Abstract:
In a method of making formed bodies with active ingredients, in particular for the pharmaceutical and chemical fields, active ingredients and optional additives are mixed and advanced in a screw and cylinder unit. The resultant material is then injected into a closed mold cavity of a molding tool and injection-molded in the molding tool to finished formed bodies.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application claims the priority of German Patent Application, Serial No. 102 13 977.6, filed Mar. 28, 2002, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a method of making formed bodies containing active ingredients. Examples of such formed bodies include tablets or pills in the pharmaceutical and cosmetic fields, so-called “carbonation tablets” for making beverages or also pellets in the chemical or detergent industries for producing cleaning solutions.  
           [0003]    The manufacture of tablets typically involves the production of a plate or a band of tablet material and subsequently punching out cylindrical tablets therefrom. Residue material, so-called pressed screen, has to be reshaped subsequently, which poses a problem, especially when sensitive active ingredients are involved, or the residue material has to be properly disposed of. Thus, conventional processes involve a two step process, namely the manufacture of a semi-finished product (band, plate) and the formation of the end product.  
           [0004]    It would therefore be desirable and advantageous to provide an improved method of making formed bodies containing active ingredients, which obviates prior art shortcomings.  
         SUMMARY OF THE INVENTION  
         [0005]    According to one aspect of the present invention, a method of making formed bodies with active ingredients, in particular for the pharmaceutical and chemical fields, includes the steps of mixing and advancing active ingredients and optional additives, in a screw and cylinder unit; injecting resultant material into a closed mold cavity of a molding tool; and forming the material in the molding tool.  
           [0006]    The present invention resolves prior art problems by employing an injection molding process to make formed bodies which contain active ingredients. The injection molding process is generally known from plastics processing. Hereby, a plastic material is plasticized by a screw and advanced for subsequent injection under pressure into a mold cavity of a mold. These steps may be realized in separate units, i.e. an extruder and an injection unit or in a single aggregate in which the screw combines plasticizing and injection functions.  
           [0007]    According to another aspect of the present invention, an injection mold assembly for making formed bodies with active ingredients, includes a screw and cylinder unit having a feed unit for supply of active ingredients and optional additives, with the screw and cylinder unit mixing the active ingredients and optional additives to form a resultant material and advancing the resultant material, and a molding tool having at least one mold cavity, in which the material is injected for subsequent injection molding of a formed body.  
           [0008]    According to another feature of the present invention, the screw and cylinder unit is constructed to include an extruder, e.g., a twin-screw extruder, which gently mixes and advances even sensitive materials. Of course, it is also possible to add sensitive active ingredients in controlled doses at a more downstream location into the extruder. The retention time of the active ingredients while under thermal stress and intense shearing stress is hereby significantly decreased. When two injection units are employed, such an extruder is able to operate continuously in a cost-efficient manner to produce formed bodies with constant quality. A high throughput may be implemented, when providing a molding tool with several mold cavities for simultaneously injection-molding a number of formed bodies.  
       
    
    
     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 currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:  
         [0010]    [0010]FIG. 1 shows a schematic illustration of one embodiment of an injection molding machine for making formed bodies with active ingredient in accordance with the present invention;  
         [0011]    [0011]FIG. 2 is a cutaway view of the injection molding machine of FIG. 1; and  
         [0012]    [0012]FIG. 3 shows a schematic illustration of a single-screw extruder for use in an injection molding machine for making formed bodies with active ingredient in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0013]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way.  
         [0014]    Turning now to the drawing, and in particular to FIG. 1, there is shown a schematic illustration of an injection molding machine for making formed bodies with active ingredient in accordance with the present invention, including a screw and cylinder unit in the form of a twin-screw extruder having a cylinder  10  and two screws  12 ,  14  accommodated in the cylinder  10  and operated by a motor M. The screws  12 ,  14  rotate in a same direction. Active ingredients and optional additives, fillers and binding agents are continuously introduced into the cylinder  10  via a feed unit  15  (FIG. 2) and mixed in the extruder, as the screws  12 ,  14  rotate, and at the same time advanced by the rotation of the screws  12 ,  14  into the direction of an outlet channel  16 . If desired, it is also possible to add more sensitive active ingredients in controlled doses at a more downstream zone into the cylinder  10  of the extruder, as indicated by reference numeral  15   a  and shown in FIG. 2.  
         [0015]    The outlet channel  16  connects to a three-way valve  40  by which the material flow is either routed via a passageway  46  to a first injection unit  20  for accumulation of material in an interior space  24  of the injection cylinder of the injection unit  20 , or via a passageway  48  to a second injection unit  30  for accumulation of material in an interior space  34  of the injection cylinder of the injection unit  30 . After either one of the injection units  20 ,  30  is filled, in the operating stage shown in FIG. 1, the injection cylinder of the injection unit  30 , a ram  36  is activated to move forward to thereby force the material in the interior space  34  via injection ducts  44  to an injection nozzle  46  and subsequently into the molding tool. Likewise, when the injection cylinder of the injection unit  20  is filled, a ram  26  is activated to move forward to thereby feed the material in the interior space  24  via injection ducts  42  to the injection nozzle  46  for subsequent injection into the molding tool.  
         [0016]    The molding tool has a first half-mold  54 , mounted on a fixed platen  50 , and a second half-mold  55 , mounted on a moving platen  50 , whereby each of the half-molds  54 ,  55  is provided with a plurality of mold cavities  56  for formation of formed bodies. During injection, the half-mold  54 ,  55  are clamped together to close the mold cavities  56 , and material is routed from the injection nozzle  46  via a manifold  58 , provided in the fixed platen  50 , to the mold cavities  56 . After conclusion of the injection molding process, the half-molds  54 ,  55  are moved apart to open for removal or expulsion of finished formed bodies  60  from the molding tool.  
         [0017]    The injection units  20 ,  30  are operated alternately, i.e. while the injection cylinder of one injection unit  20 ,  30  is filled with material, the other injection unit  20 ,  30  executes an injection process. As a consequence, a continuous operation of the twin-screw extruder can be realized with high material throughput.  
         [0018]    Of course, instead of a twin-screw extruder, as shown in FIG. 1, it is also possible to use a single-screw extruder, shown in more detail in FIG. 3 and generally designated by reference numeral  11 . Parts corresponding with those in FIG. 1 are denoted by identical reference numerals and not explained again. The single-screw extruder  11  includes a single screw  13  which not only assumes the functions of mixing and advancing the active ingredient but assumes also the injection function of material into the molding tool.  
         [0019]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, 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. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.