CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser. No. 60/535,466, filed on Jan. 8, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the art of wrapping a product. More particularly, the invention relates to a method for automatically wrapping with stretchable polymer film the sides and the top of a product that is disposed on a shipping pallet.

2. Background Art

It is common for products to be stacked on a shipping pallet for transport. In particular, certain products are sold or shipped in bags or boxes, and placing these bags or boxes on a shipping pallet allows a large quantity of them to be shipped as a single unit. Because the bags or boxes are typically smaller in area than the pallet, they are stacked in certain patterns that may become unstable when the pallet is moved. To stabilize the bags or boxes on the pallet for shipping, a stretchable polymer film that is known in the art is wrapped around the bags or boxes.

For example, bags of mulch that are ready for retail sale are more easily transported on a pallet. Typically, a first layer of bags is placed on the pallet, in which bags are arranged in a square pattern. A second layer of bags is placed directly on top of the first layer, as is a third layer, a fourth layer, and so on, until a desired number of layers is reached. When this desired number of layers is reached, the height of the bags on the pallet may be from about 5 to 7 feet tall. Such a large stack of bags on the pallet may become unstable during handling and transport of the pallet.

To make the stack of bags of product stable on the pallet, a stretchable polymer film, known in the art as stretch wrap or stretch-wrap film, is wrapped around the stack. The film is typically sold on a roll, and the roll is typically about 1 to 2 feet wide. Placement of the film on a roll allows for relatively convenient application, as the film is typically too thin to support itself, but it is relatively strong when stretched over an object. The film is also able to lightly stick to itself, so that it can be wrapped around the product stack with one layer slightly overlapping a prior layer to form a thin, tight shell about the stack. The strength of the film and its ability to lightly stick to itself typically are increased when it is placed in tension and stretched around the stack. The resulting film shell stabilizes the stack, creating a more stable shipping pallet, and also acts as a protective layer, repelling rain, snow and dirt from the product.

Of course, single or small quantities of some products are also placed on a shipping pallet, typically because it is easier to transport the products on a pallet. In this case, stretch-wrap film is wrapped around a product to help keep it from shifting and also to protect the product from rain, snow and dirt. As a result, reference herein to a product stack includes multiple products arranged on a pallet and a single product.

Application of the stretch-wrap film to a product stack on a pallet by hand is problematic, as the process can be difficult and time consuming due the requirement that tension be kept on the film as it is wrapped around the stack. As a result, automatic stretch-wrap machines have been developed.

One type of machine includes a turntable, on which is placed a pallet having a stack. A roll of stretch-wrap film is held by a head that is located beside the turntable. The head is generally aligned with the base of the stack, which is typically referred to as the home position. The film is unrolled slightly and brought into contact with the base of the stack. The turntable is then rotated, in turn causing the pallet and stack to rotate, unwinding and stretching the film from the head under tension. The head moves vertically upward as the turntable rotates, causing the film to continue to wrap around the sides of the stack while remaining in tension, with one circumferential wrap of film slightly overlapping the prior wrap. When the head reaches a level that is generally aligned with the top of the stack, the head reverses direction and wraps the stack downwardly as it returns to the home position at the base of the pallet. The film is then cut or torn and the wrapping process is complete.

Another type of automatic stretch-wrapping machine keeps the pallet and stack static, while a head having a roll of film is mounted on an arm that rotates around the stack. The head is generally aligned with the base of the stack and the film is unrolled slightly and brought into contact with the stack. The arm then rotates, causing the head to rotate about the stack. The head moves upwardly as it rotates around the stack and the film unrolls from the head in tension, causing the film to wrap around the stack, with each wrap slightly overlapping the prior wrap. This continues until the head reaches a level generally aligned with the top of the stack, at which time the vertical direction is reversed and the head wraps the stack downwardly as it returns to the base the stack, where the film is cut or torn to complete the wrapping process.

Both of these prior art machines only wrap the sides of the product stack and not the top of the stack. Because many pallets with product stacks are stored outdoors, the film is unable to protect the top of the stack from rain, snow and dirt, allowing these elements to contact the top of the stack and also run down the stack inside the film, possibly damaging the product. Moreover, sunlight contacting the top of the stack can possibly undesirably discolor or otherwise damage portions of some products.

To attempt to overcome this disadvantage in the prior art, a separate, pre-manufactured cap or sheet of polymeric film has been placed on the top of the stack before the stack is stretch wrapped. The sides of stack are then stretch wrapped as described above, with the stretch-wrap film securing the cap to the top of the stack. However, the use of a cap involves significant additional costs for the cap itself and for additional labor or equipment to place the cap on the stack. Also, because the cap is typically placed on the top of the stack by hand, it can be misaligned, creating a gap between the cap and the shrink wrap that still allows moisture to contact the product.

Furthermore, the cap usually does not tightly bond to the rest of the stretch-wrap film. The lack of a bond is due to the inability of the cap to stick to film, since it may be made from a different material as the film, and the fact that the cap is not under the same tension as the stretch-wrap film. This results in a discontinuous fit between the cap and the stretch-wrap film, which allows moisture to run in between the cap and the film, continuing to run the risk of possible damage to the product in the stack.

As a result, a need exists for a process that overcomes the disadvantages of the prior art by stretch-wrapping the top of a stack of product, resulting in improved protection for the product, reduced cost and increased production efficiency.

BRIEF SUMMARY OF THE INVENTION

An objective of the present invention is to provide a method for wrapping the top of a product with the same machine that wraps the sides of the product.

Another objective of the present invention is to provide a method for providing increased protection for the top of a product.

Yet another objective of the present invention is to provide a method for automatically wrapping the top of a product at a reduced cost.

These objectives and others are also obtained by the method for wrapping a product of the present invention, in which the product includes a plurality of sides and a top, the general nature of which may be stated as including the steps of providing a wrapping material adjacent the product for wrapping the product. The wrapping material is wrapped about the top of the product, and when the top is wrapped, a first upper corner of the product is engaged by the wrapping material. The wrapping material is laid across the top of the product from the first upper corner to a second upper corner of the product. The second upper corner is engaged by the wrapping material, whereby the wrapping material is secured across the top of the product.

The general nature of the method for wrapping a product of the present invention, in which the product includes a plurality of sides and a top, may also be stated as including the steps of providing a wrapping material adjacent the product for wrapping the product. The wrapping material is wrapped about the sides of the product and a first upper corner of the product is engaged by the wrapping material. The wrapping material is laid across the top of the product from the first upper corner to a second upper corner of the product and the second upper corner is engaged by the wrapping material. The wrapping material is moved from the second upper corner to a third upper corner of the top of the product and the third upper corner is engaged by the wrapping material. The wrapping material is laid across the top of the product from the third upper corner to a fourth upper corner of the product. The fourth upper corner is engaged by the wrapping material, whereby the wrapping material is secured across the top of the product.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The preferred embodiment of the invention, illustrative of the best mode in which applicant has contemplated applying the principles of the invention, is set forth in the following description and is shown in the drawings, and is particularly and distinctly pointed out and set forth in the appended claims.

FIG. 1 is a fragmentary side perspective view of a product and a bottom portion of an exemplary stretch-wrap machine that is capable of performing the method of the present invention;

FIG. 2 is a fragmentary side perspective view of a top portion of the product and the machine shown in FIG. 1;

FIGS. 3A-3E include schematic plan views of a product at various steps of the method of the present invention;

FIG. 4 is a fragmentary side perspective view of a portion of the product and a portion of the exemplary machine capable of performing the method of the present invention, shown in a step of the method of present invention, with hidden areas represented by dashed lines;

FIG. 5 is a fragmentary side perspective view of a portion of the product and a portion of the exemplary machine capable shown in FIG. 4, in another step of the method of the present invention, with hidden areas represented by dashed lines;

FIG. 6 is a fragmentary side perspective view of a portion of the product and a portion of the exemplary machine capable shown in FIG. 4, in yet another step of the method of the present invention, with hidden areas represented by dashed lines; and

FIG. 7 is a fragmentary side perspective view of a portion of the product and a portion of the exemplary machine capable shown in FIG. 4, in still another step of the method of the present invention, with hidden areas represented by dashed lines.

Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the drawings, wherein the illustrations are provided to show a preferred embodiment of the invention and not to limit the same, the method of the present invention is described for the purpose of convenience with reference to an exemplary stretch-wrap machine that is capable of performing the method, indicated generally at 10 and shown in FIGS. 1-2. It is to be understood that other machines may be adapted to perform the method without affecting the overall concept of the invention. In addition, reference herein is made to a stack of bags for the purpose of illustration only, as the invention applies to any product that is wrapped with stretch film.

With particular reference to FIG. 1, a product 12, also referred to as a product stack or a pallet stack, is shown inside stretch-wrap machine 10. Stretch-wrap machine 10 includes a frame 14 with vertical members 16, each of which has a bottom end 18 and a top end 22 (FIG. 2). Vertical members 16 are arranged in a square, with bottom ends 18 attached to a floor or foundation 20. Stack 12 is placed in the approximate center of the square formed by vertical members 16. Optionally, stack 12 is transferred into place in machine 10 by a conveyor 26.

With additional reference to FIG. 2, horizontal frame members 24 are attached to and extend between corresponding top ends 22 of vertical frame members 16 to form integral structural frame 14. A medial frame member 28 extends across horizontal frame members 24 directly above stack 12. A mounting plate 30 is rotatably connected to medial frame member 28 directly above stack 12, and a radial arm 32 having a first end 34, a second end 36 and a midpoint 38 is rigidly mounted to the mounting plate. Radial arm 34 is connected to mounting plate 30 at midpoint 38. A vertical rail 40 extends downwardly from first end 34 of radial arm 32, while a counterweight 41 extends downwardly from second end 36.

Vertical rail 40 terminates at a bottom end 42 that is at about the same level as a bottom 68 of pallet stack 12. A drive unit (not shown) causes radial arm 32 to rotate, which in turn causes vertical rail 40 to rotate within the square formed by vertical frame members 16 and around stack 12. Slidably connected to vertical rail 40 via a bearing clamp 48 is a carriage or head 44. Head 44 is able to move from bottom 42 of vertical rail 40 up to radial arm 32 at the top of the rail. It is to be noted that the top of vertical rail 40, and thus the upper limit of vertical movement of head 44, is well above a top 70 of pallet stack 12. A control conduit 46 contains power and control cables to operate and control head 44.

Head 44 includes a mounting roller 50 that holds a roll 52 of stretch-wrap film 54 and a series of tensioning rollers 56, as known in the art. Tensioning rollers 56 spread film 54 out and act to control the tension of the film during the wrapping process to ensure that the film stretches properly and does not distort.

Head 44 of stretch-wrap machine 10 moves around pallet stack 12 in a circular pattern as radial arm 32 rotates. As radial arm 32 rotates, head 44 is also able to move vertically up and down along rail 40, allowing film 54 to be wrapped around pallet stack 12 according to the method of the present invention, as will be described in detail below. It is to be noted that radial arm 32 preferably is driven in a single direction during the wrapping process, such as a counterclockwise direction, to maintain tension on film 54 for wrapping.

It is important to note that the foregoing description of stretch-wrap machine 10 is by way of example only, as other machines known in the art may be adapted to perform the method without affecting the overall concept of the invention. For example, a machine with fewer than four vertical members 16, or a machine that employs a fixed head 44 and instead moves product stack 12, may be used. Having thus described exemplary stretch-wrap machine 10 capable of performing the method of the invention, the method of the present invention for stretch wrapping product or pallet stack 12 will now be described. For the purpose of clarity of description, reference herein is made to a bottom 64 and a top 66 of head 44, as shown in FIGS. 1 and 4-7. In addition, pallet stack 12 includes bottom 68 and top 70, as shown in FIGS. 1 and 5.

Turning now to FIGS. 3A-E, pallet stack 12 also includes a first corner C1, a second corner C2 and a first side S1 that extends between the first corner and the second corner, as well as a third corner C3 and a second side S2 that extends between the second corner and the third corner. A third side S3 extends between third corner C3 and a fourth corner C4, and a fourth side S4 extends between the fourth corner and first corner C1. In the method of the present invention, head 44 preferably causes stretch film 54 to make four passes, indicated as lines P1-P4, across top 70 of pallet stack 12.

To begin the stretch-wrap process, bottom 64 of head 44 is on the same general horizontal level as bottom 68 of pallet stack 12 (FIG. 1). Stretch-wrap film 54 from roll 52 is placed into contact with pallet stack 12 near bottom 68. Radial arm 32 is driven in either a clockwise or counterclockwise direction, causing vertical rail 40 and head 44 to rotate about pallet stack 12. For the purpose of clarity, reference herein will be made to radial arm 32 rotating in a counterclockwise direction. Referring to FIG. 4, As head 44 travels about pallet stack 12, film 54 unrolls from roll 52 and tensioning rollers 56 are adjusted to maintain the proper amount of tension on the film. As head 44 rotates, it also moves vertically upward along vertical rail 40 at a speed that allows stretch-wrap film 54 to wrap around sides S1-S4 of pallet stack 12 in a continuous overlay manner as known to those skilled in the art.

Head 44 continues at a set speed about pallet stack 12 until the head is at a vertical level at which top 70 of the pallet stack is between bottom 64 and top 66 of the head. At that position, once a layer of film has been wrapped about the top edge of sides S1-S4, the top-wrapping procedure commences.

With reference to FIG. 3, and generally to FIGS. 4-7, head 44 moves around first corner C1 of pallet stack 12, and as it does so, the head moves upwardly along vertical rail 40 until head bottom 64 is at a level generally above top 70 of the pallet stack. Thus, at a point along first side S1 just past first corner C1, head 44 is at a level that is above top 70 of pallet stack 12. The movement of head 44 along top 70 and then to a level above the top after it passes first corner C1 causes a bottom edge 72 of film 54 to catch the upper portion of the first corner of pallet stack 12, as shown in particular in FIG. 6.

To make first pass P1, shown in FIGS. 3A and 3E, head 44 moves counterclockwise around to opposing third corner C3, while bottom 64 of the head remains at a level above pallet stack 12 to ensure that film 54 does not prematurely catch on sides S1 and S2 of the stack. The movement of head 44 causes film 54 to extend over top 70 of stack 12 from first corner C1 to third corner C3. To secure film 54, once head 44 reaches a point along second side S2 near third corner C3, the head moves downwardly along vertical rail 34 until bottom 64 of the head is at a level that is below top 70 of pallet stack 12. Head 44 continues to move counterclockwise around third corner C3 and along third side S3, thus causing bottom edge 72 of film 54 to catch the top of the third corner, keeping the film tight across stack top 70.

Head 44 moves along third side S3 of pallet stack, remaining at a level where bottom 64 of the head is below top 70 of pallet stack 12. To make second pass P2, as shown in FIGS. 3B and 3E, head 44 moves around fourth corner C4, and at a point along fourth side S4 just past the fourth corner, the head moves upwardly until bottom 64 of the head is at a level that is above top 70 of pallet stack 12. This movement of head 44 causes bottom edge 72 of film 54 to catch fourth corner C4. Head 44 continues to move counterclockwise at a level above top 70 of stack 12 over to second corner C2. At a point along first side S1 just before second corner C2, head 44 moves downwardly until bottom 64 of the head is at a level that is below top 70 of stack 12, causing film 54 to extend across the top of the stack from fourth corner C4 to the second corner. Head 44 continues around second corner C2 to second side S2 and film 54 catches on the second corner, securing the tension of the film across top 70 of stack 12.

At this point, film 54 is in an X-shaped pattern across top 70 of pallet stack 12, but the film may not be wide enough to cover the entire top surface. In addition, a second alternating layer of film 54 on top 70 of pallet stack 12 typically is desired. Thus, head 44 proceeds to third pass P3, as shown in FIGS. 3C and 3E. Head 44 continues along second side S2 and around third corner C3, remaining at a level where bottom 64 of the head is below top 70 of stack 12. When head 44 reaches a point along third side S3 just past third corner C3, the head moves upwardly until bottom 64 of the head is at a level above top 70 of stack 12, causing bottom edge 72 of film 54 to catch on third corner C3. Head 44 continues to move counterclockwise at a level above top 70 of stack 12 over to first corner C1. At a point along fourth side S4 just before first corner C1, head 44 moves downwardly until bottom 64 of the head is at a level below top 70 of stack 12, causing film 54 to extend across the stack from third corner C3 to the first corner. Head 44 continues around first corner C1 to first side S1 and film 54 catches on the first corner, securing the tension of the film across top 70 of stack 12.

Head 44 proceeds to fourth pass P4, as shown in FIGS. 3D and 3E. Head 44 continues along first side S1 and around second corner C2, remaining at a level where bottom 64 of the head is below the level of stack top 70, as shown in FIG. 5. When head 44 moves just past second corner C2 along second side S2, the head moves upwardly until bottom 64 of the head is at a level above top 70 of stack 12, causing bottom edge 72 of film 54 to catch on second corner C2, as shown in FIG. 7. Head 44 continues to move counterclockwise at a level above top 70 of stack 12 over to fourth corner C4. At a point along third side S3 just before fourth corner C4, head 44 moves downwardly until bottom 64 of the head is at a level below top 70 of stack 12, causing film 54 to extend across the stack from second corner C2 to the fourth corner. Head 44 continues around fourth corner C4 to fourth side S4 and film 54 catches on the fourth corner, securing the tension of the film across top 70 of stack 12.

Once head 44 reaches fourth side S2 of pallet stack 12 after the above top-wrapping, the head preferably slides downwardly along vertical rail 34 and continues to move counterclockwise, creating a second layer of film 54 around sides S1-S4 of the stack from top 70 to bottom 68. Once head 44 reaches a level at about pallet stack bottom 68, film 54 on stack 12 is separated from film roll 52 via cutting or tearing, completing the stretch-wrap process.

Top surface 70 of pallet stack 12 is thus covered with film 54 according to the method of the present invention. Because the process keeps tension on film 54 as top 70 of pallet stack 12 is wrapped, the film is tight and stable, creating a sealed protective layer. This tension is maintained during the wrapping process by the movement of head 44 downwardly to a level where bottom 64 is below top 70 of stack 12 and then upwardly above the stack, as bottom edge 72 of film 54 catches each respective corner C1-C4. Preferably, the speed of the rotational movement of radial arm 32 and the speed of the vertical movement of head 44 along rail 40 are variable, which allows the above-described passes P1-P4 to be efficiently accomplished.

The method of the present invention provides protection for top 70 of product stack 12, without the use of a separate cap. This leads to reduced material cost, as there is no need to purchase a separate cap, as well as reduced labor cost, since positioning of the cap on top 70 of pallet stack 12 is eliminated.

The ability to automatically stretch-wrap sides S1-S4 and top 70 of pallet stack 12 in one operation creates at least one consistent layer of film 54 about stack 12. This layer of film 54 is relatively sealed about top 70 of stack 12, protecting the product in the stack and thereby reducing the possibility of damage to the product caused in the prior art by elements such as rain, snow and dirt. Such reduction of damage in turn results in less product that must be scrapped, creating additional cost savings.

It is important to note that the aforementioned steps are not confined to a particular order or sequence. For example, top 70 of stack 12 may be wrapped before sides S1-S4 are wrapped, without affecting the concept of the invention. In addition, while reference has been made to a product stack 12 on a pallet, the invention applies to any product that is wrapped with stretch film, including a single product or multiple products, whether or not they are disposed on a pallet. Moreover, the description of stretch-wrap machine 10 has been by way of example only, as other machines known in the art may be adapted to perform the method without affecting the overall concept of the invention. For example, a machine that employs a fixed head 44 and instead moves product stack 12, may be adapted to accomplish the method of the present invention.

Accordingly, the method for wrapping product of the present invention is simplified, provides an effective, safe, inexpensive, and efficient system which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior art wrapping systems, and solves problems and obtains new results in the art.

In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.

Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described.

Having now described the features, discoveries and principles of the invention, the manner in which the improved method for wrapping product is constructed, arranged and used, the characteristics of the construction and arrangement, and the advantageous, new and useful results obtained; the new and useful steps, elements, arrangements, parts and combinations, are set forth in the appended claims.