Abstract:
Disclosed is a preform carrier for carrying a preform used to blow mold plastic bottles and the like. The preform is cylindrical and has an open end defining a neck. The preform carrier includes a base and retaining means for retaining the preform carrier to a pallet used for transporting preforms from one location to another location, such as from a heating station to the blow mold. The preform carrier also has a plurality of resilient gripping fingers extending from the base and adapted to be received through the open end of the perform and to extend into the neck of the perform. The gripping fingers securely and releasably carry the preform from one location to the other location.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a carrier for tubular articles, and more particularly to a carrier for gripping and transporting tubular preforms of thermoplastic material from which bottles are formed by a blow molding process. The preform carrier of the present invention is adapted to carry heated bottle preforms to a heating station and then to a bottle blowing station.  
         BACKGROUND OF THE INVENTION  
         [0002]    Blow-molding thermo-plastic organic resins to form hollow container such as bottles for beer, carbonated beverages, and the like, is a known art and is the preferred use of the present invention. Suitable thermo-plastic resins include resins that are biaxially orientable such as polyethylene, terephthalate, and polypropylene. Preferred resins are linear polyesters such as polyethyleneteraphthalate (PETE) or polybutyleneteraphthalate (PBTE). The biaxial orientation property requires delivering the resin to the blow-mold at a temperature where it can so orient, which is generally within the range between the resin softening point and the resin melting point. The resin should also be heated evenly over the portions to be blown in order to produce an evenly expanded final product.  
           [0003]    In apparatus for making bottles by the reheat and blow molding technique, the preform is injection molded to provide a tubular structure that is open at one end and closed at the other end, similar to a test tube. The neck portion, sometimes referred to as the finish, is completely formed during the injection molding process, and the preforms can be cooled and stored for later use. When a bottle is to be formed, the body of the preform is reheated in a suitable heating station, and the heated preform is thereafter carried to and placed in a bottle mold with the neck or finish extending outwardly of the mold. Pressurized air is then introduced into the preform through the neck to expand the preform body against the mold walls to form the desired bottle.  
           [0004]    In the reheat and blow molding process, performs are transported from one station to another and possibly also within the stations. Thus, disposed upstream of the working station at which the blow molding operation is carried out is a heating station where the preform is heated to a temperature which is as high as possible while however still being below the vitreous transition temperature of the resin. Although the temperatures reached are below the vitreous transition temperature of the plastic material used, the preform is deformable.  
           [0005]    Transportation of preforms to the heated station, and then of the heated preforms to the blow mold, is often carried out by employing a pallet or other conveyor means that includes several preform carriers to hold the preforms at their neck or finish area. Some pallets are arranged to carry the preforms in an inverted condition, with the open end of the preform facing in a downward direction. Other machines carry the preforms in an upright condition, with the open end facing upwardly.  
           [0006]    When handling upright preforms, it is easier to grip the preforms internally, at the interior of the neck, rather than exteriorly, because the threads make it difficult to securely grip the outer portion of the neck without thread damage, and they also make it difficult to obtain a tight seal between the carrying device and the threads, to prevent loss of blowing pressure during the blowing operation.  
           [0007]    One form of preform carrier for transporting tubular preforms in an upright condition by supporting the preform at the interior surface of the neck is shown in U.S. Pat. No. 4,678,425. The preform carrier disclosed in that patent is referred to as a spindle nose, and is in the form of an annular sleeve of plastic material that is flexible to provide a seal between it and the preform.  
           [0008]    Another form of preform carrier is disclosed in U.S. Pat. No. 4,763,778. This carrier is a collet, meaning that the preform is gripped and held on the outside of the neck portion. FIG. 1 shows prior art illustrated in U.S. Pat. No. 4,763,778, namely an assembly that includes a gripping member  16  that is inserted into the neck of a preform  14 . The diameter of the gripping member  16  can be altered using a shaft and garter assembly. The diameter is decreased to allow the gripping member  16  to be inserted into the open end of the preform  14 , and then allowed to increase thereby gripping and holding the preform.  
           [0009]    One significant disadvantage with the preform carriers of the prior art is that the preforms may not always be carried in a very vertical orientation, but rather may sometimes become tilted off the vertical axis. This is of concern when the preform enters the heating station for two reasons. First, the preform would not be uniformly heated, but instead one part of it would be heated more than other parts, resulting in a poorly formed bottle. Second, and perhaps more importantly, the preform may be sufficiently tilted off the vertical axis that it comes into contact with a heating element in the heating station. Typically, such an element is a relatively expensive heating lamp, requiring that production be interrupted and the expensive lamp replaced.  
           [0010]    Therefore, there is a need for a preform carrier that overcomes the shortcomings of the prior art and ensures that the preforms are held in a vertical orientation.  
         SUMMARY OF THE INVENTION  
         [0011]    According to one aspect of the present invention, there is provided a preform carrier for carrying a preform having an open end defining a neck, the preform carrier comprising:  
           [0012]    (a) a preform carrier base having retaining means for retaining the preform carrier to a pallet used for transporting a plurality of preforms from one location to another;  
           [0013]    (b) a plurality of resilient gripping fingers extending from the preform carrier base and adapted to be received through the open end and to extend into the neck of the preform;  
           [0014]    whereby the gripping fingers carry securely and releasably the preform. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The preferred embodiments of the present invention will be described with reference to the accompanying drawings in which like numerals refer to the same parts in the several views and in which:  
         [0016]    [0016]FIG. 1 is a simplified, partially cutaway drawing of prior art apparatus employed for releasably holding a preform.  
         [0017]    [0017]FIG. 2 is a perspective view of one embodiment of the preform carrier of the present invention.  
         [0018]    [0018]FIG. 3 is a top view of the preform carrier of FIG. 2.  
         [0019]    [0019]FIG. 4 is a cutaway side view of the preform carrier of FIG. 3 taken along lines A-A.  
         [0020]    [0020]FIG. 5 is a perspective view of a further embodiment of the preform carrier of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    The present invention will be described with reference to its preferred embodiments.  
         [0022]    Referring now to the drawings, and particularly to FIG. 1, there is shown schematically a pallet assembly  10  including a pair of prior art preform carriers  12  that are carried in the pallet. The pallet assembly may hold up to from 200 to 400 preforms and is suitably supported for movement along a machine frame (not shown) that carries and supports the preform carriers  12 . The pallets are adapted to be carried along suitable frame members so that the preforms  14  traverse a path that may include preform loading, reheating, blowing and ejecting work stations.  
         [0023]    Preforms  14  are preferably injection molded at another location and then loaded onto the pallet and releasably held by the preform carrier  20  as the preform  14  moves from the loading station, through the heating and blow molding stations, until the formed bottle is ejected.  
         [0024]    [0024]FIG. 2 shows in a perspective view a preferred embodiment of the preform carrier  20  of the present invention. The preform carrier  20  includes a preform base  22 , which in this embodiment, a circular plate of diameter greater than the diameter of the neck of the preform to be releasably carried and held. Extending from one face  24  of the base  22  are a plurality of resilient gripping fingers  26 . In the preferred embodiment shown in FIG. 2, there are twelve such gripping fingers  26 , however, any suitable number may be used, preferably from 3 to 24, and most preferably from 8 to 16.  
         [0025]    The gripping fingers  26  are disposed on the face  24  in a generally circular configuration, as is best seen in FIG. 3, to form a generally cylindrical shape. The outer most outside edges  28  of the gripping fingers  26  when seen from the top plan view of FIG. 3, generally define a circle having a diameter substantially the same as, or slightly greater than the inside diameter of the neck of a preform  14 .  
         [0026]    Each gripping finger  26  is spaced from an adjacent gripping finger  26  by a space  30 . Spaces  30  between the gripping fingers  26  assist in cooling the gripping fingers  26  and preform carrier  20 , thereby keeping the preform carrier  20  of the present invention at a temperature cooler than other preform carriers. Gripping fingers  26  are resilient and capable of flexing so that the diameter of the circle defined by the outside edges  28  can be decreased to fit into the open end of a preform  14 .  
         [0027]    Preform carrier  20  further includes a retaining means for releasable engagement of the preform carrier  20  to the pallet. In the preform carrier  20 , the retaining means is a centrally located hole  32  in base  22 . Hole  32  is used to releasably secure the preform carrier  20  to a pallet by means of a suitable nut, bolt or other retainer.  
         [0028]    As best seen in FIG. 4, gripping fingers  26  have a length defined by the distance from the face  24  of base  22  to the end  34 . When viewed in side elevation, gripping fingers  26  each have an outside face generally denoted by numeral  36  and an inside face  38 . Outside face  36  is of varying contour along the length of the gripping fingers  26 . Adjacent the face  24  of base  22 , each gripping finger  26  has a first segment  40  having a thickness (defined as the distance from the inside face  38  to the outside face  36  of the gripping fingers  26 ) smaller than the thickness of the second segment  42 . In second segment  42 , the outside face  28 ′ is the outer most edge of the gripping fingers  26 .  
         [0029]    A third main segment  44  is located after second segment  42 , with the thickness of third segment  44  being substantially the same as that of first segment  40 . An intermediate portion  46  is located between second and third segments  42  and  44 ; the thickness of intermediate portion  46  decreases gradually. A second intermediate portion  48 , having a gradually increasing thickness, is located between third segment  44  and fourth segment  50 . Fourth segment  50  has a thickness equal to that of second segment  42 , so that outside faces  28  and  28 ′, when viewed in top plan view, generally define a circle having a diameter substantially the same as, or slightly greater than the inside diameter of the neck of a preform  14 .  
         [0030]    Between fourth segment  50  and end  34  is a slanted portion  52  that has a slanted outside face  54 . Slanted face  54  assists in guiding preform carrier  20  into the open end of the neck of a preform  14  when the preform  14  is loaded onto the preform carrier  20 .  
         [0031]    First segment  40  of reduced thickness provides some resiliency to the gripping fingers  26 , allowing them to bend inwardly (towards the center of the preform carrier  20 ) when preform carrier  20  is inserted into the neck of a preform  14 . Once inserted into the neck, the resiliency of the gripping fingers  26  causes the latter to spring back and grip the interior walls of the neck of the preform  14 . The gripping fingers  26  thus act as a mandrel for the loading and unloading of the preform  14 . Once a bottle has been blown from the preform  14  is allowed to cool if necessary, the bottle can be “ejected” from the preform carrier  20  by causing the bottle to slide off the preform carrier  20 .  
         [0032]    The preform carrier  20  may be made of stainless steel, or other suitably equivalent material. Preferably, there are no plastic or rubber parts in the preform carrier  20 , except for plastics and rubbers that can withstand the temperatures encountered in the heating stations (about 270° C.). Stainless steel provides the preform carrier  20  with adequate resiliency and stability for repeated heating and cooling throughout the entire reheat and blow molding process. If necessary, the preform carrier  20  may be heat treated in known ways to provide the gripping fingers  26  with the desired resiliency. A preferred stainless steel is SS 420 grade heat treated to 52 to 54 Rockwell hardness.  
         [0033]    The particular design of the preform carrier  20 , and in particular the gripping fingers  26 , allows a preform  14  to be held in a very vertical orientation, without undue tilting or wobbling as the pallet carries the preform  14  from station to station. This prevents the preform  14  from tilting to an off-vertical position, thereby reducing the risk of inconsistent heating of the preform and/or damage to the heating lamps.  
         [0034]    In a further embodiment as shown in FIG. 5, the preform carrier  20  may also include a cylindrically shaped plug  60  that fits within the space  62  defined by the inside faces  38  of the gripping fingers  26 . The outer diameter of the plug  60  is less than the diameter defined by the inside faces  38 . The plug  60  prevents the gripping fingers  26  from bending too much towards the inside of the preform carrier  20  when being inserted into the neck of a preform  14 , thereby breaking the gripping fingers  26 . The plug  60  may be held in place by suitable retaining means such as a bolt, etc.  
         [0035]    It will be understood by those skilled in the art that the specific shape of the gripping fingers  26 , and in particular the contour of the outside face  36  may vary. For example, the shapes of some of the segments and intermediate portions shown and described herein may be changed, so long as the gripping fingers  26  retain sufficient resiliency to allow them to bend when being inserted into the neck of a preform  14  and then grip the preform and releasably hold it as it is carried from station to station.  
         [0036]    Although the present invention has been shown and described with respect to its preferred embodiments, it will be understood by those skilled in the art that other changes, modifications, additions and omissions may be made without departing from the substance and the scope of the present invention as defined by the attached claims.