Windshield Wiper

A windscreen wiper (windshield wiper in North America) is a device used to wipe rain and dirt from a windscreen. Almost all automobiles are equipped with windscreen wipers, often by legal requirement.

Wipers can also be fitted to other vehicles, such as buses, trams, locomotives, aircraft and ships.

A wiper generally consists of an arm, pivoting at one end and with a long rubber blade attached to the other. The blade is swung back and forth over the glass, pushing water from its surface. The speed is normally adjustable, with several continuous speeds and often one or more "intermittent" settings. Most automobiles use two synchronized radial type arms, while many commercial vehicles use one or more pantograph arms.
Mercedes-Benz pioneered a system called the Monoblade in which a single wiper extends outward to get closer to the top corners, and pulls in at the ends and middle of the stroke, sweeping out a somewhat 'W'-shaped path.

Some larger cars are equipped with "hidden" (or "depressed-park") wipers. When wipers are switched off, a "parking" mechanism or circuit moves the wipers to the lower extreme of the wiped area, near the bottom of the windshield, but still in sight. To hide the wipers, the windshield extends below the rear edge of the hood, and the wipers park themselves below the wiping range at the bottom of the windshield, but out of sight.

Wipers may be powered by a variety of means, although most in existence today are powered by an electric motor through a series of mechanical components, typically two 4-bar linkages in series or parallel. Vehicles with air operated brakes sometimes use air operated wipers, run by bleeding a small amount of air pressure from the brake system to a small air operated motor mounted just above the windscreen. These wipers are activated by opening a valve which allows pressurized air to enter the motor.

Early wipers were often powered by manifold vacuum, but this had the drawback that manifold vacuum alters depending on throttle position and is almost non-existent under wide-open throttle; the wipers would slow down or even stop. This problem was overcome somewhat by using a combined fuel/vacuum booster pump. Some cars, mostly from the 1960s and 1970s, had hydraulically driven wipers.

On the earlier Citroën 2CV, the windscreen wipers were powered by a purely mechanical system: a cable connected to the transmission, to reduce cost this cable powered also the speedometer. The wipers' speed was therefore variable with car speed. When the car was waiting at a crossroad, the wipers were not powered, thus a handle under the speedometer allowed to power them by hand.

Most windscreen wipers operate together with a windscreen washer; a pump that supplies water and detergent (usually a blend called windscreen wiper fluid) from a tank to the windscreen through small nozzles, mounted on the hood or on the wipers, known as a 'wet-arm' system.

Some automobiles have small 'windscreen' wipers/washers on the headlights. In more modern vehicles, these have been replaced with a powerful jet spray, without wipers.
Some vehicles are fitted with wipers (with or without washers) on the back window as well. Rear-window wipers are typically found on hatchbacks, station wagons, sport utility vehicles, minivans, and some sports cars. They were first implemented in the 1970s, but SUVs did not use them until the 1980s.

Nowadays some cars include intelligent (automatic) windscreen wipers that detect the presence and amount of rain using a rain sensor, and automatically adjusts the speed of the blades according to the amount of rain detected.