JP2022085524A - container - Google Patents

Abstract

The present invention provides a container which is excellent in hermeticity and does not generate shavings from the cap. A container includes a main body (10) having a fitting portion (32) formed with a screw thread (33), and a lid screw-fitted to the fitting portion. The thread is formed in a continuous spiral from the start point to the end point. The main body is formed by injection molding of synthetic resin and has a burr on the thread, and the projection length L2 of the portion with the burr is 20% or more and 70% or less of the maximum projection length L1 of the screw thread. [Selection drawing] Fig. 4

Description

The present invention relates to a container, more particularly a container having threads for screw fitting the lid.

Resin containers that are sealed by screw fitting caps are widely used. Such containers may be formed by injection molding.

When the container is manufactured by injection molding, it is inevitable that burrs will be generated near the parting line, which is the joint of the mold. When burrs occur on the threads, the outer diameter of the threads increases by the amount of the burrs. As a result, there is a possibility that the cap may be scraped by the burr and a problem of generating shavings may occur.

The plastic bottle described in Patent Document 1 has a discontinuous thread for degassing at the time of opening.

Japanese Unexamined Patent Publication No. 2018-177336

By arranging the discontinuous portion of the screw thread described in Patent Document 1 in the vicinity of the parting line, it is possible to prevent the outer diameter of the screw thread from increasing by the amount of the burr.
However, as a result of examination by the inventor, it was found that the airtightness may not be sufficient by this method, although the details will be described later.
The inventor has completed the present invention through further studies.

An object of the present invention is to provide a container having excellent airtightness and free from shavings of a cap.

The present invention is a container provided with a main body having a fitting portion on which a thread is formed and a lid to be screw-fitted to the fitting portion.
The threads are formed in a spiral shape without a break from the start point to the end point.
The main body is formed by injection molding of synthetic resin and has burrs on the threads.
The protruding length of the portion with burrs is 20% or more and 70% or less of the maximum protruding length of the thread.

The container according to the present invention has excellent airtightness and does not generate shavings from the cap.

It is a perspective view which shows the container which concerns on one Embodiment of this invention. It is a perspective view which shows the main body of the container. It is a partially enlarged view which shows the fitting part of the main body. It is a partially enlarged view which shows the state which the main body was seen from above. It is a partially enlarged view which shows the state which looked at the main body which concerns on the modification of this invention from above.

An embodiment of the present invention will be described with reference to FIGS. 1 to 5.
FIG. 1 is a perspective view showing a container 1 according to the present embodiment. The container 1 has a substantially cylindrical shape, and includes a main body 10 and a lid 20 that is attached to the main body 10 and seals the internal space of the main body 10.
In the present embodiment, the outer shape of the container 1 is substantially cylindrical, but the outer shape is not particularly limited. For example, the maximum diameter of the lid may be smaller than the main body by reducing the diameter of the upper part of the main body, or the outer shape of the container to which the lid is attached can be substantially polygonal by changing the outer shape of the main body and the lid. May be.

FIG. 2 is a diagram showing a main body 10 with the lid 20 removed. The main body 10 has an opening 31 at the top. A certain range from the upper end of the main body 10 is a fitting portion 32 screw-fitted with a lid (not shown). One screw thread 33 is formed on the outer peripheral surface of the fitting portion 32.

FIG. 3 is an enlarged view of the fitting portion 32. The screw thread 33 projects on the outer peripheral surface of the fitting portion 32, and extends in the vertical direction while spirally rotating around the fitting portion 32. Although the amount of protrusion of the screw thread 33 from the outer peripheral surface differs depending on the portion as described later, it is continuously formed from the lower start point 33a to the upper end point 33b without interruption.

In the present embodiment, the length of the screw thread 33 is such that it makes about 1.5 turns around the fitting portion 32, but this is an example and can be set as appropriate. From the viewpoint of ensuring the sealing by fitting the lid 20, a length that makes one or more turns around the fitting portion 32 is preferable.
As shown at the left and right ends of FIG. 3, the cross-sectional shape of the screw thread 33 is substantially triangular. As a result, in the thread 33, the intermediate portion 33c in the vertical direction protrudes most from the outer peripheral surface of the fitting portion 32. Such a cross-sectional shape is also an example, and for example, a cross-sectional shape having substantially the same protrusion length in the vertical direction can be used.

The main body 10 is made of synthetic resin, and at least the fitting portion 32 including the screw thread 33 is formed by injection molding using two molds. The accommodating portion 40 below the fitting portion 32 may be formed by injection molding like the fitting portion 32, or may be formed by another method such as blow molding.

By being formed by injection molding using two molds, parting lines, which are joints of the two molds, are generated at two places in the fitting portion 32. In the screw thread 33 of the present embodiment, a total of three places, one on the front side shown in FIG. 3 and two places on the rear side which cannot be seen in FIG. 3, are hung on the parting line PL.

In injection molding, resin burrs always occur along the parting line. Although there is a possibility that burrs can be reduced by elaborately forming the mold or adjusting the injection pressure of the resin, it is impossible to eliminate the burrs themselves with the current technique.

The burr generated on the screw thread 23 becomes a protrusion that increases the protrusion length from the outer peripheral surface of the fitting portion. This protrusion does not cause much problem when the resin forming the main body 10 is relatively soft. However, when the main body 10 is made of a hard resin such as polyethylene terephthalate (PET) because the main body 10 is required to have high rigidity, the protrusions strongly rub the inner surface of the lid 20 when the lid 20 is fitted. There is a problem that the lid 20 is scraped. When the lid 20 is scraped, shavings adhere to the fitting portion after opening and spoil the appearance. If the degree of scraping is large, the lid may be damaged and resealing may not be possible.

The inventor first tried to solve this problem by dividing the threads into a plurality of regions to make them discontinuous and locating the non-threaded portions on the parting line. As a result, the burr caused by the parting line is lower than the screw thread although it is generated on the outer peripheral surface of the fitting portion, so that the lid is not scraped.
However, on the other hand, by providing the discontinuous portion in the screw thread, the rigidity of the fitting portion is lowered, and it becomes easy to be deformed by an external force. As a result, there has been a situation in which a desired rigidity cannot be imparted to the main body even though a hard resin such as PET is used, which may result in a tipping over.

The inventor further studied and solved the above problem by changing the shape without discontinuing the threads.
FIG. 4 is a partially enlarged view of the main body 10 as viewed from above. The intermediate portion 33c of the screw thread 33 protrudes from the outer peripheral surface 32a of the fitting portion 32 by the protrusion length L1, but the protrusion length is small in a certain region including the portion including the parting line. As a result, the screw thread 33 has a small diameter portion 35 having a protrusion length smaller than that of L1 at one position before and after the parting line PL is applied.

Specifically, the screw thread 33 has an arcuate basic shape, but a part thereof is formed in a direction orthogonal to the line connecting the parting line and the central axis C of the main body 10 when the main body 10 is viewed from above. Is cut off.

In the present embodiment, since the central axis C of the main body 10 coincides with the cylindrical central axis of the fitting portion 32, the outer peripheral surface 32a of the fitting portion 32 and the intermediate portion 33c of the thread 33 are the main body 10. Is located approximately on the circumference centered on the central axis C when viewed from above. Therefore, the protrusion length L1 is the difference between the radius of the circle formed by the outer peripheral surface 32a and the radius of the circle formed by the intermediate portion 33c when the main body 10 is viewed from above.
The distance between the small diameter portion 35 and the central axis is the shortest in the portion where the parting line PL is applied, and the protrusion length L2 in this portion is substantially the minimum. The protruding length of the small diameter portion 35 from the outer peripheral surface 32a gradually increases as the distance from the parting line PL increases, and approaches L1.

By changing the shape of the small diameter portion 35 according to the design of the mold, the protrusion length L2 changes. Theoretically, if the protrusion length L2 including the burr formed on the parting line is set to L1 or less, which is the maximum protrusion length of the thread, the lid will not be scraped, but the protrusion amount of the burr should be controlled. Is not easy. On the other hand, the inventor has found that if the protrusion length L2 is made too small, another problem arises.

If the protrusion length L2 is too small, the contact area between the screw thread 33 and the inner surface of the lid 20 decreases. If this phenomenon becomes excessive, it becomes difficult to seal the main body 10 with the lid 20.
This phenomenon appears as a decrease in overrun torque when the lid 20 is screw-fitted to the main body 10. The overrun torque means the amount of force required for the screw-fitted lid to get over the screw thread and run idle. If the overrun torque is small, the lid easily spins idle, which causes a problem in the capping process by the filling machine, and the sealing is insufficient and the quality deteriorates.

As a result of the study by the inventor, it has been clarified that when the protrusion length L2 is 20% or more and 70% or less of the protrusion length L1, it is possible to both prevent the lid from being scraped and to ensure that the closure has an appropriate overrun torque. rice field. Therefore, by forming the mold of the main body 10 so that the protrusion length L2 including the estimated maximum protrusion length of the burr formed on the parting line is within the above range, the protrusion length L2 satisfies the above numerical range. The main body 10 of this embodiment can be manufactured.

The decrease in overrun torque and poor sealing are also caused by deformation due to insufficient rigidity of the mating part. In the container of the present embodiment, although the screw thread 33 has a small diameter portion 35, the screw thread itself is continuously continuous from the start point to the end point, so that the entire fitting portion is more than the configuration provided with the above-mentioned discontinuity portion. The rigidity of the can be kept high. As a result, the overrun torque can be suitably maintained, and the inside of the main body 10 can be reliably sealed by fitting the lid 20 with screws.

An experimental example regarding the screw thread of this embodiment is shown below.
The main body was manufactured by injection molding using PET, and the lid was manufactured by injection molding using polypropylene (PP). At this time, Experimental Examples 1 to 4 were prepared by differentiating only the mode of the small diameter portion of the screw thread as follows. Experimental Examples 1 and 2 satisfy the above-mentioned numerical range.
Experimental Example 1: The protrusion length L2 is 60% of the protrusion length L1.
Experimental Example 2: The protrusion length L2 is 30% of the protrusion length L1.
Experimental Example 3: The protrusion length L2 is 80% of the protrusion length L1.
Experimental Example 4: The protrusion length L2 is 10% of the protrusion length L1.

The container of each example was set in a capping machine, the tightening torque was set to 490 N · cm, and capping was performed while measuring the torque value with a torque meter. When the cap slipped, the torque value at that time was set as the overrun torque, and when capping was performed without any problem, the overrun torque value was set to "490 Ncm or more".
Further, the lid was removed from the container after capping, and the presence or absence of shavings on the lid at the fitting portion was visually evaluated.
The results are shown in Table 1.

In Experimental Examples 1 and 2, the lid was not scraped, and an overrun torque value of 450 N · cm or more was secured. When the overrun torque value is 400 N · cm or more, a reliable seal can be ensured in most applications, which is a good result.

In Experimental Example 3 in which the protrusion length L2 exceeds 70% of the protrusion length L1, the overrun torque value was good, but the lid was scraped, which was considered to be due to burrs.
In Experimental Example 4 in which the protrusion length L2 was less than 20% of the protrusion length L1, the lid was not scraped, but the overrun torque value was less than 300, and the seal could not be sufficiently sealed.

Although one embodiment of the present invention has been described above, the specific configuration is not limited to this embodiment, and includes changes and combinations of configurations within a range that does not deviate from the gist of the present invention. Some changes are illustrated below, but not all, and other changes are possible. Two or more of these changes may be combined as appropriate.

-The shape of the small diameter portion is not limited to that described above. The small diameter portion 35A of the modified example shown in FIG. 5 is not orthogonal to the line connecting the central axis C and the parting line PL, and has two slopes extending from the screw thread 33 toward the parting line PL. Even with such a small diameter portion, the same effect can be obtained if the protrusion length L2 satisfies the above-mentioned numerical range.

-Instead of changing the shape of the mold, a small diameter portion may be formed by scraping a part of the screw thread after molding. However, the method of changing the shape of the mold is preferable because the main body according to the present invention can be manufactured only by injection molding.

-The technical idea according to the present invention is particularly effective when the main body is made of a relatively hard resin. For example, other than the above-mentioned PET, it is also suitable when the main body is formed of polypropylene, polyethersulfone (PES), polyphenylsulfone (PPSU), polycarbonate or the like.

-The structure of the fitting portion according to the present invention can also be applied to a preform which is an intermediate product for manufacturing a PET bottle.

1 Container 10 Main body 20 Closure 32 Fitting part 33 Thread 33a Start point 33b End point 35, 35A Small diameter part L1 Maximum protrusion length of screw thread L2 Protrusion length of part with burr

Claims (4)

A body with a threaded fitting and
A lid that is screw-fitted to the fitting portion and
Equipped with
The threads are formed in a seamless spiral from the start point to the end point.
The main body is formed by injection molding of synthetic resin and has burrs on the threads.
The protruding length of the portion with the burr is 20% or more and 70% or less of the maximum protruding length of the thread.
container. The thread has a small diameter portion having a relatively small protrusion length from the fitting portion.
Having the burr in the small diameter portion,
The container according to claim 1. The burr is formed along the seam of the mold used for the injection molding.
The container according to claim 1. The synthetic resin contains any of polyethylene terephthalate, polyethersulfone, polyphenylsulfone, and polycarbonate.
The container according to claim 3.

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