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Josephashwin FranklinKwongvoon Wong

Chen Lin

•Windshield Wiper

• Soft Top Mechanism

Cascading Four-bar Mechanisms

•Open Loop Four-bar Configuration- Used in Industrial robots- Usually requires multiple actuators to control motion

•Pantograph Linkage- Originally used in scaled diagrams- Linkages consist of Parallelograms

http://auto.howstuffworks.com/convertible2.htm

Open Loop Four-bar

L= 4, J1= 3, J2= 0 DOF = M =3

Pantograph Linkage

L= 4, J1= 3, J2= 0 DOF = M = 1

Reason for Four-Bar Design Pantograph serves as a locking mechanism Use of Limiting Position simplifies complex

motion Parallel linkages prevent further motion when

collinear

The four-bar linkage has been show as the simplest possible pin-jointed mechanism

Allows for single degree of freedom controlled motion

Grashof Condition

S+L<P+QClass I case:• Ground either link

adjacent to the shortest and you get a crank-rocker

• The shortest link will fully rotate

• the other link pivoted at the ground will oscillate

Tandem system is widely used in the front windshield

One Motor runs both wipers

Parallelogram linkage translates motion to wipers

DOF= 3*(6-1)-2*7=1

Four and Six-bar is a parallelogram linkage.

Duplicate the rotary motion of the driver crank at the driven bar.

Most Common Type of Windshieldmechanism

The coupler of the parallelogram linkage is in curvilinear translation

Remaining at the same angle while all points on it describe identical circular paths

Crank Rocker Input toWindshield Wiper

Varying ???

The slider-crank mechanism Variations of grounding

different links

Inversion D

Window Single Arm

DOF = 3*(4-1)-2*4= 1

We can imagine that the coupler link length is very small

How is the condition when driver link length change?

Diagram of Rear Wiper

Flexblade(TM) Wiper .Its life can extend from months to years

The four-bar linkage mechanism will still be used in this wiper system for a long time

How Windshield Wipers Work. (2006) In: How Stuff Works Available: <http://auto.howstuffworks.com/wiper2.htm> [2007, October 12].

Norton, R.L. Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms and Machines. 3rd ed. New York, McGraw-Hill Co. 2006.

How soft top convertible works. (2006) In: How Stuff Works Available: <http://auto.howstuffworks.com/wiper2.htm> [2007, October 12].

Pantographs.(2006) In: Wikipedia The Free Encyclopedia:

<http://en.wikipedia.org/wiki/Pantograph> [2007, October 12].

• Questions?

The crank-rocker system will change to be two crank system

• Contact points in trains

• Linkages on locomotives

• Pushrods mechanism• Car door linkages

Rear windshield wiper

Single application of

Four-bar mechanism

• Similar to

How is the difference of Rear wiper?