HK1100538A - Cooling circuit for cooling neck rings of preforms - Google Patents

Abstract

A cooling circuit for a neck ring of a preform is conformed to the surface of the neck ring by providing a neck ring in two parts. The first part supports the neck ring and provides strength and durability to the neck ring insert. The second part is formed of porous steel impregnated with highly thermally conductive metal and includes a cooling channel that provides substantially uniform cooling around the neck ring of the preform.

Description

Cooling circuit for cooling neck rings of preforms

Technical Field

The present invention relates generally to injection molding of preforms, and more particularly, but not exclusively, to a mold insert for forming a neck ring on a preform and a method for manufacturing a mold insert.

Background

U.S. patent No. 5,599,567 to Gellert describes a neck ring insert for a preform mold having a compliant cooling channel in the insert. The cooling circuit described in Gellert moves coolant vertically in an external channel and then horizontally to an internal channel forming an internal cooling circuit. The cooling circuit has both horizontal and vertical portions and is ultimately connected to an external exhaust channel. This channel structure results in a faster cooling of the portion of the neck ring near the beginning of the cooling channel. Uneven cooling of the neck ring is undesirable.

U.S. reissue patent No. 38,396 to Gellert describes a method of manufacturing a neck ring insert for a preform mold. A first portion of the neck ring is manufactured by investment casting, and a portion of the cooling circuit is formed on an exterior surface of the casting. An outer portion is brazed to the casting to form a neck ring and includes cooling channels connected to the cooling channels on the first portion. The cooling channel thus formed is a continuous channel that provides the same non-uniform cooling as provided in U.S. patent No. 5,599,567 to Gellert, referenced above.

There is a need for a neck ring insert that is simple and convenient to manufacture and cools uniformly.

Disclosure of Invention

The present invention provides a two-part neck ring insert having a cooling circuit that provides substantially uniform cooling to the neck of the preform.

The present invention also provides a modular construction of the neck ring insert that enables it to combine features of strength and simplicity of manufacture with the ability to easily change the cooling channels to provide the most desirable cooling to each different type of neck ring.

The present invention also provides a cooling module that is not preform specific but can be used with preforms having different neck ring shapes and sizes.

The present invention also provides a neck ring insert that can be composed primarily of a high thermal conductivity material that does not compromise the strength and wear characteristics of the neck ring insert.

The present invention also provides a neck ring insert that allows for controlled cooling of the preform neck ring, and more particularly, allows for more uniform cooling across the preform neck ring.

More specifically, the present invention provides a cooling device for attachment to a neck ring half shell. The cooling device includes: a porous steel superstructure, preferably impregnated with a highly thermally conductive metal; and a branching coolant passage extending in opposite directions adjacent to an inner circumference of the cooling device.

In addition, the present invention provides a cooling insert for cooling selected portions of a molding device. The insert includes: a housing having an inner surface that mates with the first outer surface of the selected portion and a second outer surface; a cooling attachment having an inner surface mating with said second outer surface; and a cooling circuit located within the cooling attachment. The cooling circuit has an inlet portion for providing coolant to a bypass channel adjacent a mating inner surface of the accessory. The shunt channel forms two channels that extend in opposite directions parallel to the mating inner surface of the accessory.

In addition, the present invention provides an apparatus for cooling preforms, comprising: an injection mold having a mold cavity therein; means for injecting molten plastic into the mold to form a preform; and means for cooling said plastic from a molten state to a solid state in heat exchange relationship with said mold cavity. The heat exchange member includes neck ring half shells each having an inner surface conforming to a neck ring surface of the preform and an outer surface. A cooling attachment having an inner surface that mates with the outer surface can be securely fastened to the outer surface of each neck ring half. The cooling circuit within the cooling attachment has an inlet portion for providing coolant to a bypass channel adjacent a mating inner surface of the attachment. The shunt channel forms two channels that extend in opposite directions parallel to the mating inner surface. Each branch channel leads to a respective return channel. Each return channel extends toward a location near the inlet portion to return coolant to an outlet portion located near the inlet portion.

Drawings

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

figure 1 is a cross-sectional view of a prior art preform mold stack.

FIG. 2 is a cross-sectional view of a portion of a preform mold stack modified to include the neck ring insert of the present invention.

FIG. 3 is an isometric view of a neck ring half insert according to the present invention.

FIG. 4 is another isometric view of the neck ring half insert from a different angle than that shown in FIG. 3.

FIG. 5 is an isometric exploded view of the neck ring half insert shown in FIG. 3.

FIG. 6 is an isometric view of a cooling pack attachment which generally illustrates the cooling circuit of the present invention.

FIG. 7 is an isometric view of the cooling circuit of the present invention.

Fig. 8 is an isometric view of the neck ring half insert of the present invention.

FIG. 9 is an isometric view of an alternate embodiment of the cooling circuit of the present invention.

Detailed Description

The preform mold typically includes a stack of mold inserts. Each insert forms a portion of the preform being molded. The stack of inserts is carried by two or more mold plates supported in a mold shoe (mold shoe). A hot runner manifold distributes the injected plastic melt from a central feed gate to hot runner nozzles that connect to the molding cavities formed in each insert stack. The cold half of the mold includes the mold insert stack and the portion of the mold shoe on which the mold insert stack is mounted. The hot half of the mold includes a hot runner assembly that includes a sprue bush and several nozzles, and a mold plate adjacent to the manifold.

FIG. 1 shows a portion of a prior art preform mold stack 10, the stack including a core cooling channel 12, a core cooling tube 14, neck ring cooling channels 16, neck rings 18, a core 20, a lock ring 101, a mold cavity 22, a cavity insert 58, and mold cooling channels 24 extending circumferentially around the cavity. FIG. 1 also shows a PET preform 26, a mold gate insert 100, and an injection nozzle 28. The core cooling passage 12 includes a cooling inlet 32 and a cooling outlet 34. The mold stack 10 is located on a core plate 50, a stripper plate 52, a neck ring guide or slide 54, a cavity plate 56 and a cavity insert 58. A full description of the structure and operation of preform molding equipment can be found in U.S. Pat. No. 6,413,075 assigned to the present assignee.

The neck ring 18 is formed of two neck ring halves. Each half is formed as a single piece and is made of a hard durable material such as tool steel or stainless steel. The cooling channel is formed in the neck ring by drilling. This restricts the coolant channel to a substantially straight cylindrical hole that does not provide an ideal cooling path for cooling the preform neck. The neck ring must be made of this high strength material to withstand high injection pressures and clamping forces.

Each neck ring half 18 can be modified by forming each half as two parts. As shown in fig. 1, the first component is made of tool steel or stainless steel. However, this first part does not comprise any cooling channels. The second part is formed by a three-dimensional printing process or other powder forming technique (e.g., investment casting). The three-dimensional printing process or other powder forming technique allows for the formation of ideal cooling channels within the structure. This provides the neck ring halves with high strength provided by the first component and high thermal conductivity provided by the second component.

In the preform mold stack shown in FIG. 2, the neck rings 18 have been replaced with new neck rings formed in accordance with the present invention. Each neck ring half consists of a neck ring half shell 6 and a cooling pack attachment 11. The neck ring half shell 6 is made of strong tool steel, as is the prior art half ring shell 18. The cooling pack attachment 11 is manufactured by investment casting, three-dimensional printing or similar methods as will be described further below. The core insert 20A is similar in shape to the core insert 20 in fig. 1 and shapes the preform in the mold in a well-known manner. Lock ring 42 in combination with cavity lock ring 4 clamps half shell 6 and accessory 11 to mold cavity 44 as is well known in the art. The mold gate insert 100A provides support for the injection nozzle 28A.

Each neck ring half shell 6 has an inlet port 46 and an outlet port 48. The ports shown in fig. 2 and designated (46, 48) may be the inlet ports or the outlet ports. Each cooling pack attachment 11 includes an inlet passage 21 and an outlet passage 29. In the cross-sectional view shown in fig. 2, the channels designated (21, 29) may be either the inlet channel 21 or the outlet channel 29. Accessory 11 also includes return channels 27 and 37 and cooling paths 23 and 33. The channels 27 and 37 and paths 23 and 33 will be described more fully with reference to fig. 3-33.

As shown more particularly in fig. 3-9, each neck ring insert of the present invention comprises a neck ring half shell 6 and a cooling pack attachment 11. The shell 6 and the appendage 11 are formed separately and joined together by brazing or welding or any other suitable method that allows the two parts to be joined tightly.

The half shell 6 is made of tool steel or stainless steel or other suitable high strength material in a manner well understood in the molding art. Because tool steel is a relatively poor thermal conductor, the shell 6 is manufactured so that its walls are as thin as possible but remain strong enough to withstand the stresses of multiple injection cycles.

The attachment 11 is formed separately and preferably by using a three-dimensional printing method. This method is fully described in U.S. Pat. Nos. 5,204,055 and 5,387,380 to Sachs et al. By using the method, a first layer of metal powder particles (e.g., stainless steel or H-13 steel) is deposited on a substrate. The particles are uniformly deposited at a density that will ultimately provide a preferred porosity of up to 40%. After each layer is deposited, a layer of adhesive material is formed on the metal layer where it is desired to form a solid part of the structure of the appendage 11. Several successive layers of metal powder particles and bonding layers are deposited until the full size of the attachment 11 is reached. The part is heated in an oven to cure the bonded metal powder into a porous substrate and at the same time the bonding material evaporates. This leaves the desired cooling channels for the porous attachment.

This porous structure may be infused with a material to improve the thermal cooling characteristics of the structure. For example, to improve the cooling properties of the neck ring, the porous structure may be infused with a material having a high thermal conductivity. Ideally, the portion of the porous structure closest to the neck ring of the preform should be highly thermally conductive. The remainder of the porous structure need not be highly thermally conductive and may in fact be infused with an insulating material to limit the cooling loss of the preform neck ring being cooled.

One method of infusing a porous attachment is to place it adjacent a block of metal having a high thermal conductivity or in a bath containing such metal and energise it so that the high thermal conductivity metal infuses the porous attachment and thereby improves its thermal conductivity. This results in an attachment 11 that retains the strength of the tool steel, has a relatively high thermal conductivity, and a number of cooling channels ideally suited for controllably cooling the molding device to be cooled.

The neck ring shell 6 includes a partial molding surface detail geometry 13 that is suitable for molding the part produced. As shown in fig. 5, surface 15 is machined to mate with a corresponding machined surface 17 on attachment 11. The cooling attachment 11 can be mass-produced and retained as an inventory for attachment to a custom neck ring shell 6, which custom neck ring shell 6 can be designed for a variety of different neck ring designs. Thus, an efficient uniform cooling circuit is provided for multiple types of neck rings.

Fig. 5 shows a view of the neck ring 6 and the attachment 11, with the cooling circuit 8 shown separately from the attachment 11. The actual cooling circuit 8 is formed in the attachment 11 by the three-dimensional printing process or investment casting process described above. Which are individually presented herein to better illustrate their unique shapes and features.

Fig. 6 illustrates generally a preferred cooling circuit 8 formed in the attachment 11.

Figure 7 shows in detail the shape of the preferred cooling circuit 8. The inlet 21 receives coolant (e.g., water) and delivers it directly to the forward end of the cooling channel (at 31). The coolant flow is split at 31 into two separate cooling paths 23 and 33 located adjacent the periphery of the neck ring half shell 6 and following the contour of the shell 6. At the ends of the neck ring half shells, the cooling channels are 180 degree inverted at 25 and 35 and return in return channels 27 and 37 to outlet channel 29 near the center of the neck ring shell 6.

The cooling circuit 8 has many advantages over previously designed cooling circuits for preform neck rings. First, the cooling circuit is symmetrical so that all regions of the neck are cooled at a substantially similar rate. Dividing the flow path in half reduces the length of each cooling path in half so that the coolant is discharged from the cooling circuit before it becomes too hot to effectively cool the neck rings. More importantly, the cooling circuit can be made in any desired shape. In the present example for cooling the neck rings, the cooling circuit 8 is rectangular in cross-section, with the long sides of the rectangle parallel to the length direction of the preform and the narrow width of the channel perpendicular to the length of the preform. This ensures that more coolant flows against the surface to be cooled.

FIG. 8 shows the mounting of the cooling assembly 11 on the neck ring half shell 6.

Fig. 9 illustrates another embodiment of a cooling circuit with baffles 40 in the coolant flow path. The baffle 40 creates turbulence in the flow path and improves heat transfer from the neck ring to the coolant in the cooling circuit. It is apparent that by a three-dimensional printing process or an investment casting process, it is possible to position the baffle 40 having any desired shape anywhere in the cooling circuit in the cooling pack attachment 11.

It will of course be understood that the above description has been given by way of example only and that modifications in detail can be made within the scope of the invention.

Claims (28)

1. A cooling device for attachment to a neck ring half shell, the cooling device comprising a structure having bifurcated cooling channels extending in opposite directions around an inner circumference of the cooling device.

2. A cooling device for attachment to a neck ring half shell, the cooling device comprising a porous steel superstructure poured from a highly thermally conductive metal and a shunt coolant channel extending in opposite directions adjacent an inner circumference of the cooling device.

3. The cooling device according to claim 1 or 2, wherein the porous steel superstructure is formed using a three-dimensional printing process or an investment casting process.

4. A cooling insert for cooling a selected portion of a molding device, said insert comprising:

a housing having an inner surface mating with a first outer surface of the selected portion and a second outer surface;

a cooling attachment having an inner surface mating with said second outer surface; and

a cooling circuit within the cooling attachment, the cooling circuit having an inlet portion for providing coolant to a bypass channel adjacent the mating inner surface of the attachment, the bypass channel forming two channels extending in opposite directions parallel to the mating inner surface of the attachment.

5. An improved neck ring cooling insert for cooling a neck ring of a molded preform, said insert comprising:

a neck ring half shell having an inner surface conforming to a neck ring surface of the preform and an outer surface;

a cooling attachment having an inner surface complementary to and securely fastenable to said outer surface; and

a cooling circuit within the cooling attachment, the cooling circuit having an inlet portion for providing coolant to a bypass passage adjacent the mating inner surface of the attachment, the bypass passage dividing to form two passages extending in opposite directions parallel to the mating inner surface, each bypass passage leading to a respective return passage, each return passage extending toward a location adjacent the inlet portion to return the coolant to an outlet portion adjacent the inlet portion.

6. The insert of claim 5, wherein the channel in the cooling circuit is generally rectangular in cross-section with a longer side adjacent the conforming inner surface of the appendage.

7. The insert of claim 5, wherein the inlet portion engages the shunt channel at a substantially central point in the shunt channel such that the individual portions of the shunt channel are of substantially equal length.

8. The insert of claim 6, wherein the inlet portion engages the shunt channel at a substantially central point in the shunt channel such that the individual portions of the shunt channel are of substantially equal length.

9. The insert of any of claims 5, 6, 7 or 8, wherein each portion of the shunt channel reverses direction 180 degrees as it approaches an edge of the half shell and returns to the outlet portion on a path parallel to and rearward of an initial portion of the shunt channel.

10. The insert of any of claims 5, 6, 7, or 8, wherein a number of baffles are located in the cooling channel.

11. A neck ring insert for securing and cooling a preform, comprising a pair of neck ring cooling inserts, each insert comprising:

a neck ring half shell having an inner surface conforming to a neck ring surface of the preform and an outer surface;

a cooling attachment having an inner surface complementary to and securely fastenable to said outer surface; and

a cooling circuit within the cooling attachment, the cooling circuit having an inlet portion for providing coolant to a bypass passage adjacent the mating inner surface of the attachment, the bypass passage dividing to form two passages extending in opposite directions parallel to the mating inner surface, each bypass passage leading to a respective return passage, each return passage extending toward a location adjacent the inlet portion to return the coolant to an outlet portion adjacent the inlet portion.

12. The insert of claim 11, wherein the channel in the cooling circuit is generally rectangular in cross-section with a longer side adjacent the conforming inner surface of the appendage.

13. The insert of claim 11, wherein the inlet portion engages the shunt channel at a substantially central point in the shunt channel such that the individual portions of the shunt channel are of substantially equal length.

14. The insert of claim 12, wherein the inlet portion engages the shunt channel at a substantially central point in the shunt channel such that the individual portions of the shunt channel are of substantially equal length.

15. The insert of any of claims 11, 12, 13 or 14, wherein each portion of the shunt channel reverses direction 180 degrees as it approaches an edge of the half shell and returns to the outlet portion on a path parallel to and rearward of an initial portion of the shunt channel.

16. The insert of any of claims 11, 12, 13 or 14, wherein a number of baffles are located in the cooling channel.

17. An apparatus for cooling a preform, comprising:

an injection mold having a mold cavity therein;

means for injecting molten plastic into said mold to form a preform;

means in heat exchange relationship with said mold cavity for cooling said plastic from a molten state to a solid state; the heat exchange member includes: a pair of neck ring half shells, each half shell having an inner surface conforming to a neck ring surface of the preform and an outer surface; a cooling attachment having an inner surface complementary to and securely fastenable to said outer surface; and a cooling circuit located within said cooling attachment, each said cooling circuit having an inlet portion for providing coolant to a bypass channel adjacent said mating inner surface of said attachment, each said bypass channel being divided to form two channels extending in opposite directions parallel to said mating inner surface, each bypass channel leading to a respective return channel, each said return channel extending toward a location adjacent said inlet portion for returning said coolant to an outlet portion adjacent said inlet portion.

18. A cooling attachment for providing cooling to a preform, the attachment securable to a neck ring half insert that supports and retains a threaded portion of the preform, the cooling attachment comprising:

an inner surface complementary to and securely fastenable to said outer surface; and

a cooling circuit within the cooling attachment, the cooling circuit having an inlet portion for providing coolant to a bypass passage adjacent the mating inner surface of the attachment, the bypass passage dividing to form two passages extending in opposite directions parallel to the mating inner surface, each bypass passage leading to a respective return passage, each return passage extending toward a location adjacent the inlet portion to return the coolant to an outlet portion adjacent the inlet portion.

19. An apparatus for cooling a plurality of preforms, comprising:

an injection mold having a plurality of mold cavities therein;

means for injecting molten plastic into each of said mold cavities to form a preform;

means in heat exchange relationship with each of said mold cavities for cooling said plastic from a molten state to a solid state;

each of the heat exchange members includes: a pair of neck ring half shells, each neck ring half shell having an inner surface conforming to a neck ring surface of a preform and an outer surface; a cooling attachment having an inner surface conforming to and securely fastened to said outer surface; and a cooling circuit within the cooling attachment, each of the cooling circuits having an inlet portion for providing coolant to a bypass channel adjacent the mating inner surface of the attachment, each of the bypass channels forming two channels extending in opposite directions parallel to the mating inner surface and opening into a respective return channel, each of the return channels extending toward a location adjacent the inlet portion for returning the coolant to an outlet portion adjacent the inlet portion.

20. The cooling apparatus of claim 19, wherein the channel in the cooling circuit is generally rectangular in cross-section with a longer side of the channel adjacent the conforming inner surface of the appendage.

21. A cooling apparatus according to claim 19, wherein each of the inlet portions engages a respective one of the branch channels at a substantially central point therein such that the separate portions of the branch channels are of substantially equal length.

22. A cooling apparatus according to claim 20, wherein each of the inlet portions engages a respective one of the branch channels at a substantially central point therein such that the separate portions of the branch channels are of substantially equal length.

23. A cooling apparatus according to any one of claims 19, 20, 21 or 22, wherein each portion of each said bypass channel reverses direction 180 degrees as it approaches an edge of a respective half shell and returns to said outlet portion on a path parallel to and rearward of an initial portion of said bypass channel.

24. The cooling apparatus of any of claims 19, 20, 21, or 22, wherein a number of baffles are located in each of the cooling channels.

25. An insert according to any of claims 4, 5, 6, 7, 8, 11, 12, 13 or 14 wherein the cooling attachment comprises a porous steel superstructure impregnated with a highly thermally conductive metal.

26. The insert of any of claims 4, 5, 6, 7, 8, 11, 12, 13, or 14, wherein the cooling attachment comprises a porous steel superstructure infused with a highly thermally conductive metal, and the cooling attachment is formed using a three-dimensional printing process or an investment casting process.

27. The apparatus of any of claims 19, 20, 21 or 22, wherein the cooling attachment comprises a porous steel superstructure infused with a highly thermally conductive metal.

28. The apparatus of any of claims 19, 20, 21 or 22, wherein the cooling attachment comprises a porous steel superstructure infused with a highly thermally conductive metal, and the cooling attachment is formed using a three-dimensional printing process or an investment casting process.