Limiting locking and unlocking mechanism and normally-open type fireproof door electric door closer comprising limiting locking and unlocking mechanism

Abstract

The utility model relates to a limit locking and unlocking mechanism and a normally open type fireproof door electric door closer comprising the same, the limit locking and unlocking mechanism comprises a limit support, a driving assembly and an execution assembly, the limit support is fixed in a sliding groove, the driving assembly and the execution assembly are both arranged in the limit support, and the limit support is fixed in the sliding groove. The execution assembly is composed of a double-end curved surface connecting rod, an upper pin shaft and a lower pin shaft, the limiting support comprises fixing plates which are oppositely arranged in a spaced mode in the front-back direction, horizontal sliding ways and vertical sliding ways are correspondingly formed in the two fixing plates, the double-end curved surface connecting rod is located between the two fixing plates, and the front end and the rear end of the upper pin shaft are slidably connected into the horizontal sliding ways. The front end and the rear end of the lower pin shaft are slidably connected into the vertical slideways. The door closer locking and unlocking mechanism has the advantages that the traditional idea that the door closer locking and unlocking mechanism is designed according to the lever principle is broken through, some mechanisms playing a middle transmission role are omitted, the number of spare and accessory parts is small, the structure is simple, assembling is convenient, and therefore the failure rate is low, cost is low, and safety is good; the door closer has multiple door closing modes and is comprehensive in function.

Description

Technical Field

[0001] The utility model belongs to the technical field of building fire safety equipment, relates to the structural improvement of an electric door closer, and particularly relates to a limit locking and unlocking mechanism and a normally open fire door electric door closer including the same. Background Art

[0002] Fire door closers are mainly applied to fire doors in various public places or commercial occasions. Due to the large flow of people in public places or commercial occasions, the fire doors are frequently opened and closed. The sound of the fire doors hitting the door frames is incompatible with the quiet and peaceful public environment, and the pedestrian passage efficiency will be greatly reduced. At the same time, the high-frequency impact between the fire doors and the door frames will also sharply shorten the service life of the fire door system. Fire doors in places where people often pass through in buildings should preferably be normally open fire doors, and the normally open fire doors should be able to automatically close in case of a fire and should have the function of signal feedback.

[0003] The normally open fire door electric door closer mainly has two working states: In the daily state, the limit locking mechanism built in the fire door electric door closer takes effect, keeping the fire door normally open; when a fire alarm occurs, the communication module of the fire door electric door closer receives the door closing signal from the system host, making the limit locking ineffective, and the fire door closes, and after closing in place, it feeds back information to the system host. In the prior art, the fire door closer should include three door closing methods, namely: a. Electric control for automatic door closing; b. Manual lever for door closing; c. Forced push for door closing. These three door closing methods correspond to different usage scenarios: Electric control for door closing is applied to the remote control room; manual lever for door closing is mainly convenient for engineering and technical personnel to install and debug; forced door closing is applied to the fire scene for emergency door closing by escape personnel.

[0004] Currently, the existing normally open fire door electric door closers on the market have the following problems or deficiencies:

[0005] I) The normally open fire door closer only has the function of electric control for door closing, which cannot meet various application scenarios. Most importantly, when a fire occurs and emergency door closing is required, it is easy to damage the door closer, causing the spread of the fire and easily leading to major safety accidents.

[0006] (II) Although some of the existing door closers on the market can achieve the function of forced door closing, the magnitude of the forced door closing force cannot be relatively accurately limited within a certain range. There are two reasons as follows: 1) The transmission structure is relatively complex, and the influencing factors of the force magnitude are relatively complex; 2) The holding force inside the product is unstable and cannot be accurately controlled. The above two reasons will both lead to the inability to accurately define the forced door closing force. If the set value of the forced door closing force is too small, in the normal state, it is easy to be affected by factors such as wind pressure and accidental collision, resulting in the accidental closing of the fire door; in addition, if the set value of the forced door closing force is too large, in an emergency, it is very difficult to forcibly close the fire door, or the product will be damaged after forced closing, resulting in the inability to effectively isolate the fire source and being unfavorable for the safe escape of personnel.

[0007] (III) There are many parts, the structure is complex, and the assembly is difficult. Therefore, the product failure rate is high, resulting in high comprehensive costs. Therefore, it is necessary to improve the structure of the fire door closer in the existing technology to solve the above technical problems. Utility Model Content

[0008] The present utility model provides a limit locking and unlocking mechanism and a normally open fire door electric door closer including the same, aiming to overcome the above deficiencies existing in the electric door closer with a conventional structure in the prior art.

[0009] The technical solution for the present utility model to solve the above technical problems is as follows: A limit locking and unlocking mechanism is used to limit, lock, unlock and release a slider on the opening slideway at the lower side of the chute of a normally open fire door electric door closer. It includes a limit bracket, a driving component and an execution component. The limit bracket is fixed in the chute, and both the driving component and the execution component are arranged in the limit bracket. The execution component is composed of a double-headed curved surface connecting rod, an upper pin shaft and a lower pin shaft. The upper pin shaft and the lower pin shaft are respectively vertically fixed to the upper end and the lower end of the double-headed curved surface connecting rod in the front-rear direction. The limit bracket includes fixing plates arranged at intervals relatively in the front and rear. Horizontal slideways and vertical slideways are correspondingly opened on both of the fixing plates. The double-headed curved surface connecting rod is located between the two fixing plates. The front and rear ends of the upper pin shaft are slidably connected in the horizontal slideway, and the front and rear ends of the lower pin shaft are slidably connected in the vertical slideway. When the telescopic end of the driving component extends, it can push the upper end head to move in the horizontal slideway, and at the same time, the lower end head moves downward along the vertical slideway and abuts against the hook head of the slider for limit locking.

[0010] Based on the above technical solution, the present utility model can also be improved as follows.

[0011] Further, the double-headed curved surface connecting rod is composed of cylindrical heads at both ends and an intermediate rod connecting the two cylindrical heads. The axis of the intermediate rod is perpendicular to the axis of the cylindrical head.

[0012] Furthermore, one end of the horizontal slide is connected to the upper end of the vertical slide, and a non-return bar extending obliquely toward the horizontal slide is provided at the upper end of the vertical slide, and the upper part of the non-return bar is hollowed out to form a yield groove.

[0013] Furthermore, the anti-return stop bar is in the shape of an arc bar, and rounded corners are used for transition at the upper and lower edges of the end surface of one end of the anti-return stop bar facing the horizontal slide and at the junction with the side wall of the vertical slide.

[0014] Furthermore, the driving component is a bidirectional holding electromagnet, and the telescopic end is a free end of a push rod of the bidirectional holding electromagnet.

[0015] Furthermore, the position limiting bracket is provided with an inspection hole for a screwdriver or a pin to be inserted into to move the push rod to extend or retract.

[0016] Furthermore, it also includes a manual lever, one end of which is located outside the limit bracket, and the other end of which extends into the limit bracket and is connected to the push rod.

[0017] Furthermore, the hook head is pressed against the curved surface of the upper end through an inclined surface, the angle between the inclined surface and the horizontal plane is α, and the angle value of α is between 50-80 degrees. When the upper end is pressed against the hook head, the angle between the double-headed curved connecting rod and the horizontal plane is β, and the angle value of β is between 70-80 degrees.

[0018] Furthermore, the double-ended curved connecting rod is made of wear-resistant and weather-resistant hard metal or hard plastic.

[0019] The utility model also provides a normally open fireproof door electric door closer, which includes a slide groove, a slider, a transmission connecting rod, a hydraulic device, an electric control mechanism and the above-mentioned limit locking and unlocking mechanism, one end of the transmission connecting rod is connected to the hydraulic device, and the other end is connected to the slider, and one end of the lower surface of the slider is provided with the hook head for locking the limit with the upper end of the double-headed curved connecting rod.

[0020] Compared with the prior art, the beneficial effects of the utility model are:

[0021] The actuator assembly of the limit lock and unlock mechanism of a normally open electric door closer with a conventional structure usually includes many parts and components that are connected to each other in a transmission manner. The actuator assembly mainly uses the lever principle to convert the large door closing force provided by the hydraulic device when the fire door is normally open into a smaller door opening state holding force provided by a driving component such as an electromagnet. Due to the large number of parts and complex structure, the actuator assembly is not only inconvenient to install and maintain, but also has a high manufacturing cost and is more prone to failure. The actuator assembly of the limit lock and unlock mechanism provided by the utility model only includes a double-headed curved connecting rod and upper and lower pins, which are used in conjunction with the horizontal and vertical slides on the limit bracket, breaking through the traditional concept of designing using the lever principle, omitting some mechanisms that play an intermediate transmission role, having a small number of parts, a simple structure, and easy assembly. Therefore, the product has a low failure rate during use, low cost and good safety.

[0022] The limit locking and unlocking mechanism provided by the utility model has a simple structure and few parts, so the force transmission process is also relatively simple, and there are fewer factors affecting the forced door closing force. Therefore, the forced door closing force range can be accurately designed and limited, and the deficiency that the forced door closing force of the door closer with forced door closing function in the prior art cannot be relatively accurately limited within a certain range is effectively overcome.

[0023] The normally open fireproof door electric door closer provided by the utility model can include three closing modes: electric control door closing, manual lever door closing and forced push door closing. It can correspond to different usage scenarios, has comprehensive functions and good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An axonometric view of a normally open fire door electric door closer equipped with the limit locking and unlocking mechanism provided by the utility model;

[0025] Figure 2 for Figure 1 A cross-sectional view of a slider, a slide slot and various components in the slide slot of the electric door closer shown;

[0026] Figure 3 for Figure 1 An axonometric view of a limit bracket of a limit locking and unlocking mechanism in the electric door closer shown;

[0027] Figure 4 for Figure 1 An axonometric view of an actuator assembly of a limit locking and unlocking mechanism in the electric door closer shown;

[0028] Figure 5 This is an enlarged view of the actuator after it is installed in the horizontal and vertical slides of the limit bracket;

[0029] Figure 6 for Figure 1 A cross-sectional view of a locked state of a limit lock and unlock mechanism in the electric door closer shown;

[0030] Figure 7 is Figure 1 a sectional view of the limit locking and unlocking mechanism of the electric door closer shown in the unlocked state;

[0031] Figure 8 is a schematic diagram when the manual lever of the limit locking and unlocking mechanism is a rotatable lever;

[0032] Figure 9 is a schematic diagram when the manual lever of the limit locking and unlocking mechanism is a horizontally slidable lever.

[0033] In the accompanying drawings, the list of components represented by each reference numeral is as follows:

[0034] 10, chute; 20, slider; 30, limit bracket; 40, drive assembly; 50, execution assembly; 60, transmission connecting rod; 70, hydraulic device;

[0035] 201, hook head; 301, fixing plate; 302, horizontal slideway; 303, vertical slideway; 304, anti-reverse stop bar; 305, relief groove; 306, manual lever; 401, push rod; 501, double-headed curved surface connecting rod; 502, upper pin shaft; 503, lower pin shaft; 504, upper end head; 505, lower end head. Specific embodiments

[0036] The principles and features of the present invention will be described below in conjunction with the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0037] In the description of the present invention, if terms indicating directions such as "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", etc. are used, the directions or positional relationships indicated are based on the directions or positional relationships shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be construed as a limitation to the present invention.

[0038] Such as Figures 1 to 9As shown in the figure, the present utility model provides a limit locking and unlocking mechanism, which is used to limit, lock or unlock and release a slider 20 on the lower side opening slideway of a chute 10 of an electric door closer for a normally open fire door. The limit locking and unlocking mechanism includes a limit bracket 30, a driving component 40 and an execution component 50. The limit bracket 30 is fixed in the chute 10, and the driving component 40 and the execution component 50 are both arranged in the limit bracket 30. The execution component 50 is composed of a double-headed curved surface connecting rod 501, an upper pin shaft 502 and a lower pin shaft 503. The upper pin shaft 502 and the lower pin shaft 503 are respectively vertically fixed to the upper end head 504 and the lower end head 505 of the double-headed curved surface connecting rod 501 in the front-back direction. The limit bracket 30 includes fixing plates 301 arranged at intervals opposite to each other in the front-back direction. Horizontal slideways 302 and vertical slideways 303 are correspondingly formed on both of the fixing plates 301. The double-headed curved surface connecting rod 501 is located between the two fixing plates 301. The front and rear ends of the upper pin shaft 502 are slidably connected in the horizontal slideways 302, and the front and rear ends of the lower pin shaft 503 are slidably connected in the vertical slideways 303. When the telescopic end of the driving component 40 extends, it can push the upper end head 504 to move in the horizontal slideways 302, and at the same time, the lower end head 505 moves downward along the vertical slideways 303 and abuts against the hook head 201 of the slider 20 to limit and lock it.

[0039] It should be noted that the limit bracket realizes the axial position adjustment and fixed installation in the chute through fastening screws. When the driving component makes the telescopic end extend in place and gives a holding force, the double-headed curved surface connecting rod is pushed to rotate, and the lower end extends downward and abuts against and locks the hook head of the slider. After the driving component stops giving the holding force to the telescopic end, the upper end head of the double-headed curved surface connecting rod loses the abutting force against the hook head and unlocks. Specifically, as Figures 5 to 7 shown, during the elongation process of the telescopic end, the upper pin shaft moves along the horizontal slideway in the positive X-axis direction, and the lower pin shaft moves along the vertical slideway in the positive Y-axis direction (here, the positive Y-axis direction is the vertically downward direction). In this way, the entire double-headed curved surface connecting rod rotates, and the lower end head gradually extends out from the lower end of the vertical slideway and abuts against the inclined surface of the hook head of the slider to realize limit locking. When unlocking is required, the driving component is powered on and the telescopic end moves in the negative X-axis direction. The lower end head of the double-headed curved surface connecting rod loses the abutting and limiting effect of the telescopic end on it. Therefore, the slider can move in the positive X-axis direction under the action of the closing force of the hydraulic device transmitted through the transmission connecting rod, disengaging from the double-headed curved surface connecting rod. Subsequently, the slider continues to move in the positive X-axis direction under the action of the hydraulic device until the fire door closes in place.

[0040] Under the action of the driving component, the upper pin shaft moves in the positive X-axis direction, the lower pin shaft moves in the positive Y-axis direction, the double-headed curved surface connecting rod rotates, and the lower end head moves in the positive Y-axis direction and locks into the hook head of the slider, locking the movement of the slider. As Figure 6As shown in the figure, the mechanism is locked. In this locked state, the force exerted by the slider on the double-ended curved connecting rod through the hook head will disperse most of the force in the Y direction. The force in the Y direction is borne by the limit bracket, and a small part of the force acts in the X direction. The drive component only needs a small force to keep the slider locked. After unlocking, the hook head and the double-ended curved connecting rod are disengaged. Figure 7 As shown, after the driving assembly releases the holding force, the slider hook loses the ability to counteract the force exerted by the hydraulic device on the slider in the door closing direction, and the slider and the double-ended curved connecting rod move away from each other to complete the unlocking, and under the action of the hydraulic device, the fire door will automatically close.

[0041] In one embodiment of the present invention, Figure 4 and Figures 6 to 9 As shown, the double-ended curved connecting rod 501 is composed of cylindrical heads at both ends and an intermediate rod connecting the two cylindrical heads, and the axis of the intermediate rod is perpendicular to the axis of the cylindrical heads.

[0042] It is understandable that the appearance of the double-ended curved connecting rod is similar to a link of a bicycle transmission chain, but the specific structure is different. The cylindrical head and the middle rod of the double-ended curved connecting rod in the utility model are integrally formed, and the two cylindrical heads are provided with through holes along the central axis for the upper pin shaft or the lower pin shaft to pass through and fix. The middle section of the through hole channel is provided with an anti-slip cylindrical ring convex, and the middle part of the upper pin shaft or the lower pin shaft is provided with a ring groove that matches the anti-slip cylindrical ring convex, and vice versa. It should be noted that the double-ended curved connecting rod of the utility model is an axisymmetric and centrosymmetric design, mainly to enable the product to achieve error prevention during assembly and increase the interchangeability of batch parts. Double-ended curved connecting rods of other shapes or structural forms should also be included in the protection scope of the utility model if they can achieve the mechanical transmission effect that is basically the same, equivalent or similar to that of the utility model, such as the double-ended curved connecting rod adopts a non-axisymmetric or centrosymmetric structure, or the double-ended curved connecting rod adopts a split assembly molding, etc.

[0043] In one embodiment of the utility model, one end of the horizontal slide 302 is connected to the upper end of the vertical slide 303, and a non-return bar 304 extending obliquely toward the horizontal slide 302 is provided at the upper end of the vertical slide 303, and a clearance groove 305 is formed by hollowing out the top of the non-return bar 304.

[0044] It should be noted that a horizontal slide does not mean strictly along the horizontal direction. Similarly, a vertical slide does not mean strictly along the vertical direction. Products with the above-mentioned slides that have a certain angle deviation during specific production should also be included in the protection scope of the present utility model.

[0045] In an embodiment of the present utility model, the anti-reverse stop bar 304 is in an arc strip shape, and fillet transitions are used at both the upper and lower edges of the end face of the anti-reverse stop bar 304 facing the horizontal slideway 302 and at the junction with the side wall of the vertical slideway 303.

[0046] The setting of the anti-reverse stop bar and the relief groove can ensure that after the upper pin shaft of the double-headed curved surface connecting rod extends upward along the vertical slideway and contacts the anti-reverse stop bar, when a greater force is applied, the anti-reverse stop bar is elastically deformed towards the relief groove, so that the upper pin shaft can smoothly slide into the horizontal slideway, and then the anti-reverse stop bar resets. The end of the anti-reverse stop bar facing the horizontal slideway can effectively prevent the upper pin shaft from disengaging from the horizontal slideway in the natural state.

[0047] In an embodiment of the present utility model, the driving assembly 40 is a bidirectional holding electromagnet, and the telescopic end is the free end of a push rod 401 of the bidirectional holding electromagnet. The bidirectional holding electromagnet has two shafts, the front and the rear. The free end of the front shaft is the telescopic end, which contacts and interacts with the upper end head curved surface wall (cylindrical wall) of the double-headed curved surface connecting rod. A reset spring member is provided at the rear shaft, and the rear shaft can also be used to connect with a manual pulling rod.

[0048] In an embodiment of the present utility model, a maintenance hole is provided on the limit bracket 30 for a screwdriver or a pin to extend into to toggle the telescopic movement of the push rod 401.

[0049] In an embodiment of the present utility model, as Figure 8 and Figure 9 shown, it further includes a manual pulling rod 306. One end of the manual pulling rod 306 is located outside the limit bracket 30, and the other end extends into the limit bracket 30 and is connected to the push rod 401.

[0050] It should be noted that, in Figure 8 , the middle of the manual pulling rod is rotatably connected to the limit bracket. One end of the manual pulling rod is located inside the limit bracket and is connected to the rear shaft of the driving assembly, and the other end extends out from a long slot opened on the limit bracket. In Figure 9 , the manual pulling rod is horizontally slidably connected to the limit bracket. A part of the manual pulling rod is located outside the limit bracket for convenient manual operation by a person, and the other part extends into the limit bracket and is connected to the rear shaft of the driving assembly.

[0051] In an embodiment of the present utility model, the hook head 201 abuts against the curved surface part of the upper end head 504 through an inclined surface. The included angle between the inclined surface and the horizontal plane is α, and the angle value of α is between 50 - 80 degrees. When the upper end head 504 abuts against the hook head 201, the included angle between the double-headed curved surface connecting rod 501 and the horizontal plane is β, and the angle value of β is between 70 - 80 degrees.

[0052] It should be noted that the specific angular value ranges selected for the above-mentioned included angles α and β are only preferred angular values rather than the angles that must be selected to implement the present utility model. During actual production, if the driving component can provide a relatively large holding force, other relatively smaller values can also be selected for the above-mentioned angular values.

[0053] In an embodiment of the present utility model, the double-headed curved surface connecting rod 501 is made of wear-resistant and weather-resistant hard metal or hard plastic.

[0054] The present utility model also provides an electric door closer for normally open fire doors, which includes a chute 10, a slider 20, a transmission connecting rod 60, a hydraulic device 70, an electric control mechanism, and the above-mentioned limit locking and unlocking mechanism. One end of the transmission connecting rod 60 is connected to the hydraulic device 70, and the other end is connected to the slider 20. One end of the lower surface of the slider 20 is provided with the hook head 201 for abutting, locking, and limiting the upper end 504 of the double-headed curved surface connecting rod 501.

[0055] It should be noted that the electric control mechanism of the above-mentioned electric door closer for normally open fire doors includes a circuit board assembly, a door closing detection assembly, etc. The circuit board assembly is installed at the corresponding position of the limit bracket as the core component of the control system, used to control the operation of the driving component, and as the control center for feedback of opening and closing signals; the door closing detection assembly is installed in the tail end of the chute, which includes a micro switch. When the slider moves to the tail end of the chute and presses the micro switch elastic piece of the door closing detection assembly, the door closing signal can be immediately fed back to the circuit board assembly, and then the door closing signal is fed back to the fire control host to form a closed loop of fire control management.

[0056] The above are only the preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A limit locking and unlocking mechanism is used to limit, lock, unlock and release a slider (20) on the lower opening slideway of a chute (10) of an electric door closer for a normally open fire door. It is characterized in that The invention comprises a limit bracket (30), a driving assembly (40) and an execution assembly (50), wherein the limit bracket (30) is fixed in the slide groove (10), the driving assembly (40) and the execution assembly (50) are both arranged in the limit bracket (30), the execution assembly (50) is composed of a double-headed curved surface connecting rod (501), an upper pin shaft (502) and a lower pin shaft (503), the upper pin shaft (502) and the lower pin shaft (503) are respectively fixed vertically to the upper end (504) and the lower end (505) of the double-headed curved surface connecting rod (501) in the front-back direction, the limit bracket (30) comprises a fixing plate (301) arranged relatively spaced apart in the front and back directions, the two fixing plates (301) are arranged in a spaced relationship with each other, and the fixing plates (301) are arranged in a spaced relationship with each other. A horizontal slideway (302) and a vertical slideway (303) are correspondingly provided on the fixed plate (301), the double-headed curved connecting rod (501) is located between the two fixed plates (301), the front and rear ends of the upper pin shaft (502) are slidably connected in the horizontal slideway (302), and the front and rear ends of the lower pin shaft (503) are slidably connected in the vertical slideway (303), and when the telescopic end of the driving component (40) is extended, the upper end head (504) can be pushed to move in the horizontal slideway (302) and at the same time, the lower end head (505) moves downward along the vertical slideway (303) and then abuts against the hook head (201) of the slider (20) for limit locking.

2. The limit locking and unlocking mechanism according to claim 1, characterized in that, The double-ended curved surface connecting rod (501) is composed of cylindrical heads at two ends and an intermediate rod connecting the two cylindrical heads, and the axis of the intermediate rod is perpendicular to the axis of the cylindrical heads.

3. The limit locking and unlocking mechanism according to claim 1, characterized in that, One end of the horizontal slideway (302) is connected to the upper end of the vertical slideway (303), and a non-return bar (304) extending obliquely in the direction of the horizontal slideway (302) is provided at the upper end of the vertical slideway (303), and the upper part of the non-return bar (304) is hollowed out to form a clearance groove (305).

4. The limit locking and unlocking mechanism according to claim 3, characterized in that, The non-return stop bar (304) is in the shape of an arc strip, and the upper and lower edges of the end surface of the non-return stop bar (304) facing the horizontal slideway (302) and the part connected with the side wall of the vertical slideway (303) are both rounded.

5. The limit locking and unlocking mechanism according to claim 1, characterized in that, The driving component (40) is a bidirectional holding electromagnet, and the telescopic end is the free end of a push rod (401) of the bidirectional holding electromagnet.

6. The limit locking and unlocking mechanism according to claim 5, characterized in that The position limiting bracket (30) is provided with an inspection hole for a screwdriver or a pin to be inserted into to move the push rod (401) to extend or retract.

7. The limit locking and unlocking mechanism according to claim 5, characterized in that, It also includes a manual lever (306), one end of which is located outside the limit bracket (30), and the other end of which extends into the limit bracket (30) and is connected to the push rod (401).

8. A limit locking and unlocking mechanism according to any one of claims 1 to 7, characterized in that, The hook head (201) is pressed against the curved surface of the upper end (504) via an inclined surface, the angle between the inclined surface and the horizontal plane is α, and the angle value of α is between 50-80 degrees. When the upper end (504) and the hook head (201) are pressed against each other, the angle between the double-headed curved connecting rod (501) and the horizontal plane is β, and the angle value of β is between 70-80 degrees.

9. The limiting locking and unlocking mechanism according to claim 8, wherein, The double-ended curved surface connecting rod (501) is made of hard metal or hard plastic that is wear-resistant and weather-resistant.

10. An electric door closer for normally open fire doors, characterized in that, It includes a chute (10), a slider (20), a transmission connecting rod (60), a hydraulic device (70), an electric control mechanism, and the limit locking and unlocking mechanism according to any one of claims 1 to 8. One end of the transmission connecting rod (60) is connected to the hydraulic device (70), and the other end is connected to the slider (20). One end of the lower surface of the slider (20) is provided with a hook head (201) for abutting, locking, and limiting the upper end head (504) of the double-headed curved surface connecting rod (501).

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