Mechanical connections come in various forms from short couplings to couplings at the end of long torque tubes. Depending on the application, the connection's design requirements beyond torque and speed specifications can include flexibility, ease of installing and removing, low or high torsional stiffness and more. “Today's designers are using more servo motors to improve machine speed and accuracy,” says Robert Mainz, Zero-Max sales manager. “As speeds increase, so does stress on mechanical components. The first mechanical component to see increased stress is the shaft coupling.” For Zero-Max, the answer was an aluminum composite for the disc in its coupling. For the other manufacturers in this section, aluminum also provides a critical material in their coupler design.
COUPLINGS WITH ALUMINUM HUBS
In Zero-Max CD couplings, aluminum hubs provide low weight and low inertia with the working portion consisting of an aluminum composite material. Designed for servo motor and other precision motion control applications, the couplings provide an optimum combination of high torsional stiffness and high dynamic load capacity and can withstand high reverse loads. In contrast, bellows-style couplings are too brittle to withstand the stress of high-speed reversing and beam-style couplings have relatively low torsional stiffness that limits speed and machine accuracy. Available in clamp-style hubs with or without keyways, the aluminum hub single flex model's torque capacities range from 40 to 1,436 Nm and more with speed ratings from 4,400 to 17,000 rpm.
COUPLING SYSTEM
The TOK Coupling System from Reich Kupplungen in the Ringfeder Corp. addresses the needs of combustion engine test bench shafts. Connecting combustion engines to dynamometers for engine testing and evaluation, the couplings target applications that require different engine types or changes to test parameters. The self-centering couplings are completely backlash and maintenance free. Two flexible coupling elements provide the lowest possible torsional stiffness that can be changed by replacing the flexible elements. Applications can dictate coupling selection from five different options such as cardan or universal joint shaft connections for standard applications, intermediate shaft for low stiffness and constant velocity shaft for high-speed testing. Versions for maximum torque handle ranges from 420 to 4,000 Nm, while versions for maximum engine speeds run from 7,000 to 10,000 rpm. Capable of absorbing axial, radial and angular misalignment, aluminum construction also makes the coupling lightweight.
PRECISION LINE SHAFT
Similar to the structure of precision couplings, precision line shafts connect a motor to a driven load but allow a separation that could be as much as 6m. R+W's EZ 2 line shaft with a split clamping hub provides connectivity for 12 to 2,150 Nm loads. The elastomer insert with shore hardness of 98 A or 64 D dampens vibrations and a machined aluminum tube eliminates the need for an intermediate support bearing. The vibration damping line shaft's split hubs allow complete removal in a lateral direction. Depending on the chosen elastomer insert, the temperature range can be as high as -30 to 120C (-22 to 248F). Fit tolerance on the hub/shaft connection is 0.01 to 0.05 mm. As long as tolerances are not exceeded, the maintenance-free shafts have an infinite life.
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