FR3083157A1 - POST-COOLING DEVICE FOR PREFORMS - Google Patents

Abstract

The invention relates to a post-cooling device during the injection of polyethylene terephthalate (PET) preforms for the manufacture of bottles by blow-drawing. External tubes (1) placed on a module, support horizontal air boxes (2) which are each supplied by Vortex tubes (3) which generate a flow of refrigerated air, while the external tubes (1) are provided with refrigerated air supply ports (4) in the internal area of the air boxes (2), as well as air exhaust ports (5) on their front face to guide the flow of refrigerated air along an internal telescopic gripping and cooling tube (6), integral with a piston (7), which move longitudinally in the tube (1) under a second pressure of refrigerated air, to cover the preform (9) positioned on the punch of the mold (10) and then be pushed back into the external tube (1) during the ejection of said preform, to complete its cooling in the external tube (1).

Description

The invention relates to a post-cooling device during the injection of polyethylene terephthalate (PET) preforms for the manufacture of bottles by blow-drawing.

The preform is usually in the form of a cylindrical tube closed at one end and open at the other end which forms the neck of the preform provided with a retaining flange for conveying in the blow-stretch machine. The lower part of the preform located under the retaining flange constitutes the deformable zone during the stretch-blow molding operation. This part is of a suitable thickness to allow the shaping of the bottle according to the size and the desired weight of said bottle.

The external diameter of the preform in the deformation zone is generally of the order of four to six millimeters smaller than the diameter of the retaining flange, and the thickness of material in this deformation zone is defined as a function of the mass of material necessary for the stretching - blowing operation.

This thickness in the deformation zone which can be of the order of 2 to 4 millimeters or more, greatly penalizes the cooling cycle of the preform during injection and has a negative influence on the rate of production of said preforms.

To remedy this drawback, the current technique consists in fractioning the cooling by performing a first cooling in the injection mold,

-2 then by transferring the preforms between 70 ° C and 90 ° C, in a post-cooling module of three or four stations which each include the same number of post-cooling tubes as the number of mold cavities, and that these tubes are cooled by circulating water to 8 ° C, to finalize the cooling of the preforms.

According to this process, a preform with a length of 110 millimeters, a wall thickness of 2.76 millimeters in the deformable zone and a weight of 26.7 grams, requires a total cycle time of 10.2 seconds which is distributed over the as follows: 2.6 seconds for filling the imprint; 3.2 seconds for the holding pressure; 2.2 seconds for the first cooling in the mold so that the preform is rigid enough for transfer to the post-cooling module. Then it takes another 2.2 seconds to open the mold, transfer the preforms to the post-cooling module at a temperature of around 70 ° C, and close the mold for a new injection cycle. The preforms then continue their cooling in the post-cooling module for the duration of three or four injection cycles depending on the number of stations in said module to reach a temperature of approximately 50 degrees.

The present invention proposes to further reduce the total cycle time, by transferring to the post-cooling module the first cooling time of 2.2 seconds which was carried out in the mold. For this, the injection mold is opened at the end of the holding pressure when the preform is

-3 still at a temperature of 120 ° C, and the transfer of the preform is carried out using an internal tube for grip and telescopic cooling which comes to cover the preform, when the latter is still positioned and cooled on the punch of the mold, to accompany it without risk of deformation in the after-cooling module during ejection, in order to carry out more intensive cooling by refrigerated air.

To this end, the invention relates to a post-cooling module of the type indicated in the preamble, characterized in that each horizontal row of external cooling tubes, placed on said module, supports horizontal air boxes supplied with air. refrigerated by Vortex tubes and that these external tubes are provided with air supply orifices to direct the refrigerated air onto a telescopic internal cooling tube which also acts as a means of gripping the preform to take it in the post-cooling module.

The first cooling of 2.2 seconds in the mold is therefore transferred to the post-cooling module, combined with more intensive cooling by refrigerated air at minus 20 ° C, and allows the total cycle to be reduced by 2.2 seconds, thus going from 10.2 seconds 8 seconds for the type of preform stated in the preamble. A productivity gain of around 27.5%

The present invention and its advantages will appear more clearly in the following description which represents an embodiment given by way of nonlimiting example, with reference to the appended drawings, in which:

FIG. 1 represents a sectional view of a group of four stations of cooling tubes and of the corresponding refrigerated air box.

FIG. 2 represents an external tube according to the invention, with the telescopic internal cooling tube returned to the cooling position.

Figure 3 is a perspective view of Figure 1.

FIG. 4 represents an external tube according to the invention, with the telescopic internal cooling tube deployed which covers the preform.

FIG. 5 shows the positioning of the internal telescopic cooling tube when it is pushed back during ejection of the preform.

With reference to FIGS. 1 and 2, it can be observed that the external tubes (1) placed on the cooling module (not shown) support a horizontal air box (2) supplied by a Vortex effect tube (3). The external tube (1) is provided with refrigerated air supply orifices (4) at the level of the air box (2), and refrigerated air evacuation orifices (5) on its front face. . The internal telescopic gripping and cooling tube (6) is fixed on a piston (7) provided with a stop cup (8) for the preform (9) which has been ejected from the punch (10) of the impression of the injection mold. The piston (7) has on its front face an external hub (11) for fixing the internal telescopic gripping and cooling tube (6), and an internal hub (12) for fixing the preform bottom stop cup ( 8). The length of these fixing hubs (11) and (12) projecting from the front face of the piston (7) corresponds to the length of the preform neck (13) increased by the distance of

-5 guard (A) which separates the necks (13) of the preforms (9) positioned on the other tubes (1)) and the bottom of the preform positioned on the punch (11) when the injection mold is opened for the transfer of the preforms (9) (Fig.l). The length of the telescopic internal gripping and cooling tube (6) is determined by the length of the deformable zone of the preform (9), increased by the length of the preform neck (13) and the clearance distance (A) . The internal telescopic gripping and cooling tube (6) and the external hub (11) of the piston (7) respectively have concentric orifices for supplying refrigerated air (14) and (15) aligned with the orifices (4) of the external tube (1) when the piston (7) is in abutment in the rear position in said tube. The telescopic internal gripping and cooling tube (6) also includes refrigerated air discharge orifices (16) juxtaposed with the preform bottom stop cup (8) which matches the profile of the preform bottom (9 ). The preform bottom stop cup (8) and the internal fixing hub (12) of said cup are provided with a central orifice (17) which opens into the chamber (18) located at the rear of the piston (7 ) for the passage of air from the vacuum effect for retaining the preform (9) in the internal telescopic gripping and cooling tube (6) during the final cooling.

Referring to Figure 3, we see the external cooling tubes (1), an air box (2), a Vortex tube (3), with the first external tube (1) including the internal telescopic tube for gripping and cooling (6) is in the deployed position and covers the preform (9) which is still positioned on the punch (10) of the mold

-6d'injection. We also see the refrigerated air discharge ports (5) placed on the front of the external cooling tubes (1).

Referring to Figure 4, we can see the outer tube (1), provided with refrigerated air supply ports (4) and refrigerated air discharge ports (5), the internal tube gripping and cooling (6) which is deployed and covers the deformable zone of the preform (9), the tube (6) fixed on the piston (7), provided with a preform bottom stop cup (8) in its front part and a compression / decompression chamber (18) in its rear part.

Referring to Figure 5, we note that the internal telescopic gripping and cooling tube (6) has been pushed back by the drawer (not shown) which forms the neck of the preform (9). The piston (7) obstructs the refrigerated air supply orifices (4) of the external tube (1) when the drawer of the neck of the preform reaches the end of the ejection stroke, while the chamber (18) passes through. decompression by the vacuum effect for retaining the preform (9) in the internal gripping and cooling tube (6), to drive the piston (7) in rear stop in the external tube (1) according to Figure 2.

The device which is the subject of the present invention operates as follows:

The cooling module is introduced between the plates of the mold which is opened at the end of the holding pressure, when the preforms are still at a temperature of the order of 120 ° C. During this phase, the internal gripping and cooling tubes (6) are in the retracted position and the air flow is refrigerated

-7continues to cool them, and blows forward external tubes (1) through the holes (5), while the punches (10) of the impressions continue to cool the preforms. When the module has coaxially positioned a series of empty internal gripping and cooling tubes (6), relative to the preforms (9) positioned on their punches (10), a first pulse of 0.2 seconds of refrigerated compressed air and at a pressure of 8 bars in the chamber (18) advances the empty internal gripping and cooling tubes (6) in abutment towards the front of the external tube (1). During the advance of the internal gripping and cooling tubes (6), the masses of refrigerated air contained between the external tubes (1) and the internal tubes (6) are propelled by the piston (7) through the orifices (5) to cool the external surface of the preforms being covered by the telescopic tubes (6). During this advance of the internal telescopic tubes, part of the refrigerated air which is propelled into the chambers (18) to move the pistons (7) towards the front of the external tube (1), passes through the orifices (17) of the pistons (7) to effectively cool the preform bottoms (9) and this air pressure at 8 bars also makes it possible to dampen the contact between the preforms (9) and the stopper cups (8). When the internal gripping and cooling tubes (6) have covered the entire deformation zone of the preforms (9), the mold drawers which shape the neck (13) push back the internal telescopic tubes (6) when ejecting the preforms (9) to extract them from the punches (10) without deformation. This push pushes back the piston (7) which obstructs, momentarily at the end of the ejection stroke (Fig. 4), the refrigerated air supply orifices (4) of the external tubes (1), and the vacuum effect in the rooms of

-8decompression (18) brings said pistons into rear stop in the external tubes (1). As soon as the front part of the pistons (7) is positioned behind the refrigerated air supply orifices (4), the pressure of 8 bars of the refrigerated air keeps the pistons in rear stop in the external tube (1 ), and the flow of air cooled to minus 20 ° C effectively cools the preform bottom stop cups ((8) as well as the external walls of the internal gripping and cooling tubes (6).

The air cooled to minus 20 ° C provides intensive cooling which makes it possible to extract the preforms (9) immediately after the holding pressure in the mold, when they are still at a temperature of 120 ° C, and to bring them at a temperature of around 50 ° C during the four injection cycles which followed the transfer of said preforms (9) into the post-cooling tubes (1) and (6).

The initial cooling time of 2.2 seconds usually carried out in the mold has been transferred to the post-cooling module, and takes place during the 2.2 seconds of opening the mold, transferring the preforms and closing the mold.

Claims (1)

Claim 1. Device for post-cooling polyethylene terephthalate (PET) preforms for the manufacture of bottles by blow-drawing, comprising a set of cooling tubes placed on a mobile module, external to the injection mold, characterized in that the external tubes (1) placed on said module, support horizontal air boxes (2) which are each supplied by Vortex effect tubes (3) which generate an air flow under a pressure of 8 bars, at a negative temperature of less 20 ° C, while the external tubes (1) are provided with refrigerated air supply ports (4) in the internal area of the air boxes (2), as well as air exhaust ports ( 5) on their front face to guide the flow of refrigerated air along an internal telescopic gripping and cooling tube (6), integral with a piston (7), and with a bottom stop stop cup preform (8), which move longitudinally in the tube (1) under a 0.2 second pulse of refrigerated compressed air and at a pressure of 8 bars, to cover the preform (9) positioned on the punch (10) of the mold, before being pushed back into position the tube (1) during the ejection of the preform by the demolding drawers of the preform necks (not shown) which are fixed on the ejection table, bringing the piston (7) behind the supply ports of refrigerated air (4) to allow the flow of refrigerated air to flow over the cup (8) and the internal telescopic tube (6). 10 Claim 2. Device according to claim 1, characterized in that the length of the telescopic internal gripping and cooling tube (6) is determined by the length of the deformable zone of the preform (9), increased by the length of the preform neck (13 ) and the guard distance (A) which separates said necks (13) and the bottom of the preforms (9) in the open position of the injection mold for the transfer of the preforms (9). Claim 3. Device according to Claim 1, characterized in that the piston (7) has on its front face an external hub (11) for fixing the internal telescopic gripping and cooling tube (6), and an internal hub (12) for fixing of the preform bottom stop cup (8). Claim 4. Device according to claim 3, characterized in that the external hub (11) of the piston (7) has air supply orifices (15) for directing the flow of refrigerated air onto the preform bottom stop cup (8). Claim 5. Device according to claim 3, characterized in that the piston (7) has in its rear part a decompression chamber (18) opening onto the central orifice (17) arranged on the internal hub (12) of the piston (7) and on the bottom stopper cup of -11 preform (8), to maintain the preform (9) by suction effect in the telescopic internal gripping and cooling tube (6) against the cup (8) during the cooling phase. Claim 6. Method for implementing the device according to claim 1, characterized in that the drawers for removing the preform necks (not shown) which are fixed to the ejection table, push the internal telescopic tube (6) back when ejection of the preform (9) to extract said preform from the punch (10) without deformation, and to bring the piston (7) to the obstruction of the refrigerated air supply orifices (4) of the external tube (1). (Fig.5) Claim 7. Method of implementing the device according to claim 5, characterized in that the suction effect also drives the piston (7) backwards in the external tube (1) when the rear part of the piston (7) obstructs the refrigerated air supply orifices (4) of said external tube (1) at the end of the preform ejection stroke. Claim 8. Device according to claim 1, characterized in that the internal telescopic gripping and cooling tube (6) has refrigerated air inlet orifices (14) concentric with the orifices (15) of the piston (7), and orifices air flow (16) juxtaposed with the preform bottom stop cup (8) to allow cooling of the latter. -12 Claim 9. Device according to claim 8, characterized in that the refrigerated air supply orifices (4) on the external tubes (1) are positioned at the orifices (14) and (15) when the piston (7) is in rear position in the external tube (1), and that the pressure of 8 bars in the external tube (1) keeps the piston (7) in the rear position during the cooling effected by the flow of refrigerated air. Claim 10. Method of implementing the device according to claim 5, characterized in that the piston (7) is pushed into the tube (1) by a first pulse of compressed air at 8 bar in the chamber (18) which advances the piston (7) beyond the refrigerated air supply ports (4) and the pressure of 8 bars of the refrigerated air then pushes the piston into abutment towards the front of the external tube (1), in contact with the drawers which shape the preform necks, while part of the refrigerated air which is propelled into the chamber (18) passes through the orifice (17) of the piston (7) and the cup (8) to cool effectively the bottom of the preform (9) and absorb the contact between the preform and the stopper cup (8).