Patent ID: 7162900

Claim:
A master key comprising: a key base including a key handle, a fixing seat connected to said key handle, and a sleeve connected to said fixing seat, said fixing seat having a plurality of angularly spaced apart spring holes, said sleeve having a sleeve wall projecting from said fixing seat in a direction away from said key handle; a key tube including a large cross-section tube section, and a small cross-section tube section, said small cross-section tube section being fixed to said fixing seat and surrounded by said spring holes, said large cross-section tube section being inserted into said sleeve, said large cross-section tube section including a front end opposite to said small cross-section tube section, and a plurality of long and short grooves that are spaced apart angularly on an outer surface of said large cross-section tube section and that extend from said front end toward said small cross-section tube section, said long grooves being aligned with said spring holes, respectively, said short grooves respectively defining shoulder faces facing said front end of said large cross-section tube section; a plurality of key springs disposed respectively within said spring holes; and a plurality of slide pieces disposed respectively and slidably within said long grooves and biased by said springs.