Patent Application
20060096249
The present invention relates generally to machines, assemblies, and related methods for shrink wrap packaging loads. Particularly, the present invention relates to machines, assemblies, and related methods, where cutting of film is performed in a particular way.
In conventional shrink wrapping, a load is fed to a wrapping zone in which a shrink wrap film is placed on the load. The film is cut into pieces or sheets before or during the placement on the load. The load and film are then passed into a heating tunnel causing the film to shrink and compress against the load. Typically, the film is cut into sheets large enough to allow for some overlap between edges when placed on the load. During the heating process, the edges may therefore be sealed together forming a unitary package.
Some users of shrink wrapping machines use the machines to shrink wrap loads having different sizes, such as groups of small or large bottles, or small or large groupings of bottles. In such situations, various machine parameters have to be altered when the load size is changed. For example, the length of the sheet of film may have to be enlarged to accommodate a larger load. Also, the path of the portion of the machine that places the film on the load and/or the speed of wrapping along the path may have to be changed if the load is of a different size.
Conventional shrink wrap machines have attempted to address issues raised by shrink wrapping differently sized loads using a number of approaches. While these approaches may work in certain situations, they have been expensive in terms of complication of parts and assembly of the parts, the cost of more highly skilled laborers needed to operate the machinery, and in terms of repair and replacement of expensive worn parts. For example, conventional shrink wrapping machines have utilized adjustable wrap guides that alter the wrap path followed for wrapping a load. These guides have been complex to properly adjust and calibrate, and may require removal and replacement of a driven wrap chain. Such chain replacement can be complex and time consuming. Also, conventional shrink wrap machines have utilized complex servomotor and/or clutch arrangements to drive wrap guides at the varying speeds used during a wrap cycle. These parts are expensive to procure, maintain, and replace. Thus, it would be desirable to achieve simpler solutions than have been currently proposed for machines capable of shrink wrapping loads of different sizes.
Conventional shrink wrapping machines have also utilized servomotors and/or clutches to drive a cutting knife to cut the film to size for shrink wrapping. The placement of the cutting knife within the machine is fixed. Therefore, since the film speed during a wrap varies, often dictated by the size of the load, the film speed may or may not be at a desirable speed at the time that cutting is necessary for proper film sheet sizing. For example, the film may have to be cut at an undesirably high speed for certain load sizes. Cutting at a high speed can produce inaccurate cuts. Alternatively, complex drive systems have been used to slow down or stop the film for cutting when the proper cut location reaches the fixed knife (see, for example, U.S. Pat. No. 6,128,888). Such systems are also unnecessarily complex and such artificial manipulation of film speed for cutting causes an uneven flow and induces wear on machine parts.
According to certain aspects of the invention, a machine is disclosed for shrink wrapping a load of a given size, the machine including a supply conveyor for supplying the load to a wrapping zone, and a wrap conveyor disposed in the wrapping zone, the wrap conveyor receiving the load from the supply conveyor. A film supply supplies a film to the wrapping zone. The film supply includes a cutting mechanism having a position selectively fixed within a cutting zone. A wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the wrap conveyor so as to place the film on the load. The wrap guide includes a wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed. The cutting mechanism cuts the film when the film speed is below the maximum speed. A heat supply shrinks the film so as to shrink wrap the load. Various options and modifications are possible.
For example, the film supply may include a track extending along the cutting zone, and the cutting mechanism may be positionable along the track. The film supply may include a variable speed vacuum belt operative downstream of the cutting mechanism for moving the film to the wrapping bar. A servomotor may drive the vacuum belt at a varying speed corresponding to the speed of the wrapping bar, and the cutting mechanism may be driven by the servomotor. The cutting mechanism may be triggered by an electronic clutch, and may rotate substantially synchronized with the film speed. The cutting mechanism may include a cutter triggered when the film is substantially at or proximate the minimum speed. The film supply may include a film supply roll and a plurality of dance bars. The position of the cutting mechanism may be dependent on one or more of: the size of the load, a length of the film after cutting, a point in a wrap cycle in which the cutting mechanism cuts the film, and an amount of leading edge of film placed beneath the load during the wrap cycle.
According to certain other aspects of the invention, a cut film supplying assembly is disclosed for a machine for shrink wrapping a load of a given size, the assembly including a wrap conveyor disposed in a wrapping zone, and a film supply for supplying a film to the wrapping zone. The film supply includes a cutting mechanism having a position selectively fixed within a cutting zone. A wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the load on the wrap conveyor so as to place the film on the load. The wrap guide includes a wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed. The cutting mechanism cuts the film when the film speed is below the maximum speed. As above, various options and modifications are possible.
According to other aspects of the invention, a machine is disclosed for shrink wrapping a load of a given size, the machine including a supply conveyor for supplying the load to a wrapping zone, and a wrap conveyor disposed in the wrapping zone, the wrap conveyor receiving the load from the supply conveyor. A film supply supplies a film to the wrapping zone, and a wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the wrap conveyor so as to place the film on the load. The wrap guide moves the film along the wrap path at a speed varying between a maximum speed and a minimum speed. A selectively fixable cutting means cuts the film when the film speed is below the maximum speed. A heat supply shrinks the film so as to shrink wrap the load. Again, various options and modifications are possible.
According to other aspects of the invention, a cut film supplying assembly is disclosed for a machine for shrink wrapping a load of a given size, the assembly including a wrap conveyor disposed in a wrapping zone, the wrap conveyor receiving the load from the supply conveyor, and a film supply for supplying a film to the wrapping zone. A wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the load on the wrap conveyor so as to place the film on the load. The wrap guide moves the film along the wrap path at a speed varying between a maximum speed and a minimum speed. A selectively fixable cutting means cuts the film when the film speed is below the maximum speed. As above, various options and modifications are possible.
According to other aspects of the invention, a machine is disclosed for shrink wrapping a load of a given size, the machine including a supply conveyor for supplying the load to a wrapping zone, and a wrap conveyor disposed in the wrapping zone, the wrap conveyor receiving the load from the supply conveyor. A film supply supplies a film to the wrapping zone, the film supply including a cutting mechanism having a position selectively fixed within a cutting zone. A wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the wrap conveyor so as to place the film on the load. The wrap guide includes at least one wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed. The cutting mechanism cuts the film when the film speed is substantially at or proximate the minimum speed. A heat supply shrinks the film so as to shrink wrap the load. Again, various options and modifications are possible.
According to other aspects of the invention, a cut film supplying assembly is disclosed for a machine for shrink wrapping a load of a given size, the assembly including a wrap conveyor disposed in a wrapping zone, and a film supply for supplying a film to the wrapping zone. The film supply includes a cutting mechanism having a position selectively fixed within a cutting zone. A wrap guide is disposed in the wrapping zone for guiding film received from the film supply in a wrap path proximate the load on the wrap conveyor so as to place the film on the load. The wrap guide includes at least one wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed. The cutting mechanism cuts the film when the film speed is substantially at or proximate the minimum speed. Again, various options and modifications are possible.
According to other aspects of the invention, a method is disclosed for selectively shrink wrapping a first load of a first size and a second load of a second size, the method including the steps of: (a) fixing a cutting mechanism in a first position in a cutting zone, the first position dependent upon the size of the first load; (b) supplying the first load of the first size to a wrapping conveyor; (c) supplying a film for wrapping the first load; (d) driving a wrap guide in a wrap path proximate the wrap conveyor so as to place the film on the first load, the wrap guide including a wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed; (e) cutting the film with the cutting mechanism when the film speed is below the maximum speed; (f) heating the film so as to shrink wrap the first load; (g) fixing the cutting mechanism in a second position within the cutting zone, the second position dependent upon the size of the second load; and (h) repeating steps (b) to (f) with the second load. Various options and modifications are possible.
For example, step (e) may include cutting the film when it is substantially at or proximate the minimum speed. Also, steps (a) and (g) may include moving the cutting mechanism along a track and fixing the cutting mechanism at the respective first or second position along the track. The first and second positions may be determined based on one or more of: the size of the load, a length of the film after cutting, a point in a wrap cycle in which the cutting mechanism cuts the film, and an amount of leading edge of film placed beneath the load during the wrap cycle.
According to other aspects of the invention, a method is disclosed for shrink wrapping a load having a size, the method including the steps of: (a) selecting a cutting position from a range of cutting positions within a cutting zone dependent on the size of the load; (b) fixing a cutting mechanism in the cutting position; (c) supplying the load to a wrapping conveyor; (d) supplying a film for wrapping the load; (e) driving a wrap guide in a wrap path proximate the wrap conveyor so as to place the film on the load, the wrap guide including a wrapping bar that moves along the wrap path so as to move the film at a speed varying between a maximum speed and a minimum speed; (f) cutting the film with the cutting mechanism when the film speed is below the maximum speed; and (g) heating the film so as to shrink wrap the first load. Again, various options and modifications are possible.
For example, step (f) may include cutting the film when it is substantially at or proximate the minimum speed. Also, step (a) may include moving the cutting mechanism along a track and fixing the cutting mechanism at the selected cutting position along the track. Further, the selected cutting position may be determined based on one or more of: the size of the load, a length of the film after cutting, a point in a wrap cycle in which the cutting mechanism cuts the film, and an amount of leading edge of film placed beneath the load during the wrap cycle.
Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. In discussing various embodiments, like or similar reference numerals are used below with like or similar parts of various embodiments.
Supply conveyor 12 includes a supply belt 34 and a flight bar assembly 36 for driving loads received from the infeed conveyor 32 to wrapping zone 14. Supply belt 34 may be driven or undriven, or may be replaced by rollers. Flight bar assembly 36 may include a plurality of flight bars 38 driven on chains 40 by a conventional motor drive with servo-clutches. Flight bars 38, supply belt 34 and infeed conveyor 32 may all be driven at synchronous speeds as controlled by a programmable logic controller, as desired. Sensors 42 may be provided within supply conveyor 12 to detect presence of loads being pushed by flight bars 38 for feedback loop control of various aspects of machine 10.
Film supply 22 may include rollers 44 for supporting one or more film rolls 46 for supplying film to machine 10. Rollers 44 may be driven or undriven. The film F is paid out from film roll 46 through a series of rollers 48. If desired, rollers 48 may comprise a portion of a conventional dance bar assembly used to provide more steady rotation of roll 46 while the downstream speed of film F varies due to wrapping cycle film speed changes, as is known.
Cutting assembly 24 includes a frame 60 including a base 62 and side pieces 64. Mounting plates 66 are attached to side pieces 64. Roller 52 is an idler roller mounted between side pieces 64. Rollers 54 and 58 are idler rollers mounted between mounting plates 66. At least one of pinch rollers 56 mounted between mounting plates 66 is driven. It should be understood that various different arrangements of rollers or other structures for passing film F from film supply 22 to and through cutting assembly 24 could be utilized, if desired.
A vacuum belt 68 is mounted between side pieces 64. Vacuum belt 68 may be a conventional vacuum belt used for transmitting film in a desired direction, as is known. Vacuum belt 68 may be driven with a variable speed so as to move cut film at a desired wrapping speed. Thus, vacuum belt 68 may be driven via a variable speed servomotor, a controlled by a conventional programmable logic device. Film speeds during different portions of a wrapping cycle will be discussed in further detail below.
Cutting assembly 24 further includes a cutting mechanism 70 mounted within frame 60. As shown, cutting mechanism 70 may include a cutting blade 72 rotationally mounted within mounting plates 66. Cutting mechanism 70 may be driven by the same servomotor used to drive vacuum belt 68, and is triggered by an electronic clutch 74. It can be desirable to cause cutting blades 72 to be rotated by the servomotor and electronic clutch 74 so as to be substantially synchronized in tangential speed with the speed of film F. It is believed that such synchronization of the cutting mechanism and the film speeds creates a more accurate cut.
In some aspects of the present invention, it is desirable to selectively fix the position of the cutting mechanism within a cutting zone within cutting assembly 24. As shown in
As will be discussed in further detail below, use of handle 80 to position cutting mechanism 70 within the cutting zone between rack gears 76 can provide certain benefits in certain applications. For example, cutting mechanism 70 may be placed in a position so as to achieve a certain length of cut film, or so as to cut the film at a certain point in the wrap cycle, or at a certain film speed, or within a range of film speeds. However, it should be understood that the movable cutting mechanism 70 is not required for all aspects of the invention.
It should also be understood that other cutting mechanism location adjustment designs could be substituted for the rack and pinion arrangement shown in
Wrap guide 16 further includes at least one wrapping bar 104 driven along the wrap path. Wrapping bar 104 is mounted to a follower 106 that follows a chain 116 along a track 117. Fixed portion 110 of wrap path 108 is disposed within fixed portion 100 of wrap guide 16. Removable portion 112 of wrap path 108 is disposed within removable portion 102 of wrap guide 16. Linkages 114 are connected to followers 106, and are in turn driven by chain 116. Driven gear 118 drives chain 116, and gear 120 is an idler gear. Machine main drive assembly 122 is schematically shown as connected to driven gear 118 by belt 124.
If desired, main drive assembly 122 may be utilized to drive chain 116 at a substantially constant speed. The track 117 followed by chain 116 is fixed. However, wrap path 108 may have differing shapes, depending upon the size of the load, the length of the linkages 114, etc. Thus, by designing track portion 112 accordingly, different sized loads may be wrapped without modifying main drive assembly 122 or chain 116 or its path. The profile along portion 112 of track 108 defines the path that wrap bars 104 take along the wrap path when wrapping a load with film. Quick-connect assembly devices such as clamps 126 may be utilized to readily attach and detach removable portion 102 so as to change the track portion 112 if desired. Thus, if different sized loads are to be wrapped using machine 10, a simple change out of portions 102 on either side of wrap guide 116 can accommodate the different sized loads by providing a different wrap path. By designing track portion 112 and linkage length 114 accordingly, varying wrap paths can be achieved. In such situation, chain 116 may continue to be driven at a substantially constant speed using main drive 122. Further, the orientation and/or location of chain 116 within machine 10 need not be changed, or the actual chain itself need not be changed out for different loads. Thus, it is a relatively simple matter to change the size and/or shape of load being wrapped by machine 10 by simply changing out the removable portions 102 of a first predetermined size for a second alternate removable portions of another predetermined size to provide alternate wrap paths of different configurations. However, the track 117 followed by chain 116 does not change when removable portions 102 are changed.
The wrap path 108 generated by fixed and removable portions 100 and 102, in combination with linkage 114 causes the cut film to accelerate substantially between the positions of
Also, driving a wrap assembly by driving wrap bars through such a linkage attached to a substantially constant speed loop, such as chain 116, allows for a relatively simple mechanism for providing a wrap path having a wrap bar that moves at a substantially varying speed. Therefore, instead of complex servomotors and controls, a simpler and less expensive drive may be used along with a linkage and wrap path spaced from a chain track, to achieve a desired changing film speed during load wrapping.
One example of such a film speed distribution is shown in
It should be understood that the speed profile as shown in
If desired, it can be useful in certain applications to selectively cut the film at particular points along the speed curve. For example, it may be desired to cut the film when it is moving at a speed less than the maximum speed. It may also be useful to cut the film at a minimum speed, or somewhat proximate the minimum speed. In such case a less expensive low speed clutch may be used and synchronizing blade speed and film speed is less complicated. Thus, if desired, the position of cutting mechanism 70 within the cutting zone may be altered by using the rack and pinion gears 76 and 78 so as to locate the cutting mechanism so as to achieve cutting at a desired film speed for the desired application. Accordingly, one may therefore choose a position of cutting mechanism 70 depending upon one or more of a size of the load, a length of the film after cutting (so as to wrap the film about the load), a point in the wrap cycle in which the cutting mechanism is to cut the film, an amount of leading edge of the film to be placed beneath the load during the wrap cycle, etc. Therefore, having a cutting mechanism with an adjustable positioning device can provide certain benefits.
It is believed that programming can be created to assist in setting the optimal position of the cutting mechanism within the cutting zone based on various system parameters, such as load size, wrap path dimensions, machine speed, etc. Such optimum position could also be determined empirically through testing and experience. In any event, the optimal placement may be provided to a machine user for manual manipulation or may be automatically achieved by a drive mechanism, for example through the use of programmable logic servomotors, position sensors, etc. If desired, such positioning could be automatically achieved during operation as well based on various sensor input.
According to certain other aspects of the invention, methods of using the above shrink wrap machine components are also contemplated within the scope of the invention. For example, it is within the scope of the invention to wrap a load of a certain size using a first removable portion of a wrap guide, switching out that removable portion for an alternate removable portion of a different size defining a different wrap path, and then wrapping a load of a different size. Similarly, one may fix the cutting mechanism at a certain position, run the machine to wrap a load of a given size, and then move cutting mechanism to a different position so as to cut film so as to wrap loads of a different size. The methods may be complementary or may be employed separately, if desired. Thus, the machine and methods described above provide a flexible wrapping machine that can be utilized for different loads and for different applications, where change out and down time, if loads of different sizes are to be wrapped, is reduced.
It should be understood that various other modifications and combinations of the above embodiments are contemplated and are also within the scope of the present invention. Thus, the present invention contemplates that any and all such subject matter is included within the scope of the present invention.
