Method for transferring preforms to a conveyor

Abstract

The invention relates to a method for transferring containers, in particular preforms (12) made of thermoplastic material, comprising a neck (16) having a main axis (A), passing out through an opening (24) delimited by a free edge of the neck referred to as the "rim (26)", the container being transferred to a conveyor (36) in which the container is held by a gripping member (38) nested axially with the neck (16) during a fitting operation, characterised in that, during the fitting operation, the neck (16) is clamped axially between a reaction face (68) facing the rim (26) and a holding face (70) axially opposite the reaction face (68), the holding face (70) bearing against the rim (26).

Description

Description Title of the invention: METHOD FOR TRANSFERRING PREFORMS ON A CONVEYOR Technical field of the invention

[0001] The invention relates to a method for transferring containers, and in particular preforms made of thermoplastic material, comprising a neck having a main axis, opening through an opening delimited by a free edge of the neck called a "mouth", the container being transferred to a conveyor in which the container is held by a gripping member axially fitted with the neck during a dressing operation. Technical background

[0002] The present invention relates to improvements made to a method for transferring containers or preforms having a neck, in particular bottles, onto a conveyor in which each container is held by an individual gripping member fitted with its neck. The gripping members travel along a closed loop path to transport the containers from a loading point to an unloading point. The gripping members are generally made in the form of mandrels axially forced into the neck of the container, during an operation called a lining operation.

[0003] These gripping members are spaced apart by a predetermined pitch over a section of their path passing through the loading point and the unloading point of the preforms. The containers are brought to the loading point one after the other, spaced apart by the predetermined pitch.

[0004] Such a transfer method is particularly suitable for container manufacturing and / or filling plants. Thus, in container manufacturing plants, preforms are transported by such a conveyor through a heating station before the heated preforms are transformed into final containers by a forming operation, in particular by biaxial stretching.

[0005] In this type of installation, the transport of preforms to the loading point is commonly ensured by transfer wheels, of which many designs are known.

[0006] Each preform is loaded onto an associated gripping member during the dressing operation, during which the gripping member is forced into the neck of the preform, the preform being supported by the transfer wheels.

[0007] Furthermore, in the stations for heating the thermoplastic material constituting the preforms, which are used in the container manufacturing installations, the transfer of the preforms can be ensured by notched or clamping plates which grip the preforms and bring them under the moving mandrels.

[0008] In these known installations, the path of the gripping members in plane projection is tangent at a single point of tangency with the trajectory of the preforms carried by the transfer wheel.

[0009] The rotational drive of the transfer wheel and the vertical translational drive of the gripping members are synchronized so that a gripping member and a preform carried by the transfer wheel are presented in synchronism at the point of tangency, directly above each other. At this single point of tangency, the dressing operation is carried out. The descent of the gripping member previously raised to the retracted position and its fitting into the neck of the underlying preform are controlled for example by a cam system.

[0010] However, the dressing operation must be carried out very quickly because the preforms only cross the path of the gripping members at a single point. Such a dressing operation is not suitable for a high operating rate of the loading device. Indeed, the higher the running speed of the gripping members, the faster the dressing operation must be carried out. However, at a high rate, the gripping member is likely to be insufficiently fitted into the neck of the preform. The preform then risks falling from the gripping member.

[0011] To solve this problem, it has already been proposed to equip the conveyor with double grippers which move together with an associated gripping member over a portion of the path comprising the loading point and the unloading point. Thus, instead of carrying out the dressing operation only at the point of tangency, each double gripper grips a preform at the point of tangency. The double gripper grips the neck of the preform on either side of the flange so as to block the neck vertically in both directions by direct contact with the flange in order to ensure that the preform is properly held, even when the latter is not perfectly centered relative to the gripping member. The dressing operation of the gripping member is then carried out along a portion of the path shared by the double gripper and the associated mandrel. Thus, the dressing operation is spread over the entire portion of the path instead of being carried out at a single point.This dressing operation can therefore be carried out over a sufficiently long period to guarantee reliable nesting of the preforms, even if the production rate increases.

[0012] When the preforms leave the heating station, the neck of the preform is again gripped by the double gripper to be able to uncouple the mandrel, during an operation called stripping, and transfer the preform to an output conveyor.

[0013] However, the double gripper occupies the only two spaces that allow a preform to be correctly gripped by its neck using grippers, namely the area located di- directly under the collar, and a groove located directly above the collar, this groove being generally intended to subsequently receive a tamper-evident ring from a container cap. For this reason, this groove will subsequently be called the "tamper-evident groove".

[0014] However, in some installations it is proposed to grip the preforms leaving the heating station by means of articulated arms equipped with grippers to transfer the preforms in a single step from the unloading point of the heating station to the next station, for example the biaxial stretch forming station. However, with the double gripper device, it is not possible to grip the neck either below the collar or by the tamper-evident groove.

[0015] To overcome this problem, it is necessary to provide a notched output wheel that is suitable for unclipping the preforms from the double gripper, then a second wheel rotating in the correct direction before the preforms are gripped by the mobile arms equipped with grippers. Such a solution is expensive, bulky and lengthens the travel time of the preforms in the installation.

[0016] There is therefore a need to find a method allowing both reliable nesting of the preforms on the conveyor of the heating station and offering the possibility of quickly transferring the preforms to the station following the heating station. Summary of the invention

[0017] The invention proposes a method for transferring containers, and in particular preforms made of thermoplastic material, comprising a neck having a main axis, opening through an opening delimited by a free edge of the neck called the "mouth", the container being transferred to a conveyor in which the container is held by a gripping member axially fitted with the neck during a dressing operation.

[0018] The method carried out according to the teachings of the invention is characterized in that, during the dressing operation, the neck is clamped axially between a reaction face facing the rim and a holding face axially opposite the reaction face, the holding face bearing against the rim.

[0019] According to another aspect of the method carried out according to the teachings of the invention, the reaction face is in contact with a collar of the neck.

[0020] According to another aspect of the method carried out according to the teachings of the invention, each gripping member of the conveyor comprises an ejection member mounted to slide axially on the gripping member between an extreme fitting position allowing the axial fitting of the gripping member with the neck and an extreme unfitting position towards which the ejection member is slid so that a contact face of the ejection member presses on the rim of the neck to completely disengage it from the gripping member, the holding face being formed by the contact face of the ejection member.

[0021] The invention also proposes a device for implementing the method according to the teachings of the invention, the device comprising:

[0022] - at least one container transport fork which moves in coincidence with an associated gripping member of the conveyor, an upper face of the transport fork forming the reaction face;

[0023] - means for distributing the preforms which comprise means for individually receiving each container so as to successively lead each container to a point of tangency with the trajectory of the transport fork at which the container is transferred to the transport fork;

[0024] - the transport fork being mounted to slide axially between a transfer position in which the transport fork is positioned at the same level as the individual receiving means for gripping the neck when the container is carried by the dispensing means and a nesting position in which the neck of a container carried by the transport fork is intended to be nested with the gripping member.

[0025] The device produced according to the teachings of the invention is characterized in that it comprises a sliding control mechanism for the holding face which is slidably mounted on a carriage on which the associated transport fork is fixed so that, when the control mechanism is immobilized relative to the carriage, the sliding of the transport fork jointly causes the sliding of the holding face.

[0026] According to another aspect of the device produced according to the teachings of the invention, the sliding travel of the control mechanism relative to the carriage is less than the sliding travel of the ejection member between its two extreme positions, the mechanism being controlled between a neck clamping position in which it is brought closer to the transport fork to urge the holding face towards the reaction face and a neck release position in which it is moved away from the transport fork to no longer urge the holding face to clamp against the rim.

[0027] According to another aspect of the device produced according to the teachings of the invention, the transport fork is controlled in sliding by a cam path fixed relative to the ground which cooperates with a cam follower which is carried by the carriage.

[0028] According to another aspect of the device produced according to the teachings of the invention, the transport fork is elastically returned to its upper nesting position.

[0029] According to another aspect of the device produced according to the teachings of the invention, the sliding control mechanism of the holding face comprises a follower cam which is mounted to slide axially in the carriage, and which cooperates with a cam path fixed relative to the ground.

[0030] According to another aspect of the device produced according to the teachings of the invention, the sliding control mechanism of the holding face is elastically returned to its clamping position.

[0031] According to another aspect of the device produced according to the teachings of the invention, the control mechanism comprises a control fork slidably mounted in the carriage and which cooperates with a face of the ejection member to urge the ejection member downwards.

[0032] According to another aspect of the device produced according to the teachings of the invention, the device comprises a plurality of transport forks mounted integral in rotation with a drive wheel around which the gripping members are indexed during their movement, each carriage being mounted to slide axially on the drive wheel. Brief description of the figures

[0033] 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 briefly described below.

[0034] [Fig. 1] is a top view which schematically represents a container manufacturing installation produced according to the teachings of the invention.

[0035] [Fig.2] is a perspective view showing a preform intended to feed the installation of [Fig.1].

[0036] [Fig. 3] is an axial sectional view showing a gripping member of the conveyor of a heating station of the installation of [Fig. 1], the gripping member being equipped with a preform ejection member in an extreme coating position.

[0037] [Fig. ] is a view similar to that of [Fig. 3], in which the preform ejection member occupies an extreme stripping position.

[0038] [Fig.5] is a perspective view showing a drive wheel of the heating station conveyor device of [Fig.l] and in which a preform is held by both a conveying fork and an associated conveying member.

[0039] [Fig.6] is a perspective view showing a device fitted to the drive wheel of [Fig.5] and which enables a preform dressing or stripping operation to be carried out relative to a transport member of the conveyor of the heating station, a carriage of the device being shown in transparency to enable the various components of said device to be clearly seen.

[0040] [Fig.7] is a detail view showing an upper end of the device of [Fig.6], said end comprising a transport fork and a control fork.

[0041] [Fig.8] is a developed side view of the travel of a device of [Fig.6] along part of a circular path guided by the drive wheel.

[0042] [Fig.9] is a perspective view showing an input wheel, a transfer wheel and a portion of the drive wheel of the installation of [Fig.1],

[0043] [Fig.10] is a larger scale detail view of [Fig.9] which shows a notch of the transfer wheel passing at a point P3 of the preform path as shown in [Fig.8], corresponding with a transport fork.

[0044] [Fig.11] is a perspective view showing a preform being supported by a transport fork at point P3 of its path as shown in [Fig.8].

[0045] [Fig.12] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.11].

[0046] [Fig.13] is a perspective view showing a preform being supported by a conveyor fork between points P3 and PI of its path as shown in [Fig.8],

[0047] [Fig.14] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.13].

[0048] [Fig.15] is a perspective view showing a preform being supported by a transport fork at point PI of its path as shown in [Fig.8].

[0049] [Fig.16] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.15].

[0050] [Fig.17] is a perspective view showing a preform being supported by a transport fork at point P5 of its path as shown in [Fig.8].

[0051] [Fig.18] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.17].

[0052] [Fig.19] is a perspective view showing a preform being picked up by a transport fork just before it arrives at point P6 of its path as shown in [Fig.8].

[0053] [Fig.20] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.19].

[0054] [Fig.21] is a perspective view showing a preform being supported by a transport fork at point P6 of its path as shown in [Fig.8].

[0055] [Fig.22] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.21].

[0056] [Fig.23] is a perspective view showing a preform being supported by a transport fork at point P2 of its path as shown in [Fig.8].

[0057] [Fig.24] is a detail view similar to [Fig.8] showing the preform and transport fork in the position shown in [Fig.22].

[0058] [Fig.25] is a top view of detail 25 of [Fig.9]. Detailed description of the invention

[0059] In the remainder of the description, a vertical orientation will be used, without limitation, which is indicated by the arrow “V” in the figures pointing from bottom to top. The vertical direction is used here as a geometric reference. It is directed parallel to the direction of nesting of the preforms 12 with gripping members 38. A plane extending orthogonally to the vertical direction “V” will be referred to as a “horizontal” plane.

[0060] Subsequently, elements having an identical structure or similar functions will be designated by the same reference.

[0061] [Fig.l] shows part of an installation 10 for manufacturing final containers, in particular bottles, by biaxial stretching of initial containers made of thermoplastic material.

[0062] The initial containers are here preforms 12 which are made of a thermoplastic material, such as polyethylene terephthalate (PET), and which are intended to be transformed into final containers, such as bottles, after a first heating operation to soften the thermoplastic constituting them, then a second blowing or stretch-blow molding operation, to conform the preform 12 into a final container.

[0063] [Fig.2] shows such a preform 12. The preform 12 has a main axis “A” which here extends in the vertical direction “V”.

[0064] The preform 12 comprises a body 14 which extends vertically along the axis “A”. The body 14 opens vertically upwards via a neck 16 and is closed at the opposite end by a bottom 18. The body 14 here has a generally cylindrical shape.

[0065] The neck 16 comprises a bearing surface 20 by means of which the preform 12 is capable of being supported. Advantageously, the neck 16 of the preform 12 comprises at least one collar 22 which extends in a horizontal plane relative to the axis “A”. The collar 22 is located in a junction zone of the neck 16 with the body 14. It extends radially projecting outwards, in particular relative to the body 14. The bearing surface 20 of the preform 12 is formed by a lower annular face of said collar 22. The collar 22 further has an upper annular face 23 opposite the bearing surface 20.

[0066] The neck 16 has an upper end edge which circumferentially delimits an opening 24 for access to the interior of the body 14 of the preform 12. This edge will be the sequel called “drinking 26”.

[0067] In the embodiment, the neck 16 has on its outer cylindrical surface a thread 28 intended to allow the container to be subsequently closed, for example by a screw cap. Alternatively, the thread can be replaced by elastic fitting means with a cap.

[0068] The neck 16 also includes an annular groove 30 which is arranged directly above the collar 22. In a non-limiting manner, this groove 30 is for example intended to receive a tamper-evident ring temporarily secured to a cap until the container is opened. This groove will hereinafter be called the “tamper-evident groove 30”.

[0069] The description of the neck 16 which has just been given also applies to a container obtained from such a preform 12. The neck 16 of the preform 12 already has its final shape. Indeed, it is recalled that since the neck 16 has its final shape, only the body 14 of the preform 12 is intended to undergo a forming operation to conform the preform 12 into a final container.

[0070] Referring again to [Fig.l], the manufacturing installation 10 here comprises a heating station 32 and a forming station 34, in particular by stretch-blow molding.

[0071] The heating station 32 is equipped with a conveyor 36 which makes it possible to transport the preforms 12 in a row along a transport path from a point “PI” for loading the preforms 12 to a point “P2” for unloading the preforms 12. The path of the preforms 12 passes through at least one heating zone (not shown) in which the body 14 of each preform 12 is heated to a temperature suitable for forming the preform 12 into a final container in the forming station 34.

[0072] For this purpose, the conveyor 36 comprises gripping members 38 which are intended to be fitted in the direction of the axis “A” into the neck 16 of a preform 12.

[0073] The gripping members 38 move along a closed loop 39 extending in a horizontal plane. A portion of the closed loop 39 forms the transport path of the preforms 12. For this purpose, each gripping member 38 is carried by a transport element (not shown).

[0074] Each conveying element is, for example, a link. All conveying elements are then hinged to each other to form a closed flexible element such as an endless conveyor chain extending in a horizontal plane.

[0075] In this case, the gripping members 38 are driven by at least one drive wheel around which the chain is engaged. Each gripping member 38 carried by the chain is spaced from the next gripping member 38 by a determined pitch “S”.

[0076] In a variant of the invention not shown, the transport chain makes it possible to compact the preforms by folding in an accordion fashion when it passes through a heating zone as described in detail in document EP-B 1-2,623,439.

[0077] In a variant of the invention not shown, instead of forming links of a chain, each transport element is formed by an independent shuttle. The conveying device then comprises at least one linear motor to control the movement of each shuttle independently of each other along the closed loop 39. Such a conveying device for a heating station is for example described in document FR-A1-3.035.651.

[0078] In the latter case, the linear motor comprises a stator comprising a series of windings which are distributed along the closed circuit. Each winding is individually controlled to locally induce a magnetic field independently of the other windings which acts on the shuttles to cause their movement. For this purpose, the shuttles carry a magnetic element capable of interacting with the magnetic field emitted by the stator windings. The windings are for example controlled by an electronic control unit (not shown) which is programmed appropriately.

[0079] The linear motor thus comprises a single stator, formed by the magnetic path, and several shuttles, forming "rotors", controlled independently along said stator.

[0080] Whatever the embodiment chosen for the transport elements, each gripping member 38 is here formed by a mandrel, as shown schematically in Figures 3 and 4. The gripping member 38 is capable of being fitted vertically into the neck 16 of the preform 12 by passing through its opening 24, during a dressing operation, with a tight fit to ensure the immobilization of the preform 12 by friction with an internal cylindrical wall 17 of the neck 16.

[0081] According to a non-limiting exemplary embodiment shown in Figures 3 and 4, the gripping member 38 here comprises at least three segments 40, two of which are visible in section in [Fig. 3], which are arranged around the axis "A". Each segment 40 is pushed radially outwards into an expanded position by a ring 42 made of an elastomeric material which is received in a central groove 44 of the gripping member 38. Thus, each segment 40 is capable of being pushed radially by the ring 42 against the internal cylindrical wall 17 of the neck 16 to grip the preform 12 by friction. In this respect, the portion of the gripping member 38 intended to be received clamped inside the neck 16 has, in the expanded state, an external diameter which is slightly greater than the internal diameter of the neck 16 of the preforms 12 intended to be taken over.

[0082] Thus, during an operation of dressing the preform 12 by the gripping member 38, the gripping member 38 is inserted vertically inside the neck 16 of the preform 12 by relative vertical sliding of the gripping member 38 relative to the preform 12, which causes a retraction of the segments 40 against the elastic return force exerted by the ring 42, as shown in [Fig. 3].

[0083] Each gripping member 38 is more particularly carried by a rod 46, also called a turntable, with a vertical axis which extends vertically downwards from the transport element. The rod 46 is coaxial with the axis “A” of the preform 12 carried by the gripping member 38.

[0084] The rod 46 is for example mounted to rotate around its axis relative to the transport element in order to be able to rotate the preform 12 on itself around its axis “A” during its transport by the conveyor 36.

[0085] Each gripping member 38 also comprises an ejection member 48 which comprises a lower contact face 50 which is intended to come into contact with the rim 26 of a preform 12 carried by the gripping member 38.

[0086] In the embodiment shown in the figures, the ejection member 48 is in the form of a sleeve delimited vertically downwards by the contact face 50 which has a continuous annular shape. The ejection member 48 is arranged around the rod 46.

[0087] Alternatively, the ejection member is formed of several fingers, for example three fingers, a lower end of which forms a portion of the contact face 50. The contact face 50 is then discontinuous.

[0088] The ejection member 48 is mounted to slide vertically on the gripping member 38 between:

[0089] - an extreme fitting position in which the gripping member 38 projects vertically downwards relative to the contact face 50 to allow the vertical fitting of the gripping member 38 with the neck 16, as illustrated in [Fig. 3]; and

[0090] - an extreme stripping position in which the contact face 50 is located below the gripping member 38 so that the contact face 50 of the ejection member 48 presses on the rim 26 of the neck 16 to completely disengage it from the gripping member 38, as illustrated in [Fig.4].

[0091] The ejection member 48 here comprises several guide columns 52, for example three columns 52, which extend vertically upwards. Each column 52 is fixed relative to the ejection member 48.

[0092] Each guide column 52 is received in a sliding manner vertically in an associated passage orifice 54 of a radial plate 56 which extends in a ra- of the rod 46 so that each column 52 projects vertically above an upper face of the plate 56. The plate 56 is integral with the rod 46, 11 is for example made in one piece with the rod 46.

[0093] An elastic return means 58, here a helical spring, is interposed between a shoulder 61 of the upper end of each column 52 and the upper face of the plate 56. The elastic return means 58 thus makes it possible to elastically return the ejection member 48 to its extreme dressing position.

[0094] [Fig. 1] shows a curved portion 39 A of the closed loop 39 along which the gripping members 38 move. This portion includes the loading point “PI” and the unloading point “P2”. Along this portion of the closed loop 39, the gripping members 38 are held at a pitch “S” from each other by a drive wheel 60.

[0095] When the transport elements form a chain, this drive wheel 60 can also have a function of guiding and / or driving the transport chain.

[0096] The drive wheel 60 is rotatably mounted about a central vertical axis "D" and is rotated in a counterclockwise direction with reference to [Fig.1].

[0097] The turning portion 39A of the closed loop 39 follows a peripheral rim portion of the drive wheel 60. The turning portion 39A here forms a semicircle.

[0098] The closed loop 39 also comprises a rectilinear downstream portion 39B which is arranged tangentially to the drive wheel 60 downstream of the turning portion 39A in the counterclockwise direction of rotation. The closed loop 39 also comprises a rectilinear upstream portion 39C which is arranged tangentially to the drive wheel 60 upstream of the turning portion 39A in the counterclockwise direction of rotation.

[0099] The conveyor 36 is capable of successively transporting each preform 12 carried by a gripping member 38 from the loading point “PI” at which the preform 12 is taken by the gripping member 38, to an unloading point “P2” at which the preform 12 is released from the gripping member 38. From the unloading point “P2” to the loading point “PI”, the gripping members 38 move empty.

[0100] The manufacturing facility 10 includes means for distributing the preforms 12 which are intended to convey the preforms 12 one after the other to the conveyor 36.

[0101] The distribution means here comprise a horizontal input transfer wheel 62 which is mounted to rotate around its central vertical axis "E".

[0102] The input transfer wheel 62 comprises at its periphery means for individually receiving each preform 12, formed here by notches 64 for receiving the necks 16 of the preforms 12. The notches 64 are mutually spaced circumferentially. entially of the pitch "S". These notches 64 are capable of receiving the necks 16 of the preforms 12 and of supporting the preforms 12 thanks to their projecting collar 22 which bears on the periphery of the notches 64 by their bearing surface 20.

[0103] The notches 64 of the input transfer wheel 62 are here arranged at a lower altitude than that of the gripping members 38 of the conveyor 36.

[0104] As shown in [Fig.l], in planar projection, the input transfer wheel 62 is here arranged tangent to the turning portion 39A of the loop 39 closed at a first point of tangency "P3". The first point "P3" of tangency is arranged upstream of the loading point "PI".

[0105] The input transfer wheel 62 is rotated about its axis "E" in a clockwise direction with reference to [Fig.l]. The rotation speed of the input transfer wheel 62 is synchronized with the rotation speed of the drive wheel 60 so that a gripping member 38 and a notch 64 of the input transfer wheel 62 are simultaneously presented at the first point of tangency "P3" directly above each other.

[0106] The drive wheel 60 also includes means intended to hold the preforms 12 during the coating operation by the gripping members 38.

[0107] For this purpose, the drive wheel 60 comprises receiving means, such as transport forks 66 as shown in FIGS. 5 to 7. Each transport fork 66 delimits a housing of a shape complementary to the shape of the neck 16 of each preform 12.

[0108] Each transport fork 66 here grips an associated preform 12 just below the collar 22.

[0109] The transport forks 66 are carried by the drive wheel 60. The transport forks 66 are thus driven by the drive wheel 60 along a circular path.

[0110] According to a variant of the invention not shown, the receiving means are clamps which have jaws which are articulated between a closed position and an open position, the jaws being elastically returned to their closed position.

[0111] According to a variant of the invention not shown, the transport forks are carried by a plate with an axis coaxial with the axis "D" of the drive wheel 60.

[0112] The transport forks 66 are distributed over the entire circumference of the drive wheel 60, substantially at the same altitude as the notches 64 of the input transfer wheel 62. The transport forks 66 are circumferentially spaced from each other by the predetermined pitch "S" so that a transport fork 66 is arranged vertically under each gripping member 38.

[0113] Thus, in planar projection the circular trajectory of the transport forks 66 is superimposed on the trajectory of the gripping members throughout the portion 39A of turn. In other words, in planar projection, the trajectory of the gripping members 38 coincides with the trajectory of the transport forks 66 throughout the turn portion 39A. Furthermore, each transport fork 66 moves vertically in coincidence with an associated gripping member 38 of the conveyor 36.

[0114] As shown in [Fig.5], each transport fork 66 is intended to grip a preform 12 just below the collar 22 so as to extract the preform 12 from the input transfer wheel 62 and to support it during the dressing operation.

[0115] The transport fork 66 grips the preform 12 below the collar 22 so that the bearing surface 20 of the collar 22 rests on an upper face, called the reaction face 68, of the transport fork 66. The reaction face 68 is thus in contact with the collar 22. The reaction face 68 is turned towards the rim 26 of the neck 16, here upwards. When the preform 12 is gripped by the transport fork 66, its tamper-evident groove 30 is left free. The transport fork 66 supports the preform 12, but it does not limit its vertical upward movement.

[0116] As will be explained later, during the dressing operation, the preform 12 is transported by the transport fork 66 until it fits into the gripping member 38.

[0117] The invention proposes a method for transferring the preform 12 onto the conveyor 36 in which, during the dressing operation, the neck 16 of the preform 12 is clamped vertically between the reaction face 68 of the transport fork 66 and a holding face 70 vertically opposite the reaction face 68, the holding face 70 bearing against the rim 26. Thus, the vertical upward movement of the preform 12 is intended to be limited solely by contact of the rim 26 with the holding face 70 vertically opposite the reaction face 68. This makes it possible to correctly hold the preform 12 during the dressing operation while leaving the tamper-evident groove 30 of the neck 16 free.

[0118] In a non-limiting manner, the holding face 70 is here formed by the contact face 50 of the ejection member 48. During the dressing operation, the ejection member 48 is therefore slidably controlled so as to clamp the neck 16 against the transport fork 66.

[0119] According to another aspect of the invention, the operation of coating the preform 12 by the gripping member 38 requires a vertical sliding movement of the preform 12 into a nesting position relative to the gripping member 38. Indeed, in the embodiment shown in the figures, the gripping members 38 are not mounted to slide vertically relative to the drive wheel 60.

[0120] According to the teachings of the invention, the transport forks 66 are advantageously mounted to slide vertically relative to the drive wheel 60 between a low transfer position in which the transport fork 66 is arranged at the same height as the notches 64 of the input transfer wheel 62, as illustrated in FIGS. 11, 13 and 23 and a high nesting position in which the neck 16 of the preform 12 carried by the transport fork 66 is at the same height as the gripping members 38 so that the gripping member 38 is nested vertically in the neck 16, as illustrated in [Fig. 15] and 23.

[0121] Thus, according to the embodiment shown in [Fig. 5], the transport forks 66 are mounted to slide vertically on the drive wheel 60, while the gripping members 38 remain fixed in a vertical direction relative to the drive wheel 60. Thus, it is the transport forks 66 which vertically lift the preforms 12 in order to fit them with the gripping members 38 during the dressing operation.

[0122] As shown in [Fig.5], the movements of the transport forks 66 and / or the ejection members 48 are here controlled by cams.

[0123] In a variant not shown, the movements of the transport forks and / or cams are controlled by pneumatic cylinders or electric motors.

[0124] As shown in Figures 5 and 6, each transport fork 66 is attached to an associated carriage 72. The carriage 72 is mounted to slide vertically on the drive wheel 60 by means of a slide 73 fixedly mounted on the drive wheel 60. A cam follower 74 is here formed by a roller which is rotatably mounted at a free lower end of the carriage 72 of each transport fork 66.

[0125] The cam follower 74 is intended to cooperate with a cam path 76 which is here formed by the lower surface of a covering rail 78 fixed relative to the ground. The covering rail 78 is fixed relative to a frame on which the drive wheel 60 is rotatably mounted. The rail 78 is shown in more detail in a developed view in [Fig. 8]. The direction of movement of the gripping member 38 is indicated by the arrow “F1”.

[0126] Referring again to [Fig. 5], each transport fork 66 is elastically returned to its upper nesting position by a return spring 80 which is interposed between a face integral in movement with the carriage 72, here located at an upper end of the spring 80, and a fixed face of the drive wheel 60, here located at an upper end of the slide 73.

[0127] In the event of a malfunction in which the spring 80 is not sufficiently reactive, a counter rail 82 is provided, arranged opposite the covering rail 78 and cooperating with the cam follower 74 to push the transport fork 66, by via the carriage 72, towards its nesting position.

[0128] As shown in Figures 5 to 7, the device further comprises a mechanism for controlling the sliding of the holding face 70 relative to the transport fork 66 which is mounted on the carriage 72.

[0129] The control mechanism here comprises a second control fork 84 which is intended to be received around the ejection member 48, in line with a drive face 87 facing upwards throughout the portion 39A of the turn. The control fork 84 is intended to urge the drive face 87 downwards as will be explained later.

[0130] In the embodiment shown in the figures, the control fork 84 is here received in an external groove 85 of the ejection member 48, the drive face 87 forming a lower face of the groove 85. Thus, the control fork 84 is engaged with the ejection member 48 between an engagement point “P6” located at an upstream end of the turning portion 39A and a release point “P5” located at a downstream end of the turning portion 39A, as shown in [Fig. 1]. The control fork 84 is thus temporarily secured in vertical sliding with the ejection member 48 when the ejection member 48 travels along the turning portion 39A.

[0131] The groove 85 is delimited vertically by two horizontal faces. The groove 85 has a height slightly greater than the thickness of the control fork 84 so that the control fork 84 is received in the groove 85 with vertical clearance. This clearance makes it easier to insert and remove the control fork 84 from the groove 85.

[0132] The control fork 84 is arranged vertically above and at a distance from the transport fork 66. The control fork 84 is more particularly arranged above the carriage 72.

[0133] The control fork 84 is slidably mounted in the carriage 72 between a lower clamping position, illustrated in Figures 13 and 23, and an upper release position, illustrated in Figures 11, 15, 17 and 21. The control fork 84 is thus controlled between its lower clamping position, in which it urges the drive face 87 to press the ejection member 48 against the rim 26, and its upper release position relative to the transport fork 66, in which the fork is vertically spaced from the transport fork 66 to stop urging the ejection member 48 against the rim 26.

[0134] In the lower clamping position, the fork 84 controls the ejection member 48 in a position for clamping the neck 16 of the preform 12 carried by the transport fork 66 in which the holding face 70 of the ejection member 48 bears against the rim 26 so as to clamp the bearing surface 20 of the collar 22 against the reaction face 68 of the transport fork 66.

[0135] In the upper release position, the control fork 84 is vertically spaced from the transport fork 66 so that the holding face 70 is no longer clamped against the rim 26. The neck 16 of the preform 12 is thus no longer clamped between the ejection member 48 and the transport fork 66.

[0136] The travel of the control fork 84 between these two positions relative to the carriage 72 is very substantially less than the sliding travel of the ejection member 48 between its extreme stripping position and its extreme dressing position. Thus, it is the combined sliding of the carriage 72 relative to the drive wheel 60, on the one hand, and of the control fork 84 relative to the carriage 72, on the other hand, which allows the control fork 84 to control the sliding of the ejection member 48 between its extreme stripping position and its extreme dressing position.

[0137] The control fork 84 being slidably mounted in the carriage 72, when the control fork 84 is immobilized in one of its positions relative to the carriage 72 and the control fork 84 is engaged with the ejection member 48, the sliding of the transport fork 66 jointly causes the sliding of the holding face 70 so that the holding face 70 remains fixed relative to the transport fork 66 during its sliding.

[0138] As shown in [Fig. 6], the control fork 84 is here guided in sliding between its two positions in the carriage 72 by a rod 86 which extends vertically downwards. The rod 86 is received in a guide orifice 88 of the vertical axis of the carriage 72.

[0139] The control fork 84 is here slidably controlled by a first cam system which is used when the transport fork 66 occupies its transfer position. For example, a cam follower 90 is here formed by a roller which is mounted at a lower end of the rod 86 protruding through a lower end of the guide orifice 88 below the carriage 72.

[0140] The cam follower 90 is intended to cooperate with a cam path 92 of a control rail 94 fixed relative to the ground to push the control fork 84, and therefore the holding face 70, towards its fitting position, as shown in [Fig.8].

[0141] The control fork 84 is here elastically returned to its release position by an elastic return member 96, such as a spring, which is interposed between a face fixed relative to the carriage 72 and a face fixed relative to the control fork 84. The face fixed relative to the carriage 72 is here arranged above the face fixed relative to the control fork 84 and the elastic return member 96 works in compression.

[0142] In the embodiment shown in [Fig. 6], the carriage 72 comprises a vertical column 98 which projects above the carriage 72 and on which a body of the control fork 84 is mounted to slide vertically. The elastic return member 96 is arranged around the column 98 and is interposed between a head of the column 98, forming the fixed face relative to the carriage 72, and an upper face of the body of the control fork 84, forming the fixed face relative to the control fork 84.

[0143] The elastic return member 96 exerts a force greater than the force exerted by the elastic return means 58 of the ejection member 48. More particularly, the stiffness of the return member 96 is here greater than the stiffness of the elastic return means 58 of the ejection member 48. Thus, when the control fork 84 is engaged with the ejection member 48, the elastic return means 58 does not exert a force sufficient to return the ejection member 48 to its extreme protective position.

[0144] The control fork 84 is also capable of being controlled towards its release position by a second cam system which acts when the transport fork 66 occupies its nesting position. In the embodiment shown in [Fig. 7], this second cam system comprises a lever 100 oriented generally radially relative to the axis of the drive wheel 60. The lever 100 is pivotally mounted around a central axis “G” tangent to the direction of rotation of the drive wheel 60.

[0145] The lever 100 has two free ends here provided with rollers 102, 104. The first roller 102 is arranged at a distal end of the lever 100 relative to the control fork 84. It is intended to come into contact with a face 106 of the drive wheel 60 when the transport fork 66 occupies its nesting position, as shown in [Fig. 5]. During this contact, the distal end of the lever 100 is pushed downwards, causing the lever 100 to tilt and the second roller 104 arranged at the proximal end of the lever 100 relative to the control fork 84 to lift. The second roller 104 then comes into contact with a lower face fixed relative to the control fork 84. This thus causes the control fork 84 to lift upwards.

[0146] Referring again to [Fig. 1], the preforms 12 are here distributed in a row at the entrance of the manufacturing installation 10 by a slide 108 in which the preforms 12 slide while pushing themselves towards a downstream end. Each preform 12 is then loaded onto a horizontal entry wheel 110 having notches 112 at its periphery. Each notch 112 loads a preform 12. Thus, the preforms 12 are spaced apart by the determined pitch “S” in the entry wheel 110.

[0147] As shown in [Fig.9], each notch 112 of the input wheel 110 is delimited in top view by an edge in the shape of an arc of a circle extending over an angle less than or equal to 180°. The imaginary straight line segment connecting the two ends of the arc of a circle is called the chord. The imaginary straight line intersecting the chord orthogonally in its middle in the horizontal plane is called the arrow “H”. To be able to efficiently load each preform 12 coming from the inlet slide 108, the arrow “H” of each notch 112 is here oriented in an inclined manner at an angle “h” relative to the purely radial direction “R” relative to the axis of rotation of the inlet wheel 110. Thus, a downstream edge of the notch 112, according to the direction of rotation of the inlet wheel 110, projects radially relative to an upstream edge of the notch.

[0148] As shown in [Fig. 10], the transport fork 66 has the same configuration as the notches 112 of the input wheel 110. When the transport forks 66 take charge of the preforms 12, they are arranged at the same altitude as the notches 112 to be able to grip each preform 12 under the collar 22. Therefore, if the transport fork 66 were to grip the preforms 12 directly on the input wheel 110, the downstream edge of the transport fork 66 would strike the downstream edge of the notch 112.

[0149] To solve this problem, the manufacturing installation 10 comprises the input transfer wheel 62 which is arranged between the input wheel 110 and the conveyor 36. The notches 64 of the input transfer wheel 62 have the shape of an arc of a circle which extends over an angle of less than 180° and whose arrow is directed purely radially relative to the axis of rotation of the input transfer wheel 62, as indicated by the straight line “R” in [Fig. 10]. This makes it possible to avoid interference between the transport forks 66 and the input transfer wheel 62.

[0150] Due to this configuration of the notches 64 of the input transfer wheel 62, the path of the preforms 12 in the input transfer wheel 62 is bordered by a counter rail 114 fixed relative to the ground so as to hold the preforms 12 in the notches 64, as shown in [Fig.1].

[0151] The operation of the installation during the coating operation of the preforms 12 is now explained with reference to figures 11 to 24.

[0152] As shown in [Fig. 11], each transport fork 66 passes the first point of tangency "P3" of the input transfer wheel 62 and the closed loop 39, at the same time as a notch 64 of the input transfer wheel 62 carrying a preform 12. The transport forks 66 being arranged substantially at the same altitude as the notch 64, the transport fork 66 is able to grip the preform 12 under the collar 22. The preform 12 is thus transferred from the input transfer wheel 62 onto the drive wheel 60.

[0153] As shown in [Fig.8], to position the transport fork 66 at the good altitude, the cam path 76 has a first descent slope 76A which is intended to control the descent of the transport fork 66 towards its low transfer position. This descent slope 76A is arranged upstream of the tangency point “P3”. Thus, as illustrated in [Fig.12], at the tangency point “P3”, the transport fork 66 is already controlled by the cam path 76 in the transfer position against the elastic return force of the spring 80.

[0154] At the tangency point “P3”, the control fork 84 is already engaged with the ejection member 48. The sliding of the carriage 72 towards its low transfer position jointly causes the control fork 84 to slide, causing the ejection member 48 to slide towards its extreme stripping position. However, at the tangency point “P3”, the ejection member 48 does not completely occupy its extreme stripping position. As shown in [Fig. 1 1], the control fork 84 is in fact controlled in its upper release position so that the ejection member 48 is slightly raised above the level of the rim 26, under the effect of the elastic return means 58 of the ejection member 48, to allow the transport fork 66 to load the preform 12 without the latter coming into contact with the ejection member 48.To enable the control fork 84 to be controlled into its release position, the cam path 92 of the control rail 94 comprises a rising ramp 92A (shown in [Fig.8]) arranged downstream of the tangency point “P3”, the cam path 92 maintaining the control fork 84 in its release position during passage of the tangency point “P3”, as shown in [Fig.12].

[0155] When the preform 12 is gripped by the transport fork 66, it thus occupies its transfer position in which the axis "A" of the preform 12 is coaxial with the axis of the gripping member 38, the gripping member 38 thus being arranged opposite and at a distance from the neck 16 of the preform 12. The control fork 84 occupying its release position, the ejection member 48 does not interfere with the preform 12 during its transfer.

[0156] As shown in [Fig.l], the first point "P3" of tangency is arranged on the portion 39A of the turn of the closed loop 39, upstream of the loading point "PI" which is arranged on the portion 39A of the turn of the closed loop 39 downstream of the first point "P3" of tangency, for example at the point "P5" of clearance located at the downstream end of the portion 39A of the turn. Thus, the dressing operation advantageously lasts the time that the transport fork 66 travels an angular sector "P3-P1" of angle "a".

[0157] The trajectory of the preform 12 carried by the transport fork 66 and that of the gripping member 38 are superimposed along the angular sector "P3-P1" which forms, in plane projection, a first line of intersection between the trajectory of the gripping organs 38 and that of the transport forks 66.

[0158] Thus, between the first point "P3" of tangency and the loading point "PI", the preform 12 is carried by the transport fork 66.

[0159] As shown in Figures 15 and 16, the cam track 76 also includes a second downstream slope 76B which is intended to control the rise of the transport fork 66 towards its nesting position. At least a portion of the counter rail 82 is more particularly opposite the downstream slope 76B to ensure that the transport fork 66 is controlled towards its nesting position even in the case where the return spring 80 is not able to effectively return the transport fork 66 towards its nesting position.

[0160] The second downstream slope 76B extends here over at least part of the portion 39 A of the turn corresponding to the angular sector of angle "a", so that the dressing operation can be carried out for a sufficiently long time to ensure reliable fitting of the gripping member 38 into the neck 16 of the preform 12.

[0161] However, before the transport fork 66 begins to slide towards its nesting position, the ejection member 48 is controlled into its extreme stripping position as illustrated in FIGS. 13 and 14. For this purpose, the control fork 84 is controlled towards its clamping position. This ensures that the preform 12 is held coaxially with the gripping member 38 during the stripping operation.

[0162] In the example shown in the figures, the control fork 84 is controlled towards its clamping position by a downward downstream slope 92B of the cam path 92 of the control rail 94. This downward slope 92B is arranged upstream of the upward slope 76B of the rail 78. Thus, the elastic return member 96 makes it possible to elastically return the control fork 84 towards its clamping position, against the weaker elastic return force exerted by the elastic return means 58.

[0163] Throughout the dressing operation illustrated in Figures 13 to 16, the control fork 84 is held in its clamping position by the elastic return member 96.

[0164] At the end of the dressing operation, as illustrated in [Fig. 15], the preform 12 is integral in movement with the gripping member 38 and the ejection member 48 occupies its extreme dressing position.

[0165] Furthermore, at the exit of the portion 39A of the turn, the control fork 84 is intended to be released from the groove 85 of the ejection member 48. Similarly, the preform 12 is intended to be separated from the transport fork 66 to allow the preform to continue its movement along the loop 39 closed with the gripping member 38 while the transport fork 66 continues its trajectory. circular. If the neck 16 of the preform 12 remained clamped between the transport fork 66 and the control fork 84, this would cause friction with the preform 12 and with the drive face 87 when they separated. Thus, not only is holding the preform 12 no longer useful but it is also not desired.

[0166] Thus, at the end of the dressing operation and before the gripping member 38 reaches the release point “P5”, the control fork 84 is moved away from the drive face 87.

[0167] In the example shown in the figures, this is achieved by means of the control fork 84 which is here automatically controlled into its release position when the carriage 72 reaches its nesting position to allow the ejection member 48 to no longer be stressed by the control fork 84. The control fork 84 is here slid vertically upwards in the groove 85, thanks to the vertical play, while the ejection member 48 remains in its extreme fitting position. The control fork 84 is thus moved away from the drive face 87 of the ejection member 48.

[0168] The carriage 72 being in the high position, the control fork 84 is controlled towards its release position by contact between the roller 102 at the distal end of the lever 100 and the face 106 opposite the drive wheel 60 when the transport fork 66 completes its movement towards its nesting position.

[0169] As shown in Figures 17 and 18, before the gripping member 38 reaches the release point “P5”, the transport fork 66 is also moved away from the collar 22. The preform 12 is in fact entirely carried by the gripping member 38. The transport fork 66 is thus controlled in an intermediate position, slightly below its nesting position. The travel of the transport fork 66 between its nesting position and its intermediate position is less than the vertical clearance between the drive face 87 of the ejection member 48 and the control fork 84. Thus, even in the intermediate position of the transport fork 66, the control fork 84 is not in contact with the drive face 87.

[0170] In the embodiment shown in [Fig. 18], this is achieved by means of a slight downward slope 76C of the cam path 76 which is arranged downstream of the upward slope 76B. Thus, when the gripping member 38 reaches the release point “P5”, the preform 12 is no longer in contact with the transport fork 66 at all, which avoids unwanted friction.

[0171] As illustrated in Figures 19 and 20, during their movement along their circular trajectory from the point “P5” of release of the portion 39A of the turn to the point “P6” of engagement of the portion 39A of the turn, the transport forks 66 are held in their nested position by the return spring 80 and the control forks 84 are held in their released position against the elastic return force of the elastic return member 96 by the lever 100 in contact with the face 106 of the drive wheel 60.

[0172] Just before arriving at the engagement point "P6" located at the upstream end of the turn portion 39A, the transport fork 66 is again controlled towards its intermediate position by means of a slight downward slope 76D arranged at a downstream end of the cam path 76, as illustrated in [Fig.22].

[0173] Thus, when the transport fork 66 arrives at the engagement point “P6”, it again engages with a preform 12 carried by a gripping member 38, in particular after heating the body 14 of the preform 12, as illustrated in [Fig. 21]. The control fork 84 then engages with the ejection member 48 associated with said gripping member 38. At this engagement point “P6”, the transport fork 66 is still located slightly below the collar 22 without touching it. Similarly, with the control fork 84 occupying its release position, the latter is engaged in the groove 85 of the ejection member 48 without being in contact with its drive face 87.

[0174] As shown in [Fig.l], the installation 10 also includes an output transfer wheel 116.

[0175] The output transfer wheel 116 is arranged substantially at the same altitude as the input transfer wheel 62. It comprises articulated arms each equipped at its end with a gripper 118 for gripping a preform 12 by its neck 16. The output transfer wheel 116 is mounted to rotate in a clockwise direction around an axis "F". The grippers 118 move along a closed-loop trajectory which is tangent to the circular trajectory of the transport forks 66 at a second point "P4" of tangency.

[0176] The rotational speed of the output transfer wheel 116 is synchronized with the rotational speed of the drive wheel 60 so that a gripper 118 of the output transfer wheel 116 passes simultaneously with a transport fork 66 to the second point "P4" of tangency which is arranged downstream of the engagement point "P2".

[0177] In planar projection, the trajectory of the transport forks 66 and the trajectory of the gripping members 38 are superimposed between the engagement point "P6" and the second tangency point "P4".

[0178] The second point "P4" of tangency is more particularly arranged upstream of the first point "P3" of tangency relative to the direction of rotation of the drive wheel 60.

[0179] Thus, between the moment at which the preform 12 is gripped at the engagement point “P2” by a transport fork 66 and the moment at which the preform is transferred onto the output transfer wheel 116 at the second point "P4" of tangency, the preform 12 is engaged with the transport fork 66 at the right of the associated gripping member 38.

[0180] During a stripping operation from the engagement point “P6” to the second unloading point “P2”, the preform 12 is disengaged from the gripping member 38 by a progressive downward vertical sliding movement of the carriage 72 which begins after the engagement point “P6” and which ends substantially at the unloading point “P2”, as illustrated in FIGS. 23 and 24. This downward sliding movement is controlled by the downward slope 76A of the rail 78 which is arranged between the engagement point “P6” and the unloading point “P2”. In this movement, the carriage 72 drives the control fork 84 downwards. Due to this sliding, the lever 100 is no longer in contact with the face 106 of the drive wheel 60, which has the effect of elastically returning the control fork 84 to its clamping position by the elastic return member 96, such as a spring.

[0181] The control fork 84 being engaged with the ejection member 48, the sliding of the control fork 84 together with the carriage 72 causes the ejection member 48 to slide towards its extreme stripping position. This has the effect of disengaging the preform 12 from the gripping member 38. The collar 22 of the preform 12 is thus pushed into contact with the transport fork 66 by the ejection member 48.

[0182] During this stripping operation, the preform 12 is thus carried by the transport fork 66. The neck 16 is more particularly clamped between the holding face 70 of the ejection member 48, in contact with the rim 26, and the reaction face 68 of the transport fork 66, in contact with the bearing surface 20 of the collar 22.

[0183] The transport fork 66 leaving the tamper-evident groove 30 of the preform 12 free, the clamp 118 of the output transfer wheel 116 grips the preform 12 by its tamper-evident groove 30 at the second point “P4” of tangency.

[0184] This allows the gripper 118 to grip the preform in a stable manner without risking dropping the preform 12 or causing it to rotate randomly around its axis “A”. It is in fact preferable for the preform 12 to rotate as little as possible between its exit from the heating station 32 and its entry into the forming station 34, in particular when the body 14 of the preform 12 has been heated according to a determined heating profile involving differentiated heating around its axis “A”.

[0185] It is preferable that the preform 12 is no longer in contact with the ejection member 48 when it passes through the second point “P4” of tangency to prevent the neck 16 of the preform 12 from rubbing. To this end, the upward slope 92A of the rail 94 of control is arranged between the unloading point “P2” and the second tangency point “P4”, after the transport fork 66 has reached its transfer position.

[0186] Thus, the same transport forks 66 are used successively to carry the preforms 12 during the dressing operation, then during the stripping operation.

[0187] The invention thus makes it possible to firmly hold the preforms 12 during the dressing and stripping operations while making it possible to securely and stably grip the heated preforms at the outlet of the heating station by means of clamps. This is further accomplished while reducing costs due to the use of the ejection member 48 to perform both the preform stabilization function and the preform stripping function.

Claims

Claims

1. Method for transferring containers, and in particular preforms (12) made of thermoplastic material, comprising a neck (16) having a main axis (A), opening through an opening (24) delimited by a free edge of the neck called "mouth (26)", the container being transferred to a conveyor (36) in which the container is held by a gripping member (38) axially fitted with the neck (16) during a dressing operation, characterized in that, during the dressing operation, the neck (16) is clamped axially between a reaction face (68) facing the mouth (26) and a holding face (70) axially opposite the reaction face (68), the holding face (70) bearing against the mouth (26).

2. Method according to the preceding claim, characterized in that the reaction face (68) is in contact with a collar (22) of the neck (16).

3. Method according to any one of the preceding claims, characterized in that each gripping member (38) of the conveyor (36) comprises an ejection member (48) mounted to slide axially on the gripping member (38) between an extreme dressing position allowing the axial fitting of the gripping member (38) with the neck (16) and an extreme undressing position towards which the ejection member (48) is slid so that a contact face (50) of the ejection member (48) presses on the rim (26) of the neck (16) to completely disengage it from the gripping member (38), the holding face (70) being formed by the contact face (50) of the ejection member (48).

4. Device for implementing the method according to any one of the preceding claims, the device comprising: - at least one fork (66) for transporting a container which moves in coincidence with an associated gripping member (38) of the conveyor (36), an upper face (68) of the transport fork (66) forming the reaction face (68); - means (62) for distributing the preforms (12) which comprise means (64) for individually receiving each container so as to successively lead each container to a point (P3) of tangency with the trajectory of the transport fork (66) at which the container is transferred to the transport fork (66); - the transport fork (66) being mounted to slide axially between a transfer position in which the transport fork (66) is positioned at the same level as the individual receiving means (64) to grip the neck (16) when the container is carried by the dispensing means and a nesting position in which the neck (16) of a container carried by the transport fork (66) is intended to be nested with the gripping member (38); characterized in that the device comprises a sliding control mechanism for the holding face (70) which is slidably mounted on a carriage (72) on which the associated transport fork (66) is fixed so that, when the control mechanism is immobilized relative to the carriage (72), the sliding of the transport fork (66) jointly causes the sliding of the holding face (70).

5. Device according to the preceding claim taken in combination with claim 3, characterized in that the sliding travel of the control mechanism relative to the carriage (72) is less than the sliding travel of the ejection member (48) between its two extreme positions, the mechanism being controlled between a clamping position of the neck (16) in which it is brought closer to the transport fork (66) to urge the holding face (70) towards the reaction face (68) and a release position of the neck (16) in which it is moved away from the transport fork (66) to no longer urge the holding face (70) to clamp against the rim (26).

6. Device according to any one of claims 4 or 5, characterized in that the transport fork (66) is controlled in sliding by a cam path (76) fixed relative to the ground which cooperates with a cam follower (74) which is carried by the carriage (72).

7. Device according to any one of claims 4 to 6, characterized in that the transport fork (66) is elastically returned to its upper nesting position.

8. Device according to any one of claims 4 to 7, characterized in that the sliding control mechanism of the holding face (70) comprises a cam follower (90) which is mounted to slide axially in the carriage (72), and which cooperates with a cam path (92) fixed relative to the ground.

9. Device according to the preceding claim, characterized in that the sliding control mechanism of the holding face (70) is elastically returned to its clamping position.

10. Device according to any one of claims 4 to 9 taken in combination with claim 3, characterized in that the control mechanism comprises a control fork (84) slidably mounted in the carriage (72) and which cooperates with a face (87) of the ejection member (48) to urge the ejection member (48) downwards.

11. Device according to any one of claims 4 to 10, characterized in that the device comprises a plurality of transport forks (66) mounted integral in rotation with a drive wheel (60) around which the gripping members (38) are indexed during their movement, each carriage (72) being mounted to slide axially on the drive wheel (60).

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