Abstract:
A method for wrapping a product, in which the product includes a plurality of sides and a top. The method includes the steps of providing a wrapping material adjacent the product for wrapping the product. When wrapping the top of the product, 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 wrapping material may also be laid across the top of the product from a third upper corner to a fourth upper corner and engage the third and fourth corners. The sides of the product may be wrapped before or after the top of the product is wrapped.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/535,466, filed on Jan. 8, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     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.  
         [0004]     2. Background Art  
         [0005]     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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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.  
         [0009]     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.  
         [0010]     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.  
         [0011]     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.  
         [0012]     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.  
         [0013]     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.  
         [0014]     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.  
         [0015]     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  
       [0016]     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.  
         [0017]     Another objective of the present invention is to provide a method for providing increased protection for the top of a product.  
         [0018]     Yet another objective of the present invention is to provide a method for automatically wrapping the top of a product at a reduced cost.  
         [0019]     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.  
         [0020]     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  
       [0021]     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.  
         [0022]      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;  
         [0023]      FIG. 2  is a fragmentary side perspective view of a top portion of the product and the machine shown in  FIG. 1 ;  
         [0024]      FIGS. 3A-3E  include schematic plan views of a product at various steps of the method of the present invention;  
         [0025]      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;  
         [0026]      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;  
         [0027]      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  
         [0028]      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. 
     
    
       [0029]     Similar numerals refer to similar parts throughout the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     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.  
         [0031]     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 .  
         [0032]     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 .  
         [0033]     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 .  
         [0034]     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.  
         [0035]     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.  
         [0036]     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 .  
         [0037]     Turning now to FIGS.  3 A-E, pallet stack  12  also includes a first corner C 1 , a second corner C 2  and a first side S 1  that extends between the first corner and the second corner, as well as a third corner C 3  and a second side S 2  that extends between the second corner and the third corner. A third side S 3  extends between third corner C 3  and a fourth corner C 4 , and a fourth side S 4  extends between the fourth corner and first corner C 1 . In the method of the present invention, head  44  preferably causes stretch film  54  to make four passes, indicated as lines P 1 -P 4 , across top  70  of pallet stack  12 .  
         [0038]     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 S 1 -S 4  of pallet stack  12  in a continuous overlay manner as known to those skilled in the art.  
         [0039]     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 S 1 -S 4 , the top-wrapping procedure commences.  
         [0040]     With reference to  FIG. 3 , and generally to  FIGS. 4-7 , head  44  moves around first corner C 1  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 S 1  just past first corner C 1 , 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 C 1  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 .  
         [0041]     To make first pass P 1 , shown in  FIGS. 3A and 3E , head  44  moves counterclockwise around to opposing third corner C 3 , 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 S 1  and S 2  of the stack. The movement of head  44  causes film  54  to extend over top  70  of stack  12  from first corner C 1  to third corner C 3 . To secure film  54 , once head  44  reaches a point along second side S 2  near third corner C 3 , 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 C 3  and along third side S 3 , thus causing bottom edge  72  of film  54  to catch the top of the third corner, keeping the film tight across stack top  70 .  
         [0042]     Head  44  moves along third side S 3  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 P 2 , as shown in  FIGS. 3B and 3E , head  44  moves around fourth corner C 4 , and at a point along fourth side S 4  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 C 4 . Head  44  continues to move counterclockwise at a level above top  70  of stack  12  over to second corner C 2 . At a point along first side S 1  just before second corner C 2 , 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 C 4  to the second corner. Head  44  continues around second corner C 2  to second side S 2  and film  54  catches on the second corner, securing the tension of the film across top  70  of stack  12 .  
         [0043]     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 P 3 , as shown in  FIGS. 3C and 3E . Head  44  continues along second side S 2  and around third corner C 3 , 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 S 3  just past third corner C 3 , 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 C 3 . Head  44  continues to move counterclockwise at a level above top  70  of stack  12  over to first corner C 1 . At a point along fourth side S 4  just before first corner C 1 , 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 C 3  to the first corner. Head  44  continues around first corner C 1  to first side S 1  and film  54  catches on the first corner, securing the tension of the film across top  70  of stack  12 .  
         [0044]     Head  44  proceeds to fourth pass P 4 , as shown in  FIGS. 3D and 3E . Head  44  continues along first side S 1  and around second corner C 2 , 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 C 2  along second side S 2 , 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 C 2 , as shown in  FIG. 7 . Head  44  continues to move counterclockwise at a level above top  70  of stack  12  over to fourth corner C 4 . At a point along third side S 3  just before fourth corner C 4 , 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 C 2  to the fourth corner. Head  44  continues around fourth corner C 4  to fourth side S 4  and film  54  catches on the fourth corner, securing the tension of the film across top  70  of stack  12 .  
         [0045]     Once head  44  reaches fourth side S 2  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 S 1 -S 4  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.  
         [0046]     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 C 1 -C 4 . 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 P 1 -P 4  to be efficiently accomplished.  
         [0047]     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.  
         [0048]     The ability to automatically stretch-wrap sides S 1 -S 4  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.  
         [0049]     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 S 1 -S 4  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.  
         [0050]     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.  
         [0051]     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.  
         [0052]     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.  
         [0053]     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.