Two-wheel and four-wheel conversion type trolley

Abstract

The invention discloses a two-wheel and four-wheel conversion type trolley. The trolley comprises a first platform and a grab rail, wherein the first platform is provided with a front face and a back face which are arranged oppositely; the grab rail is rotationally connected to one end of the first platform, and a grab rail locking mechanism acts on the grab rail to limit rotation of the grab rail; a pair of first rolling wheels and a pair of second rolling wheels are arranged on the back face of the first platform, the pair of second rolling wheels are arranged at the end, close to the grab rail, of the back face, two rolling wheel base bodies in the pair of second rolling wheels are fixed relative to the grab rail through a connecting body, and the first rolling wheels are arranged at the other end of the back face; according to the cart mechanism, the cart mechanism can have a two-wheel use state, a four-wheel use state and a folding storage state through the arrangement of the second rolling wheels, and therefore the cart mechanism can contain large-size goods, and meanwhile the state of the cart mechanism can be automatically changed according to the size of the goods.

Description

Technical Field

[0001] This invention relates to the field of handcart technology, and more specifically to a two-wheeled to four-wheeled convertible handcart. Background Technology

[0002] A handcart is a short-distance, human-powered tool for transporting goods. It is characterized by its low cost, simple maintenance, flexible operation, and light weight, enabling efficient transport of goods in confined spaces where motor vehicles cannot easily pass (such as warehouse aisles, supermarket shelves, or indoor spaces). Its core structure includes a carrying platform, frame, wheels, and handles. Based on the number of wheels, it can be categorized into one-wheeled, two-wheeled, three-wheeled, and four-wheeled types. One-wheeled carts are suitable for rough paths and turning on the spot; two-wheeled carts (such as "tiger carts") excel at carrying packaged goods; and four-wheeled carts use casters to enhance steering flexibility. Modern handcarts have further evolved into specialized variants such as silent, anti-static, height-adjustable, and folding types. For example, silent handcarts use polyurethane wheels and precision bearings to reduce noise, making them suitable for quiet locations such as libraries and hotels; folding carts achieve portability and storage through an articulated structure. Their applications cover logistics warehousing, construction, and household goods, with irreplaceable economic and convenience, especially in short-distance, light-load transportation.

[0003] Currently, handcarts on the market are mainly two-wheeled and four-wheeled.

[0004] Two-wheeled handcarts are favored for their compact size, but their loading capacity is limited by the size of the carrying platform. Due to their two-wheel design, the wheels become the pressure points during use, and the carrying platform and support are arranged at an angle, requiring goods to be stacked on the inclined platform. During this process, the carrying platform bears significant pressure, and to prevent bending, its size is usually small, resulting in limited loading capacity and difficulty in accommodating larger items, such as large household appliances like televisions and refrigerators.

[0005] In contrast, four-wheeled handcarts have a platform parallel to the ground, allowing them to carry more and larger items. However, these handcarts are generally larger and not suitable for use in the vicinity of a home. For example, when moving luggage around the home, a single cardboard box often fails to fully utilize the platform, resulting in wasted space.

[0006] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0007] The purpose of this invention is to provide a two-wheeled to four-wheeled convertible handcart.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A two-wheeled to four-wheeled convertible handcart includes a first platform having a front and a back arranged opposite to each other, and a handrail.

[0010] The handrail is rotatably connected to one end of the first platform, and a handrail locking mechanism is provided on the handrail to restrict its rotation; a pair of first rollers and a pair of second rollers are provided on the back of the first platform. The pair of second rollers is located at one end of the back near the handrail, and two of the roller seats are fixed relative to the handrail by a connecting body. The first rollers are located at the other end of the back; there is a set distance between the axis of the second rollers and the rotation center of the handrail. When the handrail is driven to rotate, the connecting body can drive the second rollers to revolve around the rotation center of the handrail.

[0011] It also includes a linkage mechanism, which comprises a first link and a second link. The ends of the first link and the second link are hinged together, and the direction of their hinge axis is parallel to the rotation center direction of the rotatable connection between the handrail and the first platform. The end of the first link away from the second link is hinged relative to the back side, and the end of the second link away from the first link is hinged relative to the connecting body. A link locking mechanism is also provided at the hinge point of the first link and the second link. The link locking mechanism acts at the hinge point of the first link and the second link to lock and restrict the relative rotation of the first link and the second link about their hinge axis.

[0012] The handcart has a four-wheeled usage mode and a two-wheeled usage mode;

[0013] When the trolley is in four-wheel use mode, the handlebar is at a near-vertical angle to the first platform and is locked by the handlebar locking mechanism. The first and second rollers support the first platform against the ground. The first and second connecting rods are in a straight line and are locked by the connecting rod locking mechanism. The straight line formed by the first and second connecting rods forms an acute angle with the first platform. Furthermore, the straight line formed by the first and second connecting rods, the line connecting the hinge point of the second connecting rod and the connecting body to the rotation center of the handlebar, and the line connecting the rotation center of the handlebar to the hinge point of the first connecting rod and the back side form a triangular support structure.

[0014] When the trolley is in two-wheel use mode, the handlebar rotates to the extension direction of the first platform and is locked by the handlebar locking mechanism. The first link and the second link form an acute angle, so that the second roller approaches the back of the first platform to be folded up.

[0015] By rotating the handlebar, which simultaneously drives the second roller, the handcart can be switched between the four-wheeled and two-wheeled usage states.

[0016] In the above solution, the trolley mechanism can be configured with a second roller to have two-wheeled, four-wheeled, and folded storage modes. This allows the trolley mechanism to not only accommodate larger items but also automatically adjust its mode according to the size of the items.

[0017] Preferably, the end of the first link away from the second link is hinged and slidably connected to the back side, and the sliding direction is set along the direction of approaching and moving away from the handrail;

[0018] The roller seats of the pair of first rollers are symmetrically arranged and each is rotatably connected to the first platform about the direction of approaching and moving away from the handrail, so that the first rollers have an upright state and a flipped-up storage state; the hinged and slidably connected end of the second link acts on the first roller, enabling it to switch between its upright state and flipped-up storage state.

[0019] The handcart also has a foldable storage configuration;

[0020] When the handrail is in the folded storage state, the handrail rotates to be close to the front, causing the first link and the second link to be in a straight line and slide together toward the handrail by a set length, so that the straight line formed by the first link and the second link is parallel to or intersects the extension line of the length direction of the first platform at an acute angle, so that the second roller rotates to the outer side of the end of the first platform, and the first roller rotates to the flipped storage state.

[0021] With the above design, the trolley can also enter a folding and storage state. In order to enter the folding and storage state, the handlebar rotates to be close to the front, causing the first link and the second link to be in a straight line and slide together toward the handlebar for a set length (this length is set according to the needs and needs to meet the purpose of pulling the rotating plate to fold up). This makes the straight line formed by the first link and the second link parallel to or intersect the extension line of the first platform in the length direction, so that the second roller rotates to the outer end of the first platform, and the first roller rotates to the flipped and stored state.

[0022] Preferably, the linkage locking mechanism includes a sliding locking block and a locking part, wherein one of the sliding locking block and the locking part is disposed on the first linkage and the other is disposed on the second linkage; the sliding locking block and the locking part are disposed opposite to each other; when the first linkage and the second linkage are in a straight line, the sliding locking block and the locking part are directly opposite each other, and the sliding locking block acts on the locking part to lock the relative position of the first linkage and the second linkage; and the sliding locking block can be driven by external force to disengage from the locking part to unlock.

[0023] With the above design, the first link and the second link can be quickly and freely unlocked or locked in a straight line or at an acute angle.

[0024] Preferably, in the contact area between the first link and the second link, one side is provided with a guide groove, and the other side is provided with a first sliding post and a second sliding post; the guide groove is an annular structure arranged around the hinge axis of the first link and the second link, and a first holding point is provided in the guide groove;

[0025] The first sliding post and the second sliding post are arranged at a distance from each other around the hinge axis of the first link and the second link.

[0026] When the first link and the second link rotate and bend to an acute angle, the first sliding column is at the first holding point, and the first link, the second link and the back side form a triangular structure.

[0027] When the first link and the second link are in a straight line, the first sliding post acts as the locking part and engages with the sliding lock block to lock, while the second sliding post is located in the guide groove.

[0028] With the above design, the first link and the second link can switch between a straight line state and an acute angle state.

[0029] Preferably, the linkage locking mechanism includes a traction rope;

[0030] A sliding groove for accommodating a sliding lock block is provided on the first link or the second link;

[0031] The sliding groove has a long strip-shaped structure;

[0032] The sliding lock block is slidably connected in the sliding slot. An elastic element acts on the sliding lock block. The sliding lock block is provided with a locking slot for limiting the first sliding post. The elastic element is configured to drive the sliding lock block to move toward the first sliding post so that the locking slot has a tendency to engage and lock the first sliding post.

[0033] The end of the traction rope is connected to the sliding lock block; when in use, under the action of external force, pulling the traction rope drives the sliding lock block to move backward, causing the lock slot to disengage from the first sliding post and unlock.

[0034] Preferably, the linkage locking mechanism further includes a sliding operation button;

[0035] The sliding operation button is slidably set relative to the first platform and is positioned when it is slid to a certain position;

[0036] One end of the traction rope is connected to the sliding operation button, and the other end is connected to the sliding lock block. In use, under the action of external force, the sliding operation button pulls the traction rope, driving the sliding lock block to disengage from the locking part to unlock.

[0037] The above design makes operation simpler and more convenient when the first link and the second link move relative to each other.

[0038] Preferably, in the flipped storage state, the first roller is flipped towards the center area of ​​the back side, and a torsion spring acts on the first roller, the elastic force of the torsion spring forcing the first roller to remain in the flipped storage state.

[0039] A slider is connected to the back of the first flat plate via a slide rail;

[0040] One end of the sliding body is hinged to the first connecting rod, and the other end is hinged to a pulling connecting rod;

[0041] The first platform has a rotating plate rotatably connected to one end of a first roller. The rotation center line of the rotating plate is parallel to the line connecting the two first rollers. The rotating plate is hinged to the pulling rod. The rotating plate has mating parts on both sides that cooperate with the roller seats of the first rollers.

[0042] When the handcart is in four-wheel use mode and two-wheel use mode, the mating part of the rotating plate abuts against the roller seats of the two first rollers, supporting the two first rollers in an upright state; the rotating plate or sliding body has an elastic element to keep the rotating plate supporting the two first rollers in an upright state.

[0043] When the trolley is in the folded storage state, the handlebar rotates to approach the front, causing the first connecting rod to slide a set distance toward the handlebar side. Through the sliding body and the pulling connecting rod, the rotating plate rotates and moves toward the first platform. The mating part of the rotating plate disengages from the roller seats of the two first rollers, and the two first rollers return to the flipped storage state due to the elastic force of the spring.

[0044] The above design enables the first roller to move together with the second roller.

[0045] Preferably, the first platform has an installation notch at one end, and the handrail is rotatably connected within the installation notch;

[0046] The handrail locking mechanism includes a positioning rod, which is inserted through the handrail and the axis of the positioning rod is parallel to the extension line of the width direction of the first platform.

[0047] The side wall of the handrail is provided with a long sliding groove at the position corresponding to the positioning rod. The sliding groove has a tightening end near the connecting body and a shifting end away from the connecting body. A spring is applied to the positioning rod so that the positioning rod always tends to slide from the shifting end to the tightening end.

[0048] A positioning chuck is provided in the installation notch at the position corresponding to the handrail, and the edge of the surface of the positioning chuck is provided with a first positioning point and a second positioning point.

[0049] When the trolley is in four-wheel use mode and the handlebar is upright, the positioning rod is in the tightened end of the sliding groove, and at the same time the end is embedded in the first positioning point to lock it.

[0050] Under the action of external force, the drive positioning rod slides from the tightening end to the switching end to disengage from the first positioning point, so that the handrail can be freely rotated;

[0051] When the trolley is in two-wheel use mode, when the handlebar is rotated to the extension direction of the first platform, the positioning rod is in the tightened end of the sliding groove, and at the same time the end is embedded in the second positioning point to lock.

[0052] With the above design, the handrail can change position and be positioned according to the change of two wheels and four wheels.

[0053] Preferably, the rotating plate is provided with spacer holes so that the outer edge of the rotating plate forms a frame-like embedded part;

[0054] Each pair of first rollers has a raised portion on its opposite side surface of the roller seat. The raised portion has a recessed groove on its periphery, which is configured to accommodate the embedded portion. The raised portion also has a beveled block protruding from the side near the rotating plate.

[0055] When the trolley is switched between four-wheel and two-wheel use modes, the rotating plate flips down, and its mating part slides into the inclined block of the roller seat of the two first rollers until the recessed groove engages with the embedded part, supporting the two first rollers in an upright state.

[0056] With the above design, the rotating plate can fully open the two first rollers.

[0057] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0058] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.

[0059] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0060] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing this case.

[0061] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.

[0062] The working principle and advantages of this invention are as follows:

[0063] The present invention can enable the trolley mechanism to have a two-wheeled use mode, a four-wheeled use mode, and a folded storage mode by setting the second roller, so that the trolley mechanism can not only accommodate large-sized goods, but also automatically change the state of the trolley mechanism according to the size of the goods.

[0064] Specifically, based on the horizontal plane (i.e., the ground), in the four-wheel usage state, the front is parallel to the horizontal plane, the handrail is upright, the first link and the second link are in a straight line and set at an acute angle to the back. Furthermore, the straight line formed by the first link and the second link, the line connecting the hinge point of the second link and the connecting body to the rotation center of the handrail, and the line connecting the rotation center of the handrail to the hinge point of the first link and the back form a triangular support structure. Through the support structure, the line connecting the center point of the second roller and the lowest point of the wheel surface is kept perpendicular to the horizontal plane. The lowest points of the wheel surfaces of the two first rollers and the two second rollers are all tangent to the horizontal plane. At this time, the first platform can hold more and larger products.

[0065] To enable two-wheel operation, the handrail is flipped to the rear side until it is in a straight line with the first platform. At the same time, the linkage locking mechanism is released, driving the connecting body to rotate. This causes the second roller to rotate to the side of the first platform. The first and second linkages rotate and bend at a set angle to form a linkage mechanism with a locking function. This linkage mechanism maintains the state of the second roller so that only the wheel surfaces of the two first rollers tangent to it are on the horizontal plane. At this point, the trolley mechanism has two wheels.

[0066] The difference between this application and existing technologies lies in its ability to switch between four-wheel and two-wheel usage modes, thus enhancing the adaptability and flexibility of the cart mechanism in different usage scenarios. Furthermore, the coordinated control of the linkage mechanism with locking and limiting functions formed by the first and second links, along with the linkage locking mechanism, achieves stable switching and maintenance of the structure, enhancing the safety and reliability of the cart. In practical applications, the cart mechanism's state switching operation is simple, allowing users to quickly adjust the state according to actual needs without the need for additional tools, saving operation time and improving efficiency. Attached Figure Description

[0067] Appendix Figure 1This is a schematic diagram of the handcart in a two-wheeled usage state according to an embodiment of the present invention;

[0068] Appendix Figure 2 This is a perspective view of the handcart in a two-wheeled usage state according to an embodiment of the present invention;

[0069] Appendix Figure 3 This is a schematic diagram of the rear structure of the first platform when the handcart is in two-wheel use mode according to an embodiment of the present invention;

[0070] Appendix Figure 4 This is a perspective view of the handcart in a four-wheeled usage state according to an embodiment of the present invention;

[0071] Appendix Figure 5 This is a front view of the handcart in a four-wheeled usage state according to an embodiment of the present invention.

[0072] Appendix Figure 6 This is a schematic diagram of the structure of the handcart in the present invention after the sliding body and the pulling link are connected when the handcart is in four-wheel use state.

[0073] Appendix Figure 7 This is a schematic diagram of the rear structure of the handcart in the four-wheel usage state according to an embodiment of the present invention;

[0074] Appendix Figure 8 This is a side view of the handcart in a four-wheeled usage state according to an embodiment of the present invention;

[0075] Appendix Figure 9 This is a perspective view of the handcart in the folded storage state in an embodiment of the present invention;

[0076] Appendix Figure 10 This is a perspective view of the back of the trolley in the folded storage state according to an embodiment of the present invention;

[0077] Appendix Figure 11 This is a schematic diagram of the rear structure of the trolley in the folded storage state according to an embodiment of the present invention;

[0078] Appendix Figure 12 This is a front view of the trolley in a folded storage state according to an embodiment of the present invention.

[0079] Appendix Figure 13 This is a schematic diagram of the structure of the first link and the second link in an embodiment of the present invention when they are rotated and bent to a set angle;

[0080] Appendix Figure 14 for Figure 13 A schematic diagram of the cross-sectional structure along line AA.

[0081] Appendix Figure 15This is a schematic diagram of the structure in an embodiment of the present invention when the first connecting rod and the second connecting rod are in a straight line and are set at an acute angle to the back surface;

[0082] Appendix Figure 16 for Figure 15 A schematic diagram of the cross-sectional structure along the middle BB;

[0083] Appendix Figure 17 This is a schematic diagram of the structure in an embodiment of the present invention when the length extension lines of both the first link and the second link are parallel to the back surface.

[0084] Appendix Figure 18 for Figure 17 A schematic diagram of the cross-sectional structure along the CC line.

[0085] In the attached diagrams above: 1. First platform; 2. Front view; 3. Back view; 4. Handrail; 5. First roller; 6. Second roller; 7. Connector; 8. Linkage mechanism; 9. First link; 10. Second link; 11. Linkage locking mechanism; 12. Sliding end; 13. Limiting plate; 14. Guide groove; 15. Sliding slot; 16. First holding point;

[0086] 18. Hollowed-out section; 19. Limiting disc; 20. Actuating end; 21. Hinge column; 22. First sliding column; 23. Second sliding column; 24. Sliding operation button; 25. Traction rope; 26. Sliding lock block; 27. Elastic element; 28. Locking slot; 29. ​​Slide rail; 30. Sliding body; 31. Pulling linkage; 32. Square hole; 33. Elastic element; 34. Shaft; 35. Rotating part; 36. Mounting notch; 37. Positioning rod; 38. Sliding through groove; 39. Tightening end; 40. Reversing end; 41. Springback element; 42. Positioning chuck; 43. First positioning point; 44. Second positioning point; 45. Hollowed-out shovel plate; 46. Protrusion; 47. Rotating plate;

[0087] 51. Torsion spring sleeve; 52. Roller seat; 53. Front roller body; 54. Limiting surface;

[0088] 471. Spacing hole; 461. Recessed groove; 462. Beveled block; 463. Embedded part;

[0089] 100. Rotating part; 101. Abutting surface. Detailed Implementation

[0090] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0091] Example: The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the examples of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0092] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms.

[0093] See appendix Figure 1 - Figure 18 As shown, a two-wheeled and four-wheeled convertible handcart includes a first platform 1 having a front 2 and a back 3 arranged opposite to each other, and a handrail 4.

[0094] The handrail 4 is rotatably connected to one end of the first platform 1. A handrail locking mechanism is provided on the handrail 4 to restrict its rotation. The back side 3 of the first platform 1 is provided with a pair of first rollers 5 and a pair of second rollers 6. The pair of second rollers 6 is located at one end of the back side 3 near the handrail 4, and the two roller seats 52 of the pair of second rollers 6 are fixed relative to the handrail 4 by a connecting body 7. The first rollers 5 are located at the other end of the back side 3. There is a set distance between the axis of the second rollers 6 and the rotation center of the handrail 4. When the handrail 4 is driven to rotate, the connecting body 7 can drive the second rollers 6 to revolve around the rotation center of the handrail 4.

[0095] It also includes a linkage mechanism 8, which includes a first link 9 and a second link 10. The ends of the first link 9 and the second link 10 are hinged together, and the direction of their hinge axis is parallel to the direction of the rotation center connecting the handrail 4 and the first platform 1. The end of the first link 9 away from the second link 10 is hinged relative to the back surface 3, and the end of the second link 10 away from the first link 9 is hinged relative to the connecting body 7. A linkage locking mechanism 11 is also provided at the hinge of the first link 9 and the second link 10. The linkage locking mechanism 11 acts at the hinge of the first link 9 and the second link 10 to lock and restrict the relative rotation of the first link 9 and the second link 10 about their hinge axis.

[0096] The handcart has a four-wheeled usage mode and a two-wheeled usage mode;

[0097] When the trolley is in four-wheel use mode, the handlebar 4 is at a near-vertical angle to the first platform 1 and is locked by the handlebar locking mechanism. The first roller 5 and the second roller 6 support the first platform 1 on the ground. The first connecting rod 9 and the second connecting rod 10 are in a straight line and are locked by the connecting rod locking mechanism 11. The straight line formed by the first connecting rod 9 and the second connecting rod 10 forms an acute angle with the first platform 1. Furthermore, the straight line formed by the first connecting rod 9 and the second connecting rod 10, the line connecting the hinge point of the second connecting rod 10 and the connecting body 7 to the rotation center of the handlebar 4, and the line connecting the rotation center of the handlebar 4 to the hinge point of the first connecting rod 9 and the back 3 form a triangular support structure.

[0098] When the trolley is in two-wheel use mode, the handlebar 4 rotates to the extension direction of the first platform 1 and is locked by the handlebar locking mechanism. The first connecting rod 9 and the second connecting rod 10 form an acute angle, so that the second roller 6 approaches the back 3 of the first platform 1 to be folded up.

[0099] By rotating the handlebar 4, which simultaneously drives the second roller 6 to move, the handcart can switch between the four-wheeled and two-wheeled usage states.

[0100] The first roller 5 and the second roller 6 are both common rollers in the prior art, such as casters, so they will not be described in detail.

[0101] In this invention, the first connecting rod 9 and the second connecting rod 10 can be connected by a hinge post 21, which can be in the shape of an I-beam.

[0102] In this invention, the handrail 4 has a U-shaped structure.

[0103] In this invention, the second roller 6 allows the trolley mechanism to have a two-wheeled usage state, a four-wheeled usage state, and a folded storage state. This enables the trolley mechanism to not only accommodate larger items but also automatically adjust its state according to the size of the goods. Two sets of linkage mechanisms 8 are provided, specifically as follows: Figure 2 .

[0104] Specifically, based on the horizontal plane (i.e., the ground), in the four-wheel use state, the front 2 is parallel to the horizontal plane, the handrail 4 is upright, the first connecting rod 9 and the second connecting rod 10 are in a straight line and set at an acute angle to the back 3. Furthermore, the straight line formed by the first connecting rod 9 and the second connecting rod 10, the line connecting the hinge point of the second connecting rod 10 and the connecting body 7 to the rotation center of the handrail 4, and the line connecting the rotation center of the handrail 4 to the hinge point of the first connecting rod 9 and the back 3 form a triangular support structure. Through the support structure, the line connecting the center point of the second roller 6 and the lowest point of the wheel surface is kept perpendicular to the horizontal plane. The lowest points of the wheel surfaces of the two first rollers 5 and the two second rollers 6 are all tangent to the horizontal plane. At this time, the first platform 1 can place more and larger products.

[0105] To enter the two-wheel use mode, the handrail 4 is flipped towards the back side 3 until it is in a straight line with the first platform 1. At the same time, the linkage locking mechanism 11 is released, driving the connecting body 7 to rotate, causing the second roller 6 to rotate to the side of the first platform 1. The first link 9 and the second link 10 rotate and bend to a set angle (e.g., Figure 2As shown, a linkage mechanism 8 with a locking and limiting function is formed, and the state of the second roller 6 is maintained by the linkage mechanism 8 so that only the wheel surfaces of the two first rollers 5 tangent to it are on the horizontal plane. At this time, the trolley mechanism has two wheels.

[0106] The difference between this application and existing technologies lies in its ability to switch between four-wheel and two-wheel usage modes, thus enhancing the adaptability and flexibility of the cart mechanism in different usage scenarios. Furthermore, the coordinated control of the linkage mechanism 8 (with locking and limiting function formed by the first link 9 and the second link 10) and the linkage locking mechanism 11 achieves stable switching and maintenance of the structure, enhancing the safety and reliability of the cart. In practical applications, the cart mechanism's state switching operation is simple, allowing users to quickly adjust the state according to actual needs without the need for additional tools, saving operation time and improving efficiency.

[0107] Preferably, the end of the first link 9 away from the second link 10 is hinged and slidably connected to the back surface 3, and the sliding direction is set along the direction of approaching and moving away from the handrail 4;

[0108] The roller seats 52 of the pair of first rollers 5 are symmetrically arranged and each is rotatably connected to the first platform 1 about the direction of approaching and away from the handrail 4, so that the first rollers 5 have an upright state and a flipped and stored state; the hinged and slidably connected end of the second link 10 acts on the first rollers 5, enabling them to switch between the upright state and the flipped and stored state.

[0109] The handcart also has a foldable storage configuration;

[0110] When the handrail 4 is in the folded storage state, the handrail 4 rotates to approach the front 2, causing the first connecting rod 9 and the second connecting rod 10 to be in a straight line and slide together toward the handrail 4 for a set length, so that the straight line formed by the first connecting rod 9 and the second connecting rod 10 is parallel to or intersects the extension line of the length direction of the first platform 1 at an acute angle, so that the second roller 6 rotates to the outer side of the end of the first platform 1, and the first roller 5 rotates to the flipped storage state.

[0111] With the above design, the trolley can also enter a folding and storage state. In order to enter the folding and storage state, the handlebar 4 rotates to be close to the front 2, causing the first link 9 and the second link 10 to be in a straight line and slide together toward the handlebar 4 for a set length (this length is set according to the requirements and needs to meet the purpose of pulling the rotating plate 47 to fold up). The straight line formed by the first link 9 and the second link 10 is parallel to or intersects the extension line of the length direction of the first platform 1 at an acute angle (the acute angle here is very small, close to zero degrees), so that the second roller 6 rotates to the outer end of the first platform 1, and the first roller 5 rotates to the flipped and stored state.

[0112] Preferably, the linkage locking mechanism 11 includes a sliding locking block 26 and a locking part. One of the sliding locking block 26 and the locking part is disposed on the first linkage 9, and the other is disposed on the second linkage 10. The sliding locking block 26 and the locking part are disposed opposite to each other. When the first linkage 9 and the second linkage 10 are in a straight line, the sliding locking block 26 and the locking part are directly opposite each other, and the sliding locking block 26 acts on the locking part to lock the relative position of the first linkage 9 and the second linkage 10. Furthermore, the sliding locking block 26 can be driven by external force to disengage from the locking part to unlock.

[0113] With the above design, the first link 9 and the second link 10 can be quickly and freely unlocked or locked in a straight line or at an acute angle.

[0114] Preferably, in the contact area between the first connecting rod 9 and the second connecting rod 10, one side is provided with a guide groove 14, and the other side is provided with a first sliding post 22 and a second sliding post 23; the guide groove 14 is an annular structure arranged around the hinge axis of the first connecting rod 9 and the second connecting rod 10, and a first holding point 16 is provided in the guide groove 14.

[0115] The first sliding post 22 and the second sliding post 23 are arranged at a distance from each other around the hinge axis of the first connecting rod 9 and the second connecting rod 10.

[0116] When the first link 9 and the second link 10 are rotated and bent at an acute angle, the first sliding column 22 is at the first holding point 16, and the first link 9, the second link 10 and the back surface 3 form a triangular structure.

[0117] When the first link 9 and the second link 10 are in a straight line, the first sliding post 22 acts as the locking part and engages with the sliding lock block 26 to lock, and the second sliding post 23 is located in the guide groove 14.

[0118] With the above design, the first link 9 and the second link 10 can switch between a straight line state and an acute angle state.

[0119] Preferably, the linkage locking mechanism 11 includes a traction rope 25;

[0120] A sliding groove 15 for accommodating the sliding lock block 26 is provided on the first link 9 or the second link 10;

[0121] The sliding groove 15 has a long strip-shaped structure;

[0122] The sliding lock block 26 is slidably connected in the sliding groove 15. An elastic element 27 acts on the sliding lock block 26. The sliding lock block 26 is provided with a locking groove 28 for limiting the first sliding post 22. The elastic element 27 is configured to drive the sliding lock block 26 to move toward the first sliding post 22 so that the locking groove 28 has the tendency to engage and lock the first sliding post 22.

[0123] The end of the traction rope 25 is connected to the sliding lock block 26; in use, under the action of external force, the traction rope 25 is pulled, which drives the sliding lock block 26 to move backward, so that the lock slot 28 is disengaged from the first sliding post 22 and unlocked.

[0124] In specific implementation, the first connecting rod 9 includes a sliding end 12 and a limiting plate 13 respectively disposed at both ends; the end of the sliding end 12 is hinged to the back surface 3, one side surface of the limiting plate 13 is provided with an approximately annular guide groove 14, and the other side surface is provided with a sliding groove 15, the sliding groove 15 is located in the central area of ​​the annulus, the guide groove 14 is provided with a first holding point 16, the depth of the guide groove 14 is greater than the depth of the sliding groove 15, and a hollow part 18 is formed at the intersection of the guide groove 14 and the sliding groove 15. The hollow part 18 can not only accommodate the end of the first sliding column 22, but also accommodate the sliding lock block 26.

[0125] The second connecting rod 10 includes a limiting disc 19 and an actuating end 20 connected to the connecting body 7. The surface of the limiting disc 19 is in contact with the surface of the limiting disc 13 that is provided with a guide groove 14, and a hinge post 21 is provided between the two. The limiting disc 19 is provided with a first sliding post 22 and a second sliding post 23. The axes of the first sliding post 22 and the second sliding post 23 are parallel to the hinge post 21 and are arranged around the hinge post 21 at intervals.

[0126] Preferably, the linkage locking mechanism 11 further includes a sliding operation button 24;

[0127] The sliding operation button 24 is slidably disposed relative to the first platform 1 and is positioned when it is slid to a certain position;

[0128] One end of the traction rope 25 is connected to the sliding operation button 24, and the other end is connected to the sliding lock block 26. In use, under the action of external force, the sliding operation button 24 pulls the traction rope 25, driving the sliding lock block 26 to disengage from the locking part to unlock.

[0129] With the above design, the operation is simpler and more convenient when the first link 9 and the second link 10 move relative to each other.

[0130] In specific implementation, the sliding operation button 24 is inserted through the first platform 1 and is slidably set relative to the first platform 1. The sliding direction of the sliding operation button 24 is parallel to the length direction of the first platform 1. The sliding lock block 26 is located between the hollow part 18 and the elastic member 27. Through the action of the elastic member 27, the sliding lock block 26 always has a tendency to slide towards the hollow part 18.

[0131] Specifically, when the trolley mechanism is in two-wheel operation, the first link 9 and the second link 10 will rotate and bend to a set angle (acute angle). At this time, the first sliding column 22 is at the first holding point 16. Since the first holding point 16 is the endpoint, the first sliding column 22 will no longer rotate. The first link 9, the second link 10 and the back 3 form a triangular structure. Through the triangular structure, the connecting body 7 will not move arbitrarily, ensuring that the trolley mechanism always remains in a two-wheel state.

[0132] When the trolley mechanism is in four-wheel use mode and folded storage mode, the first link 9 and the second link 10 are in a straight line. At this time, the first sliding post 22 corresponds to the hollow part 18 and extends into the hollow part 18. At the same time, the locking groove 28 on the sliding lock block 26 is locked at the end of the first sliding post 22. The second sliding post 23 is in the guide groove 14. Since the first sliding post 22 is locked by the locking groove 28 on the sliding lock block 26, the first link 9 and the second link 10 no longer rotate relative to each other at will.

[0133] Meanwhile, when locked, the elastic element 27 (optional spring) pushes the sliding lock block 26 to slide towards the hollow part 18, so that the locking groove 28 on the sliding lock block 26 limits the first sliding post 22, so that the first connecting rod 9 and the second connecting rod 10 can no longer rotate around the hinge post 21.

[0134] Once unlocking is required, simply push the sliding operation button 24 to slide on the front 2. The sliding operation button 24 will then move the traction rope 25. The moving traction rope 25 will then pull the sliding lock block 26 to slide, driving the sliding lock block 26 towards the elastic member 27, so that the elastic member 27 stores force. At the same time, the locking slot 28 on the sliding lock block 26 will also disengage from the first sliding post 22, allowing the first link 9 and the second link 10 to rotate around the hinge post 21.

[0135] Preferably, in the flipped storage state, the first roller 5 is flipped towards the center area of ​​the back side 3, and a torsion spring acts on the first roller 5. The elastic force of the torsion spring forces the first roller 5 to remain in the flipped storage state.

[0136] The back surface 3 of the first flat plate is connected to a slider 30 via a slide rail 29;

[0137] One end of the sliding body 30 is hinged to the first connecting rod 9, and the other end is hinged to a pulling connecting rod 31;

[0138] The first platform 1 has a rotating plate 47 rotatably connected to one end of a first roller 5. The rotation center line of the rotating plate 47 is parallel to the line connecting the two first rollers 5. The rotating plate 47 is hinged to the pulling rod 31. The two sides of the rotating plate 47 are provided with mating parts that cooperate with the roller seat 52 of the first roller 5.

[0139] When the handcart is in four-wheel use mode and two-wheel use mode, the mating part of the rotating plate 47 abuts against the roller seat 52 of the two first rollers 5, supporting the two first rollers 5 in an upright state; an elastic element 33 is applied on the rotating plate 47 or the sliding body 30 to keep the rotating plate 47 supporting the two first rollers 5 in an upright state.

[0140] When the trolley is in the folded storage state, the handlebar 4 rotates to approach the front 2, causing the first connecting rod 9 to slide a set distance toward the handlebar 4. Through the sliding body 30 and the pulling connecting rod 31, the rotating plate 47 rotates and moves toward the first platform 1. The mating part of the rotating plate 47 disengages from the roller seat 52 of the two first rollers 5, and the two first rollers 5 return to the flipped storage state due to the elastic force of the spring.

[0141] The above design enables the first roller 5 to move together with the second roller 6.

[0142] In specific implementation, the back side 3 is provided with a slide rail 29, and a sliding body 30 is slidably connected in the slide rail 29; one end of the sliding body 30 is hinged to the first connecting rod 9, and the other end is hinged to a pulling connecting rod 31; the front side 2 of the first platform 1 is provided with a square hole 32 at one end near the first roller 5, and a rotating plate 47 is provided in the square hole 32. One end of the rotating plate 47 is rotatably connected to the inner wall of the square hole 32, and the other end extends towards the second roller 6 as a free end; the free end is hinged to the pulling connecting rod 31.

[0143] Specifically, in the two-wheeled use state, the first link 9 and the second link 10 rotate and bend to a set angle. At this time, the sliding body 30 does not move towards the second roller 6, and pulls the link 31, the rotating plate 47 and the first platform 1 to form a triangular structure. The mating part of the rotating plate 47 abuts against the roller seat 52 of the two first rollers 5, supporting the two first rollers 5 in an upright state.

[0144] Once the trolley mechanism enters the storage state, the handlebar 4 rotates to approach the front 2, causing the first connecting rod 9 to slide a set distance toward the handlebar 4. Through the sliding body 30 and the pulling connecting rod 31, the rotating plate 47 rotates and moves toward the first platform 1. The mating part of the rotating plate 47 disengages from the roller seat 52 of the two first rollers 5, and the two first rollers 5 return to the flipped storage state due to the spring force.

[0145] The elastic element 33 can be a spring. With the above design, the first link 9 can always have a tendency to slide toward the first roller 5. Thus, when the trolley mechanism is deployed, the position of the first link 9 can be automatically adjusted to cooperate with the second link 10, thereby improving the stability and reliability of the trolley deployment.

[0146] It should be noted that the elastic element 33 ensures that the first link 9 always moves in the direction of the first roller 5. This helps to prevent slack between the second link 10 and the first link 9 during the unfolding of the trolley, meaning that the rotating plate 47 also tends to move away from the square hole 32.

[0147] Preferably, the first platform 1 has an installation notch 36 at one end, and the handrail 4 is rotatably connected in the installation notch 36;

[0148] The handrail locking mechanism includes a positioning rod 37, which is inserted through the handrail 4. The axis of the positioning rod 37 is parallel to the extension line of the width direction of the first platform 1.

[0149] The side wall of the handrail 4 is provided with a long sliding groove 38 at the position corresponding to the positioning rod 37. The sliding groove 38 has a tightening end 39 near the connecting body 7 and a shifting end 40 away from the connecting body 7. A spring-loaded element 41 is applied to the positioning rod 37 so that the positioning rod 37 always has the tendency to slide from the shifting end 40 to the tightening end 39.

[0150] A positioning chuck 42 is provided in the mounting notch 36 at the position corresponding to the handrail 4. The edge of the surface of the positioning chuck 42 is provided with a first positioning point 43 and a second positioning point 44.

[0151] When the trolley is in four-wheel use mode and the handlebar 4 is raised, the positioning rod 37 is in the tightening end 39 in the sliding groove 38, and at the same time the end is embedded in the first positioning point 43 to lock.

[0152] Under the action of external force, the drive positioning rod 37 slides from the tightening end 39 to the switching end 40 to disengage from the first positioning point 43, so that the handrail 4 can be freely rotated.

[0153] When the trolley is in two-wheel use mode, when the handlebar 4 is rotated to the extension direction of the first platform 1, the positioning rod 37 is in the tightening end 39 in the sliding groove 38, and at the same time the end is embedded in the second positioning point 44 to lock.

[0154] With the above design, the handrail 4 can change position and be positioned according to the change between two wheels and four wheels.

[0155] Specifically, when the handrail 4 is in the upright position, the positioning rod 37 is embedded in the first positioning point 43, thereby achieving stable support for the handrail 4. When it is necessary to flip the handrail 4 to a state parallel to the first platform 1, an external force is applied to disengage the positioning rod 37 from the first positioning point 43 and slide it along the sliding groove 38 to the switching end 40. At this time, the handrail 4 can be flipped freely. After flipping to the correct position, the spring 41 pulls the positioning rod 37 back to the tightening end 39 and embeds it in the second positioning point 44, thereby achieving positioning of the handrail 4 in the parallel state. When the handrail 4 is flipped to a position close to the front 2, the positioning rod 37 is at the tightening end 39 of the sliding groove 38, and its end does not contact the inner wall of the mounting notch 36, maintaining a certain gap to avoid interfering with the flipping action of the handrail 4.

[0156] It should be noted that, in specific implementation, the connecting body 7 includes a shaft 34 fixedly mounted on the back side 3. The axis of the shaft 34 is parallel to the extension line of the width direction of the first platform 1. The two ends of the shaft 34 are respectively positioned and connected to two second rollers 6. Two rotating parts 35 are provided around the shaft 34. These two rotating parts 35 are symmetrically and spaced apart with the line connecting the midpoints of the two sides in the width direction of the back side 3 as the reference axis. Each rotating part 35 is configured to rotate around the connecting body 7. The end of each rotating part 35 is hinged to the end of a second connecting rod 10.

[0157] When in use, in the folded state, the rotating part 35 extends out of the end of the first platform 1 with the second roller 6. The length extension lines of both the first link 9 and the second link 10 are parallel to the back surface 3. The link locking mechanism 11 locks the state of the first link 9 and the second link 10. At the same time, the radial plane of the first roller 5 is parallel to the back surface 3, and the handrail 4 flips to be close to the front surface 2.

[0158] Next, to enter the four-wheel use mode, the handlebar 4 is lifted upwards, and the rotating part 35 rotates towards the first roller 5, causing the axle 34 to rotate and move the second roller 6 to a position in contact with the ground. When the rotating part 35 rotates around the connecting body 7, it drives the first connecting rod 9 and the second connecting rod 10, which are in a straight line, to move together towards the first roller 5. When the second roller 6 moves to the position in contact with the ground, the second connecting rod 10 and the first connecting rod 9 are in a straight line and are in contact with the back. 3 forms an acute angle. At the same time, the moving first link 9 pushes the slider 30 toward the second roller 6, so that the slider 30 pushes the pulling link 31 and the rotating plate 47 in sequence. When the pulling link 31 is pushed, it will give the rotating plate 47 a thrust, so that the rotating plate 47 pushes the two first rollers 5 toward the ground until the pulling link 31, the rotating plate 47 and the first platform 1 form a triangular structure. At the same time, the rotating plate 47 gradually tilts, pushing the inclined surface on the inclined block 462 to slide, thereby pushing the first rollers 5 to stand up.

[0159] Once the two-wheel state is required, the restriction of the linkage locking mechanism 11 is released, and the handrail 4 is guided to rotate from the front 2 to the back 3 until the handrail 4 is in a straight line with the first platform 1. When the handrail 4 rotates, it will drive the connecting body 7 to rotate, so that the second roller 6 rotates to the side of the first platform 1. The first link 9 and the second link 10 rotate and bend to a set angle to form a limiting structure. The linkage locking mechanism 11 is reset, and the state of the second roller 6 is maintained by the limiting structure so that only the wheel surfaces of the two first rollers 5 tangent to it are on the horizontal plane. At this time, the trolley mechanism has two wheels.

[0160] Preferably, the rotating plate 47 is provided with a spacer hole 471 so that the outer edge of the rotating plate 47 forms a frame-shaped embedding part 463;

[0161] Each pair of roller seats 52 on the first rollers 5 has a protrusion 46 on its opposite side surface. The protrusion 46 has a recessed groove 461 on its periphery. The recessed groove 461 is configured to accommodate the embedded part 463. The protrusion 46 has a beveled block 462 protruding from the side of the protrusion 46 near the rotating plate 47.

[0162] When the trolley is switched between four-wheel and two-wheel use modes, the rotating plate 47 flips down, and its mating part slides into the inclined block 462 of the roller seat 52 of the two first rollers 5 until the recessed groove 461 engages with the embedded part 463, supporting the two first rollers 5 in an upright state.

[0163] With the above design, the rotating plate 47 can fully open the two first rollers 5.

[0164] In specific implementation, such as Figure 2 and Figure 3 As shown, the rotating plate 47 is provided with a spacer hole 471, and the outer edge of the rotating plate 47 and the inner wall of the spacer hole 471 form an embedded part 463; the front side 2 is rotatably connected to a hollowed-out shovel plate 45 at the end away from the handrail 4, and the roller seat 52 on the pair of first rollers 5 are provided with protrusions 46 on opposite sides of the surface. The periphery of the protrusions 46 is recessed with grooves 461, which are configured to accommodate the embedded part 463, and the protrusions 46 are close to the limiting surface. A sloping block 462 is provided protruding from one side of the limiting surface 54. The width of the sloping block 462 increases from the side closer to the limiting surface 54 to the side farther away from the limiting surface 54. When the first roller 5 rotates to the point where its radial plane is parallel to the back surface 3, the protrusion 46 passes through the spacer hole 471 and extends out of the hollow hole on the hollow shovel plate 45. It is configured to limit the handrail 4 that has been flipped to approach the front surface 2 through the recessed groove 461. The minimum width area on the sloping block 462 abuts against the embedded part 463.

[0165] With the above design, the rotating plate 47 can push the first roller 5 to stand up.

[0166] Specifically, such as Figure 3 When the rotating plate 47 is tilted, the lowest point of the wheel surface of the front roller body 53 is tangent to the horizontal plane, and the limiting surface 54 abuts against the contact surface 101 of the rotating part 100, which restricts the roller seat 52 to rotate only towards the back side 3. At the same time, the embedding part 463 is embedded in the recessed groove 461, so that the first roller 5 can further rotate only towards the back side 3.

[0167] Furthermore, the outer surface of the embedded part 463 abuts against the widest area on the inclined block 462.

[0168] Once the rotating plate 47 is parallel to the back surface 3, the protrusion 46 vertically passes through the spacer hole 471 and extends out of the hollow hole on the hollow shovel plate 45. At the same time, the handrail 4, which has been flipped to approach the front surface 2, is limited by the recessed groove 461. The narrowest area on the inclined block 462 abuts against the embedded part 463, that is, the inner wall of the spacer hole 471.

[0169] Once the rotating plate 47 gradually tilts, it pushes the inclined surface on the inclined block 462 to slide, thereby pushing the first roller 5 to stand up.

[0170] It should be noted that in some specific embodiments, the peripheral surface of the end of the first platform 1 away from the handrail 4 has a rotating part 100, the axis of the rotating part 100 is parallel to the length direction of the first platform 1, and the rotating part 100 has an abutting surface 101 on the side facing the first roller 5; (the limiting surface of the outer wall of the closed end of the U-shaped structure of the roller seat 52 is horizontal, and the abutting surface is also horizontal)

[0171] The first roller 5 includes a torsion spring sleeve 51 rotatably sleeved on the rotating part 100. A roller seat 52 is positioned and connected on the torsion spring sleeve 51. The roller seat 52 has an approximately U-shaped structure. The open end of the U-shaped structure of the roller seat 52 is positioned and connected to the front roller body 53. The outer wall of the closed end of the U-shaped structure of the roller seat 52 is provided with a limiting surface 54.

[0172] In both four-wheel and two-wheel usage modes, the lowest point of the wheel surface of the front roller body 53 is tangent to the horizontal plane, and the limiting surface 54 abuts against the contact surface 101 of the rotating part 100, thereby restricting the roller seat 52 to rotate only towards the back side 3.

[0173] Working principle:

[0174] In its folded storage state, as Figure 9 - Figure 12 as well as Figure 17At this time, the rotating part 35 extends out of the end of the first platform 1 with the second roller 6. The first connecting rod 9 and the second connecting rod 10 are in a straight line and parallel to the back surface 3. At the same time, the first sliding post 22 corresponds to the hollow part 18 and extends into the hollow part 18. The locking groove 28 on the sliding lock block 26 locks the end of the first sliding post 22. The second sliding post 23 is in the guide groove 14. Since the first sliding post 22 is locked by the locking groove 28 on the sliding lock block 26, the first connecting rod 9 and the second connecting rod 10 no longer rotate relative to each other at will. At the same time, the radial plane of the first roller 5 is parallel to the back surface 3, and the handrail 4 flips to approach the front surface 2.

[0175] Furthermore, the protrusion 46 will pass through the spacer hole 471 and extend out of the hollow hole on the hollow shovel plate 45. At the same time, the recessed groove 461 on the protrusion 46 will limit the handrail 4 that has been flipped to approach the front 2. Meanwhile, the narrowest area on the inclined block 462 abuts against the embedded part 463.

[0176] Afterwards, in order to enter the four-wheel use state, such as Figure 4 - Figure 8 When the handrail 4 is lifted upwards, the rotating part 35 rotates towards the first roller 5, causing the shaft 34 to rotate and move the second roller 6 to a state of contact with the ground. When the rotating part 35 rotates around the connecting body 7, it drives the first connecting rod 9 and the second connecting rod 10, which are in a straight line, to move together towards the first roller 5. When the second roller 6 moves to a state of contact with the ground, the second connecting rod 10 and the first connecting rod 9 are in a straight line and form an acute angle with the back 3. At the same time, the moving first connecting rod 9 pushes the sliding body 30 towards the second roller 6, so that the sliding body 30 pushes the pulling connecting rod 31 and the rotating plate 47 in sequence. When the pulling connecting rod 31 is pushed, it gives a thrust to the rotating plate 47, so that the rotating plate 47 pushes the two first rollers 5 towards the ground until the pulling connecting rod 31, the rotating plate 47 and the first platform 1 form a triangular structure. At the same time, the rotating plate 47 gradually tilts, pushing the inclined surface on the inclined block 462 to slide, thereby pushing the first roller 5 to stand up.

[0177] In order to enter the two-round usage state, such as Figure 1 - Figure 3Push the sliding operation button 24 to move it along the traction rope 25. The moving traction rope 25 then drives the sliding lock block 26 to disengage from the second sliding column 23. At this time, the handrail 4 is lifted upward, and the rotating part 35 rotates in the direction of the first roller 5, guiding the handrail 4 to flip from the front 2 to the back 3 until the handrail 4 is in a straight line with the first platform 1. When the handrail 4 rotates, it drives the connecting body 7 to rotate, causing the second roller 6 to rotate to the side of the first platform 1. The first connecting rod 9 and the second connecting rod 10 rotate and bend at a set angle to form a limiting structure. At this time, the state of the second roller 6 is maintained by the limiting structure so that only the wheel surfaces of the two first rollers 5 tangent to it are on the horizontal plane. At this time, the trolley mechanism has two wheels.

[0178] The specific principle by which this limiting structure maintains the state of the second link 10 is as follows:

[0179] The moving traction rope 25 drives the sliding lock block 26 to disengage from the second sliding column 23. At this time, the first connecting rod 9 and the second connecting rod 10 will rotate and bend to a set angle (acute angle). At this time, the first sliding column 22 is at the first holding point 16. Since the first holding point 16 is the endpoint, the first sliding column 22 will no longer continue to rotate. The first connecting rod 9, the second connecting rod 10 and the back 3 form a triangular structure (the triangular structure here is the limiting structure, the principle is to support and limit the rotating plate 47 through the triangle). Through the triangular structure, the connecting body 7 and the rotating plate 47 will not move arbitrarily, ensuring that the trolley mechanism always remains in the two-wheel use state.

[0180] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A two-wheel four-wheel conversion stroller, characterized in that: it comprises a first platform (1) having a front face (2) and a back face (3) arranged oppositely, and a handrail rod (4); the handrail rod (4) is rotatably connected to one end of the first platform (1), and a handrail locking mechanism is arranged on the handrail rod (4) to limit the rotation of the handrail rod (4); the back face (3) of the first platform (1) is provided with a pair of first rollers (5) and a pair of second rollers (6), the pair of second rollers (6) are arranged at one end of the back face (3) close to the handrail rod (4), and the two roller bodies (52) of the pair of second rollers (6) are fixed relative to the handrail rod (4) through a connecting body (7), and the first rollers (5) are arranged at the other end of the back face (3); the axis of the second rollers (6) and the rotation center of the handrail rod (4) have a set distance, when the handrail rod (4) is driven to rotate, the connecting body (7) can drive the second rollers (6) to revolve around the rotation center of the handrail rod (4); it further comprises a linkage mechanism, the linkage mechanism comprises a first linkage rod (9) and a second linkage rod (10), the first linkage rod (9) and the second linkage rod (10) are hingedly connected at the ends, the hinged axis direction is parallel to the direction of the rotation center of the rotation connection between the handrail rod (4) and the first platform (1); one end of the first linkage rod (9) away from the second linkage rod (10) is hingedly connected to the back face (3), and one end of the second linkage rod (10) away from the first linkage rod (9) is hingedly connected to the connecting body (7); a linkage locking mechanism (11) is further arranged at the hinged connection between the first linkage rod (9) and the second linkage rod (10), and the linkage locking mechanism (11) acts on the hinged connection between the first linkage rod (9) and the second linkage rod (10) to lock and limit the relative rotation of the first linkage rod (9) and the second linkage rod (10) around the hinged axis; the stroller has a four-wheel use state and a two-wheel use state; when the stroller is in the four-wheel use state, the handrail rod (4) and the first platform (1) are in a near-perpendicular angle state and are locked by the handrail locking mechanism, the first rollers (5) and the second rollers (6) support the first platform (1) on the ground, the first linkage rod (9) and the second linkage rod (10) are in a straight line state and are locked by the linkage locking mechanism (11), the straight line formed by the first linkage rod (9) and the second linkage rod (10) is arranged at an acute angle with the first platform (1), and the straight line formed by the first linkage rod (9) and the second linkage rod (10), the line connecting the hinged point of the second linkage rod (10) and the connecting body (7) to the rotation center of the handrail rod (4), and the line connecting the rotation center of the handrail rod (4) to the hinged point of the first linkage rod (9) and the back face (3), form a triangular support structure; when the stroller is in the two-wheel use state, the handrail rod (4) is rotated to the extension direction of the first platform (1) and is locked by the handrail locking mechanism, and the first linkage rod (9) and the second linkage rod (10) are in an acute angle state, so that the second rollers (6) are close to the back face (3) of the first platform (1) to be stored. ​ ​ ​ ​ ​ ​ By rotating the handrail rod (4) and synchronously driving the second roller (6) to move, the trolley is converted between the four-wheel use state and the two-wheel use state.

2. The two-wheel to four-wheel convertible stroller of claim 1, wherein: The end of the first connecting rod (9) away from the second connecting rod (10) is hingedly and slidingly connected to the back surface (3), and the sliding direction is arranged along the direction close to and away from the handrail rod (4); The roller seat bodies (52) of the pair of first rollers (5) are symmetrically arranged and are respectively rotationally connected to the first platform (1) along the direction close to and away from the handrail rod (4), so that the first rollers (5) have a standing state and a turned-over storage state; the hingedly and slidingly connected end of the second connecting rod (10) acts on the first rollers (5) and can convert the first rollers (5) between the standing state and the turned-over storage state; The trolley also has a folding storage state; When the handrail rod (4) is in the folding storage state, the handrail rod (4) is rotated to be close to the front surface (2), the first connecting rod (9) and the second connecting rod (10) are in a straight line state and are slid together towards the handrail rod (4) by a set length, the straight line formed by the first connecting rod (9) and the second connecting rod (10) is parallel to or intersects at an acute angle with the length direction extension line of the first platform (1), so that the second roller (6) is rotated to the outside of the end of the first platform (1), and the first roller (5) is rotated to the turned-over storage state.

3. The two-wheel to four-wheel convertible stroller of claim 1, wherein: The connecting rod locking mechanism (11) comprises a sliding lock block (26) and a locking portion, one of which is arranged on the first connecting rod (9) and the other of which is arranged on the second connecting rod (10); the sliding lock block (26) and the locking portion are oppositely arranged; when the first connecting rod (9) and the second connecting rod (10) are in a straight line state, the sliding lock block (26) and the locking portion are opposite, and the sliding lock block (26) acts on the locking portion to lock the relative position of the first connecting rod (9) and the second connecting rod (10); and the sliding lock block (26) can be driven by an external force to separate from the locking portion to be unlocked.

4. The two-wheel to four-wheel convertible stroller of claim 3, wherein: The abutting regions of the first connecting rod (9) and the second connecting rod (10) are provided with a guide sliding groove (14) on one and first and second sliding columns (22) and (23) on the other; the guide sliding groove (14) is a circular ring structure arranged around the hinge axis of the first connecting rod (9) and the second connecting rod (10), and the guide sliding groove (14) is provided with a first maintenance point (16) therein; The first and second sliding columns (22) and (23) are arranged apart around the hinge axis of the first connecting rod (9) and the second connecting rod (10); When the first connecting rod (9) and the second connecting rod (10) are rotated and bent to an acute angle state, the first sliding column (22) is at the first maintenance point (16), and the first connecting rod (9), the second connecting rod (10) and the back surface (3) form a triangular structure; When the first connecting rod (9) and the second connecting rod (10) are in a straight line state, the first sliding column (22) is engaged with the sliding lock block (26) as the locking portion to be locked, and the second sliding column (23) is in the guide sliding groove (14).

5. The two-wheel to four-wheel convertible stroller of claim 4, wherein: The connecting rod locking mechanism (11) comprises a traction rope (25); A sliding slot (15) for accommodating a sliding lock block (26) is arranged on the first connecting rod (9) or the second connecting rod (10); The sliding slot (15) is in a long strip structure; The sliding lock block (26) is slidingly connected in the sliding slot (15), an elastic member (27) is arranged on the sliding lock block (26), a locking slot (28) for limiting the first sliding column (22) is arranged on the sliding lock block (26), and the elastic member (27) is configured to drive the sliding lock block (26) to move towards the first sliding column (22) side to make the locking slot (28) have a tendency to lock the first sliding column (22); The traction rope (25) is connected with the sliding lock block (26) at the end; in use, under the action of external force, the traction rope (25) is pulled to drive the sliding lock block (26) to retreat to make the locking slot (28) disengage from the first sliding column (22) to be unlocked.

6. The two-wheel to four-wheel convertible stroller of claim 5, wherein: The connecting rod locking mechanism (11) further comprises a sliding operation knob (24); The sliding operation knob (24) is slidingly arranged relative to the first platform (1) and is positioned when sliding to a certain position; One end of the traction rope (25) is connected with the sliding operation knob (24), and the other end is connected with the sliding lock block (26); in use, under the action of external force, the sliding operation knob (24) pulls the traction rope (25) to drive the sliding lock block (26) to disengage from the locking part to be unlocked.

7. The two-wheel to four-wheel convertible stroller of claim 1, wherein: In the turnover storage state, the turnover direction of the first roller (5) is towards the center area of the back (3), and a torsional spring is arranged on the first roller (5), and the elastic force of the torsional spring forces the first roller (5) to remain in the turnover storage state; The back (3) of the first flat plate is connected with a sliding body (30) through a sliding rail (29); One end of the sliding body (30) is hinged with the first connecting rod (9), and the other end is hinged with a pulling connecting rod (31); One end of the first platform (1) is rotatably connected with a rotating plate (47) of the first roller (5), the rotating center line of the rotating plate (47) is parallel to the connecting direction of the two first rollers (5), the rotating plate (47) is hinged with the pulling connecting rod (31), and the two sides of the rotating plate (47) are provided with matching parts matched with the roller seats of the first rollers (5); When the trolley is in the four-wheel use state and the two-wheel use state, the matching parts of the rotating plate (47) abut against the roller seats of the two first rollers (5) to support the two first rollers (5) in the standing state, and the elastic elements are arranged on the rotating plate (47) or the sliding body (30) to keep the rotating plate (47) supporting the two first rollers (5) in the standing state; When the trolley is in the folding storage state, since the handrail (4) is rotated to be close to the front (2), the first connecting rod (9) is slid towards the handrail (4) by a set distance, the sliding body (30) and the pulling connecting rod (31) drive the rotating plate (47) to rotate and approach the first platform (1), the matching parts of the rotating plate (47) disengage from the roller seats of the two first rollers (5), and the two first rollers (5) are reset to the turnover storage state due to the elastic force of the spring.

8. The two-wheel to four-wheel convertible stroller of claim 7, wherein: The first platform (1) is provided with an installation gap (36) at the end, and the handrail rod (4) is rotationally connected in the installation gap (36); The handrail locking mechanism comprises a positioning rod (37), the positioning rod (37) is arranged on the handrail rod (4), and the axis of the positioning rod (37) extends in parallel to the extension line of the width direction of the first platform (1); A long strip-shaped sliding channel (38) is arranged at the corresponding position of the side wall of the handrail rod (4) and the positioning rod (37), the sliding channel (38) has a tightening end (39) arranged close to the connecting body (7) and a transposition end (40) arranged away from the connecting body (7), a resilient member (41) is arranged on the positioning rod (37), so that the positioning rod (37) always has a tendency to slide from the transposition end (40) to the tightening end (39); A positioning chuck (42) is arranged at the corresponding position of the handrail rod (4) in the installation gap (36), and the surface edge of the positioning chuck (42) is provided with a first positioning chuck point (43) and a second positioning chuck point (44); When the trolley is in the four-wheel use state and the handrail rod (4) is erected, the positioning rod (37) is located at the tightening end (39) in the sliding channel (38), and the end is embedded in the first positioning chuck point (43) to be locked; Under the action of external force, the positioning rod (37) is driven to slide from the tightening end (39) to the transposition end (40) to be separated from the first positioning chuck point (43), so that the handrail rod (4) can be freely turned over; When the trolley is in the two-wheel use state, the handrail rod (4) is rotated to the extension direction of the first platform (1), the positioning rod (37) is located at the tightening end (39) in the sliding channel (38), and the end is embedded in the second positioning chuck point (44) to be locked.

9. The two-wheel to four-wheel convertible stroller of claim 8, wherein: The rotating plate (47) is provided with a spacing hole (471), so that the outer edge of the rotating plate (47) forms a frame-shaped embedded part (463); The roller seat bodies (52) on the pair of first rollers (5) are provided with a protruding part (46) on the opposite side surfaces, the circumferential side of the protruding part (46) is concave and provided with a recessed groove (461), the recessed groove (461) is configured to accommodate the embedded part (463), and the protruding part (46) is provided with an inclined surface block (462) on the side close to the rotating plate (47) When the trolley is switched to the four-wheel use state and the two-wheel use state, the rotating plate (47) is turned down, the matching part is in sliding cooperation with the inclined surface block (462) of the roller seat body (52) of the two first rollers (5) until the recessed groove (461) is matched with the embedded part (463), and the two first rollers (5) are supported in the erected state.

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