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Our windshield wipers are an important tool on our car, especially during the rainy seasons. They have changed dramatically over the years, from the manual device that had to be moved from side to side by a handle from inside the vehicle, to the automatic ones we use today. We all know how to use them, but do we know how they work?
The windshield wipers are powered by a small motor, which has a worm gear attached.
A worm gear is a device that has a spiral cut into it, attached to it is a gear that is round with teeth around the outside. As the spiral (the worm) turns, it cuts into the teeth of the gear therefore turning the gear. There is a rod attached to the centre of the gear, so that as the gear turns, so does the rod. On the end of the rod is a small cam, this also turns as the rod turns.
The blades attached to the windshield wiper arms are made of rubber, and have to apply precise pressure to the windshield to prevent smudges or leaving lines as they move from side to side. This is achieved by having up to eight different connections attaching the rubber blade to the arm. The arms are each attached to a vertical rod and these rods are joined together by a longer horizontal rod. Attached to the end of the horizontal rod, is another rod that runs diagonally to the cam. As the cam turns, it moves the attached diagonal rod in a circular motion. This then moves the horizontal rod from side to side, which then in turn moves the vertical rods in the same way; therefore moving the windshield wipers to and from.
Most cars have different speed settings for the windshield wipers. When it is raining heavily we generally select the high speed motion, by doing this the maximum power is sent to the windshield wiper motor increasing its speed. When it is raining lightly we select the intermittent position and the power is then reduced and cut to the motor for a short time after each wipe.
Over the years there have been many new inventions to create different systems for cleaning the dirt, rain and snow from our windshields, however many of these didn’t really take off as drivers found them more annoying than helpful.
The latest innovation in windscreen wipers is the rain sensing wipers. This new creation detects moisture on the windscreen and selects the appropriate speed that the wipers should use automatically. It works by using a sensor that sends out an ultra violet light. When the windscreen is clear the light can reflect back to the sensor, but when there is rain and moisture on the windscreen then less light returns to the sensor. This information allows the sensor to determine how much it is actually raining and change the speed of the wipers accordingly.