Abstract:
A blow molding machine capable of relatively high production rates at relatively low cost is provided. The blow molding machine comprises a base, a reciprocating shuttle mechanism supported by the base, a single blow molding station supported by the base, and adapted to receive a parison for forming the hollow article at the blow molding station, a pair of cooling stations supported by the base on flanking sides of the blow molding station, a pair of blow pin carriages spaced from one another, each of which is connected to the shuttle mechanism and is indexable to the blow molding station and to one of the cooling stations. Each blow pin carriage can comprise one or more blow pin assemblies that are movable independent of the shuttle mechanism between a rest position and a blow position.

Description:
FIELD OF INVENTION 
     This invention relates to machines and sub-assemblies thereof for manufacturing hollow articles from thermoplastic materials by blow molding. 
     BACKGROUND OF INVENTION 
     Blow molding is a fabrication method for hollow thermoplastic shapes. 
     Two general classes of plastic products are made in this manner—packaging products and technical parts. Packaging products include such items as bottles, jars, jugs, cans, and the like. Technical parts include automotive components such as bumpers, fuel tanks, functional fluid containers, ducting, and the like. 
     The blow molding process can be of two general types: extrusion blow molding and injection blow molding. In extrusion blow molding, a parison is lowered between mold halves from an extruder. The mold halves then close around the parison, and the mold is transferred to a blowing station where the parison is then expanded against a mold cavity by introduction of a blowing gas, usually air. In injection molding, a thermoplastic material is first injection molded into a preform parison which is then transferred to a blow mold and expanded in the same manner as in an extrusion blow molding process. In both cases, however, the parison is transported from a parison receiving station to a blow molding station to complete the fabrication of a hollow plastic article. 
     In continuous extrusion, a molten parison is produced from an extruder die without interruption, and a segment thereof is severed and positioned into a mold. In many blow molding machines, the molds are moved from station to station on rotating vertical wheels, on a rotating horizontal table, or with a reciprocating action of a shuttle mechanism. 
     Most of the current blow molding machines utilize the reciprocating mold concept according to which the molds are shuttled back and forth from the parison receiving station to the blow molding station. A major drawback of the reciprocating mold concept, however, is a limitation on production rate because of the multiple stations in the process, namely the parison insertion station, the blow molding station, and the cooling station. Another drawback of the reciprocating mold concept is that many heavy parts must be moved during the blow molding process. For example, an entire shuttle mechanism with multiple blow molding stations and parison receiving stations may need to be moved during the process. Another concern present in many existing blow molding machines is the number of moving parts in the machines. 
     A further problem with most blow molding concepts is that after the parison is positioned in a mold, the mold is then taken to a separate blowing station where the air or other fluid is injected into the parison to form the hollow article. The time required to move the mold from the station where the parison is positioned to the blow molding station creates stress on the parison before inflation because of cooling that occurs with the parison, which makes the inflation process more difficult. 
     In view of the relatively large commercial demand for various types of plastic articles, it would be desirable to have a blow molding machine of relatively high capacity that can produce high quality articles at a relatively low cost, and which avoid the problems discussed. The present invention satisfies this desire by reducing the amount of tooling, reducing the mass of moving parts, reducing the traveling distance of moving parts, reducing the stress on the parison before inflation, minimizing in-mold time for the hollow article to improve cavity utilization, and maximizing cooling effectiveness. 
     SUMMARY OF THE INVENTION 
     The present invention provides a blow molding machine capable of relatively high production rates at relatively low cost, which requires fewer moving parts and reduces stress on the parison. 
     The foregoing advantages are achieved by a blow molding machine having a single blow molding station that also is adapted to receive a parison. In particular, the blow molding machine comprises a base, a reciprocating shuttle mechanism supported by the base, a single blow molding station supported by the base, which is adapted to receive a parison for forming the hollow article at the blow molding station, a pair of cooling stations supported by the base on flanking sides of the blow molding station, a pair of reciprocating blow pin carriages spaced from one another, each of which is connected to the shuttle mechanism and is indexable between the blow molding station and one of the cooling stations. Each blow pin carriage comprises one or more blow pin assemblies whose vertical positions relative to the shuttle mechanism are independently adjustable between a rest position and a blow position. The blow molding station is fixed relative to the base, and the blow pin carriages are indexed to the blow molding station alternatively. The shuttle mechanism, which moves in a substantially horizontal plane relative to the base, may be driven and controlled in any convenient manner, e.g., by a hydraulic driving mechanism, a mechanical driving device, or any other driving device as is known in the art, such as a pneumatic cylinder, a solenoid device, or the like. 
     The present invention may be adapted to mold a single hollow article or multiple hollow articles at a time. For example, if a single hollow article is to be formed, a single parison is received by a mold configured with a single cavity to form a single hollow article, such as a bottle. If multiple articles are to be formed, a single parison combined with a multiple cavity mold, or multiple parisons with a multiple cavity mold may be used. 
     As discussed above, parison used in blow molding can either be extruded, or preformed. The present blow molding machine may be arranged to accept either extruded parison or preforms into the blow molding station. 
     Once the parison is received at the blow molding station, the mold, which typically comprises two complementary mold halves, is closed around the parison, and in the case of an extruded parison, pinches shut one end of the parison. A blow pin carriage that comprises at least one blow pin assembly is juxtaposed relative to the mold, and the blow pin is moved to a blow position and is engaged with the mold. When the blow pin carriage is juxtaposed relative to the mold, the blow pin assembly can be engaged with the open end of the parison. Air or some other gaseous fluid is injected into parison, which causes the parison to be inflated inside the mold so as to form the molded article. The mold is then opened, and the molded hollow article is carried by the blow pin carriage to one of a pair of cooling stations that flank the molding station. 
     The present invention, when adapted to receive extruded parison, also preferably includes a top plate that is supported by the shuttle mechanism and is adapted to move in a substantially horizontal plane relative to the base. This top plate defines one or more apertures through which the parison may be received to be formed into a hollow article. As the formed hollow article is carried from the blow molding station to the cooling station, flash produced during the molding operation is supported by the top plate, and particularly by an edge of one of the apertures in the top plate. 
     The cooling station is comprised of a holding mechanism, which may be any device or arrangement that can be used to receive and grasp a molded hollow article as is known in the art. Preferably, this holding mechanism includes one or more pairs of gripping rails juxtaposed relative to one another and spaced to receive and grasp a molded hollow article in between the gripping rails. After the molded hollow article is received and grasped by the holding mechanism, such as the gripping rails, the blow pin assembly is retracted downwardly from the blow position to a rest position such that the blow pin assembly is sufficiently lowered out of the hollow article so that it may be moved in a substantially horizontal plane back to the, blow molding station, and away from the cooling station for the next operating cycle. Alternatively, if the molded hollow article is sufficiently cooled during its transport from the blow molding station to the cooling station, the hollow article may be ejected upon reaching the cooling station. 
     After a hollow article is molded, and as it is being carried to one of the cooling stations by a first of the blow pin carriages, the second blow pin carriage is indexed with the blow molding station, is raised to a blow position, and engaged with the mold. A parison is then inflated and molded in the same manner as previously discussed. Once this second hollow article is molded, and the mold is opened, the molded hollow article is carried by the blow pin carriage to the cooling station on the opposite flank from the previous cooling station. The first blow pin carriage is shuttled back to the blow molding station as the second hollow article is transported to the opposite cooling station. This alternating process cycle is continued as long as desired. 
     In one embodiment of the present invention, a formed hollow article is held at the cooling station until the next formed hollow article is carried by the blow pin carriage to the cooling station and knocks the first hollow article out of the cooling station holding mechanism. For example, where the holding mechanism is the pair of gripping rails juxtaposed relative to one another and spaced to receive and grasp a molded hollow article in between the rails, the next formed hollow article is carried to and in between the rails. As the second molded hollow article is carried between the two rails, it pushes the previous hollow article out of the cooling station into a bin or the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings. 
     FIG. 1 is a perspective view of a blow molding machine that shows an embodiment of the present invention. 
     FIG. 2 is a partial side elevation schematic view of a blow molding machine that may be embodied in the present invention. 
     FIG. 3 is a partial side elevation view of a blow molding station showing a blow molding station. 
     FIG. 4 is a partial side elevation of an embodiment of one of the pair of cooling stations that may be embodied in the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention disclosed herein is susceptible to embodiment in many different forms. Shown in the drawings and described in detail hereinbelow are certain preferred embodiments of the present invention. The present disclosure, however, is an exemplification of the principles and features of the invention, but does not limit the invention to the illustrated embodiments. 
     For ease of description, the blow molding machine of this invention will be described as it exists in a normal operating position, and terms such as upper, lower, top, bottom, vertical, horizontal, etc. will be used with reference to that position. Also for ease of description, the invention will be described in the context of the formation of single bottles with a single mold. 
     Referring to FIG. 1, an embodiment of a blow molding machine  10  suitable for molding a hollow article  15 , such as a plastic bottle, from a thermoplastic parison  20  according to the present invention is shown. Also shown in FIG. 1 is a base  35 , a reciprocating shuttle mechanism  40  supported by the base  35 , a single blow molding station  25  with a pair of spaced cooling stations  30 ,  31  (FIG. 2) flanking the blow molding station  25 , a pair of blow pin carriages  45 ,  46  spaced from one another, each of which is connected to the shuttle mechanism  40  and is indexable between the blow molding station  25  and one of the cooling stations  30  by linear reciprocatable movement. Each blow pin carriage  45 ,  46  comprises one or more blow pin assemblies  50 ,  51  that extend upwardly from their respective carriages and are movable not only horizontally by the shuttle mechanism  40 , but also independently of the shuttle mechanism  40  between a rest position and a blow position as described in detail below. The positions of the blow molding station  25  and the cooling stations  30 ,  31  (FIG. 2) are adjustably fixed relative to the base  35 . In other words, during normal operation of the blow molding machine  10 , the blow molding station  25  and cooling stations  30 ,  31  are stationary relative to the base  35 . The blow molding station  25  and cooling stations  30 ,  31  may be configured to be individually adjusted between molding operations depending on the subsequent molding operation intended. 
     The parison  20  to be molded may be supplied by a continuous extruder  55  (FIG.  1 ). Instead of continuous extrusion, the parison to be molded can also be supplied to the blow molding station  25  as a preform. (not shown). Both continuous extrusion devices and parison preform insertion devices are well known in the art. Therefore, it is contemplated that any suitable extrusion device or preform insertion device may be utilized with the present invention. It is preferred that the parison  20  is extruded such that it will be engaged from below by one of the blow pin assemblies  50 ,  51 . In this preferred arrangement, the top of the extruded parison  20  is pinched and sealed shut by the closing of complementary mold halves  60 ,  63 , which together form the mold (FIG.  2 ). 
     Referring to FIG. 2, the reciprocating shuttle mechanism  40  is movable in a substantially horizontal plane relative to the base  35 . FIG. 2 shows the blow molding machine  10  with the cooling stations  30  and  31 , and the blow molding station  25 . The location of the cooling station  30  and blow pin carriage  45  together with blow pin assembly  50  are shown in phantom, but the components that preferably make up the cooling station  30 , such as gripping rails, are not shown, but are substantially the same as those shown with cooling station  31 . The shuttle mechanism  40  moves in a reciprocating manner. In the preferred embodiment, the shuttle mechanism  40  is moved by hydraulic cylinder  70  which is also supported by the base  35 . Alternatively, any other device for actuating the shuttle mechanism  40  may be used, such as a solenoid device, a mechanical driving device, a pneumatic cylinder or the like. In the preferred embodiment of the present invention, the shuttle mechanism  40 , which is a relatively heavy part of blow molding machine  10 , is movable only in a substantially horizontal plane, and is not movable vertically relative to the base  35 . 
     The shuttle mechanism  40  indexes blow pin assemblies  50 ,  51  with the blow molding station  25  and the cooling stations  30 ,  31 . In FIG. 2, blow pin assembly  50  is shown engaged with the mold  65  at the blow molding station  25 . Blow pin assembly  50  is also shown with blow pin carriage  45  in phantom at cooling station  30 , to indicate where blow pin assembly  50  may be indexed when at cooling station  30 . 
     Specifically shown in FIGS. 1 and 2, mounted on the shuttle mechanism  40  are a pair of blow pin carriages  45 ,  46 . In this preferred embodiment, a top plate assembly  80  is also mounted on the shuttle mechanism  40 . As shown in FIG. 2, top plate  80  defines one or more apertures  82 ,  84  through which the parison  20  may be passed to be formed into a hollow article  15 . After the hollow article  15  is formed, and as formed hollow article  15  is carried from the blow molding station  25  to one of the cooling stations  30 ,  31 , a flash portion  21  generated during the molding process is supported by the top plate  80 , and more particularly by an edge of the apertures in the top plate  82 ,  84 . Gripping rails  95 ,  96  retain the molded hollow article  15  at cooling stations  30 ,  31  after the blow pin has been withdrawn from the molded hollow article  15 . 
     Referring to FIG. 3, each of the blow pin carriages  45 ,  46  includes at least one blow pin assembly  50 ,  51 . As discussed, each blow pin carriage  45 ,  46  may also have multiple blow pin assemblies if desired. In the embodiment shown, where only a single hollow article  15  is being formed per molding operation at the blow molding station  25  (FIG.  3 ), each blow pin carriage  45 ,  46  has only one blow pin assembly  50 ,  51 . Shown in FIG. 3 is blow pin assembly  50 , which is of a type conventionally used in an extrusion blow molding apparatus, but may be of any arrangement that is capable of inflating a parison in a mold, either concurrently extruded or preform. Each of the blow pin carriages  45 ,  46  is adapted to engage the mold constituted by mold halves  60  and  63  at the blow molding station  25  (FIG.  3 ), and to enable its respective blow pin assembly  50 ,  51  to engage and inflate the parison  20  so as to form the hollow article  15 , such as a bottle. The parison  20  is engaged from below the mold halves  60 ,  63 . Each of the blow pin carriages  45 ,  46  is also adapted to carry a molded hollow article  15  after it has been formed from the parison  20  so that the hollow article  15  may be transported from the blow molding station  25  to one of the cooling stations  30 ,  31  (FIG. 2) by a blow pin carriage  45 ,  46  without the use of an additional carrying device. For example the formed molded hollow article  15  may simply rest on the blow pin carriage  45 ,  46 . In a preferred embodiment, the blow pin assemblies  50 ,  51  themselves, each of which is part of a blow pin carriage  45 ,  46 , may be adapted to carry a molded hollow article  15  as shown in FIG. 3 with respect to blow pin assembly  50 . It is further preferred that the top plate  80  supports flash portion  21  during the transport of the formed hollow article  15  to one of the cooling station  30 ,  31 . 
     As also shown in FIG. 3, the mold halves  60  and  63  are moved from an open mold position to a closed mold position by hydraulic cylinders  61  and  62  (FIG.  1 ), or by any other suitable clamping mechanism. In the closed mold position the parison is enveloped by the mold halves  60  and  63 . As the mold is closed, one of the blow pin carriages  45  or  46  is engaged with the mold, and a blow pin assembly  50  or  51  is engaged with the parison so as to inflate the parison  20  to form the hollow article  15 . As discussed, with an extruded parison, the mold halves  60 ,  63 , pinch together when closed to seal the top end of the parison  20  to be molded. In a preferred embodiment, the blow pin assembly  50 ,  51  is upwardly extending and positioned so that the blow pin assembly  50 ,  51  engages the parison  20  from below at the open bottom end of the parison  20  when the respective blow pin carriages are elevated. As shown in FIG. 2, blow pin carriage  45  is shown in blow position (blow pin assembly  50  is obstructed by mold  65 ), such that blow pin carriage  45  and blow pin assembly  50  are elevated relative to the blow molding station  25  and engage the parison within mold  65  to form the hollow article  15 . 
     After the hollow article  15  is formed, the mold halves  60  and  63  (FIG. 3) are opened to allow the formed hollow article  15  to be transported away from the blow molding station  25  to one of the pair of cooling stations  30 ,  31  flanking the blow molding station  25 . As discussed above, a preferred embodiment of an extrusion blow molding machine includes a top plate assembly  80  that is reciprocated above the mold  65 , and which supports the hollow article  15  by the flash portion  21 . 
     As shown in FIG. 2, blow pin carriage  45  is indexable with the blow molding station  25  and cooling station  30 , and blow pin carriage  46  is indexable with blow molding station  25  and cooling station  31 . The blow pin carriages  45  and  46  are indexable with the blow molding station  25  and one of the cooling stations  30  or  31  via conveyance by the shuttle mechanism  40  horizontally along the base  35 . In a highly preferred embodiment, while one of the blow pin carriages, for example blow pin carriage  45 , is indexed with the blow molding station  25 , the other blow pin carriage  46  is indexed with cooling station  31 . 
     Also shown in FIG. 2, each of the blow pin carriages  45 ,  46  is individually reciprocatable in a substantially vertical plane between a rest position and a blow.position. The blow position is the relatively higher position of each of the blow pin carriages  45  and  46 , i.e., the blow pin carriage is raised sufficiently to engage the mold  65  enveloping the parison  20  at the blow molding station  25 . As discussed below, a molded article  15  is moved in a horizontal direction to one of the cooling stations  30 ,  31 . The blow pin carriages preferably remain in the blow position as it is shuttled to the cooling station as depicted with blow pin carriage  45  shown at the blow molding station  25 , and shown in phantom at cooling station  30 . The rest position is discussed in greater detail below, but refers to the relatively lower position of blow pin carriages  45 ,  46 . The blow pin carriages  45 ,  46  may be individually raised or lowered between the blow position and rest position by a hydraulic mechanism  90 . The mechanism for reciprocating the blow pin carriages  45 ,  46  may be any device suitable for raising and lowering the blow pin carriages  45 ,  46 , such as a solenoid device, a mechanical arrangement, a pneumatic cylinder, a cam and cam follower arrangement, or the like. 
     In a preferred embodiment, each cooling station  30 ,  31  includes a mechanism for holding a formed hollow article. This holding mechanism can be any arrangement suitable for holding a hollow article. In a particularly preferred embodiment shown in FIG. 4, the holding mechanism is constituted by spaced pairs of gripping rails  95 ,  96  juxtaposed relative to one another and spaced so that the formed hollow article  15  is received between the gripping rails  95 ,  96  such that the hollow article  15  is held by the slight pinching of the gripping rails  95 ,  96 . The gripping rails  95 ,  96  are preferably supported by the base via one of cooling station supports  77 or  78  (FIG.  2 ), or any other convenient manner. Alternatively, if the molded hollow article  15  has been sufficiently cooled during its transport to the cooling station  30  or  31 , the hollow article  15  may be ejected upon reaching the cooling station  30  or  31 , or soon thereafter. The flash  21 , is preferably removed in a separate process. 
     As shown in FIGS. 2 and 4, as the hollow article  15  is held by the holding mechanism, such as gripping rails  95 ,  96 , the blow pin carriage  46  and blow pin assembly  51  is reciprocated from the blow position to a rest position. The rest position is a position where the blow pin carriage  46  and blow pin assembly  51  are in a relatively lower position relative to the formed hollow article  15  such that the blow pin carriage  46  and blow pin assembly  51  can clear the hollow article  15  and be shuttled horizontally away from the cooling station  31  and to the blow molding station  25 . In one embodiment, each of the blow pin assemblies  50 ,  51  may be fixed relative to its respective blow pin carriage  45  or  46  such that the reciprocal motion of each blow pin carriage  45 ,  46  is the means for engaging its respective blow pin assembly  50  or  51  with the parison  20 . In an alternative embodiment, each of the blow pin assemblies  50 ,  51  may be raised or lowered independently of its respective blow pin carriage  45  or  46  to the rest position and blow position. Alternatively still, any combination of movements of the blow pin carriages  45 ,  46  and the blow pin assemblies  50 ,  51  may be used. 
     In another embodiment of the present invention, a formed hollow article  15  is held at a cooling station  30 ,  31  until the next formed hollow article is carried by the blow pin carriage  50 ,  51  to the cooling station  30 ,  31  and knocks or pushes the first hollow article out from between the gripping rails  95 ,  96 . Specifically, where a first formed hollow article is held between the pair of gripping rails  95 ,  96 , a second formed hollow article is carried in between the gripping rails  95 ,  96  and pushes the first hollow article out of the cooling station  30 . Alternatively, the formed hollow article may be ejected from the cooling station  30  by any means known in the art. After the formed hollow article  15  has been ejected from the cooling station, any remaining flash may be trimmed from the hollow article, by any convenient method known in the art (not shown). 
     The foregoing description and the drawings are illustrative of the present invention and are not to be taken as limiting. Still other variants and rearrangements of parts within the spirit and scope of the present invention are possible and will be readily apparent to those skilled in the art.