Patent Publication Number: US-2015076735-A1

Title: Injection molding machine

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to injection molding machines. 
     Injection molding is a manufacturing technique for making parts from plastic and other materials where molten material (e.g., plastic, metal, ceramic) is injected at high pressure into a mold. Injection molding is accomplished by injection molding machines that clamp mold portions together and inject molten material into the mold. Typically the mold is held together by a mechanical force imparted on the mold by a platen. Melted material is injected into the mold by an injection device. Once the molten material cools within the mold, the mold is opened (e.g., first and second mold portions are separated) and the molded part is removed. The injection molding machine has a large amount of idle time that is inherently built into the process due to the need to wait for the material to cool and harden in the mold prior to opening the mold. Conventional injection molding machines incorporate the mold into the platen that clamps the mold and receives the injection material. The cycle is completed when the mold is opened and the part is ejected. 
     The number of parts that may be produced by an injection molding machine is dependent on the cycle time of the process. The cycle time is determined by the time required to inject the molten injection material into the mold, solidify the injection material, open the mold, eject the part(s) and close the mold. 
     A need remains for an injection molding machine having reduced cycle time and increased throughput. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, an injection molding machine is provided that includes first and second molds each having a first mold portion and a second mold portion used to form a molded part. The injection molding machine includes a platen holding the first mold at an injection station where an injection unit injects injection material into the first mold prior to transferring the first mold away from the platen to one or more secondary stations. The second mold is positioned remote from the platen at the one or more secondary stations where the second mold is cooled, the first and second mold portions of the second mold are opened, the molded part is ejected, and the first and second mold portions of the second mold are closed prior to transferring the second mold to the platen. The opening and closing of the first and second mold portions occurs remote from the platen. 
     Optionally, the one or more secondary stations may include a mold opening station having a mold opening unit. The first mold may be transferred to the mold opening unit in a closed state after the injection material is injected into the first mold at the injection station. Optionally, the one or more secondary stations may include a mold closing station having a mold closing unit. The first mold may be transferred to the mold closing unit from the mold opening unit in an open state. The first mold may be closed by the mold closing unit prior to transferring the first mold to the injection station. Optionally, the one or more secondary stations may include an ejection station between the mold opening station and the mold closing station. The first mold may be transferred from the mold opening station to the ejection station in the open state. The molded part may be ejected from the first mold at the ejection station. The first mold may be transferred to the mold closing station from the ejection station in the open state. 
     Optionally, the first mold portion may be movable away from the second mold portion to an open position. The first mold portion may enter the injection station and leave the injection station in a closed position. 
     Optionally, the injection molding machine may include a rotary wheel. The first and second mold may be mounted to the rotary wheel and may be moved from the injection station to the one or more secondary stations by the rotary wheel. The rotary wheel may stop the first mold at one of the injection station or one of the one or more secondary stations for processing. The rotary wheel may stop the second mold at a different one of the injection station or one of the one or more secondary stations, 
     Optionally, the injection molding machine may include locking elements used to hold the first and second mold portions relative to one another. The locking elements may hold the first and second mold portions closed as the first mold is transferred away from the platen. The one or more secondary stations may include a mold opening station remote from the injection station. The locking elements may be released at the mold opening station to allow the mold to open. 
     Optionally, the platen may press against the first mold at the injection station to hold the first and second mold portions closed during the injection process and may release from the first mold prior to transferring the first mold to the one or more secondary stations. The first and second mold portions may remain closed when the platen releases from the mold. 
     Optionally, the injection molding machine may include a third mold positioned remote from the platen at a corresponding one of the one or more secondary stations when the first mold is at the injection station. The injection molding machine may include a fourth mold positioned remote from the platen at a corresponding one of the one or more secondary stations when the first mold is at the injection station. 
     In a further embodiment, an injection molding machine is provided that includes a rotary wheel, a plurality of molds mounted to the rotary wheel each having a first mold portion and a second mold portion used to form a molded part, an injection unit at an injection station for injecting injection material into a corresponding mold during an injection process and a platen at the injection station for holding closed the corresponding mold during the injection process. The rotary wheel is rotated to move the plurality of molds into the injection station during the injection process and then out of the injection station to one or more secondary stations where such molds are cooled, the first and second mold portions are opened, the molded part is ejected, and the first and second mold portions are closed prior to transferring such second mold back to the injection station. 
     In a further embodiment, a method of injection molding molded parts is provided that includes positioning a first mold at an injection station, where the first mold has a first mold portion and a second mold portion used to form a molded part. The method includes clamping the first and second mold portions at the injection station using a platen, injecting injection material into the first mold at the injection station, and transferring the first mold away from the injection station. The method includes opening the first and second mold portions remote from the platen, ejecting the molded part from the first mold remote from the platen, and closing the first mold remote from the platen. A second mold is positioned remote from the platen when the first mold is positioned at the injection station. The second mold is positioned at the injection station when the first mold is at least one of being opened, having the molded part ejected from the first mold, or being closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an injection molding machine formed in accordance with an exemplary embodiment. 
         FIG. 2  illustrates a portion of the injection molding machine formed in accordance with an exemplary embodiment. 
         FIG. 3  illustrates a portion of the injection molding machine formed in accordance with an exemplary embodiment. 
         FIG. 4  illustrates a portion of the injection molding machine formed in accordance with an exemplary embodiment. 
         FIG. 5  is a chart illustrating processing of molded parts using the injection molding machine. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates an injection molding machine  100  formed in accordance with an exemplary embodiment. The injection molding machine  100  is used to manufacture molded parts. The injection molding machine  100  includes a plurality of molds  102  used to form the molded parts. Each mold  102  includes a first mold portion  104  and a second mold portion  106 . Injection material is injected into a cavity  108  in the molds  102  between the first and second mold portions  104 ,  106 . Optionally, the molds  102  may be identical to form the same molded part. Alternatively, one or more of the molds  102  may be different to form different parts. For example, the cavity  108  may have a different shape in different molds  102  to form different shaped molded parts. 
     The injection molding machine  100  includes a frame  110 . A rotary wheel  112  is mounted to the frame  110  and is rotatable by an electric motor (not shown) about an axis of rotation  114 . In an exemplary embodiment, the rotary wheel  112  is oriented horizontally (in an X-Y plane) and the axis of rotation  114  is substantially vertical (along a Z direction). Alternatively, the rotary wheel  112  may be oriented along a different plane, such as a vertical plane. The molds  102  are mounted on the rotary wheel  112 . Rotation of the rotary wheel  112  in a clockwise direction (in the direction of arrow A) positions each mold  102  successively at a plurality of stations. Among the stations are an injection station  120  where the injection material is injected into the mold  102  at the injection station  120 . One or more other secondary stations are provided downstream of the injection station  120 . 
     In an exemplary embodiment, the injection molding machine includes a cooling station  122 , a mold opening station  124  and a mold closing station  126 . The molded parts are cooled at the cooling station  122 . The molds  102  are opened at the mold opening station  124 . The molded parts may be ejected from the mold  102  at the mold opening station  124 . Alternatively, the injection molding machine  100  may include an additional station, such as an ejection station, where the molded parts are ejected from the mold  102 . The mold  102  is closed at the mold closing station  126  prior to the mold  102  being transferred back to the injection station  120  to mold a new molded part. Other stations may be provided in alternative embodiments. Any of the secondary stations may be combined in alternative embodiments. 
     In an exemplary embodiment, the first and/or second mold portions  104 ,  106  are movable relative to one another between open and closed states. The injection material may be injected into the mold  102  when the second mold portion  106  is in a closed state. In the open state, the molded part may be ejected and removed from the cavity  108  of the mold  102 . The first mold portion  104  may be a stationary or fixed mold portion mounted to the rotary wheel  112  and the second mold portion  106  may be a movable mold portion movable with respect to the first mold portion  104 . The first mold portion may be referred to hereinafter as fixed mold portion  104  and the second mold portion  106  may be referred to hereinafter as movable mold portion  106 . Optionally, the second mold portion  106  may be movable in a substantially vertically direction (along the Z direction), 
     In an exemplary embodiment, both the fixed mold portion  104  and the movable mold portion  106  of each mold  102  is movable by the rotary wheel  112  to each of the stations  120 ,  122 ,  124 ,  126 . As such, each of the functions or processes of the injection molding process may be performed independently. For example, the cooling and ejection of the molded parts may be performed at a location remote from the injection station  120 . The overall cycle time for manufacturing the molded parts may be reduced by allowing one mold to cool while a molded part is removed from a different mold and while yet another mold  102  is being injected with injection material. The throughput of the molded parts from the injection molded machine  100  is improved by decoupling the different molding processes and allowing the different molding processes to occur at different locations or stations. Providing multiple molds  102  with the fixed and movable mold portions  104 ,  106  allows the different molding processes to occur at different locations or stations. 
     The injection molding machine  100  includes an injection unit  130  at the injection station  120 . The injection unit  130  may be any appropriate injection unit capable of injecting material into the mold  102 . The injection unit  130  may be a hydraulic injector, and electric ejector, a screw type injector or another type of injector. 
     The injection molding machine  100  includes a platen  132  at the injection station  120 . The platen  132  applies pressure (force) to the mold  102  to hold the first and second mold portions  104 ,  106  in the closed state during injection of injection material into the mold  102  at the injection station  120 . The platen  132  may include any appropriate mechanical assembly such as, for example, hydraulic cylinders and/or mechanical linkages, to allow the platen  132  to open and close against the mold  102 . The platen  132  may be connected to the frame  110  and may be movable relative to the frame  110  between clamped and unclamped positions. 
     During the molding process, once one of the molds  102  is positioned at the injection station  120 , the platen  132  may be moved to the clamped position to hold the mold  102  closed. The platen  132  receives material from a nozzle  134  of the injection unit  130 . The platen  132  has a flow channel (not shown) that extends through the platen  132 . The flow channel may be aligned with a runner within the mold  102  that extends into the cavity  108 . Injection material may be injected into the mold  102  from the nozzle  134  through the flow channel. The injection material, for example pellets, may be supplied to the nozzle  134  from a hopper (not shown). The injection unit  130  receives the injection material and forces the injection material into the mold  102 . The injection unit  130  may include a heating unit to melt the injection material into a molten state. During each cycle, the injection unit  130  provides a shot of injection material that fills the internal cavity  108  of the mold  102 . Optionally, the injection material may be a plastic resin material. The injection material may be polypropylene, polyvinyl chloride (PVC), polycarbonate, polyethylene terephthalate (PET), and the like. The injection material may be a non-polymer material in alternative embodiments, such as glass, metal, and the like. 
     Once the injection material is injected into the mold  102 , the platen  132  may be unclamped to release the mold  102 . The rotary wheel  112  may then transition the mold  102 , including both the fixed mold portion  104  and the movable mold portion  106 , to the cooling station  122 . At the cooling station  122 , the injection material within the mold  102  cools and hardens. Such cooling and hardening may occur at the cooling station  122  while another mold  102  is injected with injection material at the injection station  120 . As such, a second mold  102  may be injected during the time period in which the previous mold  102  is cooling. The cycle time for producing the molded parts may thus be reduced. 
     Once the mold  102  is cooled, the rotary wheel  112  transitions the mold  102  to the mold opening station  124 . The injection molding machine  100  includes a mold opening unit  140  at the mold opening station  124 . The mold opening unit  140  is used to open the mold  102  for extraction of the molded part. Any type of mold opening unit  140  may be used to open the mold  102 . In an exemplary embodiment, the mold opening unit  140  includes an opening device  142  that engages the second mold portion  106  and moves the second mold portion  106  to an open position. The opening device  142  may mechanically engage the second mold portion  106  to move the second mold portion  106  to an open position. The opening device  142  may be mechanically coupled to the second mold portion  106 , such as by a threaded connection, a latching connection, a clamping connection, and the like. Alternatively, the opening device  142  may be connected to the second mold portion  106  by a magnetic connection, a vacuum connection, or another type of connection. The opening device  142  may include a cam system for opening the second mold portion  106 . For example, the cam system may have a cam that engages cam followers on the top, bottom or sides of the second mold portion  106  to separate and open the movable mold portion  106 . The opening device  142  may be electrically driven, hydraulically driven or driven by other means. 
     In an exemplary embodiment, the injection molding machine  100  includes locking elements  144  that are used to secure the second mold portion  106  in a closed state. For example, the locking elements  144  may be secured to the rotary wheel  112  along exterior sides of the mold  102 . The locking elements  144  may engage the first mold portion  104  and/or the second mold portion  106 . The locking elements  144  may be used to secure the first mold portion  104  to the rotary wheel  112 . The locking elements  144  may be coupled to the second mold portion  106  to hold the second mold portion  106  in the closed state. The locking element  144  may be unlocked to allow the second mold portion  106  to move to the open state. For example, the opening device  142  may overcome any locking force of the locking elements  144  to allow the second mold portion  106  to move to the open state. In an exemplary embodiment, the locking elements  144  may be configured to hold the second mold portion  106  in the open state to allow the mold  102  to be transferred from the mold opening station  124  to the mold closing station  126 . 
     Once the mold  102  is opened, the molded parts may be ejected from the mold  102 . Optionally, the molded parts may be ejected using a robot having a gripper or vacuum for removing the molded part from the mold  102 . Alternatively, an operator may remove the molded part from the mold  102 . Optionally, the mold  102  may be transferred from the mold opening unit  140  at the mold opening station  124  to another station, such as an ejection station, where the molded part may be ejected from the mold  102 , rather than ejecting the molded part at the mold opening station  124 . 
     Once the mold  102  is transferred to the mold closing station  126 , the mold  102  may be closed. For example, the movable mold portion  106  may be moved to the closed state. The injection molding machine  100  includes a mold closing unit  146 . The mold closing unit  146  includes a closing device  148 . Any type of mold closing unit  146  may be used to open the mold  102 . In an exemplary embodiment, the closing device  148  engages the second mold portion  106  and moves the second mold portion  106  to a closed position. The closing device  148  may mechanically engage the second mold portion  106  to move the second mold portion  106  to the closed position. The closing device  148  may be mechanically coupled to the second mold portion  106 , such as by a threaded connection, a latching connection, a clamping connection, and the like. Alternatively, the closing device  148  may be connected to the second mold portion  106  by a magnetic connection, a vacuum connection, or another type of connection. The closing device  148  may include a cam system for closing the second mold portion  106 . The closing device  148  may be electrically driven, hydraulically driven or driven by other means. 
     After the mold  102  is closed, the mold  102  may be transferred back to the injection station  120  where injection material may again be injected into the mold  102 . The mold  102 , including the fixed mold portion  104  and movable mold portion  106 , is transferred to the injection station  120  by the rotary wheel  112  in the closed state. The fixed mold portion  104  and movable mold portion  106 , which is separate and discrete from the platen  132 , is positioned below the platen  132 . Once positioned, the platen  132  may be clamped against the mold portions  104 ,  106  to hold the mold closed during the injection process. 
       FIG. 2  illustrates a portion of the injection molding machine  100  formed in accordance with an exemplary embodiment. The rotary wheel  112  is illustrated with the molds  102  mounted thereto. Molded parts  160  are shown in phantom in some of the molds  102 . The molds  102  are located at the injection station  120 , cooling station  122 , mold opening station  124 , and mold closing station  126 . The molds  102  are positioned equidistant from one another about the rotating wheel  112 , such as at 90° from one another. The molded parts  160  are ejected from the molds  102  when the molds  102  are open, such as at the mold opening station  124  or the mold closing station  126 . 
       FIG. 3  illustrates a portion of the injection molding machine  100  formed in accordance with an exemplary embodiment.  FIG. 3  shows the rotary wheel  112  with a plurality of the molds  102  mounted thereto.  FIG. 3  illustrates five stations, including an ejection station  162 , in addition to the injection station  120 , cooling station  122 , mold opening station  124 , and mold closing station  126 . The stations are located equidistant apart at approximately 72° apart from one another. The molded parts  160  are ejected from the molds  102  at the ejection station  162 . 
     Providing an ejection station  162  in addition to the other stations may increase the throughput of the injection molding machine  100  by reducing the total cycle time for processing the molds  102  and molded parts  160 . For example, in the embodiment having four stations ( FIG. 2 ), the time period needed to process the molds  102  and molded parts  160  at the mold opening station  124  may be longer than the processing time at any other station because both the mold opening process and the molded part ejection process occurs at the mold opening station  124 . By adding an additional station, such as the ejection station  162  ( FIG. 3 ), the waiting time per station may be reduced. Such reduction and waiting time per station equates to a faster cycle time for the injection molding machine  100 , allowing more molded parts  160  to be manufactured per hour. 
       FIG. 4  illustrates a portion of the injection molding machine  100  formed in accordance with an exemplary embodiment.  FIG. 4  illustrates the rotary wheel  112  having a plurality of molds  102  mounted thereto. Three stations are illustrated in  FIG. 4 . For example, the injection station  120 , mold opening station  124  and mold closing station  126  are provided. The stations are located equidistant apart at approximately 120° apart from one another, 
     Having three stations on the rotary wheel  112 , as opposed to four or five or more stations, may allow for a reduction in size of the rotary wheel  112 . For example, the molds  102  may be positioned closer to one another when only three molds  102  are mounted on the rotary wheel  112 . The reduction in size of the rotary wheel  112  may correspond to a reduction in size of the injection molding machine  100 , allowing additional injection molding machines  100  in a given area of floor space within a factory. 
     The molding processes may be divided among the stations. For example, injection may occur at the injection station  120 . Cooling of the mold  102  may occur at the injection station  120  prior to moving the mold  102  to the mold opening station  124 . Further cooling of the mold  102  may occur at the mold opening station  124  prior to opening the mold  102 . Ejection of the molded parts  160  may occur at the mold opening station  124  or the mold closing station  126 . 
     In an exemplary embodiment, the molds  102  may be used to manufacture different molded parts  160 . For example, the molded parts  160  illustrated in  FIG. 4  have different shapes. It is preferable that the different molded parts  160  have similar temperature profiles (e.g. cooling rates). 
       FIG. 5  is a chart illustrating processing of molded parts using the injection molding machine  100  having four stations compared to a conventional single mold injection molding machine. Both processes are shown over a time period. Both processes include the same steps of injection, cooling, opening of the mold, ejection of the molded part, and closing of the mold prior to the next injection process. With the conventional mold, there is a long wait time before the injection unit of the conventional molding machine is used to manufacture the second mold. Conversely, with the injection molding machine  100 , the injection station, which is identified as station  1  in  FIG. 5 , has a high use rate. The high rate of use of the injection station reduces cycle time for manufacturing molded parts and increases the throughput for the injection molding machine  100 . 
     Four molds  102  are illustrated in  FIG. 5  and identified as mold  1 , mold  2 , mold  3 , and mold  4 . Each of the molds  102  is located at a different station, identified as station  1 , station  2 , station  3 , and station  4  in  FIG. 5 . Station  1  is an injection station, station  2  is a cooling station, station  3  is a mold opening station and an ejection station, and station  4  is a mold closing station. The molds and molded parts are processed at each of the stations. At any particular time, each of the molds are located at a different station and remain at such station for a predetermined time period where the mold and molded part are processed. After such processing, the molds  102  are transitioned to the next station, For example, mold  1  goes from station  1  at time period T2 to station  2  at time period T3. Similarly, mold  2  transitions from station  2  to station  3 , mold  3  transitions from station  3  to station  4  and mold  4  transitions from station  4  to station  1 . The molds are again processed at the corresponding stations from time T3 to T4 and then the molds are again transitioned to the next station. Such processing and transition continues to occur allowing injection of different molds at each sequential time period (e.g. T1, T3, T5, T7, T9, T11). 
     Comparing the process of the injection molding machine  100  to the conventional machine, between T1 and T9 the injection molding machine  100  injects four shots into each of the four molds, whereas the conventional mold has only injected a single shot into the single mold of the conventional machine. Increased throughput is evidenced by the use of multiple molds and the increased use of the injection unit at the injection station. Transitioning the molds out of the injection station such that a new mold can he transferred into the injection station while other processing steps occur for the first mold reduces the cycle time and increases the throughput. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.