Schmidt Offset Couplings
Schmidt offset couplings enable a variable parallel offset between two shafts. They are adaptable to wide variations in radial displacement while running under load. Invented in the early 1960s by Richard Schmidt, and added to the Zero-Max line of flexible shaft couplings in 1984, Schmidt couplings were originally developed under commission from NASA for use in propulsion systems for rockets in zero-gravity environments.
Zero-Max Schmidt Couplings
Zero-Max offers a variety of Schmidt coupling designs, including offset couplings, inline couplings, and 5-D couplings.
These couplings provide the utmost precision for parallel offset shafts. They transmit constant angular velocity and torque in a wide range of parallel shaft misalignments. Schmidt offset couplings impose no radial loads on shafts or bearings, and eliminate radial shaft vibrations. No performance is lost by increasing offset.
Schmidt Inline Couplings are designed with high torsional stiffness. These linkage couplings accommodate small parallel shaft misalignments at constant angular velocity. Designed as dropout couplings, they are easy to install and offer excellent drive performance for low to medium shaft speeds and in medium- to high-torque applications.
These couplings provide parallel shaft misalignment and a ± 5° angular misalignment with moderate axial shaft displacement capabilities. These couplings maintain constant angular velocity at all misalignment modes. Featuring easy to maintain spherical roller bearings, Schmidt 5-D couplings are recommended for high torque, low RPM applications.
Schmidt Coupling Operation
Schmidt couplings guarantee a completely true angle of rotation at all times. Richard Schmidt’s design uses a unique arrangement of discs and links—three discs rotating in unison, interconnected in series by six or more rotating slider links. The center disc is free to assume its own center of rotation, and all three discs rotate with equal velocity.
The pushing and pulling forces of a Schmidt coupling alternate and overlap in a sinusoidal pattern, resulting in zero net external forces. Additionally, the constant-velocity relationship between input and output shafts connected by a Schmidt coupling is not affected by changes in radial displacement, preserving balance in the system.
Bearing-mounted connections between the Schmidt coupling’s links and discs are equally spaced at 120° on same-diameter pitch circles. The offset distance can be varied steplessly between nearly zero and a maximum of twice the length of the links. While the system is in operation, there is zero phase shift between shafts.
Schmidt Offset Coupling Advantages
By providing a solution to large radial displacement between shafts, the invention of the Schmidt coupling opened up new possibilities in transmission design. Because these couplings maintain constant transmission ratios between input and output shafts while the shafts undergo radial shifts in their relative positions, gear-and-belt transmissions can be built with fewer gears and pulleys.
Schmidt couplings enable a variable parallel offset between two shafts. They provide constant speed velocity with extremely low backlash, and their compact designs provide large floor space savings. Schmidt couplings are especially good for roll applications, such as paper processing or converting.
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