Mechanical intermediate position limiting actuator and method for limiting the position of the actuator

Abstract

The application relates to an intermediate-position mechanical-limiting actuating cylinder and a limiting method thereof. The actuating cylinder comprises a cylinder body, a rod-equipped piston, a support and a floating piston. The cylinder body is a cylindrical cavity structure, and oil passages are arranged on the outer wall of the cylinder body at different positions. The front end of the rod-equipped piston is sleeved into the inside of the cylinder body, the rear end of the rod-equipped piston extends out of the cylinder body in the axial direction, and the rod-equipped piston can slide in the axial direction in the cavity of the cylinder body. The support is arranged in the cavity formed by the cylinder body and the rod-equipped piston, and is coaxially sleeved on the outside of the rear end of the rod-equipped piston. The floating piston is coaxially arranged on the outside of the support. The front end of the support is provided with a limiting end face, the rear end of the support is fixedly connected with the radial inner wall of the cylinder body, the cylindrical side wall of the floating piston is arranged close to the axial inner wall of the cylinder body, and the rear end of the floating piston is arranged close to the outer wall of the support. According to the intermediate-position mechanical-limiting actuating cylinder, the support fixed in the inside of the cylinder body and the floating piston are designed, so that the actuating cylinder can be in a mechanical limiting state at a specific intermediate position, and the actuating cylinder has the characteristics of simple structure and convenient operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic actuators, and in particular relates to an actuator cylinder with mechanical intermediate position limitation and a limiting method thereof. Background Art

[0002] As aircraft speeds and weights continue to increase, manual control of aircraft and certain components (such as retracting and extending landing gear and flaps) is becoming increasingly difficult. Consequently, the use of hydraulically and electrically driven components is increasing. Electric drives offer greater agility, but when high power is required, they require heavy electric motors, and the connection between the motor and the driven components is also complex. Consequently, aircraft hydraulic systems are typically used to retract and extend landing gear, flaps, and speed brakes.

[0003] In hydraulic systems, hydraulic actuators are components that perform work on the outside world, directly converting hydraulic energy into mechanical energy. Among reciprocating hydraulic actuators, hydraulic actuators are widely used and have evolved into various types, including three-position actuators and locking actuators.

[0004] In order to enable the piston rod of an actuator to be mechanically limited even at a specific intermediate position without requiring complex displacement signals and control systems, a new three-position actuator is needed. This actuator allows the piston rod to be mechanically limited not only at both ends but also at a specific intermediate position. Therefore, the present invention aims to provide an actuator with a mechanical intermediate position limit to address the current problem of requiring mechanical intermediate position limits for actuators. Summary of the Invention

[0005] In response to the shortcomings in the relevant technologies, the present invention provides an actuator cylinder with mechanical limit in the middle position and a limiting method thereof, wherein the actuator cylinder is designed with a bracket fixed inside the cylinder body and a floating piston, so that the actuator cylinder can be in a mechanically limited state at a specific middle position. This actuator cylinder has the characteristics of simplified structure and easy operation, and can solve the current technical problem that the actuator cylinder needs to be mechanically limited in the middle position.

[0006] The present invention provides an actuator with a mechanical limit at an intermediate position, comprising:

[0007] The cylinder has a cylindrical cavity structure, and oil ports are opened at different positions on the outer wall of the cylinder to allow pressure oil or return oil to provide hydraulic power;

[0008] The piston with a rod has a front end that is sleeved into the interior of the cylinder and a rear end that extends axially out of the cylinder, and can slide axially along the cavity in the cylinder under hydraulic power;

[0009] The bracket is cylindrical in shape as a whole, is disposed in the cavity formed by the cylinder and the piston with rod, and is coaxially sleeved on the outer side of the rear end of the piston with rod; and

[0010] The movable piston is cylindrical in shape as a whole and is arranged on the same side as the bracket and coaxially arranged outside the bracket;

[0011] Among them, the front end of the bracket is provided with a limiting end surface, and the rear end of the bracket is fixedly connected to the radial inner wall of the cylinder; the cylindrical side wall of the floating piston is arranged close to the axial inner wall of the cylinder, and the rear end of the floating piston is arranged close to the outer wall of the bracket. The floating piston as a whole can slide axially along the cavity in the cylinder under hydraulic power.

[0012] In some embodiments, the piston with rod includes a piston and a piston rod, the front end of the piston rod is fixedly connected to the piston, and the rear end of the piston rod extends axially out of the cylinder.

[0013] In some embodiments, the connection portion between the piston and the inner wall of the cylinder is sealed by a seal, and the rear end of the piston rod is sealed to the inner wall of the cylinder by a seal, and the seal is a sealing ring.

[0014] In some embodiments, the bracket is a cylindrical cavity structure with a limiting end surface at the front end, the rear end of the bracket is fixedly connected to the radial inner wall of the cylinder, and the rear end of the piston rod extends to the outside of the cylinder after passing through the cavity structure of the bracket;

[0015] The limiting end surface is a folded edge formed by folding the front end of the cylindrical cavity structure outward, and is used to limit the axial position of the floating piston.

[0016] In some embodiments, the cylindrical side wall of the movable piston and the axial inner wall of the cylinder are sealed by a seal, and the rear end of the movable piston and the outer wall of the bracket are sealed by a seal, which is a sealing ring.

[0017] In some embodiments, the length of the cylindrical side wall of the traveling piston is greater than the cylindrical side wall of the bracket, so that the bracket is entirely accommodated inside the traveling piston.

[0018] In some embodiments, an axially protruding step is further provided on the piston near the piston rod, and the height of the step is equal to the thickness of the cylindrical side wall of the movable piston;

[0019] When the actuator is in the open state, the rear end of the floating piston is close to the rear end of the outer wall of the bracket, and the step on the piston is used to closely contact the cylindrical side wall of the floating piston. The axial position of the rod piston is defined by the cylindrical side wall of the floating piston.

[0020] When the actuator is in the middle state, the step is used to closely contact the cylindrical side wall of the floating piston, which is used to limit the axial position of the rod piston. At the same time, the rear end of the floating piston slides axially to the front end of the bracket under the action of hydraulic pressure and is restricted by the limiting end face to determine the axial position of the floating piston, and finally the actuator is in the middle state.

[0021] In some embodiments, a first oil port is opened at the rear end of the cylinder for introducing pressure oil or return oil, and the first oil port is arranged above the piston rod for introducing pressure oil or return oil, a second oil port is opened at the top of the cylinder close to the first oil port, and a third oil port is opened at the front end of the cylinder along the axial direction for introducing pressure oil or return oil.

[0022] In some embodiments, the cavity formed by the cylinder, the piston with rod, the bracket and the floating piston is the first cavity, the cavity formed by the cylinder, the bracket and the floating piston is the second cavity, and the cavity formed by the cylinder and the front end of the piston is the third cavity;

[0023] Among them, the first cavity is connected to the first oil port, so that the pressure oil or return oil enters the first cavity after entering from the first oil port, the second cavity is connected to the second oil port, so that the pressure oil or return oil enters the second cavity after entering from the second oil port, and the third cavity is connected to the third oil port, so that the pressure oil or return oil enters the third cavity after entering from the third oil port, providing hydraulic power for the axial movement of the floating piston and the rod piston.

[0024] The present invention further provides a method for limiting an actuator cylinder with a mechanical limit in an intermediate position, which is performed using the actuator cylinder with a mechanical limit in an intermediate position described in any of the above embodiments, and includes the following steps:

[0025] When the actuator is in a contracted state, pressure oil is introduced into the first cavity from the first oil port, return oil is introduced into the second cavity from the second oil port, and return oil is introduced into the third cavity from the third oil port. Under the action of the hydraulic pressure, the rear end of the movable piston moves toward the rear end along the outer wall of the bracket until the rear end of the movable piston and the rear end of the bracket abut against each other, and at the same time, the piston with rod moves axially toward the front end of the cylinder.

[0026] When the actuator cylinder is in the open state, return oil is introduced into the first cavity from the first oil port, return oil is introduced into the second cavity from the second oil port, and pressure oil is introduced into the third cavity from the third oil port. Under the action of the hydraulic pressure, the rear end of the movable piston moves toward the rear end along the outer wall of the bracket until the rear end of the movable piston and the rear end of the bracket are in close contact with each other. At the same time, the rod piston moves axially toward the rear end of the cylinder under the action of the hydraulic pressure until the step on the piston is in close contact with the cylindrical side wall of the movable piston. At this time, the axial position of the rod piston is limited by the cylindrical side wall of the movable piston.

[0027] When the actuator is in the middle state, return oil is introduced into the first cavity from the first oil port, pressure oil is introduced into the second cavity from the second oil port, and pressure oil is introduced into the third cavity from the third oil port. Under the action of hydraulic pressure, the rear end of the swimming piston moves toward the front end along the outer wall of the bracket. The rear end of the swimming piston determines its axial position under the restriction of the limiting end face. At the same time, the step is in close contact with the cylindrical side wall of the swimming piston. At this time, the axial position of the rod piston is limited by the cylindrical side wall of the swimming piston.

[0028] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0029] 1. The intermediate position mechanically limited actuator proposed in this invention utilizes a combination of a bracket fixed inside the cylinder and a movable piston to enable the actuator to be mechanically limited at a specific intermediate position. This simplifies the design and operation while optimizing the adaptability of the actuator, resolving the technical issue of existing actuators being unable to achieve mechanical limiting at intermediate positions.

[0030] 2. The intermediate position mechanically limited actuator cylinder proposed in the present invention only comprises a cylinder body and components such as a piston with a rod, a bracket and a floating piston arranged inside the cylinder body, and has the characteristics of simple structural design and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 A cross-sectional view of an embodiment of an actuator with a mechanical limit at an intermediate position according to the present invention in a retracted state;

[0033] Figure 2 A cross-sectional view of an embodiment of an actuator with a mechanical limit at an intermediate position according to the present invention in an open state;

[0034] Figure 3 This is a cross-sectional view of an actuator with mechanical intermediate position limiting in an intermediate state according to an embodiment of the present invention.

[0035] In the above figures:

[0036] 1. Cylinder; 2. Piston; 3. Piston rod; 4. Bracket; 5. Floating piston; 6. Sealing ring; 7. Limit end face; 8. Step; 9. First oil port; 10. Second oil port; 11. Third oil port; 12. First cavity; 13. Second cavity; 14. Third cavity. DETAILED DESCRIPTION

[0037] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be understood that the terms "center", "transverse", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0039] The terms "first," "second," and "third" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features indicated. Therefore, a feature specified as "first," "second," or "third" may explicitly or implicitly include one or more of such features.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0041] Reference Attachment Figure 1 As shown, in an exemplary embodiment of the intermediate position mechanically limited actuator cylinder of the present invention, the intermediate position mechanically limited actuator cylinder has a main structure comprising: a cylinder body 1 and a piston with a rod, a bracket 4 and a floating piston 5 arranged inside the cylinder body 1. These components will be described in detail below:

[0042] From the attached Figure 1It can be seen that the actuator cylinder with mechanical limit in the middle position is in a retracted state. The actuator cylinder specifically includes a cylinder body 1, which is actually a cylindrical cavity structure, and a plurality of oil ports are opened at different positions on the outer wall of the cylinder body 1 for introducing pressure oil or return oil to provide hydraulic power; a piston with a rod is provided inside the cylinder body 1, and the front end of the piston with a rod is inserted into the cylinder body 1, and the rear end thereof extends axially to the outside of the cylinder body 1, and can slide axially along the cavity inside the cylinder body 1 under the action of hydraulic power; a bracket 4 is also provided in the cavity structure formed by the cylinder body 1 and the piston with a rod, and the bracket 4 is coaxially sleeved on the outside of the rear end of the piston with a rod, and the bracket 4 is cylindrical as a whole; a floating piston 5 is coaxially sleeved on the outside of the bracket 4, and this component is also a cylindrical structure.

[0043] Furthermore, the rod-mounted piston specifically includes two parts, a piston 2 and a piston rod 3. The front end of the piston rod 3 is fixedly connected to the piston 2 and is inserted into the interior of the cylinder 1. The rear end of the piston rod 3 extends axially to the outside of the cylinder 1. In order to improve the sealing between the rod-mounted piston and the cylinder 1, the present invention seals the connecting part between the piston 2 and the inner wall of the cylinder 1 through a seal, and the rear end of the piston rod 3 is sealed with the inner wall of the cylinder 1 through a seal. The seal used is a sealing ring 6 (there is no specific limitation on the type and material of the sealing ring, and those skilled in the art can select it according to actual needs).

[0044] The bracket 4 is a cylindrical cavity structure with a stopper end surface 7 at its front end. The rear end of the bracket 4 is fixedly connected to the radial inner wall of the cylinder 1. The rear end of the piston rod 3 extends through the bracket 4 cavity structure and extends to the exterior of the cylinder 1. The stopper end surface 7 is a folded edge formed by the front end of the cylindrical cavity structure of the bracket 4, which is used to limit the axial position of the floating piston 5. The floating piston 5 is also a cylindrical structure. Its cylindrical sidewall (also called the "axial section") is positioned closely against the axial inner wall of the cylinder 1 and is sealed by a seal. The rear end of the floating piston (also called the "radial section") is positioned closely against the outer wall of the bracket 4 and is also sealed by a seal. Ultimately, the floating piston 5 can slide axially along the cavity of the cylinder 1 under hydraulic power. The seal used is also a sealing ring 6 (the type and material of the sealing ring are not specifically limited and can be selected by those skilled in the art based on actual needs). Moreover, the cylindrical sidewall of the floating piston 5 is longer than that of the bracket 4, allowing the bracket 4 to be completely accommodated within the floating piston 5.

[0045] In addition, an axially raised step 8 is provided on the piston 2 near the piston rod 3. The height of the step 8 is consistent with the thickness of the cylindrical side wall of the floating piston 5. The actual function of the step 8 is as follows:

[0046] Combined with attachment Figure 2It can be seen that when the actuator cylinder is in the open state, the rear end ("radial section") of the floating piston 5 is close to the rear end of the outer wall of the bracket 4. In the cavity structure inside the cylinder 1, the piston with rod slides axially toward the rear end of the cylinder 1 under the action of hydraulic pressure, so that the step 8 on the piston 2 is in close contact with the cylindrical side wall ("axial section") of the floating piston 5. At this time, the axial position of the piston with rod is limited by the cylindrical side wall of the floating piston 5.

[0047] Combined with attachment Figure 3 It can be seen that when the actuator is in the middle state, the step 8 is in close contact with the cylindrical side wall of the floating piston 5 (i.e., the "axial section"), which is used to limit the axial position of the rod piston. At the same time, the rear end of the floating piston 5 (i.e., the "radial section") slides axially to the front end of the bracket 4 under the action of hydraulic pressure and is limited by the limiting end face 7 to determine the axial position of the floating piston 5, ultimately placing the actuator in the middle state. It can be seen that the present invention, through the combined design of the bracket 4 and the floating piston 5, which are only fixed inside the cylinder body 1, enables the actuator to be in a mechanically limited state at a specific middle position. It can optimize the adaptability of the actuator while simplifying the design and operating difficulty, and solve the technical problem that the existing actuator cannot achieve mechanical limitation at the middle position.

[0048] It should be further explained that multiple oil passages are provided at different locations on the outer wall of the cylinder 1, specifically including: a first oil passage 9 provided at the rear end of the cylinder 1 for introducing pressure oil or return oil, and the first oil passage 9 is provided above the piston rod 3; a second oil passage 10 provided at the top of the cylinder 1 near the first oil passage 9 for introducing pressure oil or return oil; and a third oil passage 11 provided along the axial direction at the front end of the cylinder 1 for introducing pressure oil or return oil. The cylinder 1 and the multiple components inside the cylinder 1 also form multiple cavity structures. Specifically, the cavity formed by the cylinder 1, the piston with rod, the bracket 4 and the floating piston 5 is the first cavity 12; the cavity formed by the cylinder 1, the bracket 4 and the floating piston 5 is the second cavity 13; and the cavity formed between the cylinder 1 and the front end of the piston 2 is the third cavity 14. The connection relationship between the above-mentioned cavities and oil ports is as follows: the first cavity 12 can be fluidly connected to the first oil port 9, so that the pressure oil or return oil entering from the first oil port 9 enters the first cavity 12; the second cavity 13 can be fluidly connected to the second oil port 10, so that the pressure oil or return oil entering from the second oil port 10 enters the second cavity 13; the third cavity 14 can be fluidly connected to the third oil port 11, so that the pressure oil or return oil entering from the third oil port 11 enters the third cavity 14, providing hydraulic power for the axial movement of the floating piston 5 and the rod piston.

[0049] The following is combined with Figure 1-3 The working process of the actuator with mechanical limit in the middle position of the present invention in different states is described in detail:

[0050] Attachment Figure 1 It is a cross-sectional schematic diagram of the actuator with mechanical limit in the middle position of the present invention in the retracted state. When the actuator is in the retracted state, pressure oil is introduced into the first cavity 12 from the first oil port 9, return oil is introduced into the second cavity 13 from the second oil port 10, and return oil is introduced into the third cavity 14 from the third oil port 11. Under the action of hydraulic pressure, the rear end ("radial section") of the movable piston 5 moves toward the rear end along the outer wall of the bracket 4 until the rear end of the movable piston 5 and the rear end of the bracket 4 are in close contact with each other. Under the action of hydraulic pressure, the piston with rod moves axially toward the front end of the cylinder 1.

[0051] Attachment Figure 2 It is a cross-sectional schematic diagram of the actuator cylinder with mechanical limit in the middle position of the present invention in the open state. When the actuator cylinder is in the open state, return oil is introduced into the first cavity 12 from the first oil port 9, return oil is introduced into the second cavity 13 from the second oil port 10, and pressure oil is introduced into the third cavity 14 from the third oil port 11. Under the action of hydraulic pressure, the rear end of the movable piston 5 (i.e., the "radial section") moves toward the rear end along the outer wall of the bracket 4 until the rear end of the movable piston 5 and the rear end of the bracket 4 are in close contact with each other. Under the action of hydraulic pressure, the piston with rod moves axially toward the rear end of the cylinder 1 until the step 8 on the piston 2 is in close contact with the cylindrical side wall (i.e., the "axial section") of the movable piston 5. At this time, the axial position of the piston with rod is limited by the "axial section" of the movable piston 5.

[0052] Attachment Figure 3 It is a cross-sectional schematic diagram of the actuator cylinder with mechanical limit in the middle position of the present invention in the middle state. When the actuator cylinder is in the middle state, return oil is introduced into the first cavity 12 from the first oil port 9, pressure oil is introduced into the second cavity 13 from the second oil port 10, and pressure oil is introduced into the third cavity 14 from the third oil port 11. Under the action of hydraulic pressure, the rear end (i.e., the "radial section") of the movable piston 5 moves toward the front end along the outer wall of the bracket 4. The rear end of the movable piston 5 determines its axial position under the restriction of the limiting end face 7 of the bracket 4. At the same time, the step is in close contact with the cylindrical side wall (i.e., the "axial section") of the movable piston, i.e., the axial position of the rod piston is limited by the "axial section" of the movable piston 5. At this time, the rod piston is in the middle position of the cylinder 1.

[0053] Through the description of multiple embodiments of the actuator cylinder with mechanical intermediate position limit and the limiting method thereof of the present invention, it can be seen that the actuator cylinder with mechanical intermediate position limit and the limiting method thereof of the present invention have at least one or more of the following advantages:

[0054] 1. Simple structure and easy operation. The actuator cylinder with mechanical limit in the middle position proposed by the present invention adopts a combined design of a bracket fixed inside the cylinder body and a floating piston, so that the actuator cylinder can be mechanically limited in a specific middle position. While simplifying the design and operation difficulty, it optimizes the adaptability of the actuator cylinder and solves the technical problem that existing actuator cylinders cannot achieve mechanical limit in the middle position.

[0055] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, persons skilled in the art should understand that the specific implementation methods of the present invention may still be modified or some technical features may be replaced by equivalents without departing from the spirit of the technical solutions of the present invention, and all of these should fall within the scope of the technical solutions claimed for protection by the present invention.

Claims

1. An actuator with mechanical limit in the middle position, characterized in that: include: The cylinder body has a cylindrical cavity structure, and oil ports are provided at different positions on the outer wall of the cylinder body for introducing pressurized oil or return oil to provide hydraulic power; A piston with a rod, the front end of which is sleeved into the interior of the cylinder and the rear end of which extends axially out of the cylinder, and can slide axially along the cavity in the cylinder under the hydraulic power; The bracket is cylindrical in shape as a whole, is disposed in the cavity formed by the cylinder and the piston with rod, and is coaxially sleeved on the outer side of the rear end of the piston with rod; and The movable piston is cylindrical in shape as a whole, is arranged on the same side as the bracket, and is coaxially arranged outside the bracket; The front end of the bracket is provided with a limiting end surface, and the rear end of the bracket is fixedly connected to the radial inner wall of the cylinder; the cylindrical side wall of the floating piston is arranged closely against the axial inner wall of the cylinder, and the rear end of the floating piston is arranged closely against the outer wall of the bracket. The floating piston as a whole can slide axially along the cavity in the cylinder under hydraulic power; The rod piston comprises a piston and a piston rod, the front end of the piston rod is fixedly connected to the piston, and the rear end of the piston rod extends axially out of the cylinder; A first oil port is provided at the rear end of the cylinder body for introducing pressure oil or return oil, and the first oil port is provided above the piston rod; a second oil port is provided at the top of the cylinder body near the first oil port for introducing pressure oil or return oil; a third oil port is provided at the front end of the cylinder body along the axial direction for introducing pressure oil or return oil; The cavity formed by the cylinder, the piston with rod, the bracket and the floating piston is the first cavity, the cavity formed by the cylinder, the bracket and the floating piston is the second cavity, and the cavity formed by the cylinder and the front end of the piston is the third cavity; Among them, the first cavity is connected to the first oil port, so that the pressure oil or return oil enters the first cavity after entering from the first oil port, the second cavity is connected to the second oil port, so that the pressure oil or return oil enters the second cavity after entering from the second oil port, and the third cavity is connected to the third oil port, so that the pressure oil or return oil enters the third cavity after entering from the third oil port, providing hydraulic power for the axial movement of the floating piston and the rod piston.

2. The actuator with mechanical limit in the middle position according to claim 1, characterized in that: The connecting portion between the piston and the inner wall of the cylinder is sealed by a sealing member, and the rear end of the piston rod is sealed with the inner wall of the cylinder by a sealing member, and the sealing member is a sealing ring.

3. The actuator with mechanical limit in the middle position according to claim 1, characterized in that: The bracket is a cylindrical cavity structure with a limiting end surface at the front end, the rear end of the bracket is fixedly connected to the radial inner wall of the cylinder, and the rear end of the piston rod extends to the outside of the cylinder after passing through the cavity structure of the bracket; The limiting end surface is a folded edge formed by folding the front end of the cylindrical cavity structure outward, and is used to limit the axial position of the floating piston.

4. The actuator with mechanical limit at the intermediate position according to claim 3, characterized in that: The cylindrical side wall of the movable piston is sealed with the axial inner wall of the cylinder through a sealing member, and the rear end of the movable piston is sealed with the outer wall of the bracket through a sealing member, and the sealing member is a sealing ring.

5. The actuator with mechanical limit at the intermediate position according to claim 4, characterized in that: The length of the cylindrical side wall of the traveling piston is greater than the cylindrical side wall of the bracket, so that the bracket is entirely accommodated in the interior of the traveling piston.

6. The actuator with mechanical limit at the intermediate position according to claim 5, characterized in that: An axially raised step is also provided on the piston near the piston rod, and the height of the step is equal to the thickness of the cylindrical side wall of the floating piston; When the actuating cylinder is in the open state, the rear end of the traveling piston is in close contact with the rear end of the outer wall of the bracket, the step on the piston is used to be in close contact with the cylindrical side wall of the traveling piston, and the axial position of the rod piston is defined by the cylindrical side wall of the traveling piston; When the actuator cylinder is in the middle state, the step is used to closely contact the cylindrical side wall of the floating piston, so as to limit the axial position of the rod piston. At the same time, the rear end of the floating piston slides axially to the front end of the bracket under the action of hydraulic pressure and is restricted by the limiting end face to determine the axial position of the floating piston, so as to finally put the actuator cylinder in the middle state.

7. A method for limiting the position of an actuator with mechanical limit in the middle position, characterized in that: The method is performed using an actuator with an intermediate position mechanical limit according to any one of claims 1 to 6, comprising the following steps: When the actuator is in a contracted state, pressure oil is introduced into the first cavity from the first oil port, return oil is introduced into the second cavity from the second oil port, and return oil is introduced into the third cavity from the third oil port. Under the action of the hydraulic pressure, the rear end of the movable piston moves toward the rear end along the outer wall of the bracket until the rear end of the movable piston abuts against the rear end of the bracket, and at the same time, the piston with rod moves axially toward the front end of the cylinder. When the actuator cylinder is in the open state, return oil is introduced into the first cavity from the first oil port, return oil is introduced into the second cavity from the second oil port, and pressure oil is introduced into the third cavity from the third oil port. Under the action of the hydraulic pressure, the rear end of the floating piston moves toward the rear end along the outer wall of the bracket until the rear end of the floating piston and the rear end of the bracket are in close contact with each other. At the same time, the rod piston moves axially toward the rear end of the cylinder under the action of the hydraulic pressure until the step on the piston is in close contact with the cylindrical side wall of the floating piston. At this time, the axial position of the rod piston is limited by the cylindrical side wall of the floating piston. When the actuator is in the middle state, return oil is introduced into the first cavity from the first oil port, pressure oil is introduced into the second cavity from the second oil port, and pressure oil is introduced into the third cavity from the third oil port. Under the action of hydraulic pressure, the rear end of the floating piston moves toward the front end along the outer wall of the bracket. The rear end of the floating piston determines its axial position under the restriction of the limiting end face, and the step is in close contact with the cylindrical side wall of the floating piston. At this time, the axial position of the rod piston is limited by the cylindrical side wall of the floating piston.

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