A metal safety cap for a jar, bottle or tin

Abstract

A two-part metal safety cap comprises an inner threaded metal cap formed from sheet metal, which has an internal thread for engaging with a screw thread to seal a container, tin or jar and an outer ca

Description

Field This invention relates to a safety cap made of metal for a container, more particularly but not exclusively, to a cap for a jar, bottle or tin which might contain medicaments, tablets or items that may be unsafe to young or vulnerable people, such as cleaning chemicals supplied as powders or in solid form. Background Some containers, such as those containing medicines, usually require the use of child resistant packaging or child-proof caps. This has previously been achieved by using a two-part cap comprising an inner threaded element, which engages with the screw thread on the container, and an external element which encloses the internal element, and the external element is free to rotate separately in the opening direction unless engaged. Engagement features, such as toothed inner and exterior elements, enable the inner and outer caps to engage to drive the inner element to open and close the container. One example of an engagement features requires a specified action (such as pressing down or squeezing the side of the cap) such that the outer cap is then able to drive the internal cap to open the container. Therefore, unless there is combined pushing and twisting, the container cannot be opened which is what prevents young children from accessing contents such as tablets. Conventionally these caps are typically formed from a food safe synthetic plastics material, such as polyethylene terephthalate (PET), polypropylene, polyvinyl chloride (PVC), polystyrene and polycarbonate. Polyethylene terephthalate (PET) is non-toxic, light in weight, strong and durable and so has been used for many years with a wide range of contents. However, these synthetic plastics are not easily recyclable, take many thousands of years to degrade, for example in landfill, and cannot easily be incinerated as they give off toxic and noxious fumes. Prior Art Published Taiwanese patent application TWM 2 677 200 (Huang Huan-Tsai) discloses a metal can lid consisting of an inner lid which in use is placed around a rim of a bottle or can. A rolling machine is used to form a spiral groove to form threads in the lid which converge to close the bottle (or can). United States patent US 3 797 688 (Porcelli et al) discloses a closure which is essentially formed from a synthetic plastic material and has central spigot with a body which requires further fabrication stages in order to secure the two parts together. A top wall of the outer cap has a central opening into which the spigot (formed on a top wall of the inner cap) extends. The spigot is deformed to form a bead thereby connects the two caps whilst still permitting their relative rotation. United States patent US 5 370 251 (Buono) describes a child-resistant closure for a bottle made from synthetic plastic material. It has inter-engaging tabs or fingers which are located within lower portion of one part of the cap. Separate features provide engagement on an upper portion. United States patent application US 2004 / 0195197 (Miceli et al) disclosures a synthetic plastics moulding which requires a bespoke tab. The inner cap is coaxially positioned and nested within the outer cap such that a row of angular abutments, on the inner cap engage with a row of angular abutments of the outer cap upon rotation of the outer cap in a closing direction. United States patent application US 2022 / 0041350 (Berge), discloses a removable cap which includes a silicon product with an overlap having a side engagement. The side engagement mates with an existing closure device on the container using a heat activated adhesive. International patent application WO 9001451 (Van Blarcom Closures Inc) discloses a tamper-evident child resistant closure device having two sets of teeth: one on each of an inner cap and an outer cap. The sets of teeth engage to enable removal and closure of the device. Many of the aforementioned systems and manufacturing processes require additional tooling, materials and complex moulding techniques. In addition, most are formed from synthetic plastics materials or a mixture of different types of materials and so are not readily recyclable. In many of the aforementioned closure devices, a user is required to remove a tear off tamper-evident strip which is not required by the present invention because it simply fits to a threaded portion of the container and so does not require any additional parts. The moulding tools and steps required to fabricate these intricate features are expensive and complex. In addition, the child-resistant closure is not easily recyclable. Another aim of the present invention is to provide a child-proof or child resistant cap from a material that is durable, food safe and recyclable. Standard metal continuous thread caps have no mechanism which requires a combination of actions or forces together with the unscrewing action in order to open the closure. Therefore, simply replacing two-part synthetic plastics caps with a two-part metal cap is impractical because once squeezed laterally, metal deforms plasticly and so does not recover in the same manner as synthetic plastics caps. An aim of the present invention is to overcome the aforementioned problems. Summary of the Invention According to a first aspect of the invention there is provided a two-part metal safety cap comprising an inner metal cap, formed from sheet metal, having a threaded inner portion for screwing onto a container, such as a bottle or jar, and a metal outer cap, formed from sheet metal, surrounding and enclosing the inner metal cap whereby the inner metal cap is free to rotate therewithin, and a friction surface treatment or coating is applied to at least one mating face of the inner metal cap and metal outer cap to transfer torque from the outer metal cap to the inner metal cap when an axial force is applied to the metal outer cap to the inner metal cap. According to a second aspect of the invention there is provided a two-part metal safety cap comprising an inner metal cap, formed from sheet metal, having a threaded inner portion for screwing onto a container, such as a bottle or jar, and a metal outer cap, formed from sheet metal, surrounding and enclosing the inner metal cap whereby the inner metal cap is free to rotate therewithin, and a friction material is located between the metal outer cap and the inner metal cap to transfer torque from the outer metal cap to the inner metal cap when an axial force is applied to the metal outer cap to the inner metal cap. Unlike prior art closure devices, which are in part or wholly formed from a moulded synthetic plastics material, the inner and outer caps (or shells) are formed from sheet metal and so lends itself readily to recycling. The current invention is of an over cap formed from either sheet aluminium or tinplate designed to prevent a child or patient from inadvertently opening a tablet bottle or a container with a poisonous or corrosive contents. Adding a child resistant mechanism, which requires a combination of actions and forces together, to achieve an unscrewing action in order to open a closure of a bottle or jar overcomes the aforementioned problems. Inter-engaging the inner and outer caps by pressing the two caps together allows transfer of torque from the outer metal cap to the inner metal cap, so that removal of the inner cap from a container is possible. Without the compressive axial force, the metal outer cap, which retains the enclosed inner metal cap, can normally rotate freely around the inner cap when simply turned. The friction surface treatment or coating is applied to either the underside of the metal outer cap face or an upper outer surface side of the inner metal cap surface, or both. The friction material is located between an internal (top) surface of the metal outer cap and an outer top surface of the inner metal cap. Ideally the friction material is compressible. The friction material is from the group comprising: natural rubber, synthetic foam and a resiliently deformable polymeric material. Creating in combination a child resistant cap made from either sheet aluminium or tinplate together therefore provide a sustainable solution to this specific requirement that has only been able to be achieved using synthetic plastics materials. The invention enables standard types of metal continuous thread caps, already designed for use with industry standard container neck sizes and threads, and so eliminates any need for the users to change or develop other tooling or neck forms to allow its use. It is appreciated that the degree of difficulty to be designed into the opening requirements can be achieved by the respective degree and type of friction surface or coating applied, of the type size and configuration of the friction material incorporated between the outer and inner shells. It is appreciated that the different engagement mechanisms may be used, such as friction surfaces which may have a friction lining, engagement means, pips or a rubber coating to increase friction and so improve coupling of torque between the inner and outer caps. Advantageously a coating is applied to at least one surface of at least one of the caps. The coating is a food grade protective coating and prevents corrosion and ensures the cap is safe for use in food and beverages. Outer surfaces of the cap may also have decorative coatings, coloured lacquers or printed designs, or embossed or debossed features for branding and marketing purposes. In a yet further embodiment, additional engagement means, such as teeth or serrations may be formed around an exterior edge portion of the metal inner threaded metal cap and corresponding teeth formed around an inner edge portion of the metal outer cap, so that the respective portions engage one with another when the metal outer cap is pressed axially towards the inner threaded metal cap. The metal outer cap retains the inner threaded metal cap by way of a retaining means which permits relative rotation of the inner threaded metal cap within the outer cap, when both are removed from the container. Optionally a spacer is provided so that in an undepressed state, the inner and outer caps are urged apart, and rotation of the outer cap does not result in rotation of the inner cap. Preferably the retaining means is a curl fold formed in the outer cap and / or at least one clip disposed around a rim of the outer cap and / or at least one bead disposed around a rim of the outer cap. Ideally a portion of the side wall of the outer cap is folded or curled over to retain the inner cap and this provides strength to the outer cap. The inner cap is dimensioned to fit snugly within the outer cap to ensure there is sufficient overlap of the curl which also prevents the inner cap from rattling inside the outer cap as well as retaining it therein. In some embodiments the outer cap and the inner threaded metal cap are formed from aluminium. Use of electro-magnetic sorting systems are able to temporarily magnetise these items enabling them to be removed from the waste stream. Alternatively, at least one of the outer cap and the inner threaded metal cap may be formed from a ferro-magnetic material, such as steel which may be tin plated. Where sealing is required the inner metal threaded cap may include a liner which is a chemically compatible material that is located between the cap and the jar, tin or bottle. To assist a user a marker or indicator may be provided on the caps which indicates the opening requirements. Advantages of the invention are that it enables a conventional, existing threaded metal cap to be used as the inner threaded cap and thus no modification of existing production and food container filling lines is required. According to a third aspect of the invention there is provided a method of producing a two-part metal safety cap for a container, the two-part metal safety cap includes metal outer cap portion and an inner metal cap portion, the method comprising the steps of: a) forming a metal outer cap; b) locating a material wad between an inner top surface of the metal outer cap and an outer top surface of the inner metal cap; c) placing the inner metal cap within the metal outer cap; and d) forming a curl around a lower edge of the metal outer cap to retain the inner metal cap therewithin. According to a fourth aspect of the invention there is provided a method of producing a two-part metal safety cap for a container, the two-part metal safety cap includes metal outer cap portion and an inner metal cap portion, the method comprising the steps of: a) forming a metal outer cap; b) applying a friction surface or coating to at least one of an underside of the face of the metal outer cap, or an upper face of the inner metal cap; c) placing the inner metal cap within the metal outer cap; and d) forming a curl around a lower edge of the metal outer cap to retain the inner metal cap therewithin. In one aspect existing threaded metal caps can be used and fitted into a suitably sized metal outer cap either by coating an external surface with a suitable friction imparting material or adhering a friction layer or regions thereon. Optionally therefore existing types of inner metal cap may be used which already have a thread formed around at least a portion of their rim. This reduces cost as the invention may be used, in some embodiments as a retrofit option. Other aspects of the invention may be incorporated or formed by appropriate variations to steps of the method, examples of which are shown in Figure 6 and described in detail below. The invention will now be described, by way of examples only, and with reference to the following Figures in which: Brief Description of the Drawings Figures 1A and 1B show side elevation and plan views respectively of an inner metal cap; Figures 2A and 2B are corresponding views of the outer cap which revolves around the inner part; Figure 3A is a part sectional detailed view of an insert which is located between an exterior or outer cap and surrounding an inner threaded metal cap; Figure 3B shows an overall, part sectional view of the insert, located between the outer cap and inner threaded metal cap; Figure 4 is an overall view showing how the inner cap is retained within the outer cap by way of a curl or hem; Figure 5 shows in detail how folded hem retains the inner cap within the outer cap; and Figure 6 is a flow diagram showing key steps of one method of fabricating the two-part metal cap. Detailed Description of Preferred Embodiment of the Invention Figures 1A and 1B show side elevation and plan views respectively of a standard threaded cap forming the inner metal cap 10 which has a threaded portion 20 for attaching to a threaded opening of a container, such bottle or jar (not shown). The inner threaded metal cap 10 has a shoulder portion 25 for retaining a liner (not shown). The metal from which cap 10 is formed may be pressed steel, typically 0.21 mm thick ±20% or aluminium typically 0.28 mm thick +20% and has a diameter of between 18 and 120 mm and preferably between 30 mm and 100 mm. An outer edge or rim 28 of the inner metal cap 10 may be milled and have grooves or notches, but preferably has a smooth finish. Typically, the height of the rim is between 10 mm and 14 mm. The metal from which outer cap 40 is formed may be pressed steel, typically 0.21 mm thick +20% or aluminium typically 0.28 mm thick +20% and has a diameter sufficient to enable the inner cap 10 to fit and locate therein with sufficient clearance to enable one to rotate freely with respect to the other, but to prevent the inner cap from falling or becoming dislodged from the outer cap once the retaining means 50 has been formed. An outer edge or rim 60 of the outer metal cap 40 may be milled and / or have grooves or notches, but preferably has a smooth finish. Figure 3B shows the arrangement of the friction 55 material between the underside of the face of the outer shell and upper side of the face of the inner shell which allows torque to be transferred from an outer cap 40 to the inner threaded metal cap 10 once the outer cap 40 is pressed axially towards the inner threaded metal cap. This enables removal of the inner cap 10 from the container. A retaining device 50, shown in Figure 3A, retains the inner metal cap 10 within the outer cap 40. One example of a manufacturing process, for a preferred embodiment of the invention, is summarised in Figure 6. Figure 3A is a part sectional view of the exterior of cap 40 surrounding inner threaded metal cap 10 which are shown in exploded detail in Figure 3B. The respective degree and type of friction surface or coating applied, can be varied to control or vary the ease of opening and closing of the metal safety cap through that the degree to which the respective amount and nature of friction material that engages with a surface, when the outer cap 40 is pressed axially towards the inner threaded metal cap 10 and twisted with respect thereto. Separately the type size and configuration of the friction material 55 incorporated between the outer and inner caps (or shells) can be varied in size, shape or number to control or vary the ease of opening and closing of the metal safety cap through that the degree to which the respective amount and nature of friction material that engages with a surface, when the outer cap 40 is pressed axially towards the inner threaded metal cap 10 and twisted with respect thereto. The friction features 55 are specified dimensioned and sized so they have sufficient points of contact, when properly aligned one with another, to enable them to contact a surface (or one another if formed on two surfaces) fit together when the outer cap 40 is depressed with enough engagement to allow the unscrewing rotation force to be transferred from the outer cap 40 to the inner cap 10. Referring to Figure 6, a method of fabrication of one embodiment of the invention will now be described with reference firstly to the outer cap or outer shell and then with reference to the insertion of the friction material or inner cap or inner shell. The inner shell or cap is ideally a standard threaded cap formed from sheet of metal with a thread formed around an open end of the inner cap to engage directly with a thread on a jar or bottle opening neck. This reduces the cost of the overall two-part metal cap as existing inner metal caps with threads already formed on them may be used. An outer shell is formed from sheet metal with a predefined and sized shape dimensioned to enable the insertion of an inner shell with sufficient clearance for the inner shell to rotate freely, but not to enable the inner cap to fall out once the retaining device is formed. A friction surface 55 or coating is applied to the underside of the face of the outer cap and / or the upper outside of the upper face of the inner cap, or the friction material is inserted into the outer cap. When the friction material is inserted into the outer cap it may be bonded to the inner surface of the outer cap or retained therein by way of a bead or formation or another retainer or retaining means, or bonded to the outer surface of the inner cap. The inner cap 10 is then inserted within the outer cap 40. A curl 50 acts as a retaining means and is formed on the outer cap to help ensure a safe forming of a cut metal edge. This curl is also sized to retain the inner shell or cap 10 within the outer shell or cap 40. The curl 50 when formed also retains the inner cap within the outer cap. This second or retaining stage is performed after application of the friction surface or coating or insertion of the friction material inner cap into the outer cap in order to retain the inner cap in the outer and so as to provide a sufficient overlap of the curl 50, and in some embodiments is optionally flattened, to provide sufficient axial space for depressing the outer cap onto the inner cap and to enable unscrewing of the inner cap from a thread of a bottle or jar, as described above. Figure 4 shows a detailed view of a corner portion of the two-part metal safety cap and how the inner cap is retained within the outer cap, for example, using a curl 50 or by folding or squashing an edge to form a hem or fold. Variation to the aforementioned embodiments may be made, without departing from the scope of protection as defined by the claims. For example, although inner portion of inner threaded metal cap 10 shown in Figure 4, has a threaded part 20. Standard threaded caps may be formed from in either sheet aluminium or tinplate steel and are typically available in a range of sizes from 18 mm to 120 mm in diameter. Thread forms are specified to fit industry standard container neck sizes and threads. As both sheet aluminium and tinplate steel are easily identifiable and separable in the waste stream, they may be recycled through smelting, during which process any inserted sealing wad or liner is burnt off. Thus, these two-part metal safety caps provide a sustainable solution to closure requirements. It will be appreciated that variation to the aforementioned embodiments may be made, without departing from the scope of protection as defined by the claims.

Claims

1. A two-part metal safety cap comprising an inner metal cap, formed from sheet metal, having a threaded inner portion for screwing onto a container, such as a bottle or jar, and a metal outer cap, formed from sheet metal, surrounding and enclosing the inner metal cap whereby the inner metal cap is free to rotate therewithin, and a friction surface treatment or coating is applied to at least one mating face of the inner metal cap and metal outer cap to transfer torque from the outer metal cap to the inner metal cap when an axial force is applied to the metal outer cap to the inner metal cap.

2. A two-part metal safety cap comprising an inner metal cap, formed from sheet metal, having a threaded inner portion for screwing onto a container, such as a bottle or jar, and a metal outer cap, formed from sheet metal, surrounding and enclosing the inner metal cap whereby the inner metal cap is free to rotate therewithin, and a friction material is located between the metal outer cap and the inner metal cap which to transfer torque from the outer metal cap to the inner metal cap when an axial force is applied to the metal outer cap to the inner metal cap.

3. A two-part metal safety cap as claimed in claim 2 wherein the friction material is located between an under side of the face of the metal outer cap and an upper side of the face of the inner metal cap.

4. A two-part metal safety cap as claimed in claim 1 wherein the friction surface treatment or coating is applied to an under side of the face of the metal outer cap, or an upper side of the face of the inner metal cap, or both.

5. A two-part metal safety cap as claimed in either claim 2 or 3 where the friction material is compressible.

6. A two-part metal safety cap as claimed in any of claims 1, 3 or 5 wherein the friction material is from the group comprising: natural rubber, synthetic foam or a resiliently deformable polymeric material.

7. A two-part metal safety cap as claimed in any preceding claim wherein the inner metal cap and / or the metal outer caps are formed from aluminium gauge 0.28 mm ± 20% or tinplate gauge 0.21 mm ± 20%.

8. A two-part metal safety cap as claimed in claims 1 to 7 wherein the metal outer cap has an inward deformation / curl along a rim of its open end.

9. A two-part metal safety cap as claimed in any preceding claim wherein at least the inner metal cap has a protective coating applied thereto.

10. A two-part metal safety cap according to any preceding claim wherein the inner metal cap includes a liner.

11. A two-part metal cap according to any preceding claims wherein the inner metal cap is between 18 mm and 120 mm in diameter.

12. A method of forming a two-part metal safety cap comprising the steps ofa) forming a metal outer cap;b) applying a friction surface or coating to at least one of an underside of the face of the metal outer cap, or an upper side of the face of the inner metal cap;c) placing the inner metal cap within the metal outer cap; andd) forming a curl around a lower edge of the metal outer cap to retain the inner metal cap therewithin.

13. A method of forming a two-part metal safety cap comprising the steps of a) forming a metal outer cap;b) locating a friction material (friction wad) between an inner top surface of the metal outer cap and an outer top surface of the inner metal cap;c) placing the inner metal cap within the metal outer cap; andd) forming a curl around a lower edge of the metal outer cap to retain the inner metal cap therewithin.

14. A method as claimed in claim 12 or 13 wherein forming the metal outer cap and / or the inner metal cap includes the step of pressing sheet metal.

15. A method as claimed in any of claims 12 to 14 wherein the inner metal cap and / or metal outer caps are formed form aluminium gauge 0.28 mm ± 20% or tinplate gauge 0.21 mm ± 20%.

16. A method as claimed in any of claims 12 to 15 wherein a protective coating is applied to at least one surface of the inner metal cap or metal outer cap.

17. A method as claimed in any of claims 12 to 16 includes applying a film of oil to at least one surface of the inner metal cap or metal outer cap during a forming step.

18. A container having a threaded neck portion and including a two-part metal safety cap according to any of claims 1 to 9 located thereon and screwed onto the threaded neck portion to form a closed container volume.

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