JP2008254049A - Shell press forming method of can lid, and shell press die used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming means capable of performing the shell press forming for manufacturing a can lid provided with a stepped chuck wall 4 having a lower wall part 4a of a gentle slope and an upper wall part 4b of a steep slope via bent part 4c of an intermediate portion in the height direction with high efficiency without causing any squeezing wrinkle or breakage, by the forming operation of one process. <P>SOLUTION: A press die is used, which has an inner pressure sleeve 22 on a punch unit 20 side for forming a chuck wall 4 as an independent elevating/lowering one to be elastically urged in a constantly downward direction by a cushion means 25. The chuck wall 4 is preliminarily formed on a forming blank 1A with the elastic urging force downward of the inner pressure sleeve 22 being as a punching force. While elastically pressing the formed chuck wall 4 from an upper side by the inner pressure sleeve 22, a strengthened annular groove 3 is formed by deep-draw in a state in which the chuck wall is allowed to function as a wrinkle holder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a can lid mainly applied to metal cans for beverages such as beer cans and carbonated beverage cans, more specifically, mainly applied to metal cans such as aluminum (including aluminum alloys) cans and steel cans. The present invention relates to a shell press molding method for manufacturing a push-open type can lid and a shell press mold used therefor.

  In general, this type of can lid is mostly made of aluminum, and is provided with a tightening portion to the can body side through a reinforcing annular groove for reinforcement at the periphery of the central panel portion, while the central panel portion has a notched annular shape. An opening score is formed, and a tab for opening the can is provided at a position corresponding to the opening piece surrounded by the opening score. The opening score is cut, and the opening piece is pushed inward into the can so as to be positioned so as to open the drinking mouth or spout.

  Recently, one of the most important issues for can manufacturers is the further reduction of material costs, and even thinner cans are required for can lids. As a part of this, it is generally referred to as Super End (trademark) as seen in Patent Documents 1 to 4 below. For example, the panel thickness is reduced from 0.245 mm to 0.240 mm, while the panel thickness is reduced. An improved can lid with a reduced diameter (hereinafter referred to as “panel reduced-diameter can lid”) has been proposed and has come into practical use.

  As this type of panel diameter-reduced can lid, it has been proposed to be provided with a straight slowly inclined chuck wall as shown in Patent Document 1. That is, the area of the center panel region is reduced by making the chuck wall linearly inclined, for example, in the range of 20 to 70 °, particularly 40 to 60 °, which is gentler than before. Although the can lid according to this proposal is effective in that it can save the can lid material, there is a problem with the ability to double-tighten the can body on the can body. That is, in the tightening operation by the double tightening device that is generally used, since the entire chuck wall has a gentle inclination angle until reaching the upper end portion, there is sufficient contact resistance between the chuck wall and the seaming chuck. It is difficult to obtain, and since the gap angle between the seaming chuck and seaming roll is large, the backup during winding is insufficient, and the winding part is easily loosened by the spring back, so that the fastening stability and sealing performance are good. The problem is that some unstable elements remain.

Therefore, as means for solving such problems, improvement proposals as shown in Patent Documents 2 to 4 have been made thereafter. In these improvement proposals, the chuck wall is bent at an intermediate portion in the height direction to form a two-step stepped chuck wall having a steeply inclined upper wall portion and a gently inclined lower wall portion.
Japanese Patent No. 3809190 JP 2003-205940 A JP 2002-178072 A JP 2003-136168 A

  However, a new manufacturing problem has been raised in the can lid formed on such a stepped chuck wall.

  In general, the manufacture of can lids consists of a shell press molding process in which a dish-shaped molded product called a shell is formed from an aluminum strip having a predetermined thickness, and a rivet molding process, a score molding process, a center panel recess, and a finger hook recess. It is manufactured through a conversion press molding process of 8 to 10 processes including a panel foam molding process, a tab attachment process, a lettering molding process, and the like. In the shell press molding process, after punching a circular blank for molding from a strip-shaped aluminum base plate, the blank is mainly subjected to drawing to leave a circular center panel at the center and reinforce the outer periphery. A reinforced annular groove is formed, a chuck wall extends upward from the outer wall thereof, and a molded body in which a seaming panel having an arc-shaped cross section serving as a tightening portion extends from the upper end of the chuck wall. .

  However, when forming a molded body having a stepped chuck wall as described above in this shell press molding process, if the molding is performed by a single press operation in accordance with the conventional drawing press molding method, the chuck wall portion is drawn. Wrinkles and scratches are likely to occur, and conversely, if the wrinkle pressing force at the chuck wall forming portion is increased in order to suppress the generation of wrinkles, the risk of squeezing due to material breakage increases.

  For this reason, as described in Patent Document 3, as a method of shell press molding of a can lid provided with a stepped chuck wall, the drawing process is divided into two times and preformed into a rough shape at the first time. After that, a molding method (see FIGS. 4 and 5 of Patent Document 3) is proposed in which redrawing is added at the second time to finish the shape of the final shell molded body.

  However, when the shell press molding is to be performed in two press steps in this way, in addition to the decrease in productivity due to an increase in the number of man-hours, it is still not possible to wipe out the worries of wrinkles and scratches. A new problem has arisen that requires the preparation of a special shell press suitable for such a two-time press work, making it difficult to use a conventional shell press as it is.

  In the production of a panel reduced-diameter metal can lid having a stepped chuck wall in the background of the prior art as described above, the present invention performs the first shell molding by shell press molding once. A shell press molding method and a shell press molding die used therefor, which can be performed with high efficiency only in the pressing step of the above, while sufficiently suppressing generation of wrinkles and scratches and without causing drawing cracks. The purpose is to provide.

  In the above object, the present invention first presents the following shell press molding methods [1] to [5].

[1] A chuck wall is provided on the outer peripheral edge of the center panel via a reinforced annular groove, and the chuck wall is sharply connected to a lower wall portion having a gentle slope through a bent portion provided at an intermediate portion in the height direction. In a shell press molding method for manufacturing a panel reduced diameter can lid configured as a stepped chuck wall having an inclined upper wall portion,
Using a press die provided with an inner pressure sleeve on the punch unit side for forming the chuck wall as an independently elevating and lowering member that is always elastically biased downward by a cushion means,
After preforming the chuck wall on the molding blank using the elastic biasing force downward of the inner pressure sleeve as a punching force,
A can lid shell press molding method, characterized in that deep drawing press molding of the reinforced annular groove is performed while elastically pressing the molded chuck wall from above with the inner pressure sleeve.

  [2] When press forming of the reinforced annular groove is finished, punching of the punch unit is performed by bringing the upper surface of the inner pressure sleeve into contact with the bottom surface of the punch core or the punch core block for controlling the elevation of the punch core block. 2. The can lid shell press molding method according to item [1], wherein the bottom dead center control for stopping the stroke is performed.

[3] A chuck wall is provided on the outer peripheral edge of the center panel via a reinforced annular groove, and the chuck wall is sharply connected to a lower wall portion having a gentle slope through a bent portion provided at an intermediate portion in the height direction. In a shell press molding method for manufacturing a panel reduced diameter can lid configured as a stepped chuck wall having an inclined upper wall portion,
The fixed-side die unit includes a die core ring having a wall forming surface corresponding to the outer surface shape of the stepped chuck wall, while the movable-side punch unit is a wall corresponding to the inner surface shape of the gently inclined lower wall portion. An inner pressure sleeve having a molding surface and constantly elastically biased downward by the cushion means;
A predetermined portion of the blank punched out from the base plate by the downward movement of the punch unit is elastically squeezed between the wall molding surface of the die core ring and the wall molding surface of the inner pressure sleeve. After preforming the chuck wall,
While this pre-formed chuck wall is maintained in a state where it is elastically crushed with a predetermined wrinkle holding pressure between both the die side and punch side wall forming surfaces, an annular groove forming projecting downward to the outer peripheral edge is formed. The punch core having the convex portion is moved downward, and the reinforced annular groove is formed by allowing the groove-forming convex portion to enter between the die core and the die core ring,
Then, simultaneously with the completion of the formation of the annular groove, the downward step surface for controlling the bottom dead center provided on the punch core block for raising and lowering the punch core is brought into contact with the upper surface of the inner pressure sleeve to lower the punch unit. A method for shell press molding of a can lid, characterized in that dead point control is performed.

  [4] The above [1] to [3], wherein the chuck wall has an inclination angle of 40 to 60 ° with respect to the can axis of the lower wall portion and the inclination angle of the upper wall portion is set to 1 to 39 °. A method for shell press molding of a can lid according to any one of the above.

  [5] The above [3] or [4], wherein the cushion means uses 5 to 7 coil springs having a spring constant of 19.6 to 29.4 N / mm (2.0 to 3.0 kgf / mm). ] The shell press molding method of the can lid as described in.

  In addition, the present invention presents a shell press mold configured as described in the following [6] to [8] as a tool used for carrying out the above shell press molding method.

[6] A chuck wall is provided on the outer peripheral edge of the center panel via a reinforced annular groove, and the chuck wall is rapidly connected to a lower wall portion having a gentle slope through a bent portion provided at an intermediate portion in the height direction. A shell press molding die for manufacturing a panel reduced-diameter can lid, which is configured as a stepped chuck wall having an inclined upper wall portion and further has a seaming panel extending from the outer periphery of the chuck wall. And
It consists of a fixed-side die unit and a movable-side punch unit that moves up and down with respect to this die unit.
The die unit includes a fixed die core disposed in the center, and a fixed die core ring disposed on the outer side through an annular groove forming space.
The die core has a flat panel molding surface corresponding to the lower surface shape of the center panel of the can lid on the upper surface,
The die core ring has a bulging arc-shaped flange molding surface corresponding to the bottom surface shape of the can lid seaming panel on the outer peripheral side of the upper surface, and corresponds to the outer surface shape of the chuck wall of the can lid on the inner peripheral side. While being made to have a wall molding surface
The punch unit has a punch core disposed in the center, an inner pressure sleeve that can be moved up and down independently, and is disposed outside the punch core. The inner pressure sleeve is disposed outside the punch core. The upper pressure sleeve is interposed between the punch core block and the inner pressure sleeve, and the inner pressure sleeve is always elastically biased downward. A plurality of coil springs arranged at equal intervals in the circumferential direction,
The punch core has a panel molding surface corresponding to the upper surface of the center panel of the can lid on the lower surface side, and a reinforced annular groove molding convex portion protruding downward at the peripheral portion,
The inner pressure sleeve has an inclined wall molding surface and a bent portion molding surface corresponding to the outer surface shape of at least the lower wall portion and the bent portion of the chuck wall of the can lid on the lower surface of the outer peripheral edge portion thereof,
The upper pressure sleeve has a concave arc-shaped flange molding surface corresponding to the upper surface of the seaming panel of the can lid on the lower surface,
The punch core block is interlocked with the punch core to integrally move the punch core up and down, and the inner pressure sleeve is relatively raised against the urging force of the coil spring to a predetermined upper limit position. When it reaches, it has a downward step surface for bottom dead center control that contacts the upper surface of the inner pressure sleeve,
In the shell forming process of the can lid, the peripheral edge of the blank was first squeezed between the flange forming surfaces of the die core ring and the upper pressure sleeve with a predetermined pressure with respect to the circular blank punched from the base plate. After that, the stepped chuck wall is formed by the inner pressure sleeve by the elastic biasing force of the coil spring, and then the reinforced annular groove is formed by the annular groove forming convex portion by further lowering the punch core. It is characterized in that the bottom dead center control of the punch block is performed by the downward step surface for controlling the bottom dead center of the punch core block being brought into contact with the upper surface of the inner pressure sleeve at the time of forming the groove. Mold for shell press molding of can lid.

  [7] The coil spring is a compression coil spring having a spring constant of 19.6 to 29.4 N / mm (2.0 to 3.0 kgf / mm), and is disposed between opposing surfaces of the inner pressure sleeve and the punch core block. The mold for shell press molding of the can lid according to the above item [6], wherein 5 to 7 pieces are arranged in the circumferential direction.

  [8] The shell of the can lid according to the above [6] or [7], wherein the coil spring is provided in a spring accommodating recess formed opposite to the upper surface of the inner pressure sleeve and the lower surface of the punch core block. Die for press molding.

  According to the shell press molding method of a can lid as described in the above items [1] to [5] according to the present invention, the molding of the shell molded body can be completed by a single drawing press process. That is, the shell molded body can be completed by only one-step operation of the punch unit. Therefore, in comparison with the conventionally proposed molding method that performs the two-time drawing, productivity can be improved, and the molding die is replaced using a conventionally used shell press machine for can lid production. This is also advantageous in that it can be molded.

  The reason why molding by pressing in such a single step is possible is because the possibility of drawing wrinkles and cracks and further drawing cracks is eliminated. The reason for the elimination is estimated as follows. Is done.

  First, the inner pressure sleeve on the punch unit side for forming the stepped chuck wall portion is elastically urged downward by the cushion means at all times, and this elastic urging force is used as a punching force first. First, a stepped chuck wall portion is preformed. After the molding, the reinforced annular groove portion which is relatively severely drawn is subsequently molded while the chuck wall portion is elastically pressed by the inner pressure sleeve. Therefore, at the time of drawing the annular groove, the wall forming surface of the inner pressure sleeve functions as an elastic wrinkle retainer, and a drawing wrinkle based on the compressive force in the circumferential direction is generated at the chuck wall portion to be formed. To prevent. In addition, at the time of forming the annular groove, the lower wall portion of the chuck wall that is particularly gently inclined is already inclined in the range of 40 to 60 ° with respect to the can shaft. The molding material is fed relatively smoothly with respect to the radial tensile force acting on the portion, and the load applied to the load traction portion in contact with the annular groove forming convex portion is reduced. Therefore, the maximum punching force is reduced, and thus the occurrence of drawing cracks is prevented while the occurrence of drawing cracks is also suppressed.

  In the molding method of the present invention, at the time when the press molding of the reinforced annular groove is finished, the punch core or the punch core block for controlling the elevation of the punch core block is controlled on the upper surface of the inner pressure sleeve. The downward step surface is brought into contact with the punch unit, and the punching process is performed by this contact, that is, the bottom dead center control is performed in which the descending punching stroke is stopped and reversed. Therefore, the mechanical reduction force applied instantaneously to the inner pressure sleeve at the time of contact improves the forming accuracy of the chuck wall, and does not cause excessive forming. It is possible to prevent the strength from being lowered due to.

  Moreover, according to the metal mold | die for shell press as described in said [6]-[8] item which concerns on this invention, the above shaping | molding methods can be performed reliably and the effect similar to them can be enjoyed. .

  Next, a preferred embodiment of the present invention will be described.

  FIG. 1 shows a shell molded body which is an intermediate molded product of an aluminum panel reduced diameter can lid to be manufactured according to the present invention, and shows a preferred embodiment thereof.

As shown in FIG. 1, the shell molded body (1) has a reinforcing reinforced annular groove (3) also called a counter sink on the periphery of the central panel portion (2). A gently inclined chuck wall (4) extends from the upper end of the outer wall (3a) of the annular groove (3). The chuck wall (4) has a slanted lower wall portion (4a) having an inclination angle (θ ₁ ) with respect to the can axis of 40 ° to 60 ° and an inclined portion extending through a rounded bent portion (4c). The angle (θ ₂ ) is formed in a refractive shape with a steep upper wall portion (4b) having a slope of 1 ° to less than 40 °. The upper wall portion (4b) having a relatively small inclination angle with respect to the can axis is provided in order to improve the ease and certainty of the can lid fastening operation. Further, from the upper end of the chuck wall (4), a seaming wall (5) that constitutes a tightening portion for attachment to the can body is extended. In addition, the seaming wall (5) of FIG. 1 is shown in a state in which the flange portion of the shell molded body (1) after shell press molding is subjected to curling and curled.

By the way, when the inclination angle (θ ₁ ) of the lower wall portion (4a) of the chuck wall (4) exceeds the upper limit of 60 °, it is a connection portion with the outer wall (3a) of the annular groove (3). The processing rate of the bent portion (6) increases, and processing embrittlement easily occurs. When the bent portion (6) becomes brittle due to processing, when a buckling occurs in which the upper surface of the can lid bulges due to an abnormal increase in the internal pressure of the can, cracking occurs and the contents are easily ejected. In addition, the area of the center panel (2) becomes excessively small, and the possibility that the opening operation by the tab is hindered increases.

On the other hand, when the inclination angle (θ ₁ ) is less than 40 °, the cost reduction effect due to the saving of the can lid material is small.

A particularly preferable range of the inclination angle (θ ₁ ) of the lower wall portion (4a) is 50 to 55 °. On the other hand, a particularly preferable range of the inclination angle (θ ₂ ) of the upper wall portion (4b) with respect to the can axis is 20 to 30 °.

  The above-mentioned shell reduction body (1) of the panel reduced diameter can lid is formed by a shell press machine using a molding die as shown in FIGS.

  2 to 4, the molding die includes a fixed-side die unit (10) and a movable-side punch unit that is positioned above the die unit (10) and is moved up and down with respect to the die unit. (20).

  The die unit (10) on the lower side of the fixed side includes a fixed die core (11) disposed at the center and a fixed die core ring disposed around the outside via an annular groove forming space (13). (12). And the said die core (11) has the flat panel shaping | molding surface (11a) corresponding to the lower surface shape of the center panel (2) of a shell molded object (1) on the upper surface. The die coring (12) has a bulging arc-shaped flange forming surface (14) corresponding to the shape of the lower surface of the seaming panel (5) of the shell molded body (1) at a position near the outer periphery of the upper surface. The wall forming surface (15) corresponding to the outer surface (lower surface) shape of the chuck wall (4) is provided on the inner peripheral side. The wall forming surface (15) has a gently inclined lower forming surface (15a), a steeply inclined upper forming surface (15b), and a concave bent portion (15c) therebetween.

  The punch unit (20) includes a punch core (21) disposed at the center, and an inner pressure sleeve that can be moved up and down independently and is disposed so as to cover the outer peripheral surface and the upper surface side peripheral portion of the punch core (21). (22), an upper pressure sleeve (23) further disposed on the outer side thereof, a punch core block (24) disposed in a central portion above the punch core (21), the punch core block (24), A plurality of coil springs (25) arranged at equal intervals in the circumferential direction and interposed between the inner pressure sleeve (22) and elastically urging the inner pressure sleeve (22) downward at all times. ).

  The punch core (21) has an annular groove forming convex part (27) protruding downward from the peripheral part.

  The inner pressure sleeve (22) is positioned above the lower molding surface (15a) and the bent portion (15c) of the gentle slope of the wall molding surface (15) of the die core ring (12). An inclined wall molding surface (22a) corresponding to at least the lower wall portion (4a) and the bent portion (4c) of the chuck wall (4) of the molded body (1) is provided on the lower surface of the outer peripheral edge portion. And a bent portion molding surface (22c). In this embodiment, an inclined wall forming surface corresponding to the steeply inclined upper forming surface (15b) of the die core ring (12) is not provided, but the upper pressure sleeve (23) is formed with a slightly thinner width. It is also possible to keep it. The inner pressure sleeve (22) normally stands by with the lower end of the wall forming surface (22a) positioned substantially at the same height as the lower end of the annular groove forming convex portion (27).

  The upper pressure sleeve (23) is disposed so as to be opposed to the flange molding surface (14) of the die core ring (12) and has a seaming panel (1) on the lower surface. It has a concave arcuate flange forming surface (28) corresponding to the upper surface of 5).

The punch core block (24) is interlocked with the punch core so as to be moved up and down integrally with the punch core (21), and the inner pressure sleeve (22) is attached to the coil spring (25). Having a downward bottom dead center control step surface (24a) that comes into contact with the upper surface (22b) of the inner pressure sleeve (22) when it is relatively raised against the force and reaches a predetermined upper limit position; Has been made,
The coil spring (25) is a compression coil spring having a spring constant of 19.6 to 29.4 N / mm (2.0 to 3.0 kgf / mm) for each spring, and the spring is an inner pressure. Each spring receiving recess (29), which is formed between the upper surface of the sleeve (22) and the step surface (24a) of the punch core block (24), is loaded in a slightly compressed state. 5-7 pieces are arranged at equal intervals in the circumferential direction. As a result, the inner pressure sleeve (22), excluding its own weight, is always in the range of 1300-1700N (130kgf-170kgf), preferably 1400-1600N, more preferably about 1500N (150kgf). It is assumed that the elastic urging force below is working.

  In addition, in FIGS. 2-4, (16) shows a cut edge, (26) shows a punch shell, and (1A) shows a circular blank punched from a base plate.

  Next, the shell press molding process of the shell molded body (1) performed using the molding die will be described with reference to FIGS.

FIG. 2 shows an initial state of molding, that is, when the punch unit (20) is lowered, a circular blank (1A) is punched from the base plate with the cut edge (16) and the punch shell (26). The peripheral edge of the shaft is approximately synchronized with the punching, and the axis line is formed between the flange forming surface (14) of the die core ring (12) and the flange forming surface (28) of the lower surface of the upper pressure sleeve (23) by air pressure. It shows a state when it is held at a predetermined pressure in the direction. At this time, the air pressure applied to the upper pressure sleeve (23) side is generally set to about 0.294 to 0.392 MPa (3 to 4 kgf / cm ² ) in order to function as a wrinkle presser. .

  Subsequently, the punch unit (20) is further lowered toward the molding position. FIG. 3 shows the state during the molding.

  As shown in the figure, at first, the inner pressure sleeve (22) and the punch core (21) are lowered synchronously, and their lower ends abut against the upper surface of the blank (1A) almost simultaneously. Further, by further lowering, the wall forming surface (22a) and the bent portion forming surface (22c) on the lower surface of the inner pressure sleeve (22) mainly push down the blank (1A), and eventually the blank (1A) is die-cored. This is elastically pressed against the wall forming surface (15) on the (12) side, and the chuck wall (4) along the wall forming surface (15) is preformed. Since this preforming is performed as a drawing with the urging force of the coil spring (25) as a punching force, it is still guaranteed that the chuck wall (4) with a sufficiently high accuracy is still necessarily formed. Is not to be done.

  Subsequently, the downward movement of the punch core block (24) is continued. However, since the inner pressure sleeve (22) is prevented from further downward movement by the die core ring (12), the inner spring sleeve (22) is kept in a stopped state at that position while causing compression deformation of the coil spring (25). As shown in FIG. 4, only the inner punch core (21) continues to move downward.

  That is, the inner pressure sleeve (22) is relatively lifted relative to the punch core (21), but since the downward biasing force is always acting by the coil spring (25), the blank ( The 1A) side chuck wall (4) molding part is always held in an elastically pressed state from above by the wall molding surface (22a). This pressing force functions as a wrinkle presser that prevents the generation of wrinkles on the chuck wall (4).

  Therefore, the inner groove portion adjacent to the chuck wall (4) is formed between the die core (11) and the die core ring (12) by the annular groove forming convex portion (27) on the lower surface of the outer peripheral edge of the punch core (21). Is pressed toward the annular groove forming space (13) between the two and the reinforced annular groove (3) is drawn.

  When the reinforced annular groove (3) is drawn, a tensile force is applied to the chuck wall (4) portion through a portion (load towing portion) that contacts the top surface of the annular groove forming convex portion (27). In spite of the fact that the chuck wall (4) part is a stepped part of the refracting shape, it is elastically provided by the inner pressure sleeve (22), and further, the lower wall below the intermediate bent part (4c). It is only pressed down by the region extending to the portion (4a), and the steeply inclined upper wall portion (4b) is not subjected to a pressing force, so that the material can be fed relatively smoothly in the radial direction. Is called.

  Accordingly, the punching force required for forming the reinforced annular groove (3) is not increased suddenly, and the material is prevented from being squeezed (load traction or bottom breakage). Moreover, in the chuck wall (4) portion, the lower wall portion (4a) that is particularly prone to compressive strain in the circumferential direction is elastically pressed from above by the wall molding surface (22a) that is an inclined surface. The generation of wrinkles is effectively prevented.

  When the formation of the reinforced annular groove (3) is completed, the punch core block is formed on the upper surface (22b) of the inner pressure sleeve (22) before the coil spring (29) reaches the compression limit as shown in FIG. The downward step surface (24a) for controlling the bottom dead center of the lower surface of (24) is simultaneously brought into contact. And by this contact, the bottom dead center control which stops the downward movement of a punch unit (20) is performed, and a punch unit (20) is immediately turned into an upward movement.

  However, when the upper surface (22b) of the inner pressure sleeve (22) and the step surface (24a) of the punch core block (24) come into contact with each other, the inner pressure sleeve (22) It receives a downward pressing action by contact with the core block (24). For this reason, the preformed chuck wall (3) is momentarily strongly directed toward the wall molding surface (15) side of the die core ring (12) by the wall molding surface (22a) on the lower surface of the inner pressure sleeve (22). Pressed. Therefore, the chuck wall (4) is finally formed into a finish molding state with high accuracy.

  According to the embodiment of the present invention, by performing the molding operation as described above, the panel reduced diameter die having a refraction-type chuck wall in one step by one lifting / lowering operation of the punch unit (20). The shell molded body of the can lid can enjoy the merit of being able to be manufactured with high efficiency without causing cracks, wrinkles and scratches.

  In the above-described embodiment, the shell press molding of the can lid provided with the two-step stepped chuck wall having only one bent portion has been described, but three or more steps of inclination are provided via two or more bent portions. Even in the case of shell press molding of a can lid provided with a wall portion, the present invention can be similarly applied.

It is sectional drawing of the shell molded object of the can lid shape | molded by this invention. It is sectional drawing which shows the initial state of shaping | molding by the metal mold | die of preferable embodiment of this invention. It is sectional drawing which shows the state at the time of the intermediate process of a formation process. It is sectional drawing which shows the state at the time of completion | finish of draw forming of a formation process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shell molded body of can lid 1A ... Circular blank 2 ... Center panel 3 ... Reinforced annular groove 4 ... Chuck wall 4a ... Lower wall part 4b ... Upper wall part 4c ... Bending part 5 ... Seaming panel 10 ... Die unit 11 ... Die core 11a ... Panel forming surface 12 ... Die core ring 13 ... Ring groove forming space 14 ... Flange forming surface 15 ... Chuck wall forming surface 20 ... Punch unit 21 ... Punch core 22 ... Inner pressure sleeve 22a ... Wall forming surface 22b ... Upper surface 22c ... Bending portion molding surface 23 ... Upper pressure sleeve 24 ... Punch core block 25 ... Coil spring (cushion means)
27 ... Convex portion for reinforcing annular groove 28 ... Flange forming surface 29 ... Coil spring accommodating recess

Claims (8)

A chuck wall is provided on the outer peripheral edge of the center panel through a reinforced annular groove, and the chuck wall has a gently sloping lower wall portion and a steeply sloping upper portion through a bent portion provided at an intermediate portion in the height direction. In a shell press molding method for manufacturing a panel reduced diameter can lid configured in a stepped chuck wall having a wall portion,
Using a press die provided with an inner pressure sleeve on the punch unit side for forming the chuck wall as an independently elevating and lowering member that is always elastically biased downward by a cushion means,
After preforming the chuck wall on the molding blank using the elastic biasing force downward of the inner pressure sleeve as a punching force,
A can lid shell press molding method, characterized in that deep drawing press molding of the reinforced annular groove is performed while elastically pressing the molded chuck wall from above with the inner pressure sleeve.   When the reinforced annular groove has been press-molded, the punching stroke of the punch unit is stopped by bringing the bottom surface of the punch core or the punch core block that controls the elevation of the punch core into contact with the upper surface of the inner pressure sleeve. The method of forming a shell press for a can lid according to claim 1, wherein the bottom dead center is controlled. A chuck wall is provided on the outer peripheral edge of the center panel through a reinforced annular groove, and the chuck wall has a gently sloping lower wall portion and a steeply sloping upper portion through a bent portion provided at an intermediate portion in the height direction. In a shell press molding method for manufacturing a panel reduced diameter can lid configured in a stepped chuck wall having a wall portion,
The fixed-side die unit includes a die core ring having a wall forming surface corresponding to the outer surface shape of the stepped chuck wall, while the movable-side punch unit is a wall corresponding to the inner surface shape of the gently inclined lower wall portion. An inner pressure sleeve having a molding surface and constantly elastically biased downward by the cushion means;
A predetermined portion of the blank punched out from the base plate by the downward movement of the punch unit is elastically squeezed between the wall molding surface of the die core ring and the wall molding surface of the inner pressure sleeve. After preforming the chuck wall,
While this pre-formed chuck wall is maintained in a state where it is elastically crushed with a predetermined wrinkle holding pressure between both the die side and punch side wall forming surfaces, an annular groove forming projecting downward to the outer peripheral edge is formed. The punch core having the convex portion is moved downward, and the reinforced annular groove is formed by allowing the groove-forming convex portion to enter between the die core and the die core ring,
Then, simultaneously with the completion of the formation of the annular groove, the downward step surface for controlling the bottom dead center provided on the punch core block for raising and lowering the punch core is brought into contact with the upper surface of the inner pressure sleeve to lower the punch unit. A method for shell press molding of a can lid, characterized in that dead point control is performed.   4. The chuck wall according to claim 1, wherein an inclination angle of the lower wall portion with respect to the can axis is 40 to 60 °, and an inclination angle of the upper wall portion is set to 1 to 39 °. Shell press molding method for can lids.   The can lid according to claim 3 or 4, wherein the cushion means uses 5 to 7 coil springs having a spring constant of 19.6 to 29.4 N / mm (2.0 to 3.0 kgf / mm). Shell press molding method. A chuck wall is provided on the outer peripheral edge of the center panel through a reinforced annular groove, and the chuck wall has a gently sloping lower wall portion and a steeply sloping upper portion through a bent portion provided at an intermediate portion in the height direction. A mold for shell press molding for manufacturing a panel reduced diameter can lid, further comprising a wall portion and a stepped chuck wall having a wall portion and a seaming panel extending from the outer periphery of the chuck wall,
It consists of a fixed-side die unit and a movable-side punch unit that moves up and down with respect to this die unit.
The die unit includes a fixed die core disposed in the center, and a fixed die core ring disposed on the outer side through an annular groove forming space.
The die core has a flat panel molding surface corresponding to the lower surface shape of the center panel of the can lid on the upper surface,
The die core ring has a bulging arc-shaped flange molding surface corresponding to the bottom surface shape of the can lid seaming panel on the outer peripheral side of the upper surface, and corresponds to the outer surface shape of the chuck wall of the can lid on the inner peripheral side. While being made to have a wall molding surface
The punch unit has a punch core disposed in the center, an inner pressure sleeve that can be moved up and down independently, and is disposed outside the punch core. The inner pressure sleeve is disposed outside the punch core. The upper pressure sleeve is interposed between the punch core block and the inner pressure sleeve, and the inner pressure sleeve is always elastically biased downward. A plurality of coil springs arranged at equal intervals in the circumferential direction,
The punch core has a panel molding surface corresponding to the upper surface of the center panel of the can lid on the lower surface side, and a reinforced annular groove molding convex portion protruding downward at the peripheral portion,
The inner pressure sleeve has an inclined wall molding surface and a bent portion molding surface corresponding to the outer surface shape of at least the lower wall portion and the bent portion of the chuck wall of the can lid on the lower surface of the outer peripheral edge portion thereof,
The upper pressure sleeve has a concave arc-shaped flange molding surface corresponding to the upper surface of the seaming panel of the can lid on the lower surface,
The punch core block is interlocked with the punch core to integrally move the punch core up and down, and the inner pressure sleeve is relatively raised against the urging force of the coil spring to reach a predetermined upper limit position. When it reaches, it has a downward step surface for bottom dead center control that contacts the upper surface of the inner pressure sleeve,
In the shell forming process of the can lid, the peripheral edge of the blank was first squeezed between the flange forming surfaces of the die core ring and the upper pressure sleeve with a predetermined pressure with respect to the circular blank punched from the base plate. After that, the stepped chuck wall is formed by the inner pressure sleeve by the elastic biasing force of the coil spring, and then the reinforced annular groove is formed by the annular groove forming convex portion by further lowering the punch core. The bottom dead center control of the punch unit is performed when the downward step surface for controlling the bottom dead center of the punch core block is brought into contact with the upper surface of the inner pressure sleeve when the formation of the groove is completed. Mold for shell press molding of can lid.   The coil spring is a compression coil spring having a spring constant of 19.6 to 29.4 N / mm (2.0 to 3.0 kgf / mm), and is disposed between the opposing surfaces of the inner pressure sleeve and the punch core block in the circumferential direction. 7. A mold for shell press molding of a can lid according to claim 6, wherein 5 to 7 pieces are disposed on the top.   The mold for shell press molding of a can lid according to claim 6 or 7, wherein the coil spring is provided in a spring accommodating recess formed to face the upper surface of the inner pressure sleeve and the lower surface of the punch core block.

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