Abstract:
A relief valve for a liquid container, the valve comprising a substantially conical body extending into the container, and tapering inwardly away from an external wall of the container, at least one air inlet passage through the substantially conical body; and a flexible diaphragm extending over the conical body, being attached at its outer periphery around the substantially conical body and having a central opening surrounding the substantially conical body above the air inlet passage so as to seal the air inlet passage until the pressure within the container falls below a predetermined level.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a US National Stage of International Application No. PCT/GB2009/002672, filed 16 Nov. 2009, which claims the benefit of GB 0820978.5, filed 17 Nov. 2008, both herein fully incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention is directed to a relief valve.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     In particular, the invention is directed to a relief valve for a dispenser which dispenses liquid soap or the like. In such a dispenser, as the liquid is dispensed from the container, the pressure within the container drops. Once the pressure drops below a certain level, air would be drawn in through the liquid outlet, thereby interfering with the outlet flow.  
         [0004]     To prevent this, a separate pressure relief valve is provided to allow air into the container once the pressure within the container drops below a certain level.  
         [0005]     It is known to make such check valves from an elastomeric material with a slit. Such a valve is disclosed in WO 00/27746. The relief valve is intended to be used with the container in an inverted configuration. It is convenient for the relief valve to be in the cap of the container as the main part of the container is a simple molding without complex parts. However, in an inverted configuration, the weight of the liquid bears on the relief valve if it is within the cap. A slit elastomeric valve therefore has to be robust enough to withstand this, but, at the same time, must be able to open reliably when the pressure within the container drops below a certain level.  
         [0006]     The present invention aims to provide a pressure relief valve that can operate well in the cap of a container when the container is in an inverted configuration with the cap lowermost. At the same time, the valve should be simple in structure and suited to mass production.  
         [0007]     According to the present invention, there is provided a relief valve for a liquid container, the valve comprising a substantially conical body extending into the container, and tapering inwardly away from an external wall of the container, at least one air inlet passage through the substantially conical body; and a flexible diaphragm extending over the conical body, being attached at its outer periphery around the substantially conical body and having a central opening surrounding the substantially conical body above the air inlet passage so as to seal the air inlet passage until the pressure within the container falls below a predetermined level.  
         [0008]     The substantially conical body with the air inlet passage can simply be part of the molding of the underlying container. All that is then required is the flexible diaphragm which can readily be fitted in place.  
         [0009]     The conical body supports the diaphragm, and the weight of the liquid in the container only serves to enhance the seal under normal circumstances. Because of the underlying support, the diaphragm material can be made very thin as the material itself does not need to support the weight of the liquid without buckling. This thin diaphragm layer is then readily displaceable by the incoming air when the pressure within the container drops.  
         [0010]     The diaphragm may seal against the wall of the conical body itself. In this case, if the angle of inclination of the diaphragm is less than the angle of inclination of the conical body, this creates a natural biasing force to hold the diaphragm on the body.  
         [0011]     However, preferably, a cylindrical post is upstanding from the conical body and the central opening in the flexible diaphragm is a tight fit against the post to form the seal. This forms a more positive and more easily repeatable seal than sealing against the conical body itself.  
         [0012]     The relief valve is preferably applied to a container having a cap and a bottle, the container having an outlet in the cap and being arranged to dispense liquid from the container when in an inverted configuration, the relief valve being in the cap.  
         [0013]     Preferably, the liquid container has an outlet valve to control the flow of liquid out of the container. In this case, the flexible diaphragm is preferably integral with the outlet valve. If the outlet valve is resiliently biased by biasing elements these are also preferably integral with the diaphragm and the outlet valve. This simplifies the structure of the relief valve as the flexible diaphragm can effectively be molded into an existing component rather than being a separate component in its own right.  
         [0014]     As mentioned above, the relief valve is designed to prevent air from entering through a liquid outlet, as this disrupts the liquid flow and does not dispense the desired dose. A refill unit for dispensing a liquid designed to be used in a inverted configuration, with the outlet at its lowermost end, will typically comprise a bottle forming the main body of the unit with a cap at its lowermost end. In such a unit, it is desirable to place the outlet and the relief valve in the cap. This allows the bottle to be formed as a simple molding such as a blow molding, while the cap can be a more complex molding comprising a number of pieces. However, this brings the relief valve into close proximity to the outlet thereby reintroducing the possibility of incoming air being entrained in the outgoing liquid and disrupting the flow. This imposes limitations on the placing of the outlet and relief valve and also means that the diameter of the cap must be reasonably large in order to provide adequate separation between the outlet and the relief valve.  
         [0015]     According to a second aspect of the present invention, a refill unit for a dispenser has a cap at one end which, in use, is the lowermost end, an outlet in the cap with an outlet valve and associated valve seat for allowing selective dispensing of liquid from the unit, a pressure relief valve within the cap for allowing air to enter the unit if the internal pressure drops below a certain level, and a shroud in the form of a wall surrounding at least the side of the pressure relief valve facing the outlet and extending to a location above the valve seat when the unit is in its usual orientation with the cap at the lowermost end.  
         [0016]     The shroud prevents there being a direct path for the incoming air to the liquid outlet, thereby allowing the relief valve to be positioned closer to the outlet valve. This allows greater flexibility of the positioning of the relief valve and the outlet, and allows the cap to be reduced in size.  
         [0017]     There may be a single relief valve, or there may be more than one relief valve. If there is more than one relief valve, each pressure relief valve is associated with a shroud in the form of a wall surrounding at least the side of the pressure relief valve facing the outlet and extending to a location above the valve seat when the unit is in its usual orientation with the cap at the lowermost end.  
         [0018]     The pressure relief valve preferably comprises a resilient component which is deformable when the internal pressure drops below the certain level, the resilient component being attached to the cap by being sandwiched between the cap and a fixing plate, wherein the shroud is provided in the fixing plate.  
         [0019]     The resilient component is preferably integral with the outlet valve. The outlet valve may be biased by biasing elements, which may also be integral with the outlet valve and resilient component. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     A relief valve in accordance with the present invention will now be described with reference to the accompanying drawings, in which:  
         [0021]      FIG. 1  is a cross-section through a dispenser;  
         [0022]      FIG. 2  is a cut-away perspective view of the refill being introduced into the dispenser but not yet being engaged, the refill having a relief valve which is not in accordance with the present invention;  
         [0023]      FIG. 3  is a view similar to  FIG. 2  showing the refill in an intermediate position;  
         [0024]      FIG. 4  is a view similar to  FIGS. 3 and 4  showing the refill in its fully engaged position;  
         [0025]      FIG. 5  is a perspective view of the cap assembly prior to assembly;  
         [0026]      FIG. 6  is a perspective view of the cap assembly after assembly;  
         [0027]      FIG. 7  is a cross-section showing the engagement between the bottle neck and cap assembly;  
         [0028]      FIG. 8  is a perspective view of the cap with the frangible members intact;  
         [0029]      FIG. 9  is a view similar to  FIG. 7  after the bottle has been removed from the cap;  
         [0030]      FIG. 10  is a view similar to  FIG. 8  after the frangible members have broken off;  
         [0031]      FIG. 11  is an exploded perspective view of a cap of a second refill unit having a relief valve which is in accordance with the present invention;  
         [0032]      FIG. 12  is a view similar to  FIG. 11  showing the assembled cap;  
         [0033]      FIG. 13  is a cross-sectional view through the pressure relief valve of the second example; and  
         [0034]      FIG. 14  is a view similar to  FIG. 13  showing the pressure relief valve in an open configuration to allow the flow of air.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0035]     The dispenser is a hands-free dispenser which is generally suitable for domestic use. The dispenser is primarily intended to dispense liquid soap, but may also be used to dispense other liquid or semi-liquid products (ideally with a viscosity greater than water), such as hand cream, body lotion, moisturiser, face cream, shampoo, shower gel, foaming hand wash, shaving cream, washing up liquid, toothpaste or a sanitising agent such as alcohol gel.  
         [0036]     The dispenser comprises two main parts, namely a refill  1  and a base unit  2 . The refill  1  provides a reservoir of liquid to be dispensed and is fitted to the base unit  2  as set out below.  
         [0037]     The base has an interface  3  into which liquid is dispensed from the refill unit. The interface  3  is in fluid communication with a dispensing tube  4 . A pump  5  is selectively operable to pump a metered dose of the liquid along dispensing tube  4  and out of dispensing head  6 .  
         [0038]     The base has an infrared transmitter  7 A which transmits an infrared beam through a window  8  to a receiver  7 B to sense the presence of a user&#39;s hands in the vicinity of the dispenser. Control circuitry reacts to a signal from the proximity sensor to activate the pump. The illustrated sensor is a break beam sensor, but may also be a reflective sensor. Although an infrared sensor is shown, any known proximity sensor such as a capacitive sensor may be used.  
         [0039]     The device may be mains powered or battery powered. Alternatively, it may be a manually operated pump device in which a user pushes a lever to displace the product.  
         [0040]     The interface between the refill  1  and base unit  2  will now be described in greater detail with reference to FIGS.  2  to  10 .  
         [0041]     The base unit  2  comprises a cowling  10  which forms a cup-shaped housing surrounding a significant portion of the refill to protect and support it. A spigot  11  projects through the base of the cowling  10  and is sealed to the cowling  10  by an O-ring seal  12 . The spigot has a plurality of castellations  13  in its top surface. A second O-ring seal  14  surrounds the spigot  11  beneath the castellations  13 .  
         [0042]     The refill  1  comprises a bottle  20  to which a cap  21  is fixed. The bottle  20  has a neck  22  which fits over and seals with an annular flange  23  within the cap  21 . The cap  21  has an upwardly depending skirt  24  (when in the inverted orientation shown in the drawings) which forms the outer surface of the cap. Working inwardly from the skirt  24 , the next feature of the cap is an outer annular wall  25  which is generally co-axial with the skirt  24 .  
         [0043]     This is shown in detail in FIGS.  5  to  10 .  
         [0044]     The outer annular wall  25  consists of a pair of retaining members  26  and a pair of support members  27  which alternate with one another and each extend for approximately a quarter of the circle as shown in  FIGS. 5, 6 ,  8  and  10 . The profile of the support members  27  is as shown in  FIG. 2 . These members extend directly up from the lower wall of the cap, are parallel sided and have an inclined upper surface  28 . The profile of the retaining members  26  is shown in  FIGS. 7 and 9 . Unlike the support members  27 , these are not fixed to the wall of the cap. Instead, they are fixed at either end to the support members  27  by frangible members  29  as best shown in  FIGS. 6 and 8 . The retaining members  26  are parallel sided and have an inclined upper surface  35  as shown in  FIGS. 7 and 9 .  
         [0045]     As shown in  FIGS. 7 and 9 , the neck  22  of the bottle has an inclined outer surface  36  which is complimentary to the inclined surfaces  28  and  35  of the annular wall  25 . Behind the inclined outer surface  36  is a shoulder  37  which faces the main body of the bottle  20 . This inclined outer surface  36  and shoulder  37  is only present in the vicinity of the retaining members  26  and not in the vicinity of the support members  27 . Adjacent to the support members  27 , the neck  22  has a parallel sided configuration as shown in  FIG. 2 .  
         [0046]     In order to insert the bottle  20  into the cap  21 , the bottle  20  is pushed down with its neck fitting over the annular flange  23 . The inclined outer surface  36  of the bottle co-operates with the inclined surfaces  28 ,  35  to displace the retaining members  26  radially outwardly until the shoulder  37  snaps into place behind the retaining members  26  as shown in  FIG. 7 . When the bottle  20  is pulled off of the cap  21 , the shoulders  37  bear against the retaining members  26 , thereby breaking frangible members  29  so that the retaining members  26  become detached from the cap  21  as shown in  FIGS. 9 and 10 . Once this has happened, it is no longer possible to retain the cap on a bottle, thereby preventing subsequent use of the refill  1 .  
         [0047]     It should be noted that it is not necessary for both of the retaining members  26  to become fully detached from the lid. It is possible that only one of these becomes detached, or that one or both are simply displaced to a location at which they can no longer engage with the neck of the bottle.  
         [0048]     Returning now to FIGS.  2  to  4 , the liquid outlet and associated valve will now be described.  
         [0049]     The liquid outlet from the reservoir is provided by an annular wall  30  surrounding a central opening  31 . At the top of the annular wall  30  is an inclined surface  32  (see  FIG. 4 ) which provides a valve seat for outlet valve element  33 . This is shown in the form of a U-shape cup-like member, but may equally be a solid member or a hollow ball-like member. The outlet valve element  33  is biased into its closed position by a plurality of biasing elements  34 . These are attached at their upper end towards the top of the valve element  33  and are attached at their lower ends at a location radially outward of the annular wall  30  and below the top of the annular wall  30 . They are preferably formed integrally with the valve element  33 .  
         [0050]     As shown in FIGS.  2  to  4 , when the refill  1  is lowered into the base unit  2 , the spigot  11  engages with the lower surface of the valve element  33  as shown in  FIG. 3 . Further downward movement of the refill causes the valve element  33  to be lifted from its seat, and also brings the O-ring  14  into sealing engagement with the annular wall  30 . The valve element  33  is lifted to the position shown in  FIG. 4 . In this position, liquid in the bottle  20  can flow around the biasing elements  34 , and enter the spigot via the castellations  13  and hence flow into the base unit  2 . Liquid is prevented from escaping between the spigot  11  and annular wall  30  by the O-ring seal  14 . This arrangement offers a simple and mess-free way for a consumer to insert a refill regardless of the fill level of the refill.  
         [0051]     In order to remove a refill, the consumer lifts it out of the base whereupon the biasing elements  34  cause the valve element  33  to return to the seat  32 . During this movement, the seal between the spigot  11  and annular wall  30  is maintained by the O-ring seal  14 . A spent refill is then replaced by a new one following the above procedure.  
         [0052]     The cap is provided with a pair of pressure relief valves  40 . Each is formed by an annular boss  41  integral with the cap  21 . A pressure relief valve element  42  is seated on the top of the annular boss  41  and is biased in place by a pair of biasing elements  43  (as shown, for example, in  FIG. 5 ). The biasing force is such that, under normal conditions, the pressure relief valve element  42  forms an air tight seal on the boss  41 . However, when the pressure within the bottle  20  drops below a certain level, the pressure differential across the relief valve element  42  is sufficient to overcome the force exerted by biasing elements  43  and to allow air into the bottle  20 . This reduces the pressure differential thereby restoring the air tight seal without leakage of fluid.  
         [0053]     Each pressure relief valve  40  is surrounded by an annular barrier  44  which extends axially to a level axially above the level of the top of the annular wall  30 . Thus, when the valve element  33  is open, any air entering the relief valve  40  will not become entrained in the outgoing liquid stream. In practice, this means that the relief valve can be placed closer to the outlet, thereby resulting in a more compact cap. Although two relief valves are shown, a single valve, or more than two valves could be provided if necessary.  
         [0054]     The manner in which the cap is assembled is illustrated in  FIGS. 5 and 6 .  
         [0055]     The assembly is a three-part structure consisting of the cap  21 , a valve plate  45  and a fixing plate  46 . The cap has a number of moulded features including the annular flange  23 , annular wall  25  and annular bosses  41 . In addition, the cap  21  has a plurality of fixing posts  47 .  
         [0056]     The valve plate  45  is an elastomeric material and is integrally formed with the valve element  33 , biasing elements  34 , relief valve element  42  and biasing elements  43 . The valve plate has a plurality of locating holes  48  which correspond to the fixing posts  47 .  
         [0057]     The fixing plate  46  is made of a rigid plastics material and is integrally formed with the annular barrier  44 . As with the valve plate  45 , the fixing plate  46  is also provided with a plurality of locating holes  49  which correspond to the fixing posts  47 .  
         [0058]     To assemble the cap, the three components are placed on top of one another as shown in  FIG. 6  with the fixing posts entering the locating holes to ensure that the components are correctly aligned. Heat or adhesive is then applied to the top of the fixing posts  47  to secure the fixing posts to the fixing plate  46 . The elastomeric valve plate  45  is thereby sandwiched between the cap  21  and fixing plate  46  which holds the valve elements  33  and  42  in position.  
         [0059]     A second example of a cap for a refill unit will now be described with reference to FIGS.  11  to  14 .  
         [0060]     The structure of the outlet valve element  33  in the second example is essentially the same as the first example, and will not be described again in relation to the second example.  
         [0061]     As can be seen from  FIG. 11 , the cap  21  is integrally molded with a number of features, such as the annular walls  25  and  30  and a conical part  50  of the pressure relief valve which will be described below. A resilient lip  53  (described in more detail below) for the pressure relief valve is provided integrally molded with the valve plate  45 . The fixing plate  46  is also provided with a shield  57  for the relief valve. This is equivalent to the barrier  44  in  FIG. 2 , but only extends around the side of the relief valve facing the outlet valve element  33 . The barrier  44  and shield  57  could be used interchangeably in the two examples.  
         [0062]     The cap assembly is assembled in the same manner as in the first example.  
         [0063]     The pressure relief valve  60  is illustrated in  FIGS. 13 and 14 .  
         [0064]     The valve has the conical part  50  which is an integral part of the cap  21  as mentioned above. At the top of the conical part  50  is a cylindrical post  61 . The resilient lip  53  is effectively a hollow frustoconical extension of the valve plate  52  of resilient material which extends along the conical part  50  from which it diverges slightly and is a tight fit against the post  61 . At least one air inlet  62  (also shown in  FIG. 11 ) passes through the wall of the conical part  50  and is normally covered by the resilient lip  53  as shown in  FIG. 11 . When the pressure in the bottle  20  falls as liquid is emptied the pressure differential across the resilient lip  53  will eventually become sufficient to displace the lip  53  to a sufficient degree to allow air A into the bottle  20  as shown by the arrows in  FIG. 8 . It should be noted that the degree to which the resilient lip  53  lifts from the conical element  50  has been exaggerated in  FIG. 8  and that, in practice, this will be almost imperceptible.  
         [0065]     Instead of sealing against the post, the resilient lip  53  may seal against the conical part  50 . In this case, the lip will not diverge from the conical part as shown. Instead, it would actually have an angle of incline less than the angle of the conical part  50  so as to be naturally biased onto the conical part.