| 摘要 |
<p>Apparatus with multiple operating phases, comprising a composite mandrel (1) with multiple operating phases, to form stable bell mouths (21) on the terminal junction sections of pipes (20) made of thermoplastic material, comprising: a preliminary intervention portion (13), comprising a hollow rubber element able to be freely introduced into the terminal section (2), inflatable until pre-forming a first bell mouth (21"); a first portion (11) of the type with mechanical sectors (6) radially movable from a first retracted position, wherein it can be freely introduced into the terminal section (2), to a second extreme expanded position, with greater diameter (D12) than the diameter of the aforesaid first bell mouth (21"), forming a precise temporary bell mouth (21") of maximum dilation; a second portion (12), geometrically fixed and consecutive to the first one, with diameter equal to the inner, nominal and final diameter (DN) of the definitive bell mouth (21), said mandrel (1) providing first for pre-forming the bell mouth (21') with diameter (D12) greater than the nominal one (DN), which will be free of any impression, since it is pre-dilated by the preliminary portion (13), free of any discontinuity and subsequently dilated to a very reduced, albeit precise, extent by the first portion (11), then calibrating it on the second portion (12) to the nominal diameter, during its spontaneous retraction. <IMAGE></p> |
