Folding structure of a collapsible cargo conversion frame and a cargo bike or e-bike

Abstract

The utility model discloses a folding structure of foldable goods conversion frame and cargo carrying bicycle or electric vehicle for cargo carrying bicycle or electric vehicle, fixed mounting is on main frame. The folding structure includes: two symmetrical folding arms, forms goods carrying space under the unfolded state, can be folded to compact state under the folding state, central folding hinge is set up in the middle position of two symmetrical folding arms, as folding rotating pivot point, and two symmetrical folding arms are connected through central folding hinge and form the collapsible carrying structure, folding locking mechanism is used for locking the unfolded state. Central folding hinge includes hinge body and unfolding limit support part, and unfolding limit support part is used for preventing symmetrical folding arm from continuing to rotate outward when symmetrical folding arm unfolds to the preset angle, and the stability of frame when carrying goods is ensured.

Description

Technical Field

[0001] This utility model relates to the technical field of bicycle or electric vehicle accessories, specifically to a folding structure for a foldable cargo conversion frame for cargo bicycles or electric vehicles. Background Technology

[0002] Cargo bicycles and electric bikes are important tools for short-distance urban transportation and logistics distribution, widely used in last-mile delivery, home shopping, and small business operations. These vehicles typically have a cargo-carrying frame near the front or rear wheels for transporting packages, goods, or other items.

[0003] Most existing cargo bicycles use a fixed cargo frame structure. For example, US Patent 11260928B2 discloses a cargo bicycle whose cargo frame is fixedly mounted on the frame, forming a stable cargo space. This fixed frame has good structural strength and stability when carrying cargo.

[0004] However, fixed cargo frames have obvious drawbacks: First, fixed frames take up a lot of space, and the vehicle is still large when it is not needed for carrying cargo, making it inconvenient to park or pass through narrow spaces, and also unsuitable for indoor storage at home; Second, fixed frames increase the overall size of the vehicle, making it extremely inconvenient to carry on public transportation or park in spaces with limited space such as apartments and offices; Third, fixed frames have a limited range of uses and cannot flexibly switch between cargo carrying mode and normal riding mode according to the user's actual needs.

[0005] In addition, although there are some detachable cargo frames on the market, the disassembly and installation process is usually cumbersome, requires tools, and the disassembled frame parts are inconvenient to carry and store, making them less practical.

[0006] Therefore, there is a need for a foldable cargo frame structure that can provide stable and reliable cargo carrying function, can be quickly folded and stored when not in use to reduce space occupation, and is easy to operate and lock reliably. Summary of the Invention

[0007] The purpose of this utility model is to provide a folding structure for a foldable cargo conversion frame, so as to solve the technical problems of existing fixed cargo frames that occupy a lot of space, are inconvenient to store, and cannot flexibly switch between cargo carrying mode and ordinary riding mode according to usage needs.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A foldable cargo conversion frame folding structure for use on cargo bicycles or electric vehicles, fixedly mounted on a main frame, includes: two symmetrical folding arms that form a cargo carrying space in the unfolded state and can be folded into a compact state in the folded state; a central folding hinge located at the middle of the two symmetrical folding arms as a folding rotation pivot point, the two symmetrical folding arms being interconnected via the central folding hinge to form a foldable carrying structure; and a folding locking mechanism for locking the unfolded state; wherein the central folding hinge includes a hinge body and an unfolding limiting support, the middle ends of the two symmetrical folding arms being rotatably connected to both sides of the hinge body; the unfolding limiting support is located on the central folding hinge and is used to prevent the symmetrical folding arms from continuing to rotate outward when the two symmetrical folding arms are unfolded to a preset angle.

[0009] Preferably, the symmetrical folding arm forms a U-shaped or rectangular cargo carrying space when unfolded.

[0010] Preferably, the folding locking mechanism adopts a pin-type, snap-type, or bolt-type locking structure.

[0011] Preferably, the folding locking mechanism adopts a spring-loaded locking structure, comprising: a knob fixing seat, fixedly mounted on the main frame; an adjusting knob, rotatably mounted on the knob fixing seat, the adjusting knob including a knob body and a screw, the screw passing through a threaded hole in the knob fixing seat; a compression spring, sleeved on the screw of the adjusting knob; a locking seat, sleeved below the compression spring, the lower end of the compression spring pressing against the top surface of the locking seat; and two guide rods, disposed on both sides of the locking seat and extending to both sides along the opening and closing direction of the two symmetrical folding arms.

[0012] Preferably, the end of the guide rod has a spherical structure.

[0013] Preferably, the compression spring is in a pre-compressed state in its natural state, and can continuously provide downward elastic pressure.

[0014] Preferably, the symmetrical folding arm is further provided with a support and stabilizing rod. The support and stabilizing rod is provided in pairs, with two rods in total, and is respectively provided on the two symmetrical folding arms. One end of the support and stabilizing rod is rotatably connected to the symmetrical folding arm through a hinged connector, and the other end is fixedly connected or in support contact with the symmetrical folding arm or support structure in the unfolded state.

[0015] Preferably, the support stabilizing rod is provided with a locking mechanism at its extended position.

[0016] Preferably, the support and stabilizing rod is stored in one of the following ways: flip-up and abutment type, that is, the support and stabilizing rod is flipped around the hinge axis of the hinge connector and abutted against the side of the symmetrical folding arm or placed parallel to the longitudinal direction of the symmetrical folding arm; disassembly and storage type, that is, the support and stabilizing rod is separated from the symmetrical folding arm by quickly disassembling the hinge connector.

[0017] This utility model also provides a cargo bicycle or electric vehicle, including: a main frame, the main frame including wheels, front fork, handlebars, seat post, head tube and down tube; the folding structure of the above-mentioned foldable cargo conversion frame is fixedly installed on the main frame.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. This utility model achieves flexible conversion between the cargo frame and the storage mode by setting up foldable symmetrical folding arms and central folding hinge. When it is not needed to carry cargo, the frame can be folded into a compact state, which greatly reduces the space occupation and makes it easy to park and store in narrow spaces.

[0019] 2. The central folding hinge's unfolding limit support provides reliable structural support and limiting function when the symmetrical folding arm is unfolded to a preset angle, preventing the frame from over-expanding or deforming, and ensuring structural stability and safety when carrying goods.

[0020] 3. When the folding locking mechanism adopts a spring-pressing structure, the elastic force provided by the compression spring in the pre-compression state can achieve quick self-locking after the symmetrical folding arms are brought together, without the need for additional operation; at the same time, the locking force can be flexibly adjusted according to the load requirements by adjusting the knob, which not only meets the convenient operation under light load, but also ensures safety and reliability under heavy load.

[0021] 4. The guide rod end adopts a spherical structure design, which can provide smooth guidance during the symmetrical folding arm approaching, reduce operating resistance, avoid jamming, and make folding and unfolding operations easier and more convenient.

[0022] 5. The support and stabilizing bar provides additional structural reinforcement to the frame in the unfolded state, improving load-bearing capacity and resistance to deformation; its flip-up and snap-fit ​​or quick-disassembly storage method ensures the compactness of the folded state without affecting the overall storage effect. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the foldable cargo conversion frame of this utility model on a cargo bicycle in the folded state; Figure 2 for Figure 1 The enlarged view at point A shows the structure of the central folding hinge and the unfolding limiting support. Figure 3 for Figure 1 The enlarged view at point B shows the structure of the folding locking mechanism; Figure 4 A schematic diagram of the overall structure of a foldable cargo conversion frame equipped with support and stabilizing bars; Figure 5 A partially enlarged view of the stabilizer bar locking mechanism.

[0024] Figure label: Main frame 01, front fork 011, handlebars 012, seat post 013, head tube 014, down tube 015, foldable cargo conversion frame 100, symmetrical folding arm 110, central folding hinge 120, unfolding limit support 121, folding locking mechanism 130, compression spring 131, locking seat 132, guide rod 133, knob fixing seat 134, adjustment knob 135, support and stabilizing bar 140, hinge connector 141, locking mechanism 142. Detailed Implementation

[0025] Example

[0026] like Figure 1 As shown, this embodiment provides a folding structure for a foldable cargo conversion frame, used for cargo bicycles or electric vehicles. This folding structure is fixedly mounted on the main frame 01 via a foldable cargo conversion frame 100. The main frame 01 includes components such as wheels, a front fork 011, handlebars 012, a seat post 013, a head tube 014, and a down tube 015, constituting a cargo bicycle similar to that in prior patent publication US11260928B2.

[0027] The foldable cargo conversion frame 100 includes: two symmetrically arranged folding arms 110, a central folding hinge 120 located at the middle of the two symmetrical folding arms 110 as a folding rotation pivot point, and a folding locking mechanism 130 located near the central folding hinge 120 or at a key position of the symmetrical folding arms 110 for locking the unfolded state.

[0028] The two symmetrical folding arms 110 are connected to each other by a central folding hinge 120 to form a foldable load-bearing structure. The symmetrical folding arms 110 extend longitudinally along the frame and form a U-shaped or rectangular cargo carrying space when unfolded. When folded, they can be folded into a compact state to reduce space occupation. The folding locking mechanism 130 can adopt a pin-type, snap-on, or bolt-type locking structure to ensure that the foldable cargo conversion frame 100 will not be accidentally folded when carrying cargo.

[0029] The central folding hinge 120 includes a hinge body and an unfolding limiting support 121. The hinge body is a pivot connection structure, and the middle ends of two symmetrical folding arms 110 are rotatably connected to both sides of the hinge body by pins or bearings, so that the two symmetrical folding arms 110 can rotate relative to each other around the rotation axis of the hinge body, thereby realizing the unfolding and folding action of the foldable cargo conversion frame 100.

[0030] Specifically, the unfolding limiting support 121 is disposed on the central folding hinge 120, and is used to provide structural support and limiting function when the foldable cargo conversion frame 100 is unfolded to the working state. The unfolding limiting support 121 is a rigid rod or support arm structure, one end of which is hinged or fixedly connected to the hinge body of the central folding hinge 120, and the other end extends to a suitable position to form a supporting connection with the main frame 01 or the symmetrical folding arms 110. When the two symmetrical folding arms 110 unfold and rotate outward from the folded state, the unfolding limiting support 121 provides abutment support to the symmetrical folding arms 110. That is, when the symmetrical folding arms 110 rotate to a preset unfolding angle (usually the angle that forms a U-shaped or rectangular load-bearing space), the unfolding limiting support 121 reaches its unfolding limit position, and prevents the symmetrical folding arms 110 from continuing to rotate outward through its own rigid structure, thereby locking the foldable cargo conversion frame 100 in the unfolded state. This limiting mechanism ensures that the foldable cargo conversion frame 100 maintains a stable geometry when carrying cargo, preventing the frame from being accidentally over-expanded or deformed due to external forces or cargo weight.

[0031] In a further specific embodiment, a buffer pad or elastic limiting block may be provided at the end of the unfolding limiting support 121. When the symmetrical folding arm 110 unfolds into place and contacts the unfolding limiting support 121, the buffer pad or elastic limiting block can absorb the impact energy during the unfolding process.

[0032] In a further specific implementation, such as Figure 3 As shown, the folding locking mechanism 130 adopts a spring-compression locking structure. This structure is supported by a cantilever, for example, on the main frame 01. It mainly includes: a knob fixing seat 134 fixedly installed on the structural support; an adjusting knob 135 rotatably installed on the knob fixing seat 134; a compression spring 131 and a locking seat 132 sleeved from top to bottom on the screw of the adjusting knob 135; and two guide rods 133 arranged on both sides of the locking seat 132 and extending to both sides along the opening and closing direction of the two symmetrical folding arms 110. The ends of the two guide rods 133 are both spherical structures.

[0033] Specifically, the knob fixing seat 134 has a threaded hole at its center for engaging with the screw of the adjusting knob 135. The adjusting knob 135 includes a knob body and a screw. The knob body is a disc-shaped or cylindrical structure that can be held and rotated by the operator. The central axis of the knob body is fixedly connected to or integrally formed with a screw, which extends downward and passes through the threaded hole of the knob fixing seat 134, and continues downward through the compression spring 131 and the locking seat 132. By rotating the knob body, the screw can move up and down under the action of the threaded engagement, thereby adjusting the compression of the compression spring 131, and thus changing the clamping force of the locking seat 132 on the symmetrical folding arm 110.

[0034] A compression spring 131 is sleeved on the upper part of the screw of the adjusting knob 135. Its upper end presses against the bottom surface of the knob body or the support surface of the knob fixing seat 134, and its lower end presses against the top surface of the locking seat 132. In its natural state, it is in a pre-compressed state and can continuously provide downward elastic pressure. The locking seat 132 is sleeved below the compression spring 131 and is also sleeved on the screw of the adjusting knob 135. The locking seat 132 can slide up and down along the screw, but is pressed against the symmetrical folding arm 110 by the elastic force of the compression spring 131, thereby achieving clamping and locking. The base of the guide rod 133 is fixed on both sides of the locking seat 132. Its extension direction is consistent with the opening and closing movement direction of the two symmetrical folding arms 110. The end adopts a spherical structure design. The arc surface of the sphere can form a progressive contact with the arm surface of the symmetrical folding arms 110 during the process of the symmetrical folding arms 110 approaching each other, which plays a role in smooth guidance and precise positioning, and avoids the end of the symmetrical folding arms from getting stuck or deviating when entering the locking seat 132.

[0035] In a further specific embodiment, the symmetrical folding arm 110 is also provided with a support and stabilizing bar 140, which provides additional structural reinforcement and stable support when the foldable cargo conversion frame 100 is in the unfolded state. The support and stabilizing bar 140 is provided in pairs, with two bars in total, respectively positioned at corresponding locations on the two symmetrical folding arms 110.

[0036] Specifically, each support and stabilizing rod 140 is a slender rod-like structure, which can be made of metal tubing or high-strength alloy material, possessing sufficient rigidity and bending strength. One end of the support and stabilizing rod 140 is rotatably connected to the side or inner side of the symmetrical folding arm 110 via a hinged connector 141. The hinged connector 141 allows the support and stabilizing rod 140 to rotate in a vertical plane around the hinge axis, realizing the unfolding and retraction of the support rod. The other end of the support and stabilizing rod 140 extends to a suitable position on the symmetrical folding arm 110, and in the unfolded state, this end can form a fixed connection or support contact with the symmetrical folding arm 110 or other support structures.

[0037] When the foldable cargo conversion frame 100 is in the unfolded working state, the two support and stabilizing rods 140 unfold outward or downward from their hinge points, forming a support system similar to a truss structure with the symmetrical folding arm 110.

[0038] The support and stabilizing rod 140 is equipped with a locking mechanism 142 at its extended position to fix the extended support and stabilizing rod 140 in the working position. The locking mechanism 142 can be a pin type, a quick-release type, or a spring positioning pin type structure.

[0039] When the foldable cargo conversion frame 100 needs to be folded and stored, the support stabilizing bar 140 has flexible storage methods: the first storage method is a flip-and-fit type. The operator first releases the locking mechanism 142, and then flips the support stabilizing bar 140 to the side around the hinge axis of the hinge connector 141, so that the support bar is against the side of the symmetrical folding arm 110 or placed parallel to the longitudinal direction of the symmetrical folding arm. In this fitted state, the outer contour of the support stabilizing bar 140 is basically consistent with that of the symmetrical folding arm 110, and does not protrude outside the folding envelope of the frame.

[0040] The second storage method is a disassembly and storage type. The support and stabilizing rod 140 is connected to the symmetrical folding arm 110 through a quick-release hinge connector 141, which allows the support rod to be quickly disassembled when needed.

[0041] In a further specific embodiment, the hinged connector 141 may adopt a damped hinge structure.

[0042] In a further specific embodiment, the support stabilizer bar 140 can be designed as a telescopic adjustable structure, such as a sleeve telescopic mechanism or a multi-segment folding mechanism.

[0043] See Figures 1-5 The working principle is as follows: As the foldable cargo conversion frame 100 rotates from the unfolded state to the folded state, the two symmetrical folding arms 110 rotate towards each other around the central folding hinge 120, gradually approaching each other. During this approaching process, the spherical structures at the ends of the guide rod 133 contact the arm surfaces of the corresponding symmetrical folding arms 110. The arcuate surfaces of the spheres act as guides, directing the ends of the two symmetrical folding arms 110 along the correct trajectory into the receiving space of the locking seat 132. Because the arcuate guide surfaces of the spheres can form line contact or small-area contact with the surfaces of the symmetrical folding arms 110, the frictional resistance between the contact surfaces is small, resulting in less resistance to the symmetrical folding arms 110 during the approaching process, allowing the operator to complete the folding action relatively easily. As the symmetrical folding arms 110 continue to approach, the spherical structures continue to guide, ensuring that the ends of the two symmetrical folding arms 110 are aligned and simultaneously enter the receiving space of the locking seat 132.

[0044] When the two symmetrical folding arms 110 are fully brought together, the compression spring 131 is in a pre-compressed state, exerting downward elastic pressure on the locking seat 132. This pressure is transmitted through the locking seat 132 and the guide rod 133 to the ends of the symmetrical folding arms 110 that have entered their receiving space, keeping the two symmetrical folding arms 110 pressed against each other under the action of elastic force, achieving initial locking and preventing the foldable cargo conversion frame 100 from accidentally unfolding due to slight vibration or external force during normal use. This pre-compressed elastic force provides a rapid self-locking mechanism, requiring no additional locking operation from the operator; the symmetrical folding arms 110 automatically lock when brought together.

[0045] If a stronger locking effect is needed to support heavier loads or handle more complex road conditions, the operator can rotate the adjustment knob 135 downwards. The screw moves downwards under the action of the threaded engagement, further compressing the compression spring 131 fitted onto the screw. This increases the compression of the spring 131, significantly increasing the downward pressure of the spring on the locking seat 132. As the adjustment knob 135 continues to rotate, the locking seat 132, under greater elastic pressure, generates a stronger clamping force on the ends of the symmetrical folding arms 110 that enter its receiving space. The connection between the two symmetrical folding arms 110 becomes more secure and reliable, making the entire foldable cargo conversion frame 100 a high-rigidity load-bearing structure capable of stably withstanding the weight of the cargo and various dynamic loads and impacts during riding. By rotating the adjustment knob 135, the operator can flexibly adjust the locking force according to actual load requirements, satisfying both convenient operation under light loads and ensuring safety and reliability under heavy loads.

[0046] The compression spring 131 plays a crucial role in the locking mechanism: its pre-compression provides initial elastic force, enabling the frame to quickly self-lock without additional operation, automatically locking after the symmetrical folding arms come together. Simultaneously, the adjustable additional compression amount via knob 135 allows the locking force to be flexibly adjusted according to actual load requirements, satisfying convenient operation under light loads while ensuring safety and reliability under heavy loads. Furthermore, the continuous elastic pressure of the spring automatically compensates for potential loosening of the connection due to vibration, temperature changes, etc., ensuring long-term stability of the lock. Even during long-term use, if the clearance between the end of the symmetrical folding arm 110 and the locking seat 132 slightly increases due to wear or other reasons, the elastic force of the compression spring 131 automatically compensates for this clearance change, maintaining a clamping effect on the symmetrical folding arm 110 and ensuring the reliability of the locked state.

[0047] The spherical structure design at the end of the guide rod 133 has several advantages: First, the arc shape of the spherical surface can form a progressive guiding contact with the surface of the symmetrical folding arm 110 at different stages of its approach. Regardless of the angle at which the symmetrical folding arm 110 approaches, the spherical surface can smoothly guide it into the correct position, avoiding the jamming phenomenon that may occur with sharp corners or planar structures. Second, compared with line contact or surface contact, spherical contact has lower contact stress and frictional resistance, resulting in less resistance to the symmetrical folding arm 110 during the guiding process. This allows the operator to complete the folding action more easily, improving the convenience and comfort of operation. Third, the two guide rods 133 are symmetrically distributed on both sides of the locking seat 132. Their spherical ends can simultaneously provide balanced guiding forces to both symmetrical folding arms 110 when guiding them in, ensuring that the ends of the two symmetrical folding arms 110 can be aligned and enter the receiving space of the locking seat 132 simultaneously. This avoids the problem of uneven loading or jamming caused by one side entering first, ensuring the smoothness of the locking process and the symmetry of the locked state. In addition, the smooth surface of the sphere structure makes it difficult for dirt to accumulate, and it can maintain good guiding performance even when used in dusty or slightly polluted environments, reducing the frequency of maintenance.

[0048] In the locked state, the safety of the folding locking mechanism 130 is reflected in several aspects: First, the continuous elastic pressure provided by the compression spring 131 forms a passive anti-loosening mechanism. Even when encountering vibrations and impacts from bumpy roads during riding, the spring's elastic force can always keep the symmetrical folding arm 110 pressed tightly, preventing the locking mechanism from loosening due to vibration. Second, the adjustable locking force of the adjustment knob 135 provides active safety assurance. The operator can actively increase the locking force according to the weight of the cargo and road conditions, allowing the safety margin of the locking mechanism to be adjusted according to actual needs, providing a higher level of safety when carrying heavy cargo or dealing with harsh road conditions. Third, the mechanical locking structure does not rely on electricity or other energy sources, eliminating the risk of locking failure due to power failure or energy depletion, and has high reliability. Fourth, the spherical end of the guide rod 133 acts as a limit after the symmetrical folding arm 110 is locked, preventing the symmetrical folding arm 110 from moving laterally or rotating within the locking seat 132, further enhancing the stability of the locked state.

[0049] When the foldable cargo conversion frame 100 needs to be unfolded from its folded state, the operator first rotates the adjusting knob 135 upwards in the opposite direction. The screw moves upwards under the action of the threaded engagement, reducing the compression of the spring 131 and decreasing the clamping force of the locking seat 132 on the symmetrical folding arms 110. Then, the operator forces the symmetrical folding arms 110 in the opposite direction to overcome the remaining spring force, causing the ends of the symmetrical folding arms 110 to disengage from the receiving space of the locking seat 132 and the positioning of the guide rod 133, thus releasing the locking state between the two symmetrical folding arms 110. During the process of the ends of the symmetrical folding arms 110 disengaging from the spherical structure of the guide rod 133, the arc shape of the spherical surface also serves as a guide, allowing the symmetrical folding arms 110 to smoothly exit the locked position, avoiding jamming or requiring excessive operating force during unlocking. After the lock is released, the symmetrical folding arms 110 are then rotated in the unfolding direction around the central folding hinge 120 to unfold the foldable cargo conversion frame 100 to its working state. The entire locking and unlocking process is simple and intuitive. The spring-loaded structure ensures high reliability in the folded state and makes unfolding relatively effortless and controllable.

[0050] In a further specific embodiment, to improve the accuracy and reliability of locking, the inner wall of the receiving space of the locking seat 132 may be provided with a positioning groove or positioning step that matches the shape of the end of the symmetrical folding arm 110. When the end of the symmetrical folding arm 110 is fully inserted into the receiving space, the end of the symmetrical folding arm 110 engages with the positioning groove or positioning step, further restricting the lateral or longitudinal movement of the symmetrical folding arm 110 and enhancing the stability of locking. The positioning groove or positioning step can also provide tactile feedback when the symmetrical folding arm 110 enters the locking seat 132, allowing the operator to clearly perceive whether the symmetrical folding arm 110 is fully in place, avoiding insufficient locking due to the symmetrical folding arm 110 not being fully inserted.

[0051] In a further specific embodiment, the ball end of the guide rod 133 may be made of a wear-resistant material, such as hardened steel, ceramic, or high-performance engineering plastic, to improve its wear resistance and service life. The ball surface may also be surface treated, such as chrome plating, nickel plating, or coated with a lubricating coating, to further reduce the coefficient of friction, improve guiding performance, and enhance corrosion resistance.

[0052] The above description is merely a specific example of this utility model and does not constitute any limitation on this utility model. Obviously, those skilled in the art, after understanding the content and principle of this utility model, may make various modifications and changes in form and details without departing from the principle and structure of this utility model. However, these modifications and changes based on the concept of this utility model are still within the protection scope of the claims of this utility model.

Claims

1. A folding structure for a foldable cargo conversion frame, used for cargo bicycles or electric vehicles, fixedly mounted on a main frame (01), characterized in that, include: Two symmetrical folding arms (110) form a cargo carrying space when unfolded and can be folded into a compact state when folded. A central folding hinge (120) is located at the middle of the two symmetrical folding arms (110) as a folding and rotation pivot point. The two symmetrical folding arms (110) are connected to each other through the central folding hinge (120) to form a foldable load-bearing structure. A folding locking mechanism (130) is used to lock the unfolded state; The central folding hinge (120) includes a hinge body and an unfolding limiting support (121), and the middle ends of the two symmetrical folding arms (110) are rotatably connected to both sides of the hinge body. The unfolding limiting support (121) is disposed on the central folding hinge (120) and is used to prevent the two symmetrical folding arms (110) from continuing to rotate outward when they are unfolded to a preset angle.

2. The folding structure of the foldable cargo conversion frame according to claim 1, characterized in that, The symmetrical folding arm (110) forms a U-shaped or rectangular cargo carrying space when unfolded.

3. The folding structure of the foldable cargo conversion frame according to claim 1, characterized in that, The folding locking mechanism (130) adopts a pin-type, snap-on, or bolt-type locking structure.

4. The folding structure of the foldable cargo conversion frame according to claim 1, characterized in that, The folding locking mechanism (130) adopts a spring-loaded locking structure, including: A knob mounting base (134) is fixedly installed on the main frame (01); An adjustment knob (135) is rotatably mounted on the knob mounting base (134). The adjustment knob (135) includes a knob body and a screw, the screw passing through a threaded hole in the knob mounting base (134). A compression spring (131) is sleeved on the screw of the adjusting knob (135); A locking seat (132) is sleeved below the compression spring (131), and the lower end of the compression spring (131) presses against the top surface of the locking seat (132); Two guide rods (133) are provided on both sides of the locking seat (132) and extend to both sides along the opening and closing direction of the two symmetrical folding arms (110).

5. The folding structure of the foldable cargo conversion frame according to claim 4, characterized in that, The end of the guide rod (133) is a spherical structure.

6. The folding structure of the foldable cargo conversion frame according to claim 4, characterized in that, The compression spring (131) is in a pre-compressed state in its natural state and can continuously provide downward elastic pressure.

7. The folding structure of the foldable cargo conversion frame according to claim 1, characterized in that, The symmetrical folding arm (110) is also provided with a support and stabilizing rod (140). The support and stabilizing rod (140) is provided in pairs, with a total of two rods, which are respectively provided on the two symmetrical folding arms (110). One end of the support stabilizing rod (140) is rotatably connected to the symmetrical folding arm (110) via a hinged connector (141), and the other end forms a fixed connection or support contact with the symmetrical folding arm (110) or the support structure in the unfolded state.

8. The folding structure of the foldable cargo conversion frame according to claim 7, characterized in that, The support stabilizer bar (140) is provided with a locking mechanism (142) at its extended position.

9. The folding structure of the foldable cargo conversion frame according to claim 8, characterized in that, The support and stabilizing bar (140) has one of the following storage methods: Flip-on type: The support stabilizing rod (140) is flipped around the hinge axis of the hinge connector (141) and placed against the side of the symmetrical folding arm (110) or parallel to the longitudinal direction of the symmetrical folding arm (110). Disassembly and storage type: The support stabilizing rod (140) can be separated from the symmetrical folding arm (110) by quickly disassembling the hinge connector (141).

10. A cargo bicycle or electric vehicle, characterized in that, include: The main frame (01) includes wheels, a fork (011), a handlebar (012), a seat post (013), a head tube (014), and a down tube (015); and a folding structure including the foldable cargo conversion frame of claim 1, which is fixedly mounted on the main frame (01).

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