This invention pertains to skids for shipping goods, and more particularly to corrugated skids comprising two pieces of corrugated paperboard that are uniquely assembled simply by folding together and having additional fibrous reinforcement pieces, with higher density than the corrugated blanks, mechanically attached by horizontal interference fits to increase performance capabilities. The special added reinforcements, which do not require use of adhesives for assembly and are recyclable with the corrugated board, allow the skids a much higher rated load, better resist moisture as well as greater durability and more applications.

Background of the Invention

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 for reducing costs, 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.

One particularly attractive type of corrugated pallets are corrugated skids, or pallets without a bottom deck. Not having a bottom deck reduces wasted corrugated board area that simply rests on the ground and it further allows easier fork lift entry as the operator can set the forks directly on the ground without causing potential damage to a bottom deck

Unfortunately, corrugated skids have not been readily usable in applications requiring open racking, long term use in moist environments and support ribs can become damaged from careless forklift operators. New improvements to corrugated skids are desired to overcome these deficiencies and make corrugated skids more durable while still being readily recyclable.

Summary of the Invention

The invention provides a corrugated skid comprised of two die cut blanks that are folded together to produce strong load support with minimized corrugated board use and rapid and easy assembly. The load capacity and durability are greatly enhanced through the use of added reinforcements made from higher density fibrous material than the blanks themselves. The reinforcements are uniquely attached to the skids through use of horizontal mechanical interference fits such that they increase the rated load as well moisture resistance due to their higher density. The reinforcements are preferably made from a wood derivative material such as paperboard, medium density fiberboard or strawboard such that they can be readily recycled with the corrugated blanks.

We have found that conventional corrugated skids are not strong and durable enough for many applications. Also, if skids were constructed 100% of high density material instead of corrugated paperboard, they would be too difficult to assemble and costly, as well as undesirably increased weight. Such pallets would offer few benefits over traditional wood skids. Surprisingly, we have found that addition of only a small amount of higher density reinforcements to lightweight corrugated skids is all that is needed to adequately increase strength and moisture resistance, through unique construction, placement and attachment. To maintain the low cost and rapid assembly, it is desirable to avoid lengthy waiting for adhesives to set or for costly gluing equipment. We have found that the small amount of higher density reinforcements can in fact be added to corrugated skids, without adhesive, but mechanically through interference fits using an inventive construction. The skids with integral reinforcements in accordance with the invention can be easily assembled in under a minute and have greatly improved performance for use in a wider range of challenging applications.

The corrugated skid is used for supporting a load with a deck maintained above a supporting surface. The skid comprises two planar corrugated blanks including a top blank and a bottom blank, and multiple reinforcement pieces having higher density than that of said blanks. The top blank comprises multiple cut out windows spaced between rib portions that fold vertically out of the plane of the top blank to produce double thickness top blank ribs with central crest fold lines. The bottom blank comprises multiple rib portions that fold vertically out of the plane of the bottom blank to produce double thickness bottom blank ribs with central crest fold lines. The top and bottom blanks are assembled together with the top blank ribs and the bottom blank ribs intersecting perpendicularly. Multiple higher density reinforcement pieces are mechanically locked to the skid by horizontal interference fits with the top blank ribs and/or bottom blank ribs, whereby the multiple higher density reinforcement pieces increase the load capacity of the corrugated skid through transfer of load between the deck and the supporting surface.

In one embodiment, the multiple higher density reinforcement pieces comprise paperboard tubes that assemble vertically onto the top blank ribs and/or bottom blank ribs such that the interference fit with the ribs occurs with the inner diameter of the tubes. Although the top and bottom blanks ribs may have different lengths, in an additional preferred embodiment, they are approximately equal horizontal lengths and intersect each other at the approximate center of the tubes. This provides the most reliable mechanical connection between the tubes and ribs.

In another embodiment, of the invention, the multiple higher density reinforcement pieces comprise sheets inserted between layers of the top blank ribs or bottom blank ribs. The sheets which can be constructed of medium density fiberboard, straw board or other material that can preferably be recycled directly with the corrugated sheets. The sheets may be notched to allow installation with the top blanks ribs, however this can weaken the beam strength of the

reinforcement. In yet further embodiment, the top blank ribs comprise slots to accept insertion of the higher density reinforcement pieces. This construction can allow the skids to be stored in unsupported open racking because of the added beam strength. The reinforcement inserts may be multiple short pieces, however it can be desirable to reduce the number of inserts to ease assembly. Accordingly, the multiple higher density reinforcement pieces advantageously can run

continuously in the direction of the bottom blank ribs across all ribs in said bottom blank.

Besides increased stacking strength resulting from the interference fit reinforcement pieces as well as potential ability to be used in open racking, the invention provides additional benefits as well. The reinforcement with higher density than the corrugated blanks also provides dramatically increased moisture resistance. The skids can even be set in standing water for a duration of time, which is not possible for pallets without the integral reinforcement. Corrugated pallets usually lose most of their strength in high humidity conditions such as ship by sea container and airfreight shipment sitting on a wet tarmac. The invention overcomes this deficiency, greatly expanding the market applications for corrugated pallet use. Accordingly, in an additional embodiment, the corrugated skid comprises two corrugated blanks including a top blank and a bottom blank, and multiple reinforcement pieces of a material having higher density, strength and stiffness than that of the blanks. The top blank comprising multiple cut out windows spaced between rib portions that fold vertically to produce double thickness top blank ribs with central crest fold lines. The bottom blank comprises multiple rib portions that fold vertically to produce double thickness bottom blank ribs with central crest fold lines. The top and bottom blanks are assembled together with the top blank ribs and bottom blank ribs intersecting perpendicularly. The multiple higher density reinforcement pieces include tubes that slide onto the ribs where they intersect and are mechanically locked to the skid by horizontal interference fits with the top blank ribs and/or bottom blank ribs, whereby the multiple higher density reinforcement pieces increase the moisture resistance capacity of the skid by having a higher moisture resistance than the corrugated blanks Different materials for the reinforcements can be utilized, but it is preferable that they constructed from low cost material with higher density than the corrugated blanks and which can be readily recycled. Preferable materials include paperboard, low, medium or high density fiberboard or strawboard. In a further embodiment, the reinforcement benefits are maximized through the use of reinforcement pieces are composed of fibrous material with density that is equal or greater than three times the density of the corrugated blanks.

Description of the Drawings

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:

Fig. 1 is a plan view drawing of a top blank of a corrugated skid with integral

reinforcements in unassembled flat blank state in accordance with the invention.

Fig. 2 is an isometric drawing of the top blank with ribs folded of the corrugated skid with integral reinforcements of Fig. 1 in accordance with the invention.

Fig. 3 is an isometric drawing of the top blank with ribs folded and reinforcing inserts installed for the bottom blank ribs of the corrugated skid with integral reinforcements shown in Figs 4 and 5 in accordance with the invention. Fig. 4 is an isometric drawing of the top and bottom blanks aligned prior to assembly together of the corrugated skid with integral reinforcements shown in Figs. 1-5 in accordance with the invention.

Fig. 5 is an isometric drawing of the assembled corrugated skid with integral

reinforcements of Fig. 1 in accordance with the invention.

Fig. 6 is side view drawing of the corrugated skid with integral reinforcements of Fig. 5 shown holding a load of boxes in an open rack in accordance with the invention.

Fig. 7 is an isometric drawing of top and bottom blanks of an alternate configuration corrugated skid with integral reinforcements in unassembled flat blank state in accordance with the invention.

Fig. 8 is an isometric drawing of the corrugated skid with integral reinforcements of Fig. 7 in accordance with the invention, showing the top and bottom blanks with ribs folded and aligned prior to assembly together.

Fig. 9 is an isometric drawing of the top and bottom blanks of the corrugated skid of Figs. 7 and 8, assembled in accordance with the invention.

Fig. 10 is bottom plan view drawings of the corrugated skid of Figs. 7-9, with paperboard integral reinforcements in the form of core tubes pressed onto the ribs in accordance with the invention.

Fig. 11 is a bottom view in use diagram of the corrugated skid with integral reinforcements of Figs. 7-10 in accordance with the invention while in use being moved by a sloppy forklift operator.

Fig 12 is a comparison of the densities of the corrugated blanks as well as reinforcements made from paperboard cores and medium density fiberboard inserts in accordance with the invention

Fig. 13 is a comparison of rated load capability between a corrugated only skid and reinforced skids in accordance with the invention.

Fig. 14 is a comparison of rated load capability in high humidity between a corrugated only skid and reinforced skids in accordance with the invention. Description of the Preferred Embodiment

Turning to the drawings, wherein like reference characters designate identical or corresponding parts, Fig. 1 shows plan view of a top blank 31 of a corrugated skid with integral reinforcements in unassembled flat blank state. The top blank 31 comprises a die cut sheet of corrugated paperboard having rib sections 32, 33, 34. Each rib section 32, 33, 34 has notches 37, 38, 39 for later assembly with a bottom blank of the corrugated skid. Extending from the notches 37, 38, 39 are cuts 40, 41 to allow subsequent insertion of reinforcing inserts 61, 62, 63, shown in Figs. 3 and 4. The top blank comprises multiple cut out windows 35, 36 spaced between rib portions 32, 33, 34 that fold vertically out of the plane of the top blank as shown in Fig. 2, to produce double thickness top blank ribs with central crest fold lines 42.

An isometric drawing of the top blank 31 with ribs 32, 33, 34 folded perpendicularly from top blank 31 of Fig. 1 is shown in Fig. 2. Notches 37, 38, 39 each opening upward with the top blank 31 upside down. Cuts 41 extend from the bottom of the notches 37, 38, 39 to the blank 31.

An isometric drawing of the top blank 31 is shown in Fig. 3, with ribs folded and reinforcing inserts installed for the bottom blank ribs 72, 73, 74, shown in Fig. 4. Fiberboard, chipboard or Masonite inserts 61, 62, 63 are inserted into rib notches 37, 38, 39 and slid into the cuts into engagement with the underside of the folded blank 31. The inserts may be fabricated from other materials including stronger ones where required for heavy load racking. However, wood based products are typically preferable to allow easy recycling with the corrugated paperboard blanks. Inserts typically have a thickness of 3-5 mm.

An isometric drawing of the top and bottom blanks aligned prior to assembly together of the corrugated skid in accordance with the invention is shown in Fig. 4. The top blank 31 has ribs 32, 33, 34 folded vertically with central crest fold lines 42. Fiberboard inserts 61, 62, 63 are inserted into the notches 37, 38, 39. Bottom blank 71 has its ribs 72, 73, 74 also folded from the blank 71 and positioned in vertical alignment just above the inserts 61, 62, 63 of the top blank 31. The bottom blank 71 also comprises slots 75 for receiving the penetration of top blank ribs 32, 33, 34 upon assembly The bottom blank also further comprises notches 76 that will be mated with top blank notches 37, 38, 39 and receive the inserts upon assembly. The cuts 40, 41 and the slots 75 grip the inserts in a firm interference fit to hold it in place and improve the structural integrity of the skid. Although shown with notches 37, 38, 3 cut all the way to the top deck 31, the inserts may alternately be notched instead to facilitate assembly while maintaining the integrity of the top blank ribs 32, 33, 34. Alignment holes 64 and 65 may be provided to assist in alignment of the top and bottom blanks 31 and 32 using pins mounted on an assembly table or in an assembly machine (not shown). An isometric drawing of the assembled corrugated skid with integral reinforcements of Figs. 1 -4 in accordance with the invention is shown in Fig. 5. The bottom blank 71 and top blank 31 are assembled together such that top blank ribs 32, 33, 34 penetrate the bottom blank and project equidistant and are flush with bottom blank ribs 72, 73, 74. Top blank ribs 32, 33, 34 intersect perpendicularly with bottom blank ribs 72, 73, 74 having top blank notches 37, 38, 39 interlocking with bottom blank notches 76. The inserts 61, 62, 63 are located inside the middle of bottom blank ribs 72, 73, 74, to reinforce and carry beam bending load in operation. The inserts 61, 62, 63 are interference fit by the horizontal squeezing of the top ribs 32, 33, 34 and bottom ribs 72, 73, 74. The corrugated skid with integral reinforcements assembly is now complete and can be flipped right side up and put in use.

A side view drawing of the assembled corrugated skid 80 of Fig. 5 is shown holding a load of boxes in an open rack is shown in Fig. 6. The skid 80 is shown holding a load in an open warehouse rack 101, 102 without wire decking support. The skid 80 is loaded with 1000 lbs of boxed goods 103, which is being temporarily stored prior to shipment. The inserts 61, 62, 63 are carrying the beam bending load in the unsupported span 104 between the racks 101, 102. Besides allowing support of loads in unsupported open racking the integral reinforcements greatly increases the stacking strength or rated load for non-racked shipments as well as moisture resistance.

Although the most cost effective construction of the corrugated skid with integral reinforcements 80 is through using corrugated paperboard blanks and fiberboard inserts, the corrugated skid with integral reinforcements may also be constructed from corrugated plastic blanks and use plastic or other material inserts as well, depending on the shipping requirements. Corrugated plastic skids with integral reinforcements can provide the benefits of even further increased water resistance and more durability for multiple use shipping.

One problem utilizing corrugated skids is that careless forklift drivers may not take much effort to align the forks with the fork openings in the skid, and inaccurately enter or exit a skid with the forklift, causing damage to the support ribs from unnecessary impact. This and other potential problems is solved with the use of an alternate configuration corrugated skid 120 shown in Fig. 7 in unassembled flat blank state. The skid includes two blanks, a bottom blank 121 and a top blank 122 and is constructed to provide four way entry The bottom blank 121 has rib sections 123, 124, 125 as well as a deck section 134 on both sides of the rib sections. Slots 126 and notches 127 are later used for assembly of the top and bottom blanks 122, 121 together. Fork passage cut outs 128, 129 will later provide fork openings between the rib sections, as shown in Fig. 9, for entry of forks of forked equipment for lifting the skid and its load.

The top blank 122 comprises rib sections 130, 131, 132 and deck 135. The top blank 135 shown in Fig. 7 beneath the top blank (because after assembly the assembled skid will be flipped over) comprises multiple cut out windows 140, 141 spaced between rib portions 130, 131,132 that fold vertically out of the plane of the top blank to produce double thickness top blank ribs with central crest fold lines 142. The bottom blank comprises multiple rib portions 123, 124, 125 that fold vertically out of the plane of the bottom blank to produce double thickness bottom blank ribs with central crest fold lines 144.

An isometric drawing of the skid 120, with the ribs of the top and bottom blanks 121, 122, folded and aligned prior to assembly together is shown in Fig. 8. The bottom blank 121 has ribs 123, 124, 125 folded vertically extending from deck portions 134. The top blank 122 has ribs 130, 131, 132 vertically extending from deck portions 135. Slots 126 in the deck portions 134 allow for penetration by top blank ribs 130, 131, 132 upon assembly. Notches 127 mate with notches 133

Fig. 9 shows the skid 120 with the bottom blank 121 vertically assembled with top blank 122 such that decks 134 and 135 are assembled adjacent or in contact with each other. Bottom blank ribs 123, 124, 125 intersect and lock together with top blank ribs 130, 131, 132.

Fig 10 is a bottom plan view drawing of the alternate configuration of the corrugated skid 120 showing the integral reinforcements in the form of paperboard core tubes 181 pressed onto the intersecting support ribs 122, 123, 124, 130, 131, 132 to protect them from impact damage resulting from careless operation of forked lifting equipment, as illustrated in Fig. 11. The cores, like the inserts in the first configuration, both greatly increase the rated load capacity and moisture resistance as well due to their higher density than the corrugated blanks The cores 181 are preferably spiral wound paper, which is commonly available and of thickness sufficient to prevent impact damage. The cores 181 are preferably cut to the length equivalent to the height of the bottom of the skid such that they support the deck 134. The cores 181 are preferably sized such that they are held in place by a mechanical interference fit, so that no glue is required and installation is very quick and easy. Although glue is not necessary, increased strength and stiffness could be available by dipping the cores in liquid glue before pushing them onto the intersecting ribs. The cores could be pushed all the way onto the intersecting ribs so the glue is spread along the outside vertical edges of the intersecting ribs and also around the interface of the top of the cores and the underside of the deck 134. The interference fit between the cores 181 and the intersecting ribs holds the core firmly in contact with ribs and also with the underside of the deck while the glue sets.

Additional strength and stiffness may be achieved by inserting short lengths of the reinforcing inserts 61, 62, 63 into the rib sections 123, 124, 125, between the double thicknesses thereof, before the top and bottom blanks 121, 122 are assembled. Although this would be unnecessary for most applications, there may be applications where the improved strength of the rib intersections would improve the damage tolerance that such an arrangement would provide.

A bottom view in use diagram 200 of the alternate configuration of corrugated skid with integral reinforcements of Fig. 7 in accordance with the invention while in use being moved by a sloppy forklift operator is shown in Fig. 11. The damage tolerant corrugated skid 201 is being entered by forklift 202 while being misaligned. Fork impacts 204, 205 with cores 181 protect the support ribs 125, 130 which might otherwise be damaged. As a result, the skid 201 gets shifted sideways 206 instead of becoming damaged.

Although the most cost effective construction of the alternate configuration of corrugated skid with integral reinforcements is through using corrugated paperboard blanks and paper core tubes, the skid may also be constructed from corrugated plastic with plastic core tubes for highly wet environments or multiple use applications.

This invention provides a unique shipping platform that can be rapidly assembly from two corrugated blanks and strategic placement of a small amount of higher density reinforcements that greatly increases strength, durability and moisture resistance. The invention allows a low cost and lightweight pallet to be used for much wider and more challenging applications.

A comparison of the densities of the corrugated blanks as well as reinforcements made from paperboard cores and medium density fiberboard inserts in accordance with the invention is shown in Fig. 12. The use of integral reinforcements with the skid in accordance with the invention is effective because they have higher density than the corrugated blanks. This allows them to have higher strength, stiffness and moisture resistance. The comparison 300 shows typical corrugated blanks for skids 301 at 160 kg/m3, paperboard cores 302 at about 375% increase to 600 kgm3 and medium density fiberboard inserts 303 at 720 kgm3. In a preferred embodiment of the invention, the reinforcements have a density equal to or greater than 3 three times the density of the corrugated blanks. The high density allow for limited required amount of reinforcement to make a substantial increase in skid durability and performance. A comparison of rated load capability between a corrugated only skid and reinforced skids in accordance with the invention is shown in Fig. 13. The comparison 310 shows the skid with only corrugated blanks 311 having a rating of 905 kg. The skid with paperboard cores 312 more than doubles that rating to 1910 kg while the skid with medium density fiberboard inserts 313 increases further up to 2100 kg.

Besides normal dry use, skids can encounter high humidity in certain countries and on long shipping transit by sea containers. Corrugated blanks because of their low density have a high tendency to absorb moisture and lose strength and stiffness. A comparison of rated load capability in high humidity between a corrugated only skid and reinforced skids in accordance with the invention is shown in Fig. 14. The comparison 320 shows that the skid with only corrugated blanks 321 loses substantial strength down to only 330 kg. How the skids with integral reinforcements in accordance with the invention only experience a minor drop in performance. The skid with paperboard cores 322 drops in rated load only to 1800 kg. The skid with medium density fiberboard inserts 323 also only has a minor drop in rated load to 1930 kg.

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. For example, there may be applications where the requirements of additional strength and stiffness that applying glue either between the two layers of the deck, or between the double thicknesses of the ribs, or both, justify the additional manufacturing time and cost that would be incurred in additional cost in doing so. 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: