FR2720323A1 - Device for fixing a blow-molding end of an extrusion-blow molding machine to produce hollow bodies. - Google Patents

Abstract

The bit holder receiving the blowing nozzle 5 is connected to a housing insert which is held in a housing 22 in a plane E movable on all sides within limits, and is fixed by a fork device 26 biased by a locking actuation means. The insert resting on the support plate 8 is effected by arranging sliding plates 30, 30a towards the support plate 8 in a floating manner, while the support on the bottom of the housing 22 is effected via a ball bearing. The fork 26 biased by the locking actuating means 28 clamps the insert and thus the tip 5 relative to the plate 8. A simplified and exact alignment of the tip 5 relative to a tool in which it is inserted is possible thanks to the free and separate adjustment of the nozzle 5.

Description

The invention relates to a device for attaching a mouthpiece

  blowing an extrusion blow molding machine for producing hollow bodies, comprising a housing which can be fixed on a support plate of the extrusion blow molding machine, and which serves for mounting a bit holder of blowing on which is fixed the blowing nozzle, the penetrating blowing nozzle for the blowing operation by its tip in a drilling of a tool which has a chamber adapted to the

shape of the hollow body to produce.

  In blow molding machines, to align the nozzle with the tool, it is necessary to loosen the fixing which usually takes place by means of Allen screws and clamping elements in T-slots. the support plate of the extrusion blow molding machine. By carefully inserting the blow nozzle into the tool or lifting the tool into engagement with the blow nozzle, the hand is made to approximate alignment, and later, after careful tightening, one corrects respectively again the alignment, until the desired working position is reached. Here, it is important that due to the clamping screws that are put in place, there may be a change in position when tightening. In addition, support relationships are such that exact alignment is not possible, or it is only with considerable work. This is all the more the case when it is a machine with several tools and several blowing tips arranged next to each other. The work of

  setting multiplies in correspondence.

  The objective underlying the invention is to provide a device for attaching a blowing nozzle of an extrusion blow molding machine, by means of which the alignment work for the blowing tip is facilitated when the exchange of it or the tool, and thanks to which we

gets a more accurate alignment.

  According to the invention, this objective is achieved by the fact that the nozzle holder is connected to a housing insert, and is guided in a plane of adjustment with respect to which the axis of the blowing tip s extends perpendicularly, movably relative to the housing in all directions, and by associating with the housing a locking device which acts on the housing meshes, whereby it is possible to fix the nozzle in its respective setting position in the

adjustment plan.

  The advantage of this embodiment is that the nozzle can, when moving to the drilling of the tool, align automatically, and this to all sides. Then, the locking device can be actuated so that the housing insert is fixed in its position. At the same time, the position of the blowing tip relative to the tool is also

fixed.

  According to a first variant, it is possible for the housing insert to be connected in one piece to the blowing nozzle holder. But preferably, the blowing nozzle holder is connected to the housing insert in an adjustable manner towards the axis of the blowing nozzle. In order to limit the bearing force of the blow-out nozzle in the tool bore, the blow-off bit holder is adjustably supported against a pressure spring. In order to be able to adjust the basic position, adjustment members are provided by means of which the height position of the blowing bit holder can be adjusted with respect to the housing insert. In this case, the adjusting members preferably comprise a setting nut which can be adjusted on a thread of the adjustment pin of the housing insert. Thus, the basic position can be fixed by locking members which act on the adjusting nut. The blow-off nozzle holder is adjustably guided towards the axis of the blow-off nozzle by means of a guide shaft in a bore of the housing insert. This can be done with

  interposition of guide bushes.

  Advantageous support of the blowing tip results from the fact that the housing insert bears directly against the support plate and can be pressed against it. However, a support in the housing is also possible. The possibility of adjustment is favored by the fact that it is carried out with the interposition of a sliding plate or of two sliding plates movable relative to each other, which are arranged between the

  bearing surface of the housing or support plate and the housing insert.

  Preferably, the sliding plates are arranged floating in a recess of the housing insert. This favors the friction relations, so that during a lateral adjustment, it can not arise from so-called "stick-slip" effect. The frictional relationships can also be positively influenced by the fact that the sliding plates are made of a hardened steel, and that their sliding surfaces are ground. In addition, the slide plates can be used to adjust the clearance for adjustment of the housing insert in the plane of adjustment between the bearing surface of the support plate and the housing. For this purpose, it is possible to choose sliding plates

of different thicknesses.

  In order to establish for the adjustment the most favorable friction relations possible between the housing insert and the housing, a low friction bearing is arranged between them. Preferably, the bearing is made in the form of a ball bearing, whose balls are guided in rolling in a cage on planar adjustment surfaces on the one hand of the housing and on the other hand of the housing minsert . Due to the combination of the floating sliding plates and the ball bearing, virtually no adjustment resistance is achieved when the detached housing insert is adjusted for self-centering relative to the drilling of the tool. . Thanks to this, the adjustment accuracy is improved. For the low-friction bearing, it is also possible to consider a hydrostatic bearing or

an assembly on a cushion of air.

  A particularly advantageous embodiment is achieved by providing a locking device which comprises a locking fork and an actuating means with which the locking fork can be urged. In this case, the locking fork is rotatably mounted on the housing at one end about an axis of rotation which intersects at right angles and at a distance from the axis of the blowing nozzle. The actuating means acts on the other end of the locking fork. The housing insert has two parallel grooves which are traversed by the locking fork with its two forks. The fork arms in the tightened state urge the bearing surface of the grooves. In order to improve the support relationships for clamping between the fork arms and the bearing surfaces of the grooves of the housing insert, the clamping surfaces protrude from the bearing surfaces and can be realized convex or curved. Mounting via the axis of rotation preferably takes place at the free ends of the fork arms. The actuating device solicits in correspondence the soul connecting the two fork legs. Thanks to this, we obtain a solid unit through which we can

  transmit high blocking forces.

  According to a first embodiment, the actuation may comprise a clamping screw which acts with a conical surface on an oblique surface of the locking fork or on a conical surface of a rod connected to the locking fork, the screw of clamping and the rod being arranged at right angles to one another. With this, it is possible to pull the clamping screw laterally out of the housing, so that the actuation thereof is also favorable to the setting operation, because it has a good accessibility in spatial relationships narrow, especially where there are several

  blowing arranged next to each other.

  However, it is also possible to provide the actuation in the form of a clamping screw which passes through a threaded bore of the housing and which directly urges the other end of the locking fork. In this case, the clamping screw is placed in a bore which extends parallel to the axis of the blowing endpiece. In the first embodiment, the bore in which the clamping screw is inserted extends in a plane which is arranged at a right angle with respect to the axis of the nozzle, that is to say in parallel to the adjustment plan. In addition, it is also possible that the tightening screw or screws directly bias the housing insert or fix it against the support plate. Preferred embodiments of the invention are schematically illustrated in the drawings. The figures show: fig. 1 a side view of an arrangement of a support plate on a support of the extrusion blow molding machine, with the fastening device connected thereto for the blowing tip; Fig. 2 a front view of an arrangement having a plurality of discharge nozzles arranged next to each other, in which only the support plate with the fixing device and parts of the guide for it are illustrated; Fig. 3 a side view of FIG. 2 with a fixing device illustrated in section, the section plane comprising the axis of the blowing nozzle; Fig. 4 the blowing tip with its tip in the remote position of the tool, on an enlarged scale; Fig. The blowing tip in the retracted state with respect to the tool; Fig. 6 an enlargement of a detail which relates to the mounting of the housing insert and the locking device; Figs. 7 and 8 a half-section and a view of the housing insert as a detail, on an enlarged scale; Figs. 9 and 10 two different views of the locking fork, of which fig. 10 is an illustration in section, on an enlarged scale; Fig. 11 an illustration corresponding to FIG. 6, however with a blocking device modified with respect thereto; Fig. An enlarged illustration of the mounting of the housing insert in the housing in a modified form, and FIG. 13 another embodiment for mounting and blocking of

the housing insert.

  Fig. 1 illustrates a side view of a portion of an extrusion blow molding machine for producing hollow bodies, comprising the support 1, from which extend downwards guide rails 2 arranged parallel to each other. These are connected to each other at their lower ends by a cross 3. The cross is made in the form of a tray. It carries a scraper 4 through which the blowing nozzle 5 extends. The blowing nozzle 5 has a vertical axis 6. This blowing nozzle 5 is fixed via a fixing device 7 to the support plate 8 which is movably guided in the vertical direction on the guide rails 2. The fastening device 7 is connected to the support plate 8 via screws which engage in blocking pads. The blocking pads can be moved in T-slots 9, so that the fixing device 7 can be moved with the blowing tip 5 in the plane of representation of the

  Fig. 1 or out of it, on the support plate 8.

  The fixing device 7 is used for aligning and fixing the blowing nozzle 5 with respect to the scraper 4 or the tool 11. The plate 8 is movable by means of a control unit 10 in the vertical direction , that is to say in the direction of the axis 6. In this case, the blowing nozzle 5 is moved with its tip 13 through the scraper 4 towards the tool 1 1 in its piercing. introduction 12 or out of it. For the blowing operation, the tip 13 of the blowing nozzle is introduced into the bore 12 of the tool 11. Through the blowing nozzle 5, air is introduced via connections in order to inflate the extruded pipe received in the tool 1 1, to form a hollow body in that the pipe bears against the wall of the chamber of the tool 11, and thus receives its shape. After completion of the blowing operation, the tool 11 is opened and the blowing nozzle 5 is moved upwards towards its axis 6. The scraper 4 is used to move the nozzle away from the nozzle.

  blowing 5 formed parts possibly still attached.

  The figs. 4 and 5 illustrate in more detail the two positions that can take the blowing nozzle 5 relative to the tool 11. FIG. 4 watch

  the position remote from the blowing nozzle 5 with respect to the tool 11.

  It can be seen that the tool 11 has a bore 12 which has upwardly a conical opening 34 and which opens out into the chamber

  32. The blowing nozzle 5 has a tip 13 reduced in diameter.

  The tip 13 of the blowing tip is made of a material harder than the trunk of the blowing tip 5 itself. It represents an interchangeable piece which is adapted to the respective tool 11. It presents a jump of diameter. The resulting edge serves as a cutting and sealing edge 33. This cutting and sealing edge 33 cooperates with the conical bore 34. FIG. 5 illustrates the blowing nozzle 5 with its tip 13 inserted into the tool 11. It can be seen that the cutting edge and sealing edge 33 rests in the conical bore 34. Here, we also see that the centering of the blowing tip 5 with the cutting and sealing edge 33 with respect to the bore 34 is of particular importance. An eccentricity would lead to bending of the blowing tip 5 and thus to the loss of the function of the cutting edge.

cutting and sealing 33.

  In order to be able to make an exact adjustment of the blowing nozzle 5 with respect to the tool 11, provision is made for the fastening device 7 according to the invention, for which a first embodiment has been illustrated in FIG.

  the figs. 2, 3 and 6 again enlarged with respect to FIG. 1.

  Here, the support plate 8 is illustrated only by phantom lines. We see in fig. 2 that several blow-out nozzles 5 have been arranged next to one another. It is therefore an extrusion blow molding machine comprising several tools arranged next to each other, or a forming tool comprising several forming chambers which are

  arranged next to one another and operated simultaneously.

  The blowing nozzle 5 movable along an axis 6 is received on a blowing nozzle holder 14 centrally by its upper end and enlarged in diameter and therefore remote from the scraper 4. For this purpose, it is centered by its diameter. The tip holder 14 has a guide shaft 15 which extends along the axis 6 upwards towards the support plate 8, but ends before the -this. A clamping plate 16 connects to the bit holder 14 upwards towards the support plate 8; this clamping plate 16 has a chamber in which is arranged a stack of springs 17 which is biased by an adjusting nut. The guide shaft 15 passes through this chamber, that is to say the clamping plate 16 and the adjusting nut 18, and penetrates a hole in the housing insert 20. The adjusting nut 18 is provided with a tapping and it is screwed with it on a corresponding thread of the adjustment heel 21 of the housing insert 20. With this, one can adjust the height position of the tip 13 of the tip of blowing. The position can be ensured by a locking ring 19 which clamps the adjusting nut 18 on the adjusting heel 21 of the housing insert 20. Nevertheless, the blowing tip 5 can perform light movements towards its axis 6, which are determined by the spring 17 in the context of the adjustment mobility of the clamping plate 16 with the bit holder 14 bearing axially against it relative to

  the adjusting nut 18 and thus with respect to the housing insert 20.

  The blowing nozzle 5 is pressed by the spring 17, with its tip 13 and in particular with its cutting and sealing edge 33 resting against the conical bore 34 of the tool 11. The housing insert 20 is in a housing 22, held movable in all directions in the plane of adjustment E on which the axis 6 of the blower nozzle 5 is mounted vertically, so that adjustment can be made to the blow nozzle 5 relative to the tool 11. When the necessary adjustment position is reached, the position is fixed by means of a locking device. In addition, we see in fig. 3 that screws 23 are provided for fixing the fixing device 7 and its housing 22 on the support plate 8. The housing 22 is supported by its bearing surface 24 against the support surface 25 of the support plate 8. The locking device comprises a locking fork 26 whose two fork arms 36, 37 are retained in a rotation bearing of the housing, which is represented by the axis of rotation 27. A blocking actuation 28 illustrated in greater detail in FIG. 6 acts on the other end of the locking fork 26. The guide shaft 15 is guided exactly and freely in guide bushes 29 of the adjusting nut 18 and the

adjustment heel 21.

  The support of the housing insert 20 against the support surface 25 is effected via sliding plates 30, 30a. A bearing 31 serves to support between the housing insert 20 and the housing 22, this bearing 31 is a low-friction bearing and may be in the form of a ball bearing or also in the form of a ball bearing. another free and low friction bearing, for example in the form of an air-cushion bearing or a hydrostatic bearing. The free mobility determines the accuracy of the adjustment and the self-centering of the blowing nozzle 5 with respect to the tool 11. The blocking device which can be conducted via the blocking actuation 28 in the active position or out of it, firmly holds only that position which is essentially established by itself. It can be seen that in the case where several blowing nozzles 5 are provided in a juxtaposed arrangement, the adjustment work is clearly facilitated by self-centering, whereas this work is carried out, in the usual embodiments, exclusively by attaching the bit holder 14 to the support plate 8 by adjustment in its T-grooves. Before referring to the mutual association of the locking fork 26 and the housing insert 20, it will be explained firstly their construction by referring to Figs. 7 to 10. In figs. 7 and 8, there is shown the housing insert 20. The housing insert 20 has the adjustment heel 21 provided with a thread and a base 54 which connects to the top, and which is enlarged in diameter and which has a cylindrical outer diameter. Two

  grooves 52, 53 parallel to one another are formed in this base 54.

  The surface of the base 54 arranged downwardly towards the adjusting heel 21, represents an adjusting surface 49 which cooperates with the housing insert. In the front surface of the base 54, which is turned away from this adjustment surface 49, a recess 47 has been provided for the floating reception of the two sliding plates 30a. The inner surfaces of the two grooves 52, 53, arranged towards the recess 47, serve as bearing surfaces 55, 56 for the fork of

  blocking described in relation to FIGS. 9 and 10.

  The fork 26 shown in figs. 9 and 10 has two fork arms 36, 37 which are connected to each other by the web 38. In addition, the fork arms 36, 37 have, at their free ends, through-holes 57 for their articulated attachment. on the housing 22. The core 38 has a blind hole 39. Approximately in the middle with respect to the axial extension of the locking fork 26, it exists on both arms

  fork 36, 37 a projection which forms a clamping surface 42.

  The cooperation of the housing insert 20 according to Figs. 7 and 8, and the locking fork 26 according to Figs. 9 and 10 with the housing 22 and with the blocking actuator 28 will now be explained with reference to FIG. 6. FIG. 6 shows that the housing insert 20 can be moved in the housing 22 in the context of the radial freedom of the outer diameter of the adjustment heel 21 in the passage 46 of the bottom 45 of the housing. The locking fork 26 is held in rotation in the housing 22 by means of a bolt which is inserted into the holes 57 and which forms the axis of rotation 27. The housing insert 20 is received between the two fork arms 36, 37, the forks extending through the grooves 52, 53 of the housing insert 20. However, there is a clearance between the two, so that an adjustment is possible both in the longitudinal direction of the fork arm 36, 37, that transversely to them. The protrusions of the two fork arms 36, 37 with the clamping surfaces 42 are directed upwards, towards the support plate 8, and they

  are used for clamping against the bearing surfaces 55, 56 of the grooves 52, 53.

  Thanks to this, the housing msert 20 is pressed via the sliding plates 30, 30a which are arranged in a floating manner with radial clearance in the recess 47, against the support surface 25 of the support plate 8. In addition, the housing insert 20 is guided on the support surface 48 of the housing base 45, by its adjustment surface 49 and with the interposition of a ball bearing in the form of the bearing 31. The bearing 31 comprises a cage 51 in which balls 50 are received in windows in peripheral distribution. The cage 51 with the balls 50 is movable rolling towards all sides in the recess 35 of the housing 22 between the adjusting surfaces 48, 49. As long as the blocking actuating means 28 is not tight, it as a result of the floating mounting of the sliding plates 30, 30a on the one hand, and the balls 50 on the other hand, an extremely free mobility of the housing insert relative to the housing 22 in the adjustment plane E. This free mobility causes a very precise adjustment and self-centering of the blowing nozzle 5 with respect to the tool 11. The adjustment position obtained can be fixed by clamping the locking actuation means 28 and thus by pressing. of the clamping surface 42 against the bearing surfaces 55, 56 of the housing insert 20. In doing so, the housing insert 20 is clamped against the support plate 8. The locking actuating means 28 comprises a rod 40 plugged into the bore 39 of the soul 38 of the fork of b locus 26 and protruding axially out of it, the rod 40 having at its end protruding from the bore 39 a conical surface 41. The rod 40 extends with its axis substantially parallel to the axis 6 of the blowing tip 5 At right angles to the latter, a threaded bore 58 is provided in the housing 20. This threaded bore 58 opens into a passage 60 in which the rod 40 also extends through its conical surface 41. A locking screw 43 is screwed into the threaded bore 58, and is in the form of a hexagon socket head screw and also has a conical surface 44 which cooperates with the conical surface 41. When actuating the locking screw 43 in the screwing direction, its conical surface 44 biases the conical surface 41 of the rod 40. This moves the locking fork 26 counterclockwise about the axis of rotation 27, so that that the clamping surfaces 42 of its fork arm 36, 37 urge the bearing surfaces 55, 56 of the two grooves 52, 53 of the housing insert 20 and move and tighten it up against

the support plate 8.

  Fig. 11 illustrates a modification of the embodiment according to FIGS. 2, 3 and 6. Here, there is provided a locking screw 43a which is screwed into a threaded hole 58a which extends parallel to the axis 6 of the blowing nozzle 5, and which acts directly, by its front surface. or a corresponding annular surface in the form of a locking surface 59, on the web 38 of the locking fork 26 rotating about the axis of

  rotation 27. The locking screw 43a has a hand grip.

  Fig. 12 illustrates another variant of mounting and locking in the housing 22 of the housing insert 20 constructed in two parts. In this case, the housing 22 is constructed in two parts 22a, 22b which are connected to each other by means of screws 61 which pass through spacing sleeves 62 through which the two housing parts 22a, 22b

  are kept at a distance from each other.

  The insert has sections through which the spacer sleeves 62 are loosely surrounded, so that mobility to all sides of the housing insert 20 in the housing 22 is ensured. The housing portion 22a formed in the form of a plate has a cavity 63 in which is received a plate 64 provided with air passage holes distributed peripherally; this plate has, towards the bearing surface against which the housing insert 20 is pressed, open channels or recesses through which air is introduced into the intermediate chamber, so that the housing insert 20 is lifted slightly when the locking screw locking device 43b is released, and it can be easily moved to all sides on the air bag. Next, the locking screw located in the housing portion 22a, which clamps the housing insert 20 against the housing portion, is tightened.

  housing 22b. The housing part 22b is fixed on the support plate 8.

  In the embodiment illustrated in FIG. 13, the housing insert 20 can also be moved in the housing 22 laterally with respect to the plane of the drawing, and in the plane of the drawing or out of it to all sides. A sliding plate 30b has been integrated into the housing 22 against which the housing insert 20 is supported. The housing insert 20 is held in abutment against the sliding plate 30b by means of traction springs 65. blocking device comprises a locking plate 66 which is clamped against the housing insert via locking screws 43c which can be screwed into threaded bores of the housing 22, so that the housing insert is fixed with respect to the plate sliding of the housing 22. For movement, the locking screws 43c are released. In doing so, the housing insert 20 is held in abutment against the sliding plate 30b by means of the tension springs 65; nevertheless, it can be moved to all sides within limits along the sliding plate 30b in the housing 22 due to the suspension. When you reach the setting position

  correct, we tighten the locking screws 43c.

Claims (20)

claims   1. Device for attaching a blow-off nozzle (5) of an extrusion blow molding machine, comprising a housing (22) which can be fixed on a support plate (8) of the extrusion machine. blowing, and which serves to mount a blow-off nozzle holder (14) on which is fixed the blowing nozzle (5), the blowing nozzle (5) penetrating by its point (13), for the blowing operation, in a bore (12) of a tool (11) which has a chamber (32) adapted to the shape of the hollow body to be produced, characterized in that - the bit holder (14) is connected to a housing insert (20) and is movably guided to all sides within limits relative to the housing (22) in an adjustment plane (E) with respect to which the axis (6) of the blowing tip (5) extends perpendicularly, and in that - it is associated with the housing (22) a locking device (26, 43, 43a) which acts on the housing insert (20), whereby the endpiece blowing (5 ) can be fixed in its respective setting position in the setting (E).   2. Device according to claim 1, characterized in that the housing insert (20) is connected in one piece at the bit holder (14).   3. Device according to claim 1, characterized in that the end holder (14) is connected to r rmsert housing (20) in an adjustable manner in the direction of the axis (6) of the mouthpiece blowing (5).   4. Device according to claim 3, characterized in that the end holder (14) is supported in an adjustable manner   against a pressure spring (17).   5. Device according to either of claims 3 and 4,   characterized in that adjusting members (18, 21) are provided by which the basic position of the bit holder (14) with respect to the housing (20) is adjustable.   6. Device according to claim 5, characterized in that the adjusting members comprise an adjusting nut (18) which can be adjusted on a thread of an adjusting heel (21). the housing insert (20).   7. Device according to claim 3, characterized in that the end holder (14) is movably guided in the direction of the axis (6) of the blowing nozzle (5) by means of a shaft of   guiding (15) in a drilling of the housing msert (20).   8. Device according to any one of claims 1 to 7,   characterized in that the housing insert (20) is supported and can be tightened   against the housing (22) or against the support plate (8).   9. Device according to claim 8, characterized in that the support is carried out with the interposition of a sliding plate or two sliding plates (30, 30a) movable one by report to the other.   10. Device according to claim 9, characterized in that the sliding plates (30, 30a) are arranged   floating in a recess (47) of the housing insert (20).   11. Device according to either of claims 9 and 10,   characterized in that the sliding plates (30, 30a) are made of hardened steel and that their sliding surfaces are ground.   12. Device according to claim 1, characterized in that the housing insert (20) is supported via a bearing to   low friction (31) for adjustment on the housing (22).   13. Device according to claim 12, characterized in that the bearing (31) is represented by a ball bearing whose balls (50) are guided in rolling in a cage (51) on adjustment surfaces (48, 49). housing (22) on the one hand, and   the housing insert (20) on the other hand.   14. Device according to claim 1, characterized in that the locking device comprises a locking fork (26) and an actuating means, in that the locking fork (26) is mounted by a rotating end on the housing (22) about an axis of rotation (27) which intersects at right angles and at a distance the axis (6) of the blowing nozzle (5) in that the actuating means acts on the other end of the locking fork (26), and in that the housing insert (20) has two parallel grooves (52, 53) which are traversed with side clearance by the locking fork (26) with its two arms. fork (36, 37), and the latter requests in a tight state the   bearing surfaces (55, 56) of the grooves (52, 53).   15. Device according to claim 14, characterized in that the fork arms (36, 37) have surfaces   clamping member (42) protruding from the bearing surfaces (55, 56).   Device according to claim 14, characterized in that the clamping surfaces (42) are convex or convex.   Device according to claim 14, characterized in that the free ends of the fork arms (36, 37)   represent one of the ends of the locking fork (26).   18. Device according to claim 14, characterized in that the actuation comprises a clamping screw (43) which urges with a conical surface (45) an oblique surface of the locking fork (26) or a conical surface (41). a rod (40) connected to the locking fork (26), the clamping screw (43) and the rod (40)   being arranged at right angles to each other.   19. Device according to claim 14, characterized in that the actuation comprises a clamping screw (43a) which passes through a threaded bore (58a) of the housing (22), and which directly urges the other end of the locking fork (26) or the insert of housing (20).   20. Device according to claim 12, characterized in that the bearing (31) comprises a chamber for the solicitation by a fluid under pressure, in particular air, for the reduced friction.