Patent Application
20170101198
This invention relates to the packaging of products, with particular application to products that are made up of numerous product elements or pieces that can shift in position, orientation, and placement relative to each other, and that are not attached to each other, such that a collection of such product elements is susceptible to settling, whereby the collection of product elements can have different overall volumes, or can rise to different heights in a given bag or package, depending on how well packed the product elements are relative to each other. Non-limiting examples of such products are dry food products such as a load or serving of popped popcorn, chips (such as potato chips, corn chips, tortilla chips, or pita chips), breakfast cereals, certain pet foods, and the like, but can also include non-food products such as pet bedding, and certain types of hardware items, chemicals, and plant seeds. We refer to such a product as a “collective product”. The collective product may be homogeneous, whereby the product elements are all or substantially all of the same type or class, e.g., substantially all the product elements may be popped popcorn pieces, or they may all be potato chips, and so forth. Alternatively, the collective product may be non-homogeneous, whereby some product elements are of a different type or class than other product elements, e.g. as in the case of a breakfast cereal that includes both flakes of grain (a first type of product element) and individual nuts or nut pieces (a different second type of product element), optionally also including another third type of product element, etc. The invention relates to methods, machines, and systems for packaging such collective products in a bag or package that comprises a flexible packaging material.
Vertical Form Fill and Seal (VFFS) machines have been used for many years to package a wide variety of products in bags made with flexible packaging material.
In a VFFS machine, product is inserted into flexible packaging material as the packaging material is being formed into a flexible package, the product flowing along a downwardly-directed path, by the force of gravity into a package pre-form. The process involves:
One objective of the packager, who uses VFFS machines, is to meet regulatory requirements that the package state the quantity of product in the package. The quantity of product in the package is typically printed on the package, stating the weight of product contained in the package. Thus, it is critical to the packager that the weight of product in the package is always within the tolerances allowed by e.g. government regulation.
In meeting the weight requirements, the packager faces a variety of challenges. For example, the raw material used in manufacturing the e.g. food product may vary with time, or may vary when sourced from more than one supplier. The process used in manufacturing the e.g. food product may also vary with time, or may vary between different manufacturing facilities. The packaging material may also vary with time, or may vary when sourced from more than one supplier.
The challenge for the packager is to provide a quality package, where the weight of product in the package consistently meets regulatory requirements, where the packages use a consistent quantity/length of packaging material for each package unit, while consistently presenting the consumer with a package which appears to be “full” of the product.
If the package appears to be less than “full”, the consumer perceives that he/she has been cheated. If the package is overfull, the packager experiences an unacceptably high incidence of leakers which must be discarded as not meeting quality standards.
Another objective of the packager relates to the cost of the packaging material. It is not uncommon for the cost of the packaging material to represent a significant fraction of the overall cost of producing the packaged product. Accordingly, the packager has an incentive to limit the quantity of packaging material used in fabricating each unit of the packaged product.
Certain characteristics of the finished product can provide additional challenges to the packager. For example, the product may be fragile, and/or the product may be light weight, and/or the product may be non-uniform, product element to product element. Such product characteristics are taken into consideration when setting up the packaging operation.
An example of a non-uniform product, e.g. where product density changes due to manufacturing variations from one batch, or from one portion of a batch, to another, is popped popcorn. In the process of popping popcorn, the first popped kernels or pieces tend to be relatively light or less dense because they have little opportunity to absorb popping oil, and thus remain relatively dry and light. However, other popcorn seeds remain in the popping oil for longer periods before popping, and the longer this time period is, the denser or heavier these later popped kernels tend to become. Thus, if care is not taken to thoroughly mix the batch of popped popcorn before packaging, a first charge of popcorn for a first bag may predominantly comprise the relatively lighter, less dense popcorn pieces, and a second charge of popcorn for a second bag may predominantly comprise the heavier, more dense popcorn pieces. The first charge will thus occupy a larger volume than the second charge, even though the two charges are the same weight or mass. With a packaging process designed to seal all bags regardless of such variability, the second bag will have an excessive amount of air (referred to as head space) in the package. By using a bag length dictated by the lower density, higher volume product charge, the packaging process produces an excessive amount of head space for packages containing the higher density, lower volume product charges.
Even where the product is not fragile, or not light weight, or not non-uniform, the product can still arrive in the package pre-form in a bulk density which is less than desired. Accordingly, increasing the bulk density of the product in the package, as well as improving the consistency of the density, package to package, is desirable for the packager.
The package forming action of a vertical form fill and seal operation starts by drawing a generally continuous length of flexible packaging material from one or more rolls of e.g. flexible film or flexible laminate and advancing the packaging material to typically the top of a rigid, typically metal, forming tube, wrapping the packaging material about the forming tube, and drawing the packaging material in a downward direction along an outer surface of an outside wall of the forming tube, thus to define side walls of the package/bag being produced.
In the process of so transforming the flat roll stock into a tubular construct, the flat roll stock is advanced over and about a forming shoulder which is located at the top of the forming tube. As the packaging material passes over and about the forming shoulder, the flat roll stock is converted to a tubular construct. The forming tube is so sized and configured that, as the packaging material is formed about the forming tube and into the tubular construct, the width of the continuous length packaging material is overlapped longitudinally onto itself. A longitudinal seal is subsequently formed by a heated elongate platen pressing the packaging material against the forming tube at the longitudinal overlap. In the alternative, the longitudinal seal can be formed as what is known as a fin seal.
A transverse seal bar forms a first transverse seal across the width of the tubular construct below the forming tube at about the same time, transforming the tubular structure into a longitudinally sealed, tubular construct, contiguous with a trailing portion of the roll stock, the tubular construct defining a package pre-form sealed closed at the lower end thereof and being open at the respective upper end of the tubular construct.
Simultaneously with the forming of the first transverse seal at the lower end of the tubular construct, the transverse seal heads also form a second transverse seal immediately adjacent the first transverse seal, at the top of the underlying, and next preceding, tubular construct, thus to close and seal that next preceding tubular construct as a closed and sealed package. The transverse seal apparatus can also make a transverse cut across the width of the tubular construct between the first and second transverse seals.
The transverse seal formed at the bottom of the formed tube of packaging material, in combination with the longitudinal seal along the length of the tube, provides a partially confined volume as a package pre-form, such that the so-partially-formed tube can receive and contain, and thereby capture and hold, and control the location of, the measured quantity of product which is subsequently dropped downwardly into the tube.
Once the package has been partially formed by the formation of the longitudinal seal, and by the formation of the first transverse seal at the bottom of the partially-formed package, a measured quantity of product is fed to a location over the top of the package, and is dropped downwardly under the force of gravity into the forming tube, and into the partially formed, longitudinally sealed tubular package construct. After the predetermined quantity of product has been dropped, or during such drop, the packaging material is again advanced, downwardly below the forming tube, as the next following length of packaging material is fed over the forming tube. The next following length of packaging material is sealed longitudinally at the platen and is sealed transversely below the forming tube. As the transverse seal jaws move against the packaging material to form the lower transverse seal in the next following length of packaging material, the seal jaws also form the top, and closing, seal in the underlying package and optionally cut the so closed and sealed underlying package away from the overlying next following length of packaging material.
The basic concept of the vertical form fill and seal design requires that flexible packaging material to be drawn/moved one package/unit each time a measured quantity of product is fed/dropped into the top of the forming tube.
Multiple different methods have been used to draw the film about the forming shoulder and down over the forming tube. Early machines had movable transversely-extending seal jaws generally mounted to a carriage which moved the jaws up and down, as well as moving the seal jaws transversely toward and away from the packaging material in forming the transverse seals.
Such movement of the transverse seal jaws was typically a sinusoidal motion whereby the transverse seal jaws moved upwardly to the top of the stroke, below the forming tube, as the jaws transitioned from a closed, sealing configuration, to a generally open configuration. At the top of the stroke, the sealing jaws would close on the next length of the flexible packaging material, above the product which had been dropped into the package pre-form, and thereby flatten the top of the tube while sealing the top of the underlying filled package and the bottom of the overlying next second length of packaging material which was still in the process of being formed into a package, and wherein the longitudinal seal had already been formed.
Heat would be applied to the closed seal jaws so as to seal the packaging material transversely on itself and to cut away the closed and sealed package/bag as the next second length of the packaging material was drawn over and onto the forming tube as the still-closed sealing jaws moved in a downward direction. During the downward pull, a knife, or a heated wire, located between the upper and lower sealing jaws severed the underlying filled package from the overlying tube which was still in the process of being formed.
When the sealing jaws had progressed down by a unit package length, the sealing jaws were opened to release the so-sealed and severed underlying package. This automatically stopped the film pull and stopped the transverse-seal-and-cut operation. At the same time, the product-filled first package, which had just been produced and cut away, dropped onto a discharge conveyor or the like, and the next/second overlying length of packaging material, already longitudinally sealed, was drawn to a position where the top of that length of material was below the forming tube.
The platen then made the longitudinal seal on the next/third length of packaging material, after which a next second measured quantity of product was dropped into the top of the forming tube thus into the partially-formed second package, while the now-open transverse seal jaws moved to the upper extremity of their range of movement where the pull cycle began again, with the transverse seal jaws closing on the top of the second length of packaging material, thus flattening the packaging material between the seal jaw surfaces at the top of the second package being formed, with the product trapped between the earlier-formed bottom seal of that second bag, and the now-being-formed top seal.
Speeds in the above-described method were limited by the inertias involved in moving the heavy transverse sealing structure up and down. An additional problem related to the requirement to provide electrical power to seal jaw heaters, and to provide cable connections to temperature sensors. Because of the constant flexing of the respective electrical connections when moving the seal jaws up and down, the electrical cables would periodically break, accompanied by corresponding maintenance and out-of-service costs.
In a subsequent version of VFFS devices, pull belt devices were located on each side of the rigid forming tube, alongside the platen, to pull the packaging material. These devices consisted of two belts, either driven by a single prime mover operating in cooperation with a gearbox, or driven by two individual prime movers, each driving one of the pull belts. Such devices would run for a programmed period of time to pull/draw a desired length of flexible packaging material onto the forming tube, and then stop while the platen engaged the packaging material in forming a longitudinal seal. The significant advantage with the pull belt system was that the transverse sealing hardware/jaws could be fixed vertically in position with respect to the machine frame, thus to move only horizontally. While the open/close motion still had to be accommodated by the electrical cables, this eliminated the up and down motion of the jaws of the previous generation of VFFS machines, with a respective reduction in cable failures.
Another version of the pull belt design had the pull belts continuously advancing while incorporating a drive for moving the pull belts into contact with the flexible packaging material to pull packaging/bag material down along the rigid forming tube, and for moving the pull belts away from the packaging material when it was not desired to pull packaging material down along the forming tube.
Pull belts driven by various means were known during this time, but one of the problems commonly experienced was a difficulty when pulling certain films (flexible packaging materials), particularly very delicate films such as filter paper, or films that had an extremely high coefficient of friction between the inside surface of the film and the outside surface of the forming tube. If pulling the film along the forming tube was difficult or impractical as a result of the film's tendency to stick to the tube, in some cases, the pressure of the pull belts against the tube (with the film sandwiched therebetween) was increased so the pull belts would more securely engage the film. However, if the coefficient of friction between the film and the forming tube was greater than the coefficient of friction between the film and the pull belts, this approach would not work to help move the film. In such cases, other techniques were employed to reduce the amount of pull required to move the film over the forming shoulder and along the forming tube. One such early technique involved reducing the coefficient of friction between the packaging material (film) and the forming tube by placing Teflon™ tape, or another slippery or low-friction material, on the outside of the forming tube such that the pull belt would press against, and the film would contact, the low-friction tape or other material rather than the higher friction surface of the original forming tube. Another early technique employed what was referred to as a power unwind. This typically took the form of a motorized means that was either placed on the film roll (i.e. on the roll of flexible packaging material), or incorporated in the film unwind mechanism, and was used in conjunction with a film tension detector. In either case, the motorized means would activate or engage to provide tension relief when the detected film tension was high, and would deactivate or disengage to provide less or no tension relief when the detected film tension was lower. Machines made by the Hayssen Manufacturing Company used a nip roller assembly between the film unwind stand and the forming shoulder. This nip roller assembly, also referred to as a measure roll, served two functions: (1) as a power unwind to reduce the pull required by the pull belts to pull the film over the forming shoulder, and (2) to meter the film, such that the bag length could be determined directly by the rotation of the measure rolls, and both the bag length and film pull velocity could be directly controlled by controlling the rotation of the measure rolls. Reference is made to U.S. Pat. No. 4,288,965 (James), U.S. Pat. No. 4,391,079 (Cherney), U.S. Pat. No. 5,377,474 (Kovacs et al.), U.S. Pat. No. 5,485,712 (Cherney et al.), and U.S. Pat. No. 6,131,373 (Chemey).
Thus, in subsequent versions of the pull belt design, a set of measure rollers was added upstream from the pull belts to better control the bag length. Bag length was initially entered in machine degrees in a software program or recipe which could be stored for future use. In some software versions, bag length can instead be entered into the control system in terms of millimeters rather than in machine degrees or time.
In this regard, “machine degrees”, sometimes alternatively referred to herein as “pull degrees”, or simply “degrees”, is a machine system parameter known to those of ordinary skill in the art, and is directly proportional to time as measured in seconds (or milliseconds, etc.). “Machine degrees” is thus simply an alternative measure of time. The machine degrees parameter is convenient and helpful in the design and operation of machine systems because it is standardized or scaled to the repetitive cycle time of the machine, e.g., to the time required for a packaging machine to completely process one bag or package of product, measured e.g. from the start of the cycle for one bag to the start of the cycle for the next bag. The multiplicative factor or scaling factor that relates machine degrees to time in seconds is such that there are exactly 360 machine degrees (beginning at 0 and ending at 359) in one complete cycle of the machine process, i.e., in one cycle time. Thus, for example, 36 machine degrees can always be used to represent precisely one-tenth of one complete machine cycle (or cycle time), regardless of how long that machine cycle lasts in terms of seconds, and regardless of how many bags per minute the machine is producing.
In some versions which used the measure rollers, a mechanical gearbox with a fixed gear ratio was used to drive the measure roller, which determined the bag length, whereby the gearbox controlled the operation of the system.
Stepper or servo motors have been used as prime movers for advancing flexible packaging material (film) in VFFS systems. That is, advancement of the flexible packaging material in such systems has been carried out by stepper or servo motors coupled to pull belts in contact with the flexible packaging material to accomplish the advancement. In such cases, a “⅓-⅓-⅓” velocity profile was typically used for ease of calculation. That is, the total pull time T was divided into three equal parts, where the stepper or servo motor caused the packaging material to accelerate (starting from a zero velocity) over the course of the first ⅓ of the pull time, then advanced the packaging material at a substantially constant velocity for the next ⅓ of the pull time, and then decelerated the packaging material over the course of the final ⅓ of the pull time, finishing again at a zero velocity. In most cases, such as in the case of a single-pull profile, the total pull time T refers to the time required to pull the packaging material a length equal to the bag length. However, in other cases, such as where the bag length is close to, equal to, or greater than the length of the longitudinal seal made by the heated platen (e.g. for a two-unit pull), the total pull time may refer to the time required to pull the packaging material a substantial portion, e.g. at least ⅓ or at least ½, but less than all, of the bag length, the exact amount depending on design details of the bag and of the packaging machine. In any case, a given film pull corresponding to one total pull time T is generally separated from an immediately preceding or an immediately subsequent film pull (which may have the same total pull time T or a different total pull time, and may have the same pull length or a different pull length, relative to the given film pull) by at least one sealing operation, whether it be a transverse seal, a longitudinal seal, or both a transverse seal and a longitudinal seal. Pull parameters for a ⅓-⅓-⅓ exemplary prior art, single-pull profile, can be calculated as follows: The velocity profile is assumed to be the ⅓-⅓-⅓ profile, but can be changed as required.
If a 250 mm bag is desired with 15 degrees of machine motion at 30 packages per minute, the programmed data are as follows:
Bag Length=250 mm
Packages/minute=2 seconds per machine cycle
15 Degrees=15/360 (2000 milliseconds)=83⅓ ms
Command Counts=1000 Counts/Revolution
For this example, the calculation of velocity can be accomplished as follows:
The profile of
Velocity Calculation
VMAX can be determined from the following equation:
Distance=(2×VMAX×T)/3
With Distance=250 mm=1.543 revolutions=1543 counts and T=83% ms
VMAX=(3×Distance)/(2× T)=4629 counts/166% ms=27.77 counts/ms=27,774 counts/sec
Acceleration=VMAX/(T/3)=27774×3/T=999,864 Counts/Sec/Sec
Deceleration=−Acceleration=−999,864 counts/sec/sec Acceleration and Deceleration Calculations
The above algorithms provide key elements of the pull, the maximum velocity, and the acceleration and deceleration factors. If no registration is required, a controller, using the calculated profile, will operate the system satisfactorily, dispensing the desired bag lengths. Changing any pull parameter (pull length, pull degrees, or machine speed) will cause the system to recalculate the parameters and adjust the respective drives accordingly.
The above calculation illustrates the computation for a single pull. Conventionally, a unit package is pulled in one or two pulls depending on the length of the longitudinal seal. If the package length is longer than the longitudinal platen seal bar, then two or more pulls are used for a given package unit.
In some applications of VFFS packaging, some of the product, when dropped down through the forming tube, ended up in the sealing area of the packaging material after completion of the film pull or pulls. Closing of the seal jaws when product is in the seal area results in product being trapped in the attempted seal thus producing what is referred to in the industry as a leaker. This allowed the product to spill out of the bag, or allowed air to enter what should have been a sealed, air-tight package, whereby the resulting package could not pass quality control inspection.
One proposed solution to this problem of product ending up in the seal area was to make the bag longer by using longer lengths of packaging material for each bag, in anticipation that all product would fall past the seal area. While lengthening the bag resulted in some reduction in the number of leakers, packaging material is typically a substantial factor in the cost of producing a unit of packaged goods, especially in the case of snack food products. As a result, there is a financial incentive/motivation to limit the cost of packaging material. Accordingly, lengthening the bag is not an acceptable long-term option.
Another proposed solution to the leaker problem is to not use a longer length of packaging material, but rather to employ a shaker/settler which, for example may be a plate which repeatedly contacts and thus agitates, the partially-formed package, for example agitating a plate against the bottom of the package pre-form, after the product is dropped into the package pre-form. Such agitation against the outside of the packaging material settles the product in the package before the top seal is formed. In some implementations, such shaking provides enough settling of the product in the packaging material, and enough agitation of the product elements that any product elements in the seal area fall away from the seal area, and thus enable successful sealing of the package, sometimes while using a relatively shorter length of the packaging material.
Some snack food products which are not particularly fragile, such as popcorn, or more agitation tolerant products, are well suited to use of a shaker plate to help settle the product in the package in order to limit the amount of packaging material being used or to effect release of product from the seal area. However, using a mechanical settler/shaker is a problem for more fragile products such as numerous varieties of chips, and flake products such as breakfast cereals, which can be broken by the use of a machine element mechanically agitating against the outside surface of the packaging material.
Where, in the prior art, a plate or other shaker impacts the outside surface of the packaging material in the partially formed package, shaking typically takes place after the pull of packaging material has been completed and the packaging material is not moving, in which case the shaking adds to the total machine cycle time, and thus results in a lower number of packages being produced per minute. In some implementations, shaking constitutes a machine element tapping the outside surface of the packaging material on a side of the package pre-form, in order to encourage settling of the product contained in the package pre-form, after the product is deposited into the package pre-form and during the subsequent downward pull of packaging material. Regardless of the shaking configuration, such shakers/settlers share some common drawbacks, as follows:
Most implementations involve shaking the filled bag after the pull is completed, which adds to the total machine cycle time resulting in a lower through-put of packages per minute.
No matter what mechanism is used to impact the outer surface of the packaging material, the mechanical shaker/settler requires a driver coupled to a mechanical system to impart the shaking activity, thus requiring additional energy to operate the system.
For all known shakers, the mechanical systems can be adjusted to modify the shaking action being imposed on to the packaging material and the product being run. Thus, every time the machine is set up to run a different product SKU (stock keeping unit), the machine must be adjusted for producing that SKU. Such set-up capability adds a significant increment in initial equipment cost to the machine operator, as well as increased set-up time for any given product run, and additional machine elements to be maintained and/or repaired.
The somewhat violent nature of the shaking activity results in not infrequent mechanical failures of the shaking system, which failures are associated with increased maintenance and repair costs, as well as downtime costs.
The somewhat violent nature of the shaking activity can cause breakage or deformation of product in the package.
It is therefore desirable to provide an improved packaging system and methods which provide for product settling while overcoming the above problems.
Accordingly, it is desirable to provide systems and methods which leave the seal area clear of product without increasing the length of packaging material used per package unit.
It is also desirable to provide systems and methods which cause product to settle in the package pre-form before the final transverse closure seal is formed.
It is further desirable to provide such systems and methods wherein the application of energy to cause settling of the product is sufficiently gentle that product in the bag is not unacceptably damaged.
It is still further desirable to provide such systems and methods wherein the intensity of the agitation of the packaging material can be adjusted according to the energy input tolerance of the product being packaged.
It is yet further desirable to provide such systems and methods wherein the finished package presents the consumer with an apparently full package while using a consistent length/quantity of packaging material and limiting the quantity of packaging material used.
One, some, or all of these and other objectives may be achieved by the various embodiments illustrated herein for the invention.
This invention provides vertical form fill and seal (VFFS) machines and systems, and the like, with a settling feature capable of avoiding any external object impacting the outer surface of the packaging material, and which causes settling of a collective product contained in a package being formed, before the final transverse seal is made to form the closed and sealed package. The new settling feature can employ the same mechanism that is used to advance or pull the packaging material through the VFFS machine, but where that mechanism is controlled or driven in a rapid sequence of short, strong accelerations or decelerations or both, to impart a jerking motion or agitation to the tubular package pre-form and its contents, thus promoting settling of the product in such pre-form. (Agitation of the tubular package pre-form by other means, such as by the use of mechanical vibrating or shaking devices that contact the bottom, side, or any outer surface or other surface of the package pre-form can thus be eliminated, or, if desired, such other means of agitation can be used in combination with the disclosed settling techniques and systems.) The disclosed settling feature is highly adjustable, whereby the intensity of the energy transferred to the packaging material can be adjusted according to how fragile, or not, is the product which is to be packaged. Reduced product damage or breakage can thus be achieved. For a product such as (popped) popcorn, which has a relatively lower sensitivity to the settling energy input, the input energy intensity can be set relatively higher whereby the length of time over which the settling energy input is needed, in order to achieve a particular degree of settling, may be relatively shorter. By contrast, for a product such as potato chips, which have a relatively higher sensitivity to the intensity of the settling energy, the energy intensity input can be set relatively lower whereby the product is effectively caused to settle as desired, without the product being damaged by the settling process. However the length of time over which the settling energy input is needed in order to achieve a given degree of settling may be relatively longer for a lower energy intensity input than for a higher energy intensity input.
The disclosed methods and systems may be used to produce sealed packages of a given collective product, where such a sealed package can (a) incorporate less flexible packaging material, e.g., have a shorter bag length, or (b) have a smaller percentage of damaged product, or both (a) and (b), relative to a counterpart or comparable sealed package made by previously known methods and systems.
The settling feature is provided by using the VFFS machine controller to drive the drive system (that is to say, to drive the system that pulls the flexible packaging material through the machine), for example to drive measure rollers, and respective pull belts, at rapidly changing speeds, whereby the measure rollers and pull belts advance the packaging material in a series of jerks, which can also be referred to as a stutter-step drive of the rollers and belts. The collective stutter step advance of the measure rollers and pull belts causes the packaging material to advance at a corresponding stutter step motion and rate.
The stutter step advance of the packaging material causes motion both in the packaging material and within the product contained in the packaging material.
The overall result of the so-imposed motion is that the product elements in the package-being-formed are set into motion. Product elements which are loosely attached to the packaging material in the seal area are released from such attachment and tend to fall by gravity into the mass of the contained product, whereby the seal area is freed from at least some, typically all, of the product which would have otherwise stayed attached to the packaging material in the seal area. In addition, the collective motion of the packaging material and the contained product elements causes the product to settle in the package pre-form such that the height of the top of the product is lowered. Such lowering of the top of the product contents in the package pre-form enables the packager to limit the quantity of packaging material used to package the product.
Also disclosed are methods of making a sealed package containing a charge of compound product, such a method including: forming a tubular package pre-form by steps that include wrapping flexible packaging material around a forming tube, sealing edge portions of the packaging material together to form a longitudinal seal, and sealing other portions of the packaging material together to form a first transverse end seal; advancing the flexible packaging material along and past the forming tube using a pulling apparatus adapted to engage and pull the flexible packaging material; and loading the charge of compound product into the tubular package pre-form through the forming tube. The method also includes agitating the tubular package pre-form using the pulling apparatus to settle the compound product in the tubular package pre-form. The agitating step may form a portion of the advancing step, or it may correspond to the entire advancing step. The agitating preferably includes advancing the flexible packaging material in a series of jerks using the pulling apparatus.
The pulling apparatus may advance the flexible packaging material in a uni-directional manner, and the pulling apparatus may be or include a pull belt. The agitating step may begin before the loading step ends. The agitating step may be carried out over an agitation period and the loading may be carried out over a loading period, and the agitation period may at least partially overlap the loading period, for example, in some cases the agitation period may substantially completely overlap the loading period. Alternatively, the agitation and loading periods may not overlap at all. Also disclosed are sealed packages made by the disclosed methods, each such sealed package containing a charge of compound product that has been settled using the disclosed techniques.
Also disclosed are vertical form fill and seal (VFFS) machines that include: an unwind station for receiving a roll of flexible packaging material; a forming tube around which the flexible packaging material can be wrapped; a pulling apparatus adapted to engage and pull the flexible packaging material along and past the forming tube; one or more seal stations, disposed proximate the forming tube, at which edge portions of the flexible packaging material are sealed together to form longitudinal seals, and other portions of the flexible packaging material are sealed together to form transverse end seals, thereby to form a series of tubular package pre-forms from the flexible packaging material; a drop station from which a charge of compound product can be dropped into a given one of the tubular package pre-forms through the forming tube; and a controller coupled to at least the pulling apparatus, the one or more seal stations, and the drop station, wherein the controller is configured to agitate the tubular package pre-form using the pulling apparatus to promote settling of the compound product in the given tubular package pre-form. The pulling apparatus may be or include a pull belt, and the controller may be configured to agitate the tubular package pre-form by operating the pull belt according to a series of short jerks.
The invention is not limited in its application to the details of construction, or to the arrangement of the components or methods set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various other ways. Also, it is to be understood that the terminology and phraseology employed herein is for purpose of description and illustration and should not be regarded as limiting. Like reference numerals are used to indicate like components.
Turning now to
Packaging material 40 is selected, designed, and/or configured such that any two facing surfaces of the packaging material can be heat sealed to each other. Thus, overlapping opposing surfaces are sealed to each other to form longitudinal seals, and facing elements of a given surface are sealed to each other to form transverse seals.
A typical product which is dropped from hopper 42 is a collective product as described above, e.g., a dry food product. Examples of such dry food products are various snack products such as chip products. Potato chips, corn chips, tortilla chips, pita chips and the like are representative of such snack products. Another common product is dry breakfast cereals and other grain-related products. Still another product is popped popcorn. Such products have a number of product characteristics which make them susceptible to initially arriving in the bottom of the package pre-form in a relatively less dense condition, and which presents problems for the packager. Common characteristics may include, without limitation, one, some, or all of:
Even where the product is not fragile, not light weight, not non-uniform, the product can still arrive in the package pre-form in a bulk density which is less than desired. Accordingly, increasing the bulk density of the product in the package, as well as improving the consistency of the density, package to package, is desirable for the packager.
As the product drops from hopper 42 into the package pre-form, the respective product elements lodge with respect to each other and with respect to the side walls of the package pre-form in keeping with their respective physical properties. Especially the light weight, varying configurations, and the friction properties affect the way the product elements come to rest relative to each other when first dropped into the package pre-form.
Still referring to
Note by inspection of the figure that situations can occur at certain times in the machine cycle where a portion (e.g. an upper portion) of a charge of product may be present in the forming tube 30, even though the entire charge of product may also be simultaneously present in the package pre-form. This is because an upper portion of the package pre-form is ordinarily wrapped around the forming tube 30. As product first begins to drop from the hopper 42 into the (empty) package pre-form, it may initially fall through and then past (out of) the forming tube 30, coming to rest and beginning to accumulate at or near the bottom of the package pre-form just above the transverse bottom seal 52. Immediately thereafter, subsequent falling product elements drop onto the accumulating mass of product (inside the package pre-form) at higher and higher positions relative to the transverse bottom seal 52, until a portion of the product charge may be present in the forming tube 30, and simultaneously present in the package pre-form, as shown. Stated differently, the package pre-form can, and often does (depending on the volume of the product being packaged), extend into the forming tube 30, and this situation can exist while the charge of product is being dumped into the package pre-form.
The jerky stutter step advance is indicated in
The stutter step advance may occur only during the period when the product is being dropped into the package pre-form, or only after the entire charge of product has been dropped into the package pre-form, or the stutter step advance may occur both during and after the product drop, e.g., the stutter step advance may begin during (or even before) the period when the product is being dropped into the package pre-form, and it may end after the entire charge of product has been dropped into (and is present in) the package pre-form.
Because the invention operates with a series of jerks, and intermediate periods of lesser velocity, or no velocity, the acceleration required to maintain desired throughput rates may, as a result, exceed the limitations/capabilities of the system, in which case adjustments may need to be made to one or more of the system parameters. For example, the total time required to complete a pull may have to be increased.
Assuming, for example, a 250 mm pull in 833 ms in 5 individual pulls, using the equations shown above, the calculation is as follows:
Length per segment=250/5=50 mm.
Pull time per segment=83⅓/5=16.67 ms. Velocity Calculation
VMAX can then be determined as follows:
Distance=(2×VMAX×T)/3.
With Distance=50 mm=0.3086 revolutions=308 counts and T=16.67 ms.
VMAX=(3×Distance)/(2× T)=924 counts/33.34 ms=27.71 counts/ms=27,710 counts/sec.
Acceleration=VMAX/(T/3)=27710×3/16.67=4,986,803 counts/sec/sec.
Deceleration=−Acceleration=−4,986,803 counts/sec/sec. Acceleration and Deceleration Calculations
The above calculations show that the acceleration and deceleration requirements can become excessive and impose restrictions on the amount of film which can be pulled in the desired amount of time within the response limits of the system.
Certain steps can be taken to resolve the situation, for example and without limitation, one, some, or all of:
One example of a flow chart that can be used, for example in a PLC or other controller in any of the described packaging systems, to accomplish the desired results of settling the collective product inside the package pre-form by short stutter step pulls is shown as
As the measure rolls and pull belts engage the packaging material and affect the stutter step/jerk motion of advancing the packaging material, a number of motion-related effects related to product settling, which we refer to as motion elements, can occur within the advancing package pre-form.
A first motion element is the primary motion of the packaging material, which creates a first motion differential between the packaging material and the contact product elements which are in contact with the packaging material.
A second motion element is the motion which is thus imparted to those contact product elements whereby those contact product elements, themselves, move.
A third motion element is a second motion differential which is created between the contact product elements and those non-contact product elements which are not in contact with the packaging material and which are in contact with the contact product elements.
A fourth motion element is the motion of those so contacted non-contact product elements, which is imparted by the contact product elements.
A fifth motion element is the motion imparted to all the remaining non-contact product elements as those product elements come into contact with a product element which is already in motion.
From the foregoing description, the reader will appreciate that both the ordinary film pull and the disclosed stutter step pulls typically move the flexible packaging material in only one direction, namely, forward, or downward as represented in the orientation of
A Hayssen® Ultima® VFFS machine is equipped with an Omron™ programmable logic controller (PLC) as the control system, uniquely programmed to operate according to the invention. The exemplary control system employs stepper motor technology to drive the measure rolls and pull belts. The configuration is illustrated in
The pull belts follow the commanded position of the measure roll axis in an open loop configuration using stepper motors.
In the alternative, servo motors, or stepper motors with encoders attached for position feedback, can be used in a closed loop configuration with the measure roll axis designated as the master axis.
Another approach is to attach an encoder to the master axis and allow the pull belt axis to follow the encoder rather than the commanded position of the master axis. This forms a closed loop system which is very much like the closed loop servo system.
Conventionally, a unit package is pulled in one or two, optionally three or more, pulls depending on the length of the longitudinal back seal. If the package length is longer than the platen seal bar, the pull typically consists of two pulls, each of which approximates half of a unit package length. The longitudinal back seal is performed at the end of each pull when the packaging material is not moving, such that the ends of the respective longitudinal seals overlap each other, the lengths of the overlapping seals depending on the lengths of the packages being formed.
If the package length is equal to, or greater than, the length of the longitudinal platen seal bar, the invention comprehends the use of two pulls, or more, with a stutter step motion coincident with at least one of the pulls, to help the settling of product in the package pre-form. Restated, any time the package material is driven, with product in the package pre-form, the stutter step/jerk type drive is used unless multiple pulls are used, or the stutter function is disabled by the operator, for a given package unit.
Thus, an answer to the settling problem is found by breaking the continuous normal pull into a series of shorter pulls or jerks between engagements of the longitudinal platen against the packaging material to form the longitudinal seals. In the series of short jerks, which series is referred to as a stutter step profile, each individual jerk in the series moves the film by a distance which is small relative to the distance moved by a conventional film pull, e.g., by less than ⅓, or less than ⅕, or less than 1/10 of the bag length.
For example, if it is desired to pull a 20 inch bag, rather than making a single 20 inch pull, the invention makes a series of short, jerky pulls, for example 20 one-inch pulls, or ten two-inch pulls, or five four-inch pulls, or six 3.33-inch pulls, each pull coming to a complete stop, or at least reducing pull speed, before starting the next pull. Since the machine controller, e.g. a programmable logic computer or programmable logic controller (PLC), is capable of dividing the pull by any number, using a variety of maximum velocities, a variety of minimum velocities, a variety of acceleration rates, a variety of deceleration rates, the film pull can be divided into any number of segments, recognizing that the greater the number of pulls, potentially the greater the total pull time, which may impact the total cycle time for forming, filling, and sealing the package.
The velocity of a given one of the pulls of the packaging material in forming a given package in the prior art is, for example and without limitation, commonly represented as a ⅓-⅓-⅓ profile. The first third of the pull starts at zero velocity and accelerates to the maximum velocity (VMAX). The second third of the pull is accomplished at the maximum calculated velocity for that pull, and the third and final portion of the pull decelerates the packaging material pull from the maximum velocity to zero velocity. This is the motion standard for the velocity calculations required to produce a package of a desired length in the prior art. The same time and velocity principles apply in the invention.
As illustrated in prior art
The velocity/time profile for such an advance of the packaging material using a three step, jerky/stutter step, pull is illustrated in
In general, the profiles of
release of product from the seal area,
optimized product settling in the package,
use of limited package material length,
consistency of package results, and
acceptable quality control.
The calculations herein provide the key elements of the pull, the maximum velocity of each pull, and the minimum velocity of each jerk/stutter step as well as acceleration and deceleration factors for each pull. If no registration is required by printing on the packaging material, such calculated profile will operate the system, dispensing the desired package unit length each cycle. Where registration is required, registration sensor 26 senses a registration mark on the packaging material and alerts controller 12, which adjusts the drives to the measure rollers and/or the pull belts, thus to adjust the position of the registration mark relative to the cut-off of the finished, closed and sealed package.
Where more than one pull of packaging material, and more than one platen engagement are used for a given package unit, at least one, but not necessarily all, of the platen engagements, to form a longitudinal seal comes after a stutter step advance. Namely, some of the pulls/advances can be non-stutter step pulls/advances where multiple platen engagements are used for a given package unit. Accordingly, the stutter step jerky advance is used after at least a portion of the charge of product has been fed into the package pre-form, and may not be used during an advance where no product has yet been fed into the package pre-form.
Thus, for example, for a two-step advance of the packaging material, where the packaging material is advanced two times and two longitudinal seals are made, for a given package unit, the first advance may take place immediately after at least a portion of a charge of product elements has been fed into the package pre-form. Given that the product is in the package pre-form, and an objective of the jerky stutter step advance is to settle the product and/or remove product from the seal area, that first advance may follow a stutter step profile while the second advance may follow a profile more like that of
In any event, the settling provided by the invention can be achieved without any mechanical device touching any outside surface of that portion of the packaging material which extends past the exit end of the forming tube, and without any physical touching of the packaging material by a human operator.
In a further embodiment, not illustrated specifically in the drawings, the advance of the packaging material can start as a conventional acceleration to maximum velocity as in
Changing any pull parameter, such as pull length, pull degrees, machine speed, acceleration rate, deceleration rate, minimum velocity, maximum velocity, time at maximum velocity, time at minimum velocity, or print registration, will cause the system to recalculate the remaining pull parameters.
As used herein, a “jerk” advance of the packaging material means either both rapidly accelerating the packaging material and then decelerating the packaging material, or rapidly accelerating the packaging material, rapidly slowing the acceleration, and then again rapidly accelerating the packaging material.
In the alternative, a jerk can be a strong force rapidly applied to the packaging material in the direction of advance of the packaging material so as to rapidly apply acceleration tension to the film, such as a force calculated to reach a VMAX packaging material acceleration in ⅓ the anticipated pull time, but wherein the packaging material is prevented from advancing by a brake system. Such jerk force causes sufficient e.g. lateral flexing of the packaging material in the package pre-form to cause displacement of any product from the seal area and to at least initiate product element settling in the package pre-form.
At least first and second jerks are employed either before or after, or both before and after, the formation of a given one of the longitudinal seals. Thus, where a jerk-type advance of packaging material is used, at least two jerks are used to advance or otherwise tension the packaging material after formation of a given longitudinal seal and before formation of the next longitudinal seal.
We now provide some additional discussion of aspects of the inventive techniques and systems set forth in the detailed description above. Much of this additional discussion simply emphasizes or otherwise repeats information that is explicit or implicit (or both) in the foregoing description.
The settling techniques and systems described herein preferably employ the same mechanism that is used to advance or pull the packaging material through the VFFS machine, but they control or drive that mechanism in a rapid sequence of short, strong accelerations or decelerations or both, to impart a jerking motion or agitation to the package pre-form and its contents, and thus promoting settling of the product in such pre-form. (Agitation of the package pre-form by other means, such as by the use of mechanical vibrating devices that contact the bottom, side, or any outer surface or other surface of the package pre-form can thus be eliminated, or, if desired, such other means of agitation can be used in combination with the disclosed settling techniques and systems.)
The onset of the jerky stutter step advance occurs at a time that is delayed relative to time=0. Furthermore, the time axis is labeled both in terms of machine degrees, and in terms of milliseconds. The time values given in the figure—where the jerky stutter step advance begins at 10 machine degrees or 55 msec, and ends at 50 machine degrees or 275 msec—are realistic for the following specific but non-limiting conditions:
In one approach, we recognize that since the entire stutter step pull or advance is made up of four individual, and substantially similar, stutter step pulls, each stutter step pull must advance the packaging material by 200 mm/4=50 mm. Furthermore, each stutter step pull is represented by one triangular-shaped portion of the profile. Each such triangular-shaped portion can be reconfigured into a rectangle of equal area, the rectangle having a height of VMAX(14) and a width of 5 machine degrees (or 27.5 msec). The area of this rectangle is VMAX(14)*27.5 msec, which must equal the 50 mm length calculated above. Solving for VMAX(14), we get a value of 50 mm/27.5 msec, or about 1.8 mm/msec.
We can also calculate the acceleration and decelaration associated with the stutter step pulls, which acceleration and deceleration may for example be supplied by one or more stutter step motors coupled to the pull belts in contact with the packaging material. If we assume each triangular shape of the velocity profile is symmetrical, with equal magnitudes of acceleration and deceleration, we can then recognize that the velocity of the packaging material changes from 0 to VMAX(14), i.e., from 0 to about 1.8 mm/msec in 27.5 msec, for an acceleration of about 0.066 mm/msec2 (and a deceleration of about—0.066 mm/msec2). By appropriately applying these parameters to the control algorithm of the packaging system, we can generate a pull velocity profile consisting of four 50 mm stutter step pulls in 40 machine degrees, or 220 milliseconds, substantially as shown in
In some cases it is desirable or necessary to introduce variability into the stutter step advance. An example of such variability is shown in
Of course, it is also possible, and simplest, to configure the packaging system so that the individual stutter step pulls, in a series of such pulls that form a stutter step advance, are substantially identical to each other, as shown in
In order to make the most efficient and effective use of the time allocated to the stutter step advance, it is desirable to maximize the number of jerks over the course of the pull. This can be done by using a velocity/time profile whose maximum velocity time period (the dwell time at the maximum velocity) is zero or substantially zero (see e.g.
To maximize the productivity of the packaging machine—and minimize the cycle time required to process one bag or package of product—it is also desirable to begin or initiate the stutter step advance as early in the machine cycle as possible, e.g., while product is being loaded or dropped into the open-ended package pre-form, and before the entire charge of product is contained in such pre-form. In such cases, depending upon factors such as the type of product being loaded, the speed with which the product is dropped into the package pre-form, the size of the charge of product, the bag length, the total pull time T of the stutter step advance, and so forth, the stutter step advance may be finished by the time product loading is complete (and the entire charge of the product is contained in the pre-form), while in other cases the stutter step advance may not be finished but may continue or extend beyond such time as the product loading is complete.
In this regard, the relationship between the time when the stutter step advance (agitation to promote product settling in the package pre-form) is occurring and when product loading and other machine or system processes are occurring in the context of one complete machine cycle is best illustrated in
The timeline of
The functions shown in
In
The start and end times of the various line segments in the figure are shown to be separated from each other for generality and for purposes of illustration so that the various times can be given the unique labels t1, t2, t3, etc. However, the reader will understand that some of the labeled times can be the same or substantially the same. For example, t1 can equal t3, and t2 can equal t4, such that the film pull function (segment 1502) and the agitation function (segment 1504) occur at the same time periods. The time difference t4−t3 equals the total pull time T of the stutter step advance as discussed above.
Of particular significance is the relationship between the agitation function and the hopper dump (or product fill) function. In the prior art, where a bottom shaker plate was used to agitate and settle the contents of the packaging tube pre-form, agitation did not begin until the full charge of product was contained in the open-ended package pre-form. (Furthermore, the localized nature of the agitation at the bottom of the bag tended to result in product damage or breakage.) However, in the disclosed technique, at least some of the agitation can occur while the product is still being loaded into the packaging tube pre-form (e.g., while some product elements are still being dropped into the pre-form), and as the pre-form is being lowered by operation of the film advance function towards the take-away conveyor 38 as seen in
Thus, if we refer to the time during which the agitation occurs as an agitation period (such as segment 1504), and the time during which product loading occurs as a loading period (such as segment 1506), then the agitation period preferably overlaps the loading period. That is, at least some of the agitation preferably occurs while the open-ended package pre-form is being filled, or before the last product element of the charge of product is contained in the package pre-form. In some cases, the agitation period and loading period may satisfy one or both of the following relationships: the agitation period overlaps at least half of the loading period; and the loading period overlaps at least half of the agitation period (e.g. overlaps at least half of the total number of jerky stutter step pulls, assuming such jerky pulls are of substantially equal duration).
Despite the preference for an overlapping agitation and loading period, in some circumstances—depending on details of the collective product, flexible packaging material, package dimensions, and features and limitations of the VFFS machine—it may be neither practical nor desirable to have such an overlap. Furthermore, the relationship of the agitation period (such as segment 1504) to the loading period (such as segment 1506), and to other functions represented by segments in
For example, there are many situations when running a VFFS machine in which it is highly desirable to begin the product loading (hopper dump) while the heat seal jaws are closed to form the bottom transverse seal of the package pre-form, or even to begin such loading slightly before the heat seal jaws close (in view of the short time delay between the moment when the first product elements begin falling from the hopper and the moment those product elements reach the bottom of the package pre-form). In this way, we can avoid transferring to the newly formed, virgin transverse bottom seal the full force of the product being dropped, and can instead cushion at least some of that force by the heat seal jaws, the closed heat seal jaws also serving to shield the virgin bottom seal from the full brunt of such force and prevent a failure of such seal. This can be of particular concern when the flexile packaging material is or comprises a polyethylene film, since a seal formed by two polyethylene film portions can be quite weak at the moment the heat seal jaws open due to the gelatinous, molten condition of the seal, before the heated seal region is allowed to thoroughly or even partially cool and harden.
Consequently, the loading period (see segment 1506) can be shifted relative to its position shown in
Of the many possible situations the machine designer may encounter using the disclosed agitation techniques and machine cycles, we note the following three:
The reader should therefore be careful in interpreting the machine cycle depicted in
The reader will note that the single VFFS cycle of operation of
The functions shown in
Examples of output devices the PLC may couple to include: a pull belt (or pair of pull belts) to accomplish the film advance and stutter step agitation; actuator(s) to move the pull belt(s) into and out of contact with the packaging material; a measure roll; a hopper device or devices to accomplish dumping one load or charge of the collective product from the hopper into the tubular construct by opening the hopper, as well as filling another load of the product into the hopper; a heated platen seal bar to accomplish longitudinal sealing of the tubular construct, and associated actuator(s); transverse seal jaws to accomplish transverse or end sealing of the tubular construct; and a knife, heated wire, or other known device to cut through the flexible packaging material between transverse seals, so that individual bags or packages can be produced from the continuous roll of packaging material. Examples of input devices the PLC may couple to include one or more: film registration sensors; temperature sensors; weight sensors; jaw closed indicators; low film indicators; pushbuttons; selector switches; operator touch screens; program entry devices; and the like.
Although the invention has been described with respect to various embodiments, this invention is also capable of a wide variety of further and other embodiments within the spirit and scope of the appended claims.
Those skilled in the art will now see that certain modifications can be made to the apparatus and methods herein disclosed with respect to the illustrated embodiments, without departing from the spirit of the instant invention. And while the invention has been described above with respect to the preferred embodiments, it will be understood that, in light of the disclosure here, the invention can be adapted to numerous rearrangements, modifications, and alterations, and all such arrangements, modifications, and alterations are intended to be within the scope of the appended claims.
To the extent the following claims use means plus function language, it is not meant to include there, or in the instant specification, anything not structurally equivalent to what is shown in the embodiments disclosed in the specification.
This is a continuation-in-part (CIP) application of U.S. patent application Ser. No. 15/217,494 (attorney docket V01.005-02US), “Settling Product in a Package”, filed Jul. 22, 2016 and currently pending, which claims priority under 35 U.S.C. 119(e) to U.S. provisional patent application 62/199,785 (attorney docket V01.005-01UP), “Settling Product in a Bag”, filed Jul. 31, 2015 and now expired. Each of these applications is fully incorporated herein by reference, except to the extent it or they may be directly contrary to the present application.
| Number | Date | Country | |
|---|---|---|---|
| 62199785 | Jul 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15217494 | Jul 2016 | US |
| Child | 15388749 | US |
