METHOD AND DEVICE FOR MANAGING PREFORMS IMMOBILIZED IN A HEATING DEVICE

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a method for managing captive preforms immobilized in a heating station during a production interruption, as well as a heating station for implementing the method. TECHNICAL BACKGROUND OF THE INVENTION

[0002] The invention is intended to be implemented in an installation for manufacturing containers made of thermoplastic material and in particular polyethylene terephthalate (PET) by forming, in particular by blowing or stretch-blow molding, preforms. Such an installation makes it possible to produce containers in very large series at very high rates.

[0003] It is known to produce containers from thermoplastic material, such as polyethylene terephthalate (PET), by a preform forming process.

[0004] According to a well-known technique, such containers are produced in two main stages.

[0005] In a first step, a PET preform is injection molded. This preform comprises a substantially tubular body which is closed at one of its axial ends, the opposite end being open by means of a neck. The neck has, from this injection molding operation, the final shape of the container neck. Generally, the container neck has a thread.

[0006] In a second forming step, the hot preforms are placed in mold cavities. Then, a pressurized forming fluid is injected into the preforms to press the preform wall against the cavity walls to shape the preform into the final container. This blow molding operation is generally accompanied by a stretching operation consisting of inserting an elongation rod into the preform through its neck in order to axially stretch the preform wall.

[0007] In many cases, preforms are manufactured by injection at one location and are blow-molded to the final container shape at a second location on a specific manufacturing facility. Such technology allows the blow-molding operation to be carried out as close as possible to the bottling site, and the injection operation can be carried out at any location. Indeed, it is relatively easy and inexpensive to transport small preforms, while transporting containers after blowing has the disadvantage of being economically unprofitable due to their very large volume.

[0008] To enable its forming, the body of the preform is heated beyond a glass transition temperature to make the wall of the body malleable. On the contrary, the neck is kept at a temperature below the glass transition temperature to prevent its deformation. For this purpose, the manufacturing installation includes a heating station which allows the body of the preforms to be heated to the temperature required to carry out the forming step.

[0009] Conventional heating stations are equipped with halogen incandescent lamps, which radiate according to Planck's law on a continuous spectrum.

[0010] Before starting any production, it is advisable to preheat the heating station to bring it, using lamps, to a suitable temperature capable of giving the preforms a thermal profile allowing subsequent forming.

[0011] This preheating is slow and requires delicate adjustments.

[0012] Furthermore, lamps generally radiate heat in all directions. To increase the efficiency of the heating station, it is known to arrange reflectors that allow the heating radiation to be reflected towards the preforms.

[0013] Since the radiation emitted by the lamps is not directional, many elements of the heating station, including the reflectors, accumulate heat during preheating. As a result, during an untimely production stoppage, switching off the lamps does not allow an immediate drop in the temperature inside the heating station. The various heated elements in fact release the accumulated heat through a phenomenon of thermal inertia. As a result, the preforms blocked in the heating station continue to heat up in an uncontrolled manner, making them unsuitable for forming. The immobilized preforms thus heated must therefore be discarded. One installation is described in particular in document DE1 0259589.This document describes a hollow body manufacturing installation comprising a preform heating station, a blowing station, and at least one preform inspection station located upstream and / or downstream of the heating station. This preform inspection makes it possible to eject preforms detected as defective upstream and downstream of the heating station depending on the detected defect.

[0014] Document US2013277892 describes a method for managing captive preforms immobilized in a heating station during a production interruption, the heating station being part of a facility for manufacturing containers made of thermoplastic material by forming the preforms heated by the heating station, the preforms following a production flow through the manufacturing facility. The method consists of blocking from the production flow the so-called "cold" captive preforms, which have been immobilized before entering the furnace, and ejecting from the production flow the so-called "hot" captive preforms, which have been at least partially heated, to a waste stream. 11 BRIEF SUMMARY OF THE INVENTION

[0015] The invention provides a method for managing captive preforms immobilized in a heating station during a production interruption, the heating station being part of an installation for manufacturing containers made of thermoplastic material by forming the preforms heated by the heating station, the preforms following a production flow through the manufacturing installation, the heating station comprising: a preform conveying device comprising individual supports circulating in a closed circuit, each individual support being intended to transport a preform in continuous movement along a predetermined transport path forming a section of the production flow, from an entry point to an exit point, a heating cavity bordered by at least one row of monochromatic electromagnetic radiation emitters controlled between an off state and an on state, the heating cavity being crossed by the transport path; the method consisting of ejecting from the production flow the captive preforms called "cold", which have been immobilized before being exposed to the electromagnetic radiation emitted by the emitters, towards a recycling flow, and ejecting from the production flow the captive preforms called "hot", which have been at least partially exposed to the electromagnetic radiation emitted by the emitters, towards a waste flow separate from the recycling flow.

[0016] According to other characteristics of the method carried out according to the teachings of the invention: the cold captive preforms and the hot captive preforms are selectively ejected from the production flow by two separate preform ejection devices; the cold captive preforms and the hot captive preforms are ejected from the production flow by a common ejection device; the cold captive preforms, respectively the hot captive preforms, ejected by the common ejection device are selectively directed to the recycling flow, respectively to the scrap flow, by a sorting device; the cold captive preforms are ejected from the production flow upstream of the heating cavity; the cold captive preforms are ejected from the production flow downstream of the heating cavity;the cold captive preforms are ejected from the production flow downstream of the outlet point of the heating station, for example when the preforms are taken over by a transfer wheel arranged directly downstream of the heating station; the emitters of the heating cavity are kept in an off state as long as cold captive preforms circulate in the heating cavity; at least a portion of the cold captive preforms oriented towards the recycling flow are subsequently transformed into a final container by forming after heating; the cold captive preforms oriented towards the recycling flow are again introduced into the production flow upstream of the heating station;at least a portion of the cold captive preforms directed towards the recycling stream are destroyed and their material is reused to manufacture new preforms - the manufacturing facility comprises a forming station which is arranged downstream of the heating station along the production flow, the hot captive preforms being ejected from the production flow downstream of the heating station, for example at the forming station. ;

[0017] The invention also proposes a heating station for implementing the method, comprising a first ejection device arranged along the transport path downstream of the heating cavity making it possible to selectively eject a preform from its individual support upstream of the exit point, the preform thus ejected being directed towards the waste stream, and that it comprises a second ejection device arranged along the transport path making it possible to selectively eject a preform from its individual support upstream of the exit point, the preform thus ejected being directed towards a recycling stream towards the entry point of the heating station.

[0018] The invention also proposes a container manufacturing installation for implementing the method, comprising a common device for ejecting captive preforms, the manufacturing installation comprising a device for selectively sorting the preforms ejected by said common ejection device towards a recycling flow or towards a waste flow. BRIEF DESCRIPTION OF THE FIGURES

[0019] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: there figure 1 is a top view which schematically represents an installation for manufacturing containers from preforms produced according to the teachings of the invention; the figure 2is a side view which schematically represents a portion of a preform conveying device belonging to a heating station of the installation of the figure 1 ; there figure 3 is a view similar to that of the figure 2 which represents the conveying device passing at the level of a preform ejection device of the heating station towards a waste flow; the figure 4 is a view similar to that of the figure 3 which represents the conveying device passing at the level of a preform ejection device of the heating station towards a recycling flow; the Figure 5 is a side view which schematically represents means for sorting preforms ejected by a common ejection means selectively towards a waste stream or towards a recycling stream. DETAILED DESCRIPTION OF THE FIGURES

[0020] In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

[0021] In the remainder of the description, longitudinal orientations will be adopted, directed according to the direction of movement of the preforms along their transport path, vertical orientations, directed according to the direction of gravity, and transverse orientations indicated by the trihedron L,V,T of the figures, without limitation.

[0022] In the remainder of the description, the terms "upstream" and "downstream" will be used in reference to the direction of movement of the preforms along their production flow "P" and in particular along their transport path.

[0023] We represented at the figure 1a station 10 for heating preforms 12 made of thermoplastic material. The heating station 10 belongs to an installation 11 for manufacturing containers made of thermoplastic material by forming, in particular stretch-blow molding, said preforms 12.

[0024] The preforms 12 move in a line through the manufacturing installation 11 following a production flow "P" from an entry point "A" of the heating station 10 to an exit from the manufacturing installation 11 in the form of finished containers conforming to a specification, after forming in a forming station 13. Along the production flow "P", the preforms 12 and the final containers move in a line and they are held individually by individual supports such as clamps, notches, molds, etc.

[0025] The heating station 10 comprises a device 14 for conveying the preforms 12 in a row. The conveying device 14 comprises individual supports 16 circulating in a closed circuit in the heating station 10. Each individual support 16 is intended to transport a preform 12 in continuous movement along a predetermined transport path 18 from an entry point "A" of the heating station 10 which is supplied by a row of preforms 12 to an exit point "B" in the direction of the forming station 13, in particular for blow molding or stretch blow molding. The transport path 18 forms a section of the flow "P" for producing the preforms 12.

[0026] The manufacturing installation 11 comprises a device 15 for aligning and straightening the preforms 12 into which the preforms 12 are poured in bulk and in which the preforms 12 are aligned and straightened. This aligning and straightening device 15 supplies the heating station 10 with preforms 12. There are numerous alignment and straightening devices, such as centrifuge devices and gravity rail devices. These devices are well known and will not be detailed later.

[0027] The conveying device 14 is here supplied with cold preforms 12 by a transfer wheel 17 interposed between the aligning and straightening device 15 and the heating station 10. The transfer wheel 17 is arranged tangentially to the entry point "A", while the hot preforms 12 are taken care of individually by a transfer wheel 19 arranged tangentially to the exit point "B". From the exit point "B" to the entry point "A", the individual supports 16 of the conveying device 14 circulate empty.

[0028] Generally, each individual support 16 comprises means capable of driving the preform 12 in rotation about its main axis during its movement along at least part of the transport path 18 to allow homogeneous heating of the body of the preform 12. Such an individual support 16 is sometimes called a "spinner".

[0029] In the embodiment shown in figures 2 to 4 , the conveying device 14 here comprises a plurality of transport elements 22 forming the links of a closed transport chain 26, a portion of which is visible at the figure 2 . The transport chain 26 is flexible. For this purpose, the transport elements 22 are mounted articulated to each other around vertical axes "X0". The transport chain 26 is mounted movable relative to a frame fixed relative to the floor of the heating station 10.

[0030] Referring again to the figure 2 , each transport element 22 carries at least one individual support 16. Each individual support 16 comprises a mandrel 21.

[0031] In a known manner, the mandrel 21 is provided with elastic means (not shown), such as an O-ring, advantageously made of an elastic material (such as an elastomer), and the external diameter of which is equal to or slightly greater than the internal diameter of the neck of a preform 12, so as to ensure the support of the preform 12 by friction against the internal wall of the neck, when the mandrel 21 is inserted into the neck of the preform 12.

[0032] In the example shown in the figures, each individual support 16 can be controlled between an active position in which the preform 12 moves in a manner integral with the individual support 16, and an inactive position in which the preform 12 is completely free relative to the individual support 16.

[0033] The mandrel 21 is here mounted to slide in vertical translation along a vertical axis, relative to the transport element 22. The mandrel 21 is fixed to the lower end of a cylindrical rod 20.

[0034] The mandrel 21 is mounted to slide vertically relative to the transport element 22, between an inactive position in which the mandrel 21 is retracted relative to a stop face 24 (on the right at figure 3 ), and an active position ( figure 2 and left to the figure 3 ) in which the mandrel 21 projects downwards relative to the stop face 24 to fit into the neck of a preform 12. By way of non-limiting example, the stop face 24 is here mounted fixed relative to the transport element 22.

[0035] According to a non-limiting example, the mandrel 21 is here elastically returned to its active position, while it is controlled to its inactive position by cooperation between a cam follower roller 25, arranged here at an upper end of the rod 20, with a cam 27, illustrated in figure 3 , which acts against the elastic restoring force.

[0036] More particularly, in the active position, the mandrel 21 is intended to be fitted into the neck of a preform 12, while in the inactive position, the mandrel 21 is intended to be extracted from the neck of said preform 12, the preform 12 bearing against the stop face 24 to allow its extraction.

[0037] In a variant of the invention not shown, the mandrel is intended to grip the neck of the hollow body from the outside. This variant is well known to those skilled in the art and will therefore not be described in more detail below.

[0038] According to a variant of the invention, not shown, the preforms are loaded or unloaded from their support by pick-up clamps which move jointly with the supports over at least part of their path, the clamps being axially movable relative to the support to allow the preforms to be fitted into or removed from their mandrel. In this case, the mandrels are not sliding relative to the transport element. The clamps are, for example, carried by a guide wheel of the transport chain.

[0039] Referring again to the figure 1, the conveying device 14 further comprises a first wheel 28A for guiding the transport chain 26 and a second wheel 28B for guiding the transport chain 26, each rotatably mounted on the frame of the heating station 10 about a respective vertical axis "X1, X2". The transport chain 26 is meshed around the two guide wheels 28A, 28B. One of the two guide wheels, called the driving wheel, is rotated by a motor to set the transport chain in motion in order to move the transport elements 22 along the closed circuit. The guide wheels 28A, 28B here rotate in an anticlockwise direction, as indicated by the arrow "F1" of the figure 1 .

[0040] In a variant of the invention not shown, the transport chain makes it possible to compact the preforms by folding in an accordion shape when it passes into the heating cavity as described in detail in document EP-B1-2.623.439.

[0041] According to a variant of the invention (not shown), the conveying device is formed of transport elements which are not connected to each other and which form shuttles circulating on rails arranged in a closed circuit. The carriages and the rails form, for example, a linear motor, the rail forming a flattened "stator" and the carriage forming a rotor of said linear motor. Such a conveying device for a heating station is for example described in document FR-A1-3.035.651.

[0042] Furthermore, each individual support 16 is capable of rotating the preform 12 around its axis during its movement along the transport path 18 to enable the homogeneous heating of said preform 12.

[0043] According to a first example not shown, the individual support 16 is driven in rotation by a pinion secured to the mandrel 21 which cooperates with a fixed rack of the heating station 10.

[0044] According to another example not shown, the individual support 16 is driven in rotation by means of an electric motor on board the transport element 22.

[0045] Referring again to the figure 1 , the heating station 10 also comprises a heating cavity 30 crossed by the transport path 18 to allow the heating of the preforms 12 during their movement. The heating cavity 30 is arranged on a portion of the transport path 18, near the point "B" where the preforms exit.

[0046] The heating cavity 30 is intended to heat the bodies of the preforms 12 beyond their glass transition temperature to allow their forming by the forming station 13 while they are hot.

[0047] The heating cavity 30 is lined with a series of adjacent emitters 32, for example two rows of emitters 32 facing each other.

[0048] Each transmitter 32 is equipped with sources of monochromatic electromagnetic radiation (in particular lasers), the emission spectrum of which extends mainly into the infrared range.

[0049] In theory, a monochromatic source is an ideal source emitting a sine wave of a single frequency. In other words, its frequency spectrum consists of a single line of zero spectral width (Dirac).

[0050] In practice, such a source does not exist, a real source having a frequency emission spectrum which extends over a band of low but non-zero spectral width, centered on a main frequency where the intensity of the radiation is maximum. For the purposes of the present application, such a real source is considered to be monochromatic. Similarly, for the purposes of the present description, a multimode source is considered to be monochromatic, that is to say emitting on a discrete spectrum comprising several narrow bands centered on distinct main frequencies.

[0051] The advantage of monochromatic radiation is that, if well chosen, it can be concentrated on one (or more) frequency(ies) for which (or for which) the thermal behavior of the material of the preforms 12 is, in terms of absorption, particularly interesting.

[0052] For example, to obtain rapid heating on the surface of the preforms 12, one (or more) frequency(ies) in the infrared can be chosen for which the material is very absorbent. Conversely, to obtain slower but more uniform heating in the thickness of the preforms 12, one (or more) frequency(ies) can be chosen for which the material is relatively less absorbent.

[0053] In practice, the sources with which the emitters 32 are provided are lasers (for example laser diodes) emitting in the infrared and organized by juxtaposition and superposition to form one or more matrices.

[0054] In this case, each array may be an array of vertical cavity surface emitting laser (VCSEL) diodes, each diode emitting, for example, a laser beam with a unit power of the order of a milliwatt at a wavelength of approximately 1 µm.

[0055] These sources are radiant, that is to say that the emitted radiation is transmitted to the preforms 12 without the air serving as a transmission vector.

[0056] The sources convert the electrical power supplied to them into an electromagnetic field radiated into the cavity.

[0057] The emitters 32 are controlled between an off state, in which they do not emit any radiation, and an on state in which they are supplied with electrical power to emit radiation. This electrical power can be variable. According to an embodiment not shown, the heating station advantageously comprises, for the electrical power supply of the emitters 32, a power variator. This variator can be analog or electronic.

[0058] In normal operation of the heating station 10, the emitters 32 are controlled so as to heat the body of the preforms 12 according to a determined thermal profile which is adapted to the shape of the final container to be formed.

[0059] A heating station 10 operating using this technology has many advantages over a conventional halogen lamp oven. Among other things, in this type of heating station 10: the emitters 32 radiate in the infrared without diffusion of heat, which, unlike a halogen oven, makes any ventilation unnecessary; the preforms 12 can be heated according to more precise thermal profiles; no preheating is necessary.

[0060] The inventors have noticed that, in addition to these known advantages, the thermal inertia of the heating station 10 has become negligible, in particular due to the absence of heat diffusion. In other words, the preforms 12 heat up beyond their glass transition temperature only when they are directly exposed to the radiation emitted by the emitters 32 in the heating cavity 30.

[0061] In the event of an accidental interruption in the circulation of the preforms 12 in the heating station 10, the preforms 12 carried by the conveying device 14 become captive inside the heating station 10. They are thus immobilized on the transport path 18. Such preforms 12 will subsequently be called "captive preforms 12".

[0062] The captive preforms 12 which are immobilized upstream of the heating cavity 30 have not yet been exposed to the radiation of the emitters 32. They are therefore bathed in an atmosphere cold relative to their glass transition temperature. These preforms 12 will subsequently be called "cold captive preforms 12".

[0063] The captive preforms 12 which are immobilized in the heating cavity 30 or downstream of the heating cavity have been at least partially exposed to the radiation of the emitters 32. These preforms 12 will subsequently be called "hot captive preforms 12" because their body has been heated to a temperature approaching or exceeding their glass transition temperature.

[0064] To prevent the captive preforms 12 immobilized in the heating cavity 30 from melting, the emitters 32 are switched off as soon as an interruption in the circulation of the preforms 12 is detected.

[0065] When hot captive preforms 12 are immobilized for too long, their body temperature slowly decreases, causing crystallization of the thermoplastic material. Such a preform 12 can no longer become malleable again upon heating, and therefore can no longer be used to form a final container. These preforms 12 are traditionally sent to the scrap heap.

[0066] At the end of the production interruption, the heating station 10 therefore contains two types of captive preforms 12, namely cold captive preforms 12 and hot captive preforms 12.

[0067] The invention proposes a method for managing captive preforms 12 which consists of sorting the cold captive preforms from the hot captive preforms. The cold captive preforms are more particularly ejected from the production flow "P", without having been exposed to the radiation of the emitters 32, towards a recycling flow. The hot captive preforms 12 are ejected from the production flow towards a waste flow separate from the recycling flow.

[0068] The invention thus proposes a management method which makes it possible to take advantage of the fact that the material constituting the cold captive preforms 12 still has the structural properties allowing it to undergo a forming operation after heating for the production of final containers. The invention proposes more particularly to discard the hot captive preforms 12 and to exploit the captive preforms 12.

[0069] Thus, contrary to what is currently practiced, not all captive 12 preforms are discarded. This allows for significant savings for the container manufacturer.

[0070] For example, at least a portion of the cold captive preforms 12, which are directed towards the recycling stream 42, are subsequently transformed into the final container by forming after heating either by said manufacturing installation 11 or by another similar manufacturing installation located elsewhere.

[0071] In the case of heating by the heating station 10, the cold captive preforms 12 directed towards the recycling stream 42 are again introduced into the production stream "P" at the start of the heating station 10. The recycled cold captive preforms 12 are for example mixed in bulk with new preforms 12 in the line-up and straightening device 15, as indicated by the arrow 42 of the figure 1 .

[0072] According to a variant of the invention, at least a portion of the cold captive preforms 12, which are directed towards the recycling stream 42, are destroyed and their material is reused to manufacture new preforms 12, for example by injection molding or by extrusion.

[0073] According to a first embodiment of the invention, the cold captive preforms and the hot captive preforms are selectively ejected from the production flow by two separate preform ejection devices from the production flow "P". Thus, the manufacturing installation 11 comprises a first ejection device 34 which ejects the hot captive preforms 12 towards a waste flow 38, and a second ejection device 41 which ejects the cold captive preforms towards a recycling flow 42.

[0074] In this case, the sorting of the two types of captive preforms 12, i.e., the hot captive preforms 12 and the cold captive preforms 12, is carried out while the captive preforms 12 are still following the production flow "P". One of the two ejection devices 34, 41, which is arranged upstream along the production flow "P" relative to the other of the two ejection devices 34, 41, is controlled to selectively eject the type of captive preforms 12 with which it is associated, thus leaving the captive preforms 12 of the other type to continue their movement in the production flow "P" to the other of the two ejection devices 34, 41.

[0075] The number of preforms 12 to be ejected by the ejection device 34, 41 located furthest upstream is for example determined as a function of the speed of movement of the preforms. The speed of movement of the preforms makes it possible to estimate the time required to pass all the hot captive preforms 12 to the level of the furthest upstream ejection device 34, 41 by taking into account the distance between the start of the heating cavity 30 and said furthest upstream ejection device 34, 41.

[0076] In a variant of the invention not shown, a detector is arranged in the installation to detect the passage of the hot captive preforms 12 at the level of each ejection device 34, 41. This is for example a temperature detector.

[0077] According to an exemplary embodiment of the invention, the heating station 10 is here equipped with the first device 34 for ejecting the hot captive preforms 12 which comprises ejection means which are arranged along the transport path 18 downstream of the heating cavity 30 and upstream of the outlet point "B". The ejection means make it possible to selectively release a preform 12 from its individual support 16 upstream of the outlet point "B". The preform 12 thus ejected is directed towards a waste stream 38, for example towards a skip 36.

[0078] According to the non-limiting example illustrated in figure 3, the ejection means here comprise a switch 40 which is controlled between a retracted position, indicated in broken lines, in which the roller 25 of the individual support 16 passes below the cam 27, the mandrel 21 thus remaining in the active position, and a bifurcation position, indicated in solid lines, in which the switch 40 is interposed on the path of the roller 25 to guide the latter in the direction of the cam 27 to control the mandrel 21 in the inactive position and thus eject the preform 12.

[0079] When a preform 12 is ejected by the ejection means of the first ejection device 34, it falls towards the waste bin 36, possibly via a slide or conveyor belt.

[0080] In a variant of the invention not shown, the hot captive preforms are ejected from the preform production flow "P" downstream of the heating station, for example at the forming station 13, at the same time as non-compliant containers after forming.

[0081] In the example shown in figures 1 And 4 , the ejection of the cold captive preforms 12 from the production flow "P" is carried out in the heating station 10. For this purpose, the heating station 10 comprises, in addition to the first ejection device 34 associated with the hot captive preforms 12, a second ejection device 41 which is intended to selectively eject preforms 12 from their individual support 16. The preforms 12 ejected by the second ejection device 41 are thus extracted from the transport path 18, and they follow a recycling flow 42.

[0082] As shown in more detail in the figure 4, the second ejection device 41 comprises ejection means which are distinct from the ejection means of the first ejection device 34 but which fulfill the same function. Thus, the ejection means of the second ejection device 41 make it possible to selectively release a preform 12 from its individual support 16. The ejection means are here arranged upstream of the outlet point "B" of the heating station 10.

[0083] In a non-limiting manner, the ejection means of the second ejection device 41 here have the same structure as the ejection means of the first ejection device 34. Thus, according to the example illustrated in figure 4, the ejection means here comprise a switch 46 which is controlled between a retracted position, indicated in broken lines, in which the roller 25 of the individual support 26 passes below the cam 27, the preform 12 thus not being ejected, and a bifurcation position, indicated in solid lines, in which the switch 46 is interposed on the path of the roller 25 to guide the latter in the direction of the cam 27 to control the mandrel 21 in the inactive position and thus eject the preform 12.

[0084] The preform 12 thus ejected by the second ejection device 41 is directed towards the recycling flow 42.

[0085] The second ejection device 41 is here arranged upstream of the heating cavity 30, in the immediate vicinity of its upstream end.

[0086] In a variant of the invention not shown, the second ejection device 41 is arranged in another position of the transport path 18 located between the entry point "A" and the heating cavity 30, for example at the level of the bend formed around the second wheel 28B.

[0087] According to another variant of the invention, not shown, the second ejection device 41 is arranged downstream of the heating cavity 30.

[0088] According to another variant of the invention, not shown, the ejection of the cold captive preforms from the production flow "P" to the recycling flow 42 is carried out downstream of the outlet point "B" of the heating station 10, for example when the preforms are taken over by transfer wheels interposed between the heating station 10 and the forming station 13. The second ejection device 41 is thus arranged downstream of the outlet point "B" along the production flow "P".

[0089] Of course, when the second ejection device 41 is arranged downstream of the heating cavity 30, the method provides that the emitters 32 of the heating cavity 30 are kept in an off state as long as captive "cold" preforms 12 circulate in the heating cavity 30.

[0090] In the example shown in figures 1 And 4 , the recycled cold captive preforms 12 are ejected towards a conveyor belt 44 which carries the ejected preforms 12 towards the device 15 for placing in line and straightening the cold preforms with a view to supplying the heating station 10. The recycled preforms 12 are thus mixed in bulk with new preforms 12 upstream of the heating station 10.

[0091] Alternatively, the recycled preforms 12 are stored in a bin while awaiting recovery. In a non-limiting manner, the recovery may consist either of subsequently returning the preforms 12 thus recycled to the device 15 for putting online and straightening the heating station 10, or of using them on another manufacturing installation of the same type as the manufacturing installation 11 to form finished containers, or of destroying them and using their material to form new preforms 12.

[0092] According to a second embodiment of the invention, the cold captive preforms 12 and the hot captive preforms 12 are ejected from the production flow "P" by a common ejection device 34. The "cold" captive preforms, respectively the "hot" captive preforms, are then sorted after ejection by the common ejection device 34. They are thus selectively directed towards the recycling flow 42 or towards the waste flow 38, by a sorting device 50.

[0093] The common ejection device 34 is identical to the first ejection device 34 already described in the first embodiment. In this embodiment, the common ejection device 34 is arranged downstream of the heating cavity 30. The common ejection device 34 is arranged along the production flow "P", for example downstream of the outlet point "B" of the heating station 10 or upstream of the outlet point "B" of the heating station 10.

[0094] The captive preforms 12 are all ejected towards a common ejection stream across which the sorting device 50 is arranged. The sorting device 50 makes it possible to selectively direct the ejected captive preforms 12 towards the recycling stream 42 or towards the waste stream 38.

[0095] In the example shown in the Figure 5 , the ejected preforms 12 fall for example into a common chute 48 which has two outlets: a first outlet 48A directed towards the recycling flow 42 and a second outlet 48B directed towards the waste flow 38. The preforms 12 are directed towards one or other of the outlets 48A, 48B by a mobile pallet, here forming the sorting device 50, for example pivotally mounted between two switching positions.

[0096] The sorting device 50 is for example controlled between its two positions as a function of the speed of movement of the preforms 12 along the production flow "P". The speed of movement of the preforms 12 makes it possible to estimate the time required to evacuate all the hot captive preforms 12 by taking into account the distance between the start of the heating cavity 30 and said common ejection device 34.

[0097] In a variant of the invention not shown, a detector is arranged in the installation to detect the passage of the hot captive preforms 12 from the common ejection device 34. This is for example a temperature detector.

[0098] When implementing the method according to any of the embodiments, at the end of the interruption, the conveying device 14 is restarted to convey the captive preforms 12 along the production flow "P".

[0099] When the hot captive preforms 12 pass the associated ejection device 34, the latter is commanded to eject them towards the waste stream 38. All the hot captive preforms 12, which have been immobilized after being exposed to the electromagnetic radiation emitted by the emitters 32, are thus ejected towards the waste stream because they are likely to be unsuitable for forming final containers.

[0100] Likewise, when the cold captive preforms 12 pass at the level of the associated ejection device 34 or 41, depending on the embodiment, the latter is controlled to eject them towards the recycling flow 42.

[0101] Of course, when the device 34, 41 for ejecting the cold captive preforms 12 is arranged downstream of the heating cavity 30, the emitters 32 of the heating cavity 30 are kept in an off state to prevent the cold captive preforms 12 from being heated while they circulate in the heating cavity 30 to reach said ejection device 34, 41.

[0102] The invention advantageously makes it possible to recover the cold captive preforms 12 by separating them from the hot captive preforms 12, the material of which can no longer be used for the manufacture by blow molding of objects made of thermoplastic material.

Claims

1. Method for managing of captive preforms (12) immobilized in a heating station (10) during an interruption of production, the heating station (10) forming part of an installation (11) for production of thermoplastic material containers by forming the preforms heated by the heating station (10), the preforms (12) following a production stream (P) through the production installation (11), the heating station (10) including: - a device (14) for conveying preforms (12) including individual supports (16) circulating in a closed circuit, each individual support (16) being intended to transport a preform (12) in continuous movement along a predetermined transport path (18) forming a section of the production stream (P) from an entry point (A) to an exit point (B), - a heating cavity (30) bordered by at least one row of emitters (32) of monochromatic electromagnetic radiation commanded between an extinguished state and a lit state, the heating cavity (30) being crossed by the transport path (18); the method consisting in ejecting from the production stream (P) the so-called "cold" captive preforms that have been immobilized before they have been exposed to the electromagnetic radiation emitted by the emitters (32) to a recycling stream (42) and in ejecting from the production stream (P) the so-called "hot" captive preforms that have been at least partly exposed to the electromagnetic radiation emitted by the emitters (32) to a reject stream (38) separate from the recycling stream (42).

2. Method according to the preceding claim, characterized in that the cold captive preforms (12) and the hot captive preforms (12) are selectively ejected from the production stream (P) by two distinct devices (34, 41) for ejecting preforms (12).

3. Method according to Claim 1, characterized in that the cold captive preforms (12) and the hot captive preforms (12) are ejected from the production stream (P) by a common ejector device (34).

4. Method according to the preceding claim, characterized in that the cold captive preforms (12), respectively the hot captive preforms (12), ejected by the common ejector device (34) are selectively switched to the recycling stream (42), respectively to the reject stream (38), by a sorting device (50).

5. Method according to Claim 2, characterized in that the cold captive preforms (12) are ejected from the production stream (P) upstream of the heating cavity (30) .

6. Method according to any one of Claims 1 to 4, characterized in that the cold captive preforms (12) are ejected from the production stream (P) downstream of the heating cavity (30).

7. Method according to the preceding claim, characterized in that the cold captive preforms (12) are ejected from the production stream (P) downstream of the exit point (B) of the heating station (10), for example when the preforms (12) are taken up by a transfer wheel arranged directly downstream of the heating station (10).

8. Method according to the preceding claim, characterized in that the emitters (32) of the heating cavity (30) are maintained in an extinguished state for as long as the cold captive preforms (12) circulate in the heating cavity (30).

9. Method according to any one of the preceding claims, characterized in that at least some of the cold captive preforms (12) oriented toward the recycling stream (42) are subsequently transformed into finished containers by forming after heating.

10. Method according to the preceding claim, characterized in that the cold captive preforms (12) oriented toward the recycling stream are again introduced into the production stream (P) upstream of the heating station (10).

11. Method according to any one of the preceding claims, characterized in that at least some of the cold captive preforms (12) oriented toward the recycling stream (42) are destroyed and the material thereof is re-used to produce new preforms (12).

12. Method according to any one of the preceding claims, characterized in that the production installation (11) includes a forming station (13) that is arranged downstream of the heating station (10) along the production stream (P), the hot captive preforms (12) being ejected from the production stream (P) downstream of the heating station (10), for example at the level of the forming station (13).

13. Heating station (10) for executing the method according to any one of Claims 1 to 12, including a first ejector device (34) arranged along the transport path (18) downstream of the heating cavity (30) allowing selective ejection of a preform (12) from its individual support (16) upstream of the exit point (B), the preform (12) ejected in this way being directed toward the reject stream (38), and including a second ejector device (41) arranged along the transport path (18) allowing selective ejection of a preform (12) from its individual support (16) upstream of the exit point (B), the preform (12) ejected in this way being directed toward a recycling stream (42) in the direction of the entry point (A) of the heating station (10).

14. Container production installation (11) for executing the method according to any one of Claims 1 to 12, including a common device (34) for ejecting the captive preforms (12), the production installation (11) including a device (50) for selectively sorting the preforms (12) ejected by said common ejector device (34) toward a recycling stream (42) or toward a reject stream (38) .