Standardized transportation carrier

Abstract

The utility model provides a standardized transport vehicle. The standardized transport vehicle comprises a bottom frame and a first side piece assembly. The chassis comprises a main beam and a vertical rod, the vertical rod is arranged at the end of the main beam and comprises a fixed rod and a detachable rod, the fixed rod is connected to the main beam, and the detachable rod is detachably connected to the fixed rod. The first side panel assembly is movably connected to the vertical rod between a deployed position and a retracted position, and the first side panel assembly is provided with a through opening for the vertical rod to pass through when the first side panel assembly is in the retracted position. The fixing rod does not protrude out of the first side piece assembly located at the retracting position in the vertical direction. The standardized transportation carrier has the advantages of being high in space utilization rate and beneficial to storage and transportation.

Description

Technical Field

[0001] The present application generally relates to the technical field of transport vehicles, and more particularly to a standardized transport vehicle. Background Art

[0002] At present, with the development of the transportation field, modular and standardized design is becoming more and more important. Transport vehicles with modular and standardized design can improve the flexibility and reusability of vehicles. In addition, parts can also be universal, which is convenient for maintenance, replacement and upgrading, and prolongs the service life of transport vehicles, which is green and environmentally friendly. In addition, transport vehicles with modular and standardized design can also play a role in improving space utilization.

[0003] Current transport vehicles, especially six-wheeled dollies, are difficult to stack and place well due to their irregular shapes when stored, resulting in low space utilization, which affects the storage and transportation of the transport vehicles. Utility Model Content

[0004] A series of simplified concepts are introduced in the utility model content section, which will be further described in detail in the detailed implementation section. The utility model content section of this application does not mean to attempt to define the key features and essential technical features of the technical solution claimed for protection, nor does it mean to attempt to determine the scope of protection of the technical solution claimed for protection.

[0005] In order to at least partially solve the above problems, the present application provides a standardized transport vehicle, which comprises:

[0006] A chassis, the chassis comprising a main beam and a vertical rod, the vertical rod being arranged at an end of the main beam, and the vertical rod comprising a fixing rod and a disassembly rod, the fixing rod being connected to the main beam, and the disassembly rod being detachably connected to the fixing rod;

[0007] a first side panel assembly, the first side panel assembly being movably connected to the vertical rod between a deployed position and a retracted position, the first side panel assembly being provided with a through opening for passing through the vertical rod in the retracted position;

[0008] Wherein, the fixing rod does not protrude from the first side panel assembly located at the retracted position along the vertical direction.

[0009] According to the standardized transport carrier of the present application, when the first side panel assembly is in the retracted position, the vertical rod passes through the through opening of the first side panel assembly, and the disassembly rod of the vertical rod is removed. At this time, the fixed rod does not protrude from the first side panel assembly in the vertical direction, so it is convenient to stack the standardized transport carriers, improve space utilization, and facilitate the storage and transportation of the transport carriers.

[0010] Optionally, the disassembly rod includes a protruding portion and a penetrating portion, the penetrating portion is connected to the protruding portion, and the penetrating portion is penetrated into the fixing rod.

[0011] Optionally, a nut is provided in the penetration portion, the penetration portion is provided with a first mounting hole, the fixing rod is provided with a second mounting hole, and the vertical rod further includes a fastener, the fastener penetrates the second mounting hole, the first mounting hole and cooperates with the nut thread.

[0012] Optionally, the first mounting hole is arranged on the bottom surface of the penetration portion, and the second mounting hole is arranged on the bottom surface of the fixing rod.

[0013] Optionally, a projection of the protruding portion along the vertical direction coincides with a projection of the fixing rod along the vertical direction.

[0014] Optionally, the first side panel assembly includes a first wheel set, a first side panel frame and a first column, wherein a first end of the first column is connected to the first side panel frame, and a second end of the first column is connected to the first wheel set;

[0015] The first column is connected to the vertical rod, and the through opening is arranged on the first column.

[0016] Optionally, the first column is provided with a long slot, and the standardized transport vehicle further comprises:

[0017] Base plate;

[0018] A flip lifting mechanism, the flip lifting mechanism comprising a flap and a lifting pin, the lifting pin is penetrated to the fixing rod and penetrated to the first column through the long slot, a first end of the flap is connected to the bottom plate, and a second end of the flap is pivotally connected to the first column around a first pivot axis parallel to the axis of the lifting pin;

[0019] Wherein, during the process of the bottom plate being attached to at least a portion of the first side plate frame, the flap lifts the lifting pin in a vertical direction.

[0020] Optionally, the standardized transport vehicle also includes a second side panel assembly, and the first side panel assembly and the second side panel assembly are respectively arranged at two ends of the base frame; a second wheel group is arranged in the middle of the base frame, and the second side panel assembly includes a third wheel group; the second wheel group is a fixed wheel group and has a braking device, and the second wheel group and the third wheel group are both universal wheel groups.

[0021] Optionally, the first side panel frame is provided with a locking member, and the locking member is used to lock the bottom plate attached to the first side panel frame.

[0022] Optionally, the second side panel assembly includes a second side panel frame and a second column, the first end of the second column is connected to the second side panel frame, the second end of the second column is connected to the third wheel set, and the second column is connected to the base frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following drawings of the embodiments of the present application are hereby used as part of the present application for understanding the present application. The drawings show the embodiments of the present application and their descriptions, and are used to explain the principles of the present application. In the drawings,

[0024] Figure 1 It is a three-dimensional schematic diagram of a standardized transport carrier according to a preferred embodiment of the present application, in which the first side panel assembly is in an unfolded position and the bottom plate is in a working state;

[0025] Figure 2 is a three-dimensional schematic diagram of a standardized transport carrier according to a preferred embodiment of the present application, wherein the first side panel assembly is in an unfolded position and the bottom plate is in the process of being flipped to the first side panel assembly;

[0026] Figure 3 It is a three-dimensional schematic diagram of a standardized transport carrier according to a preferred embodiment of the present application, in which the first side panel assembly is in the unfolded position and the bottom plate is flipped to the first side panel assembly;

[0027] Figure 4 It is a three-dimensional schematic diagram of a standardized transport carrier according to a preferred embodiment of the present application, in which the bottom plate is flipped to the first side panel assembly, and the first side panel assembly is in a retracted position;

[0028] Figure 5 is a three-dimensional schematic diagram of the chassis;

[0029] Figure 6 is a three-dimensional schematic diagram of a fixing rod;

[0030] Figure 7 is a three-dimensional schematic diagram of a disassembly rod;

[0031] Figure 8 For along Figure 1 an enlarged schematic diagram of part A in FIG. ; and

[0032] Fig. 9 for Figure 2 An enlarged schematic diagram of part B in FIG.

[0033] Description of Reference Numerals

[0034] 100: Base frame 101: Main beam

[0035] 102: vertical rod 103: second wheel group

[0036] 104: Removal rod 105: Fixing rod

[0037] 106: protrusion 107: penetration

[0038] 108: Second mounting hole 109: Nut

[0039] 150: Side panel 151: Bottom panel

[0040] 152: first plug hole 153: second plug hole

[0041] 154: Connecting plate 155: Install square tube

[0042] 110: Base plate 111: Fastener

[0043] 112: protrusion 120: first side panel component

[0044] 121: Long groove 122: First wheel group

[0045] 123: first side frame 124: first column

[0046] 125: Through hole 126: Locking piece

[0047] 130: Flip lifting mechanism 131: Flip plate

[0048] 132: Lifting pin 133: Split pin

[0049] 134: Gasket 140: Second side panel assembly

[0050] 141: The third wheel set 142: The second side plate frame

[0051] 143: Second column AX1: First pivot axis

[0052] AX2: Second pivot axis D1: Vertical direction

[0053] D2: Length direction D3: Width direction DETAILED DESCRIPTION

[0054] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application embodiments can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application embodiments, some technical features well known in the art are not described.

[0055] Herein, ordinal numbers such as “first” and “second” cited in the present application are merely identifications and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term “first component” itself does not imply the existence of the “second component”, and the term “second component” itself does not imply the existence of the “first component”.

[0056] In this document, “upper”, “lower”, “front”, “back”, “left”, “right”, etc. are only used to indicate the relative position relationship between related parts, rather than to limit the absolute positions of these related parts.

[0057] In this document, “equal”, “same”, etc. are not strictly limited in a mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and are allowed in manufacturing or use.

[0058] Unless otherwise stated, the numerical ranges herein include not only the entire range within its two endpoints but also include several sub-ranges contained therein.

[0059] Figures 1 to 9 A standardized transport vehicle according to the present application is shown, and the standardized transport vehicle includes a chassis 100 and a first side panel assembly 120. The chassis 100 includes a main beam 101 and a vertical rod 102, the vertical rod 102 is arranged at the end of the main beam 101, and the vertical rod 102 includes a fixed rod 105 and a disassembly rod 104, the fixed rod 105 is connected to the main beam 101, and the disassembly rod 104 is detachably connected to the fixed rod 105.

[0060] The first side panel assembly 120 is movably connected to the vertical rod 102 between a deployed position and a retracted position. The first side panel assembly 120 is provided with a through hole 125 for passing through the vertical rod 102 in the retracted position.

[0061] The fixing rod 105 does not protrude from the first side panel assembly 120 in the retracted position along the vertical direction D1.

[0062] According to the standardized transport carrier of the present application, when the first side panel assembly 120 is in the retracted position, the vertical rod 102 passes through the opening 125 of the first side panel assembly 120, and the disassembly rod 104 of the vertical rod 102 is removed. At this time, the fixing rod 105 does not protrude from the first side panel assembly 120 along the vertical direction D1, so it is convenient to stack the standardized transport carrier, improve the space utilization rate, and facilitate the storage and transportation of the transport carrier.

[0063] The standardized transport vehicle further includes a flipping and lifting mechanism 130 and a bottom plate 110. The bottom plate 110, the bottom frame 100 and the first side panel assembly 120 can be switched into various forms through the flipping and lifting mechanism 130. Figure 1For the working state of the standardized transport vehicle, the first side panel assembly 120 is located in the unfolded position and extends along the vertical direction D1. Figure 2 The bottom plate 110 is turned toward the first side panel assembly 120 by the turning and lifting mechanism 130 until Figure 3 As shown, the bottom plate 110 is attached to the first side panel assembly 120, and the standardized transport carrier can be moved laterally and folded. Figure 4 The bottom plate 110 is attached to the first side panel assembly 120 and flipped to the retracted position along with the first side panel assembly 120, so that the standardized transport carrier can be stacked.

[0064] Reference Figure 1 and Figure 2 The standardized transport vehicle further includes a second side panel assembly 140. The first side panel assembly 120 and the second side panel assembly 140 are respectively arranged at both ends of the chassis 100 along the length direction D2. The first side panel assembly 120 includes a first wheel assembly 122. A second wheel assembly 103 is arranged in the middle of the chassis 100. The second side panel assembly 140 includes a third wheel assembly 141. The second wheel assembly 103 is a fixed wheel assembly and has a brake device. Both the second wheel assembly 103 and the third wheel assembly 141 are universal wheel assemblies.

[0065] When the base frame 100 is in a horizontal position (eg Figure 1 As shown in the figure, the second wheel set 103 is lower than the first wheel set 122 and the third wheel set 141. Therefore, when the standardized transport vehicle is in normal use, the second wheel set 103 contacts the ground, and the chassis 100 has a slight tilt angle, so that the first wheel set 122 or the third wheel set 141 contacts the ground. At this time, there are two wheel sets (four wheels in total) supporting the chassis 100 and the bottom plate 110, so as to facilitate the transportation of goods, etc. Since the second wheel set 103 has a brake device, the standardized transport vehicle can be braked and controlled.

[0066] When the bottom plate 110 is flipped and fitted to the first side panel assembly 120, the vertical rod 102 is lifted relative to the first side panel assembly 120 by the flipping and lifting mechanism 130, so that the second wheel set 103 is lifted off the ground. At this time, the standardized transport vehicle moves through the first wheel set 122 and the third wheel set 141, and can be horizontally overlapped with another standardized transport vehicle, thereby saving storage space.

[0067] Then it is more specific to the structure of standardized transport vehicles. Figure 2The first side panel assembly 120 further includes a first side panel frame 123 and a first column 124. Along the vertical direction D1, the upper end of the first column 124 is connected to the first side panel frame 123, and the lower end of the first column 124 is connected to the first wheel set 122. The first column 124 is connected to the vertical rod 102, and the through-hole 125 is provided on the first column 124. When the first side panel assembly 120 is in the retracted position, the vertical rod 102 passes through the through-hole 125 to the first column 124, so that there is a limit between the first side panel assembly 120 and the bottom frame 100, so that the first side panel assembly 120 is more stable in the retracted position.

[0068] Combination Figure 5 and Figure 3 As shown, the chassis 100 further includes a mounting square tube 155, which is disposed at one end of the main beam 101 away from the first side panel assembly 120 and fixed to the main beam 101, and the lower end of the mounting square tube 155 is connected to the third wheel assembly 141. The second side panel assembly 140 further includes a second side panel frame 142 and a second column 143. Along the vertical direction D1, the upper end of the second column 143 is connected to the second side panel frame 142, and the lower end of the second column 143 is passed through the upper end of the mounting square tube 155 into the mounting square tube 155 and fixed to the mounting square tube 155 by a fastener 111 (not shown in the figure) such as a latch or a bolt, so that when the standardized transport vehicle is in a folded state (refer to Figure 4 ), the second column 143 and the mounting square tube 155 can be removed, so that the second column 143 and the second side panel frame 142 are horizontally stacked above the first side panel assembly 120, reducing the height dimension of the standardized transport vehicle along the vertical direction D1 for easy transportation.

[0069] Reference Figure 5 and Figure 6 The fixing rod 105 is in a square tube shape, and the side wall of the fixing rod 105 is fixedly connected to one end of the main beam 101 close to the first side panel assembly 120 .

[0070] Reference Figure 7 The disassembly rod 104 includes a protruding portion 106 and a penetrating portion 107. The penetrating portion 107 is connected to the protruding portion 106, and the penetrating portion 107 is penetrated into the fixing rod 105, so that the connection between the disassembly rod 104 and the fixing rod 105 is more stable.

[0071] In detail, the protruding portion 106 is in a square tube shape, and the penetration portion 107 includes two side panels 150, a connecting plate 154, and a bottom panel 151. The side panels 150 and the connecting plate 154 both extend along the vertical direction D1, and the two side panels 150 are spaced apart along the width direction D3 of the standardized transport vehicle and are respectively connected to the vertical sides of the connecting plate 154. The bottom panel 151 is disposed at the lower ends of the side panels 150 and the connecting plate 154, and the bottom panel 151 is fixedly connected to the side panels 150 and the connecting plate 154, respectively. In addition, the upper ends of the connecting plate 154 and the side panels 150 are connected to the bottom surface of the protruding portion 106. When the disassembly rod 104 and the fixing rod 105 are fixed, the penetration portion 107 penetrates into the fixing rod 105 until the bottom plate 151 contacts the inner bottom surface of the fixing rod 105, and the bottom surface of the protrusion 106 abuts against the upper end of the fixing rod 105, so that the disassembly rod 104 and the fixing rod 105 have good integrity after being connected together, which is conducive to the assembly of the vertical rod 102 and the first column 124. In addition, the vertical rod 102 has a larger size along the vertical direction D1, which can better cooperate with the first column 124 (especially vertical relative movement).

[0072] Optionally, the projection of the protrusion 106 along the vertical direction D1 coincides with the projection of the fixing rod 105 along the vertical direction D1, so that the side wall of the vertical rod 102 formed after installation between the disassembly rod 104 and the fixing rod 105 is smooth, further enhancing the integrity of the disassembly rod 104 and the fixing rod 105, and facilitating the assembly of the vertical rod 102 and the first column 124.

[0073] Optionally, a nut 109 is provided in the penetration portion 107, the penetration portion 107 is provided with a first mounting hole (not shown in the figure), and the fixing rod 105 is provided with a second mounting hole 108. The vertical rod 102 further includes a fastener 111, which penetrates the second mounting hole 108 and the first mounting hole and is threadedly matched with the nut 109, so that the disassembly rod 104 and the fixing rod 105 are fixed together, realizing the detachable installation of the disassembly rod 104 and the fixing rod 105, and facilitating the removal of the disassembly rod 104 after the standardized transport carrier is folded.

[0074] Specifically, if Figure 6 and Figure 7As shown, the first mounting hole and the nut 109 are provided on the bottom panel 151, and the second mounting hole 108 is provided on the bottom surface of the fixing rod 105. When the penetration portion 107 of the disassembly rod 104 is penetrated into the fixing rod 105 and in place, the bottom panel 151 of the penetration portion 107 contacts the inner bottom surface of the fixing rod 105, and the first mounting hole is aligned with the second mounting hole 108, so that it is convenient to install the fastener 111 from the bottom of the fixing rod 105, so that the disassembly rod 104 and the fixing rod 105 are connected together. In addition, when the standardized transport carrier is folded, there is no structural obstruction on the bottom surface of the fixing rod 105, so that the staff can remove the fastener 111 from the bottom surface of the fixing rod 105 to realize the removal of the disassembly rod 104.

[0075] Now let's get into details about the structures of the flipping and lifting mechanism 130 and the base plate 110 .

[0076] like Figure 8 and Fig. 9 As shown, the first column 124 is provided with a long slot 121, and the flip lifting mechanism 130 includes a flap 131 and a lifting pin 132. The lifting pin 132 is passed through the fixed rod 105 and through the long slot 121 to the first column 124, so that the vertical rod 102 can be moved along the vertical direction D1 relative to the first column 124 and can be pivotally arranged around the second pivot axis AX2 (i.e., the axis of the lifting pin 132).

[0077] Specifically, refer to Figure 6 The side wall of the fixing rod 105 is provided with a first plug hole 152, referring to Figure 7 Correspondingly, the side wall of the side panel 150 is provided with a second plug hole 153. When the disassembly rod 104 is fixed to the fixing rod 105, the first plug hole 152 is aligned with the second plug hole 153 for passing the lifting pin 132, so that the connection between the lifting pin 132 and the vertical rod 102 is more stable.

[0078] Optionally, combined Figure 8 As shown, the flip lifting mechanism 130 also includes two split pins 133 and two washers 134. Along the width direction D3, the two washers 134 are sleeved on the lifting pin 132 and arranged on both sides of the first column 124. The split pin 133 is passed through the lifting pin 132 and arranged on the side of the washers 134 away from the first column 124, thereby limiting the lifting pin 132, realizing the detachable installation of the lifting pin 132, and making the vertical rod 102 and the first column 124 stably connected.

[0079] Combination Figure 3 As shown, the first end of the flap 131 is connected to the bottom plate 110 by a fastener 111, referring to Figure 8 and Fig. 9The second end of the flap 131 is pivotally connected to the first column 124 around a first pivot axis AX1 parallel to the axis of the lifting pin 132. In the process of the bottom plate 110 being attached to at least part of the first side plate frame 123, the flap 131 lifts the lifting pin 132 along the vertical direction D1, so that the lifting pin 132 moves along the long slot 121, thereby lifting the vertical rod 102 relative to the first column 124 along the vertical direction D1, thereby lifting the end of the bottom frame 100 close to the first side plate assembly 120, so that the second wheel set 103 can be lifted off the ground, and then the standardized transport vehicle can move laterally by relying on the first wheel set 122 and the third wheel set 141, so as to facilitate the stacking of the standardized transport vehicles.

[0080] Optionally, refer to Fig. 9 The flap 131 can be a plate-like structure with two bending angles, so that the lifting pin 132 is guided to the inclined surface in the middle of the flap 131 when the bottom plate 110 drives the flap 131 to move upward, and when the lifting pin 132 is located at the top end of the long groove 121, the lifting pin 132 is located at the clamping position between the bending angle of the flap 131 and the top end of the long groove 121, so as to facilitate the first side plate frame 123 and the bottom plate 110 to stably pivot around the second pivot axis AX2.

[0081] Optionally, the first side frame 123 is provided with a locking piece 126, which is used to lock the bottom plate 110 attached to the first side frame 123, so that the bottom plate 110 and the first side frame 123 can be connected together to facilitate subsequent overall folding.

[0082] Furthermore, a protrusion 112 is provided at one end of the base plate 110 away from the flap 131, and the locking member 126 is pivotally connected to the first side plate frame 123. When the base plate 110 is attached to the first side plate frame 123, the locking member 126 is rotated so that the locking member 126 is sleeved on the protrusion 112 attached to the base plate 110, thereby locking the base plate 110 and the first side plate frame 123 together, preventing the base plate 110 from shaking during the process of pivoting the first side plate frame 123 to a horizontal position, thereby folding the standardized transport vehicle.

[0083] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field of this application. The terms used herein are only for describing specific implementation purposes and are not intended to limit this application. Terms such as "setting" appearing in this article can mean that one component is directly attached to another component, or that one component is attached to another component through an intermediate. Features described in this article in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise specified.

[0084] The present application has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and description, and are not intended to limit the present application to the described embodiments. It can be understood by those skilled in the art that more variations and modifications can be made according to the teachings of the present application, and these variations and modifications all fall within the scope of protection claimed in the present application.

Claims

1. A standardized transport vehicle, characterized in that: The standardized transport vehicle includes: A chassis, the chassis comprising a main beam and a vertical rod, the vertical rod being arranged at an end of the main beam, and the vertical rod comprising a fixing rod and a disassembly rod, the fixing rod being connected to the main beam, and the disassembly rod being detachably connected to the fixing rod; a first side panel assembly, the first side panel assembly being movably connected to the vertical rod between a deployed position and a retracted position, the first side panel assembly being provided with a through opening for passing through the vertical rod in the retracted position; Wherein, the fixing rod does not protrude from the first side panel assembly located at the retracted position along the vertical direction.

2. The standardized transport vehicle according to claim 1, characterized in that: The disassembly rod comprises a protruding portion and a penetrating portion, wherein the penetrating portion is connected to the protruding portion and the penetrating portion is penetrating into the fixing rod.

3. The standardized transport vehicle according to claim 2, characterized in that: A nut is arranged in the penetration portion, the penetration portion is provided with a first mounting hole, the fixing rod is provided with a second mounting hole, and the vertical rod further comprises a fastener, the fastener penetrates the second mounting hole and the first mounting hole and cooperates with the nut thread.

4. The standardized transport vehicle according to claim 3, characterized in that: The first mounting hole is arranged on the bottom surface of the penetration portion, and the second mounting hole is arranged on the bottom surface of the fixing rod.

5. The standardized transport vehicle according to claim 2, characterized in that: A projection of the protruding portion along the vertical direction coincides with a projection of the fixing rod along the vertical direction.

6. The standardized transport vehicle according to claim 1, characterized in that: The first side panel assembly includes a first wheel set, a first side panel frame and a first column, wherein a first end of the first column is connected to the first side panel frame, and a second end of the first column is connected to the first wheel set; The first column is connected to the vertical rod, and the through opening is arranged on the first column.

7. The standardized transport vehicle according to claim 6, characterized in that: The first column is provided with a long slot, and the standardized transport vehicle further comprises: Base plate; A flip lifting mechanism, the flip lifting mechanism comprising a flap and a lifting pin, the lifting pin is penetrated to the fixing rod and penetrated to the first column through the long slot, a first end of the flap is connected to the bottom plate, and a second end of the flap is pivotally connected to the first column around a first pivot axis parallel to the axis of the lifting pin; Wherein, during the process of the bottom plate being attached to at least a portion of the first side plate frame, the flap lifts the lifting pin in a vertical direction.

8. The standardized transport vehicle according to claim 7, characterized in that: The standardized transport vehicle also includes a second side panel assembly, and the first side panel assembly and the second side panel assembly are respectively arranged at two ends of the base frame; a second wheel group is arranged in the middle of the base frame, and the second side panel assembly includes a third wheel group; the second wheel group is a fixed wheel group and has a braking device, and the second wheel group and the third wheel group are both universal wheel groups.

9. The standardized transport vehicle according to claim 7, characterized in that: The first side plate frame is provided with a locking member, and the locking member is used to lock the bottom plate attached to the first side plate frame.

10. The standardized transport vehicle according to claim 8, characterized in that: The second side panel assembly includes a second side frame and a second column, wherein a first end of the second column is connected to the second side frame, a second end of the second column is connected to the third wheel set, and the second column is connected to the bottom frame.

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