Patent ID: 6883789

Claim:
A machine tool main spindle balancer of a machine tool with a main spindle unit, which is equipped with a main spindle to which a tool is mounted and an electric motor for driving said main spindle, and is driven up and down by means of an elevating mechanism, comprising: a gas spring, comprising a cylinder body filled with a compressed gas and a rod that extends from the inside of said cylinder body downward, and is arranged in a vertical position to support said main spindle unit to reduce the load of said elevating mechanism, wherein said cylinder body has a head-side end wall member and a rod-side end wall member that hermetically seal a compressed gas, said head-side end wall member having a filling valve for filling the compressed gas, said rod-side end wall member having a sleeve member that constitutes a circumferential wall around a rod insertion hole, said sleeve member being hermetically and detachably mounted on said rod-side end wall member, and said sleeve member also being provided with annular sealing members for sealing between said sleeve member and said rod, and, wherein said sleeve member can be removed after removing said filling valve for discharging the compressed gas in the cylinder body and then holding said rod in place with a bolt inserted through a filling valve mounting hole provided on said head-side end wall member, on an upper end of said rod.