GB2253698A - Method and apparatus for testing packages - Google Patents

Abstract

A method and apparatus for determining whether or not a vacuum is maintained within vacuum packages 20 comprises applying acoustic signals from a signal generator 24 to each package by means of a transducer 26, detecting signals transmitted through or reflected from the package using transducer 28 which may be placed on any face of the package and determining from the characteristics of the received signals whether or not the vacuum has been maintained within the package. <IMAGE>

Description

Improvements Relating to the Testing of Packages This invention relates to the testing of packages, and in particular concerns a method and means for testing the soundness of a package of a type comprising an outer envelope or case which is filled with a material and then is vacated, ie a vacuum is applied thereto, and then the package is sealed so that the vacuum will be retained therein. The aforementioned "soundness" of the package to be checked is in fact an indication as to whether or not the vacuum has been maintained.

In, for example, the packaging of tea when tea leaf has been picked in a tea plantation or estate, it is subjected to various processes including comminution and drying, and eventually the resulting tea is placed in flexible bags which are sealed, and the sealed bags are then placed in transport containers, typically cardboard boxes. To keep the tea as fresh as possible until it arrives at its destination, it has been proposed that the inside of the flexible bag should be vacated and then the bag sealed, the bag being of a gas impermeable material so that when the bag is sealed, the vacuum will be retained therein.The maintenance of the vacuum is important to the freshness of the tea, and as it may be some time between packaging of the tea at the plantation or estate and eventual opening of the sealed bag for use of the tea, it is desirable that during this time the package should be checked in order to assess its soundness.

At present, the method of performing this check is to perform a visual and tactile examination. The visual and tactile examination is possible because when the vacuum inside the sealed bag exists, the sealed bag presents a drawn and sometimes crinkled or folded appearance and is hard to the touch, but in any case will be held firmly against the bag contents, whereas if the vacuum has failed, the bag will adopt a more relaxed and loose appearance and is softer to the touch. Visual examination is relatively simple to perform, but it does create considerable and perhaps unexpected problems. Thus, when the bags are inside outer containers such as cardboard boxes, then the boxes must be opened in order that the visual examination can take place.

Secondly, it is usual for the boxes to be stacked on palettes, and if the individual packages are to be visually checked, the packages must be unstacked for the performance of the visual examination. The unstacking of the packages means that the packages eventually are moved into processing machines by hand whereas if they could be retained in the stacked form, they could be delivered to automatic handling machinery for the opening and emptying of the packages.

The present invention seeks to provide a method and means whereby the soundness of the vacuum packages can be checked simply and efficiently, without requiring the visual examination as mentioned above.

In accordance with the present invention in its broadest aspect, a method of checking the soundness of a vacuum package comprises applying sonic signals thereto, detecting the effect on the sonic signals via the package, and assessing the soundness of the package from the received signals.

Specifically, the sonic signals are selected to frdm arrange of frequencies such that the received signal differentiates between a sound and an unsound pack to the greatest extent.

When the package is sound, it will behave more in the nature of a solid block and the sonic signals will be less affected by the sound package, whereas if the package is not sound, and thus therefore contains air or other undesirable gas, it will attenuate the sonic signals so that the received signals will differ markedly from the received signals when the package is sound.

The method is particularly useful for the specific tea packages mentioned above, but it is to be pointed out that the invention is not to be considered as being limited to such packages, because in fact the size of package to which the invention may be applied can vary widely. It may well be that depending upon the size of the package, so the frequency of the sonic signals will be varied so as to achieve the application of sonic signals which are close to the resonant frequency, so that the signals will be dramatically affected if the package is not sound.Although it is prefered that the outer casing of the package should be of a flexible material, it is not strictly necessary to the invention that this should be so, and the outer casing can be made up of a number of layers, for example the flexible material of the bag and the outer case material of the container, but obviously in any particular package, the advantage of the invention may be reduced or nonexistant if a very small flexible bag is placed in a very large outer container.

However, even when the outer containers each comprises an evacuated flexible bag, then the effect achieved by the invention would still apply.

The apparatus for performing the method according to the invention comprises a sonic transmitter and receiver, which may be embodied in a single unit or may be seperate items which in the case of rectilinear packages could be applied to opposite or adjacent faces, or could be applied to the same face when performing the method of the invention. It will be understood that by the utilisation of the method and means according to the invention, the soundness of packages arranged in a stack may be checked without removing the packages from the stack or without carrying out any individual visual inspection.

The apparatus may be provided with a signal indicator, such as a reading or a visual indicator such as a warning lamp to indicate when any particular package is indicated as not being sound.

The sonic signals which are applied may preferably be sine wave signals, but obviously it is not necessary to use such wave form. Any suitable wave form may be used, and different wave forms will of course provide different result characteristics.

In one embodiment of the means for carrying out the invention, a seperate speaker forming the sonic transmitter is provided and is connected to a signal generating source, whilst a microphone is connected to a signal receiver pad, and the speaker and pad are applied to respective sides or respective regions of each package to be checked. When the equipment is installed in apparatus for the automatic handling or processing of the packages, the equipment may be arranged to check the soundness of each package in sequence with the operation of the apparatus, and means may be provided automatically to reject any package which is not sound. In other cases the apparatus may be adapted to be carried by hand and the person transporting the apparatus can use it on the packages one by one as needed.

In a particularly suitable arrangement, the transmitter and receiver may be embodied in a single unit, for example a hand held unit, which is simply applied to the package surface, the sonic signals are applied, and the unit gives an indication as to whether or not the package is sound.

As mentioned herein, whilst the invention has particular application for checking the soundness of vacuum packages containing tea, it is not intended that the invention should be limited to such application, nor is it intended at this time that the invention should be limited to packages of which the outer case is of flexible material.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, within: Fig. 1 is a perspective view of a "sound" package; Fig. 2 is a view similar to Fig 1 showing the package after loss of vacuum has occured; Figs. 3 and 4 respectively are views of the packages in the Figs. 1 and 2 condition but in sectional elevation; Fig. 5 shows how the packages may be assessed according to the embodiment of the invention; and Fig. 6 shows a method of assessing packages according to a further embodiment of the invention.

Referring to Fig. 1, a rectangular package 10 comprises an outer casing 12 of a flexible impermeable material such as metallic foil or gas barrier laminate or the like, and the package in this instance as shown in Fig. 3 contains a body of tea 14. The package 10 after filling with the tea has been sealed and then evacuated and the evacuation has the effect of pulling the casing material onto the body of tea so that ripples or slight folds 16 form therein. These formations in fact provide a visual indication as to whether or not the package is "sound"; that is to say whether or not the vacuum has been maintained inside the package. If it has not, then the ripples and ridges 16 tend to disappear and the package will take on an appearance more as indicated in Fig.

2. In Fig. 4 where the package has leaked, the package may contain air as indicated at 18, and generally the tea will be looser than in the sound package shown in Figs. 1 and 3.

When tea is transported from a plantation it will be contained in packages in outer containers 20 of cardboard, and indeed the containers 20 typically will be stacked on palettes 22 as shown in Fig. 5 which shows a stack seven high each layer containing four packages 20 arranged with their larger faces horizontal.

It will be understood that visually to check the packages 20 in the stack would require opening of each of the outer containers 20 to view the inner packing, and this of course requires a considerable amount of effort. Furthermore, it either requires the restacking of the packages if they are to be presented on palette 22 to automatic handling e.g.

emptying machinery, or it may simply be more convenient to feed the individual and destacked packages into such machinery.

The present invention recognizes that a sound package as shown in Fig. 1 will behave sonically in a substantially different fashion to the unsound package of Fig. 2 insofar as the application of a sonic signal to the sound package of Fig 1 will provide much less attenuation of the signal than in the case of the package of Fig. 2, due to the fact that the package of Fig. 2 contains air. The difference in effect on the sonic signal between the packages of Figs. 1 and 2 will be more marked if the signal is at frequency close to the natural frequency of the sound package of Fig. 1. The present invention makes use of this phenomenon and provides that sonic signals are applied to the packages especially when in the stacked condition as shown in Fig. 5 so that the soundness of the packages can be checked without having to open the outer containers 20.

As shown in Fig. 5, a signal generator 24 has an output connected to a speaker 26, and the speaker is applied to a side face of one of the packages 20. To the other face of the package 20 is applied pick up head 28 adapted to pick up the sonic signals issuing from speaker 26 and to convert same into any suitable output form such as for example a sonic signal in earphones 30, an output speaker 32 provided with a warning indicator light 34 or a visual display of signal level 36, or any combination of these. It has been found that even where the packing is contained within an outer container such as cardboard box 20, there is still a marked difference in output signal compared to a sound and an unsound package.

It will be noted from Fig. 5 that it is not necessary to destack the packages to perform the check, and in various manifestations of the apparatus for carrying out the invention, many possibilities present themselves. For example the apparatus could be embodied in a single hand held unit which is simply applied to each package. Warning signals and other means can be activated when packages are indicated as being unsound and so on.

The method can be adopted in a situation where packages are conveyed one by one, for example as shown in Fig. 6.

Packages 20 are conveyed one by one in a direction of arrow 38 in Fig. 6, and the speaker 26 and pick up 28 are located to opposite sides of a conveying path for the packages, said head and pick up being movable towards and away from the packages indicated by arrows 40 and 42 so that they can be synchronized with the advancement of the packages so as to test each package in turn, and a downstream pusher 44 can be arranged to eject any unsound package as indicated by dotted lines and reference 46, from the conveying path.

The frequency of the signal supplied will be dependant upon the size of package and its contents, so as to try and match the frequency of the signal to the natural frequency of the package. Typically with the packages which are dispatched from tea plantations, we have found that a sonic signal of a frequency of 600 Hz has shown itself to be suitable.

The invention is not however to be considered as being limited to any particular size or package as it can be applied to packages large and small.

The apparatus may be fixed into position as in the case of the Fig. 6 arrangement, or it may be a portable unit to be carried by a person entrusted with the work of checking the soundness of packages for example in the stack as shown in Fig. 5.

Claims (16)

1. A method of checking the soundness of a vacuum package comprising applying sonic signals thereto, detecting the effect on the sonic signals via the package, and assessing the soundness of the package from the received signals.

2. A method according to Claim 1, wherein the sonic signals are selected to form a range of frequencies such that the received signal differentiates between a sound and an unsound pack to the greatest extent.

3. A method according to Claim 1 or 2, wherein the package contains tea.

4. A method according to any preceding claim wherein the frequency of the sonic signals is varied so as to achieve the application of sonic signals which are close to the resonant frequency of the package, so that the signals will be dramatically affected if the package is not sound.

5. A method according to any preceding claim wherein the outer casing of the package is of a flexible material.

6. A method according to Claim 5, wherein the outer casing is made up of a number of layers, for example the flexible material of the bag and the outer case material of the container.

7. A method of checking the soundness of a vacuum package substantially as herein described.

8. Apparatus for performing the method according to any preceding claim comprising a sonic transmitter and receiver, which may be embodied in a single unit or may be separate items which in the case of rectilinear packages could be applied to opposite or adjacent faces, or could be applied to the same face.

9. Apparatus according to Claim 8, wherein the apparatus is provided with a signal indicator, such as a reading or a visual indicator such as a warning lamp to indicate when any particular package is indicated as not being sound.

10. Apparatus according to Claims 8 or 9, wherein the sonic signals which are applied are sine wave signals.

11. Apparatus according to Claims 8, 9 or 10, wherein a separate speaker forming the sonic transmitter is provided and is connected to a signal generating source, whilst a microphone is connected to a signal receiver pad, and the speaker and pad are applied to respective sides or respective regions of each package to be checked.

12. Apparatus according to any of Claims 8 to 11, wherein the apparatus is for the automatic handling or processing of the packages, the apparatus being arranged to check the soundness of each package in sequence with the operation of the apparatus.

13. Apparatus according to Claim 12, including means automatically to reject any package which is not sound.

14. Apparatus according to any of Claims 8 to 13, wherein the transmitter and receiver are embodied in a single unit, for example a hand held unit, which is simply applied to the package surface, the sonic signals are applied, and the unit gives an indication as to whether or not the package is sound.

15. Apparatus according to any preceding Claim 8 to 13, wherein the sonic wavelengths and receiver are mounted in relation to a station in which the package is adapted to be placed or through which it is adapted to be moved to check the soundness of the package when in said station.

16. Apparatus for checking the soundness of a vaccum package substantially as hereinbefore described with reference to the accompanying drawings.