Plastic article or earthenware shaping or treating: apparatus – Female mold and means to shape parison directly by internal...
Reexamination Certificate
1998-12-30
2001-06-12
Moy, Joseph M. (Department: 3727)
Plastic article or earthenware shaping or treating: apparatus
Female mold and means to shape parison directly by internal...
C425S523000, C425S531000, C425S812000, C264S523000
Reexamination Certificate
active
06244852
ABSTRACT:
The present invention relates to a method of producing a receptacle consisting of a substantially stiff outer receptacle and an easily deformable inner bag which are made from respectively different thermoplastic materials that do not form a welded joint with one another, said receptacle comprising a receptacle opening and at least one wall opening provided in the outer receptacle, through which pressure is compensated in the area between the inner bag and the outer receptacle, with a parison, which consists of at least two tubings, being coextruded and arranged between the opened halves of a blow mold, the blow mold being closed when said parison has reached the length required for producing the receptacle, the bottom area of the receptacle to be produced having formed therein an outwardly projecting web made of welded material of said outer receptacle, in which web the welded bottom seam of the inner bag is clamped and held in axial direction, and the parison being inflated by a pressure medium for contact with the wall of the blow mold and removed from the blow mold. Furthermore, the present invention relates to such receptacles whose at least one pressure compensating opening is formed in a special manner.
A method of the type in question is disclosed in DE 41 39 555 C2. The closed and at least partly welded bottom seam of the outer receptacle is formed by shaping the squeeze area of the blow mold at the bottom side in a special manner, with excess material being squeezed off and material of the outer receptacle being united at both sides to form a web of kite-shaped cross-section from which the welded bottom seam of the inner receptacle slightly recedes towards the interior of the receptacle due to the impact pressure built up in the cavity forming the web, so that the material of the outer receptacle is welded together over part of the web. The weld seam of the inner bag is clamped in the area positioned thereabove. The projecting web provided at the bottom of the outer receptacle may also have a different cross-sectional shape, for instance an arched shape.
As for the formation of the welded bottom seam of the outer receptacle and the clamping of the weld seam of the inner bag provided at the bottom side, explicit reference is here made to the content disclosed in DE 41 39 555 C2.
A pump for discharging the receptacle contents received in the inner bag may be provided on the receptacle opening of the receptacle of the type in question. However, the receptacle may also be a squeeze-type receptacle in the case of which the outer receptacle is squeezed together by hand to subsequently assume its initial shape again.
In the receptacle which is known from DE 41 39 555 C2, pressure compensation which becomes necessary due to a decrease in volume of the inner bag, which has been caused by the discharge of the receptacle contents, is carried out with the aid of unwelded shoulder seams of the outer receptacle which are formed in that the coextruded blank has a diameter which is greater than the neck portion of the blow mold, so that the blank is squeezed off in the shoulder portion and on the neck of the receptacle to be produced when the blow mold is closed for eliminating excess material. This is done without the formation of an outwardly projecting web as in the case of the bottom seam so that, during the smooth squeeze-off operation in the squeeze area of the shoulder portion and of the neck portion, material of the inner bag remains between the spaced-apart material of the outer receptacle, so that the last-mentioned material cannot be welded together, since the material of the inner bag does not recede. Hence, a closed weld seam is formed on the inner bag and ensures a leakage-proof inner bag, and air can enter through the shoulder seams of the outer receptacle, which is open at both sides, from the surrounding atmosphere for pressure compensation.
This configuration has the disadvantage that, starting from the open shoulder seams of the outer receptacle, the receptacle consists of two shells which rest on one another in a substantially loose manner. When the receptacle is equipped with a pump and when the pump is put on the two neck halves in a slightly inclined manner, the two shells may get slightly displaced relative to one another, whereby a step is formed on the upper edge, as a result of which the receptacle is no longer leakproof, since even a rubber insert provided at this place could not compensate for the resulting unevenness. Moreover, only receptacles with shoulder sections can be provided in the known manner with the open pressure compensating seams, whereas in the case of so-called wide-necked vessels, which are devoid of any shoulder sections, no pressure compensating openings can be formed in this way.
It is the object of the present invention to provide a method of producing pressure compensating openings in the wall of the outer receptacle in the case of receptacles of the type under consideration without any leakage problems arising therefrom on the receptacle opening. The method is meant to be also applicable to so-called wide-necked vessels.
It is also an object to indicate a receptacle which includes pressure compensating openings in its outer receptacle without the above-mentioned drawbacks being observed.
These objects are achieved with the features of patent claim 1.
Advantageous developments of the present invention are characterized in the dependent claims.
According to the present invention the wall openings of the outer receptacle are formed subsequent to the blow molding process in that at least one, preferably two or even more openings are cut, punched, punctured or pierced into the wall of the outer receptacle in a mechanical manner, or, however, are cut in by laser, with an inner wall section possibly remaining unaffected at the beginning to prevent damage to the adjacent inner bag in a reliable manner. The reason for this is that certain tolerances of the wall thickness of the outer receptacle are unavoidable and that in practice there are no measuring methods in the present case for measuring the respective wall thickness with an extremely great accuracy so as to guarantee a complete mechanical severing through the wall of the outer receptacle and to ensure full protection of the inner bag against the cutting operation, etc. According to the invention the remaining inner wall section is then broken open or torn up by applying a force. The inner bag cannot be damaged thereby.
In a development of the present invention, the measure which is taken in a first method consists in that the at least one wall opening, preferably two (or even more) wall openings are formed in that a cut or notch is cut or punched into the wall of the outer receptacle or is formed by means of a laser, said cut or notch penetrating through the wall except for a small residual wall section, and that the residual wall section is opened by applying a force.
This cutting or punching process takes place in a preferably non-cutting manner with a sharp knife or a punching tool or by means of a laser, so that no particles detach that would have to be sucked off if a possible contamination was to be ruled out. However, it is also within the scope of the present invention that a small amount of wall material can be cut away if, for instance, a slightly larger wall opening is desired for faster pressure compensation. The necessary pressure compensation, however, is already accomplished—though at a slightly slower pace—through a capillary-like opening, as is e.g. created by a smooth cut.
For performing the method, an apparatus according to the invention may be used which includes a clamping block which at least partly encloses the finished blown receptacle, which has preferably already cooled down. The clamping block may have formed therein a slot which extends up to the receptacle wall and has a knife projecting thereinto, with the knife being pivotably held outside the clamping block. When the knife is being pivoted by a drive means, the knife tip performs such a circular mov
GAPLAST GmbH
Moy Joseph M.
Pyle & Piontek
LandOfFree
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