FR2930474A1 - Plastic material part i.e. flask cover, fabricating device, has suction unit with nozzle blowing air jet passing above part, where angle between axis of jet and suction surface of part is lower than ten degrees - Google Patents

Abstract

The device (1) has a molding tool for molding or forming a plastic material part (2) i.e. flask cover, and a demolding unit for demolding the part. The demolding unit has a suction unit with a nozzle (5) blowing an air jet (3) passing above the part, where angle between an axis (30) of the jet and a suction surface (21) of the part is lower than 10 degrees. The air jet is supplied through a canalization (6) connected to a reservoir, and diameter of on outlet opening (4) of the nozzle is equal to a percentage of length (lp) of the surface (21). An independent claim is also included for a method for fabricating a plastic material part.

Description

The invention relates to devices and processes for the manufacture of plastic parts and mainly to their demolding or ejection mode. It is applicable to injection molding, thermoforming and cutting processes. The demolding or the ejection of the parts is carried out by an air jet mode, in particular for which a direct air jet is not possible or insufficient or problematic or for which demoulding with mechanical elements turns out to be complex and expensive. The invention also relates to plastics tools. The invention is particularly suitable for demolding and / or ejecting vial cap cap, cap lid, seal for cap, pellet and hinged parts.

In conventional injection equipment, the parts are evacuated by ejectors that come out, push the piece out of the mold such as Patent WO9837280. However, these ejectors leave marks on the part from the seal line formed on the periphery of each ejector on the surface of the mold cavity. On the other hand, by pushing the piece, it can be deformed locally. In addition, the cooling time is longer so that the room is more rigid at the time of ejection. Its cycle time is therefore longer. Finally, the actuating mechanism of these ejectors is very complex and expensive when the demolding of the part must be operated in several steps in the case of complex forms to be demolded. If the movement occurs in a direction not perpendicular to the bearing surface of the part, case complex shapes or hinged parts, the tip of the ejector can mark the piece by ripping on it which generates defects in aspect and / or break primers. Another method of demolding is to blow air between the core and the workpiece (Patent W 09206834) or on the workpiece. In the latter case an air jet is directly applied to a surface portion which drives the workpiece in the direction of the air flow. For this purpose part of the tooling emerges to reveal the orifice of the air jet such as a valve, or needles (Patent EP 0606037) or a mold release tray. The jet applied directly to the part propels it vigorously. The projected part can get stuck in a piece of equipment in front and stop the production cycle. Also depending on the shape of the part, the air jet may be misdirected relative to the surface of the room, and therefore has a limited action especially in the case of a valve. In addition, a valve or needles or drawer leave molding marks, which is not always appropriate for some appearance parts. Yet another solution is used in particular for rubber or thermoplastic elastomer parts which comprise part of their undercut shape on their core (Patent FR2633209). The piece is inflated to dislodge it from its core. The material in this case can easily be deformed, and must be sufficiently deformable for this type of process to avoid tearing. Other methods use retractable elements to release the retention zones of the parts and thus be able to unmold the parts. The mechanism of the retractable elements is often complex and expensive. Also there are movements between the parts of the mechanism, which generates wear and higher maintenance costs. Sometimes a vacuum system (or similar system, Patent EP 0919352) arranged on a robotic arm is used: each suction cup sucks the parts by depression. This system works very well, however, it remains relatively expensive because requires a gantry, a robot and the suction gripper. In addition the cycle time is extended for the introduction of the robot into the mold and its withdrawal. This system is interesting if the parts need to be neatly stored, but not for economical manufacture. The objectives of the present invention are to overcome the disadvantages of the interior art by providing a simple and economical solution to implement while being very effective. These objectives are achieved (economic, reduced traces of molding or ejection, reduced maintenance costs, improved cycle time, risk of jamming of part after reduced ejection) thanks to the invention, which relates to a device and a method of manufacture of plastic parts with a specific and innovative demolding and / or ejection mode, using an air jet in a particular way. The subject of the invention is a device for manufacturing plastic parts, comprising tooling, for molding or shaping a piece of plastics material, and demolding means, for unmolding said part, characterized in that said means for demolding comprises suction means comprising at least one nozzle capable of blowing an air jet passing above said part, the angle between the axis of said air jet and at least one suction surface of said piece being less than 25 °, preferably less than 10 °. Indeed, the demolding operation concerned, comprises at least one phase of disengagement of at least a part of the part of its imprint (or its core) of the tooling, disengagement being obtained at least in part by a suction induced by at least one jet of air exiting a nozzle. Said jet of air blows in front of said suction surface of at least a portion of said piece, and generates a stream of air passing over said suction surface of said piece in a direction substantially parallel or slightly inclined by relative to said suction surface of at least a portion of said workpiece whose initial release movement of said workpiece portion is substantially perpendicular to said suction surface.

The term "nozzle" means the element forming the end of the pipe, from which the jet of air escapes. Preferably this channel end is straight or composed of a convergent cone angle less than or equal to 60 °. The air jet is provided only when the part part has to be released, for its demolding and / or ejection. The jet is controlled using a solenoid valve 25 for example. The jet of air causes a depression above the room due to the speed of the flow of air generated passing above. It sucks the piece to unmold. Once at least one portion has been cleared of its footprint, this part of the workpiece enters the stream of air of another jet or jet of air which further entrains it in its race to continue the next phase of demolding. or ejecting the part. The higher the speed of the jet, the more the pressure decreases, thus the suction obtained by the depression applied to the workpiece is more important. In addition, the suction effect is greater on a workpiece having a major part of its relatively planar suction surface, so that the depression applied to the workpiece surface exerts sufficient force in the direction of the workpiece. clearance of the room. The cooling time of the part is advantageously shortened because the part is less stressed by this demolding or ejection mode, moreover the jet also cools the part. The device is simple and therefore economical to install and maintain. If the airflow is located too close to the room and it blows laterally on the room, air can rush between the room and the footprint and can tend to replate part of the room in its footprint (or its nucleus) because of the depression induced in this gap. Therefore, at least one stream of air must pass over at least the part of the part to be moved. For safety reasons, it is advisable to limit the air pressure in the circuit to 18 bars, and preferably less than 12 bars. Other features and advantages of the invention will emerge more clearly on reading the following description of a preferred embodiment of the invention, given by way of illustrative and nonlimiting example, and drawings in which: FIG. 1 shows a cross-sectional view of an injection molding tool of plastic covers with an air jet for demoulding and ejection according to the invention; FIG. 2 shows a tool with two plastic parts subjected to same air jet for their demolding and ejection according to the invention • Figure 3 indicates a mode of placing pellet impressions and air jets in a multi-cavity tool, in a transverse view (joint plane) according to the invention; FIG. 4 illustrates a portion of a plug injection tool with a flip-top lid for a bottle, in section, according to the invention. FIG. 5 shows an example of multi-cavity tooling of hinged parts arranged symmetrically with opposing jets, in a sectional view, according to the invention; FIG. 6 shows another example of jetting arrangement; Bending air in a transverse view (joint plane) of a tool, according to the invention • Figure 7 shows a sectional view of a plug injection mold part with lid for a bottle whose lid is foldable in the tool itself, according to the invention.

FIG. 1 shows an embodiment of the invention applied to an injection tool 1 of a part 2 representing a cover. The device 1 is characterized in that the outlet orifice 4 of said nozzle 5 has a diameter equal to a percentage of the length lp of said suction surface 21, said percentage being between 3% and 20%, said percentage preferably being substantially equal to 10%. For most applications, the diameter of this orifice 4 is between 1 and 5 mm. The equivalent diameter is considered for this orifice as conventionally defined in fluid mechanics, even if the shape is not circular. Also the device 1 is characterized in that the ratio between, on the one hand, the distance L between the outlet orifice 4 of said nozzle 5 and said part 2, and, on the other hand, the diameter of said outlet orifice 4, is between 4 and 40, said ratio being preferably between 10 and 25. In addition, the device 1 is characterized in that the axis 30 of said air jet 3 is located, with respect to said surface of suction 21 of said part 2, at a height d1 at least equal to the depth p 1 of the impression or core surface 8 of said mold 1 situated opposite said asphalting surface 21. dl height of the air jet 3 is less than the length lp of said suction surface 21, the ratio between said height lp of the air jet 3 and the length of said suction surface 21 is preferably between 1 / 3 and 2/3. Thus, the part (2) released from the impression surface 20 in the direction 12 by the first effect of the flow of air 3 which sucks it in, enters this stream 3 at an angle sufficient for the flow of air drives it in the direction of the flow, for its ejection.

The respect of these parameters makes it possible to obtain a better effect for the release of the part 2, without having to use too much air pressure or a large flow rate in order to reduce the consumption of compressed air. According to another characteristic, the device 1 comprises a plate 10, substantially parallel to the surface 21 of said part 2, the plate 10 comprising an upper portion, on which said nozzle 5 is arranged, and a lower portion, corresponding to the joint plane. 87 on which is disposed the cavity or the core of said mold 1, a step 11 connecting said upper and lower portions, the height of said step 11 being at least equal to the diameter of the outlet orifice 4 of said nozzle 5, the height of said step 10 being preferably equal to or greater than five times the diameter of the outlet orifice 4 of said nozzle 5. The inclination of the jet or the plate is less than 25 ° relative to the surface 21 of the part of room 2 to release, ideally less than 10 °. The air jet 3 is directed such that the flow of air generated lick the surface of the plate 10 in line with the step 11. The effect of depression on the surface 21 of the room 2 is accentuated and improved demolding.

In FIG. 2, the device concerning multi-cavity tooling comprises a nozzle 5 which generates a stream of air 3 above each of the two pieces 2. According to another aspect of the invention, the device is characterized in that said air jet 3 passes over said suction surface 21 of the part 2 by moving away from it, at an angle taken between the suction surface 21 and the axis of the air jet 3 After release of their core 8, the parts 2 are driven by the same stream of air 3, according to the direction 12.

Another feature of the device 1 according to the invention is illustrated in FIG. 3. It consists in the fact that said air jet 3 is fed by a pipe 6 connected to a reservoir 60 situated in the vicinity, and under internal pressure less than 18 bars, preferably less than 12 bars. In order to improve the power of the air jet 3 and its effect, a tank 60 under pressure is arranged upstream of the nozzle 5, in particular if the compressor is remote, so that there is a volume of compressed air sufficient to feed the air jet 3. For multi-cavity tooling, a compressor or booster can be used with higher pressure for better effect. However the volume of the tank allows to restrict, for safety, the pressure to be used. The channels 6 and the elements of the pneumatic circuit 5, 60, 61 are defined so as to reduce the pressure drops and to have balanced circuits, for a better effect on the demolding and / or the ejection of each of the parts 2 The opening and closing of the circuit 6 are controlled by means of a solenoid valve 61 in order to control the air jet 3. When the ejection follows this first phase of separation of part 2 from its footprint, according to a advantageous solution, the air jet 3 is directed to the device for receiving parts 13, without crossing obstacles (column, demolding finger, mold closing wedge), often downwards, in order to drive the parts directly in the tray 13 or on the coin recovery mat. Thus the risk of jamming of the parts 2 in a part of the tool 1 is very small. In the case presented, a separate air jet acts on each of the parts 2 of the tool mufti- imprint, without disrupting the path of other parts 2 to prevent a malfunction. The set of air jets 3 converges towards the tank 13. The device 1 according to the invention, in FIG. 4, has an additional characteristic. It comprises complementary means to help disengage said part, for example a stripper, a valve disposed under said part, or an ejector. To further promote the separation of the mold part, according to a variant of the invention, the release phase of at least a part of the part of its fingerprint is initialized by the at least partial lifting of the least part of the room. This initial lifting is carried out by actuating an ejector or with a valve 51 with the aid of compressed air which pushes at least part of the part or by some other means. The fact of taking off the part of its imprint allows ambient air to intrude between the part and the impression, so the atmospheric pressure is applied on the face 20 of the part facing the cavity. The release effect 12 induced by the depression obtained by the air jet 3 is accentuated. In fact the movement of the part is facilitated by a greater difference in pressures exerted on the lower surfaces 20 and 21 of the upper part 2. Also when the part, due to its shape and the shrinkage obtained during cooling after injection, tends to stick to the impression or the nucleus, its detachment may require greater effort, especially if there is an undercut portion. Thus one or more additional air jets can be applied to complete the effect of the first air jet 3, and promote demolding. Thus the device 1 according to another characteristic, comprises one or more additional nozzle (s) 51,52 able to blow one or more additional jet (s) of air (s) 32. The use of an air jet under the part through a nozzle 51 allows to have an overpressure on the face 20 while the air jet 3 generates a vacuum on the face 21 from the induced movement to the air surrounding the face 21 Thus mold release is further favored. The addition of a nozzle 52 blowing an air jet 32 laterally further helps the clearance of the room 2, especially until the room 2 enters directly into the stream of air 3.

Figure 4 also illustrates another application of the invention. Indeed in this case, the complete plastic part comprises a tip 23 and a lid 2 foldable on the end piece 23 from its hinge 24, and is a bottle cap. In order to achieve this type of part economically, the cover 2 is folded over the tip 23 in the tool itself, not on a separate station. The footprint 8 of the part portion 2 is put on a drawer. But this drawer can not move back because of the undercut area between parts 2 and 23. It should have a combined movement of descent and recoil, which complicates the mechanism and is expensive. Thus the invention makes it possible to clear the part 2 in a simple and economical way. Once the part 2 released from its footprint 8, in particular by the effect of the air jet 3, the drawer can move back laterally. Also as soon as the lid 2 is sufficiently raised and it enters the stream of air 3, it leads more and the flap on the tip 23. Then an additional device comes clip the lid 2 on its tip 23 if necessary, using a pivoting bar on an axis or a sliding finger, not shown in Figure 4.

Figure 5 illustrates the case of a tool mufti imprints with the molded parts in several rows, where it is advisable that the jets of air can not be confronted.

Thus a screen 38 or a baffle is placed after the piece 2 and obstructs the air jets 3 and 33 opposite so as not to disturb the effect of the jet facing the piece placed symmetrically. The air jets can be directed differently so that they do not adversely affect the other parts, as in Figures 3 or 6.

In Figure 6, two nozzles 5, 54 generate two air jets 3, 34 diverging, both passing above the suction surface 21 of the part 2, to clear its footprint. Thus the symmetrical arrangement in the tooling is allowed without risk of disturbance of the suction phenomenon, because the junctions of the symmetrical air streams 3, 33 are remote parts 2.

FIG. 7 further details an example of a device shown in FIG. 4. The clearance of the part part 2 is accompanied by a valve 55 placed under the part 2. The impression 8 is fixed on another element 80 constituting a drawer actuated by a demolding finger 72 at the opening of the mold 1. The recoil of this slide according to the Y axis is achieved when the lid 2 is sufficiently rectified. Then another device (not shown) completes folding the cover 2 on its end 23. At the end of the cycle the part portion 23 is removed from its core 81 with the help of the element 83, which then holds it that the core 81 moves back along the axis X. According to another aspect, the invention relates to a method of demolding a plastic part, characterized in that it comprises a step of disengaging said part consisting in blowing a air jet above said part, the angle between the axis of said air jet and at least one suction surface of said part being less than 25 °, preferably less than 10 °. Indeed, the invention relates to a method of manufacturing plastic parts whose demolding operation comprises at least one phase of disengagement of at least a part of the part 2 of its footprint or core 8 of the mold, characterized in that that the clearance is obtained at least in part by suction induced by at least one air jet 3, using a tool 1 having at least one compressed air outlet 4 blowing air in front of said part of the piece 2, and generating a stream of air 3 passing above said part portion in a direction substantially parallel or slightly inclined with respect to the surface 21 of said part of the part 2 whose initial release movement 12 is substantially perpendicular to this surface. When the ejection follows this first piece separation phase 2 of its footprint 8, according to an advantageous solution, the air jet 3 is directed towards the device 13 for receiving parts, without crossing obstacles. The invention particularly relates to molding manufacturing methods. According to an advantageous solution of the invention, the phase of disengagement of the part is followed by an ejection or evacuation or reversal phase induced by at least one jet of air 3, at least part of the piece, passing through the stream of air of at least one of said air jet which drives it, using a tool 1 according to the invention, having at least one compressed air outlet blowing from the air near the part to be disengaged in a direction substantially equivalent to the direction of movement of said part part to have its demolding position, or its evacuation (or recovery or reversal of the part part 2). Another solution is particularly advantageous for the demolding of plastic parts, a part of which is hinged to the rest of the room, must be folded, such as in the case of a bottle cap lid (example in FIGS. to 7), which is folded before closing by clipping with a complementary device (rotation of a bar about an axis or support with a sliding finger). It consists of the method according to the invention, relating to the release of a part 2 which is integrated into an assembly comprising a hinge 24 and a base 23, characterized in that said step of clearing the part 2 is followed by a phase pivoting said part 2 around said hinge 24, consisting of driving said part 2 by at least one air jet 3 placed in front of said part 2, the height d1 of the air jet 3 being less than the length lp of said suction surface 21 of said part 2, and at least equal to the depth p 1 of the impression surface or of the core 8 of the mold, situated opposite said suction surface 21.

Another advantageous solution of the invention consists in operating the disengagement phase or the reversal or ejection phase by a succession of air jets in order to obtain the movement of at least said part of the part into several parts. steps or to promote the mobility of the room by a series of jolts. This succession of jets is obtained by means of a solenoid valve or a distributor or an oscillating flap or rotating in a pipe, controlled by an actuator or a demolding finger or a notched ramp.

According to yet another advantageous solution, said demolding or ejection operation of at least a part of the part is induced by at least one short jet of air. In fact, in order to save compressed air, it is proposed to generate a short pulse with a higher pressure. whose effect is more effective.

Claims (12)

REVENDICATIONS1. Device 1 for manufacturing plastic parts, comprising tooling, for molding or shaping a plastic part 2, and demolding means for demolding said part 2, characterized in that said demolding means comprise means suction nozzle comprising at least one nozzle 5 capable of blowing an air jet 3 passing above said part 2, the angle between the axis of said air jet 3 and at least one suction surface 21 of said part 2 being less than 25 °, preferably less than 10 °. 2. Device 1 according to claim 1, characterized in that said air jet 3 passes above said suction surface 21 of the part 2 away from it. 3. Device 1 according to claim 1 or 2, characterized in that said air jet 3 is supplied by a pipe 6 connected to a reservoir 60 located nearby, and under internal pressure of less than 18 bar, preferably less than 12 bars. 4. Device 1 according to any one of claims 1 to 3, characterized in that the outlet orifice 4 of said nozzle 5 has a diameter equal to a percentage of the length 1p of said suction surface 21, said percentage being between 3% and 20%, said percentage being preferably substantially equal to 10%. 20 5. Device 1 according to any one of claims 1 to 4, characterized in that the ratio between, on the one hand, the distance L between the outlet orifice 4 of said nozzle 5 and said part 2, and, d on the other hand, the diameter of said outlet orifice 4 is between 4 and 40, said ratio preferably being between 10 and 25. 6. Device 1 according to any one of claims 1 to 5, characterized in that the axis 30 of said air jet 3 is located, relative to said suction surface 21 of said piece 2, at a height d1 at least equal to the depth p1 of the impression or core surface 8 of said mold 1 situated opposite said suction surface 21. 7. Device 1 according to claim 6, characterized in that said height dl 30 of the air jet 3 is less than the length lp of said suction surface 21, the 12rapport between said height dl of the air jet and the length lp of said suction surface 21 being preferably between 1/3 and 2/3. 8. Device 1 according to any one of claims 1 to 7, characterized in that it comprises a plate 10, substantially parallel to the surface 21 of said part 2, the plate 10 having an upper portion, on which is disposed said nozzle 5, and a lower portion corresponding to the joint plane 87 on which is disposed the cavity or the core of said mold 1 ', a step 11 connecting said upper and lower portions, the height of said step 11 being at least equal to diameter of the outlet orifice 4 of said nozzle 5, the height of said step 10 being preferably equal to or greater than five times the diameter of the outlet orifice 4 of said nozzle 5. 9. Device 1 according to any one of claims 1 to 8, characterized in that it comprises complementary means to help disengage said part, for example a stripper, a valve 55 disposed in said part, or an ejector. 10. Device according to any one of claims 1 to 9, characterized in that it comprises one or more additional nozzle (s) 51, 52, 54 able to blow one or more jet (s) additional air (s) 3, 32, 34. 11. A method of demolding a plastic part 2, characterized in that it comprises a step of disengaging said part 2 consisting of blowing an air jet 3 above said part 2, the angle between the axis 30 of said air jet 3 and at least one suction surface 21 of said part 2 being less than 25 °, preferably less than 10 °. 12. The method of claim 11, relating to the release of a part 2 which is integrated in an assembly comprising a hinge 24 and a base 23, characterized in that said step of clearing the part 2 is followed by a phase of pivoting of said part 2 around said hinge 24, consisting of driving said part 2 by at least one jet of air 3 placed in front of said part 2, the height d1 of the air jet 3 being less than the length lp of said surface 21 of said part 2, and at least equal to the depth p1 of the impression surface or the core 8 of the mold, situated opposite said suction surface 21.