From brushwood broom to electric sweepers
Nowadays, streets, sidewalks and larger outdoor areas are cleaned with ride-on sweepers. Often still with diesel-powered machines, but more and more frequently now also with the electrically powered version of the sweeper. But this was not always the case. A brief look at the history of street cleaning.
In the beginning was the brushwood broom
As early as the Middle Ages, brushwood, i.e. thin twigs, was tied together to form brooms and used for sweeping. From about the 17th century, hand brooms were manufactured by machine. These offered the advantage of a higher bristle density, but for floors with many joints, the brushwood broom offers the advantage of its bristles of different lengths to get better into the joints. A good compromise is offered by today’s industrially manufactured claw broom.
The hand sweeper is beeing developed
Since pushing dirt along in front of you was not particularly efficient, the hand sweeper was developed as the next evolutionary step in street cleaning. Still manually operated, the efficiency increased fivefold. Both, rotating rollers and horizontally rotating brooms are used here. The dirt is transported directly into a collection container.
The first street sweepers pulled by horse or powered by steam engine
In the 1840s, Joseph Whitworth invented the first street sweeper in Manchester, England.
Nevertheless, Charles Brooks is often credited as the inventor of the street sweeper, filing his patent for a street sweeper in the United States in 1896. However, this machine was only a further development. As early as 1849, C.S. Bishop had applied for a patent for a street sweeper in the USA. In total, more than 300 street sweeper patents had been issued in the U.S. before 1900.
Most street sweepers of the 19th century were horse-drawn. Chains and gears were used to harness the rotation of the wheels of the carriage to drive the rotating brushes.
In 1868, a self-propelled sweeper for cleaning railroad tracks was patented in the USA that was powered by a steam engine.
With the Industrial Revolution, the level of automation is increasing
The sweeper design generally consists of rotating rollers and one or more disc brushes that transport the swept material under the vehicle to the suction chute. A fan is used to create a vacuum that transports the debris into the dirt container. In truck-mounted sweeper the fan is driven by a separate (diesel) engine.
There are other collection methods. A distinction is made between the 3 categories:
- Pick-up by suction
- Mechanical pick-up
- Combination of suction and mechanical pick-up
Mechanical collection works in a similar way to manual collection with a hand brush and dustpan. Today, mechanical pick-up is primarily still found in manual sweepers. Street sweepers in the municipal and industrial /service sector mostly work with suction pick-up.
In order to retain respirable dust, a dry filter is installed in the suction air stream of mechanical sweepers. The filter, which is usually mounted in the upper rear section of the sweeping container, is equipped with an automatic pneumatic cleaning device that periodically cleans the filter elements according to the counterflow principle. The particles separated by the filter fall directly into the container and are disposed of with the rest of the sweepings.
Self-propelled street sweepers are often designed to be right-hand drive to provide the operator with a better view of the street gutter and side brush. In countries like the UK where cars drive on the left side of the road sweepers usually come with a left-hand drive.
Companies from Germany and Switzerland, in particular, were involved with the development of self-collecting suction sweepers, which are still in use today with a comparable principle. The sweeping-suction principle made it possible to transport the swept material in front of a suction mouth by means of two side brooms and possibly a third front broom. From here it is conveyed by a vacuum (generated by a suction turbine) into the sweepings container. By adding water to the side brooms and the suction chute, it is possible to bind the dust. Particle sizes down to 2.5 millionths of a millimeter can be captured (PM 2.5).
The second category is mechanical sweepers. These are able to pick up even larger particles from the ground, as they do not have a suction hose. This system also enables much faster sweeping. However, the dimensions of these machines are not suitable for sidewalk cleaning, as they are too large and heavy.
In 2008, a new revolution came with the development of a 3.5 ton machine that was able to clean sidewalks without a special permit according to §35StVO. (This is particular to German legislation, but there are comparable rules in several other countries). This paragraph states that no more than 3.5t can be driven on the sidewalk. 7 to 10 years later, many large manufacturers built 3.5t machines.
At the same time, this was the first properly functioning quick-change system that allowed the user to turn a sweeper into a four-wheel drive winter maintenance vehicle within 15 minutes. This, in turn, allowed cities to keep much smaller numbers of vehicles on hand.
The vehicle could also be converted into a watering or street-washing vehicle. Wet cleaning via a scrubbing deck brush was possible for the first time, even working backwards.
Even mowing directly into the sweepings container was possible for the first time.
Current trend
The current trend is clearly towards electric sweepers to keep emissions out of city centers. In combination with green electricity or, even better, photovoltaics on the roof of the building yard, cities and service providers can make street cleaning climate-neutral.