Derrick

Claim 1

IN A PORTABLE-TYPE DERRICK HAVING AN EXTENSIBLE BOOM, SAID BOOM COMPRISING A STATIONARY INNER TUBULAR SECTION AND AN OUTER TUBULAR SECTION HAVING GUIDE MEANS DISPOSED INTERIORLY THEREOF AND FIXED TO SAID OUTER TUBULAR SECTION, SAID OUTER TUBULAR SECTION DISPOSED IN TELESCOPIC COACTING ENGAGEMENT INTERIORLY OF SAID INNER TUBULAR SECTION FOR VARYING THE EFFECTIVE LENGTH OF SAID BOOM, MEANS ON SAID BOOM MOUNTING AN ASSOCIATED WORK MECHANISM, AN INNER CAPSULE SECTION MOUNTED GENERALLY STATIONARY INTERIORLY OF SIAD INNER TUBULAR BOOM SECTION, AN OUTER CAPSULE SECTION MOUNTED WITHIN AND DISPOSED FOR SLIDING MOVEMENT WITHIN THE GUIDE MEANS INTERIORLY OF SAID OUTER TUBULAR BOOM SECTION, ONE END OF SAID OUTER CAPSULE SECTION ENCOMPASSING THE ASSOCIATED END OF SAID INNER CAPSULE SECTION FOR TELESCOPIC COACTING MOVEMENT LENGTHWISE OF SAID INNER CAPSULE SECTION UPON MOVEMENT OF SAID OUTER TUBULART SECTION A RECIPROCAL MOTOR MEANS COUPLED TO SAID INNER TUBULAR SECTION AND TO SAID GUIDE MEANS FOR SELECTIVE EXTENSION AND RETRACTION OF SAID OUTER TUBULAR BOOM END CAPSULE SECTION, AND A PRETENSIONED COILED CONDUIT DISPOSED INTERIORLY OF SAID INNER AND OUTER CAPSULE SECTIONS FOR RESILIENT EXTENSION AND RETRACTION UPON ACTUATION OF SAID MOTOR MEANS, SAID CONDUIT PROJECTING FROM ONE TO END OF SAID INNER CAPSULE SECTION AND CONNECTED AT THE OTHER OF PRESSURIZED OPERATING FLUID, AND CONNECTED AT THE OTHER END TO SAID MECHANISM.