Abstract:
A release mechanism operating to release molded articles from a third mold portion includes a guide coupled to the second mold portion forming a cam track. A cam follower coupled to the surfaces of the third mold portion, which are holding the molded articles, is engaged in the cam track when the second and third mold portions are within a pre-selected distance of each other. The cam follower interacts with the cam track to cause some initial movement of the surfaces holding the molded articles to a pre-release position for the holding surfaces so that the molded articles are loosely retained by the holding surfaces. A power operator, carried by the third mold portion and coupled to the article holding surfaces, is responsive to a signal to move the article holding surfaces from the pre-release position to a full release position when a molded article receiver is suitably positioned to receive the molded articles. The molded article receiver includes receiver tubes for receiving the molded articles. The receiver tubes have an open forward end configured to receive a molded article, a closed rearward end including a surface contact element movably situated with respect to the forward end. The surface contact element is configured to conform to a portion of the surface of the molded article. A vacuum duct couples the closed rearward end to a source of vacuum for assisting in the retention of the molded articles within the receiver tubes. An air cylinder is coupled to each surface contact element, and a pressure duct couples to each air cylinder to a source of air pressure for controlling the position of the surface contact element with respect to the forward end of the receiving tube.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed generally to molds for use in injection molding machines and to related apparatus used in conjunction with the molds to process articles produced in the molds. The invention pertains to the operation of elements for causing relative movement of some portions of the molds with respect to other portions, particularly in conjunction with the motion of the related molded article processing apparatus. The present invention is more particularly related to such apparatus for use in three portion molds consisting essentially of a mold cavity assembly, a mold core assembly and an intermediate assembly including space surface defining elements that cooperate with the mold core and cavity assemblies to define the space in which articles are molded of plastic, the apparatus regulating the movement of the space surface defining elements during movement of the intermediate assembly relative to the other portions of the mold and relative to the related molded article processing apparatus. The invention has particular utility in a molding operation in which the related molded article processing apparatus comprises a molded article receiver unit designed to enter into an interval or opening between the mold cavity assembly and the other mold assemblies subsequent to formation of the molded article. Of particular interest is the controlled positioning and/or timing of release of the molded article from the intermediate assembly into the molded article receiver unit. 
     Brun, Jr., et al., U.S. Pat. No. 5,531,588 discloses an adjustable cam track for a mold having a mold cavity assembly, a mold core assembly that is movable relative to the mold cavity assembly, and a stripper assembly movably interposed between the mold core and cavity assemblies. The stripper assembly has at least one pair of space defining surfaces that together with the mold cavity and core assemblies, defines at least one space for receiving plastic material injected therein to form at least one molded article. The mold core assembly and the stripper assembly can be moved away as a coupled pair from the mold cavity assembly to remove the at least one molded article from the mold cavity assembly. The mold core assembly and the stripper assembly are then separated to remove the at least one molded article from the mold core assembly. The adjustable cam track of Brun, Jr., et al., includes a guide fixed to the stripper assembly. A cam follower is coupled to the space defining surfaces of the stripper assembly platen and is engaged in the adjustable cam track so that movement of the cam follower causes movement of each pair of space defining surfaces relative to each other to release the molded article from the molding machine. The adjustable a cam track also includes a cam insert that is adjustably positionable with respect to the guide to adjust the point of release of the molded article. The cam insert includes a first toothed rack, and a second toothed rack removably fixed to the guide and engaging the first toothed rack to fix the position of the cam insert relative to the guide only at certain preselected locations. 
     The previously described adjustable cam track of Brun, Jr., et al., has been used in the manufacture of parisons for containers at rates that required special handling of the parisons upon their removal from the mold core assembly. This special handling was accomplished with a molded article receiver assembly that was movable into the interval between the mold cavity assembly and the mold core assembly when the mold was in an open position such as that disclosed in Delfer III, U.S. Pat. No. 4,721,452. Ideally, the position of the molded article receiver assembly was such that movement of the stripper assembly relative to the mold core assembly inserted the parisons into the molded article receiver assembly. This was followed immediately by the release of the parisons by the pair of space defining surfaces, which only occurred when the parisons were properly located in the molded article receiver assembly. However, as a practical matter, even slight misalignment between the mold core assembly and the molded article receiver assembly caused one or more of the parisons to be significantly damaged as they were inserted into the molded article receiver assembly. Furthermore, since release of the parisons was related only to the relative position of the stripper assembly relative to the mold core assembly, is was also necessary to accurately position the molded article receiver assembly and coordinate the timing of such positioning so that as little damage as possible occurred. While substantial efforts were focused on insuring the proper alignment between the mold core assembly and the molded article receiver assembly during the movement of the stripper assembly, this did not always accomplish the desired end. 
     In co-pending U.S. application Ser. No. 09/726,743, filed Nov. 30, 2000 and assigned to the same assignee, an adjustable cam track is disclosed that includes a guide coupled to a mold core assembly, the guide defining a first portion of the adjustable cam track. A cam follower is engaged in the cam track and is coupled to the space defining surfaces carried by the stripper assembly for causing relative movement of each pair of space defining surfaces as the stripper assembly moves relative to the mold core assembly. The cam follower is engaged in the first portion of the cam track when the mold portions are in the closed position. The first portion of the cam track also includes a ramp to an intermediate portion defining the prerelease position of each pair of space defining surfaces so that the molded article is loosely retained by the space defining surfaces. This loose retention accommodates for any small amount of misalignment between the molded article receiver assembly during the transfer of the molded articles from the stripper assembly to the molded article receiver assembly. The adjustable cam track of the co-pending application also includes a cam insert defining a second portion of the adjustable cam track. The path defined by the cam insert is generally a matter of choice of design except that it defines the point of release of the molded article from the space defining surfaces. The cam insert is adjustably positionable with respect to the guide to adjust the point of release with respect to the ramp defining the onset of prerelease, thereby permitting the adaptation of the cam track to molded articles of a variety of sizes. However this adjustment of position of the cam insert is one made to generally coordinate the position of the release, but is not responsive to the timing of the achievement of the specified position by the molded article receiver apparatus. 
     It is therefore desirable that each pair of space defining surfaces of the stripper assembly be allowed to separate slightly, but not entirely, from the molded articles so that the molded articles are only loosely retained in a prerelease position. This prerelease position allows some play in the position of the molded articles relative to the stripper assembly thus permitting some variation in position of the molded article receiver assembly at the time of introduction of the molded articles. Due to the variation in length of the molded articles, it is also desirable to modify or adjust the position of product release from the stripper assembly in relation to the position of onset of the prerelease position. It is also desirable for the product release from the stripper assembly to occur in response to an indication of the attainment of a specified position by the molded article receiver assembly. 
     SUMMARY OF THE INVENTION 
     Accordingly, an article molding assembly of the present invention includes a mold and a release mechanism for releasing molded articles from the mold. The mold includes a first mold portion, a second mold portion that is movable with respect to the first mold portion, and a third mold portion. The third mold portion is movably interposed between the first and second portions and has at least one pair of space defining surfaces which, together with the first and second mold portions, defines in a closed position at least one space for receiving plastic material injected therein to form one or more molded articles. The second and the third mold portions are movable away from the first mold portion to permit removal of the molded articles from the first mold portion. The second mold portion is also movable away from the third mold portion to remove the molded articles from the second mold portion. The release mechanism operates to release the molded articles from the third mold portion. In an embodiment of particular interest, the first mold portion is a mold cavity plate including a plurality of cavities and the second mold portion is a mold core plate supporting a like plurality of cores adapted to inserted into the cavities when the mold is in a closed position. The third mold portion is a stripper plate that supports a like plurality of sets of engaging elements such as thread splits. The thread splits or other similar elements function, in conjunction with the core and cavity portions of the mold, to define the spaces into which plastic can be injected to form the articles having a desired configuration. The release mechanism acts to release the molded articles from the thread splits or similar article engaging elements, generally into a cooling mechanism that will complete the cooling cycle needed for the formation of the molded articles, thereby shortening the residence time of the molded articles in the mold subsequent to injection. 
     The release mechanism of the present invention includes a guide coupled to the second mold portion. The guide controls the relative position of the sets of space defining surfaces that, together with a first and second mold portions, define in the closed position the space for receiving injected plastic material to form the molded articles. The guide generally includes a first portion having a closed end and including a pair of inner sides confronting each other to define a cam track. The inner sides in the first portion are spaced sufficiently from each other to accommodate a cam follower that is closely received between the inner sides when the mold portions are in the closed position. The first portion can also include a ramp leading to an intermediate portion. The intermediate portion functions to define a pre-release position for the pairs of space defining surfaces so that the molded articles are loosely retained by the space defining surfaces. In a preferred embodiment, one of the inner sides in the intermediate portion is inclined away from the other inner side thus expanding the space that can be occupied by the cam follower toward a second portion. The second portion includes an open end so that the cam follower can move outside the space between the inner sides of the cam track. Further, the inclined away inner surface is adapted to contact the cam follower as the third mold portion moves from the full release position toward the second mold portion. The cam follower then travels along the inclined away inner surface to return the space defining surfaces to a closed position. 
     As has already been indicated, a cam follower that is coupled to the sets of space defining surfaces of the third mold portion is engaged in the cam track when the second and third mold portions are within a pre-selected distance of each other. The cam follower interacts with the inner surfaces of the cam track to cause relative movement of the sets of space defining surfaces. The cam follower is generally closely engaged in the first portion of the cam track when the mold portions are in the closed position. The cam follower can be less closely engaged in the intermediate portion defining the pre-release position of the sets of space defining surfaces. The cam follower can be completely outside the cam track defined by the confronting inner surfaces at the point of full release of the molded articles. 
     The release is achieved by a power operator, such as a fluid operated cylinder, solenoid, or other similar device carried by the third mold portion and coupled to the space defining surfaces. The power operator is responsive to a signal to move the sets of space defining surfaces from the pre-release position to a full release position. In the preferred embodiment the signal is supplied by a molded article receiver in sufficiently close proximity to the third mold portion that the molded articles are transferred from the third mold portion to the molded article receiver at such time as the articles are released by the sets of space defining surfaces. 
     In a particularly desirable embodiment, the molded article receiver includes at least one corresponding receiver tube alignable with each set of space defining surfaces for receiving the molded article, and at least one sensor for detecting any deposition of a molded articles into a receiver tube, the sensor being coupled to a signal source for sending said signal to said power operator. In this embodiment the receiver tube can include an open forward end configured to receive a molded article and a closed rearward end having a surface contact element movably situated with respect to the forward end and configured to conform to a portion of the surface of the molded article. A vacuum duct couples to the closed rearward end of the receiver tube to a source of vacuum for assisting in the retention of a molded article within the receiver tube. An air cylinder is coupled to the surface contact element, and a pressure duct couples each air cylinder to a source of air pressure for controlling the position of the surface contact element with respect to the forward end of the receiver tube. 
     In the usual operation of an injection molding machine, molded articles are formed in a mold having a first mold portion, a second mold portion movable with respect to the first mold portion. In molding machines of particular interest to the present invention, a third mold portion is movably interposed between the first and second portions that has at least one pair of space defining surfaces for each space defined between the first and second mold portions for receiving plastic material to form molded articles. The second and the third mold portions generally are movable relative to the first mold portion to permit removal of the molded articles from the first mold portion. The second mold portion is movable relative to the third mold portion to permit removal of the molded articles from the second mold portion. When the second and third mold portions have moved as a unit sufficient distance to remove the molded articles from contact with the first mold portion and provide a gap between the first and second mold portions, a molded article receiver moves into proximity with the third mold portion. The present invention is directed toward removing the molded articles from the third mold portion and introducing the molded articles into the receiver for further treatment, generally cooling, without damaging the newly molded articles. 
     The release of the molded articles from the third mold portion into the molded article receiver is accomplished by providing a guide coupled to the second mold portion that forms a cam track. A cam follower is coupled to the pairs of space defining surfaces of the third mold portion, the cam follower engaging the cam track at least when the second and third mold portions are in a closed position as well as when second and third mold portions are within a pre-selected distance of each other. While the cam track and follower are engaged, the cam follower interacts with the cam track to cause relative movement of each pair of space defining surfaces. As the third mold moves toward the molded article receiver, the cam follower moves to a portion of the cam track including a ramp defining a pre-release position of each pair of space defining surfaces mounted to the third mold portion so that the molded articles are loosely retained by the space defining surfaces. In this loosely retained position, the articles can be inserted into appropriate receivers, such a receiving tubes, despite some amount of misalignment between the receivers and the molded articles. This has the advantage of reducing the amount of damage suffered by the newly molded articles and prevents any machine lock-up due to minor misalignment between the molded article receiver and the articles being held by the third portion of the mold. Additional insertion of the molded article into the molded article receiver is achieved by movement of the third mold portion even further away from the second mold portion, to a point where the cam is no longer captured in the cam track and no longer controls the position of the pairs of space defining surfaces. 
     Once the molded articles are at least partially received in the receiver elements or tubes of the molded article receiver through movement of the third mold portion away from the second mold portion, a signal is provided to a power operator carried by the third mold portion and coupled to the space defining surfaces. The signal causes the power operator to move each pair of space defining surfaces from the pre-release position toward a full release position for releasing the molded articles from the third mold portion into the molded article receiver. The signal can be provided by a proximity detector situated on the third mold portion that senses, for example, the position of the third mold portion in relation to either the second mold portion or preferably the molded article receiver. A signal can also be provided by a sensor situated on the molded article receiver that senses, for example, the position of the third mold portion or preferably any deposit of molded articles into a receiver tube of the molded article receiver. In any case, the sensor is generally coupled to a signal generator capable of sending a signal to the power operator situated on the third mold portion. Desirably, the signal causing the power operator to move the space defining surfaces on the third mold portion is generated before the molded articles are fully deposited into the receiver elements or tube of the molded article receiver. This has the advantage of preventing damage to the portion of the molded article being held by the space defining surfaces that might occur if completed positioning is required prior to release due to “bottoming out” of the molded article within the article receiver element or tube. 
     Further avoidance of damage caused by “bottoming out” can be achieved by providing within each receiver tube an open forward end configured to receive a molded article and a closed rearward end including a surface contact element movably situated with respect to the forward end. The surface contact element is configured to conform to a portion of the surface of the molded article, and to be easily moved away from the forward end by contact with a molded article as it is deposited within the tube. To assist in this rearward movement, the closed rearward end of the receiver tube is coupled to a source of vacuum. There is also an air cylinder coupled to the movable surface contact element, the air cylinder being provided with sufficient air pressure to bias the surface contact element toward the open forward end of the receiver tube. The vacuum coupled to the closed rearward end of the receiver tube is generally insufficient to overcome the bias provided to the surface contact element by the air pressure within the air cylinder when no molded article is present within the receiver tube. However, when a molded article is located within the receiver tube, the vacuum becomes enhanced and assists in locating a molded article within the receiver tube in contact with the surface contact element. This vacuum action had the advantage of centering the molded article within the receiving tube so that the spacing of the cooling tubes now controls the spacing of the molded articles, even though the article spacing may have varied from that dimension due to the loose holding arrangement between the molded articles and the pairs of space defining surfaces prior to insertion of the molded articles into the receiving tubes. 
     In a particularly desirable embodiment, the signal, which causes operation of the power operator on the third mold portion releasing the molded articles from the space defining surfaces, is provided said signal from the molded article receiver to said power operator to cause movement of each pair of space defining surfaces from the pre-release position to a full release position only after the molded article is in contact with the surface contact element. This ensures that the molded articles are suitably positioned to allow the vacuum to overcome the bias provided by the air pressure within the air cylinders so that the surface contact element and molded article are displaced toward the receiver tube closed end thus uncoupling the molded article from the third mold portion, usually causing a displacement of the molded article away from the plane generally defined by the third mold portion. The release of the molded articles from the space defining surfaces under operation of the vacuum is sufficiently gentle that the surfaces of the molded articles held by the space defining surfaces are not damaged during the release process. 
     After the molded articles are safely situated in the molded article receiver, the molded article receiver is withdrawn from the gap between the first and second mold portions. After a suitable lapse of time and after the molded article receiver is moved to a suitable location, the air cylinder is provided with sufficient air pressure to displace the surface contact element toward the open end with sufficient speed to eject the molded article from the receiver tube for further processing. Generally, subsequent to the release of the molded articles from the pairs of space defining surfaces, and at the same time that the molded article receiver is removed from the gap between the first and second mold portions, the third mold portion is moved back toward the second mold portion so that the cam follower re-enters the cam track. The cam track is provided with an inclined surface adapted to contact the cam follower as the third mold portion moves from the full release position toward the second mold portion. This contact between the cam follower and inclined surface of the cam track returns the space defining surfaces to a closed position. This operation has the advantage of ensuring the repeatability of the positioning of the space defining surfaces without requiring very highly calibrated power operators coupling the space defining surfaces to the third mold portion. 
     Other features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the illustrated preferred embodiment shown in the accompanying figures showing the best mode of the present invention as understood by the inventors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic plan view of an injection molding machine including an article molding assembly of the present invention. 
     FIG. 2 is a front elevation view of a third mold portion including the power operators of the present invention partially broken away to show certain features and operation through phantom depiction. 
     FIG. 3 is a detail view of one side of the third mold portion, cam follower and power operator shown in FIG.  2 . 
     FIG. 4 is a side elevation view of a guide including a cam track of the present invention. 
     FIG. 5 is a partial sectional view of a molded article receiver of the present invention showing a surface contact element and molded article. 
     FIGS. 6A-D are four views of a surface contact element suitable for use in tube of a molded article receiver shown in FIG.  5   
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An injection molding machine  10  is shown in FIG. 1 to include an extruder  13  coupled to a fixed platen  9  and a movable platen  8  coupled to a clamping mechanism  7  including hydraulic cylinder  16 . Tie rods  15  tie the fixed platen  9  to the clamping mechanism  7  and the movable platen  8  reciprocates on tie rods  15  relative to the fixed platen  9  in a cycle determined by a suitable control system  6  in a well known manner. A first mold portion  11 , which contains a plurality of cavities, is coupled to the fixed platen  9 . A second mold portion  12 , which includes a like plurality of cores  14 , the number of cores corresponding to the number of cavities, is coupled to the movable platen  8 . A third mold portion  18  is situated between the first and second mold portions  11  and  12 , and includes a plurality of pairs of space defining surfaces that surround each of the cores  14 . The mold portions  11 ,  12  and  18  are shown in FIG. 1 in an “open” position. The second and third mold portions  12  and  18  are movable with the movable platen  8  in the direction A into engagement with the first mold portion  11  in a “closed” position to form a plurality of spaces for receiving molten plastic from the extruder  13  to form a plurality of plastic articles  21  by injection molding in the conventional manner. The number of articles  21  formed in an injection molding cycle will depend on the number of cavities and cores included in the mold portions  11  and  12 . 
     Subsequent to the formation of the plastic articles  21  by the injection of molten plastic, the mold portions  12  and  18  move away from mold portion  11  and toward the illustrated “open” position together as a unit with the formed plastic articles  21  on cores  14 . Retention of the plastic articles can be aided by shrinkage of the articles onto cores  14 . When in the “open” position, an interval or gap  17  is created between the cavity mold portion  11  and the cores  14  that permits the insertion in the direction B of an article carrier plate  20  of a molded article retrieval apparatus  22 . The article carrier plate  20  is moved into and out of the gap  17  between the mold portions  11  and  18  by a trolley system  19  that is coupled to the fixed platen  9 . The article carrier plate  20  can be provided with one or more sets of receivers for receiving the molded plastic articles  21 , each set of receivers being equal to the number of cores  14  on mold portion  12 . Removal of the plastic articles  21  from cores  14  onto the article carrier plate  20  is accomplished by the movement of the third mold portion  18  in the direction C toward the interposed article carrier plate  20 . During such movement, the pairs of space defining surfaces, which surround each of the cores  14  and engaging each of the molded articles, strips the molded articles from the cores and into the waiting receivers of the article carrier plate  20 . To enhance the reliability of successful placement of the molded articles into the receivers of the article carrier plate  20  with the least likelihood of damage, the spacing of the pairs of space defining surfaces are controlled by a release mechanism of the present invention described below. 
     FIG. 2 shows a face  24  of the third mold portion  18  that confronts the first mold portion  11 . A plurality of pairs of space defining surfaces  22   a  and  22   b , commonly known in the trade as “thread splits”, are mounted to the face  24 . The thread splits  22   a  and  22   b  cooperate with the cores  14  of the second mold portion  12  and the cavities of the first mold portion  11  to complete the definition of the spaces that receive the plastic from the injection extruder  13  to form the molded articles  21 . The space defining surfaces  22   a  and  22   b  hold the articles  21  as they are stripped from the cores  14 . Each half  22   a  and  22   b  of each of the thread splits is mounted to separate slides  25  and  26 , respectively, by clamps  23 . The slides  25  and  26  reciprocate laterally within channels defined by brackets  27  and  28  that are fixed to face  24  of the third mold portion  18 . While FIG. 2 shows nine such sets of thread splits, it will be appreciated that the number of sets is a matter of choice of design and depends directly on the number of cores  14  on the first mold portion  12 . 
     The slides  25  are secured together by tie members  29  while slides  26  are tied together by tie members  30  such that the lateral movement of all slides  25  or  26  is uniform and coordinated. The movement of all slides  25  is not directly coupled to the movement of all slides  26 . A plurality of actuating rods  31  are fixed to the laterally outermost slides  25  and  26 . The actuating rods  31  extend outward through blocks  33  that are coupled to the sides of third mold portion  18 . The actuating rods  31  are coupled to movable actuating beams  40   a  and  40   b  located on either side of the third mold portion  18 . Any lateral movement of slides  25  and tie members  29  is caused by corresponding movement of the actuating rods  31  and actuating beam  40   a . Likewise, any lateral movement of slides  26  and tie members  30  is caused by corresponding movement of the actuating rods  31  and actuating beam  40   b.    
     The actuating beams  40  can be moved by two independent means. A first means for moving the beams is a cam follower  41  fixed to each end of each beam  40 . The cam followers  41  can be rollers or slides that are designed for interaction with a cam track  42  that is fixed to the second mold portion  12 . A second means for moving the beams is a power operator  44  that is coupled between each beam  40  and block  33  fixed to the third mold portion  18 . The power operator  44  can be any suitable mechanism that is capable of causing reciprocal motion of one of the beams  40  relative to the third mold portion  18 , for example, a pneumatic or other fluid actuated cylinder and piston, a solenoid including a throw member, or a motorized pinion gear coupled to a rack. Other suitable power operators will be apparent to those skilled in the art. 
     FIG. 3 illustrates a particularly preferred embodiment of the release mechanism of the present invention. Any dimensional changes between FIGS. 2 and 3 are merely to provide clarity of structure and operation, and neither Figure should be considered a scale drawing. Each of the actuating rods  31  are shown in FIG. 3 to be formed by a bolt  45  extending through beam  40  and block  33 , the bolt  45  being secured to one of the outermost slides (either  25  or  26  depending on which side of the mold is being considered). Each bolt  45  is surrounded by a sleeve  46  that abuts the slide  25 ,  26 . The sleeve  46  is movable relative to beam  40  and block  33 . A compression spring  47  biases the sleeve  46  toward the slide  25 ,  26 . The block  33  also includes a plurality of stops  48  held in recesses in the inside surface of the block by fasteners  49  so that a portion protrudes inward beyond the inner surface  50  of block  33 . A plurality of shock absorbers  51  are also located in block  33  having movable plungers  52  that protrude toward the adjacent surface  53  of slides  25 ,  26 . The shock absorbers  51  are threaded or otherwise secured into recesses in block  33 , and have a rearward extension including an adjustment screw  54  for adjusting the resistance applied by the shock absorber. A sensor  55  senses the arrival of the slides  25 ,  26  in substantial contact with block  33 . The sensor  55  can be any sort of electromechanical switch that is coupled to a suitable cable  56  leading to the control  6  for the molding machine  10  or other suitable control mechanism. 
     Any movement of the beam  40  away from block  33  results in a corresponding movement of the slides  25  or  26  to which the beam  40  is attached through actuating rods  31 . As the slide  25  or  26  approaches block  33 , it is initially slowed in its travel by contact with the plungers  52  of shock absorbers  51  and then stopped by the protruding stops  48 . Any movement of the beam  40  back toward block  30  applies a force through compression spring  47  and sleeve  46  against surface  53  of beam  25 ,  26 . In the absence of any resistance, the applied force is sufficient to cause a corresponding movement of the adjacent beam  25 ,  26  as well as the related beams connected thereto through slides  29  or  30  as shown in FIG.  2 . In the event of some resistance (usually due to an incompletely released molded article or other mechanical obstruction) the travel provided by the sliding sleeve  46  and compression spring  47  allows the beam  40  to return toward the illustrated position without a corresponding movement of the slides  25 ,  26 , thereby protecting the slides and related structures from physical damage. 
     As indicated earlier, a first means for moving the beams is a cam follower  41  fixed to each end of each beam  40 . The cam followers  41  can be rollers or slides that are designed for interaction with a cam track  42  that is fixed to the second mold portion  12 . In the context of the present invention, a preferred cam track  42  is shown in FIG.  4 . It will be appreciated that the cam tracks  42  on opposite ends of the same beam  40  must be mirror images of each other and similarly situated with respect to the beam  40  if stress and torque on the beam  40  are to be minimized. It will also be appreciated that the illustrated cam track  42  shown in FIG. 4 would necessarily be suitably reproduced in mirror image to correctly interact with the opposite ends of the beam  40 . The following discussion of the structure of the cam track  42  and the movement of the beam in association therewith reflects this mirror image construction of the two cam tracks located at opposite ends of the beam  40 . The cam follower  41  is shown in FIG. 4 to consist of a roller  62  mounted on a spindle  63  that projects from and is secured to the end of the beam  40 . The cam follower  41  is shown in four different locations indicating different positions that the cam follower  41  is likely to occupy during movement of the beam  40  in accordance with this invention. 
     The cam track  42  comprises essentially a shaped groove  60  in a suitably dimensioned block  61  that includes a first portion  64  that receives the cam follower  41  when the mold portions  11 ,  12  and  18  are in the closed position. This location is designated in FIG. 4 by the cam follower  41  at position A. The cam track  42  includes a ramp portion  65  between the first portion  64  and a second portion  66 . As the second and third mold portions move apart from each other, the cam follower  41  moves from position A to position B traversing the ramp portion  65 , which causes the beam  40  to move slightly away from block  33 , and correspondingly causes the space defining surfaces  22   a  and  22   b  to separate only by a distance sufficient to permit the molded articles  21  to be loosely held but not released by the space defining surfaces. The second portion  66  of the cam track  41  is structured so that the cam follower  41  can move, to the right as shown in FIG. 4, through position C completely outside the end of the cam track  41 . This freedom of movement allows the third mold portion to travel toward the molded article receiver  22  by what ever distance is required to safely deposit the molded articles into the tubes  20  of the article receiver  22 . 
     Once the molded articles are delivered to the article receiver  22 , a sensor of the relative position of the third mold portion  18  and the article receiver  22  causes the power operator  44  coupled to the beam  40  to actuate thus causing movement of the beam  40  and the cam followers  41  coupled thereto to move in direction Y as shown in FIG. 4, thereby releasing the molded articles  21  from the space defining surfaces  22   a ,  22   b . The third mold portion is then caused to move back toward the second mold portion until the cam followers  41  reenter the cam track  42 . When the second and third mold portions  12  and  18  are within a pre-selected distance of each other, the cam follower  41  comes into position D and engages the cam track. As the second and third mold portions  12  and  18  come closer together, the cam follower  41  interacting with a surface  67  of the cam track  42  causes relative movement of each pair of space defining surfaces  22   a ,  22   b  back toward each other until the cam follower  41  re-enters the first portion  64  of the cam track. This closing motion of the third mold portion  18  toward the second  12  provides sufficient space for the molded article receiver  22  to exit the gap  17 . The mold portions  11 ,  12 , and  18  then return to the fully closed position to permit the subsequent injection of plastic to from another set of molded articles. 
     A detailed look at a preferred molded article receiver  22  is given by FIG.  5 . The molded article receiver  22  comprises a support plate  70  to which a plurality of tube-like molded article article receiver tubes  20  are attached. The support plate  70  is preferably made of a lightweight material such as 6061-T6 aluminum, or an engineering plastic such a ACETRON GP™, manufactured by Polymer Corporation, Reading, Pa., so that the molded article receiver as a whole has as low inertia as possible. Each of the individual article receiver tubes  20  has a sleeve  71  fixed to the frame  70  by base mounting  72 . A sleeve insert  73  is received within the sleeve  71  and base mounting  72 . A space between the sleeve  71  and the sleeve insert  73  defines a channel  74  for receiving liquid that has been thermally adjusted to a temperature selected to thermally modify or treat the molded articles  21 . The channel  74  includes both an inlet  75  and an outlet  76  that are coupled to liquid supply channel  77  and liquid drain channel  78 , respectively, which are located in frame  70 . An inner surface  79  of each sleeve insert  73  has a distal portion  80  that is configured to generally reflect or match an exterior surface portion of the molded articles  21 . A proximal portion  81  of each sleeve insert  73  is generally cylindrical and dimensioned to receive a movable surface contact element  82  for reciprocal movement within the generally cylindrical portion  81 . The sleeve inserts  73  and the contact elements  82  are preferable made of highly thermally conductive material to maximize the thermal transfer between any molded article  21  received within the sleeve insert  73  and the liquid located in channel  74 . 
     In addition to liquid channels  77  and  78 , the frame  70  also includes a vacuum duct  83 , which is coupled to a vacuum source, not shown, and to the interior of sleeve insert  73  by way of a channel  84 . The channel  84  also provides a pathway for a stem  85  coupling the contact element  82  to an air or gas spring  86 . A distal surface  87  of the contact element  82  is generally configured to reflect or match a portion of an exterior surface  90  of the molded articles  21 . The contact element  82  also includes a plurality of openings  88  through which, in the absence of a molded article  21 , air is drawn into the vacuum duct  83  through a space  89 , located between the contact element  82  and the bottom of the sleeve insert  73 , and channel  84 . As the molded article  21  contacts the distal surface  87  of the contact element  82 , the matching shape of the distal surface  87  and the molded article  21  restricts the flow of air through the openings  88 . The restricted air flow causes the vacuum in duct  83  to harden. The hardening of the vacuum in duct  83  can be sensed by a vacuum/pressure sensor, schematically shown as sensor  91 . The restricted air flow caused by the contact of the molded articles  21  and distal surfaces  87  also causes a pressure differential between the inside of the molded article  21  and space  89  below the contact element  82  that biases the contact element  82  to the right against the pressure exerted by the air or gas spring  86 . 
     The fluid pressure supplied to the gas or air spring  86  can be controlled by valve  106  coupled between a source of gas or air pressure  105  and all or some portion of the air springs  86 . The valve can be, in turn, coupled to the control system  6  of the injection molding machine  10  or to other independent controls for the apparatus  22 . In the absence of any molded article  21 , or with the molded article  21  spaced from the distal surface  87  of the contact element  82 , the fluid pressure supplied to the spring  86  exerts sufficient force to maintain the contact element  82  in an extended position as shown in the lower portion of FIG.  5 . When the fluid pressure to springs  86  is reduced, the pressure differential developed across the molded article  21  and contact element  82  is sufficient to move the contact element  82  and molded article  21  to the right, as shown in the top of FIG.  5 . However, this movement can only happen if the molded articles  21  are not restrained by the space defining surfaces  22   a , and  22   b . It will be appreciated that the contact between the distal surfaces  87  of the contact elements  82  and the surfaces  90  of all of the molded articles  21  generally occurs nearly simultaneously, or over such a short period of time, so that the change in pressure sensed by vacuum sensor  91  occurs over a similarly short period of time. This change in pressure can be used to trigger power operator  44  to move the beam  40 , and the coupled slides  25  or  26  relative to the third mold portion  18  so as to fully release the molded articles  21  from the space defining surfaces  22   a ,  22   b . With the molded articles  21  fully released, the motion between the top and bottom of FIG. 5 quickly follows, thus transferring the molded articles  21  from the space defining surface  22   a ,  22   b  of the third mold portion  18  to the molded article receiver  22 . The change in pressure sensed by vacuum sensor  91  can also be used to restrict the flow of air or other gas through valve  106  to the air springs  86 , thus ensuring retention of the molded articles  21  within the sleeve inserts  73 . This coordination of the restriction of pressure through valve  106  and the opening of the space defining surfaces  22   a ,  22   b  can also be done with a coordinated timing circuit and the system control  6 , or in other equivalent manners as will be apparent to those skilled in the art. 
     Once the molded articles  21  have been retained in the molded article retrieval apparatus  22  for sufficient time to achieve the desired thermal modification, the molded articles  21  can be released. This is achieved by reducing or eliminating the vacuum being supplied to vacuum duct  83  coupled with the supply of air or other gas to gas springs  86  in sufficient amount to rapidly move the contact elements  82  to the left as shown in FIG. 5, thereby ejecting the molded articles  21  from the article receiver  22 . If desired, each gas spring  86  can be monitored to make sure that the desired motion has taken place, and that no motion takes place when the vacuum is reapplied to vacuum duct  83 , thus signifying that to molded article  21  has been retained by the article receiver  22 . 
     A particularly desirable surface contact element  82  is shown in FIGS. 6A through 6D. FIG. 6A is a front elevation view of the distal surface  87  of the contact element shown in FIG.  5 . FIG. 6B is a sectional view of a contact element  82  taken along line B—B of FIG. 6A, and is similar to the sectional view shown in FIG.  5 . FIG. 6C is a section view of the same contact element  82  taken along line C—C of FIG.  6 A. FIG. 6D is a back elevation view of the contact element  82 . From these four views, it will be seen that the contact element has a generally concave distal surface  87 , the curvature of which is dictated by the shape of the corresponding molded articles  21  with which the contact element is to be employed. The contact element  82  has an outer cylindrical surface  92  that is substantially identical in dimension to the interior dimension of the proximal portion  81  of sleeve insert  73 , so that a smooth linear motion of the contact element  82  within the sleeve insert  73  can be obtained. The cylindrical surface  92  extends from the distal surface  87  to a first proximal surface  93 , which is ring-like and contains two sets of openings  94  and  95 . A step  96  is provided in a central portion of proximal surface  93 , which contacts a rear surface of sleeve insert  73  when the contact element  82  is in the rearward position shown in the upper portion of FIG. 5. A stem connection  97  projects rearwardly from the step  96  and includes a threaded opening  98  for coupling with stem  85  of gas spring  86 . The openings  94  are inwardly inclined as shown in FIG. 6B to intercept axial channel  99  which extends forward to an enlarged portion  101  intercepting an axial portion of distal surface  87 . The openings  95  extending longitudinally through the contact element  82  from the proximal surface  93  to a location adjacent to distal surface  87 , where short openings  100  provide peripheral access to the distal surface  87 . The enlarged portion  101  of the axial channel  99  is preferably faceted to accept a suitable tool to facilitate engagement between the threaded opening  98  for coupling with stem  85  of gas spring  86 . An inner portion of axial channel  99  is threaded to permit insertion of a plug to help maintain a vacuum when a selected portion of the apparatus is not being used. 
     While the present invention has been described in detail with reference to the accompanying drawings showing a preferred embodiment of the invention, variations and modifications exist within the scope and spirit of the invention as described and as defined in the following claims.