Windscreen wiper
A windscreen wiper or windshield wiper is a device used to remove rain, snow, ice, washer fluid, water, or other debris from a vehicle's front window. Almost all motor vehicles, including cars, trucks, buses, train locomotives, and watercraft with a cabin—and some aircraft—are equipped with one or more such wipers, which are usually a legal requirement.
A wiper generally consists of a metal arm; one end pivots, and the other end has a long rubber blade attached to it. The arm is powered by a motor, often an electric motor, although pneumatic power is also used for some vehicles. The blade is swung back and forth over the glass, pushing water, other precipitation, or any other impediments to visibility from its surface. The speed is usually adjustable on vehicles made after 1969, with several continuous rates and often one or more intermittent settings. Most personal automobiles use two synchronized radial-type arms, while many commercial vehicles use one or more pantograph arms.
On some vehicles, a windscreen washer system is also used to improve and expand the function of the wiper to dry or icy conditions. This system sprays water, or an antifreeze window washer fluid, at the windscreen using several well-positioned nozzles. This system helps remove dirt or dust from the windscreen when used in concert with the wiper blades. When antifreeze washer fluid is used, it can help the wipers remove snow or ice. For these types of winter conditions, some vehicles have additional heaters aimed at the windows, embedded heating wire in the glass, or embedded heating wire in the wiper blade; these defroster systems can melt ice or help to keep snow and ice from building up on the windscreen. Less frequently, miniature wipers are installed on headlights to ensure they function optimally.
History
Early versions
One of the earliest recorded patents for the windscreen wiper is by George J. Capewell of Hartford Connecticut, which was filed on August 6, 1896. His invention was for "windows of slow-moving craft; but it is more particularly adapted and intended for windows of rapidly-moving vehicles, such as high-speed locomotives and cars, with which it is necessary that the observer or driver should have a clear view of the path or track." Similar to current automotive wiper designs, his invention involves "usually two of these wipers, and they can be secured to the frame below the front board of the vehicle or behind the housing surrounding the window in position to be out of sight and in such manner that one will scrape off the heaviest part of the substance collected upon the glass." His patent illustration shows a circular window, although the patent notes "it is not essential that the glass be circular in form."Other early designs for the windscreen wiper are credited to Polish concert pianist Józef Hofmann, and to Mills Munitions, Birmingham, who also claimed to have been the first to patent windscreen wipers in England.
At least three inventors patented windscreen cleaning devices at around the same time in 1903; Mary Anderson, Robert Douglass, and John Apjohn. In April 1911, a patent for windscreen wipers was registered by Sloan & Lloyd Barnes, patent agents of Liverpool, England, for Gladstone Adams of Whitley Bay.
American inventor Mary Anderson is popularly credited with devising the first operational windscreen wiper in 1903. In Anderson's patent, she called her invention a "window cleaning device" for electric cars and other vehicles. Operated via a lever from inside a vehicle, her version of windscreen wipers closely resembles the windscreen wiper found on many early car models. Anderson had a model of her design manufactured, then filed a patent on June 18, 1903 that was issued to her by the US Patent Office on November 10, 1903.
Irish born inventor James Henry Apjohn patented an "Apparatus for Cleaning Carriage, Motor Car and other Windows" which was stated to use either brushes or wipers and could be either motor driven or hand driven. The brushes or wipers were intended to clean either both up and down or in just one direction on a vertical window. Apjohn's invention had a priority date in the UK of 9 October 1903.
John R. Oishei formed the Tri-Continental Corporation in 1917. This company introduced the first windscreen wiper, Rain Rubber, for the slotted, two-piece windscreens found on many of the automobiles of the time. Today Trico Products is one of the world's largest manufacturers of windscreen wipers. Bosch has the world's biggest windscreen wiper factory in Tienen, Belgium, which produces 350,000 wiper blades every day. The first automatic electric wiper arms were patented in 1917 by Charlotte Bridgwood.
Inventor William M. Folberth and his brother, Fred, applied for a patent for an automatic windscreen wiper apparatus in 1919, which was granted in 1921. It was the first automatic mechanism to be developed by an American, but the original invention is attributed by others to Hawaiian, Ormand Wall. Trico later settled a patent dispute with Folberth and purchased Folberth's Cleveland company, the Folberth Auto Specialty Co. The new vacuum-powered system quickly became standard equipment on automobiles, and the vacuum principle was in use until about 1960. In the late 1950s, a feature common on modern vehicles first appeared, operating the wipers automatically for two or three passes when the windscreen washer button was pressed, making it unnecessary to manually turn the wipers on as well. Today, an electronic timer is used, but originally a small vacuum cylinder mechanically linked to a switch provided the delay as the vacuum leaked off.
Intermittent wipers
The inventor of intermittent wipers might have been Raymond Anderson, who, in 1923, proposed an electro-mechanical design.. In 1958, Oishei et al. filed a patent application describing not only electro-mechanical, but also thermal and hydraulic designs.. Then, in 1961, John Amos, an engineer for the UK automotive engineering company Lucas Industries, filed the first patent application in the UK for a solid-state electronic design..In 1963, another form of intermittent wiper was invented by Robert Kearns, an engineering professor at Wayne State University in Detroit, Michigan.. Kearns's design was intended to mimic the function of the human eye, which blinks only once every few seconds. In 1963, Kearns built his first intermittent wiper system using off-the-shelf electronic components. The interval between wipes was determined by the rate of current flow into a capacitor; when the charge in the capacitor reached a certain voltage, the capacitor would be discharged, activating one cycle of the wiper motor, and then repeating the process. Kearns showed his wiper design to the Ford Motor Company and proposed that they manufacture the design. Ford executives rejected Kearns' proposal at the time, but later offered a similar design as an option on the company's Mercury line, beginning with the 1969 models. Kearns sued Ford in a multi-year patent dispute that Kearns eventually won in court, inspiring the 2008 feature film Flash of Genius based on a 1993 New Yorker article that covered the legal battle.
In March 1970, French automotive manufacturer Citroën introduced more advanced rain-sensitive intermittent windscreen wipers on its SM model. When the intermittent function was selected, the wiper would make one sweep. If the windscreen was relatively dry, the wiper motor drew high current, which would set the control circuit timer to a long delay for the next wipe. If the motor drew little current, it indicated that the glass was still wet, and would set the timer to minimize the delay.
Power
Wipers may be powered by a variety of means, although most in use 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 pneumatic wipers, powered by tapping a small amount of pressurized air from the brake system to a small air operated motor mounted on or just above the windscreen. These wipers are activated by opening a valve which allows pressurized air to enter the motor.
Early wipers were often driven by a vacuum motor powered by manifold vacuum. This had the drawback that manifold vacuum varies depending on throttle position, and is almost non-existent under wide-open throttle, when the wipers would slow down or even stop. That problem was overcome somewhat by using a combined fuel/vacuum booster pump.
Some cars, mostly from the 1960s and 1970s, had variable-speed, hydraulically-driven wipers, most notably the '61–'69 Lincoln Continental, '69–'71 Lincoln Continental Mark III, and '63–'71 Ford Thunderbird. These were powered by the same hydraulic pump also used for the power steering mechanism.
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 also powered the speedometer. The wipers' speed was therefore variable with car speed. When the car was stationary, the wipers were not powered, but a handle under the speedometer allowed the driver to power them by hand.
Shape
Most early wipers used a rubber blade attached to a flat metal base. But as aerodynamic and styling concerns introduced curved windshields, these proved insufficient. In 1945, John W. Anderson, founder of Trico rival Anco, filed a patent for a wiper with branched arms to keep the blade pressed uniformly against both curved and flat glass, adaptable to almost any windscreen curvature. As curved windshields became more popular and widespread, following the debut of the 1947 Studebaker Starlight Coupe, these soon became standard equipment. While they have been superseded by "beam-type" wipers with bodies made of flexible material, this type still remains the most popular.Wiper blades are made of natural rubber, EPDM rubber or a combination of both, as natural rubber performs better in cold weather but EPDM rubber doesn't "set" and resists better to thermal aging, UV, ozone and tearing. Some manufacturers coat them with graphite.