A method for pouring non-bottom-layer super-flat floor without the need for subsequent leveling

Abstract

The present invention relates to the technical field of ground or floor layers produced on-site using aggregate materials, and discloses a method for casting non-bottom-layer super-flat floors that does not require subsequent leveling. By using a sliding rail with steel bars higher than the floor slab and a scraper on the sliding rail to scrape the concrete, the problem that the compartment method cannot be implemented due to the interference of steel bars in the floor slab is solved; an independent support structure that does not contact the formwork and the supporting structure of the formwork is used to support the sliding rail, thereby avoiding deformation of the formwork and shaking of the formwork supporting structure during construction that affect the scraping of the concrete; the above two points are combined to ensure that it is feasible to scrape the non-bottom-layer floor slab to form a super-flat floor while casting. In the present invention, the top of the sliding rail is blade-shaped and in point contact with the scraper, so that even if the supporting structure of the sliding rail is skewed, it does not affect the use of the scraper. At the same time, it cooperates with a laser leveler to quickly adjust the height of the top of each sliding rail, thereby providing the scraper with a sliding rail that can meet the precision required for scraping concrete with a lower construction difficulty.

Description

Technical Field

[0001] The present invention relates to the technical field of ground or floor layers produced on site using aggregate materials, and in particular to a method for pouring a non-bottom-layer ultra-flat floor that does not require subsequent leveling. Background Art

[0002] With the growth of online shopping and the logistics industry, society's demand for logistics warehouses is increasing. Relying on manual labor for loading, unloading, and sorting goods in logistics warehouses is inefficient, so forklifts and autonomous robots are commonly used to load and unload goods onto high-bay shelves. Uneven floors can prevent forklifts and autonomous robots from aligning smoothly with specific shelves, so logistics warehouse floors require a very high degree of flatness—in other words, a super-flat floor.

[0003] There are two ways to construct super flat floors:

[0004] The first method involves pouring concrete into the concrete at once to create a flat top surface. This is typically accomplished with a vibrating beam or laser screed. Sometimes, a compartmentalized method (typically using angle steel forms, where one angle plate is vertical and the other horizontal) is also employed. For example, the method described in CN113802802A - Super Flat Flooring, involves pouring concrete into the angle steel formwork and then smoothing the concrete surface with a push-pull ruler pressed against the angle steel formwork.

[0005] The second method is to spread a layer of fine stone concrete on top after the concrete is poured and then smooth it out. This method takes a long time to complete (because it requires waiting for the previous concrete to solidify) and reduces the service life (because the fine stone concrete is not integrated with the previous concrete and will deteriorate quickly under the repeated rolling conditions in warehouses), making it unsuitable for logistics warehouses.

[0006] In addition to the above two methods, there are also solutions on the market that use various decoration materials such as epoxy resin and putty to level the ground. However, there are various problems when used in the floors of logistics warehouses (mainly because the leveling effect of these decoration materials is actually very poor, and their main function is to reduce roughness rather than leveling). Therefore, logistics warehouses currently mainly rely on the first method to carry out super-flat floor construction.

[0007] However, for logistics warehouses located on non-ground floors, there are other problems with the construction of super-flat floors:

[0008] Bulk cargo warehouses typically need to be located on the ground floor, above ground, to support the weight of the goods. However, existing logistics warehouses typically store lighter-weight express parcels, which can be supported on non-ground floor slabs. Therefore, in large cities with limited land, some logistics warehouses are also located on non-ground floors. However, the construction of super-flat floors on non-ground floors cannot be achieved with vibrating beams or laser screeds. This is because the non-ground floor is constructed on formwork. Whether using full-floor scaffolding or hanging formwork to support the floor formwork, the formwork cannot support the stable operation of vibrating beams or laser screeds like the ground (that is, the formwork will deform and the supporting structure will shake when these construction equipment is used). Even if forced, the super-flat floor cannot be achieved. Therefore, the current method for constructing super-flat floors on non-ground floors is to lay a layer of fine stone concrete on top after the floor is poured. This method is time-consuming and has a poor service life.

[0009] The inventors attempted to use a compartmentalized method on non-ground floor slabs to achieve the construction of an ultra-flat floor while pouring the floor slab. However, they discovered that this method presented insurmountable technical challenges. Unlike the ground floor, non-ground floor slabs require continuous steel reinforcement to ensure sufficient load-bearing capacity. This continuous reinforcement made compartmentalization impossible (partitioning components would not fit in, and passing the reinforcement through the partitions would not only be extremely difficult, but also prevent the height of the partitions from being adjusted). Furthermore, these partitions are also subject to formwork deformation and swaying of the supporting structure. Summary of the Invention

[0010] The invention provides a method for pouring a non-bottom-layer ultra-flat floor without the need for subsequent leveling.

[0011] The technical problem to be solved is: when constructing an ultra-flat floor on a non-ground floor slab, it is necessary to carry out subsequent leveling after the floor slab is poured, which leads to a long construction period and a poor service life of the floor.

[0012] To solve the above technical problems, the present invention adopts the following technical solution: a method for casting a non-bottom-layer super-flat floor that does not require subsequent leveling, wherein the floor slab on which the super-flat floor is located is a cast-in-place reinforced concrete floor slab, and the casting method comprises the following steps:

[0013] Step 1: Support the formwork and tie the steel bars in the floor slab;

[0014] Step 2: Install a slide rail on the concrete cover of the floor slab for the scraper bar to slide on. The top of the slide rail is in point contact with the scraper bar, and the support structure of the slide rail has no direct contact with the formwork or the support structure of the formwork. The slide rails are parallel to each other and spaced apart.

[0015] Step 3: Adjust the elevation of each slide rail so that the top of each slide rail is flush with the finished surface of the floor;

[0016] Step 4: pouring concrete;

[0017] Step 5: Verify the straightness of the scraper, then use the scraper to smooth the concrete surface to form an ultra-flat floor.

[0018] Furthermore, a support structure is provided under both ends of each slide rail, and the support structure includes a top support vertically arranged under the template and a cross-layer support rod arranged through the template. The upper end of the cross-layer support rod is supported on the bottom of the slide rail and the lower end is detachably fixed to the bottom of the template.

[0019] Furthermore, a gap of at least 5 mm is left between the cross-layer support rod and the hole wall of the hole through which the cross-layer support rod passes through the template, and the gap is filled with foam double-sided tape.

[0020] Furthermore, an internal threaded sleeve is vertically welded above the top support to match the thread of the lower end of the cross-layer support rod. The installation process of the slide rail in step 2 is as follows:

[0021] Step 2.1: Insert the cross-layer support rod into the reserved hole on the template, install the top support under the cross-layer support rod, and then screw the lower end of the cross-layer support rod into the internal threaded sleeve;

[0022] Step 2.2: Adjust the jacking height so that the top of each slide rail is close to the finished surface of the floor;

[0023] Step 2.3: Insert foam double-sided tape into the gap between the cross-layer support rod and the template, and make sure the cross-layer support rod is located in the center of the reserved hole on the template.

[0024] Furthermore, the slide rail is arranged in the pallet, and the pallet is a channel steel section with an opening facing upward. The upper end of the cross-layer support rod penetrates the pallet and the slide rail in sequence. The cross-layer support rod is also provided with a fine-tuning nut located below the pallet and a locking nut located above the slide rail.

[0025] Furthermore, in step 2.2, the jacking height is adjusted so that the elevation of the top of each slide rail is higher than the finished surface of the floor slab;

[0026] Step 3 is as follows:

[0027] Step 3.1: Install a laser leveler on a platform independent of the formwork and use it to mark the finished surface of the floor slab. Use at least two laser beams, both perpendicular to the slide rails.

[0028] Step 3.2: Adjust the elevation of the top of each rail one by one, starting from the laser leveler and working your way out. As you adjust each rail, turn the fine-tuning nut to lower it until the top of the rail is just tangent to the laser beams used for the markings. After each rail is adjusted, turn the locking nut downward to tighten the rail.

[0029] Furthermore, the slide rail is an angle steel, one steel plate of the angle steel is stuck between the left and right side walls of the pallet and the other steel plate extends vertically upward from the pallet, and the top of the cross-layer support rod is lower than the top of the angle steel.

[0030] Furthermore, the fine-tuning nut is a butterfly nut.

[0031] Furthermore, the cross-layer support rod is formed by welding two coaxially arranged segments that are thinner at the top and thicker at the bottom, and the fine-tuning nut and the locking nut are both sleeved on the upper segment.

[0032] Furthermore, in step five, the straightness of the scraper bar is verified using the following method:

[0033] The maximum allowable drop within two meters of the super-flat floor is recorded as a. Before construction, the deflection of the scraper bar is measured, and a disposable fluorescent stick that is parallel to and tightly fits the scraper bar is tied with transparent tape in the center of the scraper bar with a deflection no greater than a. The scraper bar with the fluorescent stick is transported to the construction site. If the disposable fluorescent stick is not bent and glows, it means that the straightness of the scraper bar meets the requirements.

[0034] Compared with the prior art, the non-bottom-layer super-flat floor pouring method of the present invention, which does not require post-leveling, has the following beneficial effects:

[0035] In the present invention, by using a sliding rail with steel bars higher than the floor slab and a scraper on the sliding rail to level the concrete, the problem that the compartment method cannot be implemented due to the interference of steel bars in the floor slab is solved; an independent support structure that does not contact the formwork and the formwork support structure is used to support the sliding rail, thereby avoiding deformation of the formwork and shaking of the formwork support structure during construction that affects the leveling of the concrete; the combination of the above two points ensures that it is feasible to level non-bottom floor slabs to form an ultra-flat floor at the same time as pouring;

[0036] In the present invention, the top of the slide rail is blade-shaped and in point contact with the scraper bar, so that even if the supporting structure of the slide rail is skewed, it will not affect the use of the scraper bar. At the same time, it cooperates with the laser leveling instrument to quickly adjust the height of the top of each slide rail (the laser beam marks the height of the finished surface of the floor slab, and then the slide rails are lowered one by one from near to far so that the slide rails are tangent to the laser beam), thereby providing the scraper bar with a slide rail that can meet the precision required for scraping concrete with a lower construction difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the slide rail and its supporting structure in the present invention. To facilitate reading, only one slide rail is drawn in the figure and the steel bars in the floor slab are not drawn;

[0038] Figure 2 for Figure 1 A partial enlarged view of part A in the middle;

[0039] In the figure, 1- template, 2- floor slab, 3- top support, 4- cross-layer support rod, 5- internal thread sleeve, 6- fine-tuning nut, 7- tray, 8- slide rail, 9- locking nut. DETAILED DESCRIPTION

[0040] A method for pouring a non-bottom-layer super-flat floor that does not require subsequent leveling, wherein the floor slab 2 where the super-flat floor is located is a cast-in-place reinforced concrete floor slab, and the pouring method comprises the following steps:

[0041] Step 1: Support the formwork and tie the steel bars in floor slab 2;

[0042] Step 2: Install a slide rail 8 on the concrete cover of the floor slab 2 for the scraper to slide on. The top of the slide rail 8 is in point contact with the scraper, and the supporting structure of the slide rail 8 has no direct contact with the formwork 1 or the supporting structure of the formwork 1. The slide rails 8 are parallel to each other and spaced apart.

[0043] The point contact here serves two purposes: first, it eliminates the need to adjust the support structure below the slide rail 8 to a vertical position, and its tilt does not affect its use; second, it facilitates the subsequent use of a laser leveler to ensure the appropriate elevation of the top of the slide rail 8. The lack of direct contact prevents deformation of the template 1 or shaking of the support structure of the template 1 from adversely affecting the slide rail 8.

[0044] Step 3: Adjust the elevation of each slide rail 8 so that the top of each slide rail 8 is flush with the finished surface of the floor slab 2;

[0045] Step 4: pouring concrete;

[0046] Step 5: Verify the straightness of the scraper bar, then use the scraper bar to smooth the concrete surface to form an ultra-flat floor. The scraper bar is used in the following way: it is placed perpendicular to the slide rails 8 and placed on two adjacent slide rails 8, and then scraped. Since the slide rails 8 are evenly distributed on the floor slab 2, the scraper bar can cover the entire floor slab 2.

[0047] The reason why we need to verify the straightness of the scraper bar here is that unlike construction on the ground, if you scrape the concrete flat in the air, the scraper bar may be deformed during transportation, and a scraper bar that is not straight enough cannot ensure that the concrete will have a flat surface.

[0048] Each slide rail 8 is provided with a support structure at both ends thereof. Figure 1-2 As shown, the support structure includes a jack 3 vertically installed below the formwork 1 and a cross-layer support rod 4 that penetrates the formwork 1. The upper end of the cross-layer support rod 4 is supported on the bottom of the slide rail 8 and the lower end is detachably fixed to the bottom of the formwork 1. The jack 3 here is a common support device in construction. Its upper half is used for height adjustment, and the lower half is a steel pipe.

[0049] A gap of at least 5 mm is left between the cross-layer support rod 4 and the wall of the hole where it passes through the template 1. This gap is filled with double-sided foam tape. This ensures that the cross-layer support rod 4 is not deflected by deformation or shaking of the template 1, while also preventing leakage of grout due to the gap. The double-sided foam tape is very soft, providing a cushioning effect, yet is also very sticky, making it difficult to fall off once inserted.

[0050] An internal threaded sleeve 5 is vertically welded above the top support 3 and is threadedly matched with the lower end of the cross-layer support rod 4. The installation process of the second step slide rail 8 is as follows:

[0051] Step 2.1: Insert the cross-layer support rod 4 into the reserved hole on the template 1, install the top support 3 under the cross-layer support rod 4, and then screw the lower end of the cross-layer support rod 4 into the internal threaded sleeve 5;

[0052] Step 2.2: Adjust the height of the top support 3 so that the top of each slide rail 8 is close to the finished surface of the floor 2;

[0053] Here, when adjusting the height of the jack 3, the elevation of the top of the slide rail 8 can be monitored using a level located above the template 1;

[0054] Step 2.3: Insert foam double-sided tape into the gap between the cross-layer support rod 4 and the template 1, and make the cross-layer support rod 4 be located in the center of the reserved hole on the template 1.

[0055] The slide rail 8 is set in the pallet 7, and the pallet 7 is a channel steel section with an opening facing upward. The upper end of the cross-layer support rod 4 penetrates the pallet 7 and the slide rail 8 in sequence. The cross-layer support rod 4 is also provided with a fine-tuning nut 6 located below the pallet 7 and a locking nut 9 located above the slide rail 8.

[0056] In step 2.2, adjust the height of the top support 3 so that the top of each slide rail 8 is higher than the finished surface of the floor 2;

[0057] Step 3 is as follows:

[0058] Step 3.1: Install a laser leveler on a platform independent of the formwork 1 and use the laser leveler to mark the finished surface of the floor slab 2. The marking laser beams should have at least two beams perpendicular to the slide rail 8.

[0059] In this embodiment, a platform supported by several independent supports 3 outside the template 1 is used to support the laser leveler, thereby preventing the deformation of the template 1 and the shaking of the template 1 support structure during construction from affecting the laser leveler;

[0060] Step 3.2: Adjust the elevation of the top of each slide rail 8 one by one from near to far, starting from the laser leveler. When adjusting each slide rail 8, rotate the fine-tuning nut 6 to move the slide rail 8 downward until the top of the slide rail 8 is just tangent to the laser beams used for marking. After each slide rail 8 is adjusted, rotate the locking nut 9 downward to tighten the slide rail 8.

[0061] Here, the laser beam is preferably set at a position close to both ends of the slide rail 8 (while both ends of each slide rail 8 are aligned), so that the construction personnel can adjust the fine-tuning nut 6 while observing the positional relationship between the laser beam and the slide rail 8, saving manpower and avoiding the influence of untimely communication on the adjustment accuracy. When observing, you can see that the light spot formed by the laser beam on the side of the slide rail 8 gradually moves up until it disappears. Note that the slide rail 8 cannot be moved up here. If the slide rail 8 is moved up, when the light spot appears at the top of the slide rail 8, although it can be judged that its elevation is appropriate, the subsequent slide rail 8 cannot be adjusted because the laser beam is blocked. At the same time, the top of the slide rail 8 cannot be a surface, but must be a line as in the present embodiment. When the line is tangent to the laser beam, there is only one point of tangency, which is easy to judge. If it is a surface, it is difficult to judge whether it is tangent to the laser beam.

[0062] In addition, the slide rail 8 can be painted with silver paint to facilitate identification of whether the laser beam is tangent to the slide rail 8 .

[0063] The slide rail 8 is made of angle steel, one plate of which is wedged between the left and right sidewalls of the tray 7, while the other plate extends vertically upward from the tray 7. The angle steel edge is in close contact with both sidewalls of the tray 7, ensuring a secure, precise grip. The top of the cross-layer support rod 4 is lower than the top of the angle steel, so it will not obstruct the scraper bar during concrete leveling.

[0064] If a suspended ceiling or pipelines need to be installed under the floor slab 2, or if a ceiling finish is required, the slide rails 8 and cross-layer support rods 4 can be left as embedded parts to suspend the suspended ceiling or pipeline hangers. If this is not required, the concrete above the locking nut 9 can be pre-marked. After the concrete is scraped and leveled, the slide rails 8 can be removed and the concrete can be smoothed. Finally, after the floor slab 2 is demoulded, the cross-layer support rods 4 can be cut off at the portion below the floor slab 2. Alternatively, the slide rails 8 can be left as is and only the cross-layer support rods 4 can be cut off, allowing the slide rails 8 to serve as reinforcement for the floor slab 2.

[0065] The fine-tuning nut 6 is a butterfly nut. Here, the butterfly nut is directly screwed by hand for convenience.

[0066] The cross-layer support rod 4 is composed of two coaxially arranged segments, thinner at the top and thicker at the bottom, welded together. The fine-tuning nut 6 and the locking nut 9 are both mounted on the upper segment. To prevent bending during use, the lower end of the cross-layer support rod 4 needs to have a larger cross-section. If the fine-tuning nut 6 is directly mounted on such a thick rod, it will be difficult to manually tighten it during adjustment. It can be turned smoothly for the first few times, but it will become almost impossible to turn it manually as the threads become dirty or rusted. In this embodiment, the two segments are welded using a perforated plug welding method, that is, a hole is opened at the top of the lower segment, the upper segment is inserted, and then welded.

[0067] In step 5, verify the straightness of the scraper bar using the following method:

[0068] The maximum allowable drop within two meters of the super-flat floor is recorded as a. Before construction, measure the deflection of the scraper bar, and use transparent tape to tie a disposable fluorescent stick that is parallel to and tightly fits the scraper bar in the center of the scraper bar where the deflection is no more than a. Transport the scraper bar with the fluorescent stick to the construction site. If the disposable fluorescent stick is not bent and glows, it means that the straightness of the scraper bar meets the requirements.

[0069] For shorter scraper bars, the straightness of the scraper bar can be verified by directly sticking the scraper bar to a ruler for comparison. The reason why this more complicated method is adopted in this embodiment is that in order to reduce the amount of slide rails 8 and improve construction efficiency, the scraper bar used in this embodiment is as long as 6 meters. It is difficult to verify the straightness of a scraper bar of this length with a ruler, and the available verification methods, such as using a laser straightener to measure deflection, are difficult to perform in high-altitude operations. Therefore, it is chosen here to verify the straightness on the ground before construction, and then tie a disposable fluorescent stick to the position where the scraper bar is most susceptible to deformation to ensure that the scraper bar does not bend significantly during transportation. In this embodiment, the scraper bar is hung vertically to the construction location, thereby reducing the possibility of the scraper bar bending during transportation.

[0070] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for casting a non-bottom-layer super-flat floor without the need for subsequent leveling, wherein the floor slab (2) where the super-flat floor is located is a cast-in-place reinforced concrete floor slab, characterized in that: The pouring method includes the following steps: Step 1: Support the formwork and tie the steel bars in the floor slab (2); Step 2: Install a slide rail (8) for the scraper to slide on the concrete protective layer of the floor slab (2), wherein the top of the slide rail (8) is in point contact with the scraper, and the supporting structure of the slide rail (8) has no direct contact with the formwork (1) or the supporting structure of the formwork (1); the slide rails (8) are parallel to each other and spaced apart; Step 3: Adjust the elevation of each slide rail (8) so that the top of each slide rail (8) is flush with the finished surface of the floor slab (2); The finished surface of the floor slab (2) is marked with a laser leveler, and a platform supported by an independent top support (3) outside the template (1) is used to support the laser leveler; Step 4: pouring concrete; Step 5: Verify the straightness of the scraper, then use the scraper to smooth the concrete surface to form an ultra-flat floor; A support structure is provided below both ends of each slide rail (8), the support structure comprising a top support (3) vertically provided below the template (1) and a cross-layer support rod (4) penetrating the template (1), the upper end of the cross-layer support rod (4) supporting the bottom of the slide rail (8) and the lower end being detachably fixed to the bottom of the template (1); A gap of at least 5 mm is left between the cross-layer support rod (4) and the hole wall of the hole through which it passes through the template (1), and the gap is filled with foam double-sided tape.

2. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 1 is characterized in that: An internal threaded sleeve (5) is vertically welded above the top support (3) and is threadedly matched with the lower end of the cross-layer support rod (4). The installation process of the second step slide rail (8) is as follows: Step 2.1: Insert the cross-layer support rod (4) into the reserved hole on the template (1), install the top support (3) under the cross-layer support rod (4), and then screw the lower end of the cross-layer support rod (4) into the internal threaded sleeve (5); Step 2.2: Adjust the height of the top support (3) so that the top of each slide rail (8) is close to the finished surface of the floor (2); Step 2.3: Insert foam double-sided tape into the gap between the cross-layer support rod (4) and the template (1), and make the cross-layer support rod (4) be located in the center of the reserved hole on the template (1).

3. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 2 is characterized in that: The slide rail (8) is arranged in the tray (7), and the tray (7) is a channel steel section with an opening facing upward. The upper end of the cross-layer support rod (4) penetrates the tray (7) and the slide rail (8) in sequence. The cross-layer support rod (4) is also provided with a fine-tuning nut (6) located below the tray (7) and a locking nut (9) located above the slide rail (8).

4. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 3 is characterized in that: In step 2.2, the height of the top support (3) is adjusted so that the top of each slide rail (8) is higher than the finished surface of the floor slab (2); Step 3 is as follows: Step 3.1: Install a laser leveler on a platform independent of the template (1) and use the laser leveler to mark the finished surface of the floor slab (2). The marking laser beams should be at least two and both should be perpendicular to the slide rail (8). Step 3.2: Adjust the elevation of the top of the slide rail (8) one by one from the laser leveler from near to far. When adjusting each slide rail (8), rotate the fine-tuning nut (6) to move the slide rail (8) downward until the top of the slide rail (8) is just tangent to the laser beams used for marking. After each slide rail (8) is adjusted, rotate the locking nut (9) downward to tighten the slide rail (8).

5. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 3 is characterized in that: The slide rail (8) is an angle steel, one steel plate of the angle steel is stuck between the left and right side walls of the tray (7) and the other steel plate extends vertically upward from the tray (7), and the top of the cross-layer support rod (4) is lower than the top of the angle steel.

6. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 3 is characterized in that: The fine-tuning nut (6) is a butterfly nut.

7. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 3 is characterized in that: The cross-layer support rod (4) is formed by welding two coaxially arranged segments, which are thinner at the top and thicker at the bottom. The fine-tuning nut (6) and the locking nut (9) are both sleeved on the upper segment.

8. The method for pouring a non-bottom-layer super-flat floor without the need for subsequent leveling according to claim 1 is characterized in that: In step 5, verify the straightness of the scraper bar using the following method: The maximum allowable drop within two meters of the super-flat floor is recorded as a. Before construction, the deflection of the scraper bar is measured, and a disposable fluorescent stick that is parallel to and tightly fits the scraper bar is tied with transparent tape in the center of the scraper bar with a deflection no greater than a. The scraper bar with the fluorescent stick is transported to the construction site. If the disposable fluorescent stick is not bent and glows, it means that the straightness of the scraper bar meets the requirements.

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