Abstract:
A rotary blow molding machine comprising a rotatable wheel, a plurality of mold assemblies mounted on the wheel in circumferentially spaced apart relation, each of said mold assemblies being openable to expose a finished workpiece as the mold assembly moves through a workpiece discharge station. A take-out assembly removes a finished workpiece from a mold assembly as the mold assembly moves through said discharge station, the take-out assembly including a first transfer mechanism mounted adjacent said discharge station and including a first pick-up unit for grasping a finished workpiece and moving it in a substantially linear direction upwardly away from said wheel to a transfer station. A second rotary transfer mechanism is mounted at the transfer station for receiving a workpiece from the first pick-up unit and moving the workpiece to an exit station as the first pick-up unit returns to the discharge station to pick up another finished workpiece from the wheel.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to blow molding machines and more particularly to a take-out assembly for removing a blown article such as a plastic bottle from a mold assembly on the machine and transferring it to a material-handling conveyer. 
     Blow molding machines are used to produce various types of articles and have been found to be particularly useful in making plastic bottles containing various types liquids such as cooking oils, beverages, household chemicals, etc. The machines operate by extruding into a mold cavity a parison of plastic material which is heated to a semifluid state, and then is subsequently subjected to internal pressurization through an inserted needle causing the plastic to inflate and conform to the inside surfaces of the mold cavity. 
     A popular type of blow molding machine includes a rotary wheel or turntable, which rotates about a horizontal axis. The wheel has a number of multi-piece, openable and closeable mold assemblies circumferentially spaced therearound. The wheel is rotated past a number of work stations, at a first work station the mold parts are separated to expose the mold cavity and, as the parts arrive at or pass a discharge nozzle of a plastic extruder, the cavity is charged with the heated plastic parison. That mold assembly is then clamped together and rotated to the next work station where a fluid such as air is injected into the mold to cause the parison charge to expand and conform to the inside configuration of the mold cavity. As the wheel continues to rotate, the mold assembly is cooled, thereby causing the plastic material to solidify. At a final discharge workstation, the mold assembly is opened and the finished plastic bottle is removed by a take-out assembly. 
     A production capacity is determined by the number of blow mold assemblies located around the circumference of the wheel, the speed of rotation of the wheel, and the rate at which the take-out assembly is capable of removing finished bottles from the rotating wheel. 
     In the past, take-out assemblies have been of rather complex construction and quite often have been unable to operate fast enough to permit the blow molding wheel to be operated at its maximum production capacity. Thus, the cost of producing the finished plastic articles has been unnecessarily compromised. 
     SUMMARY OF THE INVENTION 
     The primary object of this invention is to provide a blow molding machine of the rotary wheel type having a plurality of mold assemblies spaced around the circumference thereof, and a take-out assembly located adjacent a discharge station of the rotary wheel, the take-out assembly being of simple, economical, but yet reliable construction capable of operating at a capacity sufficient to enable the rotary wheel to function at its maximum designed production speed. 
     The novel take-out assembly of the invention accomplishes the above objective by providing a first substantially linear or large radius curved transfer mechanism which removes a finished bottle from a mold assembly at the discharge station of the rotating wheel and transfers that finished bottle upwardly along substantially a straight line to a second separate rotary transfer mechanism which receives the bottle from the first mechanism, rotates the bottle through 1800 into an upright position, and then places the upright bottle onto an exit transfer conveyer. The overall pickup assembly is capable of operating at higher speeds because once a finished bottle is transferred from the first mechanism to the second mechanism, the first mechanism may quickly return to the discharge station of the wheel to pick-up a finished bottle from the next mold assembly presenting itself on the wheel. During the return stroke of the first pick-up mechanism, the second rotary transfer mechanism places the first bottle onto the exit transfer conveyer and subsequently returns to its initial handoff position ready to receive the next bottle from the first linear transfer mechanism. 
     The novel take-out assembly of the invention has been especially adapted for use with a blow molding machine having an approximately fifty-three inch (53″) pitch diameter wheel with five mold assemblies positioned around the circumference thereof and capable of producing large blown plastic bottles, for example of a two and one half gallon size (4½″ wide×9″ long×15″ high) or thirty-five pound size (16″ high×9⅜″ square) capable of producing about twenty-five bottles per minute (25 bpm). The first linear transfer mechanism moves a finished bottle away from the wheel, so that the wheel may continue to rotate, along substantially a straight line through a distance of about forty-six inches to a handoff station where it is handed off to the second rotary mechanism which rotates on a radius of about twenty-four inches to place the finished bottles on the exit conveyer. Advantageously, the novel take-out mechanism of the invention is capable of operating at at least twenty-five bpm, the maximum capacity of the blow molding wheel. 
     In operation, as the wheel rotates into the take-out position at the final discharge station, the mold is opened, knockouts in the mold eject the bottle from the mold and place it on the wheel&#39;s centerline ready for pickup. The first linear transfer mechanism picks up the bottle with a combination of vacuum cups and grippers and moves the bottle along a substantially straight line to a handoff station located about three feet upwardly away from the wheel. The first mechanism pulls the bottle out of the way of the wheel so that the wheel may continue to cycle. During the linear transfer of the bottle, the bottle is rotated by a cam, track or actuator (pneumatic cylinder), so that when it reaches the handoff station the bottle is in the proper bottom up vertical orientation ready for handoff. At the handoff station, the second rotary transfer mechanism employs a head assembly with vacuum cups and/or grippers, the head assembly being first extended to grab the bottle from the first mechanism and then slightly retracted so that the first mechanism can repeat the bottle pick up cycle without interference from the second rotary mechanism. The rotary transfer mechanism then rotates the bottle through one hundred and eighty degrees to orient the bottle right side up. The head assembly is then again extended to place the bottle on the linear transfer conveyer. Alternatively, the head assembly may be extended as it is rotated. Subsequently, the head assembly is retracted to clear the conveyer and permit the rotary mechanism to rotate without interference. Operation of the first and second mechanisms is timed so that each is able to operate at sufficient speed and to cooperate with each other so that finished bottles may be removed from the rotary wheel at a speed sufficient to permit the rotary wheel to operate at its maximum designed capacity. 
     As an added advantageous feature of the novel take-out assembly, the pick up device of the first linear mechanism includes both vacuum cups and mechanical grippers, the vacuum cups normally engaging the finished blown bottle and performing the transfer operation out of the mold to the handoff station. However, if a miss blow occurs the mechanical grippers will still pick up the parison and transfer it out of the mold. At the handoff location, the second rotary transfer mechanism only has vacuum cups that cannot pick up a miss blown pan son. Therefore, when the mechanical grippers of the first mechanism release the parison, the parison is dropped and falls onto a slide which directs the miss blown parison away from the machine without causing any handling or jamming problems of the machine. 
     These and other objects of the invention will become apparent from reading the following description of the invention wherein reference is made to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary front side elevational view illustrating a conventional blow-molding machine which incorporates the novel part take-out system of the invention. 
     FIG. 2 is a top plan view of the rotary blow-molding machine taken along line  2 — 2  of FIG. 1 generally illustrating the rotary wheel. 
     FIG. 3 is a fragmentary end view of the blow-molding machine taken along line  3 — 3  of FIG.  1  and schematically illustrating the novel part take-out system of the invention. 
     FIG. 4 is an enlarged schematic illustration of the part take-out system of FIG. 1 showing the path traveled by the bottle as it is removed from the rotary blow-molding machine and placed onto an exit transfer conveyer. 
     FIG. 5 is a fragmentary schematic view taken along  5 — 5  of FIG. 4 illustrating the front face of the pick up head which forms part of the linear transfer mechanism of the take-out system. 
     FIG. 6 is a fragmentary side view taken along line  6 — 6  of FIG.  5 . 
     FIG. 7 is a fragmentary top view taken along line  7 — 7  of FIG.  5 . 
     FIG. 8 is a fragmentary bottom perspective view taken generally along line  8 — 8  of FIG.  4  and illustrating the part take-out system including the linear transfer mechanism and the rotary hand of mechanism which cooperate to move the bottle tom the rotary blow-molding machine to the discharge exit conveyer. 
     FIG. 9 is a schematic end perspective view taken along line  9 — 9  of FIG.  4  and illustrating the rotary hand off mechanism and its servo operating system. 
     FIG. 10 is a simplified top plan view of the rotary transfer mechanism taken along line  10 — 10  of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 to  3  illustrate a blow-molding machine  20  having a frame  21 , a generally conventional blow molder wheel assembly  22  and a novel part take-out assembly  24  constructed according to the invention, both mounted on frame  21 . 
     Blow molder wheel assembly  22  includes a horizontal shaft  26  rotatably mounted within bearings  28  and intermittently rotated by a suitable drive unit  30 . A plurality of separable, two-part mold assemblies  32  (e.g. five) are equally circumferentially mounted around shaft  26  via spaced collars  34  and central ring  35  fixed on the shaft and rods  36  extending between the collars and through ring  35 . Each half of mold assemblies  32  includes a tubular socket  38  which is slidably mounted on rods  36  to permit the mold assemblies to be opened via cam  42  and closed via hydraulic actuator  44 . 
     During the production cycle, as wheel  22  intermittently rotates clockwise, segments of hot molten plastic from an extrusion nozzle  43  are deposited within the opened mold assemblies  32  which occurs at about the two-o&#39;clock rotated position of the wheel as shown in FIG.  1 . After the molten parison is deposited within mold cavity  33  of a mold assembly  32 , the mold assembly is closed and air is blown into the parison via an inflation pin to expand the parison until it conforms to the internal surfaces of cavity  33  which defines the final configuration of the workpiece or part, which as illustrated is a large rectangular bottle  50  with a spout  52 , handle  54 , flash portion  56  at the top center of the bottle, and flash portion  58  at the bottom center of the bottle. 
     During continued rotation of the wheel, the mold assembly is cooled to cause the plastic material to solidify. At approximately the ten-o&#39;clock rotated position of FIG. 1, cooperating action between cam  42  and linkages  40  opens the mold assembly to expose the bottle  50 . As the mold assembly indexes to the one-o&#39;clock position, part knock-outs actuate to hold the bottle at approximately one-o&#39;clock position of the vertical center line of wheel  22  for pick up by the bottle take-out assembly  24 . Once the part take-out grabs the bottle, the knockouts retract. The bottle is removed from the mold assembly in a slightly upwardly inclined bottom up orientation. The next cycle for that opened mold assembly begins again as described above. 
     As mentioned above, the generally described construction and operation of wheel  22  is conventional. The pitch diameter of the wheel of an actual machine is about fiftythree inches, the wheel includes five mold assemblies  32  capable of molding large plastic bottles such as a 2½ gallon bottle (15″ high×4½ wide×9″ long) or a nearly five gallon bottle (16″ high×9⅜″ square), and the wheel can be rotated at a speed of five (5) rpm to produce 25 bottles per minute (bpm). As discussed initially, prior part take-out assemblies have been incapable of reliably removing bottles from the wheel at its maximum production rate of 25 bpm, and it was necessary to run the wheel at a lower speed, thus reducing the production rate of the machine. 
     The novel part take-out assembly  24  of the invention was developed to overcome that problem, thus enabling the wheel to be operated at its maximum capacity of 25 bpm. 
     As shown in FIGS. 1 and 4, the part take-out assembly  24  includes linear transfer mechanism  70  and rotary transfer mechanism  72 . Mechanism  70  includes a straight stationary track assembly  74  fixed to the frame  21  by brackets  76  and extending upwardly from wheel  22  at an angle of about 60° at about the 12:30 o&#39;clock position. A slide plate  78  is slidably mounted on track assembly  74  for up and down movement and is driven by a servo mechanism  80 . A pick up plate  82  (FIGS. 4-8) is pivotally connected at  84  to the lower end of slide plate  78 . A pair of pneumatic suction cups  86  are mounted on the front face of plate  82  at its lower end and a pair of mechanical grippers  88 , opened and closed by solenoid  90 , are mounted on the upper end of plate  82 . A bar  92  extends rearwardly from a lower corner of plate  82  and a cam roller  94  is attached thereto, the cam roller riding in a cam slot  96  formed by the front edge  98  of track  74  and an elongated bar  100  spaced therefrom by strips  102 . 
     As shown schematically in FIGS. 1 and 4, when slide plate  78  is at the bottom of track  74 , lift plate  82  is nearly horizontal but angled upwardly at a small acute angle, substantially parallel to the slightly upwardly inclined angle of bottle  50  at the discharge station of wheel  22 . The bottle is ejected from the open mold assembly at the discharge station in a bottom up orientation so that suction cups  86  engage against the front wall of the rectangular bottle and grippers  88  pinch against opposite sides of the central flashing strip  58  formed on the bottom  51  of the bottle. As plate  78  is moved upwardly in a straight line along track  74 , cam roller  94  rides in cam slot  96  which is configured so that plate  82  rotates about pivot  84  from its near horizontal orientation at which it picks up the bottle from wheel  22  to a substantially vertical orientation at its raised position at the upper handoff station  73 . As this occurs, bottle  50  travels upwardly in a substantially straight line, but it is also turned so that it is in a bottom up, vertical orientation when it reaches the handoff station  73  in readiness for transfer to the rotary transfer mechanism  72 . 
     Rotary transfer mechanism  72  includes a rotary head assembly  110  (FIGS. 1,  4 ,  8 ,  9 , and  10 ) mounted via servo mechanism  112  on frame  21  adjacent the upper end of mechanism  70  for counter clockwise rotation about an axis parallel to the axis of rotation of shaft  26  and for back and forth horizontal movement (arrow  113 ) along a line parallel to horizontal diametrical line of rotary wheel  22 . Head assembly  110  includes an outer transfer portion  114  having opposite vertical end faces  116  and  118  each provided with pneumatic suction cups  120 . A pair of spaced, horizontal support rods  122  extend outwardly beyond each face  116  and  118 . 
     As seen in FIGS. 1,  4 , and  8 , a horizontal discharge conveyer assembly  130  is mounted adjacent the left discharge end of head portion  114 , with conveyer assembly being formed by two parallel conveyer lines  132  and  134  separated by space  136 . 
     In summary, machine  20  operates as follows: 
     As wheel  22  rotates clockwise and a mold assembly  32  reaches the approximate ten o&#39;clock rotated position of FIG. 1, cam  42  and linkages  40  open that mold assembly to expose the bottle  50 . As that mold assembly rotates past the twelve o&#39;clock position, part knock-outs within that assembly extend to eject the bottle and discharge the bottle approximately on the vertical center line of wheel  22  with the bottle in a slightly upwardly inclined bottom up orientation. As illustrated schematically in FIG. 4, with slide plate  78  in its lowermost position, pick-up plate  82  under the action of cam roller  94  and cam slot  96  is in a near horizontal, slightly upwardly inclined position corresponding to the position of bottle  50  being ejected so that suction cups  86  engage against the front wall of bottle  50  and the mechanical grippers  88  pinch the flashing strip  58  on the bottom wall  51  of the bottle. The part knockouts then retract. Servo mechanism  80  then quickly moves slide plate  78  upwardly along track  74  thereby quickly removing bottle  50  away from the path of rotation of turntable  22  up to the bottle handoff station  73 . The bottle travels upwardly along a substantially linear path generally parallel to track  74 . However, as slide  78  moves upwardly, pick-up plate  82  pivots counterclockwise about the pivot point  84  under the action of cam roller  94  and slot  96  so that the bottle  50  is turned from its slightly inclined orientation at the discharge station of wheel  22  to a substantially vertical, upright bottom-up orientation at hand off station  73 . When plate  82  and bottle  50  reach the hand off station  73 , rotary head assembly  110  of rotary transfer mechanism  72  is extended horizontally from a center position by a pneumatic cylinder  112  toward bottle  50  (to the right in FIGS. 1 and 4) so that suction cups  120  engage against the back wall of bottle  50  to grasp the bottle as suction cups  86  and grippers  88  are released therefrom. Rotary head assembly  110  is then returned horizontally back to its center position, moving bottle  50  away from plate  82  and providing clearance between the bottle and suction cups  86  and grippers  88  so that slide plate  78  and pick up plate  82  can be rapidly returned downwardly along track  74  adjacent the discharge station of wheel  22  to pick up the next bottle  50  from the next mold assembly  32  on turntable  22 . Simultaneously therewith, servo mechanism  112  rotates head assembly  110  in a counterclockwise fashion through 180°, thereby rotating bottle  50  from its bottom up orientation to a bottom down upright orientation (on the left side as shown in FIG.  4 ). The head assembly  110  is then again extended slightly to the left to place the bottom  51  of the bottle on the spaced conveyor lines  132  and  134  with the flashing  58  on the bottom of the bottle positioned within the space  130 . Suction cups  120  are then released from bottle  50  and the head assembly  110  is retracted back to its center line position and the suction cups  120  on the opposite face  118  of head portion  114  are positioned at the hand off station  73  ready to receive the next bottle  50  from pick up plate  82 . The spaced fingers  122  are mounted on head portion  114  so that they are positioned to engage against the bottom  51  of each bottle straddling the bottom flashing  58  and helping to support the bottle as the bottle is rotated through 180° from its bottom up orientation at hand off station  73  to its bottom down upright orientation at the discharge conveyor assembly  130 . 
     Drive unit  30 , servo mechanism  80 , and servo mechanism  112  are operated in synchronism so that wheel  22  can be rotated at its maximum speed to produce 25 bottles per minute, in contrast to the 20 bottles per minute limited by the prior art take-out mechanisms. This substantial increase in production is attributable to the fact that the linear transfer mechanism  70  is separate from the rotary transfer mechanism  72  and once one bottle  50  is handed off from pickup plate  82  to the rotary head assembly  110 , the pick up plate  82  is quickly returned down to the discharge station of wheel  22  to pick up the next bottle  50 . Simultaneously with that movement, rotary head assembly  110  rotates the first bottle from the hand off station  73  to the discharge conveyer  130  so there is no time lost due to independent operation of the linear transfer mechanism  70  and the rotary transfer mechanism  72 . 
     The linear transfer mechanism  70  and the construction of pick up plate  82  which includes the suction cups  86  and mechanical grippers  88  provides another important feature of the invention. If a missblow occurs and the parison is not blown within the mold cavity, the grippers  82  will still pick up the parison and transfer it out of the mold assembly up to the hand off station  73 . At the hand off station, the rotary head assembly has only the vacuum cups  120  which cannot grasp a missblown parison. Therefore, when grippers  88  release the parison, the parison drops downwardly and falls onto a slide plate  140  which directs the parison away from wheel  22  and allows it to exit the machine  20  without causing any handling or jamming problems. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof The present embodiments are, therefor, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefor intended to be embraced therein.