Heavy-load large-angle single-axis swing motion platform with air-assisted mechanism

Abstract

The application relates to the technical field of single-axis swing movement platforms, in particular to a heavy-load large-angle single-axis swing movement platform with air-assisted mechanisms, which comprises a lower platform, a supporting column, an upper platform, an electric cylinder supporting seat and a servo electric cylinder, the supporting column is fixedly installed at the top middle part of the lower platform, the upper platform is rotationally installed at the top end of the supporting column and can swing in the front-rear direction, the electric cylinder supporting seat is fixedly installed at the front top middle part of the lower platform, the cylinder body of the servo electric cylinder is rotationally installed on the electric cylinder supporting seat, and the output shaft end of the servo electric cylinder is rotationally connected with the front bottom middle part of the upper platform; two groups of air-assisted mechanisms are arranged on the front and rear sides below the upper platform and are used for enabling the upper platform to swing to a larger angle under heavy load, and the application provides a single-axis swing movement platform which can swing to a larger angle under heavy load.

Description

Technical Field

[0001] This invention relates to the field of single-axis swing motion platform technology, and in particular to a heavy-duty, large-angle single-axis swing motion platform with a pneumatic auxiliary mechanism. Background Technology

[0002] Single-axis swing motion platforms, as a type of simulation motion testing equipment, are widely used in various fields such as shipbuilding, marine engineering, aerospace, defense, and industrial manufacturing.

[0003] Currently, most single-axis swing motion platforms on the market consist of a lower platform, a support column, an upper platform, bearing seats, a rotating shaft, and a servo electric cylinder. The support column is vertically fixed to the top of the lower platform. The upper platform and the support column are rotatably connected via the rotating shaft and several bearing seats. The two ends of the servo electric cylinder are hinged to the lower and upper platforms respectively. The extension and retraction of the servo electric cylinder pulls or pushes the upper platform and its load to swing back and forth along the rotating shaft above the column. Since the driving force of the upper platform and its load is provided by the servo electric cylinder throughout the swing process, and the driving force and structural strength of the servo electric cylinder have limits, the center of gravity of the upper platform and its load will shift significantly under heavy load and large angle conditions. When the swing angle exceeds a certain value, the servo electric cylinder is prone to jamming. To avoid jamming, the swing angle of the single-axis swing motion platform is usually limited to the design limit. However, this limits the motion capability of the motion platform, making it unsuitable for simulating motion scenarios with larger swing angles. Summary of the Invention

[0004] The purpose of this invention is to provide a heavy-duty, large-angle single-axis swing motion platform with a pneumatic auxiliary mechanism to solve the technical problems existing in the background art.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanisms includes: a lower platform, a support column, an upper platform, an electric cylinder support base, and a servo electric cylinder. The support column is fixedly installed at the top center of the lower platform. The upper platform is rotatably installed at the top of the support column and can swing in the front-rear direction. The electric cylinder support base is fixedly installed at the front top center of the lower platform. The cylinder body of the servo electric cylinder is rotatably installed on the electric cylinder support base. The output shaft end of the servo electric cylinder is rotatably connected to the front bottom center of the upper platform. Two sets of pneumatic auxiliary mechanisms are provided on both the front and rear sides below the upper platform to enable the upper platform to swing at a larger angle under heavy load.

[0006] Furthermore, both the lower platform and the upper platform are rectangular; the upper platform is located directly above the lower platform.

[0007] Furthermore, the support column includes: a vertical column, a horizontal beam, and a connecting column. Several vertical columns are provided, and the several vertical columns are vertically fixed at equal intervals at the top center of the lower platform. The horizontal beam is horizontally fixed at the top of the several vertical columns. A connecting column is fixedly installed at the center between two adjacent vertical columns. The upper platform is rotatably installed at the top of the horizontal beam.

[0008] Furthermore, it also includes: diagonal supports, of which four are provided, one end of each of the four diagonal supports is fixedly installed at the front and rear ends of the two outermost columns; the other end of each of the four diagonal supports is fixedly installed at the top of the lower platform.

[0009] Furthermore, it also includes: diagonal supports, of which four are provided, one end of each of the four diagonal supports is fixedly installed at the front and rear ends of the two outermost columns; the other end of each of the four diagonal supports is fixedly installed at the top of the lower platform.

[0010] Furthermore, it also includes: bearing housing three, connecting shaft one, bearing housing four, and connecting shaft two. The bearing housing three is fixedly installed on the top of the electric cylinder support base. The connecting shaft one is fixedly connected to the outer wall of the cylinder body of the servo electric cylinder. The connecting shaft one is rotatably installed on the bearing housing three. The bearing housing four is fixedly installed in the middle of the front bottom end of the upper platform. The output shaft end of the servo electric cylinder is rotatably installed on the bearing housing four through the connecting shaft two.

[0011] Furthermore, it also includes: angle limiting posts, of which four angle limiting posts are provided, one end of each of the four angle limiting posts being symmetrically fixedly installed on the upper front and rear ends of the two outermost upright posts; wherein, the two front angle limiting posts are inclined forward and upward, and the two rear angle limiting posts are inclined backward and upward; when the servo electric cylinder fails, the bottom end face of the upper platform can contact and cooperate with the other end face of the two front angle limiting posts or the other end face of the two rear angle limiting posts.

[0012] Furthermore, it also includes: a support platform, cylinder support seats, and connecting columns two. Two support platforms are symmetrically arranged front and rear. Each support platform includes: two upright columns and two crossbeams. Two upright columns are symmetrically arranged left and right, with their bottom ends fixedly installed at the top of the lower platform. The crossbeams are horizontally fixedly installed at the top of the two upright columns, with their left and right ends symmetrically fixedly installed on opposite sides of two diagonal supports on the same side as their front and rear sides. Eight cylinder support seats are symmetrically arranged front and rear. The four cylinder support seats on the front side are fixedly installed in pairs on the left and right sides of the top of the front crossbeams two. The four cylinder support seats on the rear side are fixedly installed in pairs on the left and right sides of the top of the rear crossbeams two. Four connecting columns are provided, and the four connecting columns are fixedly installed between the eight symmetrically arranged cylinder support seats.

[0013] Furthermore, the pneumatic auxiliary mechanism includes: a cylinder mounting base, a cylinder, a spherical rod end joint bearing, a roller pin, and rollers. The cylinder is fixedly mounted between two cylinder support bases in the same group via the cylinder mounting base. The spherical rod end joint bearing is fixedly mounted at the end of the cylinder's output shaft. The roller pin passes through and rotatably connects to the spherical rod end joint bearing. Two rollers are provided, and the two rollers are symmetrically rotatably mounted on the left and right sides of the roller pin located on the left and right sides of the spherical rod end joint bearing. The rollers can press against and roll against the bottom surface of the upper platform.

[0014] Furthermore, the pneumatic auxiliary mechanism also includes: two crank arms, a connecting shaft, a crank arm, a connecting shaft, and a bearing seat, each symmetrically arranged on the left and right. One end of each crank arm is rotatably mounted on both ends of the roller pin shaft. The other end of each crank arm is rotatably connected to one end of each crank arm via the two connecting shafts. The other end of each crank arm is rotatably connected to one bearing seat via the two connecting shafts. The two bearing seats are fixedly mounted on the upper ends of the two cylinder support seats in the same group. The included angle between the crank arm and its corresponding crank arm is less than 180°.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention features two sets of pneumatic auxiliary mechanisms on both the front and rear sides below the upper platform. The cylinders in these mechanisms are continuously ventilated during normal operation, and their thrust is less than the weight of the load. During the servo electric cylinder's extension and retraction, which drives the upper platform and its load to swing back and forth, the servo electric cylinder bears a portion of the weight of the upper platform and its load, thus reducing the output force of the servo electric cylinder. This allows the upper platform to swing at a greater angle under heavy loads compared to existing single-axis swing platforms without pneumatic auxiliary mechanisms. Furthermore, in the event of servo electric cylinder failure, the angle limiting posts reduce the extent of damage to the servo electric cylinder. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is an installation diagram of the support column, diagonal support, angle limiting column, support platform, cylinder support seat and connecting column two in this invention; Figure 3 This is the right view of the present invention; Figure 4 This is the front view of the present invention; Figure 5 This is a schematic diagram of the gas-assisted mechanism in this invention; Figure 6 This is a right view of the present invention in the normal operating state of the cylinder; Figure 7This is a right view of the invention in the state of the lower platform swinging backward.

[0017] The labels in the attached diagram are as follows: 1-Lower platform, 2-Support column, 201-Column 1, 202-Crossbeam 1, 203-Connecting column 1, 3-Diagonal support, 4-Upper platform, 5-Bearing seat 1, 6-Bearing seat 2, 7-Rotating shaft, 8-Electric cylinder support seat, 9-Bearing seat 3, 10-Servo electric cylinder, 11-Connecting shaft 1, 12-Bearing seat 4, 13-Connecting shaft 2, 14-Angle limiting column, 15-Support platform, 1501-Column 2, 1502-Crossbeam 2, 16-Cylinder support seat, 17-Connecting column 2, 18-Cylinder mounting seat, 19-Cylinder, 20-Fisheye rod end joint bearing, 21-Roller pin, 22-Roller, 23-Crank arm 1, 24-Connecting shaft 3, 25-Crank arm 2, 26-Connecting shaft 4, 27-Bearing seat 5. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] See Figures 1-7 As shown, a heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism includes: a lower platform 1, a support column 2, an upper platform 4, an electric cylinder support seat 8, and a servo electric cylinder 10. The support column 2 is fixedly installed at the top center of the lower platform 1. The upper platform 4 is rotatably installed at the top of the support column 2 and can swing in the front-rear direction. The electric cylinder support seat 8 is fixedly installed at the front top center of the lower platform 1. The cylinder body of the servo electric cylinder 10 is rotatably installed on the electric cylinder support seat 8. The output shaft end of the servo electric cylinder 10 is rotatably connected to the front bottom center of the upper platform 4. The servo electric cylinder adopts a direct-drive electric cylinder, which makes the response speed and swing speed of the entire platform faster, reduces transmission efficiency loss, and makes the platform more stable. Two sets of pneumatic auxiliary mechanisms are provided on the front and rear sides of the lower part of the upper platform 4 to enable the upper platform 4 to swing at a larger angle under heavy load.

[0020] In this embodiment, both the lower platform 1 and the upper platform 4 are rectangular; the upper platform 4 is located directly above the lower platform 1.

[0021] In this embodiment, the support column 2 includes: column 201, beam 202 and connecting column 203. Several columns 201 are provided, and the columns 201 are vertically fixed at equal intervals at the top center of the lower platform 1. The beam 202 is horizontally fixed at the top of the columns 201. A connecting column 203 is fixedly installed at the middle between two adjacent columns 201. The upper platform 4 is rotatably installed at the top of the beam 202.

[0022] In this embodiment, the heavy-duty large-angle single-axis swing motion platform with air-assisted mechanism further includes: inclined supports 3, four inclined supports 3 are provided, one end of the four inclined supports 3 is fixedly installed at the front and rear ends of the two outermost columns 201 respectively; the other end of the four inclined supports 3 is fixedly installed at the top of the lower platform 1 respectively; the inclined supports 3 can improve the structural stability of the support columns 2.

[0023] In this embodiment, the heavy-duty large-angle single-axis swing motion platform with air-assisted mechanism further includes: bearing seat 1 5, bearing seat 2 6, and rotating shaft 7. Several bearing seats 1 5, bearing seat 2 6, and rotating shaft 7 are evenly spaced. Several bearing seats 1 5 are fixedly installed at the bottom center of the upper platform 4, and several bearing seats 2 6 are fixedly installed at the top of the crossbeam 202. Several bearing seats 1 5 correspond one-to-one with several bearing seats 2 6 and are rotatably connected by several rotating shafts 7.

[0024] In this embodiment, the heavy-duty large-angle single-axis swing motion platform with pneumatic auxiliary mechanism further includes: bearing seat 3 9, connecting shaft 1 11, bearing seat 4 12 and connecting shaft 2 13. Bearing seat 3 9 is fixedly installed on the top of the electric cylinder support seat 8. Connecting shaft 1 11 is fixedly connected to the outer wall of the cylinder body of the servo electric cylinder 10. Connecting shaft 1 11 is rotatably installed on bearing seat 3 9. Bearing seat 4 12 is fixedly installed in the middle of the front bottom end of the upper platform 4. The output shaft end of the servo electric cylinder 10 is rotatably installed on bearing seat 4 12 through connecting shaft 2 13.

[0025] In this embodiment, the heavy-duty large-angle single-axis swing motion platform with pneumatic auxiliary mechanism further includes: angle limiting columns 14, four of which are provided. One end of each angle limiting column 14 is symmetrically fixed to the upper front and rear ends of the two outermost columns 201. The two front angle limiting columns 14 are inclined forward and upward, and the two rear angle limiting columns 14 are inclined backward and upward. When the servo electric cylinder 10 fails, the bottom end face of the upper platform 4 can contact and cooperate with the other end face of the two front angle limiting columns 14 or the other end face of the two rear angle limiting columns 14, thereby reducing the damage to the servo electric cylinder.

[0026] In this embodiment, the heavy-duty large-angle single-axis swing motion platform with pneumatic auxiliary mechanism further includes: a support platform 15, a cylinder support seat 16, and a connecting column 17. Two support platforms 15 are symmetrically arranged front and rear. The support platform 15 includes: a second column 1501 and a second crossbeam 1502. Two second columns 1501 are symmetrically arranged left and right. The bottom ends of both second columns 1501 are fixedly installed at the top of the lower platform 1. The second crossbeam 1502 is horizontally fixedly installed at the top of the two second columns 1501. The left and right sides of the second crossbeam 1502... The cylinder support seats 16 are symmetrically fixed on the opposite side of the two diagonal supports 3 on the same side as the front and rear sides; eight cylinder support seats 16 are symmetrically arranged front and rear, of which the four cylinder support seats 16 on the front side are fixedly installed in pairs on the left and right sides of the top of the front crossbeam 2 1502; the four cylinder support seats 16 on the rear side are fixedly installed in pairs on the left and right sides of the top of the rear crossbeam 2 1502; four connecting columns 2 17 are provided, and the four connecting columns 2 17 are fixedly installed between the eight symmetrical cylinder support seats 16.

[0027] In this embodiment, the pneumatic auxiliary mechanism includes: a cylinder mounting base 18, a cylinder 19, a spherical rod end joint bearing 20, a roller pin 21, and rollers 22. The cylinder 19 is fixedly mounted between two cylinder support bases 16 in the same group via the cylinder mounting base 18. The spherical rod end joint bearing 20 is fixedly mounted on the output shaft end of the cylinder 19. The roller pin 21 passes through and rotatably connects to the spherical rod end joint bearing 20. There are two rollers 22, which are symmetrically rotatably mounted on the roller pin 21 on the left and right sides of the spherical rod end joint bearing 20. The rollers 22 can press against and roll against the bottom surface of the upper platform 4. The symmetrical distribution of the rollers 22 can prevent the cylinder 19 from tilting due to uneven force drop, thereby improving the stability of the platform.

[0028] In this embodiment, the pneumatic auxiliary mechanism further includes: two crank arms 23, a connecting shaft 24, a crank arm 25, a connecting shaft 26, and a bearing seat 27, each symmetrically arranged on the left and right. One end of each crank arm 23 is rotatably mounted on both ends of the roller pin 21. The other end of each crank arm 23 is rotatably connected to one end of each crank arm 25 via the two connecting shafts 24. The other end of each crank arm 25 is rotatably connected to each bearing seat 27 via the two connecting shafts 26. The two bearing seats 27 are fixedly mounted on the upper ends of the two cylinder support seats 16 in the same group. The included angle between the crank arm 23 and its corresponding crank arm 25 is less than 180°. The crank arm assembly composed of the crank arm 23, the connecting shaft 24, the crank arm 25, the connecting shaft 26, and the bearing seat 27 can limit the rotation of the cylinder rod and further improve the support stability of the cylinder.

[0029] Working principle: When the upper platform 4 is parallel to the lower platform 1, the load is installed on the top of the upper platform 4. Since the cylinder 19 in the pneumatic auxiliary mechanism is continuously ventilated under normal operating conditions, the upper platform 4 swings back and forth under the extension and retraction of the servo electric cylinder 10. When the upper platform 4 tilts forward, its bottom surface first touches the roller 22 on the front cylinder 19. Because the load weight is greater than the thrust of the cylinder 19, the front cylinder 19 continuously retracts. During this process, the front cylinder 19 continuously provides thrust to reduce the output of the servo electric cylinder 10. After reaching its final position, the upper platform 4 moves in the opposite direction. At this time, the front cylinder 19 begins to extend, still providing thrust during extension to reduce the electric cylinder output. When the upper platform 4 tilts backward, its bottom surface first touches the roller 22 on the rear cylinder 19. Because the load weight is greater than the thrust of the cylinder 19, the rear cylinder 19 continuously retracts. During this process, the rear cylinder 19 continuously provides thrust to reduce the output of the servo electric cylinder 10. Once in position, the upper platform 4 moves in the opposite direction. At this time, the rear cylinder 19 begins to extend, still providing thrust during the extension process, reducing the output of the electric cylinder.

[0030] In the description of this invention, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", "top / bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A heavy-duty, large-angle single-axis swing motion platform with a pneumatic auxiliary mechanism, characterized in that, include: The platform consists of a lower platform (1), a support column (2), an upper platform (4), an electric cylinder support seat (8), and a servo electric cylinder (10). The support column (2) is fixedly installed at the top center of the lower platform (1). The upper platform (4) is rotatably installed at the top of the support column (2) and can swing in the front and back direction. The electric cylinder support seat (8) is fixedly installed at the front top center of the lower platform (1). The cylinder body of the servo electric cylinder (10) is rotatably installed on the electric cylinder support seat (8). The output shaft end of the servo electric cylinder (10) is rotatably connected to the front bottom center of the upper platform (4). Two sets of pneumatic auxiliary mechanisms are provided on the front and back sides of the lower platform (4) to enable the upper platform (4) to swing at a larger angle under heavy load.

2. The heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 1, characterized in that: Both the lower platform (1) and the upper platform (4) are rectangular; the upper platform (4) is located directly above the lower platform (1).

3. The heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 1, characterized in that: The support column (2) includes: column one (201), beam one (202) and connecting column one (203). There are several columns one (201). The several columns one (201) are vertically fixed at equal intervals at the top center of the lower platform (1). The beam one (202) is horizontally fixed at the top of the several columns one (201). The connecting column one (203) is fixedly installed at the middle between two adjacent columns one (201). The upper platform (4) is rotatably installed at the top of the beam one (202).

4. The heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 3, characterized in that: Also includes: The inclined support (3) is provided in four parts. One end of the four inclined supports (3) is fixedly installed at the front and rear ends of the two outermost columns (201); the other end of the four inclined supports (3) is fixedly installed at the top of the lower platform (1).

5. A heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 3, characterized in that: Also includes: Bearing seat 1 (5), bearing seat 2 (6) and rotating shaft (7) are provided with several bearing seats 1 (5), bearing seat 2 (6) and rotating shaft (7) at equal intervals. Several bearing seats 1 (5) are fixedly installed at the bottom center of the upper platform (4), and several bearing seats 2 (6) are fixedly installed at the top of the crossbeam 1 (202). Several bearing seats 1 (5) and several bearing seats 2 (6) correspond one-to-one and are rotatably connected by several rotating shafts (7).

6. The heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 1, characterized in that: Also includes: Bearing seat three (9), connecting shaft one (11), bearing seat four (12) and connecting shaft two (13). The bearing seat three (9) is fixedly installed on the top of the electric cylinder support seat (8). The connecting shaft one (11) is fixedly connected to the outer wall of the cylinder body of the servo electric cylinder (10). The connecting shaft one (11) is rotatably installed on the bearing seat three (9). The bearing seat four (12) is fixedly installed in the middle of the front bottom end of the upper platform (4). The output shaft end of the servo electric cylinder (10) is rotatably installed on the bearing seat four (12) through the connecting shaft two (13).

7. A heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 3, characterized in that: Also includes: Angle limiting posts (14), four angle limiting posts (14) are provided, and one end of the four angle limiting posts (14) is symmetrically fixed on the upper front and rear ends of the two outermost columns (201); among them, the two angle limiting posts (14) on the front side are inclined to the front and upward, and the two angle limiting posts (14) on the rear side are inclined to the rear and upward; when the servo electric cylinder (10) fails, the bottom end face of the upper platform (4) can contact and cooperate with the other end face of the two angle limiting posts (14) on the front side or with the other end face of the two angle limiting posts (14) on the rear side.

8. A heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 4, characterized in that: Also includes: The support platform (15), cylinder support seat (16), and connecting column two (17) are provided. Two support platforms (15) are symmetrically arranged front and back. The support platform (15) includes: column two (1501) and crossbeam two (1502). Two column two (1501) are symmetrically arranged left and right. The bottom ends of the two column two (1501) are fixedly installed on the top of the lower platform (1). The crossbeam two (1502) is horizontally fixedly installed on the top of the two column two (1501). The left and right ends of the crossbeam two (1502) are symmetrically fixedly installed. On the opposite side of the two diagonal supports (3) on the same side in front and behind; eight cylinder support seats (16) are symmetrically arranged in front and behind, of which the four cylinder support seats (16) on the front side are fixedly installed in pairs on the left and right sides of the top of the front crossbeam two (1502); the four cylinder support seats (16) on the rear side are fixedly installed in pairs on the left and right sides of the top of the rear crossbeam two (1502); four connecting columns two (17) are arranged, and the four connecting columns two (17) are fixedly installed between the eight cylinder support seats (16) symmetrically arranged in front and behind.

9. A heavy-duty, large-angle single-axis swing motion platform with pneumatic auxiliary mechanism according to claim 8, characterized in that: The pneumatic auxiliary mechanism includes: a cylinder mounting base (18), a cylinder (19), a fisheye rod end joint bearing (20), a roller pin (21), and a roller (22). The cylinder (19) is fixedly mounted between two cylinder support bases (16) in the same group through the cylinder mounting base (18). The fisheye rod end joint bearing (20) is fixedly mounted on the output shaft end of the cylinder (19). The roller pin (21) passes through and rotatably connects to the fisheye rod end joint bearing (20). There are two rollers (22). The two rollers (22) are symmetrically rotatably mounted on the left and right sides of the roller pin (21) located on the fisheye rod end joint bearing (20). The rollers (22) can press against and roll against the bottom surface of the upper platform (4).

10. A heavy-duty, large-angle single-axis swing motion platform with a pneumatic auxiliary mechanism according to claim 9, characterized in that: The pneumatic auxiliary mechanism further includes: two crank arms (23), a connecting shaft (24), a crank arm (25), a connecting shaft (26), and a bearing seat (27), each symmetrically arranged on the left and right. One end of each of the two crank arms (23) is rotatably mounted on the two ends of the roller pin (21). The other end of each of the two crank arms (23) is rotatably connected to one end of each of the two crank arms (25) through the two connecting shafts (24). The other end of each of the two crank arms (25) is rotatably connected to each of the two bearing seats (27) through the two connecting shafts (26). The two bearing seats (27) are fixedly mounted on the upper ends of the two cylinder support seats (16) in the same group. The included angle between the crank arm (23) and its corresponding crank arm (25) is less than 180°.

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