Background of the Invention
(Field of the Invention)
[0001] The present invention relates to a pilfer-proof synthetic resin cap.
(Description of the Prior Art)
[0002] A pilfer-proof synthetic resin cap has heretofore been known having a top panel,
a cylindrical skirt portion hung from the peripheral edge of the top panel, a circumferential
band provided at the lower end of the cylindrical skirt portion via a weakened line,
and flap pieces provided maintaining a predetermined distance on the inner surface
of the circumferential band portion to engage with a jaw portion formed at the mouth
of a container, and has been widely put into practical use.
[0003] With this cap, the circumferential band portion is secured by the flap pieces to
the mouth of the container. When the cap is opened, therefore, the weakened line is
broken and the circumferential band portion only remains at the mouth of the container
to exhibit pilfer-proof function.
[0004] In the above cap, however, the flap pieces are not strong enough to fully engage
with the jaw portion formed at the mouth of the container and, besides, the weakened
line is not often broken even when the cap is open; i.e., the cap is often entirely
removed together with the circumferential band.
[0005] Furthermore, some gap is formed between the lower end of the circumferential band
and the mouth of the container, and mischief is often done using this gap.
[0006] Japanese Laid-Open Patent Publication No. 296666/1990 discloses a cap having an upwardly
directed flexible tab formed on the circumferential band portion and interference
beads formed at the lower end of the circumferential band to inwardly protrude.
[0007] In the cap of the above prior art, an increased engaging force is obtained between
the circumferential band and the jaw portion formed at the mouth of the container
due to the flexible tab and the interference beads that work in cooperation together.
Therefore, the cap that is opened is effectively prevented from entirely removed and
besides the gap formed between the lower end of the circumferential band and the mouth
of the container is filled with the interference beads. According to the above prior
art, however, the cap is molded very difficulty since it has two kinds of protrusions,
i.e., flexible tab and interference beads on the inside of the circumferential band.
That is, the caps of this type are usually produced by such molding means as injection
molding using a suitable metal mold. In the case of the above cap, however, it will
be very difficult to remove the metal mold after the molding operation as considered
from the shape of the circumferential band portion. In fact, the above prior art does
not at all describe concerning the molding means.
Summary of the Invention
[0008] The object of the present invention, therefore, is to provide a pilfer-proof synthetic
resin cap that can be formed very easily, that is effectively prevented from entirely
escaping at the time it is opened, and that effectively prevents mischievous deeds
that may be done by utilizing the gap formed between the lower end of the circumferential
band and the mouth of the container.
[0009] According to the present invention, there is provided a pilfer-proof synthetic resin
cap comprising a top panel, a cylindrical skirt portion hung from the peripheral edge
of the top panel, a circumferential band provided at the lower end of the cylindrical
skirt portion via a weakened line, and flat pieces provided maintaining a predetermined
distance on the inner surface of the circumferential band portion to engage with the
jaw portion formed at the mouth of a container, wherein a circumferential curled portion
that is inwardly curled is formed at the lower end of the circumferential band.
[0010] According to the present invention, a distinguished feature resides in an inwardly
directed circumferential curled portion that is formed at the lower end of the circumferential
band. The circumferential curled portion reinforces the engaging force between the
flap pieces and the jaw portion at the mouth of the container and helps effectively
avoid the circumferential band from entirely escaping when the cap is opened.
[0011] Further,the gap formed between the lower end of the circumferential band and the
container is filled with the circumferential curled portion, contributing to effectively
preventing mischievous deeds that may be done by using the gap.
[0012] According to the present invention, furthermore, when the cap under the closed condition
is turned, the weakened line starts breaking with a small angle of turn of the cap
since the engaging force has been reinforced between the flap pieces and the jaw portion
at the mouth of the container. As will become obvious from an Example and a Comparative
Example appearing later, the above-mentioned angle of turn is about 200 degrees in
the case of the cap of the present invention whereas the above angle of turn is about
360 degrees in the case of the conventional cap without having the circumferential
curled portion which is very greater than that of the cap of the present invention.
A large angle of turn means that the weakened line is not broken even when the cap
is turn to such a degree that the sealing of cap is broken, which is quite undesirable
from the standpoint of preventing mischiefs. On the other hand, a small angle of turn
accomplished by the present invention as described above means that the weakened line
breaks when the cap is rotated to such a degree that the sealing of cap is broken;
i.e., breakage of the sealing of cap is revealed to the general consumers enabling
mischievous deeds to be prevented in advance.
[0013] In the cap of the present invention in which the flap pieces are protected by the
circumferential curled portion, furthermore, the flap pieces are effectively prevented
from being deformed during the period of from when the cap is molded until when the
cap is tightly fitted to the mouth of the container, which is an additional advantage
of the present invention.
[0014] In the present invention mentioned above, the circumferential curled portion can
be formed easily. For example, a cap provided, via a weakened line, with a circumferential
band having flap pieces is molded by the injection molding, and then a circumferential
cured portion is formed at the lower end of the circumferential band relying on a
very simple means.
Brief Description of the Drawings
[0015]
Fig. 1 is a diagram showing the condition where the cap of the present invention is
fitted to the mouth of a container;
Fig. 2 is a diagram showing a preferred embodiment of the cap of the present invention;
Fig. 3 is a diagram showing the condition where no peripheral curled portion is formed
in the cap of the present invention; and
Fig. 4 is a diagram illustrating means for forming the peripheral curled portion.
Detailed Description of the Invention
[0016] The invention will now be described in detail by way of an embodiment shown in the
accompanying drawings.
[0017] Fig. 1 shows the condition where the cap of the present invention is fitted to the
mouth of the container. In Fig. 1, the cap (designated generally at 1) has a cylindrical
skirt portion 3 hung from the peripheral edge of a top panel. A circumferential band
5 is provided at the lower end of the skirt portion 3 via a weakened line 4.
[0018] Flap pieces 6 are provided maintaining a predetermined distance on the inner surface
of the circumferential band 5. Each flap piece 6 is oriented in the same direction
as the direction in which the cap 1 is opened. That is, as the cap is turned so as
to be opened, the flap pieces 6 come in contact with the lower side of a jaw portion
10 of the container, whereby a great resistance force acts upon opening the cap, the
weakened line 4 is broken, and the circumferential band 5 is left at the mouth of
the container.
[0019] According to the present invention, a circumferential curled portion 7 is formed
at the lower end of the circumferential band 5. That is, when the cap is being opened
and the flap pieces 6 come into contact with the lower side of the jaw portion 10
of the container, the circumferential curled portion 7 works to push the flap pieces
6 from the lower side of the jaw portion 10, so that the flap pieces 6 are effectively
prevented from being elongated or deformed. Therefore, resistance force is reinforced
against opening the cap, and the circumferential band 5 is effectively prevented from
entirely escaping at the time of opening the cap.
[0020] As is obvious from Fig. 1, furthermore, the circumferential curled portion 7 that
is formed makes narrow the gap between the lower end of the circumferential band 5
and the wall of mouth of the container, contributing to effectively preventing any
mischievous deed that may be done by utilizing the gap.
[0021] According to the present invention as shown in Fig. 2, furthermore, notches 8 are
formed maintaining a predetermined distance at the tip of the circumferential curled
portion 7 so as to be corresponded to the flap pieces 6, such that the flap pieces
6 engage with the notches 8. That is, according to this embodiment, the flap pieces
6 are fixed in positions to some extent by the notches 8, and produce further increased
resistance force in the direction of opening the cap.
[0022] The above-mentioned cap of the present invention has an advantage in that it can
be formed very easily. That is, the cap without circumferential curled portion 7 is
formed by a widely known molding means such as injection molding as shown in Fig.
3 from which it is obvious that the lower portion of the circumferential band portion
5 (lower portion of the flap pieces 6) of the cap is substantially flat. Therefore,
the cap is removed from the metal mold without any difficulty and is molded easily.
[0023] The cap is then secured in a cap-receiving dies 20 as shown in Fig. 4, and is punched
using a punch 21 that is heated at a suitable temperature by a heater or the like,
thereby to obtain the cap having the circumferential curled portion 7 formed at the
lower end of the circumferential band 5 as contemplated by the present invention.
(Example 1)
[0024] A cap (20.4 mm in height of cap and 29.8 mm in outer diameter of cap) of a shape
shown in Fig. 1 was molded using a polypropylene resin having a density of 0.912 g/cm
3 and a melt flow rate (230°C) of 10 g/10 min.
[0025] The cap was tightly fitted to a 1500 ml polyethylene terephthalate bottle. Under
this condition, the angle of turn of the cap at which the weakened line starts breaking
was measured. Moreover, a cap without the weaking line was molded in the same manner
as described above, and was tightly fitted to the above-mentioned bottle to measure
a torque with which the cap entirely escapes from the bottle. The results were as
shown in Table 1. Measured values are averages of ten samples of each of them.
(Comparative Example 1)
[0026] A cap (19.1 mm in height of cap and 29.8 mm in outer diameter of cap) was molded
in the same manner as in Example 1 but without forming the circumferential curled
portion, and a torque with which it entirely escapes and the angle of turn at which
the weakened line breaks were measured. The results were as shown in Table 1.
