WO2012064492A1

WO2012064492A1 - Mold-tool system including manifold assembly having melt channel having melt-channel geometry for focusing melt-channel stress

Info

Publication number: WO2012064492A1
Application number: PCT/US2011/057407
Authority: WO
Inventors: Edward Joseph Jenko; Darrin Albert Macleod; James Osborne Plumpton; Manon Danielle Belzile
Original assignee: Husky Injection Molding Systems Ltd
Priority date: 2010-11-10
Filing date: 2011-10-22
Publication date: 2012-05-18

Abstract

A mold-tool system, comprising: a manifold assembly defining a melt channel, the manifold assembly having: a relatively critical operational area; and a relatively less-critical operational area being spaced apart from the relatively critical operational area. The melt channel has a melt-channel geometry. The melt-channel geometry is configured to focus, in use, melt-channel stress: (i) away from the relatively critical operational area, and (ii) toward the relatively less-critical operational area.

Description

MOLD-TOOL SYSTEM INCLUDING MANIFOLD ASSEMBLY HAVING MELT CHANNEL HAVING MELT-CHANNEL GEOMETRY FOR FOCUSING MELT- CHANNEL STRESS

TECHNICAL FIELD

An aspect generally relates to (and is not limited to) mold-tool systems including (and is not limited to) a mold-tool system including a manifold assembly having a melt channel having a melt-channel geometry for focusing a melt-channel stress.

BACKGROUND

The first man-made plastic was invented in Britain in 1851 by Alexander PARKES. He publicly demonstrated it at the 1862 International Exhibition in London, calling the material Parkesine. Derived from cellulose, Parkesine could be heated, molded, and retain its shape when cooled. It was, however, expensive to produce, prone to cracking, and highly flammable. In 1868, American inventor John Wesley HYATT developed a plastic material he named Celluloid, improving on PARKES' concept so that it could be processed into finished form. HYATT patented the first injection molding machine in 1872. It worked like a large hypodermic needle, using a plunger to inject plastic through a heated cylinder into a mold. The industry expanded rapidly in the 1940s because World War II created a huge demand for inexpensive, mass- produced products. In 1946, American inventor James Watson HENDRY built the first screw injection machine. This machine also allowed material to be mixed before injection, so that colored or recycled plastic could be added to virgin material and mixed thoroughly before being injected. In the 1970s, HENDRY went on to develop the first gas-assisted injection molding process.

Injection molding machines consist of a material hopper, an injection ram or screw- type plunger, and a heating unit. They are also known as presses, they hold the molds in which the components are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than five tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The amount of total clamp force is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from two to eight tons for each square inch of the projected areas. As a rule of thumb, four or five tons per square inch can be used for most products. If the plastic material is very stiff, more injection pressure may be needed to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force. With Injection Molding, granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heated chamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle that rests against the mold, allowing it to enter the mold cavity through a gate and runner system. The mold remains cold so the plastic solidifies almost as soon as the mold is filled. Mold assembly or die are terms used to describe the tooling used to produce plastic parts in molding. The mold assembly is used in mass production where thousands of parts are produced. Molds are typically constructed from hardened steel, etc. Hot-runner systems are used in molding systems, along with mold assemblies, for the manufacture of plastic articles. Usually, hot-runners systems and mold assemblies are treated as tools that may be sold and supplied separately from molding systems.

United States Patent Number 7614872 discloses an injection molding apparatus having a manifold and several manifold melt channels communicating with several hot runner nozzles includes a melt redistribution element. The melt redistribution element is placed at specific locations along the melt channels to balance the uneven shear stress profile accumulated during the flow of a melt along the manifold channels. The melt redistribution element has an unobstructed central melt bore having at its inlet a narrowing tapered channel portion. The melt redistribution element also includes a helical melt pathway portion that surrounds the central melt bore. The incoming melt is first subjected to a pressure increase by the tapered portion that causes the melt to flow at a higher velocity through the central melt bore. The outer portion of the melt is forced to flow along the helical path and thus it changes direction multiple times and partially mixes with the melt flowing through the central melt bore. Accordingly, at the outlet of the melt redistribution element the shear stress profile is more evenly distributed than at the inlet of the redistribution element.

SUMMARY

The inventors have researched a problem associated with known molding systems that inadvertently manufacture bad-quality molded articles or parts. After much study, the inventors believe they have arrived at an understanding of the problem and its solution, which are stated below, and the inventors believe this understanding is not known to the public.

Known methods for manufacturing a melt channel in a manifold assembly include the usage of gun drills to machine the melt channel. The resulting melt channel has a shape that is cylindrical. Although a round-shaped melt channel may be advantageous in that it has the largest flow area for the least surface area, this type of melt channel may not always provide an ideal arrangement for a melt channel. In particular for a split-manifold assembly, a split line (the lines that separates the halves of the manifold body) may be the weakest part of the manifold assembly, and typically falls at the area of highest stress in the round-shaped melt channel. A split- manifold assembly includes manufacturing two halves of a manifold body, machining the melt channel in the two halves of the manifold body, and then joining (welding) the two halves together. With round melt channels at the melt channel intersections or direction changes there is a resulting high stress in the transverse plane of the melt channel. For the split-manifold assembly, the weakest area in the manifold assembly may be on the melt channel transverse plane and the location of the split manifold joint. The inventors have identified that the round-shaped melt channel creates a hoop stress that runs perpendicular to the split line of a split manifold assembly that pulls apart the manifold assembly at the split line.

According to one aspect, there is provided a mold-tool system, comprising: a manifold assembly defining a melt channel, the manifold assembly having: a relatively critical operational area; and a relatively less-critical operational area being spaced apart from the relatively critical operational area, the melt channel having a melt-channel geometry, the melt-channel geometry being configured to focus, in use, melt-channel stress: (i) away from the relatively critical operational area, and (ii) toward the relatively less-critical operational area.

Other aspects and features of the non-limiting embodiments will now become apparent to those skilled in the art upon review of the following detailed description of the non-limiting embodiments with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

The non-limiting embodiments will be more fully appreciated by reference to the following detailed description of the non-limiting embodiments when taken in conjunction with the accompanying drawings, in which:

FIGS. 1 A, 1 B, 2A, 2B, 2C, 2D, 3A, 3B, 3C depict various schematic representations of a mold-tool system (100).

The drawings are not necessarily to scale and may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details not necessary for an understanding of the embodiments (and/or details that render other details difficult to perceive) may have been omitted.

DETAILED DESCRIPTION OF THE NON-LIMITING EMBODIMENT(S)

FIGS. 1A, 1 B, 2A, 2B, 2C, 2D, 3A, 3B, 3C depict the various schematic representations of the mold-tool system (100). The mold-tool system (100) may include components that are known to persons skilled in the art, and these known components will not be described here; these known components are described, at least in part, in the following reference books (for example): (i) "Injection Molding Handbook' authored by OSSWALD/TURNG/GRAMANN (ISBN : 3-446-21669-2), (ii) "Injection Molding Handbook' authored by ROSATO AND ROSATO (ISBN : 0-412- 99381 -3), (iii) "Injection Molding Systems" 3^rd Edition authored by JOHANNABER (ISBN 3-446-17733-7) and/or (iv) "Runner and Gating Design Handbook' authored by BEAUMONT (ISBN 1 -446-22672-9). It will be appreciated that for the purposes of this document, the phrase "includes (and is not limited to)" is equivalent to the word "comprising". The word "comprising" is a transitional phrase or word that links the preamble of a patent claim to the specific elements set forth in the claim which define what the invention itself actually is. The transitional phrase acts as a limitation on the claim, indicating whether a similar device, method, or composition infringes the patent if the accused device (etc) contains more or fewer elements than the claim in the patent. The word "comprising" is to be treated as an open transition, which is the broadest form of transition, as it does not limit the preamble to whatever elements are identified in the claim.

Turning to FIGS. 1 A and 1 B, the mold-tool system (100) includes (and is not limited to) a manifold assembly (102) defining a melt channel (104). The manifold assembly (102) has (and is not limited to): (i) a relatively critical operational area (106), (ii) and a relatively less-critical operational area (108) that is spaced apart from the relatively critical operational area (106). The melt channel (104) has (and is not limited to) a melt-channel geometry. The melt-channel geometry is configured to focus, in use, melt-channel stress: (i) away from the relatively critical operational area (106), and (ii) toward the relatively less-critical operational area (108). According to the example depicted in FIG. 1 A, the manifold assembly (102) includes a tube (110) that defines the melt channel (104). According to the example depicted in FIG. 1 B, the manifold assembly (102) includes a block (112) that defines the melt channel (104). The tube (110) and the block (112) include a metal alloy. Adjacent to each of the tube (110) and the block (112) there is a scale that indicates the maximum principal stress in units of mega Pascal (MPa).

By way of example, the melt channel (104) defined in the manifold assembly (102) has the melt-channel geometry (or a melt-channel shape) that is configured to focus melt-channel stress (or forces) to a specific area (predetermined area) of the manifold assembly (102) that has a lower negative impact to operation of the manifold assembly (102). The definition of "focus" may include directing and/or deflecting the melt-channel stress. By way of example, the melt channel (104) may include a flat wall portion (114). Turning to FIGS. 2A, 2B, 2C, 2D, the manifold assembly (102) may further include (and is not limited to) a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124). For the depicted examples of FIGS. 2A, 2B, the flat wall portion (114) may bisect and may be perpendicular and transverse to a split line (118) of the split manifold assembly (120). FIG. 2C depicts a perspective view of the manifold assembly (102) such that the melt channels are shown extending at least in part through the manifold assembly (102). FIG. 2D depicts the manifold assembly (102) with a scale that indicates the maximum stress in units of mega Pascal (MPa). An example of the relatively critical operational area (106) is the split line (118). An example of the relatively less-critical operational area (108) is the area set apart from the split line (118) located above and below the melt channel (104). The split line (118) is a critical operational area in that this area may be prone to leaking melt from the melt channel (104).

Turning to FIGS. 3A, 3B, 3C, the split manifold assembly (120) may include the melt channel (104) that has a curved portion (130). FIG. 3C depicts the manifold assembly (102) with a scale that indicates the maximum stress in units of mega Pascal (MPa). By way of another example, the melt channel (104) may have a non-round shape or geometry. By way of another example, the melt channel (104) may have a non- cylindrical shape or geometry. The shape or geometry of the melt channel (104) may include a flat wall portion (114), which may also be called a flat face portion. The flat wall portion (114) may be aligned or oriented perpendicular to a transverse plane (116) of the melt channel (104), and such that the flat wall portion (114) may be intersected by a split line (118) for the case where the manifold assembly (102) includes a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124) that is matable (that is, may be mated with) with the upper manifold block (122). A transverse plane is a plane dividing a body into upper and lower portions.

Known round-shaped melt channels may limit the proximity of the known melt channel to other known melt channels and/or features of the known manifold assembly. Some other features may be built into the known manifold assembly and may be positioned perpendicular to the transverse plane of the known melt channel, and this means that for all of the other features in the known manifold assembly, the limiting distance from the feature to the known melt channel is along the transverse plane of the known melt channel. In sharp contrast with the example depicted in the FIGS, with the melt channel (104) of the manifold assembly (102), the features of the manifold assembly (102) may be placed closer to the melt channel (104) because the high stress positions may be moved further away from the transverse plane of the melt channel (104). The melt channel 9104) may be oblong-shaped, by way of example.

By way of an example, by manufacturing the split manifold assembly (120) with the melt channel (104) as two separate grooves with vertical sidewalls and then joining the two halves of the split manifold assembly (120). The melt channel (104) may have an oblong shape (for example) may be manufactured instead of a round shape of the known melt channel. The use of the melt channel (104) reduces the stress in the split manifold assembly (120) at the split line (118). With the melt channel (104) having the flat wall portion (114) positioned perpendicular to the split line (118), the hoop stress may be reduced and the principle stress may act parallel to the split line (118). Advantageously, the shape of the melt channel (104) reduces the stress at the split line (118) of the split manifold assembly (120).

The shape of the melt channel (104) moves the high stress from the melt pressure away from the split line (118) in the split manifold assembly (120). In sharp contrast, with the known round melt-channel shape (profile), the highest stress area is typically at the split line. The known melt channel may be advantageous for melt flow but not for strength. In sharp contrast, with the melt channel (104) there may be negligible difference for melt flow, but there may be an improvement in overall strength of the split manifold assembly (120).

ADDITIONAL DESCRIPTION

The following clauses are offered as further description of the aspects of the present invention: Clause (1 ): a mold-tool system (100), comprising: a manifold assembly (102) defining a melt channel (104), the manifold assembly (102) having: a relatively critical operational area (106); and a relatively less-critical operational area (108) being spaced apart from the relatively critical operational area (106), the melt channel (104) having a melt-channel geometry, the melt-channel geometry being configured to focus, in use, melt-channel stress: (i) away from the relatively critical operational area (106), and (ii) toward the relatively less-critical operational area (108).

Clause (2): the mold-tool system (100) of clause (1 ), wherein the manifold assembly (102) includes a tube (110) that defines the melt channel (104).

Clause (3): the mold-tool system (100) of any one of the above clauses, wherein the manifold assembly (102) includes a block (112) that defines the melt channel (104). Clause (4): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) has a melt-channel geometry that is configured to focus melt- channel stress (or forces) to a specific area of the manifold assembly (102) that has a lower negative impact to operation of the manifold assembly (102).

Clause (5): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) includes a flat wall portion (114).

Clause (6): the mold-tool system (100) of any one of the above clauses, wherein the manifold assembly (102) further includes a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124).

Clause (7): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) includes a flat wall portion (114) that bisects and is perpendicular and is transverse to a split line (118) of the split manifold assembly (120).

Clause (8): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) has a curved portion (130).

Clause (9): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) has a non-round shape.

Clause (10): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) has a non-cylindrical shape.

Clause (11 ): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) includes a flat wall portion (114). Clause (12): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) includes a flat wall portion (114), the flat wall portion (114) is be aligned perpendicular to a transverse plane (116) of the melt channel (104).

Clause (13): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) includes a flat wall portion (114), the flat wall portion (114) is be aligned perpendicular to a transverse plane (116) of the melt channel (104), such that the flat wall portion (114) is intersected by a split line (118), and the manifold assembly (102) includes a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124) that is matable with the upper manifold block (122).

Clause (14): the mold-tool system (100) of any one of the above clauses, wherein the melt channel (104) has an oblong shape.

It is understood that the scope of the present invention is limited to the scope provided by the independent claim(s), and it is also understood that the scope of the present invention is not limited to: (i) the dependent claims, (ii) the detailed description of the non-limiting embodiments, (iii) the summary, (iv) the abstract, and/or (v) description provided outside of this document (that is, outside of the instant application as filed, as prosecuted, and/or as granted). It is understood, for the purposes of this document, the phrase "includes (and is not limited to)" is equivalent to the word "comprising". It is noted that the foregoing has outlined the non-limiting embodiments (examples). The description is made for particular non-limiting embodiments (examples). It is understood that the non-limiting embodiments are merely illustrative as examples.

Claims

CLAIMS WHAT IS CLAIMED IS:

1 . A mold-tool system (100), comprising:

a manifold assembly (102) defining a melt channel (104), the manifold assembly (102) having:

a relatively critical operational area (106); and

a relatively less-critical operational area (108) being spaced apart from the relatively critical operational area (106), the melt channel (104) having a melt-channel geometry, the melt-channel geometry being configured to focus, in use, melt-channel stress: (i) away from the relatively critical operational area (106), and (ii) toward the relatively less-critical operational area (108).

2. The mold-tool system (100) of claim 1 , wherein the manifold assembly (102) includes a tube (110) that defines the melt channel (104).

3. The mold-tool system (100) of claim 1 , wherein the manifold assembly (102) includes a block (112) that defines the melt channel (104).

4. The mold-tool system (100) of claim 1 , wherein the melt-channel geometry of the melt channel (104) is configured to focus melt-channel stress (or forces) to a specific area of the manifold assembly (102) that has a lower negative impact to operation of the manifold assembly (102).

5. The mold-tool system (100) of claim 1 , wherein the melt channel (104) includes a flat wall portion (114).

6. The mold-tool system (100) of claim 1 , wherein the manifold assembly (102) further includes a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124).

7. The mold-tool system (100) of claim 6, wherein the melt channel (104) includes a flat wall portion (114) that bisects and is perpendicular and is transverse to a split line (118) of the split manifold assembly (120).

8. The mold-tool system (100) of claim 1 , wherein the melt channel (104) has a curved portion (130).

9. The mold-tool system (100) of claim 1 , wherein the melt channel (104) has a non- round shape.

10. The mold-tool system (100) of claim 1 , wherein the melt channel (104) has a non- cylindrical shape.

11 . The mold-tool system (100) of claim 1 , wherein the melt channel (104) includes a flat wall portion (114).

12. The mold-tool system (100) of claim 1 , wherein the melt channel (104) includes a flat wall portion (114), the flat wall portion (114) is be aligned perpendicular to a transverse plane (116) of the melt channel (104).

13. The mold-tool system (100) of claim 1 , wherein the melt channel (104) includes a flat wall portion (114), the flat wall portion (114) is be aligned perpendicular to a transverse plane (116) of the melt channel (104), such that the flat wall portion (114) is intersected by a split line (118), and the manifold assembly (102) includes a split manifold assembly (120) having an upper manifold block (122) and a mating lower block (124) that is matable with the upper manifold block (122).

14. The mold-tool system (100) of claim 1 , wherein the melt channel (104) has oblong shape.