CN108797666B

CN108797666B - Civil engineering is with multi-functional construction equipment of environmental protection

Info

Publication number: CN108797666B
Application number: CN201810521815.2A
Authority: CN
Inventors: 赵学彬; 郭艳辉; 王赐福
Original assignee: Individual
Current assignee: Zhao Xuebin
Priority date: 2018-05-28
Filing date: 2018-05-28
Publication date: 2021-11-05
Anticipated expiration: 2038-05-28
Also published as: CN108797666A

Abstract

The invention discloses environment-friendly multifunctional construction equipment for civil engineering, which comprises a rack, wherein a hammering device is arranged on the rack, the hammering device comprises a shaft bracket and a first sliding groove, the shaft bracket and the first sliding groove are fixed on the rack, a hammering block is arranged in the first sliding groove in a sliding manner, a first driving shaft is rotatably arranged on the shaft bracket and is driven by a second motor to rotate, a first support is fixed at one end of the first driving shaft, the first driving shaft is fixed at the center of the first support, two guide columns are symmetrically arranged at two ends of the first support by taking the first driving shaft as a symmetric center, a first rotating shaft is arranged on the hammering block, a linkage rod is rotatably connected on the first rotating shaft, an annular ring is arranged at one end of the linkage rod, an annular bulge is arranged on the inner side wall of the annular ring, and a circular disc is slidably arranged on the annular bulge. The hammering device is simple in structure, reasonable in design and practical.

Description

Civil engineering is with multi-functional construction equipment of environmental protection

Technical Field

The invention relates to the technical field of buildings, in particular to environment-friendly multifunctional construction equipment for civil engineering.

Background

The robot in the prior art has a complex structure, can act only by matching a plurality of motors, and needs to be improved; the existing excavating operation device has complex structural design and high manufacturing cost; the existing hammering device is complex in structural design, high in cost and unreasonable in design.

Disclosure of Invention

The invention aims to solve the technical problem of providing environment-friendly multifunctional construction equipment for civil engineering, which aims to solve the problems that in the prior art, a robot has a complex structure, can act only by matching a plurality of motors and needs to be improved; the existing excavating operation device has complex structural design and high manufacturing cost; the existing hammering device has the technical problems of complex structural design, high cost and unreasonable design.

In order to solve the above technical problems, an embodiment of the present invention provides an environment-friendly multifunctional construction equipment for civil engineering, including a frame, wherein a hammering device is arranged on the frame, the hammering device includes a shaft bracket fixed on the frame and a first chute, a hammering block is slidably arranged in the first chute, a first driving shaft is rotatably arranged on the shaft bracket, the first driving shaft is driven by a second motor to rotate, a first bracket is fixed at one end of the first driving shaft, the first driving shaft is fixed at the center of the first bracket, two ends of the first bracket are symmetrically provided with a guide pillar by taking the first driving shaft as a symmetric center, the hammering block is provided with a first rotating shaft, the first rotating shaft is rotatably connected with a linkage rod, one end of the linkage rod is provided with an annular ring, an annular bulge is arranged on the inner side wall of the annular ring, and a circular disk is slidably arranged on the annular bulge, the eccentric position of the disc is rotatably connected with the first driving shaft, two symmetrical arc-shaped chutes are formed in the disc by taking the first driving shaft as a circle center, two guide pillars on the first support are respectively arranged in one arc-shaped chute in a sliding mode, a connecting column is arranged on the disc close to the edge, and a tension spring is arranged between the connecting column and the rack;

the walking device comprises a walking motor, six groups of walking feet and four driving gears, three groups of walking feet are symmetrically arranged on two sides of the rack, two driving gears are symmetrically arranged on two sides of the rack, each walking foot comprises a central gear, an upper first gear and a lower first gear which are positioned in the same vertical direction, the central gear, the upper first gear and the lower first gear are respectively and rotatably connected to the rack through gear rotating shafts, the upper first gear is meshed above the central gear, the lower first gear is meshed below the central gear, the center of the upper first gear is fixedly connected with an upper connecting rod, the center of the lower first gear is fixedly connected with a lower connecting rod, the outer end of the upper connecting rod is fixedly connected to the center of the second gear, and the outer ends of the upper connecting rod and the lower connecting rod are rotatably connected with a feet guide rod, the foot tool guide rod, the upper connecting rod, the lower connecting rod, the upper first gear, the central gear and the lower first gear which are meshed with each other form a parallelogram mechanism, the foot tool guide rod is rotatably connected with a third gear, the third gear is meshed below the second gear, the center of the third gear is fixedly connected with a first gear connecting rod, the outer end of the first gear connecting rod is rotatably connected with the first connecting rod, the outer end of the first connecting rod is rotatably connected with a foot tool grounding rod, the lower end of the foot tool guide rod extends downwards to be provided with a guide sliding sleeve, the foot tool grounding rod is slidably sleeved in the guide sliding sleeve, the length of the first connecting rod is larger than that of the first gear connecting rod, a driving gear is arranged between two groups of walking foot tools on the same side, the driving gear is rotatably connected to the rack through a driving shaft, and the output end of the walking motor is connected with the driving shaft for driving the walking motor to rotate, the driving shaft of the driving gear and the gear wheel shaft of the central gear are positioned on the same plane; the upper first gear, the central gear, the lower first gear and the second gear are the same gears, and the gear ratio of the second gear to the third gear is 2: 1;

the rack is made of corrosion-resistant stainless steel, and the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 17-18%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15% and the balance Fe.

Six upper connecting rods on six groups of walking foot tools are named as a left first upper connecting rod, a left second upper connecting rod, a left third upper connecting rod, a right first upper connecting rod, a right second upper connecting rod and a right third upper connecting rod according to the directions, the left second upper connecting rod is arranged between the left first upper connecting rod and the left third upper connecting rod, the right second upper connecting rod is arranged between the right first upper connecting rod and the right third upper connecting rod, the left second upper connecting rod, the right first upper connecting rod and the right third upper connecting rod have the same initial rotation angle position, and the initial rotation angles of the left first upper connecting rod and the right first upper connecting rod are different by 180 degrees.

The soil excavating device comprises a sliding groove fixed on the frame and a rotating wheel rotationally connected to the frame through a rotating shaft, the sliding groove is arranged along the horizontal direction, a sliding frame is slidably mounted on the sliding groove, a first connecting rod rotating shaft is arranged at the eccentric position of the rotating wheel, a second connecting rod rotating shaft is arranged on the sliding frame, a second connecting rod is arranged between the first connecting rod rotating shaft and the second connecting rod rotating shaft, the sliding groove is provided with a vertical guide hole, a guide rod is slidably arranged on the guide hole, a tool mounting frame is fixed at the lower end of the guide rod, a pressure spring is arranged on the guide rod, the lower end face of the pressure spring abuts against the upper surface of the tool mounting frame, the upper end face of the pressure spring abuts against the sliding frame, the tool mounting frame is provided with a hollow through groove, and an abutting rod is further rotationally arranged on the second connecting rod rotating shaft, the outer end of the propping rod props against the upper surface of the hollow through groove, the propping rod is fixed with the second connecting rod, and the lower end of the tool mounting frame is provided with an excavation tool.

The technical scheme of the invention has the following beneficial effects:

the walking device can walk stably, only one walking motor is needed to realize the alternate motion of the six supporting legs, so that the walking function is realized, and the structural design is ingenious. The invention provides an earth-moving device which can realize earth-moving by making an earth-moving tool generate an elliptical motion track through a simple mechanical structure. The hammering device is simple in structure, reasonable in design and practical.

Drawings

Fig. 1 is a schematic structural view of the present invention, in which a cross-sectional portion is a frame.

Fig. 2 is a structural view of the traveling apparatus of the present invention.

Fig. 3 is a first structural view of the walking foot tool of the walking device of the present invention.

Fig. 4 is a second configuration diagram of the walking foot tool of the walking device of the present invention.

Fig. 5 is a partial configuration view of the running gear of the present invention.

Fig. 6 is a first state change diagram of the walking foot tool of the walking device of the invention.

Fig. 7 is a state change diagram of the walking foot tool of the walking device of the present invention.

Fig. 8 is a perspective view of the earth-moving work apparatus of the present invention.

Fig. 9 is an exploded view of the earth-moving working device of the present invention.

Fig. 10 is a partial configuration view of the excavator according to the present invention.

Fig. 11 is a movement locus diagram of the earth-moving working device of the present invention.

Fig. 12 is a perspective view of the hammering apparatus of the present invention.

Fig. 13 is an exploded view of the hammering device of the present invention.

Fig. 14 shows a first state of the hammering apparatus of the present invention.

Fig. 15 is a second state diagram of the hammering apparatus of the present invention.

Fig. 16 is a third state diagram of the hammering apparatus of the present invention.

Fig. 17 is a fourth state diagram of the hammering apparatus of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

For convenience of explanation, the right direction in fig. 1 is the front, front end, front portion, forward direction, and the left direction is the rear, rear end, rear portion, backward direction.

As shown in fig. 1 to 7, an embodiment of the present invention provides an environment-friendly multifunctional construction equipment for civil engineering, including a frame 100, a traveling device 10 is provided on the frame 100, the traveling device 10 includes a traveling motor (not shown), six groups of traveling feet 11 and four driving gears 12, three groups of traveling feet 11 are symmetrically provided on two sides of the frame 100, two driving gears 12 are symmetrically provided on two sides of the frame 100, the traveling feet 11 include a central gear 13, an upper first gear 14 and a lower first gear 15 which are located in the same vertical direction, the central gear 13, the upper first gear 14 and the lower first gear 15 are respectively rotatably connected to the frame 100 through gear rotating shafts, two ends of each gear rotating shaft are respectively connected to a corresponding gear on one group of the traveling feet, the upper first gear 14 is meshed above the central gear 13, the lower first gear 15 is meshed below the central gear 13, the center of the upper first gear 14 is fixedly connected with an upper connecting rod 16, the center of the lower first gear 15 is fixedly connected with a lower connecting rod 17, the outer end of the upper connecting rod 16 is fixedly connected with the center of the second gear 18, the outer ends of the upper connecting rod 16 and the lower connecting rod 17 are rotatably connected with a foot guide rod 19, the upper connecting rod and the lower connecting rod are equal in length and are arranged in parallel, the foot guide rod 19, the upper connecting rod 16, the lower connecting rod 17, the upper first gear 14, the central gear 13 and the lower first gear 15 which are meshed with each other form a parallelogram mechanism, the specific structure is that a connecting shaft 20 is fixed at the outer ends of the upper connecting rod 16 and the lower connecting rod 17, the second gear 18 is fixed on the connecting shaft 20 of the upper connecting rod 16, the foot guide rod 19 is rotatably connected on the connecting shaft 20, and a third gear 21 is rotatably connected on the foot guide rod 19, the third gear 21 is meshed below the second gear 18, a first gear connecting rod 22 is fixedly connected at the center of the third gear 21, the outer end of the first gear connecting rod 22 is rotatably connected with a first connecting rod 23, the outer end of the first connecting rod 23 is rotatably connected with a foot grounding contact rod 24, the lower end of the foot tool guide rod 24 extends downwards to be provided with a guide sliding sleeve 25, the connecting shaft 20 at the outer end of the lower connecting rod 17 is connected with the middle position of the foot tool guide rod 19, the foot tool grounding rod 24 is slidably sleeved in the guide sliding sleeve 25, the length of the first connecting rod 23 is greater than that of the first gear connecting rod 22, a driving gear 12 is arranged between the two groups of walking foot tools 10 positioned on the same side, the driving gear 12 is rotatably connected to the frame 100 through a driving shaft 26, the output end of the walking motor is connected to the driving shaft 26 for driving the walking motor to rotate, the driving shaft 26 of the driving gear 12 and the gear rotating shaft of the central gear 13 are positioned on the same plane; the upper first gear 14, the central gear 13, the lower first gear 15 and the second gear 18 are the same gears, and the gear ratio of the second gear 18 to the third gear 21 is 2: 1, the second gear rotates one circle and can drive the third gear to rotate two circles.

Six upper links on the six groups of walking feet 11 are named as a left upper link 111, a left upper link 112, a left upper link 113, a right upper link 114, a right upper link 115 and a right upper link 116 according to the directions, the left upper link 112 is arranged between the left upper link 111 and the left upper link 113, the right upper link 115 is arranged between the right upper link 114 and the right upper link 116, the left upper link 112, the right upper link 114 and the right upper link 116 have the same initial rotation angle position, the right upper link 115, the left upper link 111 and the left upper link 113 have the same initial rotation angle position, and the initial rotation angles of the left upper link 111 and the right upper link 114 are different by 180 degrees.

During movement, the upper connecting rod, the lower connecting rod and the first gear connecting rod of each group of walking foot tools perform full rotation movement, the three groups of walking foot tools perform synchronous movement, wherein when the foot tool grounding rods of the three groups of walking foot tools are in a grounding state, the other three groups of walking foot tools are in a grounding state, and when the foot tool grounding rods of the six groups of walking foot tools simultaneously contact the ground, the state switching of the foot tools contacting the grounding rods is completed. For convenience of description, the six groups of walking feet are respectively named as a left first walking foot 101, a left second walking foot 102, a left third walking foot 103, a right first walking foot 104, a right second walking foot 105 and a right three walking foot 106, the movement tracks of the left first walking foot 101, the left third walking foot 103 and the right second walking foot 105 are the same, and the movement tracks of the left second walking foot 102, the right first walking foot 104 and the right three walking foot 106 are the same. Specifically, in the moving process, the walking device moves forward, as shown in fig. 6, taking the right walking foot 104 as an example, the driving gear drives the central gear to rotate counterclockwise, the upper first gear and the lower first gear which are engaged with the upper connecting rod rotate clockwise to drive the upper connecting rod and the lower connecting rod to synchronously rotate clockwise, because the second gear is fixed with the upper connecting rod, the second gear drives the third gear to rotate, the third gear drives the first connecting rod to swing downwards through the first gear connecting rod, because the foot tool guide rod is limited by the guide sliding sleeve, the first connecting rod drives the foot tool guide rod to move downwards, from the first state to the second state, the central gear rotates by 90 degrees, the third gear rotates by 180 degrees, the right walking foot tool completes the transition from the ground-contacting state to the ground-contacting state, and when the state two is in, make the stander in the highest position, from state two to state three, the right walking foot utensil finishes the transition from touching the ground state to off-ground state. As shown in fig. 7, taking the right second walking foot device 105 as an example, the state of the right second walking foot device corresponds to the state of the right first walking foot device in fig. 6 at the same time, and at this time, the right second walking foot device is in the ground contact state.

As shown in fig. 1 and 8 to 11, the frame 100 is further provided with an earth-moving device 60, the earth-moving device 60 includes a sliding groove 61 fixed on the frame 100 and a rotating wheel 62 rotatably connected to the frame 100 through a rotating shaft 601, the sliding groove 61 is arranged along a horizontal direction, a sliding frame 63 is slidably mounted on the sliding groove 61, a first connecting rod rotating shaft 602 is arranged at an eccentric position of the rotating wheel 62, a second connecting rod rotating shaft 603 is arranged on the sliding frame 63, a second connecting rod 64 is arranged between the first connecting rod rotating shaft 602 and the second connecting rod rotating shaft 603, both ends of the second connecting rod 64 are rotatably connected, the sliding groove 61 is provided with a vertical guide hole 605, a guide rod 65 is slidably arranged on the guide hole 605, a tool mounting frame 66 is fixed at a lower end of the guide rod 65, a pressure spring 67 is arranged on the guide rod 65, a lower end surface of the pressure spring 67 abuts against an upper surface of the tool mounting frame 66, the upper end face of the pressure spring 67 abuts against the sliding frame 63, the tool mounting frame 66 is provided with a hollow through groove 606, the second connecting rod rotating shaft 603 is further rotatably provided with an abutting rod 68, the outer end of the abutting rod 68 abuts against the upper surface of the hollow through groove 606, the abutting rod 68 is fixed with the second connecting rod 64, the lower end of the tool mounting frame 66 is provided with an excavating tool 69, the excavating tool 69 is vertically arranged, and the excavating tool can be selected to be different in length for facilitating operation. The first link shaft has a vertical position height higher than that of the second link shaft, and the earth-moving work tool is located between the first link shaft and the second link shaft in terms of a position in the horizontal direction. As shown in fig. 11, when the earth-moving device is in operation, the rotating wheel rotates counterclockwise, the second connecting rod drives the sliding frame to reciprocate horizontally on the sliding groove, so that the tool mounting frame has a reciprocating motion horizontally, and the guide rod on the sliding frame drives the tool mounting frame to reciprocate vertically, so that the earth-moving tool on the tool mounting frame can generate an elliptical motion track, thereby forming an earth-moving action.

As shown in fig. 1 and 12 to 17, a hammering device 30 is disposed on the frame, the hammering device 30 includes a shaft frame 31 fixed on the frame 100 and a first sliding chute 32, a hammering block 33 is slidably disposed in the first sliding chute 32, a first driving shaft 34 is rotatably disposed on the shaft frame 31, the first driving shaft 34 is driven to rotate by a second motor (not shown), a first bracket 35 is fixed at one end of the first driving shaft 34, the first driving shaft 34 is fixed at the center of the first bracket 35, a guide post 36 is symmetrically disposed at two ends of the first bracket 35 by taking the first driving shaft 34 as a symmetric center, a first rotating shaft 361 is disposed on the hammering block 33, a linkage rod 37 is rotatably connected to the first rotating shaft 361, an annular ring 38 is disposed at one end of the linkage rod 37, an annular protrusion 381 is disposed on an inner side wall of the annular ring 38, and a circular disk 39 is slidably disposed on the annular protrusion 381, the eccentric position of the disc 39 is rotatably connected with the first driving shaft 34, the disc 39 is provided with two symmetrical arc chutes 40 by taking the first driving shaft 34 as a circle center, the two guide pillars 36 on the first support 35 are respectively and slidably arranged in one of the arc chutes 40, the edge of the disc 39 close to the edge is provided with a connecting column 41, a tension spring 42 is arranged between the connecting column 41 and the rack 100, and after the disc rotates, the tension spring is periodically driven to rapidly reset so as to drive the hammering block to hammer. The movement state of the hammering device is described as follows: starting from the state a in fig. 14, the first driving shaft 34 rotates the first bracket 35, the guide post 36 slides relatively in the arc chute 40, the first bracket 35 is in idle rotation, the disk 39 is not driven to rotate, until the guide post 36 rotates to the state B in fig. 15, the guide post 36 starts to drive the disk 39 to rotate, the first driving shaft 34 is at the eccentric position of the disk, therefore the motion track of the disk is similar to the motion of an eccentric turntable, thus driving the hammering block to move, from the state B in fig. 15 to the state C in fig. 16, the disk drives the hammering block to retreat through an annular ring, when reaching the state C in fig. 16, the straight line where the tension spring 42 is elongated coincides with the first driving shaft, the disk is in a critical state, next time, the disk rapidly rotates by nearly half a circle due to the tension of the tension spring, thus driving the hammering block to rapidly move forward, thus realizing the hammering operation, this shows a cyclic process, as shown in state D in fig. 17.

The rack is made of corrosion-resistant stainless steel, and the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 17-18%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15% and the balance Fe. The corrosion-resistant stainless steel has excellent corrosion resistance, mechanical property and welding property.

The first embodiment is as follows:

the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 17%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15% and the balance Fe.

Example two:

the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 18%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15% and the balance Fe.

Example three:

the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 17.5%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15% and the balance Fe.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An environment-friendly multifunctional construction device for civil engineering comprises a frame and is characterized in that a hammering device is arranged on the frame, the hammering device comprises a shaft bracket and a first sliding groove which are fixed on the frame, a hammering block is arranged in the first sliding groove in a sliding manner, a first driving shaft is arranged on the shaft bracket in a rotating manner and driven to rotate by a second motor, a first support is fixed at one end of the first driving shaft, the first driving shaft is fixed at the center of the first support, two guide columns are symmetrically arranged at two ends of the first support by taking the first driving shaft as a symmetric center, a first rotating shaft is arranged on the hammering block, a linkage rod is rotatably connected on the first rotating shaft, an annular ring is arranged at one end of the linkage rod, an annular bulge is arranged on the inner side wall of the annular ring, a disc is arranged on the annular bulge in a sliding manner, and the first driving shaft is rotatably connected at the eccentric position of the disc, the disc is provided with two symmetrical arc chutes by taking the first driving shaft as a circle center, two guide pillars on the first support are respectively arranged in one arc chute in a sliding manner, a connecting pillar is arranged at the edge of the disc close to the edge, and a tension spring is arranged between the connecting pillar and the rack;

the rack is made of corrosion-resistant stainless steel, and the corrosion-resistant stainless steel comprises the following components in percentage by mass: c: 0.02%, Si: 0.8%, Mn: 1%, S: 0.01%, P: 0.03%, Cr: 20%, Ni: 17-18%, Mo: 7%, Cu: 1%, N: 0.3%, Re: 0.15%, the balance being Fe;

the soil excavating device comprises a sliding groove fixed on the frame and a rotating wheel rotationally connected to the frame through a rotating shaft, the sliding groove is arranged along the horizontal direction, a sliding frame is slidably mounted on the sliding groove, a first connecting rod rotating shaft is arranged at the eccentric position of the rotating wheel, a second connecting rod rotating shaft is arranged on the sliding frame, a second connecting rod is arranged between the first connecting rod rotating shaft and the second connecting rod rotating shaft, the sliding groove is provided with a vertical guide hole, a guide rod is slidably arranged on the guide hole, a tool mounting frame is fixed at the lower end of the guide rod, a pressure spring is arranged on the guide rod, the lower end face of the pressure spring abuts against the upper surface of the tool mounting frame, the upper end face of the pressure spring abuts against the sliding frame, the tool mounting frame is provided with a hollow through groove, and an abutting rod is further rotationally arranged on the second connecting rod rotating shaft, the outer end of the abutting rod abuts against the upper surface of the hollow through groove, the abutting rod is fixed with the second connecting rod, an earth-moving tool is arranged at the lower end of the tool mounting frame and is vertically arranged, the earth-moving tool can be selected to be different in length for facilitating operation, the vertical position of the first connecting rod rotating shaft is higher than that of the second connecting rod rotating shaft, the earth-moving tool is positioned between the first connecting rod rotating shaft and the second connecting rod rotating shaft from the position in the horizontal direction, when the earth-moving device works, the rotating wheel rotates anticlockwise, the second connecting rod drives the sliding frame to do reciprocating motion in the horizontal direction on the sliding groove, so that the tool mounting frame has reciprocating motion in the horizontal direction, and meanwhile, the guide rod on the sliding frame drives the tool mounting frame to do reciprocating motion in the vertical direction, so that the earth-moving tool on the tool mounting frame can generate an elliptical motion track, an excavation action is formed.

2. The eco-friendly multifunctional construction equipment for civil engineering work as claimed in claim 1, wherein six upper links on six sets of walking footgear are named as left one, left two, left three, right one, right two, right three upper links, respectively, in azimuth, the left two upper link is provided between the left one upper link and the left three upper links, the right two upper link is provided between the right one upper link and the right three upper links, the left two, right one, right three upper links have the same initial rotational angle position, the right two, left one, left three upper links have the same initial rotational angle position, and the initial rotational angles of the left one and right one upper links are different by 180 °.