Linear guide system

Abstract

The present application relates to a linear guide system with a first rail element and a second rail element, wherein the first rail element and the second rail element are mounted on one another so as to be linearly displaceable relative to one another in and against an extension direction, a spindle drive which has a threaded spindle and a spindle nut running on the threaded spindle, wherein the threaded spindle is mounted on the first rail element so as to be rotatable about a spindle axis or is mounted on a device which is fixed relative to the first rail element in or against the extension direction so as to be rotatable about the spindle axis, and wherein the spindle nut is fixed to the second rail element in and against the extension direction so that when the threaded spindle rotates about the spindle axis, the spindle nut moves along the threaded spindle and takes the second rail element with it.According to the invention, it is provided that the second rail element carries a spindle bearing fixed in or opposite to the extension direction relative to the second rail element, wherein the spindle bearing is designed and arranged such that the spindle bearing guides the threaded spindle relative to the second rail element at least in a first extension position of the second rail element relative to the first rail element.

Description

The present invention relates to a linear guide system having a first rail element and a second rail element, wherein the first rail element and the second rail element are mounted on one another such that they can be displaced linearly with respect to one another in and counter to a pull-out direction, a spindle drive which has a threaded spindle and a spindle nut running on the threaded spindle, wherein the threaded spindle is mounted on the first rail element such that it can rotate about a spindle axis or is mounted on a device fixed in or counter to the pull-out direction with respect to the first rail element such that the spindle nut moves along the threaded spindle in and counter to the pull-out direction, and therefore the spindle nut carries along the threaded spindle during a rotational movement of the threaded spindle about the spindle axis and carries along the second rail element.Linear guide systems, in particular telescopic rails, having at least two rail elements and optionally a rolling body cage having rolling bodies accommodated therein for reducing the friction between the rail elements, are known from the prior art in a wide variety of embodiments. They are used in various domestic appliances, but also in automobile construction and in many further applications. In a large number of fields of application, linear guide systems are already used, which are driven by motor. In this case, a spindle drive is frequently used as a linear drive. Such a spindle drive converts a rotational movement of a threaded spindle into a linear movement of a spindle nut guided on the threaded spindle and thus into a linear movement of the rail elements relative to one another.It has been found to be problematic that the threaded spindles of the spindle drives tend to wobble about their axis of rotation or oscillate with respect to the rail elements. If the threaded spindle abuts against one of the rail elements, noise is generated. Moreover, wobbling and swinging impair the haptics and the running of the guide system. The lead screws must have a high degree of straightness to avoid wobbling. In addition, the effects described on running, noise development and haptics are dependent on the rotational speed. The latter limits the travel speed of the first and second rail elements relative to one another to low speeds.DE 10 2004 057 714 A1 discloses a linear guide system having at least two rail elements which can be moved relative to one another in the longitudinal direction, wherein actuating elements are provided on the rail elements, which elements assist or inhibit the force required for the movement of the rail elements and / or which elements allow the rail elements to be locked in different positions of movement.DE 10 2007 057 113 A1 discloses a drive device, preferably for lifting columns and height-adjustable tables, which comprises a frame having a first deflecting roller and at least one second deflecting roller and a cable system running over at least the first and / or the second deflecting roller, consisting of one or more cables, wherein a rail fastened at one end to a first cable system portion is provided in a first cable system portion and a second cable system portion between the deflecting rollers, and wherein a drive element fastened at the other end of at least one rail is provided and the drive element moves the frame and the rail linearly relative to one another.U.S. Pat. No. 9,814,306 B2 discloses a calibrateable column, in particular for a piece of furniture, wherein the calibrateable column has a fixed part, at least one movable part and a calibration means and the movable part can be transferred from a retracted state into a plurality of extended states, and wherein a calibration position of the column corresponds to the position of the movable part in an extended state. Such a column can be used, for example, as a pull-out column in a piece of furniture.EP 3 919 770 B1 discloses a telescopic rail having a first rail element, a second rail element, a third rail element and a drive device, wherein the first rail element and the second rail element are mounted on one another in such a way that the first rail element and the second rail element are linearly displaceable with respect to one another in and counter to a pull-out direction, wherein the third rail element and the second rail element are mounted on one another in such a way that the third rail element and the second rail element are linearly displaceable with respect to one another in and counter to the pull-out direction, wherein the drive device is mounted on the first rail element or can be mounted on a holding element which can be connected to the first rail element, wherein the drive device is configured in such a way that, in operation of the telescopic rail, the drive device brings about a linear displacement movement of the second rail element with respect to the first rail element in or counter to the pull-out direction, wherein the telescopic rail has a traction element, wherein the traction element is fixed to the first rail element and to the third rail element, and wherein the traction element is guided on the second rail element such that a displacement movement of the second rail element relative to the first rail element leads to a displacement movement of the third rail element relative to the second rail element.EP 4 248 799 A1 discloses a linear guide system having at least one first rail element and one second rail element, which are mounted on one another such that they can be displaced linearly with respect to one another in and counter to a pull-out direction, a linear drive, which has a rotatable drive shaft and an electric motor designed for transmitting a torque to the drive shaft, wherein the linear drive is designed such that a rotational movement of the drive shaft brings about a linear movement of the first and second rail elements relative to one another in or counter to the pull-out direction, wherein a lockable element, which can be adjusted and reset between an unlocked position and a locked position, is provided, which locking element is designed such that, for blocking the rotational movement of the drive shaft in the locked position, it engages positively and / or non-positively with an engagement element connected to the drive shaft or designed as a section of the drive shaft, and an actuator is provided, which is designed for an advancement of the locking element to the engagement element from the unlocked position into the locked position and for a return of the locking element from the locked position into the unlocked position.In contrast, it is an object of the present invention to provide a motor-drivable linear guide system which reduces or avoids at least one of the aforementioned disadvantages.The aforementioned object is achieved by a linear guidance system according to the attached independent claim 1. For this purpose, in the case of the linear guide system of the type mentioned at the beginning, the second rail element carries a spindle bearing which is fixed in or counter to the pull-out direction with respect to the second rail element. The spindle bearing is configured and arranged in such a way that the spindle bearing guides the threaded spindle relative to the second rail element at least in a first pull-out position of the second rail element relative to the first rail element.The present invention is based on the concept of providing a linear guide system with a spindle drive, in which the threaded spindle is guided in a spindle bearing in addition to a drive-side bearing. This spindle bearing is supported by the second rail element and is fixed relative to the second rail element in or counter to the pull-out direction. The spindle bearing therefore simulates the relative movement of the second rail element with respect to the first rail element together with the second rail element.The mounting of the threaded spindle in the spindle bearing leads to a smoother running of the linear guide system. Longer threaded spindles can be realized, the noise generation during the movement of the first and second rail elements relative to one another is reduced and higher rotational speeds and thus higher travel speeds of the first and second rail elements relative to one another can be achieved.The mounting of the threaded spindle in a spindle bearing moved with the second rail element is also advantageous since this mounting does not have to take any account of the movement of the spindle nut relative to the threaded spindle. A collision between the spindle nut and the spindle bearing is ruled out. A mounting of the threaded spindle on the second rail element also makes it possible for a rolling body cage to be able to move between the first and the second rail element.Surprisingly, it has been found that an additional support of the threaded spindle is not absolutely necessary in all operating situations when the first and the second rail element are moved relative to one another. Embodiments are therefore conceivable in which the spindle bearing supports the threaded spindle only at the first pull-out position or around the latter, while in another, second pull-out position of the second rail element relative to the first rail element the spindle bearing can be disengaged from the threaded spindle, so that the latter then runs freely.A pull-out position in the sense of the present application is a relative position of the second rail element with respect to the first rail element measured along the pull-out direction.In one embodiment of the invention, the spindle bearing has a bearing bush receiving the threaded spindle, wherein, at least in a first pull-out position, the threaded spindle is in sliding engagement with the bearing bush during a relative movement of the threaded spindle with respect to the second rail element in or counter to the pull-out direction, such that the spindle bearing supports the threaded spindle. The bearing bush denotes that surface section of the spindle bearing which is or can be brought into sliding engagement with the threaded spindle.The bearing bush of the spindle bearing serves for supporting or mounting the threaded spindle in the radial direction, while the bearing bush is in sliding engagement with the threaded spindle exclusively in and counter to the pull-out direction. The spindle bearing is not a second threaded nut; there is no positive connection between the threaded spindle and the bearing bush in or counter to the pull-out direction.The pull-out direction is that direction in which the second rail element is moved relatively linearly with respect to the first rail element starting from a fully retracted pull-out position in order to reach a fully extended pull-out position. Accordingly, a direction opposite to the pull-out direction is the direction in which the second rail element is moved relative to the first rail element in order to return to a fully retracted pull-out position.An axial direction and a radial direction in this application relate to the axis of rotation of the threaded spindle. The axis of rotation of the threaded spindle is in one embodiment substantially parallel to the pull-out direction.In one embodiment of the invention, the bearing bush has an axial length parallel to the pull-out direction, wherein the axial length of the bearing bush is smaller than a travel path of the bearing bush relative to the threaded spindle between a maximally retracted pull-out position of the second rail element relative to the first rail element and a maximally extended pull-out position of the second rail element relative to the first rail element. A short axial length of the bearing bush compared to the maximum travel path of the second rail element relative to the first rail element leads to smooth running of the threaded spindle at reasonable forces due to the sliding friction of the bearing bush relative to the threaded spindle and to a reduced tilting between the threaded spindle and the bearing bush.In one embodiment of the invention, the bearing bush has an axial length of 40 mm or less, preferably of 30 mm or less and particularly preferably of 25 mm or less.This is opposed by the fact that an embodiment of the bearing bush, in which the bearing bush is as long as possible in the pull-out direction, holds a lubricant better for lubricating the threaded spindle with respect to the threaded nut.In one embodiment of the invention, the spindle bearing has one or more lubricant pockets in the region of the bearing bush for receiving a lubricant.In one embodiment of the invention, the bearing bush is arranged on the second rail element in such a way that, in the maximally extended pull-out position of the second rail element relative to the first rail element, the bearing bush is disengaged from the threaded spindle. It has been found that such an embodiment supports the threaded spindle in an optimized manner during the displacement movement of the first and second rail elements relative to one another. Over a major part of the travel path, the bearing bush is positioned ideally, while the disengagement of the bearing bush and the threaded spindle in the maximally extended pull-out position does not bring about any negative effects.In a further embodiment of the invention, the bearing bush is at a distance of 100 mm or less, preferably of 90 mm or less and particularly preferably of 80 mm or less, from the spindle nut in a direction parallel to the pull-out direction. The distance between the bearing bush and the spindle nut is an important parameter for achieving a smoother running of the threaded spindle. A greater spacing results in a stronger vibration of the arrangement.In one embodiment of the invention, the bearing bush of the spindle bearing is arranged on the second rail element in such a way that, in each pull-out position of the second rail element relative to the first rail element, a free end of the threaded spindle is at most 100 mm, preferably at most 90 mm and particularly preferably at most 80 mm spaced apart from the bearing bush in which the threaded spindle is accommodated. This maximum protrusion of the free end of the threaded spindle relative to the bearing bush is referred to as the maximum free (unsupported) threaded spindle length.The free end of the threaded spindle is that end of the threaded spindle which is opposite the end of the threaded spindle coupled to the motor or a coupling.In one embodiment of the invention, the bearing bush is arranged on the second rail element in such a way that, in the maximally extended pull-out position of the second rail element relative to the first rail element, the bearing bush is arranged approximately where the first rail element ends in the pull-out direction.In one embodiment of the invention, the linear guide system has a second spindle bearing with a second bearing bush, which is spaced apart from the spindle bearing, which is then referred to as the first spindle bearing, in the pull-out direction.This has proven to be expedient in particular if at least the length of the first and / or second rail element is 450 mm or more or the free unsupported spindle length in the fully retracted pull-out position would be 80 mm or more, 90 mm or more or 100 mm or more.In one embodiment, the second bearing bush of the second spindle bearing is at a distance of at most 100 mm, preferably at most 90 mm and particularly preferably at most 80 mm from the first bearing bush of the first spindle bearing.In one embodiment of the invention, the second bearing bush of such a second spindle bearing is arranged approximately on half the length of the second rail element.Embodiments with more than two spindle bearings are also possible.Instead of a second spindle bearing, it is also possible to configure the single spindle bearing such that it has a long bearing bush. In an embodiment of the invention, the bearing bush of the spindle bearing is shorter than the total length of the first rail element in the pull-out direction by a value in a range from 100 mm to 130 mm. The shortening of the positioning bushing with respect to the total length of the first rail element takes into account the motor adapter projecting into the first rail element and the length of the spindle nut and, if appropriate, the deflection unit for the belt drive for synchronizing a third rail element.In one embodiment, a long bearing bush is realized in that the spindle bearing is formed integrally with the second rail element. In one embodiment of the invention, the second rail element is designed as an extrusion profile made of plastic or metal, preferably aluminum, such that all elements of the rail element and of the spindle bearing are depicted by the extrusion profile.In one embodiment of the invention, the spindle bearing has an inlet region, wherein the inlet region adjoins the bearing bush counter to the pull-out direction and widens counter to the pull-out direction starting from a diameter of the bearing bush, wherein, during operation of the system, the free end of the threaded spindle is movable through the inlet region into the bearing bush. In one embodiment of the invention, an inner surface of the inlet region is designed in the form of a truncated cone, wherein the smaller diameter of the truncated cone is equal to the diameter of the bearing bush.In one embodiment of the invention, the spindle bearing is configured symmetrically, so that an identical shape as the bearing bush follows on the side of the bearing bush facing away from the inlet region in the pull-out direction. In this way, the mounting of the spindle bearing is neutral with respect to misorientation.In one embodiment of the invention, the spindle bearing and the second rail element are configured in two parts. In one embodiment of the invention, the spindle bearing comprises a part made of plastic, preferably an injection-molded part, which is mounted on the second rail element. In one embodiment of the invention, the part of the spindle bearing made of plastic comprises polyoxymethylene (POM).In one embodiment, the spindle bearing comprises a housing made of plastic, for example of POM. In such an embodiment, the bearing bush comprises in particular a material with a lower sliding friction compared to the housing with respect to the threaded spindle. In one embodiment, the bearing bush consists of a metal, in particular of a brass-lead sintered material. The bearing bush configured in this way is pressed into the housing in one embodiment or the bearing bush is injection-molded with the plastic of the housing in an injection molding process.In one embodiment of the invention, at least the first or the second rail element has a rail back and two limbs which carry running surfaces for rolling bodies and extend at an angle with respect to the rail back. A direction parallel to the rail backs of the first and second rail elements is also referred to as a vertical direction.In one embodiment, the spindle bearing is formed by a bearing block with the bearing bush receiving the threaded spindle and a mounting section. The mounting portion serves for connecting the spindle bearing to the second rail element. In one embodiment, the mounting portion is clamped at least in a force-fit manner between the two limbs of the second rail element. Such a configuration of the spindle bearing as a bearing block with the bearing bush and a mounting portion which can be clamped into the profile of the second rail element is adapted to the shape of such a second rail element.In one embodiment of the invention, the mounting section is clipped at least positively or non-positively into an aperture in the rail back of the second rail element.In one embodiment of the invention, the mounting portion has a projection or a depression, wherein the rail back of the second rail element has a depression or a projection complementary thereto. The projection engages in the depression, so that the bearing block is fixed positively on the second rail element in and counter to the pull-out direction. While the clamping of the mounting portion between the legs provides a positive fit for a movement of the bearing block in the vertical direction perpendicular to the pull-out direction, the clamping in the pull-out direction merely brings about a frictional connection. The combination of a projection and a complementary depression, on the other hand, also provides a positive connection between the bearing block and the second rail element in the pull-out direction.In one embodiment of the invention, the legs of the second rail element and the mounting section of the bearing block are configured such that the legs press the bearing block against the rail back of the second rail element. In this way, the bearing block is also positively secured to the second rail element in a direction perpendicular to the pull-out direction and perpendicular to the vertical direction.The installation space between the rail backs of the first rail element and the second rail element is limited in most embodiments. In an embodiment in which rolling bodies are guided between the running surfaces of the first and second rail elements in a rolling body cage, the rolling body cage must also be able to pass unimpeded between the spindle bearing and the rail back of the first rail element.One possibility of taking into account the installation space is the open configuration of the bearing bush. Therefore, in one embodiment of the invention, the bearing bush is open in sections. In such an open configuration, the bearing bush is not completely cylindrical, but the cylindrical inner wall surface of the bearing bush encloses an angle of less than 360 degrees. In one embodiment of the invention, the bearing bush is open in a region towards the rail back of the first rail element.In one embodiment of the invention, the bearing bush open in sections engages around the threaded spindle by more than 180 degrees and less than 360 degrees, in order nevertheless to achieve an adequate mounting in the radial direction of the threaded spindle.It is understood that according to the invention the spindle nut is fixed to the second rail element in a rotationally fixed manner relative to the latter, i.e. the spindle nut does not rotate with the threaded spindle.In one embodiment of the invention, the spindle nut is accommodated on the second rail element so as to float in at least one direction perpendicular to the pull-out direction. The spindle nut floatingly supported in this way serves to compensate for manufacturing tolerances. It also prevents the spindle nut from jamming on the threaded spindle when the threaded spindle oscillates or wobbles due to an imbalance. However, a spindle nut supported in such a floating manner also does not have any bearing function for the threaded spindle in a radial direction of the threaded spindle. In one embodiment of the invention, the spindle nut is mounted in a floating manner in the vertical direction and in a direction perpendicular to the vertical direction and the pull-out direction (this is also mounted perpendicular to the rail backs of the first and second rail elements). It is understood that in such an embodiment as well, the spindle nut is fixed to the second rail element in and counter to the pull-out direction in order to fulfil its drive function for the extension and retraction movement of the two rail elements relative to one another.In a further embodiment of the present invention, the linear guide system comprises an electric motor. Such an electric motor is fixed with respect to the first rail element in and counter to the pull-out direction. The threaded spindle is thereby effectively coupled to the electric motor in such a way that the electric motor sets the threaded spindle into a rotational movement during the operation of the linear guide system.An electric motor in the sense of the present invention is a motor with a rotating motor shaft for providing a torque. In one embodiment of the invention, the electric motor is selected from a group consisting of a stepper motor, a brushless direct current motor (BLDC) or a brush-type direct current motor (DC).In one embodiment of the invention, the threaded spindle is mounted on the first rail element exclusively on the electric motor.In one embodiment of the invention, the spindle bearing is assembled as the final component in the assembly of the linear guide system. In one embodiment of the invention, such an assembly takes place through a recess in the rail back of the second rail element and the spindle bearing is preferably clipped into the hole.In one embodiment of the invention, the linear guide system is selected from a group consisting of a pull-out guide, a telescopic rail and a linear guide. The generic term linear guide system includes sliding guides and rolling body guides. The term "linear guide system" is to be broadly understood to mean that not only constructions thereof are included in which the first rail element and the second rail element have approximately the same length, i.e. in particular telescopic rails, but also linear guides in which one of the rail elements, in particular the second rail element, is significantly shorter than the other rail element.In one embodiment of the invention, the first rail element is the stationary rail element.According to the present invention, the linear guide system comprises a first rail member and a second rail member. However, this does not exclude the linear guide system, in particular if it is a pull-out rail or telescopic rail, comprising further rail elements, in particular an additional third rail element, for example for providing a full pull-out.In one embodiment of the invention, the linear guide system has a first rail element, a second rail element and a third rail element. In such an embodiment, the second rail element has four running surfaces. In this case, rolling bodies roll between the two running surfaces of the first rail element and two of the four running surfaces of the second rail element, and rolling bodies roll between the other two of the four running surfaces of the second rail element and the two running surfaces of the third rail element.In one embodiment of the invention, the first and the second rail element each have two running surfaces, wherein rolling elements accommodated in a rolling element cage are arranged on the two running surfaces of the first rail element and on the two running surfaces of the second rail element. These rolling elements roll on the respective running surfaces and reduce friction between the first rail element and the second rail element. A rolling body in the sense of the present application is understood to mean a rotational body which, as an element of a guide, significantly reduces the friction between the various rail elements and thus facilitates a relative movement of two rail elements with respect to one another. Rolling elements are, for example, bearing balls, rollers, barrels, needles or cones. In one embodiment of the present invention, the rolling elements are bearing balls. It is understood that in this case the rolling body cage is a ball cage.In one embodiment of the invention, at least one of the first rail member and the second rail member is made of a material selected from a group consisting of steel sheet, aluminated steel sheet, and stainless steel.Further advantages, features and possible applications of the present invention will become apparent from the following description of an embodiment and the associated figures. In the figures, like elements are denoted by identical reference numerals. FIG. 1 is an isometric, partially transparent view of a telescopic rail according to the invention from obliquely above in the fully retracted state. FIG. 2 is an isometric, partially transparent view of the telescoping rail of FIG. 1 in the fully extended state. FIG. 3 is a sectional view through the telescopic rail from FIGS. 1 and 2 along the line A-A from FIG. 1. FIG. 4 is an isometric view of one embodiment of a spindle bearing for the telescopic rail of FIGS. 1-3. FIG. 5 is a bottom plan view of the spindle bearing of FIG. 4. FIG. 6 is a front view of the spindle bearing of FIGS. 3 and 4. FIG. 7 is a sectional view through the spindle bearing of FIGS. 3 to 6 along the line B-B of FIG. 6.FIGS. 1 to 7 illustrate a variant of a linear guide system according to the invention in the form of a telescopic extension 4. the telescopic extension 4 is a full extension with a first rail element 1, a second rail element 2 and a third rail element 3. FIG. 1 shows the telescopic extension 4 in its fully retracted state, while FIG. 2 shows a representation of the fully extended state, in which the third rail element 3 no longer has an overlap with the first rail element 1 in the extension direction 5.The second rail element 2 forms a central rail which is mounted both on the first stationary rail element 1 and movable with respect to the latter in and counter to the pull-out direction and is mounted on the third rail element 3 in and counter to the pull-out direction.The first rail element 1 and the third rail element 3 each have a C-shaped profile. A rail back 11 connects two legs 12 a, 12 b, respectively. The legs 12a, 12b form running surfaces 13 pointing towards one another. Rolling elements in the form of bearing balls 14 roll on the running surfaces 13. These bearing balls 14 roll simultaneously on running surfaces 13 of the second rail element 2. the second rail element 2 consists of two C-shaped profiles which are connected to one another at their backs 15.The telescopic extension 4 is driven by a motor 6 so that a displacement movement of the second rail element 2 relative to the first rail element 1 and of the third rail element 3 relative to the second rail element 2 takes place in an automated manner. The electric motor 6 drives a rotational movement of a threaded spindle 7 coupled to the electric motor 6 or its motor shaft.A spindle nut (not shown in the figures) is fixed to the second rail element 2 in a rotationally fixed manner relative to the latter. In addition, the spindle nut is fixed to the second rail element 2 in and counter to the pull-out direction 5. Therefore, a rotational movement of the threaded spindle 7 leads to a linear movement of the spindle nut and thus of the second rail element 2 with respect to the first rail element 1.The threaded spindle 7 is mounted on the stationary first rail element 1 only via the electric motor 6.While the spindle nut 21 is secured against rotation relative to the second rail element and in and against the pull-out direction on the second rail element 2, the spindle nut 21 is mounted in a floating manner on the second rail element 2 in two directions perpendicular to one another and to the pull-out direction 5, namely the vertical direction 8 and the direction 9 perpendicular thereto.This play of the threaded nut with respect to the second rail element 2 in the directions 8 and 9 leads, without the spindle bearing 10 according to the invention, to the threaded spindle 7 being able to wobble and / or strike with respect to the second rail element 2 in a virtually unimpeded manner. However, such a wobbling or vibrating movement of the threaded spindle 7 may lead to a generation of noise if the threaded spindle 7 strikes the second rail element 2 or the first rail element 1 and to vibrations which can also be transmitted to the elements connected to the telescopic extension 4. Therefore, according to the invention, the spindle bearing 10 is provided on the second rail element 2.The structure and function of the spindle bearing 10 will now be described with reference to the enlarged representations of the spindle bearing 10 from FIGS. 4 to 7. The spindle bearing 10 is fastened to this second rail element 2 at the position of the second rail element 2 designated by the line A-A in FIG. 1. In this way, during an extension movement of the second rail element 2 relative to the first rail element 1, the spindle bearing 10 moves along the threaded spindle until the threaded spindle slips out of the spindle bearing. In this way, the threaded spindle 7 experiences an optimum mounting or support over a large part of the travel path. The fact that the threaded spindle 7 slips out of the spindle bearing shortly before reaching the maximum extended pull-out position (see FIG. 2 ) surprisingly does not impair the running behavior of the telescopic pull-out 4.The spindle bearing 10 is a bearing block 17 produced from POM by injection molding, which is configured in one piece and is mounted on the second rail element 2 during system integration. The bearing block 17 consists of a two-part mounting section 16 a, 16 band a bearing bush 18. Due to the C-shaped profile of the second rail element 2, the mounting portion 16 a, 16 bof the bearing block 17 is clamped to the second rail element 2 such that the bearing block 17 is pressed towards the rail back 15 of the second rail element 2. The two parts of the mounting portion 16 a, 16 blead to a positive connection between the bearing block 17 and the second rail element 2 in the vertical direction 8, In contrast, the mounting portion 16 a, 16 bin the pull-out direction 5 merely brings about a frictional connection owing to the static friction between the surface of the mounting portion 16 a, 16 band the legs 12 a, 12 bof the second rail element 2. In order additionally to also provide a positive connection between the bearing block 17 and the second rail element 2 in and counter to the pull-out direction 5, the mounting portion also has a projection 16 cwhich engages in the rail back 15 of the second rail element 2 in a positive-locking manner and reliably absorbs all forces which are introduced into the bearing block 17 in and counter to the pull-out direction 5.In order that the bearing block 17 mounted on the second rail element 2 can fulfil its bearing function, it has a bearing bush 18. The bearing bush 18 is a cylindrical inner wall section 19 of the bearing block 17. the radius of the inner wall section 19 is dimensioned such that the threaded spindle 7 performs a sliding movement with respect to the inner wall section 19 and the threaded spindle 7 nevertheless experiences a bearing or support in the radial direction. The bearing block 17 further has an inlet region 20, wherein in the inlet region 20 the inner wall portion widens in the shape of a truncated cone starting from the nominal radius of the inner wall portion 19 of the bearing bush 18 outwards, i.e. counter to the pull-out direction 5. In this way, the front, free end of the threaded spindle 7 can, after leaving the bearing bush 18, again run into the latter when the second rail element 2 is retracted counter to the pull-out direction 5.In the embodiment shown, the bearing block 17 is constructed symmetrically, i.e. it also widens on the side of the bearing bush 18 facing away from the inlet region 20. The symmetry merely serves to avoid having to pay attention to the orientation of the bearing block 17 during assembly.The cylindrical inner wall portion 19 is open toward the rail back of the first rail member 1. In other words, the surface 19 does not form a complete cylinder. The inner wall section 19 however encloses the threaded spindle 7 by approximately 270°. This can be seen well in particular in the sectional view from FIG. 6. Opening the bearing bush 18 toward the rail back 11 of the first rail element 1 reduces the overall size of the bearing for the threaded spindle 7.For purposes of the original disclosure, it is pointed out that all features as become apparent to a person skilled in the art from the present description, the drawings and the claims, even if they have been described specifically only in connection with certain further features, can be combined both individually and in arbitrary combinations with other features or feature groups disclosed here, unless this has been explicitly excluded or technical circumstances make such combinations impossible or meaningless. The comprehensive explicit representation of all conceivable combinations of features is omitted here only for the sake of brevity and readability of the description.While the invention has been illustrated and described in detail in the drawings and the foregoing description, this illustration and description is by way of example only and is not intended to limit the scope of the invention as defined by the claims. The invention is not limited to the disclosed embodiments.Modifications of the disclosed embodiments will be apparent to those skilled in the art from the drawings, specification and appended claims. In the claims, the word "comprise" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference numerals in the claims are not intended to limit the scope of protection.List of reference characters1 first rail element 2 second rail element 3 third rail element 4 telescopic extension 5 extension direction 6 electric motor 7 threaded spindle 8 vertical direction 9 direction perpendicular to the vertical direction and to the extension direction 10 spindle bearing 11 rail backs 12 a, 12 bbranches 13 running surface 14 bearing ball 15 rail backs 16 a, 16 bmounting section 16 cprotruding 17 bearing block 18 bearing bush 19 inner wall section 20 inlet region 21 spindle nut

Claims

Linear guide system (4) having a first rail element (1) and a second rail element (1), wherein the first rail element (1) and the second rail element (2) are mounted on one another such that they can be displaced linearly with respect to one another in and counter to a pull-out direction (5), a spindle drive which has a threaded spindle (7) and a spindle nut (21) running on the threaded spindle (7), wherein the threaded spindle (7) is mounted on the first rail element (1) such that it can be rotated about a spindle axis or is mounted on a device (6) fixed in or counter to the pull-out direction (5) with respect to the first rail element (1), such that it can be rotated about the spindle axis, and wherein the spindle nut (21) is fixed on the second rail element (1) in and counter to the pull-out direction (5), such that the spindle nut (21) moves along the threaded spindle (7) during a rotational movement of the threaded spindle (7) about the spindle axis and drives the second rail element (2) along, characterized in that the second rail element (2) carries a spindle bearing (10) fixed relative to the second rail element (1) in or counter to the pull-out direction (5), wherein the spindle bearing (10) is designed and arranged such that the spindle bearing (10) guides the threaded spindle (7) relative to the second rail element (1) at least in a first pull-out position of the second rail element (2) relative to the first rail element (1).Linear guide system (4) according to the preceding claim, wherein the spindle bearing (10) has a bearing bush (18) receiving the threaded spindle (7), wherein, at least in the first pull-out position, the threaded spindle (7) is in sliding engagement with the bearing bush (18) during a relative movement of the threaded spindle (7) with respect to the second rail element (1) in or counter to the pull-out direction, such that the spindle bearing (10) supports the threaded spindle (7).Linear guide system (4) according to the preceding claim, wherein the bearing bush (18) has an axial length (I) parallel to the pull-out direction, wherein the axial length of the bearing bush is smaller than a travel path of the bearing bush (18) relative to the threaded spindle (7) between a maximally retracted pull-out position of the second rail element (2) relative to the first rail element (1) and a maximally extended pull-out position of the second rail element (2) relative to the first rail element (1).Linear guide system (4) according to the preceding claim, wherein the bearing bush (18) is arranged on the second rail element (1) in such a way that, in the maximally extended pull-out position of the second rail element (2) relative to the first rail element (1), the bearing bush (18) is disengaged from the threaded spindle (7).Linear guide system (4) according to the preceding claim, wherein the bearing bush (18) is at a distance (d) of 50 mm or less from the spindle nut (21) in a direction parallel to the pull-out direction (5).Linear guide system (4) according to one of Claims 2 to 5, wherein the spindle bearing (10) has an inlet region (20), wherein the inlet region (20) adjoins the bearing bush (18) counter to the pull-out direction (5) and widens counter to the pull-out direction (5) starting from a diameter of the bearing bush (18), wherein, during operation of the guide system (4), a free end of the threaded spindle (7) can be moved through the inlet region (20) into the bearing bush (18).Linear guide system (4) according to one of the preceding claims, wherein the second rail element (2) has a rail back (11) and limbs (12a, 12b) which carry two running surfaces (13) for rolling bodies (14) and extend at an angle with respect to the rail back (11), wherein the spindle bearing (10) is formed by a bearing block (17) with the bearing bush (18) which accommodates the threaded spindle (7) and a mounting portion (16a, 16b), and wherein the mounting portion (16a, 16b) is clamped at least in a force-fitting manner between the two limbs (12a, 12b).Linear guide system (4) according to the preceding claim, wherein the mounting portion has a projection (16c) or depression, wherein the rail back (15) of the second rail element (2) has a depression complementary thereto or a projection complementary thereto, such that the bearing block (17) is fixed to the second rail element (2) in a positive-locking manner in and counter to the pull-out direction (5).Linear guide system (4) according to claim 7 or 8, wherein the legs (12a, 12b) of the second rail element (2) and the mounting portion (16a, 16b) of the bearing block (17) are configured such that the legs (12a, 12b) press the bearing block (17) against the rail back (11).Linear guide system (4) according to one of Claims 2 to 9, wherein the bearing bush (18) is open in sections towards the first rail element (1).Linear guide system (4) according to one of the preceding claims, wherein the spindle nut (21) is accommodated on the second rail element (1) so as to float in at least one direction perpendicular to the pull-out direction (5).Linear guide system (4) according to one of the preceding claims, wherein the linear guide system (4) has an electric motor (6), wherein the threaded spindle (7) is operatively coupled to the electric motor (6) in such a way that the electric motor (6) sets the threaded spindle (7) in a rotational movement during the operation of the linear guide system (4).Linear guide system (4) according to the preceding claim, wherein the threaded spindle (7) is mounted on the first rail element (1) exclusively via the electric motor (6).

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