The figure shows the split ring commutator and the two carbon brushes in their respective positions.
What can you say about carbon brush and split ring commutator?
When the gaps of the split ring commutator are in alignment with the carbon brushes, then contacts are broken and the current is temporarily cut-off.
However, the coil keeps on rotating in the same direction due to its inertia until the split ring commutator and the '* carbon brushes are in contact again.