Tag Archives: screw jacks

Advantages of a U-Shaped Worm Gear Jack Screw Arrangement

In worm gear screw jacks, the “U” arrangement’s configuration is often preferred for manufacturers in the food industry.

U ArrangementFor example, a leading cookie manufacturer could be adding a new product that requires a greater distance to the top heating element of the conveyor oven. The oven originally only had a static-top heating element and with this new order, it needs to be adjustable up to 14 inches. The top heating element weighs 5,000 pounds. The manufacturer anticipates only making adjustments to the height once or twice a month.

Our specifications for the U arrangement include a single 5-Horsepower 1750 AC Motor that allows full travel in 36 seconds, food-grade grease, compression load and a double safety factor. The actuators and power train must be located outside of the oven frame. Travel rate is negligible as long as the total travel can be reached in less than 60 seconds. The application’s infrequent cycles makes the use of a machine screw jack the best fit.

Upright rotating jacks allow the jacks to be easily retrofitted to the existing oven with minimal modifications. The jacks will be fully loaded in both the retracted and extended position, but because of the retrofit condition, having a support bearing on the lift shaft will not be possible. A 10-ton jack was selected for the mounting condition to fulfill safety requirement.

For calculating column strength, check out Nook’s calculator, as well as other useful engineering calculators here.

H Arrangement of Worm Gear Screw Jacks

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.

H ArrangmentAn 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.