Linear bearing cage

Abstract

Linear bearing cage (1) comprising a base body (2) formed in a hollow cylindrical shape along an axis (a), wherein end pieces (3, 4) for forming rolling element circulation areas are arranged in the axial end regions of the base body (2), wherein a number of recesses (5) extending in the direction of the axis (a) are arranged around the circumference of the base body (2), into which raceways (6) for rolling elements (7) are inserted, characterized in that the base body (2) has a cylindrical outer surface (8) with a basic radius (r) which has a section (9) with an increased radius (R) in an axial central region (M), such that the diameter of the linear bearing cage (1) is greatest in the central region (M).

Description

The invention relates to a linear bearing cage comprising a base body which is formed hollow-cylindrically along an axis, wherein end pieces for forming rolling body circulation regions are arranged in the axial end regions of the base body, wherein a number of recesses which extend in the direction of the axis are arranged over the circumference of the base body, into which recesses raceways for rolling bodies are inserted.Linear bearing cages of the generic type are sufficiently known. The hollow cylindrical components are designed to be provided with ball circulation elements distributed around the circumference, in order to be translationally displaceable on a shaft part.Here, hollow-cylindrically closed variants of linear bearing cages are known, which encompass the shaft part over the entire circumference. Furthermore, open variants are also common which have a slot running in the axial direction at a circumferential location, i.e. do not encompass the entire circumference of the shaft element.Furthermore, linear bearing cages of the generic type differ substantially in that they can be "rigid" cages and "angle-adjustable" cages. In the rigid embodiment, the raceways (i.e. the thrust parts made of steel which are provided on the radially inwardly directed side with a raceway for the balls and which are supported on the radially outwardly directed side on an attachment part, i.e. a housing) are supported in a planar manner in the radially outer region. They accordingly offer a high load-bearing capacity, but cannot yield and adapt in the case of angular deviations. On the other hand, in the case of the angle-adjustable version, it is provided that the raceways on the radially outer side bear on the attachment part in the manner of a rocker, for which reason it is possible here for angle deviations between the shaft part and the attachment part to be able to be compensated (the angles of inclination are in this case usually on the order of magnitude of 30 angle minutes); the raceways are in this case supported by a radially outwardly extending projection, that is to say on their rear side only in the middle, with the result that, during operation, they can "oscillate" by a specific angle (adjustment angle).For particularly heavy loads, so-called "heavy variants" with an increased number of tracks are also additionally known. Higher load-bearing numbers can be achieved with this.For the angle-adjustable bearing types, a separate, i.e. a specially provided cage base body is used. The angular adjustability, i.e. the "pendulum" capability, can be produced by using raceways with a spherical outer side; i.e. the outwardly directed surface of the raceway rails is formed in a spherical manner in radial section.It is also known to enclose the linear bearing, which has been fully assembled, centrally with a metal ring and thus to enlarge it radially in the central region. In the installed state, the linear bearing can then "oscillate" in the manner explained. However, the raceway thickness is thereby reduced over the entire longitudinal extension.As already mentioned above, raceways are often also used which have an elevation or bulge in the axial central region on the radially outer side, in order thus to enable the "pendulum effect".In any of the cases mentioned, the task of the cage is to hold the raceways (i.e. the raceway rails) and to ensure the ball circulation via the forward and return. This applies to all the bearing types mentioned, i.e. to the "rigid" and to the "angle-adjustable" variant, and also to the open or open (slotted) construction.The outer shape of the cage enables the aforementioned "pendulum", i.e. the angular adjustability. As explained, specially manufactured cage base bodies are used for this purpose, just as for the "stiff" configuration. In the latter case, the outer diameter of the cage corresponds to the bore of the housing. However, in the case of the angle adjustable cages, the outside diameter is slightly smaller to allow angle adjustment.An assembly-technical effect to be taken into account is as follows: The linear bearing (in particular in the case of straight tracks on the outer side) is generally secured in the attachment part, i.e. usually in the housing, by screws or grease nipples. In the case that the housing is continuously smaller in outer diameter, there is no self-retaining effect of the linear bearing cage in the housing; a self-retaining force in the housing is only achieved when the shaft is inserted. If the raceway has the above-mentioned elevation in the radially outer region, which is intended to allow "swinging", the self-retaining effect is however present, i.e. the linear bearing cage retains its axial position in the housing even without further measures after assembly.DE 10 2013 206 352 A1 relates to linear guides and in particular ball guide channels of guide carriages for such linear guides. Such a ball guide channel is at least partially delimited by a lateral surface in the circumferential direction and is designed in such a way that at least three predefined contact surfaces spaced apart from one another in the circumferential direction are provided for a ball which circulates in the ball guide channel.DE 10 2007 012 647 A1 relates to a linear rolling bearing having a hollow cylindrical base element which protrudes axially at at least one axial end in the region of an outer sleeve in such a way that a deflecting element and a covering element can be arranged one after the other in the cavity of the protrusion.The invention is based on the object of developing a linear bearing cage of the type mentioned at the beginning in such a way that a universal cage is present which is optionally suitable, on the one hand, for the rigid mounting of a component and, on the other hand, for the angularly adjustable mounting of the component. Furthermore, the self-holding effect mentioned is intended to be provided.The solution of this object by the invention is characterized in that the base body has a cylindrical outer surface with a base radius, which has a section with an enlarged radius in an axial central region, so that a diameter of the linear bearing cage is the greatest in the central region.The section with enlarged radius preferably has a cylindrical outer surface. It is preferably arranged centrally between the axial ends of the base body.The axial extent of the section with enlarged radius is preferably between 8% and 20% of the axial extent of the base body.The increased radius is preferably between 100.5% and 105% of the base radius.The raceways may have an outer surface which is constant on a radius, in particular on the larger radius. This embodiment is then provided for a "rigid" bearing. However, it is also possible for the raceways to have an outer surface which corresponds to the shape of the base body, that is to say with the cylindrical outer surface having the base radius and the enlarged radius in the central region; this embodiment is then provided for an angle-adjustable solution.The base body is preferably designed as a one-piece plastic injection molded part. In this case, in particular the section with an enlarged radius is formed integrally with the further base body.The rolling elements are usually balls.The linear bearing cage can also have a slot extending in the direction of the axis at a circumferential location.Thus, it becomes possible to realize one and the same linear bearing cage by appropriately selecting the raceway rails and by installing said raceway rails in the cage both "rigid" cages, i.e. cages that cannot be adjusted in angle, and "cages that can be adjusted in angle.". In previously known solutions, individual cage base bodies were always used, depending on whether the "rigid" or "angle-adjustable" variant was required.Thus, while two different cage base bodies were required and had to be stored for each structural size up to now, it becomes possible by the solution according to the invention to realize the two different solutions starting from a single cage base body per structural size.According to the invention, the outer shape of the cage base body was thus adapted as mentioned, namely to the geometry of the raceways.Since according to the invention the outer shape of the cage and namely of the cage base body is adapted to the back shape of the angle-adjustable raceway plate, the same cage base body can advantageously be used both for rigid and for angle-adjustable variants.The bulge of the cage base body in the axial center ensures a self-holding force of the linear bearing cage in the housing in a simple manner. By means of only slight tool corrections of the injection-molding tool with which the cage is produced, an adaptation of the stated effect can be achieved if required.The holding force which secures the linear bearing cage in the housing is thus provided independently of whether a rigid or angle-adjustable variant is present.A deformation of the cage in the central region due to a slight diameter excess for generating the self-holding force in the housing has no negative influence on the ball channels, especially on the deflection zones, which are relatively demanding in terms of production technology.Accordingly, the advantages of the solution according to the invention can be summarized as follows:Only a single cage base body (per size) is necessary in order to realize, on the one hand, rigid linear bearing variants and, on the other hand, linear bearing variants which can be adjusted in angle.There is thus a cost saving since only one plastic injection molding tool is required for the cage base body of one size. Fewer further components (e.g. end rings) are also required, which reduces the logistic outlay and reduces the storage costs.There is also a design advantage, since only one (plastic) cage per size has to be provided (identical end rings for both variants, thus less effort in the adaptation of the individual components).The self-holding force in the housing can easily be generated and this remains the same for both variants. There is also no risk of adverse effects on the bearing function.The same outer shape of the cage can be used for the open and closed cage variant, as can the case with the "heavy" linear bearings.Exemplary embodiments of the invention are shown in the drawing. The following are shown: FIG. 1 is a schematic side view of a linear bearing cage, wherein an embodiment as a rigid bearing is shown in the upper half of the figure and an embodiment as an angle-adjustable bearing is shown in the lower half of the figure, FIG. 2 shows a perspective illustration of a linear bearing according to the invention, wherein an embodiment as a rigid bearing is provided, and FIG. 3 shows a perspective illustration of a linear bearing according to the invention, wherein an embodiment is provided as an angle-adjustable bearing.In FIG. 1, a linear bearing cage 1 is outlined in the side view, in the interior of which a number of balls 7 (see FIGS. 2 and 3 ) are guided in circulation in order to mount a housing (not shown) arranged radially on the outside in a linearly displaceable manner against a shaft (not shown) located radially on the inside. Such linear bearings are known in the prior art. The linear bearing cage 1 comprises a base body 2 which extends in the direction of an axis a in a hollow cylindrical manner and which consists of an injection-molded plastic part; furthermore, end pieces 3 and 4 which are arranged axially on the end side and form parts of a recirculating ball guide are present.A number of recesses 5 (see FIGS. 2 and 3 ) are formed in the base body 2 around the circumference of the base body 2, wherein a raceway 6 (raceway plate) is inserted in each recess 5 which is rectangular in the present case. In this respect, too, the design represents a known linear bearing cage construction.However, it is now essential that the base body 2 has a cylindrical outer surface 8 with a base radius r, which has a section 9 with an enlarged radius R in an axial center region M. It should be noted that in FIG. 1, the radial superelevation of the central region M provided with an enlarged radius is illustrated greatly exaggerated.The section 9 with enlarged radius extends over an axial extension b which makes up about 10 to 15% of the axial extension c of the base body 2.It can be seen in FIG. 1 that in the upper half of the figure a raceway 6 (shown with dashed lines) has been inserted into the recesses 5, which raceway is planar or cylindrical on the radially outer side (i.e. the surface lies on a radius) and thus, after installation in a housing, form a rigid arrangement of the linear bearing cage 1. This solution is outlined in FIG. 2.However, it can also be seen in FIG. 1 that in the lower half of the figure a raceway 6 (shown with dashed lines) has been inserted into the recesses 5, which raceway is not continuously planar or cylindrical on the radially outer side, but follows the course of the outer surface of the base body 2. Thus, the outer surface 10 of the raceway 6 is cylindrical in its lateral regions, but in the central region M the outer surface 10 follows the radial enlargement of the base body. Thus, the linear bearing cage 1 with the raceways 6 seen in the lower half of the figure is designed for an angle-adjustable configuration of the cage 1 (i.e. for "pendulum"). Such a solution is outlined in FIG. 3.List of reference characters1 Linear bearing cage 2 Base body 3 End piece 4 End piece 5 Recess 6 Raceway 7 Rolling bodies (ball) 8 Cylindrical outer surface 9 Section with enlarged radius 10 Outer surface of the raceway r Base radius R Enlarged radius M Central region a Axis b Axial extension of the section with enlarged radius c Axial extension of the base body

Claims

Linear bearing cage (1) comprising a base body (2) which is of hollow cylindrical design along an axis (a), wherein end pieces (3, 4) for forming rolling body circulation regions are arranged in the axial end regions of the base body (2), wherein a number of recesses (5) which extend in the direction of the axis (a) and into which raceways (6) for rolling bodies (7) are inserted are arranged over the circumference of the base body (2), characterized in that the base body (2) has a cylindrical outer surface (8) with a base radius (r) which has a section (9) with an enlarged radius (R) in an axial central region (M), such that a diameter of the linear bearing cage (1) is the greatest in the central region (M).Linear bearing cage according to Claim 1, characterized in that the section (9) with enlarged radius (R) has a cylindrical outer surface.Linear bearing cage according to Claim 1 or 2, characterized in that the section (9) with an enlarged radius (R) is arranged centrally between the axial ends of the base body (2).Linear bearing cage according to one of Claims 1 to 3, characterized in that the axial extent (b) of the section (9) with enlarged radius (R) is between 8% and 20% of the axial extent (c) of the base body (2).Linear bearing cage according to one of Claims 1 to 4, characterized in that the enlarged radius (R) is between 100.5% and 105% of the base radius (r).Linear bearing cage according to one of Claims 1 to 5, characterized in that the raceways (6) have an outer surface (10) which lies constantly on a radius, preferably on the larger radius (R).Linear bearing cage according to one of Claims 1 to 5, characterized in that the raceways (6) have an outer surface (10) which corresponds to the shape of the basic body (2) with the cylindrical outer surface (8) having the base radius (r) and the enlarged radius (R) in the central region (M).Linear bearing cage according to one of Claims 1 to 7, characterized in that the base body (2) together with the section (9) with an enlarged radius (R) is designed as a one-piece plastic injection-moulded part.Linear bearing cage according to one of Claims 1 to 8, characterized in that the rolling bodies (7) are balls.Linear bearing cage according to one of Claims 1 to 9, characterized in that it has a slot extending in the direction of the axis (a) at a circumferential point.

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