Patent Publication Number: US-9850082-B2

Title: Storage container

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a national stage filing under 35 U.S.C. 371 of PCT/US2012/069987, filed Dec. 17, 2012, which claims priority to U.S. Provisional Application No. 61/579,734, filed Dec. 23, 2011, the disclosure of which is incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE INVENTION 
     Provided are containers and related methods for storing and dispensing a plurality of stacked articles. More particularly, containers and methods are provided for storing and dispensing a plurality of stacked planar articles as might be encountered, for example, in a film manufacturing or shipping operation. 
     BACKGROUND 
     Film manufacturing operations commonly use specialized containers for storing and transporting films and related intermediary components for a given end product. These containers are especially useful for protecting high-grade films from the outside environment during shipment or perhaps to assist in organizing and/or dispensing their contents. In the case of optical films, for example, product is generally manufactured using a continuous roll-by-roll process, cut into individual sheets, and then manually stacked into a tray. This tray could then be transported to another location in the manufacturing facility for transport, storage, and eventually conversion (e.g. further processing and/or assembly). 
     For certain applications, protection of these films is paramount. To avoid contamination and prevent adjacent films in the stack from sticking to one another, it is common to line both sides of each sheet with a “pre-mask” film. The pre-mask film protects the underlying optical film from being scuffed and scratched from the adjacent layers of film sliding against each other. Notably, this relative sliding motion can occur at any time, including while stacking, transporting, or even during storage of these films. At some point, the optical films are converted, at which time the films are individually removed from the stack, the pre-mask layers peeled off, and the pristine film manually placed into the next converting process. Therefore, the pre-mask film not only incurs materials costs, but also extra labor, lost time, and the nuisance of their disposal. 
     As manufacturing operations have become more automated, however, it has been possible to reduce human involvement. For example, robotics can be used to pick and place films from a container into a converting process. Another example is a laser conversion process in which a computer-controlled laser beam cuts one or more film samples into pre-defined shapes prior to assembly. Automation has the potential to significantly improve the precision and reliability of a process, while lowering overall costs. 
     SUMMARY 
     One difficulty encountered when handling thin, polymeric films derives from their tendency to adhere to each other. When the sheets of film are initially stacked on top of one another, a thin layer of air is trapped between neighboring sheets. This air layer is often beneficial, because it facilitates subsequent removal of sheets from the stack. When the sheets are stacked horizontally, however, the weight of the stack causes the air to be gradually pressed out over time, leading to undesirable adhesion between the sheets. This is especially common with soft pliable films, with each tending to conform closely to the surface beneath it. When this occurs, a human will typically intervene by locating the seam between the top sheet and the layers beneath and manually peeling it off the stack. Often this is a pain staking process that offsets the aforementioned benefits of automation. 
     A second difficulty relates to the registration of the sheets in an automated process. In a conventional stacked configuration, the location of the sheets relative to each other is uncontrolled. Even if the sheets are initially aligned, they can shift within a container during transport and storage. Without a convenient way to register the sheets to an automated process, human intervention may again be required. Once again, the imposition of this manual step frustrates efforts to automate the process of picking films from the container and placing them into a conversion process. 
     The provided containers and related methods overcome these technical challenges by enabling gravitational alignment of the stacked sheets where at least two edges of each sheet are precisely aligned with matching inner walls of the container. The aligning walls of the container are provided with a low-friction surface and the container optionally includes at least one wall opposing an aligning wall that has a substantially compressible layer. By enclosing the stack of sheets along two edges, the sheets can be registered relative not only to each other but also to the container itself, thereby facilitating fully automated removal of sheets from the stack. Additionally, the presence of a compressible layer opposing one or both of the aligning walls preserves the registration of the sheets relative to each other even when that stack experiences vibrations and jostling in the container during transport. 
     In one aspect, a container for a plurality of stacked articles having a certain Shore D hardness is provided. The container comprises: a base having a bottom surface; and a frame extending outwardly from the base, the frame comprising: a first wall oriented at an oblique angle relative to the bottom surface; a second wall joined with the first wall, at least a portion of each of the first and second walls having a coefficient of friction not exceeding 0.1; and a third wall joined with the first and second walls to define a corner at least partially bounded by the first, second, and third walls, wherein at least a portion of the third wall is generally perpendicular to each of the first and second walls and comprises a non-scratching material having a Shore D hardness not exceeding the certain Shore D hardness. 
     In another aspect, a container for a plurality of stacked articles having a certain Shore D hardness is provided, the container comprising: a base having a bottom surface; and a frame extending outwardly from the base, the frame comprising: a first wall oriented at an oblique angle relative to the bottom surface; a second wall joined with the first wall to define a corner at least partially bounded by the first and second walls, at least a portion of each of the first and second walls having a coefficient of friction not exceeding 0.1; and at least one opposing wall generally facing one or both of the first and second walls, wherein at least a portion of the one or more opposing walls comprises a compressible layer that can be compressed to 75% of its original relaxed volume. 
     In still another aspect, a container for a plurality of stacked articles having a certain Shore D hardness is provided, the container comprising: a base having a bottom surface; a frame extending outwardly from the base, the frame comprising: a first wall oriented at an oblique angle relative to the bottom surface; a second wall joined with the first wall; a third wall joined with the first and second walls to define a corner at least partially bounded by the first, second, and third walls, wherein at least a portion of the third wall is generally perpendicular to each of the first and second walls and comprises a non-scratching material having a Shore D hardness not exceeding the certain Shore D hardness; and at least one opposing wall generally facing one or both of the first and second walls, wherein at least a portion of the at least one opposing wall comprises a compressible layer that can be compressed to 75 percent of its original relaxed volume. 
     In yet another aspect, a container for a plurality of stacked articles is provided, comprising: a base having a bottom surface; and a frame extending outwardly from the base, the frame comprising: a first wall oriented at an oblique angle relative to the bottom surface; a second wall joined with the first wall, at least a portion of each of the first and second walls having a coefficient of friction not exceeding 0.1; and a third wall joined with the first and second walls to define a corner at least partially bounded by the first, second, and third walls, wherein at least a portion of the third wall is generally perpendicular to each of the first and second walls and comprises a looped pile layer. 
     In yet another aspect, a method of registering a plurality of stacked articles in a container having an enclosure at least partially defined by a first wall, a second wall adjoining the first wall, and at least one opposing wall generally facing one or both of the first and second walls is provided, the method comprising: providing a low-friction surface to facilitate sliding of the articles along at least a portion of each of the first and second walls; providing a compressible layer along at least a portion of the at least one opposing wall, the layer capable of being compressed to 75 percent of its original relaxed volume; cutting the plurality of articles along two adjoining edges to define a pair of reference edges; and placing the plurality of articles into the enclosure such that the reference edges align with the first and second walls while the at least one opposing wall conforms to one or more edges of the articles that are not reference edges to preserve the alignment of the articles relative to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view showing the front, left, and top sides of a container according to one exemplary embodiment. 
         FIG. 2  is a front elevational view showing the front side of the container of  FIG. 1 . 
         FIG. 3  is a rear perspective view showing the rear, left, and top sides of the container of  FIGS. 1-2 . 
         FIG. 4  is a top view showing the top side of the container of  FIGS. 1-3 . 
         FIG. 5  is a perspective exploded view showing the front, left, and top sides of the container of  FIGS. 1-4  along with optional ancillary components. 
         FIG. 6  is a perspective view showing the front, right, and top sides of a container according to another exemplary embodiment. 
         FIG. 7  is a front elevational view showing the front side of the container of  FIG. 6 . 
         FIG. 8  is a perspective view showing the rear, left, and top sides of the container of  FIG. 6-7 . 
         FIG. 9  is a top view showing the top, left, and front sides of the container of  FIGS. 6-8 . 
     
    
    
     DEFINITIONS 
     “Oblique” means oriented neither perpendicular nor parallel relative to each other. 
     DETAILED DESCRIPTION 
     The following sections describe the provided containers and methods in greater detail by way of illustration and example. Notably, some of the angles and dimensions shown in the figures may be somewhat exaggerated to offer clarity to the viewer and therefore may not be drawn to scale. It is further understood that these containers may be provided with or without their respective contents, depending on the desired application. 
     A container according to one exemplary embodiment is illustrated in  FIG. 1  and broadly designated by the numeral  100 . The container  100  includes a left panel  110  and a right panel  112 . As shown, the panels  110 ,  112  are planar and parallel. Optionally and as shown, the panels  110 ,  112  are rigid structures that have a fixed orientation relative to each other. 
     The panels  110 ,  112  collectively provide both a base  102  for the container  100  and sidewalls of a frame  103  that extend outwardly from the base  102 . As shown in the embodiment of  FIG. 1 , the base  102  and frame  103  are integrally joined; in other words, the frame  103  is essentially an extension of the base  102 , although this need not be the case. For example, the base  102  could be a discrete component joined to the bottom of the panels  110 ,  112 . 
     The base  102  has a bottom surface  104  that rests flatly on a horizontal surface  106 . The base  102  contacts the horizontal surface  106  along an elongated footprint that allows the container  100  to stand upright without wobbling. The bottom surface  104  and the horizontal surface  106  may extend along an entire length of one side of the container  100 , as shown in  FIG. 1 , or only along a portion thereof. Alternatively, the base  102  could include three or more discrete legs (such as legs of a table) that independently contact the horizontal surface  106  along relatively smaller areas that are sufficiently spread apart to provide a stable foundation for the container  100 . 
     Referring again to  FIG. 1 , the frame  103  provides an enclosure  118  for receiving a plurality of stacked sheets  120 . In this figure, and subsequent figures, the plurality of sheets  120  are depicted as having the shape of a six-faced rectangular cuboid for the sake of simplicity. It is to be understood, however, that the sheets  120  are discrete, separable components and may be provided in non-rectangular shapes. For example, the sheets  120  could be polygonal in shape, have contiguous sides that are non-perpendicular, have one or more curved surfaces, and so forth. In an even broader sense, other stackable articles with any shape or size may be used in place of the sheets  120  depicted in the figure. 
     The enclosure  118  of the frame  103  is partially defined by a first wall  108 , second wall  114 , third wall  124 , and an opposing wall  130  generally facing the second wall  114 . Preferably, the enclosure  118  has dimensions that are static. In other words, it is preferred that the walls  108 ,  114 ,  124 ,  130  are fairly rigid and resist bending under usual operating conditions. Aspects of each wall, particularly aspects concerning their surface properties and orientation relative to each other, are described in the sections below. 
     The first wall  108  is planar and extends transversely across the space between the first and second panels  110 ,  112 . The first wall  108  is also oriented at an oblique angle relative to the plane of the bottom surface  104 . In the embodiment shown, the first wall  108  is directly attached to the panels  110 ,  112 , thereby imparting additional structural strength to the container  100 . The wall  108  could also be attached to the back wall  124 , if so desired.  FIG. 1 , and the front view presented in  FIG. 3 , further show that the stacked sheets  120  are all aligned with a flat inner surface  109  of the first wall  108 . In this preferred embodiment, the alignment between the inner surface  109  and the sheets  120  is achieved with the assistance of gravity, which tends to pull each sheet  120  downwards against the planar inner surface  109 . 
     The inner surface  109  optionally includes a low-friction surface. The low-friction surface preferably extends along surface areas of the inner surface  109  that are in contact with the sheets  120 . In some embodiments, the low-friction surface is a fluoroplastic surface. Fluoroplastics contemplated in the present description include partially fluorinated and perfluorinated fluoroplastics. Fluoroplastics include, for instance, those having interpolymerized units of one or more fluorinated or perfluorinated monomers such as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), vinylidene fluoride (VDF), fluorovinyl ethers, perfluorovinyl ethers, as well as combinations of one or more of these. Fluoroplastics may further include copolymers comprising one or more of the fluorinated or perfluorinated monomers in combination with one or more non-fluorinated comonomer such as ethylene, propylene, and other lower olefins (e.g., C2-C9 containing alpha-olefins). 
     In other embodiments, the fluoroplastic includes polytetrafluoroethylene (PTFE). When PTFE is used, it may be used as a blend with another fluoropolymer and may also contain a fluoropolymer filler (in the blend or in the PTFE only). 
     More specifically, useful fluoroplastics also include those commercially available under the designations THV (described as a copolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride), FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene), PFA (a copolymer of tetrafluoroethylene and perfluorovinyl ether), HTE (a copolymer of tetrafluoroethylene, hexafluoropropylene, and ethylene), ETFE (a copolymer of tetrafluoroethylene and ethylene), ECTFE (a copolymer of chlorotrifluoroethylene and ethylene), PVF (polyvinyl fluoride), PVDF (polyvinylidene fluoride), as well as combinations and blends of one or more of these fluoroplastics. 
     Any of the aforementioned fluoropolymers may further contain interpolymerized units of additional monomers, e.g., copolymers of TFE, HFP, VDF, ethylene, or a perfluorovinyl ether such as perfluoro(alkyl vinyl)ether (PAVE) and/or a perfluoro(alkoxy vinyl)ether (PAOVE). Combinations of two or more fluoroplastics may also be used. In some embodiments, fluoroplastics such as THV and/or ETFE and/or HTE are possible. 
     Non-fluorinated materials, such as ultra-high-molecular-weight polyethylene (UHMWPE), may alternatively be used to provide a low-friction surface. UHMWPE has comparable frictional characteristics to tetrafluoroethylene but has higher impact strength and better abrasion resistance. Particular properties of UHMWPE and blends thereof are described, for example, in Tincer, T and Coskun, M., “Melt blending of ultra high molecular weight and high density polyethylene: the effect of mixing rate on thermal, mechanical and morphological properties,” P OLYMER  E NGINEERING AND  S CIENCE,  33 (19), 1243 (1993). 
     The low-friction surface preferably has a coefficient of friction that is sufficiently low to enable individual sheets  120  to slide along the inner surface  109  in response to light forces, such as gravitational forces. In some cases, a small degree of vibration may be used to induce proper alignment of the sheets  120  along the low-friction surface. For example, the container  100  could be manually or automatically shaken to facilitate the settling and alignment of the sheets  120  against the inner surface  109 . In some embodiments, the low-friction surface has a coefficient of friction of at most 0.04, at most 0.05, at most 0.06, at most 0.07, at most 0.08, at most 0.09, or at most 0.1. 
       FIG. 2  shows the container  100  as viewed from a direction perpendicular to the major surfaces of the stacked sheets  120 . As shown in this figure, the first wall  108  (or its inner surface  109 ) is oriented at an oblique angle θ relative to a reference plane  107  parallel to the plane of the bottom surface  104 . Preferably, the oblique angle θ is sufficient to allow gravitational forces to induce the plurality of sheets  120  to register along a first dimension (here, referred to as the “x”-dimension) perpendicular to the inner surface  109  of the first wall  108 . Advantageously, this can allow the sheets  120  to be registered not only with respect to each other, but also with respect to the container  100 . In some embodiments, the angle θ is at least 5 degrees, at least 10 degrees, at least 15 degrees, at least 20 degrees, or at least 25 degrees. In some embodiments, the angle θ is at most 25 degrees, at most 30 degrees, at most 35 degrees, at most 40 degrees, or at most 45 degrees. 
     Referring again to  FIGS. 1 and 2 , the registration of the sheets  120  occurs when a bottom edge  140  of each of the plurality of sheets  120  aligns with the inner surface  109  of the first wall  108 . Preferably, the bottom edge  140  is a flat reference edge that matches a corresponding flat edge of the inner surface  109 . It may be preferred that the first wall  108  is sufficiently rigid to allow the location and orientation of the reference edge to be precisely defined in a three dimensional coordinate space. Alternatively, the bottom edge  140  could also have an edge contour that is not flat. For example, the edge  140  could have a curved surface, irregular surface, or any other contoured surface that matches at least a portion of the inner surface  109 . 
     The second wall  114  is contiguously joined to the first wall  108  with an orientation generally perpendicular to that of the first wall  108  thereby defining an edge at least partially bounded by the first and second walls  108 ,  114 . In a preferred embodiment, the second wall  114  has an inner surface  115  that is also a low-friction surface. For example, the inner surface  115  could have properties similar or identical to those previously described with respect to the inner surface  109 . As shown in  FIGS. 1 and 2 , the second wall  114  is oriented at an oblique angle α with respect to a reference plane parallel to the plane of the bottom surface  104 . In some embodiments, the angle α is at least 5 degrees, at least 10 degrees, at least 15 degrees, at least 20 degrees, or at least 25 degrees. In some embodiments, the angle α is at most 25 degrees, at most 30 degrees, at most 35 degrees, at most 40 degrees, or at most 45 degrees. If the first and second walls  108 ,  114  are perpendicular, the sum of angles θ and σ would equal 90 degrees. 
     As shown in  FIG. 2 , a side edge  142  shared by the plurality of sheets  120  flatly aligns with the complementally flat inner surface  115  of the second wall  114 . As before, the force of gravity acts upon the sheets  120 , urging the sheets  120  into respective positions that are registered along a second dimension (referred to as the “y”-dimension) perpendicular to the inner surface  115  of the second wall  114 . The first wall  108  and second wall  114  thus provide adjoining sides of the enclosure  118  that collectively act to place the sheets  120  in a precise, registered position with respect to a reference plane parallel to each of the sheets  120 . Once registered, the reference edges  140 ,  142  of each sheet  120  are aligned with corresponding inner surfaces  109 ,  115 . Providing a low-friction surface along the inner surfaces  109 ,  115  is beneficial in lowering the resistance to sliding between the edges  140 ,  142  of the sheets  120  and the first and second walls  108 ,  114 . 
     It is to be understood that the first and second walls  108 ,  114  need not be perpendicular to each other and, if so, the sheets  120  may adopt other shapes complemental to the walls  108 ,  114 . For example, in an alternative embodiment, each stacked sheet could have the shape of an equilateral triangle, with each sheet partially enclosed by adjoining planar walls forming a 60 degree angle relative to each other. As a further observation, the orientations of the first and second walls  108 ,  114  can be varied independently of the orientations of the panels  110 ,  112 . In  FIGS. 1 and 2 , for example, neither the first nor second wall  108 , 114  is directly defined by either of the panels  110 ,  112 . 
     The third wall  124  is contiguously joined with the first and second walls  108 ,  114  as shown in  FIGS. 1 and 2 , thus providing an edge that is collectively bounded by the first, second, and third walls  108 ,  114 ,  124 . The third wall  124  has a planar inner surface  125  that flatly engages the planar back surface of the stacked sheets  120 . Consequently, the sheets  120  assume a uniform stack along a third and final dimension (referred to as the “z”-dimension) perpendicular to the inner surface  125  of the third wall  124 . The first, second, and third walls  108 ,  114 ,  124  have a pre-defined configuration allowing an operator or manufacturing robot to determine, using the location and orientation of the base  104  as a reference point the location and orientation of the sheets  120  in x-y-z coordinate space. Depending on the dimensional tolerances of the container  100 , this information can be provided with a high degree of precision. As illustrated in  FIG. 2 , the sheets  120  include edges  144 ,  146  that do not contact any of the first wall  108 , second wall  114 , third wall  124 , or opposing wall  130 . Depending on the application, the respective edges  144 ,  146  of individual sheets  120  in the stack may or may not be aligned with each other. 
     In a preferred embodiment, the third wall  124  has an inner surface  125  having a non-scratching surface provided by a material with a Shore D hardness not exceeding the Shore D hardness of the sheets  120 . The non-scratching surface could take any of many different forms, including porous foams, fibrous layers, or thin films, some of which may not be subject to hardness measurements directly. Accordingly, “Shore D hardness,” as used herein, refers to a Shore D hardness measurement performed on a solid slab of the material providing the non-scratching surface. To provide some examples, PTFE has a Shore D hardness of about 58, while PET has a Shore D hardness of about 87. In an exemplary embodiment, the non-scratching surface could have a Shore D hardness of at most 90, at most 80, at most 70, at most 60, or at most 50. 
     The non-scratching surface preferably extends over some or all of the inner surface  125  and preferably extends across any portions of the inner surface  125  necessary to prevent damage to exposed faces of the sheets  120  as they are placed into, or dispensed from, the container  100 . The non-scratching surface could include, for example, a looped pile engagement surface made from poly(tetrafluoroethylene), aramid, polyester, polypropylene, nylon, and combinations thereof. These specialized surfaces can be used to avoid scuffing or abrading a polymeric film coming in contact therewith. Avoiding damage to the sheets  120  is especially important in applications involving fine or high grade films, such as optical films used in electronic devices. As a further advantage, a looped pile engagement surface could also serve a cleaning function by attracting and sequestering particulate debris present on the surfaces of the sheets  120 . Further options and advantages of these surfaces are described in greater detail in PCT Publication Nos. WO 2011/038279 (Tait, et al.) and WO 2011/038284 (Newhouse, et al.). 
     Optionally, the inner surface  125  of the third wall  125  could also have the same low friction characteristics of the first or second walls  108 ,  114 . Since the last (i.e. back-facing) member of the plurality of sheets  120  makes substantial contact with the third wall  125 , use of a low friction surface significantly facilitates alignment of the edges  140 ,  142  of this last sheet along respective first and second walls  108 ,  114 . 
       FIG. 3  shows a rear perspective view of the container  100 , revealing that the third wall  124  is oriented at a certain tilt angle β relative to the plane of the bottom surface  104  of the base  102 . Selection of a suitable tilt angle can help avoid many of the problems associated with conventional containers used in manufacturing operations. Conventional containers align the sheets horizontally, which causes tiny air pockets present between neighboring sheets to become gradually pressed out over time under the weight of the stack. It was discovered that these air pockets can be desirable because they provide a weak boundary layer that prevents sheets from sticking to one another. When the air is expelled from the interfacial surfaces separating the sheets, however, the sheets became difficult to dispense and can require an operator to manually locate a seam between the top layer and underlying layers to prevent multiple layers from inadvertently being dispensed at one time. 
     Proper choice of the tilt angle β associated with the third wall  124  can help alleviate this problem by orienting the sheets  120  to mitigate the adverse effect described above. Preferably, the tilt angle β of the third wall  124  relative to the bottom surface  104  is an acute angle approaching 90 degrees (i.e. a vertical orientation) to minimize compressive forces acting on the sheets  120  along a direction perpendicular to the third wall  124 . At the same time, however, it is preferable that the tilt angle β is not too close to 90 degrees or else gravity could cause the sheets  120  to peel away, individually or collectively, from the third wall  124  and/or topple over while being stored in the container  100 . In some embodiments, the tilt angle is at least 55 degrees, at least 60 degrees, at least 65 degrees, or at least 75 degrees. In some embodiments, the tilt angle is at most 87 degrees, at most 85 degrees, at most 83 degrees, or at most 80 degrees. 
       FIG. 4  shows the container  100  as viewed from a direction perpendicular to the horizontal surface  106 . This figure reveals that the sheets  120  are stacked flatly against each other in parallel relation, and collectively rest against the inner surface  125  of the third wall  124 . Preferably, the rearmost sheet  120  has a major surface in uniform contact with the inner surface  125 . Optionally and as shown, the third wall  124  need not be perpendicular to the panels  110 ,  112 . As further shown in the figures, the opposing wall  130  has a respective inner surface  131  and faces the second wall  114 , defining a fourth planar boundary of the enclosure  118 . While the inner surfaces  115 ,  131  of the respective walls  114 ,  130  oppose one another, they need not be parallel. 
     In some embodiments, the opposing wall  130  includes a compliant, compressible layer  147 . The compressible layer  147  can account for some or all of the inner surface  131  of the opposing wall  130 . Preferably, the compressible layer  147  extends across areas of the opposing wall  130  facing the edges  146  of the sheets  120 . In the configuration shown, the compressible layer  147  can advantageously serve a protective function after the sheets  120  have been registered against the first and second walls  108 ,  114 . The compressible layer  147  can substantially conform to the edges of individual sheets  120  and distribute compressive forces uniformly along the edge  146 . As a result, the layer  147  creates a “soft contact” between the opposing wall  130  and the sheets  120  and preserves the registration of the sheets  120  relative to each other even if they come into contact with the opposing wall  130  during handling or shipment of the container  100 . This is especially advantageous when it is desirable to align the sheets  120  along the edges  140 ,  142  but not along the edges  144 ,  146 . 
     As used herein, a “compressible material” is a material that is reduced in volume upon application of pressure. In some embodiments, the compressible layer includes an elastic compressible material. Elastic compressible materials include materials that substantially rebound (e.g., rebound to at least to 99% of the initial volume), preferably within 30 seconds at, for example, ambient temperatures, after release of the pressure used to compress the material. 
     The ratio of the compressed volume/initial volume (i.e., compressibility) can vary depending on the compressible material used. In some embodiments, the layer  147  is compressible to 75%, compressible to 65%, compressible to 55%, compressible to 45%, compressible to 35%, or compressible to 25% of its original relaxed volume. As used here, “compressibility” can describe materials that are not entirely solid—for example, a non-woven or foam material. In these cases, the initial volume can be defined with respect to an imaginary three-dimensional envelope required to contain the entire article, while the compressed volume can be defined with respect to another imaginary three-dimensional envelope that is only large enough to enclose the compressed article. 
     Examples of elastic compressible materials include, but are not limited to, polymeric foams, elastic scrims, elastic nonwovens, and combinations thereof. Particularly beneficial compressible materials include the looped pile engagement surfaces in PCT Publication Nos. WO 2011/038279 (Tait, et al.) and WO 2011/038284 (Newhouse, et al.). In some embodiments, the compressible material is a porous material. As used herein, a “porous material” is a material that includes pores (e.g., voids and/or vessels). In preferred embodiments, the pores are in communication with one another to facilitate compression of the porous material. Exemplary porous materials include foams (e.g., polymeric foams including, for example, cellulose foams), sponges, nonwoven fabrics, polymer fibers, cotton fibers, cellulose fibers, woven mats, nonwoven mats, scrims, and combinations thereof. 
       FIG. 5  shows the container  100  in exploded view with an additional front wall  150  and top wall  152 , which oppose the third wall  124  and first wall  108 , respectively. As shown, the first, second, third walls  108 ,  114 ,  124  act in combination with the opposing walls  130 ,  150 ,  152  to completely enclose the stacked sheets  120  within in the container  100 . As an option, one or more of the opposing walls  130 ,  150 ,  152  may be partially or completely removable from the frame  103  to facilitate outside access to the sheets  120 . For the convenience of an operator, one or more edges of one or both walls  150 ,  152  may be fastened to the frame  103  using a releasable latch. Alternatively, one or both walls  150 ,  152  could permit access to the enclosure  118  even while remaining attached to the frame  103 . This could be accomplished by using, for example, a hinge between the wall  150 ,  152  and its adjoining wall, allowing the wall  150 ,  152  to swing open 270 degrees and lock against the outer surface of the frame  103 . 
     Like the third wall  124 , the wall  150  has an inner surface (not visible in  FIG. 5 ) that faces the sheets  120  and includes a similar non-scratching surface (e.g. a looped pile layer) to avoid damage to the sheets  120  if contact between the sheets  120  and the inner surface of the wall  150  were to occur inadvertently during storage or transport of the container  100 . As with first, second, and third walls  124 , the inner surface of the wall  150  can advantageously be made from a low-friction surface, such as one having a coefficient of friction not exceeding 0.1. 
     Optionally and as shown, the wall  152 , which opposes the first wall  108 , has an inner surface  153  that includes a compressible layer  154 . The compressible layer  154  can serve substantially the same purpose as previously described with respect to compressible layer  147  located on the wall  130 . Accordingly, it preferred that the compressible layer  154  conforms to any uneven contours along the top edge  144  of the sheets  120  to avoid changing the registration of the sheets  120  within the stack relative to each other. Although not shown here, the sheets  120  could optionally be sized such that one or both of the compressible layers  147 ,  154  can apply gentle forces urging at least some of the sheets  120  toward the aligning edges  109 ,  115  of the container  100 . 
     Multiple views of a container assembly  200  according to another exemplary embodiment are provided by  FIGS. 6-9 . As shown, the assembly  200  has a discrete base  202  with a horizontal bottom surface  204 . In this embodiment, the assembly  200  includes a first platform  280  and a second platform  282 . The first platform  280  is connected to the base  202  by a pivot  205  allowing the first platform  280  to be rotated relative to the base  202  about a first rotation axis  211 . The second platform  282 , in turn, is joined to the first platform  280  along shared edges by a pair of hinges  284 , as shown in  FIG. 7 . The hinges  284  allow the first and second platforms  280 ,  282  to rotate about a second rotation axis  286 . In a preferred embodiment, these joints are mechanized to permit an operator to independently adjust two angles: (1) the angle between the bottom surface  204  and the first platform  280  about the axis  211 , and (2) the angle between the first platform  280  and the second platform  282  about the axis  286 . 
     Referring again to  FIGS. 6-9 , the second platform  282  is joined to a frame  203  that includes first, second, and third walls  208 ,  214 ,  224  and an opposing wall  230 , which are fixed relative to each other. As previously described with respect to the container  100 , additional walls opposing the first and third walls  208 ,  224  can be optionally included to complete the cuboid structure of the assembly  200 , although these are not shown. Characteristics of the first, second, and third walls  208 ,  214 ,  224  and the opposing wall  230  are analogous to those of the walls  108 ,  114 ,  124 , and  130  of the container  100  and will not be revisited here. 
     The ability to adjust the orientation of the frame  203  is convenient because the frame  203  can use conventional parallel and perpendicular walls while retaining many of the benefits of the container  100 . Additionally, an operator has freedom to adjust the respective slopes of the walls  208 ,  214  to assist in gravitationally aligning sheets (or other articles) as previously described. The pivot  205  and hinges  284  further allow the location and orientation of the frame  203  to be precisely positioned for a manufacturing process, such as a pick and place operation. The assembly  200  also allows the frame  203  to be collapsed flush against the base  202  to conserve space during storage. If desired, the frame  203  could have a configuration allowing the frame  203  to be reversibly attached and detached from the second platform  282 , allowing the more complex and expensive base  202  and platforms  280 ,  282  to be used interchangeably for multiple containers. 
     The container  100  and container assembly  200  may be advantageously used in any of a variety of known manufacturing or conversion processes. In an exemplary method, the container  100  or assembly  200  can be used to initially register the plurality of sheets  120  with respect to a manufacturing environment. The manufacturing environment may include, for example, robotics for transporting each of the sheets  120  to, or from, the container or assembly. Alternatively, the manufacturing environment could include a device used in processing or post-processing the sheets  120 , such as laser or optical scanner. 
     In the examples above, the manufacturing environment can be registered to the frame  103 ,  203  of the respective container or assembly using one or more registration markers located on its base  102 ,  202 . The registration markers could function mechanically, optically, or both. Registration between the manufacturing environment and the base  102 ,  202  could be accomplished, for example, by engaging the base  102 ,  202  to a horizontal surface in the manufacturing environment such that the registration markers are mechanically or visually aligned. In one embodiment, the manufacturing environment includes a pedestal having three or more physical features, such as protrusions or dimples, at known locations and having known geometries. These physical features are in registration with mating features located on the frame  103 ,  203  such that when the frame is properly positioned on the pedestal, the precise location and orientation of the frame  103 ,  203  can be automatically or semi-automatically determined from the known location and orientation of the pedestal. 
     Alternatively, in the above embodiment, the registration could be performed optically. For example, a plurality of optical indicia, such as dots, crosses, and the like, could be placed at known locations on the frame  103 ,  203 . Once the frame  102 ,  203  has been placed in the manufacturing environment, an optical scanner located in the manufacturing environment, and controlled by a computer, could then scan the frame  103 ,  203  to identify the locations of the optical indicia. The computer, given the known geometry of the frame  103 ,  203 , can use the scanned locations of the optical indicia to determine the location and orientation of the frame  103 ,  203  relative to the manufacturing environment. 
     With the manufacturing environment thus registered with the frame  103 ,  203 , the manufacturing environment now has a reference point to control devices to place and register articles within the frame  103 ,  203  or act upon any articles already situated in the frame  103 ,  203 . 
     In one exemplary method of registering a plurality of unregistered sheets  120  with the container  100 , a stack of sheets  120  is first cut along two adjoining edges to create the reference edges  140 ,  142 . Preferably, this operation is conducted using a laser cutting operation whereby the entire stack of sheets  120  is cut at one time to provide a matched geometry along each reference edge  140 ,  142 . Once the reference edges  140 ,  142  have been created, the sheets can be placed into the enclosure  118 . If needed, the enclosure  118  of the frame  103 ,  203  can then be oriented such that the junction between the first and second walls  108 ,  114  provides a lower corner datum facilitating spontaneous alignment of the reference edges  140 ,  142  with the respective first and second walls  108 ,  114  under the force of gravity. 
     In another exemplary method, the top and front sides of the container  100  or assembly  200  remain open while its enclosure is being filled. Once the loading of the container  100  or assembly  200  is complete, the top and front sides can be suitably covered by additional walls or panels (as previously described) and transported to the next value added process in the manufacturing environment. 
     All of the patents and patent applications mentioned above are hereby expressly incorporated into the present disclosure. The foregoing invention has been described in some detail by way of illustration and example for purposes of clarity and understanding. However, various alternatives, modifications, and equivalents may be used and the above description should not be taken as limiting in the scope of the invention which is defined by the following claims and their equivalents.