Patent Publication Number: US-2018050630-A1

Title: Captive beam system with rotating latch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the filing date under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/376,322, filed Aug. 17, 2016, and of U.S. Provisional Patent Application No. 62/469,941, filed Mar. 10, 2017, the entirety of which are each fully incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to captive beam systems for cargo compartments of trucks, aircraft, boats, railcars or fixed cargo compartments where the flexibility in the arrangement of beams for resting cargo thereupon is desired. 
     BRIEF SUMMARY 
     A first representative embodiment of the disclosure is provided. The disclosure provides a captive beam system. The system includes a beam assembly comprising a beam and slidably receiving a first channel unit at a first end of the beam and slidably receiving a second channel unit at a second end of the beam, the beam comprising a top surface that, when the captive beam system is installed, faces upward, wherein the top surface establishes a flat resting surface. Each of the first and second channel units comprise a first end and a second end, the second end slidably engages a respective first or second end of the beam, the first end of each channel unit extends away from the respective end of the beam, the first end of each channel unit supports a bracket and a pawl, the pawl is rotatable with respect to the first end of the channel unit. The pawl comprises a support surface that is configured, when the captive beam system is installed, to rest upon a bottom edge of an aperture disposed within a fixed track, wherein a vertical distance between the support surface and the flat resting surface of the beam is about 2.58 inches. 
     Another representative embodiment of the disclosure is provided. The embodiment includes a captive beam system. The captive beam system includes a set of supports comprising first and second tracks each extending between first end and a second end, the first and second tracks each configured for fixed attachment to walls of a container, the first and second tracks both comprising a race disposed therealong and extending from the first end at least to a position proximate to the second end of the respective support, and each of the first and second supports comprising a plurality of aligned apertures disposed through a center wall of the support with the plurality of apertures each comprising a bottom edge. A beam assembly comprises a beam and slidably receiving a first channel unit at a first end of the beam and slidably receiving a second channel unit at a second end of the beam, the beam comprising a top surface that, when the captive beam system is installed, faces upward, wherein the top surface establishes a flat resting surface. Each of the first and second channel units comprises a first end and a second end, the second end slidably engages a respective first or second end of the beam, the first end of each channel unit extends away from the respective end of the beam and engages a respective one of the first and second supports, the first end of each channel unit supports a bracket and a pawl, the pawl is rotatable with respect to the first end of the channel unit. The pawl comprises a support surface that is configured, when the captive beam system is installed, to rest upon the bottom edge of one of the plurality of apertures in the respective support, wherein a vertical distance between the support surface and the flat resting surface of the beam is about 2.58 inches. 
     Another embodiment of a captive beam system to be installed along at least one fixed track with at least one aperture with an upper edge and a bottom edge spaced apart from the upper edge and a long axis extending between the upper edge and the lower edge is disclosed. The beam system includes a beam assembly with a beam that slidably receives a first channel unit at a first end of the beam and slidably receives a second channel unit at a second end of the beam. The beam further includes a top surface that, when the captive beam system is installed, faces upward, wherein the top surface establishes a flat resting surface, and wherein each of the first channel unit and the second channel units includes a first end and a second end spaced apart from the first end. The second end of each of the first channel unit and the second channel unit slidably engages a respective first end and second end of the beam. A bracket is coupled to one of the first end of the first channel unit and the first end of the second channel unit. A pawl is configured to be rotatable with respect to the bracket. The pawl includes a support surface that is configured, when the captive beam system is installed, to rest upon the bottom edge of the at least one aperture. In addition, an upper latch is configured to be rotatable with respect to the bracket. The upper latch includes a first extension with a stop surface that is configured, when the captive beam is installed, to lie proximate to the upper edge of the at least one aperture so as to substantially prevent movement of the beam assembly in a direction along the long axis of the aperture. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of the disclosure, and be encompassed by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a beam assembly extending between vertical logistics tracks on opposite sides of a cargo compartment. 
         FIG. 2  is a side view of a channel unit of the beam assembly of  FIG. 1  extending from a track. 
         FIG. 3  is a top view of  FIG. 2 . 
         FIG. 4  is a front view of a portion of the track of  FIG. 1 . 
         FIG. 5  is a cross-sectional view of a beam of the beam assembly of  FIG. 1 . 
         FIG. 6  is a cross-sectional view of the track of  FIG. 4  about section A-A. 
         FIG. 6 a    is a cross-sectional view about section A-A of  FIG. 4  of an alternate track. 
         FIG. 7  is a perspective view of the channel unit of  FIG. 2 . 
         FIG. 8  is an exploded view of the channel unit of  FIG. 2 . 
         FIG. 9  is an exploded view of the bracket and pawl of the channel unit of  FIG. 2 . 
         FIG. 10  is a side view of the pawl of the channel unit of  FIG. 2 . 
         FIG. 11  is a side view of the pawl and the bracket pinned together, showing the hidden tab and the hidden spring biasing the pawl in the direction Z. 
         FIG. 12  is a detail view of detail A of  FIG. 5 . 
         FIG. 13  is a front view showing the beam assembly of  FIG. 1  disposed in a track neighboring a track that supports a conventional E-beam, with the beam assembly and the E-beam disposed upon apertures at the same height above the floor of the cargo compartment. 
         FIG. 14  is a perspective view of another embodiment of a bracket and a pawl in a latched configuration with a track for use with the beam assembly of  FIG. 1 . 
         FIG. 15  is a view of cross-section B-B of  FIG. 14 . 
         FIG. 16  is a perspective view of the bracket and the pawl of  FIG. 14  in an unlatched configuration. 
         FIG. 17  is a view of cross-section C-C of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION 
     Turning to  FIGS. 1-11  a captive beam system  10  is provided. The captive beam system  10  is configured to be installed within an enclosure, such as the cargo compartment of a truck, a railroad car, an aircraft, a boat, or upon other enclosures, such as shipping containers or the like. The captive beam system  10  can be disposed upon any structure with opposed vertical walls that are disposed in parallel to each other. While the captive beam system  10  can be successfully implemented in various different environments, the system will be described herein with respect to the cargo compartment of a conventional commercial semi-trailer. Any differences in the construction of the captive beam system for other environments will be specifically discussed herewithin. 
     The captive beam system  10  is configured to include a beam assembly  20  that is slidably received upon two opposed vertical tracks  100 , which are often referred to as logistics tracks. The beam assembly  20  includes a beam  40  that receives a channel unit  60  on one or both of the first and second ends  42 ,  44  of the beam assembly  40 . Each channel unit supports a bracket  80  that engages and rides within two or more races  126 ,  128  (or a single race) in the respective track, or vertical support  100 , and a pawl  70  that selectively engages an aperture  140  within the track  100  to fix the beam assembly  20  at a selected position with respect to the track  100 . 
     The track  100  may extend from the floor  1001  to the ceiling  1002  of a cargo compartment  1000 , or to a position proximal to one or both of the floor or ceiling. The track  100  may include a plurality of apertures  140  that are disposed at consisting spacing from neighboring apertures  140  along the entire length of the track, or in some embodiments, the spacing of neighboring apertures may be consistent along a portion of the length of the track  100 , or the apertures may be disposed upon the track in other arrangements that may be appropriate for positioning of a beam assembly  20  disposed thereon within the cargo container. For example, a long axis  141  of each aperture  140  is parallel and, optionally, coincident with a long axis of the track  100 . In other embodiments, however, a long axis of each aperture  140  may be aligned at an angle and, in some instances, perpendicular to, a long axis of the track  100  (not illustrated). Each of the apertures  140  in the track  140  may include a bottom edge  140   a,  which in some embodiments is disposed along the geometric bottom of the aperture  140 , while in other embodiments the bottom edge  140   a  may be along a portion of the geometric bottom of the aperture  140  but also along another portion of the aperture  140 . Alternatively, the bottom edge  140  may be disposed along another location of the aperture to support a tab  75  of a pawl  70 , such that the tab  75  is fixed to the aperture  140  as discussed below. Each aperture  140  also optionally includes an upper edge  140   b  spaced apart from the bottom edge  140   a.  In some embodiments, the upper edge  140   b  is disposed along the geometric top (i.e., closer to the ceiling  1002 ) of the aperture  140 , while in other embodiments the upper edge  140   b  may be along a portion of the geometric top of the aperture  140  but also along another portion of the aperture  140 . 
     In some embodiments, the entire length of the beam  40  between its first and second ends  42 ,  44  is hollow ( FIG. 5 ), where in other embodiments one or both of the first and second ends  42 ,  44  of the beam  40  is hollow, with remaining portions of the beam either being of solid cross-section, or including internal structural features, such as ribs, to provide for additional strength of the beam  40 . In other embodiments, one or both of the first and second ends  42 ,  44  of the beam includes an alignment feature that allows for engagement of a corresponding alignment feature upon the respective channel unit  60  to allow the channel unit  60  to rigidly support the beam  40  but to also allow relative longitudinal sliding between the beam  40  and the channel unit  60 , with the result that the overall length of the beam assembly  20  changes as the beam  40  and channel unit  60  slide with respect to each other. This allows the overall length of the beam assembly  20  to change, such as when one channel unit  60  is slid upwardly or downwardly upon its track  100  with the other channel unit  60  remaining in a fixed position upon the opposite track  100 . In embodiments where the beam  40  is hollow and the first ends  62  of the channel units  60  extend within the respective hollow beam  40 , the channel units  60  and the beam  40  can slide with respect to each other. 
     In some embodiments, the one or both of the hollow first and second ends  42 ,  44  a second end  64  of a channel unit  60  is telescopingly received within the respective hollow end portion  42 ,  44  of the beam. In this embodiment, the channel unit  60  may include an elongate slot  65  disposed through one or both right and left side walls, with the end portion  42 ,  44  of the beam including an aperture upon one or both of the rights and left side walls of the beam, with a fastener  49  that extends therethrough. This arrangement maintains a connection between the beam  40  and the channel unit  60  yet allows freedom for longitudinal, telescoping sliding therebetween to allow for the overall length of the beam assembly  20  to change, such as to allow one end of the beam assembly to be moved up or down the vertical support  100  that the channel unit  60  is connected to while the other end of the beam assembly remains stationary upon its vertical support  100 . 
     The beam  40  is best shown in  FIG. 5 . The beam  40  includes a top surface  46  that faces upward (i.e. toward the ceiling of the cargo container when the beam is installed and is positioned horizontally) and a flat resting surface  45  that extends along at least a majority of the length of the beam  40  and in some embodiments the entire length of the beam between the first and second ends  42 ,  44 . The flat resting surface  45  is the surface upon which cargo that rests upon the beam  40  engages. In some embodiments, the flat resting surface  45  may be a planar surface, while in other embodiments, the flat resting surface  45  may have features thereon, such as a roughened surface such as to increase friction between the cargo resting upon the beam  40  and the flat resting surface  45  to minimize relative movement, or for other reasons, such as to increase strength, reduce weight, or to maximize a strength to weight ratio of the beam  40 . 
     In some embodiments depicted in  FIGS. 5 and 12 , the flat resting surface  45  may include a collective planar surface formed by a plurality of formations upon the beam  40 , which may also include a plurality of other formations that are disposed upon the top surface  46  that do not contribute to the flat resting surface  45 , such as a plurality of recessed surfaces that drop below the flat resting surface  45 . The beam  40  may include a plurality of parallel ridges  45   a,  the tops of which are each aligned and collectively form the flat resting surface  45  and a plurality of valleys  45   b  between the ridges  45   a.  In some embodiments, the ridges  45   a  and valleys  45   b  extend along the length of the beam  40  between the first and second ends  42 ,  44  such that the beam  40  may be extruded with these features. In other embodiments, the ridges  45   a  and valleys  45   b  (or other structures) may be oriented in other positions or directions relative to the length of the beam  40 , such as perpendicular or at an acute or obtuse angle with respect to the longitudinal axis  40   a  of the beam  40 . 
     In some embodiments, the flat resting surface  45  may extend across the entire top surface  46  of the beam  40 , while in other embodiments the flat resting surface  45  may extend only upon a portion of the top surface  46  of the beam  40 , with other portions of the top surface  46  of the beam surrounding the flat resting surface  45 , such as disposed outboard on one or both sides of the beam  40 . In some embodiments the other portions (that do not form or contribute to the flat resting surface  45 ) may be outboard of the flat resting surface  45  proximate to one or both ends  42 ,  44  of the beam. The remaining top surface may be aligned at a constant height (vertically below the flat resting surface  45 ) or in other embodiments the remaining top surface may extend to different heights and or with different geometries, surface finishes, materials, and the like. 
     The beam  40  may additionally include opposed right and left side surfaces  47 ,  48  that each extend from opposite right and left side edges  45   c,    45   d  of the flat resting surface  45  (or edges of the top surface  46 ). In some embodiments, the right and left side surfaces  47 ,  48  may extend directly from the respective right and left side edges  45   c  ( FIG. 12 ),  45   d , such that the two surfaces form a perpendicular angle with respect to each other. In embodiments, wherein the top surface  46  of the beam  40  includes surfaces  45   e  outboard of the flat resting surface  45 , the opposed right and left side surfaces  47 ,  48  may form an edge with the portions of the top surface  45   e  disposed outboard of the flat resting surface  45 . The beam  40  may additionally include a bottom wall  50  that connects with one or both of the right and left surfaces  47 ,  48 . In some embodiments, the bottom wall  50  may be formed with same geometry and design (such as with the same materials, surface finish, etc.) as the top surface  46  of the beam (i.e. so that the beam forms a bottom flat resting surface, that is like the top flat resting surface) so that the beam  40  can be installed in either orientation, to allow for continued use of the beam  40  by flipping it over so that the initial bottom surface  50  is now oriented as the top surface (i.e. facing the ceiling of the container when horizontally aligned) if its original top flat resting surface  45  became marred or damaged by use. 
     The pawl  70  is rotatably attached to the channel unit  60  with a pin  90  that extends through an aperture  63  in the first end portion  62  of the channel unit  60 . In some embodiments, first end portion  62  of the channel unit  60  may have two extended portions of the respective right and left walls  66   a,    66   b  and the aperture  63  may extend through both of these extended walls. The pawl  70  is provided to be pivotable about the pin  90  and a spring  98  may be provided to bias the pawl  70  in a direction Z (as shown in  FIG. 11 ) such that the tab  75  of the pawl  70  is urged toward the track  100  and specifically (when properly aligned) within an aperture  140  within the track  100 . The pawl  70  may include an operator  72  that is disposed at the bottom of the pawl  70  and is configured to be manipulable by the user, either directly with the user&#39;s fingers or with a tool, to urge the pawl  70  to rotate in the opposite direction Y ( FIG. 11 ) which pulls the tab  75  away from the track  100  and specifically the aperture  140 . In some embodiments, the operator  72  is disposed at the bottom of the pawl  70 , and on an opposite side of the support surface (discussed below) from hole  71  through the pawl  70  that the pin  90  extends through. In other words, the operator  72  and the tab  75 , which includes the support surface  76 , move in the same direction as each other. In some embodiments, the pawl  70  is biased with respect to the channel unit  60  such that the operator  72  is biased away from the first end  62  of the channel unit  60 . 
     In some embodiments, the front of the tab  75  (i.e. the portion of the tab  75  that extends in a cantilevered fashion from the body of the pawl  70 ) may have a top surface  79  that is chamfered or angled such that the tab  75  is urged out of an aperture  140  when the bracket  80  and the pawl  70  is moved along the track  100  and the chamfered surface  79  comes into contact with the top edge  140   b  of an aperture  140 . 
     The tab  75  of the pawl  70  may include a support surface  76  that forms the bottom surface of the tab, and the support surface  76  engages a bottom edge  140   a  of the aperture  140  of the track  100  when the tab  75  extends within an aperture  140 . As shown in  FIG. 13 , when the tab  75  is aligned for extension within an aperture  140 , the support surface  76  is a predetermined vertical distance X from the flat resting surface  45  of the beam so that the flat resting surface  45  is at a predetermined vertical position with respect to the aperture  140  of the track. In some embodiments, this predetermined vertical distance is 2.58 inches. In other embodiments, the predetermined vertical distance is about 2.58 inches, with about defined to be plus or minus 0.25 inches from the distance specified. In other embodiments, this predetermined vertical distance X may be different when the beam assembly  20  is desired to be potentially used in conjunction with other types of beams (other than E-beam) as discussed below. 
     As shown in  FIG. 13 , the predetermined vertical distance X is established such that the flat resting surface  45  of the beam assembly  20  (when the beam  40  is aligned horizontally) is aligned along the same horizontal plane  3000  as the top surface of a conventional E-beam, when the E-beam is installed onto a neighboring track  100  within the cargo container and specifically aligned within an aperture  140  within the neighboring track that is at the same vertical position as the aperture  140  upon which the channel unit  60  is aligned with. In other embodiments where the captive beam system  10  could be used in conjunction with other conventional removable decking beam designs, and therefore the predetermined vertical distance X could be other values, based upon the design of the other conventional decking beam, and specifically the distance between the point of contact between the conventional beam and the support surface or aperture (e.g.  140 ) in the vertical logistics track, such that the conventional beam and the flat resting surface of the respective beam assembly would be aligned along the same horizontal plane. With a thorough review of this specification, one of ordinary skill in the art, who would be familiar with the standard dimensions of the conventional decking beam desired to be used would be able to construct the captive beam system such that the predetermined vertical distance X would provide for the flat resting surface  45  to be aligned along the same horizontal plane as the top surface of the conventional beam, without undue experimentation. 
     In some embodiments shown in  FIG. 13 , the cargo compartment  1000  includes an environment with a plurality of identical vertical tracks  100  disposed along the same wall, wherein at least two of the plurality of identical vertical tracks  100  are disposed such that a bottom edge  140   a  of an aperture  140  in the at least two vertical tracks is disposed at the same vertical height above a floor  1001  of an enclosure (as depicted by line  3002 ), such that when a conventional E-beam  2000  is engaged with the bottom edge  140   a  of the aperture  140  in a first of the at least two vertical tracks  100 , and the beam assembly  20  is disposed such that the support surface  76  of the pawl  70  is engaged with the bottom edge  140   a  of the aperture  140  in the second of the at least two vertical tracks  100 , a top surface  2002  of the E-beam is disposed along a horizontal plane  3000  with the flat resting surface  45  of the beam  40 . In some embodiments, the beam assembly  20  may be formed to be “low profile” such that the bottom surface  50  of the beam  40  is above the bottom surface  2009  of a conventional E-beam when positioned upon the same aperture  140  as the beam assembly  20  (as depicted as line  3001 ). 
     The bracket  80  may be attached to the channel unit with the pin  90  that pivotably supports the pawl  70 . The bracket  80  is rotatable with respect to the first end  62  of the channel unit  60  as well as the pawl  70 . As best shown in  FIGS. 8 and 11 , the bracket  80  may include a center member  84  and two or more feet  86 ,  88  that when positioned upon the track  100 , ride within the corresponding races  126 ,  128  of the track  100 , which aligns the bracket  80  and then therefore the channel unit  60  along the track  100  and allows the channel unit  60  to slide upward and downward along the track  100  until it reaches a desired position. In some embodiments, the feet  86 ,  88  extend away from each other and (when installed within the track  100 ) within opposite races  126 ,  128  that are on opposite sides of the track  100 . In embodiments where the track  100  only has a single race, the bracket  80  would also have only a single foot. As discussed above, when the channel unit  60  reaches the desired position, the tab  75  extends into the corresponding aperture  140  in the track and the support surface  76  rests upon the bottom edge  140   a  of the track that defines the aperture  140 . The center member  84  of the bracket  80  is a bearing surface that a spring  98  engages, as well as engaging a portion of the body of the pawl  70  to bias the tab  75  of the pawl  70  toward the track  100  and specifically within the aperture  140  when the channel unit  60  is aligned therewith. 
     Another embodiment of the captive beam systems include those with another embodiment of the bracket  180  and pawl  170  illustrated in  FIGS. 14-17  as will be discussed below. Unless otherwise identified expressly, the bracket  180  and pawl  170  is capable of being used with the track  100  as discussed above. Further, the bracket  180  and the pawl  170  optionally include any of the features of the bracket  80  and the pawl  70  described above even if those features are not expressly recited again below. 
     The bracket  180  includes a first side  180   a  and a second side  180   b  spaced apart from the first side  180   a  to form a channel  181  into which the pawl  170  is received. The first side  180   a  and the second side  180   b  are coupled together via a center member  184  and, optionally, a rear member  185  that is spaced apart and separated from the center member  184  by an opening  183 . The bracket  180  is configured to be coupled to the track  100  with the optional various structures and in the manner described above. 
     A hole (not labeled) through the first side  180   a  and the second side  180   b  is configured to receive a pin  190  that rotatably couples the pawl  170  to the bracket  180  and that rotatably couples the bracket  180  to the first end  62  of one of the channel units  60 . 
     The pawl  170  is configured to be rotatable with respect to the bracket  180  about the pin  190  that is inserted through the hole  171 . Similar to the pawl  70  discussed above, the pawl  170  includes a tab  175  with a support surface  176  that is configured when the captive beam system is installed to rest upon the bottom edge  140   a  of the at least one aperture  140  of the track  100 . 
     The pawl  170  also comprises an operator  172  similar in structure and operation to the operator  72  discussed above. The operator  172  is positioned in a spaced position from a support surface  176 , and on an opposite side of the support surface  176  from a position where the pawl  170  rotatably connects to the channel unit  60 . 
     The pawl  170  optionally includes an upper end  173  spaced apart from the operator  172 . The upper end  173  includes a recess  177  on a lower surface  174 . The recess  177  is configured to receive a central portion or body  192  of an upper latch  191  when the support surface  176  of the pawl  170  does not rest upon the lower edge  140   a  of the aperture  140  (i.e., when the pawl  170  is moved in the Y-direction as indicated in  FIG. 11  into its unlatched position; stated differently, the pawl  170  is positioned so as to permit the bracket  180  to be moved in a direction along the long axis  141 ). 
     A difference in the pawl  170  as compared to the pawl  70  is that the pawl  170  includes the upper latch  191  that, in some embodiments, is configured to interact with the pawl  170  and the track  100 . 
     The upper latch  191  is configured to be rotatable about an axis of rotation with respect to the bracket  180 . A pin  210  is configured to be received in a hole (not labeled) in the first side  180   a  and the second side  180   b  and through a hole  193  through the central portion or body  192  of the upper latch  191 . Thus, in some embodiments the pawl  171  and the upper latch  191  are rotatable relative to the bracket  180  around different axes of rotation. 
     The upper latch optionally includes a first extension  194  extending away from the central portion or body  192  along an axis  201 . The axis  201  may, in some embodiments, intersect the rotational axis or center of the hole  193 . The first extension  194  includes a stop surface  195  ( FIG. 17 ) that is configured, when the captive beam is installed, to lie proximate to the upper edge  140   b  of the at least one aperture  140  so as to substantially prevent movement of the beam assembly in a direction along the long axis  141  of the aperture  140 . In some instances, the stop surface  195  abuts the upper edge  140   b  while in others the stop surface  195  may simply lie proximate to the upper edge  140   b.  Regardless of the precise disposition of the stop surface  195  relative to the upper edge  140   b,  the stop surface  195  interacts with the upper edge  140   b  so as to prevent the beam assembly from moving more than 0.5 inches in a direction along the long axis  141  of the aperture  140  when the upper latch is in its latched position ( FIG. 17 ). Thus, the pawl  171  substantially prevents movement of the bracket  180  in either direction along the axis  141  by virtue of the support surface  176  resting upon the bottom edge  140   a  and the stop surface  195  interacting with the upper edge  140   b.    
     Optionally, the upper latch  191  includes a second extension  196  extending away from the central portion or body  192  along a second axis  197 . The second axis  196  intersects the first axis  201  of the first extension  194  at an angle  198 . The angle  198  may be acute, obtuse, or 90 degrees. 
     As with the pawl  70 , the pawl  170  includes a biasing mechanism  199  ( FIG. 17 ) coupled to one of the pawl  170  and the upper latch  191 . For example, the biasing mechanism  199  may be positioned between one of the center member  184  and the rear member  185  of the bracket  180  and one of the lower surface  174  of the pawl  170  and the second extension  196 . 
     In other embodiments, the biasing mechanism  198  may be a torsion spring coupled to the upper latch  191  that urges the upper latch  191  to rotate in a direction X. The rotation of the upper latch  191  in turn causes an engagement surface  200  of the second extension  196  to interact with a pawl engagement surface or pawl extension  178  of the pawl  170  and thereby urge the operator  172  to move in the direction Z ( FIG. 11 ). In other words, the upper latch  191  and the pawl  170  are rotatably coupled, i.e., as the upper latch  191  rotates about its axis of rotation the pawl  170  simultaneously rotates about its axis of rotation. 
     Regardless of the particular type and arrangement, the biasing mechanism  198  is configured to urge the operator  172  away from the channel unit  60  and towards the fixed track  100 . 
     The bracket  180  and the pawl  170  are configured to be moved along the track  100  much like the bracket  80  and pawl  70  as discussed above. When a user manipulates the operator  172  so that the support surface  176  no longer rests upon the lower edge  140   a  of the aperture  140 , the pawl engagement surface  178  interacts with the engagement surface  200  of the second extension  196  to rotate the upper latch  191  to its unlatched position ( FIG. 15 ). The rotation of the latch  191 , in turn, rotates the first extension  194  away from its proximate position near or adjacent to the upper edge  140   b  of the aperture  140 . Thus, with one movement of the operator  172 , the bracket  180  and the pawl  170  is now capable of being moved in either direction along the long axis  141  of the aperture  140 . 
     Alternatively, if the user only wishes to move bracket  180  and the pawl  170  upwards (i.e., in a direction along the long axis  141  towards the upper edge  140   b ), the user merely needs to apply sufficient force to overcome the force of the biasing mechanism  198 . More specifically, as the user moves the bracket  180  upwards, the upper edge  140   b  interacts with the stop surface  195  and, if sufficient force is applied to overcome the force of the biasing mechanism  198 , the upper latch  191  rotates about its rotational axis into its unlatched position. As the bracket  180  and pawl  170  move upwards along the axis  141  towards the upper edge  140   b,  the upper edge  140   b  next interacts with the chamfered surface  179  of the tab  175 , which in turn causes the pawl  170  to rotate about its axis of rotation. The track  100  would then keep the pawl  170  and the first extension  194  rotated as illustrated in  FIG. 15  until the pawl  170  and the first extension reach the next adjacent aperture  140 . Upon reaching the next aperture  140 , the force of the biasing mechanism  198  would urge the upper latch  191  to rotate in the direction X, which in turn would cause the pawl  170  to rotate, as discussed above, so that both the support surface  176  and the stop surface  195  can rest upon the bottom edge  140   a  and interact with the upper edge  140   b,  respectively, in their latched positions ( FIG. 17 ). The process then can be repeated for further movement of the bracket  180  and the pawl  170  in an upwards direction. 
     While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the disclosure is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the disclosure.