INJURED HAD BEEN WORKING ON GENERATOR CHANGE OUTON DRAGLINE 80. HE RETURNED TO SHOP, TAKING TOOLBUCKET OUT OF TRUCK & CARRYING IT INTO SHOP, PLACING IT IN HIS LOCKER. HAD TO LIFT BUCKET ABOUT 3 1/2' TO SHELF IN LOCKER. FELT A LITTLE PULL INSHOULDER. WOKE UP ABOUT 3:OO AM WITH SEVERE PAININ RIGHT SHOULDER.