Pallet forklift hydraulic system

Abstract

The utility model discloses a hydraulic system of a tray forklift, which particularly relates to the technical field of forklifts and comprises a power source portion, a hydraulic control portion, an execution portion and a hydraulic accessory. The power source part comprises a small-displacement oil pump motor, a small-displacement oil pump, a large-displacement oil pump motor and a large-displacement oil pump; the small-displacement oil pump motor is connected with the small-displacement oil pump, the large-displacement oil pump motor is connected with the large-displacement oil pump, and the small-displacement oil pump and the large-displacement oil pump are both connected with the hydraulic control part through a one-way valve mechanism; the execution part comprises an execution oil cylinder mechanism and a proximity switch; and the proximity switch is connected with a piston rod of the execution oil cylinder mechanism. The proximity switch is arranged to detect the position of the piston rod of the lifting oil cylinder, the oil pump motor is controlled according to the height of the pallet fork, and the lifting impact of the pallet fork to the top is reduced; and after the pallet fork is lifted to the top, if the pallet fork is continuously lifted, the oil pump motor does not work, so that the heating of the hydraulic system is small, and energy is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of forklifts, and more specifically, to a hydraulic system for a pallet forklift. Background Art

[0002] It is known that pallet forklifts are divided into electric pallet forklifts and manual pallet forklifts. Their general load is about 2 tons. They are mainly used for the transportation of goods inside and outside production lines and warehouses. Since there is no lifting gantry, pallet forklifts are only used in flat handling scenarios.

[0003] In actual use, the existing pallet forklift hydraulic system has the following problems:

[0004] 1. There is impact when the fork is raised to the top;

[0005] 2. When the fork is raised to the top, if you continue to press the lifting button, the oil pump motor will continue to work, causing the hydraulic oil to flow back to the oil tank through the overflow valve, causing the hydraulic system to generate a lot of heat and waste energy;

[0006] 3. The lifting speed is constant and inching operation is not possible.

[0007] Therefore, in view of the above problems, a pallet forklift hydraulic system is proposed as a further improvement. Utility Model Content

[0008] In order to overcome the above-mentioned defects of the prior art, an embodiment of the utility model provides a hydraulic system for a pallet forklift to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a hydraulic system for a pallet forklift, the hydraulic system comprising: a power source unit, a hydraulic control unit, an execution unit and a hydraulic accessory; the power source unit is connected to the execution unit through the hydraulic control unit, and the power source unit and the hydraulic control unit are both connected to the hydraulic accessory;

[0010] The power source unit includes: a small displacement oil pump motor, a small displacement oil pump, a large displacement oil pump motor and a large displacement oil pump; the small displacement oil pump motor is connected to the small displacement oil pump, the large displacement oil pump motor is connected to the large displacement oil pump, and the small displacement oil pump and the large displacement oil pump are both connected to the hydraulic control unit through a one-way valve mechanism;

[0011] The execution unit comprises: an execution oil cylinder mechanism and a proximity switch; the hydraulic control unit is connected to the execution oil cylinder mechanism, and the proximity switch is connected to a piston rod of the execution oil cylinder mechanism.

[0012] Furthermore, the hydraulic control unit includes: a two-position four-way solenoid valve and a two-position two-way solenoid valve; the P1 port of the two-position four-way solenoid valve is connected to the power source unit, the T port of the two-position four-way solenoid valve is connected to the hydraulic accessory, the B1 port of the two-position four-way solenoid valve is connected to the P2 port of the two-position two-way solenoid valve, and the B2 port of the two-position two-way solenoid valve is connected to the actuator.

[0013] Furthermore, the one-way valve mechanism includes: a small-displacement oil pump outlet one-way valve and a large-displacement oil pump outlet one-way valve; the output end of the small-displacement oil pump is connected to the input end of the small-displacement oil pump outlet one-way valve through a pipeline, and the output end of the large-displacement oil pump is connected to the input end of the large-displacement oil pump outlet one-way valve through a pipeline, and the output end of the small-displacement oil pump outlet one-way valve and the output end of the large-displacement oil pump outlet one-way valve are both connected to the P1 port of the two-position four-way solenoid valve through a pipeline.

[0014] Furthermore, the actuator cylinder mechanism includes: a right lifting cylinder, a left lifting cylinder and a booster cylinder; the right lifting cylinder, the left lifting cylinder and the booster cylinder are all connected to the B2 port of the two-position two-way solenoid valve, and the proximity switch is connected to the piston rod of the right lifting cylinder.

[0015] Furthermore, the hydraulic accessory includes: a hydraulic oil tank and a return oil filter; the T port of the two-position four-way solenoid valve is connected to the hydraulic oil tank through the return oil filter, and the input end of the small-displacement oil pump and the input end of the large-displacement oil pump are both connected to the hydraulic oil tank.

[0016] Furthermore, the power source unit further includes: a relief valve;

[0017] One end of the overflow valve is connected to a pipeline connecting the output end of the small-displacement oil pump outlet check valve, the output end of the large-displacement oil pump outlet check valve and the P1 port of the two-position four-way solenoid valve, and the other end of the overflow valve is connected to a pipeline connecting the T port of the two-position four-way solenoid valve and the return oil filter.

[0018] Technical effects and advantages of the utility model:

[0019] 1. Compared with the prior art, by setting a proximity switch, the proximity switch is used to detect the position of the lifting cylinder piston rod. The oil pump motor is controlled to stop before the lifting cylinder piston rod reaches the top (15mm from the top), thereby reducing the impact of the fork lifting to the top; after the fork is lifted to the top, if the lifting button is continued to be pressed, the oil pump motor will not work, the hydraulic system will generate less heat, and energy will be saved.

[0020] 2. Compared with the existing technology, by adopting dual oil pump motors + dual hydraulic oil pumps, when the lifting button is pressed lightly, the small-displacement oil pump motor is controlled to drive the small-displacement oil pump to work, and the cargo fork is slowly lifted to achieve micro-motion operation; when the lifting button is pressed hard, the small-displacement oil pump motor and the large-displacement oil pump motor are controlled to work together to achieve rapid lifting of the cargo fork. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the hydraulic system of the pallet forklift of the present utility model.

[0022] The accompanying drawings are marked as follows:

[0023] 1. Power source department;

[0024] 11. Small displacement oil pump motor; 12. Small displacement oil pump; 13. Large displacement oil pump motor; 14. Large displacement oil pump;

[0025] 15. One-way valve mechanism;

[0026] 151. Small displacement oil pump outlet check valve; 152. Large displacement oil pump outlet check valve;

[0027] 16. Overflow valve;

[0028] 2. Hydraulic control unit; 21. Two-position four-way solenoid valve; 22. Two-position two-way solenoid valve;

[0029] 3. Execution Department;

[0030] 31. Executing cylinder mechanism; 311. Right lifting cylinder; 312. Left lifting cylinder; 313. Power-enhancing cylinder;

[0031] 32. Proximity switch;

[0032] 4. Hydraulic accessories; 41. Hydraulic oil tank; 42. Return oil filter. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0034] As attached Figure 1 A hydraulic system of a pallet forklift shown in the figure comprises: a power source part 1, a hydraulic control part 2, an execution part 3 and a hydraulic attachment 4; the power source part 1 is connected to the execution part 3 through the hydraulic control part 2, and the power source part 1 and the hydraulic control part 2 are both connected to the hydraulic attachment 4;

[0035] The power source unit 1 includes: a small displacement oil pump motor 11, a small displacement oil pump 12, a large displacement oil pump motor 13 and a large displacement oil pump 14; the small displacement oil pump motor 11 is connected to the small displacement oil pump 12, the large displacement oil pump motor 13 is connected to the large displacement oil pump 14, and the small displacement oil pump 12 and the large displacement oil pump 14 are both connected to the hydraulic control unit 2 through a one-way valve mechanism 15;

[0036] Among them, the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 form a dual-oil pump motor structure, and the small-displacement oil pump 12 and the large-displacement oil pump 14 form a dual-hydraulic oil pump structure; using the dual-oil pump motor + dual-hydraulic oil pump structure, when the lifting button is lightly pressed, the small-displacement oil pump motor 11 is controlled to drive the small-displacement oil pump 12 to work, and the fork is slowly lifted to achieve micro-operation; when the lifting button is pressed hard, the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 are controlled to work together, respectively driving the small-displacement oil pump 12 and the large-displacement oil pump 14 to work, so as to achieve rapid lifting of the fork;

[0037] The actuator 3 includes: an actuator cylinder mechanism 31 and a proximity switch 32; the hydraulic control unit 2 is connected to the actuator cylinder mechanism 31, and the proximity switch 32 is connected to a piston rod of the actuator cylinder mechanism 31;

[0038] Among them, the proximity switch 32 is a position switch that can be operated without direct mechanical contact with the moving parts. When an object approaches the sensing range of the proximity switch 32, the switch can be activated without mechanical contact or applying any pressure, thereby driving a DC appliance or providing control instructions to a computer PLC device; therefore, the proximity switch 32 is connected to a piston rod of the actuator cylinder mechanism 31 to detect the position of the lifting cylinder piston rod; and then the height of the fork can be known, and then the system controls the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 according to the actual height of the fork.

[0039] In a preferred embodiment, as shown in the attached Figure 1 As shown, the hydraulic control unit 2 includes: a two-position four-way solenoid valve 21 and a two-position two-way solenoid valve 22; the P1 port of the two-position four-way solenoid valve 21 is connected to the power source unit 1, the T port of the two-position four-way solenoid valve 21 is connected to the hydraulic accessory 4, the B1 port of the two-position four-way solenoid valve 21 is connected to the P2 port of the two-position two-way solenoid valve 22, and the B2 port of the two-position two-way solenoid valve 22 is connected to the actuator 3.

[0040] If the electromagnet m1 of the two-position four-way solenoid valve 21 is energized, the two-position four-way solenoid valve 21 works in the right position, and the hydraulic oil flows from the P1 port to the B1 port;

[0041] If the electromagnet m1 of the two-position four-way solenoid valve 21 is not energized, the two-position four-way solenoid valve 21 works in the left position, and the hydraulic oil flows from the B1 port to the T port;

[0042] If the electromagnet m2 of the two-position two-way solenoid valve 22 is energized, the two-position two-way solenoid valve 22 works in the right position, and the hydraulic oil flows from the B2 port to the P2 port;

[0043] If the electromagnet m2 of the two-position two-way solenoid valve 22 is not energized, the two-position two-way solenoid valve 22 works in the left position, and the hydraulic oil flows from the P2 port to the B2 port;

[0044] In a preferred embodiment, as shown in the attached Figure 1 As shown, the one-way valve mechanism 15 includes: a small-displacement oil pump outlet one-way valve 151 and a large-displacement oil pump outlet one-way valve 152; the output end of the small-displacement oil pump 12 is connected to the input end of the small-displacement oil pump outlet one-way valve 151 through a pipeline, the output end of the large-displacement oil pump 14 is connected to the input end of the large-displacement oil pump outlet one-way valve 152 through a pipeline, and the output end of the small-displacement oil pump outlet one-way valve 151 and the output end of the large-displacement oil pump outlet one-way valve 152 are both connected to the P1 port of the two-position four-way solenoid valve 21 through a pipeline;

[0045] Among them, the small-displacement oil pump outlet check valve 151 and the large-displacement oil pump outlet check valve 152 can be used for unidirectional drainage, so that the small-displacement oil pump outlet check valve 151 is hydraulically connected to the output end of the small-displacement oil pump 12, which is used to prevent the hydraulic oil at the output end of the large-displacement oil pump 14 from flowing to the small-displacement oil pump 12; similarly, the large-displacement oil pump outlet check valve 152 is hydraulically connected to the output end of the large-displacement oil pump 14, which is used to prevent the hydraulic oil at the output end of the small-displacement oil pump 12 from flowing to the large-displacement oil pump 14.

[0046] In a preferred embodiment, as shown in the attached Figure 1 As shown, the actuator cylinder mechanism 31 includes: a right lifting cylinder 311, a left lifting cylinder 312 and a booster cylinder 313; the right lifting cylinder 311, the left lifting cylinder 312 and the booster cylinder 313 are all connected to the B2 port of the two-position two-way solenoid valve 22, and the proximity switch 32 is connected to the piston rod of the right lifting cylinder 311.

[0047] Among them, the piston rods of the right lifting cylinder 311, the left lifting cylinder 312 and the booster cylinder 313 rise synchronously. Therefore, the height of the fork can be detected by detecting the position of the piston rod of one of the lifting cylinders. Then, the system controls the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 according to the height of the fork.

[0048] In a preferred embodiment, as shown in the attached Figure 1 As shown, the hydraulic accessory 4 includes: a hydraulic oil tank 41 and a return oil filter 42; the T port of the two-position four-way solenoid valve 21 is connected to the hydraulic oil tank 41 through the return oil filter 42, and the input end of the small-displacement oil pump 12 and the input end of the large-displacement oil pump 14 are both connected to the hydraulic oil tank 41.

[0049] The output end of the hydraulic oil tank 41 is connected to the input end of the small displacement oil pump 12 and the large displacement oil pump 14 to provide hydraulic oil for the small displacement oil pump 12 and the large displacement oil pump 14; and the refluxed hydraulic oil flows back to the hydraulic oil tank 41 from the return oil filter 42;

[0050] In a preferred embodiment, as shown in the attached Figure 1 As shown, the power source unit 1 further includes: a relief valve 16;

[0051] One end of the relief valve 16 is connected to a pipeline connecting the output end of the small-displacement oil pump outlet check valve 151, the output end of the large-displacement oil pump outlet check valve 152 and the two-position four-way solenoid valve 21P1 port, and the other end of the relief valve 16 is connected to a pipeline connecting the two-position four-way solenoid valve 21T port and the return oil filter 42.

[0052] The overflow valve 16 is hydraulically connected to the small displacement oil pump outlet check valve 151 and the large displacement oil pump outlet check valve 152 to limit the maximum pressure at the output end of the small displacement oil pump 12 and the large displacement oil pump 14 to ensure the safety of the hydraulic system.

[0053] Working principle of this utility model:

[0054] 1. When the fork needs to be lifted normally, press the fork lifting button again to control the small displacement oil pump motor 11 and the large displacement oil pump motor 13 to work, respectively driving the small displacement oil pump 12 and the large displacement oil pump 14 to rotate, and then the small displacement oil pump 12 sends the hydraulic oil to the P1 port of the two-position four-way solenoid valve 21 through the small displacement oil pump outlet check valve 151, and the large displacement oil pump 14 sends the hydraulic oil to the P1 port of the two-position four-way solenoid valve 21 through the large displacement oil pump outlet check valve 152; then control the two-position four-way solenoid valve 21 to move the hydraulic oil to the P1 port of the two-position four-way solenoid valve 21. The electromagnet m1 of the solenoid valve 21 is energized. At this time, the two-position four-way solenoid valve 21 is in the right position, and the hydraulic oil flows from the P1 port to the B1 port, and from the B1 port to the P2 port of the two-position two-way solenoid valve 22. Then the electromagnet m2 of the two-position two-way solenoid valve 22 is controlled to be not energized. At this time, the two-position two-way solenoid valve 22 works in the left position, and the hydraulic oil flows from the P2 port to the B2 port, so as to supply oil to the right lifting cylinder 311, the left lifting cylinder 312 and the booster cylinder 313, and finally realize the lifting of the fork and the operation of the booster cylinder 313;

[0055] The proximity switch 32 constantly detects the position of the piston rod of the right lifting cylinder 311, that is, the height of the fork: when the piston rod of the right lifting cylinder 311 is about to reach the top, that is, the fork is 15 mm away from the top, the proximity switch 32 outputs a signal to control the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 to stop working, thereby reducing the impact of the fork being lifted to the top; at this time, if the lifting button is continued to be pressed, the corresponding oil pump motor will not work, the hydraulic system will generate less heat, and energy will be saved; since the two pumps work together, the output hydraulic oil flow is large, and the fork lifting speed is fast at this time, meeting the lifting efficiency requirements.

[0056] 2. If the fork micro-lifting is required, lightly press the fork lifting button, and then only the small-displacement oil pump motor 11 will be controlled to work, driving the small-displacement oil pump 12 to rotate, and the hydraulic oil at the output end of the small-displacement oil pump 12 will pass through the small-displacement oil pump outlet check valve 151 to the P1 port of the two-position four-way solenoid valve 21; then the two-position four-way solenoid valve 21 electromagnet m1 will be controlled to be energized, at this time the two-position four-way solenoid valve 21 is in the right position, the hydraulic oil flows from the P1 port to the B1 port, and from the B1 port to the P2 port of the two-position two-way solenoid valve 22, and then the two-position two-way solenoid valve 22 electromagnet m2 will be controlled not to be energized, at this time the two-position two-way solenoid valve 22 works in the left position, the hydraulic oil flows from the P2 port to the B2 port, and can supply oil to the right lifting cylinder 311, the left lifting cylinder 312 and the booster cylinder 313, so as to realize the lifting of the fork and the operation of the booster cylinder 313;

[0057] The proximity switch 32 constantly detects the position of the piston rod of the right lifting cylinder 311. When the piston rod of the right lifting cylinder 311 is about to reach the top, that is, 15 mm away from the top, the proximity switch 32 outputs a signal to control the small-displacement oil pump motor 11 and the large-displacement oil pump motor 13 to stop working, thereby reducing the impact of the fork lifting to the top. At this time, if the lifting button continues to be pressed, the corresponding oil pump motor will not work, the hydraulic system will generate less heat, and energy will be saved. In this mode, since only the small-displacement oil pump 12 is working, the output hydraulic oil flow is small, and the lifting speed of the fork is slow at this time, meeting the lifting micro-operation requirements.

[0058] 3. When the fork needs to be lowered, the fork lowering button is pressed to control the electromagnet m2 of the two-position two-way solenoid valve 22 to be energized. At this time, the two-position two-way solenoid valve 22 works in the right position; then the electromagnet m1 of the two-position four-way solenoid valve 21 is de-energized. At this time, the two-position four-way solenoid valve 21 works in the left position; therefore, under the action of gravity, the hydraulic oil in the rodless chamber of the left lifting cylinder 312 and the right lifting cylinder 311 flows from the B2 port of the two-position two-way solenoid valve 22 to the P2 port, from the P2 port to the B1 port of the two-position four-way solenoid valve 21, from the B1 port to the T port, and from the T port through the return oil filter 42 to the hydraulic oil tank 41, thereby realizing the lowering of the fork.

[0059] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0060] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydraulic system for a pallet truck, characterized in that: The hydraulic system comprises: a power source unit (1), a hydraulic control unit (2), an actuator unit (3) and a hydraulic accessory (4); the power source unit (1) is connected to the actuator unit (3) via the hydraulic control unit (2), and the power source unit (1) and the hydraulic control unit (2) are both connected to the hydraulic accessory (4); The power source unit (1) comprises: a small-displacement oil pump motor (11), a small-displacement oil pump (12), a large-displacement oil pump motor (13) and a large-displacement oil pump (14); the small-displacement oil pump motor (11) is connected to the small-displacement oil pump (12), the large-displacement oil pump motor (13) is connected to the large-displacement oil pump (14), and the small-displacement oil pump (12) and the large-displacement oil pump (14) are both connected to the hydraulic control unit (2) via a one-way valve mechanism (15); The actuator (3) comprises: an actuator cylinder mechanism (31) and a proximity switch (32); the hydraulic control unit (2) is connected to the actuator cylinder mechanism (31), and the proximity switch (32) is connected to a piston rod of the actuator cylinder mechanism (31).

2. A pallet truck hydraulic system according to claim 1, characterized in that: The hydraulic control unit (2) comprises: a two-position four-way solenoid valve (21) and a two-position two-way solenoid valve (22); the P1 port of the two-position four-way solenoid valve (21) is connected to the power source unit (1), the T port of the two-position four-way solenoid valve (21) is connected to the hydraulic accessory (4), the B1 port of the two-position four-way solenoid valve (21) is connected to the P2 port of the two-position two-way solenoid valve (22), and the B2 port of the two-position two-way solenoid valve (22) is connected to the actuator (3).

3. A pallet forklift hydraulic system according to claim 2, characterized in that: The one-way valve mechanism (15) comprises: a small-displacement oil pump outlet one-way valve (151) and a large-displacement oil pump outlet one-way valve (152); the output end of the small-displacement oil pump (12) is connected to the input end of the small-displacement oil pump outlet one-way valve (151) via a pipeline, the output end of the large-displacement oil pump (14) is connected to the input end of the large-displacement oil pump outlet one-way valve (152) via a pipeline, and the output end of the small-displacement oil pump outlet one-way valve (151) and the output end of the large-displacement oil pump outlet one-way valve (152) are both connected to the P1 port of the two-position four-way solenoid valve (21) via a pipeline.

4. A pallet forklift hydraulic system according to claim 2, characterized in that: The actuator cylinder mechanism (31) comprises: a right lifting cylinder (311), a left lifting cylinder (312) and a booster cylinder (313); the right lifting cylinder (311), the left lifting cylinder (312) and the booster cylinder (313) are all connected to the B2 port of the two-position two-way solenoid valve (22), and the proximity switch (32) is connected to the piston rod of the right lifting cylinder (311).

5. A pallet truck hydraulic system according to claim 3, characterized in that: The hydraulic accessory (4) comprises: a hydraulic oil tank (41) and an oil return filter (42); the T port of the two-position four-way solenoid valve (21) is connected to the hydraulic oil tank (41) via the oil return filter (42); the input end of the small-displacement oil pump (12) and the input end of the large-displacement oil pump (14) are both connected to the hydraulic oil tank (41).

6. A pallet truck hydraulic system according to claim 5, characterized in that: The power source unit (1) further comprises: a relief valve (16); One end of the overflow valve (16) is connected to a pipeline connecting an output end of the small-displacement oil pump outlet check valve (151), an output end of the large-displacement oil pump outlet check valve (152) and a P1 port of a two-position four-way solenoid valve (21), and the other end of the overflow valve (16) is connected to a pipeline connecting a T port of the two-position four-way solenoid valve (21) and an oil return filter (42).

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