Multiple small-pitch helical drives in linear and rotary actuators

A rotary actuator, comprising:

• a housing, the housing including an output sleeve constrained against axial movement but free to rotate, the output sleeve having internal helical threads;
• a small pitch helical drive assembly housed in the barrel, the assembly having:
• a base plate;
• a rear plate spaced apart from the base plate;
• at least one drive screw having a head end extending through the base plate and a shank end rotatable against the rear plate, the at least one drive screw being constrained against axial movement, but free to rotate, the at least one drive screw having helical threads defining a small but appropriate pitch being capable to convert the relative rotation of the mating parts to each screws to the relative linear motion along the axis of the screws;
• an input drive mounted in the housing and operatively connected to the small pitch helical drive assembly, the input drive being adapted for connection to a source of rotation and configured for rotating the at least one drive screw;
• a piston having:
• a piston head assembly mounted on the at least one drive screw between the base plate and the rear plate, the piston head assembly having a pair of spaced end disks, each of the spaced end disks having at least one socket defining a passage through the end disk and a corresponding nut disposed in each of the sockets, the nut engaging the helical threads of the at least one drive screw, whereby the piston head moves linearly between the base plate and the rear plate when the at least one drive screw is rotated;
• and
• a piston body extending around the piston head, the piston body having large but appropriate pitch helical threads being capable to convert the linear motion of the engaging and mating internal threads of the output sleeve to relative rotation;
• and
• wherein helical pitch reduction between the small pitch of the at least one drive screw and the large pitch of the mating threads of the piston body and the output sleeve results in large output torque.

A rotary actuator, comprising:

• a linear actuator having a barrel and a piston extendable from the barrel and retractable into the barrel;
• an auxiliary sleeve having both internal threads and external threads, the auxiliary sleeve being mounted on the piston shaft;
• an output sleeve rotatably mounted on the auxiliary sleeve, the output sleeve having a plurality of rollers extending radially inside the output sleeve, the rollers engaging the external threads of the auxiliary sleeve;
• and
• external threads disposed on the barrel, the internal threads of the auxiliary sleeve engaging the external threads on the barrel when the piston shaft is retracted so that the output sleeve is rotated by action of the rollers on the auxiliary sleeve and by rotation of the auxiliary sleeve on the barrel.