Abstract:
An apparatus for molding plastic preforms into plastic containers, includes at least one blow molding station having a cavity, within which the plastic preforms can be expanded into the plastic containers, wherein the blow molding station includes a base part that delimits the cavity and wherein the base part is releasably mounted on a carrier by a fastening mechanism. The apparatus includes a force application member to which an engageable force can be applied and which generates in a fixed condition of the base part on the carrier a holding force that keeps the base part and the carrier together.

Description:
BACKGROUND OF THE INVENTION 
     The present application relates to an apparatus for moulding plastic preforms into plastic containers. Such apparatus have been known from the prior art for a long time and usually include a plurality of blow moulding stations which are arranged on a carrier wheel and which are used for moulding plastic preforms into plastic containers by way of blow moulding. 
     Such blow moulding stations usually include two mould parts which together with a base part delimit a cavity, within which the plastic preforms are expanded. In the case of a set change-over, it is necessary to replace the base parts. In the prior art, the base parts are normally screwed onto a carrier and they therefore need to be disassembled in a relatively complex procedure in the case of an assembly change-over. Further, however, it is necessary for the base parts to be arranged in a stable manner relative to their respective carriers. 
     From EP 1 299 223 B1, an apparatus for blow moulding containers is known. Here, a base insert is provided that is connected to a positioning unit. Here, a coupling profile is used for the connection, which is formed from a coupling member connected to a base plate as well as from a counter member connected to the base member and which can be actuated by means of a manual lever in order to effect a corresponding release of the base insert. 
     U.S. Pat. No. 5,750,161 describes a quick change mechanism for a blow moulding unit. Here, a first and a second closing element are provided, wherein the second closing element is movably mounted between a position that is closed with the first closing element and a released position. 
     In the so far unpublished Patent Application DE 10 2009 035 871.4 of the applicant, a quick change mechanism for base parts is described. Here, the base mould or an adapter piece in communication with the base mould is clamped to a carrier via a rotatable connection piece. This apparatus operates satisfactorily and allows a comparatively rapid assembly and disassembly of the base parts. However, in order to clamp the base part to the carrier, a very strong force already has to be applied so as to achieve the desired final holding force. The subject matter of DE 10 2009 035 871.4 is herewith included in the subject matter of the present application by reference. 
     The present invention is therefore based on the object of providing a quick change mechanism that requires a force for assembly and disassembly, which is reduced by comparison to the described prior art. 
     SUMMARY OF THE INVENTION 
     An apparatus according to the invention for moulding plastic preforms into plastic containers includes at least one blow moulding station including a cavity, within which the plastic preforms can be or are expanded into the plastic containers. This blow moulding station has a base part that delimits the cavity, and this base part is releasably mounted to a carrier by means of a fastening mechanism. 
     According to the invention, the apparatus or this fastening mechanism includes a force application member ( 10 ) onto which an engageable force can be applied, which force application member generates a holding force on the carrier in a fastened condition of the base part, which force holds the base part and the carrier together. 
     It is therefore proposed to provide a force application member, onto which, if locking is desired, an additional force can be applied in order to generate in this way the required holding force. In this process, this holding force is preferably not generated as a result of the actual fastening process, but can be engaged by the user as and when desired. 
     Preferably, a flowable medium or a magnetic force can be applied to the force application member. For example, it would be quite possible to supply a flowable medium such as for example pressurised air and to apply in this way the engageable force onto the force application member. It would also be possible for the engageable force to be an engageable magnetic force. Thus, for example, the apparatus could include a permanent magnet or an electromagnet and the force could be engaged by activating the electromagnet, as a result of which the electromagnet and the force application member implemented as a permanent magnet repel each other, and this repulsion in turn effects the holding force. It would also be possible for the force application member itself to be implemented as an electromagnet. 
     Moreover, it would also be possible for the apparatus to include two repellent permanent magnets and for the force to be engaged in such a way that a distance between the two magnets is reduced. It would also be possible to provide an electromagnet that attracts the force application member upon activation and in this way effects the holding force. 
     In addition, it would also be possible for the engageable force to be a force that is imparted by an electric field. 
     In contrast to the described prior art, it is therefore proposed that it is not the user who has to apply all of the necessary assembly force during assembly, but that in particular during a working operation, at least a substantial or a large proportion of the holding force is also generated by the force application member onto which the flowable medium can be applied or onto which in general the engageable force can be applied. It is possible here for the force application member to be moved, for example by pressurised air, i.e. pneumatically, into a position in which it causes the base part and the carrier to be kept together. 
     The force application member can here preferably be moved in order to obtain a holding force relative to at least one further component of the fastening mechanism and in particular relative to the base part. Particularly preferably, the force application member can be moved in a straight direction and in particular in the direction, along which also the base part is moved towards the lateral parts of the blow mould or away therefrom during working operation. Preferably, the holding force is generated by a pressure applied by the flowable medium. 
     However, it would also be possible for a negative pressure or a vacuum to be used which generates said holding forces. Said holding force can act here directly between the base part and the carrier, however, it would also be possible and is in fact preferred for the holding force to be generated between other members, for example on the one hand between members mounted on the carrier and on the other hand members that are disposed on the base part. 
     It would be possible here if pressure or air pressure was applied to the force application member during working operation. 
     In an advantageous embodiment, the fastening mechanism includes at least one pin-like body disposed on a first fastening member, which body engages in a groove positioned in a second fastening member in a fastened condition of the base part on the carrier, with said pin-like body advantageously being displaceable relative to the groove. As a result of this engagement of the pin-like body in the groove, the fastening members can be orientated relative to each other. In this way, a temporary fixing or a preliminary fixing can be achieved by this mounting operation. Advantageously, however, the fastening member with the groove located therein is moved during the fixing operation. 
     In a further advantageous embodiment, the groove is designed in such a way that an end section of the pin-like body can pass through the groove in a first area and cannot pass through the groove in a second area of the groove. In this way, the groove may for example be designed like a keyhole, wherein for placing the base part on the carrier, the pin-like bodies can advantageously enter into the groove and can, for the ultimate retention thereof, preferably be in engagement with said groove. For example, the pin-like body can include at least one recess on the outer circumference thereof or can have a reduced cross section in the area of this recess. In this connection, the recess is preferably continuously formed in the pin-like body. Advantageously, the recess is designed in such a way with regard to the cross section that it can be completely displaced within the groove mentioned above. Thus, this recess comes into engagement with the groove or the edges of the groove and the pin-like body can in this way essentially no longer be moved relative to the groove in the second area of the groove in the longitudinal direction thereof or can only be moved along the width of said groove. 
     In a further advantageous embodiment, the base part is disposed on an adapter member and the adapter member is mounted on the carrier via the fastening mechanism. By means of this adapter member, different height movements of the base part relative to the blow moulding station or relative to the lateral parts can be compensated. 
     In a further advantageous embodiment, the at least one pin-like body is in communication with the base part. It is possible here for the pin-like body to be disposed directly on the base part, however, it would also be possible for the pin-like body to be disposed on the above-mentioned adapter member and this adapter member in turn on the base part. In this way, too, the pin-like body is in (indirect) communication with the base part. 
     In a further advantageous embodiment, the fastening element is rotatably arranged relative to the base part. It is possible here to rotate the fastening member about a predefined rotary axis so as to release the base part, however, it would also be possible to rotate the base part itself in order to effect the release thereof. 
     In a further advantageous embodiment, the apparatus includes at least one spring element for prestressing the pin-like body relative to the first fastening member. In a preferred embodiment, the fastening member is the above-mentioned adapter member. In this case, the pin-like body is prestressed relative to the fastening member and is preferably prestressed towards this first fastening member. 
     In a further advantageous embodiment, the first fastening member is disposed so as to be rotatable about a predefined rotary axis. Advantageously, the above-mentioned grooves extend at least partially and preferably completely in the circumferential direction of the fastening member. In this way, a release of the base part can be achieved by rotating the fastening member. Advantageously, a lever is provided on the second fastening member, by means of which the user can achieve a turning of the first fastening member. 
     In a further advantageous embodiment, a support body is provided between the first fastening member and the second fastening member in a mounted condition of the base part. Thus it is possible for the support body itself to be disposed in a stationary condition and for the base part to be placed on top of this support body. The base part can be locked relative to the carrier by turning the second fastening member without having to be rotated itself in the process. Preferably, the pin-like body/bodies extend(s) through the support body. This support body is advantageously used for centering the base part. 
     In a further advantageous embodiment, the apparatus includes at least two pin-like bodies that are spaced apart from each other. Correspondingly, preferably at least two grooves are provided in which the two pin-like bodies extend. In this way, a particularly stable locking of the base part is made possible. 
     Preferably, the two pin-like bodies are arranged opposite each other with respect to a rotary axis of the second fastening member. The grooves, too, are advantageously arranged point-symmetrically in relation to a rotary axis. 
     In a further advantageous embodiment, channels for guiding a flowable medium are provided within the first fastening member. This flowable medium may here in particular be a cooling medium for cooling the base part. Corresponding cooling channels may here be provided also in the base part itself. 
     Providing these channels for guiding a flowable medium also facilitates a quick assembly of the base part, since it becomes possible in this way not only to assemble the base part itself very quickly, but at the same time also to establish or close the necessary coolant connections. 
     Advantageously, therefore, fluid connectors are provided on the first fastening member, which extend in a longitudinal direction of the pin-like body. In this way, also the fluid connectors can be inserted into corresponding couplings when placing the base part on the second fastening member, so that in one operation also the coolant connection is established. 
     The engagement of the pin-like body in the groove, however, is here not used to generate the holding force during working connection, but only in order to build up a preliminary pressure or a preliminary holding force. 
     In a further advantageous embodiment, the force application member applies a force that urges the fastening member and the support body apart, in a condition in which a flowable medium is applied thereto. As a result of this urging-apart force, the holding force of the base part on the carrier can be achieved, as will be explained in more detail below. 
     Advantageously, a channel for the flowable medium is provided in the support body or in the fastening member. This channel is advantageously provided completely in the support body or completely in the fastening member. The flowable medium is in particular air, so that the force application member is enabled by said air pressure to exercise its force. Advantageously, said channel for the flowable medium extends in a radial direction. 
     In a further advantageous embodiment, the force application member is a piston member that is movable relative to the support body, and the flowable medium can be applied to a space between the support body and the piston member. As a result of this action on said space, the piston member can be moved away from the support body. Advantageously, the piston member is sealed relative to the support body above and below said space. To this end, for example the piston member can have a circular cross section as well as sealing means such as O-rings. This space is advantageously arranged in a ring shape around an area of the piston member. In this way, a uniform application of pressure onto the piston member becomes possible. 
     In a further advantageous embodiment, a prestressing means is provided between the support body and the second fastening member, which prestressing means urges the fastening member and the support body apart. As a result of this urging apart of the fastening member and the support body, the base part is fastened to its carrier, as will be explained in more detail below. 
     Advantageously, the apparatus also includes a reservoir for supplying a liquid medium, such as in particular pressurised air. In doing so, for example, the pressure levels that are also used for the blow moulding process may be provided for fastening the base part and the carrier. In this connection, the force by which the base part is held on the carrier may advantageously be a function of a relative position between the fastening member and the support body. Advantageously, however, the force that is applied by said prestressing means is lower than the force that is applied by the force application member during working operation. In this way it is achieved that the resistance a user has to overcome in order to release or mount the base part, is kept comparatively low. 
     In a further advantageous embodiment, the apparatus includes a second prestressing means which urges the carrier and the second fastening member apart. This second prestressing means may also be a spring. Advantageously, this second spring is weaker than the above-mentioned first spring and is preferably also weaker than the pressure that can be applied by the force application member. 
     In a further advantageous embodiment, the second fastening member is designed to be rotatable about a predefined rotary axis. This means that locking of the base part is achieved as a result of a rotary movement of said second fastening member. 
     In a further advantageous embodiment, the second fastening member is arranged to be longitudinally displaceable with regard to a predefined axis. This means that the base part can be locked by way of a pushing movement of said second fastening member. 
     The present invention is further directed to a method for fastening a base part of an apparatus for forming plastic preforms into plastic containers to a carrier. According to the invention, a holding force between the carrier and the base part is generated or increased here by applying a flowable medium to a force application member. To this end, the flowable element and in particular air is advantageously applied to an air space between the force application member and the fastening member. This holding force is advantageously generated during a working operation of the apparatus. 
     In a further advantageous method, a further holding force between the carrier and the base part is generated by a fastening mechanism, and this further holding force is lower than the force generated by the application of the force application element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and embodiments will become evident from the attached drawings, wherein: 
         FIG. 1  shows a perspective partial view of a blow moulding station of an apparatus according to the invention; 
         FIG. 2  shows a detailed view of a locking mechanism; 
         FIG. 3  shows a schematic top view of a base part; 
         FIGS. 4   a ,  4   b  show two views of a base part in an assembled condition and in a disassembled condition; 
         FIGS. 5   a ,  5   b  show two views of the base part in a fastened condition; 
         FIGS. 6   a ,  6   b  show two views of a base part in a fixed and prestressed condition; and 
         FIGS. 7   a ,  7   b  show two views of the base in a fixed and prestressed condition in which it is also under the effect of an operating force. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a partial view of a blow moulding station  1  according to the invention. This blow moulding station  1  has here lateral parts  3  (only partially shown), which together with a base part  2  (schematically shown) delimit a cavity (not shown). Reference numeral  1  identifies here the blow moulding station in its entirety. An apparatus according to the invention can comprise a plurality of blow moulding stations, which may for example be arranged on a common carrier wheel. 
       FIG. 2  shows a first view for illustrating the fastening mechanism. Here, an adapter member  4  is provided on which the base part (not shown) is fastened. On this adapter member  4 , two pin-like bodies  12  are provided, of which however only one pin-like body  12  can be seen. Further, a connector  34  is provided on the adapter member  4 , which connector is used for supplying liquid and in particular water to the coolant line located within the adapter member  4 . The adapter member  4  is here at the same time also the first fastening member in terms of the above description. Reference numeral  18  relates to the second fastening member, which is here a locking disk that is rotatably mounted about a stationary cylinder pin. 
     Reference numeral  28  relates to a support body that is disposed in a mounted condition between the adapter member  4  and the second fastening member  18 . Reference numeral  22  identifies a lever for rotating the second fastening member  18 . Reference numeral  6  identifies in its entirety the carrier on which the base part is disposed. 
     On the carrier  6 , in turn, the support body  28  is advantageously fixedly mounted. Reference numeral  32  relates to couplings into which the connectors  34  are inserted in a longitudinal direction L of the pin-like bodies  12 . 
       FIG. 3  shows a top view of part of an apparatus according to the invention, more specifically the adapter member  4  of the base part.  FIG. 1  shows here a situation in which the locking disk, i.e. the second fastening member  18  (cf.  FIG. 2 ), is open, i.e. in which the base can be attached or removed. The following figures respectively show sections along the lines A-A or B-B of  FIG. 3 . 
       FIG. 4   a  shows a section along the line A-A of  FIG. 3 . Here, too, the adapter member or the first fastening member  4  can be seen, which is indirectly disposed on a carrier  6 . This carrier  6  constitutes here a fixed unit that is fastened to the blow moulding station or the machine and that carries out the lifting movement for closing the blow mould. In the upper area of this carrier, a rotatable locking disk that can be height-adjusted along the longitudinal direction L is disposed, which may here be the second fastening member  18 . 
     Above the second fastening member  18 , a support body  28  or the base mould receptacle is provided. This support body  28  is fixedly mounted by means of fastening members  42  (such as screws) and also fixedly mounted in terms of its height (i.e. with regard to the longitudinal direction L) in relation to the carrier  6 . However, the second fastening member  18  is, as was mentioned, movable in its height to a certain extent between the carrier plate  28  and the carrier  6 , i.e. movable in the direction of the double arrow L. 
     Reference numeral  12  relates to a pin-like body that is mounted on the first fastening member  4 . The pin-like bodies  12  may here be rigidly mounted on the first fastening member  4 , however, it would also be possible for them to be prestressed relative to the first fastening member  4  using spring elements. The pin-like bodies  12  include a head  16  and a narrowed area  12   a.    
     In order to attach or remove the base, the pin-like body  12  can enter through a corresponding groove  14 , more specifically through a section  14   a  of this groove in the second fastening member  18 . In the open position as shown in  FIGS. 4   a  and  4   b , the second fastening member  18  is further pushed upwards by spring elements  33  as shown in  FIG. 4   b , so that the pin-like body  12  or the locking pin can pass through the bore  14  and initially a gap to the carrier  6  continues to remain. 
       FIGS. 5   a  and  5   b  show the fixing process for the base part. To this end, the second fastening member  18  is rotated and in this way the pin-like bodies  12  are guided via this rotary movement into the groove  14  which is designed as a keyhole-shaped groove. During the rotary movement, a certain gap  14   c  is still provided between the second fastening member  18  and the pin-like body  12  which, however, is reduced during the fixing operation and is correspondingly enlarged during the release operation. 
     Further, by rotating the second fastening member  18  it is achieved that a spring element  24  pushes the carrier plate  28  and the second fastening member  18  apart with an increasing force. To this end, spring means  24  as well as a ball  25  running in a groove are provided. This groove is positioned in the embodiment shown as an inclined surface and as a screw surface  37 . The pin-like bodies  12  will then bear against the second fastening member  18  in a prestressed condition. It will then no longer be possible to release the base part from the carrier  6 , however, the prestress effected by the spring elements  24  is too small for the working operation. The prestressing force of the spring elements  24  is deliberately selected to be so small that the forces for locking, i.e. for moving the second fastening member  18 , will not become too high. 
     Further, the second fastening member  18  is pushed downwards by the force of the spring element  33 . In this way, in the situation as shown in  FIGS. 6   a  and  6   b , the first fastening member  4  and thus also the base part is prestressed and fixed. The ball  25  will now be in its end position, where a force in an order of magnitude of between 150 N and 250 N, preferably between 180 N and 240 N, acts. The counterforce of the spring element  33  amounts to approximately 80 N. 
     Apart from that it would also be possible for the grooves to be formed with inclined surfaces in the fastening member  18  itself, and in this way a preliminary fixing of the base part is achieved as a result of a rotation of the second fastening member  18 . 
     In the situation shown in  FIGS. 7   a  and  7   b , the force application member  10  is additionally moved downwards and exercises a further force in the order of magnitude of approximately 500 N, which urges the carrier plate  28  and the second fastening member  18  apart. As a result of this force, the pin-like bodies  12  are downwardly loaded and thus the first fastening member  4  is fixedly disposed on the carrier  6 . The force application member or the piston  10  is here moved downwards by means of a pneumatic air supply  35  that supplies an air space  36 . Reference numeral  38  relates to sealing means for sealing the space  36 . The air pressure for moving the piston can here be provided from the annular channels or reservoirs which also provide the pressurised air for example for expanding the plastic containers. If the base part is to be released again, the piston member  10  is first relieved, subsequently the second fastening member can be rotated back into the opening position and finally the base part can be removed from the carrier  6 . 
     The air space  36  is here formed between the force application member  10  and the support body  28 . Advantageously, the air space  36  is designed in the shape of an annular channel. In case pressurised air is applied, the force that is uniform in the circumferential direction is applied to the force application member  10 , and this force moves said member downwards relative to the support body and thus urges the support body  28  and the second fastening member  18  apart, and the acting force is determined by the air pressure in the air space  36 . 
     Thus, for the working operation, the application member  10  in the form of the pneumatically actuated piston is then additionally engaged, which counteracts the generated operating loads (e.g. by accelerating the base mould masses). 
     The applicant reserves the right to claim all of the features disclosed in the application documents as being essential to the invention, in as far as they are novel over the prior art either individually or in combination. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Blow moulding station 
           2  Base part 
           3  Lateral parts 
           4  Adapter member, first fastening member 
           6  Carrier 
           10  Force application member, piston 
           12  Pin-like body 
           12   a  Narrowed area of the pin-like body 
           14  Groove, bore 
           14   a  Section of the groove 
           14   c  Gap 
           16  Head 
           18  Second fastening member 
           22  Lever 
           24  Spring element 
           25  Ball 
           28  Support body, support plate 
           32  Coupling 
           33  Spring element 
           34  Connector 
           35  Supply line to the air space 
           36  Air space 
           38  Sealing means 
           42  Fastening member 
         A-A Lines 
         B-B Lines 
         L Longitudinal direction