A balancing system for different compressors utilizes a counterweight having a common exterior configuration. The mass of the counterweight is optimized for each compressor by changing the size of a recess located in the counterweight. In one embodiment, the recess is an arcuately shaped recess; and...http://www.google.com.hk/patents/US20080219872?utm_source=gb-gplus-share專利 US20080219872 - SCROLL MACHINE HAVING COUNTERWEIGHTS WITH CHANGEABLE CAVITY
