AU642500B2 - Plastic closures having tear-tabs - Google Patents

Description

P/00/0011 Regulation 3,2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

64250N01 S. 55 S S

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Name of Applicant: CMB FOODGAN PLC Actual Inventor(s): Eric Trevor HOPLEY Address for service in Australia:

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CARTER SMITH BEADLE Qantas House 2 Railway Parade Camberwell Victoria 3124 Australia Attorney Code SA

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S. 55 S S Invention Title: PLASTIC CLOSURES HAVING TEAR-TABS The following statement is a full description of this invention, including the best method of performing it known to us: Our Ref-: #7124 TNB:WB 59lcmb 1- This invention relates to closures made of plastics materials, 'and especially to such closures having removable tamper-evident tear bands having integrallymoulded gripping tabs.

Closures of this type are well known. The tear band is attached to the lower end of the skirt of the cap, through a frangible connection. This may be a thin circumferential membrane or a series of spaced bridges.

The inside wall of the tear band is provided with features which cooperate with complementary features on the adjacent wall of the container to be closed, such that the closure cannot be removed from the container until after so** the tear band has been removed.

e "5 Various configurations of tear band and gripping tab have been proposed. They are all effective to a greater or lesser degree. One of the problems associated with closures of this type stems from the fact that they are normally produced by an injection moulding technique.

Briefly stated, the injection moulding process includes the steps of closing the mould parts the core and the cavity) together and filling the mould with plastics material; cooling the mould; separating the mould parts; 0 0 and stripping the moulding, i.e. the closure, off the 25 core. In stripping the moulding from the core the cavity moves away from the rest of the tool, leaving the moulding held onto the core. In the case of a threaded closure the core then usually unscrews, leaving the moulding held on the core surround. A stripper plate then drives the 30 moulding off the core surround and ejects it from the S mould. It will be appreciated that the gripping tab, although moulded integrally with the skirt of the cap, is virtually a separate moulding, since it is spaced outwardly from the cap skirt. This has led to difficulties in stripping the moulding from the mould, since the tear tab having a substantial surface area in contact with the cavity, but only an edge in touching contact with the core, the tendency is for the closure to stay on the core and for the :ear tab to remain in the cavity. As the cavity separates from the core, there is thus a tndency to rupture any thin parts of the tear band, e.g.

thile membrane or a bridge. Additionally, there are other production constraints, due to the fact that the tear tab is the last part of the mould to be filled and there is a need to pack it adequately, but not so tightly that it becomes impossible to withdraw it from the cavity. Thus, moulding the closure and removing it from the mould without damage is a tricky operation.

It is also desirable for a portion of the tear band, e.g. the tear tab, to be such that it may be readily grasped; thus, it should not be insubstantial. This in itself canll result in minor, but cumulative, drawbacks; the problem already referred to will probably be amplified if the tear tab has a large area; If the tab is substantially-sized it may present a cooling problem or at least extend the time needed to cool it adequately; with thicker sections there is a tendency towards unsightly sinkage, caused by slow cooling.

It is an object of the invention to overcome these drawbacks and to provide a closure cap of the kind mentioned above of such a configuration that the moulding **and subsequent removal from the mould is facilitated. It is also an object of the t: 20 invention to provide a closure cap of this type which is simpler to use.

According to a first aspect of the invention there is provided a closure cap of plastics material, having a removable tear-band and a gripping tab attached thereto i"..through a connecting bridge intermediate its ends, wherein the gripping tab is formed with at least one hollow cavity which extends parallel or substantially parallel to the 25 longitudinal axis of the cap, in anll end portion of the tab which is thicker than the remainder of the tab.

The portion of thicker section is suitably between two and three times as thick as the remainder of the tab. The thicker section portion may have a cylindrical configuration.

Preferably also, the connecting bridge, through which the gripping tab is 17 August 1993 attached to the tear band, is situated towards one end of the tear tab suitably that remote from the portion of thicker section.

In the accompanying drawings Figure 1 is a side elevation of a tamper-evident closure according to this invention; Figure 2 is an underneath view of the closure of Figure 1; Figure 3 is a cross-sectional elevation of an injection mould for forming the closure of Figure 1; and Figure 4 is a section of part of the mould of Figure 3, on an enlarged scale.

Referring to Figure 1, the closure has a top 1 and cylindrical skirt 2 to the lower end of which is attached, through a frangible membrane 3, a tear band 4. Tear band 4 is attached, through a connecting bridge 5, to a gripping tab 6.

Gripping tab 6 is shown better in Figure 2, which also illustrates a number of oblique ribs 7 integrally moulded into the inside wall of the tear band 4. Ribs 7 cooperate with complementary projections (not shown) on the adjacent wall of the container to be closed.

C tnz sc 7Agut19 As seen in Figure 2, one end of the gripping tab 6 is formed as a hollow cylinder 8 of diameter larger than the thickness of the remainder of the gripping tab. The other end 9 of the gripping tab is also of cylindrical form, slightly thicker than the central part of the gripping tab but not so thick as end 8. A hollow cavity parallel with the axis of the cap, is formed in the end 8 of the gripping tab. Spaced ribs 11 are formed on the major faces of the gripping tab. It will be appreciated that the closure of Figures 1 and 2 is easy to use, since the enlarged end 8 of the tab 6 may be readily grasped. As the end 8 is grasped between the thumb and forefinger, it moves away from the tear band 4. With S bridge 5 acting as a fulcrum, the smaller end 9 of the tab 6..15 6 ioves towards the tear band 4, and eventually contacts

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it. As the smaller end 9 of the tab contacts the tear °oeoo S band 4 it becomes the fulcrum point, giving a large mechanical advantage to the end 8 of the tab relative to the bridge 5, thus increasing the tearing force at the vertical membrane 12 adjacent thle bridge. If the tab 6 is angled upwards when pulling, it concentrates the force at the "free" end of the membrane 12, which facilitates rupture of the membrane 12.

a 0 Figures 3 and 4 illustrate the production of the 5* closure of Figures 1 and 2 in an injection mould o. comprising a core 22, a core surround 23, a cavity 24, and a stripper plate 25. In the closed position of the mould, shown in Figure 3, in which injection of the plastics material takes place, a pin 30 enters that part of the mould cavity forming the thickened end 8 of gripping tab 6. As is better seen from Figure 4, pin has a series of circumferential grooves 31, the purpose of which is explained below. When moulding has occurred and the mould cooled, the cavity 24 moves away from the core 22 at the parting line A-A. This leaves the closure held on the core 22 and the pin 30, aided by a retentive contribution from the grooves 31. The core 22 is then unscrewed, leaving the closure on the core surround 23 and surround 23 and pin 30. Stripper plate 25 then removes the closure from the core surround 23 and pin In forming closures of the prior art by a similar technique, the tear tab tends to move away with the cavity 24, rather than remain with the rest of the closure on the core 22. By virtue of the use of the pin 30, the whole of the closure, including the tear tab, remains on the core and can be removed without damage. It is also noteworthy that the use of the pin 30 leads to the wall thickness of the thickened end 8 of the tab 6 being significantly reduced, thus overcoming the problems associated with cooling substantial thicknesses of material referred to under and above.

The claims form part of the disclosure of this specification.

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Claims (7)

1. A closure cap of plastics material, having a removable tear-band and a gripping tab attached thereto through a connecting bridge intermediate its ends, wherein the gripping tab is formed with at least one hollow cavity which extends parallel or substantially parallel to the longitudinal axis of the cap, in an end portion of the tab which is thicker that the remainder of the tab.

2. A cap as claimed in claim 1, wherein the said end portion is between 2 and 3 times as thick as the remainder of the gripping tab.

3. A cap as claimed in claim 1 or claim 2, wherein the said portion has a cylindrical configuration.

4. A cap as claimed in any preceding claim, wherein the connecting bridge attaching the gripping tab to the tear-band is situated adjacent the end of the gripping tab remote from the said end portion thereof.

A closure cap as claimed in claim 1 or claim 2, substantially as described with reference to the drawings.

6. A method of moulding, in a mould comprising mutually axially separable mould cavity and core portions, a plastics closure cap as claimed in claim 1, wherein the gripping tab of the closure cap is moulded onto a generally elongate and axially extending further portion of the mould, and subsequent to moulding the further 20 mould portion is effective to restrain the tear-band of the closure cap from movement relative to the moulded cap while the mould cavity and core portions are separated. DATED this 17th day of August, 1993. CARTER SMITH BEADLE 2 Railway Parade Camberwell 3124 Victoria Australia .P1-7i2414 C 17 August 1993

-7 ABSTRACT A closure cap has a removable tear-band and a gripping tab attached thereto through a connecting bridge The gripping tab lies in a plane parallel or substantially parallel to the axis of the cap and is formed with at least one hollow cavity (10) extending parallel or substantially parallel to the axis of the cap. In one embodiment the hollow cavity (10) is formed in a cylindrical end of the gripping tab which is of diameter larger than the thickness of the remainder of the gripping tab. *too 9 *S S *o S S rO