CN114572897A

CN114572897A - Truck-mounted forklift

Info

Publication number: CN114572897A
Application number: CN202210326658.6A
Authority: CN
Inventors: 张根社; 葛剑威; 胡骁; 刘波; 程勇; 黄云
Original assignee: Noblelift Intelligent Equipment Co Ltd
Current assignee: Noblelift Intelligent Equipment Co Ltd
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2022-06-03

Abstract

The invention discloses a forklift truck, which comprises a truck frame, a truck body, a forward sliding frame, a forward oil cylinder, a portal frame assembly, a pallet fork, an inclined oil cylinder, a front wheel, a hydraulic system and a chain, wherein the truck body is fixedly connected with the rear part of the truck frame; the stability of transportation along with the truck is ensured, and safety accidents caused by swinging, shaking and even sliding are avoided; the operation is simple and easy, and the efficiency of loading and unloading the freight train is high.

Description

Truck-mounted forklift

Technical Field

The invention belongs to the technical field of forklifts, and particularly relates to a forklift truck.

Background

With the explosive development of the modern logistics industry, the cargo loading and unloading along with the transportation vehicles becomes an inevitable trend. For example: loading and unloading goods at a place without special loading and unloading equipment; loading and unloading goods with special type requirements on a fork of a forklift; the loading and unloading of goods in applications where only one forklift can be called for in a plurality of factories or a plurality of workshops. In order to realize the loading and unloading of goods, a truck-mounted forklift needs to be designed.

A truck-mounted forklift is a mechanical device which is loaded on a transport vehicle, travels along with the transport vehicle and finishes cargo loading and unloading, and belongs to material loading and unloading machinery. Compared with common cargo handling machines, for example: the common forklift is characterized in that the forklift can be placed on a transport vehicle, can finish the goods loading and unloading operation at any time in the whole transport process, and is particularly suitable for the goods loading and unloading operation in places without special loading and unloading equipment.

The existing truck-mounted forklift is immature in technology and mainly has the following defects:

firstly, the method comprises the following steps: the loading space of the transport vehicle is occupied, and the loading capacity of the goods is influenced.

Secondly, the method comprises the following steps: transportation along with the haulage vehicle is unstable, meets jolt highway section, breaks highway section from top to bottom, causes vehicle-mounted fork truck to sway and rock easily, and the landing even causes the incident.

Thirdly, the method comprises the following steps: the truck-mounted forklift truck has the advantages of complex operation, low efficiency of loading and unloading the truck and difficult operation.

Disclosure of Invention

The invention provides a forklift truck, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention adopts the technical scheme that: a truck-mounted forklift comprises a frame, a body, a forward sliding frame, a forward oil cylinder, a portal frame assembly, a fork, an inclined oil cylinder, a front wheel, a hydraulic system and a chain, the vehicle body is tightly connected with the rear part of the vehicle frame, the inner wall of the vehicle frame is provided with a wheel rail, two sides of the forward sliding frame are connected with the wheel rail in a rolling way through rollers, the end part of a cylinder barrel of the forward oil cylinder is connected with the rear end of the frame, the end part of a piston rod of the forward oil cylinder is hinged with the front end of the forward sliding frame, the lower end of the portal frame assembly is hinged with the front side of the advancing carriage, the fork is connected with the portal frame assembly through the fork frame, the fork frame is connected with the portal frame component through a lifting oil cylinder, the end part of a cylinder barrel of the tilting oil cylinder is hinged with the upper end of the forward sliding frame, the end part of a piston rod of the tilting oil cylinder is hinged with the rear end of the portal frame component, the front wheel is connected with the outer side of the front end of the frame, the hydraulic system is installed in the vehicle body, and the chain is connected with the two sides of the vehicle body.

Preferably, the front end of the frame is provided with a front cylinder seat, a supporting leg oil cylinder is arranged in the front cylinder seat, and the front end of the front cylinder seat is provided with a supporting leg driven by the supporting leg oil cylinder in a guiding manner.

Preferably, a steering system, a driving system, a control system, a charger and a battery pack are arranged in the vehicle body, a signal lamp control cable socket and a front illuminating lamp are arranged on the front side of the vehicle body, three-color signal lamps are arranged on the rear side of the vehicle body, and a control operation table is arranged in a cab at the upper end of the vehicle body.

Preferably, the control operation platform comprises an instrument, a turn light switch, a lighting lamp switch, a parking brake switch, a function switching switch, a horn button, a direction control handle, a key switch, an emergency power-off switch, a lifting and descending control handle, an advancing and retreating control handle, an inclined control handle and a supporting foot operation handle.

Preferably, the side surface of the bicycle body is provided with a chain switch key, a chain loosening switch and a chain tightening switch.

Preferably, the gantry assembly comprises an outer gantry, an inner gantry, an outer chain and an inner chain, the lower end of a cylinder barrel of the lifting oil cylinder is connected with the lower end of the outer gantry, the end part of a piston rod of the lifting oil cylinder is connected with the upper end of the inner gantry, upper chain wheels are symmetrically arranged at the upper end of the inner gantry, lower chain wheels are symmetrically arranged at the lower end of the inner gantry, the outer chain crosses the upper chain wheels, the lower end of the outer chain is fixedly connected with the fork frame, and the upper end of the outer chain is fixedly connected with the outer gantry; the inner chain strides over the lower end of the lower chain wheel and is fixedly connected with the fork frame, and the upper end of the inner chain is fixedly connected with the outer door frame.

A truck-mounted forklift, a hydraulic system comprises a loading vehicle operation system, and the method specifically comprises the following steps,

step S1: the lifting oil cylinder extends through the rear-pulling lifting and descending control handle, so that the fork is lifted to the same height as the fork hole at the rear part of the truck;

step S2: the front-moving oil cylinder extends by pushing the front-moving and back-moving control handle forwards, the portal frame assembly, the fork frame, the lifting oil cylinder, the fork and the inclined oil cylinder are moved to the foremost end together, and then the front-pushing direction control handle drives the forklift to move forwards, so that the fork is inserted into a fork hole at the rear part of the truck;

step S3: pressing down the function switch, and then, the lamp of the function switch is on;

step S4: by pushing the lifting operating handle forward, the lifting oil cylinder is contracted, and the forklift is lifted slowly until the frame is aligned with the lower end of the pallet fork hole part;

step S5: the forward oil cylinder is contracted by pulling the forward and backward control handle backwards, and the fork is fixed, so that the body of the forklift is close to the rear part of the truck to the maximum extent;

step S6: the tilting oil cylinder is contracted by pulling the tilting control handle backwards, and the whole forklift rotates anticlockwise around the hinged position of the forward sliding frame and the portal frame component, so that the rear end of the forklift is tilted;

step S7: pressing the function switch again, and then turning off the lamp of the function switch;

step S8: a forklift driver gets off and hangs one ends of the chain chains at two sides of the forklift body on the truck;

step S9: a chain switch key is turned on, a chain tightening switch is pressed, and the inclined oil cylinder extends to enable the rear end of the forklift to descend until the chain is completely tensioned;

step S10: butting a signal lamp control cable at the rear end of the truck with a signal lamp control cable socket;

step S11: and closing the chain switch key and pulling down the chain switch key.

A truck-mounted forklift, a hydraulic system also comprises a cargo vehicle operation system, which comprises the following steps,

step SS 1: disconnecting a signal lamp control cable at the rear end of the truck from a signal lamp control cable socket;

step SS 2: a chain switch key is turned on, a chain release switch is pressed, the inclined oil cylinder contracts, and the whole forklift rotates anticlockwise around the hinged position of the forward sliding frame and the forklift frame component, so that the rear end of the forklift is tilted until the chain is completely loosened;

step SS 3: the driver releases the chain on the two sides of the truck body from the truck;

step SS 4: a driver gets on the forklift, sits on a forklift seat in a correct posture, ties up a safety belt, and puts down a guardrail; pressing down the function switch, and then, the lamp of the function switch is on;

step SS 5: the tilting oil cylinder extends by pushing the tilting control handle forwards, and the whole forklift rotates clockwise around the hinged position of the forward sliding frame and the forklift frame component, so that the rear end of the forklift descends;

step SS 6: the forward oil cylinder extends by pushing the forward and backward operating handle forwards, and the fork is fixed, so that the body of the forklift is furthest away from the rear part of the truck;

step SS 7: the lifting oil cylinder extends through the rear pulling lifting descending control handle, and the forklift is slowly put down until the front wheels and the rear wheels of the driving system fall to the ground;

step SS 8: the fork truck is driven to run backwards through the rear-pulling direction control handle, so that the fork truck is completely separated from a fork hole at the rear part of the truck;

step SS 9: the function changeover switch is pressed again, and at the moment, the lamp of the function changeover switch is turned off.

The beneficial effect of adopting above technical scheme is:

1. the truck-mounted forklift is loaded at the rear end of the truck, does not occupy the loading space of the truck and does not influence the loading capacity of goods.

2. According to the truck-mounted forklift, the fork is inserted into the fork hole in the rear of the truck through the hydraulic system, then one ends of the chains on two sides of the truck body are hung on the truck until the chains are completely tensioned, so that the stability of the truck-mounted forklift in transportation with the truck is ensured, and the truck-mounted forklift cannot swing and shake or even slide down to cause safety accidents when encountering bumpy road sections and broken road sections.

3. The hydraulic system of the truck-mounted forklift truck disclosed by the invention has the advantages of simple operation, high truck loading and unloading efficiency and easiness in operation.

Drawings

FIG. 1 is a first assembly view of the truck-mounted lift truck of the present invention;

FIG. 2 is a second assembly view of the truck-mounted forklift of the present invention;

FIG. 3 is an enlarged view of the control console;

FIG. 4 is a third assembly view of the truck-mounted forklift of the present invention;

FIG. 5 is a partial enlarged view of the portion A in FIG. 4;

FIG. 6 is a schematic view of the advancing carriage configuration;

FIG. 7 is an assembly view of the front barrel mount, leg cylinders and support feet;

FIG. 8 is an assembly view of the mast assembly and the forks;

FIG. 9 is a schematic view of steps S1-S3;

FIG. 10 is a schematic view of step S4;

FIG. 11 is a schematic view of step S5;

FIG. 12 is a schematic view of steps S6-S7;

FIG. 13 is a schematic view of step S8;

FIG. 14 is a schematic view of steps S9-S11;

FIG. 15 is a schematic view of step SS 1-step SS 2;

FIG. 16 is a schematic view of step SS 3-step SS 4;

FIG. 17 is a schematic view of step SS 5;

FIG. 18 is a schematic view of step SS 6;

FIG. 19 is a schematic view of step SS 7;

FIG. 20 is a schematic view of step SS 8-step SS 9;

wherein:

1. a frame; 2. a vehicle body; 3. advancing the carriage; 4. moving the oil cylinder forwards; 5. a gantry assembly; 6. a pallet fork; 7. inclining the oil cylinder; 8. a front wheel; 9. a hydraulic system; 9-1, chain;

10. wheel rail 11, front barrel seat; 12. a support oil cylinder; 13. supporting legs;

20. a steering system; 21. a drive system; 22. a control system; 23. a charger; 24. a battery pack; 25. a signal lamp control cable socket; 26. a front lighting lamp; 27. three-color signal lamps; 28. controlling the operation table; 28-1, instrument; 28-2, a turn light switch; 28-3, a lighting lamp switch; 28-4, a parking brake switch; 28-5, a function switch; 28-6, a horn button; 28-7, a direction control handle; 28-8, a key switch; 28-9, an emergency power-off switch; 28-10 of a lifting and descending control handle; 28-11, moving the control handle forwards and backwards; 28-12, a tilt handle; 28-13, supporting a foot operating handle;

280. a chain switch key; 281. a chain release switch; 282. a chain tightening switch;

50. a fork carriage; 51. a lift cylinder; 52. an outer gantry; 53. an inner gantry; 53-1, upper chain wheel; 53-2, lower sprocket; 54. an outer chain; 55. an inner chain.

Detailed Description

The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings for a purpose of helping those skilled in the art to more fully, accurately and deeply understand the concept and technical solution of the present invention and to facilitate its implementation.

As shown in fig. 1 to 20, the invention is a truck-mounted forklift, which does not occupy the loading space of a truck and does not affect the loading capacity of goods; the stability of the truck-mounted forklift in transportation along with the truck is ensured, and the truck-mounted forklift cannot swing and shake or even slide to cause safety accidents when encountering bumpy road sections and broken road sections; the operation is simple, the efficiency of loading and unloading the freight train is high, and the operation is easy.

Specifically, as shown in fig. 1 to 20, a forklift truck includes a frame 1, a truck body 2, a forward carriage 3, a forward cylinder 4, a mast assembly 5, a fork 6, a tilt cylinder 7, front wheels 8, a hydraulic system 9 and a chain 9-1, wherein the truck body 2 is fixedly connected to the rear of the frame 1, the inner wall of the frame 1 is provided with a wheel rail 10, two sides of the forward carriage 3 are connected to the wheel rail 10 through a roller, the end of a cylinder barrel of the forward cylinder 4 is connected to the rear end of the frame 1, the end of a piston rod of the forward cylinder 4 is hinged to the front end of the forward carriage 3, the lower end of the mast assembly 5 is hinged to the front side of the forward carriage 3, the fork 6 is connected to the mast assembly 5 through a fork frame 50, the fork frame 50 is connected to the mast assembly 5 through a lift cylinder 51, the end of the cylinder barrel of the tilt cylinder 7 is hinged to the upper end of the forward carriage 3, the end of the piston rod of the tilt cylinder 7 is hinged to the rear end of the mast assembly 5, the front wheel 8 is connected with the outer side of the front end of the frame 1, the hydraulic system 9 is installed in the vehicle body 2, and the chain 9-1 is connected with the two sides of the vehicle body 2.

A front cylinder seat 11 is arranged at the front end of the frame 1, a supporting leg oil cylinder 12 is arranged in the front cylinder seat 11, and a supporting leg 13 driven by the supporting leg oil cylinder 12 is arranged at the front end of the front cylinder seat 11 in a guiding manner; when the heavy object is inserted and transported by the forklift truck, the supporting legs 13 driven by the supporting leg oil cylinders 12 are in contact with the ground, the front wheels 8 are lifted and separated from the ground, the stability of inserting and transporting the heavy object is ensured, and the forklift truck is prevented from forwards overturning or laterally overturning.

Be equipped with a steering system 20, actuating system 21, control system 22, charger 23 and group battery 24 in the

automobile body

2, 2 front sides of automobile body are equipped with signal lamp control cable socket 25 and

headlamp

26, 2 rear sides of automobile body are equipped with three-colour signal lamp 27, be equipped with control operation panel 28 in 2 upper end cockpit of automobile body. Through the charger 23 and the battery pack 24, energy is saved and environment is protected. The signal lamp control cable socket 25 ensures that the three-color signal lamp 27 at the rear side of the truck-mounted forklift can be used as a signal lamp of a truck, and the driving safety is ensured.

The control operation platform 28 comprises an instrument 28-1, a turn light switch 28-2, a lighting lamp switch 28-3, a parking brake switch 28-4, a function switch 28-5, a horn button 28-6, a direction control handle 28-7, a key switch 28-8, an emergency power-off switch 28-9, a lifting and descending control handle 28-10, a forward and backward moving control handle 28-11, an inclined control handle 28-12 and a supporting foot operation handle 28-13.

A chain switch key 280, a chain loosening switch 281 and a chain tightening switch 282 are arranged on the side surface of the vehicle body 2.

The gantry assembly 5 comprises an outer gantry 52, an inner gantry 53, an outer chain 54 and an inner chain 55, the lower end of a cylinder barrel of the lifting oil cylinder 51 is connected with the lower end of the outer gantry 52, the end part of a piston rod of the lifting oil cylinder 51 is connected with the upper end of the inner gantry 52, the upper end of the inner gantry 53 is symmetrically provided with an upper chain wheel 53-1, the lower end of the inner gantry 53 is symmetrically provided with a lower chain wheel 53-2, the outer chain 54 crosses the upper chain wheel 53-1, the lower end of the outer chain is fixedly connected with the fork frame 50, and the upper end of the outer chain is fixedly connected with the outer gantry 52; the inner chain 55 is fastened to the fork carriage 50 at the lower end thereof across the lower sprocket 53-2 and fastened to the outer mast 52 at the upper end thereof. The fork frame 50 is connected with the upper end of the outer gantry 52 by bypassing the upper chain wheel 53-1 through the outer chain 54, the fork frame 50 is connected with the upper end of the outer gantry 52 by bypassing the lower chain wheel 53-2 through the inner chain 55, and compared with the fork of the traditional forklift which descends by self weight, the fork frame 50 has the advantages that the lifting and descending of the fork frame 50 are under pressure, pressure can be maintained, the fork 6 is locked at any position, and the stability of inserting the fork 6 into a fork hole at the rear part of the truck is ensured.

The following specific working modes are illustrated by specific examples:

example 1:

a truck-mounted forklift, a hydraulic system 9 comprises a loading truck operation system, which comprises the following steps,

step S1: the lifting oil cylinder 51 extends through the rear-pulling lifting and descending control handle 28-10, so that the fork 6 is lifted to the same height as the fork hole at the rear part of the truck;

step S2: the forward moving oil cylinder 4 is extended by pushing the forward moving backward control handle 28-11 forward, the portal frame assembly 5, the fork frame 50, the lifting oil cylinder 51, the fork 6 and the tilting oil cylinder 7 are moved to the foremost end together, and then the fork truck is driven to move forward by pushing the direction control handle 28-7 forward, so that the fork 6 is inserted into a fork hole at the rear part of the truck;

step S3: pressing the function switch 28-5, wherein the lamp of the function switch 28-5 is on;

step S4: by pushing up the lift and lower operating handle 28-10 forward, the lift cylinder 51 is retracted and the forklift is lifted up slowly until the frame 1 is aligned with the lower end of the fork hole section;

step S5: the forward moving oil cylinder 4 is contracted by pulling the forward moving control handle 28-11 backwards, and the fork 6 is fixed, so that the forklift body 2 is close to the rear part of the truck to the maximum extent;

step S6: the tilting oil cylinder 7 is contracted by pulling the tilting control handle 28-12 backwards, and the whole forklift rotates anticlockwise around the hinged part of the forward sliding frame 3 and the door frame component 5, so that the rear end of the forklift is tilted;

step S7: pressing the function switch 28-5 again, at this time, the lamp of the function switch 28-5 is turned off;

step S8: a forklift driver gets off the truck and hangs one end of the chain 9-1 at the two sides of the truck body 2 on the truck;

step S9: the chain switch key 280 is turned on, the chain tightening switch 282 is pressed, the inclined oil cylinder 7 extends, the rear end of the forklift descends until the chain 9-1 is completely tightened;

step S10: butting a signal lamp control cable at the rear end of the truck with a signal lamp control cable socket 25;

step S11: the key 280 is turned off and the key 280 is pulled out.

Example 2:

a truck-mounted forklift, a hydraulic system 9 also comprises a truck unloading operation system, which comprises the following steps,

step SS 1: disconnecting the signal lamp control cable at the rear end of the truck from the signal lamp control cable socket 25;

step SS 2: the chain switch key 280 is turned on, the chain release switch 281 is pressed, the inclined oil cylinder 7 contracts, and the whole forklift rotates anticlockwise around the hinged position of the forward sliding frame 3 and the door frame component 5, so that the rear end of the forklift is tilted until the chain 9-1 is completely loosened;

step SS 3: the driver releases the chain 9-1 at the two sides of the vehicle body 2 from the truck;

step SS 4: a driver gets on the forklift, sits on a forklift seat in a correct posture, ties up a safety belt, and puts down a guardrail; pressing the function switch 28-5, wherein the lamp of the function switch 28-5 is on;

step SS 5: by pushing the inclined operating handle 28-12 forward, the inclined oil cylinder 7 extends, and the whole forklift rotates clockwise around the hinged part of the forward sliding frame 3 and the forklift frame component 5, so that the rear end of the forklift descends;

step SS 6: the forward moving oil cylinder 4 is extended by pushing the forward moving and backward moving control handle 28-11 forward, and the fork 6 is fixed, so that the forklift body 2 is far away from the rear part of the truck to the maximum extent;

step SS 7: the lifting oil cylinder 51 is extended by pulling back to lift and descend the control handle 28-10, and the forklift is slowly put down until the front wheels 8 and the rear wheels of the driving system 21 land;

step SS 8: the forklift is driven to travel backwards through the rear pull direction control handle 28-7, so that the goods fork 6 is completely separated from the goods fork hole at the rear part of the forklift;

step SS 9: function switch 28-5 is pressed again, at which time the lights of function switch 28-5 are illuminated.

2. According to the truck-mounted forklift, the fork is inserted into the fork hole at the rear part of the truck through the hydraulic system 9, then one ends of the chains 9-1 at the two sides of the truck body 2 are hung on the truck until the chains 9-1 are completely tightened, so that the stability of the truck-mounted forklift in transportation along with the truck is ensured, and the truck-mounted forklift cannot swing and shake or even slide down to cause safety accidents when encountering bumpy road sections and up-down broken road sections.

The present invention has been described in connection with the accompanying drawings, and it is to be understood that the invention is not limited to the specific embodiments described above, but is intended to cover various insubstantial modifications of the invention based on the principles and technical solutions of the invention; the above-mentioned conception and technical solutions of the present invention may be directly applied to other fields without any improvement, and all of them are within the scope of the present invention.

Claims

1. The utility model provides a truck-mounted fork truck which characterized in that: comprises a frame (1), a body (2), a forward sliding frame (3), a forward oil cylinder (4), a portal frame component (5), a pallet fork (6), an inclined oil cylinder (7), front wheels (8), a hydraulic system (9) and a chain (9-1), wherein the body (2) is tightly connected with the rear part of the frame (1), the inner wall of the frame (1) is provided with a wheel rail (10), the two sides of the forward sliding frame (3) are in rolling connection with the wheel rail (10) through idler wheels, the cylinder end part of the forward oil cylinder (4) is connected with the rear end of the frame (1), the piston rod end part of the forward oil cylinder (4) is hinged with the front end of the forward sliding frame (3), the lower end of the portal frame component (5) is hinged with the front side of the forward sliding frame (3), the pallet fork (6) is connected with the portal frame component (5) through a pallet fork frame (50), and the pallet fork frame component (50) is connected with the portal frame component (5) through a lifting oil cylinder (51), the end part of a cylinder barrel of the inclined oil cylinder (7) is hinged with the upper end of the forward sliding frame (3), the end part of a piston rod of the inclined oil cylinder (7) is hinged with the rear end of the door frame component (5), the front wheel (8) is connected with the outer side of the front end of the frame (1), the hydraulic system (9) is installed in the vehicle body (2), and the chain (9-1) is connected with the two sides of the vehicle body (2).

2. An on-board forklift truck as claimed in claim 1, wherein: the front end of the frame (1) is provided with a front barrel seat (11), a supporting leg oil cylinder (12) is arranged in the front barrel seat (11), and supporting legs (13) driven by the supporting leg oil cylinder (12) are arranged at the front end of the front barrel seat (11) in a guiding manner.

3. An on-board forklift as claimed in claim 2, wherein: be equipped with a steering system (20), actuating system (21), control system (22), machine (23) and group battery (24) in automobile body (2), automobile body (2) front side is equipped with signal lamp control cable socket (25) and headlamp (26), automobile body (2) rear side is equipped with three-colour signal lamp (27), be equipped with control operation panel (28) in automobile body (2) upper end cockpit.

4. An on-board forklift as claimed in claim 3, wherein: the control operation platform (28) comprises an instrument (28-1), a turn light switch (28-2), a lighting lamp switch (28-3), a parking brake switch (28-4), a function switching switch (28-5), a horn button (28-6), a direction control handle (28-7), a key switch (28-8), an emergency power-off switch (28-9), a lifting and descending operation handle (28-10), a forward and backward moving operation handle (28-11), an inclined operation handle (28-12) and a supporting foot operation handle (28-13).

5. An on-board forklift as claimed in claim 1, wherein: the side surface of the vehicle body (2) is provided with a chain switch key (280), a chain loosening switch (281) and a chain tightening switch (282).

6. An on-board forklift as claimed in claim 1, wherein: the gantry assembly (5) comprises an outer gantry (52), an inner gantry (53), an outer chain (54) and an inner chain (55), the lower end of a cylinder barrel of the lifting oil cylinder (51) is connected with the lower end of the outer gantry (52), the end part of a piston rod of the lifting oil cylinder (51) is connected with the upper end of the inner gantry (52), the upper end of the inner gantry (53) is symmetrically provided with an upper chain wheel (53-1), the lower end of the inner gantry is symmetrically provided with a lower chain wheel (53-2), the outer chain (54) spans the upper chain wheel (53-1), the lower end of the outer chain is fixedly connected with the fork frame (50), and the upper end of the outer gantry (52) is fixedly connected with the outer gantry; the inner chain (55) strides over the lower end of the lower chain wheel (53-2) to be fixedly connected with the fork frame (50), and the upper end of the inner chain is fixedly connected with the outer door frame (52).