阅读说明：本技术 顶置缓冲器二重搬入检测系统及方法 (Double-moving-in detection system and method for overhead buffer ) 是由 秦源章 于 2020-05-29 设计创作，主要内容包括：本发明涉及一种顶置缓冲器二重搬入检测系统,其包括：天车；第一感测单元,用于扫描生成水平范围的检测数据；驱动装置,用于对第一感测单元进行竖直范围移动；控制单元；天车控制系统,用于在天车移动到对应的顶置缓冲器位置时向控制单元发送检测指令以及驱动指令,控制单元根据驱动指令控制驱动装置对第一感测单元进行竖直范围移动,以及根据检测指令控制第一感测单元在移动过程中扫描生成顶置缓冲器内各水平范围的检测数据,根据顶置缓冲器内各水平范围的检测数据判断顶置缓冲器内是否有存在障碍物。其优点是：利用水平和竖直两个维度检测得到立体空间范围的检测结果,精准判断出障碍物的存在与否。(The invention relates to a double-moving-in detection system of an overhead buffer, which comprises: a crown block; a first sensing unit for scanning detection data of a generated horizontal range; a driving device for moving the first sensing unit in a vertical range; a control unit; the overhead crane control system is used for sending a detection instruction and a driving instruction to the control unit when the overhead crane moves to a corresponding overhead buffer position, the control unit controls the driving device to move in a vertical range according to the driving instruction, controls the first sensing unit to scan and generate detection data of each horizontal range in the overhead buffer in the moving process according to the detection instruction, and judges whether an obstacle exists in the overhead buffer according to the detection data of each horizontal range in the overhead buffer. The advantages are that: the detection result of the three-dimensional space range is obtained by utilizing the horizontal dimension and the vertical dimension for detection, and whether the barrier exists or not is accurately judged.)

1. A double entry detection system for an overhead buffer, comprising:

a crown block;

a first sensing unit for scanning detection data of a generated horizontal range;

the driving device is arranged on the overhead travelling crane, is connected with the first sensing unit and is used for moving the first sensing unit in a vertical range;

the control unit is respectively connected with the driving device and the first sensing unit;

the overhead traveling crane control system is respectively connected with the overhead traveling crane and the control unit and used for sending a detection instruction and a driving instruction to the control unit when the overhead traveling crane moves to a corresponding overhead buffer position, the control unit controls the driving device to move the first sensing unit in a vertical range and controls the first sensing unit to scan and generate overhead detection data of each horizontal range in the overhead buffer in a moving process according to the detection instruction, the detection data of each horizontal range in the overhead buffer is sent to the overhead traveling crane control system, and the overhead traveling crane control system judges whether an obstacle exists in the overhead buffer according to the detection data of each horizontal range in the overhead buffer.

2. The overhead buffer dual access detection system of claim 1, wherein:

the driving device is a screw rod mechanism;

the first sensing unit is arranged on a sliding block of the lead screw mechanism;

the control unit drives a motor of the screw mechanism to drive the sliding block to drive the first sensing unit to move in the vertical range.

3. The overhead buffer dual access detection system of claim 2, further comprising:

the second sensing unit is connected with the control unit and used for outputting a first sensing signal when the first sensing unit moves to the upper limit of the vertical range;

the third sensing unit is connected with the control unit and used for outputting a second sensing signal when the first sensing unit moves to the lower limit of the vertical range;

the control unit is further used for controlling the first sensing unit to start scanning from the lower limit position of the vertical range according to the first sensing signal and the second sensing signal, and ending the scanning when the first sensing unit moves to the upper limit position of the vertical range.

4. The overhead buffer dual access detection system of claim 3, wherein:

the second sensing unit and the third sensing unit are laser sensors respectively.

5. The overhead buffer dual access detection system of claim 1, wherein:

the vertical range at least includes a range from a lower edge of an obstacle on the overhead bumper to an upper edge of the overhead traveling crane transfer unit.

6. The overhead buffer double entry detection system of claim 1 or 5, wherein:

the horizontal range includes at least a range of areas where an obstacle on the overhead bumper is located.

7. A double-moving-in detection method of an overhead buffer is characterized in that:

controlling the crown block to move to a corresponding overhead buffer position;

triggering a first sensing unit, controlling a driving device to move the first sensing unit in a vertical range, so that the first sensing unit scans and generates detection data of each horizontal range in the overhead buffer in the moving process, wherein the driving device is arranged on the overhead travelling crane, and the first sensing unit is connected with the driving device;

and judging whether an obstacle exists in the overhead buffer or not according to the detection data of each horizontal range in the overhead buffer.

8. The overhead buffer double entry detection method according to claim 7, characterized in that: before the crown block moves to the corresponding overhead buffer position, the method further comprises:

setting a detection range of a horizontal range of the first sensing unit and a vertical range in which the first sensing unit moves;

the horizontal range includes at least a range of areas where an obstacle on the overhead bumper is located;

the vertical range at least includes a range of a region from a lower edge of the obstacle on the overhead bumper to an upper edge of the overhead traveling crane transfer unit.

9. The overhead buffer double entry detection method according to claim 8, characterized in that:

after the first sensing unit is triggered, the first sensing unit starts scanning from a lower edge position of an obstacle on the overhead buffer, and ends scanning when the first sensing unit moves to an upper edge position of the overhead traveling crane transfer unit under the control of the driving device.

10. The method of claim 8, further comprising, after determining that an obstacle is present in the overhead buffer:

and judging the type of the obstacle according to the detection data of each horizontal range in the overhead buffer, and carrying out corresponding alarm reminding according to different types of the obstacle.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a double-moving-in detection system and a double-moving-in detection method for an overhead buffer.

Background

An Automated Material Handling System (AMHS) for semiconductor integrated circuits includes an Overhead Hoist (OHT) traveling along a track disposed below a ceiling, and an Overhead Buffer (OHB) installed below the ceiling, wherein the Overhead Buffer is a kind of storage bay for storing Front Opening Unified Pod (FOUP) for transporting the Front Opening Unified Pod to a destination station.

Currently, when a front-mounted wafer transport box is stored when a front-mounted vehicle moves to a corresponding top buffer position, whether an object exists in the top buffer needs to be detected firstly, the detection process is called as double-input detection, the double-input detection is performed through a photoelectric sensor currently, the detection mode has the possibility of missing detection and false detection, and the accuracy is not high.

Disclosure of Invention

Accordingly, it is necessary to provide a double entry detection system and method for an overhead buffer, which can accurately detect double entry, in order to solve the problems of missing detection and erroneous detection in the conventional double entry detection.

An overhead buffer double entry detection system, comprising:

a crown block;

a first sensing unit for scanning detection data of a generated horizontal range;

the driving device is arranged on the overhead travelling crane, is connected with the first sensing unit and is used for moving the first sensing unit in a vertical range;

the control unit is respectively connected with the driving device and the first sensing unit;

the overhead traveling crane control system is respectively connected with the overhead traveling crane and the control unit and used for sending a detection instruction and a driving instruction to the control unit when the overhead traveling crane moves to a corresponding overhead buffer position, the control unit controls the driving device to move the first sensing unit in a vertical range and controls the first sensing unit to scan and generate overhead detection data of each horizontal range in the overhead buffer in a moving process according to the detection instruction, the detection data of each horizontal range in the overhead buffer is sent to the overhead traveling crane control system, and the overhead traveling crane control system judges whether an obstacle exists in the overhead buffer according to the detection data of each horizontal range in the overhead buffer.

In one embodiment:

the driving device is a screw rod mechanism;

the first sensing unit is arranged on a sliding block of the lead screw mechanism;

the control unit drives a motor of the screw mechanism to drive the sliding block to drive the first sensing unit to move in the vertical range.

In one embodiment, the method further comprises the following steps:

the second sensing unit is connected with the control unit and used for outputting a first sensing signal when the first sensing unit moves to the upper limit of the vertical range;

the third sensing unit is connected with the control unit and used for outputting a second sensing signal when the first sensing unit moves to the lower limit of the vertical range;

the control unit is further used for controlling the first sensing unit to start scanning from the lower limit position of the vertical range according to the first sensing signal and the second sensing signal, and ending the scanning when the first sensing unit moves to the upper limit position of the vertical range.

In one embodiment: the second sensing unit and the third sensing unit are laser sensors respectively.

In one embodiment: the vertical range at least includes a range from a lower edge of an obstacle on the overhead bumper to an upper edge of the overhead traveling crane transfer unit.

In one embodiment: the horizontal range includes at least a range of areas where an obstacle on the overhead bumper is located.

A double-entry detection method for an overhead buffer comprises the following steps:

controlling the crown block to move to a corresponding overhead buffer position;

triggering a first sensing unit, controlling a driving device to move the first sensing unit in a vertical range, so that the first sensing unit scans and generates detection data of each horizontal range in the overhead buffer in the moving process, wherein the driving device is arranged on the overhead travelling crane, and the first sensing unit is connected with the driving device;

and judging whether an obstacle exists in the overhead buffer or not according to the detection data of each horizontal range in the overhead buffer.

In one embodiment, before the crown block moves to the corresponding overhead buffer position, the method further comprises:

setting a detection range of a horizontal range of the first sensing unit and a vertical range in which the first sensing unit moves;

the horizontal range includes at least a range of areas where an obstacle on the overhead bumper is located;

the vertical range at least includes a range of a region from a lower edge of the obstacle on the overhead bumper to an upper edge of the overhead traveling crane transfer unit.

In one embodiment, after the first sensing unit is triggered, the first sensing unit starts scanning from a lower edge position of an obstacle on the overhead bumper, and ends scanning when moving to an upper edge position of the overhead traveling carriage under the control of the driving device.

In one embodiment, determining that an obstacle is present in the overhead buffer further comprises:

and judging the type of the obstacle according to the detection data of each horizontal range in the overhead buffer, and carrying out corresponding alarm reminding according to different types of the obstacle.

According to the overhead buffer double-moving-in detection system and method, the first sensing unit capable of scanning to generate detection data in a horizontal range is used, and the driving device is combined to drive the first sensing unit to move in a vertical range, so that the first sensing unit scans to generate detection data in each horizontal range in the overhead buffer in the moving process, detection is performed according to the two dimensions of the horizontal direction and the vertical direction, a detection result of a three-dimensional space range is obtained, and whether an obstacle exists or not is accurately judged.

Drawings

Fig. 1 is a front view of a conventional overhead buffer double entry detection system;

FIG. 2 is a schematic diagram of the system of FIG. 1 illustrating the detection process when a conventional front load lock is present in the overhead buffer;

fig. 3 is a schematic diagram of the detection process in the system of fig. 1 when foreign objects are present in the overhead buffer;

FIG. 4 is a block diagram illustrating the detection process in the system of FIG. 1 when a transparent front-mounted foup is present in the overhead buffer;

fig. 5 is a schematic diagram of the operation of the first sensing unit in the double input detection system of the overhead buffer of the present invention;

FIG. 6 is a top view of the overhead buffer dual input detection system of the present invention;

FIG. 7 is a schematic diagram of the detection process of the double-input detection system of the overhead buffer according to the present invention;

FIG. 8 is a schematic diagram of the driving device of the dual input detection system of the overhead buffer of the present invention;

FIG. 9 is a flow chart of a dual carry-in detection method of the overhead buffer of the present invention;

description of reference numerals: 1. a crown block; 11. a running part; 12. a transfer unit; 2. a front wafer transport box; 2a. an object; a FOSE type wafer pod; 3. a reflective plate; 4. an overhead buffer; 5. a first sensing unit; 51. a detectable region; 511. a horizontal range; 52. a vertical range; 6. a lead screw; 7. a slider; 8. a motor; 9. a blocking sheet; 91. a second sensing unit; 92. and a third sensing unit.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "vertical", "horizontal", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1 and 2, in the prior art, a crown block 1 is generally provided with a photoelectric sensor, when the crown block 1 needs to place a front wafer cassette 2 on an overhead buffer 4, the crown block 1 travels on a rail to move to a designated position of the overhead buffer 4 by a traveling part 11, and then firstly confirms whether the front wafer cassette 2 is on the overhead buffer 4 by a photoelectric sensor (sensor, which is generally a single-beam photoelectric sensor), specifically, the photoelectric sensor sends a light beam to a double-in detection reflection plate 3 below the overhead buffer 4, and judges whether an object exists on the overhead buffer 1 by whether the light beam is reflected by the reflection plate 3, wherein the double-in refers to continuously storing a new object on the existing object buffer 4.

As shown in fig. 3 and 4, in some cases, when a small object 2a is present on the overhead bumper 4 and cannot block the light beam emitted by the photosensor, detection leakage is easily caused, that is, the detection range is small; in other cases, when the front-mounted foup on the top buffer 4 is the FOSE-type foup 2b, since the FOSE-type foup 2b itself is transparent, the light beam emitted by the photosensor can penetrate through and reflect the reflected light by the reflective plate 4, so that the feedback obtains a false detection result, which also causes false detection.

Fig. 6 and 7 show an overhead buffer double entry detection system according to an embodiment of the present invention, including: the overhead traveling crane comprises an overhead traveling crane 1, a first sensing unit 5, a driving device, a control unit (not shown) and an overhead traveling crane control system (not shown), wherein the first sensing unit 5 is used for scanning and generating detection data of a horizontal range 511, as shown in fig. 5, the first sensing unit 5 is a sensor capable of realizing horizontal scanning, and the sensor is provided with a detectable horizontal detection area 51, which is generally a planar fan-shaped area, and in the detectable area, the horizontal range 511 required to be detected actually can be set according to the range required to be monitored actually (the shape setting can be modified by parameters), and as an example, the first sensing unit 5 can be an obstacle scanning sensor; the driving device is arranged on the overhead travelling crane 1, is connected with the first sensing unit 5 and is used for moving the first sensing unit 5 within a vertical range 52; a control unit connected to the driving device and the first sensing unit 5, respectively; the overhead crane control system is respectively connected with the overhead crane 1 and the control unit and used for sending a detection instruction and a driving instruction to the control unit when the overhead crane 1 moves to the position of the corresponding overhead buffer 4, the control unit controls the driving device to move within a vertical range 52 according to the driving instruction, controls the first sensing unit 5 to scan and generate detection data of each horizontal range in the overhead buffer 4 in the moving process according to the detection instruction, sends the detection data of each horizontal range in the overhead buffer 4 to the overhead crane control system, and the overhead crane control system judges whether an obstacle exists in the overhead buffer 4 according to the detection data of each horizontal range in the overhead buffer 4.

The top buffer double-carrying-in detection system provided by the invention has the advantages that the first sensing unit capable of generating detection data in a horizontal range in a scanning manner is used, and the first sensing unit is driven by combining the driving device to move in a vertical range, so that the first sensing unit generates the detection data in each horizontal range in the top buffer in a scanning manner in the moving process, the detection result in a three-dimensional space range is obtained according to the detection in two dimensions of the horizontal direction and the vertical direction, and the existence of obstacles is accurately judged.

In one embodiment, as shown in fig. 7 and 8, the driving device adopts a lead screw mechanism, and the lead screw mechanism generally comprises a lead screw 6, a slide block 7 arranged on the lead screw 6, and a motor 8 connected with the lead screw 6; the first sensing unit 5 is arranged on the slider 7 of the screw mechanism, and specifically, the first sensing unit 5 may be fixedly arranged on the slider 7 of the screw mechanism through, but not limited to, a connecting plate (not shown); the control unit drives the motor 8 of the lead screw mechanism to drive the first sensing unit 5 to move in the vertical range through the sliding block 7, specifically, when the motor 8 rotates forwards under the drive of the control unit, the lead screw 6 rotates forwards to drive the sliding block 7 to move upwards and the first sensing unit 5 to move upwards, and when the motor 8 rotates backwards under the drive of the control unit, the lead screw 6 rotates backwards to drive the sliding block 7 to move downwards and the first sensing unit 5 to move downwards.

In one embodiment, the definition of the vertical range 52 may be accomplished by a pair of sensing units, as an example, a second sensing unit 91 is provided on the driving device, the second sensing unit 91 is connected with the control unit for outputting a first sensing signal when the first sensing unit 5 moves to the upper limit of the vertical range 52; a third sensing unit 92 is arranged on the driving device, and the third sensing unit 92 is connected with the control unit and used for outputting a second sensing signal when the first sensing unit 5 moves to the lower limit of the vertical range 52; the control unit is configured to control the first sensing unit 5 to move only within a vertical range defined by the second sensing unit 91 and the third sensing unit 92 according to the first sensing signal and the second sensing signal, and the moving direction may be from bottom to top or from bottom to top, which is not limited herein as long as the detection data of the corresponding horizontal range 511 in each vertical range can be detected during the moving process.

As an example, the second sensing unit 91 and the third sensing unit 92 may both adopt laser sensors, in this example, a U-shaped sensor may be adopted, accordingly, only the blocking piece 9 that can pass through the U-shaped sensor during the movement process needs to be arranged at a corresponding position of the first sensing unit 5 or the slider 7, when the blocking piece 9 on the first sensing unit 5 or the slider 7 reaches the U-shaped sensor of the second sensing unit 91 during the movement process, the second sensing unit 91 sends a first sensing signal to the control unit, the control unit judges that the first sensing unit 5 reaches the upper movement limit of the vertical range 52 according to the received first sensing signal, and similarly, when the control unit receives the second sensing signal, the control unit judges that the first sensing unit 5 reaches the lower movement limit of the vertical range 52.

As an example, the control unit may control the first sensing unit 5 to start scanning from a lower limit position of the vertical range (the position where the third sensing unit 92 is located) according to the first sensing signal and the second sensing signal, end scanning when moving to an upper limit position of the vertical range (the position where the second sensing unit 91 is located), and then return to the lower limit position to wait for the next detection. As a variation, the scanning may be started from the upper limit position of the vertical range (the position of the second sensing unit 91), the scanning is ended when the mobile crane moves to the lower limit position of the vertical range (the position of the third sensing unit 92), and then the mobile crane returns to the upper limit position to wait for the next detection, however, the control unit may be designed to be a non-return cyclic scanning detection mode, that is, if the previous mobile crane scans from top to bottom, the next mobile crane scans from bottom to top are used, and this alternative scanning mode may effectively shorten the moving period of the first sensing unit 5, and it should be noted that, when the scanning mode is used, the scanning is not performed during the period from the end of the previous scanning to the time when the overhead crane moves to the next overhead buffer, and the next scanning is started only when the overhead crane moves to the next overhead buffer, therefore, the condition that the detection result is inaccurate due to the fact that the overhead travelling crane is always scanned in the travelling process is avoided.

As an example, the vertical range 52 at least includes the range from the lower edge 41 of the obstacle on the overhead buffer 4 to the area where the upper edge 121 of the transfer unit 12 of the overhead traveling crane 1 is located, the bottom of the front wafer cassette 2 or the FOSE-type wafer cassette 2b is generally on the same horizontal plane as the upper surface of the base of the overhead buffer 4, and when the overhead traveling crane 1 places the wafer cassette on the base of the overhead buffer, the transfer unit 12 with the wafer cassette first extends out and then places the wafer cassette on the base of the overhead buffer 4, so as to provide the transfer unit 12 and the wafer cassette with a sufficient operation interval, the vertical range is set to the range from the lower edge of the obstacle on the overhead buffer 4 (or the upper surface of the base of the overhead buffer 4) to the area where the upper edge of the transfer unit 12 of the overhead traveling crane 1 is located, that is the area from the bottom of the wafer cassette to the upper edge of the transfer unit 12, and it should be noted that, when no obstacle is present on the overhead bumper, the position of the lower edge 41 of the obstacle indicated in the vertical range 52 to be detected is actually the position of the upper surface of the base of the overhead bumper 4, and therefore, it can be understood that the lower edge 41 of the obstacle in the vertical range 52 is actually a virtual position representation only for representing the lowest point of the obstacle which may exist in the space, and does not necessarily refer to the lower edge of a specific obstacle; the horizontal range 511 at least includes a range of a region where an obstacle on the overhead bumper 4 is located, for example, a horizontal range where the leftmost side to the rightmost side of the obstacle is located, and the information of the scanned horizontal range 511 may be set by corresponding software, specifically, by setting the position coordinates (X/Y) to implement the distinction. The detection mode of a three-dimensional scanning space defined by the vertical range 52 and the horizontal range 511 has higher detection precision than the detection of a traditional photoelectric sensor.

As shown in fig. 9, the present invention further provides a method for detecting a dual access of an overhead buffer, which can be implemented by, but not limited to, the above system for detecting a dual access of an overhead buffer, the method for detecting a dual access of an overhead buffer comprising:

s1, controlling the crown block 1 to move to the corresponding position of the overhead buffer 4;

s2, triggering the three-dimensional space obstacle detection, specifically, triggering the first sensing unit 5, and controlling the driving device to move the first sensing unit 5 in the vertical range, so that the first sensing unit 5 scans and generates the detection data of each horizontal range in the overhead buffer 4 in the moving process, the driving device is arranged on the overhead traveling crane 1, and the first sensing unit 5 is connected to the driving device;

s3, determining whether or not there is an obstacle in the overhead buffer 4 based on the detection data of each horizontal range in the overhead buffer 4.

As an example, when there is an obstacle, it jumps to step S4; when there is no obstacle, go to step S6;

s4, judging the type of the obstacle according to the detection data of each horizontal range in the overhead buffer, specifically, synthesizing the shape and size of the obstacle detected by each horizontal plane by the overhead crane control system in the vertical direction, so as to judge the type of the obstacle, such as a wafer transfer box or other objects influencing the overhead crane goods placing, and carrying out corresponding alarm reminding according to different types of the obstacle;

s5, waiting for the operator to check and remove the alarm on site, and then returning to the step S1;

s6, putting goods on the overhead travelling crane 1;

s7, the crane 1 leaves to get the next wafer transfer box and returns to step S1 to execute the next shipment.

In one example, the following steps are also included before controlling the crown block 1 to move to the corresponding overhead buffer 4 position:

s0, setting a detection area and a trigger condition, wherein the detection area includes a horizontal range that can be scanned by the first sensing unit 5 and a vertical range that the first sensing unit 5 needs to move, the detection range of the horizontal range 511 at least includes a horizontal range in which the obstacle on the overhead buffer 4 is located, the vertical range 52 at least includes a range from a lower edge of the obstacle on the overhead buffer 4 to an upper edge of the transfer part 12 of the overhead traveling crane 1, and the trigger condition includes that the overhead traveling crane 1 moves to the corresponding overhead buffer 4.

In one embodiment, in step S2, after triggering the first sensing unit 5, the first sensing unit 5 starts scanning from the lower edge position of the obstacle on the overhead bumper 4, and ends scanning when moving to the upper edge position of the transfer unit 12 of the overhead traveling crane 1 under the control of the driving device.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.