Apparatus and method for testing stiffness of articles

A method for testing stiffness of an article along a predetermined testing axis while the article moves along a predetermined path in a conveying direction substantially transverse to said testing axis, said article having first and second opposed surfaces aligned with said conveying path in a predetermined conveying position, the method comprising the steps of:

• i) contacting said first article surface at two spaced apart portions of the article while applying a first thrust against a loaded area of said second article surface at an intermediary portion located between the spaced apart portions of the article as it moves along the conveying path, to produce an article deflection of a first magnitude extending along a first deflection axis perpendicular to the conveying direction and the testing axis;
• ii) contacting said first article surface at two spaced apart portions of the article while applying a second thrust against a loaded area of said second article surface at the intermediary portion of the article as it further moves along the conveying path, to produce an article deflection of a second magnitude extending along a second deflection axis substantially parallel to the first deflection axis, said second position differing from said first position relative to the conveying path by a predetermined differential value;
• iii) measuring respective magnitudes of said first and second thrusts;
• and
• iv) deriving an indication of the stiffness of the article from said differential value and said first and second thrust magnitudes;
• wherein each said loaded area substantially extends over the whole transverse dimension of said article while said thrust magnitudes are measured.

A method for testing stiffness of an article along a predetermined testing axis while the article moves along a predetermined path in a conveying direction substantially transverse to said testing axis, said article having first and second opposed surfaces aligned with said conveying path in a predetermined conveying position, the method comprising the steps of:

• i) contacting said first article surface at two spaced apart portions of the article while applying a first thrust against a loaded area of said second article surface at an intermediary portion located between the spaced apart portions of the article as it moves along the conveying path, to produce an article deflection of a first magnitude extending along a first deflection axis perpendicular to the conveying direction and the testing axis;
• ii) contacting said second article surface at two spaced apart portions of the article while applying a second thrust against a loaded area of said first article surface at the intermediary portion of the article as it further moves along the conveying path, to produce an article deflection of a second magnitude extending along a second deflection axis substantially parallel to the first deflection axis;
• iii) measuring respective magnitudes of said first and second thrusts;
• and
• iv) deriving an indication of the stiffness of the article from said first and second deflection magnitudes and said first and second thrust magnitudes;
• wherein each said loaded area substantially extends over the whole transverse dimension of said article while said thrust magnitudes are measured.