Abstract:
A system for forming a hollow body may include at least one closing unit positioned beneath the die of a tube extrusion device. The closing unit may include a first vertical closing plate and second vertical closing plate. Specifically, an upper horizontal closing plate is cantilevered to the first vertical closing plate carrying an upper mold half, while a lower horizontal supporting plate is cantilevered to the second vertical closing plate carrying a lower mold half. At least one hydraulic cylinder may connect to the horizontal supporting plate and be adapted to vertically displace the lower horizontal closing plate. The closing unit is configured in such a way that when the vertical closing plates are moved toward each other, the upper horizontal closing plate and the lower horizontal supporting plate interlock. The system can be configured to produce oblong hollow bodies requiring a horizontal mold parting plane.

Description:
RELATED APPLICATION 
   This application claims priority under 35 U.S.C. § 119 to German Patent Application No. 10 2004 033 131.6, entitled  A Hollow Body Blowing System  and filed on Jul. 8, 2004, the contents of which are incorporated herein by reference in their entirety. 
   FIELD OF THE INVENTION 
   This invention relates to a system for forming hollow bodies, in particular, a blow molding system that can be configured as a vertical or a horizontal system. 
   BACKGROUND 
   Blow molding systems generally fall into two categories. The first type of system includes a vertical mold parting plane (called a vertical system). The second type includes a horizontal mold parting plane (called a horizontal system). Systems for forming a hollow body including mold halves fastened to the closing plates and vertical mold parting planes are often used to produce plastic bottles and technical molded parts such as parts having an oblong shape with open ends (e.g., air guide conduits). The length of the parts that can be produced by such systems, however, is limited by various parameters including the weight of the extruded tube (which increases with increasing tube length), the type of the plastic materials forming the tube, and the diameter of the tube, the wall thickness, and other parameters. In particular, such systems are not suitable for producing seamless, oblong pipes, conduits, and similar hollow bodies whose longitudinal axes include sharp and/or multiple bends. 
   For these reasons, seamless parts are often formed using a horizontal system for forming a hollow body. For example, U.S. Pat. No. 5,030,083 to Kohno et al. shows a system including a tube extrusion device with a robot that receives a tube extruded in a suspended manner from a die and then places the tube in a cavity positioned on a lower horizontal molding portion, which, in turn, is situated on a lower closing plate. In operation the molding portion and the closing plate are moved horizontally to a closing unit, where the mold is closed by lowering an upper horizontal closing plate that carries an upper molding portion. A second carriage is connected to a carriage carrying the lower closing plate. The second carriage carries a second lower closing plate and thereon a second lower molding portion, which are moved in tandem with the first lower molding portion and its associated second closing unit. The first and second molding portions are alternately positioned under the die and their respective closing unit. Although a horizontal system forms seamless, oblong molded parts of varying geometries, it is less economical than vertical systems for producing plastic hollow bodies of large diameters (i.e., large diameters with respect to their lengths). 
   The present invention is directed to a vertical system for forming a hollow body. The system comprises a machine frame with a tube extrusion device and at least one closing unit including first and second vertical closing plates situated below the die of the extrusion device. The vertical plates are guided in opposite directions against one another such that they can be moved away from and toward one another on horizontal posts. The posts may be mounted on a carriage. The carriage can move the closing unit at a right angle to the direction of movement of the vertical closing plates, from a position under the tube extrusion die to a position under a blowing sleeve. 
   OBJECTS AND SUMMARY 
   An object of the present invention is to extend the field of application of a hollow body, blow-molding system with a vertical mold parting plane (also called a vertical mold partition) by providing a vertical system capable of performing as both a vertical or horizontal system. 
   This and other objects may be achieved using a system for forming a hollow body system in accordance with the invention. Generally, the embodiments of the present invention provide a blow molding system including a first vertical closing plate with an upper horizontal closing plate cantilevered thereto. The upper horizontal closing plate carries an upper mold half on its lower side. Similarly, a lower horizontal supporting plate can be cantilevered to the lower region of the second vertical closing plate. At least one hydraulic cylinder is connected to the lower horizontal supporting plate through a lower horizontal closing plate, and is configured to vertically displace the lower horizontal supporting plate. A lower mold half may be positioned on the upper side of the lower horizontal closing plate. In operation, when the vertical closing plates move toward each other, the edges of the upper horizontal closing plate and the lower horizontal closing plate interlock with the vertical closing plates. 
   The present invention reconfigures a hollow body blow molding system with vertical mold parting planes in such a way that it can also be used for producing oblong hollow bodies (which require a horizontal mold parting plane). As a result, the system of the current invention can also be configured to operate as a horizontal system. The hollow body mold-blowing system can be reconfigured depending on the type of hollow body sought to be produced (i.e., a hollow body requiring molds with a vertical mold parting plane or a horizontal mold parting plane). One can thus omit purchasing a second blowing system which is designed exclusively for molds with a horizontal mold parting plane. 
   The interlocking engagement between the upper horizontal closing plate and the second vertical closing plate and between the lower horizontal supporting plate and the first vertical closing plate can be achieved by pillaring the respective plates on guide bolts and complementary guide sleeves. 
   The lower horizontal closing plate is preferably guided by two guide posts and driven by a single hydraulic cylinder situated centrally under the lower horizontal closing plate. 
   The system can also comprise a tube insertion robot that receives an extruded tube (also called a preform) from the die and places the tube into the cavity of the lower blow mold half. The robot may include a single gripper operable to grasp the upper end of the tube. Alternatively, the robot can also be provided with two grippers, one configured to grasp the upper tube end the other configured to grasp the lower tube end. 
   In accordance with the further development of the invention, the tube insertion robot can also comprise squeeze pliers adapted to seal the upper tube end when removing the tube from the die. This prevents air, which can be injected during the extrusion of the tube to provide support, from escaping the tube and causing the tube to collapse during or after its insertion into the lower blow mold half. 
   When using a tube robot with only one gripper configured as squeeze pliers, the lower tube end can be sealed either by a second pair of squeeze pliers or by at least one clamping apparatus positioned along the lower mold half. 
   In order to form the tube in the closed blow mold into the finished hollow body, a blowing apparatus can be arranged on one of the mold halves. Preferably the blowing apparatus is positioned on the lower mold half. 
   The blowing apparatus may comprise a hollow needle connected to a blowing air source that can be inserted into the tube. 
   Alternatively, the blowing apparatus may comprise a blowing sleeve that calibrates and shapes one of the tube ends of the finished hollow body into an orifice or opening. The blowing sleeve can also be fixed to one of the mold halves (preferably the lower mold half). 
   According to another embodiment of the present invention, the blowing sleeve can be adapted to move such that it ejects the finished hollow body from the blow mold when it is opened. Optionally, known auxiliary apparatuses such as vacuum suction or grippers may be used in place of or in addition to the blow sleeve in order to remove the finished hollow body. 
   A preferred embodiment of the present invention may include a second, movable closing unit comprising the same configuration as the first closing unit. The second closing unit can be alternated with the first closing unit to be positioned under the tube extrusion die. The two closing units moved in tandem in a reciprocating fashion from one position under the die, where the tube is placed into the lower mold half, to another position on the one or the other side of the die, where the tube is blown into the finished hollow body, cooled, and ejected from the mold halves. 
   Preferably, the tube extrusion device is adapted to raise and lower. When using the system in conjunction with molds having a vertical mold parting plane (i.e. mold for producing tube elements or containers which are short with respect to their diameter), the die is situated in its lowermost position. When using the system with molds having a horizontal mold parting plane, the height of the die orifice depends on the length of the tube or preform to be extruded (i.e., of the length of the oblong hollow body to be produced). 
   In addition, the orientation of the tube extrusion device can be selectively positioned horizontal to or parallel to the direction of movement of the closing plates. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a side view of a blowing system including a vertical mold parting plane. 
       FIG. 2  illustrates a perspective view of the system of  FIG. 1 . 
       FIG. 3  illustrates a side view of the blowing system according to an embodiment of the invention, showing a system including a horizontal mold parting plane. 
       FIG. 4  illustrates a perspective view of the system of  FIG. 3 , showing the lower blow mold half in the insertion position. 
       FIGS. 5   a - d  illustrate the sequence of a working cycle of the system of  FIGS. 3 and 4 . 
       FIG. 6  illustrates a top view of the lower mold half in isolation. 
       FIG. 6   a  illustrates the left part of the lower mold half according to  FIG. 6 , further showing an inserted tube. 
       FIG. 7  illustrates a side view of the lower half of the mold of  FIG. 6 . 
       FIG. 8  illustrates a side view of another embodiment of the lower mold half in accordance with the present invention. 
       FIG. 9  illustrates a top view of the mold half of  FIG. 8 . 
       FIG. 10  illustrates a side view of a modified mold half in accordance with another embodiment of the present invention. 
       FIG. 11  illustrates a top view of the modified mold half of  FIG. 10 . 
       FIG. 12  illustrates a front side view of a blowing system with a closing unit. 
       FIG. 13  illustrates a front side view of a blowing system including two closing units. 
   

   Like reference numerals have been used to identify like elements throughout this disclosure. 
   DETAILED DESCRIPTION 
     FIGS. 1 and 2  illustrate a conventional hollow body blowing system with vertical mold parting partition. As shown, the system includes a machine frame  1 , on which is situated a tube extrusion device  4  with a die  5 . The extrusion device can be raised and lowered hydraulically, or by using spindles  2 ,  3 . A closing unit  6 , situated below the die, comprises a first or inner closing plate  7  and a second or outer closing plate  8 . A hydraulic cylinder  11  can move the closing plates  7 ,  8  toward and away from each other along horizontal posts  9 ,  10 . The posts  9 ,  10  and the cylinder  11  are mounted on a carriage  12  driven by a carriage cylinder (not shown) along two posts  13 ,  14  at a right angle to the movement of the closing plates  7 ,  8 , from a position beneath the die  5  to a position under a conventional blowing sleeve  15 . A first blow mold half a is fastened with the first closing plate  7 , and a second blow mold half b is fastened to the second closing plate  8 . After the extruding, a tube or preform of suitable length from the die  5  into the opened mold halves a, b, the mold is closed by the hydraulic cylinder  11 . The closing unit  6  is then moved transversely by the carriage  12  from its position beneath the die  5  to a position beneath the blowing sleeve  15 . After blowing out the hollow body and allowing the body to cool, the hydraulic cylinder  11  opens the mold and the hollow body (e.g., a product such as a handle bottle as shown in the cavity of  FIG. 2 ) in the mold half a is ejected.  FIGS. 1 and 2  do not illustrate the known auxiliary devices such as those for changing the wall thickness of the tube and for severing the tube beneath the tube and the hydraulic and cooling water connections. 
     FIGS. 3 to 7  further illustrate a system for producing hollow bodies in accordance with the present invention including a horizontal blow mold, i.e., with horizontal mold parting plane. In this system, after the removal of the blow mold halves a, b (seen in  FIGS. 1 and 2 ), an upper horizontal closing plate  20  is mounted on the upper region of the first inner closing plate  7  (e.g., by means of screws and alignment pins) such that it is cantilevered. Similarly, to the lower region of the second outer closing plate  8 , a horizontal supporting plate  21  is fastened in a cantilevered manner. The upper horizontal closing plate  20  comprises guide pins  20   a  at its outer edge facing the vertical closing plate  8  and the vertical outer closing plate  8  is provided with corresponding guide bushings  8   a . Similarly, the horizontal supporting plate  21  comprises guide pins  21   a  and the vertical inner closing plate  7  comprises guide bushings  7   a . A hydraulic cylinder  22  is fastened beneath the supporting plate  21  proximate the supporting plate center. A piston rod  22   a  penetrates the supporting plate  21 , terminating beneath a lower horizontal closing plate  23  positioned using guide posts  24 . With this configuration, the hydraulic cylinder  22  may raise and lower the supporting plate  21 . 
   An upper mold half  30   a  is fastened to the lower side of the upper horizontal closing plate  20 . A corresponding lower mold half  30   b  is screwed onto the upper side of the lower horizontal closing plate  23 . The parts  20 ,  21 ,  23  are dimensioned to enable their contact. Specifically, their width is dimensioned in the direction of movement of the vertical closing plates  7 ,  8  such that the lower mold half  30   b  can be brought into the position shown in  FIG. 4  by the hydraulic cylinder  22  (at least at the maximum opened position of the vertical closing plates  7 ,  8 ), where it is situated adjacent to the upper mold half  30   a . If required, the guide pins  20   a ,  21   a  can be received in their plates in an extendable and retractable manner. 
   Referring to  FIG. 5   a , a tube robot  40  receives the tube  50  from the die  5  by means of a gripper positioned at the end of a robot arm  41 . The gripper may be configured as squeeze pliers  42  with a pair of moveable pincers. In the meantime, the hydraulic cylinder  22  lifts the lower blow mold half  30   b  to the insertion position (shown in  FIG. 5   b ). Preferably the lower blow mold half  30   b  is at the same height relative to the upper mold half  30   a  so that the outer vertical closing plate does not obstruct the insertion movement of the robot arm  41 . 
   The lower mold half  30   b , moreover, may be supported by the closing unit  6 , which can be selectively displaced by a carriage  12 . After the insertion of the tube  50  into the cavity of the lower mold half  30   b , the hydraulic cylinder  22  lowers the lower mold half  30   b  again. The hydraulic cylinder  11  may then move the vertical closing plates  7 ,  8  to the position illustrated in  FIG. 5   c , where the upper horizontal closing plate  20  and the lower horizontal supporting plate  21  are positioned between the vertical closing plates  7 ,  8 . Thereafter the hydraulic cylinder  22  lifts the lower mold half  30   b  until it rests on the upper mold half  30   a  ( FIG. 5   d ), closing the mold. The tube is blown into the finished hollow body. After the finished hollow body cools and is ejected from the mold, the next cycle starts. 
     FIGS. 6 ,  6   a , and  7  illustrate additional features of the lower mold half  30   b . Specifically referring to  FIG. 6 , this mold half  30   b  comprises two adjusting pins  61  that correspond to bores or bushings in the upper mold half  30   a  (not shown). At its one end, the mold half  30   b  comprises a tube clamp  66  actuated by a working cylinder  67 . The mold in  FIG. 6  is opened, showing an exposed tube  50 .  FIG. 6   a  illustrates the tube clamp fixing and sealing the end of the tube  50 . A working cylinder  62  attached to the other end of the mold half  30   b  can be used to move a hollow needle  63  into the cavity  64 . When the mold is closed, the hollow needle  63  is inserted into the tube  50 . Compressed air supplied via a line  65  is injected into the tube  50 , causing it to blow up (inflate) and take the shape of the finished hollow body. 
     FIG. 7  shows the lower mold half  30   b  with the previously mentioned attached parts in a simplified side view. 
   The parts attached to the lower mold half  30   b , illustrated in  FIGS. 6 ,  6   a , and  7 , are to be understood as examples. They can be replaced by other apparatuses which are known from the state of the art. 
     FIGS. 8 and 9  show another embodiment of the lower mold half  30   b . In contrast to the  FIGS. 6 ,  6   a  and  7 , the outer vertical closing plate  8  has been omitted. As shown in  FIG. 8 , the lower blow mold half  30   b  is located on its closing plate  23 , which can be raised and lowered by the lifting cylinder  22  and guided by the guide posts  24 . The arrangement is situated on posts  9 ,  10  that support the outer vertical closing plate. The end on the left side of the cavity  64  is guided downward out of the mold half with a shape generally similar to that illustrated in  FIG. 6 . At this end, the mold half  30   b  is divided by a vertical plane extending through the cavity. The end section  30   b ′ on the left side is mounted on a yoke  70 . A hydraulic cylinder  71  is operable to displace the yoke  70  along guide rods from the illustrated opened position to a closed position. A conventional blow sleeve  72  is arranged beneath the downward-facing conical opening  64   a  of the cavity  64 . When the mold is closed, the die  72   a  of the blowing sleeve  72  moves into the opening  64   a  or orifice of the cavity  64  until a seal between the blowing sleeve and the mold is formed, providing a seal around the tube and enabling the injection of air into the tube and the creation of the finished hollow body. 
     FIGS. 10 and 11  illustrate a modification in which the left side end  30   b ″ can be swiveled downward (indicated by the arrow in  FIG. 11 ) by a hydraulic cylinder  73 . As in the case of  FIG. 8 , a blowing sleeve  72  is arranged beneath the mold half. The sleeve  72  rotates on its supporting arm  72   a  about an axis  72   b  (indicated by the arrow in  FIG. 10 ). The hollow body is formed via air injection and the finished hollow body is cooled, and the blow mold is opened. Then, the part  30   b ″ is swiveled downward (indicated by the arrow in  FIG. 11 ) and the blowing sleeve is rotated about an axis  72   b , while the die  72   c  remains inserted into the orifice of the cavity and entrains the solidified hollow body, which is then ejected from the mold without the need for any separate apparatuses for this purpose (e.g., a suction apparatus). 
     FIG. 12  illustrates a front perspective view of a blowing system equipped with the blow mold illustrated in  FIGS. 8 and 9 . 
     FIG. 13  shows the same machine, but equipped with a second closing unit  6   a . The two closing units can have identical or different blow molds. The respective lower blow mold halves can be charged using the tube insertion robot described above (not shown in  FIG. 13 ) such that one blow mold is charged while the tube previously inserted into the other blow mold is injected with air (blown out), or while the blown hollow body is cooling. Instead of the blow sleeves attached directly to the respective lower blow mold half as shown in  FIGS. 8 and 9 , the inserted tubes can also be blown out with blow sleeves such as reference numeral  15  in  FIG. 2 , which sleeves are fixed to the machine frame. They are then mounted on either side of the tube extrusion device  4 . As indicated, the closing units  6 ,  6   a  can be moved independently along the same horizontal posts  13 ,  14  ( FIG. 1 ) or can be displaced in tandem to enable their repositioning and alignment with their respective blowing sleeve.