Special Purpose Mechanisms

1
Special Purpose Mechanisms

• There are a number of special geometries of
  mechanisms that are used to perform specific
  purposes. Many have been discussed during the
  semester. A few more are discussed here.

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Parallel Mechanisms

• Parallel motion mechanism

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Parallel Mechanisms (cont.)

• Parallel stage mechanism

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Parallel Mechanisms (cont.)

• Pantograph mechanisms

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Parallel Mechanisms (cont.)

• Nuremberg Scissors

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Rotary to Linear Motion

• Wheel system (bicycle an example)
• Rack and pinion
• Lead screw
• Slider-crank mechanisms
• Straight-line mechanisms
• Scotch-yoke mechanism
• Cams, pulleys, etc.

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Rotary to Linear (cont.)

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Scotch-Yoke Mechanism

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Chebyshev Straight-Line Mech.

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Roberts Straight Line Mechanism
r3 0.5r1
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Intermittent Motion Mechanisms

• Geneva Wheel

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Intermittent Motion Mech. (cont.)

• Intermittent gears

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Intermittent Motion (cont.)

• Linear Geneva Mechanism

14
Ratcheting Mechanisms

• Allow motion in one direction only

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Mechanism Stability
A bistable mechanism has two stable equilibrium
positions
16
Switching Mechanisms

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Other Bistable Mechanism Configurations
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Infinite Variable Speed Drives

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Mechanism Resources

• Mechanism resource books
• Research journals
• Trade magazines
• Thomas Register
• Vender information and catalogs