PL243135B1 - Spherical joint - Google Patents

Abstract

The subject of the invention is a spherical joint intended for use in the joints of robots, in particular walking robots, exoskeletons and humanoid robots operating in conditions of high stability of staying in a specific position and reducing the resistance to movement during movement. The spherical joint is characterized by two cooperating spherical caps (3 and 8). At its base, the pin (1) has a bush (7) in the shape of a spherical cap (3) with an inner spherical surface (9), and the lower edge (14) of the bush (7) is located below the geometric center S1 of the spherical cap (3), which has longitudinal recesses (10) of variable shape and width located around the circumference, located from the lower edge (14) of the spherical cap (3) of the bushing (7) to point P above the inner conical surface (6) located inside the core of the pin (1 ). Between the longitudinal recesses (10) the spherical cap (3) of the bushing (7) has at least one longitudinal notch (11) on its circumference of a constant width Sp and height h1 located from the lower edge (14) of the spherical cap (3) of the bushing (7) to equator level (19) spherical surface (9) spherical cap (3). Inside the space limited by the conical surface (6) of the pin (1), there is a ball (2), which on the other side rests on the outer spherical surface (22) of the inner spherical cap (8), which is attached by means of a threaded connection to the pin ( 23). The inner spherical bowl (8) is a shell with longitudinal cutouts (12 and 13) ending in circular openings (27). And on the pin (23) a pusher (4) with a conical outer surface (24) is slidingly mounted, to which the elastic fragments (20) of the inner spherical cap (8) adhere, and a compression spring (5) is mounted on the pin (23). which on one side is pressed by the nut (15) to the front surface of the circumferential groove of the pusher (4), and between the front surface (17) of the pusher (4) and the front surface of the core (18) of the inner spherical bowl (8) there is an internal compression spring (16).

Description

The subject of the invention is a spherical joint intended for use in the joints of robots, in particular walking robots, exoskeletons and humanoid robots operating in conditions of high stability of staying in a specific position and reducing the resistance to movement during movement.

Many ball joints are known in the art.

For example, from the Polish patent description PL 211105 there is known a joint which has a spherical part, a fixed part and a protective and sealing unit, which is a cap cover with a two-stage socket with sealing elements embedded in it and adjacent to the surface of the spherical part of the joint.

EP 0 481 212 discloses a ball joint having a spherical head, a joint pin and a connecting ball pin which is arranged in a coupling housing with a vessel-shaped interior in which it can be pivoted. The ball joint is slidably mounted in a bearing attached to the joint holder.

From the Polish patent description PL 198014 there is known a ball joint consisting of two parts, the second part of which has a spherical opening snap-fitted to the first part in the shape of a sphere, with an extending neck having a hemispherical cover slidingly placed on the outer surface of the spherical opening, the diameter of the opening the diameter of the sphere is smaller than the diameter of the sphere, and the sphere with the neck is made of a single material.

US patent US 8714862 discloses a ball joint having a disc spring in an annular recess in an axially loaded lower sliding seat. The disc spring is used to preload and compress the upper seat down towards the end of the ball head. The preload impedes axial or rotational movement of the ball pin until the minimum load is applied to exceed the preload and cause movement.

Another US patent, US 9,291,195, discloses a joint which is a ball joint assembly in which the ball part of the pin is placed inside a cup-shaped bearing bush and the stem part of the ball part protrudes from the open interior through the open end of the housing for connection to another element. The lower bearing is housed in the bearing bush and includes an extension that extends into the bore of the bearing bush holding the lower bearing in a fixed position within the bearing bush.

From yet another US patent, US 8,353,776, a universal ball joint is known comprising a first rotating body and a second rotating body which are pivotally connected to each other. The first rotation body comprises an elliptical head and a connecting portion, the head having a major axis and a minor axis which is perpendicular to the major axis. The second rotating body is an elliptical ball socket pivotally coupled to the head of the first rotating body such that the head is rotatable about a major axis or a minor axis of the elliptical head.

Further US Patent No. 6,533,491 discloses a resilient ball joint in which a lower bearing defines a lower bearing surface surrounding a spherical head on the housing bore side, and an opposing upper movable bearing defines an upper bearing surface, the upper bearing being pushed by a spring at the spherical head so to be able to move towards the lower bearing when the ball head or lower bearing wears out.

Another US patent, US 7,083,356, discloses a ball joint with an angular motion limiting system that allows free rotation of a ball pin, but at the same time limits the angular movement of the same ball type pin in a certain predetermined direction. The motion limiting system according to the preferred embodiment is used in tie rods or connecting rods where rotational motion about its longitudinal axis is undesirable.

The European patent EP 1662158 discloses a ball joint having a socket with a housing housing the ball-shaped part of the joint and enabling its sliding movement. The housing holder is configured to inhibit relative movement between the holder and the receptacle. The joint comprises a truncated cone in the holder and a congruent part of the cone in the socket. In addition, the holder and socket have grooved surfaces engaged with each other to: secure the housing to the socket; preventing relative movement between the housing and the seat, and sealing the first peripheral contact surface between the housing and the seat.

EP 1797346 discloses an air spring with a ball joint which has a spheroidal bearing element in the bearing shell. The bearing shell is adjustable on the spheroidal bearing element by means of a clamping element.

From the Polish patent application P.419462, a ball joint is known, which consists of a plastic bush and a metal ball pin, embedded in the socket of the joint of the metal body. To the bottom of the bushing, through a metal washer, there is an elastic pressure ring, compressed by a cap closing the socket of the joint, which, as a result of internal pressure stresses of the system, constantly presses on the bushing, thus eliminating joint play.

EP 0075414A1 discloses a ball joint in which the head of a ball pin is mounted in a bearing ring in a socket. The bearing sleeve is surrounded by a compressed elastomeric sleeve that surrounds the bearing ring at the head equatorial region to press the ring against the head and thereby apply the torque load. The torque load can be changed by changing the hardness of the elastomeric material of which the sleeve is made.

US Patent No. 3,951,557, on the other hand, discloses a ball joint in which a split plastic bearing is brought into contact with the ball by the action of a spring which is held in the bore by a cover plate.

Another US patent, US 6,010,271, discloses a ball joint that has only one hole through which all components are installed during assembly and through which a pin protrudes. The components of the joint include a compression spring, a polymer lower bearing, a pin, and an upper metal bearing. The circumferential edges of the opening are turned or rolled to hold the components in place and compress the compression spring.

EP 1866552 Compression Ball Joint utilizing a split top bearing configured to provide a bearing surface for the top and sides of the ball pin and to allow full engagement with the housing and ball pin simultaneously.

Another published prior art is the ball joint mechanism disclosed in US 5,409,269. This solution describes a joint adapted to align two elements that form part of an adjustable gas transport device. One of these elements preferably consists of a gas conduit and a second element, preferably a nozzle, which is connected to said gas conduit and positioned in different positions relative thereto. In order to allow quick manual adjustment of the spring forces without any operation in the ball joint mechanism itself, the ball joint mechanism comprises two rotatably mounted balls, one ball being connected to one element of the adjustable device and the other ball to the other element of said adjustable device. The balls cooperate with the friction elements to provide the required frictional resistance when said balls rotate, thereby providing at least one spring element to compensate for possible wear of said friction elements and/or mating surfaces of the balls. The balls are housed in a connector housing comprising two elements which can be positioned relative to each other so that the resilient forces of the spring element can be varied by varying the mutually positioned said elements of the common housing.

In the articulation solutions described above, known from the state of the art, there were often problems related to the adjustment of the resistance to movement and play in the spherical joint ensuring rotation in any direction, as well as the possibility of preliminary adjustment of the resistance to movement. In order to meet the expectations, the applicants set themselves the goal of solving the disadvantages of the known solutions.

The aim of the present invention was also to solve the problem of the construction of joints for multi-legged walking robots and the construction of kinematic nodes cooperating with the elements of exoskeletons.

The spherical joint according to the invention comprises two cooperating spherical caps, one is located at the end of the pin and the other is the inner spherical cap of the joint.

The pin of the ball joint has a spherical cup-shaped bush with an internal spherical surface at its base, the lower edge of the bush being located below the geometric center Si of the spherical cap, which has longitudinal recesses of variable shape and width located on the perimeter located from the lower edge of the spherical cap to the point P located above the inner conical surface located inside the pin core, and between the longitudinal recesses, the spherical shell of the shell has at least one longitudinal notch of constant width Sp and height hi located between the lower edge of the spherical cup of the shell and the level of the equator of the spherical surface between the longitudinal recesses spherical bowl. Inside the space limited by the conical surface of the pin, a ball is placed, which on the other hand rests against the outer spherical surface of the inner spherical cap, which is attached to the pin by means of a threaded connection. The inner spherical cap is permanently connected to the pin, on which the force F may act in a certain phase of operation, depending on the load on the joint. The inner spherical shell is a shell with longitudinal cuts ended with circular openings. A pusher with a conical outer surface is slidably mounted on the pin, to which the elastic fragments of the inner spherical cap adhere. There is also a pressure spring mounted on the pin, which is pressed against the front surface of the circumferential groove of the pusher with a nut. In addition, between the front surface of the pusher and the front surface of the core of the inner spherical cap, there is an internal pressure spring running along the axis of the pin pin. The pusher expands the elastic fragments of the spherical cap adjacent to it as a result of moving the pusher by means of a nut screwed onto the pin. This solution of the joint structure, thanks to the use of elastic fragments of the inner bowl and the bushing, as well as the use of compression springs, enables the initial adjustment of the resistance to movement. The resistance to movement of the joint increases as a result of screwing the pressure nut onto the external thread of the pin. This entails the displacement of the pusher upwards, causing the opening of the elastic fragments of the inner spherical cap. This, in turn, leads to an increase in the friction forces between the slidingly cooperating surfaces of the inner spherical cap and the bushing.

It is advantageous if the spherical shell of the bushing has four longitudinal recesses arranged at equal angular distances around the periphery, while the recesses at the level of the equator of the spherical surface of the spherical shell are in the shape of circular openings. The spherical bowl of the sleeve on the circumference, between the recesses, has from one to three longitudinal cuts of constant width Sp. The spherical shell of the bushing has an inner spherical surface of radius Ri, and the inner spherical shell has an outer spherical surface of radius R2. The geometric center Si of the spherical cap of the pan is on the horizontal plane πι, on which the equator of the spherical surface of the spherical cap is located.

It is advantageous when the radius Ri of the inner spherical surface of the spherical cap of the mandrel is preferably greater by the value of the initial clearance than the radius R2 of the outer spherical surface of the inner spherical cap, whose geometrical center S2 is the center of rotation of the joint and it is located at a distance Js from the level of the equator of the spherical surface of the spherical cap spherical pan. Such shaping of the cooperating surfaces of the spherical cap and the bushes pressed against each other by the ball ensures stable contact along the lower edge of the bushing.

It is advantageous when the longitudinal cutouts of the inner spherical cap have alternately different heights hm and hd, with one center of the cutout openings having a height hd located on the horizontal plane ππ, and the centers of the openings of the shorter cutout having a height hd below the geometric center of the hinge S2. It is advantageous when the longitudinal cutouts of the inner spherical cap have the same width Sc and the circular cutouts of the height hd have a diameter Dc greater than the width Sc of the longitudinal cutouts, and the longitudinal cutouts of the inner spherical cap of the height hm have the same width and their circular openings have a diameter greater than the width of the longitudinal cutouts. Making holes at the ends of the cutouts increases the susceptibility of the elastic fragments of the inner spherical cap and increases the fatigue strength of the elastic fragments of the inner spherical cap by limiting the concentration of local stresses in the vicinity of the hole.

It is preferred that the spherical cap and the inner spherical cap are made of an elastic material.

The spherical joint with the spherical shells of the bushing and the spherical cap of the pin, rotatably connected to each other, enables adjustment of the moss resistance and play in the spherical joint, ensuring the rotation of the joint in any direction.

The advantage of the invention is its adaptability to changing working conditions of the joint with spherical surfaces. The adaptability of the structure is guaranteed by ensuring the elastic contact of the slidingly cooperating inner surfaces of the spherical cap and the bushing and the simultaneous rolling contact of the ball with the spherical surface of the inner cap. At the same time, due to such positioning of the working elements of the joint, the pin and the pin, the exact position of the joint center is ensured. It is uniquely determined by point contact between the surface of the sphere and the outer spherical surface of the inner cap, which in turn has a stable linear contact with the spherical surface of the bushing, regardless of the load.

The subject of the invention can be used in various assemblies and kinematic nodes, both in exoskeletons, microrobots, humanoid robots and industrial robots, as well as in working machines. Dimensions and materials of the joint elements should be selected according to the application. Preferably, the pin and the inner spherical cap are made of materials characterized by very good elastic properties, i.e. high elastic limit, high value of the ratio of elastic limit to yield point, high tensile strength. In addition, in industrial robot applications, good fatigue strength and high resistance to corrosion and abrasion are desirable. For example, the pin and the ball pin can be made of silicon steel 50S2, manganese steel 65G, chrome-silicon steel 50HS, chrome-vanadium alloy 51 CrV4 (1.8159), X 10CrNi88 (1.4310); X22 CrMoV 121 (1.4923), made of titanium alloys, e.g. Ti6A14V-PE-UHMW. These elements can also be made by sintering metal powders, for example titanium or magnesium, as well as by additive manufacturing. The remaining elements of the joint can be made of typical construction materials, such as structural steels and their alloys, as well as plastics with good mechanical properties, for example: polyamide, PBT, polycarbonate or polyester.

In order to prevent the formation of play in the joint, the spherical cap and the bushing have longitudinal cuts and circumferential recesses forming fragments with greater elasticity. The function of the joint according to the invention consists in the fact that the elastic portions of the inner spherical cap are expanded by the pusher. This causes simultaneous radial deformations of the elastic parts of the bushing and the inner spherical cap. Thanks to this solution, the adjacent fragments form a spherical contact surface. Such shaping of the inner spherical cap and the bush prevents the formation of play in the joint. An additional advantage of this solution is to increase the contact surface of slidingly cooperating spherical surfaces and to obtain an even pressure distribution between these surfaces.

The object of the invention is shown in the examples of embodiment in the drawings, in which Fig. 1 shows the ball joint in half view and half section in front view, Fig. 2 shows the ball joint in half view and half section in side view; Fig. 3 is a front view of the spherical bushed mandrel in half view and half section, and Fig. 4 shows the spherical bowl mandrel in 3D view; Fig. 5 shows the inner spherical cap in half view and half section in front view, and Fig. 6 shows the inner spherical cap in 3D view; Figure 7 shows the pusher in half view and half section; Fig. 8 is a 3D view of the pusher and Fig. 9 is a front view of the pin.

The joint contains elastic spherical cups with adjustable pressure and adaptively changing conditions of cooperation of spherical surfaces. This increases the kinematic stability and the range of possible adjustment of the joint's cooperation conditions.

The invention is used in technical systems where high motion stability is required, especially in robotics, multi-legged robots, humanoid robots, measuring devices, manipulators and industrial robots.

Example of implementation

In Fig. 1, 2 and 3, the spherical joint has a pin 1 (Fig. 3 and 4), which at its base has a spherical bowl 3 with an inner spherical surface 9 with a radius Ri, the value of which is 19 mm. The lower edge 14 of the spherical bowl 3 of the bowl 7 is located at a height hi = 10 mm below the geometric center Si located at the equator 19 of the inner spherical surface 9 of the bowl 3. On the surface of the bowl 3 there are four longitudinal recesses 10, of variable shape and width, from the bottom edge 14 of the bushing 7 to a point P located above the inner conical surface 6 hollowed out in the upper part of the bushing 7. The distance from point P to the edge 14 is 38 mm. These recesses at the level of the equator 19 of the inner spherical surface 9 of the sleeve 7 have the shape of circular openings 21 with a diameter of Dc = 8.8 mm and are arranged at equal angular intervals around the circumference. Between these recesses, the shell 7 has two longitudinal recesses 11 with a constant width Sp = 2 mm from the lower edge 14 of the shell 7 to the level of the equator 19 of the spherical cap 3. In other embodiments, there may be one to three recesses 11 with a height of h1 = 10mm.

To the inner conical surface 6 hollowed out in the core of the pin 1, a ball 2 is pressed against the outer spherical surface 22 of the inner spherical cap 8 (fig. 5 and 6) with a radius R2, the value of which is 18.5 mm. The inner spherical cap 8 is permanently connected to the pin 23 (fig. 9), on which the force F may act in a certain phase of the joint operation. At the same time, this cap is a shell with longitudinal cuts 12 of the same width s _c = 3 mm, ended with holes 27 circular shape. The inner spherical bowl 8, between the longitudinal cutouts 12, has longitudinal cutouts 13 of height h _m = 9.8 mm less d' of height hd = 18.2 mm. In addition, a pusher 4 with a conical outer surface 24 is slidingly mounted on the pin 23, which expands the elastic fragments 20 of the inner spherical cap 8 adjacent to it as a result of moving the pusher 4 by means of a nut 15 screwed onto the pin 23. Between the front surface 17 of the pusher 4 (fig. 7 and 8), and the core of the bowl 18 is fitted with a compression spring 16 running along the axis of the pin 23.

The radius R of the inner spherical surface 9 of the cap 3 is preferably greater than the radius R2 of the outer spherical surface 22 of the inner spherical cap 8, whose geometric center S2 is the center of rotation of the joint and is located at a small distance Aa = 0.5 mm from the level of the equator 19 of the inner spherical surface 9. Such a shape of the cooperating surfaces 9 and 22 of the spherical cap 3 and the bush 7, pressed against each other by the ball 2, ensures stable contact along the lower edge 14 of the bush 7.

The resilient spherical bowl 3 and the pin 1 were made of the 51 CrV4 (1.8159) chrome-vanadium alloy, and the other elements were made of the AISi5Cu2 aluminum alloy.

List of markings:

1. mandrel,

2nd ball,

3. spherical cap of the pan,

4. pusher,

5. compression spring,

6. the inner conical surface of the mandrel,

7. pan,

8. inner spherical cap,

9. inner spherical surface of the bushing,

10. choosing a pan of variable width and shape,

11. longitudinal cutout of the bushing with a constant width Sp,

12. longitudinal cutout of the inner spherical bowl with a height of hd,

13. longitudinal cutout of the inner spherical bowl with a height of h _m ,

14. lower edge of the pan,

15. compression nut,

16. internal compression spring,

17. pusher face,

18. bowl core with spherical shell,

19. equator of the spherical bowl of the pan,

20. elastic fragments of a spherical cap,

21. circular holes of the bushing,

22. outer spherical surface of the inner spherical cap,

23. pin,

24. conical surface of the pusher,

25. front surface of the circumferential groove of the pusher,

26. circumferential groove of the pusher,

27, 28 holes.

Claims (9)

1. A spherical joint comprising a pin with a bush, a ball and a pin, characterized in that it comprises two cooperating spherical caps 3 and 8, the pin 1 having at its base a bush 7 in the shape of a spherical cap 3 with an inner spherical surface 9, at whereby the lower edge 14 of the sleeve 7 is located below the geometric center Si of the spherical bowl 3, which has longitudinal recesses 10 of variable shape and width located around the perimeter located from the lower edge 14 of the bowl 3 of the bowl 7 to a point P located above the inner conical surface 6 located inside the core of the pin 1, and between the longitudinal recesses 10, the spherical cap 3 of the bush 7 has at least one longitudinal notch 11 on its periphery, with a constant width Sp and height, located from the lower edge 14 of the spherical cap 3 of the bush 7 to the level of the equator 19 of the spherical surface 9 of the spherical cap 3, and inside the space limited by the conical surface 6 of the pin 1, there is a ball 2, which on the other side rests against the outer spherical surface 22 of the inner spherical cap 8, which is attached by means of a threaded connection to the pin 23, the inner spherical cap 8 is a shell with longitudinal cutouts 12 and 13 ended with circular openings 27 and 28, and a pusher 4 with a conical outer surface 24 is slidingly mounted on the pin 23, to which the elastic fragments 20 of the inner spherical cap 8 adhere, while the pin 23 is a compression spring 5, which is pressed on one side by a nut 15 against the front surface 25 of the circumferential groove 26 of the pusher 4, and between the front surface 17 of the pusher 4 and the front surface of the core 18 of the inner spherical cap 8, an internal compression spring 16 is mounted. 2. A joint according to claim 1, characterized in that the spherical cap 3 of the bushing 7 has four longitudinal recesses 10 arranged at equal angular distances around the periphery, while the recesses 10 at the level of the equator 19 of the spherical surface 9 of the spherical cap have the shape of circular openings. 3. The joint according to claim 2, characterized in that the spherical cap 3 of the sleeve 7 has from one to three longitudinal cuts 11 of constant width Sp. 4. A joint according to claim 1, characterized in that the longitudinal bores 12 and 13 of the inner spherical cap 8 have alternately different heights h _m and hd, the centers of the bores 27 of the bore 12 with the height hd are located on the horizontal plane π2, and the centers of the holes 28 of the notch 13 with the height hd are located below the geometric center of hinge S2. 5. A joint according to claim 1, characterized in that the longitudinal recesses 12 of the inner spherical cap 8 have the same width Sc, and the circular openings 27 of the cutouts 12 with the height hd have a diameter Dc greater than the width Sc of the longitudinal cutouts 12, and the longitudinal cutouts 13 of the inner spherical cap 8 have a height of h _m have the same width, and their circular openings 28 have a diameter greater than the width of the longitudinal cutouts 13. 6. A joint according to claim 1, characterized in that the spherical cap 3 of the sleeve 7 has an inner spherical surface 9 of radius R1, and the inner spherical cap 8 has an outer spherical surface 22 of radius R2. 7. A joint according to claim 1, characterized in that the geometric center Si of the bowl, the spherical pan 3 is located on the horizontal plane πι, on which the equator 19 of the spherical surface 9 is located. 8. A joint according to claim 5, characterized in that the radius Ri of the inner spherical surface 9 of the spherical cap 3 is preferably greater by the value of the initial clearance than the radius R2 of the outer spherical surface 22 of the inner spherical cap 8, whose geometric center S2 is the center of rotation of the joint and is located at a distance As from level of the equator 19 of the spherical surface 9 of the spherical bowl of the bushing. 9. A joint according to claim 1, characterized in that the spherical cap 3 and the inner spherical cap 8 are made of an elastic material.