It is appreciated that a plurality of support joist assemblies 52 may be attached to opposing rails underneath tonneau cover 2 as shown in FIG. 1. As demonstrated, spaced apart support joist assemblies 52, underneath tonneau cover 2, will distribute and support the load of additional weight placed on top of tonneau cover 2. In certain embodiments, the top of support joist 54 may be slightly spaced apart from the underside of tonneau cover 2. This is until sufficient weight is applied to tonneau cover 2 at which point support joist 54 will support that additional load along with tonneau cover 2 itself. Illustratively, one or more foam pads or other like dampening materials may be applied to the top surface of support joist 54 to prevent rattling between the underside of tonneau cover 2 and support joist assembly 52 while the vehicle is in motion.

The sectional views of tonneau cover 2, shown in FIGS. 3 and 4, further illustrate how support joist 54 is fitted in joist hangers 56, which are supported by rails 4 and 6. Support joist 54 fits into a pocket 66 in joist hanger 56. Pocket 66 has an open top which allows support joist 54 to be placed in joist hanger 56 from the top of same. Illustratively extending from each side of the joist hangers 56 are tab flanges 58 that fit in rail channel 68 of either or both rails 4 and 6. Fasteners 62 may be used to secure tab flanges 58 onto rail channel 68. It is appreciated that other securement means may be used to attach joist hanger 56 to the rails, such as welding mechanical fasteners securing to both the joist hanger and the rail, or other like attachment structures.

Another illustrative embodiment of the present disclosure provides an extension panel 70 that extends the width (or length) of tonneau cover 2, but with support inserts 72 that are affixed to extension panel 70. Perspective views of a tonneau cover 74 are shown in FIGS. 8 and 9 that include an extension panel assembly 76 composed of the extension panel 70 and opposing support inserts 72 located on each side of same. The perspective view of tonneau cover 74, in FIG. 8, depicts extension panel assembly 76 spaced apart from tonneau cover 74. Here, it is appreciated that extension panel assembly 76 may be fully removed from tonneau cover 74. Extension panel assembly 76 may be stowed at a different location while tonneau cover 74 may otherwise operate as normal. An illustrative insert 78 may extend from a leading edge 80 of the extension panel. Insert 78 may be received in insert slot 82 in tailgate panel 84 (see FIG. 10) to align extension panel assembly 76 with respect to tonneau cover 74. This also mitigates a potential for a pinch point between the extension and tailgate panels.

The perspective view of tonneau cover 74, shown in FIG. 9, includes extension panel assembly 76 coupled to tonneau cover 74. It is appreciated from this view that tonneau cover 74 is now extended by virtue of extension panel assembly 76 to a longer length. When extension panel assembly 76 is no longer needed, it can be pulled from tonneau cover 74. Posts 86 (see FIG. 8) are removed from corresponding receivers 88 (see FIG. 10) on rails 90 and 92 similar to that described in the prior embodiments. Extension panel assembly 76, once removed, may be stowed separately from tonneau cover 74.

Underside detail views of a rear portion of tonneau cover 74 are shown in FIGS. 10 and 11. The view in FIG. 10 depicts extension panel 70 fitted adjacent the tailgate panel 84 to extend tonneau cover 74. Post 86 of support insert 72 is fitted in receiver 88. This view demonstrates how support insert 72 may be secured to extension panel 70. As shown, fasteners 94 may illustratively be employed to secure support insert 72 to extension panel 70. Further, illustratively, insert slot 82 may be formed at the rear periphery of rear frame member 96 of tailgate panel 84. Insert 78 may be part of a front frame member 98 of extension panel 70 and configured to at least partially be fitted in insert slot 82 of tailgate panel 84. It is appreciated that the insert 78 and insert slot 82 may be part of the extrusion of their respective frame members.

The underside perspective detail view of tonneau cover 74, shown in FIG. 11, is similar to that shown in FIG. 10, except with extension panel assembly 76 removed from tailgate panel 84. As depicted, post 86 is removed from receiver 88 and insert 78 removed from insert slot 82. Support insert 72 is, however, still attached to extension panel 70 via fasteners 94. It is appreciated that, alternatively, support insert 72 may be attached to extension panel 70 by other means, such as welding an integrally formed extrusion to end caps, adhesives, etc. With the extension panel assembly 76 removed, tailgate panel 84 may be unlatched and operate conventionally.

Another illustrative embodiment of the present disclosure includes a removable extension panel assembly. In this embodiment, like the prior embodiment, the extension panel is removable from the tailgate panel. A telescoping receiver includes a support extension that extends from the rail to provide support to the extension panel. An insert on the extension panel, similar to the prior embodiment, selectively fits in an insert slot at the rear extrusion of the tailgate panel (see FIG. 14).

Underside detail perspective views of a rear portion of a tonneau cover 100 are shown in FIGS. 12, 13, and 14. These views depict the structures of a removable extension panel assembly 102 in operation. The underside detail perspective view of tonneau cover 100, shown in FIG. 12, includes extension panel 104 separated from tailgate panel 106. A telescoping receiver 108 is shown attached to rail 110 with a support extension 114 recessed back on a receiver base 116. Tonneau cover 100, including tailgate panel 106, may operate as normal with respect to latching and unlatching tonneau cover 100. A support channel 118 is shown located underneath extension panel 104. Support channel 118 is configured to receive a portion of support extension 114 to carry the load applied to extension panel 104 when used with tonneau cover 100.

The underside perspective detail view of the rear portion of tonneau cover 100 is shown in FIG. 13. Here, extension panel 104 is still separated from tailgate panel 106. Support extension 114 is moved outward with respect to receiver base