2. Coupling
Shafts are mostly available up to 7 meter length due to transport
difficulty. To get a greater length, it is necessary to joint two or
more pieces of the shaft using coupling.
Purposes of Coupling used are,
To connect shafts of motor and generator which are manufactured
separately and to provide for disconnection for repairs.
To reduce the transmission of shock loads from one shaft to
another.
To allow misalignment of the shaft or to introduce mechanical
flexibility.
To introduce protection against overloads.
3. Types of couplings
(1) Rigid coupling
It is used to connect two shafts which are perfectly in axial
alignment. These couplings do not allow any relative rotation
between the two shafts.
There are basic three types of rigid coupling as follows,
Sleeve or muff coupling
Clamp or split muff or compression coupling
4. (2) Sleeve or Muff coupling
Construction
This is the simplest type of rigid coupling. It is made from cast
iron and very simple to design and manufacture. It consists of a
hollow cylinder (muff) whose inner diameter is the same as
diameter of the shaft.
5. The hollow cylinder (muff) is fitted over the ends of the two
shafts with the help of taper sunk key. A key and sleeve (muff)
useful to transmit rower from one shaft to the other shaft. It has
no projecting parts.
6. 3) Split muff coupling (clamp coupling)
Construction
In this coupling, the muff or sleeve is made into two halves parts
of cast iron and they are join together by bolts as shown in
Figure. Both the halves are held together by means of M.S stud
OR nut/Bolts.
7. (c) Flange coupling
There are basic two types,
(1) Unprotected type flange coupling
The projected portion of one of the flange and
corresponding recess on other flange are help to bring the
shafts into line and to maintain alignment.
8. (2) Protected type flange coupling
In order to prevent catching clothes of workmen in coupling the
flange is provided with a shroud which shelters the bolt head &
nuts . This coupling is called protected type flange coupling.
9. (2) Flexible couplings
This coupling is used to protect the driving and driven machine
members against harmful effects produce due to misalignment of
shafts, vibration, and sudden shock load or shaft expansion.
There are basic three types of flexible coupling as follows,
Bushed pin type flange coupling
Oldham coupling
Universal coupling
10. a) Bush pin type flange coupling
This is a modified form of protected type flange coupling
This type of coupling has a pins and it work as a coupling bolts.
The rubber or leather bushes are used over the pins. The coupling
is having two halves are dissimilar in construction. The pins are
rigidly fastened by nuts to one of the flange and kept loose in the
other flange.
11. (b) Oldham’s coupling
Construction
It consists of two flanges A and B with slots and a central floating
disc as shown in fig.
Use
Connecting two parallel shafts but not in alignment, and their
axes are at small distance apart.
12. (c) Universal coupling
Construction
It consists of two similar forks keyed on the ends of the two
shafts. These two forks are assembled to a central block by pin. A
central block having two arms at right angle to each other.
