Dispensing – Collapsible wall-type container – With casing or support
Reexamination Certificate
1999-02-10
2001-04-03
Shaver, Kevin (Department: 3754)
Dispensing
Collapsible wall-type container
With casing or support
C222S326000
Reexamination Certificate
active
06209755
ABSTRACT:
BACKGROUND OF THE INVENTION
It is known to squeeze a flowable, pasty mass such as sealing mass or dental impression mass out of a tubular bag in that the latter is introduced into a cylindrical space which is acted upon from one end by a plunger and has a discharge opening or ejection nozzle at the other end, at which the bag has been opened. In this case, particular value is placed upon the sealing of that end of the tubular bag which contains the bag opening in relation to that end of the cylindrical space which forms the discharge opening and the ejection nozzle. If, for this purpose, the tubular bag is fixedly connected to the unit forming the cylindrical space (FR-A 1 161 905), the multiple use of the squeezing-out unit for a plurality of tubular bags is made impossible. To avoid this disadvantage, an arrangement for squeezing out from exchangeable tubular bags has become known (EP-A 541 972), in which arrangement the gathered end of the tubular bag, which end forms the bag opening, is fixedly connected to a sealing ring which has a conical sealing surface which cooperates with a corresponding conical sealing surface in the discharge opening of the squeezing-out unit. Under the action of the squeezing-out plunger, the cone of the sealing ring is pressed into the conical discharge opening, provided that it has been adequately centred in advance. If the centring is inadequate, no sealing takes place. If the cone of the sealing ring sits precisely centrally in the discharge opening, it appears to be possible to achieve an adequate sealing action as long as the action of the plunger force persists. However, this sealing action ends when, upon termination of the plunger force, the arrangement “breathes”. Since, during squeezing out, the greatest part of the pressure drop does not occur in the bag opening or the discharge opening of the squeezing-out unit, but in the downstream spaces of the nozzle and of the possibly present mixing device, a considerable pressure builds up, during squeezing out, in these spaces downstream of the discharge opening, which pressures leads to corresponding expansion of the associated wallings. When the squeezing-out force of the plunger ends, this expansion then leads to a back pressure and a back flow of the mass in the region of the discharge opening. As a result of this, the cone of the sealing ring may be lifted off from its conical seat in the discharge opening; the sealed gap opens and the mass can penetrate into the space to be sealed off between sealing ring and tubular bag on the one hand and cylindrical space on the other hand. Furthermore, the mutual centering may be lost, so that the cone of the sealing ring is not passed back into the correct seat upon the next application of pressure. Accordingly, contamination of the unit cannot be entirely avoided by the known arrangement. In addition, there is the disadvantage that in the case of the exchange of the tubular bag the discharge opening must be carefully cleaned, because otherwise residues of the mass which have remained there and possibly solidified make a complete sealing off impossible, even during the action of the squeezing-out force; this then leads to further contamination of the unit. Furthermore, the known mode of sealing off requires careful production and assembly of the parts participating in the sealing off; this being costly. In another known arrangement for squeezing out from exchangeable tubular bags (FR-A 2 301 306, FIG. 4), a flat sealing ring is inserted between the flat end of the bag, which is provided with a cross-shaped incision for forming a squeezing-out opening, and the end face of the cylinder space, surrounding the discharge opening. This sealing ring is not connected to thy end of the bag. It has therefore been found that it cannot ensure a tight seal in the region of folds in the bag.
SUMMARY OF THE INVENTION
The object of the invention is to provide an arrangement for squeezing a free-flowing substance out of an elongated tubular bag which is less expensive, permits an easy exchange of the tubular bag, and nevertheless ensures adequate sealing.
The invention is based on the observation that leakage is often caused by the sealing ring being slightly oblique with respect to the axis of the bag, for example if the bag has been distorted as a result of deformation due to unskilled handling upon insertion into the cartridge. The invention avoids this effect by the sealing ring being connected to the bag in an angularly movable fashion, so that it can align itself with the associated counter sealing surface. This angular mobility is brought about by connecting the sealing ring to a disk or designing it as a disk which is adhesively bonded to the end face of the bag within an annular bead facing the latter and of a diameter which is substantially less than that of the bag. In this case, the disk region outside the annular bead remains free from the connection to the end face of the bag and can therefore move towards it on one side and away from it on the other side, the annular bead forming a kind of tilting bearing.
The capability of the sealing ring to align itself with the end face surrounding the discharge opening produces a reliable sealing-off effect. A cleaning of the end face cooperating with the sealing components is frequently unnecessary, because experience shows that the mass seldom advances to such an extent. Moreover, the cleaning of this surface is easier than that of the discharge opening, because it is more readily accessible and can be monitored more easily. The cooperating sealing surfaces place less stringent requirements on precise production and assembly, because it is not necessary to coordinate any diameters whatsoever accurately with one another. Finally, the invention has the advantage that the sealing off is independent of the respective design of the discharge opening and the tubular bags can accordingly be used in differing squeezing-out units.
In general, the end face surrounding the discharge opening of the squeezing-out unit is flat. In these circumstances, it is recommended also to design the sealing ring (possibly apart from projecting sealing components) to be flat, so that it can extend parallel to the end face. This applies in particular in circumstances in which, according to a further feature of the invention, it has an external diameter which is approximately equal to, or only slightly smaller than, the diameter of the cylindrical space. The result of this is a good guiding and centering of the end of the tubular bag upon introduction into the ejection opening.
It is known to have the bag opening formed by a gathering of the bag, which gathering penetrates through the sealing ring and is cut away. According to the invention, this gathering lies freely in the discharge opening. Thereby, it is achieved that, under the action of the squeezing-out differential pressure, the gathering is applied to a greater or lesser extent to the walling of the discharge opening and there forms a sealing off upstream of the sealing ring. Even where such sealing off may not be complete, it does nevertheless obstruct the passage of the mass, so that frequently the latter does not actually reach the sealing components of the sealing ring.
The sealing component or the sealing components of the sealing ring are pressed, by the squeezing-out force exerted by the plunger on the tubular bag, against the end face of the cylindrical space and are able thereby to perform their sealing action during the squeezing-out process. They can be designed in various ways, in accordance with the known principles of sealing technology. In the simplest case, the substantially flat surface of the sealing ring or the latter itself forms the sealing component. However, it is also possible to provide particular sealing components, projecting from its surface, in any desired number. Expediently, they are designed in yielding fashion, so that they can adapt in gap-free fashion to the counter sealing surface formed by the end face. The requirements imposed upon the accur
Alix Yale & Ristas, LLP
Bui Thach H
Muhlbauer Wolfgang
Shaver Kevin
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