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
5. Swinging/Rocking Mechanism
6. 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.
7. (a) (b) (c) (d)
8. 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)
9. 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)
10. 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)
11. 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)
12. Geneva Mechanism
13. 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
14. A type of Geneva Mechanism
15. Steps in an External Geneva Drive
16. Advantages of Geneva Drive Can be made small They are able
to withstand substantial mechanical stresses Can be manufactured
cheaply
17. 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