Load-lifting structure with latch mechanism

Claim 1

IN AN INDUSTRIAL TRUCK HAVING AT LEAST TWO VERTICALLY DISPOSED TELESCOPIC MAST SECTIONS WITH ONE EXTENSIBLE IN AN UPWARD DIRECTION FROM THE OTHER, ELEVATABLE CARRIAGE MECHANISM AT THE BASE OF AND VERTICALLY SHIFTABLE ALONG SAID ONE SECTION, AND VERTICALLY SHIFTABLE HOIST MECHANISM CONNECTED TO AND FOR MOVING THE CARRIAGE MECHANISM, THE IMPROVEMENT COMPRISING MEANS OPERABLE DURING RAISING OF ONE OF SAID MECHANISMS TO MAINTAIN THE SEQUENCE OF FIRST MOVEMENT OF THE MECHANISM UPWARDLY RELATIVE TO SAID ONE SECTION AND THEN UPWARD MOVEMENT OF SAID ONE SECTION RELATIVE TO THE OTHER SECTION, AND OPERABLE ON RETURN OF THE MECHANISM TO MAINTAIN A REVERSE SEQUENCE, SAID MEANS COMPRISING A PAIR OF LATCH DEVICES MOUNTED ON SAID ONE SECTION IN AN INTERLOCKED POSITION, MEANS ON SAID OTHER SECTION OPERATED UPON BY SAID LATCH DEVICES WITH THE LATTER IN SUCH INTERLOCKED POSITION TO PREVENT MOVEMENT OF SAID ONE SECTION RELATIVE TO SAID OTHER SECTION, AND MEANS MOUNTED ON SAID ONE OF SAID MECHANISMS ENGAGEABLE WITH ONE OF SAID LATCH DEVICES ON POSITIONING OF SAID MECHANISM UPWARDLY ON SAID ONE SECTION AND OPERABLE ON ENGAGEMENT TO PRODUCE UNLOCKING OF THE DEVICES FROM EACH OTHER AND FREEING OF SAID ONE SECTION FOR MOVEMENT UPWARDLY ON THE OTHER SECTION, SAID MEANS ON SAID OTHER SECTION ENGAGING THE OTHER OF SAID LATCH DEVICES AND OPERATING TO PLACE THE LATCH DEVICES IN ANOTHER INTERLOCKED POSITION AFTER FREEING OF SAID ONE SECTION AND ON MOVEMENT OF SAID ONE SECTION UPWARDLY ON THE OTHER WITH THE LATCH DEVICES IN THIS LATTER POSITION THEN OPERATING ON SAID MEAINS ON SAID ONE OF SAID MECHANISMS TO PREVENT MOVEMENT OF SAID ONE SECTION RELATIVE TO SAID ONE OF SAID MECHANISMS.