JP2010132355A - Can lid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a can lid of metal cans for drinks which can effectively prevent scores from being accidentally fractured by a buckling phenomenon due to an abnormal increase in inner pressure. <P>SOLUTION: A pair of embossed concavities 20, 20 are installed symmetrically inside each of a third quadrant and a fourth quadrant on the side where an opening piece 8 exists among four fan-shaped realms, a first through the fourth quadrants, separated by a Y-axis that passes through the center of the can lid and the tip end of the opening piece 8 and an X-axis that bisects the Y-axis at right angle and passes through the center, and all of them form a buckling guidance section. By setting the buckling guidance section 20, a large bulged buckling of a mountain shape can be generated in the X-axis direction across both the third quadrant and the fourth quadrant with the realm near the Y-axis at the top. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a can lid applied to a metal can for beverages having a relatively high positive pressure inside such as a beer can or a carbonated beverage can, more specifically, an aluminum (including aluminum alloy) can, a steel can, etc. The present invention relates to improvement of a buckling countermeasure technique that may occur due to an abnormal increase in internal pressure of a push-open type easy-open can lid applied to a metal can.

  Recently, this kind of easy open type can lid is generally made of aluminum, and a winding portion to the can body side is provided on the peripheral edge of the central panel portion through a reinforcing annular groove for reinforcement, A notch annular opening score is formed in the central panel portion, a can opening operation tab is provided at a position corresponding to the opening piece surrounded by the opening score, and the operation end side of this tab is pulled up with a fingertip. Thus, the opening score is cut by the action of the lever, and the opening piece is pushed inward into the can so as to be positioned so as to open the drinking mouth or spout.

  This kind of push-open type can lid is a pull-open because the opening score is relatively deep and the remaining thickness is extremely thin so that the opening operation can be performed reliably and lightly. There is a tendency that the score tends to break unintentionally due to the occurrence of buckling as compared to a can lid of the type.

Here, buckling means that if the internal pressure of the can increases abnormally due to vibration during transportation of the beverage can, inadvertent dropping, or storage in a high-temperature vehicle compartment, etc. When a strong force that pushes up from the outside acts, for example, when the situation greatly exceeds the specified internal pressure value of 539 KPa (5.5 Kgf / cm ² ), the peripheral portion of the can lid is accompanied by a reversal phenomenon of a part of the reinforced annular groove. Slight bulging in the initial stage in the region of the annular groove, which is a phenomenon that bulges upward in a mountain shape, is sometimes referred to as peaking.

  An example of the occurrence state of such a buckling is shown in FIGS. 10 to 12 by taking a conventional can lid (100) of the most general type as an example.

  In these figures, the can lid (100) has a reinforced annular groove (102) having a U-shaped cross section at the periphery of the central panel portion (101), and a tightening portion ( 103) is fastened and fixed to the periphery of the upper end opening of the can body (110) manufactured separately. Further, the central panel portion (101) is provided with a notched annular opening score (105) on one end side thereof in the inner region of the panel recess portion (104) (see FIG. 11) which is slightly recessed. An area surrounded by the score is an opening piece (106) that forms a drinking mouth or spout. Further, an opening tab (107) is mounted and fixed on the panel recess (104) via a rivet (108), and the distal end portion on the pressing action side faces the upper surface of the opening piece (106) on the base side. It is supposed to have been done.

  In such a can lid (100), as shown in FIG. 12 (a), the buckling is part of a peripheral annular groove (102) formed in a U-shape at the lower side. However, as the abnormal internal pressure in the can rises, it appears as a phenomenon that rises greatly upward as shown in FIG.

  The occurrence site of this buckling is originally unspecified and occurs indiscriminately at any position in the circumferential direction of the can lid. For this reason, if the occurrence location occurs in the vicinity region that directly affects the opening score (105), the score (105) is broken by buckling, resulting in fatal damage to the can. In addition, there is a risk of incurring a content ejection accident.

  Therefore, in the past, with the occurrence of buckling unavoidable, in order to minimize such score breakage accidents, the position where buckling occurs is the side on the center panel surface where the opening piece exists. Various improvement proposals as shown in Patent Documents 1 to 4 have been made on the basis of the idea of performing induction control within the opposite semicircular region. In the buckling occurrence state shown in FIGS. 10 and 11, the buckling (B) is generated on one end side of the finger hanging recess (104a) at an obliquely rearward position on the operation end side of the tab (107) by such control. Indicates the state.

Japanese Examined Patent Publication No. 7-98234 Japanese Patent No. 3223453 Japanese Patent No. 2799795 Japanese Patent No. 3796057 Japanese Patent No. 3809190 JP 2006-514595 A

  Each of the above-mentioned Patent Documents 1 to 4 makes it possible to guide and control the initial induction position of buckling in the following first quadrant and / or second quadrant area. That is, the plane of the can lid is divided into four equal parts by a straight line passing through the center and the tip of the opening piece (hereinafter referred to as “Y-axis”) and a straight line passing through the lid center perpendicular to the Y-axis (hereinafter referred to as “X-axis”). The position on the Y axis opposite to the tip of the opening piece is regarded as 12:00 of the watch, and the sector area between 12:00 and 3 o'clock is set as the first quadrant, and from this, in the counterclockwise direction, 9 o'clock and 12 o'clock The second quadrant, the third quadrant between 6 o'clock and 9 o'clock, and the fourth quadrant between 3 o'clock and 6 o'clock, at least the first occurrence of buckling is the first quadrant In the second quadrant, guidance control can be performed.

  By the way, the can lid, which has been most widely used in the past, is formed from the outer wall of the reinforced annular groove (102) at the periphery of the central panel (101) as shown in FIG. The extended chuck wall (109) rises substantially perpendicularly in parallel with the can axis direction, or even if it is inclined, it has a steep inclination angle of less than 15 ° at most. In such a can lid, even if buckling occurs, the deformation due to it ends up locally, and the score does not break unless it directly affects the score. A degree of satisfaction was obtained with the buckling countermeasure techniques such as 1 to 4.

  However, recently, even for the can lid for further cost reduction, further reduction in wall thickness is required, and as a result, measures for strengthening the pressure strength are required. An improved can lid (hereinafter referred to as “panel reduced-diameter can lid”) having a reduced panel diameter, generally referred to as Super End (trademark), as shown in FIG. 6, has been proposed and is practically used. Has reached.

  As shown in FIGS. 13 and 14, the panel-reduced can lid (200) is attached to the chuck from the outer wall of the reinforced annular groove (202), which is also called the countersink at the periphery of the central panel (201). The wall (209) is inclined obliquely upward with a relatively large inclination angle (θ) of 20 ° to 70 °, and in many cases 40 ° to 60 ° with respect to the can axis. In FIG. 14, the chuck wall (209) is shown as a linear inclined shape having a single plane. However, in a panel reduced-diameter can lid of a modified mode, Japanese Patent Application Laid-Open No. 2003-136168. As seen in the official gazette, a chuck wall may be formed in a refraction shape with a gently inclined lower wall portion and a steeply inclined upper wall portion via a hollow-shaped rounded bent portion. Therefore, in the present specification, the term “panel-reduced-type can lid” includes at least the lower wall, as well as the one having the straight chuck wall (209) as described above and the one having the refractive chuck wall. 13 and 14 is used in a concept including all can lids having a chuck wall having a tilt angle in a range of 40 ° to 60 °. In FIGS. (204) is a panel recess, (204a) is a finger-hanging recess, (205) is an opening score, (206) is an opening piece, (207) is a tab, and (208) is a rivet.

  Now, in the case of such a panel reduced-diameter can lid (200), the conventional common-sense buckling measures as described above are practically useless, but rather have harmful effects. A new problem has arisen.

  That is, in the panel diameter-reduced can lid (200), the chuck wall (209) has a gentle inclination. As a result, the blank blank diameter of the Al material for manufacturing the can lid is reduced. While the material can be reduced to save material, the reinforced annular groove (202) and the tightening portion on the periphery of the panel portion (201) in the state of being tightened and attached to the can body (110) as shown in FIG. The wall portion (209a) that is also gently inclined remains between (203). The inclined wall portion (209a) is further superior to the conventional wall-type wall portion as shown in FIG. 12 (a) in terms of pressure resistance against the increase in internal pressure of the can.

  However, once buckling begins to occur beyond the critical pressure resistance, the degree of bulging deformation including the central panel portion (201) becomes significantly large in both deformation speed and size. FIG. 15B schematically shows an example of the mode.

  Thus, in addition to the amount of deformation caused by buckling becoming very large, buckling progresses rapidly, that is, in an extremely explosive manner with a very high deformation rate per hour. In combination with the influence of the impact force at this time, when the buckling generation site is guided and controlled in the area opposite to the opening piece according to the conventional buckling countermeasure, the twisting phenomenon due to buckling The panel part (201) which floated greatly behind the tab while interfering with the operation part of the tab (207) interferes with the operation part of the tab (207), and the opening piece (206) base part as if the tab (207) is slightly twisted up. As a result, there is a risk that unintentional breakage may occur in the opening score (205), particularly in the vicinity of the rivet (208).

  The present invention effectively functions as a countermeasure against buckling even in a panel reduced-diameter can lid having a slowly inclined chuck wall under the background of the prior art as described above, and is fatal as a metal can for beverages and the like. An object of the present invention is to provide a can lid excellent in storage stability in which the occurrence of score breakage as a defect is minimized.

  Note that the present invention does not exclude application to a conventional general-purpose can lid in which the chuck wall rises substantially vertically or has an inclination angle of less than 15 °.

  The present invention provides the following means for solving the above problems.

[1] A winding portion for attachment is provided on the periphery of the central panel portion via a reinforcing annular groove for reinforcement and a chuck wall, and a notched annular opening score is formed in the central panel portion. In a pew open type can lid in which a tab for opening the can is riveted to a position corresponding to the enclosed opening piece,
Of the four fan-shaped regions in the first quadrant to the fourth quadrant defined by the Y axis passing through the center of the can lid and the tip of the opening piece and the X axis passing through the center perpendicular to the Y axis, the side where the opening piece exists In each of the third quadrant and the fourth quadrant, a buckling guiding portion for guiding and controlling a buckling occurrence site is provided in a symmetrical arrangement with the Y axis as the center,
By the arrangement of the buckling guide part, an upward bulging buckling that forms a mountain shape in the X-axis direction straddling the two regions, mainly in the regions of the third and fourth quadrants, can be generated. A can lid characterized by being made.

  [2] The above-mentioned [1], wherein at least the lower wall portion of the chuck wall extending from the upper end of the outer wall of the reinforced annular groove is set to a gentle gradient of 40 ° to 60 ° with respect to the can shaft. Can lid.

  [3] The buckling guide portion is provided in each of the fan-shaped regions in the third and fourth quadrants in which the measurement angle from the center of the can lid is in the range of 40 ° to 70 ° with the Y axis as a reference line. The can lid according to the preceding item [1] or [2], which is formed by a pair of embossed recesses projecting downward.

  [4] The can according to [3], wherein the embossed recess has an oval shape or an oval shape in a plan view, and the long axis direction is arranged in a radial radial direction from the center of the can lid. lid.

  [5] The can lid according to the above [4], wherein the embossed recess has an outer end extending to an upper end of the inner wall of the reinforcing annular groove on the outer peripheral edge of the center panel portion.

  [6] The can lid according to any one of [3] to [5], wherein the embossed recess has a depth of 0.10 to 0.75 mm.

[7] The can lid according to any one of [3] to [6], wherein the embossed recess has an upper surface area of 8.0 to 45.0 mm ² .

  The configuration described in the above item [1] of the present invention tries to guide and control the conventional buckling occurrence site in the region of the first quadrant and / or the second quadrant on the opposite side of the aperture piece, where there is no aperture score. This is exactly the opposite of the idea of guiding to the third and fourth quadrant areas. Nevertheless, the incidence of accidental score breaks due to buckling can be further reduced compared to the case of applying the prior art. The reason for this is that the buckling guides are set in a symmetrical arrangement in the third and fourth quadrants, so that the mode spans both the third and fourth quadrants. In an evenly bulging manner, it is possible to generate a mountain-shaped or hill-shaped curved bulging buckling deformed portion that is gently and gently curved in the X-axis direction with the vicinity of the Y-axis as the central apex. In addition, since a large deformation is involved, the deformation speed is relatively slow. As a result, even if an opening score exists in the buckling deformed portion, it is considered that a large shearing force does not act on the score, and the occurrence of score breakage is effectively avoided.

  Such an effect can be enjoyed as being particularly advantageous in the case of the aforementioned panel reduced diameter can lid in which the chuck wall is set to have a large and gently inclined shape. In other words, since a large buckling does not exert an acting force as when the tab is lifted to the operation end side, it is particularly advantageous in the case of a panel reduced diameter can lid as a buckling countermeasure technique. Can be applied to.

  However, even in the case of a conventional general-purpose can lid having a chuck wall substantially vertical or steeply inclined, the bulging deformation mode at the time of buckling is changed to a large curved chevron shape with a good balance between left and right. As a result of control, it is equally effective in preventing score breakage. Therefore, application of the present invention to the conventional can lid is not excluded.

  The configuration according to the above [2] is limited to application to the above-mentioned panel reduced-diameter can lid, and solves the problem of breakage caused by buckling of the panel reduced-diameter can lid, which has been regarded as difficult in the past. In addition, it is possible to provide a panel reduced-diameter can lid that is excellent in handling safety and storage stability while reducing costs by reducing the thickness and reducing the diameter.

  In the previous item [3], the buckling guiding portion is formed by engraving an embossed concave portion projecting downward. Originally, the buckling induction part is formed in a weakened part where the pressure resistance strength of the part is lower than other parts, or conversely, other parts other than the buckling induction part are relatively excellent in pressure resistance By forming the portion, it can be formed by any one of the methods described above. For specific means for forming such weakened or strengthened portions, for example, as described in Patent Document 3, the groove portion is formed by coining or scoring, instead of the groove portion. Various known means such as formation of a recess by embossing, formation of a dimple, formation of a bead, deformation of the cross-sectional shape of the inner or outer wall of the reinforced annular groove, and thinning of the groove bottom can be employed.

  Among these known means, in the case of adopting the means by forming the embossed recess as in the invention of the above item [3], in addition to the merit of easy processing, the position control of the buckling occurrence starting point is possible. This is advantageous in terms of certainty, shape control of the buckling deformation mode to a preferred chevron shape, and the like.

  The position of the embossed recess is set in each region of the third quadrant and the fourth quadrant in the range of 40 ° to 70 ° from the center of the can lid with the Y axis as a reference line. The buckling deformation that occurs from the part as the induction point or the starting point often appears in a mountain-shaped deformation manner with the Y axis line in the center as a central part in a balanced manner on the left and right, and can achieve the effect of reliably preventing score breakage. The most preferable angle range is 50 ° to 60 °.

  In addition, as described in the above item [4], when the embossed recess is an oval or an ellipse and the major axis direction is arranged in the radial radial direction of the panel portion, The buckling deformation can be reliably controlled to the most suitable region and form.

  Further, when the outer end of the embossed recess extends to the upper end of the inner wall of the reinforced annular groove as in the above item [5], as a result of confirmation by many experiments, the best bulging mountain shape mode Thus, buckling can be generated, and the above effect can be achieved more reliably.

Furthermore, as described in the above item [6], the depth of the embossed recess is set to 0.10 to 0.75 mm, and the upper surface area is set to 8.0 to 8.0 as described in the item [7]. By setting in the range of 45.0 mm ² , the above effect can be achieved even more reliably.

It is a top view of the can lid which shows suitable embodiment of the present invention. FIG. 2 is a cross-sectional view omitting an intermediate part taken along line II-II in FIG. 1. It is a perspective view which shows a state when buckling arises in the can lid | cover of FIG. It is sectional drawing of the IV-IV line of FIG. It is sectional drawing of the VV line of FIG. It is a partial top view of the can lid | cover which shows the modification of the shape of the embossing recessed part formed by application of this invention. It is sectional drawing of the VII-VII line of FIG. It is a partial top view of the can lid which shows the modification of the arrangement | positioning aspect of the embossing recessed part formed by application of this invention. It is sectional drawing of the IX-IX line of FIG. It is a perspective view which shows one typical deformation | transformation state when buckling generate | occur | produces in the conventional general purpose type can lid. FIG. 11 is a plan view of a can lid that produces the buckling of FIG. 10. FIG. 11 is a cross-sectional view taken along the line AA in FIG. 10, where (A) shows a state before occurrence of buckling and (B) shows a state after occurrence of buckling. It is a top view of the panel diameter reduction type can lid conventionally well-known. It is sectional drawing of the BB line of FIG. FIG. 14 is a cross-sectional view of a peripheral portion in a state where the can lid of FIG. 13 is wound and attached to the can body, where (a) shows a state before occurrence of buckling and (b) shows a state after occurrence of buckling.

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

  1 and 2 show a preferred embodiment of a panel reduced-diameter aluminum can lid to which the present invention can be most usefully applied.

1-2, the can lid (1) is a push-open type easy-open can lid, and a reinforcing reinforcing annular groove (3), also called a counter sink, is provided at 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 an inclination angle connected to the lower wall portion (4a) having a gentle inclination with an inclination angle (θ ₁ ) of 40 ° to 60 ° with respect to the can axis via a rounded bent portion (4c). (theta ₂₎ is formed on one of the refraction type out with the upper wall portion of the steep slope of less than 1 ° ~40 ° (4b). The upper wall portion (4b) having a relatively small inclination angle is provided in order to improve the ease and certainty of the can lid fastening operation.

  From the upper end of the chuck wall (4), a flange portion (5) constituting a winding tightening portion is further extended. On the other hand, a shallow concave panel recess portion (6) is formed in the central panel portion (2) by panel forming in the substantially central region, and a notch annular opening score (7) is formed in the inner region of the one end portion. Is formed. The portion surrounded by the opening score (7) constitutes the opening piece (8), and the opening operation tab (9) is provided in the corresponding arrangement. The tab (9) is fastened by a rivet (10) having an intermediate portion in the length direction protruding from the central panel portion (2), and an end portion (9a) on one side of the pressing action is an opening piece (8). ) Facing the upper surface near the base, and the other end (9b) for operation is arranged facing the finger hook recess (11) provided in the central panel (2).

  The can lid (1) causes the operation end (9b) of the tab (9) to be raised by the fingertip, so that the pressing action side end (9a) has an opening piece (9a) by the action of the lever around the rivet (10). The root part of 8) is strongly pressed to cause the opening score (7) to break starting from the position in the vicinity of the end part (9a). Then, by opening the opening piece (8) as it is in the can direction, the portion surrounded by the score is opened as a spout or drinking mouth.

  The structure and handling specifications of the above can lid are the same as those of a conventionally known panel reduced diameter can lid.

  In the can lid as described above, as a safety measure technique for a buckling phenomenon that occurs in association with an abnormal increase in internal pressure due to the influence of gas from the beverage contained in the can, the starting point of the buckling is used. Controlling to a specific part and controlling the buckling deformation mode to a preferable specific form prevents accidents due to accidental score breaks.

  As a countermeasure technique, a pair of left and right embossed recesses (20) (20) as guidance control means for a buckling occurrence site is provided at a specific position on the center panel (2). The embossed recesses (20) and (20) constitute the “buckle guide part” according to the present invention, and the arrangement, action, and function thereof will be described in detail below.

  First, regarding the arrangement, the entire area of the upper surface of the can lid (1) is, as described above, the Y axis that is a straight line passing through the center of the can lid and the tip of the opening piece (8), and the can lid orthogonal to this. An X-axis line that is a straight line passing through the center is conceptually divided into four fan-shaped areas, and these divided areas are referred to as first to fourth quadrants in the counterclockwise direction.

  Therefore, the pair of left and right embossed recesses (20) and (20) are located in the third and fourth quadrants on the side where the opening piece (8) exists and from the center of the can lid with reference to the Y axis. The measurement angles (α1) and (α2) are provided at positions in the range of 40 ° to 70 °.

  The embossed recesses (20) and (20) are convex downward, and the embossed recesses (20) and (20) themselves function as portions with enhanced pressure resistance, but their peripheral edges. An easily deformable portion in which residual stress is generated in the portion, that is, an easily deformable portion (21) (21) that is likely to be a buckling starting point is formed.

  Therefore, when a buckling test with repeated internal pressure load was performed on a can lid having a pair of embossed recesses (20) and (20) formed on the left and right sides, the buckling is almost always a double embossed recess ( 20) A large chevron of the chuck wall (4) portion in front of the opening piece tip that occurs in the region between the two portions starting from the easily deformable portion (21) (21) that is the peripheral portion on the Y-axis side of (20) 3 to 5, the region near the Y-axis is a slightly flat top portion, and a chevron-shaped bulge-shaped buckling deformation portion in which the chuck wall (4) is mainly curved ( It has been found that M) occurs across both the third and fourth quadrant regions. In most cases, the buckling deformed portion (M) is substantially symmetrical with respect to the Y axis, and in some cases, the buckling deformed portion (M) has a left-right asymmetric shape having a peak portion in the third quadrant or the fourth quadrant. Turned out to be. In any deformation mode, depending on the occurrence of such a buckling deformation portion (M), the region where the opening score (7) exists is greatly deformed both in the Y-axis direction and in the X-axis direction. As a result, it was confirmed that the score (7) was hardly broken due to buckling.

  The reason for the occurrence of such a buckling deformation mode is not clear, but the presence of the panel recess portion (6) has a large resistance to bending in the Y-axis direction, while the finger hook recess (11) and the two embossed recesses ( 20) Considering the flexural deformation strength of each side of the triangle formed by (20), the bottom side is relatively weak compared to the left and right oblique sides receiving the reinforcing action of the panel recess portion (6). This is considered to be because buckling deformation concentrates on the region between the embossed recesses (20) and (20) where the bottom exists, and this portion is greatly deformed.

  In this sense, the region (22) (see FIG. 1) in the vicinity of the outer peripheral edge of the panel (2) between the left and right embossed recesses (20) and (20) can also be referred to as a buckling inducing portion.

  When the embossed recesses (20) and (20) are disposed at a position less than 40 ° with respect to the Y-axis, the embossed recesses (20) and (20) are generated at the buckling inducing portion between the embossed recesses (20) and (20). There is a tendency for the buckling to be a slightly steep mountain shape, resulting in an increased risk of breaking the score (7). On the other hand, when the position is set at a position exceeding 70 °, it tends to be difficult to control the buckling occurrence starting point equally in both the third and fourth quadrants. There is an increased risk of unsettled buckling deformation leading to score rupture.

A preferable setting position of the embossed recesses (20) and (20) is a position of 50 to 60 ° at an angle (α ₁ ) (α ₂ ) from the Y axis.

  Further, according to the preferred embodiment shown in FIGS. 1 and 2, the embossed recesses (20) and (20) are formed in an oval shape in a plan view, and the major axis direction is a radial shape of the can lid (1). It arrange | positions in the aspect matched with the radial line direction. Moreover, the inner one end is close to the outer peripheral edge of the concave panel recess (6), and the outer one end reaches the upper end of the inner side wall (3b) of the reinforced annular groove (3) and crosses it. ing.

  Furthermore, the depth of the embossed recesses (20) and (20) is set in a range of 0.10 to 0.75 mm, preferably 0.30 to 0.65 mm, and more preferably 0.40 to 0.00. The range is set to 60 mm. If this is too shallow, less than 0.10 mm, it is insufficient in terms of the buckling induction control action. On the other hand, if the depth exceeds 0.75 mm, the material may break in the easily deformable portion (21) or the like due to severe processing.

Furthermore, the size of the embossed recesses (20) and (20) is not particularly limited, but is 8.0 to 45.0 mm ^{2 in} the upper surface area, preferably 10 to 30 mm ² , and more preferably 15 to It is desirable to set a range of 25 mm ² . If it is too small, it will be insufficient in terms of buckling inducing action, and if it is too large, it will be difficult to set it to a suitable position on the surface of the central panel part (2) due to area restrictions.

  In the embodiment of FIGS. 1 and 2, an example in which the embossed recesses (20) and (20) are oval as the most preferable shape mode is shown, but it may be oval.

  Moreover, as shown to FIGS. 6-7, you may form in a perfect circular embossed recess (120), and it is good also as what arranges a plurality by arranging in the radial line direction or the circumferential direction of a can lid.

  Furthermore, as shown in FIGS. 8 to 9, in the case of an oval or elliptical embossed recess (220), the major axis direction may be set and arranged in the circumferential direction of the can lid (1). good.

  In any case, it is preferable that the embossed shape does not have a clearance distance between the reinforcing annular groove (3) and the panel recess (6).

  According to the results of many experiments conducted by the present inventors, the most preferable result was obtained as a countermeasure against buckling in the embodiment of the embossed recesses (20) and (20) shown in FIGS.

[Experimental example]
Next, various experimental examples conducted for confirming the effects of the present invention will be described.

[First experiment]
As the can lid material, a push-open type panel reduced-diameter can lid having the following specifications prepared using an aluminum alloy plate material having a thickness of 0.24 mm made of JIS A5182 alloy was used.

Central panel diameter: 47mm
Reinforced annular groove: depth 2.3mm
: Groove bottom radius 0.5mm
Chuck wall tilt angle: Upper wall 28 °
Lower wall 55 °

  And about the said can lid, what formed the embossed recess as a buckling induction | guidance | derivation part in the 3rd and 4th quadrant area | region in the center panel part in various aspects shown in Table 1 (invention), and embossing A non-recessed (comparative) was prepared. Then, using these as samples, the can lids of these various samples were hermetically fixed to the upper end opening edge of a bottomed cylindrical aluminum can body by double winding by a conventional method.

  30 such cans were prepared for each of Experimental Examples 1 to 15, and the pressure-resistant buckling test described later was performed.

[Buckling test]
After cutting the can body part of the lid can of each of the above experimental examples 1 to 15 at the middle part of the height, the upper half body with the lid was used as a specimen, and a pressure tester for metal cans ("WBT-" manufactured by Technonet Co., Ltd.) 500 "), the internal pressure of the can was increased at a rate of 26 KPa / second by water pressure, and the test was terminated when the first buckling occurred and the internal pressure dropped rapidly. And about each sample, two items, "the site | part which generate | occur | produces buckling", and "the presence or absence of score fracture | rupture," were investigated and evaluated on the following reference | standard.

[Buckling occurrence site]
A specimen in which the maximum bulging deformation portion due to buckling is located in the regions of the third and fourth quadrants by visual inspection, and no significant deformation was observed in the regions of the first and second quadrants. The product having a yield of 85% or more was evaluated as ◎, the product from 60 to less than 85% was evaluated as ○, and the product from less than 60% was evaluated as ×.

[Score breakage]
Investigate the occurrence of score breakage for all 30 cans, ◎ indicates that almost 100% of the occurrence was not observed, ◯ mark that some score breakage was seen, most did not occur, Those in which almost all fractures were observed were evaluated with crosses.

  The evaluation results are shown in Table 1.

  As can be seen from the evaluation results in Table 1 above, the can lid to which the present invention is applied has a relatively remarkably high probability that the occurrence of buckling is within the region of the third and fourth quadrants compared to the comparative product. As a result, it was confirmed that it had excellent performance as a buckling countermeasure product with an extremely low score breakage rate.

[Second Experimental Example]
Various panel reduced-diameter can lids of Experimental Examples No. 16 to 24 shown in Table 2 in which the depth and area of the embossed recess were changed to various modes were used. The basic configuration specifications such as the material of the can, the central panel diameter, the reinforcing annular groove, and the chuck wall inclination angle were all the same as those in the first experimental example.

  And the said experiment example No. As in the case of the first experimental example, 16 to 24 can lids were wound and attached to the upper end opening edge of the bottomed cylindrical aluminum can barrel. A test was conducted. The evaluation criteria of the pressure-resistant buckling test were the same as those in the case of the first experimental example, and the evaluation results are also shown in Table 2.

From the evaluation results in Table 2 above, when the depth of the embossed recess is set to 0.30 mm or more and the area on the surface side is set to 13 mm ² or more, the result is particularly suitable as a countermeasure against buckling. Was found to be obtained.

DESCRIPTION OF SYMBOLS 1 ... Can lid 2 ... Central panel part 3 ... Strengthening annular groove 4 ... Chuck wall 4a ... Lower wall part 4b ... Upper wall part 5 ... Flange part 6 ... Panel recess part 7 ... Opening score 8 ... Opening piece 9 ... Tab 10 ... Rivet 20 ... Embossed recess (Buckling guiding part)
21 ... Easy deformation part M ... Buckling deformation part

Claims (1)

A winding tightening portion for attachment is provided on the periphery of the central panel portion via a reinforcing reinforcing annular groove and a chuck wall, and a notched annular opening score is formed in the central panel portion, and is surrounded by the opening score. In the can open type can lid provided with a rivet tab for opening operation at a position corresponding to the opening piece,
Of the four fan-shaped regions in the first quadrant to the fourth quadrant defined by the Y axis passing through the center of the can lid and the tip of the opening piece and the X axis passing through the center perpendicular to the Y axis, the side where the opening piece exists In each of the third quadrant and the fourth quadrant, a buckling guiding portion for guiding and controlling a buckling occurrence site is provided in a symmetrical arrangement with the Y axis as the center,
By the arrangement of the buckling guiding portion, an upward bulging buckling that forms a mountain shape in the X-axis direction straddling the two regions can be generated mainly in the regions of the third and fourth quadrants. A can lid characterized by being made.

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