into the interior of the aforementioned preformed tank and abuts against the inner surface of the aforementioned dome, and the aforementioned forming mold forms the aforementioned curved end through the pressing of the aforementioned pressing body; wherein, the aforementioned The distance between the two ground contact points of the tank axis of the preformed tank is taken as the ground diameter φ 1, and the distance between the two ground contact points of the tank axis of the aforementioned molded tank after forming is taken as the ground diameter φ 2. φ 2 is smaller than the ground diameter φ 1; wherein, the inner peripheral portion of the aforementioned foot portion in the aforementioned preformed tank has a linear diameter-reducing portion, and the linear-shaped diameter-reducing portion is length L, when the inclination angle between the ground contact surface of the aforementioned preformed tank or a surface parallel to the aforementioned ground contact surface and the aforementioned linear narrowing portion is θ , the radius of curvature R1 = 0.8 mm to 2.2 mm, and the aforementioned Length L=4.0mm~7.0mm, inclination angle θ =70°~85°; wherein, in the aforementioned preformed tank before forming the aforementioned bent end portion, and on the straight line formed by the aforementioned leg portion and a portion of the aforementioned round top portion The approximate arc length of the aforementioned radius of curvature R1 formed by the front end of the aforementioned foot on E1 is MR1, where X<MR1+L.

According to the present invention, there can be provided a can body manufacturing method and a can body production line capable of manufacturing a can body in which a coating film is formed on the bent end portion of the bottom with high precision.

1: Preformed tank

11: Opening

12: Body

13: Bottom

14: Header

15: Flange

131: round top

131a: inner surface

132: feet

132-1: Outer wall

132-2: Grounding point

132-3: Inner peripheral part

132-31: Reduced diameter part

132-4: front end

132-5: boundary point

132-6: Boundary Department

1a: tank

133: Curved end

133-1: peripheral part

133-2: Grounding point

133-3: Inner peripheral part

133-31: conical surface

133-4: boundary point

2: Forming device

21: pressing body

22: Forming mold

211: pressing surface

221: contact surface

222: curved forming surface

O: tank shaft

A1, A2: field

BS1, BS2: Maximum height

E1: dotted line

E2: solid line

G1, G2: ground plane

G1a: face

L, N, X: Length

M _R1 : arc length

R1, R2: radius of curvature

φ1, φ2: ground diameter

Fig. 1 is a longitudinal sectional view of a preformed tank in this embodiment.

Fig. 2 is a longitudinal sectional view of a can body formed from a preformed can.

FIG. 3 is an enlarged view of area A1 in FIG. 1 .

FIG. 4 is an enlarged view of area A2 in FIG. 2 .

Fig. 5 is a flow chart for explaining the manufacturing process of the can body.

FIG. 6 is a flowchart for illustrating the tank bottom reshaping step in step S106 of FIG. 5 .

Fig. 7 is a partial cross-sectional view of a molding device for molding a preformed can.

Fig. 8 is a partial cross-sectional view of a forming device for forming a preformed can.

Fig. 9 is a partial sectional view of a molding device for molding a preformed can.

Fig. 10 is a partial sectional view of a molding device for molding a preformed can.

Fig. 11 is a partial cross-sectional view of a forming device for performing a forming process with respect to a preformed can.

Fig. 12 is a partial cross-sectional view showing a part of the foot and the dome before and after forming the curved end.

Hereinafter, an embodiment of the present invention (this embodiment) will be described with reference to the drawings. Fig. 1 is a longitudinal sectional view of a preformed tank in this embodiment. Fig. 2 is a longitudinal sectional view of a can body formed from a preformed can. FIG. 3 is an enlarged view of the area A1 in FIG. 1 . FIG. 4 is an enlarged view of the area A2 in FIG. 2 . Fig. 5 is a flow chart for explaining the manufacturing process of the can body. FIG. 6 is a flowchart for illustrating the tank bottom reshaping step in step S106 of FIG. 5 . 7 to 11 are partial cross-sectional views of a forming device for forming a preformed tank. Fig. 12 is a partial cross-sectional view showing a part of a leg portion and a domed portion before and after forming a curved end portion.

Fig. 1 shows a longitudinal sectional view through the can axis O of the preformed can 1 of the present embodiment. The preformed tank 1 is formed by a bottomed cylinder and has an opening 11 , a body 12 and a bottom 13 . The body 12 and the bottom 13 have the same shape around the axis O of the tank. The tank axis O extends perpendicularly to the ground plane G1 of the preformed tank 1 . The bottom 13 has a domed top 131 recessed inside the preformed tank 1 , and an annular foot 132 protruding toward the opposite side of the domed top 131 from the recessed side. The foot 132 of the bottom 13 of the preformed tank 1 has an outer wall 132-1 connected to the body 12, a grounding point 132-2 connected to the grounding surface G1, and an inner peripheral part 132-3 connected to the dome 131 .

FIG. 2 shows a longitudinal section through the can axis O of the can body 1 a formed from the preformed can 1 . The tank axis O of the tank body 1a also extends vertically with respect to the ground plane G2. The tank body 1a is a formed tank formed by pressing the inner surface 131a and the outer wall portion 132-1 of the dome portion 131 of the preformed tank 1 against each other along the tank axis O direction. Pressing is performed against the inner surface 131 a of the dome portion 131 , whereby a part of the leg portion 132 of the preformed can 1 is deformed and formed into a bent end portion 133 . That is, the can body 1a shown in FIG. 2 has a bent end portion 133 formed by a foot portion 132 around a pressed dome portion 131 .

Also, as shown in FIG. 2 , the can body 1a has a head portion 14 that is smaller than the outer diameter of the body portion 12 and a flange portion 15 formed at the end (opening edge) of the head portion 14 on the side of the opening 11 . The flange portion 15 has a shape that is curled toward the outside of the can body 1a so that it can be wound up by a lid portion (not shown) later.

FIG. 3 shows an enlarged area A1 including the body portion 12 , the dome portion 131 , and the foot portion 132 of the preformed can 1 shown in FIG. 1 . In addition, FIG. 4 shows an enlarged area A2 including the body portion 12 of the can body 1a shown in FIG.

In the longitudinal sectional view along the tank axis O shown in FIG. 3 , the foot 132 of the bottom 13 of the preformed tank 1 is connected to the outer wall part with the body 12 by the ground point 132-2 grounded with the ground plane G1. 132-1, and the inner peripheral part 132-3 connected with the dome part 131. The front end portion 132-4 of the leg portion 132 is composed of a portion of the outer wall portion 132-1 and a portion of the inner peripheral portion 132-3, and is a slightly arc portion including the radius of curvature R1 of the ground point 132-2. point. Also, the boundary portion 132-6 is composed of a part of the inner peripheral portion 132-3 and a portion of the dome portion 131, and is a slightly arcuate portion including a radius of curvature R2 of the boundary point 132-5 between the inner peripheral portion 132-3 and the dome portion 131. .

Also, in the longitudinal section view along the tank axis O direction shown in FIG. 4, in the foot 132 of the bottom 13 of the tank body 1a formed by the preformed tank 1, the outer wall part 132-1 connected with the body 12 is connected. A curved end portion 133 is formed between the dome portion 131 . The curved end portion 133 is connected to the outer peripheral portion 133-1 connected to the outer wall portion 132-1 and the inner peripheral portion 133-3 connected to the dome portion 131 through a ground point 133-2 connected to the ground surface G2. Also, the inner peripheral portion 133-3 and the dome portion 131 are connected at a boundary point 133-4. In addition, in this FIG. 4, the inner peripheral portion 133-3 has a substantially linear tapered surface 133-31 in a vertical cross-sectional view along the tank axis O direction.

Take the maximum height from the grounding surface G1 to the dome 131 in the preformed tank 1 shown in FIG. for BS2. In this case, the following expression is satisfied.

BS2<BS1...(1)

Also, as shown in FIG. 3, the grounding diameter passing through the distance between the two grounding points 132-2 of the tank axis O of the preformed tank 1 is φ1, and the distance between the tank axis O of the formed tank body 1a as shown in FIG. The grounding diameter between the two grounding points 133-2 is φ2. In this case, the following expression is satisfied.

φ2<φ1...(2)

Specifically, BS1=13.75mm, φ1=49.0mm in the preformed tank 1, and BS2=11.20mm, φ2=45.5mm in the formed tank body 1a.

Also, as shown in FIG. 3 , the inner peripheral portion 132-3 of the leg portion 132 is viewed in a longitudinal section along the direction of the tank axis O, and the grounding point 132-2 of the leg portion 132 is used in a direction parallel to the direction of the tank axis O. The base point is tilted toward the side of the tank axis O. On the other hand, as shown in FIG. 4, in the curved end portion 133 of the tank body 1a after molding, the longitudinal section along the tank axis O direction of the connection ground point 133-2 and the inner peripheral portion 133-3 of the dome 131 Viewing, with respect to the parallel direction of the tank axis O direction, the relative direction of the tank axis O direction inclined toward the inner peripheral portion 132-3 of the leg portion 132 shown in FIG. 3 The opposite side (that is, the side in the direction of the body 12 with the ground point 133-2 as the base point in the direction parallel to the direction of the tank axis O) is inclined.

In the preformed tank 1 shown in FIG. 3 , the inner peripheral portion 132-3 of the leg portion 132 has a substantially linear reduced diameter portion 132-31 having a length L in a longitudinal cross-sectional view along the tank axis O direction. In FIG. 3 , when the angle of inclination between the grounding surface G1 (or the surface G1a parallel to the grounding surface G) of the preformed tank 1 and the substantially linear narrowing portion 132-31 in the direction of the tank axis O is θ, It is preferable to satisfy the following formula.

Radius of curvature R1=0.8mm~2.2mm, length L=4.0mm~7.0mm, inclination angle θ=70°~85°...(3)

Specific examples include curvature radius R1 = 1.7 mm, length L = 5.9 mm, and inclination angle θ = 80°.

In the can body 1a (formed can) shown in FIG. 4, the curved end 133 formed around the dome 131 is at least formed by the inner peripheral portion 132-3 of the foot 132 in the preformed can 1 shown in FIG.

In the longitudinal sectional view along the tank axis O direction shown in FIG. N is N, and in the longitudinal section view along the direction of the tank axis O shown in Figure 4, the length of the curved end 133 formed around the round top 131 in the tank body 1a (shaped tank) is X, if the following formula is satisfied, then It is preferable that the desired shape of the curved end 133 can be stably formed during reshaping of the tank bottom.

X<N...(4)

Next, the manufacturing process of the can body 1a is demonstrated using the flowchart of FIG. The tank body 1a is manufactured through the following steps S101 to S108.

(Step S101: concave pressing step)

In the concave pressing step of step S101 , for example, a metal plate such as aluminum alloy is punched into a circle, and the circular metal plate is subjected to deep drawing processing (dimple pressing) and formed into a cup-shaped body.

(Step S102: preformed can forming step)

In the preformed can forming step of step S102 after step S101, the cup-shaped body formed in step S101 is subjected to drawing and thinning processing, and after forming a bottomed cylinder with a body and a bottom, the bottomed circle The bottom of the cylinder body is further subjected to press processing etc. to form a domed top recessed inside the bottomed cylinder and a ring-shaped foot protruding to the opposite side of the domed top concave side, thereby forming the preformed tank 1 . In addition, when a lubricant or the like is used in steps S101 and S102, a washing step for removing the lubricant or the like may be provided after step S102.

(Step S103: trimming step)

The opening end of the preformed can 1 formed in step S102 forms ears so that the height is not uniform. Therefore, in the trimming step of step S103 after step S102, trimming (cutting) of the ear portion of the opening end of the preformed can 1 is performed using a trimming device so that the height of the preformed can 1 is within the entire circumference. unanimous.

(Step S104: outer coating printing step)

In step S104 after step S103, in the step S104 surface coating and printing step, at least carry out coating with paint for the surface with respect to the body portion 12 and the bottom 13 of the preformed tank 1, and after forming the coating film, paint the surface with respect to the body portion 12 surface. (outer peripheral surface) Printing of design images, etc. In addition, after forming a protective layer such as varnish on the printed layer such as the design image, drying and baking may be performed in an oven or the like. In this way, the outer surface of the preformed tank 1 can be processed into a wear-resistant smooth finish surface.

(Step S105: inner surface coating step)

In step S105, the inner surface coating step following step S104, the inner surface paint is applied to the inner surface of the preformed tank 1 . This coating can be performed by spraying, for example.

Here, the paint for the inner surface used may be, for example, a paint composition containing an epoxy-acrylic acid copolymer and an aqueous solvent. By coating the inner surface 131a of the preformed can 1 as described above, it is possible to prevent the flavor of the contents from deteriorating and to prevent metal corrosion. In addition, a drying step of drying the preformed can 1 at a high temperature of, for example, about 190° C. to 210° C. may be provided after the inner surface coating step of step S105 .

(Step S106: tank bottom remolding step)

In the tank bottom reshaping step of step S106 after step S105, the inner surface 131a and the outer wall part 131a and the outer wall part 132-1 of the dome part 131 of the preformed tank 1 painted in step S105 are opposed to each other along the direction of the tank axis O. Press the way, and the preformed tank 1 is pressed. The can body 1a (molded can) having the curved end portion 133 around the domed portion 131 is molded by this pressing. Further, details of the can bottom remolding step will be described later using FIGS. 6 to 11 .

(Step S107: necking step)

In the necking step of step S107 after step S106, the molding is carried out step by step in the end portion of the opening 11 side of the body 12 of the can body 1a by a molding tool (neck molding mold) (not shown). machining (necking machining), and forming the head 14.

(step S108: flanging step)

In the flanging step of step S108 after step S107, the edge portion (opening edge) of the opening portion 11 is curled toward the outside of the can body 1a by a roller (not shown), thereby forming the flange portion 15 . The shape of the flange portion 15 is such that the rear cover portion can be rolled up.

Also, the necking step of step S107 and the flanging step of step S108 can also be performed before the can bottom remolding step of step S106.

Through the processing of these steps S101 to S108, the can body 1a of the molded can is manufactured. Also, after step S108, the beverage of the contents is contained inside the can body 1a, and the processing of the winding step of winding and sealing the flange portion 15 and the lid portion (not shown) is performed, thereby manufacturing a beverage product. Cans for beverages.

Here, the tank bottom remolding step of the above-mentioned step S106 is described in detail using the flow chart of FIG. 6 and FIGS. 7 to 11 . In the can bottom remolding step, for example, a pressing process is performed using a molding device 2 shown in FIG. 7 . The forming device 2 is provided with a pressing body 21 inserted into the preformed tank 1 and abutting against the inner surface of the dome 131 , and a molding die 22 for forming the curved end 133 by pressing the pressing body 21 .

(Step S106-1: preform can loading step)

In the step of placing the preformed tank in step S106-1, as shown in FIG. 221 , the preformed tank 1 is placed on the molding die 22 of the molding device 2 . In addition, the molding device 2 may include a can body support portion (not shown) that supports the body portion 12 of the preformed can 1 . By fixing the position of the preformed tank 1 in the molding device 2 , the pressing process can be stably performed with respect to the preformed tank 1 .

(Step S106-2: Pressing body lowering step)

In step S106-2 of the pressing body descending step, as shown in FIG. 7 , the pressing body 21 of the molding device 2 is moved toward the inner surface 131a of the dome portion 131 (in the direction of the arrow of the tank axis O). In this FIG. 7 , the pressing surface 211 of the pressing body 21 and the dome portion 131 are shown to have approximately the same shape. However, the shape of the pressing surface 211 is not particularly limited, for example, it may have a curvature different from that of the dome portion 131 , and greater pressing pressure may be applied to the outer periphery of the dome portion 131 . Alternatively, the shape of the pressing surface 211 can be, for example, a concave shape that is larger than the pressing surface 211 shown in FIG. The outer peripheral portion 211 a in a region other than the vicinity is pressed against the dome portion 131 . Alternatively, the shape of the pressing body 21 may be a hollow shape without the pressing surface 211 outside the outer peripheral portion 211a, and similarly, only the outer peripheral portion 211a exerts pressing pressure against the dome portion 131 .

(Step S106-3: Dome inner surface abutting step)

In step S106-3, in the abutting step of the inner surface of the dome, as shown in FIG. It abuts against the inner surface 131a of the dome portion 131 and presses it. With this pressure, the abutting surface 221 of the molding die 22 exerts a pressing force on the outer wall 132-1. As shown in FIG. The abutting surface 221 is bent and deformed along the forming surface 222 . In addition, the molding device 2 may further include an air ejection unit (not shown) at the center of the molding die 22 . At this time, in the abutment step of the dome inner surface, air is ejected from the air ejection portion toward the outer surface of the dome portion 131 against which the pressing surface 211 of the pressing body 21 abuts. Thereby, the inner surface 131 a of the dome portion 131 abuts against the pressing surface 211 of the pressing body 21 in a stable state.

(Step S106-4: molding die guiding step)

In the forming mold guiding step of step S106-4, as shown in FIG. 9 , further press the pressing body 21 in the direction of the arrow relative to the inner surface 131a of the dome portion 131, so as to abut against the forming mold 22 The surface 221 further exerts a pressing force on the outer wall portion 132 - 1 , and a part of the foot portion 132 of the preformed tank 1 is guided to the curved forming surface 222 and deformed to match the shape of the curved forming surface 222 . Then form the curved end portion 133 corresponding to the shape of the curved forming surface 222 as shown in FIG. 10 . By molding this bent end portion 133, the can body 1a of the molded can is molded.

(Step S106-5: pressing body raising step)

In step S106-5, in the lifting step of the pressing body, as shown in FIG. 11 , the pressing body 21 of the molding device 2 is moved away from the inner surface 131a of the dome portion 131 along the direction of the tank axis O opposite to the pressing direction. Move in the direction of the arrow. The can body 1 a is then removed from the forming device 2 . Also, contrary to the above, the preformed tank 1 can be placed on the pressing body 21 of the forming device 2, and the forming die 22 of the forming device 2 can be separated from the outer wall 132-1 of the foot part 132 of the preformed tank 1. way to move, and the tank body 1a is taken off by the forming device 2.

As mentioned above, in the can bottom reshaping step of step S106, the curved end portion 133 is formed by pressing the inner surface 131a of the dome portion 131 . This process can make the inner peripheral portion 133-3 of the bent end portion 133 inclined in the direction parallel to the direction of the tank axis O with the ground point 133-2 as the direction side of the base point body portion 12, so that the inner peripheral portion 133-3 can be fully ensured. length. That is, compared with the conventional can bottom reshaping process using rollers, the inner peripheral portion 133-3 of the bent end portion 133 can be recessed deeper toward the side of the body portion 12, so the durability of the bottom 13 of the formed can body 1a can be improved. The compressive strength is very high.

Through the manufacturing process of the can body 1a, the inner surface of the foot portion 132 of the preformed can 1 before the bent end portion 133 is formed can ensure that the outer wall portion 132-1 or An inclined surface such as a substantially linear diameter-reducing portion 132-31. In particular, for example, compared to the inner surface of the inner peripheral wall of the annular convex portion (leg portion) of the tank of the prior art described in Patent Document 1, the slightly linear diameter-reducing portion 132-31 is based on the ground point 133-2 toward the tank. The direction of the opening of the body 1a is inclined toward the side of the tank axis O. Therefore, coating by spraying etc. The paint sprayed during work can reach the inner surface of the inner peripheral portion 132-3 as easily as the inner surface 131a of the dome portion 131 or the inner surface of the outer wall portion 132-1. Thereby, in the bottom 13 of the preformed tank 1, the inner surface of the leg portion 132 can be coated without waste, and the film thickness difference of the coating film for the inner surface can be reduced, and the film thickness can be made more uniform. Also, the same effect can be obtained when coating the outside of the foot portion 132 of the preformed tank 1 .

Then, through the manufacturing process of the can body 1a, even if it is the preformed can 1 that is painted on the inner surface and the outer surface as described above, it can be reshaped as described above relative to the domed top 131 in the subsequent can bottom reshaping step. Since the inner surface 131a is pressed to carry out can bottom reshaping, it does not receive loads such as friction from rollers as in conventional can bottom reshaping using rollers. Therefore, by coating the inside and outside of the preformed tank 1 in advance through the manufacturing process of the can body 1a, there is no problem that the coating film formed on the inside and outside of the leg is easily peeled off.

Also, if the conventional can bottom reshaping process using rollers is performed from the outside of the inner peripheral portion 132-3 of the leg portion 132 on the outer surface of the preformed can 1, the aluminum oxide film will be damaged due to friction or other loads. , There is a risk of roller processing marks (blackening) during heat sterilization after filling the contents. As a result, there is a possibility that the appearance of the molded can body 1a may be degraded. However, the problem of the deterioration of the appearance does not occur by the manufacturing process of the above-mentioned can body 1a.

Then, through the manufacturing process of the can body 1a, the inner surface 131a of the dome 131 of the preformed can 1 and the outer wall 132-1 face each other along the direction of the tank axis O and press the inside of the dome 131. On the other hand, the curved end portion 133 can be formed around the dome portion 131 to improve the compressive strength of the bottom portion 13 through the above-mentioned simple processing. Compared with performing can bottom reshaping processing with a roller from the outside of the inner peripheral portion 132 - 3 of the leg portion 132 and forming the bent end portion 133 , the above processing is easier. Also, unlike the prior art of tank bottom reshaping with rollers, the above-mentioned treatment can reduce the friction between the leg portion 132 and the molding die 22, so paint and the like will not accumulate (build up) on the molding die 22.

Next, the cross-sectional length of the bent end portion 133 formed in the leg portion 132 will be described using FIG. 12 . In Fig. 12, in the longitudinal section along the direction of the tank axis O, the dotted line E1 represents the preformed tank 1 before the curved end 133 is formed. The foot 132 and a part of the dome 131 in the figure, the solid line E2 represents the foot 132 and a part of the dome 131 in the can body 1a after the bent end 133 is formed. Moreover, in Fig. 12, the dotted line G1 represents the grounding surface of the preformed tank 1 grounded at the grounding point 132-2, and the solid line G2 represents the grounding plane of the formed can body 1a grounded at the grounding point 133-2.

In the longitudinal section view along the direction of the tank axis O shown in FIG. 12, the inner peripheral portion 132-3 of the foot portion 132 in the preformed tank 1 is shown by the dotted line E1 relative to the tank axis O perpendicular to the ground plane G1. The parallel direction of the direction is inclined toward the tank axis O direction side with the ground point 132-2 of the leg portion 132 as the base point. The above-described pressing process is performed on the inner surface 131a of the dome portion 131 of the preformed can 1, whereby the curved end portion 133 indicated by the solid line E2 is formed. In the tank body 1a (molded tank) after the bent end portion 133 is molded, the inner peripheral portion 133-3 of the bent end portion 133 connecting the ground point 133-2 of the bent end portion 133 and the dome portion 131 is relative to the tank axis O The parallel direction is to the opposite side of the tank axis O direction inclined to the inner peripheral part 132-3 of the leg part 132 (that is, the body part 12 side with the ground point 133-2 as the base point relative to the parallel direction of the tank axis O direction )tilt.

In the longitudinal sectional view along the tank axis O direction shown in FIG. The length N of the peripheral portion 132-3 is greater than the length X of the curved end portion 133 formed around the dome portion 131 in the can body 1a (formed can).

Next, take the approximate arc length M R1 of the radius of curvature R1 of the front end portion 132-4 of the leg portion 132 on the dotted line E1 as M _R1 , and take the length along the tank axis in the inner peripheral portion 132-3 of the leg portion 132 on the dotted line E1 The length of the slightly linear reduced diameter portion 132-31 in the longitudinal section in the O direction is L. If the following formula is satisfied, the shape of the desired curved end portion 133 can be stably formed during remolding of the tank bottom, so it is preferable.

X<M _R1 +L...(5)

This specific example can be M _R1 =3.44mm, L=5.9mm, X=7.03mm, for example.

In this embodiment, it is preferable to design and form the preformed tank 1 to satisfy the numerical values of the above formulas (1)-(5). The inner surface 131a of the domed top 131 of the preformed can 1 molded by this design is pressed, whereby the can body 1a (molded can) having the curved end 133 matching the shape of the curved molding surface 222 is molded.

In this can body 1a, the inner peripheral portion 133-3 of the bent end portion 133 is more deeply recessed toward the side of the body portion 12 than in the conventional can body that has undergone bottom reshaping using rollers, so the bottom of the can body 1a The compressive strength of 13 is very high.

In addition, in the above-mentioned embodiment, the coating is performed on the inner surface and the outer surface of the preformed tank 1, but the present invention is not limited thereto, and coating may be performed on at least one of the inner surface and the outer surface of the preformed tank 1. At this time, since the can bottom is reshaped by pressing against the inner surface 131a of the dome portion 131 as described above, the problem that the above-mentioned coating film is easily peeled off does not occur.

Claims (2)

A method for manufacturing a can body, which includes the following steps in sequence: a preformed can forming step, forming a domed top and a foot at the bottom of a cylindrical body with a bottom, thereby forming a preformed can, the domed top is connected to the bottomed cylinder The inner side of the bottom cylinder is concave, and the aforementioned leg is a ring-shaped leg that protrudes toward the opposite side of the concave side of the aforementioned domed top. In the longitudinal section along the direction of the tank axis, the inner circumference of the aforementioned leg is defined by the distance between the aforementioned leg. The ground point is the base point inclined to the direction of the aforementioned tank axis; the coating step is to coat at least one side of the inner surface and the outer side of the aforementioned preformed tank; The inner surface of the aforementioned dome in the aforementioned preformed tank is pressed, thereby forming a formed tank with a curved end around the aforementioned dome; wherein, in the aforementioned coating step, the inner surface of the aforementioned preformed tank is borrowed Coating by spraying; wherein, the aforementioned preformed tank formed in the aforementioned preformed tank forming step satisfies: the maximum height BS1 of the aforementioned preformed tank from the ground surface to the aforementioned domed top is greater than that of the aforementioned formed tank after forming. The maximum height BS2 from the ground to the above-mentioned domed top, that is, BS2<BS1, in the longitudinal section view along the direction of the aforementioned tank axis, the length N of the inner peripheral portion of the aforementioned foot portion is greater than the aforementioned domed top in the aforementioned molded tank after molding The length X of the above-mentioned curved end formed around the surrounding, that is, X<N; wherein, in the above-mentioned can bottom reshaping step, a molding device with a pressing body and a molding die is used to press the aforementioned pressing body on the aforementioned circle The inner surface of the top, whereby the aforementioned curved end portion of the aforementioned forming mold is formed around the aforementioned dome, and the aforementioned pressing system is inserted into the interior of the aforementioned preformed tank and abuts against the inner surface of the aforementioned dome, and the aforementioned forming mold is formed by means of the aforementioned pressing The above-mentioned curved end is formed by pressing the pressing body; wherein, the distance between the two ground points passing through the tank axis of the aforementioned preformed tank is used as the grounding diameter φ 1, and the distance between the tank shaft of the aforementioned formed tank passing through the molding is The distance between the two grounding points is used as the grounding diameter φ 2, and the grounding diameter φ 2 is smaller than the grounding diameter φ 1; wherein, the inner peripheral portion of the aforementioned foot portion in the aforementioned preformed tank has a straight-line reduced diameter portion, and the straight line In the longitudinal section along the direction of the tank axis, the length L is the length L, and the distance between the grounding surface of the preformed tank or a plane parallel to the grounding surface and the linear reducing portion is on the side of the tank axis. When the angle of inclination is θ, the radius of curvature R1=0.8mm~2.2mm, the aforementioned length L=4.0mm~7.0mm, and the angle of inclination θ=70°~85°; wherein, the aforementioned preformed tank before forming the aforementioned curved end , and on the front end portion of the aforementioned foot portion on the straight line E1 formed by the aforementioned foot portion and a part of the aforementioned dome portion, the approximate arc length of the aforementioned curvature radius R1 formed by it is M _R1 , where X<M _R1 +L . A production line for cans, which includes the following steps in sequence: forming a domed top and a foot at the bottom of a bottomed cylinder to form a preformed can, the domed top is sunken toward the inner side of the bottomed cylinder, and the aforesaid The foot is an annular foot that protrudes to the opposite side of the concave side of the domed top, and when viewed in a longitudinal section along the axis of the tank, the inner periphery of the foot is based on the grounding point of the foot to the axis of the tank The direction is inclined; coating is carried out with respect to at least one side of the inner surface and the outer surface of the aforementioned preformed tank; This is a molded can with a curved end around the domed top; wherein, in the aforementioned coating step, the inner surface of the aforementioned preformed can is painted by spraying; wherein, the preformed can formed in the aforementioned step of forming The aforementioned preformed tank satisfies: the maximum height BS1 from the ground plane to the aforementioned dome in the aforementioned preformed tank is greater than the maximum height BS2 from the ground plane to the aforementioned dome in the aforementioned molded tank after molding, that is, BS2<BS1, along the aforementioned Viewed in the longitudinal section along the axis of the tank, the length N of the inner peripheral portion of the leg is greater than the length X of the curved end formed around the dome in the formed tank after molding, that is, X<N Wherein, in the above-mentioned can bottom remolding step, a molding device with a pressing body and a molding die is used, and the aforementioned pressing body is pressed against the inner surface of the aforementioned dome, thereby molding around the aforementioned dome to correspond to the shape of the aforementioned molding mould. The aforementioned curved end, the aforementioned pressing system is inserted into the interior of the aforementioned preformed tank and abuts against the inner surface of the aforementioned dome, and the aforementioned forming mold forms the aforementioned curved end through the pressing of the aforementioned pressing body; wherein, the aforementioned The distance between the two ground contact points of the tank axis of the preformed tank is taken as the ground diameter φ 1, and the distance between the two ground contact points of the tank axis of the aforementioned molded tank after forming is taken as the ground diameter φ 2. φ 2 is smaller than the ground diameter φ 1; wherein, the inner peripheral portion of the aforementioned foot portion in the aforementioned preformed tank has a linear diameter-reducing portion, and the linear-shaped diameter-reducing portion is length L, when the inclination angle between the ground contact surface of the aforementioned preformed tank or a surface parallel to the aforementioned ground contact surface and the aforementioned linear narrowing portion is θ , the radius of curvature R1 = 0.8 mm to 2.2 mm, and the aforementioned Length L=4.0mm~7.0mm, inclination angle θ =70°~85°; wherein, in the aforementioned preformed tank before forming the aforementioned bent end portion, and on the straight line formed by the aforementioned leg portion and a portion of the aforementioned round top portion The approximate arc length of the aforementioned radius of curvature R1 formed by the front end of the aforementioned foot on E1 is MR1, where X<MR1+L.

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