noun
stairlift; chair lift for stairs
A mechanical device installed along a staircase to carry a person seated in a chair up and down the stairs, typically used in homes for elderly or disabled individuals.
祖母が足を悪くしたので、家の階段に階段昇降機を設置した。
Because my grandmother hurt her leg, we installed a stairlift on the stairs at home.
Compound of 階段 (stairs) + 昇降機 (elevator/lift). The term is a modern technical coinage.