A hydraulic cylinder stroke end locking device and locking method

Abstract

The application discloses a hydraulic oil cylinder stroke terminal locking device and a locking method, which comprises an oil cylinder assembly and a stroke terminal locking device. The oil cylinder assembly comprises an oil cylinder barrel, a double-rod type oil cylinder piston rod and a locking device mounting cylinder. The stroke terminal locking device comprises a driving mounting bracket, an electric push rod, a locking push rod, a steel ball and an oil cylinder locking seat. The front end of the driving mounting bracket is provided with a plurality of steel ball movement grooves, and the steel ball is mounted in the steel ball movement grooves; the right end of the locking push rod is provided with a steel ball unlocking groove; the oil cylinder locking seat is connected to the end of the oil cylinder piston rod, and a locking ring groove is arranged in the oil cylinder locking seat. The electric push rod drives the locking push rod to move axially, when the locking push rod moves to the left, the steel ball is separated from the unlocking groove and is pushed out radially to be clamped into the locking ring groove, so that the terminal locking of the oil cylinder piston rod is realized; when the locking push rod moves to the right, the steel ball falls into the unlocking groove, and the locking is released. The application has compact structure, can be integrated on the oil cylinder, is suitable for working conditions with limited installation space, and is reliable in locking and high in safety.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic cylinder technology, and particularly relates to a hydraulic cylinder stroke end locking device and locking method. Background Technology

[0002] In some equipment that uses hydraulic cylinders as actuators, in order to prevent equipment from going out of control due to misoperation of the hydraulic system control or internal leakage of hydraulic components, the hydraulic cylinder is usually required to have a reliable mechanical locking function at the end of its stroke.

[0003] In existing technologies, there are various ways to achieve hydraulic cylinder position locking. For example, a common solution is to use hydraulic circuits such as hydraulic locks for pressure holding and locking. However, this method cannot fundamentally solve the problem of slow piston rod slippage caused by internal leakage of hydraulic components, resulting in insufficient locking reliability.

[0004] To overcome the shortcomings of purely hydraulic locking, various mechanical locking hydraulic cylinders have emerged on the market. For example, Chinese invention patent application CN112922921A discloses a hydraulic cylinder capable of locking at any position. It achieves locking by manually rotating the screw, which incorporates a lead screw, nut locking element, and handwheel inside the piston rod. While this solution provides a large locking force, it requires manual operation, making automated control difficult, and its structure is relatively complex. Another example is Chinese utility model patent CN208702819U, which discloses a novel mechanical locking hydraulic cylinder that uses hydraulic oil to push an unlocking piston to compress a spring, thereby unlocking the steel ball. Although this solution achieves built-in locking, its unlocking action relies on additional hydraulic circuit control, increasing system complexity. Furthermore, the locking state depends on spring force, which may pose a risk of unlocking under strong vibration. Additionally, Chinese invention patent application CN108006011A discloses a double-rod hydraulic cylinder with locking and positioning functions, which uses pneumatic pressure to push a locking sleeve to compress a spring for unlocking. This solution also requires an additional pneumatic system, and the locking mechanism relies on spring reset, making it unsuitable for all operating conditions.

[0005] When the installation space for the hydraulic cylinder is limited, making it impossible to install an external auxiliary locking mechanism, designing a compact, internally integrated locking device becomes particularly important. However, existing built-in mechanical locking devices, such as Chinese invention patent applications CN105402189A and CN104763706A, mostly employ a spring-reset locking structure with hydraulic or hydrostatic assisted unlocking. These structures typically suffer from the following problems: first, the locking and unlocking process relies on complex internal oil or air circuit switching, increasing potential points of failure; second, the locking or unlocking force is significantly affected by spring performance, and its long-term reliability needs verification; and third, it is difficult to achieve precise mechanical locking at both the extended and retracted ends.

[0006] Therefore, there is an urgent need for a device that is compact in structure, can be easily integrated into a hydraulic cylinder, adopts electric active control, does not rely on additional hydraulic or pneumatic systems, and can provide highly reliable mechanical locking at the end of the stroke, in order to solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides a hydraulic cylinder stroke end locking device and locking method to achieve the requirement of locking the end position of the hydraulic cylinder stroke in a confined space.

[0008] This invention is implemented as follows: a hydraulic cylinder stroke end locking device includes a cylinder assembly and a stroke end locking device. The cylinder assembly includes a cylinder barrel, a cylinder piston rod, and a locking device mounting cylinder. The cylinder piston rod is installed inside the cylinder barrel and extends and retracts axially. The stroke end locking device includes a drive mounting bracket, an electric push rod, a locking push rod, a steel ball, and a cylinder locking seat. The drive mounting bracket is fixed to the locking device mounting cylinder, and the electric push rod is mounted on the drive mounting bracket. The movable rod of the electric push rod is connected to the locking push rod. The front end of the movable mounting bracket is machined with multiple evenly distributed circumferential grooves for moving steel balls, and the steel balls are installed in the grooves. The right end of the locking push rod is machined with a steel ball unlocking groove. The locking push rod is inserted into the drive mounting bracket and drives the steel balls to move radially within the grooves by axial movement. The cylinder locking seat is connected to the end of the cylinder piston rod and has a locking ring groove machined inside to accommodate the expanded steel balls. When the locking push rod moves to the locking position, the steel balls disengage from the unlocking groove and are pushed radially outward, locking into the locking ring groove to restrict the axial movement of the cylinder piston rod.

[0009] More preferably, the steel ball unlocking groove is a U-shaped groove with a chamfer angle greater than 45°, and the groove depth is such that when all the steel balls fall into the groove, the steel balls do not protrude outside the steel ball movement groove and are in the unlocked state.

[0010] More preferably, the rear end of the drive mounting bracket is a symmetrical frame structure, the middle of the frame is used to install the electric push rod and the locking push rod, and the front end is a hollow cylindrical flange long cylindrical structure, the cylindrical flange is used to connect the cylinder locking device mounting cylinder.

[0011] More preferably, the ball movement groove is cylindrical, with its axis perpendicular to the cylindrical axis of the drive mounting bracket, and the cylindrical groove is partially tapered outward to prevent the ball from falling out.

[0012] More preferably, the cylinder locking seat is cylindrical in shape, with threads machined on the right side to connect with the end of the cylinder piston rod, and two arc-shaped grooves machined inside the cylindrical part on the left side, corresponding to the two positions of the cylinder extension and retraction ends, respectively.

[0013] More preferably, the rear end of the electric push rod is connected to the drive mounting bracket via a pin, and the front movable rod is connected to the locking push rod via a pin.

[0014] A locking method for a hydraulic cylinder stroke end locking device includes the following steps: When it is necessary to lock the cylinder piston rod, the electric push rod is controlled to move, driving the locking push rod to move to the left; the locking push rod pushes a steel ball to disengage it from the steel ball unlocking groove, and the steel ball moves radially outward and exposes the steel ball movement groove; the locking push rod continues to move, making the steel ball tangent to the outer diameter of the locking push rod, and the steel ball remains in an bulging state under the restriction of the locking push rod and is locked into the locking ring groove of the cylinder locking seat, thereby achieving end locking of the cylinder piston rod; when it is necessary to unlock, the electric push rod is controlled to move in the opposite direction, driving the locking push rod to move to the right, causing the steel ball to fall into the steel ball unlocking groove, disengage from the locking ring groove, and the cylinder piston rod resumes free movement.

[0015] More preferably, the locking ring groove includes a retractable locking groove and an extended locking groove, which correspond to the retracted and extended end positions of the hydraulic cylinder piston rod, respectively; when the hydraulic cylinder piston rod moves to either end position, the locking push rod is driven by controlling the electric push rod to make the expanded steel ball lock into the corresponding locking groove.

[0016] More preferably, when the locking push rod moves to the left to lock, the steel ball moves along the chamfered slope of the steel ball unlocking groove on the locking push rod until it is pushed out and abuts against the outer diameter of the locking push rod.

[0017] More preferably, the electric push rod is hinged to the drive mounting bracket and the locking push rod via a pin, thereby converting the linear extension and retraction motion of the electric push rod into the axial movement of the locking push rod.

[0018] The advantages and technical effects of this invention are as follows: Compared with the existing technology that uses external locking mechanisms such as pins, this invention integrates the locking device inside the hydraulic cylinder, resulting in a compact structure that can be easily installed on the hydraulic cylinder, making it particularly suitable for applications with limited installation space. Compared with the locking structure driven by an unlocking piston spring in prior art CN208702819U, this invention uses an electric push rod as the driving element, providing more flexible control and facilitating automated control. Compared with the self-locking structure driven by pressure oil in CN104763706A, this invention does not rely on hydraulic system pressure for locking and unlocking, and can maintain the locked state even when the hydraulic system is completely de-energized or depressurized, offering higher safety and reliability. Compared with the structure in CN105402189A that relies on a spring to maintain locking, this invention actively controls the position of the locking push rod through an electric push rod to switch between locking and unlocking, resulting in clearer control logic and a more reliable locked state. This invention effectively reduces the control risk caused by hydraulic system malfunctions, providing a higher safety factor for system control. Attached Figure Description

[0019] Figure 1 It is a hydraulic cylinder assembly with a stroke end locking device installed; Figure 2 The cylinder is not locked (piston rod is freely extended); Figure 3 The cylinder is not locked (piston rod retracts freely); Figure 4 It is the cylinder lock (piston rod extended position); Figure 5 It is the hydraulic cylinder lock (piston rod retracted position); Figure 6 This is a schematic diagram of the locking device structure; Figure 7 This is a schematic diagram of the locking state of the locking device; Figure 8 This is a diagram showing the unlocked state of the locking device.

[0020] In the diagram: 1-Cylinder assembly; 1-1-Cylinder barrel; 1-2-Cylinder piston rod; 1-3-Locking device mounting sleeve; 2-Stroke end locking device; 2-1-Drive mounting bracket; 2-2-Pin; 2-3-Electric push rod; 2-4-Moving rod; 2-5-Pin; 2-6-Locking push rod; 2-7-Locking ball movable limit seat; 2-8-Steel ball; 2-9-Cylinder locking seat; 2-10-Retracting locking groove; 2-11-Extending locking groove; 2-12-Steel ball movement groove; 2-13-Steel ball unlocking groove. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] like Figures 1 to 8 As shown, the present invention provides a hydraulic cylinder stroke end locking device, including a hydraulic cylinder assembly 1 and a stroke end locking device 2.

[0023] The hydraulic cylinder assembly 1 consists of a cylinder barrel 1-1, a piston rod 1-2, and a locking device mounting cylinder 1-3. The piston rod 1-2 is a double-rod type piston rod, installed inside the cylinder barrel 1-1, and extends and retracts axially along the cylinder barrel under the drive of a hydraulic pressure oil source. The locking device mounting cylinder 1-3 is installed at the left end of the hydraulic cylinder, serving as a connecting transition piece between the drive mounting bracket 2-1 of the stroke end locking device 2 and the hydraulic cylinder assembly 1. The locking device mounting cylinder 1-3 has a cylindrical structure.

[0024] The stroke end locking device 2 consists of a drive mounting bracket 2-1, an electric push rod 2-3, connecting first pins 2-2 and 2-5, a locking push rod 2-6, a locking ball movable limit seat 2-7, a ball 2-8, and a cylinder locking seat 2-9.

[0025] The electric push rod 2-3 is mounted in the middle of the drive mounting bracket 2-1. The rear end of the electric push rod 2-3 is connected to the mounting bracket 2-1 via a first pin 2-2, and the front movable rod 2-4 of the electric push rod 2-3 is connected to the locking push rod 2-6 via a second pin 2-5. Through this connection method, the telescopic movement of the electric push rod 2-3 can be converted into the axial movement of the locking push rod 2-6, thereby realizing the switching between the locking and unlocking states. This transmission structure is simple and reliable, and easy to install and maintain.

[0026] The rear end of the mounting bracket 2-1 has a symmetrical frame structure. The middle of the frame is used to install the electric push rod 2-3 and the locking push rod 2-6. The front end of the mounting bracket 2-1 is a hollow cylindrical flange structure. The cylindrical flange is used to connect the locking device mounting cylinder 1-3, fixing the stroke end locking device 2 to the rear end of the hydraulic cylinder. This structure integrates the locking device with the cylinder as a whole, occupying little space and suitable for working conditions with limited installation space.

[0027] The end of the long cylindrical structure at the front end of the mounting bracket 2-1 is machined with multiple evenly distributed circumferentially distributed ball bearing grooves 2-12. The ball bearing grooves 2-12 are cylindrical, with their axes perpendicular to the cylindrical axis of the mounting bracket 2-1. The cylindrical grooves 2-12 are partially tapered outwards, and the same number of steel balls 2-8 as the grooves 2-12 are installed within them. Due to the outward tapering of the cylindrical grooves 2-12, the steel balls will not fall out. This structure ensures reliable positioning of the steel balls within the grooves, avoiding the risk of steel balls falling out.

[0028] Locking push rod 2-6 is the driving component for locking the position of the steel ball. Locking push rod 2-6 is cylindrical. The left end of locking push rod 2-6 has a mounting pin hole connected to the movable rod 2-4 of the electric push rod via a pin. The right end of locking push rod 2-6 is inserted into the cylindrical hole at the right end of the mounting bracket 2-1. The right end of locking push rod 2-6 has a steel ball unlocking groove 2-13, which is a U-shaped groove with a chamfer greater than 45°. The groove depth ensures that when all the steel balls fall into the groove, the steel balls do not protrude outside the steel ball movement groove 2-12 (e.g., ...). Figure 8 (As shown). A chamfer greater than 45° facilitates the smooth movement of the steel ball in and out of the unlocking slot during unlocking and locking, preventing jamming.

[0029] The cylinder locking seat 2-9 is cylindrical in shape. The right side of the locking seat 2-9 is threaded to connect with the end of the piston rod 1-2 of the cylinder. The left end of the cylindrical cylinder of the locking seat 2-9 has two arc-shaped locking ring grooves. The locking ring grooves are the retractable locking groove 2-10 and the extended locking groove 2-11. The two locking ring grooves correspond to the two positions of the retracted end and the extended end of the cylinder, respectively. The shape of the ring grooves matches the steel ball 2-8.

[0030] The operating principle of the cylinder stroke end locking device of the present invention is as follows: When the locking push rod 2-6 moves to the right, the steel ball 2-8 will fall into the unlocking groove 2-13 and be in the unlocked state. At this time, the steel ball 2-8 retracts into the steel ball movement groove 2-12 and does not protrude from the groove. The cylinder locking seat 2-9 is released from the lock of the steel ball 2-8 and can move freely along the cylinder axis within the cylinder barrel 1-1 together with the cylinder piston rod 1-2. This unlocked state ensures that the cylinder piston rod can freely extend and retract under normal working conditions.

[0031] When the locking push rod 2-6 moves to the left, it pushes the steel ball 2-8, causing it to disengage from the unlocking groove 2-13. The steel ball moves radially outward until it exposes the steel ball movement groove 2-12. Simultaneously, the steel ball 2-8 is tangent to the outer diameter of the locking push rod 2-6, and it will not retract under the restriction of the locking push rod 2-6, thus remaining in a locked state. When the steel ball 2-8 expands and falls into the locking groove 2-10 or 2-11 of the hydraulic cylinder locking seat 2-9, the hydraulic cylinder piston rod 1-2 is restricted in its axial movement by the steel ball 2-8, achieving end locking of the hydraulic cylinder piston rod. In this locked state, the steel ball and the outer diameter of the locking push rod are tangent, forming a self-locking mechanism. Even if the electric push rod loses power, the locked state can still be maintained, exhibiting high reliability.

[0032] Before using the cylinder stroke end locking device of the present invention, the locking device mounting cylinder 1-3 needs to be installed on the left end of the cylinder, and the cylindrical flange of the drive mounting bracket 2-1 is fixedly connected to the locking device mounting cylinder 1-3, so that the entire locking device is fixedly installed at the rear end of the hydraulic cylinder. The cylinder locking seat 2-9 is fixedly connected to the end of the cylinder piston rod 1-2 through the right-side thread. The power cord and control cord of the electric push rod 2-3 are connected to the external control system.

[0033] The locking method of the hydraulic cylinder stroke end locking device of the present invention, based on the above-mentioned hydraulic cylinder stroke end locking device, specifically includes the following steps: When it is necessary to lock the piston rod 1-2 of the hydraulic cylinder, the control system sends an action command to the electric push rod 2-3. The movable rod 2-4 of the electric push rod 2-3 retracts, driving the locking push rod 2-6 to move axially to the left via the second pin 2-5. During the leftward movement of the locking push rod 2-6, its right end outer diameter gradually approaches and pushes the steel ball 2-8, causing the steel ball 2-8 to move along the chamfered slope of the unlocking groove 2-13 and gradually disengage from the unlocking groove 2-13. The steel ball 2-8 moves radially outward within the steel ball movement groove 2-12 until it is exposed. When the locking push rod 2-6 continues to move to the left until its outer diameter is tangent to the steel ball 2-8, the steel ball 2-8 remains in an extended state under the limiting action of the outer diameter of the locking push rod 2-6 and cannot retract. At this time, if the cylinder piston rod 1-2 has moved to the extended or retracted end position, the expanded steel ball 2-8 is precisely inserted into the corresponding annular groove 2-10 or 2-11 on the cylinder locking seat 2-9. The steel ball 2-8 is simultaneously limited by the constricting edge of the steel ball movement groove 2-12 and the outer diameter of the locking push rod 2-6, and cannot retract radially, thereby restricting the relative axial movement between the cylinder locking seat 2-9 and the mounting bracket 2-1, and realizing reliable end locking of the cylinder piston rod 1-2.

[0034] In this locking method, when the locking push rod 2-6 moves to the left, the steel ball 2-8 moves along the chamfered slope of the unlocking groove 2-13. The chamfer angle is greater than 45°, which allows the steel ball to smoothly transition between the unlocking groove and the outer diameter of the locking push rod, avoiding jamming. In the locked state, the steel ball 2-8 is tangent to the outer diameter of the locking push rod 2-6, and the outer diameter surface of the locking push rod 2-6 provides radial support. Even if the electric push rod 2-3 loses power, the position of the locking push rod 2-6 will not change, and the steel ball 2-8 will always remain in an extended state, ensuring reliable locking. At the same time, the cylinder locking seat 2-9 is provided with a retractable locking groove 2-10 and an extended locking groove 2-11, corresponding to the two positions of the cylinder extension and retraction ends, respectively. Locking can be achieved regardless of whether the cylinder piston rod 1-2 is at the extension or retraction end, satisfying the locking requirements at both ends of the cylinder stroke.

[0035] When unlocking is required, the control system sends a reverse command to the electric push rod 2-3. The movable rod 2-4 of the electric push rod 2-3 extends and pushes the locking push rod 2-6 axially to the right via the second pin 2-5. When the unlocking groove 2-13 at the right end of the locking push rod 2-6 moves to the position of the steel ball 2-8, the steel ball 2-8 falls into the unlocking groove 2-13. Since the groove depth of the unlocking groove 2-13 is sufficient to prevent the steel ball 2-8 from protruding from the steel ball movement groove 2-12 when it is fully inside the groove, the steel ball 2-8 retracts radially into the steel ball movement groove 2-12, completely disengaging from the retraction locking groove 2-10 of the cylinder locking seat 2-9 or extending out of the locking groove 2-11. At this time, the axial limit between the cylinder locking seat 2-9 and the mounting bracket 2-1 is released, and the cylinder piston rod 1-2 returns to its free movement state, and can extend or retract normally under the drive of the hydraulic pressure oil source. Throughout the unlocking process, steel ball 2-8 smoothly rolls into the groove along the chamfered slope of unlocking groove 2-13, with a stable movement and rapid response.

[0036] During the locking and unlocking process described above, the rear end of the electric push rod 2-3 is hinged to the mounting bracket 2-1 via the first pin 2-2, and the front movable rod 2-4 is hinged to the locking push rod 2-6 via the second pin 2-5. This converts the linear extension and retraction motion of the electric push rod 2-3 into the axial movement of the locking push rod 2-6, resulting in high transmission efficiency and reliable operation. Operators can issue locking or unlocking commands through the control system at any time according to actual working conditions, achieving active control of the cylinder piston rod at the end of its stroke. This eliminates reliance on the pressure status of the hydraulic system, making it particularly suitable for situations where the hydraulic system may malfunction or lose pressure.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydraulic cylinder stroke end locking device, comprising a cylinder assembly (1) and a stroke end locking device (2), wherein the cylinder assembly (1) comprises a cylinder barrel (1-1), a cylinder piston rod (1-2), and a locking device mounting sleeve (1-3), wherein the cylinder piston rod (1-2) is installed inside the cylinder barrel and extends and retracts axially, characterized in that: The stroke end locking device (2) includes a drive mounting bracket (2-1), an electric push rod (2-3), a locking push rod (2-6), a steel ball (2-8), and a hydraulic cylinder locking seat (2-9). The drive mounting bracket (2-1) is fixed on the locking device mounting cylinder (1-3), the electric push rod (2-3) is mounted on the drive mounting bracket (2-1), and the movable rod (2-4) of the electric push rod (2-3) is connected to the locking push rod (2-6). The front end of the drive mounting bracket (2-1) is machined with a plurality of steel ball movement grooves (2-12) evenly distributed around the circumference, and the steel balls (2-8) are installed in the steel ball movement grooves (2-12); The right end of the locking push rod (2-6) is machined with a steel ball unlocking groove (2-13). The locking push rod (2-6) is inserted into the drive mounting bracket (2-1) and drives the steel ball (2-8) to move radially in the steel ball movement groove (2-12) by axial movement. The cylinder locking seat (2-9) is connected to the end of the cylinder piston rod (1-2), and a locking ring groove is machined inside to accommodate the expanded steel ball (2-8); When the locking push rod (2-6) moves to the locked position, the steel ball (2-8) disengages from the steel ball unlocking groove (2-13) and is pushed radially outward, locking into the locking ring groove to restrict the axial movement of the cylinder piston rod (1-2).

2. The hydraulic cylinder stroke end locking device according to claim 1, characterized in that: The steel ball unlocking groove (2-13) is a U-shaped groove with a chamfer angle greater than 45°. The groove depth is such that when all the steel balls (2-8) fall into the groove, the steel balls (2-8) do not protrude from the steel ball movement groove (2-12) and are in the unlocked state.

3. The hydraulic cylinder stroke end locking device according to claim 1, characterized in that: The rear end of the drive mounting bracket (2-1) is a symmetrical frame structure, with the middle of the frame used to install the electric push rod (2-3) and the locking push rod (2-6), and the front end is a hollow cylindrical flange long cylindrical structure, with the cylindrical flange used to connect the cylinder locking device mounting cylinder (1-3).

4. A hydraulic cylinder stroke end locking device according to claim 1, characterized in that: The ball movement groove (2-12) is cylindrical, and its axis is perpendicular to the cylindrical axis of the drive mounting bracket (2-1). The cylindrical groove is partially narrowed at the outward position to prevent the ball (2-8) from falling out.

5. A hydraulic cylinder stroke end locking device according to claim 1, characterized in that: The cylinder locking seat (2-9) is cylindrical in shape. The right side is threaded and connected to the end of the cylinder piston rod (1-2). The left end of the cylindrical tube has two arc-shaped grooves inside, corresponding to the two positions of the cylinder extension and retraction ends, respectively.

6. A hydraulic cylinder stroke end locking device according to claim 1, characterized in that: The rear end of the electric push rod (2-3) is connected to the drive mounting bracket (2-1) via a first pin (2-2), and the front movable rod (2-4) is connected to the locking push rod (2-6) via a second pin (2-5).

7. A locking method using the hydraulic cylinder stroke end locking device as described in any one of claims 1-6, characterized in that, Includes the following steps: When it is necessary to lock the cylinder piston rod (1-2), control the electric push rod (2-3) to move, driving the locking push rod (2-6) to move to the left; The locking push rod (2-6) pushes the steel ball (2-8) to disengage it from the steel ball unlocking groove (2-13), and the steel ball (2-8) moves radially outward and exposes the steel ball movement groove (2-12). Continue moving the locking push rod (2-6) so that the steel ball (2-8) is tangent to the outer diameter of the locking push rod (2-6). Under the restriction of the locking push rod (2-6), the steel ball (2-8) remains in an expanded state and is stuck in the locking ring groove of the cylinder locking seat (2-9), thereby achieving end locking of the cylinder piston rod (1-2). When unlocking is required, the electric push rod (2-3) is controlled to reverse, driving the locking push rod (2-6) to move to the right, so that the steel ball (2-8) falls into the steel ball unlocking groove (2-13), disengaging from the locking ring groove, and the hydraulic cylinder piston rod (1-2) resumes free movement.

8. The locking method according to claim 7, characterized in that, The locking ring groove includes a retractable locking groove (2-10) and an extended locking groove (2-11), which correspond to the retracted and extended end positions of the hydraulic cylinder piston rod (1-2), respectively. When the hydraulic cylinder piston rod (1-2) moves to any end position, the locking push rod (2-6) is driven by the electric push rod (2-3) to move, so that the expanded steel ball (2-8) is locked into the corresponding locking groove.

9. The locking method according to claim 7, characterized in that, When the locking push rod (2-6) moves to the left to lock, the steel ball (2-8) moves along the chamfered slope of the steel ball unlocking groove (2-13) on the locking push rod (2-6) until it is pushed out and abuts against the outer diameter of the locking push rod (2-6).

10. The locking method according to claim 7, characterized in that, The electric push rod (2-3) is hinged to the drive mounting bracket (2-1) and the locking push rod (2-6) via the first and second pins, which converts the linear extension and retraction motion of the electric push rod (2-3) into the axial movement of the locking push rod (2-6).

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