Compressor with rotation detecting mechanism

A compressor comprising a casing including a plurality of casing members hermetically fastened by a plurality of fastening means having a portion inside and a portion outside of the casing;

• means for introducing a fluid to be compressed into the compressor;
• means for collecting a compressed fluid and passing the compressed fluid from the compressor and compressing means comprising means for compressing a fluid a drive shaft inserted into the casing for rotation therein and operatively connected to a drive source by means of a magnetic clutch, said drive shaft having arranged thereon and magnetically coupled thereto a rotatable member having a periphery for rotation with said drive shaft, said drive shaft and rotatable member comprised at least partly of a ferromagnetic material and said means for compressing the fluid operatively arranged with said drive shaft, the improvement which comprises:
• forming a non-uniform magnetic field at the periphery of the rotatable member comprising magnetic flux leaking from the magnetic clutch along the drive shaft to said rotatable member, said rotatable member being arranged to form a magnetic circuit with the portion of the fastening means inside the casing, a magnetic flux detecting means arranged outside the casing near the portion of said fastening means outslide of the casing whereby said magnetic flux detecting means detects the magnetic flux at the portion of the fastening means outside the casing, said magnetic flux changing with rotation of said rotatable member and means for receiving a signal from said flux detecting means for determining rotation of the rotatable member from the changes in the magnetic flux.