JP6252764B2 - Molding method of square can - Google Patents

Description

  The present invention relates to a method for forming a square can, and more particularly to a method for forming a square can from a bottomed cylindrical can.

  Conventionally, in the case of a metal square can, in the case of a two-piece can, a blank can is drawn and redrawn to form a bottomed cylindrical can, and the cylindrical can is formed into a square can with a square die and a square punch. A method is generally known (for example, Patent Document 1). In addition, as a method for forming a bottomless rectangular can body as a three-piece can, a bottomless cylindrical body that is seam-bonded is pressed inward by an outer mold having a cross-sectionally shaped processing surface, and the side wall portion is A method is known in which a corner is formed by pressing a part of a cylindrical body that forms a corner with an inner mold having a processed surface having a circular arc cross section at the tip while forming the corner (Patent Document 2). The latter method is not expected to be applied to molding a rectangular can from a bottomed cylindrical can, and is difficult to apply.

JP 2010-167659 A JP2011-50979A

In the method of forming the conventional bottomed cylindrical can into a square can, when the can bottom portion is deformed from a circle to a square shape, the corner and the straight portion are inevitably elongated and deformed. This affects the side wall surface of the can body and causes a problem that the side wall surface is bent or distorted.
On the other hand, in recent years, decorative cans decorated with beautiful printing and painting with metal cans are in circulation. In the case of a cylindrical can, these decorations can be performed in one step by multi-colored curved surface printing, but in the case of a rectangular can, in order to obtain the same decoration quality as a cylindrical can, it is necessary to print four sides separately. . In that case, a complicated printing process and apparatus such as positioning of the can are required, and productivity is deteriorated as compared with the cylindrical can, and a dedicated decoration facility must be provided. In order to avoid this, for example, a method of decorating a can body by curved surface printing in the state of a cylindrical can as shown in FIG. 14 (b-1) and then forming the cylindrical can into a rectangular can is considered. In the case of a cylindrical can having a can bottom (a so-called two-piece can), when the cylindrical can is formed into a rectangular can by the above-described conventional method, a part of the can bottom wraps around the side wall to the decorative surface of the side wall (b-2). ), There is a problem that distortion occurs and the shape is deformed, and high-quality decoration is not obtained. Furthermore, in order to avoid this problem, a method of obtaining a final print screen after the molding using a print screen in which the distortion is corrected in advance can be considered, but in reality, the material is anisotropic or non-uniform. It is difficult to obtain highly accurate decoration due to instability factors such as sex. When comparing cylindrical cans and square cans from the viewpoint of display properties, it is always difficult to display product names etc. facing the front in the case of cylindrical cans. Can be easily displayed with the product name facing forward, and can be displayed without gaps, and has the advantage of high storage efficiency. However, for the above reasons, a rectangular can with high-quality decoration has been obtained. Absent.
Therefore, the present invention can form a rectangular can that can obtain a decorative effect equivalent to that of a cylindrical can and high productivity without causing bending or distortion in the decorative surface of the can body even after forming the rectangular can. It is intended to provide a method.

As a result of studying the cause of distortion in the can body (decorative surface) when forming a bottomed cylindrical can into a square can with a square die, as shown in the schematic diagram of FIG. When the can B is molded into the bottom of the can B, the amount of movement of the cylindrical can portion A-1 that becomes the corner portion B-1 of the square can is small even when the corner portion B-1 of the square can is formed. On the other hand, since the portion A-2 that becomes the straight portion B-2 is located outside the rectangular can B, when the portion A-2 is pushed into the rectangular die, a part of the remaining can bottom material accompanying the diameter reduction is obtained. It wraps around the side walls and causes them to be distorted and deformed. The present invention has been achieved as a result of further research based on this finding.
That is, the manufacturing method of the rectangular can of the present invention that solves the above-described problem is a method of forming a rectangular can having a can bottom and forming a rectangular can having a straight portion and a rectangular portion in a cross section. Means for moving the outer periphery of the cylindrical bottom of the cylindrical can that is to be a straight portion in the bottom of the can having a shape corresponding to the surface, and the cylindrical can that is to be a corner at the bottom of the rectangular can By means of moving the outer periphery of the can bottom radially outward, the shape of the outer periphery of the can bottom is transformed into a shape corresponding to the cross-section of the square can, and the circumference of the can body before and after the deformation is substantially changed. It is characterized by not.
By employ | adopting the said structure, a can barrel side wall will only be bent and a deformation | transformation will not arise in a decorating surface.

Therefore, by decorating the cylindrical can before the square forming shape, it is possible to maintain a beautiful decorative surface applied to the cylindrical can, and to obtain an efficiently decorated rectangular can.
And in the manufacturing method of the said square can, in the can bottom of the said square can, the can bottom outer peripheral part of the cylindrical can scheduled to become a straight part moves radially inward, and a part of the can bottom moves radially inward In this case, it is desirable that a convex part is formed on a part of the bottom of the can so that a part of the material of the deformed part can be absorbed by the convex part in the linear part and can be molded better.
In addition, a material supply part is formed on a part of the bottom of the cylindrical can that is supposed to be a corner in the can bottom of the square can, and while pressing the material supply part by a crushing means inserted into the can, By moving the outer periphery of the cylindrical bottom of the cylindrical can, which is supposed to be a corner at the bottom of the rectangular can, the corner can be satisfactorily formed without giving distortion to the side wall.

Further, in the method for forming the rectangular can, the linear portion is formed by means for moving the outer periphery of the bottom of the cylindrical can radially inward, and the corner by the means for moving the outer periphery of the bottom of the cylindrical can radially outward. It can be formed efficiently by performing the partial molding in the same process or by using a pressing tool to move the outer peripheral portion of the bottom of the cylindrical can inward in the radial direction.
In addition, in the method for forming a rectangular can, the strength of the side wall can be improved by forming an emboss on the side wall of the square can by the pressing tool and the shaft inserted into the can, and the can material can be made thinner. This is desirable.

According to the method of the present invention, the shape of the outer periphery of the bottom of the can can be transformed into a shape corresponding to the cross section of the rectangular can, and the circumferential length of the can body before and after the deformation can be substantially unchanged. The side walls are simply bent and the decorative screen is not distorted. Moreover, in the label decorating method which adhere | attached the printing film, peeling of the film by shaping | molding can be prevented. Furthermore, when the hologram decoration is used, the decoration screen is not distorted, so that the decoration quality and color developability are maintained.
In addition, it is possible to decorate cylindrical cans with conventional decorating equipment, and to maintain the beautiful decorative surface applied to cylindrical cans after forming them into square cans. Can be obtained efficiently.
Furthermore, when moving the outer peripheral part of the cylindrical bottom of the cylindrical can, which is supposed to be a straight part, in the rectangular can bottom, radially inwardly, when moving a part of the can bottom radially inwardly, By forming the convex part, a part of the material of the deformed part can be drawn into the convex part of the bottom of the can and absorbed by the straight part, so that the surplus material is prevented from turning to the side wall and the side wall is distorted. It can shape | mold well, without making it.
Furthermore, a material supply part is formed on a part of the bottom of the cylindrical can that is to be a corner in the bottom of the square can, and while pressing the material supply part by a crushing means inserted into the can, The material can be supplied to the corners projecting outward from the outer periphery of the cylindrical can by moving the outer periphery of the cylindrical can to be a corner at the bottom of the square can radially outward. It is possible to reduce the influence of molding distortion on the can body portion, to prevent thinning of the outer peripheral portion of the corner portion, and to form the corner portion well.

Further, in the rectangular can molding, the molding device is formed by performing the molding of the linear portion and the corner portion in the same process, or by using the pressing tool to move the outer peripheral portion of the cylindrical bottom of the cylindrical can in the radial direction. It can be simplified and molded efficiently.
Furthermore, by forming embossing on the side wall at the same time as forming the rectangular can, the rigidity of the side wall can be effectively improved, the can material can be made thinner, and the embossed pattern can be made horizontal or vertical. By doing so, the squareness of the side wall can be secured.

It is a schematic diagram which shows the shaping | molding method of the square can which concerns on this invention. The cross section of the shaping | molding part of the corner | angular part in the shaping | molding method of the square can which concerns on embodiment of this invention is shown, (a) shows before the shaping | molding start, (b) shows the state after completion | finish of shaping | molding. The cross section of the molding part of the straight line part is shown, (a) shows the state before the start of molding, and (b) shows the state after the end of molding. It is a block diagram which shows the square can manufacturing process to which the shaping | molding method of the square can which concerns on embodiment of this invention is applied. (A)-(c) is a front view which shows embodiment of the embossing pattern given to the side wall of a square can. 1 shows an embodiment of a rectangular can manufacturing apparatus for carrying out the rectangular can forming method of the present invention, in which the right half from the center line shows the state of the corner forming part and the left half of the straight part forming part before the start of forming. The state at the time of the shaping | molding start in the apparatus of FIG. 6 is shown. The state at the time of completion | finish of shaping | molding in the apparatus of FIG. 6 is shown. (A) is a principal part enlarged view in FIG. 7, (a)-(c) shows an example of the shape of the material supply part C. FIG. It is a principal part enlarged view in FIG. It is a perspective view which shows embodiment of the square can shape | molded by this invention. It is a perspective view which shows embodiment of the 2 piece can which wound the lid | cover on the square can shape | molded by this invention. An example of the shape of the thread | bottom-bottom-shaped protrusion provided in the can bottom part of the square can obtained by this invention is shown. (A) The square can obtained by this invention and (b) The state change of the decorating surface of the square can obtained by the conventional method is shown typically. It is a schematic diagram which shows an example of the conventional method.

Hereinafter, an embodiment of a method for forming a rectangular can according to the present invention will be described with reference to the drawings.
FIG. 1 is a virtual view of a cylindrical can A and a rectangular can B having the same circumferential length as viewed from the bottom of the can with the same axis center in order to explain the basic concept of the present invention. In this figure, when the cylindrical can A is formed into a square can B having the same circumference, the portion A-1 corresponding to the corner B-1 of the square can is located inside the square can, so that portion expands outward. Since it is opened and stretched to become B-1, and the insufficient material is drawn from the can bottom and the can body, the can body near the bottom is also distorted. Conversely, since the portion A-2 that becomes the straight portion B-2 is located outside the straight portion of the rectangular can, the portion A-2 is pushed in from the outside to form the straight portion B-2. Therefore, at that time, the straight portion is reduced in diameter so that the material is left, and the material turns to the side wall portion, so that the side wall portion is distorted.

In order to solve this problem, the following method was adopted in the method for forming a rectangular can according to this embodiment.
Step 1: When forming a cylindrical can by squeezing and ironing, a convex material supply part C was formed on the inner side at the bottom of the can which is supposed to be a corner in the cross section of the square can. In the present embodiment, the material supply unit C shown in FIG. 2A is formed so as to be diagonally positioned at four positions serving as corners as shown in FIG. 1, but the present invention is not necessarily limited thereto. When decorating a cylindrical can, it can also be performed before forming the material supply part C in a cylindrical can, and may be performed after that.
Step 2: As shown in FIGS. 2 (a) and 2 (b), the material supply part C provided at the bottom of the cylindrical can A is crushed by a crushing part 5-1 on the end face of the shaft 5 as a crushing means. However, the corners at the four corners can be obtained by moving the outer periphery of the can bottom radially outward by the extension tool 6 which is a means for moving the outer periphery of the cylindrical bottom of the cylindrical can scheduled to become the corner. Is molded.
Step 3: As shown in FIGS. 3 (a) and 3 (b), the cylindrical can A is radiused by the pressing tool 3 which is a means for moving the outer peripheral portion of the cylindrical bottom of the cylindrical can to be a linear portion inward in the radial direction Push inward. At that time, by forming the pull-in portion D into which the material is pulled into a part of the can bottom, the material pushed in the radial direction is absorbed by the pull-in portion.

As described above, by forming the material supply part C in advance in a part of the bottom of the can bottom near the can bottom outer peripheral part A-1 that is to be the corner of the rectangular can, from the outer periphery of the cylindrical can during the corner forming The material can be supplied from the material supply unit to the corner portion that is formed to protrude outward, and the influence of molding distortion on the can body portion can be reduced. At the same time, as the side wall is pushed by the pressing tool, a material pull-in part D is formed at the bottom of the can, and surplus material due to the reduced diameter is drawn into the pull-in part, preventing the movement of the material to the can body As a result, distortion generated in the can body can be reduced.
As a result, the shape of the outer periphery of the bottom of the cylindrical can can be transformed into a shape corresponding to the cross section of the square can, and the circumferential length of the can body before and after the deformation can be substantially unchanged. Is simply bent, and no deformation occurs on the can body surface.

An embodiment of the rectangular can molding method of the present invention comprising the above steps will be described in more detail using the apparatus shown in FIGS.
FIGS. 2 and 3 are schematic views of the main part, and the rectangular can forming apparatus according to the present embodiment includes a shaft 5 to be inserted into the inside of the cylindrical can and a pressing tool 3 that presses the position to be a linear portion of the rectangular can from the outside. And a combination with the lower mold 4.
The shaft 5 for forming the straight portion and the bottom portion of the square can consists of a combination of four expansion tools 6 (FIG. 2) for moving the corner position outward and forming the corner portion. The concave portions 8 (FIG. 3) for forming the lead-in portions are formed on the inner circumferences of the positions where the straight portions are formed. The end surface of the shaft is formed in a shape that matches the shape of the inner peripheral surface of the straight portion of the rectangular can to be molded.

  The lower die 4 is a forming die for forming the bottom portion of the rectangular can in cooperation with the shaft 5, and is formed on a part of the can bottom inside the outer peripheral portion which becomes a linear portion at a position corresponding to the concave portion 8 on the shaft end surface. A plurality of protrusions 9 (FIG. 3) for drawing material are formed so as to form convex portions as a plurality of drawing portions D.

In the rectangular can forming apparatus having the above-described structure, the rectangular can B is formed from the separately formed bottomed cylindrical can A as follows.
In the case of a decorative can, the outer peripheral surface is appropriately decorated such as printing or painting in the state of a cylindrical can. When the cylindrical can is formed, a convex portion that becomes the material supply portion C is formed on the inner periphery of each position that is to be a corner portion of the rectangular can. At the start of molding after setting the shaft 5 to be positioned inside the cylindrical can A on which the convex portions are formed, the diagonal cross section II of the corner shown in FIG. 1 is in the state shown in FIG. The section II-II of the straight line is the state shown in FIG.
When the extension tool 6 is expanded diagonally outward while the shaft 5 is further lowered from this state, the convex portion which is the material supply portion C of the bottom portion of the cylindrical can is flattened by the crushing portion E on the end surface of the shaft 5. While being crushed, the corners are formed by expanding the outer peripheral side wall of the can bottom with the expansion tool 6. At that time, since the material flows from the material supply section to the corner formed, the corner can be formed without distorting the outer peripheral side wall of the can bottom.

On the other hand, on the straight part forming surface, the shaft 5 is lowered simultaneously with the corner forming, and the pressing tool 3 is contracted and moved from the outer four surfaces toward the inside of the can to press the outer peripheral part of the cylindrical can to form the square side surface. Is molded. At that time, the shaft 5 descends as the pressing tool 3 contracts, so that the bottom surface of the can bottom hits the projection 9 formed on the top surface of the lower mold 4 and the shaft end surface formed opposite to the projection. The excess material in the bottom of the can that is pushed into the recess 8 and is reduced in diameter by the pressing tool 3 is drawn into the recess 8 of the shaft (FIG. 3 (b)). Distortion applied to the outer periphery can be reduced as much as possible.
As a result, the outer peripheral portion of the can bottom can be formed into a square shape by substantially reducing the distortion of both the straight portion and the corner portion as much as possible and converting it to substantially the same length. Along with this, the can body at the top of the peripheral wall of the bottom of the can is formed by isometric conversion that simply undergoes bending processing, so that the decorative effect applied to the outer peripheral surface of the cylindrical can can be achieved without causing distortion on the decorative surface. Can be maintained.

  Therefore, according to the method for forming a rectangular can of the present invention, when obtaining a decorative rectangular can, as shown in the block diagram of FIG. 4, it is used as it is until the decoration process in the existing production line of the two-piece cylindrical can. It is possible to form a cylindrical can with a bottomed cylindrical can decorated with a square can molding line by the molding method according to the present embodiment, and then perform neck flange molding etc. on the square can molding line, similar to a cylindrical can A square can decorated with can be obtained with high production efficiency.

  Further, for example, an embossing as shown in FIG. 5 can be applied to the straight portion of the can body formed into a square can as required. Embossing can be performed in a separate process after the angulation, or in the same process as the angulation. When performing simultaneously with molding, the embossing die is formed on the linear part molding surface of the shaft, and the opposing die is formed on the opposing surface of the pressing tool, thereby simultaneously forming the linear part of the rectangular can from the cylindrical can. The shaft can be embossed by the cooperative action of the shaft. In addition, the emboss shape is a shape having a horizontal line or a vertical line as shown in E1 to E3 shown in FIGS. 5A to 5C, for example, thereby improving the rigidity of the can body and ensuring the squareness of the side wall. can do. Alternatively, embossing having a shape corresponding to the print screen can be performed.

  The can formed into a square is then subjected to neck-in molding and flange molding as necessary. It should be noted that a square can for winding a rectangular can lid can be obtained by necking in the can opening at the time of neck-in molding, and a circular shape can be obtained by necking in the can opening. A square can having a circular top end with a lid wound is obtained. Furthermore, by forming a mouth-and-neck part having a screw part in the opening part, a so-called bottle can having a square body part to which a screw cap can be attached can be obtained.

FIGS. 6-10 shows the Example of the shaping | molding apparatus of the square can which implements the shaping | molding method of the square can of this invention.
In the figure, the right half from the center line shows the cross section of the corner forming part, and the left half shows the cross section of the straight part forming part. The rectangular can molding apparatus according to the present embodiment includes an upper mold assembly 10 and a lower mold assembly 30, both of which are disposed so as to be relatively close to each other in the coaxial direction. The upper mold base 11 of the upper mold assembly 10 is provided with an inner mold assembly 12 and a pressing tool operating rod 25 having a contact head 26 at the lower end.

  The inner assembly 12 is composed of a combination of a shaft 13 for forming a straight portion and a bottom portion of a square can, and four expansion tools 14 for moving the position of the corner portion to the outside and forming the corner portion. On the lower end surface, there are formed a crushing portion and a concave portion 16 that forms a lead-in portion on the inner circumference of the position where each linear portion on the outer periphery of the can bottom is formed as described above. The expansion tool 14 is formed in a bell crank shape composed of a can body expansion portion 17 and a drive portion 18, and its pivot point is pivotably attached to a pivot 19 provided on a bracket above the shaft as shown in the figure. It has been. An abutting portion 20 is provided at the distal end of the driving portion 18 so as to abut on a head portion 46 of an extension tool operating rod 45 erected on a lower mold 30 to be described later to swing the can body expanding portion 17. The distal end portion of the can body expanding portion 17 of the expansion tool 14 is formed in a wedge shape as shown in the drawing, the distal end thereof is positioned on the inner peripheral portion of the can bottom forming portion, and the distal end is swung to swing the outer periphery of the bottom portion of the can barrel. The part can be expanded from the inside.

  The lower mold base 31 of the lower mold assembly 30 has a linear guide against the can body so that the pressing tool 32 for forming the linear portion of the can body presses the can body portion including the outer periphery of the can bottom from the outside. 33 so that it can reciprocate in the horizontal direction along 33. The lower mold base 31 is provided with a pressing tool driving member. The pressing tool driving member is configured such that a bell crank 35 is swingably supported by a member 34 erected on a lower mold base. The bell crank 35 swings when the abutting head 26 of the pressing tool operating rod 25 provided in the upper mold assembly abuts on the abutting portion 37 provided on the drive arm 36, and is provided at the lower part thereof. The abutting portion 38 presses the pressing tool 32 to push the can body into the straight portion.

  The lower mold base 31 is fixed with a lower mold 40 at a position facing the end surface of the upper mold shaft 13. The lower die 40 is a forming die that forms the bottom of the rectangular can in cooperation with the shaft 13, and an outer peripheral portion that forms a linear portion of the can bottom at a position facing the concave portion 16 at the lower end of the shaft 13 on the upper end surface thereof. A plurality of projections 41 are formed for drawing the material so as to form a plurality of convex portions inside. Further, an extension tool driving rod 45 for operating the extension tool 18 provided on the upper mold is erected on the lower mold base 31.

  Therefore, in the above embodiment, the outer periphery of the can bottom and the outer periphery of the cylindrical can where the pressing tool 32, the bell crank 35 serving as the pressing tool driving member, and the pressing tool operating rod 25 are expected to be linear portions are arranged in the radial direction. Means to move in the direction. Further, the expansion tool 14 and the expansion tool driving rod 45 constitute a means for moving the outer periphery of the bottom of the cylindrical can, which is planned to be a corner, radially outward.

The angle forming apparatus configured as described above is in a state shown in FIG. 6 before molding, and is in a state where a cylindrical can (elementary can) is attached to the outer peripheral portion of the inner mold assembly 12.
When the upper die is lowered from this state, as shown in FIG. 7, the contact head portion 26 of the pressing lever 25 provided on the upper die and the contact portion 37 of the bell crank 35 provided on the lower die come into contact. In the corner forming portion, the contact portion 20 of the extension tool 14 comes into contact with the head of the extension tool operating rod 45 erected on the lower mold base so that the extension tool 14 and the pressing tool are operated. Become. Further, in this state, as shown in an enlarged view in FIG. 9 (a), the bottom surface of the cylindrical can A, which is to be a straight portion, comes into contact with the projection 41, which is a lower drawing portion forming means, and the corner portion and The end surface of the shaft 13 is in contact with the upper surface of the material supply unit C formed on the planned bottom of the can.

  When the shaft further descends from this state, the pressing tool, the shaft and the expansion tool are operated together, the bottom surface of the can bottom hits the protrusion 41 formed on the top surface of the lower mold 40, and the pressing is performed as the shaft descends. The excess material of the bottom of the can, which is pushed in by the tool 32 and reduced in diameter, is drawn into the concave portion 16 of the shaft to form the lead-in portion D on the bottom surface of the can, thereby forming the linear portion. At the same time, when the expansion tool is opened, the outer periphery of the bottom of the can is expanded while crushing the material supply part C by the shaft, and the corners of the four corners are formed, and the state shown in FIG. finish.

As mentioned above, although one Example of the square can shaping | molding apparatus which implements this invention was described, a square can shaping | molding apparatus is not restricted to the said Example, A various design change is possible within the range of the technical idea. For example, although the expansion tool and the pressing tool are not shown, they can be driven by an actuator such as a hydraulic pressure or pneumatic pressure, a servo motor, etc. in synchronization with the lowered position of the shaft.
Furthermore, the material supply part and the lead-in part formed on the bottom of the cylindrical can are not limited to a single convex part per corner, but a plurality of small convex parts or appropriately shaped convex parts are adopted. In addition, the lead-in portion is not limited to the case where one convex portion is formed with respect to one linear portion, and is formed in a lower mold so that a plurality of minute convex portions or appropriately shaped convex portions can be formed. The shape and number of convex portions can be arbitrarily changed. Moreover, the direction of a convex part can also be provided not only inside a can bottom but toward an outer side. Furthermore, the shape of the material supply unit is the material shown in FIG. 9C when the material supply unit C-1 shown in FIG. 9B, for example, is formed by overhanging or a cylindrical can is formed by impact molding. A plate thickness distribution may be changed as in the supply unit C-2.
As the material of the can, known materials such as steel and aluminum and composite materials thereof can be applied. In addition, the decorative surface is not limited to a printed or painted surface, and a known decorative method such as a film body laminated with a film label can also be applied. As a matter of course, the present invention is not limited to a decorative can but can also be applied to forming a normal can body. Further, the can body can be applied to a can having a polygonal cross section such as a pentagon or a hexagon.
In order to improve the transportability and the like, the rectangular can formed by this forming method may be further formed by additionally processing a thread bottom-like protrusion as shown in FIG.

  FIG. 11 shows a rectangular can formed by the above rectangular can forming apparatus. The can body 51 of the rectangular can 50 formed from the cylindrical can has no wrinkles or distortion, and an image 52 printed on the cylindrical can by multicolor curved surface printing. There was no distortion, and a high-quality decorative can was obtained. FIG. 12 shows a state in which the opening of the obtained rectangular can is formed into a cylindrical shape after neck formation, flange formation is performed to form a can body, and a can lid 53 with a steion tab is wound up. FIG. 13 is an external view of the bottom of a rectangular can having a thread bottom protrusion formed on the bottom of the can. In this embodiment, the thread bottom protrusion 54 is formed as an annular protrusion.

FIG. 14 schematically shows the state change of the decorative surface E when the rectangular can B is formed from the cylindrical can A by the rectangular can obtained by the method of the present invention and the conventional forming method.
According to the method of the present invention, the side wall is bent at the time of molding into a rectangular can, and the can body part is converted into an equal length from a cylindrical can to a rectangular can. Therefore, as shown in FIG. Wrinkles and distortion do not occur, and the decorative surface has no distortion and can maintain the state of the cylindrical can.
On the other hand, in the case of the conventional method, as shown in the same figure (b-2), wrinkles and distortion generate | occur | produce in a can body, and the decoration state of a cylindrical can cannot be maintained.

  INDUSTRIAL APPLICABILITY The present invention can be suitably applied to form a rectangular can from a bottomed cylindrical can, and in particular, a high-quality decorative can can be obtained with high efficiency and has high industrial applicability.

3, 32 Pressing tool 4, 40 Lower mold 5, 13 Shaft 6, 14 Expansion tool 8, 16 Recess 9, 41 Protrusion 10 Upper mold assembly 11 Upper mold base 17 Can body expansion part 18 Drive part 19 Pivot 25 Pressing tool operation ２６ 26 Abutting head 30 Lower die assembly 31 Lower die base 33 Linear guide 34 Member 35 Bell crank 36 Driving arm 37, 38 Abutting portion 45 Extension tool driving rod 50 Square can A Cylindrical can A-1 A-2 Can bottom outer periphery of cylindrical can A-2 Can bottom outer periphery of cylindrical can scheduled to be a straight part B Square can B-1 Corner of a square can B-2 Straight part of a square can C Material supply part D Retraction part

Claims (7)

  In a method for forming a rectangular can having a shape having a shape corresponding to a transverse section of a rectangular can, in a method for forming a rectangular can having a straight portion and a corner in a transverse section, The bottom of the can by means of moving the outer periphery of the bottom of the can radially inward and by means of moving the outer periphery of the cylindrical bottom of the cylindrical can scheduled to become a corner at the bottom of the rectangular can A method for forming a rectangular can, characterized in that the shape of the outer periphery is deformed into a shape corresponding to a cross section of the rectangular can, and the peripheral length of the can body before and after the deformation is not substantially changed.   The method for forming a rectangular can according to claim 1, wherein at least a cylindrical surface of the cylindrical can is decorated.   When the can bottom outer peripheral portion of the cylindrical can which is to be a straight portion in the can bottom of the rectangular can is moved radially inward, a portion of the can bottom is protruded radially inward. The method for forming a square can according to claim 1 or 2, wherein the step is formed.   A material supply part is formed in a part of the bottom of the cylindrical can which is to be a corner at the bottom of the square can, and the square shape is pressed while pressing the material supply part by a crushing means inserted into the can. The method for forming a rectangular can according to any one of claims 1 to 3, wherein the outer periphery of the bottom of the cylindrical can which is to become a corner portion at the bottom of the can is moved radially outward.   The straight part forming by means for moving the outer peripheral part of the cylindrical can bottom in the radial direction and the corner part forming by means for moving the outer peripheral part of the cylindrical can radially outward are performed in the same process. The method for forming a square can according to any one of claims 1 to 4.   The method for forming a rectangular can according to any one of claims 1 to 5, wherein means for moving the outer peripheral portion of the bottom of the cylindrical can radially inward is performed by a pressing tool.   The method for forming a rectangular can according to claim 6, wherein an emboss is formed on a side wall of the rectangular can by the pressing tool and a shaft inserted into the can.