The invention is characterized by a special configuration of the fixing means of the extremities of the tubular preform (1), as well as by a system for evacuating through micropores the fluid which heats the preform (1) and the incorporation in the mold of an intermediary skirt (6) for heating purposes and subsequent refrigeration of the pipe mold. <IMAGE>
1. Plastic tube manufacturing procedure, of the type of tubes which are axially orientated by heating of the preform (1) up to forming temperature, with subsequent stretching, consecutive cooling and cutting of its ends, characterised in that it comprises : - the external jacketing of the mould (2), - a special configuration of the tubular preform (1) ends attachment means. - an evacuation system by micro-pores (2.3) of the fluid which heats the preform. 2. Plastic tube manufacturing procedure according to the first claim, characterised in that the mould (2) is internally filled with water and heated at a temperature comprised between 90° C and 100° C, for a time which varies from six minutes to one hour, whilst water is also inserted through the preform (1), circulating it from one end to the other for the same period of time. 3. Plastic tube manufacturing procedure according to the previous claims, characterised in that next, this water circulation is then conventionally closed by the preform (1), and air is injection inside the same at room temperature and at a pressure comprised between 10 bar and 30 bar, causing the progressive output of water through the mould (2) micropores (2.3). 4. Plastic tube manufacturing procedure according to the previous claims, characterised in that the subsequent radial expansion of the preform (1) and the simultaneous orientation of the plastic polymer molecules of the same are subsequently proceeded with, this expansion being started when a pressure comprised between 10 and 15 bar is reached, in the tubular section with generatrices in convex shape and maximum radius corresponding to the central zone (1.1) of the preform (1) in expansion. 5. Plastic tube manufacturing procedure according to the previous claims, characterised in that when around 25 bar is reached, the adaptation of the preform (1) in expansion to the final shape is started in progressive manner, from the centre towards its side ends, all the complete process being performed within a few seconds. 6. Plastic tube manufacturing procedure, according to the previous claims, characterised in that after the cooling of the tube exterior, with water circulating between the jacket and the mould (2) of the same, at a temperature of around 12° C from 1 to 5 minutes, the same being reached in the mould (2) and on the external face (1.2) of the tube in contact with the same, with which the corresponding temperature of the internal tube face (1.3) is reduced to below 90° C, sufficient to reach the appropriate rigidity for its subsequent handling, without collapsing, next removing the water from its interior by means of air at 10 bar, applied for brief seconds. 7. Plastic tube manufacturing procedure according to the previous claims, characterised in that the residual water from the thus formed tube bottom (1.4) is removed by means of a tube (7) inserted by the final end of the same. 8. Plastic tube manufacturing procedure, according to the previous claims, characterised in that once the tube has been depressurised, also within brief seconds, the opening of the mould (2) is proceeded with and the cycle repeated. 9. Plastic tube manufacturing procedure, according to the first claim, characterised in that the preform (1) is attached in the tube mould (2) by inserting in the preform (1) a guide (3) with a head (3.1) provided with an elastic O-Ring (3.2) with the internal diameter of this preform (1), in an appropriate material to resist the predicted service conditions and with sufficient elasticity so that the pressure exerted on it by the guide head causes its elastic deformation and with this, the immobilisation and attachment by compression of the preform (1). 10. Plastic tube manufacturing procedure according to the first claim, characterised in that alternatively, the gripping system of the preform (1) ends is carried out by means of metallic clamps (4) provided with tapered grooves (4.1) of the attachment head (4.2), for insertion and wedging in them of notches (4.3) which are antagonistic to the part (4.4) triggered in the threaded sleeve (4.5) which joins to the tensing sleeve (4.6) of the mould (2) locking part (5). 11. Plastic tube manufacturing procedure, according to the first claim, characterised in that the water removal system consists of micropores (2.3) performed on the mould (2) periphery, aligned and advantageously spaced from each other, as well as distributed in regular form along its surface, except at the gripping ends of the preform (1). 12. Plastic tube manufacturing procedure, according to the first claim, characterised in that the heating and cooling means consist of an external jacket (6), included between both preform (1) end gripping systems and which is provided with water input (6.1) and output (6.2) connections, that of the heating feeding circulating water at a temperature comprised between 95 and 100° C and that of the cooling, feeding it at 12° C and returning between 50 and 14° C. 13. Plastic tube manufacturing procedure according to the first claim, as well as to claims 9 through 12, characterised in that the mould (2) is provided at its ends with conventional locking means, which consist of flanges and end covers, through screws (2.1) as likewise, the gripping system of the preform insertion mouth, whilst the locking system of the other end consists of locking clips (2.2) with frusto-conical internal section. 14. Plastic tube, according to claims 1 through 8, characterised in that once the thus manufactured tube has been removed, it is cut at its ends (1.5), from the start of both opposed tapered transition zones of the preform (1) tube.