A fastening device drives one or more fasteners into a workpiece. The fastening device generally includes a tool housing and a multistage solenoid having at least a first stage, a second stage and an armature member that travels therebetween. The multistage solenoid is contained within the tool housing....http://www.google.com.au/patents/US7537145?utm_source=gb-gplus-sharePatent US7537145 - Multistage solenoid fastening device
