Four-wheel quick-release type large-base cart

Abstract

The invention relates to the technical field of carts, in particular to a four-wheel quick-release large-base cart which comprises a transmission assembly, a gravity center compensation assembly and a direction reset mechanism. The transmission assembly is arranged in the supporting column. The gravity center compensation assembly is installed in the base in a sliding mode and connected with the transmission assembly. The direction resetting mechanism is connected with the universal wheel; when the bearing platform is rotated, a balancing weight in the gravity center compensation assembly is driven by the transmission assembly to slide reversely along the compensation sliding rail, so that gravity center shift caused by rotation of the bearing platform is counteracted; when the bearing platform is adjusted, the direction resetting mechanism enables the four universal wheels to slowly and automatically recover to the posture that the axes are parallel to the short sides of the base with the four universal wheels arranged in a rectangular shape; the problem that an existing four-wheel medical trolley overturns due to center-of-gravity shift when the angle of a bearing platform is adjusted is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of trolley technology, in particular to a four-wheel quick disassembly type large base trolley. BACKGROUND

[0002] The medical trolley is an indispensable auxiliary equipment in the medical field, which provides a mobile working platform for various medical instruments and nursing supplies. At present, the medical trolley is usually composed of multiple universal wheels, a support column and a bearing platform arranged on the support column. The structure is simple, and the bearing instrument can be conveniently disassembled and replaced.

[0003] In order to facilitate observation of the device screen for operation, the top bearing platform of the medical trolley on the market is usually designed as a structure capable of angle adjustment, and a multi-gear locking pin is used to realize the fixation of the inclination angle. In order to ensure the stability of the trolley in the stationary state, the universal wheels of the base are generally equipped with independent brake devices. Medical staff can lock one or more wheels by stepping on the brake pedal to prevent the trolley from sliding accidentally. When the medical staff tilts the bearing platform with heavy medical equipment forward by a large angle for convenient operation, the total center of gravity of the trolley will be significantly shifted forward. This change of center of gravity will reduce the anti-overturning stability of the trolley. In the case of forward center of gravity, if the medical staff forgets or fails to lock all the universal wheels in time, or the ground is slightly uneven, the trolley is prone to forward tipping due to the broken balance, which may cause damage to the expensive medical equipment, and may also cause harm to the medical staff or patients on site if a long bracket is installed on the bearing platform. Even if the universal wheels are locked, if the directions of multiple universal wheels are inconsistent, the forward center of gravity will still make the trolley in a critical unstable state, and slight external impact may cause overturning.

[0004] In view of the above situation, in order to overcome the above technical problems, the present application designs a four-wheel quick disassembly type large base trolley. SUMMARY

[0005] The present application provides a four-wheel quick disassembly type large base trolley, which solves the problem that the existing four-wheel medical trolley will overturn due to the shift of center of gravity when adjusting the angle of the bearing platform. By setting the transmission assembly and the center of gravity compensation assembly, when the bearing platform is rotated, the counterweight in the center of gravity compensation assembly is driven by the transmission assembly to slide reversely along the compensation slide rail, so as to offset the shift of center of gravity caused by the rotation of the bearing platform. In addition, the direction resetting mechanism can make the four universal wheels slowly and automatically recover to the posture that the axis of the base short side is parallel to the four universal wheels arranged in a rectangle, so as to ensure that the trolley will not tip over.

[0006] To achieve the above purpose, the present application provides the following technical scheme: The application discloses a four-wheel fast disassembly type large base trolley which comprises universal wheels, a base, a support column and a bearing platform, and further comprises a transmission assembly, a gravity center compensation assembly and a direction resetting mechanism; the support column is a hollow structure; the transmission assembly is arranged in the support column; the gravity center compensation assembly is slidably arranged in the base and connected with the transmission assembly; when the bearing platform rotates, the gravity center compensation assembly is driven to slide by the transmission assembly to adjust the gravity center position; the direction resetting mechanism is connected with the universal wheels; when the trolley stops moving, the direction resetting mechanism drives the universal wheels to rotate to a state that the axis is parallel to the moving direction of the gravity center compensation assembly.

[0007] Preferably, the transmission assembly comprises a fixing seat, a locking piece, a driving bevel gear, a transmission shaft and a rotating bearing; the fixing seat is arranged at the top of the support column; the locking piece is rotatably arranged on the fixing seat; the driving bevel gear is connected with the locking piece; the transmission shaft is rotatably arranged at the center of the support column; and the rotating bearing is connected between the support column and the transmission shaft.

[0008] In the above scheme, the locking piece (i.e. the angle adjusting handle or knob of the bearing platform, which is not described herein) is rigidly connected with the driving bevel gear; when the medical staff rotates the locking piece, the driving bevel gear rotates around a horizontal axis, and another bevel gear arranged at the top of the transmission shaft is driven to rotate, so that the movement is converted into the rotation of the transmission shaft around a vertical axis; the rotating bearing ensures that the transmission shaft can rotate smoothly and with low resistance at the center of the support column; and the transmission assembly can adjust the gravity center compensation assembly to timely adjust the gravity center when the medical staff adjusts the inclination angle of the bearing platform, so that the trolley is prevented from falling.

[0009] Preferably, the top of the transmission shaft is provided with a transmission bevel gear, and the bottom is provided with a driving gear; the transmission bevel gear is engaged with the driving bevel gear, and the transmission ratio range of the driving bevel gear and the transmission bevel gear is 1:2 to 1:4.

[0010] In the above scheme, the medical staff usually adjusts the angle of the bearing platform by a small angle (for example, 0-25°); if the transmission ratio is 1:1, the transmission shaft also only rotates by 25°, and the driving gear at the bottom rotates by an angle which is too small to drive the counterweight to produce a meaningful compensation displacement; by setting the amplification transmission ratio of 1:2 to 1:4, the small input action can be significantly amplified to a sufficient rotation stroke (for example, 50° to 100°) of the transmission shaft, so that the subsequent gravity center compensation assembly can obtain sufficient driving force and displacement, thereby making the compensation effect sensitive and effective.

[0011] Preferably, the gravity center compensation assembly comprises a compensation groove, a compensation sliding rail, a counterweight and a driving rack; the compensation groove is arranged in the base; the compensation sliding rail is arranged in the compensation groove; the counterweight is slidably arranged on the compensation sliding rail; and the driving rack is connected with the counterweight and engaged with the driving gear.

[0012] In the above scheme, the counterweight can be adjusted by sliding in the base, and the driving rack will move linearly under the driving of the driving gear when the angle of the bearing platform is adjusted. The weight of the counterweight and the transmission ratio between the driving gear and the driving rack can be freely adjusted according to the weight of the different instruments installed on the bearing platform, so as to accurately adjust the center of gravity. Since it is a pure mechanical hard connection, the compensation action of the counterweight and the adjustment action of the bearing platform are completely synchronous and have no delay. The counterweight moves to its position in real time when the bearing platform rotates, ensuring that the trolley is in a moment of balance during the adjustment process.

[0013] Preferably, the direction reset mechanism comprises a rotating groove, a fixed plate, a rotating plate, a reset spring and a friction disc; four support arms are connected to the base; the rotating groove is arranged on the support arm; the universal wheel comprises a fixed ring and a rotating shaft support; the fixed ring is connected with the rotating groove through threads; the rotating shaft support is rotatably installed in the fixed ring; the fixed plate is connected with the inner wall of the rotating groove; the rotating plate is connected with the rotating shaft support; the reset spring is connected between the fixed plate and the rotating plate; the friction disc is connected with the fixed plate and the lower surface of the friction disc is in contact with the top of the rotating shaft support.

[0014] In the above scheme, the fixed plate and the friction disc remain stationary, the rotating shaft support of the universal wheel is connected with the rotating plate and rotates with the universal wheel; when the universal wheel is deflected, the rotating plate will stretch or compress the reset spring connected between it and the fixed plate, and once the external steering force disappears, the reset spring will restore to its original state and drive the rotating plate and the rotating shaft support to return to the initial position. In this process, the lower surface of the friction disc is in continuous contact with the top of the rotating shaft support, providing damping effect to prevent the trolley from overturning due to too fast and violent reset action.

[0015] Preferably, the fixed plate and the rotating plate are separated by 180° when the reset spring is not deformed.

[0016] In the above scheme, the interval between the fixed plate and the rotating plate can ensure that the universal wheel can rotate by 180° in the clockwise and counterclockwise directions, ensuring that the trolley can easily turn in any direction during use, and ensuring the flexibility and convenience of medical staff during use.

[0017] Preferably, the four universal wheels are arranged in a rectangular shape, and the lower axis of the initial position of the universal wheel is parallel to the short side of the rectangle; the moving direction of the counterweight is perpendicular to the long side of the rectangle formed by the four universal wheels; and the driving bevel gear axis is parallel to the long side of the rectangle formed by the four universal wheels.

[0018] In the above scheme, the biggest overturning risk of the trolley comes from the direction of the center of gravity movement, that is, the short side direction of the rectangle, the inclination of the bearing platform and the deviation of the center of gravity occur in the lateral direction (short side direction), which is the "short board" in the physical size of the trolley and is the dimension most prone to side overturning. The long side of the rectangle provides a very wide front and rear wheelbase to provide stronger anti-rollover ability like a Z-shaped step, and when the counterweight moves, all the universal wheels are adjusted to the direction in which the axis is parallel to the short side direction, at this time, even if the steering of the universal wheel is not locked, the trolley will not move due to the adjustment of the bearing platform and the sliding of the counterweight.

[0019] Preferably, the lower surface of the friction disc is a microwave wave structure made of a high-molecular flexible material; and the top of the rotating shaft frame is a microwave wave structure made of a hard material.

[0020] In the above scheme, when rotating at low speed (passive reset), the rigid top of the rotating shaft frame has enough time to "sink into" and cause sufficient elastic deformation of the flexible wave structure. In this slow "rubbing" process, the internal friction (hysteresis effect) of the material is very significant, which can generate a large damping force to enable the universal wheel to reset slowly. When rotating at high speed (active deflection), due to the high speed, the molecular chains of the flexible material cannot respond in time, showing the "frequency hardening" characteristic, and its surface is similar to a rigid bumpy plate. The top of the rotating shaft frame "slides" on it at high speed, and the hysteresis effect is greatly weakened, so it only receives a small sliding friction force. When the medical staff needs to quickly turn, it feels light and sensitive, and when the trolley stops and the universal wheel automatically resets, the process becomes smooth and slow, preventing the trolley from overturning.

[0021] Compared with the prior art, the beneficial effects of the present application are: 1. Compared with the existing medical trolley, by arranging the transmission assembly and the center of gravity compensation assembly, when the medical staff adjusts the angle of the bearing platform, the transmission assembly can simultaneously convert the rotating motion of the bearing platform into the linear sliding motion of the counterweight block in the center of gravity compensation assembly. The stable torque generated by the sliding of the counterweight block can accurately offset the overturning torque generated by the rotation of the bearing platform and the forward movement of the center of gravity of the equipment in real time, so that the whole vehicle is in a state of torque balance during adjustment, preventing the trolley from overturning due to angle adjustment.

[0022] 2、The application arranges four universal wheels in a rectangle, and sets a direction reset mechanism, when the trolley stops moving, the universal wheels will automatically restore to the posture that the wheel shaft is parallel to the short side of the rectangle, meanwhile, the long side of the rectangle provides very wide front and rear wheelbase, which can provide stronger anti-side falling ability like a Z-shaped step, and the short side of the rectangle arrangement is the same as the moving direction of the counterweight, when the counterweight moves, all the universal wheels are adjusted to the direction that the shaft line is parallel to the short side, at this time, even if the steering of the universal wheel is not locked, the trolley will not move because of the adjustment of the bearing platform and the sliding of the counterweight, ensuring the overall stability of the trolley.

[0023] 3、The application sets a friction disc, the lower surface of the friction disc is set as a microwave wave structure supported by flexible high polymer material, and the top of the shaft frame is a microwave wave structure made of hard material, when the universal wheel is driven to quickly steer by external force, the material cannot fully deform, presents "pseudo-rigidity", the hysteresis effect is weak, so the friction resistance is extremely small, ensuring the light and sensitive steering feeling, and under the condition of no external force, the universal wheel will be reset under the reset spring force, in the reset process, the material has enough time to deform and recover, the significant internal friction and hysteresis effect will generate a larger damping force, consume part of the rebound energy, so that the reset process is more stable and slow, ensuring the overall stability of the trolley. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0025] Figure 1 is the overall structural diagram of the present application; Figure 2 is the internal structure diagram of the strut of the present application; Figure 3 is the exploded view of the present application; Figure 4 is Figure 3 is the enlarged view of structure A in the middle; Figure 5 is the sectional view of the present application; Figure 6 is the internal structure sectional view of the compensation groove of the present application; Figure 7 is the schematic view of the universal wheel structure of the present application; Figure 8 is the perspective view of the direction reset mechanism of the present application.

[0026] In the figure: 1, universal wheel; 11, fixed ring; 12, rotating shaft frame; 2, base; 21, support arm; 3, support column; 4, bearing platform; 5, transmission assembly; 51, fixed seat; 52, locking piece; 53, driving bevel gear; 54, transmission shaft; 541, transmission bevel gear; 542, driving gear; 55, rotating bearing; 6, gravity compensation assembly; 61, compensation groove; 62, compensation slide rail; 63, counterweight; 64, driving rack; 7, direction reset mechanism; 71, rotating groove; 72, fixed plate; 73, rotating plate; 74, reset spring; 75, friction disc. DETAILED DESCRIPTION

[0027] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings in the specification and specific embodiments.

[0028] Please refer to Figures 1 to 8 , the present application provides a four-wheel quick-release type large base cart, the technical scheme is as follows: As a specific embodiment of the present application, refer to Figure 1 , Figure 2 and Figure 3The application discloses a four-wheel fast dismounting type large base 2 stroller, which comprises universal wheels 1, a base 2, a support column 3 and a bearing platform 4; the wheel surface material of the universal wheels 1 is made of thermoplastic rubber or medical-grade polyurethane which has high elasticity and high wear resistance, compared with the traditional hard nylon wheel, the soft tread can effectively absorb the tiny impact and vibration caused by the uneven ground when being in contact with the ground, and convert the rigid collision into elastic deformation, so that the generation of rolling noise is eliminated from the source, and the silent moving effect is realized; the support column 3 is made of light-weight high-strength material, and the upper weight is reduced, aluminum alloy is selected as the material of the support column 3, and the strength and hardness of the aluminum alloy can meet the bearing requirements through heat treatment, the aluminum alloy has good bending resistance and torsion resistance, the base 2 is made of high-density and high-rigidity metal material, cast iron is adopted, the density of the cast iron is about three times of the aluminum alloy material of the support column 3, the cast iron can make itself become a huge and uniformly distributed bottom counterweight, the center of gravity of the whole vehicle can be greatly pulled close to the ground, and the cast iron has excellent rigidity and outstanding vibration absorption performance, a solid and heavy cast iron base 2 can effectively absorb the tiny vibration from the ground and the shaking generated in the operation process, and provide an extremely stable working platform for the upper precise instrument; the stroller further comprises a transmission assembly 5, a center of gravity compensation assembly 6 and a direction resetting mechanism 7; the support column 3 is a hollow structure; the transmission assembly 5 is arranged in the support column 3; the center of gravity compensation assembly 6 is slidingly installed in the base 2 and connected with the transmission assembly 5, the bearing platform 4 is driven to slide by the transmission assembly 5 to adjust the center of gravity position when rotating; the direction resetting mechanism 7 is connected with the universal wheels 1, and the direction resetting mechanism 7 drives the universal wheels 1 to rotate to the state that the axis is parallel to the moving direction of the center of gravity compensation assembly 6 when the stroller stops moving.

[0029] As a specific embodiment of the application, reference is made to Figure 2 、 Figure 3 、 Figure 4 and Figure 5The transmission assembly 5 comprises a fixing base 51, a locking member 52, a driving bevel gear 53, a transmission shaft 54 and a rotating bearing 55. The fixing base 51 is installed on the top of the support column 3. The locking member 52 is rotatably installed on the fixing base 51. The driving bevel gear 53 is connected with the locking member 52. The transmission shaft 54 is rotatably installed in the center of the support column 3. The rotating bearing 55 is connected between the support column 3 and the transmission shaft 54. Since the locking member 52 (i.e. the angle adjusting handle or knob of the bearing platform 4, which serves as a rotating shaft and drives the driving bevel gear 53 to rotate when being rotated, and the handle is provided with a positioning pin loaded by a spring, and the fixing base 51 is provided with a plurality of positioning holes matched with the positioning pin, when the angle needs to be adjusted, the user needs to pull out the positioning pin, rotate the handle to the desired position, and then release the positioning pin to automatically insert into the nearest positioning hole, so as to realize the locking of the angle) is rigidly connected with the driving bevel gear 53, when the medical staff rotates the locking member 52, the driving bevel gear 53 will rotate around a horizontal axis, and another bevel gear installed at the top of the transmission shaft 54 will be driven to rotate around a vertical axis, so as to convert the movement into the rotation of the transmission shaft 54 around the vertical axis. The rotating bearing 55 ensures that the transmission shaft 54 can stably and low-resistance rotate in the center of the support column 3. It is ensured that the transmission assembly 5 can adjust the gravity center compensation assembly 6 in time to adjust the gravity center when the medical staff adjusts the inclination angle of the bearing platform 4, so as to prevent the cart from falling down.

[0030] As a specific embodiment of the present application, refer to Figure 2 , Figure 3 , Figure 4 and Figure 5 The top of the transmission shaft 54 is provided with a transmission bevel gear 541, and the bottom is provided with a driving gear 542. The transmission bevel gear 541 is engaged with the driving bevel gear 53, and the transmission ratio range of the driving bevel gear 53 and the transmission bevel gear 541 is 1:2 to 1:4. The medical staff usually adjusts the angle of the bearing platform 4 in a small range (for example, 0-25°). If the transmission ratio is 1:1, the transmission shaft 54 also only rotates 25°, and the driving gear 542 at the bottom rotates in a too small angle to drive the counterweight 63 to generate a meaningful compensation displacement. By setting the amplification transmission ratio of 1:2 to 1:4, the small input action can be significantly amplified to a sufficient rotation stroke (for example, 50° to 100°) of the transmission shaft 54, so as to ensure that the subsequent gravity center compensation assembly 6 obtains sufficient driving force and displacement, thereby making the compensation effect sensitive and effective.

[0031] As a specific embodiment of the present application, refer to FIG Figure 2 , Figure 5 and Figure 6The gravity center compensation assembly 6 comprises a compensation groove 61, a compensation sliding rail 62, a counterweight 63 and a driving rack 64; the compensation groove 61 is arranged in the base 2; the compensation sliding rail 62 is arranged in the compensation groove 61; the counterweight 63 is slidingly arranged on the compensation sliding rail 62; the driving rack 64 is connected with the counterweight 63, and the driving rack 64 is engaged with the driving gear 542. The counterweight 63 can be adjusted in the base 2, and the driving rack 64 will be driven to move linearly by the driving gear 542 when the bearing platform 4 is adjusted in angle. For different instruments installed on the bearing platform 4, the weight of the counterweight 63 and the transmission ratio between the driving gear 542 and the driving rack 64 can be freely adjusted to accurately adjust the gravity center. Since it is a pure mechanical hard connection, the compensation action of the counterweight 63 and the adjustment action of the bearing platform 4 are completely synchronous and have no delay. When the bearing platform 4 rotates, the counterweight 63 will move to the position in real time, so that the trolley is in a moment of balance during the adjustment process.

[0032] As a specific embodiment of the present application, referring to Figure 2 、 Figure 7 and Figure 8 , the direction reset mechanism 7 comprises a rotating groove 71, a fixed plate 72, a rotating plate 73, a reset spring 74 and a friction disc 75; the base 2 is connected with four supporting arms 21; the rotating groove 71 is arranged on the supporting arm 21; the universal wheel 1 comprises a fixed ring 11 and a rotating shaft support 12; the fixed ring 11 is connected with the rotating groove 71 through threads; the rotating shaft support 12 is rotatably arranged in the fixed ring 11; the fixed plate 72 is connected with the inner wall of the rotating groove 71; the rotating plate 73 is connected with the rotating shaft support 12; the reset spring 74 is connected between the fixed plate 72 and the rotating plate 73; the friction disc 75 is connected with the fixed plate 72 and the lower surface of the friction disc 75 is in contact with the top of the rotating shaft support 12. The fixed plate 72 and the friction disc 75 remain stationary, the rotating shaft support 12 of the universal wheel 1 is connected with the rotating plate 73 and rotates with the universal wheel 1; when the universal wheel 1 is deflected, the rotating plate 73 will stretch or compress the reset spring 74 connected between it and the fixed plate 72, and once the external steering force disappears, the reset spring 74 will restore to the original state and drive the rotating plate 73 and the rotating shaft support 12 to return to the initial position. In this process, the lower surface of the friction disc 75 is in continuous contact with the top of the rotating shaft support 12 to provide damping effect, preventing the trolley from being overturned due to the reset action being too fast or too violent.

[0033] As a specific embodiment of the present application, referring to Figure 7 and Figure 8, the fixed plate 72 and the rotating plate 73 are separated by 180° when the reset spring 74 is not deformed. By setting the interval between the fixed plate 72 and the rotating plate 73, it can be ensured that the universal wheel 1 can rotate by 180° in both clockwise and counterclockwise directions, ensuring that the trolley can easily turn in any direction during use, and ensuring that medical staff can use it flexibly and conveniently.

[0034] As a specific embodiment of the present application, refer to Figure 5 and Figure 6 , the four universal wheels 1 are arranged in a rectangular shape, and the axis of the universal wheel 1 in the initial position is parallel to the short side of the rectangle; the moving direction of the counterweight 63 is perpendicular to the long side of the rectangle formed by the four universal wheels 1; the axis of the driving bevel gear 53 is parallel to the long side of the rectangle formed by the four universal wheels 1. The tilt of the load platform 4 and the shift of the center of gravity occur in the lateral direction (short side direction), which is the "short side" of the physical size of the trolley and is also the dimension that is most prone to tipping over. The long side of the rectangle provides a very wide front and rear wheelbase, which can provide stronger resistance to lateral tipping like a striding stance, and when the counterweight 63 moves, all the universal wheels 1 are adjusted to a direction in which the axis is parallel to the short side direction, at this time, even if the steering of the universal wheel 1 is not locked, the trolley will not move due to the adjustment of the load platform 4 and the sliding of the counterweight 63.

[0035] As a specific embodiment of the present application, refer to Figure 7 and Figure 8 , the lower surface of the friction disc 75 is a micro-wavy structure made of a high-molecular flexible material; the top of the shaft holder 12 is a micro-wavy structure made of a hard material. The high-molecular flexible material here can be selected from nitrile rubber, polyurethane elastomer or viscoelastic silica gel, and its Shore hardness is preferably in the range of A30 to A60, the micro-wavy structure is a radial wave, and the number of wave crests is preferably 30 to 60; the wave height is preferably 0.2mm to 0.8mm; when rotating slowly (passive reset), the rigid top of the shaft holder 12 has enough time to "sink into" and cause sufficient elastic deformation of the flexible wavy structure, and in this slow "rubbing" process, the internal friction (hysteresis effect) of the material is very significant, which can generate a large damping force, so that the universal wheel 1 can reset slowly, and the restoring torque that the reset spring 74 can generate when deformed is designed to be always greater than the friction torque generated between the friction disc 75 and the shaft holder 12; while rotating at high speed (active deflection), due to the high speed, the molecular chains of the flexible material cannot respond in time, showing the characteristic of "frequency hardening", and its surface is similar to a rigid bumpy plate, on which the top of the shaft holder 12 slides at high speed, and the hysteresis effect is greatly weakened, so it only receives a small sliding friction force; when the medical staff needs to quickly turn, the feeling is light and sensitive, while when the trolley stops and the universal wheel 1 automatically resets, the process becomes smooth and slow, preventing tipping over.

[0036] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations and modifications are intended to be included within the scope of the application as defined in the following claims and the equivalents thereof.

Claims

1. A four-wheel quick-release base trolley, comprising a universal wheel (1), a base (2), a support column (3) and a load platform (4); characterized in that: It also includes transmission assembly (5), gravity compensation assembly (6) and direction reset mechanism (7); the strut (3) is hollow structure; the transmission assembly (5) is arranged in the strut (3) inside; the gravity compensation assembly (6) is slidably installed in the base (2) and is connected with transmission assembly (5), when the bearing platform (4) rotates, the gravity compensation assembly (6) is driven to slide by transmission assembly (5) and adjusts the gravity position; the direction reset mechanism (7) is connected with the universal wheel (1), when the trolley stops moving, the direction reset mechanism (7) drives the universal wheel (1) to rotate to the state that the axis is parallel with the moving direction of the gravity compensation assembly (6).

2. A four wheeled quick release base stroller according to claim 1, characterized in that: The transmission assembly (5) includes fixed seat (51), locking piece (52), drive bevel gear (53), transmission shaft (54) and rotating bearing (55); the fixed seat (51) is installed at the top of the strut (3); the locking piece (52) is rotatably installed on the fixed seat (51); the drive bevel gear (53) is connected with the locking piece (52); the transmission shaft (54) is rotatably installed at the center of the strut (3); the rotating bearing (55) is connected between the strut (3) and the transmission shaft (54).

3. A four wheeled quick release base trolley as claimed in claim 2, wherein: The top of the transmission shaft (54) is provided with a transmission bevel gear (541), and the bottom is provided with a drive gear (542); the transmission bevel gear (541) is engaged with the drive bevel gear (53), and the transmission ratio range of the drive bevel gear (53) and the transmission bevel gear (541) is 1:2 to 1:

4.

4. A four wheeled quick release base trolley as claimed in claim 3, wherein: The gravity compensation assembly (6) includes compensation slot (61), compensation slide rail (62), counterweight block (63) and drive rack (64); the compensation slot (61) is opened in the base (2); the compensation slide rail (62) is arranged in the compensation slot (61); the counterweight block (63) is slidably installed on the compensation slide rail (62); the drive rack (64) is connected with the counterweight block (63), and the drive rack (64) is engaged with the drive gear (542).

5. A four wheeled quick release base stroller according to claim 1, wherein: The direction reset mechanism (7) includes rotating slot (71), fixed plate (72), rotating plate (73), reset spring (74) and friction disc (75); the base (2) is connected with four support arms (21); the rotating slot (71) is opened on the support arm (21); the universal wheel (1) includes fixed ring (11) and rotating shaft frame (12); the fixed ring (11) is connected with the rotating slot (71) through threads; the rotating shaft frame (12) is rotatably installed on the fixed ring (11); the fixed plate (72) is connected with the inner wall of the rotating slot (71); the rotating plate (73) is connected with the rotating shaft frame (12); the reset spring (74) is connected between the fixed plate (72) and the rotating plate (73); the friction disc (75) is connected with the fixed plate (72), and the lower surface of the friction disc (75) is in contact with the top of the rotating shaft frame (12).

6. A four wheeled quick release base trolley as claimed in claim 5, wherein: The fixed plate (72) and the rotating plate (73) are separated by 180° when the reset spring (74) is not deformed.

7. A four wheeled quick release base cart according to claim 4, wherein: Four said universal wheels (1) are arranged in a rectangle, and the axis of the universal wheel (1) is parallel to the short side of the rectangle in the initial position; the moving direction of the counterweight (63) is perpendicular to the long side of the rectangle formed by the four universal wheels (1); the axis of the driving bevel gear (53) is parallel to the long side of the rectangle formed by the four universal wheels (1).

8. A four wheeled quick release base cart according to claim 5, wherein: The lower surface of the friction disc (75) is a micro-wavy structure made of a high polymer flexible material; the top of the shaft support (12) is a micro-wavy structure made of a hard material.

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