Abstract: A tamping unit includes tamping tines and a squeezing drive for squeezing the tamping tines. A vibration exciter has an outer cylinder and an inner cylinder. The inner cylinder is disposed coaxially to a cylinder axis and is mounted for displacement in an axial direction along sliding or gliding surfaces in the outer cylinder. A ring-shaped recess is provided between the two sliding or gliding surfaces which are spaced from one another in the axial direction. A spacer ring, which subdivides the ring-shaped recess into two fluid channels, is connected selectively to the inner or outer cylinder. The fluid channels are spaced from one another relative to the axial direction. The two fluid channels can be hydraulically actuated alternatingly by feed lines for vibration excitation.

Abstract: A tamping unit includes tamping tines and a squeezing drive for squeezing the tamping tines. A vibration exciter has an outer cylinder and an inner cylinder. The inner cylinder is disposed coaxially to a cylinder axis and is mounted for displacement in an axial direction along sliding or gliding surfaces in the outer cylinder. A ring-shaped recess is provided between the two sliding or gliding surfaces which are spaced from one another in the axial direction. A spacer ring, which subdivides the ring-shaped recess into two fluid channels, is connected selectively to the inner or outer cylinder. The fluid channels are spaced from one another relative to the axial direction. The two fluid channels can be hydraulically actuated alternatingly by feed lines for vibration excitation.