JP2013079096A - Container made of synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a container made of synthetic resin capable of reliably generating decompression absorbing action by sufficiently deforming a bottom part when the inner pressure becomes a negative pressure.SOLUTION: The container made of the synthetic resin is configured such that a mouth part 3 is disposed on the upper end part of a barrel part 5, and the lower end part of the barrel part 5 is closed by the bottom part 6 integrated with the barrel part 5, wherein the bottom part 6 includes: an outside inclination wall 11 which is continued to the lower end part of the barrel part 5 and is inclined to the center axial line direction of the barrel part 5 toward the lower side of the barrel part 5; a ground part 12 which is a part continuous to the outside inclination wall 11; an inside inclination wall 13 which is inclined to the center axial line direction of the barrel part 5 toward the upper side of the barrel part 5 from the ground part 12; and a bottom plate part 14 which is formed to continue the inside inclination wall 13, is surrounded by the inside inclination wall 13 and closes the bottom part 6. Therein, when the inner pressure is a negative pressure, the bottom part 6 is deformed to be recessed to the inner part of the barrel part 5, with a connection part between the lower end part of the barrel part 5 and the outside inclination wall 11 as the starting point.

Description

  The present invention relates to a container formed from a synthetic resin such as polyethylene terephthalate (PET).

  A preform made from a synthetic resin such as polyethylene terephthalate, and then a container made of synthetic resin formed into a bottle shape by stretch blow molding or the like is used for beverages containing various beverage products. Used as a container. Recently, attempts have been made to reduce the wall thickness of containers in order to effectively use resources.

  On the other hand, in such a container, after filling and sealing the content liquid, the content liquid cools down, or moisture in the internal solution permeates through the container, thereby reducing the volume of the content liquid and lowering the internal pressure. There is a case. When the inside of the container has a negative pressure, a deformation such as a depression of a portion having low rigidity occurs, but the appearance of the product is deteriorated depending on the portion where the deformation occurs. Conventionally, a technique for causing such a negative pressure to be deformed at a specific location has been developed. For example, Patent Document 1 is configured to cause a deformation at the bottom due to a negative internal pressure. A synthetic resin casing is described. A leg wall portion that forms a ground contact surface is formed at the bottom of the housing described in Patent Document 1, and a depressed wall portion that is recessed in a dome shape is formed on the inner peripheral side of the leg wall portion. In addition, a circumferential groove is formed over the entire circumference at the boundary between the leg wall portion and the depressed wall portion. Therefore, when the inside of the housing becomes negative pressure, the depressed wall portion is deformed in a direction to enter the inside of the housing, and in that case, the deformed wall portion is easily deformed since the circumferential groove is opened. It is said that.

  Further, Patent Document 2 discloses a plastic container configured to prevent fluctuations in the liquid level after filling by deforming the bottom of the container inward during filling when the inside becomes negative pressure. In the container described in Patent Document 2, when the circumferential protrusion is formed on the outer peripheral side of the grounding portion and the grounding portion is pushed up, the deformation starting from the circumferential projection is deformed. It has come to occur.

JP 2007-269392 A JP 2006-8200 A

  Even if the bottom part is deformed toward the inside of the container as described in Patent Document 1 and Patent Document 2 described above, the appearance of the casing or the container as a product is not particularly deteriorated. However, as described in Patent Document 1, in the configuration in which the depressed wall portion, which is a portion on the inner peripheral side from the leg wall portion forming the grounding portion, is deformed inward of the housing, the structure is relatively thin. Since the vicinity of the center portion of the thick bottom portion is deformed, it is difficult to secure a sufficient amount of deformation, and the intended purpose may not be achieved.

  Further, the circumferential protrusion described in Patent Document 2 serves as a base point for deformation of the bottom when a vertical load is applied to the container. This is because the bottom itself is a molding factor. Since it is inevitably thick and the bottom itself is difficult to deform, it is assumed that deformation is caused by applying a load artificially, so it is deformed at a pressure that makes the internal pressure negative. Therefore, in order to prevent abnormal deformation due to negative pressure, there is an inconvenience that the body portion must be thick.

  The present invention has been made paying attention to the above technical problem, and can surely cause deformation of the bottom due to negative pressure inside, and also prevents grounding stability and insufficient strength or the like. It aims at providing the container made from a synthetic resin which can be suppressed.

  In order to achieve the above object, the invention of claim 1 is characterized in that a mouth and neck portion sealed by a cap is provided at an upper end portion of the trunk portion, and a lower end portion of the trunk portion is closed by a bottom portion integral with the trunk portion. In the synthetic resin container, the bottom portion is an outer inclined wall that is continuous with a lower end portion of the barrel portion and is inclined toward the central axis direction of the barrel portion and downward of the barrel portion, and an outer inclined wall thereof A grounding portion that is a continuous portion, an inner sloped wall that slopes from the grounding portion toward the center axis of the trunk and upwards of the trunk, and is formed continuously from the inner sloped wall. A bottom plate portion that is surrounded by an inner inclined wall and closes the bottom portion, and when the internal pressure is negative pressure, the bottom portion starts from a connection portion between the lower end portion of the barrel portion and the outer inclined wall. It is configured to be deformed indented inside It is an butterfly.

  The invention according to claim 2 is the synthetic resin container according to claim 1, wherein a groove is formed from the outer inclined wall to the inner inclined wall.

  Further, the invention of claim 3 is the invention of claim 2, wherein the groove portion is linear and a plurality of grooves are provided radially, and one end portion of each groove portion is formed in the width direction of the outer inclined wall. The synthetic resin container is provided at a position closer to a connecting portion between the lower end portion of the body portion and the outer inclined wall than the central portion of the body portion.

  Further, the invention of claim 4 is the invention according to any one of claims 1 to 3, wherein a lower straight portion having a cylindrical outer peripheral surface parallel to a central axis of the barrel portion is provided at a lower end portion of the barrel portion. The outer inclined wall is a synthetic resin container characterized in that it is inclined in a range of 40 ° to 60 ° with respect to the lower straight portion.

  According to the present invention, when the internal pressure becomes negative pressure, the vicinity of the outer peripheral edge of the outer inclined wall, that is, the boundary portion (connecting portion) between the outer inclined wall and the lower end portion of the trunk portion is the starting point. It is deformed so as to be recessed toward the inside. That is, this is a deformation such that the entire bottom portion is recessed inside the body portion, and therefore, a sufficient amount of deformation can be secured and an excellent reduced pressure absorption performance can be exhibited.

  According to the second aspect of the present invention, the groove is formed from the outer inclined wall forming the bottom portion to the inner inclined wall continuous therewith, so that the bottom portion is thick due to a molding process factor. Even so, when the internal pressure of the container becomes negative, it deforms so that the groove closes, so the outer inclined wall and inner inclined wall can be easily deformed toward the inside of the container, and excellent vacuum absorption performance Can be demonstrated.

  In particular, according to the invention of claim 3, since the groove portion is formed at a position close to the connection portion between the lower end portion of the body portion that is the starting point of deformation and the outer inclined wall, the deformation starting from the connection portion. Can be sufficiently generated, and can be uniformly deformed over the entire circumference of the bottom, so that the container can be stably installed in an upright state.

  Furthermore, according to the invention of claim 4, it is possible to generate sufficient decompression absorption performance and to prevent or suppress the outer inclined wall from being excessively deformed.

An example of the container which concerns on this invention is shown, (a) is a front view, (b) is a bottom view. The outline shape at the time of cut | disconnecting the bottom part of the container along a center axis line is shown, (a) is a shape before a deformation | transformation, (b) is a figure which shows the shape after a deformation | transformation. It is a diagram which shows the analysis result of the volume variation | change_quantity with respect to the negative pressure for every inclination | tilt angle with respect to the lower straight part of an outer side inclination wall.

  A synthetic resin container according to the present invention (hereinafter sometimes simply referred to as a container) is a container in which at least a body part and a bottom part are formed of a synthetic resin, and the contents are filled and sold, or It is a container that is sealed when displayed for sale, and thus the internal pressure may be negative. One example is a container called a plastic bottle, which is configured as shown in FIG. A container 1 shown in FIG. 1 is a cylindrical mouth-and-neck part 3 in which a screw part 2 to which a cap (not shown) is screwed is formed, and gradually from the lower end part of the mouth-and-neck part 3 toward the lower side. A tapered shoulder 4 that is expanded in diameter, a cylindrical body 5 that is continuous with the lower end of the shoulder 4, and a bottom 6 that is integrated with the body 5 so as to close the lower end of the body 5. And have. This type of container 1 is called a bottle-type container or a PET bottle, and the whole excluding the cap is biaxially stretched in such a way that the heated preform is stretched in the longitudinal direction by a stretching rod and in the transverse direction by air blow. It is integrally formed by blow molding. Therefore, the vicinity of the lower end portion of the body portion 5 and the peripheral portion of the bottom portion 6 are relatively thin, the body portion is then relatively thin, and the vicinity of the center portion of the bottom portion 6 is relatively thick. The synthetic resin as the material is a conventionally known resin such as a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, or an olefin resin such as polyethylene or polypropylene.

  The mouth-and-neck portion 3 includes a screw portion 2 formed on the upper outer peripheral surface, a jaw portion 7 formed below the screw portion 2 and to which a pilfer proof band (not shown) of the cap is locked, and a jaw portion 7 and a support ring 8 formed outwardly in the radial direction of the container.

  The outer peripheral surface of the shoulder portion 4 is a tapered surface linearly expanded from the lower end of the mouth / neck portion 3.

  A plurality of annular concave beads 9 extending in the lateral direction are formed at equal intervals on the outer peripheral surface of the body portion 5. This is for making it difficult to deform the body portion 5 by compensating for the decrease in rigidity accompanying the thinning of the body portion 5. Further, a straight cylindrical lower straight portion 10 extending along the axial direction of the container 1 is formed downward from the concave bead 9 formed at the lowermost portion of the body portion 5.

  The bottom portion 6 is formed continuously with the lower end portion of the lower straight portion 10 in the body portion 5 and is formed in a cup shape with the center portion of the bottom surface protruding upward. The cup-shaped contour is shown in FIG.

  As shown in FIGS. 1A and 1B, the bottom 6 has an outer inclined wall 11 that is inclined inward and downward in the radial direction of the container 1 from the lower end of the lower straight portion 10 of the trunk portion 5, and An annular grounding portion 12 continuously connected to the inner peripheral side of the outer inclined wall 11, an inner inclined wall 13 inclined inward and upward in the radial direction of the container 1 from the annular grounding portion 12, and an inner inclined wall 13 and a bottom plate portion 14 projecting inward of the container 1.

  In addition to the general configuration described above, the container 1 according to the present invention has a groove 15 for facilitating deformation at the bottom 6. Specifically, a plurality of groove portions 15 extending in the radial direction of the container 1 are provided at equal intervals in the range from the outer inclined wall 11 to the inner inclined wall 13 through the annular grounding portion 12 (in the illustrated example). 8). The outer end portion of the groove portion 15 in the radial direction of the container 1 is above the connection portion (boundary portion) between the lower straight portion 10 and the outer inclined wall 11, that is, the center portion in the width direction of the outer inclined wall 11. It is set at a position close to the connecting part (boundary part). The outer inclined wall 11 is inclined with respect to the lower straight portion 10 in a range of 40 ° to 60 °.

  If the internal pressure becomes negative after the container 1 is filled with the contents and sealed with the cap, the bottom 6 is deformed. This deformation occurs starting from a portion on the outer peripheral side of the bottom portion 6, more specifically, a boundary portion (connecting portion) between the lower straight portion 10 and the outer inclined wall 11 described above. When the bottom portion 6 is recessed inside the container 1 starting from this boundary portion, the outer inclined wall 11 is displaced so that the end on the grounding portion 12 side rotates inward of the container 1 with the boundary portion as the center. . Accordingly, the position of the grounding portion 12 is also displaced, and the diameter of the grounding portion 12 is reduced. When the diameter of the ground contact portion 12 is reduced, the circumferential length of the ground contact portion 12 is shortened. Therefore, a compressive force along the surface direction (circumferential direction) acts on the outer inclined wall 11 and the inner inclined wall 13 around the ground contact portion 12. To do. On the other hand, since the groove part 15 extended in the radial direction of the container 1 is formed in these parts, compressive force is absorbed by deform | transforming so that the groove part 15 may close. Since the reaction force against the deformation of the bottom portion 6 is reduced in this way, the bottom portion 6 can be easily deformed so as to be recessed toward the inside of the container 1. In order to surely cause such deformation, the opening angle between the outer inclined wall 11 and the inner inclined wall 13 is preferably in the range of 90 ° to 150 ° (preferably 110 ° to 150 °). The state after deformation is shown as the contour shape of the bottom 6 in FIG. In FIG. 2B, the chain line indicates the shape before deformation. As a result, the entire bottom portion 6 is deformed, and a reduced-pressure suction performance that reduces the negative pressure of the container 1 can be sufficiently generated. In addition, it is preferable to set the length of the inner inclined wall 13 in the radial direction of the container 1 to the length of the outer inclined wall 11 in the radial direction of the container 1 to be at least twice as long. The inner inclined wall 13 itself can be deformed so as to bend in the width direction, and the reduced-pressure absorbability can be further improved.

  In the container 1 according to the present invention described above, since the groove portion 15 is formed uniformly over the entire bottom portion 6, it is possible to prevent or suppress deformation bias and associated ground contact stability degradation. Furthermore, in the container 1 according to the present invention, the portion of the bottom portion 6 between the groove portions 15 is connected to the lower straight portion 10 described above, and the strength or rigidity of the portion itself is not low. The support strength by the grounding portion 12 when the entire container 1 is upright is not particularly lowered, and therefore the grounding stability of the entire container 1 is not impaired.

Here, the result of having analyzed the volume change of the bottom part at the time of pressure reduction of the synthetic resin container which concerns on this invention with the simulation method using a finite element method is demonstrated. The thickness of the bottom portion was set so as to have a plate thickness distribution when a preform having a basis weight of 20 g was biaxially stretch-blown into the shape of the synthetic resin container of the present invention. Moreover, the shape setting of a bottom part is as follows. In addition, the following code | symbol is attached | subjected to (a) of FIG.
Bottom outer diameter (D): 67.5mm
Diameter of grounding part (d1): 53.5mm
Diameter (d2) of connecting portion between inner inclined wall and bottom plate portion: 27 mm
Inclination angle (θ1) with respect to horizontal direction of inner inclined wall: 12.9 °
Height from the grounding part to the upper end of the bottom plate part (h): 9 mm
Groove depth: 1.25mm
Groove width: 1.2 mm
Number of grooves: 8 at regular intervals

  The angle of inclination (θ2) with respect to the lower straight portion of the outer inclined wall of such a synthetic resin container is 5 levels of 30 °, 40 °, 50 °, 60 °, and 70 ° with the position of the grounding portion fixed. The amount of change in volume when the internal pressure of the container was gradually reduced was analyzed with respect to the model changed in (1). The result is shown in FIG. 3, and when the internal pressure of the container is -15 kPa (a state where the pressure is reduced by 15 kPa compared to the state before the pressure reduction) and the inclination angle (θ2) is 30 °, the volume change at the bottom is 1.3 ml. When the tilt angle is 40 °, the volume change amount is 2.3 ml. When the tilt angle is 50 °, the volume change amount is 3.3 ml. When the tilt angle is 60 °, the volume change amount is 4.4 ml. When the inclination angle was 70 °, the volume change amount was 4.8 ml. When the inclination angle is 70 °, when the decompression amount of the container is increased, the outer inclined wall is inverted so as to be inclined inward and upward in the radial direction of the container, and the connecting portion between the lower straight portion and the outer inclined wall There was a risk of contact. As a result of the analysis, the inclination angle (θ2) with respect to the lower straight portion of the outer inclined wall of the synthetic resin container of the present invention can prevent the inversion of the outer inclined wall while ensuring a sufficient amount of vacuum absorption. A range of 40 ° to 60 ° is preferred.

  In addition, this invention is not limited to the specific example mentioned above, Comprising: The cross-sectional shape and number of a groove part can be set suitably. Further, the target container may have a shape other than the shape described above.

  DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Screw part, 3 ... Mouth and neck part, 4 ... Shoulder part, 5 ... Trunk part, 6 ... Bottom part, 10 ... Lower straight part, 11 ... Outer inclined wall, 12 ... Grounding part, 13 ... Inner inclination Wall, 14 ... bottom plate part, 15 ... groove part.

Claims (4)

In the synthetic resin container in which the mouth and neck part sealed by the cap is provided at the upper end part of the trunk part and the lower end part of the trunk part is closed by the bottom part integral with the trunk part,
The bottom portion is an outer inclined wall that is continuous with a lower end portion of the trunk portion and is inclined in a direction of a central axis of the trunk portion and downward of the trunk portion, and a grounding portion that is a portion continuous with the outer inclined wall. And an inner inclined wall that inclines toward the central axis of the trunk from the grounding portion and toward the upper side of the trunk, and is formed continuously from the inner inclined wall and surrounded by the inner inclined wall. A bottom plate portion that closes the bottom portion,
When the internal pressure is negative, the bottom portion is configured to be recessed and deformed inside the barrel portion from the connection portion between the lower end portion of the barrel portion and the outer inclined wall as a starting point. container.   The synthetic resin container according to claim 1, wherein a groove is formed from the outer inclined wall to the inner inclined wall. The groove portion is linear and has a plurality of radial portions, and one end portion of each groove portion has a lower end portion of the trunk portion and the outer inclined wall from a central portion in the width direction of the outer inclined wall. The synthetic resin container according to claim 2, wherein the synthetic resin container is provided at a position close to the connecting portion. A lower straight part having a cylindrical outer peripheral surface parallel to the central axis of the trunk part is provided at the lower end part of the trunk part,
The synthetic resin container according to any one of claims 1 to 3, wherein the outer inclined wall is inclined with respect to the lower straight portion within a range of 40 ° to 60 °.

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