Abstract:
An anvil assembly having a housing and two rotatable inserts with flat upper surfaces against which the heated shoes of a package sealing machine may press a covering sheet onto a plastic package tape. The inserts have a limited range of rotation so that they automatically align themselves to be parallel to the heated shoes when they are contacted thereby. This rotatable insert feature obviates the need for precise, laborious alignment efforts. Alternatively, a pair of rotatable blades are pivotally attached to the shoes and act against a fixed anvil surface, thereby automatically aligning themselves to be parallel to the anvil surface.

Description:
RELATED APPLICATION  
       [0001]    The following application is a continuation in part of copending U.S. patent application Ser. No. 09/846,753 filed May 1, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The field of the present invention pertains generally to packaging for electronic components. More specifically, the present invention pertains to a device used to seal plastic containers for electronic components which includes an anvil and a heated shoe assembly.  
           [0003]    Automating the process of making electronic circuitry necessarily includes presenting electronic components to a robot in a consistent, predictable orientation so that the robot may grasp the component and place it onto a circuit board. Requiring a robot to select and orient the components from a bin, for example, would be impractical, if not impossible. Even if the components are placed on the circuit board manually, presenting the components in a consistent, orderly fashion increases the productivity of the worker.  
           [0004]    Proper packaging methods can ensure that the components are presented to an operator, assembler, or a robot in a predictable, repeatable manner. One such packaging method results in a string or “tape” of plastic pockets, each containing a component. This method includes a forming a strip of plastic into an elongate tape of pockets which are roughly centered between the longitudinal edges of the tape. The pockets do not extend all the way to the edges of the tape such that two horizontal flanges exist on either side of the pockets. The flanges run the length of the tape and provide a surface to which a cover sheet may be attached to secure the components within the pockets. An example of this type of packaging is shown in FIG. 1.  
           [0005]    One manufacturing problem that this packaging presents pertains to the accuracy required by the machinery used to secure the covering sheet to the flanges. Whether the covering sheet is secured to the flanges with an adhesive or by heat sealing, a rigid surface below the flange and above the sheet are used to press the sheet and the flange against each other. The assembly above the flange is referred to as a shoe and the surface below is referred to as an anvil. Because the flange and the cover are extremely thin, there is little room for error in the alignment of the opposing rigid surfaces. If, for example, the surfaces are not completely parallel, one side of the rigid surface will be closer to its opposing counterpart than the other side. As the two rigid surfaces approach each other in a sealing operation, the closer side will make contact first, thereby pressing the cover and the flange together, but will prevent the other side from ever making contact and, thus, from forming a proper seal. The result will be a length of the tape wherein one side of the cover is secured and the other is not. If allowed to repeat, there will be produced a component tape having areas in which the cover is secured alternating with areas in which the cover is not secure.  
           [0006]    There is a need for a anvil having flat surfaces which automatically assume an orientation which is parallel to the flat surface against which they are being pressed.  
           [0007]    There is further a need for an improved anvil that obviates the need for periodic realignment.  
           [0008]    There is a need for an improved heated shoe having operative surfaces which automatically assume an orientation which is parallel to the flat surface against which they are being pressed.  
           [0009]    There is a further need for an improved heated shoe assembly that obviates the need for periodic realignment.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    A “floating” anvil assembly is provided having a pair of inserts with two flat contact surfaces against which a heated shoe may be pressed. The inserts have a predetermined range of rotation about an axis such that when the shoe is pressed against each of the inserts, the contact surfaces of the inserts assume a parallel relationship with the contact surfaces of the shoes.  
           [0011]    More specifically, the anvil assembly of the present invention generally comprises a base to which a pin is operably connected. A first and second insert are rotatable around the pin over a predetermined angular range. The base is preferably shaped like a horseshoe, opening upwardly, with the inserts positioned on the insides of, and adjacent to, the base side walls.  
           [0012]    The flat contact surfaces of the inserts are constructed and arranged to act against a separate surface of the package sealing machine during a sealing operation. The upper surfaces preferably end slightly below the walls of the base so that the upper inside sides of the base walls may act against the sides of the packaging tape to maintain the alignment of the tape as it is fed over the inserts. The predetermined range of rotation is provided by the shape of the lower edges of the inserts. The lower edges of the inserts act against the bottom of the base during rotation, thereby defining the forward and rearward limits of rotation.  
           [0013]    In operation, the anvil assembly is placed in a heat sealing machine and a packaging tape is fed over the inserts so that the flanges of the tape ride on the top surfaces of the inserts and the pockets of the tape extend between the inserts. A heated shoe having heated surfaces drops down and acts against the top surfaces of the inserts to press the cover sheet and the flanges of the tape together. The inserts may rotate slightly so that the top surfaces of the inserts are parallel to the heated surfaces of the shoe. The shoe remains pressed against the inserts for a predetermined period of time until enough heat is absorbed by the packaging to create a seal between the flange of the package and the covering sheet. The shoe is then lifted and the tape is advanced, guided by the walls of the base, and the process repeats.  
           [0014]    The ability of the inserts to rotate slightly ensures that the pressure felt by the packaging will be substantially even across the extents of the upper surfaces of the inserts. If the inserts were fixed relative to the base, the inserts would have to be perfectly parallel to the surfaces of the packaging machine in order to accomplish placing even pressure across the extents of the inserts.  
           [0015]    In an alternate embodiment, a floating shoe assembly is provided having a pair of independent shoes moveable along a single line or arc, each having a heated blade which presses against rigid contact surfaces of an opposing anvil. The blades have a predetermined range of rotation about an axis generally perpendicular to the line of movement of the shoe, such that when the blades are pressed against the contact surfaces of the anvil, the blades assume a parallel relationship with the contact surfaces of the anvil. The anvil and pair of shoe assemblies are configured to provide sealing to both sides of a tape in a manner similar to the embodiment described above.  
           [0016]    More specifically, each shoe assembly of this embodiment generally comprises a pin operably connected to a shoe. The blade is rotatable around the pin over a predetermined angular range. The shoe is preferably shaped like a horseshoe, opening downwardly, with the blade substantially filling and extending from the opening of the horseshoe. The inner side walls of the horseshoe provide lateral support for the blade, along with the pin.  
           [0017]    The pin and blade are constructed and arranged to provide a small space between the upper surface of the blade and the inner top surface of the shoe. This small space or gap provides the range of rotation for the blade. As it may be desired to place a heating element in the shoe as opposed to, or in conjunction with, the blade, for heating the blade, it is important that the gap be relatively small and that the width of the blade closely matches the width of the opening of the horseshoe. This arrangement maximizes surface to surface contact between the blade and the shoe, thereby increasing the heat transfer therebetween.  
           [0018]    It is therefore an object of the present invention to provide an anvil assembly having contact surfaces which rotate to assume a parallel relationship with the heated surfaces of a shoe acting the anvil assembly.  
           [0019]    It is further an object to provide an anvil assembly which obviates the need for realigning a packaging machine on a regular basis.  
           [0020]    It is also an object to provide a shoe assembly having rotatable blades for acting against a fixed anvil.  
           [0021]    These and further objects and advantages of the present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The illustrative embodiments may best be described by reference to the accompanying drawings where:  
         [0023]    [0023]FIG. 1 is a perspective view of a component tape and covering sheet to which the present invention is directed;  
         [0024]    [0024]FIG. 2 is a perspective view of a preferred anvil assembly of the present invention;  
         [0025]    [0025]FIG. 3 is a plan view of a preferred anvil assembly of the present invention;  
         [0026]    [0026]FIG. 4 is a cutaway side elevation of preferred anvil assembly of the present invention taken generally along lines  4 - 4  of FIG. 3;  
         [0027]    [0027]FIG. 5 is a front elevation of the preferred anvil assembly of the present invention;  
         [0028]    [0028]FIG. 6 is a perspective view of the anvil assembly of the present invention receiving a packaging tape;  
         [0029]    [0029]FIG. 7 is a cutaway side elevation of preferred anvil assembly of the present invention showing the range of motion of the inserts around the pin;  
         [0030]    [0030]FIG. 8 is a front elevation of the preferred anvil assembly of the present invention carrying a packaging tape which is cutaway to show how the tape is received by the anvil assembly;  
         [0031]    [0031]FIG. 9 is a front elevation of a sealing machine having rotatable blades;  
         [0032]    [0032]FIG. 10 is a side elevation of a sealing machine having rotatable blades;  
         [0033]    [0033]FIG. 11 is a front sectional view of a shoe having a rotatable blade;  
         [0034]    [0034]FIG. 12 is a perspective cutaway of a rotatable heated blade inserted in a shoe;  
         [0035]    [0035]FIG. 13 is a side sectional view of a rotatable shoe rotated to its limit in a first direction; and,  
         [0036]    [0036]FIG. 14 is a side sectional view of the rotatable shoe of FIG. 13 rotated to its limit in a second direction. 
     
    
       [0037]    All Figures are drawn for ease of explanation of the basic teachings of the preferred embodiments only. The extensions of the Figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following description has been read and understood. Further, the exact dimensional proportions to conform to the specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following description has been read and understood.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    Referring now to the Figures, there is shown an anvil assembly  10  useable with a packaging machine for pressing a covering sheet onto a package. The anvil assembly  10  is attachable to the packaging machine and provides a pair of flat surfaces against which heated shoes may press a cover sheet and a packaging tape together. The anvil assembly  10  generally has inserts  12 , a base  14 , and a pin  16 . The pin  16  is supported by the base  14  and the inserts  12  have a limited range of rotation around the pin  16 .  
         [0039]    The inserts  12  have top surfaces  20  which are straight, flat and have widths  22 . Widths  22  define the maximum width of the seals that may be made between the covering sheet and the flanges of the packaging tape. It is envisioned that the inserts  12  of the anvil assembly  10  are removable and interchangeable with inserts  12  of various sizes such that a given anvil assembly  10  may be used in sealing operations involving packaging tapes of various sizes. Though the shape of the inserts is shown as being rectangular in the Figures, it is envisioned that a plurality of shapes could be used so long as the top surfaces  20  are straight and flat as shown in the Figures. Rectangular inserts  12 , however, are simple and efficient to manufacture.  
         [0040]    It is also envisioned that the two inserts  12  used during a given sealing operation may be of different widths  22  to match packaging tapes having flanges of different widths. For example, a packaging tape may have part of one flange perforated for use as a feed tape. Though the cover may not extend over this part, the insert  12  on the side of the flange defining the feed tape will be wide enough to support the wider flange.  
         [0041]    The base  14  is sturdy and attachable to the heat sealing machine. Preferably, the base  14  has two walls  24  that extend upwardly from a floor  26 . The walls  24  define two holes  28  through which the pin  16  may be inserted. The Figures show these holes  28  located relatively in the center of the walls  24 . The pin  16  functions to support the inserts  12  and to define and axis of rotation around which the inserts  12  rotate. In order to provide balance to the inserts  12 , it is important that the pins are located midway between the forward edge  40  and rearward edge  38  of the inserts  12 . This ensures even pressure will be felt by the entire top surfaces  20  of the inserts  12 . However, the vertical placement of the pin  16  may vary.  
         [0042]    The walls  24  of the base  14  are separated by a distance  34  which is approximately equal to, or slightly greater than, the width of the packaging tape that will pass through a channel  46  defined by the walls  24  and the pin  16  during a sealing operation. The walls  24  act as a guide against the sides of the tape to maintain the tape in proper alignment with the anvil assembly  10  and the packaging machine. To this end, it is preferable that the inserts  12  do not extend to the top surface of the walls  24 . Rather, the inserts  12  are constructed and arranged so that their top surfaces  20  are located below the tops of the walls  24  by a distance  36  which is equal to or slightly greater than the thickness of the tape flange and covering material.  
         [0043]    Similarly, the bottom edges of the inserts  12  do not extend to the floor  26  of the base  13  when the bottom edges of the inserts  12  are parallel to the floor  26 . As shown in FIG. 7, in order to provide the desired range of rotation α of the inserts  12 , the inserts  12  are elevated above the floor  26  by a predetermined elevation  30 . Elevation  30  is calculated, based on the length  32  of the inserts  12 , to provide a range of rotation α which is less than 180°, preferably between +/−0.5° to +/−2.5°, more preferably on the order of +/−1.0°. The length  32  affects the forward and rearward rotation limits of the inserts  12  in that the rearward bottom edge  38  abuts against the floor  26  when the inserts  12  have reached their rearward rotation limits, and the forward edge  40  abuts against the floor  26  when the inserts  12  have reached their forward rotation limits. Therefore, the length  32  of the inserts  12 , as well as the elevation  30  above the floor  26 , determine the range of rotation α.  
         [0044]    A relatively small range of rotation α, such as +/−1.0°, is adequate to accomplish the objects of the invention because the degree of error in the setup of an anvil assembly in a packaging machine does not exceed this range. Providing an excessively large range of rotation a could be disadvantageous as the excessive angular movement of the inserts  12  during a sealing operation may impart a horizontal force on the packaging tape, thereby causing it to “walk” in a forward or rearward direction.  
         [0045]    It is envisioned that the base  14  be of any suitable shape which accomplishes the functions described herein. However, like the inserts  12 , the relatively rectangular design of the base  14  which is shown in the Figures, is advantageous for purposes of accurate and efficient manufacturing, and ease of attachment to the packaging machine.  
         [0046]    In order to form a proper seal between the covering film and the flanges of the packaging tape, it is important that the inserts  12  remain separated and close to or abutting the inside surfaces of the walls  24 . This is best accomplished by providing a spring  42  which winds around the pin  16  and is biased to push the inserts  12  apart. Maintaining the inserts  12  in this spaced apart relationship also ensures that an appropriate gap  44  exists between the inserts  12  to allow room for the pockets of the packaging tape to pass. A preferred embodiment, shown in FIG. 8, provides a tubular spacer  43 , surrounding pin  16 , cut to a predetermined length in order to maintain proper spacing between the inserts  12  while allowing the inserts  12  to rotate freely through the range of rotation α, adjacent the walls  24 . Alternatively, washers or similar rigid stops could be attached to, or formed on, the pin  16  in order to keep the inserts  12  from drifting along the pin  16  toward each other.  
         [0047]    Referring now to FIGS.  9 - 14 , there is shown an alternative embodiment of the present invention whereby a floating shoe assembly  100  is used to act against a rigid anvil  102 . The shoe assembly  100  is considered “floating” because it includes a blade  104  which is rotatably attached to a shoe  106  via a pin  108 .  
         [0048]    The shoe  106  preferably includes a wall  110  and more preferably a pair of opposing walls  110  that define a hole  112  therethrough for receiving the pin  108 . The walls  110  may be connected by a ceiling  114  such that the walls  110  and the ceiling  114  together form a downwardly opening “U” shape. Thus, the walls  110  form a groove  116  therebetween upwardly defined by the ceiling  114 . The walls  110  are constructed and arranged such that the groove  116  is sized to receive the blade  104  and provide lateral support therefore.  
         [0049]    The blade  104  fits within the groove  116 , as stated, and includes a surface  118  for acting against the anvil  102  during a sealing operation. The surface  118  may be shaped to provide the desired seal width and to impart a predetermined pressure against the anvil  102 . It is envisioned that a plurality of interchangeable blades  104  are provided with the assembly  100  for providing a variety of surfaces  118 . One skilled in the art will see that a variety of options exist for heating the blade  104 . A preferred option is a heating element  120 , inserted into a receiving hole  122 .  
         [0050]    When the blade  104  is inserted into the groove  116  and the pin  108  is in place, there exists a small gap  124  between the ceiling  114  and the top of the blade  118 . This gap  124 , as best seen in FIG. 11, defines a range of rotation of the blade  104  around the pin  108 . Using a parallel relationship between the top of the blade  104  and the ceiling  114  as a zero reference, a first direction range of rotation, β, is shown in FIG. 13 and is limited by the eventual contact between the blade  104  and the ceiling  114 . Likewise, a second direction range of rotation, γ, is shown in FIG. 14 and is similarly limited by the eventual contact between the blade  104  and the ceiling  114 .  
         [0051]    The range of rotation in either direction may be relatively small to accomplish the objects of the invention. For instance, the first direction range of rotation, β, is preferably between 0.1° and 2.5°, more preferably on the order of 0.5° to 1.0°. Similarly, the second direction range of rotation, γ, is preferably between 0.1° and 2.5°, more preferably on the order of 0.5° to 1.0°.  
         [0052]    Turning now to FIGS.  9 - 10 , there is shown a sealing machine  126  utilizing the floating shoe assembly  100  of the present invention. The machine includes two shoe assemblies  100  arranged to seal both sides of a package tape simultaneously. Though the present invention encompasses two assemblies  100  connected together such that both assemblies  100  move in concert, preferably, the assemblies  100  are constructed and arranged to move independently of each other. Independent movement ensures that variances in the thickness of the flanges of the package tape do not adversely affect the sealing of the opposite flange.  
         [0053]    As shown in the Figures, the assemblies  100  are operably attached to the machine  126  so that they may be moved into and out of operable proximity to the anvil  102 . Specifically, the assemblies  100  are moveable between a first position  128 , (FIG. 10) in which the blade surface  118  is displaced from the anvil  102 , to a second position  130 ,(FIG. 9) wherein the blade surface  118  is close enough to the anvil  102  to operably seal a package flange therebetween without cutting the package. Preferably, this relationship is accomplished by way of guide bars  132 .  
         [0054]    Guide bars  132  extend from a top surface of the machine  126  and a lower portion of the guide bars  132  pass through a respective hole in the shoe assembly  100  such that the shoe assembly  100  may slide along the guide bar  132  between the first position  128  and the second position  130 . It is preferable to provide two guide bars  132  per shoe assembly  100 . Parallel guide bars  132  provide a linear path for the shoe assembly  100  between the first position  128  and the second position  130 . Springs  134  are provided that bias the shoe assemblies  100  upwardly toward the first position  128  to prevent unwanted contact between the blade surface  118  and the package flange when the package tape is being advanced.  
         [0055]    Those skilled in the art will further appreciate that the present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof. In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. For example, the guide bars  132  could be omitted and an arcuate path could be formed between the first position  128  and the second position  130  by operable connecting the shoe assemblies  100  to swing arms pivotally connected to the sealing machine  126 .  
         [0056]    Accordingly, the present invention is not limited in the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.