MECH 3440-Notes 3 - Couplings

• a device used to connect two shafts together at their ends for the purpose of transmitting power
• primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both

• 1. temperature
• 2. torque and power rating
• 3. RPM4. S.F.; type of load (shock, fluctuating, etc.)
• 5. misalignment issues
• 6. purchase, installation and maintenance costs

• 1. Angular misalignment
• 2. Offset misalignment

• Clamp or sleeve coupling
• Modified clamp coupling
• Spider or jaw and slider coupling
• Chain coupling
• Grid-flex coupling
• Gear coupling
• Para-flex or elastomeric coupling
• Fluid coupling

• 
• basic type of coupling
• consists of a pipe whose bore is finished to the required tolerance based on the shaft size
• a keyway in made in the bore in order to transmit the torque by means of the key
• Two threaded holes are provided in order to lock the coupling in position
• ADV: Rigid coupling for transmitting high torques at high speeds

• 
• sleeve used in this type is split from one side
• shafts are entered and keyed to this sleeve and then split sides are screwed together

• 
• modified based on fit

• 
• Both half of the couplings have three shaped lugs
• When the coupling halves are fitted together the lugs on one half fit inside the spaces
• between the lugs on the other side
• When the coupling halves are fitted together the lugs on one half fit inside the spaces
• between the lugs on the other side
• The drive is by the lugs transmitting the torque
• through the rubber spider spacer
• DISADV: only used for low power drives

• 
• Chain Couplings transmit torque through two hubs with hardened sprocket teeth and a double width roller chain
• ADV: High torque capacity and least expensive coupling in the medium torque range

• 
• use two slotted hubs with a steel grid running between them to transmit torque
• The coupling flexes by allowing the grid to slide along the slots in the hubs
• ADV: Torsionally flexible and resilient - vibration reduction up to 30%

• 
• gear coupling is a mechanical device for transmitting torque between two shafts that are not collinear
• consists of a flexible joint fixed to each shaft
• two joints are connected by a third shaft, called the spindle
• ADV: coupling is capable of high speeds and high power capacity = high torque
• DISADV: it requires lubrication

• 
• employ a molded, non-lubricated elastomeric
• flexing member loaded in shear
• ADV: Finished Bore Flanges offer extra bore capacity that allows smaller coupling selections
• ADV: designed to accomodate concurrent angular, parallel, and axial misalignment and ensure fast, easy installation

- When the motor is rotated, the fluid is picked up in the vanes of the impeller and thrown outwards, across the gap, towards the vanes of the runner. As a result of the fluid kinetic energy, the runner begins to rotate and drive the driven machine