Dog Scares Off Armed RobberHAYWARD — An armed robber fled without a word from a Hayward service station late yesterday upon encountering a large German .Shepherd whose main duty is to scare robbers away.The robber fled from Ted^s Union 76 Station, 33 West Win-ton Ave., where the dog had bitten and scared off another would-be robber last year.Sheriff’s deputies said the attendant. Steven Montague, 18, saw the gunman enter a room in the station building about 9:45 p.m. The robber, realizing he would have to walk to another door to reach the cash register, pointed his gun at Montague until he reached the other door, and fled, seeing the dog eyeing him.Another attempted Hayward robbery was unknowingly foiled about 11 p.m. by a Seven-Eleven Market clerk who locked Ik* front door just as two masked robbers arrived.Police said the two men, one armed, shook the front door and pointed the pistol at clerk Greg Magario, 17, who refused tn open the store, at 2175 Aldengate Way.The robbers walked away and a short time later two men were arrested within a short distance of the store. Charged with attempted armed robbery were Manuel Trujillo, 21, 27737 Pensacola Way, Hayward, and William R. Patterson, who refused to give his address.Police said a witness earlier had seen two men walk to a car parked near the store and then leave on foot when the car refused to start. Two masks and a key fitting the car were found near where Ihe two men were arrested.