1. 1. Pantograph, Swinging/Rocking Mechanism, Geneva Mechanism
2. 2. Pantograph
3. 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. 4. Some Application of Pantograph Drafting Sculpture and minting Acoustic cylinder duplication Milling Machine
5. 5. Swinging/Rocking Mechanism
6. 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. 7. (a) (b) (c) (d)
8. 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. 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. 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. 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. 12. Geneva Mechanism
13. 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. 14. A type of Geneva Mechanism
15. 15. Steps in an External Geneva Drive
16. 16. Advantages of Geneva Drive Can be made small They are able to withstand substantial mechanical stresses Can be manufactured cheaply
17. 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
18. 18. Variants of Geneva Mechanism Internal Geneva mechanism External Geneva mechanism Spherical Geneva mechanism Internal Geneva mechanism Spherical Geneva mechanism