Patent Application
20230356453
This application claims priority to Italian application No. 102022000009221 filed on 5 May 2022 which is incorporated by reference in its entirety
The object of the present invention is a machine and a process for bending thermoplastic tubes.
Thermoplastic tubes are used to convey liquids and vapours in many applications. These tubes have very stable proprieties in a variety of heath and light conditions and are consequently suitable for transporting a wide range of liquids for a wide range of applications, think, by way of non-limiting example, to the automotive sector and specifically to transportation of fuel and vapours thereof.
In the various applications adopted by the various production industries, tubes shall be bent with various bend radii, bending rotations and distances between the various curves. This bending process requires a sequence of heating, bending, and cooling operations on portions of the tube to be bent.
Many methods are in use for bending thermoplastic tubes. In the known bending methods, the tube, in its straight form, is heated with hot air or other means. The tube is cold inserted into moulded dies manually by forcing its position and is subsequently connected to a device that blows hot and cold air alternatively, in order to model and cool the tube. Once the desired shape of the tube is obtained, this one is removed from the shaping tool.
This bending method is very delicate, and the tools used are expensive and not easily re-configurable.
A thermoplastic tube bending method is also known in which, while a pre-heated portion of the tube is bent and cooled, another portion of the tube is heated in order for it to be subsequently bent and cooled, and so on for all specified working cycles of the tube to be bent.
A drawback of this further thermoplastic tube portion bending method is in that the time duration of a tube portion bending and cooling phase is, in most cases, longer than the time duration of the heating phase of the other portion of the tube to be bent. Remember that the portion of the tube to be bent shall be sufficiently heated in order to render the tube sufficiently plastic for being bent, but at the same time the portion of the tube shall not lose its original cold structure and shape. Therefore, the heating phase is a very delicate one. Bringing to, but even more important maintaining the portion of the tube to be bent at the desired heating temperature in order to render it sufficiently plastic for bending for the time duration necessary for submitting another portion of the tube to bending and cooling entails major drawbacks.
In order to overcome the drawbacks of the known methods, the present invention provides a new and advantageous machine for bending filiform thermoplastic materials, such as a thermoplastic tube, to embody a new and advantageous filiform thermoplastic material such as a tube, here below simply referred to as “tube”, bending process by heating a bending core heated and positioned inside the tube to be bent, capable of heating the portion of the tube to be bent and of recovering of the thermal energy in excess to prepare the subsequent portion of the tube to be heated and bent. Said method according to the present invention allows to bend the tube while preventing waste of energy. Such bending core is formed of a set of sectors that can be heated in an independent and programmable manner. Said bending machine and procedure are better described in the following paragraphs.
Thanks to this innovative and advantageous bending process, tube bending can be performed by using a new and advantageous tube bending machine which comprises a tube positioner assembly, a bending head provided with a tube blocking device, at least one die, at least one contrast device, and a puller assembly connected to a tie rod. Said tie rod, moved by the puller, is integrally connected to a core body in order for said core body to be positioned inside the tube to be bent. The positioning of the core body inside the tube to be bent aims at heating the portion of the tube to be bent, as better illustrated here below, in order to render the portion of the tube to be bent sufficiently plastic for being advantageously bent accurately and with an optimum quality of bending and of the bent thermoplastic material.
The core body is heated by using a heating apparatus, preferably an induction one comprising an inductor device such as an induction coil. Said heating apparatus might also be formed, for example, of a set of electrical resistors and could in any way consist of any heating apparatus. Said heating apparatus is governed by a programmable control unit. Said programmable control unit is suitable for giving instructions to the heating apparatus for selecting the sectors of the core body to be heated and the temperature the sectors should reach on the basis of a predetermined working program, by receiving a signal that represents the temperature reached by the portion of the heated core body and/or from the portion of the tube to be bent from a temperature sensor, which every sector of the core body is provided with.
In order to better select the portions of the core body to be heated, while preventing energy dispersion, and to concentrate the core body heating only in the section of interest and consequently to only heat the portion of the tube to be bent, a suitable core body is formed of at least two sectors independent of each other.
While bending the portion of the tube to be bent, it is necessary to be in a position to calibrate said portion of the tube. Said calibration is implemented by a set of articulated elements suitable for performing such calibration of the portion of the tube to be bent, which are positioned at one end of the core body, specifically in that portion which is opposed to the point of contact of the core body with the tie rod.
Upon finishing the bending process of the portion to be bent, the bent portion of the tube is still in its plastic status and needs to come back to a rigid status by cooling, an operation that is facilitated and speeded up by way of an air cooling device.
The machine for bending tubes described here above is suitable for implementing an innovative and advantageous bending process on a thermoplastic tube, which comprises eight phases.
In the first phase of said process, the portion of the tube to be bent is positioned in the bending area interposed between the die of the bending head and the contrast device by way of a positioner assembly, which a heating apparatus, preferably an induction one comprising an inductor device such as an induction coil, is connected to. Said heating apparatus is governed by a programmable control unit, whereby a core body is heated according to a specific program. The core body is positioned inside the thermoplastic tube by way of a tie rod moved by a puller assembly, said core body being integral with the tie rod. Said core body is formed of at least two sectors independent of each other.
In the second phase of the process, the portion of the tube to be bent is blocked by a blocking device mounted on the bending head.
In the third phase of the process, the portion of the tube to be bent is heated by way of a heating apparatus, preferably an inductor device, which heats the portion of the tube to be bent through the heating of one or several sectors of the core body depending on the portion of the tube to be bent. Such capability of heating each of said sectors independently of each other is implemented by the heating apparatus, said heating apparatus being governed by the programmable control unit which continuously receives a signal that represents the temperature reached by the sectors submitted to heating and/or the temperature of the tube to be bent from a temperature sensor, which every sector of the core body is provided with. The intensity of the heating provided by the heating apparatus of the various sectors of the core body is controlled and governed according to a specific program by the programmable control unit, which modifies the heating intensity according to a signal that represents the temperature reached by the individual sectors and/or the temperature of the portion of the tube to be bent. Such signal is continuously sent by the temperature sensor which every sector of the core body is provided with.
In the fourth phase of the process, the positioner assembly is retracted to reach a position outside the bending area, once the portion of the tube to be bent reaches a temperature suitable for rendering the portion of the tube to be bent sufficiently plastic for being bent.
In the fifth phase of the process, the portion of the tube to be bent is positioned inside the throat of the die and is blocked in said portion of the tube to be bent by way of a contrast device.
In the sixth phase of the process, the portion of the tube to be bent is bent byway of the movement of the bending head and the curve of the portion of the tube to be bent is calibrated by way of articulated elements placed at the end of the core body in a position opposed to the point of contact of the tie rod with the core body.
In the seventh phase of the process, the core body is retracted byway of the retraction of the puller assembly connected to the tie rod, said core body being integral with the tie rod, up to reaching the portion of the tube that will be subjected to the subsequent bending phase. In the same phase, the bent tube is cooled upon completion of the bending cycle. Such cooling takes place by way of a device used for air cooling the portion of the bent tube. Retracting the bending core in the portion of the tube to be bent during the subsequent cycle results in a sectorial passive heating action. Such sectorial passive heating allows to prepare the portion of the tube to be bent in the subsequent bending cycle a little bit before said portion of the tube starts its sectorial active heating phase aiming at bringing the latter portion of the tube to a temperature suitable for rendering it sufficiently plastic for being bent. Such retraction makes it possible to recover the residual heat of the bending core thus rendering the process more efficient.
In the eighth phase of the process, the device used to block the portion of the bent tube is released and the die, the contrast device, and the bending head are retracted to their rest positions in order to start a new bending process.
Then, once the mentioned eight phases are over, the process restarts from the first phase in order to bend a tube according to the predetermined working program, also governed by the mentioned programmable control unit.
The process continues with the seventh phase, not shown in the figures, whereby the core body (9) is retracted by way of the retraction of the puller assembly (6) connected to the tie rod (7), said core body (9) being integral with the tie rod (7), up to reaching the portion of the tube that will be submitted to the successive bending phase and the bent portion of the tube (T2) is cooled by way of an air cooling device (12) upon completion of the bending cycle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022000009221 | May 2022 | IT | national |
