FR2662969A1 - Apparatus for the high-frequency moulding of plastic - Google Patents

Abstract

Apparatus for the high-frequency moulding of liquid or viscous plastic. It comprises a platform (platen) (13) which can move translationally, suitable for receiving a mould (m1, m2) and means for supplying the latter, a jib-crane (bracket) device associated with the stand (10) of the apparatus and a movable gantry-crane (portal-frame) device (71) of which is fitted with means (80) for gripping a part (m1) of the mould in order to open the latter, a high frequency generator for applying a field, mechanical means for driving the platform, the gantry-crane device and a press, and a programmer for controlling the succession of operations required for opening and/or closing the mould as well as for injecting plastic.

Description

 The invention relates to a high frequency plastic molding apparatus.

 There is already known, for example from FR-A-2 630 960, in the name of the Applicant, a process and a device for manufacturing molded plastic objects from liquid or viscous plastisol injected into a mold, which after filling under pressure and, if necessary, depression of its internal cavity is subjected to the action of a high frequency electric field of an appropriate generator. Such a technique is used, for example, for the manufacture of peripheral seals overmolded on panes or panes.

If the process and the device developed by the
The Applicant provides good results, the work carried out has however shown that it is still possible to improve them, in particular as regards the duration of the manufacturing time and the automation thereof.

 It is therefore a general object of the invention to provide an improved device for high-frequency molding of liquid or viscous plastic material, the operating possibilities of which are considerably increased compared to those of known devices.

 It is also an object of the invention to provide a device for high-frequency molding of liquid or viscous plastic material which makes it possible to obtain complex parts in a simple and safe manner with a high production rate.

An apparatus for high-frequency molding of liquid or viscous plastic material comprising a nozzle for injecting, into a mold, plastic material under pressure and a nozzle for connecting the cavity of said mold to the atmosphere or to a source of vacuum, with a double-acting valve device for controlling the opening and closing of said nozzles associated with each mold which it equips and which is made of a material having no dielectric loss is characterized, according to the invention, in what he understands
a plate movable in translation suitable for receiving the mold and the feed members thereof;
a bracket associated with the frame of the apparatus and of which a mobile gantry is provided with means for gripping part of the mold for the opening of the latter;
a shielding enclosure comprising an entry opening of the plate and which encloses a press capable of cooperating with the mold for maintaining the latter in closed condition under pressure during the application of the high frequency electric field;
a high frequency generator connected to said enclosure for the application of said field;
a moving assembly carrying quick coupling means for the connection of the mold supply members to a metering pump for injecting the liquid or viscous plastic material into the mold
mechanical means for driving the plate, the gantry, the press and the members associated therewith; and
a programmer to control the sequence of operations required to open and / or close the mold, inject plastic, close the pressure mold, apply the high-frequency electric field, extract the tray out of the enclosure and opening the mold.

 According to another characteristic of the invention, all the pipes, tubes and, in general, pipes for conveying the liquid or viscous plastic material arranged on the movable plate and which thus penetrate into the application enclosure of the high frequency electric field are connected to ground to form a Faraday cage and, thus, screen said electric field so that the plastic material, such as a liquid or viscous resin which remains enclosed in said pipes after the quick coupling device has been separated from the injection nozzles is not subject to said electric field.

Other characteristics and advantages of the invention will appear from the following description, given by way of example and with reference to the appended drawing in which
- Figure 1 is an overall plan view of the device according to the inventiqn;
- Figure 2 is a top view, on a larger scale, of a part of the apparatus;
- Figure 3 shows, in side view, the bracket and the mobile gantry of an apparatus according to the invention;
- Figure 4 illustrates the process of injecting plastic into a mold;
- Figures 5 and 6 are front and side views, respectively, of the press device of an apparatus according to the invention.

 Reference is first made to FIG. 1 which shows, schematically, the assemblies constituting an apparatus according to the invention, namely a table T for receiving a mold M, a press P enclosed in a bell or enclosure of shielding, a high frequency electric field generator G, connected by a connection C to the enclosure housing the press, a demolding assembly E consisting mainly of a bracket provided with a mobile gantry, a dosing pump D connected, of a on the one hand, to a reserve tank R of plastic material to be injected and, on the other hand, to a mobile assembly I comprising quick coupling means. A control panel D enclosing a programmer and a cooling group F are also part of the device.

 As shown in FIGS. 2 and 3, the table T is essentially constituted by a frame 10 resting on the ground by a base 11. On the frame are fixed two rails 12 serving for the translational guidance of a plate 13, which carries the mold M in two parts m1 and m2 with substantially horizontal joint plane and which is provided, for example, for the manufacture of a peripheral joint overmolded on the free edge of a glass or window pane. On the plate 13 can be coupled a cylinder 14, advantageously a pneumatic cylinder without rod with which is associated a drive and indexing toc for the translational movement of the plate between a position shown in solid lines and a position shown in dotted lines and which is the one in which the plate is inside the bell or shielding enclosure 15 enclosing the press P.

 The latter rests on a chassis 16, Figures 5 and 6, which carries a box spring 17 on which take # support cylinders 18, preferably flexible cylinders with membrane is known, which are intended to lift, in the direction of the arrow p , the movable plate 20 of the press P to bring it closer to the upper plate 21 of said press, both the plate 20 and the plate 21 comprising cooling means, most simply with circulation of supplied water and returning to the group of cooling F by pipes like 22 and 23.

The bell or shielding enclosure 15 has on its front face 25 opposite the table T an opening 26 allowing the introduction into the enclosure and the extraction from it of the mold carrier plate 13, a hatch 27 being provided for closing the opening 26 and which can be locked by a pivoting arm 28 intended to perfect and guarantee effective shielding against the radiation emitted by the generator
G and transmitted inside the bell 15 by the connection arm C.

 To obtain a satisfactory insulation also contributes two insulating cheeks 30a and 30b while, for the adaptation and the application of the high frequency field coming from the generator G, a variable capacitor 31 is housed in the enclosure 15 above of the upper plate 21 of the press while being carried by connecting rods 32 and 33 allowing it to be brought closer or further apart from said upper plate.

For filling the mold in plastic, liquid or viscous material, contained in the reserve R using the metering pump D, the invention provides organs for supplying and recovering the overflow of plastic material comprising, on the one hand, at least one double-acting valve device 40, made of TEFLON (a Brand
Registered with the company DU PONT DE NEMOURS) and which thus does not present a dielectric loss, end pieces 41 and 42 of quick couplings connected by pipes 43 and 44 to the valve device 40, -the said pipes being connected to ground to form Faraday cage and thus screen to the electric field, and, on the other hand, end pieces 45 of quick couplings connected by pipes 46 of pneumatic fluid to the valve device (s) 40. The ends 41, 42 and 45 are carried by a plate 50 placed in the vicinity of an edge 51 of small dimension of the plate 13 on which the tubes 43, 44 and 46 are fixed (the representation of FIG. 4 being schematic only).

 The device (s) 40, the plastic injection and discharge nozzles in the mold that it (s) control and these nozzles themselves are advantageously of the type of the devices described in FR-A-2 630 960, in particular Figure 2 of this Application which is explicitly referred to here. To connect the end pieces 45 and the pneumatic fluid lines 46 for controlling the valve devices 40, on the one hand, and also for the introduction and recovery of the surplus plastic material injected into the mold from the end pieces 41 and 42 and pipes 43 and 44, on the other hand, the device comprises, as shown in FIG. 4, a movable assembly I of which a plate 53 carries end caps 54, 55 and 56 forming quick couplings with the corresponding end caps of the plate 50. The crew I is designed to be driven in a translational movement in the direction of the double arrow f (which is the longitudinal direction of movement of the plate 13) but also in the direction of the double arrow g which is that up and down to allow precise positioning of the plate 53 opposite the plate 50 regardless of the thickness of the mold but also to allow to eclipse said crew under the table T in condi non-operative. To control the movement in the direction of the double arrow f, the crew I is connected to the rod 60 of a pneumatically actuated cylinder 61 while a cylinder 62 advantageously, also, pneumatic and whose rod is shown at 63 is provided for the upward and downward movement of said crew. As can be seen in FIG. 4, also, a flexible tube 65 connects the nozzle 54 to the metering pump D while a flexible tube 66 connects the nozzle 55 to a reservoir for collecting the excess plastic material injected into the mold.

 To further increase the possibilities of operating the device, the invention provides for associating with the table T a demolding assembly E consisting mainly of a bracket 70 on which is mounted a mobile gantry 71. The latter, which can be raised or lowered, -to the distance or to the approximation of the mold M when the plate 13 is in the condition shown in solid lines in FIG. 2 and in FIG. 3, that is to say facing the stem-, can also be inclined by an angle of about thirty degrees on the horizontal, -in order to facilitate the access of a mold attendant-, by pivoting around a horizontal axis 85.The vertical movement of the gantry 71 is advantageously controlled by a motor 72 placed in the upper part of the bracket 70 and which drives an endless screw 73 on which is mounted a nut 74 secured to the gantry via a plate 78, while a jack 75, whose rod 76 is articulated at 77 on the plate 78 carrying the bearings materializing the axis 85, makes it possible to tilt said gantry.

 For the opening of the mold M and the separation of its constituent parts m1 and m2, the gantry 71 is provided with gripping means 80, advantageously with pneumatic suction cups, of the part m2 of the mold (sometimes also known as counter mold) and safety arm 81.

 The operation of this device results immediately from the above and is explained below, -without this indication having any limiting nature whatsoever-, with reference to the manufacture of a peripheral seal overmolded on a window pane or glazing. The plate 13 and the mold M being in the condition shown in FIG. 3 and in solid lines in FIG. 2, that is to say facing the demolding assembly E, a window or glazing is placed on the lower part m1 of the mold M which is positioned on the plate 13 between small jacks 86 and 86 'which limit the crushing of the mold when the latter is introduced as explained below in the press P.

The counter mold m2 is then put in place on the mold part m1 and the triggering of a cycle, from the control panel D, causes, by means of the jack 14, the displacement of the plate 13 inside. of the shielding bell 15, the hatch 27 of which is then in the high position releasing the opening 26. At the end of introduction of the plate into the shielding bell 15, the programmer controls the jacks 61 and 62 to bring the crew I into look at the plate 50, on the one hand, then bring the end pieces 41, 42, 45 closer to the end pieces 54, 55, 56 and make the connection of the pipes linked to these end pieces.

The liquid or viscous plastic material is then transferred under pressure by the metering pump D from the reserve R into the mold after passing through the valve device (s) 40, the injection being carried out at ambient temperature until completely filling the mold and the excess plastic being collected, if necessary, in a pot or settling tank from which the material can be recycled. After filling the mold, the moving element I is again moved to decouple the end pieces 41, 42, 45 from the end pieces 54, 55, 56, the hatch 27 is closed and the pivoting arm 28 made operative to lock it. jacks 18 moves the movable plate 10 of the press when the plate 21 is brought closer to keep the mold under pressure during the polymerization of the plastic material injected under the effect of the high frequency field applied by the generator G. At the end of this phase, during which the upper 21 and lower 20 plates are cooled by circulation of water, the arm 28 is released, the hatch 27 open and the jack 14 which carries a drive for the plate 13 is again rendered operative to hang on said plate, on the one hand, and extract it from the shielding bell, on the other hand. When said plate is again facing the demolding assembly E, the pneumatic means 80 of the movable gantry 71 are made operative to grip the counter mold m2, the gantry being then moved to move the countermold from the part m1 and allow the extraction of the window or glazing provided with its overmolded seal.

Claims (5)

 1. Apparatus for high-frequency molding of liquid or viscous plastic material comprising a nozzle for injecting, into a mold, plastic material under pressure and a nozzle for connecting the cavity of said mold to the atmosphere or to a source of vacuum, with a double-acting valve device for controlling the opening and closing of said nozzles associated with each mold which it equips and which is made of a material having no dielectric loss, characterized in that it comprises  a plate (13) movable in translation suitable for receiving the mold (M) and feed members thereof;  a bracket (E) associated with the frame (10) of the apparatus and of which a mobile gantry (71) is provided with means (80) for gripping a part (m1) of the mold for the opening of the latter;  a shielding enclosure (15) comprising an inlet opening (26) of the plate (13) and which encloses a press (P) capable of cooperating with the mold to maintain the latter in the closed condition under pressure during the application of the high frequency electric field;  a high frequency generator (G) connected to said enclosure (15) for the application of said field;  a movable assembly (I) carrying means (54, 55, 56) of quick couplings for the connection of the mold supply members to a metering pump (D) for injecting the liquid or viscous plastic material into the mold ( M);  mechanical means for driving the plate, the gantry, the press and the members associated therewith; and  a programmer to control the sequence of operations required for opening and / or closing the mold, injecting plastic, closing the pressure mold, applying the high frequency electric field, extracting the tray out of the enclosure and opening the mold.  2. Apparatus according to claim 1, characterized in that all the pipes, tubes and conduits (43, 44) for conveying the liquid or viscous plastic material arranged on the movable plate (13) and which thus penetrate into the enclosure (15) of application of the high frequency electric field are connected to ground to form a Faraday cage and, thus, a screen for said electric field.  3. Apparatus according to any one of Claims 1 or 2, characterized in that the movable assembly (I) carrying the means (54, 55, 56) of quick couplings is movable horizontally and vertically so as to be able to be eclipsed under the plate (13) in its unconditioned condition -operative.  4. Apparatus according to any one of Previous claims, characterized in that the mold (M) is placed on the plate (13) between actuator type devices (86, 86 ') intended to limit the crushing of the mold in the press (P).  5. Apparatus according to any one of Previous claims, characterized in that the mobile gantry (71) is mounted with the possibility of pivoting around a horizontal axis (85) of a plate (78) movable vertically in translation.