Apparatus for Determining the Hardness of Cigarettes as Deduced "Modulus of Hardness" / Ableitung des Härtemoduls als belastungsunabhängiges Mass der Cigarettenhärte

1. An apparatus designed by the Scientific Department of the company Martin Brinkmann AG is presented for determining the hardness of cigarettes, i.e. their degree of filling. The deformation of test pieces caused by several measuring arms of identical weight is measured in a prism at the rate of 30 pieces per minute.

2. The intensity of the deforming forces is calculated. This calculation does take into account the changes in shape produced by both the arms and the positional support in the measuring prism. A unit of measure termed ''modulus of hardness" (Haerte-Modul) is established by formal analogy with the modulus of elasticity.

3. The relations existing between the deformations caused respectively by the arms (a) and by the support (a'), the measurable value of the total deformation (agem) and the modulus of hardness are deduced from tables correspondingly set up by reckoning. The deduction is based on the cross-sectional area of the power of the arm application (1 mm) to the exclusion of longitudinal forces and, furthermore, on the postulated fact of cigarettes being ideally cylindrical and in themselves homogeneous bodies.

4. The experimentally proved fulfilment of Hooke's Law confirms the truth of the authors' theoretical suppositions. The relative deformation is found to be proportional to the load, if the calculation of the deformation is made according to the chord and not according to the circular arc. The results hitherto obtained show the measured values to depend only to a small extent on the calibre of the test piece.

5. The values determined on the basis of the modulus of hardness thus deduced are found to quantitatively and qualitatively represent the cigarette's physical property in question to an optimum extent. They are shown to be plausible with regard to the modulus of elasticity of other materials commonly used as for example rubber. The hardness values ascertained prove to be inversely proportional to the logarithm of the duration of load application. It is above all the influence exerted by the duration of load application that makes the hardness values of cigarettes differ from the elasticity values of other materials.

6. The particular conditions of the measurement of the hardness of filter cigarettes as well as the influence exercised by longitudinal forces on the measurement of filter rods are pointed out.