Apparatus and methods for in-line testing of the internal pressure of flexible containers traveling along a production line at high speeds. The apparatus inspects semi-rigid plastic and thin-walled liquid filled containers by analyzing the output from a load cell that indirectly measures the reaction force applied to a container through the intermediary of a load cell roller that, in turn, supports a flexible belt that directly contacts containers while moving them through an inspection station without interrupting the flow of the production line. Containers are contacted only by a flexible portion of a conveyor belt to minimize structural and aesthetic damage to them that might otherwise occur during the inspection process.

A method of measuring the squeeze force of a package includes applying a compression force to the package, and measuring the compression force as a function of volume change of the package. The compression force may be applied by placing the package in a force tester, and compressing the package with a movable crosshead. A device for measuring the squeeze force of a package containing a fluid may include a force tester and a fluid gauge, where the force tester includes a movable crosshead and a force gauge attached to the crosshead. The device may also include a holder to secure a bottle for testing.

A seal checker capable of reliably detecting a faulty seal at a vertical seal portion of a packaging bag or a portion thereof covered by the vertical seal portion is provided. A lower transfer conveyor conveys a packaging bag such that a vertical seal portion thereof moves along the conveyance direction. The upper and lower transfer conveyors sandwich and press the packaging bag therebetween. A servo motor detects the distance between the transfer conveyors when the packaging bag is pressed thereby. A control unit determines the seal properties of the packaging bag based on the distance detected by the servo motor. A gap is provided on a conveyance surface of one of the transfer conveyors to which the vertical seal portion faces, which extends in the conveyance direction and prevents the vertical seal portion from being pressed.

For the purpose of testing deformable containers (2) for tightness, a negative pressure is generated in the container (2) and the internal pressure is then measured. The negative pressure is generated by deformation of the container (2). A sealing strip (6) is set on the container opening (8) in order to maintain the negative pressure in the container (2). In non-tight containers, the pressure increases relatively rapidly again to the ambient pressure.

Leak testing a closed container with at least one flexible wall area is performed with the method and apparatus wherein a biasing arrangement compresses or expands the container under test. A biasing force is monitored with a force detector applicable to the wall of the container. The force detector generates an electric output first biasing force signal at a first point in time which is stored for comparison with the monitored biasing force signal at a second subsequent point in time to generate a difference signal as a leak indicative signal. Another difference signal is generated at the first point in time from the first force measuring signal stored and the first force measuring signal. This latter difference signal is stored as a zero offset signal which is used to compensate zero offset of the generated difference signal used as a leak indicative signal.