CN110195798B - A self-locking valve and system - Google Patents

Abstract

The invention relates to the technical field of valves, and discloses a self-locking valve, which comprises a valve rod, wherein the top of the valve rod is connected with a clamping piece for driving the valve rod to rotate, and the self-locking valve is characterized in that: the valve rod and the clamping piece are provided with a self-locking mechanism, and the self-locking mechanism comprises an opening and closing stroke slot hole formed in the clamping piece, a pushing block fixed on the valve rod and capable of relatively running in the opening and closing stroke slot hole, and clamping grooves respectively formed in the clamping piece and the valve rod and matched with each other; the clamping piece is connected with the valve rod in a rotating fit way. The self-locking valve can realize the self-locking function of the valve in the closed state, and the valve cannot be directly opened again after self locking. The valve can be prevented from being opened by misoperation and accidents caused by misoperation. The safety operation of the valve is improved, and the personal safety of staff is ensured.

Description

A self-locking valve and system

Technical Field

The present invention relates to the field of valve technology, and in particular to a self-locking valve and a system.

Background Art

Valves are pipe accessories used to open and close pipes, control flow direction, and adjust and control the parameters (temperature, pressure, and flow) of the conveying medium. Valves are control components in fluid conveying systems and have functions such as shutoff, regulation, diversion, backflow prevention, pressure stabilization, flow diversion, or overflow pressure relief. Valves used in fluid control systems come in a wide variety of varieties and specifications, from the simplest shutoff valves to various valves used in extremely complex automatic control systems.

Valves are distributed in every corner of urban pipeline construction, such as water pipelines, natural gas pipelines, heating pipelines, etc., and are closely related to the safety of people's living environment. In addition, valves are also widely used in the fields of chemical industry, pharmaceutical industry, etc. to control process equipment or production processes. When the valve is working, pipeline maintenance, or an emergency occurs, the valve needs to be shut down urgently to prevent the medium in the pipeline from continuing to be transported and causing harm to the downstream. However, in the use of existing valves, anyone can open or cut off the valve, and the above-mentioned arbitrary operability has great safety hazards and management loopholes. Due to the specific problems in the use of the above-mentioned valves, a self-locking, safe and effective valve is urgently needed. In the event of an emergency or accident (possible) when the pipeline is normally transporting the medium, anyone can close and cut off the valve to avoid accidents or safety accidents, or minimize the damage caused by the accident. In addition, the valve is locked after closing, and no one can directly open the valve again. The opening of this valve requires professional management personnel or authorized operators to use a key to open the closed valve. Prevent the valve from being opened again by mistake when the emergency event has not been handled, causing an accident.

Summary of the invention

The present invention aims to provide a self-locking valve and a system to solve the above-mentioned technical problems in the prior art.

The technical solution adopted by the present invention is:

A self-locking valve comprises a valve stem, the top of the valve stem is connected to a clamping piece that drives the valve stem to rotate, the valve stem and the clamping piece are provided with a self-locking mechanism, the self-locking mechanism comprises an opening and closing stroke slot hole formed on the clamping piece, a push block fixed to the valve stem and capable of relatively moving in the opening and closing stroke slot hole, and clamping grooves respectively formed on the clamping piece and the valve stem and cooperating with each other; the clamping piece is rotatably connected to the valve stem.

According to the self-locking valve provided by the present invention, the self-locking mechanism is a closed position self-locking mechanism. When the valve stem is in the open position, the push block is at the starting end of the opening and closing stroke slot hole; the opening and closing stroke slot hole is arc-shaped and coaxial with the valve stem.

According to the self-locking valve provided by the present invention, the self-locking mechanism is an open-position self-locking mechanism. When the valve stem is in the closed position, the push block is at the end of the opening and closing stroke slot hole; the opening and closing stroke slot hole is arc-shaped and coaxial with the valve stem.

According to the self-locking valve provided by the present invention, a handle is fixedly connected to the engaging member.

According to the self-locking valve provided by the present invention, the clamping grooves are respectively arranged on the rotating surface along the axial direction of the clamping member and the valve stem.

According to the self-locking valve provided by the present invention, the valve stem is externally sleeved with a coaxially arranged valve stem sealing joint, and a limiting mechanism is arranged on the valve stem sealing joint and the engaging member.

According to the self-locking valve provided by the present invention, the limiting mechanism includes a locking portion formed at the top of the valve stem sealing joint, and a clamping portion formed at the bottom of the clamping piece.

According to the self-locking valve provided by the present invention, the locking part and the engaging part are respectively provided with two step surfaces of different heights, and are engaged with each other; the spacing between the two steps of the locking part is adapted to the opening and closing stroke of the engaging part, and a blocking part is fixed on the valve stem to limit the movement between the two steps of the locking part.

According to the self-locking valve provided by the present invention, the top end of the valve stem is detachably and fixedly connected with a clamping piece locking assembly, which includes a screw and a pressure plate for pressing the clamping piece against the top end of the valve stem.

Another technical solution adopted by the present invention is:

A self-locking valve system comprises the self-locking valve described in any one of the above technical solutions, characterized in that it also comprises an unlocking key, which is engaged with the locking slot.

The beneficial effects of the present invention are:

This self-locking valve can realize the self-locking function when the valve is in the closed state. After self-locking, the valve cannot be directly opened again. It can avoid the accident caused by the wrong operation of the valve. It improves the safe operation of the valve and ensures the personal safety of the staff.

The self-locking valve can also realize the self-locking function when the valve is in the open state. After self-locking, the valve cannot be directly closed again. It can avoid the wrong operation of closing the valve and interrupting the material transportation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram (exploded view) of a preferred embodiment of the present invention;

In order to clearly show the structure, FIG1 also shows a partial enlarged view of the locking portion and multi-view views of the handle and the engaging portion;

FIG2 is a schematic top view of FIG1 (with the engaging portion and the handle omitted);

FIG3 is a schematic structural diagram (half-section view) of a preferred embodiment of the present invention;

FIG4 is a schematic structural diagram of a preferred embodiment of the present invention (full cross-sectional view);

FIG5 is a schematic diagram showing a working example of a preferred embodiment of the present invention;

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the 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 or be constructed and operated in a specific orientation, and therefore they cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; of course, it can also be a mechanical connection or an electrical connection; in addition, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Embodiment 1

As shown in Figures 1 to 5, the present invention provides a self-locking valve, including a valve stem 8, the top of the valve stem 8 is connected to a clamping piece that drives the valve stem to rotate, the valve stem 8 and the clamping piece are provided with a self-locking mechanism, the self-locking mechanism includes an opening and closing stroke slot hole 16 opened on the clamping piece, a push block 11 fixed to the valve stem 8 and capable of relatively running in the opening and closing stroke slot hole 16, and clamping grooves respectively opened on the clamping piece and the valve stem 8 and matching with each other; the clamping piece is rotatably matched with the valve stem 8.

The self-locking mechanism is a closed position self-locking mechanism. When the valve stem 8 is in the open position, the push block 11 is at the starting end of the opening and closing stroke slot hole 16; the opening and closing stroke slot hole 16 is arc-shaped and coaxial with the valve stem 8.

The valve stem 8 is sleeved with a coaxially arranged valve stem sealing joint on its exterior, and a limiting mechanism is arranged on the valve stem sealing joint and the engaging member.

The limiting mechanism includes a locking portion 5 formed at the top of the valve stem sealing joint and a clamping portion 19 formed at the bottom of the clamping member.

The locking portion 5 and the engaging portion 19 are respectively provided with two step surfaces of different heights, and are engaged with each other; the spacing between the two steps of the locking portion 5 is adapted to the opening and closing stroke of the engaging member, and a blocking member 7 is fixed on the valve stem 8 to limit the movement between the two steps of the locking portion 5.

Specifically, the locking portion 5 is formed with a first step 13 and a second step 12, there is a gap between the first step 13 and the second step 12, and the first step 13 is higher than the second step 12; the blocking member 7 extends outward from the radial direction of the cylindrical surface of the valve stem 8 and is confined in the gap; the push block 11 is arranged above the blocking member 7.

The blocking member 7 is a blocking column, a blocking pin, or a blocking block.

The push block 11 is configured as a key, and a key slot is correspondingly provided on the cylindrical surface of the valve stem 8, and the key is fixedly embedded in the key slot.

There are two blocking members 7, which are symmetrically distributed on both sides of the valve stem 8. Since the blocking member 7 is arranged in the gap, the blocking member 7 will be restricted by the first step 13 and the second step 12 when rotating with the valve stem 8, and will not escape from the gap.

Usually, the first step 13 and the second step 12 are arranged opposite to each other. The first step 13 and the second step 12 are in the shape of arc plates, which are integrally formed with the locking portion 5 and the valve stem sealing joint.

The engaging portion 19 is in a circular shape, and the through hole in the center is used for the valve stem 8 to be inserted and fixed; the inner arc surface of the opening and closing stroke slot hole 16 passes through the through hole; the push block 11 is penetrated and restricted in the opening and closing stroke slot hole 16, and the starting end of the opening and closing stroke slot hole 16 can push the push block 11 to drive the valve stem 8 to rotate; the bottom surface of the engaging portion 19 is formed with a third step 18, and the third step 18 is adapted to the first step 13 and the second step 12; the third step 18 is in surface contact with the second step 12, and the third step 18 is limited by the first step 13 when rotating with the handle 17.

In addition, the self-locking valve also includes a valve body, which is mainly composed of a shell and a ball 2. The ball 2 is arranged in the shell and is sealed. A valve stem sealing joint is formed on the upper part of the shell. The top of the ball 2 is fixedly connected to the valve stem 8, and the valve stem 8 extends outward through the valve stem sealing joint and is sealed and connected to the valve stem sealing joint. The clamping part 19 is adapted to and clamped with the locking part 5. The push block 11 and the blocking member 7 are fixed on the valve stem 8, specifically on its outer circumferential surface. A torque M is applied to the handle 17 (the handle 17 is fixedly connected to the clamping part 19), and the push block 11 is pushed on the handle 17. Under the action, the valve stem 8 is driven to rotate, thereby driving the ball 2 to rotate, and it is pushed by the starting end of the opening and closing stroke slot hole 16. At the same time, the engaging part 19 rotates on the locking part 5 and drives the blocking member 7 to lock in the first position, and the ball 2 and the shell form a closed-circuit valve; a reverse torque T is applied to the handle 17 (the handle 17 is fixedly connected to the engaging part 19), the push block 11 is fixed, the engaging part 19 reversely rotates on the locking part 5 and is locked in the second position. At this time, the push block 11 changes from the starting end of the opening and closing stroke slot hole 16 to the end, while the valve stem 8 and the ball 2 maintain their original positions and do not rotate.

As for the valve body, its technical solution belongs to the prior art. A valve cover 4 having a (hard) sealing function is arranged in the spherical shell, and both ends of the spherical shell are fixedly connected to the valve cover 4 connected to the pipeline.

The valve stem sealing joint is cylindrical or truncated cone-shaped, with a avoidance hole in the center for the valve stem 8 to pass through, and a sealing member is arranged between the through hole wall and the valve stem 8 .

The sealing connection (seal) between the valve stem 8 and the valve stem sealing joint also belongs to the prior art. For example, multiple seals are arranged between the valve stem 8 and the flange, specifically O-type sealing rings, and an outer pressure ring 6 is nested outside the valve stem 8 above the top O-type sealing ring. The outer pressure ring 6 presses the O-type sealing ring downward, and the O-type sealing ring is deformed to block the gap between the valve stem 8 and the flange to play a sealing role.

The clamping part 19 is fixedly connected with a handle 17, and the operator manually pulls the handle 17 to rotate the clamping part 19 to drive the valve stem 8 to rotate. Of course, the clamping part 19 can also be equipped with a pneumatic or electric automatic valve opening execution tool for automatically opening and closing the valve.

The top end of the valve stem 8 is detachably fixedly connected with a snap-fit locking assembly, which includes a screw 10 . The screw 10 is screwed into the end of the valve stem 8 and presses the snap-fit against the pressure plate 10 at the top end of the valve stem 8 .

The working principle of the first embodiment of the present invention is:

The various parts of the valve cooperate with each other according to the design principle, assembly relationship and connection relationship. When the valve is in the normal open position (i.e. the valve is in the passage, open state (see Figure 5-1)), the handle 17 can be directly operated to rotate clockwise (industry rules, usually clockwise closed) to close the valve (see Figure 5-2). If you want to operate the handle 17 to open the valve again (rotate the handle 17 counterclockwise), at this time, the handle 17 can only rotate in the reverse direction for a certain angle (the specific angle depends on the gap, 90 degrees in the figure), and the valve is still in the closed position (i.e. the valve is closed and closed (see Figure 5-3)), thereby achieving the valve closed position locking state, that is, the valve can only be closed but not opened, and the valve cannot be directly opened again when it is closed. This self-locking valve is also called a closed position self-locking valve.

Specific analysis:

See the working principle of the second embodiment of the present invention below.

Embodiment 2

As shown in Figures 1 to 5, the present invention provides a self-locking valve system, including the self-locking valve of the first embodiment of the above technical solution, and also including an unlocking key 20, which is engaged with the card slot. The unlocking key is inserted into the card slot for meshing connection; when the valve is opened, the reverse torque T drives the engagement portion 19 to rotate, and drives the valve stem 8 to rotate in the opposite direction through the unlocking key, breaking the idle state of the engagement portion 19, and the engagement portion 19 drives the blocking member 7 to lock in the second position, and the ball 2 and the shell form an open circuit to open the valve.

The clamping groove is respectively arranged on the rotating surface along the axial direction of the clamping member and the valve stem 8. Specifically, the clamping groove is divided into a first groove 14 and a second groove 15. The first groove 14 is vertically opened on the cylindrical surface of the valve stem 8; the second groove 15 is vertically opened on the wall of the through hole, and the second groove 15 and the first groove 14 can be matched to form a clamping groove, which is a lock hole.

In addition, a notch is provided on the pressing plate 9 of the locking assembly of the engaging member to avoid the lock hole, so that the lock hole is exposed.

The working principle of the second embodiment of the present invention is:

The various parts of the valve cooperate with each other according to the design principle, assembly relationship, and connection relationship. When the valve is in the normal open position (i.e., the valve is in the passage and open state (see Figure 5-1)), the handle 17 can be directly operated to rotate clockwise (industry rules, usually clockwise to close) to close the valve (see Figure 5-2). If you want to operate the handle 17 to open the valve again (rotate the handle 17 counterclockwise), at this time, the handle 17 can only rotate in the reverse direction for a certain angle (the specific angle depends on the gap, 90 degrees in the figure), and the valve is still in the closed position (i.e., the valve is closed and closed (see Figure 5-3)), thereby achieving the valve closed position locking state, that is, the valve can only be closed but not opened. If the valve needs to be opened again, the operator needs to insert the special unlocking key 20 into the lock hole formed by the engaging portion 19 of the handle 17 and the valve stem 8 (when the valve is in the closed position (see Figure 5-4)), and then rotate the handle 17 counterclockwise, and the valve can be opened normally); after the valve passage is opened to the full extent (see Figure 5-5), remove the unlocking key 20, and the valve returns to its normal working state. At this time, the valve can be directly closed, but cannot be directly opened after closing.

Specific analysis:

As shown in Figure 1, surface A and surface B are the top surfaces of the first step 13 and the second step 12 on the locking part 5, respectively, and surface B is lower than surface A. The two side surfaces of the first step 13 and the second step 12 are the closing limit surfaces Q2 and Q1, and the opening limit surfaces S1 and S2 (see the above explanation for the open position and the closed position). That is, when the blocking member 7 is restricted against the Q2 and/or Q1 surfaces, the valve is in a closed state; and when the blocking member 7 is restricted against the S1 and/or S2 surfaces, the valve is in an open state. K3 and Q4 are the two end surfaces of the opening and closing stroke slot hole 16 on the engaging part 19. K1 and K2 are the two side surfaces of the key, of which K1 is the driving plane. The key fits into the opening and closing stroke slot hole 16, and the K3 surface of the opening and closing stroke slot hole 16 on the engaging part 19 can push it to drive the valve stem 8 to rotate. Surface P is the outer cylindrical surface of the limiting column or limiting pin. The E and F surfaces are the top surfaces of the third step 18 on the engaging portion 19, the side surface S3 of the third step 18 is the closing limit surface of the engaging portion 19, and Q3 is the opening limit surface of the engaging portion 19. The E surface of the engaging portion 19 is in surface contact with the B surface of the locking portion 5, and the F surface is in surface contact with the A surface, and the engaging portion 19 and the locking portion 5 are meshed together.

As shown in Figure 5-1, the valve is in the normal open position. At this time, a bending moment M is applied (usually the handle 17 is rotated 90 degrees clockwise) to close the valve, as shown in Figure 5-2. During the clockwise rotation of the handle 17, the K3 surface of the opening and closing stroke slot 16 on the engaging portion 19 is always in contact with the K1 surface of the key on the valve stem 8, thereby driving the valve stem 8 and the ball 2 to rotate clockwise until the P surface of the valve stem 8 simultaneously hits the S1 surface of the first step 13 and/or the S2 surface of the second step 12 and is restricted from further rotation (the position of each component at this time is the first position), and the valve can be closed, as shown in Figure 5-2. When the valve stem 8 rotates, the ball 2 always performs synchronous rotation.

As shown in Figure 5-2, the valve is in a closed and self-locking state. 1. When the handle 17 continues to apply bending moment M, the handle 17 rotates clockwise, and the Q3 surface of the third step 18 on the engaging portion 19 just contacts the Q2 surface of the first step 13 on the locking portion 5, so the handle 17 can no longer be rotated clockwise, and the valve stem 8 will not rotate (the position of each component at this time is the first position). The valve is always in a closed state. 2. At this time, if a reverse bending moment T is applied (usually the handle 17 is reversed 90 degrees counterclockwise), the engaging portion 19 is just idling, and it cannot drive the valve stem 8 to rotate synchronously. During the reverse process of the counterclockwise operating handle 17, the key on the valve stem 8 is just idling in the opening and closing stroke slot 16, that is, the K1 surface and the K2 surface are idling in the opening and closing stroke slot 16, and the K3 surface and the Q4 surface cannot push the K1 surface and the K2 surface to drive the valve stem 8 to rotate. At this time, the valve is in a closed state. As shown in Figure 5-2, when the handle 17 continues to rotate counterclockwise, the S3 surface on the engaging portion 19 just hits the S1 surface of the first step 13 on the locking portion 5 and is blocked, so the handle 17 can no longer rotate (the position of each component at this time is the second position). In this process, the counterclockwise rotation of the handle 17 fails to drive the valve stem 8 to rotate synchronously to open the valve, and the valve is always in the closed position, that is, the valve is self-locking and cannot be opened, as shown in Figure 5-3.

As shown in Figure 5-4, the valve can only be opened and closed normally when the unlocking key 20 is inserted. When the valve is in the closed position, turn the handle 17, and the handle 17 is idle at this time, so that the second groove 15 and the first groove 14 cooperate to form a lock hole, and the unlocking key 20 is inserted from the lock hole. The unlocking part of the unlocking key 20 snaps the second groove 15 and the first groove 14 together, so that the valve stem 8 and the snapping part 19 can be linked. A new transmission chain is formed between the snapping part 19 (handle 17) and the valve stem 8. The operating handle 17 rotates counterclockwise, and the valve stem 8 and the ball 2 rotate synchronously, and the valve can be opened. The valve is in a passage state, as shown in Figure 5-5. If the unlocking key 20 is pulled out at this time, the operating handle 17 rotates clockwise to close the valve, and the valve cannot be opened directly after closing. The principle is the same as above and will not be repeated.

Embodiment 3

The technical solution of the self-locking valve in the first embodiment can also be applied to the state where the pipeline is always open and cannot be closed. For example, the refrigerant is transported to the equipment for cooling the equipment. When the refrigerant is interrupted, the equipment cannot get sufficient heat dissipation and is burned. At this time, this kind of self-locking valve is an open-position self-locking valve, and the specific application is: the valve is closed in the closed position, and the pipeline is closed; when the refrigerant needs to be transported, the operating handle 17 opens the valve, the pipeline is open, and the refrigerant starts to be transported; during the refrigerant transportation, the valve is in the open position, and it cannot be directly closed again, and the valve is in the open position locked state; that is, the valve can only be opened and not closed, and the valve cannot be directly closed again when it is in the open position.

When the valve needs to be closed, the unlocking key 20 is engaged with the card slot; only then can the valve be closed.

The specific technical solution is:

A self-locking valve comprises a valve stem 8, the top of the valve stem 8 is connected to a clamping piece for driving the valve stem to rotate, the valve stem 8 and the clamping piece are provided with a self-locking mechanism, the self-locking mechanism comprises an opening and closing stroke slot hole 16 provided on the clamping piece, a push block 11 fixed on the valve stem 8 and capable of relatively running in the opening and closing stroke slot hole 16, and clamping grooves respectively provided on the clamping piece and the valve stem 8 and cooperating with each other; the clamping piece is rotatably connected to the valve stem 8.

The self-locking mechanism is an open position self-locking mechanism. When the valve stem 8 is in the closed position, the push block 11 is at the end of the opening and closing stroke slot hole 16; the opening and closing stroke slot hole 16 is arc-shaped and coaxial with the valve stem 8.

When the opening and closing stroke slot hole 16 rotates counterclockwise with the handle 17 and the engaging part 19, its end can push the push block 11 to drive the valve stem 8 and the ball 2 connected thereto to rotate counterclockwise, and the valve is opened. Thereafter, when the handle 17 and the engaging part 19 rotate clockwise, the push block 11 changes from the end of the opening and closing stroke slot hole 16 to the starting end (the push block 11 "idles" in the opening and closing stroke slot hole 16, but in fact the push block 11 does not rotate, and the phenomenon of idling is a relative rotation caused by the rotation of the engaging part 19), while the valve stem 8 and the ball 2 remain in their original positions and do not rotate, and the valve is no longer closed and is in an open position self-locking state.

The specific working principle of the open position self-locking valve can be easily understood by referring to the working principle of the closed position self-locking valve in the second comparative embodiment, and will not be described in detail.

Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

The names of the components represented by the reference numerals in the above text are as follows:

Valve body 1, ball 2, valve seat 3, valve cover 4, locking part 5, outer pressure ring 6, blocking member 7, valve stem 8, pressure plate 9, screw 10, push block 11, second step 12, first step 13, first groove 14, second groove 15, opening and closing stroke slot hole 16, handle 17, third step 18, engaging part 19, unlocking key 20.

Claims (7)

1. A self-locking valve, comprising a valve stem, a clamping piece connected to the top of the valve stem for driving the valve stem to rotate, characterized in that: a self-locking mechanism is arranged on the valve stem and the clamping piece, the self-locking mechanism comprises an opening and closing stroke slot hole provided on the clamping piece, a push block fixed on the valve stem and capable of relatively running in the opening and closing stroke slot hole, and clamping grooves respectively provided on the clamping piece and the valve stem and cooperating with each other; the clamping piece is rotatably connected and cooperated with the valve stem; a coaxially arranged valve stem sealing joint is sleeved on the outer side of the valve stem, and a limiting mechanism is arranged on the valve stem sealing joint and the clamping piece, the limiting mechanism comprises a locking portion formed on the top of the valve stem sealing joint, and a clamping portion formed at the bottom of the clamping piece, the locking portion and the clamping portion are respectively provided with two step surfaces of different heights, and are locked and cooperated with each other; the spacing between the two steps of the locking portion is adapted to the opening and closing stroke of the clamping piece, and a blocking member is fixed on the valve stem to limit the movement between the two steps of the locking portion. 2. The self-locking valve according to claim 1 is characterized in that: the self-locking mechanism is a closed position self-locking mechanism, when the valve stem is in the open position, the push block is at the starting end of the opening and closing stroke slot hole; the opening and closing stroke slot hole is arc-shaped and coaxial with the valve stem. 3. The self-locking valve according to claim 1 is characterized in that: the self-locking mechanism is an open-position self-locking mechanism, when the valve stem is in the closed position, the push block is at the end of the opening and closing stroke slot hole; the opening and closing stroke slot hole is arc-shaped and coaxial with the valve stem. 4. The self-locking valve according to claim 1, characterized in that a handle is fixedly connected to the engaging member. 5. The self-locking valve according to claim 1, characterized in that the clamping grooves are arranged on the rotating surface along the axial direction of the clamping piece and the valve stem respectively. 6. The self-locking valve according to claim 1 is characterized in that: the top end of the valve stem is detachably fixedly connected with a snap-fit locking assembly, and the snap-fit locking assembly includes a screw and a pressure plate that presses the snap-fit against the top end of the valve stem. 7. A self-locking valve system, comprising the self-locking valve according to any one of claims 1 to 6, characterized in that it also comprises an unlocking key, which is engaged with the locking slot.