Methods for fabricating lightweight metal ladders

Claim 1

THE METHOD OF MAKING A LIGHWEIGHT METAL LADDER COMPRISING THE STEPS OF: (A) PROVIDING A HOLLOW CORRUGATED LADDER RUNG BY: (A) EXTRUDING A METAL TUBE THROUGH A CORRUGATED ANNULAR DIE; (B) NECKING THE ENDS OF SAID TUBE TO FORM SHOULDERS BETWEEN THE TUBULAR PORTION AND THE NECKED PORTIONS THEREOF, AND TAPERING THE NECK PORTIONS OUTWARDLY TO PROVIDE FRUSTO CONICAL PLUGS OF DECREASING DIAMETER OUTWARD OF SAID SHOULDERS; (B) PROVIDING LADDER SIDE RAILS BY: (A) FORMING THIN METAL CHANNELS HAVING FLAT WEB PORTIONS THERETO; (B) PUNCTURING THE WEB OF SAID RAILS TO FORM APERTURES AT EQUALLY SPACED INTERVALS THEREALONG; (C) SIMULTANEOUSLY CUPPING THE PERIPHERY OF SAID APERTURES TO FORM NORMALLY EXTENDING FLANGES SUBSTANTIALLY EQUAL IN INNER DIAMETER TO THE AVERAGE DIAMETER OF SAID PLUGS; (D) SIMULTANEOUSLY FORMING RUNG-SERRATION MATCHING SERRATIONS ON THE INNER SURFACE OF SAID FLANGES; AND (C) ASSEMBLING SAID LADDER BY: (A) FORCING THE PLUGS OF SAID RUNG INTO THE FLANGED SIDES OF THE APERTURES ON SAID SIDE RAILS UNTIL SAID SHOULDERS BOTTOM AGAINST THE ENDS OF SAID FLANGES TO ELASTICALLY DEFORM SAID FLANGES AND SAID PLUGS AND THEREBY FORMING TIGHT INTERFERENCE FITS THEREBETWEEN; AND (B) EXPANDING THE OUTER ENDS OF SAID PLUGS TO CONFORM TO THE SURFACES OF SAID FLANGE AND SAID WEB PORTION TO FIX SAID RUNGS AND SAID SIDE RAILS FIRMLY TOGETHER.

Claim 2

THE METHOD OF MAKING A LIGHWEIGHT METAL LADDER COMPRISING THE STEPS OF: (A) PROVIDING A HOLLOW CORRUGATED LADDER RUNG BY: (A) EXTRUDING A METAL TUBE THROUGH A CORRUGATED ANNULAR DIE; (B) NECKING THE ENDS OF SAID TUBE TO FORM SHOULDERS BETWEEN THE TUBULAR PORTION AND THE NECKED PORTIONS THEREOF, AND TAPERING THE NECK PORTIONS OUTWARDLY TO PROVIDE FRUSTO CONICAL PLUGS OF DECREASING DIAMETER OUTWARD OF SAID SHOULDERS; (B) PROVIDING LADDER SIDE RAILS BY: (A) FORMING THIN METAL CHANNELS HAVING FLAT WEB PORTIONS THERETO; (B) PUNCTURING THE WEB OF SAID RAILS TO FORM APERTURES AT EQUALLY SPACED INTERVALS THEREALONG; (C) SIMULTANEOUSLY CUPPING THE PERIPHERY OF SAID APERTURES TO FORM NORMALLY EXTENDING FLANGES SUBSTANTIALLY EQUAL IN INNER DIAMETER TO THE AVERAGE DIAMETER OF SAID PLUGS; (D) SIMULTANEOUSLY FORMING RUNG-SERRATION MATCHING SERRATIONS ON THE INNER SURFACE OF SAID FLANGES; AND (C) ASSEMBLING SAID LADDER BY: (A) FORCING THE PLUGS OF SAID RUNG INTO THE FLANGED SIDES OF THE APERTURES ON SAID SIDE RAILS UNTIL SAID SHOULDERS BOTTOM AGAINST THE ENDS OF SAID FLANGES TO ELASTICALLY DEFORM SAID FLANGES AND SAID PLUGS AND THEREBY FORMING TIGHT INTERFERENCE FITS THEREBETWEEN; AND (B) EXPANDING THE OUTER ENDS OF SAID PLUGS TO CONFORM TO THE SURFACES OF SAID FLANGE AND SAID WEB PORTION TO FIX SAID RUNGS AND SAID SIDE RAILS FIRMLY TOGETHER.