High-pressure water fast heating device for coffee machine
Patent Information
- Application Number
- CN202620179069.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-06
- Publication Date
- 2026-10-30
- Estimated Expiration
- 2036-02-06
AI Technical Summary
这种制取热水的方式由于是先将整个水箱内的水全部加热后，才能冲调咖啡，因此制取热水速度较慢，导致整个冲泡咖啡的时间较长；且这种方式制取热水的效率低，能耗高
[0017]本实用新型的有益效果是：本实用新型的咖啡机的高压水快速加热装置包括绝缘外壳组件、金属加热筒、内芯体，所述金属加热筒设置于所述绝缘外壳组件内，所述内芯体的外壁设有螺旋沟槽，所述内芯体适配容置于所述金属加热筒的内腔，所述螺旋沟槽的侧壁顶部与所述金属加热筒的内壁紧密适配连接，以使所述螺旋沟槽与所述金属加热筒的内壁之间形成自上向下延伸的螺旋状导流流道；所述绝缘外壳组件的上下两端分别设有冷水进水流道、热水出水流道；所述金属加热筒的上下两端分别固定密封耐高压连接上金属封板、下金属封板，所述上金属封板、所述下金属封板分别固定密封耐高压连接一个高压水嘴；两个所述高压水嘴的内端分别与所述导流流道的上下开口相连通，外端分别与所述冷水进水流道、所述热水出水流道相连通且密封连接；形成由所述冷水进水流道、所述上金属封板的高压水嘴、所述导流流道、所述下金属封板的高压水嘴、所述热水出水流道依次连通的高压水流道；所述金属加热筒的外壁设有电加热装置，用于加热所述金属加热筒，并通过所述金属加热筒对流经所述导流流道内的水进行快速加热；本实用新型克服了现有技术的缺陷和不足，通过设置自上向下延伸的螺旋状导流流道，使水流的截面积大大缩小，使得对所述金属加热筒的加热热量能够迅速传导到水流上，同时水流的流道加长，满足了制取水量的需要，将整体水箱的水转换为细长的水流道对其整个流道快速加热，不仅制取热水速度快、效率高、平均能耗低，而且安全性高，制取热水温度高，完全满足压力咖啡机的冲泡水速热和高温需求；同时，在所述内芯体的外壁直接开设螺旋沟槽，并通过所述金属加热筒的上下两端分别固定密封耐高压连接上金属封板、下金属封板，所述上金属封板、所述下金属封板分别固定密封耐高压连接一个高压水嘴，使得所述高压水流道结构强度大，耐压性能好，经测试，本实用新型的高压水快速加热装置可以承受高达25bar的水压而正常快速的制取高温热水和蒸汽；故本实用新型是一种制取热水速度快、效率高、平均能耗低、耐高压的咖啡机的高压水快速加热装置，该咖啡机的高压水快速加热装置能够在需要冲泡咖啡时，即时提供高温高压热水，出水即热水。
Smart Images
Figure CN224911042U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to accessories for coffee machines, specifically to a high-pressure water rapid heating device for coffee machines. Background Technology
[0002] Coffee is one of the world's three major beverages. Coffee machines are mainly used on desktops in homes or offices. They are connected to mains electricity via a power cord and use water, coffee grounds, coffee packets, coffee capsules, etc. to brew coffee.
[0003] Common pressure espresso machines require a high-pressure supply of hot water and steam so that users can adjust the coarseness and weight of the coffee grounds according to the water pressure to make espresso with the desired flavor. The pressure of the hot water supply line is high, sometimes reaching up to 25 bar. Current pressure espresso machines typically fill the water tank first, then use an electric heating element to directly heat the tank. Once the water reaches the required temperature, a pressure pump delivers the hot water to the brewing chamber to brew the coffee. This method of hot water production is slow because it heats the entire tank before brewing, resulting in a longer brewing time. Furthermore, this method is inefficient and energy-intensive. Additionally, a rapid heating device that directly heats cold water in the pipeline has emerged; however, existing rapid heating devices can only withstand normal atmospheric pressure and cannot handle the high pressure of 9 bar or more in pressure espresso machines, let alone the high pressure of 25 bar. Utility Model Content
[0004] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a high-pressure water rapid heating device for coffee machines that can produce hot water quickly, efficiently, with low average energy consumption and high pressure resistance. This high-pressure water rapid heating device for coffee machines can provide high-temperature and high-pressure hot water instantly when coffee needs to be brewed, and the water is hot as soon as it comes out.
[0005] The technical solution adopted by the high-pressure water rapid heating device for coffee machines of this utility model is as follows: The high-pressure water rapid heating device for coffee machines of this utility model includes an insulating outer shell assembly, a metal heating cylinder, and an inner core. The metal heating cylinder is disposed inside the insulating outer shell assembly. The outer wall of the inner core is provided with a spiral groove. The inner core is adapted to be housed within the inner cavity of the metal heating cylinder. The top of the side wall of the spiral groove is tightly fitted and connected to the inner wall of the metal heating cylinder, so that a spiral flow channel extending from top to bottom is formed between the spiral groove and the inner wall of the metal heating cylinder. The upper and lower ends of the insulating outer shell assembly are respectively provided with a cold water inlet channel and a hot water outlet channel. The upper and lower ends of the metal heating cylinder are respectively fixed... A fixed, high-pressure resistant upper metal sealing plate and a lower metal sealing plate are connected, and each of the upper and lower metal sealing plates is fixedly and sealed to a high-pressure water nozzle. The inner ends of the two high-pressure water nozzles are respectively connected to the upper and lower openings of the guide channel, and the outer ends are respectively connected to the cold water inlet channel and the hot water outlet channel and are sealed to each other. A high-pressure water channel is formed by sequentially connecting the cold water inlet channel, the high-pressure water nozzle of the upper metal sealing plate, the guide channel, the high-pressure water nozzle of the lower metal sealing plate, and the hot water outlet channel. The outer wall of the metal heating cylinder is provided with an electric heating device for heating the metal heating cylinder and rapidly heating the water flowing through the guide channel through the metal heating cylinder.
[0006] The inner core has blind holes at both ends. The inner ends of the two high-pressure water nozzles are fixedly sealed with a high-pressure resistant plug. The plugs are adapted to the blind holes to position and limit the inner core.
[0007] The plug has a water passage hole on its side that is connected to the central hole, and the central hole is connected to the high-pressure water nozzle.
[0008] The high-pressure water nozzle is connected and fixed to the upper metal sealing plate, the lower metal sealing plate, and the plug, as well as the metal heating cylinder is connected to the upper metal sealing plate and the lower metal sealing plate by welding.
[0009] The cold water inlet channel and the hot water outlet channel are each provided with a stepped cavity; the high-pressure water nozzle includes a central column, the central column is provided with a central channel and the outer wall is provided with a middle annular groove; a first sealing ring and a second sealing ring are respectively provided outside the central column and inside the middle annular groove, which are respectively adapted to and sealed to the two stepped inner walls of the stepped cavity.
[0010] The electric heating device is a coated heating resistor, which is spirally arranged around the outer wall of the metal heating cylinder. The outer walls of the metal heating cylinder are respectively provided with conductive clamps that are electrically connected to the two ends of the coated heating resistor.
[0011] One end of the metal heating cylinder is connected to a grounding wire.
[0012] The inner core is a solid cylinder.
[0013] The insulating outer shell assembly includes a first half-shell, a second half-shell, a top cover, and a bottom cover. The first half-shell and the second half-shell are laterally connected and fixed to each other. The top cover and the bottom cover are respectively connected and fixed to the top and bottom of the first half-shell and the second half-shell to form a cage-like frame structure for enclosing and housing the metal heating cylinder. The cold water inlet channel is located inside the top cover, and the hot water outlet channel is located inside the bottom cover.
[0014] The bottom cover has a temperature measuring hole on its side, which is connected to the hot water outlet channel. A first NTC temperature sensor is installed in the temperature measuring hole to measure and transmit the hot water outlet temperature.
[0015] The bottom surface of the bottom cover is provided with a temperature measuring groove, and a pressure plate with a size larger than its bottom opening is provided in the temperature measuring groove. The two ends of a spring press against the pressure plate and the second NTC temperature sensor respectively, so that the second NTC temperature sensor is in close contact with the lower metal sealing plate, which is used to measure and transmit the temperature of the metal heating cylinder, so as to shut down the electric heating device when the temperature is too high and prevent dry burning.
[0016] The first half-shell has two mounting holes for mounting two temperature control switches. The temperature control switches are attached to the outside of the metal heating cylinder and are used to turn off the electric heating device when the set temperature is reached. The two temperature control switches are respectively equipped with automatic reset and manual reset to achieve dual temperature control protection.
[0017] The beneficial effects of this utility model are as follows: The high-pressure water rapid heating device for the coffee machine of this utility model includes an insulating outer shell assembly, a metal heating cylinder, and an inner core. The metal heating cylinder is disposed inside the insulating outer shell assembly. The outer wall of the inner core is provided with a spiral groove. The inner core is adapted to be housed within the inner cavity of the metal heating cylinder. The top of the side wall of the spiral groove is tightly fitted and connected to the inner wall of the metal heating cylinder, so that a spiral flow channel extending from top to bottom is formed between the spiral groove and the inner wall of the metal heating cylinder. The upper and lower ends of the insulating outer shell assembly are respectively provided with a cold water inlet channel and a hot water outlet channel. The upper and lower ends of the metal heating cylinder are respectively fixed tightly. A high-pressure resistant upper metal sealing plate and a lower metal sealing plate are connected, and each of the upper and lower metal sealing plates is fixedly and sealed to a high-pressure water nozzle. The inner ends of the two high-pressure water nozzles are respectively connected to the upper and lower openings of the guide channel, and the outer ends are respectively connected to the cold water inlet channel and the hot water outlet channel and sealed. This forms a high-pressure water channel in which the cold water inlet channel, the high-pressure water nozzle of the upper metal sealing plate, the guide channel, the high-pressure water nozzle of the lower metal sealing plate, and the hot water outlet channel are sequentially connected. The outer wall of the metal heating cylinder is provided with an electric heating device for heating the metal heating cylinder and through the metal heating cylinder, the water flowing through the guide channel... The water in the flow channel is rapidly heated. This invention overcomes the defects and shortcomings of the prior art by setting a spiral flow channel extending from top to bottom, which greatly reduces the cross-sectional area of the water flow, allowing the heat from the metal heating cylinder to be quickly transferred to the water flow. At the same time, the flow channel is lengthened to meet the water production needs, converting the water in the entire water tank into a slender flow channel for rapid heating of the entire channel. This not only produces hot water quickly, efficiently, and with low average energy consumption, but also ensures high safety and produces hot water at high temperatures, fully meeting the rapid heating and high-temperature requirements of pressure coffee machines. Furthermore, spiral grooves are directly opened on the outer wall of the inner core, and the metal... The upper and lower ends of the heating cylinder are respectively fixed and sealed with a high-pressure resistant upper metal sealing plate and a lower metal sealing plate. The upper and lower metal sealing plates are respectively fixed and sealed with a high-pressure water nozzle, which makes the high-pressure water flow channel structure strong and pressure resistant. After testing, the high-pressure water rapid heating device of this utility model can withstand water pressure of up to 25 bar and normally and quickly produce high-temperature hot water and steam. Therefore, this utility model is a high-pressure water rapid heating device for coffee machines that produces hot water quickly, efficiently, with low average energy consumption and high pressure resistance. This high-pressure water rapid heating device for coffee machines can provide high-temperature and high-pressure hot water instantly when coffee needs to be brewed, and the water is hot water as soon as it comes out. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the overall structure of the high-pressure water rapid heating device of the coffee machine according to an embodiment of the present invention;
[0019] Figure 2 This is a schematic diagram of the overall structure of the high-pressure water rapid heating device of the coffee machine according to another perspective of this utility model embodiment;
[0020] Figure 3 This is an exploded structural diagram of the high-pressure water rapid heating device of the coffee machine according to an embodiment of the present invention;
[0021] Figure 4 This is a longitudinal sectional view of the high-pressure water rapid heating device of the coffee machine according to an embodiment of the present invention;
[0022] Figure 5 This is another longitudinal sectional view of the high-pressure water rapid heating device of the coffee machine according to an embodiment of the present invention;
[0023] Figure 6 This is another longitudinal sectional view of the high-pressure water rapid heating device for a coffee machine according to an embodiment of the present invention. Detailed Implementation
[0024] like Figures 1-6 As shown, the high-pressure water rapid heating device for a coffee machine according to this embodiment includes an insulating outer shell assembly 1, a metal heating cylinder 2, and an inner core 3. The metal heating cylinder 2 is disposed inside the insulating outer shell assembly 1. The outer wall of the inner core 3 is provided with a spiral groove 31. The inner core 3 is adapted to be housed within the inner cavity of the metal heating cylinder 2. The top of the side wall of the spiral groove 31 is tightly fitted and connected to the inner wall of the metal heating cylinder 2, so that a spiral flow channel 30 extending from top to bottom is formed between the spiral groove 31 and the inner wall of the metal heating cylinder 2. The upper and lower ends of the insulating outer shell assembly 1 are respectively provided with a cold water inlet channel 10 and a hot water outlet channel 20. The upper and lower ends of the metal heating cylinder 2 are respectively fixedly sealed with a high-pressure resistant metal sealing plate 51. The lower metal sealing plate 52, the upper metal sealing plate 51, and the lower metal sealing plate 52 are respectively fixedly and sealed to a high-pressure water nozzle 6; the inner ends of the two high-pressure water nozzles 6 are respectively connected to the upper and lower openings of the guide channel 30, and the outer ends are respectively connected to the cold water inlet channel 10 and the hot water outlet channel 20 and sealed; forming a high-pressure water channel in which the cold water inlet channel 10, the high-pressure water nozzle 6 of the upper metal sealing plate 51, the guide channel 30, the high-pressure water nozzle 6 of the lower metal sealing plate 52, and the hot water outlet channel 20 are sequentially connected; the outer wall of the metal heating cylinder 2 is provided with an electric heating device 4 for heating the metal heating cylinder 2 and rapidly heating the water flowing through the guide channel 30 through the metal heating cylinder 2.
[0025] The electric heating device 4 is a coated heating resistor, which is spirally arranged around the outer wall of the metal heating cylinder 2. Conductive clamps 41 are respectively provided at both ends of the outer wall of the metal heating cylinder 2, and are electrically connected to the two ends of the coated heating resistor. One end of the metal heating cylinder 2 is connected to a grounding wire 42, ensuring good safety and preventing electric shock accidents caused by leakage.
[0026] Specifically, the insulating outer shell assembly 1 includes a first half-shell 11, a second half-shell 12, a top cover 13, and a bottom cover 14. The first half-shell 11 and the second half-shell 12 are laterally connected and fixed to each other. The top cover 13 and the bottom cover 14 are respectively connected and fixed to the top and bottom of the first half-shell 11 and the second half-shell 12, forming a cage-like frame structure for enclosing and housing the metal heating cylinder 2. The cold water inlet channel 10 is disposed in the top cover 13, and the hot water outlet channel 20 is disposed in the bottom cover 14.
[0027] Furthermore, the side of the bottom cover 14 is provided with a temperature measuring hole 15, which is connected to the hot water outlet channel 20. A first NTC temperature sensor 91 is installed in the temperature measuring hole 15 to measure and transmit the hot water outlet temperature. The bottom surface of the bottom cover 14 is provided with a temperature measuring groove 90. A pressure plate 93 with a size larger than its bottom opening is provided in the temperature measuring groove 90. The two ends of a spring 94 press against the pressure plate 93 and the second NTC temperature sensor 92 respectively, so that the second NTC temperature sensor 92 is tightly fitted with the lower metal sealing plate 52, which is used to measure and transmit the temperature of the metal heating cylinder 2, so as to shut off the electric heating device 4 when the temperature is too high and prevent dry burning. The first half-shell 11 is provided with two mounting holes 70 for installing two temperature control switches 7. The temperature control switches 7 are attached to the outside of the metal heating cylinder 2 and are used to shut off the electric heating device 4 when the set temperature is reached. The two temperature control switches 7 adopt automatic reset and manual reset respectively to achieve dual temperature control protection.
[0028] Furthermore, each end of the inner core 3 is provided with a blind hole 32. The inner ends of the two high-pressure water nozzles 6 are respectively fixedly sealed with a high-pressure resistant metal plug 8. The plug 8 is adapted to the blind hole 32 to position and limit the inner core 3, preventing it from moving inside the metal heating cylinder 2. The side of the plug 8 is provided with four water passage holes 81 that communicate with the central hole 80. The central hole 80 communicates with the high-pressure water nozzle 6 to prevent the plug 8 from blocking the water flow. The cold water inlet channel 10 and the hot water outlet channel 20 are each provided with a stepped cavity 200. The high-pressure water nozzle 6 includes a central column 62, which has a central channel 60 inside and a middle annular groove 61 on its outer wall. A first sealing ring 101 and a second sealing ring 102 are respectively provided outside the central column 62 and inside the middle annular groove 61, which are adapted to and sealed to the two stepped inner walls of the stepped cavity 200. The double sealing structure makes the high-pressure water nozzle 6 firmly and reliably sealed with the cold water inlet channel 10 and the hot water outlet channel 20, and can withstand high temperature and high pressure water flow to avoid leakage.
[0029] Furthermore, the inner core 3 is a solid cylinder with high strength and good high pressure resistance; the high pressure water nozzle 6 is connected and fixed to the upper metal sealing plate 51, the lower metal sealing plate 52, and the plug 8, as well as the metal heating cylinder 2 is connected and fixed to the upper metal sealing plate 51 and the lower metal sealing plate 52 by welding, which ensures stable connection, high strength, and the ability to withstand high pressure water flow.
[0030] This embodiment overcomes the defects and shortcomings of the prior art. By setting a spiral flow channel extending from top to bottom, the cross-sectional area of the water flow is greatly reduced, allowing the heating heat of the metal heating cylinder to be quickly transferred to the water flow. At the same time, the lengthened water flow channel meets the water production needs, converting the water in the entire water tank into a slender flow channel for rapid heating of the entire channel. This not only produces hot water quickly, efficiently, and with low average energy consumption, but also ensures high safety and produces hot water at high temperatures, fully meeting the rapid heating and high-temperature requirements of pressure coffee machines. Furthermore, spiral grooves are directly formed on the outer wall of the inner core, and the upper and lower sides of the metal heating cylinder... The upper and lower metal sealing plates are fixedly and sealed with high-pressure resistant connections at both ends. Each of the upper and lower metal sealing plates is fixedly and sealed with a high-pressure water nozzle, resulting in a high-pressure water flow channel structure with high strength and good pressure resistance. Testing shows that this high-pressure water rapid heating device can withstand water pressures up to 25 bar and normally and quickly produce high-temperature hot water and steam. Therefore, this invention is a high-pressure water rapid heating device for coffee machines that provides fast hot water production, high efficiency, low average energy consumption, and high pressure resistance. This device can instantly provide high-temperature, high-pressure hot water when coffee is needed, providing hot water immediately upon dispensing.
[0031] This invention can be widely applied in the field of coffee machine accessories.
Claims
1. A high-pressure water rapid heating device for a coffee machine, characterized in that: The assembly includes an insulating outer shell assembly (1), a metal heating cylinder (2), and an inner core (3). The metal heating cylinder (2) is disposed inside the insulating outer shell assembly (1). The outer wall of the inner core (3) is provided with a spiral groove (31). The inner core (3) is adapted to be housed in the inner cavity of the metal heating cylinder (2). The top of the side wall of the spiral groove (31) is tightly fitted and connected to the inner wall of the metal heating cylinder (2) so that a spiral guide channel (30) extending from top to bottom is formed between the spiral groove (31) and the inner wall of the metal heating cylinder (2). The upper and lower ends of the insulating outer shell assembly (1) are respectively provided with a cold water inlet channel (10) and a hot water outlet channel (20). The upper and lower ends of the metal heating cylinder (2) are respectively fixedly sealed with a high-pressure resistant upper metal sealing plate (51) and a lower metal sealing plate (52). The lower metal sealing plate (52) and the upper metal sealing plate (51) are respectively fixedly sealed and connected to a high-pressure water nozzle (6); the inner ends of the two high-pressure water nozzles (6) are respectively connected to the upper and lower openings of the guide channel (30), and the outer ends are respectively connected to the cold water inlet channel (10) and the hot water outlet channel (20) and sealed; forming a high-pressure water channel in which the cold water inlet channel (10), the high-pressure water nozzle (6) of the upper metal sealing plate (51), the guide channel (30), the high-pressure water nozzle (6) of the lower metal sealing plate (52), and the hot water outlet channel (20) are connected in sequence; the outer wall of the metal heating cylinder (2) is provided with an electric heating device (4) for heating the metal heating cylinder (2) and rapidly heating the water flowing through the guide channel (30) through the metal heating cylinder (2).
2. The high-pressure water rapid heating device for a coffee machine according to claim 1, characterized in that: The inner core (3) is provided with blind holes (32) at both ends. The inner ends of the two high-pressure water nozzles (6) are respectively fixedly sealed and connected to a plug (8). The plug (8) is adapted to the blind holes (32) to position and limit the inner core (3).
3. The high-pressure water rapid heating device for a coffee machine according to claim 2, characterized in that: The plug (8) has a water passage hole (81) on its side that is connected to the center hole (80), and the center hole (80) is connected to the high-pressure water nozzle (6).
4. The high-pressure water rapid heating device for a coffee machine according to claim 2, characterized in that: The high-pressure water nozzle (6) is connected and fixed to the upper metal sealing plate (51), the lower metal sealing plate (52), and the plug (8), as well as the metal heating cylinder (2) is connected and fixed to the upper metal sealing plate (51) and the lower metal sealing plate (52) by welding.
5. The high-pressure water rapid heating device for a coffee machine according to claim 2, characterized in that: The cold water inlet channel (10) and the hot water outlet channel (20) are respectively provided with stepped cavities (200); the high-pressure water nozzle (6) includes a central column (62), the central column (62) is provided with a central flow channel (60) and an outer wall is provided with a middle annular groove (61); a first sealing ring (101) and a second sealing ring (102) are respectively provided outside the central column (62) and inside the middle annular groove (61), respectively, which are adapted to and sealed to the two stepped inner walls of the stepped cavity (200).
6. The high-pressure water rapid heating device for a coffee machine according to claim 1, characterized in that: The electric heating device (4) is a coated heating resistor, which is spirally arranged around the outer wall of the metal heating cylinder (2). The two ends of the outer wall of the metal heating cylinder (2) are respectively provided with conductive clamps (41) which are electrically connected to the two ends of the coated heating resistor.
7. The high-pressure water rapid heating device for a coffee machine according to claim 1, characterized in that: One end of the metal heating cylinder (2) is connected to a grounding wire (42).
8. The high-pressure water rapid heating device for a coffee machine according to claim 1, characterized in that: The inner core (3) is a solid cylinder.
9. The high-pressure water rapid heating device for a coffee machine according to claim 1, characterized in that: The insulating outer shell assembly (1) includes a first half-shell (11), a second half-shell (12), a top cover (13), and a bottom cover (14). The first half-shell (11) and the second half-shell (12) are laterally connected and fixed to each other. The top cover (13) and the bottom cover (14) are respectively connected and fixed to the top and bottom of the first half-shell (11) and the second half-shell (12) to form a cage-like frame structure for enclosing and containing the metal heating cylinder (2). The cold water inlet channel (10) is located inside the top cover (13), and the hot water outlet channel (20) is located inside the bottom cover (14).
10. The high-pressure water rapid heating device for a coffee machine according to claim 9, characterized in that: The bottom cover (14) has a temperature measuring hole (15) on its side, which is connected to the hot water outlet channel (20). A first NTC temperature sensor (91) is installed in the temperature measuring hole (15) to measure and transmit the hot water outlet temperature.
11. The high-pressure water rapid heating device for a coffee machine according to claim 9, characterized in that: The bottom surface of the bottom cover (14) is provided with a temperature measuring groove (90). The temperature measuring groove (90) is provided with a pressure plate (93) with a size larger than its bottom opening. The two ends of a spring (94) press against the pressure plate (93) and the second NTC temperature sensor (92) respectively, so that the second NTC temperature sensor (92) is tightly attached to the lower metal sealing plate (52) for measuring and transmitting the temperature of the metal heating cylinder (2) so as to shut off the electric heating device (4) when the temperature exceeds the limit and prevent dry burning.
12. The high-pressure water rapid heating device for a coffee machine according to claim 9, characterized in that: The first half-shell (11) is provided with two mounting holes (70) for mounting two temperature control switches (7). The temperature control switches (7) are attached to the outside of the metal heating cylinder (2) and are used to turn off the electric heating device (4) when the set temperature is reached. The two temperature control switches (7) adopt automatic reset and manual reset respectively to achieve dual temperature control protection.