Rolling bearing for sliding on a rail

Abstract

The invention relates to a rolling bearing (2) for sliding on a rail (1). The rolling bearing (2) comprises an inner ring (3), an outer ring (4), a plurality of first rolling bodies (5) and a plurality of second rolling bodies (6), wherein the plurality of first rolling bodies (5) is arranged between the inner ring (3) and the outer ring (4) in such a way that the outer ring (4) can be rotated in a circumferential direction (U) with respect to the inner ring (3). Furthermore, the plurality of second rolling bodies (6) is arranged on the inner ring (3) in such a way that the inner ring (3) can be moved along the rail (1) by means of the second rolling bodies (6).

Description

[0001] Rolling bearings for sliding on a rail

[0002] The invention relates to a rolling bearing for sliding on a rail.

[0003] Cable-operated robot arms, thanks to their low inertia, are ideal candidates for generating user-friendly interactions and high-speed movements, particularly in Industry 4.0 and healthcare applications. Cable-operated robot arms can perform high-speed tasks, enable safe interaction, and exhibit a smooth morphology similar to a human arm. In this scenario, the shoulder and wrist can each have three degrees of freedom, comprised of multiple curved rails. Each rail, with its trajectory, drives other components (e.g., a gripper or an upper arm) in normal and tangential directions. However, this structure requires a pulley system with numerous bearings, shafts, and rollers to bear the reaction load and reduce frictional losses.

[0004] The object of the invention is to propose a new bearing design that enables a slide to slide and rotate along a curved track with a particularly low coefficient of friction, while simultaneously allowing for high bearing load capacity and adaptability. This object is achieved by the subject matter of claim 1. Preferred embodiments are described in the dependent claims, the description, and the figures.

[0005] The present disclosure proposes equipping a robot arm, particularly a cable-driven one, with a rolling bearing capable of adapting to various trajectories and cross-sections of a curved track or rail of the robot arm. Specifically, a bore in the inner ring of the rolling bearing can conform to the cross-sectional shape of the curved track and slide on low-friction roller pins / needles. The rolling bearing can achieve performance comparable to a bearing-shaft-roller assembly on the curved track and can replace it when optimizing the design. Since curved tracks are used in many applications, such as rail conveyors, machines, or other devices, the invention offers an advantageous way to streamline and optimize the structure of such mechanisms.

[0006] According to the present disclosure, the rolling bearing comprises an inner ring and an outer ring. The inner ring of the bearing can have an identical shape to the cross-section of the track. A pattern of grooves for receiving needles / roller pins can be present on the contact surfaces with the track. These needles can be in direct contact with the surfaces of the track and roll about their axes as the rolling bearing slides on the track. The outer ring can be spaced apart from the inner ring by a circular pattern of a plurality of balls. Thus, thanks to the rolling friction generated by the needles and balls, the rolling bearing can slide on and rotate about the track with very low frictional loss. Furthermore, the bearing allows for a higher bearing load than a multi-ball system and can be used for complex trajectories with different cross-sectional shapes.In this invention, the number of needles can depend on the cross-sectional shape of the rail and on how many arrangements are provided.

[0007] In this context, according to one aspect of the invention, a rolling bearing is provided for sliding on a rail. A rolling bearing is a machine element that serves to reduce friction between two moving parts. It generally consists of an inner ring, an outer ring, and a series of rolling elements (such as balls or rollers) placed between the rings. In this sense, the rolling bearing according to the invention can comprise an inner ring and an outer ring. The inner ring is the part of the bearing that is connected to the rail, while the outer ring can be connected to a slide. The rolling bearing can further comprise a plurality of first rolling elements. The first rolling elements can be placed between the two rings and enable low-friction movement between them. The rolling bearing can also comprise a plurality of second rolling elements.

[0008] It is provided that the majority of first rolling elements are arranged between the inner and outer rings in such a way that the outer ring can be rotated circumferentially relative to the inner ring. In a manner known per se, the first rolling elements rolling between the inner and outer rings reduce the frictional resistance. Furthermore, it is provided that the majority of second rolling elements are arranged on the inner ring in such a way that the inner ring can be displaced along the rail by means of the second rolling elements. The rail can, in particular, be bent or curved. The second rolling elements roll along the rail, thus reducing wear. The friction of the rolling bearing sliding on the rail, in particular the curved rail, is reduced by the generation of the rolling friction force at the contact surfaces. Moreover, this enables a particularly high bearing load.

[0009] In particular, the rolling bearing can be a ball bearing. In this context, one embodiment provides that the first rolling elements are spherical. The balls can be held in a ball cage, which distributes them evenly and protects them from collisions. Advantages of using balls as the first rolling elements include, for example, low friction, low wear, low clearance, and low maintenance.

[0010] The second rolling elements can be needles. In one embodiment, the second rolling elements are needle-shaped. They resemble needles. These are thin cylindrical rollers that are very long compared to their diameter. This type of rolling element is also called needle rollers and differs from conventional cylindrical rollers in its design and load limits. The needle-shaped profile of the needle roller is created by a drummed or slightly ground end face in combination with an elongated outer surface. Compared to the heavy-duty cylindrical rollers, it can withstand medium to high rotational speeds, radial and axial forces, but is significantly more compact, allowing for shorter static dimensions in the needle roller bearing.

[0011] The invention is applicable to complex trajectories with different rail cross-sectional shapes, particularly polygonal cross-sections. Depending on the cross-sectional shape, the number of second rolling elements can vary, for example, three second rolling elements for a triangle or four second rolling elements for a rectangle. In this context, one embodiment provides that the number of second rolling elements corresponds to the number of surfaces the rail has. For example, if the rail has a triangular cross-section, then the rail has three surfaces. In this case, the rolling bearing also has three second rolling elements. For a square cross-section, four second rolling elements are used accordingly, for a hexagonal cross-section, six second rolling elements, and so on.

[0012] In particular, four needles can be used with a rectangular cross-section of the rail. In this context, one embodiment provides that the rail has a rectangular cross-section with four outer faces. The cross-section can be either rectangular or square. Furthermore, it is provided that four needle-shaped secondary rolling elements are arranged circumferentially, offset from each other by 90°. If the rail has a rectangular or square cross-section, then the rail has four surfaces. In this case, the rolling bearing also has four needle-shaped secondary rolling elements arranged at 90° intervals.

[0013] The inner surfaces of the inner ring have a geometry that corresponds to the cross-section of the rail. In this context, one embodiment provides that the inner ring has four flat inner surfaces arranged circumferentially at 90° intervals. Furthermore, the four needle-shaped secondary rolling elements are each located in the region of one of the four inner surfaces.

[0014] The rolling bearing can be part of a system comprising the rolling bearing and a rail having a curved path and a polygonal cross-section. In one embodiment, the rolling bearing further comprises a rail. This embodiment is characterized in particular by the fact that the rail is curved and has a polygonal cross-section. A curved rail is a structural component with a bent or curved surface. It is often used in mechanical engineering applications to enable movement along a specific path or curve. These rails can be made of various materials such as metal or plastic and serve to convert linear motion into curved or bent motion.Furthermore, it is provided that the inner ring of the rolling bearing is attached to the rail in such a way that the majority of second rolling elements roll along the rail.

[0015] The system described above can be used, in particular, in a robot arm. In this context, one embodiment provides that the rolling bearing further comprises a robot arm. This embodiment is characterized, in particular, by the fact that the rail forms part of the robot arm. A robot arm is a mechanical device used to perform various tasks by grasping, moving, or positioning objects. A typical robot arm consists of several links or segments connected by joints. These joints enable the robot arm to perform a variety of movements, including rotations and translations in various directions. Robot arms are used in a wide range of applications, from the manufacturing industry to medicine and aerospace, to automate repetitive or hazardous tasks and increase efficiency.The robot arm can be cable-operated in particular.

[0016] The rail can form part of a joint in the robot arm. In one embodiment, the rail is designed to act as a joint in the robot arm. A joint is a movable connection between two or more bodies or components that allows movement in at least one direction. Joints can take various forms and configurations, depending on the application requirements. They serve to improve the flexibility and mobility of mechanical structures by enabling different types of movement, such as rotation, bending, pivoting, or translation.

[0017] In particular, the joint in question is a shoulder joint of the robot arm. In this context, one embodiment provides that the joint is a shoulder joint of the robot arm. The shoulder joint of a robot arm is the joint that allows the arm to rotate around a horizontal axis. It is the joint that connects the arm to the main body or base of the robot and gives it the ability to perform lateral movements, similar to the movement of the human shoulder joint. The shoulder joint is often the first joint in a multi-axis robot arm and plays a crucial role in positioning the arm in space and in aligning its other joints for specific tasks.

[0018] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures.

[0019] Figure 1 shows a perspective view of a curved rail along which a rolling bearing can be moved.

[0020] Figure 2 shows a side view of the rail and the roller bearing according to Figure 1.

[0021] Figure 3 shows a side sectional view of the rail and the rolling bearing according to

[0022] Figure 1 ,

[0023] Figure 4 shows a cross-sectional view of the rail and the rolling bearing according to Figure 1 and

[0024] Figure 5 shows a robot arm in which the rail and the roller bearing according to Figure 1 can be inserted, with the robot arm as a whole shown on the right and a shoulder joint of the robot arm shown enlarged on the left.

[0025] Figures 1 to 4 show a curved rail 1 and a rolling bearing 2. The rolling bearing 2 has an inner ring 3 and an outer ring 4. Furthermore, the rolling bearing 2 comprises a plurality of first rolling elements 5 in the form of balls and a plurality of second rolling elements 6 in the form of needles. In the embodiment shown in Figures 1 to 4, a total of 18 first rolling elements 5 are arranged equidistantly in a circumferential direction U between the inner ring 3 and the outer ring 4. In the embodiment shown, a total of four second rolling elements 6 are also arranged in the circumferential direction U, offset from each other by 90°. The inner ring 3 can be rotated relative to the outer ring 4, with the first rolling elements 5 rolling in a known manner on the facing surfaces of the inner ring 3 and the outer ring 4.

[0026] As can be seen particularly well in Fig. 4, the rail 1 in the illustrated embodiment has a polygonal cross-section, specifically a square cross-section. Corresponding to the square cross-section and the longitudinally curved profile L, the rail 1 has four curved outer surfaces 7 to 10 extending in the longitudinal direction L, namely a curved first outer surface 7, a curved second outer surface 8, a curved third outer surface 9, and a curved fourth outer surface 10. Corresponding to the four outer surfaces 7 to 10 of the rail 1, the inner ring 3 has four inner surfaces 11 to 14, which are arranged offset from each other by 90° in the circumferential direction U.Specifically, a first inner surface 11 of the inner ring 3 runs parallel to and at a small distance from the first outer surface 7 of the rail 1, a second inner surface 12 of the inner ring 3 runs parallel to and at a small distance from the second outer surface 8 of the rail 1, a third inner surface 13 of the inner ring 3 runs parallel to and at a small distance from the third outer surface 9 of the rail 1, and a fourth inner surface 14 of the inner ring 3 runs parallel to and at a small distance from the fourth outer surface 10 of the rail 1.

[0027] The four needle-shaped second rolling elements 6 are each attached to the inner ring 3 in the region of one of the four inner surfaces 11 to 14. The four needle-shaped second rolling elements 6 are oriented such that they roll on their respective outer surfaces 7 to 10 of the rail 1 when the rolling bearing 2 is moved along the rail 1. Figure 5 shows a robot arm 15 with a lower arm 16 and an upper arm 17, which can be attached by means of a shoulder joint 18 to another part of a robot (not shown), in particular to a shoulder of the robot. The shoulder joint 18 has several curved rails 1. The rolling bearing 2 shown in Figures 1 to 4 can be placed on the rails 1 shown in Figure 5 and moved along these rails 1. In the embodiment shown in Figure 5, two rails 1 are arranged parallel to each other.Accordingly, two rolling bearings 2 according to Figures 1 to 4 can each be placed parallel to one another on two of the parallel rails 1. A slide (not shown) can be attached to one or both of the parallel rolling bearings 2, which can be moved along the rail 1 with the rolling bearing 2. The slide can, for example, be attached to the outer ring 4 of the rolling bearing 2, so that the slide can also be rotated relative to the inner ring 3.

[0028] List of reference signs

[0029] 1 rail

[0030] 2 rolling bearings

[0031] 3 inner ring

[0032] 4 outer ring

[0033] 5 first rolling elements

[0034] 6 second rolling elements

[0035] 7 first outdoor area

[0036] 8 second outdoor area

[0037] 9 third outdoor area

[0038] 10 fourth outdoor area

[0039] 11 first inner surface

[0040] 12 second inner surface

[0041] 13 third inner surface

[0042] 14 fourth interior surface

[0043] 15 robot arm

[0044] 16 Forearm

[0045] 17 Upper arm

[0046] 18 Shoulder joint

[0047] L Longitudinal direction

[0048] U circumferential direction

Claims

Patent claims 1. Rolling bearing (2) for sliding on a rail (1), the rolling bearing (2) comprising • an inner ring (3), • an outer ring (4), • a plurality of first rolling elements (5) and • a plurality of second rolling elements (6), wherein the plurality of first rolling elements (5) is arranged between the inner ring (3) and the outer ring (4) such that the outer ring (4) is rotatable in a circumferential direction (U) to the inner ring (3), wherein the plurality of second rolling elements (6) is arranged on the inner ring (3) such that the inner ring (3) is displaceable along the rail (1) by means of the second rolling elements (6).

2. Rolling bearing (2) according to claim 1 , characterized in that the first rolling elements (5) are spherical.

3. Rolling bearing (2) according to claim 1 or 2, characterized in that the second rolling elements (6) are needle-shaped.

4. Rolling bearing (2) according to one of the preceding claims, characterized in that a number of the second rolling elements (6) correspond to a number of surfaces which the rail (1) has.

5. Rolling bearing (2) according to claim 3, characterized in that the rail (1 ) has a rectangular cross-section with four outer sides (7 to 10), and four needle-shaped second rolling elements (6) are arranged in a circumferential direction (U) offset from each other by 90°.

6. Rolling bearing (2) according to claim 5, characterized in that the inner ring (3) has four flat inner surfaces (11 to 14) which are arranged offset from each other by 90° in the circumferential direction (U), and the four needle-shaped second rolling elements (6) are each arranged in the area of ​​one of the four inner surfaces (11 to 14).

7. Rolling bearing (2) according to one of the preceding claims, the rolling bearing (2) further comprising a rail (1) , characterized in that the rail (1) is curved and has a polygonal cross-section, wherein the inner ring (3) of the rolling bearing (2) is attached to the rail (1) such that the plurality of second rolling elements (6) roll along the rail (1).

8. Rolling bearing (2) according to claim 7, the rolling bearing (2) further comprising a robot arm (15), characterized in that the rail (1 ) forms a part of the robot arm (15).

9. Rolling bearing (2) according to claim 8, characterized in that the rail (1 ) forms a joint of the robot arm (15).

10. Rolling bearing (2) according to claim 9, characterized in that the joint is a shoulder joint (18) of the robot arm (15).

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