A method for mounting a bushing in a seat of a housing, and a device and a tool for accomplishing the method

Abstract: The application refers to a method for mounting a bushing (5) in a seat of a housing (3) for allowing it thereupon to be readily displaceable in circumferential direction, in axial direction or combinations thereof in a slip-stick free manner, including positioning a lining (15) having a low friction surface (15b) between the seat (4) of the housing (3) and said bushing (5), and affixing said lining to said seat (4) in a manner, such that the low friction surface is facing the bushing (5), a device and a tool to be used during such mounting, said device comprises a thin layer (15b) of a low friction material provided in the seat (4) of the housing (3), said thin layer being interposed between the seat surface (4) and the external surface of the bushing (5), and said tool comprising a carrier (7) having an outer shape substantially corresponding to the interior shape of the housing seat (4), an inflatable tubular member (10) wound thereabout in a flat state and with the windings in close lateral contact with each others, said tubular member being provided with at least one opening (18) for introduction and discharge of a gas such as air under pressure.

Description: The present invention relates to a method for mounting an eccentric bushing in a seat of a housing, e.g. a bearing housing for allowing it thereupon to be readily displaceable in circumferential direction, or in axial direction or in a combination of circumferential and axial directions in a slip-stick free manner. (US-3 453 031 A). For different types of rolling mills it is common that they have at least a pair of cooperating rollers, one or more of said rollers, usually the lower one, being rotary journalled at a fixed level, whereas the other one, commonly the upper roller, is rotary journalled in a manner allowing it to be raised and lowered relative to the lower, fixed roller in order to alter the mutual distance between the rollers, for effecting adjustment of the roll-nip, i.e. the working space between the rollers at rolling operations. Such adjustment is required during the pace of the rolling operation for reducing the measure to which the blank shall be rolled. One method for making possible such adjustability of one of the rollers of a rolling mill is to provide the bearing housings of the adjustable (top) roller with an internal eccentric bushing, in which the outer rings of the bearings supporting the roller are mounted. Thereby it is possible to adjust the level of the adjustable (top) roller by angularly displacing the eccentric linings in their seats in the bearing housing, thereby adjusting the mutual distance between the axes of the two rollers. As stated above it is desirable that such adjustment can be effected during rolling operations, i.e. without the necessity of making the rollers cease from rotating or even without having them relieved from the often very high operating load. Hitherto the eccentric bushings of such assemblies and also centric bushings of other assemblies often have been made from different metallic materials, which thereby together with the metallic seat in the bearing housing form material combinations such as steel/steel, bronze/steel, etcetera. This has created problems difficult to master, since the different material combinations used, have proven themselves to give raise to high and uneven friction, poor precision, low repetition accuracy and so called stick-slip effects, i.e. the materials at the interface between the bearing housing seat and the bushing will tend to smear, thereby causing the bushing to adhere to the seat, thereby withstanding the external force given thereto for making it move angularly and or axially in the seat and then suddenly to come loose and move in peripheral direction in an uncontrolled manner in the seat. DE 16 05 082 A refers to a shaft roller bearing for a rail vehicle, where it for preventing fretting corrosion between the outer ring of the bearing and the seat of a housing, is provided a bushing preventing direct contact between bearing ring and seat. The bushing can be made from a plastic material based on polytetrafluoro ethylene. The purpose of this bushing thus is to prevent contact between the metallic surfaces, and it is not intended to allow the outer bearing ring to move circumferentially in relation to the housing seat. GB 2 074 691 discloses a process and installation for internally lining a conduit, for making the conduit fluidtight. Here is used a substantially cylindrical, balloon-shaped fluidtight envelope, which is inflated to press the lining against the inner wall of the conduit, during the time a resin adhesive between the lining and the conduit under influence of the pressure and a controlled temperature is setting. Such an open balloon would inevitably have a tendency of obtaining a substantially elliptic cross-section, thereby giving insufficient pressing force at the axial ends of the conduit. The purpose of the present invention is to propose a method for mounting an eccentric bushing in a seat of a bearing housing for allowing it thereupon to be readily displaceable in circumferential and axial directions in a slip-stick free manner, thereby solving i.a. the problems mentioned above and to provide an assembly, which gives a possibility of exact adjustment of the angular and also the axial position of the bushing, thereby also making it possible continuously to control the roll-nip in a rolling mill without such undesired results as earlier experienced and this is achieved in the manner defined in the accompanying claim 1. The invention also refers to a device for accomplishing the method and this device is defined in claim 6. Finally the invention refers to a tool for accomplishing this method, and this tool is defined in the accompanying claim 8. Hereinafter the invention will be further described with reference to an embodiment illustrated in the accompanying drawings. Fig. 1 shows in cross section a part of a roll journal of a rolling mill, with a bearing in which the journal is supported and a bearing housing having an eccentric bearing seat bushing. Fig. 2 is a schematic front view of the bearing housing according to Fig. 1, intimated together with a mounting tool for said bushing. Fig. 3 is a schematic end view of the bearing housing shown in Fig. 2. Fig. 4 is a section along line IV-IV in Fig. 3, Fig. 5 is a part of the section from Fig. 4, shown in bigger scale, and Fig.s 6 and 7 show a mounting means for mounting the bushing in the bearing housing shown in cross section and from the end side respectively. Fig. 1 shows schematically a part of a roll journal 1 of a rolling mill, journalled in a two-row spherical roller bearing 2 positioned in a bearing housing 3. The bearing housing has a seat 4, and an eccentric bushing 5 interposed between the seat 4 and the outer race ring of the roller bearing 3. By means of this eccentric bushing 5, which is arranged to be rotatable within the bearing housing seat, it is possible to displace the roll journal relative to the centre of the bearing housing, thereby altering the position of the roll journal and the milling roll vertically. The bearing has been mounted on the roll journal 1 in conventional manner and is secured axially on the roll journal with common positioning and locking means, which are no part of the invention as such and therefore will not be further described. It also is evident that the spherical roller bearing shown in Fig. 1 of the drawing can be replaced for any other suitable bearing or bearing combination without departing from the inventive idea. Furthermore it is evident that it is not vital for the invention that the bushing to be secured in this manner is an eccentric bushing, but any type of bushing can be mounted and secured in the same manner and with the same advantages as the eccentric bushing intended for controlling roll-nip in a rolling mill. Between the housing seat 4 and the eccentric bushing 5 is arranged a layer or lining 15, having a low friction surface facing the bushing 5, and which is preferably, but not necessarily based on polytetrafluoro ethylene, PTFE. It was considered that this material must be fixedly attached to the bearing housing seat in order to give a desired effect, and it also was considered that the best manner to arrest the lining was by way of glueing. However, tests made showed that it was impossible to affix a pure PTFE layer to the bearing housing, in such a manner that it would adhere thereto. A material thought to be appropriate was found in the dry sliding bearing material GLYCODUR®, although also other materials having about the same properties, would be useful for this lining. The GLYCODUR® has a sheet steel backing, which is copper plated and on its low friction surface has a porous layer of tin bronze, having a thickness of 0.2 to 0.35 mm and the pores are filled with polytetrafluoro ethylene, PTFE, together with other friction-reducing additives. The opposite side of the thin steel backing has a very thin tin layer covering the copper layer. Tests made for affixing the GLYCODUR® strip to the seat in the bearing housing failed, as the material would not adhere to the seat surface, no matter which type of glue, which was used and no matter which surface finish the seat was given. The solution proved itself to be to remove the copper and tin layers on the rear side of the backing, thus that the surface to be glued to the bearing housing seat was pure steel. With a GLYCODUR® strip thus treated it was found that a sufficient adherance was obtained between the steel surface of the strip and the surface of the bearing housing seat when using a glue, e.g. such as ARALDITE® AV144-2/HV 997. However it was found that it still was difficult to obtain an even and satisfactory distribution of the glue over the entire interface. For this reason was developed a tool, which is schematically shown in Fig.s 2 to 5, and which incorporates a tubular carrier 7, two sleeves 8, 9 positioned over said carrier 7, an inflateable member 10 (see Fig.4) positioned over the tubular carrier member 7. The two sleeves are positioned spaced apart over said tubular carrier with a mutual spacing corresponding to the axial length of the GLYCODUR® strip to be affixed to the bearing housing seat. Each one of said sleeves 8, 9 having, at least at their ends facing each other, a wall thickness, which corresponds to the thickness of the GLYCODUR® strip to be affixed to the bearing housing seat. The outer envelope surface of the tubular carrier member 7 has a recessed portion 11 situated between its ends and having a depth sufficient to accomodate said inflateable member 10, when this is in non-inflated condition. The sleeves 8,9 are positioned over the ends of the tubular carrier member 7, and are located so that they cover at least a short axial portion of the inflateable member 10 at each end of the said recessed portion 11, thereby clamping the axial end portions of said inflateable member into the recessed portion 11. One of said sleeves, in Figs 2, 4 and 5 the right hand sleeve 8 is equipped with a radially outwardly projecting end shoulder 12 against which a washer 13 abuts. At the opposite sleeve 9, e.g. Fig. 4, is provided a second, radially projecting washer 14, which can be detachably attached to the said sleeve 9 in a suitable manner, e.g. by means of a screw joint. For the inflateable tubular member 10 can preferably be used a flat-wound hose, which thereby is arranged with the adjacent loops of the hose laying in close contact with each other to form a substantially continuous coil of an inflatable tubing. The low friction material, such as e.g. GLYCODUR® is provided in form of a split ring-formed bushing 15 as shown in Fig.s 6, 7, and which is positioned upon the flat-wound hose or similar inflatable member in the space between the inwardly facing ends of the two sleeves 8,9, whereby the low friction material is positioned with the low friction surface facing the inflatable member and with the backing, i.e. the steel surface facing outwards. The low friction material hereby will lay flush with the upper surfaces of the axially adjoining sleeves 8,9, as the inwardly facing ends of these are of the same thickness as the low friction material. Between the inflateable member and the portions of the sleeves contacting them and also between the inflateable member and the low friction material is preferably positioned a plastic film layer 16 arranged to seal off the space in order to prevent glue from leaking out. For securing the flat-wound hose 10 to the tubular carrier member 7 a string of glue (not shown) is preferably positioned between the hose and the carrier member. When the low friction material layer shall be affixed to the seat of the bearing housing, an appropriate amount of a suitable adhesive is positioned in the seat. The carrier 7 with the inflatable member 10 arranged in the recessed portion 11 thereof, the sealing plastic film 16, the low friction material 15, the end sleeves 8, 9 and one of the end washers, i.e. the one 13 supported by the shoulder 12 of the right hand end sleeve 8, are together as a unit pushed sideways into the interior of the housing, until the said end washer 13 with its side face comes to engagement against the outer side face of the housing 17, as intimated in Fig. 2. The other end washer 14 then is attached to the opposite end sleeve , i.e. in the embodiment intimated it is screwed on to it. In this position with the two end washers 13, 14 engaging opposite external end faces of the bearing housing 3, the tubular member or hose 10 is inflated, whereby the flat-wound hose will expand radially from the surface of the carrier 7, thereby uniformly pressing the steel backing of the GLYCODUR® lining 15 against glue earlier applied to the internal surface of the bearing housing seat. By applying a sufficient pressure inside the hose it is possible to cause the glue to be uniformly pressed out over the bearing housing seat surface and to make the lining be in close contact against it during the time required for the glue to stiffen, thereby ascertaining that the lining is securely connected to the seat. For this purpose the hose is provided with a hose connection 18 which is connectable to a not shown source of pressurized gas, e.g. air. Although not shown in detail the hose connection 18 is preferably equipped with valve means operable to allow the pressure medium, such as air, to be introduced into and discharged from the hose. The lining 15, as shown in Fig.s 6 and 7 in cross section and side view respectively, as earlier mentioned can preferably be in form of a bushing with a longitudinal slot 19, whereby the lining can be easily adapted to the seat to which it shall be affixed in spite of any variations in seat dimensions and the like. In the case this lining 15 is a strip of GLYCODUR® or the like, it comprises an external steel backing 15a and an internal low friction layer 15b, preferably based on PTFE or another similar low friction material. Although not shown in the drawings it can be appropriate to secure the end edges of the low friction lining to the bearing housing by stop screws or the like for prevent flaking, and in the case of mounting an eccentric bushing for obtaining a slip-stick free adjustability of the roll-nip in a rolling mill it also is advantageous to treat the surface of the eccentric bushing facing away from the low friction material with a surface treatment for preventing rust. The invention is not limited to the embodiment shown in and described in connection to the accompanying drawings, but modifications and variations are possible within the scope of the accompanying claims.

Claims: A method for mounting an eccentric bushing (5) in a seat of a housing (3) for allowing it thereupon to be readily displaceable in circumferential direction or axial direction or a combination of circumferential and axial directions in a slip-stick free manner, characterized in, positioning a lining (1) having a low friction surface (15b) between the seat (4) of the housing (3) and said bushing (5), and affixing said lining to said seat (4) in a manner, such that the low friction surface is facing the bushing (5). A method as claimed in claim 1, characterized in, using a low friction lining (15) having a low friction sliding surface (15b) based on polytetrafluoro ethylene (PTFE) and a steel backing (15a). A method as claimed in claim 2, characterized in, using a PTFE-based low friction lining (15) made from GLYCODUR®, modified to have a pure steel surface (15a) to be affixed to the said seat (4). A method as claimed in anyone of claims 1-3, characterized in, glueing the backing side (15a) of the low friction lining (15) to the interior of the housing seat (4), and pressing during the time the adhesive is curing, the lining radially outwards against the seat surface over substantially the entire extension thereof. A method as claimed in anyone of claims 1-4, characterized in, using an inflatable tubular member (10) wound in flat state about a carrier (7) having a substantially cylindrical outer surface, positioning said carrier with the flat tubular member (10) positioned thereabout in the opening of the housing (3) with the surface of the tubular member inside the low friction lining (15), inflating the inflatable tubular member (10) until it engages under pressure radially against the low friction lining (15) on the side surface (15b) thereof facing away from the housing seat (4), and maintaining said pressure for a time sufficient for allowing the adhesive to set, and thereupon releaving the pressure from the inflatable member (10) and removing it from the housing. A device for accomplishing the method for mounting an eccentric bushing (5) in a seat (4) of a housing (3), preferably a bearing housing, for allowing it thereupon to be readily displaceable in circumferential and axial directions in a slip-stick free manner as claimed in claim 1, characterized therein, that a thin layer (15b) of a low friction material is provided in the seat (4) of the housing (3), said thin layer being interposed between the seat surface (4) and the external surface of the bushing (5). A device as claimed in claim 8, characterized therein, that a joint, preferably a glue joint is provided for firmly connecting the thin low friction layer (15b) to the surface of the seat (4). A tool for accomplishing the method according to anyone of claims 1-5, characterized therein, that the tool comprises a carrier (7) having an outer shape substantially corresponding to the interior shape of the housing seat (4) an inflatable tubular member (10) wound thereabout in a flat state and with the windings in close lateral contact with each others, said tubular member being provided with at least one opening (18) for introduction and discharge of a gas such as air under pressure.

Inventors: ABRAHAMSSON LARS, KJELLBERG HANS, SUNDQVIST SVEN, ABRAHAMSSON, LARS, KJELLBERG, HANS, SUNDQVIST, SVEN
Applicants: SKF AB, AKTIEBOLAGET SKF
Application year: 1997
Main classification: F16C23
IPC codes: F16C21, F16C23, F16C33, F16C13, F16C35