Ceiling grid system with interlocked joints

Claim 1

In sub-ceiling grid apparatus: laterally spaced inverted Tbar main runners; laterally spaced inverted T-bar interconnecting runners crossing said main runners and adapted to be supported by said main runners; said T-bar runners including lower horizontal flanges; a main runner splice between adjacent end portions of aligned main runner sections; an intersecting runner splice between adjacent end portions of aligned intersecting runner sections; each main runner splice comprising a first planar Lshaped lower portion of a first main runner section having an upwardly extending first lug, a second planar L-shaped upper portion of a second adjacent main runner section having a downwardly extending second lug interlocked with said first lug to interconnect said first and second main runner sections in alignment with each other; said second lug being spaced from an opposed vertical surface in said first section to provide a first vertical slot extending upwardly from said first L-shaped lower portion and opening upwardly through an upper terminal surface of said main runner splice; each intersecting runner splice comprising a third planar L-shaped lower portion of a third intersecting runner section having an upwardly extending third lug, a fourth planar L-shaped upper portion of a fourth adjacent intersecting runner section having a downwardly extending fourth lug interlocked with said third lug to interconnect said third and fourth intersecting runner sections in alignment with each other; said third L-shaped lower portion having a second vertical slot opening downwardly through a lower terminal surface of said intersecting runner splice; whereby relative vertical shifting of said main and intersecting runners toward each other places said intersecting runner splice in said first vertical slot and said main runner splice in said second vertical slot with said main runner splice straddling said third and fourth intersecting runner sections and said intersecting runner splice straddling said first and second main runner sections to retain said first and second lugs interlocked and said third and fourth lugs interlocked; the lower horizontal flanges of one of said runners being removed at its splice to enable such lower flanges to be disposed on opposite sides of and coplanar with the lower horizontal flanges of the other of said runners at its splice.