Coupling Design | Requirement , Types , Design Of Sleeve coupling
DESIGN OF COUPLING
Shaft couplings are used in machinery for several purposes
1. To provide for connection of shaft of units those are manufactured separately.
2. To provide for misalignment of the shaft or to introduce mechanical flexibility.
3. To reduce the transmission of shock loads from one shaft to another.
4. To introduce protection against over loads.
REQUIREMENT OF A GOOD SHAFT COUPLING
1. It should be easy to connect or disconnect.
2. It should transmit the full power from one shaft to the other shaft without losses.
3. It should hold the shaft in perfect alignment.
4. It should have no projecting parts.
5. To provide for the connection of shafts of units that are manufactured separately such as a motor and generator and to provide for disconnection for repairs or alternations.
6. To provide for misalignment of the shafts or to introduce mechanical flexibility.
7. To reduce the transmission of shock loads from one shaft to another.
TYPES OF SHAFT COUPLINGS:-
1. Rigid coupling
- It is used to connect two shafts which are perfectly aligned. The types are
- Sleeve (or) muff coupling
- Clamp (or) split muff (or) compression coupling
- Flange coupling
2. Flexible coupling
It is used to connect two shafts having lateral and angular misalignments. The types are
- Bushed pin type coupling
- Universal coupling
- Oldham coupling
SLEEVE (or) MUFF COUPLING
It is made of cast iron. It consists of a hollow cylinder whose inner diameter is that same as that of the shaft. It is fitted over the ends of two shafts by means of a gib head key. The power transmitted from one shaft two other shafts by means of a key and a sleeve.
Outer diameter of sleeve D=2d+13mm
Length of sleeve L=3.5d
D= diameter of shaft
• The sleeve is designed by considering it as a hollow shaft.
- T= Torque transmitted by coupling.
- τc =Permissible shear stress for the material of the sleeve which is cast rion.
• Torque transmitted by a hollow section
T = (π/16)×τc× ( D^4 – d^4 )/ D
= (π/16)×τc×D^3 (1-K ^4)
… (∵k = d / D)
• From this expression, the induced shear stress in the sleeve may be checked
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