Multistage wire drawing apparatus

An apparatus for hot drawing of a work made of sintered metal powder having a high melting point, comprising:

• first, second and third drawing means arranged in series in order, each of said drawing means including a heating device, a die through which said work heated by said heating device passes, and a chuck head means for moving said work along a direction in which said work is drawn;
• first and second tension measuring means, said first tension measuring means, arranged between said first drawing means and said second drawing means, for measuring a tension therebetween, and said second tension measuring means, arranged between said second drawing means and said third drawing means, for measuring a tension therebetween;
• first comparator means coupled to said first tension measuring means, for comparing the tension measured by said first measuring means with a reference tension to determine a deviation of the tension measured by said first measuring means from said reference tension;
• second comparator means, coupled to said second tension measuring means, for comparing the tension measured by said second measuring means with said reference tension to determine a deviation of the tension measured by said second measuring means from said reference tension;
• means for calculating theoretical speeds of said chuck head means in said first and third drawing means, using as a reference, a theoretical speed of said chuck of said chuck head means in said second drawing means;
• and
• first drive controlling means, coupled to said calculating means, said first comparator means and said chuck head means of said first drawing means, for controlling a speed of said chuck head means in said first drawing means according to a comparison of the deviation determined by said first comparator means and the theoretical speed of said chuck head means of said first drawing means calcualted by said calculating means;
• second drive controlling means, coupled to said calculating means, said second comparator means and said chuck head means of said third drawing means, for controlling a speed of said chuck head means in said third drawing means according to a comparison of the deviation determined by said second comparator means and the theoretical speed of said chuck head means of said third drawing means calculated by said calculating means.