Electric gear shifting trundle and working method thereof

Abstract

The invention relates to an electric gear-shifting trundle and a working method thereof, and is characterized in that the electric gear-shifting trundle comprises a trundle main frame and a trundle piece rotationally connected to the trundle main frame, a trundle piece tooth groove 36.1 is formed in the inner circumferential wall of the trundle piece, and a brake pad 10 capable of being inserted into or far away from the trundle piece tooth groove 36.1 is arranged on the trundle main frame; the push rod is driven by a motor controlled by a central controller to ascend and descend, the wedge block 13 is connected with the lower end of the push rod, and the wedge face on the wedge block 13 is matched with the brake pad 10 to drive the brake pad 10 to slide so as to be inserted into or away from a wheel piece tooth groove 36.1. A tooth piece is installed on the trundle main frame in a limiting mode, a gear 33 capable of being meshed with the tooth piece 9 is installed on the lower portion of the push rod, and when the push rod ascends and descends, the gear and the tooth piece are meshed or disengaged, and then relative rotation of the trundle main frame and the push rod is limited. According to the electric gear-shifting trundle, gear shifting of the trundle can be achieved through work of the motor.

Description

Technical Field

[0002] The invention relates to the field of caster structures, in particular to an electric gear-changing caster and a working method thereof. Background Art

[0004] Casters are widely used, such as in wheelchairs, medical equipment and other vehicle bodies. In order to realize the functions of braking or unlocking the brakes of casters, current casters are all operated manually or by foot, such as the Chinese patent "A multi-pedal controlled caster and its use method", announcement number CN116039288B, "A brake caster" announcement number CN117644743B, etc.

[0005] With the application of medical carrier platforms at home and abroad, a series of requirements have been put forward for caster central control technology: 1. Maneuverability: Medical vehicles need to be able to move flexibly and be controlled flexibly in the complex environment of the hospital, and to be precisely controlled in a limited structural space; 2. Quietness: The hospital needs to be quiet to facilitate the rest and treatment of patients, so the control implementation process should not produce redundant sounds other than the function, or the volume of the function implementation process should be too loud; 3. Stability and reliability: Medical carriers often carry important medical equipment or patients. The central control structure of the casters must ensure stable operation under various load conditions to avoid loss of control, jamming or failure to ensure the safety of medical operations.

[0006] 4. Convenience: Central control methods are becoming more and more simple, direct, convenient and effective.

[0007] The existing casters are unable to achieve gear shifting of the casters through the operation of the motor, and to meet the requirements of unified control. Summary of the invention

[0008] In view of the above-mentioned deficiencies in the prior art, the present invention provides an electric gear-changing caster and a working method thereof, wherein the electric gear-changing caster can achieve gear changing of the caster through the operation of a motor.

[0009] The present invention provides an electric gear-changing caster, which is characterized by comprising a caster main frame and a wheel piece rotatably connected to the caster main frame, the inner peripheral wall of the wheel piece being provided with a wheel piece tooth groove, the caster main frame being provided with a brake piece capable of being inserted into or away from the wheel piece tooth groove, the caster main frame being provided with a push rod driven to rise and fall by a motor controlled by a central controller and a wedge block connected to the lower end of the push rod, the wedge surface on the wedge block cooperating with the brake piece to drive the brake piece to slide so as to be inserted into or away from the wheel piece tooth groove; a tooth piece is installed at the upper limit position of the caster main frame, a gear capable of meshing with the tooth piece is installed on the lower part of the push rod, and when the push rod is raised and lowered, the gear and the tooth piece are meshed or disengaged, thereby limiting the relative rotation of the caster main frame and the push rod.

[0010] The working method of the electric gear-changing caster of the present invention is characterized by: (1) Full braking: The output end of the motor rotates, causing the push rod to rise and retract to the shortest distance. The push rod is at the uppermost initial position. At this time, the gear and the gear are engaged, so that the outer push rod stops rotating relative to the caster main frame, and the main shaft is linked to stop rotating, so that the caster cannot rotate around the main shaft; the wedge block is also at the uppermost initial position, and the brake pad is pushed to the outermost side under the action of the torsion spring elastic force, so that the brake pad enters the wheel tooth groove to stop the wheel rotation; (2) Fully free state: When the output end of the motor rotates, the push rod extends to the middle preset position, that is, the inner push rod moves downward, and the outer push rod moves downward in conjunction with the compression spring force. At this time, the gear and the tooth plate are disengaged, and the rotational freedom of the outer push rod is restored. The main shaft is linked to restore the rotational freedom with the caster main frame and the main board, that is, the caster can rotate relative to the main shaft; the wedge block is in the middle preset position at this time, and the brake pad is pushed out of the wheel plate tooth groove under the action of the wedge surface of the wedge block, and the rotation of the wheel plate is restored; (3) Orientation state: When the output end of the motor rotates, the push rod extends to the limit distance, that is, the inner push rod continues to move downward, and the outer push rod continues to move downward under the action of the compression spring elastic force. At this time, the gear and the tooth plate are out of meshing state, and the directional plate is pre-pressed on the upper end surface of the directional function slot of the main board under the action of the spring force. When the main shaft and the outer push rod rotate freely relative to the main board at a certain angle, the directional plate enters the directional function slot of the main board. At this time, the spring force is released to press the wedge block downward instantly. Under the action of the wedge surface force, the brake pad continues to move away from the wheel plate tooth groove. At this time, the outer push rod stops rotating, and the main shaft stops rotating, and the wheel plate still rotates freely; (4) On the contrary, the motor drives the push rod to retract, and the above functions are realized in the order of (3), (2), and (1).

[0011] Of course, the motor can also drive the push rod to extend and retract to a preset distance to selectively realize the different functional states of the above-mentioned casters without strictly following the logical order.

[0012] The electric gear-changing caster can achieve gear changing of the caster through the operation of the motor, and can achieve unified control of each caster through a central controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0015] The central control reset pedal and its combined connection method of the present invention are further described in detail below in conjunction with the accompanying drawings and specific implementation structures.

[0016] Figure 1 An exploded view of the components of the electric-controlled caster of the present invention; Figure 2 It is a partial three-dimensional schematic diagram of the assembly structure of the present invention; Figure 3 It is a schematic diagram of the cross-sectional structure of the present invention (full brake); Figure 4 It is a schematic diagram of the mainboard components of the present invention; Figure 5 It is a schematic diagram of the push rod components of the present invention; Figure 6 It is a schematic diagram of the inner push rod structure of the present invention; Figure 7 It is a schematic diagram of the structure of the outer push rod of the present invention; Figure 8 It is a schematic diagram of the nut structure of the present invention; Fig. 9 It is a schematic diagram of the rod sleeve structure of the present invention; Fig.10 It is a schematic diagram of the wedge structure of the present invention; Fig.11 It is a schematic diagram of the brake pad structure of the present invention; Fig.12 It is a schematic diagram of the tooth structure of the present invention; Fig.13 It is a schematic diagram of the structure of the guide rail block of the present invention; Fig.14 It is a schematic diagram of the structure of the bracket of the present invention from two viewing angles; Fig.15 It is a schematic diagram of the knob structure of the present invention; Fig.16 , 17 for Figure 1 A partial view of Fig.18 It is a schematic diagram of the cross-sectional structure of the present invention in a fully free state; Fig.19 It is a schematic diagram of the cross-sectional structure of the oriented state of the present invention; Fig. 20 It is a stereoscopic view of the outer push rod, gear and directional plate; In the figure: 1-spindle cover; 2-large washer; 3-castor main frame; 3.1 spindle (fixedly connected to the vehicle body); 3.2 shaft sleeve (sleeve is fixed to the main board and rotates relative to the spindle); 3.3 main board; 3.3.1 directional function slot; 3.3.2 shaft locking function slot; 3.3.3 brake function slot; 3.3.4 Limiting hole; 3.3.5-bolt hole (for connecting and fixing with the shell screw); 3.4-axial channel; 4-motor; 5-inner push rod; 5.1 step column; 5.2 internal threaded hole; 6-gasket; 7-compression spring; 8-spring; 9-tooth plate; 9.1 tooth groove; 9.2 first limiting groove; 10-brake pad; 10.1 square hole; 10.2 horn protrusion; 10.3-cage; 10.4 guide groove; 11-wire clamp (for passing and fixing the plug nail with hole, wedge block and outer push rod); 12-plug nail with hole (for connecting and fixing the wedge block to the outer push rod); 13-wedge block ;13.1 wedge surface;13.2 stepped hole (for inserting the lower end of the outer push rod);13.3 guide groove (for cooperating with the main board to limit the position, so as to guide the lifting and lowering of the wedge);14-sleeve;15-stud screw (for screwing to the lower end of the inner push rod and supporting the sleeve);16-outer bushing;17-empty tube cross bar;18-circlip (for limiting the motor AB shell);19-motor AB shell (for wrapping around the outer periphery of the motor and inserting into the main shaft);20-nut (locked on the upper end of the outer push rod to limit the spacer and compression spring);20.1 hexagonal hole (for using a wrench to lock the nut with the outer push rod) ; 20.2 external thread; 21-external push rod; 21.1 flat position; 21.2 first polygonal shaft section; 21.3 cylinder; 21.4 wire hole; 21.5 retaining ring groove; 21.6 internal thread; 21.7 second polygonal shaft section; 22-rod sleeve (formed by two halves); 22.1 round hole (for insertion of the protruding column with slope); 22.2 reinforcing rib; 22.3 female groove (fitted with male groove); 22.4 male groove; 23-knob; 23.1 butterfly; 23.2 large protrusion; 23.3 small protrusion; 23.4 round hole; 24-circumferential inner torsion spring (installed in the guide block so as to 1. The brake pad is reset by the knob); 25-guide rail block; 25.1 arc guide groove; 25.2 torsion spring limit groove (for installing circumferential inner torsion spring); 25.3 inner guide groove (for guiding the lifting and sliding of the bracket); 25.4 screw column; 25.5 step surface; 26-bracket; 26.1 protrusion of the column with slope; 26.2 step hole; 26.3 guide groove; 26.4 hexagonal groove; 27-torsion spring (for squeezing and pushing the brake pad); 28-locking bolt; 29-hexagonal nut; 30-cross pan head screw; 31-internal thread bushing; 32-directional plate; 32.1 second limit groove; 33-gear; 34- E-type retaining ring; 35-enclosure; 36-wheel plate; 36.1-wheel plate tooth groove. Specific implementation structure In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In conjunction with the accompanying drawings, some implementation structures of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0022] An implementation structure of the present invention is as follows Figures 1 to 5 As shown, The electric gear-changing caster of the present invention comprises a caster main frame 3 and a wheel piece 36 rotatably connected to the caster main frame 3. The caster main frame 3 comprises a main board 3.3 and a casing 35, etc. The wheel piece 36 is rotatably connected to the caster main frame 3 through an outer bushing 16 and a hollow tube cross bar 17, etc. The wheel piece 36 is in contact with the ground. The main board 3.3 of the caster main frame 3 is rotatably connected to a main shaft 3.1 on the upper part through a bearing. When in use, the main shaft 3.1 is detachably fixedly connected to the support leg of the vehicle body, that is, the main shaft 3.1 is fixed relative to the vehicle body.

[0023] A wheel tooth groove 36.1 is provided in a circumferential array on the inner circumferential wall of the wheel disc 36, and a brake pad 10 capable of being inserted into or away from the wheel tooth groove 36.1 is provided on the caster main frame, and a push rod (including an inner push rod 6 and an outer push rod 21) driven to rise and fall by a motor 4 controlled by a central controller and a wedge block 13 fixedly connected to the lower end of the push rod are provided on the caster main frame, and the wedge surface on the wedge block 13 cooperates with the brake pad 10 to drive the brake pad 10 to slide to be inserted into or away from the wheel tooth groove 36.1; in a preferred embodiment, a torsion spring 27 or a push spring capable of pushing the brake pad 10 toward the wheel tooth groove 36.1 is provided on the main board, and when the push rod is driven to descend, the wedge surface on the wedge block 13 drives the brake pad 10 to overcome the thrust of the torsion spring (or the thrust of the push spring) and move away from the wheel tooth groove 36.1.

[0024] In another embodiment (comparatively preferred embodiment), the brake pad 10 is pushed into the wheel tooth groove 36.1 when the push rod is lowered. Then, since the brake pad 10 is not able to enter the wheel tooth groove 36.1 immediately when it is squeezed and pushed by the wedge block 13 and the outer push rod 21, the reason is that when the wheel rotates at a faster speed, the brake pad 10 repeatedly enters and exits the wheel tooth groove 36.1, and will react on the wedge block 13 and the outer push rod 21. Then, the output shaft of the motor has to bear the force of axial movement, and the motor is easily damaged, affecting its service life. The present application adopts the above-mentioned preferred embodiment, and can be in the case where the brake pad 10 repeatedly enters and exits the wheel tooth groove 36.1 (at this time, the wedge block 13 has been separated from the brake pad 10, and the repeated movement of the brake pad 10 has no effect on the wedge block 13). At this time, the torsion spring bears the action of repeated compression, and this repeated compression will not greatly affect the service life of the torsion spring.

[0025] During the lifting process, the outer push rod 21 drives the gear 33 and the directional plate 32 to rise and fall. The meshing of the gear 33 and the tooth plate 9, or the embedding of the directional plate 32 into the directional function groove 3.3.1, will not be completed in one go, which may easily cause the outer push rod to move in both axial and radial directions. The radial movement is overcome by the cooperation between the outer push rod and the axial channel 3.4 of the main shaft, while the axial movement is overcome by the connection structure between the inner push rod and the outer push rod. Therefore, the connection structure between the inner push rod and the outer push rod of the present application is conducive to avoiding the axial movement of the motor shaft caused by the axial movement of the outer push rod when the motor is directly connected to the outer push rod, thereby affecting the service life.

[0026] A tooth plate 9 is installed at the upper limit position of the caster main frame, and a gear 33 capable of meshing with the tooth plate 9 is installed on the lower part of the push rod. When the push rod is raised or lowered, the gear and the tooth plate are meshed or disengaged, thereby limiting the relative rotation of the caster main frame and the push rod.

[0027] The push rod includes an inner push rod 5 and an outer push rod 21. The main shaft 3.1 is provided with an axial channel 3.4 for fixing the motor 4 and limiting the rotation of the outer push rod. The output shaft end of the motor is threadedly connected with the internal threaded hole 5.3 at the first end of the inner push rod 5. The outer push rod 21 is provided with a stepped channel 21.8 for passing the inner push rod 5. Gaskets 6 are sleeved in the stepped channel and at both ends of the inner push rod 5. A compression spring 7 is provided between the two gaskets so that the outer push rod 21 and the inner push rod 5 are pressed against each other to form a whole.

[0028] The main board to which the caster main frame is fixedly connected is provided with a braking function groove 3.3.3 for guiding the brake pad 10 to slide, and the inclination angle can be an angle of 15-35 degrees with the horizontal plane. The middle part of the brake pad 10 has a square hole 10.1 that cooperates with the wedge surface on the wedge block 13, so that when the wedge block 13 is lifted and lowered, the brake pad 10 is driven to slide in the braking function groove 3.3.3, thereby inserting the horn protrusion 10.2 on the brake pad 10 into or away from the wheel tooth groove 36.1. The wedge block 13 is fixedly installed (fixed by plugging and connecting the line card 11) on the lower end of the outer push rod 21.

[0029] The middle part of the above-mentioned tooth piece 9 has a tooth groove 9.1 that meshes with the gear 33, and the side part of the tooth piece 9 is provided with a first limiting groove 9.2 that cooperates with the locking shaft function groove 3.3.2 on the main board. The locking shaft function groove 3.3.2 is provided with a spring 8 for pressing the tooth piece 9. The middle part of the gear 33 has a polygonal through hole, and the outer push rod has a first polygonal shaft section 21.2 that matches the polygonal through hole. The gear 33 is sleeved on the first polygonal shaft section of the outer push rod and is limited in axial movement by the limiting member. When the outer push rod is lifted and lowered to make the gear 33 mesh with the tooth groove 9.1 of the tooth piece 9, the relative rotation of the main board, the caster main frame and the outer push rod is limited. Since the main shaft and the outer push rod themselves cannot rotate relative to each other (through the flat position 21.1 provided on the outer push rod, a platform surface corresponding to the flat position 21.1 is provided in the axial channel to limit the rotation of the outer push rod, and the outer push rod can move axially in the main shaft), at this time, the main board, the caster main frame and the main shaft cannot rotate relative to each other.

[0030] The above-mentioned outer push rod is provided with a second polygonal shaft section 21.7, and the second polygonal shaft section is sleeved with a directional plate 32 which is subject to axial limiting movement. The main board is provided with a directional functional groove 3.3.1, and the directional plate 32 is provided with a second limiting groove 32.1 which can be embedded in the directional functional groove 3.3.1 when the push rod is raised or lowered. When the outer push rod is subjected to the lifting action to make the directional plate 32 embedded in the directional functional groove 3.3.1, the relative rotation of the main board, the caster main frame and the outer push rod is limited. Since the main shaft and the outer push rod themselves cannot rotate relative to each other (through the flat position 21.1 provided on the outer push rod, a platform surface corresponding to the flat position 21.1 is provided in the axial channel to limit the rotation of the outer push rod, and the outer push rod can move axially in the main shaft), at this time, the main board, the caster main frame and the main shaft cannot rotate relative to each other.

[0031] The above-mentioned outer push rod is sleeved with a rod sleeve 22 for axial limited movement between the directional piece 32 and the gear 33, and the rod sleeve 22 is slidably connected to the main board. A knob 23 is installed on the caster main frame, and the inner end of the knob 23 is connected to the bracket 26. The bracket 26 is provided with a sloped column protrusion 26.1 embedded with the rod sleeve 22. A guide block 25 is installed on the main board, and an arc guide groove 25.1 is provided in the guide block 25. The sloped column protrusion 26.1 of the knob 23 passes through the arc guide groove 25.1 and is connected to the rod sleeve 22. When the knob 23 is rotated, the rod sleeve 22 is driven to rise and fall through the sloped column protrusion 26.1, and the outer push rod is driven to rise and fall through the rod sleeve 22, that is, the knob 23 is rotated to different circumferential positions, so that the bracket and the outer push rod are lifted and lowered to different height positions, so that the caster is in different working positions.

[0032] An internal thread 21.6 is provided at the upper end of the outer push rod, and a nut 20 is screwed on the internal thread 21.6. The inner push rod is passed through the nut 20, and the gasket abuts against the lower end of the nut 20, and another gasket abuts against the bottom of the groove of the stepped channel. A column head screw 15 is screwed on the lower end of the inner push rod, and a sleeve is abutted between the column head screw 15 and the gasket.

[0033] Working method of the electric gear-changing caster of the present invention: (1) Full braking: The output end of the motor rotates, causing the push rod to rise and retract to the shortest distance. The push rod is at the uppermost initial position. At this time, the gear 33 is meshed with the tooth plate 9, so that the outer push rod 21 is stopped relative to the caster main frame, and the main shaft 3.1 (fixed to the vehicle body) is stopped, so that the caster cannot rotate around the main shaft; the wedge block 13 is also at the uppermost initial position, and the brake pad 10 is pushed to the outermost side under the elastic force of the torsion spring 27, so that the brake pad 10 is inserted into the wheel tooth groove 36.1, so that the wheel 36 is stopped; (2) Fully free state: the output end of the motor rotates, causing the push rod to extend to the middle preset position, that is, the inner push rod 5 moves downward, and the outer push rod 31 moves downward under the elastic force of the compression spring 7. At this time, the gear 33 is disengaged from the tooth plate 9, and the rotational freedom of the outer push rod 31 is restored, and the main shaft 3.1 is linked to restore the rotational freedom with the caster main frame and the main board, that is, the caster can rotate relative to the main shaft; the wedge block 13 is in the middle preset position at this time, and the brake pad 10 is pushed out of the wheel plate tooth groove 36.1 under the action of the wedge surface 13.1 of the wedge block, and the rotation of the wheel plate 36 is restored; (3) Orientation state: the output end of the motor rotates, causing the push rod to extend to the limit distance, that is, the inner push rod 5 continues to move downward, and the outer push rod 31 continues to move downward under the elastic force of the compression spring 7. At this time, the gear 33 is out of mesh with the tooth plate 9, and the directional plate 32 is pre-pressed on the upper end surface of the directional function groove 3.3.1 of the main board 3.3 under the action of the spring force. When the main shaft 3.1 and the outer push rod rotate freely relative to the main board at a certain angle, the directional plate 32 enters the directional function groove 3.3.1 of the main board. At this time, the spring force is released to press the wedge block 13 downward instantly. Under the force of the wedge surface 13.1, the brake pad 10 continues to move away from the wheel tooth groove 36.1. At this time, the outer push rod 31 stops rotating, and the main shaft 3.1 stops rotating, and the wheel 36 still rotates freely; (4) On the contrary, the motor drives the push rod to retract, and the above functions are realized in the order of (3), (2), and (1).

[0034] Of course, the motor can also drive the push rod to extend and retract to a preset distance to selectively realize the different functional states of the above-mentioned casters without strictly following the logical order.

[0035] The electric gear-changing caster can achieve gear changing of the caster by operating the motor, and when there are multiple casters, the control circuits of the motors of the multiple casters can extend out of the casters and be connected to a central controller, so that unified control of each caster can be achieved through the central controller.

[0036] The present invention can also realize that the caster is in different working positions through the knob, the guide rail block and the bracket: (1) When the brake is fully applied, turn the knob clockwise, and the push rod will be moved to the middle preset position, and the caster will be in a fully free state; (2) In the fully free state, turn the knob counterclockwise, that is, the push rod is moved to the uppermost initial position, and the caster state changes to full brake.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention.

Claims

1. An electric gear-changing caster, characterized in that: The invention comprises a caster main frame and a wheel piece rotatably connected to the caster main frame, wherein the inner peripheral wall of the wheel piece is provided with a wheel piece tooth groove (36.1), the caster main frame is provided with a brake piece (10) capable of being inserted into or away from the wheel piece tooth groove (36.1), the caster main frame is provided with a push rod driven to rise and fall by a motor controlled by a central controller and a wedge block (13) connected to the lower end of the push rod, the wedge surface on the wedge block (13) cooperates with the brake piece (10) to drive the brake piece (10) to slide so as to be inserted into or away from the wheel piece tooth groove (36.1); the caster main frame is provided with a tooth piece at the upper limit position, and a gear (33) capable of meshing with the tooth piece (9) is provided on the lower part of the push rod, and when the push rod is raised and lowered, the gear and the tooth piece are meshed or disengaged, thereby limiting the relative rotation of the caster main frame and the push rod.

2. The electric gear-changing caster according to claim 1, characterized in that: The upper part of the main plate of the caster main frame is rotatably connected to a main shaft via a bearing, the push rod comprises an inner push rod (5) and an outer push rod (21), an axial hole for fixing the motor and limiting the rotation of the outer push rod is provided in the main shaft body, the output shaft end of the motor is threadedly connected to the internal threaded hole at the first end of the inner push rod (5), a stepped channel for passing the inner push rod (5) is provided in the body of the outer push rod (21), gaskets (6) are sleeved in the stepped channel and at both ends of the inner push rod (5), and a compression spring (7) is provided between the two gaskets so that the outer push rod (21) and the inner push rod (5) are pressed against each other to form a whole.

3. The electric gear-changing caster according to claim 1 or 2, characterized in that: A brake function groove (3.3.3) for guiding the brake pad (10) to slide is obliquely provided on the main plate of the caster main frame. The middle part of the brake pad (10) has a square hole (10.1) that cooperates with the wedge surface on the wedge block (13) so that when the wedge block (13) is moved up and down, the brake pad (10) is driven to slide in the brake function groove (3.3.3), thereby causing the horn protrusion (10.2) on the brake pad (10) to be inserted into or away from the wheel tooth groove (36.1). The wedge block (13) is fixedly mounted on the lower end of the outer push rod (21).

4. The electric gear-changing caster according to claim 3, characterized in that: The tooth plate (9) has a tooth groove (9.1) meshing with the gear (33) in the middle part, and a first limiting groove (9.2) cooperating with the shaft locking groove (3.3.2) on the main board is provided on the side of the tooth plate (9), and a spring (8) for pressing the tooth plate (9) is provided in the shaft locking groove (3.3.2) for pressing the tooth plate (9). The gear (33) has a polygonal through hole in the middle part, and the outer push rod has a first polygonal shaft section matching the polygonal through hole. The gear (33) is sleeved on the first polygonal shaft section of the outer push rod and is limited in axial movement by a limiting member. When the outer push rod is lifted and lowered to mesh the gear (33) with the tooth groove (9.1) of the tooth plate (9), the relative rotation of the main board, the caster main frame and the outer push rod is limited.

5. The electric gear-changing caster according to claim 4, characterized in that: The outer push rod is provided with a second polygonal shaft section, the second polygonal shaft section is sleeved with an orientation piece (32) subject to axial limiting movement, the main board is provided with an orientation function groove (3.3.1), and the orientation piece (32) is provided with a second limiting groove (32.1) capable of being embedded in the orientation function groove (3.3.1) when the push rod is raised or lowered.

6. The electric gear-changing caster according to claim 1, characterized in that: The outer push rod is provided with a flat position (21.1), and a platform surface is provided in the axial hole, which corresponds to and cooperates with the flat position (21.1) to limit the rotation of the outer push rod.

7. The electric gear-changing caster according to claim 1, characterized in that: The main board is provided with a torsion spring (27) capable of pushing the brake pad (10) toward the wheel tooth groove (36.1); when the push rod is driven downward, the wedge surface on the wedge block (13) drives the brake pad (10) to overcome the thrust of the torsion spring and move away from the wheel tooth groove (36.1).

8. The electric gear-changing caster according to claim 5, characterized in that: A rod sleeve (22) for axially limiting movement is sleeved on the outer push rod between the directional plate (32) and the gear (33); a knob (23) is mounted on the caster main frame; the inner end of the knob (23) is connected to a bracket (26); the bracket (26) is provided with a sloped column protrusion (26.1) embedded in the rod sleeve (22); when the knob (23) is rotated, the outer push rod is driven to rise and fall through the rod sleeve (22).

9. The electric gear-changing caster according to claim 5, characterized in that: The upper end of the outer push rod is provided with an internal thread (21.6), a nut (20) is screwed on the internal thread (21.6), the inner push rod is passed through the nut (20), the gasket abuts against the lower end of the nut (20), another gasket abuts against the bottom of the groove of the stepped channel, the lower end of the inner push rod is screwed with a column head screw (15), and a sleeve is abutted between the column head screw (15) and the gasket.

10. A method for operating the electric gear-changing caster according to claims 5-9, characterized in that: (1) Full braking: The output end of the motor rotates, causing the push rod to rise and retract to the shortest distance, and the push rod is in the uppermost initial position. At this time, the gear (33) is meshed with the tooth plate (9), so that the outer push rod (21) is stopped relative to the caster main frame, and the main shaft (3.1) is stopped, so that the caster cannot rotate around the main shaft; the wedge block (13) is also in the uppermost initial position, and the brake pad (10) is pushed to the outermost side under the action of the elastic force of the torsion spring (27), so that the brake pad (10) is inserted into the wheel plate tooth groove (36.1), so that the wheel plate (36) is stopped; (2) Fully free state: the output end of the motor rotates, causing the push rod to extend to the middle preset position, that is, the inner push rod (5) moves downward, and the outer push rod (31) moves downward in linkage with the elastic force of the compression spring (7). At this time, the gear (33) and the tooth plate (9) are disengaged, the rotational freedom of the outer push rod (31) is restored, and the main shaft (3.1) is linked to restore the rotational freedom with the caster main frame and the main board, that is, the caster can rotate relative to the main shaft; the wedge block (13) is at the middle preset position at this time, and the brake pad (10) is pushed out of the wheel plate tooth groove (36.1) under the action of the wedge surface (13.1) of the wedge block, thereby restoring the rotation of the wheel plate (36); (3) Orientation state: when the output end of the motor rotates, the push rod is extended to the limit distance, that is, the inner push rod (5) continues to move downward, and the outer push rod (31) continues to move downward under the elastic force of the compression spring (7). At this time, the gear (33) and the tooth plate (9) are out of meshing state, and the directional plate (32) is pre-pressed on the upper end surface of the directional function groove (3.3.1) of the main board (3.3) under the action of the spring force. When the main shaft (3.1) and the outer push rod are freely rotated relative to the main board by a certain angle so that the directional plate (32) enters the directional function groove (3.3.1) of the main board, the spring force is released to press the wedge block (13) downward instantly. Under the force of the wedge surface (13.1), the brake pad (10) continues to move away from the wheel plate tooth groove (36.1). At this time, the outer push rod (31) stops rotating, and the main shaft (3.1) is also stopped rotating, and the wheel plate (36) still rotates freely; (4) On the contrary, the motor drives the push rod to retract, and the above functions are realized in the order of steps (3), (2), and (1).

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