A high pier bridge pier formwork installation correction device

Abstract

This invention belongs to the field of bridge construction technology and provides a high-pier bridge pier column formwork installation and correction device, including a bracket, a U-shaped base, several wheels rotatably connected to the side of the U-shaped base, a Y-shaped support rod fixedly connected to the U-shaped base, at least two support rods symmetrically fixed to the Y-shaped support rod, and a correction component provided at the end of the Y-shaped support rod. This invention automatically detects whether the device is level by setting an alarm component and issues an alarm signal, avoiding the tedious operation of repeatedly measuring the levelness manually, thus improving calibration efficiency. Through the meshing of the worm gear and worm wheel driven by a motor, the angle of the connecting rod is automatically adjusted until the device is level. This process requires no manual intervention, improving calibration accuracy and efficiency. Furthermore, multiple hydraulic cylinders apply uniform radial force to the formwork, precisely controlling the deviation of the formwork to ensure that the verticality of the formwork meets the design requirements, which is more accurate than manual adjustment.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology, specifically a device for installing and correcting formwork for high-pier bridge columns. Background Technology

[0002] With the rapid development of transportation infrastructure construction, especially the construction of mountain highways and large bridges, high pier bridge column formwork is an indispensable part of the construction. High pier bridge column formwork is a special formwork system used for concrete pouring of high pier columns in bridge construction. The main function of high pier bridge column formwork is to provide molding molds for concrete pouring, ensuring that the shape, size and appearance quality of the concrete structure meet the design requirements.

[0003] However, traditional template verticality calibration mainly relies on manual experience, which makes it difficult to guarantee high accuracy. Especially in the construction of high piers, even small deviations in the template can lead to structural deformation after concrete pouring. Template installation and calibration mainly rely on manual measurement using level and theodolite, which requires multiple adjustments to meet the requirements. This is inefficient, prone to errors, and time-consuming and labor-intensive.

[0004] To address the problems raised in the background art, those skilled in the art have proposed a high-pier bridge pier column formwork installation and correction device.

[0005] The information disclosed above in this background section is only for enhancing the understanding of the background technology of this invention, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-pier bridge pier column formwork installation and correction device, which solves the problem that in the prior art, formwork installation and calibration mainly rely on manual measurement using level instruments and theodolites, requiring multiple adjustments to meet the requirements.

[0007] To achieve the above objectives, the present invention provides a high-pier bridge pier column formwork installation and correction device, including a bracket, the bracket including a U-shaped base, a plurality of wheels rotatably connected to the side of the U-shaped base, a Y-shaped support rod fixedly connected to the U-shaped base, at least two support rods symmetrically fixed to the Y-shaped support rod, and a correction component provided at the end of the Y-shaped support rod; The correction assembly includes a base disposed at the end of a Y-shaped support rod, a worm gear fixedly connected to the base, a connecting seat slidably connected to the base, a worm gear rotatably connected to the connecting seat, a motor fixedly connected to the connecting seat, a connecting rod fixedly connected to the connecting seat, a driving component disposed at the end of the connecting rod, a clamping plate disposed on the driving component, a hydraulic cylinder disposed on the clamping plate, an elastic block fixedly connected to the end of the hydraulic cylinder, and an alarm component disposed on the connecting rod.

[0008] Preferably, the driving component includes a motor fixedly connected to the connecting rod, a fixing plate fixedly connected to the end of the connecting rod, a sliding groove provided on the fixing plate, a first rotating plate rotatably connected to the fixing plate, an arc-shaped groove provided on the first rotating plate, and an L-shaped rod slidably connected in the arc-shaped groove.

[0009] Preferably, the alarm component includes a second rotating plate rotatably connected to a connecting rod, a weight fixedly connected to the bottom of the second rotating plate, a lever fixedly connected to the side of the second rotating plate, a buzzer fixedly connected to the connecting rod, and a switch provided on the buzzer.

[0010] Preferably, the output end of the motor is fixedly connected to the end of the worm gear, the worm gear meshes with the worm wheel, the fixed plate has a hole, the output end of the motor is fixedly connected to the first rotating plate through the hole, the end of the L-shaped rod is slidably connected in the slide groove, and there are two slide grooves, arc grooves, L-shaped rods and clamping plates, which are evenly distributed in a circle. There are multiple hydraulic cylinders on the two clamping plates, which are also distributed in a circle.

[0011] Preferably, the clamping plate is provided with a clamping assembly, the clamping assembly including a cross groove formed on the clamping plate, a slider slidably connected in the cross groove, and a hanging lug symmetrically fixed to the end of the slider.

[0012] Preferably, the clamping assembly further includes a V-shaped groove formed on the slider, and a V-shaped rubber sheet is disposed in the V-shaped groove.

[0013] Preferably, the hanging ear is located on the top of the clamping plate, the shape of the slider is adapted to the shape of the cross groove, the V-shaped rubber sheet completely covers the V-shaped groove, and two clamping components are provided and arranged symmetrically.

[0014] Preferably, the Y-shaped support rod is provided with a disassembly assembly at its end, the disassembly assembly including a telescopic rod fixedly connected to the end of the Y-shaped support rod, and the base is provided with an insertion hole.

[0015] Preferably, the disassembly and assembly assembly further includes a vertical plate fixedly connected to the telescopic rod, and a threaded rod is threadedly connected to the end of the Y-shaped support rod, with a knob fixedly connected to one end of the threaded rod.

[0016] Preferably, the end of the telescopic rod is inserted into the insertion hole, the outer diameter of the end of the telescopic rod is adapted to the inner diameter of the insertion hole, and the end of the threaded rod away from the knob is fixedly connected to the upright plate. There are two telescopic rods, upright plates, threaded rods and knobs, and they are arranged symmetrically.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention automatically detects whether the device is level by setting an alarm component and issues an alarm signal, avoiding the tedious operation of repeatedly measuring the levelness manually, thus improving calibration efficiency. Through the meshing of the worm gear and worm wheel driven by the motor, the angle of the connecting rod is automatically adjusted until the device is level. This process does not require manual intervention, greatly improving calibration accuracy and efficiency. Furthermore, multiple hydraulic cylinders apply uniform radial force to the template, and precise control is made according to the template deviation to ensure that the verticality of the template meets the design requirements. This is more accurate than manual adjustment and reduces the risk of template deformation.

[0018] 2. This invention creates a V-shaped groove on the slider. When the two clamping plates clamp the cylindrical template, the joint between the two semi-circular templates is located within the V-shaped groove, and the slider provides extrusion force, which can effectively tighten the joint between the two semi-circular templates, preventing grout leakage and template deformation, and improving construction quality.

[0019] 3. This invention, by setting up a disassembly and assembly component, rotates the threaded rod, and drives the telescopic rod to extend and retract through the vertical plate, so that the end of the telescopic rod can be inserted or pulled out in the insertion hole of the base, thereby completing the quick disassembly and assembly of the base, so as to maintain or replace each component.

[0020] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of a high-pier bridge pier column template installation and correction device according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of a high-pier bridge pier column formwork installation and correction device according to an embodiment of the present invention; Figure 3 for Figure 2 Enlarged structural diagram at point A; Figure 4 for Figure 1 Enlarged structural diagram at point B; Figure 5 This is an exploded view of the structure of the driving component of a high-pier bridge pier column formwork installation and correction device according to an embodiment of the present invention; Figure 6 This is an exploded view of the pressing assembly of a high-pier bridge pier column template installation and correction device in an embodiment of the present invention; Figure 7 This is a schematic diagram of the disassembly and assembly components of a high-pier bridge pier column template installation and correction device according to an embodiment of the present invention.

[0022] In the diagram: 1. Bracket; 11. U-shaped base; 12. Wheel; 13. Y-shaped support rod; 14. Support rod; 2. Correction assembly; 21. Base; 211. Worm gear; 22. Connecting seat; 23. Worm; 24. Motor; 25. Connecting rod; 26. Drive component; 261. Motor; 262. Fixing plate; 263. Slide groove; 264. First rotating plate; 265. Arc groove; 266. L-shaped rod; 27. Clamping plate 28. Hydraulic cylinder; 281. Elastic block; 29. ​​Alarm component; 291. Second rotating plate; 292. Drop block; 293. Lever; 294. Buzzer; 295. Switch; 3. Clamping assembly; 31. Cross groove; 32. Slider; 33. Hanging lug; 34. V-groove; 35. V-shaped rubber sheet; 4. Assembly / disassembly assembly; 41. Telescopic rod; 42. Socket; 43. Vertical plate; 44. Threaded rod; 45. Knob. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the drawings are schematic and not illustrated to scale. For clarity and convenience, the relative sizes and proportions of the parts shown in the drawings have been exaggerated or reduced in size. Any size is only illustrative and not limiting.

[0024] Example 1: Please see Figure 1 - Figure 7 As shown, a high-pier bridge pier column formwork installation and correction device includes a support 1. The support 1 includes a U-shaped base 11. Several wheels 12 are rotatably connected to the side of the U-shaped base 11. A Y-shaped support rod 13 is fixedly connected to the U-shaped base 11. At least two support rods 14 are symmetrically fixed to the Y-shaped support rod 13. A correction component 2 is provided at the end of the Y-shaped support rod 13. The U-shaped base 11 serves as the basic support structure of the entire device and is used to support other components. Several wheels 12 are rotatably connected to its side to facilitate the movement and positioning of the device. The Y-shaped support rod 13 is used to support the correction component 2 and provide sufficient height and stability. The support rods 14 are symmetrically fixed to the Y-shaped support rod 13 to enhance the stability and load-bearing capacity of the entire support 1 and prevent the device from tilting or shaking during operation. The correction assembly 2 includes a base 21 located at the end of the Y-shaped support rod 13. A worm gear 211 is fixedly connected to the base 21. A connecting seat 22 is slidably connected to the base 21. A worm gear 23 is rotatably connected to the connecting seat 22. A motor 24 is fixedly connected to the connecting seat 22. A connecting rod 25 is fixedly connected to the connecting seat 22. A driving component 26 is located at the end of the connecting rod 25. A clamping plate 27 is located on the driving component 26. A hydraulic cylinder 28 is located on the clamping plate 27. An elastic block 281 is fixedly connected to the end of the hydraulic cylinder 28. An alarm component 29 is located on the connecting rod 25. The base 21 is used to install the worm gear 211 and other correction assemblies 2, serving a supporting and positioning function. The worm gear 211 and... The worm gear 23 engages to achieve angle adjustment. The connecting seat 22 is used to install the worm gear 23 and the motor 24, and simultaneously drives the connecting rod 25 to perform angle adjustment. The worm gear 23 engages with the worm wheel 211, and the angle adjustment is achieved by driving the motor 24. The motor 24 is used to drive the worm gear 23 to rotate. The connecting rod 25 is used to install the drive component 26 and the alarm component 29, and achieves the calibration function through angle adjustment. The clamping plate 27 is used to clamp the template. The hydraulic cylinder 28 applies radial force to ensure the verticality of the template. The elastic block 281 is fixedly connected to the end of the hydraulic cylinder 28 for contact with the template, providing cushioning and protection.

[0025] Specifically, the driving component 26 includes a motor 261 fixedly connected to the connecting rod 25, a fixing plate 262 fixedly connected to the end of the connecting rod 25, a groove 263 provided on the fixing plate 262, a first rotating plate 264 rotatably connected to the fixing plate 262, an arc-shaped groove 265 provided on the first rotating plate 264, an L-shaped rod 266 slidably connected in the arc-shaped groove 265, the motor 261 is used to drive the first rotating plate 264 to rotate, the fixing plate 262 and the first rotating plate 264, the groove 263 is used to provide guidance for the L-shaped rod 266, the L-shaped rod 266 slides radially along the groove 263, the first rotating plate 264 is used to install the arc-shaped groove 265 and the L-shaped rod 266, the arc-shaped groove 265 applies a compressive force to the L-shaped rod 266 as the first rotating plate 264 rotates, and the L-shaped rod 266 is used to connect the clamping plate 27.

[0026] Furthermore, the alarm component 29 includes a second rotating plate 291 rotatably connected to the connecting rod 25. A weight 292 is fixedly connected to the bottom of the second rotating plate 291, and a lever 293 is fixedly connected to the side of the second rotating plate 291. A buzzer 294 is fixedly connected to the connecting rod 25, and a switch 295 is provided on the buzzer 294. The second rotating plate 291 is used to install the weight 292 and the lever 293. The weight 292 is used to toggle the switch 295 of the buzzer 294. The buzzer 294 is a 1407 passive piezoelectric buzzer manufactured by Shenzhen Xinghuaxin Electronic Technology Co., Ltd., used to emit an alarm sound. The switch 295 is provided on the buzzer 294 and is used to control the switch 295 state of the buzzer 294.

[0027] Furthermore, the output end of the motor 24 is fixedly connected to the end of the worm 23, the worm 23 meshes with the worm wheel 211, the fixed plate 262 has a hole, the output end of the motor 261 passes through the hole and is fixedly connected to the first rotating plate 264, the end of the L-shaped rod 266 is slidably connected in the slide groove 263, the slide groove 263, the arc groove 265, the L-shaped rod 266 and the clamping plate 27 are all provided in two and are evenly distributed in a circle, and the hydraulic cylinders 28 on the two clamping plates 27 are all provided in multiple and are distributed in a circle.

[0028] As can be seen from the above, when the device is placed on the ground, the second rotating plate 291 remains vertical due to the gravity of the weight block 292. If the device is not horizontal, the second rotating plate 291 will tilt, causing the lever 293 to activate the switch 295 of the buzzer 294, which will sound an alarm to remind the operator that the device needs adjustment. This avoids the tedious manual measurement of levelness and improves calibration efficiency. The operator starts the motor 24, and the output of the motor 24 drives the worm gear 23 to rotate. Because the worm gear 23 meshes with the worm wheel 211, the connecting seat 22 slides on the base 21, thereby driving the connecting rod 25 to adjust the angle. When the connecting rod 25 is adjusted to a horizontal state, the weight block 292 and the connecting rod... 25. When the device is vertical, lever 293 stops toggling switch 295, and buzzer 294 stops alarming. At this point, the device is in a horizontal state. This process requires no manual intervention, greatly improving calibration accuracy and efficiency. The device is ready to proceed to the next step. Motor 261 is started, driving the first rotating plate 264 to rotate. Under the pressure of the two arc-shaped grooves 265, the two clamping plates 27 clamp the template. Multiple hydraulic cylinders 28 apply uniform radial force, which contacts the template through elastic blocks 281, ensuring the template's verticality meets design requirements. This allows for precise control based on template deviation, ensuring the template's verticality meets design requirements. It is more accurate than manual adjustment and reduces the risk of template deformation.

[0029] Example 2: Please see Figure 6As shown, this embodiment is basically the same as the previous embodiment, except that a clamping assembly 3 is provided on the clamping plate 27. The clamping assembly 3 includes a cross groove 31 opened on the clamping plate 27. A slider 32 is slidably connected in the cross groove 31. A hanging ear 33 is symmetrically fixed to the end of the slider 32. The cross groove 31 is opened on the clamping plate 27 for sliding connection of the slider 32. The slider 32 is slidably connected in the cross groove 31 for installing the hanging ear 33 and V-groove 34. The hanging ear 33 is symmetrically fixed to the end of the slider 32 for fixing the slider 32.

[0030] Specifically, the clamping assembly 3 also includes a V-shaped groove 34 formed on the slider 32. A V-shaped rubber sheet 35 is provided in the V-shaped groove 34. The V-shaped groove 34 is used to install the V-shaped rubber sheet 35. The V-shaped rubber sheet 35 is set in the V-shaped groove 34 to clamp the joint of the two semi-circular templates, ensuring a tight joint and preventing grout leakage and deformation.

[0031] Furthermore, the lug 33 is set on the top of the clamping plate 27, the shape of the slider 32 is adapted to the shape of the cross groove 31, the V-shaped rubber sheet 35 completely covers the V-shaped groove 34, and there are two clamping components 3 arranged symmetrically.

[0032] As can be seen from the above, by opening a V-shaped groove 34 on the slider 32, when the two clamping plates 27 clamp the cylindrical template, the splice between the two semi-circular templates is located in the V-shaped groove 34, and the slider 32 provides extrusion force, which can effectively press the splice between the two semi-circular templates, avoid grout leakage and template deformation, and improve construction quality.

[0033] Example 3: Please see Figure 7 As shown, this embodiment is basically the same as the previous embodiment, except that the Y-shaped support rod 13 is provided with a disassembly and assembly component 4 at its end. The disassembly and assembly component 4 includes a telescopic rod 41 fixedly connected to the end of the Y-shaped support rod 13. The base 21 is provided with an insertion hole 42. The telescopic rod 41 is fixedly connected to the end of the Y-shaped support rod 13 and is used to insert into the insertion hole 42 of the base 21. The insertion hole 42 is opened on the base 21 and is used for inserting or pulling out the telescopic rod 41.

[0034] Specifically, the disassembly and assembly assembly 4 also includes a vertical plate 43 fixedly connected to the telescopic rod 41, a threaded rod 44 threadedly connected to the end of the Y-shaped support rod 13, and a knob 45 fixedly connected to one end of the threaded rod 44. The vertical plate 43 is used to install the threaded rod 44, which is threadedly connected to the end of the Y-shaped support rod 13 to fix the telescopic rod 41. The knob 45 is used to manually rotate the threaded rod 44 to insert or pull out the telescopic rod 41.

[0035] Furthermore, the end of the telescopic rod 41 is inserted into the insertion hole 42, and the outer diameter of the end of the telescopic rod 41 is adapted to the inner diameter of the insertion hole 42. The end of the threaded rod 44 away from the knob 45 is fixedly connected to the upright plate 43. There are two telescopic rods 41, upright plate 43, threaded rod 44 and knob 45, and they are arranged symmetrically.

[0036] As can be seen from the above, by rotating the threaded rod 44, the vertical plate 43 is moved, so that the end of the telescopic rod 41 is fixed in the insertion hole 42. The knob 45 is fixedly connected to one end of the threaded rod 44, which makes it easy for the operator to manually rotate the threaded rod 44. By rotating the threaded rod 44 in the opposite direction, the telescopic rod 41 is pulled out of the insertion hole 42, thus completing the disassembly of the base 21. This facilitates the maintenance and replacement of the equipment. The design of the disassembly and assembly component 4 makes the installation and disassembly of the base 21 more convenient, reducing maintenance time and labor intensity. There are two telescopic rods 41, vertical plate 43, threaded rod 44 and knob 45, which are arranged symmetrically to ensure the stability and reliability of the device.

[0037] All standard parts used in this invention can be purchased commercially, and irregularly shaped parts can be customized according to the description and drawings. The specific connection methods for each part all employ conventional methods such as bolts, rivets, and welding, which are mature technologies in the prior art. The machinery, parts, and equipment all use conventional models in the prior art, and the circuit connections also use conventional connection methods in the prior art, which will not be detailed here. Any content not described in detail in this specification belongs to the prior art known to those skilled in the art.

[0038] The accompanying drawings of the embodiments disclosed in this invention only involve structures related to the embodiments disclosed in this invention. Other structures can refer to general designs. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0039] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for installing and correcting formwork for high-pier bridge columns, characterized in that: Includes a bracket (1), the bracket (1) includes a U-shaped base (11), the side of the U-shaped base (11) is rotatably connected to a number of wheels (12), a Y-shaped support rod (13) is fixedly connected to the U-shaped base (11), at least two support rods (14) are symmetrically fixed to the Y-shaped support rod (13), and a correction component (2) is provided at the end of the Y-shaped support rod (13). The correction component (2) includes a base (21) disposed at the end of the Y-shaped support rod (13), a worm gear (211) fixedly connected to the base (21), a connecting seat (22) slidably connected to the base (21), a worm gear (23) rotatably connected to the connecting seat (22), a motor (24) fixedly connected to the connecting seat (22), a connecting rod (25) fixedly connected to the connecting seat (22), a driving component (26) disposed at the end of the connecting rod (25), a clamping plate (27) disposed on the driving component (26), a hydraulic cylinder (28) disposed on the clamping plate (27), an elastic block (281) fixedly connected to the end of the hydraulic cylinder (28), and an alarm component (29) disposed on the connecting rod (25).

2. The high-pier bridge pier column formwork installation and correction device according to claim 1, characterized in that: The driving component (26) includes a motor (261) fixedly connected to the connecting rod (25). A fixing plate (262) is fixedly connected to the end of the connecting rod (25). A sliding groove (263) is provided on the fixing plate (262). A first rotating plate (264) is rotatably connected to the fixing plate (262). An arc-shaped groove (265) is provided on the first rotating plate (264). An L-shaped rod (266) is slidably connected in the arc-shaped groove (265).

3. The high-pier bridge pier column formwork installation and correction device according to claim 1, characterized in that: The alarm component (29) includes a second rotating plate (291) rotatably connected to the connecting rod (25), a weight (292) fixedly connected to the bottom of the second rotating plate (291), a lever (293) fixedly connected to the side of the second rotating plate (291), a buzzer (294) fixedly connected to the connecting rod (25), and a switch (295) provided on the buzzer (294).

4. The high-pier bridge pier column formwork installation and correction device according to claim 2, characterized in that: The output end of the motor (24) is fixedly connected to the end of the worm (23), the worm (23) meshes with the worm wheel (211), the fixed plate (262) has a hole, the output end of the motor (261) is fixedly connected to the first rotating plate (264) through the hole, the end of the L-shaped rod (266) is slidably connected in the slide groove (263), the slide groove (263), the arc groove (265), the L-shaped rod (266) and the clamping plate (27) are all provided in two and are evenly distributed in a circle, and the hydraulic cylinders (28) on the two clamping plates (27) are all provided in multiple and are distributed in a circle.

5. The high-pier bridge pier column formwork installation and correction device according to claim 1, characterized in that: The clamping plate (27) is provided with a pressing component (3), the pressing component (3) includes a cross groove (31) opened on the clamping plate (27), a slider (32) is slidably connected in the cross groove (31), and a hanging ear (33) is symmetrically fixed at the end of the slider (32).

6. The high-pier bridge pier column formwork installation and correction device according to claim 5, characterized in that: The clamping assembly (3) also includes a V-groove (34) formed on the slider (32), and a V-shaped rubber sheet (35) is provided in the V-groove (34).

7. The high-pier bridge pier column formwork installation and correction device according to claim 6, characterized in that: The hanging ear (33) is set on the top of the clamp (27), the shape of the slider (32) is adapted to the shape of the cross groove (31), the V-shaped rubber sheet (35) completely covers the V-shaped groove (34), and the clamping assembly (3) is provided in two symmetrical arrangements.

8. The high-pier bridge pier column formwork installation and correction device according to claim 1, characterized in that: The Y-shaped support rod (13) is provided with a disassembly assembly (4) at its end. The disassembly assembly (4) includes a telescopic rod (41) fixedly connected to the end of the Y-shaped support rod (13). The base (21) is provided with an insertion hole (42).

9. The high-pier bridge pier column formwork installation and correction device according to claim 8, characterized in that: The assembly / disassembly assembly (4) also includes a vertical plate (43) fixedly connected to the telescopic rod (41), and a threaded rod (44) is threadedly connected to the end of the Y-shaped support rod (13), and a knob (45) is fixedly connected to one end of the threaded rod (44).

10. The high-pier bridge pier column formwork installation and correction device according to claim 9, characterized in that: The end of the telescopic rod (41) is inserted into the socket (42), and the outer diameter of the end of the telescopic rod (41) is adapted to the inner diameter of the socket (42). The end of the threaded rod (44) away from the knob (45) is fixedly connected to the upright plate (43). There are two telescopic rods (41), upright plate (43), threaded rods (44) and knobs (45) in a symmetrical arrangement.

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