Electro-hydraulic linear actuators withstand shock loads

Anders Karlsson, Product Specialist Linear Actuators for Thomson, says: "Specifying solutions for applications requiring high force in a compact space is now possible, while still realising the benefits of an electrically driven actuator. With our unique reservoir design and pump configuration, we have miniaturised a hydraulic system and embedded it into a package that is even smaller than a ball screw-style electromechanical system. The result is a compact, electro-hydraulic actuator rated for heavy loads and capable of withstanding large amounts of shock loading with fluid-powered actuation that cushions the actuator components."

Conventional hydraulic cylinder-based systems require a complex assembly of hoses, pumps, valves and reservoirs. This infrastructure can be costly to install, operate and maintain, and the fluid itself requires careful handling. Thomson Warner Linear H-Track actuators resolve this issue with a miniaturised hydraulic pump that is powered by a DC motor. The pump, cylinder and reservoir are a single unit that fits into a small housing about the size of a screw-type actuator. This hybrid actuator has a force rating of 21kN and can achieve travel speeds of nearly 100mm/s. Users can select between motors and pumps to optimise for higher load capacity or higher speed than can typically be attained with ball screw-based designs.

Using hydraulic power to create linear motion also has a cushioning effect that enables the system to absorb shock loads that might otherwise damage a ball screw or the extension tube, especially if the shock load occurred while the actuator was extended.

High configuration flexibility

The ability to configure multiple pump and cylinder sizes enables Thomson to create H-Track units with various speed and load capacities. Its exclusive pumping and reservoir architecture minimises components and optimises the volume/pressure differential. A patented split-tank shuttle valve with back pressure relief adds further efficiencies. Other H-Track features include:

• Bore and rod combinations that allow for multiple configurations
• Stroke lengths up to 406mm with solid rods allow for increased resistance to buckling
• A pin-to-pin length shorter than traditional electromechanical actuators
• Immunity to vibrational drifting; hydraulic self-locking
• Protection from load runaway by installing meter-out circuits on one or both sides of the actuator
• A cover-tube reservoir that cools the fluid
• A flexible lid on a vented, isolated reservoir that allows for actuator and pump operation in any orientation without entraining air or cavitation

The Thomson Warner Linear H-Track actuator is well suited for space-constrained applications that would usually use a screw-type actuator but would benefit from higher force handling, speeds or tolerance to shock loading. It is also suitable for applications that typically use hydraulic cylinders but in which the external pump and hose assemblies are consuming too much space or requiring too much maintenance. Typical H-Track applications include:

• Snowploughing - preventing bending of ball screw, extension tube or gearing if the plough collides with a hidden obstacle while the actuator is fully extended
• Agricultural plough depth control - controlling depth of blade penetration to optimise the placement of seeds from automatic seeders
• Larger agricultural sprayer transport - protecting from overload on actuators used to fold larger sprayer booms for transport
• Mower deck lifts - improving control of increasingly larger mower decks

Electro-hydraulic actuators are also being used in a wide variety of other applications as well, including turf care, lawn and gardening, marine hatch lifts, industrial pallet lifts, UTV tailgate locks and dump boxes, and construction quick-attach bucket releases.

In addition to providing strength and resilience, H-Track electro-hydraulic actuators are designed for use in challenging environments. They are sealed to eliminate leakage of hydraulic fluids. They are also rated IP67 and IP69K for static loads, IP65 for dynamic loads and for 500-hour salt spray resistance. Units have a wide operating temperature range of -40 to +82degC.

Thomson Warner Linear H-Track linear actuators are available immediately in stroke lengths of up to 406mm. Follow the link for more information oabout Thomson Warner Linear H-Track linear actuators.