阅读说明：本技术 空调系统及控制方法 (air conditioning system and control method ) 是由 李建军 周晓晓 张萌 秦雨峰 钟建法 于 2019-08-16 设计创作，主要内容包括：本发明涉及一种制冷技术,特别是涉及空调系统及控制方法。一种空调系统包括蒸发冷凝器及气液分离器,所述蒸发冷凝器的出口与所述气液分离器连接,所述空调系统还包括补液管路,所述补液管路设于蒸发冷凝器入口与气液分离器之间,气液分离器通过补液管路向蒸发冷凝器补充介质。一种控制方法,所述控制方法利用一种空调系统。本发明的优点在于：通过设置补液管路,满足所述气液分离器气液分离、存储多余介质及补充介质的功能,减省储液器的安装,从而节省安装空间,降低成本。(The invention relates to a refrigeration technology, in particular to an air conditioning system and a control method. The utility model provides an air conditioning system includes evaporative condenser and vapour and liquid separator, evaporative condenser's export with vapour and liquid separator connects, air conditioning system still includes the fluid infusion pipeline, the fluid infusion pipeline is located between evaporative condenser entry and the vapour and liquid separator, and vapour and liquid separator supplements the medium to evaporative condenser through the fluid infusion pipeline. A control method utilizes an air conditioning system. The invention has the advantages that: through setting up the fluid infusion pipeline, satisfy the gas-liquid separator gas-liquid separation, save unnecessary medium and the function of supplementary medium, the installation of saving the reservoir to save installation space, reduce cost.)

1. The utility model provides an air conditioning system, includes evaporative condenser and vapour and liquid separator, evaporative condenser's export with vapour and liquid separator connects its characterized in that:

The air conditioning system further comprises a liquid supplementing pipeline, the liquid supplementing pipeline is arranged between an inlet of the evaporative condenser and the gas-liquid separator, and the gas-liquid separator supplements media to the evaporative condenser through the liquid supplementing pipeline.

2. the air conditioning system of claim 1, wherein: and a first cut-off part is arranged on the liquid supplementing pipeline, one end of the first cut-off part is connected with the gas-liquid separator, and the other end of the first cut-off part is connected with the evaporative condenser.

3. the air conditioning system of claim 1, wherein: one end of the gas-liquid separator is provided with a heating element, and the heating element is used for heating a medium.

4. The air conditioning system of claim 1, wherein: the air conditioning system further comprises a condenser and a compressor, wherein the inlet of the compressor is connected with the gas-liquid separator, and the outlet of the compressor is connected with the condenser.

5. The air conditioning system of claim 4, wherein: the air conditioning system further comprises a throttling element, and the throttling element is arranged between the evaporative condenser and the condenser.

6. The air conditioning system of claim 5, wherein: the air conditioning system further comprises a second cut-off piece, and two ends of the second cut-off piece are respectively connected with the throttling element.

7. The air conditioning system of claim 4, wherein: the air conditioning system further comprises a third cut-off piece, one end of the third cut-off piece is connected with the evaporator condenser and the gas-liquid separator respectively, and the other end of the third cut-off piece is connected with the condenser.

8. the air conditioning system of claim 4, wherein: the air conditioning system further includes a first sensor disposed at an outlet of the condenser, the first sensor detecting a degree of supercooling at the outlet of the condenser.

9. A control method characterized by: the control method is used for an air conditioning system, the air conditioning system comprises a gas-liquid separator, a condenser, an evaporative condenser and a liquid supplementing pipeline, the liquid supplementing pipeline is provided with a first cut-off part, the outlet of the condenser is provided with a first sensor, and the method comprises the following steps:

Acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set first threshold value and a set second threshold value;

When the supercooling degree is larger than a first threshold value, closing the first cutoff part, and stopping supplementing the medium to the evaporative condenser by the gas-liquid separator;

and when the supercooling degree of the outlet of the condenser is smaller than a second threshold value and smaller than a first threshold value, the first cutoff part is opened, and the medium in the gas-liquid separator flows to the evaporative condenser through the liquid supplementing pipeline.

10. The control method according to claim 9, characterized in that: the air conditioning system further comprises a throttling element, the evaporative condenser, the gas-liquid separator, the condenser and the throttling element form a first loop, and the control method further comprises the following steps:

While the first loop is running;

acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set third threshold value and a set fourth threshold value;

When the supercooling degree is greater than a third threshold value and is greater than the first threshold value, the second threshold value and the fourth threshold value, the opening degree of the throttling element is increased, and the medium is stored in the gas-liquid separator;

And when the supercooling degree is smaller than or equal to a fourth threshold value, smaller than the third threshold value, the first threshold value and larger than the second threshold value, reducing the opening degree of the throttling element to the opening degree of the throttling element corresponding to the third threshold value.

Technical Field

The invention relates to a refrigeration technology, in particular to an air conditioning system and a control method.

Background

In an air conditioning system, the gas-liquid separator plays roles in gas-liquid separation, filtration, noise reduction and medium buffering, the liquid storage device is used for storing redundant media, particularly a composite air conditioner, and the liquid storage device can balance different requirements of two loops on the media.

in the prior art, often be equipped with reservoir and vapour and liquid separator simultaneously, satisfy stock solution, fluid infusion and gas-liquid separation's requirement, but because air conditioning unit installation space is limited, set up two accessories simultaneously and cause the installation space extravagant, and increased the cost.

disclosure of Invention

in order to solve the above problems, the present invention provides an air conditioning system and a control method.

In order to achieve the purpose, the invention adopts the following technical scheme:

The utility model provides an air conditioning system, includes evaporative condenser and vapour and liquid separator, evaporative condenser's export with vapour and liquid separator connects, air conditioning system still includes the fluid infusion pipeline, the fluid infusion pipeline is located evaporative condenser entry with between the vapour and liquid separator, vapour and liquid separator passes through the fluid infusion pipeline is right evaporative condenser supplements the medium.

It can be understood that when the medium in the air conditioning system pipeline is too little, and the supercooling degree is too small, the medium is supplemented through the liquid supplementing pipeline, and when the medium in the air conditioning system pipeline is too much, the medium which is not evaporated in the evaporative condenser is stored in the gas-liquid separator.

In one embodiment, a first cut-off part is arranged on the liquid supplementing pipeline, one end of the first cut-off part is connected with the gas-liquid separator, and the other end of the first cut-off part is connected with the evaporative condenser.

It can be understood that the first cut-off member is used for realizing the communication or the cut-off of the fluid supplementing pipeline.

in one embodiment, one end of the gas-liquid separator is provided with a heating element for heating the medium.

It can be understood that when the degree of subcooling is too small, the heating element heats the medium in the gas-liquid separator to evaporate the medium and increase the pressure, so that the medium can smoothly enter the evaporative condenser through the liquid supplementing pipeline.

In one embodiment, the air conditioning system further comprises a condenser and a compressor, wherein an inlet of the compressor is connected with the gas-liquid separator, and an outlet of the compressor is connected with the condenser.

In one embodiment, the air conditioning system further comprises a throttling element disposed between the evaporative condenser and the condenser.

it will be appreciated that the throttling element is open when the outdoor ambient temperature is greater than the temperature value T and closed when the outdoor ambient temperature is less than the temperature value T.

In one embodiment, the air conditioning system further comprises a second cut-off piece, and two ends of the second cut-off piece are respectively connected with the throttling element.

It is understood that the second cutoff member is opened when the outdoor ambient temperature is less than the temperature value T, and is closed when the outdoor ambient temperature is greater than the temperature value T.

In one embodiment, the air conditioning system further includes a third shut-off member, one end of the third shut-off member is connected to the evaporator condenser and the gas-liquid separator, respectively, and the other end of the third shut-off member is connected to an outlet of the compressor.

It is understood that the third shut-off member is open when the outdoor ambient temperature is less than the temperature value T, and is closed when the outdoor ambient temperature is greater than the temperature value T.

in one embodiment, the air conditioning system further comprises a first sensor disposed at an outlet of the condenser, the first sensor detecting a degree of supercooling at the outlet of the condenser.

It is understood that the first sensor includes a temperature sensor and a pressure sensor, and the supercooling degree at the outlet of the condenser is detected and calculated by the first sensor.

The invention also provides the following technical scheme:

A control method utilizes an air conditioning system, the air conditioning system comprises a gas-liquid separator, a condenser, an evaporative condenser and a liquid supplementing pipeline, a first cut-off part is arranged on the liquid supplementing pipeline, a first sensor is arranged at an outlet of the condenser, and the method comprises the following steps:

acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set first threshold value and a set second threshold value;

When the supercooling degree is larger than a first threshold value, closing the first cutoff part, and stopping supplementing the medium to the evaporative condenser by the gas-liquid separator;

And when the supercooling degree of the outlet of the condenser is smaller than a second threshold value and smaller than a first threshold value, the first cutoff part is opened, and the medium in the gas-liquid separator flows to the evaporative condenser through the liquid supplementing pipeline.

In one embodiment, the air conditioning system further comprises a throttling element, the evaporative condenser, the gas-liquid separator, the condenser and the throttling element form a first loop, and the control method further comprises the following steps:

when the first loop is operational:

acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set third threshold value and a set fourth threshold value;

when the supercooling degree is greater than a third threshold value and is greater than the first threshold value, the second threshold value and the fourth threshold value, the opening degree of the throttling element is increased, and the medium is stored in the gas-liquid separator;

And when the supercooling degree is smaller than or equal to a fourth threshold value, smaller than the third threshold value, the first threshold value and larger than the second threshold value, reducing the opening degree of the throttling element to the opening degree of the throttling element corresponding to the third threshold value.

Compared with the prior art, the air conditioning system and the control method provided by the invention are provided with the liquid supplementing pipeline, and the liquid supplementing pipeline is connected with the gas-liquid separator and the evaporative condenser, so that the gas-liquid separator can meet the functions of gas-liquid separation and medium storage and supplement, the installation of a liquid storage device is reduced, the installation space is saved, and the cost is reduced.

Drawings

fig. 1 is a schematic structural diagram of an air conditioning system according to the present invention.

the symbols in the drawings represent the following meanings:

100. An air conditioning system; 100a, an evaporative condenser; 101a, a first interface; 102a, a second interface; 103a, a third interface; 104a, a fourth interface; 100b, a gas-liquid separator; 101b, a connecting port; 102b, a heating element; 100c, a liquid supplementing pipeline; 101c, a first cut-off; 100d, a throttling element; 100e, a second section; 100f, a third section; 100g, a compressor; 100h, a condenser; 100i, heat pipe evaporator; 10. a first circuit; 20. a second loop; 30. a third loop.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "mounted on" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.

unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.

The invention provides an air conditioning system 100, which is applied to a backplane air conditioner of a data machine room and is used for solving the problem of local hot spots, and of course, in other embodiments, the air conditioning system 100 can also be applied to other occasions.

specifically, the air conditioning system 100 includes an evaporative condenser 100a and a gas-liquid separator 100b, the evaporative condenser 100a is provided with four interfaces, wherein a first interface 101a is communicated with a second interface 102a, a third interface 103a is communicated with a fourth interface 104a, and the first interface 101a of the evaporative condenser 100a is connected with an inlet of the gas-liquid separator 100 b. The outlet of the evaporation side of the evaporative condenser 100a in the present invention corresponds to the first port 101a in the present embodiment, and the inlet of the evaporation side of the evaporative condenser 100a corresponds to the second port 102a in the present embodiment. When the medium in the air conditioning system 100 is excessive, the medium that is not evaporated on the evaporation side of the evaporative condenser 100a is stored in the gas-liquid separator 100 b.

Further, the air conditioning system 100 further includes a liquid supplementing pipeline 100c, one end of the gas-liquid separator 100b near the bottom is provided with a connecting port 101b, one end of the liquid supplementing pipeline 100c is connected with the connecting port 101b at the bottom of the gas-liquid separator 100b, the other end is connected with the second port 102a of the evaporative condenser 100a, and when the medium in the air conditioning system 100 is too small, the medium is supplemented through the liquid supplementing pipeline 100 c.

The design volume of the gas-liquid separator 100b is the maximum medium charge minus the minimum medium charge during the operation of the air conditioning system 100, and the preset gas-liquid separation space, and it is worth explaining that different gas-liquid separation spaces can be preset according to different designs.

The air conditioning system 100 further includes a compressor 100g and a condenser 100h, an inlet of the compressor 100g is connected to an outlet of the gas-liquid separator 100b, and an outlet of the compressor 100g is connected to one end of the condenser 100 h.

Preferably, the liquid replenishing pipe 100c is provided with a first cut-off member 101c, one end of the first cut-off member 101c is connected to the connection port 101b of the gas-liquid separator 100b near the bottom, and the other end is connected to the second connection port 102a of the evaporative condenser 100 a. When the medium in the air conditioning system 100 is too small, the first shut-off member 101c is opened, and the gas-liquid separator 100b replenishes the medium to the evaporative condenser 100a through the liquid replenishing pipe 100c, thereby replenishing the medium to the air conditioning system 100, and when the medium in the air conditioning system 100 is too small, the first shut-off member 101c is closed. In the present embodiment, the first shut-off member 101c is a solenoid valve, but in other embodiments, other valve members having the same function may be used.

Furthermore, a heating element 102b is disposed at an end of the gas-liquid separator 100b near the connection port 101b, and when the medium in the air conditioning system 100 is too small, the heating element 102b is turned on to heat the medium in the gas-liquid separator 100b to increase the pressure of the medium, so that the medium can flow into the fluid replenishing pipeline 100c more smoothly to replenish the medium. In the present embodiment, the heating element 102b is an electric heating wire, but in other embodiments, other heating elements having the same function may be used.

The air conditioning system 100 further includes a throttling element 100d, and the throttling element 100d is disposed between the evaporative condenser 100a and the condenser 100h, i.e., one end of the throttling element 100d is connected to the second port 102a of the evaporative condenser 100a, and the other end is connected to the condenser 100 h. When the outdoor environment temperature is lower than the temperature value T, the throttling element 100d is closed, and when the outdoor environment temperature is higher than the temperature value T, the throttling element 100d is opened.

Preferably, in the present embodiment, the throttling element 100d is an electronic expansion valve, but in other embodiments, other valve elements having the same function may be used. In the present embodiment, the temperature value T is 10 ℃, and of course, in other embodiments, the temperature value T may be other values as needed.

further, the air conditioning system 100 further includes a second shut-off member 100e, and both ends of the second shut-off member 100e are respectively connected to the throttling element 100d, that is, the second shut-off member 100e is disposed in parallel with the throttling element 100 d. When the outdoor ambient temperature is less than the temperature value T, the second cut-off member 100e is opened, and when the outdoor ambient temperature is greater than the temperature value T, the second cut-off member 100e is closed. In the present embodiment, the second shut-off member 100e is a solenoid valve, but in other embodiments, other valve members having the same function may be used.

Referring to fig. 1, the air conditioning system 100 further includes a third cut-off member 100f, an inlet end of the third cut-off member 100f is connected to the first port 101a of the evaporative condenser 100a and an inlet of the gas-liquid separator 100b, and an outlet end of the third cut-off member 100f is connected to the outlet of the compressor 100g and the condenser 100 h. In the present embodiment, the third shut-off member 100f is a check valve, but in other embodiments, a valve member having a shut-off function such as another solenoid valve may be used.

Preferably, the air conditioning system 100 further includes a first sensor (not shown) including a temperature sensor (not shown) and a pressure sensor (not shown), the first sensor being disposed at an outlet of the condenser 100h, and the supercooling degree is calculated by a temperature signal detected by the temperature sensor and a pressure signal detected by the pressure sensor. And comparing the detected supercooling degree with the set supercooling degree, wherein the detected supercooling degree indicates that the medium in the air conditioning system 100 is too much when the detected supercooling degree is too large, and the detected supercooling degree indicates that the medium in the air conditioning system 100 is too little when the detected supercooling degree is too small.

Further, the air conditioning system 100 further includes a heat pipe evaporator 100i, and both ends of the heat pipe evaporator 100i are respectively connected to the third interface 103a and the fourth interface 104a of the evaporative condenser 100 a.

The first and second ports 101a and 102a of the evaporative condenser 100a, the gas-liquid separator 100b, the compressor 100g, the condenser 100h, and the throttling element 100d form a first circuit 10, the third and fourth ports 103a and 104a of the heat pipe evaporator 100i and the evaporative condenser 100a form a second circuit 20, and the first and second ports 101a and 102a of the evaporative condenser 100a, the gas-liquid separator 100b, the third shut-off member 100f, the condenser 100h, and the second shut-off member 100e form a third circuit 30. The medium in the second circuit 20 may be the same as the medium in the first and third circuits 10 and 30, and may be different from the medium.

in the working process, when the outdoor ambient temperature is less than the temperature value T, the second cut-off member 100e and the third cut-off member 100f are opened, in this embodiment, the cut-off member 100f is turned on in one direction, the compressor 100g and the throttling element 100d are turned off, and the second circuit 20 and the third circuit 30 are operated. The medium absorbs heat in the evaporative condenser 100a and evaporates to exchange heat with the medium in the second circuit 10, a part of the medium flows through the open third shut-off member 100f, releases heat in the condenser 100h, and then flows through the open second shut-off member 100e, and the surplus medium is stored in the gas-liquid separator 100 b.

When the outdoor ambient temperature is greater than the temperature value T, the second circuit 20 and the first circuit 10 operate. The second block 100e and the third block 100f are closed and the compressor 100g and the throttling element 100d are opened, in this embodiment, the outlet end of the block 100f is connected to the outlet of the compressor 100g, and since the exhaust port of the compressor 100g is at a high pressure, the block 100f is not conducted in the direction from the evaporative condenser 100a to the condenser 100 h. The medium absorbs heat and evaporates in the evaporative condenser 100a, exchanges heat with the medium in the second loop 20, enters the gas-liquid separator 100b for gas-liquid separation, the liquid medium enters the gas-liquid separator 100b, the gaseous medium enters the compressor 100g for compression, the high-temperature and high-pressure gaseous medium enters the condenser 100h for heat release and condensation, is throttled and depressurized by the throttling element 100d, and finally returns to the evaporative condenser 100 a. When the medium in the first circuit 10 is insufficient, the heating element 100d and the first shut-off member 101c are turned on, and the pressure increases after the medium is heated, so that the medium can smoothly flow into the first connection port 101a of the evaporative condenser 100a to supplement the medium.

The present invention also provides a control method using an air conditioning system 100, including a second block 100e, a third block 100f, a throttling element 100d, a gas-liquid separator 100b, an evaporative condenser 100a, a condenser 100h, a first sensor and a fluid infusion line 100c, wherein a heating element 102b is provided in the gas-liquid separator 100b, the first sensor is used for detecting a supercooling degree of an outlet of the condenser 100h, and the fluid infusion line 100c is provided with a first block 101c, the control method including:

Acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set first threshold value and a set second threshold value;

When the supercooling degree of the outlet of the condenser 100h is detected to be greater than the first threshold value and greater than the second threshold value, the first cutoff member 101c and the heating element 102b are closed, and the gas-liquid separator 100b does not supplement the medium to the evaporative condenser 100a any more;

When the supercooling degree of the outlet of the condenser 100h is smaller than the second threshold value and smaller than the first threshold value, the first cutoff member 101c and the heating element 102b are turned on, the heated medium is supplemented to the evaporative condenser 100a through the liquid supplementing pipe 100c until the supercooling degree of the outlet of the condenser 100h reaches the first threshold value, and the first cutoff member 101c and the heating element 102b are turned off. In this embodiment, the first threshold is greater than the second threshold.

The control method further comprises the following steps:

when the outdoor environment temperature is greater than the temperature value T, the first loop 10 operates;

acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a set third threshold value and a set fourth threshold value;

When the supercooling degree of the outlet of the condenser 100h is detected to be larger than the third threshold value and larger than the first threshold value, the second threshold value and the fourth threshold value, the opening degree of the throttling element 100d is increased, and the medium is stored in the gas-liquid separator 100 b;

when the supercooling degree of the outlet of the condenser 100h is detected to be smaller than or equal to the fourth threshold value, smaller than the third threshold value, the first threshold value and larger than the second threshold value, the opening degree of the throttling element 100d is reduced to the opening degree of the throttling element 100d corresponding to the third threshold value, namely, the opening degree is reduced to the opening degree before the throttling element 100d is increased, and the throttling element 100d is not adjusted along with the supercooling degree any more.

During operation, the control method of the air conditioning system 100 is as follows:

When the outdoor environment temperature is higher than the temperature value T, the second cut-off piece 100e and the third cut-off piece 100f are closed, the throttling element 100d is opened, and the first loop 10 and the second loop 20 operate;

Acquiring the supercooling degree detected by the first sensor, and comparing the supercooling degree with a first threshold value, a second threshold value, a third threshold value and a fourth threshold value which are set;

When the fact that the supercooling degree of the outlet of the condenser 100h is larger than the third threshold value, the first threshold value, the second threshold value and the fourth threshold value is detected, the opening degree of the throttling element 100d is increased, the medium which is not evaporated in the evaporative condenser 100a is stored in the gas-liquid separator 100b, and the supercooling degree of the outlet of the condenser 100h is gradually reduced along with the reduction of the amount of the medium in the pipeline;

When the supercooling degree of the outlet of the condenser 100h is detected to be smaller than or equal to the fourth threshold value, smaller than the third threshold value, the first threshold value and larger than the second threshold value, the opening degree of the throttling element 100d is reduced to the opening degree of the throttling element 100d corresponding to the third threshold value, namely, the opening degree of the throttling element 100d is reduced to the opening degree before the throttling element 100d is increased, and the throttling element 100d is not adjusted along with the supercooling degree any more;

when the supercooling degree of the outlet of the condenser 100h is smaller than the second threshold value and smaller than the third threshold value, the first threshold value and the fourth threshold value, the throttling element 100d is not adjusted along with the supercooling degree, the first cutoff part 101c and the heating element 102b are opened, and the heated medium replenishes the medium to the evaporative condenser 100a through the liquid replenishing pipeline 100 c;

when the supercooling degree of the outlet of the condenser 100h is detected to be greater than the first threshold value, greater than the second threshold value and the fourth threshold value and less than the third threshold value, the throttling element 100d is not adjusted along with the supercooling degree, and the gas-liquid separator 100b does not supplement media to the evaporative condenser 100a any more;

When the outdoor ambient temperature is lower than the temperature value T, the throttling element 100d is closed, the second cut-off piece 100e and the third cut-off piece 100f are opened, the third circuit 30 and the second circuit 20 operate, and the control methods of the first cut-off piece 101c and the heating element 102b are as described above and will not be described herein again.

In this embodiment, the third threshold is set to 8 ℃, the first threshold is set to 6 ℃, the fourth threshold is set to 5 ℃, and the second threshold is set to 2 ℃, of course, in other embodiments, the first threshold, the second threshold, the third threshold, and the fourth threshold may be set to other values according to actual needs.

for the layout of the second cut-off 100e, the third cut-off 100f, the throttling element 100d, the gas-liquid separator 100b, the evaporative condenser 100a, the condenser 100h, the first sensor, the liquid replenishing pipeline 100c, the heating element 102b and the first cut-off 101c, please read the above description, and will not be repeated herein.

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.