Heat transmitting tubes having helical fin means

Claim 1

IN ASSEMBLED COMBINATION, A HEAT TRANSFER TUBE AND MEANS PROVIDING AN EXTENDED SURFACE HEAT TRANSFER FIN STRUCTURE ON SAID TUBE COMPRISING A PREFORMED LONGITUTINALLY FOLDED METALLIC STRIP WOUND SUBSTANTIALLY HELICALLY EDGEWISE UPON AND ALONG SAID TUBE, SAID STRIP HAVING A SPACED SERIES OF CONTINUOUS SLOTS EXTENDING PARTLY ACROSS ITS WIDTH TO FORM A NUMBER OF SPACED FLAT FINGERS THAT IN THE FOLDED FIN STRUCTURE HAVE FREE INNER ENDS AND ARE INTEGRALLY INTERCONNECTED AT THEIR OUTER ENDS BY A LONGITUDINALLY CONTINUOUS PORTION, SAID STRIP BEING SO FOLDED AS TO PROVIDE AT THE INNER END OF EACH FINGER AND ANGULARLY EXTENDING RELATIVELY FLAT BASE PORTION THAT IS ATTACHED TO THE PERIPHERY OF SAID TUBE, AND MEANS SECURING SAID FREE INNER ENDS OF SAID FINGERS ALONG THE PERIPHERY OF SAID TUBE WHEREBY THE FIN STRUCTURE COMPRISES RADIALLY EXTENDING CIRCUMFERENTIALLY SPACED FLAT FINGERS INTERCONNECTED BY A LONGITUDINALLY CONTINUOUS OUTER EDGE PORTION WITH SAID SLOTS BEING CONTINUOUSLY OPEN SUBSTANTIALLY BETWEEN SAID TUBE AND SAID OUTER EDGE PORTION.