One of the most common arrangements used for worm gear screw jacks is the “H” arrangement. The name comes from the arrangement’s shape, which is made up of four jacks, three gearboxes and a 3 HP AC Motor capable of a dual-speed 1750/800.

An example of this arrangement could be a manufacturer of steel frames for the commercial dairy industry is building a material lift which contains a stack of prefabricated frames. The material lift will index up as each frame is removed by an automated grip from the top of the stack. The jack will index up 1 inch in 2 seconds every 30 seconds. After the last frame is removed, the jacks will fully retract to the collapsed position in 6 seconds waiting for the next load of frames. Complete cycle time is 10 minutes running 6 hours per day, 5 days a week. The design calls for a four-jack arrangement lifting from underneath the lifting stage, driven by a single motor.

The frequency of these cycles and suggested design life makes the use of a ball screw jack the best option for this application. Using upright translating jacks allows the jacks to be located under the material lift without creating obstruction.

When fully loaded, the frames hold a total weight of 16,800 pounds, but when the load is fully extended, the weight is less than 5,000 pounds. The compression load travels 6 inches. The desired design life for the arrangement is one year, as the application is expected to go through 3,120 cycles a year.