Festo Belt Drives 2, Промышленное обслуживание

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© Festo Didactic 54977-3C
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Variable-speed belt drives
Variable-speed belt drives are used when changing speed is required due to an
increase or a decrease in load, or any change in the operating conditions. They
are an inexpensive solution to vary speed since they only require a
constant-speed motor.
To obtain a specific speed ratio, one or more variable-pitch pulley(s), such as the
one shown in Figure 30, can be used. Variable-pitch pulleys are often installed
on the driving shaft, but can also be installed on the driven shaft depending on
the application.
Figure 30. Variable-pitch pulley.
A typical variable-pitch pulley has two flanges and a threaded hub that allows the
adjustment of the groove width. Adjusting the groove width raises or lowers the
belt in the groove to position the belt pitch line at a point that yields the desired
speed ratio. A variable-pitch pulley has two setscrews used to lock the pulley
onto the shaft and to lock the threaded hub into position. Figure 31 shows the
closed and opened position of a variable-pitch pulley.
Variable-Speed Belt Drives
Information Job Sheet
3
Flange
Threaded hub
Threaded hub
tightening setscrew
Shaft tightening
setscrew