A self-locking flat hinge with seamless connection and no protrusions

Abstract

A self-locking flat hinge with seamless connection and no protrusions relates to the field of hinge design technology. The hinge base is integrally formed of a main connecting rod and an L-shaped fixing plate. A protrusion is provided on one side of the main connecting rod's head end, and the L-shaped fixing plate is provided outside the protrusion. The main connecting rod is drilled with a secondary shaft hole and two primary shaft holes, and a locking block groove is machined at the end. The secondary connecting rod is drilled with two secondary shaft holes, and a connecting ear and a torsion spring groove are provided at the connecting end of the locking block. A stepped groove is machined at the free end. During assembly, the two hinge base ends are symmetrically placed against each other. Four primary shafts are inserted into primary shaft hole one, two secondary shafts are inserted into secondary shaft hole one, two torsion springs are mounted on the inside of the secondary shafts, two locking blocks are mounted on the outside of the secondary shafts, two secondary connecting rods are mounted on the outer ends of the four primary shafts, and two L-shaped fixing plates secure the two connecting structures. This design enables seamless connection of the connecting structures at both ends in the folded and unfolded states, and there are no protrusions on the surface after unfolding, meeting the requirements of flat antennas for folded volume and unfolded flatness.

Description

Technical Field

[0001] The invention relates to the technical field of hinge design, in particular to a self-locking flat hinge with no protrusions and capable of seamless connection. Background Art

[0002] In order to meet the needs of communication and measurement, artificial satellites generally need to be equipped with antennas. Among them, foldable and unfoldable flat-panel antennas are currently the most widely used antenna structure.

[0003] Flat panel antennas, especially large ones, must maintain a seamless connection after unfolding. This requires extremely high flatness, minimizing protrusion above the surface. Furthermore, because satellites must be as compact as possible for launch, flat panel antennas must also maintain seamless contact when folded to minimize space usage. However, conventional hinges, designed to ensure seamless contact when folded, will have at least half of the shaft and part of the sleeve protruding from the surface of the connection structure after unfolding due to structural reasons, affecting surface flatness.

[0004] Therefore, it is necessary to design a self-locking flat hinge for structures with high flatness requirements such as flat antennas of artificial satellites, which can achieve seamless connection of the connecting structures at both ends when folded, and automatically lock without protrusions after unfolding, so as to meet the requirements of occupied space when folded and flatness after unfolding. Summary of the Invention

[0005] To address the shortcomings of the background technology, the present invention provides a self-locking flat hinge with seamless connection and no protrusions. While ensuring the functions of unfolding and automatic locking, it can simultaneously achieve seamless connection of the connecting structures at both ends in the folded and unfolded states. After unfolding, the hinge has no protrusions on the surface of the connecting structure, meeting the strict requirements of the flat antenna for folded volume and unfolded flatness.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a self-locking flat hinge without protrusions that can be seamlessly connected, comprising two hinge bases, two secondary connecting rods, two locking blocks, two secondary shafts, two torsion springs and four main shafts, wherein: each of the hinge bases is made into one body by a main connecting rod and an L-shaped fixing plate, the main connecting rod body is a rectangular cross-section rod and one side of its head end is transversely thickened and provided with a protrusion, the thickness of the protrusion is consistent with the thickness of the rectangular cross-section rod, the L-shaped fixing plate is horizontally arranged at the outer edge of the protrusion, a secondary shaft hole and two main shaft holes are transversely drilled on the main connecting rod, The two main shaft holes are respectively located at the center of the raised portion and the position adjacent to the end of the rectangular cross-section rod. The secondary shaft hole is located above the main shaft hole adjacent to the raised portion on the rectangular cross-section rod. A locking block groove is processed at the end of the rectangular cross-section rod of the main connecting rod. The locking block groove is divided into two parts: an arc-shaped notch and a convex strip arranged horizontally on its top; each of the secondary connecting rod bodies is a rectangular cross-section rod with rounded corners at both ends, and two main shaft holes are drilled horizontally on the secondary connecting rod. The two main shaft holes are respectively located on the secondary connecting rod near the two ends; each of the locking block bodies is a rectangular block and its width is consistent with the thickness of the raised portion of the hinge base. A connecting ear is integrally provided on the outer side of the connecting end and a second secondary shaft hole is drilled horizontally, space is reserved on the inner side of the locking block connecting end and a torsion spring groove is machined, and a stepped groove is machined horizontally on the top of the free end of the locking block; when assembling, the two hinge bases are placed together so that the side with the raised portion at the end of the rectangular cross-section rod is close to each other, and the four main shafts are grouped in twos and the two main shafts in each group are respectively inserted into the main shaft hole 1 of one hinge base located at the raised portion and the main shaft hole 1 of the other hinge base near the end position, the two secondary shafts are respectively inserted into the secondary shaft holes 1 of the two hinge bases, the two torsion springs are respectively mounted on the inner sides of the two secondary shafts, and the two locking blocks are respectively The secondary shaft holes are set on the outside of the two secondary shafts and the corresponding torsion springs are ensured to be stuck in the torsion spring grooves. The two secondary connecting rods are inserted into the outer ends of the four main shafts through the four main shaft holes. The L-shaped fixing plates of the two hinge bases are respectively fixed to the two connecting structures by bolts. The two connecting structures are respectively processed with hinge grooves for accommodating the hinge bases at the connecting ends of the folding side surfaces. The two connecting structures are respectively processed with bolt grooves at the corresponding positions on the back of the folding side to hide the bolts under the back of the folding side. The corresponding position of the opening and closing side of one of the connecting structures is processed with an arc-shaped avoidance groove to make space for the corners of the other connecting structure.

[0007] Furthermore, the two hinge bases are respectively processed with sliding surface one at the bottom of one side of the convex strip of the locking block groove, and the sliding surface one is an arc-shaped concave structure. The two locking blocks are respectively processed with sliding surface two on one side of the step groove, and the sliding surface two is an arc-shaped convex structure. When the hinge is fully expanded to the horizontal, the sliding surface one is locked and matched with the corresponding sliding surface two.

[0008] Furthermore, the two secondary shafts and the four main shafts are assembled with the two hinge bases using interference fit, and the two locking blocks are assembled with the two secondary shafts, and the two secondary connecting rods are assembled with the four main shafts using clearance fit.

[0009] Furthermore, a weight-reducing hollow portion is drilled transversely on each of the main connecting rods of the two hinge bases, and the weight-reducing hollow portion is located in the middle of the two main shaft holes.

[0010] Furthermore, the two secondary connecting rods are respectively transversely drilled with a second weight-reducing hollow portion, and the second weight-reducing hollow portion is located in the middle position of the secondary connecting rod.

[0011] Furthermore, the hinge grooves of the two connecting structures are machined to have the same width as the maximum transverse width of the hinge, thereby restricting the two secondary connecting rods to prevent the hinge from disintegrating.

[0012] Compared with the prior art, the beneficial effects of the present invention are: the present invention is mainly used for structures with high requirements on flatness, such as flat-panel antennas of artificial satellites. It is designed based on a cross four-link structure and is a centrally symmetrical structure, which is conducive to processing and production, and can achieve seamless connection of the connecting structures at both ends in the folded and unfolded state. It can be unfolded normally and automatically locked. After unfolding and locking, the seamless connection of the connecting structures at both ends can still be guaranteed, and there is no part of the hinge protruding from the surface of the connecting structure, which meets the application requirements of structures such as flat-panel antennas carried in artificial satellites for folding volume and unfolding flatness. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is an exploded schematic diagram of the hinge of the present invention;

[0014] Figure 2 is a schematic diagram of the hinge of the present invention in a fully folded state;

[0015] Figure 3 Schematic diagram of a partially unfolded state of the hinge of the present invention;

[0016] Figure 4 Schematic diagram of the hinge of the present invention in a locked state when fully extended;

[0017] Figure 5 It is a schematic diagram of the principle of the folding and unfolding process of the hinge of the present invention.

[0018] In the figure: 110 and 120 are hinge bases; 101 is the main connecting rod; 102 is an L-shaped fixing plate; 103 and 104 are main shaft hole one; 105 is secondary shaft hole one; 106 is weight-reducing hollow one; 107 is a locking block groove; 108 is sliding surface one; 210 and 220 are secondary connecting rods; 201 and 202 are main shaft hole two; 203 is weight-reducing hollow two; 310 and 320 are locking blocks; 301 is secondary shaft hole two; 302 is a torsion spring groove; 303 is sliding surface two; 410, 420, 430 and 440 are main shafts; 450 and 460 are secondary shafts; 510 and 520 are torsion springs; 600 and 700 are connecting structures; 601 and 701 are hinge grooves; 602 and 702 are bolt grooves; 603 is an arc-shaped avoidance groove. DETAILED DESCRIPTION

[0019] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] like Figures 1 to 5 As shown, a self-locking flat hinge with no protrusions and seamless connection includes two hinge bases 110 and 120, two secondary connecting rods 210 and 220, two locking blocks 310 and 320, two secondary shafts 450 and 460, two torsion springs 510 and 520, and four main shafts 410, 420, 430 and 440.

[0021] The self-locking flat hinge is a centrally symmetrical structure. Figure 1The figure shows the disassembled structure of each component. Since the two hinge bases 110 and 120 have identical structures, the hinge base 110 is used as an example to describe its specific structure. It is made up of a main connecting rod 101 and an L-shaped fixing plate 102. The main connecting rod 101 is a rectangular cross-section rod with a transversely thickened protrusion on one side of its head end. The thickness of the protrusion is consistent with that of the rectangular cross-section rod. The L-shaped fixing plate 102 is horizontally arranged at the outer edge of the protrusion and is machined with multiple bolt holes for bolting the structure to be connected. A secondary shaft hole 105, a weight-reducing hollow 106, and two main shaft holes 103 and 104 are drilled transversely on the main connecting rod 101. The two main shaft holes 103 and 104 are respectively drilled at the center position of the raised portion of the main connecting rod 101 and near the end position of the rectangular cross-section rod. The weight-reducing hollow 106 is drilled on the rectangular cross-section rod of the main connecting rod 101 and is located in the middle position of the two main shaft holes 103 and 104. The secondary shaft hole 105 is drilled on the rectangular cross-section rod of the main connecting rod 101 and is located above between the main shaft hole 103 of the raised portion and the weight-reducing hollow 106. A locking block groove 107 is machined at the end of the rectangular cross-section rod of the main connecting rod 101. The locking block groove 107 is composed of an arc-shaped notch and a convex strip arranged horizontally at its top. A sliding surface 108 is machined at the bottom of one side of the convex strip of the locking block groove 107. The sliding surface 108 is an arc-shaped concave structure. The locking block grooves 107 of the two hinge bases 110 and 120 are respectively used to engage with the two locking blocks 310 and 320 during the locking stage. Since the two secondary connecting rods 210 and 220 have completely identical structures, the specific structure of the secondary connecting rod 210 will be described as follows. Its main body is a rectangular cross-section rod with rounded corners at both ends. A weight-reducing hollow 203 and two main shaft holes 201 and 202 are drilled horizontally on the secondary connecting rod 210. The two main shaft holes 201 and 202 are drilled near the two ends of the secondary connecting rod 210, and the weight-reducing hollow 203 is drilled in the middle of the secondary connecting rod 210.Since the two locking blocks 310 and 320 have exactly the same structure, the specific structure is described by taking the locking block 310 as an example. Its main body is a rectangular block and its width is consistent with the thickness of the raised portion of the hinge base 110 / 120. A connecting ear is integrally provided on the outer side of the connecting end of the locking block 310 and a secondary shaft hole 301 is drilled horizontally. Space is reserved on the inner side of the connecting end of the locking block 310 and a torsion spring groove 302 is machined. A stepped groove is machined horizontally on the top of the free end of the locking block 310, and a sliding surface 303 is machined on one side of the stepped groove. The sliding surface 303 is an arc-shaped convex structure. When the hinge is fully engaged, When unfolded to horizontal, the stepped grooves at the top of the free ends of the two locking blocks 310 and 320 respectively engage with the convex strips at the top of the locking block grooves 107 at the ends of the two hinge bases 110 and 120 to achieve locking. The arc-shaped outward-convex sliding surface 2 303 on one side of the stepped groove ensures that the free ends of the two locking blocks 310 and 320 will not be stuck during the hinge unfolding process. The arc-shaped inward-convex sliding surface 108 on one side of the locking block groove 107 is adapted to the sliding surface 2 303 to ensure seamless contact between the free ends of the two locking blocks 310 and 320 and the ends of the two hinge bases 110 and 120 after the hinge is fully unfolded.

[0022] When assembling the hinge, place the two hinge bases 110 and 120 in a centrally symmetrical manner so that the sides of the rectangular cross-section rods with the raised portions at the end thereof are placed together. Assemble one side of the hinge bases 110 and 120. First, insert one end of the two main shafts 410 and 420 into the main shaft hole 103 located at the raised portion of the hinge base 110 and the main shaft hole 104 located near the end of the hinge base 120. Then, insert one of the secondary shafts 450 into the secondary shaft hole 105 of the hinge base 110. Then, fit one of the torsion springs 510 onto the secondary shaft 450. Then, fit one of the locking blocks 310 onto the secondary shaft 450 through its secondary shaft hole 2 301, and ensure that the torsion spring 510 is stuck in the corresponding torsion spring groove 302. Finally, insert one of the secondary connecting rods 210 through the two main shaft holes. The second and second shafts 201 and 202 are inserted into the outer ends of the two main shafts 410 and 420; the assembly on the other side is similar. First, one end of the remaining two main shafts 430 and 440 is inserted into the main shaft hole 103 located at the raised part of the hinge base 120 and the main shaft hole 104 near the end position of the hinge base 110, and then another secondary shaft 460 is inserted into the secondary shaft hole 105 of the hinge base 120. Then, another torsion spring 520 is mounted on the secondary shaft 460, and then another locking block 320 is mounted on the secondary shaft 460 through its secondary shaft hole 2 301, and it is ensured that the torsion spring 520 is stuck in the corresponding torsion spring groove 302. Finally, another secondary connecting rod 220 is inserted into the outer ends of the two main shafts 430 and 440 through the two main shaft holes 201 and 202. It is worth noting that the two secondary shafts 450 and 460 and the four main shafts 410, 420, 430 and 440 adopt an interference fit when assembled with the two hinge bases 110 and 120, and can be inserted and fixed without other parts; while the two locking blocks 310 and 320 adopt a clearance fit when assembled with the two secondary shafts 450 and 460, and the two secondary connecting rods 210 and 220 adopt a clearance fit when assembled with the four main shafts 410, 420, 430 and 440, and can rotate freely.

[0023] Combine Figure 2 and Figure 5 As shown, the fully folded state of the hinge and the corresponding structural form of the hinge at this stage (see Figure 5In actual application, the two connecting structures 600 and 700 to be connected are assembled through self-locking flat hinges. A hinge groove 601 for accommodating one of the hinge bases 110 is processed at the connecting end of the folded side surface of one connecting structure 600, and a hinge groove 701 for accommodating the other hinge base 120 is processed at the connecting end of the folded side surface of the other connecting structure 700. The two hinge bases 110 and 120 are respectively connected and fixed to the L-shaped fixing plate 102 and the two connecting structures 600 and 700 by bolts. Since the hinge is in a loose state after assembly and is prone to disintegration, it can be controlled during processing. The width of the hinge grooves 601 and 701 is the same as the maximum lateral width of the hinge. The sidewalls of these grooves constrain the two secondary links 210 and 220 in the hinge, preventing disassembly. Furthermore, bolt grooves 602 are machined on the folding side of one connecting structure 600, corresponding to the bolt mounting locations on the hinge base 110. Bolt grooves 702 are machined on the folding side of the other connecting structure 700, corresponding to the bolt mounting locations on the hinge base 120. These bolts are concealed beneath the folding sides of the two connecting structures 600 and 700, minimizing protrusion. In this state, the folding side surfaces of the two connecting structures 600 and 700 seamlessly contact each other. The main link 101 of the two hinge bases 110 and 120 and the two secondary links 210 and 220 form a four-link structure shaped like an hourglass. The two locking blocks 310 and 320 are blocked from rotation by their corresponding hinge bases 120 and 110, and are not in the locked position.

[0024] Combine Figure 3 and Figure 5 As shown, the partially unfolded state of the hinge and the corresponding structural form of the hinge at this stage (see Figure 5 (See the three middle figures.) The hinge begins to unfold under the action of an external force. Assuming one connecting structure 600 is fixed, the other connecting structure 700 follows the movement of the main connecting rod 101 of the corresponding hinge base 120. Its trajectory at some point is not circular. At this point, the two locking blocks 310 and 320 begin to deflect while following the movement, respectively, under the action of the two torsion springs 510 and 520. The free ends of the two locking blocks 310 and 320 remain in close contact with the main connecting rod 101 of the corresponding hinge bases 120 and 110. During this period, the sliding surfaces 303 provided on the free ends of the two locking blocks 310 and 320 effectively prevent them from getting stuck at any point during movement. After the two connecting structures 600 and 700 are unfolded to a certain angle, there is a position on the opening and closing side of one of the connecting structures 600 that may hinder the other connecting structure 700. Therefore, an arc-shaped avoidance groove 603 can be laterally polished at the corresponding position of the opening and closing side of one of the connecting structures 600 to make room for the corners of the other connecting structure 700 that turns here, so that it can continue to fully unfold.

[0025] Combine Figure 4 and Figure 5 As shown, the fully extended state of the hinge and the corresponding structural form of the hinge at this stage (see Figure 5 (See the bottom image in the figure below.) When the opening and closing sides of the two connecting structures 600 and 700 come into contact, the corners of the movable connecting structure 700 just rotate out of the arc-shaped avoidance groove 603 of the fixed connecting structure 600, preventing the two connecting structures 600 and 700 from interfering with each other. Ultimately, the main connecting rod 101 of the two hinge bases 110 and 120 and the two secondary connecting rods 210 and 220 form a straight line. At this time, the free ends of the two locking blocks 310 and 320 are respectively locked with the locking block grooves 107 machined at the ends of the corresponding two hinge bases 120 and 110, completing the hinge locking state.

[0026] When fully extended, the hinge has two possible motions:

[0027] The first is that the angle between the folding side surfaces of the two connecting structures 600 and 700 changes, and the structures move in a rotational and translational manner. When this angle tends to increase, that is, when the hinge is over-extended, the bottoms of the opening and closing sides of the two connecting structures 600 and 700 abut against each other, preventing further rotation and translation. When this angle tends to decrease, that is, when the hinge folds back, the upper sides of the stepped grooves at the free ends of the two locking blocks 310 and 320 are squeezed by the top ridges of the locking block grooves 107 at the ends of the two hinge bases 120 and 110. Because the force point is higher than the axis of the secondary shaft hole 301 of the two locking blocks 310 and 320, the free ends of the two locking blocks 310 and 320 tend to rotate upward. However, the ridges at the tops of the corresponding locking block grooves 107 block this movement, preventing the free ends of the two locking blocks 310 and 320 from rotating, and the lock cannot be automatically released, preventing the hinge from further rotation and translation.

[0028] The second type involves the folding side surfaces of the two connecting structures 600 and 700 remaining parallel, and the two secondary connecting rods 210 and 220 also remaining parallel, resulting in the structure moving in a parallelogram-like translational manner. When the movable connecting structure 700 tends to move downward, the opening and closing side surfaces of the two connecting structures 600 and 700 come into contact, preventing further movement. When the movable connecting structure 700 tends to move upward, the upper edges of the opening and closing side surfaces of the two connecting structures 600 and 700, as well as the adjacent surfaces of the two locking blocks 310 and 320 and the corresponding hinge bases 120 and 110, all come into contact, preventing further movement.

[0029] In summary, the hinge structure, combined with the two locking blocks 310 and 320 and the two connecting structures 600 and 700, can achieve locking in a fully extended state.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other configurations without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations coming within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0031] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A self-locking flat hinge with no protrusions and seamless connection, characterized by: The self-locking flat hinge is a centrally symmetrical structure, comprising two hinge bases, two secondary connecting rods, two locking blocks, two secondary shafts, two torsion springs and four main shafts, wherein: each of the hinge bases is integrated with a main connecting rod and an L-shaped fixing plate; the main connecting rod body is a rectangular cross-section rod and one side of its head end is transversely thickened and provided with a raised portion; the thickness of the raised portion is consistent with the thickness of the rectangular cross-section rod; the L-shaped fixing plate is horizontally arranged at the outer edge of the raised portion; a secondary shaft hole and two main shaft holes are transversely drilled on the main connecting rod; the two main shaft holes are respectively located at the center of the raised portion. and the adjacent end position of the rectangular cross-section rod, the secondary shaft hole one is located above the main shaft hole one adjacent to the raised portion on the rectangular cross-section rod, and a locking block groove is processed at the end of the rectangular cross-section rod of the main connecting rod, and the locking block groove is divided into two parts: an arc-shaped notch and a convex strip arranged horizontally on its top; each of the secondary connecting rod bodies is a rectangular cross-section rod with rounded corners at both ends, and two main shaft holes two are drilled horizontally on the secondary connecting rod, and the two main shaft holes two are respectively located on the secondary connecting rod adjacent to the two ends; each of the locking block bodies is a rectangular block and its width is consistent with the thickness of the raised portion of the hinge base, and a connecting block is integrally provided on the outer side of the locking block connecting end The ear is drilled horizontally with a secondary shaft hole two, space is reserved on the inner side of the locking block connection end and a torsion spring groove is machined, and a stepped groove is machined horizontally on the top of the free end of the locking block; when assembling, the two hinge bases are placed together so that the side with the raised portion at the end of the rectangular cross-section rod is close to each other, and the four main shafts are grouped in twos and the two main shafts in each group are respectively inserted into the main shaft hole one at the raised portion of one hinge base and the main shaft hole one near the end of the other hinge base, the two secondary shafts are respectively inserted into the secondary shaft holes one of the two hinge bases, the two torsion springs are respectively sleeved on the inner sides of the two secondary shafts, and the two locking blocks are respectively passed through the secondary The second set of shaft holes is mounted on the outside of the two secondary shafts and ensures that the corresponding torsion springs are inserted into the torsion spring grooves. The two secondary connecting rods are inserted into the outer ends of the four main shafts through the four main shaft holes. The L-shaped fixing plates of the two hinge bases are respectively fixed to the two connecting structures by bolts. The two connecting structures are respectively processed with hinge grooves for accommodating the hinge bases at the connecting ends of the folding side surfaces. The two connecting structures are respectively processed with bolt grooves at the corresponding positions on the back of the folding side to hide the bolts under the back of the folding side. The corresponding position of the opening and closing side of one of the connecting structures is processed with an arc-shaped avoidance groove to make space for the corners of the other connecting structure.

2. A seamless, protrusion-free, self-locking flat hinge according to claim 1, characterized in that: The two hinge bases are respectively processed with sliding surface one at the bottom of one side of the convex strip of the locking block groove, and the sliding surface one is an arc-shaped concave structure. The two locking blocks are respectively processed with sliding surface two on one side of the step groove, and the sliding surface two is an arc-shaped convex structure. When the hinge is fully expanded to the horizontal, the sliding surface one is locked and matched with the corresponding sliding surface two.

3. A seamlessly connected, protrusion-free, self-locking flat hinge according to claim 1 or 2, characterized in that: The two secondary shafts and the four main shafts all adopt interference fit when assembled with the two hinge bases, and the two locking blocks all adopt clearance fit when assembled with the two secondary shafts, and the two secondary connecting rods all adopt clearance fit when assembled with the four main shafts.

4. The self-locking flat hinge with no protrusion and seamless connection according to claim 1, characterized in that: A weight-reducing hollow portion is drilled transversely on the main connecting rods of the two hinge bases, and the weight-reducing hollow portion is located in the middle of the two main shaft holes.

5. The self-locking flat hinge with no protrusion and seamless connection according to claim 1, characterized in that: The two auxiliary connecting rods are also respectively drilled with a second weight-reducing hollow portion transversely, and the second weight-reducing hollow portion is located in the middle position of the auxiliary connecting rod.

6. The self-locking flat hinge with no protrusion and seamless connection according to claim 1, characterized in that: The hinge grooves of the two connecting structures are machined to have the same width as the maximum transverse width of the hinge, thereby restricting the two secondary connecting rods to prevent the hinge from disintegrating.

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