Manually operated modulation valve

Claim 1

IN A MANUALLU ADJUSTABLE VALVE FOR MODULATING HYDRAULIC PRESSURE WHEREIN THE VALVE IS HYDRAULICALLY DISPOSED BETWEEN A SOURCE OF HYDRAULIC FLUID AND A HYDRAULICALLY ACTUATED MECHANISM, THE COMBINATION COMPRISING; A VALVE SPOOL SLIDABLY DISPOSED IN A VALVE BORE, THE BORE HAVING AN OUTLET ORIFICE LEADING TO THE MECHANISM AND AN INLET ORIFICE LEADING TO THE SOURCE OF FLUID, SAID VALVE SPOOL HAVING AN EXTREME POSITION IN ONE DIRECTION IN WHICH SAID SPOOL DOES NOT OBSTRUCT FLUID FLOW FROM THE INLET TO OUTLET, AND AN EXTREME POSITION IN THE OTHER DIRECTION IN WHICH SAID SPOOL PREVENTS FLUID FLOW BETWEEN THE INLET AND OUTLET; A VALVE SPRING DISPOSED TO ACT ON SAID VALVE SPOOL AND PROVIDE A FORCE URGING SAID VALVE SPOOL IN THE DIRECTION IN WHICH FLUID FLOW BETWEEN THE INLET AND OUTLET IS NOT OBSTRUCTED; MANUALLY ADJUSTABLE MEANS ASSOCIATED WITH SAID SPRING AND OPERATIVE TO VARY THE FORCE WHICH SAID SPRING APPLIES TO SAID SPOOL, SAID ADJUSTABLE MEANS HAVING THE REACTION FORCE OF SAID SPRING APPLIED THEREAGAINST WHEREBY SAID ADJUSTABLE MEANS IS POSITIONED TO CONDITION SAID SPRING TO APPLY THE MINIMUM FORCE TO SAID SPOOL IN THE ABSENCE OF MANUAL OPERATION OF SAID ADJUSTABLE MEANS; MEANS APPLYING THE PRESSURE AT THE OUTLET ORIFICE TO SAID SPOOL TO PROVIDE A FORCE WHICH ACTS AGAINST SAID SPRING AND URGES SAID SPOOL TO A POSITION IN WHICH FLUID FLOW BETWEEN THE INLET AND OUTLET IS BLOCKED WHEREBY THE PRESSURE IN THE OUTLET IS MAINTAINED AT A PRESSURE DEPENDENT UPON THE POSITION OF SAID ADJUSTABLE MEANS AND THE SPRING FORCE CREATED THEREBY; AND MEANS LOCKING SAID ADJUSTABLE MEANS IN POSITION AGAINST THE REACTION FORCE OF SAID SPRING ONLY WHEN SAID ADJUSTABLE MEANS IS URGED TO THE EXTREME POSITION WHICH CORRESPONDS TO A MAXIMUM FORCE BEING APPLIED TO SAID SPOOL BY SAID SPRING, SAID ADJUSTABLE MEANS OPERATING INDEPENDENTLY OF SAID LOCKING MEANS IN ALL OTHER POSITIONS.