PLASTIC SCREW CAP WITH GOOD WASHABILITY

Abstract

There is provided a plastic screw cap with a tamper-evident band that ensures improved removal of washing water. A plastic screw cap (1) includes: a top plate (3); a skirt wall (5); and a TE band (tamper-evident band) that is connected to a lower end of the skirt wall (5) via a breakable bridge and includes on its inner surface a locking projection (19) capable of being locked to a lower surface of a container jaw portion (53). The TE band (7) includes on its inner surface a flow path forming projection (30) that is located above the locking projection (19) and abuts an outer surface of the container jaw portion (53) to form a flow path between the container jaw portion (53) and an inner surface of the skirt wall (5).

Claims

1. A plastic screw cap including: a top plate; a skirt wall that extends downward from a peripheral edge of the top plate and includes on its inner surface a thread to be screwed to an outer surface of a container mouth portion; and a tamper-evident band that is connected to a lower end of the skirt wall via a breakable bridge and includes on its inner surface a locking projection capable of being locked to a lower surface of a container jaw portion, wherein the tamper-evident band further includes on its inner surface a flow path forming projection that is located above the locking projection and abuts an outer surface of the container jaw portion to forma flow path between the container jaw portion and an inner surface of the skirt wall.

2. The plastic screw cap according to claim 1, wherein in a region continuing to an upper surface of the locking projection, an annular inclined surface or a circumferentially intermittent arc-shaped inclined surface is formed such that it becomes gradually thicker from top toward an upper end joint of the locking projection, and the flow path forming projection is disposed above the annular inclined surface or the arc-shaped inclined surface.

3. The plastic screw cap according to claim 1, wherein a plurality of the locking projections are formed at regular intervals in a circumferential direction, and the flow path forming projection is disposed between and above each pair of adjacent two locking projections.

4. The plastic screw cap according to claim 1, wherein the flow path forming projection has an axially extending rib shape or a block shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1: a partial vertical cross-sectional view showing a plastic cap of the present invention and a container mouth portion;

[0019] FIG. 2: a view showing an A-A cross section in FIG. 1;

[0020] FIG. 3: views for explaining the function of a flow path forming projection in the present invention;

[0021] FIG. 4: a partial exploded view of a TE band in the plastic cap of the present invention; and

[0022] FIG. 5: a view showing an example of another embodiment of the flow path forming projection in the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0023] Referring to FIG. 1, a plastic screw cap (hereinafter, may be referred to simply as a cap) of the present invention is denoted as a whole by reference numeral 1. The cap 1 is screwed and attached to a container mouth portion 50. On the outer surface of the container mouth portion 50, a thread (external screw) 51 is formed. A jaw portion (bead) 53 with a larger diameter than the thread 51 is formed below the thread 51. A support ring 55 with a much larger diameter is formed on the lower side of the jaw portion 53 for the purpose of portability, positioning and the like.

[0024] The cap 1 has a top plate 3 and a skirt wall 5 extending downward from the peripheral edge of the top plate 3. The lower end of the skirt wall 5 is connected with a TE band (tamper-evident band) 7 via a plurality of breakable bridges (not shown in the drawing). A slit 9, which is a minute void, is formed between the lower end of the skirt wall 5 and the upper end of the TE band 7.

[0025] The skirt wall 50 includes on its inner surface a thread (internal screw) 11 to be screwed to the thread 51 provided in the container mouth portion 50.

[0026] On the inner surface of the top plate 3, an inner ring 13 is provided to extend downward away from the skirt wall 5. On the outer side of the inner ring 13, a short auxiliary projection 15 inclined outward is formed circumferentially. Between the inner ring 13 and the auxiliary projection 15, a small flat projection 17 is formed circumferentially.

[0027] On the inner surface of the TE band 7, a hooked locking projection 19 is formed.

[0028] With this structure, when the cap 1 placed on the container mouth portion 50 is rotated in the closing direction, the cap is allowed to descend as the thread 11 of the cap 1 and the thread 51 of the container mouth portion 50 are screwed together. Accordingly, the upper end of the container mouth portion 50 is inserted into the space between the inner ring 13 and the auxiliary projection 15 formed on the inner surface of the top plate 3 until the upper end surface of the container mouth portion 50 abuts the flat surface of the small flat projection 17, whereby the container mouth portion 50 is sealed. At this time, the locking projection 19 of the TE band 7 climbs over the jaw portion 53 and is located on the lower side of the jaw portion 53.

[0029] On the upper side of the locking projection 19 provided on the inner surface of the TE band 7, an inclined surface 21 is formed such that it becomes gradually thicker from top to bottom toward the upper end joint of the locking projection 19. The inclined surface 21 is detailed in Patent Document 1, for example.

[0030] When the cap 1 in a closed state is rotated in the opening direction, the skirt wall 5 is allowed to ascend as the thread 11 and the thread 51 are unscrewed, while the TE band 7 is restricted in its ascending movement because the ascending locking projection 19 is locked to the lower surface of the jaw portion 53. As a result, stress is concentrated in the breakable bridges (not shown in the drawing) connecting the skirt wall 5 and the TE band 7, allowing the bridges to be broken. Thus, the TE band 7 is separated from the skirt wall 5. At this time, if the TE band 7 ascends sharply in response to the rotation in the opening direction, the locking projection 19 may climb over the jaw portion 23, causing the TE band 7 still connected to the skirt wall 5 to slip out of the container mouth portion 50. To avoid this, the inclined surface 21 is formed, so that the TE band 7 is allowed to ascend gradually until the locking projection 19 is locked to the jaw portion 53. Thus, the TE band 7 is effectively prevented from slipping out.

[0031] As such, if the TE band 7 is separated from the cap 1 removed from the container mouth portion 50, it is a clear indication that the cap has been opened.

[0032] According to the cap 1 with the TE band 7 in the present invention, the TE band 7 includes on its inner surface a flow path forming projection 30 that is provided on the upper side of the locking projection 19, as shown in FIG. 1. The flow path forming projection 30 is provided such that it is located to face and abut the jaw portion 53.

[0033] As shown in FIG. 2 (showing an A-A cross section in FIG. 1), a space X is formed between the inner surface of the TE band 7 and the outer surface of the jaw portion 53 around the flow path forming projection 30.

[0034] Referring to FIG. 3, the function of the flow path forming projection 30 will be explained. Ina conventional cap without the flow path forming projection 30 as shown in FIG. 3(a), the inner surface of the TE band 7 is in contact with the outer surface of the jaw portion 53. With this structure, even when air is blown through the slit 9 to a liquid droplet Y of washing water, which may be pooled on the upper surface of the jaw portion 53, the liquid droplet Y comes out through the slit 9 due to the absence of a flow path for the liquid droplet Y below the jaw portion 53. As a result, the liquid droplet Y flows through the slit 9, adheres to the outer surface of the TE band 7 and causes the ink-jet print or the like made on the outer surface of the TE band 7 to be blurred.

[0035] In the present invention, on the other hand, the flow path forming projection 30 provided on the inner surface of the TE band 7 allows the space X to be formed between the inner surface of the TE band 7 and the outer surface of the jaw portion 53 around the flow path forming projection 30. Further, a gap is formed between the locking projection 19 and the lower surface of the jaw portion 53. Thus, there is a flow path leading to the lower side of the jaw portion 53 between the jaw portion 53 and the inner surface of the skirt wall 5. With this structure, as shown in FIG. 3(b), when air is blown through the slit 9 to the liquid droplet Y of washing water, which may be pooled on the upper surface of the jaw portion 53, the liquid droplet Y flows through the flow path to the lower side of the jaw portion 53 and is discharged without adhering to the outer surface of the TE band 7.

[0036] As described above, the cap 1 of the present invention is capable of successfully removing washing water, thereby effectively preventing, for example, the print from being blurred by washing water remaining in the cap 1.

[0037] In order to maximize the water removal effect of the flow path forming projection 30 in the present invention, it is preferred that a plurality of the locking projections 19 are formed at intervals in the circumferential direction depending on the size of the cap 1, and that the flow path forming projections 30 are formed between and above the respective adjacent locking projections 19, as shown in FIG. 4 showing a partial exploded view of the TE band 7. For example, in a case where the cap has a nominal diameter of 28 mm, it is desirable that approximately three to nine locking projections 19 are formed at total intervals of approximately 1% to 50% of the circumference of the TE band 7. This allows the sufficient space X to be formed around the flow path forming projections 30, thereby effectively removing washing water by air blow. As shown in FIG. 5, the flow path forming projection 30 may axially overlap both ends of the locking projections 19 in the circumferential direction, as long as the flow path forming projection 30 is located above the locking projections 19.

[0038] The flow path forming projection 30 has an axially extending rib shape in the example shown in FIG. 4, or alternatively it can have a block shape as shown in FIG. 5. In either case, the shape and height of the flow path forming projection 30, the positional relationship between the flow path forming projection and the locking projections 19, and the like may be set to maximize the water removal effect in consideration of die cutting properties during molding of the cap. For example, the height of the flow path forming projection 30 is suitably approximately 0.05 to 0.30 nm. In the example shown in FIG. 4, only the single flow path forming projection 30 is provided between and above the adjacent locking projections 19; however, a plurality of the flow path forming projections 30 may be provided.

[0039] As shown in Patent Document 1, minute ribs are sometimes formed on the inclined surface 21 that is located above the locking projection 19 on the inner surface of the TE band 7. These ribs are provided to allow the TE band 7 separated from the cap 1 to fall immediately without staying on the outer surface of the jaw portion 53. Since these ribs are not intended for the formation of the flow path for removing washing water, they are extremely low in height and are formed at lower positions than the flow path forming projection 30 in the present invention; thus, they achieve almost no water removal function.

[0040] The above-described cap 1 of the present invention can be easily produced from a thermoplastic resin such as an olefin-based resin (e.g., polypropylene, polyethylene, etc.) by injection molding or embossing.

EXPLANATIONS OF LETTERS OR NUMERALS

[0041] 1: Cap [0042] 3: Top plate [0043] 5: Skirt wall [0044] 7: TE band [0045] 9: Slit [0046] 13: Inner ring [0047] 19: Locking projection [0048] 30: Flow path forming projection [0049] 50: Container mouth portion [0050] 53: Jaw portion [0051] X: Space [0052] Y: Liquid droplet of washing water