JP4993247B2 - Synthetic resin housing - Google Patents

Description

  The present invention relates to a synthetic resin casing, and more particularly to the shape of the bottom of a casing used for retorting.

  In the case of a synthetic resin casing made of polyethylene terephthalate (hereinafter referred to as PET) resin used for applications in which the internal pressure changes, the bottom surface of the bottom is recessed and an annular grounding portion is formed around the recess. A so-called champagne bottom-shaped casing is used (see, for example, Patent Document 1).

  In addition, as in fruit juice drinks and dairy products containing carbon dioxide, the housing is in a pressurized state and can be filled with contents that require heat sterilization (hereinafter referred to as a heat-resistant pressure housing). However, in such applications, a so-called high temperature filling method is used by filling the content liquid at a temperature of about 90 ° C., so that the conventional champagne bottom-shaped synthetic resin as described above is used. When the steelmaking body is used, pressurization under high temperature causes a so-called “bottom drop” in which the bottom part is inverted and protrudes toward the outside of the housing, and the housing cannot stand normally. End up.

Patent Document 2 discloses that the bottom portion for use as the above-mentioned heat-resistant pressure housing and the shape thereof are mainly controlled by controlling the crystallinity and thickness of the grounding portion formed in an annular shape on the bottom surface. There is a description of the restrained enclosure.
Utility Model Registration No. 2607701 Japanese Patent Laid-Open No. 2005-104500

  On the other hand, in recent years, synthetic resin casings such as PET bottles have been used for foods that require retort processing. The retort treatment is performed for several tens of minutes at a temperature of about 120 to 130 ° C. using pressurized heated water or steam in a retort kettle with food filled in a casing and the mouth tube sealed with a cap. As a result, the housing is exposed under conditions of higher temperature and pressure that are more severe than those of the high temperature filling method.

The object of the present invention is to create a bottom shape of a synthetic resin casing that does not bottom out under retort processing conditions, and maintains a good standing and appearance even after retorting, and can be used with confidence. The purpose is to provide a housing.

The means of the first invention for solving the above technical problem is:
A synthetic resin casing used for retorting,
The bottom part is connected to the lower end of the body part and has a heel part that is reduced in diameter with an outward radius of curvature and reaches the bottom surface. An annular grounding part is disposed on the bottom surface, and the bottom surface is defined with the grounding part as a base end. It is a bottomed cylindrical shape that is recessed to form a hemispherical shell-shaped bottom raising part,
Setting the value of the outer diameter of the contact portion to a range of 55 to 85% of the maximum diameter of the heel portion;
The value of the height of the bottom raised portion should be in the range of 40% or more of the outer diameter of the grounding portion,
The radius of curvature of a pair of left and right arcs from the vicinity of the base end to the vicinity of the top that determines the main curved shape in the vertical section of the bottom raised portion is set to a range exceeding 1/2 of the outer diameter of the grounding portion;
The left and right arcs intersect at the top to form a vertex;
It is in.

The above-described configuration of the first invention mainly includes the following three requirements relating to the shape of the bottom portion of the housing, particularly the shape of the raised bottom portion.
(1) The value of the outer diameter of the grounding portion is in the range of 55 to 85% of the maximum diameter of the heel portion.
(2) The value of the raised height of the raised portion is set to a range of 40% or more of the outer diameter of the grounding portion.
(3) The value of the radius of curvature of a pair of left and right arcs from the vicinity of the base end that determines the main curved shape of the bottom raised portion to the vicinity of the top portion is set to a range exceeding 1/2 of the outer diameter of the grounding portion . The arcs intersect at the top to form a vertex.

First, the requirement (1) is a requirement relating to the diameter of the annular grounding portion serving as the base end of the raised bottom portion. By setting the outer diameter to be in a range of 55% or more of the maximum diameter of the heel portion, the casing is erected. It is possible to secure the sex and to prevent the fall.
In addition, if the outer diameter of the grounding portion is too large, the heel portion needs to be blow-molded in a deep drawing shape, and there is a problem such as locally forming a thin-walled portion, but this outer diameter is the maximum diameter of the heel portion. By setting it to 85% or less, such a problem related to blow molding can be avoided.
In addition, since the grounding portion may have a width of up to about 2 mm, in this requirement, the range is determined by the outer diameter of the grounding portion (the diameter of the outer peripheral edge) in order to clarify the range of dimensions.

Next, requirements (2) and (3) are requirements for determining the shape of the hemispherical shell of the bottom raised portion. Of these, (2) is a requirement regarding the height of the bottom raising. When the bottom raising height of the bottom raising portion is low, the bottom raising portion becomes a flat curved shape as a whole. On the other hand, the pressing force acting outward along the central axis direction becomes relatively large with respect to the pressing force acting in the lateral direction, and the reverse deformation is likely to occur.
Here, by setting the value of the raised height to be in the range of 40 % or more of the outer diameter of the ground contact portion, the pressing force acting in the lateral direction can be increased, the reverse deformation is suppressed, and the severe in retort processing Even under conditions, it is possible to reliably prevent reverse deformation of the bottom raised portion .
Contact name is the upper limit of the raised height, blow moldability, it can be appropriately determined in consideration of the capacity of the shape and wall thickness, and the bottle of the ground portion.

(3) relates to the radius of curvature of the arc extending from the vicinity of the base end to the vicinity of the apex that determines the main curved shape of the bottom raised portion. If the value of the radius of curvature is too small, the bottom raising height cannot be sufficiently increased, and a flat portion or a curved surface portion having an outward curvature radius is inevitably formed near the top of the bottom raised portion. Thus, under the high temperature and pressure of the retort process, the part becomes the starting point, and the reverse deformation progresses, resulting in a bottom-down state.
Here, in accordance with the requirement of (3), by setting the value of the radius of curvature to a range of 1/2 or more of the outer diameter of the grounding portion, the entire bottom raised portion can be formed into a convex curved shape inward. In addition, there can be no starting point of the reversal deformation related to the falling of the bottom.

  As described above, in relation to the shape of the bottom raised portion, the values of the diameter of the ground contact portion, the height of the bottom raised portion, and the radius of curvature are within the ranges of (1), (2), and (3). However, it is possible to prevent the occurrence of reverse deformation of the hemispherical shell-shaped bottom raised portion formed at the bottom, and to provide a casing without falling off.

According to a second aspect of the present invention, in the first aspect of the invention, the width of the grounding portion is set to a value of 2 mm or less.

With the above configuration of the second invention , the grounding property of the housing can be sufficiently ensured by setting the annular grounding portion width to 2 mm or less. This width is preferably narrower and linear from the viewpoint of grounding properties, but can be determined in consideration of blow moldability. In other words, if the width of the grounding portion is large, the inner diameter side of the grounding portion tends to protrude outward (bottom drop) due to an increase in the internal pressure of the container, and there is a possibility that grounding stability cannot be secured. In order to prevent this, the width of the grounding portion should be 2 mm or less, preferably 1 mm or less. However, if the ground contact width is further reduced, it is considered that the formability (blow moldability) at the time of blow molding is inferior.

The present invention has the above-described configuration, and has the following effects.
In the first invention , the value of the height of the grounding portion, the height of the bottom raising portion and the value of the radius of curvature are related to the shape of the bottom raising portion, such as setting the value of the height of the bottom raising to a range of 40% or more of the outer diameter of the grounding portion By making it within a certain range determined by each requirement of this claim, it prevents the occurrence of reverse deformation of the hemispherical shell raised portion formed at the bottom even under retort processing conditions, and provides a housing with no bottom loss can do.

In the second invention , the grounding property of the housing can be sufficiently secured by setting the annular grounding portion width to 2 mm or less.

Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 show an embodiment of the synthetic resin casing of the present invention. FIG. 1 is a front view of the housing 1. This housing 1 is a biaxially stretched blow molded product made of PET resin, and has a mouth tube part 2, a shoulder part 3, a body part 4, and a bottom part 5, and is a small round for 300ml use for retorting. It is a mold bottle. The mouth tube portion 2 is in a state of being whitened by the thermal crystallization process.

  In addition, two peripheral step portions 8 are provided on the upper and lower sides, and six panels 7 are formed in parallel between the peripheral step portions 8. This panel 7 has a vertically long rectangular shape as a whole, and has a concave portion 7a that is curved in a convex shape toward the inside of the casing located above with the boundary line 7c as a boundary, and a convex portion that faces outward on the lower side. It is comprised from the convex-shaped part 7b curved in the shape. And the pressure fluctuation inside the housing 1 in the pressurized state during the retorting process and in the decompressed state after cooling can be absorbed by the cooperative deformation of the concave portion 7a and the convex portion 7b.

2A is a longitudinal sectional view of the vicinity of the bottom portion 5 of the housing 1 of FIG. 1 and FIG. 2B is a bottom view thereof.
The bottom portion 5 has a bottomed cylindrical shape as a whole, and has a heel portion 11 connected to the lower end of the body portion 4 and reduced in diameter with an outward curvature radius R1 to reach the bottom surface 6. The bottom portion 6 is formed in a hemispherical shell with an inward radius of curvature R2 from the vicinity of the base end to the top, with the grounding portion 12 as a base end.

  Further, the portion from the lower end portion of the heel portion 11 through the ground contact portion 12 to the lower end portion of the bottom raising portion 13 is formed by connecting outward curved surfaces having a small curvature radius of about 1 to 4 mm. Further, the width W portion of the grounding portion 12 is formed as a flat surface.

The dimension which concerns on the bottom part 5 of the housing 1 of a present Example is shown below.
Width W of grounding part 12 0.5mm
Maximum diameter D1 of heel part 11 66 mm
The outer diameter D2 of the grounding part 12 45 mm
Bottom height H1 19mm
Curvature radius R1 21mm
Curvature radius R2 27mm
From the above dimensions,
(1) The value of the outer diameter D2 of the grounding portion 12 is 68% of the maximum diameter D1 of the heel portion 11 and is in the range of 55 to 85%.
(2) The value of the raised height H1 of the raised portion 13 is 42% of the outer diameter D2 of the grounding portion 12, and is in the range of 40 % or more.
(3) The value of the curvature radius R2 of the bottom raised portion 13 is 60% of the outer diameter D2 of the grounding portion 12, and is in a range of 1/2 or more.

  The housing 1 of the above example was filled with water and sealed with a cap, and then a retort treatment test was performed at 124 ° C. for 42 minutes. The bottom raised portion 13 did not fall off, and the deformation of the entire bottom portion 5 was minute. Thus, the stand-up property of the casing 1 by the grounding portion 12 was sufficiently satisfactory for practical use.

3 is a longitudinal sectional view showing another variation of the shape of the bottom raised portion 13 shown in FIG. 2 (a). For reference, the vicinity of the top portion 14 of the bottom raised portion 13 is sandwiched between two axes. The drawing pins P1 and the support pins P2 used in the drawing blow molding are hatched. In biaxial stretch blow molding, a test tubular preform is heated to an appropriate temperature, and the bottom of the preform is stretched in the longitudinal direction with the stretch pin P1 and the support pin P2 sandwiched therebetween, and then stretched in the lateral direction by air blow. There is a case.
In such a case, the shape of the vicinity 14 of the top portion is a shape along the tip shape of the support pin P2, and in the example of FIG. 3, a small recess is formed with an inward radius of curvature.
In addition, it is possible to prevent misalignment during blow molding by the support pins P2.

FIG. 4 shows the shape of the bottom raised portion 13 when the radius of curvature R2 of the arc forming the main curved surface of the bottom raised portion 13 is changed in the same manner as in the above embodiment. 4A shows an example in which R2 is made larger than that in the above embodiment, and FIG. 4B shows an example in which the value of the curvature radius R2 is less than ½ of the outer diameter D2 of the grounding portion 12.
In the example of FIG. 4 (a), since the radius of curvature is increased, the shape near the top is slightly sharpened. However, if there is a problem with blow moldability, it is drawn with a two-dot chain line in the figure. It can also be made into a shape with chamfering.

  On the other hand, since the bottom raised portion 13 in FIG. 4B has a small radius of curvature, the bottom raised portion 13 becomes flat near the top or convex outward. Then, when the inside of the casing is brought into a high-temperature and pressurized state by the retort processing, the reverse deformation proceeds from the vicinity of the top portion, and the bottom is lowered.

  Here, in the retort process, the pressure inside the housing 1 rises. The force acting on the bottom raising portion 13 due to this pressure is applied along the pressing force acting laterally on the bottom raising portion 13 and the central axis direction. The pressing force acting outwardly is shown by white arrows in FIG. When the bottom raising height H1 is low, or when the shape near the top is the shape shown in FIG. 4B, the magnitude of the pressing force acting in the lateral direction on the bottom raising portion 13 is reduced. As a result, the pressing force acting outward along the central axis direction becomes relatively large, and as a result, the reverse deformation proceeds from the vicinity of the top portion and the bottom falls.

As mentioned above, although the embodiment of the invention of the present application and the function and effect thereof have been described by the examples, the embodiment of the invention is not limited to this example. The kind of the synthetic resin is not limited to the PET resin, and for example, a heat-resistant resin such as a polyethylene naphthalate resin or a nylon resin can be used.
Moreover, the panel shape of the housing of the present embodiment is an example of a panel for absorbing pressure fluctuation, and other various panel shapes can be used.

  As described above, the bottom of the synthetic resin casing of the present invention does not bottom out even under severe conditions in retort processing, and can be expected to be widely used for food applications that require retort processing.

It is a whole front view which shows one Example of the synthetic resin casings of this invention. It is the longitudinal cross-sectional view of (a) bottom part vicinity of the housing of FIG. 1, and (b) bottom view. It is a longitudinal cross-sectional view which shows the other variation of the shape of the bottom raising part in Fig.2 (a). In FIG. 2A, two examples of the shape of the raised portion when the radius of curvature R2 is changed are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Housing 2; Mouth part 3; Shoulder part 4; Trunk part 5; Bottom part 6; Bottom face 7; Panel 7a; Concave part 7b; Convex part 7c; Grounding part 13; Bottom raising part 14; Near top part D1; Maximum heel diameter D2; Outer diameter (of grounding part) H1; Bottom raising height R1, R2; Curvature radius P1; Stretching pin P2;

Claims (2)

A synthetic resin casing used for retorting,
The bottom part (5) has a heel part (11) connected to the lower end of the body part (4) and reduced in diameter with an outward curvature radius (R1) to reach the bottom face (6), and a circle on the bottom face (6) An annular grounding part (12) is disposed, and the bottomed part (13) is formed into a hemispherical shell with the grounding part (12) serving as a base end, and a bottom-up cylindrical part (13) is formed.
The value of the outer diameter (D2) of the grounding part (12) is in the range of 55 to 85% of the maximum diameter (D1) of the heel part (11),
The value of the raised height (H1) of the raised portion (13) is in a range of 40% or more of the outer diameter (D2) of the grounding portion (12),
The value of the radius of curvature (R2) of a pair of left and right arcs from the vicinity of the base end to the vicinity of the top that determines the main curved shape in the longitudinal section of the bottom raised portion (13) is the value of the outer diameter (D2) of the ground contact portion (12). A range exceeding 1/2,
A synthetic resin casing characterized in that the pair of left and right arcs intersect at the top to form a vertex . The synthetic resin casing according to claim 1, wherein the width (W) of the grounding portion (12) is 2 mm or less.

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