This invention pertains to pallets for shipping goods, and more particularly to a process for assembly of corrugated paperboard pallets that enables high volume pallet manufacturing with minimal assembly operator fatigue and with minimized assembly machine costs. The process increases manufacturing reliability and reduces the time required to assemble pallets.
Pallets are said to move the world. Eighty percent of commerce ships on pallets. The pallet industry is estimated at greater than $30 B worldwide. More than 500 million pallets are manufactured in the US each year, with 1.8 billion pallets in service in the US alone.
Pallets can be made from various materials, however wood pallets currently comprise about 80% of the market. More than 40% of worldwide hardwood lumber currently goes toward the manufacturing of wood pallets. Other materials used for pallet manufacturing include plastic, metal and corrugated paperboard.
Recent regulations regarding infestation and contamination are creating a surge in interest and use of non-wood pallet alternatives. A small, but fast growing segment is the use of corrugated paperboard pallets. Many desire to replace conventional wooden pallets with corrugated pallets: increasing ability to recycle, lowering pallet weight, eliminating product contamination, reducing pallet storage volume and reducing pallet related injuries.
Many different designs of corrugated paperboard pallets have been developed to date. Despite the potential advantages of corrugated pallets, many have suffered from several different deficiencies. These deficiencies include low strength and stiffness, high use of corrugated paperboard, resulting in high material costs, along with high overhead, assembly labor and freight costs. The inherent inability to readily produce and distribute corrugated pallets in sufficiently high volume has also been of critical importance.
Regardless of the design, it is desirable to increase the speed at which corrugated pallets can be produced. Corrugated pallets can be assembled solely by hand or by machine. When assembled by hand, the assembly time can be longer than acceptable for some high use applications and/or customers. When assembled by machine, the assembly speed can be increased, however the assembly machine size and costs are increased and this in turn makes the assembly upfront and operating costs to be higher than desirable for some customers and/or parts of the world. Accordingly, a new corrugated pallet assembly process is needed that can be used to readily produce corrugated pallets in high volume, at a high rate and with simultaneous low assembly costs.
There are currently two general types of corrugated pallets; one type comprising blocks or runners of corrugated board that are stacked, rolled and/or assembled together and then bonded to top and bottom decks, and the other type comprising two sheets that are folded and assembled together to form top, bottom and integral vertical supports. The first type typically utilizes a high volume of corrugated paperboard and is expensive. Further compounding the high material costs is the complicated and time consuming assembly, which is typically done at an intermediate location, adding more logistical costs.
The second general type of corrugated pallet formed from two sheets with integral vertical supports between the two sheets is preferred because of much lower inherent board use. Regardless of the specific design, the assembly is typically accomplished in three steps; forming a top, forming a bottom and later assembly of the top with the bottom together. Although less costly than the first type of corrugated pallets because of lower material costs, manufacturing can be still too time consuming, involved and expensive.
A principle goal of the invention is to provide a process for assembly of corrugated pallets that enables high volume pallet manufacturing at a high rate with simultaneous low assembly costs. We have found that in the assembly of corrugated pallets, there are different folding and assembly operations and that some of these operations are difficult to conduct by persons by hand rapidly and repeatedly. These operations are also easily conducted by a machine. We have also found that some operations in the assembly of corrugated pallets are difficult to have performed by machine due to the required mechanical complexity, and resulting reduced reliability and greatly increased machine costs. We have found that these operations that are difficult to perform by machine are also surprisingly easy to be performed by persons by hand. This aspect of the disclosed preferred embodiments of invention therefore increases the assembly rate and reduces costs associated with corrugated pallet assembly by utilizing the synergy whereby pallet assembly is shared by both use of machine functions and person hand assembly functions. For example, operations that are difficult for persons but easy for a machine can be completed by machine, and operations that are difficult for a machine but easy by person by hand can be completed by person by hand. In the assembly process, the assembly functions can change back and forth between machine and person several times for optimal efficiency. The process reduces the time required to assemble pallets and reduces the assembly costs, with minimized assembly operator fatigue and minimized assembly machine complexity.
It is an additional goal of the invention to integrate assembly such that the process can be simplified and steps may be eliminated. For example, in the preferred embodiments, the forming of ribs can be integrated with the assembly of pallet top and bottom together. Prior art two piece pallets have ribs or vertical supports that are locked from opening by adhesive and/or mechanical locks self-contained on each separate piece. For instance, in U.S. Pat. No. 6,029,582 the individual ribs are locked together using jack flaps and sliding lock assemblies. U.S. Pat. No. 7,426,890 teaches locking of ribs using folding flap lock assemblies locked prior to nesting of pallet top and bottom using a slot and wing tab. U.S. Pat. No. 7,890,184 teaches locking support ribs using a gate flap and pass through aperture. U.S. Pat. No. 7,303,519 further teaches a machine for forming pallet tops and bottoms wherein the ribs are locked from opening through the use of adhesive. In each case, independently locked ribs provide the benefit of robust ribs that may stay intact even if pallet becomes partially disassembled.
The drawback of self-locked ribs however is that extra steps and complexity of the assembly process are required. We have found that the assembly of pallet top blank nested with pallet bottom blank can be sufficient to keep ribs locked for most pallet use. Locking of ribs from opening in this way is achieved by notches in the top ribs locking the bottom ribs from opening, and notches in the bottom ribs locking the top ribs from opening. The completion of the sides of the pallet is utilized to hold the pallet top and pallet bottom blanks together such that ribs stay locking each other. Added machine requirements of maintaining the ribs of top and bottom folded under pressure until top and bottom are nested together are desirable. However, the pallet assembly steps and time for self-locking of individual ribs can be eliminated, along with attendant substantial machine complexity and size reduction. The preferred embodiment of the invention provides a process for assembling a corrugated pallet using a mix of machine and human performed operations. An example of a corrugated pallet that can be assembled with the process of this invention includes two die cut corrugated paperboard blanks that form a pallet top and a pallet bottom. The pallet top and pallet bottom each have at least one vertically extending double thickness rib, and each rib has at least one notch, wherein the notches lock the opposing ribs from opening when the ribs on the pallet top and the pallet bottom are vertically nested together. A machine operating in accordance with this invention forms the rib on each blank by applying in-plane pressure to the blank through protruding elements on the machine that penetrate the blank or engage the edges of the blank and move in relation towards each other, and the machine maintains the in-plane pressure to keep the rib from opening until a time after the pallet top and the pallet bottom are nested together. The use of protruding elements or pins that penetrate the blanks allows for sufficiently high in-plane compression force for reliable folding of ribs.
It is desirable for the pallet assembly process to occupy the minimal amount of space for both reduction of required floor space and also reduction of the size and cost of the assembly machine. We have designed the preferred embodiments of the invention to allow the ribs on the pallet top and bottom to be formed while the blanks are vertically aligned in a horizontal position, thereby allowing the pallet top and bottom to be vertically assembled together in the same location. In an additional embodiment of the invention, the machine forms the ribs on both the pallet top and the pallet bottom and nests the pallet top and the pallet bottom together so that forming and nesting occur without bodily in-plane translation of one or both of the blanks.
For simplicity of the machine design, it is preferable to hold the blanks from only one side instead of two. Holding blanks from both the top and bottom sides results in machine parts necessarily located between the two blanks, significantly complicating the assembly and nesting of the pallet top and pallet bottom in the same location. Such machine parts would have to be moved or the blanks moved to allow nesting of the pallet top and pallet bottom. In a further embodiment of the invention, the machine utilizes vacuum to hold each blank in a fixed position while protruding elements provide in-plane pressure. In this case, the top blank is held using vacuum from the top side and the bottom blank is held using vacuum from the bottom side. Pins though each blank move toward each other to provide in-plane compression for rib folding. In-plane pressure is maintained until after the top and bottom are nested together.
During the folding of the ribs for the pallet top and pallet bottom through application of in-plane compression, there is a tendency for the ribs to fold in either the correct direction or 180 degrees opposite. For instance, ribs from the top blank should fold such that they extend downward while ribs from the bottom blank should fold such that they fold upward. To assist folding in the desired out-of-plane directions, it is desirable to apply out-of-plane force to the ribs in formation. In an additional embodiment, the machine further comprises rib folding plates that apply out-of-plane forces to the blanks to assist forming of the ribs by rotating in the out-of-plane direction when the in-plane pressure is applied. Out-of-plane force could be applied by several different means however the use of rib folding plates moving in the out-of-plane direction affords simple machine construction. More preferably, the machine further comprises rib folding plates that apply out of plane forces to the blanks to assist forming of the ribs in the desired out-of-plane directions by rotating about a fixed axis in the out-of-plane direction when in-plane compression is applied.
A drawback to this method is that the folding plates become trapped between the two sides of the ribs when folded, once rotated vertically. Surprisingly, we have found that this can be advantageous in that it can be used to maintain the ribs more accurately vertical for easier nesting of the pallet top and pallet bottom. After the pallet assembly is completed, the pallet may be vertically removed from the rib folding plates to remove the pallet from the machine. In yet an additional embodiment of the invention, the rib folding plates stay inside the ribs once formed until after the pallet top and the pallet bottom are nested together.
The assembly process of maintaining in-plane pressure to keep the ribs from opening against board memory until after the top and bottom are nested eliminates the need for self contained rib locks or the use of adhesives. Adhesives add significant costs and machine complexity as well as reduce machine reliability. Adhesives also require time to set. Likewise, integral mechanical rib locks on each blank would require machinery to engage inside the space between both the pallet top and pallet bottom, hindering nesting of the pallet top and bottom together at the same location. In a further embodiment, the assembly process utilizes no integral corrugated mechanical or adhesive locking of the ribs from opening prior to said nesting.
The process for assembling the corrugated pallet can be completed with both persons and machine for minimized assembly cost and assembly ease. Some tasks are best done by machine and other best done by person. Forming of ribs and nesting of the top and bottom together are best done by machine. Loading blanks and folding sidewalls is in many cases best done by person, since they are easy hand operations that are more difficult to automate. In an additional embodiment of the invention, at least one person loads the blanks into the machine, the machine forms the ribs, the machine nests the pallet top and the pallet bottom together, and at least one persons folds the sidewalls of the pallet in the out-of-plane direction.
The size of the machine for use with the disclosed assembly process is minimized through the use of rib folding that occurs with the blanks static. The process is more complicated than conventional corrugated folding performed by bodily moving blanks over fixed mandrels, for example on a conveyor belt, and is potentially slower. In a further embodiment, the machine forms the ribs on the blanks while bodily translationally static, and nests the pallet top and the pallet bottom together by both rotating the pallet top and for the pallet bottom so the top and bottom ribs are perpendicular to each other, and by moving the pallet top and/or the pallet bottom towards each other in the out-of-plane direction. Of course, the top and bottom blanks have portions that move in the in-plane direction inwardly during rib formation, but otherwise the blanks remain bodily static against in-plane translation.
The invention and its many advantages and features will become better understood upon reading the following detailed description of the preferred embodiments in conjunction with the following drawings, wherein:
Turning to the drawings, wherein like reference characters designate identical or corresponding parts, and more particularly to
A plan view of a set up to execute the process of
A side elevation of the pallet assembly machine 60 shown in
The machine 60 comprises a vertical beam support 61, a top cantilever support 62 and a bottom support 67. A top frame 63 is supported below the top cantilever support 62 by a bearing 64 to allow for rotation of the pallet top. Mounted on the top frame 63 is a slide support 65, supporting three rows of vacuum cups 66 that are used to grip the top blank 101, slide together while two parallel ribs are formed in the top blank 101. When the vacuum cups 66 suck the top blank 101 up against stops, the elements 74 engage the top blank 101 at the edges to apply in-plane pressure to fold the ribs as the vacuum cups 66 slide inward to hold portions of the top blank in-plane as they move inward toward each other.
The bottom frame 68 is supported above the bottom support 67 through a lift linkage 72 and a bottom bearing 69. Mounted on the bottom frame 68 is a slide support 70, supporting three rows of vacuum cups 71 that are used to grip the bottom blank 102, slide together and form two parallel ribs of the bottom blank 102. When the vacuum cups 71 suck the bottom blank 102 down against stops, the elements 75 engage the bottom blank at the edges to apply in-plane pressure for folding the ribs, while the vacuum cups 71 hold portions of the top blank in-plane as they move inward toward each other while the ribs are formed. After the top and bottom blanks 101, 102 have ribs formed and are vertically compressed together by the lift linkage 72, and sidewalls are hand assembled, the corner straps of the pallet are assembled by arms 73 on the assembly machine 60. The corner straps may alternatively be assembled by person by hand.
A perspective view of a corrugated pallet 100 assembled in accordance with the invention is shown in
The corrugated pallet 100 shown in
In
In
The corrugated pallet 100 shown in assembly in
The corrugated pallet 100 shown in assembly in
A schematic drawing of a configuration of the folding section of the pallet assembly machine of
A schematic drawing of a configuration of the folding section of the pallet assembly machine of
Obviously, numerous modifications and variations of the described preferred embodiment are possible and will occur to those skilled in the art in light of this disclosure of the invention. Accordingly, I intend that these modifications and variations, and the equivalents thereof, be included within the spirit and scope of the invention as defined in the following claims, wherein I claim:
This application is related to and claims priority for U.S. Provisional Application 61/835,547 filed on Jun. 15, 2013, and 61/929,454 filed on Jan. 20, 2014.