A well test tool for closing a well at a downhole location below the well packer and near the formation to be tested, the apparatus being openable and closable from the surface by tensioning and relaxing the cable or wire line on which it is lowered into the well, the test tool having a lock mechanism...http://www.google.es/patents/US4583592?utm_source=gb-gplus-sharePatente US4583592 - Well test apparatus and methods
