Connector for tubular frame members

In combination with a tube connector fitting for interconnecting substantially square open-ended tubes each having an interior defined by two pairs of orthogonally related parallel flat surfaces spaced apart a given distance, said tube connector fitting comprising a hub portion having tube-receiving projections extending in different directions from said hub portion, said hub portion forming tube end abutment surfaces immediately about the points said tube-receiving projections extend from said hub portion, each of said tube-receiving projections having diametrically opposed portions of maximum spacing which fit loosely within said square tube in one angular position of insertion into the tube and frictionally engaged the interior surfaces of said tube when the inserted connector fitting or tube receiving the same is rotated 45.degree. therefrom, each of said tube-receiving projections having diametrically opposed portions of lesser spacing between said diametrically opposed portions of maximum spacing which portions of lesser spacing provide clearance for the passage of internally projecting flexible resilient locking means on one of the square tubes when the tube connector fitting has said one angular position of insertion with respect thereto, and grooves formed in and extending transversely of the longitudinal axes of said tube-receiving projections which grooves are defined by recessed radially outwardly facing surfaces which at their outermost margins intersect radially outwardly extending tube projection locking shoulders, said grooves being in axial alignment with said diametrically opposed projection portions of maximum spacing, said recessed radially outwardly extending groove surfaces being spaced a greater distance from the center of the associated tube-receiving projections than the portions thereof between said recessed groove surfaces, to form locking projection deforming means when forced against the outer side surfaces of said resilient locking means of one of said tubes upon said 45.degree. rotation of the same;

• the improvement comprising open-ended square tubes inserted over said connector fitting projections, each of said square tubes having adjacent the opposite ends thereof inwardly projecting flexible resilient tongues extending longitudinally away from the adjacent tube axes and each of which present at each side thereof facing transversely of the longitudinal axis of the tube curved surfaces either of which is engagable by said recessed radially facing groove surface of said fitting when the tube is inserted fully over a fitting projection, each tongue having a length to extend somewhat beyond the point of the connector fitting projection adjacent to where the associated groove-formed locking shoulder is located when the tube is in said fully inserted position so that the adjacent groove surface engages one of said curved surfaces of the adjacent tongue and inwardly deforms and shortens axially said tongue to cause it to enter the adjacent connector fitting projection groove and resiliently engage said groove-forming locking shoulder thereof when the connector fitting or tube is rotated 45.degree. to bring the tube and connector fitting into their frictionally engaging positions, the entry of the tongue into the groove drawing the connector fitting and tube axially together to bring the end of the tube into abutment with said tube end abutment surface of the connector fitting hub portion.