Dock levelling units

Claim 1

IN A DOCK LEVELLING UNIT: A RECTANGULAR OPEN FRAMEWORK HINGE SUPPORTING ONE SIDE OF A NORMALLY HORIZONTAL RAMP PLATE THEREIN; AN ARM HAVING ONE END THEREOF PIVOTALLY MOUNTED ON SAID FRAMEWORK; A LINK HAVING ONE END THEREOF PIVOTED TO SAID ARM AND THE OTHER END OF THEREOF PIVOTED TO SAID RAMP PLATE; ADJUSTABLE SPRING MEANS BETWEEN THE OPPOSITE END OF SAID ARM AND SAID FRAMEWORK FOR NORMALLY AND RESILIENTLY PIVOTING SAID ARM AND RAISING THE OPPOSITE SIDE OF SAID RAMP PLATE ON THE HINGE SUPPORT THEREOF; A PAIR OF RUB BARS HAVING OPPOSITE ENDS OF EACH CONNECTING SAID FRAMEWORK WITH SAID RAMP PLATE; A CAM PIVOTALLY MOUNTED ON ONE OF SAID BARS AND NORMALLY CLAMPING SAID BARS TOGETHER TO FRICTIONALLY RESIST THE ELEVATIONAL MOVEMENT OF SAID RAMP PLATE; A HORIZONTAL DOG HAVING ONE END THEREOF PIVOTALLY SUPPORTED ON THE FRAMEWORK AND THE OTHER END THEREOF SUPPORTED ON THE FRAMEWORK LUG; A FLAP MEMBER HINGED TO THE OUTER SIDE OF SAID RAMP PLATE FOR SUSPENSION THEREFROM; A BEAK-SHAPED PLATE ON SAID FLAP MEMBER NORMALLY RESTING ON SAID DOG FOR SUPPORT OF THE OPPOSITE SIDE OF SAID RAMP PLATE, THE CURVED SURFACE OF SAID BEAK-SHAPED PLATE BEING ON ITS UPPER EDGE, MANUAL MEANS FOR RELEASING SAID CAM WHICH FRICTIONALLY CLAMPS SAID BARS, TO PERMIT RAISING SAID FLAP MEMBER IN RESPONSE TO UPWARD MOVEMENT OF SAID RAMP PLATE, MEANS FOR LOCKING SAID FLAP MEMBER IN RAISED POSITION RELATIVE TO SAID RAMP PLATE, SAID LOCKING MEANS BEING DE-ACTIVATED WHEN SAID FLAP MEMBER CONTACTS A TRUCK BED AS THE RAMP PLATE IS LOWERED, WHEREBY THE FLAP MEMBER WILL DROP WHEN SAID TRUCK BED IS WITHDRAWN; SAID BEAK-SHAPED PLATE ADAPTED TO SWING UNDER SAID DOG IN SAID LATTER FLAP MEMBER MOVEMENT, WHEN THE WITHDRAWN TRUCK BED IS LOWER THAN THE RAMP PLATE; AND SAID DOG LIFTABLE ON ITS PIVOTAL SUPPORT BY SAID BEAK-SHAPED PLATE TO CLEAR SAID PLATE THEREPAST IN THE EVEVATION OF THE RAMP PLATE.