GB2172239A

GB2172239A - Method and mould for a cap with a tamper-evident band

Info

Publication number: GB2172239A
Application number: GB08529387A
Authority: GB
Inventors: Henryk Dudzik
Original assignee: Mardon Illingworth Ltd
Current assignee: Impress Sutton Ltd
Priority date: 1985-03-12
Filing date: 1985-11-29
Publication date: 1986-09-17
Also published as: GB2172239B; GB8529387D0; GB8506338D0

Abstract

The cap made in the mould of the invention comprises a skirt (14) attached to a band (20) by frangible lugs (30). The band has angularly spaced inward projections (21) for engaging over a bead on a container. The cap can only be removed from the container by breaking the lugs leaving the band on the container. The top faces of the projections (21) which engage the bead are perpendicular to the axis of the cap to provide secure captivation. This is produced by moulding each projection between a mould core (40) and a slidable mould part (60). The part (60) has a boss (61) defining a face (62) perpendicular to the cap axis for forming the top face of the projection. The end face (63) of the boss is tapered outwardly from the perpendicular face (62) and contacts a complementary face (43) of the mould. The lugs are formed between the bosses. Each projection (21) slides up the corresponding complementary face (43) as the stripper (70) strips the cap off the core, thereby preventing damage to the top face of the projection. <IMAGE>

Description

SPECIFICATION Method and mould for a cap with a tamper-evident band This invention relates to a method and a mould for injection moulding a cap with a tamper-evident band.

Caps of this type are well known and comprise a cap proper having a top and a cylindrical skirt, which may have screw threads for screwing down onto the neck of a container.

At the end of the skirt remote from the top is provided a band, joined to the skirt by frangible means. The band has radially inwardly projecting members. These members are forced down over an outwardly projecting bead on the container neck during initial mounting of the cap on the neck. The members snap over the bead and co-operate with the bead to resist removal of the band. In order to open the container, therefore, the cap has to be separated from the band at the frangible means and the separated band, captive on the container neck, is evidence that the cap has been tampered with.

The cap, band and frangible means are formed as part of a single, one-piece injection moulding. The mould has separable parts, which leave the moulded cap and band on a male core for axial stripping of the cap from the core, or for unscrewing of the cap from the core. In either case, this means that it has previously been impossible for the upper face of each member (that which engages the bead) to extend in a plane perpendicular to the longitudinal axis of the cap and of the core, i.e. perpendicular to the direction of stripping. This is because such faces would engage the faces of the core which formed them and prevent removal of the band from the core. It has, therefore, been necessary to provide these upper faces of the members at an oblique angle to the longitudinal axis to permit stripping from the core.As a result, the members do not provide good security in captivating the band on the container neck and it is possible for the whole moulding to be removed from a container neck and then replaced. Where the oblique angle has been insufficiently sharp, the top faces of the members tend to be damaged as the moulding is stripped from the core.

The present invention permits the top faces of the members to be both substantial and perpendicular to the longitudinal axis of the core and cap to provide secure captivation on the container neck.

In accordance with this invention, there is provided a mould for use in moulding a cap attached by frangible means to a tamper-evident band in which the band has inwardly projecting members with the faces of the members nearer to the frangible means extending substantially perpendicular to the axis of the band and the cap, the mould comprising a core on which the cap and band are moulded, a cavity-forming portion co-operable with the core for forming the cap, and radially movable parts cooperable with the core for forming the band and the frangible means, the radially movable parts having first surfaces substantially perpendicular to the core axis for forming said faces of the members, and having second surfaces which taper outwardly away from the first surfaces and engage complementary surfaces around the core, whereby, after retraction of the cavity-forming portion and the radially movable parts, said complementary surfaces of the core serve to lead the members off the core as the moulding is removed from the core.

Preferably, two radially movable parts are provided, which are separable along a common diameter of the core, each part having a plurality of bosses formed with said first and second surfaces. The frangible means may comprise lugs formed between the radially movable parts and the core.

Also preferably, the portion of the core which defines the members tapers outwardly from said first surfaces, in the assembled state of the mould, so as to define members of substantially triangular cross-section.

The invention also provides a method of moulding a cap attached by frangible means to a tamper-evident band in which the band has inwardly projecting members with the faces of the members nearer to the frangible means extending substantially perpendicular to the axis of the band and the cap, the method comprising moulding the cap between a core and a cavity-forming portion, simultaneously moulding the frangible means and the band between radially movable mould parts and the core, said faces of the members being formed by the movable parts, and providing a tapering surface on the core between said faces and the part of the core forming the cap, whereby, after retraction of the cavity-forming part and the radially movable parts, the moulding can be removed from the core with the members being lead off by the tapering surface on the core.

Reference is now made to the accompanying drawings, wherein: Figure 1 is a sectional view of a cap with tamper-evident band made according to the present invention; Figure 2 is an underneath plan view of the cap and band; and Figure 3 is a sectional diagrammatic view of a mould for producing the cap of Figs. 1 and 2.

The cap and band moulding shown in Fig. 1 comprises a cap 10, a band 20 and frangible lugs 30 joining the band to the cap.

The cap has a top 11, formed with inner sealing projections 12, 13, and a skirt 14, formed with screw threads 15.

The frangible lugs 30 are relatively thin and join the skirt to the band, the lugs being spaced around the whole periphery of the skirt.

The band is formed with inwardly projecting members 21 which projects radially inwardly of the inner surface of the adjacent# portion of the cap. The members are located between the lugs 30. Each member 21 has a top face 22 and all the faces 22 lie in a common plane which is perpendicular to the axis of the cap and the band. Each member has a triangular cross-section and includes a tapering face 23 which extends from said perpendicular face 22 and tapers out near the bottom of the band.

The lugs join the band on a circle spaced radially outwardly of a circle on which the lugs join the cap.

Referring to Fig. 3, the mould comprises a core 40 on which the whole moulding is formed. The core includes a cylindrical surface 41, which co-operates with a cavity-forming portion 50, to form the skirt 14 of the cap.

The whole cap is formed between this portion 50 and the core 40.

A pair of sliding parts 60 are provided.

These parts have generally semi-circular cavity forming portions and are slidable in opposite directions B along a diameter of the core 40.

Only one part is shown in Fig. 3, but both are indicated in Fig. 2. These parts 60 co-operate with the core 40 to form the lugs 30 and the band 20.

A stripper bush 70 is also provided and this completes the cavity for forming the band 20.

After a moulding operation, the cavity-forming portion 50 is retracted in the axial direction of arrow A and the sliding parts are retracted in the radial directions of arrows B, leaving the moulding on the core. The stripper bush 70 is then axially moved to strip the moulding from the core 40.

Each sliding part 60 has angularly spaced bosses 61 whose end faces engage with the core. Between these bosses, cavities are defined between the sliding part and the core to form lugs 30. The bottom face 62 of each boss is flat and lies perpendicular to the core axis and the flat faces 22 of the members are formed by these bottom faces 62 of the slidable parts. The end faces 63 of the bosses taper outwardly from these faces 62. The core 40 has complementary faces 43 to the faces 63 and the complementary faces form an outward taper to the cylindrical surface 41.

After retraction of the mould parts 50 and 60, the stripper bush 70 pushes the moulding off the core 40. During stripping, there is no obstacle to the members 21, despite the fact that their top faces are perpendicular to the direction of stripping. There is sufficient resilience in the moulding for the band to be stretched over the cylindrical surface 41 of the core 40 and the complementary faces 43 serve to lead the projecting members 21 out onto the cylindrical surface 41, so that no damage is caused to the perpendicular top faces of the members.

The screw threads 15 are diagrammatically shown and have faces sufficiently angled to the cap axis to permit the cap to be stripped from the core without damage to the threads.

Claims

1. A mould for use in moulding a cap attached by frangible means to a tamper-evident band in which the band has inwardly projecting members with the faces of the members nearer to the frangible means extending substantially perpendicular to the axis of the band and the cap, the mould comprising a core on which the cap and band are moulded, a cavity-forming portion co-operable with the core for forming the cap, and radially movable parts cooperable with the core for forming the band and the frangible means, the radially movable parts having first surfaces substantially perpendicular to the core axis for forming said faces of the members, and having second surfaces which taper outwardly away from the first surfaces and engage complementary surfaces around the core, whereby, after retraction of the cavity-forming portion and the radially movable parts, said complementary surfaces of the core serve to lead the members off the core as the moulding is removed from the core.

2. A mould according to Claim 1 in which two radially movable parts are provided, each part having a plurality of said bosses each formed with said first and second surfaces, the two parts being separable along a common diameter of the core.

3. A mould according to Claim 1 or 2, wherein the frangible means comprises lugs formed between the bosses and between the radially movable parts and the core, the lug joining the band on a circle spaced radially outwardly of a circle on which the lugs join the cap.

4. A mould according to Claim 1, 2 or 3, wherein the portion of the core which defines the projecting members tapers outwardly from said first surfaces, in the assembled state of the mould, so as to define members of substantially triangular cross-section.

5. A mould substantially as herein described with reference to Figs. 2 and 3 of the accompanying drawings.

6. A method of moulding a cap attached by frangible means to a tamper-evident band in which the band has inwardly projecting members with the faces of the members nearer to the frangible means extending substantially perpendicular to the axis of the band and the cap, the method comprising moulding the cap between a core and a cavity-forming portion, simultaneously moulding the frangible means and the band between radially movable mould parts and the core, said faces of the members being formed by the movable parts, and providing a tapering surface on the core between said faces and the part of the core forming the cap, whereby, after retraction of the cavity-forming part and the radially movable parts, the moulding can be removed from the core with the members being lead off by the tapering surface on the core.

7. A method of moulding a cap, said method being substantially as herein described with reference to the accompanying drawings.