Abstract:
A device for shape-forming at least one recess in a film-type material features a die with at least one opening, at least one shaping stem that can be introduced into the opening to create the recess by shape-forming, and a clamping facility for holding the film-type material fast between the clamping facility and the die. Counter-stems which are displaceable at least within the die openings are situated in the die, whereby shape-forming regions of the shape forming stems and the counter-stems for clamping the film-shaped material are, at least in part, superimposed on each other.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to a device for shape-forming at least one recess in a film-type material, said device featuring a die with at least one opening, at least one shaping stem that can be introduced into the opening to create the recess by shape-forming and a clamping facility for holding the film-type material fast between the clamping facility and the die.  
           [0002]    It is known to manufacture base parts of blister packs, also called push-through packs, or other packaging containers with recesses or cups to accommodate contents, by means of deep-drawing, stretch-drawing or thermo-forming methods. These types of packaging may be made from thermoplastics or film-type composites, or laminates such as aluminum foils laminated with plastic films, or extrusion-deposited layers of thermoplastics.  
           [0003]    If the packaging is made from metal-containing laminates, the manufacturing process may be performed using tools comprising stems, dies and clamping facilities. During the shape forming operation, the laminate is clamped fast between the die and the clamping facility. In order to create the desired recess or cup, the laminate is pushed into the die opening by the stem, whereby the laminate is deformed by local elongation. The result is that a shaped part exhibiting one or more recesses is formed out of the originally flat laminate.  
           [0004]    In order to be able to exploit the elongation properties of the material to be thus formed, and hence to achieve recesses with a good deepening ratio i.e. large depth and small diameter, it is known from EP-A-0779143 to carry out the cold-forming deepening of metal-containing laminates in two steps. Using a first stem with a shape-forming surface of high coefficient of friction, the metal-plastic composite is pre-formed and then formed into its final shape using a second stem with a shape-forming surface of low coefficient of friction. This procedure suffers the disadvantage that two different stems have to be employed one after the other and therefore calls for a high degree of precision with respect to the positioning of both stems. In another variant, a telescopic type of two part stem is employed instead of two different stems. These stems are however complicated in design and cannot be employed for forming all the standard kinds of laminate.  
         SUMMARY OF THE INVENTION  
         [0005]    The object of the present invention is therefore to provide a device of the kind mentioned above by means of which two-stage forming can be employed for deepening purposes, achieving a good deepening ratio in a simple manner.  
           [0006]    That objective is achieved by way of the invention in that counter-stems which are displaceable at least within the die openings are situated in the die, whereby shape-forming regions of the forming stems and the counter-stems for clamping the film-shaped material can, at least in part, be superimposed on each other.  
           [0007]    The arrangement of a shaping stem and a counter-stem according to the invention offers the significant advantage over the state-of-the-art that, in a simple manner, using two successive forming steps to create a recess or cup, first the potential for forming the base part and then the potential for forming the side walls, or vice versa, can be exploited.  
           [0008]    In a preferred device according to the invention the counter-stems are positioned on a piston that can be displaced into the die along the forming axis.  
           [0009]    The surface of the forming region of the shaping stem and/or the counter-stem may locally exhibit different coefficients of friction. Because of this the friction between the shaping stem or the counter-stem and the film to be shape-formed can be adjusted such that the sliding behavior of the film on the shaping surface of the shaping stem and the counter-stem can be influenced during the forming process.  
           [0010]    The coefficient of friction of the shaping surface of the shaping stem and the counter-stem can be adjusted such that either stem is made of the appropriate material or features a corresponding coating.  
           [0011]    A low coefficient of friction is obtained e.g. using materials such as polytetrafluorethylene, polyoxymethylene (polyacetal, POM), polyethylene or polyethylene-terephthalate, or mixtures thereof. Other materials than plastics may be considered e.g. metals such as aluminum or chrome steel, in particular also with polished surfaces. Further usable materials are e.g. ceramic layers or coatings containing graphite, boron nitride or molybdenum-sulphide.  
           [0012]    Materials that may be employed to produce surfaces with high coefficients of friction are e.g. metals such as steel, or plastics such as polyacetal (POM), polyethylene, rubber, hard rubber or caoutchouc, including acrylic polymers. The metal surfaces may be given higher coefficients of friction e.g. by roughening.  
           [0013]    The outer part of the forming and counter stems in the regions of the surfaces effecting the forming may be different in shape depending on the desired shape of recess or cup. In the simplest case the shaping and counter-stems are cylindrical in shape and exhibit flat bases; however, other three-dimensional shapes such as e.g. conical, pyramid, blunted cone, blunted pyramid, segments of spheres or a drum-shape are possible. At the same time, the counter-stem may also have a corresponding shape that fits to the shaping stem.  
           [0014]    The shaping stem and/or the counter-stem may also be in two parts with a hollow cylindrical outer stem part and an inner stem part that can be slid in a telescopic manner out of the outer stem part.  
           [0015]    In a preferred version of the device according to the invention, near a clamping area at the edges of the openings of the die and the clamping device, both the die and the clamping device exhibit a substrate of material of low coefficient of friction for guiding the film. This insures that the edge of the recess is uniformly formed and pore-free.  
           [0016]    The device according to the invention is particularly suitable for producing recesses in a plastic-coated metal foil by means of cold forming, for example for manufacturing the bases for blister packs.  
           [0017]    For the purposes of shape-forming with the device according to the invention, suitable metal-plastic composite films have e.g. a metal foil of 8 to 150 μm, preferably 20 to 80 μm. Suitable metals are e.g. steel, copper and aluminum. Preferred foils of aluminum are e.g. of 98% purity or higher, whereby in particular one may employ aluminum foils of alloys of the AlFeSi or AlFeSiMn type.  
           [0018]    The plastics employed may be e.g. layers, films or laminate films of thermoplastics of the polyolefin, polyamide, polyester and polyvinylchloride series, whereby the films and film laminates may also be uniaxially or biaxially stretched. Typical examples of thermoplastics from the polyolefin series are polyethylenes, such as MDPE, HDPE, uniaxially and biaxially stretched polyethylenes, polypropylenes such as cast polypropylenes and uniaxially or biaxially stretched polypropylenes, or polyethylene-terephthalate from the polyester series. The thickness of the thermoplastic layer, in the form of a layer, film or film laminate, in the metal-plastic composite film may be e.g. 12 to 100 μm, preferably 20 to 60 μm.  
           [0019]    The metal foils and the thermoplastics may e.g. be joined together by laminate bonding, colandering or extrusion bonding into composites. To join the layers, one may employ, from case to case, laminate bonding and bonding agents, and the surfaces to be joined may be modified by a plasma, corona or flame pre-treatment.  
           [0020]    Examples of metal-plastic composite films that can be employed may have a first layer e.g. a film or laminate made up of the above mentioned thermoplastics, a second layer in the form of a metal foil and a third layer, e.g. a film or film laminate or an extruded layer made of the above mentioned thermoplastics. Further layers such as sealing layers may be fore-seen.  
           [0021]    The metal-plastic composite films may exhibit on at least one of its outer facing sides or on both outer facing sides a sealing layer in the form of a sealable film or sealing lacquer. The sealing layer is situated, for reason of its function, in the outermost layer of the composite laminate. In particular, a sealing layer may be on the outside of the composite, whereby in the case of a blister pack this sealing layer should be facing the contents side in order to perform the sealing on of the lid film or the like.  
           [0022]    Typical examples in practice of metal-plastic composite films that are formable using the device according to the invention are:  
           [0023]    oPA25/A145/PVC60  
           [0024]    oPA25/A145/oPA25  
           [0025]    A1120/PP50  
           [0026]    oPA25/A160/PE50  
           [0027]    oPA25/A160/PP60  
           [0028]    oPA25/A145/PVC100  
           [0029]    oPA25/A160/PVC60  
           [0030]    oPA25/A145/PVC, PE-coated  
           [0031]    oPA25/A145/cPA25  
           [0032]    oPA25/A160/PVC100  
           [0033]    oPA25/A160/oPA25/EAA50  
           [0034]    where oPA stands for oriented polyamide, cPA for cast polyamide, PVC for polyvinylchloride, PE for polyethylene, PP for polypropylene, EAA for ethyl-acrylic acid and Al for aluminum, and the numbers represent the thickness in μm of the layers or films. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]    Further advantages, features and details of the invention are revealed in the following description of preferred exemplified embodiments and with the aid of the accompanying drawings which show schematically:  
         [0036]    [0036]FIG. 1 a cross-section through a shaping station with a die with an opening;  
         [0037]    [0037]FIG. 2 a cross-section through a forming station with a die having a plurality of openings;  
         [0038]    [0038]FIG. 3 a plan view of the die in FIG. 2, viewed in direction A;  
         [0039]    [0039]FIG. 4 a plan view of the clamping facility in FIG. 2, viewed in direction B;  
         [0040]    [0040]FIG. 5 a longitudinal section through a version of a shaping stem with counter-stem;  
         [0041]    [0041]FIG. 6 a longitudinal section through a further version of a shaping stem with counter-stem  
         [0042]    [0042]FIG. 7 a sequence of process steps for manufacturing blister packs. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0043]    In FIG. 1 a shaping station  10  features a die  12  with an opening  14  and a clamping device  16  with clamp opening  18 . Situated in the die  12  is a piston  20  which is sealed off in a fluid-tight manner against the inner wall  22  of the die  12  by means of seals  22  and delimits with respect to the base  25  of the die  12  a cylindrical space  26 , which can be filled with hydraulic fluid  28  via pipeline  30 . The movement of the piston  20  along the direction of its z axis is controlled via a valve  32  situated in the pipeline  30 . Depending on its function, the piston  20  can be pressure-controlled and/or distance-controlled by way of the valve  32 . The distance control is symbolized in the drawing by a distance display  34 . Of course the piston movement may also be effected by means of other means e.g. mechanical means instead of hydraulic means.  
         [0044]    A distance-controlled shaping stem  36  penetrates the clamp opening  18  and can be moved in and out of the die opening  14  along a displacement axis z which coincides with the axis of the piston  20 . The base  42  of a counter-stem  40  mounted above the piston  20  lies facing the base  38  of the shaping stem along the direction of displacement z and can be advanced into the clamp opening  18 . The base  42  of the counter-stem  40  is covered with a coating  44  e.g. made of rubber.  
         [0045]    A metal-plastic composite film  46  is held under force in a clamping region  48  between the die  12  and the clamping device  16 . Next to the clamping region  48  facing the openings  14  and  18  is a ring-shaped, stepped recess  50  and  52  respectively in the periphery of the die  12  and that of the clamping device  16 . In the recesses  50 ,  52  is a ring-shaped insert  54  and  56  respectively made of a low-friction material. The film  46  slides between the inserts  54 ,  56 .  
         [0046]    The formation of a recess or cup  58  by shape-forming the film  46  clamped between the die  12  and the clamping device  16  is readily understood from FIG. 1. The film  46 , lying initially in a plane E in which it is clamped, is plastically deformed as it is pressed by the shaping stem  36  into the die opening  14 . In that process the recess  58  is formed with side wall  60  between shaping stem  36  and the inner wall  24  of the die and a base part  62  which corresponds to the base  38  and the shaping surface of the shaping stem  36 .  
         [0047]    The shaping station shown in FIGS.  2  to  4  differ from that in FIG. 1 in that the die  12  and the clamping device  16  feature a plurality of openings  14 ,  18 , in the present case  15  openings, and a pair of shaping stems  36  and counter-stems  40  facing each pair of openings  14 ,  18 . The shaping stems  36  are mounted on a support plate  64 . Displacement of the support plate  64  in direction z leads to simultaneous displacement of all shaping stems  36 . In the same manner all counter-stems  40  are mounted on a common piston  20  with the result that, on displacing the piston in the direction z, the counter-stems  40  are also displaced simultaneously. This forming station enables therefore the simultaneous formation of a number of recesses or cups  58  in the metal-plastic composite, corresponding to the number of shaping stems  36  and counter-stems  40 .  
         [0048]    The shaping stem  36  shown in FIG. 5 is made up of various parts  66 ,  68 ,  70  of materials of different friction coefficients. The surface  38  of the shaping stem  36  effecting the shape forming is comprised of the flat base  66  and the concentric, successively inclined side walls  68 ,  70 . The surface  38  effecting the shaping extends over all of the parts  66 ,  68 ,  70 . The surface areas  66 ,  68 ,  70  effecting the shaping may therefore have different coefficients of friction. For example, the parts  66 ,  68 ,  70  are of materials with increasing friction coefficients, whereby the base part  66  exhibits the lowest coefficient of friction.  
         [0049]    The shape of the base  42  of the counter-stem  40  coated e.g. with a rubber liner  44  matches that of the shape-effecting surface  38  of the shaping stem  36 .  
         [0050]    The version of shaping stem  36  shown in FIG. 6 is telescopic in structure and exhibits a first hollow-cylindrical stem  36   a  with a first ring-shaped shape-effecting surface  38   a.  Sliding in this first stem  36   a  is a moveable second stem  36   b  with a second shape-effecting surface  38   b.  This two part shaping stem  36  permits shaping with the shaping stem  36  in two steps. As in FIG. 5, the base  42  of the counter-stem  40  matches the shape-effecting surface of the shaping stem  36 , whereby a ring-shaped base part  42   a  faces the ring-shaped surface  38   a  of the shaping stem  36  and a further base  42   b  faces the shape-effecting surface  38   b  of the inner stem  36   b.    
         [0051]    In a process for manufacturing blister packs illustrated in FIG. 7 the metal-plastic composite  46  is unrolled from a roll  106  and fed discontinuously into through a shape forming station  100 . In a subsequent filling station  102  the recesses  58  are filed with contents  108  such as e.g. tablets. On advancing the shaped and filled film  46  further, a lid film  112  made e.g. of plastic-coated aluminum foil, unrolled from a storage roll  110 , is laid on top of the metal-plastic composite film  46  and sealed to it, producing the finished blister pack. The blister packs made in the form of an endless strip can then be cut into packs of the desired size.  
         [0052]    In the following, using the example shown in FIG. 1, the manner in which the shaping stem  36  and counter-stem  40  operate is explained in terms of four examples of shape-forming.  
       Shape-forming Example 1  
       [0053]    The film  46  is held, clamped between the die  12  and the clamping device  16 . The shaping stem  36  is advanced until it makes contact with the film  46  at the level of clamping E. On the opposite side, the counter-stem  40  is likewise advanced until it meets the unstretched film  46 . Via the piston  20  a preselected pressure is applied, clamping the film  46  between the base  38  of the shaping stem  36  and the base  42  or rubber cover  44  of the counter-stem  40 . The force of the shaping stem  36  is chosen to be greater than the force applied by the counter-stem  40 . As a result the shaping stem  36  penetrates the die opening  40  and at the same time pushes back the counter-stem  40 . In this first shaping step the film is stretched in a controlled manner in the side wall part  60  of the recess  58  being formed, until the forming potential of the film in the side wall part  60  is exhausted. After the elongation of the side wall part  60 , the piston  20  is drawn back along with the counter-stem  40  into its original position. In a second shaping step, the base part  62  of the recess  58  being formed is shaped by advancing the shaping stem  36  against the film  46  which up to then had been clamped against the base  42  of the counter-stem  40 .  
       Shape-forming Example 2  
       [0054]    The film  46  is held, clamped between the die  12  and the clamping device  16 . The piston  20  along with the counter-stem  40  is thereby withdrawn to its starting position. The shaping stem  36  is advanced into the die opening  14  up to a pre-selected position in which the full shape-forming potential in the base part  62  of the recess  58  being formed is reached. In this first shape-forming step the film  46  is stretched mainly in the base part  62 . In a second step the piston  20  along with the counter-stem  40  is advanced with pre-selected pressure towards the shaping stem  36  and onto the film  46  resting on the base  38  of the shaping stem  36 . Thereby, that part of the film  46  which forms the base part  62  of the recess  58  being formed is held, clamped between the base  38  of the shaping stem  36  and the base  42  or the rubber cover  44  of the counter-stem. The force of the shaping stem  36  is now chosen to be greater than that of the counter-stem  40 . The shaping stem  36  and the counter-stem  40  move therefore with the clamped film  46  towards the base  25  of the die  12 , whereby the side wall part  60  of the recess  58  being formed is stretched until the shaping potential of the film in the side wall part  60  has been fully exploited. When the shaping potential of the film  46  has been fully exploited, the shaping stem  36  and the counter-stem  40  move back to their starting positions.  
       Shape-forming Example 3  
       [0055]    The film  46  is held, clamped between the die  12  and the clamping facility  16 . The shaping stem  36  is moved back to its starting position. The counter-stem  40  moves to that position in the clamping device opening  18  at which the potential for shape forming the film in the base part  62  of the recess being formed has been fully exploited. Thereby, the base  42  of the counter-stem  40  exhibits a surface with a high coefficient of friction, with the result that the shape-forming potential of the film in the side wall part  60  of the recess  58  being formed is fully exploited in this first shape-forming step. After exhausting the shape-forming potential of the film in the side wall part  60 , the piston  20  is drawn back again to the starting position along with the counter-stem  40 . In a second shape-forming step the shape-forming stem  36  is moved into the die opening  14  until the shape-forming potential of the film in the base part  62  of the recess  58  being formed has been exhausted. To this end the surface of the base  38  of the shaping stem  36  exhibits a low coefficient of friction. In the first shaping step the film  46  may also be clamped between the shaping stem  36  and the counter-stem  40 .  
       Shape-forming Example 4  
       [0056]    The film  46  is held, clamped between the die  12  and the clamping facility  16 . The shaping stem  36  is moved back to its starting position. The piston  20  with the counter-stem  40  is moved to a pre-selected position in the clamping device opening  18  at which the shape-forming potential of the film  46  in the base part  62  of the recess  58  being formed has been fully exploited. To that end the surface of the base  42  of the counter-stem  40  exhibits a low coefficient of friction. After this first shape-forming step the piston with the counter-stem  40  is moved back to its starting position. In a second shape-forming step the shaping stem  36 , the base  38  of which has a surface with a high coefficient of friction is moved to a pre-selected position in the die opening  14  until the shape-forming potential of the film in the side wall part  60  has been exhausted. In the second shape-forming step the film  46  may also be clamped between the shaping stem  36  and the counter-stem  40 .