JP5480707B2 - Manufacturing method of can body - Google Patents

Description

  The present invention relates to a method for manufacturing a can body that constitutes a can body containing beverages, foods, and the like.

  2. Description of the Related Art Conventionally, a method for manufacturing a can body that imparts a three-dimensional appearance to a can body by recessing a part of a cylindrical can body over its entire circumference is known (see Patent Document 1 below). In this method, a pressing member is pressed from the outside to the peripheral wall of the can body, the inside of which is maintained at a predetermined pressure by gas, and a recessed deformed portion having a predetermined shape is formed on the peripheral wall of the can body.

  In recent years, beverage cans have been required to reduce the thickness of surface-treated steel sheets (steel sheets whose front and back surfaces are coated with a polyester film) as raw materials in order to save resources and reduce costs. It has been.

  According to the above method, not only can the damage of the polyester film covering the front and back surfaces of the can body be prevented, but also a can body with a very high aesthetic appearance can be produced with a gentle indentation angle over a relatively wide range of the can body. can do.

JP 2004-188493 A

  As a result of studying a method of recessing a part of the can body over the entire circumference as the appearance shape of the can body, the present inventor paneled the can body subjected to the recess processing according to the conventional method. It was found that the strength decreased.

  So-called negative pressure cans such as beverage cans such as coffee and tea, or food cans, unlike so-called positive pressure cans that contain carbonated drinks and the inside is larger than atmospheric pressure, do not provide sufficient paneling strength. In some cases, the can body easily collapses and deforms due to the vapor pressure applied during heating during the retort sterilization treatment or the impact when dropped by a vending machine.

  In view of the above, the present invention provides a can body manufacturing method capable of manufacturing a can body suitable for a beverage can body or a food can body having a sufficient paneling strength and a very high aesthetic appearance. For the purpose.

  According to the present invention, a concave processed portion is formed by recessing the entire circumference of a cylindrical metal can barrel extending in the height direction, and the upper portion and the lower end of the concave processed portion are provided with the concave portion. A first tapered wall portion that includes a non-machined portion that maintains a maximum outer diameter, and that has an upper end located within the upper half of the can body and gradually decreases in diameter from the upper end as the concave processed portion. And a second tapered wall portion whose lower end is located within the lower half of the can body and gradually decreases in diameter from the lower end upward, and as the unprocessed portion, the first tapered wall portion An upper large-diameter wall portion extending upward while maintaining a constant outer diameter from the upper end, and a lower large-diameter wall portion extending downward from the lower end of the second tapered wall portion, the height of the concave processed portion The length is set in a range of 35% to 70% with respect to the total length in the height direction of the can body, and The can body whose minimum outer diameter at the boundary between the lower end of the first taper wall portion and the upper end of the second taper wall portion is set in a range of 80% to 95% with respect to the outer diameter of the unprocessed portion. A manufacturing method of a can body for manufacturing an outer shape processing step for processing and forming the concave processed portion, and a boundary between the first tapered wall portion and the second tapered wall portion of the concave processed portion A bead processing step for forming at least one bead extending in a circumferential direction of the can body within a predetermined range, wherein the outer shape processing step is carried out by gas inside the cylindrical unprocessed can body The first taper wall portion and the second taper wall portion are maintained by maintaining the pressure and moving the pressing member in the axial direction of the can body while pressing against the peripheral wall of the can body from the outside with a predetermined shape pressing member. Forming the concave processed portion, and the bead processing step The receiving die corresponding to the shape of the bead is brought into contact with the inner surface side of the can body in which the first tapered wall portion and the second tapered wall portion are formed by the outer shape processing step, and the outer surface side of the can body is The pressing die corresponding to the receiving die is brought into contact, and the bead is formed by press-contacting both types.

  According to the present invention, after forming the concave processed portion on the can body by the outer shape processing step, the bead is formed by the bead processing step, so that not only a beautiful can body is obtained, but also high paneling strength is obtained. Can bodies can be manufactured.

  That is, according to the outer shape processing step, the pressing member presses from the outside of the can body while the inside of the can body is maintained at a predetermined pressure by the gas. At this time, since only the gas is in direct contact with the inner surface of the can body, for example, the concave processed portion can be formed without bringing the receiving die or the like into contact with the inner surface of the can body, and the inner surface of the can body can be reliably damaged. Therefore, the concave processed portion can be formed. In addition, despite the fact that the diameter of the can body is reduced over a relatively wide range, the concave body can be formed without generating wrinkles or the like on the can body, and a can body having a good appearance can be obtained. Can do.

  By the way, the present inventor has found that when the can body is reduced in diameter by the outer shape processing step to form the concave processed portion, the paneling strength is lower than that of the unprocessed can body. That is, the concave processed portion formed by the outer shape processing step has a thickness unevenness according to the degree of diameter reduction of the concave processed portion due to the movement of the pressing member in a pressed state over a wide range, Since the boundary between the first taper wall portion and the second taper wall portion or the vicinity thereof is thin, it is assumed that this is a factor that reduces the paneling strength of the can body.

  Therefore, in the present invention, the bead processing step is performed after the outer shape processing step. In the bead processing step, within a predetermined range including the boundary between the first taper wall portion and the second taper wall portion of the concave processing portion, that is, a portion where the paneling strength is reduced due to being thin or the The bead having a relatively narrow width is formed in the vicinity. By providing the bead in the concave processed portion, the paneling strength of the can body, which has been reduced by the diameter reduction processing in the outer shape processing step, is recovered and improved.

  Further, in the bead processing step, the can body is sandwiched between the receiving mold and the pressing mold, and the bead is formed by press-contacting both molds. Thus, the bead is formed in a state where the can body is regulated by the receiving die and the push die, and the first tapered wall portion and the second taper are thinned by the outer shape processing step. Even if a bead is formed at or near the boundary with the wall portion, it is possible to prevent wrinkles or the like from occurring at the portion where the bead is formed or in the vicinity thereof.

  As described above, according to the present invention, the concave body is formed by pressing the can body with the pressing member while maintaining the inside of the can body at a predetermined pressure with gas in the outer shape processing step. In addition, since the bead is formed in a state where the can body material is regulated by the receiving mold and the pressing mold in the bead processing step, the can body is free from wrinkles and appearance defects. The paneling strength of the can body, which has been reduced in the outer shape processing step, can be reliably recovered and improved.

  In the can body obtained by the method of the present invention, the length in the height direction of the concave processed portion is set in a range of 35% to 70% with respect to the total length in the height direction of the can body, and The minimum outer diameter at the boundary between the lower end of the first taper wall portion and the upper end of the second taper wall portion is set in a range of 80% to 95% with respect to the outer diameter of the upper large-diameter wall portion. ing. By having such a shape, high visibility is obtained by reducing distortion of the printed display applied to the outer surface of the can body while suppressing unevenness of the plate thickness of the can body and suppressing a decrease in paneling strength. It is done.

  In the present invention, in the case of forming the concave processed portion in which the length in the height direction of the first tapered wall portion is longer than that of the second tapered wall portion by the outer shape processing step, In the processing step, it is preferable to process and form the concave processed portion by continuously moving the pressing member from the upper end of the first tapered wall portion toward the lower end of the second tapered wall portion.

  When the first taper wall portion is formed over a longer distance than the second taper wall portion, the taper angle of the first taper wall portion with respect to the upper large-diameter wall portion is the second taper wall portion with respect to the lower large-diameter wall portion. The taper angle is made smaller than this, and the inclination becomes gentle.

  According to the inventor's knowledge, when forming the concave processed portion having such a shape, the concave processed portion is moved by moving the pressing member from the lower end of the second tapered wall portion toward the upper end of the first tapered wall portion. The thickness unevenness of the can body due to the movement of the pressing member is generated relatively abruptly in the second tapered wall portion having a large inclination, and the upper end thereof (the portion having the smallest outer diameter) ) Tends to generate wrinkles and cracks.

  Therefore, by forming the first tapered wall portion longer than the second tapered wall portion, it is possible to satisfactorily form the concave processed portion without generating wrinkles or cracks.

  Further, in the outer shape processing step of the present invention, a small diameter that extends between the lower end of the first taper wall portion and the upper end of the second taper wall portion connected to both tapered wall portions and maintaining a constant outer diameter. The wall can be formed as desired. By providing the small-diameter wall portion, the range of the portion having the smallest diameter of the can body is widened, and the position and number of the beads can be easily set.

  In the bead processing step of the present invention, at least one other bead extending in the circumferential direction of the can body is optionally formed on at least one of the upper large-diameter wall portion and the lower large-diameter wall portion. can do. Thereby, the beauty of the can body is improved and the paneling strength can be further improved.

  Further, in the present invention, the can body subjected to the processing in the outer shape processing step is suitably employed for the inner surface side covered with a polyester film and the outer surface side covered with a printed polyester film. be able to. In this case, the metal material forming the can body is protected by the polyester film covering the inner surface side and the outer surface side of the can body, and can withstand the processing by the outer shape processing step and the bead processing step, and the can The printing of the polyester film covering the outer surface side of the cylinder is maintained in a beautiful state.

  In addition, providing the bead in a region where the outer diameter of the can body is the smallest or in the vicinity thereof is effective in recovering and improving the paneling strength of the can body which has been reduced by the outer shape processing step. The shape and number are set so that the paneling strength of the can body after providing the beads is recovered and improved to 90% or more of the paneling strength of the unprocessed can body that has not undergone the outer shape processing step. Is suitable.

  In addition, the present inventor has found that if the paneling strength of the can body is 160 kPa or more according to various tests, the can body is deformed due to vapor pressure applied during heating during retort sterilization treatment or impact when dropped by a vending machine. We know that we can prevent.

  Therefore, in the bead processing step of the present invention, it is preferable that the shape and number of the beads are set so that the paneling strength of the can body provided with the beads is 160 kPa or more.

The side view of a can provided with the can body manufactured by the method of the present invention. The expanded sectional view of the principal part of the can body of FIG. Explanatory drawing which shows an external shape process. The figure which shows plate | board thickness distribution of the can body formed by the external shape process. Explanatory drawing which shows a bead processing process.

  An embodiment of the present invention will be described with reference to FIGS. A metal can 1 shown in FIG. 1 is generally called a three-piece can, and includes a can body 2 manufactured in this embodiment. A canopy 3 for closing the upper end side opening of the can body 2 is wound on the upper end of the can body 2, and a bottom cover 4 for closing the lower end side opening of the can body 2 is tightened on the lower end of the can body 2. .

  The inside of the can 1 is filled with beverages such as coffee and tea, and the contents can be drunk by breaking a break opening (not shown) provided in the canopy 3 to form a drinking mouth.

  Although not shown, the inner surface of the can body 2 is covered with a polyester film, and the outer surface side is covered with a printed polyester film, so that the metal can material of the can body 2 is protected.

  As shown in FIG. 1, the can body 2 is formed with a concave processed portion 5 which is reduced in diameter by recessing a peripheral wall. Further, the upper side of the recessed processed portion 5 is an upper unprocessed portion 6 (upper large-diameter wall portion), and the lower side of the recessed processed portion 5 is a lower unprocessed portion 7 (lower portion) having the same outer diameter as the upper unprocessed portion 6. Large-diameter wall).

  The can body 2 shown in the present embodiment is in an unprocessed state, has a thickness of about 0.2 mm, an outer diameter of 52.8 mm, and the height of the canopy 3 and the bottom cover 4 after being tightened is 114 mm. Is adopted. The can body 2 is not limited to this size, but preferably has an unprocessed outer diameter of 45 mm to 70 mm and a height of the canopy 3 and the bottom lid 4 after tightening of 60 mm to 180 mm. it can.

  Although exaggerated for convenience of explanation in FIG. 2, the recessed processed portion 5 includes a first tapered wall portion 8 that gradually decreases in diameter from the lower end of the upper unprocessed portion 6 and a first tapered wall portion 8. A small-diameter wall portion 9 that extends downward while maintaining a constant outer diameter from the lower end, and a second tapered wall portion 10 that gradually expands from the lower end of the small-diameter wall portion 9 to reach the upper end of the lower unprocessed portion 7. ing.

  The first taper wall portion 8 is larger in length in the height direction than the small-diameter wall portion 9, and the upper end of the first taper wall portion 8 is located within the upper half of the can body 2. The second taper wall 10 is smaller in length in the height direction than the small-diameter wall 9, and the lower end of the second taper wall 10 is located within the lower half of the can body 2. Therefore, the concave processed portion 5 is formed in a sufficient length by extending vertically through the vicinity of the center of the can body 2.

  A first bead 11 (corresponding to a bead in the present invention) is formed on the small diameter wall portion 9 along the circumferential direction of the can body 2. Furthermore, a second bead 12 (corresponding to another bead in the present invention) is formed in the lower unprocessed portion 7 along the circumferential direction of the can body 2. The first bead 11 and the second bead 12 impart paneling strength to the can body 2.

  As the shape of the first bead 11 and the second bead 12, the width is 2 to 6 mm (preferably 2 to 4 mm) and the depth is 0.3 to 2 mm (preferably 0.5 to 1.5 mm). ) Range.

  Further, the length of the concave processed portion 5 in the height direction is set in a range of 35% to 70% with respect to the total length of the can body 2 in the height direction.

  Further, the minimum outer diameter of the small-diameter wall portion 9 provided at the boundary between the lower end of the first taper wall portion 8 and the upper end of the second taper wall portion 10 is the outer diameter of the upper unprocessed portion 6 (can body 2 Is set to a range of 80% to 95%.

  Recess angle (taper angle) θ1 in the axial direction of the first taper wall portion 8 with respect to the upper unmachined portion 6 and the recess of the second taper wall portion 10 in the axial direction with respect to the lower unmachined portion 7 Each of the entrance angles (taper angles) θ2 is selected from a range of 2 to 30 °. Preferably, the recess angle θ1 of the first taper wall 8 is set to a range of 2 to 20 °, and the second taper wall 10 The indentation angle θ2 is in the range of 5 to 30 °. In the can body 2 of this embodiment shown in FIG. 1, the recess angle θ1 of the first taper wall 8 is about 3 °, and the recess angle θ2 of the second taper wall 10 is about 13 °. It is said that. If the recess angles θ1 and θ2 are small, the feature of the shape of the concave processed portion 5 is thinned and the aesthetic appearance is deteriorated. If it is too large, the uneven thickness of the can body 2 generated when the concave processed portion 5 is processed. Not only increases the wrinkles and the like, but also causes a significant decrease in paneling strength. Therefore, by selecting the indentation angles θ1 and θ2 from the range of 2 to 30 °, it is possible to suppress the occurrence of wrinkles and the paneling strength during the processing of the concave processed portion 5 and to have a high aesthetic appearance. 2 can be obtained.

  When the can body 2 having the above configuration forms the can body 1, a high aesthetic appearance can be obtained by the concave processed portion 5.

  Next, the manufacturing method of the can body 2 which is the gist of the present invention will be described. As shown in FIG. 3, first, the unprocessed can body 2 is sandwiched between the first holding member 13 and the second holding member 14. At this time, the inside of the can body 2 is closed by the first holding member 13 and the second holding member 14 in a hollow state.

  The first holding member 13 is connected to a rotation driving means (not shown) and includes an air introduction port 15 connected to an air supply means (not shown) at its axial center. The first holding member 13 is in airtight contact with one end edge of the can body 2. The second holding member 14 is connected to a rotatable rotating shaft 16 and abuts against the other end edge of the can body 2 in an airtight manner.

  Then, air is introduced into the can body 2 through the air introduction port 15 of the first holding member 13. At this time, the pressure of the air introduced into the can body 2 is maintained at a predetermined air pressure (for example, about 0.5 MPa) by the air supply means.

  Subsequently, the first holding member 13 is rotated by the rotation driving means. And the can body 2 rotates by the 2nd holding member 14 being provided rotatably.

  Next, the can body 2 is maintained in a rotated state, and the outer surface of the peripheral wall of the can body 2 is moved by a vertically movable and rotatable pressing roller 17 (corresponding to a pressing member in the present invention) provided outside the can body 2. Press to indent and deform. The pressing roller 17 rotates in synchronization with the can body 2. Since the can body 2 is rotating, the can body 2 is indented and deformed over the entire circumference of the peripheral wall of the can body 2.

  Further, at this time, the pressing roller 17 is moved in the axial direction of the can body 2 while changing the amount of the pressing roller 17 pushed into the peripheral wall of the can body 2 in accordance with the shape of the concave processed portion 5. The pressing roller 17 has a rounded outer peripheral end that contacts the can body 2 and is not sharp but has a predetermined radius of curvature (selectable from 2 to 5 mm, preferably about 3 mm). The sliding contact on the outer surface is performed smoothly, and the can body 2 is prevented from being damaged.

  That is, while the amount of pressing of the pressing roller 17 is gradually increased, the pressing roller 17 is moved in the axial direction of the can body 2 until the length corresponding to the first tapered wall portion 8 is reached. Thereby, the 1st taper wall part 8 is formed. Subsequently, the axis of the can body 2 is maintained until the pressing amount of the pressing roller 17 is kept constant at the lower end of the first tapered wall portion 8 reduced in diameter by a predetermined amount until the length corresponds to the small diameter wall portion 9. The pressing roller 17 is moved in the direction. Thereby, the small diameter wall part 9 is formed. Further, continuously, the pressure roller 17 is moved in the axial direction of the can body 2 until the length corresponding to the second taper wall portion 10 is reached while gradually decreasing the pressing amount of the pressure roller 17. Thereby, the 2nd taper wall part 10 is formed. The concave processed portion 5 is formed by the above continuous operation (outline processing step).

  By forming the concave processed portion 5 as described above, nothing can enter the inside of the can body 2 other than a gas of a predetermined pressure, so that the polyester film coated on the inner surface side of the can is damaged or damaged. The can body 2 having a very high aesthetic appearance can be efficiently formed.

  In addition, the first tapered wall portion 8 is first formed, and the pressing roller 17 is moved so that the second tapered wall portion 10 is formed through the small-diameter wall portion 9, whereby wrinkles and the like are generated in the concave processed portion 5. And good recessing can be performed.

  In the can body 2 in which the concave processed portion 5 is formed by the outer shape processing step, the air maintained at a predetermined pressure is extracted from the inside of the can body 2 and removed from between the first holding member 13 and the second holding member 14. . Then, after a neck-in and a can lid winding flange are formed at both ends of the can body 2, a bead processing step described later is performed.

  Here, according to the inventor's knowledge, in the thickness distribution of the concave processed portion 5 formed by the outer shape processing step, as shown in FIG. 4, the thickness of the small-diameter wall portion 9 is the smallest, and the second The plate | board thickness of the taper wall part 10 becomes the thickest. The paneling strength becomes smaller as the plate thickness becomes thinner when the same metal material is used. Therefore, it is considered that the paneling strength of the can body 2 is lowered due to the formation of the concave processed portion 5.

  Subsequently, after the holding state by the first holding member 13 and the second holding member 14 is released, the receiving die 18 is brought into contact with the inner surface side of the can body 2 as shown in FIG. The pressing die 19 is brought into contact with the side.

  The pressing die 19 includes a base portion 20 formed in a drum shape having an inner diameter larger than the outer diameter of the can body 2, a first molding convex portion 21, and a second molding convex portion 22. The first molding convex portion 21 and the second molding convex portion 22 are annularly projected on the inner periphery of the base portion 20 corresponding to the shapes of the first bead 11 and the second bead 12, respectively. Yes.

  Further, in the pressing die 19, the inner surfaces of both end portions along the axial direction of the can body 2 are in contact with the outer surfaces of the upper unprocessed portion 6 and the lower unprocessed portion 7 of the can body 2, and between the contact surfaces. It is set as the shape where the concave-shaped process part 5 of the can body 2 is located.

  The receiving mold 18 includes a rotary shaft portion 23 formed in a columnar shape having an outer diameter smaller than the outer diameter of the can body 2, a first molding concave portion 24, and a second molding concave portion 25. The first molding concave portion 24 and the second molding concave portion 25 correspond to the first molding convex portion 21 and the second molding convex portion 22.

  Further, the receiving mold 18 has both outer surfaces of both end portions along the axial direction of the can body 2 in contact with the inner surfaces of the upper unprocessed portion 6 and the lower unprocessed portion 7 of the can body 2, and between the contact surfaces. It is set as the shape where the concave-shaped process part 5 of the can body 2 is located.

  The receiving mold 18 and the pressing mold 19 are rotated synchronously (with the upper unprocessed section 6 and the lower unprocessed section 7 between the upper unprocessed section 6 and the lower unprocessed section 7 by driving a rolling drive mechanism (not shown). By rotating the matching peripheral speed of the contact surface of the receiving mold 18 and the contact surface of the pressing mold 19 together to rotate the can body 2 while holding the can body 2 and preventing slippage. Let Thereby, the can body 2 rolls the inner periphery of the pressing die 19 in the circumferential direction in accordance with the rolling of the receiving die 18 while being pressed against the pressing die 19.

  And the 1st bead 11 is formed in the part which received the press contact with the 1st shaping | molding convex part 21 and the 1st shaping | molding recessed part 24 over the perimeter of the circumferential direction of the can body 2, and a 2nd shaping | molding convex simultaneously. The second bead 12 is formed in the portion that has been pressed by the portion 22 and the second molding recess 25 (bead processing step).

  As described above, the first bead 11 and the second bead 12 are formed by the pressure contact between the receiving die 18 and the pressing die 19, and therefore, the first bead 11 is particularly formed by the small-diameter wall portion 9 having the smallest plate thickness. Even when formed, the uneven thickness of the small-diameter wall portion 9 is suppressed, and the first bead 11 can be formed without causing the uneven thickness of the small-diameter wall portion 9 to progress.

  Thereby, the 1st bead 11 is formed in the small diameter wall part 9 with the thinnest plate thickness, and the fall of the paneling intensity | strength of the can body 2 by having formed the recessed process part 5 recovers and improves. Further, the formation of the second bead 12 further increases the beauty of the can body 1 and the paneling strength of the can body 2.

  In the can body 2 obtained in this manner, the can body 2 is wrapped with a canopy 3 (or bottom cover 4) and filled with a beverage, and then the bottom cover 4 (or canopy 3) is tightened with FIG. A can body 1 shown in FIG.

  Here, the paneling strength will be described. When measuring the paneling strength, first, an empty can containing no contents such as a beverage is created in the shape of the can 1 shown in FIG. Next, this empty can is put into a pressurized container, pressurized from the outside, and the pressure at the time when the can body 2 of the can body 1 is deformed is measured. The measured value at this time is used as the paneling strength. The paneling strength of the can body 2 which has no problem in practical use is 160 kPa, but it should be higher as long as the can quality, aesthetics and the like are not deteriorated.

  When the paneling strength of the can body 2 according to the present embodiment was measured, the paneling strength of the unprocessed can body was about 200 kPa, and the paneling strength of the can body 2 was formed when the concave processed portion 5 was formed by the outer shape processing step. Dropped to about 153 kPa. However, by providing the first bead 11 on the can body 2 in which the concave processed portion 5 is formed, the paneling strength of the can body 2 is improved to about 220 kPa (about 110% of the unprocessed can body). Therefore, it became clear that the can body 2 obtained by the method of the present embodiment has a paneling strength exceeding the practical level of 160 kPa.

  Cans used as beverage cans for coffee, tea, etc. are subjected to retort sterilization (heat sterilization) after filling and sealing the contents. In that case, a differential pressure is generated in the pressure inside and outside the can filled with the contents in the retort kettle. At this time, if the paneling strength of the can body is weak, the can body may be deformed to be recessed. Further, when the can body is dropped during handling, if the paneling strength is weak, there is a problem that the can body is deformed and the commercial value is lost.

  However, as described above, the can body 2 used in the can body 1 according to the present embodiment can obtain a paneling strength exceeding the practical level. It is possible to prevent a deformation such as a prepared depression.

  In the present embodiment, the first bead 11 and the second bead 12 are formed one by one. However, a plurality of the first beads 11 and the second beads 12 are provided. It may be. Moreover, since sufficient paneling intensity | strength is obtained by forming the 1st bead 11 in the small diameter wall part 9, it is also possible not to provide the 2nd bead 12. FIG.

  Moreover, in this embodiment, although the concave processed part 5 which provided the small diameter wall part 9 between the 1st taper wall part 8 and the 2nd taper wall part 10 is shown, it is provided whether the small diameter wall part 9 is provided. This can be selected according to the desired design. When the small-diameter wall portion 9 is not provided, for example, although not shown, the lower end of the first taper wall portion 8 and the upper end of the second taper wall portion 10 are continuous, so the first taper wall portion 8 and the second taper wall portion 8 are continuous. What is necessary is just to provide the 1st bead 11 along the boundary with the wall part 10, or its vicinity.

  Furthermore, a thin surface-treated steel sheet of 0.22 mm or less is suitable as the can body material employed in the present invention. In particular, a surface-treated steel sheet in the range of 0.22 to 0.10 is suitable. If it is thicker than this range, too much load is applied at the time of outer shape processing or bead processing, and it takes time and productivity is lowered, and if it is thinner than this range, the paneling strength of the resulting can body becomes low, which is not preferable.

  Moreover, in this embodiment, about the 3 piece can which uses the cylindrical can body obtained by rounding the rectangular flat plate can body material which laminated the polyester film on both surfaces of the surface treatment steel plate, and welding a side edge part. As described above, the present invention is not limited to this, but a so-called two-piece can obtained by punching a disk-shaped plate from a surface-treated steel sheet laminated with a polyester film and integrally forming the can body and the bottom by drawing or ironing. It can also be applied to this.

  2 ... can barrel, 5 ... concave processed portion, 6 ... upper unprocessed portion (upper large-diameter wall portion), 7 ... lower unprocessed portion (lower large-diameter wall portion), 8 ... first tapered wall portion, 9 ... small diameter Wall part, 10 ... 2nd taper wall part, 11 ... 1st bead (bead), 12 ... 2nd bead (other bead), 18 ... Receiving type | mold, 19 ... Push type | mold.

Claims (7)

A concave processed portion is formed by recessing the entire circumference of a cylindrical metal can barrel extending in the height direction, and the maximum outer diameter of the can barrel is set on the upper end side and the lower end side of the concave processed portion. A first tapered wall portion having a maintained unprocessed portion, the upper end being located within the upper half of the can body and gradually reducing the diameter downward from the upper end; A lower tapered portion located within the lower half of the body and a second tapered wall portion gradually decreasing in diameter upward from the lower end, and the raw portion is fixed from the upper end of the first tapered wall portion. An upper large-diameter wall portion that extends upward while maintaining an outer diameter, and a lower large-diameter wall portion that extends downward from the lower end of the second tapered wall portion, and the length in the height direction of the concave processed portion is It is set in the range of 35% to 70% with respect to the total length in the height direction of the can body, and the first A can body having a minimum outer diameter at a boundary between a lower end of a super-wall portion and an upper end of the second tapered wall portion is set in a range of 80% to 95% with respect to the outer diameter of the unprocessed portion. A method of manufacturing a can body for performing
It extends in the circumferential direction of the can body within a predetermined range including an outer shape processing step for forming the concave processed portion and a boundary between the first tapered wall portion and the second tapered wall portion of the concave processed portion. A bead processing step of forming at least one bead,
In the outer shape processing step, the inside of the cylindrical unprocessed can body is maintained at a predetermined pressure with gas, and the pressing member is pressed against the peripheral wall of the can body from the outside by a predetermined shape pressing member. Forming the concave processed portion including the first tapered wall portion and the second tapered wall portion by moving in the axial direction of
In the bead processing step, a receiving die corresponding to the shape of the bead is brought into contact with the inner surface side of the can body in which the first tapered wall portion and the second tapered wall portion are formed by the outer shape processing step. A manufacturing method of a can body characterized in that a pressing die corresponding to the receiving die is brought into contact with the outer surface side of the plate, and the bead is formed by press-contacting both types.   In the outer shape processing step, when forming the concave processed portion in which the length of the first tapered wall portion in the height direction is longer than that of the second tapered wall portion, in the outer shape processing step, 2. The method of manufacturing a can body according to claim 1, wherein the concave processed portion is formed by continuously moving the pressing member from the upper end of the first tapered wall portion toward the lower end of the second tapered wall portion. .   In the outer shape processing step, a small-diameter wall portion is formed between the lower end of the first taper wall portion and the upper end of the second taper wall portion, connected to both the taper wall portions and extending with a constant outer diameter. The method for producing a can body according to claim 1 or 2, wherein   In the bead processing step, at least one other bead extending in a circumferential direction of the can body is formed on at least one of the upper large-diameter wall portion and the lower large-diameter wall portion. Item 4. The method for producing a can body according to any one of Items 1 to 3.   2. The can body to be processed in the outer shape processing step is characterized in that an inner surface side thereof is covered with a polyester film and an outer surface side is covered with a printed polyester film. 5. The method for producing a can body according to any one of 4 above.   In the bead processing step, the shape and number of the beads provided in the concave processing portion are the same as the paneling strength of the can body after the bead is provided. The can body manufacturing method according to any one of claims 1 to 5, wherein the can body is set so as to be recovered and improved to a strength of 90% or more of the strength.   In the bead processing step, the shape and number of the beads provided in the concave processed portion are set so that the paneling strength of the can body after providing the beads is 160 kPa or more. The method for manufacturing a can body according to any one of claims 1 to 6.

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