Brush unit for an electric machine, spring and seal arrangement for the same, and method for the production thereof

A brush unit for an electric machine has a simple and low-cost but robust design, and can be assembled at low-cost using simple process steps comprises four ring-shaped board elements are stacked on each other, namely two outer circuit boards, each of which is electrically conductively connected to one or more brushes. Two guide boards made of electrically insulative material disposed therebetween, comprise a shape having protrusions and recesses for forming radial guides for the brushes and receptacles for springs acting on the brushes. The springs are spiral springs wound around a mandrel, the flat ends thereof protruding past the springs being rotationally fixedly guided in a guide groove of each receptacle and able to engage behind a stop. In order to assemble the brush unit, the circuit and guide boards are stacked on each other in the axial direction and riveted, then the brushes are inserted in the guides in the radial direction and the springs are placed in the receptacles.