Mandrel used for digital printing on can members

1. A method of location-accurate positioning and controlled precision movement of rotationally symmetrical hollow bodies, in particular integral cans comprising a body portion and a bottom, the method comprising:

synchronously applying radially acting clamping forces to a rotationally symmetrical inside surface of a hollow body by means of a plurality of clamping surfaces provided on a rotatable clamping mandrel and forming an outwardly facing cylindrical clamping surface for engaging an inside surface of the hollow body;

rotating said clamping mandrel and said hollow body; and

synchronously disengaging said clamping surfaces from said hollow body;

wherein the radially acting clamping forces are at least one of applied and released by a pressure change caused by air flow through the clamping mandrel.

2. A method of location-accurate positioning and controlled precision movement of rotationally symmetrical hollow bodies formed integrally from a body portion and a bottom, by means of a rotatable clamping mandrel for each of the hollow bodies, the method comprising:

co-axially fitting a hollow body on to the clamping mandrel by providing a reduced pressure within the clamping mandrel;

bracing the hollow body with the clamping mandrel by a pressure force caused by the reduced pressure acting radially from the clamping mandrel, wherein the pressure force is applied by clamping segments moved outwardly and synchronously by the reduced pressure; and

rotating said clamping mandrel and said hollow body with a motion unit, the motion unit comprising a controllable drive and a shaft.

3. The method according to claim 2 , wherein the motion unit of the clamping mandrel and the hollow body are released by means of compressed air.

4. The method of claim 2 , wherein a control portion of the mandrel is provided with a return device which applies an axial force axially rearwardly away from a front end of the clamping mandrel.

5. The method according to claim 4 , wherein the return device is biased in the retracted rest position of the control portion by a spring.

6. The method of claim 4 , wherein the control portion is returned by the axial force loading after a respective removal of a hollow body from the clamping mandrel into a neutral rest position which is so positioned that even hollow bodies which fluctuate in diameter can be axially received by the clamping mandrel in the rest position of the control portion.

7. A method of location-accurate positioning and controlled precision movement of rotationally symmetrical hollow bodies formed from a body portion and an integrally adjoining bottom, by means of a controlledly moved clamping mandrel for each of the hollow bodies, comprising:

co-axially fitting a hollow body on to a clamping mandrel;

bracing the hollow body with the clamping mandrel by a reduced pressure within the clamping mandrel acting radially from the inside outwardly; and

providing a controlled precision rotational movement of the clamping mandrel with a motion unit, the motion unit comprising a controllable drive and a shaft.

8. The method according to claim 3 , further comprising the step of axially removing the hollow body from the clamping mandrel with the same compressed air.

9. The method of claim 7 , wherein the controlled precision movement is a stepwise movement.