MARINE ENGINEERING,TYPES OF COUPLING

TYPES OF COUPLING

There are two types of coupling

RIGID COUPLING AND FLEXIBLE COUPLING RIGID TYPE COUPLING

        This type of coupling has no flexibility or resilience,rigid couplings do not accommodate misalignment hence it is necessary to be connected in good alignment

Types of Rigid Couplings:-
1.  Sleeve or muff coupling
2 . Clamp coupling,compression coupling or split muff coupling
3 . Flange coupling

Sleeve or muff coupling

      

                               

It is the simplest type of rigid coupling, made of cast iron. It  consists of a hollow cylinder whose inner diameter is the same as that of the shaft. It is fitted over the ends of the two shafts by means of a Gib head key. The power is transmitted from one haft to the other shaft by means of a key and a sleeve.     It is, therefore, necessary that all the elements must be strong enough to transmit the torque.

Clamp coupling

Clamp coupling is sometimes called a compression coupling or a ribbed coupling. Clamp coupling is a modification and a improvement of the sleeve coupling. This coupling is made in two parts which are machined to fit the shaft and are finished off around the periphery and on both ends. The two halves of the coupling are clamped tightly against the surface of the shaft ends by through bolts and the entire torsional moment is transmitted entirely by friction.

Flange coupling

A flange coupling usually applies to a coupling having two separate cast iron flanges. Each flange is mounted on the shaft end and keyed to it. The faces are turned up at right angle to the axis of the shaft. One of the flange has a projected portion and the other flange has a corresponding recess. This helps to bring the shafts into line and to maintain alignment. The two flanges are coupled together by means of bolts and nuts. The flange coupling is adopted to heavy loads and hence it is used on large shafting.

TYPES OF FLANGE COUPLING

1.Unprotected type flange coupling

2.Protected type flange coupling

3.Marine  type flange coupling

1) Unprotected type flange coupling:- In an unprotected type flange coupling each shaft is keyed to the boss of a flange with a counter sunk key, and the flange are coupled together by means of bolts. Generally, three, four or six bolts are used. The keys are staggered at right angle along the circumference of the shafts in order to divide the weakening effect caused by key ways.

  2) Protected type flange coupling:- In a protected type flange coupling the protruding bolts and nuts are protected by flanges on the two halves of the coupling, in order to avoid danger to the workman.

  3) Marine type flange coupling:- In a marine type flange coupling, the flanges are forged integral with the shafts. The flanges are held together by means of tapered headless bolts numbering from four to twelve depending upon the diameter of shaft. 

FLEXIBLE COUPLINGS

 

        It is nearly impossible completely to eliminate all chance misalignment between the shafts of separately built machines, and such misalignment of shafts always leads to eventual failure of bearings or fatigue failure of shafts. The relative position of the connected shafts, inaccurate at the outset due to inevitable errors of manufacturing, is in course of time aggravated by deformations caused by the working load, temperature fluctuations, the uneven sinking of foundations or supports, etc. In such cases ineffective rigid couplings are replaced by flexible couplings. Therefore the purpose of a flexible coupling is to allow for imperfect alignment of two joining shafts, or to absorb impact from the fluctuation of torsional moment or of angular speed.

These couplings are rigid under torsion, but, allow the correction of errors in the alignment of drive shafts. 

OLDHAM TYPE COUPLING

Oldham can be used for any velocities and loads and cause small additional loads and bearings.
The special advantage of this coupling is that it can be used for shafts which are not in alignment but whose axes are parallel up to the extent of 0.05 times the shaft diameter. By using this type of coupling minor axial alignment of shafts can be compensated.

The coupling consists of two flanges keyed or secrewed to the respective shafts and the flanges have the slots on the face surface. A cylindrical piece called disc with a tongue running across each flat is present The tounges are at right angles to each other.

The Oldham joints allow rotational movement between two parallel shafts, placed near to each other.
(Parallel mis-alignment). It is made up of two hubs, and a disk, which has two grooves, at right angles to each other.
During rotation, the grooves in the hubs slide into the grooves in the disk, thus correcting the mis-alignment.

The result of this is that the drive shaft and driven shaft turn at the same speed. 

BELLOW COUPLING

These couplings link a torsional rigidity, high torque, mis-alignment and high rotational speeds. They are light in weight, they have a large range of applications and they are very good value for money.

They are made up of two hubs which are mounted on the shafts, and a bellows, which whilst being rigid under torsion, has the flexibility in a longitudinal sense to correct any mis-alignments. The bellows is welded onto the hubs. These couplings are capable of very high rotational speeds. At high speed, the least eccentricity would lead very high levels of vibration which could be detrimental to the system as a whole.

BUSHED PIN TYPE COUPLING 

The Cone Ring Couplings unique flexible element comprises tapered rubber rings mounted on steel pins. The rubber rings absorb commonly encountered misalignment, shock and vibration.

JAW TYPE COUPLING or SPIDER COUPLING

spider                     three jaw                       multi jaw

Economical, resilient coupling not requiring lubrication. The jaw coupling is torsionally flexible and designed for positive torque transmission. Jaw couplings are puncture proof , operational vibrations and shock are efficiently attenuated and reduced 

there are three jaw coupling and multi jaw coupling,

 SPRING GRIND COUPLING

Grid couplings are designed for versatility. Common hubs and grids are used within a given size range for both horizontal and vertical split cover models. Grid installation and replacement can be done without moving the hubs making maintenance very easy.

CHAIN AND SPROCKET COUPLING

Chain couplings are an economical shaft connection with easy disconnection. Chain couplings offer maximum efficiency in connecting two shafts for transmission of power.

HRC COUPLING

The HRC is a general purpose Flexible coupling available in eight sizes in taper bush style or pilot bore.

 GEAR COUPLING

With the capacity of handling heavy loads, gear couplings are much smaller and lighter than other types of couplings. Noise and vibrations are hardly produced even in high speed operation

TYRE COUPLING

Tyre Coupling to compensate for large amounts of shock loading the backlash, as well as both parallel and axial misalignment.

 TORQUE LIMITORS

The Torque Limiter has been designed to protect drive systems from unnecessary overload. When too much torque is transmitted though a drive, the Torque Limiter automatically slips on its shaft when a predetermined torque level is reached

UNIVERSAL JOINTS

universal joints are not true flexible couplings but can transmit high angular misalignment, up to 45 degrees with a single joint or 90 degrees with a double joint/pair of single joints. They are available in single, double and telescopic versions for shafts 6 to 50m. Universal joints with plain bearings suit speeds below 1000 r/min and lubrication is needed, usually provided by an enclosing gaiter. For higher speeds universal joints with needle roller bearings are used.