Feedback torque limiter

A feedback torque limiter device for an actuator having an input shaft, output shaft and gear reduction for transmitting torque from the input shaft to the output shaft, the device comprising:

• an output torque sensor that senses actuator output torque downstream from the gear reduction;
• an input torque limiter that grounds additional torque from the input shaft when engaged, the input torque limiter comprising:
• an input ball ramp that receives torque from the input shaft of the actuator;
• a mating ball ramp that transmits torque and is connected to a feedback mechanism;
• balls that transfer torque from the input ball ramp to the mating ball ramp;
• springs to hold the input ball ramp, balls and mating ball ramp in contact;
• a friction disc set;
• a stationary disc set;
• and
• bolts connecting the stationary disc set to an actuator housing;
• wherein, the input torque limiter is engaged when the feedback mechanism has moved the mating ball ramp into contact with the rotating friction disc set and the stationary disc, and any torque from input shaft through input ball ramp, balls and mating ball ramp is grounded through the friction disc set and the stationary disc set into the housing by the bolts;
• and
• wherein the feedback mechanism engages the input torque limiter when the output torque sensed by the output torque sensor reaches a predetermined value.

An actuator comprising:

• an input shaft driven by a power drive unit;
• an output shaft;
• gear reduction for transmitting rotary motion from the input shaft to the output shaft;
• a housing;
• an output torque sensor that senses actuator output torque downstream from the gear reduction and comprising:
• a torque sensor input shaft that receives torque from the gear reduction;
• a piston that connects to a feedback mechanism;
• disc springs to provide a preload torque to the piston;
• a straight ball spline connecting the piston and the actuator output shaft to transmit torque from the piston to the output shaft through balls contained in the straight ball spline;
• and
• a helical ball spline connecting the piston and the torque sensor input shaft to react torque from the torque sensor input shaft, impart torque to the straight ball spline and impart an axial load on the disc springs;
• wherein when the torque through the helical ball spline exceeds the preload torque provided by the disc springs, the piston moves towards the disc springs;
• and
• an input torque limiter that grounds additional torque from the power drive unit into the housing when engaged;
• wherein the feedback mechanism engages the input torque limiter when the output torque sensed by the output torque sensor reaches a predetermined value.

A method of limiting torque through an actuator, the method comprising:

• receiving input torque at an input shaft;
• transmitting the input torque through a gear reduction to an output shaft;
• sensing actuator output torque downstream from the gear reduction using a torque sensor input shaft to receive torque from the gear reduction, a piston to receive torque from the torque sensor input shaft, and to transmit torque to the output shaft and connects to a feedback mechanism;
• and disc springs to provide a preload torque to the piston;
• engaging an input torque limiter when the output torque sensed reaches a predetermined value;
• and
• grounding additional torque when the input torque limiter is engaged.