Patent ID: 7240771

Claim:
A multistage mast assembly for use on a lift truck, said mast assembly comprising: a first mast section slidably fixable relative to the truck, and extendible between a retracted position and an extended position; at least one first hydraulic actuator having an extendible ram fixed to said first mast section, wherein actuation of said first hydraulic actuator extends said ram to slidably move said first mast section between said retracted position and said extended position; a second mast section slidably fixed relative to said first mast section, and extendible between a retracted position and an extended position; at least one second hydraulic actuator fixed relative to said first mast section, and having an extendible ram fixed relative to said second mast section, wherein actuation of said at least one second hydraulic actuator extends said at least one second hydraulic actuator ram to slidably move said second mast section relative to said first mast section; a hydraulic supply line; a first hydraulic line supplying hydraulic fluid from said hydraulic supply line to said at least one second hydraulic actuator; a second hydraulic line in parallel with said first hydraulic line, and supplying hydraulic fluid from said hydraulic supply line to said at least one first hydraulic actuator; and a multi-position valve controlling hydraulic fluid flowing through said first hydraulic line, and having an open position and a restricted flow position, wherein hydraulic fluid flows from said supply line through said first hydraulic line to said at least one second hydraulic actuator to slidably move said second mast section relative to said first mast section when said valve is in the open position, and hydraulic fluid pressure in said first hydraulic line increases to divert hydraulic fluid from said hydraulic supply line into said second hydraulic line to actuate said at least one first hydraulic actuator and begin slidably moving said first mast section toward said first mast section extended position prior to said second mast section reaching said second mast section extended position when said valve is shifted to said restricted flow position before said second mast section reaches said second mast section extended position.