Билет 10 friction clutches
The object
of a friction clutch is to connect a stationary machine part to a
rotating part, to
bring it up to speed,
and to transmit the required power with a minimum of slippage. In
certain cases a friction clutch serves as a safety device by slipping
when the torque transmitted through it exceeds a safe value, thus
preventing the breakage of parts in the transmission train.
Friction clutches may be
divided into two main groups, according to the direction of the
acting force: axial clutches and radial or rim clutches.
Axial
clutches which have the contact pressure applied in a direction
parallel to the axis of rotation. Axial clutches, in turn, can be
subdivided into: cone clutches, disk clutches, and combined cone and
disk clutches.
In rim
clutches the contact pressure is applied upon a rim in a radial
direction. These clutches, like brakes, may be subdivided into band
clutches and block clutches, also into external, internal, and
combined internal-and-external clutches.
Magnetic clutches are usually
of the disk type.
A friction clutch used to
connect two shafts is often termed a clutch coupling or friction
coupling.
The factors which must be
taken into consideration in deciding what type of clutch is to be
used are: torque, rotative speed, available space, and frequency of
operation.