Abstract:
A modular mold clamp assembly for use in a molding machine. The assembly has a frame with a base member and oppositely-facing end members, with the oppositely-facing end members having mounting areas provided thereon. First and second platens are movably mounted on the base member between an open and a closed position. The platens are mounted on the frame and are movable relative to the frame without transmitting forces to the frame. The frame, containing the platens, can be mounted or unmounted to the molding machine by the use of mounting hardware cooperating with the mounting area of the frame.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an extrusion molding apparatus. Specifically, the present invention relates to modular mold clamping assemblies for use with the molding apparatus. 
     BACKGROUND OF THE INVENTION 
     Conventional rotary extrusion blow molding apparatuses typically have a structural frame mounted on a rotating shaft. The structural frame has a plurality of molds mounted thereon and is known in the industry as a wheel. As the wheel is rotated, the plurality of molds is rotated past an extrusion die extruding a continuous parison. Each mold typically includes two mold halves, each comprising a mold cavity half therein, such that when the mold halves are closed, the mold defines a mold cavity corresponding to the configuration of the article to be molded, such as a container. Each mold, seriatim, is rotated past the extrusion die with the mold halves in an open configuration. The mold halves of each mold are then closed around the parison to enclose the parison within the mold defined by the mold halves. A blowing needle is then inserted into the parison within the closed mold and internal pressure is introduced to the parison, forcing it to inflate and conform to the configuration of the mold cavity. The molded object is then cooled and the mold opened to release the molded object from the mold. 
     When the two mold halves are clamped over one or more parisons prior to blowing of the parisons to form plastic containers, high clamp forces are required to close the mold halves on the parisons to pinch off the plastic and to hold the mold halves closed during blow molding. Conventional mold clamp assemblies are mounted on the frame of the machine supporting the assembly and, when actuated, transmit clamping force from a drive on one side of the mold to the other side of the mold through the frame. This means that the frame supporting the molds must be sufficiently strong to counteract bending moments imposed by the high clamp force transmitted through the frame. Deformation of the frame by the clamp force is undesirable because deformation would not permit the mold faces to close parallel with one another. 
     In an attempt to improve upon existing technology, U.S. Pat. No. 7,611,657 discloses a mold clamp assembly for a rotary-type or shuttle-type blow molding machine. The clamp assembly is mounted on a frame and includes a mold opening and closing drive connected to the two mold halves independently of the frame, so that when the mold halves are closed, clamp forces are not transmitted to the mold halves through the frame. Consequently, the high clamp force required to hold the mold halves together during blow molding is not transmitted from one side of the mold to the other side of the mold through the machine frame. 
     The blow molding apparatuses described above are typically costly, heavy machines, which require a good deal of expertise to maintain. For example, when a mold clamp requires maintenance, the entire wheel must be taken off-line as the mold clamp is worked on. In addition, if the number of mold clamps of the blow molding apparatus are to be changed to accommodate molds of a different size, the cost and time required to disassemble and reassemble the apparatus is significant. 
     Accordingly, there is a need for an improved molding apparatus and mold clamp assembly which allows for ease of maintenance and ease of configuration of the apparatus. There is also a need to reduce the complexity of the molding apparatus to help reduce the cost of the manufacture and operation of the molding apparatus. In addition, there is a need to have a modular mold clamp assembly for accomplishing the above, in which the high clamp force required to hold the mold halves together during molding is not transmitted from one side of the mold to the other side of the mold through the machine frame. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a self-contained modular mold clamp assembly which in uncomplicated to remove and replace with another modular mold clamp assembly with minimal downtime for the rotary molding wheel, thereby minimizing the impact to the productivity of the operation. 
     Another object of the invention is to provide a modular mold clamp assembly which can be replaced by maintenance level personnel rather than factory technicians, thereby minimizing the cost. 
     Another object of the invention is to provide a simplified structure of a rotary molding wheel by using a modular mold clamp assembly which provides the structural support necessary between components of the rotary molding wheel. 
     Another object of the invention is to provide a modular mold clamp assembly in which the bending moments are not transferred to the components of a rotary molding wheel. 
     Another object of the invention is to provide a modular mold clamp assembly which is lightweight. 
     Another object of the invention is to provide a modular mold clamp assembly which can be mounted to the rotary molding wheel in multiple configurations, allowing the rotary molding wheel to be configured to specific needs. 
     Another object of the invention is to provide modular mold clamping stations which can be used in tandem to accommodate large molds, to allow for even distribution of forces over the entire mold, and to prevent the end of the mold halves from separating when the parison is introduced into the mold cavity. 
     One aspect of the invention is directed to a modular mold clamp assembly for use in a molding machine. The assembly has a frame with a base member, a first end member and an oppositely-facing second end member, with the oppositely-facing first and second end members having mounting areas provided thereon. First and second platens are movably mounted on the base member between an open and a closed position. A drive linkage is mounted on the base member and cooperates with the first and second platens to move the platens between the open position and the closed position. A cam follower is slidably mounted on the first end member and is coupled to the drive linkage, whereby the movement of the cam follower moves the drive linkage. The platens, drive linkage and cam follower are mounted on the frame and are movable relative to the frame without transmitting forces to the frame. The frame, containing the platens, drive linkage and cam follower, can be mounted or unmounted to the molding machine by the use of mounting hardware cooperating with the mounting area of the frame. 
     Another aspect of the invention is directed to a rotary molding machine having a pair of turntables and a plurality of modular mold clamp assemblies. The pair of turntables are rotatably mounted on at least one shaft. The plurality of modular mold clamp assemblies are mounted on and spaced around the turntable. Each modular mold clamp assembly includes a frame having a base member, a first end member and an opposed second end member, with the first and second end members integrally attached to the base member. At least one mounting rod extends from the base member. First and second platens are movably mounted on the mounting rod to permit movement of the platens toward and away from each other. A mold clamp drive is provided for opening and closing the platens. The platens and mold clamp drive are mounted on the frame and are movable relative to the frame without transmitting forces to the frame. The frame, containing the mounting rods, platens, and mold clamp, can be mounted or unmounted to the turntables of the blow molding machine by the use of mounting hardware cooperating with the mounting area of the frame. 
     Another aspect of the invention is directed to a rotary molding machine for use with mold halves that are large and require increased clamping force. The rotary molding machine has a pair of turntables rotatably mounted on a shaft or shafts. The turntables have a plurality of modular mold clamp assembly mounting stations. A tandem of modular mold clamp assemblies are mounted in at least one mounting station. A first of the tandem of modular mold clamp assemblies cooperates with a first end of first and second mold halves to apply sufficient force to maintain the first end of the first and second mold halves in the closed position. A second of the tandem of modular mold clamp assemblies cooperates with a second end of the first and the second mold halves to apply sufficient force to maintain the second end of the first and second mold halves in the closed position. The combination of the tandem of modular mold clamp assemblies properly distributes forces to the mold halves to maintain the mold halves in a closed position as required. 
     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a first embodiment of a modular mold clamp assembly for a rotary-type blow molding machine, the modular mold clamp assembly having molds inserted therein and being shown in the closed position. 
         FIG. 2  is a side view of a first embodiment of the modular mold clamp assembly for a rotary-type blow molding machine, the modular mold clamp assembly having molds inserted therein and being shown in the open position. 
         FIG. 3  is a cross-sectional view of the modular mold clamp assembly of  FIG. 1 , taken along the longitudinal axis of the modular mold clamp assembly. 
         FIG. 4  is a cross-sectional view of the modular mold clamp assembly of  FIG. 2 , taken along the longitudinal axis of the modular mold clamp assembly. 
         FIG. 5  is a top view of the modular mold clamp assembly of  FIG. 1 . 
         FIG. 6  is a cross-sectional view through a tie rod centerline of the modular mold clamp assembly of  FIG. 1 . 
         FIG. 7  is a first end view of the modular mold clamp assembly of  FIG. 1 . 
         FIG. 8  is a second end view of the modular mold clamp assembly of  FIG. 1 . 
         FIG. 9  is a perspective view of a wheel of a blow molding apparatus with several modular mold clamp assemblies attached thereto, the mold clamp assemblies being shown with no molds positioned therein. 
         FIG. 10  is a cross-sectional view of the wheel, taken along the plane of the longitudinal axis of the wheel. 
         FIG. 11  is a cross-sectional view of the wheel, taken along the line  11 - 11  of  FIG. 9 . 
         FIG. 12  is a perspective view of a wheel of a blow molding apparatus with several modular mold clamp assemblies attached in tandem thereto, the mold clamp assemblies being shown with molds positioned therein. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 9-11 , a wheel  10  of a blow molding machine is illustrated. However, the invention is not limited to a blow molding machine, as other molding machines can be used without departing from the scope of the invention. The blow molding machine has a base (not shown) upon which the wheel  10  is rotatably supported. An extruder (not shown) is positioned adjacent the wheel  10 . The wheel  10  has two essentially parallel radially extending plates or turntables  12  which carry a plurality of modular mold clamp assemblies  100 , each having an inner cavity (not depicted) to receive a parison from the extruder. The wheel  10  is mounted on a shafts  20 ,  21  which has a drive which rotates the wheel  10  and modular mold clamp assemblies  100  about a rotational axis  22  of the wheel  10  and the shafts  20 ,  21  to direct each mold secured by the modular mold clamp assemblies  100  between extrusion, blow molding, cooling and ejection stations, as is known in the art. In the depicted embodiment, the wheel  10  is configured to have eighteen modular mold clamp assemblies mounted thereon, of which four are shown. However, each wheel  10  can be configured to allow any number of modular mold clamp assemblies  100  to be secured thereto. 
     Referring to  FIGS. 1-8 , an exemplary embodiment of mold clamp assembly  100  is shown, the modular mold clamp assembly  100  having a frame  110 . The frame  110  has a base member  112  and two oppositely-facing end members  111 ,  113 . The end members  111 ,  113  extend from either end of the base member  112  in a direction that is essentially transverse to the longitudinal axis of the base member  112 . The end members  111 ,  113  are integrally attached to the base member in any known manner which has the strength characteristics required. Mounting openings  115  are provided on the frame  110  proximate the ends of the base member  112 . The openings  115  cooperate with mounting hardware to mount the modular mold clamp assembly  100  to mounting openings  25  of the turntables  12  of the wheel  10 . The base member  112  and end members  111 ,  113  are made from any material that has the strength characteristics required to support the components of the modular mold clamp assembly  100  and to provide the structural integrity required to support the radially extending turntables  12  of the wheel  10 . 
     Each modular mold clamp assembly  100  includes rods  124  mounted on base member  112  of frame  110 . The rods  124  extend essentially parallel to the longitudinal axis of the base member  112 . As best shown in  FIGS. 1 and 4 , rods  124  extend through openings in mounting brackets  114 ,  116 ,  118 ,  120 . In the embodiment shown, the mounting brackets  114 ,  116 ,  118 ,  120  are fixed to the base member  112  by bolts or other mounting hardware. Mold platens  126  and  128  are mounted on the rods  124  by slides  130  which permit movement of the platens toward and away from each other during closing and opening of mold halves  132  and  134  mounted on platens  126  and  128  respectively.  FIG. 1  illustrates assembly  100  with the mold halves closed. 
     Pin  142  extends through a portion of end member  113 . The adjacent ends of rods  124  are secured to the pin. Pivot arm  144  is rotatably mounted on pin  142  between the rods  124 . The outer end  146  of arm  144  away from the mold halves extends through an opening in end member  113  and is connected to slide car  148  by links  150 . The slide car  148  is mounted on the outside surface of the end wall  113  by slide  152  to permit movement of the car back and forth in the direction of arrow  154  shown in  FIGS. 3 and 4 . Car  148  carries cam follower roller  156 , which extends into circumferential fixed cam slot (not shown) of the blow molding machine. Rotation of wheel  10  moves follower  156  into and around the cam slot to slide car  148  inwardly and outwardly and rotate arm  144  between the positions shown in  FIGS. 1 and 2 . 
     Shift member  162  is located between mold platen  126  and end member  113 . A cylindrical rod  167  extends from an upper end  164  of member  162  and is bolted directly to mold platen  126  so that movement of member  162  toward end member  113  moves the mold platen  126  and mold half  132  toward the end member  113 . The lower end  166  of shift member  162  extends from the lower end of bracket  120  and extends below mold halves  132  and  134 . The shift member is slidably mounted on rods  124  and  168 . 
     Link  160  is pivotally connected to the inner link end  145  of arm  144  and to mold shift member  162 . The pivot connection between link  160  and member  162  is located halfway between the upper end  164  and lower end  166  of member  162  to balance forces. Shift rod  168  is parallel to the longitudinal axis of the base member  112  and extends freely through the base member  112 . The shift rod  168  is connected to the lower end  166  of member  162 . The link  160  and inner link end  145  of arm  144  form a two-link extendable and retractable drive  163  for opening and closing platens  126 ,  128  and mold halves  132 ,  134 . 
     Cross pin  170  is fixedly mounted on the ends of rods  124  extending past platen  128  and mold half  134  and rotatably supports pivot arm  172 . The lower end  174  of arm  172  is connected to the adjacent end of shift rod  168  by pivot link  176  and rod end clevis  177 . The upper end  178  of arm  172  is connected to mold clamp rod  180  by pivot link  182  and rod end clevis  183 . Clamp rod  180  is connected to platen  128  through dished washer spring pack  184 . Rod  168 , clevis  177 , link  176 , arm  172  and rod  180  are part of a mold shift mechanism for opening and closing platen  128  and mold half  134 . Mold shift mechanism is connected to drive  163  through member  162 . 
     In operation, the modular mold clamp assemblies  100  are assembled to the turntable  12  of the wheel  10 , as previously described. Water management hoses are attached to a water-connection member of each assembly  100 . The water is supplied to cool the mold, as is known in the industry. Air hoses are attached to an air-connection member of each assembly  100 . The air is used to blow air into the mold cavities and to operate the required devices to facilitate the removal of the container from the cavity, both of which are known in the industry. 
     With the mold halves  132  and  134  in the open position and drive  163  retracted as shown in  FIG. 2 , rotation of wheel  10  moves the open mold halves  132 ,  134  past the extrusion station to either side of a number of parisons extruded from an extrusion head. Rotation of the wheel  10  also moves follower  156  along a radially outward portion of a cam slot to slide car  148  radially outwardly from the position of  FIG. 2  to the position of  FIG. 1 . This movement rotates arm  144  counterclockwise from the position of  FIG. 2  to the position of  FIG. 1 . 
     Rotation of arm  144  from the position of  FIG. 2  to the position of  FIG. 1  extends drive  163  to move shift member  162  away from end member  113 . Movement of the shift member moves mold half  132  from the open position to the closed position. Movement of the shift member also actuates mold shift mechanism to move shift rod  168  away from end member  113 , rotate arm  172  and move mold half  134  from the open position to the closed position. The connection between rod  180  and spring pack  184  is adjusted so that spring pack  184  is compressed when the mold is closed. 
     During and after closing of the mold, the clamp force exerted on mold half  134  is transmitted directly to drive  163  through mold shift mechanism. An equal and oppositely-directed clamp force exerted on mold half  132  is transmitted to the drive directly through member  162 . Clamping forces are transmitted through rods  124  between cross pins  170  and fixed pin  142  which in turn is attached to end frame  113 . Clamping forces are not transmitted through frame member  110 . The end of the mold shift mechanism, cross pin  170 , adjacent end member  111  floats on the frame  110 . As a result, the frame  110  is not subjected to bending moments by the high clamp forces holding mold halves  132  and  134  closed. The frame  110  need not be strengthened against bending moments. Smaller, more efficient motors may be used to operate the machine due to weight reduction. 
     After closing of the mold to capture the parison, rotation of wheel  10  moves the closed mold halves away from the extrusion station to a blow station where the parisons are blown, and, after cooling of the blown parisons, to an ejection station where the mold is opened for ejection of blow-molded containers. During rotation to the ejection station, follower  156  is moved radially inwardly by the cam track so that arm end  146  is moved radially inwardly, about fixed pin  142 , drive  163  is retracted as shown in  FIG. 2 , and the platens  126 ,  128  and mold halves  132 ,  134  are opened by movement of the shift member  162  and mold shift mechanism. Platen  126  and mold half  132  are connected directly to shift member  162  and are opened in response to movement of the member. Platen  128  and mold half  134  are opened by movement of shift rod  168  toward side member  113 , which corresponds to rotation of arm  172  and movement of rod  180  away from side member  113  and toward side member  111 . 
     During the operation of the wheel  10 , it is not uncommon to have problems with a particular mold clamp assembly. It is also common to have scheduled maintenance. In the current state of the art, in order to repair or perform maintenance on a particular mold clamp assembly, the operation of the wheel is stopped and the repair or maintenance is performed on the mold clamp assembly as the assembly is still attached to the wheel. This can cause significant downtime for the entire operation and dramatically affects the productivity of the operation. Alternatively, the operation of the wheel is stopped and the mold clamp assembly is removed from the plates and shafts of the wheel and replaced with another mold clamp assembly. However, as the mold clamp assemblies are attached at numerous points to the structure of the wheel, this process takes a good deal of time and expertise to accomplish, thereby dramatically affecting the productivity of the operation and requiring the services of a skilled operator to accomplish the transfer. 
     In contrast, the modular mold clamp assembly  100  described herein overcomes the problems associated with the prior art. As all of the components of the modular mold clamp assembly  100  are mounted to the frame  110 , the removal of the self-contained modular mold clamp assembly  100  from the wheel  10  is greatly facilitated. In order to repair or perform maintenance on a particular mold clamp assembly  100 , the operation of the wheel  10  is stopped and the modular mold clamp assembly  100  is removed and replaced with another modular mold clamp assembly  100 . As all of the components are attached to the frame  100 , rather than to structural members of the wheel  10 , the maintenance personnel simply unscrews the hardware which attaches the frame  110  of the modular mold clamp assembly  100  to the wheel  10 , removes the modular mold clamp assembly  100 , inserts a new modular mold clamp assembly  100  and attaches the frame  110  to the wheel  10  by use of the hardware. This allows the repair or maintenance to be accomplished with minimal downtime for the wheel, thereby minimizing the impact to the productivity of the operation. Additionally, the replacement of the modular mold clamp assembly  100  can be accomplished with maintenance level personnel rather than factory technicians, thereby minimizing the cost. 
     The use of the modular mold clamp assemblies  100  also allows the structure of the wheel  10  to be simplified. As each modular member assembly  100  is self-contained, the various components of the modular mold clamp assembly  100  are not mounted to shafts or plates which extend between the turntables  12  of the wheel  10 . In addition, the base member  112  and the end members  111 ,  113  are made of materials that have the structural strength and integrity to act as supports when installed in the wheel  10 . Therefore, the wheel  10  used with the modular mold clamp assemblies  100  described herein is greatly simplified from the wheels currently in use. The shafts and plates previously required are eliminated, as the modular mold clamp assemblies  100  provide the structural support necessary between the turntables  12  of the wheel  10 . This allows the wheel  10  of the blow molding machine to have more open spaces, making any repair to the blow molding machine easier. The use of the modular mold clamp assemblies  100  as supports also reduces the overall cost of the blow molding machine, as it is less expensive to have structural modular mold clamp assemblies than to have structural shafts and plates. 
     While the base member  112  and end members  111 ,  113  must be made of material which has sufficient strength characteristics to support the components and provide the structural integrity required for the wheel  10 , the frame  110  does not need to made of material which can withstand the bending moments exerted by the high clamp forces holding molds  132  and  134  closed, as the bending moments are not transferred to the frame  110 , as was previously described. Therefore, the frame  110  need not be strengthened against bending moments, thereby allowing the frame  110  to be made of relatively lightweight material. This facilitates the removal and replacement of the modular mold clamp assembly  100  and reduces the material costs to manufacture the frame  110 . 
     Depending upon the type of container to be manufactured using the blow molding machine, the number of molding stations may vary. Consequently, it is known in the art to have wheels with different numbers of mold stations. Currently, each of the wheels must be manufactured according to the desired application, with the appropriate number of shafts extending between the turntables to provide support to the turntables and to provide the mounting structure for the mold clamp assemblies. Consequently, as each wheel is designed for a particular number of mold stations, the inventory associated with meeting the needs of applications can be extensive. 
     According to the invention described herein, the inventory required to accommodate various configurations is minimized. As the wheels do not require shafts, etc., the wheels can be manufactured to accommodate different configurations. An array of mounting openings  25  may be provided on the turntables  12  of the wheels  10 . The mounting openings  25  can be configured to accommodate multiple mold clamp assembly configurations. The modular mold clamp assemblies  100  may be used to accommodate various configurations of the wheel. The end members  111 ,  113  are positioned in line with the appropriate openings  25  of the turntables  12  of the wheel  10  and mounted thereto using the mounting hardware. This allows the same modular mold clamp assemblies  100  to be used in various machines, thereby reducing the need to manufacture specific mold clamp assemblies for specific machines. 
     While the particular embodiment shown represents a two-ton modular clamp assembly, other sizes of modular clamp assemblies are included within the scope of the invention. 
     In instances in which a large mold is required for manufacture of a container or the like, a single two-ton clamp may not be sufficient to provide the force required to maintain the mold halves in their closed position. Currently in such cases, a larger mold clamp may be used to supply the appropriate force. This requires that mold clamps of various sizes be manufactured. While these larger mold clamps supply sufficient force, the distribution of forces by the clamps on the mold is not optimum. The clamps generally cooperate with the center of the molds, exerting maximum force thereon. Therefore, the ends of the molds may not have a sufficient force applied thereto, causing the parison to flow outside of the mold cavity, which in turn can cause an undesirable container to be produced. 
     In contrast, according to the present invention, two modular mold clamp assemblies  100  may be provided adjacent each other in tandem or in line, as shown in  FIG. 12 , to accommodate large mold halves. In this embodiment, the two modular mold clamp assemblies  100 ′ and  100 ″ are mounted to the turntables  12  of the wheel  10  such that the base members  112 ′,  112 ″ are essentially parallel to each other and the platens  126 ′,  126 ″ and  128 ′,  128 ″ operate in the same plane. In so doing, mold half  132  cooperates with platens  126 ′ and  126 ″, while mold half  134  cooperates with platens  128 ′ and  128 ″. This allows platen  126 ′ to cooperate with a first end of mold half  132  and platen  126 ″ to cooperate with second end of mold half  132 . Similarly, platen  128 ′ cooperates with a first end of mold half  134  and platen  128 ″ cooperates with second end of mold half  134 . The cooperation of the modular mold clamp assemblies  100  allows sufficient closing force to be applied to a large mold without the need to have a larger, more costly mold clamp assembly. In addition, this configuration allows for the forces applied to the mold halves by the platens  126 ′,  126 ″,  128 ′ and  128 ″ to be more evenly distributed over the entire mold halves, preventing the ends of the mold halves from separating when the parison is introduced into the mold cavity. 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.