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

Inverted Translating

A machine screw mechanical actuator is the perfect solution for lifting heavy loads with minimal force. No one knows mechanical actuators better than C.H. Bull. We offer dependable, high performance Duff Norton machine screw actuators. An inverted translating machine screw mechanical actuator from Duff Norton will provide reliable performance in any application.

Request a quote on an inverted translating machine screw actuator, or contact us for more info.

Duff Norton Inverted Translating Machine Screw Actuators

Duff Norton inverted translating machine screw mechanical actuators are available with lifting capacities from 500 lbs. to 250 tons. They include a number of customizable features, making it easy to create a device that is perfectly tailored to your application (see below).

These machine screw actuators can be used singly, in pairs, or in multiple arrangements, as your load lifting needs require. Most Duff Norton machine screw actuator models operate at a uniform speed, making it possible to use actuators of different capacities simultaneously on the same load. Actuators can be operated manually or via electric, pneumatic, or hydraulic gear motors.

Most inverted translating machine screw actuators are self-locking, meaning they will hold heavy loads in place indefinitely. Duff Norton models can push, pull, apply pressure, or function as linear actuators. They are furnished with standard raises in increments of 1”; models with total raise up to 20’ are available.

Numerous screw end options are available to meet your application needs: threaded ends, clevis ends, plain ends, and top plates. Optional limit switches are available to regulate vertical travel (up or down).


•    Uniform lifting speed
•    Positive, mechanical positioning
•    Optional anti-backlash
•    Precision positioning within thousandths of an inch
•    Customizable (see below)

We also offer upright translatingupright rotating, and inverted rotating machine screw mechanical actuators, as well as Duff Norton ball screw actuators.

Customizable to Meet Your Application Requirements

Based on your specifications, C.H. Bull can provide a customized inverted translating machine screw actuator that delivers the exact performance you need. A number of features can be customized, including:

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

Request a quote on an inverted translating machine screw mechanical actuator for your application. 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 the operating parameters, including total load, load per actuator (if multiple actuators will be used), lifting speed, total travel required, load type, and ambient working temperature.

Step 2: Determine which type of actuator is best for your application. A variety of factors must be considered when selecting between a machine screw actuator or ball screw actuator. Machine screw actuators are inherently load-holding, and provide better performance for applications which experience constant vibration. Ball screw actuators are faster, more efficient, and require lower motor horsepower to lift an equivalent load.

Step 3: Calculate the required actuator performance. Select an actuator with a capacity greater than the load it must lift, then use the formulae below to calculate your requirements.

For loads greater than 25% of actuator capacity, the torque should be considered 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 above calculation to account for frictional losses.)

Calculate actuator input RPM. (WARNING: Shaft input 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 maximum HP of the actuator to the necessary input HP. If the required HP exceeds the maximum, a higher HP-rated actuator is needed.

If using a gear reducer, the motor HP must be multiplied by the reducer’s efficiency to obtain reducer output HP (actuator input HP).

For multi-actuator setups where two or more mechanical actuators are shaft driven by a single motor or gear reducer, total the input HP requirements of all actuators. If using a mitre gear box, allow for 2% power loss per every 90° of turn in the power path.

Step 4: Determine your actuator configuration requirement considering capacity, desired lifting speed, and duty cycle requirements.

Step 5: Is your load unattached or unguided? If so, the mechanical actuator must be configured so that the lifting screw extends when the actuator is in action. Duff Norton actuators include a keyed shell and screw (for machine screw actuators) or a square nut inside a square cover pipe for the end of the lifting screw (for ball screw actuators) to prevent rotation of the translating screw.

Step 6: Verify your actuator selection. Double-check your application’s load and travel requirements, as well as the ratio, capacity, and speed of your chosen actuator. Determine which end fitting (clevis end, plain end, threaded end, or top plate) is right for your needs.

Safety Warnings

Actuator input RPM should never exceed 1,800 RPM.

Never exceed the static or dynamic capacities of your actuator.

Never exceed specified horsepower limits; if maximum HP will be exceeded, reduce lifting speed, choose a different actuator ratio, or consider an actuator with higher capacity or better lifting efficiency.

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