BACKGROUND TO THE INVENTION

THIS invention relates to a child resistant closure for a container.

There are many types of child resistant closures for containers which contain harmful or potentially harmful substances. Generally, such known child resistant closures are unitary and require a special technique to unscrew the closure from the container. In some child proof closures, for example, either a top or axial force must be exerted on the closure before it will be possible to unscrew it from the container. The main problems with this type of closure are that children are able to learn the technique by watching adults, or they tend to work out the technique for themselves, or they stumble upon it through a process of trial and error thus rendering the child-proof closure useless.

It is an object of the invention to address the above problems by providing an alternative child resistant closure.

SUMMARY OF THE INVENTION

According to the invention there is provided a child resistant closure for a container, the closure comprising:

a cap having an internally threaded surface for engagement with a complementally threaded outlet on a container, and key engagement means; and

- a shield mounted rotatably to the cap and extending over the cap so as to prevent the cap from being unscrewed, the shield being provided with key access means for allowing an external key element to engage with the key engagement means on the cap to unscrew the cap from the outlet of the container.

In a preferred form of the invention, the child resistant closure includes the external key element.

Preferably, the child resistant closure comprises unidirectional engagement means for allowing the shield to engage with the outer surface of the cap when it is turned in a direction to screw the cap onto the outlet.

Typically, the unidirectional engagement means comprises a ratchet-and- pawl arrangement in the form of at least one ratchet tooth on the shield or the cap which engages with an at least one complemental pawl formation on the respective cap or shield.

Preferably, the key access means in the shield comprises at least one access aperture.

Advantageously, the key element comprises at least one keyed projection which is adapted to pass through the at least one access aperture in the shield to engage with the complemental key engagement means on the cap.

Typically, the keyed projection comprises a splined spigot and the key engagement means comprises a complementally splined socket.

The closure may further comprise a gate located between the cap and the shield to obturate the key access means, the key element being provided with gate displacement means which can displace the gate away from the

key access means to allow the key element to pass through the key access means in the shield to engage with the key engagement means on the cap.

Conveniently, the gate comprises a deformable disc, which is biased into the obturated position.

Conveniently, the key element has a peripheral skirt which is adapted to fit around the top portion of the shield when the key is brought into engagement with the cap.

Preferably, the peripheral surface of the key element is knurled.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompany drawings wherein:

Figure 1 shows a partly cut-away cross-sectional side view of a first embodiment of the child resistant closure of the invention;

Figure 2 shows an exploded view of Figure 1 :

Figure 3 shows an underplan view of a key element of the closure of Figure 1 ;

Figure 4 shows a top view of a cap of the closure of Figure 1 ;

Figure 5 shows a partly cut-away cross-sectional side view of a second embodiment of a child resistant closure in accordance with the invention;

Figure 6 shows an exploded view of Figure 5;

Figure 7 shows an underplan view of a key element of the closure of Figure 5;

Figure 8 shows an underplan view of a shield of the closure of Figure 5; and

Figure 9 shows a top view of a cap of the closure of Figure 5.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to Figures 1 to 4, a child resistant closure 10 in accordance with a first embodiment of the invention comprises a cap 12 which is provided with an internal screw thread 14 and is screwed onto a complementally threaded container outlet 16 (see Figure 1 ). A shield 18, which comprises a round top 20 having a peripheral skirt 22 fits over and is rotatably mounted to the cap 12. The cap 12 has a lip 24 which clips into a groove 26 on the shield 18 to hold the shield in place.

The outside top surface 28 of the cap 12 has four circumferentially spaced pawl grooves 30 (see Figure 4) for engagement with deformable ratchet teeth 34 which are circumferentially spaced on the inner surface 32 of the top 20 of the shield 18 (see Figure 2). The ratchet teeth 34 are oriented to engage with the grooves 30 of the cap 12 when the shield 18 is turned in a clockwise direction to screw the cap 12 onto the outlet 16. When the shield 18 is turned in an anti-clockwise cap loosening direction, the ratchet teeth 34 ride over the pawl grooves 30 and the shield 18 rotates freely about the cap 12. The arrangement of the ratchet teeth 34 with the pawl grooves 30 provides a unidirectional engagement means such that the cap 12 of the closure 10 can be screwed onto a container but cannot, by itself, be unscrewed due to the fact that it is covered by the shield 18.

The only way to unscrew the child resistant closure 10 is by way of a separate external key element. In this embodiment of the invention the key element comprises a key 36 having a round top portion 38 which has a skirt 40 extending from the periphery thereof. When the key 36 engages with the closure 10, the skirt 40 extends over the top of the shield 18. Centrally located on the inner surface 42 of the key 36 is a key projection, here a male spline 44. Key access means, here a circular access aperture 46, is provided in the shield 18 through which the spline 44 can pass for engagement with a complemental key engagement means, here a complementally shaped and sized female spline 48, which is located centrally on the top surface of the cap 12.

When the key 36 is engaged with the shield 18, as described above, rotation of the key 36 in an anti-clockwise direction causes the cap 12 to unscrew from the container outlet 16. In order to assist a user in gripping the key 36 the outer surface of the skirt 40 of the key is knurled.

A second embodiment of a child resistant closure in accordance with the invention is shown in Figures 5 to 9. The child resistant closure 50 of this embodiment comprises a cap 52 having an internal screw thread 54 allowing it to be screwed onto a complementally threaded container outlet 56. A shield 58 comprising a round top portion 60 and a skirt 62 which depends from the periphery thereof is rotatably attached to the cap 52. The inner surface 64 of the skirt 62 has a groove 66 which clips firmly over a lip 68 on the outer side 70 of the cap 52 thereby rotatably mounting the shield 58 to the cap.

The inner surface 64 of the skirt 62 on the shield 58 is provided with a series of ratchet teeth 72 (see Figure 8) which engage with pawl flaps 74 on the outer side surface 70 of the cap 52 (see Figure 9) when the shield is rotated in a clockwise direction thereby screwing the cap 52 onto the outlet 56 but which ride over the flaps 74 when the shield 58 is turned in an anti-clockwise direction so that the shield 58 rotates freely. The arrangement of the ratchet teeth 34 with the pawl flaps 74 provides a

unidirectional engagement means such that the cap 52 of the closure 50 can be screwed onto a container but cannot, by itself, be unscrewed due to the fact that it is covered by the shield 58.

In this embodiment the closure 50 further comprises a gate, here a flexible disc 76 which is located between the top surface 78 of the cap 52 and the inner surface 80 of the top portion 60 of the shield 58.

The top surface 78 of the cap 52 is again provided with key engagement means, here provided in the form of three circumferentially spaced grooves 82 (see Figure 9) and the top portion 60 of the shield 58 is provided with key access means, here corresponding apertures 84, for allowing access to the grooves 82 when brought into alignment with the grooves 82 by rotation of the shield 58. The disc 76 prevents direct access through the apertures 84 to the grooves 82.

A key 86 is provided for unscrewing the closure 50. The key 86 comprises a round base portion 88 which has a peripheral skirt 90. When the key 86 is brought into engagement with the closure 50, the peripheral skirt 90 on the key extends over the top portion of the shield 58. The key 86 comprises at least one and preferably three circumferentially spaced keyed projection, here spigots 92 (see Figure 7) which line up with the apertures 84 in the shield 58 through which they pass for engagement with the grooves 82 on the cap 52.

Gate displacement means, here a displacement spigot 94, which is longer than the spigots 92, is centrally located on the inner surface on the base 88 of the key 86. When the key 86 is brought into engagement with the closure 50, the displacement spigot 94 passes through an aperture 96 which is located centrally on the top portion 60 of the shield 58 to come into contact with and deform the disc 76 (as shown by the dotted line in Figure 5), thereby displacing the disc away from the apertures 84 in the shield 58 and allowing the key spigots 92 to engage with the grooves 82 in the cap 52. With the key 86 in place, and with the spigots 92 in engagement with

the apertures 82 in the cap 52, anti-clockwise rotation of the key 86 causes the cap to unscrew from the container outlet 56.

The key 86 is also provided with a leaf spring 98 on the inner surface of the base portion 88. When the key 86 is brought into engagement with the closure 50 the spring 98 pushes the key away from the closure 50 so that it is not accidentally left attached to the closure 50. Also, the natural resilience of the disc 76 causes it to spring back into the closed position once the key 86 is removed.

Although not shown in the drawings it is envisaged that a child resistant closure of the invention may include a tamper seal for indicating whether a container sealed by the closure has been tampered with.

The main advantage of a child resistant closure in accordance with the invention is that it is impossible to unscrew the closure without being in possession of the key. Thus, children cannot learn or teach themselves the technique of opening the container. The only requirement is that the key is safely guarded and kept out of reach of children.