Composite one-way valve and hand-held forklift

Abstract

The invention belongs to the technical field of hand-held forklifts, and discloses a composite one-way valve and a hand-held forklift. The composite one-way valve comprises a valve sleeve assembly, a first valve element assembly and a second valve element assembly, a first oil port, a second oil port and a third oil port are formed in the valve sleeve assembly, and a first cavity and a second cavity are formed in the valve sleeve assembly; the first valve element assembly can enable the first oil port and the second oil port to be cut off or achieve one-way connection from the first oil port to the second oil port under the action of hydraulic pressure. The second valve element assembly can enable the second oil port and the third oil port to be cut off or achieve one-way connection from the second oil port to the third oil port under the action of hydraulic pressure, or the first valve element assembly can push the second valve element assembly under the thrust action of the manual push rod so that media can flow to the first oil port from the third oil port. According to the composite one-way valve, the one-way locking function, the oil absorbing and pressing function and the reliable load lowering function can be integrated, and the composite one-way valve is simple and compact in structure, low in cost and small in occupied space.

Description

Technical Field

[0001] This invention relates to the field of walking forklift technology, and more particularly to a composite one-way valve and a walking forklift. Background Technology

[0002] With the development of modern industry, the handling of heavy objects in warehouses is essential. Forklifts are required for handling many heavy objects. Currently, there are electric and large forklifts, but their flexibility is limited. However, walk-behind forklifts have a high status in the warehousing and logistics industry as well as in industrial transfer equipment and products due to their low cost, flexibility and reliability.

[0003] Currently, most hand-operated forklifts on the market use a manual pump combined with multiple valves for their hydraulic drive system. This solution is costly, has a complex design, many loosely packed parts, requires high precision, and is very difficult to maintain and repair. The high cost of repairing damage makes the product uncompetitive in the market.

[0004] Therefore, there is an urgent need to provide a composite check valve and a walking forklift to solve the above problems. Summary of the Invention

[0005] One objective of this invention is to provide a composite check valve that integrates one-way locking function, oil suction and oil pressure function, and load reliable reduction function into one unit, and has a simple and compact structure, low cost, and small footprint.

[0006] Another objective of this invention is to provide a walking forklift that, by employing the aforementioned composite check valve, makes the product more competitive in the market.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A composite check valve, comprising:

[0009] A valve sleeve assembly is provided with a first oil port, a second oil port and a third oil port, the second oil port being located between the first oil port and the third oil port. The valve sleeve assembly is provided with a first cavity and a second cavity that are connected to each other. The first cavity is connected to the first oil port and the second oil port, and the second cavity is connected to the third oil port.

[0010] The first valve core assembly is slidably disposed in the first cavity. The first valve core assembly can shut off the first oil port and the second oil port, or the first valve core assembly can achieve unidirectional flow from the first oil port to the second oil port under the action of hydraulic pressure.

[0011] The second valve core assembly is slidably disposed in the second cavity. The second valve core assembly can shut off the second oil port and the third oil port, or the second valve core assembly can achieve unidirectional flow from the second oil port to the third oil port under the action of hydraulic pressure, or the first valve core assembly can push the second valve core assembly under the pushing force of the manual push rod, so that the medium flows from the third oil port to the first oil port.

[0012] As an optional solution, the valve sleeve assembly includes a main valve sleeve, a first valve seat, and a second valve seat. The main valve sleeve has a second oil port and a third oil port on its side wall. The main valve sleeve has a first cavity inside. The first valve seat is fixedly inserted through one axial end of the main valve sleeve. The first valve seat has the first oil port inside. The second valve seat is fitted onto the other axial end of the main valve sleeve and together with the main valve sleeve, defines the second cavity.

[0013] As an optional solution, the main valve sleeve is axially floatingly connected to the second valve seat.

[0014] As an optional solution, the end of the main valve sleeve facing the second valve seat is provided with a limiting shoulder, and the end of the second valve seat facing the main valve sleeve is provided with a constricted edge. The limiting shoulder extends into the inner cavity of the constricted edge, and the constricted edge can form an inwardly rolled annular limiting stop after constriction. The annular limiting stop and the limiting shoulder are axially floating and limitingly matched.

[0015] As an alternative, the limiting shoulder has an inclined surface on the side facing the constricted edge, which gradually slopes away from the axis of the main valve sleeve and toward the second valve seat along the axial direction of the main valve sleeve.

[0016] As an optional solution, the first valve core assembly includes a first sealing element and a push rod. The first sealing element is used to block the first oil port. One end of the push rod abuts against the first sealing element, and the other end of the push rod faces the second valve core assembly. The push rod can push the second valve core assembly under the thrust of the manual push rod.

[0017] As an optional solution, the valve sleeve assembly is further provided with a connecting hole, which connects the first cavity and the second cavity. The inner diameter of the connecting hole is smaller than the inner diameter of the first cavity and the second cavity. The end of the push rod away from the first sealing member extends into the connecting hole and forms an annular throttling channel with the inner wall of the connecting hole.

[0018] As an alternative, a limiting groove is provided at one end of the push rod near the first sealing member, and the first sealing member is partially accommodated in the limiting groove.

[0019] As an optional solution, the second valve core assembly includes a second sealing element and a return spring. The second sealing element is used to block the port of the second cavity near the first cavity. One end of the return spring abuts against the second sealing element, and the other end of the return spring abuts against the inner wall of the second cavity.

[0020] A forklift includes a forklift body and the aforementioned composite one-way valve. The forklift body includes a manual push rod, an oil tank, a manual piston, and a load cylinder. The oil tank is connected to a first oil port, the manual piston is connected to a second oil port, and the load cylinder is connected to a third oil port.

[0021] The beneficial effects of this invention are:

[0022] This invention provides a composite check valve. Through clever structural design, it can achieve a one-way locking function when the load is held, and can also work with a manual piston to complete oil suction and pressure, realizing a new load lifting function. It can also work with a manual push rod to achieve a reliable load lowering function. One composite check valve can be used for different working conditions and can replace the combination of manual pump and multiple valves in the prior art. Compared with the prior art, it has a simpler and more compact structure, lower cost, smaller footprint, and is easier to maintain and repair, with lower repair costs after damage.

[0023] The present invention also provides a walking forklift, which, by adopting the above-mentioned composite check valve, has low cost and makes the product more competitive in the market. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the composite check valve provided in an embodiment of the present invention;

[0025] Figure 2 This is a hydraulic schematic diagram of the composite check valve provided in an embodiment of the present invention;

[0026] Figure 3 This is a cross-sectional view of the composite check valve provided in the embodiment of the present invention under the first operating condition;

[0027] Figure 4 This is a cross-sectional view of the composite check valve provided in the embodiment of the present invention under the second operating condition;

[0028] Figure 5 This is a cross-sectional view of the composite check valve provided in the embodiment of the present invention under the third operating condition;

[0029] Figure 6 yes Figure 3 A magnified view of a portion of point A in the middle.

[0030] In the picture:

[0031] 100. Manual push rod; 200. Oil tank; 300. Manual piston; 400. Load cylinder;

[0032] 10. Valve sleeve assembly; 11. Main valve sleeve; 111. Second oil port; 112. Third oil port; 113. Limiting shoulder; 114. Bevel; 12. First valve seat; 121. First oil port; 13. Second valve seat; 131. Narrowing edge; 14. First cavity; 15. Second cavity; 16. Connecting hole;

[0033] 20. First valve core assembly; 21. First sealing component; 22. Push rod; 221. Limiting groove;

[0034] 30. Second valve core assembly; 31. Second sealing component; 32. Return spring. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] With the development of modern industry, the handling of heavy objects in warehouses is essential. Forklifts are required for handling many heavy objects. Currently, there are electric and large forklifts, but their flexibility is limited. However, walk-behind forklifts have a high status in the warehousing and logistics industry as well as in industrial transfer equipment and products due to their low cost, flexibility and reliability.

[0040] Currently, most walk-in forklifts on the market use a manual pump for hydraulic drive to lift heavy loads. A check valve is then installed to maintain the load and prevent backflow of oil when the load drops. A pressure relief valve is also installed for load descent and safety functions. This solution is used by most manufacturers. However, with increasing market competition and cost pressures, the applicant has found it very difficult to reduce costs by using the traditional solution for walk-in forklift design. This is because the solution is expensive, has a complex design structure, many non-compact parts, requires high precision, and is difficult to maintain and repair. The high repair costs after damage make the product uncompetitive in the market.

[0041] Therefore, this embodiment provides a walking forklift, which includes a forklift body and a composite one-way valve. The forklift body includes a manual push rod 100, an oil tank 200, a manual piston 300, and a load cylinder 400 that work in conjunction with the composite one-way valve. The specific structure of the forklift body is all prior art and will not be described in detail here.

[0042] like Figures 1 to 3 As shown, the composite check valve includes a valve sleeve assembly 10, a first valve core assembly 20, and a second valve core assembly 30. The valve sleeve assembly 10 has a first oil port 121, a second oil port 111, and a third oil port 112. The second oil port 111 is located between the first oil port 121 and the third oil port 112. Specifically, the oil tank 200 is connected to the first oil port 121, the manual piston 300 is connected to the second oil port 111, and the load cylinder 400 is connected to the third oil port 112. The valve sleeve assembly 10 has a first cavity 14 and a second cavity 15 that are connected. The first cavity 14 is connected to the first oil port 121 and the second oil port 111, and the second cavity 15 is connected to the third oil port 112. The first valve core assembly 20 slides... The first valve core assembly 20 is disposed in the first cavity 14 and can shut off the first oil port 121 and the second oil port 111, or the first valve core assembly 20 can achieve unidirectional flow from the first oil port 121 to the second oil port 111 under the action of hydraulic pressure. The second valve core assembly 30 is slidably disposed in the second cavity 15 and can shut off the second oil port 111 and the third oil port 112, or the second valve core assembly 30 can achieve unidirectional flow from the second oil port 111 to the third oil port 112 under the action of hydraulic pressure, or the first valve core assembly 20 can push the second valve core assembly 30 under the pushing force of the manual push rod 100 so that the medium flows from the third oil port 112 to the first oil port 121.

[0043] When using this composite check valve, such as Figure 3 As shown, when the forklift needs to lift goods, the operator manually presses down the manual piston 300. At this time, hydraulic fluid enters from the second port 111. Because the hydraulic pressure at the second port 111 is greater than that at the first port 121, the first valve assembly 20, under the action of the hydraulic pressure, closes the channel between the first port 121 and the second port 111, thus shutting off the first and second ports 111. Simultaneously, the hydraulic pressure pushes the second valve assembly 30 to the left, achieving unidirectional flow from the second port 111 to the third port 112. Hydraulic fluid enters from the second port 111 to the third port 112, pushing the load cylinder 400 to lift, thereby lifting the goods. Figure 4 As shown. When the operator manually raises the manual piston 300, the oil pressure at the second port 111 becomes negative. At this time, the oil pressure at the second port 111 is less than the oil pressure at the first port 121. Therefore, the first valve core assembly 20 moves to the left under the action of the oil pressure and opens the channel between the first port 121 and the second port 111, realizing unidirectional flow from the first port 121 to the second port 111. The oil flows from the first port 121 into the second port 111 and enters the large cavity of the manual piston 300 to complete the oil suction process. During this process, the second valve core assembly 30 closes the channel between the third port 112 and the second port 111, so that the second port 111 and the third port 112 are cut off, and the oil pressure at the third port 112 remains unchanged. Figure 5 As shown, when the forklift needs to be lowered, the operator inserts the manual push rod 100 into the first oil port 121 and pushes the first valve core assembly 20 to the left. The first valve core assembly 20 pushes the second valve core assembly 30 to the left, thus the second valve core assembly 30 moves to the left under the force and opens the channel between the third oil port 112 and the first oil port 121. The oil in the third oil port 112 can return to the first oil port 121 and enter the oil tank 200, causing the forklift to lower. When the load needs to be maintained, the second valve core assembly 30 can close the channel between the third oil port 112 and the second oil port 111, thus shutting off the second oil port 111 and the third oil port 112.

[0044] Therefore, the composite check valve provided in this embodiment, through its ingenious structural design, can achieve both one-way locking during load holding and, in conjunction with the manual piston 300, oil suction and pressure for load lifting. It can also, in conjunction with the manual push rod 100, reliably lower the load. This composite check valve is suitable for various working conditions and can replace the existing combination of a manual pump and multiple valves. Compared to existing technologies, it has a simpler and more compact structure, lower cost, smaller footprint, and is easier to maintain and repair, resulting in lower repair costs after damage. The forklift provided in this embodiment, by employing the aforementioned composite check valve, makes the product more competitive in the market.

[0045] It should be noted that the oil flowing to the third oil port 112 can withstand a load pressure of up to 40MPa; the flow rate from the second oil port 111 to the third oil port 112 can reach 15L / min, enabling the hand-held forklift to be lifted quickly.

[0046] Combination Figure 1 and Figure 3 The valve sleeve assembly 10 includes a main valve sleeve 11, a first valve seat 12, and a second valve seat 13. The main valve sleeve 11 has a second oil port 111 and a third oil port 112 on its side wall. A first cavity 14 is provided inside the main valve sleeve 11. The first valve seat 12 is fixedly inserted through one axial end of the main valve sleeve 11 and can be threaded to the main valve sleeve 11. A first oil port 121 is provided inside the first valve seat 12. The second valve seat 13 is fitted onto the other axial end of the main valve sleeve 11 and, together with the main valve sleeve 11, defines a second cavity 15. By disassembling the valve sleeve assembly 10 into multiple small, simple-structured parts, the processing difficulty and cost are reduced, manufacturing feasibility is improved, and the processing accuracy of each part is guaranteed. Furthermore, when a part is damaged, the damaged part can be replaced specifically without replacing the entire valve sleeve assembly 10, thus reducing maintenance and repair costs.

[0047] Optionally, such as Figure 3 As shown, the main valve sleeve 11 and the second valve seat 13 are axially floatingly connected. Specifically, as... Figure 6As shown, the main valve sleeve 11 has a limiting shoulder 113 at one end facing the second valve seat 13, and the second valve seat 13 has a constricted edge 131 at one end facing the main valve sleeve 11. The limiting shoulder 113 extends into the inner cavity of the constricted edge 131, and the constricted edge 131 can form an inwardly rolled annular limiting stop after constriction. The annular limiting stop and the limiting shoulder 113 are axially floating and limitingly matched. During assembly, the limiting shoulder 113 is first inserted into the constricted edge 131 for positioning. The constricted edge 131 is clamped inward by a tooling to compress the opening. After the constriction process, the constricted edge 131 will form an inwardly rolled annular limiting stop. This assembly process is simple, efficient, and low-cost, and its assembly efficiency is much higher than that of threaded connections, welding, and other processes. The annular limiting stop and the end face of the limiting shoulder 113 form an axial limiting fit, but the contact between the two is a surface contact rather than an interference fit. The reserved small gap is the axial floating stroke, which ensures that the main valve sleeve 11 has a certain amount of room to move in the second valve seat 13, so as to meet the axial displacement compensation requirements caused by impact.

[0048] It should be noted that the necking process is a cold stamping process. Under the action of the tooling, the metal material of the necked edge 131 undergoes plastic flow, wrapping around the outer edge of the limiting shoulder 113 to form a mechanical engagement. The connection strength is much higher than that of threaded connections, clamp connections, and other detachable structures, and there is no risk of stress concentration. The connection strength is high, and the impact resistance is excellent. Under the high-pressure impact load of high-pressure oil, there will be no failure problems such as loosening of threads or detachment of retaining rings. Furthermore, this connection method is achieved only through the limiting shoulder 113 of the main valve sleeve 11 and the necked edge 131 of the second valve seat 13. There is no need to add additional connecting parts such as retaining rings, retaining rings, or gaskets, nor is it necessary to machine threaded holes or weld bevels on the main valve sleeve 11 and the second valve seat 13. This greatly simplifies the connection structure, reduces the number of parts and assembly space, and results in a compact structure with no need for additional connecting parts, demonstrating significant lightweight advantages.

[0049] Optionally, such as Figure 6As shown, the side of the limiting shoulder 113 facing the constricted edge 131 is a slope 114, which is axially aligned with the main valve sleeve 11 and faces the second valve seat 13. The slope 114 gradually tilts away from the axis of the main valve sleeve 11. It is understandable that the constriction is a cold plastic forming process. When the tooling squeezes the constricted edge 131, the metal material of the constricted edge 131 needs to flow inward and fit against the limiting shoulder 113. If the limiting shoulder 113 is a right-angled stepped surface, the metal of the constricted edge 131 will rigidly rub against the right-angled edge when it flows. This not only requires a larger tooling extrusion force, but also easily leads to defects such as cracks and wrinkles on the constricted edge 131. Therefore, by setting the aforementioned inclined surface 114, it is equivalent to providing a guide for the metal flow of the constricted edge 131. The metal material smoothly rolls inward along the inclined surface 114, resulting in a smoother flow path, reduced plastic deformation resistance, and lower required tooling extrusion pressure. At the same time, the inclined surface 114 avoids stress concentration on a single edge, significantly reducing the risk of cracking and deformation of the constricted edge 131 and improving the pass rate of the constriction process. For floating connections, the inclined surface 114 optimizes the smoothness of axial floating, reduces the risk of jamming, and forms an annular sealing structure with the constricted edge 131 and the inclined surface 114 of the limiting shoulder 113. Under the impact of axial load, the constricted edge 131 and the inclined surface 114 of the limiting shoulder 113 fit more tightly, forming a self-sealing effect under high pressure impact.

[0050] Optionally, such as Figure 3 As shown, the first valve core assembly 20 includes a first sealing member 21 and a push rod 22. The first sealing member 21 is used to block the first oil port 121. One end of the push rod 22 abuts against the first sealing member 21, and the other end of the push rod 22 faces the second valve core assembly 30. The push rod 22 can push the second valve core assembly 30 under the pushing force of the manual push rod 100. Specifically, when the forklift needs to lift goods, the operator manually presses down the manual piston 300. The push rod 22 can push the first sealing member 21 to the right under the action of hydraulic pressure, so that the first sealing member 21 blocks the port of the first valve seat 12, thereby closing the channel between the first oil port 121 and the second oil port 111, and shutting off the second oil port 111 and the third oil port 112. Figure 5 As shown, when the forklift needs to be lowered, the operator pushes the first sealing member 21 to the left at the first oil port 121 by manually pushing the rod 100. The first sealing member 21 drives the push rod 22 to the left, and the push rod 22 pushes the second valve core assembly 30 to the left and opens the channel between the third oil port 112 and the first oil port 121. The oil in the third oil port 112 can return to the first oil port 121 and enter the oil tank 200, so that the forklift can be lowered.

[0051] like Figure 3As shown, the main valve sleeve 11 of the valve sleeve assembly 10 is also provided with a connecting hole 16, which connects the first cavity 14 and the second cavity 15. The inner diameter of the connecting hole 16 is smaller than the inner diameter of the first cavity 14 and the second cavity 15. The end of the push rod 22 facing away from the first sealing member 21 extends into the connecting hole 16 and forms an annular throttling channel with the inner wall of the connecting hole 16. Figure 5 As shown, when the push rod 22 pushes the second valve core assembly 30 to the left and opens the channel between the third oil port 112 and the first oil port 121, the oil in the third oil port 112 can flow to the first oil port 121 through the annular throttling channel between the push rod 22 and the connecting hole 16. The annular throttling channel can reduce the flow area and achieve the throttling effect by limiting the flow rate, so that the hand-held forklift can descend slowly.

[0052] In this embodiment, as Figure 3 As shown, the first sealing element 21 is a spherical sealing element, specifically a steel ball. The spherical sealing element contacts the port of the first valve seat 12, forming a mechanical line contact seal, ensuring reliable sealing and achieving virtually zero leakage. In other optional embodiments, the first sealing element 21 can also be conical, frustum-shaped, or cylindrical with a cone apex, as long as a line contact seal can be achieved.

[0053] Optionally, such as Figure 3 As shown, a limiting groove 221 is formed at the end of the push rod 22 near the first sealing member 21, and part of the first sealing member 21 is accommodated in the limiting groove 221. The first sealing member 21 can be fixedly connected in the limiting groove 221, so that the two can move synchronously. By setting the limiting groove 221 on the push rod 22, part of the first sealing member 21 is accommodated in the limiting groove 221 for limiting installation, thereby improving the reliability of the structure.

[0054] In this embodiment, as Figure 4 As shown, the second valve core assembly 30 includes a second sealing element 31 and a return spring 32. The second sealing element 31 is used to seal the port of the second cavity 15 near the first cavity 14. One end of the return spring 32 abuts against the second sealing element 31, and the other end of the return spring 32 abuts against the inner wall of the second cavity 15. When the load needs to be maintained, the elastic force of the return spring 32 and the hydraulic pressure can firmly press the second sealing element 31 at the port of the connecting hole 16, forming a reliable seal, so that the load can be maintained and the goods can be prevented from falling.

[0055] In this embodiment, as Figure 4As shown, the second sealing element 31 is a spherical sealing element, specifically a steel ball. The spherical sealing element contacts the left port of the connecting hole 16, forming a mechanical line contact seal. This provides a reliable seal, achieving virtually zero leakage and effectively maintaining the load. In other optional embodiments, the second sealing element 31 can also be conical, frustum-shaped, or cylindrical with a cone apex, as long as a line contact seal can be achieved.

[0056] Combination Figures 3-5 The working principle of the composite check valve provided in this embodiment is described in detail below:

[0057] like Figure 3 As shown, when the forklift needs to lift goods, the operator manually presses down the manual piston 300. At this time, oil enters from the second oil port 111. Since the oil pressure in the second oil port 111 is greater than the oil pressure in the first oil port 121, the first sealing member 21 can be forcefully blocked to seal the left port of the first valve seat 12, thereby closing the channel between the first oil port 121 and the second oil port 111, thus cutting off the first oil port 121 and the second oil port 111. At the same time, the oil pressure will overcome the elasticity of the return spring 32 and push the second sealing member 31 to the left, opening the left port of the connecting hole 16, thereby realizing unidirectional flow from the second oil port 111 to the third oil port 112. The oil enters from the second oil port 111 to the third oil port 112, pushing the load cylinder 400 to lift, thereby realizing the lifting of the goods.

[0058] like Figure 4 As shown, when the operator manually lifts the manual piston 300, the oil pressure at the second oil port 111 forms a negative pressure. At this time, the oil pressure at the second oil port 111 is less than the oil pressure at the first oil port 121. Therefore, the first sealing member 21 can move to the left under the action of the oil pressure and open the left port of the first valve seat 12, thereby opening the channel between the first oil port 121 and the second oil port 111, realizing unidirectional flow from the first oil port 121 to the second oil port 111. The oil flows from the first oil port 121 into the second oil port 111 and enters the large cavity of the manual piston 300, realizing the oil suction process. During this process, due to the elastic force of the return spring 32 and the oil pressure at the third oil port 112, the second sealing member 31 continuously blocks the left port of the connecting hole 16, closing the channel between the third oil port 112 and the second oil port 111, so that the second oil port 111 and the third oil port 112 are cut off, and the oil pressure at the third oil port 112 remains unchanged.

[0059] like Figure 5As shown, when the forklift needs to be lowered, the operator pushes the first sealing member 21 to the left at the first oil port 121 by manually pushing the rod 100. The first sealing member 21 drives the push rod 22 to the left, and the push rod 22 pushes the second sealing member 31 to the left, so that the second sealing member 31 opens the left port of the connecting hole 16, thereby opening the channel between the third oil port 112 and the first oil port 121. The oil in the third oil port 112 can flow to the first oil port 121 through the annular throttling channel between the push rod 22 and the connecting hole 16, and then return to the oil tank 200, so that the forklift lowers slowly.

[0060] When the load needs to be held, the second sealing member 31 can be firmly pressed against the port of the connecting hole 16 by the elastic force of the return spring 32 and the hydraulic pressure, forming a reliable seal so that the load can be held and the goods can be prevented from falling.

[0061] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A composite check valve, characterized in that, include: A valve sleeve assembly (10) is provided with a first oil port (121), a second oil port (111) and a third oil port (112). The second oil port (111) is located between the first oil port (121) and the third oil port (112). The valve sleeve assembly (10) is provided with a first cavity (14) and a second cavity (15) that are connected to each other. The first cavity (14) is connected to the first oil port (121) and the second oil port (111), and the second cavity (15) is connected to the third oil port (112). The first valve core assembly (20) is slidably disposed in the first cavity (14). The first valve core assembly (20) can shut off the first oil port (121) and the second oil port (111), or the first valve core assembly (20) can achieve unidirectional flow from the first oil port (121) to the second oil port (111) under the action of hydraulic pressure. The second valve core assembly (30) is slidably disposed in the second cavity (15). The second valve core assembly (30) can shut off the second oil port (111) and the third oil port (112), or the second valve core assembly (30) can achieve unidirectional flow from the second oil port (111) to the third oil port (112) under the action of hydraulic pressure, or the first valve core assembly (20) can push the second valve core assembly (30) under the thrust of the manual push rod (100) so that the medium flows from the third oil port (112) to the first oil port (121).

2. The composite check valve according to claim 1, characterized in that, The valve sleeve assembly (10) includes a main valve sleeve (11), a first valve seat (12), and a second valve seat (13). The main valve sleeve (11) has a second oil port (111) and a third oil port (112) on its side wall. The main valve sleeve (11) has a first cavity (14) inside it. The first valve seat (12) is fixedly inserted through one axial end of the main valve sleeve (11). The first oil port (121) is opened inside the first valve seat (12). The second valve seat (13) is fitted onto the other axial end of the main valve sleeve (11) and together with the main valve sleeve (11) defines the second cavity (15).

3. The composite check valve according to claim 2, characterized in that, The main valve sleeve (11) is axially floatingly connected to the second valve seat (13).

4. The composite check valve according to claim 3, characterized in that, The main valve sleeve (11) has a limiting shoulder (113) at one end facing the second valve seat (13), and the second valve seat (13) has a constricted edge (131) at one end facing the main valve sleeve (11). The limiting shoulder (113) extends into the inner cavity of the constricted edge (131). The constricted edge (131) can form an inwardly rolled annular limiting stop after constriction. The annular limiting stop cooperates with the limiting shoulder (113) in an axial floating limiting fit.

5. The composite check valve according to claim 4, characterized in that, The limiting shoulder (113) is inclined (114) on the side facing the constricted edge (131). Along the axial direction of the main valve sleeve (11) and towards the second valve seat (13), the inclined surface (114) gradually tilts away from the axis of the main valve sleeve (11).

6. The composite check valve according to claim 1, characterized in that, The first valve core assembly (20) includes a first plug (21) and a push rod (22). The first plug (21) is used to block the first oil port (121). One end of the push rod (22) abuts against the first plug (21), and the other end of the push rod (22) faces the second valve core assembly (30). The push rod (22) can push the second valve core assembly (30) under the thrust of the manual push rod (100).

7. The composite check valve according to claim 6, characterized in that, The valve sleeve assembly (10) is also provided with a connecting hole (16), which connects the first cavity (14) and the second cavity (15). The inner diameter of the connecting hole (16) is smaller than the inner diameter of the first cavity (14) and the second cavity (15). The end of the push rod (22) away from the first sealing member (21) extends into the connecting hole (16) and forms an annular throttling channel with the inner wall of the connecting hole (16).

8. The composite check valve according to claim 6, characterized in that, The top rod (22) has a limiting groove (221) at one end near the first sealing member (21), and the first sealing member (21) is partially housed in the limiting groove (221).

9. The composite check valve according to claim 1, characterized in that, The second valve core assembly (30) includes a second sealing member (31) and a return spring (32). The second sealing member (31) is used to seal the port of the second cavity (15) near the first cavity (14). One end of the return spring (32) abuts against the second sealing member (31), and the other end of the return spring (32) abuts against the inner wall of the second cavity (15).

10. A hand-operated forklift, characterized in that, The invention includes a forklift body and a composite one-way valve as described in any one of claims 1-9. The forklift body includes a manual push rod (100), an oil tank (200), a manual piston (300), and a load cylinder (400). The oil tank (200) is connected to the first oil port (121), the manual piston (300) is connected to the second oil port (111), and the load cylinder (400) is connected to the third oil port (112).

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