Hydraulic oil cylinder and stroke limiting mechanism thereof

Abstract

The utility model belongs to the technical field of common fluid working systems, and particularly relates to a hydraulic oil cylinder and a stroke limiting mechanism thereof, the hydraulic oil cylinder comprises a cylinder body, a piston rod, a limiting plate, a valve body and a valve rod, the valve body is arranged on the side wall of the cylinder body, one end of the piston rod extends into the cylinder body, the limiting plate is arranged on the piston rod, and the valve rod is arranged on the limiting plate. A cavity is formed in the valve body, and a first oil passing opening and a second oil passing opening are formed in the cavity. The inner end of the valve rod is located in the cavity, and the outer end of the valve rod is located outside the valve body. In the retraction process of the piston rod, the limiting plate is suitable for moving along with the piston rod to extrude the outer end of the valve rod, so that the inner end of the valve rod crosses the first oil passing port to cut off the oil way, and the first piston of the hydraulic oil cylinder and the first piston of the stroke limiting mechanism are arranged in the cavity in a sliding mode and can only slide in the oil way opening and closing process. And therefore, the sealing ring on the side wall of the first piston does not generate a ring cutting risk.

Description

Technical Field

[0001] This utility model belongs to the technical field of general fluid working systems, specifically relating to a straight cylinder type transmission device, and more particularly to a hydraulic cylinder and its stroke limiting mechanism. Background Technology

[0002] A hydraulic cylinder is a device that uses a hydraulic system to move a piston rod. To adapt to different working conditions, existing hydraulic cylinders can adjust their stroke.

[0003] In related technologies, such as the adjustable stroke hydraulic cylinder with application number "202020589710.3", the guide rod is pushed to move by a limiting body, so that the plug at the end of the guide rod is inserted into the oil passage, and the piston rod stops moving by disconnecting the oil passage; when the piston needs to move, the guide rod moves in the opposite direction to pull the plug out of the oil passage.

[0004] However, in the above scheme, each time the oil circuit is opened or closed, the plug needs to be inserted into or removed from the oil passage, which means that the sealing ring on the plug needs to be continuously compressed and expanded in the radial direction, accompanied by the risk of ring cutting.

[0005] Therefore, how to avoid the phenomenon of ring cutting during the insertion and removal of the plug during the opening and closing of the oil circuit is a technical problem that urgently needs to be solved by those skilled in the art.

[0006] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Utility Model Content

[0007] This disclosure provides at least one hydraulic cylinder and its stroke limiting mechanism.

[0008] In a first aspect, embodiments of this disclosure provide a hydraulic cylinder, comprising: a cylinder body, a piston rod, a limiting plate, a valve body, and a valve stem. The valve body is disposed on the side wall of the cylinder body, one end of the piston rod extends into the cylinder body, the limiting plate is disposed on the piston rod, and a chamber is formed within the valve body, the chamber having a first oil passage and a second oil passage. The inner end of the valve stem is located within the chamber, and the outer end is located outside the valve body. During the retraction of the piston rod, the limiting plate is adapted to move with the piston rod to squeeze the outer end of the valve stem, causing the inner end of the valve stem to pass over the first oil passage to cut off the oil circuit.

[0009] In one optional embodiment, a first piston is provided at the inner end of the valve stem; wherein the first piston is adapted to slide within the chamber by the action of the valve stem; during the retraction of the piston rod, the first piston is adapted to pass over the first oil passage to cut off the oil circuit.

[0010] In one alternative embodiment, the diameter of the first piston is larger than the diameter of the second oil passage.

[0011] In one optional embodiment, the first oil passage and the second oil passage are arranged sequentially along the retraction direction of the piston rod; wherein the first oil passage is located on the side wall of the chamber, and the second oil passage is located at the bottom of the chamber.

[0012] In one optional embodiment, a second piston is provided at the end of the piston rod located inside the cylinder, the second piston being adapted to divide the cylinder into a rod chamber and a rodless chamber; wherein a third oil passage is provided on the side wall of the rodless chamber, the third oil passage communicating with the first oil passage.

[0013] In one optional embodiment, a valve seat is provided in the chamber, and a sliding cavity is formed on the side of the valve seat facing the second oil passage, the sliding cavity communicating with the second oil passage; the first piston is slidably disposed in the sliding cavity, and the valve stem is adapted to pass through the valve seat and extend into the sliding cavity to connect with the first piston; the middle part of the side wall of the valve seat is recessed inward to form an annular buffer cavity, and the annular buffer cavity is provided with a plurality of fourth oil passages along the circumference; wherein, the first oil passage communicates with the annular buffer cavity, and the fourth oil passages communicate with the sliding cavity.

[0014] In one optional embodiment, a guide ring is provided between the limiting plate and the piston rod; wherein the guide ring is sleeved on the piston rod.

[0015] Secondly, this disclosure also provides a stroke limiting mechanism for a hydraulic cylinder, comprising: a valve body disposed on the side wall of the cylinder body, and having a chamber therein, the chamber having a first oil passage and a second oil passage; a first piston slidably disposed within the chamber; and a valve stem, the inner end of which is connected to the first piston, and the outer end of which is located outside the valve body; wherein, an oil passage is formed between the first oil passage, the chamber, and the second oil passage, and the outer end of the valve stem is adapted to be pressurized to drive the first piston past the first oil passage to cut off the oil passage.

[0016] In one optional embodiment, the first oil passage and the second oil passage are arranged sequentially along the retraction direction of the piston rod; wherein the first oil passage is located on the side wall of the chamber, and the second oil passage is located at the bottom of the chamber.

[0017] In one optional embodiment, a valve seat is provided in the chamber, and a sliding cavity is formed on the side of the valve seat facing the second oil passage, the sliding cavity communicating with the second oil passage; the first piston is slidably disposed in the sliding cavity, and the valve stem is adapted to pass through the valve seat and extend into the sliding cavity to connect with the first piston; the middle part of the side wall of the valve seat is recessed inward to form an annular buffer cavity, and the annular buffer cavity is provided with a plurality of fourth oil passages along the circumference; wherein, the first oil passage communicates with the annular buffer cavity, and the fourth oil passages communicate with the sliding cavity.

[0018] The beneficial effect of this utility model is that the first piston of the hydraulic cylinder and its stroke limiting mechanism is slidably arranged in the chamber. During the opening and closing of the oil circuit, it will only slide and will not produce insertion and removal actions, so that the sealing ring on the side wall of the first piston will not be cut off.

[0019] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention are realized and obtained through the structures particularly pointed out in the description and the accompanying drawings.

[0020] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the piston rod retraction process of a hydraulic cylinder provided in this embodiment of the present disclosure;

[0023] Figure 2 This is a schematic diagram of the structure when the first piston cuts off the oil passage according to an embodiment of the present disclosure;

[0024] Figure 3 This is a schematic diagram of the structure of a valve seat provided in an embodiment of the present disclosure;

[0025] Figure 4 This is a schematic diagram of the structure of a first oil outlet provided in an embodiment of this disclosure.

[0026] In the picture:

[0027] Cylinder block 1, rod chamber 11, rodless chamber 12, third oil passage 13;

[0028] Piston rod 2, second piston 21, guide ring 22;

[0029] Limit plate 3;

[0030] Valve body 4, chamber 41, first oil passage 42, second oil passage 43;

[0031] Valve stem 5, first piston 51;

[0032] Valve seat 6, sliding chamber 61, annular buffer chamber 62, fourth oil passage 63. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0034] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the figures, the thickness of parts may be exaggerated or reduced for the purpose of effectively depicting the technical content.

[0035] The following detailed description, with reference to the accompanying drawings, describes some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] like Figure 1 , Figure 2 As shown, at least one embodiment provides a hydraulic cylinder, including: a cylinder body 1, a piston rod 2, a limiting plate 3, a valve body 4, and a valve rod 5. The valve body 4 is disposed on the side wall of the cylinder body 1, the piston rod 2 is slidably disposed on the cylinder body 1, the valve rod 5 is slidably disposed on the valve body 4, and the limiting plate 3 is disposed on the piston rod 2.

[0037] In this embodiment, the piston rod 2 moves as a piston by being pushed by the hydraulic system. During the retraction of the piston rod 2, the piston rod 2 drives the limiting plate 3 to move toward the valve rod 5. When the limiting plate 3 comes into contact with the valve rod 5, it pushes the valve rod 5 to retract, causing the valve rod 5 to cut off the oil circuit to prevent the piston rod 2 from retracting, thus limiting the stroke of the piston rod 2.

[0038] like Figure 1As shown, in some embodiments, a second piston 21 is slidably disposed inside the cylinder 1, the inner end of the piston rod 2 is connected to the second piston 21, and the outer end is located outside the cylinder 1; wherein, the second piston 21 divides the cylinder 1 into a rod chamber 11 and a rodless chamber 12, a third oil passage 13 communicating with the valve body 4 is provided on the side wall of the rodless chamber 12, and a fifth oil passage communicating with the hydraulic system is provided on the side wall of the rod chamber 11.

[0039] In this embodiment, the piston rod 2 is extended or retracted by the hydraulic system. When the piston rod 2 needs to extend (e.g.) Figure 2 As shown), the hydraulic system injects oil into the valve body 4, causing the oil to flow through the valve body 4 into the rodless chamber 12, thereby pushing the second piston 21 to move. Meanwhile, the oil in the rod chamber 11 is squeezed and flows out through the fifth oil port into the hydraulic system. When the piston rod 2 needs to retract (e.g., ...), Figure 1 As shown), the hydraulic system injects oil into the rod chamber 11 through the fifth oil port, while the oil in the rodless chamber 12 is squeezed and flows into the valve body 4 through the third oil port 13, and then flows out of the valve body 4 back into the hydraulic system.

[0040] like Figure 1 As shown, in some embodiments, a chamber 41 is provided inside the valve body 4, and a first piston 51 is slidably disposed inside the chamber 41. A sealing ring is fitted on the side wall of the first piston 51 to prevent leakage; the inner end of the valve stem 5 is connected to the first piston 51, and the outer end is located outside the valve body 4.

[0041] In some embodiments, the chamber 41 is provided with a first oil passage 42 and a second oil passage 43. The first oil passage 42 is connected to the third oil passage 13, and the second oil passage 43 is connected to the hydraulic system.

[0042] like Figure 1 As shown, in some embodiments, the first oil passage 42 and the second oil passage 43 are arranged sequentially along the retraction direction of the piston rod 2; the first oil passage 42 is located on the side wall of the chamber 41, and the second oil passage 43 is located at the bottom of the chamber 41.

[0043] In this embodiment, when the piston rod 2 needs to extend (e.g.) Figure 2 As shown), the hydraulic system injects oil into the valve body 4 through the second oil port 43, so that the oil passes through the first oil port 42 and the third oil port 13 in sequence before entering the rodless chamber 12; when the piston rod 2 needs to retract (such as... Figure 1 As shown), the oil in the rodless chamber 12 sequentially passes through the third oil passage 13, the first oil passage 42, and the second oil passage 43 before entering the hydraulic system; wherein, during the retraction of the piston rod 2, when the limiting plate 3 on the piston rod 2 abuts against the outer end of the valve rod 5, the first piston 51 will move and thus pass over the first oil passage 42 (as shown). Figures 1 to 2As shown in the figure, the oil circuit is cut off at this time, and the oil in the rodless chamber 12 can no longer be discharged into the chamber 41 of the valve body 4. The piston rod 2 can no longer move, which restricts the movement stroke of the piston rod 2.

[0044] In some embodiments, the diameter of the first piston 51 is larger than the diameter of the second oil passage 43, which prevents the first piston 51 from being inserted into the second oil passage 43 and avoids the sealing ring of the side wall of the first piston 51 from being cut.

[0045] In some embodiments, the limiting plate 3 is disposed on the piston rod 2 and located outside the cylinder 1.

[0046] In this embodiment, the position of the limiting plate 3 on the piston rod 2 can be adjusted. By adjusting different positions, the hydraulic cylinder can have different strokes to meet different working conditions.

[0047] In some embodiments, a guide ring 22 is provided between the limiting plate 3 and the piston rod 2, and the guide ring 22 is sleeved on the piston rod 2; the guide ring 22 can move with the limiting plate 3, and the presence of the guide ring 22 avoids scratching the surface of the piston rod 2 when adjusting the limiting plate 3.

[0048] like Figure 3 , Figure 4 As shown, in some embodiments, a valve seat 6 is provided in the chamber 41, and a sliding cavity 61 is provided on the side of the valve seat 6 facing the second oil passage 43. The sliding cavity 61 is connected to the second oil passage 43. The first piston 51 is slidably disposed in the sliding cavity 61, and the valve stem 5 is adapted to pass through the valve seat 6 and extend into the sliding cavity 61 to connect with the first piston 51. The middle part of the side wall of the valve seat 6 is recessed inward to form an annular buffer cavity 62, and the annular buffer cavity 62 is provided with a plurality of fourth oil passages 63 of equal height along the circumference. Among them, the first oil passage 42 is connected to the annular buffer cavity 62, and the fourth oil passage 63 is connected to the sliding cavity 61.

[0049] In this embodiment, during the retraction of the piston rod 2, the oil passing through the first oil port 42 first enters the annular buffer chamber 62, then enters the sliding chamber 61 through each of the fourth oil ports 63, and then flows out through the second oil port 43. When the first piston 51 passes the fourth oil port 63, the oil passage is cut off.

[0050] like Figures 1 to 2As shown, at least one embodiment also provides a stroke limiting mechanism for a hydraulic cylinder, comprising: a valve body 4 disposed on the side wall of a cylinder body 1, and having a chamber 41 therein, the chamber 41 having a first oil passage 42 and a second oil passage 43; a first piston 51 slidably disposed within the chamber 41; and a valve stem 5, the inner end of which is connected to the first piston 51, and the outer end of which is located outside the valve body 4; wherein, an oil passage is formed between the first oil passage 42, the chamber 41, and the second oil passage 43, and the outer end of the valve stem 5 is adapted to be pressurized to drive the first piston 51 past the first oil passage 42 to cut off the oil passage.

[0051] like Figure 1 As shown, in some embodiments, the first oil passage 42 and the second oil passage 43 are arranged sequentially along the retraction direction of the piston rod 2; wherein the first oil passage 42 is located on the side wall of the chamber 41, and the second oil passage 43 is located at the bottom of the chamber 41.

[0052] like Figure 3 As shown, in some embodiments, a valve seat 6 is provided in the chamber 41, and a sliding cavity 61 is provided on the side of the valve seat 6 facing the second oil passage 43. The sliding cavity 61 is connected to the second oil passage 43. The first piston 51 is slidably disposed in the sliding cavity 61, and the valve stem 5 is adapted to pass through the valve seat 6 and extend into the sliding cavity 61 to connect with the first piston 51. The middle part of the side wall of the valve seat 6 is recessed inward to form an annular buffer cavity 62, and the annular buffer cavity 62 is provided with a plurality of fourth oil passages 63 of equal height along the circumference. Among them, the first oil passage 42 is connected to the annular buffer cavity 62, and the fourth oil passage 63 is connected to the sliding cavity 61.

[0053] In summary, the hydraulic cylinder and its first piston 51 with stroke limiting mechanism are slidably disposed in the chamber 41. During the opening and closing of the oil circuit, it will only slide and will not perform insertion or removal actions, so that the sealing ring on the side wall of the first piston 51 will not be at risk of being cut off.

[0054] In this document, when it is said that the first component is located on the second component, this can mean that the first component can be directly formed on the second component, or that the third component can be inserted between the first component and the second component.

[0055] In this document, when an element or layer is referred to as “located,” “joined to,” “connected to,” “attached to,” or “coupled to” another element or layer, it may be directly located, joined, connected, attached to, or coupled to the other element or layer, or there may be intermediate elements or layers present. Conversely, when an element is referred to as “directly on another element or layer,” “directly joined to,” “directly connected to,” “directly attached to,” or “directly coupled to” another element or layer, there may be no intermediate elements or layers present. Other terms used to describe relationships between elements should be interpreted in a similar manner (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the related listed items.

[0056] In this document, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0057] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0058] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0059] In the description of the embodiments of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0060] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence unless expressly indicated herein. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed above may be referred to as the second element, component, region, layer, or segment.

[0061] Spatially relative terms, such as “inside,” “outside,” “below,” “below,” “down,” “above,” “up,” etc., may be used herein to describe the relationship between one element or feature illustrated in the figures and another element or feature. In addition to the orientations depicted in the figures, spatially relative terms may be intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, an element described as “below” or “below” other elements or features would be oriented as “above” other elements or features. Thus, the example term “below” can cover both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0062] In the above discussion, unless otherwise stated, when used to describe numerical values, the terms “about,” “approximately,” “basically,” etc., indicate a change of + / - 10% in that value.

[0063] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A hydraulic cylinder, comprising: The cylinder body (1), piston rod (2), limiting plate (3), valve body (4), and valve stem (5) are provided, wherein the valve body (4) is disposed on the side wall of the cylinder body (1), one end of the piston rod (2) extends into the cylinder body (1), and the limiting plate (3) is disposed on the piston rod (2). The cylinder body (4) is characterized by the following features: The valve body (4) has a chamber (41) inside, and the chamber (41) has a first oil passage (42) and a second oil passage (43). The inner end of the valve stem (5) is located inside the chamber (41), and the outer end is located outside the valve body (4); During the retraction of the piston rod (2), the limiting plate (3) is adapted to move with the piston rod (2) to squeeze the outer end of the valve rod (5), so that the inner end of the valve rod (5) passes the first oil passage (42) to cut off the oil passage.

2. The hydraulic cylinder as described in claim 1, characterized in that, The inner end of the valve stem (5) is provided with a first piston (51); wherein The first piston (51) is adapted to slide within the chamber (41) by the action of the valve stem (5); During the retraction of the piston rod (2), the first piston (51) is adapted to pass over the first oil passage (42) to cut off the oil passage.

3. The hydraulic cylinder as described in claim 2, characterized in that, The diameter of the first piston (51) is larger than the diameter of the second oil port (43).

4. The hydraulic cylinder as described in claim 2, characterized in that, The first oil inlet (42) and the second oil inlet (43) are arranged sequentially along the retraction direction of the piston rod (2); wherein The first oil outlet (42) is located on the side wall of the chamber (41), and the second oil outlet (43) is located at the bottom of the chamber (41).

5. The hydraulic cylinder as described in claim 1, characterized in that, The piston rod (2) is provided with a second piston (21) at its end inside the cylinder (1). The second piston (21) is adapted to divide the cylinder (1) into a rod chamber (11) and a rodless chamber (12). The rodless cavity (12) has a third oil passage (13) on its side wall, which is connected to the first oil passage (42).

6. The hydraulic cylinder as described in claim 3, characterized in that, A valve seat (6) is provided in the chamber (41), and a sliding cavity (61) is provided on the side of the valve seat (6) facing the second oil port (43), and the sliding cavity (61) is connected to the second oil port (43); The first piston (51) is slidably disposed in the sliding cavity (61), and the valve stem (5) is adapted to pass through the valve seat (6) and extend into the sliding cavity (61) to connect with the first piston (51); The valve seat (6) has an inwardly recessed middle section of its side wall to form an annular buffer cavity (62), and the annular buffer cavity (62) has several fourth oil passages (63) along the circumferential direction. The first oil outlet (42) is connected to the annular buffer cavity (62), and the fourth oil outlet (63) is connected to the sliding cavity (61).

7. The hydraulic cylinder as described in claim 1, characterized in that, A guide ring (22) is provided between the limiting plate (3) and the piston rod (2); wherein, The guide ring (22) is fitted onto the piston rod (2).

8. A stroke limiting mechanism for a hydraulic cylinder, characterized in that, include: The valve body (4) is located on the side wall of the cylinder body (1) and has a chamber (41) inside it. The chamber (41) has a first oil passage (42) and a second oil passage (43). The first piston (51) is slidably disposed within the chamber (41); The valve stem (5) has its inner end connected to the first piston (51) and its outer end located outside the valve body (4); An oil passage is formed between the first oil port (42), the chamber (41), and the second oil port (43). The outer end of the valve stem (5) is adapted to be pressurized to drive the first piston (51) to pass over the first oil port (42) to cut off the oil passage.

9. The stroke limiting mechanism for a hydraulic cylinder as described in claim 8, characterized in that, The first oil inlet (42) and the second oil inlet (43) are arranged sequentially along the retraction direction of the piston rod (2); wherein The first oil outlet (42) is located on the side wall of the chamber (41), and the second oil outlet (43) is located at the bottom of the chamber (41).

10. The stroke limiting mechanism for a hydraulic cylinder as described in claim 9, characterized in that, A valve seat (6) is provided in the chamber (41), and a sliding cavity (61) is provided on the side of the valve seat (6) facing the second oil port (43), and the sliding cavity (61) is connected to the second oil port (43); The first piston (51) is slidably disposed in the sliding cavity (61), and the valve stem (5) is adapted to pass through the valve seat (6) and extend into the sliding cavity (61) to connect with the first piston (51); The valve seat (6) has an inwardly recessed middle section of its side wall to form an annular buffer cavity (62), and the annular buffer cavity (62) has several fourth oil passages (63) along the circumferential direction. The first oil outlet (42) is connected to the annular buffer cavity (62), and the fourth oil outlet (63) is connected to the sliding cavity (61).

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