JP7208848B2 - Manufacturing method of plastic cap - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a plastic cap comprising an inner plug that is molded integrally with a cap body and then cut off and combined with an upper lid. The present invention relates to a method of manufacturing a plastic cap capable of suppressing an increase in internal pressure in a space inside the cap when assembled with the upper lid.

In a plastic cap consisting of a cap body and a top lid that are fixed to the mouth of a container and used, a pull ring is formed on the intended opening of the top plate of the cap body when the contents are first taken out in order to ensure sealing performance. By pulling up and breaking the weakened portion, an opening for pouring out the contents is formed.
In a cap applied to a container filled with a viscous content, the content is poured out by pressing the body of the container. is preferably small. However, in a cap with a small spout, it is difficult to form a pull ring in the planned opening portion. Sometimes openings cannot be easily formed.

On the other hand, a cap that does not have a pull ring in the planned opening portion is also known. An outer lid that can be opened and closed using the hinge as a fulcrum, and an inner lid that is held in the outer lid and seals the opening of the pouring tube, wherein the inner lid includes a wall portion and the an inner ring formed inside the wall portion and fitted into the opening of the pouring tube when the upper lid is closed; the outer lid includes a top wall; and the top wall. and a tubular wall provided on the inner surface of the top wall inside the skirt wall and having a diameter larger than the opening of the pouring tube, the tubular wall comprising the A hinge cap having holding means for holding an inner lid inside thereof, wherein the inner ring is formed longer than the wall portion at least on the hinge portion side, and the inner lid extends inside the cylindrical wall. On the other hand, a cap has been proposed which is held slidably at least in the height direction and which moves together with the outer lid when the outer lid is opened and closed.

When using the hinge cap, it is not necessary to pull up the pull ring to form an opening. In addition, since the inner lid is a two-piece type cap that is assembled after being formed separately from the cap main body and the outer lid, the inner lid can move separately from the upper lid and has excellent sealing performance. is.

JP 2014-162499 A

However, since the hinge cap is a two-piece type cap, two processes are added, namely, a process of forming the inner lid and a process of assembling the inner lid to the outer lid. Therefore, it is still not sufficiently satisfactory in terms of productivity and economy as compared with molding of a one-piece type cap.
In order to solve such problems, the present inventors have proposed a plastic cap consisting of a cap body and a top lid, in which the top lid is formed with a protrusion projecting downward from the inner surface of the top surface and having an engaging portion on the outer surface. The cap body is formed with an annular side wall having an outer diameter capable of being in close contact with the inner surface of the pouring nozzle, and an inner plug having a bottom formed below the annular side wall. It is formed integrally with the cap body through a weakened portion that can be broken below a seal portion having an inner diameter that can be tightly attached to the inner plug of the pouring nozzle, and the inner surface of the annular side wall is engaged with the protrusion. We have proposed a plastic cap characterized by forming an engaged portion that can engage vertically with the joint portion (Japanese Patent Application No. 2017-129504).

The above plastic cap is excellent in productivity because the inner plug, which was conventionally formed as a separate part from the cap body and the top lid, can be integrally molded with the cap body, and exhibits excellent sealing and opening properties. It is possible to
However, the above-mentioned cap is formed by the upper lid, the top plate of the cap main body, and the upper surface of the inner plug, which are in a sealed state, by pushing up the inner plug portion from below in a state in which the upper lid is set on the cap body and sealed. There is a problem that the internal pressure of the space inside the cap rises and a gap is generated in the seal portion between the upper lid and the cap main body, or the upper lid opens when subjected to heat treatment.
If there is a gap between the sealing part of the top lid and the cap body, washing water may flow into the cap during shower cleaning after filling the contents, and the inside of the cap may leak when the top lid is open. There is also the risk of contamination. On the other hand, if the fitting between the top lid and the cap body is excessively strengthened so that the sealing state between the top lid and the cap body is not affected even when the internal pressure inside the top lid rises, the unsealing property is deteriorated.
In addition, in the above-mentioned cap, by pushing up the inner plug from below, the weakened portion connecting the cap body and the inner plug is broken and the inner plug is separated from the cap body. There has been a problem that feathering due to elongation of the resin may occur and thread-like resin pieces may be generated. If such resin pieces are generated, there is a concern that when the inner plug is assembled to the cap body, the resin pieces may be caught and cause a sealing failure, or the resin pieces may drop and enter the contents.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a plastic cap having an inner plug that is molded integrally with the cap body and then cut off and assembled to the upper lid, in which thread-like resin pieces are generated at the cut edge after the weakened portion is broken. To provide a method for manufacturing a plastic cap capable of effectively preventing this and effectively preventing the pressure rise in the space inside the cap when the inner plug is separated from the cap body and assembled to the upper lid.

According to the present invention, the cap body is fitted and fixed to the mouth of the container, which consists of a top plate portion and a skirt portion, and a pouring nozzle is formed on the outer surface of the top plate portion so as to surround the intended opening portion; The cap body comprises a top surface and an upper lid comprising a peripheral wall hanging down from the outer peripheral edge of the top surface, the top lid protruding downward from the inner surface of the top surface and having an engaging portion. is formed with an annular side wall having an outer diameter that allows close contact with the inner surface of the pouring nozzle, and an inner plug formed with a bottom portion below the annular side wall, the inner plug being the pouring nozzle It is formed integrally with the cap body via a weakened portion that can be broken below the sealing portion having an inner diameter that can be tightly attached to the inner plug, and the annular side wall has an engaging portion of the protrusion and a vertical direction. and the inner surface of the pouring nozzle has a portion capable of forming an air passage with the outer surface of the annular side wall of the inner plug detached from the cap body. A plastic cap precursor in which the air passage forming portion is located below the sealing portion and above the breakable weakened portion is used, and the upper lid is applied to the cap main body and sealed, and the middle is sealed. After breaking the breakable weakened portion by pressing the bottom portion of the plug from below, the bottom portion of the inner plug is further pressed from below to engage the engaging portion of the projecting portion and the engaged portion of the inner plug. is engageable, and the outer surface of the annular side wall and the inner surface of the pouring nozzle are brought into close contact with each other, wherein after breaking the breakable weakened portion, the pressing speed of the inner plug is slowed down Thereby, the internal pressure of the space inside the cap formed by the upper lid and the top plate portion of the cap body is released from the air passage formed between the outer surface of the annular side wall and the inner surface of the pouring nozzle. A manufacturing method is provided.

In the method for producing a plastic cap of the present invention,
1. Having a stopping step of reducing the pressing speed of the inner plug to zero in a state where the air passage is formed;
2. a plurality of inwardly protruding ribs are formed on the inner surface of the pouring nozzle, and a space between adjacent ribs serves as the air passage;
3. The pressing speed of the inner plug is slowed down or set to zero from immediately after the breakable weakened portion is broken to before the sealing portion of the annular side wall of the inner plug rides over the plurality of ribs. slow down the post-pressing speed;
4. the top lid being hinged to the cap body;
5. The pressing speed of the inner plug before breaking the breakable weakened portion is 150 mm/s or more, and the pressing speed of the inner plug after breaking the breakable weakened portion is 50 mm/s or less;
is preferred.

In the plastic cap of the present invention, the inner plug is integrally formed with the cap body via the weakened portion, and the inner plug can be separated from the cap body and assembled to the upper lid at the same time, and is excellent in productivity. there is Moreover, when the inner plug is pushed up from below, the weakened portion can be broken without generating a thread-like resin piece, and after the weakened portion is broken, the internal pressure of the cap inner space formed by the upper lid and the top plate portion of the cap main body is released. Since it can escape efficiently from the ventilation path formed between the inner surface of the pouring nozzle and the outer surface of the annular side wall of the inner plug, it is possible to effectively prevent an increase in the internal pressure in the space inside the cap. It does not damage the sealing condition of the main body. Especially in the case of a large-diameter pouring nozzle, pushing up the inner plug from below exerts a large compressive force on the space inside the cap, which tends to increase the internal pressure of the space inside the cap, so the plastic cap of the present invention is effective. is.

FIG. 4 is a top view of the hinge cap, which is an example of the plastic cap of the present invention, in a state where the upper lid is opened. 2 is a side cross-sectional view of the hinge cap shown in FIG. 1 in a state where the upper lid is opened; FIG. 1. It is a sectional side view in the state which fitted the upper cover of the hinge cap shown in FIG. 1 to the cap main body, and sealed. 4 is a side cross-sectional view for explaining a step of setting the inner plug to the upper lid from the state shown in FIG. 3; FIG. 5 is a side sectional view showing a state immediately after the inner plug is pushed up from the state shown in FIG. 4 and the weakened portion is broken; FIG. FIG. 6 is a side cross-sectional view showing a state in which the inner plug is pushed up from the state shown in FIG. 5 and an air passage is formed on the annular side wall of the inner plug and the inner surface of the pouring nozzle. FIG. 7 is a diagram showing a state in which the inner plug is pushed up from the state shown in FIG. 6 and the engaged portion of the inner plug is in the process of getting over the engaging portion of the upper lid; FIG. 8 is a side cross-sectional view showing a state in which the inner plug is pushed up from the state in FIG. 7 and set to the upper lid, and the annular side wall of the inner plug and the inner surface of the pouring nozzle are in close contact and sealed. FIG. 9 is a side cross-sectional view of the state shown in FIG. 8 when the top cover is opened;

(Plastic cap precursor)
A plastic cap precursor, which is used for manufacturing the plastic cap of the present invention and in which an inner plug is formed integrally with a cap body via a breakable weakened portion, will be described with reference to the accompanying drawings.
An example of the precursor of the plastic cap of the present invention shown in FIGS. The hinge cap is composed of an inner plug 30 which is separable through the cap main body 1 and can be integrated with the upper lid 20 after being separated from the cap body 1, and these are integrally molded.
A cap body 1 fitted and fixed to a container mouth portion (not shown) comprises a top plate portion 4 and a skirt portion 5 hanging down from the peripheral edge of the top plate portion 4 . The inner surface of the skirt portion 5 is formed with annular projections 6, 6, . It is

An annular projection 7 for engaging with and fixing the upper lid 20 is formed at the outer end of the top plate portion 4 . A pouring nozzle 8 is formed on the side). The pouring nozzle 8 has a high axial height in the pouring direction (to the left as viewed in the drawing) and is inclined low on the hinge 2 side. A sealing portion 10 having an inner diameter capable of coming into close contact with the inner plug 30 is formed on the inner surface of the pouring nozzle 8 . In addition, a plurality of ribs 9, 9, . A plurality of ribs 9, 9, . . . In the specific example shown in the figure, each of the ribs 9, 9, .
Between the adjacent ribs 9, 9, when the inner plug 30 is detached from the cap main body 1 and assembled to the upper lid 20, the cap inner space formed by the upper lid 20, the cap main body 1 top plate portion 4, and the upper surface of the inner plug. It becomes an air passage that can release the internal pressure. The formation position of the ribs 9, 9, . It is below the portion 10 and above the breakable weakening 3 . On the other hand, an inner ring 11 is formed on the inner surface of the top plate portion 4 so as to be in close contact with the inner surface of the mouth portion of the container.

The inner plug, whose entirety is indicated by 30, is a boundary between the pouring nozzle 8 and the inner surface of the top plate portion 4 so as to close the intended opening section defined by the boundary portion between the pouring nozzle 8 and the inner surface of the top plate portion 4. It is formed integrally with the cap main body 1 in a detachable state via a breakable weakened portion 3 at a portion (the edge of the portion to be opened). In this way, by positioning the weakened portion connecting the cap body 1 and the inner plug 30 downward, the axial distance between the rib 9 and the weakened portion 3 is lengthened, and the inner plug 30 is inserted into the pouring nozzle 8. The breaking of the weakened portion 3 and the timing of getting over the rib 9 when setting can be shifted, and the resistance when setting the inner plug 30 can be reduced.
The inner plug 30 has an annular side wall 31 extending downward from the breakable weakened portion 3 and a bottom portion 32 that closes the axial lower end of the annular side wall 31 . Further, as described above, the outer diameter of the annular side wall 31 is sized to be in close contact with the inner surface of the pouring nozzle 8, and the axial length of the entire inner plug is the same as that of the pouring nozzle 8 in the specific example shown in the figure. It is formed to have a length approximately equal to the height of the hinge side of the . In the specific example shown in the drawings, a stepped portion 31a is formed on the lower outer surface of the annular side wall 31 to reduce the outer diameter. The lower surface is locked by the upper surface of the ribs 9, 9, .
An annular upper lid engaging portion (engaged portion) for being engaged with an inner stopper engaging portion (engaging portion) formed on the upper lid, which will be described later, is provided above the inner surface of the annular side wall 31 of the inner plug 30. 33 are formed.
Further, an annular guide portion 34 extending axially upward is formed on the bottom portion 32 of the inner plug 30 .

The upper lid, which is indicated as a whole by 20, is formed integrally with the cap body 1 via a hinge 2 at a position on the opposite side of the upper end of the skirt portion 5 of the cap body 1 from the pouring direction.
The upper lid 20 consists of a top surface 21 and a peripheral wall 22 hanging down from the outer peripheral edge of the top surface 21. Below the inner surface of the peripheral wall 22, the annular projection 7 of the cap body 1 is engaged. An annular projection 23 is formed for fixing the upper lid 20 to the cap body 1 in the closed state. A knob 24 for lifting the upper lid 20 is formed at the lower end of the peripheral wall 22 at a position opposite to the hinge 2 . In this specification, "upward" or "downward" in the axial direction with respect to the top cover 20 means "upward" or "downward" when the top surface 21 is up (as shown in FIG. 3).
The top surface 21 is formed with a downwardly extending circumferential projection 25 whose tip coincides with the tip of the annular side wall 31 of the inner plug 30 in the closed state. By positioning the circumferential projection 25 at the tip of the annular side wall 31 of the inner plug 30, it is possible to prevent the inner plug 30 from going too far upward.
Three circular shallow grooves 29 for preventing dripping are formed outside the circumferential projection 25 of the top lid 20, and the pouring nozzle 8 of the cap body 1 due to repeated opening and closing of the top lid is formed. It is possible to suitably prevent contamination due to the content liquid around the outside.

Inside the circumferential projection 25 of the upper lid 20, an annular projecting portion 27 projecting downward is formed for fixing the inner plug 30 detached from the cap body 1. As shown in FIG. A plurality of inner plug engaging portions (engaging portions) 28 protruding outward are formed on the outer peripheral surface of the distal end of the annular projecting portion 27 at equal intervals in the circumferential direction. The inner plug engaging portion (engaging portion) 28 is formed so as to be vertically engageable with the upper cover engaging portion (engaged portion) 33 of the inner plug 30 described above. In addition, it is desirable that the ribs 9, 9, . . . Thereby, the resistance when the inner plug 30 gets over the rib 9 can be reduced.
By inserting the annular guide portion 34 of the inner plug 30 into the annular protrusion 27, the inclination of the inner plug 30 detached from the cap body 1 is prevented and the protrusion 27 falls inward when the upper lid is opened. It is possible to prevent the inner plug 30 from being detached from the upper lid 20. The tip 34a of the annular guide portion 34 is located above the engaging portion 28 of the annular projecting portion 27 in the axial direction in a state in which the inner plug is integrated with the upper lid, and is located above the upper lid engaging portion of the inner plug 30. It is positioned axially below the (engaged portion) 33 (see FIG. 8). As a result, when the inner plug is set on the upper lid, the engaging portion 28 of the protruding portion 27 can escape radially inward and smoothly get over the upper lid engaging portion (engaged portion) 33 of the inner plug 30. becomes possible.
The annular projecting portion 27 has an inner diameter larger than the outer diameter of the annular guide portion 34 and a length deeper than the length of the guide portion 34 . As a result, the inner plug 30 has a movable area with respect to the upper lid 20 .

(Manufacturing method of plastic cap)
In the method of manufacturing a plastic cap of the present invention, as shown in FIGS. 1 and 2, a plastic cap precursor is manufactured in which the cap main body 1 and the inner plug 30 are integrally formed via the breakable weakened portion 3. After that, as shown in FIG. 3, the upper lid 20 is put on the cap body 1, and the annular projection 7 of the cap body 1 and the annular ridge 23 of the upper lid 20 are engaged and fixed.
In the method of manufacturing a plastic cap according to the present invention, as shown in FIG. 4, the plastic precursor with the upper lid 20 fixed to the cap body 1 is set on a pushing-up jig 50, and the pushing-up jig is raised. It is an important feature that the pressing speed of the pushing-up jig 50 is slowed down after breaking the breakable weakened portion 3 connecting the cap body 1 and the inner plug 30 .

That is, as described above, when the push-up jig 50 is raised at a low speed to break the breakable weakened portion 3 connecting the cap body 1 and the inner plug 30, the weakened portion 3 causes the resin to stretch. As a result of the breakage, feathering may occur at the broken edge.
In the present invention, from the state shown in FIG. 4 in which the upper lid 20 is closed and the plastic cap precursor fixed to the cap main body 1 is set on the pushing-up jig 50, the pushing-up jig 50 rises and the cap body By increasing the pressing speed (V ₀ ) of the pushing-up jig 50 during the state shown in FIG. Therefore, it is possible to suppress the occurrence of feathering at the broken edge, and thus the occurrence of thread-like resin pieces. The pressing speed (V ₀ ) of the pushing-up jig can be appropriately changed depending on the material and size of the cap, the thickness of the weakened portion, etc., and is not limited to this, but the diameter of the pouring opening (the portion to be opened) is In the case of a polyethylene cap of about 3 to 30 mm, the range is preferably 150 to 400 mm/s.

Further, after the weakened portion 3 connecting the cap body 1 and the inner plug 30 is broken, if the push-up jig 50 is raised while maintaining the above-described high pressing speed (V ₀ ), the pouring Since the air passage between the plurality of adjacent ribs 9, 9, . can't escape to
In the present invention, the state shown in FIG. 5 immediately after the weakened portion 3 is broken goes through the state shown in FIGS. 6 and 7 in which the air passage is formed, and then the state shown in FIG. 8 in which the air passage is completely closed. By slowing down the pushing speed of the push-up jig 50, it is possible to efficiently release the internal pressure of the space inside the cap to the outside of the cap.
That is, in the state shown in FIG. 6, the annular side wall 31 of the inner plug 30 is in contact with the ribs 9, 9, . . . A ventilation path (gap) is formed between the ribs 9 by an inwardly projecting amount. The internal pressure of the space inside the cap, which rises due to the rise of the inner plug 30, is released to the outside of the cap (below the cap body) through this gap. The guide portion 34 of the inner plug 30 is inserted into the annular projecting portion 27 , and the upper lid engaging portion (engaged portion) 33 engages with the inner plug engaging portion (engaging portion) 28 of the annular projecting portion 27 of the upper lid 20 . , and engage with each other, and the upper part that forms a seal portion 35 with the inner surface of the pouring nozzle of the annular side wall 31 of the inner plug 30 is in a state immediately before completely overcoming the ribs 9, 9 . , and the outer surface of the annular side wall 31 are formed, the pressing speed (V ₁ ) of the lifting jig 50 is lower than V ₀ described above, the internal pressure in the space inside the cap can be efficiently released to the outside of the cap through the air passage.
The pushing speed V1 of the push _- up jig can be appropriately changed according to the size of the air passage formed by the amount of protrusion of the ribs, and a speed as low as possible reliably releases the internal pressure in the space inside the cap. From the viewpoint of productivity, it is preferable to set the speed in the range of 10 to 50 mm/s.
The speed change from the high pressing speed (V ₀ ) of the pushing jig for breaking the weakened portion to the low pressing speed (V ₁ ) of the pushing jig for efficiently releasing the internal pressure of the space inside the cap is , the inner plug or the lifting distance of the push-up jig can be determined in advance.

From the state shown in FIG. 7, the inner plug 30 further rises in the pouring nozzle 8, and the portion of the annular side wall 31 of the inner plug 30 that becomes the sealing portion 35 completely overcomes the ribs 9, 9, . . . When the portion 31a engages with the upper surfaces of the ribs 9, 9, . The sealing portion 35 of the is closely attached to form a sealed state capable of ensuring the liquid-tightness of the cap (FIG. 8). Therefore, from the state shown in FIG. 7 to the state shown in FIG. ₈ , the pushing speed (V ₂ ) for pushing up the inner plug 30 is not particularly limited. It is preferable to push up with the low speed _V1 as described above.
6 to 7 or before reaching FIG. 8, as described above, ribs 9, 9, . A ventilation path (gap) is formed by the amount of inward projection of 9 . While the air passage is being formed, the pressing speed (V ₀ ) for pushing up the inner plug can be set to zero, that is, after stopping the pushing up of the inner plug 30, the pressing speed can be switched to a low speed (V ₁ ). As a result, the time during which the space inside the cap is ventilated can be ensured, and the internal pressure can be reliably released.

As shown in FIG. 8, when the setting of the inner plug 30 to the upper lid 20 is completed, the internal pressure of the space inside the cap is sufficiently released and maintained at a gauge pressure of 1 kPa or less, which is substantially the same as the atmospheric pressure. . Further, since the sealing portion 10 on the inner surface of the pouring nozzle 8 and the sealing portion 35 on the outer surface of the annular side wall 31 are in close contact at a position above the ribs 9, 9, etc., liquid tightness is ensured. This seal portion 35 is not affected by the burrs of the weakened portion 3 after breakage, and can maintain the pourability of the contents of the pouring nozzle 8 . In addition, it is possible to effectively prevent the possibility of washing water entering when the cap is subjected to shower washing, and the upper lid 20 being detached from the cap main body 1 when the environmental temperature rises due to heat sterilization or the like. ing.

The plastic cap in which the inner plug 30 is set on the upper lid 20 in the state shown in FIG. removed. At this time, since the guide portion 34 of the inner plug 30 is inserted into the annular projecting portion 27, the projecting portion 27 is effectively prevented from falling inward. That is, even if the outer surface of the annular side wall 31 of the inner plug 30 and the inner surface of the pouring nozzle 8 are brought into relatively strong contact with each other to improve the sealing performance, the inner plug 30 can be prevented from coming off the upper lid 20 .

The above-described method for manufacturing a plastic cap according to the present invention can be compared with the diameter of the top plate portion of the cap body, which tends to increase the internal pressure in the space inside the cap when the inner plug is pushed up for detachment from the cap body and assembly to the upper lid. Although a hinge cap with a large-diameter pouring opening has been described, since it is not necessary to form a pouring opening with a pull ring when starting to use the contents, a plastic with a small-diameter pouring opening can be used. The cap can also be molded in a similar manner. With such a cap having a small-diameter pouring opening, it is possible to pour out as much as the container is pressed, and it is also possible to easily squeeze back, thereby effectively preventing dripping. In this specification, the small-diameter pouring opening means a pouring opening (planned opening) having a diameter that does not allow the formation of a pull ring in the planned opening, and is not limited to this. Refers to a pouring opening (planned opening) with a diameter of about 18 mm. A cap having such a small-diameter pouring opening can be suitably used for a type of container that squeezes out the content, such as a squeeze bottle. Moreover, it may be a spout that is welded and fixed to a paper container or the like.

The method of manufacturing the plastic cap of the present invention is not limited to the specific examples shown in the above drawings, and various modifications are possible.
That is, in the plastic cap precursor shown in the figure, the cap main body and the upper lid are connected by a hinge, and the cap main body, the upper lid and the inner plug are integrally molded. It may be molded and fixed to the cap body by screw engagement or the like.
The cap main body shown in the figure is a stoppering cap with a single-layered skirt portion that is fitted and fixed to the mouth of the container by the engaging portions. A double structure having an outer cylindrical wall with a score formed in the outer wall is also possible. Further, it is of course possible to use a cap body in which a screw portion is formed on a skirt portion that is fixed to the mouth portion of the container by screw engagement.

1 to 8 is formed with a stepped portion that reduces the diameter of the annular side wall below the portion of the annular side wall that serves as the seal portion, and this stepped portion forms the rib of the pouring nozzle. Although the upper surface is engaged in the vertical direction, a truncated cone shape in which a slope is formed at the boundary portion between the annular side wall and the bottom portion, or a hemispherical shape, etc. may be used without providing such a step.
The ribs formed on the inner surface of the pouring nozzle have the same length in the circumferential direction, and the ribs are formed at symmetrical positions with respect to the radial center of the pouring nozzle where the ribs are formed. Preferably, a non-existing region is formed. Thereby, the resistance when getting over the rib can be further reduced.
Although the ribs shown in the figure are formed at three equal intervals at the same axial height of the pouring nozzle, the present invention is not limited to this. A plurality of them may be formed as appropriate. Also, depending on the axial length of the pouring nozzle and the axial length of the ribs, the plurality of ribs does not necessarily have to be at the same axial height.

The breakable weakened portion, which is the connecting portion between the inner plug and the cap main body, is a rib formed on the inner surface of the pouring nozzle below the seal portion having an inner diameter that allows the outer surface of the annular side wall of the inner plug to be in close contact. In the specific example shown in the figure, the lower end of the pouring nozzle coincides with the top plate portion, and a breakable weakened portion is formed on the edge of the opening portion of the cap body. Although the inner plug was integrally formed through the inner plug, it is not limited to this aspect. For example, when the lower end of the pouring nozzle is positioned below the top plate portion, the inner plug may be integrally formed via a breakable weakened portion at the lower end of the pouring nozzle. Alternatively, in the case where the inner surface of the pouring nozzle is partially reduced in diameter and the reduced diameter portion serves as a sealing portion, the pouring nozzle below the sealing portion and the rib The inner plug may be integrally formed via a weakened portion that can be broken on the inner surface.
Furthermore, as in the specific example shown in the figure, in addition to forming a breakable weakened portion at the boundary portion (the edge of the portion to be opened) between the pouring nozzle and the inner surface of the top plate portion, a downward A tapered surface may be formed so that the inner diameter becomes wider as it goes toward the groove, and a weakened portion may be formed at the upper end of the tapered surface.

In the hinge cap, the plastic cap precursor used in the present invention can be integrally molded by injection molding or the like with the upper lid opened. Next, after the upper lid is bent and fixed to the cap main body, by pushing up the inner plug portion from below with a pressing jig or the like, the breakable weakened portion formed at the boundary between the cap main body and the upper end of the inner plug is torn, and the inner It becomes possible to fix the plug to the top lid.
The plastic cap precursor used in the present invention can be molded by conventionally known methods such as injection molding and compression molding using resins conventionally used for molding plastic caps, such as olefin resins such as polyethylene and polypropylene. .

The method for manufacturing a plastic cap of the present invention can efficiently release the increase in internal pressure in the space inside the cap that accompanies the setting of the plastic cap, in which the cap main body and the inner plug can be formed in one piece, to the upper lid of the inner plug. Since there is no problem that a gap is formed in the sealing part between the upper lid and the cap body, or that the upper lid is opened when subjected to heat treatment, it can be used in containers filled with contents at high temperature or in showers at high temperature. It can be applied to containers that require washing and cooling and can be suitably used as a method for manufacturing cormorant caps.

REFERENCE SIGNS LIST 1 cap body 2 hinge 3 weakened portion 4 top plate portion 5 skirt portion 6 annular protrusion 7 annular protrusion 8 pouring nozzle 9 rib 10 sealing portion 11 inner ring 20 upper lid 21 top surface 22 circumferential wall 23 annular protrusion 24 knob 25 circumferential projection 26 arc-shaped projection 27 annular projection portion 28 inner plug engaging portion (engaging portion) 30 inner plug 31 annular side wall; 32 bottom portion, 33 upper lid engaging portion (engaged portion), 34 guide portion, 35 sealing portion, 40 air passage (gap), 50 pressing jig.

Claims (6)

a cap body fitted and fixed to the mouth of the container, comprising a top plate and a skirt, and having a pouring nozzle formed on the outer surface of the top plate so as to surround the intended opening, a top surface, and the top surface a top cover comprising a peripheral wall depending from the outer peripheral edge,
The upper lid is formed with a protruding portion protruding downward from the inner surface of the top surface and having an engaging portion,
The cap main body is formed with an annular side wall having an outer diameter capable of coming into close contact with the inner surface of the pouring nozzle, and an inner plug having a bottom formed below the annular side wall. It is formed integrally with the cap body through a weakened portion that can be broken below a seal portion having an inner diameter that can be tightly attached to the inner plug of the discharge nozzle, and the annular side wall has an engaging portion for the protrusion. and an engaged portion that can be engaged in the vertical direction is formed,
The inner surface of the pouring nozzle has a portion capable of forming an air passage with the outer surface of the annular side wall of the inner plug separated from the cap body, and the air passage forming portion is located below the sealing portion. and using a plastic cap precursor positioned above the breakable weakened portion,
pressing the bottom of the inner plug from below to break the breakable weakened portion in a state in which the top lid is applied to the cap body and sealed; A method for manufacturing a plastic cap, comprising the step of pressing the cap from above to make the engaging portion of the projecting portion engageable with the engaged portion of the inner plug, and to bring the outer surface of the annular side wall and the inner surface of the pouring nozzle into close contact with each other. There is
After breaking the breakable weakened portion, by slowing down the pressing speed of the inner plug, the air flow path formed between the outer surface of the annular side wall and the inner surface of the pouring nozzle is removed from the upper lid and the top plate portion of the cap body. A method of manufacturing a plastic cap, characterized by releasing the internal pressure of the space formed in the cap. 2. The method of manufacturing a plastic cap according to claim 1, further comprising a stopping step of reducing the pressing speed of the inner plug to zero in the state in which the air passage is formed. 3. The method of manufacturing a plastic cap according to claim 1, wherein a plurality of inwardly protruding ribs are formed on the inner surface of said pouring nozzle, and a space between adjacent ribs serves as said air passage. From immediately after the breakable weakened portion is broken to before the sealing portion of the annular side wall of the inner plug rides over the plurality of ribs, the pressing speed of the inner plug is slowed down, or the pressing speed is set to zero. 4. The method of manufacturing a plastic cap according to claim 3, wherein the pressing speed is slowed down after the pressure is reduced. The method for manufacturing a plastic cap according to any one of claims 1 to 4, wherein the upper cover is hinged to the cap body. Claims 1 to 5, wherein the pressing speed of the inner plug before breaking the breakable weakened portion is 150 mm/s or more, and the pressing speed of the inner plug after breaking the breakable weakened portion is 50 mm/s or less. A method for manufacturing a plastic cap according to any one of 1.

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