Container Closure

Abstract

A container closure member adapted to sealably close an access opening of a glass bottle for solutions, which has a leg-like portion sealingly situated in the access opening. This closure member comprises a rubber covering plug formed with an annular protrusion and a shaped form of synthetic resin formed with an annular groove and firmly contacted with the covering plug with its annular groove receiving therein the annular protrusion of the covering plug. The diameter of the shaped form is smaller than that of a flange of the storage vessel, but larger than that of the access opening so that a tight contact between the closure member and the storage vessel can be advantageously ensured.

Description

The present invention relates to an improved closure member for solution containers and, more particularly, to a pierceable closure member for medicine bottles and a method of forming the same.

In any country where the medical administration is more or less advanced, standards for medical supplies are naturally strict with few exceptions to the quality of a closure member for containers containing therein medical injection solutions or other valuable medical solutions. In other words, the closure member of the type above referred to should have a relatively higher quality so that the valuable solution contained therein cannot be contaminated by material and/or additives employed to manufacture such closure member. Once the closure member closing a medical container such as vial or the like contaminates the solution contained therein in such a way that material and/or additives employed to manufacture such closure member has been desolved into the solution and/or that some of the additives have been adsorb to a surface portion of the closure member accessible to the solution, some or all of the characteristics, for example, the potency, the colour and the pH, of the solution will be degraded.

To avoid the above mentioned disadvantages, various proposals have heretofore been made to improve the closure member of the type above referred to. Of which, a closure member coated in part or in whole with a film of chemically stable material, for example, tetrafluoroethylene polymer or Teflon [Du Pont's Reg. trademark] has largely been accepted because of its chemical performance superior to that afforded by any other coating materials.

However, the famous saying, "So many men, so many minds," may apply even among the closure members of different structures heretofore proposed which are coated in part or in whole with a film of the chemically stable material.

Of them, exemplary types of the closure member are such as disclosed in the U.S. Pat. Nos. 3,198,368 and 3,552,591, of which a common feature resides in the employment of a disc-like film of Teflon that is contacted with the relevant surface of a rubber covering or backing member during the process of vulcanization of the latter. More specifically, the first numbered U.S. patent is directed to a closure member apparently designed such that the Teflon disc of a diameter substantially equal to that of the rubber backing is contacted with one whole surface of the rubber backing which is adapted to cover the opening of a solution container, whereas the second numbered U.S. patent is such that, although the Teflon disc has a diameter smaller than that of the rubber covering member, but larger than that of the opening of a solution container to be closed thereby, so as to contact a substantially central portion of the relevant surface of the rubber covering member, the rubber covering member is provided at its outer periphery or rim with a downwardly extending annular ridge engageable with the bevel-shaped upper peripheral edge of the flange formed around a neck portion of the solution container.

So long as the closure member is in the form of flat structure such as disclosed in the first numbered U.S. patent, it has been found that a substantially central portion of the closure member has a tendency to be depressed inwardly or outwardly of the solution container during the metal ring sealing operation in which a metal ring is sealed over the periphery of the closure member under relatively higher pressure to insure tight contact between said closure member and the container opening. Once the central portion of the closure member is depressed inwardly or outwardly as hereinbefore described, airtightness at the contact area between the closure member and the container opening will be lost to an extent that air or the valuable solution in the container is permitted to penetrate into or leak out of the container, respectively. This is true in the case where the rubber backing member is lined with the Teflon disc covering the whole surface thereof, in view of the fact that Teflon or a similar hard material has been well recognized as unable to adapt itself sufficiently to unevennesses of such a solution container made of glass, metal or other hard material unless otherwise at least a portion of the container accessible with the closure member is precisely polished.

In this respect, the closure member as disclosed in the second numbered U.S. patent has many advantages over that disclosed in the first numbered U.S. patent. However, this closure member of the second numbered U.S. patent is very complicated so that the container of special construction nust be provided to enable the closure member to exhibit its excellent performance. In other words, for this closure member, the existing container forming equipment must be remodeled, or otherwise new container forming equipment must be provided for manufacturing the container of which the flange at the neck portion can accommodate the closure member such as disclosed in the second numbered U.S. patent. This closure member is similarly in the form of substantially flat structure and, to avoid the depression at the central portion thereof, an annular groove is also formed on the relevant surface of the closure member at a position slightly spaced from the outermost rim or periphery of said closure member. In this arrangement, while the Teflon disc of a diameter larger than that of the container opening is covered over the central portion of the closure member with its peripheral edge slightly bent inwardly of the annular groove, the remaining portion of the closure member positioned between the annular groove to the outermost rim is adapted to insure tight contact between said closure member and the flange of the container.

Although the labyrinth-like annular groove formed on the relevant surface of the closure member is effective to prevent the central portion thereof from being inwardly or outwardly depressed under the influence of a relatively higher pressure usually applied during the metal ring sealing operation, it is apparent that a method of manufacturing the closure member of the above complicated construction is complicated as well. Despite the fact that the second numbered U.S. patent has also disclosed the method thereof wherein a substantially circular rubber block having one surface contacted with the Teflon disc of the diameter slightly larger than that of the rubber block is vulcanized and compression-molded into the resultant closure member in a molding machine, centering of the rubber block with respect to a stationary die of the molding machine is too difficult. For example, the die is provided with an annular projection which complies with the annular groove of the resultant closure member, the inside diameter of the annular projection being smaller than the diameter of the Teflon disc. Accordingly, prior to the compression force to be applied to the rubber block by means of a movalve die of the molding machine, the rubber block must be mounted on the stationary die in such a way that the outermost peripheral edge of the Teflon disc contacted to the rubber block should be psoitioned atop the annular projection. This procedure is too difficult, or otherwise time-consuming, so that mass production of the closure member will be hampered. The reason for the diameter of the Teflon disc being larger than the inside diameter of the annular projection of the stationary die is because the peripheral edge of the Teflon disc should, when the resultant closure member is completely formed, be slightly bent inwardly of the annular groove of the closure member to ensure that the Teflon disc is tightly engaged with the rubber covering member. However, this is apparently of no significant assistance unless the solution container, and hence the closure member, is of a relatively larger size.

Accordingly, an essential object of the present invention is to provide an improved pierceable closure member for solution containers wherein the above mentioned disadvantages inherent in the conventional closure member of this kind have substantially been eliminated.

Another object of the present invention is to provide an improved pierceable closure member for solution containers which prevents the contamination of a valuable medical or other solution contained in the container nor the loss of chemicals stored in said container.

A further object of the present invention is to provide an improved pierceable closure member for solution containers which prevents the leakage of a valuable medical or other solution stored in the container.

It is a related object of the present invention to provide a method of manufacturing the improved closure member which satisfies the above mentioned objects without any formation of pinholes in a shaped form of synthetic resin used to contact the covering plug.

According to the present invention, there is provided a container for medical injection solutions comprising a storage vessel with a defined access opening and a closure member adapted to tightly close said access opening. The closure member is formed on one surface adjacent to the access opening of the storage vessel integrally with a leg-like structure adapted to sealably inserted in the access opening, and includes a rubber covering plug formed with an annular protrusion and a shaped form made from a film of synthetic material and formed with an annular groove or recess in which said annular protrusion is tightly situated, said annular protrusion and said annular groove constituting the leg-like portion of the closure member. The diameter of the shaped form is smaller than that of the covering plug, but larger than the diameter of the access opening so that a tight contact between the closure member to the storage vessel can be ensured without any possible occurrence of leakage of a solution contained in the container.

Furthermore, in view of the provision of the leg-like portion in the closure member according to the present invention, it can be advantageously appreciated that the centering of the closure member to the access opening of the storage vessel can be facilitated without forcing one who handles the storage vessel to watch the course of procesure.

In addition, according to the present invention, the shaped form is firmly contacted with the covering plug to an extent that, even if a needle is pierced through the closure member very often in a violent manner, no detachment of the shaped form from the covering plug takes place. To this end, one surface of the shaped form to be contacted with the covering plug is roughened by the treatment with a natrium containing solution to permit the raw rubber material for the covering plug to compensate the roughness on the surface of the shaped form during the molding operation.

According to another preferred embodiment of the present invention, the leg-like portion of the closure member is inwardly ressed on the outside periphery thereof at a position adjacent to the root with the inside periphery being tapered in the direction opposite to the access opening so that, in addition to the tight contact between the covering plug and the storage vessel, another tight contact can be obtained between a portion adjacent to the free end of said leg-like portion of the closure member and the storage vessel. Since the double contacts can be available, the tightness of the container can be substantially improved.

The present invention also pertains to a method of manufacturing the closure member wherein each closure member can be obtained by molding and vulcanizing a raw rubber material in a cavity of a molding machine which defines the shape of the resultant closure member. In this method of the present invention, streams of raw rubber material are directed to the outer peripheral edge of each of the forms lying in the mold so that no warping of the peripheral edge of the form will occur during the molding operation. Of course, in view of the provision of the annular groove in the shaped form, centering of the form with respect to the mold can be easily performed without difficulty.

These and other objects and features of the present invention will become apparent from the following description taken in connection with preferred embodiments thereof with reference to the attached drawings, in which;

FIG. 1 is a schematic longitudinal section of an upper portion of a medicine bottle of which the opening is closed by a closure member constructed in accordance with the present invention,

FIG. 2 is a similar view to FIG. 1, showing another preferred embodiment of the present invention,

FIG. 3 is a schematic diagram showing a molding machine for manufacturing the closure member shown in FIG. 1 and,

FIG. 4 is a schematic diagram showing a molding machine for manufacturing the closure member shown in FIG. 2.

Referring now to FIG. 1, a solution container, for example, a medicine bottle 1 made of glass or other rigid materials as have been conventionally accepted and in cooperation with which the present invention can be practically utilized has an opening or mouth 2 defined by a neck portion 3, an uppermost portion of said neck portion 3 being integrally formed with a flange 4 of suitable thickness. In the condition shown in FIG. 1, the medicine bottle 1 is shown as having a closure member, generally indicated by 5 and constructed in accordance with the teachings of the present invention as will be mentioned later, fastened thereto so as to tightly close the bottle opening 2 by means of a metal sealing ring 6 which is fitted over the periphery of the closure member 5 by the customarily practiced metal ring sealing process.

The medicine bottle 1 having such closure member 5 may be of any type, for example, a container for a medical injection solution, a corrosive solution or other valuable solution which is to be used in installments by repeatedly sticking the needle of a syringe through the closure member 5 or to be stored for a fairly long period of time.

The closure member 5 generally comprises a covering plug 7 made of natural rubber or a synthetic rubber such as polyisoprene or chloroprene and imparted with relatively higher elasticity, strength and softness, and a form 8 made of a fluorocarbon resin such as trifluorochloroethylene polymer, tetrafluoroethylene polymer or tetrafluoroethylene hexafluoropropylene copolymer.

The covering plug 7 is integrally formed with an annular protrusion 7a of a height within the range of from 0.5 to 5 mm. which is sealably engageable in the bottle opening 2 and with a shallow recess 7b at a substantially central portion of the upper surface of said covering plug 7, said shallow recess 7b being adapted to define an area through which the needle or the like can be pierced. This covering plug 7 of the above construction has the shape substantially as shown, which can be obtained by an extrusion molding process as will be mentioned later.

The form 8 of a thickness within the range of from 0.01 to 0.3 mm., preferably, 0.07 to 0.15 mm., is integrally formed with an annular groove or recess 8a which coincides with the contour of the annular protrusion 7a of the covering plug 7 for receiving therein said protrusion 7a. This form can be obtained by heat-pressing a thin film of a fluoro-carbon resin for about one minute under a temperature of approximately 250.degree. and, thereafter, by perforating the thin film thus heat-pressed to give such form 8.

The covering plug 7 and the form 8 are tightly contacted to each other in such a way that the annular protrusion 7a of the covering plug 7 is situated within the annular groove 8a of the form 8. Of course, to ensure the tight contact therebetween, no adhesive agent is employed, but the whole surface of the form 8 in contact with the adjacent surface of the covering plug 7 has been treated with a natrium containing solution to impart roughness on said surface of said form 8, so that, during the formation of the closure member in accordance with the method of the present invention, the roughness on said surface of said form 8 can be substantially completely filled up with raw rubber material employed to form the covering plug 7. Once the rough surface of said form 8 is filled up with the raw rubber material as hereinabove mentioned, it may be possibly said that the tight contact between the covering plug 7 and the form 8 takes place in a substantially similar manner as observed in the formation of a blanket of snow on a steep mountainside or on rough ground. Accordingly, even without the use of any adhesive agent, a sufficiently acceptable contact between the covering plug 7 and the form 8 can be obtained which is more firm than that afforded where no surface of the form to be contacted with the covering plug 7 is treated with the natrium containing solution.

However, it is to be noted that, to demonstrate the optimum performance of the closure member of the present invention, the diameter D of the form 8 should be smaller than the diameter d of the flange 4 which defines the bottle opening 2 of the diameter as indicated by d.sub.1, but larger than the diameter d.sub.1 of said opening 2, so that an annular uncovered area 7c is provided on the surface of the covering plug 7 at a position between the outermost peripheral edge of the form 8 and the outermost peripheral edge of the covering plug 7. This uncovered area 7c of the covering member 7 is adapted, when the closure member 5 is in position as shown, to directly contact the relevant portion of the flange 4. In this connection, the difference between the diameter d of the flange 4 and the diameter D of the form 8, namely, the distance between the outermost peripheral edges of the flange 4 and the covering plug 7 is preferably within the range of from one thirds to two third (one-third to two-thirds) of the difference between the diameter d of the flange 4 and the diameter d.sub.1 of the bottle opening 2. If the direct contact area between the covering plug 7 and the bottle 1 or the bottle flange 4 is reduced in such a way that the difference between the diameter d and the diameter D becomes smaller than that of one-third of the difference between the diameter d and the diameter d.sub.1, a sufficient fluid-tightness can no longer be imparted between the closure member 5 and the bottle 1. On the other hand, if said direct contact area is increased in such a way that the difference between the diameters d and D becomes larger than that of two-thirds of the difference between the diameters d and d.sub.1, this may result in the reduction of the difference between the diameters d.sub.1 and D, namely, the reduction of the size of the peripheral edge of the form 8, so that, when the metal sealing ring 6 is formed over the periphery of the closure member 5, the form 8 will be no longer satisfactorily suspended in position with its peripheral edge being tightly sandwiched between the covering plug 7 and the bottle flange 4 under the influence of pressure exerted by the metal sealing ring 6.

Although in the embodiment shown in FIG. 1 the outside diameter of the annular protrusion 7a of the covering plug 7 is substantially equal to the diameter d.sub.1 of the bottle opening 2 so that the whole outside peripheral surface of the protrusion 7a may contact the inner peripheral surface of the neck portion 3 of the bottle 1, a similar annular protrusion of the outside diameter slightly larger than the diameter of the bottle opening may be utilized.

Referring now to FIG. 2, the annular protrusion 7'a integral with the covering plug 7 is inwardly recessed at a position substantially adjacent to the outside annular root of said protrusion to give a recessed gap 9 while the inside peripheral surface 7d of the protrusion 7'a is preferably tapered toward the opposite, inside annular root of said protrusion to represent a skirt-like shape. In other words, the outside diameter of the protrusion 7'a at a position substantially adjacent to the outside root thereof is smaller than that at a position where the protrusion 7'a is to be indirectly contacted with the inner peripheral surface of the neck portion 3 of the bottle 1 through the form 8.

While the covering plug 7 having the annular protrusion 7'a is formed into the shape as shown and hereinbefore described, the form 8 is correspondingly shaped so as to meet the contour of the covering plug 7 and contacted to the latter in the same manner as described in connection with the first preferred embodiment with reference to FIG. 1. However, the size of the peripheral edge of the form 8 of FIG. 2 which is suspended over the bottle flange 4 is substantially the same as hereinbefore described. In other words, the size of the peripheral edge of the form 8 of FIG. 2 is defined by the difference between the diameter D of the form 8 and the diameter d.sub.1 of the bottle opening 2.

The minimum outside diameter, as indicated by D.sub.1, of the form 8, which is slightly larger than the outside diameter of the protrusion 7'a at a position substantially adjacent to the outside root thereof, is, in view of the provision of the recessed gap 9, smaller than the outside diameter, as indicated by D.sub.2, located adjacent to the annular free end of said protrusion 7'a. The outside diameter D.sub.2 may be substantially equal to or slightly larger than the diameter d.sub.1 of the bottle opening 2. If the diameter D.sub.2 is slightly larger than the diameter d.sub.1, insertion of the closure member 5 or, more specifically, the annular protrusion 7'a, in the bottle opening 2 causes said protrusion to be compressed in the peripheral direction so that, in addition to the tight contact between the covering plug 7 and the bottle flange 4 through the uncovered area 7c, another tight contact between the closure member 5 and the bottle 1 can be advantageously obtained. This is because, as can be understood by those skilled in the art, upon compression of the annular protrusion 7'a, stress can be exerted about the annular free end of said protrusion in the radial direction to an extent that the tight contact can be ensured.

In any event, the size of the recessed gap 9 is such that the ratio of the difference between the diameters D.sub.2 and D.sub.1 to the diameter D.sub.2 is within the range of from one one-hundreth to ten one-hundreths and the radius of rounding is within the range of from 0.1 to 2.0 mm., preferably, 0.3 to 1.0 mm. This recessed gap 9 may be present or not present when the closure member 5 is inserted in the bottle opening 2.

Furthermore, the provision of the recessed gap 9 is effective to ensure the tight contact between the covering plug 7 and the form 8 in view of the fact that the skirt-like annular protrusion 7'a situated in the annular groove 8a of the form 8 which meets the contour of the protrusion 7'a carries said form 8 from the inside of the latter. Accordingly, it is apparent that, even if the surface of the form 8 has been insufficiently treated with the natrium containing solution, a possible detachment of the form 8 from the covering plug 7 can be substantially completely eliminated. Without the provision of this recessed gap 9, the performance of the closure member shown in FIG. 2 is substantially the same as that of FIG. 1, since a difference merely exists in the construction of the inside peripheral surface of the annular protrusion.

To manufacture the closure member of the construction shown in either FIG. 1 or FIG. 2, a method thereof will be hereinafter described with reference to FIGS. 3 and 4 wherein a molding machine is schematically shown as including a female mold A, a male mold B and a hydraulically operated ram C, all being separable from each other.

The female mold A is provided at its depth with a plurality of equally spaced annular groove 10, each of which corresponds to the annular protrusion of the closure member 5 and having the shape which meets the contour of the form 8 and thus the annular protrusion. The male mold B is formed with a plurality of cavities 11 for determining the shape of the covering plug during the molding operation, the number of which corresponds to that of the annular grooves 10. Each cavity 11 is communicated with a pot-like portion 12 formed in said male mold B for receiving therein a substantial amount of raw rubber material, through a plurality of passages 13 each having a diameter of the value within the range of from 0.5 to 1 mm. and equally spaced with each other such that the opening of each of said passages 13 facing to the cavity 11 is positioned above the peripheral edge of the form 8. Slidably received in said pot-like portion 12 of the male mold B is the ram C adapted to be driven by a suitable cylinder device (not shown) in a manner known to those skilled in the art. It is to be noted that the molding machine shown is of a design effective to vulcanize the raw rubber material during the molding operation.

To manufacture the closure member 5 of the present invention, a plurality of the forms 8 that have been prefabricated with its relevant surface treated with the natrium containing solution as hereinbefore described are first placed on the female mold A with the annular groove 8a of each of the forms 8 being received in the corresponding one of the annular groove 10 of said female mold A. Thereafter, the male mold B is tightly sealed with the female mold A and a substantial amount of raw rubber material for the covering plug 7 is subsequently filled in the pot-like portion 12 of the male mold B. This supply of the raw rubber material may be made manually or by means of a pumping device (not shown). The ram C is then moved toward the male mold B so that the raw rubber material in the pot-like portion 12 can be poured under pressure into the cavities 11 through the passages 13 and then the annular grooves 8a of the forms 8 and, thereafter, the raw rubber material contained in the cavities 11 is subjected to vulcanization.

Upon completion of the vulcanization, the units A, B and C are separated from each other and a plurality of the closure members 5 can be obtained by removing them from the male mold B.

It is to be noted that, since the opening of each of the passages 13 facing to the cavity 11 is designed so as to position above the peripheral edge of the form 8, streams of the raw rubber material under pressure pouring from the pot-like portion 12 into the cavity 11 through the passage 13 act to restrict the peripheral edge of the form 8 from being warped.

Of course, the depth of each of the annular grooves 10 of the female mold A is substantially equal to the height of the annular protrusion 7a or 7'a.

The only difference between the molding machines shown in FIG. 3 and FIG. 4 resides in the shape of the annular groove 10 formed in the female mold A. In other words, the machine shown in FIG. 3 is adapted to manufacture the closure member shown in FIG. 1 while that shown in FIG. 4 is adapted to manufacture the closure member shown in FIG. 2. In either case, the most important feature of the present invention resides in the location of the opening of each passage 13 facing to the cavity 11 substantially as hereinbefore described.

Furthermore, because of the provision of the annular protrusion in the closure member, centering of the form 8 with respect to the female mold A can be facilitated without any difficulty and the displacement of the form 8 with respect to the covering plug 7 or 7' will never occur even during the molding operation.

To show the performance of the closure member of the present invention, reference will be made to the following example which is not intended to limit the present invention in any respect.

EXAMPLE

A film of tetrafluoroethylene copolymer, 0.13 mm. in thickness was treated on its one surface with a halogen-eliminator containing solution which had been prepared by mixing a solution containing tetrahydrofuran and naphthalin with a dispersion containing natrium or metallic natrium of the same mole as that of the naphthalin for approximately 5 minutes. After this film had been washed with aceton and then water and dried, the film was molded by means of a press, heated up to 250.degree. and, after one minute, cooled down to 180.degree., to give the molded form 8 of the shape substantially are shown in FIG. 2. The dimensions of this form 8 including the radius of rounding of the recessed gap 9 are:

Diameter D 16.0 mm. Diameter D.sub.1 12.2 mm. Diameter D.sub.2 13.3 mm. Radius of Rounding 0.4 mm.

The form 8 thus obtained was placed on the female mold A shown in FIG. 4 and, in accordance with the procedure as hereinbefore described, the closure member, 19.0 mm. in diameter and 3.0 mm. in thickness, having an annular protrusion of 1.87 mm. in height was obtained. During the molding operation, vulcanization was carried out under pressure at 160.degree. for ten minutes.

The composition of raw rubber material for the closure member thus obtained are as follows:

Composition A Polyisoprene part 100 parts Zinc flower 5 parts Sulphur 1.5 parts Benzothiazolyl disulfide 1 part Stearic acid 1 part Silica 30 parts Composition B Chloroprene 100 parts Zinc flower 5 parts Magnesia 4 parts Ethylenethiourea 0.5 part;8c Stearic acid 1 part Silica 30 parts

A number of glass vials each having a flange 4 of 19.0 mm. in diameter d and an opening 2 of 13.0 mm. in diameter d.sub.1, the opening of each of which is tightly closed with the closure member of the above construction by means of the metal sealing ring 6, were subjected to the following various tests:

Types of Test and Results

Extract-permeability Test: This is a test to determine to what extent distilled water, contained in each glass vial at the rate of 5 ml. and heated up to 100.degree. for one hour, was contaminated by the composition of the closure member. The result of this test is expressed in the Table I in terms of UV adsorbance relative to the specific wavelength employed.

Adsorption Test: This is a test to determine to what extent the closure member adsorbs a specified compound of a solution of 5 ml. contained in each glass vial. For this compound, 0.01 percent of propylparaben and 0.1 percent of methylparaben were respectively employed. In this example, each glass vial containing the solution was allowed to stand for 30 days under room temperature, and the degree of adsorption is expressed in the Table I in terms of percentage.

Note: For comparision, each glass vial having the closure member without the form 8 contacted to the covering plug 7 was also subjected to the same tests. In addition, all of the glass vials were tested in the inverted condition. ##SPC1##

From the foregoing, it now becomes clear that the closure member constructed in accordance with the present invention is effective to maintain the fluid tightness of the container without any substantial influence on the solution contained in the container. This fact is also supported by the tightness test, the results and conditions of which are tabulated in Table II. However, it is to be noted that each glass vial under the heading, "Comparision," had its opening closed with a flat closure member comprising a rubber layer and a Teflon [Du Pont's Reg. Trademark] layer, both having the same diameter as that of the vial opening.

Although the present invention has been fully described in conjunction with the preferred embodiments thereof, it is to be noted that various changes and modifications are apparent to those skilled in the art and, therefore, the present invention is not to be limited thereby. Such changes and modifications, if they fall within the scope of the present invention, should be construed as constituting part of the present invention.

Claims

What is claimed is:

1. A container for medical injection solutions comprising a storage vessel with a defined access opening and a closure member, said closure member comprising a form composed of a thin film of a fluorocarbon resin and capable of sealably closing said opening and formed with an annular recessed portion adapted to be situated in said opening when said form is sealably covering said opening, a rubber covering plug pierceable by a hypodermic needle and formed with an annular protrusion adapted to be received in said annular recessed portion of said form, said annular protrusion being inwardly recessed at a position adjacent to the point at which said protrusion is integrally connected with the remainder of said covering plug, whereby a recessed annular gap can be obtained between the outer peripheral surface of said annular recessed portion and the inner surface of said vessel defining said access opening when said closure member sealably closes said opening, the maximum outside diameter of said form being smaller than that of said covering plug, but larger than the diameter of said opening, whereby the remaining annular surface of said covering plug which is defined by the difference between the diameters of said covering plug and said form directly contacts a flange of said storage vessel positioned adjacent to said opening in a tight manner, and sealing means for sealingly securing said closure member to said storage vessel and overlying the periphery of said covering plug.

2. A container as claimed in claim 1 wherein the surface of said form which contacts said covering plug and the surface of said plug which contacts said form are rough so that a relatively firm contact therebetween can be obtained without necessitating the use of any adhesive agent.

3. A container as claimed in claim 1 wherein said annular protrusion of said covering plug has its inside peripheral surface flared in the direction away from the access opening of the storage vessel.

4. A container as claimed in claim 7 wherein said fluorocarbon resin is selected from the group consisting of a trifluorochloroethylene polymer, a tetrafluoroethylene polymer and a tetrafluoroethylene-hexafluoropropylene copolymer.