CLOSURE DEVICE AND CONTAINER

Abstract: A closure device composed of a container and a cap of synthetic resin mounted to the neck of the container. The cap of synthetic resin comprises a cap body composed of a top plate portion and a cylindrical portion depending from a peripheral edge of the top plate portion. The cylindrical portion is compartmented by a severable weakened line into a main portion above the weakened line and a lower tamper-evidence ring portion, the main portion being formed at its inner wall surface with a thread, and the tamper-evidence ring portion being provided at its inner wall surface with fallable engaging projections. The container is formed at an outer periphery of the upper end of the neck thereof with a male thread and below the male thread with an annular expanded portion. Provided contiguous to the expanded portion is at least bridge extending means comprising depressing portions, which engage with the engaging projections of the cap to depress the same when the cap of synthetic resin mounted to the container neck is turned in an opening direction, and extended step portions adapted to engage with the engaging projections depressed by the depressing portions to prevent upward movement of the engaging projections.

Description: TECHNICAL FIELD The present invention relates to sealing devices comprising containers and synthetic resin caps having tamper-evidence properties for sealing the mouth portions of these containers, and relates to such containers. BACKGROUND ART In recent years, synthetic resin containers composed of polyethylene terephthalate (PET bottles) have come into common use as beverage containers. Synthetic resin containers have the advantageous properties of being light and shatterproof in comparison with conventional glass bottles. Additionally, as caps for this type of synthetic resin container, metallic caps of aluminum alloy or the like have been conventionally used. Using synthetic resin caps in place of these types of metallic caps has also been considered. With regard to these types of synthetic resin caps, those disclosed in Japanese Patent Application, First Publication No. Sho 62-251352 and Japanese Patent Application, First Publication No. Hei 2-296666 are known. These conventional synthetic resin caps are screwed onto containers having an external thread formed on the mouth portions and annular expanded portions below the external thread; the caps are composed of a synthetic resin cap main body formed by a top plate portion and a tubular portion which extends downward from the peripheral portions thereof, and a thin liner provided on the inner surface of the top plate portion of the cap main body, the cap main body being such that the bottom portion thereof is partitioned, by means of a horizontal score formed around the circumference while leaving a plurality of thin bridges, into a main portion above the horizontal score and a tamper-evidence ring portion below the horizontal score. A threaded portion for screwing onto the external thread on the mouth portion of the container is formed on the inner wall surface of the main portion of the cap main body, and multiple wings or tabs are provided so as to be erectable on the inner wall surface of the tamper-evidence ring portion. Additionally, as the containers, those having an external thread formed on the outer circumference of the top end portion of the mouth portion and provided with an annular expanded portion (locking ring) below the external thread are used. With these types of caps having tamper-evidence properties, it is preferable that the relationship between the seal release angle, hereinafter abbreviated to SRA, and the bridge breaking angle, hereinafter abbreviated to BBA, be held to be such that SRA - BBA = 0 degrees or greater, more preferably +30 degrees or greater, wherein SRA is the rotational angle at the moment the seal of the container is released due to the top end of the mouth portion of the container being separated from the inner surface of the cap or the liner when the cap attached to the mouth portion of the container is rotated from the initial position in the direction of opening, and BBA is the rotational angle at the position where the bridges are broken when the cap attached to the mouth portion of the container is rotated from the initial position in the direction of opening. That is, it is desirable, when opening the cap, that the bridges are broken before the seal is released due to the top end of the mouth portion of the container being separated from the liner or the like. However, with the above-mentioned synthetic resin caps, there are cases wherein the bridges formed from synthetic resin expand and the engaging projections (wings or tabs) are so soft as to bend when engaging with the annular expanded portion, as a result of which the BBA can increase and SRA - BBA can become less than 0 degrees; thus, there are points requiring improvement from the point of view of tamper-evidence properties. Techniques for separating a cap main body and a tamper-evidence ring portion with a small rotational angle in order to enhance tamper-evidence properties are disclosed, for example, in Japanese Patent Application, Second Publication No. Sho 32-1945. As sealing devices designed to increase the above-described tamper-evidence properties using synthetic resin caps, those described in Japanese Patent Application, Second Publication No. Hei 3-56990 are known. These sealing devices comprise engaging claws having engaging side edges extending downward with a tilt in the cap-opening direction underneath the external thread of the container, and engaged claws which cooperate with the above-mentioned container engaging claws formed on the inner walls of the tamper-evidence ring portion of the cap. With the sealing device of Japanese Patent Application, Second Publication No. Hei 3-56990, when the cap is turned in a cap-opening direction with the cap attached to the mouth portion of the container, the engaged claws formed on the tamper-evidence ring portion are guided to the tilted engaging side edges of the engaging claws so as to be forced downward, and the tamper-evidence ring portion is forced to move downward to accelerate tearing along the tear line formed on the cap tubular portion. However, in these conventional sealing devices, since the engaged claws formed on the cap have a fixed structure such as not to bend, the engaged claws on the cap must be forced past the engaging claws on the container when the cap is attached to the container, so that the plurality of bridges which couple the main portion of the cap tubular portion with the tamper-evidence ring portion must be reinforced to some extent, as a result of which the resistance to breakage of the bridges when the cap is opened is large and the seal cannot be easily opened. Additionally, in order to prevent the bridges from breaking when the cap is attached to the container (when the container is sealed), the tamper-evidence ring portion could be given an engaging structure for preventing relative movement in the cap-closing direction, but this presents a problem in that it would become difficult to mold the cap and the costs would increase. Furthermore, since these containers according to the conventional art are for engaging side edges of the engaged claws having fixed structures such as not to bend, these containers cannot be applied to caps provided with multiple wings or tabs which are erectable on the inner wall surface of the tamper-evidence ring portion as described in Japanese Patent Application, First Publication No. Sho 62-251352 and Japanese Patent Application, First Publication No. Hei 2-296666. That is, with the structure of the container described in Japanese Patent Application, Second Publication No. Hei 3-56990, only engaging claws having engaging side edges extending downward while tilting in the cap-opening direction are formed underneath the external thread, so that when the above-mentioned cap having the wings or tabs is attached and the cap is turned in a cap-opening direction, the wings or tabs contact the tips of the engaging claws, the tips of the wings or tabs are bent upward, allowing the engaging claws to pass without engaging the engaging claws, as a result of which the cap can be removed without breaking the bridges. Additionally, as another example of conventional art, those described in Japanese Patent Application, First Publication No. Hei 7-291317 have been proposed. The sealing device described in this publication comprises an external thread on the mouth portion of the container, an annular chin portion positioned therebelow, and ratchet claws positioned therebelow spaced along the circumferential direction. An internal thread is formed on the inner circumferential surface of the main portion of the tubular portion of the synthetic resin cap, and engaging flaps which extend upward at an incline in the radial inward direction from the base end are formed on the inner circumferential surface of the tamper-evidence ring portion spaced in the circumferential direction. When this type of sealing device formed by combining a container with a cap has the mouth-neck portions sealed by attaching the cap to the mouth portion of the container, the rotation of the cap in the cap-opening direction, not the movement in the upward direction, is inhibited due to the side edges in the circumferential direction of the engaging flaps formed on the tamper-evidence ring portion of the cap contacting the rear surfaces of the ratchet claws which extend at a steep incline. That is, the conventional sealing device composed of a synthetic resin cap and a container as mentioned above has a formation wherein, when the cap attached to the mouth portion of the container is turned in the cap-opening direction, the engaging flaps formed on the inner circumferential surface of the tamper-evidence ring portion of the cap are engaged with the ratchet claws formed on the mouth portion of the container to inhibit the rotation of the tamper-evidence ring portion in the cap-opening direction, as a result of which a force in the rotational direction is directly applied to a plurality of bridges which couple the main portion of the cap tubular portion with the tamper-evidence ring portion to break the bridges. However, with regard to the above-mentioned conventional sealing devices, since the bridges are severed by pulling apart the plurality of bridges at once, there is a risk that the rupture resistance of the bridges could increase so that the bridges are not sufficiently severed, or that the engaging flaps could be folded back due to the strong rupture resistance so as to pass the ratchet claws. That is, in the weakened line of a cap tubular portion formed from a horizontal score cut along the circumferential direction of the tubular portion while leaving a plurality of thin bridges, each bridge has a thin pillar shape composed of synthetic resin. This type of bridge is comparatively easily stretched when a tensile force is applied in the longitudinal direction, and easily and reliably severs after a certain degree of stretching. However, when shear stress arising from the movement of the main portion which is turned in the cap-opening direction with respect to the fixed tamper-evidence ring portion is instantaneously applied to this type of bridge, the bridge has a high rupture resistance. In other words, tamper-evidence ring portions coupled to main portions by means of multiple bridges in this way are not easily torn even when a rotational force is applied in the cap-opening direction. Additionally, with formations wherein bridges are severed according to conventional products as mentioned above, a large cap-opening torque is required in order to separate the tamper-evidence ring portion from the main portion, and this makes it difficult for children to open the cap. Additionally, even if one attempts to open the cap by applying a large cap-opening torque, this large force can be applied to the engaging flaps so as to cause the engaging flaps to be folded back and pass the ratchet claws, thereby making it impossible to separate the tamper-evidence ring portion. JP-A-05 112 367 describes a sealing device comprising a container and a metal cap attached to a mouth portion thereof, said metal cap has a cap main body having a top plate portion and a tubular portion extending downward from the periphery thereof, said tubular portion being partitioned by means of a tearable weakening line into an upper main portion and a lower tamper-evidence ring portion, said container has an external thread formed on an outer circumference of an upper end of said mouth portion thereof, an annular expanded portion formed underneath said external thread, and at least one bridge-stretching means which is provided continuously underneath said expanded portion. JP-A-05 112 367 uses an expanded portion which includes a depressing portion and an extended step portion. In the sealing device disclosed therein, an engaging portion having a fixed structure so as not to bend oontacts the expanded portion aside from the depressing portion and the extended step portion (see Fig. 4). According to JP-A-05 112 367, the resistance to breakage of the bridges is increased because the engaging portion engaging the expanded portion is pushed down by the depressing portion while the engaging portion cannot be deformed due to its fixed structure, and an appropriate cap-opening torque cannot be achieved. The engaging portion must be formed aside from the depressing portion and extended step portion, and this complicates the shape of the cap, increasing the manufacturing cost. DISCLOSURE OF INVENTION The present invention has the object of offering a sealing device which prevents the cap-opening torque from becoming high due to the rupture resistance of the bridges when the cap attached to the mouth portion of the container is turned in the cap-opening direction, and which can yield good tamper-evidence properties by reducing the BBA when the cap is being opened ; and the present invention has the object of offering such a container. The present invention provides a sealing device according to the preamble of claim 1 characterised in that, in combination : said cap is a synthetic resin cap said engaging projections are erectable and oriented substantially horizontally with their tips facing in a radially inward direction and are foldable upward, and said engaging projections overlapping said bridge-stretching means have their tips folded upward when said synthetic resin cap is attached to said mouth portion of the container. In the sealing device of the present invention, said depressing portion may have a structure wherein an inclined surface gradually expands downward in a cap-opening direction. In the sealing device of the present invention, said depressing portion may have a structure wherein a side which contacts the engaging projections when the cap is opened is made into an inclined surface which gradually expands downward in a cap-opening direction, and a storage guide surface having a projection height which gradually decreases in a cap-opening direction is provided on a side of the aforesaid extended step portion which is the opposite side from said inclined surface. It is preferable that the inclination angle of said inclined surface of said depressing portion be 5 ~ 50 degrees. The sealing device of the present invention may have a structure wherein an engaging claw portion for engaging said engaging projections and inhibiting the rotation of said tamper-evidence ring portion in the cap-opening direction is formed at the end of said extended step portion of the bridge-stretching means in a cap-opening direction. In the sealing device of the present invention, the weakening line of said synthetic resin cap may be a horizontal score formed by cutting said tubular portion in a circumferential direction while leaving a plurality of thin bridges. In the sealing device of the present invention, the engaging projections of said synthetic resin cap may be a plurality of erectable tabs which are formed such as to project plate-wise from an inner wall of said tamper-evidence ring portion. The sealing device of the present invention may have a structure wherein a vertical weakening line which is severed at almost the same time that the weakening line is severed so as to break said tamper-evidence ring portion into a band is formed on said tamper-evidence ring portion of said synthetic resin cap. The sealing device of the present invention should preferably be such that the bridge breaking angle which is the rotational angle of the position at which said bridges are severed when said cap attached to said mouth portion of the container is rotated in a cap-opening direction is 90 degrees or less. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a partially cut-away front view showing an example of a sealing device according to the present invention. Fig. 2 is a front section view showing the same sealing device in a sealed state. Fig. 3 is an enlarged view of significant portions of Fig. 1. Fig. 4 is a side view showing the same container. Fig. 5 is an enlarged view of significant portions of Fig. 4. Fig. 6 is a section view of significant portions showing the same sealing device in a sealed state. Fig. 7 is a section view of significant portions showing the same sealing device with the cap rotated in a cap-opening direction. Fig. 8 is a section view of significant portions of the same directly after the bridges have been severed. Fig. 9 is a front view of a container according to another mode of the present invention. Fig. 10 is an enlarged section view of significant portions of the sealing device shown in Fig. 1. BEST MODES FOR CARRYING OUT THE INVENTION Figs. 1 to 3 show an example of the sealing device according to the present invention. This sealing device comprises a synthetic resin cap (hereinafter referred to as a cap) 1 and a synthetic resin container 21. The cap 1 comprises a cap main body 4 composed of a synthetic resin such as polypropylene, comprising a top plate portion 2 and a tubular portion 3 extending downward from the periphery thereof, and a thin liner 5 composed of a soft resin placed inside the cap main body 4. The tubular portion 3 of the cap main body 4 is partitioned into an upper main portion 8 and a lower tamper-evidence ring portion 9 (hereinafter referred to as the TE ring portion) by means of a horizontal score 7 formed by cutting the tubular portion 3 along the circumferential direction while leaving a plurality of thin bridges 6. A threaded portion 10 is formed on the inner wall surface of the main portion 8, and multiple plate-shaped tabs 11 which form engaging projections are erectably provided on the inner wall surface of the TE ring portion 9. While not shown in the drawings, a vertical weakening line which breaks the TE ring portion 9 up into a band by being severed almost simultaneously with the severing of the horizontal score 6 is formed on the TE ring portion 9. The above-mentioned tabs 11 are oriented almost horizontally with their tips facing in the radial inward direction when not attached to the container, and when the cap is attached to the mouth portion 21A of the container, their top ends fold upward upon contact with the external thread 22 or the annular expanded portion 23, so that they can pass the external thread 22 or the annular expanded portion 23 with almost no resistance. The dimensions of the cap 1 and the mouth portion 21A of the container are not especially restricted, but examples for the range of preferable dimensions in a general-purpose-size cap will be given in the following embodiment. The length of projection of the tabs 11 from the inner wall surface of the TE ring portion 9 should be 1.5 ∼ 4.0 mm, more preferable about 2.0 ∼ 3.0 mm. If this projection length is less than 1.5 mm, the contact of the tabs with the outer surface of the container is reduced so as to make it difficult for the bridges to be severed when the cap is opened, while if the projection length is more than 4.0 mm, it becomes difficult to mold and difficult to cap. Additionally, the number of tabs 11 formed, circumferential lengths of the tabs 11 and the spacing between the tabs 11 is not especially restricted, but taking the case wherein 12 tabs are formed on the inner wall surface of a TE ring portion 9 having an inner diameter of approximately 29 mm as an example, the circumferential lengths of the tabs 11 should be about 4 ∼ 8 mm and the spacing between the tabs should be about 0.2 ∼ 0.8 mm. If the circumferential lengths of the tabs 11 are less than 4 mm, the engaging force of the tabs 11 on the mouth portion of the container is weakened so as to risk the occurrence of rupture defects in the bridges, and if the circumferential lengths are greater than 8 mm, the mechanical strength of the tabs 11 increases so as to make molding difficult. Additionally, the thickness of the tabs 11 can be uniform, or the tip portion sides may be made thicker. Normally, the thickness of the tabs is 0.2 ~ 1.2 mm, preferably about 0.6 ~ 1.0 mm. If the tab thickness is less than 0.2 mm, the tabs can easily bend, so as to become incapable of guiding the TE ring portion 9 downward when the cap is opened, thereby risking the occurrence of rupture defects in the bridges; if the tab thickness is greater than 1.2 mm, molding becomes difficult and the capping properties are made worse. As shown in Fig. 10, when the thickness of the tabs 11 is made greater on the tip portion side than on the base portion (the inner wall side of the TE ring portion 9), for example if the base portion length f is about 0.3 ~ 0.7 mm and the tip portion length g is about 1.5 ~ 2.5 mm, the base portion thickness h should preferably be about 0.4 ~ 0.6 mm and the tip portion thickness i should preferably be about 0.5 ~ 1.0 mm. As is clear from the results of experimental examples which will be given below, when the base portion thickness h and the tip portion thickness i of the tabs 11 are less than the above-given ranges, the strength (anti-bending strength) of the tabs 11 is weakened, so that when the cap 1 is attached to the mouth portion 21A of the container and turned in the cap-opening direction, the tabs engaged with the depressing portions 24 have their tips bent downward, so that there may be cases wherein the cap 1 could come loose from the mouth portion 21A of the container without the TE ring portion 9 becoming separated from the main portion 8. Additionally, when the base portion thickness h and the tip portion thickness i of the tabs 11 are greater than the above-given ranges, the strength of the tabs 11 (anti-bending strength) is unnecessarily increased so that the resistance when the tabs 11 pass the depressing portions 24 increases during attachment of the cap 1 to the mouth portion 21A of the container, thereby risking a problem wherein the cap 1 cannot be sufficiently closed to the standard screw completion angle. While the number of bridges 6 formed in not especially restricted, the overall sum of the cross-sectional areas of all of the bridges 6 should be about 0.3 ∼ 9.0 mm 2 , and the overall sum of the rupture strengths of the bridges 6 when pulled should be about 10 ∼ 18 kg. When the overall sum of the cross-sectional areas of the bridges 6 is greater than 9.0 mm 2 and the rupture strength (when pulled) of the bridges is greater than 18 kg, the cap can come loose without the bridges being severed when the cap is opened, or the relation BBA > SRA could arise so as to make the tamper-evidence properties (cap-opening display properties) worse. When the overall sum of the cross-sectional areas of the bridges 6 is less than 0.3 mm 2 and the rupture strength (when pulled) of the bridges is less than 10 kg, the bridges can be severed during capping. The container 21 has an external thread 22 formed on the outer circumference at the upper end portion of the mouth portion, with an annular expanded portion 23 provided underneath the external thread 22, and a flange portion 29 formed underneath the annular expanded portion 23. As shown in Figs. 3 to 5, two first bridge-stretching means 26A and two second bridge stretching means 26B are alternately provided along the circumferential direction continuously on the annular expanded portion 23; in each of the first bridge-stretching portions 26A being formed a depressing portion 24 for engaging the tabs 11 of the cap 1 and pressing down the tabs 11 when the cap 1 attached to this mouth portion 21A of the container is turned in the cap-opening direction, a horizontal extended step portion 25 which engages the tabs 11 when they are pushed down by the depressing portion 24, so as to inhibit an upward movement of the tabs 11, and at the end of the extended step portion 25 in a cap-opening direction, an engaging claw portion 28 for engaging the tabs 11 and inhibiting the rotation of the TE ring portion 9 in the cap-opening direction; each of the second bridge-stretching portions 26B having the depressing portion 24 and the extended step portion 25. The number of the first bridge-stretching means 26A and the second bridge-stretching means 26B are not especially restricted, and the number may be one or plural. On each of these depressing portions 24, the side which contacts the tabs 11 when opening the cap is made into an inclined surface which gradually expands downward toward the cap opening direction. In addition, a side of the engaging claw portion 28 in the first bridge-stretching means 26A, which is the opposite side from the inclined surface, and a side of the extended step portion 25 in the second bridge-stretching means 26B, which is the opposite side from the inclined surface, are made into storage guide surfaces 27 of which the projection height gradually decreases in the cap-opening direction. The angle of inclination  of the depressing portions 24 as shown in Fig. 3 and the angle of inclination α as shown in Fig. 5 should be 5 ∼ 50 degrees. If the angle  or α is greater than 50 degrees, the resistance of the tabs to being pressed down when the cap 1 attached to the mouth portion 21A of the container is turned in the cap-opening direction becomes too strong, and cases may arise wherein the tabs are not pressed down. Additionally, when the angle  or α is less than 5 degrees, the BBA becomes too large, which is undesirable. Additionally, the difference (a - b) between the length a from the upper end of the mouth portion 21A of the container to the lower end of the extended step portion 25, and the length b from the upper end of the mouth portion 21A of the container to the upper end of the tabs 11 of the cap 1 when attached as shown in Fig. 2 should be at least 0.5 mm. If this difference (a - b) is less than 0.5 mm, there may be cases wherein the bridges 6 are not severed due to stretching of the bridges 6. Additionally, the length c from the annular expanded portion 23 to the extended step portion 25 as shown in Fig. 3 should be 0.5 ∼ 4.0 mm. If this length c is less than 0.5 mm, the tab depressing effect is not sufficiently activated during cap-opening so as to increase the BBA, and if the length c is greater than 4.0 mm, the excess thickness is increased so as to present a disadvantage in terms of cost. Additionally, the length d of the extended step portion 25 should be 3 ∼ 10 mm. If this length d is less than 3 mm, the BBA increases, and if greater than 10 mm, the excess thickness is increased so as to present a disadvantage in terms of cost. Additionally, the length e of the depressing portion 24 should be 1.5 ∼ 8.0 mm. If this length e is less than 1.5 mm, the tab depressing effect is not sufficiently activated during cap-opening, and if the length e is greater than 8.0 mm, the excess thickness is increased so as to present a disadvantage in terms of cost. The angle of inclination β of the storage guide surface 27 as shown in Fig. 5 should be 15 ∼ 60 degrees. Additionally, the length of the engaging claw portion 28 extending from the lower end of the extended step portion 25 is such that the engaging claw portion 28 reaches the upper surface of the flange portion 29, and should normally be about 2.5 ∼ 7.0 mm. Furthermore, the outer diameters of the external thread 22, the annular expanded portion 23, and the first and second bridge-stretching means 26A,26B can be made equal. Additionally, the width of the annular expanded portion 23 should be 0.5 mm or greater, more preferably 1.0 ∼ 5.0 mm. Next, the operations of the sealing device according to the present example will be explained. After being filled with a desired content fluid, the container 21 is conveyed to a cap attachment apparatus omitted from the drawings, and the cap 1 is screwed and fitted to seal the cap 1 onto the mouth portion 21A while supporting the bottom surface of the flange 29, preferably in a suspended state. When the cap 1 is attached to the mouth portion 21A of the container, the tabs 11 of the cap 1 pass by the annular expanded portion 23 with the tips folded upward, so that no excessive forces are applied to the bridges 6. Additionally, in the final stage of attaching the cap 1, the tabs 11 which overlap the four bridge-stretching means 26A,26B in the attached state pass the annular expanded portion 23, and achieve contact with the storage guide surfaces 27 of the bridge-stretching means 26A,26B with tips slightly opened toward the radially inward side so that the tips contact the outer circumferential surface of the mouth portion of the container underneath the annular expanded portion 23. In the present example, tab storage guide surfaces 27 having projection heights which gradually decrease in the cap-opening direction are formed on the bridge-stretching means 26A,26B, as a result of which these tabs 11 are folded with the tips upward along the inclines of the storage guide surfaces 27 when the tabs 11 are moved in the cap-closing direction while contacting the storage guide surfaces 27, so that the bridges 6 are not severed. The cap 1 is attached in the state shown in Fig. 2 by twisting the cap 1 onto the mouth portion 21A of the container with a predetermined cap-closing torque value. In this state wherein the cap is attached, all of the tabs 11 of the plurality of tabs 11 on the cap 1 aside from the four which overlap the bridge-stretching means 26A,26B are in a slightly open state in the radially inward direction so that the tips contact the outer circumferential surface of the mouth portion of the container underneath the annular expanded portion 23, and the four tabs 11 overlapping the bridge-stretching means 26A,26B have their tips folded upward. Additionally, the upper end portion of the container 21 is pressed into contact with the liner 5 of the cap 1 so as to cause a slight indentation, thereby sealing the container 21. The operations for opening the cap of the sealing device when the cap is attached will be explained with reference to Figs. 6 through 8. When the cap 1 attached to the mouth portion 21A of the container as shown in Fig. 6 is turned in the cap-opening direction 50, a slight rotational movement of the cap 1 causes the upper ends (tips) of the tabs 11 on the cap-opening direction side to contact the depressing portions 24 of the bridge-stretching means 26A,26B formed on the mouth portion 21A of the container, so that the tabs 11 are gradually pushed down along the inclines of the depressing portions 24 (Fig. 7). The tabs 11, which make a rotational movement along the depressing portions 24 while they are pushed down along the inclines of the depressing portions 24, proceed smoothly from the depressing portions 24 to the horizontal extended step portions 25. When the tabs 11 reach the extended step portions, the main portion 8 is lifted upward along the external thread 22 while the TE ring portion 9 is pushed down; therefore, immediately after the rotation in the cap-opening direction is initiated, the main portion 8 and the TE ring portion 9 come apart, and a plurality of thin bridges 6 coupling the main portion 8 with the TE ring portion 9 are stretched and severed, or formed into thin threads which may be easily severed. In addition, the TE ring portion 9 can move rotationally in the cap-opening direction together with the main portion 8 until an end surface of a tab 11 reaches the engaging claw portion 28 of the first bridge-stretching means 26A. After the tabs 11 proceed from the depressing portions 24 to the extended step portions 25, there is no push-down of the TE ring portion 9; however, the main portion 8 is still lifted upward along the external thread 22, as a result of which the bridges 6 are further stretched, and completely severed while the tabs 11 are moving along the extended step portions 25. In the case where the severance does not occur while the tabs 11 are moving along the extended step portion 25, the tabs 11 are engaged with the engaging claw portions 28 formed on the first bridge-stretching means 26A, and the rotation of the TE ring portion 9 is completely inhibited, as a result of which the bridges 6 which have been stretched and weakened by the rotation of the main portion 8 are instantly severed. At almost the same time that the TE ring portion 9 is separated from the main portion 8, the vertical weakening line formed on the TE ring portion 9 is severed so as to break the TE ring portion 9 into a band, thus clearly indicating that the cap 1 has been opened. Thereafter, the main portion 8 can be removed from the mouth portion 21A of the container by rotating the main portion 8 further in the cap-opening direction. Since the sealing device of the present example has at least one bridge-stretching means 26A,26B which is provided continuously on the mouth portion 21A of the container, each of the bridge-stretching means having a depressing portion 24 which engage and depress the tabs 11 of the cap 1 when the cap 1 attached thereto is turned in the cap-opening direction, and an extended step portion 25 which engages the tabs 11 when they are pushed down by the depressing portion 24, so as to inhibit an upward movement of the tabs 11, when the cap 1 attached to the mouth portion 21A of the container is turned in the cap-opening direction, the tabs 11 adjacent to depressing portions 24 of respective bridge-stretching means 26A,26B contact the depressing portions 24 and are pushed down such that the TE ring portion 9 is pushed down; accordingly, the main portion 8 which is lifted upward along the external thread 22 and the TE ring portion 9 quickly come apart and the plurality of thin bridges 6 coupling the main portion 8 with the TE ring portion 9 are stretched. In addition, after the tabs 11 proceed to the extended step portions 25 of the bridge-stretching means 26A,26B, since the main portion 8 is still lifted upward along the external thread 22 while the TE ring portion 9 is inhibited from moving upward, these bridges 6 are severed to separate the TE ring portion 9 from the main portion 8, thereby clearly indicating that the cap has been opened. Therefore, according to this sealing device, the bridge breaking angle (BBA) which is the rotational angle of the position at which the bridges 6 are severed by rotating the cap 1 attached to the mouth portion 21A of the container in the cap-opening direction can be made 90 degrees or less, preferably 45 degrees or less; furthermore, the problem wherein the cap-opening torque is increased due to the rupture resistance of the bridges can be prevented in comparison with conventional products having the formation wherein the bridges are severed by inhibiting the rotation of the TE ring portion 9, thus allowing the cap to be opened by a suitable cap-opening torque. Additionally, by forming the engaging claw portion 28 at the end of the extended step portion 25 of at least one bridge-stretching means 26A in a cap-opening direction, for engaging tabs 11 so as to inhibit the rotation of the TE ring portion 9 in the cap-opening direction, even in the case when the tabs 11 pass the extended step portion 25 without the bridges 6 being severed, the tabs 11 engage the engaging claw portion 28, and the rotation of the TE ring portion 9 is inhibited; accordingly, the bridges 6, which have already been stretched and weakened, can be severed easily and securely. Fig. 9 shows another mode of the present invention. A sealing device according to this mode is characterized by having a container 21 which has a bridge-stretching means 26C formed by projecting an engaging claw portion 28B downward from an extended step portion 25 with such a short length that the tip of the engaging claw portion 28B does not reach the upper surface of a flange portion 29. The engaging claw portion 28B is formed to have a length k, measured from the lower surface of annular expanded portion 23, of about 2.5 ∼ 4.0 mm. If the length k is less than 2.5 mm, the engagement of the tabs 11 of the cap 1 with the engaging claw portion 28B becomes difficult. A length k greater than 4.0 mm would present a disadvantage in that when opening the cap, the cap cannot be smoothly removed since the tabs 11 contact the engaging claw portion 28B many times during the removal of the cap after the bridges are severed. In this mode, since the container 21 is provided which has the bridge-stretching means 26C formed by projecting the engaging claw portion 28B downward from the extended step portion 25 with such a short length that the tip of the engaging claw portion 28B does not reach the upper surface of the flange portion 29, the tabs do not contact the engaging claw portion, or the contact force is weakened, so that smooth removal of the cap is possible. The present invention is not limited to the above-mentioned examples, and various changes or modifications are possible. For example, when providing a plurality of bridge-stretching means 26A,26B, the positional spacing in the circumferential direction may be uniform, or a number of bridge-stretching means 26A,26B may be shifted by a few degrees in the circumferential direction. Additionally, besides attaching the cap 1 having a TE ring portion 9 as with the previous example, the container of the present invention can be applied to a synthetic resin cap of the type wherein multiple wings are formed on the inner wall surface of the TE ring portion 9. Additionally, the annular expanded portion 23 may be replaced by a broken annular type expanded portion wherein island-type expanded portions are arranged in the circumferential direction by providing at least one notched portion in the circumferential direction of the annular expanded portion. [Embodiments] Caps 1 and containers 21 having the same structures as shown in Fig. 1 were made, and the performance of sealing devices composed of these caps 1 and containers 21 was studied. Cap: Caps 1 were made by making the cap main bodies 4 constructed as shown in Fig. 1 with polypropylene as the material, and forming liners 5 composed of a polypropylene-type resin inside the cap main bodies 4 by means of an in-shell molding method. The specifics of the resulting caps 1 are as follows: Outer Diameter of Cap 30 mm Height of Cap 24.7 mm Height of TE Ring Portion 9.6 mm Circumferential Length of Tabs (12 formed on the inner surface of the TE ring portion) 6.0 mm Tab Projection Length 2.5 mm Tab Thickness 0.60 mm Sum of Cross-sectional Areas of Bridges 5.7 mm 2 Container: Containers (pet bottles) with a capacity of 1.5 liters having a mouth portion 21A as shown in Fig. 1 were made with polyethylene terephthalate as the material. The specifics of the containers 21 are as follows: Outer Diameter of Mouth Portion (minimum outer diameter) 24.94 mm Outer Diameter of External Thread and Annular Expanded Portion 27.56 mm Angles  and α of Depressing Portions 25 degrees Length of a in Fig. 2 15.4 mm Length of b in Fig. 2 13.6 mm Length of c in Fig. 3 1.8 mm Length of d in Fig. 3 6.6 mm Length of e in Fig. 3 3.9 mm Inclination Angle β of Storage Guide Surfaces 30 degrees (Experiment 1) The rupture strength of the bridges in the tensile direction of the caps were determined. The TE ring portion of each cap was affixed to the stand side of a push-pull gauge (stand: IMADA SEISAKUJO Model 5020; push-pull gauge: NTTONIC Type PDE-50R), the main portion was affixed to the terminal portion of the gauge, then a tensile force was applied across the main portion and the TE ring portion and the tensile strength at the time the bridges broke was measured. As a result, the produced caps had a rupture strength of the bridges in the tensile direction of 14 kg (average value, n = 100). (Experiment 2) Using the above-mentioned caps and containers, (1) the bridge rupture occurrence rate when the caps were attached, (2) the cap-opening torque value for opening the caps, (3) the BBA, (4) the SRA, and (5) the bridge rupture defect occurrence rate for opening the caps were evaluated. The above-mentioned containers were filled with a standard amount of hot water of 85 °C, and the caps were attached to the mouth portions by using a capping machine (ALCOA Magnatorque). The capping conditions were set to 15 kg·cm of static torque and 15 kg of top-load. (1) Bridge rupture occurrence rate when caps were attached: After the containers were capped, the caps were outwardly checked for the presence of bridge ruptures, as a result of which the bridge rupture occurrence rate was found to be 0 % (n = 100). Next, the capped containers were opened to evaluate (2) the cap-opening torque value for opening the caps, (3) the BBA, (4) the SRA, and (5) the bridge rupture defect occurrence rate. As a result, (2) the torque values for opening the caps were 13 kg·cm (one-dimensional) and 5-7 kg·cm (two-dimensional) (n = 100). The (3) BBA was approximately 40 degrees (average value, n = 100). The (4) SRA was approximately 120 degrees (average value, n = 100). The (5) bridge rupture defect occurrence rate was 0 % ( n = 100). (Experiment 3) Caps were made wherein the shapes of the tabs 11 on the caps 1 described above were such that the thickness of the tip portion was greater than the base portion (near the TE ring portion 9) as shown in Fig. 10, attached to the mouth portions 21A of the above-described containers 21, and the relationships between the cap-opening display performance and capping suitability were evaluated. The tabs 11 were made so that the total projection length (f + g) was 2.5 mm, the base portion length (f) was 0.5 mm and the tip portion length (g) was 2.0 mm, and caps of samples 1-7 and comparative products having base portion thicknesses (h) and tip portion thicknesses (i) as listed in Table 1 were made. The above-mentioned containers 21 were filled with a standard amount of hot water of 85°C, and the caps were attached to the mouth portions 21A by using a capping machine (ALCOA Magnatorque). The capping conditions were set to 15 kg·cm of static torque and 15 kg of top-load. The following categories a ∼ d were studied for each sample, and the results are recorded in Table 1. a. Strength of Bridges of Cap The rupture torque values of the bridges for opening the caps was measured (units in kg·cm). b. Strength of Tabs of Cap (Anti-bending Strength) For each cap listed in Table 1, a sample was prepared wherein the horizontal score 7 for separating the TE ring portion 9 were not formed, each sample cap was attached to a mouth portion 21A of a container and opened, and the torque value at the moment the tabs 11 inverted so that the cap 1 came loose from the mouth portion 21A of the container was measured (units in kg·cm). c. Evaluation of Cap-opening Display Ability The occurrence of cap-opening display defective products wherein the tabs 11 inverted without the bridges 6 breaking when the cap was opened so that the cap 1 came free from the mouth portion 21A of the container with the TE ring portion 9 still connected to the main portion 8 was evaluated (n = 10). The evaluations are indicated by a symbol "○" for sample caps without cap-opening display defective products, and by a symbol "×" for sample caps wherein cap-opening display defects occurred at least once. d. Evaluation of Capping Suitability The tightness of the caps when the sample caps were respectively attached to the mouth portions 21A of the container were evaluated as an average value of 10 trials (n = 10) per sample by measuring the relative rotational angles between the beginnings of the threads on the containers (upper side of the mouth portions) and the beginnings of the threads on the caps (bottom side of the caps). The evaluations are indicated by a symbol "○" for sample caps wherein the relative rotational angle (average value) was 580° ± 30°, and by a symbol "×" for sample caps which lay outside the above-mentioned angles. SAMPLE TAB THICKNESS STRENGTH OF BRIDGES (kg·cm) STRENGTH OF TABS (kg·cm) CAP-OPENING DISPLAY ABILITY CAPPING SUITABILITY Base Portion Tip Portion Comp.Ex. 0.3 mm 0.3 mm 13.2 10.8 × ○ 1 0.3 mm 0.4 mm 13.2 13.4 × ○ 2 0.4 mm 0.5 mm 13.2 20.9 ○ ○ 3 0.5 mm 0.7 mm 13.2 22.6 ○ ○ 4 0.5 mm 0.9 mm 13.2 23.6 ○ ○ 5 0.6 mm 1.0 mm 13.2 27.4 ○ ○ 6 0.7 mm 1.2 mm 13.2 30.3 ○ × 7 0.8 mm 1.4 mm 13.2 32.4 ○ × As is clear from the above experimental results, the sealing device according to the present invention was excellent in that problems of increases in the cap-opening torque due to the rupture resistance of the bridges were prevented, and in that the BBA when opening the cap was small. INDUSTRIAL APPLICABILITY As explained above, with the sealing device according to the present invention, the bridge breaking angle (BBA) which is the rotational angle of the position at which the bridges break, can be made 90 degrees or less, preferably 45 degrees or less; furthermore, problems wherein the cap-opening torque increases due to the rupture resistance of the bridges can be prevented in comparison with conventional products of the type wherein the bridges are severed by inhibiting the rotation of the TE ring portions, so as to allow the cap to be opened with an appropriate cap-opening torque. Additionally, by forming the engaging claw portion at the end of the extended step portion of at least one bridge-stretching means in a cap-opening direction, for engaging the engaging projections so as to inhibit the rotation of the TE ring portion in the cap-opening direction, even in the case when the engaging projections pass the extended step portion without the bridges being severed, the tabs engage the engaging claw portion, and the rotation of the TE ring portion 9 is inhibited; accordingly, the bridges, which have already been stretched and weakened, can be severed easily and securely. Accordingly, in accordance with the present invention, a sealing device can be provided which prevents the cap-opening torque from becoming high due to the rupture resistance of the bridges when the cap attached to the mouth portion of the container is turned in the cap-opening direction, and which can yield good tamper-evidence properties by reducing the BBA when the cap is being opened; and such a container can also be provided.

Claims: A sealing device comprising a container (21) and a cap (1) attached to a mouth portion (21A) thereof, said cap has a cap main body (4) having a top plate portion (2) and a tubular portion (3) extending downward from the periphery thereof, said tubular portion being partitioned by means of a tearable weakening line into an upper main portion (8) and a lower tamper-evidence ring portion (9), a threaded portion (10) being formed on an inner wall surface of said main portion, and engaging projections (11) being provided on an inner wall surface of said tamper-evidence ring portion, said container (21) has an external thread (22) formed on an outer circumference of an upper end of said mouth portion (21A) thereof, an annular expanded portion (23) formed underneath said external thread (22), and at least one bridge-stretching means (26A, 26B) which is provided continuously underneath said expanded portion (23), the bridge-stretching means (26A, 26B) having a depressing portion (24) which engages said engaging projections on said cap and pushes down said engaging projections (11) when said cap attached to said mouth portion of the container is twisted in a cap-opening direction, and an extended step portion (25) which engages the engaging projections (11) when they are pushed down by the depressing portion (24), so as to inhibit an upward movement of the engaging projections (11), characterised in that : said cap is a synthetic resin cap, said engaging projections (11) are erectable and oriented substantially horizontally with their tips facing in a radially inward direction and are foldable upward, and said engaging projections (11) overlapping said bridge-stretching means (26A, 26B) have their tips folded upward when said synthetic resin cap is attached to said mouth portion of the container. A sealing device in accordance with claim 1, wherein said depressing portion (24) has an inclined surface which gradually expands downward in a cap-opening direction. A sealing device in accordance with claim 2, wherein the inclination angle (, α) of said inclined surface of said depressing portion (24) is from 5 to 50 degrees. A sealing device in accordance with claim 1, wherein said depressing portion (24) is such that a side which contacts the engaging projections (11) when the cap is opened has an inclined surface which gradually expands downward in a cap-opening direction, and a side of said extended step portion (25) which is the opposite side of said inclined surface has a storage guide surface (27) having a projection height which gradually decreases in a cap-opening direction. A sealing device in accordance with claim 4, wherein the inclination angle (, α) of said inclined surface of said depressing portion (24) is from 5 to 50 degrees. A sealing device in accordance with claim 1, wherein an engaging claw portion (28) for engaging said engaging projections (11) and inhibiting the rotation of said tamper-evidence ring portion (9) in the cap-opening direction is formed at the end of said extended step portion (25) of the bridge-stretching means (26A, 26B) in a cap-opening direction. A sealing device in accordance with claim 1, wherein the weakening line of said synthetic resin cap is a horizontal score (7) formed by cutting said tubular portion (3) in a circumferential direction while leaving a plurality of thin bridges (6). A sealing device in accordance with claim 1, wherein the engaging projections (11) of said synthetic resin cap (1) are a plurality of erectable tabs which are formed such as to project from an inner wall of said tamper-evidence ring portion (9). A sealing device in accordance with claim 1, wherein a vertical weakening line which is severed at almost the same time that the weakening line is severed so as to break said tamper-evidence ring portion (9) into a band is formed on said tamper-evidence ring portion (9) of said synthetic resin cap (1). A sealing device in accordance with claim 1, wherein a bridge breaking angle which is the rotational angle of the position at which said bridges (6) are severed when said cap (1) attached to said mouth portion (21A) of the container (21) is rotated in a cap-opening direction is 90 degrees or less.

Inventors: GOMI TATSUYA, TAKAMATSU KOUICHI, GOMI, TATSUYA, TAKAMATSU, KOUICHI, TAKAMATSU, Kouichi, Shibazaki Seisakusho Ltd.
Applicants: SHIBAZAKI SEISAKUSHO LTD, SUNTORY LTD, SHIBAZAKI SEISAKUSHO LTD., SUNTORY LIMITED
Application year: 1997
Main classification: B65D41
IPC codes: B65D41