A large current pressure type manual reset temperature limiter

Abstract

A high-current pressure-type manual reset temperature limiter is based on the structure of the existing pressure-type manual reset temperature limiter. A pure copper current-passing sheet is riveted and fixed at both ends of the moving contact piece. The middle section of the current-passing sheet is provided with 2 to 6 ripples and is located above the corresponding section of the moving contact piece without contacting it. The high-current pressure-type manual reset temperature limiter can pass a rated current of 40A and is suitable for over-temperature protection of household high-power electric heating appliances.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-type manual reset temperature limiters, and in particular to a high-current pressure-type manual reset temperature limiter for over-temperature protection of household high-power electric heating appliances. Background Art

[0002] Pressure-type manual reset temperature limiter is widely used in the temperature limit protection of household electric heating appliances such as electric water heaters and water boilers. By sensing the temperature of the electric heating appliance, when its thermostat fails, the heating tube continues to heat. When the temperature is too high, the temperature limiter will disconnect its switch bipolar, so that the heating tube stops working. It is necessary to manually press the reset rod after eliminating the circuit fault and lowering the temperature to turn the switch back on. The switch component of the pressure-type manual reset temperature limiter is connected in series with the heating tube to the mains power supply circuit. When the temperature of the heat source is too high, it will automatically disconnect the circuit to play an over-temperature protection role.

[0003] Chinese patent publication number CN2350796Y discloses a pressure-type manual reset temperature limiter. The spring sheet 4 has a moving contact riveted on one end, and the other end is riveted to the spring sheet rivet foot 6 (i.e., terminal) through rivets, and then fixed to the machine base 12 with rivets. The contacts are closed at ordinary times; when the temperature of the heat source rises, the membrane box 14 moves, causing the push rod 10 to move upward to lift the spring sheet 4, thereby disconnecting the contacts. When the temperature drops, the push rod 10 needs to be pressed to reset the contacts.

[0004] In the above structure, the spring sheet 4 is a cantilever beam with one end fixed and the other end free for bending and deformation. At the same time, the main circuit current flows through the spring sheet 4 through the spring sheet rivet foot 6, then flows through the contact and then flows to the static contact sheet 5. Therefore, the spring sheet 4 needs to be both elastic and conductive, and is usually made of tin bronze or beryllium bronze. However, the conductivity of tin bronze is 13~20%IACS, and the conductivity of beryllium bronze is only 16~25%IACS. When the rated current is too large, it will lose elasticity due to heat and thus cause the temperature limiter to fail, and even cause the plastic base to melt or carbonize and burn, resulting in serious safety hazards. If the cross-sectional area of ​​the spring sheet 4 is increased to reduce its internal resistance, on the one hand, increasing the width is limited by space, and on the other hand, increasing the thickness will increase its deformation force sharply (according to the material mechanics formula, the bending deformation force of the cantilever beam and the material thickness are in a cubic ratio). If the deformation force is too large, the existing general membrane box is not enough to push it to deform. If the membrane box is increased, the volume will increase and the cost will increase significantly.

[0005] At present, the maximum overload capacity of the pressure-type manual reset temperature limiter with such structure on the market is only 25A rated current. With the continuous introduction of high-power electric heating appliances, the temperature limiter with a rated current of 25A can no longer meet the requirements. If a high-power electric heating appliance with a rated current of 40A is forcibly connected to a pressure-type manual reset temperature limiter with a rated current of 25A, the temperature will soon exceed 100℃ due to the high current flowing during normal operation, causing the spring sheet to lose its elasticity, and the moving and static contacts will soon be unable to conduct. Therefore, it is necessary to develop a pressure-type manual reset temperature limiter with a rated current of 40A. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a large current pressure type manual reset temperature limiter, which can pass a rated current of 40A and is suitable for over-temperature protection of household high-power electric heating appliances.

[0007] The technical solutions proposed by the present invention are as follows:

[0008] A large current pressure type manual reset temperature limiter, comprising a capillary, a membrane box, a base, a cover plate and a push rod, wherein two sets of independent and mutually parallel electric contact switch circuits are arranged in a cavity formed by the base and the cover plate, wherein the electric contact switch circuit is composed of a static terminal with a static contact fixedly mounted on the right end, a moving contact piece with a moving contact fixedly mounted on the left end and a moving terminal, wherein the left end of the static terminal is fixed on the base, the moving contact is directly contacted and connected with the static contact, the right end of the moving contact piece is fixedly connected to the moving terminal after being riveted and fixedly connected to the base, and the moving contact of the cantilever beam structure is fixedly connected to the moving terminal. The sheet is preset with a downward rebound force, and the middle part of the push rod is provided with a front shoulder and a rear shoulder, which are respectively in contact with the corresponding parts of the two moving contact sheets, and the bottom end of the push rod is in contact with the membrane box sheet, and is provided with a current-transmitting sheet made of pure copper sheet. The current-transmitting sheet is composed of a left section, a middle section and a right section. The middle section of the current-transmitting sheet is provided with at least 2 continuous corrugations, the left end of the left section of the current-transmitting sheet is riveted and fixed to the left end of the moving contact sheet and the moving contact, the right end of the right section of the current-transmitting sheet is riveted and fixed to the right end of the moving contact sheet and the moving terminal, and the middle section of the current-transmitting sheet has no contact with the relative section of the moving contact sheet.

[0009] The moving contact piece is made of beryllium bronze, and the cross-sectional area of ​​the moving contact piece is: width 6-9mm×thickness 0.18-0.22mm. The cross-sectional area of ​​the flow sheet is: width 6-9mm×thickness 0.18-0.22mm. The middle section of the flow sheet is provided with 2-6 continuous corrugations.

[0010] Compared with the prior art, the present invention has the following significant effects:

[0011] The present invention is based on the structure of the existing pressure-type manual reset temperature limiter, and a pure copper current-passing sheet is riveted and fixed at both ends of the moving contact piece. The middle section of the current-passing sheet is provided with 2 to 6 corrugations and is located above the corresponding section of the moving contact piece, without contacting it. In this way, the newly added current-passing sheet has good flexibility and basically does not generate an additional force in the same direction as its rebound force on the moving contact piece, that is, the mechanical properties of the original switch mechanism are basically not changed, thereby realizing that the pressure-type manual reset temperature limiter can pass the rated current of 25A to 40A. The volume of the large-current pressure-type manual reset current limiter is the same as that of the existing pressure-type manual reset temperature limiter with an overload capacity of 25A rated current, and the temperature control accuracy is also the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The present invention is a structural schematic diagram of a large current pressure type manual reset temperature limiter in a contact-connected state.

[0013] Figure 2 yes Figure 1 The figure shows a schematic diagram of the structure of a large current pressure type manual reset temperature limiter in the contact disconnected state.

[0014] Figure 3 yes Figure 1 AA section view of the structure.

[0015] The numbers in the figure indicate: 1. capillary, 2. diaphragm box, 2-1. diaphragm box sheet, 3. base, 4. 1st moving terminal, 5. cover plate, 6. 1st moving contact piece, 6-1. left end portion of 1st moving contact piece, 6-2. right end portion of 1st moving contact piece, 7. 1st current-passing piece, 7-1. left section of 1st current-passing piece, 7-2. right section of 1st current-passing piece, 7-3. middle section of 1st current-passing piece, 8. push rod, 8-1. front shoulder of push rod, 8-2. rear shoulder of push rod, 9. 1st moving contact, 10. 1st static terminal, 11. 1st static contact, 16. 2nd moving contact piece, 17. 2nd current-passing piece, 17-3. middle section of 2nd current-passing piece. DETAILED DESCRIPTION

[0016] The present invention is further described in detail by the following examples.

[0017] See also Figure 1 , Figure 2 , Figure 3As shown, a large current pressure type manual reset temperature limiter includes a capillary 1, a membrane box 2, a base 3, a cover plate 5 and a push rod 8. Two sets of independent and mutually parallel electric contact switch circuits are arranged in the cavity formed by the base 3 and the cover plate 5. The electric contact switch circuit consists of a static terminal with a static contact fixed at the right end, a moving contact piece with a moving contact fixed at the left end, and a moving terminal. The left end of the static terminal is fixed on the base 3, the moving contact is connected to the static contact in a positive contacting manner, the right end of the moving contact piece is fixed to the moving terminal by riveting and then fixedly connected to the base 3, and the moving contact of the cantilever beam structure is fixed to the base 3. The sheet is preset with a downward rebound force, and a front shoulder 8-1 and a rear shoulder 8-2 are provided in the middle of the push rod 8, which are respectively in contact with the corresponding parts of the two moving contact sheets, and the bottom end of the push rod 8 is in contact with the membrane box sheet 2-1, and is provided with a current-transmitting sheet made of pure copper sheet. The current-transmitting sheet is composed of a left section, a middle section and a right section. The middle section of the current-transmitting sheet is provided with at least 2 continuous corrugations, the left end of the left section of the current-transmitting sheet is riveted and fixed to the left end of the moving contact sheet and the moving contact, the right end of the right section of the current-transmitting sheet is riveted and fixed to the right end of the moving contact sheet and the moving terminal, and the middle section of the current-transmitting sheet has no contact with the relative section of the moving contact sheet.

[0018] The moving contact piece is made of beryllium bronze, and the cross-sectional area of ​​the moving contact piece is: width 6-9mm×thickness 0.18-0.22mm. The cross-sectional area of ​​the flow sheet is: width 6-9mm×thickness 0.18-0.22mm. The middle section of the flow sheet is provided with 2-6 continuous corrugations.

[0019] The structure and working process of a pressure-type manual reset temperature limiter with an overload capacity of 40A rated current are described in detail below. The temperature limiter mainly consists of a capillary 1, a diaphragm box 2, a base 3, a first moving terminal 4, a second moving terminal, a cover plate 5, a first moving contact piece 6, a second moving contact piece 16, a first current-passing piece 7, a second current-passing piece 17, a push rod 8, a front shoulder 8-1 of the push rod, a rear shoulder 8-2 of the push rod, a first moving contact 9, a second moving contact, a first static terminal 10, a second static terminal, a first static contact 11, and a second static contact. The left section 7-1 of the first current-passing piece 7 and the left end 6-1 of the first moving contact piece are riveted to the first moving contact 9 at the same time, and the right section 7-2 of the first current-passing piece 7 and the left end 6-1 of the first moving contact piece are riveted to the first moving contact 9 at the same time. The right end 6-2 of the contact piece is fixedly connected to the first moving terminal 4 at the same time, and the middle section 7-3 of the first current-passing piece 7 is provided with 5 corrugations and has no contact with the opposite section of the first moving contact piece 6; similarly, the left section of the second current-passing piece 17 and the left end of the second moving contact piece are riveted to the second moving contact at the same time, and the right section of the second current-passing piece 17 and the right end of the second moving contact piece are fixedly connected to the second moving terminal at the same time, and the middle section 17-3 of the second current-passing piece 17 is also provided with 5 corrugations and has no contact with the opposite section of the second moving contact piece 16; the capillary 1 is welded to the membrane box 2, and is filled with and sealed with a working fluid. In this example, the first static terminal 10 is connected to the mains phase line through its internal threaded joint, the second static terminal is connected to the mains neutral line through its internal threaded joint, and the first moving terminal 4 and the second moving terminal are connected to the electric heating device load through their internal threaded joints. When the capillary tube 1 senses a sufficiently high temperature, the working fluid liquid is partially vaporized, generating pressure, which pushes the diaphragm box sheet 2-1 of the diaphragm box 2 to flip, and pushes the push rod 8 to move upward, and the front shoulder 8-1 and the rear shoulder 8-2 of the push rod respectively push the first moving contact piece 6 and the second moving contact piece 16 to bend and deform upward, and the first current-passing piece 7 and the second current-passing piece 17 follow the deformation, so that the first moving contact 9 and the second moving contact are disconnected from the first static contact 11 and the second static contact respectively, that is, the phase line and the neutral line of the main power supply circuit are disconnected at the same time, which plays a role in temperature limiting protection. When the temperature drops, the push rod 8 is manually pressed to reset, and the diaphragm box sheet 2-1 of the diaphragm box 2 is pressed back to the initial state. At the same time, the push rod 8 no longer lifts the first moving contact piece 6 and the second moving contact piece. With the help of the rebound force of the first moving contact piece 6 and the second moving contact piece, the first current transfer piece 7 and the second current transfer piece 17 are respectively brought to restore the first moving contact 9 and the second moving contact to the state of being connected with the first static contact 11 and the second static contact.

[0020] When the push rod 8 lifts the first moving contact piece 6, the first moving contact piece 6 is a cantilever beam bending deformation, the outer side (the side away from the center of the bending deformation radius of curvature) is subjected to tensile stress, and the inner side (the side close to the center of the bending deformation radius of curvature) is subjected to compressive stress. The first flow sheet 7 is on the first moving contact piece 6, which is the inner side of the bending deformation and is subjected to lateral contraction deformation force. Since the five corrugated structures of the middle section 7-3 of the first flow sheet 7 are fully flexible, the corrugations are easily deformed by lateral compression, and only The wave crest becomes slightly higher and the wave distance becomes slightly shorter, and the lateral deformation stiffness is much smaller than the elastic modulus of the material, so basically no additional reaction force is generated; the stress conditions of the second moving contact piece 16 and the second current-transmitting piece 17 of the other set of electric contact switch circuit are the same; it can be considered that the push rod 8 only needs to overcome the rebound force of the moving contact piece to move, and the membrane box 2 can still use the previous common membrane box without increasing it; when the push rod 8 is reset, the rebound force of the moving contact piece itself can drive the corresponding current-transmitting piece to return to its initial position.

[0021] In this embodiment, two moving terminals, moving contacts, overcurrent plates, moving contacts, static terminals, and static contacts of the same shape and structure are used. The push rod adopts a double-shoulder structure to push two switches at the same time, disconnecting the phase line and neutral line of the main power supply circuit at the same time, thereby achieving a safer purpose.

[0022] In this embodiment, the first and second moving contact pieces are made of beryllium copper sheets with a thickness of 0.2 mm and a width of 8 mm, and the first and second current-carrying pieces are made of pure copper sheets with the same width and thickness as the first and second moving contact pieces. Since the resistivity of pure copper is as low as 1.72×10 -8 Ωm (conductivity 100% IACS), which is only about 1 / 4 to 1 / 5 of that of beryllium bronze, so most of the current flows through the overcurrent sheet. According to actual measurements, the temperature rise is less than 25K when a current of 40A is passed, which fully meets the requirement of passing a rated current of 40A and will not bring any adverse effects on the resilience of the moving contact piece and the plastic base 3.

Claims

1. A large current pressure type manual reset temperature limiter, comprising a capillary (1), a membrane box (2), a base (3), a cover plate (5) and a push rod (8), wherein two groups of independent and mutually parallel electric contact switch circuits are arranged in a cavity formed by the base (3) and the cover plate (5), wherein the electric contact switch circuit is composed of a static terminal with a static contact fixedly mounted on the right end, a moving contact piece with a moving contact fixedly mounted on the left end and the moving terminal, wherein the left end of the static terminal is fixed on the base (3), the moving contact is directly in contact with the static contact, the right end of the moving contact piece is fixedly connected to the base (3) after being riveted, and the moving contact piece of the cantilever beam structure is preset with a downward rebound force, the middle part of the push rod (8) is provided with a front shoulder (8-1) and a rear shoulder (8-2), which are respectively in contact with the corresponding parts of the two moving contact pieces, and the bottom end of the push rod (8) is in contact with the membrane box piece (2-1), characterized in that: A current-carrying plate made of pure copper sheet is provided, which consists of a left section, a middle section and a right section. The middle section of the current-carrying plate is provided with at least two continuous corrugations. The left end of the left section of the current-carrying plate is riveted and fixed to the left end of the moving contact piece and the moving contact. The right end of the right section of the current-carrying plate is riveted and fixed to the right end of the moving contact piece and the moving terminal. The middle section of the current-carrying plate has no contact with the opposite section of the moving contact piece.

2. The high current pressure type manual reset temperature limiter according to claim 1 is characterized in that: The moving contact piece is made of beryllium bronze, and the cross-sectional area of ​​the moving contact piece is: width 6-9 mm×thickness 0.18-0.22 mm.

3. The high current pressure type manual reset temperature limiter according to claim 1 is characterized in that: The cross-sectional area of ​​the flow plate is: width 6-9 mm×thickness 0.18-0.22 mm.

4. The high current pressure type manual reset temperature limiter according to claim 1 is characterized in that: The middle section of the flow plate is provided with 2 to 6 continuous corrugations.

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