Pressure roller arrangement, in particular for a longitudinal stretching system and an associated stretching system and a method for operating such a pressure roller arrangement

1. A pressure roller arrangement, for a longitudinal stretching system for stretching a plastic film, comprising:

a pressure roller with a roller body or roller body section with a roller surface,

the roller body or roller body section has an axial length,

the roller body or roller body section comprises, at least in one axial partial length, a nip roller film pressing region,

wherein the pressure roller arrangement further comprises a drive device,

wherein the drive device comprises a direct drive detachably mounted on at least one end-face of the pressure roller,

the direct drive protrudes only by a maximum of a partial length of less than 50% of its entire axial length beyond the end-face of the pressure roller, and

rotating parts of the direct drive are in rotational connection with the roller body or roller body section of the pressure roller.

2. The pressure roller arrangement according to claim 1 , further comprising a stationary drive housing, wherein the stationary drive housing of the direct drive, which housing protrudes into a roller cavity of the pressure roller, is supported against the outer rotating parts of the direct drive via at least one roller bearing or two mutually axially offset roller bearings, wherein the roller bearing closer to the end of the direct drive protruding from the pressure roller is a double roller bearing.

3. The pressure roller arrangement according to claim 2 , wherein a stator which is stationary together with the drive housing is arranged in the drive housing, which stator surrounds a rotor which is located therein and can be set in rotation and which is connected to a drive shaft that extends away from a front end of the pressure roller.

4. The pressure roller arrangement according to claim 3 , wherein a gear train for speed reduction in the drive housing is provided downstream of the rotor.

5. The pressure roller arrangement according to claim 3 , wherein the drive shaft proceeding from the rotor and/or an output shaft proceeding from a subsequent gear train

a) is connected directly or indirectly via a radial torque transmission member to a cylindrical or hollow cylinder-shaped torque transmission device and/or is supported thereby, and/or

b) is supported directly or indirectly via a roller bearing against a cylindrical or hollow cylinder-shaped torque transmission device,

the torque transmission device being detachably connected at an end face to the roller body of the pressure roller.

6. The pressure roller arrangement according to claim 1 , wherein the direct drive is provided with an externally protruding mounting section forming a fixed bearing, and in that on an opposite end face of the pressure roller a roller carrier which can be inserted into a cavity of the pressure roller and which protrudes at the end face is provided, which roller carrier forms a floating bearing.

7. The pressure roller arrangement according to claim 1 , wherein the direct drive has, on a mounting section protruding at an end face beyond the pressure roller

a) at least one purge air connection via which a purge medium that can flow off at an opposite end face of the pressure roller can be supplied, and

b) at least one electrical connection at least for supplying energy to an electric motor and/or for data transmission.

8. The pressure roller arrangement according to claim 7 , wherein

a purge valve and/or the electrical connection in the mounting section,

a) directly or

b) at least via a longitudinal bore which is formed in an end-face housing section of a drive housing,

opens into a drive housing interior, and

in that a ventilation bore is provided at the opposite end of the pressure roller in a roller carrier inserted there, which bore ends at the end of the mounting section in an opening to an outlet, via which the purge medium coming from a purge valve can be passed through the pressure roller.

9. The pressure roller arrangement according to claim 1 , wherein a drive housing

a) is designed in two parts and comprises a hollow cylinder-shaped housing section in the manner of a housing sleeve and an end-face housing section fixedly connected thereto in the manner of a housing cover which forms a mounting section, or

b) is formed at least substantially in one piece and comprises a sleeve-shaped housing section and an end-face housing section which forms a mounting section.

10. A stretching system comprising a pressure roller arrangement according to claim 1 .

11. A method for changing a nip in the pressure roller arrangement according to claim 1 , comprising aligning the pressure roller.