Hydraulic mechanism and method for raising and lowering a floor slab

Abstract

This invention provides a novel prefabricated construction method aimed at accelerating construction, saving on-site space, reducing foundation costs, improving worker safety, and enhancing environmental performance. [Solution] The present invention relates to a hydraulic mechanism for raising and lowering a floor slab, which operates by assembling (combining) the upper floor at a low height (above the first-floor slab level) and then lifting it to a designed height using a special lifting device. The present invention consists of the following combination of features: the building's columns function as lifting columns, with their lower ends remaining free on the foundation during the lifting process; a guide structure for the lifting columns consisting of column holes formed in the floor slab, the shape and dimensions of which correspond to those of the columns; and a sliding assembly between the column and the column hole configured to guide the column and maintain it in a vertical position throughout the entire lifting process.

Description

Technical Field

[0001] The present invention relates to the field of prefabricated housing construction, and more specifically, to a hydraulic mechanism and method for lifting and lowering a floor slab to facilitate the handling and assembly of related members in prefabricated housing construction.

Background Art

[0002] To date, numerous inventions and applications using hydraulic systems in prefabricated housing construction have been implemented worldwide. The basic principle of known methods is to combine (assemble) the building components at a low height and then lift them to the designed height using lifting devices such as hydraulic jacks, winches, hoists, screw nut mechanisms, etc. All of these lifting methods are based on the principle that the base of the lifting column must be rigidly fixed to the foundation. This rigid fixation of the lifting column to the foundation is for the purpose of ensuring the following requirements. (i) The base of the lifting column does not move freely on the foundation surface, (ii) the body of the lifting column maintains perpendicularity and verticality with respect to the foundation surface during the lifting process, and (iii) the entire lifting column has sufficient stability and capacity to withstand dynamic loads from the construction and installation of the lifted object until the target structure is completed.

Summary of the Invention

Problems to be Solved by the Invention

[0003] As shown in FIGS. 1 and 2, the conventional floor slab lifting mechanism is composed of a foundation 1, a lifting column 2, a floor slab 3, and a lifting device 5. According to the known building installation method, the lifting column 2 is rigidly fixed to the foundation 1, arranged vertically, and must be sufficiently rigid. This means the following. - The connection part 21cd between each lifting column 2 and the foundation 1 must be a fixed connection (capable of withstanding displacement forces and moments in all directions). If this requirement is not met, the lifting column may collapse during the lifting process. - The lifting columns 2 must be positioned vertically, forming an alignment Gcd perpendicular to the foundation surface, and the column heads 23 must be inserted into openings 32 formed in the floor slab 3 (i.e., Rcd must be equal to Lcd, where Rcd is the distance between the two lifting columns 2 measured from the center of each column, and Lcd is the distance between the two openings 32 measured from the center of each opening). This creates a clearance K32cd between the lifting columns 2 and the openings 32 (Figure 22). If the lifting columns 2 are not positioned vertically, especially when the lifting height is large, a very large moment will be generated at their base during the lifting process due to the considerable weight of the entire floor (or multiple floors). This moment can impair the connection between the lifting columns and the foundation, potentially causing the lifting columns to collapse. Furthermore, if the lifting columns 2 are not positioned vertically, it becomes difficult to ensure their parallelism. As a result, the point of application of the lifting force to the floor slab 3 shifts during the lifting process, causing significant damage to both the floor slab 3 and the lifting column 2 (this depends on the specific lifting method and the lifting equipment used). - Lifting column 2 must have sufficient rigidity. This is because each lifting column is generally very tall, and there are no intermediate supports along that height. If it does not have sufficient rigidity, lifting column 2 may become unstable under the lifting load.

[0004] During on-site installation and crane lifting, a considerable amount of time is required to adjust the columns vertically, making it difficult for the lifted columns to meet all three of the aforementioned requirements. Furthermore, due to the large number of columns to be lifted, the total installation time for the columns becomes substantial.

[0005] To ensure the rigidity of the lifting columns, the foundation must be extremely robust (significantly more robust than what is required for normal use), and to meet the aforementioned performance requirements, it needs to be constructed well in advance.

[0006] Conventional techniques for rigidly fixing and vertically positioning lifting columns to the foundation during building installation are extremely complex and time-consuming. This requires a large number of skilled installation workers and significantly increases construction costs. Furthermore, if the rigidly fixed lifting columns fail to achieve the required verticality, column jamming can occur during the lifting process, potentially negatively impacting construction and building quality. [Means for solving the problem]

[0007] Through research and experimentation, the inventors developed a novel and groundbreaking method for constructing prefabricated housing that deviates from the traditional principles described above.

[0008] According to the present invention, (i) the base of the lifting column does not need to be fixed to the foundation and remains free; (ii) vertical connections are defined using horizontal connection techniques; (iii) the lifting column is positioned and defined using the object to be lifted; and (iv) these objects function as the main components of the lifting mechanism. This method is characterized by a combination of the precise connection of specially designed technical elements and a defined lifting procedure.

[0009] The objective of this invention is to eliminate the aforementioned drawbacks of the prior art and thereby achieve high efficiency in terms of construction time and cost.

[0010] To achieve this objective, the present invention provides a method for constructing a prefabricated house, in which the upper floor is assembled (combined) at a low height (above the first-floor slab level), and then lifted to the designed height using a special lifting device.

[0011] The present invention comprises the following combination of features: a building column that functions as a lifting column, with its lower end remaining free on the foundation during the lifting process (thereby forming a support-type connection 21td between the column and the foundation); a guide structure for the lifting column, consisting of a column hole formed in the floor slab, whose shape and dimensions correspond to those of the column; and a sliding assembly between the column and the column hole, configured to guide the column and maintain it in a vertical position throughout the entire lifting process. [Effects of the Invention]

[0012] This invention offers significant economic and technical advantages that clearly distinguish it from conventional prefabricated housing construction methods. As shown below, it truly represents a revolutionary advance in construction in terms of productivity and cost. - Significantly faster construction: This method moves much of the work from the construction site to the factory. Lifted columns do not require time-consuming, precise positioning on the foundation. - Saving space at the construction site: Components are manufactured in advance with high precision at the factory, then transported to the site and assembled directly into the building structure. - Savings on foundation costs: This method operates on the principle that the foundation bears the vertical force from the base of the column and does not generate moments during the lifting process. - Cost reduction: This is achieved by optimizing multiple tasks, particularly by shortening construction time and reducing labor demand. - Excellent worker safety: This is made possible by performing construction work at low heights. - Improved environmental performance: This results from minimizing the emission of dust and noise at construction sites.

[0013] This invention can be extended not only to the narrow field of "prefabricated housing construction" but also to the broader field of "lift-up construction methods." To successfully achieve such an extension, it is essential to synchronize the connection between the lifting mechanism and the object to be lifted, thereby forming a specific lifting process.

[0014] The economic and technical effects analyzed above indicate that the present invention provides a comprehensive solution that brings many excellent benefits to prefabricated housing construction. This is an epoch-making one that promises to revolutionize productivity, costs, and price setting in the construction industry.

[0015] Further specific features of the present invention will become clearer through the following description of embodiments with reference to the accompanying technical drawings.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective view of the lifting mechanism in the lifted state according to the conventional embodiment. [Figure 2] It is a perspective view showing the components of the lifting mechanism according to the conventional embodiment. [Figure 3] It is a perspective view showing the lifting principle of the lifting mechanism in an embodiment of the present invention. [Figure 4] It is an exploded perspective view showing the basic component assembly of the lifting mechanism in an embodiment of the present invention. [Figure 5] It is a perspective view showing the floor slab. [Figure 6] It is a perspective view showing the concrete pouring process of the foundation in an embodiment of the present invention. [Figure 7] It is a perspective view showing the installation of the second-floor slab on the foundation in an embodiment of the present invention. [Figure 8] It is a perspective view showing the installation of the next floor slab on the lower floor slab in an embodiment of the present invention. [Figure 9] It is a perspective view showing the installation of the roof floor slab support frame on the attic floor slab in an embodiment of the present invention. [Figure 10] It is a perspective view showing the installation of the roof floor slab on the roof floor slab support frame in an embodiment of the present invention. [Figure 11] It is a perspective view showing the insertion of the column into the column hole formed in the floor slab in an embodiment of the present invention. [Figure 12]Perspective view showing the lifting of the roof floor slab in one embodiment of the present invention (if applicable, installed on the floor slab before lifting if a roof is required), and stopping at an appropriate height to install the members under the roof floor slab. [Figure 13] Perspective view showing further lifting of the roof floor slab in one embodiment of the present invention, and stopping at a predetermined height to install a floor slab strut for connecting two adjacent floor slabs. [Figure 14] Perspective view showing the installation of the attic walls and other components in one embodiment of the present invention to complete the attic. [Figure 15] Perspective view showing further lifting of the roof floor slab in one embodiment of the present invention, thereby lifting the entire assembled components of the attic, and creating sufficient space for installing a floor slab strut under the attic between the attic floor slab and the floor slab below it. [Figure 16] Perspective view showing the installation of the walls and other components on the floor below the attic in one embodiment of the present invention to complete this floor. [Figure 17] Perspective view showing the final lifting process to achieve a predetermined space for the first floor in one embodiment of the present invention, and welding the base (column footing) of the lifting column to a steel plate previously installed on the foundation. [Figure 18] Perspective view showing the installation of the walls on the first floor and the closure of the roof openings in one embodiment of the present invention. [Figure 19] Side elevation view showing the lifting mechanism in one embodiment of the present invention. [Figure 20] Longitudinal sectional view showing the lifting mechanism during the lifting process in one embodiment of the present invention. [Figure 21] Partial sectional view showing the dynamic connection assembly between the column and the column hole. [Figure 22] Kinematics diagram showing a conventional lifting mechanism. [Figure 23]This is a kinematic diagram showing the lifting mechanism in one embodiment of the present invention. [Modes for carrying out the invention]

[0017] The following description of a lifting mechanism in a preferred embodiment of the present invention is provided for illustrative purposes only and is not intended to limit the scope or use of the present invention.

[0018] The description of embodiments illustrated in accordance with the principles of the present invention and intended to be read with reference to the accompanying drawings shall be considered as part or whole of the description. In the description of embodiments disclosed herein, references to directions or orientations are provided solely for the convenience of explanation and are not intended to limit the scope of the invention in any way. Relative terms such as “down,” “up,” “horizontal,” “vertical,” “upper side,” “lower side,” “upward,” “downward,” “top,” and “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) shall be understood in reference to the directions or orientations described herein or shown in the accompanying drawings. These relative terms are for the convenience of explanation only and do not require that the apparatus be constructed or operated in a particular direction or orientation unless expressly stated. Terms such as “mounted,” “fixed,” and similar expressions refer to relationships in which structures are fixed or connected to one another, directly or indirectly through intermediate components. Furthermore, features and advantages of the invention are given as examples with reference to exemplary embodiments. Thus, the invention is not limited to these exemplary embodiments, which merely illustrate some possible non-limiting combinations of features that may exist independently or in various other combinations. The scope of the present invention is defined by the appended claims.

[0019] The lifting mechanism according to the present invention includes the following: - The concrete foundation and first-floor slab (hereinafter referred to as "foundation slab") are cast in place as a single unit. Connecting elements (e.g., foundation bolts, steel flanges, etc.) for later attachment to the columns are embedded in the foundation slab at the column locations. - The floor slab 3 includes openings 32 through which the building's columns (which also function as the building's suspension columns) 2 pass. These openings 32 are called column holes.

[0020] The design of the column holes and columns is extremely important. The cross-sectional dimensions (cross-sectional area) of the column holes must be selected so that the clearance between the column and the column hole is as small as possible in order to ensure the verticality of the column. This arrangement allows the column hole to effectively guide the column and reduces the frictional force between the column and the column hole (caused by the eccentric pressing force applied to the column by the hydraulic jack). However, if these clearances are too small, the column may get stuck in the opening due to manufacturing tolerances in both the column and the column hole. These clearances are most preferably in the range of 1.5 to 3 mm.

[0021] The depth of the column hole is also very important and must be determined in conjunction with the clearance between the column and the column hole. The depth of the column hole corresponds to the length of the column segment inserted into the opening. This depth affects the moment resistance capacity of the joint between the column and the floor slab, and this must be treated as a rigid, fixed connection. The depth H3 of the opening 32 must match the width B32 of the opening 32, or the width of the column 2, so that the bending moment acting on the column at the location of the opening 32 does not cause damage to the wall of the opening 32. Most preferably, the H3 / B32 ratio is in the range of 1.5 to 2.

[0022] If the depth of the column holes and the clearance between the columns and the column holes are appropriately selected, it is not necessary to rigidly fix the columns to the foundation during the building installation process (Figure 3). - Prefabricated floor slabs 3 manufactured in the factory should integrate as many mechanical, electrical, and plumbing (MEP) systems as possible (e.g., heating, ventilation, and air conditioning (HVAC) ducts, specific electrical equipment, junction boxes, etc.) to reduce on-site construction time. - The steel columns 2 also function as lifting columns. These columns are provided with holes or members for attaching lifting rails for a special lifting device 5, and openings for connection to the floor slab. - The special lifting device is a self-lifting hydraulic jack system. These devices rise along a lifting rail attached to a column, press against the underside of the floor slab, and lift the floor slab. The lifting device is equipped with a control system configured to control the lifting or lowering stroke of the lifting device and to synchronize the stroke of the lifting device. Each column (i.e., the lifting column) is equipped with a hydraulic jack that is supported by the underside of the floor slab of the top floor of the building, lifting that floor slab and thereby simultaneously lifting the floor slab of the next floor below. - During construction, the floor slabs 3 are not fixed to the columns 2, but are instead connected to each other by steel bars 7 with quick-connect joints for connecting to the floor slabs 3. When the top floor slab rises during the lifting process, the lifting force is transmitted through these steel bars to the floor slab directly below, which in turn transmits the lifting force to the next floor slab below. These steel bars are primarily subjected to tensile forces during lifting, but are also designed to withstand compressive forces (i.e., the weight of the upper floor) in case the hydraulic jacks fail. Thus, these steel bars 7 are called "floor slab struts" 7.

[0023] The components of the present invention are described and referenced by number in the following drawings.

[0024] Description of the installation process according to the present invention (Figures 6-18): - The foundation and the first-floor slab (foundation slab) 1 are cast in place with concrete (Figure 6). A fast-setting admixture is used to shorten the waiting time until the concrete reaches the required strength. - Prefabricated floor slabs 3 manufactured in the factory are assembled directly on top of the foundation floor slab (Figures 7-10). The floor slabs are assembled and stacked in an upward order. The second-floor floor slab is placed directly on top of the foundation floor slab, the third-floor floor slab is placed directly on top of the second-floor floor slab, and so on. The roof floor slab is also placed on top of the next floor slab below, but is placed via a steel support frame 16 to ensure sufficient space for the installation of the lifting device (i.e., sufficient height to accommodate the hydraulic jacks 5). - The floor slabs 3 are stacked so that the column holes in the floor slabs are concentrically aligned with each other and with the designated column positions on the foundation 1. - Lifting rails 10 are pre-attached to column 2. A crane is used to position column 2 into the column hole in the floor slab 3 and lower it until the lower end of column 2 rests on the surface of the foundation floor slab 1. During construction, it is not necessary to rigidly fix the lower end of the column to the foundation floor slab. The column is permanently fixed to the foundation floor slab only after the structure has been lifted to the designed height (Figure 11). - Hydraulic jack 5 is inserted into the space between the roof slab and the next floor slab below (Figure 13). The jack is mounted to engage with the lifting rail 10. Hydraulic hoses and control cables are connected to the control panel. The piston rod head is controlled to contact the underside of the roof slab. The stroke indicator of the hydraulic jack is reset to zero. (See Figure 20 for details on the connection between the column and the floor slab.) - To avoid roof installation work at high altitudes, roof 6 is installed on top of the roof floor slab. Where columns protrude above the roof, notches are cut out in the roof panels to create openings for the columns to pass through. These openings are sealed after the building is lifted into place (Figure 12). - Hydraulic jack 5 is activated and begins lifting the roof slab. The jack can be stopped at any position to facilitate the installation of systems on the underside of the roof slab (e.g., electrical wiring, sprinklers and fire water pipes, lighting fixtures and ceiling with HVAC air vents, etc.) (Figure 12). - Once the designed spacing between the two floor slabs is sufficiently achieved, the floor slab struts 7 are installed to connect the two floor slabs 3 to each other. The floor slab struts 7 are installed within the hollow space of the column 2 to avoid interference with other components (Figure 13). - Wall 4 and all floor components (e.g., windows, doors, bathrooms, interior finishes, etc.) are installed (Figure 14). - Hydraulic jack 5 is activated further, continuing to lift the roof slab. As the roof slab rises, it simultaneously lifts the floor slab of the next floor below, along with all the previously installed components of that floor (Figure 15). - The assembly and lifting process carried out on the top floor is repeated for each subsequent floor until all floors have been lifted and assembled (Figure 16). - After the entire building has been lifted to the designed height, the following steps must be taken. The base of column 2 is connected to the foundation floor slab 1 using pre-installed connection points (such as foundation bolts, welding to steel plates, or protruding reinforcing bars). • The floor slab 3 is connected to the column 2 using pre-designed connections (e.g., bolts), forming a rigid, fixed connection. To resist vertical forces, the second-floor slab 3 is connected to the column 2 by pins 8 that penetrate the entire column. In the diagram, these pins 8 are referred to as column pins. Remove the lifting device / hydraulic jack 5 and the lifting rail 10. • Seal off the opening in the roof where the pillar was protruding.

[0025] To illustrate the differences between this invention and other building lifting methods, simplified models are used as shown in Figures 22 and 23.

[0026] A notable feature contributing to the effectiveness of the present invention compared to conventional technology is that, by appropriately selecting the clearance K32td between the column hole and the column and the depth H3 of the column hole in the design (see the floor slab description above), it is not necessary to fix the lower end of the column to the foundation floor slab throughout the entire assembly and lifting process. The position of the column is determined by the position of the corresponding column hole on the floor slab. The vertical alignment Gtd of the column relative to the floor slab is determined by the value of the clearance K32td between the column hole and the column and the depth H3 of the column hole. The verticality of the column and the parallelism of the floor slab to the horizontal plane depend on the height tolerance of the column support points on the foundation. Factory-manufactured floor slabs and columns provide favorable conditions for accuracy. Construction of the foundation to achieve the surface height tolerance is also not difficult. Simply lifting the columns with a crane and placing them in the column holes is far quicker and easier than fixing dozens of columns on the surface of the foundation floor slab to ensure verticality. Because the columns can move freely within the column holes (within the manufacturing clearance), column jamming during the lifting process is less likely to occur, in contrast to columns rigidly fixed to the foundation, if the required verticality is not achieved.

[0027] Achievable benefits and effects i. Because vertical adjustment of the suspended columns (which also function as building columns) is quick, on-site installation time is significantly reduced. Saving time also leads to cost savings. ii. The installation process is simple. Lifting the columns (which also function as lifting columns) with a crane and placing them into the column holes is very easy and quick. The small clearance between the columns and the column holes, combined with the appropriate depth of the column holes, provides sufficient geometric rigidity to the building's load-bearing frame without rigidly fixing the columns to the foundation during installation. This simplicity means that a large number of skilled workers are not required during installation. iii. The lifting solution using the lifting device according to the present invention allows the lifting to be stopped at any desired height, thereby enabling workers to conveniently assemble structural members under the floor slab without the need for ladders or scaffolding. This design saves time and labor during construction. iv. By using columns as lifting columns, construction machinery can be made more compact and lightweight. Once the lifting process is complete, the lifting rails can be removed from the columns and reused to lift other structures. v. The control system for the lifting device according to the present invention is programmed using a PLC language and can synchronize the strokes of all lifting devices via stroke sensors. This system allows the stroke deviation of the hydraulic jack's piston rod head to be adjusted (set) within a range of several tens of centimeters to 1 mm. This ensures that all contact points between the jack and the underside of the floor slab always remain at the same height within the tolerance. As a result, deformation and twisting of the floor slab are prevented, thereby avoiding displacement and damage to other structural members already installed (e.g., walls, doors, ceilings, etc.). However, the smaller the set stroke deviation, the slower the lifting speed.

[0028] While the foregoing description and accompanying drawings illustrate exemplary embodiments, it should be understood that various changes, modifications, and substitutions can be made without departing from the scope and spirit of the invention as defined in the appended claims. In particular, those skilled in the art will readily recognize that the invention can be embodied in other specific forms, configurations, arrangements, proportions, dimensions, and other elements, materials, and components without departing from the essential features or intent of the invention. Those skilled in the art will also understand that the invention can be adapted in numerous structural variations, layouts, proportions, dimensions, materials, components, and other parameters tailored to specific environmental and operational requirements without departing from the principles of the invention. Accordingly, the embodiments disclosed herein should be considered in all respects as illustrative and not limiting, and the scope of the invention is defined by the appended claims rather than by the foregoing description or specific embodiments of the invention.

Claims

1. A hydraulic mechanism system for raising and lowering a floor slab, It includes a foundation floor slab (1), columns (2) that function as lifting columns, and floor slabs (3), The column (2) is inserted through the opening (32) of the floor slab (3) that is being lifted. A lifting rail (10) is arranged inside the column (2), and the outer surface of the lifting rail (10) is provided with teeth that mesh with a hydraulic jack (5) to raise and lower the hydraulic jack (5). Floor slab struts (7) are installed between vertically adjacent floor slabs (3) to transmit the lifting force while maintaining the distance between the lifted floor slabs (3), connecting the upper floor slab and the lower floor slab, so that when the upper floor slab is lifted, the lower floor slab is also lifted, and the floor slab struts (7) are positioned inside the column (2). A pin (8) is provided on the column (2) at a predetermined height to fix the floor slab (3). A hydraulic mechanism system is provided in which a steel plate (17) is provided on the foundation floor slab (1) at the position where the foundation floor slab (1) connects with the column (2).

2. A method for raising and lowering a floor slab using the hydraulic mechanism system described in claim 1, Concrete is poured for the foundation floor slab (1), and a step is installed on which the steel plate (17) is placed. A step of directly placing a prefabricated floor slab (3) manufactured in a factory onto a foundation floor slab, wherein the floor slabs (3) are stacked upwards, and the opening (32) on the floor slab (3) is aligned with the steel plate (17) installed on the foundation floor slab (1), The steps include: placing the roof floor slab on the floor slab (3) which will be the next floor below the roof floor slab via a steel support frame (16); A step of preparing a column (2) on which a lifting rail (10) is installed, and inserting the column (2) into the opening (32) of the floor slab (3) until the lower end of the column (2) rests on the surface of the foundation floor slab (1), wherein it is not necessary to fix the lower end of the column to the foundation floor slab during construction, A step of inserting a hydraulic jack (5) into the space between the roof floor slab and the next lower floor slab (3), comprising the steps of engaging the hydraulic jack (5) with the lifting rail (10) and bringing the piston rod head of the hydraulic jack (5) into contact with the lower surface of the roof floor slab, Steps include installing the roof (6) onto the roof floor slab, The steps include: activating the hydraulic jack (5) to begin lifting the roof floor slab, Once the designed distance between the roof floor slab and the floor slab (3) of the next lower floor is sufficiently achieved, the floor slab struts (7) are installed to connect the roof floor slab and the floor slab (3) of the next lower floor to each other. The steps include installing a wall (4) and all floor components between the roof floor slab (3) of the next lower floor, which has been spaced apart by lifting, and the floor slab (3) of the next lower floor, With the hydraulic jack still engaged with the internal channel of the column (2) to lift the roof slab, the hydraulic jack is further operated to continue lifting the roof slab, and as the roof slab rises, the roof slab lifts the next floor slab connected by the floor slab strut (7), The assembly and lifting process carried out on the top floor will be repeated on each subsequent floor until all floors have been lifted and assembled. After the entire building has been lifted to the designed height, the steps include connecting the base of the column (2) to the foundation floor slab (1), The steps include connecting the floor slab (3) to the column (2) to form a rigid fixed connection, The steps include connecting the second-floor floor slab (3) to the column (2) by a pin (8) that penetrates the entire column (2), The steps include removing the hydraulic jack (5) and the lifting rail (10), A step to seal the opening in the roof through which the column (2) had protruded, Includes, Column (2), which also functions as a lifting column, is not rigidly fixed to the foundation during the installation process, but merely rests freely on the foundation. The rigid connection of the column to the foundation is only made when the floor slab has been lifted to the designed height. A method to reduce on-site installation time by integrating floor slabs with mechanical, electrical, and plumbing (MEP) systems, including HVAC systems, electrical and lighting systems, water pipes, and fire extinguishing pipes, during factory manufacturing.

3. A method according to claim 2, wherein the opening (32) in the floor slab (3) through which the column (2) passes is designed to be in the range of 1.5 to 3 mm, which is the minimum clearance (K32td) between the column (2) and the inner wall of the opening (32), and the depth (H3) of the opening (32) is suitable for the width (B32) of the opening (32) and the width of the column (2), and the ratio H3 / B32 is in the range of 1.5 to 2.

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