Rolling bearings for sliding on a rail

Abstract

Rolling bearing (2) for sliding on a rail (1) having a rectangular cross-section with four outer faces (7 to 10), comprising the rolling bearing (2) • an inner ring (3), • an outer ring (4), • a plurality of first rolling elements (5) and • a plurality of second rolling elements (6) which are needle-shaped, wherein the majority of first rolling elements (5) are arranged between the inner ring (3) and the outer ring (4) such that the outer ring (4) is rotatable in a circumferential direction (U) relative to the inner ring (3), wherein the majority of second rolling elements (6) are arranged on the inner ring (3) such that the inner ring (3) can be displaced along the rail (1) by means of the second rolling elements (6), characterized in that four second rolling elements (6) are arranged offset from each other by 90° in a circumferential direction (U).

Description

[0001] The invention relates to a rolling bearing for sliding on a rail.

[0002] 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 upper arm) in normal and tangential directions. However, this structure requires a roller system with numerous bearings, shafts, and rollers to bear the reaction load and reduce frictional losses.

[0003] German patent DE 10 2010 019 529 A1 describes a bearing arrangement for a rod enabling linear movement and radial pivoting about its axis. Balls are located in an inner cage and interact with a contour of the rod and a central sleeve. An outer guide with multiple balls interacts with the central sleeve and an outer sleeve, enabling the radial pivoting movement.

[0004] FR 1 022 462 A describes a rolling bearing with two parts having concentric circular bearing surfaces, designed to be set in motion on rolling elements arranged between the bearing surfaces when a shaft, guided by one of the two parts that drives it, rotates and is subjected to a rotary motion, characterized in that the part comprises a device with rolling elements that take action when the shaft performs a translational motion parallel to the axis of rotation of the part guiding the shaft.

[0005] FR 1 017 410 A describes a ball guide system applicable to cables that facilitates changes in direction.

[0006] 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.

[0007] The present disclosure proposes equipping a robot arm, particularly one driven by a cable, 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 adapt 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] According to the invention, the second rolling elements are needle-shaped. 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 and allows for shorter static dimensions in the needle roller bearing.

[0013] The invention is applicable to a rectangular rail cross-section. The number of second rolling elements is four for the rectangle. According to the invention, the number of second rolling elements corresponds to the number of surfaces the rail has. Accordingly, four second rolling elements are used for the rectangular cross-section.

[0014] In particular, four needles are used in the case of a rectangular cross-section of the rail. In this context, the invention provides that the rail has a rectangular cross-section with four outer surfaces. The cross-section can be either rectangular or square. Furthermore, it is provided that four needle-shaped secondary rolling elements are arranged 90° offset from one another in a circumferential direction. If the rail has a rectangular or even square cross-section, then the rail has four surfaces. In this case, the rolling bearing also has four needle-shaped secondary rolling elements arranged 90° offset from one another.

[0015] 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.

[0016] 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.

[0017] The system described above can be used, in particular, in a robot arm. In this context, one embodiment provides that the rolling bearing also includes 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.

[0018] 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.

[0019] 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.

[0020] 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. Fig. 1. A perspective view of a curved rail along which a rolling bearing can be moved. Fig. 2 a side view of the rail and the roller bearing according to Fig. 1, Fig. 3 a lateral sectional view of the rail and the rolling bearing according to Fig. 1, Fig. 4 a cross-sectional view of the rail and the rolling bearing according to Fig. 1 and Fig. 5 a robot arm in which the rail and the roller bearing are located Fig. 1 can be used, with the robot arm as a whole shown on the right and a shoulder joint of the robot arm shown enlarged on the left.

[0021] The Fig. 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 area defined by the Fig. 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. Furthermore, in the illustrated embodiment, a total of four second rolling elements 6 are arranged offset from each other by 90° in the circumferential direction U. 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.

[0022] How particularly good looks Fig. As can be seen in Figure 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.

[0023] The four needle-shaped second rolling elements 6 are each attached to the inner ring 3 in the area 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 assigned outer surfaces 7 to 10 of the rail 1 when the rolling bearing 2 is moved along the rail 1. Fig. Figure 5 shows a robot arm 15 with a forearm 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 Fig. The rolling bearings shown in 1 to 4 can be attributed to the bearings shown in 2. Fig. The rails shown in the 5 diagrams are placed on 1 and moved along these rails. In the manner described by the Fig. In the embodiment shown in Figure 5, two rails 1 are arranged parallel to each other. Accordingly, two rolling bearings 2 can also be arranged according to the Fig.Bearings 1 to 4 are placed parallel to each other on two of the parallel rails 1. A slide (not shown) can be attached to one bearing 2 or to any two of the parallel bearings 2, and this slide can be moved along the rail 1 with the bearing 2. The slide can, for example, be attached to the outer ring 4 of the bearing 2, so that the slide can also be rotated relative to the inner ring 3. Reference symbol list 1 rail 2 rolling bearings 3 inner ring 4 outer ring 5 first rolling elements 6 second rolling elements 7 first outdoor area 8 second outdoor area 9 third outdoor area 10 fourth outdoor area 11 first inner surface 12 second inner surface 13 third inner surface 14 fourth interior surface 15 robot arm 16 Forearm 17 Upper arm 18 Shoulder joint L Longitudinal direction U circumferential direction

Claims

[1] Rolling bearing (2) for sliding on a rail (1) having a rectangular cross-section with four outer faces (7 to 10), comprising the rolling bearing (2) • an inner ring (3), • an outer ring (4), • a plurality of first rolling elements (5) and • a plurality of second rolling elements (6) which are needle-shaped, wherein the majority of first rolling elements (5) are arranged between the inner ring (3) and the outer ring (4) such that the outer ring (4) is rotatable in a circumferential direction (U) relative to the inner ring (3), wherein the majority of second rolling elements (6) are arranged on the inner ring (3) such that the inner ring (3) can be displaced along the rail (1) by means of the second rolling elements (6), characterized by , that four second rolling elements (6) are arranged offset from each other by 90° in a circumferential direction (U). [2] Rolling bearing (2) according to claim 1, characterized by, that the first rolling elements (5) are spherical. [3] Rolling bearing (2) according to any one of the preceding claims, characterized by , that a number of the second rolling elements (6) corresponds to a number of surfaces which the rail (1) has. [4] Rolling bearing (2) according to any one of claims 1 to 3, characterized by , 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). [5] Rolling bearing (2) according to one of the preceding claims, the rolling bearing (2) further comprising rail (1) having a rectangular cross-section with four outer faces (7 to 10), characterized by, that the rail (1) is curved and the inner ring (3) of the rolling bearing (2) is attached to the rail (1) in such a way that the majority of second rolling elements (6) roll along the rail (1). [6] Robot arm (15) comprising a rolling bearing (2) according to claim 5, characterized by , that the rail (1) forms part of the robot arm (15). [7] Robot arm (15) according to claim 6, characterized by , that the rail (1) forms a joint of the robot arm (15). [8] Robot arm (15) according to claim 7, characterized by , that the joint is a shoulder joint (18) of the robot arm (15).

Images