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(11) | EP 0 054 343 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for manufacturing tapered rods and apparatus therefor |
| (57) Method for manufacturing a tapered rod for a coil spring from a metallic material
of mainly steel in a linear state, by imparting heating to the same with a predetermined
temperature gradient pattern in the axial direction thereof while or before pulling
by tensile force the metallic material chucked at two axially distant points in either
direction in a gradually decreasing or stepwise decreasing speed, until a desired
tapered portion is formed. An apparatus preferably employed for this method comprises
a pulling mechanism (12, 22) for chucking and pulling the material, an electric current
supplying mechanism (15) for supplying predetermined amount of current to the material
between the two chucked points, a plurality of cooling means (C1- Cn) arranged axially along the material for positionwise cooling the material so
as to make the temperature gradient thereon, a temperature detecting means (16, 17)
for detecting the surface temperature of the material for feeding back the detected
data to the current supplying mechanism (15), and a heating temperature controlling
means (18) for controlling the amount of the current flowed there. |