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Rotary Solenoids Selection |
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Product comparison and links to datasheets |
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Principle of Rotary Solenoid Operation
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A rotary solenoid is an electromechanical device that converts linear motion to rotary motion by virtue of three ball bearings that travel down inclined raceways. When the coil is energized, the armature assembly is pulled towards the stator and rotated through an arc determined by the coining of the raceways. Flexibility in this design allows for the customer's load to be attached to either the shaft extension in addition to the three tapped holes on the armature plate. This compact cylindrical device has a relatively low height from the mounting surface to the top of the armature plate. |
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Snap-Acting Engagement |
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Rotary solenoids have fast acting engagement. If a controlled speed is required in a rotary stroke application, consider Ledex BTA rotary actuators |
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Unobstructed Axial Stroke |
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Axial stroke is the linear distance that the armature travels to the center of the coil as the solenoid is energized and the three bearing balls travel to the lower ends of the races.
The application should allow clearance for axial stroke, which is rarely a problem due to the relatively small magnitude of travel. Axial stroke is listed for each solenoid size and rotary stroke on the appropriate specification pages.
Solenoids without axial stroke, such as our BTA, can be tailored to your application if longitudinal movement must be avoided |
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Preloaded Axial Stroke |
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A rotary solenoid's armature produces smoother action if it is preloaded axially. It is important that the three bearing balls be kept in phase throughout the entire stroke. If they are allowed to move freely in the raceway, operation may become erratic. |
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Physical Characteristics |
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The rotary solenoid is a compact and rugged direct current electromagnet - almost solid steel and copper so as to give maximum power output with minimum size and weight. The coil is wound by a special precision winding process which puts the maximum amount of copper into the allowable space, thus resulting in each solenoid developing a tremendous torque for its size and power output. Heat-treated steel surrounds and protects the coil. The steel also provides a magnetic path of high permeability and low residual flux characteristics for efficient conversion of electrical energy to mechanical energy and fast response. |
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Determining Rotary Stroke |
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The three ball races which determine the rotary stroke are produced by a coining process. The coining of the solenoid case and armature plate determines the length and direction of the stroke and the value of starting torque. Refer to the selection charts for the standard strokes available. Special rotary strokes can be engineered for solenoids which are made to order. |
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Converting Linear to Rotary Motion |
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The rotary solenoid armature is supported by three ball bearings that travel around and down inclined ball races. When power is applied, a powerful linear electromagnetic force pulls in the armature. Rotation continues until the balls have traveled to the deep ends of the races. The result is almost frictionless conversion from linear to rotary motion. |
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High Starting Torque |
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In ordinary electromagnets, magnetic pull increases sharply as the air gap closes. In Ledex rotary solenoids, this is compensated for by the compound angle of incline of the ball races. The incline of the ball races is steep at the beginning of the rotary stroke and gradually decreases as the balls approach the deep end of the ball races, thus transferring torque to the start of the rotary stroke where it is usually needed |
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Armature Cover |
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Armature covers are available on all models, sizes and styles. They keep adjacent components or wires from interfering with the rotary and axial motion of the solenoid armature. They are also recommended for dirty or dusty environments. Armature cover models with armature end shaft extensions are equipped with a felt washer to act as a seal against the entry of dust around the shaft. |
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Armature Drive Pin |
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Armature pins are commonly used as the main power take-off to perform secondary drive operations. They also provide a convenient adapter for levers or bars which can convert the rotary stroke into linear motion. With appropriately designed linkages, a limited rotary stroke can produce several inches of linear travel. |
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Product comparison and links to datasheets |
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Configurations
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Rotary solenoids are available in seven standard configurations for most sizes. All configurations include a return spring. Models without an armature cover are equipped with three tapped holes in the armature face for load attachment purposes. |
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Rotary Solenoid Armature End Shaft Extension and Tapped Holes |
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Rotary Solenoid Base End Shaft Extension and Tapped Holes |
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Rotary Solenoid No Shaft Extensions and Tapped Holes |
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Rotary Solenoid Armature and Base End Shaft Extensions |
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Rotary Solenoid Armature Cover with Armature End Shaft Extension |
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Rotary SolenoidArmature Cover with Base End Shaft Extension |
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Rotary Solenoid Armature Cover with Armature End and Base End Shaft Extensions |
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Bobbin Wound Coil Rotary Solenoids |
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- Manufactured by automated high-speed coil winding equipment for good performance and low cost
- Torque output up to 10 lb-in (1130 mNm)
- One million operations life rating (based on 25% duty cycle at 20°C ambient operating temperature)
- Two sizes: 1-3/8 or 1-7/8 (53,3 or 47,6 mm) diameter
- Standard strokes from 25°-95°; custom strokes available, some with one-time tooling charge
- Clockwise and counterclockwise rotation
- Wide variety of configurations to accommodate mounting and environmental considerations
- Many models available from distribution
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Precision Standard Coil Rotary Solenoids |
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- Precision wound coil for excellent torque to size ratio
- Available in standard or long life versions
- One million operations life rating for standard versions; 50 million operations or 100 million operation if lubricated every 10 million operations for long life versions (life ratings based on 25% duty cycle at 20°C ambient operating temperature)
- Three sizes from 1-7/8" to 2-3/4" diameters (43 to 70 mm)
- Torque output up to 46.6 lb-in (5265 mNm)
- Standard strokes from 25°-110°; custom strokes available, some with one-time tooling charge
- Clockwise or counterclockwise rotation
- Wide variety of configurations to accommodate mounting and environmental considerations
- Hundreds of models available from distribution
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Precision Elongated Coil Rotary Solenoids |
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- Built with 30% more coil copper than precision standard coil solenoids for lower power consumption
- Precision wound coil for excellent torque to size ratio
- Available in standard or long life versions
- One million operations life rating for standard versions; 50 million operations or 100 million operations if lubricated every 10 million operations for long life versions (life ratings based on 25% duty cycle at 20°C ambient operating temperature)
- Four sizes from 1" to 1-9/16" diameters (25 to 40 mm)
- Torque output to 5.2 lb-in (588 mNm)
- Standard strokes from 25°-95°; custom strokes available, some with one-time tooling charge
- Clockwise or counterclockwise rotation
- Wide variety of configurations to accommodate mounting and environmental considerations
- Many models available from distribution
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Modified and Custom-Designed Rotary Solenoids |
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Ledex offers comprehensive design and manufacturing resources to develop application specific rotary solenoids to meet your exact performance and unit cost objectives. Even though we offer thousands of standard rotary solenoid models, almost 80% of the product we build is specifically tailored to our customers' needs. So if you don't find exactly what you're looking for, please call us to discuss your requirements. Here are a few simple design options which we frequently encounter for rotary solenoid applications: |
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- Special shafts
- Mounting studs threaded to customer specification
- Slots, flats, or holes in shafts for machine linkage
- Double return springs for critical safety redundancy
- Non-axial strokes
- Armature covers
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File Format Help
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ZIP: Some files need to be unzipped. Unzip utilities available for download for Windows / Macintosh.
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