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LINEAR ACTUATORS This Duff-Norton product line of actuators features load capacities ranging from 27 pounds to 25 Tons, gear or belt driven, acme screw and ball screw systems with various AC and DC input voltages. Duff-Norton Linear Actuators are specially designed for a variety of commercial and industrial applications. These actuators are used for opening and closing, tilting and pivoting, lifting and lowering and positioning. Applications include gates, dampers, oven and processing tank doors, antennas, orthopedic tables and other medical equipment, ergonomic furniture, and agricultural equipment, etc. Custom designs are also available for special applications. Linear Actuators are now being used in place of pneumatics and hydraulics when high maintenance and environmental problems (leaking hydraulic oil) are a concern.
Axial Load

A load whose center of gravity runs though the axis of the actuator screw

Ball Brake

Used on smaller AC motor units, the ball brake is a bi-directional brake that limits drift when the unit is under a full load

Cantilever Mount

A pin mount where the pin is not Supported on both sides. Deflection of the pin can cause binding. This type of mount is unacceptable

Current Draw

Amount of current (amperes) required by a motor to move a load. It increases as the load increases


A complete sequence of extension and retraction by the actuator

Double Lead Screw

A double lead screw has two separate threads that wrap around the outside diameter of the screw. The advantage of this type of screw is the lifting nut will travel twice the distance with each single turn of the screw

Duty Cycle

Percentage of time an actuator is in motion relative to total time. Example: If the total running time for an actuator is 20 seconds in every minute, the duty cycle is 33%

Eccentric Load

A load whose center of gravity does not go through the screw axis. Off-center loads cause binding and shorten the actuators life

Extension/Retraction Rate

The speed at which an actuator extends and retracts. In DC models the speed can depend on the load


To move the actuator in short increments

Limit Switch

A device used to limit the extension or retraction of an actuator to a pre-set position


Material to be moved by the actuator

Overload Clutch

A built-in device that slips when the actuator reaches a predetermined load limit preventing damage to the unit

Peak Load

The maximum momentary load that an actuator can control

Pivot Mount

A clevis mount that allows the actuator to pivot while in operation


A device that provides position feedback information from an actuator

Restraining Torque

The amount of torque exerted on the brackets during operation

Screw Pitch

The screw pitch is the distance from a point on a screw thread to the equivalent point on an adjacent thread

Side Load

A load exerted on the side of the actuator housing or translating tube. Side loading can shorten the life of an actuator. Also called radial load

Spring Brake

A bi-directional no-back type brake that is automatically activated by pinion torsion and released when the motor turns

Spur Gear

A gear wheel with radial teeth parallel to its axis

Static Load

The maximum load an actuator can hold when not operating

Stroke Length

The total travel of the translating tube from retracted to fully extended

Tension Load

A load that pulls on the actuator along the axis of its screw

Translating Tube

The tube that extends in and out of the actuator

Wiper Seal

A seal between the actuator housing and the translating tube to keep contaminants out of the actuator. Also called a scraper seal