portion disposed at the cap 4 into a separate component and to couple it with the cap 4 by means such as push in welding etc the rest of the constructions of this embodiment are the same as those of the first embodiment therefore an explanation will be omitted fig4 shows an enlarged sectional view of a cap in a modified example of the second embodiment in the cap 4 shown in fig4 the first screw portion 4 e capable of coupling with the screw portion 3 d of the power cutoff member 3 is formed around the cap outer peripheral portion but means for coupling with the rotary shaft 5 of the compressor inside the cap 4 may be a spline structure 4 k in place of the screw in this embodiment the construction of this embodiment may be applied to the first embodiment referring to fig3 and 4 like reference numerals are used to identify like constituent elements as in the first embodiment shown in fig1 and 2 next the effects and operations of the embodiments described above will be explained the following effects can be expected by the power transmission apparatus according to the first embodiment of the invention in the power transmission apparatus having the power cutoff member torque limiter installed inside the hub the torque limiter can be operated at a desired torque by arranging the cap having the flange at the distal end portion of the rotary shaft of the compressor therefore in the power transmission apparatus having the torque limiter it becomes possible to eliminate the problems such as sinking of the.