JP4553677B2 - Plastic cap - Google Patents

Description

    The present invention relates to a synthetic resin cap, and more particularly to a synthetic resin cap that is screwed into a container opening to seal a container.

  Conventionally, a synthetic resin cap that is screwed into a container mouth portion to seal the container has a female screw formed on the inner peripheral surface of the skirt wall and is tightened by screwing with a male screw formed on the outer peripheral surface of the container mouth portion. Thus, the close contact between the liner formed on the inner surface of the top wall and the top of the container mouth, or the close contact between the annular seal hanging from the inner surface of the top of the cap and the top of the container mouth is ensured to ensure the sealing of the container. Therefore, in order to guarantee the sealing performance, a screw strength that enables strong screw tightening is required. On the other hand, from the viewpoint of resource saving and low cost, it is desirable to reduce the amount of resin used in the cap as much as possible. In addition, reducing the amount of resin can shorten the cooling time in the molding process, thereby speeding up the molding cycle, increasing productivity and reducing power consumption, and recycling used caps. Recycling costs and energy can be reduced from the viewpoint, and it is desirable from the viewpoint of application to environmental problems, and further reduction in the amount of resin is required. Conventionally, various attempts have been made to reduce the amount of resin while ensuring sealing performance. However, ensuring sealing performance and reducing the amount of resin are contradictory, and no more effective measures have been found.

  On the other hand, in the screw cap, in order to clean the screw threaded portion after sealing on the female screw formed on the inner peripheral surface of the skirt wall, or to improve the exclusion of water droplets mixed in the inner peripheral surface of the cap at the time of shower cooling, In order to reduce the opening torque, and to form a vent passage that prevents blowout when opening carbonated beverages, etc., a plurality of missing portions are provided at equal intervals in the circumferential direction in the form of longitudinal grooves. (For example, see Patent Documents 1 and 2). Providing a missing part in the thread results in a reduction in the amount of resin. However, in these cases, the amount of missing parts is small compared to the effective length of the screw thread, so the amount of resin is reduced only a little. Conventionally, the shape of the female screw has been devised for the purpose of reducing the amount of resin. I can't find it.

Further, the conventional threaded cap has a disadvantage that the thread is undercut at the time of molding and is overlapped in the axial direction, so that forcible removal occurs at the time of mold release, and so-called screw dripping phenomenon tends to occur. That is, even if the screw thread is provided with a missing portion in the form of a longitudinal groove as described above, the inconvenience cannot be solved as long as the missing portion is few and the screw thread overlaps in the axial direction. In addition, from the viewpoint of cleanability, by providing the screw thread with the notched portion in the form of the vertical groove, the cleaning water that has entered the cap flows downward through the vertical groove, so that the cleanability is improved. It is still unsatisfactory to completely remove water droplets adhering to the surface.
JP 2002-173157 A JP 2004-91023 A

  As a means to reduce the amount of resin in the cap, it is conceivable to reduce the thickness of the entire cap. However, if the thickness is reduced, the strength will naturally decrease, causing a number of problems such as deformation and loss of sealing performance, or easy occurrence of sink marks. However, there is a limit to thinning. The present applicant, as a synthetic resin cap capable of overcoming this problem and reducing the amount of resin while ensuring the sealing performance of the cap, has a plurality of recesses on the outer peripheral surface of the skirt wall at intervals in the circumferential direction. Has previously been proposed to extend from the upper end of the skirt wall to the skirt of the tamper evidence band (Japanese Patent Application No. 2004-141291). The proposal made it possible to reduce the amount of resin while avoiding a decrease in strength of the skirt wall. Further, as described above, the conventional synthetic resin cap having a female screw is not yet satisfactory in terms of preventing the female screw from sagging and cleaning the inside after sealing.

  Therefore, the present invention aims to provide a synthetic resin cap that can be screwed and further improved in the proposed synthetic resin cap so that the amount of resin can be further reduced and is excellent in moldability and cleanability. Technical problem to be solved that can be screwed onto the container to maintain a predetermined sealing property, further reduce the amount of resin required for cap molding, facilitate releasability after molding, and improve cleanability It is what.

  The synthetic resin cap of the present invention that solves the above-mentioned problems is a synthetic resin cap that has a top wall and a skirt wall, and is screwed to a male screw formed on the outer peripheral surface of the container mouth to seal the container. In accordance with the thread pitch of the container to be screwed onto the inner peripheral surface, at least the upper and lower surfaces in the axial direction have a threaded projection having a curved surface to be screwed with the screw at the container mouth, and at least the length of the threaded projection in the lead angle direction. It is characterized by being scattered at longer intervals.

  The shape of the threaded protrusion is not particularly limited as long as the upper surface and the lower surface in the axial direction have a curved surface that is threadedly engaged with the screw of the container mouth portion. It can be formed into a substantially hemispherical body. By forming it in a hemisphere, the amount of resin can be reduced, and in particular, release at the time of molding becomes easy, screw dripping resistance is improved, and cleaning properties are also improved. It is desirable that the screw protrusions be arranged so that the screw protrusions adjacent to each other between the upper and lower sides in the axial direction do not overlap with each other when viewed in the axial direction. This facilitates mold release during molding, makes the screw tightening force uniform in the circumferential direction, and can effectively prevent a decrease in the screw tightening strength of the container even with intermittent screw projections. . The screw protrusions are dotted along the lead angle direction at intervals of a predetermined angle α with the center of the screw diameter in the peripheral direction as a starting point. It is said. The predetermined angle α is 5 ° to 30 °, preferably 10 ° to 30 °.

  Furthermore, in the synthetic resin cap, the resin amount is further reduced by arranging concave portions having a predetermined width in the circumferential direction and extending in the axial direction on the outer peripheral surface of the skirt wall at predetermined intervals in the circumferential direction. be able to. And, by forming the threaded protrusion at the position of the inner peripheral surface of the skirt wall corresponding to the position where the concave portion of the outer peripheral surface of the skirt wall is formed, it is possible to effectively reduce the strength of the skirt wall due to the formation of the concave portion. This can be compensated for and can improve moldability and contribute to a reduction in the amount of resin.

  As described above, according to the present invention, the amount of resin required for cap molding can be further reduced in a screw cap that is screwed into a container having a screw formed in the container port to maintain a predetermined sealing property, and A synthetic resin cap capable of facilitating release after molding and improving the washability can be obtained. And since the amount of resin required for cap molding can be reduced, the cooling time at the time of molding can be shortened, productivity can be improved, power consumption can be reduced, and recycling costs can also be reduced. This can save energy. By forming the screw projections in a hemispherical body, the amount of resin can be reduced, and in particular, release at the time of molding is facilitated, anti-screwing is improved, and cleaning properties are also improved. Further, the screw projections are arranged in the circumferential direction with the center of the screw diameter as a base point so that the positional relationship of the screw projections adjacent to each other between the upper and lower sides in the axial direction does not overlap the centers of the screw projections when viewed in the axial direction. By disposing the spacing between adjacent screw projections, it becomes easy to release during molding, and the screw tightening force becomes uniform in the circumferential direction. A decrease in screw tightening strength can be effectively prevented.

  Furthermore, in the synthetic resin cap, by arranging the recesses on the outer peripheral surface of the skirt wall at predetermined intervals in the circumferential direction, it is possible to further reduce the amount of resin while preventing a decrease in the strength of the skirt wall. Then, by forming the screw projection so as to be located at the corresponding position of the inner peripheral surface of the skirt wall corresponding to the position where the concave portion is formed, it is possible to effectively compensate for the decrease in strength due to the concave portion formation and to improve the moldability. Can be improved.

Hereinafter, embodiments of the synthetic resin cap of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partially cutaway front view of a synthetic resin cap according to the present embodiment, FIG. 2 is a front sectional view thereof, FIG. 3 is a bottom view, and FIG.
The synthetic resin cap 1 of this embodiment is molded from a polyolefin resin or other appropriate synthetic resin, and is weakened so that it can be broken in the circumferential direction at the top wall 2, the skirt wall 3 hanging from the top wall, and the lower end of the skirt wall. It is composed of a tamper evident band (hereinafter referred to as a TE band) 4 provided via a line 7. On the inner peripheral surface of the skirt wall, as shown in FIG. 2, a hemisphere 5 that forms a screw projection along the lead angle of the screw at a position corresponding to the female screw of the conventional screw cap is approximately 1.75 turns. Are provided at predetermined intervals over the range. Semi sphere, the center cross-section, so that substantially the same screw length as normal threads as indicated in section 5 'in FIG. 2, the radius R ₁ is defined, the radius to the skirt portion opposite directions curved in the R ₂ radius is continuous to the skirt wall inner surface. The hemisphere may not be a perfect hemisphere but may be a substantially hemisphere.

  As shown in FIG. 4, in the hemisphere 5, the hemispherical centers of adjacent hemispheres 5 in the circumferential direction are scattered according to the screw pitch at an angular interval of α ° in the circumferential direction with the center of the hemisphere as a base point. . It is desirable to arrange so that the angle α between adjacent hemispheres is in the range of 5 to 30 °. When the angle is 5 ° or less, the hemisphere is substantially continuous, and the reduction efficiency of the resin amount is poor. When the angle is 30 ° or more, the interval is too large, the screwing force becomes weak, and it is difficult to maintain the sealing performance. The arrangement of the hemisphere 5 is such that the positional relationship between adjacent hemispheres between the upper and lower sides in the axial direction is an interval of an angle (α / 3) ° to (α / 2) ° in the circumferential direction from the center of the hemisphere. It is desirable to provide a staggered position. That is, the hemispheres 5 do not overlap on the same line when viewed in the cap axis direction, and are always arranged so as to be alternately positioned at the vertical pitch. It is desirable to arrange so that the angle α between adjacent hemispheres in the axial direction is in the range of 5 to 30 °. In the embodiment of FIG. 4, the angles of the hemispheres 5 adjacent to each other in the circumferential direction are provided by being shifted by 30 ° at the effective screw portion, and 15 hemispheres adjacent in the circumferential direction between the vertical pitches when viewed in the axial direction. It is arranged so that it is at intervals. By providing the offset in the axial direction in this way, even if the interval between the adjacent hemispheres in the circumferential direction is large, the interval between the hemispheres when viewed in the axial direction is almost half that interval. A uniform screwing force can be obtained effectively. In FIG. 4, a small hemisphere 8 having a diameter smaller than that of the hemisphere 15 is disposed in a portion corresponding to the starting position of the screw thread, and the first portion of the small hemisphere 8 corresponds to the starting position of the effective screw. The hemisphere 5 is arranged. In the present embodiment, the angle β between the small hemisphere 8 and the first hemisphere is arranged at an interval of approximately 40 °.

  By arranging the hemispheres 5 so as not to overlap in the axial direction as described above, the space between the hemispheres can be increased, and not only the amount of resin is saved, but also synthetic resin cap molding. Even when forcibly removing at the time of mold release, the mold release property is good, so-called screw dripping can be prevented, and the resin molding yield can be improved. Further, by forming the portion corresponding to the female screw in a hemispherical row arranged at a predetermined interval in this way, a cleaning effect for removing dirt adhered to the inner peripheral surface of the skirt wall and the outer peripheral surface of the container mouth performed after the cap sealing is performed. Will also improve. That is, in the cleaning performed on the sealed container, water sprayed toward the cleaning slit 6 formed in the upper part of the cap skirt wall passes through the slit between the inner peripheral surface of the skirt wall and the outer peripheral surface of the container mouth. The washing water that has penetrated into the gap can pass through the gaps between the hemispheres and escape downward, so that the washing effect can be enhanced and it can also be prevented from remaining as water droplets in that portion. Since the screw projection is a hemispherical body, the washing water adhering to it is slid down and can be satisfactorily removed without remaining there.

The synthetic resin cap of the present embodiment is further devised as follows in order to reduce the amount of resin. That is, in this embodiment, the entire skirt wall is not thinned, but the skirt wall is thinned intermittently at equal intervals in the circumferential direction, thereby reducing the influence on the overall strength reduction and reducing the amount of resin. I tried to plan. Therefore, a plurality of recesses 10 are formed on the outer peripheral surface of the skirt wall at intervals in the circumferential direction, and the recesses 10 extend from the upper part of the skirt wall over the weakening line 7 to the TE band 4 as shown in FIG. Extends to the hem.
As a result, when there is an unauthorized opening, the recess 10 is displaced at the position of the weakening line along with the displacement of the TE band and the skirt wall. A plurality of the recesses 10 are formed at equal intervals in the circumferential direction, preferably 3 to 12, more preferably 6 to 12. The circumferential width of the recess 10 is substantially the same from the upper end to the lower end, and is slightly smaller than the circumferential interval between adjacent recesses. The depth of the concave portion can be appropriately set in consideration of the thickness of the skirt wall or the ease of punching, but generally about 0.10 to 0.80 mm is convenient. When the depth of the concave portion is excessive, the strength of the skirt wall is excessively decreased. Conversely, when the depth is too shallow, the amount of the synthetic resin used is reduced only slightly.

  And in order to reduce the influence on the strength reduction of the recess 10, the position of the recess on the outer periphery of the skirt wall and the positional relationship of the hemisphere 5 formed on the inner periphery of the skirt wall are also devised. is there. That is, as apparent from FIG. 4, the pitch of the hemisphere and the pitch of the recess 10 are related so that the hemisphere 5 is located on the inner peripheral wall corresponding to the formation position of the recess on the outer periphery of the skirt wall. Thereby, the thickness reduction of the skirt wall by the recessed part 10 is supplemented by the hemisphere. Further, the recess 10 is formed with a relatively small protrusion 11 extending in the axial direction at an intermediate position thereof. The ridge 11 functions as a reinforcing rib for the thin-walled portion, and also has an effect of more effectively preventing finger slipping at the time of opening.

  In the illustrated synthetic resin cap 1, an inner ring 13 and an outer ring 14 for sealing the container are formed on the inner surface of the top wall 2, but these structures and functions are conventionally known. Since it is employable, detailed description is abbreviate | omitted. And in the synthetic resin cap of this embodiment, in order to reduce the resin amount of the cap, the top wall of the portion located inside the inner ring is made thin. If the top wall is thin, sink marks are likely to occur. To prevent this, a plurality of ribs 15 are formed radially at equal intervals as shown in the figure. A plurality of flaps 12 are formed below the inner peripheral surface of the TE band 4 so as to be able to swing upward as locking pieces formed on the outer peripheral portion of the container mouth and locked to the jaws. However, the structure of the TE band is not limited thereto, and any known shape can be adopted. Further, in order to further reduce the thickness of the synthetic resin cap, as proposed in the above-mentioned application relating to the applicant's application, a thinned portion is provided on the inner peripheral surface of the skirt wall and a thinned portion is provided on the flap portion. May be.

  The synthetic resin cap of the present embodiment is configured as described above, and can be mounted in the same manner as an ordinary synthetic resin cap with a screw. FIG. 5 shows a state in which the synthetic resin bottle is screwed into the container mouth, and the hemisphere 5 is screwed with a male screw 21 formed on the outer peripheral surface of the container mouth 20 in the same manner as a normal continuous female screw thread. Yes. In this state, even if the hemispheres 5 are scattered at intervals of approximately 30 ° in the lead angle direction, the hemispheres are more densely and uniformly distributed in the circumferential direction when viewed in the axial direction where the force acts. Since it is scattered, a uniform screw tightening force can be obtained. However, even if a uniform screw tightening force can be obtained, a decrease in screw tightening force cannot be avoided as compared with the case where continuous screw threads are formed. It is more effective when applied to a container whose internal pressure is negative. In the above embodiment, the hemispheres are provided at equal intervals in the lead angle direction in order to maintain a uniform screw tightening force. However, the hemispheres may be provided non-uniformly without being limited to equal intervals.

  In the above embodiment, the case where the screwing protrusion is formed of a hemisphere has been described. However, the screwing protrusion is not necessarily limited to a hemisphere, and at least the upper surface and the lower surface in the axial direction are screws of the container mouth. For example, the hemisphere may have a shape obtained by cutting the hemisphere vertically or obliquely so that the end surface in the lead angle direction is a U-shaped plane, or in the lead angle direction. It may be a thin scissors shape whose end face is cut vertically or obliquely. Furthermore, in the said embodiment, although the cap formed in the container opening applied to the single thread screw was shown, the present invention can also be applied to the case of a double thread or a multiple thread. In that case, what is necessary is just to arrange | position a screwing protrusion along the lead angle of a multi-thread screw.

  The synthetic resin cap of the present invention can reduce the amount of resin to be molded, increase production efficiency, increase the resistance to twisting at the time of molding, improve the yield, contribute to resource saving, energy saving, and excellent cleaning properties. Therefore, it can be applied to various containers as a single- or multi-strand synthetic resin cap, and more particularly to a negative pressure container.

It is a partially broken front view of the synthetic resin cap which concerns on embodiment of this invention. It is the front sectional drawing. It is the bottom view. It is an AA arrow line view in FIG. FIG. 2 is a partially cutaway front view corresponding to FIG. 1 in a state where the cap is attached to the container mouth of the synthetic resin cap according to the embodiment of the present invention.

Explanation of symbols

1 Cap of Synthetic Resin 2 Top Wall 3 Skirt Wall 4 Tamper Evidence Band 5 Hemisphere (Screw Projection)
6 Cleaning slit 7 Weakened wire 10 Recessed portion 11 Projection 12 Locking piece 13 Inner ring 14 Outer ring 15 Rib

Claims (4)

Has a top wall and a skirt wall, the synthetic resin cap to seal the container is screwed to the male threads formed on the container mouth portion outer peripheral surface, in accordance with the thread pitch of the vessel in the skirt circumference, at least the shaft screwing protrusion direction of the upper and lower surfaces is having a curved surface of the screw screwed in the container mouth part, will be interspersed at intervals longer than the lead angle direction length of at least該螺fitting protrusions,該螺fitting protrusions is approximately An effective screw portion that is a substantially hemispherical shape having a screw length radius and is arranged so that the screw protrusions adjacent to each other in the axial direction are positioned so that the screw protrusion centers do not overlap when viewed in the axial direction. The synthetic resin cap is characterized in that the centers of the screw projections are scattered in the circumferential direction and in the lead angle direction at intervals of a predetermined angle α ° with the center of the screw diameter as a base point . The positional relationship between the screw projections adjacent to each other between the upper and lower sides in the axial direction is shifted by an angle of (α / 3) ° to (α / 2) ° in the circumferential direction with the center of the substantially hemisphere as a base point. The synthetic resin cap according to claim 1. The synthetic resin cap according to claim 1 or 2 , wherein recesses having a predetermined width in the circumferential direction and extending in the axial direction are arranged on the outer peripheral surface of the skirt wall at predetermined intervals in the circumferential direction.   4. The synthetic resin cap according to claim 3, wherein the threaded protrusion is formed at a corresponding position of the inner peripheral surface of the skirt wall corresponding to a position where the concave portion of the outer peripheral surface of the skirt wall is formed.

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