Abstract:
The invention pertains to a coupling for a liquid product packaged and dispensing assembly in which liquid is pumped from a container via the coupling through a tube to the point of use. The coupling has a first interconnectable member with a hollow post and a biased sleeve closing openings in the hollow post and a second interconnectable member with a hollow sheath and a biased piston closing an opening at the end of the sheath. The parts are configured so that, upon connection, the post unseats the piston while the sheath displaces the sleeve, thereby allowing liquid flow. The piston and the post are configured such that, upon connection, any fluid residing between them is displaced.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a coupling for interconnecting two hollow bodies, such as a container and a tube. 
     BACKGROUND OF THE INVENTION 
     Such a coupling is known from, e.g., European patent application 0 270 302, which describes a coupling for a liquid product packaging and dispensing assembly in which liquid is pumped from a container via the coupling through a tube to the point of use. The coupling has a first interconnectable member with a hollow post and a biased sleeve closing openings in the hollow post and a second interconnectable member with a hollow sheath and a biased piston closing an opening at the end of the sheath. The parts are configured so that, upon connection, the post unseats the piston while the sheath displaces the sleeve, thereby allowing liquid flow. 
     In one form, the container may be collapsible and is preferably situated inside a box for convenience during storage and transport. EP 0 270 302 mentions that a problem arising with such containers resides in that upon uncoupling the container from the tube, residues of the liquid which has been flowing through the coupling between them are apt to be spilled. This can be hazardous if the liquid is noxious, for example if the liquid is a very alkaline product such as industrial mechanical dishwashing liquid. 
     The coupling according to EP 270 302 indeed has the advantage that when it is disconnected both hollow bodies are sealed, and that it reduces spillage. However, it appeared that after disconnection liquid residues often stay behind on the end of the hollow post and/or on the piston head. These residues of course can be harmful to the persons working with the coupling. Further, the said residues solidify and over time form a crust on the piston head, which crust interferes with the tightness of the seal between the piston head and its seat. 
     The invention aims to provide a coupling of the above-mentioned type wherein the above-mentioned disadvantages are substantially obviated. 
     SUMMARY OF THE INVENTION 
     To this end, the coupling of the invention is characterised in that, upon connection of the members, the central area of the surface of the piston head initially contacts just the central area of the surface of the closed end of the post and the established contact area subsequently expands away from its centre thus displacing any fluid residing between the said surfaces. 
     It is preferred that the surface of the piston head is convex and the surface of the closed end of the post is concave, the radius of curvature of the piston head being smaller than the radius of curvature of the closed end of the post. Also, the piston head and/or the closed end of the post preferably is made of a flexible material. 
     If the piston is gas permeable and liquid impermeable, substantial underpressures in the container and malfunctions resulting from such underpressures, such as interruption of the flow, are avoided. 
     It will generally be desirable for the various parts to be co-axial, that is to say for the sheath and piston to be co-axial and for the sleeve and post to be co-axial and, moreover, for all four of them to lie on a common axis when coupled. 
     The invention will be further explained by reference to the drawings in which an embodiment of a coupling of the invention is schematically shown. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 shows a schematic cross-section of a coupling in accordance with the present invention, at the first stage of establishing a connection. 
     FIGS. 2 and 3 show a schematic cross-section of the coupling of FIG. 1, respectively at the second and third stage of establishing a connection. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a coupling for interconnecting two hollow bodies, such as a collapsible or rigid container and a tube. The coupling comprises a first interconnectable member  10  comprising a housing  11  and, fitted within the housing  11 , a hollow post  12  of which the interior communicates with the interior of the body to which the first member is attached. The post  12  has a closed end  13  and four openings  14  situated behind the closed end  13 . The post  12  is surrounded by a seal sleeve  15  which is biased by a spring  16  into a position covering the openings  14  to prevent outflow from the interior of the post  12 . The housing  11  is fitted with a cylindrical key  17 , which is provided with spiral grooves  18  on its inner side and which preferably has an inner diameter within a range from 40 to 80 mm. 
     FIG. 1 further shows a second interconnectable member  20  comprising a cap  21  having a cylindrical portion or wall  22  having an outer diameter smaller than the inner diameter of the key  17  and provided with two lugs or projections  23  on its outer side. The projections  23  are each located at a distance from the end of the cylindrical wall  22 , so that the second member  20  must be inserted into the first member over a certain length “L”, for example 13 mm, before the projections  23  arrive at the beginning of the corresponding grooves  18 . Said length “L” should preferably be in excess of 10 mm (and, for practical reasons, preferably be smaller than 25 mm). 
     Conversely, grooves can be provided on the outer side of the cap  21 . In that case, projections should be provided on the inner side of a cylindrical wall in the first member located at a certain distance from the end the said wall. 
     The pitch of the grooves  18  preferably exceeds the inner radius of the key  17 , so as to enable connection through limited rotation of the members  10 ,  20 . 
     A basket  24  is fitted in the under side of the cap  21 , which basket  24  comprises a piston  25  provided with a piston head  26 . The cap ( 21 ) and basket ( 24 ) form a hollow sheath. The piston  25 ,  26  is biased by means of a spring  27  into a position closing an aperture  28  in the cap  21 . The cap  21  comprises an annular raised edge  29 , which has an inner diameter substantially equal to or slightly larger than the outer diameter of the seal sleeve  15  of the first member  10 . A rubber ring  30  is fitted inside the annular edge  29 , which ring  30  has a height smaller than the height of the annular edge  29  and has an inner diameter substantially equal to or slightly larger than the outer diameter of the post  12  of the first member  10 . The ring  30  is provided with three annular ridges  31  on its inner surface, which will improve the close fit and, upon disconnection of the members  10 ,  20 , will wipe the post  12  as it is drawn through the ring  30 . 
     The piston head  26  is made of an flexible material, e.g. an elastomer, and its surface is convex. Further, the surface of the closed end  13  of the post  12  is concave, with the radius of curvature of the piston head  26  being selected smaller than the radius of curvature of the closed end  13  of the post  12 . Thus, any fluid present between the said surfaces is displaced during connection of members  10 ,  20  and fluid build-up or inclusion between the said surfaces is avoided. 
     Further, the piston  25  can be provided with a gas permeable and liquid impermeable membrane  41  so as to reduce underpressure in the container, which underpressure for instance results from the removal of liquid from the container. If such a membrane  41  is being used, the piston head  26  should be gas permeable. This can be achieved by simply providing a perforation or hole  42  in the piston head  26 . To improve gas communication between the membrane and the interior of the container, one or more openings  43  can be provided in the wall of the piston  25 . 
     Alternatively, the said membrane can be positioned in the cap  21 , thus enabling the reduction of underpressure even when the members  10 ,  20  are connected. 
     The membrane is preferably made of a microporous polymer film or foil, such as (bi-axially) stretched PTFE. 
     FIG. 1 shows the first stage of establishing the interconnection between the members  10  and  20 . The tolerance “T” between the wall  22  and the key  17  (i.e., half the difference between the inner diameter of the key  17  and the outer diameter of the wall  22 ) amounts to 0.5 mm and preferably lies within a range from to 0.3 to 1.0 mm, or, more generally, within a range from 0.5 to 2% of the inner diameter of the key  17 . Owing to this tolerance the cap can be easily inserted in the said key  17 . If the ratio of this tolerance “T” and the length “L” over which the second members must be inserted into the first member (i.e., “T/L”) is smaller than 0.10, the centering of the members with respect to each other will occur effectively and automatically and the risk of any of the projections  23  missing the beginning of the grooves  18  is avoided. Also, the post  12  and the piston  24  will also center automatically during the next stage of establishing the connection. 
     It is noted that the coupling may comprise two or more of the said projections and corresponding grooves, with at least two of the projections being different in shape and/or width and the corresponding grooves being matched accordingly. In an environment where several containers with different contents are being used, a mix-up of interconnectable members can be avoided by using different combinations of such different projections. The advantages of employing couplings with the ratio “T/L” in the fore-mentioned range are all the more noticeable when the number of (different) projections in a particular coupling increases. 
     After insertion and centering, the members  10  and  20  are, as shown in FIGS. 2 and 3, rotated with respect to one another, thus establishing contact between the seal sleeve  15  and the rubber ring  30 . During further rotation, the post  12  starts moving relative to the biased seal sleeve  15  because the latter is halted by the said ring  30 . 
     By this action the post  12  is now inserted in and surrounded by the ring  30  and the ring  30  is (slightly) compressed in the axial direction by the seal sleeve  15  as result of which the ring  30  begins to expand (slightly) in the radial direction towards the post  12 . In this stage, the friction between the post  12  and the ring  30  is still relatively low, so as to allow easy rotation of the members by an operator. Further , the central area of the surface of the piston head  26  will now contact the central area of the surface of the closed end  13  of the post  12 . The established contact area will subsequently expand away from its centre thus displacing any fluid residing between the said surfaces and contamination or crust formation by such fluid during or after disconnection of the coupling is avoided. 
     FIG. 3 shows the final stage of establishing the connection. The members  10 ,  20  have been rotated over a total angle of approximately 45° and the ring  30  is compressed to such an extend that it completely seals off the post  12 . The shape of the inner side of the ring  30  is now adapted to the shape of the post  12  and a close fit is obtained, even if the post  12  has been subjected to considerable wear after several years of use. 
     One of the members may be provided with a cam  32 , whereas the other member is provided with a thin plastic finger  33 . The cam  32  and finger  33  are positioned such that, during rotation of the members  10 ,  20 , the cam  32  passes the finger  33 , causing the finger  33  to bend and, substantially simultaneously to establishing an adequate connection, snap back into its original position so as to produce an audible sound, e.g. a distinct click, and warn the operator that no further rotation is required. 
     Alternatively, a finger can be provided in the key  17  at the end of at least one of the grooves  18 . Once the projections  23  reach the end of their respective grooves and the members  10 ,  20  are rotated slightly further, the projection or projections  23  will pass the finger or fingers. Thus, the finger or fingers are caused to bend and snap back in manner similar to that described above or, in case of a rigid finger, the projection is halted until it slips abruptly and collides with a stop positioned behind (as seen in the direction of movement of the projection) the finger. 
     In a further development of the invention, one of the two members includes or is connected to a chamber having means for detecting the presence of liquid in the chamber. 
     Preferably, this will be the member which is connected to a tube. This preferred feature is useful in systems handling a liquid product where it is necessary or desirable to detect that the container has emptied and then shut off a pump and/or sound an alarm calling for the container to be replaced. For detecting liquid in the chamber, the chamber may contain a Reed-element or spaced apart electrodes so that the liquid when present provides a conductive path between the electrodes. Whatever means are used to detect the presence of liquid, it may be desirable for the chamber to have a valve which is biased closed but arranged open to admit air to the chamber in the event that a pre-determined sub-atmospheric pressure is created within the chamber, for example if a pump drawing from the chamber is continuing to run when the supplying container is empty. 
     Although the form of the coupling according to the invention was described particularly for the application indicated above, it can also be employed in other applications where it would be advantageous to provide a coupling preventing leakage from two hollow bodies when these are disconnected and also minimising spillage during the said disconnection. 
     Thus, the invention is not restricted to the above described embodiment which can be varied in a number ways within the scope of the claims.