WO2012051079A1

WO2012051079A1 - Mold-tool system having outlets directing melt stream along intersecting transmission paths

Info

Publication number: WO2012051079A1
Application number: PCT/US2011/055495
Authority: WO
Inventors: Patrice Fabien Dezon-Gaillard; Paul R. Blais; Abdeslam Bouti; Gilles Lacome
Original assignee: Husky Injection Molding Systems Ltd
Priority date: 2010-10-12
Filing date: 2011-10-08
Publication date: 2012-04-19

Abstract

A mold-tool system (100), comprising: a nozzle tip (102); and an outer surface (106) of the nozzle tip (102) defining a plurality of outlets (108) being configured to direct, in use, a melt stream (103) along transmission paths (110) extending along the outer surface (106), the transmission paths (110) intersecting each other.

Description

MOLD-TOOL SYSTEM HAVING OUTLETS DIRECTING MELT STREAM ALONG

INTERSECTING TRANSMISSION PATHS

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 having outlets directing a melt stream along intersecting transmission paths.

BACKGROUND

The first man-made plastic was invented in Britain in 1 851 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 1 868, 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 1 940s 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. 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.

The inventors have arrived at an understanding that environmental stress cracking resistance (ESCR) may be an important factor or point for certain molders, and potentially a main driver for new developments and/or new investments. ESCR may limit process window, melt temperature range, maintenance intervals, part thickness and resin type. ESCR may be an important criterion for molded closures, as well as for thin walled molded articles, molded silicone tube articles, etc. The start of molded part failure may be at the weld line of a molded part where various flow fronts exiting from a nozzle tip may meet. According to one aspect, there is provided a mold-tool system (100), comprising: a nozzle tip (102); and an outer surface (106) of the nozzle tip (102) defining a plurality of outlets (108) being configured to direct, in use, a melt stream (103) along transmission paths (110) extending along the outer surface (106), the transmission paths (110) intersecting each other. A technical effect of the above arrangement may provide a nozzle tip that forces a resin flow to overlap at weld lines with a solid layer within a gate bubble. The overlapping area of the resin may continue into a molded part, and is currently believed to increase ESCR, as will be described below in more detail.

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, 1 C, 2A, 2B, 2C 3A, 3B, 4, 5, 6, 7, 8, 9A, 9B, 10, 11 B, 11 C, 12B, 12C depict schematic representations of examples of the mold-tool system (100); and

FIGS. 11 A, 12A depict schematic representations of melt cross sections made by usage of the mold-tool system (100) of FIGS. 11 B, 11 C, 12C, 12C, respectively.

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)

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 an injection molding system (known and not depicted) may have the mold-tool system (100). It will be appreciated that for the purposes of this document, the phrase "includes (but 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. The mold-tool system (100) may include (and is not limited to): (i) a nozzle tip (102), and (ii) an outer surface (106). The outer surface (106) of the nozzle tip (102) defines a plurality of outlets (108) that are configured to direct, in use, a melt stream (103) along transmission paths (110) extending along the outer surface (106). The transmission paths (110) intersect each other. More specifically, and not limited thereby, the nozzle tip (102) may be configured to connect, in use, to a nozzle body (104). The nozzle body (104) may be configured to convey, in use, the melt stream (103). The nozzle tip (102) may be configured to receive, in use, the melt stream (103) from the nozzle body (104). the plurality of outlets (108) are positioned relative to each other. And more specifically, the plurality of outlets (108) may be configured to convey, in use, the melt stream (103) from inside the nozzle tip (102) along the outer surface (106) of the nozzle tip (102). More specifically, the transmission paths (110) intersect each other so that the melt stream (103) becomes intermixed, at least in part, along an outer surface (106) of the nozzle tip (102). The nozzle tip (102) may be surrounded by a tip insulator (105). According to an example, the plurality of outlets (108) may include (and is not limited to): (i) non-chamfered outlets (120), and (ii) chamfered outlets (122) positioned relative to the non- chamfered outlets (120). The chamfered outlets (122) may have flared portions extending toward a tip portion of the nozzle tip (102). The non-chamfered outlets (120) may have flared portions extending toward an apex (130) of the nozzle tip (102). The non-chamfered outlets (120) and the chamfered outlets (122) may be lined up equidistant from the apex (130). An option may be to stagger positions of the plurality of outlets (108) relative to the apex (130). Another option may be to stagger positions of the plurality of outlets (108) relative to each other. The plurality of outlets (108) may be staggered relative to each other, and/or each of the plurality of outlets (108) may be of different sizes relative to each other, etc. FIG. 1 C depicts a particle trace showing an overlap between the flow lines existing from the plurality of outlets (108). It will be appreciated that the overlap between the flow lines continues into the part being molded; that is, the molded part (140). The overlap exists at an intermixing zone (132). A technical effect of the above arrangement may provide a nozzle tip that forces a resin flow to overlap at weld lines with a solid layer within a gate bubble. The overlapping area of the resin may continue into a molded part, and is currently believed to increase ESCR. A potential technical effect may provide overlapping of molding material from each of the plurality of outlets (108) causes a weld line in the molded part (140) to become blurred or blended or less well defined.

FIG. 2A, 2B depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): staggered outlets (202) that are positioned in a staggered arrangement relative to each other. A mold cavity 150 is used to form the molded part (140).

FIG. 2C depicts another particle trace showing an overlap between the flow lines existing from the plurality of outlets (108) of FIGS 2A, 2B. FIG. 3A depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may be staggered relative to each other or staggered relative to the tip portion of the nozzle tip (102). Some of the outlets (108) are positioned the same distance X a tip portion of the nozzle tip (102), while other outlets (108) are positioned another distance Y from the tip portion of the nozzle tip (102). It will be appreciated that any number of outlets (108) may be used. The flow from the outlet (108) that is positioned closer to the gate may become pushed against the nozzle tip (102) due to the flow from other outlets (108). A technical effect may be provided in which overlapping of the melt (molding material) from each of the outlets (108) causes a weld line to become blurred or blended or less well defined. Specifically, the plurality of outlets (108) may include (and is not limited to): a first row of outlets (302), and a second row of outlets (304) that is offset from a first row of outlets (302).

FIG. 3B depicts yet another particle trace showing an overlap between various flows of melt from the outlets (108). A first particle flow (352) flows from the first row of outlets (302), a second particle flow (354) flows from the second row of outlets (304), a third particle flow (356) flows from the first row of outlets (302), and it is clear that there is a merging, at least in part, of the flow of resin as a result of the arrangement of the of outlets of FIG. 3A.

FIG. 4 depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): slots (404) that are configured to create a fan flow of melt. The slots (404), for example, may be bean-shaped holes or slots to create the fan flow. The fan size may be adjusted accordingly.

FIG. 5 depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): relatively larger outlets (502), and relatively smaller outlets (504). The flow of melt from the relatively smaller outlets (504) is pushed against the nozzle tip (102) due to a higher flow rate associated with the relatively larger outlets (502). The flow front may have same speed. The relatively smaller outlets (504) may be positioned or located in front of the relatively larger outlets (502).

FIG. 6 depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): a first row of outlets (602), a second row of outlets (604), and a third row of outlets (606). The first row of outlets (602), the second row of outlets (604) and the third row of outlets (606) form a multi-level staggered arrangement of the plurality of outlets (108). The flow front may have the same speed.

FIG. 7 depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): an apex outlet (702), and a collection of non-apex outlets (704). The apex outlet (702) may be positioned on an apex of the nozzle tip (102). The collection of non-apex outlets (704) may be set apart from the apex outlet (702).

FIG. 8 depicts another example of the mold-tool system (100) in which the nozzle tip (102) may include (and is not limited to): a tip portion (810), and a nozzle tip stem portion (812) that is attached to the tip portion (810), and a flange portion (814). The nozzle tip stem portion (812) extends from the flange portion (814). The plurality of outlets (108) may include (and is not limited to): stem outlets (802) defined by the nozzle tip stem portion (812), and flange-through holes (804) defined by the flange portion (814). The nozzle tip stem portion (812) may also be called a torpedo or a flow pin. FIG. 9A depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): a first set of outlets (902), and a second set of outlets (904). The first set of outlets (902) permit the melt to flow clockwise, and the second set of outlets (904) permit the melt to flow counter clock wise. A tip portion (910) extends at an apex of the nozzle tip (102).

FIG. 9B depicts a flow pattern arising from the mold-tool system (100) of FIG. 9A.

A first particle flow (952) flows from a first outlet, a second particle flow (954) flows from a second outlet, a third particle flow (956) flows from a third outlet (etc), and it is clear that there is a merging, at least in part, of the flow of resin as a result of the arrangement of the of outlets (904) of FIG. 9A. The molded part (140) may be formed in which the weld lines are merged together thus improving the strength of the molded part (140).

FIG. 10 depicts another example of the mold-tool system (100) in which the plurality of outlets (108) may include (and is not limited to): angled flow slots (1002). Some of the flow that exist the outlets (108) follow the angled flow slots (1002) and some of the flow follows the outer surface (106) of the nozzle tip (102) toward a mold gate (not depicted but known). This arrangement creates an overlap of flow layer. The resin flow may partly follow the angled flow slots (1002) and partly be directed axially toward the mold gate. These fan layers may become overlapped such that the weld line may be covered by a full layer.

FIG. 11 B depicts another example of the mold-tool system (100) in which the nozzle tip (102) may include (and is not limited to): a torpedo (1120), a torpedo tip (1122) extending from the torpedo (1120), and a flange (1124). The torpedo (1120) extends from the flange (1124). The plurality of outlets (108) may include (and is not limited to): accurate shaped outlets (1102) defined by the flange (1124). The accurate shaped outlets (1102) may take on the shape of a kidney bean, for example. The arrangement depicted in FIGS. 11 B shows the accurate shaped outlets (1102) arranged in two levels: an inner level and an outer level, with fins (1130) arranged in a staggered fashion. This arrangement may allow for a discontinuity of the weld line which may have the benefit to arrest any cracks initiated inside or outside the molded part.

FIG. 11 C depicts another example of the mold-tool system (100) in which the nozzle tip (102) may include (and is not limited to): a torpedo (1120), a torpedo tip (1122) extending from the torpedo (1120), and a flange (1124). The torpedo (1120) extends from the flange (1124), and the torpedo (1120) and the flange (1124) define a melt inlet (1140). The plurality of outlets (108) may include (and is not limited to): accurate shaped outlets (1102) defined by the torpedo (1120). The accurate shaped outlets (1102) may take on the shape of a kidney bean, for example. The flange (1124) may define torpedo fins (1150) that are staggered relative to each other and may be positioned between the accurate shaped outlets (1102). The torpedo (1120) defines, at least in part, a melt inlet (1140). In this configuration, the accurate shaped outlets (1102) are positioned staggered from upstream to downstream to produce the weld line configuration as depicted in FIG 11 A. This arrangement may have the advantage to arrest any cracks initiated outside or inside the molded part. The flange (1124) defines a melt inlet (1140), and a melted resin may flow along a melt flow direction (1141 ).

FIG. 11A depicts a melt cross-section (1151 ) that is located downstream of the flange (1124) or the nozzle tip (102) in a mold gate that shows the weld lines (1160) that are positioned in a staggered relationship which helps to reduce or avoid crack propagation during ESCR (environmental stress cracking). This arrangement may allow crack arrest of ESCR initiated inside or outside the molded part.

FIG. 12B depicts another example of the mold-tool system (100) in which the nozzle tip (102) may include (and is not limited to): a torpedo (1120), a torpedo tip (1122) extending from the torpedo (1120), and a flange (1124). The torpedo (1120) extends from the flange (1124). The plurality of outlets (108) may include (and is not limited to): spiral shaped outlets (1202) defined by the flange (1124). In this configuration, the spiral shaped outlets (1202) are staggered from upstream to downstream in a spiral manner to increase the length of the weld lines (1160) and thus improve crack arrest between the two level of molded part wall as depicted in FIG. 12A. The depicted arrangement of FIG. 12B may have the advantage to arrest cracks initiated outside or inside the molded part, and also produce relatively longer weld lines (1160) that require relatively higher energy to propagate cracks through the molded article. The flange (1124) defines a melt inlet (1140), and a melted resin may flow along a melt flow direction (1141 ).

FIG. 12C depicts another example of the mold-tool system (100) in which the nozzle tip (102) may include (and is not limited to): a torpedo (1120), a torpedo tip (1122) extending from the torpedo (1120), and a flange (1124). The torpedo (1120) extends from the flange (1124). The torpedo (1120) and the flange (1124) define a melt inlet (1140). The plurality of outlets (108) may include (and is not limited to): spiral shaped outlets (1202) defined by the torpedo (1120). In this configuration, the fins (1130) are spiral shaped in order to increase the length of the weld line, and to overlap them as depicted in FIG. 12A. In this

arrangement, a crack propagating from the inside or the outside wall through the molded part wall may be arrested because of the discontinuity of the weld line, as well as the extend length of the weld line that requires a relatively higher energy for propagation.

FIG. 12A depicts a melt cross-section (1251 ) downstream of the flange (1124). The weld lines (1160) have very extended length and are overlapped to reduce or avoid crack propagation during ESCR (environmental stress cracking). This arrangement may allow crack arrest of ESCR initiated inside or outside the molded part by overlapping the weld lines (1160) and also by increasing the energy required for crack propagation due to the extended length of the weld line (1160).

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

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

a nozzle tip (102); and

an outer surface (106) of the nozzle tip (102) defining a plurality of outlets (108) being configured to direct, in use, a melt stream (103) along transmission paths (110) extending along the outer surface (106), the transmission paths (110) intersecting each other.

2. The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) is configured to connect, in use, to a nozzle body (104), the nozzle body (104) is configured to convey, in use, the melt stream (103), and the nozzle tip (102) is configured to receive, in use, the melt stream (103) from the nozzle body (104);

the plurality of outlets (108) are positioned relative to each other, the plurality of outlets (108) are configured to convey, in use, the melt stream (103) from inside the nozzle tip (102) along the outer surface (106) of the nozzle tip (102); and

the transmission paths (110) intersect each other so that the melt stream

(103) becomes intermixed, at least in part, along the outer surface (106) of the nozzle tip (102).

3. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) includes:

non-chamfered outlets (120); and

chamfered outlets (122) positioned relative to the non-chamfered outlets (120). 4. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) include:

staggered outlets (202) being positioned in a staggered arrangements relative to each other. 5. The mold-tool system (100) of claim 1 , wherein: the plurality of outlets (108) include:

a first row of outlets (302); and

a second row of outlets (304) being offset from the first row of outlets (302). 6. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) include:

slots (404) being configured to create a fan flow of melt.

7. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) include:

relatively larger outlets (502); and

relatively smaller outlets (504), flow of melt from the relatively smaller outlets (504) is pushed against the nozzle tip (102) due to a higher flow rate associated with the relatively larger outlets (502).

8. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) include:

a first row of outlets (602);

a second row of outlets (604); and

a third row of outlets (606);

the first row of outlets (602), the second row of outlets (604) and the third row of outlets (606) forming a multi-level staggered arrangement of the plurality of outlets (108). 9. The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) include:

an apex outlet (702) being positioned on an apex of the nozzle tip (102); and a collection of non-apex outlets (704) being set apart from the apex outlet

(702).

10. The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) includes:

a tip portion (810); and

a nozzle tip stem portion (812) being attached to the tip portion (810); and a flange portion (814), the nozzle tip stem portion (812) extending from the flange portion (814);

the plurality of outlets (108) includes:

stem outlets (802) defined by the nozzle tip stem portion (812); and flange-through holes (804) defined by the flange portion (814).

The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) includes:

a first set of outlets (902); and

a second set of outlets (904), the first set of outlets (902) permit, in use, a melt to flow clockwise, and the second set of outlets (904) permit the melt to flow counter clock wise.

The mold-tool system (100) of claim 1 , wherein:

the plurality of outlets (108) includes:

angled flow slots (1002).

The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) includes:

a torpedo (1120);

a torpedo tip (1122) extending from the torpedo (1120); and

a flange (1124), the torpedo (1120) extending from the flange (1124); the plurality of outlets (108) includes:

accurate shaped outlets 1102 (Kidney bean shaped) defined by the flange (1124).

The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) includes:

a torpedo (1120);

a torpedo tip (1122) extending from the torpedo (1120); and

a flange (1124), the torpedo (1120) extending from the flange (1124), and the torpedo (1120) and the flange (1124) define a melt inlet (1140);

the plurality of outlets (108) includes:

accurate shaped outlets 1102 (Kidney bean shaped) defined by the torpedo

(1120).

15. The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) includes:

a torpedo (1120);

a torpedo tip (1122) extending from the torpedo (1120); and

a flange (1124), the torpedo (1120) extending from the flange (1124);

the plurality of outlets (108) includes:

spiral shaped outlets 1202 defined by the flange (1124).

16. The mold-tool system (100) of claim 1 , wherein:

the nozzle tip (102) includes:

a torpedo (1120);

a torpedo tip (1122) extending from the torpedo (1120); and

the plurality of outlets (108) includes:

spiral shaped outlets 1202 defined by the torpedo (1120).

17. An injection molding system having the mold-tool system (100) of any one of claims 1 to 16.