S.No CONTENTS PAGE NO.

1. Abstract 1

2. Introduction to CAD SYSTEMS 2

2.1. Overview

2.2. Uses

3. Introduction to AUTO CAD 6

2.1. History

2.2. Design

2.2.1. File formats and versions

2.2.2 Compatibility with other software

2.2.3 Extensions

2.2.4 Vertical integration

2.3. Variants

2.3.1 AutoCAD LT

2.3.2 Student versions

3. Introduction to Oldham coupling 12

3.1 uses

4. Types of Couplings 21

4.1 Flexible

4.2 Constant velocity

5. Overview of Oldham coupling 30

5.1 Coupling maintenance and failure

5.2 Checking the coupling balance

5.3 Applications

5.4 Parts of Oldham coupling

6: Working & Advantages

Conclusion 31

ABSTRACT

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 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.

CHAPTER-1:INTRODUCTION TO CAD SYSTEM

Computer-aided design (CAD) is the use of computer systems to assist in the

creation, modification, analysis, or optimization of a design. CAD software is used to

increase the productivity of the designer, improve the quality of design, improve

communications through documentation, and to create a database for manufacturing. CAD

output is often in the form of electronic files for print, machining, or other manufacturing

operations.

Computer-aided design is used in many fields. Its use in designing electronic systems is

known as Electronic Design Automation, or EDA. In mechanical design it is known

as Mechanical Design Automation (MDA) or computer-aided drafting (CAD), which

includes the process of creating a technical drawing with the use of computer software.

CAD software for mechanical design uses either vector-based graphics to depict the objects

of traditional drafting, or may also produce raster graphics showing the overall appearance of

designed objects. However, it involves more than just shapes. As in the

manual drafting of technical and engineering drawings, the output of CAD must convey

information, such as materials, processes, dimensions, and tolerances, according to

application-specific conventions.

CAD may be used to design curves and figures in two-dimensional (2D) space; or curves,

surfaces, and solids in three-dimensional (3D) space.

CAD is an important industrial art extensively used in many applications, including

automotive, shipbuilding, and aerospace industries, industrial and architectural

design, prosthetics, and many more. CAD is also widely used to produce computer

animation for special effects in movies, advertising and technical manuals, often called

DCC Digital content creation. The modern ubiquity and power of computers means that even

perfume bottles and shampoo dispensers are designed using techniques unheard of by

engineers of the 1960s. Because of its enormous economic importance, CAD has been a

major driving force for research in computational geometry, computer graphics (both

hardware and software), and discrete differential geometry.

The design of geometric models for object shapes, in particular, is occasionally

called computer-aided geometric design (CAGD).

While the goal of automated CAD systems is to increase efficiency, they are not necessarily

the best way to allow newcomers to understand the geometrical principles of Solid Modeling.

For this, scripting languages such as PLaSM (Programming Language of Solid Modeling) are

more suitable.

1.1 Overview

Beginning in the 1980s computer-aided design programs reduced the need of draftsmen

significantly, especially in small to mid-sized companies. Their affordability and ability to

run on personal computers also allowed engineers to do their own drafting and analytic work,

eliminating the need for entire departments. In today's world, many students in universities do

not learn manual drafting techniques because they are not required to do so. The days of hand

drawing for final drawings are virtually over. Universities no longer require the use of

protractors and compasses to create drawings, instead there are several classes that focus on

the use of CAD software.

Current computer-aided design software packages range from 2D vector-based

drafting systems to 3D solid and surface modelers. Modern CAD packages can also

frequently allow rotations in three dimensions, allowing viewing of a designed object from

any desired angle, even from the inside looking out. Some CAD software is capable of

dynamic mathematical modeling, in which case it may be marketed as CADD.

CAD is used in the design of tools and machinery and in the drafting and design of all

types of buildings, from small residential types (houses) to the largest commercial and

industrial structures (hospitals and factories).

 CAD is mainly used for detailed engineering of 3D models and/or 2D drawings of

physical components, but it is also used throughout the engineering process from conceptual

design and layout of products, through strength and dynamic analysis of assemblies to

definition of manufacturing methods of components. It can also be used to design objects.

Furthermore many CAD applications now offer advanced rendering and animation

capabilities so engineers can better visualize their product designs.4D BIM is a type of virtual

construction engineering simulation incorporating time or schedule related information for

project management.

CAD has become an especially important technology within the scope of computer-aided

technologies, with benefits such as lower product development costs and a greatly shortened

design cycle. CAD enables designers to layout and develop work on screen, print it out and

save it for future editing, saving time on their drawings.

1.2 Uses

Computer-aided design is one of the many tools used by engineers and designers and is used

in many ways depending on the profession of the user and the type of software in question.

CAD is one part of the whole Digital Product Development (DPD) activity within the Product

Lifecycle Management (PLM) processes, and as such is used together with other tools, which

are either integrated modules or stand-alone products, such as:

Computer-aided engineering (CAE) and Finite element analysis (FEA)

Computer-aided manufacturing (CAM) including instructions to Computer Numerical

Control (CNC) machines

Photo realistic rendering

Document management and revision control using Product Data Management (PDM).

CAD is also used for the accurate creation of photo simulations that are often

required in the preparation of Environmental Impact Reports, in which computer-aided

designs of intended buildings are superimposed into photographs of existing environments to

represent what that locale will be like were the proposed facilities allowed to be built.

Potential blockage of view corridors and shadow studies are also frequently analyzed through

the use of CAD.

CAD has been proven to be useful to engineers as well. Using four properties which are

history, features, parameterization, and high level constraints. The construction history can be

used to look back into the model's personal features and work on the single area rather than

the whole model. Parameters and constraints can be used to determine the size, shape, and

other properties of the different modeling elements. The features in the CAD system can be

used for the variety of tools for measurement such as tensile strength, yield strength,

electrical or electro-magnetic properties. Also its stress, strain, timing or how the element

gets affected in certain temperatures, etc.

CHAPTER 2: INTRODUCTION TO AUTOCAD

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 app, currently marketed as AutoCAD 360.

Developed and marketed by Autodesk, Inc. AutoCAD was first released in December 1982

— having been purchased a year prior in its original form by Autodesk founder John Walker.

The software is currently marketed in its eighteenth generation.

As Autodesk's flagship product, by March 1986 AutoCAD had become the most

ubiquitous microcomputer design program worldwide, with functions such as "polylines" and

"curve fitting". Prior to the introduction of AutoCAD, most other CAD programs ran

on mainframe computers or minicomputers, with each CAD operator (user) working at a

graphical terminal or workstation.

AutoCAD is used across a range of industries, including architects, project managers and

engineers, among other professions, with 750 training centers established worldwide as of

1994.

2.1 History

AutoCAD was derived from a program begun in 1977 and released in 1979 called Interact

CAD, also referred to in early Autodesk documents as MicroCAD, which was written prior to

Autodesk's (then Marinchip Software Partners) formation by Autodesk cofounder Mike

Riddle. The 2014 release marked the 28th major release for the AutoCAD for Windows. The

2014 release marked the fourth consecutive year for AutoCAD for Mac.

2.2 Design

2.2.1 File formats and versions

The native file format of AutoCAD is .dwg. This and, to a lesser extent, its interchange file

format DXF, have become de facto, if proprietary, standards for CAD data interoperability.

AutoCAD has included support for .dwg, a format developed and promoted by Autodesk, for

publishing CAD data.

2.2.2 Compatibility with other software

ESRI ArcMap 10 permits export as AutoCAD drawing files. Civil 3D permits export as

AutoCAD objects and as LandXML. Third-party file converters exist for specific formats

such as Bentley MX GENIO Extension, PISTE Extension (France), ISYBAU (Germany),

OKSTRA and Microdrainage (UK).

2.2.3 Extensions

AutoCAD supports a number of APIs for customization and automation. These

include AutoLISP, Visual LISP, VBA, .NET and ObjectARX. ObjectARX is a C++ class

library, which was also the base for: (a) products extending AutoCAD functionality to

specific fields; (b) creating products such as AutoCAD Architecture, AutoCAD Electrical,

AutoCAD Civil 3D; or (c) third-party AutoCAD-based application. There is a large number

of AutoCAD plugins (add-on applications) available on the application store Autodesk

Exchange Apps .

2.2.4 Vertical integration

Autodesk has also developed a few vertical programs (AutoCAD Architecture, AutoCAD

Civil 3D, AutoCAD Electrical, AutoCAD ecscad, AutoCAD Map 3D, AutoCAD

Mechanical, AutoCAD MEP, AutoCAD Structural Detailing, AutoCAD Utility Design,

AutoCAD P&ID and AutoCAD Plant 3D) for discipline-specific enhancements. For

example, AutoCAD Architecture (formerly Architectural Desktop) permits architectural

designers to draw 3D objects, such as walls, doors and windows, with more intelligent data

associated with them rather than simple objects, such as lines and circles.

The data can be programmed to represent specific architectural products sold in the

construction industry, or extracted into a data file for pricing, materials estimation, and other

values related to the objects represented. Additional tools generate standard 2D drawings,

such as elevations and sections, from a 3D architectural model. Similarly, Civil Design, Civil

Design 3D, and Civil Design Professional support data-specific objects, facilitating easy

standard civil engineering calculations and representations. Civil 3D was originally

developed as an AutoCAD add-on by a company in New Hampshire called Softdesk

(originally DCA). Softdesk was acquired by Autodesk, and Civil 3D was further evolved.

2.3 Variants

2.3.1 AutoCAD LT

AutoCAD LT is the lower cost version of AutoCAD, with reduced capabilities, first released

in November 1993. Autodesk developed AutoCAD LT to have an entry-level CAD package

to compete in the lower price level. AutoCAD LT, priced at $495, became the first AutoCAD

product priced below $1000. It is sold directly by Autodesk and can also be purchased at

computer stores (unlike the full version of AutoCAD, which must be purchased from official

Autodesk dealers).

As of the 2011 release the AutoCAD LT MSRP has risen to $1200. While there are hundreds

of small differences between the full AutoCAD package and AutoCAD LT, currently there

are a few recognized major differences in the software's features:

3D Capabilities: AutoCAD LT lacks the ability to create, visualize and render 3D models as

well as 3D printing.

Network Licensing: AutoCAD LT cannot be used on multiple machines over a network.

Customization: AutoCAD LT does not support customization with LISP, ARX, and VBA.

Management and automation capabilities with Sheet Set Manager and Action Recorder.

CAD standards management tools.

AutoCAD 360

View 1 View 2

AutoCAD WS Mobile App (iOS)

Formerly marketed as AutoCAD WS, AutoCAD 360 is an account-based mobile and web

application enabling registered users to view, edit, and share AutoCAD files via mobile

device and web using a limited AutoCAD feature set — and using cloud-stored drawing files.

The program, which is an evolution and combination of previous products, uses

a freemium business model with a free plan and two paid levels — marketed as Pro ($4.99

monthly or $49.99 yearly) and Pro Plus ($99.99 yearly) — including various amounts of

storage, tools, and online access to drawings. 360 includes new features such as a "Smart

Pen" mode and linking to third-party cloud-based storage such as Dropbox. Having evolved

from Flash-based software, AutoCAD 360 uses HTML5 browser technology available in

newer browsers including Firefox and Google Chrome.

AutoCAD WS began with a Flash-based version for the iPhone and subsequently

expanded to include version for the iPod Touch, iPad, Android phones, and Android

tablets. Autodesk released the iOS version in September 2010, following with

the Android version on April 20, 2011. The program is available via download at no cost

from the App Store (iOS), Google Play (Android) and Amazon Appstore (Android).

In its initial iOS version, AutoCAD WS supported drawing of lines, circles, and other shapes;

creation of text and comment boxes; and management of color, layer, and measurements —

in both landscape and portrait modes. Version 1.3, released August 17, 2011, added support

of unit typing, layer visibility, area measurement and file management. The Android variant

includes the iOS feature set along with such unique features as the ability to insert text or

captions by voice command as well as manually. Both Android and iOS versions allow the

user to save files on-line — or off-line in the absence of an Internet connection.

In 2011, Autodesk announced plans to migrate the majority of its software to "the cloud",

starting with the AutoCAD WS mobile application.

According to a 2013 interview with IlaiRotbaein, an AutoCAD WS Product Manager for

Autodesk, the name AutoCAD WS had no definitive meaning, and was interpreted variously

as Autodesk Web Service, White Sheet or Work Space.

2.3.2 Student versions

AutoCAD is licensed at a significant discount over commercial retail pricing to qualifying

students and teachers, with a 36-month license available. The student version of AutoCAD is

functionally identical to the full commercial version, with one exception: DWG files created

or edited by a student version have an internal bit-flag set (the "educational flag"). When such

a DWG file is printed by any version of AutoCAD (commercial or student), the output

includes a plot stamp / banner on all four sides.

Objects created in the Student Version cannot be used for commercial use. Student

Version objects "infect" a commercial version DWG file if it is imported.

The Autodesk Education Community provides registered students and faculty with free

access to different Autodesk applications.

CHAPTER 3: 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.

Oldham coupling

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.

Consequently, the flat edge abuts the longitudinal tab that rotates the latch coupling arm

when the outer disk coupler is rotated.

A coupling is a device used to connect two shafts together at their ends for the

purpose of transmitting power. Couplings do not normally allow disconnection of shafts

during operation, however there are torque limiting couplings which can slip or disconnect

when some torque limit is exceeded.

The primary purpose of couplings is to join two pieces of rotating equipment while

permitting some degree of misalignment or end movement or both. By careful selection,

installation and maintenance of couplings, substantial savings can be made in reduced

maintenance costs and downtime.

3.1 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.

Chapter 4: Types of couplings

Rigid

A rigid coupling is a unit of hardware used to join two shafts within a motor or mechanical

system. It may be used to connect two separate systems, such as a motor and a generator, or

to repair a connection within a single system. A rigid coupling may also be added between

shafts to reduce shock and wear at the point where the shafts meet.

When joining shafts within a machine, mechanics can choose between flexible and rigid

couplings. While flexible units offer some movement and give between the shafts, rigid

couplings are the most effective choice for precise alignment and secure hold. By precisely

aligning the two shafts and holding them firmly in place, rigid couplings help to maximize

performance and increase the expected life of the machine. These rigid couplings are

available in two basic designs to fit the needs of different applications. Sleeve-style couplings

are the most affordable and easiest to use. They consist of a single tube of material with an

inner diameter that's equal in size to the shafts. The sleeve slips over the shafts so they meet

in the middle of the coupling. A series of set screws can be tightened so they touch the top of

each shaft and hold them in place without passing all the way through the coupling.

Clamped or compression rigid couplings come in two parts and fit together around the shafts

to form a sleeve. They offer more flexibility than sleeved models, and can be used on shafts

that are fixed in place. They generally are large enough so that screws can pass all the way

through the coupling and into the second half to ensure a secure hold.Flanged rigid couplings

are designed for heavy loads or industrial equipment. They consist of short sleeves

surrounded by a perpendicular flange. One coupling is placed on each shaft so the two

flanges line up face to face. A series of screws or bolts can then be installed in the flanges to

hold them together. Because of their size and durability, flanged units can be used to bring

shafts into alignment before they are joined together. Rigid couplings are used when precise

shaft alignment is required; shaft misalignment will affect the coupling's performance as well

as its life. Examples:

Sleeve coupling

A sleeve coupling consists of a pipe whose bore is finished to the required tolerance based on

the shaft size. Based on the usage of the coupling a keyway is 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.

Sleeve couplings are also known as Box Couplings. In this case shaft ends are coupled

together and abutted against each other which are enveloped by muff or sleeve. A gib head

sunk keys hold the two shafts and sleeve together

Clamp or split-muff coupling

A clamp coupling is different from the sleeve coupling in that the sleeve used in this type is

split from one side.The shafts are entered and keyed to this sleeve and then split sides are

screwed together.

4.1  Flexible

Flexible couplings are used to transmit torque from one shaft to another when the two shafts

are slightly misaligned. Flexible couplings can accommodate varying degrees of

misalignment up to 3° and some parallel misalignment. In addition, they can also be used for

vibration damping or noise reduction.

A beam coupling, also known as helical coupling, is a flexible coupling for transmitting

torque between two shafts while allowing for angular misalignment, parallel offset and even

axial motion, of one shaft relative to the other. This design utilizes a single piece of material

and becomes flexible by removal of material along a spiral path resulting in a curved flexible

beam of helical shape. Since it is made from a single piece of material, the Beam Style

coupling does not exhibit the backlash found in some multi-piece couplings. Another

advantage of being an all machined coupling is the possibility to incorporate features into the

final product while still keeps the single piece integrity.

Beam coupling

Changes to the lead of the helical beam provide changes to misalignment capabilities as well

as other performance characteristics such as torque capacity and torsional stiffness. It is even

possible to have multiple starts within the same helix.

The material used to manufacture the beam coupling also affects its performance and

suitability for specific applications such as food, medical and aerospace. Materials are

typically aluminum alloy and stainless steel, but they can also be made in acetal, maraging

steel and titanium. The most common applications are attaching encoders to shafts and

motion control for robotics.

4.2 Constant velocity

There are various types of constant-velocity (CV) couplings: Rzeppa joint, Double

cardan joint, and Thompson coupling.

Diaphragm

Diaphragm couplings transmit torque from the outside diameter of a flexible plate to the

inside diameter, across the spool or spacer piece, and then from inside to outside diameter.

The deforming of a plate or series of plates from I.D. to O.D accomplishes the misalignment.

Disc

Disc couplings transmit torque from a driving to a driven bolt tangentially on a

common bolt circle. Torque is transmitted between the bolts through a series of thin, stainless

steel discs assembled in a pack. Misalignment is accomplished by deforming of the material

between the bolts,

Fluid

A gear coupling is a mechanical device for transmitting torque between two shafts

that are not collinear. It consists of a flexible joint fixed to each shaft. The two joints are

connected by a third shaft, called the spindle.

Each joint consists of a 1:1 gear ratio internal/external gear pair. The tooth flanks and outer

diameter of the external gear are crowned to allow for angular displacement between the two

gears. Mechanically, the gears are equivalent to rotating splines with modified profiles. They

are called gears because of the relatively large size of the teeth.

Gear couplings and universal joints are used in similar applications. Gear couplings have

higher torque densities than universal joints designed to fit a given space while universal

joints induce lower vibrations. The limit on torque density in universal joints is due to the

limited cross sections of the cross and yoke. The gear teeth in a gear coupling have

high backlash to allow for angular misalignment. The excess backlash can contribute to

vibration.

Gear coupling

Gear couplings are generally limited to angular misalignments, i.e., the angle of the spindle

relative to the axes of the connected shafts, of 4-5°. Universal joints are capable of higher

misalignments.

Single joint gear couplings are also used to connected two nominally coaxial shafts. In this

application the device is called a gear-type flexible, or flexible coupling. The single joint

allows for minor misalignments such as installation errors and changes in shaft alignment due

to operating conditions. These types of gear couplings are generally limited to angular

misalignments of 1/4-1/2°.

Rag joint

Rag joints are commonly used on automotive steering linkages and drive trains. When used

on a drive train they are sometimes known as giubos.

Universal joint

Universal joints are also known as Cardan joints.

Others

Bellows coupling — low backlash

Elastomeric coupling

o Bushed pin coupling

o Donut coupling

o Spider or jaw coupling (or lovejoy coupling)

Geislinger coupling

Resilient coupling

Roller chain and sprocket coupling

CHAPTER 5: OVERVIEW OF OLDHAM COUPLING

Requirements of good shaft alignment / good coupling setup

It should be easy to connect or disconnect the coupling.

It does allow some misalignment between the two adjacent shaft rotation axes.

It is the goal to minimise the remaining misalignment in running operation to

maximise power transmission and to maximise machine runtime (coupling and

bearing and sealings lifetime).

it should have no projecting parts.

it is recommended to use manufacturer's alignment target values to set up the machine

train to a defined non-zero alignment, due to the fact that later when the machine is at

operation temperature the alignment condition is perfect

5.1 Coupling maintenance and failure

Coupling maintenance is generally a simple matter, requiring a regularly scheduled

inspection of each coupling. It consists of:

Performing visual inspections, checking for signs of wear or fatigue, and cleaning

couplings regularly.

Checking and changing lubricant regularly if the coupling is lubricated. This

maintenance is required annually for most couplings and more frequently for

couplings in adverse environments or in demanding operating conditions.

Documenting the maintenance performed on each coupling, along with the date.

Even with proper maintenance, however, couplings can fail. Underlying reasons for failure,

other than maintenance, include:

Improper installation

Poor coupling selection

Operation beyond design capabilities.

The only way to improve coupling life is to understand what caused the failure and to correct

it prior to installing a new coupling. Some external signs that indicate potential coupling

failure include:

Abnormal noise, such as screeching, squealing or chattering

Excessive vibration or wobble

Failed seals indicated by lubricant leakage or contamination.

5.2 Checking the coupling balance

Couplings are normally balanced at the factory prior to being shipped, but they

occasionally go out of balance in operation. Balancing can be difficult and expensive, and is

normally done only when operating tolerances are such that the effort and the expense are

justified. The amount of coupling unbalance that can be tolerated by any system is dictated by

the characteristics of the specific connected machines and can be determined by detailed

analysis or experience.

5.3 Applications:

It is used to transfer torque between two parallel but not collinear shafts.

Depending upon the matterial 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,

5.4 PARTS OF OLDHAM’S COUPLING

Two hubs:

It is the part which is connected to the ends of the shafts. It is a round circular

shaped disk. The disk consists of groves in the center of them which is plugged into the

projections of central disk.

Central disk:

It is the coupling part of two hubs. It consist of two projected bars on the both

sides the disk which are perpendicularly plugged into the hubs. The center disk is press-fitted

to eliminate backlash and also designed to act as a mechanical fuse. The disc slides to

accommodate large parallel misalignment.

CHAPTER 6: WORKING

Oldham’s coupling is an example of third inversion of double-slider crank

mechanism. When link 3, of the double slider crank chain shown in fig. 1.28(c), is fixed and

link 1 is free to move, third inversion is obtained which is shown in fig 1.30. In this case each

of slide blocks (i.e. link 2 and link 4) can turn about the pins A and B. If one slide block (say

link 2) is turned through a definite angle, the frame (i.e. link 1) and the other block (i.e. link

4) must turn through the same angle.

This inversion is used in Oldham’s coupling (shown in fig 1.31) which is used

for connecting two parallel shafts when the distance between the two shafts is small. The two

shafts to be connected have flanges at their end which are rigidly fastened by forging to the

shaft. This flanges from link 2 and 4. Each of these links forms a turning pair with link

3.there is diametrical slot cut in the inner face of these flanges. An intermediate piece is a

circular disk (link 1) has two tongues T1 and T2 on each face at right angle to each other.

These tongues can slide-fit in the slots in the two flanges (link 2 and 4). The link 1 can slide

or reciprocate in the slots in the flanges. Frame and bearings form the link 3 which is fixed.

When the driving shaft is rotated, the flange A (i.e. link 2) connected rigidly to

the driving shaft also rotates by the same angle, the intermediate piece also rotate by the same

angle through which flange A has rotated. Due to rotation of intermediate shaft, the flange B

(i.e. link 4) connected to the driven shaft, also rotate by the same angle. Hence link 2, 4and 1

have the same angular velocity at every instant.

The distance between the axis of the shaft is constant and hence the center of

the intermediate piece will describe a circle of diameter equal to the distance between the

axes of the shafts. There is a sliding motion between the link 1 and each of the other link 2

and 4.

APPLICATIONS

Oldham Coupling Lubrication Pump

The lubrication pump on GE Reciprocating compressors is usually Directly driven by

the compressor Shaft through an Oldham coupling Which transmits the torque from the

reciprocating compressor crankshaft to the lube oil pump. In larger and high-speed (>700

RPM) compressors, the power absorbed by the lube oil pump is very high and therefore, the

coupling is a very critical item for compressor reliability.

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

Conclusion:

In this we develop drafting or drawing of orthogonal views(such as Front View & Top

View) of a universal Joint or Coupling , by using commands in Autocad 2D Modeling

software of version 2010 and fabrication of small non-linear Oldham coupling.