Abstract:
A rotary device for a horizontal injection molding machine includes a base and a rotary table supported on the base for rotation about a vertical rotation axis upon operation of a drive. The drive includes a shaft extending downwards from the rotary table and projecting through the base.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of prior filed copending U.S. application Ser. No. 10/902,648, filed Jul. 29, 2004, which is a continuation of prior filed copending U.S. application Ser. No. 09/829,209, filed Apr. 6, 2001, now patented under U.S. Pat. No. 6,830,448, issued on Dec. 14, 2004, which in turn is a continuation of prior filed copending PCT International application no. PCT/EP00/07562, filed Aug. 4, 2000, which claims the priority of German Patent Application Serial No. 199 37 200.4, filed Aug. 6,1999. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a rotary device for a horizontal injection molding machine for turning mold portions or molded articles between the mold mounting plates about a vertical axis. The invention also relates to an injection molding machine equipped with such a rotary device.  
         [0003]     An apparatus for holding and turning molds or mold parts in a horizontal injection molding machine is known, for example, from U.S. Pat. No. 4,330,257 and European Pat. No. EP 0 922 556 A1, with the horizontal injection molding machine having mold mounting plates between which a turret (mold center platen) is slideable in longitudinal direction of the machine and provided as mold carrier with prismatic cross section which is supported for rotation about an axis extending perpendicular to the longitudinal axis of the machine. In order to shift the turret in longitudinal axis of the machine, on the one hand, and to rotate the turret about an axis extending perpendicular to the longitudinal axis of the machine, a system is provided in which the turret is rotatably supported in carriers, with the carriers slideably guided and supported at least on both lower tie bars of the injection molding machine (U.S. Pat. No. 4,330,257) or on all four tie bars (European Pat. No. EP 0 922 556 A1). To permit a precise guidance of the carrier and of the attached turret, support and guiding elements are required which are of highly precise construction and sized in narrow tolerances and which are arranged at great distances from one another as a result of the system. Thus, this support reacts sensitively to temperature fluctuations, i.e. during cool-down period and accompanying shrinkage, the clearance in the bearings increases whereas during heating period and accompanying expansion there is a risk that the support and guiding elements get jammed on the tie bars. To prevent the latter, the tolerances in the support and guiding elements should not be too narrow, i.e. sized not too precisely. A further drawback resides in the fact that the tie bars are loaded by a significant weight (inadmissible bending) depending on the design of the turret and the carriers, and that the torques encountered during rotation of the turret must be absorbed entirely by the tie bars, resulting in particular during starting and braking of the rotational movement in significant stresses.  
         [0004]     It would therefore be desirable and advantageous to provide an improved rotary device for horizontal injection molding machines, obviating prior art shortcomings. It would further be desirable and advantageous to provide an improved injection molding machine, equipped with a precisely supported and guided rotary device.  
       SUMMARY OF THE INVENTION  
       [0005]     According to one aspect of the present invention, a rotary device for use in a horizontal injection molding machine having a longitudinal direction includes a base, a table supported by the base, a drive having a motor and a shaft, the shaft extending downward from the table and projecting through the base, wherein the motor is capable of rotating the table about a vertical rotation axis, and a rack and a gear operatively configured for longitudinally shifting the base.  
         [0006]     According to another aspect of the present invention, a device for receiving a rotating mold portion includes a base, a table supported by the base, the table having a surface for receiving the rotating mold portion, a drive rotatably engaging the table, the drive including a motor and a shaft extending downward from the rotary table and projecting through the base, and a shifting mechanism having a rack engaged with a gear, the gear being fixedly and translationally attached with respect to the base.  
         [0007]     The present invention resolves prior art problems by completely separating the guidance and the support of the rotary device from the tie bars. Thus, the tie bars are not unnecessarily exposed to stress, on the one hand, and the guidance and support can be dimensioned more precise compared to the prior art.  
         [0008]     According to another feature of the present invention, the base is constructed in the form of a base which has a substantially H-shaped configuration, thereby establishing a stable support when the legs of the H-shaped base are sufficiently long, as well as allowing a simple withdrawal of a molded article into the free space between the legs of the H-shaped base. In connection with heavy mold center platens, it is advantageous to provide several linear guides and/or slideways and/or to so size the base as to reach to an area outside the zone of the mold mounting plates. By means of transport brackets and ring bolts, a complete stack mold can be dropped in closed state into the area between the mold mounting plates and mounted onto the rotary table, with centering elements being suitably provided for centering the center platen upon the rotary table.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]     Other features and advantages of the present invention will be more readily apparent upon reading the following description of a preferred exemplified embodiment of the invention with reference to the accompanying drawing, in which:  
         [0010]      FIG. 1  is a partially sectional side view of an injection molding machine equipped with a stack mold and a rotary device according to the invention;  
         [0011]      FIG. 2  is a schematic illustration of a shifting mechanism for moving the rotary device in longitudinal direction of the machine;  
         [0012]      FIG. 3  is a schematic illustration of the stack mold with transport brackets, ring bolts and release cylinders;  
         [0013]      FIG. 4  is a top view of the rotary device according to the invention;  
         [0014]      FIG. 5  is a sectional view of the stack mold, taken along the line IV-IV in  FIG. 4 , with the left half depicting a view in the direction of the arrow A in  FIG. 1 , whereas the right half depicts a view in the direction of the arrow B in  FIG. 1 ;  
         [0015]      FIG. 6  is a plan view of a drive mechanism for rotating the rotary table; and  
         [0016]      FIG. 7 a  schematic side view of another embodiment of an injection molding machine equipped with a rotary device according to the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals.  
         [0018]     The invention will now be described in more detail by way of example with reference to a horizontal injection molding machine, generally designated by reference numeral  1  and having a machine bed  2  for support of a stack mold with a fixed mold mounting plate  3  carrying a mold portion  9  and a moving mold mounting plate  4  which carries a displaceable mold portion  10 . The moving mold mounting plate  4  is guided on a machine bed guidance  23 ,  24 ,  25  and pulled by tie bars  5 ,  6 ,  7 ,  8  ( FIG. 5 ) relative to the stationary mold mounting plate  3 . Hydraulic cylinders  26  are shown for movement of the tie bars  5 ,  6 ,  7 ,  8  (only hydraulic cylinders  26  for the tie bars  6  and  8  are visible in  FIGS. 1 and 5 ). Placed between the mold portions  9 ,  10  is a center platen  11 , denoted in the following as swivel plate. The swivel plate  11  and the mold portions  9 ,  10  are each provided with, not shown, form recesses in confronting relationship to define respective cavities. Defined between the fixed mold portion  9  and the confronting side of the swivel plate  11  is the first phase of the stack mold, whereas the second phase of the stack mold is provided between the moving mold portion  10  and the confronting side of the swivel plate  11 . Injection of material in the first phase is implemented by an injection unit  12  associated to the fixed mold portion  9 , whereas the second phase injection is realized by a, not shown, generally L-shaped injection unit which is attached to the moving mold portion  10 .  
         [0019]     The swivel plate  11  is secured on a rotary device according to the invention, generally designated by reference numeral  40 . The rotary device  40  includes a generally rectangular rotary table  13  for attachment of the swivel plate  11 . The rotary table  13  is rotatably supported on a base  14  in the form of a base plate of substantially H-shaped configuration, as shown in particular in  FIG. 4 , thereby defining rear legs  15 ,  16 , forward legs  17 ,  18  and a crosspiece  50  interconnecting the rear and forward legs  15 ,  16 ,  17 ,  18 . The crosspiece  50  and the rotary table  13  are so configured that a molded article is able to drop downwards into a free space between the legs  15 ,  16 ,  17 ,  18  of the base  14 , whereby the legs  15 ,  16 ,  17 ,  18  of the H-shaped base  14  extend to an area in proximity to the mold mounting plates  3 ,  4  at formation of a slight distance (safety distance), when the stack mold is closed, as shown in  FIG. 1  with respect to the rear legs  15 ,  16 .  
         [0020]     In case of heavy center platens  11 , additional, not shown, guides may be provided for support of the base  14 , whereby the guides project underneath the mold mounting plates  3 ,  4  to an area outside thereof. In this case, the legs  15 ,  16 ,  17 ,  18  of the H-shaped base  14  may be made of wider size, or the space between the legs of the H-shaped base  14  is more or less omitted on one or both sides of the swivel plate  11  so that the base  14  becomes effectively continuous in this area.  
         [0021]     A shaft  19  (rotor) extends downwards from the rotary table  13  and is rotatably supported in a respective stator  20  and the base  14 . The rotary table  13  is rotated on the machine bed  2  by a suitable drive mechanism, which includes e.g. a ring gear  43  mounted to the rotary table  13 . The ring gear  43  is in mesh with a pinion  44  and driven by a motor  49 , e.g. hydraulic motor or electric motor, as shown in particular in  FIGS. 5 and 6 .  
         [0022]     The base  14  is supported on stable linear guides  23  (or on slideways) on the machine bed  2 , with the machine bed  2  including stable linear rails or slideways  24 ,  25  for engagement of the complementary underside of the base  15 . Disposed between the swivel plate  11  and the mold portion  9  in the first phase of the stack mold are at least two, preferably four, hydraulic release cylinders  28  in symmetric disposition, and disposed at the partition plane between the swivel plate  11  and the mold portion  10  in the second phase of the stack mold are at least two, preferably four, hydraulic release cylinders  32  in symmetric disposition, as shown in  FIGS. 3 and 5 . The release cylinders  18 ,  32  generate during opening movement a parallel, simultaneous short stroke as additional support for a parallel opening of the stack mold.  
         [0023]     The movement of the rotary device  40  in longitudinal direction of the machine bed  2  is implemented by a shifting mechanism comprised of racks or steep-threaded spindles  36 ,  37 , articulated on both sides to the mold mounting plates  9 ,  10 , and gears  41  which are respectively attached to the base  14 , as shown in particular in  FIGS. 2 and 5 . As shown in  FIG. 4 , the finished molded articles can be expelled into the free space between the legs  15 ,  16 ,  17 ,  18  of the H-shaped base  14  and carried off by a, not shown, subjacent conveyor belt. Thus, additional handling systems for withdrawal of the molded articles can be omitted. Transport brackets  39  and ring bolts  38  ( FIG. 3 ) allow a simple assembly and disassembly of the entire stack mold as a unit. Of course, it is also possible to assemble and disassemble the mold components separately, when each mold component has ring bolts  38 , and the transport brackets  39  are loosened.  
         [0024]     Securement of the mold center platen  11  on the rotary table  13  is realized by providing in the lower region of the center platen  11  one or more grooves and by providing aligned bores in the portion of the center platen  11  that is placed on the rotary table  13 , so that screw fasteners, not shown, can be screwed through these bores into the rotary table  13 , with the screw heads being accessible via the grooves. Although not shown in detail, the rotary table  13  may be provided with centering members to allow proper alignment of the center platen  11 .  
         [0025]     Instead of a mold carrier of a stack mold, it is also possible to attach on the rotary device according to the invention other elements. For example, as shown in  FIG. 7 , a holding frame  45 , i.e. a so-called index frame or a so-called index plate, may be provided for a molded article  46 , to permit a turning of this molded article  46  from a first phase to a second phase between the mold portions  9  and  10   
         [0026]     It is also possible to transmit a media such as water, oil, air, and electric signals between the center platen  11  and the rotary table  13 , e.g. via a line  42 .  
         [0027]     While the invention has been illustrated and described as embodied in a rotary device for a horizontal injection molding machine, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.