Automatic leveling system for telescopic folding arm pallet fork of forklift

Abstract

The invention discloses an automatic leveling system for a telescopic folding arm pallet fork of a forklift. The automatic leveling system comprises a leveling oil cylinder, a pallet fork overturning oil cylinder, a folding arm overturning oil cylinder, a one-way balance valve, a first two-way balance valve, a second two-way balance valve, a multi-way valve, a telescopic arm structure, a folding arm structure, a pallet fork assembly and a forklift body. A large arm of the telescopic arm structure is connected with the forklift body in the mode that the large arm can rotate around an A'point, the O 'end of the leveling oil cylinder is hinged to the forklift body, and the C' end of the leveling oil cylinder is hinged to the large arm. The O end of the pallet fork overturning oil cylinder and the head end of the folding arm structure are connected with the end of a telescopic auxiliary arm of the telescopic arm structure in the mode that the O end of the pallet fork overturning oil cylinder and the head end of the folding arm structure can rotate around the O point, the C end of the pallet fork overturning oil cylinder is hinged to the pallet fork assembly, and the pallet fork assembly is connected with the tail end of the folding arm structure in the mode that the pallet fork assembly can rotate around the A point. The automatic leveling device is high in flexibility during operation, and has an automatic leveling function aiming at different working conditions.

Description

Technical Field

[0001] The invention relates to a forklift, in particular to an automatic leveling system for a telescopic folding arm fork of a forklift. Background Art

[0002] At present, telescopic forklifts can be used for cargo insertion, palletizing, earthwork loading, unloading and other operations, and their accessories generally include large and small forks. However, the structure of the telescopic forklift limits the expansion of its functions. For example, the angle of the forklift is not flexible enough and it cannot operate at different angles. If the telescopic arm structure of the telescopic forklift itself is equipped with a folding arm, its operational flexibility can be enhanced. However, when the telescopic forklift has both a telescopic forklift and a folding arm, the existing automatic leveling solution for the fork will not be able to achieve automatic leveling of the fork, and automatic leveling of the fork will become a new problem. Therefore, an automatic double leveling system for the fork adapted to the telescopic folding arm forklift is urgently needed to be developed.

[0003] CN220056230U discloses a mechanical hydraulic leveling structure of a telescopic jib forklift, which includes a fork, an upper leveling oil cylinder, a telescopic jib boom, a chassis and a lower leveling oil cylinder, one end of the telescopic jib boom is hinged to the chassis, the fork is hinged to the other end of the telescopic jib boom, the two ends of the upper leveling oil cylinder are respectively connected to the fork and the telescopic jib boom, the two ends of the lower leveling oil cylinder are respectively connected to the chassis and the telescopic jib boom, the upper leveling oil cylinder is used to control the rotation of the fork relative to the telescopic jib boom, and the rod chamber and the rodless chamber of the lower leveling oil cylinder are respectively connected to the rod chamber and the rodless chamber of the upper leveling oil cylinder through an oil pipe to form a closed oil circuit. This structure has the effect of improving the stability of the leveling of the fork of the telescopic jib forklift, but it is only applicable to telescopic jib forklifts, not to telescopic folding arm forklifts. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an automatic leveling system for a forklift telescopic folding arm fork, which has a telescopic arm structure and a folding arm structure, has high flexibility during operation, and not only has the function of ensuring automatic leveling of the fork assembly during the telescopic arm structure variable amplitude operation, but also has the function of ensuring automatic leveling of the fork assembly during the folding arm operation.

[0005] The invention discloses an automatic leveling system for a telescopic folding arm fork of a forklift, comprising a leveling cylinder, a fork tilting cylinder, a folding arm tilting cylinder, a one-way balancing valve, a first two-way balancing valve, a second two-way balancing valve, a multi-way valve, a telescopic arm structure, a folding arm structure, a fork assembly and a forklift body; The upper arm of the telescopic arm structure is connected to the forklift body in a manner that it can rotate around point A', the O' end of the leveling cylinder is hinged to the forklift body, and the C' end of the leveling cylinder is hinged to the upper arm; the O end of the fork flip cylinder and the head end of the folding arm structure are both connected to the end of the telescopic auxiliary arm of the telescopic arm structure in a manner that they can rotate around point O, the C end of the fork flip cylinder is hinged to the fork assembly, and the fork assembly is connected to the tail end of the folding arm structure in a manner that it can rotate around point A; the A' point is located on the side of the leveling cylinder away from the fork flip cylinder, and the A point is located on the side of the fork flip cylinder away from the leveling cylinder; the two ends of the folding arm flip cylinder are respectively hinged to the folding arm structure and the telescopic arm structure; The oil port A1 of the multi-way valve is connected to the rod chamber oil port of the folding arm turning oil cylinder through the first two-way balancing valve; the oil port B1 of the multi-way valve is connected to the rodless chamber oil port of the folding arm turning oil cylinder through the first two-way balancing valve; The oil port A2 of the multi-way valve is connected to the rod chamber oil port of the leveling cylinder through the one-way balancing valve and to the rod chamber oil port of the fork flipping cylinder through the second two-way balancing valve; the oil port B2 of the multi-way valve is connected to the rodless chamber oil port of the leveling cylinder through the one-way balancing valve and to the rodless chamber oil port of the fork flipping cylinder through the second two-way balancing valve.

[0006] Further, the multi-way valve includes a second electrically-controlled reversing valve part, and the valve core movement of the second electrically-controlled reversing valve part can block both the oil port A2 and the oil port B2 of the multi-way valve, connect the oil port A2 of the multi-way valve with the high-pressure oil inlet circuit and the oil port B2 of the multi-way valve with the high-pressure oil return circuit, or connect the oil port A2 of the multi-way valve with the high-pressure oil return circuit and the oil port B2 of the multi-way valve with the high-pressure oil inlet circuit.

[0007] Furthermore, the multi-way valve also includes a first electrically controlled reversing valve part, and the valve core movement of the first electrically controlled reversing valve part can block both the oil port A1 and the oil port B1 of the multi-way valve, connect the oil port A1 of the multi-way valve with the high-pressure oil inlet circuit and the oil port B1 of the multi-way valve with the high-pressure oil return circuit, or connect the oil port A1 of the multi-way valve with the high-pressure oil return circuit and the oil port B1 of the multi-way valve with the high-pressure oil inlet circuit.

[0008] Furthermore, it also includes a system controller, wherein the system controller has an automatic leveling control program built therein, and the automatic leveling control program is configured as follows: Working condition a, in response to the automatic leveling control program being started, executing the automatic leveling command of the telescopic jib variable amplitude operation; controlling the valve core of the first electrically controlled reversing valve part to move to the middle position, so that the oil port A1 and the oil port B1 of the multi-way valve are both blocked; controlling the valve core of the second electrically controlled reversing valve part to move to the middle position, so that the oil port A2 and the oil port B2 of the multi-way valve are both blocked, so that the rod chamber oil port of the leveling oil cylinder and the rod chamber oil port of the fork flipping oil cylinder are connected through the one-way balancing valve and the second two-way balancing valve, and the rodless chamber oil port of the leveling oil cylinder and the rodless chamber oil port of the fork flipping oil cylinder are connected through the one-way balancing valve and the second two-way balancing valve; Working condition b, in response to the automatic leveling control program being started, the automatic leveling command for the folding angle increasing operation is executed; the valve core of the second electrically controlled reversing valve part is controlled to move upward, so that the oil port A1 of the multi-way valve is connected to the high-pressure oil return circuit and the oil port B1 of the multi-way valve is connected to the high-pressure oil inlet circuit, and the folding arm flip cylinder is extended; the valve core of the first electrically controlled reversing valve part is controlled to move downward, so that the oil port A2 of the multi-way valve is connected to the high-pressure oil inlet circuit and the oil port B2 of the multi-way valve is connected to the high-pressure oil return circuit, and the fork flip cylinder is shortened; Working condition c, in response to the automatic leveling control program being started, the automatic leveling command for the folding and retracting operation is executed; the valve core of the second electrically controlled reversing valve part is controlled to move downward, so that the oil port A1 of the multi-way valve is connected to the high-pressure oil inlet circuit and the oil port B1 of the multi-way valve is connected to the high-pressure oil return circuit, and the folding arm flip cylinder is shortened; the valve core of the first electrically controlled reversing valve part is controlled to move upward, so that the oil port A2 of the multi-way valve is connected to the high-pressure oil return circuit and the oil port B2 of the multi-way valve is connected to the high-pressure oil inlet circuit, and the fork flip cylinder is extended; Working condition d: in response to the closing of the automatic leveling control program, the valve core of the second electrically controlled reversing valve part is controlled to move upward or downward to shorten or extend the fork flip cylinder; the valve core of the second electrically controlled reversing valve part is controlled to move to the middle position to achieve that the oil port A2 and the oil port B2 of the multi-way valve are both blocked.

[0009] Furthermore, the cylinder diameters of the leveling cylinder and the fork tilting cylinder are the same, and the rod diameters of the two are also the same.

[0010] Furthermore, the multi-way valve also includes two first electro-hydraulic proportional control valve parts and two second electro-hydraulic proportional control valve parts, the two first electro-hydraulic proportional control valve parts are used to control the valve core movement of the first electrically controlled reversing valve part, and the two second electro-hydraulic proportional control valve parts are used to control the valve core movement of the second electrically controlled reversing valve part.

[0011] Furthermore, the fork assembly is integrated with an angle sensor, which is used to detect the angle between the fork assembly and the horizontal plane in real time and send a fork angle signal to the system controller. The system controller receives the fork angle signal. When the angle reaches a dangerous value, the system controller will cut off the power supply to stop the current operation.

[0012] The beneficial effects of the present invention are: (1) The present invention enables the forklift to have both a telescopic arm structure and a folding arm structure, which makes it highly flexible when performing operations such as cargo insertion, stacking, earthwork shoveling, and unloading. The telescopic arm structure and the folding arm structure cooperate to reduce the minimum operating height of the upper end of the fork and increase the operable range and operating amplitude. In addition, two different leveling control mechanisms are provided to match the telescopic arm structure and the folding arm structure, which not only have the function of ensuring the automatic leveling of the fork assembly when the telescopic arm structure changes amplitude, but also have the function of ensuring the automatic leveling of the fork assembly when the folding arm is in operation.

[0013] (2) The present invention also has a safety protection function and can also shield the automatic leveling function of the fork assembly when only the arm is folded. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration: Figure 1 It is a schematic diagram of the structural principle of the present invention; Figure 2 This is a schematic diagram of the structural arrangement of the present invention (the angle between the telescopic arm structure and the horizontal plane is 0°); Figure 3 This is a schematic diagram of the structural arrangement of the present invention (the angle between the telescopic arm structure and the horizontal plane is 50°).

[0015] The following are marked in the accompanying drawings: 1-leveling cylinder, 2-fork tilting cylinder, 3-folding arm tilting cylinder, 4-one-way balancing valve, 5-first two-way balancing valve, 6-second two-way balancing valve, 7-multi-way valve, 701-first electric control reversing valve part, 702-second electric control reversing valve part, 703-first electro-hydraulic proportional control valve part, 704-second electro-hydraulic proportional control valve part, 801-high-pressure oil inlet, 802-high-pressure oil return, 901-low-pressure oil inlet, 902-low-pressure oil return; 10-telescopic arm structure, 1001-big arm, 1002-telescopic auxiliary arm, 11-folding arm structure, 12-fork assembly. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0017] like Figure 1-Figure 3 As shown, an automatic leveling system for a telescopic folding arm fork of a forklift in this embodiment includes a leveling cylinder 1, a fork flipping cylinder 2, a folding arm flipping cylinder 3, a one-way balancing valve 4, a first two-way balancing valve 5, a second two-way balancing valve 6, a multi-way valve 7, a telescopic arm structure 10, a folding arm structure 11, a fork assembly 12 and a forklift body; The upper arm 1001 of the telescopic arm structure 10 is connected to the forklift body in a manner that it can rotate around point A', the O' end of the leveling cylinder 1 is hinged to the forklift body, and the C' end of the leveling cylinder 1 is hinged to the upper arm 1001; the O end of the fork flip cylinder 2 and the head end of the folding arm structure 11 are both connected to the end of the telescopic auxiliary arm 1002 of the telescopic arm structure 10 in a manner that they can rotate around point O, the C end of the fork flip cylinder 2 is hinged to the fork assembly 12, and the fork assembly 12 is connected to the folding arm structure 1 in a manner that it can rotate around point A. 1; the A' point is located on the side of the leveling cylinder 1 away from the fork flip cylinder 2, and the A point is located on the side of the fork flip cylinder 2 away from the leveling cylinder 1; the two ends of the folding arm flip cylinder 3 are respectively hinged to the folding arm structure 11 and the telescopic arm structure 10, specifically: the E end of the folding arm flip cylinder 3 is hinged to the folding arm structure 11, the telescopic auxiliary arm 1002 of the telescopic arm structure 10 is provided with an extended mounting portion extending toward the side away from the folding arm structure 11, and the F end of the folding arm flip cylinder 3 is hinged to the extended mounting portion of the telescopic auxiliary arm 1002; The oil port A1 of the multi-way valve 7 is connected to the rod chamber oil port of the folding arm turning cylinder 3 through the first two-way balancing valve 5; the oil port B1 of the multi-way valve 7 is connected to the rodless chamber oil port of the folding arm turning cylinder 3 through the first two-way balancing valve 5; The oil port A2 of the multi-way valve 7 is connected to the rod chamber oil port of the leveling cylinder 1 through the one-way balancing valve 4 and to the rod chamber oil port of the fork flipping cylinder 2 through the second two-way balancing valve 6; the oil port B2 of the multi-way valve 7 is connected to the rodless chamber oil port of the leveling cylinder 1 through the one-way balancing valve 4 and to the rodless chamber oil port of the fork flipping cylinder 2 through the second two-way balancing valve 6.

[0018] A luffing device is provided between the telescopic arm structure 10 and the forklift body, and the luffing device and the forklift body are not shown in the figure. The luffing device may be a luffing cylinder in the prior art, and the luffing cylinder can change the angle of the upper arm 1001 of the telescopic arm structure 10 relative to the horizontal plane (i.e., the luffing), so that the telescopic arm structure 10, the folding arm structure 11 and the fork assembly 12 as a whole rotate upward or downward with point A' as the rotation center.

[0019] The forklift has both a telescopic arm structure 10 and a folding arm structure 11, which makes it more flexible when performing operations such as cargo insertion, stacking, earth shoveling, and unloading boxes. The cooperation of the telescopic arm structure 10 and the folding arm structure 11 can reduce the minimum operating height of the upper end of the fork and increase the operable range and amplitude.

[0020] The one-way balancing valve 4 is integrated on the leveling cylinder 1 to balance the load of the leveling cylinder 1 and lock it. The second two-way balancing valve 6 and the first two-way balancing valve 5 are respectively integrated on the fork tilting cylinder 2 and the folding arm tilting cylinder 3 to balance the load of the fork tilting cylinder 2 and the folding arm tilting cylinder 3 and lock them. The multi-way valve 7 can distribute the flow to each cylinder to ensure the automatic leveling function of the fork.

[0021] The hydraulic oil circuit composed of the leveling cylinder 1, the fork tilting cylinder 2, the one-way balancing valve 4, the second two-way balancing valve 6 and the multi-way valve 7. When the oil port A2 and the oil port B2 of the multi-way valve 7 are blocked, if the telescopic arm structure 10 rotates upward under the drive of the variable amplitude device, it will drive the piston rod of the leveling cylinder 1 to move and extend it, so that the oil in the rod cavity of the leveling cylinder 1 is pressed into the rod cavity of the fork tilting cylinder 2, and the oil in the rodless cavity of the fork tilting cylinder 2 flows to the rodless cavity of the leveling cylinder 1, driving the piston rod of the fork tilting cylinder 2 to move and shorten it. If the telescopic arm structure 10 rotates downward under the drive of the variable amplitude device, it will drive the piston rod of the leveling cylinder 1 to move and shorten it, so that the oil in the rodless chamber of the leveling cylinder 1 is pressed into the rodless chamber of the fork flip cylinder 2, and the oil in the rod chamber of the fork flip cylinder 2 flows to the rod chamber of the leveling cylinder 1, driving the piston rod of the fork flip cylinder 2 to move and extend it. In summary, it can be achieved that when the piston rod of the leveling cylinder 1 moves, the piston rod of the fork flip cylinder 2 is linked in the opposite direction, and the linkage between the fork flip cylinder 2 and the leveling cylinder 1 can make the fork assembly 12 rotate downward or upward with point A as the rotation center, compensating for the angle of the folding arm structure 11 and the fork assembly 12 rotating upward or downward with point A' as the rotation center due to the angle change of the telescopic arm structure 10, so that the fork assembly 12 automatically maintains the original angle basically unchanged when the telescopic arm structure 10 changes amplitude. If the fork assembly is in a horizontal state in the initial state, the fork assembly 12 will always maintain a substantially horizontal posture when the telescopic arm structure 10 changes its amplitude.

[0022] In addition, the hydraulic oil circuit composed of the folding arm turning cylinder 3, the first two-way balance valve 5 and the multi-way valve 7, when the oil port A1 and the oil port B1 of the multi-way valve 7 are opened, the multi-way valve 7 can drive the fork assembly 12 to rotate upward or downward with the point O as the rotation center when the high-pressure hydraulic oil is provided to the folding arm turning cylinder 3. At this time, the oil port A2 and the oil port B2 of the multi-way valve 7 are also opened, and the multi-way valve 7 will simultaneously provide high-pressure hydraulic oil to the fork turning cylinder 2, so that the fork turning cylinder 2 drives the fork assembly 12 to rotate downward or upward with the point A as the rotation center, compensating for the angle of the fork assembly 12 rotating upward or downward with the point O as the rotation center caused by the driving of the folding arm turning cylinder 3, so that the fork assembly 12 can automatically maintain the original angle basically unchanged when the folding arm structure 11 changes its amplitude. If the fork assembly in the initial state is in a horizontal state, then when the telescopic arm structure 10 changes its amplitude, the fork assembly 12 will always maintain a basically horizontal posture.

[0023] Finally, the automatic leveling function can also be turned off, that is, by isolating the linkage leveling of the fork flip cylinder 2 and the folding arm flip cylinder 3, so that when high-pressure hydraulic oil is provided to the folding arm flip cylinder 3 through the multi-way valve 7, the fork assembly 12 can be driven to rotate upward or downward with point O as the rotation center, thereby changing the angle of the fork assembly 12 and realizing picking up goods at different angles.

[0024] In this embodiment, the multi-way valve 7 includes a second electrically controlled reversing valve unit 702, and the valve core movement of the second electrically controlled reversing valve unit 702 can block the oil port A2 and the oil port B2 of the multi-way valve 7, connect the oil port A2 of the multi-way valve 7 with the high-pressure oil inlet circuit 801 and the oil port B2 of the multi-way valve 7 with the high-pressure oil return circuit 802, or connect the oil port A2 of the multi-way valve 7 with the high-pressure oil return circuit 802 and the oil port B2 of the multi-way valve 7 with the high-pressure oil inlet circuit 801.

[0025] In this embodiment, the multi-way valve 7 also includes a first electrically controlled reversing valve unit 701, and the valve core movement of the first electrically controlled reversing valve unit 701 can block the oil port A1 and the oil port B1 of the multi-way valve 7, connect the oil port A1 of the multi-way valve 7 with the high-pressure oil inlet circuit 801 and the oil port B1 of the multi-way valve 7 with the high-pressure oil return circuit 802, or connect the oil port A1 of the multi-way valve 7 with the high-pressure oil return circuit 802 and the oil port B1 of the multi-way valve 7 with the high-pressure oil inlet circuit 801.

[0026] The valve core of the first electrically controlled reversing valve unit 701 moves to the middle position, and the oil ports A1 and B1 of the multi-way valve 7 are blocked. The valve core of the first electrically controlled reversing valve unit 701 moves downward, and the oil port A2 of the multi-way valve 7 is connected to the high-pressure oil inlet 801, and the oil port B2 of the multi-way valve 7 is connected to the high-pressure oil return 802. The valve core of the first electrically controlled reversing valve unit 701 moves upward, and the oil port A2 of the multi-way valve 7 is connected to the high-pressure oil return 802, and the oil port B2 of the multi-way valve 7 is connected to the high-pressure oil inlet 801.

[0027] The valve core of the second electrically controlled reversing valve unit 702 moves to the middle position, and the oil ports A2 and B2 of the multi-way valve 7 are blocked. The valve core of the first electrically controlled reversing valve unit 701 moves downward, and the oil port A2 of the multi-way valve 7 is connected to the high-pressure oil inlet 801, and the oil port B2 of the multi-way valve 7 is connected to the high-pressure oil return 802. The valve core of the first electrically controlled reversing valve unit 701 moves upward, and the oil port A2 of the multi-way valve 7 is connected to the high-pressure oil return 802, and the oil port B2 of the multi-way valve 7 is connected to the high-pressure oil inlet 801.

[0028] The one-way balancing valve 4 has a one-way valve part, a control chamber, a pressure diaphragm and a one-way throttle valve part. The one-way balancing valve 4 has oil ports C1, V1, C2 and V2. The oil ports V1 and V2 of the one-way balancing valve 4 are respectively connected to the rodless chamber and the rod chamber of the leveling cylinder 1. The oil port C2 of the one-way balancing valve 4 is also connected to the oil port A1 of the second two-way balancing valve 6 and the oil port A2 of the multi-way valve 7. The oil port C1 of the one-way balancing valve 4 is also connected to the oil port A2 of the second two-way balancing valve 6 and the oil port B2 of the multi-way valve 7. The one-way valve part of the one-way balancing valve 4 allows the hydraulic oil to flow from the oil port C1 of the one-way balancing valve 4 to its oil port V1. The oil port C1 of the one-way balancing valve 4 leads to the control chamber. The oil ports C2 and V2 of the one-way balancing valve 4 lead to the control chamber through the one-way throttle valve part. After the high-pressure hydraulic oil of the oil ports C1, C2 and V2 of the one-way balancing valve 4 enters the control chamber, it acts on the pressure diaphragm to enable the hydraulic oil to flow in both directions between the oil port C1 of the one-way balancing valve 4 and its oil port V1.

[0029] The second two-way balancing valve 6 has two one-way valve parts, two control chambers and two pressure diaphragms. The second two-way balancing valve 6 has oil ports A1, B1, A2 and B2. The oil ports B1 and B2 of the second two-way balancing valve 6 are respectively connected to the rod chamber and the rodless chamber of the fork tilting cylinder 2. The oil port A1 of the second two-way balancing valve 6 is also connected to the oil port C2 of the one-way balancing valve 4 and the oil port A2 of the multi-way valve 7. The oil port A2 of the second two-way balancing valve 6 is also connected to the oil port C1 of the one-way balancing valve 4 and the oil port B2 of the multi-way valve 7. One of the one-way valve parts of the second two-way balancing valve 6 allows the hydraulic oil to flow from the oil port A2 of the second two-way balancing valve 6 to its oil port B2, and the other one-way valve part allows the hydraulic oil to flow from the oil port A1 of the second two-way balancing valve 6 to its oil port B1. One of the control chambers and the pressure diaphragm of the second two-way balancing valve 6 is located between the oil port A2 and the oil port B2 of the second two-way balancing valve 6. The oil ports A2, B2 and A1 of the second two-way balancing valve 6 are all connected to the control chamber. After the high-pressure hydraulic oil of the oil ports A2, B2 and A1 of the second two-way balancing valve 6 enters the control chamber, it acts on the pressure diaphragm to enable the hydraulic oil to flow bidirectionally between the oil port A2 and the oil port B2 of the second two-way balancing valve 6. The other control chamber and the pressure diaphragm are located between the oil port A1 and the oil port B1 of the second two-way balancing valve 6. The oil ports A1, B1 and A2 of the second two-way balancing valve 6 are all connected to the control chamber. After the high-pressure hydraulic oil of the oil ports A1, B1 and A2 of the second two-way balancing valve 6 enters the control chamber, it acts on the pressure diaphragm to enable the hydraulic oil to flow bidirectionally between the oil port A1 and the oil port B1 of the second two-way balancing valve 6.

[0030] The first two-way balancing valve 5 has two one-way valve parts, two control chambers and two pressure diaphragms. The first two-way balancing valve 5 has oil ports A1, B1, A2 and B2. The oil ports B1 and B2 of the first two-way balancing valve 5 are respectively connected to the rodless chamber and the rod chamber of the folding arm turning cylinder 3. The oil port A1 of the first two-way balancing valve 5 is connected to the oil port B1 of the multi-way valve 7, and the oil port A2 of the first two-way balancing valve 5 is connected to the oil port A1 of the multi-way valve 7. One of the one-way valve parts of the first two-way balancing valve 5 allows the hydraulic oil to flow from the oil port A2 of the first two-way balancing valve 5 to its oil port B2, and the other one-way valve part allows the hydraulic oil to flow from the oil port A1 of the second two-way balancing valve 6 to its oil port B1. One of the control chambers and the pressure diaphragm of the first two-way balancing valve 5 is located between the oil port A2 and the oil port B2 of the first two-way balancing valve 5. The oil ports A2, B2 and A1 of the first two-way balancing valve 5 are all connected to the control chamber. After the high-pressure hydraulic oil of the oil ports A2, B2 and A1 of the first two-way balancing valve 5 enters the control chamber, it acts on the pressure diaphragm to enable the hydraulic oil to flow bidirectionally between the oil port A2 and the oil port B2 of the first two-way balancing valve 5. The other control chamber and the pressure diaphragm are located between the oil port A1 and the oil port B1 of the first two-way balancing valve 5. The oil ports A1, B1 and A2 of the first two-way balancing valve 5 are all connected to the control chamber. After the high-pressure hydraulic oil of the oil ports A1, B1 and A2 of the first two-way balancing valve 5 enters the control chamber, it acts on the pressure diaphragm to enable the hydraulic oil to flow bidirectionally between the oil port A1 and the oil port B1 of the first two-way balancing valve 5.

[0031] In this embodiment, a system controller is also included, and the system controller has an automatic leveling control program built in it. The automatic leveling control program is configured as follows: Working condition a, in response to the automatic leveling control program being started, the automatic leveling command of the telescopic jib 1002 variable amplitude operation is executed; the valve core of the first electrically controlled reversing valve unit 701 is controlled to move to the middle position, so that the oil port A1 and the oil port B1 of the multi-way valve 7 are both blocked; the valve core of the second electrically controlled reversing valve unit 702 is controlled to move to the middle position, so that the oil port A2 and the oil port B2 of the multi-way valve 7 are both blocked, so that the rod chamber oil port of the leveling cylinder 1 is connected to the rod chamber oil port of the fork flipping cylinder 2 through the one-way balancing valve 4 and the second two-way balancing valve 6, and the rodless chamber oil port of the leveling cylinder 1 is connected to the rodless chamber oil port of the fork flipping cylinder 2 through the one-way balancing valve 4 and the second two-way balancing valve 6.

[0032] Under the above working condition a, the preferred solution is that the cylinder diameters of the leveling cylinder 1 and the fork tilting cylinder 2 are the same, and the rod diameters of the two are also the same. At this time, when the oil ports A2 and B2 of the multi-way valve 7 are blocked, if the telescopic arm structure 10 rotates upward under the drive of the variable amplitude device, it will drive the piston rod of the leveling cylinder 1 to move and extend it, so that the oil in the rod chamber of the leveling cylinder 1 is pressed into the rod chamber of the fork tilting cylinder 2, and the oil in the rodless chamber of the fork tilting cylinder 2 flows to the rodless chamber of the leveling cylinder 1, driving the piston rod of the fork tilting cylinder 2 to move and shorten it. If the telescopic arm structure 10 rotates downward under the drive of the variable amplitude device, it will drive the piston rod of the leveling cylinder 1 to move and shorten it, so that the oil in the rodless chamber of the leveling cylinder 1 is pressed into the rodless chamber of the fork flip cylinder 2, and the oil in the rod chamber of the fork flip cylinder 2 flows to the rod chamber of the leveling cylinder 1, driving the piston rod of the fork flip cylinder 2 to move and extend it. In summary, it can be achieved that when the piston rod of the leveling cylinder 1 moves, the piston rod of the fork flip cylinder 2 is linked in the opposite direction, and the linkage between the fork flip cylinder 2 and the leveling cylinder 1 can make the fork assembly 12 rotate downward or upward with point A as the rotation center, compensating for the angle of the folding arm structure 11 and the fork assembly 12 rotating upward or downward with point A' as the rotation center due to the angle change of the telescopic arm structure 10, so that the fork assembly 12 automatically maintains the original angle basically unchanged when the telescopic arm structure 10 changes amplitude. If the fork assembly is in a horizontal state in the initial state, the fork assembly 12 will always maintain a substantially horizontal posture when the telescopic arm structure 10 changes its amplitude.

[0033] Working condition b, in response to the automatic leveling control program being started, the automatic leveling command for the folding angle increase operation is executed; the valve core of the second electrically controlled reversing valve unit 702 is controlled to move upward, so that the oil port A1 of the multi-way valve 7 is connected to the high-pressure return oil circuit 802 and the oil port B1 of the multi-way valve 7 is connected to the high-pressure inlet oil circuit 801, and the folding arm flip cylinder 3 is extended; the valve core of the first electrically controlled reversing valve unit 701 is controlled to move downward, so that the oil port A2 of the multi-way valve 7 is connected to the high-pressure inlet oil circuit 801 and the oil port B2 of the multi-way valve 7 is connected to the high-pressure return oil circuit 802, and the fork flip cylinder 2 is shortened.

[0034] Working condition c, in response to the automatic leveling control program being started, the automatic leveling command for the folding and retracting angle operation is executed; the valve core of the second electrically controlled reversing valve unit 702 is controlled to move downward, so that the oil port A1 of the multi-way valve 7 is connected to the high-pressure oil inlet circuit 801 and the oil port B1 of the multi-way valve 7 is connected to the high-pressure oil return circuit 802, and the folding arm flip cylinder 3 is shortened; the valve core of the first electrically controlled reversing valve unit 701 is controlled to move upward, so that the oil port A2 of the multi-way valve 7 is connected to the high-pressure oil return circuit 802 and the oil port B2 of the multi-way valve 7 is connected to the high-pressure oil inlet circuit 801, and the fork flip cylinder 2 is extended.

[0035] Under the above-mentioned working conditions b and c, the preferred solution is that the multi-way valve 7 also includes two first electro-hydraulic proportional control valve parts 703 and two second electro-hydraulic proportional control valve parts 704, the two first electro-hydraulic proportional control valve parts 703 are used to control the valve core movement of the first electrically controlled reversing valve part 701, and the two second electro-hydraulic proportional control valve parts 704 are used to control the valve core movement of the second electrically controlled reversing valve part 702. Specifically, two of the oil ports of the two first electro-hydraulic proportional control valve parts 703 are respectively connected to the oil inlet of the low-pressure oil inlet circuit 901 and the low-pressure oil return circuit 902, and one of the oil ports of the two first electro-hydraulic proportional control valve parts 703 is respectively connected to the control chambers on the upper and lower sides of the valve core of the first electro-hydraulic proportional control valve part 703, and the valve core movement of the first electro-hydraulic proportional control valve part 703 is controlled by electric current, thereby changing the hydraulic oil pressure flowing to the upper and lower sides of the valve core of the first electric-controlled reversing valve part 701, thereby realizing the coordinated control of the valve core movement of the first electric-controlled reversing valve part 701 by electric current and hydraulic pressure, and then realizing the change of the size and direction of the hydraulic oil flowing out of the oil ports A2 and B2 of the first electric-controlled reversing valve part 701. The working principle of the second electro-hydraulic proportional control valve part 704 is the same as that of the first electro-hydraulic proportional control valve part 703, which will not be repeated here. To summarize, the two first electro-hydraulic proportional control valve parts 703 and the two second electro-hydraulic proportional control valve parts 704 can be used to change the size and direction of the hydraulic oil flowing out of the oil ports A2 and B2 of the first electrically controlled reversing valve part 701, as well as to change the size and direction of the hydraulic oil flowing out of the oil ports A1 and B1 of the first electrically controlled reversing valve part 701, thereby being able to execute the automatic leveling command for the folding angle increase operation in working condition b and the automatic leveling command for the folding angle reduction operation in working condition c.

[0036] The leveling cylinder 1 is configured so that its output power is smaller than the variable amplitude load, that is, the piston rod of the leveling cylinder 1 can only be driven to move by the rotation of the upper arm 1001 of the telescopic arm structure 10, but cannot be driven to rotate the upper arm 1001 of the telescopic arm structure 10 by the oil pressure difference between the rodless chamber and the rod chamber in the leveling cylinder 1.

[0037] Under the above working conditions b and c, after the oil ports A1 and B1 of the multi-way valve 7 are opened, the multi-way valve 7 can drive the fork assembly 12 to rotate upward or downward with point O as the rotation center when providing high-pressure hydraulic oil to the folding arm tilting cylinder 3. At this time, the oil ports A2 and B2 of the multi-way valve 7 are also opened, and the multi-way valve 7 will simultaneously provide high-pressure hydraulic oil to the fork tilting cylinder 2, so that the fork tilting cylinder 2 drives the fork assembly 12 to rotate downward or upward with point A as the rotation center, compensating for the angle of the fork assembly 12 rotating upward or downward with point O as the rotation center caused by the driving of the folding arm tilting cylinder 3, so that the fork assembly 12 can automatically maintain the original angle basically unchanged when the folding arm structure 11 changes its amplitude. If the fork assembly is in a horizontal state in the initial state, then when the telescopic arm structure 10 changes its amplitude, the fork assembly 12 will always maintain a basically horizontal posture.

[0038] The flow is automatically distributed to the fork flip cylinder 2 and the folding arm flip cylinder 3 through two first electro-hydraulic proportional control valve parts 703 and two second electro-hydraulic proportional control valve parts 704. The specific flow distribution principle is as follows: Assuming that the cross-sectional area of ​​the rodless cavity of the fork flip cylinder 2 is S, the cross-sectional area of ​​the rod cavity is S1, and the stroke is L, when the folding arm structure 11 and the fork assembly 12 rotate in opposite directions and at the same speed, the time for the fork flip cylinder 2 to complete the stroke is t, the flow required for extension is V1, and the flow required for retraction is V2; Assuming that the cross-sectional area of ​​the rodless cavity of the folding arm flip cylinder 3 is S', the cross-sectional area of ​​the rod cavity is S1', and the stroke is L', when the folding arm structure 11 and the fork assembly 12 rotate in opposite directions and at the same speed, the time for the folding arm flip cylinder 3 to complete the stroke is t', the flow required for extension is V1', and the flow required for retraction is V2'; then the following relationship exists when the folding arm structure 11 and the fork assembly 12 rotate in opposite directions and at the same speed: 1. S, S1, S', S1', L, L' are known quantities; 2. t = t'; 3. S1·L / V2=t=t'=S'·L' / V1'that is, V1'=V2·S'·L' / S1·L 4. S·L / V1=t=t'=S1'·L' / V2'that is, V2'=V1·S1'·L' / S·L Therefore, by setting the extension flow V1' of the folding arm turning cylinder 3 and the retraction flow V2 of the fork turning cylinder 2 according to the relationship V1'=V2·S'·L' / S1·L, the fork assembly 12 can be turned downward at the same angle when the folding arm structure 11 is turned upward; by setting the retraction flow V2' of the folding arm turning cylinder 3 and the extension flow V1 of the fork turning cylinder 2 according to the relationship V2'=V1·S1'·L' / S·L, the fork assembly 12 can be turned upward at the same angle when the folding arm structure 11 is turned downward, thereby realizing automatic leveling of the fork.

[0039] Working condition d: in response to the closing of the automatic leveling control program, the valve core of the second electrically-controlled reversing valve unit 702 is controlled to move upward or downward to shorten or extend the fork flip cylinder 2; the valve core of the second electrically-controlled reversing valve unit 702 is controlled to move to the middle position, so that the oil port A2 and the oil port B2 of the multi-way valve 7 are both blocked.

[0040] The automatic leveling system of the telescopic folding arm fork of the forklift is provided with an operation switch. Under the above-mentioned working condition d, the operation switch is operated to send a shutdown signal to the system controller, and the automatic leveling control program is turned off. The automatic leveling function can be turned off, that is, by isolating the linkage leveling of the fork flip cylinder 2 and the folding arm flip cylinder 3, when high-pressure hydraulic oil is provided to the folding arm flip cylinder 3 through the multi-way valve 7, the fork assembly 12 can be driven to rotate upward or downward with point O as the rotation center, thereby changing the angle of the fork assembly 12, thereby realizing picking up goods at different angles.

[0041] In this embodiment, an angle sensor is integrated on the fork assembly 12. The angle sensor is used to detect the angle between the fork assembly 12 and the horizontal plane in real time, and send a fork angle signal to the system controller. The system controller receives the fork angle signal. When the angle reaches a dangerous value, the system controller will cut off the power supply to stop the current operation. Specifically, the angle sensor detects the angle between the fork assembly 12 and the horizontal plane in real time, and sends a fork angle signal to the system controller. After receiving the fork angle signal, the system controller determines whether the angle is within a preset angle range. If the angle is not within the preset angle range, it is considered that the angle has reached a dangerous value, and the system controller will cut off the power supply to stop the current operation to ensure the safety of the operation. If the angle is within the preset angle range, it is considered that the angle has not reached a dangerous value and normal operation can be performed.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An automatic leveling system for a telescopic folding arm fork of a forklift, characterized in that: It comprises a leveling cylinder (1), a fork tilting cylinder (2), a folding arm tilting cylinder (3), a one-way balancing valve (4), a first two-way balancing valve (5), a second two-way balancing valve (6), a multi-way valve (7), a telescopic arm structure (10), a folding arm structure (11), a fork assembly (12) and a forklift body; The upper arm (1001) of the telescopic arm structure (10) is connected to the forklift body in a manner that allows it to rotate around point A'; the O' end of the leveling cylinder (1) is hinged to the forklift body; and the C' end of the leveling cylinder (1) is hinged to the upper arm (1001); the O end of the fork flipping cylinder (2) and the head end of the folding arm structure (11) are both connected to the end of the telescopic auxiliary arm (1002) of the telescopic arm structure (10) in a manner that allows it to rotate around point O; The C end of the oil cylinder (2) is hinged to the fork assembly (12), and the fork assembly (12) is connected to the tail end of the folding arm structure (11) in a manner that it can rotate around point A; the point A' is located on the side of the leveling oil cylinder (1) away from the fork tilting oil cylinder (2), and the point A is located on the side of the fork tilting oil cylinder (2) away from the leveling oil cylinder (1); the two ends of the folding arm tilting oil cylinder (3) are respectively hinged to the folding arm structure (11) and the telescopic arm structure (10); The oil port A1 of the multi-way valve (7) is connected to the rod chamber oil port of the folding arm turning oil cylinder (3) through the first two-way balancing valve (5); the oil port B1 of the multi-way valve (7) is connected to the rodless chamber oil port of the folding arm turning oil cylinder (3) through the first two-way balancing valve (5); The oil port A2 of the multi-way valve (7) is simultaneously connected to the rod chamber oil port of the leveling cylinder (1) through the one-way balancing valve (4) and to the rod chamber oil port of the fork tilting cylinder (2) through the second two-way balancing valve (6); the oil port B2 of the multi-way valve (7) is simultaneously connected to the rodless chamber oil port of the leveling cylinder (1) through the one-way balancing valve (4) and to the rodless chamber oil port of the fork tilting cylinder (2) through the second two-way balancing valve (6).

2. The automatic leveling system for telescopic folding arm forks of forklifts according to claim 1 is characterized in that: The multi-way valve (7) comprises a second electrically controlled reversing valve part (702), and the movement of the valve core of the second electrically controlled reversing valve part (702) can block both the oil port A2 and the oil port B2 of the multi-way valve (7), enable the oil port A2 of the multi-way valve (7) to be connected to the high-pressure oil inlet circuit (801) and the oil port B2 of the multi-way valve (7) to be connected to the high-pressure oil return circuit (802), or enable the oil port A2 of the multi-way valve (7) to be connected to the high-pressure oil return circuit (802) and the oil port B2 of the multi-way valve (7) to be connected to the high-pressure oil inlet circuit (801).

3. The automatic leveling system for telescopic folding arm forks of forklifts according to claim 2 is characterized in that: The multi-way valve (7) further comprises a first electrically controlled reversing valve unit (701), wherein the movement of the valve core of the first electrically controlled reversing valve unit (701) can block both the oil port A1 and the oil port B1 of the multi-way valve (7), enable the oil port A1 of the multi-way valve (7) to communicate with the high-pressure oil inlet circuit (801) and the oil port B1 of the multi-way valve (7) to communicate with the high-pressure oil return circuit (802), or enable the oil port A1 of the multi-way valve (7) to communicate with the high-pressure oil return circuit (802) and the oil port B1 of the multi-way valve (7) to communicate with the high-pressure oil inlet circuit (801).

4. The automatic leveling system for telescopic folding arm forks of a forklift according to claim 3 is characterized in that: The system controller also includes an automatic leveling control program built into the system controller, and the automatic leveling control program is configured as follows: Working condition a: in response to the automatic leveling control program being started, the telescopic jib (1002) automatic leveling command for variable amplitude operation is executed; the valve core of the first electrically controlled reversing valve unit (701) is controlled to move to a middle position, so that the oil ports A1 and B1 of the multi-way valve (7) are both blocked; the valve core of the second electrically controlled reversing valve unit (702) is controlled to move to a middle position, so that the oil ports A2 and B2 of the multi-way valve (7) are both blocked, so that the rod chamber oil port of the leveling cylinder (1) is connected to the rod chamber oil port of the fork tilting cylinder (2) through the one-way balancing valve (4) and the second two-way balancing valve (6), and the rodless chamber oil port of the leveling cylinder (1) is connected to the rodless chamber oil port of the fork tilting cylinder (2) through the one-way balancing valve (4) and the second two-way balancing valve (6); Working condition b: in response to the automatic leveling control program being started, the automatic leveling command for the folding angle increasing operation is executed; the valve core of the second electrically controlled reversing valve unit (702) is controlled to move upward, so that the oil port A1 of the multi-way valve (7) is connected to the high-pressure oil return circuit (802) and the oil port B1 of the multi-way valve (7) is connected to the high-pressure oil inlet circuit (801), and the folding arm flip cylinder (3) is extended; the valve core of the first electrically controlled reversing valve unit (701) is controlled to move downward, so that the oil port A2 of the multi-way valve (7) is connected to the high-pressure oil inlet circuit (801) and the oil port B2 of the multi-way valve (7) is connected to the high-pressure oil return circuit (802), and the fork flip cylinder (2) is shortened; Working condition c: in response to the automatic leveling control program being started, the automatic leveling command for the folding and retracting operation is executed; the valve core of the second electrically controlled reversing valve unit (702) is controlled to move downward, so that the oil port A1 of the multi-way valve (7) is connected to the high-pressure oil inlet circuit (801) and the oil port B1 of the multi-way valve (7) is connected to the high-pressure oil return circuit (802), and the folding arm flip cylinder (3) is shortened; the valve core of the first electrically controlled reversing valve unit (701) is controlled to move upward, so that the oil port A2 of the multi-way valve (7) is connected to the high-pressure oil return circuit (802) and the oil port B2 of the multi-way valve (7) is connected to the high-pressure oil inlet circuit (801), and the fork flip cylinder (2) is extended; Working condition d: in response to the automatic leveling control program being closed, the valve core of the second electrically controlled reversing valve unit (702) is controlled to move upward or downward, so as to shorten or lengthen the fork tilting cylinder (2); the valve core of the second electrically controlled reversing valve unit (702) is controlled to move to a neutral position, so that both the oil port A2 and the oil port B2 of the multi-way valve (7) are blocked.

5. The automatic leveling system for telescopic folding arm forks of a forklift according to claim 4, characterized in that: The cylinder diameters of the leveling cylinder (1) and the fork tilting cylinder (2) are the same, and the rod diameters of the two are also the same.

6. The automatic leveling system for telescopic folding arm forks of a forklift according to claim 4, characterized in that: The multi-way valve (7) further comprises two first electro-hydraulic proportional control valve parts (703) and two second electro-hydraulic proportional control valve parts (704), wherein the two first electro-hydraulic proportional control valve parts (703) are used to control the movement of the valve core of the first electrically controlled reversing valve part (701), and the two second electro-hydraulic proportional control valve parts (704) are used to control the movement of the valve core of the second electrically controlled reversing valve part (702).

7. The automatic leveling system for telescopic folding arm forks of a forklift according to claim 4, characterized in that: The fork assembly (12) is integrated with an angle sensor, which is used to detect the angle between the fork assembly (12) and a horizontal plane in real time and send a fork angle signal to a system controller. The system controller receives the fork angle signal. When the angle reaches a dangerous value, the system controller cuts off the power supply to stop the current operation.

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