FR2720676A1 - Plasticizing and injection unit for injection molding machines for the manufacture of rubber or plastic articles. - Google Patents

Abstract

The invention relates to a plasticizing and injection unit for injection molding machines for the production of rubber or plastic articles, comprising a plasticizing screw (13) rotating in a screw cylinder (14) and movable. axially in a screw antechamber (5), the end of which facing said screw antechamber (5) is equipped with a non-return system (27) movable in synchronism with said screw, in the direction of flow of the material of rubber or plasticized plastic, a filter screen (28) which completely covers the free section for the passage of the flow of rubber material or plasticized plastic material being arranged, upstream of the non-return system (27), in such a way way that it can be moved in the screw antechamber (5), in synchronism with the plasticizing screw (13) and the non-return system (27).

Description

Laminating and injection unit for rear molding machines

  The invention relates to a plasticization and injection unit for injection molding machines for the manufacture of rubber or plastic articles, comprising a rotating plasticization screw. in a screw cylinder and axially displaceable in a screw anteroom, the end of which faces towards said screw anteroom is equipped with a non-return system movable in synchronism

with said screw.

  Plasticization and injection units of this type are described for example in the German patents DE 32 47 272 C2, DE 37 02 191 C2, DE 37 17 735 CI and DE 40 38 843 C2. They serve on the one hand to bring the rubber or the plastic material to be plasticized introduced by the rotational movement of the plasticizing screw into the screw cylinder, at the end of said screw cylinder opposite to the injection mold, from the solid state in the flowing state and, on the other hand, to be injected, by means of the axial displacement of the plasticizing screw into the screw anteroom, the rubber or the plastic material accumulated in said screw anteroom within an interval of predetermined time - as short as possible and under predetermined pressure, in the cavity (ies) of the injection mold. The respectively installed anti-return system prevents rubber or plasticized plastic from returning during the injection process into the screw cylinder instead of flowing into the cavity (ies)

of mold.

  The advantage offered by these plasticization and injection units lies notably in the fact that they require fewer mobile elements than a system made up of a particular plasticization unit and an injection unit. additional powered by it, which in all cases leads to a reduction in costs, and that they also have a smaller footprint than a two-part system formed by a plasticizing unit and a injection unit, which generally also brings economic benefits. However, the aforementioned plasticization and injection units - in a single part - have the drawback that, even after at least ten years of use and improvement, they offer no possibility of compensating once again - at least partially - before the injection process, possible differences between the rubber or the plasticized plastic injected into the anteroom of the screw with regard to the degree of melting and / or the mixture with additives which are not introduced only together with the starting material in the plasticizing cylinder, or to retain the insufficiently melted starting material or fortuitous agglomerations of additives, especially minerals - or even foreign bodies accidentally reaching the plasticizing screw, before they do not reach the main channel or the carrot channel system towards the mold cavity (ies). Often, however, this has the effect that, in less severe cases, the rubber or plastic articles have a variable composition and therefore of poor quality, so that in case of doubt, they must be disposed of as waste. , whereas in more serious cases, there are blockages of the main channel or of the system of carrot channels and respectively of the dies coupled with these, which implies a shutdown of the whole machine injection molded for cleaning and maintenance

long and expensive.

  For plasticizing screws for the continuous plasticization of rubber or plastic intended for example for the supply of flat dies for the manufacture of sheets or plates or blow molds for the manufacture of flexible pipes, it was certainly known until 'here, at least since the publication of British patent GB I 011 950, to install at the outlet of the plasticizing cylinder a fixed interchangeable filter screen in the form of a "strainer", but a transposition of this system to the plasticization and injection units considered - in a single part - in the revealed form proved to be impossible. It would have involved the installation of such a filtration system at the outlet of the screw anteroom. This would however have the effect that - unlike continuous lamination with only small pressure differences at the outlet of the lamination cylinder - said filtration system would be exposed to each injection process to considerable compression forces due to the rubber or plasticized plastic to be expelled from the anteroom of the screw, which would already result in itself - for rubber injection molding machines, injection pressures of 2000 bar are not unusual - immense wear and therefore frequent changes to the filtration system, with the corresponding unprofitable machine downtime required for repair and maintenance work, not to mention the fact that stronger components included in the plasticized material such as incompletely melted starting material, agglomerations of additives - granular (fine-grained) - and / or foreign bodies have sunk with considerable kinetic energy into the system of

  filtration and very quickly cause its engorgement and destruction.

  The present invention therefore aims to create for plasticization and injection units for injection molding machines for the manufacture of rubber or plastic articles, comprising a plasticization screw rotating in a screw cylinder and movable axially in a screw anteroom, the end of which faces towards said screw anteroom is equipped with a non-return system displaceable in synchronism with said screw, a filtration system which makes it possible, on the one hand, to compensate in a very large measure of slight differences in the degree of melting and / or mixing with additives inside the rubber or plasticized plastic material penetrating into the anteroom of the screw, and this even before this passes into said anteroom of screws, and on the other hand, to retain more solid constituents interposed in the rubber or plasticized plastic material, for example d u partially melted starting material and / or agglomerations of additives - granular (fine-grained) - and / or foreign bodies, so that these can be removed by occasional cleaning of the

  filtration which can then be used again.

  According to the invention, this object is achieved by the fact that, in the direction of flow of the rubber or plastic material, a filter screen completely covering the free section for the flow of the rubber or plastic material stream. plasticized is arranged upstream of the non-return system in such a way

4 2720676

  that it can be moved in the anteroom of the screw, in synchronism with the screw

  laminating and anti-return system.

  This arrangement is particularly advantageous because it has the effect that all of the rubber or plastic material passes through, before reaching the screw anteroom, a filtration system in the form of a screen which, on the one hand, automatically subjects it to an additional internal stirring and, on the other hand, rids it - depending on the width of the mesh of the filter screen - of the solid or fairly solid constituents possibly intercalated by retaining them, without the filter screen being exposed to pressure forces considerable causing wear by the rubber or plasticized plastic material expelled at each process of injection of the screw anteroom into the cavity (ies) of the mold, taking into account the fact that, in the present case, the filter screen is crossed by the rubber or plasticized plastic material only during the respective filling period of the screw anteroom - which takes place exclusively at small pressure differences - but that

  this current is interrupted during each injection process by the anti-system

  return. Unexpectedly, the operation of a plasticization and injection unit according to the invention revealed the frankly advantageous additional effect that the filter screen causes very effective degassing of the rubberized or plasticized plastic material, the gas which accumulates in the space between the filtering screen and the non-return system which can be evacuated from the plasticization and injection unit by means of a ventilation device of well known type. This results in further improvement and homogenization of the rubber or material articles.

plastic respectively produced.

  In accordance with another particularity of the plasticization and injection unit according to the invention, it is also advantageous that the filtration system in the form of a screen is interchangeable, since such a construction of suitable type, for example a filter screen consisting of two semi-circular filter frames with corresponding filter plates and which can be mounted, by means of well-known screw or quick-clamp fittings, on the tip of the plasticizing screw, between the ends of the screw and non-return system, considerably facilitates the occasional cleaning of the filter screen, especially if there is another filter screen of this type, so that the operation of the injection molding machine must not be interrupted that for the release and respectively the insertion of the tip of the plasticizing screw, for example by the temporary removal of part of the plasticizing screw, e t for the replacement of the filter screens between them, while the actual cleaning of the filter plate can be done outside the injection molding machine, during its subsequent operation. In a particular embodiment of the plasticizing and injection unit according to the invention, it is further advantageous that the plasticizing screw can be moved, together with the screw cylinder, in the screw anteroom, being since in this case access to the filter screen can be considerably simplified and accelerated by designing the device for the synchronous movement of the plasticizing screw and the screw cylinder in the screw anteroom so that it can also ensure a synchronous outlet of the ends of the plasticizing screw and of the screw cylinder plunging into the screw anteroom, a particular advantage consisting in that the filter screen and the non-return system are maintained by the screw cylinder in a position defined in front of the end of the plasticizing screw facing

the screw anteroom.

  A particular advantage is also offered by an embodiment of the plasticization and injection unit considered in which the screw cylinder carries at its end turned towards the screw anteroom, an insert element in the form of a cap shaped at the top. piston of the piston-cylinder system formed by the screw cylinder and the screw anteroom and intended for the injection of rubber or plasticized plastic material into one or more mold cavities, which attached element is so coupled removable with the screw cylinder, keeps the filter screen and the non-return system inside in the predetermined position in front of the end of the plasticizing screw facing the screw anteroom, and has an outlet opening for plasticized rubber or plastic material, directed towards the screw anteroom, since this construction brings a reduction all t quite considerable of the time interval required for the replacement of a filtration system to be cleaned by a perfectly operational filtration system, in particular if, on the one hand, use is made for blocking the insert element in cap shape on the screw cylinder, a screw connection, quick-tightening or direct threading of a well-known type, or if, on the other hand, inside the hat-shaped insert, the screen filter is positioned only by suitable stops between the non-return system, the cap-shaped insert and the end closest to the screw cylinder. In this case, it has been found that it is possible to achieve replacement intervals of the order of I to 2 min, taking into account the simplicity of handling, this operation can also be carried out at the temperature of normal service, whereas corresponding measures, for example the replacement of non-return systems or parts thereof - normally require, for prior art injection molding machines, time intervals of

  about half an hour to an hour.

  An advantage is also provided by a particular feature of the plasticization and injection unit according to the invention in which the filter screen consists of several wire mesh arranged one behind the other and maintained in the predetermined arrangement by a frame of adequate construction, since such devices are in principle well known and tested, so that, on the one hand, they do not give rise, during their manufacture, nor in service, or for their cleaning, to problems or particular disturbances and that, on the other hand, they are easy to handle, which has the effect of further facilitating their replacement on a plasticization and injection unit of the kind considered, in particular if the frame is made up of two mounts in the form of plates provided with suitable openings, which receive in a common recess the wire mesh and are assembled therewith. u by means of well-known connecting elements, for example screws or

  bolts, to form a package-like block.

  The description which follows, with reference to the drawings annexed as examples

  non-limiting, will make it possible to understand clearly how the invention can be implemented

convenient.

  FIG. 1 represents, diagrammatically, a vertical section of a significant part for the invention of a rubber injection molding machine of the well known type, with filter screen integrated between the end on the mold side of the plasticizing screw and the upstream anti-return system; 2 shows, on a larger scale, a detail of the filter screen according to the invention according to FIG. 1 and its arrangement in the region of the mold side end of

the associated plasticizing screw.

  Fig. 1 first shows a part of a rubber injection molding machine mounted on the upper end 1 of a closing device operating in a vertical position - disclosed for example in German patent DE 40 38 843 C2 - which is not shown here explicitly in the interest of a better overview, which comprises on the one hand a plasticizing unit 2 and, on the other hand, a drive group 4 shaped as a piston-cylinder 3 for injecting a mixture of plasticized rubber into the mold cavity (ies) provided in the locking system not shown, as well as a cylinder block 6 forming an anteroom of screws 5, followed by a return device 7 which carries the injector 8, the latter opening into a not shown carrot channel or into the corresponding inlet of a carrot channel system. The cylinder block 6, the deflection device 7 with the injector 8 and the end, opposite the piston 9, of the piston rod 10 of the drive group 4 for the injection of the plasticized material which is considered here as being a mixture of plasticized rubber, but which can also be constituted, in an injection molding machine, by a plasticized plastic material, are force fitted on the upper end 1 of the mechanism

  locking by means of a reception system 11.

  The plasticizing unit 2 basically consists of a plasticizing screw 13 coupled with a rotational drive system 12, and a screw cylinder 14 enveloping the latter, said screw cylinder carrying on the one hand a stop bridge 15 on which act anchor rods invisible in the present representation and located in the same horizontal plane as the screw cylinder 14, the other ends of which are coupled by adhesion with stops 16 on the cylinder casing 17 mobile of the drive unit 4 for injection, and having on the other hand, at the end of the plasticizing screw 13 opposite the screw anteroom 5, a filling opening 18 for the introduction of bands 19 of raw material in the screw cylinder 14. The end section 20 of the plasticizing screw 13 facing the screw anteroom 5 is provided with a non-return system as well as a filter screen and is shaped, moreover , of such so that it acts in the anteroom of screw 5 as a piston for the injection of the plasticized material via the return device 7 and the injector 8 into the mold cavity (ies), when the cylinder housing 17 of the piston-cylinder system 3 is moved in the direction opposite to the anteroom of

screw 5.

  A possible embodiment of the end section 20 of the plasticizing screw 13 is shown in detail in FIG. 2. The screw cylinder 14 which envelops the plasticizing screw 13 here carries an insert in the form of a cap 21, the open end of which faces the screw anteroom 5 and which, in the case shown, must be considered as being blocked on the screw cylinder 14 by means of a direct screwing 22. This blocking can naturally also be achieved with any other suitable variant of well-known type, for example using screw connections oriented radially by relative to the axis of rotation of the plasticizing screw 13, spring-controlled and suitably oriented bolts, bayonet sockets or similar quick-connect fittings. The cap-shaped insert 21 has, in its part opposite the end of the plasticizing screw 13, an outlet opening 23 which, when pressure is applied to the side of the insert 21 in cap-shaped, on the plasticized rubber (or plastic) material accumulated in the anteroom of screw 5 in front of the outlet opening 23, is closed by a non-return system 27 constituted here by a

  ball 24, cage 25 and valve seat 26.

  Between the end of the screw cylinder 14 and the valve seat 26 is also disposed, inside the insert 21 in the form of a cap, a filter screen 28 according to the invention which is composed of two mounts 30, 31 in the form of plates provided with suitable openings 29, and several lattices 33 of metal wire placed one behind the other in a common recess 32 constituted by the mounts 30, 31 in the form of plates. The entire filtration system 28 is assembled by means of suitable connection elements 34, for example screws or bolts, in a packet-shaped block which, in the case shown, is unequivocally positioned in the assembly of the system shown, by the sole application against surfaces of the screw cylinder 14, of the insert 21 in the form of a cap and of the valve seat 26, formed into suitable stops. This allows a rapid replacement of a filtration system to be cleaned 28 by a perfectly operational filtration system of the same type, in particular if the piston-cylinder system 3 shown in FIG. 1 is designed in such a way that it allows not only to draw the end section 20 of the plasticizing screw 13 still engaged in the screw anteroom 5, even more deeply in said screw anteroom 5, but also to remove it completely ,

  if necessary, of said screw anteroom 5.

  Of course, the present patent application does not only relate to the embodiment of a plasticization and injection unit according to the invention shown and explained in detail with reference to FIGS. 1 and 2, but it also relates to any conceivable embodiment of the plasticization and injection unit considered, characterized in that, in the direction of flow of the rubber or plasticized plastic material, a screen filter (28) completely covering the free section for the passage of the current of rubber or plasticized plastic material is arranged, upstream of the non-return system (27), so that it can be moved in the anteroom screw (5), in synchronism with the screw

  plasticization (13) and the non-return system (27).

  List of references 1 Upper end of the locking system of a rubber injection molding machine 2 Laminating unit 3 Piston-cylinder system 4 Drive unit for injection Screw anteroom 6 Cylinder block 7 Return device 8 Injector 9 Piston Piston rod 11 Reception 12 Rotary drive 13 Plasticizing screw 14 Screw cylinder Stopper bridge 16 Stops 17 Cylinder housing 18 Filling opening 19 Strips of raw material Terminal section of the plasticizing screw facing towards screw anteroom 21 Cap-shaped insert 22 Screw connection 23 Outlet opening 24 Cage ball 26 Valve seat 27 Non-return system 28 Filter screen 29 Openings, 31 Plate-shaped mounts 32 Recess 33 Wire mesh 34 Connection elements 1!

Claims (8)

  1. - Plasticizing and injection unit for injection molding machines for the manufacture of rubber or plastic articles, comprising a plasticizing screw rotating in a screw cylinder and moved, axially cabled in a screw anteroom , the end of which faces towards said screw anteroom is equipped with a non-return system displaceable in synchronism with said screw, characteristic 6 th that, in the direction of flow of the rubber or plasticized plastic material, a filter screen (28) entirely covering the free section for the passage of the stream of rubber or plasticized plastic material is arranged, upstream of the non-return system (27), in such a way that it can be moved in the '' screw anteroom (5), synchronized with the plasticizing screw (13) and the system non-return (27).   2. - plasticization and injection unit according to claim 1, characterized in   that the filter screen (28) is removably mounted.   3. - plasticization and injection unit according to one of claims 1 or 2,   characterized in that the plasticizing screw (13) can be moved together   with the screw cylinder (14), in the screw anteroom (5).   4. - plasticization and injection unit according to claim 3, characterized in that the filter screen (28) and the non-return system (27) are held by the screw cylinder (14) in a position defined in front of the end (20) of the plasticizing screw   (13) facing the screw anteroom (5).   5. - plasticization and injection unit according to one of claims 3 or 4,   characterized in that the screw cylinder (14) carries at its end turned towards the screw anteroom (5), an insert (21) in the form of a cap shaped as the piston head of the piston-cylinder system formed by the screw cylinder (14) and the screw anteroom (5) and intended for injecting rubber or plasticized plastic material into one or more mold cavities, which insert is detachably coupled with the cylinder screw (14), keeps inside the filter screen (28) and the non-return system (27) in the predetermined position in front of the end (20) of the plasticizing screw (13) facing the anteroom screw (5), and has an outlet opening (23) for the rubber material or material   plasticized plastic, directed towards the anteroom of screw (5).   6. - plasticization and injection unit according to claim 5, characterized in that, inside the insert (21) hat-shaped, the filter screen (28) is positioned only by adequate stops between the non-return system (27), the insert (21) in the form of a cap and the end closest to the screw cylinder (14). 7. - Plasticization and injection unit according to any one of   Claims 1 to 6, characterized in that the filter screen (28) consists of   several wire mesh (33) arranged one behind the other and held   in the predetermined layout by a suitable construction frame.   8. - plasticization and injection unit according to claim 7, characterized in that the frame consists of two mounts (30, 31) in the form of plates provided with suitable openings (28), which receive in a common recess (32) the trellis (33) of metal wire and are assembled with these by means of connection elements (34) well known, for example screws or bolts, to constitute a block shaped package.