Patent Publication Number: US-2017369196-A1

Title: Thermoforming trim removal systems and methods

Description:
BACKGROUND 
     Thermoforming involves heating plastic materials until pliable, then forming the plastic into a product. For example, thermoforming is used in packaging systems both to create molded containers and to seal the tops of containers with a film of plastic material. When thermoforming a product or sealing a container, excess plastic material (“trim”) is cut away and removed. 
     For example, trim is often excess plastic material at the outer edges of a product that is held by a fixed clamping or piercing process to convey the product through one or more machines of a manufacturing and packaging process. For example, the outer edges of the plastic material might be held in place by a series of clamps or a series of spikes on an endless chain or belt of a circulating feed system. An endless chain of the circulating feed system is typically located along each lateral edge of a conveyor to engage and hold the edges of the product to the chains in order to feed the product through the machines of the manufacturing process. Once the top of a container is sealed with plastic film, the outer edge trim is cut away while still held by the clamps or spikes. Before the endless chain is circulated back to the beginning of the machine, the trim material must be removed from the clamps or spikes to avoid getting caught in the sprockets of the endless chain. That can lead machine damage, stretching of chain requiring costly replacement, sanitation issues and can present a significant operational cost if the machine must be shut down to clear a blockage. Existing systems for removing thermoforming trim typically include a vacuum system to suction the trim into a waste receptacle having a removable rigid collection bin or reels onto which the trim is rolled. For example, the clamps might be opened to allow the vacuum system to remove the trim. However, such a system might not effectively remove all the trim, for example if a piece of trim is not effectively released for a variety of typical reasons. These issues might be especially prevalent in machines used on the food industry. There exists an unmet need for improved, cost-effective systems and methods for removing and disposing of thermoforming trim that overcome deficiencies of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Other aspects, features, and advantages of described embodiments will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements. 
         FIG. 1  shows a schematic side view of a thermoforming trim removal system in accordance with exemplary embodiments; 
         FIG. 2  shows a partial top perspective view of a thermoforming trim removal system in accordance with exemplary embodiments; 
         FIG. 3  shows a partial perspective view of a transport clamp chain and drive sprocket of a thermoforming trim removal mechanism in accordance with exemplary embodiments; 
         FIG. 4  shows a perspective view of a sprocket cam of a thermoforming trim removal mechanism in accordance with exemplary embodiments; 
         FIG. 5  shows a perspective view of the sprocket cam of  FIG. 4  in an assembled configuration with the drive sprocket of  FIG. 3  in accordance with exemplary embodiments; and 
         FIG. 6  is a flowchart illustrating steps for removing trim by a thermoforming trim removal system in accordance with exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The ensuing detailed description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description will provide those skilled in the art with an enabling description for implementing the exemplary embodiments. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention, as set forth in the appended claims. 
     To the extent directional terms are used in the specification and claims to describe portions of the present invention (e.g., upper, lower, etc.), these terms are merely intended to assist in describing and claiming the invention and are not intended to limit the invention in any way. In the figures, elements that are similar to those of other embodiments of the present invention are represented by reference numerals increased by a value of 100. Such elements should be regarded as having the same function and features unless otherwise stated or depicted herein, and the discussion of such elements may therefore not be repeated for multiple embodiments. In addition, reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features. 
       FIG. 1  shows a schematic view of thermoform packaging machine  100 . As shown, thermoform packaging machine  100  comprises forming station  102 , loading station  104 , pre-sealing station  108 , sealing station  110 , and cutting station  114 , which are arranged on machine frame  122  in sequence indicated by production direction D. In general, thermoform packaging machine  100  is employed to automatically package one or more products within a thermoformed package by conveying the products through thermoform packaging machine  100  in production direction D. For example, forming station  102  thermoforms pockets in a packaging material to be filled with one or more products. The one or more products are placed in the thermoformed pockets at loading station  104 . Pre-sealing station  108  covers the products that are placed in the packaging material, for example with film or foil  116  from material roll  112 . Sealing station  110  might typically vacuum seal the package and cover material, for example by removing or substituting the atmosphere in the troughs by an exchange gas or gas mixture, for example, by gas flushing. Once the package is sealed, cutting station  114  removes excess cover material (“trim”). For example, cutting station  114  might perform transverse cutting unit and longitudinal cutting to remove trim from all sides of the packaged products and to separate adjacent packages. Film or foil  116  might be made of one or more polyethylene plastics such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), as well as known biodegradable plastics or other flexible materials known in the art (i.e., polymeric and/or non-polymeric) having strength characteristics suitable for use in thermoforming packaging. 
     Although not shown in  FIG. 1 , packaging machine  100  might be coupled to a conveyor belt for transporting finished packages that have been separated from one another. Although not shown in  FIG. 1 , thermoform packaging machine  100  generally will also include a controller for controlling and monitoring the processes taking place in thermoform packaging machine  100  and displaying indications to an operator of thermoform packaging machine  100 . 
     As shown in  FIG. 1 , thermoform packaging machine  100  includes sealing station  110  and cutting station  114 . As shown in  FIG. 2 , sealing station  110  and cutting station  114  include film conveying units  202  that grips the film  116  and advances it in production direction D to cover the packages. As described herein, the film conveying unit might be configured, for example, as transport clamp chains arranged on either side of the film  116  within machine frame  122 . In thermoforming machines of the prior art, it is common for excess portions of film  116  (“trim”) cut away in cutting station  114  not to release from the transport clamps and to wind back into the sprockets of sealing station  110  and/or cutting station  114  for advancing the transport clamp chains (e.g., sprockets  204 ,  206 ,  208 ,  212 ,  214  and  216 , or equivalent sprockets, not shown, at the opposing end of cutting station  114 ). This is a significant cause of down time for thermoform packaging machines of the prior art. 
       FIG. 3  shows a perspective view of a transport clamp chain  202  and drive sprocket  310  of thermoform packaging machine  100 . As shown in  FIG. 3 , transport clamp chain  202  includes a plurality of clamp link members  300  that is driven to move products along thermoform packaging machine  100  in production direction D by drive sprocket  310  having a plurality of sprocket teeth  308 . Drive sprocket  310  is driven by drive axle  312 , which has an outer radius of R. Each clamp link member  300  includes clamp  302 , spring  304 , clamp release surface  306 , and clamp grip surface  314 . Spring  304  operates to keep clamp  302  closed against clamp grip surface  314  (e.g., to grip thermoform film  116  to package items in thermoform packaging machine  100 . Clamp  302  remains closed unless clamp release surface  306  is pressed, which opens clamp  302  upward from clamp grip surface  314 . Drive sprocket  310  has a distance, D 1 , between its center point and the bottom surface of each clamp link member  300  (e.g., clamp release surface  306 ). In thermoform packaging machines of the prior art, clamp  302  of each of the various clamp link members  300  might be opened, for example by passing clamp release surface  306  over a raised surface, after trim is cut away from the packages at cutting station  114 . However, thermoform packaging machines of the prior art often fail to effectively remove all the trim, for example if a piece of trim is stuck to a clamp or a clamp fails to open. This situation might occur since the thermoform film is heated and might be sticky, and might be especially prevalent in machines for processing sticky items, such as food items. Stuck trim material can then get caught in the various sprockets (e.g., drive sprocket  310 ) and clamp chain  202 , which can result in thermoform packaging machine  100  needing to be taken out of service for cleaning and repair. 
       FIG. 4  shows a perspective view of sprocket cam  400  for use with drive sprocket  310  to prevent stuck trim material from getting stuck in drive sprocket  310 . As shown in  FIG. 4 , sprocket cam  400  might typically be implemented in two halves, shown as first half  402  and second half  404 , which are held together, for example on drive axle  312 , by bolts  406   a  and  406   b  with nuts  408   a  and  408   b . As shown in  FIG. 4 , each of first half  402  and second half  404  have a cutout having a radius of R 1 . In exemplary embodiments, R 1  is substantially equal to R, the radius of drive axle  312  such that sprocket cam  400  (e.g., both first half  402  and second half  404 ) can be tightly clamped to drive axle  312 . Also as shown in  FIG. 4 , each of first half  402  and second half  404  have a radius of R 2 . In exemplary embodiments, R 2  is slightly larger than the distance, D 1 , between the center of drive sprocket  310  and the bottom surface of each clamp link member  300  (e.g., clamp release surface  306 ). Thus, sprocket cam  400  is sized to release each clamp  302  by pressing against clamp release surface  306  as each clamp link member comes into contact with cam  400  as transport clamp chain  202  is driven by drive sprocket  310 . Further, R 2  might be smaller than the radius of drive sprocket  310 , such that the clamp link members  300  do not become disengaged from sprocket teeth  308  of drive sprocket  310  as each clamp link member comes into contact with cam  400  as transport clamp chain  202  is driven by drive sprocket  310 . 
       FIG. 5  shows a perspective view of the sprocket cam of  FIG. 4  in an assembled configuration with drive sprocket  310 . As shown in  FIG. 5 , R 2  is slightly larger than the distance, D 1 , between the center of drive sprocket  310  and the bottom surface of each clamp link member  300  (e.g., clamp release surface  306 ). Thus, sprocket cam  400  is sized to release each clamp  302  by pressing against clamp release surface  306  as each clamp link member comes into contact with cam  400  as transport clamp chain  202  is driven by drive sprocket  310 . Further, R 2  might be smaller than the radius of drive sprocket  310 , such that the clamp link members  300  do not become disengaged from sprocket teeth  308  of drive sprocket  310  as each clamp link member comes into contact with cam  400  as transport clamp chain  202  is driven by drive sprocket  310 . 
     Thus, as shown in  FIGS. 4 and 5 , sprocket cam  400  forces open each clamp link member  300 , thus reducing or eliminating the possibility of trim material not being removed due to a stuck or unopened clamp. Further, sprocket cam  400  is installed on at least the first drive sprocket after the trim material is cut (e.g., after cutting station  114 ) to prevent trim material from becoming stuck in subsequent drive sprockets of thermoform packaging machine  100 . In some embodiments, sprocket cam  400  might be installed on one or more additional drive sprockets of thermoform packaging machine  100 , such that, at each drive sprocket, each clamp link member  300  is opened so that excess trim material can be removed. Also, in this embodiment, the sprocket cam  400  is designed to be retrofitted to a sprocket. Alternatively, the sprocket cam  400  structure could be provided as an integral part of the drive sprocket  310  and drive axle  312  or another sprocket and axle. Accordingly, the present invention provides a second cam-release surface that engages the clamp chain  202  after the clamp chain has come in contact with a primary cam-release, which is typically located just after the cutting station  114 . 
     Although not shown in  FIG. 3 , a trim removal system might be placed at a bottom of drive sprocket  310  such that any trim material can be removed before transport clamp chain  202  is fed around any additional sprockets of thermoform packaging machine  100 . In exemplary embodiments, the trim material might be removed by a vacuum system, for example such as described in related U.S. Patent Application No. Publication No. 2014/0345078 A1, published Nov. 2, 2014, which is hereby incorporated by reference as if fully set forth. In other embodiments, an air blower might be employed rather than a vacuum system to blow trim material from the clamps. In yet other embodiments, a combination of an air blower and vacuum system might be employed. Further, although shown in  FIGS. 4 and 5  as a sprocket cam, other implementations of actuators to release the clamps, such as a rod or bar, might be employed. 
       FIG. 6  is a flowchart of exemplary thermoform packaging process  600 . At step  602 , the packaging process is started, for example by thermoform packaging machine  100 . At step  604 , thermoform packaging machine  100  places an item to be packaged in a container base, for example at loading station  104  as described in regard to  FIG. 1 . At step  606 , thermoform film  116  is placed over the item and container base to allow the item to be sealed within the container base, for example at pre-sealing station  108  as described in regard to  FIG. 1 . At step  606 , the container might be vacuum sealed, for example at sealing station  100  as described in regard to  FIG. 1 . At step  608  trim material is removed from the sides of the packaged products and adjacent packages are separated, for example at cutting station  114  as described in regard to  FIG. 1 . At step  610 , sprocket cam  400  opens each clamp  302  of each clamp link member  300  as they are driven by drive sprocket  310 . At step  612 , the trim material is removed by a trim removal system. For example, the trim removal system might be placed at a bottom of drive sprocket  310  such that any trim material can be removed before transport clamp chain  202  is fed around any additional sprockets of thermoform packaging machine  100 . In exemplary embodiments, the trim material might be removed by a vacuum system, for example such as described in related U.S. patent application Ser. No. 14/284,698 filed May 22, 2014. At step  614 , packaging process  600  completes. 
     Thus, as described herein, described embodiments provide an improved trim material removal system to prevent trim material from becoming lodged in the sprockets of the thermoform packaging machines, thus reducing production down time and costs. 
     The terms “downstream” and “upstream”, as used in the specification and claims, mean the relative location of two elements along the path of travel of the clamping chains, taking into account their direction of travel. For example, if the cutting station  114  is referred to as being downstream from the sealing station  110 , this means that a clamp link member  300  will pass through the cutting station  114  station after passing through the sealing station  110  when the chain is moving in its normal direction of travel. 
     Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.” 
     As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion. 
     It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps might be included in such methods, and certain steps might be omitted or combined, in methods consistent with various described embodiments. 
     As used herein in reference to an element and a standard, the term “compatible” means that the element communicates with other elements in a manner wholly or partially specified by the standard, and would be recognized by other elements as sufficiently capable of communicating with the other elements in the manner specified by the standard. The compatible element does not need to operate internally in a manner specified by the standard. Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about” or “approximately” preceded the value of the value or range. 
     Also for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. Signals and corresponding nodes or ports might be referred to by the same name and are interchangeable for purposes here. 
     It will be further understood that various changes in the details, materials, and arrangements of the parts that have been described and illustrated in order to explain the nature of the described embodiments might be made by those skilled in the art without departing from the scope expressed in the following claims. 
     Aspects of the Invention 
     Additional aspects of the invention include: 
     Aspect 1: A thermoforming system comprising: 
     a frame; 
     a forming station, a loading station, and a sealing station; 
     at least one chain, each of the at least one chain comprising a continuous loop having a plurality of links, each of the plurality of links having a clamp that is biased to engage a clamp grip surface and a clamp release surface that is operationally configured to cause the clamp to move out of contact with the clamp grip surface when the clamp release surface is pressed toward the clamp; 
     a plurality of sprockets including a drive sprocket, each of the plurality of sprockets being attached to an axle that is supported by the frame, each of the plurality of sprockets having teeth adapted to engage the at least one chain, the drive socket being connected to a drive mechanism operationally configured to provide a rotational movement of the drive socket in a first rotational direction, thereby causing each of the at least one chain to move in a first direction of travel; 
     a cutting station operationally configured to cut a trim portion away from a remaining portion of a thermoformed package being conveyed by the at least one chain, the cutting station including a first clamp disengagement device operationally configured to cause the clamp to disengage the clamp grip surface of each of the plurality of links as each of the plurality of links passes through the cutting station; 
     a supplemental clamp disengagement device comprising a cam located adjacent to at least one of the plurality of sprockets located between the cutting station and the forming station, the cam being affixed to the axle to which the at least one of the plurality of sprockets is attached, the cam having an outer surface that is positioned to engage the clamp release surface of each of the plurality of links as each of the plurality of links pass over the at least one of the plurality of sprockets, thereby causing the clamp to temporarily disengage the clamp grip surface. 
     Aspect 2: The system of any of aspects 1 and 3-5, wherein the cam is located adjacent to the drive sprocket. 
     Aspect 3: The system of any of aspects 1-2 and 4-5, wherein the cam comprises a plurality of parts that are removably attachable to each other, thereby enabling the cam to be installed on the axle while the at least one of the plurality of sprockets is installed on the axle. 
     Aspect 4: The system of any of aspects 1-3 and 5, further comprising a trim separation device that is operationally configured to apply a force to the trim portion in a direction that will cause the trim portion to disengage from the clamp grip surface and at a location in which the clamp is disengaged from the clamp grip surface of each of the plurality of links as each of the plurality of links pass over the at least one of the plurality of sprockets. 
     Aspect 5: The system of any of aspects 1-4, wherein the trim separation device comprises a blower or vacuum. 
     Aspect 6: A method of operating a thermoform film machine, the method comprising the steps of: 
     (a) driving at least one chain in a direction of travel in a continuous loop, each of the at least one chain comprising a continuous loop having a plurality of links, each of the plurality of links having a clamp that is biased to remain in contact with a clamp grip surface and a clamp release surface that is operationally configured to cause the clamp to move out of contact with the clamp grip surface when the clamp release surface is pressed toward the clamp; 
     (b) forming at least one pocket in a package material at a forming station located along the continuous loop; 
     (c) sealing a cover over the package material at a sealing station; 
     (d) separating a trim portion from a thermoformed container at a cutting station after performing step (c); 
     (e) retaining the trim portion between a clamp and clamp grip surface of at least one link of the at least one chain after performing step (d); 
     (f) causing the clamp of each of the plurality of links to disengage from the clamp grip surface at a location downstream from step (d); 
     (g) allowing the clamp of each of the plurality of links to reengage the clamp grip surface at a location downstream from step (f) and upstream of step (h); and 
     (h) causing the clamp of each of the plurality of links to disengage from the clamp grip surface at a location downstream from the step (g) and upstream from the forming station. 
     Aspect 7: The method of any of aspects 6 and 8-11, wherein step (h) comprises providing a cam located adjacent to a sprocket, engaging a clamp release surface with an outer surface of the cam, thereby causing the clamp of each of the plurality of links to disengage from the clamp grip surface at a location downstream from the step (g) and upstream from the forming station. 
     Aspect 8: The method of any of aspects 6-7 and 9-11, wherein step (a) comprises driving the at least one chain in a continuous loop using a drive socket and step (h) comprises providing a cam located adjacent to the drive sprocket, engaging a clamp release surface with an outer surface of the cam, thereby causing the clamp of each of the plurality of links to disengage from the clamp grip surface at a location downstream from the step (g) and upstream from the forming station. 
     Aspect 9: The method of any of aspects 6-8 and 10-11, further comprising: 
     (i) using a stream of air to induce separation of any trim located on the clamp grip surface at a location at which step (h) is being performed. 
     Aspect 10: The method of any of aspects 6-9 and 11, wherein step (i) comprises blowing a stream of air to induce separation of any trim located on the clamp grip surface at a location at which step (h) is being performed. 
     Aspect 11: The method of any of aspects 6-10, wherein step (i) comprises using a vacuum stream to induce separation of any trim located on the clamp grip surface at a location at which step (h) is being performed. 
     Aspect 12: A method of retrofitting a fully assembled thermoforming machine to provide a secondary trim portion release, the thermoforming machine having two chains that each travel in a continuous loop, each of the two chains being guided by a plurality of sprockets and driven by a drive socket that is attached to a drive axle, each of the two chains including a plurality of links, each of the plurality of links having a clamp grip surface, a clamp that is biased to engage the clamp grip surface and a clamp release surface that is rigidly connected to the clamp, the method comprising the step of: 
     attaching a cam comprising at least two parts to the drive axle in a position adjacent to the drive sprocket, the cam having an outer surface that is positioned to engage the clamp release surface of each of the plurality of links as each of the plurality of links passes over the drive sprocket, thereby causing the clamp to temporarily disengage from the clamp surface.