Patent Publication Number: US-2022234269-A1

Title: Injection molding apparatus with a thermal bridge

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of prior U.S. Appl. No. 62/912,158, filed Oct. 8, 2019, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an injection molding apparatus, and in particular, to an injection molding apparatus with a thermal bridge. 
     BACKGROUND 
     Egress of molding material and/or molding material byproducts from a hot runner channel through the interface between a valve pin and a valve pin seal is undesirable. 
     SUMMARY 
     Embodiments hereof are directed to a hot runner system. A manifold receives molding material from a source and has a manifold channel that extends between a manifold inlet and a manifold outlet. A nozzle delivers molding material to a mold cavity. The nozzle has a nozzle channel in fluid communication between the manifold channel and the mold cavity. A valve pin seal is located at an upstream end of the nozzle. A valve pin is slidably received in the valve pin seal. The valve pin extends through the manifold and the nozzle and is connected to an actuator for translating the valve pin between an open position and a closed position. The hot runner system further includes a thermal bridge in conductive thermal communication with the valve pin seal and a cooled mold plate. 
     Embodiments hereof are directed to an injection molding apparatus having a plurality of mold plates that define an enclosure in which a hot runner system is received. A manifold receives molding material from a source and has a manifold channel that extends between a manifold inlet and a manifold outlet. A nozzle delivers molding material to a mold cavity. The nozzle has a nozzle channel in fluid communication between the manifold channel and the mold cavity. A valve pin seal is located at an upstream end of the nozzle. A valve pin is slidably received in the valve pin seal. The valve pin extends through the manifold and the nozzle and is connected to an actuator for translating the valve pin between open and closed positions. The hot runner system further includes a thermal bridge. In operation the thermal bridge is in conductive thermal communication with the valve pin seal and a cooled one of the plurality of mold plates. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view of an injection molding apparatus having a hot runner system with a thermal bridge in accordance with an embodiment of the present disclosure. 
         FIG. 2  is a sectional view of the injection molding apparatus taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is an enlarged view of a portion  3  of  FIG. 1 . 
         FIG. 4  is an enlarged view of a portion  4  of  FIG. 2 . 
         FIG. 5  is a perspective view of the upstream end of a nozzle and thermal bridge shown removed from the injection molding apparatus of  FIG. 1 . 
         FIG. 6  is a perspective view of the upstream end of a nozzle and a thermal bridge in accordance with another embodiment of the present disclosure. 
         FIG. 7  is a sectional view of the upstream end of the nozzle and thermal bridge of  FIG. 6 , taken along line  7 - 7  and shown installed in a portion of an injection molding system which is similar to portion  3  of  FIG. 1 . 
         FIG. 8  is a sectional view of the upstream end of the nozzle and thermal bridge of  FIG. 6 , taken along line  8 - 8  and shown installed in a portion of an injection molding system which is similar to portion  4  of  FIG. 2 . 
         FIG. 9  is a perspective view of the upstream end of a nozzle and a thermal bridge in accordance with yet another embodiment of the present disclosure. 
         FIG. 10  is a sectional view of the upstream end of the nozzle and thermal bridge of  FIG. 9 , taken along line  10 - 10  and shown installed in a portion of an injection molding system which is similar to portion  3  of  FIG. 1 . 
         FIG. 11  is a sectional view of the upstream end of the nozzle and thermal bridge of  FIG. 9 , taken along line  11 - 11  and shown installed in a portion of an injection molding system which is similar to portion  4  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, “downstream” is used with reference to the general direction of molding material flow from an injection unit to a mold cavity of an injection molding system and to the order of components, or features thereof, through which the molding material flows from an inlet of the injection molding system to the mold cavity. “Upstream” is used with reference to the opposite direction. As used herein, the phrase, “conductive thermal communication” refers to components forming a physical pathway, through which heat can travel. Further, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, summary or the following detailed description. 
     Referring now to  FIGS. 1 and 2  in which  FIG. 1  is a sectional view of an injection molding apparatus  100  having a hot runner system  102  in accordance with an embodiment of the present disclosure, and  FIG. 2  is a sectional view of injection molding apparatus  100  taken along line  2 - 2  of  FIG. 1 . Injection molding apparatus  100  includes a plurality of mold plates which form an enclosure  106  in which hot runner system  102  is received. As shown, injection molding apparatus  100  includes a first mold plate  103 , a second mold plate  104 , and a third mold plate  105 . Mold plates  103 ,  104 ,  105  are held together by fasteners (not shown) and typically include additional fastening/aligning components such as dowels and the like (not shown). While injection molding apparatus  100  is shown having three mold plates  103 ,  104 ,  105 , injection molding apparatus  100  can include other than three mold plates. 
     Hot runner system  102  delivers molding material received from a source, typically an injection molding machine (not shown), to a mold cavity  108  (shown schematically in  FIGS. 1 and 2 ) which defines the shape of a molded article that is formed in injection molding apparatus  100 . Hot runner system  102  includes a manifold  110 , a nozzle  112 , a valve pin  114 , and an actuator  116 , for example, a fluid driven actuator as shown in  FIGS. 1 and 2 . Manifold  110  and nozzle  112  include respective manifold and nozzle heaters  118 ,  120  which, in operation, maintain manifold  110  and nozzle  112  at a suitable processing temperature. Enclosure  106  includes a pocket  122  in second mold plate  104  that surrounds manifold  110  and is enclosed by third mold plate  105 , and a well  124  that surrounds nozzle  112 . Mold plates  103 ,  104 ,  105  include cooling channels, such as cooling channels  126 ,  126 ′ in second mold plate  104 , cooling channels  128 ,  128 ′ in first mold plate  103 , and cooling channels  127 ,  127 ′ in third mold plate  105 . Cooling fluid is circulated through cooling channels  126 ,  126 ′,  127 ,  127 ′, 128 ,  128 ′ to maintain first, second and third mold plates  103 ,  104 ,  105  at a suitable molding temperature which is less than the operational temperature of hot runner system  102 . 
     Referring to  FIG. 1 , manifold  110  includes a manifold channel  130  that extends between a manifold inlet  132  (shown in phantom) and a manifold outlet  134 . In operation, manifold  110  receives molding material from a source, via manifold inlet  132 , and delivers molding material to nozzle  112  via manifold outlet  134 . Manifold  110  further includes a valve pin passageway  136  through which valve pin  114  extends. Nozzle  112  delivers molding material to mold cavity  108 . Nozzle  112  includes a nozzle channel  138  in fluid communication between manifold channel  130  and mold cavity  108 . Valve pin  114  extends across manifold  110 , through valve pin passageway  136 , and through nozzle channel  138 . Referring to  FIG. 2 , at its upstream end, valve pin  114  is coupled to actuator  116  which translates valve pin  114  between a closed position and an open position. In its closed position, valve pin  114  is positioned to block a mold gate  140  to prevent moldable material from entering mold cavity  108 ; in its open position, valve pin  114  is separated from mold gate  140  to allow molding material to be injected into mold cavity  108 . In some applications, actuator  116  is configured to move valve pin  114  to an intermediate position that is between its open position and its closed position. Actuator  116  includes a stationary part  142  secured to third mold plate  105  and a movable part  144  to which valve pin  114  is coupled to be movable therewith. As shown herein, actuator  116  is a fluid driven actuator by way of example and not limitation. 
     Referring now to  FIGS. 3 and 4 , in which  FIG. 3  is an enlarged view of a portion  3  of  FIG. 1  and  FIG. 4  is an enlarged view of a portion  4  of  FIG. 2 . An upstream end of nozzle  112  includes a valve pin seal  146 . Valve pin seal  146  has a valve pin bore  148  extending therethrough in which valve pin  114  is received. At least a portion of valve pin bore  148  is sized to slidably mate with valve pin  114  to form a sealing interface  150 , as shown in  FIG. 3 . To reduce or prevent migration of molding material out of nozzle channel  138  via sealing interface  150 , valve pin bore  148  and valve pin  114  are closely sized. In the current embodiment, valve pin seal  146  is a portion of a bushing component  152  that is located at the upstream end of nozzle  112  and (as shown in  FIG. 3 ) bushing component  152  defines an upstream portion  139  of nozzle channel  138 . 
     In accordance with embodiments hereof, hot runner system  102  includes a thermal bridge  154  that is in conductive thermal communication with valve pin seal  146  and is in conductive thermal communication with second mold plate  104  (see  FIG. 4 ), which is cooler than valve pin seal  146 . Thermal bridge  154  longitudinally overlaps valve pin seal  146  to transfer heat away from valve pin seal  146  to second mold plate  104 . In such a configuration, valve pin seal  146  is disposed between valve pin  114  and thermal bridge  154 . 
     Continuing with  FIG. 4  and referring to  FIG. 5  which is a perspective view of the upstream end of nozzle  112  and thermal bridge  154  shown removed from injection molding apparatus  100  of  FIG. 1 . With reference to valve pin seal  146 , thermal bridge  154  includes a proximal portion  156  and a distal portion  158  that is laterally spaced apart from proximal portion  156  by a medial portion  157 . When thermal bridge  154  is installed in injection molding apparatus  100 , distal portion  158  is spaced apart, across well  124 , from proximal portion  156 . Proximal portion  156  is in conductive thermal communication with valve pin seal  146 . A proximal heat transfer interface  160  (see  FIG. 4 ) is defined between valve pin seal  146  and proximal portion  156 . Distal portion  158  is in conductive thermal communication with second mold plate  104 . Thermal bridge  154  is seated against second mold plate  104  at distal portion  158 , for example, against a surface of pocket  122 , and is secured in place by, for example a fastener  162 , such as a shoulder bolt as is shown in  FIG. 4 , which both secures and locates thermal bridge  154 . A distal heat transfer interface  164  is defined between distal portion  158  and second mold plate  104 . As shown, distal heat transfer interface  164  is, for example, a planar abutting connection between distal portion  158  and second mold plate  104 . In an embodiment of the present disclosure, the surface area of distal heat transfer interface  164  is equal to or greater than the surface area of proximal heat transfer interface  160  which improves heat transfer from valve pin seal  146  to second mold plate  104  in comparison to a configuration in which the surface area of distal heat transfer interface  164  is less than the surface area of proximal heat transfer interface  160 . 
     In operation, heat from nozzle heater  120  is transferred to valve pin seal  146  which can increase the size of valve pin bore  148  relative to the size of valve pin  114 . To mitigate this, thermal bridge  154  provides a pathway through which heat can be evacuated away from valve pin seal  146 , which can reduce the impact of heat from nozzle heater  120  on the size of valve pin bore  148 . In addition, removing heat from valve pin seal  146  can have the effect of increasing the viscosity of or solidifying molding material, and/or molding material byproducts, that may migrate between valve pin  114  and valve pin bore  148  which reduces the likelihood of or prevents molding material from egressing hot runner system  102  from between valve pin  114  and valve pin bore  148 . 
     To encourage heat transfer from valve pin seal  146  to second mold plate  104 , which, in operation, is cooler than valve pin seal  146 , thermal bridge  154  is made from a material that is more thermally conductive than the material from which valve pin seal  146  is made. Non-limiting examples of such a material for thermal bridge  154  include a copper alloy such as Beryllium Copper or a Beryllium-free Copper alloy such as AMPCO 940. 
     Continuing with  FIGS. 3 and 4 , at least a portion of the length of thermal bridge  154  is surrounded by a walled passageway  166 . Walled passageway  166  can be formed in a variety of ways. For example, as shown in  FIGS. 3 and 4 , walled passageway  166  includes a slot  167  in the upstream end of nozzle  112  (also shown in  FIG. 5 ), that extends laterally outward from valve pin seal  146  and a second slot  169  in the downstream side of manifold  110  that extends laterally outward from valve pin passageway  136 . Walled passageway  166  is sized to be spaced apart from thermal bridge  154  by an air gap which thermally insulates thermal bridge  154  from manifold  110  and nozzle  112 , other than the conductive thermal communication between thermal bridge  154  and valve pin seal  146 . This arrangement promotes an efficient heat transfer pathway from valve pin seal  146  to second mold plate  104  while also maintaining effective heat transfer between manifold  110  and nozzle  112  at the interface between manifold outlet  134  and nozzle channel  138 . 
     As shown in  FIG. 5 , distal portion  158  optionally includes a base portion  168  which is an enlargement of at least a portion of distal portion  158  through which thermal bridge  154  is in conductive thermal communication with second mold plate  104 . Base portion  168  increases the surface area of distal heat transfer interface  164  which can improve the effectiveness of thermal bridge  154  in comparison to a version of thermal bridge  154  without base portion  168 . 
     Continuing with  FIGS. 3 and 4 , in the current embodiment valve pin seal  146  is a tubular shaped structure in which valve pin  114  is slidably received. Proximal portion  156  of thermal bridge  154  has an opening  170  that extends axially therethrough and surrounds valve pin seal  146 . Thermal bridge  154  is in conductive thermal communication with the outer circumference of valve pin seal  146  through opening  170 . This engagement between valve pin seal  146  and proximal portion  156  creates a longitudinally extending annular shaped proximal heat transfer interface  160  between thermal bridge  154  and valve pin seal  146 . Surrounding valve pin seal  146  with thermal bridge  154  allows heat to be transferred circumferentially away from valve pin seal  146 . In some applications this configuration may be beneficial for evenly affecting the temperature around the circumference of valve pin seal  146 . In some applications it may be enough for thermal bridge  154  to partially surround valve pin seal  146 , for example in embodiments in which it might be beneficial to draw heat away from a specific portion of valve pin seal  146 . 
     Valve pin seal  146 , including at least a portion of sealing interface  150  (see  FIG. 3 ), optionally projects beyond the upstream end of nozzle  112  and into valve pin passageway  136  in manifold  110 . This configuration increases the distance between sealing interface  150  and nozzle heater  120 , which may lessen the impact of nozzle heater  120  on the size of valve pin bore  148 . To accommodate valve pin seal  146 , valve pin passageway  136  includes an enlarged portion  172  (see  FIG. 4 ) which is sized to prevent contact and thus heat transfer between manifold  110  and valve pin seal  146 . In an alternative embodiment (not shown) valve pin passageway  136  is sized to accommodate valve pin seal  146  without having an enlarged portion. 
     Referring to  FIG. 4 , thermal bridge  154  optionally includes a sleeve  174  in which valve pin seal  146  is received. Sleeve  174  projects axially from proximal portion  156 . Opening  170  extends through sleeve  174  and surrounds valve pin seal  146 . To accommodate sleeve  174 , enlarged portion  172  of valve pin passageway  136  is sized to receive sleeve  174  and prevent contact between manifold  110  and sleeve  174  which could diminish the effectiveness of thermal bridge  154 . In an alternative embodiment (not shown) valve pin passageway  136  is sized to accommodate valve pin seal  146  and sleeve  174  without having an enlarged portion. 
     Referring now to  FIG. 6 ,  FIG. 7 , and  FIG. 8 , in which  FIG. 6  is a perspective view of the upstream end of nozzle  112  and a thermal bridge  154   a  in accordance with another embodiment of the present disclosure in which thermal bridge  154   a  is in conductive thermal communication with second mold plate  104   a  at two locations. Features and aspects of the current embodiment may be used with the other embodiments disclosed herein.  FIG. 7  is a sectional view of the upstream end of nozzle  112  and thermal bridge  154   a  taken along line  7 - 7  of  FIG. 6  and shown installed in a portion of an injection molding apparatus  100   a  which is similar to portion  3  of  FIG. 1 , and  FIG. 8  is a sectional view of the upstream end of nozzle  112  and thermal bridge  154   a  taken along line  8 - 8  of  FIG. 6  and shown installed in a portion of injection molding apparatus  100   a  which is similar to portion  4  of  FIG. 2 . Thermal bridge  154   a  includes a proximal portion  156   a  in conductive thermal communication with valve pin seal  146   a  and a first distal portion  158   a  that is spaced apart from proximal portion  156   a  and in conductive thermal communication with second mold plate  104   a . A proximal heat transfer interface  160   a  is defined between valve pin seal  146   a  and proximal portion  156   a , and a first distal heat transfer interface  164   a  is defined between first distal portion  158   a  and second mold plate  104   a . Thermal bridge  154   a  is seated against second mold plate  104   a  at first distal portion  158   a , for example, against a step  175  in well  124   a , as is shown in  FIG. 8 , and is secured in place by, for example a fastener such as a shoulder bolt (not shown). In the current embodiment valve pin seal  146   a  is a portion of a bushing component  152   a  that is located at the upstream end of nozzle  112 . 
     Referring to  FIGS. 6 and 8 , thermal bridge  154 A includes a second distal portion  176   a  that is spaced apart from proximal portion  156   a  and from first distal portion  158   a . Second distal portion  176   a  is in conductive thermal communication with second mold plate  104   a . A second distal heat transfer interface  178   a  is defined between second distal portion  176   a  of thermal bridge  154   a  and second mold plate  104   a . Thermal bridge  154   a  is seated against second mold plate  104   a  at second distal portion  176   a , for example, against step  175  in well  124 , and is secured in place by, for example a fastener  162   a , such as a shoulder bolt. In an embodiment of the present disclosure, the surface area of first distal heat transfer interface  164   a  is different than the surface area of second distal heat transfer interface  178   a . For example, as shown in  FIG. 8 , the surface area of first distal heat transfer interface  164   a  is greater than the surface area of second heat transfer interface  178   a.    
     Referring to  FIG. 6 , first distal portion  158   a  and second distal portion  176  includes respective base portions, i.e. first base portion  168   a  and a second base portion  180   a  through which thermal bridge  154   a  is in conductive thermal communication with second mold plate  104   a . As can be seen in  FIG. 6 , base portion  168   a  of first distal portion  158   a  partially surrounds the upstream end of nozzle  112  which increases the surface area of first distal heat transfer interface  164   a . In an embodiment of the present disclosure (not shown) first base portion  168   a  surrounds nozzle  112  and is in conductive thermal communication with second distal portion  176   a . Such a configuration increases the surface area of a heat transfer interface between thermal bridge  154   a  and second mold plate  104   a.    
     Referring now to  FIG. 9 ,  FIG. 10 , and  FIG. 11 , in which  FIG. 9  is a perspective view of the upstream end of a first nozzle  112 , a second nozzle  112 ′ and a thermal bridge  154   b  in accordance with another embodiment of the present disclosure in which thermal bridge  154   b  is in conductive thermal communication with two valve pin seals  146   b ,  146   b ′, each associated with a respective nozzle  112 ,  112 ′, and is in conductive thermal communication with second mold plate  104   b . Features and aspects of the current embodiment may be used with the other embodiments disclosed herein.  FIG. 10  is a sectional view of a portion of an injection molding apparatus  100   b  (similar to portion  3  of  FIG. 1 ) taken along line  10 - 10  of  FIG. 9 , and  FIG. 11  is a sectional view of a portion of injection molding apparatus  100   b  (similar to portion  4  of  FIG. 2 ) taken along line  11 - 11  of  FIG. 9 . Second nozzle  112 ′ is like first nozzle  112 . An upstream end of first nozzle  112  and an upstream end of second nozzle  112 ′ include respective valve pin seals  146   b ,  146   b ′. In the current embodiment valve pin seals  146   b ,  146   b ′ are unitary portions of respective nozzles  112 ,  112 ′. Thermal bridge  154   b  is in conductive thermal communication with valve pin seals  146   b ,  146   b ′ of first and second nozzles  112 ,  112 ′ and with second mold plate  104   b  as shown in  FIG. 11 . Thermal bridge  154   b  includes a first proximal portion  156   b , a second proximal portion  182   b  laterally spaced apart from first proximal portion  156   b , and a first distal portion  158   b  spaced apart from first proximal portion  156   b  and second proximal portion  182   b . As shown in  FIG. 9  by way of example, first distal portion  158   b  first proximal portion  156   b , and second proximal portion  182   b  are in line with each other. Referring to  FIG. 11 , first proximal portion  156   b  is in conductive thermal communication with valve pin seal  146 . A first proximal heat transfer interface  160   b  is defined between valve pin seal  146   b  and first proximal portion  156   b . Second proximal portion  182   b  is in conductive thermal communication with valve pin seal  146   b ′. A second proximal heat transfer interface  184   b  is defined between valve pin seal  146   b ′ and second proximal portion  182   b . First distal portion  158   b  is in conductive thermal communication with second mold plate  104   b ; a first distal heat transfer interface  164   b , laterally adjacent to nozzle  112 , is formed between first distal portion  158   b  and second mold plate  104   b.    
     Continuing with  FIGS. 9 and 11 , thermal bridge  154   b  includes a second distal portion  176   b  in conductive thermal communication with second mold plate  104   b . A second distal heat transfer interface  178   b , laterally adjacent to nozzle  112 ′ is formed between second distal portion  176   b  and second mold plate  104   b . As shown in  FIG. 9  by way of example second distal portion  176   b  is in line with first distal portion  158   b , first proximal portion  156   b , and second proximal portion  182   b . Second distal portion  176   b  forming second distal heat transfer interface  178   b  with second mold plate  104   b  is optional and can be omitted if not needed. 
     Referring to  FIG. 9 , thermal bridge  154   b  optionally includes a transverse portion  186   b  that projects at an angle a from thermal bridge  154   b . By way of example transverse portion  186   b  projects from thermal bridge  154   b  midway between first proximal portion  156   b  and second proximal portion  182   b . Also, by way of example, the angle a at which transverse portion  186   b  projects from thermal bridge  154   b  is 90 degrees. Transverse portion  186   b  is in conductive thermal communication with second mold plate  104   b . A first transverse heat transfer interface (not shown) is formed between the bottom of transverse portion  186   b  as shown in the page view of  FIG. 9  at location  188   b  and second mold plate  104   b . Transverse portion  186   b  crosses thermal bridge  154   b  to create a second transverse portion  190   b  which is in conductive thermal communication with second mold plate  104   b  to create a second transverse heat transfer interface (not shown) between second transverse portion  190   b  and second mold plate  104   b . Second transverse portion  190   b  and second transverse heat transfer interface are optional and can be omitted if not needed. As shown in  FIG. 9 , first and second transverse portions  186   b ,  190   b  optionally include first and second transverse base portions  192   b ,  194   b.    
     While various embodiments have been described above, they are presented only as illustrations and examples, and not by way of limitation. Thus, the present invention should not be limited by any of the above-described embodiments but should be defined only in accordance with the appended claims and their equivalents.