Device for serial treatment of hollow bodies comprising a treatment rod slidingly controlled by an electric actuator and treatment method

TECHNICAL FIELD OF THE INVENTION

0001The invention relates to a device for the series treatment of hollow bodies made of thermoplastic material comprising a treatment rod which is intended to be inserted into the hollow body, the device relating to means for controlling the sliding of the rod.

0002The invention also relates to a process for the series treatment of preforms implementing such a treatment device.

TECHNICAL BACKGROUND OF THE INVENTION

0003The invention relates more particularly to a device for mass processing of hollow bodies made of thermoplastic material, in particular preforms made of thermoplastic material, comprising:<ul id="ul0001" list-style="dash" compact="compact"><li>at least one individual transport member for a hollow body;</li><li>at least one treatment rod which is associated with said transport member, the treatment rod being mounted to slide axially with respect to the transport member;</li><li>controlled means for moving each treatment rod between a retracted position in which the treatment rod is retracted above the hollow body transported by the transport member, and an extended position in which the treatment rod is intended to be inserted axially into the hollow body transported by passing through a neck of said hollow body.</li></ul>

0004Treatment devices of this type make it possible in particular to treat preforms which are intended for the manufacture, by blow molding or by stretch-blow molding, of containers made of thermoplastic material.

0005In the description and in the claims, the term "treatment" encompasses both physical intervention operations on the hollow body, such as a sterilization or cooling operation, and control operations, such as a measurement of the temperature inside the hollow body.

0006In this type of device, the transport members move by scrolling one behind the other along a closed circuit. The transport members are for example carried by a chain or by a carousel.

0007The hollow bodies are loaded one by one onto the device in a loading zone. Then they are moved by the transport members along a path. During their transport the hollow bodies are treated. At the end of the journey, the hollow bodies are unloaded from the transport members one after the other in an unloading zone.

0008When it comes to preforms, the hollow bodies continue their movement on other devices towards a forming station, while the transport members return to their starting point to take on other hollow bodies. treat.

0009In the treatment devices already known, the sliding of the treatment rods is controlled by a cam which is arranged along the path of the hollow body.

0010Cam sliding means are generally very bulky. To reduce the pitch between two successive transport members, several treatment rods are mounted on the same sliding carriage. Thus, all the rods mounted on said carriage are simultaneously slidable so as to process several hollow bodies at the same time.

0011However, the cam sliding control means do not make it possible to quickly and easily adjust the sliding stroke of the treatment rods. In particular, it is not possible to individually adjust the sliding stroke of each rod as a function of the size of each hollow body during operation of the treatment device.

0012In addition, the fact that several rods are controlled simultaneously does not allow hollow bodies to be processed over their entire path. Indeed, considering a series of several successive hollow bodies intended to be treated by as many treatment rods mounted on a common carriage, the first hollow bodies of the series must first carry out an "empty" movement, that is i.e. without processing, until the last hollow body in the series is loaded onto the processing device before processing can begin. Likewise, the processing stops simultaneously for all the hollow bodies in the series as soon as the first hollow body has reached the unloading zone.

0013The presence of these "empty" movements unnecessarily increases the duration of presence of each hollow body on the processing device.

0014Treatment devices are also known in which the means for controlling the sliding of the rods are formed by pneumatic cylinders which operate "all or nothing". The sliding stroke of each treatment rod is adjusted simultaneously for all the treatment rods of the device by positioning a stop element common to all the cylinders. This device makes it possible to roughly adjust the stroke of the treatment rods for different types of hollow bodies.

0015Nevertheless, the common adjustment of the stroke of the treatment rods does not make it possible to obtain a fine adjustment making it possible to precisely adapt the stroke of each rod to the actual height of each hollow body. This is particularly important when the treatment device is arranged after a hollow body heating station. Indeed, the heating causes shrinkage of the thermoplastic material constituting the hollow bodies. The effects of this shrinkage on the height of the hollow bodies is of the order of a few millimeters. In addition, the shrinkage is disparate for each preform, and it is very complex or even impossible to determine the exact height of a preform after it has been heated.

0016However, some treatments require fine adjustment of the stroke of the treatment rods during operation of the treatment device in order to be able to adapt it to the height of each preform taken individually. Such adaptation is not possible with known processing devices.

0017The document<patcit id="pcit0001" dnum="EP2176052A"><text>EP2176052</text></patcit> describes a treatment of preforms by ignition of an explosive gas mixture. The document<patcit id="pcit0002" dnum="US6984360B"><text>US6984360</text></patcit> describes a method of sterilizing a container.

BRIEF SUMMARY OF THE INVENTION

0018The invention provides a device according to claim 1.

0019According to other characteristics of the device produced according to the teachings of the invention:<ul id="ul0002" list-style="dash"><li>the treatment rod comprises means for detecting when its free end is at the determined distance from the bottom of the preform;</li><li>the treatment rod is formed by a nozzle intended to inject a fluid into the hollow body;</li><li>the treatment rod carries at its lower end a means for measuring the temperature;</li><li>the treatment rod comprises means for emitting sterilizing electromagnetic radiation, for example light-emitting diodes emitting ultraviolet radiation.</li></ul>

0020The invention also relates to a method according to claim 6.

0021According to other characteristics of the process:<ul id="ul0003" list-style="dash" compact="compact"><li>the method includes prior steps for measuring the height of each hot preform, each prior step for measuring a preform occurring before the start of the step for processing said preform to allow the electronic control unit to stop the treatment rod at the determined distance from the bottom of said preform;</li><li>each treatment step comprises an operation of detecting the bottom of said preform which is carried out during the sliding of the treatment rod towards its extended position to allow the electronic control unit to stop the treatment rod at the determined distance from the bottom of said preform.</li></ul>

BRIEF DESCRIPTION OF FIGURES

0022Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:<ul id="ul0004" list-style="dash" compact="compact"><li>the<figref idref="f0001">figure 1</figref> is a schematic view which represents an installation for manufacturing containers in series by forming preforms of thermoplastic material, the installation comprising a processing device produced according to the teachings of the invention;</li><li>the<figref idref="f0001">picture 2</figref> is a schematic top view which represents a part of the device for processing the<figref idref="f0001">figure 1</figref> comprising hollow body transport members;</li><li>the<figref idref="f0002">picture 3</figref> is a schematic view in partial axial section of the<figref idref="f0001">picture 2</figref> wherein a treatment rod occupies a retracted position;</li><li>the<figref idref="f0002">figure 4</figref> is a schematic view in partial axial section of the<figref idref="f0001">picture 2</figref> wherein a treatment rod occupies an extended position;</li><li>the<figref idref="f0002">figure 5</figref> is a schematic side view showing means for measuring the height of a preform;</li><li>the<figref idref="f0002">figure 6</figref> is a view similar to that of the<figref idref="f0002">figure 5</figref> which represents a treatment rod equipped with means for detecting the approach of the bottom of the preform.</li></ul>

DETAILED DESCRIPTION OF FIGURES

0023In the remainder of the description, elements having an identical structure or analogous functions will be designated by identical reference signs.

0024In the remainder of the description, an axial orientation directed upwards in a direction parallel to that of the sliding axis of the treatment rods and indicated by the arrow "A" in the figures will be adopted in a non-limiting manner.

0025Schematically represented in<figref idref="f0001">figure 1</figref> an installation 10 for mass production of containers made of thermoplastic material. In a non-limiting manner, the containers here are bottles and the thermoplastic material is formed by polyethylene terephthalate, subsequently designated by its acronym “PET”.

0026The containers are obtained by hot forming preforms 12 of thermoplastic material.

0027For the description and for the claims, the term "hollow body" refers to a hollow object having an opening formed by a neck. In this description, the hollow bodies are formed by preforms 12.

0028Such preforms 12 are generally obtained by injection. As depicted at<figref idref="f0002">figure 5</figref>, they have a cylindrical body 14 with a tubular wall which is closed at one of its axial ends, here lower, by a bottom 13 and which is extended at its other end, here upper, by a neck 16, also tubular.

0029The neck 16 delimited axially downwards by a flange 18. The neck 16 is generally injected so as to already have its final shape while the body 14 of the preform 12 is required to undergo a relatively large deformation to form the final container during of a forming operation.

0030The bottom 13 of the preform 12 thus forms a wall having an inner face forming a bottom 15 which delimits axially downwards the inner cavity of the preform 12 and an outer face 17.

0031By referring to the<figref idref="f0001">figure 1</figref>, the installation 10 comprises a station 20 for heating the preforms 12. By way of non-limiting example, the heating station 20 is formed by a tunnel in which heating means (not shown) are arranged, such as lamps infrared or means for emitting microwave radiation. A means 22 for conveying the preforms 12 is arranged so as to make the preforms 12 pass along the heating means from an entrance to an exit of the tunnel.

0032The running direction of the preforms 12 is indicated by the arrows of the<figref idref="f0001">figure 1</figref>.

0033Alternatively, the heating station is formed of individual cavities equipped with heating means and each receiving a preform.

0034On leaving the heating station 20, the part to be deformed of the preforms 12, generally the body 14, is made malleable by heating beyond a glass transition temperature, while the parts not to be deformed, in general the neck 16, are kept at a temperature low enough to retain their original shape.

0035The installation 10 also comprises a station 24 for forming the preforms 12 thus heated. The forming station 24 is arranged downstream of the heating station with reference to the flow of preforms 12 in the installation 10.

0036The forming station 24 here has the form of a carousel 26 carrying a plurality of forming stations 28 . Each forming station 28 is thus capable of moving around the axis of the carousel 26 between a loading point for the hot preforms 12 and an unloading point for the final containers before resuming a new cycle.

0037These are stations 28 for forming by stretch-blow molding the preforms 12. With regard to stations 28 for forming by blow molding, the fluid is generally formed by a pressurized gas.

0038It will however be understood that the invention is also applicable to other types of forming stations, in particular to forming stations by injecting a pressurized liquid into the preform.

0039During the container forming operation, the carousel 26 is driven in a rotational movement to allow the movement of the preforms 12/final containers from the loading point to the unloading point. Thus, a new preform 12 can begin the forming operation while the previous preform 12 has not yet completed its forming cycle. This makes it possible to maintain a high rate for the mass production of containers 12.

0040The manufacturing installation 10 also comprises a device 30 for the serial processing of the preforms 12 which is interposed between the heating station 20 and the forming station 24 according to the flow of the preforms 12.

0041The processing device 30 comprises at least one member 32 for individually transporting a preform 12.

0042The processing device 30 shown in<figref idref="f0001">picture 2</figref> more particularly comprises a transport wheel 34 which is rotatably mounted around an axis "B" of axial orientation. The transport wheel 34 has at its periphery notches each of which forms an individual transport member 32 . As depicted at<figref idref="f0002">picture 3</figref>, each notch has dimensions suitable for the collar 18 of a preform 12 to be placed on the periphery of the notch. Thus the preforms 12 can be transported along an arcuate path when the transport wheel 34 is rotated by a motor (not shown) from a loading zone to an unloading zone.

0043In a not shown variant of the invention, each transport member is formed by a gripper which is capable of gripping the preform, for example by gripping the outer cylindrical wall of the neck of the preform while leaving the neck accessible to a rod 38 of treatment as will be explained later.

0044As shown in dashed lines at<figref idref="f0001">picture 2</figref>, each transport member 32 is associated with a processing station 36 which is integral in movement with said associated transport member 32 .

0045The processing device 30 here comprises a plurality of transport members 32 each of which comprises an associated processing station 36 for processing the preforms 12 in series at a high rate.

0046The processing stations 36 are identical in their structure and in their arrangement with respect to the transport member 32 with which they are associated.

0047As illustrated in the<figref idref="f0002">picture 3</figref>, each treatment station 36 comprises an axial treatment rod 38 which comprises a free lower end 40 .

0048The free lower end 40 of the treatment rod 38 is intended to be inserted axially into the preform 12 by passing through the neck. For this purpose, the treatment rod 38 is arranged axially in line with the opening of the neck 16 of the preform 12 carried by the transport member 32.

0049The treatment rod 38 is slidably mounted relative to the transport wheel 34 between:<ul id="ul0005" list-style="dash" compact="compact"><li>a retracted position, as shown in<figref idref="f0002">picture 3</figref>, in which the treatment rod 38 is retracted above the transported hollow body, here the preform 12, and;</li><li>an extended position, as shown in<figref idref="f0002">figure 4</figref>, wherein the rod 38 treatment is inserted by axial sliding downwards in the preform 12 transported by the member 32 of transport.</li></ul>

0050The sliding of the rod 38 treatment is guided by a guide means, such as a sleeve 41, which is fixed relative to the wheel 34 of transport.

0051In its retracted position, the free end 40 of the treatment rod 38 is arranged axially above the neck 16 of the preform 12 so as to allow lateral loading, that is to say in a direction orthogonal to the axial direction, of a new preform on the transport member 32, or the lateral unloading of a preform 12 already treated.

0052In its extended position, the free end of the treatment rod 38 is stopped at a determined axial distance "D" from the bottom of the preform 12.

0053Each treatment station 36 comprises controlled means for moving the treatment rod 38 between its retracted position and its extended position.

0054According to the teachings of the invention, the controlled means of setting in motion are formed by an electric actuator 42 whose interruption of operation is controlled by an electronic control unit 44, illustrated in<figref idref="f0001">figure 1</figref>, to stop the treatment rod 38 in its extended position.

0055The electric actuator 42 comprises a static element 46 which is mounted fixed relative to the transport wheel 34, and a mobile element 48 which is capable of moving axially parallel to the treatment rod 38. The movable element 48 is driven by an electric motor (not shown).

0056The electric current supply to the electric motor is individually controlled by the electronic control unit 44.

0057Treatment rod 38 is mechanically fixed with movable element 48 via a flange 50. Thus, treatment rod 38 is integral in axial movement with movable element 48.

0058By way of non-limiting examples, the electric actuator 42 is formed by a linear electric motor, or by a tubular electric jack, or else by a so-called “brushless” screw motor.

0059By the terms "controlled interruption of operation", it will be understood that the stopping of the treatment rod 38 in its extended position is effected without contact with a mechanical stop. In other words, stopping the treatment rod 38 in its extended position is effected by interrupting the supply of electric current to the electric actuator 42 controlled by the electronic control unit 44.

0060As depicted in<figref idref="f0002">figures 3 and 4</figref>, each treatment rod 38 is actuated individually by an associated individual electric actuator 42 . Thus, the movable element 48 of each electric actuator 42 is linked with a single associated treatment rod 38 .

0061In addition, each electric actuator 42 is controlled individually by the electronic control unit 44. In other words, each electric actuator 42 is controlled independently of the other electric actuators 42 of the device.

0062According to a first application of the invention, the treatment rod 38 carries at its free lower end 40 a means (not shown) for measuring the temperature inside the preform, for example a temperature sensor. Thus, in the extended position of the treatment rod 38, the temperature sensor is able to measure the temperature prevailing inside the preform 12 at the determined distance "D" from the bottom 15 of the preform 12.

0063Such a treatment rod 38 is used in particular at the outlet of the heating station 20 to check that the preforms 12 have indeed been heated to a set temperature.

0064As a variant, the treatment rod is also stopped in at least one intermediate position between its retracted position and its extended position in order to be able to measure the temperature prevailing inside the preform at a second distance from the bottom of the preform which is greater at the determined distance.

0065According to a second application of the invention, the treatment rod 38 is formed by a nozzle which comprises at its free lower end 40 at least one orifice for injecting a fluid, for example a gas. The treatment rod 38 is thus capable of injecting the fluid into the preform 12 when it occupies its extended position.

0066Such a treatment rod 38 can be used to cool certain portions of the wall of the preform 12 on leaving the heating station 20 . This makes it possible in particular to create a determined heating profile of the body 14 of the preform 12, that is to say that the body 14 of the preform 12 is not heated uniformly. Thus, it is possible to promote the deformation of the hotter parts of the preform 12 during the forming operation, while the colder parts of the preform 12 are less deformed. Such a process, called "preferential heating", makes it possible to obtain final containers having a complex shape.

0067For this application, the fluid jets can be oriented radially relative to the axis of the preform 12. This use requires precise positioning of the treatment rod 38 in the extended position relative to the bottom 15 of the preform 12 so that the heating profile of the preform 12 is controlled.

0068According to a third application of the invention, the treatment rod comprises means for emitting sterilizing electromagnetic radiation, for example light-emitting diodes emitting ultraviolet radiation. Such emission means are for example arranged at the free end 40 of the treatment rod 38 .

0069A sterilization treatment carried out with such a treatment rod 38 is all the more effective if the means for emitting the radiation are arranged close to the wall portion of the preform 12 to be sterilized. Indeed, it is known that the intensity of electromagnetic radiation decreases as the square of the distance between the emission source and the wall to be sterilized. Thus, the sterilization of the bottom 15 of the preform 12 will be effective all the more quickly as the free end 40 of the treatment rod 38 is close to it.

0070However, care must be taken that the end of the treatment rod 38 does not come into contact with the bottom 15 of the preform 12 at the risk of damaging the preform 12 and/or the means for emitting the radiation.

0071The three applications previously described require precise positioning of the treatment rod 38 in the extended position so that the free end 40 of the treatment rod 38 is stopped precisely at the determined distance "D" from the bottom 15 of the preform 12.

0072However, it has been found that after they have been heated by the heating station 20, the preforms 12 made of thermoplastic material, and in particular of polyethylene terephthalate, undergo shrinkage. This shrinkage results in particular in a reduction in the axial height of the preform 12 which may be up to several millimeters. For a batch of identical preforms 12 before their heating, the reduction in height of each preform 12 is disparate.

0073Consequently, the extended position of the treatment rod 38 must be defined individually for each of the preforms 12 so that the distance "D" determined between the free end 40 of the treatment rod 38 and the bottom 15 of the preform 12 is precisely respected for each of the preforms 12.

0074To this end, the treatment device 30 comprises means for controlling the sliding stroke of the treatment rod 38 up to its extended position as a function of the position of the bottom 15 of the preform 12 in the member 32 of transport so that, in its extended position, the free end 40 of the treatment rod 38 is stopped at the determined distance "D" from the bottom 15 of the preform 12 whatever the axial dimension of the preform 12. Thus, the sliding stroke of the treatment rod 38 from its retracted position to its extended position is adapted to the actual size of the associated preform 12.

0075The retracted position of the treatment rod 38 is fixed in the same way, regardless of the preform 12 loaded on the corresponding transport member 32, while the extended position is likely to change depending on the actual dimensions of the preform 12 loaded. on the member 32 corresponding transport.

0076According to the invention, the servo means comprise means 52 for measuring the axial height of said preform 12. The measuring means 52 are arranged so as to measure the height of the preform 12 before the treatment rod 38 n be inserted there.

0077The height of the preform 12 is here defined as the axial dimension between the flange 18 and the outer face 17 of the base 13.

0078The measuring means 52 are capable of communicating the result of the height measurement of the preform 12 to the electronic control unit 44.

0079In the example shown in<figref idref="f0001">figure 1</figref>, the measuring means 52 are arranged so as to measure the height of the preforms 12 before they are loaded onto the transport members 32 .

0080As a variant, the measuring means are arranged so as to measure the height of the preforms after they have been loaded onto the transport members. The measuring means are for example on board the transport wheel.

0081In the example shown in<figref idref="f0002">figure 5</figref>, the preform 12 is carried by a gripping member 54 similar to the transport member of the processing device 30 . The gripping member 54 moves in a known reference plane making it possible to know the precise position of the flange 18 of the preform 12.

0082The measuring means 52 are here formed by optoelectronic cells 56 operating according to a so-called “dam mode” or “through beam” mode. The cells 56 are arranged in a fixed manner along the path of the preforms 12, in a column, a determined pitch separating two adjacent cells 56. Each cell 56 is arranged at a determined axial distance from the flange 18 of the preform 12.

0083The optoelectronic cells 56 are arranged so as to emit radiation radial with respect to the axis of the preform 12 in an emission plane.

0084When the preform 12 intersects the emission plane, it intersects certain rays emitted by upper cells 56, while other rays emitted by lower cells 56 pass under the bottom 13 of the preform 12. Each cell 56 comprises means to detect if its radius has been cut by the preform 12.

0085It is possible to deduce therefrom the height of the preform 12 with a precision equal to the pitch determined between two cells 56.

0086In a variant of the invention, not shown, the measuring means are formed by a fixed laser scanning sensor which makes it possible to measure the height of the preform, or any other measuring means arranged fixed along the path, or on board the wheel. .

0087The position of the bottom 15 is deduced from this height measurement by taking into account the thickness of the bottom 13 of the preform 12. By combining the measurement of the total height of the preform 12 and the measurement of the thickness of the bottom 13 of the preform 12, the electronic control unit 44 is capable of determining the precise position of the bottom 15 of the preform relative to the transport wheel 34 by knowing the precise position of the collar 18 of the preform 12.

0088The thickness of the bottom 13 of the preform 12 is for example measured on a single preform 12 of the batch. Indeed, the thickness of 13 varies very little relative to the decrease in total height of the preform 12. The measured thickness is thus sufficiently precise to be applied to each preform 12.

0089As a variant, the measuring means also comprise a sensor which is capable of measuring the thickness of the bottom of the preform. It is for example a confocal sensor or an interferometric sensor. According to other variants of the invention, not shown, any other known means of non-contact measurement of the position of the bottom of the preform with respect to its upper end can be used.

0090We will now describe a process for the serial treatment of the preforms 12 after a prior heating operation of said preform 12 by the heating station 20 . During this process, all the preforms 12 are successively processed by the various processing stations 36 .

0091The processing method comprises successive steps “E1” of individual processing of each preform 12 by the processing device 30 produced according to the first embodiment of the invention.

0092The processing device 30 comprising several identical processing stations 36, each preform 12 is processed by one of the processing stations 36 .

0093During each processing step "E1", the processing rod 38 is inserted into the preform 12 loaded in the associated transport member 32 until it reaches its extended position. The stroke of the treatment rod 38 is adapted to said preform by the servo means so that the free end 40 of the treatment rod 38 is stopped at the determined distance "D" from the bottom of said preform 12.

0094The processing device 30 produced according to the teachings of the invention thus allows an adaptive stroke of the actuating rod 38 as a function of the height of each preform 12.

0095To enable the stroke of the processing rod 38 to be controlled, the method also comprises successive “E0” steps for measuring the height of each hot preform 12.

0096Each step "E0" of measuring a preform occurs before the start of step "E1" of processing said preform 12 to allow the electronic control unit 44 to stop the processing rod 38 at the determined distance. of the bottom 15 of said preform 12.

0097To this end, the measurement means 56 communicate to the electronic control unit 44 the results of the measurement of said preform 12 in order to interrupt the operation of the electric actuator 42 when the free end 40 of the rod 38 of treatment is at the determined distance "D" from the bottom 15 of said preform 12.

0098The application of the processing method by the device 30 shown in<figref idref="f0001">figure 1</figref> begins after a preform 12 has left the heating station 20, a measurement of its height is carried out by the measurement means 54 during the preliminary measurement step "E0".

0099Then, said preform 12 is loaded onto one of the transport members 32 of the wheel 34 for transport. The treatment rod 38 then occupies its retracted position.

0100Step "E1" of processing said preform 12 is then triggered. The electronic unit 44 activates the operation of the electric actuator 42 in order to cause the treatment rod 38 to slide towards its extended position.

0101Depending on the measurement of the height of the preform 12 carried out during the preliminary measurement step "E0", the electronic control unit 44 interrupts the operation of the electric actuator 42 to stop the sliding of the rod 38 from sliding when its free end 40 arrives precisely at the determined distance "D" from the bottom 15 of the preform 12.

0102At the end of the treatment of the preform 12 by the treatment rod 38, the electronic control unit 44 again activates the operation of the electric actuator 42 to cause the treatment rod 38 to slide to its retracted position.

0103This process is repeated individually for each of the preforms 12 leaving the heating station 20 .

0104According to a second embodiment of the invention shown in<figref idref="f0002">figure 6</figref>, the control means 52 comprise detection means 58 which make it possible to detect when the free end 40 of the treatment rod 38 is at the determined distance "D" from the bottom 15 of the preform 12. These detection means 58 are embarked on the stem 38 of treatment.

0105The detection means 58 are capable of communicating to the electronic control unit 44 a signal warning that the free end 40 of the treatment rod 38 is at the determined distance "D" from the bottom 15 of the preform 12.

0106The detection means 58 are for example formed by a capacitive sensor adapted to the determined distance "D" to be measured. The sensor is then arranged on the treatment rod 38, close to its free end 40.

0107As a variant, the detection of the distance between the free end of the treatment rod and the bottom of the preform is formed by a sonar, or a radar, or any other device capable of measuring a distance without contact between the free end of the treatment rod and the bottom of the preform, and capable of being embarked on the treatment rod.

0108The method of implementing the processing device 30 according to the second embodiment of the invention is similar to that of the first embodiment of the invention. Only the differences will be described subsequently, the remainder of the process remaining identical.

0109This method does not include a prior measurement step.

0110On the other hand, each step "E1" of processing a preform 12 comprises an operation of detecting the bottom 15 of said preform 12 which is carried out during the sliding of the treatment rod 38 by the means 58 of detection.

0111Thus, depending on the measurement taken, the control unit 44 stops the treatment rod 38 at the determined distance "D" from the bottom 15 of said preform 12 by interrupting the operation of the electric actuator 42.

0112The processing device 30 produced according to any one of the embodiments of the invention thus makes it possible to adapt the sliding stroke of the processing rod 38 individually for each preform 12. This in particular makes it possible to process more efficiently and more quickly the preforms 12 while avoiding damage to the preforms 12 and/or the treatment rods 38.

0113The method implementing the treatment device 30 advantageously makes it possible to adapt the sliding stroke of the treatment rod 38 to each hot preform 12, taking into account the random shrinkage caused by the heating of the preforms 12.

0114The processing device described above is also likely to be arranged upstream of the heating station. The treatment device is thus capable of adapting the sliding stroke of each treatment rod in the event of a dimensional anomaly in a batch of preforms. This makes it possible to avoid damaging the treatment rod by contact with the bottom of the preform which is shorter than the others.