Glossary: Windshield wiper

A windshield wiper is a mechanism which moves a rubber blade back and forth to wipe the windshield, operated electrically, by vacuum or by compressed air. However, all present-day automobiles are equipped with electrically operated wipers. Wipers are used to remove rain water, moisture and dirt from the windshield. Usually there are two synchronized radial type arms which help in doing the above. Mercedes-Benz created a system called the ‘Monoblade‘ in which a single blade could do the job of two blades. The wiper arm extends outward to get closer to the top corners, and pulls in at the ends and middle of the stroke. Thus one blade was enough to sweep across the entire surface area of the windshield. In some cars, smaller wipers were used to clean the headlights.

Vehicles with air operated brakes use air powered wipers. Here, pressurized air is used to power the motor. In earlier times, intake manifold vacuum was used as the power source. But the main drawback was that the wiper speed was fully dependent on the throttle position. At wide open throttle conditions, the wipers would stop working due to loss of manifold vacuum as the manifold pressure would be almost equal to the atmospheric pressure. Other manufacturers tried powering the wipers by the engine. They connected the wipers directly to the transmission. But the wiper speed was dependent on the engine speed and at idling conditions, it wouldn’t work properly.

The wiper blade is connected in six to eight places to the arm. This ensures proper and uniform cleaning across the windshield. The speed of the wiper is controlled by a switch on the side of the steering column and the time delay between the blade movements can be controlled. In some modern cars, the wipers work automatically when it rains. In this system, a rain sensor is used, which uses hygroscopic material to activate a switch. In other systems, optical sensors are employed which sense moisture on the windshield and control the wiper speed accordingly. All these systems come with a overriding switch.