End recirculator for ball screw mechanism

Abstract

To provide a compact and simple ball screw mechanism that recirculates.SOLUTION: A recirculator 30 for a nut 12 of a ball screw mechanism 1 comprises an annular body 32 which has a reference axis 300 intentionally aligned with a spiral axis of the nut 12, and the annular body 32 comprises a support surface 36 configured to support the nut 12 of the ball screw mechanism 1 in a support direction having an axial component parallel with the reference axis 300, and a guide structure 34 configured to guide a ball in a recirculation path open on a screw groove defined with a screw thread in a recirculation channel of the nut 12, wherein the support surface 36 is located crossing the recirculation path and at least in part in a sectional plane perpendicular to the reference axis 300.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of ball screws, and more particularly to ball screw recirculators with external recirculation. [Background technology]

[0002] Chinese Utility Model No. 217481881 presents a ball screw mechanism with external ball recirculation through two end recirculators located at both ends of the nut, with the balls connected by a recirculation channel parallel to the screw axis. In addition to their ability to redirect the balls as they recirculate through the recirculation channel, the end recirculators disclosed therein have the feature of retaining grease in the annular space between the nut and the screw.

[0003] One drawback of such end recirculators is the axial space they occupy, since the two functions of ball guiding and grease retention are performed by areas axially separated from each other. Therefore, these recirculators can only be used in ball screw mechanisms whose application does not require extensive optimization of space requirements. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to overcome the drawbacks of the prior art and to propose a compact and simple solution for a recirculating ball screw mechanism. [Means for solving the problem]

[0005] According to a first aspect of the present invention, a recirculator for a nut of a ball screw mechanism is proposed, the recirculator comprising an annular body around a reference axis of the recirculator intended to be aligned with the helical axis of the nut, the annular body comprising a support surface configured to support the nut of the ball screw mechanism in a support direction having an axial component parallel to the reference axis, and a guide structure configured to guide balls in a recirculation path that opens at a first guide end into a recirculation channel of the nut and at a second guide end onto a thread groove defined by the thread of the nut, characterized in that the support surface lies at least partially in a cross-sectional plane that intersects the recirculation path and is perpendicular to the reference axis.

[0006] The recirculator provides a large contact and support surface for the nut in a small volume, ensuring a good seal between the recirculator and the nut, and guiding the balls of the ball screw mechanism.

[0007] According to one embodiment, the support surface is flat, making the part more compact and simplifying its manufacture. Alternatively, a frusto-conical support surface is conceivable.

[0008] According to one embodiment, the support surface extends over an angular sector around the reference axis and does not intersect with the recirculation path, thus distributing the support and ball guiding functions around the reference axis. Preferably, the angular sector has an apex angle greater than π / 2 radians, preferably greater than 3π / 4 radians, but less than 3π / 2 radians, preferably less than 5π / 4 radians, for example 7π / 6 radians.

[0009] According to one embodiment, the guide structure projects radially outward from the annular body.

[0010] According to one embodiment, the first guide end of the guide structure protrudes in particular axially relative to the annular body to form a curved recirculation path, and the first guide end protrudes axially from the annular body of the recirculator so as to open into the recirculation channel of the nut.

[0011] According to one embodiment, the second guide ends of the guide structure extend on both sides of the cross-sectional plane.

[0012] According to one embodiment, the second guide end of the guide structure is formed by a spatula. Preferably, the spatula projects in a direction tangent to the nut thread. In this way, the recirculator allows the balls to be smoothly recirculated through the spatula to achieve a smooth, shock-free transition or loss of efficiency between the path defined by the nut thread and the recirculation path.

[0013] According to one embodiment, the recirculation path at the first guide end is perpendicular to the support plane.

[0014] According to one embodiment, the annulus comprises a sealing lip extending radially inward from the recirculator annulus, preferably the sealing lip is helical in shape, more preferably the sealing lip makes at least 1 / 2 helical turn, preferably at least 3 / 4 helical turn, in this way forming an inverse shape to the thread groove of the screw and thus limiting the leakage of lubricant such as grease necessary for smooth operation of the ball screw mechanism.

[0015] According to one embodiment, the recirculator is a monolithic unit, preferably made of plastic. The material may be conventional plastic, partially or completely recycled plastic, or completely or partially bio-based. Metal finishing, for example by machining or sintering, is also possible. Preferably, the recirculator can be molded without undercuts, allowing molded manufacturing and reducing costs associated with cycle times or the complexity of mold or tool manufacturing. However, other manufacturing methods, such as additive manufacturing, are also possible. Designs with different material properties and / or multiple materials are also possible.

[0016] According to another aspect, the present invention relates to a ball screw mechanism comprising: a screw having an internal helical thread groove and a central axis; a nut having an external helical thread groove and a recirculation channel; at least two balls arranged between the internal helical thread groove of the screw and the external helical thread groove of the nut; and at least one end recirculator arranged at one of the axial ends of the nut to ensure recirculation of the balls, the end recirculator comprising a support surface for the nut and a guide structure for holding the balls within a defined recirculation path, wherein the end recirculator is superior in that it is as described above.

[0017] According to one embodiment, the axial end has a receiving surface that contacts the support surface of the recirculator, and the support surface of the recirculator and the receiving surface of the nut have complementary shapes so that the recirculator can be connected to the nut to form a homogeneous assembly.

[0018] According to one embodiment, the axial end is provided with an annular skirt protruding axially from the receiving surface, the annular skirt and the receiving surface defining a volume in which the annular body of the recirculator is at least partially, preferably entirely, accommodated, allowing the recirculator to be axially inserted into the nut and protected by the nut, improving the compactness and connection of the assembly formed by the nut and the recirculator.

[0019] According to one embodiment, the annular axial end has a radial notch that is continuous with the recirculation channel so as to accommodate the guide structure within the guide area when the guide structure is in the use position and so as not to have any protruding elements relative to the outer surface of the nut, thus eliminating the risk of snagging during handling or loss of radial compactness.

[0020] According to one embodiment, the notch forms a receiving area that forms at least one guide surface for gentle recirculation of the balls between the recirculation channel and the recirculator.

[0021] Naturally, the ball screw mechanism may comprise two recirculators according to the first aspect of the invention, located at the two axial ends of the nut.

[0022] According to a particularly advantageous embodiment, the end recirculator has one or more guide surfaces that face one or more guide surfaces of the nut to define a recirculation path between the two ends. Using the end recirculator and the nut to define the recirculation path provides a more compact arrangement. [Brief explanation of the drawings]

[0023] Other features and advantages of the present invention will become apparent from the following disclosure, taken in conjunction with the accompanying drawings.

[0024] [Figure 1] FIG. 1 shows a ball screw mechanism comprising a screw, a nut, and two end recirculators. [Figure 2] FIG. 2 shows an isometric perspective view of the nut. [Figure 3A] FIG. 3A shows an isometric perspective view of the end recirculator. [Figure 3B] FIG. 3B shows a bottom view of the end recirculator. [Figure 3C] FIG. 3C shows a front view of the end recirculator. [Figure 3D] FIG. 3D shows a rear view of the end recirculator. [Figure 3E] FIG. 3E shows a top view of the end recirculator. [Figure 4] FIG. 4 shows an axial cross-sectional view of the ball screw mechanism.

[0025] For greater clarity, identical or similar elements are identified by the same reference numerals in all figures. DETAILED DESCRIPTION OF THE INVENTION

[0026] FIG. 1 shows a ball screw mechanism 1 comprising two threaded components, namely a screw 10 and a nut 12, a ball, and two end recirculators 30, all aligned on a reference axis 100 of the ball screw mechanism 1 that is aligned with a reference axis 110 of the screw 10, a reference axis 120 of the nut 12, and a reference axis 300 of each of the two end recirculators 30.

[0027] 1 and 4 has an axis of symmetry 400 perpendicular to axis 100, so that the description of the recirculator 30 at one end of the nut 12 can be interchanged with the recirculator 30 at the opposite end of the nut. However, this symmetry is merely optional and not limiting.

[0028] The screw 10 is preferably made of metal, such as steel, and has threads 14 that form an internal helical thread groove 16 about a reference axis 110 of the screw 10, the internal helical thread groove 16 pointing radially outward from the reference axis 110.

[0029] Nut 12, shown in detail in Figures 2 and 4, is preferably made of metal, e.g., steel, and is generally cylindrical. Nut 12 has a nut thread 114 facing radially inward, forming an external helical thread 116 about a reference axis 120, and an outer surface 25 facing radially outward. Outer surface 25 is cylindrical and axially traversed by recirculation channel 18. Recirculation channel 18 is radially spaced apart from nut 12 thread 116 and preferably spans several revolutions thereof. In this embodiment, recirculation channel 18 is open, i.e., forms a groove in outer surface 25 of nut 12, although this configuration is optional and recirculation channel 18 may alternatively be fully or partially closed around its circumference depending on design requirements.

[0030] The nut 12 further has two axial ends 20 that face the two opposing axial ends of the recirculation channel 18. Each of the axial ends 20 is annular and has a receiving surface 22 and an annular skirt 24 that protrudes axially outward from the receiving surface 22. The skirt 24 has a diameter slightly smaller than the diameter of the outer surface 25, which can be used, for example, to fasten a flange for a component fixed to the nut 12 or to fasten a bellows seal. The skirt 24 has an inner annular surface 74 that faces radially toward the reference axis 120. The receiving surface 22 and the skirt 24 are configured to receive the end recirculator 30 and define a storage volume for the end recirculator 30. Each axial end 20 has a radial notch 26 bounded by the end face 118 of the recirculation channel 18, which divides the skirt 24 so that it forms only a cylindrical arc. The notch 26 defines a receiving area 40 whose shape corresponds to the inverse shape of the guide structure 34 of the end recirculator 30, described below.

[0031] In another embodiment, the recirculation channel 18 is closed, i.e., integrated into the nut 12. Optionally, the notch 26 does not divide the entire skirt 24, such that said skirt 24 is annular.

[0032] The receiving area 40 formed in the nut 12 by the notch 26 includes two support planes 42 on either side of a first guide surface 44 of the nut 12 that leads to the recirculation channel 18, as well as a second guide surface 45 and a spatula support 46.

[0033] The receiving surface 22 forms a planar annular arc about the reference axis 120 and extends from the notch 26 in a clockwise 210 or counterclockwise 220 direction over an angular sector having an apex angle greater than π / 2 radians, preferably greater than 3π / 4, and less than 3π / 2, preferably less than 5π / 4, e.g., 7π / 6, to form the inverse shape of the support surface 36 described below.

[0034] The end recirculator 30 is preferably made of plastic so that it can be manufactured as a single piece, and at the same time, by molding without undercuts, thus reducing part manufacturing time and lowering costs. The plastic material may be conventional plastic, partially or fully recycled plastic, and / or fully or partially bio-based plastic. However, if desired, the end recirculator 30 can be made of other materials, such as metal, using machining and / or sintering techniques, and can be composed of several parts if desired. Many designs of different properties and / or materials are also possible.

[0035] The two end recirculators 30 are identical and feature an annular body 32 and a guide structure 34 that projects radially outward relative to the annular body 32 and axially toward the nut 12 .

[0036] Annular body 32, shown in detail in Figures 3A, 3B, 3C, 3D, and 3E, has an outer annular surface 76 facing radially outward and an inner annular surface 78 facing radially toward reference axis 300. Additionally, annular body 32 includes a planar support surface 36 in support plane 130 and configured to support nut 12 on receiving surface 22 when end recirculator 30 is in its use position. Support surface 36 is in the form of a flat annular arc extending over an angular sector about reference axis 300, with an apex angle greater than π / 2 radians, preferably greater than 3π / 4, but less than 3π / 2, preferably less than 5π / 4, e.g., 7π / 6, extending in a clockwise direction 210 from guide structure 34. Annular body 32 further features a sealing lip 38 extending radially inward from annular body 32 of end recirculator 30. The sealing lip 38 is disposed on the inner annular surface 78 of the recirculator 30 and forms an opposite shape, in particular a similar shape, to the internal helical thread groove 16 without contacting the thread 10 .

[0037] The guide structure 34 has a positioning body 58 and a spatula 48 that forms an open guide duct 70 for the ball along a curved path between a first guide end 62 that opens into the recirculation channel 18 and a second guide end 72 that opens into the thread grooves 16, 116 of the screw 10 and nut 12.

[0038] The first guide end 62 projects axially relative to the cross-sectional plane 130, while the second guide end 72 projects "diagonally" between the thread grooves 16, 116 of the screw 10 and the nut 12. Furthermore, the second guide end 72 intersects with the cross-sectional plane 130.

[0039] More specifically, the positioning body 58 has an outer wall 60, two side walls 64, two lateral walls 66, and an inner wall 68. The outer wall 60 is located radially outward from the other walls, while the inner wall 68 is located radially inward from the other walls. One of the two lateral walls 66 overlaps the annular body 32, while the other lateral wall forms a first guide end 62 that projects axially relative to the cross-sectional plane 130 and is designed to open onto the recirculation channel 18, as shown in FIG. 3A. The positioning body 58 has a guide notch 54 that opens into the outer wall 60 at the first guide end 62 when the recirculation channel 18 is open, as in this case.

[0040] The spatula 48 forms the second guide end 72 of the open guide duct 70, opens onto the thread grooves 16, 116 of the screw 10 and nut 12, and is configured to smoothly redirect the balls from the recirculation channel 18 to the thread grooves 16, 116 of the screw 10 and nut 12 and vice versa. To this end, the spatula 48 is oriented radially and perpendicularly radially to guide the balls toward the recirculation channel 18 or the thread grooves 16, 116, and optionally has a minimal axial component so that the ball guidance by the spatula 48 is tangent to the helical thread grooves 16, 116. The spatula 48 has a guide surface 50 configured to direct the balls during recirculation and a rear surface 52 located opposite the guide surface 50. The guide surface 50 is a groove, the contour of which may be, for example, a circular arc or ogive-shaped, and defines a recirculation path between the two ends 62, 72 of the groove. The spatula 48 intersects with a support plane 130. Notably, the guide surfaces 44, 45 of the nut 12 face the guide surface 50 of the recirculator, so that the recirculation path is bounded by the guide surface 50 of the end recirculator 30 and the first and second guide surfaces 44, 45 of the nut 12 over its entire length between the two ends 62, 72 of the groove.

[0041] The sealing lip 38 extends from the spatula 48 onto the inner annular surface 78 of the end recirculator 30 and is formed at the rear surface 52 of the spatula 48 in the same clockwise rotational direction 210 as the support surface 36, i.e., clockwise 210, for at least one-half of a helical revolution, preferably at least three-quarters of a helical revolution, but not a complete helical revolution. The sealing lip 38 intersects with the support plane 130.

[0042] The guide structure 34 and the annular body 32 are complementary to the receiving area 40 and receiving surface 22 of the nut 12, respectively.

[0043] The balls may be made of, for example, steel or ceramic, and are sized and positioned to circulate in a closed circuit between the outer helical thread groove 116 of the nut 12 and the inner helical thread groove 16 of the screw 10, between the guide surfaces 50 of each end recirculator 30 and the first and second recirculation surfaces 44, 45 of the nut 12, and within the recirculation channel 18, preferably without separators between the balls.

[0044] During assembly, the end recirculators 30 are axially inserted into the nut 12, one at each of the two axial ends 20, making the ball screw mechanism 1 more compact. The following assembly description details the positioning of a single end recirculator 30. This description, of course, also applies to the second end recirculator 30. The end recirculators 30 are inserted axially into the axial ends 20 with the annular bodies 32 contracted against the inner annular surface 74 so that the end recirculators 30 are in their operating position when the support surfaces 36 of the end recirculators 30 abut the receiving surfaces 22. The support surfaces 36 then contact the receiving surfaces 22, while the annular surfaces 76 of the end recirculators 30 contact the inner annular surface 74 of the skirt 24. The sealing lips 38 extend the helical pattern of the threads of the nut 12.

[0045] Furthermore, the guide structure 34 is housed in the receiving area 40 and is in contact with the nut 12. More precisely, the inner wall 68 rests against the support plane 42, one of the two side walls 64 and two transverse walls 66 is in contact with the nut 12, the spatula 48 rests against the spatula support 46, and at the first guide end 62, the spatula 48 opens tangentially onto the second guide surface 45 of the nut 12, which itself opens onto the first guide surface 44, which opens onto the recirculation channel 18. The guide surfaces 44, 45 of the nut 12 allow a transition from the recirculation channel 18 to the spatula 48 of the end recirculator 30 and vice versa, enabling a smooth recirculation path between the recirculation channel 18 and the end recirculator 30.

[0046] The screw 10 can be screwed into the assembly formed by the nut 12 and the two end recirculators 30. The sealing lip 38 fits non-contactingly into the internal helical thread groove 16, minimizing leakage of lubricant, such as grease, into the ball screw mechanism 1. The balls can then be inserted one by one through the recirculation channel 18 into the ball screw mechanism 1. The balls travel along the helical thread grooves 16, 116 through the end recirculators 30. The ball screw mechanism 1 shown in FIG. 4 is then closed by a sleeve shrunk onto the outer surface 25 of the nut 12, thus closing the recirculation channel 18.

[0047] The examples shown in the figures and described above are presented for illustrative purposes only, and other embodiments can be envisioned, particularly by combining features of the various embodiments described.

[0048] For example, the end recirculator 30 may have a handle with a chamfer and edges on the support surface 36, allowing it to snap into a corresponding inverted shape disposed on the receiving surface 22 of the nut 12.

Claims

1. A recirculator (30) for a nut (12) of a ball screw mechanism (1), said recirculator (30) comprising an annular body (32) around a reference axis (300) of said recirculator (30) intended to be aligned with the helical axis of said nut (12), said annular body (32) having a support surface (36) configured to support the nut (12) of said ball screw mechanism (1) in a support direction having an axial component parallel to said reference axis (300); and a guide structure (34) configured to guide balls within a recirculation path that opens at a first guide end (62) into a recirculation channel of the nut (12) and at a second guide end (72) onto a thread groove (116) defined by the threads of the nut (12), wherein the support surface (36) is at least partially located within a cross-sectional plane (130) that intersects the recirculation path and is perpendicular to the reference axis (300).

2. The recirculator (30) of claim 1, wherein said support surface (36) is flat.

3. 3. The recirculator (30) according to claim 1, wherein the support surface (36) extends over an angular sector about the reference axis (300) that does not intersect with the recirculation path.

4. 4. The recirculator (30) of claim 3, wherein the angular sector has an apex angle greater than π / 2 radians, preferably greater than 3π / 4 radians, and less than 3π / 2 radians, preferably less than 5π / 4 radians, for example 7π / 6 radians.

5. The recirculator (30) of any one of claims 1 to 4, characterized in that the guide structure (34) projects radially outward from the annular body (32).

6. 6. The recirculator (30) according to claim 1, wherein the first guide end (62) of the guide structure (34) projects in particular axially relative to the annular body (32).

7. 7. The recirculator (30) of claim 1, wherein the second guide end (72) of the guide structure (34) extends on both sides of the cross-sectional plane (130).

8. 8. The recirculator (30) according to any one of claims 1 to 7, characterized in that the second guide end (72) of the guide structure (34) is formed by a spatula (48).

9. 9. The recirculator (30) of claim 8, wherein said spatula (48) projects in a direction set to tangent to the threads (116) of said nut.

10. 10. The recirculator (30) according to any one of claims 1 to 9, characterized in that the recirculation path at the first guide end (62) is perpendicular to the support plane (130).

11. 11. The recirculator (30) of claim 1, wherein the annular body (32) comprises a sealing lip (38) extending radially inward from the annular body (32) of the recirculator (30).

12. The recirculator (30) of claim 11, wherein the sealing lip (38) is helical.

13. 13. Recirculator (30) according to claim 11 or 12, characterized in that the sealing lip (38) makes at least 1 / 2 of a helical revolution, preferably at least 3 / 4 of a helical revolution.

14. A recirculator (30) according to any one of claims 1 to 13, characterized in that it is in one piece and is preferably made of plastic.

15. A recirculator (30) according to any one of claims 1 to 14, characterized in that it can be formed without undercuts.

16. A ball screw mechanism (1), a screw (10) having an internal helical thread (16) and a central axis (110); - a nut (12) having an external helical thread (116) and a recirculation channel (18); at least two balls arranged between the internal helical thread (16) of the screw (10) and the external helical thread (116) of the nut (12); at least one end recirculator (30) arranged at one of the axial ends (20) of the nut (12) for recirculation of the balls, the end recirculator comprising a bearing surface (36) for the nut (12) and a guide structure (34) for keeping the balls within a defined recirculation path; A ball screw mechanism (1), characterized in that the end recirculator (30) is as claimed in any one of claims 1 to 15.

17. 17. The ball screw mechanism (1) according to claim 16, characterized in that the axial end (20) has a receiving surface (22) that contacts the support surface (36) of the recirculator (30), and the support surface (36) of the recirculator (30) and the receiving surface (22) of the nut (12) have complementary shapes.

18. 18. The ball screw mechanism (1) according to claim 17, characterized in that the axial end (20) comprises an annular skirt (24) protruding axially from the receiving surface (22), the annular skirt (24) and the receiving surface (22) defining a volume in which the annular body (32) of the recirculator (30) is at least partially, preferably entirely, accommodated.

19. 19. Ball screw mechanism (1) according to claim 18, characterized in that said annular skirt (24) has a radial notch (26) that is continuous with said recirculation channel (18).

20. 20. The ball screw mechanism (1) according to any one of claims 16 to 19, characterized in that the end recirculator (30) has one or more guide surfaces (50) facing one or more guide surfaces (44, 45) of the nut (12) to define the recirculation path between the two ends (62, 72).

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