Abstract:
A machine for crystallizing a thermoplastic preform or container is constructed from modular subassemblies and utilizes a preheated plug to provide the sole upright support for a workpiece in the crystallizing process. The first modular subassembly includes the workpiece in-feed and plug preheat structures and incorporates the drive apparatus for the entire machine. The opposed end of the crystallizing machine is constructed of a subassembly which operates to provide the turnaround and tensioning takeup for the carrier mechanism transporting the workpieces. Positioned between the first subassembly and the opposed end subassembly are heating and cooling processing modules which can be provided in any number depending on the size constraints and workpiece quantity restraints desired. The processing modules provide the heating and crystallizing processes for the desired area of the workpiece and the cooling process of the workpiece prior to unloading.

Description:
This application is a Continuation of Ser. No. 09/349,047 filed Jul. 7, 1999, now U.S. Pat. No. 6,139,812. 
    
    
     TECHNICAL FIELD 
     This machine relates to a process and apparatus for use in strengthening the finish area of a hollow blow molded container manufactured from a thermoplastic, such as a thermoplastic polyester or a biaxially oriented polyethylene terephthalate resin. 
     BACKGROUND ART 
     A hollow blow molded thermoplastic, such as a thermoplastic polyester or a biaxially oriented polyethylene terephthalate resin, “PET”, container, commonly used to contain food or beverage, has excellent physical properties, durability, and a wide range of applications. However, when used in hot-fill applications, certain portions of the container which are not subjected to the biaxial orientation during the blow molding process, such as the neck area seal edge or thread, commonly referred to as the finish area, are found to soften and deform in an undesirable manner because the temperature of the food or beverage fill is often above the glass transition temperature of the plastic. Many methodologies and processes have been tried in attempts to strengthen the neck area of such containers by enhancing the density of the resin and opacifying and whitening the neck due to the crystallization of the thermoplastic resin by heat treating the neck. 
     Strengthening the neck area of a thermoplastic container greatly increases the craze resistance of the neck area, improves the mechanical rigidity and increases impact resistance, wear resistance, and external pressure resistance of the container. However, a common side effect of such a thermal treatment of the neck area of the container is an undesirable deformation of the neck area, thus leading to problems with capping and sealing the container. 
     U.S. Pat. No. 4,476,084 provides a solution to the problem of deformation during heat treating by placing a cold die pin or plug into the bore of the neck prior to heating. The cold die pin assists in maintaining the proper size and shape of the neck during the crystallization process. Others have found similar solutions. See, for example, U.S. Pat. Nos. 4,388,356, 4,379,099, 4,572,811, 4,590,021 and 5,261,545. The use of such cold plugs and dies however have led to problems when speed of manufacture is a priority. Inefficient heating, failure to properly position the plug and deformation of the thermoplastic container due to the weight of the plug have commonly been experienced, thereby leading to a further search for a fast, efficient way of crystallizing the neck area of the thermoplastic container. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The crystallizing machine and its process of this invention improves upon the efforts of the prior art in many ways. The machine makes use of a preheated plug which is inserted into the mouth or neck of a thermoplastic preform or container, commonly known as a workpiece. While the workpiece is described herein as being a thermoplastic, it is preferable that it be a thermoplastic polyester, and even more preferable that it be polyethylene terephthalate (PET). For the purposes of this description, references will be made to PET workpieces. However, this description is not intended to be limiting on the invention described herein. The workpiece is carried solely in an upright position by the preheated plug through the crystallizing process. The preheated plug assures even and efficient heating when crystallizing the finish area of the workpiece and constrains the shape of the finish area to a predetermined size and shape during the crystallizing process. 
     The crystallizing machine of the present invention is constructed from modular subassemblies. The first modular subassembly includes the workpiece in-feed and plug preheat operations and incorporates the power source and drive apparatus for the entire machine. The opposed end of the crystallizing machine is constructed of a module or subassembly which operates to provide the turnaround and tensioning for the transport member carrying the workpieces. Positioned between the first modular subassembly and the opposed end modular subassembly are heating and cooling processing modules or subassemblies which can be provided in any number, depending on the size constraints and workpiece quantity restraints desired. The processing modules provide the heating and crystallizing processes for the finish area of the workpiece and the cooling process for the workpiece prior to unloading. 
     For the purposes of the following description of the preferred embodiment, reference will be had to the following drawings and the crystallizing machine of the present invention will be described as having four subassemblies. However, the description of the invention is not intended to be limiting upon the scope of the claims which follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a right side elevation view with cutaway of the crystallizer machine of the present invention. 
     FIG. 2 is a right side elevation view with cutaway of the crystallizer machine of the present invention with access doors removed. 
     FIG. 3 is a left side elevation view with cutaway of the crystallizer machine of the present invention. 
     FIG. 4 is a left side elevation view with cutaway of the crystallizer machine of the present invention with access doors removed. 
     FIG. 5 is a cutaway right side elevation view of the processing modules of the crystallizer machine of the present invention. 
     FIG. 6 is a cutaway left side elevation view of the processing modules of the crystallizer machine of the present invention. 
     FIG. 7 is a top view with cutaway of the crystallizer machine of the present invention. 
     FIG. 8 is a front elevation view of the preheat, pickup and drive module of the crystallizer machine of the present invention. 
     FIG. 9 is a detail side elevation view of the preheat, pickup and drive module of the crystallizer machine of the present invention. 
     FIG. 10 is an elevation view of the in-feed apparatus of the preheat, pickup and drive module of FIG.  9 . 
     FIG. 11 is an end view of the workpiece stripper of the in-feed apparatus of FIG.  10 . 
     FIG. 12 is a top view of the in-feed apparatus of FIG.  10 . 
     FIG. 13 is a back elevation view of the processing modules of the crystallizer machine of the present invention. 
     FIG. 14 is a detail elevation view of the preheating source used in the crystallizer machine of the present invention. 
     FIG. 15 is a detail elevation view of the cooling source and the heating source used in the crystallizer machine of the present invention. 
     FIG. 16 is a detail elevation view of the cooling source used in the crystallizer machine of the present invention. 
     FIG. 17 is a perspective view of one embodiment of a workpiece pickup plug of the crystallizer machine of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-6, the crystallizer machine of the present invention as described herein is shown to have four modular sections. The number of modular sections can be varied as desired by increasing the number of processing sections, as shown in FIGS. 5 and 6, in order to meet design demands for workpiece size, material and speed of operation. For the purposes of this description, the crystallizer machine will be described as having four distinct modular sections: the preheat, pickup and drive module  10  as shown in FIGS. 1-4; the takeup module  11  as shown in FIGS. 1-4; and the heating and cooling processing modules  12 ,  13  as shown in FIGS. 5 and 6. The modules of the crystallizing machine are designed to provide a mezzanine level  14 , when joined together into a single operative machine. The mezzanine level  14  carries the cold air generating units  15  and blower fan units  16  and provides a walkway  17  for the operators. The mezzanine level  14  is accessible by a ladder or step assembly  18  provided on the end of the preheat, pickup and drive module  10  and includes safety railings  19  provided about the perimeter of the mezzanine level  14 . The floor of the mezzanine  14  incorporates a hot air plenum  21  and a cold air plenum  22  as shown in FIG.  13 . 
     Access doors  20  are provided on the front and back of the preheat, pickup and drive module  10 , as shown in FIGS. 1 and 3, which when opened, provide access to the machinery contained within the module  10  and when closed, provide a safety barrier. The access doors  20  preferably have glass windows through which the operator can observe the machinery operation. 
     Referring again to FIGS. 1 and 3, the takeup module  11  includes a pair of top access doors  23  located on the front and back of the module  11  and a set of bottom access doors  24  also located on the front and back of the module. The access doors  23 ,  24  when closed, facilitate the maintenance of desired internal atmosphere regulation, as it relates to the heating and cooling in the crystallizing process. The access doors  23 ,  24  are also used as safety shields when the machine is in operation and provide access to the internal machinery when opened. 
     Referring also to FIGS. 1 and 3, the processing modules  12 ,  13  each include a pair of top access doors  25  and a set of bottom access doors  26 . As with the access doors for the other modules, the access doors  25 ,  26  when closed, facilitate the maintenance of desired internal atmosphere regulation, as it relates to the heating and cooling in the crystallizing process. The access doors  25 ,  26  also provide a safety shield for the operator when closed and provide access to the internal machinery when opened. 
     Referring now to FIGS. 2 and 4, the drive mechanism for the crystallizer machine is located in the preheat pickup and drive module  10 . The drive mechanism includes a motor  27  engaged with a drive shaft  28  through a gear reducer  29 . The drive mechanism further includes a brake assembly, detailed in FIG. 9, composed of a disc brake rotor  30  fixed to the drive shaft  28 , brake shoes  31 , and brake actuator  32 . A drive sprocket rotary cam  33  is engaged with the drive shaft  28  and a drive sprocket  34  is also engaged with the drive shaft  28  through coupler  35 . A secondary drive shaft  36  is engaged with the drive sprocket  34  and receives drive forces imparted by the drive motor  27  through the drive shaft  28  and coupler  35 . The secondary drive shaft  36  provides driving forces through the 90° gear box  37  to a timing belt drive pulley  38 . 
     Referring now to FIGS. 8-12, the timing belt drive pulley  38  is engaged with a timing belt driven pulley  39  by drive timing belt  40 . Thus, drive power is imparted from the drive motor  27  to the in-feed apparatus, shown in detail in FIGS. 9-12, by the in-feed drive shaft  41 . The details of the in-feed mechanism will be discussed below. 
     Referring to FIGS. 2,  4 ,  5 ,  6 ,  8  and  13 , the transport member is shown. A top rail  42  is aligned with the drive sprocket rotary cam  33  and a takeup traction wheel rotary cam  43  which is located in the takeup module  11 . The top rail  42  extends the full length of the crystallizing machine. A bottom rail  53  is aligned with the drive sprocket  34  and extends the full length of the crystallizing machine to a lower takeup traction wheel  44 , also located in the takeup module  11 . The takeup traction wheel rotary cam  43  and takeup traction wheel  44  assembly is joined together by a shaft  45  mounted in a spherical bearing which is bolted to a frame member  46 . The frame member  46  is mounted on a slide bar frame  47 . A pneumatic piston actuator  48  is engaged with the frame member  46  and provides a positive force against the frame member  46 , thereby tensioning the takeup traction wheel rotary cam  43  and traction wheel  44  assembly to provide full tension and takeup on the plug carrier  49  which is engaged between the drive sprocket  34  and the lower takeup traction wheel  44 . 
     Referring now to FIGS. 9-12, the preheat, pickup and drive module  10  is shown in detail. Viewing FIG. 9, the drive sprocket rotary cam  33  is in alignment with the top rail  42 . Cam follower members  50  are engaged with the top rail  42  for guided travel thereon around the machine. Referring to FIGS. 2,  4 ,  5  and  6 , it can be seen that the cam follower members  50  will travel along the top rail  42  from the drive sprocket rotary cam  33 , past the takeup traction wheel rotary cam  43  and return to the drive sprocket rotary cam  33 . The drive sprocket rotary cam  33  is elevated in relation to the top rail  42  for reasons set forth below. Each cam follower member  50  carries an elongated quill  51  at the end of which is a plug  52  which is preferably composed of a coated metal, such as hard coat anodized aluminum. Drive sprocket  34  and lower takeup traction wheel  44  are in alignment with the bottom rail  53 . A plug carrier  49  is fixed to travel on the bottom rail  53  as it is driven by the drive sprocket  34 . The plug carrier  49  includes a plurality of cam members  56  which ride on the bottom rail  53 . The plug carrier  49  also includes a plurality of openings, preferably two per plug carrier link through which the quills  51  extend. Workpiece strippers  55  are fixed to the plug carrier  49  in alignment with the openings and the quills  51  and plugs  52  extend therethrough. Each workpiece stripper  55  and its respective quill  51  and plug  52  have matching centerlines. The plug carrier  49  provides the drive movement to the combined plurality of top cam follower members  50  and attached quills  51  and plugs  52  and bottom cam members  56  with workpiece strippers  55 . The top cam follower member  50  and top rail  42  combination provides vertical centering for the plug  52  and the bottom cam member  56  and bottom rail  53  combination provides horizontal centering for the plug  52 . Thus, the plug centerline is maintained on very rigid vertical and horizontal axes. 
     The top rail  42  is designed to have a first elevated portion  54  located on the left side of processing module  12 , as shown in FIG. 6, and a second elevated portion  101 , shown in FIG. 4, located on the left side of the preheat, pickup and drive module  10 , which aligns the rail  42  with the drive sprocket rotary cam  33 . The top rail  42  also includes an inclined portion  102  which immediately follows the drive sprocket rotary cam  33  located on the right side of the preheat, pickup and drive module  10 , as shown in FIGS. 2 and 9. In operation, it can be seen that when the cam follower members  50  with attached quill  51  are traveling along the top rail  42  around the drive sprocket rotary cam  33 , the respective plugs  52  are pulled up and positioned within the workpiece stripper  55 . As each cam follower member  50  with attached quill  51  travels down the inclined portion  102  of the top rail  42 , the quill  51  gradually is extended through the workpiece stripper  55 , thereby positioning the plug  52  to a predetermined location below the workpiece stripper  55 . It is in this position that the plug  52  engages the workpiece to carry it through the processing operations of the crystallizing machine. After the workpiece is fully processed, the cam follower member  50  travels up the first elevated portion  54  of the top rail  42  which pulls the plug  52  up into the workpiece stripper  55 , thus forcing the workpiece to be removed from its engagement of the plug  52 . The finished workpiece is then removed from the crystallizer machine by the exit conveyor  103 , shown in FIGS. 3 and 6. As the cam follower member  50  continues to travel along top rail  42 , it exits the first elevated portion  54 , moving to a lower position, thereby extending the plug  52  from the workpiece stripper  55 . The plug  52  is then preheated by heat lamps  96 , as will be described in detail later herein. As the cam follower member  50  travels up the second elevated portion  101  of the top rail  42 , the preheated plug  52  is retracted into the workpiece stripper  55 . The cam follower member  50  is carried by the drive sprocket rotary cam  33  to the inclined portion  102  of the rail  42 . As the cam follower member  50  travels down the inclined portion  102 , the preheated plug  52  extends out of the workpiece stripper  55  to engage a new workpiece. 
     Referring still to FIGS. 9-12, the in-feed apparatus is shown in detail. The in-feed apparatus is positioned within the preheat pickup and drive module  10  to feed workpieces  57  into engagement with the preheated plug  52 . The in-feed apparatus includes a support frame  58  which carries a drive shaft  41  mounted in bearings  59 . The drive shaft  41  has the driven timing belt pulley  39  fixed on one end which is engaged with the drive timing pulley  38  by the drive timing belt  40  which receives input from the secondary drive shaft  36  as shown in FIG. 8. A pair of opposed support blocks  60  are fixed for movement on rods  61  which are mounted on the support frame  58 . The support blocks  60  are capable of movement toward and away from each other on the rods  61  in order to accommodate different size workpiece. Located between the support blocks  60  is a conveyor belt and platform  62  which carries bottles or workpieces from a feed bin (not shown) which is positioned adjacent the crystallizer machine of this invention. The conveyor  62  aligns the workpieces for movement through the in-feed apparatus. Each support block  60  carries a drive sprocket  63  mounted on a phase adjustable hub  64  and bearing housing  65 . The drive sprocket  63  receives drive input from the drive shaft  41  through 90° bearings  66  and drive shafts  67 . Located at the ends of the support blocks  60  in opposition to the drive sprockets  63  are takeup sprockets  68 . The takeup sprockets  68  are mounted on keyed bearing hubs  69  positioned in a slot located in the support block  60 . Air cylinders  70  are fixed to each keyed bearing hub  69  to provide a positive force against takeup sprockets  68  and thereby create tension on the cleated chain  71  which is engaged by each set of drive sprockets  63  and takeup sprockets  68 . The cleated chain  71  is composed of a chain member  72  having cleats  73  attached thereto. The cleats  73  are adjustable on the chain member  72  and can be positioned to provide differing centerlines to adapt the cleated chain  71  to different size workpieces entering the in-feed apparatus. The cleated chains  71  are driven through the drive shafts  67  and drive sprockets  63  in rotationally opposite directions to provide movement in coordination with the moving conveyor belt  62 , thereby centering the workpieces  57  in alignment with the centerlines of the plugs  52  which are in position above the in-feed apparatus. Thus, as each quill  51  and plug  52  is extended in a downward direction by the cam follower members  50  traveling down the inclined portion  102  of the top rail  42 , the plug will cleanly engage the open mouth of the workpiece as shown in FIG.  9 . 
     A stop  74  driven by a pneumatic air cylinder  75 , shown in FIGS. 10 and 12, is positioned at the mouth of the in-feed conveyor  62  to prevent movement of workpieces into the cleated chain  71  area during non-operation of the crystallizing machine and shutdown of the in-feed apparatus. A bump bar  76 , shown in FIG. 10, is positioned at the end of the conveyor belt  62  where the workpieces  57  engage the plugs  52 . The bump bar  76  provides an upward force on the surface of the conveyor belt  62  which acts to firmly press and seat the workpiece  57  onto the plug  52 . The bump bar  76  is driven by a cam member  77  engaged by a belt  78  to a drive pulley  79 . The drive pulley  79  receives its drive from the drive shaft  41  through a 90° bearing  80  and drive shaft  81 . A conveyor head pulley  82  is also positioned to receive drive from the drive shaft  81 . The conveyor belt  62  is driven by the conveyor head pulley  82  and is carried by pulleys  83 , including takeup pulley  84  which is tensioned by an air cylinder  85 . 
     Also positioned on support frame  58  is an in-feed workpiece stripper  86 , shown in FIGS. 10 and 11, composed of a pair of cushioned rollers  87  mounted on an adjustable support block  88  and driven by drive shafts  89  which receive input through 90° bearings  90  attached to the in-feed drive shaft  41 . Infrared or dielectric sensors (not shown) are used to indicate whether the workpiece  57  has been firmly engaged with the plug  52 . If the workpiece is not firmly engaged with the plug  52 , the in-feed workpiece stripper  86  is activated and the rollers  87  engage the workpiece and remove it from the plug  52 . 
     Referring now to FIG. 13, and FIGS. 2,  4  and  5 , the heating and cooling apparatuses of the crystallizer machine of the present invention are detailed. FIG. 13 shows a back elevation view of the crystallizer machine showing the top rail  42  and bottom rail  53  which carry the cam follower members  50 ,  56 , quill  51 , workpiece stripper  55  and plug  52 . FIG. 13 also shows the blower  16  for supplying cooling air to the cooling air plenum  22  which in turn supplies the cooling air to the cooling air duct  91  located at the bottom of the crystallizer machine. The cooling air duct  91  runs the length of the machine and supplies cooling air to the individual air knives  92  through adjoining duct work  93 . Positioned in the duct work  93  are individual valve controls  94  which are used to regulate the amount of cooling air traveling to each set of air knives  92 . Referring to FIGS. 15 and 16, the cooling air knives  92  include nozzles  95  which are rotatably mounted on the duct work  93 . The duct work  93  includes flexible joints  104 . Thus, the nozzles  95  may be adjusted by rotation and by movement of the duct work  93  about the joints  104  to adapt to differing sizes of workpieces. Referring to FIG. 15, the structure wherein the cooling air knives  92  are used in cooperation with heat sources to provide crystallizing temperature and cooling temperature simultaneously is shown. Positioned immediately above the air knives  92 , as shown in FIG. 15, are heat lamps  96  positioned within reflectors  97 . The heat lamps  96  are used to apply heat to the finish area of the workpiece  57  to cause crystallization thereof while the air knives  92  are intended to cool the workpiece  57  immediately below its finish area to prevent crystallization thereof. Finally, in the preheat section of the preheat pickup and drive module  10 , as shown in FIGS. 4 and 14, the heat lamps  96  are used to preheat the plug member  52  and no air knives are in operation. Thus, in operation, the plug member  52  is preheated prior to insertion into the mouth of the workpiece. The workpiece then travels past the heat lamps  96  and air knives  92  such that the finish area of the workpiece receives heat from the preheated plug  52  and the heat lamps  96  to crystallize the finish area. The workpiece finally passes the cooling air nozzle as shown in FIG. 16 prior to exiting the machine. 
     Referring now to FIGS. 2 and 5, the right side elevation of the crystallizer machine of the present invention is shown. The processing modules  12  and  13 , shown in FIG. 5, and the takeup module  11  include a plurality of the heat lamps  96 , reflectors  97 , and air knives  92 , as shown in FIG. 15, which extend the full length on the right side of the processing modules  12  and  13  and up to a point proximate the takeup wheels  43 ,  44  of the takeup module  11 . To ensure a full understanding of the Figs., the air knives, heat lamps and reflectors are only partially shown in number in the Figures. The plug  52  is preheated to a temperature of between 150° F. to 170° F. prior to insertion into the mouth of the workpiece  57 . As the preheated plug  52  carries the workpiece past the heat lamps  96  and reflectors  97 , the finish area of the PET workpiece is gradually heated to a crystallizing temperature of approximately 350° F. while the air knives  92  maintain the remainder of the body of the workpiece cool. 
     Appropriate sensors (not shown) are located throughout the crystallizing machine and are used to monitor the temperature of the preheated plug  52 , monitor the proper seating of the mouth of the workpiece  57  with the plug  52 , monitor the exhaust heat and monitor the cooling air temperatures. Other sensors may be used throughout the system as desired. All sensors provide signals to a central processing unit (not shown) which coordinates the operation of the crystallizing machine. Hot air is removed from the crystallizing machine through the hot air plenum  21  and exhausted to atmosphere. 
     To provide even preheating of the plug  52 , the quill  51  has a gear  98  positioned immediately above the plug  52  which engages a stationary gear drive member  99 , as shown in FIG.  14 . Movement of the workpiece and engagement between the gear  98  and stationary gear drive  99  causes the plug  52  to continually rotate as it moves past the preheat sources, thereby providing even heat application to the surface of the plug  52 . As shown in FIGS. 15 and 16, the engagement between the gear  98  and the stationary gear drive member  99  will impart continuous rotation to the workpiece engaged with the plug  52  as it travels past the various heat sources and cooling sources. 
     Referring now to FIGS. 4 and 6, the left side elevation of the takeup module  11  includes air knives  92  without heat lamps  96  as shown in FIG.  16 . Cooling of the crystallized PET workpiece is effected by directing cool air from the air knives  92  over the entire workpiece  57 . The workpiece continues to pass by cooling air knives  92  located on the back of the processing module  13  and part of the processing module  12  until the workpiece is removed and directed down the exit conveyor  103  located in processing module  12 , as shown in FIGS. 3 and 6. After the workpieces have been removed from the plug  52 , the plug  52  passes the preheating source consisting of heat lamps  96  and reflectors  97  without air knives, as shown in FIG. 14 to effect preheating of the plugs  52 . 
     Referring now to FIG. 17, the preferred embodiment of the plug  52  is shown. The plug  52  is essentially a hollow shell constructed of hard coat anodized aluminum. The shell construction allows for rapid preheating of the plug  52 . An engagement aperture  105  is positioned on the centerline of the plug  52  to receive the quill  51  and attach the plug  52  thereto by conventional means. The outside diameter D of the plug  52  closely approximates the inside diameter of the mouth of the workpiece to provide a snug secure fit when the plug  52  is inserted into the mouth of the workpiece. The plug  52  tapers inward and downward from the outside diameter D to a smaller diameter d which assists the plug  52  to be inserted into the mouth of the workpiece. Flexible wire springs  100  are positioned about the tapered portion of the plug  52 , defining an outside diameter slightly larger than diameter D. The wire springs  100  flex when inserted into the mouth of the workpiece and expand to exert forces on the interior of the workpiece, thereby assisting in securing the workpiece on the plug  52 . 
     The above description of the preferred embodiment of the crystallizer machine of this invention is intended to be illustrative in nature and is not intended to be necessarily limiting upon the potential equivalents when determining the scope and content of the following claim.