Abstract: A releasable ribbon locking device is used to keep a ribbon taut in a typewriter ribbon cartridge. The device includes a locking member carrying a blade or brake urged by a spring into abutting relationship with a rotatable ribbon supply support to prevent unwinding of fresh ribbon from the supply. A lock release member is movably coupled to the locking member and supports a ribbon tensioning element in engagement with a portion of the ribbon extending from the ribbon supply. In operation, a ribbon feed mechanism pulls on the ribbon which moves the lock release member through the tensioning element and correspondingly moves the locking member to rotatably free the ribbon supply support from abutment with the brake and allows the ribbon to unwind from the supply.