Device for sealing shaft bearings or shaft bearing housings
The invention relates to a device for sealing shaft bearings or shaft bearing housings, in particular of self-aligning roller bearings for prepressing rollers or the like, having a special ring or special sleeve which surrounds the shaft, is advantageously made of stainless steel and has on the outer circumferential surface at least one annular projection which extends into at least one annular groove at at least one end of the bearing housing. According to the invention, the concern here is primarily to inexpensively develop bearing housings, in particular production bearing housings, for operating conditions with exacting requirements on the sealing of the bearing. The main object of the invention is on the one hand to use production self-aligning roller bearings, which are very moderately priced, for prepressing rollers, e.g. in double endless-belt screen presses or the like, or to adapt them to such installations, and on the other hand, despite difficult operating conditions, to increase the working time of such inexpensive production bearings. Moreover, such a modification or adaption of the production bearings is to be made possible simply and without a crucial amount of labour and material. However, it is not sufficient as a rule to merely replace the conventional bearing seals by such seals of higher quality and longer life. 
     The aims described above can be achieved in a device for sealing bearings of the type described at the beginning when the annular projection of projections of the special ring or special sleeve inserted in the housing and enclosing the shaft with sealed clearance are fitted into the housing groove(s) for the standard seal(s) for production bearing housings, and when at least one, expediently two, annular recess(es) for a radial lip seal(s) are provided on the inner circumferential surface, preferably on the front end(s) of the special ring or the special sleeve. Such special rings or special sleeves can easily be inserted into the split bearing housings, it only being necessary, with regard to the space requirement of these special rings or sleeves, to select bearing housings or housing caps with larger openings for the shaft or roller neck to be mounted. For the use of the device according to the invention, the annular projection or projections are therefore fitted into the housing groove(s) for the standard seal(s) of production bearing housings. In order to keep down the weight of the special ring or the special sleeve and accordingly to minimise the material requirement for this, it is favourable if, in the area of the recesses for the radial lip seals, the diameter of the outer circumferential surface of the special ring or the special sleeve is larger than next to the annular projection or projections so that, as viewed in axial section, the special ring or special sleeve forms a step in the transition from its centre part to its end part(s). 
     The sealing effect can be improved still further if, for the purpose of forming a labyrinth seal, one front end of the special ring or the special sleeve extends into an annular recess in the end area of the shaft, in particular the roller neck, widened outside the housing of the bearing, which annular recess is advantageously formed partly by means of a further sleeve drawn on to the shaft, in particular the roller neck, and partly in the shaft or the roller neck itself, with the outer circumferential surface of the special ring or the special sleeve and the recess or the inner circumferential surface of the second mentioned sleeve forming a labyrinth gap in this area. This can be effected practically in such a way that the further sleeve, at the front end and therefore in the area of the special ring or special sleeve extending in at this location, is recessed in an annular shape on the inner circumferential surface. 
     If a simple embodiment is desired, the bearing-side front end of the step of the end part of the special ring or the special sleeve, which end part is located outside the bearing housing, will be in alignment with the bearing-side front end of the widened shaft, in particular of the roller neck, e.g. of the prepressing roller or the like. The penetration of water, the diverse treatment media or the like into the bearing and even into the labyrinth seal can be additionally impeded if the bearing-side front end of the step of the end part of the special ring or special sleeve, which end part is located outside the bearing housing, is set back relative to the bearing-side front end of the widened shaft, in particular of the roller neck, e.g. of the prepressing roller or the like. This inhibiting effect is intensified if, according to a further inventive variant, the shaft, in particular the roller neck, widened outside the bearing housing, additionally has at its end facing the bearing housing an annular widened portion on its outer circumferential surface. 
     The bearing cap and the special ring or the special sleeve according to the invention can be sealed toward the inside of the bearing housing by O-rings known per se, the O-ring for the special ring being arranged between the annular projection and the base of the housing groove accommodating it. 
    
    
     Exemplary embodiments of the invention are described with reference to the drawing. 
     FIG. 1, partly in side view and--in particular in the area of the bearings--partly in longitudinal section, shows a prepressing roller which is supported in self-aligning roller bearings developed according to the invention. 
     FIG. 2, represents an end elevation hereto. 
     FIG. 3, illustrates, in an enlarged scale hereto and in longitudinal section, several variants of the bearing arrangement according to the invention. 
    
    
     As FIGS. 1 and 2 first of all show, the devices according to the invention are provided for sealing bearings or bearing housings, for example for self-aligning roller bearings 19 for prepressing rollers 17. The bearing housings 1 are of conventional split construction, as revealed in particular by FIG. 2. According to the invention, the main concern here is to provide production bearing housings 1 with a very good seal. For this purpose, a special ring or a special sleeve 2 with at least one annular projection 7 on the outer circumferential surface 8 and at least one, expediently two annular recesses 3 for a radial lip seal(s) 3&#39; on the inner circumferential surface 9 is inserted into the production bearing housing 1, as shown by FIG. 1 and, in an enlarged scale thereto, by FIG. 3. At the same time, the abovementioned projection or projections 7 extend into at least one annular groove 10 at at least one end of the bearing housing, and this recess or recesses 3 are provided on the front end(s) 11,12 of this special ring. It should be especially emphasized that the annular projection or projections 7 are fitted into the housing groove(s) 10 for the standard seal(s) 6 of production bearing housings 1. The special ring or the special sleeve 2 is advantageously shaped in such a way that, in the area of the recesses 3 for the radial lip seals 3&#39;, the diameter of the outer circumferential surface 8 of the special ring or the special sleeve 2 is larger than next to the annular projection or projections 7 so that, as viewed in axial section, the special ring or special sleeve 2 forms a step 2&#34;&#39; in the transition from its centre part 2&#39; to its end part(s) 2&#34;. Thus adequate space is created for sound or effective seals 3&#39; without the circumferential surface of the special rings 2 having to be made thick, which results not only in advantages with regard to the expenditure but also with regard to the space requirement for the special ring, or it enables the bearing size or the bearing diameter to be kept sufficiently small. 
     The special bearing sealing according to the invention, during the operation of the prepressing rollers or the like 17, serves to shield in a particularly efficient manner self-aligning roller bearings 19 or the like or to shield the inside of their bearing housings 1 and the oil or lubricant or bearing grease located therein in particular from the water, treatment agent, etc. passing from the endless-belt screen or other conveying device, which is guided by the prepressing roller 17 or the like, to the bearing (housing) or the roller neck 14. This effect is increased if, for the purpose of forming a labyrinth seal, one front end 12 of the special ring 2 extends into an annular recess 13&#39; in the end area 13 of the shaft, in particular the roller neck 14, widened outside the housing 1 of the bearing, which annular recess 13&#39; is advantageously formed partly by means of a sleeve 4 drawn onto the shaft, in particular the roller neck, and partly in the shaft or the roller neck 14 itself, with the outer circumferential surface of the special ring and the recess 13&#39; of the inner circumferential surface of the sleeve 4 forming a labyrinth gap 15 in this area. FIG. 1 shows an embodiment in this respect with a recess 13&#39; arranged directly in the widened shaft or in the widened roller neck. In contrast, FIG. 3 represents a variant with the drawn-on sleeve 4, a design which can be preferred for reasons of manufacture. In this case, the sleeve 4, at the front end and therefore in the area of the special ring 2 extending in at this location, is expediently recessed in an annular shape 16 on the inner circumferential surface. 
     As shown in particular by FIG. 3 by solid lines, the bearing-side front end 2 IV  of the step 2&#34;&#39; of the end part 2&#34; of the special ring o the special sleeve 2, which end part 2&#34; is located outside the bearing housing 1, can be in alignment with the bearing-side front end 13&#39; of the widened shaft, in particular of the roller neck 14, e.g. of the prepressing roller or the like 17. In many cases, however, better protection is achieved, in particular protection against corrosion, for the seal and the bearing or bearing housing if the bearing-side front end 2 V  of the step 2&#34;&#39; of the end part 2&#34; of the special ring or special sleeve 2, which end part 2&#34; is located outside the bearing housing 1, is set back relative to the bearing-side front end 13&#34; of the widened shaft, in particular of the roller neck 14, e.g. of the prepressing roller or the like 17. This design is indicated by a broken line in FIG. 3. 
     Washing liquid, e.g. washing water, chemicals, fibrous materials and other materials, etc., to be treated which could pass from the endless-belt screen or the like to the bearing are additionally shielded according to the further development of the invention if the shaft, in particular the roller neck 14, widened outside the bearing housing 1, has at its end 14&#39; facing the bearing housing 1 an annular widened portion 18 on its outer circumferential surface. This variant, too, is shown by a broken line in FIG. 3. 
     The special ring or the special sleeve 2 is expediently made of stainless steel. The invention enables on the one hand production bearings, in particular production self-aligning roller bearings, which are very moderately priced, to be used for prepressing rollers, e.g. in double endless-belt screen presses or the like, or enables them to be adapted to such installations, and on the other hand, despite difficult operating conditions, it enables the working time of such inexpensive production bearings to be increased. The surface of the prepressing roller is here provided with a coating 20 made, for example, of plastic. This coating can also be omitted, in particular if the roller is made of an appropriately resistant alloy. 
     As the representations (FIG. 1 and FIG. 3) further show, the annular projection or projections 7 of the special ring or special sleeve 2, in particular in the housing groove or housing grooves 10, can be sealed by an O-ring 6 or the like which is arranged in particular between the outer circumferential surface of the annular projection 7 and the inner circumferential surface of the housing groove 10, it being possible for the bearing cap 5 to be sealed in the same way.