Patent Publication Number: US-2006011029-A1

Title: Apparatus and process for severing meat trays

Description:
RELATED PATENT DATA  
      This application claims the benefits of U.S. patent application Ser. No. 09/866,088, entitled “A Thermal Plastic Expanded Foam Meat Tray and Method and Apparatus for Precisely Trimming the Meat Tray From an Expanded Foam Web”, which was filed May 25, 2001, and which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD  
      This invention pertains to thermal plastic expanded foam meat trays and methods and apparatus for trimming the meat trays from an expanded foam web.  
     BACKGROUND OF THE INVENTION  
      Often it is necessary, after food is placed in the meat tray, to cover the top opening with a plastic or metal film having an airtight seal all around the top opening flange to help preserve the food, minimize oxidation and prevent food contamination while the food is being transported and presented for sale. Thus it is very important that top flanges of the thermal plastic expanded foam meat trays be accurately trimmed to provide a uniform seal surface on the flange to receive the plastic or metal film.  
     SUMMARY OF THE INVENTION  
      An apparatus and method are provided for forming a thermal plastic expanded foam rectangular meat tray that is trimmed from a thermal plastic expanded foam web. The thermal plastic expanded foam is a thermoformable plastic material such as a polystyrene foam. The meat tray includes alignment features that accurately align the meat tray when severing the formed meat tray from a web of thermal plastic expanded foam material.  
      According to one aspect, a thermal plastic expanded foam rectangular meat tray is configured to be trimmed from a thermal plastic expanded foam web. The meat tray includes a substantially rectangular bottom wall, and side walls. The side walls extend upward and outward from the bottom wall integrally interconnected to each other at four corners. Each of the side walls has an inclined lower section and an upper section that extends upwardly and terminating in a lip that extends outward around the periphery of the tray. The upper wall section has internal inclined corner surfaces extending upward and outward to the lip at the four corners. Each of the corner surfaces is specifically provided to receive an internal complementary mating corner alignment fixture in order to maintain the tray accurately aligned at the corners as the tray is being trimmed from the thermal plastic expanded foam web.  
      According to another aspect, a process is provided for severing uncut thermoformed rectangular meat trays with precisely trimmed lips from a thermal plastic expanded foam web in which each meat tray has diagonally opposing steeply inclined interior corner surfaces. The process includes: (a) moving the web to place at least one of the rectangular meat trays between a rectangular meat tray punch and a rectangular meat tray die, in which the rectangular punch has an alignment fixture thereon with complementary steeply inclined exterior alignment surfaces for engaging the steeply inclined interior corner surfaces of the meat trays; (b) moving the punch and die relative to each other a first distance to insert the alignment fixture within the meat tray with the alignment surfaces engaging the diametrically opposed interior corner surfaces of the meat tray to accurately align the meat tray longitudinally, laterally and angularly with respect to the punch and die; and (c) while maintaining the alignment surfaces in engagement with the corner surfaces, moving the punch and die relative to each other a second distance to sever the meat tray from the web with a precisely formed lip about its periphery.  
      According to yet another aspect, the trim apparatus is provided for severing uncut thermal formed rectangular meat trays to produce precisely trimmed lips when removing the trays from a thermal plastic expanded foam web. Each meat tray has diagonally opposing steeply inclined interior corner surfaces. The trim apparatus includes a rectangular meat tray die, a rectangular meat tray punch, an alignment fixture, a placement means for placing an untrimmed meat tray between the punch and the die, and drive means operatively connected to the die and punch. The rectangular meat tray punch opposes the rectangular meat tray die. The alignment fixture is mounted on the punch having complementary exterior alignment corner surfaces thereon for engaging the steeply inclined interior corner surfaces of the meat tray to maintain the meat tray in alignment in longitudinal, lateral and angular directions. The drive means are operatively connected to the die and punch for moving the punch and die relative to each other a first distance in order to move the alignment fixture into the meat tray with the exterior alignment corner surfaces engaging the steeply inclined interior corner surfaces of the meat tray to accurately align the meat tray in the longitudinal, lateral, and angular directions. The drive means are further operatively connected to the die and punch for moving a second distance to accurately trim the meat tray from the web with a precisely formed lip about its periphery while the fixture corner surfaces are engaging the tray corner surfaces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the invention are described below with reference to the following accompanying drawings.  
       FIG. 1  is a schematic view of a thermal expanded foam web passing by a preheat station, a meat tray forming station, and a trim press station for forming unique rectangular-shaped meat trays and separating the formed meat trays from the web;  
       FIG. 2  is an isometric view of a preferred embodiment of the unique meat tray;  
       FIG. 3  is a top view of the meat tray shown in  FIG. 2 ;  
       FIG. 4  is a side view of the meat tray shown in  FIG. 3 ;  
       FIG. 5  is a fragmentary vertical cross-sectional view taken along line  5 - 5  in  FIG. 3 ;  
       FIG. 6  is a fragmentary vertical cross-sectional view taken along line  6 - 6  in  FIG. 3 ;  
       FIG. 7  is an enlarged fragmentary top view taken along circle line  7  in  FIG. 3  showing a corner of the meat tray;  
       FIG. 8  is an fragmentary isometric view of a punch platen used at the trim station, along with other components, for separating formed trays from the web;  
       FIG. 9  is a fragmentary isometric view of a female die platen used in conjunction with the punch platen shown in  FIG. 8  for separating formed meat trays from the web;  
       FIG. 10  is a fragmentary vertical cross-sectional view through opposing punch platen and female die platen showing vertical movement of the punch platen to trim one of the meat trays from the web;  
       FIG. 11  is a horizontal cross-sectional view taken along line  11 - 11  in  FIG. 10  emphasizing an alignment fixture mounted on the punch platen for aligning the meat tray as the tray is being trimmed and separated from the web; and  
       FIG. 12  is a vertical cross-sectional view taken along line  12 - 12  in  FIG. 11  illustrating the insertion of the alignment fixture into an upper portion of meat tray to align the meat tray prior to the tray being trimmed from the web. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).  
       FIG. 1  illustrates a thermal plastic expanded foam web or sheet  8  passing through a pre-heat station  52  and a meat tray forming station  54  for forming meat trays  10 . The web  8  with the formed trays then moves to a meat tray trim station  56  for separating the formed meat trays  10  from the web  8  and then past a web comminuting station  57  for shredding the remaining web after the meat trays  10  have been removed from the web  8 . The web  8  is incrementally fed to the meat tray trims station  56  by a conveying means generally designated by the numeral  58  in  FIG. 1 . Such a conveying means  58  includes drive motors  60  and  62  that drive web rollers (not shown) for moving the web  8 . The motors  60  and  62  are controlled by a servo motor controller  64 . Such a conveying means is shown in more detail in U.S. Pat. No. 6,067,886 granted to the present Applicant on May 30, 2000 and entitled “A Machine Trim Press Having Counterbalance Features”. Such patent is incorporated herein by reference.  
       FIGS. 2-7  illustrate a preferred embodiment of the unique rectangular-shaped meat tray  10 . The expanded foam meat tray  10  has a rectangular bottom wall  12  with long side walls  14  and  16  that are interconnected by short end or side walls  18  and  24 . The short side wall  18  is formed integrally with the long side walls  14  and  16  at curved wall corners  20  and  22 . The short side wall  24  is formed integrally with the long side walls  14  and  16  at curved wall corners  26  and  28 . The side walls  14 ,  16 ,  18  and  24  extend upward and outward from the bottom wall  12  to a peripheral outwardly extending flange or lip  30 . The lip  30  has an upper surface  32  that forms a seal surface for enabling films to be laid over the tray and affixed to the surface  32  to provide airtight seal protection to the food product placed in the tray  10 . The side walls  14 ,  16 ,  18  and  24  extend upward and outward at an obtuse angle “A” of between 110 degrees and 140 degrees relative to the bottom wall  12  ( FIGS. 5 and 6 ). The side walls  14 ,  16 ,  18  and  24  have lower wall sections  34  that extend upward and outward to upper wall sections  36 . The upper wall section  36  extends upward and outward from an external nesting shoulder  40  to the peripheral lip  30 . The upper wall sections  36  have a series of internal stepped ribs  38  formed therein to provide strength and rigidity to minimize bulging of the side walls.  
      Importantly, each of the wall corners  20 ,  22 ,  26 , and  28  has an internal inclined alignment corner surface  42  formed therein extending downwardly from the inside of the lip  30  toward the bottom wall  12  for receiving a complementary surface of an alignment fixture to maintain the meat tray  10  in alignment, in the longitudinal, lateral, diagonal and angular directions, while the tray  10  is being precisely trimmed from the web  8  at the trimming station  56 . Preferably the alignment corner surfaces  42  extend downward at a steep obtuse angle “B” of between 94 degrees and 105 degrees relative to the bottom wall  12  ( FIGS. 4 and 5 ). Preferably angle “B” is between 94 degrees and 100 degrees. Preferably the alignment corner surfaces  42  extend downward from the lip  30 , on the inside of the upper wall sections  36 , eliminating part or all of one or more ribs  38  in the corners  20 ,  22 ,  26 , and  28 .  
      Preferably the alignment corner surfaces  42  are convex curved as seen in the top views  FIGS. 3 and 7 . Preferably the alignment corner surfaces are curved in an arc of more than 90 degrees, but less than 180 degrees, with a radius of curvature  44  about a center of curvature  46  ( FIG. 7 ). Preferably each alignment corner surface  42  is conical in shape having a wide curved arc in the horizontal direction and a steep inclined shallow conical wall element in the vertical direction.  
      A trim press is located at the trimming station  54  for trimming and separating one or more meat trays  10  at a time from the web  8 . The reader is directed to previously mentioned U.S. Pat. No. 6,067,886 for many of the details of such a trim press. For purpose of brevity the above-mentioned U.S. Pat. No. 6,067,886 is incorporated by reference should the reader desire such detail. For the purpose of this application, the important features are a unique punch platen  70  and a complementary die platen  72 , which are described in more detail with reference to  FIGS. 8-12 .  
      The punch platen  70  has a plurality (row) of rectangular male punch elements of plates  74  mounted thereon. Each punch plate  74  has a generally rectangular peripheral cutting edge  76  surrounding a front face surface  78 .  
      The die platen  72  has a plurality (row) of female die elements  80  that are complementary to the punch plates  74 . Each of the die elements  80  has an internal cutting edge  81  surrounding a generally rectangular pass-through opening  82 .  
      Importantly, each of the male punch plates  74  has a meat tray alignment fixture  84  projecting forward of the front face surface  78  that moves in conjunction with a respective plate  74  for initially entering the meat tray  10  and aligning the meat tray  10  longitudinally, laterally and angularly with respect to the respective punch plate  74  and die element  82 . As the fixture  84  enters the rectangular meat tray  10  it engages the alignment corner surfaces  42  to stretch at least the upper section  36  of the meat tray in the diagonal directions as well as in the longitudinal, lateral and angular directions to enable the lip  30  to be trimmed precisely as the cutting edges  76  and  81  sever the meat tray from the web  8 .  
      Preferably, each alignment fixture  84  has a thin, generally rectangular-shaped plate or spider body  86  with an enlarged central void or opening  88 . Enlarged corner elements  90  extend outward at the corners. Each element  90  has a peripheral exterior side surface  92  complementary to the internal corner alignment surface  42  of the meat tray  10  for engaging the internal corner alignment surface  42  as the fixture  84  enters the top opening of the meat tray  10 . Preferably each of the exterior side surfaces  92  is steeply inclined at an acute angle “C” of between 75 degrees and 86 degrees relative to the bottom wall of the meat tray ( FIG. 12 ). More preferably the acute angle “C” is between 80 degrees and 86 degrees. Also preferably each of the exterior side surfaces  92  has an arc in the horizontal direction of greater than 90 degrees.  
      The alignment fixture  84  is mounted to the punch plate  74  by at least two diagonally spaced support bolts  94 . The bolts  94  have bolt shafts  96  slidably mounted in a countersunk bore  98  formed in the punch plate  74  to enable the thin plate  86  to move from an extended position to a retracted position relative to the front face surface  78 . Each bolt  94  has an outer end  99  that is threaded in a complementary threaded aperture in the thin plate  86 .  
      The alignment fixture  84  further includes guide rods  100  that are mounted in the face surface  78  and extend outward projecting through guide apertures  102  in the thin plate  86  to maintain the fixture  84  aligned with the punch plates  74  as the thin plate  86  moves between the extended position and the retracted position. Corner coil springs  108  are mounted between the alignment fixture  84  and the punch plate  74  to bias the alignment fixture  84  to the extended position. The corner coil springs  108  are seated in shallow spring cavities  104  and  106  formed respectively in the punch plate  74  and the thin plate  86 .  
      The punch platen  70  is reciprocated to and from the die platen  72  by a punch drive  110 . See the above-identified U.S. Pat. No. 6,067,886 for specific structural details. As the punch platen  70  is moved a first distance toward the die platen  72 , the alignment fixture  84  is moved into the top opening of the meat tray ( FIG. 12 ) with the exterior side surfaces  92  engaging the interior corner alignment surfaces  42  of the meat tray to accurately align the meat tray  10  relative to the cutting edges  76  and  81 . As previously mentioned, the alignment fixture  84  aligns the meat tray  10  diagonally between the corners, as well as longitudinally, laterally and angularly relative to the cutting edges  76  and  81 .  
      Further movement of the punch platen  70  moves the aligned meat tray  10  into the die opening  82  with the lip  30  engaging the die element  80 , causing the alignment fixture  84  to move from the extended position to the retracted position while maintaining alignment, and brings the cutting edges  76  and  81  into cutting relationship with the web  8  to trim the lip  30  and sever the meat tray from the web  8 . Once the trays  10  are severed from the web  8 , the coil springs  108  bias the alignment fixture  84  outward from the plate  74 , pushing the severed meat tray  10  into the pass-through opening  82  and onto an exit conveyer (not shown).  
      In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.