JP4725748B2 - Parallel link mechanism - Google Patents

Description

The present invention relates to a link mechanism of a parallel link including a pair of links arranged in parallel via a ball joint .

  2. Description of the Related Art Conventionally, in the field of industrial robots and the like, a mechanism that enables a movement with a high degree of freedom in three dimensions called a so-called parallel mechanism is widely known. For example, in an industrial robot adopting a parallel mechanism, a plurality of (mostly three) arms support a hand part as a gripping element, and these arms move flexibly so that the hand part has high accuracy and high accuracy. A wide range of operation is realized. As each arm, there is known an arm composed of a pair of links whose upper and lower ends are connected in parallel via a ball joint, and both links are given a tensile biasing force by a spring device. Specifically, the cup-shaped receiving part formed at the end of the link is engaged with a spherical ball part formed in a joint interposed between the two links, and the ball part is detached from the receiving part. As a purpose, a spring device that applies a tensile biasing force is mounted between both links.

  As a spring device applied to the link mechanism as described above, there is one that uses a tension spring as a biasing element (document unknown). However, in a tension spring, if both links are unfolded excessively, the spring may be fully extended, that is, may be plastically deformed in the additional direction (tensile direction). Moreover, there is a possibility that the connecting portion between the both ends of the tension spring and the link or the like is disengaged.

  As a technique that can solve the above problems, Patent Document 1 describes a spring device that uses a single compression spring as an urging element. The spring device is arranged between the first tension device having a first angle device that can be displaced in parallel with each other, the first tension device having a second angle device, and the angle devices. It consists of a compression spring. Then, the receiving portion is pressed against the ball portion constituting the ball joint by the elastic biasing force that biases the link derived from the compression spring in the direction in which the link is approached, and the receiving portion is prevented from coming off from the ball portion. Further, since the compression spring is used as the biasing element, problems such as the extension of the spring and the disconnection of the connecting portion that could not be avoided in the tension spring can be solved.

JP-T-2002-529258

  The problem with the spring device described in Patent Document 1 is that when the spring constant of the compression spring is increased to increase the urging force, the ball portion is difficult to come off from the receiving portion, but the receiving portion is strongly pressed against the ball portion accordingly. As a result, the ball portion or the receiving portion is likely to be worn in the normal operating state of the link mechanism. In addition, since the ball portion is strongly pressed against the receiving portion, there is a disadvantage in that the load on the motor that drives the link mechanism is increased and power consumption is increased. Conversely, if the spring constant of the compression spring is reduced, wear of the receiving part and the ball part can be suppressed, but the tensile biasing force acting between the links is reduced, and the receiving part may come off from the ball part.

An object of the present invention is to provide a relatively small pulling force in a state where the objects are kept at an appropriate distance, and when the distance between the objects is large, a large pulling force is obtained. The object is to provide a spring device that exerts power.
In other words, when applied to a link mechanism having a pair of links arranged in parallel via a ball joint, in the state where the links are kept at an appropriate distance, the links are relatively An object of the present invention is to provide a spring device that can apply a small tensile biasing force and can provide a large tensile biasing force when the distance between the links is increased to prevent the receiving portion from coming off from the ball portion.
Further, the object of the present invention is to provide a relatively small tensile biasing force to both links in a state where the links are maintained at an appropriate distance, and when the distance between the links increases, It is to provide a link mechanism that can reliably prevent the receiving portion from coming off from the ball portion.

The link mechanism of the parallel link according to the present invention is mounted between a pair of links for the purpose of giving a tensile biasing force to these links and a pair of links whose both ends are arranged in parallel via ball joints. Spring device.
The spring device includes a first compression spring, a second compression spring that is arranged in series with the first compression spring, and has a spring constant smaller than that of the first compression spring, and the second compression spring. And a stopper for regulating the compression limit.
The spring device applies a tensile biasing force between the links by using an elastic biasing force of the first and second compression springs to return from a compressed state to a natural length state.
The spring device is configured to apply a tensile biasing force derived from a combined spring constant of the two compression springs arranged in series between the links until the second compression spring reaches a compression limit by the stopper. In addition, after the second compression spring reaches the compression limit, a tensile biasing force derived from a spring constant of the first compression spring is applied between the links .
The term “compression spring” as used herein means a compression coil spring that exerts an urging force outward in the axial direction in a compressed state.

Specifically, in the spring device constituting the link mechanism of the parallel link of the present invention , the first compression spring is accommodated and the cylindrical first case connected to one of the links , and the second compression spring There is accommodated, it is inserted a tubular second case connected to the other link, through the rod hole has one end provided on one of the first case in the first case, the other end the and a rod which is inserted into the second case through a rod hole formed in one of the second case.
Before Symbol first compression spring, the inner surface of the end wall having the rod hole of the first case, between one end portion of the rod, is assembled in a fitted state in the rod, the second compression spring, the inner surface of the end wall having the rod hole of the second case, between one end of the rod, is assembled in the state fitted on the rod.
The first and second cases are configured to reciprocate in the axial direction of the rod.
The first and second compression springs exhibit an elastic biasing force that resists displacement movement in a direction in which the facing distance between the end walls of the first and second cases and the end of the rod is reduced. Thus, a tension biasing force is applied between the links .

The stopper may be provided at one end of the rod that receives the second compression spring .

The first case and the second case are preferably formed in the same shape.

Spring means constituting the parallel link of the link mechanism of the present invention comprises a first compression spring and the second compression spring and a cylindrical case which is accommodated in a serial manner, to one end of the axial direction of the case is inserted, a first rod connected to one link, is inserted into the other end side in the axial direction of the case can be made and a second rod connected to the other link.
Said first rod and the second rod is configured to be reciprocated in the axial direction of the case, the axial end walls of the case, the rod hole to allow insertion of the first and second rod Is provided. The first and second compression springs are assembled in a compressed manner between the inner surface of the end wall of the case having the rod hole and one end of the rod.
The first and second compression springs exhibit an elastic urging force that resists displacement movement in a direction in which the facing distance between the end wall of the case and the ends of the first and second rods decreases. Thus, a tension biasing force is applied between the objects .

The stopper may be provided on the second rod .

  In the present invention, since the biasing element of the spring device is configured by linearly arranging two types of springs having different spring constants, the first compression spring and the second compression spring, the spring constant of the entire biasing element. As such, it can be suppressed more than the spring constant of each of the first and second compression springs. That is, if the spring constant of the first compression spring is k1 and the spring constant of the second compression spring is k2, the combined spring constant k0 of (k1 · k2) / (k1 + k2) is obtained as the whole biasing element. More specifically, when k1 is 6 (N / mm) and k2 is 3 (N / mm), a combined spring constant k0 of 2 (N / mm) is obtained for the entire biasing element. In addition, when the compression spring having a small spring constant reaches the compression limit, only the compression spring having the other spring constant is compressed, so that the spring constant of the biasing element matches the other spring constant (k1). As a result, the spring constant is increased (k0 → k1), and the spring device exhibits a large tensile biasing force.

Therefore, when the objects (links) are kept at an appropriate distance, these objects are attached with a combined spring constant (k0) lower than the spring constants of the first compression spring and the second compression spring. The pulling force of the force element is demonstrated. When the distance between the objects (links) increases and one compression spring reaches the compression limit, a large pull biasing force derived from the other compression spring having a large spring constant is exhibited.

However, in the link mechanism of the engaging Rupa Parallel link with the present invention, in a state where the link each other is kept in a proper gap distance, giving a relatively small tensile biasing force to both links, yet spacing the links with each other As the distance increases, a large pulling force can be applied to reliably prevent the receiving part from coming off from the ball part. That is, in a state where the links (objects) constituting the link mechanism are maintained at an appropriate interval distance, the composite spring constants (lower than the spring constants of the first compression spring and the second compression spring) are applied to these links. At k0), the tension biasing force of the biasing element is exerted, and the pressing force of the receiving portion against the ball portion of the ball joint can be suppressed by suppressing the tension force acting on both links. Therefore, it is possible to effectively prevent the ball portion or the receiving portion from being worn. Since a load required by a driving mechanism such as a motor for driving the link mechanism can be suppressed, it is possible to prevent an unnecessary increase in power consumption. On the other hand, when an external force is applied in the direction in which both links are separated and the distance between the links increases, a large pull biasing force derived from the other compression spring having a large spring constant is exerted. Can be reliably prevented from coming off.

  The first compression spring is assembled in a compressed state between the inner surface of the end wall having the rod hole of the first case and one end of the rod, and the second compression spring is attached to the end wall of the end wall having the rod hole of the second case. According to the spring device assembled in a compressed state between the inner surface and the other end of the rod, the compression spring can be expanded and contracted while being accommodated in the case. It is possible to prevent the object from coming off, and to apply an appropriate tensile biasing force to the object. It is also excellent in that it is possible to reliably prevent the occurrence of malfunction due to dust adhering to the compression spring.

  A so-called yield point where the compression spring is over-compressed and loses its elasticity when a stopper that restricts the compression limit of the first compression spring and / or the second compression spring is provided at at least one end of the rod. Can avoid the danger of exceeding. Since the compression limit of a compression spring with a small spring constant can be defined reliably, it is possible to control the transition point where the biasing element moves from the composite spring constant to the spring constant of a large compression spring, and the spring device operates more reliably. Can be made.

  If the first case and the second case are formed in the same shape, both cases can be made into a common part, and the manufacturing cost of the spring device can be reduced.

  According to the spring device in which the first and second compression springs are compressed and assembled between the inner surface of the end wall having the rod hole of the case and one end of the rod, the first and second compression springs are compressed in a state of being accommodated in the case. Since the spring can be expanded and contracted, it is possible to prevent the compression spring from coming off from the axial direction of the rod, and to always apply an appropriate tensile biasing force to the object. It is also excellent in that it is possible to reliably prevent the occurrence of malfunction due to dust adhering to the compression spring.

  If each of the first rod and the second rod is provided with a stopper that restricts the compression limit of the first compression spring and / or the second compression spring, the compression spring is excessively compressed and loses elasticity. The risk of exceeding the yield point can be avoided. Since the compression limit of a compression spring with a small spring constant can be defined reliably, it is possible to control the transition point where the biasing element moves from the composite spring constant to the spring constant of a large compression spring, and the spring device operates more reliably. Can be made.

  If the 1st rod and the 2nd rod are formed in the same shape, both rods can be made into common parts, and reduction of the manufacturing cost of a spring device can be aimed at.

(First Embodiment) FIGS. 1 to 6 show a first embodiment according to the engaging Ruri link mechanism parallel mechanism of the industrial robot to the present invention. As shown in FIGS. 3 and 4, the parallel mechanism 1 includes a base 2 suspended and supported on a ceiling, a rail, and the like, three arms 6 connected to the base 2, and free ends of the arms 6. It has the link mechanism 3 connected, and the operation part 4 supported by the lower end of these link mechanisms 3. The operation unit 4 is attached with a hand unit that is a gripping element for the workpiece. Each arm 6 is independently driven by a drive motor 5 provided on the base 2. A rotating shaft 8 extends from the base 2 via a universal joint, and the hand portion is rotated by the rotating shaft 8.

  Each link mechanism 3 includes a pair of links 7 and 7 arranged in parallel, and these links 7 and 7 are connected by a total of four ball joints 9 arranged at the upper end and the lower end. . In FIG. 1, the code | symbol 10 shows the joint member which connects the ball joints 9 and 9 of an upper end and a lower end. The joint member 10 on the upper end side is provided at the free end of the arm 6, and the joint member 10 on the lower end side is provided in the operation unit 4.

  As shown in FIG. 1, each ball joint 9 includes a spherical ball portion 11 provided at the end portion of the joint member 10 and a cup-shaped receiving portion 12 formed at the end portion of the link 7. The concave surface 12a of the receiving portion 12 is formed on the inner surfaces facing each other in both links 7 and 7, and about half of the ball portion 11 receives the receiving portion 12 in a normal state.

  A spring device 15 that applies a pulling urging force to the links 7 and 7 is attached closer to the center in the length direction of the links 7 and 7 than the joint members 10. As shown in FIGS. 2 and 5, each spring device 15 is arranged between the first and second cases 16, 17, the first and second compression springs 19, 20, and both cases 16, 17. It is composed of one rod 21 or the like. Specifically, each spring device 15 is connected to the left case 7 so as to be swingable around the shaft 36L and to the right link 7 so as to be swingable around the shaft 36R. The second case 17, the first compression spring 19 housed in the first case 16, the second compression spring 20 housed in the second case 17, and one end side inserted into the first case 16. The other end side is constituted by a rod 21 or the like inserted into the second case 17. As shown in FIGS. 2 and 5, the first case 16 and the second case 17 have a bottomed cylindrical shape having openings on the left and right inner sides, and the openings of the cases 16 and 17 include Disc-shaped sealing members 23 and 24 having rod holes 23 a and 24 a that allow insertion of the rod 21 are fixed by screws 25. The sealing members 23 and 24 constitute end walls of the cases 16 and 17. Both compression springs 19 and 20 are compression coil springs, and are attached to the rod 21 in an outer fitting state in the assembled state as shown in FIG.

  The rod 21 includes a horizontally long rod body 22 and end fittings 27 and 28 fastened and fixed to the left and right ends of the rod body 22 by screws 26. Flange portions 27a and 28a are provided at the end portions of the end fittings 27 and 28. In the assembled state, the first compression spring 19 is connected to the flange portion 27a of the end fitting 27 and the end wall (sealing) of the first case 16. It is held in a compressed state between the inner surface of the member 23). The second compression spring 20 is held in a compressed state between the flange portion 28 a of the end fitting 28 and the inner surface of the end wall (sealing member) 24 of the second case 17.

  Ring-shaped stoppers 31 and 31 for restricting the compression limit of the compression springs 19 and 20 are formed on the outer peripheral surfaces of the connecting portions of the end fittings 27 and 28 with the rod body 22 so as to protrude. The outer diameter of the stoppers 31 and 31 is set larger than the inner diameter of the rod holes 23a and 24a of the sealing members 23 and 24. However, when the spacing distance between the links 7 and 7 becomes large and the compression springs 19 and 20 are compressed, the stoppers 31 and 31 come into contact with the inner surfaces of the sealing members 23 and 24, so that the compression spring 19 • 20 compression limits are regulated.

  As shown in FIG. 5, a small-diameter ring 32 is attached to the inner peripheral surfaces of the rod holes 23 a and 24 a of the sealing members 23 and 24. Further, a large-diameter ring 33 is attached to the outer peripheral surfaces of the flanges 27a and 28a of the end fittings 27 and 28. These rings 32 are in contact with the outer peripheral surface of the rod body 22 and the ring 33 is in contact with the inner surface of the cylindrical wall of the cases 16 and 17, thereby preventing rattling of the cases 16 and 17 during reciprocating movement relative to the rod 21. . Further, if the ring 32 is mounted on the inner peripheral surfaces of the rod holes 23a and 24a, the effect of dust entry into the cases 16 and 17 can be expected. These rings 32 and 33 are made of an elastic material such as silicon rubber.

  The bottom wall 16a of the first case 16 has a male threaded portion 34 projecting outward. The male threaded portion 34 is inserted into a through hole 35a provided in the bracket 35L, and the male threaded portion 34 has a nut. By tightening 39, the bracket 35 </ b> L is fixed to the outer surface of the first case 16. The bracket 35R is fixed to the outer surface of the second case 17 by the same procedure.

  The first case 16 and the second case 17 or the sealing members 23 and 24 are formed in the same shape and are made into common parts. Further, the end fittings 27 and 28 of the rod 21 are also formed in the same shape and are made into common parts. Thus, by making various parts into common parts, the trouble of parts management is reduced, and it can contribute to the reduction of the overall cost of the spring device 15.

  In addition, in this embodiment, it is noted that the compression springs 19 and 20 having different spring constants are employed. That is, the compression springs 19 and 20 have different wire diameters or different numbers of turns, and the main points are different spring constants. In the first embodiment, the spring constant (k1) of the first compression spring 19 is made larger than the spring constant (k2) of the second compression spring 20.

  In the spring device 15 configured as described above, the first compression spring 19 pushes between the inner surface of the flange portion 27a of the end fitting 27 of the rod 21 and the end wall (sealing member 23) of the first case 16. The second compression spring 20 is urged to spread, and the second compression spring 20 pushes between the inner surface of the flange portion 28a of the end fitting 228 of the rod 21 and the end wall (sealing member 24) 17a of the second case 17. Energize. That is, in the assembled state in the cases 16, 17, the first compression spring 19 has a small facing distance between the end wall (sealing member 23) of the first case 16 and the flange portion 27 a of the end fitting 7 of the rod 21. The second compression spring 20 exerts an elastic urging force that resists displacement movement in the direction in which the end wall 28 of the second case 17 (sealing member 24) faces the flange portion 28a of the end fitting 28 of the rod 21. It exerts an elastic biasing force that resists displacement movement in the direction of decreasing. Due to the elastic biasing force of the first and second compression springs 19 and 20 as described above, the spring device 15 assembled between the links 7 and 7 is pulled in the direction in which the distance between the links 7 and 7 is reduced. By exerting a force, the receiving portion 12 of the ball joint 9 is pressed against the ball portion 11 to prevent the receiving portion 12 from coming off from the ball portion 11. As described above, both the links 7 and 7 constituting each link mechanism 3 are maintained in a state of being parallel to each other via the joint member 10 and are combined in the vertical and lateral directions with the ball joint 9 as a fulcrum. Oscillation is possible.

  When an external force is applied from the assembled state as described above and the distance between the links 7 and 7 is increased, the compression springs 19 and 20 are further compressed. The compression allowance of the compression springs 19 and 20 at this time is large for the first compression spring 19 having a large spring constant and small for the second compression spring 20 having a small spring constant. Therefore, the end wall (sealing member 24) of the second case 17 comes into contact with the stopper 31 of the end fitting 28, and the second compression spring 20 reaches the compression limit before the first compression spring 19. After the second compression spring 20 reaches the compression limit in this manner, when an external force is further applied to the links 7 and 7 and the distance between the two compression points 7 and 7 is increased, only the first compression spring 19 is compressed. . The compression limit of the first compression spring 19 is also regulated by the stopper 31 of the rod 21.

  Next, the change in the spring constant of the spring device 15 according to the change in the distance between the links 7 and 7, in other words, the change in the pulling force of the spring device 15 will be described with reference to FIG. In FIG. 6, X0 indicates the compression amount (displacement amount) of the urging element when the spring device 15 is attached between the links 7 and 7 (initial state). That is, in the initial state in which the spring device 15 is mounted between the links 7 and 7, the springs 19 and 20 are compressed by X0, and at this time, the spring device 15 exerts a tensile biasing force of F0. At this time, the combined spring constant (k0) of the entire urging element composed of the first compression spring 19 and the second compression spring 20 is smaller than the individual spring constants (k1 and k2) of the compression springs 19 and 20. It becomes. That is, since the combined spring constant (k0) of the two compression springs arranged in series is represented by (k1 · k2) / (k1 + k2), for example, the spring constant of the first compression spring 19 is 6 ( N / mm) and the spring constant of the second compression spring 20 is 3 (N / mm), the combined spring constant (k0) of 2 (N / mm) is obtained for the spring device 15 as a whole.

  Therefore, in the initial state as described above, the biasing element of the spring device 15 has a composite spring constant (k0) smaller than the spring constants (k1 and k2) of the individual compression springs 19 and 20. A small tensile biasing force derived from the small composite spring constant (k0) is applied between the links 7 and 7. As a result, the pulling force acting on both links 7 and 7 can be suppressed and the pressing force of the receiving portion 12 against the ball portion 11 of the ball joint 9 can be suppressed, so that the ball portion 11 or the receiving portion 12 is worn. It can be effectively prevented. In addition, since the load required by a drive mechanism such as the motor 5 that drives the link mechanism 3 can be suppressed, there is an advantage that an unnecessary increase in power consumption can be prevented. Further, the small pull biasing force derived from the composite spring constant (k0) as described above is maintained until the end wall (sealing member) 24 contacts the stopper 31 and the second compression spring 20 reaches the compression limit. (X1 in FIG. 6). In FIG. 6, X1 indicates the amount of displacement of the entire biasing element when the second compression spring 20 reaches the compression limit.

  When an external force is further applied to the links 7 and 7 from this state and the distance between the two 7 and 7 is increased, only the first compression spring 19 is compressed. In this state, a large tensile biasing force derived from the large spring constant (k1) of the first compression spring 19 is exhibited. In FIG. 6, the displacement amount X <b> 2 indicates the displacement amount when the receiving portion 12 is detached from the ball portion 11. At this time, when the spring constant is k0 (indicated by a broken line in FIG. 6), the receiving portion 12 is detached from the ball portion 11 by the external force of F1, whereas when the spring constant is k1, The receiving portion 12 does not come off from the ball portion 11 until the external force F2 is applied. Thereby, it is possible to reliably prevent the receiving portion 12 from coming off from the ball portion 11.

  As described above, according to the spring device 15 according to the present embodiment, a weak tensile biasing force is exhibited in a normal use state, and a large tensile biasing force is exhibited when the distance between the links 7 and 7 is increased. Therefore, according to the spring device 15, the conflicting problems of preventing the wear of the ball part 11 and the receiving part 12 in the normal use state and preventing the receiving part 12 from coming off from the ball part 11 can be solved simultaneously. Can do.

(Second Embodiment) FIGS. 7 to 9 show a second embodiment applying the engaging Ruri link mechanism parallel mechanism of the industrial robot to the present invention. As shown in FIGS. 7 and 8, the spring device 15 according to the second embodiment includes a cylindrical case 40 in which a first compression spring 19 and a second compression spring 20 are accommodated in series, and the case 40. A first rod 41 inserted from the left end and connected to the left link 7 via a bracket 35L, and a second rod inserted from the right end of the case 40 and connected to the right link 7 via a bracket 35R. Rod 42. The first rod 41 and the second rod 42 are configured to be able to reciprocate in the axial direction of the case 40. As shown in FIG. 9, a sealing member 43 having a rod hole 43 a allowing insertion of the first rod 41 is fixed to the left end of the case 40 with a screw 46, and a second rod 42 is attached to the right end of the case 40. An end wall 44 having a rod hole 44 a that allows insertion of the screw is fixed by a screw 46.

  As shown in FIG. 9, the first rod 41 has a cylindrical rod body 41 a and a flange portion 41 b that projects from one end of the rod body 41 a, and a screw hole for the bolt 50 on the other end. 41c is formed. A stopper 41d is formed at the center of the rod body 41a in the axial direction so as to protrude from the inner surface of the end wall (sealing member 43) of the opposing case 40 so as to restrict the compression limit of the first compression spring 19. ing. The second rod 42 has the same shape as the first rod 41, and includes a rod body 42a, a flange portion 42b, a screw hole 42c, and a stopper 42d. After the compression springs 19 and 20 are fitted on the rod main bodies 41a and 42a so as to fit outside, the bolts 50 are inserted into the case 40 from the outside through the through holes 35a of the brackets 35L and 35R and the rod holes 43a and 44a. The brackets 35L and 35R and the rods 41 and 42 are connected by inserting and screwing the male threaded portion 50a of the bolt 50 into the screw holes 41c and 42c. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same members, and descriptions thereof are omitted.

  The spring device 15 having the above configuration has the same operational effects as the spring device 15 according to the first embodiment. That is, the first and second compression springs 19 and 20 are formed between the end walls (sealing members 43 and 44) of the case 40 and the end portions (flange portions 41b and 42b) of the first and second rods (41 and 42). A tensile biasing force is applied between the links 7 and 7 by exerting an elastic biasing force that resists displacement movement in a direction in which the facing distance becomes smaller.

  Therefore, in the normal operating state of the link mechanism 3, the spring device 15 biases both the links 7 and 7 with a small pull biasing force derived from the combined spring constant (k0). It is possible to effectively prevent the ball portion 11 from being pressed with an appropriate force and the ball portion 11 or the receiving portion 12 to be worn. After the second compression spring 20 reaches the compression limit, the links 7 and 7 are prevented from being greatly displaced in the separating direction because the links 7 and 7 are pulled by the large pulling force of the first compression spring 19. Further, it is possible to reliably prevent the receiving portion 12 from coming off from the ball portion 11 of each ball joint 9.

To a first embodiment of the present invention is a vertical sectional view showing an essential part of the engagement ruri link mechanism. It is the sectional view on the AA line of FIG. It is a top view of the parallel mechanism to which the present invention is applied. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is an exploded view of the spring device of the first embodiment. It is a figure for demonstrating the urging | biasing force of the spring apparatus of 1st Embodiment. To a second embodiment of the present invention is a vertical sectional view showing an essential part of the engagement ruri link mechanism. It is CC sectional view taken on the line of FIG. It is an exploded view of the spring apparatus of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Link mechanism 7 Link 9 Ball joint 15 Spring apparatus 16 1st case 17 2nd case 19 1st compression spring 20 2nd compression spring 21 Rod 23 End wall (sealing member) of 1st case
23a Rod hole 24 End wall of second case (sealing member)
24a Rod hole 31 Stopper 40 Case 41 First rod 42 Second rod 43 Case end wall (sealing member)
43a Rod hole 44 End wall of case (sealing member)
44a Rod hole

Claims (6)

A pair of links whose ends are arranged in parallel via a ball joint;
For the purpose of giving a tensile biasing force to these links, a spring device mounted between both links,
With
The spring device is
A first compression spring;
A second compression spring disposed in series with the first compression spring and having a spring constant smaller than the spring constant of the first compression spring;
A stopper for regulating the compression limit of the second compression spring;
With
The spring device applies a tensile biasing force between the links by using an elastic biasing force of the first and second compression springs to return from a compressed state to a natural length state,
The spring device gives a tension biasing force between the links derived from a combined spring constant of two compression springs arranged in series until the second compression spring reaches a compression limit by the stopper, A link of a parallel link , wherein after the second compression spring reaches a compression limit, a tension biasing force derived from a spring constant of the first compression spring is applied between the links. mechanism. The spring device is
A cylindrical first case that houses the first compression spring and is connected to one of the links ;
A cylindrical second case that houses the second compression spring and is connected to the other link ;
One end is inserted into the first case the first case via a rod hole formed in one of the other end through a rod hole formed in one of said second casing in said second casing A rod to be inserted ,
With
The first compression spring is assembled in an externally fitted state to the rod between the inner surface of the end wall having the rod hole of the first case and one end of the rod .
The second compression spring, the inner surface of the end wall having the rod hole of the second case, between one end of the rod, is assembled in a fitted state in the rod,
The first and second cases are configured to reciprocate in the axial direction of the rod;
The first and second compression springs exhibit an elastic biasing force that resists displacement movement in a direction in which the facing distance between the end walls of the first and second cases and the end of the rod decreases. The link mechanism of the parallel link according to claim 1, wherein the link bias mechanism is configured to apply a tensile biasing force between the links. The link mechanism for a parallel link according to claim 2 , wherein the stopper is provided at one end of the rod that receives the second compression spring . The link mechanism of the parallel link according to claim 2 or 3, wherein the first case and the second case are formed in the same shape . The spring device is
A cylindrical case in which the first compression spring and the second compression spring are accommodated in series;
A first rod inserted into one end of the case in the axial direction and connected to one link ;
A second rod inserted into the other end side in the axial direction of the case and connected to the other link ;
With
Said first rod and the second rod is configured to be reciprocated in the axial direction of the case,
Rod holes that allow insertion of the first and second rods are provided in both end walls in the axial direction of the case,
The first and second compression springs are assembled in a compressed manner between the inner surface of the end wall having the rod hole of the case and one end of the rod,
The first and second compression springs exhibit an elastic biasing force that resists displacement movement in a direction in which the facing distance between the end wall of the case and the ends of the first and second rods decreases. The link mechanism of the parallel link of Claim 1 comprised so that tension | pulling urging | biasing force might be given between the said target objects . The parallel link mechanism according to claim 5 , wherein the stopper is provided on the second rod .

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