Patent Publication Number: US-7588439-B2

Title: Compensating core for use with a molding system

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to, but is not limited to, molding systems, and more specifically the present invention relates to, but is not limited to, a compensating core for use with a molding system and the molding system incorporating same. 
     BACKGROUND OF THE INVENTION 
     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. 
     A typical molding system includes an injection unit, a clamp assembly and a mold assembly. The injection unit can be of a reciprocating screw type or of a two-stage type. The clamp assembly includes inter alia a frame, a movable platen, a fixed platen and an actuator for moving the movable platen and to apply tonnage to the mold assembly arranged between the platens. The mold assembly includes inter alia a cold half and a hot half. The hot half is usually associated with one or more cavities (and, hence, also sometimes referred to by those of skill in the art as a “cavity half”), while the cold half is usually associated with one or more cores (and, hence, also sometimes referred to by those of skill in the art as a “core half”). The one or more cavities together with one or more cores define, in use, one or more molding cavities. The hot half can also be associated with a melt distribution system (also referred to sometimes by those of skill in the art as a “hot runner”) for melt distribution. The mold assembly can be associated with a number of additional components, such as neck rings, neck ring slides, ejector structures, wear pads, etc. 
     As an illustration, injection molding of PET material involves heating the PET material (ex. PET pellets, PEN powder, PLA, etc.) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into the one or more molding cavities defined, at least in part, by the aforementioned one or more cavities and one or more cores mounted respectively on a cavity plate and a core plate of the mold assembly. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient enough 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 mold. 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. Accordingly, by urging the core plate away from the cavity plate, the molded article can be demolded, i.e. ejected from 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, ejector pins, etc. 
     SUMMARY OF THE INVENTION 
     According to a first broad aspect of the present invention, there is provided a core insert for use in a molding system. The core insert comprises a core base for defining, in use, a portion of a molding cavity; a core support for supporting, in use, the core base relative to a core plate of the molding system; a compensator associated, at least partially, with the core support to permit at least a degree of axial movement to the core base. 
     According to a second broad aspect of the present invention, there is provided a sliding interface defined, in use, between: a core base for defining, in use, a portion of a molding cavity; and a core support for supporting the core base relative to a core plate of a molding system; the core base and the core support constituting to a core insert, the sliding interface configured to permit a degree of lateral movement to the core base. 
     According to a third broad aspect of the present invention, there is provided a compensating portion defined in a core support used for supporting a core base relative to a core plate of a molding system; the compensating portion configured to permit a degree of axial movement to the core base. 
     According to a fourth broad aspect of the present invention, there is provided a compensator comprising one of: (a) a sliding interface defined, in use, between (i) a core base for defining, in use, a portion of a molding cavity; and (ii) a core support for supporting the core base relative to a core plate of a molding system; the core base and the core support constituting to a core insert; and a compensating portion defined in said core support; and (b) a spring connection between said core base and said core support, the compensator for affording, in use, at least a degree of axial movement to the core base. 
     According to another broad aspect of the present invention, there is provided a mold stack comprising: a compensating core insert complementary to a cavity insert, the compensating core insert and the cavity insert configured to jointly define, in use, at least a portion of a molding cavity, the compensating core insert configured to have a degree of axial and lateral movement relative to at least the cavity insert. There is further provided a molding system incorporating the mold stack. 
     According to yet another broad aspect of the present invention, there is provided a core insert for use in a molding system. The core insert comprises a core base having a cavity defining portion for defining, in use, a portion of a molding cavity; a core support that is configured to cooperate with a base portion of the core base; a compensator associated, at least partially, with the core support to permit at least a degree of axial movement to the core base. 
     According to yet another broad aspect of the present invention, there is provided a core support that is configured to cooperate with a base portion of a core base. The core support comprises a compensator to permit a degree of flexibility to the core support whereby to permit at least a degree of axial movement to the core base. 
     According to yet another broad aspect of the present invention, there is provided a core base. The core base comprises a cavity defining portion configured to define, in use, a portion of a molding cavity; a base portion configured to cooperate, in use, with a core support, a portion of the base portion being configured to define, in use, a portion of a sliding portion between the core base and the core support. 
     According to another broad aspect of the present invention, there is provided a retaining member for coupling, in use, a core base to a core support, the core base and the core support for use with a molding system. The retaining member comprises a first end and a second end, each of the first end and the second end comprising a respective plurality of fingers; the respective plurality of fingers is actuatable between (i) a retracted position, where the respective plurality of fingers are insertable, respectively, into a first internal bore and a second internal bore associated, respectively, with the core support and the core base; and (b) an expanded position, where the respective plurality of fingers engage, respectively) a first retaining lip and a second retaining lip, associated, respectively, with the first internal bore and the second internal bore. 
     These and other aspects and features of 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 embodiments of the present invention (including alternatives and/or variations thereof) may be obtained with reference to the detailed description of the exemplary embodiments along with the following drawings, in which: 
         FIG. 1  is a cross-section view of a portion of a mold stack according to a non-limiting embodiment of the present invention. 
         FIG. 2  is a cross-section view of a core insert of the mold stack of  FIG. 1 , according to a non-limiting embodiment of the present invention. 
         FIG. 3  is a cross-section view of a core insert according to another non-limiting embodiment of the present invention. 
         FIG. 4  is a perspective view of the core insert of  FIG. 3 . 
         FIG. 5  is a perspective view of another embodiment of the core insert of  FIG. 1 . 
         FIG. 6  is a cross-section view of the core insert of  FIG. 5 . 
         FIG. 7  is a cross-section view of a cavity insert, a cavity plate and a gate insert of the mold stack of  FIG. 1 , according to a non-limiting embodiment of the present invention. 
         FIG. 8  is a perspective view of a cavity plate of the mold stack of  FIG. 1  with a plurality of retaining structures disposed thereupon, according to a non-limiting embodiment of the present invention. 
         FIG. 9  is a perspective view of the retaining structure of  FIG. 8 . 
         FIG. 10  is a perspective view of the cavity insert of  FIG. 7 . 
         FIG. 11  is a cross-section view of a portion of the mold stack of  FIG. 1 , in a mold closed position. 
         FIG. 12  is a cross-section view depicting a portion of the mold stack of  FIG. 1 , with a retaining member implemented according to an alternative non-limiting embodiment of the present invention. 
         FIG. 13  is a cross-section view of a core insert with a compensator implemented according to another non-limiting embodiment of the present invention. 
         FIG. 14  is a schematic view of a manifold and slides of the mold stack of  FIG. 1 , according to a non-limiting embodiment of the present invention. 
         FIG. 15  is a partial section view of a compensating coupling of  FIG. 14 , according to a non-limiting embodiment of the present invention. 
         FIG. 16  is a perspective view of the compensating coupling of  FIG. 15 , according to a non-limiting embodiment of the present invention. 
     
    
    
     The drawings are not necessarily to scale and are may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the exemplary embodiments or that render other details difficult to perceive may have been omitted. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Inventors have appreciated that there exists a premature wear problem associated with various components of a known injection molding system. The premature wear problem can be broadly categorized, depending on severity and/or location of the problem, as fretting, galling or hobbing. Inventors believe that the premature wear problem(s) is(are) attributable, at least in part, to some or all of the following issues: (a) excessive clamping force, (b) insufficient clamping force, (c) process parameters of filling the molding cavity with the melt, (d) geometry of the mold stack components, (e) platen parallelism (or lack thereof), (f) number of cavities in a given size of a cavity plate, (g) material used for various mold stack components (ex. tapers, etc.) and (i) relative position of various mating mold stack components (ex. mis-alignment of individual mating mold stack components). Naturally, the premature wear problem can be attributable to other known or to be appreciated issues. 
     Inventors have further appreciated that in a mold stack of a given size, clamping force is not distributed equally along a cross-section of the mold stack that traverses an operational axis of a molding system. Some areas of the cross-section experience higher clamping force, while other area of the cross-section experience lower clamping force. 
     With reference to  FIG. 1 , there is depicted a portion of a mold stack  100  according to a non-limiting embodiments of the present invention. The mold stack  100  comprises a stripper plate  102  and a cavity plate  104 . Even though not shown in  FIG. 1 , the mold stack  100  further comprises a core plate, which abuts the stripper plate  102  at a rear extremity thereof vis-à-vis the cavity plate  104 . There is also provided a core insert  105 , which is associated with a core plate (not depicted) and is positioned, in use, through aperture(s) in the stripper plate  102 . Associated with the cavity plate  104  are a cavity insert  106  and a gate insert  108 . Coupled to the stripper plate  102  and disposed intermediate the stripper plate  102  and the cavity plate  104 , is a split mold insert assembly  110 . The split mold insert assembly  110  can comprise a plurality of slides  112 , only two of which are depicted in  FIG. 1 . Coupled to each of the pair of slides  112  is a split mold insert  114 , also referred to by those of skill in the art as a “neck ring”. Two split mold inserts  114  form a split mold insert pair. The function of the split mold inserts  114  is well known to those of skill in the art and, as such, need not be discussed here at any length. In the specific non-limiting embodiment of  FIG. 1 , the split mold insert  114  is coupled to the slide  112  in a so-called “front-face coupling arrangement”, which is more particularly described in a patent application bearing a application Ser. No. 11/740,564 filed with the United States Patent Office on Apr. 26, 2007 and assigned to Assignee of the present patent application, content of which is incorporated by reference herein in its entirety. However, in alternative embodiments of the present invention, the split mold insert  114  can be coupled to the slide  112  in other known arrangement, such as, for example, the typical “top-face coupling arrangement”. 
     Also depicted in  FIG. 1 , is a retaining structure  116  coupled to the cavity plate  104 . Structure and function of the retaining structure  116  will be explained in greater detail herein below. However, for the time being suffice it to say, that the retaining structure  116  cooperates with a respective one of the pair of slides  112  to position and to retain the respective one of the pair of slides  112  in an operating position. 
     Further depicted in  FIG. 1 , is a wear plate  118  coupled to the stripper plate  102 , intermediate the stripper plate  102  and the pair of slides  112 . The purpose of the wear plate  118  is to prevent substantial damage to the pair of slides  112  and/or the stripper plate  102  during lateral movement of the pair of slides  112  relative to each other. Within alternative non-limiting embodiments of the present invention, the wear plate  118  can be omitted from the architecture of the mold stack  100 . This is particularly applicable in those embodiments of the present invention, where an actuator that actuates the lateral movement of the pair of slides  112  provides for lifting of the pair of slides  112  relative to the stripper plate  102 . An example of such a solution is disclosed in a PCT patent application PCT/CA2007/000392 filed with Canadian Intellectual Property Office as a Receiving Office for PCT on Mar. 8, 2007, content of which is incorporated by reference herein in its entirety. 
     Within the non-limiting illustration of  FIG. 1 , the core insert  105 , the cavity insert  106 , the gate insert  108  and the two split mold inserts  114  are depicted in a so-called mold closed position. Within the mold closed position, a portion of the core insert  105 , a portion of the cavity insert  106 , a portion of the gate insert  108  and a portion of each of the two split mold inserts  114  cooperate to define a molding cavity  120 . A shape of the molding cavity corresponds to a shape of a molded article  122 . Within specific non-limiting embodiment depicted in  FIG. 1 , the molded article  122  comprises a preform that is capable of being subsequently blow-molded into a final-shaped article, such as beverage container. However, it should be expressly understood that the molded article  122  can be of any other shape and/or configuration. Accordingly, it should be clear that teachings of embodiments of present invention apply to a mold stack  100  and a molding system incorporating the mold stack  100  that can be configured to produce different types of molded articles  122 , such as, but not limited to, preforms, thin wall containers, closures and the like. 
     Also provided within  FIG. 1 , is a first interface  124  defined between the split mold inserts  114  and the cavity insert  106 . In the specific embodiment illustrated, the first interface  124  comprises a pair of complementary tapers defined on the split mold inserts  114  and the cavity insert  106 . There is also provided a second interface  126  defined between the core insert  105  and the split mold inserts  114 . In the specific embodiment illustrated, the second interface  126  comprises a pair of complementary tapers defined on the split mold inserts  114  and the core insert  105 . It should be understood that in alternative non-limiting embodiments of the present invention, the first interface  124  and/or the second interface  126  can be implemented differently and, as such, do not need to necessarily include tapers. The first interface  124  and/or the second interface  126  can be implemented in any alternative shape, such as a cylindrical shape, spherical shape and the like. 
     With reference to  FIG. 2 , which depicts in more detail the core insert  105  of the mold stack  100  of  FIG. 1 , structure of the core insert  105  according to a non-limiting embodiment of the present invention will now be described in greater detail. The core inserts  105  implemented according to various embodiments of the present invention can be thought of as a “compensating core insert”. The core insert  105  comprises a core base  202  and a core support  204 . A portion of the core base  202  (i.e. a “cavity defining portion”) defines a portion of the molding cavity  120 . Generally speaking, the purpose of the core support  204  is to support the core base  202 , in an operating position, where it is affixed to the core plate (not depicted) in a floating arrangement, as will be described in greater detail herein below. To this extent, the core support  204  cooperates with a portion of the core base  202  (i.e. a “base portion”). 
     The core support  204  comprises a compensator  206 . Generally speaking, the purpose of the compensator  206  is to compensate for mis-alignment potentially present between various parts of the mold stack  100 . For example, the compensator  206  may be configured to compensate for height differences in various parts of the mold stack  100  in a direction depicted in  FIG. 2  at “F” (or, in other words, axial mis-alignment). Additionally or alternatively, the compensator  206  may be configured to compensate for mis-alignment in a direction depicted in  FIG. 2  at “S 1 ” (or, in other words, lateral mis-alignment). 
     More specifically, in the embodiment depicted in  FIG. 2 , the compensator  206  comprises a compensating portion  208  and a sliding interface  210 . The compensating portion  208  is defined in the core support  204  and in the example being presented herein comprises a conical spring member, which in the cross section depicted in  FIG. 2  is generally S-shaped. Generally speaking, the purpose of the compensating portion  208  is to allow a degree of axial flexibility to the core support  204 . The degree of axial flexibility allows to compensate for the mis-alignment of the stack components. Accordingly, the dimension of the compensating portion  208  is selected such that to provide the degree of flexibility to the core support  204 , while providing operational stability, while in use. For the avoidance of doubt, the term “operational stability” as used herein above and herein below is meant to define an operational state between various components of the mold stack  100  which is suitable for proper operation of the mold stack  100 , i.e. injection of melt under pressure of formation of the molded article  122 . The sliding interface  210  is a sliding interface defined between the core support  204  and the core base  202 . In alternative non-limiting embodiments of the present invention, the compensator  206  can comprise just the compensating portion  208 . In yet further non-limiting embodiments of the present invention, the compensator  206  can comprise just the sliding interface  210 . 
     As is best seen in  FIG. 1 , there is provided a core clearance  160  defined between the core base  202  and the core support  204 . The core clearance  160  is configured to provide a degree of float to the core base  202  relative to the core support  204 . Accordingly, the dimension of the core clearance  160  is selected such that to provide the degree of float to the core base  202 , while providing operational stability, while in use. It can be said that a combination of the core clearance  160 , the sliding interface  210  and the compensating portion  208  permits the core base  202  to move relative to the core support  204  in a direction depicted in  FIG. 2  at “S 2 ” (i.e. axial move) and in a direction depicted in  FIG. 2  as “S 1 ” (i.e. lateral move). More specifically, the core clearance  160  and/or the sliding interface  210  allows for the lateral move and the compensating portion  208  allows for the axial move. 
     In the embodiment depicted in  FIG. 2 , the core base  202  further comprises a connecting portion  218 . The connecting portion  218  can comprise a spigot that cooperates, in use, with a complementary spigot connection associated with the core plate (not depicted). As can be clearly seen in  FIG. 2 , the connecting portion  218  protrudes beyond a rear extremity of the core support  204 . However, in an alternative non-limiting embodiment of the present invention, the connecting portion  218  can be substantially flush with the rear extremity of the core support  204 . This is illustrated in  FIG. 3 , which illustrates another non-limiting embodiment of the core insert  105   a . The core insert  105   a  can be substantially similar to the core insert  105  and, as such, like elements are depicted with like numerals. However, in the embodiment of  FIG. 3 , the core insert  105   a  comprises a connecting portion  218   a  which is substantially flush with the rear extremity of the core support  204 . An additional technical effect of this embodiment of the present invention is the additional ability for the core base  202  to shift relative to the core support  204  (and, therefore, relative to the core plate, which is not depicted) in a direction depicted in  FIG. 3  at “CS”. 
     A coupling between the core base  202  and the core support  204  will now be explained in greater detail. With reference to  FIG. 4 , which depicts a perspective view of the core insert  105   a  of  FIG. 3 , there is provided a retaining member  216 . In the specific non-limiting embodiment being presented herein, the retaining member  216  comprises a snap ring. A non-limiting example of a snap ring that can be adapted to implement embodiments of the present invention comprises a Seeger circlip ring E 1570 available from Meusburger (http://www.meusburger.com/). However, it should be understood that any other suitable type of a releasable fastener can be used. 
     The core support  204  comprises a retaining step  212  and the core base  202  comprises an undercut  214 . The retaining step  212 , the undercut  214  and the retaining member  216  cooperate to maintain the core base  202  affixed to the core support  204 . More specifically, the core base  202  is installed within the core support  204 . The retaining member  216  is then stretched (for example, using a tool or the like) to an open position and pulled over a rear extremity of the core base  202 . Once the so-stretched retaining member  216  is positioned substantially close over the undercut  214 , the retaining member  216  is allowed to return to a closed position where it is positioned partially within the undercut  214 . An outer portion of the retaining member  216  protrudes radially and cooperates with the retaining step  212  to maintain the core based  202  and the core support  204  in this operational configuration. 
     As is best seen in  FIG. 4 , there is also provided is a sealing member  402 , such as an O-ring and the like, to seal against coolant leaks. 
       FIG. 5  and  FIG. 6  depict another non-limiting embodiment of how a coupling between a core base  202   a  and a core support  204   a  can be implemented. Within the embodiment of  FIG. 5  and  FIG. 6 , there is provided a retaining member  502 . As us best seen in  FIG. 6 , the retaining member  502  is implemented as a retaining clip. The retaining member  502  comprises a first end  504  and a second end  506 . The first end  504  comprises a plurality of fingers  508  and the second end  506  comprises a plurality of fingers  510 . The core support  204   a  comprises a first internal bore  511  and the core base  202   a  comprises a second internal bore  513 . The first internal bore  511  comprises a first retaining lip  512  and the second internal bore comprises a second retaining lip  514 . The plurality of fingers  508  and the plurality of fingers  510  are actuatable between (i) a retracted position, where the plurality of fingers  508  and the plurality of fingers  510  can be inserted, respectively, into the first internal bore  511  and the second internal bore  513 ; and (b) an expanded position, where the plurality of fingers  508  engage the first retaining lip  512  and the plurality of fingers  510  engage the second retaining lip  514 . As is best seen in  FIG. 6 , there is provided the sliding interface  210  and an internal clearance  620 , which allow for a degree of movement of the core base  202   a  relative to the core support  204   a.    
     It should be understood that  FIGS. 2-6  depict just a few possible implementations for the core base  202 ,  202   a  and the core support  204 ,  204   a . It should be further understood that numerous alternative implementations are possible. For example, a shape of the compensating portion  208  is not particularly limited. Even though  FIGS. 2-6  depict the compensating portion  208  as having a “S-shaped” configuration in the cross-section of  FIGS. 2-6 , in alternative embodiments of the present invention, the compensating portion  208  can have other shapes, such as, for example, “Z-shape” and the like. Generally speaking, the compensating portion  208  can be implemented in any suitable form factor that allows a degree of resiliency. 
     It should also be understood that the precise location of the compensating portion  208  along a length of the core support  204  is not particularly limited. For example, as can be seen by comparing the core support  204   a  of  FIG. 5  with the core support  204  of  FIG. 2  or  FIG. 3 , the position of a compensating portion  208   a  is much closer to a rear extremity of the core support  204   a  than the position of the compensating portion  208  of the core support  204 . Other alternatives are, of course, possible. 
     In yet further non-limiting embodiments of the present invention, the compensator  206  can be implemented differently. For example, the compensator  206  can be implemented as a spring connection between the core base  202  and the core support  204 . A non-limiting example of such an implementation is depicted in  FIG. 13 .  FIG. 13  depicts a core insert  105   b  implemented according to an alternative non-limiting embodiment of the present invention. More specifically, the core insert  105   b  comprises a compensator  206   a , which in this embodiment is implemented as a spring connection. An example of structure that can be used to implement these embodiments comprises a disk spring and the like. It should be noted that the placement and/or the structure of the spring connection can be implemented differently. 
     With reference to  FIG. 7 , a portion the cavity plate  104 , the cavity insert  106  and the gate insert  108  of  FIG. 1 , according to a non-limiting embodiment of the present invention, are depicted. The cavity insert  106  implemented according to embodiments of the present invention can be thought of as a “compensating cavity insert”. Similarly, the gate insert  108  implemented according to embodiments of the present invention can be thought of as a “compensating gate insert”. 
     To this extent, there is provided a cavity clearance  702  defined between the cavity insert  106  and the cavity plate  104 . The cavity clearance  702  provides for a degree of movement of the cavity insert  106  within the cavity plate  104 . Accordingly, the dimension of the cavity clearance  702  is selected such that to provide the degree of movement to the cavity insert  106 , while providing operational stability, while in use. In the non-limiting embodiment of  FIG. 7 , the cavity insert  106  is coupled to the cavity plate  104  by means of first flexible fasteners  704 . Generally speaking, the first flexible fasteners  704  can be implemented by any suitable means that secures the cavity insert  106  to the cavity plate  104 , while allowing a degree of movement to the cavity insert  106  vis-à-vis the cavity plate  104 . An example of the structure suitable for implementing the first flexible fasteners  704  is a two-piece shoulder screw. An example of such two-piece shoulder screw can be implemented as a socket head shoulder screw available from SPS Technologies, Unbrako Engineered Fasteners (http://www.unbrako.com.au/). However, in alternative non-limiting embodiments other types of fasteners can be used, such as, for example, standard shoulder screws and the like. 
     With brief reference to  FIG. 10 , which depicts a perspective view of the cavity insert  106 , the cavity insert  106  comprises a plurality of cooling channels  1200 . The function of the plurality of cooling channels  1200  is generally known and can be broadly categorized as supplying coolant (such as water or another suitable coolant medium) to provide for cooling of the cavity insert  106  during specific portions of a molding cycle. In the specific non-limiting embodiment depicted in  FIG. 10 , the cooling channels  1200  comprise a plurality of elongated grooves extending substantially along an outer periphery of the cavity insert  106  in a direction of the operational axis of the mold stack  100 . In some embodiments of the present invention, the plurality of cooling channels  1200  can be produced by using a rolling machine. However, a plethora of alternative tools can be used for producing the cooling channels  1200 , such as, but not limited to, milling tools, machining tools, as well as various erosion techniques. In alternative non-limiting embodiments of the present invention, other configurations of the cooling channels  1200  can be used, such as, but not limited to a spiral configuration and the like. Also depicted in  FIG. 10  is a plurality of coupling interfaces  1202  configured to accept, in use, the aforementioned first flexible fasteners  704 . 
     With continued reference to  FIG. 7 , the cavity insert  106  comprises a step  720 . The step  720  is configured to accept, in use a lip  722  of the gate insert  108 . Accordingly, it can be said that an interface  724  defined between the cavity insert  106  and the gate insert  108  comprises a first contact surface  726  and a second contact surface  728 , the first contact surface  726  and the second contact surface  728  being disposed in different planes and separated by a traversing third contact surface  730 . However, in alternative non-limiting embodiments of the present invention, the interface  724  can be implemented differently, for an example, as a single contact surface (not depicted) known to those of skill in the art. 
     There is also provided a gate insert clearance  706  defined between the gate insert  108  and the cavity plate  104 . The gate insert clearance  706  provides for a degree of movement of the gate insert  108  within the cavity plate  104 . Accordingly, the dimension of the gate insert  108  is selected such that to provide the degree of movement, while providing operational stability, while in use. In the non-limiting embodiment of  FIG. 7 , the gate insert  108  is coupled to the cavity plate  104  by means of second flexible fasteners  708 . Generally speaking, the second flexible fasteners  708  can be implemented by any suitable means that secures the gate insert  108  to the cavity plate  104 , while allowing a degree of movement to the gate insert  108  vis-à-vis the cavity plate  104 . An example of the structure suitable for implementing the second flexible fasteners  708  is a two-piece shoulder screw. An example of such two-piece shoulder screw can be implemented as a socket head shoulder screw available from SPS Technologies, Unbrako Engineered Fasteners (http://www.unbrako.com.au/). However, in alternative non-limiting embodiments other types of fasteners can be used, such as, for example, standard shoulder screws and the like. 
     Also depicted in  FIG. 7  is a first sealing member  710  and a second sealing member  712 . The first sealing member  710  is positioned in an annular groove  714  defined between a front face of a shoulder  716  of the core insert  105  and a rear extremity face of the cavity plate  104 . The second sealing member  712  is positioned in an annular groove  717  defined between a front face of a shoulder  718  of the gate insert  108  and a front extremity of the cavity plate  104 . An additional technical effect of this placement of the first sealing member  710  and the second sealing member  712  includes ability to provide an effective seal even with larger dimensions of the cavity clearance  702  and/or the gate insert clearance  706 . Another technical effect of these embodiments of the present invention may include prevention of a “bounce-back effect” of the cavity insert  106  after being aligned to or, in other words, after movement to a desired position. For the avoidance of doubt, term “bounce-back effect” is meant to denote an effect whereby the cavity insert  106  experiences an urge to move to (or, in other words, “bounce back”) to a position within the cavity plate  104  that it was in prior to be aligned to the desired position. In the specific embodiment of  FIG. 7 , there is also provided a third sealing member  750  provided between the lip  722  and the step  720 . 
     However, in alternative non-limiting embodiments of the present invention, the first sealing member  710  and/or the second sealing member  712  can be positioned along an outer circumference of the cavity insert  106 , as is known in the art. 
     It is worthwhile noting that  FIG. 7  depicts one embodiments of how the compensating cavity insert  106  and the compensating gate insert  108  can be implemented. It should be appreciated that other alternative implementations are possible. One example of alternative implementation is disclosed in a U.S. patent application bearing application Ser. No. 11/741,761 filed on Apr. 29, 2007 and assigned to the Assignee of the present patent application, content of which is incorporated by reference herein in its entirety. 
     With reference to  FIG. 8 , a perspective view of the cavity plate  104  according to a non-limiting embodiment of the present invention is depicted. The cavity plate is associated with a retaining structure  116   a . Within specific embodiment of the present invention depicted in  FIG. 8 , the cavity plate  104  is associated with a plurality of retaining structures  116   a . With continued reference to  FIG. 8  and with reference to  FIG. 9 , a non-limiting embodiment of one such retaining structure  116   a  is depicted. The retaining structure  116   a  comprises a body  902 . Defined in the body  902  is a relief element  904 . Generally speaking, the purpose of the relief element  904  is to provide a degree of flexibility to the body  902  of the retaining structure  116   a . Accordingly, the dimension of the relief element  904  is selected such that to provide the degree of flexibility to the retaining structure  116   a , while providing operational stability, while in use. 
     Within the specific non-limiting embodiment of  FIG. 9 , the relief element  904  comprises a groove defined along a length of the body  902 . However, in alternative non-limiting embodiments of the present invention, the relief element  904  can be implemented as a groove (or another shape) defined along at least a portion of the length of the body  902 . 
     As will be recalled from the description of  FIG. 1 , the purpose of the retaining structure  116   a  is to position and to retain the respective one of the pair of slides  112  in an operating position. Traditionally, structures similar to the retaining structure  116   a  have been manufactured to tight tolerances using various precise-machining techniques. A technical effect of embodiments of the present invention may include decreased or no requirement to precise-machine the retaining structure  116   a , as the relief element  904  can compensate for imprecision(s) in the dimensions of the body  902 . 
     In the embodiment being described herein, the body  902  comprises a coupling interface  906 . The coupling interface  906  can comprise two bores for accepting a pair of suitable fasteners (such as bolts, etc.) therethrough for coupling to the cavity plate  104 . It should be appreciated that the number of bores/fasteners used is not particularly limited. Similarly, other structures to implement the coupling interface  906  can be used and are known to those of skill in the art. The body  902  further comprises a first positioning interface  908 . The first positioning interface  908  cooperates with a second positioning interface  808  defined on a face of the cavity plate  104 , as is best seen in  FIG. 8 . In the specific non-limiting embodiment depicted herein, the first positioning interface  908  comprises a protruding leg and the second positioning interface  808  comprises a groove, the shape of the groove being complementary to the shape of the protruding leg. The first positioning interface  908  and the second positioning interface  808  are dimensioned in this complementary relationship such that to precisely position the retaining structure  116   a  vis-à-vis the cavity plate  104  and, more specifically, vis-à-vis a respective pair of slides  112  when the mold stack  100  is in the operating position. 
     Accordingly, the retaining structure  116   a  implemented according to embodiments of the present invention can be thought of as a “compensating retaining structure”. As is shown in  FIG. 8 , there are also provided a plurality of non-compensating retaining structures  810 . The plurality of non-compensating retaining structures  810  are located at a periphery of the cavity plate  104  and, more specifically, on opposing ends of the cavity plate  104  relative to the operating axis of the mold stack  100 . In alternative non-limiting embodiments, compensating retaining structures similar to the retaining structure  116   a  can be used instead of the non-compensating retaining structure  810 . 
     It should be noted that the non-limiting embodiment of the relief element  904  depicted in  FIG. 8  and  FIG. 9  is just one example of possible implementation thereof. Numerous alternative implementations are possible. For example, with reference to  FIG. 1 , another non-limiting embodiment of the retaining structure  116  is depicted. Within the embodiment of  FIG. 1 , the retaining structure  116  comprises a body  1002 . The body  1002  comprises a relief element  1004 . In the specific non-limiting embodiment of  FIG. 1 , the relief element  1004  comprises three undercuts defined in the body  1002 . The body  1002  further comprises a first positioning interface  1008 . The cavity plate  104  also comprises a second positioning interface  1010 . Similar to the first positioning interface  908  and the second positioning interface  808 , the first positioning interface  1008  and the second positioning interface  1010  are dimensioned in a complementary relationship such that to precisely position the retaining structure  116  vis-à-vis the cavity plate  104  and, more specifically, vis-à-vis a respective pair of slides  112  when the mold stack  100  is in the operating position. 
     It should be noted that the number of, the shape of or location of the undercuts that constitute to the relief element  1004  is not particularly limited. An example of an alternative non-limiting implementation for the relief element  1004  is depicted in  FIG. 12 . A retaining member  116   b  of  FIG. 12  comprises a relief element  1004   a . The relief element  1004   a  comprises three undercuts, however, the positioning of the three undercuts is different from that of  FIG. 1 . More specifically, two of the three undercuts of  FIG. 12  are positioned at a different angle vis-à-vis a perimeter of the retaining member  116   b  compared to the three undercuts of the relief element  1004  of  FIG. 1 . Naturally, other alternative implementations are also possible. 
     In yet further embodiments of the present invention, the retaining structure  116   a  of  FIG. 8  can be implemented as a rail extending along the length of the cavity plate  104 . For example, the retaining structures  116   a  depicted in  FIG. 8  as a retaining structure  116   a ′, a retaining structure  116   a ″, a retaining structure  116   a ″′ and a retaining structure  116   a ″″ can be implemented in a single rail (not depicted). Other alternatives are, of course, also possible. 
     With reference to  FIG. 14 , there is depicted a non-limiting embodiment of a compensating coupling  1400  between a water manifold  1402  and the plurality of slides  112 . The manifold  1402  comprises an inlet  1404  for operatively coupling to a coolant supply  1408 . The manifold  1402  further comprises an internal manifold distribution network  1406  coupled to the inlet  1404  and to a plurality of outlets  1407 , each of the plurality of outlets  1407  being associated with a given one of the plurality of slides  112 . Each of the plurality of slides  112  comprises an internal slide distribution network  1410 . The combination of the internal manifold distribution network  1406  and the internal slide distribution network  1410  allows for supply of coolant (such as water and the like) to the plurality of slides  112  and, accordingly, to the plurality of split mold inserts  114 . In the embodiment depicted in  FIG. 14 , there is also provided the compensating coupling  1400  between each of the plurality of outlets  1407  and each internal slide distribution network  1410 . 
     With further reference to  FIG. 15  and  FIG. 16 , structure of the compensating coupling  1400  will now be described in greater detail. More specifically, the manifold  1402  comprises a receptacle  1502  for receiving the compensating coupling  1400  therethrough. Dimension of the compensating coupling  1400  is selected relative to the receptacle  1502  such that to permit a degree of movement to the compensating coupling  1400  vis-à-vis the receptacle  1502 . This, in turn, permits a degree of movement to the plurality of slides  112  vis-à-vis the manifold  1402 . The compensating coupling  1400  comprises a coupling inlet  1602  and a coupling outlet  1604 , communicatively coupled by an internal channel (not separately numbered). 
     Even though within the specific non-limiting embodiment of  FIG. 14 , the compensating coupling  1400  is implemented as a compensator of the mold stack  100 , this need not be so in every embodiment of the present invention, As such, in alternative non-limiting embodiments of the present invention, a coupling between the manifold  1402  and the plurality of slides  112  can be implemented in any other known manner. 
     As has been described herein above, the mold stack  100  comprises one or more compensator(s). For example, the mold stack  100  can implement one or more of the following compensators: (a) the compensating core insert  105 , (b) the compensating cavity insert  106 , (c) the compensating gate insert  108 ; (d) the compensating retaining structure  116  and (e) the compensating coupling  1400 . Accordingly, it can be said that the mold stack  100  that implements one or more of these compensators can be thought of as a “compensating mold stack”. In some embodiments of the present invention, the compensating mold stack  100  can include one or more of these compensators or variations thereof. In other embodiments of the present invention, the compensating mold stack  100  can include two or more of these compensators of variations thereof. In yet further embodiments, the compensating mold stack  100  can include all of these compensators or equivalents thereof. Naturally, the compensating mold stack  100  may have a number of additional compensators. 
     Given the architecture of the mold stack  100  described above, a process of alignment of various components of the mold stack  100  will now be described in greater detail. In some non-limiting embodiments of the present invention, the split mold inserts  114  are used as a master for alignment of various components of the mold stack  100 . In a specific example, when the mold stack  100  is urged into the operating position (i.e. the mold closed position), the pair of slides  112  cooperates with the pair of retaining structures  116 ,  116   a  to position the split mold inserts  114 . It will be recalled that the retaining structures  116 ,  116   a  include a relief element  904 ,  1004 ,  1004   a . Even though the relief element  904 ,  1004 ,  1004   a  provides for some degree of flexing, the retaining structure  116 ,  116   a  is rigid enough to provide for positioning of the split mold inserts  114 . 
     Once the split mold inserts  114  have been positioned, the core insert  105  is positioned vis-à-vis the split mold inserts  114 . Recalling that (i) there exists the second interface  126  between the core insert  105  and the split mold inserts  114 ; and (ii) that the core insert  105  can be implemented as a compensating core insert; the core insert  105  aligns its position with the position of the split mold inserts  114 . Similarly, the cavity insert  106  is positioned vis-à-vis the split mold inserts  114 . Recalling that (i) there exists the first interface  124  between the cavity insert  106  and the split mold inserts  114 ; and (ii) that the cavity insert  106  can be implemented as a compensating cavity insert; the cavity insert  106  aligns its position with the position of the split mold inserts  114 . Naturally, the precise timing of the positioning of the core insert  105  and positioning of the cavity insert  106  can occur substantially simultaneously or one after another with certain overlap or without certain overlap therebetween. 
     Recalling that the gate insert  108  can be implemented as a compensating gate insert, the gate insert  108  is also aligned with a positioning of a hot runner nozzle (not depicted). Inventors believe that alignment of the gate insert  108  vis-à-vis the hot runner nozzle will allow for positioning of an orifice (not depicted) of the hot runner nozzle and sufficient seal therebetween. 
     With reference to  FIG. 11 , a portion of the mold stack  100  of  FIG. 1  is depicted according to a non-limiting embodiment of the present invention. More specifically, the mold stack  100  of  FIG. 11  is depicted in the mold-closed position.  FIG. 11  is meant to depict one of the technical effects of the mold stack  100  having one or more compensating components. Within this particular illustration, the mold stack  100  is depicted as having the compensating core insert  105  (i.e. the core base  202  and the core support  204 ). It can be clearly seen in FIG.  11  that in the mold closed position, the core base  202  has shifted vis-à-vis the core support  204  (and, accordingly, vis-à-vis the core plate, which is not depicted). More specifically, the lateral shift of the core base  202  has resulted in a core clearance  160   a  being greater than a core clearance  160   b . It has also results in a lateral shift  210   a  associated with the sliding interface  210 . 
     A technical effect of embodiments of the present invention, amongst others, can include decrease premature wear of various components of the mold stack  100 . Alternatively or additionally, the premature wear may be re-distributed to less expensive components of the mold stack  100 . Another technical effect of embodiments of the present invention can include improved tolerance to force distribution imperfections. Another technical effect of embodiments of the present invention may include decreased costs associated with producing various components of the mold stack  100 . It should be expressly understood that various technical effects mentioned herein above need not be realized in their entirety in each and every embodiment of the present invention. 
     Description of the 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 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: