“An important function of these actuators in steel plants is to open and close furnace doors – a task that hydraulic equipment and workers are unable to safely perform because of extremely high temperatures,” explains Becker Engineering pro-duct manager Eugene Davids. “These worm-gear machine screw and ball screw linear actuators also provide motion control for positioning dampers, valves, rollers, levellers, ramps, presses and other equipment used in the steel industry,” he adds.
A motorised Uni-Lift can also push material in and out of a heattreatment oven.
Uni-Lift design features include interchangeability, a 250-t maximum capacity, over-sized gear centres for optimum strength, efficiency, high input speeds and minimum backlash for extended duty cycles. High-strength steel, with precision- formed worm threads, offers long service and smooth transfer of torque to the gear nut. Gearing is supported by tapered roller bearings to provide both axial and side support. Bearings are preloaded for maximum support of all moving components. In standard units, the load screw translates through the unit to push or pull when the screw is fixed to the load. It is externally restricted to prevent rotation. The load screw of the rotating design unit is fixed to the worm gear, causing the screw to rotate. A flanged nut travels along the load screw to push or pull the load.
The load must be fixed to the travelling nut and restricted from rotation, in order to prevent linear motion. In applications where rotation cannot be prevented externally, the keyed designed jack is recommended. These units are keyed internally to prevent rotation of the screw to produce linear motion. Most actuators are operated by an electric motor, but air or hydraulic motors can also be used. Hand wheels are used for manual operation.
Uni-Lifts can be mounted in any position – vertical, horizontal or in between.
In applications where driving a direct shaft connection to the motor or reducer is impractical, the actu-ator can be operated by a sprocket and chain drive.
Each selected component should have a torque rating that exceeds the portion of the system torque it transmits and accurate alignment of these power transmission components is critical for efficient operation.
Misalignment causes premature wear and possible failure.
Add-on options include antibacklash, gear nuts, and double clevis and motor reducers. Optional gear ratios are available to provide mounting variable input revolutions per minute and load screw speeds.
Emergency stop nuts are recommended as a safety precaution, but are intended for use only as secon-dary stops in case of overtravel emergencies.
Gear damage may result if they are used as the primary travel limit, unless other means of overload protection are incorporated into the system.
It is important that these emer-gency stop nuts are positioned so that stop contact for all units will occur simultaneously, to equally distribute the system stall load should overtravel occur.
Other accessories include boots, top plates, clevis attachments, motor adaptors, limit switches and position indicators.
Uni-Lift actuators, which are designed with an adequate safety margin to prevent loss of control of the load being moved or positioned, offer efficient performance, smooth movement and extended service life.