The document discusses three mechanisms: the pantograph, swinging/rocking mechanisms, and the Geneva mechanism.
The pantograph is a mechanical linkage that allows identical or scaled copies of an image to be traced. Swinging/rocking mechanisms use cranks, slots, levers or cams to produce oscillating motions of less than 360 degrees.
The Geneva mechanism uses a pin on a rotating drive wheel that engages with a slot on the driven wheel to produce intermittent rotary motion, advancing it by one step. It was first used in mechanical watches and has applications in movie projectors and automation equipment.
3. Introduction
It 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. Using the same principle, different kinds of pantographs are used for other
forms of duplication in areas such as sculpture, minting, engraving and milling.
Because of the shape of the original device, a pantograph also refers to a kind of structure that can
compress or extend like an accordion, forming a characteristic rhomboidal pattern. This can be found in
extension arms for wall-mounted mirrors, temporary fences, scissor lifts, and other scissor
mechanisms such as the pantograph used in electric locomotives and trams.
4. Some Application of Pantograph
Drafting
Sculpture and minting
Acoustic cylinder duplication
Milling Machine
7. Introduction
In swinging or rocking mechanisms (which are also called as oscillators), the output link rocks or
swings oscillates through an angle less than 360 degree.
9. Here fig.(a) shows a swinging mechanism, in which rotating crank-a
and coupler-b containing a toothed rack meshes with output gear-c
to produce the oscillating motion of gear-c (output link-c).
(a)
10. Fig.(b) shows swinging mechanism, in which rotating crank-b drives a link-c
(which is a slider), which slides in output link-d (which is a slotted link),
producing an oscillating or rocking motion. This mechanism is a crank and
slotted lever quick return mechanism. The quick return is observed because
crank rotates through a larger angle on the forward stroke of link-d than on
the return stroke.
(b)
11. Fig.(c) shows a swinging mechanism, in which rotating crank-b drives
rocker-d (oscillating lever-d) through a coupler-c. This is a four bar
linkage and typically called crank-and-rocker mechanism or crank-and-
lever mechanism. The characteristics of rocking motion depend on the
dimension of the links and the placement of the fixed points of link.
(c)
12. Fig.(d) shows a swinging mechanism, in which the rotating
cam-b drives follower-d, in a rocking motion. This is a cam-and-
follower mechanism. There are many cam-and-follower
mechanism used in engineering applications. In each case, the
cams can be formed to produce rocking motion of followers.
(d)
14. Background
The Geneva drive 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.
The name derives from the device's earliest application in mechanical
watches, Geneva, Switzerland being an important center of watchmaking.
The Geneva drive is also commonly called a Maltese cross mechanism due to the
visual resemblance when the driven wheel has four spokes
17. Advantages of Geneva Drive
Can be made small
They are able to withstand substantial mechanical stresses
Can be manufactured cheaply
18. Uses And Application
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.
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
