FAVATA, Domenico (Konzerbrück 31, Konz, 54329, DE)
| WHAT IS CLAIMED IS: 1. A method for cleaning a mold stack of a mold, the mold stack defining a molding cavity and further defining venting surfaces, and fluid supply channels adapted to direct a pressure blast of a working fluid from a fluid pressure assembly, comprising: a molding operation, the molding operation including closing the mold, molding a molded article in the molding cavity, and further including evacuating air from the molding cavity through the venting surfaces; a part transfer operation, the part transfer operation including opening the mold and transferring the molded article out of the mold, assisted at least in part by the pressure blast provided by the fluid pressure assembly through the fluid supply channels; and a cleaning operation, the cleaning operation including partially closing the mold; and cleaning the mold stack by generating another pressure blast, the other pressure blast being directed from the fluid supply channels through the venting surfaces. 2. The method of claim 1 , wherein closing the mold includes locating a neck ring assembly within a seat on a lock ring, the lock ring defining at least a portion of the fluid supply channels. 3. The method of claim 1 , wherein the working fluid comprises compressed air 4. The method of claim 1 , wherein the cleaning operation occurs after one of: a predetermined number of molding cycles, upon a sensor indicating that cleaning is necessary and after a controller receives a cleaning decision made by an operator. 5. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces and the intensive pressure blast comprises one of a second working fluid and a mixture of the working fluid and the second working fluid. 6. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces and the intensive pressure blast comprises one of a second working fluid and a mixture of the working fluid and the second working fluid, the working fluid being compressed air and the second working fluid being a cleaning solution. 7. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces and the intensive pressure blast comprises the working fluid being applied for at least one of a longer duration and a higher pressure than the pressure blast of the cleaning operation. 8. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces; and the intensive cleaning operation occurs after a predetermined number of molding cycles. 9. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces; and the intensive cleaning operation occurs upon a sensor indicating that cleaning is necessary. 10. The method of claim 1 , further comprising: an intensive cleaning operation, the intensive cleaning operation including partially closing the mold; and cleaning the mold stack using an intensive pressure blast provided by the fluid pressure assembly, the intensive pressure blast being directed from the fluid supply channels through the venting surfaces; and the intensive cleaning operation occurs after a controller receives a cleaning decision made by an operator. 1 1. A molding system, comprising: a mold, the mold including a mold stack for defining, in use, a molding cavity for a molded article; a fluid pressure assembly, operable to generate a pressure blast of a working fluid, the pressure blast being directed into the mold via fluid supply channels, the pressure blast being operable to effect, at least in part, removal of the molded article from the mold stack; and wherein the mold stack includes venting surfaces for evacuating air from the molding cavity during molding of the molded article when the mold is closed; and the venting surfaces are in communication with the fluid supply channels when the mold is at least partially opened so that another pressure blast generated when the mold is at least partially open clean, at least partially, the mold stack. 12. The molding system of claim 1 1 , wherein the mold stack includes a mold core for defining a portion of the molded article; and a lock ring, located coaxially around the mold core; the lock ring defining at least a portion of the fluid supply channels for directing the pressure blast to effect, at least partially, removal of the molded article from the mold core. 13. The molding system of claim 1 1 , wherein the mold stack includes a mold core for defining a portion of the molded article; and a lock ring, the lock ring being coaxially located around the mold core; a portion of the fluid supply channels being defined with the lock ring, the fluid supply channels operable to direct the pressure blast to effect, at least partially, removal of the molded article from the mold core; and a neck ring assembly, the neck ring assembly being movable relative to the lock ring between a first position where the neck ring assembly defines another portion of the molded article and a second position, where the neck ring assembly is located away from the lock ring to permit the removal of the molded article from the mold core. 14. The molding system of claim 1 1 , wherein the mold stack includes a mold core for defining a portion of the molded article; and a lock ring, the lock ring being coaxially located around the mold core; a portion of the fluid supply channels being defined with the lock ring, the fluid supply channels operable to direct the pressure blast to effect, at least partially, removal of the molded article from the mold core; a neck ring assembly, the neck ring assembly being movable relative to the lock ring between a first position where the neck ring assembly defines another portion of the molded article and a second position, where the neck ring assembly is located away from the lock ring to permit the removal of the molded article from the mold core; and the venting surfaces being defined on the neck ring assembly for the evacuating air from the molding cavity; and wherein the venting surfaces are in communication with the fluid supply channels on the lock ring when the neck ring assembly is in the first position. 15. The molding system of claim 1 1 , further comprising: a human-machine interface for controlling the fluid pressure assembly. 16. The molding system of claim 1 1 , wherein the working fluid is compressed air. 17. The molding system of claim 1 1 , wherein the fluid pressure assembly is operable to selectively generate pressure blasts of the working fluid, a second working fluid and a mixture of the working fluid and the second working fluid. 18. The molding system of claim 1 1 , wherein in the fluid pressure assembly is operable to selectively generate pressure blasts of the working fluid, a second working fluid and a mixture of the working fluid and the second working fluid, the working fluid being compressed air and the second working fluid being a cleaning solution. 19. A mold stack for defining, in use, a molding cavity for a molded article, the mold stack including: a mold core for defining a portion of the molded article; a lock ring, the lock ring being coaxially located around the mold core; fluid supply channels defined with the lock ring, the fluid supply channels operable to direct a pressure blast of a working fluid to effect, at least in part, removal of the molded article from the mold core; a neck ring assembly, the neck ring assembly being movable relative to the lock ring between a first position where the neck ring assembly defines another portion of the molded article and a second position, where the neck ring assembly is located away from the lock ring to permit the removal of the molded article from the mold core, the neck ring assembly further includes venting surfaces for evacuating air from the molding cavity, the venting surfaces being in communication with the fluid supply channels on the lock ring when the neck ring assembly is in the first position. 20. The mold stack of claim 19, wherein the neck ring assembly includes a pair of neck ring halves, and the venting surfaces include vent relief faces defined on opposed surfaces of each neck ring half of the pair of neck ring halves. 21. The mold stack of claim 19, wherein the neck ring assembly includes a pair of neck ring halves, and the venting surfaces include vent relief faces defined on opposed surfaces of each neck ring half of the pair of neck ring halves, the neck ring assembly further including vent grooves in communication with the vent relief faces, the vent grooves also being in communication with the fluid supply channels when the neck ring assembly is in the first position. 22. In a method for molding a molded articles using a mold stack of a mold, the mold stack defining a molding cavity and further defining venting surfaces, and fluid supply channels adapted to direct a pressure blast of a working fluid from a fluid pressure assembly, the method for molfing including a (i) a molding operation, the molding operation including closing the mold, molding a molded article in the molding cavity, and further including evacuating air from the molding cavity through the venting surfaces; and (ii) a part transfer operation, the part transfer operation including opening the mold and transferring the molded article out of the mold, assisted at least in part by the pressure blast provided by the fluid pressure assembly through the fluid supply channels; the improivement comprising: executing a cleaning operation, the cleaning operation including partially closing the mold; and cleaning the mold stack by generating another pressure blast, the other pressure blast being directed from the fluid supply channels through the venting surfaces. |
TECHNICAL FIELD The present disclosure generally relates to, but is not limited to, a molding system, and more specifically the present invention relates to, but is not limited to, a molding stack for a preform, the mold stack having vent cleaning.
BACKGROUND
Molding is a process by virtue of which a molded article can be formed from molding material by using a molding system. Various molded articles can be formed by using the molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from polyethylene terephthalate (PET) material is a preform that is capable of being subsequently blown into a beverage container, such as, a bottle and the like.
As an illustration, injection molding of PET material involves heating the PET material (or other suitable molding material for that matter) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into a molding cavity defined, at least in part, by a female cavity piece and a male core piece mounted respectively on a cavity plate and a core plate of a mold. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient to keep the cavity and the core pieces together against the pressure of the injected PET material. The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected PET material is then cooled to a temperature sufficient to enable ejection of the so-formed molded article from the molding cavity. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core piece. Accordingly, by urging the core plate away from the cavity plate, the molded article can be subsequently demolded by ejecting it off the core piece. Ejection structures are known to assist in removing the molded articles from the core halves. Examples of the ejection structures include stripper plates, stripper rings and neck rings, ejector pins, etc. When dealing with molding a preform that is capable of being subsequently blown into a beverage container, one consideration that needs to be addressed is forming a so-called "neck region". Typically and as an example, the neck region includes (i) threads (or other suitable structure) for accepting and retaining a closure assembly (ex. a bottle cap), and (ii) an anti- pilferage assembly to cooperate, for example, with the closure assembly to indicate whether the end product (i.e. the beverage container that has been filled with a beverage and shipped to a store) has been tampered with in any way. The neck region may comprise other additional elements used for various purposes, for example, to cooperate with parts of the molding system (ex. a support ledge, etc.). As is appreciated in the art, the neck region can not be easily formed by using the cavity and core halves. Traditionally, split neck rings (sometimes referred to by those skilled in the art as "neck rings") have been used to form the neck region.
SUMMARY According to a first embodiment, there is provided a method for cleaning a mold stack of a mold, the mold stack defining a molding cavity and further defining venting surfaces, and fluid supply channels adapted to direct a pressure blast from a fluid pressure assembly, comprising: a molding operation, the molding operation including closing the mold, molding the molded article in the molding cavity, and further including evacuating air from the molding cavity through the venting surfaces. The method further includes a part transfer operation, the part transfer operation including opening the mold and transferring the molded article out of the mold, assisted at least in part by the pressure blast provide by the fluid pressure assembly through the fluid supply channels. The method further includes a cleaning operation, the cleaning operating including partially closing the mold; and cleaning the mold stack by generating another pressure blast, the pressure blast being directed from the fluid supply channels through the venting surfaces.
According to another embodiment, there is provided a molding system, comprising: a mold, the mold including a mold stack for defining, in use, a molding cavity for a molded article. The molding system further includes a movable platen and a stationary platen, the movable platen and the stationary platen cooperatively operable to open and close the mold. The molding system further includes fluid pressure assembly, operable to generate a pressure blast, the pressure blast being directed into the mold via fluid supply channels, the pressure blast being operable to effect, at least in part, removal of a molded article from the mold stack. The mold stack includes venting surfaces for evacuating air from the molding cavity during molding of the molded article when the mold is closed; and the venting surfaces are in communication with the fluid supply channels when the mold is at least partially opened so that another pressure blast generated when the mold is at least partially open clean, at least partially, the mold stack.
According to another aspect, there is provided a mold stack for defining, in use, a molding cavity for a molded article, the mold stack including: a mold core for defining a portion of the molded article; a lock ring, the lock ring being coaxially located around the mold core; fluid supply channels defined with the lock ring, the fluid supply channels operable to direct a pressure blast to effect, at least in part, removal of the molded article from the mold core; a neck ring assembly, the neck ring assembly being movable relative to the lock ring between a first position where the neck ring assembly defines another portion of the molded article and a second position, where the neck ring assembly is located away from the lock ring to permit removal of the molded article from the mold core. The neck ring assembly further includes venting surfaces for evacuating air from the molding cavity, the venting surfaces being in communication with the fluid supply channels on the lock ring when the neck ring assembly is in the first position.
These and other aspects and features of non-limiting embodiments of the present invention will now become apparent to those skilled in the art upon review of the following description of specific non-limiting embodiments of the invention in conjunction with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS A better understanding of the non-limiting embodiments of the present invention (including alternatives and/or variations thereof) may be obtained with reference to the detailed description of the non-limiting embodiments along with the following drawings, in which:
Fig. 1 is a side plan view of a molding system according to a first embodiment;
Fig. 2 is a cross-sectional view of a mold stack for a mold mounted to the molding system of Fig. 1 ;
Fig 3 is a cross-sectional view of a neck ring assembly and a lock ring for the mold stack of Fig. 2; Fig 4 is a cross-sectional perspective view of the neck ring assembly and lock ring shown in Fig. 3;
Fig. 5 is a view of a flow chart for a method of cleaning the mold stack of the molding system of Fig. 1 ;
Fig. 6 is a view of a flow chart for another method of cleaning the mold stack of the molding system of Fig. 1 ;
Fig. 7 is a side plan view of a molding system according to another first embodiment; and Fig. 8 is a view of a flow chart for a method of cleaning the mold stack of the molding system of Fig. 7.
DETAILED DESCRIPTION OF EMBODIMENTS
With reference to Figure 1 , there is depicted a non-limiting embodiment of a molding system 20 which can be adapted to implement embodiments of the present invention. For illustration purposes only, it shall be assumed that the molding system 20 comprises an injection molding system for processing molding material, such as, PET for example. However, it should be understood that in alternative non-limiting embodiments, the molding system 20 may comprise other types of molding systems, such as, but not limited to, compression molding systems, metal molding systems and the like. It should be further understood that embodiments of the present invention are applicable to the molding system 20 incorporating any multicavitation mold, including PET molds, thinwall articles molds, closures molds and the like.
Within the non-limiting embodiment of Figure 1 , the molding system 20 comprises a stationary platen 22 and a movable platen 24. The molding system 20 further comprises an injection unit 26 for plasticizing and injection of molding material. In operation, the movable platen 24 is moved towards and away from the stationary platen 22 by means of stroke cylinders (not shown) or any other suitable means.
A first mold half 28 can be associated with the stationary platen 22 and a second mold half 30 can be associated with the movable platen 24. Cooperatively, the first mold half 28 and the second mold half 30 define a mold 34. Between its two halves, mold 34 contains one or more mold stacks 36, each mold stack 36 operable, in use, to define a molded article (not shown) within a molding cavity 52. Mold stacks 36 are described in greater detail below. Figure 1 depicts the first mold half 28 and the second mold half 30 in a so-called "mold open position" where the movable platen 24 is positioned generally away from the stationary platen 22 and, accordingly, the first mold half 28 is positioned generally away from the second mold half 30. In the mold open position, a molded article (not depicted) can be removed from the first mold half 28 and/or the second mold half 30.
The first mold half 28 and the second mold half 30 can also be in a "mold closed position" (not depicted). The first mold half 28 and the second mold half 30 are urged together (by means of movement of the movable platen 24 towards the stationary platen 22) and cooperate to define (at least in part) the molding cavities 52 (Fig. 2) into which the molten plastic (or other suitable molding material) can be injected, as is known to those of skill in the art. It should be appreciated that one of the first mold half 28 and the second mold half 30 can be associated with a number of additional mold elements, such as for example, leader pins and leader bushings (neither depicted), the leader pins cooperating with the leader bushings to assist in alignment of the first mold half 28 with the second mold half 30 in the mold closed position, as is known to those of skill in the art.
The molding system 20 can further comprise a robot 32 operatively coupled to the stationary platen 22. Those skilled in the art will readily appreciate how the robot 32 can be operatively coupled to the stationary platen 22 and, as such, it will not be described here in any detail. Generally speaking, the purpose of the robot 32 is to remove molded articles from the first mold half 28 and/or to implement post mold cooling of the molded articles. Schematically depicted in Figure 1 , the robot 32 is of a side-entry type. However, it should be understood that in alternative non-limiting embodiments of the present invention the robot 32 can be of a top-entry t pe. It should also be expressly understood that the term "robot" is meant to encompass structures that perform a single operation, as well as structures that perform multiple operations.
Control of molding system 20 by an operator is provided by a Human-Machine Interface, namely HMI 38. HMI 38 includes a controller that is adapted to control the operational parameters of molding system 20, including the operation of injection unit 26, the robot 32 and the movable platen 24. HMI 38 may also control other features of the molding system 20 and the use of other auxiliary equipment (not depicted). Referring now to Fig. 2, one of the mold stacks 36 is described in greater detail. The mold stack 36 includes a neck ring assembly 44 that together with a mold cavity insert 46, a gate insert 48 and a mold core 50 defines a molding cavity 52. Thus, the mold core 50 defines one portion of the molded article, the neck ring assembly 44 defines another portion of the molded article, etc. A lock ring 54 is located coaxially around a portion of the length of mold core 50. Molding material can be injected into the molding cavity 52 from injection unit 26 via a receptacle (not separately numbered) in the gate insert 48 to form the molded article.
Several types of the neck ring assembly 44 are known in the art. For example, the neck ring assembly 44 can be of a cavity-lock type (not depicted) or a core-lock type (depicted in Figure 2), depending on an arrangement that is used for locking the neck ring assembly 44, in use, relative to the mold cavity insert 46 and the mold core 50. The neck ring assembly 44 can also define a portion of the neck region or, alternatively, the whole of the neck region "encapsulating" the entire neck region. Another of the functions performed by the neck ring assembly 44 is to assist in ejecting the molded article off the mold core 50 by "sliding" the molded article off of the mold core 50.
The neck ring assembly 44 is operable to split into a two neck ring halves, namely neck ring half 45 and neck ring half 47, the two of which are operable to translate away from each other during a part transfer operation (described in greater detail below). Each of neck ring half 45 and 47 is mounted on adjacent slides of a slide pair (not depicted). The slide pair is slidably mounted on a top surface of a stripper plate (not depicted). As commonly known, and as, for example, generally described in United States patent 6,799,962 to Mai et al (granted on October 5, 2004), the stripper plate (not depicted) is configured to be movable relative to the mold cavity insert 46 and the mold core 50, when the mold 34 is arranged in an open configuration, whereby the slide pair, and the complementary neck ring halves 45 and 47 mounted thereon, can be laterally driven, via a cam arrangement (not shown) or any other suitable known means, from their first position adjacent the mold core 50 to their second position for the release of the molded article from the molding cavity 52.
The lock ring 54, at its distal end, further defines a seat 56, which the neck ring assembly 44 abuts against while the neck ring assembly 44 is in its first position. In the presently-illustrated embodiment, seat 56 comprises a tapered surface, and each of neck ring half 45 and neck ring half 47 includes an opposing mated tapered surface.
As will be described in greater detail below, each mold stack 36 in mold 34 is operably connected to a fluid pressure assembly 58 (Fig. 1 ) by a fluid supply channel 62 (depicted in Fig. 4). Fluid pressure assembly 58 is operable to supply a pressure blast of a working fluid 60 via fluid supply channel 62 into molding cavity 52 to assist with part removal. An example of working fluid 60 would be compressed air. Mold stack 36 is also operably connected to the HMI 38 (Fig. 1 ). Fluid pressure assembly 58 can, as presently depicted includes a compressor or can include a pressurized tank or other pressurized source of the working fluid 60. HMI 38 is adapted to control the operational parameters of fluid pressure assembly 58. Examples of operational parameters controlled by HMI 38 include, but are not limited to, the duration of the pressure blast of the working fluid 60, the delay onset for the pressure blast of the working fluid 60, and the operational pressure of the pressure blast for the working fluid 60.
Referring now to Figs. 3 and 4, the neck ring assembly 44 and portions of lock ring 54 are shown in greater detail. Lock ring 54 includes a portion of the fluid supply channels 62. Fluid supply channels 62 provide communication between the fluid pressure assembly 58 (Fig. 1 ) and fluid outlets 66. The fluid outlets 66 are located on a distal end of lock ring 54 and are positioned so that the expressed pressurized fluid is directed towards an end of the molded article (not shown) to assist with part removal from the mold core 50 when the neck ring assembly 44 is split and the neck ring halves 45 and 47 are located away from mold core 50 (Fig. 2) during the part removal phase. Lock ring 54 further includes a collector groove 80 for receiving air that is being displaced from molding cavity 52 when the molding cavity 52 is being filled with melt. The received air in collector groove 80 is then evacuated from the mold stack 36 out through one or more exhaust ports 82 into the ambient atmosphere.
The pair of split neck ring halves 45 and 47 cooperatively define a substantially cylindrical cavity around mold core 50 (Fig. 2). Each of neck ring half 47 and neck ring half 47 defines a number of molding features for the molded article, and in particular the neck finish of the molded article. For example, the presently-illustrated split neck ring assembly 44 includes as molding features a thread feature 70, and a support ledge feature 72. The neck ring assembly 44 may define other molding features for the molded article such as cam surfaces, part indicia or the like (not shown).
Each of split neck ring halves 45 and 47 includes a split face 74. When located within seat 56, the split faces 74 abut against each other in an opposing relationship, define a part line feature on the molded article, providing an air-tight seal between the two split faces 74. Each split face 74 includes vent groove 76. Vent groove 76 is open at a first end to provide a groove inlet 51. The other end of vent groove 76 is closed. When the two split neck rings halves 45 and 47 are seated within seat 56, the groove inlet 51 is aligned with fluid outlets 66, providing communication of the working fluid 60 between fluid supply channel 62 and vent groove 76.
Split face 74 further includes one or more venting surfaces, such as vent relief faces 78. Each vent relief face 78 provides a tapered surface that generates a gap between the opposing vent relief faces 78. The presently illustrated embodiment includes two different vent relief faces 78a and 78b, each having different slopes. Vent relief face 78b is sloped more steeply than vent relief face 78a. When the pair of split neck ring halves 45 and 47 are abutted together, the vent relief faces 78 provide an air gap between the opposing split faces 74 leading from the molding cavity 52 to vent groove 76. For some applications, portions of the neck ring assemblies 44 could be coated with an anti-stick coating (such as, Grease Free Coating, Diamond Like Carbon coating, TEFLON® coatings and the like) or another coating with similar properties. In particular, areas of the neck ring assemblies 44 that could be coated with the anti-stick coating include the thread feature 70, the support ledge feature 72, vent groove 76 and vent relief faces 78a and 78b. Portions of lock ring 54 can also be coated with the anti-stick coating or another material with similar properties. In particular, the vent relief faces 78a and 78b and the fluid outlets 66 can be coated with the anti- stick coating.
Referring now to Fig. 5, method for cleaning a molding cavity 52 during a molding cycle 100 for molding system 20 will be described. Each molding cycle 100 forms and then removes a molded article from the molding system 20. In the presently-illustrated embodiment, molding cycle 100 includes a molding operation 102, a part transfer operation 104 and a mold cleaning operation 106. During the molding operation 102, the molded article is formed. The movable platen 24 is moved towards the stationary platen 22, thereby effectively closing mold 34. Molding material from injection unit 26 enters molding cavity 52 through an opening in gate insert 48, thus displacing the air located within molding cavity 52. The air, which is being so-evacuated from the molding cavity 52, primarily escapes through a gap (not shown) between mold core 50 and lock ring 54 into the collector groove 80 and the fluid outlets 66 defined in lock ring 54. It then escapes through exhaust ports 82 which provide communication between collector groove 80 and the outside of lock ring 54. Alternatively, air could also escape through fluid supply channels 62 if the fluid supply channels 62 connect to other venting structures (none depicted), such as those venting features that can be additionally defined between the neck ring assembly 44 and the lock ring 54.
After the molding cavity 52 is filled and the molded article is formed, solidified and sufficiently cooled, the part transfer operation 104 commences. The movable platen 24 is moved away from the stationary platen 22, opening mold 34. The split neck ring halves 45 and 47 are displaced out of seat 56 and away from mold core 50 (and each other). The molded article is removed from mold core 50 using the robot 32 or other part-removal mechanism (also not depicted). During at least a portion of the part transfer operation 104, fluid supply channels 62 direct the pressure blast of the working fluid 60 (i.e., a stream of compressed air) towards the molded article, assisting at least partially, removal of the molded article from mold core 50. The pressure blast of the working fluid 60 is typically engaged after a brief onset delay from the start of the part transfer operation 104 and is applied for a predetermined period of time. Both settings are usually determined by the machine operator using HMI 38. After the part transfer operation 104 occurs, and the molded article is removed from mold core 50, the mold cleaning operation 106 occurs. Mold 34 remains at least partially opened, i.e., the movable platen 24 remains stationary or is moved only partially towards stationary platen 22. The split neck ring halves 45 and 47 are relocated back into seat 56 so that fluid outlets 66 on the lock ring 54 are aligned with vent grooves 76 on each of the split neck ring halves 45 and 47. The fluid supply channels 62 direct another pressure blast of the working fluid 60 (i.e., a second pressure blast of compressed air) into vent grooves 76. The pressure blast of the working fluid 60 subsequently travels across the vent relief faces 78a and 78b removing, at least partially, any surface deposits (such as PET gas deposits) found in the vent grooves 76 or on the vent relief faces 78a and 78b. The surface deposits are dispersed out into the molding cavity 52 and out into the ambient atmosphere.
The duration of the second pressure blast can be relatively brief (for example, 0.1 to 1.0 seconds), which will be activated during the closing movement of the mold 34, but has to stop before start of injection during the next molding cycle 100. The mold cleaning operation 106 could be initiated once the ejector has reached its back position. Alternatively, the mold cleaning operation 106 could start prior the mold 34 fully closing. The engagement of the fluid pressure assembly 58 could also start prior to the split neck ring halves 45 and 47 being fully positioned within seat 56, albeit at a lower pressure. Once the pressure blast is finished, the method returns to molding operation 102 to begin a new molding cycle 100. It is noted that the second pressure blast can be applied in a pulsing manner. For example, the second pressure blast can be applied several times (on or off) within the time-frame of up to 1.0 seconds, as an example. Referring now to Fig. 6, an alternative method for cleaning the molding cavities 52 of molding system 20 during a molding cycle 200 will be described. Molding cycle 200 includes a molding operation 202, a part transfer operation 204, a mold cleaning decision 205, and an optional cleaning operation 206. During the molding operation 202, the molded article is formed, as is described in greater detail with reference to molding operation 102 above.
During the part transfer operation 204, the molded article is transferred off of mold core 50, as is described in greater detail with reference to part transfer operation 104 above.
During mold cleaning decision 205, the system controller determines if the mold 34 should be cleaned. If the answer is "Yes", then the method advances to cleaning operation 206. If the answer is "No", then the method returns to molding operation 202 to begin a new molding cycle 200. The determination on whether the mold 34 should be cleaned is not particularly limited and can include:
i) a manual input provided by an operator using HMI 38;
ii) a system setting within molding system 20 to activate a mold cleaning operation after a predetermined number of molding cycles 200 (for example, every 100 or 200 molding cycles); and iii) a determination made by a controller within molding system 20 based upon received sensor readings of part quality of the molded article or other sensor readings, such as a signal received from a preform inspection system (not depicted) and the like. During the cleaning operation 206, the mold stack 36 is cleaned, as is described in greater detail with reference to mold cleaning operation 106 above. The method returns to molding operation 202 to begin a new molding cycle 200.
Referring now to Fig. 7, another embodiment of the invention is shown generally at 20B. Molding system 20B includes a mold stack 36, which is similar to the one described above. Mold 34 is connected to a fluid pressure assembly 58B.
Fluid pressure assembly 58B is similar to fluid pressure assembly 58, and is operable to provide pressure blasts of the working fluid 60 as described above. However, fluid pressure assembly 58B is further operably connected to source of a second working fluid 86. The second working fluid 86 is different than the working fluid 60. The choice and strength of the second working fluid 86 is not particularly limited and may vary depending on the molding application. Examples of the second working fluid 86 include a cleaning solution such as an alcohol or solvent, water or a mixture of different liquids. In alternative embodiments, the second working fluid 86 may include dry ice mixture. Fluid pressure assembly 58B is operable to selectively provide pressure blasts of the working fluid 60, the second working fluid 86, or a pressure blast which mixes the working fluid 60 and the second working 86 to fluid supply channels 62 (i.e., a mixture of compressed air and cleaning solvent). Some operations within molding system 20 may require pressure blasts of the working fluid 60 and others require pressure blasts from the second working fluid 86 or mixtures of the working fluid 60 and the second working fluid 86. For example, a parts transfer operation may use just the working fluid 60 and a cleaning operation use the second working fluid 86 (or a mixture of the working fluid 60 and the second working fluid 86). Pressure blasts from the second working fluid 86 (or mixtures of the working fluid 60 and the second working fluid 86) can be characterized as "intensive" pressure blasts. Depending on the solution and intensity of the intensive pressure blast, the mold 34 may need to dry off before the next molding cycle is initiated. As such, the intensive pressure blast may not occur during a regular molding cycle interval (such as described above with respect to molding cycle 100). Instead, molding system 20B would stop movable platen 24 until mold 34 was dry. Alternatively, after the intensive blast has been applied, the second working fluid 86 can be stopped and the working fluid 60 can be used to effectively dry off the mold 34. The intensive pressure blast may also have a longer duration or a higher pressure than the normal pressure blast.
Referring now to Fig. 8, an alternative method for cleaning a mold 34 during a molding cycle 300 will be described with reference to molding system 20B (depicted in Fig. 6). Molding cycle 300 includes a molding operation 302, a part transfer operation 304, a mold cleaning operation 306, an intense cleaning decision 308 and an optional intensive cleaning operation 310.
During the molding operation 302, the molded article is formed within molding system 20B, as is described in greater detail with reference to molding operation 102 above. During the part transfer operation 304, the molded article is transferred off of mold core 50, as is described in greater detail with reference to part transfer operation 104 above. Specifically, fluid pressure assembly 58B generates a pressure blast of the working fluid 60 to assist in parts transfer. During the mold cleaning operation 306, the mold stack 36 is cleaned, as is described in greater detail with reference to mold cleaning operation 106 above. Specifically, in this instance, fluid pressure assembly 58B generates a pressure blast of the working fluid 60 to clean out the mold stack 36. The method then advances to the intensive cleaning decision 308. During the intensive cleaning decision 308, the system controller determines if the mold 34 should have an intensive cleaning. If the answer is "Yes", then the method advances to intensive cleaning operation 310. If the answer is "No", then the method returns to molding operation 302 to begin a new molding cycle 300. The determination on whether the mold 34 should be cleaned is not particularly limited and can include:
i) a manual input provided by an operator using HMI 38;
ii) a system setting to activate a mold cleaning operation after a predetermined number of molding cycles 300; and iii) a determination made by the system controller based upon received sensor readings of part quality of the molded article or other sensor readings.
During the intensive cleaning operation 310, mold 34 remains at least partially opened, i.e., the movable platen 24 remains stationary or is moved only partially towards stationary platen 22. The split neck ring halves 45 and 47 are relocated back into seat 56 so that fluid outlets 66 on the lock ring 54 are aligned with vent grooves 76 on each of the split neck ring halves 45 and 47. The molding features receive an intensive pressure blast from the second working fluid 86, which as described above could include a cleaning solution, or a combination of the working fluid 60 and the second working fluid 86.
The intensive pressure blast travels across the vent relief faces 78a and 78b removing, at least partially, any surface deposits (such as PET gas deposits) found in the vent grooves 76 or on the vent relief faces 78a and 78b. The surface deposits are dispersed out into the molding cavity 52 and out into the ambient atmosphere. The duration of the second pressure blast can be comparatively longer than the first pressure blast. Depending on the solution and intensity of the intensive pressure blast, the mold 34 may need to dry off before the method can return to the next molding operation 302. Instead, molding system 20B would stop movable platen 24 until mold 34 was dry.
Those of skill in the art will recognize that variations can be applied to the molding cycle of molding system 20B. For example, in some applications, the cleaning operation 306 (which uses the working fluid 60 for its pressure blasts) could be omitted, and, instead, the molding system 20 would rely upon the intensive pressure blasts of intensive cleaning operation 310 to keep the surfaces of the mold stack 36 clear of surface deposits. Alternatively, cleaning operation 306 could generate pressure blasts that use the second working fluid 86 or a mixture of the working fluid 60 and the second working fluid 86. In this instance, the pressure blast of cleaning operation 306 would still be less intensive than the intensive pressure blast of intensive cleaning operation 310 as it typically would be undesirable to wait for the mold 34 to dry prior to initiate the next molding cycle. Other variations in the molding cycle regarding the application of the working fluid 60 and the second working fluid 86 will occur to those of skill in the art, depending on the molding application. In alternative embodiments of the present invention, during the cleaning operation (whether the standard cleaning operation or the intensive blast based cleaning operation), the ejector plate can be configured to move back and forth, with a pre-defined stroke, such as every 0.1 to 10 mm, as an example. Using this alternative implementation, a rear surface (not separately numbered) of the neck ring assembly 44 and/or the lock ring 54 can be cleaned.
In other embodiments of the present invention, structures and method disclosed above can be used to clean other surfaces of the mold stack 36. For example, the core lock venting surfaces, grooves and venting holes in the lock ring 54 and the like.
Description of the non-limiting embodiments of the present inventions provides examples of the present invention, and these examples do not limit the scope of the present invention. It is to be expressly understood that the scope of the present invention is limited by the claims. The concepts described above may be adapted for specific conditions and/or functions, and may be further extended to a variety of other applications that are within the scope of the present invention. Having thus described the non-limiting embodiments of the present invention, it will be apparent that modifications and enhancements are possible without departing from the concepts as described. Therefore, what is to be protected by way of letters patent are limited only by the scope of the following claims:
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