Heat treatment unit comprising a device for measuring the initial temperature of preforms

Abstract

The invention relates to a heat treatment unit (4) comprising: - a chamber (16) extending between an entrance (18) and an exit (20), - a heating device designed to heat preforms, - an upstream measurement device for measuring an initial temperature (Ti) of the preforms (2) at the entrance (18) of the chamber (16), - at least one control module (24) designed to regulate the heating power (Pc) of the heating device (10). The control module (24) is configured to regulate the heating power (Pc) in the event of a variation in the measured initial temperature (Tim) as a function of the predetermined heating temperature (Tc), the measured initial temperature (Tim), the rate (C) of travel of the preforms through the chamber and at least one constant coefficient (K) for a container (1) that is to be produced.

Description

Heat treatment unit including a device for measuring the initial temperature of preforms

[0001] The present invention relates to a preform heat treatment unit of a container manufacturing installation, of the type comprising: - a chamber extending between an inlet, through which the preforms are introduced into the chamber, and an outlet, through which the heated preforms exit the chamber, - a heating device extending between the inlet and outlet of the chamber, said heating device being arranged to heat said preforms between the inlet and outlet of the chamber, - at least one upstream measuring device for at least one initial temperature of the preforms at the inlet of the chamber, - at least one control module arranged to adjust the heating power of said heating device, said heating power being arranged so that the preforms are heated to at least one predetermined heating temperature at the outlet of the chamber.

[0002] The invention also relates to a method of heating preforms using such a heat treatment unit.

[0003] It is known to heat preforms in a container production facility in order to make these preforms malleable and allow their subsequent deformation, for example by stretch blow molding, in order to produce containers from the heated preforms.

[0004] To do this, a succession of preforms is for example put into circulation in a heat treatment unit, or furnace, in which the preforms pass in front of heating elements so that the preforms are heated to a heating temperature allowing their subsequent deformation in a forming station.

[0005] To ensure proper heating of the preforms, it is known to implement a control loop, in which the heating power setting of the heating elements is controlled by the temperature of the heated preforms measured at the outlet of the heating unit enclosure in order to avoid any drift in the heating temperature of the preforms from the desired temperature.

[0006] However, the initial temperature of the preforms, before heating, also influences the heating power required to raise their temperature to the desired heating temperature. Thus, a preform stored cold before being introduced into the heat treatment unit requires more heating power than the same preform stored at room temperature, for example.

[0007] It has been proposed to take into account the initial temperature of the preforms to adjust the heating power in the heat treatment unit. To do this, it has been proposed to measure the temperature before heating and to adapt the heating power according to the measured temperature and parameters relating to the preforms being heated, such as mass, absorption coefficient, and specific heat capacity of the preforms to be heated.

[0008] However, such an adjustment of the heating power is not entirely satisfactory. It requires knowledge of very specific preform parameters that are generally not provided by the preform manufacturers.

[0009] One of the aims of the invention is to provide a heating unit comprising a heating device whose heating power can be easily adjusted by taking into account the initial temperature of the preforms.

[0010] To this end, the invention relates to a heat treatment unit of the aforementioned type, in which the control module is configured to adjust the heating power Pc of the heating device during a variation of the initial measured temperature Ti m by the upstream measuring device, the heating power being adjusted according to the predetermined heating temperature Tc and the initial measured temperature Ti m, of the rate C of preforms passing through the enclosure and of at least a constant coefficient K for a desired container to be made from the preforms passing through the enclosure, said coefficient K being calculated from a production recipe allowing to obtain said desired container from a preform having an initial temperature Ti given, heated by a heating power Pc and having a heating temperature Tc at the exit of the enclosure in which the preforms circulate at a rate C corresponding to a number of preforms exiting the enclosure per hour.

[0011] The control module for the heat treatment unit according to the invention therefore allows the heating power of the heating device to be adjusted solely based on parameters relating to the heat treatment unit and not on intrinsic parameters of the heated preforms. The parameters used by the control module are thus easily accessible and do not require obtaining information from the preform manufacturers.

[0012] The heat treatment unit according to the invention may comprise one or more of the following features, considered alone or in any technically feasible combination: the coefficient K is calculated according to the following formula:

[0013]

[0014] The control module is configured to adjust the heating power when the initial temperature is measured, according to the following formula:

[0015]

[0016] in which PC ais the adjusted heating power; - the heating device comprises a plurality of heating elements distributed within the enclosure along a path of preforms flowing through the enclosure between the inlet and outlet, the control module being configured to adjust the heating power of each heating element of the heating device during a variation of the initial measured temperature, the heating power of each heating element being adjusted so that the preforms flowing successively past said heating elements have the predetermined heating temperature at the outlet of the enclosure; - the adjustment of the heating power of each heating element is done by modifying a percentage of the maximum heating power to which each heating element is likely to heat the preforms flowing through the enclosure;- the control module is configured to adjust the heating power of the heating elements successively from the entrance to the exit of the chamber according to the progress between the entrance and exit of a preform with a modified initial measured temperature; - the control module is configured to adjust the heating power of a heating element before a preform with a modified initial measured temperature passes in front of said heating element so as to take into account the time required to adjust the heating power of the heating element to go from an initial heating power to the adjusted heating power;- the upstream measuring device is arranged at a distance from the first heating element arranged in the enclosure between the inlet and the outlet so that the measurement of the initial temperature of a preform, the calculation of the adjusted power and the adjustment of this heating power by control module are done before the preform passes in front of said first heating element to take into account the time of adjustment of the heating power of the first heating element to go from an initial heating power to the adjusted heating power; - the upstream measuring device includes an infrared pyrometer and / or an image acquisition device in the infrared range of the preforms;- the heat treatment unit further includes a downstream measuring device for the temperature of the preforms heated at the outlet of the chamber, the control module being configured to adjust the heating power of the heating device according to the heating temperature of the preforms heated by the downstream measuring device.;

[0017] According to another aspect, the invention also relates to a method for heating preforms using a heat treatment unit as described above, comprising the following steps: - determining recipe parameters for obtaining a desired container from preforms heated in the heat treatment unit, these recipe parameters including the heating power of the heating device and the rate at which the preforms pass through the chamber, - determining at least one initial temperature of the preforms and at least one heating temperature of the preforms when the heat treatment unit applies said recipe parameters, - calculating at least one coefficient from said recipe parameters, said initial temperature and said heating temperature,- to pass preforms through the heat treatment unit to heat the preforms to at least a predetermined heating temperature corresponding to said heating temperature, - to measure the initial temperature of the preforms at the inlet of the heat treatment unit, - when the measured initial temperature is different from the initial temperature used to calculate the coefficient, to adjust the heating power of the heating device according to the predetermined heating temperature, the measured initial temperature, the rate of preform passage through the chamber and the calculated coefficient.

[0018] Other aspects and advantages of the invention will become more apparent from the following description, given solely by way of non-limiting example, and made with reference to the drawings in which: a schematic top view of a container production installation comprising a heat treatment unit according to the invention.

[0019] With reference to the, we describe a plant for producing containers 1 from a succession of preforms 2. Such a plant includes, in a known way and in the order of circulation of the preforms 2 and the containers 1 in the plant, a heat treatment unit 4, or furnace, a transfer wheel 6 and a forming station 8.

[0020] The heat treatment unit 4 is arranged to heat a succession of preforms 2 transported into the heat treatment unit 4 by a preform gripping and displacement system 2 so as to pass them past a heating device 10, as will be described in more detail later.

[0021] At the outlet of the heat treatment unit 4, the transfer wheel 6 is arranged to collect the heated preforms 2 and to transfer them to the forming station 8.

[0022] The forming station 8, for example, consists of a carousel carrying several molds 12 that form molding cavities in the shape of the containers 1 to be produced. The heated preforms 2 are each placed in a mold and deformed to acquire the shape of a container 1, for example, by stretch blow molding. At the exit of the forming station, the formed containers 1 are collected, for example, by means of another transfer wheel 14, to be conveyed to other stations in the installation, such as a labeling station, a filling station, and a station for applying a cap to the containers.

[0023] As previously stated, such an installation is known and will not be described in further detail here. It is understood, however, that the installation layout shown in Figure 1 is given only as an example and that the invention applies to any type of installation layout provided that it includes a heat treatment unit.

[0024] The heat treatment unit 4 comprises a chamber 16 extending between an inlet 18 and an outlet 20. The preforms 2 enter the chamber 16 through the inlet 18, are heated, while circulating in the chamber 16, by the heating device 10 and the heated preforms 2 exit the chamber 16 through the outlet 20 where they are recovered by the transfer wheel 6.

[0025] Within the enclosure 16, the preforms 2 circulate along a flow path, comprising at least one section passing alongside the heating device 10. Such a section is designated by the term "heating section" 21. In the heating section 21, the heating device 10 is arranged to emit thermal radiation towards the preforms 2 circulating alongside it in order to raise the temperature of the body of the preforms 2 above the glass transition temperature of the material forming the body so that the body acquires a malleable character allowing its deformation to form a container 1. For this purpose, the heating device 10 includes, for example, at least one heating element 22 extending alongside the body of the preforms 2 passing alongside the heating element 22 in the heating section 21.

[0026] Each heating element 22 comprises, for example, a plurality of monochromatic or pseudo-monochromatic electromagnetic radiation sources. More specifically, each heating element 22 is, for example, a laser emitter, and the radiation sources are laser chips arranged to emit laser radiation in the infrared range along an emission direction corresponding to the direction separating the heating element 22 from the body of the preforms 2 circulating in the heating section 21 of the heat treatment unit 4. The radiation sources are, for example, arranged side by side on a support so as to form at least one row of radiation sources extending along the longitudinal direction. In one embodiment, the radiation sources form at least one upper row and at least one lower row arranged one above the other along the elevation direction.

[0027] Such heating elements are described, for example, in document FR 3 124 030, and those skilled in the art may refer to this document for further details, particularly concerning the structure of each radiation source, the arrangement of the radiation sources on a support, the connection of the radiation sources to each other, and the cooling of the heating elements. It is understood that the invention is not limited to heating elements formed by laser emitters and also applies to other types of heating elements, such as halogen-type incandescent tubular lamps.

[0028] The heating device 10 is specifically arranged to increase the temperature of the entire body of the preforms 2. To this end, the heating device 10 comprises, for example, at least one column of heating elements 22 arranged one above the other in a direction of elevation substantially parallel to the axis of the preforms 2 as they circulate in the chamber 16 and substantially perpendicular to the direction of emission of the heating elements 22. Thus, when the body of a preform 2 passes a column of heating elements 22, each heating element 22 in the column heats an area of ​​the body of the preform 2 extending over a portion of the height of the body of the preform 2, measured along the axis of the preform 2. The number of heating elements 22 in the column is arranged so that the entire body of the preform 2 is heated by the heating elements 22.

[0029] Alternatively or in addition, the heating device 10 comprises a plurality of at least heating elements 22 forming a line of heating elements 22 extending along the direction of movement of the preforms 2 in the heating section 21. In other words, as a preform 2 advances in the heating section 21, its body passes successively in front of several heating elements 22 arranged adjacent to each other along the direction of movement of the preform 2 so that the body of this preform is exposed to thermal radiation over the entire length of the heating section 21, measured along the direction of movement of the preforms 2 in the heating section 21.

[0030] According to one embodiment, the heating device 10 comprises a plurality of columns of heating elements 22 arranged side by side along the direction of circulation of the preforms 2 in the heating section 21. In other words, according to this embodiment, each zone of the body of the preform 2 extending over a part of the height of the body of the preform 2 passes in front of a succession of heating elements 22 extending to the same height along the direction of elevation so that the whole body of the preform 2 is heated over the entire length of the heating section 21.

[0031] According to one embodiment, the heating device 10 comprises heating elements 22 arranged on either side of the preforms 2 in a direction perpendicular to the axis of the preforms 2 corresponding to the direction of emission of the heating elements 22. In other words, when a preform 2 travels in the heating section 21, it passes between at least two heating elements 22 arranged opposite each other or offset from each other according to the direction of movement of the preform 2 in the heating section 21.

[0032] According to one embodiment, the heating device 10 is formed by two walls made up of successive columns of heating elements 22, each column extending in the direction of elevation and the columns being arranged side by side in the direction of circulation of the preforms 2 in the heating section 21. When the preforms 2 circulate in the heating section 21, they pass between the two walls so that the whole body of the preforms 2 is heated efficiently over the entire length of the heating section 21.

[0033] According to one embodiment, the preform 2 is further rotated about its axis while it circulates in the heat treatment unit 4 so that the entire circumference of the body is exposed to radiation from the heating elements 22. It should be noted, however, that, for example in the case of asymmetric deformation of the body of the preform 2 to form a container, the heating temperature of all or part of the areas of the body of the preform is not necessarily uniform over the entire circumference of the preform.

[0034] According to one embodiment, as shown in the figure, the heat treatment unit 4 comprises at least two heating sections 21 as described above, the heating sections 21 being separated from each other according to the direction of circulation of the preforms 2 in the heat treatment unit 4. In other words, according to this embodiment, the preforms 2 pass through an area in which they are not exposed to thermal radiation between two heating sections 21.

[0035] The temperature to which the body of each preform 2 is heated at the outlet of the chamber 16, called the heating temperature Tc, depends on the heating power Pc of the heating device 10 formed by the heating element(s) 22 of the heating section(s) 21 of the heat treatment unit 4. In other words, the heating power Pc of the heating device 10 corresponds to the sum of the heating powers of all the heating elements 22 present in the heat treatment unit 4 <to be confirmed>.

[0036] The heating power Pc of the heating device 10 is adjustable by means of a control module 24 of the heat treatment unit 4. Specifically, the control module 24 allows adjustment of the heating power of each heating element 22 that makes up the heating device 10. The control module 24 thus allows adjustment of the heating intensity of each zone of the preform 2 body in order to manage the temperature profile applied to it. Indeed, as is known, zones of the body of the same preform 2 are not necessarily heated to a uniform temperature. The temperature of a zone depends, in particular, on the shape of the container 1 to be produced from the preform 2. More specifically, the more a given zone of a preform 2 must be deformed, or stretched, to form the container 1, the higher the temperature to which it must be heated.The control module 24 thus allows the heating power of a particular heating element 22 to be adjusted according to the temperature to which the area of ​​the body of the preform 2 corresponding to this particular heating element 22 must be heated.

[0037] When the heating section 21 comprises several columns of heating elements 22, the heating power of the heating elements 22 in the same row—that is, the heating elements 22 extending to the same height in the direction of elevation—is constant. Thus, when the control device 24 controls the heating power of a particular heating element 22, this heating power is applied to all the heating elements 22 located at the same height as that particular heating element. However, if the vessel 1 to be formed has at least one portion in which the cross-section is not circular, the heating power of the heating elements 22 located at the height of this portion can be modulated to allow for asymmetrical deformation of the preform 2 in this portion.

[0038] As will be described later, the control module 24 is configured to adjust the heating power Pc of the heating device 10 according to an initial measured temperature Ti m preforms 2. By initial temperature, we mean the temperature of the preforms 2 before they are exposed to the thermal radiation of the heating device 10, that is to say the temperature of the preforms 2 at the entrance 18 of the enclosure 16 of the heat treatment device 4.

[0039] For this purpose, the heat treatment unit 4 includes at least one upstream measuring device 26 of the initial temperature Ti of the preforms 2 at the inlet 18 of the enclosure 16.

[0040] The upstream measuring device 26 is arranged to measure the body temperature of the preforms 2 at at least one point on the body as these preforms 2 enter the enclosure 16 through its inlet 18 or in the vicinity of this inlet 18 before entering a heating section 21 of the heat treatment unit 4. As shown in the figure, the upstream measuring device 26 is, for example, located between the inlet 18 of the enclosure 16 and a first heating section 21 so as to measure the temperature of the preforms 2 as they move through the enclosure 16 towards the first heating section 21. The upstream measuring device 26 includes, for example, an infrared pyrometer and / or an image acquisition device in the infrared range of the preforms 2, more particularly of their body. In one embodiment, the initial temperature Ti is measured at several points on the body of the preforms 2.The temperatures are acquired by a processing device 28 of the upstream measuring device 26 and one or more initial measured temperatures Ti. m are transmitted to control module 24.

[0041] The heating power Pc of the heating device 10 is adjusted by the control module 24, taking into account an initial measured temperature Ti m Preforms 2 will now be described.

[0042] According to the invention, for a preform 2, the heating power Pc is adjusted according to at least one heating temperature to which the preform 2 must be heated, called the predetermined heating temperature Tc, and at least one initial measured temperature Ti m , of the rate C of preforms passing through enclosure 16 and of at least a constant coefficient K for a desired container 1 to be made from preform 2.

[0043] The predetermined heating temperature Tc corresponds to the temperature to which the body of the preform 2 must be heated to obtain the desired container, i.e., a container with the desired material distribution after deformation and stretching of the preform 2 in a mold 12 of the forming station 8. According to one embodiment, the heating power Pc is adjusted taking into account several predetermined heating temperatures Tc in different areas of the body of the preform 2. In this case, a coefficient K is calculated as described below for each of these areas. The heating power Pc is then also adjusted for each of these areas.

[0044] The initial measured temperature Ti m is the temperature obtained using the upstream measuring device 26. The initial measured temperature Ti mFor example, the temperature is acquired at the same point on the body of preform 2 used to determine the predetermined heating temperature Tc. When several predetermined heating temperatures Tc are taken into account, several initial measured temperatures Tim of the same areas of the body of preform 2 are acquired and the heating power Pc for these areas is adjusted as described below.

[0045] The rate C of preform 2 passing through chamber 16 corresponds to the number of preform 2 exiting chamber 16 per hour when the container production plant is operating. This rate C corresponds, for example, to the number of molds 12 in the forming station 8 multiplied by the rate of each mold 12 per hour, that is, the number of containers 1 formed by a mold 12 in one hour. In other words, if the forming station 8 has N molds 12 and each mold has a rate of R containers per hour, then C = N*R. Indeed, since the containers are formed by the preforms 2 exiting the heat treatment unit 4, the container forming rate corresponds to the rate C of preform 2 passing through the heat treatment unit.

[0046] The coefficient K is calculated from a heating recipe for a given preform 2 to produce a desired container 1. Such a heating recipe corresponds to various settings of the heat treatment unit 4 which, when applied, allow the preform 2 to be heated to the predetermined heating temperature Tc. The preform 2, heated to this predetermined heating temperature Tc, forms the desired container when deformed and stretched in a mold 12 of the forming station 8. These recipe parameters include the feed rate C of the preforms 2 in the chamber 16 and a heating power Pc of the heating device 10. To determine the coefficient K, the heat treatment unit 4 is set with these recipe parameters, and at least one preform 2 is heated by passing it through the heat treatment unit 4.The initial temperature Ti of the preform 2 at the inlet 18 of the chamber and the heating temperature Tc of the preform 2 at the outlet 20 of the chamber 18 are then recorded. According to one embodiment, the coefficient K is then calculated according to the following formula:

[0047] According to other embodiments, one or more other parameters can be taken into account to calculate the K coefficient. Thus, the formula for calculating the K coefficient can be refined, for example, to take into account the ambient temperature or one or more other parameters having a more minor influence on the heating of the preforms 2.

[0048] To determine the heating temperature Tc, a downstream measuring device 30 is used, for example, to measure the temperature of the preforms 2 heated at the outlet 20 of the chamber 16. The downstream measuring device 30 is arranged to measure the body temperature of the preforms 2 at at least one point on the body when these preforms 2 exit the chamber 16 through its outlet 20 or are in the vicinity of this outlet 20 after exiting a heating section 21 of the heat treatment unit 4. As shown in the figure, the downstream measuring device 30 is, for example, located between a second heating section 21 and the outlet 20 of the chamber 16 so as to measure the temperature of the preforms 2 as they move through the chamber 16 towards the outlet 20 of the chamber. The downstream measurement device 30 includes, for example, an infrared pyrometer and / or an image acquisition device in the infrared domain of the preforms 2, more particularly of their body.According to one embodiment, the heating temperature Tc is measured at several points on the body of the preforms 2. The temperatures are acquired by a processing device 32 of the downstream measuring device 30, and one or more measured heating temperatures Tc are transmitted to the control module 24 to calculate the coefficient K. Such a downstream measuring device 30 can also be used to implement a control loop for the heating power Pc of the heating device 10. Indeed, the downstream measuring device 30 can be used to measure the temperature of all the preforms 2 exiting the chamber 16 in order to verify that their heating temperature conforms to the predetermined heating temperature Tc, thus obtaining the desired container 1 after deformation and stretching of the preforms 2 in the forming station 8.If a drift is observed in the heating temperature of the preforms 2, the control module 24 can correct the heating power Pc of the heating device 10 in order to bring the heating temperature Tc back into the desired range or to the desired value.

[0049] Alternatively, the predetermined heating temperature Tc is obtained by a numerical thermal heating model, i.e. by simulating the heating of a given preform to obtain the desired container 1 after deformation and stretching of this preform in the forming station 8.

[0050] For a recipe relating to a given container 1, the coefficient K is considered constant because: - the mass of a preform 2 is substantially the same from one preform to another to manufacture the given container; - the optical transfer efficiency of a heating element 22 to the preforms 2 is constant during the production of the containers 1, especially when the heating elements 22 are laser emitters, as described previously; - the specific heat varies very little in the heating temperature range of the preforms 2 for a given preform material, especially when the preforms 2 are made of polyethylene terephthalate (PET).

[0051] Thus, the method of adjusting the heating power Pc according to the invention makes it possible to take into account only parameters relating to the heat treatment unit 4 which are easily accessible and not the characteristics specific to the preforms 2 which are generally not communicated by the preform manufacturers.

[0052] Starting from at least one predetermined heating temperature Tc, which corresponds to the heating temperature Tc determined to calculate the coefficient K, and from at least one initial measured temperature Ti mBased on the preform feed rate C in chamber 16 and the coefficient K, the control module 24 can calculate the heating power Pc of the heating device 10 to heat the preforms 2 to the predetermined heating temperature Tc, taking into account the initial temperature of the preforms 2 to adjust this heating power Pc when the initial temperature of the preforms 2 varies from one preform to another or, more generally, from one batch of preforms 2 to another. Indeed, the preforms 2 are generally introduced into the container production plant 1 in batches, and the temperature of the preforms 2 can vary from one batch to another, for example, depending on whether the batch was stored at ambient temperature or under refrigeration before being introduced into the container production plant.

[0053] Thus, during a variation of the initial temperature Ti mmeasured by the upstream measuring device 26, the control module 24 is configured to adjust the heating power according to the following formula:

[0054] in which PC a is the adjusted heating power.

[0055] It should be noted that the heating power Pc can be adjusted globally for the entire heating device 10 or for a subset of the heating elements 22 of the heating device 10. Similarly, the heating power Pc can be adjusted differently from one group of heating elements 22 to another depending on the initial measured temperatures Ti mwhen these are acquired at several points on the preform body 2, as previously indicated. Thus, it may be advantageous, for example, to adjust the heating power of a line of heating elements 22 extending to the same height in a heating section differently from the heating power of another line of heating elements 22 when the areas of the preform body heated by these lines need to be heated to different temperatures. In this case, several K coefficients are calculated, for example, one K coefficient per line of heating elements 22.

[0056] The initial measured temperatures Ti m can also be averaged over several successive preforms 2 for the calculation of the adjusted heating power Pc a in order to avoid overly frequent adjustments as soon as a minimal variation of the initial measured temperature is observed.

[0057] Once the PC heating power a has been calculated, the control module 24 applies a setpoint to the heating device so that the heating elements 22 apply this adjusted heating power Pc a .

[0058] In one embodiment, the heating power of the heating elements 22 of the heating device 10 is controlled by the control module 24 by modifying a percentage of the maximum heating power of each heating element 22 capable of heating the preforms 2 circulating in the chamber 16. In this case, the setpoint for adjusting the heating power is applied by modifying this percentage of the maximum heating power. In this embodiment, the heating power Pc of the vessel production recipe used to calculate the K coefficient is converted into a corresponding percentage of the maximum heating power %Pmax to which each heating element is capable of heating the preforms. When the heating power needs to be adjusted, the adjusted percentage of the maximum heating power %Pmax a is then calculated as follows:

[0059] According to one embodiment, the control module 24 is configured to adjust the heating power of the heating elements 22 successively from the inlet 18 to the outlet 20 of the chamber 16 as a function of the progress between the inlet 18 and the outlet 20 of a preform 2 having a modified initial temperature Ti m In other words, according to this embodiment, the heating power modification instruction is only applied when preforms 2 have a modified initial temperature Ti m pass in relation to the heating elements 22 and not for heating elements 22 extending too far downstream of these preforms 2. Indeed, since the heat treatment unit 4 operates continuously, preforms with different initial temperatures may be simultaneously present in the chamber 16. It is therefore necessary to ensure that the adjusted heating power Pc ais applied only to preforms for which this adjusted heating power Pc a was calculated and not for preforms with a different initial temperature.

[0060] According to one embodiment, the control module 24 takes into account several parameters to apply the setpoint so that the adjusted heating power Pc a is applied by a heating element 22 at the moment when a preform 2 has a modified initial temperature Ti m , for which this adjusted heating power was calculated, passes in relation to this heating element 22. These parameters include, for example: - the proportion of preforms 2 exhibiting the modified initial temperature Ti mentering enclosure 16 compared to those already present in enclosure 16 and having a different initial temperature; - the modular resolution of the heating elements 22, - the speed of movement of the preforms 2 in the enclosure; and - the distance between two successive preforms 2, i.e. the pitch between the preforms circulating in enclosure 16.

[0061] Advantageously, the control module 24 is further configured to apply the adjusted heating power setpoint, taking into account the time required for a heating element 22 to apply the adjusted heating power Pc ato the preforms 2 with a modified initial temperature passing by. In other words, the control module 24 drives the heating elements 22 slightly in advance of the preforms 2 passing by these heating elements to allow time for these heating elements 22 to adjust to the new setpoint. Thus, the control module 24 is configured to adjust the heating power of a heating element 22 before a preform 2 with a modified initial temperature Ti m passes in front of this heating element 22 so as to take into account the adjustment time of the heating power of the heating element 22 to go from an initial heating power to the adjusted heating power Pc a .

[0062] Advantageously, the upstream measuring device 26 is arranged at a distance from the first heating element 22 arranged in the enclosure 16 between the inlet 18 and the outlet 20 so that the initial temperature Ti is measured m of a preform 2, the calculation of the adjusted power Pc a and the adjustment of this heating power by control module 24 is made before the preform 2 passes in front of this first heating element 22 to take into account the adjustment time of the heating power of the first heating element 22 to go from an initial heating power to the adjusted heating power Pc aThe term "first heating element" refers to the heating element closest to the inlet 18 of the chamber 16, i.e., the first heating element 22 past which the preforms pass as they move through the chamber 16 from inlet 18 to outlet 20. This ensures that the desired heating power is applied when the preform enters a heating section. The heating elements 22 located downstream of the first heating element 22 can then be controlled sequentially as described above so that they apply the adjusted heating power Pc. a as preform 2 passes in front of them.

[0063] In one embodiment, the calculation of the heating power Pc, taking into account the initial temperature of the preform as described above, is not applied to one or more zones of the preforms 2, particularly for zones where the required heating power is low. Regulating the heating power of the other zones then allows the preforms 2 to be heated satisfactorily.

[0064] It should be noted that the heating power can advantageously be adjusted separately for each heating section 21 of the heat treatment unit 4. In other words, the control module 24 can be configured to apply the process described above independently for each heating section 21. In this case, as shown in the figure, the heat treatment unit 4 includes, for example, an intermediate preform temperature measuring device 34 upstream of each heating section 21 in order to measure the temperature of the preforms 2 before they enter a heating section 21.The heating power of the heating elements 22 of this heating section 21 can then be adjusted by the control module 24 as described previously by calculating an adjusted heating power based on the temperature of the preforms 2 measured by the intermediate measuring device 34, this measured temperature corresponding to the initial measured temperature described previously. The temperatures are acquired by a processing device 36 from each of the intermediate measuring devices 34, and one or more measured heating temperatures are transmitted to the control module 24.

[0065] The heat treatment unit 4 and the preform heating process 2 described above make it possible to ensure optimal heating of the preforms 2 taking into account their initial temperature in a simple way and from parameters which can be determined or acquired directly in the container production plant 1 including this heat treatment unit 4.

Claims

A heat treatment unit (4) for preforms (2) of a container manufacturing installation (1), comprising: - a chamber (16) extending between an inlet (18), through which the preforms (2) are introduced into the chamber (16), and an outlet (20), through which the heated preforms (2) exit the chamber (16), - a heating device (10) extending between the inlet (18) and the outlet (20) of the chamber (16), said heating device (10) being arranged to heat said preforms (2) between the inlet (18) and the outlet (20) of the chamber (16), - at least one upstream measuring device (26) for at least one initial temperature (T i) of the preforms (2) at the inlet (18) of the chamber (16), - at least one control module (24) arranged to adjust the heating power (Pc) of said heating device (10), said heating power (Pc) being arranged so that the preforms (2) are heated to at least a predetermined heating temperature (Tc) at the outlet (20) of the chamber (16), characterized in that the control module (24) is configured to adjust the heating power (Pc) of the heating device (10) during a variation of the initial measured temperature (Ti) m ) by the upstream measuring device (26), said heating power (Pc) being adjusted according to the predetermined heating temperature (Tc), of the initial measured temperature (Ti m), of the rate (C) of preforms passing through the enclosure and of at least one constant coefficient K for a desired container (1) to be made from the preforms (2) passing through the enclosure (16), said coefficient (K) being calculated from a production recipe allowing to obtain said desired container (1) from a preform having an initial temperature (Ti) given, heated by a heating power (Pc) and having a heating temperature (Tc) at the exit of the enclosure in which the preforms (2) circulate at a rate (C) corresponding to a number of preforms (2) exiting the enclosure per hour. Heat treatment unit according to claim 1, in which the coefficient K is calculated according to the following formula: Heat treatment unit according to claim 1 or 2, wherein the control module (24) is configured to adjust the heating power upon a variation of the initial measured temperature (Ti m ) according to the following formula: in which (Pc a ) is the adjusted heating power. A heat treatment unit according to any one of claims 1 to 3, wherein the heating device (10) comprises a plurality of heating elements (22) distributed within the chamber (16) along a path of preform (2) flow within the chamber between the inlet (18) and the outlet (20), the control module (24) being configured to adjust the heating power of each heating element (22) of the heating device (10) in response to a change in the initial measured temperature (Ti). m), the heating power of each heating element (22) being adjusted so that the preforms (2) circulating successively in front of said heating elements (22) have the predetermined heating temperature (Tc) at the outlet (20) of the enclosure (16). Heat treatment unit according to claim 4, wherein the adjustment of the heating power of each heating element (22) is done by modifying a percentage (%Pmax) of the maximum heating power to which each heating element (22) is capable of heating the preforms (2) circulating in the enclosure (16). A heat treatment unit according to claim 4 or 5, wherein the control module (24) is configured to adjust the heating power of the heating elements (22) successively from the inlet (18) to the outlet (20) of the chamber (16) as a function of the progress between the inlet (18) and the outlet (20) of a preform (2) having a measured initial temperature (Ti m ) modified. Heat treatment unit according to claim 6, wherein the control module (24) is configured to adjust the heating power of a heating element (22) before a preform (2) having a measured initial temperature (Ti m ) modified scrolls past said heating element (22) so as to take into account the adjustment time of the heating power of the heating element (22) to go from an initial heating power to the adjusted heating power (Pc a ). A heat treatment unit according to any one of claims 4 to 7, wherein the upstream measuring device (26) is arranged at a distance from the first heating element (22) arranged in the enclosure (16) between the inlet (18) and the outlet (20) such that the initial temperature of a preform (2) is measured, and the adjusted power (Pc) is calculated. a ) and the adjustment of this heating power by control module (24) are made before the preform (2) passes in front of said first heating element (22) to take into account the adjustment time of the heating power of the first heating element (22) to go from an initial heating power to the adjusted heating power (Pc a ). Heat treatment unit according to any one of claims 1 to 8, wherein the upstream measuring device (26) comprises an infrared pyrometer and / or an image acquisition device in the infrared range of preforms. Heat treatment unit according to any one of claims 1 to 9, further comprising a downstream measuring device (30) for the temperature of the preforms (2) heated at the outlet (20) of the chamber (16), the control module (24) being configured to adjust the heating power of the heating device (10) as a function of the heating temperature (Tc) of the preforms (2) heated measured by the downstream measuring device (30). A method for heating preforms (2) using a heat treatment unit (4) according to any one of claims 1 to 10, comprising the following steps: - determining recipe parameters for obtaining a desired container (1) from preforms (2) heated in the heat treatment unit (4), these recipe parameters including the heating power (Pc) of the heating device (10) and the feed rate (C) of the preforms (2) in the chamber (16), - determining at least one initial temperature (Ti) of the preforms (2) and at least one heating temperature (Tc) of the preforms (2) heated when the heat treatment unit (4) applies said recipe parameters, - calculating at least one coefficient (K) from said recipe parameters, said initial temperature (Ti) and said heating temperature (Tc),- to pass preforms (2) through the heat treatment unit (4) to heat the preforms (2) to a predetermined heating temperature corresponding to said heating temperature (Tc), - to measure at least one initial temperature of the preforms (2) at the inlet (18) of the heat treatment unit (4), - when the initial temperature measured (Ti, m ) is different from the initial temperature (Ti) used to calculate the coefficient (K), adjust the heating power of the heating device (10) according to the predetermined heating temperature (Tc), the initial measured temperature (Ti m ), the rate (C) of preform movement in the enclosure and the calculated coefficient (K).

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