Method of heating thermoplastic bottle of preform and method of controlling temperature of heating member utilized by the heating method

A method of controlling the temperature of a heating member, to be used as an internal heating member for internally heating a preform to be formed into an article, such that said temperature of said heating member remains substantially constant throughout a period of time within which said heating member is utilized to internally heat said preform at said substantially constant temperature of said heating member, comprising the steps of:

• providing said heating member with an inner cavity;
• depositing a substance, having a melting point which substantially corresponds to a predetermined temperature at which said preform is to be heated, into said inner cavity of said heating member;
• measuring the temperature of said heating member;
• heating said heating member to a temperature level which is at least equal to said melting point of said substance disposed within said inner cavity of said heating member if said measured temperature of said heating member is below said melting point of said substance disposed within said inner cavity of said heating member;
• and
• inserting said heating member, having a temperature at least equal to said melting point of said substance disposed within said inner cavity of said heating member, into said preform so as to heat said preform at said substantially constant temperature as controlled by means of said melted substance disposed within said inner cavity of said heating member.

A method of heating a preform which is to be subsequently formed into an article, comprising the steps of:

• providing an internal heating member which is movable along a circulating path;
• providing external heating means at an external heating station fixed along said circulating path;
• measuring the temperature of said internal heating member prior to the insertion of said internal heating member into a preform to be heated;
• adjusting the temperature of said internal heating member to a predetermined temperature by heating said internal heating member in accordance with any difference between said measured temperature and said predetermined temperature;
• inserting said internal heating member, which has been heated to said predetermined temperature, into said preform to be heated;
• circulating said internal heating member, having said preform disposed thereon, past said external heating means such that said preform is simultaneously heated both externally and internally by said external heating means and said internal heating member;
• removing said heated preform from said internal heating member;
• transferring said removed heated preform to an additional processing station at which said removed heated preform will be formed into said article;
• and
• recirculating said internal heating member along said circulating path.