阅读说明：本技术 一种变密度的三维织物及其织造方法 (Variable-density three-dimensional fabric and weaving method thereof ) 是由 王群 朱梦蝶 李小欢 刘延友 胡方田 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种变密度的三维织物及其织造方法,所述三维织物的密度沿厚度方向、宽度方向或长度方向中的一种方向变化或两种以上方向同时变化,变密度的三维织物通过层连结构连接,不同密度区域界面层间相互连接、纱线连续,整体连续织造成型。本发明的变密度的三维织物具有组织结构多样、织物尺寸控制范围大、可设计性强、结构紧密、整体性好、织造过程简单、适于连续化织造等优点,用该织物复合增强的变密度材料具有低热胀系数、高耐热性、高比强度、高比模量、抗冲击、耐磨损和抗老化等优点,可广泛应用于汽车、航空、航天、机械制造、石油等领域。(The invention discloses a variable-density three-dimensional fabric and a weaving method thereof, wherein the density of the three-dimensional fabric changes along one direction or more than two directions of the thickness direction, the width direction or the length direction, the variable-density three-dimensional fabric is connected through a layer connecting structure, the interface layers of different density areas are connected with each other, the yarns are continuous, and the three-dimensional fabric is integrally and continuously woven and formed. The variable-density three-dimensional fabric has the advantages of various organizational structures, large fabric size control range, strong designability, compact structure, good integrity, simple weaving process, suitability for continuous weaving and the like, and the variable-density material compositely reinforced by the fabric has the advantages of low thermal expansion coefficient, high heat resistance, high specific strength, high specific modulus, impact resistance, wear resistance, ageing resistance and the like, and can be widely applied to the fields of automobiles, aviation, aerospace, mechanical manufacturing, petroleum and the like.)

1. The variable-density three-dimensional fabric is characterized in that the density of the three-dimensional fabric changes along one direction or more than two directions of the thickness direction, the width direction or the length direction, the variable-density three-dimensional fabric is connected through a layer connecting structure, the interface layers of different density areas are connected with each other, yarns are continuous, and the three-dimensional fabric is integrally and continuously woven and formed.

2. The variable density three-dimensional fabric of claim 1, wherein the layer structure is one or more of an orthorhombic three-dimensional, shallow cross-curved, shallow cross-straight, deep cross-curved, deep cross-straight, twill, satin, or hollow sandwich structure.

3. The variable density three-dimensional fabric according to any one of claims 1 or 2, wherein the three-dimensional fabric is formed by weaving one or more high-performance fibers in a mixed manner.

4. The variable-density three-dimensional fabric as claimed in claims 1 to 3, wherein the three-dimensional fabric is woven by using yarns with one or more than two fineness.

5. The variable-density three-dimensional fabric as claimed in claims 1 to 3, wherein the three-dimensional fabric is woven by using one or more than two yarns in the ratio of the number of strands.

6. The variable density three-dimensional fabric according to claims 1 to 3, wherein the warp density of the three-dimensional fabric is one or more than two.

7. The variable density three-dimensional fabric according to claims 1 to 3, wherein the weft density of the three-dimensional fabric is one or more than two.

8. The variable density three-dimensional fabric as claimed in claims 1 to 3, wherein the density of the three-dimensional fabric is varied within a range of 0.08g/cm³-1.5g/cm³。

9. The method for weaving a variable density three-dimensional fabric according to claims 1 to 8, characterized by comprising a step of weaving each density region separately and a step of weaving each different density region at the interface junction.

10. The weaving method according to claim 9, characterized in that it comprises in particular the following steps connected in sequence:

(1) arranging the number of warp yarn layers of the fabric according to the requirements of the weave structure of different density areas of the fabric, the interface connection structure of the different density areas, the yarn type, the yarn fineness, the yarn strand number proportion, the warp yarn density and the weft yarn density to form an X layer of warp yarns and a Y row of warp yarns;

(2) passing each warp yarn of each layer through a corresponding warp yarn tension control device to control the tension of the warp yarns;

(3) respectively threading the warp yarns into corresponding heddles and reed teeth according to the arrangement of the warp yarn layer number;

(4) adjusting the warp tension one by one to meet the weaving requirement;

(5) according to the requirements of the weave structure of the fabric, the shedding device starts to circularly move from bottom to top or from top to bottom according to the warp interweaving rule according to the sequence of a first density area, the junction of the first density area and the second density area, the junction of the second density area and the third density area, the junction of an N-1 th density area and an N density area of a third density area … … and an N density area in turn, and the corresponding warp is driven to circularly move from bottom to top or from top to bottom, and each movement forms an equal-height opening;

(6) after an opening is formed each time, a weft yarn is introduced by a weft insertion device, after the weft insertion is finished, a beating-up device horizontally moves towards a fabric fell, and the weft yarn is beaten into the fell to finish beating-up;

(7) and after beating-up is finished, pulling the fabric to a forming direction for a certain distance according to the weft density requirement of the fabric, and after pulling is finished, carrying out next motion cycle until the weaving of the whole fabric is finished.

Technical Field

The invention relates to the technical field of three-dimensional fabric weaving, in particular to a three-variable-density three-dimensional fabric and a weaving method thereof.

Background

The variable density material is a novel composite material which is compounded by two or more materials and has continuously changed components and structures, the mechanical property and the function of the variable density material continuously change along a certain direction, and the variable density material is a novel functional material which is developed to meet the requirements of high-tech fields such as modern aerospace industry and the like and can repeatedly and normally work under the limit environment. The variable density material has the advantages of low thermal expansion coefficient, high heat resistance, enhanced surface performance of a material structure, high specific strength, high specific modulus, impact resistance, wear resistance, aging resistance and the like in the aspect of a power structure, is favored by people, and can be widely applied to the fields of automobiles, aerospace, machinery manufacturing, petroleum and the like in the future.

The variable density composite material has good integrity and interlayer performance, and the variable density fabric is the key of the variable density composite material as a reinforcement of the composite material. At present, the variable density fabric is mainly realized by a three-dimensional knitting process, a fine knitting and puncturing process, a weaving process and a needling process.

Chinese patent CN 107956024a introduces a three-dimensional fabric with a gradient structure and a preparation method thereof, warp yarns and weft yarns of each layer are bound into a whole by binding yarns, and the diameters of the weft yarns of different layers on the same section are gradually decreased from top to bottom layer by layer, so that gaps between adjacent weft yarns on the same layer are in gradient change. The fabric has the advantages of single connection mode, single structure and single density change form, the warp and weft yarns are bound into a whole by binding yarns in the fabric forming process, the connection performance between fabric layers is weak, a large number of gradient pores exist in the thickness direction, the fabric integrity is poor, the strength and the mechanical property are low, and the fabric is not beneficial to meeting the wide application requirements in different fields.

Chinese patent CN 110284256a describes a three-dimensional knitting method of variable density fabric along thickness direction, which is based on three-dimensional four-step knitting method, dividing knitting yarn into inner layer knitting yarn and encrypted outer layer knitting yarn, making the inner layer knitting yarn and encrypted outer layer knitting yarn exchange positions in sequence, making the fiber part of the encrypted layer and the non-encrypted part knitting together, and making the connection between each layer of yarn tight by the inner and outer layer yarn changing way, realizing the knitting of variable density fabric along thickness direction. The fabric has the advantages of single connection mode, single structure, single density change form, incapability of realizing continuous weaving, poorer fabric uniformity and limited wide application in different fields due to the compact structure of three-dimensional weaving.

Disclosure of Invention

The invention aims to provide a variable-density three-dimensional fabric and a weaving method thereof, aiming at the problems that the existing variable-density three-dimensional fabric is single in connection mode, single in structure and single in density change form, cannot realize continuous weaving and is difficult to meet the wide application requirements of different fields.

The first technical scheme adopted by the invention is as follows: the density of the three-dimensional fabric changes along one direction or more than two directions of the thickness direction, the width direction or the length direction, the three-dimensional fabric with variable density is connected through a layer connection structure, the interface layers of different density areas are connected with each other, the yarns are continuous, and the three-dimensional fabric is integrally and continuously woven and formed.

The second technical scheme adopted by the invention is an improvement on the first technical scheme, and the second technical scheme adopted by the invention is as follows: the layer connection structure is one or more than two of an orthogonal three-dimensional, shallow cross-bending connection, shallow cross-direct connection, deep cross-bending connection, deep cross-direct connection, twill, satin or hollow sandwich structure.

The third technical solution adopted by the present invention is an improvement of the first or second technical solution, and the third technical solution adopted by the present invention is: the three-dimensional fabric is formed by weaving one or more than two high-performance fibers in a mixed mode.

The fourth technical solution adopted by the present invention is an improvement of the first, second, or third technical solution, and the fourth technical solution adopted by the present invention is: the three-dimensional fabric is woven by using yarns with one or more than two fineness degrees.

The fifth technical solution adopted by the present invention is an improvement of the first, second, or third technical solution, and the fifth technical solution adopted by the present invention is: the three-dimensional fabric is woven by one or more than two yarns in the ratio of the number of the yarns.

The sixth technical solution adopted by the present invention is an improvement of the first, second, or third technical solution, and the sixth technical solution adopted by the present invention is: the warp density of the three-dimensional fabric is one or more than two.

The seventh technical solution adopted by the present invention is an improvement of the first, second, or third technical solution, and the seventh technical solution adopted by the present invention is: the weft density of the three-dimensional fabric is one or more than two.

The eighth technical solution adopted by the present invention is an improvement of the first, second, or third technical solution, and the eighth technical solution adopted by the present invention is: the density variation range of the three-dimensional fabric is 0.08g/cm³-1.5g/cm³。

The ninth technical solution adopted by the present invention is an improvement of the first to eighth technical solutions, and the ninth technical solution of the present invention is: the weaving method of the variable-density three-dimensional fabric comprises the step of weaving each density area separately and the step of weaving the interface joint of each different density area.

The tenth technical solution adopted by the present invention is an improvement of the ninth technical solution, and the tenth technical solution adopted by the present invention is: the method specifically comprises the following steps of:

(1) arranging the number of warp yarn layers of the fabric according to the requirements of the weave structure of different density areas of the fabric, the interface connection structure of the different density areas, the yarn type, the yarn fineness, the yarn strand number proportion, the warp yarn density and the weft yarn density to form an X layer of warp yarns and a Y row of warp yarns;

(2) passing each warp yarn of each layer through a corresponding warp yarn tension control device to control the tension of the warp yarns;

(3) respectively threading the warp yarns into corresponding heddles and reed teeth according to the arrangement of the warp yarn layer number;

(4) adjusting the warp tension one by one to meet the weaving requirement;

(5) according to the requirements of the weave structure of the fabric, the shedding device starts to circularly move from bottom to top or from top to bottom according to the warp interweaving rule according to the sequence of a first density area, the junction of the first density area and the second density area, the junction of the second density area and the third density area, the junction of an N-1 th density area and an N density area of a third density area … … and an N density area in turn, and the corresponding warp is driven to circularly move from bottom to top or from top to bottom, and each movement forms an equal-height opening;

(6) after an opening is formed each time, a weft yarn is introduced by a weft insertion device, after the weft insertion is finished, a beating-up device horizontally moves towards a fabric fell, and the weft yarn is beaten into the fell to finish beating-up;

(7) and after beating-up is finished, pulling the fabric to a forming direction for a certain distance according to the weft density requirement of the fabric, and after pulling is finished, carrying out next motion cycle until the weaving of the whole fabric is finished.

The invention has the beneficial effects that: the variable-density three-dimensional fabric obtained by the invention can realize density changes of the three-dimensional fabric along the thickness direction, the width direction and the length direction through fabric structure change, yarn type change, yarn fineness change, yarn strand number proportion change, warp density change and weft density change, is integrally and continuously woven and formed, is connected among fabric layers, and has the advantages of various organizational structures, large fabric size control range, strong designability, compact structure, good integrity, simple weaving process operation, suitability for continuous weaving and the like. The variable density material compositely reinforced by the fabric has the advantages of low thermal expansion coefficient, high heat resistance, high specific strength, high specific modulus, impact resistance, wear resistance, ageing resistance and the like, and can be widely applied to the fields of automobiles, aviation, spaceflight, machine manufacturing, petroleum and the like.

Drawings

Fig. 1 is a schematic structural view of a three-dimensional fabric of which density varies in the thickness direction according to a first embodiment of the present invention.

Figure 2 is a schematic representation of the warp yarn movement pattern of the cover sheet over the first density zone in accordance with the first embodiment of the present invention.

Fig. 3 is a schematic diagram showing the warp yarn motion pattern of the intermediate core layer in the first density region according to the first embodiment of the present invention.

Figure 4 is a schematic representation of the warp yarn movement pattern of the lower sheet layer of the first density zone of the first embodiment of the present invention.

FIG. 5 is a schematic representation of the warp yarn motion pattern for the first embodiment of the present invention in which the upper cover layer is interwoven with the intermediate core layer in the first density zone.

Figure 6 is a schematic representation of the warp yarn movement pattern of the lower sheet layer of the first density zone of the first embodiment of the present invention.

Figure 7 is a schematic representation of the warp yarn motion profile for the plies above the first density zone of the first embodiment of the present invention.

FIG. 8 is a schematic representation of the law of motion of the warp yarns interweaving the lower cover sheet and the intermediate core under the first density zone in accordance with the first embodiment of the present invention.

FIG. 9 is a schematic view of the warp yarn motion pattern at the interface between the first density region and the second density region according to the first embodiment of the present invention.

FIG. 10 is a schematic view of the interface between the second density region and the third density region and the law of motion of the warp yarns in the third density region according to the first embodiment of the present invention.

Fig. 11 is a schematic structural view of a three-dimensional fabric of which density is simultaneously changed in the thickness direction and the width direction according to a second embodiment of the present invention.

FIG. 12 is a schematic representation of the warp yarn motion profile of a first density zone in the thickness direction according to a second embodiment of the present invention.

FIG. 13 is a schematic view showing the warp yarn motion pattern at the interface between the first density region in the thickness direction and the second density region in the thickness direction and at the second density region in the thickness direction according to the second embodiment of the present invention.

Fig. 14 and 15 are schematic diagrams illustrating the warp motion laws at the interface between the thickness direction second density region and the thickness direction third density region and at the thickness direction third density region according to the second embodiment of the present invention.

Fig. 16 is a structural view of a three-dimensional fabric of which density is simultaneously varied in the thickness direction and the length direction according to a third embodiment of the present invention.

FIG. 17 is a schematic representation of the warp yarn motion profile for the first density zone in the thickness direction according to the third embodiment of the present invention.

FIG. 18 is a schematic view showing the warp yarn motion pattern at the interface between the first density region in the thickness direction and the second density region in the thickness direction and at the second density region in the thickness direction according to the third embodiment of the present invention.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

Example 1

Referring to fig. 1, in the present embodiment, density variation of three regions of a fabric along a thickness direction is realized through weave structure variation and weft density variation, a weave structure of a first density region 11 is a hollow sandwich layer, a weave structure of a second density region 13 is shallow cross-bending connection, a weave structure of a third density region 15 is an orthogonal three-direction, an interface connection portion 12 of the first density region and the second density region is connected by a shallow cross-bending connection structure, an interface connection portion 14 of the second density region and the third density region is connected by a shallow cross-bending connection structure, and yarns are continuous.

In this embodiment, the variable density three-dimensional fabric is woven by 500tex glass fiber.

The process parameters for the variable density three-dimensional fabric of example 1 are shown in table 1.

Table 1 process parameters for a variable density three dimensional fabric of example 1

Referring to fig. 2 to 10, the weaving method of the variable density three-dimensional fabric of the present embodiment includes the following steps:

1. arranging the number of warp yarn layers in each density area according to the requirements of the size of the fabric, the weave structure of each area with different density and the density;

2. passing each warp yarn of each layer through a warp yarn tension control device to control the tension of the warp yarns;

3. according to the arrangement of the warp yarn layer number, a first warp yarn of each layer of warp yarn penetrates into a first row of harness wires one by one, and then penetrates into the same reed dent; the second warp of each layer of warp penetrates into the second row of heddles one by one, then penetrates into the same reed dent, and the warp of each layer penetrates into the corresponding heddles one by one according to the rule, and then penetrates into the corresponding reed dent;

4. adjusting the tension of the warp yarns one by one to ensure that the warp yarns meet weaving requirements;

5. according to the requirements of a set fabric weave structure, the heald lifting device starts to circularly move from bottom to top or from top to bottom to drive corresponding warps to circularly move from bottom to top or from top to bottom, and each movement forms an equal-height opening, and the specific movement steps are as follows in sequence:

5.1, independently weaving the hollow sandwich structure of the first density area 11, wherein the motion law of each layer of warp yarn is shown in figures 2-8;

5.2, weaving the interface joint 12 of the first density area and the second density area and weaving the shallow cross-linking structure of the second density area 13, wherein the motion law of warp yarns of each layer is shown in figure 9;

5.3, weaving of the junction 14 of the interface of the second density zone with the third density zone and weaving of the orthogonal three-way structure of the third density zone 15, the movement law of the warp yarns of each layer is shown in figure 10.

6. After an opening is formed each time, a weft yarn is introduced by a weft insertion device, after the weft insertion is finished, a beating-up device horizontally moves towards a fabric fell, and the weft yarn is beaten into the fell to finish beating-up;

7. and after beating-up is finished, pulling the fabric to a forming direction for a certain distance according to the set weft density of the fabric, and after pulling is finished, carrying out the next motion cycle until the weaving of the whole fabric is finished.

Example 2

Referring to fig. 11, the present embodiment provides a three-dimensional fabric with density varying along the thickness direction and the width direction simultaneously, the density varying of the three regions along the thickness direction and the three regions along the width direction is realized through structure variation, warp density variation, yarn fineness variation, and yarn type variation, the weave structure of the first density region 21 in the thickness direction is three orthogonal directions, the weave structure of the second density region 23 in the thickness direction is shallow cross-linking, the weave structure of the third density region 25 in the thickness direction is shallow cross-linking, the interface junction 22 between the first density region and the second density region in the thickness direction is connected by a shallow cross-linking structure, the interface junction 24 between the second density region and the third density region in the thickness direction is connected by a shallow cross-linking structure, the first density region in the width direction uses 190tex quartz fibers, the second density region in the width direction uses 220tex quartz fibers, the third density region in the width direction uses 330tex glass fibers, the connection between the layers of the structural interface is continuous and the yarn is continuous.

In the embodiment, the variable-density three-dimensional fabric is woven by using 190tex quartz fiber, 220tex quartz fiber and 330tex glass fiber.

The process parameters for the variable density three-dimensional fabric of example 2 are shown in table 2.

Table 2 process parameters for variable density three dimensional fabrics of example 2

The weaving method of the variable density three-dimensional fabric of the embodiment with reference to fig. 12 to 15 includes the following steps:

1. arranging the number of warp yarn layers in each density area according to the requirements of the size of the fabric, the weave structure of each area with different density and the density;

2. passing each warp yarn of each layer through a warp yarn tension control device to control the tension of the warp yarns;

3. according to the arrangement of the warp yarn layer number, a first warp yarn of each layer of warp yarn penetrates into a first row of harness wires one by one, and then penetrates into the same reed dent; the second warp of each layer of warp penetrates into the second row of heddles one by one, then penetrates into the same reed dent, and the warp of each layer penetrates into the corresponding heddles one by one according to the rule, and then penetrates into the corresponding reed dent;

4. adjusting the tension of the warp yarns one by one to ensure that the warp yarns meet weaving requirements;

5. according to the requirements of a set fabric weave structure, the heald lifting device starts to circularly move from bottom to top or from top to bottom to drive corresponding warps to circularly move from bottom to top or from top to bottom, and each movement forms an equal-height opening, and the specific movement steps are as follows in sequence:

5.1, independent weaving of an orthogonal three-dimensional structure of the first density zone 21 in the thickness direction, the law of motion of the warp yarns of each layer being as shown in figure 12;

5.2, weaving an interface joint 22 of the first density area in the thickness direction and the second density area in the thickness direction, and weaving a shallow cross-bending connection structure of the second density area 23 in the thickness direction, wherein the motion law of each layer of warp yarn is shown in figure 13;

5.3, weaving the interface connection part 24 of the second density area in the thickness direction and the third density area in the thickness direction, and weaving the shallow cross-direct connection structure of the third density area 25 in the thickness direction, wherein the motion law of the warp yarns of each layer is shown in figures 14 and 15.

6. After an opening is formed each time, a weft yarn is introduced by a weft insertion device, after the weft insertion is finished, a beating-up device horizontally moves towards a fabric fell, and the weft yarn is beaten into the fell to finish beating-up;

7. and after beating-up is finished, pulling the fabric to a forming direction for a certain distance according to the set weft density of the fabric, and after pulling is finished, carrying out the next motion cycle until the weaving of the whole fabric is finished.

Example 3

Referring to fig. 16, the present embodiment provides a three-dimensional fabric with density varying along the thickness direction and the length direction simultaneously, the density variation of the two regions of the fabric along the thickness direction and the two regions along the length direction is realized through the change of the weave structure, the change of the weft density, and the change of the ratio of the number of yarn strands, the weave structure of the first density region 31 in the thickness direction is three orthogonal directions, the weave structure of the second density region 33 in the thickness direction is shallow cross-linking, the interface connection point 32 between the first density region and the second density region is connected by a shallow cross-linking structure, and the ratio of the number of yarn strands used for the first density region in the length direction is 1: 1, the ratio of the number of the yarns used for the second density area in the length direction is 1: and 2, interlayer connection and yarn continuity at the interface connection positions of different structures.

In the embodiment, the variable-density three-dimensional fabric is woven by using 330tex glass fibers.

The process parameters for the variable density three-dimensional fabric of example 3 are shown in table 3.

Table 3 process parameters for variable density three dimensional fabrics of example 3

Referring to fig. 17 to 18, the weaving method of the variable density three-dimensional fabric of the present embodiment includes the following steps:

1. arranging the number of warp yarn layers in each density area according to the requirements of the size of the fabric, the weave structure of each area with different density and the density;

2. passing each warp yarn of each layer through a warp yarn tension control device to control the tension of the warp yarns;

3. according to the arrangement of the warp yarn layer number, a first warp yarn of each layer of warp yarn penetrates into a first row of harness wires one by one, and then penetrates into the same reed dent; the second warp of each layer of warp penetrates into the second row of heddles one by one, then penetrates into the same reed dent, and the warp of each layer penetrates into the corresponding heddles one by one according to the rule, and then penetrates into the corresponding reed dent;

4. adjusting the tension of the warp yarns one by one to ensure that the warp yarns meet weaving requirements;

5. according to the requirements of a set fabric weave structure, the heald lifting device starts to circularly move from bottom to top or from top to bottom to drive corresponding warps to circularly move from bottom to top or from top to bottom, and each movement forms an equal-height opening, and the specific movement steps are as follows in sequence:

5.1, independent weaving of the three-dimensional orthogonal structure of the first density zone 31 in the thickness direction, the law of motion of the warp yarns of each layer being as shown in figure 17;

5.2, weaving an interface joint 32 of the first density area in the thickness direction and the second density area in the thickness direction, and weaving a shallow cross-bending connection structure of the second density area 33 in the thickness direction, wherein the motion law of each layer of warp yarn is shown in figure 18;

6. after an opening is formed each time, a weft yarn is introduced by a weft insertion device, after the weft insertion is finished, a beating-up device horizontally moves towards a fabric fell, and the weft yarn is beaten into the fell to finish beating-up;

7. and after beating-up is finished, pulling the fabric to a forming direction for a certain distance according to the set weft density of the fabric, and after pulling is finished, carrying out the next motion cycle until the weaving of the whole fabric is finished.

According to the embodiments, density change of the fabric is realized by adjusting the fabric structure, the yarn type, the yarn fineness, the yarn strand number proportion, the warp density, the weft density and the like of each density area according to the fabric size and the fabric density requirements of each different density area, arrangement of the warp yarn layer rows is performed according to the structure parameters of each density area, regular movement of warp yarns is performed according to the requirements of the organization structure of each density area, and the variable-density three-dimensional fabric meeting the requirements can be obtained by sequentially opening and weft-inserting weaving. The variable-density three-dimensional fabric obtained by the invention is integrally and continuously woven and formed, is connected among fabric layers, and has the advantages of various weave structures, large fabric size control range, strong designability, compact structure, good integrity, simple weaving process operation, suitability for continuous weaving and the like. The variable density material compositely reinforced by the fabric has the advantages of low thermal expansion coefficient, high heat resistance, high specific strength, high specific modulus, impact resistance, wear resistance, ageing resistance and the like, and can be widely applied to the fields of automobiles, aviation, spaceflight, machine manufacturing, petroleum and the like.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.