Abstract:
A lip rolling machine for forming a lip on the rim of preformed containers such as cups, including a set of spaced apart tubular oven guide bars guiding a train of nested cups through an oven for preheating the rims thereof. One of the guide bars is driven to be rotated driven by a variable speed motor and a belt drive so as to maintain rotation of the train of cups while passing through the oven. One embodiment includes a fixed inner tube having an outer tube rotated on the inner but.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application No. 61/686,386 filed on Apr. 4, 2012. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention concerns machines for the manufacture of thermoformed plastic containers, such as cups, and more particularly machines for forming a lip bead on the rim of molded cups, generally referred to as lip curling or rolling machines. Such apparatus has been known for many years in the industry, and is described in U.S. Pat. No. 3,337,919 issued on Aug. 29, 1967 for a “Container Rim Beading Apparatus”. This type of machine includes a feed mechanism receiving a continuous train of previously molded nested cups that is conveyed into a feed mechanism which advances and rotates the train of cups at a set rate through a heating oven and into the lip forming mechanism where the lips are formed. The train of nested cups is advanced on a set of three liquid cooled guide bars extending through the oven, the guide bars spaced around the perimeter of the cups to contact the rims at three points. The heating of the cups in the oven softens the cup rims prior to the cups being advanced into a lip curling mechanism in order to properly carry out the formation of the lip. The nesting of the cups exposes only the rims so that the oven heating is thereby concentrated on the cup rims. 
         [0003]    Improvements to the conveyor, feed mechanism, guide bar spacing adjusting mechanisms, an oven mounting, and lip curling mechanism are all described and claimed in U.S. Pat. Nos. 6,135,754; 6.093,010; and 6,164,949, assigned to the assignee of the present application, each hereby incorporated herein by reference. 
         [0004]    These components of the machines are each designed to be adjustable to accommodate different size containers. The adjustable size capability requires significant maintenance support, particularly in being initially set up for a run of each size and type of container. It is critical that the feed rate be set to match the rate of processing of the cups in the lip curling screw mechanism in order that the cups stay fully nested while in the oven for proper heating of the rim only. That is, if the feed rate is too slow, the cups become separated and the cup bodies become partially exposed to be heated and softened. The feed of the cups also must not be too high as this will unduly compress the stack and cause twisting and snaking of the nested cup train in the oven. The proper feed rate is mostly a function of the stack height of a given cup configuration, as the rate of feed of the train of nested cups into the curling screws necessarily varies with the number of cups per unit length in the train. 
         [0005]    The oven encloses the train of nested cups which are guided in their movement through the oven by the set of three oven guide bars, which are arranged to contact the rims of the cups at three points around their perimeter. 
         [0006]    The guide bars are tubular and have coolant circulated therethrough at a temperature and flow rate which are controlled so as to create the just proper degree of heating of the cup rims. 
         [0007]    The train of nested cups is rotated as well as axially advanced by the feed mechanism at the entrance to the oven so as to produce uniform heating of the rims of the cups as they travel through the oven. 
         [0008]    The guide bars themselves conventionally do not rotate, and friction between the rotating cup rims and the stationary guide bars can appreciably retard the rotation of the train of nested cups to varying degrees as it moves through the oven. Any variation in the rate of rotation of the cups in turn adversely affects the uniformity of the heating of the rims which in turn lowers the quality of formed lips produced in the lip forming mechanism. 
         [0009]    The nested cup train may also not be advanced at a uniform rate due to friction with the guide bars to also affect the heating and therefore the lip forming process. The rate of advance of the cups must be closely matched to the rate of operation of the lip curling mechanism as noted above. 
         [0010]    It is an object of the present invention to provide an arrangement in a lip curling apparatus for maintaining uniform rotation and advance of the train of nested cups within the preheating oven to insure proper heating. 
       SUMMARY OF THE INVENTION 
       [0011]    The above recited object and other objects which will become apparent upon a reading of the following specification and claims are achieved by an arrangement for rotating at least one of the guide bars extending within the preheating oven to thereby continue to drive and rotate the nested cup train after it leaves the feed mechanism and as it moves through the oven. This arrangement includes a rotational drive rotating one guide bar which is supported on bearings while receiving a flow of coolant through the guide bar. 
         [0012]    The guide bar includes a tube rotatably mounted on bearings carried by a pair of stationary end piece assemblies, each of which being connected to an arm of a respective spacing adjusting mechanisms. 
         [0013]    A partially exposed toothed sheave is attached to one end of the tube driven by a recirculating belt powered by a variable speed D.C. electric motor to rotate the central hollow tube at a high speed so that the frictional contact with the cup rims also rotates the train of nested cups but at a much lower rate of rotation. This enables adjustment of the rate of rotation of the train of nested cups. 
         [0014]    The guide bar may also be rotatable on a fixed inner tube held between the end piece assemblies which receive coolant flow via a fixed fitting included in end piece assemblies at each end of the inner tube. An outer tube may be is rotatably mounted on the inner fixed tube by heat resistant bearings and is rotated by a variable speed D.C. electric motor driving a belt circulated around sheaves included in a belt tensioner and engaging a toothed sheave fixed to the outer tube. A closely fit bushing is interposed between the inner fixed tube and the outer tube in order to hold the outer tube straight during its rotation to minimize any tendency to whip while being rotated due to a lack of straightness. 
         [0015]    The space between the inner fixed tube and rotated outer tube is preferably filled with oil to not only lubricate the bearings but also to act as a heat transfer agent conducting heat into the coolant flowing through the inner fixed tube which is hereby conducted away from the bearings supporting the outer tube since the coolant is kept at a temperature approximately 30° F. cooler than the surface of the outer sleeve. This also extends the service life of these bearings. 
         [0016]    In an alternative arrangement, a single tube is rotatably mounted on end fittings fixed to either end of the tube which extend within a respective end piece assembly, supported on bearings included in the end piece assemblies. Rotary unions provide a respective fluid connections to a coolant source establishing flow through the single tube. 
         [0017]    The rotated and non rotated guide bars may be slightly skewed from one end to the other to augment the axial drive force created by the feed mechanism to aid in maintaining the axial advance of the train of nested cups through the oven and into the lip curling mechanism. 
         [0018]    This arrangement enables a closely controlled rate of rotation and axial feed of the train of nested cups to reliably achieve a quality rolled lip on the rims of the cups. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a diagrammatic representation of the lips curling apparatus of the present invention. 
           [0020]      FIGS. 2A and 2B  are pictorial views of either components of the lip end curling apparatus depicted diagrammatically in  FIG. 1 . 
           [0021]      FIG. 3  is an end view of a transverse section taken through the guide bar set. 
           [0022]      FIG. 3A  is a view of a transverse section through the guide bar set looking in the opposite direction. 
           [0023]      FIG. 3B  is a fragmentary top view of the guide bar drive motor and associated components. 
           [0024]      FIG. 4  is a top view of a rotated guide bar broken away in the middle portion. 
           [0025]      FIG. 5  is an enlarged lengthwise sectional view of the opposite ends of the rotated guide bar shown in  FIG. 4 , with a block diagram representation of associated coolant supply. 
           [0026]      FIG. 6  is a fragmentary side view of one end of the rotated guide bar shown in  FIG. 4 . 
           [0027]      FIG. 7  is an enlarged sectional taken through the rotated guide bar. 
           [0028]      FIG. 8  is a view of the guide bar in the direction of the arrows in  FIG. 4 . 
           [0029]      FIG. 9  is a lengthwise sectional view of a rotated guide bar according to another embodiment of the invention with a block diagram depiction of the associated coolant supply system. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
         [0031]    Referring to the drawings, and particularly  FIG. 1 , a lip rolling apparatus  10  of the type described above is shown. 
         [0032]    A train of nested cups C (lying on their sides) is supplied from a cup forming machine  12 . Typically, accumulating devices (not shown) may be used to insure a constant supply of nested cups to the lip curling apparatus  10  via a conveyor  14 . 
         [0033]    A transition conveyor  14 A receives the nested cups and feeds them accurately into the center space between a set of feed rollers in a feed roller mechanism  16 , described in detail in U.S. Pat. No. 6,135,754, incorporated herein by reference. As described therein, the feed roller mechanism  16  comprises a set of rollers each mounted for powered rotation, and with the axes of rotation arranged about the center line of a circle defined by the feed roller outer perimeters, so as to engage the rims of the cups C to rotate the same. The rollers  16  are adjustably tilted slightly out of the plane of the spacing circle to create a frictional force also tending to advance the cups through a preheating oven  18 . 
         [0034]    The cup rims are heated in the oven  18  to be softened in preparation to being formed in the lip curling screw mechanism  20  in the well known manner. The cups are supported and guided on a set of oven guide bars  22 A,  22 B,  22 C while in the oven  18  while being exposed to heating elements (not shown) in the oven  18 . The spacing of each end of the set of three guide bars  22 A,  22 B,  22 C is adjustable to be fit to the size of container be formed, as described in U.S. Pat. No. 6,093,010. 
         [0035]    The cup feed rate established by the feed mechanism  16  is finely adjustable to be closely matched to the rate that the cups are processed by the lip curling screw mechanism  20 , as described above. In addition, the diameter of the circular space defined between the feed rollers must be adjustable if the machine  10  is to be used for variously sized cups. 
         [0036]    The lip curling mechanism  20  also is adjustable quickly and easily to be able to form a lip on different container sizes, as is described in detail and claimed in U.S. Pat. No. 6,164,949, also incorporated herein by reference. 
         [0037]    Both of these adjustments may be made “on the fly”, i.e., when the machine is running, in order to more easily determine if a proper adjustment has been accomplished, and to eliminate the need to interrupt production in order to make adjustments. 
         [0038]    A single electric motor M drives both the feed roller mechanism  16  and the lip curling mechanism  20  as described in the patents referenced above. 
         [0039]    A control panel (not shown) and coolant connections to the curling screw mechanism  20  and guide bars  22  are also omitted in this view for the sake of clarity. A temperature control unit (not shown) maintains the temperature of the coolant, so as to keep the temperature of the curling screws and guide bars in the proper range. Such temperature controllers are commercially available, a suitable controllers being Model TNY4 from AEC (Applied Engineering Co.). 
         [0040]    The oven guide bars  22  have left and right end spacing adjustment mechanisms  24 A,  24 B located at respective ends of the oven  18 . The oven  18  itself can be formed in two halves, opened by a clam shell mechanism (not shown). In addition, the entire oven  18  with the end plates  26 A,  26 B guide bars  22 A,  22 B,  22 C and guide bar adjustment mechanisms  24 A,  24 B may be swung away as described in U.S. Pat. No. 6,093,010. 
         [0041]    Receptacles  17  are mounted to machine end plates  25  (only one shown in  FIGS. 2A ,  2 B) connected by rods  19 . The receptacles  17  can be released to allow connector rods  19 , oven support plates  26 A,  26 B, guide bar adjusting mechanisms  24 A,  24 B, guide bars  22 A,  22 B,  22 C and the oven  18  itself to be swung away by power cylinder  23 . As mentioned above, two halves of the oven  18  can also be swung open both by a conventional clamshell mechanism as stated in U.S. Pat. No. 6,093,010. 
         [0042]      FIG. 2  is a pictorial view of some of the components of the lip curling apparatus  10  with the oven  18  and lip curling mechanism  20  omitted for clarity. 
         [0043]    The guide bar adjustment mechanisms  24 A,  24 B are mounted on oven support end plates  26 A,  26 B connected together with rods  21 . Each guide bar adjustment mechanism  24 A,  24 B includes three pivot arms  28 ,  30 ,  32 , each holding one end of a respective one of the three guide bars  22 A,  22 B,  22 C (best seen in  FIG. 3 ). 
         [0044]    The spacing of each set of ends of the guide bars  22 A,  22 B,  22 C may be independently adjusted by manual movement of a handle portion  34  or a hand wheel on pivot arm  28  as described in detail in U.S. Pat. No. 6,093,010. 
         [0045]    Connecting links  36 ,  38  create simultaneous movement of all three pivot arms  28 ,  30 ,  32 . According to the teachings of the present invention, the lower middle guide bar  22 B is rotated by a D.C. variable speed motor  40  located at the entry end of the oven  18  mounted to plate  26 A oven support end plate  26 A, which drives a synchronous belt  42 . A belt tensioner  44  accommodates any adjustment movement of the rotated guide bar  22 B. 
         [0046]      FIGS. 4-8  show details of one embodiment of a rotated oven guide bar  22 B according to the invention, which is composed of an inner fixed tube  46  and an outer rotatable tube  48  patentably mounted on the inner fixed tube  46 . 
         [0047]    The outer tube  48  rotatable mounting includes two pairs of ceramic hybrid bearings  50  located at either end of the inner fixed tube  46  to rotatably support the outer rotated tube  48  on the inner fixed tube  46 . Such bearings can run at higher temperatures than standard bearings, and thus are better able to operate at high speed under the high temperature conditions in the oven  18 . 
         [0048]    The space between the two set of bearings  50  is largely occupied by a closely fit fiberglass bushing  52  and the remaining space is filled with a high temperature lubricant. The fiberglass bushing  52  is closely fit within the outer rotated tube  48  to restrain the rotating outer tube and limit any tendency to whip caused by any minor lack of straightness thereof, as the outer tube  48  is rotated at high speed. The speed of rotation of the outer tube  48  is on the order of several thousand rpm is this high speed being necessary since the outer tube  48  is substantially smaller in diameter than the diameter of the cup rims. 
         [0049]    Seals  54  are provided to retain the lubricant in the space between the fixed inner tube  46  and the rotated outer tube  48 . The lubricant acts to lubricate the bearings  50  but also acts to conduct heat away from the outer tube  48  (which is heated by the oven heaters) and into the coolant flowing through inner fixed tube  46 . 
         [0050]    Coolant is supplied from a coolant source  56  flowing into and out of elbow fittings  58  and  60  fixed at respective ends of the inner fixed tube  46 , the temperature of which is maintained by a controller as mentioned above. 
         [0051]    The rotation of the relatively small diameter outer sleeve  48  is at a high rate, i.e., on the order of 4000 rpm since the cup rims have a substantially larger diameter, necessitating the higher rate of rotation of the sleeve  48  to maintain the lower desired rate of rotation of the nested cups, i.e., approximately 1000-1200 rpm. 
         [0052]    The bearings  50  benefit from the fact that the temperature of the outer tube  48  is desirably at approximately 150° F.-180° F., with the inner fixed tube  46  kept at around 30° F. less. 
         [0053]    Thus, heat generated by the bearings  50  is conducted into the coolant flow and the bearings  50  will therefore have a much longer service life. 
         [0054]    The outer tube  48  is rotated by the belt  42  engaging a toothed sheave  62  attached to the outer tube  48  by an extension  64  fastened to the sheave  62  by screws  65 , the extension  64  threaded into the left end of the outer tube  48  as seen in  FIG. 5 . 
         [0055]    A fixed outer cover  66  encloses a pair of split mounting collars  68 ,  70  also included clamped together over the end of the fixed tube  46  by means of screws  72 . The cover  66  is secured by screws  74  ( FIG. 7 ). 
         [0056]    The right end of the cover  66  has an opening on one side, exposing the toothed sheave  62  to enable partial wrapping of the belt  42  around the toothed sheave  62  (shown in  FIGS. 3 and 3B ) which enables driving the outer tube  48  at a high rotational speed. 
         [0057]    The left end of the guide bar  22 B is attached to the middle pivot arm  30  of the adjustment mechanism  24 A by a shoulder bolt  76  passing through a slotted opening  82  in a connector piece  78  secured to split collars  68 ,  70  by screws  80 . 
         [0058]    The right end of the guide bar  22 B is likewise attached to the other guide bar adjustment mechanism  24 B by a connector piece  84  secured to the right end of fixed inner tube  46  attached with a shoulder bolt  86  to the right end pivot arm  30 . The connector piece  84  is attached to a split collar  88  by screws  90  ( FIG. 8 ) passed through a slot  92  in a cover sleeve  94 , held in place with screws  96  ( FIG. 8 ). 
         [0059]    The two adjustment mechanisms  24 A,  24 B are independently operable to enable creation of a slight skewing of the guide bars  22 A,  22 B,  22 C which can be set to create an axial driving force on the train of nested cups by the rotation of the guide bar  22 B, contributing to the axial advancing force developed by the feed mechanism  16 . This helps maintain a precisely set axial advance rate of the train of nested cups C. 
         [0060]    The adjustable speed of the variable speed motor  40  allows fine adjustment of the rate of rotation of the train of nested cups C to achieve proper heating and the rate of advance to be very closely matched to the rate at which the cups are processed in the lip curling mechanism  20 . 
         [0061]      FIG. 9  shows a second embodiment in which the rotated guide bar  22 B is comprised of a single tube  94  which is supported by end support assemblies  95  receiving a pair of rotating end fittings  96  affixed to a respective in sets of bearings  98  held by a split sleeve clamp  100 . 
         [0062]    A rotary union  102  is installed at each end to provide a fluid connection to and from a coolant source  104  to the inside bore of the end pieces  96  and the inner space  106  within the tube  94 , enabling circulation of the coolant therethrough. The rotary union  102  is preferably designed to have a larger than standard inside bore diameter to allow freer flow of coolant therethrough. 
         [0063]    A toothed sheave  108  is affixed to the left end fitting  96  as by a key  110  and exposed to enable engagement by a toothed belt driven by a motor as described above. A filter  112  may be provided to remove entrained particles to thereby prevent clogging of the internal passage of the unions  102 .