Child-resistant closure

Abstract: A two-piece child-resistant closure utilises a particular ratchet configuration of ratchet teeth (24, 26) and ramps (32) which due to the relative placement of the elements thereof provides negligible reverse torque during undepressed counter-clockwise rotation of the outer closure member. Negligible reverse torque is defined as the torque caused by frictional contact of outer (12) and inner (14) caps when the undepressed closure is turned in the removal direction being insufficient to cause undesired or accidental removal of the closure from the container.

Description: This invention relates to a child-resistant closure. Child-resistant closures comprising two nested cap members are well known in the art. Typically, the inner and outer cap members of these closures are provided with cooperating sets of ratchet teeth which engage each other when the outer cap member is rotated in the direction to apply the closure to an associated container (usually the clockwise direction). When the outer cap member is rotated in the removal direction (typically counter-clockwise), these ratchet teeth cam or ratchet past each other on inclined surfaces, so that the closure generally cannot be removed by mere counter-clockwise rotation. To provide positive engagement of the inner and outer closure members for removal, the known devices have employed sets of cooperating ratchet teeth or projections, which are normally held separated by a resilient or spring means. To remove these closures, the outer member must be variously squeezed, pushed, or otherwise manipulated to overcome the separating means, and bring the respective ratchet teeth into positive driving engagement. The problem with known child-resistant closures which utilise a ratchet feature to apply torque to screw on the closure is that this same feature must frictionally ride over itself under undepressed reverse torque of the closure to prevent unscrewing of the closure. In other words, all of the ratchet teeth on the inner and outer cap members must slide over one another. The frictional force created during this process is sometimes enough to unscrew the closure at low application torques. In other words, if the closure has not been relatively tightly placed on the container neck, it is possible that the closure may be accidentally and undesirably removed simply by virtue of the frictional force caused by the ratchet teeth sliding over one another during undepressed rotation of the outer cap member in the removal direction. To ensure that the ratchet teeth on the closure slide over one another without exerting sufficient torque or friction to unscrew the inner cap when the outer cap is turned in the removal direction, Patent Specification US-A-3 776 407 discloses the use of reduced thickness areas at the locations of the ratchet teeth of the outer cap to provide increased wall flexibility and a reduction in torque applied to the inner cap by the outer cap when the outer cap ratchets past the inner cap. While the reduction in the skirt wall thickness is effective to increase the flexibility of the skirt in those areas and therefore generally accomplishes its intended purpose, the reduction of the thickness achieved by providing recessed areas in the outer wall circumferential surface has demonstrated some disadvantages, since the recessed areas necessarily result in a deviation from the desired overall circular configuration of the outer skirt surface. According to the invention there is provided a child-resistant closure to seal an open-topped container having an external screw thread formed on the neck of the container, the closure comprising: an outer cap having a first top end wall and a first skirt depending from the outer edge thereof; an inner cap having a second top end wall and an internally threaded second skirt depending from the outer edge thereof for engagement with the external screw thread on the container, the outer cap overlying the inner cap and being concentric therewith with the inner cap captive within the outer cap; first ratchet teeth on a lower face of the first top end wall of the outer cap; second ratchet teeth on the upper face of the second top end wall of the inner cap; and spring means to bias the first top end wall upwardly away from the second top end wall, and thereby prevent the first ratchet teeth on the outer cap abutting the second ratchet teeth on the inner cap until a downward force and a torque are simultaneously applied to the outer cap to remove the closure from the container; characterised by ramp members on the upper face of the second top end wall of the inner cap, which ramp members are abutted by the first ratchet teeth when the outer cap is only turned in the application direction to cause the two caps to rotate together and thereby cause the internal threads on the inner cap to cooperate with the external screw threads on the container to tighten the closure on the container; and the first ratchet teeth on the outer cap sliding up and over the ramp members on the inner cap with negligible back-ratchet torque when the outer cap is turned in the removal direction without the application of a downward force on the outer cap. In such a closure the reverse torque resulting from the frictional force caused by the ratchet teeth sliding over one another is insufficient to effect removal of the closure. Thus the invention can provide a child-proof closure that may not be removed from the associated container as a result of rotation of the outer cap in the removal direction, unless the inner and outer caps are positively manipulated by exerting downward force on the outer cap. The particular ratchet configuration and placement of the elements thereof can provide negligible reverse torque during undepressed counter-clockwise rotation of the outer cap. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 is an elevational sectional view of a child-resistant closure according to the invention having nested inner and outer caps: Figure 2 is an enlarged fragmentary perspective view of the top of the inner cap of the closure; Figure 3 is an elevational sectional view of the blank for the outer cap of the closure; Figure 4 is an elevational section view of the blank for the inner cap of the closure; Figure 5 is a bottom view of the outer cap; Figure 6 is a plan view of the top of the inner cap; Figure 7 is an enlarged view of vent lugs used to assist in assembly of the closure; Figure 8 is a top view of the outer cap; and Figure 9 comprises three elevational sectional views A to C illustrating use of the closure; and in particular, Figure 9 (A) illustrates the relative position of the elements of the closure when the outer cap is undepressed; Figure 9 (B) illustrates the position of the elements of the closure during a torqueing operation; and Figure 9 (C) illustrates the position of the elements of the closure during an untorqueing operation. Referring to the drawings and firstly to Figure 1, there is shown a child-resistant, two-piece closure, generally indicated by 10, fastened to a container indicated generally by 11. The closure 10 includes an outer cap 12 overlying an inner cap 14, with the inner and outer caps being concentrically aligned. To fasten the closure 10 to the container 11, a generally cylindrically shaped skirt 15 of the inner cap 14 is formed with a container fastening means such as a spiral screw thread 16 which cooperates with a corresponding shaped screw thread 18 on the container 11. The outer 12 and inner 14 caps are each preferably formed in a single piece by moulding a relatively hard resilient plastics such as polypropylene. The outer cap 12 is formed with a circular first top panel 28 (best seen in Figure 3) integrally moulded with a depending skirt portion 20. Moulded onto the underside of the panel 28 and extending radially downwardly are a plurality of first ratchet teeth 24, as well as a plurality of spring tabs 36. Moulded on the upper side of the panel 28 may be indicia 50 detailing use of the closure assembly (see Figure 8). The inner cap 14 is formed with a circular second top panel 30 (best seen in Figure 4) integrally moulded with a depending skirt portion 22. Moulded onto the topside of the second panel 30 are a plurality of second ratchet teeth 26 interposed with a plurality of ramps 32, and a raised platform 38. The second ratchet teeth 26 are generally equally spaced from and angularly spaced about an axis through the second panel 30, with the parallel sides of each of the teeth being generally perpendicular to the plane of the lower surfaces of the top end wall. The second ratchet teeth 26 and the ramps 32 are placed in alternating fashion (though, as will be obvious to those skilled in the art, need not be alternating) about the topside of the second panel 30. A circular channel 40 (shown in section in Figure 4, and best seen in Figure 6) separates the ratchet teeth 26 and the ramps 32 from the platform 38. Turning back to Figure 1, and particularly to the inner cap 14, a retention bead 34 is moulded into the exterior surface of the depending skirt 22. The retention bead 34 extends about the entire circumference of the depending skirt 22 (though it need not do so) and is preferably of a diameter greater than that of a retention bead 42 formed in the depending skirt 20 of the outer cap 12. The closure 10 is formed by assembling the outer cap 12 and the inner cap 14. To assemble the completed closure 10, the retention bead 42 of the outer cap 12 is deformed over the retention bead 34 of the inner cap 14, in the process causing the depending skirt 20 of the outer cap 12 to spring outwardly slightly. Once the larger diameter retention bead 42 has passed over the retention bead 34, the depending skirt 20 springs back inwardly trapping the inner cap 14 within the outer cap 12. As there is thereby formed an appreciable gap 46 between the interior of the depending skirt 20 and the exterior of the depending skirt 22, the outer cap 12 may rotate with respect to the inner cap 14. As will be appreciated by those skilled in the art, in order to provide venting during assembly of the inner and outer caps, vent lugs 48 are provided at regular intervals about the skirt 22 of the inner cap 14 (see Figure 7). To apply the closure 10 by screwing the thread 16 of the inner cap 14 onto the cooperatively threaded portion 18 of the container 11 in the application direction (which is clockwise when viewed from the top of the closure in the drawings), the first ratchet teeth 24 interlock with the ramps 32. Figure 9 (B) illustrates the position of these elements during application of the closure. The ramps 32 and the second ratchet teeth 26 have different functions depending on whether the closure is being applied to the container (torqueing) or being removed (untorqueing). In other words, the ramps 32 define both a low friction surface during undepressed counter-clockwise rotation of the closure and a contact area when torqueing (clockwise rotation) the closure onto the container. As explained in more detail below, during the torqueing operation the first ratchet teeth 24 do not contact the second ratchet teeth 26. The second ratchet teeth 26 do, however, define the contact area for untorqueing (removal) of the closure 10 from the container when the outer cap 12 has been depressed. One advantage of the described construction is that, unlike known closures, there is little, in fact negligible, back-ratcheting action or torque resulting when the undepressed closure is rotated in the counter-clockwise direction; back-ratchet torque which, if the closure is not relatively tightly screwed to the container, could result in undesired removal of the closure in known devices. Accordingly, a child who merely rotates the outer cap of the closure 10 in the removal direction should not be able to unscrew the closure 10 from the container 11. When viewed from above, the first ratchet teeth 24 and the ramps 32 are shaped in such a manner as to provide negligible reverse torque during undepressed counter-clockwise rotation of the outer closure. In particular, the first ratchet teeth 24 are generally equally spaced from and angularly spaced about an axis through the centre of the first top panel 28, with the parallel sides of each of the teeth being generally perpendicular to the plane of the upper surfaces of the first top panel 28. By contrast, the radially arranged ramps 32(see Figure 2) have a helical contour, projecting upwardly from the upper surface of the second top panel 30 to an apex or highest edge 44 of the ramps 32. This contour allows a smooth, over-riding action between the contact parts, the first ratchet teeth 24 and the apex 44 of the ramps 32, when the undepressed closure 10 is rotated in the removal (counter-clockwise) direction. The resulting reverse torque, as assisted by the action of the spring tabs 36 (as explained below), is insufficient to effect undesired removal of the closure. The desired effect of negligible reverse torque is reinforced by the fact that the first ratchet teeth 24 do not contact the second ratchet teeth 26 during undepressed counter-clockwise rotation of the closure 10. To maintain the radially-extending teeth 24, 26 normally spaced apart from one another in the absence of any downwardly exerted pressure on the outer cap 12, the spring tabs 36 contact the platform 38, which stresses the tabs 36 and provides a restoring force to lift the teeth 24, 26 apart when the manually exerted downward force is released. The spring tabs 36 take the form of tabs integrally moulded with the underside of the first top panel 28. The spring tabs 36 extend radially inwardly with respect to the vertical axis of the outer cap 12; and their angle of inclination may be varied so long as the teeth 24, 26 are, as described herein, held apart. The shape and/or the number of spring tabs 36 effect the vertical placement of the outer 14 and inner 16 caps respectively, and affect the amount of force required to depress the outer cap 14 for removal of the closure 10. The embodiment illustrated (Figure 5) shows four spring tabs 36, but more or less than four tabs may be employed if desired. As will be understood by those skilled in the art, it is important that the restorative force caused by the spring tabs 36 not be so great as completely to separate the first ratchet teeth 24 from the ramps 32. That is, the spring tabs 36 also serve as a spacing mechanism for the vertical placement of the outer cap 12 relative to the inner cap 14. As illustrated in Figure 9 (A), the at rest position for the closure is a clearance position wherein the relevant contact positions (for purposes of effecting back-ratchet torque) between the outer and inner caps are at the contact of the spring tabs 36 with the platform 38 and at the contact point of the apex 44 of the ramps 32 and the first ratchet teeth 24. As illustrated in Figure 9 (C), to remove the closure 10 from the container 11 it is necessary to press downwardly on the outer cap 12 and simultaneously apply a torque on the outer cap skirt 20 in the removal direction. With downward pressure of sufficient magnitude applied to the outer cap 12, the first ratchet teeth 24 are in interlocking engagement with the second ratchet teeth 26. With the respective radially-extending teeth 24, 26 engaged or meshed together, a torque applied to the outer cap skirt 20 in the removal direction causes a similar torque to be translated through the engaged teeth to the inner cap 14 which then unscrews its thread 16 (and hence the closure 10) from the container thread 18. In an undepressed condition there is negligible back-ratchet torque during operation.

Claims: A child-resistant closure (10) to seal an open-topped container (11) having an external screw thread (18) formed on the neck of the container (11), the closure (10) comprising: an outer cap (12) having a first top end wall (28) and a first skirt (20) depending from the outer edge thereof; an inner cap (14) having a second top end wall (30) and an internally threaded second skirt (22) depending from the outer edge thereof for engagement with the external screw thread (18) on the container (11), the outer cap (12) overlying the inner cap (14) and being concentric therewith with the inner cap (14) captive within the outer cap (12); first ratchet teeth (24) on a lower face of the first top end wall (28) of the outer cap (12); second ratchet teeth (26) on the upper face of the second top end wall (30) of the inner cap (14); and spring means (36) to bias the first top end wall (28) upwardly away from the second top end wall (30), and thereby prevent the first ratchet teeth (24) on the outer cap (12) abutting the second ratchet teeth (26) on the inner cap (14) until a downward force and a torque are simultaneously applied to the outer cap (12) to remove the closure (10) from the container (11); characterised by ramp members (32) on the upper face of the second top end wall (30) of the inner cap (14), which ramp members (32) are abutted by the first ratchet teeth (24) when the outer cap (12) is only turned in the application direction to cause the two caps to rotate together and thereby cause the internal threads (16) on the inner cap (14) to cooperate with the external screw threads (18) on the container (11) to tighten the closure (10) on the container (11); and the first ratchet teeth (24) on the outer cap (12) sliding up and over the ramp members (32) on the inner cap (14) with negligible back-ratchet torque when the outer cap (12) is turned in the removal direction without the application of a downward force on the outer cap (12). A closure according to claim 1, wherein: the first ratchet teeth (24) are generally equally spaced from and angularly spaced about an axis through the centre of the first top end wall (28); and the parallel sides of each of the first ratchet teeth (24) are generally perpendicular to a plane formed by a lower surface of the first top end wall (28). A closure according to claim 1 or claim 2, wherein: the second ratchet teeth (26) are generally equally spaced about an axis through the centre of the second top end wall (30); and the parallel sides of each of the second ratchet teeth (26) are generally perpendicular to a plane formed by an upper surface of the second top end wall (30). A closure according to any one of claims 1 to 3, wherein the second ratchet teeth (26) and the ramps (32) are placed in alternating fashion about an upper surface of the second top end wall (30). A closure according to any one of claims 1 to 4, wherein the ramps (32) define both a low friction surface during undepressed removal direction rotation of the closure (10) and a contact area during tightening rotation of the closure (10). A closure according to any one of claims 1 to 5, wherein the ramps (32) are radially arranged and have a helical contour projecting upwardly from an upper surface of the second top end wall (30) to an apex (44). A closure according to any one of claims 1 to 6, wherein the spring means comprises at least one spring tab (36) extending radially inwardly from a lower face of the first top end wall (28) and cooperating with a raised platform (38) extending upwardly from an upper face of the second top end wall (30). A closure according to claim 7, wherein in the absence of any downwardly exerted pressure on the outer cap (12), the spring tabs (36) contact the platform (38), which stresses the spring tabs (36) and provides a restoring force to separate the first and second ratchet teeth (24, 26) when the downward force is released. A closure according to claim 7, wherein the at rest position for the closure (10) is a clearance position wherein the contact positions between the outer and inner caps (12, 14) are at a first contact point of the spring tabs (36) with the platform (38) and at a second contact point at an apex (44) of the rips (32) and the first ratchet teeth (24).

Inventors: KOO JAMES Y C, KOO, JAMES Y.C.
Applicants: KERR GROUP INC, KERR GROUP, INC.
Application year: 1993
Main classification: B65D50
IPC codes: B65D50