What is a Linear Actuator?

An electric linear actuator converts the rotational motion of a motor into the linear motion of a rod that moves forwards and backwards, and which provides push and pull forces in those two directions. The actuator can be stopped at any time during its movement, although the maximum holding force must be considered.

A linear actuator can lift, tilt, push or pull objects using electric control. Industrial linear actuators are often used in hazardous environments or to manage heavy or extreme loads. Actuators are accurate, efficient and have a long lifetime.

The key components of an actuator are a motor, a reduction gear, lead screw, drive nut and push/pull tube. As the lead screw is rotated by the motor and gearbox, the drive nut extends and retracts the push pull tube which is then attached to the load.

Applications for an Electric Linear Actuator

Electric linear actuators are used in any applications that needs, safe and clean movement with accurate and smooth motion control. They are easy to install, and unlike hydraulic or pneumatic systems do not require liquids, tanks, hoses or pumps, not do they suffer oil leaks. They have long lifetimes with little or no maintenance.

They provide accurate variable control over position, acceleration and velocity.

Practical examples include the control of doors, valves, hatches and chutes; load management such as earth shoring or retention; control of hoppers and bulk storage; management of height and tilt, such as hospital beds and variable height workstations.

What is the difference between an Electric Actuator and a Pneumatic or Hydraulic Actuator?

Both pneumatic and hydraulic actuators use fluid or compressed air to push a ram backwards and forwards. An electric actuator uses a motor to drive a lead screw which converts rotary motion into linear motion. Electric Actuators can maintain full thrust with power off and will not consume power when not operating.

What is the difference between Static Load and Dynamic Load?

Static load, which is also called the holding load, is the force applied to the linear actuator when it is not in motion. Dynamic load, also known as working or lifting load, is the force applied to the linear actuator while it is in motion; or to put it another way, it is the force that can be applied to push or pull something.

What are the normal directions (vectors) for loads applied to Linear Actuators?

Electric linear actuators can be used to push or pull along the axis of the shaft and can provide tension or compression forces, or a combination of both. Eccentric and side loading should be avoided.

Are side loading and eccentric loading allowed for Linear Actuators?

Any force which is not applied along the axis (or centreline) of the screw shaft will have an element of that force which is perpendicular to the shaft. That side or radial loading, also called eccentric loading, should be avoided as it can cause binding, excessive wear and shorten the life of the linear actuator.

Are Linear Actuators available in different speeds and thrust Forces?

Linear actuators are available in a variety of linear speeds and Thrust Forces; these are usually designed in through a combination of motor speed and torque, gear box ratio and screw thread pitch.

What duty cycle can be expected of a Linear Actuator?

The duty cycle rating for a linear actuator is normally expressed as cycles per minute or percentage of the ‘on time’ (the ratio of on time to total time).

What type of mountings are available for Linear Actuators?

Trunnion mount, end swing pin, front flange mount, side flange mount.

Special mountings can also be designed to suit applications. Electric actuators can also be mounted in any orientation.

It is acceptable to run a Linear Actuator into a hard stop?

Generally, no. This can damage the internal screw or drive nut, can damage the gearbox, or can overload the motor.

Our linear actuators operate in a wide range of different industrial applications. We are typically the linear actuator solution of choice where durability, high forces and loads, and ability to perform in extreme environments are critical factors.

Industrial Sectors for Linear Actuators

Industrial Sectors:

• Quarrying and Aggregates
• Nuclear
• Ministry of Defence
• Maltings
• Iron, Steel & Glass Manufacture
• Railways
• Mineral Processing
• Power Stations
• Coal/Mining Preparation
• Conveyors and Handling Systems
• Cement Manufacture
• Biomass Production and Handling
• Oil & Gas
• Sugar Processing
• Water Treatment
• Baggage Handling
• Ventilation Control
• Theatrical and Promotional Stage Back Drops and Equipment

Uses of Industrial Electric Linear Actuators

Within the sectors above you will find our industrial linear actuators used for a number of common functions:

Solids, Liquids & Powder Flow Control

• Conveyor systems
• Positioners and diverters
• Movement of screens & large debris screens
• Control of flaps and chutes
• Control of valves and gates
• Glass dosing equipment
• Sluice gate control
• Movement of screens & large debris screens
• Volume control

Air Flow and Ventilation Control

• Control of valves and vents
• Ventilation chutes
• Louvers and dampers
• Boiler and furnace dampers
• Weather / moisture and salt spray control
• Volume control
• Isolation and retention
• Smoke & fire dampers

Mechanical Handling

• Crane & grapple operation
• Control opening & closing of access doors
• Door interlocks
• Carriage locks
• Operation of remote windows, doors

Position control

• Control of trap doors, stage scenery and back drops
• Railway De-railers
• Railway Switch points
• Signalling control

Linear Actuator Glossary

Absolute accuracy

This is the maximum difference between the actual position and the desired position. It is affected by issues such as backlash, hysteresis, drift, nonlinearity of the drive or the measurement system, and mechanical distortion.

Backlash

Backlash is a positional error that is evident when reversing direction. Its causes are mechanical play in the drive train or by friction in the guiding system. Mechanical play is influenced by tolerances for components such as gearheads or bearings.

Several factors affect the amount of backlash, such as load, direction, temperature, acceleration and wear.

Bidirectional repeatability

The accuracy with which an actuator returns to a position after any change in position.

Power consumption

Maximum power consumption under full load.

Push/Pull force

Maximum force delivered by the actuator in the direction of motion.

Push/Pull Speed

Maximum speed at which the actuator can extend and retract.

Stroke

Distance between the fully extended actuator and fully retracted actuator; the maximum length of movement that the actuator can supply.

Motor Speed

Maximum rotational speed of the motor, expressed as rpm (revolutions per minute)

Motor Power

Maximum power consumed by the motor when the actuator is operating under full load.