Compensator and pressure limiting device

Claim 1

A COMPENSATOR AND PEAK PRESSURE LIMITING DEVICE FOR USE WITH A VARIABLE DISPLACEMENT PUMP IN A LOAD SENSITIVE HYDRAULIC SYSTEM COMPRISING, A HOUSING DEFINING A CYLINDRICAL OPENING, A PRESSURE COMPENSATOR SPOOL MOUNTED FOR RECIPROCAL MOVEMENT IN SAID CYLINDRICAL OPENING IN SAID HOUSING, SAID HOUSING DEFINING A SUMP PASSAGE, A COMPENSATOR PASSAGE FOR CONNECTION TO A PRESSURE COMPENSATOR PISTON ON SAID PUMP AND A PUMP PRESSURE PASSAGE FOR CONNECTION TO THE HIGH-PRESSURE SIDE OF SAID PUMP WITH SAID PASSAGES AXIALLY SPACED AND IN COMMUNICATION WITH SAID CYLINDRICAL OPENING, SAID HOUSING AND COMPENSATOR SPOOL DEFINING A PILOT PRESSURE CHAMBER RECEIVING A RESILIENT MEANS BIASING SAID COMPENSATOR SPOOL TO A POSITION PROVIDING COMMUNICATION BETWEEN SAID SUMP PASSAGE AND SAID COMPENSATOR PASSAGE FOR APPLYING SUMP PRESSURE TO THE COMPENSATOR PISTON, ORIFICE MEANS CONNECTING SAID PILOT PRESSURE CHAMBER TO SUMP, SAID PUMP PRESSURE PASSAGE TRANSMITTING PRESSURIZED FLUID FROM SAID PUMP TO BIAS SAID COMPENSATOR SPOOL AGAINST THE FORCE OF SAID BIASING MEANS TO PROVIDE COMMUNICATION BETWEEN SAID PUMP PRESSURE PASSAGE AND SAID COMPENSATOR PASSAGE FOR APPLYING PRESSURIZED FLUID TO THE PRESSURE COMPENSATOR PISTON, SAID HOUSING DEFINING A PILOT PRESSURE PASSAGE ADAPTED FOR CONNECTION TO A PILOT PRESSURE LINE IN SAID HYDRAULIC SYSTEM AND SAID PILOT PRESSURE CHAMBER, A PEAK PRESSURE LIMITING VALVE IN SAID PILOT PRESSURE PASSAGE, RESILIENT MEANS BIASING SAID PEAK PRESSURE LIMITING VALVE TO A NORMALLY OPEN POSITION PERMITTING COMMUNICATION BETWEEN THE PILOT PRESSURE LINE AND SAID PILOT PRESSURE CHAMBER, SAID LIMITING VALVE INTERRUPTING COMMUNICATION BETWEEN SAID PILOT LINE AND SAID PILOT PRESSURE CHAMBER WHEN THE PEAK PILOT PRESSURE REACHES A PREDETERMINED VALUE TO ALLOW PUMP PRESSURE TRANSMITTED THROUGH SAID PUMP PRESSURE PASSAGE TO BIAS SAID COMPENSATOR SPOOL FOR TRANSMISSION OF PUMP PRESSURE THROUGH SAID COMPENSATOR PASSAGE AND APPLY PUMP PRESSURE TO SAID COMPENSATOR PISTON AND THEREBY PREVENT THE PUMP FOR PRODUCING EXCESSIVE PRESSURE IN SAID HYDRAULIC SYSTEM.