Preform gripping device in a heat conditioning unit

Abstract

Title: Preform gripping device in a thermal conditioning unit. Gripping device (26) for a neck (10) of a preform (4) in a thermal conditioning unit (16) comprising: - a shaft (54) defining an axis B of rotation of the preform; - a head (50) mounted coaxially to the axis B, at a distal end of the shaft (50) and comprising contact means (56) for gripping the neck (10) of the preform 4; - a substantially tubular radiator (52) through which said shaft (54) extends, which is fixed to the distal end of said shaft (54) and / or the head (50); characterized in that it comprises a skirt (60) said to be protective extending coaxially to the axis B of the mandrel and extending from the distal end of the radiator (52) to cover said contact means (56). Figure for the summary: Figure 7

Description

Title of the invention: Preform gripping device in a thermal conditioning unit. Technical field

[0001] The present invention relates to a device for the transport and gripping of a tubular preform with rotation of the preform around its main axis, more particularly in a thermal conditioning unit.

[0002] The invention relates to the field of manufacturing hollow bodies from thermoplastic material, manufacturing for which a preform is first produced by injection molding. The preform is then formed into a container in a container manufacturing plant. State of the art

[0003] The prior art of container manufacturing installations is known, which includes a thermal conditioning unit also called a furnace where the preform is thermally conditioned and a blow molding unit to obtain the final container where the preform is formed by a blow molding operation or by stretch blow molding operations.

[0004] The preform generally has a tubular cylindrical body which is closed at one of its axial ends and which is extended at its other end by a neck, also tubular.

[0005] The neck extends axially from a main annular collar which is arranged at the junction of the neck and the body of the preform, to an annular lip also called the drinking lip, which delimits an axial opening of the neck.

[0006] The neck generally has its final shape, while the body of the preform undergoes plastic deformation to form the final container during the blow molding operation. To perform this blow molding operation, the body of the preform must be heated to a temperature above the glass transition temperature of the material. This is achieved by thermally conditioning the preform by circulating it inside a furnace, using a conveyor system that follows a heating path. The furnace includes heating elements, such as infrared lamps or laser diodes, in front of which the preforms move via the conveyor system.

[0007] During its movement in the oven, the preform is advantageously driven in rotation around its main axis in order to homogenize the heating.

[0008] The preforms are generally held on the transport device by gripping means.

[0009] The preform is transferred, or loaded, at the furnace inlet by means of transferring the preform from a preform feeding device to the transport device.

[0010] The operation of grasping a preform by the gripping devices is called "clothing".

[0011] Similarly, at the exit of the oven, the operation of unloading the heated preform from the gripping devices is called "undressing".

[0012] Traditionally, gripping devices grasp the preforms by the inner face of the neck using gripping means. The gripping means then moves vertically downward along the principal axis of the preform relative to the transfer means in order to allow the insertion of the gripping means into the neck. For this purpose, the transport devices move above the transfer means.

[0013] Conversely, the gripping device detaches from the preforms by means of the support of an ejection face of the ejector on the rim of the preform and the raising of the gripping means along the main axis of the preform relative to the transfer means in order to allow the separation of the gripping means from the neck.

[0014] The trajectory of a preform carried by the transfer means is generally tangent to the trajectory of the transport devices at a point or, at best, the two trajectories are superimposed over a short distance. This area of ​​superposition at a point or over a short distance is hereafter referred to as the "clothing zone".

[0015] In order for the dressing operation to take place, the gripping means must be synchronized with the transfer means so that the gripping means are actuated exactly at the dressing area.

[0016] Similarly, in order for the undressing operation to take place, the gripping means must be synchronized with the transfer means so that the gripping means are actuated exactly at the undressing area.

[0017] Such gripping means are well known. This is the case, in particular, of European patent EP0935572 which describes a device for the transport and gripping of preforms.

[0018] When heating a preform, however, care should be taken to avoid heating its neck, as the neck already has its final shape, i.e., the shape it has in the finished container. Therefore, the neck should not be made malleable by heating it along with the body of the preform, which will be deformed later during a blow molding operation.

[0019] However, when the preforms circulate in the heat conditioning unit, the neck may be irradiated by radiation emitted from radiation sources. Radiation sources include infrared lamps or laser diodes.

[0020] In the case of infrared lamps, the emitted radiation propagates in all directions. Therefore, it has become apparent that some of the radiation emitted by the infrared lamps can reach the neck after penetrating inside the preform.

[0021] In the case of laser diodes, the preforms can circulate on two rows, the dispersion of the radiation emitted by the laser diodes means that part of the emitted radiation is applied to the necks of the preforms in the most distant row and therefore causes heating of the necks.

[0022] To limit this unwanted heating, the neck of the preforms moving through the chamber can be ventilated to cool it. However, such ventilation does not allow for sufficiently targeted cooling of the neck of the preforms, and the part of the body extending immediately below the neck is also likely to be cooled, even though this is precisely a critical area that undergoes significant deformation during the blow molding of the containers and therefore requires specific heating. Disclosure of the invention

[0023] One of the aims of the invention is to overcome this drawback by proposing a gripping device that effectively protects the neck of the preform.

[0024] To this end, and in accordance with the invention, a device for gripping a neck of a preform in a thermal conditioning unit is proposed, comprising: - a shaft defining an axis B of rotation of the preform; - a head mounted coaxially to axis B, at a distal end of the shaft and comprising contact means intended to grasp the neck of the preform; - a substantially tubular radiator through which extends said shaft which is secured to the distal end of said shaft and / or the head; characterized in that it comprises a so-called protective skirt extending coaxially to the axis B of the chuck and extending from the distal end of the radiator to cover said contact means.

[0025] According to another aspect of the invention, the protective skirt and the radiator are one piece, said skirt protruding at the distal end of the radiator.

[0026] According to another aspect of the invention, the protective skirt is attached to the distal end of the radiator by protruding from the latter.

[0027] According to another aspect of the invention, the protective skirt is attached to the distal end of the shaft so that it protrudes from the radiator.

[0028] According to another aspect of the invention, the protective skirt has a tubular shape with a circular straight section surrounding the head.

[0029] According to another aspect of the invention, the protective skirt is fixed relative to the nose of the swivel.

[0030] According to another aspect of the invention, the length of the protective skirt along axis B is such that, when a preform is put on the head, said protective skirt is not in contact with any element of said preform.

[0031] According to another aspect of the invention, the protective skirt comprises an outer surface made of a reflective material.

[0032] According to another aspect of the invention, the contact means comprise a plurality of rings which are regularly distributed around the axis B of the head and which are mounted radially movable in the nose of the turntable between a retracted position allowing free axial sliding of the nose of the turntable in the neck of a preform and an expanded position allowing the neck gripping of a preform.

[0033] According to another aspect of the invention, the contact means comprise elastic return means for the jaws to their expanded position.

[0034] According to another aspect of the invention, an ejection means comprising at least one part called an "ejection finger" extending parallel to the axis B and on the periphery of the nose of the turntable, which is mounted to slide axially relative to the head between an upper transport position in which one end of the ejection finger does not exert any pressure on the preform and a lower ejection position in which the end of the finger exerts a pressure on the neck of the preform to eject it.

[0035] According to another aspect of the invention, the ejection finger includes at its distal end a ring intended to come into contact with a drinking hole of the neck of the preform.

[0036] Another object of the invention relates to a preform thermal conditioning unit characterized in that it comprises at least one gripping device according to the invention. Brief description of the drawings

[0037] Other advantages and features will become clearer from the following description of several embodiments, given by way of non-limiting examples, of the gripping clamp according to the invention, based on the following drawings:

[0038] [Fig-1] is a schematic general view of a production installation of containers seen from above, in which the preforms circulate in a row;

[0039] [Fig.2] is a schematic top view of part of a heating section of a heat treatment unit, in which the preforms circulate on two rows;

[0040] [Fig.3] is a detail view of the medallion in [Fig.1] representing a preform;

[0041] [Fig.4] is an overview of a chain link of a toumette according to art anterior, that is to say without the protection of the neck;

[0042] [Fig.5] is a view of the toumette and the nose of the toumette according to the invention;

[0043] [Fig.6] and [Fig.7] are partial vertical cross-sectional views of the nose of the toumette 46 in a resting position according to the invention;

[0044] [Fig.8] and [Fig.9] are the different positions of the ejector; Method of embodying the invention

[0045] In the following description, elements having an identical structure or analogous functions will be designated by the same reference.

[0046] The longitudinal, vertical and transverse orientations will be adopted without limitation with reference to the trihedron (L, V, T) represented in the figures.

[0047] By convention, the longitudinal and transverse directions are fixed in relation to the molding devices so that the open or closed position occupied has no effect on said orientations.

[0048] The terms "front" and "rear" will also be used, without limitation, with reference to the longitudinal orientation, as well as "upper" and "lower" with reference to the vertical orientation, and finally "left" or "right" and "inside" or "outside" with reference to the transverse orientation.

[0049] Figure [1] schematically represents a series production installation 1 of containers 2 made of thermoplastic material from preforms 4.

[0050] In the following description, the preforms 4 and the containers 2 move within the production installation along a circulation path from upstream to downstream. The preforms 4 are moved along a heating path by conveying means which will be detailed later.

[0051] In [Fig.1], the preforms move in a line, i.e. one behind the other in the thermal conditioning unit.

[0052] Without limitation, the containers 2 are herein bottles. The thermoplastic material is, for example, herein formed by polyethylene terephthalate, hereinafter referred to by its acronym "PET".

[0053] Figure 3 shows an example of such a preform 4. The preform 4 has a principal axis "X" shown vertically in the figure. It has a cylindrical body 6 with tubular walls, closed at one of its axial ends by a bottom 8, and open at its other end by a neck 10, also tubular. The neck 10 is delimited downwards by a collar 12 and upwards by an upper end edge called the drinking rim 14.

[0054] The neck 10 generally presents its final shape while the body 6 of the preform 4 is intended to undergo a relatively large deformation to form the final container 2 during a forming step.

[0055] The neck 10 has a thread to allow the container to be subsequently closed by a screw cap; it is also generally provided with an annular groove 13 which is axially delimited by the collar 12 and a ridge (not shown). This groove 13 is intended to subsequently receive a tamper-evident ring attached in a separable manner to the cap in order to guarantee the integrity of the container (bottles, flasks, etc.) to the consumer upon purchase.

[0056] As shown in [Fig.1], the container manufacturing installation includes at least one heat conditioning unit 16, and one forming unit 18.

[0057] The heat conditioning unit 16, also called an oven, heats a series of preforms 4 to a reference temperature. The reference temperature is chosen so that the body 6 of each preform 4 exiting the heat conditioning unit 16 is in a malleable state, allowing the heated preform body 6 to be deformed to form the container 2 in the forming unit 18. The reference temperature is between the glass transition temperature and the crystallization temperature of the plastic material of the preform 4. In the case of PET, the reference temperature is, for example, close to 110°C. The value of the reference temperature may vary depending on the product with which the container 2 will be filled or the container filling technique. Thus, the reference temperature is different for hot filling or for a carbonated product, for example.

[0058] According to the embodiment shown in [Fig.1], the heat conditioning unit 16 is a scroll oven, in which the preforms 4 are transported to be exposed to a plurality of heating radiation sources 22.

[0059] For this purpose, the thermal conditioning unit 16 includes a means of conveying the preforms 4 through the thermal conditioning unit 16 along a heating path extending between an inlet E and an outlet S of the thermal conditioning unit 16.

[0060] As shown in Figures 1, 2 and 4, the conveying means 24 comprises a succession of gripping devices 26, each capable of supporting a preform 4, mounted on a chain, moving along the heating path in the thermal conditioning unit 16.

[0061] In another embodiment not shown, the conveying means 24 comprises, for example, a series of gripping devices, each capable of supporting a preform, mounted on a linear motor-type shuttle circulating on a closed magnetic loop. The movement of each of these shuttles is controlled independently of each other by a control unit (not shown in the figures).

[0062] Figure 4 illustrates the gripping device 26, which is well known to those skilled in the art. Each gripping device 26 is, for example, suitable for receiving a preform 4 by fitting the neck 10 onto a swivel 27. Each swivel 27 is, for example, rotatable relative to the chain around an axis A of rotation coinciding with the principal axis X of a preform 4 when the latter is supported by the swivel 27.

[0063] As illustrated in [Fig.1], the thermal conditioning unit 16 also includes a heating cavity which comprises two side walls facing each other and at least one of these walls being the one which supports several radiation sources 22, arranged one above the other and one next to the other facing the preforms.

[0064] In other words, the heat conditioning unit 16 comprises a plurality of radiation sources 22 distributed along the heating path and at a height substantially corresponding to the height of the preforms, such that the entire height of the body 6 of each preform is exposed to the radiation sources 22 along the preform's path within the heat conditioning unit 16. By rotating the preforms around their main axis A, the rollers 27 allow the entire body 6 of the preforms to be uniformly exposed to the radiation sources 22. In this particular embodiment, the radiation sources 22 are distributed on only one side of this path, and a reflective wall 23 is arranged on the other side of the heating path to reflect the radiation back towards the preforms.

[0065] In another embodiment not shown, the radiation sources 22 can be distributed on either side of the heating path without going out of the scope of the invention.

[0066] It should also be noted that the radiation sources 22 are arranged, where appropriate, so as not to expose the neck 10 to the heat emitted by the radiation sources 22. Indeed, as previously stated, only the body 6 of the preform is formed to produce the container 2. Therefore, the neck 10 must not be deformed during forming and must not be heated. To prevent heating of the neck 10, the heat conditioning unit 16 may include a ventilation device positioned at the necks to remove the heat that could be absorbed by the necks.

[0067] Each radiation source 22 is formed by an incandescent lamp emitting infrared radiation.

[0068] In another embodiment, each radiation source 22 is a laser diode emitting infrared radiation.

[0069] In other words, each radiation source 22 emits a laser (for example laser diodes) emitting in the infrared and arranged by juxtaposition and / or superposition to form one or more matrices.

[0070] In another embodiment, each radiation source 22 is a microwave generator.

[0071] Alternatively, the thermal conditioning unit 16 illustrated in [Fig.2] comprises a transport section 25, in which the preforms 4 are moved one after the other in a single row along a longitudinal direction T, and a heating section 29, in which the preforms 4 are moved in two parallel rows RI, R2 extending along the longitudinal direction T.

[0072] Each gripping device 26 moves along a loop between the transport section 25 and the heating section 29; that is, the gripping devices 26 release the preforms they were transporting at the exit point S and return to the entry point E to pick up new preforms to be heated. This variant is described in European patent EP

[0073] Then, once the preform 4 has been heat-conditioned in the heat conditioning unit 16, it is transferred to the forming unit 18 to be formed there.

[0074] As illustrated in [Fig. 1], the unit for forming containers 2 from preforms 4 consists of a forming wheel 28 rotating a plurality of forming stations from an inlet to an outlet, at which a succession of containers 4 are formed from the preforms 4. The axis of rotation of the forming wheel 28 is, for example, substantially parallel to the main axis X of the preforms 4 when they are transported by the forming wheel 28.

[0075] Each blowing station includes a mold 30 forming a molding cavity having the shape of the container 2 to be formed and arranged to receive a preform 4 so that the body 6 of the preform extends into the molding cavity.

[0076] As shown in [Fig.4], the gripping device 26 includes a support 32 also called a link, which although shown individually in this figure, is in fact integrated into a chain which includes a multitude of such links.

[0077] In this embodiment, the link, preferably metallic (e.g. steel), comprises two superimposed arms 34, 36, which protrude laterally from a core 38. The arms 34, 36 are pierced with coaxial holes 40 which together define a main axis.

[0078] The gripping device 26 also includes: - a mandrel 42 with axis A of revolution is mounted in the holes 40 of the link via a sliding pivot joint relative to the link. Thus, the main axis of the holes 40 and the axis of revolution of the mandrel 42 are coaxial; - a pinion 44 is rotationally fixed to one of the free ends of the chuck 42. The pinion 44 is advantageously formed on a spool-shaped end 35, which is press-fitted onto the chuck 42; - the toumette 27 includes at least: - a 46 toumette nose which is fixed to the other end of the mandrel. This assembly is designed to be removable. The toumette nose is intended to receive the neck 10 of the preform 4; - an ejector 48 is secured to the support 32 by fastening means. This ejector 48 has a substantially cylindrical shape and includes at one of its ends at least one surface 62 called the preform ejection surface;

[0079] The chuck and the nose 46 of the toumette extend coaxially to the ejector 48 in such a way that the free end of the nose 46 of the toumette protrudes from the ejector 48.

[0080] According to an alternative embodiment, not shown in the figures, the support 32 can be a linear motor also comprising at least one hole and in which the chuck, the sprocket, the pinion are mounted by sliding pivot, without going out of the scope of the invention.

[0081] Well known to the man skilled in the art, [Fig.4] illustrates the nose 46 of toumette.

[0082] The toumette 27 is a mobile assembly intended to ensure the gripping of a preform 4 by its neck 10, and mounted on the link with two degrees of freedom a translation along the main axis A and a rotation around the main axis A.

[0083] As illustrated in [Fig.5], the nose 46 of the toumette includes a radially expanding head 50 which is press-fitted into the neck 10 of the preform 4, a radiator 52, and a shaft 54.

[0084] The cylindrical head 50 with vertical axis "B" whose outer diameter is slightly smaller than the inner diameter of the neck 10 so that there remains a radial sliding clearance between the head 50 and the neck 10 when the head 50 is fitted into the neck 10.

[0085] The head 50 comprises contact means 56 in the form of ring sectors. Each contact means 56 is received sliding radially in a radial housing of the head 50 between:

[0086] - a gripping position in which the contact means 56 are retracted towards the "B" axis of the head allowing a radial force to be exerted against the wall of the neck of the gripped preform;

[0087] - a resting position in which they are likely to accommodate a new preform to be transported through the thermal conditioning unit.

[0088] In this embodiment illustrated in this figure, the contact means 56 are elastically constrained towards the rest position, i.e. towards their expanded position, by means of an elastic ring also called an elastic return means which is radially intercalated between the bottom of the housing made in the head and the ring sector.

[0089] The head 50 is delimited vertically downwards by a section of larger diameter delimiting an annular shoulder face which is turned upwards and which forms a positioning face against which the drinking 14 is received vertically when fitting the head 50 into the neck 10.

[0090] The radiator 52 is arranged under the head 50 and includes fins 58 which have an overall cylindrical shape, coaxial with the axis B of the head and whose diameter is equivalent to the diameter of the section with a larger diameter than the head.

[0091] The shaft 54 ​​is fixed at one of its ends to the radiator and head assembly, while the other end of the shaft 54 ​​is fixed to the chuck 42 in a detachable manner well known to those skilled in the art.

[0092] The head 50, the radiator 52, the shaft 54, the chuck 42 are coaxial.

[0093] Fig. 6 and Fig. 7 illustrate partial vertical cross-sectional views of the turntable nose 46 according to the invention in a rest position, i.e. in the position where the contact means 56 are extended radially and therefore capable of receiving a new preform to be transported through the thermal conditioning unit 16.

[0094] The preformed swivel nose 46 includes the shaft 54, the head (not shown in this figure), the radiator 52, a protective skirt 60 and the ejector 48.

[0095] The shaft 54 ​​defines an axis B of rotation of the preform on which the head 50 is mounted coaxially to the axis B at the so-called distal end of the shaft 54 ​​and opposite this end is free to be detachably attached to the chuck (not shown). For example, the means of attaching the shaft 54 ​​to the chuck 42 is a bayonet-type mounting.

[0096] The tubular-shaped radiator 52 is traversed by the shaft 54, which is fixed at its distal end to the head (not shown). The radiator 52 is arranged under the head 50 and includes the fins 58, which are positioned radially with respect to the axis B of the shaft 54.

[0097] The head 50 comprises the contact means 56, which are in the form of ring sectors. Each contact means 56 is received by sliding radially in a radial housing of the head 50 between:

[0098] - a gripping position, not shown in this figure, in which the contact means 56 are retracted towards the axis "B" of the head 50 allowing a radial force to be exerted against the wall of the neck of the gripped preform;

[0099] - a resting position in which they are likely to accommodate a new preform to be transported through the thermal conditioning unit 16.

[0100] Alternatively, the head 50 for grasping the preforms can take other forms and structures known to those skilled in the art. The contact means 56 can take the form of balls as described in European patent EPI880825.

[0101] The protective skirt 60 extending coaxially to the axis B of the shaft 54 ​​and the chuck 42 and extending from the distal end of the radiator and covers the contact means 56.

[0102] The tubular protective skirt 60 is positioned opposite the head 50, thus protecting the neck 10 of the preform 4 when it is fitted onto the head 50. When the preform is not fitted onto the head, then the contact means 56 and the elastic ring(s), not shown, which are radially interposed between the bottom of the housing made in the head 50 and the contact means 56 are not protected, even though they also do not support the radiation emitted by the radiation sources.

[0103] In other words, the protective skirt 60 protects both the neck of the preform when it is present and the head when there is no preform fitted onto the head, for example during the heating phases of the conditioning unit.

[0104] As shown in [Fig. 7], the protective skirt 60 and the radiator 52 form a single piece. In other words, the protective skirt 60 and the radiator 52 form a single unit.

[0105] As shown in [Fig.6], it is understood that the protective skirt 60 and the radiator 52 can be two separate parts.

[0106] It is also understood that the protective skirt 60 can be in two pieces which can slide relative to each other.

[0107] In this embodiment in figures 6 and 7, the protective skirt 60 is immobile relative to the head 50 and the contact means 56. In this case, it is the assembly, head 50 and skirt 60, that descend to grasp the preform.

[0108] Alternatively, the head 50 is movable in translation along the vertical axis B relative to the protective skirt 60, which remains stationary. In this case, the head 50 descends to grasp the preform, then it rises again so that the neck is protected from radiation by the protective skirt 60 during the heating of the preform body.

[0109] In another embodiment, the protective skirt 60 is movable in translation along the vertical axis of the head 50, which remains stationary. In this case, the preform is moved to be grasped by the head 50. This type of covering is described in European patent EP1922273B1 of the applicant.

[0110] The ejector 48 includes a cylindrical base 61 with axis B, which includes a central hole through which the shaft 54 ​​passes and which is positioned above the radiator 52.

[0111] The base 61 has on its periphery ejection fingers 63 parallel to the axis B.

[0112] One end of each of these ejection fingers 63, called proximal, is fixed to the base 61 while the opposite end, called distal, is free and intended to come to rest against a part of the rim of the preform to effect the ejection of the latter.

[0113] The ejection fingers 63 pass through the fins 58 of the radiator 52, at their peripheries.

[0114] At the level of the protective skirt 60, the ejection fingers 63 are interposed radially between the protective skirt 60 and the head 50.

[0115] In other words, the ejector includes at least one ejection finger 63 which extends parallel to the axis B and over the head 50. The ejection fingers 63 are mounted to slide axially relative to the head 50 between an upper transport position in which the end of the ejection finger 63 does not exert any pressure on the preform and a lower ejection position in which the end of the ejection finger 63 exerts a pressure on the neck of the preform to eject it.

[0116] Fig. 8 and Fig. 9 represent the different positions of the ejector 48, either the lower position or the low position, called the ejection position, or the upper position or the high position, called the transport position.

[0117] Fig. 8 illustrates the ejector in the ejection position.

[0118] In this position, the ejection fingers 63 are aligned with the contact means 56 and have released them from the preform during the downward movement. In other words, during the descent of the ejector, the ejection fingers 63, pressing on the contact 13 of the preform, pull the preform 4 down with them, thus separating the neck 10 of the preform 4 from the contact means 56 of the head 50.

[0119] Fig. 9 illustrates the ejector in a transport position.

[0120] In this position, the contact means 56 are engaged with the neck 10 of the preform to hold it during the transfer of the latter into the thermal conditioning unit 16 and the ejection fingers 63 may be in contact with a part of the rim, but without exerting any force on the latter or may not be in contact with the rim 13 of the preform.

[0121] The transition from a rest position to a transport position and vice versa is achieved by a mechanism for moving the ejector which is not shown but is well known to those skilled in the art.

Claims

Demands

1. 1. A gripping device (26) for a neck (10) of a preform (4) in a thermal conditioning unit (16) comprising: - a shaft (54) defining an axis B of rotation of the preform; - a head (50) mounted coaxially to the axis B, at a distal end of the shaft (50) and comprising contact means (56) for gripping the neck (10) of the preform 4; - a substantially tubular radiator (52) through which said shaft (54) extends, which is fixed to the distal end of said shaft (54) and / or of the head (50); characterized in that it comprises a skirt (60) said to be protective extending coaxially to the axis B of the mandrel and extending from the distal end of the radiator (52) to cover said contact means (56).

2. 2. Gripping device according to claim 1 characterized in that the protective skirt 60 and the radiator (52) are one piece, said skirt (60) protruding at the distal end of the radiator (52).

3. 3. Gripping device according to claim 1 characterized in that the protective skirt (60) is attached to the distal end of the radiator (52) by protruding from the latter.

4. 4. Gripping device according to any one of claims 1 to 3 characterized in that the protective skirt (60) is attached to the distal end of the shaft (54) so ​​that it protrudes from the radiator (52).

5. 5. Gripping device according to any one of claims 1 to 4 characterized in that the protective skirt (60) has a tubular shape of circular straight section surrounding the head (50).

6. 6. Gripping device according to any one of claims 1 to 5 characterized in that the protective skirt (60) is fixed relative to the nose (46) of the swivel.

7. 7. Gripping device according to any one of claims 1 to 6 characterized in that the length of the protective skirt (60) along the axis B is such that, when a preform (4) is fitted over the head (50), said protective skirt (60) is not in contact with any element of said preform (4).

8. 8. Gripping device according to any one of claims 1 to 7 characterized in that the protective skirt (60) comprises an outer surface made of a reflective material.

9. 9. Gripping device according to any one of claims 1 to 8 characterized in that the contact means (56) comprise a plurality of rings which are regularly distributed around the axis B of the head (50) and which are mounted movably radially in the nose (46) of the turntable between a retracted position allowing free axial sliding of the turntable nose in the neck (10) of a preform (4) and an expanded position allowing gripping of the neck (10) of a preform (4).

10. 10. Gripping device according to claim 9 characterized in that the contact means comprise elastic return means for the jaws to their expanded position.

11. 11. Gripping device according to any one of claims 1 to 10 characterized in that it comprises an ejector (48) having at least one part called "ejection finger (63)" extending parallel to the axis B and on the periphery of the nose (46) of the turntable, which is mounted to slide axially relative to the head (50) between an upper transport position in which one end of the ejection finger (63) does not exert a thrust on the preform (4) and a lower ejection position in which the end of the finger exerts a thrust on the neck (10) of the preform (4) to eject it.

12. 12. Gripping device according to claim 11 characterized in that the ejection finger (63) comprises at its distal end a ring intended to come into contact with a rim (14) of the neck (10) of the preform (4).

13. 13. Heat conditioning unit (16) for preforms (4) characterized in that it comprises at least one gripping device (26) according to any one of claims 1 to 12.

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