A door closer support arm

Abstract

The application discloses a door closer supporting arm, which comprises a supporting arm body, a mounting seat and a locking screw assembly. The supporting arm body is provided with a mounting hole and internally arranged with a first tooth disc capable of being lifted; the mounting seat is provided with a second tooth disc in engagement with the first tooth disc. The locking screw assembly comprises a locking screw, a nut and a unique separable gasket, the gasket is hinged by two halves, the inner side is formed with a reverse round table hole matched with the screw, and is limited by a fusible restraint and an energy storage spring. In normal state, the fusible restraint restrains the gasket as a whole, the supporting nut is used for maintaining the engagement of the tooth discs, so that the supporting arm is fixed; when fire occurs, the fusible restraint is broken, the spring opens the gasket, the gasket slides outward along the reverse round table, the pre-tightening force of the nut is lost, the tooth discs are disengaged, the supporting arm is unlocked and automatically closes the door under the action of the door closer. The application can automatically release the locking of the supporting arm and the mounting seat through a pure mechanical structure in a high-temperature fire environment, and realizes passive, reliable and rapid closing of the fireproof door.

Description

Technical Field

[0001] This invention relates to the field of door control hardware technology, and in particular to a door closer support arm. Background Technology

[0002] Fire doors are critical fire-resistant partitions in building fire protection systems. Under normal circumstances, they should meet the needs of personnel passage, and in the event of a fire, they must reliably and automatically close to prevent the spread of fire and smoke, ensuring building fire safety. Currently, most fire door closing support structures on the market use fixed locking structures or electrically controlled unlocking structures. Fixed locking structures cannot unlock and release the closing stroke autonomously during a fire, failing to meet the automatic closing requirements of fire codes. Electrically controlled unlocking structures rely on the coordinated operation of circuits, sensors, and control systems. Under harsh conditions such as high temperatures, smoke, and power outages associated with fires, the electrical components are prone to failure, leading to unlocking failures, poor stability and reliability, and serious fire safety hazards. Meanwhile, the existing locking and limiting structures of the support arms are relatively traditional, with insufficient limiting and fixing capacity under normal conditions. When subjected to the vibration loads generated by frequent opening and closing of the door leaf over a long period, they are prone to loosening, displacement, or even mis-locking, resulting in poor overall durability and operational stability. Furthermore, existing structures generally lack purely mechanical autonomous temperature-controlled unlocking designs, failing to achieve passive emergency unlocking actions under conditions of no power supply or signal dependence. Therefore, there is an urgent need to provide a simple, stable, and reliable mechanical temperature-controlled unlocking door closer support arm structure to overcome the shortcomings of existing technologies, such as poor reliability, low adaptability, and weak adaptability to working conditions. Summary of the Invention

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a door closer support arm that can automatically release the lock between the support arm and the mounting base through a purely mechanical structure in high-temperature fire environments, thereby achieving passive, reliable, and rapid closing of fire doors.

[0004] The technical solution adopted by this invention to solve its technical problem is: A door closer support arm, including The support arm body is provided with a mounting hole, and a first toothed disc that can move along the height direction is provided in the mounting hole. The first toothed disc is provided with a first through hole. The mounting base is located below the mounting hole, and the top surface is provided with a second toothed disc that meshes with the first toothed disc; A locking screw assembly includes a locking screw, a locking nut, a separable washer, a fusible constraint, and an energy storage spring. The lower end of the locking screw is fixedly connected to the second gear plate, and the upper end extends through the first through hole and the separable washer to the top of the mounting hole and engages with the locking nut. The separable washer is formed by two hinged half-wafers, with the inner sides of the two half-wafers forming an inverted frustum-shaped inner hole and fitted onto the locking screw. The locking screw has an inverted frustum-shaped shaft section that matches the inverted frustum-shaped inner hole. The fusible constraint connects the two half-wafers and, at room temperature, constrains the two half-wafers to remain in a closed state to support the locking nut and maintain the locking preload, ensuring tight meshing between the first and second gear plates. The support arm body remains relatively fixed to the mounting base. The energy storage spring is pre-installed between the two half-wafers and, under normal conditions, is limited and stores energy by the fusible constraint. When the ambient temperature rises to the melting point of the fusible constraint, the fusible constraint melts and fails, and the energy storage spring releases its elastic force to separate the two half-wafers. After separation, the half-wafers slide outward along the conical surface of the inverted frustum shaft section under the axial pressure of the locking nut. The preload of the locking nut is released, the first toothed disc and the second toothed disc disengage, and the support arm body can rotate freely relative to the mounting base, thereby realizing the automatic closing of the fire door.

[0005] According to an embodiment of the present invention, a door closer support arm has at least the following beneficial effects: The door closer support arm, through the anti-rotation and height-direction movable engagement of the first toothed disc and the mounting hole, the meshing and locking of the first and second toothed discs, and the engagement structure of the inner hole of the truncated cone of the separable gasket and the truncated cone shaft section of the locking screw, in normal use, is held together by a fusible constraint, stabilizing the locking nut to maintain the preload, ensuring the toothed discs are always tightly engaged, thereby guaranteeing the support arm and mounting base are firmly fixed, effectively resisting the vibration and impact caused by frequent opening and closing of the door, and preventing loosening or mis-locking. Under high-temperature fire conditions, the fusible constraint melts and fails, the energy storage spring releases its elastic force, and the two halves of the gasket spring apart. The separated gasket slides radially along the conical surface of the truncated cone shaft section, causing the locking nut to lose support, the preload is quickly released, the first and second toothed discs disengage, the support arm and mounting base are unlocked and can rotate freely, thereby driving the fire door to close automatically. This structure relies entirely on mechanical action to unlock and close the door, without the need for power supply, sensors, or control systems. This significantly improves reliability and safety in extreme environments such as high temperature, smoke, and power outages. The structure is simple and compact, highly adaptable, and easy to promote and apply in various fire door closers.

[0006] According to some embodiments of the present invention, one end of the support arm body is provided with two parallel cantilever arms, the mounting hole is provided through the two cantilever arms, and a swing arm connected to the first gear plate is provided between the two cantilever arms. The swing arm is provided with a semi-circular bayonet, and the inner side of the two cantilever arms is provided with a spring-loaded steel ball that cooperates with the bayonet.

[0007] The advantages are: by setting a semi-circular latch on the swing arm and cooperating with the resilient steel ball in the cantilever, a stable stopping and positioning force is provided for the support arm, so that the door can be suspended at any commonly used angle; at the same time, the latching force is set to be manually overcome, so that in an emergency there is no need to wait for the temperature control to unlock, the operator can directly apply force to push the door and force it past the steel ball latching point to achieve rapid closure, taking into account both daily positioning and emergency escape needs.

[0008] According to some embodiments of the present invention, an installation channel is provided between the two cantilever arms, and a support spring and the steel ball are sequentially assembled in the installation channel. The support spring is used to provide an elastic clamping force for the engagement and positioning of the steel ball with the bayonet.

[0009] The advantage is that by using the support spring to provide a continuous elastic clamping force to the steel ball, the appropriate and stable locking resistance between the steel ball and the swing arm latch is ensured. This not only guarantees the positioning feel and anti-sway capability in daily use, but also ensures that the pushing force required to manually close the door is within an acceptable range for the human body, avoiding operational difficulties due to excessive resistance.

[0010] According to some embodiments of the present invention, the mounting channel is a threaded hole, and an adjusting nut for pressing against the support spring is screwed into the threaded hole. The end face of the adjusting nut is provided with an internal hexagonal hole, and the side of the support arm body is provided with an adjusting window communicating with the threaded hole.

[0011] The advantages are: the compression of the support spring can be flexibly adjusted through the adjusting nut in the threaded hole, thereby precisely changing the tightening force of the steel ball, realizing personalized adjustment of the stopping feel of the support arm and calibration of the force required for manual forced closing of the door. The design of the adjustment window greatly facilitates the force calibration operation during on-site installation and maintenance.

[0012] According to some embodiments of the present invention, the threaded hole extends to one end of the support arm body opposite to the cantilever, and an extension arm is fitted on the side of the adjustment window away from the cantilever. The extension arm is provided with a screw portion that mates with the threaded hole for adjusting the overall assembly length of the support arm body.

[0013] The advantages are: by designing through the threaded hole and configuring an extension arm with a screw, the overall length of the support arm body can be flexibly adjusted, effectively eliminating hole position errors during installation, making it adaptable to the needs of door panels of different thicknesses or special installation spacing, and significantly improving the product's versatility and the fault tolerance rate of on-site installation.

[0014] According to some embodiments of the present invention, the end faces of the swing arm that are in contact with the first gear disk are respectively provided with circumferentially arranged docking grooves and docking blocks, the docking grooves and the docking blocks are fitted and matched to realize the circumferential fixation of the swing arm and the first gear disk.

[0015] The advantage is that by setting circumferential array of docking blocks and docking grooves on the opposite end faces of the swing arm and the first toothed disc, circumferential rigid fixation is achieved by using the interlocking and matching of the two. This not only ensures the reliability of torque transmission, but also allows the initial angle between the swing arm and the support arm body to be changed by adjusting the interlocking phase of the two. This allows for flexible adjustment of the stopping angle of the door leaf during installation, meeting the positioning requirements in different scenarios.

[0016] According to some embodiments of the present invention, an avoidance notch is provided between the opening and closing ends of the two half-wafers, and positioning posts are symmetrically arranged on both sides of the avoidance notch, and the energy storage spring is compressed and sleeved between the two positioning posts.

[0017] The advantage is that setting a clearance notch and a positioning post at the opening and closing end of the half-wafer provides a precise assembly positioning reference for the energy storage spring, preventing the spring from deflecting or twisting during operation, ensuring that its elastic force can be released stably in the preset direction, thereby improving the reliability and response speed of the gasket separation when the temperature control is unlocked.

[0018] According to some embodiments of the present invention, two half washers are provided between the two half washers, the outer sides of the two half washers are provided with grooves that engage with the clearance notch, and the inner sides of the two half washers are provided with the inverted frustum-shaped inner hole.

[0019] The benefits are as follows: The addition of two halves of the washer, which are engaged and limited by the slots and the notches of the half-wafers, together form a conical support surface that fits the inverted frustum shaft section of the locking screw. This further disperses the axial pressure applied by the locking nut, providing uniform pressure support for the half-wafers and preventing localized deformation and chipping of the half-wafers. At the same time, it guides and constrains the opening and closing sliding path of the half-wafers. After the fusible constraint melts, the two halves of the washer can spread out radially synchronously with the half-wafers, ensuring a smooth and synchronous release of the preload and improving the overall stability of the unlocking action and the structural pressure-bearing durability.

[0020] According to some embodiments of the present invention, the two half-wafers are respectively provided with opposing raised portions at the ends away from the hinge, and the two raised portions are respectively provided with mounting posts facing opposite directions. The two ends of the fusible constraint member are respectively provided with fixing holes that match the mounting posts and are assembled and fixed.

[0021] The advantages are: setting a raised part and a corresponding mounting post at the free end of the half-wafer optimizes the position of the stress support point of the fusible constraint, enabling it to bear tensile stress more evenly at room temperature, avoiding premature fracture caused by stress concentration, and facilitating the rapid assembly and replacement of the fusible component, thus improving maintenance efficiency.

[0022] According to some embodiments of the present invention, the fusible constraint is a low-melting-point alloy fusible sheet, which is fixed across two half-wafers to limit the relative opening and separation of the two half-wafers at room temperature.

[0023] The advantages are: using a low-melting-point alloy fusible sheet as a fusible constraint component, taking advantage of the metal alloy's precise melting point, fast thermal response and anti-aging properties, ensures that the mechanism can quickly and accurately melt when the temperature reaches the set threshold in the early stage of a fire, avoiding malfunctions or failures to operate due to material property drift, and ensuring the reliability of temperature control unlocking.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of an embodiment of the present invention; Figure 2 for Figure 1 A cross-sectional schematic diagram; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 for Figure 1 A schematic diagram of the decomposition process; Figure 5 for Figure 4 Installation diagram of the first and second gear discs; Figure 6 for Figure 4 Schematic diagram of a separable gasket; Figure 7 for Figure 4 A schematic diagram of the middle half washer.

[0027] Reference numerals: Support arm body 100, mounting hole 110, first gear plate 120, first through hole 130, mounting base 140, second gear plate 150, locking screw 160, locking nut 170, fusible constraint 180, energy storage spring 190, half washer 200, inverted frustum-shaped inner hole 210, inverted frustum shaft section 220, cantilever 230, swing arm 240, semi-circular bayonet 250, steel ball 260, mounting channel 270, adjusting nut 280, internal hexagonal hole 290, adjusting window 300, extension arm 310, screw part 320, mating block 330, mating groove 340, clearance notch 350, positioning post 360, slot 370, raised part 380, mounting post 390, half washer 400, support spring 410. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0030] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" and "second" are mentioned, this is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation, connection, and linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] The following is for reference. Figures 1-7A door closer support arm is described in detail with reference to a specific embodiment. It is to be understood that the following description is merely illustrative and not intended to limit the invention.

[0033] like Figure 1 As shown, a door closer support arm mainly consists of a support arm body 100, a mounting base 140, and a locking screw 160 assembly.

[0034] Among them, such as Figure 2-4 As shown, one end of the support arm body 100 has two parallel cantilever arms 230, forming an installation space between them. Mounting holes 110 penetrate these two cantilever arms 230. Resilient steel balls 260 are located inside each cantilever arm 230, and a swing arm 240 is located between the two cantilever arms 230. The swing arm 240 is connected to the mounting base 140 via a first gear plate 120. To ensure positioning while also accommodating emergency escape needs, the swing arm 240 has a semi-circular latch 250. This latch cooperates with the steel balls 260 inside the cantilever arms 230, providing a stable stopping force for the door, allowing it to hover at any angle. It also includes a manually overpowered locking force, allowing personnel to quickly close the door in an emergency without waiting for temperature control unlocking, by directly applying force to push the door past the steel ball 260 locking point. To adjust the engagement force, an installation channel 270 is provided between the two cantilever arms 230. A support spring 410 and a steel ball 260 are sequentially installed inside. The support spring 410 provides a continuous elastic clamping force to the steel ball 260, ensuring moderate and stable engagement resistance. Furthermore, the installation channel 270 is designed as a threaded hole and equipped with an adjusting nut 280. By rotating the adjusting nut 280, the compression of the support spring 410 can be precisely changed, thereby achieving personalized adjustment of the stopping feel and calibration of the manual closing force. The adjustment window 300 on the side of the support arm body 100 provides great convenience for on-site calibration. In addition, the threaded hole extends to the other end of the support arm body 100, and an extension arm 310 can be installed through the adjustment window 300. The screw portion 320 of the extension arm 310 engages with the threaded hole, allowing for flexible adjustment of the overall length of the support arm to accommodate different installation spacings.

[0035] like Figure 4As shown, regarding the transmission connection between the support arm and the first gear plate 120, the end faces of the swing arm 240 and the first gear plate 120 that are in contact with each other are respectively provided with circumferentially arranged docking grooves 340 and docking blocks 330. Through the fitting and matching of the docking grooves 340 and the docking blocks 330, not only is the circumferential rigid fixation of the swing arm 240 and the first gear plate 120 achieved, ensuring the reliability of torque transmission, but also the installer is allowed to change the initial included angle of the swing arm 240 by adjusting the fitting phase of the two, so that the stopping angle of the door can be flexibly set during the installation stage. The mounting base 140 is located below the mounting hole 110 of the support arm body 100, and its top surface is provided with a second gear plate 150. The first gear plate 120 is located in the mounting hole 110, and can move along the height direction but is circumferentially limited with the mounting hole 110. Its top surface is provided with a toothed structure that meshes with the second gear plate 150, such as Figure 5 As shown. This anti-rotation and height-adjustable design ensures that the first gear 120 can smoothly disengage from the second gear 150 during unlocking, thereby releasing the rotational freedom of the support arm. In actual installation and debugging, the construction personnel can adjust the stopping angle by adjusting the meshing phase of the first gear 120 and the second gear 150, or by adjusting the engagement position of the docking block 330 and the docking groove 340 for dual adjustment. After installation, if a fine adjustment of the stopping angle is required, simply loosen the locking nut 170 slightly while the support arm is under stress, so that the first gear 120 and the second gear 150 are slightly disengaged, rotate the support arm body 100 to the target angle, and then tighten the nut. The operation is extremely convenient.

[0036] The locking screw 160 assembly is the core component for achieving temperature-controlled unlocking. For example... Figure 3 and Figure 4 As shown, the lower end of the locking screw 160 is connected and fixed to the second gear disc 150, and the upper end passes through the first through hole 130 of the first gear disc 120 and the separable washer in sequence before engaging with the locking nut 170. Figure 6 As shown, the separable gasket is formed by two hinged half-wafers 200, with an inverted frustum-shaped inner hole 210 on its inner side, which precisely matches the inverted frustum-shaped shaft section 220 on the locking screw 160. A clearance notch 350 is provided between the opening and closing ends of the two half-wafers 200. Energy storage springs 190 are fitted onto the positioning posts 360 on both sides of the notch. This structure provides a precise positioning reference for the springs, preventing them from deflecting and ensuring that the spring force is stably released along a preset direction. A matching half-washer 400 is also provided at the corresponding position of the clearance notch 350, such as... Figure 7As shown, the outer sides of the two half-washers 400 are provided with grooves 370 that can engage with the clearance notch 350. The inner sides of the two half-washers 400 together form a tapered through hole that fits the inverted frustum shaft section 220 of the locking screw. The half-washers 400 are assembled between the inner wall of the half-washer 200 and the outer wall of the locking screw 160. To ensure the stability of the locked state, the grooves 370 and the snap-fit ​​structure enhance the overall bending strength of the washer, preventing the half-washer 200 from deforming under the preload of the locking nut 170, and ensuring the assembly accuracy even after long-term use. The end of the two half-washers 200 away from the hinge is provided with a raised part 380 and a mounting post 390. The fusible constraint 180 is preferably a low-melting-point alloy fusible sheet with tin as the main component. Tin-based alloys have the characteristics of accurate melting point, fast thermal response and excellent anti-aging properties. Its two ends are fixed to the two mounting posts 390 through fixing holes. At room temperature, the fusible link binds the two halves of the washer 200 together as a whole, and the half washer 400 together supports the locking nut 170 to maintain the preload, so that the first gear 120 and the second gear 150 are tightly engaged. When the fire reaches the melting point, the fusible link melts quickly, and the energy storage spring 190 releases its elasticity to separate the two halves of the washer 200. The half washer 400 slides radially along the inverted frustum-shaped conical surface along with the half washer 200, which causes the preload of the locking nut 170 to be released. The first gear 120 and the second gear 150 are disengaged, and the support arm is then unlocked and can rotate freely.

[0037] In the specific installation and adjustment process, preliminary positioning is performed first. After fixing the mounting base 140 to the door leaf or door frame, the installer places the first gear plate 120 into the mounting hole 110 of the support arm body 100. Then, the swing arm 240 is placed under the first gear plate 120. By adjusting the engagement position of the mating block 330 on the swing arm 240 and the mating groove 340 on the first gear plate 120, the circumferential angle of the swing arm 240 relative to the first gear plate 120 is changed, completing the first coarse adjustment of the support arm's stopping angle. Next, the locking screw 160 assembly is passed through each component. At this time, the locking nut 170 does not need to be fully tightened, allowing the first gear plate 120 and the second gear plate 150 to be in a loose state of partial engagement. The support arm body 100 is rotated to the required precise stopping position, and then the locking nut 170 is tightened. The first gear plate 120 and the second gear plate 150 are pressed together using a separable washer, completing the second fine adjustment. If the angle needs to be adjusted during use, there is no need to disassemble the swing arm 240. Simply loosen the locking nut 170 slightly when the support arm is under stress, so that the first gear 120 and the second gear 150 are slightly disengaged. Then rotate the support arm body 100 to the target angle and tighten the nut. The operation is extremely convenient.

[0038] Under normal conditions, the tin-based fusible link remains solid, firmly binding the two halves of the washer 200. The locking nut 170 presses and engages the first gear 120 and the second gear 150 through the washer. The support arm and the mounting base 140 are relatively fixed, and the door leaf is held at a specific angle by the cooperation of the steel ball 260 and the latch. When manual closing is required, the push applied by the user overcomes the clamping force of the steel ball 260, causing the swing arm 240 to rotate and drive the support arm to move without damaging the structure. When a fire occurs and the temperature rises, the low-melting-point alloy fusible link melts rapidly, the energy storage spring 190 springs the two halves of the washer 200 apart, and the washer slides outward along the inverted frustum shaft section 220. The locking force disappears instantly, the first gear 120 moves upward and disengages, the support arm and the mounting base 140 are unlocked, and the fire door automatically closes under the action of the door closer.

[0039] In summary, this invention achieves multiple beneficial effects through a purely mechanical structure. First, the use of low-melting-point alloy materials such as tin-based fusible links ensures the accuracy and reliability of temperature-controlled unlocking, completely eliminating reliance on power supplies and control systems, and enabling reliable operation even in extreme environments such as smoke and power outages. Second, the dual adjustment mechanism of the first gear disc 120 and the docking block 330, along with the design that allows for fine-tuning after installation by simply loosening the nut, provides multi-dimensional installation and adjustment capabilities, greatly improving product adaptability and on-site fault tolerance. Third, the positioning of the steel ball 260 and the circumferential array interlocking structure ensure both stable stopping during daily use and meet the rapid closing requirements for emergency escape. Finally, detailed designs such as the avoidance notch 350, the slot 370, and the raised portion 380 collectively ensure the durability and operational consistency of the core unlocking mechanism under long-term vibration environments. The overall structure is compact, highly reliable, and possesses strong practical value and promising prospects for widespread application.

[0040] In the description of this specification, the references to terms such as "an embodiment, some embodiments, illustrative embodiments, example, specific example, or examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A door closer support arm, characterized in that, include: The support arm body (100) is provided with a mounting hole (110), and a first toothed disc (120) movable in the height direction is provided in the mounting hole (110). The first toothed disc (120) is provided with a first through hole (130). Mounting base (140) is located below the mounting hole (110), and a second gear (150) is provided on the top surface to mesh with the first gear (120). The locking screw (160) assembly includes a locking screw (160), a locking nut (170), a separable washer, a fusible restraint (180), and an energy storage spring (190). The lower end of the locking screw (160) is connected and fixed to the second gear plate (150), and the upper end extends through the first through hole (130) and the separable washer to the mounting hole (110) and engages with the locking nut (170). The separable washer is formed by two hinged half-wafers (200), and the inner sides of the two half-wafers (200) form an inverted frustum-shaped inner hole (210) which is fitted onto the locking screw (160). The screw (160) is provided with an inverted frustum shaft section (220) that is adapted to the inverted frustum-shaped inner hole (210); the fusible constraint (180) connects the two half-wafers (200), and constrains the two half-wafers (200) to maintain a closed overall state at room temperature, so as to support the locking nut (170) to maintain the locking preload, so that the first gear plate (120) and the second gear plate (150) are tightly meshed, and the support arm body (100) and the mounting base (140) remain relatively fixed; the energy storage spring (190) is pre-installed between the two half-wafers (200), and is limited and stored by the fusible constraint (180) under normal conditions; When the ambient temperature rises to the melting point of the fusible constraint (180), the fusible constraint (180) melts and fails, and the energy storage spring (190) releases its elastic force to separate the two half-wafers (200). After separation, the half-wafers (200) slide outward along the conical surface of the inverted frustum shaft section (220) under the axial pressure of the locking nut (170). The preload of the locking nut (170) is released, the first toothed disc (120) and the second toothed disc (150) disengage, and the support arm body (100) can rotate freely relative to the mounting base (140) to realize the automatic closing of the fire door.

2. The door closer support arm according to claim 1, characterized in that: The support arm body (100) has two parallel cantilever arms (230) at one end. The mounting hole (110) is provided through the two cantilever arms (230). A swing arm (240) connected to the first gear plate (120) is provided between the two cantilever arms (230). The swing arm (240) has a semi-circular bayonet (250). The inner side of the two cantilever arms (230) has a spring-loaded steel ball (260) that cooperates with the bayonet.

3. The door closer support arm according to claim 2, characterized in that: An installation channel (270) is provided between the two cantilever arms (230). A support spring (410) and a steel ball (260) are sequentially installed in the installation channel (270). The support spring (410) is used to provide an elastic clamping force for the steel ball (260) to engage and position with the bayonet.

4. The door closer support arm according to claim 3, characterized in that: The installation channel (270) is a threaded hole, and an adjusting nut (280) for pressing against the support spring (410) is screwed into the threaded hole. The end face of the adjusting nut (280) is provided with an internal hexagonal hole (290), and the side of the support arm body (100) is provided with an adjusting window (300) communicating with the threaded hole.

5. The door closer support arm according to claim 4, characterized in that: The threaded hole extends to one end of the support arm body (100) away from the cantilever (230). An extension arm (310) is mounted on the side of the adjustment window (300) away from the cantilever (230). The extension arm (310) is provided with a screw part (320) that mates with the threaded hole, which is used to adjust the overall assembly length of the support arm body (100).

6. The door closer support arm according to claim 2, characterized in that: The swing arm (240) and the first gear disk (120) are respectively provided with circumferentially arranged docking grooves (340) and docking blocks (330) on their respective end faces that are in contact with each other. The docking grooves (340) and the docking blocks (330) are fitted and matched to realize the circumferential fixation of the swing arm (240) and the first gear disk (120).

7. The door closer support arm according to claim 1, characterized in that: A clearance notch (350) is provided between the opening and closing ends of the two half-wafers (200), and positioning posts (360) are symmetrically arranged on both sides of the clearance notch (350). The energy storage spring (190) is compressed and sleeved between the two positioning posts (360).

8. The door closer support arm according to claim 7, characterized in that: Two half washers (400) are provided between the two half washers (200), and the outer side of the two half washers (400) is provided with a groove (370) that engages with the clearance notch (350). The inner side of the two half washers (400) is provided with the inverted frustum-shaped inner hole (210).

9. The door closer support arm according to claim 8, characterized in that: The two half-wafers (200) are provided with opposing raised portions (380) at the ends away from the hinge. The two raised portions (380) are respectively provided with mounting posts (390) facing opposite directions. The fusible constraint (180) has fixing holes at both ends that match the mounting posts (390) and is assembled and fixed.

10. The door closer support arm according to claim 1, characterized in that: The fusible restraint (180) is a low-melting-point alloy fusible sheet, which is fixed across two half-wafers (200) to limit the relative opening and separation of the two half-wafers (200) at room temperature.

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