Abstract:
A roller bearing cage includes the following features: 
     The cage comprises an annular circumferential element, from which bridge elements branch off, roller bodies of the roller bearing being disposable between the bridge elements, 
     the circumferential element comprises a plurality of uniform section elements, and 
     the initially-loose section elements and bridge elements are connected with each other to form the cage.

Description:
CROSS-REFERENCE 
     This application is the U.S. national stage filing of International Application No. PCT/EP2008/009163 filed Oct. 30, 2008, which claims priority to German patent application no. 10 2007 052 507.0 filed Nov. 2, 2007. 
     TECHNICAL FIELD 
     The invention concerns a roller bearing cage. 
     RELATED ART 
     A roller bearing cage is known, e.g., from DE 79 35 982 U1, which is comprised of two side parts and a plurality of bridge parts that are separately manufactured and connected with the side parts by welding or the like, wherein the bridge parts form pockets between them for accommodating the roller bodies. The side parts and bridge parts are manufactured from flat or profile-milled wire and the bridge parts are stamped to form the slip surfaces for the roller bodies. 
     SUMMARY 
     It is an object of the present invention to provide an improved roller bearing cage that is, in particular, producible in a simple and thus cost-effective manner. 
     In one aspect of the present teachings, a roller bearing cage includes the following features:
         an annular circumferential element, from which bridge elements branch off, roller bodies of the roller bearing being disposable between the bridge elements,   the circumferential element comprises a plurality of uniform section elements, and   the initially-loose section elements and bridge elements are connected with each other to form the cage.       

     Consequently, the section elements are advantageously producible, e.g., in a simple and cost-effective manner by cutting an appropriately-profiled bar or strip material, preferably made of steel, into sections. Relative to roller bearing cages that are machined from a hollow cylinder-like pipe, the roller bearing cage according to the present invention naturally also offers the advantage that no material waste results from a machining, in particular, of the cage pockets, and thus a material savings advantageously results relative to such a method. 
     In an advantageous embodiment, the bridge elements are formed so as to be uniform, so that they are also producible in a simple and cost-effective manner by cutting an appropriately-profiled bar or strip material, preferably made of steel, into sections. 
     In another aspect of the present teachings, snap-fit possibilities for the roller bodies are realizable for a cage made from steel, as have been otherwise known only for brass and/or plastic cages, wherein such a design is possible irrespective of whether it concerns a composite cage or a cage produced from one piece, e.g., a steel pipe segment. 
     In an advantageous embodiment, the circumferential element on the one hand and the bridge elements on the other hand are formed with different properties. In this case, it is advantageously possible to pair different materials and, e.g., to produce less heavily-loaded elements from cheaper materials depending on the application. Further, it is also possible to form one of the elements from a heat-treated steel for a high wear resistance and to leave other elements untreated, e.g., for a high ductility. 
     In a further advantageous embodiment, it is possible form at least one of the elements in a coated manner. In this case, due to the formation of the roller bearing cage from circumferential and bridge elements, it is much simpler and thus also more cost-effective to perform the coating of individual elements, e.g., the bridge elements. The same applies to a further advantageous embodiment, in which droplet-shaped impressions are provided on the surfaces of the bridge elements that face the roller bodies and function as lubrication pockets. In one embodiment, the lubrication pockets can be disposed in a left axial half of the bridge element oblique relative to a line extending obliquely from the right roller bearing area to the roller bearing middle point and can be formed in the right half in a correspondingly mirrored manner. 
    
    
     
       Further advantages, features and details of the invention are derivable from the exemplary embodiments described in the following with the assistance of the Figures. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows in perspective view a cylindrical roller bearing cage composed of elements, 
         FIG. 2A  shows in perspective view a further cylindrical roller bearing cage composed of elements, 
         FIG. 2B  shows in perspective view a further cylindrical roller bearing cage composed of elements, 
         FIG. 3  shows a cross-section through a pocket of a cage similar to the cage of  FIG. 1  having a snap-fit functionality for the roller bodies due to a special spacing of bridge elements, 
         FIG. 4  shows in perspective view a circumferential segment of a cage similar to the cage of  FIG. 1  having a snap-fit functionality for the roller bodies due to a special construction of the bridge elements, 
         FIG. 5  shows in perspective view a pocket of a cage similar to the cage of  FIG. 1  having a snap-fit functionality for the roller bodies due to nibs on the circumferential elements, 
         FIG. 6  shows in perspective view a pocket of a cage similar to the cage of  FIG. 1  having a retaining function for the roller bodies due to nibs on the circumferential elements, 
         FIG. 7  shows in perspective view a pocket of a cage similar to the cage of  FIG. 1  having pins parallel to the bridge elements, and 
         FIG. 8  shows in perspective view and in two opposite observation directions a pocket of a cylindrical roller bearing cage composed of elements, in which the elements are held together by snap-rings. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As an exemplary embodiment of the invention,  FIG. 1  shows a cylindrical roller bearing cage composed of elements  10  and  20 . The cylindrical roller bearing cage comprises an annular circumferential element on each of its two axial ends and a plurality of bridge elements  20  connecting the two circumferential elements with each other. The left portion of  FIG. 1  shows in an exploded view that the two annular circumferential elements are formed by a plurality of uniform section elements  10  that are assembled together into the annular circumferential elements. Thus, the section elements  10  are produced in a simple and cost-effective manner by cutting an appropriately-profiled bar or strip material made of steel into sections. 
     The bridge elements  20  are also produced in a simple and cost-effective manner by a cutting an appropriately-profiled bar or strip material made of steel into sections. In particular, the side surfaces of the bridge elements  20 , which are provided for lying opposite of the outer surfaces of the cylindrical rollers, are formed in a curved-manner corresponding to the roller outer surface, which advantageously improves the formation of the lubricating film. 
     The connection points of the section elements  10  are formed such that a V-shaped inward bulge or recess results in the radial direction at the connection point, into which bulge or recess the axial ends of the bridge elements  20  are inserted in a fitted manner, so that the positions of the bridge elements  20  on the circumferential elements are predetermined in the circumferential direction. In general, the connection points are formed such that each radially-outward-facing recess is V-shaped, U-shaped or trapezoid-shaped with straight, convex or concave legs of the V-, U- or trapezoid shape. The individual elements  10  and  20  are then connected with each other in a fusion-bonded manner, e.g., by welding. This welding can take place, e.g., according to a laser-, electron- or plasma-method. In other embodiments, the elements  10  and  20  can also be soldered with each other, e.g., by an inductive hard soldering or laser hard soldering, or can also be adhered with each other. 
     Thus, each of the section elements  10  in the areas, in which it is connected with the two adjacent section elements  10 , forms a potential slip surface for a roller end side that is disposed radially further inward relative to the remaining end surface of the section element  10 , so that a potential slip surface extending as far radially as possible results in the radial direction as viewed for the roller end sides, which advantageously provides a supplemental tilting prevention system for the cylindrical rollers. This larger radial extension at least in areas of the circumferential element is advantageously achievable with the cage composed of elements  10  and  20  irrespective of the radial thickness of the bridge elements  20 . Thus, a comparatively large connection surface for the axial ends of the bridge elements  20  to the section elements  10  is also advantageously achievable. 
     In the cylindrical roller bearing cage of  FIG. 1 , the individual elements  10  and  20  can initially be connected with each other and then the cage can be assembled by inserting rollers into the corresponding cylindrical roller bearing. However, it is also possible, in particular in connection with a track element having rims on both ends of the cylindrical roller end sides, to dispose the elements  10  and  20  around the rollers laid in said track element and then to connect, so that the track element forms a captive unit with the cylindrical rollers and the cage. 
     On the other hand, construction of the elements  10  and  20  from other materials, e.g., other metallic alloys as well as also plastic, and their production by sintering and/or injection molding, is also possible in other implementations. Further, a conical roller bearing cage can also be formed in a manner comparable to the above-described cylindrical roller bearing, wherein in this case the two circumferential elements differ solely in their diameter and thus two types of section elements are to be provided. 
     Due to the fact that the cage of  FIG. 1  has a substantially smooth outer surface, it is usable, in particular, e.g., as a cage that is shoulder-guided on a correspondingly-formed outer track element. In this case, the bridge elements  20  are, with particular advantage, supplementally so-to-speak mechanically secured on the radially outward side by the shoulder of the outer track element, while the bridge elements  20  are retained on the radially inward side by the circumferential elements composed of the section elements  10 . 
     For producing a corresponding cage that is shoulder-guided on a correspondingly-formed inner track, different section elements merely have to be utilized, as is illustrated in  FIG. 2A . In this case, the bridge elements  20 ′ are now secured on the radially inward side by the at least one shoulder of the inner track element and are retained on the radially outward side by the circumferential elements composed of the section elements  10 ′. In  FIG. 2A , the cylindrical roller bearing cage composed of the section elements  10 ′ and the bridge elements  20 ′ now has a substantially smooth inner surface. 
     As a further exemplary embodiment of the invention,  FIG. 2B  shows a cylindrical roller bearing cage composed of section elements  10 * and bridge elements  20 * that differs from the cage of  FIG. 2A , in essence, in that the bridge elements  20 * are retained on the radially outward side merely by their fusion-bonded connection with the section elements  10 *, which can be completely sufficient depending upon the application. Otherwise, the preceding description for  FIGS. 2A and 2B  applies in a corresponding manner. In other embodiments, instead of a pure inner- or outer shoulder-guidance, the cages can be formed for a combined inner- and outer guidance, pure roller guidance, other guidance types such as track guidance and/or combinations thereof. 
     As a further exemplary embodiment of the invention,  FIG. 3  shows a cross-section through a pocket of a cage similar to the cage of  FIG. 1 . In this case, the cage of  FIG. 3  is formed such that the bridge elements  20 ″ defining the pocket have an opening width X relative to each other that is approximately 3/10 mm smaller than the diameter D of the cylindrical roller  30 ″. As a result, the cylindrical rollers  30 ″ can be snap-fit into the cage composed of the section elements  10 ″ and bridge elements  20 ″, wherein the cage with the rollers  30 ″ snap-fit therein represents a captive transport unit, but the rollers  30 ″ are also removable again by a simple snapping-out. As a result, it is possible, with particular advantage, to produce said snap-fit function by using steel material for the elements. Otherwise, the preceding description applies in a corresponding manner. 
     As a further exemplary embodiment of the invention,  FIG. 4  shows in perspective view pockets of a cage similar to the cage of  FIG. 1  for realizing a snap-fit possibility for cylindrical rollers  30 ″. For this purpose, impressions  22 ″′ are introduced in the radial direction on the narrow, radially-inward side surfaces of the bridge elements  20 ″′ at two points along its axial extension, so that nib-like outward bulges  24 ″′ result in the circumferential direction on both sides of the impressions  22 ″′, which produce the snap-fit function for the cylindrical rollers  30 ″′. The lower part of  FIG. 4  shows a cut-out enlargement of the area indicated with a circle in the upper part of  FIG. 4 . Otherwise, the preceding description applies in a corresponding manner. 
     As a further exemplary embodiment of the invention,  FIG. 5  shows in perspective view a U-shaped pocket of a cage similar to the cage of  FIG. 1  defined by adjacent bridge elements  20 ″″ at both end sides of the annular circumferential element  10 ″″ with cylindrical rollers  30 ′″ inserted therein. For realizing a snap-fit function for the cylinder rollers  30 ″″ in the pocket, axially-inwardly-projecting, cylinder-like nibs  12 ″″ are provided at the inwardly-oriented end sides of adjacent section elements  10 ″″ in their connection area. Otherwise, the preceding description applies in a corresponding manner. 
     As a further exemplary embodiment of the invention,  FIG. 6  shows in perspective view a pocket of a cage similar to the cage of  FIG. 1  with cylinder rollers  30 ″″′ inserted therein. Similar to  FIG. 5 , nibs  12 ″″′ are provided in  FIG. 6  that have, however, a geometry adapted to the cylinder roller shape in a suitable manner. In particular in the embodiments of  FIGS. 5 and 6 , the nibs  12 ″″ and  12 ″″ can also be formed such that a snap-in and a snap-out of the cylinder rollers  30 ″″ and  30 ″″′ is not possible any longer, so that a connection of the section elements  10 ″″ or  10 ″″′, respectively, and bridge elements  20 ″″ or  20 ″″′, respectively, with cylinder rollers  30 ″″ or  30 ″″′, respectively, inserted therein takes place. 
     As a further exemplary embodiment of the invention,  FIG. 7  shows in perspective view a cage similar to the cage of  FIG. 1  with cylinder rollers  30 ″″″ inserted therein. The connection areas of the section elements  10 ″″″ are formed such the adjacent section elements  10 ″″″ form axial through-holes  16 ″″″. After inserting the cylinder rollers  30 ″″″ into the cage pocket, pins  18 ″″″ are pushed through the axial through-holes  16 ″″′ and affixed, so that another guiding surface for the cylinder roller surface results for the cylinder rollers  30 ″″″ inserted in the pocket and thus counteracts a twisting of the cylinder rollers  30 ″″″ with particular advantage. 
     As a further exemplary embodiment of the invention,  FIG. 8  shows in perspective view and in two opposing observation directions a pocket of a cage composed of bridge elements  20 ″″″′ and section elements  10 ″″″′. Different from the preceding exemplary embodiments, the elements  10 ″″″′ and  20 ″″″″ in this cage are not connected with each other in a fusion-bonded manner, but rather are held together by two snap rings  35 ″″″′ that are in-laid in an interference-fit in corresponding grooves formed on the elements  10 ″″″′ and  20 ″″″′. Further, the section elements  10 ″″″″ are formed so as to be clippable together. Such a cage is simple to assemble with particular advantage, but can also again be disassembled. In other embodiments, other annular retaining elements can naturally be utilized instead of snap rings  35 ″″″′.