Patent Description:
With the development of society, people's demand for production and living materials has greatly increased, and the number and frequency of commodity exchange and circulation have increased rapidly, which has promoted the development of an express logistics industry. As an important transportation device, a shuttle car reciprocates on shuttle shelves of a three-dimensional warehouse, and realize in and out of the warehouse for a container, thereby greatly improving the efficiency of picking. The shuttle is widely used in various industries such as food and medicine, baggage handling, postal express and industrial logistics.

The shuttle shelf is usually arranged in a multi-layer shelf structure, and at least one horizontal shuttle rail is provided on each layer of shelves. The shuttle runs on the horizontal shuttle rail. A hoist is placed next to the shuttle rail. When the shuttle needs to enter an upper or lower shuttle rail from the current shuttle rail, it is necessary to move first a platform of the hoist next to the current shuttle rail, and then the shuttle enters the platform of the hoist. After that, the hoist raises or lowers the platform, so that the platform reaches the shuttle rail of a destination floor, and finally the shuttle enters the shuttle rail of the destination floor.

When the demand for outbound and inbound orders is large, if all shuttles can only reciprocate along the horizontal shuttle rail, and the hoist is required for switching when between shuttle rails, the shuttle congestion will be inevitably caused.

It should be noted that the information disclosed in the Background section above is only for enhancing the understanding of the background of the present invention, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

patent No. <CIT> describes a mobile robot base configured for mounting four powered caster wheel modules. Each of these modules includes a translation motor, a steering motor and a wheel. Further relevant technical information may be found at least in publications including: International patent application No. <CIT>: International patent publication No. <CIT>; and Chinese patent application No. <CIT>.

A main objective of the present invention is to overcome at least one of the defects in the prior art and provides a transmission device for a transport cart, which includes: a crawling assembly, a rotary drive assembly, and a crawling drive assembly.

According to an embodiment of the present invention, four crawling assemblies are provided, and the transmission device further includes a telescopic drive assembly.

According to an embodiment of the present invention, the crawling assembly further includes:.

According to an embodiment of the present invention, the input shafts of two crawling assemblies located on the first sliding rail are arranged coaxially, and the input shafts of two crawling assemblies located on the second sliding rail are arranged coaxially;.

According to an embodiment of the present invention, the first motor is in belt transmission, chain transmission, or gear transmission with the two connection shafts, respectively.

According to an embodiment of the present invention, the rotary drive assembly includes a transmission shaft parallel to the connection shaft and rotatable about its own axis, and a second motor for driving the transmission shaft to rotate;
two ends of the transmission shaft are in transmission connection with the rotary cylinders of two crawling assemblies located on the first sliding rail, respectively, and every two rotary cylinders located on a same side are in transmission connection.

According to an embodiment of the present invention, the rotary cylinders are in belt transmission or chain transmission, the transmission shaft is in belt transmission, chain transmission, or gear transmission with the rotary cylinders, and a main shaft of the second motor is in belt transmission, chain transmission, or gear transmission with the transmission shaft.

According to an embodiment of the present invention, the connection shaft is splined with the input shaft, the input shaft is capable of sliding axially relative to the connection shaft, and one of the connection shaft and the input shaft is a spline shaft, while the other is a spline tube;.

According to an embodiment of the present invention, the linear actuator includes:.

According to an embodiment of the present invention, a main shaft of the third motor are in belt transmission, chain transmission, or gear transmission with the two screw rods, respectively.

According to an embodiment of the present invention, the transmission device further includes a first base and a second base, both of which are configured to be fixedly connected with a cart body of the transport cart;.

According to an embodiment of the present invention, two first bases and two second bases are provided, the two first bases are separated from each other, and the two second bases are separated from each other.

According to an embodiment of the present invention, the driving wheel is provided with a first rotating shaft, and the first rotating shaft is rotationally connected with the wheel frame;.

According to an embodiment of the present invention, the transmission mechanism further includes.

According to an embodiment of the present invention, a middle part of the second rotating shaft is rotationally connected with the wheel frame, the second bevel gear and the second cylindrical gear are arranged at two ends of the second rotating shaft, respectively, and the first bevel gear is located between the second bevel gear and the second cylindrical gear.

According to an embodiment of the present invention, the crawling assembly further includes a bearing, an outer ring of the bearing abuts against an inner wall of the rotary cylinder, and an inner ring of the bearing is sleeved on the input shaft.

According to an embodiment of the present invention, the central axis passes through a center of the driving wheel, two guide wheels are provided, and the two guide wheels are arranged on opposite sides of the driving wheel respectively, and have equal distances from the central axis.

According to an embodiment of the present invention, the telescopic drive assembly further includes.

According to an embodiment of the present invention, the driving wheel is a flat wheel, a synchronous wheel, a gear, or a sprocket.

The present invention also proposes a transport cart, which includes the transmission device as described above.

As may be seen from the above technical solutions, advantages and positive effects of the transport cart of the present invention can be as follows.

The transport cart equipped with the transmission device according to the present invention can run along a horizontal rail and a vertical rail, and can quickly complete the switching between the horizontal rail and the vertical rail. Compared to a transport cart according to the prior art, travel of the transport cart according to the present invention is more flexible, especially on a rail network interwoven by horizontal and vertical rails. When a forward direction is congested, the rail may be changed to avoid the congested rail, and the operation efficiency is higher.

By considering the following detailed description of preferred embodiments of the present invention in conjunction with accompanying drawings, various objectives, features, and advantages of the present invention will become more apparent. The accompanying drawings are merely exemplary illustrations of the present invention, and are not necessarily drawn to scale. In the accompanying drawings, same reference numerals always refer to the same or similar parts.

However, the embodiments may be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein. Instead, these embodiments are provided so that the present invention will be more complete, so as to convey the idea of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and the repeated description thereof will be omitted.

<FIG> and <FIG> show a three-dimensional shelf <NUM> according to an embodiment of the present invention. Referring to <FIG> and <FIG>, the three-dimensional shelf <NUM> includes a shelf body <NUM> and a guide rail assembly <NUM> arranged on a side of the shelf body <NUM>. In a warehouse, there may be multiple three-dimensional shelves <NUM>, which are arranged side by side, and the number of the three-dimensional shelves <NUM> may be four. As shown in <FIG>, every two adjacent three-dimensional shelves <NUM> form a group, and the two three-dimensional shelves <NUM> in the same group are separated from each other, so as to form an aisle with a uniform width between the two three-dimensional shelves <NUM>. The guide rail assembly <NUM> on the three-dimensional shelf <NUM> is arranged on a side of the three-dimensional shelf <NUM> close to the aisle, so that two guide rail assemblies <NUM> are arranged at two sides of the aisle, respectively. Crawling assemblies <NUM> on both sides of a transport cart <NUM> can cooperate with the two guide rail assemblies <NUM>, respectively, and move along the guide rail assemblies <NUM>, so as to realize traveling of the transport cart <NUM> in the aisle.

Referring to <FIG>, the guide rail assembly <NUM> includes a steering guide rail <NUM>, a first rail <NUM> and a second rail <NUM>. The steering guide rail <NUM>, the first rail <NUM>, and the second rail <NUM> are all mounted on the shelf body <NUM>. The first rail <NUM>, the second rail <NUM>, and the steering guide rail are all arranged in a same plane, which is preferably a vertical plane. The first rail <NUM> extends along a horizontal straight line, and the second rail <NUM> extends in a vertical direction. The first rail <NUM> and the second rail <NUM> intersect perpendicularly. The steering guide rail <NUM> is mounted at the intersection of the first rail <NUM> and the second rail <NUM>. Each of the first rail <NUM> and the second rail <NUM> is divided into multiple segments by the steering guide rail <NUM>.

Referring to <FIG>, the steering guide rail <NUM> includes a mounting base <NUM> and a rotatory part <NUM>. The mounting base <NUM> is mounted on a vertical column <NUM>. The rotatory part <NUM> is mounted on the mounting base <NUM> and is located on a side of the mounting base <NUM> away from the shelf body <NUM>. The rotatory part <NUM> is rotationally connected with the mounting base <NUM>, and the rotatory part <NUM> is capable of rotating relative to the mounting base <NUM>. The rotatory part <NUM> rotates around a central axis perpendicular to a bottom face of a guide-rail groove <NUM>. The central axis is a straight line passing through a center of the guide-rail groove <NUM> and perpendicular to the bottom face of the guide-rail groove <NUM>. The rotatory part <NUM> includes the guide-rail groove <NUM>, which is located on a side of the rotatory part <NUM> away from the shelf body <NUM>. The guide-rail groove <NUM> includes two straight grooves. Lengths of the two straight grooves are equal. The two straight grooves intersect perpendicularly, and the intersection is their midpoint, which is the center of each guide-rail groove <NUM>. The two straight grooves are both perpendicular to a rotation axis of the rotatory part <NUM>, and the rotation axis passes through the center of each guide-rail groove <NUM>. The guide-rail groove <NUM> may be a cross shape or an asterisk shape. Two ends of the straight groove extend to edges of opposite sides of the rotatory part <NUM>, respectively.

In an embodiment, a mounting hole <NUM> is provided on the mounting base <NUM>, and the mounting hole <NUM> is a round hole. The mounting hole <NUM> is provided in the middle part of the mounting base <NUM>, and the mounting hole <NUM> may be a through hole. The rotatory part <NUM> is provided with a rotating shaft <NUM>. The rotating shaft <NUM> is arranged on a side of the rotatory part <NUM> close to the mounting base <NUM>, and extends into the mounting hole <NUM>. A diameter of the rotating shaft <NUM> is smaller than that of the mounting hole <NUM>, and an axis of the rotating shaft <NUM> is coaxial with an axis of the mounting hole <NUM>.

The steering guide rail <NUM> also includes a slewing bearing <NUM>. The slewing bearing <NUM> includes an inner ring, an outer ring, and a roller arranged between the inner ring and the outer ring. The slewing bearing <NUM> is preferably a ball bearing. The inner ring of the slewing bearing <NUM> is sleeved on the rotating shaft <NUM>, and the inner ring preferably has an interference fit with the rotating shaft <NUM>. An outer circumferential wall of the outer ring of the slewing bearing <NUM> abuts against an inner circumferential wall of the mounting hole <NUM>, and there is an interference fit between the outer ring of the slewing bearing <NUM> and the mounting hole <NUM>.

In this way, the mounting base <NUM> and the rotatory part <NUM> may be rotationally connected together through the slewing bearing <NUM>, and the mounting base <NUM> and the rotatory part <NUM> are rotationally matched precisely.

The steering guide rail <NUM> also includes a thrust bearing <NUM>, which may be one of a thrust cylindrical roller bearing, a thrust tapered roller bearing, and a thrust ball bearing. The thrust bearing <NUM> is sandwiched between the mounting base <NUM> and the rotatory part <NUM>, and are arranged coaxially with the slewing bearing <NUM>.

In this way, the thrust bearing <NUM> can carry the largest portion of an axial load, and the slewing bearing <NUM> has a longer service life. In addition, the fit between the mounting base <NUM> and the rotatory part <NUM> is also tighter, and it is not easy to move relatively.

Referring to <FIG>, the first rail <NUM> is a straight rail, and is provided with a first groove <NUM>. The first groove <NUM> extends along the first rail <NUM>. That is, the first groove <NUM> extends in the horizontal direction. The second rail <NUM> is a straight rail, and is provided with a second groove <NUM>. The second groove <NUM> extends along the second rail <NUM>. That is, the second groove <NUM> extends in the horizontal direction. One end of the first groove <NUM> and one end of the second groove <NUM> extend to the rotatory part <NUM>. When the rotatory part <NUM> rotates, the rotatory part <NUM> can rotate to a position where the guide-rail groove <NUM> is connected with the first groove <NUM> and the second groove <NUM>. That is, a straight groove in the guide-rail groove <NUM> is connected with the first groove <NUM>, and the other straight groove is connected with the second groove <NUM>.

Bottom walls of the first groove <NUM>, the second groove <NUM> and two straight grooves of the guide-rail groove <NUM> may be mounted with transmission elements extending along an extending direction of the groove. The transmission element may be a synchronous belt, a rack or a chain.

There are multiple first rails <NUM> and second rails <NUM>. The first rails <NUM> and the storage brackets <NUM> are arranged in a one-to-one correspondence, and each first rail <NUM> is arranged on an edge of the storage bracket <NUM> corresponding to the first rail <NUM>. The multiple second rails <NUM> are arranged on multiple vertical columns <NUM>, respectively. The second rails <NUM> and the vertical columns <NUM> on the same side of the three-dimensional shelf <NUM> are arranged in a one-to-one correspondence, and each second rail <NUM> is arranged on the vertical column <NUM> corresponding to the second rail <NUM>. The multiple first rails <NUM> and the multiple second rails <NUM> are located in the same vertical plane, and the multiple first rails <NUM> and the multiple second rails <NUM> are interwoven into a rail network. There are also multiple steering guide rails, and the multiple steering guide rails are arranged at each intersection in the rail network, respectively.

<FIG> shows a transport cart <NUM> in an embodiment of the present invention. As shown in <FIG>, such transport cart <NUM> is preferably an automated guided vehicle.

The transport cart <NUM> includes a cart body <NUM> and a transmission device <NUM>. The transmission device <NUM> is mounted on the cart body <NUM>. The transmission device <NUM> is used to drive the cart body <NUM> to move along the guide rail assembly <NUM>. The cart body <NUM> may be provided in a substantially rectangular structure. The cart body <NUM> includes a front end <NUM> and a rear end <NUM> opposite to the front end <NUM>. The front end <NUM> may be the front end <NUM> of the cart body <NUM>, and the rear end <NUM> may be the rear end <NUM> of the cart body <NUM>.

The transmission device <NUM> includes four crawling assemblies <NUM>, a crawling drive assembly and a rotary drive assembly. The four crawling assemblies <NUM> are arranged on two opposite sides of the cart body <NUM>, respectively. Both the crawling drive assembly and the rotary drive assembly are arranged inside the cart body <NUM>. The transport cart <NUM> is located between two guide rail assemblies <NUM> when crawling along the rail, and the crawling assemblies <NUM> on both sides of the transport cart <NUM> abut against the guide rail assemblies <NUM> on both sides, respectively, so as to support the transport cart <NUM>.

In embodiments, two crawling assemblies <NUM> are arranged on opposite sides of the front end <NUM> of the cart body <NUM>, respectively, and the other two crawling assemblies <NUM> are arranged on opposite sides of the rear end <NUM> of the cart body <NUM>, respectively. The four crawling assemblies <NUM> support the cart body <NUM> at positions close to four corners of the cart body <NUM>, which is more stable and reliable.

Referring to <FIG>, each crawling assembly <NUM> includes a wheel frame <NUM>, a driving wheel <NUM> and a guide wheel <NUM>. The wheel frame <NUM> is configured in a substantially straight shape, and the wheel frame <NUM> extends from a side of the cart body <NUM> in a direction away from the cart body <NUM>. The wheel frame <NUM> includes a first end and a second end opposite to the first end, and the wheel frame <NUM> extends from the first end to the second end. The first end of the wheel frame <NUM> faces the cart body <NUM>, and the second end of the wheel frame <NUM> faces away from the cart body <NUM>. The second end of the wheel frame <NUM> can protrude outward from the side of the cart body <NUM>. The driving wheel <NUM> and the guide wheel <NUM> are both mounted on the second end of the wheel frame <NUM>. The driving wheel <NUM> may be in a form of a flat wheel, a pulley, a gear, a sprocket, and the like. An axis of the driving wheel <NUM> is perpendicular to an extending direction of the wheel frame <NUM>. The guide wheel <NUM> is arranged on a side of the driving wheel <NUM>, and an axis of the guide wheel <NUM> is parallel to the extending direction of the wheel frame <NUM>. The axis of the guide wheel <NUM> lies in a plane that passes through a center of the driving wheel <NUM> and is perpendicular to the axis of the driving wheel <NUM>, so that an outer peripheral surface of the driving wheel <NUM> faces the guide wheel <NUM>, and the guide wheel <NUM> is always in a travelling direction of the driving wheel <NUM>.

In embodiments, the wheel frame <NUM> is capable of rotating around a central axis of the extending direction of the wheel frame <NUM>, and the central axis is perpendicular to an axis of the driving wheel <NUM>. The central axis preferably passes through a center of the driving wheel <NUM>. Since the wheel frame <NUM> is capable of rotating around its central axis, the traveling direction of the driving wheel <NUM> may be changed by rotating the wheel frame <NUM>. The rotary drive assembly is used to drive the wheel frame <NUM> to rotate, and the crawling drive assembly is used to drive the driving wheel <NUM> to roll.

Widths of the first groove <NUM>, the second groove <NUM> and the guide-rail groove <NUM> are all greater than a diameter of the guide wheel <NUM>, and the guide wheel <NUM> can extend into the first groove <NUM>, the second groove <NUM> and the guide-rail groove <NUM>. When the transport cart <NUM> moves horizontally along the first groove <NUM>, since the diameter of the guide wheel <NUM> is larger than the width of the driving wheel <NUM>, the guide wheel <NUM> is hung on a side wall of the first groove <NUM> and carries the cart body <NUM>. When the driving wheel <NUM> moves vertically along the second groove <NUM>, the driving wheel <NUM> carries the cart body <NUM>, and the guide wheel <NUM> interacts with a side wall of the second groove <NUM> to guide the driving wheel <NUM> to move along the first groove <NUM>.

When the transport cart <NUM> needs to travel from the first rail <NUM> to the second rail <NUM>, the rotatory part <NUM> is rotated in advance to a position where the guide-rail groove <NUM> is connected with the first groove <NUM> and the second groove <NUM>, and the crawling drive assembly drives the driving wheel <NUM>, so that the crawling assembly <NUM> enters the guide-rail groove <NUM> from the first groove <NUM>. At this time, states of the crawling assembly <NUM> and the rotatory part <NUM> are as shown in <FIG>. Then the rotary drive assembly drives the wheel frame <NUM> to rotate by <NUM>°, and the rotatory part <NUM> is driven to rotate when the wheel frame <NUM> rotates. When the rotatory part <NUM> rotates by <NUM>°, the guide-rail groove <NUM> is connected with the first groove <NUM> and the second groove <NUM> again, respectively. At this time, the states of the crawling assembly <NUM> and the rotatory part <NUM> are as shown in <FIG>. The transport cart <NUM> may continue to travel toward the second groove <NUM>, until it enters the second groove <NUM>, thereby rendering the transport cart <NUM> running from the first rail <NUM> to the second rail <NUM>. Similarly, the transport cart <NUM> may also travel from the second rail <NUM> to the first rail <NUM>. In this case, the transport cart <NUM> can run both in the horizontal direction and the vertical direction along the guide rail assembly <NUM>, and the transport cart <NUM> has a more flexible running route.

The rail network is a rectangular grid, and the smallest cell is a rectangular grid. The transport cart <NUM> can travel along the rail network, and the transport cart <NUM> can turn at each steering guide rail <NUM> and switch between rails arbitrarily, so that the running routes of the transport cart <NUM> are more diverse. When the rail in the traveling direction of the transport cart <NUM> is congested, the transport cart <NUM> can bypass the congestion by switching between rails without waiting for the rail to be cleared, which greatly improves the handling efficiency of the transport cart <NUM>.

The driving wheel may be a flat wheel, a synchronous wheel, a gear or a sprocket. When the driving wheel <NUM> is the synchronous wheel, the gear or the sprocket, it can engage with corresponding transmission elements mounted in the first groove <NUM>, the second groove <NUM>, and the two straight grooves of the guide-rail groove <NUM>, so as to prevent slipping.

Further, two guide wheels <NUM> are provided. The two guide wheels <NUM> are both arranged on the end of the second end of the wheel frame <NUM>. The two guide wheels <NUM> are located on opposite sides of the driving wheel <NUM>, respectively. The wheel frame <NUM> rotates around its central axis, wherein the central axis passes through the center of the driving wheel <NUM>, and distances from the central axis to the axes of the two guide wheels <NUM> are equal.

The driving wheel <NUM> is arranged between the two guide wheels <NUM>, which can completely avoid friction between the driving wheel <NUM> and a side wall of the groove. When the transport cart <NUM> moves horizontally in the first groove <NUM>, the two guide wheels <NUM> are hung on the side wall of the first groove <NUM> and carry the cart body <NUM>, and distances from the two guide wheels <NUM> to the center axis of the wheel frame <NUM> are equal. Deflection moments applied to the wheel frame <NUM> by the two guide wheels <NUM> cancel each other, and the force on the wheel frame <NUM> is more reasonable.

Further, referring to <FIG>, each crawling assembly <NUM> includes a transmission mechanism <NUM>, an input shaft <NUM>, a rotary cylinder <NUM> and a mounting seat <NUM>.

The mounting seat <NUM> is arranged on the cart body <NUM>. In embodiments, the mounting seat <NUM> includes a bottom plate <NUM> and two side plates <NUM>. The two side plates <NUM> are located on a same side of the bottom plate, and both are perpendicular to the bottom plate <NUM>. The two side plates <NUM> are parallel to each other. The two side plates <NUM> are both provided with mounting through holes <NUM>, which are circular through holes. The two mounting through holes <NUM> are aligned with each other. That is, the two mounting through holes <NUM> are coaxially arranged.

The rotary cylinder <NUM> includes a cylinder body <NUM>. The cylinder body <NUM> has a cylindrical shape, and a diameter of the cylinder body <NUM> is smaller than that of the mounting through hole <NUM>. The cylinder body <NUM> is arranged in the mounting through hole <NUM>. The cylinder body <NUM> is rotationally connected with the mounting seat <NUM>. In embodiments, the crawling assembly <NUM> further includes two slewing bearings <NUM>, and inner rings of the two slewing bearings <NUM> are sleeved on both ends of the cylinder body <NUM>, respectively. The slewing bearing <NUM> may be a radial bearing or a deep groove ball bearing. Outer rings of the two slewing bearings <NUM> are mounted in the mounting through hole <NUM> and form a fixed connection with the mounting through hole <NUM>. There may be an interference fit between the outer ring of the slewing bearing <NUM> and the mounting through hole <NUM>. In this way, the rotary cylinder <NUM> is rotationally connected with the mounting seat <NUM> through the slewing bearing <NUM>. It should be understood that the slewing bearing <NUM> may not be provided, and a clearance fit between the mounting through hole <NUM> and the rotary cylinder <NUM> may also realize the rotational connection between the rotary cylinder <NUM> and the mounting seat <NUM>.

The first end of the wheel frame <NUM> is fixedly connected with an end of the rotary cylinder <NUM>. An end of the first end of the wheel frame <NUM> and an end of the rotary cylinder <NUM> may be welded, screwed or bolted to each other. In this way, the wheel frame <NUM> is mounted onto the rotary cylinder <NUM>, and the rotary cylinder <NUM> can drive the wheel frame <NUM> to rotate around an axis of the rotary cylinder <NUM>. In this case, the center axis of the wheel frame <NUM> coincides with the axis of the rotary cylinder <NUM>.

The driving wheel <NUM> includes a wheel body <NUM> and a first rotating shaft <NUM>. The wheel body <NUM> is circular with a through hole provided in the middle. The first rotating shaft <NUM> is cylindrical, and is coaxially arranged with the wheel body <NUM>. The driving wheel <NUM> is sleeved on the first rotating shaft <NUM> and forms a fixed connection with the first rotating shaft <NUM>. There may be an interference fit between the driving wheel <NUM> and the first rotating shaft <NUM>. The first rotating shaft <NUM> is rotationally connected with the second end of the wheel frame <NUM>. The extending direction of the first rotating shaft <NUM> and the extending direction of the wheel frame <NUM> are perpendicular to each other. In embodiments of the present invention, two bearings <NUM> are provided in the second end of the wheel frame <NUM>, and inner rings of the two bearings <NUM> are sleeved on both ends of the first rotating shaft <NUM>, respectively. Two through holes <NUM> are provided on inner walls at both sides of the wheel frame <NUM>, respectively, and outer rings of the two bearings <NUM> are arranged in the two through holes <NUM>, respectively, thus forming a fixed connection with the mounting through holes <NUM>. Through such arrangement, the driving wheel <NUM> and the wheel frame <NUM> form a rotational connection therebetween. A portion of the wheel body <NUM> is accommodated in the wheel frame <NUM>, and a portion protrudes out from the second end of the wheel frame <NUM>.

The input shaft <NUM> has a straight bar shape, and is coaxially arranged with the rotary cylinder <NUM>. A diameter of the input shaft <NUM> is smaller than that of an inner hole of the input shaft <NUM>. The input shaft <NUM> penetrates through the rotary cylinder <NUM> and extends into the wheel frame <NUM> from the first end of the wheel frame <NUM>. The input shaft <NUM> is capable of rotating relative to the wheel frame <NUM>, and its rotation mode is to rotate around its own axis. In embodiments, the crawling assembly <NUM> further includes a bearing <NUM> arranged between the input shaft <NUM> and the rotary cylinder <NUM>. The bearing <NUM> is arranged in the rotary cylinder <NUM>, an inner ring of the bearing <NUM> is sleeved on the input shaft <NUM>, and an outer ring of the bearing <NUM> abuts against an inner wall of the rotary cylinder <NUM>. Two bearings <NUM> may be provided, which are arranged at both ends of the rotary cylinder <NUM>, respectively. An axis of the input shaft <NUM> passes through the center of the driving wheel <NUM> and is perpendicular to the axis of the driving wheel <NUM>.

The transmission mechanism <NUM> is arranged in the wheel frame <NUM>. The transmission mechanism <NUM> is in transmission connection with the input shaft <NUM> and the driving wheel <NUM>, respectively, and is used for transmitting a torque delivered by the input shaft <NUM> to the driving wheel <NUM>, so as to drive the driving wheel <NUM> to roll. The transmission mechanism <NUM> includes a first bevel gear <NUM>, a second rotating shaft <NUM> and a second bevel gear <NUM>. The second rotating shaft <NUM> is parallel to the first rotating shaft <NUM>, and is arranged at the first end of the wheel frame <NUM>. The second bevel gear <NUM> is sleeved on the second rotating shaft <NUM> and forms a fixed connection with the second rotating shaft <NUM>. The second rotating shaft <NUM> is inserted into a shaft hole in the wheel frame <NUM> and is in clearance fit with the shaft hole. The second rotating shaft <NUM> can rotate around its own axis in the shaft hole. The first bevel gear <NUM> is sleeved on an end of the input shaft <NUM> that extends into the wheel frame <NUM> and engages with the second bevel gear <NUM>. An intersection angle between the two shafts is equal to <NUM>°. The cooperation between the first bevel gear <NUM> and the second bevel gear <NUM> can change a direction of the input torque.

The second rotating shaft <NUM> is in transmission connection with the first rotating shaft <NUM>. The second rotating shaft <NUM> and the first rotating shaft <NUM> may be in belt transmission, chain transmission or gear transmission. In embodiments, the gear transmission is adopted between the second rotating shaft <NUM> and the first rotating shaft <NUM>, and the transmission mechanism <NUM> further includes a first cylindrical gear <NUM>, a second cylindrical gear <NUM>, a third cylindrical gear <NUM>, and a spindle <NUM>. The first cylindrical gear <NUM> is sleeved on the first rotating shaft <NUM> and is fixedly connected with the first rotating shaft <NUM>. The second cylindrical gear <NUM> is sleeved on the second rotating shaft <NUM> and is fixedly connected with the second rotating shaft <NUM>. The spindle <NUM> is arranged between the first rotating shaft <NUM> and the second rotating shaft <NUM> and is parallel to the first rotating shaft <NUM>. The third cylindrical gear <NUM> is sleeved on the spindle <NUM>, and is capable of rotating around an axis of the spindle <NUM>. The spindle <NUM> is fixed on the inner wall of the wheel frame <NUM>. The third cylindrical gear <NUM> is in clearance fit with the spindle <NUM>, and is capable of rotating around the spindle <NUM>. The first cylindrical gear <NUM> engages with the third cylindrical gear <NUM>, and the third cylindrical gear <NUM> engages with the second cylindrical gear <NUM>.

In embodiments, after the input shaft <NUM> is driven by an external force to rotate around its own axis, the input shaft <NUM> drives the first bevel gear <NUM> to rotate, the first bevel gear <NUM> drives the second rotating shaft <NUM> to rotate, the second rotating shaft <NUM> drives the second cylinder gear <NUM> rotates, the second cylindrical gear <NUM> drives the third cylindrical gear <NUM> to rotate, the third cylindrical gear <NUM> drives the first cylindrical gear <NUM> to rotate, and the first cylindrical gear <NUM> drives the driving wheel <NUM> to roll, whereby the torque input from the input shaft <NUM> can drive the driving wheels <NUM> to roll.

The crawling drive assembly is used to drive the input shaft <NUM> to rotate, thus driving the driving wheel <NUM> to roll. The rotary drive assembly is used to drive the rotary cylinder <NUM> to rotate, thus driving the driving wheel <NUM> to turn.

The driving wheel <NUM> is mounted on the wheel frame <NUM>, and the wheel frame <NUM> is mounted on the rotary cylinder <NUM>. The rotary drive assembly drives the rotary cylinder <NUM> to change the traveling direction of the driving wheel <NUM>. The axis of the input shaft <NUM> passes through the center of the driving wheel <NUM> and is perpendicular to the axis of the driving wheel <NUM>, and the input shaft <NUM> is coaxially arranged with the rotary cylinder <NUM>. Thus, the turning of the driving wheel <NUM> driven by the rotary cylinder <NUM> and the rolling of the driving wheel <NUM> driven by the input shaft <NUM> do not interfere with each other. In addition, the input shaft <NUM> can extend into the cart body <NUM>, and is driven to rotate by the crawling drive assembly arranged inside the cart body <NUM>, so as to drive the driving wheel <NUM> to roll, without the need for arranging the crawling drive assembly on the wheel frame <NUM>, which makes the overall structure of the transport cart <NUM> more compact.

Further, the spindle <NUM> is arranged between the first rotating shaft <NUM> and the second rotating shaft <NUM>, and axes of the first rotating shaft <NUM>, the second rotating shaft <NUM>, and the spindle <NUM> are coplanar. In this way, the first cylindrical gear <NUM>, the second cylindrical gear <NUM>, and the third cylindrical gear <NUM> are sequentially arranged along a straight line, so that a volume of the wheel frame <NUM> is smaller.

Further, the middle part of the second rotating shaft <NUM> is rotationally connected with the wheel frame <NUM>. The second bevel gear <NUM> and the second cylindrical gear <NUM> are arranged at both ends of the second rotating shaft <NUM>, respectively, and the first bevel gear <NUM> is located between the second bevel gear <NUM> and the second cylindrical gear <NUM>. Through such arrangement, the transmission mechanism <NUM> may be made more compact and smaller in size, and the force on the second rotating shaft <NUM> is also more reasonable.

Further, the rotary cylinder <NUM> further includes a flange <NUM>. The flange <NUM> is arranged at an end of the cylinder body <NUM> connected with the wheel frame <NUM>, and extends radially outward from an end of the cylinder body <NUM>. The flange <NUM> has a circular ring shape, and an outer diameter of the flange <NUM> is larger than an inner diameter of the mounting through hole <NUM>. The crawling assembly <NUM> also includes a thrust bearing <NUM> coaxially arranged with the cylinder body <NUM>. The thrust bearing <NUM> is sandwiched between the flange <NUM> and an outer wall of the mounting seat <NUM>. In this way, the thrust bearing <NUM> can carry the axial load transmitted from the wheel frame <NUM> and prevent the slewing bearing <NUM> from carrying excessive axial load. Furthermore, a side of an outer edge of the flange <NUM> close to the mounting seat <NUM> is recessed inward to form an annular gap, and the thrust bearing <NUM> is mounted in the annular gap. In this way, the thrust bearing <NUM> is restricted to prevent the thrust bearing <NUM> from moving at will.

Further, referring to <FIG>, the transmission device <NUM> further includes a telescopic drive assembly. The telescopic drive assembly includes a first sliding rail <NUM>, a second sliding rail <NUM>, two first sliding blocks <NUM>, two second sliding blocks <NUM> and a linear actuator.

The two first sliding blocks <NUM> are arranged on the first sliding rail <NUM>, and the two second sliding blocks <NUM> are arranged on the second sliding rail <NUM>. The first sliding block <NUM> can slide along the first sliding rail <NUM>, and the second sliding block <NUM> can slide along the second sliding rail <NUM>. The first sliding rail <NUM> is arranged at the front end <NUM> of the cart body <NUM>, and the second sliding rail <NUM> is arranged at the rear end <NUM> of the cart body <NUM>. The first sliding rail <NUM> and the second sliding rail <NUM> are both parallel to the input shaft <NUM>. That is, they are parallel to the center axis of the wheel frame <NUM>. The first sliding rail <NUM> and the second sliding rail <NUM> are preferably equal in length and aligned with each other. Lines connecting four end points of the first sliding rail <NUM> and the second sliding rail <NUM> can form a rectangle. The first sliding rail <NUM> and the second sliding rail <NUM> are both fixedly connected with the cart body <NUM>, which may be screw connection, bolt connection or welding.

The mounting seats <NUM> of the two crawling assemblies <NUM> are arranged on the two first sliding blocks <NUM>, respectively, and the mounting seats <NUM> of the other two crawling assemblies <NUM> are arranged on the two second sliding blocks <NUM>, respectively. The bottom plates <NUM> of the mounting seats <NUM> are fixedly connected with respective sliding blocks, and the mounting seat <NUM> and each sliding block may be connected by screws, welding, riveting or bolting.

The first ends of the wheel frames <NUM> of the two crawling assemblies <NUM> located on the two first sliding blocks <NUM> respectively are arranged opposite to each other, and the first ends of the wheel frames <NUM> of the two crawling assemblies <NUM> located on the two second sliding blocks <NUM> respectively are arranged opposite to each other. Through such arrangement, the driving wheels <NUM> and the guide wheels <NUM> on the four crawling assemblies <NUM> face the two sides of the transmission device <NUM>, respectively. In addition, the linear actuator can drive respective crawling assemblies <NUM> to slide along their respective sliding rails. When the linear actuator moves the crawling assemblies <NUM> to the middle of each sliding rail at the same time, the crawling assemblies <NUM> may be retracted into the cart body. At this time, the cooperation between the crawling assembly <NUM> and the guide rail assembly <NUM> may be released. In contrast, when the four crawling assemblies <NUM> are moved to respective ends of the first sliding rail <NUM> and the second sliding rail <NUM>, respectively, the crawling assemblies <NUM> can extend out from the cart body, thereby cooperating again with the crawling assembly <NUM>.

Referring to <FIG>, the transport cart <NUM> further includes a ground running mechanism <NUM> arranged at the bottom of the cart body <NUM> and having an ability of running along the ground. The ground running mechanism <NUM> includes multiple universal wheels <NUM> and two driving wheels <NUM>. The multiple universal wheels <NUM> are located at two ends of the bottom of the cart body <NUM>, respectively. There may be four universal wheels <NUM>, which are arranged at four corners of the bottom of the cart body <NUM>, respectively, and the universal wheels <NUM> support the cart body <NUM>. The two driving wheels <NUM> are located on both sides of the middle part of the bottom of the cart body <NUM>, respectively. Each driving wheel <NUM> rolls autonomously to drive the cart body <NUM> to travel along the ground. The differential driving between the two driving wheels <NUM> can make the transport cart turn.

Referring to <FIG>, the second rail <NUM> extends to a bottom end of the shelf body <NUM>. The transport cart <NUM> can carry goods from other places along the ground to the vicinity of the three-dimensional shelf <NUM>, and then travels into the aisle between two three-dimensional shelves <NUM>. Then the crawling assemblies <NUM> extend from both sides of the cart body <NUM> and into second rails <NUM> located on both sides of the transport cart <NUM>. In this way, the transport cart <NUM> can crawl on the three-dimensional shelf <NUM> through the crawling assembly <NUM>. The goods on the transport cart <NUM> may be transported to the storage bracket <NUM> of the shelf body <NUM> through a forklift assembly on the transport cart <NUM>. Correspondingly, the forklift assembly of the transport cart <NUM> may also take out goods from the three-dimensional shelf <NUM>, and then the transport cart <NUM> moves to the bottom of the three-dimensional shelf <NUM> through the crawling assembly <NUM>, until the ground running mechanism <NUM> of the transport cart <NUM> touches the ground, and then the crawling assembly <NUM> is retracted into the cart body <NUM>. Thus, the crawling assembly <NUM> is separated from the second rail <NUM> and then the goods are transported along the ground to a designated location. In this way, it is realized that the transport cart <NUM> can not only travel along the ground, but also travel on the three-dimensional shelf <NUM>, thereby achieving wider adaptability and stronger functions of the transport cart <NUM>.

Further, referring to <FIG> and <FIG>, the transmission device <NUM> further includes two first bases <NUM> and two second bases <NUM>. The first bases <NUM> are both fixedly connected with the front end <NUM> of the cart body <NUM> and are close to the first sliding rail <NUM>, and the second bases <NUM> are both fixedly connected with the rear end <NUM> of the cart body <NUM> and are close to the second sliding rail <NUM>. The two first bases <NUM> are separated from each other, and the two second bases <NUM> are separated from each other.

The first base <NUM> includes a first horizontal plate <NUM> and a first vertical plate <NUM> fixedly connected with the first horizontal plate <NUM>. The first horizontal plate <NUM> is connected with the bottom of the cart body <NUM>, and may be a screw connection or a bolt connection. The first vertical plate <NUM> is perpendicular to the first horizontal plate <NUM>, and is provided with a first through hole <NUM>, a second through hole <NUM>, and a third through hole. Two first vertical plates <NUM> are arranged in parallel, and both are perpendicular to the input shaft <NUM>. A first bearing, a second bearing and a third bearing are sequentially arranged in the first through hole <NUM>, the second through hole <NUM> and the third through hole, respectively. Two first bearings are arranged coaxially, two second bearings are arranged coaxially, and two third bearings are arranged coaxially.

The second base <NUM> includes a second horizontal plate <NUM> and a second vertical plate <NUM> fixedly connected with the second horizontal plate <NUM>. The second horizontal plate <NUM> is connected with the bottom of the cart body <NUM>, and may be a screw connection or a bolt connection. The second vertical plate <NUM> is perpendicular to the second horizontal plate <NUM>, and is provided with a fourth through hole <NUM> and a fifth through hole <NUM>. Two second vertical plates <NUM> are arranged in parallel, and both are perpendicular to the input shaft <NUM>. A fourth bearing and a fifth bearing are sequentially arranged in the fourth through hole <NUM> and the fifth through hole <NUM>, respectively. Two fourth bearings are arranged coaxially, and two fifth bearings are arranged coaxially.

Axes of the first bearing, the second bearing, the third bearing, the fourth bearing, and the fifth bearing are all parallel to the axis of the input shaft <NUM>. The axes of all the rotary cylinders <NUM> and the axes of all the input shafts <NUM> are parallel to each other.

The crawling drive assembly includes two connection shafts <NUM> and a first motor <NUM>. The two connection shafts <NUM> are both straight bar shapes. One of the connection shafts <NUM> penetrates through the first through holes <NUM> of the two first bases <NUM>, and the two first bearings are sleeved on both ends of the connection shaft <NUM>. The other connection shaft <NUM> penetrates through the fourth through holes <NUM> of the two second bases <NUM>, and the two fourth bearings are sleeved on both ends of the connection shaft <NUM>, respectively. In this way, the two connection shafts <NUM> form a rotational connection with the first base <NUM> and the second base <NUM>, respectively, and the connection shaft <NUM> is parallel to the input shaft <NUM>.

The input shafts <NUM> of the two crawling assemblies <NUM> located at the front end <NUM> are coaxially arranged, and ends of the two ends of the connection shaft <NUM> located at the front end <NUM> of the cart body are connected with the ends of the two input shafts <NUM>, respectively. The input shafts <NUM> of the two crawling assemblies <NUM> located at the rear end <NUM> are coaxially arranged, and ends of the two ends of the connection shaft <NUM> located at the rear end <NUM> of the cart body <NUM> are connected with the ends of the two input shafts <NUM>, respectively. In this case, rotation of one connection shaft <NUM> can drive the two input shafts <NUM> to rotate at the same time, thereby driving the two driving wheels <NUM> to roll. The connection shaft <NUM> may be splined with the input shaft <NUM>.

The first motor <NUM> is mounted on the cart body <NUM>. A main shaft of the first motor <NUM> is arranged parallel to the connection shaft <NUM>. The main shaft of the first motor <NUM> and the two connection shafts <NUM> may be in belt transmission, chain transmission or gear transmission, so that the first motor <NUM> can synchronously drive the four driving wheels <NUM> to roll.

In embodiments, the main shaft of the first motor <NUM> and the two connection shafts <NUM> are in belt transmission. Specifically, the crawling drive assembly further includes two first slave pulleys <NUM>, a first driving pulley <NUM> and a first transmission belt <NUM>. The first slave pulley <NUM> and the first driving pulley <NUM> are preferably synchronous pulleys, and the first transmission belt <NUM> is preferably a synchronous belt. The two first slave pulleys <NUM> are sleeved on the two connection shafts <NUM>, respectively. The first slave pulleys <NUM> are fixedly connected with the connection shaft <NUM>. The first driving pulley <NUM> is sleeved on the main shaft of the driving motor and is located between the two first transmission belts <NUM>. The first transmission belt <NUM> is ringlike. The first transmission belt <NUM> is hooped on the two first slave pulleys <NUM> and abuts against the first driving pulley <NUM> tightly, so that the belt transmission is formed between the first motor <NUM> and the connection shaft <NUM>.

Furthermore, the crawling drive assembly further includes two first tensioning wheels <NUM>. The two first tensioning wheels <NUM> are arranged on both sides of the first driving pulley <NUM> and tighten an outer side of the first transmission belt <NUM>, so as to increase a contact area between the first driving pulley <NUM> and the first transmission belt <NUM>, thus avoiding slip between the first driving pulley <NUM> and the first transmission belt <NUM>.

Further, referring to <FIG>, the rotary drive assembly includes a second motor <NUM> and a transmission shaft <NUM>. The transmission shaft <NUM> is arranged at the front end <NUM> of the cart body <NUM>, and an axis of the transmission shaft <NUM> is parallel to the axis of the rotary cylinder <NUM>. The transmission shaft <NUM> includes a first sub-shaft <NUM> and two second sub-shafts <NUM>. The two second sub-shafts <NUM> are arranged at both ends of the first sub-shaft <NUM>, respectively, and are arranged coaxially with the first sub-shaft <NUM>. One end of each of the two second sub-shafts <NUM> is connected with a respective end of the first sub-shaft <NUM>.

The first sub-shaft <NUM> penetrates through the second through holes <NUM> of the two first bases <NUM>, and the two second bearings are sleeved on both ends of the first sub-shaft <NUM>, respectively. In this way, the transmission shaft <NUM> is rotationally connected with the cart body <NUM>, and the transmission shaft <NUM> can rotate around its own axis.

The second motor <NUM> is fixed at the bottom of the cart body <NUM>, and is preferably arranged below the first sub-shaft <NUM>. A main shaft of the second motor <NUM> and the first sub-shaft <NUM> are parallel to each other, and the main shaft of the second motor <NUM> and the first sub-shaft <NUM> are in transmission connection with each other. The main shaft of the second motor <NUM> and the first sub-shaft <NUM> may be in gear transmission, belt transmission or chain transmission. In embodiments, the second motor <NUM> and the first sub-shaft <NUM> are in belt transmission. Specifically, the rotary drive assembly further includes a second driving pulley <NUM>, a second slave pulley <NUM>, and a second transmission belt <NUM>. The second slave pulley <NUM> and the second driving pulley <NUM> are preferably synchronous pulleys, and the second transmission belt <NUM> is preferably a synchronous belt. The second driving pulley <NUM> is sleeved on the main shaft of the second motor <NUM>. The second slave pulley <NUM> is sleeved on the first sub-shaft <NUM>. The second transmission belt <NUM> is ringlike. The second transmission belt <NUM> is hooped on the second driving pulley <NUM> and the second slave pulley <NUM>, so that the belt transmission is formed between the first sub-shaft <NUM> and the main shaft of the second motor <NUM>.

The two second sub-shafts <NUM> may be in transmission connection with the rotary cylinders <NUM> of the two crawling assemblies <NUM> on the first sliding rail <NUM>, respectively, and the rotation of the first sub-shaft <NUM> can drive the rotary cylinder <NUM> to rotate. For example, the second sub-shaft <NUM> and the rotary cylinder <NUM> may be in gear transmission, belt transmission or chain transmission. In embodiments, the second sub-shaft <NUM> and the rotary cylinder <NUM> are in belt transmission. The rotary drive assembly further includes a third driving pulley <NUM>, a third slave pulley <NUM> and a third transmission belt <NUM>. The third slave pulley <NUM> and the third driving pulley <NUM> are preferably synchronous pulleys, and the third transmission belt <NUM> is preferably a synchronous belt. The third driving pulley <NUM> is sleeved on the second sub-shaft <NUM>. The third slave pulley <NUM> is sleeved on the rotary cylinder <NUM>. The third transmission belt <NUM> is ringlike. The third transmission belt <NUM> is hooped on the third driving pulley <NUM> and the third slave pulley <NUM>, so that the belt transmission is formed between the second sub-shaft <NUM> and the rotary cylinder <NUM>.

The two rotary cylinders <NUM> on one side of the cart body <NUM> are in transmission connection, and the two rotary cylinders <NUM> on the other side of the cart body <NUM> are in transmission connection. The two rotary cylinders <NUM> may be in belt transmission, rack and pinion transmission or chain transmission. In embodiments, the two rotary cylinders <NUM> are in belt transmission. The rotary drive assembly further includes two fourth driving pulleys <NUM>, two fourth slave pulleys <NUM>, and two fourth transmission belts <NUM>. The fourth slave pulley <NUM> and the fourth driving pulley <NUM> are preferably synchronous pulleys, and the fourth transmission belt <NUM> is preferably a synchronous belt. The two fourth driving pulleys <NUM> are sleeved on the two rotary cylinders <NUM> located at the front end <NUM> of the cart body <NUM>, respectively. The two fourth slave pulleys <NUM> are sleeved on the two rotary cylinders <NUM> located at the rear end <NUM> of the cart body <NUM>, respectively. The two fourth transmission belts <NUM> are both ringlike. One fourth transmission belt <NUM> is hooped on one fourth driving pulley <NUM> and one fourth slave pulley <NUM> on one side of the cart body <NUM>, and the other fourth transmission belt <NUM> is hooped on one fourth driving pulley <NUM> and one fourth slave pulley <NUM> on the other side of the cart body <NUM>.

In this way, the rotation of the main shaft of the second motor <NUM> can drive the transmission shaft <NUM> to rotate, and the rotation of the transmission shaft <NUM> drives the two rotary cylinders <NUM> located at the front end <NUM> of the car body <NUM> to rotate. Then, the rotation of the two rotary cylinders <NUM> can drive the other two rotary cylinders <NUM> to rotate, so that the second motor <NUM> can synchronously drive the four driving wheels <NUM> to turn. In embodiments, axes of the four driving wheels <NUM> are parallel to each other.

Furthermore, the telescopic drive assembly further includes two support seats <NUM> fixedly connected with the two mounting seats <NUM> at the front end <NUM>, respectively. The two support seats <NUM> are also rotationally connected with the second sub-shafts <NUM> respectively. In embodiments, a sixth bearing is mounted on the support seat <NUM>, and the sixth bearing is sleeved on the second sub-shaft <NUM>.

The first sub-shaft <NUM> is splined with the second sub-shaft <NUM>, and torque may be transmitted between the first sub-shaft <NUM> and the second sub-shaft <NUM>. The second sub-shaft <NUM> can slide axially with respect to the first sub-shaft <NUM>. In embodiments, the first sub-shaft <NUM> is a spline tube, and the second sub-shaft <NUM> is a spline shaft. It should be understood that the first sub-shaft <NUM> may also be configured as the spline shaft, and the second sub-axis <NUM> may also be configured as the spline tube.

The connection shaft <NUM> is splined with the input shaft <NUM>, and torque may be transmitted between the connection shaft <NUM> and the input shaft <NUM>. The input shaft <NUM> can slide axially with respect to the connection shaft <NUM>. In embodiments, the connection shaft <NUM> is the spline tube, and the input shaft <NUM> is the spline shaft. It should be understood that the connection shaft <NUM> may also be configured as the spline shaft, and the input shaft <NUM> may also be configured as the spline tube.

Referring to <FIG> and <FIG>, the linear actuator is used to drive the mounting seat <NUM> to slide relative to the cart body <NUM>. When the linear actuator drives the mounting seat <NUM> and slides towards the car body <NUM> at the same time, the crawling assembly <NUM> can leave the guide rail assembly and retract into the car body <NUM>. The linear actuator drives the mounting seat <NUM> to slide outside the car body <NUM> at the same time, and the crawling assembly <NUM> may be engaged with the guide rail assembly. When the crawling assembly <NUM> expands and contracts, the second sub-shaft <NUM> follows and slides relative to the first sub-axis <NUM>, and the transmission shaft <NUM> follows and slides relative to the connection shaft <NUM>. Thus, the crawling drive assembly and the rotary drive assembly can still maintain normal operation.

In embodiments, the linear actuator includes two screw rods <NUM>, four screw nuts <NUM> and a third motor <NUM>. Both ends of the screw rod <NUM> are provided with two external thread segments <NUM> with opposite rotation directions. One screw rod <NUM> penetrates through the third through holes of the two first bases <NUM>, and the two third bearing s761 are sleeved on the screw rod <NUM>. The other screw rod <NUM> penetrates through the fifth through holes <NUM> of the two second bases <NUM>, and the two fifth bearings are sleeved on the screw rod <NUM>. In this way, the two screw rods <NUM> both form rotational connections with the cart body <NUM>, and are located at the front end <NUM> and the rear end <NUM> of the cart body <NUM>, respectively.

The two screw nuts <NUM> are sleeved on the two external thread segments <NUM> of the screw rod <NUM> at the front end <NUM>, respectively, and the other two screw nuts <NUM> are sleeved on the two external thread segments <NUM> of the screw rod <NUM> at the rear end <NUM>, respectively. The four screw nuts <NUM> are also fixedly connected with the four mounting seats <NUM> respectively.

The main shaft of the third motor <NUM> is in transmission connection with the two screw rods <NUM>, and the third motor <NUM> can drive the two screw rods <NUM> to rotate synchronously. When the third motor <NUM> drives the two screw rods <NUM> to rotate, the screw rods <NUM> drive the screw nuts <NUM> to slide along the screw rods <NUM>, and the screw nuts <NUM> drive the mounting seat <NUM> to slide.

Further, the main shaft of the third motor <NUM> and the two screw rods <NUM> are in belt transmission. The telescopic drive assembly further includes a fifth driving pulley <NUM>, two fifth slave pulleys <NUM>, and a fifth transmission belt <NUM>. The fifth slave pulley <NUM> and the fifth master pulley <NUM> are preferably synchronous pulleys, and the fifth transmission belt <NUM> is preferably a synchronous belt. The fifth driving pulley <NUM> is sleeved on the main shaft of the third motor <NUM>. The two fifth slave pulleys <NUM> are sleeved on the two screw rods <NUM>, respectively. The fifth driving pulley <NUM> is located between the two fifth slave pulleys <NUM>. The fifth transmission belt <NUM> is ringlike. The fifth transmission belt <NUM> is hooped on the two fifth slave pulleys <NUM>, and abuts against the fifth driving pulley <NUM>.

Claim 1:
A transmission device for a transport cart, comprising: a crawling assembly (<NUM>), a rotary drive assembly, and a crawling drive assembly, wherein
the crawling assembly (<NUM>) comprises:
a wheel frame (<NUM>), comprising a first end and a second end opposite to the first end, the wheel frame (<NUM>) extending from the first end to the second end;
a driving wheel (<NUM>), mounted at the second end and having an axis perpendicular to an extending direction of the wheel frame (<NUM>); and
a guide wheel (<NUM>), mounted at the second end and having an axis parallel to the extending direction of the wheel frame (<NUM>),
wherein, the rotary drive assembly is configured to drive the wheel frame (<NUM>) to rotate around a central axis of the extending direction of the wheel frame (<NUM>), and the crawling drive assembly is configured to drive the driving wheel (<NUM>) to roll.