A high temperature sensitivity jump temperature controller

Abstract

A highly sensitive snap-action thermostat comprises a housing, a cover, and a bimetallic disc. A circular spring is disposed within a two-stage circular groove in the housing, the inner ring of which is supported in the middle of the plane of the first-stage circular groove. The bimetallic disc, supported on the outer ring of the circular spring, is elastically connected to the cover. Three to six evenly spaced limiting bosses are provided on the housing outside the two-stage circular groove. This structure allows the bimetallic disc to be in an elastically floating, pressurized state within the enclosed space formed by the two-stage circular groove and the cover. This ensures that, regardless of the installation position of the cover and the heating surface of a corresponding household appliance, the bimetallic disc and the cover maintain elastic contact before the snap action. During the snap action, the circular spring does not interfere with the bimetallic disc or the actuating rod. Consequently, the snap-action thermostat exhibits high temperature sensitivity and high actuation temperature stability.

Description

Technical Field

[0001] The present invention relates to the technical field of snap-type thermostats, in particular to a snap-type thermostat with high temperature sensitivity. Background Art

[0002] A snap-action thermostat uses a bimetallic disc as its heat-sensitive actuator. The bimetallic disc is enclosed in a housing or guide frame and a cover. When heated, the arc of the bimetallic disc slowly descends until the set temperature is reached, at which point it snaps back, pushing a leaf spring through an internal actuating rod, disconnecting the moving and fixed contacts. This type of thermostat is widely used in a variety of household appliances, including coffee makers, water dispensers, water heaters, microwave ovens, and electric heaters, for temperature control or protection. It serves as a key safety feature in heating appliances.

[0003] There is a snap-action thermostat, which mainly consists of a first housing 21, a first short rivet 22, a first cover 23, a first actuating rod 24, a first bimetallic disc 25, a first long rivet 26, a first terminal 27, a first spring 28, a first cover 29, a first moving contact 30, a first fixed contact 31 and a first fixed contact plate 32. Figure 1 As shown. Because this snap-action thermostat must ensure the unrestricted free rotation of the first bimetallic disc 25, the height of the enclosed space formed by the first cover 23 and the first housing 21, where the first bimetallic disc 25 is located, must be greater than the height of the curved portion of the first bimetallic disc 25. If the snap-action thermostat is installed in a household appliance at different locations, the gap between the first bimetallic disc 25 and the first cover 23 becomes uncertain.

[0004] Since the temperature-sensing deformation of the bimetallic disc is a process that changes from slow to sudden, a certain gap must be maintained between the operating rod and the bimetallic disc to ensure that the moving contact and the fixed contact remain closed during the slow deformation process. When the thermostat is installed upside down on the heating element, the bimetallic disc separates from the cover under the action of gravity, and a certain gap exists between them. The heat of the heating element is transferred to the bimetallic disc through the cover installed on its surface; when there is a gap between the bimetallic disc and the cover, the heat is conducted by radiation through the air with extremely poor thermal conductivity. The speed of heat conduction is much slower than the conduction through the metal solid when the bimetallic disc is in contact with the metal cover, resulting in the temperature sensitivity of the thermostat being much worse when installed upside down than when installed upright.

[0005] Chinese patent publication number CN209401557U, titled "A Snap-Type Thermostat for Rapid-Heating Tubes," discloses a structure for improving the temperature sensitivity of snap-type thermostats. The structure involves adding a gasket (3) between the bimetallic temperature sensor (2) and the guide frame (4), and opening a hole in the cover (1) to elevate the bimetallic temperature sensor so that it comes into direct contact with the heating element. This structure has the following disadvantages:

[0006] (1) After being installed on the heating element, the bimetallic temperature sensor 2 is subjected to rigid compression, and its operating temperature will change;

[0007] (2) The hole in the middle of the cover 1 will cause the bimetallic temperature sensor 2 to be exposed to the outside, which is easy to be damaged by collision during transportation and installation, thereby causing the operating temperature of the sudden jump thermostat to change or even fail.

[0008] Chinese patent publication number CN206584865U, entitled "Anti-dry-burn thermostat for instant heaters," discloses a bimetallic thermostat equipped with a spring 11, whose ends respectively abut against a ceramic guide frame 14 and a bimetallic strip 12. A hole is opened in the middle of the stainless steel cover 3, allowing the bimetallic strip 12 to protrude downward from the bottom surface of the stainless steel cover 3 by 0.1 to 1 mm. After the thermostat is installed on the heating surface, the bimetallic strip 12 is pressed into contact with the heating surface, in the hope of improving temperature sensitivity. However, the thermostat structure has the following drawbacks:

[0009] (1) The conical spring 11 acts on the middle part of the bimetallic strip 12. The elastic force of the conical spring 11 will hinder the bimetallic strip 12 from turning over, which will prolong the action time, thereby prolonging the time for arc generation when the moving and fixed contacts are separated, and shortening the service life of the thermostat.

[0010] (2) Since the central opening of the stainless steel cover 3 exposes the bimetallic strip 12, it is easy to be damaged by collision during transportation and installation, which may cause the operating temperature of the sudden jump thermostat to change or even fail. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a snap-action thermostat with high temperature sensitivity. Since a circular basin spring is provided between the shell and the bimetallic disc, the bimetallic disc can be in an elastic floating and pressurized state in the closed space formed between the shell and the cover. In this way, no matter where the cover of the snap-action thermostat and the heating surface of the household appliance that are tightly connected to each other are installed, it can be ensured that the middle part of the bimetallic disc maintains elastic contact connection with the cover before its snap action. Moreover, since the circular basin spring is only elastically contacted with the outer circumference of the bimetallic disc through the outer ring, it has no interference with the action and flipping of the bimetallic disc, so it has no effect on the action temperature of the snap-action thermostat, thereby significantly improving the temperature sensitivity and the stability of the action temperature of the snap-action thermostat.

[0012] The technical solution proposed by the present invention is as follows:

[0013] A high temperature sensitivity snap-type thermostat, comprising a housing, a short rivet, a cover, an action rod, a bimetallic disc, a long rivet, a terminal, a spring, a cover plate, a moving contact, a fixed contact and a fixed contact plate. A two-stage circular groove is provided in the middle of the housing 1. A circular vertical through hole is provided in the center of the two-stage circular groove to be connected to the action rod for up and down sliding. A circular basin spring piece is also provided. The circular basin spring piece is provided with an inner ring and an outer ring arranged in a high and low pattern. 3 to 6 equally distributed straight bars are connected between the inner ring and the outer ring. The circular basin spring piece is placed on the first-stage circular plane of the two-stage circular groove. The inner ring is in contact and connected with the outer side of the through hole of the first-stage circular plane. There is a clearance fit between the outer circumference of the outer ring and the second-stage outer ring vertical surface of the two-stage circular ring groove, the outer ring is elastically contacted and connected with the outer circumference of the bottom surface of the bimetallic disc, the middle part of the upper surface of the bimetallic disc is elastically contacted and connected with the middle part of the bottom surface of the cover, the outer circumference of the bimetallic disc and the second-stage outer ring vertical surface of the two-stage circular ring groove are clearance fit, and 3 to 6 equally distributed limiting bosses are provided on the outer shell of the second-stage outer ring vertical surface of the two-stage circular ring groove, and a corner of the square limiting boss facing the center of the second-stage circular ring plane is set as a vertical cylindrical surface, and the cylindrical surface is tangent to the second-stage outer ring vertical surface below.

[0014] The height of the circular basin spring in a free state is: when the cover is not encapsulated, the outer circumference of the bimetallic disc supported on the circular basin spring does not exceed the upper end surface of the limiting boss.

[0015] After the package is sealed, the circular spring piece is in a compressed state. At this time, the spring force F1 generated by the circular spring piece is 10 to 20 times the weight of the bimetallic disc.

[0016] After the bimetallic disc is actuated, the actuating rod is pushed toward the spring, the moving contact and the fixed contact are separated, and the circular spring is in a released state. At this time, the spring force F2 generated by the circular spring is 2 to 5 times the weight of the bimetallic disc.

[0017] The inner surface of the cover is provided with 3 to 6 grooves that match the shapes of the upper parts of the corresponding limiting bosses.

[0018] The central aperture of the inner ring of the circular basin shrapnel is slightly larger than the diameter of the through hole of the two-stage circular groove.

[0019] Compared with the prior art, the present invention has the following significant effects:

[0020] (1) Since a circular basin spring is provided on the first circular plane of the two-stage circular ring groove, the bimetallic disc supported on the outer circular ring of the upper end of the circular basin spring is in an elastic floating and pressurized state in the closed space formed by the two-stage circular ring groove and the cover. At this time, the bimetallic disc can not only float up and down or flip over in a sudden action, but also, no matter which angular position the cover of the sudden jump thermostat and the heating surface of the household appliance that are closely attached to each other are in a 360° space, before the sudden action, the middle part of the bimetallic disc always maintains elastic contact connection with the cover, thereby improving the temperature sensitivity of the sudden jump thermostat and the stability of the operating temperature; at the same time, since the circular basin spring is in a pressure state, the bimetallic disc can also float up and down or flip over in a sudden action. The spring force F1 in the contracted state and the spring force F2 in the released state are strictly controlled within a small range, not exceeding 20 times the weight of the bimetallic disc. Moreover, since the circular spring is only elastically connected to the outer circumference of the bimetallic disc through its outer ring, it has no interference with the sudden action and flipping of the bimetallic disc, and therefore has no effect on the accuracy of the operating temperature of the bimetallic disc. The operating temperature of the bimetallic disc in the sudden action thermostat of this structure is the same as the operating temperature of the sudden action thermostat in its free state. In this way, the sudden action thermostat becomes a sudden action thermostat that can be installed in all directions and has high temperature sensitivity and very stable operating temperature.

[0021] (2) 3 to 6 equally distributed limiting bosses are provided on the outer shell of the second-stage outer ring vertical surface of the two-stage circular groove. They are used to enable the bimetallic disc supported on the circular basin spring to obtain an accurate positioning position on the two-stage circular groove before sealing the cover, thereby providing favorable conditions for the smooth and quick sealing of the cover. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The utility model is a structural diagram of an existing sudden jump type temperature controller.

[0023] Figure 2 The figure is a schematic structural diagram of a high temperature sensitivity snap-type thermostat according to an embodiment of the present invention.

[0024] Figure 3 yes Figure 2 Schematic diagram of the structure of the snap-action thermostat with the cover removed.

[0025] Figure 4 yes Figure 2 Schematic diagram of the three-dimensional structure of the shell shown.

[0026] Figure 5 yes Figure 2 Schematic diagram of the structure of the circular basin shrapnel shown. DETAILED DESCRIPTION

[0027] The present invention is further described in detail by the following examples.

[0028] See also Figures 2 to 5 As shown, a high temperature sensitivity snap-type thermostat includes a housing 1, a short rivet 2, a cover 3, an operating rod 4, a bimetallic disc 5, a long rivet 6, a terminal 7, a spring 8, a cover 9, a moving contact 10, a fixed contact 11 and a fixed contact plate 12. A two-stage annular groove 1-2 is provided in the middle of the housing 1. A circular vertical through hole 1-2-4 is provided in the center of the two-stage annular groove 1-2 to connect with the operating rod 4 for vertical sliding connection. A circular basin is also provided. The shrapnel 13 is provided with an inner ring 13-1 and an outer ring 13-2 arranged in a high and low pattern. 3 to 6 straight strips 13-3 are connected between the inner ring 13-1 and the outer ring 13-2. The shrapnel 13 is placed on the first-stage circular plane 1-2-1 of the two-stage circular groove 1-2. The inner ring 13-1 is connected to the outer side of the through hole 1-2-4 of the first-stage circular plane 1-2-1. The outer circumference of the outer ring 13-2 is in contact with the second-stage outer ring vertical surface 1-2-3 of the two-stage circular ring groove 1-2, and there is a clearance fit between the outer circumference of the outer ring 13-2 and the second-stage outer ring vertical surface 1-2-3 of the two-stage circular ring groove 1-2. The outer ring 13-2 is elastically contacted and connected with the outer circumference of the bottom surface of the bimetallic disc 5. The middle part of the upper surface of the bimetallic disc 5 is elastically contacted and connected with the middle part of the bottom surface of the cover 3. The outer circumference of the bimetallic disc 5 and the second-stage outer ring vertical surface 1-2-3 of the two-stage circular ring groove 1-2 are in contact with each other. 3 to 6 equally distributed limiting bosses 1-1 are provided on the outer shell 1 of the second-stage outer ring vertical surface 1-2-3 of the two-stage circular ring groove 1-2. One of the square limiting bosses 1-1 has a corner facing the center of the second-stage circular ring plane 1-2-2 set as a vertical cylindrical surface 1-1-1, and the cylindrical surface 1-1-1 is tangent to the second-stage outer ring vertical surface 1-2-3 below.

[0029] The height of the circular basin spring piece 13 in the free state is such that when the cover 3 is not encapsulated, the outer circumference of the bimetallic disc 5 supported on the circular basin spring piece 13 does not exceed the upper end surface of the limiting boss 1-1.

[0030] After the sealing cover 3 is encapsulated, the circular spring piece 13 is in a compressed state. At this time, the spring force F1 generated by the circular spring piece 13 is 10 to 20 times the weight of the bimetallic disc 5 .

[0031] After the bimetallic disc 5 is actuated, the actuating rod 4 is pushed toward the spring 8, the moving contact 10 and the fixed contact 11 are separated, and the circular basin spring 13 is in a released state. At this time, the spring force F2 generated by the circular basin spring 13 is 2 to 5 times the weight of the bimetallic disc 5.

[0032] The inner surface of the cover 3 is provided with 3 to 6 grooves that match the shape of the upper portion of the corresponding limiting boss 1 - 1.

[0033] The central aperture of the inner ring 13-1 of the circular basin spring piece 13 is slightly larger than the diameter of the through hole 1-2-4 of the two-stage circular groove 1-2.

[0034] In this embodiment, before the sudden jump thermostat is packaged, the circular basin spring piece 13 is placed on the first-stage circular ring plane 1-2-1 of the two-stage circular ring groove 1-2, with the inner circular ring 13-1 at the bottom and the outer circular ring 13-2 at the top, and the bimetallic disc 5 is placed on the outer circular ring 13-2 of the circular basin spring piece 13. Since 3 to 6 limiting bosses 1-1 are provided, the height of the circular basin spring piece 13 in the free state is controlled. At this time, the bimetallic disc 5 is below the upper end surface of the limiting boss 1-1, the cover 3 is placed above the bimetallic disc 5, and then the package is performed. After packaging, the bimetallic disc 5 is located in the closed space formed by the cover 3 and the two-stage circular groove 1-2 and is in an elastic floating pressure state. At this time, the circular basin spring 13 is in a compressed state, and the circular basin spring 13 applies a spring force F1 to the bimetallic disc 5, ensuring that the jump-type thermostat can ensure direct elastic contact and connection between the bimetallic disc 5 and the cover 3 at any installation angle in the 360° three-dimensional space.

[0035] In this embodiment, the circular spring element 13 is stamped from stainless steel. Its height and rigidity in its free state ensure that the bimetallic disc 5 does not protrude above the upper end surfaces of the four limiting bosses 1-1 before installation on the cover 3. After installation, the compressed circular spring element 13 generates a spring force F1 that is 10 to 20 times the weight of the bimetallic disc 5, ensuring a tight elastic contact between the center of the bimetallic disc 5 and the cover 3. The spring force F2 of the circular spring element 13 in its released state after the bimetallic disc 5 snaps is 2 to 5 times the weight of the bimetallic disc 5, which is in the range of 1 to 2.5 gf. After the bimetallic disc 5 is actuated, its flipped middle portion is located in the basin cavity of the circular basin spring piece 13, but has no contact with the corresponding portion of the circular basin spring piece 13. Therefore, during the entire process of the bimetallic disc 5 suddenly flipping and pushing the actuating rod 4 to move downward, the circular basin spring piece 13 does not interfere with the bimetallic disc 5 and the actuating rod 4, thereby not affecting the actuating temperature and reset temperature of the snap-action thermostat.

[0036] In this embodiment, the cover 3 is made of aluminum alloy, which has a thermal conductivity of 158 W / (m·K). The bimetallic disc 5 is made of nickel-iron alloy, which has a thermal conductivity of 12 W / (m·K), both of which are much greater than the thermal conductivity of air, which is 0.024 W / (m·K). Therefore, the heat of the cover 3 can be quickly transferred to the bimetallic disc 5 through the elastic contact part and diffused throughout the entire bimetallic disc 5, resulting in a high temperature response sensitivity.

[0037] A comparative test was conducted using an existing snap-action thermostat (A) and this high-sensitivity snap-action thermostat (B). Using the double-slot method in Appendix BB of GB14536.10, the snap-action thermostat was brought into instantaneous contact from room temperature (28°C) to a constant-temperature (146±1°C) heating surface. Based on the thermostat disc's operating temperature of approximately 103°C, the temperature change during operation was approximately 63.2% of the total amplitude. The resulting operating time is approximately equal to the response time constant. The operating times of the two snap-action thermostats were recorded in the test. The results are shown in the table below:

[0038] Test results of existing snap-action thermostat (A) - horizontal upright orientation:

[0039]

[0040] Existing snap-action thermostat (A) - horizontal inverted orientation test results:

[0041]

[0042] The test results of this high temperature sensitivity snap-action thermostat (B) - horizontal upright direction:

[0043]

[0044] The high temperature sensitivity snap-action thermostat (B) - horizontal inverted direction test results:

[0045]

[0046] It can be seen that the test results of the high-sensitivity snap-action thermostat (B) in the upright and inverted directions are almost the same. When installed horizontally and inverted, its disconnection time is shortened by more than half compared to the existing snap-action thermostat (A), greatly improving the temperature sensitivity and achieving significant technical results.

Claims

1. A high temperature sensitivity snap-action thermostat, comprising a housing (1), a short rivet (2), a cover (3), an operating rod (4), a bimetallic disc (5), a long rivet (6), a terminal (7), a spring (8), a cover plate (9), a moving contact (10), a fixed contact (11) and a fixed contact plate (12), wherein a two-stage annular groove (1-2) is provided in the middle of the housing (1), a circular vertical through hole (1-2-4) is provided at the center of the two-stage annular groove (1-2), and the operating rod (4) is connected to the circular vertical through hole (1-2-4) for upward and downward sliding, and characterized in that: A circular basin shrapnel (13) is also provided. The circular basin shrapnel (13) is provided with an inner circular ring (13-1) and an outer circular ring (13-2) arranged in a high and low pattern. Three to six equally distributed straight strips (13-3) are connected between the inner circular ring (13-1) and the outer circular ring (13-2). The circular basin shrapnel (13) is placed on the first circular ring plane (1-2-1) of the two-stage circular ring groove (1-2). The inner circular ring (13-1) is in contact with the outer side of the through hole (1-2-4) of the first circular ring plane (1-2-1). The outer circumference of the outer circular ring (13-2) and the second outer circular ring vertical surface (1-2-3) of the two-stage circular ring groove (1-2) are in clearance fit. The outer circular ring (13-2) is in contact with the second outer circular ring vertical surface (1-2-3) of the two-stage circular ring groove (1-2). The outer circumference of the bottom surface of the bimetallic disc (5) is elastically contacted and connected, the middle portion of the upper surface of the bimetallic disc (5) is elastically contacted and connected with the middle portion of the bottom surface of the cover (3), the outer circumference of the bimetallic disc (5) and the second-stage outer ring vertical surface (1-2-3) of the two-stage circular groove (1-2) are clearance-fitted, and 3 to 6 equally distributed limiting bosses (1-1) are provided on the outer shell (1) of the second-stage outer ring vertical surface (1-2-3) of the two-stage circular groove (1-2), and one corner of the square limiting boss (1-1) facing the center of the second-stage circular plane (1-2-2) is set as a vertical cylindrical surface (1-1-1), and the cylindrical surface (1-1-1) is tangent to the second-stage outer ring vertical surface (1-2-3) below.

2. The high temperature sensitivity snap-type thermostat according to claim 1, characterized in that: The height of the circular basin shrapnel (13) in a free state is such that when the cover (3) is not encapsulated, the outer circumference of the bimetallic disc (5) supported on the circular basin shrapnel (13) does not exceed the upper end surface of the limiting boss (1-1).

3. The high temperature sensitivity snap-type thermostat according to claim 1, characterized in that: After the sealing cover (3) is encapsulated, the circular basin shrapnel (13) is in a compressed state. At this time, the spring force F1 generated by the circular basin shrapnel (13) is 10 to 20 times the weight of the bimetallic disc (5).

4. The high temperature sensitivity snap-type thermostat according to claim 1, characterized in that: After the bimetallic disc (5) is actuated, the actuating rod (4) is pushed toward the spring (8), the moving contact (10) and the fixed contact (11) are separated, and the circular basin spring (13) is in a released state. At this time, the spring force F2 generated by the circular basin spring (13) is 2 to 5 times the weight of the bimetallic disc (5).

5. The high temperature sensitivity snap-type thermostat according to claim 1, characterized in that: 3 to 6 grooves are provided on the inner surface of the cover (3) and the shapes of the upper parts of the corresponding limiting bosses (1-1) are matched.

6. The high temperature sensitivity snap-type thermostat according to claim 1, characterized in that: The central aperture of the inner circular ring (13-1) of the circular basin shrapnel (13) is slightly larger than the diameter of the through hole (1-2-4) of the two-stage circular groove (1-2).

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