Cassette stem device

Claim 1

A CASSETTE FORM OF EXTENSIBLE AND RETRACTABLE STEM DEVICE ADAPTED TO BE DRIVEN DURING EXTENSION AND RETRACTION AND COMPRISING IN COMBINATION; AT LEAST ONE STEM STRIP OF A LENGTH AND WIDTH WHICH WHEN FREE DEFINES A TUBE HAVING A CONCAVE INNER SURFACE AND OF RELATIVELY SMALL DIAMETER AS COMPARED WITH ITS LENGTH THE SIDE EDGES OF SAID STRIP BEING OVERLAPPED THROUGHOUT THE LENGTH OF THE TUBE AND THE WIDTH OF SAID STRIP BEING GREATER THAN THREE TIMES THE DIAMETER OF THE TUBE DEFINED THEREBY; AN INNER CYLINDRICAL DRUM MEMBER HAVING AN AXIS OF ROTATION; MEANS ANCHORING ONE END OF SAID STRIP SUBSTANTIALLY TANGENTIALLY TO SAID DRUM MEMBER TO DISPOSE THE CONCAVE INNER SURFACE THEREOF OUTWARDLY AND ADAPTING THE FULL WIDTH OF SAID STRIP TO BE REELED UPON SAID DRUM IN FULL CONTACT OF THE CONVEX SURFACES OF SAID STRIP THEREWITH; ENCYCLIC RETAINING MEANS AT EACH END OF SAID DRUM CONTROLLING THE PATH OF MOTION OF THE STRIP REELED ON SAID DRUM THROUGH ABOUT 300 DEGREES OF ARC OF A PREDETERMINED RADIUS SUBSTANTIALLY GREATER THAN THE RADIUS OF SAID DRUM AND ON A TANGENT LINE FROM ONE END OF SAID ARC EXTENDING IN THE SAME TANGENT DIRECTION AS THE TANGENTIAL ANCHORAGE OF SAID STRIP TO SAID DRUM; A FORM ROLLER ENGAGEABLE WITH THE STRIP COILED BETWEEN SAID DRUM AND SAID ENCYCLIC MEANS AND LOCATED SUBSTANTIALLY AT THE POINT OF TANGENCY OF SAID TANGENT LINE WITH SAID ARC MEANS FOR DRIVING SAID DRUM FOR EXTENSION AND RETRACTION OF SAID STRIP AT THE SAME VELOCITY ON SAID LINE OF TANGENCY; AND A DOCTOR MEMBER SUBSTANTIALLY AT THE NIP OF TANGENCY OF SAID STRIP AND THE COILED STRIP WITHIN SAID ENCYCLIC RETAINING MEANS BETWEEN THE OTHER END OF SAID ARC AND SAID TANGENT LINE.