Patent Publication Number: US-4546085-A

Title: Cell cultivation container

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a cell cultivation container having a mouth portion provided with a screw cover. 
     In the growing of cells it is customary to use containers provided with an airtight screw cover in order to prevent contamination of the cell material and also to prevent the escape of cells or substrate to the surroundings. 
     However, the use of such airtight screw covers involves various practical problems. Thus, an equalization must be performed from time to time of the overpressure building up in the cultivation container, i.e. because the temperature in the container is increased from that of the surroundings to the optimum temperature of about 37° C. for the cultivation of the cells. The overpressure is mainly due to the fact that the gas mixture present above the substrate tends to expand at the noted temperature increase. 
     In cell cultivation containers a NaHCO 3  -solution is frequently used for maintaining a constant pH-value. Typically, a NaHCO 3  -solution is used having a NaHCO 3  -content of 0.8-3.5 g/l, preferably about 2.2 g/l. Such a buffer solution gives the desired pH-value only if a given CO 2  partial pressure above the substrate is maintained, and it is therefore necessary to introduce CO 2  into the cultivation container from time to time. 
     The equalization of the above-mentioned overpressure and the introduction of CO 2  into the container are normally performed by turning the screw cover sufficiently to establish a communication between the interior of the container and a surrounding gas mixture, such as atmospheric air with an addition of 5% CO 2 . However, in the case of the known screw covers it is not possible to ascertain exactly when the cover has been sufficiently opened to establish such communication, yet not opened to such an extent that material may unintentionally escape from the container, or contaminating matter, including micro-organisms, may penetrate into the container. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a cell cultivation container of the kind referred to, which is so constructed such that when the screw cover is turned in the opening direction a predetermined opening of the container is obtained, even if the angle of turning varies within certain limits. 
     According to the invention, there is provided a cell cultivation container having a mouth portion provided with a screw cover, the zone of the mouth portion adjacent the edge of the mouth having a greater inner diameter than the remaining zone of the mouth portion, two or more inwardly protruding, axially extending projections being provided in the first mentioned zone of the mouth portion, the screw cover being constructed with an inner skirt having an outer annular bead which is so constructed that in the fully tightened position of the screw cover the bead is in sealing engagement with the zone of the mouth portion having the smaller inner diameter, while in a partly unscrewed position of the cover the bead engages only the inwardly protruding, axially extending projections in the zone of the mouth portion having the greater inner diameter. 
     When the screw cover of the cultivation container according to the invention is partly screwed off, the outer annular bead of the inner skirt will be moved from a position in which it sealingly engages the zone of the mouth portion having the smaller inner diameter into the zone where the axially extending projections are arranged, and a communication is thereby established between the interior of the container and the surrounding air through passages formed between successive axially extending projections, the outer bead and the inner face of the mouth portion between successive projections. The cross sectional area of each of these passages is determined, for a given outer diameter of the annular bead, by the inner diameter of the mouth portion in the zone where the axially extending projections are arranged. 
     The length of the axially extending projections and the pitch of the screw thread of the screw cover determine the limits within which the screw cover can be turned while maintaining a constant cross sectional area of the passages between successive axially extending projections, and these factors can be so adapted that a well defined passage area can be obtained, even if the angle of turning varies within wide limits. 
     For reasons of production the axially extending projections, of which, e.g., six may be provided, are preferably constructed with plane inner faces. 
     It is observed that the axially extending projections may have a larger extension in the circumferential direction of the mouth portion than the intervening spaces, in which case the latter will assume the character of recesses in a zone of the mouth portion having the same inner diameter as the remaining zone of the mouth portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a longitudinal section along the line I--I in FIG. 2 through the mouth portion of a cell cultivation container according to an embodiment of the invention, the screw cover being removed. 
     FIG. 2 shows a cross section of the mouth portion along the line II--II in FIG. 1. 
     FIG. 3 shows a longitudinal section through a screw cover for the cultivation container of FIGS. 1 and 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The cultivation container shown in FIGS. 1 and 2 consists of a container portion 1 and a mouth portion 2, the latter being provided with an outer screw thread 3 and being constructed interiorly with two zones of different diameter, viz. a zone 4 having a smaller diameter and a zone 5 having a greater diameter, the zone 5 being situated adjacent the edge of the mouth. In the zone 5 six equi-distant inwardly protruding and axially extending projections 6 having plane inner faces are provided. 
     At its bottom side the container portion 1 is constructed with some ribs 7 to keep the container portion raised above the supporting surface. 
     The screw cover shown in FIG. 3 comprises an outer skirt 10, which via a connecting piece 11 is connected with an inner U-shaped skirt 12. The screw cover also has a dish-shaped central portion 13. On the inner side of the outer skirt 10 a screw thread 14 is provided for engagement with the outer screw thread 3 of the mouth portion 2 of FIGS. 1 and 2. On the outer side of the U-shaped inner skirt 12 an annular bead 15 is provided. 
     When the screw cover of FIG. 3 is fully screwed onto the mouth portion 2 of FIGS. 1 and 2, the bead 15 will be present in the zone 4 and will be in sealing engagement with the inner side of the mouth portion in this zone 4. 
     When the screw cover is partly screwed off, the bead 15 moves towards the edge of the mouth and reaches the zone 5. In this zone the bead will only be in contact with the plane faces of the projections 6 and thereby passages having a well defined cross-sectional area are formed in the intervals between the projections 6. This well defined cross-sectional area will be maintained when the screw cover is turned more or less away from the closing position, as long as the bead 15 is kept within a zone corresponding to the axial length of the projections 6. When the angle of turning is kept within an interval corresponding to the axial length of the projections, a well defined venting of the cultivation container and/or a well defined introduction of surrounding air into the container can therefore be obtained. 
     Both the container as such and the screw cover are preferably made from a plastic material.