Measuring and testing – With fluid pressure – Leakage
Patent
1994-11-23
1996-08-06
Williams, Hezron E.
Measuring and testing
With fluid pressure
Leakage
73 52, 73 41, 73 454, G01M 336
Patent
active
055422888
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for testing packages, particularly of food stuffs. The testing may be to establish that packages are properly sealed and/or that they are properly filled.
BACKGROUND ART
Known testing equipment tends to be slow and/or unreliable. For example, U.S. Pat. No. 4,649,740 discloses apparatus in which flexible packages are indexed through at least two test stations. At each station, a package stops and a load is applied by probe rods. Two successive stations apply the same load, and the effective thickness of a flexible package is measured in each case. The two thickness measurements are compared, and a difference is deemed to show a defective package. The idea is that a leaky package will be partly deflated at the first station, so that the effective thickness detected at the second station will be less. But we find that this is not reliable. For example, a grossly leaky package will be fully deflated at the first station. The reading at the second station will therefore be the same as at the first, and the package will be accepted as correct. Furthermore, the procedure is slow, owing to its reliance on static testing.
DISCLOSURE OF INVENTION
In one aspect the present invention provides a package testing apparatus having a test station and conveying means for conveying packages along a path extending through the test station, the test station comprising at least one load means, means for effecting relative reciprocation of the or each load means towards and away from the path to apply a load to a package being conveyed along the path and to detect the effect of the load on the package; wherein the or each load means has a package-contacting surface portion that is displaceable in the conveying direction so that a load can be applied to a package while it is being conveyed.
The package-contacting surface portion may be provided by one or more displaceably mounted belts, wheels or rollers. These may be displaceable by contact with packages and/or be driven in synchronism with the conveying means.
The effect of a load on a package may be detected by assessing the resistance of the package when subjected to a load by the load means. This may be done by detecting how far the load means can travel under a predetermined force and/or by detecting the force required to cause a certain amount of travel or a certain degree of deformation of the package. Generally, detection of the travel for a predetermined load is preferred.
Preferably the test station has a plurality of load means spaced along the path. Preferably a first load means for applying a first load is upstream of a second load means for applying a second load greater than the first load; and there are means for providing outputs related to the resistances to said first and second loads, comparing said outputs, and deriving thence a package quality output. With such an arrangement, a grossly leaky package that is fully deflated by the first load means will show a different change in resistance from a sound package; and a slightly leaky package will be different yet again. Thus it is possible to set the apparatus to accept packages having not more than a predetermined degree of leakiness.
The concept of applying a second load that is greater than a first load, and gauging the difference in response, is of wide utility, not restricted to apparatus as defined above, in which there are loads with displaceable package-contacting surface portions. That is, however, preferred. But broadly, the invention provides, in a second aspect, testing apparatus having a test station, and conveying means for conveying packages along a path extending through the test station, wherein the test station comprises first and second load means spaced along The path for applying predetermined loads to packages conveyed along the path, the second (downstream) load means being arranged to apply a greater load than the first load means; said test station further including means for assessing the resistances to the
REFERENCES:
patent: 4148213 (1979-04-01), Prakken
patent: 4649740 (1987-03-01), Franklin
patent: 4671101 (1987-06-01), Franklin
Japanese Patent Abstracts, vol. 13, No. 540, 5 Dec. 1989 directed to JP 1-223323 of 6 Sep. 1989.
Ishida-Nonpareil Limited
Larkin Daniel S.
Williams Hezron E.
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