The Dirtwhacker Conveyor Belt Cleaner – a Brief History
The Dirtwhacker Conveyor belt cleaner is designed to be a Secondary Cleaner. It is positioned between 0-200 mm behind the head drum on a conveyor system.
The development of the Dirtwhacker belt cleaner goes back to the 1990’s when Justin Mat, a belt cleaner supplier in South Africa was challenged by a mine manager to “go away and come back only when you have developed a ‘maintenance free, belt friendly belt cleaner’”. Justin took him seriously and the development went as follows:
Justin spoke to the suppliers of rubber belts and enquired as to what is the best/safest material to use as a scraper – the answer was “anything that is blunt and does not get hot”. The reasoning was that a blunt blade and a blade that does not get hot cannot damage the belt.
Justin then explored at which angle of attack of the blade to the belt would give optimum cleaning. He dragged a belt over a blade, changing the angle of the blade for each experiment . The outcome was that a 90 degree angle offers the best blade/belt position.
But how to keep a blade at a constant 90 degrees to the belt when the belt is moving a speeds of 0.5-8 m/sec tangentially over the belt? This problem was overcome by positioning the blade at the edge of a parallelogram – regardless of the angles within the parallelogram, the blade would always be at right angles to the belt.
Finally, the question of how to maintain the blade against the belt as typically a parallelogram structure would collapse to a lying flat position. A rubber bladder was fed through the centre of the parallelogram and inflated to a pressure of 40-60 kPa.
Note, each blade on a Dirtwhacker belt cleaner is 150 mm wide. It has its own parallelogram and hence each blade acts independently of any other blade in the scraper, all the time riding on a cushion of air. The single bladder runs through all the parallelograms which has a fixed end cap on one side and a air inlet port (similar to a car tyre) and a pressure gauge at the other side.
So the result is a scraper blade that is constantly being pushed upwards by the air pressure in the bladder and is held “down” by the position of the scraper close to the head drum. The result is that the rubber belt is squeezed between the bald and the head drum. Evidence is the dirt is forced off the belt just prior to the blade due to the squeezing of the rubber and open up of the rubber structure, thereby causing the dirt to fall out. The outcome is then a cleaned belt going over a blunt blade, resulting in significantly less carry back, belt wear and roller wear compared to other scrapers.