JP2012096798A - Synthetic resin round bottle body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable depressed deformation of a bottom wall face of a bottom part accompanying increase in a decompression degree without damaging self-supporting performance of a bottle body and exhibit sufficient decompression absorbing performance by the entire bottle body including the depressed deformation of the bottom part, in the synthetic resin round bottle body in which a decompression absorbing panel is not arranged and surface stiffness of a peripheral wall of a barrel part is set large.SOLUTION: The round bottle body is formed by biaxial stretch blow molding, and a plurality of peripheral grooves are arranged on the peripheral wall of the bottle body so as to enable elastically compressed deformation in the longitudinal direction by action of pressing force in the longitudinal direction along with increase in the decompression degree within the bottle body. On the bottom face of the bottom part, a projection functioning as a ground part is protruded downwardly on the inner side of a peripheral edge part, and a depressed recess is disposed in a central part. Along with increase in the decompression degree within the bottle body, the height dimension of the barrel part is shortened accompanying compressed deformation of the peripheral grooves, and the decompression absorbing function is exhibited caused by depressed upward deformation of the depressed recess. Instead of the projection, the peripheral edge part functions as the ground part.

Description

The present invention relates to a synthetic resin round casing that absorbs this reduced pressure without disposing a reduced pressure absorption panel in the body when the inside is in a reduced pressure state.

  Conventionally, polyethylene terephthalate (hereinafter referred to as PET) resin biaxially stretched blow-molded casings, so-called PET bottles, have excellent transparency, mechanical strength, heat resistance, gas barrier properties, etc., and are used for various beverages. Widely used as a container. Conventionally, there is a so-called high-temperature filling method for filling a PET bottle with content liquids such as fruit juices and teas that require sterilization, and the liquid content is filled into the casing at a temperature of about 90 ° C. Then, the cap is sealed and then cooled, and the inside of the housing is in a considerably reduced pressure state.

  For this reason, for applications involving high-temperature filling as described above, for example, as described in Patent Document 1, a so-called decompression absorption panel, which is an area where the body portion is easily deformed in a depressed state by intentional decompression, is used. By disposing and deforming this vacuum absorption panel into a depressed shape at the time of decompression, while maintaining a good appearance, it is possible to secure rigidity as a housing in parts other than the vacuum absorption panel, and transport the housing A so-called decompression absorption function is exhibited so as to prevent troubles in the line, stacked storage, vending machines and the like.

  On the other hand, as described in Patent Document 2, there is a synthetic resin casing made to exhibit a reduced pressure absorption function by a depression-like deformation of the bottom wall of the bottom without forming a reduced pressure absorption panel in the body portion, Such a housing has a design advantage that can smooth the appearance of the body, and even when a shrink label is installed, it can suppress the generation of wrinkles and uneven expansion and contraction on the label, and it has a clean appearance. It can be made to present.

Here, the casing 101 shown in FIG. 9 is an example of a synthetic resin casing that exhibits a reduced pressure absorption function due to the depression-like deformation of the bottom wall of the bottom 105, (a) is a front view, (B) is a bottom view.
In this casing 101, a plurality of circumferential groove ribs 107 are arranged on the peripheral wall of the trunk portion 104, thereby increasing the surface rigidity of the peripheral wall of the trunk portion 104, and when the internal pressure is reduced, the trunk portion 104 is provided. While maintaining this shape, the reduced pressure absorbing function is exhibited by further deformed deformation (deformation in the direction of the arrow in FIG. 9A) of the depressed recess 115 of the bottom 105.

Japanese Patent Laid-Open No. 08-048322 JP 2007-269392 A

However, the housing 101 of the type shown in FIG. 9 is also required to reduce the thickness of the housing in order to save resources and reduce costs. As further depression-like deformation progresses,
While the depression deformation in the depression 115 does not proceed uniformly over the entire circumference, as shown in the bottom view of FIG. 9B, while forming a number of folds V in the radial direction and the circumferential direction, The crease V advances to the peripheral portion 112 that is unevenly advanced and is arranged at the peripheral portion of the bottom portion 105 and that functions as a grounding portion, impairing the appearance, and further, the housing 101 is self-supporting. There is a problem that it results in a loss of performance.

  Further, as described above, the casing 101 of the type shown in FIG. 9 is provided with a plurality of circumferential groove ribs 107 on the peripheral wall of the trunk portion 104, thereby increasing the surface rigidity of the peripheral wall of the trunk portion 104. In addition, since the decompression absorption function due to the depression-like deformation of the peripheral wall of the body portion 104 cannot be expected, when the degree of decompression increases in applications that require high temperature filling, the decompression absorption function due to the depression-like deformation of the bottom wall is not sufficient. For example, there is a problem that a portion from the tapered cylindrical shoulder portion 103 to the upper end portion of the body portion 104 is locally depressed and deformed.

Therefore, in order to solve the above-described problems in the prior art, the present invention increases the degree of pressure reduction in a synthetic resin round casing with increased surface rigidity of the peripheral wall of the trunk without providing a vacuum absorbing panel. A structure that allows the bottom wall of the bottom to be depressed and deformed without impairing the independence of the frame, and that can fully exhibit the vacuum absorption function as a whole, including the deformation of the bottom wall. The challenge is to create a structure.

Of the means for solving the above problems, the main configuration of the present invention is as follows.
In a synthetic resin round casing having a biaxial stretch blow molded cylindrical body,
A plurality of circumferential grooves are arranged on the peripheral wall of the trunk,
The circumferential groove is formed by bending the circumferential wall into a concave shape when viewed in a longitudinal section so that it can be elastically compressed and deformed in the longitudinal direction by the action of the longitudinal pressing force accompanying an increase in the degree of decompression inside the housing. With configuration,
On the bottom surface of the bottom portion, a ridge that functions as a grounding portion formed by projecting the bottom wall downward from the rim portion is arranged on the inner side of the peripheral portion, and the inner side of the ridge is the base end in the central portion. As a configuration in which a concave recess formed by sinking the bottom wall upward and inward is provided,
As the decompression degree inside the enclosure increases,
The reduced-pressure absorption function is exhibited by the shortening of the height of the body part due to the compression deformation of the groove width of the circumferential groove and the depression-like upward displacement of the bottom wall from the protrusion to the depression recess. Instead of this, the peripheral portion exhibits a function as a grounding portion.

An unprecedented feature of the above-structured housing is
At the bottom surface of the bottom portion, a protrusion is provided to project downward between the recessed portion provided at the peripheral portion and the central portion, and the circumferential groove provided on the peripheral wall of the trunk portion is provided with a degree of decompression inside the housing. A configuration that allows compression deformation in the vertical direction as it rises,
When the degree of decompression inside the housing rises, sufficient decompression absorption function is fully demonstrated due to the combination of the concave deformation of the bottom wall and the shortening of the body height due to the compression deformation of the circumferential groove. In addition, the peripheral portion is replaced with a protrusion, and the function as a grounding portion is exhibited so that the independence of the frame is reliably maintained.

Here, before the bottom wall portion from the ridge to the depressed recess (hereinafter sometimes referred to as a depressed deformed portion) is displaced upward due to reduced pressure, the ridge is configured to exhibit the function as a grounding portion. In the state in which the depressed deformed portion is displaced upward due to the reduced pressure and the tip portion from which the protrusion protrudes is displaced above the peripheral portion, the peripheral portion functions as a grounding portion.
In this way, by sharing the function of the grounding portion between the ridge and the peripheral portion, the ridge can be sufficiently displaced upward without deteriorating the independence of the housing during decompression.

In addition, the vacuum absorption function at the bottom can be increased by thinning the bottom wall, but on the other hand, when the wall is thinned, the so-called bottom-down problem and the bottom grounding function in the high-temperature filling process are reduced. In some cases, it may be difficult to demonstrate the vacuum absorption function required only at the bottom, but according to the above configuration, the vacuum absorption function is achieved by shortening the height of the trunk. It becomes possible to supplement with.
From a different perspective, it can be said that the degree of freedom in shape design including the thickness of the bottom can be increased by the complementary function by shortening the height of the body.

In addition, the longitudinal cross-sectional shape including the groove width, groove depth, etc. of the circumferential groove, the arrangement position and the number of arrangements, etc. are the appearance design, the required vacuum absorption function, the surface of the body part by the circumferential groove It can be set appropriately in consideration of the reinforcing effect related to rigidity and the degree of reduction in the buckling strength in the vertical direction due to the arrangement of the circumferential groove.
Of course, if the number of arrangements is increased, the reduced pressure absorption function can be exhibited.

  Another configuration of the present invention is that, in the main configuration, the depth of the circumferential groove is 2 mm or more.

Still another configuration of the present invention is that, in the main configuration described above, an inclination angle of the groove side wall of the circumferential groove from the horizontal direction is set to 45 ° or less.
The inclination angle is 0 ° or more.

The ease of elastic compression deformation in the longitudinal direction of the circumferential groove due to the action of the vertical pressing force depends on the wall thickness of the circumferential wall and the longitudinal sectional shape of the circumferential groove (groove width, groove depth, groove side wall It can be set appropriately depending on the angle of inclination from the horizontal direction)
With the above configuration, the groove depth is 2 mm or more, and the inclination angle of the groove side wall from the horizontal direction is 45 ° or less, so that the circumferential groove can be made smooth smoothly in the vertical direction by the progress of the degree of decompression in the housing. It can be deformed into a compressed state, and the reduced pressure absorption function can be exhibited smoothly.

  Still another configuration of the present invention is that, in the main configuration described above, the peripheral portion has an inclined surface shape inclined obliquely upward toward the central axis direction of the housing.

In the high-temperature filling step, the case having the above-described structure is considered to be that immediately after the high-temperature content liquid is filled and sealed with a cap, the synthetic resin forming the case is softened and the case is in a pressurized state. Thus, the problem that the bottom wall of the housing is deformed in a bulging shape downward, that is, the so-called bottom falling phenomenon is effectively suppressed.
And by making the peripheral part into the inclined surface shape inclined obliquely upward toward the central axis direction of the casing by the above configuration, the bottom-down phenomenon can be effectively suppressed, and then the casing is When the reduced pressure state is reached, the depressed deformed portion can be uniformly displaced upward in a depressed shape so that the reduced pressure absorption function can be exhibited smoothly and sufficient self-sustainability by the peripheral edge portion can be ensured.

  According to still another configuration of the present invention, the depressed concave portion has a shape in which a flat cross-sectional shape changes from a circle near the center to an equilateral triangular shape at the base end.

With the above configuration, the formation of the folds at the depression deformed portion at the time of decompression can be specified in a flat cross-sectional shape and dispersed in the direction in which the vertices of the regular triangle are located, and the formation of the folds at the annular flat portion can be further determined. It can be effectively suppressed.
In addition, since the depression-like deformation mode can be controlled, it is possible to exhibit a constant reduced pressure absorption function more stably.

  According to still another configuration of the present invention, a groove-like recess formed by stepping the bottom wall upward and inward is provided at the boundary between the inner peripheral edge of the peripheral edge and the outer peripheral edge of the protrusion. It is said.

With the above-described configuration, the depression-like upward displacement of the depression-deformed portion in the decompressed state can be smoothly advanced from the groove-like depression as a starting point, and the deformation as a peripheral portion can be suppressed to function as the ground-contact portion of the marginal portion. Can be exhibited stably.

Since the synthetic resin casing of the present invention has the above-described configuration, the following effects are exhibited.
In the case of the main configuration of the present invention, when the degree of decompression inside the housing is increased, the height of the body portion can be shortened by the depression deformation of the bottom wall and the compression deformation of the circumferential groove. Together, a sufficient decompression absorption function is sufficiently exhibited, and the peripheral portion exhibits a function as a grounding portion instead of the protrusion, so that the self-supporting property of the casing is reliably maintained.

It is a front view which shows 1st Example of the housing of this invention. It is a bottom view of the housing of FIG. It is an outer contour line figure of a peripheral wall which shows a peripheral groove neighborhood of a case of Drawing 1 by carrying out a longitudinal section. FIG. 3 is an enlarged longitudinal sectional view taken along the line AA in FIG. 2, enlarging the vicinity of the bottom of the housing of FIG. 1. It is a front view which shows 2nd Example of the housing of this invention. It is a bottom view of the housing of FIG. (A) is the longitudinal cross-sectional view of the peripheral part of the bottom part shown along the BB line in FIG. 6 of the housing of FIG. 5, and the vicinity of a protrusion, (b) is about the housing for a comparison ( It is a longitudinal cross-sectional view shown similarly to a). It is a bottom view which shows the other example of the shape of a bottom part. (A) which shows the housing of a prior art example is a front view, (b) is a bottom view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below along the examples with reference to the drawings.
1 to 4 show a first embodiment of a synthetic resin casing according to the present invention. FIG. 1 is a front view, FIG. 2 is a bottom view, and FIG. 4a is an outer contour diagram, and FIG. 4 is an enlarged longitudinal sectional view taken along line AA in FIG.
This housing 1 is a round housing having a mouth tube portion 2, a shoulder portion 3, a cylindrical body portion 4 and a bottom portion 5. The body portion 4 has a maximum diameter of 66 mm, an overall height of 134 mm, and a capacity of 280 ml. A biaxial stretch blow molded product made of PET resin.

As shown in FIG. 3, the peripheral wall 4a of the body part 4 is provided with four peripheral grooves 6 having a concave cross-sectional shape by bending the peripheral wall 4a.
The cross-sectional shape of the circumferential groove 6 is trapezoidal, the groove depth D of the circumferential groove 6 is 5 mm, the groove width Wct at the groove upper end 6a is 5 mm, the groove width Wcb at the groove bottom 6c is 1.75 mm, and the groove side wall The inclination angle A from the horizontal direction of 6b is 20 °.

A bottom portion 5 is connected to the lower end of the body portion 4 via a heel wall portion 11 formed in a curved cylindrical shape. A peripheral edge portion 12 of the bottom surface of the bottom portion 5 is an annular flat portion 12a.
In addition, a circumferential ridge 13a is provided on the inner side of the peripheral edge portion 12 as a ridge 13 that functions as a grounding portion formed by projecting a bottom wall downward from the annular flat portion 12a. In this case, a concave recess 15 formed by recessing the bottom wall upward and inward through a stepped portion 15s formed in a reduced diameter is provided with the inner side of the circumferential protrusion 13a as a base end. .
In addition, a groove-like recess 17 formed by stepping the bottom wall upward and inward is provided at the boundary between the inner peripheral edge of the peripheral edge 12 and the outer peripheral edge of the protrusion 13.

The circumferential ridge 13a is formed of a pair of side walls 13s and a flat tip flat portion 13t, and its cross-sectional shape is trapezoidal (can be U-shaped). The protruding height H from the portion 12a is 2 mm, and the width W of the tip flat portion 13t is 6 mm.
Further, the shape of the depressed recess 15 is such that its flat cross-sectional shape gradually changes from a circle near the center to a regular triangle at the base end.
Here, when the ridge 13 is used as the grounding portion as described above, there is a concern that the independence may be lowered as compared with the case where the peripheral edge portion 12 is used as the grounding portion. By considering the protruding height within a predetermined range in consideration, even when the housing is about to fall down, the annular flat portion 12a, which is the peripheral portion 12, can contact the grounded surface and be supported. The independence of the housing can be maintained without reducing the falling angle.

With the above-described configuration, in the case 1 of this embodiment, when the inside of the case 1 is in a reduced pressure state due to cooling after the high-temperature filling process, the body 4 The cylindrical shape of the peripheral wall 4a is maintained without being locally inverted and deformed.
Then, a pressing force acts on the peripheral wall 4a in the vertical direction as shown by a white arrow in FIG. 3, and the peripheral groove 6 elastically moves as schematically shown by a two-dot chain line in FIG. , The height dimension of the body part 4 is shortened by being deformed in a compressed state in the vertical direction,
As schematically shown by a two-dot chain line in FIG. 4, the circumferential protrusion 13 a having a trapezoidal cross-sectional shape is deformed so as to extend, and a depressed deformation portion extending from the circumferential protrusion 13 a to the depressed recess 15. 16 is displaced upward (see the direction of the white arrow in FIG. 4),
The shortening of the height dimension of the body part 4 and the upward displacement of the depressed deformation part 16 combine to fully exhibit the reduced pressure absorption function.

Further, in the state where the depressed deformed portion 16 is displaced upward due to the reduced pressure, the annular flat portion 12a functions as a grounding portion instead of the circumferential protrusion 13a. Retained.
Here, by disposing a groove-like recess 17 at the boundary between the inner periphery of the peripheral edge 12 and the outer periphery of the ridge 13, the depression-like deformed portion 16 in the decompressed state starts from the groove-like recess 17 as a starting point. The upward displacement can be progressed smoothly, and distortion function in the peripheral edge portion 12 can be suppressed and the function of the peripheral edge portion 12 as a ground contact portion can be exhibited more stably.

  Next, FIGS. 5 to 7 show a housing of a second embodiment of the present invention, FIG. 5 is a front view, and FIG. 6 is a bottom view. The overall shape of the housing 1 is substantially the same as the housing shown in FIGS. 1 and 2, and the shape of the ridge 13 is a protruding height H of 2 mm and a width W of 8 mm.

FIG. 7A is an enlarged vertical cross-sectional view of the main part in the vicinity of the peripheral edge 12 and the ridge 13 of the casing of the comparative example according to this embodiment, and FIG.
As for the shape of the bottom portion 5, the protrusions 13 are continuously provided from the heel wall portion 11 via the peripheral edge portion 12 in both cases, and at the boundary portion between the inner peripheral edge of the peripheral edge portion 12 and the outer peripheral edge of the protrusion 13. Is provided with a groove-shaped recess 17 formed by stepping the bottom wall upward and inwardly in a step shape.

In both cases, the width Wp of the peripheral edge portion 12 is 3 mm, but in the case of the comparative example, the peripheral edge portion 12 is horizontal and has an annular flat portion 12a.
As shown in FIG. 7A, the casing of the second embodiment is characterized in that the peripheral edge portion 12 has an inclined surface inclined obliquely upward toward the central axis direction of the casing.
When the degree of inclination of the inclined surface is expressed by the height difference h (see FIG. 7A) between the lower end 12b of the peripheral edge portion 12 and the inner peripheral edge, the height difference h is set to 0.5 mm.

Here, in the high temperature filling step, immediately after filling the high temperature content liquid and sealing with the cap, the synthetic resin forming the casing is softened and the inside of the casing is in a pressurized state. A so-called bottoming phenomenon occurs in which the bottom wall of the body is deformed in a bulging shape downward (in the direction of the white arrow in FIG. 7A).
This bottoming phenomenon becomes larger as the filling temperature of the content liquid becomes higher and the wall thickness of the housing is made thinner, and when it is increased to a certain extent, when the housing is in a decompressed state, The depression-like upward displacement occurs unevenly and unevenly. As a result, the reduced pressure absorption function is not sufficiently exhibited, and further, local deformation occurs at the peripheral portion, and the independence of the housing is impaired. There is a fear.

  The housing of the second embodiment is for dealing with the further increase in the filling temperature of the content liquid and the further thinning of the wall thickness of the housing as described above, and the peripheral portion 12 is shown in FIG. As described above, the bottoming phenomenon is effectively suppressed by making the inclined shape.

In addition, if the inclination of the peripheral edge portion 12 is excessively increased, the bottom drop can be sufficiently suppressed, but on the other hand, the depressed deformation portion 16 is difficult to be displaced upward during decompression, and the decompression absorption function is sufficiently exerted. It will not be done.
Accordingly, the width Wp of the peripheral edge portion 12 is 2 to 4 mm (3 mm in the case of the second embodiment) in consideration of the function as the ground contact portion after the depression-like upward displacement of the depression deformation portion 16 at the time of decompression. ) And the height difference h is in the range of 0.2 to 0.8 mm (0.5 mm in the case of the second embodiment). The function can be fully exhibited.

As mentioned above, although the structure of this invention and its effect were demonstrated along the Example, embodiment of this invention is not limited to the said Example.
First, the longitudinal cross-sectional shape including the groove width, groove depth, groove sidewall inclination, and the like, and the position and number of arrangements of the circumferential groove, in addition to the appearance design and the required vacuum absorption function, the circumferential groove It can be set as appropriate in consideration of the reinforcing effect related to the surface rigidity of the body portion due to the above and the degree of reduction in the buckling strength in the vertical direction due to the arrangement of the circumferential groove.

Further, as shown in FIG. 8 which shows three other examples (a), (b), and (c) of the shape of the bottom, the shape of the bottom is not limited to the above-mentioned embodiment, and various variations are adopted. can do.
In the above-described embodiment, the flat cross-sectional shape of the recessed recess 15 is an equilateral triangular anisotropy shape, but the flat cross-sectional shape can be a circular shape as shown in FIG. Further, as shown in FIG. 8B, the step portion 15s may have a polygonal shape.

In addition, the shape of the ridge 13 such as the width and the height of the protrusion considers the size and thickness of the housing, the independence of the housing, etc., and calculates the deformation mode such as the ease of deformation of the bottom wall. It can be set as appropriate based on the test results.
Further, the ridge 13 is not limited to the circumferential ridge 13a as in the above-described embodiment. As shown in FIG. 8C, a large number of ridges 13 (8 in the example of FIG. 8C). The projecting ridge 13 may be arranged in a circumferential shape with the notch 13K interposed therebetween.

Further, the groove-shaped concave portion 17 can be disposed as needed, and the shape such as the width and the groove depth can be appropriately determined.
Further, whether the peripheral edge portion 12 is horizontally flat, inclined, or the degree of inclination can be appropriately determined in consideration of the filling temperature of the content liquid, the degree of thinning, and the like. Is.

The synthetic resin casing of the present invention combines the depression deformation of the bottom wall of the bottom part with the compression deformation of the circumferential groove of the trunk part to sufficiently exhibit a sufficient decompression absorption function, and is self-supporting even during decompression. It has a smooth peripheral wall because it does not have a vacuum absorbing panel in the body part, and even when a shrink label is externally mounted, it can exhibit a clean appearance without wrinkles, etc. It can be expected to develop a wide range of applications in the required bottle field.

DESCRIPTION OF SYMBOLS 1; Housing 2; Mouth part 3; Shoulder part 4; Trunk part 5; Bottom part 6; Circumferential groove 6a; Groove upper end 6b; Groove side wall 6c; Groove bottom 11: Heel wall part 12: Peripheral part 12a; 13; ridge 13K; notch 13a; peripheral ridge 13t; flat tip portion 13s; side 15; depression 15s; step 16; depression deformed portion 17; groove-like depression 101; Trunk portion 107; peripheral groove rib 112; peripheral edge 115; recessed recess A; inclination angle D; groove depth Wcb; groove width Wct (at the groove upper end); groove width V (at the groove bottom); Projection height W (of the ridge); width Wp (of the ridge); width (of the peripheral edge)

Claims (6)

In a synthetic resin round casing having a cylindrical body (4) that is biaxially stretch blow molded, a plurality of circumferential grooves (6) are disposed on the peripheral wall (4a) of the body (4), The circumferential groove (6) can be elastically compressed and deformed in the longitudinal direction by the action of the longitudinal pressing force accompanying the increase in the degree of decompression inside the housing, and the circumferential wall (4a) has a concave shape when viewed in the longitudinal section. It is configured to be bent, and it functions as a grounding portion formed by projecting a bottom wall downward from the peripheral edge (12) inside the peripheral edge (12) of the bottom surface of the bottom (5). The ridge (13) is disposed, and the central portion is provided with a depressed recess (15) formed by denting the bottom wall upward and inward with the inner side of the ridge (13) as a base end. ,
As the degree of decompression inside the housing increases, the height of the body (4) is shortened due to the compression deformation of the circumferential groove (6), and the depression (15) Synthetic resin round with a configuration in which the vacuum absorption function is exhibited by the depression-like upward displacement of the bottom wall between and the peripheral edge portion (12) functions as a grounding portion instead of the protrusion (13). Shaped body. The synthetic resin casing according to claim 1, wherein the groove depth (D) of the circumferential groove (6) is 2 mm or more. The synthetic resin casing according to claim 1 or 2, wherein an inclination angle (A) of the groove side wall (6b) of the circumferential groove (6) from the horizontal direction is 45 ° or less. The synthetic resin casing according to claim 1, 2, or 3, wherein the peripheral edge portion (12) has an inclined surface inclined obliquely upward toward the central axis direction of the casing. The synthetic resin casing according to claim 1, 2, 3, or 4, wherein the depressed concave portion (15) has a shape in which a flat cross-sectional shape changes from a circular shape near the central portion to a regular triangular shape at the base end portion. A groove-shaped recess (17) formed by stepping the bottom wall upwardly and inwardly at the boundary between the inner peripheral edge of the peripheral edge (12) and the outer peripheral edge of the ridge (13) is provided. 1, 2, 3, 4 or 5 synthetic resin casing.

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