PANTOGRAPHSWINGING MECHANISMGENEVA MECHANISM

By:

NIMESH SUTHAR(12BME052)

ABHISHEK THAKKAR(12BME053)

NAISHAL THAKKAR(12BME054)

PANTOGRAPH

What is “PANTOGRAPH” ?

A pantograph is a mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen. If a line drawing is traced by the first point, an identical, enlarged, or miniaturized copy will be drawn by a pen fixed to the other.

Basic elements of PANTOGRAPH

It’s a simple pair kinematic mechanism consisting of :

1)Four links2)Pivot points3)One anchor point4)Tracing Pointer5)Pen holder

Proof:

∆ODA & ∆OCE are similar.As ∠COE is common, & ∠ADO=∠ECO, as AD||EC.

Hence, OD ‗ OA ‗ AD ___(1) OC OE EC

As all links are rigid,from thedisplaced position,we have:

CO=C’O , DA=D’A’ , OD=OD’CE=C’E’ , CD=C’D’ (2)

Þ OD’ ‗ A’D’ => ∆OD’A’ ~ ∆OC’E’ , as ∠C’OE’ is common. OC’ E’C’Þ OD’ ‗ A’D’ ‗ OA’ (3) OC’ E’C’ OE’

From equation 1,2,&3

Þ OA ‗ OA’ OE OE’

And ∠EOE’ is commonHence, ∆OAA’ ~ ∆OEE’

Þ AA’ EE’

Hence , it is proved that the pantograph produces similar objectsor images depending upon the scale defined.

APPLICATIONS:

1. Pantograph is incorporated into a milling machine with a revolving cutter instead of a pen, and a tray at the pointer end to fix precut lettered plates. In this way machinists can neatly and accurately engrave numbers and letters onto a part.

2. It is used in “LONGARM QUILTING” for stitching a custom pattern onto the quilt using a laser pointer.

In swinging/rocking mechanisms the output link swings/rocks/oscillates through an angle less than 360 degreeAlso to increase the no of revolutions the output shaft can be geared to the second shaft to produce large number of oscillations

What is mean by swinging?move to and fro or to oscillate.This mechanism is based on this basic motion.

SWINGING/ROCKING MECHANISMS

The swinging mechanisms can be observed in different types of systems such as:

1. Toothed-Rack System2. Crank and Slotted Lever Mechanism3. Crank and Rocker Mechanism4. Cam and Follower Mechanism

Swinging/Rocking Mechanisms

• Here the rotating crank(a) and the coupler(b) containing toothed rack meshes with the output gear (c) to produce the swinging/rocking motion of the gear

Toothed Rack System

The above figure shows a swinging mechanism in which rotating crank(2) drives the slider link(1) which slides on the output link producing an oscillating motion.

Crank and Slotted Lever Mechanism

This mechanism is called crank and slotted lever mechanism.The quick return is observed because the crank rotates through a large angle of forward stroke than on the return stroke .

Crank and Slotted Lever Mechanism

In the above mechanism the rotating crank(2) drives the rocker (oscillating lever(4)) through the coupler(3).This is a four-bar-linkage and called as crank and rocker mechanism.The characteristics of the rocking motion depends on the dimensions of the links.

Crank and Rocker Mechanism

APPLICATIONS• A common application of the crank rocker

mechanism is the windshield wiper

1. In this type of mechanism the rotating cam(c) drives the follower(d) in rocking motion via sliding interface(b).

2. The cam can be formed to produce the rocking motion of the follower. As the cam rotates it is the profile or shape of the cam that causes the follower to move in a particular way.

Cam and Follower Mechanism

GENEVA MECHANISM

GENEVA MECHANISM

Geneva mechanism was originally invented by a swiss watch maker.

The Geneva mechanism is basically a timing device. The name derives from the devices �earliest application in Mechanical watches , Switzerland and Geneva being an important center of watchmaking.

The geneva mechanism or geneva drive is also commonly called a Maltese cross mechanism In �the most common arrangement, the driven wheel has four slots and thus advances for each rotation of the drive wheel by one step of 90°. If the driven wheel has n slots, it advances by 360°/n per full rotation of the drive wheel. due to the visual resemblance.

GENEVA MECHANISM

The Geneva drive or Maltese �cross is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps.

GENEVA MECHANISM

One application of the Geneva drive is in movie projectors: the film does not run continuously through the projector. Instead, the film is advanced frame by frame, each frame standing still in front of the lens for 1/24 of a second (and being exposed twice in that time, resulting in a frequency of 48 Hz). This intermittent motion is achieved using a Geneva drive.

GENEVA MECHANISM

Other applications of the Geneva drive include the pen change mechanism in plotters, automated sampling devices, indexing tables in assembly lines, tool changers for CNC machines, banknote counting and so on. The Iron Ring Clock uses a Geneva mechanism to provide intermittent motion to one of its rings.

GENEVA MECHANISM

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