Tamping machine

A tamping machine for tamping ballast underneath ties of a track, comprising:

• a) a machine frame extending in a longitudinal direction and supported on the track by two undercarriages for mobility in an operating direction;
• b) a sub-frame arranged between the said undercarriages and supported for mobility on the track by a further undercarriage comprising a unit motive drive, the sub-frame being connected to the machine frame by means of a frame support for displacement relative thereto in the longitudinal direction;
• c) a vertically adjustable tamping unit and track lifting unit arranged on the sub-frame between the further undercarriage and the frame support;
• and
• d) an acceleration drive provided for assisting the unit motive drive in displacing the sub-frame in the longitudinal direction, the acceleration drive being rigidly connected to the sub-frame by means of a drive fastening and comprising a piston end including a bracing plunger provided for temporary application to the machine frame, wherein a maximum stroke m of the acceleration drive is shorter than a maximum displacement path a of the sub-frame relative to the machine frame.

A method of assisting a relative displacement between a machine frame (2), moving continuously in an operating direction (12), and a sub-frame (11) which is displaceable relative thereto in the operating direction (12) with the aid of an acceleration drive (21), wherein a displacement cycle is composed of an advancing motion of the sub-frame (11) in the operating direction (12) and a subsequent local stoppage of the sub-frame (11) while the machine frame (2) moves on continuously, comprising the following steps:

• a) simultaneous actuation of a unit motive drive (18) of the sub-frame (11) and the acceleration drive (21) for effecting an advancing motion of a bracing plunger (24), butting against the sub-frame (11), together with the sub-frame (11) from an initial position to an end position;
• b) detaching the bracing plunger (24) from the sub-frame (11) and moving the latter forward by means of the unit motive drive (18);
• c) switching the acceleration drive (21) to a floating position;
• d) running the bracing plunger (24), moved forward as a result of the continuous advance of the machine frame (2), up against the sub-frame (11) which is stopped locally for carrying out a track tamping operation;
• and
• e) automatic return of the bracing plunger (24) into the initial position due to the displacement of the machine frame (2) relative to the locally stopped sub-frame (11).

A tamping machine for tamping ballast underneath ties of a track, comprising;

• a track-bound machine frame defining an axis and having two undercarriages for mobility in an operating direction;
• a self-propelled sub-frame arranged between the undercarriages and having an undercarriage for support on the track, said sub-frame being connected to the machine frame for displacement relative thereto in the direction of the axis;
• a vertically adjustable tamping unit and track lifting unit arranged on the sub-frame;
• and
• an acceleration drive constructed to assist the displacement of the sub-frame and including a piston having an end and a movable bracing plunger connected to the end of the piston for applying a propulsion force to move the sub-frame, wherein the acceleration drive has a maximum stroke which is shorter than a maximum displacement of the sub-frame relative to the machine frame.

A tamping method, comprising the steps of:

• mounting a tamping unit to a sub-frame of a tamping machine to allow movement thereof relative to a machine frame of the tamping machine;
• assisting an acceleration of the sub-frame by a primary drive through actuation of a secondary drive through application of a propulsion force by means of a bracing plunger so that the sub-frame is advanced from a trailing end position to a leading end position in relation to the machine frame, whereby the bracing plunger no longer applies the propulsion force upon the sub-frame in the leading end position;
• stopping the sub-frame when reaching the leading end position for allowing the tamping unit to execute a tamping operation, while the tamping machine continues to advance;
• and
• switching the bracing plunger into a pressureless state to automatically return the sub-frame to the trailing end position, as the tamping machine continues to advance.