JP4761786B2 - Method of manufacturing tapered can having annular thick part on side wall - Google Patents

Description

The present invention relates to a method for manufacturing a tapered can having an inverted frustoconical side wall formed by drawing and having a diameter of an opening larger than that of a bottom. In particular, taper cans with increased taper strength (inclination angle with respect to the can axis) with increased strength of the side wall of the can body without increasing the overall wall thickness of the side wall, forming wrinkles and cracks, steps on the side wall, etc. The present invention relates to a manufacturing method that can be molded without causing defects.

Beverages and food containers are often different from the place where the container is manufactured and the place where the contents are filled, and it is large to store the container at each stage after the container is manufactured, during transportation and before filling the contents. Space is required. An example of a container that can reduce such storage space is a tapered container. Tapered container has a side wall portion of the inverted truncated cone shape larger than the diameter of the diameter bottom portion of the opening portion side and stacked, because the overlap in so that the container to each other match fit each other, as compared with the cylindrical container , Storage space can be greatly reduced. Further, the tapered container is easy to hold when being held by hand, and is also effective for differentiating products from the difference in the external shape of the cylindrical container.

  As a material for the tapered container having such advantages, resin, paper, and the like are often used, but various methods for manufacturing a tapered can manufactured from a metal plate have been proposed.

  As with other containers, taper cans are also desired to have a thinner can body in order to reduce the weight of the container and reduce material costs. However, the thickness of the material is reduced to ensure the strength required for the container. There is a limit. For tapered cans that have a relatively high can height useful as a beverage container (height dimension is larger than the diameter dimension of the opening), the side wall tends to deform as the can height increases. The strength of the part was required, and it was difficult to reduce the thickness of the side wall part.

  On the other hand, in cans formed by ironing, such as conventional DI cans, as shown in Patent Document 1, the can body side wall is thinned, and the can body is thinned by providing an annular thick portion. However, there is a technique to maintain the strength of the can body part, but such a technique cannot be applied to a tapered can whose side wall part is not cylindrical, and the wall thickness of the side wall part is made uniform by thinning the metal plate used for forming. Therefore, there is a limit to reducing the thickness and weight.

  In addition, such a tapered can having a relatively high can has a side wall formed into a tapered shape by drawing and is manufactured by a manufacturing method as shown in FIG. In this method, a taper can is manufactured by forming a cup having an opening diameter larger than the diameter of the opening of the taper can to be manufactured, and gradually forming the cup into a tapered shape. However, in such a method, the molding height at one time is limited, and the limit is about 15 mm at the maximum in a steel plate having a thickness of about 0.1 to 1 mm generally used for can manufacturing. If it exceeds, it will break. Therefore, as the can height increases, the number of steps has to be increased, and there is a problem that the equipment becomes larger and the manufacturing cost increases. In addition, a lot of drawing marks and wrinkles remain in the tapered portion of the can body, which is not preferable in terms of appearance. Such a problem in appearance appears more markedly as the metal plate becomes thinner.

  As a method for solving this problem, it has been proposed to produce a tapered can by forming a stepped portion on the side wall of the cup and forming the side wall portion having the stepped portion into a tapered shape. According to this method, the number of steps can be reduced, and the drawing marks and wrinkles generated in the tapered portion of the can body can be reduced.

  As an example of a method for forming the side wall portion having such a step portion into a tapered shape, for example, Patent Document 2 can be cited. In Patent Document 2, an intermediate molded body in which a cup body is drawn to form a horizontal stepped portion is formed, and further, pressure is applied to the horizontal stepped portion to perform a squeezing process on the bottom portion. A technique for manufacturing a taper can is described by forming the step part, and forming an intermediate formed body having the step part with a taper-shaped punch and die.

Patent Document 3 describes a method in which a plurality of steps of an intermediate formed body are formed in one step, and the steps of the intermediate formed body are formed using only a punch and a die without using a wrinkle presser.
US Patent 3610018 Japanese Patent Laid-Open No. 1-150418 US Pat. No. 4,263,800

  However, as described in Patent Document 2, when the side wall portion of the intermediate formed body having a horizontal step portion is formed into a taper shape, the horizontal step portion is deformed from a horizontal state to a taper angle α of the final formed body. Therefore, the deformation of the step portion is large, the required molding force is increased, and molding breakage is likely to occur. In addition, when the step is formed into a tapered shape, the deformation is unstable, and when the material is pulled out from the horizontal step and the side wall is formed into a taper while being stretched, irregularities, wrinkles, etc. occur. Therefore, there is a problem that the side wall is not formed into a smooth taper shape. In addition, the material is drawn out from the horizontal step portion, and the side wall portion is formed into a taper shape while being stretched, so that the required molding force increases, so that the wall thickness of the side wall portion becomes substantially constant and the strength of the can is increased on the side wall. An annular thick part cannot be formed.

  In Patent Document 2, when the second step is formed, pressure is applied to the horizontal step, and the bottom step is formed without using a die to form the second step. Therefore, the shape of the second step is likely to vary, and when forming the taper shape, vertical streak-like wrinkles and cracks are generated in the region where the step was formed, or the side wall portion However, the taper is not formed into a smooth taper shape, and a part of the step portion formed before the taper forming remains and causes unevenness or a step on the surface.

  On the other hand, as a function of the taper can, when trying to reduce the storage space by stacking, it is effective even with a small taper angle α of less than 1.5 °, but the larger the taper angle α, the more space saving. Can be planned. In addition, as for ease of holding when holding the can by hand, a small taper angle α of less than 1.5 ° is insufficient to feel that it is easy to hold, and an angle exceeding 1.5 ° is required. . Further, when used for the purpose of differentiating in appearance from a cylindrical can, it is desirable that the taper angle α is larger.

  However, in the invention described in Patent Document 2, as described in the upper right column on page 6, the control of the material is maintained and the generation of wrinkles is avoided by setting the taper angle α to about 1.5 °. is doing. Therefore, when a can with a large taper angle α to be molded according to the present invention, particularly a can with a taper angle α exceeding 1.5 ° is to be molded by the method described in Patent Document 2, control of the material is maintained. There was a problem that vertical wrinkle-like deep wrinkles occurred in the can height direction.

  Further, in the invention of Patent Document 3, since the wrinkle presser is not used, there is a problem that when the taper angle is large, the amount of drawing becomes large and extreme wrinkles are generated in the can after taper molding.

The present invention has been made paying attention to the above technical problem, and the can height dimension is larger than the opening diameter dimension, that is, the ratio of the can height dimension to the opening diameter dimension is 1 or more. In addition, a taper can having a large taper angle α, particularly a so-called metal thin plate that is prone to forming defects, and when forming a taper can having a taper angle α of more than 1.5 °, molding breakage or side wall It is an object of the present invention to provide a method for manufacturing a tapered can that is less likely to cause molding defects such as wrinkles and steps, and that can be formed with few steps even when a tapered can having a large taper angle α is formed.

The present invention, in order to solve the above problems, the invention of claim 1, stamping sheet metal in a substantially disc shape, the circular plate, a cup forming step of forming the bottomed cylindrical cup body, In the taper can manufacturing method, comprising: a step forming step for forming an intermediate formed body having a step portion on a side wall from the cup body; and a taper forming step for forming the side wall portion of the intermediate formed body into a taper shape. In the step forming step, the side wall portion of the cup body is sandwiched between the inclined wrinkle pressing surface of the wrinkle presser and the inclined entrance surface of the die, and the punch is arranged so as to have the same axis as the wrinkle presser and the die. Moves relatively to the die side, abuts against the bottom of the cup body, and pushes the cup body into the die side, thereby reducing the inner diameter of the side wall of the cup body toward the bottom side. Vertical section is inclined An inclined step portion is formed to form the intermediate formed body, and the side wall portion including the inclined step portion of the intermediate formed body is formed into a wrinkle holding member having substantially the same taper angle in the taper forming step. A punch placed between the taper-shaped outer surface and the taper-shaped inner surface of the die and disposed so as to have the same axial center as the crease retainer and the die moves relatively to the die side and contacts the bottom of the intermediate formed body. A method for manufacturing a tapered can, wherein the side wall portion of the intermediate formed body is formed into a tapered shape by contacting and pressing the intermediate formed body toward the die.

Further , the invention according to claim 2 is characterized in that the inclined step portion and the inclined step are formed in a cross section in which the inclined step portion formed in the step forming step includes an axis of symmetry of the bottomed cylindrical cup body. A triangular region virtually formed by being surrounded by a straight line connecting the upper end and the lower end of the side wall portion of the intermediate molded body and the side wall portion excluding the portion is formed on the opening side across the inclined step portion 2. The method of manufacturing a tapered can according to claim 1 , wherein the area of the region is formed so that the area of the region formed on the bottom side is substantially equal.

According to the first aspect of the present invention, even when a tapered can having a large taper angle α is formed, since the step portion formed in the intermediate molded body is inclined, the step portion is horizontal when forming into a tapered shape. Compared with the case of the above, the deformation of the stepped part formed until reaching the tapered side wall of the final product is relatively small, and without forming defects such as wrinkles, cracks and irregularities after taper forming And molding breakage hardly occurs. Also, when forming an intermediate molded body by forming an inclined step portion on the side wall portion of the cup body, the side wall portion is sandwiched by a die and a wrinkle retainer, and the can body is inclined by being pushed into the die side by a punch. Since the step portion is formed, the step size is accurately formed without variation, and when the taper can is formed by taper forming in the subsequent process, the size of the step portion of the intermediate molded product varies. Occurrence of molding defects such as wrinkles and irregularities can be prevented. Further, in the taper forming step, the inclined step portion of the intermediate formed body is sandwiched by a die and a wrinkle presser, and the can body is pushed to the die side by a punch, whereby a tensile force acts on the side wall portion and the side wall portion is stretched. Thus, it is possible to manufacture a tapered can having a good appearance and high quality. Also, in the step forming process, the step portion is drawn while being pinched by a die and a wrinkle retainer, so that the wall thickness of the step portion becomes thick, and a tensile force acts on a substantially vertical side wall portion excluding the step portion. When the side wall is stretched and formed into a taper shape, the region that had formed the step portion before the taper molding is taper-molded with a thick wall to increase the height of the tapered side wall portion. An annular thick part can be formed with a predetermined width in the vertical direction.

According to the invention of claim 2 , in the cross section of the cup body in which the inclined step portion is formed, the side surface portion perpendicular to the inclined step portion, the opening side end point of the side surface portion of the cup body, and the bottom side of the cross section. A substantially triangular region formed by being surrounded by an inclined straight line connecting the points has an area of the region formed on the opening side and an area of the region formed on the bottom side in each step portion. Inclined steps are formed to be equal. Therefore, it is possible to suppress the side wall portion of the intermediate molded body from being excessively compressed toward the center side, to prevent generation of wrinkles, to suppress excessive expansion to the outside of the side wall portion, and to prevent generation of cracks.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a longitudinal cross-sectional shape of a molded body in each molding step of the present invention, and FIG. 2 is a vertical sectional view of an essential part of an example of a step forming apparatus for an intermediate molded body used in the method for manufacturing a tapered can of the present invention. FIG. 3 is an enlarged longitudinal sectional view of a part (a part surrounded by a broken line in FIG. 2) showing a molding state of the molding apparatus shown in FIG. Since the main part of the mold of the molding apparatus is symmetric with respect to the axis of the punch, only one part of the symmetric part is shown in FIG.

  As shown in FIG. 1, in the present invention, first, a cup body Cs (straight can) having a substantially vertical side wall is formed by drawing from a thin metal plate, and is inclined on the side wall of the straight can in the subsequent step forming process. The taper can (Ct) is manufactured by forming the intermediate step (C1, C2), smoothing the step portion in the taper forming step, and forming the side wall portion into a taper shape. .

  A step forming apparatus 11 shown in FIG. 2 includes an annular die 12, a cylindrical wrinkle presser 13, and a columnar punch 14 each having the same central axis as in the conventional drawing apparatus. An inclination angle θ is given to the annular die entrance surface 15 on the front end surface of the die 12 on the wrinkle holding side with respect to the axis a of the punch 14, and the die entrance surface 15 is inclined. The die 12 is movable in the axial direction, descends and comes into contact with the cup body Cs held by the wrinkle presser 13 as shown in FIG. 3 (A), and the wrinkle presser as shown in FIG. 3 (B). A predetermined wrinkle pressing force is applied and pressed between the surface 16 and the outer periphery of the bottom of the cup body Cs.

  A wrinkle pressing surface 16 constituted by a surface that can come into contact with the die entrance surface 15 of the die 12 is provided on the tip end surface of the wrinkle pressing member 13 disposed facing the die 12. The wrinkle holding surface 16 is given the same inclination angle as the die entrance surface 15 and is inclined. The wrinkle presser 13 is movable in the axial direction, and moves with a predetermined wrinkle presser force applied with the outer periphery of the cup body Cs sandwiched between the die entrance surface 15 and the wrinkle presser surface 16. As shown to (B), the step part 1 which inclined in the predetermined position of the cup body Cs is formed. The punch 14 is fixed to the inner side of the wrinkle presser 13 so as to have the same axis, and as shown in FIG. 3B, a cup body is annularly formed between the punch 14 and the inner peripheral edge of the die 12. A slight gap corresponding to the wall thickness of the side wall portion of Cs is formed. Therefore, from the starting position as shown in FIG. 2, as shown in FIG. 3A, the die 12 moves downward during processing and contacts the wrinkle presser 13 via the outer periphery of the bottom of the cup body Cs. Since the die 12 and the wrinkle retainer 13 are moved further downward while the outer periphery of the cup body Cs is sandwiched, the cup body Cs can be drawn so as to form the stepped portion 1. Yes.

  A process for forming an intermediate formed body having an inclined step portion by drawing using such a forming apparatus will be described below. First, a thin metal plate is punched into a substantially disk shape, and the disk is formed by drawing, and if necessary, redrawing or ironing is performed. A cup body Cs having an opening diameter substantially the same as that of the product is formed. The metal plate used in the present invention may be an aluminum or aluminum alloy plate or steel plate that is usually used for can manufacturing, and a laminate plate or a pre-coated plate in which a resin coating layer is formed on one side or both sides may be used. it can.

  In FIG. 1, drawing and redrawing are performed to form a flanged cup body Cs whose side wall portion is substantially vertical. When using a laminated plate or pre-coated plate as the material, the peripheral edge of the plate is not processed by providing the flange 3, so that when the punched plate is drawn, the film on the peripheral edge of the plate Generation | occurrence | production of the small piece of a film which generate | occur | produces when a part of torn, so-called film hair can be prevented. Moreover, since it can be used when extracting the cup body Cs, the intermediate molded body, and the final molded body from the punch or the wrinkle presser, the mechanism of the molding apparatus can be simplified.

  The cup body Cs thus formed is held so as to cover the tip of the wrinkle presser 13 as shown in FIG. Next, when the die 12 is moved to the wrinkle holding 13 side, the tip of the die 12 comes into contact with the outer peripheral portion of the bottom surface of the cup body Cs, and the die entrance surface 15 and the wrinkle holding surface 16 sandwich the cup body Cs therebetween, A predetermined wrinkle holding force is applied. In the case of an aluminum can using an aluminum alloy plate, the wrinkle holding force is preferably 4.5 kN to 10 kN. If the wrinkle holding force is smaller than this range, wrinkles may occur. If the wrinkle holding force is larger than this range, molding breakage may occur at the bottom or side wall of the can.

When the die 12 is further lowered, as shown in FIG. 3B, the tip of the punch comes into contact with the central portion of the bottom of the cup body Cs, so that the cup body Cs is relatively pushed to the die side. While the body Cs is given a tensile force by the tip of the punch, the sliding surface between the die entrance surface 15 and the wrinkle holding surface 16 is subjected to a drawing process while being deformed in an inclined shape, and the inclined step portion 1, step portion is deformed. A first side wall portion 4 ′ that is a large-diameter side wall portion on the opening side from the portion 1 and a second side wall portion 5 ′ that is a small-diameter side wall portion on the bottom side from the step portion 1 are formed. Here, the inclined step portion 1 that is sandwiched between the die entrance surface 15 and the wrinkle holding surface 16 and formed by drawing is a thin-walled side wall that is formed on the intermediate formed body C1 by increasing the wall thickness. The wall thickness of the second side wall portion 5 ′ is thinned because it is stretched by receiving a tensile force. Then, by pressing the die 12 by a predetermined amount, the intermediate formed body C1 having the inclined step portion 1 at a desired position can be formed. Thus the first stepped portion against the intermediate molded body formed in accordance with the shape of such a can height and the taper angle of the taper can be produced ultimately, further subjected to processing, a plurality of stages The intermediate molded body in which the portion is formed can be molded.

  Next, a case where an intermediate formed body having a plurality of steps is formed will be described. FIG. 4 shows a state in which the intermediate molded body C1 formed with the first step is held by the wrinkle retainer 23 of the second step forming device. The second stage step forming device is different from the first step forming apparatus in that the side surface of the wrinkle retainer 23 is held so that the intermediate formed body on which the first step is formed can be held. This is that the portion has a large diameter portion 27 substantially equal to the inner diameter of the large diameter portion of the intermediate molded body and a small diameter portion 28 substantially equal to the inner diameter of the small diameter portion of the intermediate molded body. Due to the shape of the side surface portion of the wrinkle retainer 23, the intermediate molded body C1 can be held and misalignment during molding can be prevented.

  In forming the second stepped portion, it is necessary to hold at least the second side wall portion 5 ′, which is the small diameter portion of the intermediate molded body C <b> 1, with the wrinkle presser 23. The large-diameter portion 27 on the side surface is not directly involved in the molding of the stepped portion, but is for holding the intermediate molded body C1 and making it difficult to cause a positional shift during molding. The large-diameter portion 27 on the side surface does not necessarily have to be held in contact with the inner surface of the first side wall portion 4 ′, which is the large-diameter portion of the intermediate molded body C1.

  About another structure, it is the same as that of the 1st step part forming apparatus. As shown in the portion surrounded by the broken line in FIG. 4, that is, FIGS. 5A and 5B, the intermediate molded body C1 is moved to the second stage by the same operation as the molding of the first stage. An intermediate molded body having two step portions, in which a step portion 2 is formed, a third side wall portion 6 having a smaller diameter than the second side wall portion 5 having the same inner diameter as the second side wall portion 5 ′ of the intermediate molded body C1 is formed. C2 is formed. By repeating such a process, an intermediate formed body having a predetermined number of steps can be formed.

Here, a method for determining the shape of the intermediate molded body (the number of steps, the position in the height direction, and the inclination angle) will be described. The number of steps formed in the intermediate molded body is determined by the shape of the cup body Cs and the final product and the amount of drawing when the intermediate molded body is formed. As shown in FIG. 6, a total drawing amount A (mm), which is a half of the difference between the tapered can opening inner diameter D1 and the tapered can bottom inner diameter D2, is obtained. Then, the maximum value Bmax (mm) of the throttle amount B during the formation of the step portion 1 shown in FIG. 7, the stepped portion number d of the preform is obtained by the following expression. In FIG. 6, α represents a taper angle, and Ht represents a can height.
d = A / Bmax (1)
However, round up after the decimal point.

The maximum value Bmax of the drawing amount is determined by various factors such as the workability of the material, the shape of the molded body, the specifications of the molding apparatus, and the like, but it is preferably in the range of 5.0 mm or less when molding the tapered can. When the maximum value Bmax of the drawing amount exceeds 5.0 mm, the width of the stepped portion is too large, so that unevenness may remain in the tapered final product, and a smooth tapered surface may not be formed. Based on the number of steps of the intermediate molded body thus obtained, the actual drawing amount B in each step is determined. When the stepped portion is formed by drawing, if the drawing amount B is less than 2.5 mm, the width of the wrinkle holding when forming the stepped portion on the intermediate formed body is narrowed, and the wrinkle added per unit area is reduced. There is a risk that the pressing force becomes larger than necessary and the molding breaks. Therefore, in order to avoid this molding fracture, the drawing amount B is determined so as to be within the range of 2.5 mm or more with the maximum drawing value Bmax or less.

  Further, when there are a plurality of step portions, it is preferable to set the aperture amount B of each step portion as uniform as possible. This is because the side surface of the final molded body can be formed into a smooth and good surface when forming into a tapered shape.

  In the present invention, the amount of drawing when the step portion of the intermediate formed body is drawn can be made relatively large. This is because if the stepped portion is inclined, the deformation of the stepped portion when forming the taper shape in the final process is smaller than when the stepped portion is horizontal. This is because molding defects such as wrinkles, cracks, and breakage are unlikely to occur. Here, the shape of the step part of the intermediate molded body is shown in FIG. When the inclination angle θ of each step formed in the intermediate molded bodies C1 and C2 is less than 20 °, the wrinkle pressing force acting in the direction perpendicular to the inclined surface of the step is small, and the tensile force applied to the material is small. Therefore, wrinkles are likely to occur when the step portion of the intermediate formed body is formed. Moreover, when it exceeds 60 degrees, taper shaping | molding is not fully performed but an unevenness | corrugation will remain easily on the taper can side wall of a final molded object. Therefore, the inclination angle θ is preferably 20 ° to 60 °. In addition, an arc portion is formed at the connecting portion between the inclined step portion and the vertical side wall portion, and when the radius of curvature Ra, Rb of the arc of the connecting portion is less than 1 mm, after the taper molding, An annular streak tends to remain, and when it exceeds 5 mm, wrinkles are likely to occur. Therefore, the curvature radii Ra and Rb are preferably 1 mm or more and 5 mm or less.

  Moreover, the determination method of the formation position (height) of the step part in an intermediate molded object is demonstrated using FIG. In the figure, a case where two steps are formed is shown.

  What is indicated by a broken line is a straight line connecting the opening-side end point A and the bottom-side end point B of the side surface portion of the intermediate molded body in the cross-sectional shape of the intermediate molded body, and in determining the formation position of the stepped portion. The area of the region (S2) formed on the upper side (opening side) of each step portion among the substantially triangular regions surrounded by the intersections between the broken line and the step portion and the vertical portion (solid line) of the intermediate molded body (Hereinafter referred to as the upper virtual deformation area) and the area (hereinafter referred to as the lower virtual deformation area) of the region (S1) formed on the lower side (bottom side) of each step portion are substantially equal in each step portion. Thus, the position (height X, Y) for forming the stepped portion is determined. When the lower virtual deformation area S1 is smaller than the upper virtual deformation area S2, the side wall portion of the intermediate molded body is compressed toward the center side when the step portion is formed into a taper shape, and thus wrinkles are likely to occur. Further, when the lower virtual deformation area S1 is larger than the upper virtual deformation area S2, the side wall portion is expanded outward when forming into a taper shape, so that cracks are likely to occur. By determining the shape of the intermediate molded body by such a method, the number of steps of the intermediate molded body is reduced as much as possible while maintaining the moldability when being formed into a tapered can which is the final molded body. Since the number of processes can be reduced, the equipment cost is reduced and the productivity is improved.

  In the next step, taper molding is performed on the intermediate molded body molded in the shape thus determined in a taper shape in the side wall portion of the intermediate molded body C2. FIG. 10 shows the configuration of the taper forming apparatus. The difference from the step forming apparatus for the intermediate formed body C2 is that the entrance surface 35 of the die 32 and the wrinkle holding surface 36 of the wrinkle holding member 33 have substantially the same tapered shape corresponding to the shape of the side wall portion of the final formed body Ct. It is comprised so that it can shape | mold to a taper-shaped side wall on both sides of the side wall part of the intermediate molded object C2.

The process of forming a tapered can with this taper forming apparatus will be described. FIG. 11A, which is a portion surrounded by a broken line in FIG. 10, shows a state in which the intermediate formed body C <b> 2 in which two inclined steps are formed by the wrinkle presser 33 is held by the punch 34 and the wrinkle presser 33. Indicates. The outer diameter of the punch tip is substantially equal to the inner diameter of the lowermost step portion (the portion where the inner diameter is minimum) of the intermediate molded body C2, and the intermediate molded body C2 is held by the punch tip. Next, as shown in FIG. 11 (B), the die 32 descends, comes into contact with the side wall portion of the intermediate molded body C2, and is sandwiched between wrinkle presses, whereby the inclined step portion of the intermediate molded body C2 is formed. The side wall part containing is shape | molded in a taper shape. Furthermore, when the die 32 and the wrinkle presser 33 are lowered while sandwiching the side wall portion, the bottom portion of the intermediate formed body C2 comes into contact with the front end portion of the punch 34, and the entrance surface 35 of the die 32 contacts the wrinkle presser surface 36 of the wrinkle presser 33. The step portion is smoothed while applying a pulling force to the entire side wall portion to prevent the generation of wrinkles, and finally a smooth tapered side wall portion is formed. Here, when the manufactured tapered can is used as a container that is used by manually holding the side wall part, such as a beverage can, the taper angle of the side wall is the same as that of a currently commonly used tapered container. Is preferably 3 ° to 6 °. Thereafter, processing is appropriately performed to produce a final product. The inner surface coating and outer surface printing can be performed on the cup body before taper molding, or can be performed on a disk-shaped metal plate before molding.

  Examples of the present invention will be specifically described below. The tapered can to be prepared is a tapered can having an inner diameter D1 of the opening of 66 mm, an inner diameter D2 of the bottom of 54 mm, a height Ht of the can of 111 mm, and a taper angle α of the side wall of 3 °.

The total amount of drawing A was 6 mm, the amount of drawing B was 3 mm, and an intermediate molded body C2 having two steps was formed, and then the tape was formed. The angles θ of the step portions of the intermediate molded body C2 are both 30 °, and the position in the height direction where the step portions are formed is determined by the above-described method using the lower virtual deformation area S1 and the upper virtual deformation area in each step portion. The lower end of the first stage (opening side upper stage) is 88 mm from the bottom, and the lower end of the second stage (bottom side lower stage) is 48 mm from the bottom so that S2 is substantially equal. Were determined. The first stage S1 is 19.3 mm ^2, S2 is 18.8 mm ^2, and the second stage S1 is 17.3 mm ^2, S2 became 17.5 mm ^2. When the ratio (S1−S2) / S1 of the difference between S1 and S2 with respect to S1 is obtained, they are 2.6% and −1.5%, respectively, and it is determined that S1 and S2 are almost equal in each step. In addition, the height Hd of the stepped portion was about 5.2 mm.

  The material used was a thermochromic polyester resin as a resin for an aluminum alloy plate (3004 alloy tempered H19, plate thickness 0.27 mm) treated with phosphoric acid chromate, and the resin layer thickness was on both sides of the aluminum alloy plate. It is a resin-coated aluminum plate prepared by applying a thermosetting polyester resin with a roll coater so as to have a thickness of 3 μm and setting the baking conditions to a plate temperature of 260 ° C. and a baking time of 20 seconds.

Then, normal butyl stearate as a lubricant was applied to both surfaces of this resin-coated aluminum plate by gravure coating as a coating amount of 100 mg / m ² . The aluminum alloy plate coated with the lubricant is cut into a disk having a diameter of 180 mm, a cup having an inner diameter of 118 mm and a height of about 43 mm is formed by the first drawing, and further, the inner diameter is 90 mm and the height is reduced by the second drawing. A cup having a flange of about 70 mm and a width of 2 mm was molded. Further, the cup was drawn to form a cup body (straight can) Cs having an inner diameter of 66.4 mm and a height of about 100 mm.

  Next, the cup body Cs was formed into a stepped portion to form an intermediate formed body C2 having two inclined stepped portions. The aperture amount B of each step portion was 3 mm, the inclination angle θ of the step portion was 30 °, and the radius of curvature of the arc portion formed at the connecting portion between the inclined step portion and the vertical side wall portion was 3 mm. First, the step portion of the first step is drawn at a drawing ratio of 1.10 so that the height from the bottom of the cup body Cs to the lower end of the step portion is 85 mm and the inner diameter of the small diameter portion is 60 mm. 1 was molded to prepare an intermediate molded body C1. The height to the lower end of the first step of the intermediate formed body C2 formed in the subsequent process is 88 mm, but the lower step is formed by drawing at the time of the subsequent second step. Since the can height increases, the height of the step portion of the intermediate molded body C1 is set to 85 mm in this step. In the next step, the height to the lower end of the second step is set to 48 mm, and the third side wall 6 (the small diameter side wall below the second step) is narrowed so that the inner diameter becomes 54 mm. Drawing was performed at a ratio of 1.11 to form the stepped portion 2 to prepare an intermediate molded body. At this time, the lower part from the second stepped portion was drawn by drawing and the can height was increased, and the lower end of the first stepped step became 88 mm from the bottom.

  Then, the side wall part was shape | molded in the taper shape with the taper shaping | molding body C2 by which the step part was formed in the side wall part 2 steps | paragraphs. The taper angle α of the molded side wall portion was about 3 °, and the height of the can was about 111 mm. Thus, a desired tapered can was formed.

  When a molding test of about 300 cans was performed by such a molding method, a smooth tapered surface was formed on the side wall portion without any defects such as wrinkles and steps. There was no occurrence of defects such as wrinkles, cracks and molding breaks in each step during the molding.

Next, a plurality of cans having different step angles θ of the intermediate molded body C2 were molded under the above conditions, and the respective molded states were visually evaluated and compared. The results are shown in Table 1.

  In Examples 1, 2, and 3, defects such as cans and steps did not occur on the side wall, and a smooth tapered surface was formed. On the other hand, in the comparative example in which the step portion was horizontal, extreme wrinkles and steps were generated, and a product having a quality that could be used as a product could not be molded.

  From the above, even in the case of forming a tapered can having a large taper angle α in a tapered can having a relatively high height (the height is larger than the diameter of the opening), the intermediate formed body C2 is formed. Since the step part is inclined, when the step part is formed into a tapered shape, the deformation of the formed step part until it reaches the tapered side wall of the final product compared to when the step part is horizontal is performed. It is relatively small and can be formed without forming defects such as wrinkles, cracks, and steps after taper forming, and molding breakage hardly occurs. Furthermore, since the shape of the inclined step portion formed in the intermediate formed body C2 is sandwiched and formed by a die and a wrinkle presser, the step portion shape is formed with high accuracy, and the occurrence of molding defects is less in subsequent taper forming. It is possible to produce a tapered can with good appearance and high quality.

  Further, in the cross section of the cup body Cs in which the inclined step portion is formed, an inclined straight line connecting the side surface portion perpendicular to the inclined step portion and the opening end point of the side surface portion of the cup body Cs and the point on the bottom side of the cross section. The substantially triangular region formed by being surrounded is inclined stepwise so that the area of the region formed on the opening side is substantially equal to the area of the region formed on the bottom side in each step part. Part is formed. Therefore, it is possible to suppress the side wall portion of the intermediate molded body C2 from being compressed toward the center side in the taper forming step, to prevent the generation of wrinkles, and to suppress the expansion to the outside of the side wall portion, thereby preventing the occurrence of cracks.

  In addition, about the taper can which performed said shaping | molding, the result of having measured the relationship between the height from a bottom part and wall thickness is shown in FIG. As a result, the region where the step portion was formed before the taper molding, that is, the range from the position of 88 mm from the bottom, which is the height to the lower end of the step portion of the first step of the intermediate molded body C2, to the upper portion of about 10 mm. The wall thickness of the side wall portion is increased in a range from the position of 48 mm, which is the height to the lower end of the second step of the intermediate molded body C2, to the upper portion of about 10 mm. This is because the wall thickness of each step portion of the intermediate molded body C2 is formed to be thick at the time of taper molding, and remains after the taper molding is finished in the thick state. Is formed in a ring shape with a predetermined width in the height direction. In the case of conventional molding, since the side wall portion is formed in a tapered shape while being stretched, the thickness of the central portion is reduced in the height direction, so that the strength of the side wall portion is increased by providing this thick portion. be able to. Therefore, since the strength can be maintained even if the plate thickness is thin, the weight and cost of the can can be reduced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in a step forming apparatus and a taper forming apparatus, a die is fixed, and a punch and a wrinkle retainer are used as shafts. You may shape | mold so that it can move to a direction. Further, in determining the shape of the intermediate molded body C2, the amount of steps may be increased by reducing the drawing amount regardless of the step height determination method employed in the present embodiment. In this case, although the number of steps required for molding the intermediate molded body C2 increases, it prevents the remaining traces or wrinkles from forming on the side wall portion of the tapered can of the final molded body, and has a better appearance and distortion. A smooth taper shape can be formed.

It is a figure which shows the shape of the can of each process in an example of embodiment of this invention. It is a principal part longitudinal cross-sectional view of an example of the step part shaping | molding apparatus of an intermediate molded body which shape | molds the 1st step part to a cup body. It is a partially expanded longitudinal cross-sectional view which shows the shaping | molding state of the step part shaping | molding apparatus of the intermediate molded object shown in FIG. It is a principal part longitudinal cross-sectional view of an example of the step part shaping | molding apparatus of the intermediate molded body which shape | molds the step part of a 2nd step to the intermediate molded body by which the step part of the 1st step was shape | molded. It is a partially expanded longitudinal cross-sectional view which shows the shaping | molding state of the step part shaping | molding apparatus of the intermediate molded object shown in FIG. It is a longitudinal cross-sectional view which shows an example of the shape of the taper can which has the taper-shaped side wall shape | molded by this invention. It is a schematic diagram which shows the state of the step part shaping | molding of an intermediate molded object. It is sectional drawing which shows the shape of the step part of an intermediate molded object. It is a schematic diagram explaining the method of determining the shape and position of a step part from the shape of an intermediate molded object and the taper can of a final product. It is a principal part longitudinal cross-sectional view of an example of the taper shaping | molding apparatus which shape | molds the side wall part of an intermediate molded object in a taper shape. It is a partially expanded longitudinal cross-sectional view which shows the shaping | molding state of the taper shaping | molding apparatus shown in FIG. It is a diagram showing a conventional tapered can manufacturing method. It is a figure which shows the relationship between the height from the bottom part of the shape | molded taper can, and wall thickness.

Explanation of symbols

  Cs: cup body (straight can), C1, C2: intermediate molded body, Ct: final molded body (tapered can), D1: taper can opening inner diameter, D2: taper can bottom inner diameter, α: taper angle, θ: step Inclination angle of the part, Ht: Height of the taper can, Hd: Height of the step part of the intermediate formed body, 1, 2 ... Step part, 3 ... Flange part, 4 ... First side wall part of the intermediate formed body C2, 4 '... 1st side wall part of intermediate molded body C1, 5 ... 2nd side wall part of intermediate molded body C2, 5' ... 2nd side wall part of intermediate molded body C1, 6 ... 3rd side wall part of intermediate molded body C2, 11 , 21 ... Step forming apparatus, 27 ... Wrinkle holding large diameter part of the step forming apparatus, 28 ... Wrinkle holding small diameter part of the step forming apparatus, 31 ... Taper forming apparatus, 12, 22, 32 ... Dies, 13, 23 , 33 ... Wrinkle retainer 14, 24, 34 ... Punch, 15, 5, 35 ... die entrance surface, 16, 26, 36 ... wrinkle pressing surface.

Claims (2)

A metal thin plate is punched into a substantially disk shape, and a cup forming step for forming a bottomed cylindrical cup body from the disk, and a step forming for forming an intermediate formed body having a step portion on the side wall from the cup body. In the method of manufacturing a taper can having a step and a taper forming step of forming the side wall portion of the intermediate formed body into a taper shape,
In the step forming step, the side wall portion of the cup body is sandwiched between the inclined wrinkle pressing surface of the wrinkle presser and the inclined entrance surface of the die, and is arranged so as to have the same axis as the wrinkle presser and the die. The punch moves relatively to the die side, abuts against the bottom of the cup body, and pushes the cup body to the die side, whereby the inner diameter of the cup body decreases toward the bottom side. Forming the intermediate molded body by forming an inclined step having an inclined longitudinal section,
In the taper forming step, the side wall portion including the inclined step portion of the intermediate molded body is sandwiched between the tapered outer surface of the wrinkle presser having substantially the same taper angle and the tapered inner surface of the die, and the wrinkle presser is inserted. And a punch arranged so as to have the same axial center as the die moves relatively to the die side, contacts the bottom of the intermediate molded body, and pushes the intermediate molded body to the die side, thereby A method for manufacturing a tapered can, wherein the side wall portion of the molded body is formed into a tapered shape. In the cross section including the axis of symmetry of the bottomed cylindrical cup body, the inclined step portion formed in the step forming step, the side wall portion excluding the inclined step portion and the inclined step portion, and the intermediate formed body A triangular region that is virtually formed by being surrounded by a straight line connecting the upper end and the lower end of the side surface portion of the side portion is formed on the bottom side with the area of the region formed on the opening side across the inclined stepped portion The method for manufacturing a tapered can according to claim 1, wherein the area of the region to be formed is substantially equal.

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