COOLING TUBE AND METHOD OF USING THE SAME
FIELD OF THE INVENTION The present invention is generally concerned with cooling tubes and is applicable in particular, but not exclusively, to cooling tubes used in a plastics injection molding machine for cooling plastic parts, such as plastic parisons. or plastic preforms. More particularly, the present invention is concerned with a structural configuration of these cooling tubes and also with a method of manufacturing and using such tubes, for example in the context of a manufacturing process for preforms made of polyethylene terephthalate (PET). ) or the like. BACKGROUND OF THE INVENTION In order to accelerate the cycle time, the molding machines have evolved to include post-mold cooling systems that operate simultaneously with the injection mold cycle. More specifically, as long as an injection cycle is taking place, the post-mold cooling system, which commonly acts in a complementary manner with a robot part removal device, is operative in a previously formed set of molded articles. that have been removed from the mold at a point where they are still hot, but sufficiently
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solids to allow limited handling. The conditioning of temperature (or cooling) of post-mold molding, splicing or tubing is well known in the art. Commonly, such devices are made of aluminum or other materials that have good thermal conductivity. Furthermore, it is known to use fluid cooled cooling tubes for the post-molding temperature conditioning of the molded plastic parts, such as plastic parisons or plastic preforms. Commonly such tubes are formed by conventional machining methods from solid raw material. In order to improve cooling efficiency and cycle time performance, EP 0 283 644 discloses a multi-position separation plate having the ability to store multiple sets of preforms for more than one injection cycle. In other words, each set of preforms is subjected to an increased period of increased conduction cooling by retaining the preforms in the cooling tubes for more than one injection cycle. With the increased cooling, the quality of the 'reforms is improved. At a point at the appropriate time, a set of preforms are ejected (usually by a mechanical ejection mechanism) from the separation plate onto a conveyor to allow a new set of preforms to be inserted into the set of cooling tubes now empty. European Patent EP 0 266 804 discloses an intimate fitting cooling tube for use with an arm end tool [EOAT]. The intimate fit cooling tube is water cooled and is arranged to receive a partially cooled preform. More particularly, after the preform has undergone some cooling inside the closed mold, the mold is opened, the EOAT is extended between the cavity and the sides of the mold core and the preform is discharged from a core to the cooling tube that then it acts to cool the outside of the preform by means of thermal conduction. However, as the preform cools it will shrink and consequently can loosen the contact across its entire circumference with the cooling tube producing an unequal cooling effect. A problem with known cooling tube arrangements is that the preform (at some point, if not from the point of introduction) loses contact with the internal side walls of the cooling tube, such loss of thermal contact decreases the Cooling efficiency and causes uneven cooling. How it will be understood, uneven cooling can induce defects of parts, which include deformation of the overall shape and crystallization of the plastic (resulting in areas that are visibly turbid). In addition, the lack of contact may cause ovality through the circumference of the preform, while the loss of the cooling effect may mean that a preform is removed from the cooling tube at an excessively high temperature. In order to cause surface scratching and overall dimensional deformation, the premature removal of a preform at an excessively high temperature may also result in the semi-molten exterior of the preform either to the tube or other preform; all these effects are clearly undesirable and the result in the rejection of parts and costs increased to the manufacturer. Accordingly, it is desirable to configure the cooling tube to include means for obtaining and / or maintaining contact between the outer surface of the preform and the inner side walls of the cooling tube. US Patent No. 4,047,873 discloses an injection blow mold in which the cavity has a porous sintered side wall that allows a vacuum to draw the parison into contact with the side walls of the cooling tube. U.S. Patent No. 4,047,873 discloses a method and apparatus for producing axially oriented blow molded articles wherein the longitudinal and radial expansion steps are sequentially carried out in a longitudinal stretch die and a radial stretch blow mold, respectively . In particular, a method for the longitudinal stretching of the parison in the longitudinal stretch mold comprising a cavity formed in a solid structure and a plurality of pressure control zones configured along it is described. Japanese Patent Publication 56113433 discloses a process for producing hollow parts including the steps of extrusion molding a foam parison to a vacuum forming mold comprising a cavity formed in a porous structure and subsequently vacuum forming the parison to the hollow part, whereby the foam cells in the hollow part do not collapse. German patent publication DE 197 07 292 discloses a method and apparatus for producing aseptic bottles which includes the steps of extrusion molding a parison to a vacuum forming mold and subsequently expanding the parison in the mold by vacuum suction by means of which germs do not enter the bottle as is the case with conventional blow molding. U.S. Patent No. 4,208,177 discloses an injection molding cavity containing a porous member communicating with a passage of cooling fluid that subjects the cooling fluid to different pressures to vary the flow of fluid through the porous plug. U.S. Patent Nos. 4,295,811 and 4,304,542 disclose an injection-blown core having a porous metal wall portion. An article "Plastics Technology Online" entitled "Porous Molds' Big Dra" by Mikell Knights, printed on the Internet on July 27, 2002, reveals a porous tooling compound called METAPOR ™. The article reveals the technique of polishing this material to slightly close the pores to improve the surface finish and reduce porosity. An article by International Mold Steel, Inc., entitled "Porous Aluminum Mold Materials" by Scott W. Hopkins, printed on the Internet on July 27, 2002, also reveals porous aluminum mold materials. The materials and applications disclosed in the above two articles relate to vacuum thermoforming of plastics in the mold itself, in which preheated plastic sheets are stretched to a single mold half via a vacuum stretch through the porous structure of the mold half. Another problem with known cooling tubes is that they are expensive and take a long time to be manufactured and assembled. In addition, the operational mass (that is, including cooling water) of the cooling tube is of particular concern considering that a typical robot extraction system may include one or more sets of cooling tubes in an array and therefore the mass cumulatively supported by the robot quickly becomes a consideration of significant operation and / or design (ie, considerations of inertia or momentum for the robot). In addition, the robot commonly operates to separate many dozens of preforms in a single cycle (with the PET systems present producing up to one hundred and forty-four preforms per injection cycle) in such a way that the energy expended by the robot and the technical specification of the robot are unfortunately high. The provision in operation of a high specification robot therefore imposes considerable financial cost penalties on an end user. Therefore, it is desirable to configure and manufacture the cooling tube according to a simplified structure and methods, respectively. In addition, it is desirable to configure the cooling channels as relatively open channels in an effort to reduce the operational mass of the cooling tube. U.S. Patent Nos. 4,102,626 and 4,729,732 are typical of prior art systems since they show a cooling tube formed with an external cooling channel machined on the outer surface of a tube body, a sleeve is then mounted to the body for enclose the channel and provide a sealed sealed path for the liquid refrigerant to circulate around the body. WO 97/39874 discloses a tempering mold having circular cooling channels included within its body. EP 0 700 770 discloses another configuration that includes an internal and external cooling tube assembly to form cooling channels therebetween. U.S. Patent No. 5,870,921 discloses an extrusion mold for use in the production of extruded aluminum alloy articles or tube having a recess with defined internal dimensions. BRIEF DESCRIPTION OF THE INVENTION According to a first aspect of the present invention, a structure and / or steps are provided for a post-molding cooling device for operation on a portion of a newly molded malleable injection molded article. The post-molding cooling device includes a porous structure with an internal surface formed in the porous structure that provides a cavity that is profiled to substantially reflect the portion of the molded article. The porous structure is also configured to cooperate in fluid communication with a vacuum source to provide a reduced pressure adjacent to the internal surface that causes a reformation of the malleable molded article portion as an external surface thereof is stretched in intimate contact with the internal surface. Advantageously, the inner surface of the porous structure further has an internal profile which is substantially (but not high and exactly tolerated) the final desired dimensions of the molded article. The porous structure is further configured for connection, in use, with a cooling structure for cooling the porous structure and the portion of the molded article in contact therewith. Advantageously, the portion of the malleable part in contact with the internal surface of the post-molding cooling device is provided with a final shape which is defined by the inner surface and the molded article is cooled quickly and efficiently by means of intimate contact with the cooled porous structure. According to a preferred embodiment of the present invention, the post-molding cooling device is provided as a cooling tube assembly for operating in a malleable molded plastic part. The cooling tube assembly comprises a tube body and a porous insert located in the tube body. The porous insert includes an internal surface and an external surface. The inner surface is profiled to reflect at least a portion of the profile of the molded plastic part. The cooling tube assembly further includes at least one vacuum channel in fluid communication with the porous insert. The vacuum channel configured for connection, in use, with a vacuum source to provide reduced pressure adjacent to the inner surface to cause an outer surface of the malleable molded plastic part, which can be located within the tube assembly cooling, contacting the inner surface to allow a substantial portion of the external surface of the malleable part in cooling to obtain a profile substantially corresponding to the profile of the inner surface. The cooling tube assembly also includes a cooling structure configured for connection in use, with a heat dissipation path for cooling the molded plastic part in contact with the inner surface of the porous insert. According to an alternative embodiment of the present invention, the cooling tube assembly includes the porous insert arranged in the extruded tube body. Preferably, the cooling tube assembly further includes a cap arranged at a distal end thereof, an inner surface of the cap provides a closed end for the inner surface of the porous insert and is profiled to substantially reflect an end portion of the molded article. According to an alternative embodiment of the present invention, the cooling tube assembly includes a tube body and the porous structure is provided along a porous coating applied to an inner surface of the tube body. According to a further alternative embodiment of the present invention, the post-molding cooling device is configured for use in an arm end tool. According to a further alternative embodiment of the present invention, the post-molding cooling device is configured for use in an injection molding system. According to a second aspect of the present invention, a method is provided for the post-molding cooling of a portion of a newly molded malleable injection molded article, the method includes the steps of: (i) receiving the portion of the molded plastic part the post-molding cooling device; (ii) providing a reduced pressure adjacent a profiled internal surface of the post-molding cooling device to effect a reformation of the portion of the malleable molded article as an external surface thereof is stretched in intimate contact with the inner surface, and (iii) extracting the heat from the molded article through the post-molding cooling device to solidify the molded article to an extent that the shape of the outer surface can be conserved without further cooling and (iv) ejecting the plastic article. molded; wherein the molded article is rapidly and efficiently cooled by intimate contact with the cooled porous structure and the outer surface of the molded article is provided with a final shape which is defined by the profile of the profiled internal surface of the post cooling device -molding According to a third aspect of the present invention, a structure and / or steps are provided for a molded article in the form of at least a portion of its outer surface defined by a profiled internal surface of the post-molding cooling device . Thus, the portion of the outer surface of the molded plastic part takes a surface finish that reflects that of the profiled internal surface, which includes marks corresponding to interstitial spaces of the porous structure within a range of about 3 to 20 microns. According to a fourth aspect of the present invention, a structure and / or steps are provided for a cooling tube for cooling a portion of an injection molded article received therein. According to a preferred embodiment, the cooling tube includes an extruded tube body having an internal surface and an external surface and a plurality of cooling channels disposed therebetween which are arranged in a longitudinal direction of the tube body. The cooling tube further includes a connecting channel configured between the cooling channels for interconnecting the cooling channels to at least one cooling circuit, a seal configured at each end of the tube body to close the cooling channels, and a inlet and an outlet in the body of the tube for the at least one cooling channel. The cooling tube also includes a plug disposed at a distal end of the body of the tube. The inner surface of the tube body and an internal surface configured in the plug are machined to provide a profiled cavity substantially conforming to the profile of an outer surface of the molded article. According to a fifth aspect of the present invention, a method for extruding the cooling tube includes the steps of: (i) extruding a tube body having an inner surface, an outer surface and a plurality of cooling channels disposed between the same ones that are arranged in a longitudinal direction of the body of the tube; (ii) machining the inner surface of the tube body to substantially conform to the outer surface of the molded article and (iii) forming a connecting channel between the cooling channels; and (iv) forming the plug. The present invention advantageously provides a cooling tube structure which functions to rapidly and efficiently cool a newly molded plastic part located inside the cooling tube, whereby the robustness of the preform is improved and the cycle time is generally improved . Furthermore, in the context of PET cooling and the undesirable production of acetalde ldo arising from the prolonged exposure of the preform to relatively high temperatures, the rapid cooling provided by the present invention beneficially reduces the risk of the presence of unacceptably high levels of acetaldehyde in the finished plastic product, such as a beverage container. Beneficially, the present invention seeks to maintain a required and defined shape of the molded part, such as a preform. In addition, the present invention advantageously provides an extruded cooling tube which is easily manufactured which is of light construction, which, beneficially, reduces the specification requirements of the robot and / or improves the engine cycle time. In addition, the cooling tube has improved cooling capabilities as a consequence of an improved and integrally formed channeling. In addition, alternative embodiments of the present invention provide cooling tube assemblies that are capable of vacuum forming a molded article. BRIEF DESCRIPTION OF THE FIGURES Exemplary embodiments of the present invention will now be described with reference to the appended figures, in which. - Figure 1 is a plan view of a typical injection molding machine including a robot and an arm end tool; Figure 2 illustrates a section through a cooling tube assembly according to a preferred embodiment of the present invention; Figure 3 illustrates a sectional view, but exaggerated, through the assembly of cooling tube of the embodiment of Figure 2, with a freshly molded part, freshly charged; Figure 4 illustrates a section through the cooling tube assembly of Figure 2 at a later point in time; Figure 5 illustrates a section through the cooling tube assembly of an alternative embodiment; Figure 6 illustrates a sectional view 5-5 of Figure 5; Figure 7 illustrates a section through the cooling tube assembly of a second alternative embodiment; and Figure 8 illustrates a section through the cooling tube assembly of a third alternative embodiment; Figure 9 is a sectional view of a cooling tube according to a preferred embodiment of the present invention; Fig. 10 is a view along section "A-A" of the cooling tube of Fig. 9; Figure 11 is an isometric view of a porous insert of cooling tube and Figure 12 is a sectional view of a cooling tube according to an alternative embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention will now be described with respect to embodiments in which a porous cooling tube is used in a plastic injection molding machine, although the present invention is equally applicable to any technology in which, immediately after the formation of parts, the cooling of the part is undertaken by means of a cooling tube or the like. For example, the present invention may find application in a transfer mechanism of parts of an injection molding machine and a blow molding machine.
Figure 1 shows a typical injection molding machine 10 capable of cooperating with a device supporting the cooling tube of the present invention. During each injection cycle, the molding machine 10 produces a variety of plastic preforms (or parisons) corresponding to the number of mold cavities defined by complementary mold halves 12, 14 located within the machine 10. The molding machine by injection 10 includes, without specific limitation, a molding structure such as a fixed plate 16 and a movable plate 18. In operation, the movable plate 18 is moved relative to the fixed plate 16 by means of stroke cylinders (not shown) ) or the like. The clamping force is developed in the machine as will be readily appreciated, by the use of tie rods 20, 22 and a machine clamping mechanism (not shown) that commonly generates a clamping force of the mold (ie, closing arch) that uses a hydraulic system. Together, the mold halves 12, 14 constitute a mold having in general one or more mold cavities 22, 24, with the mold halves 12, 14, each located in one of the movable plate 14 and the fixed plate 16. A robot 26, adjacent to the fixed plate 16 and movable plate 14, is provided for carrying an arm end tool (EOAT) 28, such as an extraction plate. The extraction plate 28 contains a plurality of preform cooling tubes 30 corresponding at least in number with the number of preforms 32 produced in each injection cycle and can be a multiple thereof. In use, in an open position of the mold (as shown in Figure 1), the robot 26 moves the extraction plate in alignment with, commonly one side of the mold core and then waits until the molded articles (eg preform example 32) are separated from the respective cores to the cooling tubes 30 aligned respectively by the operation of a separation plate 33. The cooling tubes 30 are generally formed to ref the external profile of the molded article (e.g. 32), such that in the context of a PET preform, the cooling tubes 30 are preferably hollow tubes with open ends formed cylindrically, each having a channel in the base thereof connected to a vacuum or suction unit. operative to extract and / or simply maintain the preforms 32 in the tubes 30. In general, the extraction plate 28 will be cooled either by connection to a heat sink or and / or by a combination of appropriate techniques, in which internal water channels are included, as will be understood. Figure 2 shows a cooling tube assembly 50 comprising an internal porous insert 52 preferably made of a material such as porous aluminum having a porosity in the range of about 3 to 20 microns. The porous properties of the substrate are generally obtained either from its material configuration or a chemical removal (or adjustment) treatment process in which interstitial spaces are induced to the substrate, thereby producing an internal structure that is somewhat analogous to either a honeycomb or a hardened sponge. The present invention can make use of communication channels through the substrate material having an external size in the range of 3 to 20 microns, although those readily commercially available materials, such as METAPOR ™ and PORCERAX ™ (both manufactured by the International Mold Steel Corporation), are discussed with respect to the preferred embodiments described herein. The porosity is any case, function of the surface finish and machining of the surface work can affect the porosity through the material, as will be understood. In a preferred embodiment, the internal porous insert 52 is fabricated from a structure having strength and mechanically resilient properties, although the internal porous insert could also be manufactured from substances such as graphite. It is preferable that the internal porous insert 52 is a thermal conductor, while it is particularly preferable that the thermal conduction properties are good, for example a metal-based material or sintered composite material. As will be understood, METAPOR ™ is a combination of aluminum and epoxy resin having a mixing ratio of between about 65-90% aluminum powder and 35-10% epoxy resin. A typical cooling tube assembly 50 can have an internal length dimension of approximately 100 millimeters (mm), with an inner diameter of approximately 25 mm and an external diameter of 40 mm, these dimensions reflect the size of the molded article. Of course, tubes of different diameters and lengths can be manufactured to adapt the particular preform shape that is cooled. From a practical perspective, the porous insert 52 is preferably located in a tube body 54, which is surrounded by a sleeve 56. The cooling channels (or passages) 58 are optionally cut or otherwise formed adjacent to the tube body 54. and transporting a cooling fluid (e.g., air, gas or liquid) to cool the body 54 and the insert 52, thereby removing the heat from the molded plastic part in the porous insert 52. Each cooling channel is preferably configured to have a cross section comprising a plurality of elongated, arcuate grooves extending around more than 50% of the circumference of an internal diameter of a respective cooling cavity. Alternatively, the body 54 of the tube could simply be thermally coupled to a heat sink to reduce the overall combined weight of the tubes and the arm end tool 28, provided that the heat sink is capable of extracting sufficient heat from a preform in unit time. The seals 60-63 between the sleeve 56 and the body of the tube 54 contain the cooling fluid in the slits 4. Channels 66 are cut or otherwise formed on the outer surface of the porous insert 52 and provide a means for applying a vacuum through the porous structure of the porous insert 52. In addition to the channels 66, the outer surface of the porous insert 52 is configured in such a way that good surface contact is maintained between the insert 52 and the body of the tube 54, to optimize by this the heat transfer from the porous insert to the molded plastic part. The vacuum is applied through the porous insert, such that a newly loaded molded plastic part 32, shown in Figure 3, is caused to expand in size to touch an inner surface 82 of the porous insert as shown in FIG. Figure 4. Thus, the heat is conducted from the molded plastic part 32 to, and through the porous insert 1 to the cooled tube body 54. It will be noted that the position of a dome portion 80 of the preform 32 is exaggerated in the 3 and that Figure 3 is representative of a time when the preform is introduced to the cooling tube assembly 50. Under the application of suction or vacuum, a pressure lower than the ambient pressure is present to the exterior of the insert 52, thus causing that the air flows through the porous insert 52 from the internal surface 82 thereof and to the channels 66. This suction, at the same time, causes a lower pressure than the environmental pressure on the external surface of the part of the pl molded plastic, causing it to come into contact with the inner surface 82 of the porous insert 52. In a PET environment, with a METABOR ™ insert having interstitial spaces of 3-20 microns, operational vacuum pressures for the system are obtainable in the range of approximately 254 to 762 millimeters (10 to 30 inches) of mercury (using a Becker U3.6s evacuation pump). Nevertheless, it will be understood that the applied vacuum pressure is finally determined by (and is a function of) the mechanical properties of the plastic material. A positive pressure can also be applied (by means of a fluid injector and flange seals) to the inside of the preform to cause the preform to come in contact with at least a portion of the inner surface of the cooling tube, although This requires a sealed system. Any suitable pressure differential can therefore be applied to the inner surface of the cooling tube and the outer surface of the plastic part, depending on the shape of the part and the cycle time provided for cooling. It is preferred that the entire outer surface of the preform (cylindrical outer surface and spherical outer surface at the distal tip, that is, dome 80) is brought into contact with the porous insert cooling tube, although an external profile of the preform it can in effect prevent this along with, for example, any inward tapering portion 84 proximate the neck finish of the preform 32. However, the cooling tube and vacuum structure may be designed to bring any portions of the preform in contact with the cooling tube, depending on the design of the plastic part and the portions of it that need cooling. In addition, the vacuum (or positive pressure) can be applied in one, two or three or more stages to affect several cooling profiles of the plastic part. For example, a thick portion of a preform may be brought into immediate contact with the cooling tube, while a thinner portion of the preform may be brought into contact with the cooling tube at a later time. In general, the preform is in contact with the cooling tube 50 for a sufficient time only to allow robust handling of the preform without fear of damage arising, this depending on the material of the preform, design and cross section profile. The porosity of the porous insert 52 can be lowered to improve the surface finish (ie, inner surface 82) of the porous insert 52 in contact with the molded plastic part and thereby minimize any marking of the surface of the molded part. However, the reduction of the porosity of the insert 52 also reduces the flow of air passing through it. A modest flow reduction can be tolerated since this does not extensively impede the effect of the created vacuum or diminishes its intensity, especially since, once the surface of the molded part comes into contact with the insert, the entire flow of air stops. The air flow velocity only affects the speed at which the vacuum is created when the molded part 32 initially enters the tube 52. The reduction of porosity is obtained by milling and rectification procedures, while additional process steps of rectification with Abrasive stone or electric discharge can clear debris from the interstitial spaces of the surface to increase porosity. In any case, the flow velocity through the material is a function of both the applied pressure and the porosity, as will be easily understood. To the interior of the cooling tube 50, due to the partially cooled, but still malleable, state of the molded part at the entrance to the molded plastic part, the vacuum will cause the molded plastic part to expand in diameter and perhaps in length. The molded part is subjected to a vacuum applied to most of its external surface, while its internal surface is exposed to ambient pressure. In Figure 5, the supporting edge 100 of the molded part 32 prevents the part from further entering the tube 50 as the part cools and shrinks. In this case, the vacuum removes the closed end of the part additionally to the tube, while the support flange prevents the opposite end from following it. In all embodiments, the vacuum causes the part to change shape to substantially eliminate the tolerance that initially exists between the outer surface of the part and the corresponding internal surface of the porous insert 52. In the case of molded plastic parts having aspects in diameter, such as the inwardly tapered portion 84, these will not be substantially altered in shape during this expansion phase. The configuration and size of the internal dimensions of the porous insert 52 are realized in such a way that the diameter coincides or is slightly larger than the corresponding diameter of the part that is cooled, thus preventing substantial disfigurement of the plastic part shape. The end seal 104 (of Figure 3) at the open end of the cooling tube 50 provides a means to initially establish (and as necessary maintain) the vacuum within the assembly and continue to cause part 8. If there are sections of the insert porous 52 not engaging portions of the preform, such as the region 106 shown in Figure 4, below the support flange 100, then the end seal 104 is required to ensure that the molded parts remain in contact with the wall internal 82 and thereby resist the shrinking effect of the part 8 as it cools, otherwise the end seal 104 may be omitted. If the vacuum were not present, the shrinkage of the part 8 would cause a separation between the outer wall of the part and the internal cooling wall of the insert 52 (and hence a resulting loss of suction), thereby greatly impeding the transfer of heat from the part to the insert 52 and to the cooling tube. Thus, the continuous supply of the vacuum ensures intimate contact between the outer surface of the molded part and the inner wall 82 of the insert is maintained to maximize the cooling performance. Returning to Figure 3, the cooling assembly 50 is preferably secured to an extraction carrier or plate 110 by a screw 112. The insert 52 is retained in the assembly by a collar 114, which is threaded onto the body of the tube 54 or attached or otherwise engaged by any other conventional means. An inlet 116 of the cooling fluid channel and an outlet of the cooling fluid channel 118 are provided in the carrier plate 110. A vacuum channel (or passage) 120 is also provided in the carrier plate 110. After it has elapsed a sufficient cooling time, the vacuum is replaced with pressurized air flow (by inverting the function of the vacuum pump), and the part is ejected from the cooling tube assembly 50 by this pressure. Figures 5 and 6 show an alternative embodiment for a cooling tube 150 in which the tube body 54 and the sleeve 56 are replaced with an extruded tube containing integral cooling channels. An aluminum extrusion 152 forms the body of the tube and contains integral cooling channels 154 which are alternately connected to each other by slits 156 at each end of the tube. Sealing rings 158 close the ends of the tube to complete the integrity of the cooling circuit. A porous aluminum insert 160 having external slits 162 which act as a channel for the vacuum, is located (inside the cooling tube 150) by a spacer 164 and a collar 166 attached to the tube by means of a threading or any other mechanism of conventional support. The cooling tube assembly is fastened to the carrier plate 110 by any appropriate external fastening means, such as a bolt 168. This alternative embodiment has a lower manufacturing cost and improved cooling efficiency by virtue of its body component extruded Figure 7 shows a second alternative embodiment for cooling a molded part having a different shape. In this arrangement, the end seal (reference number 104 of Figure 3) between the upper part of the cooling tube and the lower side of the supporting edge 100 is not necessary. A porous insert 200 is retained within the extruded tube 152 by a collar 201 which is threaded 202 over the top of the cooling tube (in this case the extruded tube 152 or held by any appropriate means) The collar 152, commonly made of aluminum or the like, extends inwardly to conform to the internal shaped form 204 of an open end of the insert 200 that coincides or is slightly larger than that of the part that is cooled.The collar 201 provides a seal of sufficient effectiveness to allow the vacuum applied to the porous insert causes the part to expand in size and fit intimately against the inner surface of the insert and to cool it in. In some cases, it is preferred that the part have a looser fit in the tube when it first enters. In this case, Figure 8 shows how a flange seal 210 can provide the initial seal necessary to allow a vacuum becomes effective after loading a looser fitting part. Methods of construction and use of the cooling tubes (in an operational environment) of the present invention to accentuate the cooling and formation of parts have been described above. Briefly, a porous cooling tube constructed according to one of the embodiments of the present invention is manufactured by milling or extruding a cooling tube assembly having a porous cooling tube insert and optional, but preferable, fluid channels of cooling. The porous insert can be polished, painted or otherwise treated to reduce porosity and provide a finer finish to the outside of the molded part. The cooling fluid channels may be completely enclosed within the tube or may be formed by placing a sleeve over open channels formed in the outer surface of the porous insert. Vacuum channels can be milled or extruded on an external surface of the porous insert or can be provided with a separate structure adjacent to the outer surface of the porous insert. The closed end of the cooling tube may be machined to the tube or may comprise a plug fitted to an open end of a cooling cylinder. Then appropriate seals are adjusted either to one end or the other of the cooling tube to provide the required pressure handling, as described above. In operation, the newly molded plastic part is removed from a mold cavity and transported by the carrier plate to a cooling station, where one or a plurality of cooling tubes are placed. The plastic part is inserted into the cooling tube and preferably sealed therein. A vacuum (or partial vacuum) is then applied through the porous insert from the outer surface thereof to the inner surface thereof, causing the plastic part to expand in length and diameter to contact the inner surface of the insert. porous. The cooling fluid circulates through the cooling channels, extracting heat from the porous insert, which extracts the heat from the molded part. When sufficient cooling is complete (when the outer surfaces of the molded part have solidified and obtained sufficient stiffness (the vacuum is released and the molded part is ejected, for example to a packing tray.) If desired, a positive pressure may be applied. to be applied through the vacuum channels to force the molded part from the cooling tube.Thus, what has been described is a new cooling tube assembly for the improved cooling of partially cooled molded parts which provide a means to maintain an intimate surface contact between the outer surface of the part and the inner cooled surface of the tube during the cooling cycle The developed post-molding cooling device preferably uses a vacuum to slightly expand the part to contact the cooled surface and to maintain contact as the part cools, thereby counteracting the shrinkage which tends to extract the part away from the cooled surface. The present invention can also be described with respect to embodiments in which the cooling tube includes an extruded tube. The extruded cooling tube has particular use in a plastic injection molding machine, although the present invention is equally applicable to any technology in which, following the formation of parts, cooling of that part is undertaken by means of a cooling tube or the like. For example, the present invention may find application in a transfer mechanism of parts of an injection molding machine and a blow molding machine.
Figure 9 shows a cross-sectional view through a cooling tube 350 of one embodiment of the present invention. The cooling tube 350 preferably comprises an extruded one-piece tube 352 with an outer surface 384, an inner surface 382 for operating on the preform 32. the cooling tube 350 includes a cooling circuit for cooling the inner surface 382 including channels cooling elements 382 longitudinally oriented formed by extrusion between the inner surface 382 and the outer surface 384 of the tube 352. The cooling channels 354 are connected together in a desired flow configuration by any number of connecting channels 356 and the connected cooling circuit to a source and coolant sink through inlet and outlet channels 390 and 392. The connecting channels 356 are located on the top and base of the tube 352, between the outer surface 384 and the inner surface 382 and extend between two or more cooling channels 354. The connecting channels 356 are closed on one side by sealing rings 358. Sealing rings 358 including seals 359 are retained in a slot in the top and bottom of cooling tube 350 by insertion rings 366 or other known fastening means. The cooling tube 350 further includes a central plug 364 inserted into its base and retained by the shoulder 367. The central plug 364 includes a contoured inner surface 303 for supporting and otherwise operating on the bottom of a preform 32. The central plug 364 also includes a pressure channel 394, for connection to a vacuum source for the purpose of assisting in the transfer of a preform 32 to the cooling tube 350. The cooling and inlet channels of refrigerant 390 and 392 of the cooling circuit are provided in the central plug 364. The tube 352 preferably comprises a one piece extruded tube with longitudinal cooling channels 354 which may have a cross section profile selected from a wide range of shapes. The use of conventional machining techniques (eg, milling) to machine the channels 354 with the shape shown in Figure 10 is not generally practical beyond a length of approximately 4 times the diameter of the cutting element that is used, limiting by this the length of the cooling tube manufactured by this method at an inappropriately small interval. Accordingly, an extruded tube can be identified as one having an integral cooling channel having a length greater than 4 times the smaller diameter of the cooling channel 354 or one having a substantially constant non-cylindrical cooling channel shape 354.
The cooling channels 354 formed in the extrusion process provide channels for the cooling fluid to circulate in the tube, extracting heat from the preform 32 through the inner surface of the tube 382. The cooling tube may include 4 cooling channels 354 (as shown in Figure 10). The shapes of the channels 354 are preferably arcuate elongated grooves having a larger cooling surface area than the perforated holes. Preferably, the cumulative angular extension of all elongated slots is greater than 180 degrees, the angular extent of each elongated slot being the measure of the contained angle of a concentric arc with the cooling tube with its end points defining a maximum arc length through the elongated slot. Such form works to optimize the thermal transfer of a preform 32 due to the distribution of refrigerant that extends around a substantial portion of, in proximity to the inner surface 382 that is brought into contact with the preform 32 and also due to the speed of high volumetric flow of the refrigerant supported by the large cross section profile of the coolant channel 53. In addition, the cross-sectional profile of the channel 354 of the preferred refrigerant provides a relatively lightweight cooling tube 350, which results in a reduction in overall mass in the carrier plate assembly 11 which can be considerable given that some carrier plate assemblies include more than 432 tubes (this is a carrier plate assembly with 3 sets of 144 cooling tubes), thereby enabling a lighter work and hence a lower cost robot to be used and / or allowing the plate to be moved faster, thereby saving a cycle time and reducing energy consumption. In an alternative embodiment of the invention, the four arcuate shaped channels shown in Figure 10 could be changed to only 2 larger arched shapes (not shown) in such a way that one channel represents the entrance and the other the exit, simplifying by this the connecting channels 356. The central plug 364 preferably includes a contoured inner surface 303 formed to substantially coincide with that of the part that is cooled. The central plug 364 is preferably manufactured from aluminum and functions to cool the gate area of the preform to define a channel for the vacuum and to facilitate the coupling of the cooling channels to the carrier plate 11, where necessary. The provision of pressure channel 394 is preferable in the center of the plug. In one embodiment, the central plug 364 is retained between the shoulder 367 of the cooling tube and the extraction plate 28. A tube holder 368, such as a screw or bolt, is provided for coupling the cooling tube 350 to the plate Extraction 28. Alternative means for mounting the plug 14 and securing the cooling tube 350 to the extraction plate 28 can be used. Exemplary physical dimensions of a cooling tube 350 for an arbitrary preform 32 according to the present invention suggest a representative length of approximately 100 mm in length, an inner diameter of approximately 25 mm and an external diameter of approximately 41 mm. For such an arbitrary cooling tube, the cooling channels 354 are preferably about 1-4 mm thick, about 80 mm in circumference and about 100 mm (preferably the same length as the tube) of axial length. Of course, tubes of different diameters and lengths would be manufactured to adapt to the geometry of any preform 32 and hence wide variations in the dimensions of the coolant channel 354 are possible. The cooling tube 350 is preferably manufactured from aluminum. According to the present invention, an extrusion process is used to form a tube 352 that includes the cooling channels and a hole, the hole preferably being sized to be smaller than any of the plastic parts intended for cooling in the tube . The extrusion process is consistent with known techniques. Then the tube 352 is cut to the length and the molding surface and any other desirable aspects such as connection channels 356, slits of the sealing ring 358 and any inlet / outlet or pressure channels of the refrigerant, coupling structure, etc.) they are machined. Then the central plug 364 is machined, which includes the addition of desirable aspects (such as coolant channel 390, 392 and pressure channel 394). The central plug 364 with all the necessary seals is then installed in the cooling tube 350 and the sealing rings 358 with seals 359 installed to the sealing ring grooves in the upper and lower part of the cooling tube 350, in such a way that all the assembly is ready for installation on the extraction plate 28. In a preferred embodiment, the connection channels 356 at the upper end of the tube 352 can be provided by machining through alternative separation walls (not shown) of the cooling channel 354. At the end of the extraction plate 28 (bottom) of the tube 352Similar alternative partition walls (not shown) are machined to connect the cooling channels 354 and provide connections to the cooling fluid inlet channel 390 and the cooling fluid outlet channel 392. Alternatively, the cooling channels 354 in the wall of the tube could be connected directly to the corresponding holes in the extraction plate 28. In an alternative embodiment of the present invention (not shown) the cooling tube is extruded to define a tube formed cylindrically | with an internal surface, an external surface and at least one cooling channel 354 formed on the external surface of the tube 352. A tubular sleeve fits around the tube 352 thereby enclosing the cooling channels 354. Seals are provided between the tube 352 and sleeve to provide a watertight connection. The cooling channels can be connected as previously described in the preferred embodiment of the invention. In an alternative embodiment of the present invention (not shown) the cooling tube is extruded to define a cylindrically formed tube with an inner surface, an outer surface and at least one cooling channel 354 formed on the outer surface of a tubular sleeve which fits around the tube 352 thereby enclosing the cooling channels 354. Seals are provided between the tube 352 and the sleeve to provide a watertight connection. The cooling channels can be connected as previously described in the preferred embodiment of the invention. In operation, the cooling tube is used similarly to that described in U.S. Patent 4,729,732. It is preferred that the internal dimensions of the cooling tube be slightly smaller than the external dimensions of the preform that is cooled. Thus, as the preform shrinks, its external size is reduced and a vacuum acting through the central plug extracts the part additionally to the cooling tube, in such a way that an intimate adjustment or contact of the outer surface of the preform It is maintained with the inner surface of the cooling tube. Alternatively, the internal dimensions of the cooling tube can be manufactured to be the same size or slightly larger than the external size of the preform that is cooled, to allow an air flow to be extracted beyond the external surfaces of the part. through emptiness. In more detail, after the preforms are formed in the injection molding machine, the mold is opened by the stroke of the movable plate 18 away from the fixed plate 16 and the robot arm (which carries the plate assembly carrier 11) moves between the mold halves 12 and 14 in such a manner that the cooling tubes 50 can receive a set of preforms 32 that are ejected from the cores 23. Applied suction can be used to encourage transfer of the preforms 32 from the cores 23 to the cooling tubes 350 and / or to retain the preforms therein. Then the carrier plate assembly 11 is removed from between the mold halves 12, 14 and then oriented in such a way that the carrier plate assembly 11 is sequentially or selectively positioned adjacent to a cooling station, a receiving station or a conveyor. Then the preforms can be transferred to it. In addition to the improved cooling tube cooling performance, there is a substantial benefit in the reduced cost of manufacturing. An extruded cooling tube according to the present invention can benefit from a cost reduction in relation to a tube conventionally manufactured due to substantially reduced machining requirements. In an alternative embodiment of the invention (not shown) the vent tube assembly 350 of Figure 9 can be modified to include a tubular porous insert 452, as shown in Figure 11, along the inner surface 382 for vacuum forming a preform 32 and for improving the cooling efficiency of the preform 32 due to a better heat conduction interface (ie, a larger surface contact area and a more intimate fit). The porous insert 452 includes an inner surface 482 and an outer surface 483, the inner surface 482 is contoured to substantially correspond to the final desired molding surface of the preform 32, the outer surface 483 can be segmented by a set of pressure channels longitudinally directed 466. The pressure channels 466 provide a conduit for establishing a very low vacuum pressure region in proximity to the porous insert portion 452 between the inner surface 482 and the outer surface 483 and thereby evacuate the air through of the porous structure of the porous insert 450 for the purpose of extracting a deformable preform 32 in contact with the contoured inner surface 482 of the porous insert 452, thereby vacuum forming the preform 32. The porous insert 452 is preferably manufactured from a highly material thermally conductive such as aluminum. The selection of the material for the porous insert is further characterized by the requirement of a porous structure with a porosity preferably in the range of about 3-20 microns. In addition, the porous insert 452 can be advantageously manufactured in a process that includes the extrusion step. Yet another alternative embodiment of the invention is shown in Figure 12, wherein a cooling tube assembly 450 is provided for vacuum forming a preform 32. The cooling tube assembly 450 including a tube 454 that can be machined from available tube inventory, however, an extruded tube such as tube 352 (as exemplified in Figure 9) can also be used. The tube 454 includes an insertion hole 455 for receiving a porous insert 452, as exemplified in Figure 11. The porous insert 452 is retained in the tube 454 by a central plug 464, the central plug 464 received in a first and second perforation for plug 457, 458 of tube 454. Central plug 454 is additionally retained in tube 454 by its shoulder 467 abutting against the tier between the first and second plug perforations 457, 458. Projection 467 on the central plug 464 corresponds to a tier in the diameter of the central plug 464 with a narrow portion at its upper end that provides an annular channel 465 between the central plug 464 and the second plug hole 458 of the tube 454. The annular channel 465 connects the channels of pressure 466 of the porous insert 452 with a channel 420 that is formed in the central plug 464 which is in turn connected in use to a first vacuum channel in the extraction plate 28. The ta central ply 464 includes a contoured inner surface 403 that substantially corresponds to the dome portion of the preform 32 that can be used to cool and cool the region. The central plug 464 further includes an inlet and outlet coolant channel 490, 492 and a pressure channel 494, for connection to coolant inlet and outlet channels 116, 118 and a second pressure channel in the exhaust plate 28, respectively. The inlet and outlet channels 490, 492 of the central plug 464 are further connected to a cooling slot 493 formed on the outer surface of the tube 454, thereby forming a cooling circuit. The cooling tube assembly 454 further includes a sleeve 456 that is retained on the outer surface of the tube 454. Seals 459 are also provided between the sleeve 456 and the tube 454 and between the central plug 464 and the tube 454 to provide leak-tight connections air and water between the components forming the cooling tube assembly 450. The tube 454 further includes a slit at its open end for receiving an end seal 404 which provides in use an air tight seal between the flange 100 of support of the preform and the assembly of cooling tube 450 to enclose the volume formed between the preform 32 and the cooling tube assembly 450, thereby enabling the development of the required low vacuum forming pressure. The primary components of the cooling tube assembly 450 are preferably manufactured from a highly thermally conductive material, such as aluminum. The operation of the cooling tube assembly 454 installed on the extraction plate 28 of the carrier plate assembly 11 will now be described. The extraction plate 28 provides coolant fluid inlet and outlet channels and first and second vacuum channels to correspond with the holes on the central plug 464. In use, a preform 32 is attracted to the cooling tube assembly 450 by a relatively high flow rate suction through the pressure channel 454 which further retains the preform 32 once the preform support flange 100 is sealed against the end seal 404 thereby stopping the air flow. A high vacuum is then applied through the vacuum channel 420 in the central plug 464, then through the annular channel 465 and pressure channels 466, after which the vacuum acts through the porous wall of the porous insert 452. The volume of air between the preform 32 and the inner surface 482 of the porous insert 452 is at least partially evacuated to cause attraction or removal of the outer surface of the preform in contact with the porous insert 452. Once in contact with the 452, the preform 32 is cooled by conduction, its heat moves through a path from the external surface of the preform to the porous insert 452, to the tube 454 and to the circulating coolant. Once sufficient heat has been removed from the preform 32 to ensure that it retains its shape, the high vacuum acting through the vacuum channels 466 is released and a positive pressure is applied through the pressure channel 494 to assist in the ejection of the preform 32.
Thus, what has been described is an extruded cooling tube for a plastic part, a porous insert for use with a cooling tube assembly for vacuum forming preforms, various advantageous embodiments of cooling tube assemblies, manufacturing methods of those mentioned above and a method for using a cooling tube assembly, which will greatly reduce the cost of the tubes in the injection molding and / or improve the quality of the molded preform 32. All the US patent documents and patents Foreign items and articles discussed above are incorporated by reference herein in the detailed description of the preferred embodiment. The individual components shown in outline or designated by blocks in the appended figures are all well known in the injection molding art and their specific construction and operation are not critical to the operation or better mode of carrying out the invention. While the present invention has been described with respect to what is currently considered the preferred embodiments, it will be understood that the invention is not limited to the disclosed embodiments. For example, while the preferred embodiment of the present invention discusses the present invention in terms of a porous insert, it will be appreciated that the insert could indeed be made by a thermally conductive but porous coating applied to a profiled housing, although the use of an insert benefits from the ease of manufacture and assembly. The application of the cooling technology is not limited, as will be understood, to the size or weight (for example, of the preforms) with the criteria that define being the ability to establish a vacuum to encourage contact of an external surface of the molded article. with the internal surface of the porous profiled substrate. Furthermore, while the cooling tube assembly of the present invention has been described in the context of a plastic injection molding machine, it will be appreciated that it is equally applicable to any technology in which, following the formation of parts , the cooling thereof is undertaken by means of a cooling tube or the like, for example in a mechanism for transferring parts between an injection molding machine and a blow molding machine. The scope of the following claims will be adapted to the broadest interpretation to encompass all such modifications and equivalent structures and functions. It is noted that, with regard to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.