JP5802452B2 - Manufacturing method of expanded can body - Google Patents

Description

  The present invention relates to a method for manufacturing an expanded can body that obtains a can body that is expanded to a predetermined outer diameter by pressing a cylindrical can body from its inner peripheral surface side.

  When manufacturing a can body such as a beverage can, a method of obtaining a can body having a predetermined outer diameter by expanding a cylindrical can body by pressing it from its inner peripheral surface side is known (for example, the following patents) Reference 1). In this type of method, a plurality of split tools inserted into the can body in a converged state are moved radially outward within the can body, and along the circumferential direction of the can body provided on the outer surface of each split tool. By pressing the inner peripheral surface of the can body outward with a pressing surface that is curved, the outer surface is expanded to a predetermined outer diameter. However, according to this method, since a gap is generated between each split-type tool moved radially, the expanded can body has a streak mark (hereinafter referred to as a spread mark) corresponding to the gap. Arise.

  Therefore, in order to prevent the occurrence of the spread marks and obtain a smooth outer surface can body, the pressing radius is smaller than the circumscribed circle of the pressing surface of each split tool when moved radially. There is known one in which a can body is expanded using a split tool having a surface (see Patent Document 2 below).

Japanese Patent Publication No.54-6987 Japanese Patent Laid-Open No. 10-85874

  However, even if the radius of curvature of the pressing surface of each split mold tool is set as described in Patent Document 2, as long as each split mold tool is moved radially, there is a gap between the split mold tools when pressing the inner surface of the can body. Creates a gap. For this reason, it is not possible to sufficiently suppress the occurrence of expansion marks corresponding to the gaps between the split mold tools in the expansion can body.

  In view of the above points, an object of the present invention is to provide a method for manufacturing an expanded can barrel that can obtain an expanded can barrel having a smooth outer surface using a plurality of split tools.

In order to achieve such an object, the present invention provides a method for manufacturing an expanded can body to obtain an expanded can body for a beverage can by pressing the inner peripheral surface of a cylindrical can body outward. After inserting a plurality of split tools having pressing surfaces that are curved along the circumferential direction of the can body into the can body in a converged state, each split tool is moved radially outward, A first expansion molding step for expanding the can body to a predetermined outer diameter by pressing the inner peripheral surface of the can body with the pressing surface, and an inner periphery of the can body expanded by the first expansion molding step Each of the split molds of the can body formed in the first expansion molding step by rotating the can body or each of the split mold tools in the circumferential direction of the can body after separating the split mold tools from the surface The pressing position changing step of making the pressing surface of the split-type tool face the spread mark corresponding to between the tools, and the pressing position changing step. By moving each split tool radially outward at the position, each expansion mark on the inner peripheral surface of the can body is pressed by the pressing surface of each split tool to expand the can body to a predetermined outer diameter. e Bei and 2 of the expansion molding step, the pressing surface of each of the split tool length corresponding to the circumferential direction of the can body is a can body to a predetermined outer diameter at said first expansion molding step It is larger than the distance between each split tool when it is expanded, and the pressing surface of each split tool is the inner circumference of the can body when its radius of curvature is expanded to a predetermined outer diameter. It is the same as the radius of curvature of the surface, and both side edges in the circumferential direction of the pressing surface of each split tool are chamfered by a curved surface .

  According to the method of the present invention, first, in the first expansion forming step, each split tool is moved radially outward to expand the can body to a predetermined outer diameter. Subsequently, the can body or each split tool is rotated by the pressing position changing step. Thereby, the press position with respect to the internal peripheral surface of the can body by the press surface of each split type tool is changed. Next, in the first expansion molding step, each split tool is moved radially outward to expand the can body to a predetermined outer diameter.

  In the first expansion molding step, the inner peripheral surface of the can body is pressed by the pressing surface of each split tool moved radially outward, so that each split tool generated when spread in the circumferential direction Corresponding to the gaps, streaky spread marks are formed on the can body along both side edges of each pressing surface. In the present invention, by providing the subsequent pressing position changing step and the second expansion molding step, the expansion marks formed by the first expansion molding step can be extended and erased.

  That is, in the pressing position changing step, the pressing surface of each split mold tool is opposed to the expansion mark of the can body, and in this state, the pressing surface of each split tool is the can body in the second expansion forming step. Press the spread mark. At this time, the portion where the expansion mark of the can body is formed is pressed by the pressing surface of each split tool and is stretched in the circumferential direction along the pressing surface. Thereby, the expansion mark of the can body can be extended and an expanded can body having a smooth outer surface can be obtained.

Each of the split mold tools has a length dimension corresponding to the circumferential direction of the can body on the pressing surface of each of the split mold tools when the can body is expanded to a predetermined outer diameter in the first expansion molding step. Since the relative dimension between the can body and the pressing surface of each split tool is relatively small in the pressing position changing step, the pressing surface and the expansion mark are quickly and reliably formed. Can be made to face each other.
In addition, by setting the radius of curvature of the pressing surface of each split tool as in the present invention, it is possible to form an inconspicuous shape in the first expansion molding process, and in the second expansion molding process. The spread marks can be easily extended and erased.
Further, by chamfering the curved side surfaces on both side edges in the circumferential direction on the pressing surface of each of the split mold tools, the spread marks generated in the can body in the first expansion molding process are alleviated from being angular. The spread trace can be formed in an inconspicuous shape, and the spread trace can be easily extended and erased in the second spread molding step.

Moreover, in the said press position change process of this invention, it is preferable to make the expansion mark of the said can body face the center position of the press surface of the said split type tool. In this case, when the pressing surface extends the spread trace, the spread trace can be stretched in a balanced manner toward both sides in the circumferential direction via the spread trace, and the spread trace can be efficiently extended and erased. it can.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory sectional drawing which shows schematic structure of the apparatus used by embodiment of this invention. Explanatory drawing which shows typically the arrangement | sequence state of a split type tool. The perspective view of a split type tool. The perspective view of a columnar member. Explanatory sectional drawing which expands and shows a part of split type tool. The block diagram which shows each process in this embodiment. Explanatory drawing which shows typically the state of the split tool and can body in each process of this embodiment.

  In this embodiment, as shown to Fig.1 (a) and (b), the die apparatus 2 which inserts in the inside of the can body 1 and expands the can body 1 to a predetermined outer diameter is used. As schematically shown in FIGS. 2 (a) and 2 (b), the mold apparatus 2 includes a plurality of (12 in this embodiment) split molds 3 having the same shape and arranged circumferentially. Yes. As shown in FIG. 3, each split tool 3 has a length corresponding to the height dimension of the can body 1, and a pressing surface 4 that is in contact with the inner peripheral surface of the can body 1 is formed on the outer surface thereof. Has been.

  As shown in FIGS. 1A and 1B, a columnar member 5 is provided inside each split tool 3. As shown in FIG. 4, the columnar member 5 has a shape that gradually decreases in diameter toward the lower side, and a tapered surface 6 is formed on the outer periphery thereof. As shown in FIGS. 1A and 1B, an inclined surface 7 corresponding to the tapered surface 6 of the columnar member 5 is formed inside each split tool 3.

  As shown in FIG. 3, the split tool 3 is formed with a groove 8 at its upper end and lower end. As shown in FIGS. 1A and 1B, a ring-shaped spring member 9 is attached to the groove 8. The spring member 9 urges each split tool 3 in a direction to converge.

  The columnar member 5 is moved up and down by a lifting means (not shown). When the columnar member 5 moves downward, the tapered surface 6 moves along the inclined surface 7 of each split tool 3 and moves each split tool 3 outward in the horizontal direction against the bias of the spring member 9. Let Thereby, each split-type tool 3 moves radially outward, and the split-type tools 3 adjacent to each other are spread apart in the circumferential direction as shown in FIG. On the contrary, when the columnar member 5 moves upward, the tapered surface 6 moves along the inclined surface 7 of each split tool 3, and is converged by the biasing of the spring member 9 as shown in FIG. It is said.

  The pressing surface 4 of the split tool 3 is curved into a shape along the circumferential direction of the can body 1, and the length dimension corresponding to the circumferential direction of the can body 1 is in the expanded state shown in FIG. Are formed so as to be larger than the distance between the split tools 3.

  The radius of curvature of the pressing surface 4 of the split tool 3 is formed to the same radius of curvature as the inner peripheral surface of the can body 1 (final shape can body 1) when expanded to a predetermined outer diameter. Furthermore, as shown in FIG. 5, chamfering 10 with curved surfaces is applied to both ends of the pressing surface 4.

  Further, the columnar member 5 is rotationally driven around its axis by a rotational driving means (not shown). Since each split tool 3 is pressed against the outer periphery of the columnar member 5 by the bias of the spring member 9, each split tool 3 also rotates as the columnar member 5 rotates.

  Next, a method for expanding the can body 1 to a predetermined outer diameter using the mold apparatus 2 having the above configuration will be described. In the present embodiment, as shown in FIG. 6, a first expansion molding process 11, a pressing position changing process 12, and a second expansion molding process 13 are sequentially performed on the unprocessed can body 1. By performing, the can body 1 expanded to a predetermined outer diameter is obtained.

  In the first expansion molding step 11, first, as shown in FIGS. 1 (a) and 7 (a), each split tool 3 in a converged state is inserted into the unprocessed can body 1. Next, as shown in FIGS. 1B and 7B, the columnar member 5 is moved downward, and each split tool 3 is moved radially. Thereby, each split-type tool 3 spreads the can body 1 from the inside, and the can body 1 is expanded and formed. The pressing force of each split tool 3 against the can body 1 is set in consideration of the spring back of the can body 1 when the pressing force is released.

  At this time, spread marks 14 are generated in the can body 1 at a position corresponding to the gap between the split tools 3. The spread marks 14 remain on the can body 1 even when the pressing by each split mold tool 3 is released, and the appearance of the can body 1 is deteriorated.

  Therefore, subsequently, a pressing position changing step 12 is performed. In the pressing position changing step 12, first, as shown in FIG. 7C, each split tool 3 is moved in the convergence direction, and the pressing surface 4 is separated from the inner peripheral surface of the can body 1. Next, as shown in FIG. 7D, each split tool 3 is rotationally moved in the circumferential direction of the can body 1. At this time, the split tool 3 is rotated and moved until the spread mark 14 generated in the can body 1 faces the center of the pressing surface 4 of the split tool 3. When the number of the split tool 3 is 12 as in the present embodiment, the split tool 3 may be rotated so that the rotation angle is 15 ° with respect to the can body 1.

  And the 2nd expansion molding process 13 is performed. In the second expansion molding step 13, as shown in FIG. 7D, the pressing surface 4 of the split tool 3 and the expansion trace 14 of the can body 1 face each other in FIG. As shown in FIG. 4, the split mold tools 3 are moved radially, and the can body 1 is expanded by the pressing surface 4 until it reaches a predetermined outer diameter. At this time, the pressing surface 4 expands the can body 1 so as to extend the expansion mark 14, so that the expansion mark 14 is extended and erased by each split tool 3 as shown in FIG. When the pressing is released, the outer surface of the can body 1 is formed smoothly.

  Thereafter, neck-in processing or frenching processing is performed on the end of the can body 1 taken out from the split mold tool 3 in a converged state.

  As described above, the pressing position changing process 12 and the second expansion molding process 13 are provided following the first expansion molding process 11, thereby extending and extinguishing the expansion marks 14 and smoothing the outer surface. An expanded can body 1 can be obtained.

In the present embodiment, the pressing surface 4 of the split tool 3 and the inner peripheral surface of the final shape can body 1 are set to have the same radius of curvature, so that the first expansion forming step 11 performs the expansion. can be formed in a shape which does not stand out traces 14, Ru can erase expanding mark 14 easily extended in a second expansion molding step 13.

Moreover, in this embodiment, what provided the chamfer 10 by the curved surface on the both sides of the press surface 4 of the split-type tool 3 was used . If determined that this chamfered 10 provided in the first expansion molding step 11 can be relaxed to expansion mark 14 is formed by angular, reliably expanded by the second expansion molding step 13 Ru can be made to eliminate the marks 14.

  Further, in the present embodiment, the cylindrical can body 1 having both ends opened for use in a so-called three-piece can body is expanded, but other than that, although not shown, it is used for a so-called two-piece can body. The same can be applied to the bottomed cylindrical can body.

  Further, in the pressing position changing step of the present embodiment, the split tool 3 is rotated with respect to the can body 1, but the can body 1 is rotated in the circumferential direction with respect to the split tool 3. You may do it.

  Moreover, in this embodiment, after the 1st expansion molding process 11, although the press position change process 12 and the 2nd expansion molding process 13 were each performed once, the press position change process 12 is carried out if desired. And the 2nd expansion molding process 13 may be repeated in multiple times.

  DESCRIPTION OF SYMBOLS 1 ... Can barrel, 3 ... Split type tool, 4 ... Pressing surface, 10 ... Chamfering, 11 ... 1st expansion molding process, 12 ... Pressing position change process, 14 ... Expansion trace, 13 ... 2nd expansion Molding process.

Claims (2)

In the manufacturing method of the expanded can body to obtain the can body for the beverage can expanded by pressing the inner peripheral surface of the cylindrical can body outward,
After inserting a plurality of split tools having pressing surfaces that are curved along the circumferential direction of the can body into the can body in a converged state, each split tool is moved radially outward, A first expansion molding step of pressing the inner peripheral surface of the can body with the pressing surface to expand the can body to a predetermined outer diameter;
The can barrel or each split tool is rotated and moved in the circumferential direction of the can body after separating each of the split mold tools from the inner peripheral surface of the can body expanded by the first expansion molding step, A pressing position changing step in which the pressing surface of the split mold tool is opposed to the expansion mark corresponding to each of the split mold tools of the can body formed in the first expanding molding process;
By moving each split mold tool radially outward at the position changed by the pressing position changing step, each expansion mark on the inner peripheral surface of the can barrel is pressed by the press face of each split mold tool. the example Bei a second expansion molding step of expanding to a predetermined outer diameter,
The pressing surface of each split tool has a length dimension corresponding to the circumferential direction of the can body between the split tools when the can body is expanded to a predetermined outer diameter in the first expansion forming step. Is larger than the spacing dimension of
The pressing surface of each of the split tool is the same as the curvature radius of the inner peripheral surface of the can body when the radius of curvature is expanded to a predetermined outer diameter,
The manufacturing method of the expansion can body characterized by the chamfering by the curved surface is given to the both-sides edge of the circumferential direction in the press surface of each said split type tool . The method for manufacturing an expanded can body according to claim 1 , wherein, in the pressing position changing step, an expansion mark of the can body is opposed to a center position of the pressing surface of the split tool .

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