Patent ID: 7222484

Claim:
A hydraulic system comprising: a supply conduit receiving fluid under pressure from a source; a return conduit for conveying fluid back to the source; a pressure relief passage; a first control valve connected to the supply conduit and the return conduit and having a first workport for connection to a first hydraulic actuator, wherein the first control valve has a first position in which the supply conduit is connected to the first workport and a second position in which the return conduit is connected to the first workport; a primary pressure relief valve limiting pressure in the supply conduit to less than a first pressure limit; a second control valve connected to the supply conduit and the return conduit and having a second workport for connection to a second hydraulic actuator, wherein the second control valve has a first position in which the supply conduit is connected to the second workport and a second position in which the return conduit is connected to the second workport, the second control valve having a first outlet port coupled to the pressure relief passage; a third control valve connected to the supply conduit and the return conduit and having a third workport for connection to a second hydraulic actuator, wherein the third control valve has a first position in which the supply conduit is connected to the third workport and a second position in which the return conduit is connected to the third workport, the third control valve having a second outlet port coupled to the pressure relief passage; and a secondary pressure relief valve connected to the pressure relief passage and limiting pressure that the second control valve applies to the second workport and the third control valve applies to the third workport to less than a second pressure limit.