Mechanism

1. Mechanism Machines are mechanical devices used to accomplish work. A mechanism is a heart of a machine. It is the mechanical portion of the machine that has the function of transferring motion and forces from a power source to an output. Mechanism is a system of rigid elements (linkages) arranged and connected to transmit motion in a predetermined fashion. Mechanism consists of linkages and joints. UC Berkeley

2. Can crusher Simple press Rear-window wiper Example of Mechanism UC Berkeley

3. Moves packages from an assembly bench to a conveyor Microwave carrier to assist people on wheelchair Lift platform Example of Mechanisms UC Berkeley

4. Lift platform Front loader Device to close the top flap of boxes Example of Mechanisms UC Berkeley

5. Rowing type exercise machine Conceptual design for an exercise machine Example of Mechanisms UC Berkeley

6. Example of Mechanisms Extension position Flexed position Six-bar linkage prosthetic knee mechanism UC Berkeley

7. Four-Bar Linkage UC Berkeley

8. Four-Bar Linkage Categories UC Berkeley

9. Four-Bar Linkage Categories UC Berkeley

10. 4-Bar mechanisms UC Berkeley

11. S + l > p + q 4-Bar mechanisms 4 double rocker mechanisms UC Berkeley

12. The Slider-Crank Mechanism UC Berkeley

13. The Slider-Crank Mechanism UC Berkeley

14. Slider-Crank Mechanism - Inversion UC Berkeley

15. Function Generation Mechanisms A function generator is a linkage in which the relative motion between links connected to the ground is of interest. Mechanism Categories A four-bar hand actuated wheelchair brake mechanism UC Berkeley

16. Mechanism Categories Function Generation Mechanisms A four-bar drive linkage for a lawn sprinkler UC Berkeley

17. Mechanism Categories Motion Generation Mechanisms In motion generation, the entire motion of the coupler link is of interest (rigid body guidance). New Rollerblade brake system UC Berkeley

18. Mechanism Categories Motion Generation Mechanisms Four-bar automobile hood linkage design UC Berkeley

19. Mechanism Categories Path Generation Mechanisms In path generation, we are concerned only with the path of a tracer point and not with the motion (rotation) of the coupler link. Crane – straight line motion UC Berkeley

20. Primary Joints UC Berkeley

21. Higher Order Joints UC Berkeley

22. Motion Generation Mechanisms Moving a storage bin from an accessible position to a stored position Rotating a monitor into a storage position UC Berkeley

23. Motion Generation Mechanisms Moving a trash pan from the floor up over a trash bin and into a dump position Lifting a boat out of water UC Berkeley

24. Function Generation MechanismsGraphical Solution Two position synthesis – Design a four-bar crank and rocker mechanism to give 45o of rocker rotation with equal time forward and back, from a constant speed motor input. 1 – Draw the rocker O4B in both extreme positions, B1and B2 in any convenient location with angle θ4 = 45o. 2 – select a convenient point O2 on line B1B2 extended. 3 – Bisect line B1B2 , and draw a circle with that radius about O2. 4 – Label the two intersection of the circle with B1B2 extended, A1 and A2. 5 – Measure O2A (crank, link2) and AB (coupler, link3). UC Berkeley

25. Function Generation MechanismsGraphical Solution UC Berkeley

26. Crank-Rocker Mechanism UC Berkeley

27. Motion Generation MechanismsGraphical Solution Two position synthesis – C1D1 and C2D2 • Draw the link CD in its two desired positions, C1D1 and C2D2 • Connect C1 to C2 and D1 to D2. • Draw two lines perpendicular to C1 C2 and D1D2 at the midpoint (midnormals) • Select two fixed pivot points, O2 and O4, anywhere on the two midnormals. UC Berkeley

28. Motion Generation MechanismsGraphical Solution Two position synthesis (coupler output) – C1D1 and C2D2 The rigid body to be moved from position 1 to 2 is secured to link 3. UC Berkeley

29. Motion Generation MechanismsGraphical Solution Two position synthesis (coupler output) with Dyad added. 1 – Select any point B1 on link O2C1. Locate B2. 2 – Choose O6 anywhere on B1B2 extension. 3 – Draw a circle from O6 with radius B1B2/ 2. Mark the intersection with B1B2 extension as A1 and A2. UC Berkeley

30. Motion Generation MechanismsGraphical Solution Two position synthesis (coupler output) with Dyad added. UC Berkeley

31. Motion Generation MechanismsGraphical Solution Two position synthesis (rocker output) – C1D1 and C2D2 UC Berkeley

32. 2 Position Motion – rocker output UC Berkeley

33. Motion Generation MechanismsGraphical Solution Three position synthesis – C1D1, C2D2andC3D3 • Draw the link CD in its three desired positions. • Follow the same procedure,draw construction lines, C1C2, C1C3 and C2C3. Same for point D. • Draw three midnormals for each point. • Locate the intersection of the three midnormal, O2 and O4 are the two fixed pivot points. UC Berkeley

34. Motion Generation MechanismsGraphical Solution Three position synthesis – C1D1, C2D2andC3D3 UC Berkeley

35. 3 Position Motion UC Berkeley

36. 3 Position Motion UC Berkeley

37. 3 Position Motion UC Berkeley

38. Slider-Crank Mechanism The mechanism has a stroke B1B2 equal twice the crank length r2. Locations B1 and B2are called the extreme positions (limiting) of the slider In-line slider crank mechanism UC Berkeley

39. Slider-Crank Mechanism Offset slider-crank mechanism UC Berkeley

40. Straight line Mechanisms UC Berkeley

41. Straight Line Mechanism UC Berkeley

42. Scotch Yoke Mechanism UC Berkeley

43. Geneva Mechanism UC Berkeley

44. Linear Geneva Mechanism UC Berkeley

45. Ratchet Mechanism UC Berkeley

46. Straight Beam Walking Mechanism UC Berkeley

47. UC Berkeley

48. Roller and Flat Follower Cams UC Berkeley

49. Cylindrical Cam Mechanism UC Berkeley

50. Gears – Rack and Pinion UC Berkeley