Coin-operated lock for a trolley system including especially shopping and luggage trolleys

A coin-operated lock adapted for installation on a trolley being part of a system of such trolleys, especially shopping and luggage trolleys, said lock being arranged for release of a secured trolley by insertion of a coin, and for repayment of the amount deposited when the trolley is returned, the lock having two blockable keyholes for accepting separate keys, one of which being anchored to the trolley on which the lock is mounted, the lock being further arranged so that when a coin is inserted, one keyhole is released for accepting and securing the said key anchored to the same trolley, so that the other keyhole secures a key belonging to another trolley or a coupling unit, so that the other keyhole--when the said key anchored to the same trolley is inserted in the former keyhole--is released for release of the other key, and so that the former keyhole is released for release of the said key secured therein and anchored to the same trolley and for repayment of the coin when the other key is inserted in the other keyhole, characterized in that keys (4) adapted for insertion into keyholes (2 and 3) have interacting blocking means (12) adapted as codification units (13, 14, 15, 16) which only permit insertion and withdrawal respectively of a key (4) if the code of this key fits together with the code of the other key so that only keys fitting together can be moved relative to each other for insertion and withdrawal purposes respectively.