Abstract:
Disclosed are a molded article picker for a post-mold device and a related method for the use of the molded article picker for handling a molded article. The molded article picker includes a floating element being configured to be movable between an extended position and a retracted position and biased in the extended position. Furthermore, the molded article picker comprises a pressure structure extending through the floating element. The floating element is cooperable with the molded article to define a substantially enclosed volume including the pressure structure. The pressure structure is configured such that by evacuating the substantially enclosed volume the molded article is sealed to the floating element and the floating element is drawn into the retracted position, thereby transferring the molded article to the molded article picker.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to molded article pickers, and more specifically the present invention relates to, but is not limited to, a post-mold device including such a molded article picker, a molding system including the post-mold device, and a related method for the use of the molded article picker for handling a molded article. 
       BACKGROUND OF THE INVENTION 
       [0002]    A lot of injection molded articles, for example plastic preforms of the variety that are for blow molding into beverage bottles, require extended cooling periods to solidify into substantially defect-free molded articles. To the extent that the cooling of the molded article can be effected outside of the injection mold by one or more so-called post-mold devices, the productivity of the injection mold may be increased (i.e. by reducing the cycle time). A variety of such post-mold devices, and related methods, are known and have proven effective in optimizing, i.e. reducing, the injection molding machine cycle time. 
         [0003]    In a typical injection molding system a just-molded, and hence only partially cooled, molded article is ejected from the injection mold and into a post-mold device, commonly known as a take-out device or end-of-arm-tool (EOAT), having a plurality of cooled carriers (otherwise known as a cooling tube, take-out tube, cooling sleeve, amongst others) for post-mold cooling of the molded article outside of the mold. 
         [0004]    U.S. Pat. No. Re. 33,237 describes a post-mold device for removing partially cooled injection molded preforms from the core side of an injection mold. The preforms are ejected from the mold directly into cooled carriers (such as that described in commonly assigned U.S. Pat. No. 4,729,732), and transported by the post-mold device to an outboard position adjacent the mold. The post-mold device may include multiple sets of carriers to accommodate multiple sets of preforms (i.e. multiple shots or batches of preforms). 
         [0005]    Commonly assigned U.S. Pat. No. 6,171,541 describes another post-mold device that includes a set of cooling pins for insertion into the interior of a partially cooled preform, the preform arranged in a cooled carrier of a first post-mold device, to discharge a cooling fluid therein. An example of the foregoing is sold under the trade name of COOLJET, a trade-mark of Husky Injection Molding Systems Limited. 
         [0006]    Commonly assigned U.S. Pat. No. 7,104,780 describes a post-mold device similar to that of the &#39;541 patent further including molded article pickers for removal of the preform from the cooled carrier of the first post-mold device. The molded article picker includes a pin operable to cooperate with a vacuum source to evacuate a volume defined within the preform to cause the preform to remain therewith as the molded article picker is moved away from the carrier. The second post-mold device, mounted to a frame, may be rotated by 90 degrees to a discharge position and the vacuum to the molded article pickers may be terminated to allow the preforms to fall off the pins. 
         [0007]    An example of the foregoing post-mold device is sold under the trade name of COOLPIK, a trade-mark of Husky Injection Molding Systems Limited. The molded article picker of the second post-mold device further includes a sealing surface disposed on a front face of a tooling plate to sealingly cooperate with a front face of the preform in response to the evacuation of the volume. According to this solution the preform is transferred over a small gap between the front face of the preform, arranged in the carrier of the first post-mold device, and the sealing surface of the molded article picker. 
         [0008]    Although the above solution already constitutes a substantial improvement with respect to the prior art it has been found that in practice the transfer of the molded article from a carrier to the molded article picker sometimes fails. It is believed that this improper transfer is caused by an insufficient vacuum applied and the air flow resulting therefrom to transfer the molded article across the gap between the front face of the molded article and the sealing surface of the molded article picker. This occurs especially with molded articles having a shallow draft on the outside thereof. Consequently, it can happen that molded articles are not transferred properly, i.e. are left in the carrier, and, thus, block this carrier for the introduction of a molded article of the next shot of molded articles, which for obvious reasons is highly undesirable. 
         [0009]    There is, thus, a need for a molded article picker providing for an improved reliability of transfer of a molded article from a carrier on a first post-mold device to such a molded article picker on a second post-mold device. 
       SUMMARY OF THE INVENTION 
       [0010]    According to a first aspect of the present invention, there is provided a molded article picker for a post-mold device for transferring a molded article. The molded article picker includes a floating element being configured to be movable between an extended position and a retracted position and a pressure structure. The floating element is cooperable with the molded article to define a substantially enclosed volume including the pressure structure. The pressure structure is configured such that by evacuating the substantially enclosed volume the molded article is sealed to the floating element and the floating element is drawn into the retracted position, thereby transferring the molded article to the molded article picker. 
         [0011]    According to a second aspect of the present invention, there is provided a post-mold device including a tooling plate and a molded article picker as described in the previous section arranged on the tooling plate. 
         [0012]    According to a third aspect of the present invention, there is provided a molding system comprising a post-mold device, having a tooling plate and a molded article picker as described above arranged on the tooling plate for transferring a molded article. 
         [0013]    According to a fourth aspect of the present invention, there is provided a method for transferring a molded article, comprising the steps of bringing a floating element of a molded article picker in an extended position, at least in part, into abutment with a surface of the molded article and evacuating the enclosed volume defined by the molded article and the floating element such that the molded article is sealed to the floating element and the floating element is drawn into a retracted position, thereby transferring the molded article. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    A better understanding of the exemplary embodiments of the present invention (including alternatives and/or variations thereof) may be obtained with reference to the detailed description of the exemplary embodiments along with the following drawings, in which: 
           [0015]      FIG. 1  is a plan view of an injection molding machine including a presently preferred embodiment of the molded article picker being arranged on a tooling plate of a post-mold device; 
           [0016]      FIG. 2  is a plan view of a partially assembled tooling plate of a post-mold device that includes the presently preferred molded article picker. 
           [0017]      FIG. 3  is a sectional view of the molded article being transferred from a carrier to the presently preferred embodiment of the molded article picker with the floating element in the extended position; 
           [0018]      FIG. 4  is a sectional view of the molded article being transferred from the carrier to the presently preferred embodiment of the molded article picker with the floating element in the retracted position; 
           [0019]      FIG. 5  is a sectional view of an alternative embodiment of the molded article picker with the floating element in the extended position. 
           [0020]      FIG. 6  is a sectional view of the alternative embodiment of the molded article picker of  FIG. 5  with the floating element in the retracted position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    With reference to  FIG. 1 , a top plan view of an exemplary injection molding machine  10  is shown, comprising an injection unit  11 , a clamp unit  12 , a first post-mold device  13 , and a second post-mold device  14 . An injection mold comprising a cavity and core half  35 ,  17 , is shown arranged between the stationary and moving platens  16 ,  41  of the clamp unit  12 . The mold  35 ,  17  including molding inserts (not shown) of a stack assembly defining a molding cavity. 
         [0022]    The first post-mold device  13  is mounted on the stationary platen  16  and includes a beam  20  that projects to one side of the machine (e.g. the non-operator side) and upon which rides a carriage  21 , moved along the beam by (typically) a servo-electric driven belt drive (not shown). A tooling plate  107  is attached to the carriage  21 . Multiple sets of carriers  108 , e.g. three sets in the exemplary embodiment, are mounted on plate  107  and may be cooled for transporting multiple molded shots of molded articles  109  (the ‘molded article’ also will be henceforth referred to as a ‘preform’ in keeping with the context of the exemplary embodiment) ejected from the mold from an inboard (loading) position (not shown). 
         [0023]    The second post-mold device  14  includes a tooling plate  100  upon which are mounted multiple sets of cooling pins  112 , two sets in the exemplary embodiment, and a set of molded article pickers  120  in accordance with the preferred embodiment. In  FIG. 1 , the molded article pickers  120  are provided in every third row. In other words, for every molded article picker  120  there are two cooling pins  112  on the tooling plate  100 . However, the person skilled in the art will appreciate that the number of sets of cooling pins  112  could be different, i.e. for every molded article picker  120  there could be only one cooling pin  112  or more than two cooling pins  112 , or the cooling pins  112  may be omitted entirely. 
         [0024]    A rotatable mount  40 ,  45  attaches the tooling plate  100  to moving platen  41  for rotation through an arc. The rotation of the tooling plate  100  can be effected, for example, by an electric drive (not shown) mounted to the rotatable mount  40 ,  45 . 
         [0025]    In operation, a shot or batch of molded articles or preforms  109  are transferred into a set of empty carriers  108  when the mold is open and the tooling plate  107  is positioned such that the empty carriers  108  are aligned with molded articles on the core half  17 . The tooling plate  107  is then moved to its outboard position by the carriage  21 , as shown in  FIG. 1 . The mold is then closed and clamped for the next molding cycle. 
         [0026]    Meanwhile, as the mold closes, the tooling plate  100  of the second post-mold device  14  moves towards the molded article carriers  108 , whereby the sets of cooling pins  112  are arranged within the interior of the corresponding preforms  109  that have been most recently molded, and the molded article pickers  120  are arranged to engage an end portion, and in particular the front face  110  (as shown in  FIGS. 3 &amp; 4 ), of the preforms  109  that have been in the carriers  108  the longest, as will be described in more detail further below. In the embodiment shown in  FIGS. 1 &amp; 2 , a set of preforms  109  will have been held by the carriers  108  through three molding cycles before they are engaged by the molded article pickers  120  and withdrawn from the carriers  108 . The tooling plate  100  is then rotated by  90  degrees and the articles held by the molded article pickers  120  are dropped onto a conveyor (not shown) beneath the machine. The remaining articles continue to be held in their carriers  108  by means of a vacuum. 
         [0027]    As shown in  FIG. 2 , the tooling plate  100  includes apertures for accommodating a plurality of columns and rows of molded article cooling devices  112  (the cooling device may be, for example, a cooling pin in keeping with the context of the exemplary embodiment, and henceforth will be referred to as such), and molded article pickers  120  (a representative pair of cooling pins  112  and a molded article picker  120  are shown for the three sets of this exemplary embodiment). In particular, in this configuration the apertures of every third column are configured to accommodate a molded article picker  120  and the apertures of the remaining columns are configured to accommodate cooling pins  112 . 
         [0028]    A preferred embodiment of a molded article picker  120  according to the present invention is depicted in  FIGS. 3 &amp; 4 . A sectional view of the tooling plate  100  of the second post-mold device  14  is shown including two cooling pins  112  and a molded article picker  120  according to the preferred embodiment of the present invention, respectively cooperating with three preforms  109 A,  109 B and  109 C being held within three carriers  108  of the first post mold device  13 . 
         [0029]    The molded article picker  120  according to the preferred embodiment of the present invention comprises a floating element  123  that is movably connected to and guided by a base element  140  which, in turn, is mounted to the tooling plate  100 . The person skilled in the art, however, will appreciate that, alternatively, the base element  140  also could be an integral part of the tooling plate  100 . As will be described in more detail further below the floating element  123  can be moved between an extended or forward position (shown in  FIG. 3 ) and a retracted or rear position (shown in  FIG. 4 ). 
         [0030]    The floating element  123  of the molded article picker  120  according to the preferred embodiment of the present invention is spring-biased in the extended position for receiving molded article  109  by means of at least one biasing and guiding assembly. Each biasing and guiding assembly comprises a compressible spring  126  that is coiled about a respective cylindrical guiding pin  128  depending from a radial flange  119  of the floating element  123 . The cylindrical guiding pin  128  is slidably arranged and guided within a cylindrical guiding recess  130  formed in the base element  140  and the tooling plate  100 . The preferred embodiment of the molded article picker  120  shown in  FIGS. 3 &amp; 4  comprises three such biasing and guiding assemblies consisting respectively of a compressible spring  126 , a cylindrical guiding pin  128  and a corresponding cylindrical guiding recess  130 . The three biasing and guiding assemblies of the preferred embodiment of the present invention are positioned with an angle of  120  degrees between each other relative to the central symmetry axis of the molded article picker  120  and radially spaced therefrom close to the outer edge of the radial flange  119 . Such a configuration is preferable in order to avoid any misalignment between the molded article picker  120  and a preform  109  to be transferred. The person skilled in the art, however, will appreciate that a molded article picker  120  according to the preferred embodiment of the invention likewise could comprise less or more than three biasing and guiding assemblies. 
         [0031]    In addition to the above described biasing and guiding assemblies the motion of the floating element  123  of the molded article picker  120  according to the preferred embodiment between the extended or forward and the retracted or rear position is furthermore guided by a cylindrical lower guiding portion  125  of a pressure structure, preferably a vacuum pin  124 , which is arranged within a cylindrical bore through the base element  140 . The arrangement of the vacuum pin  124  within the cylindrical bore through the base element  140  should allow for a guided gliding movement of the vacuum pin  124  within the cylindrical bore and at the same time substantially prohibit the flow of fluid between the inner face of the cylindrical bore and the outer face of the guiding portion  125  of the vacuum pin  124 , as will be outlined in more detail below. 
         [0032]    When no external forces are applied to the floating element  123  of the molded article picker  120  according to the preferred embodiment, due to the tendency of the at least one compressible spring  126  to relax itself from being compressed the floating element  123  will be spring-biased in the extended or forward position, as shown in  FIG. 3 . In order to avoid a detachment of the floating element  123  from the base element  140  and, thus, the tooling plate  100  due to the force exerted by the at least one spring  126 , the floating element  123  comprises a retainer  142  at the lower end of the guiding portion  125  of the vacuum pin  124 . Any further motion of the floating element  123  and, thus, the vacuum pin  124  beyond the extended position or forward position thereof is impeded due to the abutment of the retainer  142  and the bottom face of the base element  140 . 
         [0033]    The molded article picker  120  comprises furthermore a compliable sealing element  122  disposed on the upper face of the radial flange  119  of the floating element  123 . Preferably, the sealing element  122  is made from a silicone rubber and is bonded to the radial flange  119  and adjacent portions of the floating element  123  in proximity thereto, as shown in  FIGS. 3 &amp; 4 , by means of a suitable adhesive material. In addition, a further retainer  127  can be provided in order assist in retaining the compliable sealing element  122  on the upper face of the of the radial flange  119  of the floating element  123 . 
         [0034]    In operation, when the tooling plate  100  of the second post-mold device  14  approaches the tooling plate  107  of the first post-mold device  13 , during mold closing, the molded article picker  120  engages the molded article  109  by bringing the front face  110  of the molded article  109  in close contact and preferably into abutment with the upper face of the sealing element  122  on the upper face of the radial flange of the floating element  123 . As it is made of a compliant material, preferably silicone rubber, upon contact with the front face  110  of the molded article  109  the sealing element  122  will be deformed and compressed. However, due to the force exerted upon the radial flange  119  of the floating element  123  by the at least one compressed spring  126  as well as the tendency of the deformed sealing element  122  to restore its original shape, a fluid-tight seal will be formed between the front face  110  of the molded article  109  and the sealing element  122  disposed on upper face of the radial flange  119  of the floating element  123  of the molded article picker  120  according to the preferred embodiment of the present invention. Thereafter, a pressure channel  138  formed between the lower face of the tooling plate  100  and a backing plate  134  affixed thereto and in fluid communication with the interior of the vacuum pin  124  is connected via a manifold (not shown) to a pressure source and the enclosed volume V 1  defined by the interior of the molded article  109  and the interior of the vacuum pin  124  is evacuated via the pressure channel  138 . As the enclosed volume V 1  defined by the interior of the molded article  109  and the interior of the vacuum pin  124  is essentially sealed from the environment, the floating element  123  is withdrawn by the vacuum force into the retracted or rear position shown in  FIG. 4 . Consequently, the molded article  109  being sealed to the floating element  123  (or more specifically to the sealing element  122  disposed on the upper face of the radial flange  119  thereof) is removed from the molded article carrier  108  and transferred to the molded article picker  120 . Thereafter the second post mold device  14  may be retracted and the first post mold device  13  is then free to retrieve the next shot of molded articles  109  from the molding structure  17 ,  35 . 
         [0035]    For preform  109  shown in the exemplary embodiment the floating element  123  is displaced by a distance of about 7 mm from its retracted or rear position to its extended or forward position, e.g. after the vacuum has been turned off and the preforms  109  have been dropped onto a conveyor. Preferably, the equilibration between the abutment of the front face  110  of a preform  109  of a subsequent batch and the sealing element  122  and the force exerted by the at least one spring  126  causes the floating element  123  to be displaced by about 2 mm in the direction of the retracted or rear position. Out of this position the floating element  123  and the molded article  109  sealed thereto are moved into the retracted or rear position over a distance of about 5 mm by applying a vacuum to the enclosed volume V 1  defined by the interior of the molded article  109  and the vacuum pin  124  via the pressure channel  138 . 
         [0036]    As can be taken from  FIG. 4 , in the retracted or rear position of the floating element  123  the radial flange  119  thereof is seated in a cup-shaped recess defined by the top face and the side face of the base element  140 , such that the upper end of the sealing element  122  is substantially flush with the upper face of the tooling plate  100 . In this position, the guiding pins  128  essentially fill the whole space provided by the guiding recesses  130 , thereby compressing the springs  126 . Optionally, a cylindrical sealing ring or gasket  132  could be provided in the top face of the base element  140  to provide for a fluid-tight engagement between the sealing ring  132  and the bottom face of the radial flange  119  in the retracted or rear position of the floating element  123 . Sealing rings could also be provided along the interfaces between the base element  140  and the tooling plate  100  and/or the tooling plate  100  and the backing plate  134 . 
         [0037]    With reference to  FIGS. 5 &amp; 6  another exemplary embodiment of a molded article picker  220  is depicted mounted to a second post mold device  214 .  FIG. 5  depicts the molded article picker  220  in a configuration just prior to receiving a molded article  209 , i.e. in the extended or forward position, whereas  FIG. 6  depicts the molded article picker  220  in a configuration after having received and withdrawn a molded article  209  from a carrier (not shown) of the first post-mold device (not shown), i.e. in the retracted or rear position. 
         [0038]    The molded article picker  220  includes a floating element  223  that is biased by a spring  226  to the extended or forward position, as shown in  FIG. 5 , for receiving the molded article  209 . The floating element  223  retracts under a vacuum force, compressing the spring  226 , to the retracted or rear position as shown in  FIG. 6 . The molded article picker  220  also includes a pressure structure comprising a vacuum pin  224  that is mounted to a tooling plate  200  via a base element  240  and a cup-shaped cylinder element  250  that is retained on the tooling plate  200  by a flange portion  244  of the base element  240 . Preferably, the cylinder element  250  is retained on a front face of the tooling plate  200  by the base element  240  such that the cylinder element  250  has a limited degree of radial freedom such that it may align with a radial piston-like flange  219  of the floating element  223 . The floating element  223  includes a guide portion  225  having an inner surface that cooperates with an outer surface of the vacuum pin  224  such that the floating element  223  is kept in longitudinal axial alignment with the vacuum pin  224  as the floating element  223  is moved between its extended or forward position and its retracted or rear position. The floating element  223  also includes a spring seat  227  that receives a forward portion of the spring  226 . A rear portion of the spring  226  cooperates with a front face of the base element  240 . The spring  226  is kept in longitudinal alignment with the vacuum pin  224  and with the floating element  223  by close cooperation of the spring  226  around a spring guide portion  228  defined on the outer surface of the vacuum pin  224 . The vacuum pin  224  also includes a retainer  242 , preferably a spring clip, arranged in a groove defined around the vacuum pin  224 . The retainer  242  cooperates with a front face of the guide portion  225  of the floating element  223  to define a forward limit ( FIG. 5 ) of travel of the floating element  223 . The rear travel limit ( FIG. 6 ) of the floating element  223  is defined by close cooperation of a rear face of the radial piston-like flange  219  and a front face of the base element  240 . In this embodiment the floating element  223  may be fabricated, for example, from an ultrahigh molecular weight polyethylene (UHMWPE) such that a front face of the radial piston-like flange  219  is compliant to an extent that is provides a sealing face  222  that may readily form a seal with the front face  210  of the molded article  209 . 
         [0039]    As can be taken from  FIGS. 5 &amp; 6 , a pressure channel  238  is defined between a pocket formed in the tooling plate  200  and a backing plate  234  arranged behind the tooling plate  200 . In operation, the pressure channel  238  is to be connected to a pressure source, positive or negative, such as may be provided, for example, by a compressor or a vacuum pump, respectively. Furthermore a pressure channel  243  is formed in the base member  240  for connecting the pressure channel  238  of the tooling plate  200  with a pressure channel  221  that extends through the vacuum pin  224 .In addition, an actuator pressure channel  229  is defined through a sidewall of the vacuum pin  224 . The actuator pressure channel  229  is preferably arranged on the vacuum pin  224  in a location adjacent the base member  240 .Lastly a close-fit, preferably fluid-tight, cooperation between an outer circumferential surface  246  of the radial piston-like flange  219  and an inner surface  252  is defined along the cylinder member  250  and may, optionally, include a piston seal disposed there between. 
         [0040]    In operation, the second post mold device  14  is translated to cause the molded article picker  220  to engage the molded article  209 , as explained previously with respect to the first exemplary embodiment, such that the front face  210  of the molded article  209  is arranged in close proximity, preferably in abutment, with the sealing face  222  of the floating element  223 . Thereafter, the pressure channel  238  is connected to a pressure source and an enclosed volume V 1 ′ ( FIG. 6 ) defined between the interior of the molded article  209  and the exterior of the molded article picker  220  is evacuated through the combination of the pressure channels  221 ,  243 , and  238 . Also, the enclosed volume V 2 ′ ( FIG. 5 ) defined between the cup-shaped cylinder member  250  and the radial piston-like flange  219  of the molded article picker  220  and the outer surface of the vacuum pin  224  is evacuated through the combination of pressure channels including pressure channels  229 ,  221  (partly),  243 , and  238 , whereby the floating element  223  is retracted by a vacuum force to the retracted or rear position, as shown with reference to  FIG. 6 , and, consequently, the molded article  209  being sealed to the sealing face  222  of the floating element  223  is removed from the molded article carrier (not shown). Thereafter, the second post mold device  14  may be retracted and the first post mold device  13  is then free to retrieve the next shot of molded articles  209  from the molding structure  17 ,  35 . 
         [0041]    The description of the exemplary embodiments provides examples of the present invention, and these examples do not limit the scope of the present invention. It is understood that the scope of the present invention only is limited by the claims. The inventive concepts described above may be adapted for specific conditions and/or functions, and may be further extended to a variety of other applications that are within the scope of the present invention. For instance, it might well be the case that for molded articles having a shape different to the one of a preform a pressure structure other than a vacuum pin might be better suited to perform the function of the present invention, i.e. to seal the molded article to the floating element and to withdraw the floating element into its retracted position. Having thus described the exemplary embodiments, it will be apparent that modifications and enhancements are possible without departing from the concepts as described. Therefore, what is to be protected by way of letters patent are limited only by the scope of the following claims.