String trimmer
A brushcutter, more powerful version in most brush cutters, called also in the weakest trimmer is a motor-driven device for mowing grass, herbaceous plants or woody undergrowth. More powerful devices can when equipped with a circular saw blade for cutting smaller trees and to about seven inches trunk diameter, such as thinning operations, are used. The use for mowing is done in commercial applications due to its relatively low surface coverage preferably where due to slope, poor accessibility, tightness or obstacles or lack of soil bearing capacity larger devices like bar mower or mower can not be used. The drive used in less powerful brushcutters partially electric motors, but otherwise save weight constructed two- or four-stroke gasoline engines to about 4 kW.
Function and structure
The operating principle is at brushcutter and clearing saw the same: By means of a shaft driven by the engine, partly through a gearbox, a schnellrotierendes cutting tool which cuts the Good to be mowed in the so-called breakpoint method without counter blade. As cutting tools, various systems are used, either one or more mounted on a sturdy trimmer head, nylon threads, washers with plastic wings as a knife or steel cutter discs or circular saw blades. At less powerful brushcutters can be found usually only one thread head as a cutting tool.
However, the motor is located in small, lower-performance equipment immediately above the cutting head, wherein powerful devices generally as balancing weight at the upper end of the sense shaft. Smaller units are held in a handle structure, in addition larger devices have a strap or carrying harness worn around the neck. It also devices are available, in which the motor is mounted on a guide on the device to be worn Kraxe and the cutting head is driven by a partially flexible shaft.
Diameter discs
The knives slice of a brush cutter, depending on the application, different forms: double-edged double-knife ( " grass blade " ) for light duty mowing of grass, star-shaped knife ( " brush cutter ") for the mowing of matted grass or undergrowth or circular saw blades for the removal of woody plants to to thin trees.
Thread heads
The attached in a line head thread pieces or rolled on a spool threads are stretched by the centrifugal force during operation and hit the blades of grass from. They have the advantage of adapting to obstacles (rocks, walls, trees ); sensitive bark of trees or walls are thus less severely damaged in case of accidental contact, you can mow close up to the subject.
The threads are - in contrast to the knife slices - very easy to replace: the end of the thread is worn out, a new piece will be either used or the thread simply withdrawn from the coil present in the string head. In many brushcutters the pulling of the thread is facilitated by a semi-automatic mechanism. It knocks the mowing head to the ground, and stressed easily gas. By tapping on the bottom of a large button is pressed, which releases the thread, so that another piece of the wound yarn is drawn by the centrifugal force from the head.
Security
The equipment should be operated only with the appropriate safety equipment:
- For lawn trimmers: sturdy shoes
- In brushcutters: thread cover, goggles, sturdy shoes
- In brushcutters: blade cover, goggles, hearing protection, cut resistant suit, gloves, safety shoes.
Because of the stones hurled around, etc. the risk posed to other than the equipment operator pursuant to the provisions of the German professional associations also nobody should stand in the vicinity ( 15 m) of the working device.
History
A precursor of the brushcutter is the Mulchmähsichel. It is a device for mowing weeds in unclear, small, or steep grassy areas such as vineyards. The Mulchmähsichel was invented in 1962 by Klaus Thormaehlen. A realization, however, never took place.