Roll

The invention relates to a roll comprising a roll jacket which is rotatably journalled on a stationary carrier with at least one approximately stationary active element being arranged between the roll jacket and the carrier, and with the space between the carrier and the roll jacket being at least partially filled with a liquid. Such rolls are used in the manufacture or treatment of material webs.

By way of example, a roll having support elements is known. Such a roll has a roll jacket which is built up of layers which have different physical characteristics. Because of the hydrostatic lubrication of the support elements, the space between the carrier and the roll jacket is at least partially filled with a fluid lubricant. As result, at high web speeds over the roll the eddying or turbulence of the lubricant through non-rotating support elements consumes a considerable proportion of the drive power which leads to heating of the lubricant. This has a particularly negative effect with rolls which should have a relatively cold surface or with rolls in which the material of the roll jacket or of the roll jacket layer does not withstand heating.

These circumstances gain in significance when, due to the use of flexible roll jackets or of high pressing pressures, having high contact pressures on the surfaces of the roll, the spacings between the support elements has to be reduced. Additional turbulence or swirling of the lubricant takes place. This can be counteracted by cooling the lubricant outside of the roll, which is naturally disadvantageous from an energetic viewpoint.

In a roll including a roll jacket (1) rotatably journalled on a stationary carrier (2) for rotation in a circumferential direction (U) with a space between the roll jacket and the stationary carrier, an improved support for the roll jacket is disclosed. At least one stationary active element (3) is arranged between the roll jacket (1) and the stationary carrier (2) having an axial width relative to an axis extending in an axial direction of said roll jacket. A radially outwardly disposed active element head (6) contacting the roll jacket at a radially outwardly directed surface (9) on the stationary active element (3) supports the roll jacket. The space (4) between the stationary carrier (2) and the roll jacket (1) is at least partially filled with a lubricant liquid which is entrained by rotation of the roll jacket. The improvement to the stationary active element includes at least one passage (5) having respective passage openings and having a cross section sufficient for fluid flow extending in the circumferential direction (U) of the roll jacket passing through the radially outwardly disposed active element head (6). This one passage substantially enlarges the total cross section of the flow paths for the liquid to produce a low flow resistance for liquid entrained by the roll jacket.

The invention is thus based on the object of reducing the undesired turbulence losses in rolls.

Due to the fact that each active element has as far as possible at least one passage which extends in the circumferential direction of the roll both the number and also the total cross section of the flow paths are increased. The number of total cross-section increase is associated with a reduction of the turbulence. It is entirely possible for parts of the passage boundary to be removed. If the passages lie at an angle to the circumferential direction of the roll and/or extend in curved manner to one end of the roll, then the possibility additionally exists of directing the liquid to the discharge devices which are mainly arranged at the side.

The passages should be located in the vicinity of the roll jacket. This is especially the case if only a part of the intermediate space is filled with liquid. Moreover, the flow speed is greatest in the vicinity of the roll jacket. The flow resistance, and thus also the turbulence, can be reduced when at least a part of the passage boundary directed towards the roll jacket is extended beyond the respective passage opening. This extension beyond the passage opening is preferably a flexible extension part secured to the active element. This flexible extension part can extend up to contacting guidance at the inner side of the roll jacket or can extend up to a minimal spacing from the inner side of the roll jacket.

The invention will be explained in more detail in the following with respect to four embodiments, with the terms "axial" and "radial" always being related to the roll. In the accompanying drawing there are shown:

FIG. 1 is a plan view onto the radially outwardly directed surface 9 of an active element 3 of the first embodiment;

FIG. 2 is a section A--A in accordance with FIG. 1;

FIG. 3 is a plan view onto the radially outwardly directed surface 9 of an active element 3 of the second embodiment;

FIG. 4 is a section B--B in accordance with FIG. 3;

FIG. 5 is an axially extending section of an active element 3 of the third embodiment, and

FIG. 6 is a plan view of the radially outwardly directed surface 9 of an active element 3 of the fourth embodiment.

All embodiments have the common feature that the roll jacket 1 is rotatably arranged on a fixed carrier 2 and is journalled or supported thereon by means of a plurality of active elements 3 in the form of hydrostatic support elements.

Liquid lubricant arises and collects in the space 4 between the roll jacket 1 and the carrier 2 and is generally led away via openings in the carrier 2.

In order to reduce turbulence losses of the liquid caused by the active elements 3 a plurality of passages 5 pass through each active element 3 and extend approximately in the circumferential direction U of the roll. These passages are located in the head of the active element 6 in the vicinity near the roll jacket 1.

The active elements 3 are each slidingly guided via their feet 10 in a respective recess 11 of the carrier 2. A pressure space 12 is present in the recess 11 between the carrier 2 and the foot 10 of the respective active element. A line 13 for liquid under pressure opens into each pressure space (line 13 is only shown in FIG. 5). The radially outwardly directed surface 9 of the active element head 6 has a plurality of hydrostatic bearing pockets 14 which are respectively connected with the pressure space 12 via a bore 15 in each case.

In the first three embodiments illustrated in FIGS. 1 to 5 the passages 5 extend in the circumferential direction U of the roll. In the first embodiment, the head 6 of the active element is extended beyond the boundary 16 of the bearing pockets 14 in the circumferential direction U so that the passage opening lies at least substantially at the inner side of the roll jacket 1. In order to prevent a pressure built up between the roll jacket 1 and this extension part 7 the extension part 7 has a plurality of openings 8 to the interior of the roll. Furthermore, as seen in FIG. 2, the cross section of the passage 5 increases in step-like manner in the direction of rotation D of the roll. This design can be used in rolls having a fixed direction of rotation D and leads to a reduction of the friction of the liquid at the walls of the passage and also of the flow resistance.

FIGS. 3 and 4 show the second embodiment with only the passage boundary directed to the roll jacket 1 being extended by a flexible extension piece 7. The flexible extension piece 7 is secured to the active element 3 beyond the respective passage opening. It either extends up to the inner side of the roll jacket and contacts it with guidance or terminates at a minimal spacing from the inner side of the roll jacket 1. In this case the extension piece 7 also has openings 8 to the interior of the roll.

The third embodiment illustrated in FIG. 5 shows the possibility of enlarging the flow paths between the active elements 3. The axial width of the heads 6 of the working elements in the vicinity of the roll jacket 1 continuously reduces towards the carrier 2. Moreover, side surfaces of the working element heads 6 which extend in the circumferential direction U of the roll are led together so closely in the radially outermost region that they communicate via a seal 17. This reduces the flow away of oil over these side surfaces and thus contributes to reducing the pump power. A combination with other embodiments is in this case possible without any difficulties.

The fourth embodiment shown in FIG. 6 is distinquished from the first embodiment of FIGS. 1 and 2 in that the radially outwardly directed surface 9 of the active element head 6 has the shape of a parallelogram; Two side surfaces of the parallelogram extend in the axial direction and with the other two surfaces extending obliquely to the circumferential direction U of the roll. This has advantages, in particular when using flexible roll jackets 1, since this leads to the contact pressure along the roll being made more uniform by the pressure sinks between the active elements 3. The technical design is shown with passages 5 extending at a maximum angle of 25.degree. to the circumferential direction U of the roll. These passages aid the supply of the liquid to the means for leading the oil away which are mainly present at the ends of the roll. The same applies to the use of passages 5 which extend in a curved manner.

The invention is naturally not restricted to use with only hydrostatic support elements. Thus, by way of example, use with hydrodynamic support sources, and also with active elements which exert a positive or negative pressure on the roll jacket 1 with reference to the surrounding pressure within the roll is also possible. Furthermore, the roll jacket 1 can naturally also have the shape of a flexible press hose, or the like.