Abstract:
A method of loading a moldset having a core plate and a cavity plate into an injection molding machine. The method comprises the steps of latching a cavity plate to a core plate using a removable latch, guiding the core plate into an open mold along a face in the mold while maintaining separation between the face and the core plate and maintaining the cavity plate spaced from hot runner nozzles in a hot runner in the mold, closing the mold to engage the cavity plate with the hot runner nozzles, securing the cavity plate to the hot runner, removing the latch between the cavity plate and the core plate, and opening the mold. The face may be a face of a movable platen or a back surface of a hot runner.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, generally, to an injection molding machine, and more particularly, but not exclusively, the invention relates to three level stack mold injection molding machine. 
     2. Background Information 
     The state of the art includes U.S. Pat. No. 5,707,666 that provides a four level mold having linkage for moving the molds that is capable of moving the molds simultaneously and in unison so that the molds open and close together. The linkage would not permit the use of a side entry robot nor does it show open and easy access through the top of the machine. 
     U.S. Pat. No. 5,518,387 describes a swing arm device for removing parts from a mold. The motion of the swing arm device is synchronized with the opening and closing of the mold to speed up part retrieval. 
     U.S. Pat. No. 5,185,119 shows a stack mold in Tandem configuration with cores aligned the same way. In this machine the mold is operated on alternate cycles so each side opens sequentially rather than simultaneously. 
     U.S. Pat. Nos. 6,027,681 and 6,099,784 describe a stack mold that has unequal strokes so that different parts can be molded in the adjacent molds. 
     U.S. Pat. No. 6,155,811 describes a two level mold that is mounted on linear bearings. This is the type of machine that has been modified by the present invention to provide a three level stack mold in the space occupied by the two level stack mold described in this patent. 
     U.S. Pat. Nos. 5,908,597 and 6,036,472 describe multiple stack mold machines that use rack and pinion devices to open and close the mold and includes part ejection means that is operated independently of the rack and pinion devices. 
     An article on page 14 of the September, 1991 issue of Plastics World describes a mold change system that includes self-locating/leveling mold guide slots. 
     An article by P. Glorio of Incoe Corp. published in ANTEC &#39;88, pages 255 to 258 describes the development of quick mold change systems including systems that use hydraulically actuated wedge-lock clamps. 
     U.S. Pat. No. 4,473,346 describes a single level molding system where the molding dies are insertable and removable in either the horizontal or vertical direction. 
     U.S. Pat. No. 4,500,274 describes a quick-change mold system that includes adapter plates provided with service fittings that interconnect and disconnect upon insertion and removal of the molds together with the adapter plates. 
     U.S. Pat. No. 4,500,275 describes a quick-change mold system that includes a locator clamp for facilitating the insertion and removal of a mold from a molding machine 
     U.S. Pat. No. 4,568,263 describes the use of locator wedge clamp assemblies mounted on and extending from the platens 
     U.S. Pat. No. 5,096,404 describes the use of rollers and guide rails for aligning a mold press in a vertical plane above the injection molding machine. 
     U.S. Pat. No. 5,096,405 describes a mounting plate attachable to a molding machine platen. The mounting plate has a plurality of retention slots with hydraulically actuated clamps in the slots. Actuation of the clamps presses a mold part toward the platen in an adjusted position. 
     With the cost of injection molding machines and the competitive pricing of products made thereon, it is essential that the machine be as productive as possible. In the case where the machine must be capable of making a number of different parts, this requires that mold changes be quick and inexpensive. It is also cost effective to minimize the space requirements of the machine. In addition, it is essential that parts be removed from the molds as quickly as possible so the cycle time of the machine can be as short as possible. It is also advantageous to provide a machine that requires only a single set of hot runner plates for all moldsets usable on the machine. 
     The present invention provides an injection molding machine that enables mold changes to be made quickly and easily, provides robot accessibility to the parts that may be of a variety of heights without modifying the space requirements of the mold and allows a three level stack mold for high profile parts to be placed in space that was previously fully occupied by a two level stack mold. 
     The invention is achieved by creating a three level stack mold that provides open access to the molds from all sides when the molds are open. Side access is provided by designing a linkage for the stack mold that surrounds the mold opening but does not cross it when the molds are open. Moving all physical connections such as water and electrical lines to the side edges of the mold provides access through the top and bottom. To avoid any electrical faults caused by water leaks from occurring, the electrical connections are made at the top of the mold and the water connections at the lower point of the mold. Air connections are also provided at the top of the machine to avoid or minimize contamination of the air lines by a failure in the water supply system. 
     When the molds need to be changed, the mold is closed and each cavity plate is latched to its respective core plate. The mold is then opened and each moldset of a cavity plate and a core plate is removed from the machine as a single unit along guides. When the cavity and core plate moldset is fully removed, a new moldset of a cavity plate and a core plate is inserted into the mold and guided by the same grooves. The grooves guide the core plate so that it is slightly separated from the platen until it is very near its home position. When it reaches this position a wedge surface forces the core plate against the platen and automatically locks it into position on the platen. At the same time the air and water connections automatically connect to the core plate by automatic docking mechanisms. When the core plate is in position, the mold is closed and the cavity plate is disconnected from the core plate and firmly attached to the hot runner plate. 
     The invention also provides a machine in which all three moldsets in the three level stack mold are oriented in the same direction. This enables uniform robot actuation for all three moldsets without the need to reorientate molded parts. This further simplifies the retrieval of molded parts. 
     With this configuration, the robot can be located in the same position for all parts and enter between the cavity and core faces without interference with either face. The linkage assembly surrounds the mold opening when the mold is open and eliminates the need for robot adjustment when the molds are changed. This also provides weight distribution and manufacturing benefits. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of loading a moldset having a core plate and a cavity plate into an injection molding machine. The method preferably comprises the steps of latching a cavity plate to a core plate using a removable latch, guiding the core plate into an open mold along a face in the mold while maintaining separation between the face and the core plate and maintaining the cavity plate spaced from hot runner nozzles in a hot runner in the mold, closing the mold to engage the cavity plate with the hot runner nozzles, securing the cavity plate to the hot runner, removing the latch between the cavity plate and the core plate; and opening the mold. The method may further include step of bolting the cavity plate to the hot runner. The face may be a face of a movable platen or a back surface of a hot runner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a rear perspective view of the injection-molding machine with the mold closed. 
         FIG. 2  is a rear perspective view of the injection-molding machine with the mold open. 
         FIG. 3  is a rear perspective view of the injection-molding machine having the three hot runners ready to be loaded into the machine. 
         FIG. 4  is a rear perspective view of the injection-molding machine with the three hot runners mounted in the machine and the moldsets in position to be loaded into the machine. 
         FIG. 5  is a second rear perspective view of the machine with the moldsets in position to be loaded into the machine. 
         FIG. 6  is a rear side view of a three level stack mold injection-molding machine with the mold open. 
         FIG. 7  is a rear perspective view of a three level stack mold machine with the mold open. 
         FIG. 8  is a schematic side view of a linkage assembly for the front of a three level stack mold showing the assembly when the mold is open. 
         FIG. 9  is a schematic side view of the linkage assembly for the front of the machine showing the linkage when the mold is open and when the mold is closed. 
         FIG. 10  is a perspective view of the mold for a three level stack-molding machine in a partially assembled condition. 
         FIG. 11  is a perspective view of a portion of the guide assembly for the core plate. 
         FIG. 12  is a perspective view of the guide assembly with a core plate entering the guide assembly. 
         FIG. 13  is a bottom perspective view of the guide assembly and core plate. 
         FIG. 14  is a perspective view of the movable platen with core plate guides. 
         FIG. 15  is a partial perspective view of a movable platen with a core plate fully engaged with the platen. 
         FIG. 16  is a bottom perspective view of the molding machine. 
         FIG. 17  is a perspective view of a moldset partially loaded into a machine. 
         FIG. 18  is a perspective view of a core plate with guides and a core plate separation block. 
         FIG. 19  is an enlarged view of a part of the core plate and the core plate separation block. 
         FIG. 20  is side view of the core plate and core plate separation block. 
         FIG. 21  is a perspective view of the core plate and core plate separation block. 
         FIG. 22  is a perspective view of a dial indicator device for indicating proper positioning of the core plate. 
         FIG. 23  is a partially cut-away view of a guide with the dial indicator. 
         FIG. 24  is a perspective view of the water manifold mounted on a carrier. 
         FIG. 25  is a perspective view of the two carrier assemblies with manifolds and hot runners. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 1 and 2 , the injection-molding machine  10  includes a machine frame  12  and a stationary platen  14  supporting a fixed hot runner  30 . Column housing  20  is connected to the molding machine  10  at clamp block  16 . Clamp column  22  clamps the moldsets  24 ,  26  and  28  closed during an injection cycle of the molding machine  10 . Moldsets  26  and  28  with their associated hot runners  33  and  34  are mounted on carriers  70 . Movable platen  32  and carriers  70  have rollers  128  that travel on frame  12 . A stroke cylinder is fixed inside the column housing  20  and drives the clamp column  22  to stroke the movable platen  32 . Stroking of the platen  32  drives the linkage assembly  38  to open and close the moldsets  24 ,  26  and  28 . The four tiebars  18  are tensioned by the operation of the clamp piston inside clamp block  16 . 
     Mold cavity plates  40 ,  42  and  44  are mounted on fixed hot runner  30  and movable hot runners  33  and  34 , respectively. Mold core plate  52  is mounted on movable platen  32  and core plates  48  and  50  are mounted on movable hot runners  33  and  34 . With this configuration, all the mold cores face in the same direction. This enables any take out robots to be orientated in a single direction so the ejection and removal of molded parts is simplified. This also allows each of the two central moving sections of the three level stack mold machine to be identical to one another. This provides manufacturing benefits as only a single design is required. Furthermore, as each section is identical, a more balanced weight distribution is maintained within the machine. 
     Water service lines  62  to the machine  10  are arranged inside of the legs of the machine  10 . The electrical lines  54  and  56  are shown connected to movable hot runners  33  and  34  over flexible cables joined to brackets  58  and  60 . Flexible water lines  62  are similarly connected to the underside of water manifolds  120 . The service connections will be fully described hereinafter. 
       FIG. 3  shows the unassembled machine with the fixed hot runner  30  and the movable hot runners  33  and  34  poised above the machine ready to be loaded onto the machine. Of course, in actual operation, only one of the hot runners at a time would be in position to be loaded onto the machine. 
     Fixed hot runner  30  is lowered onto the machine and bolted by bolts  64  to stationary platen  14 . The fixed hot runner  30  is supplied with water connection hoses from the machine to cool hot runner manifold plate  200  and also provide a water circuit to the cavity plate  40 . However, movable hot runners  33  and  34  need to be guided onto the machine frame. Key slots.  65  and  66  engage keys  68  on carriers  70 . The water connections or nipples  118  protruding from the service manifolds  120  engage female fittings on the base of manifold plates of hot runners  33  and  34  to provide a secure water supply to the hot runners  33  and  34 . 
       FIGS. 4 and 5  show the machine  10  with the movable platen  32 , movable hot runners  33  and  34  and fixed hot runner  30  installed and the moldsets  24 ,  26  and  28  positioned over the machine ready to be loaded into the machine  10 . Each core plate in each moldset  24 ,  26  and  28  has a guide slot  74 . Each guide slot  74  engages a guide bar  75  on the movable platen  32  or one of the movable hot runners  33  or  34 . 
     In the embodiment shown in the Figures, a central sprue bar  76  extends through the moldset  24 . To enable the moldset  24  to be loaded into the machine  10 , slots  78  and  80  are provided in the core plate  48  and cavity plate  40  of moldset  24 . 
     The guide slots  74  on each side of the core plate include core plate separation blocks  140  and  142 . The operation of these separation blocks  140  and  142  will be more fully described hereinafter. 
       FIGS. 6 to 9  illustrate the construction and operation of the linkage assembly for moving the mold between the open and closed positions. There are two assemblies  38  on the machine. The first assembly  38  shown on the back of the machine  10  in  FIGS. 6 and 7  has an anchor point  84  at the base of stationary platen  14  for the short pivoting arm  86 . A second short pivoting arm  88  is connected to anchor point  90  near the top of movable platen  32 . Extending arms  92  and  94  are pivotably connected to carriers  70  at the mid-point of the carriers  70 . The lower end of arm  92  is pivotably connected to arm  86  and the upper end of arm  94  is pivotably connected to arm  88 . Two curved or L-shaped arms  96  and  98  connect the arms  92  and  94  together. 
     The lengths of the linking arms  86 ,  88 ,  92 ,  94 ,  96  and  98  are adjusted so that the moldsets  24 ,  26  and  28  open and close simultaneously and the linking arms  86 ,  88 ,  92 ,  94 ,  96  and  98  do not interfere with side access to the open mold. In the present embodiment, the lower portion  92   a  of arm  92  is longer than the upper portion  92   b . For arm  94 , the upper portion  94   b  is longer than the lower portion  94   a . The arms  96  and  98  are curved to ensure that they do not extend across the access to the cores and cavities when the mold is open. 
     The linkage assembly  38  at the front of the machine is the reverse of the assembly  38  on the back of the machine. To emphasize the similarities between the two assemblies, similar elements have been designated with a prime. As shown in  FIGS. 8 and 9 , arm  86 ′ is connected to an upper anchor point  84 ′ on stationary platen  14  and arm  88 ′ is connected to a lower anchor point  92 ′ on movable platen  32 . Extending arms  92 ′ and  94 ′ are pivotably connected to carriers (not shown) on the machine in the same manner as arms  92  and  94 . However, the longer portion  92   a ′ of arm  92 ′ is the upper portion of the arm and the longer portion  94   b ′ is the lower portion of arm  94 ′. By reversing the two assemblies  38 , the forces driving the molds between the open and closed positions are balanced and the molds close uniformly. 
     The linking arms  86 ′,  88 ′,  92 ′,  94 ′,  96 ′ and  98 ′ are also dimensioned so that they do not interfere with access to the cores and cavities when the mold is open. Thus, the molding machine provides ready access to the open molds from above, below and both sides. As will become apparent hereinafter, this enables the rapid and simple ejection of molded parts and easy and rapid replacement of moldsets. 
       FIG. 10  shows the cavity plates  40 ,  42 , and  44 , core plates  48 ,  50  and  52  and the fixed hot runner  30  and movable hot runners  33  and  34  separate from the injection-molding machine. Cavity plate  40  is attached to core plate  48  by latches  100  (only one shown). Each hot runner includes four hot runner leader pins  102  to align the respective cavity plate with the hot runner. Hot runner nozzles  104  extend out of each hot runner and into the associated cavity plate. Four straight interlocks  101  at the midsection of each cavity plate  42  and  44  interface with matching slots  103  on the respective hot runners. Cavity plate  40  only has three interlocks  101  because a slot  80  is formed in the plate  40  to permit the plate  40  to slide over the sprue bar  76 . The leader pins  102  ensure reasonable alignment of the cavity plates with the associated hot runner and the precise shape of the interlocks  101  and slots  103  tightly align the nozzles  104  with the gates of the cavities in the cavity plates. The outermost ends of the interlocks  101  are slightly tapered to ensure that the interlocks  101  enter into the slots  103  and do not have sharp corners that can impact on one another and cause damage. This ensures that the moldsets can be changed often without the creation of alignment concerns over time. 
     One embodiment of the guide slots for guiding the core plates onto the hot runners  33  and  34  is shown schematically in  FIG. 11 . At the top of each hot runner  33  and  34  and movable platen  32  is a guide plate  106 . The guide plate  106  has a tapered surface  108  for receiving and guiding the core plate into the receiving slot  110 . A slightly raised surface  112  on the outer surface of each guide plate  106  forces the core plate away from the hot runner or movable platen so that the core plate does not scuff against the hot runner plate or the movable platen as it is being guided and loaded onto the machine. 
       FIG. 12  shows a core plate  114  being guided into a slot  110  and being pushed slightly away from the surface of the movable platen  32  by the raised surface  112 . A cavity plate  116  is attached to the core plate  114 . Water connections or nipples  118  extend from the water manifold  120  and will engage in connectors on the base of the core plate  114  when the core plate is placed in molding position. Guide pin  119  guides the core plate  114  onto the water manifold  120  to ensure a secure connection of the connectors  118  to the female connectors on the core plate  114 . 
       FIG. 13  is a partial assembly showing the guide slot  74  on core plate  52  just entering the guide plate  106 . The tapered surface  115  at the front edge of slot  74  permits the core plate  52  to align with the guide plate  106 . The raised surface  112  on the guide plate  106  moves the core plate  52  away from the surface of the movable platen  32  so the core plate  52  does not scuff against the surface of the platen  32  as it is being loaded into the machine. The female connectors  121  on the underside of core plate  52  engage connectors  118  when the core plate is fully loaded into the movable platen  32 . 
       FIG. 14  is a perspective view of the movable platen  32  with the guide plates  106  and  122  installed. The guide plates  106  are mounted on an upper portion of the platen  32  and lower guide plates  122  are mounted on a lower portion of the platen  32 . Wedge plates  124  are mounted on water manifold  120 . A wedging surface  126  is formed on the upper end of plates  124  and engage the front face of the core plate when it is nearing its fully mounted position. The wedging surfaces  126  force the core plate into firm contact with the platen  32 . It is noted that each core plate is loaded in this same manner so it is unnecessary to describe the loading operation for the other two core plates onto the movable hot runners  33  and  34 . 
       FIG. 15  shows the core plate  52  fully installed on platen  32  and wedged tightly against platen  32  by wedge surface  126  on wedge plate  124  and a wedging surface on the separation block  140 . The separation block  140  is more fully described hereinafter. 
       FIG. 16  shows the flexible water lines  62  extending to the manifolds  120  on each hot runner. One set of lines  62  extends under tiebars  18  on one side of the machine and the other set of lines  62  extends along the underside of the other lower tiebar  18 . Lines  62  are out of the way of the mold opening so parts can be dropped downwardly without encountering interference from any components of the machine. 
       FIG. 17  shows a core plate  50  secured to movable hot runner  33 . Cavity plate  42  is secured to core plate  50  by latches  100  (only one shown) and is ready to be secured to the hot runner plate. 
     With this new design, the replacement of molds and servicing of the machine are much simplified over earlier designs 
     First, the mold guides  106  and  122  are installed on the movable platen  32  and movable hot runners  33  and  34 . The water manifolds  120  and wedge plates  124  are also installed on the movable platen  32  and movable hot runners  33  and  34 . The water manifolds  120  are installed on carriers  70  and the flexible water lines  62  attached from below. As shown in  FIG. 3 , the movable hot runners  33  and  34  are each installed on carriers  70  and the hot runner  30  is bolted to the fixed platen  14 . Next, as shown in  FIG. 5 , the moldsets  24 ,  26  and  28  are lowered onto the hot runners  33  and  34  and the movable platen  32 , one at a time. A dial indicator, to be described hereinafter, is provided to indicate when the moldset is properly seated and the air and water connections are secure. When the moldset is in place it is bolted to its associated platen or hot runner and the crane hook is removed. After all three moldsets have been bolted, the machine is slowly closed to permit the cavity plates  40 ,  42  and  44  to engage hot runner leader pins  102 , straight interlocks  101  and hot runner nozzles  104 . Clamp tonnage is then applied and each cavity plate is partially bolted to the hot runner associated with it. The bolts are sufficient in number to ensure that the cavity plate is secure when separated from the core plate. The stack mold carrier to hot runner bolts are now tightened. At this point, the latches  100  and the moldset lift bars are removed. The molds can now be slowly opened with the core plates separating from the cavity plates. When the molds are open the remaining cavity plate bolts can be tightened and the electrical cables attached to the top of the hot runners. The machine is now ready to mold parts. 
     When replacement of the moldsets is required, the procedure is reverse. The mold is opened and latches  100  are slid onto the cavity plates. Most of the bolts securing the cavity plate to the hot runner are removed. The remaining bolts need only hold the cavity plate in position. The mold is closed and the latches  100  are attached to the core plate. The remaining bolts securing the cavity plate to the hot runner are removed and the mold is opened. The bolts attaching the core plate to its associated moving platen  32  or hot runner are removed. Now the crane hook can be attached to the moldset and the moldset removed from the machine. 
     The injection molding machine provides pre-assembled moldsets for each family of parts to be molded so that the moldsets can be changed quickly and efficiently. The guided moldset loading ensures that the moldsets install with minimal operator intervention. The hose-less coupling of the services ensures quick, sure and easy coupling of services to the machine and moldsets. The open linkage assembly ensures that parts can be readily retrieved by a robot from either side of the machine or simply freely dropped through the bottom of the machine. The robot could even enter from atop the machine. 
       FIGS. 18 to 21  illustrate apparatus for automatically connecting air supplies to the core plate. The apparatus also provides guide surfaces to keep the core plate away from the hot runner or platen faces during loading of the core plate and positively moving the core plate toward the platen or hot runner face when the core plate is near the end of travel. During removal, the apparatus moves the core plate away from the platen or hot runner face at the start of travel. The apparatus also provides means for indicating the positive loading of the core plate. In this embodiment, the core plate  148  has guide slots  174  for guiding the core plate  148  onto guide plate  206  in the same manner as previously described with reference to core plate  48 . Core plate  148  includes core plate separation blocks  140  and  142 . Each separation block  140  and  142  includes an air channel or channels to provide air to the core plate to enable ejection of parts from the cores on the core plate. This creates a separation of the air supply from the water supply at the base of the core plate thus reducing the possibility of contamination of the air supply in the event that the water supply remains pressurized when a core plate is not in position on the mold. Each guide plate  206  includes an air channel with a discharge outlet  144 . As the core plate  148  slides into position, an air opening  138  in the undersurface of each core plate separation block  140  and  142  engages a discharge outlet  144 . To ensure that the opening  138  makes an airtight seal with the outlets  144 , each outlet  144  has a compressible and pliable exit surface. In some instances, it may be desirable to provide the openings  138  with a similar compressible and pliable surface. A preferred material for the discharge outlets  144  is Ultra High Molecular Weight Polyethylene (UHMWPE). 
     The angular surface  146 , shown in  FIG. 20 , on the separation blocks  140  and  142  engages a camming surface (not shown) on the guide plate  206 . The camming surface forces the separation blocks  140  and  142  and joined core plate  148  towards the platen or hot runner when the core plate is nearing its end of travel. A distance of approximately 50 mm from the end of travel is considered a reasonable place for this camming action to start. At the same time as this camming action is initiated, the wedge surfaces  126  on the wedge plates  124  are forcing the lower portion of the core plate  148  toward the face of the hot runner or platen. Thus, the core plate is forced toward the platen or hot runner in an upright manner so that it engages the platen or hot runner face evenly. This camming action also causes the opening  138  to positively engage with the discharge outlet  144 . 
     The angular surface  150 , shown in  FIG. 21 , on the core plate separation blocks  140  and  142  acts with corresponding sloped surfaces (not shown) on the guide plates  206  to cam the core plate away from the platen or hot runner face upon initial movement of the core plate during extraction of the core plate from the mold. 
     Another feature of the machine is the provision of a dial indicator  130  shown in  FIGS. 22 and 23 . Compression of the extended rod  132  by the downward movement of the core plate separation blocks  140  and  142  indicate directly whether the blocks  140  and  142  and the core plate  148  to which they are attached have been properly secured in the machine. The dial indicators  130  are situated under an overhang of the guide plate  206  so that they are protected from incidental contact. The use of two indicators provides an operator with the choice of standing on either side of the machine while the core plates are being installed. In operation, the dial indicators would be set during the initial or first installation of a moldset in the machine. This setting would be used to measure the proper insertion of subsequent moldsets. 
     As shown in  FIGS. 24 and 25 , the water manifolds  120  are bolted to the carriers  70  and provide nipple connections  118  to the hot runners  33  and  34  and the core plates (not shown). When the hot runners and core and cavity plates are guided onto the carriers  70 , the nipple connectors  118  automatically engage corresponding openings in the hot runners and core and cavity plates. The guide pins  152  on the top of the water manifold  120  serve to guide a core plate  48  or  148  onto the manifold  120  and ensure that the tapered female connectors  121  on a core plate  48  or  148  are aligned with the nipples  118  along the front edge of the manifold  120 . 
     It will, of course, be understood that the above description has been given by way of example only and that modifications in detail may be made within the scope of the present invention.