Windscreen wiper

From Wikipedia, the free encyclopedia

windscreen wiper on a parked car.

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. Though confusingly, some legal systems require wipers without requiring a windscreen.

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.

Most windscreen wipers operate together with a windscreen washer; a pump that supplies water and detergent 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 detects 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.

[edit] History

Inventor J. H. Apjohn came up with a method of moving two brushes up and down on a vertical plate glass windshield in 1903.

Mary Anderson is said to have invented the windshield wiper swinging arm in the United States, where she patented the idea in 1905. The idea was initially met with resistance, but was a standard feature on all American cars by 1916.

In April 1911, the first British patent for windscreen wipers was registered by Sloan & Lloyd Barnes, patent agents of Liverpool, England, for Gladstone Adams of Whitley Bay. The first designs for the windscreen wiper are also credited to Józef Hofmann, better known as a pianist.

In 1970. Saab Automobile introduced headlight wipers across the product range. These operated on a horizontal reciprocating mechanism, with a single motor. They were later superseded by a radial spindle action wiper mechanism, with individual motors on each headlamp.

In the late 20th century, rain-sensing windshield wipers appeared on various models, one of the first being Buick's Park Avenue Ultra. As of early 2006, rain-sensing wipers are standard on all Cadillacs, and are available on many other GM, Peugeot, Citroën, Toyota, Mercedes, Honda and Renault as well as many other main-stream manufacturers.