Dispensing – Collapsible wall-type container – With casing or support
Reexamination Certificate
1999-07-22
2001-03-27
Derakshani, Philippe (Department: 3754)
Dispensing
Collapsible wall-type container
With casing or support
Reexamination Certificate
active
06206244
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This is the national stage of International Application No. PCT/EP97/04338 filed Aug. 8, 1997.
BACKGROUND OF THE INVENTION
It is known to squeeze a free-flowing, pasty mass, such as a sealing compound or dental impression mass, out of a tubular bag by the latter being put into a cylinder space which is acted upon from one end by a piston and has a discharge opening or delivery nozzle at the other end, at which the bag is open. In this case, it is particularly important that that end of the tubular bag which contains the bag opening is sealed off from that end of the cylinder space and of the delivery nozzle which forms the discharge opening. If, for this purpose, the tubular bag is firmly connected to the device forming the cylinder space (FR-A 1 161 905), repeated use of the squeezing-out device for a plurality of tubular bags is made impossible. If the tubular bag is connected to the delivery nozzle in one piece or via thread (DE-A 35 00 625), the exchange of the tubular bag is prevented or made more difficult, provided the nozzle is also not designed as a throw-away part. The latter is often not possible or is undesirable. The arrangement of sealing elements between the end of the tubular bag and the delivery nozzle or discharge opening (EP-A 319 666), which sealing elements are to be fixed by special clamping or screw parts, also makes exchange difficult. To avoid these disadvantages, the arrangement mentioned in the preamble of claim
1
for squeezing out interchangeable tubular bags has been disclosed (EP-A 541 972), in which the gathered-up end, forming the bag opening, of the tubular bag is firmly connected to a sealing ring, which has a conical sealing surface, which interacts with a correspondingly conical sealing surface in the discharge opening of the squeezing-out device. Under the action of the squeezing-out piston, the cone of the sealing ring is pressed into the conical discharge opening, provided it is adequately centred beforehand. In the event of inadequate centring, sealing is not achieved. If the cone of the sealing ring sits in an exactly centred manner in the discharge opening, it appears possible to achieve an adequate sealing effect as long as the effect of the piston force continues. However, this sealing effect ceases when the arrangement “breathes” if the piston force ceases. Since, during the squeezing-out, most of the pressure drop does not take place in the bag opening or the discharge opening of the squeezing-out device but in the downstream spaces of the nozzle and the mixing device which is possibly present, a considerable pressure, which leads to corresponding extension of the associated walls, builds up during the squeezing-out in these spaces downstream of the discharge opening. If the squeezing-out force of the piston ceases, this extension leads to a back pressure and a backflow of the mass in the region of the discharge opening. As a result, the cone of the sealing ring may be lifted from its conical seat in the discharge opening; the sealing gap opens and the mass can penetrate into the space, to be sealed off, between the sealing ring and the tubular bag on the one hand and the cylinder space on the other hand. The mutual centring may also be lost, so that the cone of the sealing ring is not returned into the correct seat when pressure is next applied. Contamination of the device cannot therefore be completely avoided by the known arrangement. In addition, there is the disadvantage that the discharge opening has to be carefully cleaned when the tubular bag is changed, since otherwise possibly consolidated residues of the mass which remain there make complete sealing impossible even during the effect of the squeezing-out force, a factor which then leads to further contamination of the device. The known type of sealing also requires careful production and assembly of the parts which are involved in the sealing, and this is expensive. It is known (EP-A-663348) to counteract these disadvantages by the ring which bears the cone having a rim diameter which exceeds the inside diameter of the cylinder space accommodating the tubular bag and by said ring being fixed in a circumferential groove, which is formed between the end of the wall of the cylinder space and a lid forming the delivery nozzle. However, this has the disadvantage that the tubular bag can only be used in such devices whose cylinder space contains said circumferential groove and has a lid on the delivery side, the lid having to be opened in order to insert the tubular 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 easy exchange of the tubular bag, and nonetheless ensures adequate sealing.
The effect of the sealing elements of the sealing ring solely on the end face surrounding the discharge opening or on that edge of the discharge opening which is formed by this end face makes careful cleaning of the discharge opening, to which access is more difficult, unnecessary. Cleaning of the end face is also frequently unnecessary, since experience shows that the mass rarely penetrates so far. In the region of the edge, any residues of the mass are displaced without impairing the sealing effect. The interacting sealing surfaces impose a smaller requirement for accurate production and assembly, since it is not necessary to exactly match any diameters to one another. Finally, the invention has the advantage that the sealing is independent of the respective design of the discharge opening, and the tubular bags can therefore be used in different squeezing-out devices. The sealing effect also cannot be impaired by any inclination of the sealing ring.
In general, the end face surrounding the discharge opening of the squeezing-out device is flat. It is then advisable to also design the sealing ring (apart from projecting sealing elements) to be flat, so that it can extend parallel to the end face. This especially applies when, according to a further feature of the invention, it has an outside diameter approximately equal to the diameter of the cylinder space. As a result, effective guidance and centring of the tubular bag end is obtained during insertion into the delivery opening. Furthermore, it is advantageous if the rim of the sealing ring has a considerable height, which prevents the canting of the sealing ring when the tubular bag is being inserted into the cylinder space from its rear side remote from the delivery side. This height is preferably at least 4 mm or 6% (better 10%) of the diameter. Furthermore, it may be expedient if the circumferential surface is entirely or partly conical or bevelled or rounded off at one or both edges in order to facilitate the insertion into the cylinder space and if need be to also avoid the canting.
In order to avoid the lifting of the sealing elements from the end face of the cylinder space, the sealing ring, according to a further feature of the invention, may be provided with a retaining part arresting it in the sealing position. The invention prefers two embodiments of this idea. The first is distinguished by the fact that the retaining part is designed as a clamp interacting with the inner wall of the cylinder space. This is preferably achieved by the disc which forms or retains the sealing ring being flexible and by its outside diameter being slightly larger than the inside diameter of the cylinder space. If the disc is pushed against the end face during the squeezing-out activity of the piston, its outer rim, which bears under deformation against the inner surface of the cylinder space, bends slightly rearwards, the angle between this rim and the normal to the cylinder wall being so small in longitudinal section that self-locking takes place. This means that the disc is secured in the position which it thus attains. It cannot give way if the piston force ceases, and the sealing elements remain pressed against the end face under the elastic force of the disc deforma
Alix Yale & Ristas, LLP
Bui Thach H
Derakshani Philippe
Wolfgang Muhlbauer
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