Dispensing – Processes of dispensing
Patent
1992-10-27
1994-05-10
Huson, Gregory L.
Dispensing
Processes of dispensing
2221795, 222420, 222189, B67B 700
Patent
active
053100859
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The present invention relates to the packaging industry and more particularly to the packaging of sterile substances to be dispensed in portions such as eye lotions.
Substances of this type have been packaged in rigid containers with separate droppers, then in elastically deformable containers with a dropper nozzle, always with the risk of contamination of the unused liquid which is kept for subsequent use within the container after contact with the atmosphere. It has subsequently been proposed to employ containers in which sterility of the contents is preserved by a sterilizing filter interposed within the opening of the container, which can consist of a ceramic component but which consists in most cases of a microporous membrane of plastic material as described in particular in French patent No. 2,422,569. However, there inevitably remains a small quantity of liquid outside the membrane after a delivery. This liquid thus fails to escape external contamination. A subsequent delivery of liquid which has been kept in a sterile condition is then contaminated by said liquid which has remained outside the membrane.
Sterilizing filters constituted by microporous membranes have the property of becoming impermeable to air in the wet state except under high pressure. This property has so far been considered as a drawback. French patent 2,422,569 proposes to form in the membrane a zone which is impermeable to liquids but permeable to air, for example by local waterproofing with silicone in the case of aqueous liquid. This enables an elastically deformable container to suck-in air in order to compensate for the volume of liquid delivered and thus recover its initial shape. But, the differential pressure on each side of the membrane which permits suction of air is lower than the pressure which would permit suction of the liquid. As a result, the liquid which has passed through the membrane cannot be recovered and kept in a sterile condition.
If a membrane having zones which are permeable to air or to liquids is not employed, French patent 2,422,569 mentions the possibility of employing non-elastic deformable containers, for example of thin aluminum, having a volume which decreases in proportion to the number of deliveries performed. But, containers of this type are incapable of sucking-in the liquid which has passed through the membrane and thus remains in contact therewith after a delivery.
The invention, on the contrary, takes advantage of this alleged drawback in order to avoid any loss and contamination of the liquid which remains in contact with a microporous membrane after a delivery.
The object is achieved by keeping the membrane moistened by the liquid between successive deliveries and therefore impermeable to air while continuously subjecting it to a differential pressure of suction of the liquid, the value of which is not sufficient to permit forcible suction of air through the wet membrane.
The minimum differential pressure which permits air to pass through a wet microporous membrane is commonly determined by the so-called "bubble point" test whereby one face of the wet membrane is subjected to an increasing air pressure. The specific value retained for the "bubble point" is the differential pressure which causes the appearance of a continuous flow of bubbles downstream of the membrane. The bubble-point values specific to each type of membrane are usually provided by their manufacturers.
The invention thus relates to a method for dispensing portions of sterile liquid enclosed in a container under the control of a microfiltering membrane, which is permeable to the liquid but impermeable to air when wet and which is interposed within the neck, without contaminating the liquid remaining between deliveries. The method is distinguished by the fact that the membrane is moistened with liquid from within the interior of the container prior to the first delivery; the desired quantity of liquid is delivered through the membrane by exerting pressure on the liquid within the container; the li
REFERENCES:
patent: 2363474 (1944-11-01), Schlesinger
patent: 3248017 (1966-04-01), Allen
patent: 4248361 (1981-02-01), Moyle
patent: 4463880 (1984-08-01), Kramer et al.
patent: 4950237 (1990-08-01), Henault et al.
patent: 5105993 (1992-04-01), La Haye et al.
Chibret Henri
Lontrade Jean-Pierre
Huson Gregory L.
Transphyto SA
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