A three-axis automatic ground cylinder material taking equipment

Abstract

The present invention relates to a three-axis automatic ground cylinder reclaiming device with a high degree of automation, greatly shortening the material digging time and solving the problem of excessive residue on the cylinder wall. The support mechanism is fixedly arranged on the ground, the X-direction walking mechanism is arranged on the support mechanism, the Y-direction walking mechanism is arranged on the X-direction walking mechanism, the Z-direction walking mechanism is arranged on the Y-direction walking mechanism, and the material digging mechanism is arranged on the Z-direction walking mechanism. The material digging mechanism includes a motor planetary reducer, an electric push cylinder seat, an outer ring, an electric push cylinder, a lifting plate, a long connecting rod, a scraper, a motor reducer, a ball screw, a main mounting plate, a short connecting rod and a bucket piece. The present invention is widely used in the technical field of ground cylinder reclaiming.

Description

Technical Field

[0001] The invention relates to a three-axis automatic ground cylinder material taking device, belonging to the technical field of ground cylinder material taking. Background Art

[0002] When fermenting in fermentation vats, the brewing industry requires raw materials to be stored in underground vats for fermentation. This involves the process of loading and unloading the raw materials before and after fermentation is complete. Traditionally, workers use tools such as shovels to load and unload the raw materials. This laborious and inefficient manual labor is no longer sufficient for the large-scale production needs of modern brewing companies.

[0003] At present, some material-removing equipment has appeared on the market, but there are problems such as low degree of automation, long digging time, and a lot of residue on the cylinder wall. Summary of the Invention

[0004] The invention discloses a three-axis automatic cylinder material taking device, which has a high degree of automation, greatly shortens the material digging time, and solves the problem of excessive cylinder wall residue.

[0005] The technical solution adopted by the present invention is: a three-axis automatic ground cylinder material reclaiming equipment, including a support mechanism, an X-direction walking mechanism, a Y-direction walking mechanism, a Z-direction walking mechanism and a digging mechanism; the support mechanism is fixedly arranged on the ground, the X-direction walking mechanism is arranged on the support mechanism, the Y-direction walking mechanism is arranged on the X-direction walking mechanism, the Z-direction walking mechanism is arranged on the Y-direction walking mechanism, and the digging mechanism is arranged on the Z-direction walking mechanism. The digging mechanism includes a motor planetary reducer, an electric push cylinder seat, an outer ring, an electric push cylinder, a lifting plate, a long connecting rod, a scraper, a motor reducer, a ball screw, a main mounting plate, a short connecting rod and a bucket piece;

[0006] The upper end of the power input shaft of the motor planetary reducer is fixed to the lower side of the Z-direction walking mechanism through the first motor, and the lower end of the power output shaft of the motor planetary reducer is fixedly provided with an electric push cylinder seat, and the electric push cylinder is fixedly provided inside the electric push cylinder seat, and the push rod of the electric push cylinder faces downward, and an annular lifting plate is fixedly provided on the push rod of the electric push cylinder; a plurality of long connecting rods are evenly distributed on the lifting plate in an annular manner, the upper ends of the long connecting rods are hinged on the lifting plate, and the lower ends of the long connecting rods are hinged with a scraper;

[0007] The main mounting plate is fixed to the lower side of the electric push cylinder seat, and a plurality of bucket pieces are evenly distributed in an annular shape on the main mounting plate. Two motor reducers are symmetrically arranged on the outer side of the electric push cylinder seat, and the power input end of the motor reducer is connected to the second motor, and the power output end of the motor reducer is connected to a ball screw, and the ball screw passes through the main mounting plate and is fixed to the outer ring below the main mounting plate. A plurality of short connecting rods are evenly distributed in an annular shape on the outer ring, and the upper ends of the short connecting rods are hinged to the outer ring, and the lower ends of the short connecting rods are hinged to the middle part of the inner side of the bucket piece;

[0008] One end of the scraper is hinged on the long connecting rod, and the other end of the scraper is hinged on the inner lower end of the bucket piece.

[0009] Furthermore, a universal adjustment ball is provided between the power output shaft of the motor planetary reducer and the electric push cylinder seat, the upper end of the universal adjustment ball is connected to the power output shaft of the motor planetary reducer through a flange, a mounting seat is provided on the outer side of the universal adjustment ball, the upper end of the mounting seat is fixed to the housing of the motor planetary reducer, and a fixing plate is fixedly provided horizontally at the lower end of the mounting seat;

[0010] The structure of the universal adjustment ball includes: a universal ball, a main shaft, a top plate, a transmission shaft, a transmission seat, a blocking block and a rotating seat. The upper side of the top plate is fixed to the flange, and the lower side of the top plate is evenly distributed with multiple transmission shafts in a ring shape.

[0011] The rotating seat is fixedly arranged on the upper side of the fixed plate, the universal ball is matched and arranged in the rotating seat, two semicircular blocking blocks are symmetrically fixedly arranged on the upper side of the rotating seat, the main shaft passes through the universal ball, the rotating seat and the fixed plate, and a gap is left between the main shaft and the pipe-through portion of the rotating seat and the fixed plate. The lower end of the main shaft is fixedly connected to the electric push cylinder seat, and a limiting plate is integrally provided on the upper end of the main shaft. The limiting plate is located on the top of the universal ball, and the limiting plate cooperates with the blocking block to limit the inclination angle of the main shaft;

[0012] A plurality of U-shaped notches are provided on the outer edge of the transfer seat corresponding to the transmission shaft, and the transmission shaft is inserted into the U-shaped notches respectively. The transfer seat, the limit plate and the universal ball are connected together by screws.

[0013] Furthermore, a plurality of long guide shafts are arranged between the lifting plate and the electric push cylinder housing, a plurality of short guide shafts are arranged between the outer ring and the housing of the motor reducer, and limit blocks are provided at the lower ends of the long guide shafts and the short guide shafts. The limit blocks of the short guide shafts are used to limit the opening of the bucket piece, and the limit blocks of the long guide shafts are used to limit the lifting angle of the scraper blade.

[0014] Furthermore, an electric slip ring is provided on the lower side of the fixing plate, and the electric slip ring is used to supply power to the electrical components below the fixing plate.

[0015] Furthermore, the support mechanism includes support legs and connecting beams; the four support legs are vertically fixed on the ground at the edge of the cylinder area, and the two connecting beams are correspondingly fixed laterally on the upper sides of the two support legs to form two gantry structures, and the two X-direction walking mechanisms are matched and movably arranged on the gantry structures.

[0016] Furthermore, the X-axis walking mechanism includes an X-axis motor reducer, an X-axis walking seat, an X-axis connecting beam and an X-axis walking wheel; the two X-axis walking seats are respectively arranged along the two connecting beams, and multiple X-axis walking wheels are arranged between the X-axis walking seat and the connecting beam. One of the X-axis walking wheels of each X-axis walking seat is connected to an X-axis motor reducer, and the body of the X-axis motor reducer is fixedly set on the X-axis walking seat. Two X-axis connecting beams are longitudinally and parallelly arranged on the upper sides of the two X-axis walking seats, and the Y-direction walking mechanism is matched and arranged on the X-axis connecting beam.

[0017] Furthermore, the Y-direction walking mechanism includes a Y-axis motor reducer, a Y-axis walking wheel and a Y-axis main frame; the Y-axis main frame is movably arranged on two X-axis connecting beams through four Y-axis walking wheels, wherein two Y-axis walking wheels are provided with Y-axis motor reducers, and the Z-direction walking mechanism is fixedly arranged on the Y-axis main frame.

[0018] Furthermore, the structure of the Z-direction walking mechanism includes a multi-section telescopic electric cylinder, a guide rail slider and a Z-axis main frame; the cylinder body of the multi-section telescopic electric cylinder is fixedly arranged on the lower middle part of the Y-axis main frame, and the Z-axis main frame is fixedly arranged on both sides of the Y-axis main frame. The guide rail slider is pushed to move back and forth along the Z-axis main frame by the telescopic rod of the multi-section telescopic electric cylinder and the Z-axis main frame through the telescopic movement of the multi-section telescopic electric cylinder, and the digging mechanism is fixedly arranged on the guide rail slider.

[0019] Furthermore, the scraper is triangular in shape.

[0020] The beneficial effects of the present invention are as follows: the control of the electric push cylinder and the electric motor in the present invention both adopts a torque control mode. During the digging process of the bucket, as the inner diameter of the cylinder wall gradually decreases, the closing degree of the bucket piece controlled by the motor and the scraper controlled by the electric push cylinder will decrease as the inner diameter of the cylinder wall gradually decreases under the torque mode of their respective motors; so that the lower end of the bucket piece and the scraper can be completely fitted with the cylinder wall without damaging the cylinder, so that the material on the cylinder wall is completely scraped clean, solving the problem of excessive residue on the cylinder wall. The entire process does not require manual intervention and has a high degree of automation. The bucket piece and scraper are lowered to a set depth, and after multiple diggings, the mash in the cylinder is just dug out, greatly shortening the digging time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention.

[0023] Figure 2 It is a structural schematic diagram of the digging mechanism in the present invention.

[0024] Figure 3 It is a schematic cross-sectional view of the universal adjustment ball in the present invention.

[0025] Figure 4 It is a schematic diagram of the state of the digging mechanism entering the cylinder and scraping materials in the present invention.

[0026] Figure 5 This is a schematic diagram of the state of the digging mechanism in the present invention taking materials out of the cylinder.

[0027] In the picture:

[0028] 1. Support mechanism; 11. Support legs; 12. Connecting beam;

[0029] 2. X-axis travel mechanism; 21. X-axis motor reducer; 22. X-axis travel seat; 23. X-axis connecting beam; 24. X-axis travel wheel;

[0030] 3. Y-axis travel mechanism; 31. Y-axis motor reducer; 32. Y-axis travel wheel; 33. Y-axis main frame;

[0031] 4. Z-direction travel mechanism; 41. Multi-section telescopic electric cylinder; 42. Guide rail slider; 43. Z-axis main frame;

[0032] 5. Digging mechanism; 51. Motor planetary reducer; 52. Electric push cylinder seat; 53. Outer ring; 54. Electric push cylinder; 55. Lifting plate; 56. Long connecting rod; 57. Scraper; 58. Motor reducer; 59. Ball screw; 510. Main mounting plate; 511. Short guide shaft; 512. Short connecting rod; 513. Bucket piece; 514. Universal adjustment ball; 5141. Universal ball; 5142. Main shaft; 5143. Top plate 5143; 5144. Transmission shaft; 5145. Transfer seat; 5146. Stop block; 5147. Rotating seat; 5148. Limit plate; 515. Flange; 516. Mounting seat; 517. Fixed plate; 518. Long guide shaft; 519. Limit block; 520. Electric slip ring. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example

[0035] As attached Figures 1 to 5 As shown, the present invention provides a three-axis automatic ground cylinder material taking device, comprising: a supporting mechanism 1, an X-direction walking mechanism 2, a Y-direction walking mechanism 3, a Z-direction walking mechanism 4 and a digging mechanism 5.

[0036] The support mechanism 1 includes support legs 11 and connecting beams 12, which mainly provide support for the entire device.

[0037] The X-direction traveling mechanism 2 includes two X-axis motor reducers 21, an X-axis traveling seat 22, an X-axis connecting beam 23, and an X-axis traveling wheel 24, which mainly enables the entire device to travel in the X-direction.

[0038] The Y-direction walking mechanism 3 includes a Y-axis motor reducer 31, a Y-axis walking wheel 32 and a Y-axis main frame 33, which mainly enables the entire device to move in the Y direction.

[0039] The Z-direction walking mechanism 4 includes a multi-section telescopic electric cylinder 41, a guide rail slider 42 and a Z-axis main frame 43, which mainly enables the entire device to move in the Z direction.

[0040] The digging mechanism 5 includes a motor planetary reducer 51, a universal adjustment ball 52, an electric slip ring 53, an electric push cylinder 54, a long guide shaft 55, a long connecting rod 56, a scraper 57, a motor reducer 58, a ball screw 59, a short guide shaft 511, a short connecting rod 512 and a bucket piece 513.

[0041] The part above the electric slip ring 53 in the digging mechanism 5 is fixed on the Z-direction walking mechanism 4. The output ends of the two motor reducers 58 are connected to the ball screw 59. The lower end of the ball screw 59 is connected to the upper end of the short connecting rod 512. The lower end of the short connecting rod 512 is connected to the bucket piece 513, so as to control the opening and closing of the bucket piece 513 in the mechanism. The short guide shaft 511 guides the lifting and lowering of the ball screw 59 in the connecting rod mechanism.

[0042] The lower end of the electric push cylinder 54 is connected to the upper end of the long connecting rod 56, and the lower end of the long connecting rod 56 is connected to the lower end of the scraper 57. In addition, the lower end of the bucket piece 513 is connected to the upper end of the scraper 57 through a hinge; the function of this mechanism is: during the digging process of the bucket, the electric push cylinder 54 causes the scraper 56 to stick to the inner wall of the ground cylinder, and the motor planetary reducer 51 drives the lower part of the digging mechanism 5 to rotate continuously; the electric slip ring 53 can prevent too many motor wires from being entangled during the rotation process.

[0043] The working process of this equipment is as follows: the digging mechanism 5 is transported to the top of the cylinder through the action of the X-direction walking mechanism 2 and the Y-direction walking mechanism 3; the Z-direction walking mechanism 4 acts to make the entire digging mechanism 5 begin to descend, so that the lower end of the bucket piece 513 of the digging mechanism 5 is almost flush with the surface of the cylinder edge.

[0044] After the above actions are in place, the motor planetary reducer 51 acts to rotate the lower part of the entire digging mechanism 5; at the same time, the motor reducer 58 and the electric push cylinder 54 act to expand the bucket piece 513 and the scraper 57 until the lower end of the bucket piece 513 and the scraper 57 are attached to the inner wall of the ground cylinder; at this time, the lower part of the digging mechanism 5 is still rotating, and the Z-direction walking mechanism 4 starts to act, causing the entire digging mechanism 5 to start to descend. When it descends to a certain height, the bucket piece 513 is just filled with material or almost filled, the bucket piece 513 and the scraper 57 are closed, and the Z-direction walking mechanism 4 is lifted to complete one digging; this is repeated until the material in the entire ground cylinder is dug out.

[0045] The universal adjustment ball 52 of the present invention is installed at the output end of the motor planetary reducer 51, and its structural diagram is shown as follows: Figure 3 As shown; the ball structure in the middle of the universal adjustment ball 52 can tilt to either side under the action of external force; when the center of the digging mechanism 5 in the free state is not in a straight line with the center of the cylinder, during the digging process, the scraper 57 closer to the cylinder wall will contact the cylinder wall first. At this time, the force acting on the bucket piece 513 and the scraper 57 continues to act, and the bucket piece 513 and the scraper 57 are still stretched, which will force the ball in the middle of the universal adjustment ball 52 to tilt to one side, and the lower half of the digging mechanism 5 tilts to the side farther from the scraper 57 and the cylinder wall, until the lower end of the bucket piece 513 and the scraper 57 are attached to the inner wall of the ground cylinder; the macroscopic effects are: first, it can further compensate for the walking accuracy of the roller-type crane in the X and Y directions; second, it can compensate for the situation where the center line of the ground cylinder is not perpendicular to the ground.

[0046] In the present invention, the electric push cylinder 54 and the motor 58 are both controlled in a torque control mode. During the digging process of the bucket, as the inner diameter of the cylinder wall gradually decreases, the bucket piece 513 controlled by the motor 58 and the scraper 57 controlled by the electric push cylinder 54, under the torque mode of their respective motors, the closing degree of the bucket piece 513 and the scraper 57 will decrease as the inner diameter of the cylinder wall gradually decreases; so that the lower end of the bucket piece 513 and the scraper 57 can be completely fitted with the cylinder wall without damaging the ground cylinder, so that the material on the cylinder wall is completely scraped clean, solving the problem of excessive residue on the cylinder wall. The whole process does not require human intervention and has a high degree of automation. The bucket piece and the scraper are lowered to a set depth. The volume of the mash in the ground cylinder at the set depth does not exceed the loading volume in the bucket. After multiple digging, the mash in the cylinder is just dug out. For example: the depth of the ground cylinder is 1.2 meters, the bucket is lowered 400mm for the first time, 800mm for the second time, and 1200mm for the third time. The mash in the cylinder is just dug out in three times, which greatly shortens the digging time.

[0047] The above are only specific application examples of the present invention and do not constitute any limitation to the protection scope of the present invention; any technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

Claims

1. A three-axis automatic ground cylinder material taking device, comprising a support mechanism (1), an X-direction walking mechanism (2), a Y-direction walking mechanism (3), a Z-direction walking mechanism (4) and a digging mechanism (5); the support mechanism (1) is fixedly arranged on the ground, the X-direction walking mechanism (2) is arranged on the support mechanism (1), the Y-direction walking mechanism (3) is arranged on the X-direction walking mechanism (2), the Z-direction walking mechanism (4) is arranged on the Y-direction walking mechanism (3), and the digging mechanism (5) is arranged on the Z-direction walking mechanism (4), characterized in that: The digging mechanism (5) includes a motor planetary reducer (51), an electric push cylinder seat (52), an outer ring (53), an electric push cylinder (54), a lifting plate (55), a long connecting rod (56), a scraper (57), a motor reducer (58), a ball screw (59), a main mounting plate (510), a short connecting rod (512) and a bucket piece (513); The upper end of the power input shaft of the motor planetary reducer (51) is fixed to the lower side of the Z-direction walking mechanism (4) through the first motor, and the lower end of the power output shaft of the motor planetary reducer (51) is fixedly provided with an electric push cylinder seat (52), and the electric push cylinder (54) is fixedly provided inside the electric push cylinder seat (52), and the push rod of the electric push cylinder (54) faces downward, and an annular lifting plate (55) is fixedly provided on the push rod of the electric push cylinder (54); a plurality of long connecting rods (56) are evenly distributed in an annular manner on the lifting plate (55), the upper ends of the long connecting rods (56) are hinged to the lifting plate (55), and the lower ends of the long connecting rods (56) are hinged to a scraper (57); The main mounting plate (510) is fixed on the lower side of the electric push cylinder seat (52), and a plurality of bucket pieces (513) are evenly distributed in an annular shape on the main mounting plate (510). Two motor reducers (58) are symmetrically arranged on the outer side of the electric push cylinder seat (52), and the power input end of the motor reducer (58) is connected to the second motor, and the power output end of the motor reducer (58) is connected to a ball screw (59). The ball screw (59) passes through the main mounting plate (510) and is fixed on the outer ring (53) located below the main mounting plate (510). A plurality of short connecting rods (512) are evenly distributed in an annular shape on the outer ring (53), and the upper ends of the short connecting rods (512) are hinged to the outer ring (53), and the lower ends of the short connecting rods (512) are hinged to the middle part of the inner side of the bucket piece (513); One end of the scraper (57) is hinged to the long connecting rod (56), and the other end of the scraper (57) is hinged to the inner lower end of the bucket piece (513).

2. The three-axis automatic cylinder material taking equipment according to claim 1 is characterized in that: A universal adjustment ball (514) is provided between the power output shaft of the motor planetary reducer (51) and the electric push cylinder seat (52), the upper end of the universal adjustment ball (514) is connected to the power output shaft of the motor planetary reducer (51) through a flange (515), a mounting seat (516) is provided on the outer side of the universal adjustment ball (514), the upper end of the mounting seat (516) is fixed to the housing of the motor planetary reducer (51), and a fixing plate (517) is fixedly provided horizontally at the lower end of the mounting seat (516); The structure of the universal adjustment ball (514) includes: a universal ball (5141), a main shaft (5142), a top plate (5143), a transmission shaft (5144), a transmission seat (5145), a blocking block (5146) and a rotating seat (5147); the upper side of the top plate (5143) is fixed to the flange (515), and the lower side of the top plate (5143) is evenly distributed with a plurality of transmission shafts (5144) in a ring shape; The rotating seat (5147) is fixedly arranged on the upper side of the fixed plate (517), and the universal ball (5141) is matched and arranged in the rotating seat (5147). Two semicircular blocking blocks (5146) are symmetrically fixed on the upper side of the rotating seat (5147). The main shaft (5142) passes through the universal ball (5141), the rotating seat (5147) and the fixed plate (517), and the main shaft (5142) is fixedly arranged with the rotating seat (5147). A gap is left between the rotating seat (5147) and the pipe-through portion of the fixed plate (517); the lower end of the main shaft (5142) is fixedly connected to the electric push cylinder seat (52); a limit plate (5148) is integrally provided on the upper end of the main shaft (5142); the limit plate (5148) is located on the top of the universal ball (5141); the limit plate (5148) cooperates with the blocking block (5146) to limit the inclination angle of the main shaft (5142); A plurality of U-shaped notches are provided on the outer edge of the transmission seat (5145) corresponding to the transmission shaft (5144), and the transmission shaft (5144) is inserted into the U-shaped notches accordingly. The transmission seat (5145), the limiting plate (5148) and the universal ball (5141) are connected together by screws.

3. The three-axis automatic cylinder material taking equipment according to claim 1 is characterized in that: A plurality of long guide shafts (518) are provided between the lifting plate (55) and the housing of the electric push cylinder (54), a plurality of short guide shafts (511) are provided between the outer ring (53) and the housing of the motor reducer (58), and a limit block (519) is provided at the lower end of each of the long guide shafts (518) and the short guide shaft (511). The limit block (519) of the short guide shaft (511) is used to limit the opening of the bucket piece (513), and the limit block (519) of the long guide shaft (518) is used to limit the lifting angle of the scraper piece (57).

4. The three-axis automatic cylinder material taking equipment according to claim 2, characterized in that: An electric slip ring (520) is provided on the lower side of the fixed plate (517), and the electric slip ring (520) is used to supply power to the power-consuming part below the fixed plate (517).

5. The three-axis automatic cylinder material taking equipment according to claim 1, characterized in that: The support mechanism (1) comprises support legs (11) and connecting beams (12); the four support legs (11) are vertically fixed on the ground at the edge of the ground cylinder area, the two connecting beams (12) are correspondingly fixed laterally on the upper sides of the two support legs (11) to form two gantry structures, and the two X-direction walking mechanisms (2) are matched and movably arranged on the gantry structures.

6. The three-axis automatic cylinder material taking equipment according to claim 5, characterized in that: The X-axis travel mechanism (2) comprises an X-axis motor reducer (21), an X-axis travel seat (22), an X-axis connecting beam (23) and an X-axis travel wheel (24); the two X-axis travel seats (22) are respectively arranged along the two connecting beams (12); a plurality of X-axis travel wheels (24) are arranged between the X-axis travel seat (22) and the connecting beam (12); one of the X-axis travel wheels (24) of each X-axis travel seat (22) is connected to the X-axis motor reducer (21); the body of the X-axis motor reducer (21) is fixedly arranged on the X-axis travel seat (22); two X-axis connecting beams (23) are longitudinally and parallelly arranged on the upper sides of the two X-axis travel seats (22); and the Y-direction travel mechanism (3) is matched and arranged on the X-axis connecting beam (23).

7. The three-axis automatic cylinder material taking equipment according to claim 6, characterized in that: The Y-direction walking mechanism (3) comprises a Y-axis motor reducer (31), a Y-axis walking wheel (32) and a Y-axis main frame (33); the Y-axis main frame (33) is movably arranged on two X-axis connecting beams (23) through four Y-axis walking wheels (32), wherein two Y-axis walking wheels (32) are provided with a Y-axis motor reducer (31); and the Z-direction walking mechanism (4) is fixedly arranged on the Y-axis main frame (33).

8. The three-axis automatic cylinder material taking equipment according to claim 7, characterized in that: The structure of the Z-direction walking mechanism (4) includes a multi-section telescopic electric cylinder (41), a guide rail slider (42) and a Z-axis main frame (43); the cylinder body of the multi-section telescopic electric cylinder (41) is fixedly arranged at the lower middle part of the Y-axis main frame (33), the Z-axis main frame (43) is fixedly arranged on both sides of the Y-axis main frame (33), the guide rail slider (42) is between the telescopic rod of the multi-section telescopic electric cylinder (41) and the Z-axis main frame (43), and the guide rail slider (42) is pushed to reciprocate along the Z direction along the Z-axis main frame (43) by the telescopic movement of the multi-section telescopic electric cylinder (41), and the digging mechanism (5) is fixedly arranged on the guide rail slider (42).

9. The three-axis automatic cylinder material taking equipment according to claim 1, characterized in that: The scraper (57) is triangular in shape.

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