A device for urging an output arm member in incremental rotary steps and an information storage device provided therewith

摘要

A device for urging an output arm member (12) in incremental rotary steps comprises a housing (11), a stepper motor (14) for driving a shaft (15), a first engagement member (1) having first engagement teeth of one angular size and a second engagement member (2) having second engagement teeth for detachable engagement with the first engagement teeth, the second engagement member being connected to the housing. A third engagement member (3) has third engagement teeth and is connected with the first engagement member such that the first and third engagement members move together. The third engagement teeth have a smaller or larger angular size than the angular size of the first engagement teeth. A fourth engagement member (4) is connected with the arm member (12) and has fourth engagement teeth for detachable engagement to the third engagement teeth. The fourth engagement member is engaged through reduction gearing so arranged and disposed to translate incremental rotation of the shaft (15) to increments substantially equal to the difference between the angular sizes of the first and second engagement teeth to the shaft. The arrangement is such that this engagement of the first and third engagement members from the second and fourth engagement members, respectively, allows the first and third engagement members to move in a rotary direction responsive to the shaft and re-engagement of the first and second engagement members to the third and fourth engagement members, respectively produces realignment of the third and fourth engagement teeth to an accuracy of the same order of magnitude as is the difference between the angular sizes of the first and second engagement teeth.