Ledex® Rotary Solenoids - Three-Ball Race

About this product

Often Imitated, Never Excelled

The Ledex three-ball race rotary solenoid, designed by Ledex founder G.H. Leland in 1944, was the first of its kind on the market, offering rotational motion in a compact and energy-dense form. It is named for its use of three inclined ball races (i.e., metal rings with rolling ball bearings inside) which act as integral mechanisms to create rotational motion. These ball races are arranged in a helix configuration, similar to a strand of DNA. Leland’s original design is still the basis for the industry-leading solenoids produced by Johnson Electric today.

Long service life: 1–5 million cycles or more, or up to 50 million cycles with long-life parts

More torque than any competitor offering of the same size

Shock- and vibration-resistant

Extreme temperature functionality: -55°C–130°C (-67°F–266°F) or higher with minor customizations

Short axial stroke

Standard integrated return spring

Many standard sizes available for next-day shipment across North America

Multiple Configurations

Seven unique design configurations are offered in each product size to support different application interface methods.

Armature end shaft extension and tapped hole

Base end shaft extension and tapped holes

No shaft extensions and tapped holes

Armature end and base end shaft extensions

Armature cover with armature end shaft extension

Armature cover with base end shaft extension

Armature cover with armature end and base end shaft extensions

Ideal for Applications Like These

Door/safety interlocks

Vending machines

Warehouse automation/sortation

Laboratory/medical diagnostic equipment

What is axial stroke?

Axial stroke is the linear distance that the armature travels to the center of the coil as the rotary solenoid is energized and the three bearing balls travel to the lower ends of the races. Your application should allow clearance to ensure the axial stroke is unobstructed. This is rarely a problem because of the relatively small magnitude of travel.

What if my application doesn't have room for axial stroke clearance?

Solenoids without axial stroke, such as our BTA®, Ultimag®, and Solligence™ fast rotary actuators, can be tailored to your application if longitudinal movement must be avoided.

Is it practical to restrict the rotary stroke of the solenoid?

Although some users of standard Ledex® solenoids have achieved good results with certain methods of restricting the rotary stroke, it's generally a best practice to match the selected solenoid to the exact rotary stroke required by the application (e.g., don't use a 45° stroke solenoid when only 35° of stroke are needed).

Ideally, the complete rotary stroke of the solenoid should be utilized because the contour of the ball race determines the torque output. If the armature is not allowed to completely energize or de-energize, the starting and ending torque will deviate from the designated output.

If some mechanical means is used to prevent the balls from reaching the deepest part of the races, it is technically possible to increase life expectancy and achieve quieter operation. However, this type of stroke restriction may make it necessary to employ some additional bearing method to keep the balls in phase. Our application engineers will be glad to assist you with any unusual requirements.

Can the three-ball race solenoid be used for controlled action?

Three-ball race units have a fast, snap-acting engagement. If controlled speed is required, consider BTA®, Ultimag®, or Solligence™ actuators.

Can the armature pin be used as the main power take-off for secondary drive operations?

Yes. It can also provide a convenient adaptor for a lever or bar to convert the rotary stroke into linear motion. With appropriately designed linkages, a limited rotary stroke can produce several inches of travel.

You have a lot of different rotary solenoids to choose from, and we're not sure what we'll need. Can you help?

Consider using a stock model prototype as a quick and inexpensive way to determine your exact requirements. You can also take advantage of our Ohio-based engineering team, which has comprehensive design and manufacturing resources available to support you.

In addition, a solenoid demonstration board is available, which will enable you to test any size solenoid at various voltages, duty cycles, and power levels.