Abstract:
A system is provided for use with a container molding machine having a mold wheel, the mold wheel having a plurality of molds for molding the containers, each of the molds having an opening direction substantially parallel to a rotational axis of the mold wheel. The system has a mold opening controller and a receiving device for receiving the containers dropped from the mold wheel and transferring the containers to a container conveyor. The receiving device has a longitudinal direction substantially perpendicular to the opening direction of the molds and substantially parallel to a longitudinal axis of the container when released from the mold. The longitudinal direction of the receiving device is non-horizontal.

Description:
[0001]     This application is a continuation of U.S. patent application Ser. No. 10/426,963 filed May 1, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a container molding process. More particularly, the invention relates to systems and methods for increasing the production rate of a wheel type blow-mold machine.  
         [0003]     One commonly used wheel type blow-mold machine produces continuous extrusion blow-molded plastic containers. It will be understood that to form a polyolefin continuous extrusion blow-molded plastic container, a parison can be heated in an extruder, captured by a mold, and blown in the mold. Specifically, to form the cavity of the container, a parison can be extruded into the mold and as the mold comes together, a pneumatic blow pin, for example, can pierce the parison and blow the parison up against the walls of the mold. The mold typically contains flash pockets above and below the cavity in the mold to capture the excess of the parison that is forced above and below the cavity. When the parison is blown inside the mold, it is forced into the flash pockets and portions of the parison must adhere together. The excess flash can then be cut away from the container after it is ejected from the mold.  
         [0004]     There is a benefit that can be realized by producing wheel type blow-mold machines capable of high production rates and of modifying existing wheel type blow-mold machines to increase their production rates.  
       SUMMARY OF THE INVENTION  
       [0005]     Embodiments of the invention provide systems and methods for increasing the production rates of wheel type mold machines, for example, wheel type blow-mold machines, while maintaining a significant portion of the structure of existing wheel type mold machines.  
         [0006]     Embodiments of the invention provide a system for use with a container molding machine having a mold wheel, the mold wheel having a plurality of molds for molding the containers, each of the molds having an opening direction substantially parallel to a rotational axis of the mold wheel. The system has a mold opening controller and a receiving device for receiving the containers dropped from the mold wheel and transferring the containers to a container conveyor. The receiving device has a longitudinal direction substantially perpendicular to the opening direction of the molds and substantially parallel to a longitudinal axis of the container when released from the mold. The longitudinal direction of the receiving device is non-horizontal.  
         [0007]     Other embodiments of the invention provide an apparatus for blow molding containers. The apparatus has a mold wheel having a rotational axis, a plurality of molds attached to the mold wheel, the molds being openable for discharging the containers after molding, and each of the molds having an opening direction substantially parallel to the rotational axis of the mold wheel, and an air blower for introducing blow air into the molds to form the containers within the molds. The apparatus also has a mold opening controller for controlling when the molds are opened and closed, and a receiving device for receiving the containers dropped from the mold wheel and transferring the containers to a container conveyor. The receiving device has a longitudinal direction substantially perpendicular to the opening direction of the molds and substantially parallel to a longitudinal axis of the container when released from the mold. The longitudinal direction of the receiving device is non-horizontal.  
         [0008]     Other embodiments of the invention provide a method of increasing the production rate of a container molding machine having a mold wheel, the mold wheel having a plurality of molds for molding containers, each of the molds having an opening direction substantially parallel to a rotational axis of the mold wheel. The method increases a rotational duration over which the molds are held in a closed position to mold the containers, increases a rotational duration over which blow air is introduced to each of the molds, and angles a receiving device for receiving the containers dropped from the mold wheel and transferring the containers to a container conveyor. The receiving device has a longitudinal direction substantially perpendicular to the opening direction of the molds and substantially parallel to a longitudinal axis of the container when released from the mold. The angling of the receiving device is such that the longitudinal direction of the receiving device is non-horizontal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention is explained below in further detail with the aid of exemplary embodiments shown in the drawings, wherein:  
         [0010]      FIG. 1  is a side schematic view of a currently used wheel type blow-mold machine: and  
         [0011]      FIG. 2  is a side schematic view of an example of an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     The invention is explained in the following with the aid of the drawings in which like reference numbers represent like elements.  
         [0013]      FIG. 1  shows a wheel type blow-mold machine for producing containers  10 . The machine shown in  FIG. 1  has a mold wheel  100  that revolves, in this example clockwise, around a central axis  110 . Mold wheel  100  has  12  molds  120  attached to its outer perimeter. Although  12  molds  120  are shown in this example, it is noted that any practical number of molds can be used.  
         [0014]     In the case of a continuous extrusion blow-molded plastic container producing process, each mold  120  has two parts that are pressed together to form a mold cavity. The mold parts are then separated from each other to allow the molded container to drop from the mold. In the example shown in  FIG. 1 , the parison is captured between the mold parts as the mold parts come together at point  210  along the rotational path of wheel  100 . At point  210  or soon thereafter, blow air is introduced into the parison to blow the parison up against the interior walls of the mold. The blow air continues for a blow air duration  200  and is turned off at point  220 . While the blow air&#39;s primary function is to inflate the parison to form the container, it also serves the function of cooling the container material sufficiently before the mold parts are opened and the molded container is released from mold  120 . A significant factor in determining the highest acceptable rotational rate of wheel  100  is the amount of time needed for the molded container to cool sufficiently before it is released from mold  120 .  
         [0015]     At some point after the blow air is turned off at point  220 , mold  120  begins to open, resulting in container  10  dropping from mold  120  at drop point  300 . Container  10  falls in direction A from mold  120  into a receiving device  400 . Receiving device  400  receives container  10  in a manner as to not damage container  10  and moves container  10  away from mold wheel  100  before the next container is released from the next mold  120 . Receiving device  400  can be attached to a conveyor to move the completed containers  10  to the next step in the processing such as, for example, flash removing and container separation.  
         [0016]     The opening and closing points of molds  120  can be controlled by use of a cam shape such that each mold opens and closes at a predetermined position along the rotation of the wheel. Similarly, the points at which the blow air is turned on and off can be controlled by a cam.  
         [0017]      FIG. 2  shows an example of an embodiment of the invention. In the example shown in  FIG. 2 , the blow air duration  200 ′ is longer than the blow air duration  200  shown in  FIG. 1 . For example, blow air duration  200 ′ can be 230° compared to a duration of 200° of blow air duration  200 . As stated above, molds  120  must stay closed a sufficient length of time for containers  10  to achieve sufficient rigidity before molds  120  are opened. The maximum allowable rotational speed of mold wheel  100  is limited by this required cooling time of containers  10  before molds  120  can be opened.  
         [0018]     In the example shown in  FIG. 1 , 5.2 seconds of blow air on-time is achieved with a wheel rotational speed of  6 . 5  revolutions per minute and 200° of blow air duration. By increasing the blow air duration (as shown in  FIG. 2 ) to 230°, the rotational speed of wheel  100  can be increased while still maintaining the required blow air on-time. For example, wheel  100  shown in  FIG. 2  provides 5.3 seconds of blow air on-time at a rotational speed of 7.3 revolutions per minute. Therefore, the example shown in  FIG. 2  provides slightly increased blow air on-time (cooling time) than the device shown in  FIG. 1  while increasing the rotational speed of mold wheel  100 . This increase in rotational speed is directly proportional to an increase in production of containers. Mold wheels such as mold wheel  100  commonly produce two (or more) containers  10  in each mold  120 . In the case of mold wheel  100  having twelve molds  120  with each mold forming two containers  10 ,  24  containers  10  are formed with each revolution of wheel  100 . Therefore, at 6.5 revolutions per minute, 156 containers are produced in one minute (6.5×24) and at 7.3 revolutions per minute,  175  containers are produced in one minute (7.3×24). As can be seen from these calculations, the systems and methods of the invention can greatly increase the productivity of mold wheels.  
         [0019]     In order to allow the increased blow air duration  200 ′ (as compared to blow air duration  200 ), receiving device  410  is position as shown in  FIG. 2 . This position of receiving device  410  allows more rotational duration between blow air off point  230  and drop point  310  than would exist if the receiving device was positioned as shown in  FIG. 1 .  
         [0020]     Particular embodiments of the invention provide for opening the molds such that each of the containers is released from the mold wheel after the mold molding that container has rotated past a lowest point of rotation of the mold wheel. For example, the molds can be opened such that each of the containers is released from the mold wheel between 5° and 40° of rotation past the lowest point of rotation of the mold wheel. More particularly, the molds can be opened such that each of the containers is released from the mold wheel between 10° and 30° of rotation past the lowest point of rotation of the mold wheel. More particularly still, the molds can be opened such that each of the containers is released from the mold wheel approximately 15° of rotation past the lowest point of rotation of the mold wheel.  
         [0021]     The invention can provide a blow air controller for controlling blow air that molds the containers within the molds. The blow air controller turns the blow air on and off such that the blow air is on in each mold for at least 200° of rotation of the mold wheel. In another embodiment, the blow air can be on for each mold for at least 220° of rotation of the mold wheel. In yet another embodiment, the blow air can be on for each mold for approximately 240° of rotation of the mold wheel.  
         [0022]     In order for receiving device  410  to catch containers  10  as they drop from wheel  100  in such a way as to minimize damage to containers  10  and to minimize bouncing of containers  10 , receiving device  410  is tilted at an angle α. Angle α is determined based on the drop direction B at which containers  10  drop from molds  120  which is, in turn, dependant upon the point at which molds  120  open and the rotation speed of wheel  100 . To further increase the effectiveness of receiving device  410 , the distance d from mold  120  to receiving device  410  can be adjusted. For particular existing mold wheels  100 , it is preferable to reduce distance d, for example by 4″, when modifying the existing wheel with the systems and methods of the invention.  
         [0023]     As stated above, the blow air on and off points and mold opening and closing points can be controlled by cams. If such cams are used, the cams may need adjusting to provide the blow air and mold control required by the invention. In addition, if the rotational speed of mold wheel  100  is changed, a gear ratio change in the drive mechanism of wheel  100  may be necessary.  
         [0024]     The invention has been described in detail with respect to preferred embodiments and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. The invention, therefore, is intended to cover all such changes and modifications that fall within the true spirit of the invention.