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Design and Fabrication of Oldham coupling Report Download

ABSTRACT

The middle disc rotates around its centre at the same speed as the input and output shafts. Its centre traces a circular orbit, twice per rotation, around the midpoint between input and output shafts. Often springs are used to reduce backlash of the mechanism.

An advantage to this type of coupling, as compared to two universal joints, is its compact size. The coupler is named for John Oldham who invented it in Ireland, in 1821, to solve a paddle placement problem in a paddle steamer design. AutoCAD is a software application for 2D and 3D computer-aided design (CAD) and drafting — available since 1982 as a desktop application and since 2010 as a mobile web- and cloud-based application.
In this paper we draft/ draw the Oldham coupling of Orthographic views in the AutoCAD 2010 2D modelling Software.

INTRODUCING TO OLDHAM COUPLING

An Oldham coupling has three discs, one coupled to the input, one coupled to the output, and a middle disc that is joined to the first two by tongue and groove. The tongue and groove on one side is perpendicular to the tongue and groove on the other. The middle disc rotates around its center at the same speed as the input and output shafts. Its center traces a circular orbit, twice per rotation, around the midpoint between input and output shafts. Often springs are used to reduce backlash of the mechanism. An advantage to this type of coupling, as compared to two universal joints, is its compact size. The coupler is named for John Oldham who invented it in Ireland, in 1821, to solve a paddle placement problem in a paddle steamer design.

A transmission apparatus to hold a lock core of a supplemental lock includes an inner housing, a lock coupler, a latch bolt coupler, a restitution element and a cover. The inner housing has a lock core chamber. The lock coupler is rotatably mounted in the lock core chamber and includes a rotatable outer disk coupler and two lock coupling arms. The outer disk coupler has a flat edge. The lock coupling arms connect to the lock core that rotates the outer disk coupler. The latch bolt coupler is rotated by the lock coupler and includes a latch coupling arm and a longitudinal tab. The restitution element is mounted around the latch coupling arm. The cover is attached to the rear of the inner housing.

Uses

Shaft couplings are used in machinery for several purposes, the most common of which are the following.

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 alterations.
To provide for misalignment of the shafts or to introduce mechanical flexibility.
To reduce the transmission of shock loads from one shaft to another.
To introduce protection against overloads.
To alter the vibration characteristics of rotating units.

Video Animation of Oldham Coupling :

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Applications:

It is used to transfer torque between two parallel but not collinear shafts.
Depending upon the material of the 3 discs , oldham coupling can be used in many devices. They can easily be used in servo mechanisms.
Application of Oldhams coupling It was basically invented to connect two parallel non co axial shafts. It is a really good mechanism and transmits the same speed and same direction of rotation. It is not of much importance now as gears are being used.
An Oldham coupling is a flexible shaft coupling that consists of two hubs (each with a fin or tenon) and one midsection (with grooves that fit those fins, one on each side of the midsection, and perpendicular to one another).
The Oldham coupling is an outstanding design for torque transmission between two shafts which might be slightly misaligned. The coupling accommodates this misalignment,

ADVANTAGES OF OLDHAM’S COUPLING

Protects driven component by serving as a mechanical “fuse” – an inexpensive replaceable plastic midsection shears under excess load.
Protects support bearings by exerting consistently low reactive forces, even under large misalignments
Homokinetic transmission – driving and driven shafts rotate at exactly the same speed at all times.
Zero backlash and high torsional stiffness.
Electrical insulation.
Accommodates large radial misalignment in a short length.
Easy installation in blind or difficult installations when through-bores are used.
Economically priced compared to other couplings with similar performance characteristics.
Inexpensive replaceable wear element.
Low moment of inertia.
No velocity variation as with universal joints.
High lateral misalignments possible.
High torque capacity.
Ease of dismantling.

DISADVANTAGES OF OLDHAM’S

Limited angular displacement of shafts
Need for periodic lubrication due to relative sliding motion unless nylon or rubber construction is employed
Possible loss of loose members during disassembly
Accommodates a relatively small angular misalignment

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Design and Fabrication of Oldham coupling Report PDF Download