| 摘要 |
<p>Method and apparatus for forming stable and internally regular bell mouths on the terminal junction section (2) of pipes (20) made of thermoplastic material, preventively heated to the plastic state, comprising the following successive phases and tools: a first mandrel (11) structured with fixed geometry and with smooth external surface, able to be progressively introduced into the terminal section (2) to produce a forced dilation until the pre-forming of a first temporary bell mouth (21'), of maximum dilation, whose inner diameter exceeds the final nominal inner diameter of the definitive bell mouth (21), after heating the terminal section (2) in differentiated form, by means of a furnace (44) which brings the terminal section (2) to an external temperature (TE) exceeding the inner temperature (Tl), sufficient to assure a correct plastic deformation, in spite of the reduced thickness of the pipe (20) and the action of the mandrel (11); a mandrel for the calibration of the definitive bell mouth, able freely to be introduced preventively into the temporary bell mouth (21'), with external diameter equal to the final nominal inner diameter of the definitive bell mouth (21) thereby calibrating it; cooling the definitive bell mouth. <IMAGE></p> |
