Abstract:
A container for flowable substances includes a rigid, concave lower part having an outlet and an upper part including of a convex flexible film that is mirror-inverted with respect to the inner contour of the lower part. The upper and lower parts may be in the shape of hemispheres. The upper part is surrounded by a housing body which is tightly connected with the lower part and may be connected to a pressure source for emptying the container. In the emptied condition of the container, the film lies flush at the inner contour of the lower part of the container. For emptying, air pressure is applied to the upper part of the container. The outlet is provided with a closure in the shape of a disc which is rotatable about an axis offset from the opening of the outlet and has a passage for inserting a dispensing nipple.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This applications claims the benefit of priority to International Patent Application No. PCT/EP2009/053010 filed 13 Mar. 2009, which further claims the benefit of priority to German Patent Application No. 102008014773.7 filed 18 Mar. 2009, the entire contents of which are incorporated herein by reference. 
     
    
     DESCRIPTION OF THE PRIOR ART  
       [0002]    In metering flowable substances (e.g., adhesives, sealing and moulding materials) in electronics applications, in dentistry or in the general joining technology, it is of crucial significance that the substrate is applied absolutely free of bubbles. Specifically in an automatic production process, where minute quantities of a substance are applied on a substrate, air bubbles existing in the adhesive result in defective parts, i.e., rejects. 
         [0003]    In addition to the necessity of having all parts checked and faulty items sorted out, the occurrence of bubbles usually requires the entire line to be stopped and cleaned in a time-consuming way. The smaller the metered quantities the more rejects are produced when bubbles occur. 
         [0004]    Expensive adhesives and sealants and dental moulding materials are often offered to customers in commercially available rigid disposable cartridges as primary containers. Such cartridges are emptied by means of a piston which is advanced either mechanically or by compressed air. Experience teaches that cartridges which were filled and sealed in a bubble-free manner arrive at the customer full of bubbles. 
         [0005]    This is explained as follows: Many one-component adhesives must be cooled or deep-frozen during their entire storage time to prevent premature curing. At temperatures below room temperature, the difference in thermal expansion coefficients causes the liquid to shrink more than the rigid plastics material of the primary container. At low temperatures, the liquid substance will turn into a solid block which partly separates from the cartridge wall. This process creates a vacuum within the cartridge chamber, which will suck air into the cartridge through the friction-fitted, immobile closure piston and, possibly, also through the front closure. When the content of the cartridge is re-melted, air bubbles will be found throughout the liquid substance. When the cartridge is frozen and re-melted several times, the gradually retreating closure piston will each time draw more and more air into the chamber. 
         [0006]    The same action is observed with substances which do not require deep-freezing. If an adhesive is filled in a vessel at room temperature it will expand during storage at a higher temperature (e.g., in summer). It will then push back the friction-fitted but movable closure plug. When subsequently cooled down to room temperature, the adhesive will shrink while the closure plug will be retained by friction in its withdrawn position. This creates a vacuum that will draw air into the chamber past the piston. If this cartridge is shipped by air cargo, the temperature change occurring at every starting and landing will cause the closure plug to move backward by a noticeable distance. 
         [0007]    As a result, it must be assumed that cartridges originally filled in an absolutely bubble-free manner, after storage and transport are not free from bubbles when available to the user, and that serious problem are encountered when these cartridges are used in production. 
         [0008]    An originally bubble-free viscous liquid can be full of bubbles if an open package (such as an open bottle or a cartridge without a piston) is exposed over an extended period of time to pressurized air for metering. Over the time, an increasing portion of the pressurized gas will dissolve in the substance. When this substance, upon leaving the metering valve, is exposed to the normal atmospheric pressure, the dissolved gas will expand and many small air bubbles will be found in the previously bubble-free substance. 
         [0009]    The same phenomenon is observed with a filled cartridge which has a piston and is emptied by means of pressurized air. If there is a leak between the advancing piston and the cartridge wall, pressurized air will pass the piston to reach the liquid and over the time dissolve in the material. 
         [0010]    There may be ways to achieve a permanently save freedom of bubbles in a flowable substance contained in a metering container even under changing temperatures if the rigid wall of a cartridge is replaced by a flexible film. In accordance with, e.g., DE 103 11 080 A1, the flowable substance is still contained in a conventional rigid cartridge; however, the closure piston is made of a solid outer ring with the piston head consisting of a flexible film. Changes in the volume of the substance due to temperature are taken up by the flexible film without any movement of the piston. It is a disadvantage of this solution that, when emptied by means of pressurized air, air will enter the filling substance, passing between the piston ring and the cartridge wall. On the other hand, when the filling substance is pressed out mechanically, high pressure may push the substance rearward past the piston, which causes contamination and loss of substance. 
         [0011]    Commercially available packages for flowable substances, such as dental substances, adhesives and sealing materials, are thin composite films which are closed by metallic clips at the front and rear ends; compare EP 0 541 972 A1, DE 91 03 038 U1, EP 0 787 655 A1, DE 43 35 970 A1. The filling is done in a bubble-free manner using a conventional “sausage stuffing” equipment. 
         [0012]    To ensure precise and clean emptying, these cylindrical tubular bags are provided at one end with a dispensing port which is usually slid onto the bag and glued thereto. For emptying, the film is mechanically cut within the area of the dispensing port. 
         [0013]    This type of film container has two essential disadvantages. 
         [0014]    It has been found that the metallic end closures are never tight with respect to thin flowing materials or components. This is due to the fact that the composite film, which has been formed into the hose, must be reduced from a large diameter to a very small diameter. The folds, which are thus necessarily created, permit small amounts of liquid to escape even when very strong closure clips are used. Over an extended storage time, low-viscosity components of the filling substance escape by capillary action and contaminate the whole bag. To protect the packaging and the user&#39;s hand during unpacking, film containers of this type are preferably shipped in plastic bags. As another disadvantage, the composition of the originally filled material changes due to the escape of the low-viscosity component. 
         [0015]    The escape of a liquid component at the leaky locations of this film bag is increased when the container is emptied by a dispensing device. In this case, high dispensing forces are exerted on the film bag, and the liquid dispensed under such pressure will contaminate the dispensing device. 
         [0016]    The second essential disadvantage of this film container with respect to bubble-free metering resides in the fact that air is trapped in the folds between the film folded at the container end and the dispensing port glued thereto, which air cannot be removed. When a film bag is automatically perforated by means of a spike (EP 0 787 655 A1), a large volume of air further exists between the film bag and the end of the dispensing port. When the film container is emptied, this air will escape, driven by the dispensing forces, at unpredictable times in the form of air bubbles and produce waste. 
         [0017]    Further, similar film containers are shown in JP 07 171 461 A and EP 1 331 174 A1. 
         [0018]    The commercially available film containers have, as a common feature, a cylindrical film tube which is usually folded and welded into a hose. Dispensing is done by either pressurized air or a mechanically advanced piston. To prevent the thin film of the container or the welded seam from tearing under high dispensing pressures, the film bag is placed in a stable cylindrical sleeve. The inner diameter of the sleeve and the outer diameter of the film bag are to be matched very precisely. If the film hose is too large, it cannot be moved into the sleeve, whereas if it is too small, the film will be ruptured when emptied by pressure. 
         [0019]    When the cartridge is emptied, the internal pressure generated will strongly press the film hose of the container against the wall of the sleeve. When emptying the cartridge, the film is axially moved along the sleeve wall whereby the film is folded in an uncontrolled manner. This means that high frictional forces are generated during emptying, which counteract the emptying force. 
         [0020]    These frictional forces depend, on the one hand, on the viscosity of the filling material, the emptying force, the amount of overlap of the welded film and the difference between the outer diameter of the film bag and the inner diameter of the cartridge. They are further strongly dependent on the emptying process proper. For instance, they are small when the film bag starts to collapse, while they rise during the emptying process and increase extremely at the end of the emptying process. 
         [0021]    If the cartridge is emptied by means of a constant air pressure, the metered amounts dispensed over a defined unit of time become very different due to the frictional effects mentioned above. For this reason, such a device is principally not useful for most metering jobs. Even with a mechanical advancement, strong variations of the amounts being dispensed must be expected. 
         [0022]    There are further disadvantages in dispensing residual amounts. Due to the irregular formation of folds in the film during the emptying process, closed pockets will form and take up filling material which cannot be pressed out. 
         [0023]    U.S. Pat. No. 4,282,986 dicloses a container for flowable substances, which comprises a rigid concave lower part provided with an outlet and an upper part consisting of a flexible film having a convex shape essentially mirror-inverted with respect to the inner contour of the lower part. This is specifically a container for drugs which permits simple handling also by older patients. It is not concerned with the problem of avoiding bubbles as explained above. 
       SUMMARY OF THE INVENTION 
       [0024]    It is an object of the invention to provide a metering container for flowable substances, a device for emptying such a container and methods of filling and emptying the container, wherein the substance is assured to be free of bubbles during storage and shipping even under greatly changing temperatures and pressures and during emptying and changing the container. 
         [0025]    It is also an object of the invention that uniformly metered amounts may be dispensed when a uniform dispensing pressure is applied over a predetermined unit of time. This uniformity of the metered amount being dispensed should be maintained throughout the metering process from the full container to the almost empty container. 
         [0026]    To meet these objects a container for flowable substances comprises a rigid concave lower container portion provided with an outlet and an upper container portion formed by a flexible film having a convex shape essentially mirror-inverted with respect to the inner contour of the lower container portion, the outlet including a closure having a disc rotatable about an axis offset from an opening of the outlet, and a passage for receiving a dispensing nipple. 
         [0027]    A device for emptying such a container comprises a vessel for receiving the container, a dispensing nipple adapted to be inserted in the passage of the closure, and means for creating pressure between the dispensing nipple and the container. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    In the drawings, 
           [0029]      FIG. 1  is a longitudinal section through the main portion of a filled metering container for explaining the principle underlying the invention; 
           [0030]      FIG. 2  is a section similar to  FIG. 1  through the container prior to being filled; 
           [0031]      FIG. 3  is a section similar to  FIG. 1  through the container including a pressure vessel; 
           [0032]      FIG. 4  is a partial section through the lower part of the container in a non-filled condition; 
           [0033]      FIG. 5  is a partial section similar to  FIG. 4  through the lower part of the container with interrupted grooves; 
           [0034]      FIG. 6  is a section through the film, which is deep-drawn at a plurality of locations near the outlet; 
           [0035]      FIG. 7  shows the lower part of the container with filling level detectors; 
           [0036]      FIG. 8  is a section through the lower part of the container with a closure in the closed position; 
           [0037]      FIG. 9  is a section through the lower part of the container showing the closure in the open position; 
           [0038]      FIG. 10  is a schematic representation of an emptying device; 
           [0039]      FIG. 11  is a section through a different embodiment of the lower part of the container having a closure diaphragm; 
           [0040]      FIG. 12  is a representation corresponding to  FIG. 11 , showing the closure diaphragm opened; and 
           [0041]      FIG. 13  is a section through a further embodiment of the lower part of the container having a different container outlet. 
       
    
    
     DETAILED DESCRIPTION 
       [0042]      FIG. 1  shows the body of a metering container  14  without a pressure tank and without a closure. The lower part  10  of the container  14  consists of a rigid injection-moulded part of synthetic resin and may have a rotationally symmetrical (e.g., spherical) inner contour. The lower end may be provided with an outlet  13 , which is only schematically shown in this figure, and the upper end may have a peripheral flange  12 . 
         [0043]    The upper part of the container  14  consists of a thin film  11  which may have a thickness of, e.g., between 50 μm and 500 μm, and may be shaped substantially mirror-inverted with respect to the inner contour of the lower part  10 . The film  11  may be made of a material that is impermeable to the filling substance, e.g., a plastic film of PE or PET or a plastic composite film laminated with aluminium. The shape of the film  11  can be obtained by deep-drawing. 
         [0044]    There may be substances which during storage require a certain amount of oxygen or another gas to prevent them from curing prematurely. Since such dissolved gas is consumed during storage, oxygen must be continuously supplied from the ambient air. If the film  11  is oxygen permeable, the supply of oxygen may take place continuously, uniformly and, specifically, across a large area. 
         [0045]    The upper and lower parts may be hermetically sealed to one another by gluing or welding in the area of their largest diameter at the flange  12 . If this device is filled through its inlet or outlet in a bubble-free manner and closed in an airtight fashion, the result is a metering container that is hermetically sealed against the ambience. Once filled and sealed, no air or foreign material can enter this container  14  during storage or shipment and no filling material can escape from the container  14 . Volumetric changes of the filling substance caused by even extreme changes in temperature may be completely compensated by the flexibility of the thin film  11  so that no over pressure or vacuum will be generated within the container  14  itself. 
         [0046]      FIG. 2  shows the container  14  prior to be filled with a liquid. The flexible film  11  is folded inward to lie flush at the inner contour of the lower part  10 . Any residual amount of air at the outlet  13  is sucked by applying a vacuum. Subsequently, the liquid is pressed into the container  14  under vacuum. 
         [0047]      FIG. 3  shows the container  14  with a cylindrical body  18  integrally formed with the flange  12  or tightly connected thereto, the upper end of the body  18  being closed by a double-walled cover  19 . The body  18  and the cover  19  serve to protect the flexible film  11  against mechanical damages and incident light. The cover  19  is made of two disc-shaped walls  21  interconnected by a number of spacers  20  and having none-aligned pressure equalising holes  22 . 
         [0048]    To fill the container  14  in a bubble-free manner, the film  11  is pressed or sucked to the inner contour of the rigid lower part  10 . The residual volume is exposed to vacuum through the outlet  13 , and the container  14  is subsequently filled from below. 
         [0049]    For emptying, the container  14  is connected to a pressure chamber or inserted into the same (as explained below with reference to  FIG. 10 ), the pressure chamber sealingly surrounding at least the upper most part of the body  18 . The pressurized air flowing through the holes  22  is uniformly applied to the film  11  and presses the liquid uniformly through the outlet  13  from the container  14 . When the body  18  and the lower part  10  of the container may be thin-walled to save weight and cost, it is useful to form the pressure chamber in such a way that, during emptying, it surrounds the entire container  14  and the body  18  with the exception of the outlet  13 . 
         [0050]    Metered emptying of the container  14  is achieved by a uniform application of pressure to the film  11  (e.g., using pressurized air). The tight peripheral sealing at the flange  12  prevents air from entering the container  14 . The film  11  itself will be deformed very uniformly throughout the emptying process without building up any resistance because there is no wall friction and because the film is not folded by an advance movement. 
         [0051]    If pressure is applied to the film  11  via a hydraulic liquid, the container  14  is also suitable for volumetric metering. 
         [0052]    When the emptying process terminates, the film  11  will lie flush at the inner contour of the lower part  10  of the container without folds. Since the film  11  is deformed without any forces throughout the emptying process, the metered amounts dispensed over a fixed unit of time under constant air pressure will be constant. 
         [0053]      FIG. 4  shows the lower part  10  of the container  14  with grooves  25  radially extending toward the outlet  13  of the container  14 . The grooves ensure that the amount of liquid dispensed over time remains constant until the container is completely empty. Protruding webs  26  may be provided near the outlet  13  to prevent the film  11  from impeding or inhibiting the complete emptying by blocking the opening of the outlet  13  near the end of the emptying process. The webs  26  hold the film  11  at a distance from the opening of the outlet  13  to make sure that the liquid can freely flow out until the container  14  is completely empty. 
         [0054]    In an adhesive processing production line, information about the remaining quantity available is required particularly near the end of the container emptying process. Only this makes it possible to change containers in proper time and avoid incorrect metering. With conventional cartridges, this can be done by, e.g., detecting the position of a closure piston. This is not readily available with the present container  14  because its rear end is closed by the flexible film  11  rather than by a rigid piston. This film is irregularly deformed during emptying and may be therefore not readily available as a filling level indicator. However, toward the end of the emptying process, the film  11  will lie flush at the inner contour of the lower part  10 . 
         [0055]    In the embodiment shown in  FIG. 5 , some of the webs  26  may be interrupted near the outlet  13  (not shown in this figure). Inductive or capacitive sensors  41  may be provided in these areas  27  at the outer side of the lower part  10 , the sensor signals being supplied to an evaluation circuit (not shown). 
         [0056]    As shown in  FIG. 6 , the film  11  may be provided with recesses  28  in the areas  27  of the lower part  10  of the container with metallic sheets  40 , which may be circular, being placed in the recesses. 
         [0057]      FIG. 7  shows the lower part  10  in the emptied state in which the film  11  contacts the inner wall of the lower part  10 . In this condition, the metallic sheets  40  may be detected by the sensors  41 . 
         [0058]    In this way, contact of the film  11  may be detected in the nearest environment of the container outlet  13  thereby providing an indication of the residual amount of adhesive. Since the film  11  will not uniformly contact the container wall at all locations, the position of the film may be detected at a plurality (e.g., four) peripheral locations. The evaluation circuit can operate in such a way that it provides a warning for the change of containers when the film  11  contacts one of these locations. If it contacts, for instance, three locations, the system may switch-off the entire line to avoid metering errors. 
         [0059]    If it is intended to maintain the substance free of bubbles throughout the metering process until the substance may be dispensed from downstream metering valve, it may be necessary to ensure that no air enters the container  14  when the latter may be coupled to a supply hose of a metering system. 
         [0060]    When commercially available cartridge closures may be used, the film  11  presents an additional problem when the above described container  14  may be opened. For instance, with low-viscosity products, when the closure cap is removed, the filling substance will flow out because it is not retained by the flexible film  11  as it would be by a cartridge piston. On the other hand, if the outlet is held upward, the container  14  will suck in air because of the weight of the filling substance and the flexible film  11 . 
         [0061]    To solve this problem, a disc  30  may be provided at the end at the outlet  13  at the lower part  10  of the container  14 , as shown in  FIG. 8 , the plane surface of the disc hermetically closing the outlet  13 . The liquid  33  of the container  14  contacts this plane without bubbles. A sealing lip  35  (e.g., an O-ring) provides maximum tightness during storage and shipping. 
         [0062]    The rotationally symmetric disc  30  may be mounted for rotation about an axis which may be offset with respect to the outlet  13 . The disc  30  has a passage  31  for receiving a nipple  32  of a supply hose. The passage  31  has a conical or calotte-shaped inward taper (upward in  FIGS. 8 and 9 ) which may be shaped so that the difference between the diameter of the passage  31  and that of the nipple  32  decreases from an initially positive value to at least zero or less. This specific shape of the passage  31  prevents the formation of an air cushion when the nipple  32  may be inserted. The supply hose leads to the actual downstream metering valve (not shown). 
         [0063]    By rotating the disc  30  about its axis, the nipple  32  may be moved directly under the outlet  13  of the container  14  and may be pressed by a spring  34  a small distance into the passage  31  ( FIG. 9 ). If the supply hose was completely filled with liquid, it may be certain that no air enters the supply line while it is being connected. Because the outlet  13  is thus not open toward the environment at any time, substance can never flow out and air can never be sucked in. Thus, the behaviour of the film described above has no effect. Connecting and changing a metering container  14  take place in a bubble-free manner. 
         [0064]    In practice, it may be possible that metering containers may be emptied only in part during a production day. Such partially filled containers must be stored in a refrigerated or frozen condition overnight, over a weekend or until the next production order may be processed. The arrangement shown in  FIGS. 8 and 9  prevents undesired air bubbles from entering into the supply line and ensures a reliable and bubble-free production process even when partially filled metering containers  14  may be removed and re-connected. 
         [0065]    The emptying device shown schematically in  FIG. 10  comprises a pressure vessel  50  with a bayonet-type lid  51  as known from EP 0 532 945 A1. The nipple  32  may be supported by an intermediate wall  52  through a compression spring  34 , the wall  52  also carrying an upward projecting locking pin  53 . A supply hose  54  coupled to the nipple  32  leads to an outer connecting piece  55 . 
         [0066]    The pressure vessel has such an inner diameter that it surrounds the container  14  placed therein with little clearance. When the lid  51  is closed, the container  14  which may be provided with the body  18  shown in  FIG. 3  may be pressed downward onto the nipple  32  which may be biased by the spring  34  so that the nipple may be centred within the conical or calotte-shaped passage  31 . Simultaneously, the locking pin  53  engages a stud hole  57  provided in the locking disc  30  of the container  14 . For subsequent locking, the lid  51  may be rotated with respect to the pressure vessel  50  wherein the lid entrains the container  14  while the disc  30  is fixed by the locking pin  53 . In this manner, the container  14  may be opened simultaneously with the closing of the pressure vessel  50 , whereupon the container  14  can be emptied through the supply hose  54  by introducing pressure into the vessel  50 . 
         [0067]    When disc  30  is in the closed position shown in  FIG. 8  and the nipple  32  may be pressed tightly against the solid part of the closure  29 , liquid may be prevented from flowing out of the supply hose  54 . Further, the described arrangement does not require a valve in the nipple  32 , which would impede the volume flow and lead to higher cleaning expenditure. 
         [0068]    In an alternative embodiment, a soft resilient slotted closure diaphragm  60  may be mounted directly at the outlet  13  of the container  14 . The lower part is shown with the diaphragm  60  closed in  FIG. 10  and open in  FIG. 12 . The diaphragm  60  provides sufficient resistance against an intentional flowing out of the liquid or sucking in of air during assembly. 
         [0069]    In a further alternative shown in  FIG. 13 , the diaphragm  60  may be replaced by an insert member  62  having fine through bores (capillaries)  63  (of a diameter of, e.g., 0.1 to 1.0 mm) which prevent an unintentional flowing out of the liquid due to their flow resistances.