Screw cap core sealing piece structure

Abstract

A screw cap for a container is disclosed that includes a screw cap body (10) and an expandable core seal (24) with an annular sealing element (30). When the screw cap body (10) is screwed onto the container, the peripheral portion (36) of the seal energizing element (38) expands radially. The peripheral portion (36) is joined to a backing (34) of the annular sealing element (30), the backing (34) comprising a plurality of independent axially extending segments (42, Fig. 4). As a result, axial compression of the seal energizing element (38) tends not only to radially expand adjacent portions of the sealing element (30), but also to rotate the axially extending section (42) upward and outward. As a result, the sealing pressure of the annular sealing element (30) is distributed more uniformly.

Description

Technical Field

[0001] The present invention relates to screw caps for containers. More particularly, the present invention relates to screw caps provided with a core seal that is expandable to engage the inner surface of the container neck. Background Art

[0002] Various forms of this expandable core seal are known from GB2280895. In one form shown therein, the expandable core has a face seal ring that rests against the edge of the container neck in use and a central section that protrudes on the face seal ring when the core is in a relaxed (contracted, unsealed) state. Therefore, the central section of the expandable core rests against the inner surface of the top wall of the lid applied to the container neck. The slightly flexible outer skirt usually hangs vertically from the inner edge of the face seal ring to rest against the inner surface (bore) of the container neck in use. The flared (trumpet-shaped) inner skirt connects the lower periphery of the outer skirt to the outer periphery of the central section. At least the lower outer peripheral portion of the inner skirt has a certain flexibility. When the lid is applied to the container neck, the face seal ring rests against the edge of the container neck. Then, when the lid is further moved axially onto the container neck, the central section of the core seal continues to move axially with the lid into the container neck. The outer skirt and the lower periphery of the inner skirt are restricted from axial movement relative to the container neck by the engagement of the face seal ring with the rim of the container neck. Thus, continued application of the cap causes compressive collapse and corresponding radial expansion of the lower periphery of the inner skirt. This radial expansion causes corresponding radial expansion of the outer skirt, particularly at and towards its lower (inner) end. Thus, the outer skirt expands into sealing engagement with the inner surface of the container neck.

[0003] In another form shown in GB2280895, the inner skirt has a shallow truncated cone shape and is obviously connected to the lower periphery of the outer skirt and the outer periphery of the central section by corresponding outer peripheral living hinges and inner peripheral living hinges. The top wall of the cap is fixed to the central section of the expandable core. In the relaxed, contracted, unsealed state of the core seal, the outer peripheral living hinge is placed below the inner peripheral living hinge. When the cap is applied to the container neck, the shallow truncated cone inner skirt begins to flatten, thereby resisting the application of the cap and expanding at least the lower part of the outer skirt toward the inner surface of the container neck again and then sealingly engaging with the inner surface of the container neck. When the inner skirt has been twisted into a generally flat shape, it reaches an "over-center" state, in which it quickly snaps into an everted shape, in which the inner peripheral living hinge is placed below the outer peripheral living hinge. This draws the cap top wall toward (or in the absence of any other cap-to-neck securing means, into) engagement with the face seal ring and container neck rim; at the expense of some relaxation of the sealing expansion of the outer skirt.

[0004] This expandable core seal can be used to originally seal conventional inner screw threaded cap to conventional outer threaded container neck. The outer skirt can have a facing layer made of relatively flexible material to make up for any irregularities in the inner surface of the container neck and seal against it. The backing structure for the outer skirt and the entire inner skirt can be formed by relatively harder, more creep-resistant materials. The final torque limit ("target torque") can be selected to be screwed on, which ensures that the facing layer is appropriately deformed into a complete circumferential sealing engagement with the inner surface of the container neck. Under this torque, there will be significantly more deformation in the inner skirt than in the outer skirt facing layer. Therefore, the expansion of the container neck, such as due to the increase in temperature, or the thinning of the facing layer due to creep does not cause any significant relaxation of the ability to press the facing layer against the inner surface of the container neck and maintain it in sealing contact with the inner surface of the container neck. If the cap is screwed to a torque higher than the torque required for first achieving a good circumferential seal, the further deformation of the inner skirt absorbs the excess strain to a great extent. Thereby, the facing layer is protected from over-tensioning, improper twisting and extrusion.Thus, the expanded core container closure seal disclosed in GB2280895 has good fault tolerance to prevent poor neck inner surface finish and inaccurate tightening torque.

[0005] The amount of radial expansion possible of the outer skirt is limited by the elastic limit of the material from which the outer skirt is formed. The maximum amount of expansion possible of the outer skirt also depends to a large extent on the distance that the central section protrudes above the face seal ring when the core is in a relaxed state, or the axial distance between the inner circumferential living hinge and the outer circumferential living hinge when the core is in a relaxed state, respectively, for the two expandable core seal types above.

[0006] In the case of screwing a threaded container cap, the expansion of the expandable core seal from a relaxed, fully contracted, unsealed state to a sealed state preferably occurs during the last few turns of the screw cap (or even during a small portion of the last turn). This ensures that when the cap is tightened to the target torque, it is in a predictable axial position, where the length of the cap and the neck thread is sufficient to engage with each other. This results in a firm interconnection between the cap and the container, so that the cap will not, for example, "pop off" under rough handling or under internal pressure due to heating or stirring the container contents that release gas or storing or transporting a container that is at least partially filled with gas under low ambient pressure (such as in an aircraft or at high altitude). The accurate final axial positioning of the cap is also usually necessary to ensure the correct mutual engagement and safe operation of the cooperative anti-tampering features that are respectively arranged on the cap and the container neck. Therefore, the face seal ring is axially positioned relative to the screw cap so that it contacts the edge of the container neck, and only when the screw cap is less than one turn (or in the case of a screw cap with fine threads, possibly several turns) before the cap is completely screwed onto the container neck, the expansion of the outer skirt begins. The necessity of such an arrangement therefore further limits the possible expansion range of the core seal. Sometimes, in the case of a particularly oversized container neck (out of tolerance, as may occur, for example, in the case of a blow-moulded container, the neck inner diameter of which varies greatly in nature; and / or because nominal standard manufacturing dimensions in practice vary between different manufacturers), the available expansion range of the core seal is insufficient to form a reliable seal inside the container neck bore. On the other hand, if the core is allowed to expand initially by many turns before the cap is fully screwed on, the possible expansion range of the core seal increases, but the final axial position of the screw cap when the target torque is reached then becomes unacceptably unpredictable.

[0007] WO2020 / 200619 discloses a screw cap and core seal arrangement, wherein an elastically deformable seal energizing element has a rotational connection with a cap body end wall. The connection includes a cam surface, and when the cap body is screwed onto the container neck, the cam surface converts the relative rotation between the cap body and the seal energizing element into an axial movement of the seal energizing element. When the cap is screwed onto the container neck, this axial movement is added to the movement of the cap body end wall. Therefore, when the cap is twisted to its final fully screwed position on the container neck, the cap can provide a highly expandable core seal that can be operated with little rotation.

[0008] However, the elastically deformable seal enabling element disclosed in WO2020 / 200619 again mainly (if not exclusively) acts on the farthest lower end of the seal element arranged in the container neck. According to one embodiment, if it is necessary to load the seal element more evenly, the relative upper end of the seal element (closest to the mouth of the container neck) can be expanded outwardly by a separate annular wall, which is optionally suspended from the inner surface of the end wall of the cap body. The inclined section at the upper end of the seal element is forced to expand radially because it is pushed against the overhanging annular wall during the final tightening of the screw cap body on the container neck. If there is rotational sliding between the elastically deformable seal enabling element and the container neck, the effective operation of the core seal of WO2020 / 200619 may also be hindered.

[0009] US3788510 relates to a kind of cap liner, and it can be enabled to surround the upper edge zone of the neck of container.The upper part of the annular wall portion of this liner is enabled by a shallow tapered web, and the vertex of this web is pushed down by the inner face of the cap end panel.The lower edge of the wall portion has a hook-shaped profile, including a downwardly beveled and outwardly directed face and an internal convex shoulder facing upward.This convex shoulder facing upward substantially engages the flat convex shoulder facing downward in the bottleneck portion perpendicular to the main axis of the neck.The base of the tapered web is away from the hook-shaped lower edge of the wall portion, and therefore almost has no ability to expand, or provides a tighter sealing to engage with each other between the convex shoulders.The wall portion is conformal with the container neck and against the necessary flexibility of the container neck sealing, and also means that the stress and strain at the base of the tapered web remain confined there. Summary of the invention

[0010] The present invention aims to alleviate at least some of these problems and therefore provides a screw cap comprising:

[0011] a cover body including an end wall and an internally threaded annular side wall depending from the end wall;

[0012] an annular sealing element concentrically disposed within and spaced from the annular sidewall so that the annular sealing element is receivable within the externally threaded container neck when the screw cap is screwed onto the container neck;

[0013] a stopper engageable with the container neck so as to support the annular sealing element within the container neck when the screw cap is screwed onto the container neck;

[0014] an elastically deformable seal-enabling element, the elastically deformable seal-enabling element comprising a central portion supported against an end wall of the cap body and a peripheral portion connected to an annular sealing element; the seal-enabling element being constructed and operably arranged within the cap body such that when the cap body is screwed onto the container neck, axial compression of the seal-enabling element between the central portion and the peripheral portion causes radial expansion of the seal-enabling element at the peripheral portion, thereby causing the annular sealing element to radially expand toward the inner surface of the container neck;

[0015] The annular sealing element includes a backing formed of a relatively stiff but resilient material and a facing formed of a relatively more pliable material, wherein the backing extends in a direction away from the end wall of the cover body to below the level of the stop;

[0016] Features:

[0017] The peripheral portion of the seal-enabling element is connected to the backing at the horizontal plane at or below the stopper, and the backing below this horizontal plane includes a plurality of independent axially extending sections. With this arrangement, the axial compression of the seal-enabling element not only makes the peripheral portion of the seal-enabling element and the adjacent portion of the seal element tend to expand radially, but also makes these axially extending sections tend to rotate upward and outward. When the cover is screwed onto the container neck, both of these trends are resisted by the surrounding container neck. When the trend of the backing section rotating upward and outward is added to the trend of the radial expansion of the annular sealing element at the horizontal plane around the seal-enabling element, the sealing pressure of the inner surface of the annular sealing element against the container neck is distributed more evenly across the entire axial range of the sealing element. This improves the sealing performance of the sealing element. If the cover is screwed to a torque higher than the torque required to first achieve a good circumferential seal, the excess strain is absorbed to a large extent not only by the further deformation of the seal-enabling element, but also by the bending stress in the section of the backing. Thus, the facing is protected from excessive tension, improper distortion, creep relaxation and extrusion. Therefore, the screw cap of the present invention has excellent sealing performance and tolerance to prevent poor neck inner surface finish and inaccurate tightening torque.

[0018] The seal energizing element, the annular seal element, the stopper, the backing and the facing can comprise the part of the expandable plug seal subassembly in the screw cap. The plug seal subassembly and the cap body can comprise a snap-fit ​​connection, by which the plug seal subassembly remains in the cap body even when the screw cap is not screwed onto the container neck. The snap-fit ​​connection can comprise a recess at the center of the seal energizing element, into which a projection extending from the end wall of the cap body is received in a snap-fit ​​manner. The projection can comprise a plurality of axially extending fingers or sections. The projection can comprise an enlarged end, which is received in an undercut portion of a recess at the center of the seal energizing element in a snap-fit ​​manner. The snap-fit ​​connection can allow relative rotation between the seal energizing element and the cap body, whereby when the screw cap is screwed on or off, there is usually essentially no relative rotation between the annular seal element and the container neck.

[0019] The stop can be, for example, integrally formed with the expandable plug seal subassembly as an annular flange extending radially from the upper portion of the backing. The backing and the seal-enabling element can include through grooves extending radially in the seal-enabling element and axially in the annular sealing element; thereby allowing easier radial expansion of the plug seal by widening the grooves to absorb most of the strain generated. The axially extending through grooves can be used to define multiple independent axially extending sections of the backing. These grooves can continue into the annular flange forming the stop. Additionally or alternatively, these grooves can be combined with, extend into, or become radial through grooves in the seal-enabling element. The facing can cover at least the outer circumference of the annular sealing element, and can sealingly cover the through grooves therein, so that when the plug seal expands, the facing is sealed against the inner surface of the container neck around the entire circumference of the inner surface of the container neck, thereby hermetically sealing the container. The facing can also cover the lower surface of the annular flange forming the stopper, so that when the cap body is screwed onto the container neck, the edge of the container neck is sealed airtightly. The bottom surface of the sealing energizing element can have a covering made of softer and more compliant material, to seal the groove therein. This covering can be continuous with the facing, so as to prevent contact between the other components of the packaging material and the screw cap. Therefore, PCR material can be used to make these other components, while still allowing the screw cap to be used in food grade or similar sanitary applications. Backing and facing can be formed by insert molding (double injection molding). The sealing energizing element can include a dome shape, which becomes flatter and radially expands when the stopper engages the container neck, the cap body is screwed onto the container neck and the cap body end wall is pressed down on the center of the sealing energizing element.

[0020] The expandable plug sealing subassembly may include a through-aperture, to which a gas-permeable but liquid-impermeable diaphragm is fixed to provide a gas discharge path. For example, the through-aperture may be formed in a seal-enabling element. The through-aperture may be formed in a recess at the center portion of the seal-enabling element. This recess may be part of a snap-fit ​​connection as described above. The inner surface of the stopper and / or the end wall of the cover body may be provided with a groove or a protrusion, which, when the screw cap is fully tightened, separates the stopper from the inner surface of the end wall of the cover body, thereby providing a gas flow path, which connects the space between the seal-enabling element and the end wall of the cover body to the atmosphere via the inner thread of the cover body. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention and some of its further optional features and advantages are described below with reference to the illustrative embodiments shown in the accompanying drawings, in which:

[0022] Figure 1 is an exploded perspective view of a screw cap body, an expandable plug subassembly, and a corresponding container neck from one side viewed from above;

[0023] Figure 2 yes Figure 1 An exploded bottom perspective view of the components shown in ;

[0024] Figure 3 Corresponds to Figure 1 , but showing these components in partial cross-section;

[0025] Figure 4 and Figure 5 is a perspective view, partially in section, viewed from above from one side, showing the screw cap body and expandable plug subassembly snap-fitted together and the resulting screw cap partially screwed onto the neck of a container;

[0026] Figure 6 It is a partially cutaway stereoscopic view from one side, wherein the components such as Figure 4 and Figure 5 Assemble as in;

[0027] Figure 7 is a side elevational view of an expandable plug body subassembly similar to that shown in the previous figures, and

[0028] Figure 8 is a diametrical cross-sectional view through a modified form of an expandable plug body plug assembly that may be used as a component in a screw cap embodying the present invention. DETAILED DESCRIPTION

[0029] First turn Figure 1The illustrative screw cap includes a cap body 10 within which an expandable plug sealing subassembly 24 is relatively rotatably received, as further explained below. Figure 1 Also shown is a complementary container neck 26 which can be closed and sealed by the cap body 10 and the attached plug sealing subassembly 24. The cap body 10 comprises a disc-shaped end wall 12 and a generally cylindrical side wall 14 depending from the periphery of the end wall 12. The bottom of the side wall 14 opposite the end wall 12 is provided with a protective flange 16 extending radially outwards, below which an anti-tampering ring 18 is frangibly attached in a known manner. The screw cap body 10 and the anti-tampering ring 18 can be manufactured as a single component from a suitable plastic material such as PE or PCR plastic, for example by injection molding. Figure 2 and Figure 3 As best shown in FIG. 1 , the cap body side wall 14 is formed with an internal screw thread 20. A projection 22 formed by a pair of axially extending fingers or segments 28 depends centrally from the interior face of the cap body end wall 12. The projection 22 forms part of a snap fit connection by which the plug seal subassembly 24 is rotationally retained in the cap body 10 even when the screw cap is not screwed onto the container neck 26. Each axially extending finger or segment 28 has an enlarged end 28a.

[0030] Figure 3-Figure 6 Annular sealing element 30 of plug seal subassembly 24 is shown. More specifically, the cross-sectional views of these figures show the structure of annular sealing element 30, including its backing 34 and its facing 44. Backing 34 is formed of a relatively hard but resilient material, such as a suitable PCR plastic material, which has sufficient elasticity to return to its original shape when external stress is removed. Facing 44 is formed of a softer, more compliant material, such as a suitable elastomer (such as NBR, EPDM, neoprene or silicone elastomer). For example, the material used to form facing 44 can be selected to be compatible with the container contents (e.g., not reacting with it).

[0031] The stopper for supporting the annular sealing element 30 within the container neck 26 when the screw cap 10 , 24 is screwed on may include an annular flange 32 projecting radially outwardly from at or near the upper end of the backing 34 .

[0032] The seal enabling element 38 illustrated in the drawings has a shallow generally frustoconical configuration, but this is not essential to the present invention. Other (usually generally dome-shaped) configurations are also possible, which allow the seal enabling element to expand radially due to compression applied axially between its central portion and peripheral portion when the cap body 10 is screwed onto the container neck 26.

[0033] In use, the apex or center portion 39 of the seal energizing element 38 points to the center of the end wall 12 of the cap body. A recess 43 with a circular cross section is provided, which has an entrance at this apex and a depth extending axially below. The recess 43 has a peripheral retaining lip 50 extending inwardly, which forms an undercut or recessed portion at the bottom of the recess, and the enlarged end 28a of the axially extending finger-shaped portion or section 28 can be snap-fitted into the undercut or recessed portion. Thus, the plug seal subassembly 24 is rotatably retained in the cap body 10. The apex or center portion 39 of the seal energizing element, the recess 43 and the projection 22 also form a rotary thrust bearing, thereby allowing the cap body 10 to rotate relative to the plug seal subassembly 24 when the cap is screwed on or off the container neck 26, and the plug seal subassembly 24 remains stationary in the container neck 26. However, the described snap-fit ​​interconnections 22, 43 between the cover body 10 and the plug seal subassembly 24 are not essential to the present invention. The apex 39 of the seal enabling element 38 may simply abut directly or indirectly against the interior face of the cover body end wall 12 to form a rotational thrust bearing. Other retaining mechanisms / rotational thrust bearings disposed between the cover body 10 and the plug seal subassembly 24 are also possible, as known to those skilled in the art.

[0034] The peripheral portion 36 of the elastically deformable seal-enabling element 38 is connected to the backing 34 of the annular sealing element 30 at a position at or below the level of the stop (radially protruding annular flange) 32. The backing 34 extends below this connection and is divided into a corresponding plurality of axially extending radially distributed segments 42 ( Figure 4 ).like Figure 3 and Figure 6 As shown in , the portion of the backing 34 extending below the coupling or seal-enabling element periphery 39 is approximately twice as deep as the portion of the backing extending between the couplings up to the level of the flange. However, other configurations are also effective in providing the beneficial sealing effects of the present invention. For example, the coupling or seal-enabling element periphery 36 can be disposed at the level of the flange 32, whereby the entire backing 34 extends below the coupling 36; or the coupling 36 can be disposed at a level approximately three-quarters of the way down the backing 34 below the flange 32; or the coupling 36 can be disposed at a level anywhere within this range.

[0035] The edge of the groove 40 and the corresponding edge of the axially extending section 42 are Figure 4 Indicated by dotted lines, it is still covered by the facing 44 in this partial cross-sectional view. Figure 3, the material through the backing 34 and the seal enabling element 38 is shown in cross-section on the left hand side of the plug seal subassembly 24. However, a slot 40 through the backing 34 is shown in cross-section on the right hand side. Typically, this slot can be filled with a facing material 44. (The slot 40 widens during the required deformation of the annular seal element 30, thereby allowing separation of any filler material, so that pressure interference of the material is not an issue). For clarity of the illustration, Figure 3 The right hand side of the figure shows that the groove 40 is empty. In order to make it easier for the frustoconical or dome-shaped seal-enabling element 38 to expand radially under axial compression, it can be provided with a plurality of radially distributed radially extending through grooves 40a. The grooves 40 in the backing 34 can extend into the seal-enabling element 38, for example, so as to combine with, extend into, or become the radial through grooves 40a, such as Figure 3 The upper end 40b of the groove 40a terminates near the apex or central portion 39 of the seal enabling element, such as at or near the recess 43. The groove 40 in the backing 34 may also have an upwardly extending through continuation 40c, which may terminate in a radially protruding annular flange (stop) 32 so as to leave a series of relatively small bridges 32a ( Figure 3 ), thereby holding the flange 32 together. This increases the out-of-plane flexibility of the flange 32, thereby allowing it to more easily adapt to corresponding irregularities in the upper end surface of the container neck 26. The grooves 40c and 40a also increase the radial flexibility of the annular sealing element 30, thereby allowing it to better adapt to the non-roundness of the container neck bore. The facing 44 can continue radially outward onto the lower surface of the annular flange 32 to help form a seal with the upper end surface of the container neck 26. The backing 34, together with the stop flange 32 and the seal-enabling element 38, can be formed as a one-piece component, such as by injection molding.

[0036] In its relaxed state, the diameter of the annular sealing element 30 tapers slightly in the axial direction away from the flange 32. This enables the expandable plug seal subassembly 24 to be guided and more easily pushed into the bore of the container neck 26 when the cap body 10 is screwed into place on the container neck. As a result, the flange (stop) 32 eventually rests on the upper end surface of the container neck 26. When the plug seal subassembly 24 in its relaxed state is first secured to / fully inserted into the cap body 10, there is a gap 52 ( 1.5 m) between the upper surface of the flange 32 and the adjacent portion of the cap body end wall 12. Figure 4). After the flange (stop) 32 rests on the upper end surface of the container neck 26, continuing to screw the cap body 10 causes the gap 52 to decrease and the dome seal energizing element 38 to become flatter. This flattening causes the seal energizing element 38 to expand radially, and the presence of the radial through groove 40a helps this flattening and radial expansion. The radial expansion of the seal energizing element 38 forces the adjacent upper part of the annular seal element 30 to be more closely engaged in the bore of the container neck 26. Due to being connected to its periphery 36, the flattening of the seal energizing element 38 also causes the axially extending section 42 of the backing 34 to pivot upward and outward. The ungrooved portion of the flange (stop) 32 and / or the adjacent edge of the container neck can help this pivotal movement by acting as a fulcrum. Therefore, as the cap body is continued to be screwed, the taper of the annular seal element 30 is reduced. Therefore, the annular seal element 30 is pressed against the bore of the container neck 26 with a more uniform pressure across its axial range (and evenly around its circumference). A point is reached at which further expansion of the annular sealing element 30 is substantially completely limited by the container neck. Further screwing of the cap body 10 beyond this point (e.g., to completely eliminate the gap 52) primarily results in further bending of the segment 42 and the seal-enabling element 38, and thus additional locking bending stresses within the segment 42 and the seal-enabling element 38. These locking stresses (prestresses) can be used to maintain a uniform sealing pressure between the annular sealing element 30 and the bore of the container neck 26, even in the presence of creep in the facing 44 and / or the container neck 26. Thus, a low and predictable tightening torque (to completely eliminate the gap 52 and cause the tamper-evident ring 18 to engage the one-way teeth 54 on the container neck 26) is achieved. Figure 5 ) results in a reliable and durable sealing closure that can accommodate a wide variety of container neck bore sizes and profiles. With the gap 52 eliminated, when the final tightening torque is applied to the screw cap body 10, the facing 44 on the underside of the flange 32 is forced into a tighter sealing engagement with the corresponding rim surface of the container neck 26.

[0037] A cover 44a made of a softer and more compliant material (such as, but not limited to, the material of the facing 44) may be applied to the bottom surface of the seal-enabling element 38 to seal the groove 40a without significantly affecting the ability of the seal-enabling element 38 to radially expand under axial compression. This cover 44a may be continuous with the facing 44 and thus also cover the radially inner surface of the axially extending section 42, the groove 40a, and the lower edge of the backing 34. For example, the facing 44 and the cover 44a may be insert molded (double-molded) onto the underside of the flange 32, onto both sides of the backing 34, and onto the bottom surface of the seal-enabling element 38 in a single operation. Thus, the facing 44 and the cover 44a may not only seal the grooves 40 and 40a, but may also seal the groove 40c (if present). The facing 44 and cover 44a can also provide a continuous, uninterrupted layer that seals around the entire circumference of the bore of the container neck 26 and spans this bore to isolate the container contents from other components of the screw cap. Thus, these other components can be made of PCR plastic without risk of contaminating the container contents even when the screw cap is used in pharmaceutical, food or other similar hygienic applications.

[0038] Figure 2 and Figure 6 The plug seal 24 shown in FIG. 1 is slightly different from Figure 3 The version shown in Figure 2 and Figure 6 In the embodiment, the central area of ​​the seal enabling element 38 (for example, the bottom wall 43a ( Figure 6 ), if present) is not covered by the cover 44a. This exposed portion 43a is provided with a plurality of through-going apertures 62. Three such apertures may be used, but other numbers are also suitable, including one. Figure 6 62 ; the third orifice is cut away. A microporous, gas-permeable, liquid-impermeable membrane 64 is sealingly secured at its periphery to the exposed central region 43a of the seal-enabling element 38 so as to cover and surround the orifices 62 .

[0039] For the purpose of illustration and not for any technical requirement, Figure 2 and Figure 6, the microporous diaphragm 64 is shown as being partially transparent so that the orifice 62 can be seen therethrough. For "discharge" applications, the diaphragm 64 can be secured to an exposed area of ​​the seal-enabling element 38 that is directly surrounded by the cover 44a (e.g., secured to the lower surface of the bottom wall 43a of the enclosure of the pocket 43, if present). For "discharge" applications (not shown), the diaphragm can be secured to the opposite side of the seal-enabling element 38, such as secured to the upper surface of the bottom wall 43a of the enclosure of the pocket 43, if present. In each case, the seal-enabling element 38 thereby supports and protects the diaphragm 64 from rupture due to overpressure.

[0040] Additional gas venting passages may be provided in the form of shallow grooves 66 (or other suitably shaped passages) extending across the radial width of the flange / stop 32 on its side facing away from the container. These passages thus lead from the space between the plug seal 24 and the cap body end wall 12 to the annular area occupied by the container neck 26. Thus, they provide a gas venting path between the interior of the container and the atmosphere via the internal threads 20 of the screw cap body 10. Additionally or alternatively, to complete the gas venting pathway, similar gas venting passages, conduits, spacer ridges or the like may be provided in or on the following locations: the protrusion 22, the inner surface of the recess 43, the apex 39 of the seal enabling element 38 and / or the inner surface of the cap body end wall 12. Optionally, as Figure 3 As shown above, in non-gas venting applications, orifice 62 may be present in seal enabler element 38 but not covered and sealed by, for example, cover 44a. In this way, the same molding tool may be used to form seal enabler element 38 in both gas venting and non-gas venting versions of the screw cap.

[0041] refer to Figure 7 , the radially outer surface of the annular sealing element 30 tapers substantially constantly from the stopper (radially protruding annular flange) 32 until a rounded bottom edge is formed where the facing 44 and the cover 44a wrap around the distal tip of the segment 42. This profile allows the plug seal assembly 30 to be easily guided into the bore of the container neck when the screw cap is screwed onto the container neck. Other profiles are also possible. Figure 8 , where a lower portion of the radially outer surface of the annular sealing element is tapered and an upper portion of this surface (adjacent the stopper / flange 32 and adjacent the coupling portion 36) is generally cylindrical. When the cap is screwed onto the container neck, the expansion of the plug seal assembly 24 may result in a generally uniform pressure on this cylindrical portion of the facing 44 as it is pressed against the bore of the container neck.

[0042] Already used Figure 7 and Figure 8The core sealing subassembly 24 shown in was tested, in each case the core sealing subassembly 24 being assembled to a 60 mm screw cap (Applicant's modified 60 mm "Plasticap" (RTM) cap). The test cap was screwed onto a simulated fuel drum neck with a torque of 5 Nm. The simulated fuel drum neck was machined internally to simulate a 3 mm bore ovalization - that is, the difference between the major and minor diameters of the bore was 3 mm, the major and minor diameters being at right angles to each other. No leakage was observed when the cap / neck was immersed in a water tank and pressurized to 318 mbar using compressed air. In another test, the cap was screwed onto a conventional sample fuel drum with a torque of 5 Nm. The fuel drum was filled with water at room temperature and kept inverted for a period of up to 24 hours. Again, no leakage was observed. In a third test, the fuel drums were pressurized with air and each was assembled with a cap according to Figure 7 and Figure 8 Two ordinary empty fuel cans were fitted with the test caps (again with a closing torque of 5 Nm) until significant expansion ("inflation") occurred. The air pressure required to do this was recorded (5.5 bar and 6.0 bar, respectively). The fuel cans were then immersed in a water tank. Again, no leakage was observed. Therefore, the test caps performed well at low closing torques, even though substantial deformation of the container neck bore occurred.

Claims

1. A screw cap, comprising: a cover body including an end wall and an internally threaded annular side wall depending from the end wall; an annular sealing element concentrically disposed within and spaced from the annular sidewall so that the annular sealing element is receivable within an externally threaded container neck when the screw cap is screwed onto the container neck; a stopper engageable with the container neck so as to support the annular sealing element within the container neck when the screw cap is screwed onto the container neck; an elastically deformable seal-enabling element, the elastically deformable seal-enabling element comprising a central portion supported against the end wall of the cap body and a peripheral portion connected to the annular seal element; the seal-enabling element being constructed and operably arranged within the cap body such that when the cap body is screwed onto the container neck, axial compression of the seal-enabling element between the central portion and the peripheral portion causes radial expansion of the seal-enabling element at the peripheral portion, whereby the annular seal element radially expands toward the inner surface of the container neck; The annular sealing element includes a backing formed of a relatively stiff but resilient material and a facing formed of a relatively more pliable material, wherein the backing extends in a direction away from the end wall of the cover body to below the level of the stop; Features: The peripheral portion of the seal enabling element is joined to the backing at a level at or below the stop, and the backing below this level includes a plurality of independent axially extending segments.

2. The screw cap according to claim 1, wherein: The seal-enabling element, the annular sealing element, the stopper, the backing, and the facing comprise portions of an expandable plug seal subassembly positionable within the screw cap.

3. The screw cap according to claim 2, wherein: The plug sealing subassembly and the cap body include a snap-fit ​​connection by which the plug sealing subassembly is retained in the cap body even when the screw cap is not screwed onto the container neck.

4. The screw cap according to claim 3, wherein: The snap-fit ​​connection includes a recess at a central portion of the seal-enabling element into which a protrusion extending from the cover body end wall is snap-fittedly received.

5. The screw cap according to claim 4, wherein: The projection includes a plurality of axially extending fingers or segments.

6. The screw cap according to claim 4 or 5, wherein: The protrusion includes an enlarged end portion that is snap-fit ​​received in an undercut portion of a recess at a central portion of the seal-enabling element.

7. The screw cap according to any one of claims 3 to 6, wherein: The snap-fit ​​connection allows relative rotation between the seal enabling element and the cap body, whereby there is generally substantially no relative rotation between the annular sealing element and the container neck when the screw cap is screwed on or off.

8. The screw cap according to any one of claims 2 to 7, wherein: The stop is integrally formed with the expandable plug sealing subassembly as an annular flange extending radially from an upper portion of the backing.

9. A screw cap according to any preceding claim, wherein: The backing and the seal enabler element include through grooves extending radially in the seal enabler element and axially in the annular sealing element.

10. The screw cap according to claim 9, wherein: The axially extending through slots are used to define a plurality of independent axially extending sections of the backing.

11. The screw cap according to claim 9 or 10, wherein: The axially extending through-groove continues into an annular flange forming the stop.

12. The screw cap according to any one of claims 9 to 11, wherein: The axially extending through-grooves are coupled to, extend into or become radial through-grooves in the seal enable element.

13. The screw cap according to any one of claims 9 to 12, wherein: The bottom surface of the seal enabler has a covering made of a softer and more compliant material to seal the groove therein.

14. The screw cap according to claim 13, wherein: The covering is continuous with the facing.

15. A screw cap according to any preceding claim, wherein: The seal enabling element includes a dome shape that becomes flatter and expands radially when the stop engages the container neck, the cap body is screwed onto the container neck, and the cap body end wall presses down on a central portion of the seal enabling element.

16. The screw cap according to claim 2, wherein: The expandable plug sealing subassembly includes a through-aperture to which a gas permeable, liquid impermeable membrane is secured to provide a gas venting path.

17. The screw cap according to claim 16, wherein: The through-going aperture is formed in the seal enabling element.

18. The screw cap according to claim 17, wherein: The through-aperture is formed in a recess at a central portion of the seal enabling element.

19. The screw cap according to claim 18, wherein: The recess comprises a recess of the snap-fit ​​connection as defined in any of claims 4-6.

20. The screw cap according to any one of claims 16 to 19, wherein: The stopper and / or the inner side surface of the end wall of the cap body are provided with a groove or a protrusion, and when the screw cap is completely tightened, the groove or the protrusion separates the stopper from the inner side surface of the end wall of the cap body.

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