WO2004048919A1

WO2004048919A1 - Method and apparatus for testing integrity of sealed containers

Info

Publication number: WO2004048919A1
Application number: PCT/AU2003/001579
Authority: WO
Inventors: Andrew James Donald; George Kourdelis
Original assignee: Andrew Donald Design Engineers Pty Ltd
Priority date: 2002-11-26
Filing date: 2003-11-25
Publication date: 2004-06-10
Also published as: AU2002952919A0

Abstract

A method and apparatus for testing the integrity of a container (of the type defined) both rely for their effectiveness on monitoring or detecting changes in the level op the content of a container (or containers) when subjected to a pressure other than ambient. A container which is in any way defective will experience a lasting charge in its level of content once a test cycle has been completed and the pressure in the testing apparatus or chamber has been returned to ambient.

Description

METHOD AND APPARATUS FOR TESTING INTEGRITY OF SEALED CONTAINERS

Field of the Invention

The present invention relates, in general terms, to a method of and apparatus for testing the integrity of a container or package. More particularly, but not exclusively, the invention relates to a method of and apparatus for testing the integrity of containers, packages, or the like receptacles of the general type which are constructed principally of a flexible material and which are adapted, in use, to retain or hold a quantity (predetermined, prescribed or otherwise) of a substantially non-compressible material, more especially a liquid, as the contents thereof.

Throughout the ensuing description reference will be made to especially preferred embodiments of the method and apparatus in accordance with the present invention, for use in testing to determine whether packages, containers, sachets or the like receptacles of this general type, hereinafter referred to collectively as "containers", for such substantially non-compressible materials have one or more holes, discontinuities or the like therein which may allow for either (i) undesirable leakage of content therefrom and/or (ii) ingress of other material thereinto, subsequent to creation of the overall container, introduction of content thereinto and sealing thereof, and prior to any additional processing, marketing and/or storage of a thus sealed container. It should be understood, however, that the ensuing description does indeed relate merely to preferred embodiments of the invention, with the invention under no circumstances to be considered to be in any way limited to any such preferred embodiments as disclosed herein. In particular it should be understood that the expression "container" as employed throughout this specification is intended to refer to any means or receptacle, constructed principally or partially of a flexible material, employed for purposes of housing a substantially non-compressible material, as for example a liquid or, for that matter, a substance in powdered or granular form.

Description of the Prior Art

It should be understood that containers of this general type enjoy frequent usage nowadays, for example in the medical and/or pharmaceutical industries, as for the packaging of predetermined dosages or amounts of any number of different substances, for a variety of different purposes. By way of example only such containers, sometimes referred to as "ampoules", may contain a vaccine or the like, or may be used for holding blood, plasma or the like, or indeed may be utilised for retaining, prior to dispensing, any pharmaceutical or the like material or medicament in substantially liquid (or even solid or semi- solid) form. Contamers ofthis type may be of any suitable size and shape, dependent upon the desired context of usage. In actual fact, however, containers of this general type may also be employed for housing substances, as for example pharmaceuticals or medicaments, in other than a liquid form, as for example in a powdered or granular form.

Whilst the method and apparatus in accordance with the present invention are particularly suited for testing the integrity of containers for medicines/medicaments, they can be used equally successfully for testing the integrity of any container intended to be filled, or partially filled, with content (of any type) and then sealed. Other possible contexts of usage, therefore, include flexible containers for the storage of foodstuffs (of any given type), especially in liquid form.

Regardless of content, any container of this general type is preferred to be leak- proof and intact (once sealed), as well as being not prone to contamination, as for example by ingress of other material, whether gaseous, liquid or solid, prior to use. This is perhaps nowhere more so the case than when the container is intended to house, for example, a predetermined dosage or amount of a particular substance, as for example for a medical purpose, such as a prescribed dosage of a medicament. The consequences of a container holding, at point of use, less than the prescribed dosage due to leakage, or in the alternative having been tainted by some other substance having gained entry thereinto, may be potentially catastrophic for the end user, this especially if such contents are intended for treatment of a life-threatening or uncomfortable condition.

Containers, more commonly referred to as sachets or ampoules, when intended to house or contain a prescribed/predetermined dosage of a medicament, are generally manufactured, filled and sealed in high-speed processes. Despite practical requirements, in effect regardless of what production techniques are employed, there can be expected to be defects in at least a percentage of containers of this general type as manufactured (generally in high-speed, high output operations). In the past a number of methods and means have been employed for purposes of testing the integrity of such containers of this general type. Such prior art methods and means, for example, have entailed subjecting the containers to vacuum and then monitoring parameters of the containers, such as for example internal pressure, volume, etc., for purposes of determining variations therein, with such variations intended to be indicative of any leakage of content.

Various means have been employed for purposes of effecting the relevant monitoring. Such prior art methods and apparatus have been found to be quite expensive, to not readily lend themselves to use with high-speed manufacturing processes, to be subject to practical problems and difficulties, and not to be overly successful when any hole, aperture or discontinuity is of a reduced size, as for example of the order of one Angstrom or less. By way of example only, when a testing method relies on the existence of a vacuum for its effectiveness, serious problems in practical and engineering terms can be expected to be encountered in terms of creating, and then maintaining, the requisite vacuum. The normally employed procedures for testing such ampoules or sachets, as exiting from a production line, have involved subjecting what is referred to as a "rack" of such ampoules or sachets to a monitoring/testing regime. Such a rack may contain any number, but preferably from four (4) to ten (10) such ampoules or sachets. The prior art methods, however, suffered from the drawback of only being able to determine that a member (or members) of a rack being tested was defective. They could not isolate which member (or members) was (or were) actually defective. In the result the practice has been to reject the entire rack, this regardless of whether one, or all, of the members thereof were defective. The significance of this inability to actually identify or isolate a defective container, in terms of wastage of product (content) should be self-evident.

The present invention seeks to overcome the problems and disadvantages associated with the prior art by providing an improved method of and apparatus for testing the integrity of a container (as hereinbefore described) which does not rely for its effectiveness on any need for sealing of the actual testing environment (whereby to maintain a pre-established pressure) during operation/testing. The present invention also allows for actual identification or isolation of an individual container.

The invention also seeks to provide a method and apparatus which will give rise to a satisfactory testing regime virtually regardless of the actual size of any hole, aperture or discontinuity which might exist in any such container. Indeed the method and apparatus of the invention are capable of detecting a hole as small as five (5) microns in size.

The invention further seeks to provide a method and apparatus which will expedite testing of such containers by significantly reducing the time involved in any test cycle, and yet is capable of detecting the ingress into a container of any unwanted substance or material. In accordance with a first aspect of the present invention, therefore, there is provided a method for testing the integrity of a container (as hereinbefore defined), said method including the steps of: subjecting said container to a pressure other than ambient; observing and/or monitoring any change in the level of the content of said container; returning the pressure to ambient; and observing and/or monitoring any change in the level of the content of said container subsequent thereto, wherein any residual change in the level of the content of the container at the end of a test cycle is an indication of the existence of a leak in said container.

In accordance with another aspect of the present invention there is provided an apparatus for testing the integrity of a container (as hereinbefore defined), said apparatus including: a test chamber or receptacle for receiving at least one of said containers for purposes of testing, said chamber having associated therewith: means which allow for continuous observation and/or monitoring of the level of content within said at least one container; means for introducing a gas into said test chamber, from a supply or reservoir therefor, whereby to generate a pressure other than ambient within such chamber and to give rise to the imposition of a load on said container; and means for subsequently restoring the pressure within said container to ambient.

Preferably the method and apparatus in accordance with the invention are carried out at a pressure greater than ambient or atmospheric. It should be realised, however, that in practical terms, and dependent upon the nature of the container being tested, then a pressure less than ambient may be involved.

Description of the Drawings

In order that the invention may be more clearly understood and put into practical effect reference will now be made to especially preferred embodiments of a method and apparatus in accordance with the invention. The ensuing description is given by way of non-limitative example only and is with reference to the accompanying drawings, wherein:

FIG. 1 is a side elevational view of two separate containers in accordance with the present invention, the first in its normal or unpressurised condition and the second when pressurised, such showing how, as pressure increases on the exterior of a container, when intact and properly sealed, the container will collapse to equalise the inside pressure with the outside, resulting in an increase of the level of content within the container;

FIG. 2 is a schematic drawing of an apparatus for testing in accordance with the present invention;

FIG. 3 is a process flow diagram showing, schematically and sequentially, the steps involved in carrying out the method and apparatus of the invention; and

FIG. 4 is a perspective view of one embodiment of an apparatus in accordance with the present invention, intended to be added (in any suitable manner) to a production line for containers.

Description of the Preferred Embodiments

The method in accordance with the present invention involves the placing of one or more sealed containers within a given space or test chamber and subjecting such container or containers to a testing cycle, during the course of which the pressure within the test chamber itself is altered. The or each container will have a preferably predetermined amount of content, as for example in the form of a non-compressible liquid, housed therewithin, and will further include a head space above the surface of the content which will contain either a compressible gas or air. The test chamber will include means for viewing and measuring/monitoring variations in the level of content within the container throughout the course of the relevant test cycle.

In an especially preferred embodiment the container to be tested will be in the form of a body having at least one flexible surface that is in contact with the contents thereof, such surface preferably further including at least one section constructed from a transparent material, whereby to allow for viewing and monitoring of the level of content of the container throughout the course of a test cycle. In the especially preferred embodiment illustrated and described herein, such viewing and monitoring may be achieved manually, with the tester visually observing and noting any changes in the level of content within a given container during the course of any test cycle. It should be realised, however, that a variety of different means, other than "manual", may be employed for effecting the desired monitoring. By way of example only, any suitable and known manual and/or automatic means may be employed, as for example a ccd camera-based vision system or a moving single point laser sensor. Electrical or electronic sensor means may also be employed to detect and monitor any changes in content level within a given container. In actual fact, on-going developments in the relevant technology will mean that, with the passage of time, further ways and means of effecting the desired monitoring may present themselves. The actual means employed for achieving the desired observing/monitoring is not of the essence of the invention, with any suitable method and means to be included within the scope of the present invention.

There will now be described, in more detail, a typical test sequence or cycle in accordance with the method and apparatus of the present invention.

Initially one (or more) containers 1 - with content and sealed - are located in a test chamber 2, of any given size and shape, and the chamber 2 is closed. In that regard it should be noted that, whilst in one possible embodiment the chamber 2 may be so constructed as to be capable of actually being sealed - meaning being made proof against leakage of content or ingress of air or other gas/material - such need not be the case. Preferably the, or each, container 1 to be tested is adapted to be so disposed or oriented within the chamber 2 itself that, with a change in shape or collapse of the overall container 1 due to the application of a load/pressure thereto, it will be possible to readily observe or monitor any change in the level of the content within the or each container 1 itself. In an especially preferred embodiment, and whereby to ensure that the surface level of content will exhibit a rise, under pressure or load, which will be more readily detectable, then the smallest cross-section of the body of the container 1 should be aligned towards the horizontal plane.

With the chamber 2 thus closed, and yet not necessarily sealed, the actual surface level of the content of the or each container 1 will be noted, such to constitute a datum for subsequent observation. A suitable gas, even air, may then be introduced into the test chamber 2 - using any suitable means 3 - whereby to give rise to an increase in the pressure existing within the chamber 2 itself. This increase in pressure will result in the container 1 undergoing a change in shape - as for example by collapsing inwardly over at least a portion thereof. After a short interval under such other than ambient pressure, in particular a time sufficient to allow for a virtual state of equilibrium of the container 1 and its contents to be reached, thus to in turn allow the surface level of the content of the container 1 to stabilise, the actual level of content within the container 1 will again be monitored and measured, relative to the aforementioned datum. If the container 1 is intact, with no holes/leaks whatsoever which would allow for either leakage from the container 1 of content or, in the alternative, entry into the container 1 of other material, as for example gas, then upon subjection thereof to an elevated pressure there will be a discernible, and sustainable, change in the level of content for so long as that other than ambient pressure is maintained. If there is a major leak (or leaks), then in all likelihood there will be little, if any, detectable change in the level of content within the container 1 , even under other than ambient pressure, because gas from the chamber 2 will be able to enter the container 1, equalising internal and external pressures thereof.

A further short interval after the initial pressurisation of the chamber 2, the level of content within the container 1 will again be measured/observed, and compared with the aforementioned datum. The method and apparatus in accordance with the present invention is such that, by observing/measuring/noting the level of content within a container 1, firstly when initially placed in the test chamber 2, secondly once stabilised under a pressure other than ambient within that chamber 2, and then after a further short period, and comparing and contrasting the results, there will be secured an indication as to whether the container 1 is intact (leak-free), has a small source for either leakage of content therefrom or entry of other material thereinto, or has a major or large source of leakage and/or ingress, as explained hereinafter.

Firstly, with an increase of pressure within the test chamber 2 from a first ambient value to a second larger value, the flexible body of a "good" test container, meaning a container 1 which is intact and which has no apertures, holes or discontinuities therein (of any size), will tend to collapse inwardly in an attempt to equalise the pressure within the test container 1 with that existing in the test chamber 2 itself. As the test container 1 collapses inwardly its internal volume will be reduced, thereby causing the surface level of any content inside to rise. Such an increase or rise may be observed/monitored visually, or by any other suitable means or method.

With the increase of pressure within the test chamber 2 from a first value to a second elevated value, and where a faulty container 1 is being tested, as for example a container which has a hole (or holes) of a sufficient size to allow any air or gas in the test chamber 2 to freely pass therethrough whereby to equalise the pressure within the test container 1 to match the pressure within the test chamber 2, as for example a hole (or holes) of a diameter in excess of 0.15mm, the reaction during testing will be effectively instantaneous. The flexible body of the test container 1 will substantially retain its initial shape, since gas can freely pass both into and out of the container, equalising the pressure within the camber, and the surface level of the contents will remain substantially constant. With an increase of pressure within the test chamber 2 from the first ambient value to the second elevated value, and with a faulty test container 1 of a type that has one or more small holes, as for example of a diameter less than 0.15 mm, of a size where the air or gas in the test chamber 2 only passes through slowly to gradually increase the pressure within the test container 1 to match the pressure within the test chamber 2, then the test container 1 initially collapses inwardly, causing the surface level of the liquid to rise. However, as the air or gas passes through into that container 1 the body of the test container 1 will tend to slowly return to its original shape, and the content level will fall progressively until such time as the pressure inside the test container 1 matches the pressure within the test chamber 2. As such, the content level will initially rise, then gradually return to the datum level (or thereabouts).

For most applications normal dry filtered compressed air is a satisfactory medium for pressurising or increasing the pressure within the test chamber 2. However, where very small holes in the test containers are to be detected, and/or the test cycle is required to be of a short duration, such as for in-line testing of mass-produced containers, helium gas may used, since it will penetrate flaws or holes down to about one Angstrom in size.

When a test container 1 is loaded into the test chamber 2, the chamber 2 is closed and a pressurising gas or air supply enters through a port 3 located at the top thereof. This supply is maintained at a set pressure point during each phase of the testing in order to maintain the pressure in the test chamber 2 at the set point even if the chamber 2 is not perfectly sealed.

When helium (or any other gas having a density or molecular weight lower than air ) is used, the test chamber 2 is closed after the test container 1 is loaded and a helium supply introduced at the top of the chamber via the port 3. A purging valve 4 (or the equivalent) positioned at the lowest point of the test chamber 2 remains open for a time to allow the denser gases at the bottom of the chamber 2 to be displaced. The purging valve 4 is then closed. As the pressure within the test chamber 2 rises to the second pressure setting, the surface level of the content in the test container 1 shpuld undergo a corresponding rise. Test measurements of the surface level of the content in the test container 1 are taken after the test chamber 2 pressure has stabilised at the second pressure value and again after another short interval. By comparing the measurements it is possible to distinguish whether the test container 1 is leaking.

The purging valve 4 has two functions. Firstly, when helium is used as the test gas the purging valve 4 at the bottom of the test chamber 2 remains open for a period of time while the helium is fed into the top of the chamber. Since helium is lighter than air, then the helium fills the chamber 2 from the top down and the heavier air (or other gas) is expelled from the test chamber 2 through the purging valve 4. Secondly, when each test is completed the purging valve 4 is immediately opened to return the test chamber 2 back to the first pressure setting (the datum). Any content displaced from the test container 1 during the test will collect at the lowest point of the chamber 2 and be exhausted from the test chamber 2 via the purging valve 4.

The method and apparatus in accordance with the present invention are best suited for the testing of containers constructed of any material which is flexible, or at least partially flexible, yet has a degree of "memory", meaning a tendency to want to return to its original condition (shape) if disturbed in any way and once the disturbing means or medium been removed or withdrawn.

In a more practical vein, however, the tendency of any container to firstly deform under load and then return to its original shape once the load is removed is also dependent upon other factors, as for example the actual shape of the container itself.

By way of example only, for containers intended to house liquids, such will generally be of a shape, or formed from a material, which allows for ready restoration of the original shape. However, for a container intended to hold a solid or powder substance, the material of construction need not be as flexible and have the same degree of "memory". For such contexts of usage the applicant's method and apparatus could allow for testing of such containers at a pressure less than ambient. It should be realised, however, that the method and apparatus of the invention do not rely for their effectiveness on a sealed testing chamber or environment. There is in fact no need for the possibly complicated, and accordingly expensive, sealing means necessary with prior art techniques.

In an alternative embodiment, therefore, the method may involve substantially reducing the pressure within the test chamber (using any known and suitable means).

The apparatus in accordance with the present invention is designed (and intended) to be a stand-alone type unit, which can be readily incorporated into existing finishing lines, as well as included in newly-created lines. In that regard reference is now made to FIG. 3, which is a schematic representation or process flow diagram identifying the various steps involved in effecting the method and utilising the apparatus in accordance with the present invention. In essence, the steps involved can be summarised as follows:

(1) product containers loaded into chamber;

(2) chamber closed (not necessarily perfectly sealed);

(3) surface level of contents in product is noted (taken as the datum); (4) a suitable gas is introduced into the chamber and continues to be introduced to maintain the desired pressure in the chamber during testing;

(5) once pressure is established, a measurement of the liquid level is taken relative to the datum;

(6) after a further short period of time, the level will be taken again to determine if a leak exists;

(7) pressure then released from chamber through the purging valve; and (8) product is removed from the chamber.

In an especially preferred embodiment, not shown, an apparatus in accordance with the present invention will consist of at least two testing units, each comprised of two ampoule or container racks having inserts intended to suit ampoules/containers of differing types (sizes, shapes, etc). The system will be such that one unit will be being loaded with containers to be tested, whilst the other is undergoing testing. Preferably some form of clamping means - of any known type - may be employed to assist in unloading and loading of the test units.

Preferably lighting means (of any suitable type) and other necessary components may be included to facilitate monitoring. In one especially preferred embodiment (not shown), a suitable vision system, light and other components may be located within a test unit or chamber, with relevant information from a test to be displayed, for purposes of viewing and/or storing, on a monitor or the like.

In the arrangement of FIG. 4 side-by-side racks 5 of containers - in this particular instance each rack includes two sets often (10) containers - are adapted to be sequentially subjected to a testing procedure in accordance with the invention. Means of any suitable type are employed to sequentially pass pairs of racks 5 through a given testing station.

The apparatus effectively operates as two (2) units, the arrangement being such that, whilst one unit or rack (5) is being loaded, the other is being tested. Each unit is preferably comprised of two ampoule rack compartments 5, which have inserts to suit different ampoule types (shapes, sizes and configurations or the equivalent, will be employed to move a clamping system between the two unites, so that one unit is open to allow loading and unloading, whilst the other is closed (sealed) to facilitate testing. A suitable vision system, lighting assembly and other components preferably required to further facilitate testing can be appropriately located within the overall unit shown in FIG. 4, with testing information being capable of being displayed on a monitor to be located nearby. In an especially preferred embodiment the aforementioned camera means and appropriate lighting means may be located in the rear of the unit shown in FIG. 4.

The method and apparatus in accordance with the invention have been particularly designed with self-checking protocols which make the procedure of testing effectively failsafe. The following is an explanation of the various situations which can present themselves.

For a container/ampoule to successfully negotiate a testing procedure, thereby signifying it has no detectable holes or discontinuities therein, then the following requirements must be met:

(i) the liquid or content level must rise during pressurisation;

(ii) that level must stabilise under uniform pressure;

(iii) when the pressurising gas is expelled, the level must return to its original position; (iv) the ampoule must return to its original shape; and

(v) the system must confirm that the content level has followed this sequence and that the shape of the container has changed (during pressurisation) and then returned to its original (size and shape) at the completion of the test cycle. Where a container is (or more than one container in a rack is) faulty, then the or each container which has hole (s) or discontinuities will display one of the following characteristics:

(a) the level of content does not rise under pressure; or

(b) the level rises but does not stabilise. If the fault has not been identified during pressurisation, then after the gas has been expelled a faulty ampoule/container will display one of the following characteristics:

(a) the level of content does not immediately return to its original level; or

(b) the ampoule body has expanded and remained expanded after release of pressure.

During a test the system monitors a sequence of changes to the liquid (content) levels as outlined previously. Provided the gas supply is able to maintain a stable pressure within the chamber during a test a satisfactory test sequence can be performed. The system test pressure is monitored for stability.

The system checks for a change in the level of the liquid (content) as the test chamber pressure increases and looks for stability in the level and the gas pressure within the chamber has stabilised. If there is a technical fault, and the pressure does not stabilise, or the vision system is not picking up a signal, the ampoule rack will be rejected, as the vision system cannot verify that the ampoules have satisfied all of the criteria needed to pass the leak detection.

The method and apparatus in accordance with the present invention exhibit a number of important advantages over the arrangements previously known and in use.

Firstly they allow for ready detection, in a cost-effective and extremely efficient manner, of a lack of integrity in any given container, regardless of the size of the hole, aperture or discontinuity responsible for such lack of integrity. The applicant's method and apparatus will readily detect ingress of gas or other unwanted material into a container as being tested. To the best knowledge of the applicant no prior art detection system, which principally rely on creation of vacuum and testing in vacuo, has the ability to detect such ingress. Secondly there is no need for the test chamber to be "perfectly" sealed. This is in marked contrast to certain, if not the majority, of the prior art arrangements. So long as a substantially stable pressure can be maintained within the test chamber, and hence on the container being tested, then there is no need for the chamber itself to have a gas-tight seal. More importantly, and since the method and apparatus rely for their effectiveness on monitoring of changes in the level of content, they do not require a sealed testing environment, this regardless of whether relying on a testing pressure greater than or less than ambient (even if approaching vacuum). The practical consequences thereof, in terms of reduction in cost of both manufacture and operation of the overall apparatus, should be self-evident. Furthermore, and by not needing to have the test chamber sealed, then consistency of testing is more or less assured. There is no need to expend time, effort and money in ensuring that, between test cycles and prior to each cycle, sealing of the chamber is achieved.

Thirdly, the present invention allows for detection of even microscopic discontinuities/holes etc. In that regard it should be understood that the relevant authorities, as for example the Federal Drug Authority in the United States, are nowadays becoming increasingly more demanding in their requirements for containers or ampoules of the type used for packaging pharmaceuticals and the like products. Such ampoules must be capable of being tested to guarantee that there does not exist any hole therein which is greater than five (5) microns. A "normal" gas, as for example air, will not be capable of passing through a hole of that size, or less. However a lower molecular weight, lighter gas such as helium will be able to pass through holes of that size.

The present applicant's method and apparatus ensures uniformity of testing procedures and, as a consequence, uniformity of end products - the containers.

It should further be understood that with the method and apparatus of the present invention testing can be done, repetitively and accurately, at normal production line speed. This is of especial significance when compared with the known art.

With the present method and apparatus, not only is it possible to determine that, in a given rack (from four to ten) of containers being tested there exists one (or more) defective containers, more importantly it is possible to actually identify the (or each) defective container. This is in marked contract to the prior art methods, and is especially significant in terms of minimising unnecessary wastage.

In an especially preferred embodiment, with the present applicant's invention higher pressures may be employed within the test chamber, to thereby subject the container being tested to greater pressure differentials. In that regard it must be realised that, with methods and apparatus that rely on testing in vacuum, the pressure differential is limited - to one bar or atmosphere. In contrast thereto, with the present method and apparatus much higher pressure differentials may be employed, giving rise to significant and readily detectable variations in content level within a container. This is especially important when one realises that, generally speaking, any holes which may exist in such containers can be expected to be quite small. In a purely practical vein, pressure differentials of 2, 3 bar or higher may be employed.

Finally, it is to be understood that the preceding description refers merely to preferred embodiments of the present invention and that variations and modifications will be possible thereto without departing from the spirit and scope of the invention, the ambit of which is to be determined from the follow claims.

Claims

1. A method for testing the integrity of a container (as hereinbefore defined), said method including the steps of: locating a container within a test chamber and subjecting at least a portion of said container to a pressure other than ambient; observing and/or monitoring any change in the level of the content of said container; returning the pressure to ambient; and observing and/or monitoring any change in the level of the content of said container subsequent thereto, wherein any residual change in the level of the content of the container at the end of a test cycle is an indication of the existence of a leak in said container.

2. The method as claimed in claim 1, wherein said pressure other than ambient is achieved by introducing a gas into said test chamber.

3. The method as claimed in claim 2, wherein said introduced gas is air.

4. The method as claimed in claim 2, wherein said introduced gas is helium.

5. The method as claimed in claim 4, wherein said introduced gas has a density or molecular weight which is less than air.

6. The method as claimed in claim 1, wherein said pressure other than ambient is a pressure in excess of 1 atmosphere.

7. The method as claimed in claim 7, wherein said pressure is in excess of two atmospheres.

8. The method as claimed in claim 7, wherein said observing and/or monitoring step is effected manually.

9. The method as claimed in claim 7, wherein said observing and/or monitoring step is effected other than manually using a ccd camera- based vision system or a single point laser sensor.

10. The method as claimed in claim 7, wherein said observing and/or monitoring step is effected using electrical or electronic sensor means.

11. An apparatus for testing the integrity of a container (as hereinbefore defined), said apparatus including: a test chamber or receptacle for receiving at least one of said containers for purposes of testing, said chamber including: means which allow for continuous observation and/or monitoring of the level of content within said at least one container; means for introducing a gas into said test chamber, from a supply or reservoir therefor, whereby to generate a pressure other than ambient within said chamber and give rise to the imposition of a load on said container; and means for subsequently restoring the pressure within said chamber to ambient.

12. The apparatus as claimed in claim 11, wherein said test chamber includes an inlet port, for the introduction of pressurising medium; and at least one outlet means, for relaxation of pressure and to allow for egress of unwanted material from the chamber upon completion of a testing cycle.

13. The apparatus as claimed in claim 12, wherein said at least one outlet means is a purging valve, disposed at or in the vicinity of the bottom of said test chamber.

14. The apparatus as claimed in claim 13, wherein said pressure other than ambient is achieved by introducing a gas into said test chamber.

15. The apparatus as claimed in claim 14, wherein said introduced gas is air.

16. The apparatus as claimed in claim 14, wherein said introduced gas is helium.

17. The apparatus as claimed in claim 14, wherein said introduced gas has a density or molecular weight which is less than air.

18. The apparatus as claimed in claim 11 , wherein said pressure other than ambient is a pressure in excess of 1 atmosphere.

19. The apparatus as claimed in claim 11, wherein said pressure is in excess of two atmospheres.

20. The apparatus as claimed in claim 19, wherein said observing and/or monitoring step is effected manually.

21. The apparatus as claimed in claim 19, wherein said observing and/or monitoring step is effected other than manually using a ccd camera- based vision system or a single point laser sensor.

22. The apparatus as claimed in claim 19, wherein said observing and/or monitoring step is effected using electrical or electronic sensor means.