Road maintenance device

Abstract

The utility model provides a road maintenance device which is characterized in that a first movable box body and a second movable box body are movably installed on the upper surface of a base through track grooves and track wheels, the first movable box body and the second movable box body are each internally provided with a containing frame, and a first water vapor inlet pipe is arranged at the top end of the first movable box body; compared with the prior art, the concrete test block curing device has the advantages that due to the design of the placing frame, most of the area of the lower surface of a concrete test block makes contact with water vapor, and the problem that the concrete curing effect is poor due to the fact that the concrete test block cannot make contact with the water due to shielding is solved; the contact area of the concrete test block placed on the concrete test block and the external environment can be increased, so that a plurality of surfaces of the concrete test block can be in the same temperature and humidity environment at the same time, and the performance of the concrete test block cured in the optimal environment can be detected.

Description

Technical Field

[0001] The utility model discloses a highway maintenance device, which relates to the field of municipal maintenance equipment. Background Art

[0002] At present, a large amount of concrete is needed in municipal service construction, which is mainly used in municipal highway maintenance construction. During municipal highway maintenance construction, the quality of concrete needs to be tested. Only after meeting the standards can it be put into municipal highway concrete construction. The quality of highway concrete is generally verified by concrete test blocks. After the concrete is poured into the test blocks, it needs to be cured. Generally, a concrete curing box is used to cure the concrete test blocks. However, during the curing of the existing concrete curing box, the humidity at various positions in the box is different, especially the bottom of the test block is easily blocked and difficult to contact with moisture, resulting in different moisture in various parts of the test block, reducing the performance of the test block, and making it difficult to detect the true performance of the concrete. Therefore, there is an urgent need for a curing device for testing concrete test blocks during municipal highway maintenance construction to solve the above problems. Utility Model Content

[0003] In view of the deficiencies in the prior art, the purpose of the utility model is to provide a highway maintenance device to solve the problems raised in the above-mentioned background technology. The utility model is easy to use, easy to operate, good in stability and high in reliability.

[0004] In order to achieve the above-mentioned purpose, the utility model is realized through the following technical scheme: a highway maintenance device, including a base, a movable box body 1, a movable box body 2, a water vapor inlet pipe 1, a water vapor inlet pipe 2 and a placement rack, the upper surface of the base is movably installed with the movable box body 1 and the movable box body 2 through track grooves and track wheels, the movable box body 1 and the movable box body 2 are movably connected through a fishing platform lock, a placement rack is installed inside the movable box body 1 and the movable box body 2 respectively, the water vapor inlet pipe 1 is arranged at the top of the movable box body 1, and the water vapor inlet pipe 2 is arranged at the top of the movable box body 2.

[0005] Furthermore, the movable box body 1 and the movable box body 2 have the same specifications, and the movable box body 1 includes an outer shell, an inner cavity, an inner shell, a temperature and humidity sensor, a support grid, a support plate and a through hole. The inner shell is fixed to the inside of the outer shell through the support plate, and the through hole is opened on the surface of the support plate. An inner cavity is provided between the outer shell and the inner shell, and a plurality of temperature and humidity sensors are provided inside the inner shell, and the plurality of temperature and humidity sensors are arranged at multiple positions inside the inner shell. The support grid is arranged at the bottom of the inner cavity, and the support grid includes a horizontal plate, a vertical plate and a trapezoidal through groove.

[0006] Furthermore, there are multiple horizontal plates, and multiple vertical plates, and the multiple horizontal plates are connected by vertical plates. A trapezoidal through groove is provided on the lower side of the horizontal plate, and the trapezoidal through groove is arranged on the lower side of the vertical plate. There are multiple support plates, and the multiple support plates are arranged in parallel on the upper side of the inner cavity. Multiple through holes are distributed in a straight line on the surface of the support plate, and multiple small circular holes are evenly distributed on the surface of the inner shell.

[0007] Furthermore, the placement frame includes a rotating base, a support column, a support assembly and a connecting hole. The rotating base is fixed at the bottom of the inner shell body, and a support column is movably installed on the upper side of the rotating base through a bearing and a bearing sleeve. The support assembly is arranged on the upper end side surface of the support column. There are multiple support assemblies, two of which are arranged at the same height and symmetrically arranged about the support column axis. Four of the support assemblies form a group, and the four support assemblies are each arranged at an angle of ninety degrees. The connecting hole is arranged inside the support column, and the connecting hole vertically penetrates the support column. A cavity is provided at the bottom of the rotating base, and a limiting ring is provided at the lower end of the support column, and the connecting hole is connected to the cavity.

[0008] Furthermore, the support assembly includes a placement plate, a support head, a strip dovetail block, a dovetail groove, a drainage hole, a support component, a connecting hole, a strip through hole, a dispersion chamber and a mounting hole. The upper surface of the placement plate is provided with a mounting hole, and the upper surface of the placement plate is threadedly connected with the support head through the mounting hole. The dispersion chamber is arranged inside the placement plate, and a strip through hole is arranged in the middle of the lower surface of the placement plate. The lower surface of the placement plate is provided with a strip dovetail block, and the strip dovetail blocks are provided in three groups. The placement plate is movably mounted on the upper side of the support component through the strip dovetail block and the dovetail groove. A plurality of ventilation holes are arranged in the middle of the upper surface of the support component, an airway is arranged inside the support component, and a drainage hole is arranged at the right end of the airway. The lower ends of the plurality of ventilation holes are connected with the inside of the airway, and the airway is connected with the connecting hole.

[0009] Furthermore, the air vent is located at the lower side of the strip through hole, and the air vent is connected to the strip through hole, the support head includes a cylindrical tube section and an inverted frustum section, the lower end of the cylindrical tube section is threadedly connected to the mounting hole, the lower end of the inverted frustum section is fixedly connected to the upper end of the cylindrical tube section, the diameter of the inverted frustum section gradually increases from bottom to top, the collecting chamber is arranged inside the inverted frustum section, the inner diameter of the collecting chamber gradually increases from bottom to top, the upper surface of the inverted frustum section is horizontal, and a plurality of small holes are evenly distributed on the upper surface of the inverted frustum section, the outer end sections of the three groups of strip dovetail blocks are the same length, and the length of the strip dovetail in the middle of the inner end sections of the three groups of strip dovetail blocks is smaller than the strip dovetail blocks of the inner end sections on both sides thereof.

[0010] The beneficial effects of the utility model are as follows: by setting the movable box body 1 and the movable box body 2 and cooperating with the base, the whole device is divided into two parts. In actual use, the movable box body 1 and the movable box body 2 can be combined and dispersed by separation and combination, so that the placement rack can be directly exposed to the outside, which is convenient for taking concrete test blocks and improving work efficiency. At the same time, water vapor is input into the inner cavity of the movable box body 1 and the movable box body 2 through the water vapor entry pipe 1 and the water vapor entry pipe 2, so that humid air flows to the test blocks on the placement rack from various positions, so that the surface of the test block contacts the water vapor more evenly, and multiple temperature and humidity sensors arranged at multiple angles can effectively monitor the air humidity and temperature inside the movable box body 1 and the movable box body 2. The design of the placement rack makes most of the area of ​​the lower surface of the concrete test block contact with water vapor, avoiding the problem of poor concrete curing effect due to being blocked and unable to contact moisture, so that the concrete test block placed thereon can increase the area in contact with the external environment, so that multiple surfaces of the concrete test block can be in the same temperature and humidity environment at the same time, which is conducive to detecting the performance of the concrete test block after curing in the optimal environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0012] Figure 1 This is a schematic diagram of the structure of a highway maintenance device of the utility model;

[0013] Figure 2 It is a schematic diagram of the internal structure of a movable box in a highway maintenance device of the utility model;

[0014] Figure 3 It is a schematic diagram of a support grid in a highway maintenance device of the utility model;

[0015] Figure 4 It is a schematic diagram of a support plate in a highway maintenance device of the utility model;

[0016] Figure 5 It is a schematic diagram of a placement rack in a highway maintenance device of the utility model;

[0017] Figure 6 It is a schematic diagram of a support assembly in a highway maintenance device of the utility model;

[0018] Figure 7 It is a schematic diagram of a top view of a supporting component in a highway maintenance device of the utility model;

[0019] Figure 8 It is a schematic diagram of a top view of a placement plate in a highway maintenance device of the utility model;

[0020] Fig. 9 It is a schematic diagram of the internal structure of a placement plate in a highway maintenance device of the utility model;

[0021] Fig.10 It is a schematic diagram of the connection between the rotating base and the supporting base in a highway maintenance device of the utility model;

[0022] Fig.11 It is a schematic diagram of a cross-section of a supporting component in a highway maintenance device of the utility model;

[0023] In the figure: 1-base, 2-movable box body 1, 21-outer shell, 22-inner cavity, 23-inner shell, 24-temperature and humidity sensor, 25-support grid, 251-horizontal plate, 252-vertical plate, 253-trapezoidal through groove, 26-support plate, 261-through hole, 3-water vapor inlet pipe 1, 4-water vapor inlet pipe 2, 5-movable box body 2, 6-placement rack, 61-rotating base, 62-support column, 63-support assembly, 631-placement plate, 632-support head, 633-strip dovetail block, 634-dovetail groove, 635-drainage hole, 636-support component, 637-ventilation hole, 638-strip through hole, 639-dispersion cavity, 6310-mounting hole, 64-connecting hole. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific implementation methods.

[0025] See also Figure 1 and Fig.11 The utility model provides a technical solution: a highway maintenance device, including a base 1, a movable box body 2, a movable box body 5, a water vapor inlet pipe 3, a water vapor inlet pipe 4 and a placement rack 6. The upper surface of the base 1 is movably installed with the movable box body 2 and the movable box body 5 through track grooves and track wheels. The movable box body 2 and the movable box body 5 are movably connected through a fishing platform lock. A placement rack 6 is installed inside the movable box body 2 and inside the movable box body 2 5 respectively. The water vapor inlet pipe 3 is arranged at the top of the movable box body 2, and the water vapor inlet pipe 4 is arranged at the top of the movable box body 2.

[0026] The movable box body 1 2 has the same specifications as the movable box body 2 5. The movable box body 1 2 includes an outer shell 21, an inner cavity 22, an inner shell 23, a temperature and humidity sensor 24, a support grid 25, a support plate 26 and a through hole 261. The inner shell 23 is fixed to the inside of the outer shell 21 through the support plate 26. The through hole 261 is opened on the surface of the support plate 26. An inner cavity 22 is provided between the outer shell 21 and the inner shell 23. A plurality of temperature and humidity sensors 24 are provided inside the inner shell 23, and the plurality of temperature and humidity sensors 24 are arranged at multiple positions inside the inner shell 23. The support grid 25 is arranged at the bottom of the inner cavity 22. The support grid 25 includes a horizontal plate 251, a vertical plate 252 and a trapezoidal through groove 253.

[0027] There are multiple horizontal plates 251 and multiple vertical plates 252, and the multiple horizontal plates 251 are connected by the vertical plates 252. A trapezoidal through groove 253 is provided on the lower side of the horizontal plate 251, and the trapezoidal through groove 253 is arranged on the lower side of the vertical plate 252. There are multiple support plates 26, and the multiple support plates 26 are arranged in parallel on the upper side of the inner cavity 22. Multiple through holes 261 are distributed in a straight line on the surface of the support plate 26, and a plurality of small circular holes are evenly distributed on the surface of the inner shell 23.

[0028] The placement frame 6 includes a rotating base 61, a support column 62, a support assembly 63 and a connecting hole 64. The rotating base 61 is fixed at the bottom of the inner shell 23. The support column 62 is movably installed on the upper side of the rotating base 61 through a bearing and a bearing sleeve. The support assembly 63 is arranged on the upper end side surface of the support column 62. There are multiple support assemblies 63. Two support assemblies 63 are arranged at the same height and are symmetrically arranged about the support column 62 axis. Four support assemblies 63 form a group, and the four support assemblies 63 are each arranged at an angle of ninety degrees. The connecting hole 64 is arranged inside the support column 62. The connecting hole 64 vertically penetrates the support column 62. A cavity is provided at the bottom of the rotating base 61, and a limiting ring is provided at the lower end of the support column 62. The connecting hole 64 is connected to the cavity.

[0029] The support assembly 63 includes a placement plate 631, a support head 632, a strip dovetail block 633, a dovetail groove 634, a drainage hole 635, a support component 636, a connecting hole 64, a strip through hole 638, a dispersion cavity 639 and a mounting hole 6310. The placement plate 631 has a mounting hole 6310 on its upper surface. The support head 632 is threadedly connected to the upper surface of the placement plate 631 through the mounting hole 6310. The dispersion cavity 639 is arranged inside the placement plate 631. A strip through hole 638 is provided in the middle, a strip dovetail block 633 is provided on the lower surface of the placement plate 631, and there are three groups of strip dovetail blocks 633. The placement plate 631 is movably mounted on the upper side of the support component 636 through the strip dovetail block 633 and the dovetail groove 634. A plurality of ventilation holes 637 are provided in the middle of the upper surface of the support component 636. An airway is provided inside the support component 636, and a drainage hole 635 is provided at the right end of the airway. The lower ends of the plurality of ventilation holes 637 are connected with the inside of the airway, and the airway is connected with the connecting hole 64.

[0030] The air hole 637 is located at the lower side of the strip through hole 638, and the air hole 637 is connected to the strip through hole 638. The support head 632 includes a cylindrical tube section and an inverted cone section. The lower end of the cylindrical tube section is threadedly connected to the mounting hole 6310, and the lower end of the inverted cone section is fixedly connected to the upper end of the cylindrical tube section. The diameter of the inverted cone section gradually increases from bottom to top. The collecting cavity is arranged inside the inverted cone section, and the inner diameter of the collecting cavity gradually increases from bottom to top. The upper surface of the inverted cone section is horizontal, and a plurality of small holes are evenly distributed on the upper surface of the inverted cone section. The outer end sections of the three groups of strip dovetail blocks 633 are the same length, and the length of the strip dovetail in the middle of the inner end sections of the three groups of strip dovetail blocks 633 is smaller than the strip dovetail blocks 633 of the inner end sections on both sides thereof.

[0031] Specific implementation method: In actual use, when it is necessary to place a concrete test block on the placement rack 6 in the movable box body 1 2 and the movable box body 2 5 for curing, first open the movable box body 1 2 and the movable box body 2 5 in opposite directions on the base 1, so that the originally combined movable box body 1 2 and the movable box body 2 5 are separated in opposite directions. After the movable box body 1 2 and the movable box body 2 5 are separated, the concrete test block that needs to be cured is first placed on the placement plate 631 so that the lower surface of the test block contacts the upper surface of the support head 632. Since the upper surface of the support head 632 is horizontal, the test block will not be placed unsteadily. Then, the entire placement plate 631 is picked up to avoid damage to the concrete test block on the placement plate 631. When the three groups of strip dovetail blocks 633 on the lower surface of the placement plate 631 are respectively plugged into the dovetail grooves 634 at the corresponding positions, at this time, a group of strip dovetail blocks 633 in the middle of the lower surface of the placement plate 631 and the dovetail groove 6 in the middle of the upper surface of the support component 636 are connected. 34 sliding connection, when the inner end of a group of strip dovetail blocks 633 in the middle of the lower surface of the placement plate 631 is plugged into the inner end of the dovetail groove 634 in the middle of the upper surface of the support component 636, the inner ends of the other two groups of strip dovetail blocks 633 are plugged into the inner ends of the dovetail grooves 634 on both sides of the upper surface of the support component 636. When the plug-in limit is reached, the placement plate 631 is completely clamped on the upper side of the support component 636. Since the support column 62 is movably installed on the upper side of the rotating base 61 through bearings and bearing sleeves, the entire support column 62 can be rotated, which is more convenient for plugging in the placement plate 631. At the same time, there are multiple support components 63, two of which are set at the same height and symmetrically about the support column 62 axis. Four support components 63 form a group, and the four support components 63 are each set at a ninety-degree angle. This allows multiple concrete test blocks to be placed on the placement rack 6 with a large distance between each other and will not affect each other's absorption of moisture.

[0032] Specific implementation method: After the concrete test block is placed, the movable box body 1 2 and the movable box body 2 5 are manually moved in opposite directions. After the movable box body 1 2 and the movable box body 2 5 are fixed by the fishing platform lock, the water vapor-rich air can be input into the inner cavity 22 inside the movable box body 1 2 and the movable box body 2 5 through the water vapor entry pipe 1 3 and the water vapor entry pipe 2 4 respectively. Since a plurality of small circular holes are evenly arranged on the surface of the inner shell 23 inside the inner cavity 22, the water vapor in the inner cavity 22 of the movable box body 1 2 and the movable box body 2 5 can pass through a plurality of evenly distributed small holes on the surface of the inner shell 23. The circular holes respectively enter the interior of the movable box body 1 2 and the movable box body 2 5, so that the test blocks on the placement rack 6 of the movable box body 1 2 and the movable box body 2 5 can be in an environment with uniform humidity. The setting of the support plate 26 improves the compressive strength of the inner cavity 22. The multiple temperature and humidity sensors 24 set at multiple angles can understand the temperature and humidity conditions of each position in the movable box body 1 2 and the movable box body 2 5 at the first time. At the same time, since the connecting hole 64 is set inside the support column 62, the connecting hole 64 vertically penetrates the support column 62, a cavity is provided at the bottom of the rotating base 61, and a limit ring is provided at the lower end of the support column 62. The connecting hole 64 is connected to the cavity, and the water vapor at the bottom of the inner cavity 22 enters the cavity through the small circular hole, and then enters the connecting hole 64 inside the support column 62 through the cavity. Since a plurality of vent holes 637 are provided in the middle of the upper surface of the support component 636, an airway is provided inside the support component 636, and a drainage hole 635 is provided at the right end of the airway. The lower ends of the plurality of vent holes 637 are connected to the inside of the airway, and the airway is connected to the connecting hole 64, so that the water vapor enters the dispersion cavity 639 through the airway, the plurality of vent holes 637 and the strip-shaped through hole 638. Then, since the support head 632 includes a cylindrical tube section, an inverted cone section, and an inverted cone section, the water vapor enters the dispersion cavity 639 through the airway, the plurality of vent holes 637 and the strip-shaped through hole 638. The diameter of the segment increases gradually from bottom to top, and the collecting chamber is arranged inside the inverted frustum segment. The inner diameter of the collecting chamber increases gradually from bottom to top, and a plurality of small holes are evenly distributed on the upper surface of the inverted frustum segment, so that water vapor can contact the lower surface of the test block at the upper end of the support head 632 through the plurality of small holes, avoiding the problem of poor concrete curing effect due to the inability to contact moisture due to obstruction, so that the concrete test block placed thereon can increase the area in contact with the external environment, so that multiple surfaces of the concrete test block can be in the same temperature and humidity environment at the same time, which is conducive to detecting the performance of the concrete test block after curing in the optimal environment.

[0033] The above shows and describes the basic principles and main features of the utility model and the advantages of the utility model. For those skilled in the art, it is obvious that the utility model is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the utility model. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the utility model is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0034] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A highway maintenance device, comprising a base (1), a movable box body 1 (2), a movable box body 2 (5), a water vapor inlet pipe 1 (3), a water vapor inlet pipe 2 (4) and a placement rack (6), characterized in that: A movable box body 1 (2) and a movable box body 2 (5) are movably mounted on the upper surface of the base (1) via a track groove and a track wheel. The movable box body 1 (2) and the movable box body 2 (5) are movably connected via a fishing platform lock. A placement rack (6) is mounted inside the movable box body 1 (2) and inside the movable box body 2 (5), respectively. A water vapor inlet pipe 1 (3) is mounted at the top end of the movable box body 1 (2), and a water vapor inlet pipe 2 (4) is mounted at the top end of the movable box body 2 (5).

2. A road maintenance device according to claim 1, characterized in that: The movable box body 1 (2) and the movable box body 2 (5) have the same specifications. The movable box body 1 (2) comprises an outer shell (21), an inner cavity (22), an inner shell (23), a temperature and humidity sensor (24), a support grid (25), a support plate (26) and a through hole (261). The inner shell (23) is fixed inside the outer shell (21) via the support plate (26). The support plate (26) has a through hole (261) on its surface. An inner cavity (22) is provided between the outer shell (21) and the inner shell (23). A plurality of temperature and humidity sensors (24) are provided inside the inner shell (23), and the plurality of temperature and humidity sensors (24) are arranged at a plurality of positions inside the inner shell (23). A support grid (25) is provided at the bottom of the inner cavity (22). The support grid (25) comprises a horizontal plate (251), a vertical plate (252) and a trapezoidal through groove (253).

3. A road maintenance device according to claim 2, characterized in that: A plurality of the transverse plates (251) are provided, and a plurality of the vertical plates (252) are provided. The plurality of the transverse plates (251) are connected via the vertical plates (252). A trapezoidal through groove (253) is provided on the lower side of the transverse plates (251). A trapezoidal through groove (253) is provided on the lower side of the vertical plates (252). A plurality of the support plates (26) are provided, and the plurality of the support plates (26) are arranged in parallel on the upper side of the inner cavity (22). A plurality of through holes (261) are distributed in a linear manner on the surface of the support plates (26), and a plurality of small circular holes are evenly distributed on the surface of the inner shell (23).

4. A road maintenance device according to claim 1, characterized in that: The placement rack (6) comprises a rotating base (61), a support column (62), a support assembly (63) and a connecting hole (64). The rotating base (61) is fixed to the bottom of the inner shell (23). The upper side of the rotating base (61) is movably mounted with a support column (62) through a bearing and a bearing sleeve. The upper end side surface of the support column (62) is provided with a support assembly (63). There are multiple support assemblies (63). Two support assemblies (63) are arranged at the same height and are symmetrically arranged about the support column (62) axis. Four support assemblies (63) form a group, and the four support assemblies (63) are arranged at an angle of ninety degrees. A connecting hole (64) is provided inside the support column (62). The connecting hole (64) vertically penetrates the support column (62). A cavity is provided at the bottom of the rotating base (61). A limiting ring is provided at the lower end of the support column (62). The connecting hole (64) is connected to the cavity.

5. A road maintenance device according to claim 4, characterized in that: The support assembly (63) comprises a placement plate (631), a support head (632), a strip dovetail block (633), a dovetail groove (634), a drainage hole (635), a support component (636), a connecting hole (64), a strip through hole (638), a dispersion cavity (639) and a mounting hole (6310). The placement plate (631) has a mounting hole (6310) on its upper surface. The support head (632) is threadedly connected to the placement plate (631) on its upper surface via the mounting hole (6310). The placement plate (631) has a dispersion cavity (639) inside. The placement plate (631) has a lower surface A strip through hole (638) is provided in the middle, a strip dovetail block (633) is provided on the lower surface of the placement plate (631), and three groups of the strip dovetail blocks (633) are provided. The placement plate (631) is movably mounted on the upper side of the support component (636) through the strip dovetail block (633) and the dovetail groove (634). A plurality of ventilation holes (637) are provided in the middle of the upper surface of the support component (636), an airway is provided inside the support component (636), and a drainage hole (635) is provided at the right end of the airway. The lower ends of the plurality of ventilation holes (637) are connected to the inside of the airway, and the airway is connected to the connecting hole (64).

6. A road maintenance device according to claim 5, characterized in that: The vent hole (637) is located at the lower side of the strip through hole (638), and the vent hole (637) is connected to the strip through hole (638). The support head (632) includes a cylindrical tube section and an inverted frustum section. The lower end of the cylindrical tube section is threadedly connected to the mounting hole (6310). The upper end of the cylindrical tube section is fixedly connected to the lower end of the inverted frustum section. The diameter of the inverted frustum section gradually increases from bottom to top. A collecting cavity is provided inside the inverted frustum section. The inner diameter of the collecting cavity gradually increases from bottom to top. The upper surface of the inverted frustum section is horizontal, and a plurality of small holes are evenly distributed on the upper surface of the inverted frustum section. The outer end sections of the three groups of the strip dovetail blocks (633) are the same length. The strip dovetail in the middle of the inner end sections of the three groups of the strip dovetail blocks (633) is shorter than the strip dovetail blocks (633) of the inner end sections on both sides thereof.

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