Reaction Vessel Closure

Abstract

A vessel for small quantities of liquid including a top closure comprising a pierceable foil responsive to puncture by an obliquely sharpened cannula by elastic deformation of the prick hole into close bearing contact with the cannula.

Description

BACKGROUND OF THE INVENTION

The invention relates to reaction vessels for holding small quantities of liquids. In particular, this invention relates to reaction vessels which may be handled automatically and which include top closures.

It is common to use small vessels for the processing of small quantities of liquids. During such processing, for example, portions of the liquid within the reaction vessel may be extracted or inserted with a pipette, or cannula. Generally, test tubes are not suitable because due to their dimensions they tend to spread out the small quantities of liquid, they are cumbersome to clean, and they are relatively expensive.

On the other hand, it has also become common to process small quantities of liquids while using small plastic reaction vessels. Such vessels, for example, may be about 30 mm. high and have a diameter of 15 mm. These vessels are cheap to produce and need not be cleaned since they are dispensable. This is advantageous because it saves the cost of cleaning and also eliminates possible faulty reactions due to deficient cleaning.

It is important to provide a closure for the reaction vessel that can be easily handled, particularly during the processing of the liquid and still more particularly, in the event that the processing is automatic. During automatic processing, a portion of the liquid is often taken out by means of a cannula introduced into the vessel. In the event of a series of tests, the cannula may be brought successively into different vessels, each containing different liquids. The cannula is customarily cleaned internally between successive operations. On the other hand, there is a danger during such series tests that errors will be introduced due to the entrainment of liquid on the outside of the cannula.

In the past, test tubes and reaction vessels have been sealed with cotton wads or elastic covers such as rubber stoppers. It is particularly undesirable to use cotton wads with reaction vessels because they do not make a tight seal and they will often foul the stored liquid. These prior sealing means offer no solution to the problem of entrainment of liquids on the outside of the cannulas and they prove a nuisance when they must be completely opened before the introduction of the cannula.

A still further problem encountered when using reaction vessels arises because such vessels are sometimes heated. Due to the resulting volume expansion of the contents of the vessel, if the vessel cover is clamped closed, there is a danger that the cover will be forcibly ejected. In the event of this occurrence, the vessel closure is completely removed and creates the possibility of vaporization or evaporation of the contents. In fact, during certain processes, even the temporary removal of a cover gives rise to this possible disadvantage.

SUMMARY OF THE INVENTION

The problems noted above are solved by the unique combination of vessel and closure means utilized in the present invention. The reaction vessel disclosed herein provides a closure which permits the extraction or introduction of liquid by means of a cannula while avoiding entrainment of liquids upon the outside surface of the cannula and, furthermore, insures a continuous largely dust-free closure following introduction of the cannula.

An object of the invention is to provide an improved reaction vessel having a closure means which automatically cleans the external surface of the cannula that is used to pierce it.

Another object of the invention is to provide an improved reaction vessel having a closure means which does not require removal during extraction of samples therefrom.

Another object of the invention is to provide an improved reaction vessel having a closure means which provides dust-free closure following introduction of a cannula and after extraction thereof.

Another object of the invention is to provide an improved reaction vessel that can be heated without danger of having the contents force complete removal of the closure means.

In accordance with the invention, there is provided a reaction vessel having a closure comprising a pierceable foil. The thickness of this foil is related to its elasticity such that when the foil is pierced by a cannula, the elastic deformation of the prick hole edge effects a bearing contact of the foil on the external wall of the cannula.

In one illustrative embodiment of the invention, the foil is joined to the upper edge of the vessel by welding. In another illustrative embodiment of the invention, a hollow-type cover is employed adapted for insertion within the throat of the vessel. In this latter embodiment, the bottom of the cover comprises the aforementioned foil and exhibits the characteristics hereinbefore described.

A more complete understanding of the objects and features of the present invention will be available following a consideration of the specific illustrative embodiments shown in the illustrated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view through a vessel having a closure according to one illustrative embodiment of the invention; and

FIG. 2 shows a cross-sectional view through a vessel having a closure according to a second illustrative embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, it will be seen that a typical reaction vessel 1 is illustrated. The upper edge of this reaction vessel has an outwardly extending edge flange 2. A foil 3 is stretched over this edge flange and is welded to the periphery thereof. The foil has a thickness with respect to its elasticity such that when it is pierced by a sharpened cannula, the elastic deformation of the prick hole edge effects a bearing contact upon the walls of the cannula.

In use, it has been found that a suction cannula sharpened with an angle smaller than 20.degree. may be advantageously employed. When utilizing such a cannula with a foil having a thickness of about 0.1 mm., as the foil is pierced by the cannula, it arches downward to a certain degree causing an elastic expansion at the instant of piercing. This expansion recedes following the piercing so that due to the elasticity of the foil, it hugs closely to the cannula wall about the periphery of the prick hole edge. When the cannula is later extracted, a good wiping effect is achieved. Still further, when the cannula is extracted, there remains at most only a very small opening and therefore the covering is substantially preserved. It has been found that in order to achieve the desired wiping effect, a foil thickness of 0.08 to 0.35 mm. is advantageous and a foil thickness ranging from 0.1 to 0.3 mm. is preferable.

The foil 3 in FIG. 1 is preferably affixed to the vessel edges 1 under slight tension. With this type of construction, a thickness of foil in the lower range of the above-cited range will be preferred. Advantageously, a foil thickness of about 0.1 mm. can be used for this welded closure arrangement. It has been discovered that with the welded foil closure, it is possible to heat the reaction vessel over 100.degree. C. Under the resulting pressure, an unpierced foil closure will expand and arch due to the volumetric expansion of the contents of the vessel; nevertheless, when subsequently pierced, the area of the foil surrounding the prick will retain enough natural elasticity to effect the desired wiping of the cannula when it is extracted.

An ancillary feature of the present invention resides in the fact that the prick hole also fulfills an identification function. As a result of the prick hole, there is a discrete mark on the vessel cover which indicates with certainty that the particular vessel has been served with the cannula. In automatic processing systems particularly, this positive indication of prior processing may be of extreme importance.

FIG. 2 illustrates another top closure utilizing the principles of the present invention. As shown in this FIG., a hollow cover 4 is inserted into the upper edge of the vessel 1. The dimensions of the hollow cover are such that it is pressed into the upwardly chamfered throat of the reaction vessel. The bottom of cover 4 is formed of a foil 5 which may be present, for example, at the lower section of the hollow cover edge 6. As a result of the hollow cover edge, it is possible upon insertion to achieve a satisfactory edgewise support so that a somewhat greater foil thickness is appropriate. This greater thickness permits certain advantages and heightens the desirable effects achievable through the elasticity of the cover. In fact, it has been found advantageous with closures of the type shown in FIG. 2 to utilize a foil thickness in the range between 0.2 and 0.3 mm. Within this size range, one finds that the cover tends to fit tightly to the vessel and there is little danger of loosening during cannula extraction or as a result of increased pressure within the vessel itself.

In connection with the closure shown in FIG. 2, the somewhat thicker dimension of the foil proves advantageous because during extraction of a cannula, there is a canting or upward tilting of the prick hole edge which provides a greater wiping surface and consequently a better wiping effect.

The preceding description has set forth two specific embodiments of the invention. No detailed comments concerning the material of either the reaction vessel or the closure means have been made. Advantageously, the foil, like the vessel, may be made of a polypropylene-based plastic. On the other hand, there is no intention to limit the invention to the use of any particular material. It is intended in the following claims to include all such modifications and variations of the disclosed embodiments as come within the skill of those in the art.

Claims

What I claim is:

1. A reaction vessel for small quantities of liquid and having a top closure adapted to be pierced by a sharpened cannula, said top closure consisting of a foil bridging substantially the entire throat of said vessel, said foil exhibiting sufficient elasticity to provide elastic deformation of a prick hole edge to effect bearing contact upon the outer wall of such a cannula.

2. A reaction vessel according to claim 1, characterized in that said foil has a thickness within the range of 0.08 to 0.35 mm.

3. A reaction vessel according to claim 1 wherein said foil is joined to the upper vessel edge by welding.

4. A reaction vessel according to claim 3 wherein said foil is applied under a slight tension.

5. A reaction vessel according to claim 3 wherein the thickness of said foil is in the range of 0.08 to 0.2 mm.

6. A reaction vessel according to claim 3 wherein said foil is approximately 0.1 mm. thick.

7. A reaction vessel according to claim 1 wherein said foil is an integral part of a removable cover and said cover includes a reinforced edge, said cover being adapted for insertion into the upper throat of the vessel.

8. A reaction vessel according to claim 7 wherein the thickness of the foil is in the range of 0.2 to 0.3 mm.

9. A reaction vessel according to claim 1 wherein the foil and the vessel are both fabricated from a polypropylene-based plastic.

10. A reaction vessel according to claim 7, wherein said cover and said vessel are formed as integral components of a single polypropylene-based plastic unit.

11. A reaction vessel for small quantities of liquid, having a substantially cylindrical upper body portion with a top closure adapted to be pierced by a sharpened cannula; said top closure consisting of a foil substantially bridging the opening of said upper body portion; said foil and said vessel being fabricated of polypropylene-based plastic; and said foil having a thickness of 0.08 to 0.35 mm. and being characterized by sufficient elasticity such that the prick hole edge effects bearing contact upon the outer wall of a piercing cannula.

12. A reaction vessel according to claim 11, wherein said foil is an integral part of a removable cover having a reinforced edge and dimensioned to fit within the opening of said upper body portion, and wherein said cover is an integral part of said vessel.