Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1995-08-22
1996-11-12
Chilcot, Richard
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
73854, G01N 320
Patent
active
055742270
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus and method for measuring the creasing characteristics of paper board.
In high speed box making machines and automated packing lines it is important that the consistency and quality of creases is closely controlled and maintained. If this is not done successfully the potential to form false creases in paper board which can cause the jamming of machines or the production of malformed boxes is increased.
Thus it is important to be able to assess the variation in creasing characteristics in different types of paper board. The characteristics of interest include the peak force required to fold the board, the ratio of forces required to fold creased and uncreased board and the force required to fold the board at a predetermined angle.
The measurement of the peak force required to fold the paper board is useful in assisting the box maker to assess the quality of the board and therefore the parameters under which box production can occur with minimal jamming and production of malformed boxes.
The determination of the peak force generated at a specified angle during the folding of paper board can also be useful to know for specific operations. Some packing machines only fold the crease through a small angle --less than the angle at which the maximum force will occur. If this smaller force proves to be a significant fraction of the force required for uncreased board there is the possibility that an uncreased part of the board will fold rather than the crease itself, leading to deformation of the box and runnability problems. Alternatively, if the force at the required angle is much less than the uncreased paper board creasing force then there will be no problem--independent of whether the peak force is close to the uncreased board creasing force or not.
The ratio of forces required to fold creased and uncreased board provides a useful assessment of the potential to form false creases. In order to determine the quality of creases in a board sample, a Score Bend Test has been used for quantifying "crease quality". It involves the measurement of the force required to fold a creased line and the measurement of the force required to fold an uncreased line parallel to the crease. Usually, the crease quality is expressed as a % Score Ratio or a foldability coefficient which is calculated as the ratio of the peak folding force of the creased board to the peak folding force of the uncreased board.
As the measurement of peak folding force, peak force at an angle and the calculation of the % Score Ratio to determine the crease quality of board is important in the manufacture of boxes and board products there have been numerous attempts to develop a machine which measures crease quality and other characteristics of both corrugated boards and carton boards quickly and easily.
In one conventional instrument for measuring these forces, the specimen is placed across the top of a "Y-shaped" support and a pressure bar is situated above the support. The Y-shaped support moves upwards controlled by a motor such that the test specimen is forced against the pressure bar which is connected to a mechanical force gauge. The pressure bar must be positioned either over the score line of a creased sample or over the flute tip of the corrugations of an uncreased sample. Such machines are cumbersome and time consuming to use because the sample must be positioned on the support and aligned very carefully. Misalignment of the sample will lead to an inaccurate result. These machines are also fairly complicated because they require a motor to move the Y-shaped support. They are also bulky which is not desirable in manufacturing plants, due to the requirement that the apparatus be combined with a motor.
Additionally there have been other types of apparatus proposed which measure the flexural resistance of board products. The flexural resistance measurements provide an indication of the boards tendency to buckle under load which is an important characteristic to consider when the board is to be used in industrial
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Amcor Limited
Chilcot Richard
Noori Max H.
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