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Mechanical Actuators
A Leader in Heat Transfer Components, Products and Systems

Inverted Rotating

A ball screw mechanical actuator is the perfect device for your high-speed load-lifting needs. C.H. Bull offers a variety of reliable, high performance Duff Norton ball screw actuators. Duff Norton’s inverted rotating ball screw actuators provide fast and efficient lifting performance for any application. 

Request a quote on an inverted rotating ball screw actuator, or contact us to learn more.

Duff Norton Inverted Rotating Ball Screw Actuators

Duff Norton manufactures inverted rotating ball screw mechanical actuators in a range of capacities from 500 lbs. to 50 tons. They are customizable in a number of ways, making it easy to create a device that is uniquely tailored to your requirements (see below).

Duff Norton ball screw actuators move loads and apply force more efficiently than other types of mechanical actuators. They are up to six times faster than machine screw actuators, and their ball screw design lessens friction for reduced power use.

These mechanical actuators can handle full load in tension or compression, and can be operated by hydraulic, electric, or pneumatic motors. All Duff Norton ball screw actuators are furnished with standard raises in increments of 1”. Multiple units can be synchronized for simultaneous use on the same load.

To meet the needs of your application, several screw end options are available—plain ends, threaded ends, clevis ends, and top plates. Optional limit switches can be used to manage the actuator’s vertical travel (up or down).

C.H. Bull also offers upright rotatingupright translating, and inverted translating ball screw mechanical actuators, as well as Duff Norton machine screw actuators.

Customizable to Meet Your Application Requirements

To give you a ball screw actuator that provides the perfect level of performance for your application, C.H. Bull can provide customized units. Customizable features include:

•    Lifting capacity
•    Motor type
•    Screw end type 
•    Stroke length
•    Limit switch
•    and more

Request a quote on the inverted rotating ball screw mechanical actuator your application requires. Contact C.H. Bull for more information on these or any of our quality products.

Selecting the Right Mechanical Actuator for Your Needs

Step 1: Define your operating parameters. Consider total load, load per actuator (if multiple units will be used), lifting speed, total required travel, load type, and ambient working temperature.

Step 2: Determine which type of actuator is best for your application. Various factors should be considered when choosing between a ball screw actuator and a machine screw actuator. Ball screw actuators provide faster and more efficient performance, and require less horsepower to lift an equivalent load. Machine screw actuators provide inherent load holding capabilities and are better suited to high-vibration applications.

Step 3: Calculate required actuator performance. Start with an actuator with capacity greater than the load it will lift. Then, use the following formulae to calculate your performance requirements.

For loads greater than 25% of actuator capacity, consider torque proportional to the load. 

A) Actuator torque (in.-lbs.) = Actuator load (lbs.) x worm torque at full load

Actuator capacity (lbs.)
(For loads less than 25% of actuator capacity, add “Worm torque at no load” to the torque formula to account for frictional losses.)

Calculate the actuator’s input RPM. (WARNING: Shaft input speed should never exceed 1,800 RPM.)

B) Input RPM = Desired lifting speed (in./min.) x turns of worm for 1” lift
Calculate the actuator’s input HP.

C) Actuator input HP = Actuator torque (in.-lbs.) x RPM

Compare the actuator’s maximum HP rating and the necessary input HP. If the maximum is exceeded, select a higher HP-rated actuator. 

For multi-unit installations where two or more mechanical actuators will be shaft driven by a single motor or gear reducer, combine the HP requirements of all actuators. When using a mitre gear box, allow for 2% power loss for every 90° turn in the power path.

Step 4: Determine the best actuator configuration for your needs. Consider your application’s speed, capacity, and duty cycle requirements. 

Step 5: If your load is free-rotating or unattached, the actuator must be configured so that the lifting screw will extend as the actuator moves. To stop the translating screw from rotating, Duff Norton provides a square nut inside a square cover pipe for the end of the lifting screw (for ball screw actuators) or a keyed shell and screw (for machine screw actuators). 

Step 6: Review your actuator selection. Double-check the load and travel requirements of your application, and the capacity, ratio, and speed of the selected actuator. Determine which end fitting—plain, threaded, clevis, or top plate—is best for your needs.

Safety Warnings

Actuator input speeds should never exceed 1,800 RPM.

Never exceed the static or dynamic capacities of your mechanical actuator.

Never exceed the specified horsepower limits of the actuator. If max HP must be exceeded, consider reducing the lift speed, select a different actuator ratio, or choose an actuator with higher capacity or greater efficiency. 

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