A negative pressure sand box for lost foam casting

Abstract

This utility model relates to the field of negative pressure sand box technology, and provides a negative pressure sand box for lost foam casting. By placing the lost foam mold into the molding sand within the negative pressure sand box, castings are produced. The box includes a box body, mounting cylinders, and positioning rods. Several mounting cylinders are inserted through and sway-mounted on the side wall of the box body. Several positioning rods correspond one-to-one with the mounting cylinders, and the positioning rods are slidably disposed within the mounting cylinders. The positioning rods can slide along the axial direction of the mounting cylinders to adjust the length of the positioning rods extending into the box body. One end of the positioning rod located inside the box abuts against the outer wall of the lost foam mold. The positioning rods can abut against the outer wall of the mold from all sides of the box body, forming all-round support and fixation, resisting the lateral thrust generated by the molding sand, preventing the mold from flipping or shifting, and ensuring that the mold always maintains a preset position in the molding sand. The combination of the swaying mounting cylinders and the slidable positioning rods allows for flexible adaptation to lost foam molds of different shapes and sizes.

Description

Technical Field

[0001] This utility model relates to the field of negative pressure sand box technology, specifically to a negative pressure sand box for lost foam casting. Background Technology

[0002] In the lost foam casting process, the negative pressure sand box is the core equipment for achieving model positioning and sand mold compaction, and its performance directly affects the dimensional accuracy and molding quality of the casting. In existing technologies, after the lost foam model is placed in the negative pressure sand box, it usually relies on the natural accumulation of dry sand or a simple support structure to maintain the model's position. However, this fixing method has insurmountable technical defects, leading to model displacement problems.

[0003] Model displacement is primarily caused by the significant fluidity of dry sand. During the filling and vibration process, the relative motion between sand particles easily generates lateral thrust on the model. This is especially true for thin-walled, irregularly shaped, or large models, where the friction between the model and the sand particles is insufficient to resist the impact of the sand flow, making them prone to tilting or translation. Secondly, due to the uneven distribution of self-weight, the model assembly is prone to torque-like displacement during sand particle settling, and existing sand boxes lack a collaborative positioning mechanism for the assembled model.

[0004] Model misalignment can lead to poor casting dimensional accuracy and insufficient or excessive machining allowances on key mating surfaces. Misalignment between the model and the gating system can alter the path of molten metal filling, resulting in defects such as incomplete filling and cold shuts. Utility Model Content

[0005] To overcome the above-mentioned defects, the present invention provides a negative pressure sand box for lost foam casting, which solves the technical problem in the prior art that the lost foam model cannot be fixed in the negative pressure sand box when it is placed in the negative pressure sand box, resulting in the model position shifting.

[0006] According to one aspect, at least one embodiment of the present invention provides a negative pressure sand box for lost foam casting, wherein castings are produced by placing a lost foam mold into molding sand within the negative pressure sand box, comprising: Box; The mounting cylinder has a plurality of cylinders, which are disposed through and swingably mounted on the side wall of the housing. The positioning rods are provided in multiples, each corresponding to a mounting cylinder. The positioning rods are slidably disposed within the mounting cylinders and can slide along the axial direction of the mounting cylinders to adjust the length of the positioning rods extending into the housing. One end of the positioning rod located inside the housing abuts against the outer wall of the lost foam mold.

[0007] Optionally, a plurality of through holes are provided on the side wall of the housing, and each through hole corresponds to a mounting cylinder, with the mounting cylinder passing through the through holes; A rotating seat, wherein there are several rotating seats, each of which corresponds to one of the through holes. The rotating seats are rotatably mounted on the inner wall of the box. The rotating seats are used to block the through holes. The rotating seats rotatably abut against one end face of the through hole facing the inside of the box. The mounting cylinder is disposed through the rotating seat, and the mounting cylinder can swing vertically about the rotating seat as an axis of rotation under the drive of the rotating seat.

[0008] Optionally, the mounting cylinder has a circular hole on the outer wall of the housing, and a limit rod can be detachably installed in the circular hole; The positioning rod has several insertion holes on its outer wall, and these insertion holes are arranged along the axial direction of the positioning rod. When one of the insertion holes is aligned with the circular hole, the limiting rod can be inserted into the insertion hole aligned with the circular hole to fix the positioning rod.

[0009] Optionally, an elastic push seat is provided at one end of the mounting cylinder outside the housing. The elastic push seat is sleeved on the positioning rod and is used to push the positioning rod.

[0010] Optionally, a rubber pad is provided at one end of the positioning rod located inside the box, and the rubber pad is used to abut against the surface of the lost foam mold.

[0011] Optional, also includes: A negative pressure air duct is provided on the outer peripheral wall of the box, and air holes corresponding to the negative pressure air duct are opened on the side wall of the box. The negative pressure air duct is connected to the inside of the box through the air holes. The filter plate is provided in a plurality of parts, and the plurality of filter plates are disposed on the inner peripheral wall of the box. The filter plates cover the air holes and are used to prevent molding sand from entering the negative pressure air duct. The negative pressure air duct has several air extraction ports, and these air extraction ports are connected to the negative pressure air duct.

[0012] Optionally, the negative pressure air duct and the filter plate are also provided inside and outside the bottom of the housing.

[0013] Optionally, the filter plate is detachably connected to the inner wall of the housing by double-ended nuts and bolts.

[0014] Optional, also includes: The lifting handles are of several kinds, and the several lifting handles are symmetrically arranged on the two opposite outer side walls of the box.

[0015] Optional, also includes: The rollers are a plurality of rollers, which are rotatably disposed at the bottom of the housing.

[0016] The beneficial effects of this utility model are as follows: In this invention, multi-directionally distributed positioning rods abut against the outer wall of the mold from all sides of the housing, forming comprehensive support and fixation. During sand filling and vibration compaction, they resist the lateral thrust generated by sand particles, preventing the mold from tilting, flipping, or shifting, ensuring that the mold always maintains its preset position in the molding sand. The combination of the swingable mounting cylinder and the sliding positioning rods allows for flexible adaptation to lost foam molds of different shapes and sizes. Because the mold is fixed during sand filling and vibration, casting dimensional deviations caused by mold displacement are avoided, contributing to the production of castings with precise dimensions and stable quality, meeting high production requirements, and improving the overall product quality. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the accompanying drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of this utility model and these drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a negative pressure sand box for lost foam casting in one embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure of the negative pressure sand box for lost foam casting from another angle in the embodiment; Figure 3 for Figure 2 A magnified view of a section at point A in the middle; Figure 4 for Figure 1 A schematic diagram of the positioning rod and elastic push seat in the embodiment; Figure 5 for Figure 4 A magnified view of a section at point B.

[0019] In the diagram: 1. Box body; 11. Rotating seat; 101. Through hole; 102. Air hole; 103. Air extraction port; 2. Mounting cylinder; 21. Elastic push seat; 201. Round hole; 3. Positioning rod; 301. Insertion hole; 4. Limiting rod; 5. Rubber pad; 6. Negative pressure air duct; 7. Filter plate; 8. Hanging handle; 9. Roller. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit its scope.

[0021] To keep the drawings concise, only the parts relevant to the utility model are shown schematically in each drawing; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of the components with the same structure or function is schematically shown, or only one is labeled. In this document, "a" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0022] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0025] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] like Figures 1-5As shown, this invention illustrates a negative pressure sand box for lost foam casting in one embodiment. The lost foam mold is placed into the molding sand within the negative pressure sand box to cast castings. The box includes a box body 1, mounting cylinders 2, and positioning rods 3. The box body 1 is a cuboid structure, capable of accommodating molding sand and the lost foam mold. Several mounting cylinders 2 are evenly distributed at the corners of the four side walls of the box body 1. Each mounting cylinder 2 is a cylindrical tube that penetrates the side wall of the box body 1 and is hinged to the side wall for a swing-swing connection. The positioning rods 3 are cylindrical rods, corresponding one-to-one with the mounting cylinders 2. The diameter of the positioning rods 3 is smaller than the inner diameter of the mounting cylinders 2, allowing them to slide freely axially within the mounting cylinders 2 to adjust the length of the positioning rods 3 extending into the box body 1. One end of the positioning rod 3 inside the box body 1 abuts against the outer wall of the lost foam mold.

[0027] Specifically, after placing the lost foam casting mold into the housing 1, the installation cylinder 2 is tilted at an angle according to the shape and size of the mold. Then, the positioning rod 3 is pushed into the housing 1 so that one end of the positioning rod 3 inside the housing 1 abuts against the outer wall of the lost foam casting mold. After adjusting the position of all the positioning rods 3, dry sand is filled into the housing 1. During the sand filling process, the vibration device vibrates the housing 1 to compact the dry sand. Due to the abutting action of the positioning rods 3, the lost foam casting mold will not tilt, flip, or shift under the lateral thrust of the sand particles.

[0028] The swingable mounting cylinder 2 and the sliding positioning rod 3 can adapt to lost foam molds of different shapes and sizes, fix the mold in multiple directions, resist the lateral thrust generated by sand particles during sand filling vibration, prevent mold displacement, and improve the dimensional accuracy of castings.

[0029] For example, such as Figure 3 As shown, in some examples, several through holes 101 are provided on the side wall of the housing 1. Each through hole 101 corresponds to a mounting cylinder 2, and the mounting cylinder 2 passes through the through hole 101. The rotating seat 11 is cylindrical and is rotatably mounted on the inner wall of the housing 1 via bearings. The rotating seat 11 is horizontally positioned at the four corners of the housing 1, and the edge of the rotating seat 11 contacts the end face of the through hole 101 facing inwards from the housing 1. The through hole 101 and the rotating seat 11 are adapted to each other. The setting of the rotating seat 11 achieves the sealing of the through hole 101, avoids the problem of molding sand leakage, and ensures the normal operation of the negative pressure sand box. At the same time, the setting of the rotating seat 11 makes the swing of the mounting cylinder 2 more flexible and can adapt to the complex shape of the lost foam mold. It should be noted that the mounting cylinder 2 is vertically installed through the center of the rotating seat 11. The mounting cylinder 2 is fixedly connected to the rotating seat 11. When it is necessary to adjust the angle of the mounting cylinder 2, the rotating seat 11 is rotated, and the mounting cylinder 2 swings vertically with the rotating seat 11 as the axis of rotation, thereby changing the angle at which the positioning rod 3 abuts against the lost foam mold. During the sand filling and vibration process, the contact between the rotating seat 11 and the through hole 101 can prevent molding sand from leaking out of the through hole 101.

[0030] For example, such as Figure 5 As shown, in some examples, the mounting cylinder 2 has a circular hole 201 on its outer wall of the housing 1. The limiting rod 4 is a cylindrical rod with a diameter matching the circular hole 201. One end of the limiting rod 4 has a handle for easy insertion and removal. The positioning rod 3 has several insertion holes 301 arranged axially on its outer wall, with the diameter of the insertion holes 301 being the same as the diameter of the limiting rod 4. Specifically, after adjusting the length of the positioning rod 3 inside the housing 1, when the positioning rod 3 abuts against the lost foam mold, one of the insertion holes 301 on the positioning rod 3 is aligned with the circular hole 201 on the mounting cylinder 2. Then, the limiting rod 4 is inserted from the circular hole 201 into the corresponding insertion hole 301 to fix the position of the positioning rod 3 and prevent it from sliding during vibration. When it is necessary to readjust the length of the positioning rod 3, the limiting rod 4 can be pulled out.

[0031] The position of the positioning rod 3 can be quickly and securely fixed by the cooperation of the limiting rod 4 and the insertion hole 301, ensuring that the positioning rod 3 stably abuts against the lost foam mold and further preventing the lost foam mold from shifting.

[0032] For example, such as Figure 4 As shown, in some examples, the elastic push seat 21 consists of a base and a spring. One end of the spring is fixed to the bottom of the sleeve, and the other end is connected to the end of the mounting cylinder 2 located outside the housing 1. The spring is sleeved on the positioning rod 3, which is fixedly connected to the base. After the positioning rod 3 abuts against the lost foam mold, the spring of the elastic push seat 21 always applies a pushing force towards the housing 1 to the positioning rod 3, so that the positioning rod 3 abuts tightly against the mold.

[0033] Specifically, after the molding sand covers the lost foam mold, the positioning rod 3 needs to be separated from the mold. This is achieved by pulling the base to stretch the spring, then pulling the positioning rod 3 away from the mold. Next, the limiting rod 4 is inserted from the round hole 201 into the corresponding insertion hole 301, fixing the position of the positioning rod 3. Then, a negative pressure pump is used to remove the air from the negative pressure sand box. The elastic push seat 21 provides a continuous and stable pushing force to the positioning rod 3, ensuring that the positioning rod 3 always contacts the lost foam mold, enhancing the positioning effect and reducing mold offset.

[0034] For example, such as Figure 4As shown, in some examples, a rubber pad 5 is provided at one end of the positioning rod 3 inside the housing 1. The surface of the rubber pad 5 is flat and matches the shape of the end of the positioning rod 3. When the positioning rod 3 abuts against the surface of the lost foam mold, the rubber pad 5 directly contacts the mold surface. Due to the elasticity and friction of the rubber material, it can both tightly adhere to the mold surface and increase the friction between the rubber pad and the mold. The rubber pad 5 avoids rigid contact between the positioning rod 3 and the lost foam mold, preventing damage to the mold surface; at the same time, the elasticity and friction of the rubber pad 5 can enhance the connection stability between the positioning rod 3 and the mold, further preventing the mold from shifting during vibration.

[0035] For example, such as Figure 1 As shown, in some examples, the negative pressure duct 6 is a pipe made of channel steel, installed on the outer peripheral wall of the housing 1, arranged in a cross pattern on the four outer peripheral walls of the housing 1. Multiple air vents 102 are provided on the side wall of the housing 1, and the air vents 102 communicate with the interior of the negative pressure duct 6. Filter plates 7 are detachably fixed to the inner peripheral wall of the housing 1, with each filter plate 7 covering the corresponding air vent 102. Several exhaust ports 103 are provided along the length of the negative pressure duct 6, and the exhaust ports 103 are connected to an external negative pressure pump.

[0036] Specifically, first, a layer of molding sand is laid at the bottom of the housing 1, then the lost foam mold is placed in, and the mold is held in place by the rubber pad 5 on the positioning rod 3. Sand is then filled in, and after the sand is compacted, molten metal for casting is poured in. Next, the top cover of the housing 1 is placed on top. Finally, the negative pressure pump is connected to the exhaust port 103, and the negative pressure pump is started. Air inside the housing 1 enters the negative pressure duct 6 through the air hole 102 and is then extracted through the exhaust port 103, creating a negative pressure inside the housing 1. Under this negative pressure, the molding sand is further compacted. The filter plate 7 prevents molding sand from entering the negative pressure duct 6, preventing duct blockage. The negative pressure duct 6 and the exhaust port 103 ensure a uniform negative pressure inside the housing 1, improving the compactness of the molding sand; the filter plate 7 prevents molding sand from entering the duct, ensuring the normal operation of the negative pressure system and reducing equipment failure.

[0037] It should be noted that the negative pressure sand box is also equipped with several sand cleaning ports. The sand cleaning ports are located at the bottom of the four walls of the box body 1 and are connected to the negative pressure air duct 6. The sand cleaning ports and the air extraction port 103 are located in the same vertical direction. When the molding sand enters the negative pressure air duct 6, it will fall to the bottom of the negative pressure air duct 6 due to gravity. Then, the sand cleaning ports are opened to remove the small amount of molding sand that has entered the negative pressure air duct 6, thus solving the problem of molding sand accumulating in the negative pressure air duct 6 and affecting the working efficiency of the negative pressure pump.

[0038] For example, such as Figure 1As shown, in some examples, a negative pressure air duct 6 is also provided on the outside of the bottom of the housing 1, and a filter plate 7 is also provided inside the bottom. The negative pressure air duct 6 at the bottom is connected to the negative pressure air duct 6 on the side wall of the housing 1. The filter plate 7 at the bottom covers the opening where the bottom negative pressure air duct 6 connects to the inside of the housing 1.

[0039] During the negative pressure extraction process, the negative pressure duct 6 at the bottom of the housing 1 and the negative pressure duct 6 on the side wall work simultaneously. Air inside the housing 1 is extracted not only from the air vents 102 on the side wall but also from the openings of the negative pressure duct 6 at the bottom, resulting in a more uniform negative pressure distribution within the housing 1. The filter plate 7 at the bottom prevents molding sand from entering the negative pressure duct 6. The presence of the negative pressure duct 6 and filter plate 7 at the bottom increases the extraction path and area, making the negative pressure within the housing 1 more uniform, further improving the compactness of the molding sand, and helping to ensure the molding quality of the castings.

[0040] It should be noted that multiple through holes are provided along the edge of the filter plate 7, and corresponding threaded holes are provided on the inner wall of the housing 1. One end of the double-ended nut connects to the threaded hole on the inner wall of the housing 1, and the other end passes through the through hole of the filter plate 7 and connects to the bolt. The filter plate 7 is fixed to the inner wall of the housing 1 by tightening the bolt. When the filter plate 7 becomes clogged or damaged after a period of use, the bolt is unscrewed, the filter plate 7 is removed for cleaning or replacement, and then the new or cleaned filter plate 7 is re-fixed to the inner wall of the housing 1 using the double-ended nut and bolt. The filter plate 7 adopts a detachable connection method, which facilitates cleaning and replacement of the filter plate 7, reduces maintenance costs, ensures the filtration effect of the filter plate 7, and ensures the normal operation of the negative pressure system.

[0041] For example, such as Figure 2 As shown, in some examples, the negative pressure sand box also includes lifting handles 8, with several lifting handles 8 symmetrically welded to the upper parts of the opposite two outer side walls of the box body 1. When the negative pressure sand box needs to be moved, the lifting handles 8 are hooked onto the crane hooks, and the sand box is lifted to the desired position by the crane. During the casting process, if it is necessary to flip the sand box, this can also be achieved using the lifting handles 8. The lifting handles 8 facilitate the handling and flipping of the negative pressure sand box, reduce the labor intensity of manual handling, and improve work efficiency.

[0042] For example, such as Figure 1 As shown, in some examples, the negative pressure sand box also includes rollers 9, which are track wheels, and there are several of them, each fixed to the bottom of the box body 1 by bolts. The track wheels under the negative pressure sand box reduce movement resistance by rolling on the track, which facilitates integration and adaptation with automated equipment for production. At the same time, it facilitates transportation to the sand pouring position, and works with the flipping component to complete the sand cleaning, thus comprehensively optimizing the efficiency, accuracy, stability and safety of casting production.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A negative pressure sand box for use in lost foam casting, which casts a casting by placing a lost foam mold into molding sand in the negative pressure sand box, characterized by, include: Box (1); Mounting cylinder (2), there are several mounting cylinders (2), and several mounting cylinders (2) are disposed through and swing on the side wall of the box body (1); Positioning rod (3), there are several positioning rods (3), each of the positioning rods (3) corresponds to one of the mounting cylinders (2), and the positioning rods (3) are slidably disposed in the mounting cylinders (2). The positioning rods (3) can slide along the axial direction of the mounting cylinders (2) to adjust the length of the positioning rods (3) extending into the box body (1). One end of the positioning rod (3) located inside the box body (1) abuts against the outer wall of the lost foam mold.

2. The negative pressure sand box for lost foam casting according to claim 1, wherein The box body (1) has several through holes (101) on its side wall. The through holes (101) correspond one-to-one with the mounting cylinder (2). The mounting cylinder (2) passes through the through holes (101). Rotary seat (11), there are several rotating seats (11), and each of the several rotating seats (11) corresponds to one of the through holes (101). The rotating seats (11) are rotatably disposed on the inner wall of the box (1). The rotating seats (11) are used to block the through holes (101). The rotating seats (11) rotatably abut against one end face of the through holes (101) facing the inside of the box (1). The mounting cylinder (2) is disposed through the rotating seat (11), and the mounting cylinder (2) can swing vertically with the rotating seat (11) as the axis of rotation under the drive of the rotating seat (11).

3. The negative pressure sand box for lost foam casting according to claim 1, wherein The mounting cylinder (2) has a circular hole (201) on the outer wall of the box (1), and a limit rod (4) is detachably installed in the circular hole (201). The positioning rod (3) has a plurality of insertion holes (301) on its outer wall. The plurality of insertion holes (301) are arranged along the axial direction of the positioning rod (3). After one of the insertion holes (301) is aligned with the circular hole (201), the limiting rod (4) can be inserted into the insertion hole (301) aligned with the circular hole (201) to fix the positioning rod (3).

4. The negative pressure sand box for lost foam casting according to claim 2, wherein The mounting cylinder (2) is provided with an elastic push seat (21) at one end outside the box (1). The elastic push seat (21) is sleeved on the positioning rod (3) and is used to push the positioning rod (3).

5. The negative pressure sand box for lost foam casting according to claim 1, wherein A rubber pad (5) is provided at one end of the positioning rod located inside the box, and the rubber pad (5) is used to abut against the surface of the lost foam mold.

6. The negative pressure sand box for lost foam casting according to claim 1, wherein Also includes: Negative pressure air duct (6), the negative pressure air duct (6) is set on the outer peripheral wall of the box (1), and the side wall of the box (1) is provided with air holes (102) corresponding to the negative pressure air duct (6), and the negative pressure air duct (6) is connected to the inside of the box (1) through the air holes (102); The filter plate (7) has a plurality of filter plates (7), which are disposed on the inner peripheral wall of the housing (1). The filter plates (7) cover the air hole (102) and are used to block molding sand from entering the negative pressure air duct (6). The negative pressure air duct (6) is provided with a number of air extraction ports (103), and the number of air extraction ports (103) are connected to the negative pressure air duct (6).

7. The negative pressure sand box for lost foam casting according to claim 6, wherein The negative pressure air duct (6) and the filter plate (7) are also provided inside and outside the bottom of the box (1).

8. The negative pressure sand box for lost foam casting according to claim 7, characterized in that, The filter plate (7) is detachably connected to the inner wall of the box (1) by a double-headed nut and bolts.

9. A negative pressure sand box for lost foam casting according to claim 1, characterized in that, Also includes: Hanging handle (8), there are several hanging handles (8), and several hanging handles (8) are symmetrically arranged on the two opposite outer side walls of the box (1).

10. A negative pressure sand box for lost foam casting according to claim 1, characterized in that, Also includes: Rollers (9), there are several rollers (9), and several rollers (9) are rotatably disposed at the bottom of the box body (1).

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