Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3855531 A
Publication typeGrant
Publication dateDec 17, 1974
Filing dateJun 28, 1972
Priority dateJul 1, 1971
Also published asCA959936A1, DE2231441A1
Publication numberUS 3855531 A, US 3855531A, US-A-3855531, US3855531 A, US3855531A
InventorsFielibert J, Van Rooijen A
Original AssigneeLever Brothers Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of testing the seals of food containers and containers suitable therefor
US 3855531 A
Abstract
A thin-walled flexible container containing sterilised foodstuff is tested by measuring the electrical conductivity of a path from the interior of the container through the seal to the outside. A container which can be so tested non-destructively is described.
Images(2)
Previous page
Next page
Description  (OCR text may contain errors)

United States Patent [191 Fielibert et a1.

[ Dec. 17, 1974 METHOD OF TESTING THE SEALS OF FOOD CONTAINERS AND CONTAINERS SUITABLE THEREFOR [75] Inventors: Jozef Frans Fielibert, Zevenaar;

Adrianus Van Rooijen, Didam, both of Netherlands [73] Assignee: Lever Brothers Company, New

York, NY.

221 Filed: June 28,1972

21 Appl. No.: 266,939

30 Foreign Application Priority Data July 1, 1971 Netherlands 7109071 52 US. Cl 324/65 R, 53/78, 73/52, 324/65 P 51 Int. Cl GOlr 27/02 [58] Field of Search 324/65 R, 65 P; 73/52; 53/78 Primary Examiner-Robert .1. Corcoran Attorney, Agent, or FirmLever Brothers Company [5 7] ABSTRACT A thin-walled flexible container containing sterilised foodstuff is tested by measuring the electrical conductivity of a path from the interior of. the container through the seal to the outside. A container which can be so tested non-destructively is described.

2 Claims, 3 Drawing Figures PATEF-ITED W SHEET 1 BF 2 lrIIIIIIIl/lIl/r PATENTEDBEBTYIBH sumzurg METHOD OF TESTING THE SEALS OF FOOD CONTAINERS AND CONTAINERS SUITABLE THEREFOR This invention relates to the control of packaging, particularly for foodstuffs in sealed containers, and specifically to checking the seals of such containers.

Semi-rigid and flexible containers are being used more and more for the packaging of products, particularly foodstuffs which have been preserved by sterilisation. These semi-rigid or flexible containers, manufactured from materials such as metal (e.g., aluminium) coated on one or both sides with plastic or optionally made entirely of plastic, give good protection as regards tightness with respect to the surroundings as long as no damage occurs, for example as a result of rough handling. However, a source of trouble is provided by the seals for which it is not possible to guarantee tightness in 100 percent of cases, no matter what method of sealing is used, for example heat-sealing, electric or acoustic welding, etc. It will be realised that if a sterilised food container has a leak in its seal, the contents rapidly become contaminated.

Therefore, during the packaging of foodstuffs according to the above mentioned method, random test ing of the tightness of the seals is regularly carried out by the industry during production. Not only are these random tests extremely time consuming with the methods used up to now (e.g., a biological test), but they also generally have the disadvantage that they must be carried out in a manner which is wholly destructive for the containers which have been filled with the product, closed and possibly thereafter sterilised.

A quick and non-destructive method was sought according to which all the containers, if necessary, could be subjected to an effective control of the imperviousness to leakage as they leave the production line. We have realised that measurement of electric resistance across the seal yields favourable and reproducible results. Although electrical resistance testing is known from the prior art for other purposes, eg, for rubber articles (Austrian patent specification No. 147,124), it

cannot be used for the purpose aimed at here without the necessary adjustment.

Accordingly the invention provides a sealed container containing a product and incorporating an'electrode which provides an electrically conductive path between the product and the exterior of the container, said electrode being electrically insulated in such a manner as to enable conductivity between the product and the exterior of the container to be measured when at least the seal of the container is immersed in an electrolyte.

The conductivity (or resistance) can be measured in conventional manner by measurement of the current flow produced by a constant potential between the electrolyte and electrode while the container is suitably immersed, and this provides a measure of the effectiveness of the seal.

It should be realised that the invention is only applicable to the measurement of containers containing a product which is electrically conductive. This applies to most sterilised foodstuffs.

The electrode may be incorporated in the container permanently during formation of the container or during the sealing of its lid, or may be only temporarily incorporated during the testing operation.

A particularly convenient form of the former makes use of a strip of foil, or wire which passes through the container seal, i.e., it is sandwiched between the mating sealed surfaces at the seal, from outside the container to the product inside.

Desirably the wire or strip at points outside the container should have an insulating coating to prevent risk of direct electrical contact between the wire or strip and the electrolyte, and there should be no electrical contact with the walls of the container if the latter includes a layer of metal foil.

A method according to the invention comprises incorporating an electrode in said container which provides an electrically conductive path between the product and the exterior of the container immersing the container in an electrolyte, making an electrical connection to the exterior of said electrode while maintaining electrical insulation between said electrode and the electrolyte, measuring the conductivity between said electrical connection and the electrolyte, and removing the container from said electrolyte and from the electrical connection.

In a particularly convenient form where the electrode is only temporarily incorporated in the container, said electrode is a conductive needle which is injected through a point in the walls of the container and is subsequently removed, and the method further comprises resealing thev container at said point in its walls.

A convenient apparatus for carrying out this form of the process according to the invention incorporates both a conductive needle electrode and means for provision of a drop of molten plastic to re-seal the hole formed by the needle.

This latter method is particularly suitable for containers manufactured entirely from plastic.

In certain cases however this method could also be useful for semi-rigids made of metal. It is then neces sary though that, at least during the measuring, the product cannot come into contact with the cut edge caused in the metal by the conductive probe needle, or alternatively that the needle is insulated from the metal.

The device for carrying out the method according to the invention is provided with a bath filled with electroconductive and satisfactorily moistening liquid (electrolyte) in which the containers, and at least the part of them that is to be controlled, can be partially or wholly immersed, and further with a measuring device comprising a voltage source, a micro-ammeter and two electrodes, one of which sticks into the electrolyte and one of which is intended for contact with the product present in the container to be immersed in the bath. The second electrode may simply be the wall of the bath if it is electrically conductive.

For this we preferably make use of containers provided with a conductor which is electrically insulated from the wall of the container. This can be provided in the wall previously or can be inserted right through the seal during the sealing operation.

In another embodiment the electrode intended for contact with the product consists, according to the invention, of a conductive probe needle which is provided with a driving device for limited longitudinal movement of the needle between a measuring position and a withdrawn resting position, while means are present for dosing a measured amount of liquid plastic after each measuring operation. Except for the part at and near the extremity, the conductive probe needle can be provided with an insulating coating.

Containers which have been controlled according to the methods indicated are easy to identify either because of the plugging of the control hole in their bottom wall or because of the presence of an electrode.

The invention will be further explained with reference to the drawing. In this:

FIG. 1 is a sketch showing the principle involved in carrying out a measuring on a container provided with a plate electrode;

FIG. 2 shows, on an enlarged scale, the arrangement with a container provided with a tape electrode;

FIG. 3 shows schematically an apparatus for measuring the imperviousness to leakage, more particularly intended for containers made entirely from plastic.

In the figures an electrolyte bath is indicated by 1, containers to be investigated by 2 and a product present in the containers by 3.

In FIG. 1 is represented schematically a measuring operation on a container which has previously been provided with a plate electrode which at 4 on the bottom, electrically isolated from the metal outer side of the container, can be connected to the measuring system. The latter is only very schematically illustrated in the drawing and consists of a voltage source and a ,u-ammeter connected to it in series.

In FIG. 2 a more easily realised tape or wire electrode 5 is shown which can be welded within the seal when the latter is being affected. This can be carried out with standard containers in the production line, irrespective of the kind of container. In FIG 2 a container with an outside of metal (e.g., aluminium) is shown; the tape or wire electrode can, however, also be applied to containers made entirely of plastic. The electrode carries an external insulating coating to provide electrical insulation from the electrolyte.

Finally, in FIG. 3 an apparatus is shown which is preferably intended for measuring the imperviousness to leakage of containers made entirely of plastic, e.g., polypropene. Herein a conductive probe needle 6 is carried by a driving device 7 and moved manually from a withdrawn resting position to the measuring position, as shown in the figure. In doing so, the bottom wall of the container 2 is pierced and the needle is caused to extend into the conductive product. The conductivity measurement is then made.

On the upper side of the needle, a piston 8 is attached which, when the needle is subsequently withdrawn, is forced down by the driving device 7 (a form of screw jack) and pushes in front of it a measured amount of liquid plastic, in the present case also polypropene, which is present in the reservoir 9. The plastic is kept at the right temperature by the heating spiral 10 which surrounds the reservoir 9.

The liquid plastic flows on to the bottom wall of the container, whereby the hole that has been made in the bottom is closed.

As has already been mentioned in the introduction to the description, it is possible to use the aforementioned apparatus for metallic semi-rigids but only, however, if the cut edge is sufficiently insulated electrically from the product and/or the needle.

What is claimed is:

1. A method of testing the effectiveness of the seal of a free-standing thin-walled container containing therein an electrically conductive food product said container providing an electrically insulated barrier between the food product and the exterior of the container comprising the steps of inserting an electrode in a wall of the container, the electrode being in electrical contact at one portion thereof with the food product and in electrical contact at another portion thereof with a point outside of the container while being electrically insulated from the container immersing the container in an electroltye, connecting the portion of the electrode outside of the container with a source of electrical current while maintaining electrical insulation between said electrode and the electrolyte, removing the container from the electrolyte and removing the electrode. from the wall of the container.

2. A method according to claim 1 in which said electrode is a conductive needle which is injected through a point in the walls of the container and is subsequently removed, and the method further comprises rescaling the container at said point in its walls.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1843234 *Mar 24, 1931Feb 2, 1932Karnes James CTesting sealed containers and method of testing containers
US2503992 *Jun 20, 1947Apr 11, 1950Us Rubber CoInner tube tester
US3383863 *Aug 3, 1966May 21, 1968Joe R. BerryPond, tank and pit liner and method of detecting leaks
CA604278A *Aug 30, 1960Bulpitt And Sons LtdMeans for and method of testing reduced pressure in sealed metal containers
DE338299C *Aug 20, 1921Max SteffenVakuumpruefer fuer Einkochglaeser
SE130557C * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4503710 *Jun 8, 1983Mar 12, 1985Conoco Inc.Crack detection by electrical resistance
US5285678 *Dec 21, 1988Feb 15, 1994Seal Integrity Systems, Inc.Container seal testing and pressurization
US5562024 *Jun 6, 1995Oct 8, 1996Polny, Jr.; Thaddeus J.Apparatus for electroheating food employing concentric electrodes
US5571550 *Jun 3, 1993Nov 5, 1996Polny, Jr.; Thaddeus J.Methods for electroheating food employing concentric electrodes
US5572123 *Jun 7, 1995Nov 5, 1996University Of AlaskaApparatus and method for on-line inspection of electrically conductive food products using liquid electrolyte
US5583960 *Jun 1, 1994Dec 10, 1996David ReznikElectroheating apparatus and methods
US5607613 *Jun 6, 1995Mar 4, 1997Reznik; DavidElectroheating of food products using low frequency current
US5609900 *Mar 21, 1996Mar 11, 1997Reznik; DavidElectroheating of food products using low frequency current
US5630360 *Mar 18, 1996May 20, 1997Polny, Jr.; Thaddeus J.Apparatus for electroheating food employing concentric electrodes
US5636317 *May 30, 1995Jun 3, 1997Reznik; DavidMethod of heating a conductive fluid
US5741539 *Mar 18, 1996Apr 21, 1998Knipper; Aloysius J.Shelf-stable liquid egg
US5758015 *Mar 18, 1996May 26, 1998Polny, Jr.; Thaddeus J.Methods and apparatus for electroheating food employing concentric electrodes
US5760295 *Nov 6, 1996Jun 2, 1998Joven Denki Kabushiki KaishaMethod for inspecting sealed package
US5768472 *Jun 2, 1995Jun 16, 1998Reznik; DavidApparatus and methods for rapid electroheating and cooling
US5771336 *Mar 18, 1996Jun 23, 1998Polny, Jr.; Thaddeus J.Electrically stable methods and apparatus for continuously electroheating food
US5863580 *Jun 27, 1997Jan 26, 1999Reznik; DavidElectroheating a proteinaceous biological compound, cooling
US5900270 *Sep 22, 1997May 4, 1999Cobe Laboratories, Inc.Technique for testing and coating a microporous membrane
US5962776 *Oct 6, 1997Oct 5, 1999Lehmann; MartinMethod for tightness testing of closed vessels, test chamber tester and testing system therefor
US6029421 *Jul 19, 1996Feb 29, 2000Tetra Laval Holdings & Finance S. A.Method of quality control and appropriately prepared packaging container and blank
US6185987Sep 7, 1999Feb 13, 2001Martin LehmannMethod for tightness testing of closed containers, test chamber, test system, and tester therefor
US6223898Dec 20, 1999May 1, 2001Tetra Laval Holdings & Finance S.A.Quality control packaging container
US6411110 *Aug 17, 1999Jun 25, 2002Micron Technology, Inc.Apparatuses and methods for determining if protective coatings on semiconductor substrate holding devices have been compromised
US6593759Apr 2, 2002Jul 15, 2003Micron Technology, Inc.Apparatuses and methods for determining if protective coatings on semiconductor substrate holding devices have been compromised
US6807846 *Jan 14, 2002Oct 26, 2004The Quaker Oats CompanyMobile pneumatic apparatus and method for testing a container seal
US7571636 *Dec 13, 2005Aug 11, 2009Mocon, Inc.Detecting and reporting the location of a leak in hermetically sealed packaging
US7578170 *Dec 13, 2005Aug 25, 2009Mocon, Inc.Instrument and method for detecting and reporting the size of leaks in hermetically sealed packaging
US7624623Dec 13, 2005Dec 1, 2009Mocon, Inc.Instrument and method for detecting leaks in hermetically sealed packaging
WO1996024036A1 *Jan 29, 1996Aug 8, 1996Quaker Oats CoSeal integrity evaluation method
WO1996041208A1 *Jun 7, 1996Dec 19, 1996Univ VanderbiltApparatus and method for on-line inspection of electrically conductive food products
WO2001075414A1 *Apr 4, 2001Oct 11, 2001Chubpak Australia Pty LtdPerforation detection method
WO2011081801A1 *Dec 8, 2010Jul 7, 2011Nestec S.A.Seal integrity evaluation device and method of use thereof
Classifications
U.S. Classification324/693, 53/508, 324/718, 426/112, 426/87, 73/52, 426/107, 426/232
International ClassificationG01M3/40, G01M3/00
Cooperative ClassificationG01M3/40
European ClassificationG01M3/40