Patent Publication Number: US-2022212841-A1

Title: Capsule and plug for a concentrated refill capsule

Description:
TECHNICAL FIELD 
     The present invention relates to a cap assembly and plug for a concentrated cleaning product refill capsule system, the plug being configured to break a frangible seal within a cap assembly and deliver concentrated cleaning fluid to a refillable vessel. 
     BACKGROUND OF THE INVENTION 
     Any discussion of prior art throughout the specification should in no way be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. 
     WO2007/145773 describes a mixing unit comprising a sealed container joined to a second container. 
     JP2012-158361 describes a refill container that can facilitate refilling work. 
     Liquid cleaning and hygiene products, such as multi-purpose surface cleaner, glass cleaner, or degreaser, are often supplied in ready-to-use concentrations in a wide variety of containers, with a wide variety of dispensing systems. Typically, such liquid cleaning products comprise one or more active ingredients diluted with water (or another solvent) to a concentration that is suitable for use in the home or commercial environment. 
     Cleaning products supplied in a ready-to-use concentration are advantageous in that the products can be supplied in a safe and effective concentration, and can be appropriately labelled. Ready-to-use products are also more convenient for the user, since they do not require dilution or reconstitution before use. 
     One example of a widely used container system for cleaning products is a spray bottle comprising a trigger actuator. Such systems generally comprise a bottle comprising a body and a neck, the neck being configured to engage a removable spray nozzle. The spray nozzle is generally secured to the neck of the bottle by way of complementary screw threads on the neck and on the nozzle. After use, the container or vessel in which the cleaning product was supplied is typically discarded and a replacement acquired. 
     Although the spray bottle in which cleaning products are supplied generally have a lifetime that extends beyond the point at which the cleaning product has been depleted, the practice of refilling spray bottles with cleaning product is not widespread in a domestic setting. 
     In a commercial or industrial setting, spray bottles are sometimes refilled for re-use by diluting a predetermined volume of concentrated liquid with water. The concentrated cleaning liquid may be supplied in a bottle, which typically has a larger volume than the spray bottles used by cleaning professionals due to the fact that the concentrate vessel is not carried throughout the cleaning process. 
     However, although it is known to supply concentrated cleaning fluids for dilution prior to use, the practice of refilling spray bottles with water and a concentrated cleaning fluid is not widespread due to the many challenges in safely and effectively managing concentrated products, especially in a home environment. 
     Handling of concentrated cleaning fluids requires care both during refilling of a spray vessel and with regard to storage of the concentrated liquid. To avoid risks to health, even more so than diluted cleaning fluids, concentrated cleaning fluids should be transported and stored securely, and kept out of reach of children and animals. 
     Moreover, concentrated (undiluted) cleaning fluids may cause damage to surfaces within the home, and, thus, spillages should be avoided to avoid damage to clothing and household items. 
     Further difficulties may be encountered in ensuring that the concentrated cleaning product is diluted to a safe and effective concentration. Over-dilution of a concentrated cleaning fluid with water may lead to inferior cleaning results. Under-dilution of a concentrated cleaning fluid may present a risk to health, damage to household items and excessive consumption of the concentrated cleaning fluid. 
     Despite a desire to reduce the plastic waste generated by discarding empty bottles, and a desire to reduce the costs and resources required to ship and store ready-to-use cleaning products, refill systems that are suitable and convenient for use in domestic and professional settings are not widely available. 
     The present inventors have been able to solve many of the problems associated with conventional cleaning product dispensing systems and have been able to develop a refill capsule system for use with spray bottles (and other cleaning product vessels) that can overcome many of the above problems. 
     An object of the present invention is to provide a refill capsule and an associated plug configured to rupture a seal over the refill capsule that overcome the above mentioned disadvantages associated with current cleaning products that allows vessels or containers for cleaning products to be reused. 
     It is another object of the invention to provide a refill system comprising a plug that allows a user to safely and reliably deliver a predetermined volume of concentrated cleaning fluid to a spray bottle or similar vessel for dilution. 
     It is another object of the invention to provide a refill capsule and an associated plug that allows for safe and reliable delivery of a concentrated cleaning fluid to a refillable vessel. 
     It is yet another object of the invention to provide a refill capsule and a cap assembly comprising a plug that can be simply and reliably coupled to a refillable vessel to discharge the concentrated liquid into the refillable vessel. 
     These and other objects are accomplished by the invention described in the following text and figures. 
     SUMMARY OF THE INVENTION 
     In a first aspect of the present invention, there is provided a plug configured to rupture a frangible seal which closes and seal a refill capsule for a concentrated cleaning liquid. The plug comprises an abutment surface for beating against a closure member to break a frangible seal securing the closure member in place. The plug is configured to allow the flow of fluid therethrough. 
     The plug according to the invention is described in the claims appended herewith. Optional features are described in the dependent claims. 
     The plug according to the invention allows a volume concentrated cleaning fluid to be safely and conveniently stored and transported. A cap system comprising the improved plug can be engaged, for example by virtue of a threaded engagement, with a refillable vessel. Upon engagement of the system with a refillable vessel, the plug moves within the cap assembly and the frangible seal is configured to break under the influence of the plug, thereby releasing the concentrated cleaning fluid contained in a capsule to flow through the plug into the refillable vessel. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, it should be note that the term ‘comprising’ encompasses the terms ‘consisting essentially of’ and ‘consisting of’. Where the term ‘comprising’ is used, the listed steps or options need not be exhaustive and further steps or features may be included. As used herein, the indefinite article ‘a’ or ‘an’ and its corresponding definite article ‘the’ means at least one, or one or more, unless specified otherwise. 
     The terms ‘upstream’ and ‘downstream’ as used herein refer to the direction of flow of fluid through the refill system during use, with fluid flowing from an upstream end to a downstream end. In the context of the present invention, fluid flows from an upstream refill capsule system into a downstream refillable vessel. The proximal direction is the upstream direction, whilst the distal direction is the downstream direction. 
     In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount. 
     The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only, and are not intended to limit the disclosure in any way. 
     The invention is not limited to the examples illustrated in the drawings. Accordingly it should be understood that where features mentioned in the claims are followed by reference numerals, such numerals are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting to the scope of the claims. 
     The present invention relates to a plug for a refill capsule system. The plug is configured to be secured within a cap assembly, and is configured to move between a first position and a second position with the cap assembly to break a frangible connection therein. The plug according to the invention comprises an improved configuration compared to known seal-rupturing plugs, as will be described in further detail below. 
     The plug according to the invention generally comprises a tubular body with an open proximal end and an open distal end. The open proximal end is surrounded by a first rim, which defines an opening. The rim further comprises at least first and second projections extending in a proximal direction from the rim, with the proximal surface of the projections providing a proximal-facing abutment surface for bearing against a frangible sealing component. The proximal-facing abutment surface extends in a first plane that is orthogonal to a longitudinal axis A of the tubular body, and has at least two fold rotational symmetry with respect to the longitudinal axis A. 
     For example, the proximal-facing abutment surface of the plug can be provided by a continuous circumferential rim of the tubular body, terminating in a plane Q. Alternatively, the proximal-facing abutment surface can comprise a discontinuous rim comprising a plurality of projections equally spaced circumferentially around the rim of the tubular body, wherein the projections extend in a proximal direction from the rim and terminate in the plane Q. The projections may take the form of teeth spaced equally around the circumference of the rim. For example, in the case of an abutment surface comprising two teeth, the teeth may be disposed diametrically opposite each other. 
     By providing a rotationally symmetric abutment surface configured to apply a net force along the longitudinal axis A, and perpendicular to the plane in which the frangible connection extends, the frangible connection can be configured to snap, failing around its circumference, rather than peeling from an initial breach around the seal. Such a circumferential failure of the seal can result in a snap or click sound that is audible to the user, thereby providing positive feedback that the frangible connection has been successfully broken and that the liquid contained in a capsule body can escape. 
     The plug also comprises an outwardly extending flange comprising a distal-facing abutment surface for abutting a rim of a refillable vessel. 
     The flange can be provided on a skirt that extends around the tubular body, the skirt comprising a generally tubular skirt wall arranged coaxially with respect to the tubular body, and being spaced apart from the tubular body in a radial direction to form a plug recess between the skirt wall and the tubular body. 
     Optionally, the skirt wall can be connected to the tubular body at a distal end of the tubular body, and extend proximally from the connection point to circumferentially surround the tubular body. The proximal end of the skirt wall can comprise a free end. The flange can extend from the free end of the skirt wall. 
     The free end of the skirt wall can further comprises a proximal sealing rim for sealing against a sealing surface of a cap assembly. The sealing rim can be provided on a proximal surface of the flange that provides the distal-facing abutment surface. In some examples, the proximal sealing rim may taper to a peak. 
     By providing a sealing rim, a seal can be formed between the proximal sealing rim and a corresponding surface of an associated cap assembly, for example, a connection wall joining the inner and outer walls of a dual-walled cap assembly. The sealing rim may be peaked. This can form an improved seal against the sealing surface of the cap assembly. The sealing peak may terminate in the same plane as the proximal-facing abutment surface. 
     The tubular body can further comprise at least one cut-out or slot in a wall of the tubular body. The cut out or slot can provide a discontinuity in the rim of the plug such that a broken cap part cannot settle over the cap to block the proximal opening of the tubular body because the rim does not extend in the same plane around the full circumference of the tubular body. This discontinuity may thus improve flow through the tubular body of the plug. 
     The rim can comprises two or more cut-outs, and preferably, two diametrically opposed cut outs. 
     The tubular body can further comprise a protrusion or ridge extending around an outer surface of the tubular body. Such a ridge can provide engagement of the plug with a cap assembly comprising a similar ridge, a corresponding groove, or solely by way of increasing the contact force between the plug and a cap assembly within a system. 
     The free proximal end of the skirt wall can further comprise at least one claw extending radially from the flange. The at least one claw can comprise a corresponding engagement feature (e.g. a screw thread) in the cap assembly. The claw can be configured to flex to allow movement of the plug in a proximal direction, but to prevent or resist movement of the plug in a distal direction. Optionally, the at least one claw comprises a curved claw with a distal-facing concave surface and a proximal-facing convex surface. 
     Advantageously, the at least one claw can comprises two claws, preferably three claws, and more preferable four or more claws. 
     The advantages of the plug assembly are applicable in many combinations of cap assemblies. In at least one exemplary configuration, the plug can be combined with a cap assemble to form a cap system. 
     The cap assembly can comprise an inner wall defining a conduit through the cap assembly, the conduit extending from an upstream end to a downstream end. An outer wall may surround the inner wall along at least a first portion of its length, wherein the outer wall is spaced from the first portion of the inner wall to define a circumferential void between the inner and outer walls extending from an open downstream end to a closed upstream end. A connecting wall can extend between the inner and outer walls to prevent fluid flow through the void, the connecting wall forming the closed upstream end of the void. 
     The cap assembly may further comprise a closure member configured to seal the conduit, the closure member comprising an upstream side and a downstream side. The closure member is sealed to the inner wall with a peripheral frangible connection located between proximal and distal ends of the conduit. 
     Preferably, the frangible connection extends in a plane P, which is orthogonal to a longitudinal axis of the conduit. 
     In such an exemplary configuration, the plug can be disposed within the cap assembly such that the outer wall of the cap assembly surrounds the plug (preferably extending beyond the distal end of the plug) and the inner wall of the cap assembly extends into the plug recess. 
     In this position, the proximal-facing abutment surface of the plug is aligned with and opposes the bearing surface of the closure member such that the plug can be moved in a proximal direction, to bear against the bearing surface of the cap, and break the frangible seal. 
     The frangible connection can be configured in different ways. For example, the frangible connection can be disposed between a first peripheral recess formed between the inner wall and a downstream side of the closure member, and a second peripheral recess between the inner wall and an upstream side of the closure member. 
     In an alternative configuration, the downstream recess can be omitted and instead inner surface of the inner wall immediately upstream of the frangible connection can be off-set radially from an inner surface of the wall immediately downstream of the frangible connection. Preferably, the upstream inner surface is offset radially outwardly from the downstream inner surface. 
     Offsetting the inner surface of the inner wall immediately upstream and immediately downstream of the closure member may provide multiple advantages. For example, offsetting the radial position of the inner wall immediately upstream and downstream of the closure member can control the width of the frangible connection at its thinnest part. This provides a well-defined region in which the frangible connection breaks. Moreover, offsetting the radial position of the upstream inner wall compared to the downstream inner wall ensures that the closure member can be pushed into a region of the conduit that has a greater cross-sectional area than the cross-sectional area of the closure member. This can ensure that the closure member is pushed into a region in which it cannot block the conduit. 
     In plug/cap assembly combinations, the bearing surface of the cap assembly can extend in a plane that is orthogonal to the longitudinal axis of the conduit. Combined with the orthogonal proximal-facing abutment surface of the plug, this can ensure that the frangible connection snaps rather than peels. 
     The closure member in the cap assembly may be hollow and tapered, and taper from a downstream base to an upstream peak. For example, the closure member may be conical or frustoconical. 
     The hollow closure member may be open at the base, and is preferably oriented with the peak in an upstream direction and the base in a downstream direction. 
     The outer wall of the cap assembly can also comprises engagement means, e.g. a screw thread on its inner surface, and wherein the claws of the plug are configured to engage the engagement means of the cap assembly. 
     In at least some configurations, the inner wall of the cap assembly can comprise a protrusion or ridge extending radially inwardly from an inner surface of the inner wall. The ridge on the cap assembly can be configured to cooperate with a ridge on the plug to reduce the likelihood that the plug moves in the distal direction during transit or storage. 
     The plug described here may also be combined with the cap assembly in a refill system, which further comprises a capsule body for containing a concentrated cleaning product, wherein the capsule body is engaged with the cap assembly, and wherein an internal volume of the capsule body is in fluid communication with an upstream end of the conduit. The capsule body comprises an opening surrounded by a rim, and wherein the rim is configured to bear against the connecting wall of the cap assembly. 
     In an exemplary system, a shrink wrap cover extends around at least a portion of the capsule and at least a portion of the cap assembly. 
     It will be appreciated that the advantages provided by the plug described herein are not limited to the exemplary combinations described below. For example, the plug described herein may be combined with the cap assembly shown in the illustrated examples, or with other compatible cap assemblies. For example, although the illustrated examples include a plug in combination with a dual-walled cap assembly, plugs according to the present invention can also be combined with cap assemblies comprising a frangible seal formed across a single-walled conduit. 
     As used herein, the term ‘refill capsule’ refers to a capsule body suitable for a container for concentrated cleaning fluid. 
    
    
     
       FIGURES 
       By way of example, the present invention is illustrated with reference to the following figures, in which: 
         FIG. 1  shows a longitudinal cross-sectional perspective view of a refill capsule system comprising a refill capsule, a plug, and a cap assembly according to the present invention; 
         FIG. 2A  shows a longitudinal cross-sectional view of the refill system before rupture of the frangible seal; 
         FIG. 2B  shows a longitudinal cross-sectional view of the refill system after rupture of the frangible seal; 
         FIG. 3A  shows a longitudinal cross-sectional view of a cap assembly according to a first configuration, the cap assembly comprising a frangible seal; 
         FIG. 3B  shows an enlarged view of the frangible seal of  FIG. 3A  according to a first configuration; 
         FIG. 3C  shows an enlarged view of the frangible seal of  FIG. 3A  according to a second configuration; 
         FIG. 4A  shows a longitudinal cross-sectional view of a plug according to a first configuration; 
         FIG. 4B  shows a longitudinal cross-sectional view of a plug according to a second configuration; 
         FIG. 4C  shows a perspective view of the plug shown in  FIG. 4B ; 
         FIG. 5  shows an enlarged longitudinal cross-sectional view of a proximal end of a refill capsule system comprising the cap system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE FIGURES 
     In the detailed description of the figures, like numerals are employed to designate like features of various exemplified devices according to the invention. 
       FIG. 1  shows a refill system for containing a concentrated cleaning fluid and configured for use with a refillable vessel.  FIG. 1  shows a cross-sectional view of an assembled refill system comprising a capsule body  100 , a cap assembly  200 , and a plug  300 . 
     As shown in  FIG. 1 , the capsule body  100  comprises a generally hollow receptacle configured to receive a volume of concentrated cleaning fluid. The concentrated cleaning fluid is contained within an internal volume  102  of the capsule body  100 . The capsule body  100  comprises a neck  104  comprising an open end surrounded by a rim  108 . The neck  104  comprises a capsule thread  106  configured to engage a corresponding screw thread on the cap assembly  200 . 
     As shown in  FIG. 1 , a longitudinal axis A extends through the open end of the capsule body  100  from a closed end of the capsule body  100 , through the cap assembly  200 , and the plug  300 . 
     The cap assembly  200  is configured to seal the capsule body  100  and extends from an upstream end to a downstream end. The upstream direction is the direction towards the capsule body  100  and the downstream end direction is the direction toward the refillable vessel, when the system is in use. 
     The cap assembly  200  defines a conduit  203  through the cap assembly  200  though which fluid can flow to exit the capsule body  100 . The conduit  203  extends through the cap assembly  200  from an open upstream end to an open downstream end. A closure member  208  seals the conduit  203  to prevent fluid communication between the upstream end and the downstream end of the conduit  203 . The closure member  208  is sealed to the inner wall of the conduit by a frangible connection  210 , which can be broken by applying pressure to the closure member  208 . 
     The plug  300  is disposed within the cap assembly  200  and is configured to bear against the closure member  208  to break the frangible connection  210  as the cap assembly  200  is screwed onto (or otherwise engaged with) a refillable vessel. The plug  300  comprises a tubular body having providing an internal bore through which cleaning fluid can escape through once the plug  300  has been used to rupture the seal in the cap assembly  200 . 
     Advantageously, the refill system can be wrapped in a shrink wrap cover. The shrink wrap cover can cover the whole cap assembly  200  and the capsule body  100 , or it may cover only a portion of the 
     capsule body  100  and the capsule assembly  200 . Advantageously, it may extend around the cap system such that the join between the capsule body  100  and the cap assembly  200  is surrounded by a shrink wrap cover. By shrink wrapping the capsule body  100  and the cap assembly  200  together, the likelihood of the cap assembly  200  being inadvertently removed from the capsule body  100  is further reduced. 
     Use of the System 
     Referring now to  FIGS. 2A and 2B , use of the system will be described in more detail. 
       FIGS. 2A and 2B  show an enlarged view of the refill system comprising cap assembly  200 , and plug  300 . The capsule body  100  is omitted for clarity.  FIGS. 2A and 2B  also show the upper portion of a refillable vessel  400  with a neck  402  that defines an opening in fluid communication with an interior volume of the refillable vessel  400 . 
       FIG. 2A  shows the system before use with the closure member  208  sealed within the conduit  203 . As shown in  FIG. 2A , the refill system is supplied with the plug  300  disposed within the cap assembly  200 . In the configuration shown in  FIG. 2A , the plug  300  occupies a first position in which it is spaced apart from (i.e. not in direct contact with) the closure member  208 . 
     The plug  300  is mounted within the cap assembly  200  such that it is secured in place against accidental movement (e.g. during transport or storage). However, the plug  300  and the cap assembly  200  are configured such that the plug  300  can be pushed axially towards the closure member  208  by bearing on a distal-facing abutment surface provided on the plug  300 . 
     The plug  300  can be secured or mounted within the cap assembly  200  in different ways. An exemplary plug and cap assembly combination will be discussed in further detail with reference to  FIGS. 3A-5 . 
     The cap assembly  200  comprises one or more first screw threads  230  (or other engagement means) configured to engage a corresponding vessel screw thread on a refillable vessel  400 . The screw thread  230  allows the cap assembly  200  to be screwed onto the neck  402  of the refillable vessel  400 . The first screw thread(s)  230  are provided on an inner surface of the cap assembly  200 , whilst the vessel thread  404  of the refillable vessel  400  is provided on an outer surface of the refillable vessel  400 . Therefore, as the cap assembly  200  is screwed onto the neck  402  of the refillable vessel  400 , the neck  402  of the refillable vessel  400  and the rim  406  with which the neck  402  terminates are guided into the cap assembly  200 . 
     Referring now to  FIG. 2B , the plug  300  is disposed within the cap assembly  200  such that the introduction of the neck  402  into the cap assembly  200  tends to bear against the plug  300 , pushing it in an upstream direction, towards the capsule body  100  and into contact with the closure member  208 . 
     As shown in  FIG. 2B , as the rim  406  advances within the cap assembly  200 , the plug  300  is first brought into abutment with the closure member  208  and then begins to exert a force thereagainst as the rim  406  forces the plug to advance further relative to the cap assembly  200 . As the plug  300  bears against the closure member  208 , the force exerted against the closure member  208  increases to a point at which the frangible connection between the closure member and the conduit  203  fails, and the closure member  208  is pushed in an upstream direction such that it no longer seals the conduit  203 .  FIG. 2B  thus shows the second position of the plug  300 . 
     Once the seal provided by the closure member  208  is broken, concentrated cleaning fluid can flow from the internal volume  102  of the capsule body  100 , through the conduit  203  of the cap assembly  200 , through the internal bore of the plug  300 , and into the refillable vessel  400  below. 
     Once the capsule body  100  has been emptied, the cap assembly  200  can be unscrewed from the neck  402  of the refillable vessel  400 , and discarded safely. 
     By providing a refill system as described above, it is possible to provide a safe, convenient, and effective way of delivering a controlled quantity of concentrated cleaning fluid to a refillable vessel. 
     Several advantages may be provided by the system described here, which may result in an improved refill system. 
     Improved Cap Assembly 
     The cap assembly  200  will now be described in more detail with reference to  FIGS. 3A-3C .  FIG. 3A  shows a cross-sectional view of the cap assembly  200  described above.  FIG. 3B  shows an enlarged cross-sectional view of a frangible connection  210  according to a first exemplary configuration.  FIG. 3C  shows an enlarged cross-sectional view of a frangible connection  210  according to a second exemplary configuration. For clarity, the plug  300  is omitted from  FIGS. 3A-3C . 
     The cap assembly is preferably molded to form at least the closure member, connecting portion, and conduit as a continuous molded piece. The connecting portion may be configured to be the thinnest portion of the cap assembly. The connection portion may be between 0.05 and 0.2 mm thick, more preferably between 0.1 and 0.2 mm thick. The cap assembly can be formed from a molded polymer material, for example a polypropylene material. The polymer material can be injection molded. 
     The cap assembly  200  described herein includes a number of improvements that may provide enhanced performance. The cap assembly  200  may comprise an improved wall structure, an improved frangible connection, enhanced safety features, and improved audible and tactile feedback to the user. Each of these improvements will be described in more detail below. Moreover, it will be appreciated that the features described below may be incorporated in a refill system alone, or in combination with other features to provide a further improved product. 
     As shown in  FIG. 3A , the cap assembly  200  comprises an inner wall  202  that defines a conduit  203  extending from an open upstream end to an open downstream end. A closure member  208  is positioned within the conduit  203  and has an upstream side  208   a  and a downstream side  208   b . The closure member  208  is sealed around its periphery to the inner wall  202  with a frangible connection  210 . The frangible connection  210  is located between the upstream open end and the downstream open end of the conduit  203  and will be described as in more detail with reference to  FIGS. 3B and 3C . 
     An outer wall  204  extends around the inner wall  202 . The outer wall  204  is connected to the inner wall  202  by a connecting wall  212 . The connecting wall  212  extending between the inner and outer walls  202 ,  204  prevents the flow of fluid through the cap assembly  200  in the space between the inner and outer walls  202 ,  204 . The only route through which fluid may flow through the cap assembly  200  is thus through the conduit  203  when the frangible connection  210  has been broken. 
     The inner wall  202  is arranged coaxially within the outer wall  204  to form a circumferential void  214  between the inner and outer walls  202 ,  204 . In the embodiment shown in  FIG. 3A , the connecting wall  212  connects to each of the inner and outer walls  202 ,  204  part way along their length. This forms an upstream void  214   a  between the inner and outer walls  202 ,  204  upstream of the connection wall  212 , and a downstream void  214   b  between the inner and outer walls  202 ,  204  downstream of the connecting wall  212 . 
     By providing an upstream void  214   a , the seal between the capsule body  100  and the cap assembly  200  can be improved because the inner wall  202  can be specially adapted for forming a seal between the cap assembly  200  and the capsule body  100  within the neck  104  of the capsule body  100 , whilst the outer wall can be  203  can be specially adapted to form a seal between the cap assembly  200  and the capsule body  100  around the neck  104  of the capsule body  100 . 
     In at least some examples, the outer wall  204  can provide a child-resistant closure with the capsule body  100 . For example, the outer wall  204  can comprise a plurality of ratchet teeth (not shown) that mate with a plurality of ratchet teeth on the capsule body  100  to allow the cap assembly  200  to be screwed onto the capsule body  100 , but prevent the cap assembly  200  from being unscrewed from the capsule assembly. The child resistant closure may prevent the cap assembly  200  from being unscrewed from the capsule body  100  entirely (or at least without breaking the cap assembly  200 ) or it may be configured to prevent the cap assembly  200  from being unscrewed from the capsule body  100  unless a predetermined axial force is applied to the cap assembly  200  in a direction towards the capsule body  100 . 
     Moreover, by providing an upstream void  214   a  to accommodate the neck  104  of the capsule body  100 , the neck  104  can be used to provide structural reinforcement to the cap assembly  200  to minimise the degree to which is flexes as pressure is applied to rupture the frangible connection  210 . By minimising the degree to which the cap assembly  200  can flex under pressure from the plug  300 , the frangible connection  210  is more likely to fail suddenly under pressure, resulting in a snap or click that provides audible and tactile feedback to the user that the seal is broken and that the concentrated liquid can be dispensed. 
     By providing a downstream void  214   b , at least a portion of the plug  300  can be accommodated between the inner and outer walls  202 ,  204  downstream of the connecting wall  212 . This provides a space in which the plug  300  can be retained within the cap assembly  200  during transport and storage, and held securely in place until the user screws the refill system onto a refillable vessel. By providing the plug  300  in a downstream void, the plug can be shielded from accidental contact by handlers, thereby reducing the risk that the plug  300  is accidentally moved between the first and second positions during transit or storage. 
     It will be appreciated that although the provision of an upstream void  214   a  and a downstream void  214   b  can be combined to provide enhanced advantages over known systems, in at least some examples the cap assembly  200  can comprise only an upstream void  214   a  or only a downstream void  214   b.    
     The conduit  203  provided by the inner wall  202  of the cap assembly  200  can have a variable diameter along its length. For example, the diameter of the conduit  203  upstream of the frangible connection  210  can be larger than the diameter of the conduit  203  downstream of the frangible connection  210 . By increasing the diameter of the conduit  203  upstream of the frangible connection  210 , the closure member  208  can be pushed by the plug  300  into a region of the conduit  203  that has a larger diameter than the closure member  208 . This further reduces the likelihood that the closure member  208  can occlude the conduit  203  to prevent the egress of cleaning fluid from the capsule body  100  through the cap assembly  200  and the plug  300 , once the plug has been moved to its second position. 
     In the embodiment shown in  FIG. 3A , the inner wall  202  is shaped with a barrel shaped or bulbous upstream end portion to provide a barrel seal for sealing with the neck  104  of the refill capsule body  100 . The inner wall  202  is configured to sit within the opening of the capsule body  100  and form a seal between an outer surface of the inner wall and an inner surface of the opening. 
     Instead of comprising a cylindrical shape having sides that are substantially parallel, the upstream end of the conduit  203  can be barrel shaped, steadily decreasing in transverse cross-sectional diameter (i.e. a cross-section in a plane perpendicular to the longitudinal axis A) from a maximum diameter upstream of the frangible connection  210  towards the upstream rim of the inner wall  202 . By varying the diameter of the conduit  203  at the upstream end, variation in manufacturing tolerances can be accounted for and/or a tighter seal can be provided between the capsule body  100  and the cap assembly  200  because the narrower open end of the conduit  203  can be inserted into the neck  104  of the capsule body  100 , and a tight seal can be formed between the barrel sealing rim and the neck of the capsule body  100 . 
     As shown in  FIG. 3A , the connecting wall  212  may further comprise a circumferential notch  234  or channel adjacent the inner wall  202  on the upstream side. The notch  234  reduces the thickness of the connecting wall  212  at the point where the inner wall  202  joins the connecting wall  212 . This can increase the degree to which the upstream portion of the inner wall  202  can flex inwardly to fit within the neck  104  of the capsule body  100  (as shown in  FIG. 5 ). 
     The inner wall  202  downstream of the closure member  208  has a generally cylindrical form, with substantially parallel walls. The downstream end of the inner wall  202  is configured to fit within the neck  404  of the refillable vessel  400 . 
     As shown in  FIG. 3A , the inner surface of the inner wall  202  can comprise a radially inwardly protruding ridge or protrusion  216 . The ridge or protrusion  216  can advantageously engage a corresponding protrusion on the plug  300 , as will be described in more detail below with reference to  FIG. 5 . 
     As shown in  FIG. 3A , the closure member  208  is positioned within the conduit  203  and closes the conduit to prevent the passage of fluid therethrough unless the frangible connection  210  is broken. 
     The closure member  208  shown in  FIG. 3A  comprises a tapered shape, extending from a downstream base  219  to an upstream peak  218 . For example, the closure member can comprise a conical or frustoconical shape. The base  219  is preferably open to allow access to the hollow interior of the closure member  208  from the downstream side. By providing a hollow, peaked closure member  208 , the likelihood of the closure member  208  settling over the opening formed through the inner conduit after the seal has been broken is reduced. To the contrary, the buoyancy provided by the hollow closure member  208  means that the closure member tends to float away from the conduit  203 . 
     The base  219  of the closure member provides a bearing surface  220  against which the plug  300  can bear to apply pressure to rupture the frangible connection  210 . The bearing surface  220  preferably extends in a plane that is orthogonal to the longitudinal axis A. 
     The frangible connection  210  preferably also extends in a plane perpendicular to the longitudinal axis A. The frangible connection  210  can extend in the same plane as the bearing surface  220 , or in a plane parallel to the plane R. 
       FIGS. 3B and 3C  each show an enlarged view of a frangible connection  210  formed between the closure member  208  and the inner wall  202  according to the invention. 
     As shown in  FIGS. 3B and 3C , the frangible connection  210  extends between the inner wall  202  and an outer perimeter of the closure member  208 . The frangible connection  210  is preferably between 0.05 and 0.2 mm thick. However, the skilled person will appreciate that other dimensions may be chosen depending on the materials used and the dimensions of the cap system. 
     The thickness (in a longitudinal direction) and the width (in a radial direction) of the frangible connection are preferably closely controlled. By controlling the width and the thickness of the frangible connection  210 , the reliability with which the frangible connection  210  fails may be more reliable. This may provide a more consistent user experience. 
     The thickness and the width of the frangible connection can be controlled in different ways. 
     For example, in the exemplary configuration shown in  FIG. 3B , the frangible connection  210  is formed between two opposing recesses or notches  222 ,  224 . The recesses or notches  222 ,  224  are shown in  FIG. 3B , which is a cross-sectional view. However, it will be appreciated that for a closure member  208  having a circular transverse cross-section, the recesses, or notches  222 ,  224  may be formed as circumferential channels or annular grooves. 
     The first recess  224  is formed upstream of the frangible connection  210 , between an upstream side  208   a  of the closure member  208  and an interior surface of the inner wall  202 . The second recess  224  is formed downstream of the frangible connection  210 , between a downstream side  208   b  of the closure member  208  and an interior surface of the inner wall  202 . By forming a frangible connection  210  between two opposing recesses or channels, the thickness (in a longitudinal direction) and the width (in a transverse direction) of the frangible connection  210  can be controlled and minimised. 
     The notches  222  and  224  (or the channels) extend from an open end to a closed end, with the frangible connection  210  forming the closed end in each case. The closed end of each recess or channel may advantageously have a rounded profile, as shown in  FIG. 3B . By providing a frangible connection  210  between opposing rounded notches or channels, the width of the frangible connection at the thinnest part can be closely controlled. 
     It will be appreciated that the transverse width of the thinnest part of the frangible connection  210  can be controlled by varying the radius of curvature of the rounded notches. The radius of curvature of the first notch or recess  222  can be chosen to be substantially the same as the second notch or recess  224  or it may be different. 
     The second (downstream) notch or channel  224  in the example illustrated in  FIG. 3B  means that the frangible connection  210  extends in a different plane to the bearing surface  220 . However, in an alternative exemplary configuration, the second circumferential notch  224  can be omitted. 
     An alternative exemplary configuration is shown in  FIG. 3C . As shown in  FIG. 3C , the first (upstream) recess  222  is present. In the illustrated configuration, the recess  222  comprises a closed end, having a flat lower surface  223 . The flat lower surface  223  of the recess  222  extends between the inner wall  202  and the closure member  208  and forms the upper surface of the frangible connection  210 . 
     The lower surface of the frangible connection  210  extends in the same plane as, and is contiguous with, the bearing surface  220 . As shown in  FIG. 3C , the width of the frangible connection  210  at its thinnest part can be controlled by forming the recess  222  such that the inner surface of the inner wall  202  immediately upstream of the frangible connection  210  is positioned radially outwardly or the inner surface of the inner surface of the inner wall  202  immediately downstream of the frangible connection  210 . By offsetting in the point at which the inner surface of the inner wall  202  upstream of the frangible connection  210  with respect to the inner surface of the wall downstream of the frangible connection, the width of the frangible connection  210  at its thinnest point can be reduced to a dimension that is smaller than the width of the recess  222 . This allows the formation of a frangible  210  connection having a width dimension smaller than any of the parts required to form the connection (e.g. in the mold). This can allow for a further improved frangible connection  210 . 
     Referring again to  FIG. 3A , the frangible connection  210  preferably extends in a plane P that is orthogonal to the longitudinal axis A of the cap assembly  200 . By providing a flat seal (with respect to the longitudinal axis A), the frangible connection  210  tends to snap arounds its circumference at substantially the same time as the plug  300  (with its proximal-facing abutment surface  305  also oriented orthogonal to the longitudinal axis A) bears on the bearing surface  220 . This is contrast to a frangible connection  210  that extends in a plane extending at a non-perpendicular angle to the longitudinal axis A, which tends to peel from the ‘lower’ end (the portion of the frangible connection  210  that is first brought into close proximity with the plug  300 ) towards the ‘upper’ end (the portion of the seal that is furthest from the advancing plug  300 ). Such peeling is often imperceptible to the user of the assembly, and may result in the user removing the cap assembly from the refillable vessel prematurely with the seal partially intact. 
     By contrast, one of the advantages of the frangible connection  210  breaking around the perimeter of the closure member  208  at the same time is that the frangible connection  210  may fail suddenly, causing a snap or click as the frangible connection  210  is broken. The snap or click failure of the frangible connection  210  can provide audible and/or tactile feedback to the user that the component sealing the refill system has been broken and that the concentrated cleaning fluid disposed within the capsule body  100  will be dispensed. 
     In the embodiments shown in  FIGS. 2A-5 , the system is configured such that the movable plug  300  bears against the bearing surface  220  of the closure member  208  as the plug  300  is moved between the first position and the second position. The plug  300  is moved between its first position and its second position due to the force exerted on the plug  300  by the rim of a refillable vessel  400  as the neck of the refillable vessel  400  is advanced into the cap assembly. 
     However, it will be understood that plug  300  may be omitted from some exemplary configurations and the cap assembly  200  can be configured such that the bearing surface  220  of the closure member  208  is brought into contact with the rim  406  of the refillable vessel directly to break the frangible connection  210 . Such exemplary configurations fall within the scope of the present disclosure. 
     For example, the frangible connection  210  described above can be provided in a refill system having a cap assembly  200  that screws directly onto the neck of a refillable vessel  400 . In such systems, the cap can be configured such that the rim of the refillable vessel  400  bears directly on the closure member to break the frangible connection  210  and allow concentrated cleaning fluid to flow through the cap assembly  200  into the refillable vessel  400 . 
     The Plug 
     The plug  300  will now be described in more detail with reference to  FIGS. 4A-4C . 
     The plug  300  described herein includes a number of improvements that may provide enhance performance. The plug  300  may comprise an improved wall structure, an improved bearing surface for rupturing the frangible connection  210 , enhanced safety features, and features that contribute to improved audible and tactile feedback to the user. Each of these improvements will be described in more detail below. Moreover, it will be appreciated that the features described below may be incorporated in a refill system alone, or in combination with other features to provide a further improved product. 
       FIG. 4A  shows a cross-sectional view of the plug  300  comprising a proximal-facing abutment surface configured according to a first exemplary configuration.  FIG. 4B  shows a cross-sectional view of the plug  300  comprising a proximal-facing abutment surface configured according to a second exemplary configuration.  FIG. 4C  shows a perspective view of the plug  300  of  FIG. 4B . 
     As shown in  FIG. 4A , the plug  300  comprises a generally tubular body  302  defining an internal conduit therethrough, with a proximal rim  304  surrounding an upstream opening of the tubular body  302 . The proximal rim  304  comprises a proximal-facing abutment surface  305  configured to bear against the bearing surface  220  of the closure member  208  as the plug  300  is moved from the first position, to the second position, as described above. 
     In the embodiment shown in  FIG. 4A , the plug  300  further comprises a generally tubular skirt wall  306  that is arranged coaxially with respect to the tubular body  302 , and surround the tubular body  302  along at least part of its length to provide a dual-walled plug  300 . The skirt wall  306  is spaced apart from the tubular body  302  (in a radial direction) to form a plug recess  308  between the skirt wall  306  and the tubular body  302 . 
     The skirt wall  306  is connected at its distal end to the distal end of the tubular body  302 , and comprises a free proximal end. The free proximal end of the skirt  306  further comprises an outwardly extending flange  310  that provides a distal-facing abutment surface  312  for abutting a rim  406  of a refillable vessel  400  (see  FIGS. 2A and 2B ). 
     By providing a plug  300  comprising an inner tubular body  302  and an outer skirt  306 , the plug  300  can be more securely retained within the cap assembly  200 . For example, the plug recess  308  can accommodate a component (e.g. inner wall  202 ) of the cap assembly  200  to retain the plug  300  securely within the cap assembly  200  until the user screws the system onto a refillable vessel  400 . 
     The proximal-facing abutment surface  305  can be configured in different ways, as will now be described with reference to  FIGS. 4A and 4B . 
     As described above, the proximal-facing abutment surface  305  of the plug  300  is configured to be brought into contact with the bearing surface  220  of the closure member  208  as the plug  300  moves between its first position and its second position (see FIGS.  2 A and  2 B). As the proximal-facing abutment surface  305  is brought into contact with the bearing surface  220  of the closure member  208  and advanced further in a proximal direction, the frangible connection  210  breaks and the closure member  208  is lifted away from a position in which it occludes the conduit  203 . 
     The proximal-facing abutment surface  305  of the plug can be configured to distribute the applied force evenly around the circumference of the frangible connection  210 . In other words, the proximal-facing abutment surface  305  can be configured in such a manner that results in a net force being applied to the closure member  208  along the longitudinal axis A, and perpendicular to the plane in which the frangible connection  210  extends. Accordingly, the proximal-facing abutment surface  305  of the plug  300  preferably has at least two fold rotational symmetry with respect to the longitudinal axis A. 
     In the exemplary configuration shown in  FIG. 4A , the proximal-facing abutment surface  305  of the plug  300  is provided by a circumferential rim  304  of the tubular body  302 , terminating in a plane. By providing a circumferential rim in a plane perpendicular to the longitudinal axis A, the proximal-facing abutment surface  305  is simultaneously brought into contact with the bearing surface  220  around the circumference of the closure member  208 . 
     The rim  304  that provides the proximal-facing abutment surface  305  may be continuous or can comprise one or more cut-outs  316 . 
     In an alternative shown in  FIG. 4B , the proximal-facing abutment surface  305  can comprise a discontinuous rim comprising a plurality of projections  307  (extending in a proximal direction) equally spaced circumferentially around the rim  304  of the tubular body  302 , wherein the projections  307  terminate in a plane perpendicular to longitudinal axis A. The projections may take the form of teeth spaced equally around the circumference of the rim. For example, in the case of an abutment surface comprising two teeth, the teeth may be disposed diametrically opposite each other. A perspective view of a plug  300  comprising two diametrically opposed teeth is shown in  FIG. 4C . 
     By providing a rotationally symmetric abutment surface configured to apply a net force along the longitudinal axis A, and perpendicular to the plane in which the frangible connection  210  extends, the frangible connection  210  can be configured to snap, failing around its circumference, rather than peeling asymmetrically from an initial breach around the seal. Such a circumferential failure of the seal can result in a snap or click sound that is audible to the user, thereby providing positive feedback that the frangible connection has been successfully broken and that the liquid contained in a capsule body can escape. 
     In addition or as an alternative to the features described above, the plug configurations described above can comprise additional feature to enhance the functionality of the plug  300 . The following additional features may be combined with the abutment surface configurations described above with reference to  FIGS. 4A-4C . 
     The distal-facing abutment surface  312  at the free end of the skirt wall  306  can be configured to provide multiple additional advantages. For example, the free end of the skirt wall  306  can comprise a proximal seal  318  configured to seal against the connecting wall  212  of the cap assembly  200 . The proximal seal  318  can comprise a circumferential ridge comprising a peak. The peak provides a small surface area to be brought into contact with the connecting wall  212 , thereby improving the seal. 
     The free proximal end of the skirt wall  306  can also comprise a one or more claws  320  configured to engage the threads  230  of the cap assembly  200 . The engagement of the claw(s)  320  with the thread  230  can provide additional security that the plug  300  will remain in place within the cap assembly  200 . 
     The claw(s)  320  may also retain the plug  300  within the cap assembly  200  after the product has been used. Since the plug  300  must be pushed into the cap assembly  200  to rupture the frangible connection  210 , the claws are preferably configured to such that they can ride over the threads  230  of the cap assembly  200  as the plug  300  advances towards the closure member  208 . The claw(s)  320  may thus comprise a distal facing concave surface and a convex proximal surface. 
     As shown in  FIG. 4 , the plug  300  may further comprise a circumferential ridge or protrusion  314  on an outer surface of the tubular body  302 . The ridge or protrusion  314  can be configured to engage with a corresponding ridge or protrusion (e.g. ridge  216 ) on a complementary cap assembly  200 . This may further improved the retention of the plug  300  within the cap assembly  200  before use, for example during transport and storage. 
     As shown in  FIG. 4 , the plug  300  can also comprise one or more cut-outs or slots  316  in the wall of the tubular body  302 . The cut-outs or slots preferably extend from the proximal rim  304  of the tubular body  302  in a distal direction. The discontinuity in the rim  304  formed by the cut-outs or slots  316  may advantageously improve the flow of fluid through the cap assembly  200  and the plug  300  after the frangible connection  210  has been broken, by ensuring that the closure member  208  cannot form a seal against the rim  304  of the plug  300 . 
     In the embodiment shown in  FIGS. 4A-4C , the plug  300  comprises two diametrically opposed cut-outs  316  (although only one is visible in the cross-sectional view shown in  FIG. 4 ). However, one cut-out may be provided, or three or more cut-outs can be provided in the tubular body  302 . 
     Providing a discontinuity in the proximal-facing abutment surface  305  of the tubular body  302  may also provide the additional advantage of reducing the surface area of the proximal-facing abutment surface  305  that is brought into contact with the bearing surface  220  of the closure member  208 , thereby increasing force per unit area exerted on the closure member  208 . 
     Although not illustrated in the drawings, it will be appreciated that the closure member  208  may be modified (in addition to or as an alternative to the plug  300 ) to enhance the flow of cleaning fluid through the plug  300  and cap assembly  200  in a similar manner. For example, the closure member  208  may be modified to provide a discontinuity, such as a cut-out or recess, in the bearing surface  220  of the closure member  208  that prevents the closure member  208  from forming a seal with the plug  300  after the frangible connection  210  has been broken. 
     As will be appreciated, a plug  300  comprising a planar rim  304  and a closure member  208  comprising a planar bearing surface  220  may form a seal against each other in the event that the closure member  208  settles over the opening of the tubular member  302  of the plug  300 . Should the planar surfaces align and come into contact to form a seal around the perimeter of the rim  304 , the closure member  208  could prevent the egress of fluid from the capsule body  100  after the frangible connection  210  has been broken. 
     However, by providing one or more cut-outs or slots in either (or both) of the rim  304  or the bearing surface  220 , in the event that the closure member  208  settles against the tubular body  302  of the plug  300 , fluid contained in the capsule body  100  may still flow through the tubular body  302  of the plug  300  by way of the openings formed by the slots of cut-outs. 
     As shown in  FIG. 4 , the plug  300  may further comprise at least one barrier or beam  322  that extends across the distal opening of the tubular body  302 . The beam  322  may extend across the diameter of the distal opening, or multiple beams can extend across the opening. The beam is configured to allow the flow of fluid therepast, but prevent or restrict the insertion of an object (e.g. a finger) into the conduit formed by the tubular body  302 . This minimises the likelihood of the frangible connection  210  being broken inadvertently or improperly by way of an object passing through the tubular body  302 . 
     The Refill System 
     As will now be described with reference to  FIG. 5 , when assembled, the capsule body  100 , the cap assembly  200 , and the plug  300  can provide a system providing yet further advantages. 
       FIG. 5  shows an enlarged view of the distal end of the refill system. The neck  104  of the capsule body  100  is clearly shown, and the rim  108  that surrounds the opening in the neck  104 . The neck  104  of the capsule body  100  also comprises one or more threads  106  extending around the neck  104  (on an outer surface), which are configured to engage corresponding threads in the cap assembly  200 . 
     The cap assembly  200  is also clearly shown. The cap assembly  200  comprises the dual walled construction described above with reference to  FIGS. 3A and 3B . An inner surface of the outer wall  204  comprises one or more second screw threads  232  that are configured to engage the threads  106  on the capsule body  100 . 
     The cap assembly  200  is screwed onto the capsule body  100  such that the rim  108  of the neck  104  is disposed within the upstream void  214   a . Advantageously, the rim  108  of the neck  104  abuts the connecting wall  212  of the cap assembly  200 . By engaging the capsule body  100  with the cap assembly  200  such that the rim  108  of the capsule body  100  abuts the connecting wall of the cap assembly  200 , the neck  104  of the connecting wall  212  against flexing as the plug  300  bears against the closure member  208 . Moreover, by abutting the rim  108  of the capsule body  100  against the connecting wall  212  of the cap assembly  200 , additional security against leakage from the capsule body  100  can be provided. 
     The cap assembly  200  is further configured such that the upstream end of the inner wall  202  (which is optionally configured as a barrel shaped seal, as described above) is disposed within the neck  104  of the capsule body  100 . The inner wall  202  thus forms an additional seal with the neck  104  of the capsule body  100 . 
     The engagement between the plug  300  and the cap assembly  200  will now also be described with reference to  FIG. 5 . As shown in  FIG. 5 , the plug  300  is disposed within the cap assembly  200 . The plug  300  shown in  FIG. 5  is structurally similar to the plug  300  described with reference to  FIG. 4 . 
     As illustrated, the plug  300  is disposed within the cap assembly  200  such that the distal end of the inner wall  202  of the cap assembly  200  is disposed within the recess  308  formed between the tubular body  302  and the skirt wall  306 . During assembly, the ridge  314  on the plug  300  is pushed passed the corresponding ridge  216  on the inner wall  202  of the cap assembly  200 . The engagement of the ridges  216  and  314  may help to retain the plug  300  within the cap assembly  200  during transport and storage of the system  10 . 
     The one or more claws  320  of the plug  300  may also help to retain the plug  300  within the cap assembly  200  by engaging the threads  230  on the interior surface of the outer wall  204 . Preferably, at least two claws are provided to securely engage the thread(s)  230  on of the cap. 
     The combination of the plug  300  and the cap assembly  200  described herein may be configured to prevent the closure member  208  blocking the flow of fluid through the cap assembly  200  after the frangible connection  210  has been broken. 
     For example, as illustrated in the embodiment shown in  FIG. 5 , the inner wall  202  of the cap assembly  200  can be configured to have a first diameter downstream of the frangible connection  210  and a second, larger diameter upstream of the frangible connection  210 . To ensure that the closure member  208  is pushed or lifted into a position in which it cannot seal against the inner wall  202  of the cap assembly  200  after the frangible connection  210  has been broken, the plug  300  can be configured such that the rim or abutment surface  304  can be moved upstream past the point at which the frangible connection  210  joins the closure member  208  to the inner wall  202 . This can be achieved by ensuring that the maximum distance of travel of the plug  300  is not limited by the cap assembly  200  until the rim  204  has pushed the closure member  208  into the increased diameter portion of the conduit  203 . 
     In the example shown in  FIG. 5 , the maximum travel of the plug  300  towards the frangible connection  210  is the point at which the seal  318  on the skirt wall  306  abuts the connecting wall  212  of the cap assembly  200 . In the embodiment illustrated, the rim  304  of the tubular body  302  and the seal  318  terminate in the same transverse plane. To ensure that the travel of the plug  300  is not limited until after the closure member has been lifted away from the narrower part of the conduit  203 , the frangible connection  210  is positioned downstream of the connecting wall  212 . 
     Alternatively (or additionally), the rim or abutment surface  304  of the plug  300  can extend proximally beyond the sealing surface  318  of the skirt wall  306 . 
     The capsule body  100 , cap assembly  200 , and plug  300  can be made of any suitable material known in the art. For example, the capsule body  100 , cap assembly  200 , and the plug  300  may be made of polyethylene or polypropylene, and may be formed by injection moulding techniques. Advantageously, the capsule body  100  can be formed of polyethylene, whilst the cap assembly  200  and the plug  300  can be formed of polypropylene. 
     It will be appreciated that aspects of the present invention include embodiments in which the features described above are provided alone or in combination with other features described here. For example, the frangible connection described above can be provided in a refill system having a cap assembly that screws directly onto the neck of a refillable vessel. In such systems, the cap can be configured such that the rim of the refillable vessel bears directly on the closure member to break the frangible connection and allow concentrated cleaning fluid to flow through the cap assembly into the refillable vessel. 
     Moreover, the plug described herein may be provided in a cap assembly having a different sealing arrangement to the arranged described herein. For example, the cut-outs and slots in the plug assembly that prevent a closure member sealing against the opening in the plug can be employed in cap assemblies with different structures, and with different closure members. 
     While the invention has been described with reference to exemplary or preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular or preferred embodiments or preferred features disclosed, but that the invention will include all embodiments falling within the scope of the appended claims. 
     The invention also comprises systems according to the following clauses: 
     Clause 1. A plug ( 300 ) for use in a cap assembly of a refill capsule, the plug ( 300 ) comprising:
         a tubular body ( 302 ) with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim ( 304 ), and wherein the rim ( 304 ) further comprises at least first and second projections ( 307 ) extending in a proximal direction from the rim ( 304 ), wherein a proximal surface of the projections provides a proximal-facing abutment surface ( 305 ) for bearing against a bearing surface ( 220 ) of a frangible sealing component of a cap assembly;   wherein the proximal-facing abutment surface ( 305 ) extends in a plane that is orthogonal to a longitudinal axis (A) of the tubular body ( 302 );   a skirt extending around the tubular body ( 302 ), and comprising a tubular skirt wall ( 306 ) arranged coaxially with respect to the tubular body ( 302 ), the skirt wall ( 306 ) being spaced apart from the tubular body ( 302 ) in a radial direction to form a plug recess ( 308 ) between the skirt wall ( 306 ) and the tubular body ( 302 ),   wherein the plug ( 300 ) further comprises an outwardly extending flange ( 310 ) comprising a distal-facing abutment surface ( 312 ) for abutting a rim ( 406 ) of a refillable vessel ( 400 ), and   wherein the proximal-facing abutment surface ( 305 ) has at least two fold rotational symmetry with respect to the longitudinal axis (A).       

     Clause 2. The plug ( 300 ) according to any preceding Clause, wherein the free end of the skirt wall ( 306 ) further comprises a proximal sealing rim ( 318 ) for sealing against a sealing surface ( 212 ) of a cap assembly ( 200 ). 
     Clause 3. The plug ( 300 ) according to any preceding Clause, wherein the proximal sealing rim ( 318 ) tapers to a peak. 
     Clause 4. The plug ( 300 ) according to any preceding Clause, wherein the sealing peak ( 318 ) terminates in the same plane as the proximal abutment surface ( 305 ). 
     Clause 5. The plug ( 300 ) according to any preceding Clause, wherein the tubular body ( 302 ) further comprises at least one cut-out ( 316 ) or slot distal in a wall of the tubular body ( 302 ). 
     Clause 6. The plug ( 300 ) according to any preceding Clause, wherein the cut-out ( 316 ) extends in a distal direction from the rim to form a discontinuity in the rim ( 304 ) of the plug ( 300 ), the rim ( 304 ) preferably comprising two or more cut-outs, and preferably, two diametrically opposed cut outs ( 316 ). 
     Clause 7. The plug ( 300 ) according to any preceding Clause, wherein the tubular body ( 302 ) comprises a protrusion or ridge ( 314 ) extending around an outer surface of the tubular body ( 302 ). 
     Clause 8. The plug ( 300 ) according to any preceding Clause, wherein the free proximal end of the skirt wall ( 306 ) further comprises at least one claw ( 320 ) radially outwardly of the distal abutment surface ( 312 ). 
     Clause 9. The plug ( 300 ) according to any preceding Clause, wherein the at least one claw ( 320 ) curves away from the distal abutment surface ( 312 ) to provide a distal concave surface and a proximal convex surface. 
     Clause 10. The plug ( 300 ) according to any preceding Clause, wherein the at least one claw ( 320 ) comprises two claws, preferably three claws, and more preferable four or more claws ( 320 ). 
     Clause 11. A cap system for a refill capsule, the cap system comprising:
         the plug ( 300 ) of according to any preceding embodiment; and   a cap assembly ( 200 ) comprising:
           an inner wall ( 202 ) defining a conduit ( 203 ) through the cap assembly ( 200 ), the conduit ( 203 ) extending from an upstream end to a downstream end;   an outer wall ( 204 ) surrounding the inner wall ( 202 ) along at least a first portion of its length, wherein the outer wall ( 204 ) is spaced from the first portion of the inner wall ( 202 ) to define a circumferential void ( 214   b ) between the inner and outer walls ( 202 ,  204 ) extending from an open downstream end to a closed upstream end;   a connecting wall ( 212 ) extending between the inner and outer walls ( 202 ,  204 ) to prevent fluid flow through the void ( 214   b ), the connecting wall ( 212 ) forming the closed upstream end of the void ( 214   b );   wherein the cap assembly ( 200 ) further comprises a closure member ( 208 ) configured to seal the conduit ( 203 ), the closure member ( 208 ) comprising an upstream side ( 208   a ) and a downstream side ( 208   b ),   wherein the closure member ( 208 ) is sealed to the inner wall ( 202 ) with a peripheral frangible connection ( 210 ) located between proximal and distal ends of the conduit ( 203 ),   wherein the frangible connection ( 210 ) extends in a plane P, which is orthogonal to a longitudinal axis (A) of the conduit ( 203 ); and   
           wherein the plug ( 300 ) is disposed within the cap assembly ( 200 ) such that the outer wall ( 204 ) of the cap assembly ( 200 ) surrounds the plug ( 300 ), and the inner wall ( 202 ) of the cap assembly ( 200 ) extends into the plug recess ( 308 ), and   wherein the proximal abutment surface ( 304 ) of the plug ( 300 ) is aligned with and opposes the bearing surface ( 220 ) of the closure member ( 208 ).       

     Clause 12. The system according to any preceding Clause, wherein the frangible connection ( 210 ) is disposed between a first peripheral recess ( 222 ) formed between the inner wall ( 202 ) and a downstream side ( 208   b ) of the closure member ( 208 ), and a second peripheral recess ( 224 ) between the inner wall ( 202 ) and an upstream side ( 208   b ) of the closure member ( 208 ). 
     Clause 13. The system according to any preceding Clause, wherein the bearing surface ( 220 ) extends in a plane that is perpendicular to the longitudinal axis (A) of the conduit ( 203 ). 
     Clause 14. The system according to any preceding Clause, wherein the closure member ( 208 ) is conical or frustoconical, and extends from a base to a peak ( 218 ). 
     Clause 15. The system according to any preceding Clause wherein the closure member ( 208 ) is hollow, and open at the base, and preferably wherein the closure member ( 208 ) is oriented with the peak ( 218 ) in an upstream direction and the base in a downstream direction. 
     Clause 16. The system according to any preceding Clause, wherein the outer wall ( 204 ) comprises engagement means, e.g. a screw thread ( 230 ) on its inner surface, and wherein the claws ( 320 ) are configured to engage the engagement means ( 230 ). 
     Clause 17. The system according to any preceding Clause, wherein the inner wall ( 202 ) comprises a protrusion or ridge ( 216 ) extending radially inwardly from an inner surface of the inner wall ( 202 ). 
     Clause 18. A refill system ( 10 ) comprising the system according to any preceding Clause, wherein the refill system further comprises a capsule ( 100 ) for containing a concentrated cleaning product, wherein the capsule ( 100 ) is engaged with the cap assembly ( 200 ) and wherein an internal volume of the capsule ( 100 ) is in fluid communication with an upstream end of the conduit ( 203 ). 
     Clause 19. The refill system ( 10 ) according to any preceding Clause, wherein the capsule ( 100 ) comprises an opening surrounded by a rim ( 104 ), and wherein the rim ( 104 ) bears against the connecting wall ( 212 ) of the cap assembly ( 200 ). 
     Clause 20. The refill system ( 10 ) according to any preceding Clause, further comprising a shrink wrap cover extending around at least a portion of the capsule ( 100 ) and at least a portion of the cap assembly ( 200 ). 
     Clause 21. A cap assembly ( 200 ) for a refill capsule, the cap assembly comprising:
         an inner wall ( 202 ) defining a conduit ( 203 ) through the cap assembly ( 200 ), the conduit ( 203 ) extending from an upstream end to a downstream end;   an outer wall ( 204 ) surrounding the inner wall ( 202 ) along at least a first portion of its length, wherein the outer wall ( 204 ) is spaced from the first portion of the inner wall ( 202 ) to define a circumferential void ( 214 ) between the inner and outer walls ( 202 ,  204 );   a connecting wall ( 212 ) extending between the inner and outer walls ( 202 ,  204 ) to prevent fluid flow through the void ( 214 ) between the inner and outer walls ( 202 ,  204 );   wherein the cap assembly ( 200 ) further comprises a closure member ( 208 ) configured to seal the conduit ( 203 ), the closure member ( 208 ) comprising an upstream side ( 208   a ) and a downstream side ( 208   b ), and a bearing surface ( 220 ) on its downstream side;   wherein the closure member ( 208 ) is sealed to the inner wall ( 202 ) with a peripheral frangible connection ( 210 ) located between proximal and distal ends of the conduit ( 203 ),   wherein the peripheral frangible connection ( 210 ) extends in a plane P, that is preferably orthogonal to a longitudinal axis (A) of the conduit ( 203 );   wherein an inner surface of the inner wall ( 202 ) immediately upstream of the closure member ( 208 ) is off-set radially from an inner surface of the wall ( 202 ) immediately downstream of the closure member ( 208 ).       

     Clause 22. The cap assembly ( 200 ) according to any preceding Clause, wherein the bearing surface ( 220 ) extends perpendicular to the longitudinal axis (A) of the conduit ( 203 ). 
     Clause 23. The cap assembly ( 200 ) according to any preceding Clause, wherein the closure member ( 208 ) is hollow, and tapers from a downstream base ( 221 ) to an upstream peak ( 218 ). 
     Clause 24. The cap assembly ( 200 ) according to any preceding Clause, wherein the closure member ( 208 ) is open at the base. 
     Clause 25. The cap assembly ( 200 ) according to any preceding Clause, wherein the bearing surface ( 220 ) is adjacent to the frangible connection ( 210 ). 
     Clause 26. The cap assembly ( 200 ) according to any preceding Clause, wherein the conduit ( 203 ) has a first cross-sectional diameter at the upstream end and a second cross-sectional diameter at the downstream end, and wherein the first cross-sectional diameter is greater than the second cross-sectional diameter. 
     Clause 27. The cap assembly ( 200 ) according to any preceding Clause, wherein the void comprises a downstream void ( 214   b ) extending from an open downstream end and terminating in a closed end at the connecting wall ( 212 ). 
     Clause 28. The cap assembly ( 200 ) according to any preceding Clause, wherein the void comprises an upstream void ( 214   a ) extending from an open upstream end, and terminating in a closed end at the connection wall ( 214 ). 
     Clause 29. The cap assembly ( 200 ) according to any preceding Clause, wherein the void comprises an upstream void ( 214   a ) and a downstream void ( 214   b ), and wherein the upstream and downstream voids ( 214   a ,  214   b ) are separated from each other by the connecting wall ( 212 ). 
     Clause 30. The cap assembly ( 200 ) according to any preceding Clause, wherein the outer wall ( 204 ) downstream of the connection wall ( 212 ) comprises engagement means, e.g. a screw thread ( 230 ), configured to engage corresponding engagement means ( 404 ) on a refillable vessel ( 400 ). 
     Clause 31. The cap assembly ( 200 ) according to any preceding Clause, wherein the outer wall ( 204 ) upstream of the connecting wall ( 212 ) comprises engagement means, e.g. a screw thread ( 232 ), configured to engage corresponding engagement means ( 106 ) on a refill capsule ( 100 ). 
     Clause 32. The cap assembly ( 200 ) according to any preceding Clause, wherein the inner wall ( 202 ) comprises a protrusion or ridge ( 216 ) extending radially inwardly from an inner surface of the inner wall ( 202 ). 
     Clause 33. The cap assembly ( 200 ) according to any preceding Clause, wherein the cap assembly ( 200 ) comprises polypropylene. 
     Clause 34. A cap system comprising the cap assembly ( 200 ) according to any preceding embodiment, and further comprising a plug ( 300 ), wherein the plug ( 300 ) is movably mounted within the cap assembly ( 200 ) for movement in an axial direction, and wherein the plug ( 300 ) is configured to bear upon the bearing surface ( 220 ) of the closure member ( 208 ) to break the frangible connection ( 210 ). 
     Clause 35. The system according to any preceding Clause, wherein the plug ( 300 ) comprises:
         a tubular body ( 302 ) with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim ( 304 ) that provides an proximal abutment surface for bearing against the bearing surface ( 220 ) of the closure member ( 208 );   a skirt extending around the tubular body ( 302 ), and comprising a tubular skirt wall ( 306 ) arranged coaxially with respect to the tubular body ( 302 ), the skirt wall ( 306 ) being spaced apart from the tubular body ( 302 ) in a radial direction to form a plug recess ( 308 ) between the skirt wall ( 306 ) and the tubular body ( 302 ):   wherein the skirt wall ( 306 ) extends from a skirt distal end at which it is connected to the distal end of the tubular body ( 303 ), to a free proximal end,   wherein the free proximal end of the skirt comprises:   an outwardly extending flange ( 310 ) comprising a distal facing abutment surface ( 312 ) for abutting a rim ( 406 ) of a refillable vessel ( 400 ), and   wherein the plug ( 300 ) is disposed within the cap assembly ( 200 ) such that the downstream end of the inner wall ( 202 ) is disposed within the plug recess ( 308 ).       

     Clause 36. A refill system ( 10 ) comprising the cap system any preceding Clause, wherein the refill system further comprises a capsule body ( 100 ) for containing a concentrated refill fluid, wherein the capsule body ( 100 ) is engaged with the cap assembly ( 200 ) and wherein an internal volume of the capsule body ( 100 ) is in fluid communication with an upstream end of the conduit ( 203 ). 
     Clause 37. The refill system ( 10 ) according to any preceding Clause, wherein the capsule ( 100 ) comprises an opening surrounded by a rim ( 108 ), and wherein the rim ( 108 ) abuts the connecting wall ( 212 ) of the cap assembly ( 200 ). 
     Clause 38. The refill system ( 10 ) according to any preceding Clause, further comprising a shrink wrap cover extending around at least a portion of the capsule ( 100 ) and at least a portion of the cap assembly ( 200 ). 
     Clause 39. A cap assembly ( 200 ) for a refill capsule, the cap assembly comprising:
         an inner wall ( 202 ) defining a conduit ( 203 ) through the cap assembly ( 200 ), the conduit ( 203 ) extending from an upstream end to a downstream end;   an outer wall ( 204 ) surrounding the inner wall ( 202 ) along at least a first portion of its length, wherein the outer wall ( 204 ) is spaced from the first portion of the inner wall ( 202 ) to define a circumferential void ( 214   a ,  214   b ) between the inner and outer walls ( 202 ,  204 );   a connecting wall ( 212 ) extending between the inner and outer walls ( 202 ,  204 ) to prevent fluid flow through the void between the inner and outer walls ( 202 ,  204 );   wherein the cap assembly ( 200 ) further comprises a closure member ( 208 ) configured to seal the conduit ( 203 ), the closure member ( 208 ) comprising an upstream side ( 208   a ) and a downstream side ( 208   b ), and a bearing surface ( 220 ) on its downstream side;   wherein the closure member ( 208 ) is sealed to the inner wall ( 202 ) with a peripheral frangible connection ( 210 ) located between proximal and distal ends of the conduit ( 203 ),   wherein the peripheral frangible connection ( 210 ) extends in a plane P, which is orthogonal to a longitudinal axis (A) of the conduit ( 203 );   wherein the frangible connection is disposed between a first peripheral recess ( 222 ) formed between the inner wall ( 202 ) and the downstream side ( 208   b ) of the closure member ( 208 ), and a second peripheral recess ( 224 ) between the inner wall ( 202 ) and the upstream side ( 208   b ) of the closure member ( 208 ).       

     Clause 40. The cap assembly ( 200 ) according to any preceding Clause, wherein the bearing surface ( 220 ) extends perpendicular to the longitudinal axis (A) of the conduit ( 203 ). 
     Clause 41. The cap assembly ( 200 ) according to any preceding Clause, wherein the closure member ( 208 ) is tapered, e.g. conical or frustoconical, and extends from a base ( 220 ) to a peak ( 218 ). 
     Clause 42. The cap assembly ( 200 ) according to any preceding Clause, wherein the closure member ( 208 ) is hollow and open at the base. 
     Clause 43. The cap assembly ( 200 ) according to any preceding Clause, wherein the closure member ( 208 ) is oriented with the peak ( 218 ) in an upstream direction and the base in a downstream direction. 
     Clause 44. The cap assembly ( 200 ) according to any preceding Clause, wherein the bearing surface ( 220 ) is adjacent to the frangible connection ( 210 ). 
     Clause 45. The cap assembly ( 200 ) according to any preceding Clause, wherein the conduit ( 203 ) has a first cross-sectional diameter upstream of the frangible connection ( 210 ) and a second cross-sectional diameter at the downstream of the frangible connection ( 210 ), and wherein the first cross-sectional diameter is greater than the second cross-sectional diameter. 
     Clause 46. The cap assembly ( 200 ) according to any preceding Clause, wherein the circumferential void comprises a downstream void ( 214   b ) extending from an open downstream end and terminating in a closed end at the connecting wall ( 212 ). 
     Clause 47. The cap assembly ( 200 ) according to any preceding Clause, wherein the void comprises an upstream void ( 214   a ) extending from an open upstream end, and terminating in a closed end at the connection wall ( 214 ). 
     Clause 48. The cap assembly ( 200 ) according to any preceding Clause, wherein the void comprises an upstream void ( 214   a ) and a downstream void ( 214   b ), and wherein the upstream and downstream voids ( 214   a ,  214   b ) are separated from each other by the connecting wall ( 212 ). 
     Clause 49. The cap assembly ( 200 ) according to any preceding Clause, wherein the outer wall ( 204 ) downstream of the connection wall ( 212 ) comprises engagement means, e.g. a screw thread ( 230 ), configured to engage corresponding engagement means ( 404 ) on a refillable vessel ( 400 ). 
     Clause 50. The cap assembly ( 200 ) according to any preceding Clause, wherein the outer wall ( 204 ) upstream of the connecting wall ( 212 ) comprises engagement means, e.g. a screw thread ( 232 ), configured to engage corresponding engagement means ( 106 ) on a refill capsule ( 100 ). 
     Clause 51. The cap assembly ( 200 ) according to any preceding Clause, wherein the inner wall ( 202 ) comprises a protrusion or ridge ( 216 ) extending radially inwardly from an inner surface of the inner wall ( 202 ). 
     Clause 52. The cap assembly ( 200 ) according to any preceding Clause, wherein the cap assembly ( 200 ) comprises polypropylene. 
     Clause 53. A cap system comprising the cap assembly ( 200 ) according to any preceding Clause, and further comprising a plug ( 300 ), wherein the plug ( 300 ) is movably mounted within the cap assembly ( 200 ) for movement in an axial direction, and wherein the plug ( 300 ) is configured to bear upon the bearing surface ( 220 ) of the closure member ( 208 ) to break the frangible connection ( 210 ) as it is advanced in a proximal direction. 
     Clause 54. The system according to any preceding embodiment, wherein the plug ( 300 ) comprises:
         a tubular body ( 302 ) with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim ( 304 ) that provides an proximal-facing abutment surface for bearing against the bearing surface ( 220 ) of the closure member ( 208 );   a skirt extending around the tubular body ( 302 ), and comprising a tubular skirt wall ( 306 ) arranged coaxially with respect to the tubular body ( 302 ), the skirt wall ( 306 ) being spaced apart from the tubular body ( 302 ) in a radial direction to form a plug recess ( 308 ) between the skirt wall ( 306 ) and the tubular body ( 302 ),   wherein the skirt wall ( 306 ) extends from a skirt distal end at which it is connected to the distal end of the tubular body ( 303 ), to a free proximal end,   wherein the free proximal end of the skirt comprises:   an outwardly extending flange ( 310 ) comprising a distal facing abutment surface ( 312 ) for abutting a rim ( 406 ) of a refillable vessel ( 400 ), and   wherein the plug ( 300 ) is disposed within the cap assembly ( 200 ) such that the downstream end of the inner wall ( 202 ) is disposed within the plug recess ( 308 ).       

     Clause 55. A refill system ( 10 ) comprising the system according to any preceding Clause, wherein the refill system further comprises a capsule ( 100 ) for containing a concentrated refill fluid, wherein the capsule ( 100 ) is engaged with the cap assembly ( 200 ) and wherein an internal volume of the capsule ( 100 ) is in fluid communication with an upstream end of the conduit ( 203 ). 
     Clause 56. The refill system ( 10 ) according to any preceding Clause, wherein the capsule ( 100 ) comprises an opening surrounded by a rim ( 108 ), and wherein the rim ( 108 ) abuts the connecting wall ( 212 ) of the cap assembly ( 200 ). 
     Clause 57. The refill system ( 10 ) according to any preceding Clause, further comprising a shrink wrap cover extending around at least a portion of the capsule ( 100 ) and at least a portion of the cap assembly ( 200 ). 
     Clause 58. A plug ( 300 ) for use in a cap assembly of a refill capsule, the plug ( 300 ) comprising:
         a hollow tubular body ( 302 ) with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim ( 304 ) that provides a proximal abutment surface for bearing against a frangible sealing component of a cap assembly;   wherein the proximal abutment surface lies in a plane that is orthogonal to a longitudinal axis of the tubular body, and surface surrounds, in total, at least half of the open proximal end;   a skirt extending around the tubular body ( 302 ), and comprising a tubular skirt wall ( 306 ) arranged coaxially with respect to the tubular body ( 302 ), the skirt wall ( 306 ) being spaced apart from the tubular body ( 302 ) in a radial direction to form a plug recess ( 308 ) between the skirt wall ( 306 ) and the tubular body ( 302 ),   wherein the skirt wall ( 306 ) extends from a skirt distal end at which the skirt wall ( 306 ) is connected to the tubular body ( 302 ), to a free proximal end,   wherein the free proximal end of the skirt comprises:
           an outwardly extending flange ( 310 ) comprising a distal facing abutment surface ( 312 ) for abutting a rim ( 406 ) of a refillable vessel ( 400 ).   
               

     Clause 59. The plug ( 300 ) according to any preceding Clause, wherein the free end of the skirt wall ( 306 ) further comprises a proximal sealing rim ( 318 ) for sealing against a sealing surface ( 212 ) of a cap assembly ( 200 ). 
     Clause 60. The plug ( 300 ) according to any preceding Clause, wherein the proximal sealing rim ( 318 ) tapers to a peak. 
     Clause 61. The plug ( 300 ) according to any preceding Clause, wherein the sealing peak ( 318 ) terminates in the same plane as the rim ( 304 ). 
     Clause 62. The plug ( 300 ) according to any preceding Clause, wherein the tubular body ( 202 ) further comprises at least one cut-out ( 316 ) or slot to form a discontinuity in the first rim ( 304 ), preferably two or more cut-outs, and preferably, two diametrically opposed cut outs. 
     Clause 63. The plug ( 300 ) according to any preceding Clause, wherein the tubular body ( 302 ) comprises a protrusion or ridge ( 314 ) extending around an outer surface of the tubular body ( 302 ). 
     Clause 64. The plug ( 300 ) according to any preceding Clause, wherein the free proximal end of the skirt wall ( 306 ) further comprises at least one claw ( 320 ) radially outwardly of the distal abutment surface ( 312 ). 
     Clause 65. The plug ( 300 ) according to any preceding Clause, wherein the at least one claw ( 320 ) curves away from the distal abutment surface ( 312 ) to provide a distal concave surface and a proximal convex surface. 
     Clause 66. The plug ( 300 ) according to any preceding Clause, wherein the at least one claw ( 320 ) comprises two claws, preferably three claws, and more preferable four or more claws ( 320 ). 
     Clause 67. A cap system for a refill capsule, the cap system comprising: 
     the plug ( 300 ) of any preceding claim; and a cap assembly ( 200 ) comprising: an inner wall ( 202 ) defining a conduit ( 203 ) through the cap assembly ( 200 ), the conduit ( 203 ) extending from an upstream end to a downstream end; 
     an outer wall ( 204 ) surrounding the inner wall ( 202 ) along at least a first portion of its length, wherein the outer wall ( 204 ) is spaced from the first portion of the inner wall ( 202 ) to define a circumferential void ( 214   b ) between the inner and outer walls ( 202 ,  204 ) extending from an open downstream end to a closed upstream end; 
     a connecting wall ( 212 ) extending between the inner and outer walls ( 202 ,  204 ) to prevent fluid flow through the void ( 214   b ), the connecting wall ( 212 ) forming the closed upstream end of the void ( 214   b ); 
     wherein the cap assembly ( 200 ) further comprises a closure member ( 208 ) configured to seal the conduit ( 203 ), the closure member ( 208 ) comprising an upstream side ( 208   a ) and a downstream side ( 208   b ), 
     wherein the closure member ( 208 ) is sealed to the inner wall ( 202 ) with a peripheral frangible connection ( 210 ) located between proximal and distal ends of the conduit ( 203 ),
         wherein the frangible connection ( 210 ) extends in a plane P, which is orthogonal to a longitudinal axis (A) of the conduit ( 203 ); and   wherein the plug ( 300 ) is disposed within the cap assembly ( 200 ) such that the outer wall ( 204 ) of the cap assembly ( 200 ) surrounds the plug ( 300 ), and the inner wall ( 202 ) of the cap assembly ( 200 ) extends into the plug recess ( 308 ), and   wherein the proximal abutment surface ( 304 ) of the plug ( 300 ) is aligned with and opposes the bearing surface ( 220 ) of the closure member ( 208 ).       

     Clause 68. The system according to any preceding Clause, wherein the frangible connection ( 210 ) is disposed between a first peripheral recess ( 222 ) formed between the inner wall ( 202 ) and a downstream side ( 208   b ) of the closure member ( 208 ), and a second peripheral recess ( 224 ) between the inner wall ( 202 ) and an upstream side ( 208   b ) of the closure member ( 208 ). 
     Clause 69. The system according to any preceding Clause, wherein the bearing surface ( 220 ) extends in a plane that is perpendicular to the longitudinal axis (A) of the conduit ( 203 ). 
     Clause 70. The system according to any preceding Clause, wherein the closure member ( 208 ) is conical or frustoconical, and extends from a base to a peak ( 218 ). 
     Clause 71. The system according any preceding Clause, wherein the closure member ( 208 ) is hollow, and open at the base, and preferably wherein the closure member ( 208 ) is oriented with the peak ( 218 ) in an upstream direction and the base in a downstream direction. 
     Clause 72. The system according to any preceding Clause, wherein the outer wall ( 204 ) comprises engagement means, e.g. a screw thread ( 230 ) on its inner surface, and wherein the claws ( 320 ) are configured to engage the engagement means ( 230 ). 
     Clause 73. The system according to any preceding Clause, wherein the inner wall ( 202 ) comprises a protrusion or ridge ( 216 ) extending radially inwardly from an inner surface of the inner wall ( 202 ). 
     Clause 74. A refill system ( 10 ) comprising the system according to any preceding Clause, wherein the refill system further comprises a capsule ( 100 ) for containing a concentrated cleaning product, wherein the capsule ( 100 ) is engaged with the cap assembly ( 200 ) and wherein an internal volume of the capsule ( 100 ) is in fluid communication with an upstream end of the conduit ( 203 ). 
     Clause 75. The refill system ( 10 ) according to any preceding Clause, wherein the capsule ( 100 ) comprises an opening surrounded by a rim ( 104 ), and wherein the rim ( 104 ) bears against the connecting wall ( 212 ) of the cap assembly ( 200 ). 
     Clause 76. The refill system ( 10 ) according to any preceding Clause, further comprising a shrink wrap cover extending around at least a portion of the capsule ( 100 ) and at least a portion of the cap assembly ( 200 ). 
     Clause 77. A cap system comprising:
         a cap assembly ( 200 ) comprising:
           an inner wall ( 202 ) defining a conduit ( 203 ) through the cap assembly ( 200 ), the conduit ( 203 ) extending from an upstream end to a downstream end; and   an outer wall ( 204 ) surrounding the inner wall ( 202 ) and spaced from the inner wall ( 202 ) to define a circumferential void ( 214   a ,  214   b ) between the inner and outer walls ( 202 ,  204 );   wherein the cap assembly ( 200 ) further comprises a closure member ( 208 ) configured to seal the conduit ( 203 ), the closure member ( 208 ) comprising an upstream side ( 208   a ) and a downstream side ( 208   b ), and a bearing surface ( 220 ) on its downstream side ( 208   b );   wherein the closure member ( 208 ) is sealed to the inner wall ( 202 ) with a frangible connection ( 210 ) located between proximal and distal ends of the conduit ( 203 ),   wherein the frangible connection ( 210 ) extends in a first plane, which is orthogonal to a longitudinal axis (A) of the conduit ( 203 ); and   
           wherein the system further comprises a plug ( 300 ) comprising:
           a tubular body ( 302 ) with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim ( 304 ), and wherein the rim ( 304 ) further comprises a proximal abutment surface ( 305 ), extending in a second plane, for bearing against the bearing surface ( 220 ) of the closure member ( 208 ),   wherein the plug ( 300 ) further comprises an outwardly extending flange ( 310 ) comprising a distal-facing abutment surface ( 312 ) for abutting a rim ( 406 ) of a refillable vessel ( 400 ), and   wherein the plug ( 300 ) is movable between a first position, in which the proximal abutment surface ( 305 ) is located downstream of the frangible connection ( 210 ), and a second position in which the proximal abutment surface ( 305 ) is located upstream of the frangible connection ( 210 ), to thereby break the frangible connection ( 210 ), and   wherein abutment surface ( 305 ) is configured to bear against the bearing surface of the closure member as the plug moves from the first position to the second position such that a net force applied to the closure member is along the longitudinal axis A, and perpendicular to the first and second planes.   
               

     Clause 78. The cap system according to any preceding Clause, wherein the proximal abutment surface of the plug has at least two fold rotational symmetry with respect to the longitudinal axis A. 
     Clause 79. The cap system according to any preceding Clause, wherein the closure member ( 208 ) is hollow, and tapers from a downstream base ( 219 ) to an upstream peak ( 218 ). 
     Clause 80. The cap system according to any preceding Clause, wherein the base ( 219 ) comprises an opening, and wherein the bearing surface ( 220 ) surrounds the opening. 
     Clause 81. The cap system according to any preceding Clause, wherein the conduit ( 203 ) has a first cross-sectional diameter at the upstream end and a second cross-sectional diameter at the downstream end, and wherein the first cross-sectional diameter is greater than the second cross-sectional diameter. 
     Clause 82. The cap system according to any preceding Clause, wherein the plug further comprises a skirt wall ( 306 ) arranged coaxially with and extending around the tubular body ( 302 ), the skirt wall ( 306 ) being spaced apart from the tubular body ( 302 ) in a radial direction to form a plug recess ( 308 ) between the skirt wall ( 306 ) and the tubular body ( 302 ). 
     Clause 83. The cap system according to any preceding Clause, wherein the inner wall ( 202 ) comprises a protrusion or ridge ( 216 ) extending radially inwardly from an inner surface of the inner wall ( 202 ). 
     Clause 84. The cap system according to any preceding Clause t, wherein the outer wall of the cap assembly ( 200 ) comprises at least one screw thread on an internal surface of the outer wall, and wherein the skirt wall ( 306 ) of the plug ( 300 ) comprises at least one radially outwardly extending claw configured to engage the screw thread. 
     Clause 85. The cap system according to any preceding Clause, wherein the tubular body ( 302 ) comprises a protrusion or ridge extending radially outwardly from an outer surface of the tubular body ( 302 ). 
     Clause 86. The cap system according to any preceding Clause, wherein the abutment surface ( 305 ) is provided by one or more projections ( 307 ) extending proximally from the rim ( 304 ), the projections ( 307 ) terminating in a proximal surface extending in a plane (P) orthogonal to the longitudinal axis (A). 
     Clause 87. The cap system according to any preceding Clause, wherein the one or more projections ( 307 ) comprises a plurality of projections, equally spaced circumferentially around the rim ( 304 ). 
     Clause 88. The cap system according to any preceding Clause, wherein the abutment surface ( 305 ) is provided in the same plane as the rim ( 304 ). 
     Clause 89. The cap system according to any preceding Clause, wherein the rim ( 304 ) further comprises a cut-out ( 316 ) to form a discontinuity in the rim ( 304 ). 
     Clause 90. The cap system according to any preceding Clause, wherein the free proximal end of the skirt wall ( 306 ) further comprises at least one claw ( 320 ) extending radially outwardly from the skirt wall ( 306 ). 
     Clause 91. A refill system comprising the cap system of any preceding Clause, and further comprising: 
     a capsule body ( 100 ) for containing a concentrated cleaning product, wherein the capsule body ( 100 ) is engaged with the cap assembly ( 200 ) and wherein an internal volume ( 102 ) of the capsule body ( 100 ) is in fluid communication with an upstream end of the conduit ( 203 ). 
     Clause 92. The refill system according to any preceding Clause, further comprising a shrink wrap cover extending around at least a portion of the capsule body ( 100 ) and at least a portion of the cap assembly ( 200 ).