Patent ID: 7140993

Claim:
An electro-hydraulic apparatus for a power transmission having a plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide six forward ratio ranges, said electro-hydraulic apparatus comprising: a supply of electrical power to activate said electro-hydraulic apparatus; first and second logic valves each positionable to a latched position and an unlatched position; first and second trim valve means for providing maximum output pressure when said electrical power is discontinued; third and fourth trim valves controlled by normally closed solenoid valves that have a minimum output pressure when said electrical power is discontinued; said trim valves and said logic valves cooperating to provide control of the torque-transmitting mechanisms to establish said six forward ratios wherein said first trim valve is effective to maintain said first logic valve in said latched position during the first, second, third, and fourth of said forward ratio ranges, said second trim valve is effective to maintain said second logic valve in said latched position during the fourth, fifth, and sixth forward ratio ranges; said first trim valve and said first logic valve being effective to maintain a first of said torque-transmitting mechanisms engaged during an electrical power discontinuance occurring in either said third or fourth ratio range, said second trim valve and said second logic valve being effective to maintain a second of said torque-transmitting mechanisms engaged during an electrical discontinuance occurring in said third ratio range, said second trim valve and said second logic valve being effective to maintain said second logic valve stroked and a third of said torque-transmitting mechanisms engaged during an electrical discontinuance occurring in said fourth ratio range, and said first trim valve, said first logic valve in said unlatched position, and said second logic valve in said latched condition cooperating to maintain said second torque-transmitting mechanism engaged during an electrical power discontinuance in said fifth ratio range; and said electro-hydraulic apparatus being effective to maintain the transmission in third ratio range in the event of an electrical discontinuance during operation in either said first, second, or third forward ratio range, in said fourth forward ratio range during an electrical discontinuance during operation in said fourth range, and in said fifth forward ratio range in the event of an electrical discontinuance during operation in either said fifth or sixth ratio range.