Bidirectional drive coupling

In combination:

• rotatable input and output shafts coaxially positioned in an end-to-end relationship in which the ends are at least proximate to each other;
• a first rotary drive member fixed to the input shaft and coaxially rotatable therewith, the drive member being positioned on the input shaft at least proximate the output shaft;
• second and third rotary drive members positioned to each side of the first drive member, the second drive member being carried on the input shaft and the third drive member being carried on the output shaft, each being axially movable to engage the first drive member, adjacent portions of the first drive member and the second and third drive members being provided with cooperating means for forming a driving-driven relationship when either of the second or third drive members is axially moved into contact with the first drive member thereby causing rotation of the second or third drive member by the first drive member upon its rotation;
• means for selectively placing the second and third drive members into individual contact with the first drive member and for placing both of the second and third drive members out of contact with the first drive member;
• two rotary gears, one gear being adjacent a side of the second drive member opposite the side which contacts the first drive member, and being in a substantially axially fixed position on the input shaft, the other gear being adjacent a side of the third drive member opposite the side which contacts the third drive member, and being substantially axially fixed on the output shaft, the one gear being rotatable on the input shaft and the other gear being fixedly attached to the output shaft for rotation therewith, the gears and second and third drive members forming two drive member-adjacent gear pairs;
• a plurality of complementary, radially distributed, overlapping helical camming surfaces on adjacent portions of the second and third drive members and the gears, the surfaces extending between each drive member-gear pair to drivingly couple them together for rotation, the complementary driving helical surfaces of one drive member-gear pair being opposite handed relative to those of the other drive member-gear pair, the camming surfaces of each pair being in mutual overlapping relationship over the complete range of axial movement of the respective second or third drive members whereby contact and rotation of either the second or third drive member with the first drive member causes rotation of the respective adjacently coupled gear through driving engagement between the corresponding complementary camming surfaces and the driving engagement of the camming surfaces urges the second and third drive member axially toward the drive member for more positive contact therewith while continuing to rotate the adjacent gear, and
• gear means interconnecting the two rotary gears whereby rotation of the gear on the input shaft causes rotation of the gear on the output shaft.