Seal for sealing a circumferential gap between two machine components

1. A seal for sealing a circumferential gap between two machine components, one of the machine components being mounted such that it can be rotated in the axial direction relative to the other machine component, comprising:

a main seal with at least one shoe for establishing a contact-free sealing action between the machine components, and with at least one spring element which supports the shoe on one of the machine components in such a way that a radial movement of the shoe is possible as a reaction to the exertion of fluid pressure on the shoe, and

an auxiliary seal which seals the spring element in the axial direction, the auxiliary seal having at least two layers which adjoin one another in the axial direction,

wherein the layers comprise at least in each case two sheets which are positioned radially next to one another,

wherein, per layer, one of the sheets is stationary and the other sheet is mounted movably, by being fastened to the shoe,

wherein two movable sheets of in each case two layers which adjoin one another directly having a different width, as viewed in the radial direction, the wider one of the two movable sheets being combined with a thinner, stationary sheet in order to configure the layer, and the thinner one of the two movable sheets being combined with a wider, stationary sheet in order to configure the layer, and

wherein the wider movable sheet of the one layer overlapping in the radial direction with the wider stationary sheet of the respective other layer.

2. The seal as claimed in claim 1 ,

wherein, per layer, a plurality of movable sheets are provided in the circumferential direction, and the wider, movable sheets of the one layer overlap in the circumferential direction with the thinner, movable sheets of the other layer.

3. The seal as claimed in claim 1 ,

wherein the layers are arranged out of contact with one another at least in the overlapping region.

4. The seal as claimed in claim 1 ,

wherein the sheets of one layer are arranged out of contact with one another.

5. The seal as claimed in claim 1 ,

wherein, at least in the case of one layer, the number of movable sheets corresponds to the number of shoes.

6. The seal as claimed in claim 1 ,

wherein the stationary sheet of the innermost layer is formed by way of an intermediate plate.

7. The seal as claimed in claim 1 ,

wherein the movable sheets of the innermost layer are formed by way of a radial attachment of the shoes.

8. The seal as claimed in claim 1 ,

wherein three layers are provided, the axially innermost and outermost layers being of identical construction.

9. The seal as claimed in claim 1 , further comprising:

a carrier for the main seal, the stationary sheets being fastened to the carrier.

10. A unit comprising:

two machine components, one of the machine components being mounted such that it can be rotated in the axial direction relative to the other machine component, and

a circumferential gap being configured between the two machine components, in which circumferential gap a seal as claimed in claim 1 is arranged,

wherein the axial thickness of the axially innermost layer is selected in such a way that the size of a gap between the shoe and the opposite machine component can be set by way of the position of the auxiliary seal.

11. The unit as claimed in claim 10 ,

wherein the axially innermost layer is arranged below the sealing layers merely as a spacer element without a sealing action.