Abstract:
A molding arrangement is provided for multi-level stack molds wherein mold sets and runners are made up of modular sections interchangeable individually or as larger assemblies for exchanging molds for one part for those for different parts or exchanging runners between hot tip and valve gate designs to accommodate different molding arrangements. The arrangement has discrete melt paths for each mold level, at least some of which extend around rather than through the mold levels and which incorporate readily separable connectors. This enables one set of molds and possibly as well the runners for one mold level to be interchanged without interfering with the mold and runner arrangement for an adjacent level.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to injection molding apparatus. More particularly this invention relates to multi-level stack molds having hot runner systems. Still more particularly this invention relates to exchanging mold and runner systems to produce different parts on a given injection molding machine.  
       BACKGROUND OF THE INVENTION  
       [0002]     “Family molding” is a term used to refer to the molding of different parts in a given mold set. In the case of stack molds, different parts may be produced on different levels. Sometimes, although not exclusively so, the parts may form components of a larger assembly, such as a container and its lid.  
         [0003]     A common arrangement for delivering melt to a mold is referred to as a “hot runner system”. Two variants of hot runner systems are “valve gate” hot runners and “hot tip” hot runners. Either uses a nozzle to introduce melt into a gate which provides an inlet to a space defined between core and cavity parts of a mold. A valve gate system has a retractable valve pin extending axially along the nozzle into the gate for opening and closing the gate.  
         [0004]     A hot tip system controls the temperature of a nozzle tip which registers with the gate to control melt flow. Heat is removed to solidify melt in the tip thereby blocking the tip. Heat is added to remelt the solidified melt and recommence melt flow through the nozzle.  
         [0005]     Valve gated systems have a lower shear rate at the gate providing more gentle flow. Valve gated systems are however more expensive and wear prone than hot tip systems.  
         [0006]     One application for hot runner systems is in what is aptly named as “in mold labelling” or “IML”. In IML, one or more labels is/are placed into a mold cavity prior to mold closing. The mold is subsequently closed and melt injected to cause the label to fuse into the melt and appear on the outer face(s) of a finished part.  
         [0007]     In some applications, one face or side (typically the bottom face or side) may not require a label. For a rectangular container this may be referred to as “four-sided labelling”. In other applications labels will be required on all sides or faces which, in the case of a rectangular container may be referred to as “five-sided labelling”. The terms “four-sided” and “five-sided” are used herein for convenience bearing in mind that the challenges posed by either also translate into other container configurations. For example a conical or cylindrical container may have one wraparound label (analogous to four sides) and may or may not have a label requited on its bottom or base (analogous to the “fifth” side). Also, containers with other shapes may be contemplated. Furthermore labels may be desired on the “bottom” face or side but not on all of the adjoining sides (such as in “three-sided” labelling).  
         [0008]     In general, hot tip arrangements don&#39;t work well in IML situations where a label is present opposite to the nozzle, such as in a three or five-sided label for a rectangular container having a label and a melt entry point on its base. Generally in such situations the melt would damage the label and get past the edges of the label to mask its face. Hot tip arrangements however work well for three or four-sided labelling of a similar container with no label on its base.  
         [0009]     According to traditional mold design, molds and runner systems were designed as a dedicated set and changing from one part configuration to another required in effect replacing virtually everything between the fixed and movable platens of the injection molding machine. Furthermore, changing parts also required changing any mold take-off arrangements (such as robotics) as a new set would be unlikely to discharge parts in a location similar to the previous set.  
         [0010]     In order to make parts economically with dedicated mold and runner arrangements, a rather significant production run would be required. Dedicated systems are expensive to build and significant downtime is required to effect changeover. The associated costs for using dedicated arrangements will make molding in some markets uneconomical because the volume won&#39;t justify the cost.  
         [0011]     Consider for example a rectangular container and lid as a family mold. The same container may be desired by different customers for different products. The different customers will have different labelling requirements, not only graphically but also as to whether or not all of the faces of the containers are to be labelled. Accordingly, situations may arise where the same general container shape may require valve gated runners or hot tip runners depending on labelling requirements. Furthermore a common lid may be usable with different containers. In order to serve such markets with minimal capital investment, versatile mold arrangements are required.  
         [0012]     It is an object of the present invention to provide a molding arrangement wherein different mold sets may be readily interchanged without changing runner systems and wherein at least portions of a runner system may be readily interchanged between hot tip and valve gate designs in order to effect corresponding mold changes such as may be required for different labelling requirements.  
       SUMMARY OF THE INVENTION  
       [0013]     The invention, in very general terms provides a molding arrangement for multi-level stack molds wherein mold sets and runners are made up of modular sections interchangeable individually or as larger assemblies for exchanging molds for one part for those for different parts or exchanging runners between hot tip and valve gate designs to accommodate different molding arrangements. The arrangement has discrete melt paths for each mold level, at least some of which extend around rather than through the mold levels and which incorporate readily separable connectors. The melt paths can be configured to accommodate different materials. This enables one set of molds and possibly as well the runners for one mold level to be interchanged without interfering with the mold and runner arrangement for an adjacent level.  
         [0014]     More particularly a modular injection mold and manifold is provided for a multi-level stack mold assembly mountable between a stationary platen and a fixed platen of an injection molding machine wherein the stationary platen has at least one sprue bushing providing at least first and second melt sources. The arrangement includes a first manifold module mountable to the stationary platen and providing a first melt distribution conduit for receiving melt from the first melt source and delivering it to a first nozzle array associated with a first mold level of the multi-level stack mold assembly. The first mold level includes a first mold module having a first core part, first cavity part for registering with the first core part and respective gates registering with each nozzle of the first nozzle array for injecting the melt into a space defined between the first core and cavity parts in a mold closed configuration. The second manifold module is mountable between the movable platens for movement toward and away from the fixed platens and includes a second melt distribution conduit for receiving melt stationary and from the second melt source and delivering the melt to a second nozzle array associated with a second mold level of the multi-level stack mold assembly. The second mold level includes a second mold module having a second core part, a second cavity part for registering with a second core part and respective gates registering with each nozzle of the nozzle array for injecting the melt into a space defined between the second core and cavity parts in the mold closed configuration.  
         [0015]     The first and second core and cavity parts are separable in a machine direction to a mold open configuration for stripping and are connectable to the stationary and movable platens for movement between the mold open and mold closed configurations.  
         [0016]     The first and second manifold modules are configured to divert melt around rather than through the first mold module to allow the first mold module to be interchanged as a unit for a first mold module for a different part having corresponding gate positions. The first manifold module is disconnectable at the sprue bushing from the stationary platen to facilitate exchange of a given first manifold module for another first manifold module of different configuration for a different first mold module. The second manifold module receives melt from the second source through a second melt delivery conduit at least a portion of which runs through the first manifold module and which is separable along its length for mold opening and to allow exchange of the second manifold module for one of different configuration. The second mold module is removable from the second manifold module without disassembly of the second manifold module to allow exchange of one second mold module for another configured for a different part but having corresponding gate positions.  
         [0017]     The first manifold module may include a first part having a first manifold and being securable to the fixed platen and a second part having a second manifold to which the nozzle array is affixed. The first mold module may be mounted between the first and second parts. The first and second manifolds may fluidly communicate through a first melt transfer conduit having a crossover nozzle for allowing the transfer passage to separate during mold opening.  
         [0018]     The first nozzle array may consist of valve gated nozzles and the second nozzle array may consist of one of valve gated and hot tip nozzles.  
         [0019]     The first manifold may receive melt from the first and second melt sources. The first manifold may also have a first melt passageway providing fluid communication between the first melt source and the first melt delivery conduit. The first manifold may have a second melt passageway which acts as a first run of the second melt delivery conduit and provides fluid communication between the second melt source and a second run of the second melt delivery conduit. The second manifold may provide fluid communication between the first melt delivery conduit and the first nozzle array.  
         [0020]     The second manifold module may include a third manifold to which the second array of nozzles is affixed and which provides fluid communication between the second run of the second melt delivery conduit and the second nozzle array. The second run of the second melt delivery conduit may include a crossover nozzle for providing the separability along its length.  
         [0021]     The first manifold module may have a first manifold secured to the fixed platen. The first nozzle array may be affixed to the first manifold and the first nozzle array may consist of hot tip nozzles. The first manifold may have a first melt passageway providing fluid communication between the first melt source and the first nozzle array. The first manifold may include a second melt passageway which acts as a first run of the second melt delivery conduit and provides fluid communication between the second melt source and the second run of the second melt delivery conduit.  
         [0022]     The second nozzle array may consist of one of valve gated nozzles and hot tip nozzles. The second manifold module may include a third manifold to which the second nozzle array is fixed. The second manifold module may include guide means for slidably mounting the second manifold module to injection machine rails for slidably supporting the second manifold module during mold opening and closing. The core part of the first mold module may be secured to the second manifold module by a spacer plate extending therebetween. Support pins may extend from the spacer plate through and slidably engage the first core and cavity parts to align the first core and cavity parts. The first mold module and the spacer plate may be dimensioned for withdrawal between machine tie bars for exchange with corresponding components configured for molding a different injection molded part without disturbing the tie bars.  
         [0023]     Additionally the first mole module, spacer plate and the first manifold module may be dimensioned for withdrawal as a unit between the tie bars.  
         [0024]     The second manifold module may include guide means for slidably mounting the second manifold module to injection machine rails for slidably supporting the second manifold module during mold opening and closing. The second part of the first manifold module may be secured to the second manifold module and supported thereby. Support pins may extend from the second manifold module through and slidably engage the first core and cavity parts to align the first core and cavity parts. The first mold module and at least the first part of the first manifold module may be dimensioned for withdrawal between the tie bars for exchange with corresponding components configured to form a different injection molded part. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0025]     Preferred embodiments of the present invention are described below with reference to the accompanying illustrations in which:  
         [0026]      FIG. 1  is a front elevation illustrating schematically a first injection mold and manifold arrangement according to the present invention having a hot tip nozzle arrangement in a first mold level and a valve gated nozzle arrangement in a second mold level;  
         [0027]      FIG. 2  is a view corresponding to  FIG. 1  of a modular injection mold and manifold arrangement according to the present invention in which both first and second levels have valve gated nozzles;  
         [0028]      FIG. 3  is a view corresponding to  FIG. 1  without the first and second mold levels in place;  
         [0029]      FIG. 4  is a view corresponding to  FIG. 2  without the first and second mold levels in place;  
         [0030]      FIG. 5  is a view corresponding to  FIGS. 1 and 2  but illustrating only the manifold and nozzle array arrangement associated with the second mold level;  
         [0031]      FIG. 6  is an end elevation schematically illustrating the manifold arrangement associated with the first mold level;  
         [0032]      FIG. 7  is a front elevation schematically illustrating a hot tip frame module according to the present invention  
         [0033]      FIG. 8  is an end elevation schematically illustrating a manifold arrangement associated with the second mold level;  
         [0034]      FIG. 9  is a front elevation of a hot tip frame module with a stack mold module installed;  
         [0035]      FIG. 10  is a front elevation of the stack mold module of  FIG. 9 ;  
         [0036]      FIG. 11  is a front elevation of a valve gate frame module with a stack module installed;  
         [0037]      FIG. 12  is a front elevation of the valve gate frame module of  FIG. 11  without the stack module installed;  
         [0038]      FIG. 13  is an end elevation illustrating a first part of a first manifold assembly corresponding to the  FIG. 2  arrangement;  
         [0039]      FIG. 14  is an end elevation schematically illustrating a second part of a first manifold assembly corresponding to the  FIG. 2  arrangement;  
         [0040]      FIG. 15  is a front elevation of a stack module for valve gate hot runners;  
         [0041]      FIG. 16  is an end elevation of a center section with stack and frame modules installed; and  
         [0042]      FIG. 17  is an end elevation illustrating a moving platen section with stack modules installed. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0043]     A modular injection mold and manifold arrangement according to the present invention is generally indicated by reference  20  in  FIGS. 1 and 2 . The arrangement  20  is mountable between a stationary or fixed platen  22  and a movable platen  24  of an injection molding machine. The injection molding machine is not illustrated other than for scrap sections showing the relative positions of the stationary platen  22  and a movable platen  24  in  FIG. 1 . The movable platen  24  is movable toward and away from the fixed platen  22  in a machine direction as illustrated by arrows  26  in  FIG. 1 . The injection molding machine provides first and second discrete melt sources  30  and  32  respectively. The first melt source  30  may be behind the second melt source  32  in a single sprue bushing as illustrated in  FIG. 1 . Alternatively, two sprue bushings could be used to enable a different material to be used for each mold level.  
         [0044]     A first manifold module or “set”  40  is mountable to the stationary platen  22 .  FIG. 7  illustrates the first manifold module  40  on its own. The first manifold module  40  includes a first manifold  42  secured to the stationary platen  22 . As discussed in more detail below, the mounting may be to a first frame member  260  which in turn is mounted to the stationary platen  22 . The first manifold  42  is illustrated in  FIG. 6 . The first manifold  42  has a first inlet  44  for registering with the first melt source  30  and four outlets  46  fluidly communicating with the first inlet  44  in a first melt passageway  48  extending therebetween. A respective nozzle  52  of a first nozzle array  50  would receive melt from each outlet  46  of the first manifold  42 .  
         [0045]     It will be appreciated that having four outlets  46  to the first manifold  42  is exemplary. More or less may be provided as needed. In order to balance melt flow preferably (as illustrated in  FIG. 6 ) the first melt passageway  48  will be configured in equal length runs extending radially from a central inlet  44 .  
         [0046]     The first inlet  44 , outlets  46  and passageway  48  provide a first melt distribution conduit for receiving melt from the first melt source  30  and delivering it to the first nozzle array  50 . The arrangement illustrated in  FIG. 1  is configured for hot tip nozzles. As discussed in more detail below, the first manifold module may alternately be configured for valve gated nozzles.  
         [0047]     The first nozzle array  50  feeds a first mold level  60 . The first mold level  60  includes a first mold module  62  having a first core part  64 , a first cavity part  66  registering with the first core part  64  and respective gates  68  registering with each nozzle  52  of the first nozzle array  50 . The gates  68  provide a path for the injection of melt from the nozzles  52  into respective spaces  70  defined between the first core part  64  and first cavity part  66  when held together in a mold closed configuration as illustrated in  FIG. 1 .  
         [0048]     A second manifold module  80  is mounted between the stationary platen  22  and the movable platen  24 . The second manifold module  80  includes a third manifold  82  which is illustrated in  FIG. 8 . The third manifold  82  has an inlet  84  for receiving melt originating from the second melt source  32  and four outlets  86  fluidly communicating with the inlet  84  of the third manifold  82  through a second melt distribution conduit extending therebetween. The melt distribution conduit is illustrated as comprising a first leg  88  which extends to a central region  90  where it branches into four radially extending equal length legs  92 . Each leg  92  terminates in a respective outlet  86  each of which would serve a respective nozzle  102  of a second nozzle array  100 . As described above with respect to the first manifold, this is an illustration of one arrangement. More or less legs may be provided depending on the mold/nozzle configuration required.  
         [0049]     The second nozzle array  100  feeds a second mold level  110 . The second mold level  110  includes a second mold module  112  having a second core part  114  and a second cavity part  116  and respective gates  118  registering with each nozzle  102  of the second nozzle array  100 . The respective gates  118  provide a path for the injection of melt from the nozzles  102  into respective spaces  120  defined between the second core part  114  and the second cavity part  116  when held together in a mold closed configuration as illustrated in  FIG. 1 .  
         [0050]     In the embodiment/arrangement illustrated in  FIG. 1 , the first nozzle array  50  consists of hot tip nozzles which fill a container mold from its outside. Also in the  FIG. 1  illustration, the second nozzle array  100  consists of valve gated nozzles for filling a container lid mold from its inside. Such an arrangement would accord with a container having four sided labelling (i.e. no bottom label) and a container lid having a label on its upper face.  
         [0051]     The first manifold module  40  receives melt from the first melt source  30  as discussed above. The first manifold module  40 , and in particular the first manifold  42  also receives melt from the second melt source  32  through a second inlet  130  in  FIG. 6 . The first manifold  42  has a second melt passageway  132  which extends from and fluidly communicates with the second inlet  130 . The second melt passageway  132  is a first run of a second melt delivery conduit.  
         [0052]     The second melt passageway  132  directs melt radially outwardly from the second inlet  130  to a second run  140  of the second melt delivery conduit which extends generally parallel to the machine direction. The second run  140  extends between the second melt passageway  132  and the third manifold  82 . The second melt delivery conduit, consisting of the first run (i.e. the second melt passageway  132 ) and the second run  140 , provides fluid communication between the second melt source  32  and an inlet  84  of the third manifold  82 .  
         [0053]     The first manifold module  40  and the second manifold module  80  are configured to divert melt around rather than through the first mold module  62 . This is achieved, as described above, by having the second melt passageway  132  (the first run of the second melt distribution conduit) extend radially, which is transverse to the machine direction and therefore around rather than through the first mold module  62 . This enables substitution of the first mold module  62  for another without interfering with melt delivery to the second manifold module  80 .  FIG. 3  illustrates the arrangement of  FIG. 1  absent the first mold module  62  and second mold module  112 .  
         [0054]     In order to accommodate mold opening and closing, the second run  140  of the second melt delivery conduit is separable along its length by virtue of a crossover nozzle  142  where the second run  140  meets the inlet  136  of the third manifold  82 . One suitable form of crossover nozzle is as described in International Publication Number WO 2005/046960 A1.  
         [0055]      FIG. 10  illustrates on its own the first mold module  62  of the type in  FIG. 1  in which a core plate  150  carries the cores  64  and a cavity plate  152  carries the cavities  66  (only one of each are illustrated). In order to maintain precise alignment and to hold the core plate  150  and cavity plate  152  aligned when removed, guide pins  156  are provided which extend from the core plate  150  and are slidably received in the cavity plate  152 . A stripper ring  158  may also be provided about a base of the cores  64  for stripping finished parts therefrom in known arrangement. A stripper plate (not shown) may be used to carry the stripper rings  158 .  
         [0056]     It will be appreciated that any substitution of a given first manifold module  62  for another first mold module  62  will have to be for a first mold module  62  requiring similar nozzle positions and requiring similar take-off robotics as otherwise the gates  68  won&#39;t align with the nozzles  52  and the parts formed won&#39;t align with the take-off equipment. Whilst this may impose some practical limitations, it nevertheless provides very fast part changeover as compared to earlier designs requiring substantial disassembly of virtually everything between the stationary platen  22  and movable platen  24 .  
         [0057]     In a similar manner, the second mold module  112  is removable from between the second manifold module  80  and the movable platen  24  without disassembly of the second manifold module  80 . In this manner a different second mold module  112  may be substituted as long as its gates correspond in their respective positions. As mentioned above,  FIG. 3  illustrates the manifold arrangement of  FIG. 1  absent the second mold module  112 .  
         [0058]     As with the first mold module  62  the core part  114  may be carried by a core plate  115  and the cavity part  116  by a cavity plate  119 . A pair of guide pins  158  may extend from upper comers of the cavity plate  119  to be slidably received in the core plate  115 . The guide pins  158  keep the core part  114  and cavity part  118  aligned to facilitate removal as a modular unit.  
         [0059]     Should a more substantial change be desired, the entire first manifold module  60  may be substituted for a different one. The substitution may even be one of exchanging a hot tip arrangement such as illustrated in  FIG. 1  for a valve pin arrangement such as illustrated in  FIG. 2 . In  FIG. 2 , analogous components to those described above are identified by like reference numerals but followed by the suffix “a”, and the above description applies with the variations described below.  
         [0060]     In the arrangement illustrated in  FIG. 2 , a second part  40   b  to the first manifold module is provided on an opposite side of the mold module  62   a  from a first part  40   a  containing a first manifold  42   a . The first nozzle array  50   a  is affixed to a second manifold  42   b  associated with the second part  40   b  and comprises valve gate nozzles  52   a .  
         [0061]     The first manifold  42   a  is of different configuration than the first manifold  42  described above and is described in more detail below. The first manifold  42   a  and the second manifold  42   b  fluidly communicate through a first melt transfer conduit  202  which forms part of the overall first melt delivery conduit and which includes a second crossover nozzle  204  to allow its separation during mold opening.  
         [0062]      FIG. 13  illustrates the first manifold  42   a  of the  FIG. 2  embodiment. The first manifold has a first inlet  44   a  for receiving melt from the first melt source  30 . The first manifold  42   a  also has a second inlet  130  for receiving melt from the second melt source  130 . The first manifold  42   a  has a second melt passageway  132  similar to that described above for providing fluid communication between the second melt source and the second run  140  of the second melt delivery conduit.  
         [0063]     The first manifold  42   a  differs from the first manifold  42  described above in that it simply ducts melt around the first mold module  62   a  rather than directly feeding the first nozzle array  50   a . The first manifold  42   a  has a first melt passageway  210  which is part of the first melt delivery conduit and which receives melt from the first melt source through the inlet  44   a  and delivers the melt to an outlet  212 . The outlet  212  fluidly communicates with the first melt transfer conduit  202 .  
         [0064]     The second manifold  42   b  is illustrated in  FIG. 14 . The second manifold  42   b  has a melt inlet  210  which receives melt from the first melt transfer conduit  202 . The melt inlet  210  extends to and fluidly communicates with a central region  212  which in turn fluidly communicates with four radially extending passageways  48   a  which have respective outlets  46   a , each of which serves a respective of the nozzles  52   a .  
         [0065]     It will be appreciated that the entire assembly of mold and manifold sets is of considerable weight, and accordingly would benefit from being slidably supported to assist in maintaining component alignment during mold opening and closing. One manner of slidably supporting the assembly  20  is illustrated in  FIGS. 1, 2 ,  3 ,  5  and  16  in which the second manifold module  80  includes a slide  220  or other guide means for slidably supporting the second manifold module  80  on injection machine rails  230 .  
         [0066]     The second manifold  42   b  and the core part  64  of the first mold module  62  may in turn be secured to the second manifold module  80  thereby also being supported (through the second manifold module  80 ) by the slide  220 . The second manifold module  80  may be further supported by a pair of guide shafts  240  extending therethrough toward the top and either side thereof. The guide shafts  240  may be secured at a first end  242  to a second frame member  250  secured to the movable platen  24  between the movable platen and second mold module  112 . An opposite end  244  of the guide shaft  220  may be slidably received in a recess  246  extending into or through the first frame member  260 . As mentioned above, the first frame member  260  is mounted to the fixed platen  22  between the fixed platen  22  and the first manifold module  40 .  
         [0067]     The guide shafts  240  maintain the assembly  20  together in alignment enabling the entire assembly  20  to be removed as a unit with the frame members  250  and  260 .  
         [0068]     In cases where there is no second part  40   b  to the first manifold module  40 , such as illustrated in  FIG. 1  where the first nozzle array  50  consists of hot tip nozzles  52 , a spacer plate  270  may be used to take up the space which would otherwise be occupied by the second manifold part  40   b  to the first manifold module  40   a  and  40   b . The spacer plate  270  may be attached to and supported by the second manifold module  80  as described above.  
         [0069]     In cases such as illustrated in  FIG. 2  where the first mold module  40  has a first part  40   a  and a second part  40   b , the second part  40   b  may be secured to the second manifold module  80 .  
         [0070]     An injection molding machine typically has tie bars, such as illustrated by reference  300  in  FIGS. 16 and 17 , extending between the fixed platen  22  and movable platen  26 . In order to facilitate removal from above, preferably the mold plates, such as the core plate  152  and the cavity plate  150  in  FIG. 17  are dimensioned so as to have a breadth “B” less than the spacing “S” between the tie bars.  
         [0071]     The above description is intended in an illustrative rather than a restrictive sense bearing in mind that variations to the specific embodiments described may be apparent to persons skilled in such apparatus and systems without departing from the inventive concept as defined by the claims set out below. For example, although the invention has been described in conjunction with a two-level mold, it may be adaptable to stack molds having more than two levels. In such an arrangement the second mold module  112  may be affixed to an intermediate number which in turn is connected to the movable platen by a centering device to effect mold opening and closing movement.  
         [0072]     The illustrations show the second manifold module  112  in association with valve gated nozzles. It may alternatively have to be switched for a corresponding unit (along with the mold module) having hot tip nozzles.