Patent ID: 6839652

Claim:
A method for determining the temperature distribution throughout the thickness of a preform used in a container reheat stretch blow molding process, comprising: measuring the outside surface temperature of the preform at least two times during the period the preform is cooling down after exiting the heat station and before entering the blow molding station; and calculating the temperature distribution throughout the thickness of the preform based upon the measured outside surface temperatures using an algorithm comprising: curve fitting the measured outside surface temperatures to solve for A n using an equation having the formula T ⁡ ( 0 , t ) = Tc + ∑ n = 1 ∞ ⁢ ⁢ A n ⁢ ⅇ - z n 2 ⁢ α ⁢ ⁢ t ⁡ ( z n ⁢ k / h ) and using the A n values to calculate the through-the-thickness temperature distribution for the preform using an equation having the formula T ⁡ ( x , t ) = Tc + ∑ n = 1 ∞ ⁢ ⁢ A n ⁢ ⅇ - z n 2 ⁢ α ⁢ ⁢ t ⁢ v n ⁡ ( x ) , where T(x,t) is the through-the-thickness temperature distribution of the present invention, T(0,t) is the outside temperature as a function of time t which is curvefit to the experimental data to determine the unknown front factors A n , Tc is the ambient air temperature, e is the exponential equal to 2.718, v n are the eigenvectors for the nth eigenvalue z n , k is conductivity, x is the depth of the preform from the outside surface, and α is the thermal diffusivity.