Linear motion device

Abstract

A linear motion device comprising a housing (1) in which a threaded spindle (4) is rotatably mounted relative to a longitudinal axis (8), wherein an extension arm (6) projects out of the housing (1) in the direction of the longitudinal axis (8) and is fastened to a spindle nut (10) which engages with the threaded spindle (4), and wherein at least one sliding piece is fastened to the outer circumference of the spindle nut (10) via a respective wedge, said sliding piece having at least one first sliding surface (36a) extending parallel to the longitudinal axis (8) and being displaceably guided on a first bearing track (12) of the housing (1) extending parallel to the longitudinal axis (8), and wherein the sliding piece (14) has an inner bearing surface facing the wedge, and wherein the wedge has an outer bearing surface facing the sliding piece, characterized in that the two bearing surfaces have a respective profile by means of which a positive connection is formed between the wedge and the sliding piece in the direction of the longitudinal axis (8).

Description

[0001] The invention relates to a linear motion device or a linear drive according to the preamble of patent claim 1.

[0002] Conventional linear motion devices are designed as spindle drives and have a threaded spindle mounted in a housing for rotation about a longitudinal axis. The spindle engages a spindle nut within the housing that can be moved along the longitudinal axis. A lifting rod extending through the housing is attached to the spindle nut, into which the threaded spindle inserts to a greater or lesser extent depending on the operating state of the linear motion device. The lifting rod is coupled to another device to be moved or supported via a pivot point located away from the threaded spindle.

[0003] Such linear motion devices are also referred to as electric cylinders because, in terms of usability and external appearance, the housing is similar to a hydraulic cylinder and the stroke rod is similar to a piston rod. However, instead of pressure fluid, the linear motion device requires electrical current to power an electric motor to drive the lead screw in rotation.

[0004] In this type of linear motion device, the movable spindle nut is mounted in the housing in a rotationally fixed manner, so that it only executes the desired stroke movement with the rotation of the threaded spindle. To achieve this, the torque transmitted from the threaded spindle to the spindle nut via the engagement must be supported on the housing.

[0005] The published patent application DE 10 2007 043 391 A1 shows two sliding pieces or sliding blocks arranged diametrically opposite each other on the outer circumference of the spindle nut, which are fastened to the outer circumference of the spindle nut by screws. The sliding pieces can be moved in a respective groove provided on the inner walls of the housing. The sliding pieces have two roof-shaped sliding surfaces that are positioned against each other and engage with corresponding mating surfaces in the respective groove of the housing. Furthermore, the radial play of the two sliding surfaces relative to the two mating surfaces can be adjusted via a wedge bar arranged between the guide element and the spindle nut. This is achieved by moving the wedge bar parallel to the longitudinal axis.

[0006] The disadvantage of such linear motion devices is that the adjustment of the radial play by moving the wedge bar can only be carried out relatively roughly, and that the position can be lost again between the positioning of the wedge bar by a fitter and the fixing of the sliding piece with a screw.

[0007] From DE 10 2009 021 658 A1 and DE 10 2010 054 565 A1, further comparable linear motion devices are known in which the anti-rotation lock of the spindle nut is effected by means of sliding pieces.

[0008] In contrast, the object of the invention is to create a linear motion device in which the aforementioned disadvantages are avoided.

[0009] This object is achieved by a linear motion device having the features of patent claim 1.

[0010] The claimed linear motion device has a housing in which a threaded spindle is rotatably mounted with respect to a longitudinal axis, wherein a cantilever (e.g., a lifting rod) projects out of the housing in the direction of the longitudinal axis - to a varying extent depending on the operating state. The cantilever is fastened to a spindle nut which engages with the threaded spindle (e.g., via a plurality of rotating balls), which can be driven, for example, by an electric motor. At least one sliding piece is fastened to the outer circumference of the spindle nut to prevent rotation of the spindle nut. This sliding piece has a first sliding surface extending parallel to the longitudinal axis, designed as a wear surface, which is slidably guided on a first bearing track on the inner circumference of the housing, which extends parallel to the longitudinal axis. A wedge is provided between the spindle nut and each sliding piece, the thickness of which changes approximately along the longitudinal axis.The sliding piece has an inner contact facing the wedge, while the wedge has an outer contact facing the sliding piece. The two contacts have the same inclination to the longitudinal axis. According to the invention, the two contacts each have a profile via which a positive connection is created between the wedge and the sliding piece approximately in the direction of the longitudinal axis. This allows the radial play of the anti-twist device in the housing to be adjusted comparatively precisely by moving the guide piece, and between positioning the wedge and fixing the sliding piece, the positions selected by the fitter are retained by the positive connection, so that the positive connection is effective even if the sliding piece and the wedge are not yet attached to the spindle nut. Fastening is preferably via a screw. For technical reasons, the profiles can simply have a certain roughness via which the positive connection is created.Preferably, the two profiles are designed and shaped in such a way that a positive and a corresponding negative profile result.

[0011] Advantageously, the sliding element is a sliding rail and the wedge is a wedge rail, both of which have an extension along their longitudinal axis that is greater than their respective widths. This simplifies the assembly of the rails and allows the inclination of their two contact surfaces to be reduced while maintaining the same adjustment interval of the sliding rail, thus increasing the accuracy of the radial clearance adjustment.

[0012] In a particularly preferred embodiment, the profile of the inner contact surface is formed by webs, while the profile of the outer contact surface is formed by recesses adapted to the webs. This results in a grid for adjusting the radial clearance and a defined, reproducible form fit.

[0013] Preferably, the inner support is formed at the bottom of a groove in the sliding piece, into which the wedge is inserted at least partially. The groove and the wedge have approximately the same width. This provides a positioning aid and a lateral securing (circumferential direction of the spindle nut) for the wedge relative to the sliding piece.

[0014] The webs can connect two side walls of the groove with each other, thus extending over the entire width of the inner system of the sliding piece.

[0015] If the webs and the recesses are angled in the same arrow-shaped manner, a twisted installation of the wedge and / or the sliding piece is effectively prevented.

[0016] Preferably, the contact points between the webs and the recesses define a plane that is inclined to the longitudinal axis. If the webs and recesses are angled in an arrow shape, the contact points preferably define two planes that are also inclined to each other.

[0017] In most bidirectional applications of the linear motion device according to the invention, the spindle nut must be supported on both sides relative to the housing. In this case, it is preferred if the housing has at least one groove extending parallel to the longitudinal axis, into which the sliding piece extends. The first contact track and a second contact track are formed in the groove, with the first sliding surface and a second sliding surface designed as a wear surface being formed correspondingly on the sliding piece. Preferably, the two contact tracks and the two sliding surfaces are symmetrical in pairs with respect to a radial direction and are arranged in a roof-like manner relative to one another.

[0018] Preferably, the wedge and the sliding piece are accommodated, at least in sections, in a groove that extends over the entire length of the spindle nut. This provides a positioning aid and a securing mechanism in the circumferential direction of the spindle nut for the sliding piece relative to the spindle nut.

[0019] If the sliding piece is wider than the groove so that the sliding piece protrudes laterally beyond the groove, the two wear surfaces can be enlarged.

[0020] To support the spindle nut in both directions of rotation of the threaded spindle, it is preferred that the spindle nut-side groove has two side walls against which the sliding piece rests with its side flanks. Preferably, the side walls of the sliding piece and the side flanks of the spindle nut-side groove extend parallel to each other.

[0021] To secure the position of the wedge - especially in the direction of the longitudinal axis - it is preferred if it has an inner radial extension which is inserted into a recess of appropriate size in the spindle nut.

[0022] Optimal fixation, with easy adjustment of the wedge and thus the radial play of the slider, is achieved by providing a slotted hole in the slider and a hole – preferably circular – in the wedge. A screw bolt passes through both holes and is screwed into a threaded hole in the spindle nut.

[0023] Preferably, two grooves on the housing side and two grooves on the spindle nut side are provided on opposite sides of the spindle nut, into each of which a sliding block is inserted, which is in contact with two symmetrical sliding surfaces with two symmetrical sliding tracks of the two grooves on the housing side.

[0024] In the following, an embodiment of the invention is described in detail with reference to the figures. Fig. 1 shows an embodiment of the linear motion device according to the invention in a lateral sectional view; Fig. 2 the embodiment according to Fig. 1 in a cross-sectional view; Fig. 3 a spindle nut of the embodiment according to Fig. 1 and Fig. 2 in an exploded view; and Fig. 4 a sliding strip of the embodiment according to the preceding figures in a perspective view.

[0025] Fig. Figure 1 shows the embodiment of the linear motion device according to the invention in a side sectional view. It has an elongated housing 1 with a roughly square cross-section, which is closed at the front by two caps 2. In the Fig. 1 lower cap 2, an end section of a threaded spindle 4 is mounted via a roller bearing, while in the Fig. 1 upper cap 2, a cantilever 6 which is displaceable relative to the housing 1 is mounted on a sliding bearing. Fig. 1 upper end portion of the boom 6 protrudes from the housing 1. A device (not shown) can be coupled to this end portion, which is to be moved along a longitudinal axis 8 of the linear motion device.

[0026] One in Fig. 1 lower end section of the boom 6 is attached to a spindle nut 10, which is slide-mounted in the housing 1. The spindle nut 10 and the threaded spindle 4 are operatively engaged with each other via an endlessly rotating series of balls (not shown), so that the spindle nut 10 and thus the boom 6 can be moved translationally by driving the threaded spindle 4 via an electric motor (not shown).

[0027] Fig. 2 shows the embodiment according to Fig. 1 in a cross-section. In particular, the housing 1, the spindle nut 10 guided therein, and the threaded spindle 4 rotating in the spindle nut 10 are shown in section.

[0028] On two opposite inner sides of the housing 1, a groove is provided which extends at least along the entire travel path of the spindle nut 10 (cf. Fig. 1). In Fig. 2 shows that the two grooves each have a cross-section in the shape of an isosceles trapezoid. Thus, each groove has two roof-shaped and symmetrically positioned lateral support tracks 12. A sliding piece designed as a sliding strip 14 is inserted into each groove. The two sliding strips 14 are - as described with reference to Fig. 3 - is attached to the outer circumference of the spindle nut 10 and is adjustable in its radial distance from the spindle nut 10 via a respective wedge strip 16. This allows the insertion depth or the tension of the respective slide strip 14 to be adjusted relative to the groove on the housing side.

[0029] Fig. 3 shows the spindle nut 10 and the parts mounted thereon of the embodiment according to the Fig. 1 and Fig. 2 in an exploded view. The spindle nut 10 has a groove 18 on each of its outer circumference on two opposite sides, which extends over the entire length of the spindle nut 10. The two bases are arranged tangentially to the spindle nut 10 and thus parallel to each other. A recess 20 and a threaded bore 22 are provided on each base. A respective screw bolt 24 is screwed into the threaded bore 22, via which the slide bar 14 and the wedge bar 16 are clamped radially inward towards the spindle nut 10. The screw bolt 24 penetrates an elongated hole 26 in the slide bar and a circular hole 28 in the wedge bar 16.

[0030] As a positioning aid and to fix the position, in the assembled state an extension 30 of the wedge strip 16 extends into the recess 20 in the bottom of the groove 18. Furthermore, the wedge strip 16 is fixed in the lateral direction or in the circumferential direction by being inserted into a groove 32 of corresponding width, which is formed on a radially inner side of the slide strip 14. The slide strip 14, in turn, is inserted into the groove 18 of the spindle nut 10 via side flanks of its radially inner section, wherein the radially inner section of the slide strip 14 and the groove 18 have the same width. The slide strip 14 is thus supported in the circumferential direction via its side flanks on the two side walls 34 of the associated groove 18.

[0031] In the axial direction, the wedge strip 16 is fixed in position via the extension 30 and the recess 20, while the axial position of the slide strip 14 can be selected along the groove 18 and thus parallel to the longitudinal axis 8. The adjustment path is defined by the length of the slot 26. The slide strip 14 is accommodated in the groove 18 of the spindle nut 10 over the entire adjustment path with its full length. By selecting the position of the slide strip 14, its position relative to the wedge strip 16 also changes. Since the two wedge strips 16 in their Fig. 3 right area are thicker in the radial direction than in their Fig. 3 left area, the position selection of the slide bar 14 results in a different radial distance to the spindle nut 10. So that with different positions of the slide bar 14 relative to the wedge bar 16 the parallelism of its two sliding surfaces 36 a, 36 b to the respectively assigned contact tracks 12 (cf. Fig. 2) the groove on the housing side is retained, the radially outer contact of the wedge strip 16 is provided with the same pitch as the inner contact of the slide strip 14.

[0032] Fig. Figure 4 shows the internal arrangement of the slide strip 14, which extends between the two side walls 38 of the groove 32. There, evenly shaped and evenly spaced webs 40 are formed. More precisely, in the illustrated embodiment, four webs 40 are arranged on each side of the elongated hole 26, each of which is angled in an arrow shape. Each web 40 has a central curved section and two lateral straight sections, whereby the two straight sections of each web 40 are positioned relative to each other. This embodiment of the slide strip-side profile according to the invention is assigned a corresponding profile on the wedge strip side. This is best seen in the Fig.3 upper wedge strip 16. The profile of the wedge strip 16 has four recesses 42 on each side of the hole 28, which have the geometrically inverse shape of the webs 40. Thus, the two profiles provide a visual and mechanical positioning aid and, at the same time, a secure, defined locking in the position of the slide strip 14 selected by the installer. This locking remains in place during assembly until the screw bolt 24 has been screwed in and the two strips, namely the slide strip 14 and the wedge strip 16, are finally fixed.

[0033] Disclosed is a spindle drive with a stationary housing in which a threaded spindle is rotatably mounted, whereby a lifting rod can be moved out of the housing to varying distances depending on the operating state. The movement occurs along a longitudinal axis of the spindle drive. The lifting rod is fastened to a spindle nut which engages with the threaded spindle. Two slide strips are fastened to the outer circumference of the spindle nut and are slidably guided in a respective groove of the housing extending parallel to the longitudinal axis to prevent rotation. A wedge strip is inserted between each slide strip and the spindle nut, the thickness of which changes parallel to the longitudinal axis. The contact surfaces of the two slide strips and the two associated wedge strips each have a knurling which creates a positive connection between the wedge strip and the slide strip in the direction of the longitudinal axis.This allows the adjustment of the radial play of the two sliding strips in the housing to be carried out comparatively easily and in fine steps by moving the respective wedge strip. List of reference symbols 1 housing 2 caps 4 threaded spindle 6 booms 8 Longitudinal axis 10 spindle nut 12 Investment track 14 Slide bar 16 Wedge bar 18 grooves 20 recess 22 threaded hole 24 screw bolts 26 slot 28 holes 30 extension 32 grooves 34 side wall 36 a First sliding surface 36 b Second sliding surface 38 side wall 40 bridge 42 recess

Claims

[1] A linear motion device comprising a housing (1) in which a threaded spindle (4) is rotatably mounted relative to a longitudinal axis (8), wherein an extension arm (6) projects out of the housing (1) in the direction of the longitudinal axis (8) and is fastened to a spindle nut (10) which engages with the threaded spindle (4), and wherein at least one sliding piece is fastened to the outer circumference of the spindle nut (10) via a respective wedge, said sliding piece having at least one first sliding surface (36a) extending parallel to the longitudinal axis (8) and being displaceably guided on a first bearing track (12) of the housing (1) extending parallel to the longitudinal axis (8), and wherein the sliding piece (14) has an inner bearing surface facing the wedge, and wherein the wedge has an outer bearing surface facing the sliding piece, characterized by that the two systems have a respective profile by means of which a positive connection is formed between the wedge and the sliding piece in the direction of the longitudinal axis (8). [2] Linear motion device according to claim 1, wherein the profiling of the inner contact is formed by webs (40), and wherein the profiling of the outer contact is formed by recesses (42) adapted to the webs (40). [3] Linear motion device according to one of the preceding claims, wherein the inner abutment is formed in a groove (32) of the sliding piece, into which the wedge is inserted at least in sections, the groove (32) and the wedge having approximately the same width. [4] Linear motion device according to claim 2 and 3, wherein the webs (40) connect two side walls (38) of the groove (32) to each other. [5] Linear motion device according to one of claims 2 to 4, wherein the webs (40) and the recesses (42) are angled in an arrow shape. [6] Linear motion device according to claim 4 or 5, wherein contact points at which the webs (40) and the recesses (42) touch each other each define a plane which is arranged inclined to the longitudinal axis (8). [7] Linear motion device according to one of the preceding claims, wherein the housing (1) has at least one groove extending parallel to the longitudinal axis (8), in which two contact tracks (12) are formed, and wherein the first sliding surface (36 a) and a second sliding surface (36 b) are formed on the sliding piece. [8] Linear motion device according to one of the preceding claims, wherein the wedge and the sliding piece are received at least in sections in a groove (18) formed on the outer circumference of the spindle nut (10). [9] Linear motion device according to claim 8, wherein the groove (18) extends over the entire length of the spindle nut (10). [10] Linear motion device according to claim 7 and claim 8 or 9, wherein the sliding piece projects laterally beyond the groove (18). [11] Linear motion device according to claim 8 or 9, wherein the groove (18) has two side walls (34) against which a respective side flank of the slider rests. [12] Linear motion device according to one of the preceding claims, wherein the wedge has an extension (30) which is inserted into a recess (20) of the spindle nut (10). [13] Linear motion device according to one of the preceding claims, wherein an elongated hole (26) is formed in the sliding piece and a hole (28) is formed in the wedge, wherein the two holes (26, 28) are penetrated by a screw bolt (24) which is screwed into a threaded bore (22) of the spindle nut (10).

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