Handcart capable of being unfolded stably

Abstract

The utility model discloses a stable-unfolding handcart which comprises a main body platform, a front wheel assembly and a rear wheel assembly which are respectively and rotatably connected with the main body platform, and first elastic reset pieces are arranged between the front wheel assembly and the main body platform and between the rear wheel assembly and the main body platform. A wheel expander hinged to the main body platform is arranged at the front end of the main body platform, a locking device is arranged in the wheel expander, and the locking device comprises a locking piece body; a mounting seat is arranged at the rear end of the main body platform, and a handle assembly rotationally connected with the mounting seat is arranged on the mounting seat; a pull rod assembly is arranged between the mounting seat and the main body platform, the handle assembly comprises a three-way assembly, and the pull rod assembly comprises a limiting sliding piece capable of limiting rotation of the three-way assembly; the three-way assembly is provided with a wheel pushing piece used for maintaining unfolding of the rear wheel assembly. The front wheel assembly in the unfolded state is locked through cooperation of the locking device and the wheel expander, the rear wheel assembly in the unfolded state is locked through cooperation of the pull rod assembly and the handle assembly, and the whole trolley is stable and reliable in the unfolded state.

Description

Technical Field

[0001] The utility model belongs to the technical field of trolleys, and in particular relates to a trolley that is stably unfolded. Background Art

[0002] In the process of transporting goods, due to the large volume of goods, a trolley is needed to push the goods. Existing trolleys generally include a main body platform, on which a foldable front wheel assembly and a rear wheel assembly are provided. The existing patent document with publication number CN220430165U discloses a multifunctional trolley that is easy to fold and store; the trolley includes a panel, a second wheel assembly rotatably connected to the front end of the panel, and a pushing assembly and a push plate are provided on the panel to drive the second wheel assembly to unfold; the push plate is connected to the front wheel assembly through a limit lock, and then the push assembly is used to limit the unfolding angle of the push plate. In actual use, when the trolley passes over an uneven road surface, the pushing assembly is prone to failure, causing the push plate to lose its limit, so that the limit lock will detach from the front wheel assembly, and the front wheel assembly cannot be stably maintained in an unfolded state. At the same time, the folding directions of the first wheel group and the second wheel group are perpendicular to each other, and the first wheel group is folded forward and backward; there is no limit protection in front and back of the first wheel group, and the outer side of the first wheel group is easily twisted when hit by external force, thereby causing the first wheel group to switch from the unfolded state to the folded state, and the first wheel group cannot work normally. Therefore, it is necessary to design a trolley with stable unfolding to overcome the following difficulties. Summary of the invention

[0003] The utility model aims at the problems in the prior art and designs a trolley with stable unfolding. The utility model locks the front wheel assembly in the unfolded state by cooperating with a locking device and a wheel expander, and locks the rear wheel assembly in the unfolded state by cooperating with a pull rod assembly and a handle assembly. The overall unfolding state of the trolley is stable and reliable.

[0004] The invention objective of the utility model is achieved through the following technical solutions: a trolley with stable unfolding, comprising a main body platform, a front wheel assembly and a rear wheel assembly respectively connected to the main body platform for rotation, a first elastic reset member for automatic reset being arranged between the front wheel assembly and the rear wheel assembly and the main body platform; a wheel expander hingedly connected to the main body platform is arranged at the front end of the main body platform, a locking device for locking the front wheel assembly is arranged in the wheel expander, the locking device comprises a locking member body which can be telescoped relative to the front wheel assembly; a mounting seat is arranged at the rear end of the main body platform, a handle assembly connected to the main body for rotation is arranged on the mounting seat; a pull rod assembly for limiting the rotation angle of the handle assembly is arranged between the mounting seat and the main body platform, the handle assembly comprises a three-way assembly, the pull rod assembly comprises a limit sliding member capable of limiting the rotation of the three-way assembly; a wheel pushing member for maintaining the unfolding of the rear wheel assembly is arranged on the three-way assembly.

[0005] Preferably, the main platform includes columnar tubes arranged in pairs and fixedly connected thereto; the front end of the columnar tube is provided with a wheel frame sleeve fixedly connected thereto, and the rear end of the columnar tube is provided with a mounting seat fixedly connected thereto, and a first elastic reset member for automatic reset is provided in the wheel frame sleeve and the mounting seat; a wheel expander hingedly connected thereto is provided on the wheel frame sleeve, and a second elastic reset member for reset is provided between the wheel expander and the wheel frame sleeve; the front end of the columnar tube is provided with a supporting base plate hinged thereto.

[0006] The front wheel assembly is axially limited by setting a wheel frame sleeve, and the outer wall of the front wheel assembly is protected at the same time. A first elastic reset member is set in the wheel frame sleeve, so that the front wheel assembly can be automatically reset. The rear wheel assembly is axially limited by setting a mounting seat, and the outer wall of the front wheel assembly is protected at the same time. A first elastic reset member is set in the wheel frame sleeve, so that the rear wheel assembly can be automatically reset. By setting a second elastic reset member, the wheel expander will automatically reset after losing the limit of the locking member body, so that the wheel expander can automatically switch to the folded state.

[0007] Preferably, a first pin shaft is provided between the wheel expander and the wheel frame cover for hingedly connecting the two, and a second elastic reset member for automatically resetting the wheel expander is provided on the first pin shaft; a locking device is provided on the wheel expander, and the side wall of the wheel expander when unfolded is arranged adjacent to the side wall of the wheel frame of the front wheel assembly; a first through hole is provided on the front wheel assembly to accommodate a locking member body, and a second through hole is provided on the wheel frame cover to accommodate a locking member body.

[0008] In the default state, the wheel expander is in a folded state, at which time the locking member body is stuck in the second through hole; when the wheel expander is in an unfolded state, the locking member body is stuck in the first through hole, at which time the second elastic reset member is in a deformed state. When the locking member body is separated from the first through hole, the wheel expander automatically resets to the folded state.

[0009] Preferably, the locking device also includes a front wheel lock pin rod, a button, a first elastic member and a cover plate; a placement groove for placing the button is provided in the wheel expander, and the end face of the placement groove is provided with a cover plate that overlaps with it; a limiting notch for inserting the button is provided between the placement groove and the side wall of the wheel expander, and the outer contour of the limiting notch matches the outer contour of the button; a plurality of limiting grooves for placing the front wheel lock pin rod are provided on the wheel expander, and each of the limiting grooves is coaxially arranged; a locking member body fixedly connected to the front wheel lock pin rod is provided at the end of the front wheel lock pin rod, and the front wheel lock pin rod is slidably connected to the button; a first elastic member for resetting is provided between the button and the bottom of the placement groove, and the axial direction of the first elastic member is perpendicular to the axial direction of the limiting groove.

[0010] The wheel expander has two working states: unfolded and folded. The locking device locks the wheel expander through the locking member body, so that the wheel expander is stably maintained in the unfolded and folded states. In the default state, the locking member body is inserted into the second through hole, and the wheel expander is in the folded state. The operator presses the button, and the button compresses the first elastic member; when the button moves, it drives the front wheel lock pin rod to move along the axial direction of the limiting groove, and then the locking member body will move with the front wheel lock pin rod and disengage from the second through hole; then the operator pushes the wheel expander downward, and when the wheel expander rotates downward, it drives the front wheel assembly to unfold; when the locking member body is aligned with the first through hole on the front wheel assembly, the locking member body automatically snaps into the first through hole under the action of the first elastic member; at this time, the side wall of the wheel expander abuts against the wheel frame of the front wheel assembly, so the front wheel assembly can be stably in the unfolded state. When the wheel expander and the front wheel assembly need to be folded, the button is pressed, the locking member body disengages from the first through hole, and then the wheel expander rotates upward and resets under the action of the second elastic reset member; when the wheel expander rotates to a horizontal position, the locking member body is aligned with the second through hole; the locking member body automatically snaps into the second through hole, and the wheel expander can be stably in a folded state, and at this time the front wheel assembly is also automatically reset under the action of the first elastic reset member.

[0011] Preferably, an annular protrusion is provided at the end of the front wheel locking pin rod, and a first waist-shaped hole for inserting the annular protrusion is provided on the button, and the annular protrusion slides along the first waist-shaped hole when the button is pressed; the axial direction of the first waist-shaped hole is inclined to the axial direction of the limiting notch; the limiting groove and the limiting notch are arranged perpendicular to each other, and the axial direction of the limiting groove and the side wall of the wheel frame sleeve are arranged perpendicular to each other; when the wheel expander is arranged parallel to the main platform, the locking body is stuck in the second through hole, and when the locking body is in the second through hole, the front wheel assembly is in a folded state; when the locking body is stuck in the first through hole, the front wheel assembly is in an expanded state; a baffle is provided on the front wheel assembly, and when the front wheel assembly and the wheel expander are in the expanded state, the wheel expander and the baffle are fitted with each other.

[0012] By providing the first waist-shaped hole and the annular protrusion, when the button moves along the limiting notch, it can drive the front wheel lock pin rod to move along the limiting notch, thereby facilitating the control of the lock body to move relative to the first through hole and the second through hole. The limiting groove and the limiting notch are arranged perpendicular to each other, so that when the button moves, it is ensured that the lock body can be driven to move, and the axial directions of the first through hole and the second through hole are both arranged perpendicular to the lock body, so that the lock body can be reliably inserted into the first through hole and the second through hole.

[0013] Preferably, a second pin is provided between the columnar tube body and the supporting base plate to hinge the two; a positioning piece that can automatically extend and retract relative to the supporting base plate is provided in the columnar tube body, and an inner recess for placing the positioning piece is provided on the supporting base plate; an arc-shaped transition portion is provided on the edge of the supporting base plate.

[0014] The support base has two states: folded and unfolded. When the support base is folded, the support base and the main platform are arranged in close contact with each other. When the support base is unfolded, the support base and the main platform are arranged perpendicular to each other. When the trolley is used with two wheels, the front wheel assembly is unfolded and the rear wheel assembly is folded, and the support base needs to be unfolded for use, so that items can be placed between the support base and the main platform. A spring is provided in the cylindrical tube body, and the spring is connected to a positioning piece, so that the positioning piece can be extended and retracted relative to the cylindrical tube body; the positioning piece is stuck in the inner recess, so that the support base can be stably in the unfolded state. By providing an arc-shaped transition portion, the support base will not interfere with the main platform when rotating.

[0015] Preferably, a pull rod assembly is provided in the mounting seat, and the pull rod assembly includes a limit cover body, a limit push rod, a limit sliding member and a second elastic member; the pull rod assemblies are arranged in pairs, and a cross bar connecting the two pull rod assemblies is provided between the two pull rod assemblies; the mounting seat is sleeved and installed in the outer layer of the cylindrical tube body and fixedly connected thereto by screws, and a limit push rod is provided in the cylindrical tube body to be slidably connected thereto, and the limit push rod is fixedly connected to the limit sliding member; a handle assembly is provided on the mounting seat to be rotatably connected thereto, and the handle assembly includes a three-way assembly for connection; the three-way assembly includes a first slot, a second slot and a third slot that cooperate with the limit sliding member; one end of the limit push rod is provided with a limit sliding member fixedly connected thereto, and the other end of the limit push rod is provided with a cross bar sleeved therewith, and the end connected to the limit push rod and the cross bar passes through the cylindrical tube body; a second elastic member is provided in the cylindrical tube body, and a limit cover body fixedly connected thereto is provided at the end of the cylindrical tube body; one end of the second elastic member abuts against the shaft sleeve of the limit push rod, and the other end abuts against the limit cover body.

[0016] In the default state, the handle assembly and the rear wheel assembly are both in a folded state, and the limit slide is stuck in the second slot; when the trolley needs to be used with four wheels, the rear wheel assembly and the front wheel assembly need to be unfolded synchronously; the operator pulls the cross bar, and the cross bar drives the limit push rod to move, and when the limit push rod moves, it will drive the limit slide to disengage from the second slot, and the second elastic member is in a compressed state; then the handle assembly is rotated to align the first slot on the three-way assembly with the limit slide, so that the limit slide will automatically snap into the first slot, and the handle assembly can be stably maintained in the unfolded state. When the handle assembly switches from the folded state to the unfolded state, the three-way assembly drives the wheel pusher to rotate, and when the wheel pusher rotates, it will push the rear wheel assembly, so that the rear wheel assembly is automatically unfolded; when the rear wheel assembly is unfolded in place, the wheel pusher rests on the wheel frame of the rear wheel assembly. At this time, the handle assembly is locked by the limit slide, so that the wheel pusher cannot rotate. At this time, the rear wheel assembly is limited by the mounting seat and the wheel pusher, and the front, back, left, and right sides of the rear wheel assembly are protected and limited, so that the rear wheel assembly can be stably maintained in the expanded state.

[0017] Preferably, the columnar tube body is provided with a guide groove coaxially arranged therewith, the side wall of the mounting seat is provided with a guide opening, and the limit sliding member passes through the guide groove and the guide opening in sequence; the end of the three-way assembly is provided with a wheel pushing member connected with a tight fit, and the end of the wheel pushing member facing the mounting seat is provided with a spherical protrusion; when the limit sliding member is stuck in the first slot, the handle assembly and the main platform are tilted; when the limit sliding member is stuck in the second slot, the handle assembly and the main platform are fitted together, and the handle assembly and the rear wheel assembly are both in a folded state; when the limit sliding member is stuck in the third slot, the handle assembly and the main platform are parallel to each other, and the handle assembly is in an unfolded state.

[0018] By setting the guide groove and the guide opening, the limit sliding member can reliably move along the axial direction of the columnar tube body, thereby facilitating the movement of the limit sliding member relative to the three-way assembly. When the trolley is used as a four-wheel trolley, the limit sliding member is stuck in the first slot; when the trolley is used as a two-wheel trolley, the rear wheel assembly is folded, the front wheel assembly and the support base plate are unfolded, the handle assembly is unfolded and the free end of the handle assembly is away from the support base plate. When the rear wheel assembly is folded, the limit sliding member is first driven to move by the cross bar, the limit sliding member is disengaged from the first slot, and then the handle assembly is rotated to make the limit sliding member snap into the third slot. At this time, the rear wheel assembly loses the limit of the wheel pusher and will automatically fold. When the trolley needs to be folded, the limit sliding member is first disengaged from the third slot, and then the handle assembly is rotated to make it fit with the main platform, and then the cross bar is released to make the limit sliding member automatically snap into the second slot.

[0019] Preferably, the handle assembly is provided with an extension handle which can be telescoped relative to the handle assembly, and the handle assembly is provided with a switch assembly for locking; the extension handle is provided with a plurality of evenly distributed limit holes, and the switch assembly includes a handle latch for locking.

[0020] The handle assembly is provided with a switch body and a positioning pin. The switch body is connected to the handle pin through the positioning pin. The handle pins are arranged in pairs. Springs are arranged between the handle pins. When the switch body moves, the handle pins are driven to move relative to the limit hole, so that the extended handle can be locked.

[0021] Compared with the prior art, the utility model has the following beneficial effects: the utility model is provided with a front wheel assembly and a rear wheel assembly rotatably connected to the main body platform; the front wheel assembly is arranged in a wheel frame jacket, the wheel frame jacket protects the front wheel assembly, and a first elastic reset member is arranged in the wheel frame jacket to facilitate automatic reset of the front wheel assembly. A wheel expander is provided on the wheel frame jacket and is hinged to the wheel expander, and a locking device is provided on the wheel expander, and the front wheel assembly in the unfolded state is locked by the locking member body, and the wheel expander supports the side of the front wheel assembly, so that the front wheel assembly can be stably in the unfolded state. The wheel expander is located above the front wheel assembly, and the front wheel assembly is automatically controlled to unfold when the wheel expander is unfolded. When folding is required, the wheel expander and the front wheel assembly can be automatically folded by unlocking the locking device. A mounting seat is provided at the rear end of the main body platform, and the rear wheel assembly is protected by the mounting seat; a handle assembly is provided on the mounting seat and is hinged to the wheel frame jacket, and the handle assembly is locked by a pull rod assembly; the pull rod assembly includes a limit sliding member, and the limit sliding member cooperates with the three-way assembly to enable the handle assembly to have multiple working states. When the rear wheel assembly is unfolded, the handle assembly is unfolded and limited by the limiting sliding member, so that the wheel pushing member will push the rear wheel assembly away and abut against the rear wheel assembly, thereby stably keeping the rear wheel assembly in the unfolded state. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a three-dimensional diagram of the utility model;

[0023] Figure 2 A three-dimensional diagram of another viewing angle of the present invention;

[0024] Figure 3 This is an exploded view of the tie rod assembly;

[0025] Figure 4 for Figure 3 A partial enlarged view of position A in the middle;

[0026] Figure 5 is a diagram of the internal structure of the locking device;

[0027] Figure 6 for Figure 5 A partial enlarged view of position B in the middle;

[0028] Figure 7 An exploded view of the locking device;

[0029] Figure 8 This is a two-wheel use state diagram for the utility model;

[0030] Fig. 9 is a schematic diagram of the folding process of the wheel expander;

[0031] Fig.10 This is a diagram of the state of use of four wheels adopted by the utility model;

[0032] Fig.11 It is a schematic diagram of the front wheel assembly and the rear wheel assembly of the utility model when they are folded;

[0033] Fig.12 is a three-dimensional diagram of a three-way assembly;

[0034] Fig.13 A three-dimensional diagram of the support base plate;

[0035] Fig.14 Schematic diagram of the working of the tie rod assembly.

[0036] Markings in the figure: 1, main platform; 2, front wheel assembly; 3, rear wheel assembly; 4, first elastic reset member; 5, wheel expander; 51, placement groove; 52, limiting notch; 53, limiting groove; 6, locking device; 61, locking member body; 62, front wheel lock pin rod; 63, button; 64, first elastic member; 65, cover plate; 66, annular protrusion; 67, first waist-shaped hole; 7, mounting seat; 71, guide opening; 8, handle assembly; 81, three-way assembly; 82, wheel pusher; 83, spherical protrusion; 9, pull rod assembly; 91, limiting sliding member; 92, limiting cover body; 93. limit push rod; 94. second elastic member; 10. columnar tube; 101. guide groove; 11. wheel frame sleeve; 12. second elastic reset member; 13. support base plate; 14. first pin shaft; 15. first through hole; 16. second through hole; 17. stop bar; 18. second pin shaft; 19. positioning member; 20. inner recess; 21. arc-shaped transition portion; 22. cross bar; 23. first slot; 24. second slot; 25. third slot; 26. extension handle; 261. limit hole; 27. switch assembly; 271. handle latch; 272. switch body; 273. positioning pin. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings:

[0038] like Figures 1 to 14As shown, the present embodiment discloses a trolley which is stably unfolded, comprising a main body platform 1, a front wheel assembly 2 and a rear wheel assembly 3 which are rotatably connected to the main body platform 1 respectively, and a first elastic reset member 4 for automatic reset is provided between the front wheel assembly 2 and the rear wheel assembly 3 and the main body platform 1; a wheel expander 5 which is hinged to the main body platform 1 is provided at the front end thereof, and a locking device 6 for locking the front wheel assembly 2 is provided in the wheel expander 5, and the locking device 6 comprises a locking member body 61 which can be telescopic relative to the front wheel assembly 2; a mounting seat 7 is provided at the rear end of the main body platform 1, and a handle assembly 8 which is rotatably connected to the main body platform 1 is provided on the mounting seat 7; a pull rod assembly 9 for limiting the rotation angle of the handle assembly 8 is provided between the mounting seat 7 and the main body platform 1, and the handle assembly 8 comprises a three-way assembly 81, and the pull rod assembly 9 comprises a limit sliding member 91 which can limit the rotation of the three-way assembly 81; a wheel pushing member 82 for maintaining the unfolding of the rear wheel assembly 3 is provided on the three-way assembly 81.

[0039] The main platform 1 includes a columnar tube body 10 arranged in pairs and fixedly connected thereto; the front end of the columnar tube body 10 is provided with a wheel frame sleeve 11 fixedly connected thereto, and the rear end of the columnar tube body 10 is provided with a mounting seat 7 fixedly connected thereto, and a first elastic reset member 4 for automatic reset is provided in the wheel frame sleeve 11 and the mounting seat 7; a wheel expander 5 hingedly connected thereto is provided on the wheel frame sleeve 11, and a second elastic reset member 12 for reset is provided between the wheel expander 5 and the wheel frame sleeve 11; the front end of the columnar tube body 10 is provided with a supporting base plate 13 hinged thereto. A first pin shaft 14 is provided between the wheel expander 5 and the wheel frame cover 11 to hinge the two, and a second elastic reset member 12 for automatically resetting the wheel expander 5 is provided on the first pin shaft 14; a locking device 6 is provided on the wheel expander 5, and the side wall of the wheel expander 5 when unfolded is arranged adjacent to the wheel frame side wall of the front wheel assembly 2; a first through hole 15 for accommodating a locking member body 61 is provided on the front wheel assembly 2, and a second through hole 16 for accommodating a locking member body 61 is provided on the wheel frame cover 11. The locking device 6 also includes a front wheel lock pin rod 62, a button 63, a first elastic member 64 and a cover plate 65; a placement groove 51 for placing the button 63 is provided in the wheel expander 5, and the end surface of the placement groove 51 is provided with a cover plate 65 that overlaps with it; a limiting notch 52 for inserting the button 63 is provided between the placement groove 51 and the side wall of the wheel expander 5, and the outer contour of the limiting notch 52 matches the outer contour of the button 63; a plurality of limiting grooves 53 for placing the front wheel lock pin rod 62 are provided on the wheel expander 5, and each of the limiting grooves 53 is coaxially arranged; the end of the front wheel lock pin rod 62 is provided with a locking member body 61 fixedly connected to it, and the front wheel lock pin rod 62 is slidably connected to the button 63; a first elastic member 64 for resetting is provided between the button 63 and the bottom of the placement groove 51, and the axial direction of the first elastic member 64 is perpendicular to the axial direction of the limiting groove 53. An annular protrusion 66 is provided at the end of the front wheel locking pin rod 62, and a first waist-shaped hole 67 for inserting the annular protrusion 66 is provided on the button 63. When the button 63 is pressed, the annular protrusion 66 slides along the first waist-shaped hole 67; the axial direction of the first waist-shaped hole 67 is inclined to the axial direction of the limiting notch 52; the limiting groove 53 and the limiting notch 52 are arranged perpendicular to each other, and the axial direction of the limiting groove 53 and the side wall of the wheel frame sleeve 11 are arranged perpendicular to each other; when the wheel expander 5 is arranged parallel to the main platform 1, the locking body 61 is stuck in the second through hole 16, and when the locking body 61 is in the second through hole 16, the front wheel assembly 2 is in a folded state; when the locking body 61 is stuck in the first through hole 15, the front wheel assembly 2 is in an unfolded state; a baffle 17 is provided on the front wheel assembly 2, and when the front wheel assembly 2 and the wheel expander 5 are in the unfolded state, the wheel expander 5 and the baffle 17 are in contact with each other.

[0040] A second pin shaft 18 is provided between the columnar tube body 10 and the supporting base plate 13 to hinge the two; a positioning piece 19 is provided inside the columnar tube body 10 and can automatically extend and retract relative to the supporting base plate 13, and an inner recess 20 is provided on the supporting base plate 13 for placing the positioning piece 19; an arc-shaped transition portion 21 is provided on the edge of the supporting base plate 13. A pull rod assembly 9 is provided inside the mounting seat 7, and the pull rod assembly 9 includes a limit cover 92, a limit push rod 93, a limit sliding member 91 and a second elastic member 94; the pull rod assemblies 9 are arranged in pairs, and a cross bar 22 connecting the two pull rod assemblies 9 is provided between the two pull rod assemblies 9; the mounting seat 7 is sleeved and installed on the outer layer of the columnar tube body 10 and fixedly connected thereto by screws, and a limit push rod 93 is provided inside the columnar tube body 10 to be slidably connected thereto, and the limit push rod 93 is fixedly connected to the limit sliding member 91; a handle assembly 8 is provided on the mounting seat 7 to be rotatably connected thereto, and the handle assembly 8 includes a three-way assembly 81 for connection; the three-way assembly The engaging part 81 includes a first card slot 23, a second card slot 24 and a third card slot 25 which cooperate with the limiting sliding part 91; one end of the limiting push rod 93 is provided with a limiting sliding part 91 fixedly connected thereto, and the other end of the limiting push rod 93 is provided with a cross bar 22 sleeved therewith, and the end of the limiting push rod 93 connected to the cross bar 22 passes through the columnar tube body 10; a second elastic part 94 is provided inside the columnar tube body 10, and a limiting cover body 92 fixedly connected thereto is provided at the end of the columnar tube body 10; one end of the second elastic part 94 abuts against the shaft sleeve of the limiting push rod 93, and the other end abuts against the limiting cover body 92. The cylindrical tube body 10 is provided with a guide groove 101 coaxially arranged therewith, and the side wall of the mounting seat 7 is provided with a guide opening 71, and the limiting sliding member 91 passes through the guide groove 101 and the guide opening 71 in sequence; the end of the three-way assembly 81 is provided with a wheel pusher 82 connected with a tight fit, and the end of the wheel pusher 82 facing the mounting seat 7 is provided with a spherical protrusion 83; when the limiting sliding member 91 is stuck in the first slot 23, the handle assembly 8 and the main platform 1 are tilted; when the limiting sliding member 91 is stuck in the second slot 24, the handle assembly 8 and the main platform 1 are arranged to fit each other, and the handle assembly 8 and the rear wheel assembly 3 are both in a folded state; when the limiting sliding member 91 is stuck in the third slot 25, the handle assembly 8 and the main platform 1 are arranged parallel to each other, and the handle assembly 8 is in an unfolded state. The handle assembly 8 is provided with an extension handle 26 that can be extended and retracted relative to the handle assembly 8, and a switch assembly 27 for locking is provided on the handle assembly 8; the extension handle 26 is provided with a number of evenly distributed limiting holes 261, and the switch assembly 27 includes a handle latch 271 for locking. When the extension handle 26 needs to be extended and retracted, the switch body 272 is pushed, and the switch body 272 is connected to the handle latch 271 through a positioning pin 273. The handle latch 271 is set in the conduit of the handle assembly 8, and a spring is provided between the handle latch 271; then when the switch body 272 is pushed, the handle latch 271 can be extended and retracted relative to the limiting hole 261, so as to facilitate the adjustment of the position of the extension handle 26.

[0041] The specific operation process of this embodiment is as follows: in the default state, the front wheel assembly 2, the rear wheel assembly 3 and the handle assembly 8 are all in a folded state; when the four-wheeled cart needs to be used, the front wheel assembly 2 and the rear wheel assembly 3 need to be unfolded at the same time. The wheel expander 5 has two working states, unfolded and folded. The locking device 6 locks the wheel expander 5 through the locking member body 61, so that the wheel expander 5 is stably maintained in the unfolded and folded states. When the wheel expander 5 is unfolded, it simultaneously pushes the front wheel assembly 2, so that the front wheel assembly 2 is automatically unfolded. In the default state, the locking member body 61 is inserted in the second through hole 16, and the wheel expander 5 is in a folded state. The operator presses the button 63, and the button 63 compresses the first elastic member 64; when the button 63 moves, it drives the front wheel locking pin rod 62 to move axially along the limiting groove 53, so that the locking member body 61 will move with the front wheel locking pin rod 62 and disengage from the second through hole 16; then the operator pushes the wheel expander 5 downward, and when the wheel expander 5 rotates downward, it drives the front wheel assembly 2 to unfold; when the locking member body 61 is aligned with the first through hole 15 on the front wheel assembly 2, the locking member body 61 is automatically inserted into the first through hole 15 under the action of the first elastic member 64; at this time, the side wall of the wheel expander 5 abuts against the wheel frame of the front wheel assembly 2, so the front wheel assembly 2 can be stably in the unfolded state. When the wheel expander 5 and the front wheel assembly 2 need to be folded, the button 63 is pressed, the locking member body 61 disengages from the first through hole 15, and then the wheel expander 5 rotates upward and resets under the action of the second elastic reset member 12; when the wheel expander 5 rotates to a horizontal position, the locking member body 61 is aligned with the second through hole 16; the locking member body 61 automatically snaps into the second through hole 16, and the wheel expander 5 can be stably in a folded state. At this time, the front wheel assembly 2 is also automatically reset under the action of the first elastic reset member 4.

[0042] Then the rear wheel assembly 3 is unfolded. In the default state, the handle assembly 8 and the rear wheel assembly 3 are both in a folded state, and the limit sliding member 91 is stuck in the second slot 24; when the trolley needs to be used as a four-wheeled vehicle, the rear wheel assembly 3 and the front wheel assembly 2 need to be unfolded simultaneously; the operator pulls the cross bar 22, and the cross bar 22 drives the limit push rod 93 to move. When the limit push rod 93 moves, it will drive the limit sliding member 91 to disengage from the second slot 24, and the second elastic member 94 is in a compressed state; then the handle assembly 8 is rotated to align the first slot 23 on the three-way assembly 81 with the limit sliding member 91, so that the limit sliding member 91 will automatically be stuck in the first slot 23, and the handle assembly 8 can be stably maintained in the unfolded state. When the handle assembly 8 switches from the folded state to the unfolded state, the three-way assembly 81 drives the wheel pusher 82 to rotate, and when the wheel pusher 82 rotates, it pushes the rear wheel assembly 3, so that the rear wheel assembly 3 is automatically unfolded; when the rear wheel assembly 3 is unfolded to the right position, the spherical protrusion 83 of the wheel pusher 82 abuts against the wheel frame of the rear wheel assembly 3. At this time, the handle assembly 8 is locked by the limiting sliding member 91, so that the wheel pusher 82 cannot rotate. At this time, the rear wheel assembly 3 is limited by the mounting seat 7 and the wheel pusher 82, and the front, back, left, and right sides of the rear wheel assembly 3 are protected and limited, so that the rear wheel assembly 3 can be stably maintained in the unfolded state.

[0043] When the two-wheeled handcart is needed, the handle assembly 8 is rotated to be away from the supporting base plate 13, and then the limiting sliding member 91 is clamped into the third clamping groove 25, and the rear wheel assembly 3 is automatically folded. Then the supporting base plate 13 is rotated to put the supporting base plate 13 in an unfolded state.

[0044] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A trolley that can be unfolded stably, comprising a main platform (1), characterized in that: A front wheel assembly (2) and a rear wheel assembly (3) are respectively rotatably connected to the main body platform (1), and a first elastic reset member (4) for automatic reset is provided between the front wheel assembly (2) and the rear wheel assembly (3) and the main body platform (1); a wheel expander (5) is provided at the front end of the main body platform (1) and is hinged to the main body platform (1), and a locking device (6) for locking the front wheel assembly (2) is provided in the wheel expander (5), and the locking device (6) comprises a locking member body (61) that can be extended and retracted relative to the front wheel assembly (2); the main body A mounting seat (7) is provided at the rear end of the platform (1), and a handle assembly (8) rotatably connected thereto is provided on the mounting seat (7); a pull rod assembly (9) for limiting the rotation angle of the handle assembly (8) is provided between the mounting seat (7) and the main platform (1); the handle assembly (8) comprises a three-way assembly (81), and the pull rod assembly (9) comprises a limit sliding member (91) capable of limiting the rotation of the three-way assembly (81); and a wheel pushing member (82) for maintaining the unfolding of the rear wheel assembly (3) is provided on the three-way assembly (81).

2. The unfolded stable trolley according to claim 1, characterized in that: The main body platform (1) comprises a pair of columnar tubes (10) fixedly connected to each other; a wheel frame sleeve (11) fixedly connected to each other is provided at the front end of the columnar tube (10); a mounting seat (7) fixedly connected to each other is provided at the rear end of the columnar tube (10); a first elastic reset member (4) for automatic reset is provided in the wheel frame sleeve (11) and the mounting seat (7); a wheel expander (5) hingedly connected to the wheel frame sleeve (11) is provided on the wheel frame sleeve (11); a second elastic reset member (12) for reset is provided between the wheel expander (5) and the wheel frame sleeve (11); and a supporting base plate (13) hingedly connected to each other is provided at the front end of the columnar tube (10).

3. The unfolded stable trolley according to claim 2, characterized in that: A first pin shaft (14) is provided between the wheel expander (5) and the wheel frame cover (11) for hingedly connecting the two, and a second elastic reset member (12) is provided on the first pin shaft (14) for automatically reset the wheel expander (5); a locking device (6) is provided on the wheel expander (5), and a side wall of the wheel expander (5) when unfolded is arranged adjacent to a side wall of the wheel frame of the front wheel assembly (2); a first through hole (15) for accommodating a locking member body (61) is provided on the front wheel assembly (2), and a second through hole (16) for accommodating a locking member body (61) is provided on the wheel frame cover (11).

4. The unfolded stable trolley according to claim 3, characterized in that: The locking device (6) further comprises a front wheel locking pin rod (62), a button (63), a first elastic member (64) and a cover plate (65); a placement groove (51) for placing the button (63) is provided in the wheel expander (5), and an end surface of the placement groove (51) is provided with a cover plate (65) which covers the placement groove (51); a limiting notch (52) for inserting the button (63) is provided between the placement groove (51) and a side wall of the wheel expander (5), and an outer contour of the limiting notch (52) matches an outer contour of the button (63); The wheel expander (5) is provided with a plurality of limiting grooves (53) for accommodating the front wheel locking pin rod (62), and each limiting groove (53) is coaxially arranged; a locking member body (61) fixedly connected to the front wheel locking pin rod (62) is provided at the end of the front wheel locking pin rod (62), and the front wheel locking pin rod (62) is slidably connected to the button (63); a first elastic member (64) for resetting is provided between the button (63) and the bottom of the placement groove (51), and the axial direction of the first elastic member (64) is perpendicular to the axial direction of the limiting groove (53).

5. The unfolded stable trolley according to claim 4, characterized in that: An annular protrusion (66) is provided at the end of the front wheel locking pin rod (62), and a first waist-shaped hole (67) for inserting the annular protrusion (66) is provided on the button (63). When the button (63) is pressed, the annular protrusion (66) slides along the first waist-shaped hole (67); the axial direction of the first waist-shaped hole (67) is inclined to the axial direction of the limiting notch (52); the limiting groove (53) and the limiting notch (52) are perpendicular to each other, and the axial direction of the limiting groove (53) and the side wall of the wheel frame sleeve (11) are perpendicular to each other. When the wheel expander (5) is arranged in parallel with the main platform (1), the locking member body (61) is stuck in the second through hole (16), and when the locking member body (61) is in the second through hole (16), the front wheel assembly (2) is in a folded state; when the locking member body (61) is stuck in the first through hole (15), the front wheel assembly (2) is in an unfolded state; a stop bar (17) is provided on the front wheel assembly (2), and when the front wheel assembly (2) and the wheel expander (5) are in the unfolded state, the wheel expander (5) and the stop bar (17) are in contact with each other.

6. The unfolded stable trolley according to claim 2, characterized in that: A second pin shaft (18) is provided between the columnar tube body (10) and the supporting base plate (13) for hingedly connecting the two. A positioning piece (19) capable of automatically extending and retracting relative to the supporting base plate (13) is provided in the columnar tube body (10), and an inner recess (20) for placing the positioning piece (19) is provided on the supporting base plate (13). An arc-shaped transition portion (21) is provided on the edge of the supporting base plate (13).

7. The unfolded stable trolley according to claim 2, characterized in that: The mounting seat (7) is provided with a pull rod assembly (9), the pull rod assembly (9) comprising a limit cover (92), a limit push rod (93), a limit sliding member (91) and a second elastic member (94); the pull rod assemblies (9) are arranged in pairs, and a cross bar (22) connecting the two pull rod assemblies (9) is provided between the two pull rod assemblies (9); the mounting seat (7) is sleeved and installed on the outer layer of the columnar tube (10) and fixedly connected thereto by screws, and a limit push rod (93) is provided in the columnar tube (10) and is slidably connected thereto, and the limit push rod (93) is fixedly connected to the limit sliding member (91); the mounting seat (7) is provided with a handle assembly (8) rotatably connected thereto, and the handle assembly (8) comprises a three-way assembly (81) for connection; the three-way The assembly (81) comprises a first clamping groove (23), a second clamping groove (24) and a third clamping groove (25) which cooperate with the limiting sliding member (91); one end of the limiting push rod (93) is provided with a limiting sliding member (91) fixedly connected thereto, and the other end of the limiting push rod (93) is provided with a cross bar (22) sleeved therewith, and the end of the limiting push rod (93) connected to the cross bar (22) passes through the columnar tube (10); a second elastic member (94) is provided inside the columnar tube (10), and a limiting cover body (92) fixedly connected thereto is provided at the end of the columnar tube (10); one end of the second elastic member (94) abuts against the shaft sleeve of the limiting push rod (93), and the other end abuts against the limiting cover body (92).

8. The unfolded stable trolley according to claim 7, characterized in that: The columnar tube body (10) is provided with a guide groove (101) coaxially arranged therewith, the side wall of the mounting seat (7) is provided with a guide opening (71), and the limiting sliding member (91) passes through the guide groove (101) and the guide opening (71) in sequence; the end of the three-way assembly (81) is provided with a wheel pusher (82) tightly connected thereto, and the end of the wheel pusher (82) facing the mounting seat (7) is provided with a spherical protrusion (83); when the limiting sliding member (91) is stuck in the first slot (23), the handle assembly (8) and the main platform (1) are arranged in an inclined manner; when the limiting sliding member (91) is stuck in the second slot (24), the handle assembly (8) and the main platform (1) are arranged in contact with each other, and the handle assembly (8) and the rear wheel assembly (3) are both in a folded state; when the limiting sliding member (91) is stuck in the third slot (25), the handle assembly (8) and the main platform (1) are arranged parallel to each other, and the handle assembly (8) is in an unfolded state.

9. The unfolded stable trolley according to claim 1, characterized in that: The handle assembly (8) is provided with an extension handle (26) that can be telescoped relative to the handle assembly (8), and a switch assembly (27) for locking is provided on the handle assembly (8); the extension handle (26) is provided with a plurality of evenly distributed limiting holes (261), and the switch assembly (27) includes a handle latch (271) for locking.

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