A mixing and melting device for producing plastic products

Abstract

The present invention belongs to the technical field of plastic product production, and in particular, is a mixing and melting device for the production of plastic products, comprising a barrel, a discharge pipe is provided at the bottom end of the barrel, a conveying pipe is provided at the upper position of the circumferential outer wall of the barrel, a feeding pipe is provided on the conveying pipe, a mesh plate is fixed in the barrel, a main shaft is rotatably connected to the top end of the barrel, two groups of support rods are fixed to the circumferential outer wall of the main shaft, a first gear rod and a second gear rod are respectively meshed and connected to the upper and lower parts of a transmission gear, the transmission gear is rotatably connected to a guide frame, a second motor is fixed to the top end of the barrel, a flat gear is respectively installed on the output shaft of the second motor and the main shaft, and a transmission assembly is connected to the first gear rod or the second gear rod. In the present invention, when the support rod rotates, the transmission assembly will reciprocate and pull the first gear rod or the second gear rod, and then under the transmission cooperation of the transmission gear, the first gear rod and the second gear rod will move back and forth along the direction of the support rod, thereby increasing the mixing range and improving the mixing efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of plastic product production, and in particular to a mixing and melting device used for the production of plastic products. Background Art

[0002] Plastic products are made of plastic, which are high molecular compounds formed by addition polymerization or condensation polymerization, commonly known as plastics or resins. They can freely change their composition and shape. They are composed of synthetic resins and fillers, plasticizers, stabilizers, lubricants, colorants and other additives. In the process of plastic product production, the raw materials need to be mixed and fused, which is an important link in the preparation process.

[0003] However, the existing stirring structure can only stir within a fixed range. Since the viscosity of the molten plastic raw material is relatively high, the existing stirring structure is quite laborious and inefficient in mixing the plastic raw material. Therefore, corresponding improvements are made to address this problem. Summary of the invention

[0004] Based on the technical problems existing in the prior art, the present invention proposes a mixing and melting device for producing plastic products.

[0005] The present invention proposes a mixing and melting device for the production of plastic products, comprising a cylinder, a discharge pipe is provided at the bottom end of the cylinder, a conveying pipe is provided at the upper position of the circumferential outer wall of the cylinder, a loading pipe is provided on the conveying pipe, a mesh plate located below the conveying pipe is fixed in the cylinder, a main shaft is rotatably connected to the top end of the cylinder, two groups of support rods are fixed to the circumferential outer wall of the main shaft, a guide frame is provided at the end of the support rod, a transmission gear, a first gear rod and a second gear rod are provided in the guide frame, the first gear rod and the second gear rod are meshed and connected to the upper and lower parts of the transmission gear respectively, the transmission gear is rotatably connected to the guide frame, the first gear rod is connected to a counterweight structure, a second motor is fixed to the top end of the cylinder, and mutually meshing flat gears are respectively installed on the output shaft of the second motor and the main shaft. The first gear rod or the second gear rod is connected with a transmission component, a feeding component is arranged in the conveying pipe, and a heating component is also arranged in the cylinder. The plastic raw material is put into the feeding pipe, and then the raw material in the conveying pipe is conveyed to the mesh plate in the cylinder through the feeding component, and then the raw material is melted by the heating component, and the melted raw material flows into the bottom of the mesh plate. At the same time, the output shaft of the second motor drives the flat gear to rotate, and then the main shaft and the support rod are driven to rotate through the two flat gears. When the support rod rotates, the transmission component will reciprocate and pull the first gear rod or the second gear rod, and then under the transmission cooperation of the transmission gear, the first gear rod and the second gear rod will move back and forth along the direction of the support rod, thereby increasing the mixing range and improving the mixing efficiency.

[0006] Preferably, the feeding assembly includes an auger rotatably connected to the inside of the conveying pipe, a first motor is fixed to the end of the conveying pipe, the output shaft of the first motor is connected to the end of the auger, the output shaft of the first motor drives the auger to rotate, and the auger will transport the raw materials in the conveying pipe.

[0007] Preferably, the heating assembly comprises a heater, which is fixed to the top inner wall of the cylinder, and the raw material can be melted by the heater.

[0008] Preferably, the transmission assembly includes a pair of columns fixed on the top of the cylinder, a cross plate is fixed to the tops of the two columns, a center column and two wire ropes extending into the main shaft are fixed to the bottom of the cross plate, and the other end of the wire rope has multiple branches, which pass through the main shaft and are connected to the corresponding ends of the first gear rod, driving the second motor to perform periodic forward and reverse rotation. When the main shaft rotates, the wire rope will be driven to slowly wind around the center column, so that the free ends of the branches of the wire rope will gradually pull the first gear rod to the middle, and when the main shaft reverses, the wire rope will not continue to wind, so that the first gear rod will reset and move due to centrifugal action.

[0009] Preferably, the transmission assembly includes a ring sleeved on the main shaft, the circumferential outer wall of the ring is provided with a plurality of flanges distributed in a circular array, a plurality of racks are fixed on the top of the ring, the ends of the racks are fixed on the inner wall of the mesh plate, a push rod capable of contacting the flange is fixed on the inner end of the top second gear rod, and the plurality of second gear rods are fixedly connected by a connecting plate, and when the second gear rod rotates, the push rod is simultaneously driven to rotate, and when the push rod contacts the flange, it will be pushed and move outward, and at this time the first gear rod will move inward, and when the push rod is out of contact with the flange, the first gear rod will reset and move due to the centrifugal force, and the plurality of second gear rods can be moved synchronously through the connecting plate.

[0010] Preferably, the transmission assembly includes a pressure ring sleeved on the main shaft and a push block abutting the pressure ring, a pair of inner columns are fixed on the top of the pressure ring, a sleeve fixed to the cylinder body is sleeved on the top of the inner column, the sleeve and the inner column are connected by a spring, a connecting rod is fixed to the inner end of the top second gear rod, and multiple second gear rods are fixedly connected by a connecting plate, and the push block is fixed to the top of the connecting rod, and the pressure ring is periodically pressed downward, and then the pressure ring squeezes the push block downward, and the push block will move outward together with the connecting rod and the second gear rod, and the first gear rod will move inward at this time, and when the pressure ring cancels the pressure on the push block, the first gear rod will reset and move due to centrifugal action, and multiple second gear rods can move synchronously through the connecting plate.

[0011] Preferably, a second bevel gear is provided on the fixed sleeve of the main shaft, an ear plate is fixed on the top inner wall of the cylinder, and a shaft rod is rotatably connected to the ear plate, and a first bevel gear and a cam capable of pressing down the pressure ring are provided on the fixed sleeve of the shaft rod, and the first bevel gear and the second bevel gear are meshingly connected, and when the main shaft rotates, the second bevel gear is synchronously driven to rotate, and the second bevel gear is meshed to drive the first bevel gear to rotate around the shaft rod, and the shaft rod will synchronously drive the cam to rotate, and the cam will periodically press down the pressure ring.

[0012] Preferably, the transmission assembly includes a first magnet and a second magnet arranged opposite to each other, a connecting rod is fixed to the top of the first gear rod, the first magnet is fixed to the end of the connecting rod, and the second magnet is fixed to the circumferential inner wall of the cylinder. When the first magnet and the second magnet are close to each other, the magnetic repulsion force between the two will drive the first gear rod to move inward, and when the first magnet and the second magnet are away from each other, the first gear rod will reset due to the centrifugal effect.

[0013] Preferably, the counterweight structure includes a counterweight block, which is fixed to the end of the first gear rod, so that the mass on the first gear rod can be increased by the counterweight block, so that it will be subjected to greater centrifugal force during rotation.

[0014] Preferably, the counterweight structure includes a scraper, a connecting column is fixed to the outer end of the first tooth rod, and the scraper is fixed to the outer ends of multiple connecting columns. In this way, the mass on the first tooth rod can be increased by the scraper, so that it will be subjected to greater centrifugal force during rotation, and the scraper can also scrape the raw materials on the inner wall when it approaches the inner wall of the cylinder.

[0015] Compared with the prior art, the present invention provides a mixing and melting device for the production of plastic products, which has the following beneficial effects:

[0016] 1. A mixing and melting device for the production of plastic products, by setting a first gear rod and a second gear rod, the second motor output shaft drives the flat gear to rotate, and then the two flat gears drive the main shaft and the support rod to rotate. When the support rod rotates, the transmission component will reciprocate and pull the first gear rod or the second gear rod, and then under the transmission cooperation of the transmission gear, the first gear rod and the second gear rod will move back and forth along the direction of the support rod, thereby increasing the mixing range and improving the mixing efficiency.

[0017] 2. A mixing and melting device for the production of plastic products, which drives the second motor to perform periodic forward and reverse rotation by setting a wire rope. When the main shaft rotates, the wire rope will be driven to slowly wind around the central column, so that the free end of the branch of the wire rope will gradually pull the first gear rod toward the middle. When the main shaft reverses, the wire rope will not continue to wind, so that the first gear rod will reset and move due to the centrifugal effect.

[0018] 3. A mixing and melting device for the production of plastic products. By setting a sleeve ring, the second gear rod rotates to synchronously drive the push rod to rotate. When the push rod contacts the flange, it will be pushed and move outward. At this time, the first gear rod will move inward. When the push rod and the flange are out of contact, the first gear rod will reset and move due to centrifugal force. Multiple second gear rods can move synchronously through the connecting plate.

[0019] 4. A mixing and melting device for the production of plastic products, which is provided with a pressure ring, which is periodically pressed downward, and then the pressure ring squeezes the push block downward, and the push block moves outward together with the connecting rod and the second gear rod, and the first gear rod moves inward at this time. When the pressure ring cancels the pressure on the push block, the first gear rod will reset and move due to the centrifugal effect, and multiple second gear rods can be moved synchronously through the connecting plate.

[0020] 5. A mixing and melting device for the production of plastic products, by setting a first magnet and a second magnet. When the first magnet and the second magnet are close to each other, the magnetic repulsion between the two will drive the first gear rod to move inward. When the first magnet and the second magnet are away from each other, the first gear rod will reset due to the centrifugal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the overall structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0022] Figure 2 This is a schematic diagram of the internal structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0023] Figure 3 This is a schematic diagram of a wire rope installation structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0024] Figure 4 For the present invention Figure 2 A schematic diagram of the enlarged structure at point A;

[0025] Figure 5 This is a schematic diagram of a sleeve installation structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0026] Figure 6 For the present invention Figure 5 A schematic diagram of the enlarged structure at B;

[0027] Figure 7 This is a schematic diagram of a pressure ring installation structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0028] Figure 8 For the present invention Figure 7A schematic diagram of the enlarged structure at C;

[0029] Fig. 9 This is a schematic diagram of the internal structure of a sleeve of a mixing and melting device for producing plastic products proposed by the present invention;

[0030] Fig.10 This is a schematic diagram of the first magnet installation structure of a mixing and melting device for producing plastic products proposed by the present invention;

[0031] Fig.11 This is a schematic diagram of the scraper installation structure of a mixing and melting device for producing plastic products proposed by the present invention.

[0032] In the figure: 1, cylinder; 2, discharge pipe; 3, conveying pipe; 4, feeding pipe; 5, first motor; 6, auger; 7, heater; 8, main shaft; 9, support rod; 10, guide frame; 11, transmission gear; 12, first gear rod; 13, second gear rod; 14, second motor; 15, flat gear; 16, column; 17, horizontal plate; 18, center column; 19, wire rope; 20, mesh plate; 21, frame rod; 22 , collar; 23, flange; 24, push rod; 25, connecting plate; 26, connecting rod; 27, push block; 28, pressure ring; 29, ear plate; 30, shaft; 31, first bevel gear; 32, second bevel gear; 33, cam; 34, sleeve; 35, inner column; 36, spring; 37, connecting rod; 38, first magnet; 39, second magnet; 40, connecting column; 41, scraper; 42, counterweight. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] Reference Figure 1-11A mixing and melting device for producing plastic products comprises a cylinder 1, a discharge pipe 2 is arranged at the bottom end of the cylinder 1, a conveying pipe 3 is arranged at the upper position of the circumferential outer wall of the cylinder 1, a feeding pipe 4 is arranged on the conveying pipe 3, a mesh plate 20 located below the conveying pipe 3 is fixed in the cylinder 1, a main shaft 8 is rotatably connected to the top of the cylinder 1, two groups of support rods 9 are fixed to the circumferential outer wall of the main shaft 8, a guide frame 10 is arranged at the end of the support rod 9, a transmission gear 11, a first gear rod 12 and a second gear rod 13 are arranged in the guide frame 10, the first gear rod 12 and the second gear rod 13 are respectively meshed and connected to the upper and lower parts of the transmission gear 11, the transmission gear 11 is rotatably connected to the guide frame 10, the first gear rod 12 is connected to a counterweight structure, a second motor 14 is fixed to the top of the cylinder 1, and mutually meshing flat gears 15 are respectively installed on the output shaft of the second motor 14 and the main shaft 8, the first gear rod 12 or the second gear rod 13 is connected with a transmission component, a feeding component is arranged in the conveying pipe 3, and a heating component is also arranged in the cylinder 1. The plastic raw material is put into the feeding pipe 4, and then the raw material in the conveying pipe 3 is conveyed to the mesh plate 20 in the cylinder 1 through the feeding component, and then the raw material is melted by the heating component, and the melted raw material flows into the bottom of the mesh plate 20. At the same time, the output shaft of the second motor 14 drives the flat gear 15 to rotate, and then the two flat gears 15 drive the main shaft 8 and the support rod 9 to rotate. When the support rod 9 rotates, the transmission component will reciprocate and pull the first gear rod 12 or the second gear rod 13, and then under the transmission cooperation of the transmission gear 11, the first gear rod 12 and the second gear rod 13 will move back and forth along the direction of the support rod 9, thereby increasing the mixing range and improving the mixing efficiency. After the mixing is completed, the solenoid valve in the discharge pipe 2 is opened, and the raw material can flow down from the discharge pipe 2.

[0036] Among them, the feeding component includes an auger 6 rotatably connected to the inside of the conveying pipe 3, a first motor 5 is fixed to the end of the conveying pipe 3, the output shaft of the first motor 5 is connected to the end of the auger 6, the output shaft of the first motor 5 drives the auger 6 to rotate, and the auger 6 will transport the raw materials in the conveying pipe 3.

[0037] The heating assembly includes a heater 7 , which is fixed to the top inner wall of the cylinder 1 , and the raw material can be melted by the heater 7 .

[0038] In Example 1, the transmission assembly includes a pair of columns 16 fixed to the top of the cylinder 1, and a cross plate 17 is fixed to the top of the two columns 16. A center column 18 and two wire ropes 19 extending into the main shaft 8 are fixed to the bottom of the cross plate 17. The other end of the wire rope 19 has a plurality of branches, and the branches pass through the main shaft 8 and are connected to the ends of the corresponding first gear rod 12, driving the second motor 14 to perform periodic forward and reverse rotation. When the main shaft 8 rotates, the wire rope 19 will be driven to slowly wind around the center column 18, so that the free ends of the branches of the wire rope 19 will gradually pull the first gear rod 12 to the middle. When the main shaft 8 reverses, the wire rope 19 will not continue to wind, so that the first gear rod 12 will be reset and moved due to the centrifugal force.

[0039] In Example 2, the transmission assembly includes a collar 22 sleeved on the main shaft 8, and the circumferential outer wall of the collar 22 is provided with a plurality of flanges 23 distributed in a circular array. A plurality of rack rods 21 are fixed to the top of the collar 22, and the ends of the rack rods 21 are fixed to the inner wall of the mesh plate 20. A push rod 24 capable of contacting the flange 23 is fixed to the inner end of the top second gear rod 13. The plurality of second gear rods 13 are fixedly connected by a connecting plate 25. When the second gear rod 13 rotates, the push rod 24 is simultaneously driven to rotate. When the push rod 24 contacts the flange 23, it will be pushed and move outward. At this time, the first gear rod 12 will move inward. When the push rod 24 and the flange 23 are out of contact, the first gear rod 12 will reset and move due to the centrifugal force. The plurality of second gear rods 13 can move synchronously through the connecting plate 25.

[0040] In Example 3, the transmission assembly includes a pressure ring 28 sleeved on the main shaft 8 and a push block 27 abutting against the pressure ring 28, a pair of inner columns 35 are fixed on the top of the pressure ring 28, and a sleeve 34 fixed to the cylinder body 1 is sleeved on the top of the inner column 35, and the sleeve 34 and the inner column 35 are connected by a spring 36, and a connecting rod 26 is fixed to the inner end of the top second gear rod 13, and multiple second gear rods 13 are fixedly connected by a connecting plate 25, and the push block 27 is fixed to the top of the connecting rod 26, and the pressure ring 28 is periodically pressed downward, and then the pressure ring 28 squeezes the push block 27 downward, and the push block 27 will move outward together with the connecting rod 26 and the second gear rod 13, and the first gear rod 12 will move inward, and when the pressure ring 28 cancels the pressure on the push block 27, the first gear rod 12 will reset and move due to centrifugal action, and multiple second gear rods 13 can be moved synchronously through the connecting plate 25.

[0041] Furthermore, a second bevel gear 32 is fixedly sleeved on the main shaft 8, an ear plate 29 is fixedly provided on the top inner wall of the cylinder 1, and a shaft rod 30 is rotatably connected to the ear plate 29. A first bevel gear 31 and a cam 33 capable of pressing down the pressure ring 28 are fixedly sleeved on the shaft rod 30. The first bevel gear 31 and the second bevel gear 32 are meshingly connected. When the main shaft 8 rotates, the second bevel gear 32 is synchronously driven to rotate. The second bevel gear 32 is meshed to drive the first bevel gear 31 to rotate around the shaft rod 30. The shaft rod 30 will synchronously drive the cam 33 to rotate, and the cam 33 will periodically press down the pressure ring 28.

[0042] In Example 4, the transmission assembly includes a first magnet 38 and a second magnet 39 that are arranged opposite to each other. A connecting rod 37 is fixed to the top of the first gear rod 12, the first magnet 38 is fixed to the end of the connecting rod 37, and the second magnet 39 is fixed to the circumferential inner wall of the cylinder 1. When the first magnet 38 and the second magnet 39 are close to each other, the magnetic repulsion force between the two will drive the first gear rod 12 to move inward. When the first magnet 38 and the second magnet 39 are away from each other, the first gear rod 12 will reset due to the centrifugal effect.

[0043] The counterweight structure includes a counterweight block 42 , which is fixed to the end of the first gear rod 12 , so that the mass on the first gear rod 12 can be increased by the counterweight block 42 , so that it will be subjected to greater centrifugal force during rotation.

[0044] In Example 5, the counterweight structure includes a scraper 41, and a connecting column 40 is fixed to the outer end of the first tooth rod 12. The scraper 41 is fixed to the outer ends of multiple connecting columns 40. In this way, the mass on the first tooth rod 12 can be increased by the scraper 41, so that it will be subjected to greater centrifugal force during rotation, and the scraper 41 can also scrape the raw material on the inner wall when it is close to the inner wall of the cylinder 1.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A mixing and melting device for producing plastic products, comprising a cylinder (1), characterized in that: The bottom end of the cylinder (1) is provided with a discharge pipe (2), the upper part of the circumferential outer wall of the cylinder (1) is provided with a conveying pipe (3), the conveying pipe (3) is provided with a loading pipe (4), a mesh plate (20) located below the conveying pipe (3) is fixed in the cylinder (1), the top end of the cylinder (1) is rotatably connected to a main shaft (8), two groups of support rods (9) are fixed to the circumferential outer wall of the main shaft (8), a guide frame (10) is provided at the end of the support rod (9), a transmission gear (11), a first gear rod (12) and a second gear rod (13) are provided in the guide frame (10), and the first gear rod (12) and the second gear rod (13) are provided in the guide frame (10). The toothed rod (12) and the second toothed rod (13) are respectively meshed and connected at the upper and lower parts of the transmission gear (11); the transmission gear (11) is rotationally connected to the guide frame (10); the first toothed rod (12) is connected to a counterweight structure; a second motor (14) is fixed to the top of the cylinder (1); mutually meshing flat gears (15) are respectively installed on the output shaft of the second motor (14) and the main shaft (8); the first toothed rod (12) or the second toothed rod (13) is connected to a transmission assembly; a feeding assembly is arranged in the conveying pipe (3); and a heating assembly is also arranged in the cylinder (1); The transmission assembly comprises a pair of columns (16) fixed to the top of the cylinder (1), a horizontal plate (17) being fixed to the tops of the two columns (16), a central column (18) extending into the main shaft (8) and two wire ropes (19) being fixed to the bottom of the horizontal plate (17), the other end of the wire rope (19) having a plurality of branches, the branches respectively passing through the main shaft (8) and connected to the ends of the corresponding first gear rods (12); Or the transmission assembly comprises a collar (22) sleeved on the main shaft (8), the outer circumferential wall of the collar (22) being provided with a plurality of flanges (23) distributed in an annular array, a plurality of racks (21) being fixed on the top of the collar (22), the ends of the racks (21) being fixed on the inner wall of the mesh plate (20), a push rod (24) being able to contact the flange (23) being fixed on the inner end of the uppermost second gear rod (13), and the plurality of second gear rods (13) being fixedly connected by a connecting plate (25); Or the transmission assembly comprises a pressure ring (28) sleeved on the main shaft (8) and a push block (27) abutting against the pressure ring (28), a pair of inner columns (35) are fixed on the top of the pressure ring (28), a sleeve (34) fixed to the cylinder (1) is sleeved on the top of the inner column (35), the sleeve (34) and the inner column (35) are connected by a spring (36), a connecting rod (26) is fixed to the inner end of the uppermost second gear rod (13), a plurality of second gear rods (13) are fixedly connected by a connecting plate (25), and the push block (27) is fixed to the top of the connecting rod (26); Or the transmission assembly comprises a first magnet (38) and a second magnet (39) which are arranged opposite to each other, a connecting rod (37) is fixed to the top of the first gear rod (12), the first magnet (38) is fixed to the end of the connecting rod (37), and the second magnet (39) is fixed to the circumferential inner wall of the cylinder (1).

2. A mixing and melting device for producing plastic products according to claim 1, characterized in that: The feeding assembly comprises an auger (6) rotatably connected to the inside of the conveying pipe (3); a first motor (5) is fixed to the end of the conveying pipe (3); and an output shaft of the first motor (5) is connected to the end of the auger (6).

3. A mixing and melting device for producing plastic products according to claim 1, characterized in that: The heating assembly comprises a heater (7), and the heater (7) is fixed on the top inner wall of the cylinder (1).

4. A mixing and melting device for producing plastic products according to claim 1, characterized in that: A second bevel gear (32) is fixedly sleeved on the main shaft (8), an ear plate (29) is fixedly mounted on the inner wall of the top of the cylinder (1), a shaft (30) is rotatably connected to the ear plate (29), a first bevel gear (31) and a cam (33) capable of pressing the pressure ring (28) downward are fixedly sleeved on the shaft (30), and the first bevel gear (31) and the second bevel gear (32) are meshingly connected.

5. A mixing and melting device for producing plastic products according to claim 1, characterized in that: The counterweight structure comprises a counterweight block (42), and the counterweight block (42) is fixed to the end of the connecting rod (37).

6. A mixing and melting device for producing plastic products according to claim 1, characterized in that: The counterweight structure comprises a scraper (41), a connecting column (40) is fixed to the outer end of the first toothed rod (12), and the scraper (41) is fixed to the outer ends of a plurality of connecting columns (40).

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