DEVICE FOR MOLDING CONTAINERS IN THERMOPLASTIC MATERIAL AND INSTALLATION FOR
MANUFACTURE OF CONTAINERS USING THE APPLICATION
The present invention concerns the improvements made to the molding devices, by blow or stretch-blow, of containers, especially bottles, from preforms in thermoplastic material, the device comprising a portfolio-type mold having two half-shells connected between yes by means of a mutual pivot axis which coincides with the respective edges of the two half-shells and the driving means associated with the two half-shells to rotate them against each other in the direction of the mold lock or in the direction of the opening of the mold. mold, as well as facilities for the manufacture of containers that make the application of that molding device. Document FR-A-2 646 802 shows, in its figure 4, an arrangement of the portfolio mold as previously mentioned, in which the lock and the opening of the mold are obtained by an alternative rotation movement of a driving arm. This reciprocating rotation movement is described and represented as being conferred by a drive shaft perpendicular to the arm to which it is attached by means of a shroud on the edge and no information is provided on the manner in which the drive shaft is animated. The main purpose of the present invention is to propose a simple technical solution that allows to animate a mold such as that of figure 4 of the aforementioned document and also propose, due to the simplicity of these means, a complete manufacturing facility with architecture around such a single mold molding device, wherein the half-shells rotate around a fixed axis, which is simple and reliable in design, and capable of preserving synchronized operation of all its component parts. Such a device, with a single mold and a fixed pivot shaft, is certainly already known after document EP 0 456 866. In any case, this document does not address the problem of a synchronization of the opening and the lock of the mold with the operation of other elements of the machine. For this purpose, according to the first of its aspects, the invention proposes a molding device such as that mentioned in the preamble, of single mold and fixed pivot shaft, which, being arranged according to the invention, is essentially characterized in that the means The actuators comprise a movable arm mounted with free rotation on a support shaft and connected to the two mentioned half-shells, this arm, on the other hand, supporting a follower, alternatively a guide cam suitable for cooperating with a rotating guide cam, alternatively respectively a follower strip dragged on a circular path, the cam being profiled so as to cause the movement of the arm in order to order the opening and the lock of the mold, and the motor elements to drag the rotating cam, alternatively respectively the follower slice , the motor elements being synchronized with the feeding of the mold by the preforms. Preferably, the arm support shaft is located in an arm region comprised between its two extremities; a first end of the arm is connected to the two half-shells and a second end of the arm supports the follower slice, alternatively respectively the cam; in a manner known per se, the actuating elements can also comprise, on the other hand, two articulated rods of free rotation by means of one of their extremities to the first mentioned extremity of the arm and articulated with free rotation through their other extremity respectively to the two half-shells on one side and another of the axis of their mutual pivot. In an example of a preferred embodiment, the follower sleeve is carried by the arm and the rotating cam is placed on the arm., or supported by a rotating cymbal. In order to constitute a device having at the same time a reliable functioning and a simple structure, it is preferably provided that the cam is configured to cooperate with the follower slice at least after the beginning of the opening of the mold just at least at the end of the closure of the mold. mold and auxiliary lock elements, independent of the aforementioned actuating elements, are provided to keep the mold closed in the course of molding after the end of the mold lock just before the start of the mold opening; conveniently then the cam extends according to an open piece and no longer cooperates with the follower slice between at least the end of the mold lock and at least the beginning of the opening of the mold. In a particularly preferred arrangement, to which a mechanism of bringing the hot preforms with rotating clamp is associated, the rotating clamp is coaxial with the rotary cam, alternately respectively to and rotatably joined to the rotary cam, respectively respectively of it in rotation: it is thanks to this that a perfect synchronization of the operation of bringing the hot preforms into the mold (mold feeding) and of the molding operation is ensured, and this synchronization is obtained without involving external complex elements, constituting a remarkable structure by its simplicity and its weak volume. According to a second aspect of the invention, there is proposed a plant for manufacturing containers, especially bottles in thermoplastic material by blowing or stretching-blowing hot preforms, comprising: preform feeding elements presented arranged in sequence with respect to the others in a vertical position, a loading and placing wheel in a predetermined space step of the preforms supplied by the feeding element, an endless chain of transfer elements of the preforms dragged by a driving wheel and arranged to grip the preforms one by one on the loading wheel and to make them pass through a heating furnace at a temperature previously determined in the downward neck position, - a rotating insertion gripper capable of gripping the preforms one by one on the conveyor chain and bringing them inside the molding device, a molding device with a single mold of the kind mentioned herein, and - a rotating extraction clamp capable of grasping the molded containers inside the molding device and bringing them towards the evacuation elements, an installation which, being arranged according to the invention, is essentially characterized in that it comprises on the other hand - a single rotary motor, and rotating drive elements, with endless linkage, suitable for dragging, with no possibility of slipping, the previous elements of the installation when starting the single motor. Preferably the rotating insertion clamp is coaxial to the axis of rotation of the rotating cam and attached to it in rotation; in this case, it is convenient that, on the one hand, the rotating cam and the insertion clamp, on the other hand, the extraction clamp and finally, the traction wheel of the transfer chain are dragged by the respective belts and, To simplify the arrangement of the installation as much as possible, it can be conveniently provided that the load wheel is dragged by the handover chain. Thanks to the assembly of the considered arrangements, within the framework of the invention, it is possible to realize a manufacturing facility of single mold containers in which a single motor member is used for the positive drag of all the moving component elements, which are without any slipping: thus a mechanically simple and functionally reliable installation is constituted. The invention will be better understood upon reading the detailed description that follows of a preferred embodiment given solely by way of purely illustrative example. In this description reference is made to the accompanying drawings on which: Figure 1 is a schematic view, from above, of a molding device arranged according to the invention, and - Figure 2 is a very schematic view, from above, of a container manufacturing facility arranged around a single mold molding device according to Figure 1. Referring now to Figure 1, the reference numeral 1 designates in its assembly a blow molding or stretch-blow molding device for containers, especially bottles, from hot preforms in thermoplastic material such as PET polyethylene terephthalate, PEN polyethylene naphthalate, or other. The device 1 comprises a single mold 2 of the portfolio type having two half-shells 3 connected to one another by a fixed axis of mutual pivoting 4 which coincides with the respective edges of the two half-shells 3. The operating elements 5 are associated with both half-shells 3 to rotate them with respect to each other in the direction of the mold lock or in the direction of the mold opening (arrow 6). The aforementioned actuating elements 5 comprise a mounted arm 7 that freely oscillates around an axis 8 parallel to the axis 4, the axis 8 being preferably arranged between the free ends of the arm 7. At one of its ends, the arm 7 is connected for the free articulation by a common shaft 9 to the respective ends of two connecting rods 10 articulated, by their opposite ends, to the two half-shells 3 at the points thereof symmetrically separated from the axis 4. All the rotation of the arm 7 around the axis 8 in one direction or in the other, by means of an alternative movement of the axis 9 (arrow 11), the approximation or separation of the axis 4 is translated and then by closing or opening, respectively, of the mold. At its other end, the arm 7 carries an abnormal slice or follower slice 12, able to cooperate with a profiled cam 13 in the form of a hollow leak in a piece 14 animated by a rotation movement about an axis 15: for this purpose the piece 14 can be supported by a plate 16 that rotates about the axis 16. Of course, an inverse arrangement, with the follower sleeve supported by the rotating plate and the cam provided on the tip of the arm 7, can also be considered. The cam 13 in the form of a leak or throat has two substantially parallel lateral faces suitable for guiding the follower slide 12 in the radially opposite directions of movement. The cam is shaped to determine four successive functional limits of positioning of the arm, namely, as shown in Figure 1 (arrow 17 indicates the direction of continuous rotation of piece 14): limit A: start of mold opening , limit B: end of mold opening, limit C: start of mold closing, - limit D: end of mold closing. In other words, while the slice 12 is in contact with the cam 13, between the limits B and C, the mold is open and a finished container can be extracted, furthermore a hot preform can be introduced. In the same way, while the slice is free of the cam 13 between the limits D and A, the mold is closed and the blow or stretch-blow operation can be performed. The mold is kept closed in the lock position by the specified lock elements 18 and the slice 12 / cam 13 assembly will not ensure mold maintenance in the closed position: under these conditions, the cam 13 will not extend between the molds. limits
D and A: as shown in Figure 1, the cam 13 extends only over a curvilinear length between the limits A and D. In other words, when the mold is closed, the cam 13 does not cooperate with the slice 12 and the slice 12 is "in the air" (mixed stroke representation on figure 1). Thus the length of the cam 13 is optimized by being reduced to a minimum: this reduces the use of the slice and facilitates maintenance by allowing the movements of the mold to be forced while the machine is stopped and the slice is out of the cam. In the embodiment shown in figure 1, the arm 7 is not constituted in one piece, but consists of two sub-arms 7a and 7b respectively, assembled in rotation coaxially on the axis 8 and extend to one another side of him; the two sub-arms 7a and 7b are connected to one another in rotation coaxially on the axis 8 and extend to one part of the other; the two sub-arms 7a and 7b are connected to each other in rotation by means of a safety member 19, such as a torque limiter, capable of releasing the two sub-arms from each other in the case where the arm is subjected at an effort greater than a predetermined threshold. The drive of the plate 16 in rotation is ensured by a motor (especially electric motor), not shown and by an endless link 20, such as a toothed belt, which copes without slipping with a wheel or pulley 21 coaxial to the shaft 15 and joined in rotation of it. Also mounted on the shaft 15 is a rotational clamping device (not shown) which is animated by a complex movement of rotation and radial displacement under the action of a cam (for example, document FR-A- 2 479 077 describes a possible arrangement). This rotating clamp grabs the hot preforms at the exit of the oven and brings them to the open mold, the trajectory followed by the preform being schematized with 22 in a circular way on figure 1. Thanks to this arrangement, a perfect synchronism between the movement is ensured of the rotating clamp and the molding operation, in other words, between the opening and closing movements of the mold and the presentation of the preforms. The molding device that is described lends itself particularly to the realization of a complete manufacturing facility for containers made around said molding device. Figure 2 represents in a very schematic way, in top view such an installation. On Figure 2, the same numerical references are conserved to designate the same organs as in figure 1. In this installation the belt 20 that drags the shaft
by means of the pulley 21 is moved by the output wheel of an electric motor 23. The preforms are brought upright, the neck upwards, by means of a slider 24 to a single load wheel 25 and of the step-by-step which brings the preforms under the transfer elements 26. The transfer elements are constituted in the form of an elongated endless chain that rotates around two end wheels and equipped with a succession of arrest organs 27 that grip the preforms 28 arranged with the neck up on the wheel 25, furthermore they return by rotating moving with the neck downwards through an oven 29 in which they are heated. At the exit from the oven, the hot preforms are grasped by the aforementioned rotating clamp, which rotates around the axis 15, to be introduced in the open mold 2. The drag of the previous elements is carried out in the following way. A pulley 30 is driven on the shaft 15 which, by means of an endless tie 31, like a toothed belt, drives a pulley 32 associated with an angle return 33 to animate one of the areas of the end 34 of the elements of transfer 26. As for the load wheel 25, this is attached to a coaxial gear (not visible in the drawing) which meshes with the endless chain forming the transfer elements 26 and is dragged by it. On the other side of the mold 2 there is provided a rotating extraction clamp (not shown) mounted on an axis 34 and arranged to grip the containers in the open mold., in addition to extracting them according to a schematized path in the form of a circular arc path 35 that brings them to the entrance of an exit slider 36. In a variant, these are expelled on the exit slider 36 by means of a rotary mechanism 37 In this case of the rotating clamp and the mechanism 37 are associated the coaxial pulleys of rotation drive 38 and 39, respectively, on which an endless linkage passes like a toothed belt 40 carried by a pulley 41 attached to the aforementioned axis. Thanks to the arrangement described, the installation is totally animated by a single motor, with no possibility of sliding from one mechanism with respect to the other, and all the movements are perfectly synchronized. Of course, auxiliary movement intakes can be provided to displace some moving components not previously mentioned, for example, displacement of the mold bottom, displacement of the elongation trunk, blow control, gas extraction from the molding cavity at the end of the operation, etc. These auxiliary components can also be animated by individual motors providing for a synchronization taken on one of the rotating members positively driven by the motor, for example, the pull zone of the extraction clamp. In another of the safety devices such as torque limiters can be associated with each rotating organ to detect any accidental overload and cause the immediate stop of the installation. Undoubtedly, and as it turns out, on the other hand, of the foregoing, the invention is not limited to these modes of application and realization that were especially considered; it covers, on the contrary, all the variants.