Linked structure and parallel link robot

Abstract

Provided is a connection structure (10) interconnecting two links (5a), (5b) each having a longitudinal axis (C) and being spaced apart and operating in parallel, the connection structure (10) comprising: bushings (20a), (20b) at each link, the bushings (20a), (20b) each being attached so as to be rotatable about an axial line (D) orthogonal to a plane including the two longitudinal axes; a biasing mechanism (30) spanning between the bushings of the two links and applying an elastic restoring force to the two bushings in a direction causing the two bushings to come close each other; and a connection member (50) having two attachment holes through which each bushing can penetrate in the axial direction, and regulating the distance between the bushings to a prescribed distance or less. Each bushing is provided with a claw portion projecting radially outward at a portion of an axial end part in the peripheral direction. Each attachment hole is formed in a shape that allows the penetration of each bushing only in a prescribed attachment phase about the axial line coinciding with the claw portion of each bushing. The phase of each bushing about each axial line is regulated by the elastic restoring force to a phase that does not match the attachment phase.

Description

[Technical Field]

[0001] The present disclosure relates to a connection structure and a parallel link robot. [Background technology]

[0002] A spring device that connects two parallel links of a robot that employs a parallel mechanism is known (see, for example, Patent Document 1). This spring device draws the links closer to each other while preventing the distance between the links from increasing beyond a predetermined distance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-097571 Summary of the Invention [Problem to be solved by the invention]

[0004] The components connected to the two links to regulate the distance between them can easily come off when the links are moved. To prevent this, if the components connected to the links are attached using bolts or the like, tools are required for assembly and disassembly. Therefore, it is desirable to prevent the member that regulates the distance between the two links from falling off and to facilitate assembly and removal without using tools. [Means for solving the problem]

[0005] One aspect of the present disclosure is a connecting structure that interconnects two links that have longitudinal axes and operate in parallel with a gap between them, the connecting structure comprising: a bushing attached to each of the links so that it can rotate about an axis perpendicular to a plane containing the two longitudinal axes; a biasing mechanism that is stretched between the bushings of the two links and applies an elastic restoring force to the two bushings in a direction that brings them closer to each other; and a connecting member that has two mounting holes that can penetrate each of the bushings in the axial direction and that restricts the distance between the bushings to a predetermined distance or less, the bushings have claw portions that protrude radially outward at a portion of the circumferential direction of the end portion in the axial direction, each mounting hole being formed in a shape that allows each bushing to pass through only at a predetermined mounting phase about the axis that coincides with the claw portions of each bushing, and the phase of each bushing about the axis is restricted by the elastic restoring force to a phase that does not coincide with the mounting phase. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a front view illustrating an outline of a parallel link robot according to an embodiment of the present disclosure. [Figure 2] 2 is a front view showing an outline of the attachment state of a biasing mechanism of a connection structure in a pair of links of the parallel link robot of FIG. 1. FIG. [Figure 3] 2 is a cross-sectional view showing the shapes of a mounting pin and a pair of bushes provided on one link of the parallel link robot of FIG. 1. FIG. [Figure 4] 4 is a side view showing the shape of one bush of the connecting structure shown in FIG. 3. FIG. [Figure 5] FIG. 5 is a front view showing the shape of the bush shown in FIG. [Figure 6] 4 is a side view showing the shape of the other bush of the connecting structure shown in FIG. 3. FIG. [Figure 7] FIG. 7 is a front view showing the shape of the bush shown in FIG. 6. [Figure 8] 3 is a perspective view showing the shape of a hook of the connecting structure shown in FIG. 2. FIG. [Figure 9] 3 is a front view showing the shape of a connecting member of the connecting structure shown in FIG. 2. FIG. [Figure 10] 3A to 3C are diagrams illustrating a procedure for attaching the connecting members in the connecting structure shown in FIG. 2. [Figure 11] 3A to 3C are diagrams illustrating a procedure for attaching the connecting members in the connecting structure shown in FIG. 2. [Figure 12] 3 is a front view showing an outline of an attached state of a connecting member in the connecting structure shown in FIG. 2.

[0023] FIG. [Figure 13] 3 is a front view showing the outline of the shape of a biasing mechanism in a first modified example of the connecting structure shown in FIG. 2.

[0023] FIG. [Figure 14] 3 is a schematic view showing the shape of one bush in a second modified example of the connecting structure shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] A connection structure 10 and a parallel link robot 1 according to an embodiment of the present disclosure will be described below with reference to the drawings. A parallel link robot 1 according to this embodiment includes a base 2 that is fixed by hanging it from a ceiling or the like, as shown in FIG. 1 . The parallel link robot 1 also includes a movable unit 3 that is arranged below the base 2 at intervals. The parallel link robot 1 also includes three arms 4 that are supported on the base 2 so as to be rotatable about three horizontal axes A. The parallel link robot 1 also includes two pairs of parallel links 5a, 5b for each arm 4 that connect each arm 4 to the movable unit 3. The parallel link robot 1 also includes connecting structures 10, 10' that span between each pair of links 5a, 5b.

[0008] The base 2 is equipped with three servo motors 6 for respectively driving the three arms 4. The servo motors 6 are arranged at equal intervals in the circumferential direction around an axis B that passes through the center of the base 2 and extends vertically. The servo motors 6 each have a rotary drive shaft (not shown) that can be rotated around a horizontal axis A.

[0009] The base end of each arm 4 is connected to the rotary drive shaft of the corresponding servo motor 6, and is rotatable around axis A relative to the base 2. As shown in Fig. 2, the parallel link robot 1 also includes a pair of ball joints 7a, 7b that connect the tip of each arm 4 to the links 5a, 5b. Each ball joint 7a, 7b includes a ball stud 8a, 8b and a socket 9a, 9b. The ball studs 8a, 8b are attached to both outer sides of the tip of each arm 4 in the direction of the axis A (see FIG. 1).

[0010] Each pair of links 5a, 5b has a socket 9a, 9b at one end in the direction of longitudinal axis C. The socket 9a, 9b is fitted onto the ball stud 8a, 8b at the tip of the corresponding arm 4, sandwiching it from both sides in the direction of axis A.

[0011] As shown in FIGS. 2 and 3, each socket 9a, 9b is provided with a mounting pin 29 that protrudes in a direction perpendicular to the longitudinal axis C. The mounting pin 29 is press-fitted into a pin hole 9h that penetrates the socket 9a, 9b in a direction perpendicular to the longitudinal axis C, and protrudes on both sides of the longitudinal axis C. The mounting pin 29 is press-fitted from one side of the pin hole 9h until it abuts against a flange-shaped positioning portion 29p provided midway along the length. This ensures that the mounting pins 29 protruding from both sides of the outer circumferential surfaces of the sockets 9a, 9b are aligned to the same length. In the assembled state, the mounting pin 29 extends along an axis D that is perpendicular to a plane containing the longitudinal axes C of the two links 5a, 5b.

[0012] Each link 5a, 5b also has a socket 9a', 9b' similar to the one end at the other end in the direction of the longitudinal axis C. The sockets 9a', 9b' constitute ball joints 7a', 7b' together with ball studs 8a', 8b' provided on the movable part 3. Like the sockets 9a, 9b, each socket 9a', 9b' has a pin hole 9h and a mounting pin 29 press-fitted into the pin hole 9h.

[0013] The movable part 3 has a pair of parallel, flat mounting portions 3w that protrude radially outward from the outer peripheral surface at positions corresponding to each pair of links 5a, 5b. Ball studs 8a', 8b' are attached to the outside of each pair of mounting portions 3w. Sockets 9a', 9b' at the other end of each link 5a, 5b are fitted onto the ball studs 8a', 8b', respectively, sandwiching them from both outer sides in the direction of axis A.

[0014] Next, the connecting structures 10, 10' according to this embodiment will be described. In this embodiment, the three pairs of links 5a, 5b and the three upper and lower connecting structures 10, 10' each have the same configuration. Therefore, the following description will be given using the configuration of the pair of links 5a, 5b and one connecting structure 10 as an example.

[0015] 2 and 3, the connecting structure 10 includes bushings 20a and 20b attached to the sockets 9a and 9b, respectively. Also, as shown in FIG. 2, the connecting structure 10 includes a biasing mechanism 30 and a connecting member 50 that span between the sockets 9a and 9b and connect them together.

[0016] The bushings 20a and 20b are manufactured by, for example, injection molding a resin material such as silicone resin. As shown in Figures 4 to 7, the bushings 20a and 20b each have a cylindrical shape with a hollow hole 21. Hollow hole 21 has a circular cross section into which mounting pin 29 is rotatably fitted. Hollow hole 21 of bushing 20a is provided with a relief portion that corresponds to positioning portion 29p provided on mounting pin 29. This uniquely determines the combination when bushings 20a and 20b are attached to both ends of mounting pin 29.

[0017] The bushings 20a, 20b each include a first cylindrical portion 22a, 22b on one axial side and a second cylindrical portion 23 on the other axial side. The first cylindrical portions 22a, 22b each include claws (claw portions) 24a, 24b at the axial tip of the cylindrical portion, with part of the circumferential portion protruding radially outward. The claws 24a and 24b will be described later.

[0018] The second cylindrical portions 23 have an outer diameter larger than the outer diameters of the first cylindrical portions 22a, 22b. The second cylindrical portions 23 are provided with groove portions 25 recessed in the radial direction at the axially intermediate positions thereof. As a result, the second cylindrical portions 23 are provided with flange portions 26 that protrude radially outward beyond the groove portions 25 on both sides of the groove portions 25 in the axial direction.

[0019] Groove 25 includes curved groove 25a having a semicircular arc shape and a pair of parallel linear grooves 25b continuing from both ends of curved groove 25a, thereby giving groove 25 and flange 26 a non-circular cross-sectional shape.

[0020] 2, the biasing mechanism 30 includes a coil spring (elastic body) 31 and two hooks 40 disposed on both ends of the coil spring 31. The hooks 40 are connected to both ends of the coil spring 31 by hooking onto hook portions 31a on both ends of the coil spring 31, respectively. The hook portions 31a each have a hook-like shape formed by bending the wire that constitutes the coil spring 31. The coil spring 31 has a spring constant that is sufficient to apply an appropriate amount of preload to the ball joints 7a and 7b.

[0021] 8, the hook 40 is a member obtained by bending and deforming a metal round bar. The metal round bar has an outer diameter dimension equivalent to the groove width of the grooves 25 of the bushings 20a and 20b.

[0022] The hook 40 has a first connecting portion 40a whose longitudinal center is curved along an arbitrary first plane F1. The hook 40 also has a pair of second connecting portions 40b whose longitudinal ends are curved along a second plane F2 perpendicular to the first plane F1. Each second connecting portion 40b has a pair of linear portions 41b extending parallel to each other on both ends of a semicircular arc-shaped curved portion 41a.

[0023] The distance between the pair of second connecting portions 40b is equal to the distance W (see FIG. 3) between the grooves 25 of the two bushings 20a, 20b attached to the socket 9a. Further, each second connecting portion 40b has a shape that matches the shape of the groove portion 25 around the axis D.

[0024] The pair of second connecting portions 40b are hooked onto the grooves 25 of the two bushings 20a, 20b attached to the socket 9a, respectively. Then, the curved portion 41a and the two straight portions 41b of the second connecting portion 40b come into close contact with the bottom of each groove 25. That is, the curved portion 41a of the hook 40 comes into close contact with the curved groove 25a, and the straight portion 41b comes into close contact with the straight groove 25b. This connects the two bushings 20a, 20b and each hook 40 together so that they do not rotate relative to each other around the axis D of the mounting pin 29.

[0025] The hook portion 31a of the coil spring 31 is hooked onto the first connecting portion 40a of the hook 40, whose second connecting portion 40b is hooked onto the bushings 20a and 20b. When the second connecting portion 40b is hooked onto the grooves 25 of the bushings 20a and 20b, the first connecting portion 40a of the hook 40 extends parallel to the axis D of the mounting pin 29. Therefore, the hook portions 31a at both ends of the coil spring 31 are hooked onto the two hooks 40 so as to be rotatable around axes parallel to the axis D.

[0026] 9, the connecting members 50 are long, strip-shaped members formed by punching out a metal flat plate. The connecting members 50 are arranged one on each side of the sockets 9a, 9b in the direction of the axis D. Each connecting member 50 has mounting holes 51a, 51b near both ends in the longitudinal direction, penetrating in the plate thickness direction.

[0027] The mounting hole 51a has an opening shape that allows the first cylindrical portion 22a including the claws 24a of the bushing 20a to pass through in the axial direction of the first cylindrical portion 22a. The claws 24a have a width smaller than the diameter of the cylindrical portion of the first tubular portion 22a and a length that protrudes radially to a position equivalent to the outer shape of the flange portion 26. The claws 24a are flat and have a predetermined thickness. The claws 24a extend from the outer surface of the cylindrical portion of the first tubular portion 22a in a direction different from the longitudinal direction of the linear groove portion 25b, for example, in a direction that forms an angle of 120°.

[0028] The mounting hole 51a has a circular opening shape with an inner diameter slightly larger than the outer diameter of the cylindrical portion of the first tubular portion 22a, and is provided with a notch 52 in a part of the circumferential direction. The size and shape of the notch 52 are such that the claw 24a can pass through, for example, a similar shape that is slightly larger than the claw 24a.

[0029] The mounting hole 51b also has an elongated opening shape that can pass through the first cylindrical portion 22b, including the claws 24b of the bushing 20b, in the axial direction of the first cylindrical portion 22b. The claws 24b have a width dimension equivalent to the diameter of the cylindrical portion of the first cylindrical portion 22b and a length dimension that protrudes radially greater than the outer diameter of the flange portion 26. The claws 24b are also flat and have a predetermined thickness. The claws 24b extend from the outer surface of the cylindrical portion of the first cylindrical portion 22b in a direction different from the longitudinal direction of the linear groove portion 25b, for example, in a direction that forms an angle of 30°.

[0030] The mounting hole 51b has a width dimension slightly larger than the width dimension of the claw 24b and a length dimension slightly larger than the dimension of the first tubular portion 22b in the longitudinal direction of the claw 24b. The mounting hole 51b extends in the longitudinal axis direction of the connecting member 50, and allows the cylindrical portion of the first tubular portion 22b to pass through the mounting hole 51b so as to be movable in the longitudinal axis direction of the connecting member 50.

[0031] The connecting member 50 has the first cylindrical portions 22a and 22b, which are arranged on the same side in the direction of the axis D of the sockets 9a and 9b, passing through the mounting holes 51a and 51b, respectively. In this case, the lengthwise direction of the claws 24a and 24b passing through the mounting holes 51a and 51b and the lengthwise direction of the notch 52 are out of phase with each other around the axis D.

[0032] The following describes the operation of the parallel link robot 1 and the connecting structure 10 configured in this manner. In the following description, of the two connecting members 50, one connecting member 50 will be used as an example, and a description of the other connecting member 50 will be omitted.

[0033] The parallel link robot 1 according to this embodiment is assembled as follows. For assembly, a base unit, a movable part 3, three pairs of links 5a, 5b, and three connecting structures 10, 10' are prepared. The base unit is made up of a base part 2 to which three arms 4 and ball studs 8a, 8b are attached. Each link 5a, 5b has a socket 9a, 9b and a mounting pin 29 attached to one end, and a socket 9a', 9b' and a mounting pin 29 attached to the other end. To assemble the parallel link robot 1, first, two hooks 40 are connected to each of the coil springs 31 of the connecting structures 10, 10'. Specifically, the hook portions 31a on both sides of the coil spring 31 are hooked onto the first connecting portions 40a of the two hooks 40, respectively.

[0034] Next, a pair of bushings 20a, 20b are attached to the mounting pins 29 of the sockets 9a, 9b of each link 5a, 5b. The bushings 20a and 20b are brought close to each other from both sides of the sockets 9a, 9b, and the mounting pin 29 is fitted into the hollow hole 21. This allows the pair of bushings 20a, 20b to be attached rotatably around the axis D of the same mounting pin 29. Similarly, a pair of bushings 20a, 20b are attached to the mounting pin 29 of each socket 9a', 9b' of each link 5a, 5b. Also, the bushings 20a, 20b are attached to both ends of the mounting pin 29 of each socket 9a', 9b' so as to be rotatable around the axis D of each mounting pin 29.

[0035] Next, the pair of second connecting portions 40b of the hook 40 on one side of the connecting structure 10 are hooked into the grooves 25 of the bushings 20a, 20b attached to the socket 9a. Also, the pair of second connecting portions 40b of the hook 40 on the other side are hooked into the grooves 25 of the bushings 20a, 20b attached to the socket 9b. Similarly, the hooks 40 on one side of the connecting structure 10' are hooked into the grooves 25 of the bushings 20a and 20b attached to the socket 9a'. The hooks 40 on the other side are hooked into the grooves 25 of the bushings 20a and 20b attached to the socket 9b'.

[0036] Next, one of the pair of links 5a, 5b, for example, the sockets 9a, 9a' of link 5a, is brought close to the ball studs 8a, 8a', respectively. Then, the sockets 9a, 9a' are fitted onto the ball studs 8a, 8a' from the outside in the direction of axis A. After that, the other link 5b is held and pulled in the direction stretching the two coil springs 31 to widen the distance between the links 5a, 5b. Then, the sockets 9b, 9b' of link 5b are simultaneously fitted onto the ball studs 8b, 8b' from the outside in the direction of axis A, respectively. As a result, the ball studs 8a, 8b are sandwiched between the pair of sockets 9a, 9b in the direction of axis A. Similarly, the ball studs 8a', 8b' are sandwiched between the pair of sockets 9a', 9b' in the direction of axis A.

[0037] As a result, the pair of links 5a, 5b are connected by the two biasing mechanisms 30 and are attached to the arm 4 and the movable part 3. In this state, the two second connecting portions 40b of one hook 40 are hooked into the grooves 25 of the two bushings 20a, 20b that sandwich the sockets 9a, 9b, respectively. As a result, the hook 40 integrally connects the pair of bushings 20a, 20b.

[0038] Additionally, the flanges 26 adjacent to both sides of each groove 25 are positioned to sandwich the second connecting portion 40b of the hook 40 in the axial direction of the second tubular portion 23. This allows the bushings 20a, 20b to restrict movement of the hook 40 along the axial direction of the mounting pin 29. The hook 40 also restricts the bushings 20a, 20b from falling off the mounting pin 29. In other words, the bushings 20a, 20b and the hook 40 can rotate integrally around the axis D of the mounting pin 29, but do not move relative to each other in other directions. The same applies to the two bushings 20a, 20b that sandwich the sockets 9a', 9b'.

[0039] Next, the connecting member 50 is attached between the links 5a and 5b. As shown in Figure 10, the first tubular portion 22a of the bushing 20a attached to one link 5a is inserted into the mounting hole 51a of the connecting member 50. The insertion can be easily achieved by aligning the length direction of the notch 52 of the mounting hole 51a with the phase of the claw 24a of the first tubular portion 22a. After the claw 24a has passed through the mounting hole 51a, the connecting member 50 is rotated around the axis D of the bushing 20a. This causes the mounting hole 51a and the claw 24a to become misaligned, so that the connecting member 50 is attached to the first tubular portion 22a of the bushing 20a without coming off.

[0040] Next, the connecting member 50 is rotated around the axis D of the bushing 20a until the mounting hole 51b is aligned with the first cylindrical portion 22b of the bushing 20b. In this state, the phase of the claws 24b of the bushing 20b does not match the longitudinal direction of the mounting hole 51b of the connecting member 50.

[0041] 11, a force is applied to the connecting portion between the hook portion 31a of the coil spring 31 and the first connecting portion 40a of the hook 40. This causes the coil spring 31 and the hook 40 to rotate relative to each other, causing the coil spring 31 to stretch slightly and the hook 40 and the bush 20b to rotate around the axis D.

[0042] Then, when the bushing 20b has rotated until the phase of the pawl 24b is aligned with the longitudinal direction of the mounting hole 51b, the first tubular portion 22b is passed through the mounting hole 51b. Then, when the pawl 24b passes through the mounting hole 51b, the force applied to the coil spring 31 is released. As a result, as shown in FIG. 12, the phases of the pawl 24b and the mounting hole 51b are shifted, and the connecting member 50 is attached to the first tubular portion 22b so as not to come off. Similarly, the connecting member 50 of the connecting structure 10' is hung between the bushings 20a and 20b attached to the mounting pins 29 of the sockets 9a' and 9b'. In the example shown in Fig. 10, the claws 24b of the bushing 20b of the connecting structure 10' extend in a different direction from the claws 24b of the connecting structure 10. This prevents the coil spring 31 from interfering with surrounding components when the bushing 20b is passed through the mounting hole 51b of the connecting member 50 of the connecting structure 10'. The remaining two pairs of links 5a, 5b can be assembled in the same manner, and the assembly of the parallel link robot 1 is now complete.

[0043] In this way, according to this embodiment, it is possible to apply a force in a direction narrowing the gap between the pair of links 5a, 5b and prevent them from moving apart more than a predetermined distance. Another advantage is that the connecting member 50, which prevents the gap from widening, can be attached or detached without using any tools or jigs. Furthermore, the bushings 20a, 20b that support the connecting member 50 on the pair of links 5a, 5b are held in a predetermined position by the biasing mechanism 30. That is, the claws 24a, 24b and the mounting holes 51a, 51b of the connecting member 50 are positioned in a phase that prevents the connecting member 50 from falling off. This makes it possible to prevent the connecting member 50 from falling off unintentionally during operation of the links 5a, 5b, for example.

[0044] Furthermore, one of the mounting holes 51a of the connecting member 50 has a circular cross section, and the first cylindrical portion 22a does not move relative to the mounting hole 51a in the radial direction when it penetrates through it. Therefore, even when the parallel link robot 1 operates, rattle does not occur between the connecting member 50 and the bushing 20a.

[0045] Furthermore, because one of the mounting holes 51b of the connecting member 50 is an elongated hole, the first tubular portion 22b is allowed to move slightly while remaining inserted through the mounting hole 51b. This has the advantage that even if the distance between the links 5a and 5b shortens due to deterioration of the ball joints 7a and 7b over time, this shortening can be tolerated.

[0046] In this embodiment, the two hooks 40 are connected to the hook portions 31a at both ends of the coil spring 31 so as to be rotatable about an axis parallel to the axis D. Alternatively, at least one of the hooks 40 may be fixed integrally to the hook portions 31a.

[0047] For example, the hook 40 on the bushing 20a side may be fixed to the catch portion 31a by welding or the like. If the hook 40 on the bushing 20b side and the coil spring 31 can rotate relative to each other, the phase of the claw 24b can be easily aligned with the phase of the mounting hole 51b.

[0048] 13, two hooks 40 can be welded to the hook portions 31a on both sides of the coil spring 31. In this case, the assembly can be performed in a different order than the above-described assembly method. For example, first, the connecting member 50 is connected to the bushings 20a and 20b. Then, while stretching the coil spring 31, the hooks 40 welded to both sides can be hooked onto the bushings 20a and 20b.

[0049] That is, when the biasing mechanism 30 is not attached, the rotation of the bushings 20a, 20b around the axis D is not restricted. Therefore, the phase of the claws 24a, 24b is simultaneously aligned with the phase of the two mounting holes 51a, 51b of the connecting member 50, and the connecting member 50 is attached. Then, the bushings 20a, 20b are rotated around the axis D to shift the phase. Thereafter, the biasing mechanism 30 is attached to restrict the rotation of the bushings 20a, 20b. This allows the coil spring 31 and the two hooks 40 to be handled as a single unit. Furthermore, when the space for attaching the connecting structure 10 is narrow, the assembly work can be facilitated.

[0050] In this case, the phase of the claws 24a, 24b relative to the linear groove portion 25b can be freely set. Therefore, the claw 24b can also be disposed at a phase that is significantly offset from the longitudinal direction of the mounting hole 51b, thereby more reliably preventing the connecting member 50 from falling off. In particular, if the phases of the claws 24a and 24b relative to the linear groove portion 25b are the same, the same bushing 20b as the bushing 20a can be used. This reduces the number of parts, and standardizing parts also reduces manufacturing costs. Furthermore, during assembly, there is no need to worry about the type of bushing, which improves work efficiency. In this case, by maintaining the shape of the attachment hole 51b as an elongated hole, it is possible to accommodate changes in the distance between the links 5a and 5b due to aging or the like.

[0051] In this embodiment, the relative rotation between the straight portion 41b of the hook 40 and the straight groove portion 25b of the bushings 20a and 20b is restricted by contact between the straight portion 41b of the hook 40 and the straight groove portion 25b of the bushings 20a and 20b. Alternatively, the bushings 20a and 20b may not have the straight groove portion 25b.

[0052] For example, as shown in Fig. 14, the groove 25 of the bushing 20b has a non-circular cross-sectional shape such as an ellipse, and the curved portion 41a of the hook 40 is curved to a shape that matches the grooves 25 of the bushings 20a and 20b. As a result, when the biasing mechanism 30 is connected, the elastic restoring force of the coil spring 31 restricts the rotation of the bushing 20b about the axis D. As a result, similar to the above, it is possible to maintain a state in which the claws 24b of the bushing 20b and the mounting holes 51b of the connecting member 50 are out of phase with each other about the axis D. The bushing 20a and the hook 40 connected to the bushing 20a can be configured in a similar manner to obtain the same effect.

[0053] The cross-sectional shape of the groove portion 25 of the bushings 20a, 20b may be a non-circular shape other than an ellipse. Any cross-sectional shape may be adopted as long as the shape restricts rotation around the axis D by tightly contacting the curved portion 41a of the hook 40. For example, the cross-sectional shape of the groove portion 25 of the bushings 20a, 20b may be a circle that is eccentric with respect to the axis D. This also makes it possible to restrict the rotation of the bushings 20a, 20b around the axis D by bringing the curved portion 41a of the hook 40 into close contact with the groove portion 25.

[0054] Furthermore, according to this embodiment, one mounting pin 29 is press-fitted into each of the sockets 9a and 9b with both ends protruding in the direction of the axis D. Alternatively, two mounting pins 29 may be press-fitted into each of the sockets 9a and 9b from both outer sides in the direction of the axis D. For example, the mounting pin 29 may be a simple round bar, and may be press-fitted from both outer sides in the direction of the axis D to a depth of about half of the pin hole 9h.

[0055] In this embodiment, the connecting structure 10 is attached between the sockets 9a and 9b, and the connecting structure 10' is attached between the sockets 9a' and 9b'. Alternatively, the connecting structure 10' attached between the sockets 9a' and 9b' at the other ends of the links 5a and 5b may be omitted. In this case, it is sufficient that the coil spring 31 of the connecting structure 10 has a spring constant sufficient to hold the four ball joints 7a, 7b, 7a', and 7b'.

[0056] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. [Explanation of symbols]

[0057] 1 Parallel link robot 2 Foundation part 3 Moving parts 4 Arm 5a,5b Link 10,10´ connection structure 20a, 20b Bush 24a, 24b Claws (claw part) 25 Groove 30 Biasing mechanism 31 Coil spring (elastic body) 40 Hook 50 Connecting member 51a, 51b Mounting holes C Longitudinal axis D axis

Claims

1. A linking structure for interconnecting two links having a longitudinal axis and moving in parallel with a space therebetween, a bushing attached to each of the links so as to be rotatable about an axis perpendicular to a plane including the two longitudinal axes; a biasing mechanism that is stretched between the bushes of the two links and applies an elastic restoring force to the two bushes in a direction that brings them closer to each other; a connecting member having two mounting holes that can pass through each of the bushes in the axial direction and that restricts the distance between the bushes to a predetermined distance or less, the bushing has a claw portion that protrudes radially outward from a circumferential portion of an end portion in the axial direction, each mounting hole is formed in a shape that allows the bushing to pass through only at a predetermined mounting phase around the axis that coincides with the claw portion of the bushing, A connecting structure in which the phase of each of the bushes around the axis is restricted by the elastic restoring force to a phase that does not coincide with the mounting phase.

2. the bushes are disposed on both sides of the link in the axial direction, 2. The connecting structure according to claim 1, wherein the biasing mechanism is connected to the bushings on both sides of the link.

3. 2. The connecting structure according to claim 1, wherein the biasing mechanism comprises an elastic body that generates the elastic restoring force, and hooks that are disposed on both ends of the elastic body and hook onto the bushings.

4. 4. The connecting structure according to claim 3, wherein the hook and the bush have shapes that maintain a state in which relative rotation about the axis is prohibited when the hook is hooked.

5. 5. The connecting structure according to claim 4, wherein at least one end of the elastic body and the hook are connected to each other so as to be rotatable about an axis parallel to the axis.

6. The connecting structure according to claim 5 , wherein the outer peripheral surface of the bushing is provided with a groove portion, recessed radially inward, at a midpoint in the axial direction, for receiving the hook.

7. The foundation and a movable part disposed at a distance from the base part; a plurality of arms swingably connected to the base; a pair of links having parallel longitudinal axes that connect the arm and the movable portion; A parallel link robot comprising: the connecting structure according to claim 1 provided between a pair of the links.

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