WO2025019267A1

WO2025019267A1 - Lateral film pre-stretching apparatus for a wrapping machine

Info

Publication number: WO2025019267A1
Application number: PCT/US2024/037593
Authority: WO
Inventors: Pekka MUSTONEN
Original assignee: Signode Industrial Group LLC
Current assignee: Signode Industrial Group LLC
Priority date: 2023-07-14
Filing date: 2024-07-11
Publication date: 2025-01-23
Anticipated expiration: 2026-01-14
Also published as: CN121511193A

Abstract

Various embodiments of the present disclosure provide a film carriage of a wrapping machine and a method of pre-stretching a film. The film carriage includes upper and lower holders sized and shaped to hold portions of a film. In some embodiments a pre-stretcher element is offset from a line between the upper and lower holders and is positioned to pre-stretch the film. In some embodiments the upper and lower holders diverge to pre-stretch the film.

Description

LATERAL FILM PRE-STRETCHING APPARATUS

FOR A WRAPPING MACHINE

PRIORITY

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application 63/526,965, filed July 14, 2023, the entire contents of which is incorporated by reference.

FIELD

[0002] The present disclosure relates to stretch-wrapping machines, and more particularly to stretch-wrapping machines that include a pre-stretch apparatus.

BACKGROUND

[0003] Several types of known stretch-wrapping machines use stretch film to secure loads of goods on pallets. These stretch-wrapping machines include a film carriage to which a replaceable roll of stretch film is mounted. Depending on the type of stretch-wrapping machine, the film carriage rotates relative to the palletized load or the palletized load rotates relative to the film camage while the film camage vertically moves relative to the load to wrap the load with the stretch film in a spiral pattern. For instance, a turntable wrapping machine rotates a turntable carrying the palletized load while vertically moving the film carriage to wrap the load w ith the stretch film. A ring wrapping machine rotates the film carriage on a circular ring that circumscribes the palletized load while vertically moving the film carriage to wrap the load with the stretch film. A rotating arm wrapping machine rotates a cantilevered arm carrying the film carriage around the palletized load while vertically moving the film carriage to wrap the load with the stretch film.

[0004] Certain stretch-wrapping machines include pre-stretch assemblies that pre-stretch the film along its longitudinal axis after it is pulled off of the film roll and before it is applied to the load. Pre-stretching the film before applying it to the load has several benefits, including increasing the film’s containment force and extending the longevity of the film roll. One known pre-stretch assembly includes an upstream pre-stretch roller, a downstream prestretch roller, and a pre-stretch drive assembly operably connected to the upstream and downstream pre-stretch rollers to rotate them. The pre-stretch drive assembly drives the rollers so the downstream pre-stretch roller has a higher linear speed than the upstream pre- stretch roller. The linear speed (alternatively called the tangential speed) of a roller is a function of its diameter and its rotational speed and corresponds to the speed of the film contacting the roller. This linear speed differential results in the downstream pre-stretch roller imposing a stretching force on the film, resulting in the film stretching after it disengages the upstream pre-stretch roller and travels onto the downstream pre-stretch roller.

[0005] Although pre-stretching the film has several benefits, one downside is necking. Necking (also known as neckdow n) refers to the narrowing of the film's width that occurs as the film is pre-stretched — the more the film is pre-stretched, the more pronounced the necking (e.g., film pre-stretched at 190% will exhibit more necking than film pre-stretched at 150%). An exaggerated example of the necking phenomenon is shown in Figure 1. In this example, when a stretching force is applied to a film w eb FW pulled off of a film roll R, the film web FW stretches longitudinally but narrows in width from a first width W1 to a second width W2. A narrower film web results in more film needed to adequately wrap the load, which partially offsets a benefit of pre-stretching.

SUMMARY

[0006] Various embodiments of the present disclosure provide a film carriage for a wrapping machine and methods of pre-stretching film for a w rapping machine.

[0007] In one embodiment, a pre-stretch assembly for a wrapping machine comprises an upper holder, a low er holder, and a pre-stretcher element offset from a line extending between the upper holder and the lower holder. The upper holder includes first and second upper conveyance elements sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower ede holder includes first and second lower conveyance elements sized and shaped to hold the film when positioned betw een the first and second lower conveyance elements. The upper holder and the lower holder are positioned to hold respective edges of the film. The pre-stretcher element is positioned such that the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

[0008] In one embodiment, a method of pre-stretching film for a wrapping machine comprises removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge. The method also includes conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages a lower portion of the film. The upper holder and lower holder are spaced apart. The method also includes engaging a portion of the film that is between the upper holder and the lower holder with a pre-stretcher element. The pre-stretcher element is offset, in a second direction, from a line extending between the upper holder and the lower holder so as to pre-stretch the film to a second width that is greater than the first width.

[0009] In one embodiment, a pre-stretch assembly for a wrapping machine comprises an upper holder, and a lower holder. The upper holder includes adjacent first and second upper conveyance elements that form an inlet end and an outlet end. The first and second upper conveyance elements are sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower holder includes adjacent first and second lower conveyance elements that form an inlet end and an outlet end. The first and second lower conveyance elements are sized and shaped to hold the film when positioned between the first and second lower conveyance elements. The upper holder and the lower holder are positioned to hold respective portions of the film and are angled with respect to one another to diverge such that the outlet ends of the upper and lower holders are further apart than the inlet ends of the upper and lower holders and the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

[0010] In one embodiment, a method of pre-stretching film for a wrapping machine comprises removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge, and conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages a lower portion of the film. Respective inlet ends of the upper holder and lower holder are spaced apart by a first distance. Respective outlet ends of the upper holder and lower holder are spaced apart by a second distance that is greater than the first distance such that conveying the film along the first direction pulls the upper portion and lower portion of the film away from one another so as to pre-stretch the film to a second width that is greater than the first width.

BRIEF DESCRIPTION OF THE FIGURES

[0011] Figure 1 shows necking of a film w eb as a stretching force is applied to stretch the film web.

[0012] Figure 2 is a perspective view of one example embodiment of a stretch-wrapping machine of the present disclosure. [0013] Figure 3 is a block diagram showing certain components of the stretch-wrapping machine of Figure 2.

[0014] Figure 4 is a perspective view of part of the film carriage of the wrapping assembly of the stretch- wrapping machine of Figure 2.

[0015] Figure 5A is a schematic side view of a stretching portion of the film carriage of Figure 4.

[0016] Figure 5B is a schematic end view of the stretching portion of Figure 5 A.

[0017] Figure 5C is a diagrammatic end view illustrating distances associated with the prestretch assembly.

[0018] Figure 6 is a schematic top view of one example embodiment of a film holder of the present disclosure.

[0019] Figure 7 is a schematic top view of another example embodiment of a film holder of the present disclosure.

[0020] Figure 8A is a schematic top view of another example embodiment of a film holder of the present disclosure.

[0021] Figure 8B is a schematic side view of the film holder of Figure 8A.

DETAILED DESCRIPTION

[0022] While the systems, devices, and methods described herein may be embodied in various forms, the drawings show and the specification describes certain exemplary' and nonlimiting embodiments. Not all of the components shown in the drawings and described in the specification may be required, and certain implementations may include additional, different, or fewer components. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of connections of the components may be made without departing from the spirit or scope of the claims. Unless otherwise indicated, any directions referred to in the specification reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. Further, terms that refer to mounting methods, such as mounted, connected, etc., are not intended to be limited to direct mounting methods but should be interpreted broadly to include indirect and operably mounted, connected, and like mounting methods. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the present disclosure and as understood by one of ordinary skill in the art.

[0023] Various embodiments of the present disclosure provide a film carriage for a w rapping machine with pre-stretching apparatus to pre-stretch the film in a lateral direction. As used herein, “lateral” refers to the direction that runs across the film, or substantially perpendicular to the direction that the film is drawn as it is unw ound from a roll.

[0024] Figures 2 and 3 show one embodiment of the stretch-wrapping machine 1 (sometimes referred to herein as the “w rapping machine” for brevity) of the present disclosure. The wrapping machine 1 includes a wrapping-machine frame 10, a circular guide 20. a guide actuator 30, a wrapping assembly 40, a cuting-and-fixing device (not shown), an operator interface 500, and a controller 600.

[0025] The wrapping-machine frame 10 is formed from multiple tubular and/or solid members (not individually labeled) and configured to support the other components of the wrapping machine 1. The wrapping-machine frame 10 defines a w rapping area w ithin its interior and has an infeed area 10a at which a palletized load (such as a load L on a pallet P) is conveyed (such as via a conveyor C) into the wrapping area for wrapping and an outfeed area 10b at which the palletized load is conveyed (such as via the conveyor C) from the wrapping area after wrapping. The illustrated wrapping-machine frame 10 is merely one example configuration, and any suitable configuration can be employed.

[0026] The circular guide 20 serves as the mount for the wrapping assembly 40 and is movably mounted to the wrapping-machine frame 10 (such as to one or more vertical members of the wrapping-machine frame 10) such that the circular guide 20 is vertically movable relative to the wrapping-machine frame 10 between an upper position and a lower position.

[0027] The guide actuator 30 is operably connected to the circular guide 20 to move the circular guide 20 relative to the wrapping-machine frame 10 between the upper and lower positions. In certain embodiments, the guide actuator 30 includes one or more motors operably connected to the circular guide 20 via one or more belt-and-pulley assemblies to move the circular guide 20 between the upper and lower positions. In other embodiments, the guide actuator 30 includes one or more pneumatic or hydraulic cylinders operably connected to the circular guide 20 to move the circular guide 20 between the upper and lower positions. These are merely examples, and the guide actuator 30 can include any suitable actuator configured to move the circular guide 20 between the upper and lower positions.

[0028] The wrapping assembly 40 is movably mounted to the circular guide 20 such that the wrapping assembly 40 is rotatable relative to the circular guide 20. The wrapping assembly 40 includes a ring-shaped support (not shown), a film carriage 100 (Figure 4), and a wrapping-assembly actuator 400 (Figure 3).

[0029] The ring-shaped support sen es as the mount for the film carriage 100 and is movably mounted to the circular guide 20 such that the support (and the film carriage 100 and other components connected to the support) is rotatable relative to the circular guide 20. In this example embodiment, the support is movably mounted to the circular guide 20 via multiple spaced-apart rollers (not shown) that are connected to the support and positioned on a track (not shown) on the circular guide 20.

[0030] The film carriage 100 is fixedly connected to the support to move with the support (i.e., rotate relative to the circular guide 20 and move vertically relative to the wrappingmachine frame 10). As shown in Figure 4. the film carriage 100 is configured to rotatably support a replaceable roll R of film F (such as plastic stretch film), pre-stretch the film F after pulling it from the roll R, and apply the pre-stretched film to the load as the film carriage 100 rotates around the load. The film carriage 100 includes a film-carriage frame 105; film-reel supports (not labeled); a pre-stretch assembly 110; a pre-stretch drive assembly (not shown); and a plurality of idler rollers 140A, MOB, 140C, MOD, MOE, and 140F.

[0031] The film-carriage frame 105 is formed from multiple tubular and/or solid members (not individually labeled) and configured to support the other components of the film carriage 100. The illustrated film-carriage frame 105 is merely one example configuration, and any suitable configuration can be employed.

[0032] The film-reel supports are mounted near one end of the film-carriage frame 105 so the roll R of film F can be rotatably mounted to the film-reel supports. The idler rollers 140 A, MOB, 140C, MOD, MOE, and 140F, and the pre-stretch assembly 110 are mounted to or otherwise supported by the film-carriage frame 105. The first idler roller 140A is rotatably mounted (such as via bearings) to the film-carriage frame 105 downstream of the film-reel supports so the first idler roller 140 A can freely rotate relative to the film-carriage frame 105 about a rotational axis. As used herein, “downstream’' means the direction of travel of the film F as the film is pulled off the roll R and “upstream” means the direction opposite the direction of travel of the film F as the film is pulled off the roll R. The second idler roller 140B is rotatably mounted (such as via bearings) to the film carriage frame 105 downstream of the first idler roller 140A so the second idler roller 140B can freely rotate relative to the film-carriage frame 105 about a rotational axis. A slight gap (not labeled) exists between the first and second idler rollers 140A and 140B to enable the film F to pass between them.

[0033] Figures 5 A and 5B schematically depict one example embodiment of a pre-stretch assembly 110 in accordance with the disclosure. Figure 5 A shows the pre-stretch assembly 110 from a side view between two pairs of idler rollers 140A. 140B and 140C, MOD of the stretch-wrapping machine 100 of Figure 4, while Figure 5B depicts the pre-stretch assembly 110 from an end view. The pre-stretch assembly 110 includes an upper holder 120, a lower holder 130 and a pre-stretcher element in the form of a pre-stretcher roller 115. As shown in Figure 5B, the upper holder 120 includes a first upper conveyance element 122 and a second upper conveyance element 124. Likewise, the lower holder 130 includes a first lower conveyance element 132 and a second lower conveyance element 134.

[0034] As the film F passes through the pre-stretch assembly 110, the upper holder 120 holds an upper edge Fu of the film F by gripping the film between the first upper conveyance element 122 and the second upper conveyance element 124. The lower holder 130 similarly grips a lower edge FL of the film F between the first lower conveyance element 132 and the second lower conveyance element 134. To pre-stretch the film F. the pre-stretcher roller 115 is positioned vertically between the upper holder 120 and the low er holder 130 but horizontally offset from the vertical line between the holders 120, 130. With the upper and low er edges of the film F gripped within the respective holders 120, 130, the offset position of the pre-stretcher roller 115 pushes the center of the film outward. Because the distance from the upper holder 120, around the pre-stretcher roller 1 15, to the lower holder 130 is greater than the distance directly betw een the upper and lower holders 120, 130, the film F is stretched by the pre-stretcher roller 115. As shown in Figure 5A, the pre-stretched film is spread out vertically as it passes over idle rollers 140C and MOD and has a greater width than the original film.

[0035] While the illustrated embodiments show the upper and lower holders 120, 130 as holding the lateral edges of the film F, in other embodiments, the holders are positioned to hold portions of the film that are set in from the edges of the film. In other words, in some embodiments, the distance between the upper holder and the lower holder is smaller than the width of the film. [0036] In some embodiments, the pre-stretch assembly is operable to pre-stretch the width of the film in a range of 5% to 50%. Accordingly, as diagrammatically shown in Figure 5C, a first distance D 1 that extends from the upper holder 120, around the pre-stretcher roller 115, and to the lower holder 130, may be in a range of 5% to 50% greater than a second distance D2 that extends directly from the upper holder 120 to the lower holder 130.

[0037] Each of the components of the pre-stretch assembly 110, as well as the idle rollers 140A-140D, are coupled to the film-carriage frame, for example using supports. For simplicity, the full extent of those supports, and their connection to the film-carriage frame, is omitted from Figures 5A and 5B to avoid obscuring components of the pre-stretch assembly 110. For example, in Figure 5B, the pre-stretcher roller 115, which is hidden inside a depression in the film F, is shown in dashed lines and the supports are omitted.

[0038] While the pre-stretch assembly is described herein with reference to a vertical orientation, as may be typical on stretch-wrapping machines, the pre-stretch assembly may be arranged in other orientations and the terms upper and lower are used to distinguish opposing sides of the film regardless of their orientation with respect to gravity. For example, the film may be drawn from a roll in a horizontal orientation and the upper and lower holders may be positioned to receive opposing edges of the film but located at the same height.

[0039] In certain embodiments, the pre-stretcher roller has a diameter in a range of 2 cm to 10 cm and a length in a range of 20 cm to 30 cm, though other dimensions are possible. In some embodiments, the edges of the pre-stretcher roller may be rounded. For example, in the illustrated embodiment of Figures 5 A and 5B, the pre-stretcher roller 115 has a cylindrical shape with rounded edges. The rounded edges reduce localized stresses on the film at the ends of the pre-stretcher roller 115, which reduces the chances of tearing the film. In some embodiments the pre-stretcher roller 115 has a rounder shape, such as a spherical or substantially spherical shape. Further, the pre-stretcher roller may also have other shapes.

[0040] In various embodiments, the pre-stretcher element is positioned substantially equidistant from the upper holder and the lower holder. For example, a distance between the pre-stretcher element and the upper holder may be within 20% of the distance between the pre-stretcher element and the lower holder. In other embodiments, the pre-stretcher element may be closer to one of the holders than the other.

[0041] While the illustrated embodiment shows a single pre-stretcher roller 115 between the upper holder 120 and the lower holder 130, in other embodiments the pre-stretch assembly of the disclosure includes multiple pre-stretcher elements. For example, several prestretcher elements may be arranged in an arc between the upper holder and the lower holder.

[0042] Further, while the illustrated embodiment shows the pre-stretcher element in the form of pre-stretcher roller 115, in other embodiments, the pre-stretcher element has another configuration. For example, in some embodiments, the pre-stretcher element includes a low friction sphere or curved bar. In other embodiments, the pre-stretcher element includes a belt or other moving surface that contacts the film. In each case, the pre-stretcher element is offset from line between the holders in order to stretch the film in the width direction.

[0043] Figure 6 schematically illustrates another example embodiment of a pre-stretch assembly 610. The pre-stretch assembly 610 is again shown between pairs of idler rollers 640 A, 640B, and 640C, 640D. The pre-stretch assembly 610 includes an upper holder 620 and a lower holder 630. The upper holder 620 receives the film F at an inlet end 626 and the film F leaves the upper holder 620 at an outlet end 628. Similarly, the lower holder 630 receives film F at an inlet end 636 and the film exits the lower holder 30 holders at an outlet end 638. Rather than including a pre-stretcher element, the upper and lower holders 620, 630 of this embodiment are angled to diverge from one another. Specifically, the distance between the inlet end 626 of the upper holder 620 and the inlet end 636 of the low er holder 630 is smaller than the distance between the respective outlet ends 628. 638. As the film passes through the pre-stretch assembly 610, the upper and lower holders 620, 630 pull the edges of the film away from one another, thereby pre-stretching the film F.

[0044] In the illustrated embodiment shown in Figure 6, the holders 620 and 630 diverge equally from a centerline between the holders. Accordingly, the upper holder 620 has a first angle with respect to the centerline E and the lower holder 630 has an opposite angle that is equal in size to that of the upper holder 620. In other embodiments, the holders may be oriented at different angles with respect to the centerline. For example, in some embodiments, the upper holder extends parallel with the centerline and direction of travel of the film, while the lower holder is angled aw ay from the upper holder.

[0045] Figure 7 schematically illustrates an example holder 720 similar to those shown in Figures 5A, 5B, and 6. The holder 720 is shown with the first conveyance element 722 and the second conveyance element 724 positioned on opposing sides of the film F. The first conveyance element 722 includes a first endless belt 723 that extends around its perimeter. Likewise, the second conveyance element 724 includes a second endless belt 725 that extends around its perimeter. The two conveyance elements 722, 724 are positioned sufficiently close to one another that the film F may move through the two conveyance elements 722, 724 as the belts travel around the perimeter, but be firmly held between the belts to avoid the film from being pulled out of holder 720 during pre-stretching.

[0046] In some embodiments, one or both of the conveyance elements are driven, such as by one or more motors. For example, each of the conveyance elements of a holder may be driven by independently controlled drives (e.g., motors), one of the conveyance elements may be driven while the other is idle, or the opposing conveyance elements may both be coupled to one drive by gearing or linkages. Similarly, separate holders may be driven by independent drives, or they may be driven by a single drive that is coupled to the holders through linkages and/or gearing.

[0047] Figures 8A and 8B illustrate another embodiment of a holder 820. In holder 820, the film F is again positioned between a first conveyance element 822 and a second conveyance element 824. Rather than belts, the conveyance elements of holder 820 include an array of wheels 825, at least some of which may be driven. To avoid pinching the film between adjacent rows of wheels, the wheels 825 in the illustrated embodiment are staggered. While the illustrated conveyance elements include five rows each having three wheels, other arrangements of wheels are possible.

[0048] In various embodiments the holders may have a range of different dimensions. In some embodiments, each of the conveyance elements has as a width of at least 10 mm and a length of at least 70 mm.

[0049] In some embodiments, the upper and lower holders have the same configuration, e.g., components, length, and width. In other embodiments, they may be configured differently. Likewise, in some embodiments both conveyance elements of a holder are the same, as in the illustrated embodiments. In other embodiments the conveyance elements of a holder may be different. For example, in some embodiments, a holder includes one conveyance element with a belt and an opposing conveyance element with an array of wheels.

[0050] The pre-stretch assembly of the present disclosure is beneficially configured to prestretch the film in a lateral direction. The pre-stretch assembly may additionally include rollers that operate at different speeds to pre-stretch the film along its length. Further, the described holders may be driven at a surface speed greater than an upstream roller, such that the holders are operable to stretch the film along its length. The lateral pre-stretching of the disclosure avoids necking and/or can compensate for any necking that may occur if the lateral pre-stretching is combined with additional stretching along the length of the film.

[0051] The cutting-and-fixing device (not shown) is supported by the wrapping-machine frame 10 and configured to, after the load L has been wrapped, cut the film F at a position between the load L and the wrapping assembly 40 to form a trailing end of the film F and to connect the trailing end of the film F to the wrapped load L to complete the wrapping process. Cutting the film F also creates a leading end of the film F. The cutting-and-fixing device is also configured to hold the leading end after cutting the film F and to connect the leading end of the film F to the next load as it is being wrapped. The cutting-and-fixing device can be any suitable conventional cutting-and-fixing device known in the art.

[0052] Referring to Figure 3, the wrapping-assembly actuator 400 is operably connected to the wrapping assembly 40 to rotate the wrapping assembly 40 relative to the circular guide 20 and the load L. In certain embodiments, the wrapping-assembly actuator 400 includes one or more motors operably connected to the wrapping assembly 40 via one or more belt-and- pulley assemblies to rotate the wrapping assembly 40 relative to the circular guide 20 and the load L. This is merely an example, and the wrapping-assembly actuator 400 can include any suitable actuator configured to rotate the wrapping assembly 40 relative to the circular guide 20 and the load L.

[0053] The operator interface 500 is configured to receive inputs from an operator and, in certain embodiments, to output information to the operator. The operator interface includes one or more input devices configured to receive inputs from the operator. In various embodiments, the one or more input devices include one or more buttons (such as hard or soft keys), one or more switches, and/or a touch panel. In various embodiments, the operator interface 500 includes a display device configured to display information to the operator, such as information about the palletized load, the status of the wrapping operation, or the parameters of the wrapping machine 1 (e.g., the rotational speeds of the pre-stretch rollers). The operator interface can include other output devices instead of or in addition to the display device, such as one or more speakers and/or one or more lights. In certain embodiments, the operator interface 500 is formed as part of the wrapping machine 1 and is, for instance, mounted to the wrapping-machine frame 10. In other embodiments, the operator interface is remote from the wrapping machine 1. [0054] The controller 600 includes a processing device communicatively connected to a memory device. The processing device can include any suitable processing device such as. but not limited to, a general-purpose processor, a special-purpose processor, a digital-signal processor, one or more microprocessors, one or more microprocessors in association with a digital-signal processor core, one or more application-specific integrated circuits, one or more field-programmable gate array circuits, one or more integrated circuits, and/or a state machine. The memory device can include any suitable memory device such as. but not limited to, read-only memory, random-access memory, one or more digital registers, cache memory, one or more semiconductor memory' devices, magnetic media such as integrated hard disks and/or removable memory', magneto-optical media, and/or optical media. The memory device stores instructions executable by the processing device to control operation of the wrapping machine 1 (such as to carry out a wrapping operation, as described below).

[0055] The controller 600 is communicatively and operably connected to the guide actuator 30, the cutting-and-fixing device, pre-stretch actuators 150, and the wrapping-assembly actuator 400 to control operation of these components in conjunction with the wrapping operation, as described below. The controller 600 is communicatively connected to the operator interface 500 to: (1) receive signals from the operator interface 500 that represent inputs received by the operator interface 500; and (2) send signals to the operator interface 500 to cause the operator interface 500 to output (such as to display) information.

[0056] A wrapping operation in which the wrapping machine 1 is used to wrap the load L with the film F to secure the load L to the pallet P is now partially described. Initially, the circular guide 20 is at its upper position, and the cutting-and-fixing device holds the leading end of the film F. The controller 600 controls the conveyor C to move the load L on the pallet P through the infeed area 10a and into the wrapping area of the wrapping machine 1. After the load L on the pallet P reaches the wrapping area, the controller 600 controls the guide actuator 30 to lower the circular guide 20 such that the wrapping assembly 40 is at least partially vertically aligned with part of the load L. The controller 600 controls the cutting- and-fixing device to hold the leading end of the film F against or near the load L while controlling the wrapping-assembly actuator 400 to rotate the wrapping assembly 40 relative to the circular guide 20 and the load L. The rotation of the wrapping assembly 40 relative to the load L combined with the cutting-and-fixing device holding the leading end of the film F against or near the load L causes the film F to be drawn off of the roll R (optionally with the help of one or more motors to feed the film through the wrapping assembly 40), directed through the rollers of the film carriage 100, and wrapped around the load L.

[0057] Once the film F has been wrapped around the leading end, the controller 600 controls the cutting-and-fixing device to release the leading end and move away from the load L. The controller 600 continues to control the wrapping-assembly actuator 400 to rotate the wrapping assembly 40 while controlling the guide actuator 30 to vertically move the circular guide 20 such that the load L is wrapped with the film F in a spiral pattern. During wrapping, the controller 600 controls the pre-stretch actuators 150 to drive the upper and low er holders to pre-stretch the film F as it is drawn through the pre-stretch assembly 110. After wrapping is complete, the controller 600 controls the cutting-and-fixing device to cut the film F from the roll R and secure the trailing end of the film F to the load L, thereby completing the wrapping operation. The controller 600 controls the conveyor C to move the wrapped load L and pallet P from the wrapping area and through the outfeed area 10b.

[0058] Thus, in various embodiments, the present disclosure provides a pre-stretch assembly for a wrapping machine. The pre-stretch assembly comprises an upper holder, a low er holder, and a pre-stretcher element offset from a line extending betw een the upper holder and the lower holder. The upper holder includes first and second upper conveyance elements sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower holder includes first and second lower conveyance elements sized and shaped to hold the film when positioned betw een the first and second lower conveyance elements. The upper holder and the lower holder are positioned to hold respective portions of the film. The pre-stretcher element is positioned such that the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

[0059] In various such embodiments of the pre-stretch assembly, the upper holder is positioned to hold an upper edge of the film and the low er holder is positioned to hold a low er edge of the film.

[0060] In various such embodiments of the pre-stretch assembly, the first upper conveyance element comprises an endless belt.

[0061] In various such embodiments of the pre-stretch assembly, the upper holder and the low er holder have the same configuration.

[0062] In various such embodiments of the pre-stretch assembly, the upper holder is spaced from the lower holder by a first distance, wherein a second distance extends from the upper holder around the pre-stretcher element to the lower holder, and wherein the second distance is in a range of 5% to 50% greater than the first distance.

[0063] In various such embodiments of the pre-stretch assembly, the pre-stretch assembly comprises a first drive operable to drive the first upper conveyance element.

[0064] In various such embodiments of the pre-stretch assembly, the pre-stretcher element is a pre-stretcher roller.

[0065] In various other embodiments, the disclosure provides a method of pre-stretching film for a wrapping machine. The method comprises removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge. The method also includes conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages a lower portion of the film. The upper holder and lower holder are spaced apart. The method also includes engaging a portion of the film that is between the upper holder and the lower holder with a prestretcher element. The pre-stretcher element is offset, in a second direction, from a line extending between the upper holder and the lower holder so as to pre-stretch the film to a second width that is greater than the first width.

[0066] In various such embodiments of the method, the second width is in a range of 5% to 50% of the first width.

[0067] In various such embodiments of the method, the upper holder includes a first upper conveyance element and a second upper conveyance element that engage respective sides of the film.

[0068] In various such embodiments of the method, conveying the film along the first direction includes driving the first upper conveyance element.

[0069] In various other embodiments, the disclosure provides a wrapping machine. The wrapping machine comprises a wrapping-machine frame, a guide mounted to the wrapping machine frame, a guide actuator operably connected to the guide to move the guide vertically relative to the wrapping-machine frame, a wrapping assembly mounted to the guide, and a wrapping-assembly actuator operably connected to the wrapping assembly to move the wrapping assembly relative to the guide. The wrapping assembly includes a film carriage comprising a film-carriage frame, an upper holder supported by the film-carriage frame, a lower holder supported by the film-carriage frame, and a pre-stretcher element offset from a line extending between the upper holder and the lower holder. The upper holder includes first and second upper conveyance elements sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower holder includes first and second lower conveyance elements sized and shaped to hold the film when positioned between the first and second lower conveyance elements. The upper holder and the lower holder are positioned to hold respective portions of the film. The pre-stretcher element is positioned such that the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

[0070] In various other embodiments, the disclosure provides a pre-stretch assembly for a wrapping machine. The pre-stretch assembly comprises an upper holder, and a lower . The upper holder includes adjacent first and second upper conveyance elements that form an inlet end and an outlet end. The first and second upper conveyance elements are sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower holder includes adjacent first and second lower conveyance elements that form an inlet end and an outlet end. The first and second lower conveyance elements are sized and shaped to hold the film when positioned between the first and second lower conveyance elements.

The upper holder and the lower holder are positioned to hold respective edges of the film and are angled with respect to one another to diverge such that the outlet ends of the upper and low er holders are further apart than the inlet ends of the upper and lower holders and the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

[0071] In various such embodiments of the pre-stretch assembly, the upper holder is positioned to hold an upper edge of the film and the low er holder is positioned to hold a low er edge of the film.

[0072] In various such embodiments of the pre-stretch assembly, the first upper conveyance element comprises an endless belt.

[0073] In various such embodiments of the pre-stretch assembly, the pre-stretch assembly also includes a first drive operable to drive the first upper conveyance element.

[0074] In various such embodiments of the pre-stretch assembly, the upper and lower holders are each angled aw ay from a centerline between the upper and lower holders.

[0075] In various other embodiments, the disclosure provides a method of pre-stretching film for a wrapping machine. The method comprises removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge, and conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages a lower portion of the film. Respective inlet ends of the upper holder and lower holder are spaced apart by a first distance. Respective outlet ends of the upper holder and lower holder are spaced apart by a second distance that is greater than the first distance such that conveying the film along the first direction pulls the upper portion and lower portionof the film away from one another so as to pre-stretch the film to a second width that is greater than the first w idth.

[0076] In various such embodiments of the method, the second width is in a range of 5% to 50% of the first width.

[0077] In various such embodiments of the method, the upper holder includes a first upper conveyance element and a second upper conveyance element that engage respective sides of the film.

[0078] In various such embodiments of the method, conveying the film along the first direction includes driving the first upper conveyance element.

[0079] In various other embodiments, the disclosure provides a w rapping machine. The wrapping machine comprises a wrapping-machine frame, a guide mounted to the wrapping machine frame, a guide actuator operably connected to the guide to move the guide vertically relative to the wrapping-machine frame, a wrapping assembly mounted to the guide, and a wrapping-assembly actuator operably connected to the wrapping assembly to move the wrapping assembly relative to the guide. The wrapping assembly includes a film carriage comprising a film-carriage frame, an upper edge holder supported by the film-carriage frame, and a low er edge holder supported by the film-carriage frame. The upper edge holder includes adjacent first and second upper conveyance elements that form an inlet end and an outlet end. The first and second upper conveyance elements are sized and shaped to hold a film when positioned between the first and second upper conveyance elements. The lower edge holder includes adjacent first and second lower conveyance elements that form an inlet end and an outlet end. The first and second lower conveyance elements are sized and shaped to hold the film when positioned between the first and second lower conveyance elements. The upper edge holder and the lower edge holder are positioned to hold respective edges of the film and are angled with respect to one another to diverge such that the outlet ends of the upper and lower edge holders are further apart than the inlet ends of the upper and lower edge holders. [0080] Various changes and modifications to the above-described embodiments described herein will be apparent to those skilled in the art. These changes and modifications can be made without departing from the spirit and scope of this present subject matter and without diminishing its intended advantages. Not all of the depicted components described in this disclosure may be required, and some implementations may include additional, different, or fewer components from those expressly described in this disclosure. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of attachment and connections of the components may be made without departing from the spirit or scope of the claims as set forth herein. Also, unless otherwise indicated, any directions referred to herein reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the invention as taught herein and understood by one of ordinary skill in the art.

Claims

1. A pre-stretch assembly for a wrapping machine, the pre-stretch assembly comprising: an upper holder including first and second upper conveyance elements sized and shaped to hold a film when positioned between the first and second upper conveyance elements; a lower holder including first and second lower conveyance elements sized and shaped to hold the film when positioned between the first and second lower conveyance elements, wherein the upper holder and the lower holder are positioned to hold respective portions of the film; and a pre-stretcher element offset from a line extending between the upper holder and the lower holder and positioned such that the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

2. The pre-stretch assembly of claim 1, wherein the upper holder is positioned to hold an upper edge of the film and the lower holder is positioned to hold a lower edge of the film.

3. The pre-stretch assembly of claim 1, wherein the first upper conveyance element comprises an endless belt.

4. The pre-stretch assembly of claim 1, wherein the upper holder and the lower holder have the same configuration.

5. The pre-stretch assembly of claim 1, wherein the upper holder is spaced from the lower holder by a first distance, wherein a second distance extends from the upper holder around the pre-stretcher element to the lower holder, and wherein the second distance is in a range of 5% to 50% greater than the first distance.

6. The pre-stretch assembly of claim 1, further comprising a first drive operable to drive the first upper conveyance element.

7. The pre-stretch assembly of claim 1, wherein the pre-stretcher element is a pre-stretcher roller.

8. A method of pre-stretching film for a wrapping machine, the method comprising: removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge; conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages a lower portion of the film, wherein the upper holder and lower holder are spaced apart; and engaging a portion of the film that is between the upper holder and the lower holder with a pre-stretcher element, wherein the pre-stretcher element is offset, in a second direction, from a line extending between the upper holder and the lower holder so as to pre-stretch the film to a second width that is greater than the first width.

9. The method of claim 8, wherein the second width is in a range of 5% to 50% of the first width.

10. The method of claim 8, wherein the upper holder includes a first upper conveyance element and a second upper conveyance element that engage respective sides of the film.

11. The method of claim 10, wherein conveying the film along the first direction includes driving the first upper conveyance element.

12. A pre-stretch assembly for a wrapping machine, the pre-stretch assembly comprising: an upper holder including adjacent first and second upper conveyance elements that form an inlet end and an outlet end, wherein the first and second upper conveyance elements are sized and shaped to hold a film when positioned between the first and second upper conveyance elements; and a lower holder including adjacent first and second lower conveyance elements that form an inlet end and an outlet end, wherein the first and second lower conveyance elements are sized and shaped to hold the film when positioned between the first and second lower conveyance elements, wherein the upper holder and the lower holder are positioned to hold respective portions of the film and are angled with respect to one another to diverge such that the outlet ends of the upper and lower holders are further apart than the inlet ends of the upper and lower holders and the film is pre-stretched in the width direction when moved through the pre-stretch assembly.

13. The pre-stretch assembly of claim 12, wherein the upper holder is positioned to hold an upper edge of the film and the lower holder is positioned to hold a lower edge of the film.

14. The pre-stretch assembly of claim 12, wherein the first upper conveyance element comprises an endless belt.

15. The pre-stretch assembly of claim 12, further comprising a first drive operable to drive the first upper conveyance element.

16. The pre-stretch assembly of claim 12, wherein the upper and lower holders are each angled away from a centerline between the upper and lower holders.

17. A method of pre-stretching film for a wrapping machine, the method comprising: removing film from a roll, the film having a first width extending across the film from an upper edge to a lower edge; and conveying the film along a first direction using an upper holder that engages an upper portion of the film and a lower holder that engages the lower portion of the film, wherein respective inlet ends of the upper holder and lower holder are spaced apart by a first distance, and respective outlet ends of the upper holder and lower holder are spaced apart by a second distance that is greater than the first distance such that conveying the film along the first direction pulls the upper portion and lower portion of the film away from one another so as to pre-stretch the film to a second width that is greater than the first width.

18. The method of claim 17, wherein the second width is in a range of 5% to 50% of the first width.

19. The method of claim 17, wherein the upper holder includes a first upper conveyance element and a second upper conveyance element that engage respective sides of the film.

20. The method of claim 19, wherein conveying the film along the first direction includes driving the first upper conveyance element.