Abstract:
The present invention relates to containers and, more specifically, to trays that can be arranged at angles over the range from 0 to 180° so that, through this rotation, different height positions can be obtained; that include ergonomic handholds, which allow an operator to identify, by touch, the proper side for stacking or stowing or adding trays, as required; a dual guide on the base of the feet, to prevent the feet from separating when the trays are stowed; a dual track or groove along the sides, to allow so-called “shoe” or “skate” elements to slide and to prevent the trays from departing from their position; socket parts (male-female), to ensure that the upper trays do not become disengaged during sudden movements and to allow the trays to be stacked to different heights; and stops or protuberances in both the upper part and the lower part of the tray, to prevent the upper trays from sliding freely along the groove of the lower tray or along its side, depending on their position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This invention claims the benefit under 35 U.S.C. § 119 of Mexican Application No. PA/a/2004/000921 filed Jan. 28, 2004, which is herein incorporated by reference in its entirety.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to stackable containers and more specifically to stackable trays for storing or transporting articles or products with different dimensions, which trays may be oriented and safely placed on top of each other in accordance with the dimensions of the product or article to be stored or transported.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is known that one of the principal problems that currently exist in warehouses or transport vehicles is that of the space required to store or transport the largest possible quantity of articles or products without damaging them. Accordingly, users have developed, or have asked companies that are experts in the field to design, receptacles or containers that, depending on their needs, will allow them to store or transport their products or articles safely.  
         [0004]     It is widely known in the field of packaging, storage, and transportation that space is saved when receptacles or containers are stowed or stacked. However, in order for stowing or stacking to be performed, consideration must be given to the subsequent handling of the receptacles or containers and to the type of articles or products that will be stored or transported in them, as well as to the subsequent storage and transport of the empty containers or receptacles. Some of the many factors that have been considered in the design of such receptacles or containers include the height of the articles or products to be stored, transported, or distributed; the weight of the product that the receptacle or container must bear; the characteristics of the place or places in which the articles or products will be stored, transported, or distributed; the conditions under which they will be handled by the operator or seller; the conditions of the road over which they will be transported; and their subsequent stacking after they have been emptied, including cleaning and washing, etc. One of the principal techniques that have been used for the stacking of receptacles or containers is the so-called “nesting” technique, which consists of stacking the receptacles or containers at different angles so as to achieve a minimum height and a maximum height (see, for example, U.S. Pat. No. 3,780,905, of Ralph H. Herotzer; U.S. Pat. No. 3,934,724, of Lewis T. Johnson; U.S. Pat. No. 4,577,759, Pinckney Molded Plastics, Inc.; and U.S. Pat. No. 4,320,837, of James C. Carrol et al.).  
         [0005]     U.S. Pat. No. 4,936,458, of Tabler et al., describes a tray that can be nested at 90°, or stacked at 0° or 180°, through the use of feet and rails, and also describes a possible so-called “blind” stacking through the cooperation of insertion elements. It also describes the use of trays of different heights for stacking; however, it does not address the crosswise nesting of trays of different heights.  
         [0006]     U.S. Pat. No. 6,394,274, of Pinckney Molded Plastics, Inc. (Howell, Mich.), describes a bread tray that can be stacked on an identical tray that provides three levels of storage, which are obtained by rotating the trays to a given angle, depending on whether they are to be nested or stacked. This patent does address crosswise stacking. However, this patent has the disadvantage that when sudden movements occur due to handling by the operator, the upper trays are easily separated from the lower trays, thereby causing damage to the product and rendering it unacceptable to the purchaser. Moreover, the trays have a very short sliding groove, which does not allow rapid alignment during the sliding operation, and also causes the trays easily to become separated. The trays include handholds that can injure the operators or that simply are not convenient for the operators in terms of proper handling of the trays, and that are not designed to withstand rough handling by the operators or the conditions that are present in trucks when they encounter potholes, earthfills, winding roads, etc. The result is that their useful lifetime is reduced significantly, and that the trays become separated while being transported by such trucks, which can cause damage to, and rejection of, the transported products. The marks that the trays may contain in order to indicate to the operator the angle at which they are stacked tend to disappear rapidly as a result of the daily use and frequent cleaning that the tray must undergo, especially when the tray is used to transport food products that demand minimum levels of hygiene, thereby causing the operator to spend additional time determining whether a tray is stacked or nested. All of the above-mentioned trays have slots or small openings in the sides in which small amounts of the product can become lodged and can decompose, and sometimes these slots or openings can even lead to substandard cleaning of the tray. It should be noted that because of its design, it may not be possible for such a tray to be handled by an individual who has a disability or handicap. The stop elements that are used when the tray is placed in the crosswise position are not sufficient to prevent the tray from departing from its so-called “stable” position, with the result that some products are damaged when they fall off the tray. Furthermore, this tray does not have a male-female socket which, in the stacked position, allows the upper tray to be affixed securely to the lower tray. Yet furthermore, the design of this tray does not allow a tray of a different width to be stacked on top of a lower tray, and does not contemplate the combination or alternation of trays of different widths during stacking.  
         [0007]     An additional disadvantage of the tray in U.S. Pat. No. 6,394,274 is that it runs the risk that the groove or sliding guide for the feet, as well as the sides and handholds, may become deformed or break within a short period of time, because of rough handling by the operator or even because of the weight of the product plus the weight of each stacked tray.  
         [0008]     Another disadvantage of the trays in the prior art is that there is a risk that the trays will be overturned if, for example, an operator accidentally leans against the trays, because there is no balancing support on one side of the trays. Moreover, the height of the space between one tray and the next changes when the trays are rotated in order to shift from a nested position to the stacked position.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is intended to solve the above-mentioned problems. Thus, one goal of the invention is to provide a receptacle or container, specifically, a stackable or nestable tray, for the storage or transport of the tray itself or of products to be stored or transported on the tray, that has a long useful lifetime even under harsh working or handling conditions, which is achieved through a combination of structural elements, such as a sliding guide or groove, corners, male-female sockets, and chamfered corners, which combination avoids the concentration of stresses under a normal load or overload. In order to achieve this combination, consideration was given to the working conditions to which the trays would be subjected, such as dragging force, overload, the type of transport to be utilized, and the roads over which the trays would be transported, as well as careful or careless handling by various operators, including operators who may have a disability or handicap.  
         [0010]     Another goal of the invention is to provide a receptacle or container or tray with handholds that are ergonomically (anatomically) designed, in order to provide greater comfort and safety for the operator, so that the product located on the tray receives better treatment during the handling of the tray. The design of these handholds includes a series of protective strips or ridges, which make the handholds more resistant to damage caused by dragging, thereby considerably increasing the useful lifetime of the trays.  
         [0011]     Another goal of the present invention is to provide trays with differentiated handholds that allow the operator to identify, rapidly and easily, the proper side for stacking, stowing, or nesting the trays, as desired, including doing so simply by touch.  
         [0012]     Yet another goal of the present invention is to provide the trays with a dual guide or groove in the base of the feet, similar to a so-called “shoe” or skate”, to provide better fitting and securing of the trays, thereby preventing them from becoming separated during rough or sudden movements while they are being stored or transported. The dual guide or groove is located along the length of the sides of the trays, so as to allow the feet to be displaced with greater safety, by preventing the trays from becoming separated or departing from their position during transport or handling, and also by preventing the feet of the tray from exerting a force that would deform the guide or groove, or even break it, because of the weight or overweight of the products that are received, held, transported, or lodged on the trays.  
         [0013]     Yet another goal of the present invention is to provide a stackable or nestable tray that can be positioned crosswise on another tray and that can be handled by a person with a disability or handicap. This goal is achieved through the novel design of the tray, as described below.  
         [0014]     Yet another goal of the present invention is to provide trays that are narrower (but without their narrowness being a limiting factor), that can be stacked on top of other trays that are wider, and that can also be combined or interleaved, in order to store products with smaller dimensions or different capacities.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a perspective view of the tray for transporting or storing articles or products according to the present invention.  
         [0016]      FIG. 2  is a top view of the same tray, showing pairs of different recesses in the corners.  
         [0017]      FIG. 3  is a bottom view of the same tray.  
         [0018]      FIG. 4  is a side view, from the right side, showing the distribution of the handholds, the arrangement of the feet for this side, and the chamfering of the various constituent elements of the tray.  
         [0019]      FIG. 5  is a left side view of the same tray, showing the handholds of the tray, one of which is ergonomic (anatomical) and the other two of which have different angles of inclination, and their feet.  
         [0020]      FIG. 6  is a front view of the same tray, showing the various male-female socket elements and the layout of the elements for stacking or nesting the trays, and the sliding guides or grooves. This view also shows a recess in the shape of a half-moon, located approximately in the center.  
         [0021]      FIG. 7  is a rear view of the same tray, showing the various male-female socket elements and the layout of the elements for stacking or nesting the trays, and the sliding guides or grooves. The recess in the shape of a half-moon, as shown in  FIG. 6 , is not included here.  
         [0022]      FIG. 8  is a view of two trays arranged crosswise in relation to a lower tray.  
         [0023]      FIG. 9  is a front view of two trays in the stacked position.  
         [0024]      FIG. 10  is an enlarged view of Section A in  FIG. 9 .  
         [0025]      FIG. 11  is a view of two trays in the nested position.  
         [0026]      FIG. 12  is an enlarged view of Section B in  FIG. 11 , showing the connection or assembly of two trays in the stacked position.  
         [0027]      FIG. 13  is a perspective view of a second embodiment of the tray for transporting or storing articles or products according to the present invention.  
         [0028]      FIG. 14  is a front view showing the stacking of two trays according to the second embodiment on top of one tray according to the first embodiment.  
         [0029]      FIG. 15  is a perspective view of a third embodiment of the tray for transporting or storing articles or products according to the present invention.  
         [0030]      FIG. 16  is a front view showing the stacking of one tray according to the first embodiment on top of two trays according to the third embodiment.  
         [0031]      FIG. 17  is a view of an insert that can be installed opposite one of the sides of reduced height of the tray. 
     
    
     DETAILED DESCRIPTION  
       [0032]     With reference now to the figures,  FIG. 1  shows how the receptacle, container, or tray ( 1 ) is designed in a manner similar to a box, including two sides of reduced height ( 2 ), which have, on the inside of two of their corners, slots or recesses (C) for receiving or mating with a vertical structural element or rod, and two sides of greater height ( 3 ), and a floor element ( 4 ) that may have various different design patterns, or no patterns, or which may be perforated or uniformly solid, as desired, although it is preferably perforated, so as to allow ventilation when the products consist, for example, of perishable items, bread, etc. The sides of greater height have sliding elements in order to allow the sliding of an upper tray to be stacked, recesses, and coupling elements (D) (two on each side), in which feet are seated so as to allow an upper tray to be nested or stowed (see  FIGS. 8, 9 , and  11 ), thereby providing spaces of different heights, depending on the required orientation of the trays in order to store products of different heights, thereby enabling optimal use of the system for the safe and flexible placement of large or small products. The foregoing arrangement is also advantageous when towers of trays are created. These sides of greater height also include retention elements (not shown) to prevent the undesired sliding of the upper tray.  
         [0033]     As also shown in  FIG. 1 , the receptacle, container, or tray according to the present invention has two handholds or grips ( 5 ) at the center of each side of greater height ( 3 ), which can be referred to as the point of equilibrium of the tray, which are built and reinforced with vertical ribs and reinforcements ( 6 ), spaced apart from each other so as to create a comfortable virtual gripping surface that allows the tray to be grasped safely at the center of its body.  
         [0034]     These vertical ribs and reinforcements ( 6 ) significantly increase the mechanical strength of the cross-section of the handholds, thereby preventing the handhold from being deformed or even broken if the trays are pulled by a hook, either individually or in the form of towers, which is an extremely common practice in working yards. The approximate weight that can be supported by the tray according to the present invention, when located at the bottom of a tower of trays, before it is deformed or breaks, is approximately 410 to 420 kg.  
         [0035]     The handholds ( 5 ) are differentiated from each other by their lower silhouette ( 7 ) (this is the surface that faces the flat surface on which the products are loaded; see  FIGS. 4 and 5 ), which is where the palms of the hands are placed. One has a series of horizontal waves, against which the figures can comfortably be placed, and the other is a convex curved line that simply receives the fingers and the palm of the hand. This way, the direction of the trays can be determined and oriented simply by touch; i.e., the operator can tell immediately whether the tray in question can be “stacked” or “nested” on top of another tray located immediately below it. During the working day, it is very important for a user or operator to have trays with this configuration, because they significantly facilitate his task and minimize the possibility of error through the incorrect placement of a tray in relation to the tray immediately below it.  
         [0036]     It should be noted that all of the internal lines ( 8 ) where the floor joins the sides and the corners are slightly rounded ( FIG. 1  shows only three of them) so as to allow better cleaning of the tray (because product wastes, grease, or dust would very often remain trapped in the corners if the corners consisted entirely of right angles), and to avoid the concentration of stresses.  
         [0037]     The structural elements ( 9 ) are designed to strengthen the tray and to conserve the amount of material used in the construction of the tray. It should be understood that multiple configurations of the structural elements ( 9 ) are possible.  
         [0038]     The tray ( 1 ) has four handholds, one at each end of each side of greater height ( 3 ) (the trays available on the market have none). Two of them are approximately vertical ( 11 ) and are located very close to the edge, thereby allowing the user to identify, by touch, the side of the tray (that is, whether the tray is oriented in position to be stowed or stacked), and also to grasp the tray safely, comfortably, and easily, particularly when the tray must be lifted above the head of the user or operator, while the other two handholds are angled ( 12 ).  
         [0039]     Because of their angle of attack, these inclined handholds ( 12 ) help the operator to differentiate and distinguish the orientation of the tray with respect to the tray immediately below it on which it will be placed, thus making it possible to determine whether in this direction the tray ( 1 ) should be stowed or else nested on top of a lower tray (see  FIGS. 9 and 11 ).  
         [0040]     Because of their angle, the inclined handholds ( 12 ) provide better support for the tray and its contents, help provide an appropriate lever arm when the trays are stowed or nested above the operator&#39;s eye level; allow sufficient force to be applied; and support the tray in cantilevered form during a maneuver in which a tray must be held by its ends and simultaneously aligned with another tray. This design of the handholds is also useful when trays must be handled in areas other than work yards or factory facilities (because trays often need to be loaded into, and repositioned inside, transport vehicles) and in areas that customarily have a limited amount of working room, which further complicates the tasks of stowing and nesting the trays (for example, inside a freight truck or a mini-van).  
         [0041]      FIG. 2  shows recesses or female sockets (D) located on each side of greater height ( 3 ), near the approximately vertical handholds ( 11 ), so that the single ( 14 ) and compound ( 15 ) feet (see  FIG. 3 ) are seated as male elements in the nested position. Each side of greater height of the tray has a sliding element or dual grooves ( 13 ) that serves as a slider or support for the single ( 14 ) and/or compound ( 15 ) feet (see  FIG. 3 ) for the stacked position) of an upper tray. The single ( 14 ) feet have a portion that is recessed far enough to support them and allow them to slide, freely and safely, on the lower tray. One of the sides of reduced height ( 2 ) has a series of holes ( 16 ) intended to receive an insert consisting of a plastic part ( 17 ) (not shown).  
         [0042]      FIG. 3  shows the recessed portion of the single feet ( 14 ) and the recesses or slots formed in the compound feet ( 15 ), to allow them to slide on the sliding element or dual grooves ( 13 ). Multiple holes are located at intervals in order to allow waste materials to fall out. The narrow portion is taller than the broad portion, so as to allow the trays to be transported or lifted by a hoisting device, such as a freight lift.  
         [0043]      FIGS. 4 and 5  show the spatial arrangement of the handholds at the equilibrium point ( 5 ), the vertical handholds ( 11 ), and the inclined handholds ( 12 ).  FIG. 4  shows, in greater detail, the silhouette ( 7 ) of one embodiment of the handholds ( 5 ), which corresponds to the one with a convex curved line, against which the fingers and the palm of the hand simply rest for comfortable handling of the tray.  FIG. 5  shows, in greater detail, the silhouette ( 7 ) of another embodiment of the handholds ( 5 ), which corresponds to the one with undulations against which the fingers and the palm of the hand are comfortably placed. All of the corners that may come into contact with the user-operator are chamfered or rounded, to prevent injury to the body of the user-operator. The lower portion of the space formed by the handholds at the equilibrium point is rounded for better distribution of the weight stresses applied to the tray.  
         [0044]      FIG. 6  shows two vertical structural elements or rods ( 18 ) that serve as supporting legs and act as position indicators, which, in addition to being located in a hollow or groove that receives them (not shown), also join, firmly and safely, the two trays in question. These vertical structural elements or rods ( 18 ) are located on one of the sides of reduced height ( 2 ) that include the holes ( 16 ) (see  FIG. 2 ). In a preferred embodiment, these elements are not intended to serve as load-bearing supports, but only as position indicators or coupling guides.  
         [0045]     When the trays are “nested”, these vertical structural elements serve as a basic guide that, in addition to anchoring and positioning both of the trays (see  FIG. 8 ), also have a locking effect that joins the corners ( 4 ) when the trays are nested, thereby preventing deformation, abrasion, or even “pancaking”, if the trays collapse onto each other. The vertical structural element ( 18 ) is seated or nested in an internal slot or recess (C) (see  FIG. 10 ), which is located next to the compound feet ( 15 ).  
         [0046]      FIG. 6  also shows the sliding element or dual grooves ( 13 ), in the upper portion, as well as the compound feet ( 15 ) and the protuberances ( 20 ) which, in the stacked position, receive the vertical structural element ( 18 ) and can also provide support for it. This figure also shows a recess ( 22 ) in the shape of a half-moon that includes ribs or reinforcements ( 21 ) for receiving an insert, which is preferably made of plastic ( 17 ) (see  FIG. 17 ).  
         [0000]     Operation of the Dual-Guide or Dual-Groove System  
         [0047]     Four feet (in groups of two) are located on the sides of reduced height of the tray. These feet are different from each other in that two of them, which are located directly below the vertical groove of a side, serve as guide, support, and retaining elements. They form a set of dual and parallel shoes or skates, which, when they slide along the guides, serve first as a guide for maintaining the proper direction of the displacement of the upper tray when this tray is placed on top of a lower tray in order to be “stowed”.  
         [0048]     These shoes or skates thus serve as buttresses, and take the load of the weight of the tray that is sliding on top of the tray immediately below it. The same thing also occurs with the single shoes or skates of the other two feet.  
         [0049]     These dual shoes or skates also serve as limiting retention elements that prevent the deformation of the sides of the trays by “anchoring” and supporting them, and also prevent any unintended displacement, through a locking effect between the external shoe or skate and the internal rail. The foregoing mechanism is supplemented by the dual guide, which consists of two long and parallel elements, between and on which the above-mentioned shoes or skates act and interact.  
         [0050]     Located along the length of the hollow formed by the rails are small “unidirectional lugs” (not shown on the drawings) which allow displacement only in one direction, thereby locking the feet in position once they have reached the end of their travel path.  
         [0051]     The rear feet (i.e., the two that are located directly below the inclined handholds) play a role that is similar and complementary to that of the front feet, except that these feet are single instead of dual, inasmuch as, by being seated in their respective housings, they indicate when the trays are properly nested.  
         [0052]     The heights and depths with which all of these elements have been designed are such as to ensure their stability, because they cannot be loosened or “bounced” out of their channels as the result of an undesired jolt, such as one caused by a pothole in a road or by rough-surfaced highways.  
         [0053]     A further aim of the above-mentioned design is to ensure that the operator will be able to position the delivery, easily and rapidly, and ensure the smooth, continuous, and safe displacement of the parts of the tray that he is placing, in relation to the lower one, and also to ensure that it will be very difficult for multiple trays to be bounced apart or loosened, thereby causing breakage and loss of the product.  
         [0054]      FIG. 7  is a view similar to the one in  FIG. 6 , with the exception that this side has no holes ( 16 ) and no recess for inserting an insert ( 17 ) (see  FIG. 17 ).  
         [0055]      FIG. 8  shows a system or assembly of trays ( 10 ) in which the upper trays are arranged crosswise in relation to the lower tray. The upper trays are in the stacked position. It should be noted that, in order to prevent the upper tray from sliding when it is in the crosswise position, the lower part of the tray includes protuberances (not shown) that serve as a stop or as a movement-restriction element.  
         [0056]      FIG. 9  shows a system or assembly of trays ( 10 ) in the stacked position, showing how the vertical structural element ( 18 ) rests on the protuberance ( 20 ), and the single feet ( 14 ) (not shown) and the compound feet ( 15 ) (not shown) mate with the sliding element or groove ( 13 ). This position increases the useful height for storing or transporting products.  
         [0057]      FIG. 10  shows an enlarged view of the recess that serves as a support for the vertical structural element ( 18 ) in the stacked position, and the location of the protuberance ( 20 ).  
         [0058]      FIG. 11  shows two trays in the nested position, which can easily be identified by the position of the recess for the plastic insert (on the lower tray) in relation to the upper tray. This figure also shows the mating or seating of the structural element or rod ( 18 ) in a slot or recess (C) (see  FIG. 1 ), which is located at the front of the tray.  
         [0059]      FIG. 12  shows an enlarged view of the structural element ( 18 ) seated in the slot (C), and one of the single feet ( 14 ), likewise seated in its respective recess or female socket (D).  
         [0060]      FIGS. 13 and 14  reflect a second embodiment of the receptacle, container, or tray according to the present invention, and the stowing of two trays according to this second embodiment, referred to below as a longitudinal tray ( 100 ), on top of a tray ( 10 ), respectively, in which the parts that correspond to those in the first embodiment are designated by similar or identical reference numbers. It should be noted that in this case, the stowing may begin by taking two longitudinal trays as a base. During stowing, the placement of the trays may be combined, i.e., starting with two longitudinal trays and one tray according to the first embodiment, then “n” stacked trays (“n” being one or a plurality of trays), followed by the stowing of more longitudinal trays.  
         [0061]      FIGS. 15 and 16  reflect a third embodiment of the receptacle, container, or tray according to the present invention, referred to below as a transverse tray ( 100 ′), and the stowing of a tray ( 10 ) according to the first embodiment on top of two transverse trays ( 100 ′), respectively, in which the parts that correspond to those in the first embodiment are designated by similar or identical reference numbers. It should be noted that in this case, the stowing may begin by taking two transverse trays ( 100 ′) as a base in order to place on top of them a tray according to the first embodiment; however, transverse trays cannot be placed on top of trays according to the first embodiment.  
         [0062]      FIG. 17  shows an insert ( 17 ) that helps to differentiate and identify the direction of the trays. This insert is a part with a half-moon shape ( 23 ) that is inserted, first mechanically and then with the aid of heat, in the recess ( 22 ) (see  FIG. 6 ). The upper part has rods or protuberances ( 24 ). These rods are positioned for insertion in the holes ( 16 ) (see  FIG. 2 ), provided specifically to receive them, that are located in one of the sides of reduced height. This arrangement is helpful in that, when a tray is viewed from above, its position in relation to the other trays can be determined. Similarly, when a tower of trays is viewed from the front, the position of the tray can be determined. This insert may also include trademarks, logos, distinctive symbols, etc. on its front surface.  
         [0063]     The design of the receptacles or containers or trays allows uniform working distances to be maintained when the receptacles or containers or trays are oriented differently in relation to one another. Thus, when the layout of the trays in relation to each other is changed, the separation between the trays does not affect or change the useful storage space that must be provided, which always remains the same. The foregoing observation is important because it enables confident planning of the arrangement and distribution of objects or products to be transported and stored, because when the useful available space is guaranteed, and when it is known that this space will not change, the planning for the distribution and storage of the products can be done beforehand.  
         [0064]     Another important characteristic of the tray according to the present invention is the increased load capacity, which is achieved through the proper reinforcement and distribution of the ribs that form part of the structure of the four sides. The sides greater in height are the ones whose function is to bear the weight of the towers of trays full of products, and therefore have been designed such that, thanks to a system of ribs, they form a solid and rigid block that can support loads of up to 450 kg.  
         [0065]     Regarding the form and design of the four corners, the sides of reduced height have been joined to the sides of greater height, thereby forming individual angles and joints that allow the corners to support loads of up to 250 kg, as well as the pulling loads applied during dragging, of up to 450 kg.  
         [0066]     As mentioned above, the tray includes sides of reduced height that are modified by a broad curve that forms a wide window between the trays, when they are stacked or stowed, thereby allowing the contents of each tray to be viewed easily, with no need to raise them or lift them apart from each other in order to look inside them.  
         [0067]     Although all of the fundamental characteristics and features of the present invention have been described here, with reference to specific embodiments of the invention, a degree of latitude in terms of other modifications, changes, and substitutions may be made in the foregoing description, and it will be apparent that on certain occasions, some of the characteristics of the invention will be employed without the corresponding use of other characteristics, without thereby departing from the scope of the invention as established. It should be understood that any such substitutions, modifications, or variations may be made by those skilled in the art without departing from the spirit or scope of the invention. Consequently, all modifications and variations are included within the scope of the invention, as defined by the following claims.