Device for sealing off a rolling bearing

Abstract

The invention relates to a device for sealing off a rolling bearing from soiled cooling water which is discharged from the end face of the roller (1) during the operation thereof. In particular, a lubricant gap (15) between a journal bush, which is arranged on the journal of the roller, and a coaxially arranged bearing bush of a bearing housing (5), in which the roller (1) is rotatably mounted, is sealed off. The sealing device according to the invention is produced in multiple parts, including among others a gap (15) between an annular collar (7) as part of the seal and a second limb (13) of an L-shaped annular profile (11). The annular collar (7) has a discharge groove (9) on the circumference thereof for discharging the cooling water flowing from the roller (1). In order to prevent the gap (15) and a region arranged downstream of the gap (15) from being contaminated with soiled cooling water and the L-shaped annular profile (11) from becoming non-functional as a result of the soiling, not only must the discharge groove (9) have a minimum height but the ratio of the height and width of the annular discharge groove to the diameter of the base of the discharge groove must lie within specific limits.

Description

[0001] Device for sealing a roller bearing

[0002] The invention relates to a roller bearing sealing device for sealing a bearing for a roller for rolling, in particular for metal strip, against contaminated cooling water, which also runs down the end face of the roller during operation. In particular, a gap for lubricant is sealed between a journal bushing arranged on the journal of the roller and a bearing bushing arranged coaxially thereto in a bearing housing or chock in which the roller is rotatably mounted.

[0003] Such roller bearing sealing devices are generally known in the art, for example from international patent application WO 2005 / 061139 A1. The roller bearing sealing device disclosed therein is shown in Fig. 3. It is intended for arrangement between the end face 10 of a roller 1 and a chock 5, also called a bearing housing, with an associated bearing bush 6, in which the roller 1 is rotatably mounted with its roller journal 2. The roller bearing sealing device is constructed in several parts. It comprises an annular journal seal 4, which is arranged upstream of an annular seal 8 on the roller barrel side. The annular seal is firmly connected to an annular shoulder 7 of the bearing housing 5. A sealing lip 18 of the annular seal rests on the end face of the roller with sealing contact. An annular ring profile 11, with an L-shaped cross-section, is firmly connected to the end face of the roller 1 by its first leg 12.The sealing lip 18 of the ring seal rests against this first leg. A second annular leg 13 of the L-shaped ring profile encloses the ring seal 8 and areas of the ring shoulder 7 radially further outward. The ring shoulder 7 has an outwardly open closing groove 9 on its outer circumference, which is not covered, or at least only partially covered, by the second leg 13 of the L-shaped ring profile 8.

[0004] In this respect, WO 2005 / 061139 A1 discloses the preamble of patent claim 1.

[0005] In WO 2005 / 061139 A1, a distance, i.e., a gap height of 15 between the ring shoulder 7 and the second leg 13 of the L-shaped profile 11, of 0.5 mm to 1.5 mm is described as advantageous. This gap size also allows for the offset to be applied by the roller during operation. Furthermore, the gap (the labyrinth) is kept so narrow that any contaminated cooling water has only the narrowest possible path into the area of ​​the sealing lip 18. This has the positive or advantageous effect that this area does not become contaminated as quickly and thus remains functional for longer.

[0006] While this narrowed gap design may have the desired effect in a pinch, it does not address the underlying problem. This is that during rolling operations, contaminated cooling water accumulates in the drain groove to the height of the gap because it cannot drain away in sufficient quantities. If this happens, the contaminated cooling water is undesirably drawn or sucked into the gap at the opening side facing the drain groove, causing the problem in question.

[0007] The two physical effects described below are responsible for the suction of cooling water into the (annular) gap 15:

[0008] 1 . The flow condition that develops between the second leg of the L-shaped profile and the ring seal or the ring attachment is referred to in the literature as Couette flow. A Couette flow is a flow in a narrow gap that is driven by a moving wall. In the laminar case, a linear velocity profile develops between the two walls that border the gap. The gap geometry described in the WO document is formed by two nested cylinders, with one cylinder wall rotating. Here, a special case of Couette flow occurs, the so-called Taylor-Couette flow. The centrifugal forces (rotation) create so-called Taylor vortices that are perpendicular to the axis of rotation. The resulting vortex topology transports the cooling water from one opening side of the gap to the other side, or here into the area of ​​the sealing lip 18.Contaminated cooling water is sucked in from one side and transported through the gap to the seal.

[0009] A lower limit at which the Taylor vortices form can be specified by the Reynolds number Re:

[0010] R ne = — v ' d

[0011] V with: v = velocity in the gap, d = gap height, v = kinematic viscosity of the medium

[0012] The Reynolds number must be greater than a certain value:

[0013] Re > 41.3 E, where r is the mean radius of rotation. If this condition is met, the Taylor vortices described above are formed.

[0014] If one considers the known device for roll sealing and determines the Reynolds numbers using these boundary conditions, one results in Reynolds numbers that are above the limit according to the right-hand side of formula (2) for almost all cases in practice. This means that one can assume that the Taylor vortices described above will occur and that the contaminated cooling water will be undesirably sucked through the gap into the area of ​​the sealing lip 18. 2. A second aspect that leads to the same problem, that contaminated water may be transported through the gap, lies in the geometric changes in the gap geometry when viewed along the circumference. Since the roll neck bearing axis is never exactly central to the backup roll axis in operation, but is offset in the direction of this due to external load, the gap that forms between the second leg of the L-shaped profile and the ring seal orThe ring shoulder is not evenly distributed around the circumference. There is a circumferential area where the gap narrows, and there is a circumferential area where the gap widens. In the area where the gap widens, any contaminated water is sucked in and pushed out again in the opposite area of ​​the narrowing gap. The behavior is similar to a plain bearing. When pushed out, any contaminated water is pressed into the area of ​​the seal that, according to the disclosure of WO 2005 / 061179 A1, should not actually be contaminated.

[0015] In order to prevent potentially contaminated water from coming near the gap between the second leg of the L-shaped profile and the ring seal or the ring attachment, WO 2005 / 061139 A1 itself recommends using the drainage groove 9 disclosed therein on the periphery of the ring attachment.

[0016] However, studies have shown that the peripheral drainage groove can only achieve its intended effect if it meets certain dimensions.

[0017] The invention is therefore based on the object of dimensioning the drainage groove on the periphery of the annular shoulder in such a way that contamination of the gap, in particular at its inlet opening facing the drainage groove, and of a region downstream of the gap between the end face of the roll barrel and the annular seal, with contaminated cooling water is prevented as far as possible. This object is achieved by the subject matter of patent claim 1. Accordingly, the minimum height of the drainage groove is Hmin = 1.55 mm, and in addition, the ratio of the height H and width B of the drainage groove to the diameter D of the base of the drainage groove is within the limits of 0.1 120, with the discharge coefficient KA=0.00985 mm 3 / mm 2and all sizes in [mm]; and with H>Hmin

[0018] This claimed physical relationship was determined from theoretical studies and practical experience. The drainage channel dimensioned in this way is considered optimal, particularly as it is sufficiently large to counteract the accumulation of contaminated cooling water up to the level of the gap's inlet opening, thus effectively preventing the cooling water from being sucked into the gap due to the two aforementioned effects.

[0019] The description is accompanied by three figures, where

[0020] Figure 1 shows the drainage groove according to the invention in an enlarged cross-sectional view;

[0021] Figure 2 is an illustration of the lower and upper limits for the claimed ratio; and

[0022] Figure 3 shows a roller bearing sealing device according to the prior art

[0023] The invention is described in detail below with reference to the figures in the form of an exemplary embodiment. In all figures, identical technical elements are designated by identical reference numerals.

[0024] The roller bearing sealing device according to the invention is based on the roller bearing sealing device known from the prior art according to Figure 3. For its description, reference is made to the above statements on the prior art and to international patent application WO 2005 / 061139 A1. Except for the deviations and additions described below, the said description also applies to the device according to the present invention.

[0025] As stated, the present invention relates to a particular embodiment of the closing groove 9, which is shown in Figure 1 in cross-section and in an enlarged view. The annular ring extension 7 can be seen there, on the periphery of which the drainage groove 9 is formed. The base of the ring seal is spaced at a distance equal to the diameter D from the central axis of the ring extension 7, which, when the ring extension 7 is pulled onto the roll neck 2, also corresponds to the central axis of the roll neck 2. It can be seen that the left boundary wall of the closing groove 9 is overlaid by the second leg 13 of the L-shaped ring profile 11, with a gap 15 being formed between these two elements. The reference numeral 12 designates the first leg of the L-shaped ring profile 11, which is firmly mounted on the end face of the roll barrel.More precisely, the height H of the drainage groove denotes, for example, the distance between the bottom of the drainage groove 9 and the underside of the second leg 13. The minimum height Hmin is the minimum of this distance; H>Hmin applies. The reference symbol B denotes the width of the drainage groove 9.

[0026] The inventors are credited with recognizing that, in addition to the minimum height Hmin of the drainage groove, the ratio of height H and width B to diameter D must be within a specific range for the roller bearing sealing device according to the invention to achieve its intended effect. If the ratio is too small, the possibly contaminated cooling water accumulates at the gap 15 between the second leg 13 of the L-shaped profile 11 and the ring seal 8 and can be sucked into the gap by the two effects described above. The sucked-in contaminants lead to undesirable blockages in the gap and, in the downstream area, to impediments to the functioning of the sealing lip.

[0027] If the ratio of width B and height H to diameter D is too large, the flow velocity of the draining cooling water in the drainage groove 9 becomes so low that scale or dirt residues from the rolling process are not flushed away. These residues then adhere ("bake") in the drainage groove 9 due to their reactivity (corrosion, etc.) and, after a short period of operation, lead to the drainage groove becoming blocked, thus experiencing additional drainage resistance; the drainage groove can then no longer fulfill its actual task of providing a sufficiently large drainage area for the possibly contaminated cooling water. In this case, too, the possibly contaminated cooling water is dammed up to the level of the gap 15 between the second leg 13 of the L-shaped profile 11 and the ring seal or ring shoulder 7 and, due to the two effects described above, is sucked into the gap 15 and disadvantageously fed to the sealing system.

[0028] From theoretical investigations and practical experience it has been shown that a minimum height of Hmin=1.55mm must be given and that the ratio of height H and width B to diameter D must be within the following limits: BH)

[0029] 0.1 < < 120 (K A -Dn) (1 ) with the discharge coefficient KA=0, 00985 mm 3 / mm 2 and all sizes in mm; and with H>Hmin. Thus, the drainage groove 9 is considered optimal, ie, neither too small nor too large in the sense of the previous explanations.

[0030] Figure 2 illustrates the range of values ​​within which the claimed ratio may lie according to formula (1 ) with the lower limit 0.1 and the upper limit 120.

[0031] List of reference symbols

[0032] 1 roller

[0033] 2 roll necks

[0034] 3-pin bushing

[0035] 4 pin seal

[0036] 5 chocks

[0037] 6 bearing bush

[0038] 7 Ring shoulder (bearing shoulder)

[0039] 8 Ring seal

[0040] 9 Drain groove

[0041] 10 Front side

[0042] 11 L-shaped ring profile

[0043] 12 first leg

[0044] 13 second leg

[0045] 15 gap

[0046] 18 Sealing lip

[0047] B Width

[0048] D Diameter of the annular drainage groove at its bottom

[0049] Hmin Minimum height; corresponds to the minimum of H

[0050] H Height of the drain groove

Claims

Patent claims:

1. A device for sealing a roller bearing, comprising a bearing housing (5) in which a roller (1) with a roller neck (2) is rotatably mounted, comprising a neck seal (4); an annular seal (8) which is arranged upstream of the neck seal (4) on the roll barrel side and which has a sealing lip (18); an annular shoulder (7) which is arranged upstream of the bearing housing (5) in the axial direction, to which the annular seal (8) is firmly connected, and which has a circumferential outwardly open drainage groove (9) on its periphery; wherein an annular profile (11) with an L-shaped cross section and a first leg (12) and a second leg (13) is provided; wherein the annular profile (11) is firmly connected with its first leg (12) to the end face (IO) of the roller (1); wherein the sealing lip (18) of the ring seal (8) bears with sealing contact on the side of the first leg (12) facing away from the roll barrel;and wherein the second leg (13) of the L-shaped ring profile (11) covers and encloses regions of the ring shoulder (7) and the ring seal (8) to form a gap (15) and seals them off towards the roll barrel; characterized in that the minimum height Hmin of the drainage groove (9) is: Hmin= 1.55mm; and that the ratio of height H and width B of the drainage groove (9) to the diameter D of the base of the annular drainage groove is within the limits BH); 0.1 < < 120 (K A -Dn) (1 ) with the runoff coefficient KA=0.00985 mm 3 / mm 2 and all sizes in [mm]; and with H>Hmin.

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