WO2003055662A1 - Tie bar-less injection machine - Google Patents

Abstract

The invention concerns an injection machine comprising a frame (1), at least a U-shaped force recovery member (6), two fixed platens, each fixed platen being supported at the rear on a branch of the U-shape, a mobile mould-holder plate (3), sliding between the two fixed platens, and a device (5) for displacing the mobile platen (3). Each branch of the U-shape comprises two lower (19) and upper (24) elastically deformable spaced apart support zones, located respectively above and beneath the main axis (X-X') of the machine, for the fixed platens (2, 4). The invention is useful for injection-moulding of plastic materials.

Description

 I

Injection molding machine without columns

The present invention relates to a plastic injection press, of the type described in the preamble of claim 1.

The advantage of such presses, called “columnless presses”, resides in the fact that the U-shaped force-absorbing member makes it possible to eliminate the two upper tie rods for connection of the mold-carrier plates, and consequently to release access to the assembly / disassembly space of the two half-molds.

Numerous technical solutions have been proposed to enable injection presses of the above type to operate satisfactorily under real industrial conditions. The difficulty stems from the fact that, during the injection phases of the plastic material into the mold, under the effect of the very high closing forces of the mold which must be developed to balance the injection pressure, the two branches of the U of the recovery organ, e strong tend to open and lose their parallelism. This can be the cause of leaks at the level of the mold seal.

The invention aims to solve the problem of maintaining the parallelism of the two mold carrier plates in a particularly economical and effective manner.

To this end, the subject of the invention is an injection press of the aforementioned type, characterized by the characterizing part of claim 1.

The injection molding machine according to the invention can include one or more of the features of claims 2 to 23.

Examples of embodiments of the invention will now be described with reference to the accompanying drawings, in which: - Figure 1 is a schematic side view of an injection press according to the invention; FIG. 2 schematically illustrates, on a larger scale and with exaggeration, the deformation phenomena which occur during the injection phase;

- Figures 3 to 6 are views similar to Figure 2 of several variants;

- Figure 7 is a view similar to Figure 1 which shows another embodiment of the press according to the invention;

- Figure 8 shows in perspective another embodiment of the suspended flange for the press according to the invention;

- Figure 9 is an end view of a variant of the flange of Figure 8, on a smaller scale;

- Figure 10 shows in perspective a variant of the press of Figure 7, using two flanges similar to that of Figure 8; and

- Figure 11 is a similar view of another press according to the invention.

The injection press shown in FIG. 1 comprises:

- a frame 1 placed or fixed to the ground;

- a fixed mold carrier plate 2;

- a movable mold holder plate 3;

- a second fixed plate or bed base 4, - - a device 5 for moving the movable plate and for locking the closing of the mold; and

- Two lateral flanges 6 for taking up the closing forces of the mold, for example cut from a thick sheet. On each plate 2 and 3 is fixed a half-mold 7.

The mold is shown in the closed position in FIG. 1.

One of the two fixed plates, for example the plate 2, is fixed to the frame, while each of the other two plates 3, 4 is placed on respective slides 8, 9 and free to slide thereon. The box spring 4 carries a actuator body 11, the assembly 12 of which forms a piston rod is connected to the movable plate 3. As shown, carriages 203 with recirculating balls can be mounted between the underside of the plate 3 and the slides 8. Each flange 6 has a generally U-shaped. The branches of the U have, on the inside, a profiled notch 13, so that the end portions 14 of the two branches of the U, adjacent to these notches, are directed towards one another. These end parts are fixed to support cross members 15 projecting from the side provided on the upper part of each fixed plate 2, 4. Each part 14 may also have a recess 16 in its upper face, as shown.

In the region of the base of each branch of the U, each flange 6 is cut so as to define a tongue 17 of converging shape having a generally vertical direction, directed upwards, and, on the front or interior side of this tongue, an opening 18. The front face of each tongue is flat and vertical at least in its free end region 19, and an oblique slot 20 runs along the rear or outside side of the tongue.

Each fixed plate 2, 4 has in its lower region two projecting lateral cross members 21 each of which has a vertical rear face 22 which is applied, by simple support plane on plane, on the region 19 of the associated tongue 17.

As a variant, the suspension of each flange can be carried out by fixing the crosspieces 21 on the tabs 17, with the crosspieces 15 in rear-to-plan support on the end portions 14 of the U, along respective vertical surfaces 23, 24. In another variant, provision can be made to fix each flange both on the crosspieces 15 and on the crosspieces 21.

The main axis XX ′ of the press, defined by the centers of circular cutouts 102, 103 of the plates 2 and 3 which serve to center the half-molds 7, is at one level. intermediate calf of the U-shaped branches. It constitutes the injection axis, the injection taking place through the cutout 102, and coincides with the central actuation line of the jack 11-12. When the cylinder 11-12 has closed the mold and applies along the axis XX 'the locking force which makes it possible to balance the high injection pressure of the plastic material, there is a displacement of the plate 4 to the left of FIG. 1. This displacement is strictly parallel to the axis XX ′, without any tendency for one plate to tilt relative to the other.

Indeed, the plate 4 is guided in sliding by its lower part by the slide 9, and the force is applied on the end faces 24 and on the upper regions 19 of the tongues 17. The bending of these, permitted by the presence of the slots 20, leads, on each side of each flange, to identical elastic displacements of the upper 24 and lower 19 support zones, which prevents any tendency to tilt of the plate 2 as of the plate 4.

Figure 2 illustrates, with a strong exaggeration, the deformations of the right part of the flange. Analogous elastic deformations occur simultaneously in the left-hand side, considering FIG. 1, of the flanges, that is to say on the side of the bed base 4.

The variant of FIG. 3 differs from the previous one in that the tongues 17 are directed downwards and have a front support side inclined downwards and backwards, at least in their free end region 19 The crosspieces 21 have a rear support surface 22 correspondingly inclined.

When applying the locking force of the mold, this configuration of the tabs causes the application on them of a torque in the opposite direction to that which applies to the upper parts 14, which further reinforces the anti-tilt effect explained above. It should be noted that in this case, the notches 13 can have a simple shape, in particular roughly semi-circular as shown in FIG. 3.

In the variant of FIG. 4, each tongue 17, directed downwards, is located on the inner side of the branch of the corresponding U, which gives it a general shape in C. The front bearing face 19 of the tongue is vertical and coplanar with the upper bearing surface 24. The notch 13 connects the bearing surfaces 19 and 24. The rear side of the tongue is convex and delimited by an arcuate slot 20, which ends, in the region of the axis XX ′, by a substantially circular opening 25 for stress relief.

As shown in FIGS. 5 and 6, in a variant, an intermediate piece 26 of elastic compression, having a predetermined elastic modulus, can be placed in the slot 20 to perfect the control of the rearward movement of the zone of support 19. This intermediate piece may for example be a longitudinally compressed bar (FIG. 5) or a ring (FIG. 6).

As a variant, the bed base 4 can be fixed to the frame and the plate 2 can be slidably mounted thereon. In another variant, each of the two fixed plates 2, 4 can be slidably mounted on the frame. The injection press shown in Figure 7 differs from that of Figure 1 in that the flanges 6 are placed or fixed on feet 27 themselves placed or fixed to the ground.

Consequently, it is the plates and the device 5 which are suspended from the two flanges, and this by the four crosspieces 15 and 21 fixed to the surfaces 24 and 19. The slides 9 are eliminated, while the slides 8 are replaced by two supports suspended 28. These supports 28 are fixed at one end to a fixed plate, here the plate 2, and slide by their other end in openings. respective vertices 29 of the other fixed plate, here the plate 4. Any other frame element is thus eliminated.

The supports 28 may consist of rails, columns or any other similar element. In this embodiment, the two flanges 6 constitute the only frame elements of the press. In addition, the guidance of the movable plate is provided by two members 28 which do not undergo any deformation when unlocking the closure of the mold, which makes this guidance precise and reliable.

It should be noted that in each embodiment, the flanges can, as shown, be largely visible at 30 in their central region, which is subjected to low stresses in service. The lights 30 serve on the one hand to lighten the flanges without reducing the mechanical performance, and on the other hand to evacuate the molded parts after opening the mold.

The flange 106 shown in Figure 8 differs, in essence, from that of Figure 1 by removing the cutouts which define the tongues 17 and the openings 18. The lower bearing surfaces 19 are vertical and parallel to the surfaces d 'upper support 14. They are provided, on each side, on an auxiliary rectangular plate 31, fixed by its only lower region on the internal face of the latter, for example, as shown, with the interposition of a spacer plate 32. Each plate 31 has under its surface 19 a notch 33 similar to the notch 13 and which allows the elastic displacement of the surface 19 parallel to itself during injection. As a variant (FIG. 9), the spacers 32 can be replaced by an extra thickness 132 of the lower region of the plates 31.

Figure 10 shows a press similar to that of Figure 7 but equipped with two flanges 106. In this embodiment, the projections 15 and 21 of the end plates are eliminated. These trays, on the contrary, have a lower part 34 of reduced width which is inserted between the flanges 106 and bears on the surfaces 19, while the current part of the same plates, of greater width, bears directly on the upper faces 24.

In this FIG. 10, the flanges 106 and their plates 31 are fixed to feet 127 fixed or placed on the ground which carry the entire press, as in FIG. 7. The upper part of the feet 127 can possibly form the spacers 32 The guidance and the support of the movable plate 3 are obtained in a similar manner to FIG. 7. More precisely, two columns 128 are used for this purpose, fixed to the fixed plate 2 and sliding in the other fixed plate 4, these columns passing through conjugate lower orifices 35 of the plate 3.

As can be seen in FIG. 10, the plate 3 also has a narrowed lower part 34, disposed between the two flanges 106. This plate, like the plates 2 and 4, thus has a running part wider than the interval which separates the two flanges, which allows larger molds to be accepted.

As shown in FIG. 10, or can supplement this press by an injection frame 36, intended to carry the injection device for the press (not shown), which is in the form of a square. This chassis 36 is rigidly fixed, on one side, to the underside of the fixed plate 2, thus ensuring the precise positioning of the injection device relative to the closing device 5. On the other side, the chassis 36 is placed on the ground by two feet 37, which are the only feet of this chassis.

The press in Figure 11 differs from that in Figure 10 in the following points:

- The frame 36 comprises, in addition to the two outer legs 37, two inner legs 38, and is placed or fixed to the ground; - The fixed plate 2 is fixed on the chassis 36 and is therefore carried by the latter;

the feet 127 on the chassis side 36 are omitted, and the flanges 106 are, on this side suspended from the plate 2, by the regions 24 and 19, and free relative to the chassis 36.

As can be understood, when one of the two fixed plates is rigidly secured to an assembly placed or fixed to the ground, as is the case with the plate 2 in FIG. 11, the support and guide elements 28 (FIG. 7 ) or 128 (Figures 10 and 11) can be fixed to said assembly at one end and, at the other end, slide into openings 29 of the other fixed plate.

As a variant, the plates 31 can be fixed on the external face of the flanges 106.

Claims

1. Plastic injection press, of the type comprising: - means (1; 6; 106, 127; 106, 127, 36) which form a press frame; - at least one force recovery member (6), U-shaped; - Two fixed plates (2, 4), namely a fixed mold carrier plate (2) and a box spring (4), carried by the frame, each fixed plate being in rear support on a respective branch of the U; - a movable mold-holder plate (3), slidingly guided between the two fixed plates by a support and guide assembly (8; 28; 128); and - A device (5) for moving the movable plate (3) and for locking the closing of the mold (7), which rests on the one hand on the movable plate (3), on the other hand on the bed base (4 ), characterized in that each branch of the U comprises on the one hand an upper support zone (24) situated above the main axis (X-X ') of the press, on the other hand a zone d 'lower support (19) located below this axis and spaced from the upper support area, each support area being elastically deformable substantially parallel to the axis (X-X') and applying to a region of respective support (22, 23) of one of the fixed plates (2, 4). 2. Injection molding machine according to claim 1, characterized in that the three plates (2 to 4) and the device (5) for movement and locking are carried by the frame (1), and in that the force recovery member (6) is suspended from the two fixed plates (2, 4) by its upper support area (24) and / or by its lower support area (19) • 3. Injection press according to claim 2, characterized in that one of the fixed plates (2, 4) is fixed to the frame (1), while the other is slidably mounted on this frame. 4. Injection molding machine according to claim 2, characterized in that each of the two fixed plates (2, 4) is slidably mounted on the frame (1). 5. Injection molding machine according to claim 1, characterized in that the force recovery member (6) is fixed or placed on the ground, and in that the two fixed plates (2, 4) are suspended from the upper support zone (24) and / or the respective lower support zone (19) of this member. 6. Injection molding machine according to any one of claims 1 to 5, characterized in that the assembly (28; 128) for supporting and guiding the movable plate (3) is fixed by one end to one ( 2) two fixed plates (2, 4) or an element (36) integral with this plate, while its other end is slidably carried by the other fixed plate (4). 7. Injection press according to any one of claims 1 to 6, characterized in that the support and guide assembly of the movable plate (3) comprises at least one elongated support and a guide carriage (203 ) interposed between the movable plate and this support. 8. Injection molding machine according to any one of claims 1 to 7, characterized in that the lower support zones (19) are located in the vicinity of the base of the branches of the U. 9. Injection molding machine according to any one of claims 1 to 8, characterized in that each branch of the U has on its inner side, between the upper and lower bearing zones, a profiled notch (13). 10. Injection molding machine according to any one of claims 1 to 9, characterized in that each lower support zone is defined by an elastic tongue (17) deformable substantially parallel to said axis (X-X '), cut in the force recovery member (6). 11. Injection press according to claim 10, characterized in that the force recovery member (6) has a slot (20) on the rear side of each tab (17). 12. Injection press according to claim 10 or 11, characterized in that the force recovery member (6) has an opening (18) on the front side of each tongue (17), and in that each lower support region (22) of each fixed plate (2, 4) is carried by a lower support relief (21) which enters the associated opening and is applied against the corresponding tongue. 13. Injection press according to claim 10 or 11, characterized in that each tongue (17) defines the inner edge of the U, each branch of the U having a general shape in C. 14. Injection press according to any one of claims 10 to 13, characterized in that the support zone (19) of each tongue (17) is substantially vertical. 15. Injection molding machine according to any one of claims 10 to 13, characterized in that the tongues (17) are directed downwards, and in that the support zone (19) of each tongue is inclined downwards and backwards. 16. Injection press according to any one of claims 10 to 13, characterized in that an intermediate piece of elastic compression (25) is arranged in each lumen (20) delimiting at the rear a tongue (17 ). 17. Injection molding machine according to any one of claims 1 to 9, characterized in that each lower support area (19) is defined by a first end of an auxiliary plate (31) of elongated shape, the other end of which is attached to the U. 18. Injection molding machine according to claim 17, characterized in that said first end is the upper end of the auxiliary plate (31). 19. Injection press according to claim 17 or 18, characterized in that the auxiliary plate (31) has on its inner side a profiled notch (33). 20. Injection press according to any one of claims 17 to 19, characterized in that said other end (132) of the auxiliary plate (31) forms an excess thickness of the plate. 21. Injection molding machine according to any one of claims 1 to 20, characterized in that it comprises two lateral force recovery members (6). 22. Injection press according to any one of claims 1 to 21, characterized in that the press further comprises an injection frame (29) whose inner end is fixed to the fixed mold carrier plate (2) . 23. Injection press according to any one of claims 1 to 21, characterized in that the press comprises an injection frame (29) opposite the displacement and locking device (5), this injection frame being placed or fixed to the ground, in that the fixed mold-carrier plate (2) is fixed to the injection chassis and carried by it, and in that the or each force recovery member (106) is suspended mold tray fixed at one end and placed or fixed to the ground by its other end, to which the bed base (4) is suspended.