Extension guide for furniture parts that can move relative to each other

Abstract

Drawer guide for a drawer, comprising at least two drawer slides (10, 20, 30) between which at least one first rolling element (1) and at least one second rolling element (2) are arranged, which are rotatably held in at least one rolling element cage (3), wherein the at least one first rolling element (1) has a larger nominal diameter and a smaller modulus of elasticity than the at least one second rolling element (2) of the rolling element cage (3), wherein a diameter difference (Δd) between a first nominal diameter (d1) of the first rolling element (1) and a second nominal diameter (d2) of the second rolling element (2) is greater than a lower limit which is at least as large as a manufacturing tolerance (Δd1) in the diameter of the first rolling element (1), characterized in thatthat the lower limit is at least as large as the manufacturing tolerance (Δd1) in the diameter of the first rolling element (1) plus a manufacturing tolerance (Δd2) in the diameter of the second rolling element (2) and / or plus a minimum amount of at least 0.01 mm, wherein, in the case of a full extension of the extension guide, in addition to the force acting perpendicularly on the rails, a torque acts on the extension rails (10, 20, 30) and the first rolling elements (1) are subjected to different loads and thus compressed at different positions within the rolling element cage (3).

Description

[0001] The invention relates to an extension guide for furniture parts that are movable relative to each other, comprising at least two extension rails and a rolling element cage with a plurality of rolling elements, wherein at least one of the rolling elements has a larger diameter and a smaller modulus of elasticity than the remaining rolling elements of the at least one rolling element cage.

[0002] Drawer slides for furniture components that move relative to each other, such as drawers mounted within a furniture carcass, have been known in the art for a long time, for example, from German patent application DE 3536654 C2. Cylindrical rollers or balls, rotatably mounted within the roller cage, are used as rolling elements. "Hard" steel balls or rollers with a high modulus of elasticity (Young's modulus) are frequently used, as they ensure smooth operation even under high mechanical loads from a large weight that is mounted on the slide. A disadvantage can be loud rolling noises, which are more pronounced the less the drawer slide is loaded. In the case of drawers as movable furniture components, a low load is present, especially when the drawer is empty or nearly empty.The rolling noise is then further amplified by the vibrating drawer bottom and the large resonance volume available due to the empty drawer.

[0003] From publication WO 2012 / 045854 A1, it is known to use two different types of rolling elements in a roller cage to achieve low rolling noise and preferably low rolling resistance in a pull-out guide. A first type of rolling element is made of a material with a lower hardness than the second type, and the first type is larger than the second type. Regarding the size ratio of the two rolling elements, it is specified that the diameter of the second type is at least one per mille smaller than the diameter of the first type. The publication does not specify an upper limit for the diameter of the less hard second type of rolling element.

[0004] Tests have shown that with a size difference of only one part per thousand between the rolling elements of the two different types, it is not guaranteed that the rolling noise of the drawer slide will be reduced, depending on the materials used. Conversely, if too large a size difference is chosen, this can result in the destruction of the larger, softer rolling elements.

[0005] Patent application US 2,400,374 A describes a sliding table for a machine tool that incorporates integrated roller tracks for rolling elements on its sides. In addition to smaller, hard rolling elements, larger, softer rolling elements are used to intentionally create a stiffer running action for the sliding table. Patent application DE 91 12 658 U1 describes the use of smaller, hard rolling elements and larger, softer rolling elements within a linear or rotary rolling bearing to resist unwanted movement. The size or hardness ratio of the two different rolling elements is not disclosed in detail in either document. Furthermore, stiffer running action is not desirable for furniture components that move relative to each other.

[0006] It is an object of the present invention to provide an extension guide of the type mentioned at the outset in which the size difference of the various rolling elements is specified in such a way that, on the one hand, a reduction of the rolling noise is reliably achieved and, on the other hand, the extension guide is durable and, in particular, no damage to the larger, softer rolling elements is shown.

[0007] The problem is solved by an extract containing the features of the independent claim. Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0008] An extractor guide according to the invention of the type mentioned at the outset is characterized in that a diameter difference between a first nominal diameter of the first rolling element and a second nominal diameter of the second rolling element is greater than a lower limit which is at least as large as a manufacturing tolerance in the diameter of the first rolling element.

[0009] This prevents manufacturing tolerances, which are relatively pronounced in the softer, first rolling elements due to material properties, from causing the second, harder rolling elements to bear the load when the drawer slide is unloaded. This would increase the noise level when the drawer slide is operated. By taking into account at least the manufacturing tolerance in the diameter of the first rolling element, it is ensured that, especially when the drawer slide is unloaded, e.g., with an empty drawer, the drawer slides are guided by the first, softer rolling elements, resulting in quiet operation.

[0010] Furthermore, in an extension guide according to the invention, the lower limit is at least as large as the manufacturing tolerance in the diameter of the first rolling element plus a manufacturing tolerance in the diameter of the second rolling element and / or plus a minimum amount. In this way, the manufacturing tolerance of the second, harder rolling elements can also be taken into account if it is not negligibly small compared to the manufacturing tolerance of the first, softer rolling elements. Furthermore, the minimum amount ensures that the noise reduction according to the invention is also achieved with a slightly loaded extension rail. Preferably, the minimum amount depends on the difference in the modulus of elasticity between the first and the second rolling elements. According to the invention, it is at least 0.01 mm.

[0011] In a further advantageous embodiment of the drawer slide, an upper limit for the diameter difference is also provided. Preferably, the diameter difference at the upper limit is smaller than the yield strength of the first rolling element when the at least one first rolling element is compressed to the nominal diameter of the second rolling element. This ensures that even under high loads on the drawer slide, e.g., with a fully loaded drawer, overloading and subsequent destruction of the first, softer rolling elements is avoided.

[0012] The upper limit is also preferred if it depends on a load on the extension guide at which at least one second rolling element experiences a compressive load. In this way, the load on the extension guide can be adjusted at which a load change occurs between the first, softer, and second, harder rolling elements.

[0013] Furthermore, the upper limit is advantageously no larger than the sum of the manufacturing tolerance in the diameter of the first rolling elements and a maximum value, where this maximum value is preferably no more than 0.3 mm. These criteria are easily implemented and ensure, for typical material combinations for the first and second rolling elements, that the yield strength of the first rolling element is not reached, thus preventing damage to the first, softer rolling element.

[0014] In a further advantageous embodiment of the extension guide, the rolling elements run between the at least two extension rails on at least two rolling element raceways, wherein at least two of the rolling elements located one behind the other on one of the rolling element raceways are second rolling elements. Preferably, the at least one first rolling element is arranged on the same rolling element raceway of the extension guide as the at least two second rolling elements. Particularly preferably, the at least two second rolling elements are arranged at the ends of the rolling element raceways. These embodiments represent particularly favorable arrangements of the first and second rolling elements within the rolling element cage(s), in which the advantages of the invention are particularly well realized. A rolling element raceway is defined by the trajectory of a rolling element when the extension guide is actuated.Rolling elements positioned one behind the other in the direction of pull-out thus run on the same rolling element track.

[0015] In a further advantageous embodiment of the extension guide, in addition to the first and second rolling elements, further rolling elements, differing from the first and second rolling elements, are present. An extension guide according to the invention is therefore not limited to the presence of the first and second rolling elements, but can also be implemented in extension guides that have one or more types of additional rolling elements. These can, for example, absorb loads under particularly high loads on the extension guide or under certain tilting loads, especially when the extension guide is partially or fully extended, and further improve the running characteristics.

[0016] In a further advantageous embodiment of the extractor guide, the at least one second rolling element is made of steel and / or the at least one first rolling element is made of polyoxymethylene (POM) or polypropylene (PP). These material combinations are particularly well suited for implementing the invention, especially since the aforementioned materials have suitable moduli of elasticity.

[0017] The invention is explained in more detail below using exemplary embodiments and the accompanying figures. The figures show: Fig. 1 a perspective view of a first embodiment of an extractor guide; Fig. 2 a sectional view of the extension guide of the Fig. 1; Fig. 3 a perspective detail view of a rolling element cage in the first embodiment of the pull-out guide; Fig. 4 a schematic representation of the size ratios of the different rolling elements; Fig. 5a a schematic diagram illustrating the load on the different rolling elements depending on the load of a withdrawal guide in accordance with the application; Fig. 5b a schematic diagram to illustrate the sound pressure level as a function of the load on the drawer slide; Fig. 6a to 6c each show a top view of a rolling element cage with different arrangements of the various rolling elements; Fig. 7a a perspective view of a rolling element cage with rolling elements in a second embodiment; Fig. 7b a sectional view of the rolling element cage of the second embodiment and Fig. 7c a side view of the rolling element cage of the second embodiment.

[0018] The Fig. Figure 1 shows a first embodiment of a drawer slide in a perspective view. The drawer slide has at least two, in this case three, drawer slides that are preferably linearly displaceable relative to each other: an outer drawer slide 10, a middle drawer slide 20, and an inner drawer slide 30. The outer drawer slide 10 is connected to fastening means 11, which serve to fix the outer drawer slide 10, for example, to a furniture carcass. The inner drawer slide 30 has fastening means 31 with which it can be fixed to a movable furniture part, for example, a drawer. In the Fig. Figure 1 shows the outer extension rail 10 and the inner extension rail 30 cut away to give insight into the internal structure of the extension guide.

[0019] The in Fig. The drawer slide shown in Figure 1 is merely a preferred embodiment. The invention can also be implemented in differently designed drawer slides. It is not limited to the ones shown in Figure 1. Fig. The number of three rails shown, moving relative to each other, is fixed, as is the geometric design of the rails.

[0020] Fig. 2 shows the extraction guide of the Fig. 1 in cross-section. The outer extension rail 10 and the inner extension rail 30 each have a square profile with rounded corners, the opposite sides being provided with a longitudinal slot, resulting in an overall C-shaped profile. At least in the middle area, the outer extension rail 10 and the inner extension rail 30 are preferably made of sheet steel, with plastic plugs optionally inserted in the end areas. How Fig. Figure 1 shows, for example, that the fastening elements 31 are formed by such plastic plugs.

[0021] A central extension rail 20 is also provided, which has a profile similar to a double cross. The central extension rail 20 is guided by one of its cross-shaped sections via a rolling bearing arrangement in the outer extension rail 10 and the inner extension rail 30, respectively.

[0022] The rolling bearing assembly used in the first embodiment is in Fig. Figure 3 shows a more detailed perspective drawing. It features an elongated, C-shaped rolling element cage 3 in which a plurality of rolling elements 1, 2 are arranged in the rolling element bearing points 4, 5. In this case, balls are used as rolling elements 1, 2. It is understood that other types of rolling elements can also be used in the extension guides according to the invention, for example, rollers or barrel- or elliptical-shaped bodies. Such rolling elements can also be rotatably mounted in appropriately designed rolling element cages, with or without bearing journals.

[0023] In the longitudinal direction of the rolling element cage 3, rolling elements 1, 2 are arranged in six planes, grouped into two sets of three planes each in the outer region of the rolling element cage 3. Each plane contains four rolling elements 1, 2, which – as Fig. Figure 2 shows that, in the assembled state of the extension guide, the rolling elements 1 and 2 are positioned in one of the rounded corners of the outer extension rails 10 and the inner extension rail 30, respectively. In the depicted rolling element cage 3, the rolling elements 1 and 2 thus run on three different rolling element tracks. A rolling element track is defined by the trajectory of a rolling element when the extension guide is actuated. Rolling elements positioned one behind the other in the extension direction of the extension guide, or in the longitudinal direction of the rolling element cage 3, run on the same rolling element track.

[0024] The rolling element cage 3 can be made of plastic or metal, particularly sintered metal. A rolling element cage made of a multi-component material is also possible, where a base body can be made of a rigid material and the bearing areas can be made of a plastically deformable material, such as plastic. It is advantageous if at least the material of the bearing surfaces has tribologically optimized properties, so that the torque required to rotate the rolling elements is reduced as much as possible. This can also be achieved, for example, by lubricants that are already present in the material of the bearing surfaces.

[0025] Within each of the two rolling element cages 3, different types of rolling elements are provided: first rolling elements 1, which are shown without hatching in the figures, and second rolling elements 2, which are shown with hatching. The first rolling elements 1 and the second rolling elements 2 differ in both their diameter and their hardness, which is described, for example, by their modulus of elasticity. The first rolling elements 1 have a lower modulus of elasticity, meaning they are softer than the second rolling elements 2, and have a larger diameter in the unloaded state than the second rolling elements 2. Corresponding to the size difference between the first rolling elements 1 and the second rolling elements 2, the bearing points 4 and 5 are also dimensioned differently for the different types of rolling elements. The bearing points 4 and 5 are designed here such that the corresponding first and second rolling elements 1 and 2, respectively, are supported by the bearings 4 and 5.The second rolling elements 1, 2 can be pressed into the bearing positions 4, 5, whereby during pressing the edges of the bearing positions 4, 5 widen and / or the rolling elements 1, 2 are compressed. After insertion into the bearing positions 4, 5, the rolling elements 1, 2 are held in the rolling element cage 3 in the corresponding bearing positions 4, 5 so as to be as freely rotatable as possible.

[0026] The rolling elements 1, 2 can be made of metals such as brass, bronze, aluminum, or steel, or of non-metals such as polyamide, polyoxymethylene (POM), polyethylene (PE), polypropylene (PP), thermosets, or ceramics. A possible combination of softer rolling elements 1 and harder rolling elements 2 is, for example, the material combination of POM or PP for the first rolling elements 1 and steel for the second rolling elements 2.

[0027] Fig. Figure 4 defines the quantities used below. A first rolling element 1 and a second rolling element 2 are shown side by side on a plane 6. The first rolling element 1 has a first diameter d1, and the second rolling element 2 has a second diameter d2. The difference in diameter is given by a diameter difference Δd = d1 - d2. Δd is greater than zero, since by definition the first diameter d1 is larger than the second diameter d2.

[0028] Based on Fig. Section 5 below explains in more detail the functioning of the extractor guide according to the invention with the aid of two schematic diagrams.

[0029] Due to the larger diameter of the first rolling elements 1, the extension rails 10, 20 and 20, 30, respectively, run essentially only on the first rolling elements 1 when the extension guide is under light load. The smaller second rolling elements 2 either do not contact either of the two extension rails 10, 20 and 20, 30, or they run on one of the two extension rails, for example, the lower one. As the load on the extension guide increases, the larger, but softer, first rolling elements 1 are increasingly compressed until, above a certain load on the extension guide, at least one of the first rolling elements 1 is compressed to such an extent that at least one of the second rolling elements 2 comes into contact with both adjacent extension rails 10, 20 and 20, 30, respectively.Any additional load on the pull-out guide is then essentially absorbed by the second rolling elements 2, which, due to their higher modulus of elasticity, are compressed less even under further increasing loads. With a large difference in the modulus of elasticity between the first and second rolling elements 1, 2, as occurs, for example, with a material combination of POM or PP versus steel, the second rolling elements 2 act almost like a limiter.

[0030] Fig. Figure 5a illustrates the load distribution on the first and second rolling elements 1 and 2 in a diagram. The abscissa shows the total load of an extension guide, represented as the mass m with which the entire extension guide is loaded. The ordinate shows partial masses m1 and m2 of the total mass m, which are absorbed by the first rolling elements 1 (m1) and the second rolling elements 2 (m2), respectively. A load curve 41 indicates the magnitude of the partial mass m1 absorbed by the first rolling elements 1, and a load curve 42 indicates the partial mass m2 absorbed by the second rolling elements 2.

[0031] When the drawer slide is loaded in its retracted state and acts vertically downwards on the horizontally oriented rails, the load is distributed evenly first among all the first rolling elements 1 and then among all the first and second rolling elements 1, 2. In this case, which occurs, for example, with a retracted and evenly loaded drawer, a transition point at which the second rolling elements 2 are loaded can be precisely defined. With an uneven load on the drawer, or with partial or full extension of the drawer slide, a torque acts on the drawer slides 10, 20, 30 in addition to the force acting vertically on the rails. This torque causes the first rolling elements 1 to be loaded and thus compressed to varying degrees at different positions within the rolling element cage 3.The transfer of the load from the first rolling elements 1 to the second rolling elements 2, depending on the load of the extension guide, is then less discrete and is distributed over a wider load range. Accordingly, the slopes of curves 41 and 42 change continuously, particularly in the transition range.

[0032] In Fig. Figure 5b illustrates the resulting beneficial effect on noise generation during movement of the drawer slide. The abscissa shows the total load on the drawer slide, represented as the mass m with which the entire slide is loaded. The ordinate shows the sound pressure level L emitted by the drawer slide in decibels.

[0033] For comparison, two sound pressure level curves 43 and 44 are shown, of which sound pressure level curve 43 represents the rolling noise of a drawer slide equipped exclusively with hard rolling elements, for example, steel balls or rollers. High rolling noise is particularly noticeable under low load (small mass m).

[0034] In contrast, the rolling noise under low load is reduced across the entire load range shown with a pull-out guide according to the application, which uses softer first rolling elements 1 and harder second rolling elements 2. This is illustrated in the sound pressure level curve 44. The noise reduction achieved is particularly pronounced under low load, where only or primarily the softer first rolling elements 1 are subjected to the load. Under high load, where, even with the pull-out guide according to the application, the load is primarily borne by the second rolling elements 2, the sound pressure level curves 43 and 44 converge.

[0035] To ensure that the first rolling elements 1 can exert their noise-reducing effect in the lower load range when engaged with the extension rails 10, 20, the size difference Δd between the diameters d1 and d2 of the first and second rolling elements 1, 2 must meet certain criteria. The rolling elements 1, 2 exhibit certain unavoidable manufacturing tolerances with respect to their diameter. These tolerances are typically larger for the first rolling elements 1, which are made of the softer material, than for the harder second rolling elements 2. Assuming that the manufacturing tolerances Δd1 and Δd2 are equal (symmetrical) for larger and smaller diameters, the actual diameters of the first rolling elements 1 lie within the range d1 ± Δd1, and those of the second rolling elements 2 lie within the range d2 ± Δd2. d1 and d2 then accordingly denote nominal diameters.

[0036] If all the first rolling elements 1 used within a rolling element cage are larger than all the second rolling elements 2 used, the first rolling elements 1 reduce noise when the extension rails move under light loads. To ensure this, the diameter difference Δd, based on the nominal diameters d1 and d2, must be larger than the sum of the manufacturing tolerances Δd1 + Δd2. Since the manufacturing tolerances for the second, harder rolling elements 2 are usually significantly smaller than for the first, softer rolling elements 2, the manufacturing tolerance Δd2 can potentially be neglected compared to the manufacturing tolerance Δd2. This simplifies the criterion to the point that the diameter difference Δd must be larger than the manufacturing tolerance Δd1.

[0037] If a non-symmetrical manufacturing tolerance range is assumed, when determining the difference in diameter Δd between the nominal diameters d1 and d2, the lower tolerance range for the diameter tolerance of the first rolling element 1 and the upper tolerance range for the diameter tolerance of the second rolling element 2 must be considered. Therefore, the sum of the differences between the nominal diameter d1 and the smallest possible diameter of the softer, first rolling element 1, and the largest possible diameter and the nominal diameter d2 of the harder, second rolling element 2, defines a lower limit for the diameter difference Δd.

[0038] It is advantageous if, in addition to manufacturing tolerances, the different moduli of elasticity between the softer, first rolling elements 1 and the harder, second rolling elements 2 are also considered as a further criterion for the noise-reducing effect in the lower load range at the lower limit. The greater the difference between the moduli of elasticity, the greater the minimum amount should be that is added to the aforementioned manufacturing tolerance Δd1 or to the sum of the manufacturing tolerances Δd1 + Δd2. The minimum amount should advantageously be at least 0.01 mm (millimeters).

[0039] In addition, an upper limit for the diameter difference Δd must be considered. One criterion for this upper limit of Δd takes into account the material strength of the first, softer rolling elements 1. These could be destroyed if they are compressed too much with increasing load on the pull-out guide before the second rolling elements 2 limit further compression of the first rolling elements 1. Destruction of the first rolling elements 1 begins as soon as the range of elastic deformation of the first rolling elements 1 is exceeded. The range of elastic deformation of the first rolling elements d1 is exceeded as soon as a yield strength of the material of the first rolling elements 1 is exceeded. The yield strength relates to a compressive load occurring during static compression, i.e., compression without rotation of the first rolling elements 1, as well as a shear load that occurs during rotation of the first rolling elements 1 in the compressed state.

[0040] Another criterion for the upper limit of the diameter difference Δd is the load on the drawer slide, for example, the selected load weight of a drawer, above which the at least one second, harder rolling element 2 is intended to bear the majority of the load. If, for example, this selected load weight is close to the weight of the unloaded drawer, the upper limit of the diameter difference Δd is close to the lower limit of the diameter difference Δd. If the selected load weight of the drawer is close to the maximum weight of the drawer, the upper limit of the diameter difference Δd should be chosen further away from the lower limit of the diameter difference Δd.

[0041] By setting the lower limit of the diameter difference Δd, it is ensured that noise generation when the drawer is extended is minimized. By setting the upper limit of the diameter difference Δd, the load change between the first, softer and second, harder rolling elements can be controlled, and overloading of the first, softer rolling element can be prevented.

[0042] For a typical application of a drawer slide, where the first rolling elements 1 are made of POM and the second rolling elements 2 are made of steel, and which is designed for a load of 45 kg (kilograms) at a drawer extension length of 300 mm, the following condition applies to the diameter difference Δd, assuming a nominal second diameter d2 of the second rolling elements 2 of 3.9 mm: 0.02 mm < Δd < 0.17 mm. The lower limit of 0.02 mm is determined by manufacturing tolerances and the minimum value for this material pairing of POM / steel, while the upper limit of 0.17 mm is due to plastic deformation and thus material failure of the first rolling elements 1. A Young's modulus of 26,000 N (Newtons) / mm² is assumed. 2 for POM and an elastic modulus of 210,000 N / mm² 2 assumed for steel, wherein 16 first rolling elements 1 and 8 first rolling elements 2 are provided per rolling element cage 3 and the pull-out guide has a basic structure according to the first embodiment ( Fig. 1 to 3).

[0043] For a material selection of PP for the first rolling elements 1 with a modulus of elasticity of 1,500 N / mm² 2 Assuming otherwise identical assumptions, the diameter difference Δd is: 0.03 mm < Δd < 0.12 mm.

[0044] Fig. Figure 6 shows in sub-figures b) and c) alternative distributions of the first and second rolling elements 1, 2 within the rolling element cage 3. For comparison, sub-figure a) shows again the distribution already shown in the first embodiment ( Fig. The configuration specified in paragraphs 1 to 3 is repeated. It is noted that both the absolute number of first and second rolling elements 1, 2, and the ratio of the number of first and second rolling elements 1, 2, can be varied within the scope of the application compared to the embodiments presented here. Furthermore, within a pull-out guide and also within one of the rolling element cages 3, additional, different types of rolling elements can be used, which differ from the first and second rolling elements 1, 2.

[0045] Fig.Figure 7 shows a rolling element cage 3 for a further embodiment of an extension guide. In the rolling element cage 3 shown here in perspective view (part 7a), in sectional view (part 7b), and in side view (part 7c), the first and second rolling elements 1, 2 are arranged in three rows, each with four first rolling elements 1 and two second rolling elements 2. In this case, the balls are arranged longitudinally offset in one of the rows relative to the other two rows. The teaching of the application can, in principle, be applied to a multitude of embodiments of rolling element cages. Reference symbol list 1 first rolling element 2 second rolling element 3 rolling element cage 4 Bearing point for first rolling element 5 Bearing point for second rolling element 10 outer extension rail 11 Fasteners 20 medium extension rails 30 inner extension rail 31 Fasteners 41, 42 Load curve 43, 44 Sound pressure level curve d1 nominal diameter of the first rolling elements d2 nominal diameter of the second rolling elements Δd diameter difference

Claims

[1] Drawer guide for a drawer, comprising at least two drawer slides (10, 20, 30) between which at least one first rolling element (1) and at least one second rolling element (2) are arranged, which are rotatably held in at least one rolling element cage (3), wherein the at least one first rolling element (1) has a larger nominal diameter and a smaller modulus of elasticity than the at least one second rolling element (2) of the rolling element cage (3), wherein a diameter difference (Δd) between a first nominal diameter (d1) of the first rolling element (1) and a second nominal diameter (d2) of the second rolling element (2) is greater than a lower limit which is at least as large as a manufacturing tolerance (Δd1) in the diameter of the first rolling element (1), characterized by, that the lower limit is at least as large as the manufacturing tolerance (Δd1) in the diameter of the first rolling element (1) plus a manufacturing tolerance (Δd2) in the diameter of the second rolling element (2) and / or plus a minimum amount that is at least 0.01 mm, wherein, in the case of a full extension of the extension guide, in addition to the force acting perpendicularly on the rails, a torque acting on the extension rails (10, 20, 30) results and the first rolling elements (1) are subjected to different loads and thus compressed at different positions within the rolling element cage (3). [2] Extraction guide according to claim 1, wherein the minimum amount depends on the difference in the modulus of elasticity between the first and the second rolling element (1, 2). [3] Extraction guide according to claim 1 or 2, wherein an upper limit for the diameter difference (Δd) is provided. [4] Extraction guide according to claim 3, wherein the diameter difference (Δd) at the upper limit is smaller than such that a yield strength of the first rolling element (1) is reached when the at least one first rolling element (1) is compressed to the nominal diameter (d2) of the second rolling element (2). [5] Extraction guide according to claim 3 or 4, wherein the upper limit depends on a load on the extraction guide in which the at least one second rolling element (2) is subjected to a pressure load. [6] Extraction guide according to claim 5, wherein the upper limit is at most as large as the sum of the manufacturing tolerance (Δd1) in the diameter of the first rolling element (1) and a maximum amount. [7] Extraction guide according to claim 6, wherein the maximum amount is at most 0.3 mm. [8] Extraction guide according to one of claims 1 to 7, wherein the rolling elements (1, 2) run between the at least two extraction rails (10, 20, 30) on at least two rolling element raceways, wherein at least two of the rolling elements located one behind the other on one of the rolling element raceways are second rolling elements (2). [9] Extraction guide according to claim 8, wherein at least one first rolling element (1) is arranged on the same rolling element raceway of the extraction guide as the at least two second rolling elements (2). [10] Extraction guide according to claim 8, wherein the at least two second rolling elements (2) are arranged at the end of the rolling element raceway. [11] Extraction guide according to one of claims 1 to 10, in which, in addition to the first and second rolling elements (1, 2), further rolling elements are present which differ from the first and second rolling elements (1, 2). [12] Extraction guide according to one of claims 1 to 11, wherein the at least one second rolling element (2) is made of steel. [13] Extraction guide according to any one of claims 1 to 12, wherein the at least one first rolling element (1) is made of POM or PP.

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