2. Background of the Invention Apron strippers are used in a variety of article stacking applications and serve to deposit layers of articles onto an underlying support. The most common application is in palletizers. Palletizers are well-known for automatically or semi- automatically stacking layers of articles such as cartons or bags on a pallet, sheet, or other support. The typical palletizer includes vertically-spaced upper and lower conveyor assemblies which convey articles and supports, respectively.

The lower conveyor assembly of the typical palletizer includes a vertically- movable hoist (sometimes known as an indexing pallet hoist) that is raiseable to receive layers of articles one at a time from the upper conveyor assembly to form a stack and that indexes downwardly to receive each successive layer. The lower conveyor assembly may also include an outfeed conveyor for conveying a full stack away from the hoist as well as a staging mechanism and other equipment for conveying a stack of pallets, sheets, or other supports towards the hoist and for delivering the supports one at a time to the hoist.

The upper conveyor assembly of the typical palletizer is designed to 1) receive articles from an infeed conveyor, 2) form layers of articles suitable for stacking, and 3) deposit the layers one at a time onto the underlying indexing hoist. Cartons and most other articles typically are rectangular rather than square in shape. Secure stacking of these articles in layers usually requires that each layer of articles take the form of a pattern in which the articles have more than one orientation. Patterns are usually formed by turning some articles 90° as they

are conveyed along the upper conveyor assembly. As a result of this pattern formation, each article of each successive layer can be supported by two or more articles of an underlying layer to form a more secure stack by interweaving the layers.

Article patterns are typically formed by a pattern former comprising an article turner assembly, a sorter, and an accumulator. The article turner assembly and sorter, in combination, divide a lane of incoming articles of common orientation into multiple lanes of articles in which at least some of the articles in at least one of the lanes is turned so as to be orientated differently from some of the articles in the remaining lanes. The lanes of articles are accumulated in the accumulator to form the patterns.

A stripper is disposed at the downstream end in a stacking zone of a typical palletizer so as to 1) receive layers or patterns of articles one at a time from the upstream accumulator and 2)"strip"or move out from under the layer of articles to deposit that layer onto the underlying hoist one at a time thereby to form a stack. Most palletizers employ either a slide plate assembly or an apron stripper assembly for this purpose.

The typical slide plate assembly includes one or more smooth metal plates which move into the stacking zone so as to receive the layer of articles and then retract out of the stacking zone to deposit the layer of articles onto an underlying support. A slide plate assembly is disclosed, for example, in U. S. Patent No.

4,024,965 to Marth et al.

The typical apron stripper assembly includes 1) a plurality of longitudinally spaced, transversely extending slats that are movable into and out of the stacking zone and 2) a driven chain arrangement for moving the slats into and out of the stacking zone as a unit. One such apron stripper assembly is disclosed in U. S.

Patent No. 4,205,934 to Pantin et al. (the Pantin et al. patent), which discloses an apron stripper formed from a series of parallel slats each supported on and extending between a pair of parallel endless chains. The chains have an upper horizontal run and a return run disposed beneath the upper run. The chains are driven by means of a hydraulic drive motor which drives sprockets over which the chains are trained. The entire apron stripper is mounted on a vertically movable

stacking carriage. In operation, a layer of articles is placed on the stacking carriage, which is then lowered until the stripping apron is located just above the level of an underlying support such as a pallet so that the subframe and chain path of the return run straddle the support. The stripping apron is then withdrawn to deposit the layer onto the support. The stacking carriage is then moved back to its article receiving position to receive the next layer of articles.

Apron strippers offer an advantage over slide plates in that apron strippers can be operated in conjunction with other article transfer equipment so as to help convey articles into a stacking zone. Independent transfer equipment such as rakes therefore are not required. The typical slide plate assembly, on the other hand, must be positioned in the stacking zone prior to receiving a layer of articles and hence cannot aid in article transfer. However, this benefit of apron strippers comes at a cost.

Most notably, the apron stripper must be very robust to support and convey a large layer of relatively heavy articles. In a typical application in which the article layer 1) is formed in a rectangular pattern extending from four to six feet on a side and 2) consists of loaded cartons of relatively heavy goods such as beverages, the apron stripper must be able to convey and support several hundred pounds of articles. Prior art apron strippers employed metal slats to provide the required strength. The individual slats often are formed from channels or tubes in an effort to reduce weight. However, the requirement for these metal slats imparts several disadvantages to the apron stripper.

First, the channel-shaped or tubular slats must be relatively thick--on the order of 3/4"to 1"or even more. As a result, articles stacked by the typical apron stripper are dropped more than an inch, and often two inches or more, upon retraction of the stripping apron from the stacking zone and consequent deposition of the articles on the underlying stack. This relatively long drop results in significant layer disruption and consequent loose stacking.

Second, high speed palletizing operations require that the apron stripper' must be movable from its retracted or home position, to its extended or article supporting position, and back to its home position in less than five seconds, and sometimes in as little as four seconds or even less. The typical prior art apron

stripper is incapable of operating that quickly because it weighs several hundred pounds and, accordingly, has a high inertia.

Third, the metal slats of the typical apron stripper are difficult to fabricate.

The typical slat is formed from two interconnected parts including a lower, relatively thick bar of mild steel and an upper, thin sheet of stainless steel (the stainless steel sheet being added for the purposes of corrosion resistance, wear resistance, and friction reduction). The stainless steel must be welded to the mild steel at considerable delay and expense.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore a first principal object of the invention to provide an apron stripper for a palletizer or other article handling system that is light-weight and, accordingly, capable of being operated very rapidly.

Another object of the invention is to provide an apron stripper that meets the first principal object of the invention and the slats of which are very thin so as to minimize the distance through which deposited articles drop upon retraction of the apron stripper out of the stacking zone.

Yet another object of the invention is to provide an apron stripper that meets the first principal object and that can be fabricated and installed relatively easily and inexpensively.

Still another object of the invention is to provide an apron stripper that meets the first principal object and that has a service life that is at least comparable to the service life of traditional apron strippers.

In accordance with a first aspect of the invention, these objects are achieved by providing an apron stripper assembly that includes 1) an apron stripper and 2) an apron drive mechanism. The apron stripper includes a plurality of parallel slats, each of the slats being formed from a composite carbon material.

The apron drive mechanism is operable to drive the apron stripper between 1) a first position in which the apron stripper is located in a stacking zone overlying a support and is capable of supporting a layer of articles and 2) a second position in which the apron stripper moves away from the first position to form an opening through which the layer of articles may drop onto the support.

Preferably, the composite carbon material has a tensile strength above 100,000 psi, a hardness of between 40 and 90 Barcol, and a density of less than 2.0 oz/in3. An epoxy resin material having unidirectionally orientated internal carbon fibers and having a tensile strength above 140,000 psi, a hardness of 50 to 60 Barcol, and a density of less than about 1.0 oz/in3 is preferred.

Preferably, in order to minimize pattern disruption by minimizing the amount of drop that the articles undergo during stacking, each of the slats is less than 5/8"thick and, even more preferably, no more than about 7/16"thick.

A second principal object of the invention is to provide a high speed palletizer incorporating a fast-acting apron stripper.

In accordance with another aspect of the invention, this object is achieved by providing 1) a pattern former assembly which receives incoming articles and which forms layers of articles of designated patterns, 2) a vertically movable hoist, and 3) an apron stripper assembly. The apron stripper assembly is disposed so as to receive articles from the pattern former assembly and includes a plurality of parallel slats, each of the slats being formed from a composite carbon material.

The apron drive mechanism is operable to drive the apron stripper between 1) a first position in which the apron stripper is located in a stacking zone overlying a support and is capable of supporting a layer of articles and 2) a second position in which the apron stripper moves away from the first position to form an opening through which the layer of articles may drop onto the support.

A third principal object of the invention is to provide a method of stacking articles on a pallet or other underlying support using an improved apron stripper.

In accordance with yet another aspect of the invention, this object is achieved by 1) actuating an apron drive mechanism to drive an apron stripper to convey the layer of articles into a stacking zone, the apron stripper comprising a plurality of parallel slats, each of the slats being formed from a composite carbon material, and then 2) actuating the apron drive mechanism to drive the apron stripper to move out from under the layer of articles, thereby depositing the layer of articles on an underlying support.

Preferably, the articles drop less than 1"when they are deposited on the underlying support.

These and other objects, features, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred exemplary embodiment of the invention is illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: Figure 1 is a top plan view of a high speed palletizer incorporating an apron stripper assembly constructed in accordance with a preferred embodiment of the invention; Figure 2 is a side elevation view of the high speed palletizer of Figure 1; Figure 3 is a top plan view of the apron stripper assembly of the high speed palletizer of Figures 1 and 2, showing the apron stripper assembly in its retracted or"home"position; Figure 4 is a top plan view of the apron stripper assembly, showing the apron stripper assembly in an intermediate position in which it has conveyed a layer of articles into a stacking zone; Figure 5 is a top plan view of the apron stripper assembly, showing the apron stripper assembly in a pre-stripping position in which a layer of articles is compressed in preparation for a stripping operation; Fig. 6 is side elevation view of the apron stripper assembly and of adjacent portions of the palletizer; Fig. 7 is a side elevation view of the apron stripper assembly; Fig. 8 is an enlarged fragmentary end elevation view of a portion of the apron stripper assembly; Fig. 9 is sectional end elevation view of the apron stripper assembly taken generally along the lines 9--9 in Fig. 5;

Fig. 10 is an enlarged sectional side elevation view of a portion of the apron stripper assembly as shown in Fig. 9 with parts removed for clarity; Fig. 11 is a fragmentary perspective view of a portion of the apron stripper assembly; and Figs. 12 through 16 are schematic side elevation views illustrating the sequence of operation of the apron stripper assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 1. Resume Pursuant to the invention, an apron stripper is provided for stacking articles in a high speed palletizer or a similar system and is configured to be light-weight, strong, fast-acting, and inexpensive to fabricate and to install. The apron stripper comprises a plurality of parallel slats each connected at its opposite ends to a pair of transversely opposed drive chains. Each of the slats is formed from a composite nonmetallic material, preferably a pultruded composite carbon material.

The resultant apron stripper is a fraction the weight of traditional apron strippers and therefore be operated at high speeds. It is also very thin and, accordingly, requires stacked articles to undergo only a minimal drop during a stacking operation, thereby minimizing disruption of the pattern of the stacked article layer.

2. System Overview The inventive apron stripper assembly is usable in virtually any article handing system in which articles must be stacked in layers. Therefore, while the invention is described primarily in conjunction with a palletizer, it should be understood that the invention is applicable to article handling systems other than palletizers.

A high speed palletizer 20 with which the inventive apron stripper assembly is applicable now will be described with references to Figures 1 and 2. The illustrated high speed palletizer is designed to handle cartons that store beverage containers and the like and to stack these cartons on a pallet. It should be understood, however, that the invention is equally applicable to palletizers for handling bags or other articles and for stacking those articles on sheets or plastic pallets or other supports. The illustrated palletizer 20 includes an upper conveyor assembly 22 for conveying articles such as cartons and a lower conveyor assembly

24 for conveying article supports such as pallets. Both conveyors 22 and 24 are mounted on a common frame 26 formed from a plurality of interconnected metal braces.

The upper conveyor assembly 22 is designed to receive articles in a single lane from an infeed conveyor 28, to arrange the received articles in predesignated patterns P suitable for forming layers of a stack, and to deposit these layers one at a time onto a pallet hoist 66 of the underlying lower conveyor assembly 24 to form a stack. The upper conveyor assembly 22 includes an article turner assembly 30, a sorter 32, an accumulator 34, and an apron stripper assembly 36. All components of the upper conveyor assembly 22 operate at high speeds to palletize articles at a high speed of over 200 articles per minute and preferably of at least about 220 articles per minute.

Infeed conveyor 28 may comprise any conventional belt, roller, or chain conveyor configured to deliver unturned articles to the upper conveyor assembly 22 in a single lane. The illustrated infeed conveyor 28 comprises a belt conveyor having a discharge end disposed adjacent an inlet end of the article turner assembly 30. The infeed conveyor 28 comprises a belt 38 which is supported on a dedicated support frame 40 by pulleys 42 (only one of which is shown) and which is driven by a variable speed electric motor 44. Stationary guides flank the belt 38 for assuring in-line conveyance of the conveyed articles A. Each guide includes a guide bar 46 mounted on a plurality of longitudinally-spaced transverse rods 48.

Each rod 48 is attached to the underlying support frame 40 by a set screw or similar device which permits lateral adjustment of the rod 48 relative to the underlying support frame 40 to permit the lateral spacing between the guide bars 46 to be adjusted accommodate articles of varying sizes.

The article turner assembly 30, sorter 32, and accumulator 34, in combination, define a pattern former that receives conveyed articles A from the infeed conveyor 28 and that forms designated patterns P that are suitable for stacking in layers. Successive patterns P typically will take different configurations so that, when the patterns P are subsequently deposited as layers onto the underlying hoist 66 by the stripper 36, each article of each successive layer is supported by two or more articles of an underlying layer to form a more

secure stack by interweaving the layers. More specifically, the article turner assembly 30 receives the unturned articles from the infeed conveyor 28 and either turns or does not turn each article, depending upon the place that article is to take in the corresponding pattern. The sorter 32 receives articles from the article turner assembly 30 and divides the incoming articles into several different side-by- side lanes. The accumulator 34 receives articles from the sorter 32, accumulates these articles in the predesignated pattern to form the above-described layers, and holds the layers for subsequent stacking on the pallet.

The article turner assembly 30 may be located either upstream or downstream of the sorter 32. The illustrated article turner assembly 30 is located upstream of the sorter 32 and hence must be capable of selectively either turning or not turning conveyed articles if layers of designated non-uniform patterns are to be stacked. The preferred article turner assembly includes an article turner 70 and a selector mechanism 72. The selector mechanism 72 includes 1) a movable guide device taking the form of a pair of laterally-spaced guide members 74 each of which is pivotably mounted on a support plate at an upstream end thereof and 2) a corresponding pair of linear actuators 78 each taking the form of a pneumatic cylinder having a first end pivotably connected to a generally downstream portion of the respective guide member 74 and having a second end pivotably connected to a support plate 80. The article turner 70 is a so-called split-belt turner that includes a plurality (three in the illustrated embodiment) belts 90,92,94 that move at different speeds relative to one another. The selector mechanism 72 controls the orientation of incoming articles so that articles which are not to be turned are contacted by only one belt 90 and hence travel through the article turner assembly 30 while maintaining their incoming orientation, and articles which are to be turned have their orientation altered so that they contact more than one belt 90,92,94 and hence are turned by the speed differential across the belts.

Transfer or stubber belts 96 and 98 transfer articles from the split belts 90,92,94 to the sorter 32. An article turner assembly of this type is described in more detail in co-pending and commonly assigned patent application Serial No.

09/094,098 to Franklin et al., which was filed on June 9,1998 and which is entitled Method And Apparatus For The In-Line Turning Of Selected Articles And

High-Speed Palletizer Usable Therewith, the subject of which is hereby incorporated by reference in its entirety.

The sorter 32 may comprise any suitable sorter or lane former and preferably comprises a so-called"slat sorter"of the type disclosed in U. S. Patent No. 5,590,758, to Wilkins et al., the subject matter of which is hereby incorporated by reference in its entirety.

The accumulator 34 may comprise any suitable accumulation conveyor or a system of accumulation conveyors. Preferably, in order to maximize the versatility of the palletizer 20, the accumulator 34 comprises a plurality of accumulator substations 34B-34D which are arranged end-to-end with respect to one another and each of which is capable of accumulating a complete article layer. An additional substation 34A is located at the upstream end of the accumulator 34 to accumulate half an article layer preparatory to accumulating complete layers in each of the downstream substations 34B-34D. This arrangement permits layer formation to continue uninterrupted during a pallet changing operation or another time period in which articles cannot be deposited onto an underlying pallet.

Each accumulator substation 34A-34D comprises a mat top belt conveyor 50 and an end stop 52 disposed at the downstream end of the mat top belt conveyor 50. Each mat top belt conveyor 50 is driven separately by a dedicated variable speed electric motor 54. The belt of each mat top conveyor 50 is designed to minimize rolling or sliding contact between the article and the conveyor 50 and hence to minimize abrasion of the article. A mat top belt suitable for these purposes is available, for example, from Intralox Corp. of Harahan, Louisiana.

Each end stop 52 is designed to selectively 1) arrest article movement at the end of the accumulator substation 34A-34D and 2) permit article passage to downstream conveyor assembly components while acting as a support surface bridging the gap between the accumulator substation and the next downstream accumulator substation or other upper conveyor assembly component. Each illustrated end stop 52 comprises a roller 56 or the like 1) extending across the upper surface of the associated conveyor 50 and 2) attached at each of its opposite ends to the upper end of a pivot arm 58. The lower end of the pivot arms 58 of

each end stop 52 are attached to a suitable electric actuator 60. The actuator 60 associated with each end stop 52 is operable to swing the pivot arms 58 of that end stop 52 between 1) a lowered position, illustrated in Figure 2 and in phantom lines in Figure 11, in which the roller 56 bridges the gap between adjacent accumulator substations to act as a support surface for conveyed articles and 2) a raised position, best seen in Figure 1 and in solid lines in Figure 11, in which the roller 56 is engaged by articles to arrest their conveyance. Pivoting movement of the roller 56 of each end stop 52 from the raised position in solid lines in Figure 11 to the lowered position in phantom lines in Figure 11 causes the roller 56 to move downwardly and outwardly away from the articles without impacting or jarring the articles and hence prevents damage to the articles.

The stripper 36 is designed to alternately 1) help convey a layer of articles to a stacking location over the hoist 66,2) support the layer of articles at the stacking location and 3) move out from under the layer of articles and deposit the layer onto the hoist 66. The illustrated and preferred stripper assembly is an apron stripper that reciprocates into and out of the stacking zone. The apron stripper assembly is detailed in Section 3 below.

Referring now primarily to Figure 2, the lower conveyor assembly 24 includes, from upstream end to downstream end thereof, a pallet conveyor 62, a staging conveyor or infeed conveyor 64, the hoist 66, and a discharge conveyor or outfeed conveyor 68. All components of the lower conveyor assembly 24 are conventional and therefore will not be described in detail.

In use, articles A are conveyed into the upper conveyor assembly 22 one at a time by the infeed conveyor 28, turned as necessary and separated into multiple lanes by the article turner assembly 30 and the sorter 32, and accumulated in patterns P of articles on the accumulator 34. The patterns P are then conveyed one at a time onto the stripper 36, which then moves out from under the pattern P to deposit it onto an underlying pallet on the hoist 66 as a layer. Simultaneously, the pallet conveyor 62 transfers a stack of pallets into the lower conveyor assembly 24, the staging or infeed conveyor 64 receives a single pallet for transfer to the hoist 66, the hoist 66 lifts empty pallets up to the stripper 36 for article stacking and then lowers loaded pallets back down to the level of the remaining

conveyors of the lower conveyor assembly 24, and the discharge conveyor 68 conveys loaded pallets away from the palletizer 20. The hoist 66 is driven by a drive mechanism including a reversible electric motor 65 and a drive chain assembly 67, both seen best in Fig. 7.

3. Construction and Operation of Apron Stripper Assembly As discussed briefly in Section 2 above, the apron stripper assembly 36 is designed to alternately 1) receive a layer of articles A in a pattern P, 2) support the layer of articles A at a location above the hoist 66, and 3) move out from under the layer of articles so as to deposit the layer onto a stack of articles supported on the underlying hoist 66. The apron stripper assembly 36 includes as its major components 1) an apron stripper 100 and 2) an apron drive mechanism 102. In addition, a compression assembly 104, located over the apron stripper 100, is operable to compress sides of a layer of articles A that is supported on the apron stripper 100 so as to form a tighter stack upon subsequent stripping and resultant stacking. Each of these subassemblies will now be detailed in turn.

The apron stripper 100 is formed from a plurality of parallel slats 106 that are spaced longitudinally in the direction of article conveyance and that extend transversely with respect to the direction of article conveyance. The dimensions of each slat as well as the number of slats and spacing between slats may vary from application to application. The shape of each slat also may vary, but each slat will typically be much longer than it is wide and will typically between three feet long and five feet long. In the illustrated embodiment in which the apron stripper is 60" long by 54"wide, 30 evenly-spaced slats 106 are provided, each of which is 54" long by 1%"wide by 7/16"thick. Each slat is generally rectangular in transverse cross section but could, if desired, be shaped more like a teardrop or airfoil in order to reduce sliding friction with conveyed articles. In addition, it may be desirable to round at least the upper edges of the slats so that the slat lacks sharp corners which could damage an article as the article is conveyed against that edge from an adjacent, loaded slat. Contact between the article and a corner of the slat is possible due to deflection of the loaded slat relative to the unloaded slat under the weight of the article on the loaded slat.

The slats 106 are designed to meet several different criteria, some of which are usually considered to be at least somewhat contradictory. These criteria will now be briefly discussed. a. Strength The apron stripper 100 must be strong enough to support the considerable weight of the articles A that are supported on it. Each slat 106 therefore must be strong enough to support its own weight as well as its proportionate share of the weight of the layer of articles even though the layer may weigh more than 500 lbs.

Metal slats, typically formed from steel, were historically employed to provide the required strength. b. Hardness The slats 106 should be relatively hard so as to be wear resistant and abrasion resistant and so as to maintain a relatively high coefficient of sliding friction during use. Stainless steel, which typically has a hardness of 20 to 40 Rockwell C, only marginally meets this requirement. A hardness of over about 40 Barcol would be preferred. However, a hardness of over about 90 Barcol should be avoided to prevent the slat from becoming too brittle. c. Coefficient of Sliding Friction The slats 106 should have a relatively low coefficient of sliding friction so as to facilitate transfer of articles onto and off from the slats, thereby reducing power requirements. A preferred slat material would have a coefficient of sliding friction of less than that of stainless steel, which is about 0.8. However, the coefficient of friction should not be so low as to lose control of the conveyed articles. d. Weight In order to be usable in a high speed palletizing operation, an apron stripper must be capable of moving from its retracted position, to its operative position in the stacking zone, and back to its retracted position in as little as four seconds or even less. The high inertias associated with traditional heavy steel slats inhibit or even prevent operation at these speeds, particularly since the drive chains and motors of the typical apron drive mechanism must be of sufficient size and power to drive the heavy apron stripper formed by these heavy slats.

e. Thickness Articles should undergo as small a drop as possible during a stacking operation so as to minimize disruption of the pattern of the article layer. Many traditional apron strippers require an article drop of 2"or more with substantial pattern disruption. A drop of less than 1"would be preferred, and this small drop would require a slat thickness of less than 5/8"to 3/4"to provide some clearance between the bottom of the slats and the top of the uppermost layer of the stack during slat movement. f. Cost of Fabrication and Assembly Cost is always a concern. However, the traditional steel slat, being formed from a lower mild steel bar capped with a stainless steel sheet, requires substantial labor to fabricate and install due to the fact that the stainless steel sheet must be welded to the underlying mild steel bar and due to the fact that holes must be drilled through the composite member for attachment to the drive chains or other drive member (s) of the apron drive mechanism.

Two-part or even one-part metal slats traditionally used in apron strippers simply cannot meet all of the above criteria. However, it has been discovered that these criteria are met admirably by forming each of the slats 106 from a nonmetallic material such as a composite carbon material, preferably a pultruded composite carbon material. These materials are formed from a molded resin having carbon fibers inserted therein and aligned so as to maximize desired properties. A variety of resin and carbon fiber materials may be used so long as the following properties are obtained: 1) a tensile strength above 100,000 psi and preferably above 140,000 psi; 2) a weight of less than about 10 lbs per slat, preferably less than 5 lbs per slat, and even more preferably about 2-3 lbs per slat (as opposed to a standard steel slat which typically weights 15-20 lbs or more per slat); and 3) a thickness of less than 3/4", preferably less than 5/8", and even more preferably of about 7/16"or less (as opposed to the standard steel slat which has a thickness of 3/4"or more). Moreover, the slat material should preferably have 1) a hardness of between about 40 and about 90 Barcol, and preferably of between about 50 and about 60 Barcol and 2) a sliding coefficient of friction of less than about 0.8 and more preferably between about 0.1 and about 0.2.

The preferred slats 106 are made out of a pultruded carbon material manufactured by DFI Pultruded Composites, Inc., of Erlanger, KY. These slats are formed from a molded resin having a carbon material molded into it. An epoxy resin is preferred for hardness purposes. Especially preferred is a vinylester epoxy resin having internal carbon fibers that are formed from 33 MSI carbon. The carbon fibers are arranged in a unidirectional orientation parallel to the longitudinal axis of the slat. The fibers make up between 40% and 70%, and preferably about 52%, of the total volume of the composite material. The properties of the preferred pultruded composite materials are summarized in Table 1: TABLE 1: PROPERTIES OF SLAT MATERIAL

PROPERTY PREFERRED RANGE ESPECIALLY PREFERRED RANGE OR VALUE Tensile Strength More than More than 100,000 psi 140,000 psi and preferably about 145,000 psi Tensile Modulus More than 15.0 Msi About 15.8 Msi Short Beam Shear Above 8,000 psi About 8,500 psi Hardness 40-90 Barcol 50-60 Barcol Density Less than 2.0 oz/in3 Less than 1.0 oz/in3 and preferably less than 0.95 oz/in3 Coefficient of Sliding Less than 0.8 Between about 0.1 and Friction 0.2

Material properties can be varied within or even beyond the above-listed ranges in a manner of ways. For instance, the material of the slats may, if desired, be hardened by heating the molded slat. Another material such as Kevlar may be added to further increase hardness. In addition, the tensile strength and tensile modulus can be increased 15% by increasing the fiber content.

The purpose of the apron drive mechanism 102 is to selectively drive the apron stripper 100 to move between 1) a first or extended position in which the apron stripper 100 is located in the stacking zone over the hoist 66 and is capable of supporting a layer of articles arranged in a pattern A (Figs. 4 and 6), and 2) a second or home position in which the apron stripper 100 moves away from the first position to form an opening to stack the layer on the underlying hoist 66.

(Figs. 3 and 5) The second or home position is located below and adjacent to the level of the stacking zone, and the apron drive mechanism 102 therefore is arranged to convey the apron stripper 100 in a curvilinear fashion from the second position to the first position. The drive mechanism 102 also is capable of operating rapidly so as to perform a full cycle of operation in four seconds or less.

Moreover, the drive mechanism 102 is capable of operating in concert with the accumulator assembly 34 so as to assist in article layer conveyance into the stacking zone, thereby eliminating the need for a rake or other device to transfer layers of articles from the accumulator assembly 34 to the stacking zone.

In the illustrated and preferred embodiment, the apron drive mechanism 102 includes 1) a reversible electric motor 108 and 2) an actuator mechanism which is operably connected to the electric motor and to the slats so as to reciprocally drive the apron stripper 100 between the first and second positions upon motor operation. The actuator mechanism preferably comprises a pair of transversely opposed, longitudinally extending drive chains 110 and 112 attached to the opposed ends of the slats 106. As seen in Figures 5,6, and 9, each drive chain 110 or 112 rides over 1) a driven sprocket 114 located beneath the stacking zone, 2) a first idler sprocket 116 located near the rear end of the stacking zone, 3) a return sprocket 118 located at the front end of the stacking zone, and 4) a second idler sprocket 120 located beneath the stacking zone near the front end thereof. A drive shaft 122 supplies torque to the driven sprockets 114 of both of the chains 110 and 112, and a return shaft 124 connects the return sprockets 118 of the two chains 110 and 112 to one another. Torque is transferred to the drive shaft 122 from the electric motor 108 via a drive belt 126, best seen in Figure 7.

Referring now to Figures 8-10, each slat end is connected to the associated chain 110 or 112 by a so-called K-bracket attachment arrangement. This

attachment arrangement includes 1) an upper transversely extending member 130, 2) a lower support block 132, and 3) a spacer 134. The upper member 130 is attached to a link of the associated chain 110 or 112 and extends inwardly from the link so as to overlie the end of the slat 106. The lower support block 132 is positioned adjacent the bottom surface of the slat 106. The spacer 134 is inserted between the upper surface of the slat 106 and the upper member 130. The end of the slat 106 is attached to the attachment arrangement by a pair of bolts 136 each of which extends through the upper member 130, through the spacer 134, through holes in the end of the slat 106, and into a threaded bore in the lower support block 132. The holes in the end of the slat 106 preferably are formed during slat molding so as to obviate the need for subsequent drilling or boring operations.

Turning now to Figures 3-6 and 11, the compression assembly 104 is operable to compress all four sides of a layer of articles A that are arranged in a pattern P and that are supported on the apron stripper 100, thereby to form a more secure layer and, accordingly, a more secure stack. The compressor assembly 104 includes front, rear, right, and left compressors 144,146,148, and 140, respectively, all of which are moveable from a compressing position to a retracted position.

The right and left side compressors 148 and 150 extend longitudinally relative to the direction of article conveyance and are reciprocatable laterally relative to the direction of article conveyance. The upstream end of each compressor 148 or 150 is supported on the frame 26 by a guide roller 168 or 170, and the downstream end of each compressor 148 or 150 terminates in a sleeve 156 or 158. Both sleeves 156 and 158 are slidably mounted on a rod 160 extending transversely across the apron stripper assembly 36. A drive chain 162 extends in a serpentine manner from an upper end of the first sleeve 156, under a first sprocket 164, around a second sprocket 166, and to the bottom end of the other sleeve 158. The ends of the chain 162 are connected to opposed sides of a bracket 172 which is selectively driven to move transversely over the apron stripper assembly 36 by a pneumatic cylinder 174. The cylinder 174 has a rod end connected to the bracket 172 and a cylinder end connected to a support 176 that is mounted on the frame 26. Due to the serpentine arrangement of the chain

162, extension and retraction of the cylinder 174 causes the sleeves 156 and 158 to move towards and away from one another so as to cause the associated support members 148 and 150 and, hence, the compressors 140 and 142, to move in unison towards and away from the longitudinal centerline of the stacking zone.

The front compressor 144 comprises a bar that extends transversely across the apron stripper assembly 36 as best seen in Figures 3-5. First and second ends of the compressor 144 are supported on an extendible end of a linear actuator 178 and on a guide roller 180, respectively. One end of the linear actuator 178 is connected to a support 182 mounted the underlying frame 26. Retraction of the linear actuator 178 from its fully extended position of Figure 3 drives the front compressor 144 towards a transverse centerline of the stacking zone so that the compressor 144 engages the front end of the article layer as seen in Figure 4.

The rear compressor 146, which is chain-driven rather than cylinder- driven, is designed to traverse a gap G formed between the accumulator substation 34D and the stripper assembly 36 when the gap G is vacated by the roller stop 56 of the accumulator substation 34D. As best seen in Figures 7,10, and 11, the rear compressor 146 comprises a rectangular bar that extends transversely across the apron stripper assembly 36 and that is driven at its opposed ends by first and second transversely spaced, longitudinally extending drive chains 190 and 192.

The drive chains 190 and 192 are positioned transversely outside of and slightly above the drive chains 110 and 112 for the apron stripper 100 so that the apron stripper drive chains 110 and 112 are nested within the rear compressor drive chains 190 and 192. Each of the drive chains 190 and 192 extends from a lower driven sprocket 194, over an upper idler sprocket 196, around a return sprocket 198, and back to the driven sprocket 194 as best seen in Fig. 11. Both driven sprockets are driven by a common drive shaft 200, and both return sprockets ride on a common return shaft 202. The drive shaft 200 is coupled to a reversible electric motor 204 as best seen in Figure 7. Energization of motor 204 transfers torque to chains 190 and 192 via the drive shaft 200 and the driven sprockets 194, thereby driving the compressor 146 either into or out of a compressing position, best seen in Figure 6.

5. Operation of Apron Stripper Assembly The operation of the apron assembly 36 will now be detailed in conjunction with Figures 3-6 and 11-16. It should be noted that many operations that are described as being performed sequentially for the sake of convenience are, in reality, performed simultaneously to reduce cycle time as much as possible.

Figures 3 and 12 illustrate the apron stripper assembly 36 in a position in which it is primed and ready to receive a layer of articles. In this position, the roller stop 56 of the accumulator substation 36D is raised to receive a layer of articles in preparation for transfer to the stacking zone. The apron stripper 100 and right, left, front, and rear compressors 140,142,144, and 146 are all in their retracted positions at this time.

Next, a layer of articles A is transferred into the stacking zone via the following process: First, the roller stop 56 is pivoted from the raised position seen in Figures 3,6,11, and 12 to the lowered position seen in Figures 4 and 13, and the accumulator conveyor 50 is energized to initiate article transfer towards the stacking zone. The motor 108 is also energized at this time to drive the apron stripper 100 from its home position towards its extended position so that the apron stripper 100 helps convey articles into the stacking zone as best seen in Figure 13.

The linear actuator 178 for the front compressor 144 also is actuated at this time so that the front compressor 144 moves into a position serving as a stop for the article layer when the apron stripper 100 is driven into its fully extended position within the stacking zone as seen in Figure 14. At this time, the roller stop 56 pivots to its raised position as seen in Figure 14, and the rear and side compressors 146,140, and 142 are extended as seen in Figures 4 and 14, respectively. During this process, the rear compressor 146 traverses the gap G recently vacated by the roller 56.

A stripping operation is then initiated by indexing the hoist 66 to a position in which an upper support surface of the stack is positioned as close as reasonably possible, typically less than 1/4"to 1/2", beneath the bottom of the slats 106 as seen in Figure 15. The electric motor 108 for the apron stripper 100 is reversed to retract the apron stripper as seen in Figures 5 and 14, thereby depositing the layer of articles A on the underlying support surface. A new layer of articles can

be conveyed into contact with the roller stop 56 at this time as best seen in Figure 5. The electric motor 204 for the rear compressor 146 also is reversed to retract the rear compressor to its home position, and the indexing hoist 66 is again lowered sufficiently to provide adequate clearance between the upper surface of the just-deposited layer and the bottom of the slats 106. The cycle can then be repeated.

The entire process described above can be performed in as little as four seconds or less due to the relatively low inertia of the apron stripper 100 as permitted by the light-weight slats 106. Operation is additionally facilitated by the fact that a relatively small, low inertia and rapidly acting electric motor 108 can be used to drive the light apron stripper 100. Moreover, due to the thin slats 106, articles drop a minimal amount during the stripping operation, thereby minimizing pattern disruption.

Many changes and modifications may be made to the invention without departing from the spirit thereof. For instance, although the apron stripper assembly 36 has been described primarily in conjunction with a palletizer 20, it could be used with other article handling systems requiring the vertical transfer of a layer of articles. In addition, the different drive mechanisms could be used to transfer the apron stripper 100 into and out of the stacking zone. In fact, a driven slat belt and its associated drive arrangement could be used in other conveying applications using a driven flat belt to transfer articles. The scope of some of these changes are discussed above. The scope of other changes will become apparent from the appended claims.