Keeping your front and rear windscreens clear

They’ve been with us for over a hundred years and have hardly changed. They are still rubber blades that sweep water off a glass surface. But did you know that windscreen wipers were invented by a woman?

29. 1. 2021 Škoda World INNOVATION & TECHNOLOGY

Two types of motor

The movement of windscreen wipers across the front or rear windscreen is made possible by a hidden linkage mechanism driven by a direct-current electric motor. “In smaller cars like the FABIA or SCALA we use a simple wiper motor for the windscreen. We call this kind of motor rotary, as the motor’s crank attached to a shaft rotates around its own axis. The motor does not have a control unit. The operating logic – i.e. when to activate the wiping motion and at what speed – is controlled by the car’s control unit. Naturally, the advantage of this system is its simplicity, while the down side is the limited functionality compared to reversible motors,” explains Pavel Švejdar, an expert from the Wipers and Washers department.

We therefore find reversible motors in higher-end models. They operate by means of controlled synchronous rotation of the shaft in line with the currently required output, swing and speed. As a result, this design is quieter and smoother and offers a wider range of functions, such as a lower park position allowing the wipers to be concealed beneath the edge of the bonnet when they aren’t in use. But the rotary version also offers convenient functions like the service position (you can find out here how to put the wipers in that position), slower wiping when stopped at a junction, or rain-sensor control (you can find out more about sensors here).

Fine-tuning in a wind tunnel

“The motor itself is connected to a kinetic mechanism via which the rotary movement is transmitted to the wipers. Development places great emphasis on the functionality and robustness of the system as a whole at low and high temperatures and at high speeds. We also pay close attention to the noise generated by the system. The system is designed to function flawlessly at temperatures from minus thirty to plus seventy degrees,” says Švejdar, adding that the wiper blades are tested over five hundred thousand cycles. Needless to say, it’s a good idea to replace your blades much sooner, with experts recommending that new blades should be fitted every six months.

Front windscreen wiper testing

When work starts on the development of a new car model, the amount of available space, the surrounding parts and the design of the car itself are factored into the design of the wiper system. The wipers supplier then adapts the basic design to its technologies. Testing is done by both the carmaker and the wipers supplier. The process as a whole takes roughly three years.

Rear windscreen wiper testing

The wipers’ behaviour is fine-tuned down to the smallest detail in a wind tunnel. The propulsion system, the curve of the frame, the pressure exerted and the shape of the flexor have to be perfectly calibrated so that airflow does not lift the blade off the glass in places. Considerable attention is also paid to the ideal interaction of wipers and sprays, in conditions ranging from stationary to a car’s top speed. This should make it obvious that original wipers are very different from generic products that are usually intended for a wide range of models from various manufacturers. By contrast, original parts are tailor-made for a specific model.

Do your wipers jump?

In higher-end models with reversible wiper motors ŠKODA uses two park positions for the windscreen wipers: basic and extra. Maybe you’ve already noticed that from time to time when you switch off the engine or set off, the wipers seem to jump - even though it’s not raining and you didn’t touch the wiper stalk on the steering wheel. This is a protective function that prevents deformation of the rubber blade that might result from remaining in the same park position for a long time when the wipers are idle. The alternation of the two park positions is controlled by an internal algorithm defined in the wiper motor control unit’s software.

A wider area, or more stability at high speed?

Great attention is also paid to windscreen washer sprays during development. The key issue is their location, which must allow the washer fluid to cover the largest possible active (i.e. wiped by the wipers) surface of glass as evenly as possible in all conditions, at all speeds and with all types of fluid. Another objective is to make sure the washer sprays are not distracting: so the jet of fluid should be as even as possible and there should be no excess noise. In addition, there should be no moving fluid when wiping is deactivated.

Did you know?

• The biggest windscreen wiper factory in the world is in the town of Tienen in Belgium. The factory produces 350,000 wipers of seven hundred different types every day.

• Rear windscreen wipers first made their appearance in the 1940s, but it was not until the 1960s that they became widespread.

• Automatic wiper activation for a few cycles when the washers are used – something we take for granted today – premiered in cars at the end of the 1950s. While nowadays this is controlled by an electric timer, back then the necessary delay was produced by a little vacuum cylinder connected to a switch: the wipers were not activated until pressure was regained in the vacuum cylinder.

ŠKODA uses three types of washer nozzle in its cars: fluid, ball and a combination of the two. The conventional technology, i.e. ball nozzles, has one indisputable advantage: the high energy of the fluid jet, which allows accurate targeting of the impact point. That’s useful at high speeds when the jet is more stable and less affected by airflow. Its disadvantage is a small water impact area and complicated positioning of the balls.

ŠKODA uses only fluid or combined nozzles on its front windscreens. “Fluid nozzles work on a similar principle as, say, the sprinklers used to water football pitches. It’s not just a flat jet of water but a pulsing fluid jet that is created hydrodynamically by a chip integrated directly into the nozzle. The advantages of this design are that a large area of glass gets covered straightaway and it’s not hard to aim the jet. The disadvantages are less accuracy at higher speeds and, to some extent, the fact that the driver's vision is slightly impeded before the first wiper movement. On rear windscreens we use either fluid or ball nozzles, depending on the size and angle of the windscreen and the amount of room available for the mechanism,” Švejdar adds.

Fluid washer nozzle

Ball washer nozzle

Combinated washer nozzle

Cherchez la femme

The history of windscreen wipers did not start with a bang. And, as tends to be the case, there are several people who lay claim to having invented them. A functional mechanism for front windscreen cleaning was patented by three people – and all in 1903.

At the start of the 1900s, an Alabama estate agent, farmer and wine grower called Mary Anderson was on a tram while visiting New York. It was cold and wet. The rain froze on the windscreen, obscuring the driver’s view. As was customary at the time, the driver opened a side window and reached round to wipe the windscreen. But, much to the passengers’ chagrin, that let freezing cold air into the tram. Ms Anderson started to wonder about a device that could be controlled from inside.

A few months later she came up with her prototype of a rubber-sheathed wooden arm that was controlled by a lever close to the steering wheel. The lever activated a spring mechanism that moved the arm over the glass. The inventor obtained a patent on 10 November 1903 but never found an investor. Anderson’s problem was that she was ahead of her time: the automobile boom did not start until ten years after her invention. By around 1916 windscreen wipers were already a standard feature on American cars. But her patent expired before the inventor could make any money out of it.

Robert Douglass was just a few months quicker than Anderson, obtaining a patent for a “locomotive cab window cleaner” on 12 March 1903. And to make things even more confused, the Irish inventor James Henry Apjohn patented his “apparatus for cleaning carriage, motor car and other windows” on 9 October 1903.