Portable outdoor stove

Abstract

The utility model relates to the technical field of heating stoves, in particular to a portable outdoor stove which comprises a stove body, a stove cavity is arranged in the stove body, a porous infrared combustion plate is arranged in the stove cavity, the stove body is provided with an injection pipe and an ignition device, the injection pipe is communicated with the stove cavity and can provide fuel gas for the stove cavity, and the ignition device extends into the stove cavity from the lower portion of the stove body. And the ignition device can ignite the fuel gas, so that the fuel gas can be output for combustion through holes of the porous infrared combustion plate. According to the utility model, the porous infrared combustion plate is arranged at the top of the furnace chamber, and gas is fully mixed and combusted in the holes of the combustion plate to form uniform infrared radiation flame, so that the combustion efficiency is obviously improved, a stable combustion state can be kept even outdoors, and the reliability and the stability are improved. Besides, the ignition device extends into the furnace chamber from the lower part of the furnace body, so that the ignition operation is safer and more convenient, the risk of gas leakage caused by ignition failure is reduced, and the safety performance of the outdoor furnace is effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a heating stove technical field, concretely is a kind of portable outdoor stove. BACKGROUND

[0002] Portable outdoor stove is widely used in outdoor cooking, camping and other activities.The existing portable outdoor stove usually includes furnace body, furnace cavity, combustion device and ignition device.At present, the heating method of cooker used more in outdoor environment is open fire heating and radiation heating, wherein, the common open fire heating adopts the mode of nozzle combustion, and the gas is ignited after being sprayed out through nozzle to realize combustion heating.However, the nozzle flame of this combustion mode is dispersed, heat loss is large, and combustion efficiency is not high, which leads to fast gas consumption, and in outdoor environment, factors such as wind can easily affect the stability of flame, leading to insufficient combustion, and even may appear the condition of extinguishing, which affects the use experience.

[0003] And the radiation heating more adopts infrared burner, and all ignition needle assemblies of infrared burner are arranged on the side of furnace cavity, and ignition needle is bent and extends into the upper of porous ceramic plate, and ignition is completed by discharging through ignition needle when igniting, so as to complete the ignition of gas combustion.This structure is easy to be affected by external force to deform ignition needle, causing ignition difficulty, low ignition rate, especially when using piezoelectric ceramic to ignite, it is basically difficult to ignite normally, so the product needs reliable ignition to solve the ignition problem of user.

[0004] In view of the above shortcomings, we need to develop a kind of portable outdoor stove to meet the use demand of the majority of users. INVENTION CONTENTS

[0005] The utility model aims at providing a kind of portable outdoor stove to solve the problems, such as low combustion efficiency, poor flame stability, unstable and unreliable ignition, existing in prior art.The technical scheme for solving the technical problems of the utility model is as follows:

[0006] A kind of portable outdoor stove, including furnace body, the furnace cavity with top opening is arranged in the furnace body, the top of the furnace cavity is equipped with porous infrared combustion plate, the furnace body is equipped with ejector pipe and ignition device, the ejector pipe is communicated with furnace cavity, the ejector pipe can provide gas to furnace cavity, the ignition device extends into furnace cavity from the lower of the furnace body, the ignition end of the ignition device is located at the position close to porous infrared combustion plate, the ignition device can ignite gas, so that gas can be output combustion through the hole of the porous infrared combustion plate.

[0007] Further, in the preferred embodiment, the ignition device includes ignition assembly and ignition needle connected with ignition assembly, and the ignition end of the ignition needle is located above the porous infrared combustion plate.

[0008] Further, in the preferred embodiment, part of the ignition needle is inserted into the furnace cavity, and the ignition end of the ignition needle is exposed outside the top surface of the porous infrared combustion plate through one of the holes of the porous infrared combustion plate.

[0009] Further, in the preferred embodiment, the ignition assembly comprises a piezoelectric ceramic igniter and an ignition wire connected with the ignition needle and the piezoelectric ceramic igniter respectively, and the piezoelectric ceramic igniter is arranged at the bottom of the furnace body.

[0010] Further, in the preferred embodiment, the output end of the ejector pipe is connected to the bottom of the furnace body, and the ejector pipe is arranged in the vertical direction at the bottom of the furnace body.

[0011] Further, in the preferred embodiment, the cross-sectional shape of the furnace cavity is trumpet-shaped with a narrow bottom and a wide top, and the output end of the ejector pipe is in communication with the bottom end of the furnace cavity.

[0012] Further, in the preferred embodiment, the furnace body is rotatably connected with support devices, the support devices can support the furnace body and form an unfolded state when opened, and the support devices can approach the periphery of the furnace body and form a folded state when stored, the support devices are multiple and hinged to the furnace body, and the support devices comprise movable supports movably connected with the furnace body, and the movable supports approach the periphery of the furnace body and form a folded state when stored.

[0013] Further, in the preferred embodiment, the furnace body comprises a furnace head support and a fixed support connected with the furnace head support, the fixed support is provided with a connecting part corresponding to the support device, the movable support is hinged to the connecting part, and the connecting part is provided with a limiting arc-shaped slot for limiting the rotation position of the movable support.

[0014] Further, in the preferred embodiment, the support device comprises a rotation assembly hinged to the connecting part, a rotating frame of the rotation assembly is installed on the connecting part through a first hinge, and the movable support is installed on the rotating frame through a second hinge, and the movable support forms an unfolded state or a folded state through the rotation assembly.

[0015] Further, in the preferred embodiment, the movable support comprises a first support for preventing the furnace body from tilting and a second support for stabilizing the placement of a heated object, the first support and the second support are both hinged to the rotation assembly, the first support and the second support both adopt an arc-shaped claw structure, the arc-shaped claw structure of the first support has a claw tip part a, and the arc-shaped claw structure of the second support has a sawtooth part b.

[0016] Further, in the preferred embodiment, in the unfolded state, the claw tip a faces downwards, and the sawtooth b faces upwards; in the folded state, the outer arc edge of the first support and / or the outer arc edge of the second support is / are received to be circular.

[0017] The portable outdoor stove has the advantages that:

[0018] 1、The utility model discloses a plurality of porous infrared combustion plates are arranged on the top of the furnace cavity, and gas is fully mixed and burns in the holes of the combustion plate, forming uniform infrared radiation flame, which can more efficiently convert the chemical energy of the gas into heat energy, significantly improves the combustion efficiency, reduces the waste of gas, and also speeds up the heating speed. The use of the porous infrared combustion plate makes the flame distribution more uniform, even in the environment with large outdoor wind force, the stable combustion state can be maintained, the situation that the flame is blown away or extinguished is avoided, and the use reliability and stability of the outdoor stove are improved. In addition, the ignition device extends into the furnace cavity from below the furnace body, and the ignition end is located close to the porous infrared combustion plate. This design makes the ignition operation safer and more convenient, the ignition success rate is high, the risk of gas leakage caused by ignition failure is reduced, and the safety performance of the outdoor stove is effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model.

[0020] Figure 2 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model.

[0021] Figure 3 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model.

[0022] Figure 4 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model.

[0023] Figure 5 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model. Figure 4

[0024] Figure 6 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model.

[0025] Figure 7 It is a perspective view of the unfolded state of the portable outdoor stove of the utility model. DETAILED DESCRIPTION

[0026] The embodiments of the utility model will be described in detail below with reference to the drawings.

[0027] Example 1: ​

[0028] As Figures 1 to 7 shown in one of the portable outdoor stove, comprising a stove body 1, stove body 1 has a hollow cavity 11 with the top opening, the cavity 11 near the top opening of the top is provided with a plurality of porous infrared combustion plate 12, the porous infrared combustion plate 12 is a kind of heating component using porous ceramic plate combustion heating, the porous ceramic plate is a kind of ceramic material with a large number of pores inside, combined with gas combustion system, gas escapes through the small hole of ceramic plate and burns, produces infrared radiation, gas mixes with air in the small hole of porous ceramic plate and burns, the heat generated by combustion is transmitted and radiated through the pores of the ceramic plate, the combustion speed of this combustion method is very fast, and the combustion is stable.

[0029] More specifically, the stove body 1 is provided with an ejector pipe 13 and an ignition device 2, the ejector pipe 13 communicates with the cavity 11, the ejector pipe 13 can provide gas to the cavity 11, wherein the bottom of the ejector pipe 13 is provided with a plurality of dampers, the dampers are uniformly distributed on the bottom of the ejector pipe 13, the dampers can supplement the air required for combustion, the ejector pipe 13 near the damper can be connected with a gas inlet pipe, the gas enters the ejector pipe 13 from the gas inlet pipe, and finally reaches the cavity 11 to provide fuel for ignition.

[0030] More specifically, the ignition device 2 extends into the cavity 11 from below the stove body 1, the ignition end of the ignition device 2 is located near the porous infrared combustion plate 12, the ignition device 2 can ignite the gas, so that the gas can be output for combustion through the holes of the porous infrared combustion plate 12. The ignition device 2 is arranged below the stove body 1, which reduces the influence of external factors, so that the ignition operation is safer and more convenient, and the ignition success rate is high.

[0031] In use, first connect the gas source (such as gas cylinder) to the ejector pipe 13, open the gas source switch, the gas enters the cavity 11 through the ejector pipe 13, and the ignition device 2 is ignited, the ignition end of the ignition device 2 is located above the porous infrared combustion plate 12 or penetrates the hole of the porous infrared combustion plate 12, which can quickly and accurately ignite the gas. The gas is fully mixed and burned in the holes of the porous infrared combustion plate 12, forming a uniform infrared radiation flame, which heats the heated objects placed above the cavity 11.

[0032] As another embodiment 101 of embodiment 1, as Figures 1 to 5 shown in one of the portable outdoor stove, the ignition device 2 of the embodiment comprises an ignition assembly 21 and an ignition needle 22 connected with the ignition assembly 21, the ignition end of the ignition needle 22 is located above the porous infrared combustion plate 12, part of the ignition needle 22 penetrates into the cavity 11, and the ignition end of the ignition needle 22 penetrates one of the holes of the porous infrared combustion plate 12 to expose the top outer surface of the porous infrared combustion plate 12.

[0033] More specifically, the furnace body 1 comprises a metal piece 16 outside the porous infrared combustion plate 12, the metal piece 16 is provided with two electrodes 161 at a position close to the ignition end of the ignition needle 22, the electrodes 161 can generate an electric spark, when the voltage between the electrodes 161 is high enough, an electric arc can be formed in the air or fuel mixture, generating a high-temperature and high-energy electric spark, which can easily ignite when the infrared burner is ignited.

[0034] When ignited, the ignition assembly 21 generates a high-voltage spark, which is transmitted to the upper side or hole of the porous infrared combustion plate 12 through the ignition needle 22, which can quickly ignite the gas and make the gas burn fully in the holes of the porous infrared combustion plate 12, forming a uniform infrared radiation flame. Since the ignition end of the ignition needle 22 penetrates the holes of the porous infrared combustion plate 12, it can be closer to the burning position of the gas, improving the ignition success rate and combustion efficiency.

[0035] As another embodiment 102 of embodiment 1, as shown in Figures 1 to 5 A portable outdoor stove, the ignition assembly 21 comprises a piezoelectric ceramic igniter 211 and an ignition wire 212, the ignition wire 212 is connected with the ignition needle 22 and the piezoelectric ceramic igniter 211 respectively, and the piezoelectric ceramic igniter 211 is arranged at the bottom of the furnace body 1.

[0036] More specifically, the piezoelectric ceramic igniter 211 is a manual ignition device based on the piezoelectric effect and using piezoelectric ceramic as the medium, and the core of the piezoelectric ceramic igniter is a piezoelectric ceramic element. When an external force (such as pressing or impact) is applied to it, the piezoelectric ceramic will deform elastically, causing the positive and negative charge centers inside to shift, resulting in a large accumulation of free charges on the surface of the ceramic at both ends, forming a high-voltage output. When the voltage rises to a certain level, a discharge spark will be generated in the gap between the electrodes, thereby igniting the combustible gas. The piezoelectric ceramic has high stability and reliability, accurate ignition time, is not easily affected by the external environment, simple structure, long service life, and low maintenance cost.

[0037] When ignited, the piezoelectric ceramic igniter 211 can generate a high-voltage spark when subjected to an external force, such as pressing the ignition button, which is transmitted to the ignition needle 22 through the ignition wire 212, and then ignites the gas. This ignition method does not require an external power source, is simple and safe and reliable, and the piezoelectric ceramic igniter 211 has a long service life.

[0038] As another embodiment 103 of embodiment 1, as shown in Figures 1 to 5 A portable outdoor stove, the output end of the ejector pipe 13 is connected to the bottom of the furnace body 1, and the ejector pipe 13 is arranged in the vertical direction at the bottom of the furnace body 1. The ejector pipe 13 arranged in the vertical direction at the bottom of the furnace body 1 can make the gas enter the furnace chamber 11 more smoothly.

[0039] As another example 104 of the example 1, a portable outdoor stove as shown in Figures 1 to 5 The cross-sectional shape of the stove cavity 11 is in the shape of a horn with the lower part being narrow and the upper part being wide. The output end of the ejector pipe 13 is in communication with the bottom end of the stove cavity 11. The horn-shaped cross-sectional shape of the stove cavity 11 is conducive to the sufficient mixing of gas and air, improving the combustion efficiency and flame stability. After the gas enters the stove cavity 11 from the output end of the ejector pipe 13, it is fully mixed with air in the stove cavity 11, and then burns through the holes of the porous infrared combustion plate 12, forming a uniform infrared radiation flame.

[0040] As another example 105 of the example 1, a portable outdoor stove as shown in Figures 1 to 5 The output end of the ejector pipe 13 is connected to the bottom of the stove body 1, and the ejector pipe 13 is arranged in the vertical direction at the bottom of the stove body 1. The cross-sectional shape of the stove cavity 11 is in the shape of a horn with the lower part being narrow and the upper part being wide. The output end of the ejector pipe 13 is in communication with the bottom end of the stove cavity 11. The ejector pipe 13 is arranged in the vertical direction at the bottom of the stove body 1, which can make the gas enter the stove cavity 11 more smoothly. At the same time, the horn-shaped cross-sectional shape of the stove cavity 11 is conducive to the sufficient mixing of gas and air, improving the combustion efficiency and flame stability. After the gas enters the stove cavity 11 from the output end of the ejector pipe 13, it is fully mixed with air in the stove cavity 11, and then burns through the holes of the porous infrared combustion plate 12, forming a uniform infrared radiation flame.

[0041] Example 2:

[0042] As shown in Figures 1 to 7 A portable outdoor stove, the stove body 1 is rotatably connected with a support device 3. When the support device 3 is opened, it can support the stove body 1 and form an unfolded state. When the support device 3 is stored, it can be close to the side of the stove body 1 and form a folded state. The support device 3 is provided with a plurality of hinges on the stove body 1. The support device 3 includes a movable support 31 movably connected with the stove body 1. When the movable support 31 is stored, it is close to the side of the stove body 1 and forms a folded state.

[0043] The support device 3 of the present embodiment realizes the support and storage functions of the stove body 1 through the unfolding and folding of the movable support 31. In use, the movable support 31 is unfolded to support the stove body 1 and place the heated objects, keeping the stove body 1 stable, so that the heating process can proceed smoothly. When stored, the movable support 31 is folded to be close to the side of the stove body 1, reducing the volume of the stove and facilitating carrying and storage.

[0044] As another example 201 of the example 2, a portable outdoor stove as shown in Figures 1 to 7The portable outdoor stove shown includes a stove body 1 comprising a burner head support 14 and a fixed support 15 connected to the burner head support 14. The fixed support 15 has connecting portions 151 corresponding to the support devices 3. The connecting portions 151 extend axially from the fixed support 15 toward the stove body 1 and are evenly distributed around the central axis of the stove body 1 on the outer side of the fixed support 15. A movable support 31 is hinged to the connecting portions 151. The connecting portions 151 have a limiting arc-shaped groove 152 for limiting the rotational position of the movable support 31. The movable support 31 has a limiting handle that extends into the limiting arc-shaped groove 152. When rotating, the limiting handle slides in the limiting arc-shaped groove 152 and touches the groove wall of the limiting arc-shaped groove 152 to limit the range of motion of the movable support 31, thereby achieving storage positioning.

[0045] As another embodiment 202 of embodiment 2, such as Figures 1 to 7 The portable outdoor stove shown includes a support device 3 comprising a rotating assembly 32 hinged to a connecting part 151. The rotating frame 321 of the rotating assembly 32 is mounted on the connecting part 151 via a first hinge 322. The movable bracket 31 is mounted on the rotating frame 321 via a second hinge 323. The movable bracket 31 is configured to be in an unfolded or folded state via the rotating assembly 32.

[0046] More specifically, the first hinge 322 uses rivets or pins to movably connect the rotating frame 321 to the connecting part 151, so that the rotating frame 321 can rotate stably and flexibly relative to the connecting part 151, with the rotation direction around the first hinge 322 being the first rotation direction; the second hinge 323 uses a pin to movably connect the movable bracket 31 to the rotating frame 321, so that the movable bracket 31 can rotate stably and flexibly relative to the rotating frame 321, with the rotation direction around the second hinge 323 being the second rotation direction, thereby realizing the flexible adjustment and limited rotation of the movable bracket 31 in the first and second rotation directions.

[0047] More specifically, the first rotation direction is perpendicular to the axial direction of the furnace body 1, and the second rotation direction is perpendicular to the first rotation direction.

[0048] Example 3:

[0049] like Figures 1 to 7 The portable outdoor stove shown has a movable support 31 including a first support 311 for preventing the stove body 1 from tilting and a second support 312 for stably placing heated objects. Both the first support 311 and the second support 312 are hinged to a rotating assembly 32. Both the first support 311 and the second support 312 adopt an arc-shaped claw structure. The arc-shaped claw structure of the first support 311 bends and extends to a gradually narrowing claw tip a, and the arc-shaped claw structure of the second support 312 has serrated parts b arranged in a straight line.

[0050] More specifically, in the unfolded state, the claw tip a contacts the placement position in a point contact manner towards the lower side, ensuring the balanced stability of the placement support, and the sawtooth part b contacts the placement of the heated object in a point contact manner towards the upper side, ensuring the balanced stability of the supporting support.

[0051] As another example 301 of example 3, as shown in Figures 6 to 7 A portable outdoor stove in a folded state, a plurality of first supports 311 are stored back in the position close to the stove body 1, and the outer arc edge of the first support 311 is stored to be circular.

[0052] As another example 302 of example 3, as shown in Figures 6 to 7 A portable outdoor stove in a folded state, a plurality of second supports 312 are stored back in the position close to the stove body 1, and the outer arc edge of the second support 312 is stored to be circular.

[0053] As another example 303 of example 3, as shown in Figures 6 to 7 A portable outdoor stove, the storage outer diameter f of the outer arc edge of the second support 312 after storage is greater than the storage outer diameter e of the outer arc edge of the first support 311 after storage.

[0054] As shown in Figures 1 to 7 The specific implementation manner of the utility model is as follows:

[0055] In use, the first support 311 and the second support 322 are unfolded by rotating the assembly 32 to operate the movable support 31, the claw tip a of the first support 311 is unfolded to the placement position in a point contact manner towards the lower side to support the stove body 1, and the sawtooth part b of the second support 322 is unfolded to the heated object in a point contact manner towards the upper side to stably support the heated object. The claw tip a of the first support 311 can prevent the stove body 1 from tilting, and the sawtooth part b of the second support 322 can stably place the heated object, thereby improving the stability and safety of the stove.

[0056] Connect the gas source (such as a gas cylinder) to the ejector pipe 13, open the gas source switch, and the gas enters the stove cavity 11 through the ejector pipe 13, and is ignited by the ignition device 2. The ignition end of the ignition device 2 is located above the multi-hole infrared combustion plate 12 or passes through the hole of the multi-hole infrared combustion plate 12, which can quickly and accurately ignite the gas. The gas is fully mixed and burned in the hole of the multi-hole infrared combustion plate 12, forming a uniform infrared radiation flame, which heats the heated object placed above the stove cavity 11 until the heating is completed and the gas source is turned off.

[0057] When the stove is stored, the gas supply is cut off by closing the gas source switch, and the first support 311 and the second support 322 are stored in the folded state by rotating the assembly 32 to operate the movable support 31, so that the outer arc edges of the first support 311 and the second support 322 are stored in a circular shape, and then the stove is stored or stored.

[0058] The above is only used as an example to further illustrate the technical content of the present application, so that the reader can more easily understand, but does not represent that the embodiments of the present application are limited to this, any technical extension or re-creation made according to the present application is protected by the present application. The protection scope of the present application is subject to the claims.

Claims

1. A portable outdoor stove, characterized by: The application relates to a stove body (1) with a stove cavity (11) with a top opening, wherein the top of the stove cavity (11) is provided with a porous infrared combustion plate (12), the stove body (1) is provided with an injection pipe (13) and an ignition device (2), the injection pipe (13) is communicated with the stove cavity (11) and can provide gas to the stove cavity (11), the ignition device (2) extends into the stove cavity (11) from below the stove body (1), the ignition end of the ignition device (2) is located close to the porous infrared combustion plate (12), and the ignition device (2) can ignite the gas and make the gas output combustion through the holes of the porous infrared combustion plate (12).

2. A portable outdoor stove as defined in claim 1, characterized in that The ignition device (2) comprises an ignition assembly (21) and an ignition needle (22) connected with the ignition assembly (21), and the ignition end of the ignition needle (22) is located above the porous infrared combustion plate (12).

3. A portable outdoor stove as defined in claim 2, characterized in that Part of the ignition needle (22) penetrates into the stove cavity (11), and the ignition end of the ignition needle (22) penetrates through one of the holes of the porous infrared combustion plate (12) to expose the top outer surface of the porous infrared combustion plate (12).

4. A portable outdoor stove as claimed in claim 2 or 3, characterised in that: The ignition assembly (21) comprises a piezoelectric ceramic igniter (211) and an ignition wire (212), the ignition wire (212) is connected with the ignition needle (22) and the piezoelectric ceramic igniter (211) respectively, and the piezoelectric ceramic igniter (211) is arranged at the bottom of the stove body (1).

5. The portable outdoor stove of claim 1, wherein: The output end of the injection pipe (13) is connected to the bottom of the stove body (1), and the injection pipe (13) is arranged in a vertical direction at the bottom of the stove body (1); The cross-sectional shape of the stove cavity (11) is in a trumpet shape which is narrow at the bottom and wide at the top, and the output end of the injection pipe (13) is communicated with the bottom end of the stove cavity (11).

6. The portable outdoor stove of claim 1, wherein: The stove body (1) is rotationally connected with a supporting device (3), the supporting device (3) can support the stove body (1) and form an unfolded state when being opened, the supporting device (3) can approach the periphery of the stove body (1) and form a folded state when being stored, the supporting device (3) is provided with a plurality of hinged parts on the stove body (1), and the supporting device (3) comprises a movable support (31) movably connected with the stove body (1), wherein the movable support (31) approaches the periphery of the stove body (1) and forms a folded state when being stored.

7. A portable outdoor stove as defined in claim 6, wherein: The stove body (1) comprises a stove head support (14) and a fixed support (15) connected with the stove head support (14), the fixed support (15) is provided with a connecting part (151) corresponding to the supporting device (3) one by one, the movable support (31) is hinged on the connecting part (151), and the connecting part (151) is provided with a limiting arc-shaped groove (152) for limiting the rotating position of the movable support (31).

8. A portable outdoor furnace according to claim 7, wherein: The support device (3) comprises a rotating assembly (32) hinged on the connecting part (151), a rotating frame (321) of the rotating assembly (32) is installed on the connecting part (151) through a first hinge (322), the movable support (31) is installed on the rotating frame (321) through a second hinge (323), and the movable support (31) forms an unfolded state or a folded state through the rotating assembly (32).

9. A portable outdoor furnace according to claim 8, characterized in that: The movable support (31) comprises a first support (311) for preventing the furnace body (1) from tilting and a second support (312) for stably placing heated objects, the first support (311) and the second support (312) are both hinged on the rotating assembly (32), the first support (311) and the second support (312) both adopt an arc-shaped claw structure, the arc-shaped claw structure of the first support (311) has a claw tip part a, and the arc-shaped claw structure of the second support (312) has a sawtooth part b.

10. The portable outdoor stove of claim 9, wherein: In the unfolded state, the claw tip part a faces downward, and the sawtooth part b faces upward; in the folded state, an outer arc edge of the first support (311) and / or an outer arc edge of the second support (312) is / are received and circular.

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