Abstract:
In a single-component or a multi-component injection molding machine with a nozzle-side clamping plate firmly connected to a machine bed and a closing-side clamping plate supported on the machine bed so as to be movable thereon relative to the nozzle-side clamping plate, and each clamping plate carries a mold half of an injection-molding tool, the mold half or a part of the mold half on the closing-side clamping plate is rotatable about an axis of rotation extending in closing direction and is axially movable along the axis of rotation. In the closing-side clamping plate, a motor is received and which a rotatable shaft extends through the motor and is rotatable by the motor for rotating the mold half connected to the closing side clamping plate.

Description:
[0001]    This is a continuation-in-part application of international application PCT/EP02/00482 filed Jan. 18, 2002 and claiming the priority of German applications 101 02 692.7 filed Jan. 22, 2001 and 101 45 461 filed Sep. 14, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a single- or multi-component injection molding machine with a nozzle-side clamping plate firmly connected to a machine bed as well as a closing-side clamping plate which is movable relative to the nozzle-side clamping plate, wherein both clamping plates carry each a mold half of an injection-molding tool and wherein at the nozzle-side one or several injection units are provided for supplying one or more thermoplastics to the nozzles.  
           [0003]    For a better understanding of the object on which the present invention is based, such an injection-molding machine is explained below on the basis of an example of a two-component injection-molding machine with reference to FIGS.  1  to  5 .  
           [0004]    [0004]FIG. 1 is a schematic representation of a two-component injection molding machine according to the state of the art. The injection-molding machine  1  comprises a stationary machine bed  2  with a support plate  3  firmly connected thereto. The functions of an injection-molding machine as described below can be realized with a machine, which does or does not include guide bars.  
           [0005]    On the machine bed  2 , a closing unit for an injection molding tool is disposed. Shown is a two-component tool, which operates according to the principle of an indexing turntable  7   a.    
           [0006]    When, below, an operating piston  5  is referred to, it is to be understood that a drive mechanism is meant, which comprises a bell crank and/or a closing cylinder.  
           [0007]    The closing unit comprises a movable clamping plate  4 , which is slidable on the machine bed  2  by the operating piston  5  in the direction of the arrow a. The clamping plate  4  is defined as so-called “closing-side clamping plate”. On the movable closing-side clamping plate  4  a first ejector-side mold half  6  of an injection molding tool with a first mold nest  7  ( 7   a  and  7   b ) is disposed. This mold nest consists of a rotatable indexing plate  7   a  and a mold insert  7   b . Opposite the closing-side clamping plate  4 , a nozzle-side clamping plate  8  is disposed which is firmly connected to the machine bed  2 . By this clamping plate  8 , the so-called nozzle-side is defined. On the nozzle-side clamping plate  8 , the second mold half of the injection molding tool  9  is disposed which, again, includes a second mold nest (not shown), which is complementary to the first mold nest  7 . At the backside of the nozzle-side clamping plate  8 , two injection units  10 ,  11  are disposed.  
           [0008]    Upon closing the two mold halves  6  and  9 , the operating piston  5  biases the closing-side clamping plate  4  against the stationary nozzle-side clamping plate  8 . In this way, the two mold halves  6  and  9  are engaged with each other. In the interior thereof cavities are formed by the first mold nest  7  and the second mold nest, which is complementary thereto. With the two-component injection molding machine shown in FIG. 1, an upper cavity  13  is formed which is in communication with the upper injection molding unit  10  and a lower cavity, which is in communication with the lower injection molding unit  11 . With the two injection molding units  10 ,  11 , two different and/or the same plasticized thermoplastics can be injected into the upper and the lower cavity  13 ,  12 . The first thermoplastic may be for example a thermoplastic material, which is relatively hard after hardening and onto which, for example, a relatively soft sealing lip is injection molded using the second thermoplastic; or the first thermoplastic is transparent and the second thermoplastic is opaque.  
           [0009]    During the manufacture of so-called two component injection molding parts with the injection molding machine shown in FIG. 1, it is desirable during mass production that a second thermoplastic, which is introduced by way of the upper injection-molding unit  10 , is attached, for example, to a first thermoplastic which has been introduced into the lower cavity  12  by way of the lower injection molding unit  11 .  
           [0010]    For this purpose, different methods are known for bringing an unfinished injection molded body, which has been formed in the lower mold cavity  12  from the first thermoplastic, into the operating range of the upper injection molding unit  10  to provide there for the attachment, by injection-molding, of the second thermoplastic. To this end, it is known to utilize, at the ejection-side mold half, a rotating structure, which will be described in greater detail below, and which is mounted to the front side of the clamping plate  4 . The two-component injection molding method will be described in detail further below.  
           [0011]    [0011]FIG. 2 shows, different from FIG. 1, the section of an injection molding machine  1  with bars  14  in a view, which is detailed with respect to FIG. 1. Shown is a closing unit to be inserted into an injection-molding machine in a perspective exploded view. With the different kind of representation of FIG. 1 and FIG. 2, it is intended to be indicated that there are different types of machines in the injection molding field.  
           [0012]    The movable closing side clamping plate  4  is guided at its four corners by guide bars  14 . The guide bars  14  extend each between the support plate  3  shown in FIG. 1 and the nozzle-side stationary clamping plate  8 . The clamping plate  4  is movable along the bars  14  in the direction of the arrow a by an operating piston  5  (not shown in FIGS. 2 and 3). In addition, the clamping plate  4  has a central opening  15 , through which linear motion transmission elements, which are connected to an ejection unit, (not shown in FIGS. 2 and 3) can act on a stud  16  or a rotatable shaft  25  (FIG. 4), which is disposed at the rear end of a closing side tool engagement plate  17  of the molding tool in front of the closing-side clamping plate  4 . By way of the stud  16  or the rotatable shaft  25 , the sliding movement of the ejection unit (not shown) can be transmitted to the ejector pins (see FIGS. 4 and 5, reference numeral  28 ) in order to eject finished injection-molded pieces out of the closing-side mold half  6 . In FIG. 2 the closing-side mold half is in the form of a sandwich structure, which comprises the tool engagement plate  17 , support webs  18  disposed thereon and a closing-side molding plate  19  disposed on the support webs.  
           [0013]    The ejection pins are disposed between the closing-side tool engagement plate  17 , the support webs  18  and the closing-side mold plate  19 . The closing-side mold nest  7  shown in FIG. 1 consisting of a rotating indexing plate  7   a  and the mold insert  7   a  is integrated into the mold plate  19 .  
           [0014]    During movement of the closing unit into a closed position, the closing-side clamping plate  4 , together with the tool engagement plate  17 , the support webs  18  and the closing-side mold plate  19  disposed on the closing-side clamping plate  4  are pressed onto the nozzle-side mold half  9 , which consists of a nozzle-side molding plate  20  and a nozzle-side tool engagement plate  21 . In this way, the two molding plates  19 ,  20  are placed on top of each other along the separation plane W shown in FIG. 3 and define in their interior the injection-molding cavities.  
           [0015]    In connection with two-component injection molding procedures, it is known in practice to remove an unfinished injection molded body formed in the first cavity from the first cavity upon retraction of the closing side clamping plate and place it—using a robotic arm—into the second cavity  13 . Upon closing the clamping plate  4  again, the second thermoplastic material component is then injected into the second cavity  13  to be added to the unfinished injection molded body. At the same time, a new unfinished injection molding body of the first thermoplastic material can be formed in the first cavity  13  from which the unfinished injection molded body has been removed by the robotic arm. However, as a result of the transfer of the unfinished molded body by a robotic arm, the effective cycle times are relative long with this procedure and, furthermore, an expensive robotic mechanism is required.  
           [0016]    It is also known from the state of the art to engage the closing-side mold half  6  not directly with the closing-side clamping plate  4 , but rather to mount it on a so-called turntable  23  (FIG. 4). Upon movement of the clamping plate  4  onto the nozzle-side clamping plate  8 , a first cavity is formed for example by the lower closing-side mold nest and the lower nozzle-side mold nest, into which the first thermoplastic material is injected. Upon opening of the closing-side clamping plate  4 , the unfinished injection molded body remains in this case in the closing-side lower mold nest.  
           [0017]    The turntable  23 , which is generally operated by a toothed rod and a gear cooperating therewith or by a motor and a gear is rotated upon retraction of the clamping plate  4  together with the mold half  6  disposed on the turntable  23  by 180°. After the tool has again been closed, the previously lower (now upper) closing-side mold nest and the upper nozzle-side mold nest form a second cavity, in which the unfinished injection molded body is embedded. Now the second thermoplastic material is injected and is attached to the unfinished molded body. At the same time, the previously upper (now lower) closing-side mold nest and the lower nozzle-side mold nest form a first cavity into which first thermoplastic material is injected to form another unfinished molded body during the same time in which the first unfinished molded body is completed in the upper cavity.  
           [0018]    When the closing-side clamping plate  4  is again retracted the completed injection molded body is removed from the upper cavity and the turntable  23  with the second injection molded unfinished body embedded in the lower mold nest is again turned by 180° so that the cycle starts anew.  
           [0019]    Although the use of a turntable  23  as described above has the advantage that the effective cycle times are noticeably reduced when compared with the use of a robotic arm removal technique, a problem remains in that the turntable  23  has to be driven by an external drive mechanism (hydraulic piston linkage or a mechanism with a gear and a toothed rod or an electric motor). As a result, the arrangement is relatively large and heavy so that relatively long periods are required for a conversion upon disassembly or the exchange of a turntable  23 .  
           [0020]    Also, the opening stroke of the molding tool is substantially reduced because of the large installation depth of the rotating unit between the two clamping plates. This often requires the use of a larger and therefore less economical injection-molding machine as it would be necessary based on the size of the injection-molded body.  
           [0021]    [0021]FIG. 4 is a cross-sectional view of such a known rotating unit. A closing-side clamping plate  4 , which is movably supported on a machine bed is provided with a central opening  15 . On the closing side clamping plate  4 , a rotatable unit  22  is disposed. The rotatable unit  22  comprises a turntable  23 , which is connected to the clamping plate  4  and a gear  24  mounted centrally on the turntable  23 .  
           [0022]    A tool support plate  17  is disposed on the rotatable unit  20 . Support webs  18  are disposed on the support plate  17 . In the mold plate  19  which is supported by the support webs, the lower as well as the upper cavities  12  and  13  are provided into which the ejector pins  28  extent from the backside thereof.  
           [0023]    In this embodiment, the rotatable shaft  25  is axially movable relative to the gear  24  in the direction of the arrow a. This axial movement of the rotatable shaft  25  is achieved by a cylinder drive (not shown). The rotatable shaft  25  is provided along its length with a multi-groove profile, which transmits the angular positions of the gear  24  to the rotatable shaft  25 . The drive of the gear  24  in the turntable  23  is always a direct drive. When the two mold halves are engaged with each other, the rotatable shaft  25  is moved axially out of the mold nest  7  and the rotatable indexing plate  7   a  is turned by 180°.  
           [0024]    If, for certain applications, the maximum travel distance x (FIG. 1) is to be utilized the turntable  23  has to be removed from the arrangement as shown in FIGS. 4 and 5. Depending on the size and the dimensions of the toothed rod  26  and the hydraulic cylinder  27 , this may require extensive conversion efforts. The expensive internal support in the rotatable plate makes it also susceptible to servicing. It is particularly noteworthy that, in turntable drives with external hydraulic connections, also leaking problems occur frequently.  
           [0025]    It is the object of the present invention to overcome the disadvantages of the state of the art explained in connection with the description of FIGS. 4 and 5.  
           [0026]    In accordance with the invention, this is solved by the measures of claim 1.  
           [0027]    The dependent claims relate to preferred embodiments of the present invention.  
           [0028]    The advantages and features of the present invention are apparent from the following description of embodiments in connection with the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 shows schematically the design of a known injection-molding machine in a perspective view;  
         [0030]    [0030]FIG. 2 is a schematic exploded view of an opened molding tool as it is used in an injection-molding machine as shown in FIG. 1;  
         [0031]    [0031]FIG. 3 is a schematic exploded view of a closed molding tool;  
         [0032]    [0032]FIG. 4 is a cross-sectional view of a known closing-side clamping plate including a molding tool half for use in a two-component injection molding machine mounted onto an the support plate;  
         [0033]    [0033]FIG. 5 is a front view of the molding tool half of FIG. 4;  
         [0034]    [0034]FIG. 6 shows a cross-sectional representation of a movable closing-side clamping plate including a molding tool half mounted thereon for use according to the invention in connection with a two component injection molding machine;  
         [0035]    [0035]FIG. 7 is a front view of the molding tool half shown in FIG. 6 of an injection molding machine according to the invention;  
         [0036]    [0036]FIG. 8 shows a section corresponding essentially to FIG. 6 of a movable closing-side clamping plate including a mold tool half mounted thereon and an outwardly moved indexing turntable;  
         [0037]    [0037]FIG. 9 shows an injection-molding machine according to the invention; and  
         [0038]    [0038]FIGS. 10 and 11 are cross-sectional views of a mold half mounted on a support plate and including a forwardly projecting or, respectively, recessed motor for centering with a stepped tool clamping plate. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0039]    The two-component injection molding machine according to the invention as shown in FIGS. 6 and 7 includes in the closing-side clamping plate  4  a center opening  15 , in which the rotatable shaft  25  of a drive a motor  31  inserted into a recess of the clamping plate is supported. The motor  31  is disposed in the recess so as to be essentially flush with the outer surface  4   a  of the clamping plate  4 .  
         [0040]    In the embodiment of the invention as shown in FIGS. 9 and 10, the motor  31  projects slightly from the recess or is slightly recessed and the tool mounting plate is provided with a corresponding step for centering the injection-molding structure.  
         [0041]    The motor  31  is preferably a hydraulic motor, which is driven by a liquid or gaseous drive medium that is admitted by way of an admission channel  32 . A corresponding outlet channel  33  for the drive medium is shown in FIG. 7. In the view of FIG. 6, it is disposed behind the admission channel  32 . A reversal of the flow direction from the outlet channel  33  to the supply channel  32  reverses the direction of rotation of the motor. In front of the clamping plate  4 , there is the closing-side mold half which consists in the embodiment shown in FIGS. 6 and 7 of a tool support plate  17 , support webs  18  and a closing-side mold plate  19  as well as an indexing turntable  7   a . In this embodiment, the tool support plate  17  is firmly connected to the closing-side clamping plate  4 . The support webs  18  and the closing-side mold plate  19  are firmly connected to the tool support plate  17 . In the closing-side mold plate  19 , an upper and a lower mold nest  29 ,  30  are integrated in an indexing turntable  7   a  according to FIG. 6. The indexing turntable  7   a  is firmly connected to the rotatable shaft  25 .  
         [0042]    This same arrangement is also shown in FIG. 9. In the center of the motor  31  shown in FIGS. 6 and 7 a rotatable shaft  25  which extends through the motor  31  is supported in a bearing hub. The motor  31  and the rotatable shaft  25  are so designed that the rotatable shaft  25  can be moved axially in any angular position in the direction of the arrow a of FIG. 6. Furthermore, because of the form-fitting connection of the hub and the shaft, any angular position can be transmitted to the rotatable shaft  25 . The rotatable shaft rotates with the indexing turntable  7   a . In this way, the indexing turntable  7   a  can be turned by 180°, whereby the cavity  12  shown in FIG. 6 at the bottom can be moved upwardly into the position of the upper cavity  13  as shown in FIG. 6.  
         [0043]    Alternatively, a closing-side mold half may also be so designed that for example the tool support plate  17  is not firmly connected to the closing-side clamping plate  4 , but the whole arrangement of the closing-side mold half  6  consisting of the tool support plate  17 , the support webs  18 , the closing-side mold plate  19  and the indexing turntable  7   a  is connected to the rotatable shaft  25 . Depending on the design of the closing side mold half, the closing side mold half is turned completely with the rotatable shaft and/or is axially displaced or only parts therefore are rotated or moved axially.  
         [0044]    In FIGS. 10 and 11, a closing side-clamping plate  4  with a center opening  15  is shown, in which the rotatable shaft  25  is supported in a motor  31  which is integrated into the clamping plate  4 . The motor  31  is disposed in a recess in the clamping plate  4  and, in contrast to the arrangement as shown in FIG. 6 and, respectively, FIG. 8, is not disposed flush with the respective engagement surface of the clamping plate  4 . Rather, the motor is either recessed or it projects from the surface. In this way, centering during assembly of the molding tool is facilitated. The additional function of the motor of centering the molding tool reduces the set-up periods and facilitates servicing.  
         [0045]    With the design according to the invention, a highly compact arrangement for the closing unit of a multi-component injection molding machine is obtained wherein the complete closing-side mold half  6  or parts thereof and the machine-side mold half  6  are rotatable relative to each other. At the same time, the open space (travel distance x) between the closing-side and the nozzle-side clamping plates is not reduced by the installation of an additional rotating unit as it is the case in the state of the art arrangements described in connection with FIGS. 4 and 5 because of the turntable  23  used in that case.  
         [0046]    Since, in the injection-molding machine according to the invention, the motor  31  is firmly integrated into the closing-side clamping plate  4 , the additional advantage is obtained that a permanently integrated rotating function for molding tools to be mounted to the closing-side clamping plate is provided. Whereas, in a prior art injection molding machine of a design as described in connection with FIGS. 4 and 5, part of the engagement pressure must be accommodated by the housing of the gear  24  when the tool is closed, with the solution according to the invention, that is, with the integration of the motor  31  into the clamping plate  4 , all pressure forces, which are effective when the tool is closed are accommodated by components which are specifically designed for that purpose. This has the additional advantage that motors of compact design can be integrated into the closing-side clamping plate  4 .  
         [0047]    [0047]FIG. 8 shows an arrangement corresponding to that of FIG. 6. As shown, the rotating shaft  25  is displaced in axial direction forwardly (toward the machine side of the injection-molding machine), whereby the indexing turntable  7   a  can be rotated. By retracting the rotatable shaft  25  in axial direction the rotated turntable  7   a  is again returned into the closing-side mold plate  19 . The previously lower part of the mold nest  30  is then moved to the top so that a second thermoplastic material can be injected and attached to the unfinished injection molded body contained therein.  
         [0048]    With the arrangement according to the invention a novel tool- and injection molding machine concept of a very compact design for the closing unit of a single- or multi-component injection molding machine with relatively rotatable mold halves and/or molding elements has been created. The same principle can be used also for molding tools, which include more than two mold nests for more than two different thermoplastics.  
         [0049]    It is of course also possible to mount molding tools, which do not need to be rotated, on the same clamping plate  4  without removal of the motor  31 , which is firmly integrated into the closing-side clamping plate  4 , that is, the injection-molding machine according to the invention can also be operated without utilizing the rotating function of the motor.  
         [0050]    Furthermore, the release of hydraulic oil at external hydraulic connections upon exchanging the rotating drive is eliminated. Whereas in a known injection-molding machine of a design as described in connection with FIGS. 4 and 5, with a closed tool, a part and/or all of the hydraulic pressure must be accommodated by the hydraulic motor housing, in the arrangement according to the invention wherein the motor  31  is integrated into the clamping plate  4  all pressure forces are accommodated by the clamping plate  4  and the tool mounting plate  17  when the tool is closed. In contrast to the state of the art, wherein, with the arrangement as shown in FIG. 4, the motor housing must be dimensioned sufficiently large to be able to accommodate the high pressure forces present in the injection-molding machine, with the integration of the motor  31  into the closing-side clamping plate  4 , a motor  31  of substantially smaller, compact design can be provided since it is protected from exposure to high closing pressures by the clamping plate  4 .  
         [0051]    Instead of hydraulic motors, electric motors can be utilized. However, the use of a hydraulic motor with a hydraulic drive medium has the advantage that this medium can also be used as coolant for the clamping plate  4 .  
         [0052]    On the other hand, with the use of an electric motor, the rotatable mold half can be rotated in either direction and without any mechanical stops to any angular position by freely programmable movement control performance graphs.  
         [0053]    This electric motor drive concept offers further the possibility to employ molding tools, which must not be contacted by hydraulic oil. There is no danger of oil contamination of the injection cavities. The use of an electric motor also results in substantially faster machine cycles since an electric motor reacts substantially faster than a hydraulic motor. As a result, the production cycle speed is increased. Furthermore, the operating expenses of electric motors are lower.