JPH11226684A - Can body forming method, and its forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pointed rim part on a can bottom without possible generation of wrinkles or cracks to prevent generation of the bottom growth. SOLUTION: Bottom parts 22 (22a-22c) of a cut 21 are held by a punch having a ring-shaped recessed groove on the tip and a receiving die having a ring- shaped projection on the tip which can be fitted to a groove when the cup is formed out of a stock plate by a drawing apparatus. A projecting annular part 51 projecting inward in the axial direction of the cup is formed wider than a tip part 33a of a punch sleeve 33 on a punch sleeve abutting part 53 on which the punch sleeve 33 is abutted on a bottom part of the cup 21, and a pre-dome part 52 expanded inwardly in the radial direction and outwardly in the axial direction of the projecting annular part 51 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a can body, and more particularly to a method and an apparatus for forming a can body effective for forming a sharp rim portion on the bottom of a can. .

[0002]

2. Description of the Related Art Conventionally, as a can used for a beverage can or the like, a two-piece can made of an aluminum alloy having a can lid fixed to an opening of a can body formed into a bottomed cylindrical shape is known. ing. When manufacturing the can body used for the two-piece can, first, an aluminum alloy base plate is punched using a drawing device.
By drawing, a cup 1 as shown in FIG. 6A is formed.

Next, a cylindrical cup holder is inserted into the inside of the cup 1, a punch sleeve is inserted while holding the cup, re-drawing and ironing are performed, and the punch sleeve is coaxially opposed to the punch sleeve. 6B is manufactured by squeezing the peripheral edge of the bottom portion 1a while sandwiching the bottom portion 1a of the cup 1 between the dome shaped portion having a spherical tip at the front end.

As shown in FIG. 6 (b), a dome portion 3a which is spherically recessed inside the can body 2 is provided on the can bottom 3 of the can body 2.
A ring-shaped rim portion 3b connected to the periphery of the dome portion 3a and protruding outward; and a can body 2 from the rim portion 3b.
And a cone cap part 3c connected to the cylindrical part 4 is formed. The rim portion 3b is a portion serving as a leg that contacts the ground when the can body 2 is upright, and is for improving the upright stability and support strength of the can body 2.

[0005]

In recent years, the thickness of cans has been reduced from the viewpoint of resource saving and cost reduction. However, with the reduction in thickness, the strength of the can has been reduced and various problems have arisen. ing. One of them is a so-called bottom growth in which a rim portion 3b formed on the can bottom 3 is deformed so as to protrude outward in the axial direction of the can by the action of internal pressure after the contents are enclosed.

[0006] If bottom growth occurs, the height of the can becomes high, and there is a problem that the can is caught on a conveyor before the product is shipped. Therefore, conventionally, after forming the rim 3b, the rim 3b is formed into a pointed shape. Although the strength is increased so as not to cause bottom growth by performing a reforming step of re-forming, there is a problem of a decrease in productivity due to an increase in man-hours.

On the other hand, when the bottom 1a of the cup 1 is formed with a pointed rim 3b in order to eliminate the reforming step, the tip of the punch sleeve must be pointed. In this case, the can bottom 3 is not bent at the tip of the punch sleeve so as to be in close contact with the inner and outer peripheral surfaces, and a problem occurs that the cone cap portion 3c is wrinkled.

If the tip of the punch sleeve becomes sharp, the tensile stress acting on the punch sleeve contact portion where the tip of the punch sleeve contacts the inner bottom surface of the cup 1 becomes excessive, and the bottom 1a of the cup 1 is cracked. May occur.

The present invention has been made in view of the above circumstances, and a method of forming a can body capable of forming a rim portion formed on a can bottom into a sharpened shape without fear of wrinkles or cracks, and a method of forming the same. It is intended to provide a device.

[0010]

In order to solve the above-mentioned problems and to achieve the above object, a method for forming a can body according to the first aspect comprises forming a bottomed cylindrical cup from a blank by drawing. Inserting a punch sleeve while holding the cup by inserting a cylindrical cup holder into the inside of the cup to perform re-drawing and ironing, and setting the bottom of the cup to a position facing the punch sleeve. A rim portion that is sandwiched between the spherical dome molding portions and protrudes in a ring shape, a dome portion connected to the inside of the rim portion, and a cone cap portion connected to the can body side portion from outside the rim portion. In the method for forming a can body having a can bottom having the following, in forming the cup, a punch sleeve contact portion where the punch sleeve contacts a cup bottom portion in a later step, A convex annular portion that projects a line inward while wider than the tip of the punch sleeve,
A pre-dome portion bulging outward in the axial direction is formed on the radially inner side of the convex ring portion, and the outer circular arc portion of the convex ring portion is bounded by the punch sleeve contact portion as the outer peripheral surface of the tip of the punch sleeve. And bending the pre-dome portion inward in the axial direction while bending the pre-dome portion to form the can bottom.

[0011] Further, according to a second aspect of the present invention, there is provided an apparatus for forming a can body,
A drawing device for forming a cylindrical cup with a bottom from a base plate, and a cylindrical cup holder is inserted into the cup produced by the drawing device, and a punch sleeve is inserted while holding the cup to redraw. And a rim portion which is subjected to ironing and protrudes in a ring shape from the tip of the punch sleeve to the bottom of the can, a dome portion connected to the inside of the rim portion, and a cone connected to the side of the can body from outside the rim portion. In a can body forming apparatus provided with a redrawing and ironing device forming a cape part, the drawing device includes a punch that can move back and forth in the axial direction, and a receiving die that is disposed coaxially and opposed to the punch. And a configuration in which the bottom of the cup can be sandwiched by a punch and a receiving die inserted into the cup, and the tip of the punch is wider than the tip of the punch sleeve. With a ring-shaped groove is formed with, at the tip of the receiving-type, it is characterized in that the fittable ring-shaped projection is formed in the groove.

According to the method and apparatus for forming a can body having the above structure, a sharp rim can be formed on the bottom of the can without fear of wrinkles and cracks as described below.

[0013] First, in the drawing device, the cup bottom is formed by a punch and a receiving die inserted into the cup in the process of drawing the bottomed cylindrical cup from the base plate or after drawing. A convex ring portion that protrudes inward in the axial direction is formed concentrically at a portion that is sandwiched between the ring-shaped concave grooves and projections that can be fitted to each other and that are provided at the tip of the punch and the receiving mold. Is done.

Then, in the re-drawing and ironing device, a cylindrical cup holder is inserted from the opening side of the cup to hold the cup, and a punch sleeve is further inserted into the cup. The tip is brought into contact with the tip of the convex ring at the bottom of the cup.

When the punch sleeve is further moved forward, the outer circular arc portion of the convex ring portion extends along the outer peripheral end of the punch sleeve forming a concave circular arc surface at the boundary of the punch sleeve contact portion with the punch sleeve. Since it is folded so as to be in close contact, the occurrence of wrinkles in the cone cape portion is effectively suppressed.

Further, since a pre-dome portion bulging outward in the axial direction is formed radially inward of the convex ring portion at the bottom of the cup, an area (hereinafter, referred to as a radially inner portion) of the punch sleeve contact portion is formed. The surface area of the dome formation portion) is increased, and the dome portion swelling margin when forming the dome portion is secured.

Therefore, when the pre-dome portion is reversed and swelled during the formation of the dome portion, the material radially outside the punch sleeve contact portion is prevented from moving inward, and acts on the cup bottom portion. The tensile stress is effectively reduced.

Here, it is preferable that the pre-dome portion is formed so that the surface area of the dome forming portion is equal to the surface area of a portion radially inside the punch sleeve contact portion after the dome portion is formed. .

In this case, the radially outer portion of the bottom portion of the cup is only bent along the outer peripheral surface at the tip end of the punch sleeve, and the dome forming portion on the radially inner side is bordered on the punch sleeve contact portion. Is only swelled upside down, so that the material in the radially outer portion than the punch sleeve contact portion does not move so as to be drawn inward, and the occurrence of cracks can be more effectively prevented. Can be.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a drawing device used in the method for forming a can bottom according to the present embodiment.

As shown in FIG. 1, this drawing device is of a horizontal type and has a blank punch 11 having a circular through hole 11a, a punch 12 which can be fitted into the through hole 11a, Blank holder 1 that is extrapolated to the outer periphery of the blank 12 and that is arranged to face the blank punch 11
3, a receiving die 14 disposed coaxially with the punch 12 and a knockout 15 concentrically disposed on the outer periphery of the receiving die 14.

The punch 12 has a cylindrical shape and can be moved back and forth in the axial direction (horizontal direction). When the punch 12 is moved forward, it penetrates through the through hole 11a of the blank punch 11 and the tip of the receiving die 14 To come into contact with. In addition, a ring-shaped concave groove 1 having a wider groove width than a cylindrical punch sleeve, which will be described later, is provided at the tip of the punch 12.
2a is formed.

As shown in FIG. 2, the distance between the tip of the receiving die 14 and the side surface 16a of the base 16 supporting the blank punch 11 on the side of the cup outlet is as shown in FIG. Are arranged so as to be larger than the height by a predetermined amount.

The receiving die 14 can be slightly moved back and forth to absorb shock. When the punch 12 moves forward and reaches its bottom dead center, the punch 12 and the receiving die are moved. 14 can be held between the cup 21. Further, a ring-shaped projection 14a that can be fitted into a concave groove 12a formed at the tip of the punch 12 is provided at the tip of the receiving die 14.

On the other hand, the knockout 15 can be moved back and forth in the axial direction (horizontal direction), and the tip of the knockout 15 is substantially flush with the flat portion 14A of the tip of the receiving die 14. Extrapolated, the bottom dead center during the forward movement is
The amount by which the knockout 15 projects from the flat portion 14A of the receiving mold 14 is set to be smaller than the predetermined amount.

Next, after redrawing and ironing the cup 21 produced by the above-mentioned drawing device, the bottom of the can body is formed, thereby forming an axial direction as shown on the right side of the center line in FIG. A rim portion 22a projecting outward in a ring shape, a dome portion 22b extending radially inward from the tip of the rim portion 22a, and a cone cap portion 22c extending from the tip end of the rim portion 22a to the can body side surface portion 23 The redrawing / ironing device for forming the above will be described.

As shown in FIG. 4, the redrawing / ironing device is of a horizontal type similarly to the above-described drawing device, and includes a redrawing / ironing portion A for performing redrawing / ironing on the cup 21; And a bottom forming part B for forming the bottom of the can body formed by the redrawing and ironing.

The redrawing / ironing portion A includes a redrawing die 3 having a circular through hole 31a as shown in FIG.
1 and circular through-holes 32aa, 32b which are coaxially arranged with the re-drawing die 31 at a predetermined interval and are respectively circular.
a, 32ca having a plurality of ironing dies 32a, 32ca
b, 32c and the through holes 31a, 32a of the redrawing die 31 and the ironing dies 32a, 32b, 32c.
a, a punch sleeve 3 that can be fitted to 32ba, 32ca
3 and a cup holder 34 which is extrapolated around the outer periphery of the punch sleeve 33 and is arranged to face the re-drawing die 31.

As shown in FIG. 5, the punch sleeve 33 has a cylindrical shape having a tapered tip portion 33a whose diameter gradually decreases toward the tip end surface, and is movable in the axial direction until reaching the bottom forming portion B. Have been.

On the other hand, as shown in FIG. 4, the bottom forming part B has a dome forming part 4 disposed on the same axis as the punch sleeve 33 behind the redrawing / ironing part A.
1, outer ring 42 and stopper ring 43
And a punch sleeve 33 into which the ironing die 32c is inserted.

The dome forming portion 41 is provided with a spacer 41b at the tip of a substantially cylindrical base form shank holder 41a.
, A base foam plug 41c having a spherical tip at the top is provided, and the base foam plug 41c is inserted into the punch sleeve 33 when the punch sleeve 33 approaches and moves. The outer ring 42 and the cylindrical stopper ring 43 are arranged concentrically on the outer periphery of the dome forming portion 41.

The distal end of the outer ring 42 is formed in a convex arcuate shape whose inner diameter decreases toward the forward direction of the punch sleeve 33 so as to fit with the distal end 33a of the punch sleeve 33. In addition, a step portion 42 a protruding radially inward is provided on the inner peripheral surface of the outer ring 42.
The step portion 42a is adapted to engage with a flange 43a provided on the stopper ring 43.

The outer ring 42 and the stopper ring 43 are connected to a rear surface of the flange 43a and a spring retainer 4 disposed rearward of the outer ring 42.
4, the coil spring 45 can be moved backward with respect to the dome forming portion 41.

In this embodiment, a forming device for a can body is constituted by the drawing device and the redrawing / ironing device having the above-mentioned structure. Next, an operation when a can body is manufactured using this molding apparatus will be described.

First, a blank (not shown) is inserted into a blank punch 1.
1 and the blank holder 13, cut the blank into predetermined dimensions with a cutter (not shown), and move the punch 12 forward in the axial direction (rightward in the figure).
(See FIG. 1). The cut base plate is formed into a flat-bottomed cup when it passes through the through hole 11a of the blank punch 11.

When the punch 12 is further moved forward, the flat bottom cup is pressed against the receiving mold 14 (see FIG. 2). At this time, the bottom of the flat-bottomed cup is recessed toward the inside of the flat-bottomed cup by a ring-shaped projection 14a formed at the tip of the receiving mold 14, and a ring-shaped groove formed at the tip of the punch 12. 12a is pressed against the inner wall surface.

As a result, the convex ring portion 5 protrudes inward in the axial direction and is wider than the tip portion 33a of the punch sleeve 33.
A cup 2 having a bottom and a pre-dome 52 bulging outward in the axial direction on the radially inner side of the convex ring 51.
1 is formed.

Next, the punch 12 is moved backward, and the cup 21 is dropped on a belt conveyor (not shown) disposed below the squeezing device, and is conveyed to the re-squeezing / ironing device.

When the punch 12 is retracted, an ejector pin (not shown) is provided near the exit of the through hole 16b in the base 16 so as to be able to protrude and retract.
, And air is blown out from an air flow hole 12 a provided inside the punch 12.

As a result, the punch 12 comes out of the cup 21 when the ejector pin hits the opening end 21a of the cup 21, and the cup is urged toward the receiving mold 14 by air.
And falls onto the conveyor without fail.

In the present embodiment, as shown in FIG. 3, when the cup 21 does not separate from the receiving die 14 side, the knockout 15 is operated, and the knockout 1
The cup 21 can be dropped by piercing the peripheral edge 21b at the bottom of the cup 21 with 5.

When the cup 21 produced by the drawing device is carried into the redrawing / ironing device by the conveyor, first, in the redrawing / ironing portion A, the cup 21 is held by a holder (not shown). Redrawing die 3
1, the punch sleeve 33 and the cup holder 34 are inserted into the cup 21 (see FIG. 4).

Next, when the punch sleeve 33 is actuated and moved forward, the front end portion 33a comes into contact with the front end of the convex ring portion 51 formed on the bottom of the cup 21 (see FIG. 5). Hereinafter, the contact portion between the convex ring portion 51 and the tip portion 33a of the punch sleeve 33 is referred to as a punch sleeve contact portion 53.

When the punch sleeve 33 is further moved forward from this state, the bottom peripheral edge 22A of the cup 21 is pinched by the cup holder 34 and the re-drawing die 31, while the convex ring 51 is bounded by the punch sleeve contact portion 53.
Is deformed so as to be bent toward the outer peripheral surface 33ab of the tip end of the punch sleeve 33.

At this time, the outer circular arc portion 51a of the convex ring portion 51
Has a convex arcuate surface bulging into the inside of the cup 21 and, conversely, is deformed while closely adhering along the outer peripheral surface 33ab of the tip of the punch sleeve 33 forming a concave arcuate surface. The generation of wrinkles in the portion 22c is effectively prevented.

Subsequently, when the punch sleeve 33 is moved forward to the left as shown in FIG.
Through the through hole 31a, and re-drawing is performed. At this time, the thickness of the side portion of the cup 21 hardly changes,
Since the diameter of the cup 21 is reduced, the height of the cup 21 is increased.

Further, the cup 21 is repeatedly passed through a plurality of ironing dies 32a, 32b, and 32c disposed at the rear, thereby repeatedly being ironed. At this time, the diameter of the cup 21 hardly changes, but since the thickness of the side portion gradually decreases, the height of the cup 21 gradually increases, and a tall can body is manufactured.

The bottom of the can body thus formed is subsequently formed in a bottom forming section B provided behind the re-drawing and ironing section A. In the bottom forming portion B, first, the can body is supported in front of the outer ring 42 by a holder (not shown), and the punch sleeve 33 having the ironing die 32c inserted therein is inserted into the can body.

When the punch sleeve 33 further moves forward from this state, the pre-dome portion 52 at the bottom of the can body is pressed against the spherical surface of the base foam plug 41c of the dome forming portion 41 and bulges inward along the spherical surface. As a result, a dome portion 22b is formed on the bottom of the can and concaved in a concave spherical shape toward the inside in the axial direction (see FIG. 5).

At this time, the area radially inward of the punch sleeve contacting portion 53 where the dome portion 22b is to be formed finally, that is, the surface area of the dome forming portion is shifted outward in the axial direction during the drawing. Inflatable pre-dome part 52
Is increased by being formed in advance, so that when forming the dome portion 22b, it is suppressed that the material in the radially outer portion than the punch sleeve contact portion 53 is drawn inward, and the material is suppressed from moving. The tensile stress acting on the bottom of the can body is effectively reduced.

At the time of drawing, the pre-dome portion 52 is formed so that the surface area of the dome forming portion is equal to the surface area of the portion radially inside the punch sleeve contact portion 53 after the dome portion is formed. Preferably.

In this case, the punch sleeve contact portion 53
From the boundary, the outer portion in the radial direction of the bottom of the cup is only bent along the outer peripheral surface 33ab of the tip of the punch sleeve 33, and the dome forming portion on the inner side in the radial direction is only reversed and swelled. The material in a portion radially outside the punch sleeve contact portion 53 does not move so as to be drawn inward. For this reason,
A can body having a sharp rim portion 22a at the bottom of the can can be manufactured without causing cracks in the punch sleeve contact portion 53.

In the present embodiment, in order to form the pre-dome portion 52 having such a structure on the bottom portion 22 of the cup 21, the ring-shaped concave groove 12a formed at the tip of the punch 12 by exchanging the inserts 61 and 62 and What is necessary is just to change the dimension of the projection 14a formed at the front end of the receiving die 14.

Further, in this embodiment, the squeezing device and the re-drawing / ironing device have both been described as being of the horizontal type, but are not limited thereto, and may be of the vertical type.

[0055]

As is clear from the above description, according to the present invention, the following effects can be obtained. (A) In the method for forming a can body according to the first aspect, the outer circular arc portion of the convex ring portion formed in advance at the time of forming the cup includes:
Since the punch sleeve is bent so as to be in close contact with the outer peripheral surface at the tip end of the punch sleeve forming a concave arc surface with the punch sleeve contact portion as a boundary, it is possible to effectively suppress the occurrence of wrinkles in the cone cape portion.

(B) Further, the pre-dome portion formed in advance at the time of forming the cup increases the surface area of the portion (dome forming portion) in the radial direction from the punch sleeve contact portion, so that the dome portion is formed. Since the dome portion swelling margin is ensured, when the pre-dome portion is reversed and swelled at the time of forming the dome portion, it is suppressed that the material radially outside the punch sleeve contact portion is drawn inward. ,
The tensile stress acting on the bottom of the cup is effectively reduced.

(C) Particularly, when forming the cup, the pre-dome portion is formed so that the surface area of the dome forming portion is equal to the surface area of the portion radially inside the punch sleeve contact portion after the dome portion forming. With respect to the punch sleeve contact portion, the radially outer portion of the cup bottom can only be bent along the outer peripheral surface of the tip of the punch sleeve, and the dome forming portion on the radially inner side can only be reversed and expanded. Therefore, the material in the outer portion in the radial direction from the punch sleeve contact portion does not move so as to be drawn inward.

Therefore, without adding a reforming step, it is possible to form a pointed rim portion on the bottom of the can while preventing the generation of wrinkles and cracks, and to manufacture a can body free from the possibility of bottom growth. .

(D) In the apparatus for forming a can body according to the second aspect, a groove which is wider than the tip of the punch sleeve is formed at the tip of the punch, and the recess is fitted to the tip of the receiving die. The simple configuration of possible ring-shaped projections allows the formation of a pointed rim on the bottom of the can without adding wrinkles and cracks, without the need for an additional reforming step, which may cause bottom growth. This makes it possible to produce a can body without any defects.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a bottomed cylindrical cup is molded from a base plate by a can body molding apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a state in which a convex ring portion and a pre-dome portion are formed on the bottom of the cup, following the state of FIG.

FIG. 3 is a longitudinal sectional view showing a state where the punch is pulled out of the cup, following the state of FIG. 2;

FIG. 4 is a longitudinal sectional view showing a state in which redrawing and ironing are being performed on a cup having a convex ring portion and a pre-dome portion formed on a bottom portion.

FIG. 5 is an enlarged view of a main part showing a state where a dome portion is being formed in the redrawing and ironing.

FIG. 6 shows a conventional can body molding method and molding apparatus.
It is a longitudinal cross-sectional view which shows the change of the shape at the time of shape | molding a can body from a cup, (a) is a cup, (b) is a can body.

[Explanation of symbols]

 Reference Signs List 12 punch 12a concave groove 14 receiving mold 14a projection 21 cup 22a rim 22b dome 22c cone cape 33 punch sleeve 33ab distal end outer peripheral surface 34 cup holder 41 dome forming part 51 convex ring part 51a outer arc part 52 predome part 53 punch sleeve Abutment

Claims (2)

[Claims] After forming a cylindrical cup with a bottom from a base plate by drawing, a cylindrical cup holder is inserted into the cup, a punch sleeve is inserted while holding the cup, and redrawing is performed. And ironing,
A rim portion protruding in a ring shape by sandwiching the bottom of the cup between the punch sleeve and a dome-shaped portion having a spherical front end arranged to face the punch sleeve; a dome portion connected to the inside of the rim portion; In a method for forming a can body having a can bottom having a cone cape part continuing from the outside of the can body to the side surface of the can body, when the cup is formed, the punch sleeve abuts on the cup bottom in a subsequent step. In the punch sleeve contact portion, a convex ring portion projecting inward in the axial direction of the cup is formed wider than the distal end portion of the punch sleeve, and a radially inner side of the convex ring portion has an axially outward portion. The pre-dome portion is formed so as to bulge into the outer periphery of the punch sleeve, and the outer arc portion of the convex ring portion is bent along the outer peripheral surface of the tip of the punch sleeve with the punch sleeve contact portion as a boundary. Can body molding method, characterized in that to form the can bottom by reversing bulges inward. 2. A squeezing device for forming a cylindrical cup with a bottom from a base plate, a cylindrical cup holder is inserted into a cup produced by the squeezing device, and a punch sleeve is inserted while holding the cup. And a rim portion protruding in a ring shape from the tip of the punch sleeve to the bottom of the can, a dome portion connected to the inside of the rim portion, and a can body from the outside of the rim portion. In a can body forming device having a re-drawing and ironing device that forms a cone cape portion connected to the side portion, the drawing device includes a punch that can move back and forth in the axial direction,
The punch includes a receiving die coaxially opposed to the punch, and has a configuration in which the bottom of the cup can be clamped by the punch and the receiving die inserted into the cup. A ring-shaped concave groove having a width wider than that of the front end of the receiving die, and a ring-shaped projection that can be fitted into the concave groove is formed at the front end of the receiving die. Molding equipment.