Abstract:
The present invention includes an apparatus and method for trimming the dome of a container comprising at least one trimming station having a plurality of guide rollers and a knife, and a rotation guide. The apparatus is adapted so that the container is in contact with the rotation guide and at least two of the guide rollers during trimming.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed generally to machinery for plastic container production and specifically to an apparatus for trimming the dome area of a blow molded plastic container.  
         BACKGROUND OF THE INVENTION  
         [0002]    Thin-walled plastic containers, such as bottles filled with milk, juice, and other liquids are generally manufactured by blow molding. A typical as-blown wide mouth blow molded container  100  is illustrated in FIG. 1. The container  100  comprises two portions, a wide mouth container portion  102  and a dome portion  104  above the designed opening of the wide mouth container portion  102 . Separating the wide mouth container portion  102  and the dome portion  104  is a radially inwardly extending circumferential trim line groove  106 . The trim line groove line  106  is molded into the container  100  at the trim line and serves to guide the trimming knife at a right angle to the axis of the container  100 .  
           [0003]    The dome portion  104  is required for the blow molding process only and is typically reclaimed after being severed from the wide mouth container portion  102 . Conventionally, the dome portion  104  includes a guide feature  108  to assist in guiding and/or driving the container through the trimming process. The dome portion  104  also includes a preform neck portion  110  which is affixed to the blow molding machine when the container  100  is blown. Typically, the preform neck portion  110  may include screw threads (not shown).  
           [0004]    For the production of wide mouth containers, the dome portion  104  is ancillary to the wide mouth container portion  102  and must be removed after the blow molding operation. In order to manufacture a container which seals properly, the dome portion  104  must be removed in such a way as to provide a smooth, clean cut opening on the container. Conventionally, removal of the dome portion  104  is accomplished by inserting a knife into the trim line groove  106  in the container  100  and rotating the container  100 . Known methods of severing the dome portion  104  include the use of fixed and rotating knives.  
           [0005]    Fixed knife methods generally comprise passing a rotating container along a long fixed knife. The container is supported and rotated by a moving belt opposite the fixed knife. Optionally, the knife is heated to aid in cutting. Although this method works, it is only suitable for low tolerances. This is because the container is only supported at two points and tends to wobble. Thus, a relatively uneven cut surface is formed.  
           [0006]    In rotating knife methods, both the container and the knife rotate. Typically, a drive wheel supports and rotates the container on one side while a rotating knife supports and cuts the container on the opposite side. The rotating knife systems have the advantage that they are smaller and take up less floor space in the manufacturing plant than the fixed knife systems. However, as in the fixed knife system, the container is only supported in two places. Thus, the container can wobble, resulting in an uneven cut surface.  
           [0007]    Wide mouth blow molded containers require a smooth, clean cut surface to ensure a good seal. However, conventional methods for removing the dome portion of blow molded containers generate significant wobble which often leaves an uneven cut surface on the container. Therefore, it would be advantageous to have an apparatus for cutting the dome portion off a blow molded container which reduced wobble and consistently produced smooth, clean cuts.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention includes an apparatus for trimming the dome of a container comprising at least one trimming station having a plurality of guide rollers and a knife, and a rotation guide, wherein the apparatus is adapted so that the container is in contact with the rotation guide and at least two of the guide rollers during trimming.  
           [0009]    In a further aspect of the invention, the apparatus further comprises a trimmer wheel.  
           [0010]    In a further aspect of the invention, the at least one trimming station is one of a plurality of trimming stations mounted to a trimmer wheel.  
           [0011]    In a further aspect of the invention, the apparatus further comprises an infeed mechanism to guide an incoming container into the trimmer wheel.  
           [0012]    In a further aspect of the invention, the infeed mechanism is selected from the group consisting of a feed screw, a starwheel, guides and combinations thereof.  
           [0013]    In a further aspect of the invention, the at least one trimming station has a first guide roller and a second guide roller.  
           [0014]    In a further aspect of the invention, the first guide roller and the second guide roller are mounted approximately 120 degrees apart.  
           [0015]    In a further aspect of the invention, the knife comprises having a flat edge on one side.  
           [0016]    In a further aspect of the invention, the at least one trimming station is adapted so that the flat edge of the knife is towards the container when the container enters the at least one trimming station.  
           [0017]    In a further aspect of the invention, the apparatus further comprises a stationary gear.  
           [0018]    In a further aspect of the invention, wherein the at least one trimming station further comprises a pinion gear.  
           [0019]    In a further aspect of the invention, the at least one trimming station is mounted to a trimmer wheel and wherein the knife is mounted on a shaft affixed to the pinion gear.  
           [0020]    In a further aspect of the invention, the apparatus is adapted so that when the trimming wheel rotates, the pinion gear orbits around the stationary gear.  
           [0021]    In a further aspect of the invention, wherein the knife rotates as the pinion gear rotates.  
           [0022]    In a further aspect of the invention, the knife is adapted so that the circumferential speed of the knife is different than the circumferential speed of the container.  
           [0023]    In a further aspect of the invention, the knife is adapted to penetrate the container approximately 3 mm.  
           [0024]    In a further aspect of the invention, the rotation guide includes teeth.  
           [0025]    In a further aspect of the invention, the teeth are adapted to make the container rotate.  
           [0026]    In a further aspect of the invention, the apparatus is adapted so that the container makes at least one full rotation during trimming.  
           [0027]    In a further aspect of the invention, the apparatus further comprises an adjacent starwheel to transfer the container to a subsequent machine.  
           [0028]    In a further aspect of the invention, the apparatus further comprising trimmed dome guides to direct the dome out of the apparatus.  
           [0029]    In a further aspect of the invention, wherein the guide rollers are shaped to fit a feature molded in the container.  
           [0030]    In a further aspect of the invention, the knife is adapted to fit in a groove in the container while cutting.  
           [0031]    A method of trimming containers comprising the steps of feeding a container to an apparatus including at least one trimming station having a plurality of guide rollers and a knife and a rotation guide, wherein the apparatus is adapted so that the container is in contact with the rotation guide and at least two of the guide rollers during trimming and trimming the container with the knife.  
           [0032]    In a further aspect of the invention, the step of trimming comprises rotating the knife.  
           [0033]    In a further aspect of the invention, wherein rotating the knife comprises rotating a knife shaft mounted to a pinion gear.  
           [0034]    In a further aspect of the invention, the step of trimming comprises penetrating the knife approximately 3 mm into the container.  
           [0035]    In a further aspect of the invention, the step of trimming comprises rotating the container.  
           [0036]    In a further aspect of the invention, the container rotates a minimum of at least one full rotation during trimming.  
           [0037]    In a further aspect of the invention, rotating the container comprises contacting the container with teeth on the rotation guide.  
           [0038]    In a further aspect of the invention, the knife rotates with a circumferential speed different than the circumferential speed of the container.  
           [0039]    In a further aspect of the invention, the step of trimming comprises orbiting the trimming station about a stationary gear.  
           [0040]    In a further aspect of the invention, the method further comprises a step of transferring the container to an adjacent starwheel.  
           [0041]    In a further aspect of the invention, the method further comprises the step of guiding a dome trimmed from the container to a discharge chute.  
           [0042]    In a further aspect of the invention, the dome is directed away from a trimmer wheel with trimmed dome guides.  
           [0043]    An apparatus for trimming a domed portion of a container comprising at least one trimming station having at least two contact points and a knife and a rotation guide having a contact point, wherein the apparatus is adapted so that the container is in contact with the at least two contact points and the guide contact point during trimming. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]    The foregoing and other features, aspects and advantages of the present invention will become apparent from the following description, appended claims and the exemplary embodiments shown in the drawings, which are briefly described below. It should be noted that unless otherwise specified like elements have the same reference numbers.  
         [0045]    [0045]FIG. 1 is a side view of a typical blow molded container.  
         [0046]    [0046]FIG. 2 is a schematic illustration of the prefered embodiment of the invention.  
         [0047]    [0047]FIG. 3 is a detailed view of a portion of FIG. 1.  
         [0048]    [0048]FIG. 4 is a sectional view along line AA in FIG. 3.  
         [0049]    [0049]FIG. 5 is a sectional view along line BB in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]    The present inventors have discovered that supporting a wide mouth blow molded container at more than two locations while cutting off the dome portion results in a significantly better and reproducible cut surface. By supporting the container in more than two locations, wobble of the container can be significantly reduced. In addition, the inventors have discovered that use of this invention allows for greater cutting speeds and container throughput. Preferably, the container is supported by a guide rail and two guide rollers. However, additional guide rollers may be added for improved stability.  
         [0051]    [0051]FIG. 2 is a schematic illustration of the preferred embodiment of the invention while FIGS.  3 - 5  are detailed and sectional views of the first embodiment. The dome trimming apparatus  200  includes an infeed mechanism  202 . In one embodiment of the invention, the infeed mechanism  202  includes an infeed guide  204  and an infeed screw  206 . However, the infeed mechanism  202  may include a starwheel (not shown), an infeed screw  206  or infeed guides  204  either singly or in combination.  
         [0052]    The infeed mechanism  202  presents a blow molded container  100  in a controlled orientation to one of a plurality of trimming stations  212  arrayed about a trimmer wheel  208 . Each trimming station  212  includes a plurality of guide rollers. In the preferred embodiment of the invention, each trimming station  212  includes two guide rollers  214 ,  216 . Preferably the guide rollers  214 ,  216  are mounted approximately 120 degrees apart. If additional guide rollers are used, the angle between rollers should be decreased.  
         [0053]    In addition to the guide rollers  214 ,  216 , the trimming stations  212  include a pinion gear  218 . The pinion gear  218  is in meshing contact with a stationary gear  210  whose center corresponds to the rotational axis of the trimmer wheel  208 . As the trimmer wheel  208  rotates, the trimming stations  212  orbit around the stationary gear  210 .  
         [0054]    Affixed to the pinion gear  218  is one end of a knife shaft  221 . Affixed to the other end of the knife shaft  221  is a knife  220 . As the trimming stations  212  orbit about the stationary gear  210 , the pinion gear  218  rotates, rotating the knife shaft  221  and the knife  220 .  
         [0055]    Generally, the knife  220  is disc shaped. However, in the preferred embodiment of the invention, the knife  220  has a flat resulting in a “D” shaped blade.  
         [0056]    As a container  100  is presented to the trimmer wheel  208 , the two rollers  214 ,  216  of the trimming station  212  and an rotation guide  222  position the container  100 . This creates three points of contact, which stabilizes the container  100  during trimming. Preferably, when the container  100  enters the trimmer wheel  208  the flat side of the knife  220  is towards the container  100 . This allows the container  100  to contact the guide rollers  214 ,  216  before the knife penetrates the container  100 .  
         [0057]    Preferably, the rotation guide  222  has a series of teeth that grab the dome portion  104  of the container  100 . As the trimmer wheel  208  rotates, the container  100  also rotates due to its contact with the teeth on the rotation guide  222 . Thus, both the container  100  and the knife  220  rotate as the trimmer wheel  208  rotates.  
         [0058]    Preferably, the circumferential speed of the knife  220  is designed to be different than the circumferential speed of the container  100 . This speed differential produces shearing action and reduces cutting forces, i.e., the forces required to cut the container. Further, in order to ensure that the dome portion  104  is completely severed from the container  100 , the container  100  rotates a minimum of one full rotation. While cutting, the knife  220  typically penetrates 3 mm into the container  100 . However, the penetration depth may be varied, the optimal depth being determined experimentally.  
         [0059]    Once the dome  104  is severed from the container  100 , the container  100  continues in the path of the trimmer wheel  208  via a container starwheel  231 . It is then transferred to an adjacent transfer starwheel  232 . The transfer starwheel  232 , with or without additional transfer guides  234 , can transfer the container  100  to another operation or onto a conveyor. The trimmed dome portion  104  is guided along a trimmed dome guide  226  to a discharge chute (not shown).  
         [0060]    To add stability to the apparatus, the preferred embodiment includes an anti-rotation arm  230 . Preferably, the anti-rotation arm connects the stationary gear  210  to the infeed mechanism  202 .  
         [0061]    In a second embodiment of the invention, the stationary gear  210  is replaced with a rotary gear (not shown). Preferably, the rotary gear is driven by an independent drive mechanism (not shown). However, the rotary gear may be connected to the same drive mechanism as the trimmer wheel  208  via gears, belts, chains or any other known technique. Use of a rotary gear rather than a stationary gear  210  increases the complexity of the dome trimming apparatus  200 , however it gives greater control over the apparatus  200 . That is, by independently controlling the speed of the rotary gear, the speed of the knife  220  may be independently controlled. Without independent control of the rotary gear, the speed of the knife  220  must be controlled by setting the pitch diameter of either the pinion gear  218  or the stationary gear  210 .  
         [0062]    The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The drawings and description were chosen in order to explain the principles of the invention and its practical application. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.