Coupling for sheet metal conduits

Claim 1

A COUPLING FOR SHEET METAL CONDUITS INCLUDING A LONGITUDINALLY-SPLIT, SUBSTANTIALLY CYLINDRICAL SHEET METAL COLLAR NORMALLY SPRINGING OPEN TO A GREATER DIAMETER THAN THE CONDUITS TO BE JOINED, FIRST AND SECOND RADIALLY OUTWARDLY DIRECTED FLANGES ON THE COLLAR, ONE ADJACENT EACH LONGITUDINAL EDGE OF THE SPLIT, SAID FLANGES BEING PARALLEL AND PROVIDING MEANS TO BE GRIPPED BETWEEN THE FINGERS AND THUMB OF AN OPERATOR TO SQUEEZE THE COLLAR TO A SMALLER DIAMETER, A SHELF OF SUBSTANTIALLY THE SAME GAUGE, MATERIAL, AND LENGTH AS THE COLLAR AND ARCUATELY CURVED TO SUBSTANTIALLY THE SAME RADIUS AS THE COLLAR, MEANS SECURING ONE END OF THE SHELF UNDER SAID FIRST FLANGE ON THE COLLAR AND POSITIONING THE OTHER END OF THE SHELF TO SLIDE BENEATH SAID SECOND FLANGE AND THE COLLAR, SAID SHELF SECURING MEANS BEING SPACED APART A DISTANCE SUFFICIENT TO PROVIDE A RESILIENTLY DEFORMABLE SLOT BETWEEN THE SHELF AND THE END OF THE COLLAR ADJACENT SAID FIRST FLANGE TO PROVIDE ONE MEMBER OF A LATCH MEANS, A TONGUE ARCUATELY CURVED TO SUBSTANTIALLY THE SAME RADIUS AS THE COLLAR AND OF SUFFICIENTLY LESS AXIAL LENGTH THAN THE DISTANCE APART OF THE SHELF SECURING MEANS TO PASS BETWEEN THE COLLAR AND SHELF IN THE SLOT, MEANS SECURING ONE EDGE OF THE TONGUE TO THE COLLAR ADJACENT SAID SECOND FLANGE AND DIRECTING THE OTHER EDGE OF THE TONGUE TOWARDS THE SLOT, RADIALLY INWARDLY DIRECTED OFFSET MEANS PROVIDING A SECOND MEMBER OF A LATCH MEANS AND ON SAID OTHER EDGE OF THE TONGUE AND LOCKING BEHIND THE EDGE OF THE SHELF WHEN THE TONGUE IS STABBED THROUGH THE SLOT, SAID MEANS FORMING THE SECOND MEMBER OF A LATCH MEANS BEING SO CONSTRUCTED AND ARRANGED THAT THEY ENGAGE IN END TO END ENGAGEMENT WITH THE EDGE OF THE SHELF WHICH PROVIDES SAID ONE MEMBER OF THE LATCH MEANS.