Method and drive-out device for driving out a blade

1. A method for driving out a blade, a blade root of which is held in an elongate receiving groove of a wheel disk arranged on a stacked rotor, the method comprising:

a) providing a drive-out device, which has a driving-out ram actuated by way of a hydraulic cylinder, the drive-out device having a housing and a mechanism within the housing which transforms a straight movement of the piston rod into a straight movement of the driving-out ram, the directions of movement being different, wherein the mechanism includes a first body, which is fastened to the piston rod and defines a first sloping surface, a second body, which is fastened fixedly within the housing and defines a second sloping surface, and a third body, which is fixedly connected to the driving-out ram and slidably engages the first sloping surface;

b) positioning the drive-out device between two adjacent wheel disks of the stacked rotor in such a way that a longitudinal axis of the driving-out ram is in line with the elongate receiving groove of the blade to be driven out;

c) setting a maximum pressure to which the hydraulic cylinder can be subjected;

d) extending the driving-out ram, so that the driving-out ram presses with increasing pressure against the blade root of the blade to be driven out, wherein the pressure is increased until the maximum pressure is reached;

e) reducing the pressure to a preset minimum pressure as soon as the pressure has reached the maximum pressure and increasing the pressure to the maximum pressure as soon as the minimum pressure is reached so that a hydraulic pressure is provided to the drive-out device in a pulsating manner; and

f) cyclically repeating steps d) and e) until the blade has been removed from the elongate receiving groove.

2. The method as claimed in claim 1 , wherein the elongate receiving groove is inclined with respect to an axial direction of the stacked rotor.

3. The method as claimed in claim 1 , wherein the maximum pressure is at least 150 bar.

4. The method as claimed in claim 1 , wherein steps d) and e) are repeated with a cycle time in the range of 2 Hz to 10 Hz.

5. The method as claimed in claim 1 , wherein the maximum pressure is at least 80 bar above the minimum pressure .

6. The method as claimed in claim 1 , wherein the method is carried out in a state in which the stacked rotor is accommodated in a housing of a turbo machine.

7. The method as claimed in claim 1 , wherein the third body, defines a third and a fourth sloping surface, the third sloping surface lying against the first sloping surface and the fourth sloping surface lying against the second sloping surface and being guided.

8. The method as claimed in claim 1 , wherein the maximum pressure is at least 200 bar.

9. The method as claimed in claim 1 , wherein the maximum pressure is at least 300 bar.

10. The method as claimed in claim 1 , wherein the maximum pressure is at least 100 bar above the minimum pressure.

11. The method as claimed in claim 1 , wherein the hydraulic pressure is pulsated between a range of pressure defined by the maximum and the minimum pressure.

12. A drive-out device for carrying out a method as claimed in claim 1 , with an electrohydraulic pump, which is connected to an oil tank, a hydraulic cylinder, which is connected to the electrohydraulic pump by way of a switchable valve, a driving-out ram, which is operatively connected to a piston rod of the hydraulic cylinder in such a way that hydraulic cylinder is moved by the piston rod in a direction of a longitudinal axis as soon as the hydraulic cylinder is subjected to a pressure by the electrohydraulic pump, and a pump controller, which is designed in such a way that the pump controller switches the switchable valve to reduce the pressure as soon as the pressure has reached a preset maximum pressure, and in such a way that pump controller switches the switchable valve to increase the pressure as soon as the pressure has reached a preset minimum pressure (p min ), or as soon as a predetermined time period has elapsed.

13. The drive-out device as claimed in claim 12 , wherein the hydraulic cylinder is fastened to a housing into which the piston rod protrudes and from which the driving-out ram projects.

14. The drive-out device as claimed in claim 13 , wherein a longitudinal axis of the driving-out ram and a housing wall from which the driving-out ram projects define an angle that is different from 90° .