Universal Joints (U-Joints)
Mechanically flexible U-Joints accommodate end movement by using a telescoping shaft (square shafting or splines). U-Joints function by a sliding motion between two flanges that are fork-shaped (a yoke) and having a hole (eye) radially through the eye that is connected by a cross. They allow larger angles than flexible couplings and are used in applications where high misalignment needs to be accommodated (1 to 30 degrees).
U-joints are available with two hub styles solid and bored. Solid hubs do not have a machined hole. Bored hubs have a hole and are named for the hole shape; round, hex, or square style. Two bored styles that deviate from these common shapes are splined, which have longitudinal grooves inside the bore; and keyed, which have keyways to prevent rotation of the U-joint on the matching shaft.
There are many varieties of U-Joints, some of which are very complex. The simplest category called Cardan U-Joints, are either block-and-pin or bearing-and-cross types.
Common Cardan U-Joint Types
Block-and-Pin U-Joints
Available in both single and double configurations. A single U-Joint has two shafts with u-shaped and drilled ends, a center block, and two pins that secure the block. Vibrations, caused by velocity changes, limits this type to very low speeds. A double U-Joint has a center piece connected on each end with separate joints.
A single U-Joint compensates for angular misalignment only. A double can handle angular and parallel misalignment. If changes in misalignment or shaft end movement occur during operation, a telescoping splined shaft provides the necessary adjustment in shaft length.
Bearing-and-Cross U-Joints
Two u-shaped hubs are joined by a cross-shaped piece. Needle bearings at each end of the cross-shaped piece fit into the hub arms. They are torsionally rigid and capable of up 15 degrees of angular misalignment.
Key Manufacturers of U-Joints We Offer
- Boston Gear (Altra)
- Huco (Altra)
- Kop-Flex (Regal)
- Lovejoy (Timken)
- Martin Sprocket & Gear
- Ringfeder
- Ruland
- TB Woods (Altra)
- Zero-Max
Content on this page was created using excerpts from the Power Transmission Handbook (5th Edition), which is written and sold by the Power Transmission Distributor’s Association (PTDA). The Power Transmission Handbook is just under 400 pages and is a valuable resource for anyone involved or interested in the power transmission industry.