Vacuum sealing machine

Abstract

The invention provides a vacuum sealing machine. The vacuum sealing machine comprises a main machine body, a cover body arranged on the main machine body, a vacuum pump and a controller. A lower cavity is formed in the main machine body, and a heating assembly is arranged; the cover body is provided with an upper cavity and a pressing strip; the output end of the controller is electrically connected with the control end of the vacuum pump and the heating assembly. The controller achieves the following steps that in response to a sealing request, the heating assembly is controlled to preheat the end of the vacuum bag; when it is judged that preheating is completed, heating is stopped, and a vacuum pump is started to conduct vacuumizing operation on the closed space, so that negative pressure is formed in the closed space; when it is judged that the vacuumizing operation is completed, the heating assembly is controlled to be started to heat the end of the vacuum bag for the second time; the problems that when the vacuum bag is sealed, the sealing effect is affected due to the fact that the pressing strip cannot press the vacuum bag tightly, and films on the two sides of the vacuum bag are not flush are effectively solved, and the sealing effect is improved.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum sealers, in particular to a vacuum sealer. Background Art

[0002] Vacuum sealer is a kind of equipment widely used in food, medicine, chemical industry and other industries. Its main function is to extract the air in the product packaging bag, form a vacuum state and then seal it. The purpose of doing so is to extend the shelf life of the product, prevent oxidation, moisture, mildew and corrosion, etc.

[0003] The single-side sealing process of the existing vacuum sealer is to heat the vacuum bag first and then seal the vacuum bag; and the problem faced by the existing snap-on vacuum sealer in the process of single-side sealing is that when the vacuum sealer is in the snap-on state, the pressure strip arranged on the vacuum sealer cannot completely press the vacuum bag, and during the heating and sealing process, it will cause incomplete sealing in the sealing area, gaps or poor sealing effect. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a vacuum sealing machine that can effectively solve the above problems.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention provides a vacuum sealing machine, characterized in that it comprises: a main body, a cover body arranged on the main body, a vacuum pump and a controller;

[0007] The main body is formed with a lower chamber, and a heating component is arranged near the lower chamber;

[0008] The cover body is formed with an upper chamber, and a pressure strip is arranged near the upper chamber, and the cover body can be operated between an open state and a closed state. In the closed state, the upper chamber and the lower chamber form a closed space, and the pressure strip and the heating component abut against each other. In the open state, the upper chamber is away from the lower chamber.

[0009] The output end of the controller is electrically connected to the control end of the vacuum pump and the heating component;

[0010] The controller is configured to execute a computer program stored therein to implement the following steps:

[0011] In response to a sealing request, controlling the heating assembly to preheat an end of the vacuum bag;

[0012] When it is determined that the preheating is completed, the heating is stopped and the vacuum pump is turned on to evacuate the enclosed space so that a negative pressure is formed in the enclosed space;

[0013] When it is determined that the vacuuming operation is completed, the heating component is controlled to start heating the end of the vacuum bag for the second time.

[0014] As a further improvement, a first vacuum port and a second vacuum port are provided in the lower chamber, the first vacuum port is connected to a first vacuum pump, and the second vacuum port is connected to a second vacuum pump.

[0015] As a further improvement, the main body is provided with a lower sealing ring surrounding the lower chamber, and the main body is provided with a smooth portion on a side of the heating component away from the lower chamber.

[0016] As a further improvement, lock seats are arranged on both sides of the top of the main body, and the cover body is provided with lock buckles at positions corresponding to the lock seats.

[0017] As a further improvement, the heating component includes a support member fixedly arranged on the main body, a high-temperature tape is arranged on the top of the support member, a heating wire is arranged between the high-temperature tape and the support member, heating wire terminals are arranged at both ends of the heating wire, and springs are connected between the ends of the two ends of the heating wire and the heating wire terminals.

[0018] As a further improvement, a copper foil tape is bound between the heating wire and the heating wire terminal.

[0019] As a further improvement, the cover body is provided with an upper sealing ring surrounding the upper chamber, and the cover body is provided with an air inlet in the upper chamber.

[0020] The beneficial effects of the present invention are:

[0021] The single-side sealing structure of the vacuum sealer of the present invention can reduce the spacing caused by film misalignment when the vacuum bag is placed by arranging a smooth portion on the vacuum sealer, thereby improving the flatness of the bag mouth of the vacuum bag. A humidity sensor is connected to the second vacuum pump, and the change of the humidity sensor is fed back to the controller. The controller prolongs the heating time of the heating component to avoid problems such as incomplete sealing or gaps. The gas in the enclosed space is extracted by the second vacuum pump to put the enclosed space in a negative pressure state. The atmospheric pressure makes the pressure strip on the cover body closer to the vacuum bag, and the films on both sides of the vacuum bag are flattened when evacuating air to avoid wrinkles on the vacuum bag that affect the sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 The invention discloses a single-side sealing structure of a vacuum sealing machine and a step schematic diagram of a control method thereof.

[0024] Figure 2 The invention discloses a sectional schematic diagram of the overall structure of a single-side sealing structure of a vacuum sealing machine and a control method thereof.

[0025] Figure 3 The invention discloses a main body structure schematic diagram of a single-side sealing structure of a vacuum sealing machine and a control method thereof.

[0026] Figure 4 The invention discloses a cover structure schematic diagram of a single-side sealing structure of a vacuum sealing machine and a control method thereof.

[0027] Figure 5 The invention discloses a schematic diagram of a heating component structure of a single-side sealing structure of a vacuum sealing machine and a control method thereof.

[0028] Figure 6 The invention discloses a schematic diagram of a single-side sealing structure of a vacuum sealing machine and a control method thereof in use.

[0029] In the figure: 1-main body, 11-lower chamber, 12-lower sealing ring, 13-first air outlet, 14-second air outlet, 15-heating component, 151-high temperature tape, 152-heating wire, 153-support, 154-heating wire terminal, 155-spring, 156-copper foil tape, 16-smooth part, 17-lock seat, 2-cover, 21-upper chamber, 22-upper sealing ring, 23-air inlet, 24-pressure strip, 25-lock buckle DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] Reference Figure 1-5 As shown, a single-side sealing structure of a vacuum sealing machine and a control method thereof, comprising: a main body 1, a cover body 2 arranged on the main body 1, a vacuum pump and a controller;

[0033] The main body 1 is formed with a lower chamber 11, and a heating component 15 is arranged near the lower chamber 11; the cover body 2 is formed with an upper chamber 21, and a pressure strip 24 is arranged near the upper chamber 21, and the cover body 2 can be operated between an open state and a closed state. In the closed state, the upper chamber 21 and the lower chamber 11 form a closed space, and the pressure strip 24 and the heating component 15 abut against each other. In the open state, the upper chamber 21 is away from the lower chamber 11; a controller is arranged in the main body 1, and the output end of the controller is electrically connected to the control end of the vacuum pump and the heating component;

[0034] The controller is configured to execute a computer program stored therein to implement the following steps:

[0035] In response to a sealing request, controlling the heating assembly to preheat the end of the vacuum bag;

[0036] When it is determined that the preheating is completed, the heating is stopped and a vacuum pump is turned on to evacuate the enclosed space so that a negative pressure is formed in the enclosed space;

[0037] When it is determined that the vacuuming operation is completed, the heating component is controlled to start heating the end of the vacuum bag for the second time.

[0038] The single-side sealing structure and control method of the vacuum sealer effectively solve the problems of the pressure strip failing to press the vacuum bag tightly and the incomplete sealing caused by a small amount of moisture at the sealing point, thereby improving the sealing effect. The controller extracts the gas in the vacuum bag by connecting to the first vacuum pump and extracts the gas in the enclosed space by connecting to the second vacuum pump, so that the enclosed space is in a negative pressure state, and uses the atmospheric pressure to move the cover downward again, so that the films on both sides of the vacuum bag can fit more tightly. The controller determines whether liquid-containing items are stored in the vacuum bag by connecting to the humidity sensor. If the humidity sensor changes, the second heating time is extended to improve the sealing effect of the sealing area of ​​the vacuum bag, so that the vacuum bag forms a complete sealing strip in the sealing area to prevent the product from leaking out of the sealed bag.

[0039] Furthermore, a lower chamber 11 is provided in the main body 1, and the lower chamber 11 is used to place the vacuum bag. A first air suction port 13 and a second air suction port 14 are provided in the lower chamber 11. The first air suction port 13 is connected to a first vacuum pump through a pipeline. A multi-stage pressurization structure is provided in the first vacuum pump to improve the air suction efficiency of the vacuum pump. The second air suction port 14 is connected to a second vacuum pump through a pipeline. A lower sealing ring 12 is provided around the main body 1 at the position of the lower chamber 11. After the vacuum bag is placed in the traditional vacuum sealing machine, the bag forms a large angle bend at the edge of the main body 1, which easily causes the films on both sides of the bag to be misaligned and produce a large distance, thereby affecting the sealing effect of the vacuum bag. The main body 1 is provided with a smooth portion 16 on the side of the heating component 15 away from the lower chamber 11. The smooth portion 16 is a slope with an inclination angle of 40° to 60°. The smooth portion 16 can make the vacuum bag fall gently on the table at a small angle, shorten the distance caused by the misalignment of the films on both sides of the bag, and make the films on both sides of the vacuum bag nearly flush. Lock seats 17 are provided on both sides of the top of the main body 1, and the cover body 2 is provided with lock buckles 25 at positions corresponding to the lock seats 13. Through the cooperation of the lock seats 17 and the lock buckles 25, a pre-tightening force is generated between the main body 1 and the cover body 2. The pre-tightening force acts on the end of the vacuum bag, and the vacuum bag is pressed onto the heating component 15 through the pressure strip 24 provided on the cover body 2.

[0040] Furthermore, an upper chamber 21 is provided in the cover body 2, and the upper chamber 21 and the lower chamber 11 are closed to form a closed space. The cover body 2 is provided with an upper sealing ring 22 around the upper chamber 21. The cover body 2 is provided with an air inlet 23 in the upper chamber 21, and an air inlet valve is arranged at the air inlet 23. The control end of the air inlet valve is electrically connected to the output end of the controller. After judging that the preheating is completed, the controller closes the air inlet valve, and when performing the vacuum operation, a silicone nozzle is provided inside the air inlet 23 so that the silicone nozzle moves downward to close the lower end of the air inlet 23 during vacuuming, thereby sealing the outside world. A passage into the enclosed space; after determining that the second heating is completed, the controller opens the air inlet valve to allow outside gas to enter. When the vacuum sealer is opened, the silicone nozzle moves up to open the air inlet 23 to allow outside gas to enter the enclosed space. The cover body 2 is provided with a pressure strip 24 at a position close to the upper chamber 21, and the pressure strip 24 is provided at a position corresponding to the heating component 15. The lower sealing ring 12 and the upper sealing ring 22 are used to improve the airtightness of the enclosed space. When the cover body 2 is buckled on the main body 1, the upper sealing ring 22 and the lower sealing ring 12 squeeze each other to prevent gas from entering the enclosed space.

[0041] Furthermore, the heating component 15 includes a support member 153 arranged on the main body 1, and a high-temperature tape 151 is arranged on the top of the support member 153. The high-temperature tape 151 can effectively prevent the vacuum bag from being melted through and breaking due to excessive temperature. A heating wire 152 is arranged between the high-temperature tape 151 and the support member 153. Both ends of the heating wire 152 are provided with heating wire terminals 154. Hooks are arranged on the heating wire terminals 154. Copper foil tape 156 is tied between the heating wire terminals 154 and the heating wire 152. The copper foil tape 156 is used to enhance the conductivity of the circuit. The ends of the two ends of the heating wire 152 are connected to the heating wire terminals 154. A spring 155 is connected, one end of the spring 155 is connected to the end of the heating wire 152, and the other end of the spring 155 is connected to the hook on the heating wire terminal 154. The spring 155 is provided to straighten the heating wire 152 and make the heating wire 152 close to the support 153, so that the heat generated by the heating wire 152 is evenly transferred to the high-temperature adhesive tape 151, so as to avoid local deformation of the high-temperature adhesive tape 151 due to uneven heating, which affects the fit with the pressure strip 24. A fuse and a temperature sensor are connected between the two heating wire terminals 154. The temperature of the heating wire 152 is controlled by providing a temperature sensor to avoid the heating wire 152 being too high and causing the vacuum bag to be melted through.

[0042] Further, refer to Figure 6 As shown, the vacuum bag is divided into three areas: the area in the lower chamber 11 is divided into the first area, the area on the heating component 15 is divided into the second area, and the area outside the vacuum sealer for storing items is divided into the third area; the controller controls the heating component 15 to change the heating time by detecting the state of the first area.

[0043] The first area is the area where the vacuum bag is in the enclosed space. The enclosed space uses the first vacuum pump to extract the gas in the vacuum bag, and the second vacuum bag to extract the gas in the enclosed space. The first area is connected to the first vacuum pump through the first suction port 13, and is connected to the second vacuum pump through the second suction port 14. The gas inside the vacuum bag is discharged through the first area, and the gas inside the enclosed space is discharged through the first area.

[0044] Second area: the vacuum bag is in the area of ​​the heating component 15, and the second area is squeezed by the pressure strip 24. The heating component 15 will perform a first heating operation on the second area. The first heating will melt the second area of ​​the vacuum bag and seal the gas flow channel in the vacuum bag to prevent the gas in the bag from flowing out. The heating component 15 will perform a second heating operation on the second area. The second heating will melt the second area of ​​the vacuum bag again and cooperate with the pressure strip 24 to prevent gaps in the sealing strip and incomplete sealing.

[0045] The third area: the vacuum bag is located outside the vacuum sealer and is an area for storing articles. The vacuum bag contains the main part of the articles. The gas in this area passes through the second area and is finally extracted and discharged through the first air extraction port 13 of the first area. The gas in the third area is monitored to ensure that the articles in the bag are in the best preservation state after vacuuming.

[0046] By dividing different areas and monitoring them separately, the state of each area can be controlled more accurately, thereby improving the sealing effect of vacuum packaging. In particular, the monitoring and adjustment of the second area can effectively prevent water stains from appearing in the second area by controlling the heating component 15 and adjusting the heating time in time. By adding a vacuuming operation between the first heating and the second heating, the second area is made closer to the heating component 15. When vacuuming, the films on both sides of the vacuum bag can be flushed, and the width of the sealing strip can be expanded to ensure the final sealing quality.

[0047] Further, in step S3, the controller starts the second vacuum pump to extract the gas from the enclosed space. The second air extraction port 14 is respectively connected to the second vacuum pump and the humidity sensor. The humidity sensor is electrically connected to the controller. The humidity sensor transmits data to the controller. The second heating time is adjusted according to the change of the humidity sensor. If there is liquid remaining in the second area, the vacuum bag will be heated unevenly, and part of the second area will not be in a melted and bonded state during the first heating, affecting the final sealing effect.

[0048] Embodiment 1: A method for sealing a vacuum bag using a vacuum sealer comprises:

[0049] Step S1: Put the items to be sealed into a vacuum bag, open the cover 2 of the sealing machine, place the opening of the vacuum bag in the lower chamber 11, close the cover 2 and start the single sealing program.

[0050] Step S2: The controller responds to a single sealing request, and the controller controls the heating component 15 to preheat the second area of ​​the vacuum bag. The heating wire 152 heats up and transfers heat to the second area through the high-temperature adhesive strip 151. The second area is melted by high temperature and adhered under the action of the pressure strip 24. Furthermore, the preheating time of the heating component 15 is t0, and the preheating time is controlled within 4s≤t0≤15s. In this embodiment, t0 is preferably 10s. Controlling the time within 10s can quickly seal the vacuum bag and prevent the vacuum bag from breaking.

[0051] Step S3: The controller controls the second vacuum pump to start the vacuum pumping operation, extracting the gas in the enclosed space, generating negative pressure in the enclosed space, and at the same time partially straightening the bag mouth of the vacuum bag and making the bag mouth flush, so as to avoid wrinkles during the sealing process, so that the vacuum bag is flat and fully fitted in the second area, and the heating component 15 melts the second area of ​​the vacuum bag, and further squeezes the pressure strip 24 to expand the width of the sealing strip, so that the sealing strip is flat and has no gaps. This vacuum pumping operation only extracts the gas in the enclosed space, not the gas in the vacuum bag. Therefore, the vacuum pumping time t1 is controlled at 6s to avoid long-term vacuuming that causes the liquid in the second area to be molten to be extracted, affecting the sealing effect, and if the stored object contains liquid, the liquid remaining in the second area can also be evaporated.

[0052] Step S4: After performing the vacuum operation, the controller controls the heating component 15 to heat the second area of ​​the vacuum bag for the second time. The heating wire 152 heats up and transfers heat to the second area through the high-temperature rubber strip 151. The heating time of the heating component 15 is t2, and the heating time is controlled within 2s≤t2≤5s. t2 is adjusted according to the data feedback from the humidity sensor. If the humidity sensor does not change, the heating time of the heating component 15 is controlled to be 3s. If the humidity sensor changes, the heating time of the heating component 15 is controlled to be 5s.

[0053] Step S5: The cover body 2 and the main body 1 are unlocked by pressing the lock seat 17, and the external air enters the enclosed space through the air inlet 23, so that the air pressure in the enclosed space returns to normal.

[0054] Embodiment 2: A method for vacuum sealing a vacuum bag using a vacuum sealer includes:

[0055] Step S1: Put the items to be sealed into a vacuum bag, open the cover 2 of the sealing machine, place the opening of the vacuum bag in the lower chamber 11, close the cover 2 and start the vacuum sealing process.

[0056] Step S2: The controller responds to the vacuum sealing request, and the controller controls the first vacuum pump to start the vacuum operation to extract the gas in the vacuum bag, and at the same time partially straightens the bag opening of the vacuum bag and makes the bag opening flush, so as to avoid wrinkles in the sealing process, so that the vacuum bag is flat and fully fits in the second area. This vacuum operation only extracts the gas in the vacuum bag. Therefore, during vacuuming, t3 is controlled at 4s, and the gas in the vacuum bag is extracted to make the bag in a vacuum state.

[0057] Step S3: The controller controls the heating component 15 to preheat the second area of ​​the vacuum bag. The heating wire 152 heats up and transfers heat to the second area through the high-temperature adhesive strip 151. The second area is melted by high temperature and adhered under the action of the pressure strip 24. Furthermore, the preheating time of the heating component 15 is t0, and the preheating time is controlled within 4s≤t0≤15s. In this embodiment, t0 is preferably 10s. Controlling the time within 10s can quickly seal the vacuum bag and prevent the vacuum bag from breaking.

[0058] Step S4: The controller controls the second vacuum pump to start the vacuum pumping operation, extracting the gas in the enclosed space, generating negative pressure in the enclosed space, and at the same time partially straightening the bag mouth of the vacuum bag and making the bag mouth flush, thereby avoiding wrinkles during the sealing process, so that the vacuum bag is flat and fully fitted in the second area, and the heating component 15 melts the second area of ​​the vacuum bag, and further squeezes the pressure strip 24 to expand the width of the sealing strip, so that the sealing strip is flat and has no gaps. This vacuum pumping operation only extracts the gas in the enclosed space, not the gas in the vacuum bag. Therefore, the vacuum pumping time t1 is controlled at 6s to avoid long-term vacuuming that causes the liquid in the second area to be molten to be extracted, affecting the sealing effect, and if the stored object contains liquid, the liquid remaining in the second area can also be evaporated.

[0059] Step S5: After performing the vacuum operation, the controller controls the heating component 15 to heat the second area of ​​the vacuum bag for the second time. The heating wire 152 heats up and transfers heat to the second area through the high-temperature rubber strip 151. The heating time of the heating component 15 is t2, and the heating time is controlled within 2s≤t2≤5s. t2 is adjusted according to the data feedback from the humidity sensor. If the humidity sensor does not change, the heating time of the heating component 15 is controlled to be 3s. If the humidity sensor changes, the heating time of the heating component 15 is controlled to be 5s.

[0060] Step S6: The cover body 2 and the main body 1 are unlocked by pressing the lock seat 17, and the external air enters the enclosed space through the air inlet 23, so that the air pressure in the enclosed space returns to normal.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A vacuum sealing machine, characterized in that: include: A main body (1), a cover body (2) arranged on the main body (1), a vacuum pump and a controller; The main body (1) is formed with a lower chamber (11), and a heating component (15) is arranged near the lower chamber (11); The cover body (2) is formed with an upper chamber (21), and a pressure strip (24) is arranged near the upper chamber (21); the cover body (2) can be operated between an open state and a closed state. In the closed state, the upper chamber (21) and the lower chamber (11) form a closed space, and the pressure strip (24) and the heating component (15) abut against each other; in the open state, the lower chamber (11) is exposed, and the pressure strip (24) is away from the heating component (15); The output end of the controller is electrically connected to the control end of the vacuum pump and the heating component; The controller is configured to execute a computer program stored therein to implement the following steps: In response to a sealing request, controlling the heating assembly to preheat an end of the vacuum bag; When it is determined that the preheating is completed, the heating is stopped and the vacuum pump is turned on to evacuate the enclosed space so that a negative pressure is formed in the enclosed space; When it is determined that the vacuuming operation is completed, the heating component is controlled to start heating the end of the vacuum bag for the second time.

2. A vacuum sealer according to claim 1, characterized in that: A first air suction port (13) and a second air suction port (14) are provided in the lower chamber (11); the first air suction port (13) is connected to a first vacuum pump, and the second air suction port (14) is connected to a second vacuum pump.

3. A vacuum sealer according to claim 1, characterized in that: A lower sealing ring (12) is provided around the lower chamber (11), and a smooth portion (16) is arranged on the plane where the heating component (15) is located.

4. A vacuum sealer according to claim 1, characterized in that: Lock seats (17) are arranged on both sides of the top of the main body (1), and the cover body (2) is provided with lock buckles (25) at positions corresponding to the lock seats (17).

5. A vacuum sealer according to claim 1, characterized in that: The heating component (15) comprises a support member (153) fixedly arranged on the main body (1); a high-temperature adhesive tape (151) is arranged on the top of the support member (153); a heating wire (152) is arranged between the high-temperature adhesive tape (151) and the support member (153); heating wire terminals (154) are arranged at both ends of the heating wire (152); and springs (155) are connected between the ends of the two ends of the heating wire (152) and the heating wire terminals (154).

6. A vacuum sealer according to claim 5, characterized in that: A copper foil tape (156) is bound between the heating wire (152) and the heating wire terminal (154).

7. A vacuum sealer according to claim 3, characterized in that: An upper sealing ring (22) is provided around the upper chamber (21), and an air inlet (23) is provided in the cover body (2) inside the upper chamber (21).

8. A vacuum sealer according to claim 7, characterized in that: An air intake valve is arranged at the air intake port (23), wherein a control end of the air intake valve is electrically connected to an output end of the controller.

9. The vacuum sealer according to claim 7, characterized in that: After determining that the preheating is completed, the method further includes: closing the air intake valve.

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