Key-shift transmission

Claim 1

A key-shift transmission which comprises a speed-change shaft, a plurality of speed-change gears rotatably mounted on said speed-change shaft, a shifter sleeve slidably mounted on said speed-change shaft, and shift keys co-slidably connected to said shifter sleeve and operable to couple said speed-change gears one at a time to said speed-change shaft, characterized in: that said speed-change shaft (15) is divided into a pair of trough-shaped shaft halves (15A) each having an arched inner surface which defines a part of a cylindrical bore extending axially through said speed-change shaft thereby the said shaft being formed into a hollow shaft, each of said shaft halves including a pair of flattened end surfaces which extend axially of each said shaft half at both sides of said inner surface, one of said end surfaces having thereon an axially elongated projection (19) and the other of said end surfaces having therein an axially elongated recess (20) of a depth smaller than the height of said projection, said pair of shaft halves being engaged to each other co-rotatably by fitting said projections of the respective shaft halves into said recesses of the respective shaft halves so as to form in an outer surface of said speed-change shaft a pair of elongated axial grooves (21) which are located radially outwardly of said elongated projections of the respective shaft halves and between said flattened end surfaces of the respective shaft halves; and that a pair of said shift keys (18) are disposed within said pair of elongated axial grooves (21).